Patent ID: 6890647

Claim:
Alumina hydrate particles having a composition represented by the general formula: xM 2 O.y(NH 4 ) 2 O.Al 2 O 3 .zH 2 O 2×10 −4 ≦x≦25×10 −4 0.1×10 −4 ≦y≦20×10 −4 0.6≦z≦2.5 wherein M represents an alkali metal; when the alkali metal is in the form of M 2 O, x is the number of moles thereof per mole of Al 2 O 3 ; when ammonia is in the form of (NH 4 ) 2 O, y is the number of moles thereof per mole of Al 2 O 3 ; and z is the number of moles of hydration water (H 2 O) per mole of Al 2 O 3 , said alumina hydrate particles having: an average particle diameter of 0.02 to 0.2 μm, a total pore volume of 0.5 to 1.5 ml/g, and a volume of pores whose diameter is from 15 to 30 nm ranging from 0.3 to 1.0 ml/g.