| 摘要 |
An aqueous silica gel is produced by an acid-hardened silica hydrogel being washed with an aqueous, acid solution to give a pH of 2.5-5 in the silica hydrogel, which is dried to a water content of from 20 to 60% by weight and ground to a mean particle size of from 1 to approx. 40 μ. According to the invention, the dry gel is brought into contact with an alkaline medium in sufficient quantity for its pH to be raised to a value within the interval from 6 to 10, as measured in a 5% by weight aqueous suspension of a gel. Gaseous ammonia or, where appropriate, an aqueous alkali metal hydroxide is preferably used for this purpose. The aqueous hydrogel is in particular used in dental care agents which comprise an aqueous silica gel having a water content of from 20 to 60% by weight. This provides dental care agents which can contain valuable liquid components such as oral health agents in readily available form and which are cheap to produce and have a high polishing capacity.
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