| 摘要 |
PROBLEM TO BE SOLVED: To regulate the hardening time of anα-hemihydrate gypsum, formed as a by-product of phosphoric acid in a process for producing a wet-process phosphoric acid, and effective utilized in industries, and obtain a gypsum to enable theα- hemihydrate gypsum product such as a plaster or a joint treating material using theα-hemihydrate gypsum formed as the by-product of phosphoric acid. SOLUTION: This method for regulating the hardening time of anα-hemihydrate gypsum formed as a by-product comprises washing theα-hemihydrate gypsum formed as the by-product, drying the washedα-hemihydrate gypsum formed as the by-product, adding an inorganic alkali thereto and adding aβ-hemihydrate gypsum having 0-425μm particle diameter to the resultantα-hemihydrate gypsum at 1-50 pts.wt. mixing ratio thereof based on 100 pts.wt. total amount of the gypsum. The gypsum product is obtained by mixing one or more of a filler, a lightweight aggregate, an adhesion imparting agent, a viscosity regulating agent, a hardening retarder and an antifungal agent to a mixture of the by-productα-hemihydrate gypsum with theβ-hemihydrate gypsum.
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