Patent ID: 6458439
Filing Date: 2002-10-01
Classification: B05D,C08K,C08L,C09D,Y10T

Abstract:
A method of coating a metal substrate comprising:(a) heating the metal substrate to a temperature of about 60Â° C. to about 300Â° C. to provide a preheated metal substrate; (b) heating a solid, thermoplastic coating composition to a sufficient temperature to melt the coating composition and provide a molten coating composition, said coating composition comprising: (i) about 50% to about 100%, by total weight of the composition, of a blend of polyesters comprising (A) a first polyester having a weight average molecular weight of about 10,000 to about 80,000 and a glass transition temperature of greater than 45Â° C. to about 100Â° C., and (B) a second polyester having a weight average molecular weight of about 10,000 to about 70,000 and a glass transition temperature of about âˆ’10Â° C. to about 45Â° C., wherein the Tg of the first polyester is about 5 C.Â° to about 60 C.Â° higher than the Tg of the second polyester, and wherein the first polyester and the second polyester are present in a weight range of about 1 to 6 to about 1 to 9; (ii) 0% to about 25%, by total weight of the composition, of a modifying resin selected from the group consisting of an epoxy or phenoxy resin having an epoxy equivalent weight of about 500 to about 15,000, an acrylic resin having a weight average molecular weight of about 15,000 to about 100,000, a polyolefin resin having a weight average molecular weight of about 15,000 to about 1,000,000, and mixtures thereof; (c) extruding the molten coating composition onto a surface of the preheated metal substrate to provide a layer of molten coating composition about one to about 40 microns thick on the preheated metal substrate and provide a coated metal substrate; and (d) heating the coated metal substrate at a temperature of about 120Â° C. to about 550Â° C. for about 5 to about 30 seconds.