AMENDMENT NO. 5 TO POST-PETITION LOAN AND SECURITY AGREEMENT

Exhibit 4.1

AMENDMENT NO. 5
TO
POST-PETITION LOAN AND SECURITY AGREEMENT

This AMENDMENT NO. 5 TO POST-PETITION LOAN AND SECURITY AGREEMENT (this “Amendment”) is dated as of July 28, 2006, among the Lenders, BANK OF AMERICA, N.A., as agent for the Lenders (the “Agent”), W. R. GRACE & CO. (the “Company”) and the Subsidiaries of W. R. Grace & Co. parties hereto (collectively, the “Borrowers”).

WHEREAS, the parties hereto are parties to a Post-Petition Loan and Security Agreement dated as of April 1, 2001 (as previously amended, the “Loan Agreement”); and

WHEREAS, the parties hereto desire to amend the Loan Agreement as herein set forth:

NOW, THEREFORE, for and in consideration of the mutual covenants set forth herein and in the Loan Agreement, and for other valuable consideration, the receipt and sufficiency of which is hereby acknowledged, the parties hereto agree as follows:

1.                                                     Amendments.  Annex A to the Loan Agreement is hereby amended by amending and restating in its entirety the following definition:

“Adjusted Core EBITDA”  means the sum, without duplication, of (a) net sales from Core Operations, minus (b) Total Core Costs, plus (c) interest and royalties received in cash, plus (d) depreciation and amortization relating to the Core Operations, plus (e) up to $20,000,000 of dividends received, in the aggregate, by any of the Borrowers from any Subsidiary which is not organized under the laws of the United States of America or a political subdivision thereof and received after July 28 , 2006 and prior to the Termination Date.

2.                                                     Representations and Warranties of Each Borrower.  Each Borrower represents and warrants that the execution, delivery and performance by each Borrower of this Amendment has been duly authorized by all necessary corporate action required on its part and this Amendment is a legal, valid and binding obligation of each Borrower enforceable against each Borrower in accordance with its terms except as the enforcement thereof may be subject to (i) the effect of any applicable bankruptcy, insolvency, reorganization, moratorium or similar laws affecting creditors’ rights generally and (ii) general principles of equity (regardless of whether enforcement is sought in a proceeding in equity or at law).

3.                                                     Conditions.  This Amendment shall be effective upon satisfaction of the following conditions precedent:

(i)            This Amendment shall have been executed and delivered by each party hereto; and

(ii)           The Agent shall have received a certificate from the chief financial officer of the Company certifying that (i) immediately before and after giving

effect to this Amendment, all representations and warranties made hereunder, in the Loan Agreement and in the other Loan Documents shall be true and correct as if made on the date hereof, (ii) the Borrowers have performed and complied with all covenants, agreements and conditions contained herein which are required to be performed or complied with by the Borrowers on or before the date hereof and (iii) no Default or Event of Default shall have occurred and be continuing after giving effect to this Amendment.

4.                                       Reference to and Effect Upon the Loan Agreement.

(a)           Except as specifically amended above, the Loan Agreement and the other Loan Documents shall remain in full force and effect and are hereby ratified and confirmed.

(b)           Upon the effectiveness of this Amendment, each reference in the Loan Agreement to “this Agreement”, “hereunder”, “hereof”, “herein” or words of similar import shall mean and be a reference to the Loan Agreement as amended hereby.

5.                                       Defined Terms.  Except as otherwise defined herein, all defined terms herein shall have the meanings ascribed thereto in the Loan Agreement.

6.                                       Governing Law.  THIS AMENDMENT SHALL BE INTERPRETED AND THE RIGHTS AND LIABILITIES OF THE PARTIES HERETO DETERMINED IN ACCORDANCE WITH THE INTERNAL LAWS (PROVIDED THAT PERFECTION ISSUES WITH RESPECT TO ARTICLE 9 OF THE UCC MAY GIVE EFFECT TO APPLICABLE CHOICE OR CONFLICT OF LAW RULES SET FORTH IN ARTICLE 9 OF THE UCC) OF THE STATE OF NEW YORK TO THE EXTENT NOT PREEMPTED BY FEDERAL BANKRUPTCY LAWS; PROVIDED THAT THE AGENT AND THE LENDERS SHALL RETAIN ALL RIGHTS ARISING UNDER FEDERAL LAW.

7.                                       Headings.  Section headings in this Amendment are included herein for convenience of reference only and shall not constitute a part of this Amendment for any other purposes.

8.                                       Severability.  If any provision of this Amendment shall be prohibited by or invalid under applicable law, such provision shall be ineffective to the extent of such prohibition or invalidity, without invalidating the remainder of such provision or the remaining provisions of this Amendment.

2

9.                                       Acceptance of Signatures.  The parties agree that this Amendment will be considered signed when the signature of a party is delivered by facsimile or electronic mail transmission. Such facsimile or electronic mail signature shall be treated in all respects as having the same effect as an original signature.

I0.                                   Counterparts. This Amendment may be executed in any number of counterparts, each of which when so executed shall be deemed an original, but all such counterparts shall constitute one and the same instrument.

(Signature Pages Follow)

3

IN WITNESS WHEREOF, this Amendment has been duly executed as of the date first written above.

[Signature Page to Amendment No. 5 to
Post-Petition Loan and Security Agreement]

[Signature Page to Amendment No. 5 to
Post-Petition Loan and Security Agreement]

[Signature Page to Amendment No. 5 to
Post-Petition Loan and Security Agreement]

[Signature Page to Amendment No. 5 to
Post-Petition Loan and Security Agreement]

[Signature Page to Amendment No. 5 to
Post-Petition Loan and Security Agreement]

[Signature Page to Amendment No. 5 to
Post-Petition Loan and Security Agreement]

[Signature Page to Amendment No. 5 to
Post-Petition Loan and Security Agreement]

[Signature Page to Amendment No. 5 to

Post-Petition Loan and Security Agreement]

[Signature Page to Amendment No. 5 to

Post-Petition Loan and Security Agreement]