Imerys Pigments, Inc.

Christopher R L Golley

Robert J Pruett

John Claude Husband

Jun Yuan

Daniel John Panfil

Harry Vincent Brown, Jr

Anthony V Lyons

Michael J Garska

William L Garforth

David Leslie Light

Rajan R Iyer

Graham M Pring

Christopher Nutbeem

William H Pope

Anthony Allan May

Ernest Gay

Ronald Windell Andrews

Milton Constantin

David Andrew Greenhill

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

The present invention provides high brightness kaolins exhibiting a Brightness (GE) of at least about 90.0. The hydrous kaolin pigments of the present invention may also have, inter alia, a steepness index (d/d&#xd7;100) of at least about 39 and/or a titania concentration less than or equal to about 0.40% by weight of the pigment on a dry basis. (062) The hydrous kaolin pigment is produced by a process comprising: a) forming an aqueous suspension of a hydrous kaolin clay; b) forming a primary product by subjecting the suspension to classification or a combination of classification and griding; c), separating the kaolin from impurities by selective flocculation; and d) defining the separated kaolin. (063) The hydrous kaolins of the present invention allow coated papers to be produced at high brightness while maintaining acidic conditions on a paper machine. The invention pigmets exhibit brightness levels unexpectedly higher, e.g., about 2 to about 2.5 or more (GE) units brighter, than exhibited by previous high brightness hydrous kaolin pigments, without sacrificing other important paper properties. Paper coated with the inventive pigmants have high brightness, high whiteness, and high fluorescence levels. The present invention encompasses these pigments, compositions comprising them, and any application in which they are used.

Kaolin pigment having high brightness and narrow particle size distribution and method of preparation therefor

The present invention provides an improved method of beneficiating and dewatering kaolin clays. The product of the improved process is a brightened, dewatered kaolin, suitable for use in pigments and paper coating compositions. The improved beneficiation process provides refined kaolin for pigments and other purposes of the same or better quality as prior art processes, but with the use of fewer steps and materials, at significant cost and environmental savings.

Integrated process for simultaneous beneficiation, leaching, and dewatering of kaolin clay suspension

Bleaching a particulate calcium carbonate aqueous slurry with a reductive bleaching agent such as formamidine sulfinic acid increases the viscosity of the slurry. Combining the slurry with a metal material such as strontium hydroxide reduces any increase in viscosity of the bleached calcium carbonate slurry. Addition of the reductive bleaching agent and/or the metal material takes place prior to, during or after the manufacture of the slurry or the bleaching step. Metal materials in one embodiment include those that form substantially water insoluble precipitates of the reductive bleaching reaction products.

Stabilization of the viscosity of formamidine sulfinic acid bleached calcium carbonate slurries

Method of treating an aqueous suspension of kaolin

A pigment product suitable for use in a coating composition to provide a gloss coating on paper, the pigment product comprising a processed particulate kaolin produced from a naturally platy kaolin clay having a particle size distribution such that about 50% to 60% by weight of the particles have an esd less than 2 &mgr;m and less than 25% by weight of the particles have an esd less than 0.25 &mgr;m and a shape factor of at least 15. In processing, the crude kaolin is ground to a shape factor greater than 50 to produce even greater &ldquo;platy&rdquo; clay. The pigment product has a particle size distribution such that at least 80% by weight of the particles have an esd less than 2 &mgr;m and greater than 12% and less than 35% by weight of the particles have an esd less than 0.25 &mgr;m and whose surface area is greater than 12 m /g when measured by the BET method.

Kaolin pigments, their preparation and use

A pigment product suitable for use in a coating composition to provide a gloss coating on paper, the pigment product comprising a processed particulate kaolin produced from a naturally platy kaolin clay having a particle size distribution such that about 50% to 60% by weight of the particles have an esd less than 2 &mgr;m and less than 25% by weight of the particles have an esd less than 0.25 &mgr;m and a shape factor of at least 15. This platy clay can be blended with b-fraction clay component. In processing, the crude kaolin is ground to a shape factor greater than 50 to produce even greater &ldquo;platy&rdquo; clay. The pigment product has a particle size distribution such that at least 80% by weight of the particles have an esd less than 2 &mgr;m and greater than 12% and less than 35% by weight of the particles have an esd less than 0.25 &mgr;m and whose surface area is greater than 12 m /g when measured by the BET method.

A kaolin clay pigment comprises a coarse kaolin clay or a blend of a coarse kaolin clay with a fine kaolin clay. The coarse kaolin clay is a delaminated and defined pigment product with an overall shape factor greater than about 12. If the coarse kaolin clay is fluid at about 65% to about 75% solids, then it is used by itself as the kaolin pigment. If it is not fluid, it is blended with a fine kaolin clay in amounts ranging from about 0.1% to about 30.0% by weight of the blend. The coarse kaolin clay fraction has a Hinckley Crystallinity Index greater than about 0.6 and the fine kaolin clay has a Hinckley Crystallinity Index less than about 0.5. The pigment has a G.E. brightness of about 90.5 and a particle size distribution such that at least about 90% by weight of the particles has an e.s.d. less than about 2 &mgr;m and about 30% by weight of the particles has an e.s.d. less than about 0.25 microns. At about 65% to about 75% solids, the Hercules viscosity is greater than 250 rpm at about 18 dynes and when used in a coating formulation, exhibits improved sheet brightness, sheet gloss, sheet opacity and print gloss.

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Sandersville, GA, United States of America

Christopher R L Golley