Patent ID: 7507850

Claim:
A process for preparing a composition, comprising: carrying out a process for preparing organosilane esters of the general formula I R 1 a R 2 b R 3 c Si(OR 4 ) 4-a-b-c (I), wherein R 1 =hydrogen, alkyl or aryl, R 2 =hydrogen or alkyl, R 3 =hydrogen or alkyl and R 4 =alkyl, aryl or alkoxyalkyl, a, b and c can be identical or different and can each be 0, 1, 2 or 3, with the proviso that(a+b+c)≦3, by reacting an organohalosilane of the general formula II R 1 a R 2 b R 3 c SiX 4-a-b-c (II), wherein R 1 =hydrogen, alkyl, alkenyl or aryl, R 2 =hydrogen or alkyl, R 3 =hydrogen or alkyl and R 4 =alkyl, aryl or alkoxyalkyl, X is fluorine, chlorine, bromine or iodine, a, b and c can be identical or different and can each be 0, 1, 2 or 3, with the proviso that (a+b+c)≦3, with an alcohol of the general formula III R 4 OH (III) wherein R 4 =alkyl, aryl or alkoxyalkyl, wherein the halosilane is reacted in the liquid phase with the alcohol in the presence or absence of at least one synthesis auxiliary, hydrogen halide is removed from the system, optionally, metal alkoxide is added to the reaction mixture and the metal salt formed is filtered off, and an amount of synthesis auxiliary is added at least once before or during the subsequent work-up by distillation of the resulting product mixture, with the amount added in each case being such that no azeotrope of one or more components of the product mixture and the organosilane ester of the formula I is formed during the distillation under the conditions which prevail; wherein said synthesis auxiliary is at least one member selected from the group consisting of hydrocarbons of the general formulae C n H 2n+2 with 5≦n≦18, (IVa) C 2 H 2n with 5≦n≦8, (IVb) C n H n with 4≦n≦8, (IVc) corresponding alkyl- substituted cycloaliphatic, alkyl-substituted aromatic hydrocarbons, halogenated compounds of the abovementioned hydrocarbons and mixtures thereof; and discharging a fraction comprising more than 98% by weight of organosilane ester in the fractional distillation, to obtain a composition comprising: more than 98% by weight of organosilane ester of the formula I and less than 2% and more than 0% by weight of hydrocarbons of at least one of the formulae IVa, IVb and IVc, in each case based on the total composition.