Vacuum dispensable silicone compositions

摘要

A vacuum dispensable silicone composition comprising (A) a polydiorganosiloxane containing an average of at least two silicon-bonded alkenyl groups per molecule; (B) an organopolysiloxane resin essentially consisting of (a) R<3>2(CH2=CH)SiO1/2 siloxane units, (b) R<3>3SiO1/2 siloxane units, and (c) SiO4/2 siloxane units wherein each R<3> is independently selected from monovalent hydrocarbon or monovalent halogenated hydrocarbon groups free of aliphatic unsaturation, the mole ratio of the combination of (a) and (b) units to (c) units is from 0.6 to 1.1 and the resin contains 1 to 5 percent by weight of vinyl groups; (C) an organohydrogenpolysiloxane having an average of at least three silicon-bonded hydrogen atoms per molecule in an amount sufficient to provide from one to three silicon-bonded hydrogen atoms per alkenyl group in components (A) and (B) combined; (D) an adhesion promoter in an amount sufficient to effect adhesion of the composition to a substrate; (E) a hydrosilylation catalyst; (F) a platinum catalyst inhibitor having a boiling point greater than 150 DEG C. at 0.10 MPa in an amount sufficient to retard curing of the composition at ambient temperature; wherein the composition is substantially free of air.