| 摘要 |
PURPOSE:To obtain the title silica gel having reversible hygroscopicity, high hygroscopicity and capable of absorbing and releasing moisture by adding a mineral acid capable of dissolving calcium to an aq. slurry of calcium silicate allowing silica hydrogel to produce. CONSTITUTION:A mineral acid capable of dissolving calcium is added to an aq. slurry of calcium silicate so that the pH of the reaction soln. is controlled to 2.5-5.0 to cause a reaction. The reaction soln. is then allowed to stand and cured to form silica hydrogel, and the silica hydrogel is isolated and dried to obtain silica gel. The concn. of the slurry of calcium silicate to be treated with a mineral acid is preferably controlled to 3-25wt.%, the concn. at <3wt.% is economically disadvantageous, and the reaction to dissolve the calcium component in hydrated calcium silicate in the acid is unfavorably made nonuniform at >25wt.%.
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