Silicone composition and silicone pressure sensitive adhesive

摘要

A silicone composition for preparing a silicone pressure sensitive adhesive, the composition comprising (A) 20 to 55 parts by weight of a polydiorganosiloxane containing an average of at least two silicon-bonded alkenyl groups per molecule; (B) 45 to 80 parts by weight of an organopolysiloxane resin consisting essentially of R<3>3 SiO1/2 units and SiO4/2 units, wherein the total amount of components (A) and (B) is 100 parts by weight; (C) an organohydrogenpolysiloxane having an average of at least two silicon-bonded hydrogen atoms per molecule in an amount sufficient to cure the composition; (D) 25 to 200 parts by weight of a silica filler having an average surface area less than 25 m<2>/g; and (E) a catalytic amount of a hydrosilylation catalyst. Each R<3> is independently selected from monovalent hydrocarbon or monovalent halogenated hydrocarbon groups. The mole ratio of R<3>3 SiO1/2 units to SiO4/2 units in the organopolysiloxane resin is from 0.6:1 to 1.5:1 and the resin contains less than 2 mole percent of alkenyl groups. The sum of the average number of silicon-bonded alkenyl groups per molecule in component (A) and the average number of silicon-bonded hydrogen atoms per molecule in component (C) is greater than 4.0. A silicone pressure sensitive adhesive comprising a reaction product of the above-described composition. A multi-part silicone composition comprising components (A) through (E) in two or more parts, provided neither component (A) nor component (B) , when component (B) contains alkenyl groups, are present with components (C) and (E) in the same part.