CHEMICALLY MODIFIED SILICA FILLERS, PROCESS FOR PRODUCING, AND SILICONE COMPOSITIONS CONTAINING SAME

摘要

This invention is a process for making modified silica filler comprising the steps of: (A) contacting an acidic aqueous suspension of precipitated or colloidal silica, optionally in the presence of a surfactant and/or a water- miscible solvent, with a combination of (a) a functionalizing coupling agent , and (b) an organometallic hydrophobing compound in a weight ratio of (a) to (b) of at least 0.001 to 1 to form an acidic aqueous suspension of chemicall y treated silica filler having a pH of 2.0 or less; (B) treating the acidic aqueous suspension of the chemically treated filler with an acid-neutralizin g agent to increase the pH of the suspension to a range of from greater than 2 .0 to 10; and (C) recovering the chemically treated filler. This invention is also modified silica filler that has a pH of from about 5.0 to 10.0, where t he silica filler is made by the method of this invention. This invention is als o a curable silicone elastomer composition comprising a polyorganosiloxane, th e modified silica filler produced by the method of this invention, and a means of curing the polyorganosiloxane into an elastomer.