EXHIBIT 3.50

                            CERTIFICATE OF AMENDMENT
                                       OF
                          CERTIFICATE OF INCORPORATION

         Westlake Vinyl Corporation ("Corporation"), a corporation organized and
existing under and by virtue of the General Corporation Law of the State of
Delaware, does hereby certify:

                  FIRST: That in lieu of a meeting and vote of directors, the
Board of Directors of the Corporation, by unanimous written consent filed with
the Corporation, in accordance with the Provisions of Section 141(f) of the
General Corporation Law of the State of Delaware, have adopted a resolution
proposing and declaring advisable the following amendments to the Certificate of
Incorporation of the Corporation:

         RESOLVED, That the Certificate of Incorporation be amended by changing
Article I to read as follows:

                                    ARTICLE I

                  The name of the corporation is Westlake PVC Corporation.

         SECOND: That in lieu of a meeting and vote of stockholders, the sole
stockholder of all outstanding stock entitled to vote thereon has given written
consent to the above amendment in accordance with Section 228 of the General
Corporation Law of the State of Delaware, and said written consent has been
filed with the Corporation.

         THIRD: That said amendments were duly adopted in accordance with the
provisions of Sections 141, 216, 228 and 242 of the General Corporation Law of
the State of Delaware.

         FOURTH: That the capital of the Corporation will not be reduced under
or by reason of said amendments.

         IN WITNESS WHEREOF, Westlake Vinyl Corporation has caused this
certificate to be signed by Bob Casey, Jr., its President, and attested by Bob
Casey, Jr., its Secretary, this 20th day of August, 1991.

                                       Westlake Vinyl Corporation

                                       By: /s/Bob Casey, Jr.
                                          -------------------------------
                                            Bob Casey, Jr.

ATTEST:

By: /s/Bob Casey, Jr.
   --------------------------------
    Bob Casey, Jr.