Silicone pressure-sensitive adhesive process and product with improved lap-shear stability-I
First 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 R3 SiO1/2 units and SiO4/2 units in a mole ratio of from 0.6 to 0.9 R3 SiO1/2 units for each SiO4/2 unit present,(B) from 30 to 60 parts by weight of at least one polydiorganosiloxane consisting essentially of ARSiO units terminated with endblocking TRASiO1/2 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 ZR2 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 ZR2 SiNH2 and (ZR2 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--, G2 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--.
1 Assignment
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Accused Products
Abstract
This invention relates to silicone pressure-sensitive adhesives having improved viscosity stability, film physical property stability upon aging and lap shear stability (hold time) made by a method comprising the condensation of a benzene-soluble resin copolymer of 0.6 to 0.9 triorganosiloxy units per SiO4/2 unit which contains silicon-bonded hydroxyl radicals and a polydiorganosiloxane preferably containing silicon-bonded hydroxyl or other hydrolyzable endblocking radicals with a sufficient amount of an ammonia releasing endblocking agent containing endblocking triorganosilyl units such as hexamethyldisilazane to result in a 1:0.8 to 1:3 mole ratio of silicon-bonded hydroxyl radicals and hydrolyzable endblocking radicals to total moles of triorganosilyl units provided by the endblocking agent. The condensation is conducted with heating at 80° C.-160° C. in the presence of 0.5 to 10 moles of water per mole of ═NH present in the endblocking agent and, when necessary, in the presence of an effective amount of an organic solvent such as xylene. Condensation is preferably conducted under solvent reflux conditions. When the condensation reaction is substantially complete, the remaining endblocking agent, water and ammonia released by the endblocking agent is stripped from the composition.
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Citations
36 Claims
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1. A method of making a silicone pressure-sensitive adhesive composition having improved lap shear stability which consists essentially of the steps of:
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(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 R3 SiO1/2 units and SiO4/2 units in a mole ratio of from 0.6 to 0.9 R3 SiO1/2 units for each SiO4/2 unit present, (B) from 30 to 60 parts by weight of at least one polydiorganosiloxane consisting essentially of ARSiO units terminated with endblocking TRASiO1/2 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 ZR2 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 ZR2 SiNH2 and (ZR2 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--, G2 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--. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36)
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Specification