Layered composite pigments and method of making same

Claim 2

A composite pigment comprising one or more types of core pigment particles and one or more types of co-pigment particles prepared by mixing core pigment particles with co-pigment particles, the core pigment particles prior to mixing comprising adsorbed on their surface a dispersing agent consisting essentially of a cationic polyelectrolyte dispersant or an anionic polyelectrolyte dispersant and the co-pigment particles prior to mixing comprising adsorbed on their surface of dispersing agent consisting essentially of an anionic polyelectrolyte dispersant or a cationic polyelectrolyte dispersant which is opposite in charge to the dispersant on the core pigment particles and which provides the co-pigment particles with a charge opposite the charge of the core pigment particles, the co-pigment particles in the composite pigment being electrostatically bound to the core pigment particles, the core pigment particles and the co-pigment particles having an average particle size greater than 0.1 micron.

Claim 3

The composite pigment of claim 1 in which said core and co-pigment particles are selected from the group consisting of kaolin clays, calcined clay, calcium carbonate, titanium dioxide, calcium sulfate, aluminum trihydrate, silica, talc, zinc oxide, lithopone, satin white, plastic hollow spheres, plastic pigments, calcium silicate, and synthetic or natural binders.

Claim 4

The composite pigment of claim 2 comprising adjuvant particles incorporated into the composite pigment, said adjuvant particles being water or alkali or acid soluble binders having a particle size less than 0.1 micron.

Claim 5

The composite pigment of claim 2 comprising adjuvant particles incorporated into the composite pigment wherein said adjuvant particles are selected from the group consisting of: dyes, bactericides, defoamers, antifoamers, lubricants, optical brighteners and water retention aids.

Claim 6

The composite pigment of claim 1 comprising kaolin clay having sodium polyacrylate adsorbed on the surface thereof as either a core pigment particle or co-pigment particle, or both.

Claim 7

The composite pigment of claim 5 wherein the core pigment particle is a swollen pigment particle.

Claim 8

A coating composition comprising the composite pigment of claim 1.

Claim 9

A paper composition comprising the composite pigment of claim 1.

Claim 10

A plastic comprising the composite pigment of claim 1.

Claim 11

A rubber comprising the composite pigment of claim 1.

Claim 12

An ink comprising the composite pigment of claim 1.

Claim 13

A composite pigment dispersion comprising one or more types of core pigment particles and one or more types of co-pigment particles prepared by mixing core pigment particles with co-pigment particles, the core pigment particles prior to mixing comprising adsorbed on their surface a dispersing agent consisting essentially of a cationic polyelectrolyte dispersant or an anionic polyelectrolyte dispersant and the co-pigment particles prior to mixing comprising adsorbed on their surface a dispersing agent consisting essentially of an anionic polyelectrolyte dispersant or a cationic polyelectrolyte dispersant which is opposite in charge to the dispersant on the core pigment particles and which provides the co-pigment particles with a charge opposite the charge of the core pigment particles, the co-pigment particles in the composite pigment dispersion being electrostatically bound to the core pigment particles, the core pigment particles and the co-pigment particles having an average particle size greater than 0.1 micron.

Claim 14

A composite pigment dispersion comprising one or more types of core pigment particles and one or more types of co-pigment particles prepared by mixing core pigment particles with co-pigment particles, the core pigment particles prior to mixing comprising adsorbed on their surface a dispersing agent consisting essentially of a cationic polyelectrolyte dispersant or an anionic polyelectrolyte dispersant and the co-pigment particles prior to mixing comprising adsorbed on their surface a dispersing agent consisting essentially of an anionic polyelectrolyte dispersant or a cationic polyelectrolyte dispersant which is opposite in charge to the dispersant on the core pigment particles and which provides the co-pigment particles with a charge opposite the charge of the core pigment particles, the co-pigment particles in the composite pigment dispersion being electrostatically bound to the core pigment particles, the core pigment particles and the co-pigment particles having an average particle size greater than 0.1 micron.

Claim 15

The dispersion of claim 12 comprising an aqueous medium.

Claim 16

The dispersion of claim 12 prepared by adding a dispersion of the core pigment particles, with shear mixing, slowly to a dispersion of the co-pigment particles.

Claim 17

The dispersion of claim 14 comprising a volumetric excess of co-pigment particles, said dispersion having a net charge which is of the same sign as the co-pigment particles.

Claim 18

The dispersion of claim 14 comprising a cationic or anionic dispersant post-added to the dispersion, after admixing the core particle dispersion and the co-particle dispersion, in an amount effective to establish the net charge of the dispersion.

Claim 19

The dispersion of claim 16 comprising 0.1% to 2% of said dispersant based on pigment weight.

Claim 20

The dispersion of claim 12 in which the core and co-pigment particles are selected from the group consisting of kaolin clay, calcined clay, calcium carbonate, titanium dioxide, calcium sulfate, aluminum trihydrate, silica, talc, zinc oxide, lithopone, satin white, plastic hollow spheres, plastic pigments, calcium silicate, and synthetic or natural binders.

Claim 21

The dispersion of claim 12 in which the core pigment particle is a swollen pigment particle.

Claim 22

The dispersion of claim 12 comprising adjuvant particles incorporated into the composite pigment, said adjuvant particles being water or alkali or acid soluble binders having a particle size less than 0.1 micron.

Claim 23

The dispersion of claim 12 comprising adjuvant particles incorporated into the composite pigment wherein said adjuvant particles are selected from the group consisting of dyes, bactericides, defoamers, antifoamers, lubricants, optical brighteners, and water retention aids.

Claim 24

A coating composition comprising the dispersion of claim 12.

Claim 25

A paper composition comprising matrix forming components and the dispersion of claim 12 as a filler.

Claim 28

The method of claim 24 wherein the suspension of the core pigment particles is slowly added to the suspension of co-pigment particles with shear admixing wherein there is present in the admixture throughout the addition an abundance of co-pigment particles, the co-pigment particles defining a layered structure on the core pigment particles.

Claim 29

The method of claim 24 including the step of post-adding to the admixture a dispersant having an anionic or cationic charge in an amount effective to establish in the admixture a net charge of the same sign as said post-added dispersant.

Claim 30

The method of claim 24 wherein at least one of said core pigment or co-pigment suspension is prepared by the steps of: (a) obtaining said core pigment or said co-pigment; (b) preparing an aqueous solution or suspension of an anionic or cationic polymeric water soluble dispersant; (c) adding said pigment of paragraph (a) to said solution or suspension with mixing whereby said polymeric dispersant is adsorbed onto the surface of said pigment, said polymeric dispersant being present in said solution in an amount in the range of 0.1% to 2% based on the weight of said pigment.

Claim 31

A composite pigment dispersion prepared by the method of claim 24.

Claim 32

A composite pigment prepared by the method of claim 24, said method further including the step of drying the composite pigment.