PROCESS FOR PREPARING ORGANICALLY MODIFIED AEROGELS IN WHICH THE SALTS FORMED ARE PRECIPITATED OUT.

摘要

The invention concerns a process for preparing organically modified aerogels, in which: a) a silicic acid sol having a pH of 3/4 4.0 is prepared from an aqueous sodium silicate solution using at least one organic and/or inorganic acid; b) the resultant silicic acid sol is polycondensed to form an SiO2 gel by the addition of a base; c) the gel obtained in step b) is washed with an organic solvent until the water content of the gel is 3/4 5 wt.percent; d) the gel obtained in step c) is surface-silylated; and e) the surface-silylated gel obtained in step d) is dried. The process is characterized in that the at least one acid forms salts with the sodium silicate cations in the silicic acid sol, which salts are difficult to dissolve. Before step b) the salts produced which are difficult to dissolve are precipitated out to the greatest extent possible and separated from the silicic acid sol.