Radiation curable organosiloxane gel compositions

Claim 1

An organosiloxane gel composition that cures upon exposure to ultraviolet radiation, said composition comprising (1) a polyorganosiloxane consisting essentially of 80 to 97 mole percent of (CH 3 ) 2 SiO units, 2 to 10 mol percent of CH 3 SiO 1 .5 units, 1 to 6 mol percent of (CH 3 ) 3 SiO 0 .5 units and 0.2 to 4 mol percent of units represented by the formula (CH 3 ) a R 1 SiO.sub.(3-a)/2, where R 1 represents 3-cyclohexenyl, cyclohexenylethyl or CH 2 ═CH(CH 2 ) x , a is 1 or 2, and X represents 0 or an integer from 1 to 6, inclusive; (2) as the curing agent for said composition, a liquid organic compound containing an average of at least two mercapto groups per molecule or a liquid mercaptoalkyl substituted polydiorganosiloxane containing an average of at least two repeating units per molecule corresponding to the formula ##STR2## where R 2 represents a mercaptoalkyl radical, R 3 represents a monovalent hydrocarbon or halohydrocarbon radical, and said curing agent is compatible with the other ingredients of said composition: and 3) a photointiator in an amount sufficient to promote curing of said composition in the presence of ultraviolet radiation. where the molar ratio of mercapto groups to alkenyl radicals in said composition is 1 or less.