Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
1999-05-20
2001-11-06
Marcheschi, Michael (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C106S464000, C106S468000, C106S484000, C106S487000, C209S038000
Reexamination Certificate
active
06312511
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of kaolin clay products, including delaminated and nondelaminated kaolin clay pigment products, which are particularly useful for use in paper products. Specifically, the present invention relates to kaolin clay products having high brightness and good opacity characteristics, and methods of making and using such products.
2. Background Art
Kaolin clay pigments are obtained from kaolin crudes. The crudes can contain kaolin particles, oversize particle size impurities (grit), and fine and coarse particle size impurities, such as fine ferruginous or titaniferous impurities, which impart undesirable color to the clay. The kaolin particles typically occur in the crude over a wide range of particle sizes and shapes. Typically a kaolin crude, such as a typical Georgia crude will contain, after removing the grit, particles ranging in size from submicron or colloidal to 20 microns or larger. Typically the kaolin morphology includes arrangement in plates, which plates can be further arrayed in stacks. Particle size, impurity content and morphology can vary with location of the deposit and within any given deposit itself.
Particle size of kaolins are typically determined by sedimentation using Stokes law to convert settling rates to particle size distribution and assuming a spherical shape of the particles. Measurements of particle size determined by this method therefore are termed as e.s.d., i.e. equivalent spherical diameter, as determined by Sedigraph. Typically, kaolin particles finer than about 2 microns are composed of individual platelets, and particles larger than about 2 microns are composed of stacks or booklets of finer particles.
Previous methods of producing kaolin clay pigments for paper end uses have included steps such as delamination, which disaggregates large kaolin particles, i.e., stacks, into smaller particles having a higher aspect ratio, primarily by separating clay crystals along basal cleavages. See, e.g., U.S. Pat. Nos. 3,171,718 (Gunnet et al.); U.S. Pat. No. 5,169,443 (Willis et al.), U.S. Pat. No. 5,411,587 (Willis et al.). Typically, however, the resulting product has a brightness of around 84-85. For end uses such as use as paper coating, a kaolin having a higher brightness, and also possessing other desirable characteristics such as good opacity, would be highly advantageous for making a superior paper product. For end uses such as use as paper filling a kaolin having a higher brightness, and also possessing other desirable characteristics such as good opacity and good tensile strength, would be highly advantageous for making a superior yet economical paper product.
In paper production, currently precipitated calcium carbonate (PCC) is used as a filler in paper to reduce the percentage of pulp that must be used as filler in the paper, pulp being expensive. Precipitated calcium carbonate has been used as a filler to reduce that cost. Typically, precipitated calcium carbonate has been used at percentages around 12% to 15%. When precipitated calcium carbonate content was increased to about 18%, a reduction in paper tensile strength resulted. Therefore, PCC as a filler has been limited to about 12-15% by its degrading influence on physical properties.
The present invention provides both delaminated and nondelaminated kaolin pigments having surprising brightness of 87 or greater and even 90 or greater, and methods of making such kaolin pigments. These pigments further have good opacity and strong tensile strength. Thus the present invention provides a highly desirable pigment useful in any application wherein high brightness, opaque pigments are needed, and particularly in uses such as in paper coating applications, and in paper filling applications wherein pigments having not only high brightness and good opacity but also good tensile strength are needed.
SUMMARY OF THE INVENTION
The present invention provides a method of making a high brightness kaolin clay comprising:
a. applying magnetic separation to a blunged, degritted kaolin clay crude having a particle size distribution as follows: 50%-70% less than 2 microns, 20%-35% less than 0.5 microns and 5%-20% less than 0.3 microns, all e.s.d. as determined by Sedigraph for a period of time sufficient to achieve the desired brightness,
b. fractionating the clay to retain a fraction that is 90% less than two microns in particle size, separately from the remaining clay, wherein the retained 90% less than two micron fraction comprises the high brightness kaolin clay.
The present invention further provides a method of making a high brightness kaolin clay comprising:
a. applying magnetic separation to a blunged, degritted kaolin clay crude having a particle size distribution as follows: 50%-70% less than 2 microns, 20%-35% less than 0.5 microns and 5%-20% less than 0.3 microns, all e.s.d. as determined by Sedigraph for a period of time sufficient to achieve the desired brightness to make a purified feed;
b. fractionating the clay into a first fraction of 90% less than 2 micron and a second fraction of remaining clay,
c. blending the purified feed with the second fraction to form a blended clay having a ratio of purified feed to second fraction of from 100:0 to 0:100;
d. grinding the blended clay to a particle size of from 60 to 90% less than two microns.
The present invention additionally provides a method of making a high brightness kaolin clay comprising:
a. applying magnetic separation to a blunged, degritted kaolin clay crude obtained from an area in the Rio Capim area of Brazil having coordinates south 02°-21′, west 47°-52′ and having a particle size distribution as follows: 50-70% less than 2 microns, 20%-35% less than 0.5 microns and 5-20% less than 0.3 microns, all e.s.d. as determined by Sedigraph for a period of time sufficient to achieve the desired brightness,
b. fractionating the clay to retain a fraction that is 90% less than two microns in particle size, separately from the remaining clay, wherein the retained 90% less than two micron fraction comprises the high brightness kaolin clay.
The present invention additionally provides a nondelaminated high brightness kaolin clay having the following characteristics:
a. particle size of 90% less than two microns (e.s.d. as measured by Sedigraph) and a ratio of % less than 2.0 microns/% less than 0.5 microns≦2.0;
b. brightness of 87 or greater; and
c. Brookfield viscosity measured at 20 rpm and 71% solids of greater than 100 cp.
The present invention additionally provides a nondelaminated high brightness kaolin clay having the following characteristics:
a particle size of at least 60% less than two microns (e.s.d. as measured by Sedigraph);
b brightness of 87 or greater; and
c. Brookfield viscosity measured at 20 rpm and 71% solids of greater than 175 cp.
The present invention additionally provides a delaminated high brightness kaolin clay having the following characteristics:
a. particle size of from 60 to 90% less than two microns (e.s.d. as measured by Sediograph);
b. brightness of 87 or greater; and
c. Hercules viscosity of less than 1000 rpm at 18 dynes.
The present invention further provides a high brightness kaolin clay comprising a blend of the following component clays:
a. a nondelaminated kaolin clay having the following characteristics:
i. particle size of 90% less than two microns (e.s.d. as measured by Sedigraph) and a ratio of % less than 2.0 microns/% less than 0.5 microns≦2.0;
ii. brightness of 87 or greater; and
iii. Brookfield viscosity measured at 20 rpm and 71% solids of greater than 100 cp; and
b a delaminated kaolin clay having the following characteristics:
i. particle size of from 60 to 90% less than two microns (e.s.d. as measured by Sedigraph);
ii. brightness of 87 or greater; and
iii. Hercules viscosity of less than 1000 rpm at 18 dynes,
in a ratio of from 100:0 to 0:100.
The present invention additionally provides a high brightness kaolin clay comprising a blend of the following component clays:
a. a nondelaminated k
Bilimoria Bomi M.
Manasso John A.
Willis Mark S.
Finnegan, Henderson Farabow, Garrett and Dunner L.L.P.
Imerys Kaolin, Inc.
Marcheschi Michael
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