Imerys Minerals Limited

Deborah Susan Thrale

David Robert Skuse

David Skuse

John Anthony Purdey

Christopher Robin Golley

Mark Daniel Mortimer

David James Mogridge

A method of producing a rheologically stable concentrated aqueous suspension of a particulate alkaline earth metal carbonate which method comprises the following steps: (a) preparing a dilute aqueous suspension of the carbonate having a solids content of not more than 40% by weight; (b) dewatering the dilute aqueous suspension to form a carbonate suspension having a solids content in the range of from 45% to 65% by weight; (c) optionally mixing with the dewatered suspension formed in step (b) a dispersing agent for the carbonate to form a fluid suspension; (d) further dewatering the fluid suspension formed in step (b) by thermal evaporation under reduced pressure to raise the solids content of the suspension by a further differential amount of at least 5% by weight; and (e) after at least some of the dewatering in step (c) treating the suspension by a mechanical working process in which at least 1 kW.hr per tonne of carbonate on a dry weight basis is dissipated to refluidise the suspension.

Production of concentrated carbonate suspensions

A method of producing a dispersed aqueous suspension of an inorganic particulate material which includes the steps of (a) preparing an aqueous suspension of calcium carbonate particles having a particle size distribution such that at least 35% by weight have an esd less than 24 .mu.m, the solids concentration of the suspension being no more than 40% by dry weight; (b) concentrating the suspension by dewatering to increase the solids content to at least 60% by dry weight; and (c) adding a dispersing agent to the concentrated suspension to disperse the calcium carbonate particles and characterized in that the suspension produced by step (c) is pumpable and flowable, the dispersing agent comprising a water soluble copolymer of acrylic acid and maleic acid or a salt thereof having a molar ratio of acrylic acid units to maleic acid units of from 0.5:1 to 10:1 and a mass average molecular mass of from 1,000 to 100,000.

Dispersed aqueous suspensions

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Cornwall, United Kingdom

Deborah Susan Thrale