Coatings derived from polyesters crosslinked with melamine formaldehyde
View Patent ↗A coating composition is based on a polyester mixed with an alkyl-etherified melamine formaldehyde. The coating composition is partially cured in a first stage to provide a thermoformable partially cured, tack-free, non-blocking, coating layer, followed by application to generally a contoured substrate and thermoforming to conform thereto. The contoured partially cured coating layer is then heat cured to form a cured coating. A hydroxyl-terminated polyoxetane containing repeat units derived from oxetane monomers having one or two pendent —CH 2 —O—(CH 2 ) n —Rf groups, wherein Rf is partially or fully fluorinated, can be esterified with polyester-forming reactants to form a fluorinated polyoxetane-modified polyester.
1. A method of providing an article with a thermoformed exterior, outward facing surface, said method comprising:
a) thermoforming to an exterior surface of said article a composite so as to provide a laminate, said composite comprising a substrate bearing a coating on a surface opposite the side of said substrate contacting said exterior surface of said article; and
b) heating said laminate to a temperature of at least 83° C. for at least 30 seconds so as to cure said laminate, thereby providing said thermoformed surface,
said coating being the partially crosslinked product of ingredients that comprise a polyester, an alkyl-etherified melamine formaldehyde compound and, based on the combined weight of the polyester and alkyl-etherified melamine formaldehyde compound from about 1 to about 15% of a thermally activatable catalyst.
2. The method of claim 1 wherein said article is non-planar.
3. The method of claim 2 wherein said non-planar article is a piece of furniture.
4. The method of claim 1 wherein said substrate comprises poly(vinyl chloride).
5. The method of claim 4 wherein said laminate is heated to a temperature of from 88° to 149° C.
6. The method of claim 1 wherein said alkyl-etherified melamine formaldehyde compound comprises the reaction product of a melamine formaldehyde and at least two C 1 -C 6 alkyl alcohols.
7. The method of claim 6 wherein said at least two C 1 -C 6 alkyl alcohols comprise two alcohols having at least a two carbon atom differential in their chain lengths.
8. The method of claim 7 wherein said at least two C 1 -C 6 alkyl alcohols comprise methanol and propyl alcohol.
9. The method of claim 6 wherein said at least two C 1 -C 6 alkyl alcohols comprise three alcohols having at least a two carbon atom differential in their chain lengths.
10. The method of claim 9 wherein said at least two C 1 -C 6 alkyl alcohols comprise methanol and butyl alcohol.
11. The method of claim 1 wherein said melamine formaldehyde of said alkyl-etherified melamine formaldehyde compound comprises at least three methylol groups.
12. The method of claim 11 wherein said melamine formaldehyde of said alkyl-etherified melamine formaldehyde compound comprises at least four methylol groups.
13. The method of claim 12 wherein said melamine formaldehyde of said alkyl-etherified melamine formaldehyde compound comprises at least five methylol groups.
14. The method of claim 13 wherein said melamine formaldehyde of said alkyl-etherified melamine formaldehyde compound comprises six methylol groups.
15. The method of claim 11 wherein at least one of said at least three methylol groups is alkyl etherified.
16. The method of claim 11 wherein each of said at least three methylol groups is alkyl etherified.
17. The method of claim 11 wherein said polyester comprises fluorinated polyoxetane units.
18. The method of claim 17 wherein each of said fluorinated oxetane units comprises a pendent —CH 2 —O—(CH 2 ) n Rf group where n is an integer of from 1 to 3 inclusive.