Silicone composition and silicone pressure sensitive adhesive obtainable therefrom

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 comprising R<Sup>3</Sup><Sub>3</Sub>SiO<Sub>1/2</Sub> units and SiO<Sub>4/2</Sub> units wherein each R<Sup>3</Sup> is independently selected from monovalent hydrocarbon and monovalent halogenated hydrocarbon groups, the mole ratio of R<Sup>3</Sup><Sub>3</Sub> SiO<Sub>1/2</Sub> units to SiO<Sub>4/2</Sub> units is from 0.6:1 to 1.5:1, the resin contains less than 2 mole percent of alkenyl groups, and 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) a thixotropic agent in an amount sufficient to impart thixotropy to the composition; and (E) a catalytic amount of a hydrosilylation catalyst; wherein 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. A silicone pressure sensitive adhesive comprising a reaction product of the silicone composition. A multi-part silicone composition comprising components (A) through (E) in two or more parts, provided neither component (A) nor component (B), when components (B) contains alkenyl<!-- EPO <DP n="8001"> --> groups, are present with components (C) and (E) in the same part.