Hydrophobic waterglass based aerogels without solvent exchange or supercritical drying

摘要

The usual production of silica aerogels include supercritical drying and expensive raw materials like tetraethoxysilane which prohibit a commercialization. To avoid the costs of supercritical drying one can modify the internal surface with a silation agent. Hydrophobization of the lyogel mal;es it possible to dry at ambient pressure. The next step is to use waterglass as a cheaper silica source. This requires at least one solvent exchange from water for the surface modification. The diffusion time for solvent exchange and recycling of the water/solvent solutions by distillation cause considerable costs. A new cost-effective process has been developed to avoid these disadvantages. Silation is now carried out directly in the water phase of the hydrogel, which results in solvent exchange as well as phase separation of gelwaler and solvent. (C) 1998 Elsevier Science B.V. All rights reserved. [References: 15]