Patent No. U.S. 6,541,070 B2
Nippon Paint Co. has been granted a patent for a method of forming a composite coating film comprising applying a water-based base coat composition to a substrate and then applying a clear coat composition to it, and baking at 120° to 160° C. The water-based basecoat composition comprises a pigment and a resin emulsion obtained by emulsion polymerization of an a,b-ethylenically unsaturated monomer mixture. The a,b-ethylenically unsaturated monomer mixture has an acid value of 3 to 50 mg KOH/g and a hydroxyl value of 10 to 150 mg KOH/g and contains at least 65% by weight of a (meth)acrylic ester whose ester moiety contains 1 or 2 carbon atoms.