Production of colored and-or decorative effect multi layer coatings, e.g. for painting cars, involves overcoating basecoat with clearcoat comprising special dual-cure aqueous polyurethane dispersion

摘要

The invention relates to a method for producing a coloured and/or decorative-effect multi-layered coating on a primed or unprimed substrate. According to said method, a base lacquer layer and a clear lacquer layer are applied one on top of another, the clear lacquer containing an aqueous, blocked isocyanate group which in turn consists of or contains a polyurethane dispersion. The polyurethane consists of aliphatic polyisocyanates, compounds containing functional groups reactive to isocyanate and bonds which can be activated by actinic radiation, low-molecular aliphatic compounds containing functional groups reactive to isocyanate and dispersing functional groups, in addition to neutralising agents for said dispersing functional groups. The blocked isocyanate groups are introduced into the polyurethane dispersion by adding blocked polyisocyanates and/or by reacting blocking agents for isocyanate groups and/or compounds containing blocked isocyanate groups with the polyurethane prepolymers containing isocyanate groups. The aqueous clear lacquer can be a powder slurry.