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US 5,302,368 AGranted
Process for preparation of alumina
AssigneeSumitomo Chemical Company, Limited
InventorsTakuo Harato, Toshiki Furubayashi, Toshio Ashitani, Toru Ogawa
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Abstract
An aqueous slurry of about 100-1000 centipoises viscosity suspending about 200-2000 g/l of aluminum hydroxide particles smaller than 5 .mu.m is spray-dried, and the dried powders are calcined to obtain alumina powders. The alumina powders have a sharp particle size distribution, being suitable for electronic, abrasive and refractory applications.
Claims5
A process for preparing an .alpha.-alumina having a particle size distribution index, (D.sub.95 -D.sub.5)/D.sub.50, of not more than 1.5, comprising:
- dispersing in an aqueous medium aluminum hydroxide having average secondary particle diameters of up to about 5 .mu.m and produced by Bayer's process and/or transition alumina having average secondary particle diameters of up to about 5 .mu.m and produced by Bayer's process to form a slurry;
- adjusting the viscosity, at the temperature and pressure of the resulting slurry, to viscosities of about 100 to about 1000 centiposes;
- spray-drying the slurry to obtain dry powders;
- and
- calcining the resulting dry powders in the presence of a chlorine-containing substance at a temperature of about 1100.degree. C. to about 1500.degree. C.
2 more elements
Dependencies are inferred from the claim text.