Patent ID: 6087404
Filing Date: 2000-07-11
Classification: C01P,C09C,C09D,Y10S

Abstract:
A process for preparing a concentrated aqueous suspension of a finely ground particulate material, which process comprises:(a) preparing an aqueous suspension comprising at least 20% by weight of the particulate material comprising calcium carbonate in coarse particulate form;(b) grinding the suspension formed in step (a) in the presence of a polycarboxylate dispersing agent for the particulate material in a grinding process in which the pH of the suspension in at least part of the grinding process is about 10 or higher to produce an aqueous suspension of a finely ground product of the particulate material wherein at least 90% by weight of the particles of the particulate material have an equivalent spherical diameter of less than 2 .mu.m and at least 60% by weight of the particles of the particulate material have an equivalent spherical diameter of less than 1 .mu.m;(c) adding to the aqueous suspension of the finely ground product of the particulate material formed in step (b) an additive comprising an anionic polycarboxylate dispersing agent which adjusts the pH of the aqueous suspension whereby the aqueous suspension formed in step (c) has a pH which lies within the inclusive range 8.5 to 9.8; and wherein following addition of the said additive comprising the polycarboxylate dispersing agent in step (c), the suspension is not ground further.