Organic compounds -- part of the class 532-570 series – Organic compounds – Silicon containing
Patent
1998-11-24
1999-12-21
Nazario-Gonzalez, Porfirio
Organic compounds -- part of the class 532-570 series
Organic compounds
Silicon containing
556470, 556483, C07F 702
Patent
active
060051329
DESCRIPTION:
BRIEF SUMMARY
TECHNOLOGICAL FIELD
The invention relates to a process for the preparation of alkoxysilanes by transesterisifaction of alkoxy silanes having alkoxy radicals containing 1 to 4 carbon atoms with higher alcohols in the presence of acid or basic catalysts under a reduced pressure.
DESCRIPTION OF THE RELATED ART
U.S. Pat. No. 2,643,263 (California Research Co.; issued on Jun. 23, 1953) describes tetraalkoxysilanes which, inter alia, are prepared by reacting silicon tetrachloride with branched alcohols containing 6 to 18 carbon atoms. The preparation starting from silicon tetrachloride has the disadvantage that the products obtained show, without further involved aftertreatment, a high acidity which leads to undesi red hydrolysis of the products during storage.
WO 93/16085 (Henkel KGaA; issued on Aug. 19, 1993) discloses a process for the preparation of light-coloured tetraalkoxysilanes, tetramethoxysilane or tetraethoxysilane being transesterified in a 1st step with primary higher alcohols in the presence of basic catalysts and, in a subsequent step, a neutralization and bleaching by means of solid acidic bleaching earths and cation exchangers being carried out. The 2nd step, which preferably lasts 1 to 2 hours, is necessary in this process since during the 1st step, undesirable, dark-colored tetraalkoxysilanes, which are caused by the procedure, are formed. Furthermore, the process has the disadvantage that the 1st step is very time-consuming since, caused by the procedure, the reaction mixture can be heated only at a heating rate of 0.1.degree. to 0.5.degree. C. per minute in order to achieve a high degree of transesterification and, furthermore, relatively high end temperatures are necessary. A further disadvantage of the process is that the transesterification takes place in a molar ratio between tetramethoxysilane or tetraethoxysilane and the primary alcohols of preferably 1:4.2 to 1:4.8 and a further expensive purification step by distillation is thus necessary due to the high boiling points.
SUMMARY OF THE INVENTION
The invention relates to a process for the preparation of alkoxysilanes having alkoxy radicals containing 6 to 38 carbon atoms by transesterification of alkoxysilanes whose alkoxy groups contain 1 to 4 carbon atoms with linear and/or branched higher alcohols containing 6 to 38 carbon atoms in the presence of basic or acid catalysts under a pressure of 1 to 800 hPa and at a temperature of 25 to 150.degree. C. with continuous removal of the resulting alcohol containing 1 to 4 carbon atoms, the pressure and temperature during the transesterification being selected such that the higher alcohol employed and the silanes do not boil.
DESCRIPTION OF THE INVENTION
Within the scope of the present invention, the term "silanes" is intended to be understood also as mixtures of silanes and partial hydrolysis products thereof containing at most 5 silicon atoms, such partial hydrolysis products preferably being present only in small quantities such as, for example, up to 10 percent by weight, relative to the silane, or not at all.
The alkoxysilanes which are employed according to the invention and whose alkoxy groups contain 1 to 4 carbon atoms, can be any hitherto known alkoxysilanes, such as silanes having 1, 2, 3 or 4 Si-bound alkoxy groups, tetraalkoxysilanes having alkoxy groups containing 1 to 4 carbon atoms being preferred and tetramethoxysilane as well as tetraethoxysilane being particularly preferred.
The alkoxysilanes employed according to the invention can be a single species or also a mixture of at least two species of such alkoxysilanes.
The alcohols employed according to the invention are linear and/or branched alcohols which contain 6 to 38 carbon atoms and which can be aliphatically saturated or unsaturated.
Preferably, the alcohols employed according to the invention are aliphatically saturated alcohols containing 8 to 20 carbon atoms, such as 1-n-octanol, 1-n-decanol, 1-n-dodecanol, 1-n-tetradecanol and mixtures of linear and branched alcohols containing 13 to 15 carbon atoms, suc
REFERENCES:
patent: 2643263 (1953-06-01), Morgan
patent: 2917467 (1959-12-01), Olson et al.
patent: 4717773 (1988-01-01), Kenney et al.
Blueml Walter
Weidner Richard
Nazario-Gonzalez Porfirio
Wacker-Chemie GmbH
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