Pigment products
AssigneeImerys Pigments, Inc.
InventorsJohn Claude Husband, Desmond Charles Payton, Michele Susan Renals
Life of this patent
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Abstract
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 whose particles have a particle size distribution such that at least 80% by weight of the particles have an equivalent spherical diameter less than 2 μm and not less than 8%, preferably not less than 12%, by weight of the particles have an equivalent spherical diameter less than 0.25 μm and whose particles have a shape factor of at least 45, preferably at least 50.
Claims32
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 whose particles have a particle size distribution such that at least 80% by weight of the particles have an equivalent spherical diameter less than 2 μm and not less than 8% by weight of the particles have an equivalent spherical diameter less than 0.25 μm and whose particles have a shape factor of at least 45.
A pigment product as claimed in any one of the preceding claims and wherein at least 50% by weight of the particles have an equivalent spherical diameter in the range of from 0.75 μm to 0.25 μm.
A pigment product as claimed in any one of the preceding claims and wherein the mean equivalent spherical diameter of the particles of the product is from 0.3 μm to 0.8 μm.
A pigment product as claimed in any one of the preceding claims and wherein the shape factor of the particles of the pigment product is at least 50.
A method of treating a kaolin clay to increase the particle fineness and shape factor thereof which includes the steps of:
- (a) treating an aqueous suspension of the clay by a first comminution process to give delamination of the clay, in which an energy of not more than 75 kWh per tonne of clay on a dry weight basis is dissipated;
- (b) treating the clay after delamination in step (a) by a second comminution process to give particle comminution in which an energy of from 40 to 120 kWh per tonne of clay on a dry weight basis is dissipated.
Dependencies are inferred from the claim text.