STERLING CHEMICALS HOLDINGS INC /TX/
SC 13D/A, 1998-12-23
INDUSTRIAL ORGANIC CHEMICALS
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<PAGE>   1
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                 SCHEDULE 13D/A

                    UNDER THE SECURITIES EXCHANGE ACT OF 1934
                               (AMENDMENT NO. 4)*

                        STERLING CHEMICALS HOLDINGS, INC.
                      -------------------------------------
                                (Name of Issuer)

                     Common Stock, par value $.01 per share
                   ------------------------------------------
                         (Title of Class of Securities)

                                  85916 E 10 3
                                ----------------
                                 (CUSIP Number)

         Frank P. Diassi                              Thomas M. Hart III
c/o Sterling Chemicals Holdings, Inc.               Andrews & Kurth L.L.P.
   1200 Smith Street, Suite 1900                  4200 Texas Commerce Tower
   Houston, Texas 77002-4312                         Houston, Texas 77002
        (713) 650-3700                                  (713) 220-4200

                  -------------------------------------------
                  (Name, Address and Telephone Number of Person
                Authorized to Receive Notices and Communications)

                                December 15, 1998
             (Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report
the acquisition which is the subject of this Schedule 13D, and is filing this
schedule because of Rule 13d-1(b)(3) or (4), check the following box  [ ].

NOTE: Six copies of this statement, including all exhibits, should be filed with
the Commission. See Rule 13d-1(a) for other parties to whom copies are to be
sent.

*The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter
disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).


<PAGE>   2

                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                 PAGE 1 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    Frank P. Diassi
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY

    
- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    PF
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    United States
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          724,321
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    724,321
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     724,321
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     5.7%
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     IN
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>


<PAGE>   3
                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                 PAGE 2 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    Marianne R. Diassi
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    PF
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    United States
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          10,000
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    10,000
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     10,000
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     Less than .1% of Total Shares Outstanding
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     IN
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   4
                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                 PAGE 3 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    Hunter Nelson
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    PF
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    United States
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           64,758
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          0
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    64,758
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    0
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     64,758
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     .5%
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON 

     IN
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>
<PAGE>   5
                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                 PAGE 4 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    William C. Oehmig
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    PF
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    United States
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          361,772
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    361,772
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     361,772
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     2.8%
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     IN
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   6
                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                 PAGE 5 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    Frank J. Hevrdejs
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    PF
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    United States
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           948,782
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          0
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    948,782
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    0
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     948,782
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     7.4%
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     IN
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   7
                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                 PAGE 6 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    The Rheney Living Trust (Clarke Rheney or Susan O. Rheney, Trustees)
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    PF
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    United States
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           48,307
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          0
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    48,307
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    0
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     48,307
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     .4%
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     OO
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   8
                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                 PAGE 7 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    Clipper Capital Associates, Inc.       13-3706407
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    Not Applicable
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    Delaware     
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          2,063,204
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    2,063,204
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     2,063,204
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     16.1%
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     CO
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   9
                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                 PAGE 8 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    Clipper Capital Associates, L.P.       13-3706321
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    AF
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    Delaware     
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          2,063,204
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    2,063,204
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     2,063,204
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     16.1%
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     PN
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   10
                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                 PAGE 9 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    Clipper/Merchant Partners, L.P.          13-3737437
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    OO
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    Delaware     
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          516,031
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    516,031
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     516,031
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     4.1%
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     PN
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   11
                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                PAGE 10 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    Clipper Equity Partners I, L.P.         13-3834258
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    OO
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    Delaware     
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          444,537
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    444,537
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     444,537
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     3.5%
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     PN
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   12
                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                PAGE 11 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    Clipper/European Re, L.P.       98-0154020
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    OO
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    Delaware     
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          296,328
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    296,328
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     296,328
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     2.3%
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     PN
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   13
                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                PAGE 12 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    Clipper/Merban, L.P.        98-013328
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    OO
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    Delaware   
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          592,701
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0 
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    592,701
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     592,701
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     4.6%
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     PN
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   14
                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                PAGE 13 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    Clipper Capital Corporation       13-3706408
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    Not Applicable
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    Delaware     
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          75,900 
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    75,900 
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     75,900 
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     .6% 
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     CO
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   15
                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                PAGE 14 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    Clipper Capital Partners, L.P.                 13-3706324 
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    Not Applicable
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    Delaware     
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          75,900
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    75,900
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     75,900
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     .6%
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     PN
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   16
                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                PAGE 15 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    CS First Boston Merchant Investments 1995/96, L.P.     13-3860592
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    OO
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    Delaware     
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          75,900
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    75,900
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     75,900
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     .6%
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     PN
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   17
                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                PAGE 16 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    Robert B. Calhoun, Jr.
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                    (a) [ ]
                                                                         (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    Not Applicable
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    United States
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          2,139,104
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    2,139,104
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     2,139,104
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     16.7%
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     IN
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   18
                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                PAGE 17 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    Koch Capital Services, Inc. (f/k/a Koch Equities, Inc.)
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    AF         
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    Delaware     
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           1,181,254
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          0        
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    1,181,254
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    0        
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     1,181,254
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     9.2% 
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     CO
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   19

                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                PAGE 18 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    Koch Industries, Inc.
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    WC
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    Kansas       
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          1,181,254
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    1,181,254
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     1,181,254
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     9.2%
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     CO
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   20
                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                PAGE 19 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    Olympus Growth Fund II, L.P.
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    OO
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    Delaware     
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          678,770
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    678,770
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     678,770
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     5.3%
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     PN
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   21

                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                PAGE 20 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    OGP II, L.P.
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    Not Applicable
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    Delaware     
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          678,770
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    678,770
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     678,770
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     5.3%
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     PN
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   22

                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                PAGE 21 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    Olympus Executive Fund, L.P.
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    Not Applicable
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    Delaware     
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          7,926
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    7,926
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     7,926
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     Less than .1% of Total Shares Outstanding
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     PN
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   23

                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                PAGE 22 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    OEF, L.P.
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                  (a) [ ]
                                                                       (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    Not Applicable
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    Delaware     
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          7,926
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    7,926
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     7,926
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     Less than .1% of Total Shares Outstanding
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     PN
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   24

                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                PAGE 23 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    LJM, L.L.C.
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                  (a) [ ]
                                                                       (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    Not Applicable
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    Delaware   
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          686,696
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    686,696
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     686,696
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     5.4%
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     OO
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   25

                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                PAGE 24 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    RSM, L.L.C.
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    Not Applicable
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    Delaware     
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          686,696
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    686,696
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     686,696
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     5.4%
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     OO
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   26

                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                PAGE 25 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    Conroy, L.L.C.
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                  (a) [ ]
                                                                       (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    Not Applicable
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    Delaware   
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          686,696
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    686,696
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     686,696
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     5.4%
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     OO
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   27

                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                PAGE 26 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    Louis J. Mischianti
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                  (a) [ ]
                                                                       (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    Not Applicable
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    United States
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          686,696
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    686,696
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     686,696
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     5.4%
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     IN
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>


<PAGE>   28

                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                PAGE 27 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    Robert S. Morris
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    Not Applicable
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    United States
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          686,696
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    686,696
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     686,696
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     5.4%
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     IN
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   29
                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                PAGE 28 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    James A. Conroy
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    Not Applicable
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    United States
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          686,696
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    686,696
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     686,696
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     5.4%
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     IN
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   30
                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                PAGE 29 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    FSI No. 2 Corporation
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    WC            
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    Delaware   
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          687,548
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    687,548
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     687,548
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     5.4%
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     CO
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   31
                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                PAGE 30 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    Fayez Sarofim & Co.
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    Not Applicable
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    Texas      
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          687,548
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    687,548
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     687,548
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     5.4%
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     CO, IA
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   32
                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                PAGE 31 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    Fayez Sarofim 
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    Not Applicable
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    United States
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          687,548
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    687,548
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     687,548
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     5.4%
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     IN
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   33
                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                PAGE 32 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    Gordon A. Cain
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    PF            
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    United States
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          160,000
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    160,000
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     160,000
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     1.2%
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     IN
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   34
                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                PAGE 33 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    William A. McMinn
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    PF            
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    United States
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          40,000 
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    40,000 
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     40,000 
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     .3% 
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     IN
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>

<PAGE>   35
                                  SCHEDULE 13D

<TABLE>
<S>                                                           <C>
- --------------------------------------------------------------------------------
CUSIP NO. 85916E103                                                PAGE 34 OF 44

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

    James Crane   
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                   (a) [ ]
                                                                        (b) [x]
- --------------------------------------------------------------------------------
3   SEC USE ONLY


- --------------------------------------------------------------------------------
4   SOURCE OF FUNDS*

    PF            
- --------------------------------------------------------------------------------
5   CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
    TO ITEMS 2(d) OR 2(e)                                                   [ ]

- --------------------------------------------------------------------------------
6   CITIZENSHIP OR PLACE OF ORGANIZATION


    United States
- --------------------------------------------------------------------------------
                7   SOLE VOTING POWER
  NUMBER OF
   SHARES           0
BENEFICIALLY   -----------------------------------------------------------------
  OWNED BY      8   SHARED VOTING POWER
   EACH            
 REPORTING          30,000 
  PERSON       -----------------------------------------------------------------
   WITH         9   SOLE DISPOSITIVE POWER

                    0
               -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER
     
                    30,000 
- --------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     30,000 
- --------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES 
     CERTAIN SHARES*                                                        [x]

- --------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     .2% 
- --------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON

     IN
- --------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!
</TABLE>
<PAGE>   36
          This Schedule 13D/A Amendment No. 4 ("Amendment No. 4") amends the
Schedule 13D (the "Original Schedule 13D"), as amended by the Schedule 13D/A
Amendment No. 1 ("Amendment No. 1"), the Schedule 13D/A Amendment No. 2
("Amendment No. 2") and the Schedule 13D/A Amendment No. 3 ("Amendment No. 3";
the Original Schedule 13D, as amended by Amendment No. 1, Amendment No. 2
and Amendment No. 3 is referred to herein as the "Schedule 13D") filed jointly
by certain of the same parties filing this Amendment No. 4 with respect to the
common stock, par value $.01 per share (the "Common Stock"), of Sterling
Chemicals Holdings, Inc., a Delaware corporation ("Holdings" or the "Issuer").
Frank P. Diassi is the designated filer filing this Amendment No. 4 on behalf of
the Holders and Additional Reporting Persons identified in Item 2. Mr. Diassi
was the designated filer for Amendment No. 3 and Frank J. Hevrdejs was the
designated filer for each of the filings prior to Amendment No. 3. This
Amendment No. 4 is filed in connection with the acquisition of 300,000 warrants
to purchase Common Stock at an exercise price of $6.00 per share (the "1998
Warrants") by certain of the joint filers of this Amendment No. 4 in a private
placement transaction with the Issuer on December 15, 1998, and the concurrent
amendment of the Voting Agreement to which the Holders are parties. Capitalized
terms used but not defined in this Amendment No. 4 have the meanings previously
assigned to them in the Schedule 13D.

ITEM 1.   SECURITY AND ISSUER

          Item 1 of the Schedule 13D is amended as follows:

          This Statement on Schedule 13D relates to the beneficial ownership of
shares of Common Stock of the Issuer. The Issuer's principal executive offices
are located at 1200 Smith Street, Suite 1900, Houston, Texas 77002.

ITEM 2.   IDENTITY AND BACKGROUND

          Item 2 of the Schedule 13D is amended as follows:

          This Statement on Schedule 13D is being jointly filed by:

          (i)     Frank P. Diassi, individually and as trustee for the following
trusts: The Diassi Children's Trust U/A 12/21/89, Frank P. Diassi, Trustee; The
Gabrielle Diassi Trust U/A 9/24/90, Frank P. Diassi, Trustee; The Brianna Diassi
Trust DTD 6/15/98, Frank P. Diassi, Trustee; The Nicholas Diassi Trust DTD
6/15/98, Frank P. Diassi, Trustee (collectively, the "Diassi Trusts"); Marianne
R. Diassi; Hunter Nelson; William C. and Margaret W. Oehmig; Frank J. Hevrdejs;
The Rheney Living Trust, Clarke Rheney, Trustee or Susan O. Rheney, Trustee;
Clipper Capital Associates, L.P., Clipper Equity Partners I, L.P.,
Clipper/Merchant Partners, L.P., Clipper/Merban, L.P., Clipper/European Re,
L.P., CS First Boston Merchant Investments 1995/96, L.P. (collectively, the
"Clipper Holders"); FSI No. 2 Corp.; Koch Capital Services, Inc. ("Koch
Capital"); Olympus Growth Fund II, L.P.; and Olympus Executive Fund, L.P.
(collectively, the "Original Investors");

          (ii)     Gordon A. Cain; William A. McMinn; and James R. Crane 
(the "1998 Investors" and, together with the Original Investors, 
the "Holders"); and

          (iii)    certain additional individuals and entities affiliated with
certain of the Original Investors (the "Additional Reporting Persons").

          Each of the Holders, as party to an Amended and Restated Voting
Agreement dated December 15, 1998 by and among each of such Holders (the "Voting
Agreement"), has agreed to, among other things, certain voting provisions with
respect to the election of directors of the Issuer. The terms of the Voting
Agreement are described under Item 6 of this Amendment No. 4, and are 
incorporated herein by reference. As a result of the Voting Agreement, the
parties thereto may be deemed to be members of a "group" within the meaning of
Rule 13d-5(b)(1) under the Securities Exchange Act of 1934, as amended, and
accordingly may be deemed to have beneficial ownership of all of the shares of
Common Stock subject to the Voting Agreement. However, each of the Holders
expressly disclaims (i) membership in such group and (ii) beneficial ownership
of such 


                                       35
<PAGE>   37
shares of Common Stock, other than shares expressly identified herein as 
beneficially owned by such Holders.

          The Voting Agreement also includes certain additional parties (the
"Donees") that acquired shares of Common Stock through gifts by Messrs. Hevrdejs
and Oehmig and became parties to the Voting Agreement upon receipt of such
shares pursuant to the terms of the Voting Agreement. An amendment to the Voting
Agreement is currently being prepared (the "Proposed Amendment"), the effect of
which will be to remove the Donees as parties. The Proposed Amendment is
expected to be completed by January 31, 1999. The identities of the Donees are
as follows: Baylor School; P. Michael Gilbert; Ray W. Griffin III; Alexander
Jones; Margaret Jones, individually and as Custodian for Andrew Jones and
Michael Jones under the Texas Uniform Gifts to Minors Act ("UGMA"); Kinkaid
Investment Foundation; John K. O'Conner; Marian Oehmig Latimer; William C.
Oehmig as Custodian for Gordon D. Oehmig; Randolph D. Oehmig, individually and
as Custodian for the 1988 Oehmig Descendants Trust; Von D. Oehmig; William
Brittain Oehmig; William C. Patton and Matilda Patton; Vanderbilt University;
Stephen A. Adger; Dale E. Barnes; Bryan Clifford Campbell, individually and as
Custodian for Caroline Francis Campbell and Stephen Clifford Campbell under the
Texas UGMA; William J. Campbell, individually and as Custodian for Andrew Dyer
Campbell and William J. Campbell, Jr. under the Texas UGMA; Merrie H. Clarke,
individually and as Custodian for Julian Patrick Clarke and Sean McLean Clarke
under the Texas UGMA; Ross Eastman, as Custodian for Alexandra Eastman and Ross
Eastman, Jr. under the Texas UGMA; and Patricia Meyer Hevrdejs. The Donees
collectively hold an aggregate of 22,216 shares of Common Stock, or
approximately 0.3% of the shares subject to the Voting Agreement and
approximately 0.2% of the Total Shares Outstanding (as defined in Item 5).

          A.      The Original Investors

          Frank P. Diassi's business address is 6 Commerce Dr., Cranford, NJ
07016, and his present principal occupation or employment is Chairman of the
Board of the Issuer. In addition, Mr. Diassi serves as managing general partner
of The Unicorn Group, L.L.C., a private financial organization. Marianne
Diassi's business address is 6 Commerce Drive, Cranford, New Jersey 07016, and
her principal occupation or employment is as a private investor. The business
address of each of Hunter Nelson, William C. Oehmig and Frank J. Hevrdejs is
Eight Greenway Plaza, Suite 702, Houston, TX 77046. The present principal
occupation or employment of each of Messrs. Nelson, Oehmig and Hevrdejs is as a
principal of The Sterling Group, Inc. ("TSG"), a private investment organization
engaged in the acquisition and ownership of operating businesses. The business
address of The Rheney Living Trust, Clarke Rheney, Trustee or Susan O. Rheney,
Trustee, is 2305-C Nantucket, Houston, Texas 77057. The Rheney Living Trust was
organized under the laws of the State of Texas. Mr. Rheney's principal
occupation or employment is as a consultant with Rheney and Associates. Mrs.
Rheney's principal occupation or employment is as principal of TSG. Messrs.
Diassi, Nelson, Oehmig, Hevrdejs and Rheney and Ms. Diassi and Rheney are each
citizens of the United States.

          The Clipper Holders.

          Each of Clipper Equity Partners I, L.P. ("Clipper I"),
Clipper/Merchant Partners, L.P. ("Clipper II"), Clipper/Merban, L.P. ("Clipper
III") and Clipper/European Re, L.P. ("Clipper IV") is a Delaware limited
partnership, principally engaged in making investments. Clipper Capital
Associates, L.P. ("Clipper Associates"), a Delaware limited partnership
principally engaged in making investments, directly or indirectly through other
entities, is the sole general partner of Clipper I and Clipper II, with sole
voting and dispositive power with respect to the securities held by such
partnerships. The business address of each of such partnerships is 650 Madison
Avenue, 9th Floor, New York, New York 10022.

          Clipper Capital Associates, Inc. ("Clipper") is the sole general
partner of Clipper Associates. Clipper is a Delaware corporation principally
engaged in holding partnership interests, and serves as general partner of
Clipper Associates. The directors and executive officers of Clipper are Robert
B. Calhoun, Jr., who serves as President and Director, and Eugene P. Lynch, who
serves as Treasurer, Secretary and Director. Robert B. Calhoun, Jr. and Eugene
P. Lynch are United States citizens. The business address of Clipper, Robert B.
Calhoun, Jr. and Eugene P. Lynch is 650 Madison Avenue, 9th Floor, New York,
New York 10022.


                                       36
<PAGE>   38

          CS First Boston Merchant Investments 1995/96, L.P. ("CSFB
Investments") is a Delaware limited partnership principally engaged in making
investments. Merchant Capital, Inc. ("Merchant Capital"), a Delaware corporation
principally engaged in making investments, is the sole general partner of CSFB
Investments. Information with respect to the directors and executive officers of
Merchant Capital is listed on Appendix A hereto. The sole stockholder of
Merchant Capital is Merchant Holding, Inc., a Delaware corporation. The business
address of CSFB Investments and Merchant Capital is c/o Merchant Capital, Inc.,
Eleven Madison Avenue, New York, NY 10010.

          Pursuant to a certain management agreement (the "Management
Agreement"), Clipper Capital Partners, L.P. ("Clipper Management"), a Delaware
limited partnership principally engaged in managing investments, has sole voting
and dispositive power with respect to securities held by CSFB Investments. The
Management Agreement has been filed as an exhibit to this Statement on Schedule
13D and is incorporated herein by reference. Clipper Capital Corporation
("Clipper Capital"), a Delaware corporation principally engaged in holding
partnership interests, is the sole general partner of Clipper Management. The
directors and executive officers of Clipper Capital are Robert B. Calhoun, Jr.,
who serves as President and Director, and Eugene P. Lynch, who serves as
Treasurer, Secretary and Director. The business address of Clipper Management
and Clipper Capital is 650 Madison Avenue, 9th Floor, New York, NY 10022.

          Robert B. Calhoun, Jr. is the sole stockholder of Clipper, Clipper
Capital and Curacao. Mr. Calhoun is a citizen of the United States.

          FSI No. 2 Corporation ("FSI No. 2") is a corporation organized under
the laws of the State of Delaware principally engaged in making investments.
The officers and directors of FSI No. 2 are Fayez Sarofim, who serves as
President and Director, and Raye G. White, who serves as Executive Vice
President, Secretary, Treasurer and Director. FSI No. 2 is a 100% wholly owned
subsidiary of Fayez Sarofim & Co., a corporation organized under the laws of
the State of Texas and an investment adviser registered under the Investment
Advisers Act of 1940, as amended. Information with respect to the executive 
officers and directors of Fayez Sarofim & Co. is listed on Appendix B hereto.
Mr. Sarofim is Chairman of the Board of Directors, President and the beneficial
owner of a majority of the capital stock of Fayez Sarofim & Co. The business
address of FSI No. 2, Fayez Sarofim & Co., Mr. Sarofim and Ms. White is Two
Houston Center, Suite 2907, Houston, TX 77010. Both Mr. Sarofim and Ms. White
are citizens of the United States.

          Koch Capital Services, Inc. ("Koch Capital"), is a corporation
organized under the laws of the State of Delaware principally engaged in making
investments. Information with respect to the directors and officers of Koch
Capital is listed on Appendix C attached hereto. Koch Capital is a 100% wholly
owned subsidiary of Koch Industries, Inc. ("Koch Industries"), a corporation
organized under the laws of the State of Kansas, which is a diversified energy
company. Information with respect to the officers and directors of Koch
Industries is listed on Appendix D hereto. The business address for both Koch
Capital and Koch Industries is 4111 East 37th Street North, Wichita, KS 67220.

          Olympus Growth Fund II, L.P. ("Olympus Growth") and Olympus Executive
Fund, L.P. ("Olympus Executive") are Delaware limited partnerships principally
engaged in making investments. OGP II, L.P., a limited partnership organized
under the laws of the State of Delaware ("OGP"), is the sole general partner of
Olympus Growth. OEF, L.P., a limited partnership organized under the laws of the
State of Delaware ("OEF"), is the sole general partner of Olympus Executive. The
three general partners of both OGP and OEF are LJM, L.L.C. ("LJM"), RSM, L.L.C.
("RSM"), and Conroy, L.L.C. ("Conroy"). Each of LJM, RSM and Conroy is a limited
liability company organized under the laws of the State of Delaware. The
majority owner of LJM is Louis J. Mischianti. The majority owner of RSM is
Robert S. Morris. The majority owner of Conroy is James A. Conroy. The business
address of Olympus Growth, Olympus Executive, OGP, OEF, LJM, RSM, Conroy and
Messrs. Mischianti, Morris and Conroy is Metro Center, One Station Place,
Stamford, Connecticut 06902. Messrs. Mischianti, Morris and Conroy are presently
employed with Olympus Advisory Partners, Inc. where each is an investment
manager. Each of Messrs. Mischianti, Morris and Conroy is a citizen of the
United States.


                                       37

<PAGE>   39

          B.      The 1998 Investors

          The business address of Gordon A. Cain is Eight Greenway Plaza, Suite
702, Houston, TX 77046. The present principal occupation or employment of Mr.
Cain is as Chairman of the Board of Beta Consulting, Inc., a private company
engaged in investments. The business address of William A. McMinn is Eight
Greenway Plaza, Suite 702, Houston, TX 77046. The present principal occupation
or employment of Mr. McMinn is as Chairman of Texas Petrochemicals Corporation,
which is engaged in the manufacture of petrochemicals. The business address of
James R. Crane is 15350 Vickery Drive, Houston, Texas 77032. The present 
principal occupation or employment of Mr. Crane is President, Chief Executive
Officer and Chairman of Eagle U.S.A., Inc., which is engaged in the air freight
business. Each of the 1998 Investors is a citizen of the United States.

          During the last five years, none of the Holders nor any of the
Additional Reporting Persons, has been convicted in any criminal proceedings
(excluding traffic violations or similar misdemeanors).

          During the last five years, none of the Holders nor any of the
Additional Reporting Persons, has been a party to a civil proceeding of a
judicial or administrative body of competent jurisdiction and as a result of
such proceeding was or is subject to a judgment, decree or final order enjoining
future violations of, or prohibiting or mandating activities subject to, federal
or state securities laws or finding any violation with respect to such laws.

ITEM 3.   SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION

          Item 3 of the Schedule 13D is amended as follows:

          Each of the Original Investors acquired securities of the Issuer in
the Equity Private Placement, the January 1997 Private Placement and the July
1997 Private Placement, and certain of the Original Investors held Rollover
Shares prior to the Equity Private Placement. The source and amount of funds for
such acquisitions have been previously described in the Schedule 13D.

          On December 15, 1998, the 1998 Investors and Frank J. Hevrdejs, Frank
P. Diassi and Koch Capital (collectively, the "Purchasers") entered into
separate Standby Purchase Agreements (collectively, the "Purchase Agreements").
Pursuant to the terms of the Purchase Agreements, the Purchasers were issued the
1998 Warrants. In consideration for the issuance of the 1998 Warrants, the
Purchasers committed to purchase up to 2,500,000 shares of Common Stock, at a
price of $6.00 per share, if, as and when requested by the Issuer. In addition,
pursuant to the terms of the Purchase Agreements, the Issuer agreed to
issue to the Purchasers additional warrants to purchase up to 300,000 additional
shares of Common Stock, if, as and when they purchase shares of Common Stock
under the Purchase Agreements. Any additional warrants issued will have an
exercise price of $6.00 per share. Any shares of Common Stock purchased under
the Purchase Agreements or issued upon exercise of warrants will be subject to
the terms of the Voting Agreement, the Stockholders Agreement and the Tag-Along
Agreement (as such terms are defined in Item 6). The Purchase Agreements and the
warrant agreements for the 1998 Warrants are filed as exhibits to this Amendment
No. 4 and are incorporated herein by reference.

ITEM 4.   PURPOSE OF TRANSACTIONS

          Item 4 of the Schedule 13D is amended as follows:

          Although each of the Holders has acquired its securities for
investment purposes, by entering into the Voting Agreement, each of such Holders
has agreed to vote its shares in favor of a nominee to the Board of Directors of
Holdings selected by each of Koch Capital, the Clipper Holders and Gordon A.
Cain. All of the shares held by the Holders are currently subject to the Voting
Agreement, although it is expected that the Proposed Amendment will release a de
minimis number of shares held by certain Holders. None of the Holders has any
plans, nor has any of them made any proposals, which relate to or would result
in any of the subjects covered in paragraphs (a) through (j) of Item 4 to
the Schedule 13D, except that the parties to the Purchase Agreements may be
required by the Issuer to purchase additional shares of Common Stock, and may be
issued additional warrants in connection with such purchases, as described in
Item 3. Each of the Holders reserves the right, however, to acquire additional
shares, to dispose of shares


                                       38
<PAGE>   40

or to formulate other purposes, plans or proposals to the extent deemed
advisable in light of their respective investment policies, market conditions
and other factors.

ITEM 5.   INTEREST IN SECURITIES OF THE ISSUER

          Item 5 of the Schedule 13D is amended as follows:

          Each of the Holders, pursuant to the Voting Agreement, has agreed to,
among other things, certain voting provisions with respect to the election of
directors. As a result of the Voting Agreement, the parties thereto may be
deemed to be members of a "group" within the meaning of Rule 13d-5(b)(1) under
the Securities Exchange Act of 1934, as amended, and accordingly may be 
deemed to have beneficial ownership of all of the shares of Common Stock subject
to the Voting Agreement. There were 12,728,842 shares of Common Stock
outstanding as of December 7, 1998 (the "Total Shares Outstanding"), according
to the Issuer's Form 10-K for the fiscal year ended September 30, 1998. An
aggregate of 6,628,300 shares of Common Stock, representing approximately 52% of
the Total Shares Outstanding, are subject to the Voting Agreement (6,606,084
shares, also representing approximately 52% of the Total Shares Outstanding,
assuming removal of the Donees pursuant to the Proposed Amendment as discussed
in Item 2). In addition, the 1998 Warrants to purchase an aggregate of 300,000
shares of Common Stock were issued to the Purchasers pursuant to the Purchase
Agreements, and certain of the Original Investors hold (i) an aggregate of
137,071 additional warrants to purchase Common Stock and (ii) options to
purchase an aggregate of 37,397 shares of Common Stock. Each of such warrants
and options are currently exercisable, and are included in the following
calculations of percentages of Total Shares Outstanding as applicable pursuant
to Rule 13d-3(d)(1)(i). However, each of the Holders expressly disclaims (x)
membership in the Voting Agreement group and (y) beneficial ownership of the
shares of Common Stock subject to the Voting Agreement, other than shares
expressly identified herein as beneficially owned by such Holders. The Voting
Agreement has been filed as an exhibit to the Schedule 13D and is incorporated
herein by reference. In addition, the information contained in Item 6 of this
Schedule 13D is incorporated herein by reference.

          A.       The Original Investors

         (i)       Frank P. Diassi directly beneficially owns 643,657 shares 
of Common Stock, of which 20,000 shares are subject to issuance pursuant to the
1998 Warrants and 25,397 shares are subject to issuance pursuant to currently
exercisable options. In addition, Mr. Diassi may be deemed to indirectly
beneficially own (i) 664 shares of Common Stock held by the Issuer's employee
stock ownership plan and (ii) an aggregate of 80,000 shares held as Trustee of
the Diassi Trusts as follows: the Diassi Children's Trust, 40,000 shares; The
Gabrielle Diassi Trust, 20,000 shares; The Brianna Diassi Trust, 10,000 shares;
and The Nicholas Diassi Trust, 10,000 shares. Such shares in the aggregate
constitute approximately 5.7% of the Total Shares Outstanding. Marianne Diassi
directly beneficially owns 10,000 shares of Common Stock. Such shares in the
aggregate constitute less than 0.1% of the Total Shares Outstanding.

          (ii)     Hunter Nelson directly beneficially owns 64,758 shares of 
Common Stock, of which 4,000 shares are subject to issuance pursuant to
currently exercisable options. Such shares constitute approximately 0.5% of the
Total Shares Outstanding.

          (iii)    William C. Oehmig and Margaret W. Oehmig, as tenants in 
common, may each be deemed to directly beneficially own 361,772 shares of Common
Stock. Such shares constitute approximately 2.8% of the Total Shares 
Outstanding.

          (iv)     Frank J. Hevrdejs directly beneficially owns 948,782 shares
of Common Stock, of which 20,000 shares are subject to issuance pursuant to 
the 1998 Warrants and 4,000 shares are subject to issuance pursuant
to currently exercisable options. Such shares constitute approximately 7.4% 
of the Total Shares Outstanding.


                                       39

<PAGE>   41
          (v)      The Rheney Living Trust, and Susan O. Rheney and Clarke
Rheney as trustees of such trust, may each be deemed to directly beneficially
own 48,307 shares of Common Stock. Such shares constitute approximately 0.4% of
the Total Shares Outstanding.

          (vi)     Koch

                  (a)    Koch Capital directly beneficially owns 1,181,254
shares of Common Stock, of which 30,000 shares are subject to issuance pursuant
to the 1998 Warrants, 19,031 shares are subject to issuance pursuant to
previously issued warrants and 4,000 shares are subject to issuance pursuant to
currently exercisable options. Such shares constitute approximately 9.2% of the
Total Shares Outstanding.

                  (b)    Koch Industries, by virtue of its status as the owner 
of 100% of the outstanding capital stock of Koch Capital, may be deemed to be,
for the purposes of this Schedule 13D, the beneficial owner of all of the
1,181,254 shares of Common Stock directly beneficially owned by Koch Capital.

          (vii)   FSI No. 2

                  (a)    FSI No. 2 directly beneficially owns 687,548 shares of
Common Stock. Such shares constitute approximately 5.4% of the Total Shares
Outstanding.

                  (b)    Fayez Sarofim & Co., by virtue of its status as the
owner of 100% of the outstanding capital stock of FSI No. 2, may be deemed to
be, for the purposes of this Schedule 13D, the beneficial owner of the 687,548 
shares of Common Stock directly beneficially owned by FSI No. 2.

                  (c)    Fayez Sarofim, by virtue of his status as the owner of
a majority of the outstanding capital stock of Fayez Sarofim & Co. may be deemed
to be, for the purposes of this Schedule 13D, the beneficial owner of the
687,548 shares of Common Stock which may be deemed to be indirectly beneficially
owned by Fayez Sarofim & Co.

         (viii)   Olympus

                  (a)    Olympus Growth directly beneficially owns 678,770
shares of Common Stock, of which 58,387 shares are subject to issuance pursuant
to currently exercisable warrants. Such shares constitute approximately 5.3% of
the Total Shares Outstanding.

                  (b)    Olympus Executive directly beneficially owns 7,926
shares of Common Stock, of which 633 shares are subject to issuance pursuant to
currently exercisable warrants. Such shares constitute less than 0.1% of the
Total Shares Outstanding.

                  (c)    OGP, by virtue of its status as the sole general
partner of Olympus Growth, may be deemed to be, for purposes of this Schedule
13D, the beneficial owner of the 678,770 shares of Common Stock directly
beneficially owned by Olympus Growth.

                  (d)    OEF, by virtue of its status as the sole general
partner of Olympus Executive, may be deemed to be, for purposes of this Schedule
13D, the beneficial owner of the 7,926 shares of Common Stock directly
beneficially owned by Olympus Executive.

                  (e)    Each of LJM, RSM and Conroy, by virtue of their status
as general partners of OGP and OEF, may be deemed to be, for purposes of this
Schedule 13D, the beneficial owner of all 686,696 shares of Common Stock which
may be deemed to be indirectly beneficially owned by OGP and OEF. Such shares in
the aggregate constitute approximately 5.4% of the Total Shares Outstanding.


                                       40
<PAGE>   42

                  (f)    Each of Louis J. Mischianti, Robert S. Morris and James
A. Conroy, by virtue of their status as the majority owner of LJM, RSM and
Conroy, respectively, may be deemed to be, for purposes of this Schedule 13D,
the beneficial owner of all 686,696 shares of Common Stock which may be deemed
to be indirectly beneficially owned by LJM, RSM and Conroy, respectively.

          (ix)    The Clipper Holders

                  As more fully described below, an aggregate of 2,139,104
shares of Common Stock may be deemed to be directly or indirectly beneficially
owned by the Clipper Holders and their affiliates, which represents
approximately 16.7% of the Total Shares Outstanding.

                  (a)    Clipper I directly beneficially owns 444,537 shares of
Common Stock; Clipper II directly beneficially owns 516,031 shares of Common
Stock; Clipper III directly beneficially owns 592,701 shares of Common Stock;
Clipper IV directly beneficially owns 296,328 shares of Common Stock; CSFB
Investments directly beneficially owns 75,900 shares of Common Stock; and
Clipper Associates directly beneficially owns 3,501 shares of Common Stock. Such
amounts of shares of Common Stock include 13,605 shares which are subject to
issuance pursuant to currently exercisable warrants held by Clipper I; 18,149
shares which are subject to issuance pursuant to currently exercisable warrants
held by Clipper II; 18,149 shares which are subject to issuance pursuant to
currently exercisable warrants held by Clipper III; 9,089 shares which are
subject to issuance pursuant to currently exercisable warrants held by Clipper
IV and 28 shares which are subject to issuance pursuant to currently exercisable
warrants held by Clipper Associates.

                  (b)    By virtue of its status as the sole general partner of
Clipper I and Clipper II, and its status as sole investment general partner of
Clipper III and Clipper IV, having sole voting and dispositive power with
respect to the shares of Common Stock held by each of such partnerships, Clipper
Associates may be deemed to be, for purposes of this Schedule 13D, the indirect
beneficial owner of all of the 1,849,597 shares of Common Stock directly
beneficially owned, in the aggregate, by Clipper I, Clipper II, Clipper III and
Clipper IV.

                  (c)    Clipper Associates, pursuant to certain nominee 
agreements (collectively, the "Nominee Agreements") holds 210,106 shares of
Common Stock as nominee for individuals who have the right to receive, or the
power to direct the receipt of, dividends from, or the proceeds from the sale
of, such securities. The form of Nominee Agreement has been filed as an exhibit
to the Schedule 13D and is incorporated herein by reference. Pursuant to the
Nominee Agreements, Clipper Associates exercises sole voting and dispositive
power with respect to such shares of Common Stock.

                  (d)    By virtue of its status as the sole general partner of
Clipper Associates, Clipper may be deemed to be, for purposes of this Schedule
13D, the beneficial owner of all of the 2,063,204 shares of Common Stock deemed
to be directly and indirectly beneficially owned by Clipper Associates.

                  (e)    By virtue of its exercising sole voting and dispositive
power with respect to the shares of Common Stock directly beneficially owned by
CSFB Investments, Clipper Management may be deemed to be, for purposes of this
Schedule 13D, the beneficial owner of all of the 75,900 shares of Common Stock
directly beneficially owned by CSFB Investments.

                  (f)    By virtue of its status as the sole general partner of
Clipper Management, Clipper Capital may be deemed to be, for purposes of this
Schedule 13D, the beneficial owner of all of the 75,900 shares of Common Stock
deemed to be indirectly beneficially owned by Clipper Management.

                  (g)    By virtue of his ownership of all of the outstanding
capital stock of Clipper and his status as President and Director, Robert B.
Calhoun, Jr. may be deemed to be, for purposes of this Schedule 13D, the
beneficial owner of all of the 2,063,204 shares of Common Stock deemed to be
indirectly beneficially owned by Clipper. In addition, by virtue of his
ownership of all of the outstanding capital stock of Clipper Capital and his
status as President


                                       41
 
<PAGE>   43
and Director, Mr. Calhoun may be deemed to be, for purposes of this Schedule
13D, the beneficial owner of all of the 75,900 shares of Common Stock indirectly
beneficially owned by Clipper Capital. Mr. Calhoun also directly beneficially
owns 2,000 shares of Common Stock which are subject to issuance pursuant to
currently exercisable options, but such shares are not subject to the Voting
Agreement.

          B.      The 1998 Investors


          (i)     Gordon A. Cain directly beneficially owns 160,000 shares of
Common Stock, all of which are subject to issuance pursuant to the 1998
Warrants. Such shares constitute approximately 1.2% of the Total Shares
Outstanding.

          (ii)    William A. McMinn directly beneficially owns 40,000 shares of
Common Stock, all of which are subject to issuance pursuant to the 1998
Warrants. Such shares constitute approximately 0.3% of the Total Shares
Outstanding.

          (iii)   James R. Crane directly beneficially owns 30,000 shares of
Common Stock, all of which are subject to issuance pursuant to the 1998
Warrants. Such shares constitute approximately 0.2% of the Total Shares
Outstanding.

ITEM 6.   CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS WITH RESPECT
          TO SECURITIES OF THE ISSUER

          Item 6 of the Schedule 13D is amended as follows:

          Each of the Holders is party the Voting Agreement, pursuant to which
such Holders have agreed to, among other things, vote their respective shares of
Common Stock in favor of a nominee to the Board of Directors of Holdings
selected by each of Koch Capital, the Clipper Holders and Gordon A. Cain. The
rights of Koch Capital and The Clipper Group to select its respective nominees
under the Voting Agreement each terminates on August 21, 2006, or sooner in the
event its beneficial ownership of Common Stock represents less than 5% of the
outstanding shares of Common Stock. The right of Mr. Cain to designate a nominee
to the Board of Directors of the Company will become exercisable on February 1,
1999, or sooner if he purchases shares of Common Stock under the Purchase
Agreement to which Mr. Cain is a party. The right of Mr. Cain to select his
nominee terminates upon the earlier of (i) December 15, 2008 and (ii) the later
of (a) the expiration of the Purchase Agreement to which he is a party and (b)
the time at which Mr. Cain has beneficial ownership of less than 5% of the
outstanding shares of Common Stock.

          Each of the Holders and certain additional stockholders of the Issuer
are parties to a Stockholders Agreement, dated as of August 21, 1996 (as
amended, the "Stockholders Agreement"), which, among other things, restricts the
transfer of shares of Common Stock held by such stockholders (with certain
exceptions) unless such shares are first offered to be sold to the Issuer's
employee stock ownership plan, then to the Issuer and finally to the other
parties to the Stockholders Agreement.

          Each of the Holders and certain additional stockholders of the Issuer
have entered into a Tag-Along Agreement, dated August 21, 1996 (the "Tag-Along
Agreement"), which, among other things, provides that if any of the parties
thereto proposes to transfer, sell or otherwise dispose of an aggregate of 51%
or more of the shares of Common Stock issued and outstanding at the time of such
proposed transfer, such party must give notice of such proposed transfer to each
person that retained Rollover Shares in the Merger and each such person will
have the right to have such shares included in such transfer on a pro rata basis
and on the same terms and conditions.

          Each of the Clipper Holders, Koch Capital, Olympus Growth, Olympus
Executive, Mr. Hevrdejs, Mr. Diassi and the 1998 Investors are parties to a
Registration Rights Agreement, dated August 21, 1996 (the "Registration Rights
Agreement"), pursuant to which, among other things, for a period of ten (10)
years from such date each of the parties thereto is entitled, subject to certain
limitations, to include their shares of Common Stock in certain registrations
initiated 


                                       42
<PAGE>   44

by the Issuer under the Securities Act of 1933, as amended. The Registration
Rights Agreement also provides that the parties thereto may require the Issuer
to effect additional "demand" registrations of all or any part of such parties'
stock holdings, and in addition, contains other customary provisions.

          Clipper Associates and certain individuals are party to Nominee
Agreements which grant Clipper Associates sole voting and dispositive power with
respect to the shares of Common Stock held by Clipper Associates, as nominee for
such individuals, pursuant to such agreements.

          Clipper Management, Merchant Capital and CSFB Investments are party to
the Management Agreement which grants Clipper Management sole voting and
dispositive power with respect to the shares of Common Stock directly
beneficially owned by CSFB Investments.

          The responses to Item 2, Item 3, Item 4 and Item 5 are incorporated
into this Item 6 by reference. The Voting Agreement, the Stockholders'
Agreement, the Tag-Along Agreement, the Registration Rights Agreement, the
Nominee Agreement, the Management Agreement, the Warrant Agreements governing
the 1998 Warrants and the other warrants held by Holders, and the Purchase
Agreements are filed or incorporated by reference as exhibits to this Amendment
No. 4, and are incorporated into this Item 6 by reference.

ITEM 7.  MATERIAL FILED AS EXHIBITS

         A.       Amended and Restated Voting Agreement, dated as of December
15, 1998, by and among Sterling Chemicals Holdings Inc. and the other parties
listed therein, filed with the Commission as Exhibit 4.11(a) to the Issuer's
Annual Report on Form 10-K for the fiscal year ended September 30, 1998 and
incorporated herein by reference.

         B.1.     Sterling Chemicals Holdings, Inc. Stockholders' Agreement, 
dated effective as of August 21, 1996, filed with the Commission as Exhibit 4.10
to Issuer's Registration Statement on Form S-1 (File No. 333-04343), and
incorporated herein by reference.

         B.2.     First Amendment to Sterling Chemicals Holdings, Inc. 
Stockholders' Agreement, dated effective as of December 31, 1997, filed with the
Commission as Exhibit 4.7 to the Issuer's Quarterly Report on Form 10-Q for the
quarterly period ended March 31, 1998 and incorporated herein by reference.

         B.2.     Second Amendment to Sterling Chemicals Holdings, Inc.
Stockholders' Agreement, dated effective as of May 1, 1998, filed with the
Commission as Exhibit 4.9(b) to the Issuer's Annual Report on Form 10-K for the
fiscal year ended September 30, 1998 and incorporated herein by reference.

         C.       Registration Rights Agreement, dated as of August 21, 1996, by
and among the parties listed therein, filed with the Commission as Exhibit 4.11
to Issuer's Registration Statement on Form S-1 (File No. 333-04343), and
incorporated herein by reference.

         D.       Tag-Along Agreement, dated as of August 21, 1996, by and among
the parties listed therein, filed with the Commission as Exhibit 4.13 to
Issuer's Registration Statement on Form S-1 (File No. 333-04343), and
incorporated herein by reference.

         E.       Form of Nominee Agreement, by and among Clipper Associates and
certain individuals, filed with the Commission as Exhibit 7(E) to the Original
Schedule 13D, and incorporated herein by reference.

         F.       Management Agreement, dated as of December 29, 1995, by and
among Clipper Capital Partners, L.P., Merchant Capital , Inc., and CS First
Boston Merchant Investments 1995/96, L.P., filed with the Commission as Exhibit
7(F) to the Original Schedule 13D, and incorporated herein by reference.


                                       43
<PAGE>   45

         G.       Standby Purchase Agreement, dated as of December 15, 1998,
between Sterling Chemicals Holdings, Inc. and Frank P. Diassi, filed with the
Commission as Exhibit 10.29 to the Issuer's Annual Report on Form 10-K for the
fiscal year ended September 30, 1998 and incorporated herein by reference.

         H.       Standby Purchase Agreement, dated as of December 15, 1998,
between Sterling Chemicals Holdings, Inc. and Frank J. Hevrdejs, filed with the
Commission as Exhibit 10.30 to the Issuer's Annual Report on Form 10-K for the
fiscal year ended September 30, 1998 and incorporated herein by reference.

         I.       Standby Purchase Agreement, dated as of December 15, 1998, 
between Sterling Chemicals Holdings, Inc. and Koch Capital Services, Inc., filed
with the Commission as Exhibit 10.31 to the Issuer's Annual Report on Form 10-K
for the fiscal year ended September 30, 1998 and incorporated herein by
reference.

        *J.       Standby Purchase Agreement, dated as of December 15, 1998, 
between Sterling Chemicals Holdings, Inc. and Gordon A. Cain.

        *K.       Standby Purchase Agreement, dated as of December 15, 1998, 
between Sterling Chemicals Holdings, Inc. and William A. McMinn.

        *L.       Standby Purchase Agreement, dated as of December 15, 1998, 
between Sterling Chemicals Holdings, Inc. and James R. Crane.

         M.       Warrant Agreement, dated as of July 10, 1997, between Sterling
Chemicals Holdings, Inc. and Harris Trust and Savings Bank, as Warrant Agent,
filed with the Commission as Exhibit 4.1 to the Issuer's Quarterly Report on
Form 10-Q for the quarterly period ended June 30, 1997 and incorporated herein
by reference.

         N.       Warrant Agreement, dated as of December 15, 1998 between 
Sterling Chemicals Holdings, Inc. and Harris Trust and Savings Bank, as Warrant
Agent, filed with the Commission as Exhibit 4.3 to the Issuer's Annual Report on
Form 10-K for the fiscal year ended September 30, 1998 and incorporated herein
by reference.

- ------------------
* Filed herewith.


                                       44

<PAGE>   46


                                    SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


December 22, 1998                FRANK P. DIASSI, individually and as trustee of
                                 The Diassi Childrens Trust U/A 12/21/89, The 
                                 Gabrielle Diassi Trust U/A 9/24/90, The Brianna
                                 Diassi Trust DTD 6/15/98 and the Nicholas 
                                 Diassi Trust DTD 6/15/98


                                 /s/ FRANK P. DIASSI
                                 -----------------------------------------------
                                     Frank P. Diassi



<PAGE>   47


                                    SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


December 22, 1998



                                                          /s/ MARIANNE R. DIASSI
                                                          ----------------------
                                                              Marianne R. Diassi



<PAGE>   48


                                    SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


December 22, 1998

                                                           /s/ HUNTER NELSON
                                                           ---------------------
                                                               Hunter Nelson



<PAGE>   49



                                    SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


December 22, 1998



                                               WILLIAM C. OEHMIG AND MARGARET W.
                                               OEHMIG, TENANTS-IN-COMMON



                                               /s/ WILLIAM C. OEHMIG
                                               ---------------------------------
                                                   William C. Oehmig


                                               /s/ MARGARET W. OEHMIG
                                               ---------------------------------
                                                   Margaret W. Oehmig


<PAGE>   50




                                    SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


December 22, 1998


                                                         /s/ FRANK J. HEVRDEJS
                                                         ----------------------
                                                             Frank J. Hevrdejs



<PAGE>   51


                                    SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


December 22, 1998

                                               THE RHENEY LIVING TRUST
                                               By:   Susan O. Rheney, as Trustee


                                               /s/ SUSAN O. RHENEY
                                               ---------------------------------
                                                   Susan O. Rheney



<PAGE>   52


                                    SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


December 22, 1998

<TABLE>
<S>                                            <C>
CLIPPER CAPITAL ASSOCIATES, INC.               CLIPPER CAPITAL CORPORATION

CLIPPER CAPITAL ASSOCIATES, L.P.               CLIPPER CAPITAL PARTNERS, L.P.
    By: Clipper Capital Associates, Inc.           By: Clipper Capital Corporation
    its General Partner                            its General Partner

CLIPPER EQUITY PARTNERS I, L.P.                    CS FIRST BOSTON MERCHANT
    By: Clipper Capital Associates, L.P.               INVESTMENTS 1995/96, L.P.
    its General Partner                                   By: Clipper Capital Partners, L.P.
                                                          Attorney-in-Fact
    By: Clipper Capital Associates, Inc.                  By: Clipper Capital Corporation
    its General Partner                                   its General Partner

CLIPPER/MERCHANT PARTNERS, L.P.                    By:    /s/ EUGENE P. LYNCH
    By: Clipper Capital Associates, L.P.                  -----------------------------------
    its General Partner                            Name:  Eugene P. Lynch                 
                                                   Title: Secretary and Treasurer for all 
    By: Clipper Capital Associates, Inc.           
    its General Partner

CLIPPER/MERBAN, L.P.
    By: Clipper Capital Associates, L.P.
    its General Partner

    By: Clipper Capital Associates, Inc.
    its General Partner

CLIPPER/EUROPEAN RE, L.P.
    By: Clipper Capital Associates, L.P.
    its General Partner

    By: Clipper Capital Associates, Inc.
    its General Partner
</TABLE>


<PAGE>   53


                                    SIGNATURE

    After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


December 22, 1998


                                                     /s/ ROBERT B. CALHOUN, JR.
                                                     ---------------------------
                                                     Robert B. Calhoun, Jr.



<PAGE>   54


                                    SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


December 22, 1998


                                                     KOCH CAPITAL SERVICES, INC.


                                                     By:    /s/ C.J. NELSON
                                                            --------------------
                                                     Name:  C.J. Nelson   
                                                     Title: Vice President



<PAGE>   55


                                    SIGNATURE

    After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


December 22, 1998


                                                     KOCH INDUSTRIES, INC.

                                                     By:    /s/ C.J. NELSON
                                                            --------------------
                                                     Name:  C.J. Nelson
                                                     Title: Vice President





<PAGE>   56



                                    SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


December 22, 1998



                                          OLYMPUS GROWTH FUND II, L.P.


                                          By:  OGP II, L.P., its General Partner
                                          By:  LJM, L.L.C.
                                               its General Partner


                                          By:    /s/ LOUIS J. MISCHIANTI
                                                 -------------------------------
                                          Name:  Louis J. Mischianti
                                          Title: Member

<PAGE>   57



                                    SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


December 22, 1998



                                          OLYMPUS EXECUTIVE FUND, L.P.



                                          By:  OEF, L.P., its General Partner
                                          By:  LJM, L.L.C.
                                               its General Partner


                                          By:    /s/ LOUIS J. MISCHIANTI
                                                 -------------------------------
                                          Name:  Louis J. Mischianti
                                          Title: Member



<PAGE>   58



                                    SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


December 22, 1998



                                                      OGP II, L.P.

                                                      By:    Conroy, L.L.C.
                                                             its General Partner

                                                      By:    /s/ JAMES A. CONROY
                                                             -------------------
                                                      Name:  James A. Conroy
                                                      Title: Member



<PAGE>   59



                                    SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


December 22, 1998


                                                      OEF, L.P.

                                                      By:    Conroy, L.L.C.
                                                             its General Partner

                                                      By:    /s/ JAMES A. CONROY
                                                             -------------------
                                                      Name:  James A. Conroy
                                                      Title: Member


<PAGE>   60

                                    SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


December 22, 1998



                                                LJM, L.L.C.


                                                By:      /s/ LOUIS J. MISCHIANTI
                                                         -----------------------
                                                Name:    Louis J. Mischianti
                                                Title:   Member



<PAGE>   61


                                    SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


December 22, 1998


                                                   RSM, L.L.C.


                                                   By:    /s/ ROBERT S. MORRIS
                                                          ----------------------
                                                   Name:  Robert S. Morris
                                                   Title: Member




<PAGE>   62


                                    SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


December 22, 1998



                                                     CONROY, L.L.C.


                                                     By:    /s/ JAMES A. CONROY
                                                            -------------------
                                                     Name:  James A. Conroy
                                                     Title: Member


<PAGE>   63




                                    SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


December 22, 1998

                                                By:      /s/ LOUIS J. MISCHIANTI
                                                         -----------------------
                                                         Louis J. Mischianti


<PAGE>   64


                                    SIGNATURE


     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


December 22, 1998




                                                     /s/ ROBERT S. MORRIS
                                                     ---------------------------
                                                     Robert S. Morris



<PAGE>   65



                                    SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


December 22, 1998


                                                             /s/ JAMES A. CONROY
                                                             -------------------
                                                             James A. Conroy

<PAGE>   66



                                    SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


December 22, 1998


                                               FSI No. 2 Corporation


                                               By:    /s/ RAYE G. WHITE
                                                      --------------------------
                                               Name:  Raye G. White
                                               Title: Executive Vice President


<PAGE>   67


                                    SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


December 22, 1998

 
                                                 FAYEZ SAROFIM & CO.

                                                 By:    /s/ RAYE G. WHITE
                                                        ------------------------
                                                 Name:  Raye G. White
                                                 Title: Executive Vice President


<PAGE>   68

                                    SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


December 22, 1998


                                                       /s/ FAYEZ SAROFIM
                                                       -------------------------
                                                       Fayez Sarofim

<PAGE>   69


                                    SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


December 22, 1998


                                                        /s/ GORDON A. CAIN
                                                        ------------------------
                                                        Gordon A. Cain



<PAGE>   70


                                    SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


December 22, 1998


                                                   /s/ WILLIAM A. McMINN
                                                   ----------------------------
                                                   William A. McMinn


<PAGE>   71



                                    SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


December 22, 1998


                                                   /s/ JAMES CRANE
                                                   ----------------------------
                                                   James Crane


<PAGE>   72


                                   APPENDIX A

Directors and Executive Officers of Merchant Capital, Inc.


<TABLE>
<S>                      <C>
John M. Hennessy         Chairman of the Board of Directors
David A. DeNunzio        President, Chief Executive Officer and Director
Allen D. Wheat           Director
John Carroll             Vice President
Steven Costabile         Vice President
Thomas A. DeGennaro      Vice President, Director of Taxes
Nancy G. Farese          Vice President
Aronas E. Gudaitis       Vice President
Linda H. Hanauer         Chief Financial and Administrative Officer
Stephen A.M. Hester      Vice President
Joseph Huber             Vice President
Andrew M. Hutcher        Vice President
Melissa Lautenberg       Vice President
Kenneth J. Lohson        Vice President
Diane Manno              Vice President, Treasurer
Rhonda G. Matty          Assistant Secretary
William D. Milligan      Vice President, Assistant Controller
David C. O'Leary         Vice President
Carlos Onis              Vice President and Controller
Mark Patterson           Vice President
Henry Robin              Vice President
Lori M. Russo            Secretary
Charles Ward, III        Vice President
</TABLE>

    Each of the foregoing persons is a United States citizen. The principal 
business address of each of such persons is Credit Suisse First Boston 
Corporation, Eleven Madison Avenue, New York, New York 10010, and the present 
principal occupation or employment of each such person is serving as an 
employee of Credit Suisse First Boston Corporation.


<PAGE>   73


                                   APPENDIX B


Directors and Executive Officers of Fayez Sarofim & Co.

<TABLE>
<S>                         <C>
Fayez Sarofim               President and Director
Raye G. White               Executive VP, Secretary, Treasurer and Director
William Kline McGee, Jr.    Senior Vice President
Ralph Bowman Thomas         Senior Vice President
Russell Morris Frankel      Senior Vice President
Charles Edmund Sheedy       Senior Vice President
Russell Brian Hawkins       Senior Vice President
Alice M. Youngblood         Vice President
Nancy Vickers Daniel        Vice President
James Aloysius Reynolds     Vice President
</TABLE>

    Each of the foregoing persons is a citizen of the United States. The
principal business address of each of such persons is Two Houston Center, Suite
2907, Houston, Texas 77010, and the present principal occupation or employment
of each such person is as listed above.



<PAGE>   74


                                   APPENDIX C


Directors and Executive Officers of Koch Capital Services, Inc. and their
respective positions with Koch Industries, Inc.

<TABLE>
<CAPTION>
                        Position with Koch Capital        Position with Koch Industries
                        --------------------------        -----------------------------
<S>                     <C>                                 <C>
Paul W. Brooks          President and Director              Senior VP - Capital Services
                                                            Group

John C. Pittenger       Vice President and Director         Vice President - Capital
                                                            Services Group

John H. Bomgardner      Vice President and Assistant        Associate General Counsel
                        Secretary

H. Allan Caldwell       Secretary                           Associate General Counsel

Diana Kidd              Treasurer                           Treasurer, Koch Capital
                                                            Services, Inc.

LaVonne E. Harris       Controller                          Controller, Koch Capital
                                                            Services, Inc.

William W. Hanna        Director                            President and COO

C. J. Nelson            Director                            Vice President - International
</TABLE>

    Each of the foregoing persons is a citizen of the United States. The
principal business address of each of such persons is 4111 E. 37th Street North,
Wichita, Kansas 67220. The present principal occupation or employment of each
such person is the position each holds with Koch Industries, Inc. listed in the
far right-hand column above.

<PAGE>   75


                                   APPENDIX D


Directors and Executive Officers of Koch Industries, Inc.


<TABLE>
<S>                     <C>
Charles G. Koch         Chairman of the Board of Directors and CEO

William W. Hanna        President, COO and Director

F. Lynn Markel          Executive VP - Finance and Administration, Treasurer and
                        Director

B. R. Caffey            Executive VP - Operations and Director

Donald L. Cordes        Executive VP, Special Counsel and Director

R. H. Fink              Executive VP and Director

David H. Koch           Executive VP - Chemical Technology and Director

Joseph W. Moeller       Executive VP - International and Director

E. Pierce Marshall      Director

S. V. Varner            Director
</TABLE>

    Each of the foregoing persons is a citizen of the United States. The
principal business address of each of such persons, except for Mr. Marshall, is
4111 East 37th Street North, Wichita, Kansas 67220, and the present principal
occupation or employment of each such person, except for Mr. Marshall, is as
listed above. Mr. Marshall's principal occupation or employment is as the
president emeritus of Marshall Petroleum, Inc.; his principal business address
is 7600 West Tidwell, Suite 800, Houston, Texas 77040.

<PAGE>   76


                                 EXHIBIT INDEX

<TABLE>
<CAPTION>
EXHIBIT
 NUMBER                               DESCRIPTION
- --------                              -----------
<S>       <C>
  A.      Amended and Restated Voting Agreement, dated as of December 15,
          1998, by and among Sterling Chemicals Holdings Inc. and the other
          parties listed therein, filed with the Commission as Exhibit 4.11(a)
          to the Issuer's Annual Report on Form 10-K for the fiscal year ended
          September 30, 1998 and incorporated herein by reference.

  B.1.    Sterling Chemicals Holdings, Inc. Stockholders' Agreement, dated
          effective as of August 21, 1996, filed with the Commission as Exhibit
          4.10 to Issuer's Registration Statement on Form S-1 (File No.
          333-04343), and incorporated herein by reference.

  B.2.    First Amendment to Sterling Chemicals Holdings, Inc. Stockholders'
          Agreement, dated effective as of December 31, 1997, filed with the
          Commission as Exhibit 4.7 to the Issuer's Quarterly Report on Form
          10-Q for the quarterly period ended March 31, 1998 and incorporated
          herein by reference.

  B.2.    Second Amendment to Sterling Chemicals Holdings, Inc. Stockholders'
          Agreement, dated effective as of May 1, 1998, filed with the
          Commission as Exhibit 4.9(b) to the Issuer's Quarterly Report on Form
          10-K for the fiscal year ended September 30, 1998 and incorporated
          herein by reference.

  C.      Registration Rights Agreement, dated as of August 21, 1996, by and
          among the parties listed therein, filed with the Commission as Exhibit
          4.11 to Issuer's Registration Statement on Form S-1 (File No.
          333-04343), and incorporated herein by reference.

  D.      Tag-Along Agreement, dated as of August 21, 1996, by and among the
          parties listed therein, filed with the Commission as Exhibit 4.13 to
          issuer's Registration Statement of Form S-1 (File No. 333-04343), and
          incorporated herein by reference.

  E.      Form of Nominee Agreement, by and among Clipper Associates and certain
          individuals, filed with the Commission as Exhibit 7(E) to the Original
          Schedule 13D, and incorporated herein by reference.

  F.      Management Agreement, dated as of December 29, 1995, by and among
          Clipper Capital Partners, L.P., Merchant Capital, Inc. and CS First
          Boston Merchant Investments 1995/96, L.P., filed with the Commission
          as Exhibit 7(F) to the Original Schedule 13D, and incorporated herein
          by reference.
</TABLE>

<PAGE>   77


<TABLE>
<CAPTION>
EXHIBIT
 NUMBER                               DESCRIPTION
- --------                              -----------
<S>       <C>

  G.      Standby Purchase Agreement, dated as of December 15, 1998, between
          Sterling Chemicals Holdings, Inc. and Frank P. Diassi, filed with the
          Commission as Exhibit 10.29 to the Issuer's Annual Report on Form 10-K
          for the fiscal year ended September 30, 1998 and incorporated herein
          by reference.

  H.      Standby Purchase Agreement, dated as of December 15, 1998, between
          Sterling Chemicals Holdings, Inc. and Frank J. Hevrdejs, filed with the
          Commission as Exhibit 10.30 to the Issuer's Annual Report on Form 10-K
          for the fiscal year ended September 30, 1998 and incorporated herein
          by reference. 

  I.      Standby Purchase Agreement, dated as of December 15, 1998, between
          Sterling Chemicals Holdings, Inc. and Koch Capital Services, Inc.,
          filed with the Commission as Exhibit 10.31 to the Issuer's Annual
          Report on Form 10-K for the fiscal year ended September 30, 1998 and
          incorporated herein by reference.

 *J.      Standby Purchase Agreement, dated as of December 15, 1998, between
          Sterling Chemicals Holdings, Inc. and Gordon A. Cain.

 *K.      Standby Purchase Agreement, dated as of December 15, 1998, between
          Sterling Chemicals Holdings, Inc. and William A. McMinn.

 *L.      Standby Purchase Agreement, dated as of December 15, 1998, between
          Sterling Chemicals Holdings, Inc. and James R. Crane.

  M.      Warrant Agreement, dated as of July 10, 1997, between Sterling 
          Chemicals Holdings, Inc. and Harris Trust and Savings Bank, as Warrant
          Agent, filed with the Commission as Exhibit 4.1 to the Issuer's
          Quarterly Report on Form 10-Q for the quarterly period ended June 30,
          1997 and incorporated herein by reference.

  N.      Warrant Agreement, dated as of December 15, 1998 between Sterling
          Chemicals Holdings, Inc. and Harris Trust and Savings Bank, as Warrant
          Agent, filed with the Commission as Exhibit 4.3 to the Issuer's
          Annual Report on Form 10-K for the fiscal year ended September 30,
          1998 and incorporated herein by reference.

- ----------------
* Filed herewith
</TABLE>

<PAGE>   1
                                                                       EXHIBIT J

================================================================================

================================================================================


                           STANDBY PURCHASE AGREEMENT

                                 BY AND BETWEEN

                        STERLING CHEMICALS HOLDINGS, INC.

                                       AND

                                 GORDON A. CAIN














================================================================================
                          DATED AS OF DECEMBER 15, 1998
================================================================================



<PAGE>   2











IN MAKING AN INVESTMENT DECISION INVESTORS MUST RELY ON THEIR OWN EXAMINATION OF
THE ISSUER AND THE TERMS OF THE OFFERING, INCLUDING THE MERITS AND RISKS
INVOLVED. THE SECURITIES PURCHASED HEREUNDER HAVE NOT BEEN RECOMMENDED OR
APPROVED BY ANY FEDERAL OR STATE SECURITIES COMMISSION OR REGULATORY AUTHORITY.
FURTHERMORE, THE FOREGOING AUTHORITIES HAVE NOT CONFIRMED THE ACCURACY OR
DETERMINED THE ADEQUACY OF THIS DOCUMENT. ANY REPRESENTATION TO THE CONTRARY IS
A CRIMINAL OFFENSE.

THE SECURITIES PURCHASED HEREUNDER ARE SUBJECT TO RESTRICTIONS ON
TRANSFERABILITY AND RESALE AND MAY NOT BE TRANSFERRED OR RESOLD EXCEPT AS
PERMITTED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND THE APPLICABLE STATE
SECURITIES LAWS, PURSUANT TO REGISTRATION OR EXEMPTION THEREFROM. INVESTORS
SHOULD BE AWARE THAT THEY MAY BE REQUIRED TO BEAR THE FINANCIAL RISKS OF THIS
INVESTMENT FOR AN INDEFINITE PERIOD OF TIME.



<PAGE>   3


                              TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                                                            Page
                                                                                                            ----

<S>               <C>                                                                                        <C>
Section 1         Definitions and Interpretation............................................................   2
Section 2         Standby Commitment........................................................................   6
Section 3         Closings..................................................................................   6
Section 4         Simultaneous Closings Under Other Purchase Agreements.....................................   7
Section 5         Use of Proceeds...........................................................................   8
Section 6         Representations and Warranties of the Company.............................................   8
Section 7         Representations and Warranties of the Purchaser...........................................   9
Section 8         Compliance with Securities Laws and Agreements............................................  10
Section 9         Changes in Capital Structure..............................................................  12
Section 10        Specific Performance......................................................................  12
Section 11        Notices...................................................................................  12
Section 12        Survival..................................................................................  13
Section 13        Benefit and Burden........................................................................  13
Section 14        No Third Party Rights.....................................................................  13
Section 15        Amendments and Waiver.....................................................................  13
Section 16        Severability..............................................................................  13
Section 17        Expenses..................................................................................  13
Section 18        Governing Law.............................................................................  13
Section 19        Entire Agreement..........................................................................  14

Schedule I        Purchasers
</TABLE>

<PAGE>   4

                                                                            CAIN

                           STANDBY PURCHASE AGREEMENT

              THIS STANDBY PURCHASE AGREEMENT (this "Agreement") is made and
entered into as of December 15, 1998 by and between STERLING CHEMICALS HOLDINGS,
INC., a Delaware corporation (the "Company"), and GORDON CAIN (the "Purchaser").

                             PRELIMINARY STATEMENTS

         A.       The Company and the Purchaser are entering into this Agreement
                  to evidence the Purchaser's agreement to purchase up to
                  1,333,333 shares of common stock, par value $0.01 per share,
                  of the Company ("Common Stock").

         B.       Simultaneously with the execution and delivery of this
                  Agreement, the Company and Harris Trust and Savings Bank, as
                  agent, entered into a Warrant Agreement dated as of the date
                  hereof (the "Warrant Agreement"). In order to induce the
                  Purchaser to enter into this Agreement, the Company has issued
                  to the Purchaser on the date hereof warrants to purchase
                  160,000 shares of Common Stock (the "Initial Warrants"). The
                  Initial Warrants are evidenced by a certificate in the form
                  attached as Exhibit A to the Warrant Agreement and are subject
                  to the terms and conditions set forth in the Warrant Agreement
                  and such certificate.

         C.       In connection with the issuance of the Initial Warrants, the
                  Company and the Purchaser entered into an Adoption Agreement
                  dated as of the date hereof (the "Adoption Agreement") whereby
                  the Purchaser became a party to the Stockholders Agreement,
                  the Registration Rights Agreement and the Tag-Along Agreement
                  (as such terms are defined below).

         D.       In connection with the issuance of the Initial Warrants, the
                  Company, the Purchaser and certain other parties entered into
                  an Amended and Restated Voting Agreement dated as of the date
                  hereof (the "Voting Agreement") pursuant to which, among other
                  things, the Purchaser is entitled, on the terms and conditions
                  set forth therein, to designate one nominee for election to
                  the Company's board of directors.

         E.       Simultaneously with the execution and delivery of this
                  Agreement, the Company is entering into separate Standby
                  Purchase Agreements, substantially identical to this
                  Agreement, with the other purchasers named in Schedule I (the
                  "Other Purchasers") to evidence the Other Purchasers'
                  agreement to purchase up to the number of shares of Common
                  Stock set opposite their respective names in Schedule I.



<PAGE>   5


              NOW, THEREFORE, in consideration of the premises and the mutual
covenants and agreements set forth herein and for other good and valuable
consideration, the receipt and sufficiency of which is hereby acknowledged, the
parties hereto, intending to be legally bound, hereby agree as follows:

              Section 1. Definitions and Interpretation. Capitalized terms used
in this Agreement shall, except where the context otherwise requires, have the
following respective meanings:

              "Acts" has the meaning specified in Section 7(e).

              "Adoption Agreement" has the meaning specified in the Preliminary
       Statements of this Agreement.

              "Agreement" means this Standby Purchase Agreement, as from time to
       time amended in accordance with the terms hereof.

              "Bankruptcy Event" means that:

                     (i) the Company or any Subsidiary has (A) made a general
              assignment for the benefit of creditors, (B) filed a voluntary
              bankruptcy petition, (C) become the subject of an order for relief
              or been declared insolvent in any federal or state bankruptcy or
              insolvency proceeding, (D) instituted a proceeding or filed an
              answer in a proceeding seeking to adjudicate itself insolvent or
              seeking reorganization, arrangement, composition, readjustment,
              protection, liquidation, winding-up, dissolution or similar relief
              of it or its debts under any Debtor Relief Law, (E) filed an
              answer or other pleading admitting or failing to contest the
              material allegations of a petition filed against it in a
              proceeding of the type described in subclauses (A) through (D) of
              this clause (i), (F) sought, consented to or acquiesced in an
              order for relief or the appointment of a trustee, receiver,
              liquidator or similar official for it or for any substantial part
              of such its assets or (G) taken any action in furtherance of any
              such actions; or

                    (ii) any proceeding of the type referred to in clause (i)
              above has been filed or commenced against the Company or any
              Subsidiary or the Company or any Subsidiary by any act has
              indicated its approval thereof, consented thereto or acquiesced
              therein, or an order for relief has been entered in an involuntary
              case under any Debtor Relief Law, or an order, judgment or decree
              has been entered appointing a trustee, receiver, custodian,
              liquidator or similar official or adjudicating it insolvent, or
              approving the petition in any such proceedings.

              "Business Day" means any day which is neither a Saturday or Sunday
       nor a legal holiday on which banks are authorized or required to be
       closed in New York, New York, or Houston, Texas.

              "Closing" has the meaning specified in Section 3(a).

                                      -2-
<PAGE>   6

              "Closing Date" has the meaning specified in Section 2(b).

              "Common Shares" means the shares of Common Stock issuable to the
       Purchaser under this Agreement.

              "Common Stock" has the meaning specified in the Preliminary 
       Statements of this Agreement.

              "Company" has the meaning specified in the opening paragraph 
       hereof.

              "Debtor Relief Laws" means the Bankruptcy Code of the United
       States, and any successor statute of similar import, and all other
       applicable dissolution, liquidation, conservatorship, bankruptcy,
       moratorium, readjustment of debt, compromise, rearrangement,
       receivership, insolvency, fraudulent transfer or conveyance,
       reorganization or similar debtor relief laws from time to time in effect
       affecting the rights of creditors generally.

              "Election Notice" has the meaning specified in Section 2(a).

              "Exchange Act" means the Securities Exchange Act of 1934.

              "Form 10-K Report" has the meaning specified in Section 6(d).

              "Governmental Authority" means (i) any nation or government, (ii)
       any federal, state, county, province, city, town, municipality, local or
       other political subdivision thereof or thereto, (iii) any court,
       tribunal, department, commission, board, bureau, instrumentality, agency,
       council, arbitrator or other entity exercising executive, legislative,
       judicial, regulatory or administrative functions of or pertaining to
       government and (iv) any other governmental entity, agency or authority
       having or exercising jurisdiction over any relevant Person, item or
       matter.

              "Initial Warrants" has the meaning specified in the Preliminary 
       Statements of this Agreement.

              "Laws" means all laws, statutes, rules, regulations, ordinances,
       orders, writs, injunctions or decrees and other pronouncements having the
       effect of law of any Governmental Authority.

              "Material Adverse Effect" means a material adverse effect on the
       business, properties, assets, financial condition or results of
       operations of the Company and the Subsidiaries, taken as a whole.


                                      -3-
<PAGE>   7

              "Other Purchasers" has the meaning specified in the Preliminary
       Statements of this Agreement.

              "Person" means any individual, corporation, partnership, limited
       liability company, firm, association, joint venture, Governmental
       Authority or other entity or enterprise.

              "Purchaser" has the meaning specified in the opening paragraph
       hereof.

              "Registration Rights Agreement" means the Registration Rights
       Agreement dated as of August 21, 1996, as amended, among the Company and
       the Persons named therein.

              "SEC" means the Securities and Exchange Commission.

              "Securities" means the Common Shares, the Warrants and the Warrant
       Shares.

              "Securities Act" means the Securities Act of 1933.

              "Stockholders Agreement" means the Sterling Chemicals Holdings,
       Inc. Stockholders Agreement dated effective as of August 21, 1996, as
       amended, among the Company and the stockholders of the Company parties
       thereto.

              "Subsequent Warrants" has the meaning specified in Section 3(f).

              "Subsidiary" means any subsidiary of the Company of which greater
       than 50% of the outstanding shares of capital stock having ordinary
       voting power for the election of directors is owned directly or
       indirectly by the Company.

              "Tag-Along Agreement" means the Tag-Along Agreement, dated
       effective as of August 21, 1996, among the Company and the stockholders
       of the Company parties thereto.

              "Transaction Documents" means, collectively, this Agreement, the
       Adoption Agreement, the Registration Rights Agreement, the Voting
       Agreement, the Tag-Along Agreement, the Warrant Agreement and the
       Stockholders Agreement.

              "Voting Agreement" means an Amended and Restated Voting Agreement
       dated as of the date hereof among the Company and the Persons named
       therein.

              "Warrants" means the Initial Warrants and the Subsequent Warrants.

              "Warrant Agreement" has the meaning specified in the Preliminary
       Statements of this Agreement.

              "Warrant Shares" means the shares of Common Stock issuable to the
       Purchaser upon exercise of the Warrants.


                                      -4-
<PAGE>   8

              (b) In this Agreement, unless a clear contrary intention appears:

              (i) the words "hereof," "herein" and "hereunder" and words of
       similar import refer to this Agreement as a whole and not to any
       particular provision of this Agreement;

              (ii) reference to any gender includes each other gender and the
       neuter;

              (iii) all terms defined in the singular shall have the same
       meanings in the plural and vice versa;

              (iv) reference to any Person includes such Person's heirs,
       executors, personal representatives, administrators, successors and
       assigns; provided, however, that nothing contained in this clause (iv) is
       intended to authorize any assignment not otherwise permitted by this
       Agreement;

              (v) reference to a Person in a particular capacity or capacities
       excludes such Person in any other capacity;

              (vi) reference to any contract or agreement means such contract or
       agreement as amended, supplemented or modified from time to time in
       accordance with the terms thereof;

              (vii) all references to Sections shall be deemed to be references
       to the Sections of this Agreement;

              (viii) all references to Exhibits and Schedules shall be deemed to
       be references to the Exhibits and Schedules attached hereto which are
       made a part hereof and incorporated herein by reference;

              (ix) the word "including" (and with correlative meaning "include")
       means including, without limiting the generality of any description
       preceding such term;

              (x) with respect to the determination of any period of time, the
       word "from" means "from and including" and the words "to" and "until"
       each means "to but excluding";

              (xi) the captions and headings contained in this Agreement shall
       not be considered or given any effect in construing the provisions hereof
       if any question of intent should arise;

              (xii) reference to any Law means such Law as amended, modified,
       codified, reenacted, supplemented or superseded in whole or in part, and
       in effect from time to time; and


                                      -5-
<PAGE>   9

              (xiii) no provision of this Agreement shall be interpreted or
       construed against any party solely because that party or its legal
       representative drafted such provision.

              Section 2. Standby Commitment. (a) Upon the terms and subject to
the satisfaction or waiver of the conditions set forth herein, the Purchaser
agrees to purchase from the Company such number of shares of Common Stock (not
to exceed 1,333,333 in the aggregate) as the Company may, in its sole
discretion, specify at any time or from time to time, in each case at a price
per share, payable in cash, of $6.00. If the Company desires to require the
Purchaser to purchase shares of Common Stock as aforesaid, the Company must give
the Purchaser not less than 15 days' prior written notice (an "Election
Notice"). Each Election Notice shall (i) be given in accordance with Section 11,
(ii) refer to this Agreement, (iii) specify the number of shares to be
purchased, (iv) specify the applicable Closing Date (as defined below), which
may not be later than the third anniversary of the date hereof, and (v) state
that, in the good faith judgement of the Company, the sale of the Common Shares
referred to in such Election Notice is necessary in order for the Company to
maintain, reestablish or enhance its borrowing rights under its revolving credit
facilities and/or to satisfy any obligation under the documentation governing
its revolving credit facilities to raise additional equity capital.
Notwithstanding anything to the contrary contained herein, in no event shall the
Company be required to sell or issue any Common Shares unless the Company has
given to the Purchaser an Election Notice with respect to such Common Shares
pursuant to this paragraph (a) and then only the number of Common Shares
specified in such Election Notice. The Company may not revoke any Election
Notice given by it as aforesaid.

              (b) For purposes of this Agreement, "Closing Date" means, when
used with reference to any purchase of Common Shares, the date on which such
purchase is to be consummated; provided, however, that if such date is not a
Business Day, then the Closing Date for such purchase shall be automatically
extended to the next succeeding Business Day and, provided further, that each
Closing Date shall be at least 30 days after the immediately preceding Closing
Date, if any.

              Section 3. Closings. (a) The consummation of each purchase of
Common Stock pursuant to this Agreement (a "Closing) shall take place on the
applicable Closing Date at 10:00 a.m. (Houston time) unless a different time is
specified in the applicable Election Notice. Each Closing shall be held at the
corporate offices of the Company or at such other place as may be agreed upon by
the Company and the Purchaser.

               (b) At each Closing, the Company shall deliver to the Purchaser
(i) a duly executed certificate evidencing the Common Shares being purchased at
such Closing and (ii) a duly executed certificate of the chief executive
officer, the chief financial officer or the treasurer of the Company, dated the
applicable Closing Date, stating that the representations and warranties of the
Company contained in Section 6 are true and correct on and as of such Closing
Date with the same force and effect as though made on and as of such Closing
Date, except for any representations and warranties made as of a specified date,
which shall be true and correct in all material respects as of such specified
date, and stating that (A) no Bankruptcy Event has occurred and is continuing,
(B) the Company is generally paying its debts as they become due, (C) the
Company owns 



                                      -6-
<PAGE>   10

property having a value greater than the amount required to pay the probable
liability on its debts and (D) the Company has no plans or intentions to
initiate a Bankruptcy Event nor is it aware that any creditor of the Company
plans or intends to initiate a Bankruptcy Event.

              (c) If the first Closing occurs before March 1, 1999, then the
Company shall issue and deliver to the Purchaser at the first Closing, for no
additional consideration, a certificate (in the form attached as Exhibit A to
the Warrant Agreement) evidencing warrants to purchase that number of shares of
Common Stock (rounded to the nearest whole number) equal to the number of Common
Shares purchased by the Purchaser at the first Closing divided by 8.3333.

              (d) If the first Closing occurs before March 1, 1999, then the
Company shall issue and deliver to the Purchaser at the second Closing, for no
additional consideration, a certificate (in the form attached as Exhibit A to
the Warrant Agreement) evidencing warrants to purchase 160,000 shares of Common
Stock minus the number of Common Shares covered by the warrants issued to the
Purchaser at the first Closing.

              (e) If the first Closing occurs after February 28, 1999, then the
Company shall issue and deliver to the Purchaser at the first Closing, for no
additional consideration, a certificate (in the form attached as Exhibit A to
the Warrant Agreement) evidencing warrants to purchase 160,000 shares of Common
Stock.

              (f) All warrants issued to the Purchaser pursuant to this Section
3 are collectively referred to herein as the "Subsequent Warrants". The
Subsequent Warrants shall be subject to the terms and conditions set forth in
the Warrant Agreement and the certificates evidencing the same.

              (g) At each Closing, the Purchaser shall deliver to the Company
(i) an amount (in immediately available funds) equal to the number of Common
Shares being purchased by the Purchaser times $6.00 and (ii) a duly executed
certificate of the Purchaser, dated the applicable Closing Date, stating that
the representations and warranties of the Purchaser contained in Section 7 are
true and correct on and as of such Closing Date with the same force and effect
as though made on and as of such Closing Date, except for any representations
and warranties made as of a specified date, which shall be true and correct in
all material respects as of such specified date.

              Section 4. Simultaneous Closings under Other Purchase Agreements.
In no event shall the Purchaser be obligated to consummate any Closing unless
simultaneously with such Closing (a) the Company shall sell to the Other
Purchasers shares of Common Stock numbering, in the aggregate, not less than the
amount (rounded to the nearest whole number) determined by multiplying the
number of Common Shares being purchased by the Purchaser at such Closing times
0.875 and (b) the Company shall have received from the Other Purchasers payments
(in immediately available funds) of the purchase price for such shares, which
shall not be less than $6.00 per share.


                                      -7-
<PAGE>   11

              Section 5. Use of Proceeds. The Company shall use the proceeds 
       from the sale of Common Shares at each Closing and the proceeds from each
       sale of Common Stock to the Other Purchasers as contemplated by Section 4
       solely for general corporate purposes.

              Section 6. Representations and Warranties of the Company. The 
Company represents and warrants to the Purchaser as follows:

              (a) The Company is a corporation duly organized, validly existing
       and in good standing under the laws of the State of Delaware, and has the
       corporate power to own its property and to carry on its business as now
       being conducted.

              (b) The Company has all requisite corporate power to enter into
       and perform its obligations under the Transaction Documents and the
       Warrants and to consummate the transactions contemplated thereby. The
       Company has taken all corporate actions necessary to authorize it to
       enter into and perform its obligations under the Transaction Documents
       and the Warrants and to consummate the transactions contemplated thereby.
       The Transaction Documents have been duly executed and delivered by the
       Company and constitute legal, valid and binding obligations of the
       Company, enforceable against the Company in accordance with their terms,
       except as such enforcement may be limited by applicable bankruptcy,
       insolvency, reorganization, moratorium or similar Laws affecting
       creditors' rights generally and general equitable principles. Upon
       issuance in accordance with this Agreement and the Warrant Agreement, the
       Warrants will have been duly executed and delivered by the Company and
       will constitute legal, valid and binding obligations of the Company,
       enforceable against the Company in accordance with their terms, except as
       such enforcement may be limited by applicable bankruptcy, insolvency,
       reorganization, moratorium or similar Laws affecting creditors' rights
       generally and general equitable principles. The Common Shares have been
       duly authorized and, when issued and paid for in accordance with this
       Agreement, will be validly issued, fully paid and nonassessable. The
       Warrant Shares have been duly authorized and reserved for issuance and,
       when issued and paid for upon proper exercise of the Warrants, will be
       validly issued, fully paid and nonassessable.

              (c) Neither the execution, delivery or performance of any of the
       Transaction Documents by the Company, nor the consummation by the Company
       of the transactions contemplated thereby, will violate, or result in a
       breach of the terms of, or constitute a default under, the charter or
       bylaws of the Company or any agreement, instrument or other arrangement
       or obligation to which the Company is subject, except for such
       violations, breaches or defaults that would not have a Material Adverse
       Effect.

              (d) The Company has delivered to the Purchaser true and complete
       copies of (i) the Stockholders Agreement, the Registration Rights
       Agreement, the Tag-Along Agreement, the Warrant Agreement and the
       Company's charter and bylaws, in each case as in effect on the date
       hereof, and (ii) the Company's Annual Report on Form 10-K for the fiscal
       year ended September 30, 1998 (the "Form 10-K Report"). As of the date
       hereof, the Form 10-K Report 


                                      -8-
<PAGE>   12

       complies in all material respects with all applicable requirements of the
       Exchange Act and the applicable rules and regulations promulgated
       thereunder and does not contain any untrue statement of a material fact
       or omit to state any material fact necessary in order to make the
       statements therein, in light of the circumstances under which they were
       made, not misleading. As of the date hereof, the consolidated financial
       statements of the Company included in the Form 10-K Report comply as to
       form in all material respects with applicable accounting requirements and
       the published rules and regulations of the SEC with respect thereto. Such
       financial statements were prepared in accordance with applicable
       generally accepted accounting principles applied on a consistent basis
       during the periods involved.

              Section 7. Representations and Warranties of the Purchaser. The
Purchaser hereby represents and warrants to the Company as follows:

              (a) The Purchaser has all requisite power, authority and capacity
       to execute and deliver the Transaction Documents to which the Purchaser
       is a party (the "Purchaser Transaction Documents"), to consummate the
       transactions contemplated thereby and to perform its obligations
       thereunder. Each of the Purchaser Transaction Documents has been executed
       and delivered by the Purchaser and constitutes the legal, valid and
       binding obligation of the Purchaser, enforceable against the Purchaser in
       accordance with its terms, except as such enforcement may be limited by
       applicable bankruptcy, insolvency, reorganization, moratorium or similar
       Laws affecting creditors' rights generally and general equitable
       principles.

              (b) Neither the execution, delivery and performance by the
       Purchaser of the Purchaser Transaction Documents, nor the consummation by
       the Purchaser of the transactions contemplated thereby, will violate,
       result in a breach of the terms of or constitute a default under, any
       material agreement, instrument or other arrangement or obligation to
       which the Purchaser is subject.

              (c) The Purchaser has read and understands this Agreement,
       including the Schedules and Exhibits hereto, and acknowledges and
       understands that execution and delivery of this Agreement by the
       Purchaser creates an irrevocable obligation of the Purchaser, subject to
       the terms and conditions contained in this Agreement, to purchase the
       Common Shares.

              (d) The Purchaser is an "accredited investor" within the meaning
       of Regulation D under the Securities Act.

              (e) The acquisition of the Securities by the Purchaser is for the
       Purchaser's own account, is for investment purposes and is not with a
       view to, or for offer or sale for the Company in connection with, the
       distribution of any Securities in violation of the Securities Act, the
       Exchange Act or any state securities laws (collectively, the "Acts"). The
       Purchaser is not participating and does not have a participation in any
       such distribution or the underwriting of any such distribution, and has
       no present intention of selling or otherwise disposing of any of the
       Securities in violation of the Acts.



                                      -9-
<PAGE>   13

              (f) The Purchaser is aware that neither the SEC nor any state
       securities commission has approved or disapproved the Securities or
       passed upon the accuracy or adequacy of this Agreement or any of the
       other Transaction Documents.

              (g) The Purchaser (i) recognizes that an investment in the
       Securities involves a high degree of risk, (ii) has such knowledge and
       experience in financial and business matters as to be capable of
       evaluating the risks and merits of this investment and protecting the
       Purchaser's interests in connection with this investment and (iii) is
       able to bear the economic risk of an investment in the Securities,
       including the risk of the total loss of such investment.

              (h) The Purchaser has received copies of the Transactions
       Documents, the Form 10-K Report and the Company's charter and bylaws. The
       Purchaser has received all the information the Purchaser considers
       necessary or appropriate for deciding whether to enter into this
       Agreement or to acquire the Securities, and the Purchaser has had an
       opportunity to ask questions of and receive answers from the Company
       regarding the Company and the terms and conditions of the Securities.

              (i) The Purchaser understands that the Securities have not been
       registered under the Securities Act on the basis that the issuance or
       sale of the Securities is exempt from the registration provisions
       thereof, and that the Company's reliance on the exemption is predicated
       upon the representations of the Purchaser herein.

              (j) The Purchaser has read and understands the terms and
       provisions of the Transaction Documents and understands that, by
       executing the Adoption Agreement and the Voting Agreement, all Common
       Shares and all Warrant Shares issued to the Purchaser will automatically
       become subject to the terms and provisions of the Stockholders Agreement,
       the Tag-Along Agreement and the Voting Agreement. The Purchaser
       understands that other shares of Common Stock currently held or
       subsequently acquired by the Purchaser may also become subject to the
       terms and provisions of the Stockholders Agreement, the Tag-Along
       Agreement and the Voting Agreement pursuant to the terms thereof.

              Section 8. Compliance with Securities Laws and Agreements. The
Purchaser acknowledges, understands and agrees that the following limitations
and restrictions are applicable to the purchase, resale and distribution of the
Securities:

              (a) The Purchaser must bear the economic risk of its investment in
       the Company for an indefinite period of time because the Securities have
       not been registered under the Acts and, therefore, may not be
       subsequently offered, sold, transferred, pledged or otherwise disposed of
       unless and until they have been registered under the Acts or exemptions
       from registration thereunder are available, and the Purchaser further
       understands that only the Company can take action to register the
       Securities.



                                      -10-
<PAGE>   14

              (b) The Purchaser has been advised that the Company does not
       expect that Rule 144 under the Securities Act will be available to the
       Purchaser with respect to any of the Securities unless the Purchaser is a
       non-affiliate of the Company (and has not been an affiliate of the
       Company for at least three months) and has held such Securities for at
       least one year from the later of the date that they were issued by the
       Company or the date that they were acquired from an affiliate of the
       Company.

              (c) The certificates representing the Warrants issued pursuant to
       this Agreement will bear the legend provided for in the Warrant
       Agreement. The certificates representing the Securities issued pursuant
       to this Agreement (other than the Warrants) will bear legends in
       substantially the following form:

                    THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN
                    REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR
                    ANY STATE SECURITIES LAW (COLLECTIVELY, THE "ACTS") AND MAY
                    NOT BE OFFERED, SOLD, TRANSFERRED, PLEDGED OR OTHERWISE
                    DISPOSED OF UNLESS MADE PURSUANT TO A REGISTRATION STATEMENT
                    UNDER THE ACTS OR PURSUANT TO AN EXEMPTION FROM THE
                    REGISTRATION REQUIREMENTS THEREOF. FURTHER, SUCH SECURITIES
                    HAVE BEEN ACQUIRED FOR INVESTMENT AND MAY NOT BE OFFERED,
                    SOLD, TRANSFERRED, PLEDGED OR OTHERWISE DISPOSED OF UNLESS
                    AND UNTIL (1) SUCH SECURITIES HAVE BEEN REGISTERED UNDER THE
                    ACTS OR (2) THE HOLDER OF SUCH SECURITIES PROVIDES THE
                    COMPANY WITH (A) AN UNQUALIFIED WRITTEN OPINION OF LEGAL
                    COUNSEL, WHICH COUNSEL AND OPINION (IN FORM AND SUBSTANCE)
                    SHALL BE REASONABLY SATISFACTORY TO THE COMPANY, TO THE
                    EFFECT THAT THE PROPOSED DISPOSITION OF SUCH SECURITIES MAY
                    BE EFFECTED WITHOUT REGISTRATION UNDER THE ACTS OR (B) SUCH
                    OTHER EVIDENCE AS MAY BE REASONABLY SATISFACTORY TO THE
                    COMPANY THAT THE PROPOSED DISPOSITION OF SUCH SECURITIES MAY
                    BE EFFECTED WITHOUT REGISTRATION UNDER THE ACTS.

              (d) In addition to the legends provided in paragraph (c) above,
       the certificates evidencing the Common Shares and the Warrant Shares will
       bear legends in substantially the following forms:

                    BY THE TERMS OF THE STOCKHOLDERS AGREEMENT AND THE TAG-ALONG
                    AGREEMENT, CERTAIN RESTRICTIONS HAVE BEEN PLACED UPON THE
                    TRANSFERABILITY OF THE SECURITIES REPRESENTED BY THIS
                    CERTIFICATE. THE COMPANY WILL FURNISH A COPY OF THE
                    STOCKHOLDERS AGREEMENT AND THE TAG-ALONG AGREEMENT TO THE
                    RECORD HOLDER OF THIS CERTIFICATE WITHOUT CHARGE UPON
                    WRITTEN REQUEST TO THE COMPANY AT ITS PRINCIPAL PLACE OF
                    BUSINESS OR REGISTERED OFFICE. NO REGISTRATION OR TRANSFER
                    OF ANY SECURITIES REPRESENTED BY THIS CERTIFICATE WILL BE
                    MADE ON THE BOOKS OF THE COMPANY UNLESS AND UNTIL SUCH
                    RESTRICTIONS HAVE BEEN COMPLIED WITH.



                                      -11-
<PAGE>   15

                    THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT
                    TO THE TERMS AND CONDITIONS OF AN AMENDED AND RESTATED
                    VOTING AGREEMENT, A COPY OF WHICH IS ON FILE WITH THE
                    SECRETARY OF THE COMPANY, AND ARE HELD AND MAY BE SOLD,
                    ASSIGNED, TRANSFERRED OR OTHERWISE DISPOSED OF ONLY IN
                    ACCORDANCE WITH SUCH AGREEMENT.

              (e) Stop Transfer Instructions. The Company's stock transfer
       records will contain stop transfer instructions with respect to the
       Common Shares and the Warrant Shares to provide notice of the
       restrictions on the resale or distribution thereof imposed by the Acts
       and the Stockholders Agreement, the Tag-Along Agreement and the Voting
       Agreement.

              Section 9. Changes in Capital Structure. In the event of any
change after the date hereof in the number of issued shares of Common Stock by
reason of any stock dividend, split-up, recapitalization, merger, combination,
conversion, exchange of shares or other change in the corporate or capital
structure of the Company, then there shall be appropriate and equitable
adjustments made in the number and kind of shares of stock or other securities
of the Company thereafter issued to the Purchaser pursuant to this Agreement.

              Section 10. Specific Performance. The parties agree that the
covenants and obligations contained in this Agreement relate to special, unique
and extraordinary matters and that a violation of any of the terms hereof would
cause irreparable injury in an amount which would be impossible to estimate or
determine and for which any remedy at law would be inadequate. As such, the
parties agree that if either party fails or refuses to fulfill any of such
party's obligations under this Agreement or to make any payment or deliver any
instrument required hereunder, then the other party shall have the remedy of
specific performance, which remedy shall be cumulative and nonexclusive and
shall be in addition to any other rights and remedies otherwise available under
any other contract or at law or in equity and to which such party might be
entitled.

              Section 11. Notices. Any and all notices, requests or other
communications hereunder shall be given in writing and delivered by (a) regular,
overnight or registered or certified mail (return receipt requested), with first
class postage prepaid, (b) hand delivery, (c) facsimile or electronic mail
transmission or (d) overnight courier service, to the parties at addresses or
facsimile numbers set forth below their respective names on the signature pages
hereof, or at such other address or number as shall be designated by either
party in a notice to the other party given in accordance with this Section 11.
Except as otherwise provided in this Agreement, all such communications shall be
deemed to have been duly given, (i) in the case of a notice sent by regular
mail, on the date actually received by the addressee, (ii) in the case of a
notice sent by registered or certified mail, on the date receipted for (or
refused) on the return receipt, (iii) in the case of a notice delivered by hand,
when personally delivered, (iv) in the case of a notice sent by facsimile or
electronic mail, upon transmission subject to telephone confirmation of receipt,
and (v) in the case of a notice sent by overnight mail or overnight courier
service, the date delivered at the designated address, in each case given or
addressed as aforesaid.



                                      -12-
<PAGE>   16

              Section 12. Survival. All representations, warranties and
covenants contained in this Agreement shall survive the execution and delivery
of this Agreement, the Closings, the delivery of any Securities to the Purchaser
and the death or disability of the Purchaser.

              Section 13. Benefit and Burden. This Agreement shall inure to the
benefit of, and shall be binding upon, the Company and its successors and
assigns and the Purchaser and the Purchaser's heirs, executors, personal
representatives, administrators, successors and assigns.

              Section 14. No Third Party Rights. Nothing in this Agreement shall
be deemed to create any right in any creditor or other Person not a party
hereto, and this Agreement shall not be construed in any respect to be a
contract in whole or in part for the benefit of any third party.

              Section 15. Amendments and Waiver. No amendment, modification,
restatement or supplement of this Agreement shall be valid unless the same is in
writing and signed by the parties. No waiver of any provision of this Agreement
shall be valid unless in writing and signed by the party against whom that
waiver is sought to be enforced. No failure or delay on the part of any of the
parties in exercising any right, power or privilege hereunder, and no course of
dealing between or among the parties, shall operate as a waiver of any right,
power or privilege hereunder. No single or partial exercise of any right, power
or privilege hereunder shall preclude any other or further exercise thereof or
the exercise of any other right, power or privilege hereunder. No notice to or
demand on either party in any case shall entitle such party to any other or
further notice or demand in similar or other circumstances or constitute a
waiver of the rights of any party to any other or further action in any
circumstances without notice or demand.

              Section 16. Severability. Should any clause, sentence, paragraph,
subsection or Section of this Agreement be judicially declared to be invalid,
unenforceable or void, such decision will not have the effect of invalidating or
voiding the remainder of this Agreement, and the parties agree that the part or
parts of this Agreement so held to be invalid, unenforceable or void will be
deemed to have been stricken herefrom as if such stricken part or parts had
never been included herein.

              Section 17. Expenses. The Company will pay, or reimburse the
Purchaser for the payment of, all reasonable expenses incurred by the Purchaser
prior to the date hereof in connection with this Agreement, including all legal
and accounting fees and disbursements. Except as aforesaid, each of the parties
shall pay its own expenses incident to this Agreement, including all legal and
accounting fees and disbursements.

              Section 18. Governing Law. THIS AGREEMENT SHALL BE GOVERNED BY,
CONSTRUED UNDER, AND ENFORCED IN ACCORDANCE WITH THE LAWS OF THE STATE OF
DELAWARE, WITHOUT REFERENCE TO THE CONFLICT-OF-LAWS PROVISIONS THEREOF.



                                      -13-
<PAGE>   17

              Section 19. Entire Agreement. This Agreement sets forth all of the
promises, agreements, conditions, understandings, warranties and representations
of the parties with respect to the transactions contemplated hereby, and
supersedes all prior agreements, arrangements and understandings between the
parties, whether written, oral or otherwise, with respect to the subject matter
hereof. There are no promises, agreements, conditions, understandings,
warranties or representations, oral or written, express or implied, between the
parties concerning the subject matter hereof except as set forth herein.

              IN WITNESS WHEREOF, the parties hereto have caused this Agreement
to be executed as of the date first above written.


                                 STERLING CHEMICALS HOLDINGS, INC.



                                 By: /s/ PETER W. DE LEEUW
                                    -------------------------------------------
                                 Printed Name: Peter W. De Leeuw
                                              ---------------------------------
                                 Title: President and Chief Executive Officer
                                       ----------------------------------------

                                 Address:    Sterling Chemicals Holdings, Inc.
                                             1200 Smith, Suite 1900
                                             Houston, Texas 77002
                                             Attention: General Counsel
                                 Facsimile No.: (713) 654-9577
                                 E-Mail:  [email protected]


                                 PURCHASER:



                                 /s/ GORDON A. CAIN
                                 ----------------------------------------------
                                 Gordon A. Cain

                                 Address:  8 Greenway Plaza, Suite 702
                                         --------------------------------------
                                           Houston, Texas 77046
                                         --------------------------------------

                                         --------------------------------------

                                         --------------------------------------

                                 Facsimile No.:  (713) 877-8107
                                               --------------------------------
                                 E-Mail:          N/A
                                        ---------------------------------------



                                      -14-
<PAGE>   18



                                   SCHEDULE I
                                   PURCHASERS

                                                                        

<TABLE>
<CAPTION>

PURCHASER                                                                 NUMBER OF SHARES     PERCENTAGE ALLOCATION
- ---------                                                                 ----------------     ---------------------

<S>                                                                          <C>                      <C>   
Gordon A. Cain..................................................             1,333,333                 53.33%
William A. McMinn...............................................               333,333                 13.33%
James Crane.....................................................               250,000                 10.00%
Frank P. Diassi.................................................               166,667                  6.67%
Frank J. Hevrdejs...............................................               166,667                  6.67%
Koch Capital Services, Inc. ....................................               250,000                 10.00%
                                                                             ---------                ------
         Total..................................................             2,500,000                100.00%
</TABLE>


                                      -15-


<PAGE>   1
                                                                       EXHIBIT K

================================================================================

================================================================================


                           STANDBY PURCHASE AGREEMENT

                                 BY AND BETWEEN

                        STERLING CHEMICALS HOLDINGS, INC.

                                       AND

                                WILLIAM A. MCMINN


================================================================================

                          DATED AS OF DECEMBER 15, 1998

================================================================================

<PAGE>   2



IN MAKING AN INVESTMENT DECISION INVESTORS MUST RELY ON THEIR OWN EXAMINATION OF
THE ISSUER AND THE TERMS OF THE OFFERING, INCLUDING THE MERITS AND RISKS
INVOLVED. THE SECURITIES PURCHASED HEREUNDER HAVE NOT BEEN RECOMMENDED OR
APPROVED BY ANY FEDERAL OR STATE SECURITIES COMMISSION OR REGULATORY AUTHORITY.
FURTHERMORE, THE FOREGOING AUTHORITIES HAVE NOT CONFIRMED THE ACCURACY OR
DETERMINED THE ADEQUACY OF THIS DOCUMENT. ANY REPRESENTATION TO THE CONTRARY IS
A CRIMINAL OFFENSE.

THE SECURITIES PURCHASED HEREUNDER ARE SUBJECT TO RESTRICTIONS ON
TRANSFERABILITY AND RESALE AND MAY NOT BE TRANSFERRED OR RESOLD EXCEPT AS
PERMITTED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND THE APPLICABLE STATE
SECURITIES LAWS, PURSUANT TO REGISTRATION OR EXEMPTION THEREFROM. INVESTORS
SHOULD BE AWARE THAT THEY MAY BE REQUIRED TO BEAR THE FINANCIAL RISKS OF THIS
INVESTMENT FOR AN INDEFINITE PERIOD OF TIME.



<PAGE>   3


                                TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                        Page
<S>          <C>                                                        <C> 
Section 1    Definitions and Interpretation.............................  2
Section 2    Standby Commitment.........................................  5
Section 3    Closings...................................................  6
Section 4    Simultaneous Closings Under Other Purchase Agreements......  7
Section 5    Use of Proceeds............................................  7
Section 6    Representations and Warranties of the Company..............  7
Section 7    Representations and Warranties of the Purchaser............  9
Section 8    Compliance with Securities Laws and Agreements............. 10
Section 9    Changes in Capital Structure............................... 12
Section 10   Specific Performance....................................... 12
Section 11   Notices.................................................... 12
Section 12   Survival................................................... 12
Section 13   Benefit and Burden......................................... 13
Section 14   No Third Party Rights...................................... 13
Section 15   Amendments and Waiver...................................... 13
Section 16   Severability............................................... 13
Section 17   Expenses................................................... 13
Section 18   Governing Law.............................................. 13
Section 19   Entire Agreement........................................... 13

Schedule I   Purchasers
</TABLE>

<PAGE>   4
                                                                          MCMINN

                           STANDBY PURCHASE AGREEMENT

          THIS STANDBY PURCHASE AGREEMENT (this "Agreement") is made and entered
into as of December 15, 1998 by and between STERLING CHEMICALS HOLDINGS, INC., a
Delaware corporation (the "Company"), and WILLIAM A. MCMINN (the "Purchaser").

                             PRELIMINARY STATEMENTS

          A.   The Company and the Purchaser are entering into this Agreement to
               evidence the Purchaser's agreement to purchase up to 333,333
               shares of common stock, par value $0.01 per share, of the Company
               ("Common Stock").

          B.   Simultaneously with the execution and delivery of this Agreement,
               the Company and Harris Trust and Savings Bank, as agent, entered
               into a Warrant Agreement dated as of the date hereof (the
               "Warrant Agreement"). In order to induce the Purchaser to enter
               into this Agreement, the Company has issued to the Purchaser on
               the date hereof warrants to purchase 40,000 shares of Common
               Stock (the "Initial Warrants"). The Initial Warrants are
               evidenced by a certificate in the form attached as Exhibit A to
               the Warrant Agreement and are subject to the terms and conditions
               set forth in the Warrant Agreement and such certificate.

          C.   In connection with the issuance of the Initial Warrants, the
               Company and the Purchaser entered into an Adoption Agreement
               dated as of the date hereof (the "Adoption Agreement") whereby
               the Purchaser became a party to the Stockholders Agreement, the
               Registration Rights Agreement and the Tag-Along Agreement (as
               such terms are defined below).

          D.   In connection with the issuance of the Initial Warrants, the
               Company, the Purchaser and certain other parties entered into an
               Amended and Restated Voting Agreement dated as of the date hereof
               (the "Voting Agreement").

          E.   Simultaneously with the execution and delivery of this Agreement,
               the Company is entering into separate Standby Purchase
               Agreements, substantially identical to this Agreement, with the
               other purchasers named in Schedule I (the "Other Purchasers") to
               evidence the Other Purchasers' agreement to purchase up to the
               number of shares of Common Stock set opposite their respective
               names in Schedule I.

          NOW, THEREFORE, in consideration of the premises and the mutual 
covenants and agreements set forth herein and for other good and valuable
consideration, the receipt and sufficiency of which is hereby acknowledged, the
parties hereto, intending to be legally bound, hereby agree as follows:

<PAGE>   5

          Section 1. Definitions and Interpretation. Capitalized terms used in
this Agreement shall, except where the context otherwise requires, have the
following respective meanings:

          "Acts" has the meaning specified in Section 7(e).

          "Adoption Agreement" has the meaning specified in the Preliminary
     Statements of this Agreement.

          "Agreement" means this Standby Purchase Agreement, as from time to
     time amended in accordance with the terms hereof.

          "Bankruptcy Event" means that:

               (i)   the Company or any Subsidiary has (A) made a general 
          assignment for the benefit of creditors, (B) filed a voluntary
          bankruptcy petition, (C) become the subject of an order for relief or
          been declared insolvent in any federal or state bankruptcy or
          insolvency proceeding, (D) instituted a proceeding or filed an answer
          in a proceeding seeking to adjudicate itself insolvent or seeking
          reorganization, arrangement, composition, readjustment, protection,
          liquidation, winding-up, dissolution or similar relief of it or its
          debts under any Debtor Relief Law, (E) filed an answer or other
          pleading admitting or failing to contest the material allegations of a
          petition filed against it in a proceeding of the type described in
          subclauses (A) through (D) of this clause (i), (F) sought, consented
          to or acquiesced in an order for relief or the appointment of a
          trustee, receiver, liquidator or similar official for it or for any
          substantial part of such its assets or (G) taken any action in
          furtherance of any such actions; or

               (ii)   any proceeding of the type referred to in clause (i) above
          has been filed or commenced against the Company or any Subsidiary or
          the Company or any Subsidiary by any act has indicated its approval
          thereof, consented thereto or acquiesced therein, or an order for
          relief has been entered in an involuntary case under any Debtor Relief
          Law, or an order, judgment or decree has been entered appointing a
          trustee, receiver, custodian, liquidator or similar official or
          adjudicating it insolvent, or approving the petition in any such
          proceedings.

          "Business Day" means any day which is neither a Saturday or Sunday nor
     a legal holiday on which banks are authorized or required to be closed in
     New York, New York, or Houston, Texas.

          "Closing" has the meaning specified in Section 3(a).

          "Closing Date" has the meaning specified in Section 2(b).

          "Common Shares" means the shares of Common Stock issuable to the
     Purchaser under this Agreement.


                                      -2-
<PAGE>   6

          "Common Stock" has the meaning specified in the Preliminary Statements
     of this Agreement.

          "Company" has the meaning specified in the opening paragraph hereof.

          "Debtor Relief Laws" means the Bankruptcy Code of the United States,
     and any successor statute of similar import, and all other applicable
     dissolution, liquidation, conservatorship, bankruptcy, moratorium, 
     readjustment of debt, compromise, rearrangement, receivership, insolvency,
     fraudulent transfer or conveyance, reorganization or similar debtor relief
     laws from time to time in effect affecting the rights of creditors
     generally.

          "Election Notice" has the meaning specified in Section 2(a).

          "Exchange Act" means the Securities Exchange Act of 1934.

          "Form 10-K Report" has the meaning specified in Section 6(d).

          "Governmental Authority" means (i) any nation or government, (ii) any
     federal, state, county, province, city, town, municipality, local or other
     political subdivision thereof or thereto, (iii) any court, tribunal,
     department, commission, board, bureau, instrumentality, agency, council,
     arbitrator or other entity exercising executive, legislative, judicial,
     regulatory or administrative functions of or pertaining to government and
     (iv) any other governmental entity, agency or authority having or
     exercising jurisdiction over any relevant Person, item or matter.

          "Initial Warrants" has the meaning specified in the Preliminary 
     Statements of this Agreement.

          "Laws" means all laws, statutes, rules, regulations, ordinances,
     orders, writs, injunctions or decrees and other pronouncements having the
     effect of law of any Governmental Authority.

          "Material Adverse Effect" means a material adverse effect on the 
     business, properties, assets, financial condition or results of operations
     of the Company and the Subsidiaries, taken as a whole.

          "Other Purchasers" has the meaning specified in the Preliminary
     Statements of this Agreement.

          "Person" means any individual, corporation, partnership, limited 
     liability company, firm, association, joint venture, Governmental Authority
     or other entity or enterprise.


                                      -3-
<PAGE>   7

          "Purchaser" has the meaning specified in the opening paragraph hereof.

          "Registration Rights Agreement" means the Registration Rights 
     Agreement dated as of August 21, 1996, as amended, among the Company and
     the Persons named therein.

          "SEC" means the Securities and Exchange Commission.

          "Securities" means the Common Shares, the Warrants and the Warrant
     Shares.

          "Securities Act" means the Securities Act of 1933.

          "Stockholders Agreement" means the Sterling Chemicals Holdings, Inc.
     Stockholders Agreement dated effective as of August 21, 1996, as amended,
     among the Company and the stockholders of the Company parties thereto.

          "Subsequent Warrants" has the meaning specified in Section 3(f).

          "Subsidiary" means any subsidiary of the Company of which greater than
     50% of the outstanding shares of capital stock having ordinary voting power
     for the election of directors is owned directly or indirectly by the
     Company.

          "Tag-Along Agreement" means the Tag-Along Agreement dated effective as
     of August 21, 1996, among the Company and the stockholders of the Company
     parties thereto.

          "Transaction Documents" means, collectively, this Agreement, the 
     Adoption Agreement, the Registration Rights Agreement, the Voting
     Agreement, the Tag-Along Agreement, the Warrant Agreement and the
     Stockholders Agreement.

          "Voting Agreement" means an Amended and Restated Voting Agreement 
     dated as of the date hereof among the Company and the Persons named
     therein.

          "Warrants" means the Initial Warrants and the Subsequent Warrants.

          "Warrant Agreement" has the meaning specified in the Preliminary
     Statements of this Agreement.

          "Warrant Shares" means the shares of Common Stock issuable to the 
     Purchaser upon exercise of the Warrants.

          (b)    In this Agreement, unless a clear contrary intention appears:

          (i)    the words "hereof," "herein" and "hereunder" and words of 
     similar import refer to this Agreement as a whole and not to any particular
     provision of this Agreement;


                                      -4-
<PAGE>   8

          (ii)   reference to any gender includes each other gender and the 
     neuter;

          (iii)  all terms defined in the singular shall have the same meanings
     in the plural and vice versa;

          (iv)   reference to any Person includes such Person's heirs, 
     executors, personal representatives, administrators, successors and
     assigns; provided, however, that nothing contained in this clause (iv) is
     intended to authorize any assignment not otherwise permitted by this
     Agreement;

          (v)    reference to a Person in a particular capacity or capacities 
     excludes such Person in any other capacity;

          (vi)   reference to any contract or agreement means such contract or
     agreement as amended, supplemented or modified from time to time in
     accordance with the terms thereof;

          (vii)  all references to Sections shall be deemed to be references to
     the Sections of this Agreement;

          (viii) all references to Exhibits and Schedules shall be deemed to be
     references to the Exhibits and Schedules attached hereto which are made a
     part hereof and incorporated herein by reference;

          (ix)   the word "including" (and with correlative meaning "include")
     means including, without limiting the generality of any description
     preceding such term;

          (x)    with respect to the determination of any period of time, the
     word "from" means "from and including" and the words "to" and "until" each
     means "to but excluding";

          (xi)   the captions and headings contained in this Agreement shall not
     be considered or given any effect in construing the provisions hereof if
     any question of intent should arise;

          (xii)  reference to any Law means such Law as amended, modified, 
     codified, reenacted, supplemented or superseded in whole or in part, and in
     effect from time to time; and

          (xiii) no provision of this Agreement shall be interpreted or 
     construed against any party solely because that party or its legal
     representative drafted such provision.

          Section 2. Standby Commitment. (a) Upon the terms and subject to the
satisfaction or waiver of the conditions set forth herein, the Purchaser agrees
to purchase from the Company such number of shares of Common Stock (not to
exceed 333,333 in the aggregate) as the Company may, in its sole discretion,
specify at any time or from time to time, in each case at a price per


                                      -5-
<PAGE>   9

share, payable in cash, of $6.00. If the Company desires to require the
Purchaser to purchase shares of Common Stock as aforesaid, the Company must give
the Purchaser not less than 15 days' prior written notice (an "Election
Notice"). Each Election Notice shall (i) be given in accordance with Section 11,
(ii) refer to this Agreement, (iii) specify the number of shares to be
purchased, (iv) specify the applicable Closing Date (as defined below), which
may not be later than the third anniversary of the date hereof, and (v) state
that, in the good faith judgement of the Company, the sale of the Common Shares
referred to in such Election Notice is necessary in order for the Company to
maintain, reestablish or enhance its borrowing rights under its revolving credit
facilities and/or to satisfy any obligation under the documentation governing
its revolving credit facilities to raise additional equity capital.
Notwithstanding anything to the contrary contained herein, in no event shall the
Company be required to sell or issue any Common Shares unless the Company has
given to the Purchaser an Election Notice with respect to such Common Shares
pursuant to this paragraph (a) and then only the number of Common Shares
specified in such Election Notice. The Company may not revoke any Election
Notice given by it as aforesaid.

          (b) For purposes of this Agreement, "Closing Date" means, when used
with reference to any purchase of Common Shares, the date on which such purchase
is to be consummated; provided, however, that if such date is not a Business
Day, then the Closing Date for such purchase shall be automatically extended to
the next succeeding Business Day and, provided further, that each Closing Date
shall be at least 30 days after the immediately preceding Closing Date, if any.

          Section 3. Closings. (a) The consummation of each purchase of Common
Stock pursuant to this Agreement (a "Closing) shall take place on the applicable
Closing Date at 10:00 a.m. (Houston time) unless a different time is specified
in the applicable Election Notice. Each Closing shall be held at the corporate
offices of the Company or at such other place as may be agreed upon by the
Company and the Purchaser.

          (b) At each Closing, the Company shall deliver to the Purchaser (i) a
duly executed certificate evidencing the Common Shares being purchased at such
Closing and (ii) a duly executed certificate of the chief executive officer, the
chief financial officer or the treasurer of the Company, dated the applicable
Closing Date, stating that the representations and warranties of the Company
contained in Section 6 are true and correct on and as of such Closing Date with
the same force and effect as though made on and as of such Closing Date, except
for any representations and warranties made as of a specified date, which shall
be true and correct in all material respects as of such specified date, and
stating that (A) no Bankruptcy Event has occurred and is continuing, (B) the
Company is generally paying its debts as they become due, (C) the Company owns
property having a value greater than the amount required to pay the probable
liability on its debts and (D) the Company has no plans or intentions to
initiate a Bankruptcy Event nor is it aware that any creditor of the Company
plans or intends to initiate a Bankruptcy Event.

          (c) If the first Closing occurs before March 1, 1999, then the Company
shall issue and deliver to the Purchaser at the first Closing, for no additional
consideration, a certificate (in the form attached as Exhibit A to the Warrant
Agreement) evidencing warrants to purchase that 


                                      -6-
<PAGE>   10

number of shares of Common Stock (rounded to the nearest whole number) equal to
the number of Common Shares purchased by the Purchaser at the first Closing
divided by 8.3333.

          (d) If the first Closing occurs before March 1, 1999, then the Company
shall issue and deliver to the Purchaser at the second Closing, for no
additional consideration, a certificate (in the form attached as Exhibit A to
the Warrant Agreement) evidencing warrants to purchase 40,000 shares of Common
Stock minus the number of Common Shares covered by the warrants issued to the
Purchaser at the first Closing.

          (e) If the first Closing occurs after February 28, 1999, then the
Company shall issue and deliver to the Purchaser at the first Closing, for no
additional consideration, a certificate (in the form attached as Exhibit A to
the Warrant Agreement) evidencing warrants to purchase 40,000 shares of Common
Stock.

          (f) All warrants issued to the Purchaser pursuant to this Section 3
are collectively referred to herein as the "Subsequent Warrants". The Subsequent
Warrants shall be subject to the terms and conditions set forth in the Warrant
Agreement and the certificates evidencing the same.

          (g) At each Closing, the Purchaser shall deliver to the Company (i) an
amount (in immediately available funds) equal to the number of Common Shares
being purchased by the Purchaser times $6.00 and (ii) a duly executed
certificate of the Purchaser, dated the applicable Closing Date, stating that
the representations and warranties of the Purchaser contained in Section 7 are
true and correct on and as of such Closing Date with the same force and effect
as though made on and as of such Closing Date, except for any representations
and warranties made as of a specified date, which shall be true and correct in
all material respects as of such specified date.

          Section 4. Simultaneous Closings under Other Purchase Agreements. In
no event shall the Purchaser be obligated to consummate any Closing unless
simultaneously with such Closing (a) the Company shall sell to the Other
Purchasers shares of Common Stock numbering, in the aggregate, not less than the
amount (rounded to the nearest whole number) determined by multiplying the
number of Common Shares being purchased by the Purchaser at such Closing times
6.5 and (b) the Company shall have received from the Other Purchasers payments
(in immediately available funds) of the purchase price for such shares, which
shall not be less than $6.00 per share.

          Section 5. Use of Proceeds. The Company shall use the proceeds from
the sale of Common Shares at each Closing and the proceeds from each sale of
Common Stock to the Other Purchasers as contemplated by Section 4 solely for
general corporate purposes.

          Section 6. Representations and Warranties of the Company. The Company
represents and warrants to the Purchaser as follows:


                                      -7-
<PAGE>   11

          (a) The Company is a corporation duly organized, validly existing and
     in good standing under the laws of the State of Delaware, and has the
     corporate power to own its property and to carry on its business as now
     being conducted.

          (b) The Company has all requisite corporate power to enter into and
     perform its obligations under the Transaction Documents and the Warrants
     and to consummate the transactions contemplated thereby. The Company has
     taken all corporate actions necessary to authorize it to enter into and
     perform its obligations under the Transaction Documents and the Warrants
     and to consummate the transactions contemplated thereby. The Transaction
     Documents have been duly executed and delivered by the Company and
     constitute legal, valid and binding obligations of the Company, enforceable
     against the Company in accordance with their terms, except as such
     enforcement may be limited by applicable bankruptcy, insolvency,
     reorganization, moratorium or similar Laws affecting creditors' rights
     generally and general equitable principles. Upon issuance in accordance
     with this Agreement and the Warrant Agreement, the Warrants will have been
     duly executed and delivered by the Company and will constitute legal, valid
     and binding obligations of the Company, enforceable against the Company in
     accordance with their terms, except as such enforcement may be limited by
     applicable bankruptcy, insolvency, reorganization, moratorium or similar
     Laws affecting creditors' rights generally and general equitable
     principles. The Common Shares have been duly authorized and, when issued
     and paid for in accordance with this Agreement, will be validly issued,
     fully paid and nonassessable. The Warrant Shares have been duly authorized
     and reserved for issuance and, when issued and paid for upon proper
     exercise of the Warrants, will be validly issued, fully paid and
     nonassessable.

          (c) Neither the execution, delivery or performance of any of the
     Transaction Documents by the Company, nor the consummation by the Company
     of the transactions contemplated thereby, will violate, or result in a
     breach of the terms of, or constitute a default under, the charter or
     bylaws of the Company or any agreement, instrument or other arrangement or
     obligation to which the Company is subject, except for such violations,
     breaches or defaults that would not have a Material Adverse Effect.

          (d) The Company has delivered to the Purchaser true and complete
     copies of (i) the Stockholders Agreement, the Registration Rights
     Agreement, the Tag-Along Agreement, the Warrant Agreement and the Company's
     charter and bylaws, in each case as in effect on the date hereof, and (ii)
     the Company's Annual Report on Form 10-K for the fiscal year ended
     September 30, 1998 (the "Form 10-K Report"). As of the date hereof, the
     Form 10-K Report complies in all material respects with all applicable
     requirements of the Exchange Act and the applicable rules and regulations
     promulgated thereunder and does not contain any untrue statement of a
     material fact or omit to state any material fact necessary in order to make
     the statements therein, in light of the circumstances under which they were
     made, not misleading. As of the date hereof, the consolidated financial
     statements of the Company included in the Form 10-K Report comply as to
     form in all material respects with applicable accounting requirements and
     the published rules and regulations of the SEC with respect thereto. Such

                                      -8-
<PAGE>   12

     financial statements were prepared in accordance with applicable generally
     accepted accounting principles applied on a consistent basis during the
     periods involved.

          Section 7. Representations and Warranties of the Purchaser. The 
Purchaser hereby represents and warrants to the Company as follows:

          (a) The Purchaser has all requisite power, authority and capacity to
     execute and deliver the Transaction Documents to which the Purchaser is a
     party (the "Purchaser Transaction Documents"), to consummate the
     transactions contemplated thereby and to perform its obligations
     thereunder. Each of the Purchaser Transaction Documents has been executed
     and delivered by the Purchaser and constitutes the legal, valid and binding
     obligation of the Purchaser, enforceable against the Purchaser in
     accordance with its terms, except as such enforcement may be limited by
     applicable bankruptcy, insolvency, reorganization, moratorium or similar
     Laws affecting creditors' rights generally and general equitable
     principles.

          (b) Neither the execution, delivery and performance by the Purchaser
     of the Purchaser Transaction Documents, nor the consummation by the
     Purchaser of the transactions contemplated thereby, will violate, result in
     a breach of the terms of or constitute a default under, any material
     agreement, instrument or other arrangement or obligation to which the
     Purchaser is subject.

          (c) The Purchaser has read and understands this Agreement, including
     the Schedules and Exhibits hereto, and acknowledges and understands that
     execution and delivery of this Agreement by the Purchaser creates an
     irrevocable obligation of the Purchaser, subject to the terms and
     conditions contained in this Agreement, to purchase the Warrant Shares.

          (d) The Purchaser is an "accredited investor" within the meaning of
     Regulation D under the Securities Act.

          (e) The acquisition of the Securities by the Purchaser is for the
     Purchaser's own account, is for investment purposes and is not with a view
     to, or for offer or sale for the Company in connection with, the
     distribution of any Securities in violation of the Securities Act, the
     Exchange Act or any state securities laws (collectively, the "Acts"). The
     Purchaser is not participating and does not have a participation in any
     such distribution or the underwriting of any such distribution, and has no
     present intention of selling or otherwise disposing of any of the
     Securities in violation of the Acts.

          (f) The Purchaser is aware that neither the SEC nor any state
     securities commission has approved or disapproved the Securities or passed
     upon the accuracy or adequacy of this Agreement or any of the other
     Transaction Documents.

          (g) The Purchaser (i) recognizes that an investment in the Securities
     involves a high degree of risk, (ii) has such knowledge and experience in
     financial and business matters as to be capable of evaluating the risks and
     merits of this investment and protecting the Purchaser's

                                      -9-
<PAGE>   13

     interests in connection with this investment and (iii) is able to bear the
     economic risk of an investment in the Securities, including the risk of the
     total loss of such investment.

          (h) The Purchaser has received copies of the Transactions Documents,
     the Form 10-K Report and the Company's charter and bylaws. The Purchaser
     has received all the information the Purchaser considers necessary or
     appropriate for deciding whether to enter into this Agreement or to acquire
     the Securities, and the Purchaser has had an opportunity to ask questions
     of and receive answers from the Company regarding the Company and the terms
     and conditions of the Securities.

          (i) The Purchaser understands that the Securities have not been
     registered under the Securities Act on the basis that the issuance or sale
     of the Securities is exempt from the registration provisions thereof, and
     that the Company's reliance on the exemption is predicated upon the
     representations of the Purchaser herein.

          (j) The Purchaser has read and understands the terms and provisions of
     the Transaction Documents and understands that, by executing the Adoption
     Agreement and the Voting Agreement, all Common Shares and all Warrant
     Shares issued to the Purchaser will automatically become subject to the
     terms and provisions of the Stockholders Agreement, the Tag-Along Agreement
     and the Voting Agreement. The Purchaser understands that other shares of
     Common Stock currently held or subsequently acquired by the Purchaser may
     also become subject to the terms and provisions of the Stockholders
     Agreement, the Tag-Along Agreement and the Voting Agreement pursuant to the
     terms thereof.

          Section 8. Compliance with Securities Laws and Agreements. The
Purchaser acknowledges, understands and agrees that the following limitations
and restrictions are applicable to the purchase, resale and distribution of the
Securities:

          (a) The Purchaser must bear the economic risk of its investment in the
     Company for an indefinite period of time because the Securities have not
     been registered under the Acts and, therefore, may not be subsequently
     offered, sold, transferred, pledged or otherwise disposed of unless and
     until they have been registered under the Acts or exemptions from
     registration thereunder are available, and the Purchaser further
     understands that only the Company can take action to register the
     Securities.

          (b) The Purchaser has been advised that the Company does not expect
     that Rule 144 under the Securities Act will be available to the Purchaser
     with respect to any of the Securities unless the Purchaser is a
     non-affiliate of the Company (and has not been an affiliate of the Company
     for at least three months) and has held such Securities for at least one
     year from the later of the date that they were issued by the Company or the
     date that they were acquired from an affiliate of the Company.

          (c) The certificates representing the Warrants issued pursuant to this
     Agreement will bear the legend provided in the Warrant Agreement. The
     certificates representing the 

                                      -10-
<PAGE>   14

     Securities issued pursuant to this Agreement (other than the Warrants) will
     bear a legend in substantially the following form:

          THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN
          REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR ANY STATE
          SECURITIES LAW (COLLECTIVELY, THE "ACTS") AND MAY NOT BE OFFERED,
          SOLD, TRANSFERRED, PLEDGED OR OTHERWISE DISPOSED OF UNLESS MADE
          PURSUANT TO A REGISTRATION STATEMENT UNDER THE ACTS OR PURSUANT TO AN
          EXEMPTION FROM THE REGISTRATION REQUIREMENTS THEREOF. FURTHER, SUCH
          SECURITIES HAVE BEEN ACQUIRED FOR INVESTMENT AND MAY NOT BE OFFERED,
          SOLD, TRANSFERRED, PLEDGED OR OTHERWISE DISPOSED OF UNLESS AND UNTIL
          (1) SUCH SECURITIES HAVE BEEN REGISTERED UNDER THE ACTS OR (2) THE
          HOLDER OF SUCH SECURITIES PROVIDES THE COMPANY WITH (A) AN UNQUALIFIED
          WRITTEN OPINION OF LEGAL COUNSEL, WHICH COUNSEL AND OPINION (IN FORM
          AND SUBSTANCE) SHALL BE REASONABLY SATISFACTORY TO THE COMPANY, TO THE
          EFFECT THAT THE PROPOSED DISPOSITION OF SUCH SECURITIES MAY BE
          EFFECTED WITHOUT REGISTRATION UNDER THE ACTS OR (B) SUCH OTHER
          EVIDENCE AS MAY BE REASONABLY SATISFACTORY TO THE COMPANY THAT THE
          PROPOSED DISPOSITION OF SUCH SECURITIES MAY BE EFFECTED WITHOUT
          REGISTRATION UNDER THE ACTS.

          (d) In addition to the legends provided in paragraph (c) above, the
     certificates evidencing the Common Shares and the Warrant Shares will bear
     legends in substantially the following forms:

          BY THE TERMS OF THE STOCKHOLDERS AGREEMENT AND THE TAG-ALONG
          AGREEMENT, CERTAIN RESTRICTIONS HAVE BEEN PLACED UPON THE
          TRANSFERABILITY OF THE SECURITIES REPRESENTED BY THIS CERTIFICATE. THE
          COMPANY WILL FURNISH A COPY OF THE STOCKHOLDERS AGREEMENT AND THE
          TAG-ALONG AGREEMENT TO THE RECORD HOLDER OF THIS CERTIFICATE WITHOUT
          CHARGE UPON WRITTEN REQUEST TO THE COMPANY AT ITS PRINCIPAL PLACE OF
          BUSINESS OR REGISTERED OFFICE. NO REGISTRATION OR TRANSFER OF ANY
          SECURITIES REPRESENTED BY THIS CERTIFICATE WILL BE MADE ON THE BOOKS
          OF THE COMPANY UNLESS AND UNTIL SUCH RESTRICTIONS HAVE BEEN COMPLIED
          WITH.

          THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO THE
          TERMS AND CONDITIONS OF AN AMENDED AND RESTATED VOTING AGREEMENT, A
          COPY OF WHICH IS ON FILE WITH THE SECRETARY OF THE COMPANY, AND ARE
          HELD AND 

                                      -11-
<PAGE>   15

          MAY BE SOLD, ASSIGNED, TRANSFERRED OR OTHERWISE DISPOSED OF ONLY IN
          ACCORDANCE WITH SUCH AGREEMENT.

          (e) Stop Transfer Instructions. The Company's stock transfer records
     will contain stop transfer instructions with respect to the Common Shares
     and the Warrant Shares to provide notice of the restrictions on the resale
     or distribution thereof imposed by the Acts and the Stockholders Agreement,
     the Tag-Along Agreement and the Voting Agreement.

          Section 9. Changes in Capital Structure. In the event of any change
after the date hereof in the number of issued shares of Common Stock by reason
of any stock dividend, split-up, recapitalization, merger, combination,
conversion, exchange of shares or other change in the corporate or capital
structure of the Company, then there shall be appropriate and equitable
adjustments made in the number and kind of shares of stock or other securities
of the Company thereafter issued to the Purchaser pursuant to this Agreement.

          Section 10. Specific Performance. The parties agree that the covenants
and obligations contained in this Agreement relate to special, unique and
extraordinary matters and that a violation of any of the terms hereof would
cause irreparable injury in an amount which would be impossible to estimate or
determine and for which any remedy at law would be inadequate. As such, the
parties agree that if either party fails or refuses to fulfill any of such
party's obligations under this Agreement or to make any payment or deliver any
instrument required hereunder, then the other party shall have the remedy of
specific performance, which remedy shall be cumulative and nonexclusive and
shall be in addition to any other rights and remedies otherwise available under
any other contract or at law or in equity and to which such party might be
entitled.

          Section 11. Notices. Any and all notices, requests or other
communications hereunder shall be given in writing and delivered by (a) regular,
overnight or registered or certified mail (return receipt requested), with first
class postage prepaid, (b) hand delivery, (c) facsimile or electronic mail
transmission or (d) overnight courier service, to the parties at addresses or
facsimile numbers set forth below their respective names on the signature pages
hereof, or at such other address or number as shall be designated by either
party in a notice to the other party given in accordance with this Section 11.
Except as otherwise provided in this Agreement, all such communications shall be
deemed to have been duly given, (i) in the case of a notice sent by regular
mail, on the date actually received by the addressee, (ii) in the case of a
notice sent by registered or certified mail, on the date receipted for (or
refused) on the return receipt, (iii) in the case of a notice delivered by hand,
when personally delivered, (iv) in the case of a notice sent by facsimile or
electronic mail, upon transmission subject to telephone confirmation of receipt,
and (v) in the case of a notice sent by overnight mail or overnight courier
service, the date delivered at the designated address, in each case given or
addressed as aforesaid.

          Section 12. Survival. All representations, warranties and covenants
contained in this Agreement shall survive the execution and delivery of this
Agreement, the Closings, the delivery of any Securities to the Purchaser and the
death or disability of the Purchaser.


                                      -12-
<PAGE>   16

          Section 13. Benefit and Burden. This Agreement shall inure to the
benefit of, and shall be binding upon, the Company and its successors and
assigns and the Purchaser and the Purchaser's heirs, executors, personal
representatives, administrators, successors and assigns.

          Section 14. No Third Party Rights. Nothing in this Agreement shall be
deemed to create any right in any creditor or other Person not a party hereto,
and this Agreement shall not be construed in any respect to be a contract in
whole or in part for the benefit of any third party.

          Section 15. Amendments and Waiver. No amendment, modification,
restatement or supplement of this Agreement shall be valid unless the same is in
writing and signed by the parties. No waiver of any provision of this Agreement
shall be valid unless in writing and signed by the party against whom that
waiver is sought to be enforced. No failure or delay on the part of any of the
parties in exercising any right, power or privilege hereunder, and no course of
dealing between or among the parties, shall operate as a waiver of any right,
power or privilege hereunder. No single or partial exercise of any right, power
or privilege hereunder shall preclude any other or further exercise thereof or
the exercise of any other right, power or privilege hereunder. No notice to or
demand on either party in any case shall entitle such party to any other or
further notice or demand in similar or other circumstances or constitute a
waiver of the rights of any party to any other or further action in any
circumstances without notice or demand.

          Section 16. Severability. Should any clause, sentence, paragraph,
subsection or Section of this Agreement be judicially declared to be invalid,
unenforceable or void, such decision will not have the effect of invalidating or
voiding the remainder of this Agreement, and the parties agree that the part or
parts of this Agreement so held to be invalid, unenforceable or void will be
deemed to have been stricken herefrom as if such stricken part or parts had
never been included herein.

          Section 17. Expenses. The Company will pay, or reimburse the Purchaser
for the payment of, all reasonable expenses incurred by the Purchaser prior to
the date hereof in connection with this Agreement, including all legal and
accounting fees and disbursements. Except as aforesaid, each of the parties
shall pay its own expenses incident to this Agreement, including all legal and
accounting fees and disbursements.

          Section 18. Governing Law. THIS AGREEMENT SHALL BE GOVERNED BY,
CONSTRUED UNDER, AND ENFORCED IN ACCORDANCE WITH THE LAWS OF THE STATE OF
DELAWARE, WITHOUT REFERENCE TO THE CONFLICT-OF-LAWS PROVISIONS THEREOF.

          Section 19. Entire Agreement. This Agreement sets forth all of the
promises, agreements, conditions, understandings, warranties and representations
of the parties with respect to the transactions contemplated hereby, and
supersedes all prior agreements, arrangements and understandings between the
parties, whether written, oral or otherwise, with respect to the subject matter
hereof. There are no promises, agreements, conditions, understandings,
warranties or representations, oral or written, express or implied, between the
parties concerning the subject matter hereof except as set forth herein.

                                      -13-
<PAGE>   17
    
          IN WITNESS WHEREOF, the parties hereto have caused this Agreement
to be executed as of the date first above written.


                                   STERLING CHEMICALS HOLDINGS, INC.



                                   By: /s/ PETER W. DE LEEUW
                                      ------------------------------------------

                                   Printed Name: Peter W. DeLeeuw
                                                 -------------------------------
                                   Title: President and Chief Executive Officer
                                          --------------------------------------

                                   Address:    Sterling Chemicals Holdings, Inc.
                                               1200 Smith, Suite 1900
                                               Houston, Texas 77002
                                               Attention: General Counsel
                                   Facsimile No.: (713) 654-9577
                                   E-Mail:  [email protected]


                                   PURCHASER:


                                   /s/ WILLIAM A. MCMINN
                                   ---------------------------------------------
                                   William A. McMinn

                                   Address: Eight Greenway Plaza, Ste. 702
                                            Houston, TX 77046
                                           -------------------------------------
                                           -------------------------------------
                                   Facsimile No.: 713-877-8107
                                                 -------------------------------
                                   E-Mail:
                                          --------------------------------------


                                      -14-

<PAGE>   18


                                   SCHEDULE I
                                   PURCHASERS
<TABLE>
<CAPTION>
                                                   PERCENTAGE 
PURCHASER                       NUMBER OF SHARES   ALLOCATION
- ---------                       ----------------   ----------
<S>                                <C>               <C>   
Gordon A. Cain ...............     1,333,333         53.33%
William A. McMinn ............       333,333         13.33%
James Crane ..................       250,000         10.00%
Frank P. Diassi ..............       166,667          6.67%
Frank J. Hevrdejs ............       166,667          6.67%
Koch Capital Services, Inc....       250,000         10.00%
                                   ---------        ------
      Total ..................     2,500,000        100.00%
</TABLE>


                                      -15-

<PAGE>   1
                                                                       EXHIBIT L




================================================================================

================================================================================


                           STANDBY PURCHASE AGREEMENT
                                        
                                 BY AND BETWEEN
                                        
                       STERLING CHEMICALS HOLDINGS, INC.
                                        
                                      AND
                                        
                                  JAMES CRANE
                                        





================================================================================

                         DATED AS OF DECEMBER 15, 1998

================================================================================
<PAGE>   2
IN MAKING AN INVESTMENT DECISION INVESTORS MUST RELY ON THEIR OWN EXAMINATION OF
THE ISSUER AND THE TERMS OF THE OFFERING, INCLUDING THE MERITS AND RISKS
INVOLVED. THE SECURITIES PURCHASED HEREUNDER HAVE NOT BEEN RECOMMENDED OR
APPROVED BY ANY FEDERAL OR STATE SECURITIES COMMISSION OR REGULATORY AUTHORITY.
FURTHERMORE, THE FOREGOING AUTHORITIES HAVE NOT CONFIRMED THE ACCURACY OR
DETERMINED THE ADEQUACY OF THIS DOCUMENT. ANY REPRESENTATION TO THE CONTRARY IS
A CRIMINAL OFFENSE.

THE SECURITIES PURCHASED HEREUNDER ARE SUBJECT TO RESTRICTIONS ON
TRANSFERABILITY AND RESALE AND MAY NOT BE TRANSFERRED OR RESOLD EXCEPT AS
PERMITTED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND THE APPLICABLE STATE
SECURITIES LAWS, PURSUANT TO REGISTRATION OR EXEMPTION THEREFROM. INVESTORS
SHOULD BE AWARE THAT THEY MAY BE REQUIRED TO BEAR THE FINANCIAL RISKS OF THIS 
INVESTMENT FOR AN INDEFINITE PERIOD OF TIME.
<PAGE>   3
                               TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                           PAGE
                                                                           ----
<S>            <C>                                                         <C>
Section 1      Definitions and Interpretation..............................  2
Section 2      Standby Commitment..........................................  6
Section 3      Closings....................................................  6
Section 4      Simultaneous Closings Under Other Purchase Agreements.......  7
Section 5      Use of Proceeds.............................................  7
Section 6      Representations and Warranties of the Company...............  8
Section 7      Representations and Warranties of the Purchaser.............  9
Section 8      Compliance with Securities Laws and Agreements.............. 10
Section 9      Changes in Capital Structure................................ 12
Section 10     Specific Performance........................................ 12
Section 11     Notices..................................................... 12
Section 12     Survival.................................................... 13
Section 13     Benefit and Burden.......................................... 13
Section 14     No Third Party Rights....................................... 13
Section 15     Amendments and Waiver....................................... 13
Section 16     Severability................................................ 13
Section 17     Expenses.................................................... 13
Section 18     Governing Law............................................... 13
Section 19     Entire Agreement............................................ 13

Schedule I     Purchasers
</TABLE>
<PAGE>   4
                                                                           CRANE


                           STANDBY PURCHASE AGREEMENT

              THIS STANDBY PURCHASE AGREEMENT (this "Agreement") is made and
entered into as of December 15, 1998 by and between STERLING CHEMICALS HOLDINGS,
INC., a Delaware corporation (the "Company"), and JAMES CRANE (the "Purchaser").

                             PRELIMINARY STATEMENTS

         A.       The Company and the Purchaser are entering into this Agreement
                  to evidence the Purchaser's agreement to purchase up to
                  250,000 shares of common stock, par value $0.01 per share, of
                  the Company ("Common Stock").

         B.       Simultaneously with the execution and delivery of this
                  Agreement, the Company and Harris Trust and Savings Bank, as
                  agent, entered into a Warrant Agreement dated as of the date
                  hereof (the "Warrant Agreement"). In order to induce the
                  Purchaser to enter into this Agreement, the Company has issued
                  to the Purchaser on the date hereof warrants to purchase
                  30,000 shares of Common Stock (the "Initial Warrants"). The
                  Initial Warrants are evidenced by a certificate in the form
                  attached as Exhibit A to the Warrant Agreement and are subject
                  to the terms and conditions set forth in the Warrant Agreement
                  and such certificate.

         C.       In connection with the issuance of the Initial Warrants, the
                  Company and the Purchaser entered into an Adoption Agreement
                  dated as of the date hereof (the "Adoption Agreement") whereby
                  the Purchaser became a party to the Stockholders Agreement,
                  the Registration Rights Agreement and the Tag-Along Agreement
                  (as such terms are defined below).

         D.       In connection with the issuance of the Initial Warrants, the
                  Company, the Purchaser and certain other parties entered into
                  an Amended and Restated Voting Agreement dated as of the date
                  hereof (the "Voting Agreement").

         E.       Simultaneously with the execution and delivery of this
                  Agreement, the Company is entering into separate Standby
                  Purchase Agreements, substantially identical to this
                  Agreement, with the other purchasers named in Schedule I (the
                  "Other Purchasers") to evidence the Other Purchasers'
                  agreement to purchase up to the number of shares of Common
                  Stock set opposite their respective names in Schedule I.

              NOW, THEREFORE, in consideration of the premises and the mutual
covenants and agreements set forth herein and for other good and valuable
consideration, the receipt and sufficiency of which is hereby acknowledged, the
parties hereto, intending to be legally bound, hereby agree as follows:



<PAGE>   5

              Section 1. Definitions and Interpretation. Capitalized terms used
in this Agreement shall, except where the context otherwise requires, have the
following respective meanings:

              "Acts" has the meaning specified in Section 7(e).

              "Adoption Agreement" has the meaning specified in the Preliminary
       Statements of this Agreement.

              "Agreement" means this Standby Purchase Agreement, as from time to
       time amended in accordance with the terms hereof.

              "Bankruptcy Event" means that:

                     (i) the Company or any Subsidiary has (A) made a general
              assignment for the benefit of creditors, (B) filed a voluntary
              bankruptcy petition, (C) become the subject of an order for relief
              or been declared insolvent in any federal or state bankruptcy or
              insolvency proceeding, (D) instituted a proceeding or filed an
              answer in a proceeding seeking to adjudicate itself insolvent or
              seeking reorganization, arrangement, composition, readjustment,
              protection, liquidation, winding-up, dissolution or similar relief
              of it or its debts under any Debtor Relief Law, (E) filed an
              answer or other pleading admitting or failing to contest the
              material allegations of a petition filed against it in a
              proceeding of the type described in subclauses (A) through (D) of
              this clause (i), (F) sought, consented to or acquiesced in an
              order for relief or the appointment of a trustee, receiver,
              liquidator or similar official for it or for any substantial part
              of such its assets or (G) taken any action in furtherance of any
              such actions; or

                    (ii) any proceeding of the type referred to in clause (i)
              above has been filed or commenced against the Company or any
              Subsidiary or the Company or any Subsidiary by any act has
              indicated its approval thereof, consented thereto or acquiesced
              therein, or an order for relief has been entered in an involuntary
              case under any Debtor Relief Law, or an order, judgment or decree
              has been entered appointing a trustee, receiver, custodian,
              liquidator or similar official or adjudicating it insolvent, or
              approving the petition in any such proceedings.

              "Business Day" means any day which is neither a Saturday or Sunday
       nor a legal holiday on which banks are authorized or required to be
       closed in New York, New York, or Houston, Texas.

              "Closing" has the meaning specified in Section 3(a).

              "Closing Date" has the meaning specified in Section 2(b).




                                      -2-
<PAGE>   6

              "Common Shares" means the shares of Common Stock issuable to the
       Purchaser under this Agreement.

              "Common Stock" has the meaning specified in the Preliminary
       Statements of this Agreement.

              "Company" has the meaning specified in the opening paragraph
       hereof.

              "Debtor Relief Laws" means the Bankruptcy Code of the United
       States, and any successor statute of similar import, and all other
       applicable dissolution, liquidation, conservatorship, bankruptcy,
       moratorium, readjustment of debt, compromise, rearrangement,
       receivership, insolvency, fraudulent transfer or conveyance,
       reorganization or similar debtor relief laws from time to time in effect
       affecting the rights of creditors generally.

              "Election Notice" has the meaning specified in Section 2(a).

              "Exchange Act" means the Securities Exchange Act of 1934.

              "Form 10-K Report" has the meaning specified in Section 6(d).

              "Governmental Authority" means (i) any nation or government, (ii)
       any federal, state, county, province, city, town, municipality, local or
       other political subdivision thereof or thereto, (iii) any court,
       tribunal, department, commission, board, bureau, instrumentality, agency,
       council, arbitrator or other entity exercising executive, legislative,
       judicial, regulatory or administrative functions of or pertaining to
       government and (iv) any other governmental entity, agency or authority
       having or exercising jurisdiction over any relevant Person, item or
       matter.

              "Initial Warrants" has the meaning specified in the Preliminary
       Statements of this Agreement.

              "Laws" means all laws, statutes, rules, regulations, ordinances,
       orders, writs, injunctions or decrees and other pronouncements having the
       effect of law of any Governmental Authority.

              "Material Adverse Effect" means a material adverse effect on the
       business, properties, assets, financial condition or results of
       operations of the Company and the Subsidiaries, taken as a whole.

              "Other Purchasers" has the meaning specified in the Preliminary
       Statements of this Agreement.



                                      -3-
<PAGE>   7

              "Person" means any individual, corporation, partnership, limited
       liability company, firm, association, joint venture, Governmental
       Authority or other entity or enterprise.

              "Purchaser" has the meaning specified in the opening paragraph
       hereof.

              "Registration Rights Agreement" means the Registration Rights
       Agreement dated as of August 21, 1996, as amended, among the Company and
       the Persons named therein.

              "SEC" means the Securities and Exchange Commission.

              "Securities" means the Common Shares, the Warrants and the Warrant
       Shares.

              "Securities Act" means the Securities Act of 1933.

              "Stockholders Agreement" means the Sterling Chemicals Holdings,
       Inc. Stockholders Agreement dated effective as of August 21, 1996, as
       amended, among the Company and the stockholders of the Company parties
       thereto.

              "Subsequent Warrants" has the meaning specified in Section 3(f).

              "Subsidiary" means any subsidiary of the Company of which greater
       than 50% of the outstanding shares of capital stock having ordinary
       voting power for the election of directors is owned directly or
       indirectly by the Company.

              "Tag-Along Agreement" means the Tag-Along Agreement dated
       effective as of August 21, 1996, among the Company and the stockholders
       of the Company parties thereto.

              "Transaction Documents" means, collectively, this Agreement, the
       Adoption Agreement, the Registration Rights Agreement, the Voting
       Agreement, the Tag-Along Agreement, the Warrant Agreement and the
       Stockholders Agreement.

              "Voting Agreement" means an Amended and Restated Voting Agreement
       dated as of the date hereof among the Company and the Persons named
       therein.

              "Warrants" means the Initial Warrants and the Subsequent Warrants.

              "Warrant Agreement" has the meaning specified in the Preliminary
       Statements of this Agreement.

              "Warrant Shares" means the shares of Common Stock issuable to the
       Purchaser upon exercise of the Warrants.

              (b) In this Agreement, unless a clear contrary intention appears:



                                      -4-
<PAGE>   8

              (i) the words "hereof," "herein" and "hereunder" and words of
       similar import refer to this Agreement as a whole and not to any
       particular provision of this Agreement;

              (ii) reference to any gender includes each other gender and the
       neuter;

              (iii) all terms defined in the singular shall have the same
       meanings in the plural and vice versa;

             (iv) reference to any Person includes such Person's heirs,
       executors, personal representatives, administrators, successors and
       assigns; provided, however, that nothing contained in this clause (iv) is
       intended to authorize any assignment not otherwise permitted by this
       Agreement;

              (v) reference to a Person in a particular capacity or capacities
       excludes such Person in any other capacity;

             (vi) reference to any contract or agreement means such contract or
       agreement as amended, supplemented or modified from time to time in
       accordance with the terms thereof;

              (vii) all references to Sections shall be deemed to be references
       to the Sections of this Agreement;

              (viii) all references to Exhibits and Schedules shall be deemed to
       be references to the Exhibits and Schedules attached hereto which are
       made a part hereof and incorporated herein by reference;

              (ix) the word "including" (and with correlative meaning "include")
       means including, without limiting the generality of any description
       preceding such term;

              (x) with respect to the determination of any period of time, the
       word "from" means "from and including" and the words "to" and "until"
       each means "to but excluding";

              (xi) the captions and headings contained in this Agreement shall
       not be considered or given any effect in construing the provisions hereof
       if any question of intent should arise;

              (xii) reference to any Law means such Law as amended, modified,
       codified, reenacted, supplemented or superseded in whole or in part, and
       in effect from time to time; and

              (xiii) no provision of this Agreement shall be interpreted or
       construed against any party solely because that party or its legal
       representative drafted such provision.


                                      -5-
<PAGE>   9

              Section 2. Standby Commitment. (a) Upon the terms and subject to
the satisfaction or waiver of the conditions set forth herein, the Purchaser
agrees to purchase from the Company such number of shares of Common Stock (not
to exceed 250,000 in the aggregate) as the Company may, in its sole discretion,
specify at any time or from time to time, in each case at a price per share,
payable in cash, of $6.00. If the Company desires to require the Purchaser to
purchase shares of Common Stock as aforesaid, the Company must give the
Purchaser not less than 15 days' prior written notice (an "Election Notice").
Each Election Notice shall (i) be given in accordance with Section 11, (ii)
refer to this Agreement, (iii) specify the number of shares to be purchased,
(iv) specify the applicable Closing Date (as defined below), which may not be
later than the third anniversary of the date hereof, and (v) state that, in the
good faith judgement of the Company, the sale of the Common Shares referred to
in such Election Notice is necessary in order for the Company to maintain,
reestablish or enhance its borrowing rights under its revolving credit
facilities and/or to satisfy any obligation under the documentation governing
its revolving credit facilities to raise additional equity capital.
Notwithstanding anything to the contrary contained herein, in no event shall the
Company be required to sell or issue any Common Shares unless the Company has
given to the Purchaser an Election Notice with respect to such Common Shares
pursuant to this paragraph (a) and then only the number of Common Shares
specified in such Election Notice. The Company may not revoke any Election
Notice given by it as aforesaid.

              (b) For purposes of this Agreement, "Closing Date" means, when
used with reference to any purchase of Common Shares, the date on which such
purchase is to be consummated; provided, however, that if such date is not a
Business Day, then the Closing Date for such purchase shall be automatically
extended to the next succeeding Business Day and, provided further, that each
Closing Date shall be at least 30 days after the immediately preceding Closing
Date, if any.

              Section 3. Closings. (a) The consummation of each purchase of
Common Stock pursuant to this Agreement (a "Closing) shall take place on the
applicable Closing Date at 10:00 a.m. (Houston time) unless a different time is
specified in the applicable Election Notice. Each Closing shall be held at the
corporate offices of the Company or at such other place as may be agreed upon by
the Company and the Purchaser.

               (b) At each Closing, the Company shall deliver to the Purchaser
(i) a duly executed certificate evidencing the Common Shares being purchased at
such Closing and (ii) a duly executed certificate of the chief executive
officer, the chief financial officer or the treasurer of the Company, dated the
applicable Closing Date, stating that the representations and warranties of the
Company contained in Section 6 are true and correct on and as of such Closing
Date with the same force and effect as though made on and as of such Closing
Date, except for any representations and warranties made as of a specified date,
which shall be true and correct in all material respects as of such specified
date, and stating that (A) no Bankruptcy Event has occurred and is continuing,
(B) the Company is generally paying its debts as they become due, (C) the
Company owns property having a value greater than the amount required to pay the
probable liability on its debts and (D) the Company has no plans or intentions
to initiate a Bankruptcy Event nor is it aware that any creditor of the Company
plans or intends to initiate a Bankruptcy Event.



                                      -6-
<PAGE>   10

              (c) If the first Closing occurs before March 1, 1999, then the
Company shall issue and deliver to the Purchaser at the first Closing, for no
additional consideration, a certificate (in the form attached as Exhibit A to
the Warrant Agreement) evidencing warrants to purchase that number of shares of
Common Stock (rounded to the nearest whole number) equal to the number of Common
Shares purchased by the Purchaser at the first Closing divided by 8.3333.

              (d) If the first Closing occurs before March 1, 1999, then the
Company shall issue and deliver to the Purchaser at the second Closing, for no
additional consideration, a certificate (in the form attached as Exhibit A to
the Warrant Agreement) evidencing warrants to purchase 30,000 shares of Common
Stock minus the number of Common Shares covered by the warrants issued to the
Purchaser at the first Closing.

              (e) If the first Closing occurs after February 28, 1999, then the
Company shall issue and deliver to the Purchaser at the first Closing, for no
additional consideration, a certificate (in the form attached as Exhibit A to
the Warrant Agreement) evidencing warrants to purchase 30,000 shares of Common
Stock.

              (f) All warrants issued to the Purchaser pursuant to this Section
3 are collectively referred to herein as the "Subsequent Warrants". The
Subsequent Warrants shall be subject to the terms and conditions set forth in
the Warrant Agreement and the certificates evidencing the same.

              (g) At each Closing, the Purchaser shall deliver to the Company
(i) an amount (in immediately available funds) equal to the number of Common
Shares being purchased by the Purchaser times $6.00 and (ii) a duly executed
certificate of the Purchaser, dated the applicable Closing Date, stating that
the representations and warranties of the Purchaser contained in Section 7 are
true and correct on and as of such Closing Date with the same force and effect
as though made on and as of such Closing Date, except for any representations
and warranties made as of a specified date, which shall be true and correct in
all material respects as of such specified date.

              Section 4. Simultaneous Closings under Other Purchase Agreements.
In no event shall the Purchaser be obligated to consummate any Closing unless
simultaneously with such Closing (a) the Company shall sell to the Other
Purchasers shares of Common Stock numbering, in the aggregate, not less than the
amount (rounded to the nearest whole number) determined by multiplying the
number of Common Shares being purchased by the Purchaser at such Closing times
nine and (b) the Company shall have received from the Other Purchasers payments
(in immediately available funds) of the purchase price for such shares, which
shall not be less than $6.00 per share.

               Section 5. Use of Proceeds. The Company shall use the proceeds
from the sale of Common Shares at each Closing and the proceeds from each sale
of Common Stock to the Other Purchasers as contemplated by Section 4 solely for
general corporate purposes.



                                      -7-
<PAGE>   11

              Section 6.    Representations  and  Warranties of the Company.  
The Company represents and warrants to the Purchaser as follows:

              (a) The Company is a corporation duly organized, validly existing
       and in good standing under the laws of the State of Delaware, and has the
       corporate power to own its property and to carry on its business as now
       being conducted.

              (b) The Company has all requisite corporate power to enter into
       and perform its obligations under the Transaction Documents and the
       Warrants and to consummate the transactions contemplated thereby. The
       Company has taken all corporate actions necessary to authorize it to
       enter into and perform its obligations under the Transaction Documents
       and the Warrants and to consummate the transactions contemplated thereby.
       The Transaction Documents have been duly executed and delivered by the
       Company and constitute legal, valid and binding obligations of the
       Company, enforceable against the Company in accordance with their terms,
       except as such enforcement may be limited by applicable bankruptcy,
       insolvency, reorganization, moratorium or similar Laws affecting
       creditors' rights generally and general equitable principles. Upon
       issuance in accordance with this Agreement and the Warrant Agreement, the
       Warrants will have been duly executed and delivered by the Company and
       will constitute legal, valid and binding obligations of the Company,
       enforceable against the Company in accordance with their terms, except as
       such enforcement may be limited by applicable bankruptcy, insolvency,
       reorganization, moratorium or similar Laws affecting creditors' rights
       generally and general equitable principles. The Common Shares have been
       duly authorized and, when issued and paid for in accordance with this
       Agreement, will be validly issued, fully paid and nonassessable. The
       Warrant Shares have been duly authorized and reserved for issuance and,
       when issued and paid for upon proper exercise of the Warrants, will be
       validly issued, fully paid and nonassessable.

              (c) Neither the execution, delivery or performance of any of the
       Transaction Documents by the Company, nor the consummation by the Company
       of the transactions contemplated thereby, will violate, or result in a
       breach of the terms of, or constitute a default under, the charter or
       bylaws of the Company or any agreement, instrument or other arrangement
       or obligation to which the Company is subject, except for such
       violations, breaches or defaults that would not have a Material Adverse
       Effect.

              (d) The Company has delivered to the Purchaser true and complete
       copies of (i) the Stockholders Agreement, the Registration Rights
       Agreement, the Tag-Along Agreement, the Warrant Agreement and the
       Company's charter and bylaws, in each case as in effect on the date
       hereof, and (ii) the Company's Annual Report on Form 10-K for the fiscal
       year ended September 30, 1998 (the "Form 10-K Report"). As of the date
       hereof, the Form 10-K Report complies in all material respects with all
       applicable requirements of the Exchange Act and the applicable rules and
       regulations promulgated thereunder and does not contain any untrue
       statement of a material fact or omit to state any material fact necessary
       in order to make the statements therein, in light of the circumstances
       under which they were made, not misleading. 



                                      -8-
<PAGE>   12

       As of the date hereof, the consolidated financial statements of the
       Company included in the Form 10-K Report comply as to form in all
       material respects with applicable accounting requirements and the
       published rules and regulations of the SEC with respect thereto. Such
       financial statements were prepared in accordance with applicable
       generally accepted accounting principles applied on a consistent basis
       during the periods involved.

              Section 7. Representations and Warranties of the Purchaser. The
Purchaser hereby represents and warrants to the Company as follows:

              (a) The Purchaser has all requisite power, authority and capacity
       to execute and deliver the Transaction Documents to which the Purchaser
       is a party (the "Purchaser Transaction Documents"), to consummate the
       transactions contemplated thereby and to perform its obligations
       thereunder. Each of the Purchaser Transaction Documents has been executed
       and delivered by the Purchaser and constitutes the legal, valid and
       binding obligation of the Purchaser, enforceable against the Purchaser in
       accordance with its terms, except as such enforcement may be limited by
       applicable bankruptcy, insolvency, reorganization, moratorium or similar
       Laws affecting creditors' rights generally and general equitable
       principles.

              (b) Neither the execution, delivery and performance by the
       Purchaser of the Purchaser Transaction Documents, nor the consummation by
       the Purchaser of the transactions contemplated thereby, will violate,
       result in a breach of the terms of or constitute a default under, any
       material agreement, instrument or other arrangement or obligation to
       which the Purchaser is subject.

              (c) The Purchaser has read and understands this Agreement,
       including the Schedules and Exhibits hereto, and acknowledges and
       understands that execution and delivery of this Agreement by the
       Purchaser creates an irrevocable obligation of the Purchaser, subject to
       the terms and conditions contained in this Agreement, to purchase the
       Common Shares.

              (d) The Purchaser is an "accredited investor" within the meaning
       of Regulation D under the Securities Act.

              (e) The acquisition of the Securities by the Purchaser is for the
       Purchaser's own account, is for investment purposes and is not with a
       view to, or for offer or sale for the Company in connection with, the
       distribution of any Securities in violation of the Securities Act, the
       Exchange Act or any state securities laws (collectively, the "Acts"). The
       Purchaser is not participating and does not have a participation in any
       such distribution or the underwriting of any such distribution, and has
       no present intention of selling or otherwise disposing of any of the
       Securities in violation of the Acts.

              (f) The Purchaser is aware that neither the SEC nor any state
       securities commission has approved or disapproved the Securities or
       passed upon the accuracy or adequacy of this Agreement or any of the
       other Transaction Documents.



                                      -9-
<PAGE>   13

              (g) The Purchaser (i) recognizes that an investment in the
       Securities involves a high degree of risk, (ii) has such knowledge and
       experience in financial and business matters as to be capable of
       evaluating the risks and merits of this investment and protecting the
       Purchaser's interests in connection with this investment and (iii) is
       able to bear the economic risk of an investment in the Securities,
       including the risk of the total loss of such investment.

              (h) The Purchaser has received copies of the Transactions
       Documents, the Form 10-K Report and the Company's charter and bylaws. The
       Purchaser has received all the information the Purchaser considers
       necessary or appropriate for deciding whether to enter into this
       Agreement or to acquire the Securities, and the Purchaser has had an
       opportunity to ask questions of and receive answers from the Company
       regarding the Company and the terms and conditions of the Securities.

              (i) The Purchaser understands that the Securities have not been
       registered under the Securities Act on the basis that the issuance or
       sale of the Securities is exempt from the registration provisions
       thereof, and that the Company's reliance on the exemption is predicated
       upon the representations of the Purchaser herein.

              (j) The Purchaser has read and understands the terms and
       provisions of the Transaction Documents and understands that, by
       executing the Adoption Agreement and the Voting Agreement, all Common
       Shares and all Warrant Shares issued to the Purchaser will automatically
       become subject to the terms and provisions of the Stockholders Agreement,
       the Tag-Along Agreement and the Voting Agreement. The Purchaser
       understands that other shares of Common Stock currently held or
       subsequently acquired by the Purchaser may also become subject to the
       terms and provisions of the Stockholders Agreement, the Tag-Along
       Agreement and the Voting Agreement pursuant to the terms thereof.

              Section 8. Compliance with Securities Laws and Agreements. The
Purchaser acknowledges, understands and agrees that the following limitations
and restrictions are applicable to the purchase, resale and distribution of the
Securities:

              (a) The Purchaser must bear the economic risk of its investment in
       the Company for an indefinite period of time because the Securities have
       not been registered under the Acts and, therefore, may not be
       subsequently offered, sold, transferred, pledged or otherwise disposed of
       unless and until they have been registered under the Acts or exemptions
       from registration thereunder are available, and the Purchaser further
       understands that only the Company can take action to register the
       Securities.

              (b) The Purchaser has been advised that the Company does not
       expect that Rule 144 under the Securities Act will be available to the
       Purchaser with respect to any of the Securities unless the Purchaser is a
       non-affiliate of the Company (and has not been an affiliate of the
       Company for at least three months) and has held such Securities for at
       least one year from the later of the date that they were issued by the
       Company or the date that they were acquired from an affiliate of the
       Company.



                                      -10-
<PAGE>   14

              (c) The certificates representing the Warrants issued pursuant to
       this Agreement will bear the legend provided in the Warrant Agreement.
       The certificates representing the Securities issued pursuant to this
       Agreement (other than the Warrants) will bear a legend in substantially
       the following form:

                    THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN
                    REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR
                    ANY STATE SECURITIES LAW (COLLECTIVELY, THE "ACTS") AND MAY
                    NOT BE OFFERED, SOLD, TRANSFERRED, PLEDGED OR OTHERWISE
                    DISPOSED OF UNLESS MADE PURSUANT TO A REGISTRATION STATEMENT
                    UNDER THE ACTS OR PURSUANT TO AN EXEMPTION FROM THE
                    REGISTRATION REQUIREMENTS THEREOF. FURTHER, SUCH SECURITIES
                    HAVE BEEN ACQUIRED FOR INVESTMENT AND MAY NOT BE OFFERED,
                    SOLD, TRANSFERRED, PLEDGED OR OTHERWISE DISPOSED OF UNLESS
                    AND UNTIL (1) SUCH SECURITIES HAVE BEEN REGISTERED UNDER THE
                    ACTS OR (2) THE HOLDER OF SUCH SECURITIES PROVIDES THE
                    COMPANY WITH (A) AN UNQUALIFIED WRITTEN OPINION OF LEGAL
                    COUNSEL, WHICH COUNSEL AND OPINION (IN FORM AND SUBSTANCE)
                    SHALL BE REASONABLY SATISFACTORY TO THE COMPANY, TO THE
                    EFFECT THAT THE PROPOSED DISPOSITION OF SUCH SECURITIES MAY
                    BE EFFECTED WITHOUT REGISTRATION UNDER THE ACTS OR (B) SUCH
                    OTHER EVIDENCE AS MAY BE REASONABLY SATISFACTORY TO THE
                    COMPANY THAT THE PROPOSED DISPOSITION OF SUCH SECURITIES MAY
                    BE EFFECTED WITHOUT REGISTRATION UNDER THE ACTS.

              (d) In addition to the legends provided in paragraph (c) above,
       the certificates evidencing the Common Shares and the Warrant Shares will
       bear legends in substantially the following forms:

                    BY THE TERMS OF THE STOCKHOLDERS AGREEMENT AND THE TAG-ALONG
                    AGREEMENT, CERTAIN RESTRICTIONS HAVE BEEN PLACED UPON THE
                    TRANSFERABILITY OF THE SECURITIES REPRESENTED BY THIS
                    CERTIFICATE. THE COMPANY WILL FURNISH A COPY OF THE
                    STOCKHOLDERS AGREEMENT AND THE TAG-ALONG AGREEMENT TO THE
                    RECORD HOLDER OF THIS CERTIFICATE WITHOUT CHARGE UPON
                    WRITTEN REQUEST TO THE COMPANY AT ITS PRINCIPAL PLACE OF
                    BUSINESS OR REGISTERED OFFICE. NO REGISTRATION OR TRANSFER
                    OF ANY SECURITIES REPRESENTED BY THIS CERTIFICATE WILL BE
                    MADE ON THE BOOKS OF THE COMPANY UNLESS AND UNTIL SUCH
                    RESTRICTIONS HAVE BEEN COMPLIED WITH.



                                      -11-
<PAGE>   15

                    THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT
                    TO THE TERMS AND CONDITIONS OF AN AMENDED AND RESTATED
                    VOTING AGREEMENT, A COPY OF WHICH IS ON FILE WITH THE
                    SECRETARY OF THE COMPANY, AND ARE HELD AND MAY BE SOLD,
                    ASSIGNED, TRANSFERRED OR OTHERWISE DISPOSED OF ONLY IN
                    ACCORDANCE WITH SUCH AGREEMENT.

              (e) Stop Transfer Instructions. The Company's stock transfer
       records will contain stop transfer instructions with respect to the
       Common Shares and the Warrant Shares to provide notice of the
       restrictions on the resale or distribution thereof imposed by the Acts
       and the Stockholders Agreement, the Tag-Along Agreement and the Voting
       Agreement.

              Section 9. Changes in Capital Structure. In the event of any
change after the date hereof in the number of issued shares of Common Stock by
reason of any stock dividend, split-up, recapitalization, merger, combination,
conversion, exchange of shares or other change in the corporate or capital
structure of the Company, then there shall be appropriate and equitable
adjustments made in the number and kind of shares of stock or other securities
of the Company thereafter issued to the Purchaser pursuant to this Agreement.

              Section 10. Specific Performance. The parties agree that the
covenants and obligations contained in this Agreement relate to special, unique
and extraordinary matters and that a violation of any of the terms hereof would
cause irreparable injury in an amount which would be impossible to estimate or
determine and for which any remedy at law would be inadequate. As such, the
parties agree that if either party fails or refuses to fulfill any of such
party's obligations under this Agreement or to make any payment or deliver any
instrument required hereunder, then the other party shall have the remedy of
specific performance, which remedy shall be cumulative and nonexclusive and
shall be in addition to any other rights and remedies otherwise available under
any other contract or at law or in equity and to which such party might be
entitled.

              Section 11. Notices. Any and all notices, requests or other
communications hereunder shall be given in writing and delivered by (a) regular,
overnight or registered or certified mail (return receipt requested), with first
class postage prepaid, (b) hand delivery, (c) facsimile or electronic mail
transmission or (d) overnight courier service, to the parties at addresses or
facsimile numbers set forth below their respective names on the signature pages
hereof, or at such other address or number as shall be designated by either
party in a notice to the other party given in accordance with this Section 11.
Except as otherwise provided in this Agreement, all such communications shall be
deemed to have been duly given, (i) in the case of a notice sent by regular
mail, on the date actually received by the addressee, (ii) in the case of a
notice sent by registered or certified mail, on the date receipted for (or
refused) on the return receipt, (iii) in the case of a notice delivered by hand,
when personally delivered, (iv) in the case of a notice sent by facsimile or
electronic mail, upon transmission subject to telephone confirmation of receipt,
and (v) in the case of a notice sent by overnight mail or overnight courier
service, the date delivered at the designated address, in each case given or
addressed as aforesaid.



                                      -12-
<PAGE>   16

              Section 12. Survival. All representations, warranties and
covenants contained in this Agreement shall survive the execution and delivery
of this Agreement, the Closings, the delivery of any Securities to the Purchaser
and the death or disability of the Purchaser.

              Section 13. Benefit and Burden. This Agreement shall inure to the
benefit of, and shall be binding upon, the Company and its successors and
assigns and the Purchaser and the Purchaser's heirs, executors, personal
representatives, administrators, successors and assigns.

              Section 14. No Third Party Rights. Nothing in this Agreement shall
be deemed to create any right in any creditor or other Person not a party
hereto, and this Agreement shall not be construed in any respect to be a
contract in whole or in part for the benefit of any third party.

              Section 15. Amendments and Waiver. No amendment, modification,
restatement or supplement of this Agreement shall be valid unless the same is in
writing and signed by the parties. No waiver of any provision of this Agreement
shall be valid unless in writing and signed by the party against whom that
waiver is sought to be enforced. No failure or delay on the part of any of the
parties in exercising any right, power or privilege hereunder, and no course of
dealing between or among the parties, shall operate as a waiver of any right,
power or privilege hereunder. No single or partial exercise of any right, power
or privilege hereunder shall preclude any other or further exercise thereof or
the exercise of any other right, power or privilege hereunder. No notice to or
demand on either party in any case shall entitle such party to any other or
further notice or demand in similar or other circumstances or constitute a
waiver of the rights of any party to any other or further action in any
circumstances without notice or demand.

              Section 16. Severability. Should any clause, sentence, paragraph,
subsection or Section of this Agreement be judicially declared to be invalid,
unenforceable or void, such decision will not have the effect of invalidating or
voiding the remainder of this Agreement, and the parties agree that the part or
parts of this Agreement so held to be invalid, unenforceable or void will be
deemed to have been stricken herefrom as if such stricken part or parts had
never been included herein.

              Section 17. Expenses. The Company will pay, or reimburse the
Purchaser for the payment of, all reasonable expenses incurred by the Purchaser
prior to the date hereof in connection with this Agreement, including all legal
and accounting fees and disbursements. Except as aforesaid, each of the parties
shall pay its own expenses incident to this Agreement, including all legal and
accounting fees and disbursements.

              Section 18. Governing Law. THIS AGREEMENT SHALL BE GOVERNED BY,
CONSTRUED UNDER, AND ENFORCED IN ACCORDANCE WITH THE LAWS OF THE STATE OF
DELAWARE, WITHOUT REFERENCE TO THE CONFLICT-OF-LAWS PROVISIONS THEREOF.

              Section 19. Entire Agreement. This Agreement sets forth all of the
promises, agreements, conditions, understandings, warranties and representations
of the parties with respect to the transactions contemplated hereby, and
supersedes all prior agreements, arrangements and 



                                      -13-
<PAGE>   17

understandings between the parties, whether written, oral or otherwise, with
respect to the subject matter hereof. There are no promises, agreements,
conditions, understandings, warranties or representations, oral or written,
express or implied, between the parties concerning the subject matter hereof
except as set forth herein.

              IN WITNESS WHEREOF, the parties hereto have caused this Agreement
to be executed as of the date first above written.


                              STERLING CHEMICALS HOLDINGS, INC.



                              By: /s/ PETER W. DE LEEUW
                                 --------------------------------------------
                              Printed Name: Peter W. De Leeuw
                                           ----------------------------------
                              Title:  President and Chief Executive Officer
                                    -----------------------------------------

                              Address:    Sterling Chemicals Holdings, Inc.
                                          1200 Smith, Suite 1900
                                          Houston, Texas 77002
                                          Attention: General Counsel
                              Facsimile No.: (713) 654-9577
                              E-Mail:  [email protected]


                              PURCHASER:



                              /s/ JAMES CRANE
                              -----------------------------------------------
                              James Crane

                              Address:  P.O. Box 60467 AMF
                                      ---------------------------------------
                                        Houston TX 77205
                                      ---------------------------------------

                                      ---------------------------------------

                                      ---------------------------------------


                              Facsimile No.:  281-618-3204
                                            ---------------------------------

                              E-Mail:  [email protected]
                                      ---------------------------------------





                                      -14-
<PAGE>   18


                                   SCHEDULE I
                                   PURCHASERS


<TABLE>
<CAPTION>
PURCHASER                                                                  NUMBER OF SHARES      PERCENTAGE ALLOCATION
- ---------                                                                  ----------------      ---------------------

<S>                                                                           <C>                      <C>   
Gordon A. Cain..................................................              1,333,333                 53.33%
William A. McMinn...............................................                333,333                 13.33%
James Crane.....................................................                250,000                 10.00%
Frank P. Diassi.................................................                166,667                  6.67%
Frank J. Hevrdejs...............................................                166,667                  6.67%
Koch Capital Services, Inc......................................                250,000                 10.00%
                                                                              ---------                ------
         Total..................................................              2,500,000                100.00%
</TABLE>



                                      -15-



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