Epoxy-polyester graft copolymers suitable for chip resistant coating composition I

Claim 1

A hydroxy functional epoxy-polyester graft copolymer suitable for use in a thermosetting composition, which copolymer has a number average molecular weight (M n ) of between about 2,000 and about 20,000, said copolymer being the product of polymerization of lactone monomers in the presence of hydroxy functional epoxy ester resin precursor having reactive hydroxyl groups, said lactone monomers being polymerized and reacted with hydroxyl groups of the precursor without chain extension 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: (i) modified diepoxide being the product of polymerization of lactone monomers in the presence of diepoxide which has been chain extended substantially simultaneously with diphenol and dicarboxylic acid, 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 2500, wherein said lactone monomers reacted to form said modified diepoxide and the combined said diphenol and dicarboxylic acid, are employed in a molar ratio of at least about 2:1, respectively; and (ii) hydroxy functional secondary amine in chain termination reaction in about 1:1 equivalent ratio.