Organically modified aerogels, processes for their preparation by surface modification of the aqueous gel, without prior solvent exchange, and subsequent drying, and their use

A process for preparing an organically modified aerogel, which comprises

• a) introducing a hydrogel formed at pH greater than 3 as initial charge,
• b) modifying the surface of the hydrogel obtained in step a) by mixing the hydrogel with a silylating agent to form a hydrophobic surface modified gel, and
• c) drying the surface-modified gel obtained in step b) to form the organically modified aerogel,
• wherein a silicatic hydrogel is introduced as initial charge in step a).

A process for preparing an organically modified aerogel, which comprises:

• a) forming a silicatic hydrogel at pH≧3;
• b) subjecting the silicatic hydrogel formed in step a), optionally after intermediate treatment steps, to surface modification by mixing the hydrogel with a silylating agent to form a surface modified gel;
• and
• c) drying the surface modified gel obtained in step b), optionally after additional treatment steps, to form the organically modified aerogel
• wherein the silicatic hydrogel is prepared by bringing an aqueous waterglass solution to a pH≦3 with the aid of an acidic ion exchanger resin or a mineral acid, and polycondensing the resulting silicic acid by addition of a base to form an SiO2 gel.

A process for producing an organically modified aerogel, which comprises:

• a) forming a hydrogel at pH>3;
• b) surface modifying the hydrogel formed in step a), optionally after intermediate treatment steps, by mixing the hydrogel with a silylating agent to form a surface modified gel;
• and
• c) optionally after additional treatment steps, drying the surface modified gel obtained in step b) to form the organically modified aerogel;
• wherein steps a) and b) are carried out as a semi-continuous process, wherein a continuous or semi-continuous stream of acid is mixed with a continuous or semi-continuous stream of aqueous waterglass solution.

A process for producing an organically modified aerogels, wherein:

• a) a hydrogel is formed at pH≧3;
• b) the hydrogel formed in step a), optionally after intermediate treatment steps, is subjected to surface modification by mixing the hydrogel with a silylating agent to form a surface modified gel;
• and
• c) the surface modified gel obtained in step b), optionally after additional treatment steps, is dried to form the organically modified aerogel;
• wherein step a) and b) are carried out as a continuous process and a continuous or semi-continuous stream of acid is mixed with a continuous or semi-continuous stream of aqueous waterglass solution.