GB1082116A - Organopolysiloxane resins and their production - Google Patents

Abstract

Organopolysiloxane resin prepolymers are produced by heating a hydrolysable methyltrialkoxysilane and a hydrolysable phenyltrialkoxy-silane either together or separately with H2O and, if desired, less than 0.01 mole of an acidic catalyst per mole of silane, concentrating the resultant reaction mixture or mixtures by removing a substantial portion but not all of the volatile components, mixing the two concentrated reaction mixtures if the silanes were hydrolysed separately, and heating the resinous mixture thus obtained at a temperature above but not more than 100 DEG C. above the b.p. of H2O at the prevailing pressure to precure it. The prepolymers are cured by heating at a temperature below but not more than 60 DEG C. below the b.p. of H2O at the prevailing pressure. The reaction mixture may also contain minor amounts of other trialkoxysilanes, of mono- and di-alkoxysilanes and of alkyl orthosilicates. In one example, 11, triphenyl-, trihexyl- and diphenylsilanes are also added. Fillers such as SiO2, unreactive organosilanes, amine-clay derivatives, clays and asbestos may be added to the reaction mixtures. The prepolymers may be cast and cured to give machinable, thermoset polysiloxane bodies.