Patent ID: 7163978

Claim:
A waterborne anti-chipping coating composition for automobiles comprising fine polymer particles dispersed in an aqueous medium and an inorganic filler, characterized in that the fine polymer particles comprise: (A) 50 to 90% by weight of synthetic rubber polymer particles containing 50 to 90% by weight of a repeating unit derived from a conjugated diolefin monomer and having a glass transition temperature of −20° C. or lower and (B) 10 to 50% by weight of acrylic polymer particles having a gel content of 40–75% by weight, containing 50% by weight or more of a repeating unit derived from an acrylic ester and/or a methacrylic ester and having a glass transition temperature of 0° C. or lower; wherein the synthetic rubber polymer particles are those produced by aqueous emulsion polymerization of the following monomers (a1) to (a4) under pressure: (a1) a conjugated diolefin monomer, (a2) a methacrylic ester monomer, a vinyl cyanide monomer and/or aromatic vinyl monomer and, if desired optionally, (a3) a monomer having a carboxyl group in the molecule thereof and, if desired, (a4) a monomer other than the monomers (a1), (a2), and (a3) and copolymerizable with the monomers (a1), (a2) and (a3); wherein the methacrylic ester monomer, the vinyl cyanide monomer and/or the aromatic vinyl monomer (a2) comprise at least two monomers selected from methyl methacrylate, acrylonitrile, and/or styrene; and wherein the synthetic rubber polymer particles have a gel content of 70 to 95% by weight.