Imerys Minerals Limited

Ecc International Limited

Imerys Pigments, Inc.

David Leslie Light

Philip Kenneth Johns

Christopher R L Golley

Ernest Gay

Christopher D Paynter

Milton Constantin

A particulate product comprising kaolin produced from a method wherein the kaolin of a feed suspension is such that not more than 30% by weight has a particle size less than 2 &#x3bc;m and not more than 30% by weight has a particle size greater than 10 &#x3bc;m, wherein the kaolin of a product suspension produced is such that not more than 10% by weight has a particle size greater than 10 &#x3bc;m and not more than 10% by weight has a particle size less than 0.25 &#x3bc;m, and wherein the particulate product comprises kaolin produced from a fine fraction suspension.

Kaolin products and their production

A pigment product for use in a coating composition to provide a gloss coating on paper, the pigment product comprising a processed particulate kaolin having a particle size distribution such that at least about 80% by weight of the particles have an equivalent spherical diameter less than about 2 p,m and in the range of from about 10% to about 20% by weight of the particles have an equivalent spherical diameter less than about 0.25 wm, the particles have a shape factor in the range of from about 20 to about 36 and the particles have a particle steepness in the range of about greater than about 35, more preferably in the range of about 35 to about 40, and wherein the kaolin is derived from a secondary kaolin source.

Kaolin pigment products

There is provided a method of producing a kaolin particulate material suitable for use as an improved super-calendered filler. This method includes: (a) preparing an aqueous feed suspension of kaolin; (b) treating the kaolin of the feed suspension by attrition grinding in a vessel using grinding media granules; (c) delivering an aqueous suspension of the kaolin ground in (b) to a particle size classifier and separating the kaolin of the suspension into a coarse fraction and a fine fraction; (d) returning an aqueous suspension of the coarse fraction produced in (c) to the grinding vessel to be further attrition ground; and (e) extracting an aqueous suspension of the fine fraction produced in (c) as a product suspension. Advantageously, the kaolin of the feed suspension in (a) is such that not more than 30% by weight has a particle size less than 2 &#x3bc;m and not more than 30% by weight has a particle size greater than 10 &#x3bc;m. In addition, the kaolin of the product suspension produced in (e) is such that not more than 10% by weight has a particle size greater than 10 &#x3bc;m and not more than 10% by weight has a particle size less than 0.25 &#x3bc;m.

There is disclosed a process for preparing a filler composition suitable for incorporation in a polyester film-forming material, which process comprises the following steps: (a) calcining a crude kaolin clay under conditions such that the calcined product comprises particles consisting of aggregates of fine kaolin platelets; (b) suspending the calcined clay product from step (a) in water containing a dispersing agent for the calcined clay, so as to form a suspension containing from 40% to 70% by weight of dry calcined clay; (c) subjecting the suspension formed in step (b) to comminution by attrition grinding with a particulate grinding medium for a time sufficient to reduce the average diameter of the aggregate particles to within the range from 0.3 .mu.m to 0.9 .mu.m, and to ensure that the calcined clay is substantially free of particles having an equivalent spherical diameter larger than 5 .mu.m; and (d) heating the suspension of comminuted calcined clay formed in step (c) to a temperature in the range from 80.degree. C. to 100.degree. C. to drive off water by evaporation, a liquid glycol being added at the same time as the water is driven off to keep the volume of the suspension substantially constant. The process produces a product which has good anti-blocking characteristics, making it useful for incorporation in organic polymer film materials.

Growing community of inventors

Cornwall, United Kingdom

David Leslie Light