Oligomeric urethane acrylates, processes for their preparation and their use

Oligomeric urethane acrylates containing on average per molecule at least two structural units of the general formula I: R {-X-CH in which the index and the variables have the following meanings: n is a number from 1 to 6; R is a monovalent to hexavalent, low-molecular or oligomeric organic radical; X is oxygen atom or -C (O) -O-radical which is attached via the carbon atom with the group R; and R Processes for their preparation and their use.