Anodic electrocoating compositions

Claim 1

An aqueous electrocoating composition for electrocoating a paint film onto an anode substrate, the improvement comprising: a binder polymer comprising of (a) a styrene-allyl alcohol copolymer, (b) an unsaturated aliphatic fatty acid, (c) an α,β-unsaturated dicarboxylic acid or anhydride, and (d) an acid-functional acrylic copolymer, wherein said copolymer comprises on a weight basis: (a) between 20% and 40% of a styrene-allyl alcohol copolymer containing about 2.8 to 4.3 weight parts of copolymerized styrene per 1 weight part of copolymerized allyl alcohol wherein the copolymer has unreacted hydroxyl groups; (b) between 20% and 50% of an unsaturated aliphatic fatty acid esterified with said hydroxyl groups on said copolymer (a); (c) between 0% and 3% of an α,β-unsaturated dicarboxylic acid or anhydride esterified with said hydroxyl group on said copolymer (a); and (d) between 20% and 50% acid-functional acrylic copolymer containing double bonds coreacted by addition copolymerization with double bonds in the fatty acid and the dicarboxylic acid or anhydride (c), and said acid-functional groups on said acid-functional acrylic copolymer being neutralized whereby said binder polymer composition is solubilized in water to form an anodic electrocoating composition.