First Amendment to Credit Agreement

Exhibit 10.16

FIRST AMENDMENT TO CREDIT AGREEMENT

     THIS FIRST AMENDMENT TO CREDIT AGREEMENT (the “Amendment”) dated as of September 30, 2004, is to that certain Credit Agreement dated as of July 31, 2003 (as amended and modified from time to time, the “Credit Agreement”), by and among WESTLAKE CHEMICAL CORPORATION, a Delaware corporation (the “Borrower”), THE SUBSIDIARIES OF THE BORROWER FROM TIME TO TIME PARTIES THERETO AND IDENTIFIED AS “GUARANTORS” ON THE SIGNATURE PAGES HERETO (the “Guarantors”), THE PERSONS FROM TIME TO TIME PARTIES THERETO AND IDENTIFIED AS “LENDERS” ON THE SIGNATURE PAGES HERETO (the “Lenders”) and BANK OF AMERICA, N.A., as administrative agent (the “Agent”).

W I T N E S S E T H

     WHEREAS, the Lenders have, pursuant to the terms of the Credit Agreement, made available to the Borrower and the Guarantors a term loan in the original principal amount of $120,000,000;

     WHEREAS, the parties hereto have agreed to amend the Credit Agreement as set forth herein;

     NOW, THEREFORE, IN CONSIDERATION of the premises and other good and valuable consideration, the receipt and sufficiency of which is hereby acknowledged, the parties hereto agree as follows:

     A. Definitions. Unless the context otherwise requires, capitalized terms used but not otherwise defined herein shall have the meanings assigned in the Credit Agreement.

     B. Amendments.

     1. The definition of “Applicable Rate” in Section 1.01 of the Credit Agreement is hereby amended to read as follows:

     “Applicable Rate” means, (a) with respect to Base Rate Loans, 1.25% and (b) with respect to Eurodollar Loans, 2.25%.

     2. The definitions of “Excess Cash Flow” and “Excess Cash Flow Payment Date” in Section 1.01 of the Credit Agreement are hereby deleted.

     3. Section 2.04(b)(i) of the Credit Agreement is hereby amended to read as follows:

     (i) [Intentionally Omitted].

     4. Section 7.02(c) of the Credit Agreement is hereby amended to read as follows:

     (c) [Intentionally Omitted].

     5. A new Section 11.20 is hereby added to the Credit Agreement to read as follows:

     11.20 USA PATRIOT Act Notice.

     Each Lender and the Administrative Agent (for itself and not on behalf of any Lender) hereby notifies the Borrower that pursuant to the requirements of the USA Patriot Act (Title III of Pub. L. 107-56 (signed into law October 26, 2001)) (the “Act”), it is required to obtain, verify and record information that identifies the Borrower, which information includes the name and address of the Borrower and other information that will allow such Lender or the Administrative Agent, as applicable, to identify the Borrower in accordance with the Act.

     6. Exhibit 7.01 to the Credit Agreement is hereby deleted.

     C. Conditions Precedent. This Amendment shall be and become effective as of September 30, 2004 (the “Effective Date”) when the Agent shall have received counterparts of this Amendment, which collectively shall have been duly executed on behalf of each of the Borrower, the Guarantors, the Agent and the Lenders.

     D. Expenses. The Borrower agrees to pay all reasonable costs and expenses of the Agent in connection with the preparation, execution and delivery of this Amendment, including without limitation the reasonable fees and expenses of the Agent’s legal counsel.

     E. Effect. Except as expressly modified and amended in this Amendment, all of the terms, provisions and conditions of the Credit Agreement are and shall remain in full force and effect and are incorporated herein by reference, and the obligations of the Borrower and the Guarantors hereunder and under the other Loan Documents are hereby ratified and confirmed and shall remain in full force and effect. Any and all other documents heretofore, now or hereafter executed and delivered pursuant to the terms of the Credit Agreement are hereby amended so that any reference to the Credit Agreement shall mean a reference to the Credit Agreement as amended hereby.

     F. Representations and Warranties. The Borrower and each Guarantor represents and warrants to the Lenders that (i) the representations and warranties set forth in Article VI of the Credit Agreement are true and correct on and as of the Effective Date, except to the extent that such representations and warranties specifically refer to an earlier date, in which case they shall be true and correct as of such earlier date, (ii) no Default exists and (iii) none of the Borrower or any Guarantor has any counterclaims, offsets, credits or defenses to the Loan Documents and the performance of their respective obligations thereunder, or if the Borrower or any Guarantor has any such claims, counterclaims, offsets, credits or defenses to the Loan Documents or any transaction related to the Loan Documents, the same are hereby waived, relinquished and released in consideration of the Lenders’ execution and delivery of this Amendment.

     G. Counterparts. This Amendment may be executed in any number of counterparts, each of which when so executed and delivered shall be an original, but all of which shall constitute one and the same instrument. It shall not be necessary in making proof of this Amendment to produce or account for more than one such counterpart.

     H. Governing Law. This Amendment and the Credit Agreement, shall be governed by and construed in accordance with, the laws of the State of New York.

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     I. Successors and Assigns. This Amendment shall be binding upon and inure to the benefit of the parties hereto and their respective successors and assigns.

     J. Authorization; Enforceability. The Borrower and each Guarantor hereby represent and warrant as follows:

     1. The Borrower and each Guarantor have taken all necessary action to authorize the execution, delivery and performance of this Amendment.

     2. This Amendment has been duly executed and delivered by the Borrower and each Guarantor, and this Amendment and the Credit Agreement (as amended hereby) constitute the Borrower’s and the Guarantors’ legal, valid and binding obligations, enforceable in accordance with their terms, except as such enforceability may be subject to (a) Debtor Relief Laws and (b) general principles of equity (regardless of whether such enforceability is considered in a proceeding at law or in equity).

     3. No consent, approval, authorization or order of, or filing, registration or qualification with, any court or Governmental Authority or third party is required in connection with the execution, delivery or performance by the Borrower or any Guarantor of this Amendment.

     K. Entire Agreement.

     THIS AMENDMENT AND THE OTHER LOAN DOCUMENTS REPRESENT THE FINAL AGREEMENT AMONG THE PARTIES AND MAY NOT BE CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS, OR SUBSEQUENT ORAL AGREEMENTS OF THE PARTIES. THERE ARE NO UNWRITTEN ORAL AGREEMENTS AMONG THE PARTIES.

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     IN WITNESS WHEREOF, each of the parties hereto has caused a counterpart of this Amendment to be duly executed under seal and delivered as of the date and year first above written.