WO1996024721A1

WO1996024721A1 - Pigment filler compositions and methods of preparation and use thereof

Info

Publication number: WO1996024721A1
Application number: PCT/US1996/001549
Authority: WO
Inventors: Leo E. Nagan
Original assignee: Diatec Environmental Company
Priority date: 1995-02-08
Filing date: 1996-02-06
Publication date: 1996-08-15
Also published as: AU4915296A

Abstract

A filler composition for a papermaking process is prepared by mixing a pigment, a water soluble or dispersible polymer, and water, the pH of the resulting mixture being at least about pH 9.

Description

PIGMENT FILLER COMPOSITIONS AND METHODS OF PREPARATION AND USE THEREOF

BACKGROUND OF THE INVENTION

Field of the Invention The invention relates to methods of paper manufacture and, more particularly, the invention relates to pigment compositions and methods of making and using such compositions.

Description of Related Technology

Calcium carbonate pigment is usually the filler of choice in the manufacture of alkaline papers. Calcium carbonate pigment provides whiteness, brightness, and opacity to the paper. Because calcium carbonate is cheaper than the cellulose fiber used to make paper, it is to the economic advantage of the papermaker to use as much calcium carbonate as possible, consistent with maintaining standards with respect to, for example, tensile strength, internal bond strength, and fold strength.

Papermakers have been constrained from using inexpensive forms of calcium carbonate, which can be made at the plant site, in amounts over twelve to fourteen weight percent because of the unacceptable loss of strength of the paper at calcium carbonate addition over this range.

The strength of any paper as it is currently made has been acknowledged to be derived from hydrogen bonding between the hydroxyl sites on adjacent fiber surfaces and can be enhanced in some cases by additives mixed with the fiber/filler slurry, such as starches and gums, which can reinforce fiber-to-fiber bonding. The problem with high levels of fillers, such as calcium carbonate, is that the pigment particles can prevent too many of the hydrogen bonding sites on adjacent fibers from touching, and the consequent loss of strength leads to commercially unacceptable paper.

Starches and gums, either unmodified or modified, have been used for many years to improve the strength of paper. The standard procedure has been to add the gum or starch to a slurry of fiber and pigment filler. The literature indicates that such addition is for the most part successful at filler levels of about eleven to thirteen weight percent.

It has been disclosed that the tolerable level of clay pigment in paper may be increased by flocculation of the clay with a cationic starch prior to adding the clay to a fiber slurry. (Mather, R.D. and Jones, J.P.E.; "Production of Paper at High Filler Levels"; pp. 283-289; TAPPI Proceedings; 1982 Papermakers Conference.) A theory that may be advanced for the success of such a procedure is that the pre-flocculation or agglomeration of the clay with the starch allows the fibers to contact fewer clay surfaces than with dispersed clay, and consequently, the clay is less likely to interfere with the fiber-to-fiber hydrogen bonding that gives paper its strength. The Mather et al. article emphasizes the need for mixing the clay and the cationic starch at a low shear level to maximize agglomeration and, accordingly, to minimize the clay surface to fiber contact.

Gill et al., U.S. Patent No. 4,892,590 teaches a calcium carbonate-cationic starch binder system for use as a retention aid in papermaking. According to the Gill et al. patent, a highly dispersible, high specific area precipitated calcium carbonate (PCC) is prepared by introducing carbon dioxide into an aqueous slurry of calcium hydroxide. When precipitation of calcium carbonate is substantially complete, the slurry is heat aged at a pH from 9-11 to reduce surface area and increase dispersibility and then treated with an anionic dispersant, preferably an inorganic polyelectrolyte and more preferably sodium tripolyphosphate or sodium hexametaphosphate to result in a colloidal anionic PCC. The Gill et al. patent discloses that in the papermaking operation, the filler, PCC, and a cationic starch are individually introduced to a fiber slurry. In particular, the filler is added to a fiber slurry at a blend chest, the colloidal anionic PCC at a stuff box, and the cationic starch before the fan pump.

Shiel, U.S. Patent No. 4,174,998 discloses a flocculated filler composition for use in papermaking comprising a pigment, a starch phosphate, and an organic polymeric retention aid, such as polyacryla ide. The Shiel patent states that the filler composition components are brought together as a mixture, preferably as a dispersion in water, before being introduced into a medium containing paper fibers with the objective of increasing pigment and starch retention. The Shiel patent is silent concerning the pH of such a filler composition prior to addition to the paper fiber medium. SUMMARY OF THE INVENTION It is an object of the invention to overcome one or more of the problems described above. The invention concerns a method of preparing a filler composition for use in a papermaking process including the step of providing a composition for blending with a fiber slurry. The composition is a mixture of a pigment, a water soluble or dispersible polymer, and water. The pH of the pigment, the polymer, the water, or the mixture thereof is adjusted to result in the composition having a pH of at least about 9. The invention also comprehends a composition produced according to such a method.

Other objects and advantages of the invention will be apparent to those skilled in the art and from the following detailed description, taken in conjunction with the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

According to a preferred method of the invention, a pigment slurry, for example, a slurry of calcium carbonate and water, is adjusted to a pH of at least about 9 (preferably between pH 9 and pH 12, and most preferably at about pH 11). The pigment slurry is then mixed with an aqueous solution or dispersion of at least one water soluble or dispersible polymer, which may be either synthetic or natural. The pigment slurry/polymer mixture is then added to a fiber-containing slurry or composition in a papermaking machine.

The invention also comprehends adjusting the pH of the water or polymer components of the mixture prior to mixing with a pigment to result in a mixture having a pH of at least about 9. Furthermore, according to the invention, a pigment/water slurry and a polymer may be mixed and then the pH of the resulting mixture adjusted to at least about pH 9. Preferably, mixing of the water, pigment, and polymer, and any pH adjustment, are performed under high shear mixing conditions. Polymers according to the invention include, for example, acrylamide polymers, such as acrylamide homopolymers, methacrylamide homopolymers or copolymers of acrylamide and methacrylamide, aerylate, or metal salts of acrylic acid. The acrylamide polymer may be partially hydrolyzed. Polymers according to the invention also include polyvinyl alcohols, colloidal or polymerized silica, starches, and gums.

Any combination of any of the polymers identified herein may also be used according to the invention. The polymer addition preferably ranges between about 0.5 wt.% and about 15 wt.%, based upon the dry pigment weight.

A preferred pigment for use in the invention is calcium carbonate. A particularly preferred pigment for use in the invention is a high specific area precipitated calcium carbonate (PCC) . The invention also comprehends the use of clay and titanium pigments.

It is believed that an elevated pH creates hydrogen bonding sites on the pigment surface. The polymer also has hydrogen bonding sites. Thus, the elevated pH confers substantivity (i.e. the ability to be fixed or associated) of polymer to pigment. To treat a pigment, such as calcium carbonate in a manner that will affix the polymer or polymer mixture to the surfaces of the calcium carbonate particles, preferably the pH level of the calcium carbonate slurry is elevated substantially above its natural equilibrium level to a pH ranging between about 9 and about 12. It is believed that a benefit to the inventive method is that upon the drying of paper made with cellulose fiber and a high pH pigment/polymer composition according to the invention, the pigment particles can bond to one another and to the fiber surface via the bridging of the polymer from surface to surface through hydrogen bonding. The net result is paper that has a higher tensile strength and internal bonding strength, for example, than paper made which is not treated with a pigment/polymer composition according to the invention.

The invention also comprehends the use of alkalies such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium carbonate, calcium hydroxide, calcium oxide, and any combination thereof, to increase the pH and alkalinity of a pigment slurry to a level between about pH 9 and about pH 12. Such a pH range is considerably above the pH commonly occurring in a pigment slurry (which is rarely above about pH 8.2) . It is believed that the higher the pH of the calcium carbonate slurry, the more hydrogen bonding sites are available on the pigment particles. The polymers utilized according to the invention identified herein may be used in their unmodified form, or they may be modified in various ways that may improve their handling characteristics, their bonding capabilities, and their substantivity (i.e., ability to be fixed or associated) to the pigment particles.

If polyacry1amides are utilized in a method and composition of the invention, they may be modified through copolymerization which inserts other active units in the polymer chain such as carboxyl units, amine units, and quaternary amine units. Or they may be hydrolyzed with caustic soda to convert some of the amide units to carboxyl units. The polyacrylamides may also be converted to a polyacrylamide-phosphonate construction as shown in Nagan U.S. Patent No. 5,342,539.

When a natural polymer, i.e., starch, is utilized according to the invention, it may be modified, for example by hydroxyethylation, methoxymethylation, acid treatment, oxidation, the addition of tertiary or quaternary amine sites, chemical bonding with a latex copolymer, and phosphatizing. Gums such as guar gum, locust bean gum, and tamarind kernel may also be utilized in a method of the invention. The most common modification of guar gum is the addition of tertiary or quaternary amine sites. Some examples of benefits through modification of the polymers disclosed herein are phosphonate attachment to calcium sites and cationic quaternary amine attachments to negative sites such as carbonate or bicarbonate radicals. A preferred polymer for use in the invention is potato starch. This is most likely because it has phosphate radicals inherent in its molecular structure as well as having hydroxyl radicals. The choice of polymer in any given situation may depend on characteristics such as retention aid flocculant choice and the ionic characteristics of other system additives. The preferred addition level of polymer to pigment solids is in the range of between about 0.5 wt.% and about 15 wt.% depending, for example, upon needs for the type of paper being made, ash levels, and fiber strength characteristics.

It is believed that a great advantage of a filler pigment composition according to the invention, such as a calcium carbonate slurry adjusted to a pH of about 11 and mixed with a polymer, such as potato starch, is that the calcium carbonate pigment surface enters into hydrogen bonding with the polymer and as a result the polymer becomes firmly attached to it. The polymers then further enhance strength through bridging from pigment particle to pigment particle, and pigment particle to fiber during and after drying. Significantly increased levels of pigment in a finished paper are thus possible without dropping the paper strength below commercially acceptable levels. Instead of blocking bonding sites, the pigment can enter into bonding. The benefits to the papermaker in being able to substantially increase calcium carbonate levels further include increased opacity and brightness and reduced furnish costs. In the case of fiber replacement, the addition of, for example, 3 wt.% more calcium carbonate means the reduction of the more expensive bleached fiber by 3 wt.% resulting in a substantial decrease in paper production cost. EXAMPLES The invention is further described and illustrated by the following detailed examples which are not intended to be limiting.

Example 1 - Screening of Calcium Carbonate

Pigment Slurries

A screening was performed wherein dry films of calcium carbonate pigment slurries were formed on flat bottomed Petri dishes using precipitated calcium carbonate (PCC) having a scalenohedral crystalline structure. The papermaking industry acknowledges that the scalenohedral form interferes with the strength development in paper much more than a rhombohedral form that is typically found in ground calcium carbonate (GCC) . Because of their irregular shapes, the scalenohedral crystals cannot pack together as efficiently as the rhombohedral crystals. However, the use of scalenohedral crystals provides significantly more opacifying power, a very desirable attribute in papermaking. It is noted that the strength enhancement effects derived from a process according to the invention applies to all crystal forms of calcium carbonate. Glass was chosen as the film substrate for its known ability to enter into hydrogen bonding because of the hydroxyl radicals attached to the silicon atoms in the glass. The dried films were prepared from PCC slurries treated with both natural and synthetic polymers listed in Table I below. Such polymers are known to enter into hydrogen bonding and in so doing provide a strength reinforcing mechanism when mixed with solids that are also known to enter into hydrogen bonding. For example, paper made from cellulose fiber only can be strengthened with these materials. Dried films on glass were also prepared from untreated PCC to provide baseline data. Films were made at a pH of 8.2 (which is generally the upper limit target at which PCC slurries enter a paper machine system) as well as at elevated pH levels of up to 12.

A preferred element believed to aid in the performance of the inventive method disclosed herein is the thorough mixing of the treatment polymer and PCC particles under high shear conditions to achieve a maximum possible dispersion. To establish the PCC/polymer substantivity, the polymer/pigment mixture was mixed vigorously with a large quantity of water before it was allowed to settle. If the polymer wasn't substantive to the PCC particles, it would remain, for the most part, in the water phase and, accordingly, not be available to bind the pigment particles to one another in the film.

The following materials were utilized in the screening tests:

24 wt.% solids slurry of scalenohedral

PCC; 10 wt.% and 1 wt.% sodium hydroxide solutions; pH indicator strips by E.M. Science (pH 0- 14 and pH 6.5-10) ; flat bottomed glass Petri dishes 95 X 22 mm;

250 ml glass beakers;

1 wt.% solutions or dispersions of the treatment polymers listed in Table I; a Waring blender fitted with a 35 ml stainless steel mixing container; a convection drying oven set at 200°F; and an assortment of graduated syringes and stirring rods.

The following procedure was used for casting a film of untreated PCC:

1) 3 cc of PCC slurry was added to 90 cc of 8.2 pH water in a 250 cc beaker and stirred vigorously;

2) the resulting mixture was immediately poured into a Petri dish and allowed to settle; and

3) the supernatant was drawn off with a syringe and the remaining slurry dried in the oven. The following procedure was used for casting a film of polymer treated PCC at a pH of 8.2:

1) 20 cc of 8.2 pH water was added to the blender mini-container. 3 cc of PCC slurry at pH 8.2 was then introduced to the blender and the resulting mixture was vigorously agitated, followed by the addition of an appropriate amount (as shown in Table I) of the treatment polymer to the mixture. High shear agitation of the blender was then performed for 10 seconds;

2) the resulting composition was immediately poured into a 250 cc beaker containing 75 cc of 8.2 pH water and stirred vigorously with a stirring rod for 30 seconds; 3) the composition was then immediately poured into a Petri dish and allowed to settle;

4) the supernatant was drawn off with a syringe and the remaining slurry dried in the oven. The same steps 1) through 4) above were used to cast films of polymer treated PCC at pH levels above 8.2. The pH levels of the calcium carbonate slurries were increased to 9, 10, 11, and 12 by adding sodium hydroxide solutions after the 20 cc of water and the 3 cc of PCC slurry had been added to the blender mini-container.

The dried films were allowed to stand at room temperature and pressure for at least 12 hours in order for them to come to a stable moisture equilibrium before testing.

The strength of each film was assessed by rubbing the film with firm pressure using the underside of a full top joint of the index finger (area about 2.6 cm²) in the case of the untreated PCC film, or the top partial area (about 1.1 cm²) for the other tests recorded in Table I. The number of rubs were counted until the film broke through to the glass surface. During early screening, the number of rubs were not recorded. However, the following was recognized:

1. Untreated PCC films had no measurable strength at all. 2. The strengthening effects of polyacrylamide (PAM) were close to zero at a PCC slurry pH of 8.2, even at PAM intrinsic viscosities of 0.4 (IV 0.4) and above.

3. The strengthening effect of PAM was significant at pH 9 and became progressively better as the pH of the PCC slurry rose to pH 12.

4. At the higher pH levels a PAM with a molecular weight represented by an intrinsic viscosity of 0.2 (IV 0.2) had very little effect. The strengthening effect took hold at IV 0.4 and increased with higher molecular weights up to IV 14 which was the highest tested.

5. Increasing the pH of the PCC slurry created an increase in strength both when simply mixing the polymer with the 24 wt.% solids slurry and drying, and also when the treated slurry was added to a larger volume of water, mixed, allowed to settle, supernatant drawn off, and the remainder dried. When the higher pH slurry was added to the 8.2 pH water, the pH of the supernatant was raised only 0.1 unit for the most part and only 0.2 unit in the extreme. This appears to indicate that the caustic added to the PCC slurry goes primarily to create new hydrogen bonding sites on the pigment particle which then remain on the particle with enough monomers of the polymer firmly attached at these points to stabilize the newly created sites onto the particle surface. Unless a large excess of caustic is added, there is very little free alkalinity to materially affect the larger volume of water to which it is added.

The following Table I shows the number of rubs for the various types of treatments investigated.

TABLE I

PCC FTIJ. STREHGTH TESTS

Number of Fingertip Rubs pH of PCC Before Breakthrough to Glass Slurry When

Polymer Treated 2 wt%^J 1.5 Wt%^α 1 wt%^J

Acid Modi ied Potato Starch 11 1100+ 200+ 534

Guar Gum 11 80 80 70

Hydroxyβthylated Corn Starch 11 200+ 200+ 180

Polyvinyl Alcohol 12 140 80

Polyvinyl Alcohol 11 140 64

Polyvinyl Alcohol 10 90 66

Polyvinyl Alcohol 9 80 44

Polyvinyl Alcohol using a flocculant on the treated pigment dilute mix:

PΛM-Phoβphonate² IV 8 - 20 mol 11 200+ IV 14 - 20 BOl 11 200+ IV 19 - 20 mol 11 200+

Colloidal Silica 11 10

11 10

8.2 0

11 40 11 50 11 80+ 11 80+

11

Represents polymer treatment level (polymer solids/PCC solids) . These are flocculants used on the PVA treated pigment. Dosage was 2 lbs/ton based on dry pigment solids.

The untreated PCC tested zero using a full forefinger joint rub which represents about half of the pressure of the other rubs.

Example 2 - PCC Filled Paper Handsheets

The following laboratory paper handsheet tests show that sheets made according to the invention exhibit adequate strength requirements at significantly higher calcium carbonate pigment levels than when using untreated pigment.

A 64/40 mix (by weight) of hardwood bleached Kraft fiber and softwood Bleached Kraft fiber was refined (each separately) to a Canadian Standard Freeness (CSF) of 400 in a Valley beater. Six ten liter aliquots of 0.3 wt.% fiber were placed in six stainless steel buckets. About two grams of calcium chloride was dissolved in each bucket in an effort to replicate calcium pickup by fibers in a papermaking system making alkaline paper using calcium carbonate as a filler. Next, the pH in each bucket was adjusted to 8.2 with a sodium hydroxide solution to replicate equilibrium conditions in an alkaline papermaking system.

A scalenohedral precipitated calcium carbonate (PCC) pigment was used at a pH of 8.2 for a series of handsheets made with untreated PCC. This pH is a common upper limit target for PCC slurries used in alkaline papermaking. PCC slurries adjusted to pH 11 with sodium hydroxide were used for the handsheets made with treated pigment. The solids content of each PCC slurry was 24 wt.%. A solution/dispersion of 1 wt.% acid modified potato starch was made by slurrying the raw starch in distilled water and cooking it for 15 minutes at 190°F. In making the treated sheets, the starch was added to the pigment at a dosage of 2 wt.% based on the dry pigment weight.

A cationic polyacrlyamide (IV 13; 5 mole) was utilized as a retention aid. It was used at the rate of 0.7 lbs/ton based on the dry weight of the fiber/PCC mix.

The target weight of each handsheet was 1.2 gm which equates to an oven dry basis weight of 60 gm/m².

The target PCC levels were 14 wt.%, 20 wt.%, and 25 wt.%. A series of six handsheets were made for each of these levels, both for treated PCC and untreated PCC. Before each series of six handsheets, test sheets were run to confirm basis weight and ash levels. Quick ash level determinations were made using a Weyerhaeuser developed apparatus that utilizes an oxygen gas atmosphere to develop an instant, intense heat. For each series of six handsheets, six aliquots were taken from the bucket designated for that series and placed in one liter beakers. The aliquot volume was based on the target fiber content for that series. The beakers were set upon a six place magnetic stirring table which provided the required agitation.

For the untreated PCC series, the PCC slurry dosage was added to the beaker containing the fiber slurry under agitation. For the treated PCC series, the pigment was treated in a Waring blender mini-container of 35 cc capacity. The procedure was to add about 20 cc of pH 11 distilled water to the blender, begin agitation, add the appropriate dosage of pH 11 pigment, add the appropriate dosage of potato starch, continue agitation for ten seconds, and add the treated pigment to the fiber aliquot under agitation in the one liter beaker. In all of the series, the retention aid dosage was added to the one liter beaker immediately after the addition of the PCC. Agitation was then continued in the beaker for twelve seconds, and the beaker was handed to the lab manager for sheet formation.

Deionized water was used throughout, including the British sheet mold. In preparation for receiving the fiber/filler/retention aid mix, the sheet mold was filled to the halfway level and the pH adjusted to 8.2 with caustic soda.

TAPPI standard methods were used for sheet formation, pressing, and drying. The sheets were air dried and tested in a standard constant temperature and constant humidity room. All of the dry lab testing for strength, basis weight, and ash, etc, were performed under TAPPI/ISO standards. A typical moisture level for sheets dried and tested under these conditions is reported to be about 7 wt.%. The following Table II provides a summary of the results of the handsheet tests. TABLE II HANDSHEET STUDIES

00

¹ Based on the weight of 5 conditioned sheets per TAPPI standard T220. The average moisture of the sheets was about 7 wt.%.

² Duplicates were run on each series, 3 half sheets and 3 half sheets.

With respect to Table II, both Series 1 and Series 4 had the same fiber weight (1.05 grams). Thus, the increased basis weight of the sheets made from PCC treated according to the invention is from an increased amount of pigment only. This indicates that PCC may be increased by 2 wt.% without strength loss. At the treatment level used, this was done with only 6 lbs. starch/ton of paper level of treatment. Better results may occur with higher treatment levels of starch.

Also with respect to Table II, tensile strength is believed to be the most meaningful test. The tensile index (TI) , tensile energy absorption (TEA) , and tensile breaking length (BL) results that are often calculated in this type of testing are methods meant to even out basis weight variations based on fiber content. The higher the fiber content, the higher the tensile strength. For example, the breaking length number for a 67 gm sheet would be lowered by calculation in the TI, TEA and BL results when compared to a 65 gm sheet by what amounts to a gram difference ratio. However, when the mass increase is because of increased PCC only, this penalizing adjustment obviously would not be justified.

The foregoing detailed description is given for clearness of understanding only, and no unnecessary limitations are to be understood therefrom, as modifications within the scope of the invention may be apparent to those skilled in the art.

Claims

1. A method of preparing a filler composition for a papermaking process, the method comprising the steps of: (a) providing a composition for blending with a fiber slurry, said composition comprising a mixture of water, a pigment, and at least one of a water soluble polymer and a water dispersible polymer; and (b) adjusting the pH of at least one of said pigment, polymer, water, and mixture thereof to result in said composition having a pH of at least about 9.

2. The method of claim 1 wherein the pH of said composition is between about pH 9 and about pH 12.

3. The method of claim 1 wherein the pH of said composition is about pH 11.

4. The method of claim 1 wherein the pigment is calcium carbonate.

5. The method of claim 1 wherein the polymer is selected from the group consisting of acrylamide polymers, polyvinyl alcohols, colloidal silica, polymerized silica, starches, gums, and combinations thereof.

6. The method of claim 1 wherein the amount of polymer in said composition ranges between about 0.5 wt.% and about 15 wt.% based upon the weight of the dry pigment.

7. The method of claim 1 wherein the pH adjustment step (b) is performed by adding to at least one of said water, pigment, polymer, and mixture thereof, a compound selected from the group consisting of sodium hydroxide, ammonium hydroxide, potassium hydroxide, sodium carbonate, calcium hydroxide, calcium oxide, and mixtures thereof.

8. The method of claim 1 wherein said composition is prepared by high shear mixing.

9. The method of claim 1 wherein said pigment/polymer/water mixture is prepared by mixing said pigment with said water; subsequently adjusting the pH of the pigment/water mixture; and subsequently mixing said pigment/water mixture with said polymer.

10. The method of claim 9 wherein said mixing of said pigment/water mixture and said polymer is high shear mixing.

11. The method of claim 1 wherein said pigment/polymer/water mixture is prepared by mixing said pigment, said polymer and said water at high shear and subsequently adjusting the pH of the pigment/polymer/water mixture.

12. The method of claim 11 wherein said pH adjustment of said pigment/polymer/water mixture is performed under high shear mixing conditions.

13. A method of papermaking comprising the steps of:

(a) providing a composition for blending with a fiber slurry, said composition comprising a mixture of water, a pigment, and at least one of a water soluble polymer and a water dispersible polymer;

(b) adjusting the pH of at least one of said pigment, polymer, water, and mixture thereof to result in said composition having a pH of at least about 9; and

(c) introducing the composition into a fiber-containing medium.

14. The method of claim 13 wherein the pH of said composition is between about pH 9 and about pH 12.

15. The method of claim 13 wherein the pH of said composition is about pH 11.

16. The method of claim 13 wherein the pigment is calcium carbonate.

17. The method of claim 13 wherein the polymer is selected from the group consisting of acrylamide polymers, polyvinyl alcohols, colloidal silica, polymerized silica, starches, gums, and combinations thereof.

18. The method of claim 13 wherein the amount of polymer in the composition ranges between about 0.5 wt.% and about 15 wt.% based upon the weight of the dry pigment.

19. The method of claim 13 wherein the pH adjustment step (b) is performed by adding to at least one of said water, pigment, polymer, and mixture thereof, a compound selected from the group consisting of sodium hydroxide, ammonium hydroxide, potassium hydroxide, sodium carbonate, calcium hydroxide, calcium oxide, and mixtures thereof.

20. The method of claim 13 wherein said composition is prepared by high shear mixing.

21. The method of claim 13 wherein said pigment/polymer/water mixture is prepared by mixing said pigment with said water; subsequently adjusting the pH of the pigment/water mixture; and subsequently mixing said pigment/water mixture with said polymer.

22. The method of claim 21 wherein said mixing of said pigment/water mixture and said polymer is high shear mixing.

23. The method of claim 13 wherein said pigment/polymer/water mixture is prepared by mixing said pigment, said polymer and said water at high shear and subsequently adjusting the pH of the pigment/polymer/water mixture.

24. The method of claim 23 wherein said pH adjustment of said pigment/polymer/water mixture is performed under high shear mixing conditions.

25. A pigment filler composition for use in papermaking comprising a mixture of water, a pigment, and at least one of a water soluble polymer and a water dispersible polymer, said mixture being at at least about pH 9.

26. The composition of claim 25 wherein said mixture is at a pH of between about pH 9 and about pH 12.

27. The composition of claim 25 wherein said mixture is at about pH 11.

28. The composition of claim 25 wherein said pigment is calcium carbonate.

29. The composition of claim 25 wherein said polymer is selected from the group consisting of acrylamide polymers, polyvinyl alcohols, colloidal silica, polymerized silica, starches, gums, and combinations thereof.

30. The composition of claim 25 wherein the amount of polymer mixed with the slurry ranges between about 0.5 wt.% and about 15 wt.% based upon the weight of the dry pigment.