KR20070085901A - Pigment composition in the form of aqueous dispersion - Google Patents

Abstract

The invention relates to a pigment composition in the form of an aqueous dispersion or slurry comprising: (a) porous aggregates formed by aggregation of colloidal primary particles of silica, aluminosilicate or a mixture thereof in an aqueous sol, said porous aggregates having a mean diameter from about 0.03 to about 25 mum, and, (b) extender particles where the mean size of at least one dimension is larger than the mean diameter of the porous aggregates, wherein the weight ratio of porous aggregates to extender particles is from about 0.01:1 to about 3:1. The invention further relates to a process for its production, a compositionfor coating paper or paper board and a process for its production, and a process for coating paper or paper board and paper or paper board obtainable by the process.

Description

Pigment composition in the form of an aqueous dispersion {PIGMENT COMPOSITION IN THE FORM OF AQUEOUS DISPERSION}

The present invention relates to a pigment composition and a method for producing the same, a composition for paper or paperboard coating and a method for producing the same, and a paper or paperboard coating method and a paper or paperboard obtained by the method.

The development of ink-jet printers has led to the demand for paper suitable for that purpose. In particular, there is a need for paper that is simple to manufacture and allows for high quality ink-jet printing.

It has been disclosed to use various kinds of coatings to produce paper suitable for ink-jet printing.

US 2002/0039639 discloses incorporating a water soluble metal salt in an ink receptive layer comprising a pigment and a traditional binder.

US Pat. No. 4554181 discloses a recording surface comprising a combination of a water soluble polyvalent metal and a cationic polymer.

US 2004/0255820 discloses pigments that are surfaces treated with water soluble polyatomic metal salts.

US 2005/0106317 discloses forming at least one porous layer containing silica particles having an average second particle size of 500 nm or less, wherein the solids content of the coated inorganic particles on the porous layer is 0.33 g / A method of making an ink-jet recording material comprising coating a coating solution to prepare an inorganic particle-containing layer to be no greater than m ² .

US Patent No. 6797347 discloses an ink-jet paper comprising a base paper and a coating thereon, wherein the coating contains an inorganic pigment and a binder modified with a positively charged composite. Positively charged complexes contain polyvalent metal ions and organic ligands.

US 2003/0099816 discloses an ink jet-recording material comprising a transparent ink-receiving layer and a substrate comprising a plurality of particles and a binder formed by applying strong mechanical stress to disperse the amorphous silica particles and divide the particles. It starts.

Other examples of publications relating to coated papers are WO 03/011981, WO 01/53107, WO 01/45956, EP 947349, EP 1120281 and US 5551975.

It is an object of the present invention to provide a pigment composition that is simple to manufacture and suitable for coated paper or paperboard for ink-jet printing.

It is another object of the present invention to provide a coating formulation that is simple to apply to the surface of paper or cardboard to make it suitable for ink-jet printing.

It is yet another object of the present invention to provide paper or paperboard suitable for ink-jet printing, which is simple to manufacture.

Therefore, one aspect of the present invention relates to pigment compositions in the form of aqueous dispersions comprising:

a) a porous aggregate formed by agglomeration of colloidal first particles of silica, aluminosilicate or mixtures thereof in an aqueous sol, the porous aggregate having an average diameter of about 0.03 μm to about 25 μm, and

b) the average size of at least one dimension is greater than the average diameter of the porous aggregate, and the weight ratio of porous aggregate to extender particles is from about 0.01: 1 to about 3: 1, preferably from about 0.01: 1 to about 2: 1, most Extender particles, preferably from about 0.05: 1 to about 1.5: 1.

The average particle diameter of the colloidal first particles is preferably about 2 nm to about 75 nm, most preferably about 3 nm to about 50 nm. The surface area of the first particles is preferably from about 35 m ² / g to about 1400 m ² / g, most preferably from about 50 m ² / g to about 1000 m ² / g. In one embodiment the surface area is about 600 m ² / g or less, preferably about 450 m ² / g or less and most preferably about 300 m ² / g or less. The dry content of the aqueous sol in the first particles is preferably from about 0.5% to about 60% by weight, most preferably from about 1% to about 50% by weight.

The term diameter, as used herein, means the equivalent diameter.

The colloidal first particles of silica or aluminosilicate are preferably formed from an aqueous solution of alkali metal silicate in which the alkali metal ions have been removed via an ion exchange process or the pH of the alkali metal silicate solution has been reduced by the addition of acid. Processes based on ion exchange are described in R.K. Her, "The Chemistry of Silica" 1979, pages 333-334, following the basic principle, which results in an aqueous sol comprising colloidal negative or positively charged particles of silica or aluminosilicate. Processes based on pH-reduction of alkali metal silicates follow the basic principles described, for example, in US Pat. Nos. 5176891, 5648055, 5853616, 5482693, 6060523 and 6274112.

Particularly preferred sols comprise colloidal first particles of silica which are not surface modified or modified with metal oxides such as, for example, oxides of aluminum, titanium, chromium, zirconium, boron 똔 or other suitable metals.

Suitable aqueous sols of colloidal first particles of silica or aluminosilicate are commercially available, for example, under the Ludox ™, Snowtex ™, Bindzil ™, Nyacol ™, Vinnsil ™ or Fennosil ™ trademarks.

When silica or aluminosilicate can be dried to form a powder, the sol formed by dispersing such a powder is a colloidal particle, in which case the sol is the same as a sol prepared from alkali metal silicate by ion exchange or pH-reduction. Was found to have different properties from the sols that were not dried to powder at all.

Aggregation of the first particles in the sol to form a dispersion of porous aggregates is by any suitable method as described in R. K. Her, "The Chemistry of Silica" 1979, pages 364-407. Cohesion can be understood by measuring viscosity and applying Einstein and Mooney's equations (see, eg, R.K. Her, "The Chemistry of Silica" 1979, pages 360-364). Aggregation can be carried out as a separate step or in a mixture further comprising extender particles.

In one embodiment, the anionic sol (comprising the negatively charged colloidal first particles) and the cationic sol (comprising the positively charged colloidal first particles) are mixed from both sols. Porous aggregates of the first particles are formed.

In another embodiment salts, preferably diatoms, salts selected from polyatoms or complex salts are added to the anionic or cationic sol, also forming porous aggregates. Examples of salts are aluminum chloride, poly aluminum chloride, poly aluminum silicate sulfate, aluminum sulfate, zirconium carbonate, zirconium acetate, alkali metal borate, and mixtures thereof.

In yet another embodiment, a bridging substance is used to form aggregates from the first particles. Examples of suitable bridging materials include synthetics such as CMC (carboxymethyl cellulose), PAM (polyacrylamide), polyDADMAC (poly diallyl dimethyl ammonium chloride), polyallyl amine, polyamine, starch, guar gum, and mixtures thereof. It is a natural polyelectrolyte.

Combination methods including one, two or all three of the agglomeration methods may also be used.

Each porous aggregate is formed from at least three first particles, which inherently provide at least some degree of voids. The average particle diameter of the aggregates is preferably about 0.05 to about 10 μm, most preferably about 0.1 μm to about 1.5 μm. It should be understood that the average diameter of the porous aggregates is always greater than the average diameter of the first particles forming them.

Extender particles may be of various geometries, for example substantially flaky, rod or spherical, wherein the average size of at least one dimension is greater than the average diameter of the porous aggregate, preferably from about 1.3 to about 500 times, most preferably about 1.3 to about 200 times larger. Extender particles are preferably inorganic materials such as natural or synthetic minerals. Examples of useful materials are kaolinite, smectite, talsite, calcium carbonate minerals, precipitated silica, gel-type silica, fumed silica, precipitated calcium carbonate, and mixtures thereof.

The porous aggregate and extender particles preferably have opposite net charges. Therefore, when the porous aggregate has a positive net charge, it is preferable to use extender particles having a negative net charge, and vice versa.

At least a portion of the porous aggregate, such as about 1 to about 100 weight percent, preferably about 5 to about 100 weight percent, and most preferably about 30 to about 100 weight percent, is preferably attached to the extender particles. The average particle size of the total pigment composition is preferably from about 0.5 μm to about 50 μm, most preferably from about 1 μm to about 25 μm. The specific surface area of the total composition is preferably from about 35 m ² / g to about 1000 m ² / g, most preferably from about 50 m ² / g to about 700 m ² / g. In one embodiment the specific surface area is about 600 m ² / g or less, preferably about 450 m ² / g or less and most preferably about 400 m ² / g or less. The total content of porous aggregates and extender particles in the composition is preferably from about 1% to about 60% by weight, most preferably from about 5% to about 50% by weight, particularly most preferably from about 10% to about 50% Weight percent. The composition may also further comprise substances from flocculants such as salts and bridging agents or residual impurities from other additives or raw materials such as stabilizers.

Regardless of the agglomeration method, the composition is preferably calculated from the weight of Al ₂ O ₃ to dry porous agglomerates and extender particles, preferably from about 0.1% to about 30% by weight, most preferably from about 0.2% to about 15% by weight. At least one water soluble aluminum salt in an amount of%. Examples of salts include aluminum chloride, poly aluminum chloride, poly aluminum silicate sulfate, aluminum sulfate, zirconium carbonate, zirconium acetate, and mixtures thereof. Aluminum may be present in part or in whole on the surface of the particles of silica or aluminosilicate or in the aqueous phase. The total content of water soluble aluminum salts may be derived from those present in the cationic aluminum modified silica sol used to prepare the pigment composition. However, the pigment composition may also comprise additional aluminum salts.

Regardless of the aggregation method, the composition preferably has at least one cationic polymer having a molecular weight of about 2000 to about 1000000, more preferably a molecular weight of about 2000 to about 500000, most preferably a molecular weight of about 5000 to about 200000. It may include. The charge density of the polymer is preferably about 0.2 meq / g to about 12 meq / g, more preferably about 0.3 meq / g to about 10 meq / g, most preferably about 0.5 meq / g to about 8 meq / g. The cationic polymer is preferably about 0.1% to about 30% by weight, more preferably about 0.5% to about 20% by weight, most preferably about 1% by weight, based on the amount of dry porous aggregate and extender particles. It is present in the composition in an amount from% to about 15% by weight. Examples of suitable cationic polymers include synthetic and natural polyelectrolytes such as PAM (polyacrylamide), polyDADMAC (poly diallyl dimethyl ammonium chloride), polyallyl amines, polyamines, polysaccharides and mixtures thereof, which are cationic And preferably the molecular weight and the charge density meet the above requirements. The cationic polymer may be present partially or entirely on the particle surface of the silica or aluminosilicate or in the aqueous phase.

The pigment compositions described above are preferably stably storeable for at least one week, most preferably at least one month. The composition may be used directly for coating paper or cardboard or form an intermediate product for preparing the coating composition.

Another aspect of the present invention relates to a method of preparing the pigment composition described above. Another method involves mixing the following:

a) an aqueous dispersion of porous aggregates having an average diameter of 0.03 μm to about 25 μm, formed by agglomeration of colloidal first particles of silica, aluminosilicate or mixtures thereof in an aqueous sol, and

b) extender particles having an average size of at least one dimension greater than the average diameter of the porous aggregate,

Wherein the weight ratio of porous aggregate to extender particles is about 0.01: 1 to about 3: 1, preferably about 0.03; 1 to about 2: 1, most preferably about 0.05: 1 to about 1.5: 1.

Another alternative method involves the following steps:

a) an aqueous sol and extender particles comprising colloidal first particles of silica or aluminosilicate, from about 0.01: 1 to about 3: 1, preferably from about 0.03: 1 to about 2: 1, most preferably Mixing at a weight ratio of silica or aluminosilicate first particles to extender particles from about 0.05: 1 to about 1.5: 1; And,

b) agglomerated colloidal first particles of silica or aluminosilicate to form a porous aggregate having an average diameter of about 0.03 μm to about 25 μm but not exceeding the average size of the largest dimension of the extender particles. Forming a step.

In another alternative method, the extender particles may be added as a solid powder in the form of an aqueous dispersion or in any other suitable form. In the formation of porous aggregates, the addition of optional additives or other various embodiments, the description of the pigment compositions is mentioned.

Yet another aspect of the present invention relates to a coating composition suitable for coating paper or cardboard, comprising a pigment composition and a binder as described above. Examples of possible binders are polyvinyl alcohol, optionally modified starches, gums, protein binders (eg casein and soy protein binders), latexes and mixtures thereof. Latexes can be based on styrene butadiene, acrylate, vinyl acetate, copolymers of ethylene and vinyl acetate, styrene acrylic esters, and the like. Polyvinyl alcohol is particularly preferred. The coating composition may also include other commonly used additives such as rheology modifiers, optical brighteners, lubricants, insolubilizers, dyes, size agents, and the like. The dry content of the coating composition is preferably from about 2% to about 75% by weight, most preferably from about 10% to about 70% by weight. The amount of porous aggregate and extender particles from the pigment composition is preferably from about 30 to about 99% by weight, most preferably from about 50 to about 90% by weight, based on the dry content. The amount of binder is preferably from about 1 to about 70 weight percent, most preferably from about 10 to about 50 weight percent, based on the dry content. The total amount of other additives and impurities that may be present is preferably 0 to about 50% by weight, most preferably 0 to about 30% by weight, based on the dry content. In suitable and preferred embodiments, mention is made of the description of the pigment composition.

Yet another aspect of the present invention relates to a method of making a coating composition comprising mixing a binder with the pigment composition described above. The binder and optional additives may be added to the pigment composition in a suitable form, for example as a solid material, a liquid material, or as an aqueous solution, dispersion or slurry. In suitable and preferred embodiments, description of the coating composition is mentioned.

Another aspect of the invention relates to a method of making a coated paper or paperboard comprising applying the coating composition described above to at least one side of a paper or paperboard web.

The coating is preferably at least about 0.4 g / m ² , preferably from about 0.5 g / m ² to about 40 g / m ² , most preferably about 1 g / m from the pigment composition per coated side of paper or cardboard ^It is applied in an amount sufficient to yield from ² to about 20 g / m ² of porous aggregate and extender particles. In most cases, the dry amount of coating applied per coated side of paper or cardboard is preferably at least about 0.6 g / m ² , preferably from about 0.7 g / m ² to about 50 g / m ² , most preferably Preferably from about 1.5 g / m ² to about 25 g / m ² .

The coating is preferably treated on the uncoated side of the paper or cardboard, but may also be applied on top of an already applied coating layer, having the same or another coating composition. It is desirable not to treat another kind of coating on top of the layer formed from the coatings described herein.

The coating treatment can be carried out on a papermaking machine or paperboard machine or outside the papermaking machine or paperboard machine. In any case, any type of coating method can be used. Examples of coating methods are blade coating, air knife coating, roll coating, curtain coating, spray coating, size press coating (eg film press coating) and cast coating.

The paper is dried after the coating treatment, and in the case of coating on the instrument, drying preferably takes place in the drying zone of the instrument. Any drying means may be used, such as infrared radiation, hot air, heated cylinders or a combination thereof.

The term coating as used herein refers to a method of treating pigments on the surface of paper or cardboard, and therefore includes not only traditional coatings but also other methods such as, for example, coloring.

Paper and paperboard to be coated include chemical pulp such as sulfate, sulfite and organosolve pulp, mechanical pulp such as thermo-mechanical pulp (TMP), chemical-thermo-mechanical pulp (CTMP), refiner pulp or raw or recycled fibers. It can be made from any type of pulp, such as groundwood pulp from both bleached or unbleached pulp of hardwoods and softwoods based on or combinations thereof. Paper and cardboard from other kinds of pulp may also be coated in accordance with the present invention.

With respect to further details and embodiments of the coating composition, reference is made to the same content as the above description.

The present invention relates finally to paper or paperboard suitable for ink-jet printing, obtainable by the method described above. Preferably such paper or cardboard preferably comprises a substantially opaque layer comprising porous aggregates and extender particles from the coating composition forming the nano-structures. The dry amount of the coating is preferably at least about 0.6 g / m ² , preferably from about 0.7 g / m ² to about 50 g / m ² , most preferably from about 1.5 g / m ² to about 25 g / m ² The amount of porous aggregates and extender particles from the pigment composition per coated side of paper or paperboard is preferably at least about 0.4 g / m ² , preferably from about 0.5 g / m ² to about 40 g / m ² , most preferably Is from about 1 g / m ² to about 20 g / m ² . Preferably no other kind of coating has been treated on top of this layer.

The paper or paperboard of the present invention provides high printing density in terms of low line blur and smearing and color, and is suitable for other types of printing methods such as toner, flexography, letter press, gravure, offset lithography and screen printing. It has been found to have excellent properties for ink-jet printing that can be used easily. It is particularly advantageous that these excellent properties can be obtained in a simple manner by applying only a small amount of coating without having to treat numerous different coating layers on paper or cardboard. This also allows the coating to be processed using a size press such as a film press, which is advantageous for practical reasons. Moreover, the main components of the pigment composition can be prepared from readily available raw materials.

The invention will now be described in more detail in the following examples. Unless stated otherwise, all parts and percentages refer to parts by weight and percentage by weight.

Example 1 : Four pigment compositions were prepared:

A: Bindzil ^® CAT 220 from Eka Chemicals AB, Cationic aqueous silica sol, containing 30 wt% SiO2 with an average first particle diameter of about 15 nm was diluted to 10 wt%. The diluted silica sol was stirred in a glass beaker and the sol was stirred in glass beaker and 0.06 mol / l until the sol turned white and increased in viscosity, ie until the concentration of aluminum sulfate reached 0.0125 moles / l in solution. Drops of aluminum sulfate were added. The average diameter of the aggregates was determined to be 0.3 μm (measured by Zetamaster from Malvern instrument, monomodal analysis).

B: A 20 wt% aqueous dispersion of extender particles was prepared from coated clay (SPS, Imerys, UK). The average particle size of the clay was measured at 1.64 μm using the Malvern Instrument's Mastersizer Micro Plus (50HD method).

C: 30 ml of the clay dispersion prepared in B were diluted in the same manner as in A but mixed with 15 ml of silica which did not first aggregate.

D: 15 ml of the aggregated silica prepared in A was mixed with 30 ml of the clay dispersion prepared in B to provide a pigment composition comprising an aggregate of silica and extender particles.

Each of the pigment compositions was mixed with laboratory polyvinyl alcohol (MW 150000) dissolved in water as a 10% by weight solution to prepare a coating formulation. All formulations had a solids content of about 15% by weight and a weight ratio of polyvinyl alcohol to solid pigments of 0.5: 1.

The coating formulations were treated on the surface of uncoated copy paper (A4 sized data copy from M-real) by stretching using wire rods, and the paper was dried on a drying drum. Test pictures containing blocks of cyan, magenta, yellow and black were printed on each of the dried paper using a Hewlett-Packard inkjet printer (HP Deskjet 970Cxi). For each color the color density was measured using a color densitometer (GretagMacbeth D19C, Gretag AG) and the values are shown in the table below:

Pigment composition Coating weight (g / m2) Indigo claret yellow black Blank 0 1.08 1.18 1.01 2.40 A 3.0 1.23 1.38 1.04 2.98 B 2.8 1.31 1.56 1.12 2.10 C 3.5 0.95 1.10 0.80 2.70 D 2.5 1.41 1.66 1.16 2.80

From this experiment it can be seen that the coating formulation comprising pigment composition D provided the best overall print concentration. It can also be seen that the color printed on the paper coated with the pigment composition A was heavily stained.

Example 2: Four pigment compositions were prepared:

A: Two aqueous silica sol, anionic silica sol, Bindzil ^® 15/500, both supplied by Eka Chemicals and containing 15% by weight SiO _{2 and} having an average first particle diameter of about 6 nm, and Cationic silica sol, Bindzil ^® CAT was used. 37.5 g of 30% by weight aqueous clay dispersion (same clay as in Example 1, average particle size 1,64 μm), 90 g cationic sol, 135 g anionic sol, and 37.5 g water Mixing under stirring provided a high viscosity pigment composition comprising an aggregate of first silica particles from the sol and extender particles from the clay. The average diameter of the aggregated silica sol prior to the extender addition was determined to be 0.57 μm (monomodal analysis on Zetamaster instrument).

B: 102 g of precipitated silica, Tixosil ™ 365 SP from Rhodia, having a solids content of 22% by weight and an average particle size of 3.4 μm, was prepared using 60 g of cationic silica sol, 90 g of anionic silica sol and Mixing in the same manner as in 48 g of water and A gave a high viscosity pigment composition comprising an aggregate of first silica particles from the sol and extender particles from the precipitated silica. The average diameter of the agglomerated silica sol before the extender addition was determined to be 0.69 μm (measured by Zetamaster).

C: same clay dispersion as used in A

D: precipitated silica same as used in B.

Each of the pigment compositions was used to prepare a coating formulation by mixing with a polyvinyl alcohol binder (ERKOL ™ 26/88 from ATESEX Co., Spain). All formulations had a solids content of about 15% by weight and a weight ratio of polyvinyl alcohol to solid pigments of 0.25: 1.

The coating was treated on copy paper as in Example 1. Test pictures containing indigo, magenta, yellow, green, blue, red and black blocks were printed on each coated paper using an Epson Stylus C84 ink-jet printer using pigment inks for all colors. Printed blocks and unprinted paper were measured using a spectrophotometer (Color Touch 2 from Technidyne) and the color global volume was calculated. Global volume is estimated using dodecahedrons in the CEI L * a * b * color space, and color measurements provide corners at the dodecahedron ( " Rydefalk Staffan , Wedin Michael ; Litterature review on the color Gamut in the Printing Process - Fundamentals , PTF - report no 32, May 1997 " .

The results are shown in the table below:

Pigment composition Coating weight (g / m ² ) Global volume Blank 0 148600 A 3.7 214000 B 3.6 221900 C 3.3 187300 D 3.3 188900

From these results it was found that Pigment Compositions A and B provided a higher print material measured in global volume.

Example 3: Two pigment compositions were prepared:

A: Aqueous dispersion of 16.7 g of 30 wt% coated clay (same as in Example 1, particle size 1.64 μm), 10 g Bindzil 50/80 (50 wt% silica sol with average particle size of 40 nm , Eka Chemicals), 3 g of Eka ATC 8210 (25 wt% poly aluminum chloride from Eka Chemicals) and 70 g of water were mixed under vigorous stirring in UltraTurrax (10 000 rpm). This gave 10% by weight of the pigment dispersion with a silica to clay weight ratio of 1: 1. The average diameter of the aggregated silica sol before the extender addition was determined to be 0.45 μm (monomodal analysis at Zetamaster).

B: an aqueous dispersion of 16,7 g of 30 wt% coated clay (same as in Example 1), 5 g of silica gel type product (dry powder) and 78 g of water (UltraTurrax as in A) ), 10% by weight of the pigment dispersion (silica / clay ratio: 1: 1). This silica gel type product (Grace Davison) had a second particle size of 12 μm and a surface area of 400 g / m ² , corresponding to a first particle size of 7-8 nm.

Coating formulations having a solids content of 10% by weight and a weight ratio of polyvinyl alcohol to solid pigment of 0.25: 1 were prepared as in Example 2. The paper was treated with a coating and dried in an IR-dryer (Hedson Technologies AB, Sweden). Print tests were performed using Epson Stylus C84 and HP5652 (Hewlett Packard) ink-jet printers as described in Example 2. The results are shown in the table below:

Pigment composition Coating weight (g / m ² ) Global volume Epson Global volume HP Blank 0 185700 - Blank 0 - 162100 A 2.5 220500 - A 2.7 - 232900 B 2.3 200000 - B 2.3 - 193700

The pigment composition (A) containing silica sol aggregates provided a higher global volume than the corresponding pigment composition containing gel type silica. Careful visual inspection showed good line sharpness and no color bleeding on the printout.

Example 4: Two pigment compositions were prepared:

A: Anionic silica sol prepared by ion exchange method containing 10% by weight of SiO _{2 and} having a surface area of about 865 m ² / g was charged with 14.2 g of 2.5% by weight aqueous solution of modified carboxymethyl cellulose (CMC). The mixture was added slowly to ag silica sol while stirring, and coagulated. The modified CMC had a DS of 0.65 for the carboxyl group and was further modified by incorporation of a quaternary nitrogen group (DS 0.43) to provide the cationic nature of the product. The average particle diameter of the aggregates in the dispersion was determined to be 0.7 μm using Zetamaster. The dispersion was then vigorously mixed with 45 g of precipitated silica (Tixosil 365 SP, average particle size 3.4 μm, see Example 2) and 45 g of water.

B: An aqueous dispersion of 10 wt% precipitated silica (Tixosil 365 SP) was prepared.

Coating formulations having a solids content of about 10% by weight and a weight ratio of polyvinyl alcohol to solid pigments of 0.25: 1 were prepared as in Example 2. The coating was treated to paper and dried as in Example 3. Print tests were conducted as in Example 2 using two ink-jet printers, Epson C84 and HP 5652. The global volume was measured and the following results were obtained.

Pigment composition Coating weight (g / m ² ) Global volume Epson Global volume HP A 2.7 225000 - A 2.7 - 230700 B 2.5 209700 - B 2.4 - 222400

Pigment Composition A appears to provide better print quality than Composition B.

The present invention relates to pigment compositions in the form of aqueous dispersions or slurries comprising: (a) formed by agglomeration of colloidal first particles of silica, aluminosilicate or mixtures thereof in an aqueous sol, from 0.03 to Porous aggregates having an average diameter of 25 μm, and (b) extender particles having an average size of at least one dimension greater than the average diameter of the porous aggregates, wherein the weight ratio of porous aggregates to extender particles is from about 0.01: 1 to about 3 : 1. The invention also relates to a process for the preparation of the pigment composition, to a composition for paper or cardboard coating and to a process for the preparation of such a composition, and to a paper or cardboard coating method and to paper or cardboard obtained by such a method.

Claims (14)

Pigment compositions in the form of an aqueous dispersion, comprising: (a) in an aqueous sol, porous aggregates formed by the agglomeration of colloidal first particles of silica, aluminosilicates or mixtures thereof, and having an average diameter of 0.03 to 25 μm, and (b) Extender particles having an average size of at least one dimension greater than the average diameter of the porous aggregates, wherein the weight ratio of porous aggregates to extender particles is from 0.01: 1 to 3: 1. 2. The colloidal first particle of silica or aluminosilicate according to claim 1, wherein the colloidal first particles of silica or aluminosilicate are formed from an aqueous solution of an alkali metal silicate in which alkali metal ions are removed through an ion exchange process or the alkali metal silicate is neutralized by acid addition. A pigment composition characterized by the above-mentioned. 3. The pigment composition of claim 1, wherein at least a portion of the porous aggregate is attached to extender particles. The pigment composition of claim 1, wherein the porous aggregate and extender particles have opposite net charges (net charges). The method of claim 1, wherein the extender particles are kaolinite, smectite, thalcite, calcium carbonate mineral, precipitated silica, gel-type silica, fumed silica, precipitated calcium carbonate, and mixtures thereof. Pigment composition, characterized in that the material selected from the group consisting. 6. The pigment composition of claim 1, wherein the total content of porous aggregates and extender particles in the composition is from 1 to about 60 weight percent. 7. A process for preparing the pigment composition according to claim 1, comprising the following steps: (a) in an aqueous sol, an aqueous dispersion of porous aggregates formed by agglomeration of colloidal first particles of silica, aluminosilicates or mixtures thereof, and having an average diameter of 0.03 to 25 μm, and (b) extender particles having an average size of at least one dimension greater than an average diameter of the porous aggregate, wherein the weight ratio of porous aggregate to extender particles is from 0.01: 1 to about 3: 1. A method for preparing the pigment composition of claim 1, comprising the following steps: (a) an aqueous sol comprising a colloidal first particle of silica or aluminosilicate and an extender particle in a weight ratio of 0.01: 1 to about 3: 1 of the first particle of the silica or aluminosilicate to the extender particle; Mixing; And, (b) agglomerating the colloidal first particles of silica or aluminosilicate to form a porous aggregate having an average diameter of 0.03 um to 25 um but not exceeding the average dimension of the largest dimension of the extender particles. A coating composition suitable for paper or cardboard coating, comprising the pigment composition of claim 1 and a binder. 10. The coating composition of claim 9, wherein the binder is selected from the group consisting of polyvinyl alcohol, optionally modified starch, gum, protein binder, latex, and mixtures thereof. A method of making a coating composition, comprising mixing the pigment composition of claim 1 with a binder. A method of making a coated paper or paperboard, comprising applying the coating composition of claim 9 to at least one side of a paper or paperboard web. The method of claim 12, wherein the coating is applied in an amount sufficient to yield from 0.4 g / m ² to about 40 g / m ² of porous aggregate and extender particles from the pigment composition, per coated side of paper or cardboard. Method of making coated paper or paperboard. Paper or cardboard obtained by the method of any one of claims 12-13.