Low temperature mineralization of alumina
US6203773A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 12, 1999 |
| Grant date | Mar 20, 2001 |
| Priority date | — |
| Expiry date | Jul 12, 2019 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC01P2006/80
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
Alpha alumina particles are made by heating particles of alumina with an aqueous solution containing a dissolved fluorine-containing compound and an acid; separating the particles from the solution and then calcining the particles at a temperature not greater than about 1025.degree. C. The alumina particles preferably have an LOI in the range of about 1-20 wt. %; more preferably about 1-6 wt. %. Alpha alumina particles of the invention are more readily ground into smaller particles than alpha alumina particles made by calcining at higher temperatures. The remaining soda in the alpha alumina is found to be highly soluble in hot water. The process produces low soda content (0.01 wt. % Na.sub.2 O or less) alpha alumina crystals from alumina feedstocks with 0.5 wt. % or more initial soda levels. The alpha alumina crystals produced are as large as 30-40 microns. Most typically; the size range is between 2 and 8 microns. Because of the low mineralization temperature, the particles require significantly less grinding time to separate the component alpha crystals.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.