Chip resistant coating compositions containing epoxy-polyester graft copolymers

An organic solvent based, thermosetting coating composition comprising:

• (I) hydroxy functional epoxy-polyester graft copolymer having a number average molecular weight (M.sub.n) of between about 2,000 and about 20,000, said copolymer being the product of polymerization of epsilon-caprolactone monomers in the presence of hydroxy functional epoxy ester resin precursor having reactive hydroxyl groups, said epsilon-caprolactone monomers are polymerized and reacted with the hydroxyl groups of the precursor to form pendent hydroxyl terminated polymer chains wherein the polymerization reaction mixture comprises between about 10 and about 80 weight percent said hydroxy functional epoxy ester resin precursor and between about 90 and about 20 weight percent said lactone monomers, said precursor being the reaction product of:
• (1) modified diepoxide being the product of polymerization of epsilon-caprolactone monomers in the presence of the reaction product of (a) diepoxide selected from the group consisting of bisphenol-A epichlorohydrin epoxy resin, hydantoin epoxy resin, cyclic and acyclic aliphatic diepoxide and mixtures thereof, (b) diphenol selected from bisphenol-A, bisphenol B, and bisphenol-F, and (c) dicarboxylic acid consisting of substantially saturated, aliphatic, acyclic dimer acids of 4-42 carbons and mixtures thereof, said diepoxide being reacted substantially simultaneously with said diphenol and dicarboxylic acid in amounts sufficient to give a weight per epoxide of between about 500 and about 2,500, wherein said epsilon-caprolactone monomers reacted to form said modified diepoxide and the combined said diphenol and dicarboxylic acid are employed in a molar ratio of at least 2:1, respectively;
• and
• (ii) hydroxy functional secondary amine bearing primary hydroxyl groups in chain termination reaction in about 1:1 equivalent ratio;
• and
• II. polyfunctional, hydroxy-reactive crosslinking agent selected from blocked polyisocyanate crosslinking agent comprising at least two isocyanate groups which have been blocked by reaction with an active hydrogen bearing blocking agent and aminoplast crosslinking agent.