Aerogel composites, process for producing the same and their use
AssigneeHoechst Aktiengesellschaft
InventorsDierk Frank, Andreas Zimmermann
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Abstract
The present invention relates to mat-shaped composites having porosities above 60% and densities below 0.6 g/cm.sup.3, comprising an aerogel and fibers dispersed therein, the aerogel having cracks and the aerogel fragments enclosed by the cracks, whose average volume is 0.001 mm.sup.3 to 1 cm.sup.3, being held together by the fibers. The present invention further relates to processes for producing the composites of the invention and to their use.
Claims19
A mat-shaped composite comprising an aerogel having porosities above 60% and densities below 0.6 g/cm.sup.3 and fibers dispersed therein, the aerogel having cracks and the aerogel fragments enclosed by the cracks, whose average volume is 0.001 mm.sup.3 to 1 cm.sup.3, being held together by the fibers.
A process for producing SiO.sub.2 aerogel mats having porosities greater than 60% by volume and densities less than 0.6 g/cm.sup.3, which comprises
- a) adjusting an aqueous waterglass solution to a pH.ltoreq.3 and adding a base to the resulting silicic acid,
- b) adding fibers,
- c) allowing the silicic acid to polycondense,
- d) subjecting the gel to a deformation process to introduce cracks into it in a manner to form fiber-connected fragments having an average volume of 0.001 mm.sup.3 to 1 cm.sup.3, the gel being washed with an organic solvent before, during and/or after the deformation until the water content of the gel is .ltoreq.5% by weight,
- e1) reacting the gel obtained in step d) with a silylating agent,
- e2) optionally washing the silylated gel with an organic solvent until the residual level of unconverted silylating agent is .ltoreq.1% by weight, and
- e3) drying the silylated gel obtained in step e1) or e2) at -30.degree. to 200.degree. C. and 0.001 to 20 bar.
Dependencies are inferred from the claim text.