Patent ID: RE39650

Claim:
A process for producing trialkoxysilane of the formula HSi(OR) 3 wherein R is an alkyl group containing 1 to 6 carbon atoms inclusive, comprising (a) slurrying silicon metal in a thermally stable solvent in the presence of a surface-active additive and of a catalyst precursor which is halogen-free and which comprises copper, (b) activating said catalyst precursor, thereby generating a catalyst for the reaction of step (c), and (c) reacting said silicon metal with an alcohol of the formula ROH in the presence of the catalyst generated in step (b) to form said trialkoxysilane; wherein said surface-active additive comprises (i) a mixture of (i)(A) hydrophobized silica particles with average particle sizes in the range of 0.2-5 microns, and specific surface area between 50 and 400 square meters per gram and (i)(B) an organopolysiloxane selected from the group consisting of compounds of the general formula: R″ 3 SiO—(SiR″ 2 O) a —SiR″ 3 , cyclic compounds of the general formula: (R″ 2 SiO) b , branched oligomers and polymers of the formula and mixtures thereof, wherein R″ in each occurrence is the same or different and each is a C 1 -C 20 alkyl group, phenyl, alkyl-substituted phenyl, cycloalkyl, or alkyl-substituted cycloalkyl; a, b, k, r and s are greater than zero and have values such that the normal boiling point of the organopolysiloxane is at least 10° C. higher than the temperature of the Direct Synthesis slurry; wherein the weight ratio of (i)(A) to (i)(B) is 1:99 to 99:1, or (ii) an organofluorosiloxane selected from the group consisting of compounds of the general formula XR′ 2 SiO—(SiR′ 2 O) k —SiR′ 2 X, cyclic compounds of the general formula (R′ 2 SiO) n , branched oligomers and polymers of the formula and mixtures thereof, in which R′ has the same meaning as R″, provided that at least one R′ group is wholly or partially substituted with fluorine, X has the same meaning as R′ or is optionally an alkoxy group containing eight or fewer carbon atoms, and k, r and s are positive numbers, n is an integer greater than 3, and the values of k, n, r and s are chosen such that the fluorosilicone has a normal boiling point that is at least 10° C. higher than the temperature of the slurry at which step (c) is carried out.