Dow Corning Corporation

David J Huebner

John C Saam

Therese M Bauman

Donald R Weyenberg

Julie K Landis

This invention is a method of producing a colloidal silica reinforced polydiorganosiloxane fluid in aqueous emulsion. The method combines an acidic aqueous colloidal silica sol and low molecular weight hydroxyl endblocked polydiorganosiloxane with anionic emulsifying agent, then homogenizes the mixture to form an emulsion. Because the water in the colloidal silica sol is used to supply water for the emulsion, it is possible to produce emulsions with solid content as high as 80 percent by weight. The emulsion is then mixed with surface active anionic catalyst and aged at room temperature to allow the polydiorganosiloxane to polymerize. Polymerization is halted by adding base to bring the pH to greater than 7. The reinforced polydiorganosiloxane emulsion can be further mixed with diorganotindicarboxylate and aged to give a curable emulsion which yields an elastomer upon removal of the water. A curable emulsion can also be produced by mixing the reinforced polydiorganosiloxane emulsion with diorganotindicarboxylate and alkylorthosilicate.

Method of producing reinforced aqueous emulsion of polydiorganosiloxane

A method of producing an emulsion of crosslinked polydiorganosiloxane admixes hydroxyl endblocked polydiorganosiloxane, alkoxy silicone compound, anionic emulsifying agent, and water. The mixture is homogenized, then the emulsion is admixed with surface active anionic catalyst. Maintaining the catalyzed emulsion, having a pH of less than 5, at room temperature allows the ingredients to react to raise the molecular weight of the polydiorganosiloxane and to crosslink the polymer. The reaction is halted by adding sufficient base to raise the pH to greater than 7. The resultant latex yields an elastomer upon removal of the water. When colloidal silica is also added to the mixture before homogenization, the final latex yields a reinforced elastomer upon removal of the water.

Method of producing aqueous latex of crosslinked polydiorganosiloxane

This invention is a method of producing a latex of crosslinked polydiorganosiloxane. The latex yields an elastomer upon removal of the water. The latex is prepared by homogenizing a mixture of hydroxyl endblocked polydiorganosiloxane, less than 75 millimoles of surface active anionic catalyst per kilogram of polydiorganosiloxane where said surface active anionic catalyst is dodecylbenzene sulfonic acid or hydrogen lauryl sulfate, and water to yield an oil-in-water emulsion. This emulsion is then admixed with from 0.5 to 15 parts by weight of an alkoxy silicon compound selected from a silane of the formula R.sub.a 'Si(OR.sup.3).sub.4-a where R' is a monovalent hydrocarbon radical of up to 12 carbon atoms, R.sup.3 is an alkyl radical of 1 to 6 carbon atoms, and a is 0 or 1, a partial hydrolyzate of the silane, or mixtures of silane and partial hydrolyzate. The resulting emulsion is maintained at a temperature of about 15.degree. to 30.degree. C. for at least 5 hours at a pH of less than 5 until a crosslinked polymer is formed, then the emulsion is admixed with sufficient base to raise the pH to greater than 7. The crosslinked polymer present in the latex is reinforced by adding greater than 1 part by weight of colloidal silica sol or silsesquioxane to the latex. Removal of water from the latex results in a reinforced elastomer. This method yields a latex which can be applied and dried immediately after preparation to yield an elastomer.

Emulsions of crosslinked polydiorganosiloxanes

This invention is a method of producing an aqueous latex of crosslinked polydiorganosiloxane. The latex yields an elastomer upon removal of the water. The latex is prepared by homogenizing a mixture of hydroxyl endblocked polydiorganosiloxane; a silane of the formula R.sub.a 'Si(OR.sup.3).sub.4-a where R' is a monovalent hydrocarbon radical of up to 12 carbon atoms, R.sup.3 is an alkyl radical of 1 to 6 carbon atoms, a partial hydrolyzate, or mixture of silane and hydrolyzate, and a is 0 or 1; a surface active anionic catalyst of the formulae R.sup.2 C.sub.6 H.sub.4 SO.sub.3 H wherein R.sup.2 is a monovalent hydrocarbon radical of at least 6 carbon atoms, R.sup.2 OSO.sub.2 OH, or ##STR1## wherein R.sup.4 is H or R.sup.2 ; and water. The resulting emulsion is maintained at a temperature of 15.degree. to 30.degree. C. for at least 5 hours at a pH of less than 5 until a crosslinked polymer is formed, then this emulsion is admixed with base to a pH of greater than 7. The resulting emulsion is reinforced by adding greater than 1 part by weight of colloidal silica sol or silsesquioxane to yield a latex. Removal of water from the latex results in a reinforced elastomer. This method yields a latex which can be applied and dried immediately after mixing to yield an elastomer.

Polydiorganosiloxane latex

This invention is a method of producing a latex of crosslinked polydiorganosiloxane reinforced with colloidal silica. The method allows the production of a latex having a relatively high amount of silica present in relation to the polymer because the water used to form the emulsion can be that present in the acidic colloidal silica sol used in the method. The high solids latex can be useful as a caulking material. The method homogenizes a hydroxyl endblocked polydiorganosiloxane, a silane of the formula R'.sub.a Si(OR.sup.3).sub.4-a where R' is a monovalent hydrocarbon radical of up to 12 carbon atoms, R.sup.3 is an alkyl radical of 1 to 6 carbon atoms, a partial hydrolyzate, or mixture of silane and hydrolyzate, and a is 0 or 1; a surface active anionic catalyst of the formulae R.sup.2 C.sub.6 H.sub.4 SO.sub.3 H wherein R.sup.2 is a monovalent hydrocarbon radical of at least 6 carbon atoms, R.sup.2 OSO.sub.2 OH, or ##STR1## wherein R.sup.4 is H or R.sup.2 ; and greater than 1 part by weight of colloidal silica present as an acidic sol in water. This homogenized mixture is an oil-in-water emulsion. This emulsion is maintained at a temperature of 15.degree. to 30.degree. C. for at least 5 hours at a pH of less than 5 until a crosslinked polymer is formed. The product is a latex which produces an elastomer upon removal of the water at room temperature. Shelf stable products are produced by adjusting the pH to from 7 to 12.5.

Emulsions of reinforced polydiorganosiloxane latex

A method of blending an emulsion of an emulsion polymerized copolymer of an organic monomer and an organosilicon monomer and an emulsion of a polydiorganosiloxane to provide a reinforced elastomeric product is disclosed. The physical properties of the cured polydiorganosiloxane elastomeric product are improved by the addition of the copolymer emulsion, as compared to the addition of an organic homopolymer, particularly the tear strength. The blended emulsions and the product obtained by devolatilizing the blended emulsion is also claimed. The cured product is useful as a coating for surfaces, as a textile treatment, and as a paper treatment.

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Midland, MI, United States of America

David J Huebner