Patent ID: 6531535
Filing Date: 2003-03-11
Classification: C08F,C08G,C09D

Abstract:
An aqueous coating composition comprising at least one hydroxy-functional copolymer P, which is present as a dispersion and/or solution in water and has an acid number, based on resin solids, of <30 mg KOH/g, and one or more crosslinking resins, wherein copolymer P is obtained by successively carrying out process steps A-D:A): initially introducing A1) 0 to 40 wt. %, based on the solids content of copolymer P, of a hydroxy-functional hydrophobic copolymer having an acid number, based on solids, of <10 mg KOH/g, which is not sufficient for dispersing or dissolving A1 in water, an OH content, based on solids, of 0.5 to 7 wt. %, a number average molecular weight of 1,500 to 20,000 and a content of organic solvents of 0 to 60 wt. %, based on the weight of A1, and A2) 0 to 15 wt. %, based on the solids content of copolymer P, of additional organic solvents, into a reaction vessel and heating the reaction mixture to the polymerization temperature before, during or after step A, B): metering in 5 to 40 wt. %, based on the weight of B1+C2+D2, of a free-radical initiator B1, optionally dissolved in an organic solvent, C): simultaneously metering in 40 to 80 wt. %, based on the solids content of copolymer P, of a hydrophobic monomer mixture C1 which is substantially e from carboxyl groups and comprises c1) 30 to 90 wt. % of (meth)acrylic acid esters with C1 to C18-hydrocarbon radicals in the alcohol portion, vinylaromatics and/or vinyl esters, c2) 10 to 60 wt. % of hydroxy-functional monomers and c3) 0 to 2 wt. % of monomers containing acid groups, wherein the percentages of c1+c2+c3 adds up to 100% and a free-radical initiator C2 in amount of 25 to 90 wt. %, based on the weight of B1 +C2+D2, optionally dissolved in an organic solvent, and D): simultaneously metering in 5 to 50 wt. %, based on the solids content of copolymer P, of a hydrophilic monomer mixture D1 comprising d1) 10 to 70 wt. % of (meth)acrylic acid esters with C1 to C18-hydrocarbon radicals in the alcohol portion and/or vinylaromatics and/or vinyl esters, d2) 10 to 70 wt. % of hydroxy-functional monomers and d3) 5 to 30 wt. % of acid-functional monomers, wherein the percentages of d1+d2+d3 adding up to 100%, and a free-radical initiator D2 in an amount of 5 to 40 wt. %, based on the weight of B1+C2+D2, optionally dissolved in an organic solvent, wherein the total amount of B1+C2+D2, based on the solids content of copolymer P, is 0.8 to 5.0 wt. %.