Method of producing reinforced aqueous emulsion of polydiorganosiloxane

Claim 1

A method of preparing an aqueous emulsion of reinforced polydiorganosiloxane having a molecular weight of at least 5000 consisting essentially of (A) homogenizing 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 5 to 50 parts by weight of colloidal silica present as an acidic sol in water, (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) additional water if needed to give a non-volatile content of from 50 to 80 percent by weight, to give an emulsion, 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 stable emulsion having polydiorganosiloxane of a molecular weight of at least 5,000, reinforced with colloidal silica, and a non-volatile content of from 50 to 80 percent by weight.

Claim 2

A method of preparing an aqueous emulsion of reinforced polydiorganosiloxane having a molecular weight of at least 5000 consisting essentially of (A) homogenizing 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 5 to 50 parts by weight of colloidal silica present as an acidic sol in water, (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) additional water if needed to give a non-volatile content of from 50 to 80 percent by weight, to give an emulsion, 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 stable emulsion having polydiorganosiloxane of a molecular weight of at least 5,000, reinforced with colloidal silica, and a non-volatile content of from 50 to 80 percent by weight.