AQUEOUS PAINTS AND PROCESS FOR MANUFACTURING CAR COATING VARNISHES

摘要

The invention relates to aqueous coatings comprising (A) a water-thinnable polyacrylate resin and (B) a blocked polyisocyanate or a mixture of blocked polyisocyanates, the water-thinnable polyacrylate resin (A) being obtainable by (I) adding a component (a) consisting of (a1) 40 to 86.75% by weight of a (meth)acrylic acid ester which differs from (a2), is copolymerizable with (a2), (a3), (b1) and (b2) and is essentially free from carboxyl groups, or a mixture of such (meth)acrylic acid esters, and (a2) 12 to 50% by weight of an ethylenically unsaturated monomer which is copolymerizable with (a1), (a3), (b1) and (b2), carries at least one hydroxyl group per molecule and is essentially tree from carboxyl groups, or a mixture of such monomers, and (a3) 0 to 25% by weight of an ethylenically unsaturated monomer which is copolymerizable with (a1), (a2), (b1) and (b2), is essentially free from carboxyl groups and differs from (a1) and (a2), or a mixture of such monomers, and a component (b) consisting of (b1) 1.25 to 15% by weight of an ethylenically unsaturated monomer which carries at least one carboxyl group per molecule and is copolymerizable with (a1), (a2), (a3) and (b2), or a mixture of such monomers, and (b2) 0 to 60% by weight of an ethylenically unsaturated monomer which is free from carboxyl groups and is copolymerizable with (a1), (a2), (a3) and (b1), or a mixture of such monomers, successively or in portions in alternation to an organic solvent or solvent mixture and polymerizing these components in the presence of at least one polymerization initiator, and (II) when the polymerization has ended, at least partly neutralizing the resulting polyacrylate resin and dispersing it in water, the sum of the amounts by weight of (a1), (a2), (a3), (b1) and (b2) always giving 100% by weight, and the nature and amount of (a1), (a2), (a3), (b1) and (b2) being chosen such that the polyacrylate resin has a hydroxyl number of 60 to 180, an acid number of 10 to 100, and a glass transition temperature (TG) of -40.degree.C to +60.degree.C.