COATING COMPOSITIONS AND PROCESS FOR THE PRODUCTION OF MULTILAYER COATINGS

摘要

An aqueous coating composition, comprising A) at least one water-dilutable hydroxy-functional binder and B) at least one polyisocyanate crosslinking agent with free isocyanate groups, wherein component A) comprises A1) 40-95 wt.% of at least one water-dilutable hydroxy-functional (meth)acrylic copolymer with a hydroxyl value of 60-250 mg of KOH/g and an acid value of 5-50 mg of KOH/g, which is obtained by free-radical copolymerization performed in a non-aqueous phase, wherein the ratio of primary hydroxyl groups to secondary hydroxyl groups in the (meth)acrylate copolymer A1) is 1: 0.1 to 1 :1.2 and at least 80% of the secondary hydroxyl groups result from reaction products of a monoepoxy ester and an unsaturated acid-functional monomer, and A2) 5-60 wt.% of at least one water-dilutable polyester oligomer, wherein the total of the weight percentages of component A1) and A2) add up to 100 wt.% and wherein the free-radical polymerization for the production of component A1) is performed at least in part in the presence of component A2) and/or wherein component A2) is added during polymerization or after completion of polymerization.