Patent ID: 6440187
Filing Date: 2002-08-27
Classification: B82Y,C01F,C01P,C09G,C09K

Abstract:
A process for producing a granular: alumina powder having a single or multiple crystal structure selected from the group consisting of &ggr;, &dgr; and &thgr;-forms, a primary particle size of 10 to 50 nm, and a mean secondary particle size of 100 to 500 nm, comprising:(A) a step of adding an alkali to an aqueous alumina sot containing fibrous colloidal particles of amorphous alumina hydrate to form a reaction mixture having pH of 9 to 12; (B) a step of subjecting the reaction product obtained in step (A) to hydrothermal treatment at 110 to 250Â° C. to form an aqueous suspension containing alumina hydrate having boehmite structure; (C) a step of drying the aqueous suspension obtained in step (B) at 100Â° C. or more and then calcining the same at 500 to 1,130Â° to form alumina having a single or multiple crystal structure selected from the group consisting of &lgr;, &dgr; and &thgr;-forms; and (D) a step of dry and/or wet grinding the alumina obtained in step (C).