Fast ultraviolet radiation curing silicone composition

Claim 1

A cured product comprising a substrate with at least a surface which results from exposing to a curable amount of ultraviolet radiation a composition comprising a material which is storable in one package, is viscosity stable indicated by the failure of the 25° C. viscosity to double when heated at 100° C. for 24 hours, cures when exposed to ultraviolet radiation of 70 millijoules or less per square centimeter in one second or less where the ultraviolet radiation includes a wavelength of 365 nanometers, and is obtained by mixing (A) alkenyl functional, linear triorganosiloxy endblocked polydiorganosiloxane having a degree of polymerization of 30 to 1,000 where each silicon-bonded organic radical is selected from vinyl, methyl, phenyl, 3,3,3-trifluoropropyl, beta-(cyclohexenyl)ethyl, ethyl, cyclohexenyl, allyl, higher alkenyl radicals represented by the formula --R*(CH 2 ) r CH═CH 2 wherein R* is --(CH 2 ) s -- or --(CH 2 ) t CH═CH--, r has a value of 1, 2, or 3; s has a value of 3 or 6; and t has a value of 3, 4, or 5, and silacyclopentenyl, and having per molecule at least two silicon-bonded organic radicals selected from vinyl, beta-(cyclohexenyl)ethyl, cyclohexenyl, allyl, higher alkenyl radical and silacyclopentenyl, (B) mercapto functional crosslinker which is at least one material selected from mercapto functional polyorganosiloxanes and mercapto organic compounds, said mercapto functional polyorganosiloxanes are represented by the general formula R"R'.sub.2 SiO(R"'R'SiO).sub.x (R'RSiO).sub.y SiR'.sub.2 R" wherein each R is selected from mercaptoalkyl radicals having from 2 to 6 carbon atoms per radical; each R' is selected from methyl, phenyl, 3,3,3-trifluoropropyl, and ethyl; and each R" is selected from the radicals of --OH, R, and R'; and each R"' is selected from methyl and phenyl, on the average there being per molecule at least two mercaptoalkyl radicals, x is 0 or greater, y is 0 or greater, and the amount and kind of organic radicals represented by R, R', R", and R"' being of such a nature as to make (A) and (B) compatible, and said mercapto organic compounds have at least two mercapto groups per molecule, consisting of atoms of sulfur, carbon, and hydrogen, and optionally oxygen, having a molecular weight less than 1,000, and being of such a nature as to make (A) and (B) compatible, (C) photosensitizer, (D) storage stabilizer, and (E) optionally reinforcing agent, there being in said material from 0.5 to 1.5 total alkenyl radicals per mercapto group.