PRODUCTION OF UNIVERSAL POLYDIORGANOSILOXANE/SILICA MIXTURE BY USING HYDROLYZABLE POLYDIORGANOSILOXANE SURFACE MODIFIER, MIXTURE OBTAINED THEREBY, AND ROOM-TEMPERATURE-CURING SEALANT

摘要

A process of making a polydiorganosiloxane-silica mixture from a free-flowing, powdered, surface-modified, reinforcing silica-polydiorganosiloxane suitable, for example, for producing RTV silicone sealant compositions which are non-sag. These mixtures are made by combining, mixing and heating a reinforcing silica filler and a surface modifying agent at 90 DEG C. to 180 DEG C. using 0.1 to 0.5 parts by weight of the surface modifying agent per one part by weight of the silica. Polydiorganosiloxane is added gradually to the resulting fluidized filler over a time period of less than 10 minutes to yield the free flowing powdered reinforcing silica-polydiorganosiloxane. The final mixture is obtained by massing the concentrate and adding more polydiorganosiloxane to obtain a mixture which has from 8 to 20 weight percent silica filler. RTV silicone sealant compositions are obtained in 10 to 15 minutes from the initiation of our process.