High-solids polyurethane enamel coating composition

Claim 1

A coating composition, capable of curing at ambient temperatures, of a mixture of a polymer blend and a solvent for the polymer blend wherein the blend is 65-90% by weight of the mixture and consists essentially of (a) 25-45% by weight, based on the weight of the blend, of an organic polyisocyanate; (b) 5-25% by weight, based on the weight of the blend, of a copolymer of (1) a hydroxyalkyl ester of acrylic or methacrylic acid wherein the alkyl group has 2-10 carbon atoms and wherein the hydroxyalkyl ester is 25-35% by weight of the copolymer, and (2) at least one other ethylenically unsaturated monomer that is copolymerizable with the hydroxyalkyl ester but that is free of functional groups reactive with the polyisocyanate at ambient temperatures, wherein this monomer is selected from the group consisting of vinyl chloride, vinylidene chloride, ethylene, propylene, vinyl acetate, butadiene, styrene, α-methyl styrene, dibutyl maleate, C 1 -C 12 alkyl esters of acrylic acid, C 1 -C 12 alkyl esters of methacrylic acid, and mixtures of these wherein the copolymer has a hydroxyl content of 2-6% by weight; and (c) 40-60% by weight, based on the weight of the blend, of a saturated polyester polyol that is the reaction product of (1) pentaerythritol and at least one branched-chain glycol wherein the molar ratio of glycol to pentaerythritol is from 2:1 to 6:1, (2) an aromatic or aliphatic monocarboxylic acid selected from the group consisting of benzoic acid, paratertiary butyl-benzoic acid, triethyl benzoic acid, toluic acid, phenylacetic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and mixtures of these, and (3) a mixture of an aromatic and a aliphatic dicarboxylic acid wherein the molar ratio of aromatic acid to aliphatic acid is from 2:1 to 6:1, wherein the polyol has a hydroxyl content of 5-9% by weight.