| 摘要 |
A novel method of producing from wollastonite finely divided pigments and fillers of unusually high opacifying power, high brightness, low bulk density and low abrasiveness for use in paper, paint and other products by reacting the wollastonite in the form of a slurry with sulfuric acid, preferably at an elevated temperature, to form calcium sulfate pigment particles and to solubilize at least part of the silica in the wollastonite, followed by raising the pH of the slurry to gelate the solubilized silica and form agglomerates or aggregates of the calcium sulfate particles and the silica gel, followed by dewatering and drying under noncalcining conditions. The final state of pigment particle aggregation and stabilization of the pigment aggregates is important in imparting high surface hiding power. In a preferred embodiment, the wollastonite slurry is reacted with less than stoichiometric quantities of phosphoric acid at an elevated temperature prior to reaction with the sulfuric acid.
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