Method for multilayer coatings with self-crosslinking graft polyurethane copolymers, self-crosslinking polyurethanes and graft copolymers thereof

摘要

The invention relates to a method for producing chromophore and/or effect giving multilayer lacquers according to the wet-on-wet method. A water base lacquer is applied which contains at least one graft copolymer containing (A) at least one (meth)acrylate copolymer and (B) at least one polyurethane. The graft copolymer can be produced by (1) dispersing at least one hydrophilic or hydrophobic self cross-linking polyurethane (B) with a statistical average of at least one terminal and/or at least one lateral olefinically unsaturated group and at least one blocked isocyanate group per molecule in an aqueous medium. (2) A mixture of a at least one monomer (a1) with at least one isocyanate reactive functional group at last one monomer (a2) that can be copolymerised therewith is subsequently radically copolymerised in an emulsion in the presence of the polyurethane (B) or the polyurethanes (B). A powder slurry transparent lacquer layer is added to the resulting base lacquer layer. The base lacquer layer and the transparent lacquer layer are hardened together. The invention also relates to novel hydrophilic or hydrophobic self cross-linking polyurethanes (B) with at least one lateral and/or at least one terminal olefinically unsaturated group and at least one lateral blocked isocyanate group per molecule and graft copolymers on the basis of said polyurethanes (B) as well as the use thereof.