Weathering-stable, radiation-curable polyurethanes

The invention relates to water-dispersible, radiation-curable polyurethanes possessing improved weathering stability. The invention likewise relates to dispersions comprising such polyurethanes. The invention further relates to a method of coating substrates using the polyurethane dispersions, to the use of the polyurethanes or their dispersions as coating compositions for exterior applications, and to substrates coated with the polyurethanes. A water-dispersible, radiation-curable polyurethane composed essentially ofa) organic, aliphatic or alicyclic polyisocyanates,b) cycloaliphatic diols and/or cycloaliphatic diamines,c) compounds containing at least one isocyanate-reactive group and at least one free-radically polymerizable unsaturated group,d) compounds containing at least one isocyanate-reactive group and at least one dispersing-active group,e) if desired, compounds containing at least two isocyanate-reactive groups having a molecular weight