Solventless or high solids-containing silicone pressure sensitive adhesive compositions

Claim 1

An organopolysiloxane composition curable to produce a pressure sensitive adhesive having high tack and high peel adhesion, comprising by weight: (A) from about 50 to about 75 parts by weigh of a toluene soluble, resinous copolymer comprising R 3 SiO 1/2 units and SiO 4/2 units wherein R is a monovalent hydrocarbon radical having from 1 to about 6 carbon atoms, the resinous copolymer comprising from about 0.2% to about 5.0% by weight, based on the total weight of the copolymer, of hydroxyl radicals, at least 95% of all R groups being an alkyl group, the total number of R radicals that are alkenyl radicals being 0-0.5% of all R radicals, the molar ratio of R 3 SiO 1/2 units to SiO 4/2 units being from about 0.6 to about 0.9 inclusive; (B) an alkenyl-terminated polydiorganosiloxane having the general formula (I)   R 2 R 1 2 SiO(R 1 2 SiO) m (R 2 R 1 SiO) n SiR 1 2 R 2 wherein each R 1 is independently an alkyl group having from 1 to about 10 carbon atoms or an aryl group, R 2 is an alkenyl group having from 1 to about 10 carbon atoms, "m" and "n" are numbers such that the sum of "m"+"n" is equal to a number in the range of from about 1 to about 300; (C) an organohydrogenpolysiloxane compatible with the mixture of (A) and (B) and having the general formula (II)   R 3 2 HSiO(R 3 HSiO) a (R 3 2 SiO) b SiHR 3 2 wherein each R 3 is independently an alkyl group having from 1 to about 10 carbon atoms or an aryl group, "a" and "b" each are numbers such that the sum of "a"+"b" is a number in the range of from 1 to about 300, there being greater than two silicon-bonded hydrogen atoms per molecule of (C), no silicon atom bearing more than one silicon bonded hydrogen atom; the total of (B) and (C) being from about 25 to about 50 parts by weight; the total of (A), (B), and (C) being 100 parts by weight; the molar ratio of silicon-bonded hydrogen groups in (C) to silicon-bonded alkenyl groups in (B) being in the range of from about 0.8:1 to about 1.5:1; with the proviso that the total crosslink density of (B) and (C) is from about 0.3 to about 5.0%, and with the further proviso that the combined viscosities of (B) and (C) are from about 10 to about 500 centipoises at 25°C; (D) a catalytic amount of a hydrosilation catalyst; and (E) from 0 to about 10% by weight of an organic solvent.