Silicone pressure-sensitive adhesive process and product with improved lap-shear stability-I

Claim 1

A method of making a silicone pressure-sensitive adhesive composition having improved lap shear stability which consists essentially of the steps of: (I) mixing (A) from 40 to 70 inclusive parts by weight of at least one benzene-soluble resin copolymer containing silicon-bonded hydroxyl radicals and consisting essentially of R 3 SiO 1/2 units and SiO 4/2 units in a mole ratio of from 0.6 to 0.9 R 3 SiO 1/2 units for each SiO 4/2 unit present, (B) from 30 to 60 parts by weight of at least one polydiorganosiloxane consisting essentially of ARSiO units terminated with endblocking TRASiO 1/2 units, each said polydiorganosilozane having a viscosity of from 100 centipoise to 30,000,000 centipoise at 25° C., and each T is R-- or X--, (C) a sufficient amount of at least one organosilicon endblocking agent capable of generating an endblocking triorganosilyl unit of the formula ZR 2 Si-- to provide a 1:0.8 to 1:3 mole ratio of total silicon-bonded hydroxyl and X radicals present in said (A) and (B) to total endblocking triorganosilyl units provided by all endblocking agent present, said agent being selected from the group consisting of ZR 2 SiNH 2 and (ZR 2 Si) 2 NH, (D) from 0.5 to 10 moles of water per mole of ═NH provided by said (C), and (E) optionally, an effective amount of an organic solvent which is inert with respect to (A), (B), (C) and (D) to reduce the viscosity of a mixture of (A), (B), and (C), (II) condensing (A), (B) and (C) at a temperature of from 80° C. to 160° C. and at the same time at least periodically removing any condensation by-products from the mixture at least until a substantial amount of the endblocking triorganosilyl units have reacted with the silicon-bonded hydroxyl radicals and X radicals of said (A) and (B), and (III) stripping substantially any remaining condensation by-products and (D) from the mixture after the condensation reaction of step II is substantially complete, wherein each R is a monovalent organic radical selected from the group consisting of hydrocarbon radicals of from 1 to 6 inclusive carbon atoms, each X radical is selected from the group consisting of HO--, H-- and R'O-- radicals, each R' is an alkyl radical of from 1 to 4 inclusive carbon atoms, each A radical is selected from the group consisting of R-- and halohydrocarbon radicals of from 1 to 6 inclusive carbon atoms, each Z radical is A-- or QR"--, each R" is a divalent alkylene radical of from 1 to 6 inclusive carbon atoms, each Q is an organofunctional monovalent radical selected from the group consisting of RCOE'--, RE'OC--, NC--, R'E'--, HO--, G 2 N--, HO(R"O) n -- where E' is --0--, --NH--or --S-- where n has a value of from 1 to 6 and each G is R'-- or H--.

Claim 2

A method of making a silicone pressure-sensitive adhesive composition having improved lap shear stability which consists essentially of the steps of: (I) mixing (A) from 40 to 70 inclusive parts by weight of at least one benzene-soluble resin copolymer containing silicon-bonded hydroxyl radicals and consisting essentially of R 3 SiO 1/2 units and SiO 4/2 units in a mole ratio of from 0.6 to 0.9 R 3 SiO 1/2 units for each SiO 4/2 unit present, (B) from 30 to 60 parts by weight of at least one polydiorganosiloxane consisting essentially of ARSiO units terminated with endblocking TRASiO 1/2 units, each said polydiorganosilozane having a viscosity of from 100 centipoise to 30,000,000 centipoise at 25° C., and each T is R-- or X--, (C) a sufficient amount of at least one organosilicon endblocking agent capable of generating an endblocking triorganosilyl unit of the formula ZR 2 Si-- to provide a 1:0.8 to 1:3 mole ratio of total silicon-bonded hydroxyl and X radicals present in said (A) and (B) to total endblocking triorganosilyl units provided by all endblocking agent present, said agent being selected from the group consisting of ZR 2 SiNH 2 and (ZR 2 Si) 2 NH, (D) from 0.5 to 10 moles of water per mole of ═NH provided by said (C), and (E) optionally, an effective amount of an organic solvent which is inert with respect to (A), (B), (C) and (D) to reduce the viscosity of a mixture of (A), (B), and (C), (II) condensing (A), (B) and (C) at a temperature of from 80° C. to 160° C. and at the same time at least periodically removing any condensation by-products from the mixture at least until a substantial amount of the endblocking triorganosilyl units have reacted with the silicon-bonded hydroxyl radicals and X radicals of said (A) and (B), and (III) stripping substantially any remaining condensation by-products and (D) from the mixture after the condensation reaction of step II is substantially complete, wherein each R is a monovalent organic radical selected from the group consisting of hydrocarbon radicals of from 1 to 6 inclusive carbon atoms, each X radical is selected from the group consisting of HO--, H-- and R'O-- radicals, each R' is an alkyl radical of from 1 to 4 inclusive carbon atoms, each A radical is selected from the group consisting of R-- and halohydrocarbon radicals of from 1 to 6 inclusive carbon atoms, each Z radical is A-- or QR"--, each R" is a divalent alkylene radical of from 1 to 6 inclusive carbon atoms, each Q is an organofunctional monovalent radical selected from the group consisting of RCOE'--, RE'OC--, NC--, R'E'--, HO--, G 2 N--, HO(R"O) n -- where E' is --0--, --NH--or --S-- where n has a value of from 1 to 6 and each G is R'-- or H--.