| 摘要 |
PROBLEM TO BE SOLVED: To obtain a gypsum board which is made strong on both end parts and can be easily carried without decreasing its lightweight property by arranging a fiber-contg. foamableβ-hemihydrate gypsum in the center part in the width direction of the board and arrangingα-hemihydrate gypsum on both end parts. SOLUTION: A fiber-contg. foamableβ-hemihydrate gypsum slurry is supplied from the main mixer to the center part in the width direction of the lower board paper sheet, whileα-hemihydrate gypsum slurry is supplied from a submixer to both end parts in the width direction of the lower board paper sheet. Then a upper board paper sheet is applied thereon. By this method, theα-hemihydrate gypsum used is prepared by adding an alkali toα-hemihydrate gypsum which is produced as a by-product in the production of phosphoric acid by a wet phosphoric acid producing method using igneous phosphor mineral and sulfuric acid. Thereby, anα-hemihydrate gypsum obtd. from igneous phosphorus mineral gypsum which is conventionally not directly used for a gypsum board because of the influences of impurities included in the mineral can be used.
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