Organic compounds -- part of the class 532-570 series – Organic compounds – Silicon containing
Patent
1999-09-07
2000-10-31
Shaver, Paul F.
Organic compounds -- part of the class 532-570 series
Organic compounds
Silicon containing
C07F 708
Patent
active
061405264
DESCRIPTION:
BRIEF SUMMARY
The subject-matter of the present invention is an improved method for obtaining organosilanes and the invention relates particularly to an improved method for obtaining organosilanes in which a so-called redistribution reaction is involved. More particularly, the present invention relates to an improved method for obtaining organosilanes in which is involved a redistribution reaction between a chlorinated organohydrosilane and an organosubstituted and optionally chlorinated silane, in order to result in a product comprising a redistributed chlorinated organohydrosilane, which is extracted from the reaction mixture by distillation.
Without this being limiting, the present invention is very especially targeted at a redistribution reaction between an alkylhydrodichlorosilane and a trialkylchlorosilane, in order to result in a product comprising a redistributed dialkylhydrochlorosilane. This redistributed dialkylhydrochlorosilane is a synthetic agent which is particularly valued in a great many varied applications, for example, preparation of organosilicon monomers or more condensed base compounds.
Dialkylhydrochlorosilane is one of the by-products from the synthesis of alkylchlorosilanes according to a conventional and well known procedure which consists in reacting alkyl chloride with silicon, in the presence of a copper catalyst, in order to form alkylchlorosilanes. In this synthesis, the dialkyldichlorosilane is the main product. Compounds of the trialkylchlorosilane, alkyltrichlorosilane and alkylhydrodichlorosilane type are also obtained, in addition to the abovetargeted dialkylhydrochlorosilane by-product.
Due to the industrial interest of these by-products in the chemistry of silicones and in particular of the dialkylhydrochlorosilane, such as dimethylhydrochlorosilane, numerous proposals for procedures for obtaining these by-products have seen the light of day. One of the few which has proved itself in this respect is that which consists in carrying out a redistribution reaction between, for example, an alkylhydrodichlorosilane and a trialkylchlorosilane or between an alkylhydrodichlorosilane and a tetraalkylsilane. This redistribution results in the targeted dialkylhydrochlorosilanes, which are extracted from the reaction mixture by distillation.
In this context, numerous redistribution reactions of organosilanes, cutting and redistributing silicon-alkyl, silicon-chlorine or silicon-hydrogen bonds, in the presence of various catalysts, such as Lewis acids, are known. French Patent FR-A-2,119,477 clearly illustrates this technique for the preparation of dialkylhydrochlorosilane by redistribution/distillation. In accordance with the teaching of this patent, methylhydrodichlorosilane and trimethylchlorosilane are reacted in a methylhydrodichlorosilane/trimethylchlorosilane molar ratio of the order of 0.5 in the presence of a catalyst formed by AlCl.sub.3. The reaction mixture is placed in a reactor, under an autogenous pressure of the order of 3 to 5.times.10.sup.5 Pa, and maintained for several hours at a temperature of the order of 85 to 170.degree. C. The Applicant Company has repeated this procedure of the prior art and it has observed that the yield of the distillation, which is carried out at the end of the process in order to separate the redistributed dimethylhydrochlorosilane from the reaction mixture, is abnormally low and peaks at approximately 71%. It must be considered that such results are unsatisfactory with regard to industrial profitability.
In this state of knowledge, one of the essential objects of the present invention consists of the development of an improved method for obtaining organosilanes in which is involved a redistribution reaction between a chlorinated organohydrosilane and an organosubstituted and optionally chlorinated silane, in order to result in a product comprising a redistributed chlorinated organohydrosilane, which is extracted from the reaction mixture by distillation, which method ought to be characterized by distillation yields of final targeted product, the red
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Cathala Max
Colin Pascale
Dardare Michel
Igersheim Fran.cedilla.oise
Rhodia Chimie
Seugnet Jean-Louis
Shaver Paul F.
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