US Patent 7666970 Radiation-curing binders and a process for their preparation

The invention relates to a process for preparing binders which contain 1) allophanate groups, 2) groups that react with ethylenically unsaturated compounds with polymerization on exposure to actinic radiation (radiation-curing groups) and 3) optionally NCO-reactive groups, by reacting at temperatures ≦130° C.A) one or more NCO-functional compounds containing uretdione groups withB) one or more compounds that contain isocyanate-reactive groups and groups that react with ethylenically unsaturated compounds with polymerization on exposure to actinic radiation (radiation-curing groups), and thenC) with one or more saturated, hydroxyl-containing compounds other than B),at least one of these compounds having an OH functionality of ≧2, in the presence ofD) a catalyst containing one or more ammonium salts or phosphonium salts of aliphatic or cycloaliphatic carboxylic acids,the reaction with compounds C) taking place at least proportionally with the formation of allophanate groups.