Mixture of oligomers of condensed alkylalkoxysilanes

A mixture of oligomers of alkylalkoxysilanes condensed in the chain and/or cyclic form having a viscosity of less than 100 mPa.multidot.s, said mixture of oligomers containing less than 2% by weight of free alcohols and the condensed alkoxysilanes satisfying formula I:

• ##STR5## wherein R is an alkyl group having 3 to 18 carbon atoms, and each R' is (i) methyl, ethyl or hydrogen, or is (ii) methyl or hydrogen, or is (iii) ethyl or hydrogen, the degree of oligomerization residing in the range 2.ltoreq.x.ltoreq.20 and the quotient of the molar ratio ›Si/alkoxy group!.gtoreq.1;
• and/or
• satisfying formula II:
• ##STR6## in which R is an alkyl group having 3 to 18 carbon atoms, and R' is (i) methyl, ethyl or hydrogen, or is (ii) methyl or hydrogen or is (iii) ethyl or hydrogen, the degree of oligomerization being x.gtoreq.3 and the quotient of the molar ratio ›Si/alkoxy group!.gtoreq.1, which is obtained by hydrolyzing and condensing alkyltrialkoxysilanes, wherein the silanes bear alkyl groups with 3 to 18 carbon atoms and methoxy and/or ethoxy groups as alkoxy groups, employing more than 1 mole of water per 1 mole of Si, and employing HCl as the catalyst, and distilling the reaction mixture obtained under reduced pressure at a bottom temperature <95.degree. C.