Process for producing a low viscosity silicone resin

Claim 1

A process for producing a silicone resin which has a viscosity that does not exceed 100 centipoise at 140° C. comprising: (A) adding with continuous agitation a mixture of acetone and organohalosilanes over a period of at least 40 minutes to a heterogeneous hydrolysis mixture having a water phase and an organic phase composed of water, acetone and a water-immiscible solvent wherein in the final heterogeneous hydrolysis mixture, per part by weight of organohalosilanes there is present; (1) from at least 1.7 parts to about 10 parts of water; l (2) from about 0.2 to about 5 parts of acetone; (3) from about 0.3 to about 5 parts of a water-immiscible organic solvent, and (4) from 0 to about one mole of an aliphatic monohydric alcohol having from 1 to 8 carbon atoms per mole of halogen attached to the silicone atom of said organohalosilane; (b) maintaining the temperature of said heterogeneous hydrolysis mixture below 45° C. during step (A); (c) removing the water from said heterogeneous hydrolysis misture and reducing the acid content of the organic phase containing the formed silicone resin to below 5 parts per million; and (d) stripping off the solvent at a temperature not to exceed about 120° C. to yield a polyorganosiloxane having an average ratio from about 1 to 1.8 organo radicals per silicon atom, said organohalosilanes in Step (A) being selected from the class consisting of (a) a mixture of organotrihalosilane and diorganodihalosilane, (b) a reaction product of an aliphatic monohydric alcohol having from 1 to 8 carbon atoms and a mixture of organotrihalosilane and diorganodihalosilane which reaction product may have up to one alkoxy radical substituted for each halogen radical in said organotrihalosilane and diorganodihalosilane; (c) a mixture of the reaction product of (a) and a member selected from the organotrihalosilane and diorganodihalosilane, and where the organo radicals of said organohalosilanes are selected from the class consisting of monovalent hydrocarbon radicals and halogenated monovalent hydrocarbon radicals.