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US 4,946,666 AGranted
Process for the production of fine tabular alumina monohydrate
AssigneeVereinigte Aluminum-Werke Aktiengesellschaft
InventorNeil Brown
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Abstract
The present invention provides a process for the production of fine, tabular boehmite crystals substantially within the size range of 0.2-0.8 microns. The crystals are particularly suitable for use as a pigment/filler in paper, paint and ink applications.
Claims19
A process for the production of tabular boehmite crystals comprising the steps of:
- contacting a Bayer process liquor with an oxygen-containing gas at a temperature of between about 150.degree. C. and about 300.degree. C. and at a pressure of between about 1 bar O.sub.2 and about 150 bar O.sub.2, adjusting the molar ratio of Na.sub.2 O.sub.free to Al.sub.2 O.sub.3 in said liquor by injecting CO.sub.2 into said liquor, to be less than or equal to 1;
- cooling said Bayer process oxidized liquor under said pressure and simultaneously vigorously agitating said liquor to induce nucleation of a tabular boehmite;
- and
- recovering tabular boehmite crystals having an average diameter of between about 0.2 and 0.8 microns.
1 more element
A process for the production of tabular boehmite crystals comprising the steps of:
- providing a caustic aluminate-containing liquor with a molar ratio of Na.sub.2 O.sub.free to Al.sub.2 O.sub.3 of less than or equal to one, said liquor being essentially free of copper ions,
- maintaining said liquor at an elevated temperature and pressure,
- cooling said liquor under vigorous agitation to induce crystallization of a tabular boehmite product having an average particle size of between about 0.2 and 0.8 microns.
Dependencies are inferred from the claim text.