Shelf-stable catalyst component for RTV silicone composition

Claim 1

A process for producing a shelf-stable catalyst component for a room temperature vulcanizable silicone rubber composition comprising: (a) mixing 100 parts by weight of an organo polysiloxane fluid of a viscosity varying from 1,000 to 50,000 centipoise where the organo group is a monovalent hydrocarbon group, with a first portion of a mixture of crosslinking agent, catalytic promoter and self-bonding additive effective for providing a stable catalyzed paste base mixture of said composition upon heat cycling of said base mixture wherein said first portion constitutes 1 to 15 percent by weight of the total amount of crosslinking agent, catalytic promoter and self-bonding agent utilized in said shelf-stable catalyst component for a room temperature vulcanizable silicone rubber composition and is comprised of: (1) an alkyl silicate crosslinker of the formula: R.sub.m Si (OR.sup.1).sub.4-m or partial hydrolysis products thereof wherein R and R 1 are monovalent hydrocarbon radicals, m is 0 or 1; (2) a tin salt catalytic promoter and (3) a self-bonding additive of the formula: ##STR4## where R 2 and R 3 are alkyl radicals of 1 to 8 carbon atoms, a is 0 or 1 and Y is a nitrogen-functional radical which is a saturated, unsaturated or aromatic residue which in addition to nitrogen functionality may be functionalized by a radical selected from the class consisting of amino, cyano, thio, oxo, and ester, and multiples and combinations thereof; and after there is a uniform mixture of (a); (b) adding to the mixture from 10 to 250 parts of filler and mixing the ingredients to a uniform mixture and heating the mixture to a temperature of at least 100° C. for at least 1 hour thereby providing a stable paste-like base mixture; and (c) mixing into the base mixture a second portion consisting of the remainder of the cross-linking agent, the catalytic promoter and self-bonding additive; and mixing to a uniform fluid mixture by agitating the base mixture and the rest of the ingredients for at least 30 minutes wherein the entire process is carried out in the substantial absence of moisture.