Process for preparing calcium sulfate alpha hemihydrate
AssigneesPromineral Gesellschaft zur Verwendung von Mineralstoffen mbH, SICOWA Verfahrenstechnik fur Baustoffe GmbH & Co. KG
InventorThomas Koslowski
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Abstract
In a process for preparing calcium sulphate alpha hemihydrate essentially the form of primary crystals, the hemihydrate is milled to specific surface area of 1200 to 4000 cm.sup.2 /g, the fines are removed by screening, and a retarder and liquefier in the form of at least one fruit acid and/or its or their salt(s) are admixed. The product obtained is characterized by delayed onset of rigidity, rapid development of resistance and high resistance, and is used in particular as an injection mortar.
Claims7
A process for preparing calcium sulfate alpha hemihydrate in granular form having a specific surface area of 1200 to 4000 cm.sup.2 /g, which comprises the steps of:
- (a) milling crystalline calcium sulfate alpha hemihydrate to obtain a granular calcium sulfate alpha hemihydrate having a specific surface area of 1200 to 4000 cm.sup.2 /g;
- (b) screening the granular calcium sulfate alpha hemihydrate produced during step (a) to eliminate coarser and finer grains, after said screening said product having a specific surface area of 1200 to 4000 cm.sup.2 /g and particle size greater than 0.03 mm;
- and
- (c) admixing 0.005 to 0.05% of at least one fruit acid selected from the group consisting of malic acid, tartaric acid, citric acid, and their salts and monohydrates, with the ground and screened calcium sulfate alpha hemihydrate produced during steps (a) and (b).
Dependencies are inferred from the claim text.