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    • 46. 发明授权
    • Production of synthetic fluorspar
    • 生产合成萤石
    • US4148867A
    • 1979-04-10
    • US704252
    • 1976-07-12
    • Siegfried SchneiderHans Niederprum
    • Siegfried SchneiderHans Niederprum
    • C01F11/22C01B33/14
    • C01F11/22
    • In the production of a synthetic fluorspar of low silicon dioxide content wherein hexafluosilicic acid is added in an amount ranging from slightly below up to about stoichiometric amount to an aqueous calcium carbonate suspension at a temperature from about 0.degree. to 40.degree. C., and the calcium fluoride formed is separated off from the dilute silica sol and optionally washed out, the improvement which comprises reacting the calcium carbonate with the hexafluosilicic acid in such a way that the pH-value of the fully reacted solution amounts to between about 3.6 and 4.6, and adding a fast-reacting proton acceptor to the reaction mixture immediately before separation of the calcium fluoride in amount sufficient to raise the pH to about 5.0 to 6.4, preferably about 5.8 to 6.2. Suitable proton acceptors include the alkali metal and ammonium hydroxides carbonates and hydrogen carbonates or alkaline earth metal hydroxide. Anionic or non-ionic dispersants may also be added and the calcium fluoride is separated by decanting or centrifugation within about 1 second to 10 minutes, preferably about 4 to 10 seconds, after raising the pH. The separated calcium fluoride may be washed to remove silica sol therefrom and then again be treated to raise its pH before separation.
    • 在制备低二氧化硅含量的合成荧光粉中,其中将六氟硅酸以约低于约化学计量的量加入到约0℃至40℃的温度下的碳酸钙水溶液悬浮液中,并且 形成的氟化钙与稀二氧化硅溶胶分离并任选地洗出,其改进包括使碳酸钙与六氟硅酸反应,使得完全反应的溶液的pH值达到约3.6和4.6之间, 然后在将氟化钙分离出足以使pH升高至约5.0至6.4,优选约5.8至6.2之间的情况下,立即向反应混合物中加入快速反应的质子受体。 合适的质子受体包括碱金属和氢氧化铵,碳酸盐和碳酸氢盐或碱土金属氢氧化物。 还可以加入阴离子或非离子分散剂,并且在升高pH后,在约1秒至10分钟,优选约4至10秒内通过倾析或离心分离氟化钙。 可以将分离的氟化钙洗涤以从其中除去二氧化硅溶胶,然后在分离前再次进行处理以提高其pH。