Process for making calcium sulfate alpha-hemihydrate from calciu

Details Process for making calcium sulfate alpha-hemihydrate from calciu Process for making calcium sulfate alpha-hemihydrate from calciu

1988-05-23

1991-05-14

Straub, Gary P.

Chemistry of inorganic compounds

Treating mixture to obtain metal containing compound

Alkaline earth metal

156 43, 264333, 423170, 423171, C04B 1102, C04B 11024

Patent

active

050154508

ABSTRACT:
The process makes calcium sulfate alpha-hemihydrate from finely divided calcium sulfate dihydrate by transforming the calcium sulfate dihydrate in the presence of saturated steam. A molded body is formed from the calcium sulfate dihydrate which has a plurality of pores having a pore volume amounting to 15 to 60% by volume of the total volume of the entire molded body. More than 5% by volume of the pore volume contains air. The molded body is fed to the autoclave. In the presence of a sufficient water quantity in the pores the crystal habit and the crystal growth of the calcium sulfate alpha-hemihydrate crystals which grow in an aqueous solution phase are controlled by a process temperature in the range between 110.degree. to 180.degree. C. by the pressure of the process atmosphere in the autoclave. The molded body is removed from the autoclave after recrystallization transformation and delivered for use. Key products of this process and their derivatives are also described.

REFERENCES:
patent: 1901051 (1933-03-01), Randel et al.
patent: 3410655 (1968-11-01), Ruter et al.
patent: 4309391 (1982-01-01), O'Neill
patent: 4540555 (1985-09-01), Franke et al.
Browning, Chemical Engineering, Dec. 4, 1967, pp. 147-170.
Ullmanns Encyklopadie der Technischen Chemie, Fungizide Bis Holzwerkstoffe, erlag Chemie, Weinheim-New York, 1976, Band 12, pp. 301, 303, 304.
Baugipse, Begriff, Sorten und Verwendung, Lieferung und Kennzeichnung, DIN 1168 Teil 1, Jan. 1986, Preisgr. 4, pp. 1, 2, 3.
Baugipse, Andorderungen, Prufung, Uberwachung, DIN 1168 Teil 2, Jul. 1975 (Fachnormenausschuss Bauwesen (FNBau) im Deutschen Normenausschuss (DNA) . . . ).

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