| abstract |
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 3 3 SiO 1/2 units and SiO 4/2 units wherein each R 3 is independently selected from the group consisting of monovalent hydrocarbon and monovalent halogenated hydrocarbon groups, the mole ratio of R 3 3 SiO 1/2 units to SiO 4/2 units is from 0.6:1 to 1.5:1, the resin contains less than about 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 groups, are present with components (C) and (E) in the same part. |