| 摘要 |
1,126,572. Dispersions of silica. DEUTSCHE GOLDUND SILBER-SCHEIDEANSTALT. 21 Sept., 1965 [25 Sept., 1964], No. 40230/65. Heading C1A. [Also in Division B2] In obtaining a stable dispersion of pyrogenically obtained finely divided silica, a water soluble carboxylic acid or an inorganic mineral acid is added to an aqueous polyethylene imine solution containing 1 to 3% by weight of polyethylene imine and then the finely divided silica is added to and dispersed in this solution. The solution preferably contains 1 to 1À5% by weight of polyethylene imine and the silica has a B.E.T. surface area of from 20 to 200 m.<SP>2</SP>/g. The silica may also contain 0À3 to 1À3% by weight of a foreign oxide, this oxide being preferably alumina. The preferred acids are formic, acetic or lactic acid or hydrochloric or phosphoric acid. The dispersion is preferably adjusted to a pH value of from 5 to 6. In a particular example each 1000 parts by weight of the dispersion contains 150 to 300 parts of silica aerogel and 10-20 parts of polyethylene imine. |
