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US 4,540,439 AGranted
Process for preparation of gypsum shapes
AssigneeChemische Werke Huls Aktiengesellschaft
InventorHans-Friedrich Kurandt
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Abstract
A process for preparing shaped articles from waste gypsum from wet-process phosphoric acid production comprises: (1) mixing wet calcium sulfate hemihydrate with 0.5-20% by wt. of calcium hydroxide or calcium oxide, (2) adjusting the total water content of said mixture to 20-40% by wt., if necessary, and (3) molding shaped articles from said mixture by compression molding. The shaped objects so prepared have a low density and relatively high compressive strength.
Claims8
A shaped gypsum article prepared by a process which comprises:
- (a) controlling the water content of a moist .alpha.-calcium sulfate hemihydrate obtained by filtration from the production of phosphoric acid without preliminary purification, drying, or calcining to be in the range of from 20 to 40% by weight,
- (b) mixing the hemihydrate from step (a) with 0.5 to 20% by weight calcium hydroxide or calcium oxide, and
- (c) compression molding the mixture from step (b) without adding any additional binding agent within 8 hours of said mixing,
- wherein said article has a density of from 1.61 to 1.8 kg/dm.sup.3 and a compression strength of 200 to 285 kp/cm.sup.2 when measured by DIN 106 for the size NF=240.times.115.times.71 mm.
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Dependencies are inferred from the claim text.