| 摘要 |
Silica is precipitated from water glass solution with an organohalosilane, optionally together with up to 70% mineral acid, e.g. HCl or H2SO4. The silane may contain 2 or 3 halogen atoms, e.g. Cl, with saturated or unsaturated aliphatic, cycloaliphatic, and/or aromatic radicals having up to 20 carbon atoms; mixtures of silanes may also be used. The silane may be added to the water glass with stirring at 20-100 DEG C. to give a pH of 4-5, and the suspension is left to stand and then boiled. Alternatively, the silane and water glass may be added simultaneously to a solution of an alkali metal chloride, e.g. NaCl, to maintain a pH of 4-5, then further silane may be added to a pH of 2. NaOH solution may first be added to the water glass solution to obtain a high sodium content. |
