Patent ID: 6579410
Filing Date: 2003-06-17
Classification: C01P,C09C,D21H

Abstract:
A method of preparing a composite pigment material for use in a composition for making or coating a fibrous sheet material, which method comprises:treating an aqueous medium containing particles of a fine particulate material and fibers, said treating comprises chemically precipitating, by a precipitation reaction in the aqueous medium, crystals of a white pigment compound thereby producing a composite material, said composite material comprising a composite matrix of fibers and precipitated crystals of the white pigment compound and particles of the fine particulate material dispersed and bonded within the matrix, wherein at least 90% by weight of the fine particulate material in the treated aqueous medium has an equivalent spherical diameter as measured by sedimentation of less than 1 &mgr;m and comprises dispersed material which has not previously been used in an industrial operation, and wherein the fine particulate material and the fibers are obtained from separate stocks and are added together prior to the precipitation reaction in relative amounts required to be present in the composite pigment material, the ratio by weight of the fine particulate material to the white pigment compound being from 1:100 to 1:1, wherein said white pigment compound comprises an alkaline earth metal carbonate.