Method of improving silicone rubber composition
AssigneeDow Corning Corporation
InventorsMilton C. Murray, Joan M. Donatelli
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Abstract
A new method of producing a silicone rubber composition yields a unique composition. When the composition is further mixed with extending filler and vulcanized, the tensile strength of the vulcanized silicone rubber is improved over that obtained when the composition is not produced following the method of this invention. The method mixes polydiorganosiloxane gum, treated reinforcing silica filler, a portion of hydroxylated organosilicon compound having an average of from 1 to 20 percent by weight hydroxyl radicals and an average of from 1 to 31 percent by weight vinyl radicals; heating the mixture; then cooling and admixing another portion of the hydroxylated organosilicon compound.
Claims21
A method of producing a silicone rubber composition comprising
- (I) mixing
- (A) 100 parts by weight of polydiorganosiloxane gum having a viscosity of greater than 1000 Pa.s at 25.degree. C., wherein the organic radicals are selected from the group consisting of methyl, phenyl, vinyl, and 3,3,3-trifluoropropyl, at least 50 percent of the organic radicals being methyl and less than 2 percent being vinyl,
- (B) from 10 to 85 parts by weight of treated reinforcing silica filler having a surface area of greater than 50 m.sup.2 /g,
- (C) from 0.1 to 5 parts by weight of a hydroxylated organosilicon compound having the average unit formula ##EQU3## in which R is methyl, phenyl or 3,3,3-trifluoropropyl, Vi is vinyl, x has a value from 1.0 to 2.0 inclusive, y has a value such that there is present an average of from 1 to 20 percent by weight hydroxyl radical, z has a value such that there is present an average of from 1 to 31 percent by weight vinyl radical, and the compound is soluble in (A);
- then
- (II) heating the mixture to a temperature of from 60.degree. to 250.degree. C. for a period of from 10 minutes to 10 days to provide a product that is stable upon storage, and then
- (III) cooling the mixture to room temperature, and admixing during the cooling process when the temperature of the mixture is below 125.degree. C. or after room temperature has been reached from 0.1 to 2.5 parts by weight of the hydroxylated organosilicon compound of (C) and from 1 to 250 parts by weight of extending filler with a surface area of less than 50 m.sup.2 /g.
A method of producing a silicone rubber composition comprising
- (I) mixing
- (A) 100 parts by weight of polydiorganosiloxane gum having a viscosity of greater than 100 Pa.s at 25.degree. C., wherein the organic radicals are selected from the group consisting of methyl, phenyl, and vinyl, at least 78 percent of the organic radicals being methyl and less than 2 percent being vinyl, there being an average of at least two vinyl radicals per molecule on at least 25 percent by weight based on the total weight of polydiorganosiloxane gum present,
- (B) from 20 to 60 parts by weight of reinforcing silica filler having a surface area of greater than 50 m.sup.2 /g,
- (B') from 1 to 20 parts by weight of hydroxyl endblocked polydiorganosiloxane fluid having a viscosity of less than 1.0 Pa.s at 25.degree. C., the organic radicals being selected from the group consisting of methyl and phenyl, then
- (I') admixing
- (C) from 0.1 to 5 parts by weight of a hydroxylated organosilicon compound having the average unit formula ##EQU4## in which R is methyl or phenyl, Vi is vinyl, x has a value from 1.0 to 2.0 inclusive, y has a value such that there is present an average of from 1 to 20 percent by weight hydroxyl radical, z has a value such that there is present an average of from 1 to 31 percent by weight vinyl radical, and the compound is soluble in (A), and
- (D) from 0.01 to 2 parts by weight of a material selected from the group consisting of ammonium carbonate, ammonium bicarbonate, and ammonia, thereafter
- (II) heating the mixture to a temperature of from 100.degree. to 175.degree. C. for a period of from 10 minutes to 4 hours to provide a product that is stable on storage, thereafter,
- (III) cooling the mixture to room temperature and admixing during the cooling process when the temperature of the mixture is below 125.degree. C. or after room temperature has been reached from 0.1 to 2.5 parts by weight of the hydroxylated organosilicon compound of (C) of step (I') and from 1 to 250 parts by weight of siliceous extending filler with a surface area of less than 50 m.sup.2 /g, then
- (IV) admixing from 0.1 to 5 parts by weight of organic peroxide vulcanizing agent suitable for vulcanizing the polydiorganosiloxane gum after the mixture is below the activation temperature of the organic peroxide.
A method of producing a cured silicone rubber elastomer comprising heating the silicone rubber composition of claim 2, 17, or 9 to a temperature sufficient to activate the vulcanizing agent.
Dependencies are inferred from the claim text.