Polyurethane metallic enamel

Claim 1

A coating composition having a solids content of 5-60% by weight in an organic liquid; wherein the solids consist essentially of (1) 50-95% by weight of an acrylic polymer having a backbone consisting essentially of polymerized monomers of the group of methyl methacrylate, styrene or mixtures thereof and polymerized ethylenically unsaturated ester monomers that form ester groups pending from the carbon atoms of the polymer backbone and comprise about 10 to 75% of the total weight of the polymer and consisting essentially of ester group (A) ##STR8## and ester group (B) selected from the group consisting of ##STR9## or mixtures thereof, wherein the molar ratio of ester group (A) to ester (B) is from about 1:1.5 to 1:2.5; and wherein R 1 is a saturated hydrocarbon group having 2-4 carbon atoms, R 2 is phenylene, R 3 is a tertiary hydrocarbon group having 8 through 10 carbon atoms; (2) 1-15% by weight of cellulose acetate butyrate having a butyryl content of about 50-60% by weight, a hydroxyl content of about 1.0-3.0% by weight, and a viscosity of 0.02-0.5 seconds measured at 25° C. according to ASTM D-1343-56; (3) 0.05-1.0% by weight of an alkyl acid phosphate having 1-12 carbon atoms in the alkyl group; (4) 0.2-20% by weight of aluminum flake pigment; (5) 0.01-5% by weight of an ultraviolet light absorbing agent from the group of a substituted benzotriazole, a substituted benzophenone or a mixture thereof; (6) 0.01-0.10% by weight of an alkyl tin laurate catalyst; and (7) 3.73-48.73% by weight of a polyisocyanate of the biuret of an alkylene diisocyanate having 1-6 carbon atoms in the alkylene group.