Method for processing kaolin clay pigment and improved product thereof

Claim 2

IN THE WET PROCESSING OF KAOLIN CLAY TO PRODUCE A CLAY COATING PIGMENT WHEREIN KAOLIN CLAY IS PROVIDED IN THE FORM OF AN ACIDIC FLOOCULATED AQUEOUS PULP WHICH IS FILTERED TO REMOVE ACIDIC PULP WATER AND THE FILTRED CAY IS WASHED TO PROVIDE AN ACID CLAY FILTER CAKE AMENABLE TO DEFLOCCULATION WITH A CLAY DISPERSANT, THE IMPROVEMENT, WHEREBY THE OPACIFYING POWER OF THE CLAY IS INCREASED WITHOUT ADVERSELY AFFECTING THE CLAY RHEOLOGY, WHICH IMPROVEMENT COMPRISES MIXING INTO SAID ACIDIC FLOCCULATED PULP, BEFORE THE PULP IS FILTERED, A SMALL AMOUNT OF A COLOURLESS SOURCE OF POLYVALENT METAL CATION AND A SMALL AMOUNT OF A COLOURLESS SOURCE OF BORATE IONS, SAID SOURCES BEING ADDED IN AMOUNTS INSUFFICIENT TO NEUTRALIZE OR TO DEFLUOCCULATE THE PULP BUT BEING SUFFICIENT TO IMPROVE THE OPACITY OF COATINGS PIGMENTED WITH THE CLAT.

Claim 3

The method of claim 1 wherein the borate compound is borax added in amount within the range of 0.1 percent to 1 percent of the weight of the clay.

Claim 4

In the wet processing of kaolin clay to produce a clay coating pigment wherein kaolin clay is provided in the form of an acidic flocculated aqUeous pulp which is filtered to remove acidic pulp water and the filtered clay is washed to provide an acid clay filter cake and the filtered clay is dispersed by adding a strong clay dispersant, the improvement, whereby the opacifying power of the clay is increased, which comprises mixing a small amount of a colorless source of metal polyvalent cations into the acidic pulp before it is filtered and mixing a small amount of a colorless source of borate ions into the filtered, washed, acidic clay before adding all of the clay dispersant, the amount of the source of the borate ions being insufficient to neutralize or to deflocculate the acidic clay but being sufficient when used in combination with said source of polyvalent cations to improve the opacity of coatings pigmented with the dispersed clay.

Claim 5

In the wet processing of kaolin clay to produce a clay coating pigment wherein kaolin clay is provided in the form of an acidic flocculated aqUeous pulp which is filtered to remove acidic pulp water and the filtered clay is washed to provide an acid clay filter cake and the filtered clay is dispersed by adding a strong clay dispersant, the improvement, whereby the opacifying power of the clay is increased, which comprises mixing a small amount of a colorless source of metal polyvalent cations into the acidic pulp before it is filtered and mixing a small amount of a colorless source of borate ions into the filtered, washed, acidic clay before adding all of the clay dispersant, the amount of the source of the borate ions being insufficient to neutralize or to deflocculate the acidic clay but being sufficient when used in combination with said source of polyvalent cations to improve the opacity of coatings pigmented with the dispersed clay.

Claim 6

The method of claim 3 wherein the borate compound is borax added in amount within the range of 0.1 percent to 1 percent of the weight of the clay.

Claim 7

The method of claim 3 wherein said dispersant is a condensed phosphate salt.

Claim 8

A predispersed kaolin clay coating pigment comprising kaolin clay particles mixed with a small amount of a colorless source of polyvalent cations and a small amount of a colorless source of metal borate ions in amounts insufficient to neutralize or to deflocculate the clay but sufficient to improve the opacity of coatings pigmented with the clay, and a clay dispersant in amount sufficient to deflocculate the clay.

Claim 9

A predispersed kaolin clay coating pigment comprising kaolin clay particles mixed with a small amount of a colorless source of polyvalent cations and a small amount of a colorless source of metal borate ions in amounts insufficient to neutralize or to deflocculate the clay but sufficient to improve the opacity of coatings pigmented with the clay, and a clay dispersant in amount sufficient to deflocculate the clay.

Claim 10

The pigment of claim 6 wherein said borate compound is borax.

Claim 11

The pigment of claim 6 wherein said dispersant is a sodium condensed phosphate.

Claim 12

A predispersed kaolin clay coating pigment comprising particles of bleached kaolin clay containing added acid-soluble colorless polyvalent metal cations in amount within the range of 200 to 600 p.p.m., from 0.1 percent to 1 percent by weight of borax, and from 0.1 percent to 0.5 percent of a sodium condensed phosphate salt.

Claim 13

A predispersed kaolin clay coating pigment comprising particles of bleached kaolin clay containing added acid-soluble colorless polyvalent metal cations in amount within the range of 200 to 600 p.p.m., from 0.1 percent to 1 percent by weight of borax, and from 0.1 percent to 0.5 percent of a sodium condensed phosphate salt.

Claim 14

The pigment of claim 9 wherein said kaolin clay is a fine size fraction of a hard kaolin clay crude.

Claim 15

The pigment of claim 9 wherein said kaolin clay is a fine size fraction of a soft kaolin clay crude.

Claim 16

The pigment of claim 9 wherein said kaolin clay is a fraction of mechanically ground coarse soft kaolin clay.

Claim 17

A kaolin clay coating pigment consisting essentially of particles of kaolin clay containing an added colorless source of polyvalent metal cations and an added colorless source of borate ions in amounts insufficient to neutralize or to deflocculate the clay but sufficient to improve the opacity of the clay, said pigment being acidic and capable of being deflocculated with a sodium condensed phosphate clay dispersant to form a high solids deflocculated clay-water slurry having acceptable rheology for formulation in a paper coating composition.

Claim 18

A kaolin clay coating pigment consisting essentially of particles of kaolin clay containing an added colorless source of polyvalent metal cations and an added colorless source of borate ions in amounts insufficient to neutralize or to deflocculate the clay but sufficient to improve the opacity of the clay, said pigment being acidic and capable of being deflocculated with a sodium condensed phosphate clay dispersant to form a high solids deflocculated clay-water slurry having acceptable rheology for formulation in a paper coating composition.