Cross-linked polyester protective coatings

• US 20070054140A1
• Filed: 09/06/2005
• Published: 03/08/2007
• Est. Priority Date: 09/06/2005
• Status: Active Grant

• Current Assignee: Swimc, LLC (The Sherwin-Williams Company)
• Original Assignee: Valspar Sourcing, Inc. (Sherwin-Williams Company)
• Inventors: Mayr, Peter, Altmann, Fritz, Robinson, James
• Granted Patent: US 7,763,323 B2
• Time in Patent Office: Days
• US Class Current: 428/480
• CPC Class Codes: B05D 7/542 the two layers being cured or baked together
• CPC Class Codes: C08G 18/4027 Mixtures of compounds of group C08G18/54 with other macromolecular compounds
• CPC Class Codes: C08G 18/542 with phenols
• CPC Class Codes: C08G 18/8074 Lactams
• CPC Class Codes: C08G 2390/40 Inner coatings for containers
• CPC Class Codes: C08K 5/0025 Crosslinking or vulcanising agents; including accelerators
• CPC Class Codes: C08K 5/29 Compounds containing one or more carbon-to-nitrogen double bonds
• CPC Class Codes: C08L 2666/14 Macromolecular compounds according to C08L59/00 - C08L87/00; Derivatives thereof
• CPC Class Codes: C08L 61/06 of aldehydes with phenols
• CPC Class Codes: C08L 61/12 with polyhydric phenols
• CPC Class Codes: C08L 67/00 Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain of polyester-amides C08L77/12; of polyester-imides C08L79/08; Compositions of derivatives of such polymers
• CPC Class Codes: C09D 167/00 Coating compositions based on polyesters obtained by reactions forming a carboxylic ester link in the main chain based on polyester-amides C09D177/12; based on polyester-imides C09D179/08; Coating compositions based on derivatives of such polymers
• CPC Class Codes: C09D 175/04 Polyurethanes
• CPC Class Codes: Y10T 428/1355 Elemental metal containing [e.g., substrate, foil, film, coating, etc.]
• CPC Class Codes: Y10T 428/31786 Of polyester [e.g., alkyd, etc.]

Abstract

The invention relates to protective coating systems derived from a functional polyester resin, a cross-linker and a phenol-formaldehyde resin. Also provided is a method of coating a metal substrate using the protective coating systems to produce a cross-linked protective coating. Further provided is a composite material prepared with the coating system and, in certain embodiments, useful in fabricating metal foodstuffs storage containers. The composite material may be particularly useful in fabricating foodstuffs storage containers and “easy-open” end closures wherein the cross-linked protective coating contacts the foodstuffs.

Claims

1. A composition comprising:

a hydroxyl-functional polyester resin,

a carboxyl-functional polyester resin,

a cross-linker, and

one or more phenol-formaldehyde resin;

wherein the composition is in the form of a hardenable coating composition.

2. The composition of claim 1, wherein the composition is substantially free of BPA, BPF, BADGE and BFDGE.

3. The composition of claim 1, wherein the hydroxyl-functional polyester resin exhibits a hydroxyl number from about 5 to about 200 milligrams KOH per gram.

4. The composition of claim 1, wherein the hydroxyl-functional polyester resin exhibits a number average molecular weight from about 1,000 to about 7,500 Daltons.

5. The composition of claim 1, wherein the hydroxyl-functional polyester resin is present in an amount from about 75 to about 90 percent by weight of the hardenable coating composition on a non-volatile solids basis.

6. The composition of claim 1, wherein the carboxyl-functional polyester resin exhibits an acid number from about 100 to about 300 milligrams KOH per gram.

7. The composition of claim 1, wherein the carboxyl-functional polyester resin exhibits a number average molecular weight from about 2,000 to about 5,000 Daltons.

8. The composition of claim 1, wherein the carboxyl-functional polyester resin is present in an amount from about 0.1 to about 5 percent by weight of the hardenable coating composition on a non-volatile solids basis.

9. The composition of claim 1, wherein the cross-linker is selected from one or more of the group consisting of a phenolast cross-linker, an aminoplast cross-linker and a blocked isocyanate cross-linker.

10. The composition of claim 1, wherein the cross-linker is a blocked isocyanate cross-linker present in an amount from about 1 to about 5 percent by weight of the hardenable coating composition on a non-volatile solids basis.

11. The composition of claim 1, wherein the phenol-formaldehyde resin is present in an amount from about 1 to about 5 percent by weight of the hardenable coating composition on a non-volatile solids basis.

12. The composition of claim 1, further comprising a resole-formaldehyde resin.

13. The composition of claim 12, wherein the resole-formaldehyde resin is present in an amount from about 2 to about 5 percent by weight of the hardenable coating composition on a non-volatile solids basis.

14. The composition of claim 1, further comprising a substantially nonaqueous carrier liquid.

15. The composition of claim 1, further comprising from about 0.1 to about 5 weight percent of a catalyst on a non-volatile solids basis.

16. The composition of claim 1, further comprising a pigment.

17. A composition, comprising:

one or more functional polyester resin,

a blocked isocyanate cross-linker, and

one or more phenol-formaldehyde resin;

wherein the composition is in the form of a hardenable coating composition.

18. The composition of claim 17, wherein the one or more functional polyester resin comprises one or more functional groups selected from hydroxyl and carboxyl groups.

19. A method of applying a hardenable coating composition to a metal substrate, comprising:

applying a first hardenable coating composition to at least one surface of a substrate,

applying a second hardenable coating composition over the first hardenable coating composition, said second hardenable coating composition including;

a hydroxyl-functional polyester resin,

a carboxyl-functional polyester resin,

a cross-linker, and

a phenol-formaldehyde resin; and

curing the first and second hardenable coating compositions to provide a hardened composite coating on the substrate.

20. The method of claim 19, wherein the first hardenable coating composition is substantially identical in chemical composition to the second hardenable coating composition.

21. The method of claim 19, wherein each of the first and second hardenable coating compositions is applied at a coating weight of from about 6 to about 12 grams per square meter on a non-volatile solids basis.

22. A metal foodstuffs container having at least an interior surface coated with a hardened coating composition produced according to the method of claim 19.

23. A metal foodstuffs container according to claim 22, wherein the metal foodstuffs container is a multi-part can having at least one easy-open end closure with at least an interior surface coated with a hardened coating composition derived from:

a hydroxyl-functional polyester resin,

a carboxyl-functional polyester resin,

a cross-linker, and

a phenol-formaldehyde resin.