Appeal No. 2000-1868
Application No. 08/730,217
APPENDIX
1. A method for producing "-alumina power having a number
average particle size of 0.1 to 30 :m and a halogen content of
10 ppm or less comprising the steps of:
(i) calcining, in a calcining system, a starting material
consisting of:
(a) at least one additive, and
(b) transition alumina, an alumina compound or mixtures
thereof;
in a halogen-containing atmosphere which comprises at least
one member selected from the group consisting of a hydrogen
chloride gas, a chlorine gas, and a mixture of a chlorine gas and
steam; wherein said at least one hydrogen chloride gas, chlorine
gas or chlorine gas in said mixture of chlorine gas and steam is
present in an amount of at least 1% by volume based on the total
volume in the atmosphere; and (ii) removing halogen from said
calcined material;
wherein said at least one additive is selected from the
group consisting of a seed crystal and a shape-regulating agent,
and
wherein said halogen is removed by one of the following
methods:
a) a method in which "-alumina powder containing the
halogen is heated in an atmosphere of air at a temperature of
from 900oC to 1000oC; or
c) a method in which "-alumina powder containing the
halogen is heated under reduced pressure of 0.1 Torr or less at a
temperature of from 400oC to 1000oC.
Page: Previous 1 2 3 4 5 6 7 8 9 10
Last modified: November 3, 2007