WET SILICA GELS FOR AEROGEL AND XEROGEL THERMAL INSULATION AND PROCESSES FOR THE WET GELS

摘要

A wet silica gel can be prepared by a processcomprising the steps of contacting a stable, aqueous, fluidsilica system having a pH greater than 7.5 with an ionexchange resin which removes metal ions and replaces themwith H+ ions and thereby reduces the pH to less than 5.0,adding an organic liquid to the aqueous silica system,providing, however, that the organic liquid added stays inone phase with the aqueous, silica system, and does notcause the silica to precipitate, and adding a base to thesilica system so that the pH of the silica system is in therange of from about 5.0 to about 7.5, and allowing the wetsilica gel to form. The wet silica gel formed by thisprocess is characterized by its high organic solvent contentand the low concentration of basic metal ions.