Process for the production of coarse crystalline alumina

US4374119A · kind A · utility

Assignee

• Swiss Aluminium Ltd. · CH

Inventors

• Bernhard Schepers · Bergheim, DE
• Volker Nobbe · Neuhausen, CH
• Bernd Schröder · Jülich, DE
• Werner J. Borer · Flurlingen, CH
• Manfred Kullack · Bergheim, DE

Key dates

• Filing date: Sep 16, 1981
• Grant date: Feb 15, 1983
• Expiry date: Sep 16, 2001

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C01P2004/61
• WIPO field: Basic materials chemistry
• WIPO sector: Chemistry

Abstract

The invention describes a process for the production of coarse crystalline alumina from aluminum hydroxide, which after preparation by known methods is advantageously useful for abrasives, lapping and polishing purposes or for refractory materials. The process is characterized by aluminum hydroxide, either directly or after previous partial dehydration in the range 200.degree.-550.degree. C., being added with a mineralizer of compound type x(BF.sub.4).sub.n, wherein x stands for NH.sub.4 and metallic elements and n is for the formal valence of x, and subsequently is subjected to an elevated temperature treatment between 750.degree. C. and a value higher than the phase change temperature to .alpha.-Al.sub.2 O.sub.3.