| abstract |
Polyorganosiloxane having the substructuren where R⁸ is a divalent group generated by an addition reaction between SiH and acryloxy, methacryloxy, or alkenyl group and R⁹ is acryloxy, methacryloxy, or alkenyl, is prepared by an addition method in which an organopolysiloxane having two kinds of unsaturated groups selected from acryloxy, methacryloxy, and alkenyl and organohydrogenpolysiloxane are reacted in the presence of a platinum-type catalyst. These organopolysiloxanes are prepared without gelation and the method is highly efficient. n Radiation-curable compositions based on the polyorganosiloxane are characterized by a rapid cure upon exposure to radiation, while resisting curing inhibition even in the presence of oxygen, to give a cured material whose cured surface is slightly subject to time-dependent changes, and in particular whose peeling or release force undergoes little variation with the passage of time. |