REGULATION OF HARDENING TIME OF ALPHA-HEMIHYDRATE GYPSUM FORMED AS BY-PRODUCT OF PHOSPHORIC ACID AND GYPSUM PRODUCT USING ALPHA-HEMIHYDRATE GYPSUM FORMED AS BY-PRODUCT OF PHOSPHORIC ACID

摘要

PROBLEM TO BE SOLVED: To regulate the hardening time of an -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 the - hemihydrate gypsum product such as a plaster or a joint treating material using the -hemihydrate gypsum formed as the by-product of phosphoric acid. ;SOLUTION: This method for regulating the hardening time of an -hemihydrate gypsum formed as a by-product comprises washing the -hemihydrate gypsum formed as the by-product, drying the washed -hemihydrate gypsum formed as the by-product, adding an inorganic alkali thereto and adding a -hemihydrate gypsum having 0-425 m particle diameter to the resultant -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-product -hemihydrate gypsum with the -hemihydrate gypsum.;COPYRIGHT: (C)1998,JPO