Method of producing aqueous latex of crosslinked polydiorganosiloxane

Claim 1

A method of producing an aqueous latex of crosslinked polydiorganosiloxane consisting essentially of (A) homogenizing immediately after admixing, a mixture consisting essentially of (1) 100 parts by weight of polydiorganosiloxane of the formula HO(R.sub.2 SiO).sub.x H wherein each R is a radical selected from the group consisting of methyl, ethyl, propyl, phenyl, vinyl, allyl, and 3,3,3-trifluoropropyl, and x is an average value in the range of from 3 to 100 inclusive, (2) from 0.5 to 15 parts by weight of alkoxy silicon compound selected from the group consisting of silane of the formula R.sub.a 'Si(OR.sup.3).sub.4-a wherein R' is a monovalent hydrocarbon radical having up to 12 carbon atoms, R 3 is an alkyl radical having from 1 to 6 inclusive carbon atoms, and a is 0 or 1; a partial hydrolyzate of the silane where the partial hydrolyzate is soluble in the polydiorganosiloxane (1); and mixture of silane and partial hydrolyzate, (3) sufficient anionic emulsifying agent to give an emulsion particle of an average diameter of from 0.3 to 0.4 micrometers, wherein said emulsifying agent is an alkali metal surface active sulfonate or sulfate, and (4) water, to give a non-volatile content of from 50 to 80 percent by weight, then (B) admixing into the emulsion (A) from 15 to 100 millimoles of surface active anionic catalyst per kilogram of polydiorganosiloxane, wherein said catalyst is a surface active sulfonic acid catalyst or a surface active hydrogen sulfate catalyst, then (C) maintaining the catalyzed emulsion at a temperature of from 15° to 30° C. for at least 5 hours at a pH of less than 5 until the desired molecular weight of polydiorganosiloxane is obtained, then (D) admixing sufficient base to raise the pH of the emulsion to greater than 7, to give a latex having a non-volatile content of from 50 to 80 percent by weight, and which cures to an elastomer upon removal of the water at room temperature.

Claim 2

A method of producing an aqueous latex of crosslinked polydiorganosiloxane consisting essentially of (A) homogenizing immediately after admixing, a mixture consisting essentially of (1) 100 parts by weight of polydiorganosiloxane of the formula HO(R.sub.2 SiO).sub.x H wherein each R is a radical selected from the group consisting of methyl, ethyl, propyl, phenyl, vinyl, allyl, and 3,3,3-trifluoropropyl, and x is an average value in the range of from 3 to 100 inclusive, (2) from 0.5 to 15 parts by weight of alkoxy silicon compound selected from the group consisting of silane of the formula R.sub.a 'Si(OR.sup.3).sub.4-a wherein R' is a monovalent hydrocarbon radical having up to 12 carbon atoms, R 3 is an alkyl radical having from 1 to 6 inclusive carbon atoms, and a is 0 or 1; a partial hydrolyzate of the silane where the partial hydrolyzate is soluble in the polydiorganosiloxane (1); and mixture of silane and partial hydrolyzate, (3) sufficient anionic emulsifying agent to give an emulsion particle of an average diameter of from 0.3 to 0.4 micrometers, wherein said emulsifying agent is an alkali metal surface active sulfonate or sulfate, and (4) water, to give a non-volatile content of from 50 to 80 percent by weight, then (B) admixing into the emulsion (A) from 15 to 100 millimoles of surface active anionic catalyst per kilogram of polydiorganosiloxane, wherein said catalyst is a surface active sulfonic acid catalyst or a surface active hydrogen sulfate catalyst, then (C) maintaining the catalyzed emulsion at a temperature of from 15° to 30° C. for at least 5 hours at a pH of less than 5 until the desired molecular weight of polydiorganosiloxane is obtained, then (D) admixing sufficient base to raise the pH of the emulsion to greater than 7, to give a latex having a non-volatile content of from 50 to 80 percent by weight, and which cures to an elastomer upon removal of the water at room temperature.