Method for manufacturing a rubber sheet which is electrically insulating and thermally radiating and rubber sheets made therefrom with improve resistance to flexural fatigue

Claim 1

A method for manufacturing a rubber sheet which is electrically insulating and thermally radiating, comprising treating a network insulating material with an alkoxysilane, then coating the resulting network insulating material with a fluid silicone rubber composition, and then curing said composition, where the fluid silicone rubber composition consists essentially of (a) 100 parts by weight of a polyorganosiloxane having a viscosity at 25° C. of from 0.1 to 100 Pa·s and having an average unit formula R.sub.a R.sub.b 'SiO.sub.(4-a-b)/2 wherein each R represents a monovalent hydrocarbon radical free of aliphatic unsaturation or a halogenated monovalent hydrocarbon radical free of aliphatic unsaturation, each R' represents a monovalent aliphatically unsaturated hydrocarbon radical, a has a value from 1.90 to 2.05, b has a value from 0.005 to 0.1, and the sum of a+b has a value from 1.91 to 2.06, (b) a polyorganohydrogensiloxane having a viscosity at 25° C. of 0.007 to 5 Pa·s and having an average unit formula R.sub.c H.sub.d SiO.sub.(4-c-d)/2 wherein R is defined above, the sum of c+d has a value of 1.001 to 3, there is at least two silicon-bonded hydrogen atoms per molecule, and said polyorganohydrogensiloxane is present in an amount such that there are 0.5 to 10 equivalents of silicon-bonded hydrogen atoms per equivalent of aliphatically unsaturated hydrocarbon radical in (a), (c) from 100 to 500 parts by weight of alumina powder, and (d) a catalytic quantity of a platinum-group compound as a catalyst.

Claim 2

A method for manufacturing a rubber sheet which is electrically insulating and thermally radiating, comprising treating a network insulating material with an alkoxysilane, then coating the resulting network insulating material with a fluid silicone rubber composition, and then curing said composition, where the fluid silicone rubber composition consists essentially of (a) 100 parts by weight of a polyorganosiloxane having a viscosity at 25° C. of from 0.1 to 100 Pa·s and having an average unit formula R.sub.a R.sub.b 'SiO.sub.(4-a-b)/2 wherein each R represents a monovalent hydrocarbon radical free of aliphatic unsaturation or a halogenated monovalent hydrocarbon radical free of aliphatic unsaturation, each R' represents a monovalent aliphatically unsaturated hydrocarbon radical, a has a value from 1.90 to 2.05, b has a value from 0.005 to 0.1, and the sum of a+b has a value from 1.91 to 2.06, (b) a polyorganohydrogensiloxane having a viscosity at 25° C. of 0.007 to 5 Pa·s and having an average unit formula R.sub.c H.sub.d SiO.sub.(4-c-d)/2 wherein R is defined above, the sum of c+d has a value of 1.001 to 3, there is at least two silicon-bonded hydrogen atoms per molecule, and said polyorganohydrogensiloxane is present in an amount such that there are 0.5 to 10 equivalents of silicon-bonded hydrogen atoms per equivalent of aliphatically unsaturated hydrocarbon radical in (a), (c) from 100 to 500 parts by weight of alumina powder, and (d) a catalytic quantity of a platinum-group compound as a catalyst.

Claim 7

The method in accordance with claim in which the network insulating material is treated with a mixture of the alkoxysilane and an organotitanic acid ester.