Thermosetting acrylic copolymer compositions

Claim 1

In an aqueous thermosetting resinous coating composition of a dispersed acrylic copolymer containing active hydrogens selected from the class consisting of hydroxyl, primary amine, secondary amine, amido, thiol and carboxylic acid, and a curing agent stable in the presence of said acrylic polymer at room temperature but reactive with the active hydrogens of the acrylic polymer at an elevated temperature to form a cured product, the improvement comprising: an at least partially base neutralized acrylic polymer which has a weight average molecular weight of about 15,000 to 100,000, as determined by gel permeation chromatography using a polystyrene standard, and which is prepared from copolymerizing in the presence of a free radical initiator: (A) 20 to 40 percent by weight of a vinyl aromatic compound, (B) 10 to 35 percent by weight of an alkyl ester of methacrylic acid having 1 to 3 carbon atoms in the alkyl group, (C) 15 to 40 percent by weight of an alkyl ester of acrylic acid having 2 to 12 carbon atoms in the alkyl group or an alkyl ester of methacrylic acid having 4 to 12 carbon atoms in the alkyl group, (D) 2 to 20 percent by weight of an acrylic monomer containing active hydrogens selected from the class consisting of hydroxyl, primary amine, secondary amine, amido and thiol, (E) 2 to 15 percent by weight of an alpha, beta-ethylenically unsaturated carboxylic acid, (F) 2 to 20 percent by weight of an alkyl ester of an alpha, beta-ethylenically unsaturated carboxylic acid having 14 to 20 carbon atoms in the alkyl group, the percentage by weight of the acrylic monomers presented above being based on total weight of acrylic monomers; said coating composition containing from 20 to 60 percent by weight resin solids.