Polyester-Based Coating Composition for Metal Substrates

• US 20130224413A1
• Filed: 04/03/2013
• Published: 08/29/2013
• Est. Priority Date: 10/15/2010
• Status: Active Grant

• Current Assignee: Sherwin-Williams Company
• Original Assignee: Valspar Sourcing, Inc. (Sherwin-Williams Company)
• Inventors: Prouvost, Benoit, Stenson, Paul
• Granted Patent: US 9,187,213 B2
• Time in Patent Office: Days
• US Class Current: 428/35.8
• CPC Class Codes: B65D 1/12 Cans, casks, barrels, or drums
• CPC Class Codes: B65D 25/14 Linings or internal coatings of containers made by folding or erecting blanks made of paper B65D5/56 ; linings for domestic water storage heaters F24H1/183
• CPC Class Codes: C08J 2467/02 Polyesters derived from dicarboxylic acids and dihydroxy compounds C08J2467/06 takes precedence
• CPC Class Codes: C08J 7/0427 with only one layer of a composition containing a polymer binder with more layers C08J7/042
• CPC Class Codes: C08J 7/043 Improving the adhesiveness of the coatings per se, e.g. forming primers adhesives in the form of films or foils characterised by the primer layers between the polymer carriers and the adhesives C09J7/50
• CPC Class Codes: C08J 7/046 Forming abrasion-resistant coatings; Forming surface-hardening coatings
• CPC Class Codes: C09D 167/02 Polyesters derived from dicarboxylic acids and dihydroxy compounds C09D167/06 takes precedence
• CPC Class Codes: Y10T 428/1355 Elemental metal containing [e.g., substrate, foil, film, coating, etc.]
• CPC Class Codes: Y10T 428/31681 Next to polyester, polyamide or polyimide [e.g., alkyd, glue, or nylon, etc.]

Abstract

The present invention provides novel packaging articles, e.g., food and beverage cans, having a novel coating composition applied to at least a portion of a surface thereon. In preferred embodiments, the coating composition includes at least a film-forming amount of a copolyester resin having a backbone that includes one or more soft segments and a plurality of hard segments. The copolyester resin preferably has a glass transition temperature from about from about 10° C. to about 50° C. The present invention also provides a method for making coated articles.

Claims

1. An article, comprising:

a food or beverage container, or a portion thereof, having a metal substrate; and

a coating composition applied on at least a portion of the metal substrate, wherein the coating composition includes;

a copolyester resin having a glass transition temperature from 10°

C. to 50°

C. and the following structure;

(R¹)_r-([HARD]-X_s-[SOFT]-X_s)_n—

(R²)_r

wherein;

[HARD] independently denotes a hard segment,

[SOFT] independently denotes a soft segment,

each X, if present, is independently a divalent organic group,

each s is independently 0 or 1,

n is at least 2,

R¹, if present, is a reactive functional group, an organic group, or a soft segment that optionally includes a terminal reactive functional group or a divalent linkage group attaching the soft segment to a hard segment,

R², if present, is a reactive functional group, an organic group, or a hard segment that optionally includes a terminal reactive functional group, and

each r is independently 0 or 1; and

a crosslinker.

2. The article of claim 1, wherein the hard segments are oligomer segments, polymer segments, or a combination thereof.

3. The article of claim 1, wherein the copolyester resin has a glass transition temperature from 15°

C. to 35°

C.

4. The article of claim 1, wherein the hard segments are derived from a polyester oligomer or polymer having a number average molecular weight of at least about 500 and a glass transition temperature of from 10°

C. to 100°

.

6. The article of claim 1, wherein the soft segment comprises a substituted or unsubstituted hydrocarbon segment having at least four backbone carbon atoms.

7. The article of claim 1, wherein the soft segment comprises a linear or branched hydrocarbon moiety that includes 6 to 36 carbon atoms.

8. The article of claim 1, wherein the soft segment is derived from adipic acid, azelaic acid, a fatty-acid-based diacid, sebacic acid, succinic acid, glutaric acid, or a derivative or mixture thereof.

9. The article of claim 1, wherein:

s is 1, and

X includes an ester linkage.

10. The article of claim 9, wherein r is 1 and R¹ and R² are each a reactive functional group.

11. The article of claim 1, wherein the copolyester resin is a reaction product of reactants including:

a hydroxyl-functional polyester oligomer or polymer, and a diacid or diacid equivalent, wherein the weight ratio of polyester oligomer or polymer to diacid or diacid equivalent is from 8;

1 to 20;

1.

12. The article of claim 1, wherein the coating composition includes, based on total resin solids, at least 60 weight percent of the copolyester resin.

13. The article of claim 1, wherein the coating composition further comprises, based on total resin solids, from 2 to 20 weight percent of an acrylate copolymer.

14. The article of claim 13, wherein the acrylate copolymer includes one or more glycidyl groups.

15. The article of claim 1, wherein the copolyester resin has an acid number less than 10 and a hydroxyl number of from 10 to 50.

17. The article of claim 1, wherein the copolyester resin constitutes greater than 90 weight percent of the total amount of polyester present in the coating composition, based on total polyester solids.

18. The article of claim 1, wherein the coating composition is substantially free of bound bisphenol A and aromatic glycidyl ether compounds.

19. The article of claim 1, wherein the article includes a riveted beverage can end having the coating composition applied on at least a portion of the can end.

5. (canceled)

16. (canceled)

20. A method, comprising:

providing a coating composition that is suitable for use as a food-contact packaging coating when suitably cured, the coating composition comprising;

a copolyester resin having a glass transition temperature from 10°

C. to 50°

C. and the following structure;

(R¹)_r-([HARD]-X_s-[SOFT]-X_s)_n—

(R²)_r

wherein;

[HARD] independently denotes a hard segment,

[SOFT] independently denotes a soft segment,

each X, if present, is independently a divalent organic group,

each s is independently 0 or 1,

n is at least 1,

R¹, if present, is a reactive functional group, an organic group, or a soft segment that optionally includes a terminal reactive functional group or a divalent linkage group attaching the soft segment to a hard segment,

R², if present, is a reactive functional group, an organic group, or a hard segment that optionally includes a terminal reactive functional group,

each r is independently 0 or 1, and

the copolyester resin includes two or more hard segments; and

a crosslinker; and

applying the coating composition to at least a portion of a planar metal substrate suitable for use in forming a food or beverage container or a portion thereof.

21. A coating composition, comprising:

at least 60 weight percent, based on total resin solids, of a copolyester resin having a glass transition temperature from 10°

C. to 50°

C. and the following structure;

(R¹)_r-([HARD]-X_s-[SOFT]-X_s)_n—

(R²)_r

wherein;

[HARD] independently denotes a hard segment having a glass transition temperature of from 10°

C. to 100°

C.,

[SOFT] independently denotes a soft segment,

each X, if present, is independently a divalent organic group,

s is 1,

n is 2 or more,

R¹, if present, is a reactive functional group, an organic group, or a soft segment that optionally includes a terminal reactive functional group or a divalent linkage group attaching the soft segment to a hard segment,

R², if present, is a reactive functional group, an organic group, or a hard segment that optionally includes a terminal reactive functional group, and

each r is independently 0 or 1; and

a crosslinker;

wherein the coating composition is suitable for use as a food-contact packaging coating when suitably cured.

22. The coating composition of claim 21, wherein the coating composition, when present on a riveted beverage can end at a dry film thickness of 7 milligrams per square inch, passes less than 1 milliamps of current after being exposed for 4 seconds to a room-temperature electrolyte solution containing 1% by weight of NaCl dissolved in water.

23. (canceled)