Patent ID: 6077967
Filing Date: 2000-06-20
Classification: C07F

Abstract:
Improved method for obtaining organosilanes comprising:a redistribution reaction between a chlorinated organohydrosilane of formula (1) (R).sub.a (H).sub.b SiCl.sub.4-a-b and an organosubstituted and optionally chlorinated silane of formula (2) (R' ).sub.c SiCl.sub.4""c, in which formulae: a=1 or 2; b=1 or 2; a+b.ltoreq.3; c=1, 2, 3 or 4; and the symbols R and R' are alike or different and each represent a linear or branched C.sub.1 -C.sub.6 alkyl radical or a C.sub.6 -C.sub.12 aryl radical; said redistribution reaction taking place in the presence of an effective amount of a catalyst consisting of a Lewis acid of formula (3) M(X).sub.d, in which: M represents a metal selected from Ti, Fe, Cu, Ag, Zn, Cd, Hg, Al, Ga, In, B, Sn, Pb, Sb and Bi; X represents a halogen atom; and d represents the valency of the metal M;and a separation by distillation of the chlorinated organohydrosilane produced by redistribution; said method being characterized in that, after the redistribution, at least one compound which inhibits the redistribution catalyst is introduced, this compound corresponding to the following definitions:it comprises:(i) a silane of-formula:(R.sup.1).sub.e Si(OR.sup.2).sub.4-e ( 4)in which:the R.sup.1 symbols are alike or different and each represent: a hydrogen atom; a linear or branched C.sub.1 -C.sub.8 alkyl radical optionally substituted by one or more halogen(s); a C.sub.5 -C.sub.8 cycloalkyl radical; a C.sub.6 -C.sub.12 aryl radical or an aralkyl radical having a C.sub.6 -Cl.sub.2 aryl part and a C.sub.1 -C.sub.4 alkyl part which is optionally substituted on the aromatic part by one or more halogen(s), C.sub.1 -C.sub.3 alkyl(s) and/or C.sub.1 -C.sub.3 alkoxy(s);the R.sup.2 symbols are alike or different and each represent: a linear or branched C.sub.1 -C.sub.4 alkyl radical; or a C.sub.6 -C.sub.12 aryl radical;e is 0, 1, 2 or 3;(2i) a silicone resin having a viscosity at 25.degree. C. at most equal to 5000 mpa.multidot.s and exhibiting the following distinctive features:it has, in its structure, units chosen from those of formulae (R.sup.3).sub.3 SiO0.5 (M), (R.sup.3).sub.2 SiO (D), R.sup.3 SiO.sub.1.5 (T) and SiO.sub.2 (Q), at least one of these units being a T unit or a Q unit, in which formulae the R.sup.3 symbols, which are-alike or different, mainly have the definitions given above with respect to the R.sup.1 symbols;the proportions of the T and/or Q units, expressed by the number of T and/or Q units per 100 silicon atoms, are greater than 10%;it also possesses, per molecule, --OR.sup.4 end groups carried by silicon atoms of the M, D and/or T units, where:the R.sup.4 symbols, which are alike or different, each represent a hydrogen atom, a linear or branched C.sub.1 -C.sub.4 alkyl radical or a C.sub.6 -C.sub.12 aryl radical,the proportions of the --OR.sup.4 ends, expressed by the mean number of these ends per 1 silicon atom, vary from 0.2 to 3;it is used in proportions such that the ratio: ##EQU3## is equal to or less than 1.1.