Patent ID: 7125948

Claim:
A silicone adhesive comprising (A) a reaction mixture and (B) a crosslinking agent, which crosslinking agent (B) is a combination of (a) an organohydrogenpolysiloxane having at least two silicon atom-bonded hydrogen atoms in a molecule, said crosslinking agent (B) being present in an amount to give 0.2 to 30 mol of silicon atom-bonded hydrogen atoms per mol of alkenyl radicals in component (A), and (b) a catalytic amount of a platinum base catalyst, said reaction mixture (A) being obtained by subjecting a partially condensed mixture of (i) a diorganopolysiloxane having a hydroxyl radical at each end of its molecular chain, represented by the general formula (1): wherein R 1 and R 2 each are a substituted or unsubstituted monovalent hydrocarbon radical, the content of alkenyl radicals is 0.0005 to 0.1 mol % based on the total of R 1 and R 2 , and m is an integer of 500 to 10,000, and (ii) an organopolysiloxane copolymer having hydroxyl and alkenyl radicals in a molecule and comprising R 3 3 SiO 1/2 units and SiO 2 units as main units in a molar ratio of R 3 3 SiO 1/2 units to SiO 2 units between 0.5 and 1.5, wherein R 3 is a hydroxyl radical or a substituted or unsubstituted monovalent hydrocarbon radical, and (iii) a compound of the general formula (2): HR 4 a Si(OR 5 ) 3-a (2) wherein R 4 and R 5 each are a substituted or unsubstituted monovalent hydrocarbon radical, and “a” is an integer of 0 to 2, to addition reaction in the presence of a platinum base catalyst, wherein the partially condensed organopolysiloxane mixture and component (iii) are blended in such proportions that the ratio Y/X, of the molar amount Y of SiH radicals in component (iii) to the molar amount X of alkenyl radicals in said partially condensed organopolysiloxane mixture, is less than 1.0, and wherein component (iii) is blended and reacted in such amounts that 0.001 to 0.1 mole of alkenyl radicals are left per 100 g of the reaction mixture (A).