Process for the preparation of low-viscosity, water-dilutable urethane (meth)acrylates

A process for preparing a low-viscosity, water-dilutable polyurethane (meth)acrylate, comprising reacting components (a), (b), and (d)

• (a) at least one organic polyisocyanate with two isocyanate functions;
• (b) at least one polyoxyalkylene polyol based on a starter molecule which comprises at least three hydroxy functions and is partially reacted by esterification with (meth)acrylic acid such that on average 0.2 to 1.5 hydroxy functions still remain;
• (d) at least one compound which has at least one group which is reactive towards isocyanate and at least one ionic or potentially ionic function;
• to form said low-viscosity, water-dilutable polyurethane (meth)acrylate;
• wherein
• the reaction product of components (a), (b), and (d) has an NCO content of less than 0.5 weight %, and
• said polyurethane (meth)acrylate is not prepared from components selected from the group consisting of
• (i) organic polyisocyanates with three or more isocyanate functions, and
• (ii) polyoxyalkylene polyols which have a maximum of two hydroxy functions but no further groups which can be crosslinked by actinic radiation.