PREPARATION OF SYSTEMS OF GROUND PARTICULATE MATERIAL

摘要

There is disclosed 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 in coarse particulate form; (b) grinding the suspension formed in step (a) in the presence of a polycarboxylate dispersing agent for the particulate material; (c) adding further polycarboxylate dispersing agent to the suspension of ground material formed in step (b). The process is characterized in that the aqueous suspension formed in step (c) has a pH which lies within the inclusive range 8.5 to 9.8 and in that, following addition of the polycarboxylate dispersing agent in step (c), the suspension is not ground further. Using the method described, suspensions can be prepared which are rheologically stable with time, and which contain a relatively high proportion by weight of a finely divided pigment.