Exhibit 6 FOURTH AMENDMENT TO RIGHTS AGREEMENT AMENDMENT, dated and effective as of October 9, 1997, to the Rights Agreement, dated as of November 5, 1990 (the "Rights Agreement"), between Melamine Chemicals, Inc., a Delaware corporation (the "Company"), and Wachovia Bank and Trust Company, N.A. (now Wachovia Bank, N.A.) (the "Rights Agent"), as heretofore amended by an Amendment to Rights Agreement, dated as of August 7, 1991, between the Company and the Rights Agent (the "First Amendment"), a Second Amendment to Rights Agreement, dated as of August 3, 1994, between the Company and the Rights Agent (the "Second Amendment"), and a Third Amendment to Rights Agreement, dated as of October 9, 1997, between the Company and the Rights Agent (the "Third Amendment"), W I T N E S S E T H: WHEREAS, on November 5, 1990, the Board of Directors of the Company authorized the issuance and declared a dividend of one right (a "Right") for each share of common stock, par value $.01 per share of the Company outstanding as of the close of business on November 15, 1990, with each Right representing the right to purchase 1/100 of a share of Series A Junior Participating Preferred Stock, par value $1.00 per share, of the Company; WHEREAS, the Board of Directors of the Company further authorized the issuance of one Right with respect to each share of common stock of the Company that shall become outstanding between November 15, 1990 and the earliest of the Distribution Date, the Redemption Date and the Final Expiration Date, as defined in the Rights Agreement; WHEREAS, Section 7 of the Rights Agreement as heretofore amended defines Final Expiration Date as the "close of business on November 15, 1998;" WHEREAS, Section 27 of the Rights Agreement provides, in part, that the Company and the Rights Agent may, without the approval of, or notice to, the holders of the Rights, amend or supplement the Rights Agreement to make any provision with respect to the Rights that the Company deems necessary or desirable; and WHEREAS, the Company and the Rights Agent desire to further amend and modify the Rights Agreement in certain respects. NOW THEREFORE, in consideration of the foregoing premises and mutual agreements set forth in the Rights Agreement as heretofore amended and this Fourth Amendment, the parties hereby agree as follows: 1. The Rights Agreement, as heretofore amended, is hereby further modified and amended by deleting the first sentence of paragraph (a) of Section 1 and substituting therefor the following: (a) "Acquiring Person" shall mean any Person (as such term is hereinafter defined) who or which, together with all Affiliates and Associates (as such terms are hereinafter defined) of such Person, shall be the Beneficial Owner (as such term is hereinafter defined) of 10% or more of the Common Shares of the Company then outstanding, but shall not include (i) the Company, (ii) any Subsidiary (as such term is hereinafter defined) of the Company, (iii) any employee benefit plan of the Company or any Subsidiary of the Company, (iv) any entity holding Common Shares for or pursuant to the terms of any such plan, (v) Ashland Chemical, Inc., ChemFirst, Inc., as successor to First Mississippi Corporation, or any Affiliate or Associate of either Ashland Chemical, Inc. or ChemFirst, Inc. (each of the foregoing in this clause (v), an "Exempted Person"), unless such Exempted Person shall acquire additional Common Shares after the date hereof, or (vi) Borden Chemical, Inc. or its Subsidiaries, Affiliates or Associates (hereinafter, collectively, "Borden"). 2. The Rights Agreement, as heretofore amended, is hereby further modified and amended by adding an additional paragraph at the end of the definition of the terms "Beneficial Owner" and "beneficially own" in paragraph (c) of Section 1 reading as follows: Notwithstanding anything in this definition of Beneficial Owner and Beneficial Ownership to the contrary, Borden shall not be deemed to be the Beneficial Owner of, nor to beneficially own, any of the Common Shares of the Company solely by reason of the approval, execution or delivery by any party thereto, or by reason of the amendment or consummation of any of the transactions contemplated by (A) the Agreement and Plan of Merger by and among Borden Chemical, Inc., MC Merger Corp., and Melamine Chemicals, Inc. dated and effective as of October 9, 1997 (the "Merger Agreement"), or (B) the Tender Agreement dated October 9, 1997 by and among Borden Chemical, Inc., MC Merger Corp., and ChemFirst, Inc. (the "Tender Agreement"). 3. The Rights Agreement, as heretofore amended, is hereby further modified and amended by deleting the first sentence of paragraph (a) of Section 3 of the Rights Agreement and substituting therefor the following: (a) Until the earlier of (i) the tenth day after the Shares Acquisition Date or (ii) the tenth business day (or such later date as may be determined by action of the Board of Directors prior to such time as any Person becomes an Acquiring Person) after the date of the commencement by any Person (other than (i) the Company, (ii) any Subsidiary of the Company, (iii) any employee benefit plan of the Company or of any Subsidiary of the Company, (iv) any entity holding Common Shares for or pursuant to the terms of any such plan or (v) Borden) of, or of the first public announcement of the intention of any Person (other than (i) the Company, (ii) any Subsidiary of the Company, (iii) any employee benefit plan of the Company or of any Subsidiary of the Company, (iv) any entity holding Common Shares for or pursuant to the terms of any such plan or (v) Borden) to commence, a tender or exchange offer the consummation of which would result in any Person becoming the Beneficial Owner of Common Shares aggregating 10% or more of the then outstanding Common Shares (including any such date which is after the date of this Agreement and prior to the issuance of the Rights; the earlier of such dates being herein referred to as the "Distribution Date"), (x) the Rights will be evidenced (subject to the provisions of Section 3(b) hereof) by the certificates for Common Shares registered in the names of the holders thereof (which certificates shall also be deemed to be Right Certificates) and not by separate Right Certificates, and (y) the right to receive Right Certificates will be transferable only in connection with the transfer of Common Shares. 4. The Rights Agreement, as heretofore amended, is hereby further modified and amended by deleting paragraph (a) of Section 7 and substituting therefor the following: (a) The registered holder of any Right Certificate may exercise the Rights evidenced thereby (except as otherwise provided herein) in whole or part at any time after the Distribution Date upon surrender of the Right Certificate, with the form of election to purchase on the reverse side thereof duly executed, to the Rights Agent at the principal office of the Rights Agent, together with payment of the Purchase Price for each one one- hundredth of a Preferred Share as to which the Rights are exercised, at or prior to the earliest of (i) the close of business on November 15, 1998 (the "Final Expiration Date"), (ii) the time at which the Rights are redeemed as provided in Section 23 hereof (the "Redemption Date"), (iii) the time at which such rights are exchanged as provided in Section 24 hereof, or (iv) immediately prior to the acceptance for purchase of Common Shares by Borden pursuant to the Offer (as such term is defined in the Merger Agreement). 5. The Rights Agreement, as heretofore amended, is hereby further amended by adding the following new Section 34 at the end: Section 34. Borden Transaction. Notwithstanding anything in this Agreement to the contrary, neither (a) the approval, execution, delivery, amendment or consummation of any of the transactions contemplated by the Merger Agreement or the Tender Agreement or (b) the public announcement or making of a tender offer by Borden for Common Shares of the Company, or the acceptance for purchase of such shares thereunder, shall cause (i) Borden to become an Acquiring Person, (ii) a Shares Acquisition Date to occur, or (iii) a Distribution Date to occur. Any Distribution Date that might or could otherwise occur under this Agreement shall be indefinitely deferred until such time as the Board of Directors may otherwise determine. 6. This Fourth Amendment to the Rights Agreement shall be governed by and construed in accordance with the internal laws of the State of Delaware. 7. This Fourth Amendment to the Rights Agreement may be executed in any number of counterparts and each of such counterparts shall for all purposes be deemed an original, and all such counterparts shall together constitute but one and the same instrument. 8. Except as expressly set forth herein, this Fourth Amendment to the Rights Agreement shall not by implication or otherwise alter, modify, amend or in any way affect any of the terms, conditions, obligations, covenants or agreements contained in the Rights Agreement, as heretofore amended, all of which are ratified and affirmed in all respects and shall continue in full force and effect. IN WITNESS WHEREAS, the parties hereto have caused this Fourth Amendment to the Rights Agreement to be executed by their respective proper and duly authorized officers, as of the date first above written. ATTEST: MELAMINE CHEMICALS, INC. By: /s/ Wayne D. DeLeo By: /s/ Frederic R. Huber ------------------------- -------------------------- Wayne D. DeLeo, Vice President Frederic R.Huber and Chief Financial Officer President ATTEST: WACHOVIA BANK, N.A. By: /s/ Darrell V. Milton By: /s/ Molly A. Long --------------------- ----------------- Name: Darrell V. Milton Name: Molly A. Long Title: Assistant Secretary Title: Senior Vice President