Process for producing silica-comprising polyol dispersions and their use for producing polyurethane materials

A process for producing at least one silicate-comprising polyol, the process comprising:

• (i) admixing an aqueous silica sol (K) having an average particle diameter of from 1 to 150 nm, a silica content, calculated as SiO2, of from 1 to 60% by weight, and a pH of from 1 to 6,
• with a 0.1- to 20-fold amount, based on an amount of water in the sol, of at least one organic solvent (L) selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-2-propanol, 1-chloro-2-propanol, cyclopentanol, cyclohexanol, 1,4-dioxane, tetrahydrofuran, 2-ethoxyethanol, 1-methoxy-2-propanol, 2-methyl-2-propanol, 1-ethoxy-2-propanol, 2-methoxyethanol, dimethylformamide, acetonitrile, dimethyl sulfoxide acetone, methylethylketone, and ethylacetate, to obtain a resulting mixture;
• (ii) admixing of the resulting mixture with a polyol;
• (iii) then at least partially removing the water and organic solvent (L) by distillation, thereby obtaining a silicon dioxide dispersion in the polyol;
• (iv) subsequently to (i), (ii), and (iii), admixing the silicon dioxide dispersion in the polyol obtained in (iii) with 0.1 to 30 mol %, based on the SiO2 content, of at least one compound (S) which comprises at least a mono-, di- or tiralkoxylated silyl group and at least one substituent selected from the group consisting of an alkyl, cycloalkyl, and aryl substituent which optionally comprises at least one hetero atom, and wherein the substituent optionally comprises a group which is reactive toward an alcohol, an amine, or an isocyanate, wherein the compound (S) is silane or bis(silane);
• and
• (v) optionally, adjusting the pH of the silicate-comprising polyol to a value of from 7 to 12 by addition of a basic compound,
• wherein the adjusting (v) is optionally carried out between (iii) and (iv).