Calcium bentonite wet process slurry for case board

Abstract

A method for manufacturing a wet slurry containing a calcium bentonite filler for a cartonboard manufacturing process may include: mixing a calcium bentonite ore with water to form an initial slurry; screening the initial slurry to remove aggregate having a particle size greater than 250 microns; grinding the initial slurry until the d50 particle size of the slurry is 10 microns or less and the weight percentage of particles having a particle size of 45 microns is less than 5 wt% based on the total weight of the slurry; and screening the ground slurry to remove particles having a particle size greater than 44 microns, thereby producing a final slurry.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] The benefit of priority to U.S. Provisional Patent Application No. 63 / 488,170, filed on March 2, 2023, is hereby claimed, and the disclosure of which is incorporated herein in its entirety. Technical Field

[0003] The present disclosure relates to a method of incorporating calcium bentonite filler into linerboard using a wet slurry. Background Art

[0004] Linerboard is generally any grade of paper product suitable for the manufacture of corrugated packaging materials and containers. Given its use in corrugated packaging, linerboard is designed to have high tensile, burst, and compressive strengths. Linerboard is typically made in an acid-based process, utilizing wood fiber as the primary component of the pulp. Unlike other grades of paper, the use of mineral fillers in acidic papermaking environments such as the linerboard manufacturing process is limited. In addition, as is done in other papermaking processes, the use of mineral fillers requires the removal of fibers from the stock mix to maintain key properties such as bulk and basis weight. While this has the advantage of reducing the amount of expensive fibers required in such processes; for linerboard manufacturing, the replacement of fibers is considered detrimental to maintaining the strength properties required of linerboard. Summary of the Invention

[0005] The linerboard manufacturing industry needs an efficient method for incorporating mineral fillers into linerboard without adversely affecting the board's strength properties. Fiber is increasingly limited in supply and expensive to produce compared to minerals. The global linerboard market is projected to grow at a CAGR of 2.3% (2.1% in the United States). The disclosed method can advantageously provide a way to extend the use of optical fibers and reduce costs to meet global growth.

[0006] According to an embodiment, a method for producing a wet slurry containing calcium bentonite filler for a containerboard manufacturing process may include: sizing calcium bentonite ore (e.g., raw or mined calcium bentonite ore) to an average particle size of about 2 cm to about 8 cm; mixing the sized calcium bentonite ore with water to form an initial slurry having a solids content of about 10% to about 30%; screening the initial slurry to remove aggregate having a particle size greater than 250 microns; grinding the initial slurry until the d 50 The method comprises the steps of: milling the slurry to remove particles having a particle size of 10 microns or less and the weight percentage of particles having a particle size of 45 microns is less than 5 wt % based on the total weight of the slurry; and screening the milled slurry to remove particles having a particle size greater than 44 microns, thereby producing a final slurry, wherein the final slurry has a solids content of about 10% to about 20%.

[0007] According to an embodiment, a method for producing a wet slurry containing calcium bentonite filler for use in a containerboard manufacturing process may include: sizing calcium bentonite ore (e.g., raw or virgin mined calcium bentonite) to a particle size of about 2 cm to about 8 cm; mixing the sized calcium bentonite ore with water and a dispersant to form an initial slurry having a solids content of at least about 10%; screening the initial slurry to remove aggregate having a particle size greater than 250 microns; grinding the initial slurry until the d 50 The method comprises the steps of: milling the slurry to remove particles having a particle size of 10 microns or less and wherein the weight percentage of particles having a particle size of 45 microns is less than 5 wt % based on the total weight of the slurry; and screening the milled slurry to remove particles having a particle size greater than 44 microns, thereby producing a final slurry, wherein the final slurry has a solids content of at least about 10%.

[0008] Depending on the feed size of the mineral ore, the sizing step may be omitted. For example, if the mineral ore is mined, obtained, or otherwise provided to the process with an average particle size of about 2 cm to about 8 cm, the sizing step may be omitted or may be performed optionally.

[0009] A method for making linerboard according to the present disclosure may include: incorporating a final slurry formed by the method for making wet slurry of the present disclosure into a fiber-containing furnish for making linerboard, wherein the furnish comprises from about 2 wt % to about 20 wt % of a mineral based on the total weight of the furnish; and forming the linerboard from the furnish.

[0010] According to the present disclosure, also disclosed herein is a linerboard produced by the method of the present disclosure or containing an additive produced by the method of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a Horiba particle size distribution graph showing the particle size distribution of the precursor (initial) slurry (dispersed and passed through 60M).

[0012] Figure 2 is a Horiba particle size distribution graph showing the particle size distribution of the final slurry prepared by the method of the present disclosure.

[0013] Figure 3 is a schematic diagram of a process flow diagram of the method of the present disclosure.

[0014] Figure 4 is a schematic diagram of a dispersion unit according to the present disclosure.

[0015] Figure 5A and 5B is a graph of strength testing of handsheets formed using the fillers and methods of the present disclosure. DETAILED DESCRIPTION

[0016] The disclosed method advantageously provides calcium bentonite as a slurry, allowing for easier dispersion into existing stock mixes. To be successful, it has been determined that the retention of the calcium bentonite in the paper product should be greater than 75% without abrading the equipment used to form the wet paper. Furthermore, to make the process economically viable, 20% or less, preferably 15% or less, of the calcium bentonite ore used to form the slurry should be discarded during slurry formation. As used herein, "calcium bentonite" refers to a montmorillonite in which the primary divalent cation is calcium.

[0017] The slurry disclosed herein can have a high solids content of about 10% to about 20%. The slurry can be used directly in the linerboard manufacturing process as an additive to the furnish to provide a larger amount of calcium bentonite filler than previously used in the linerboard industry. For example, the linerboard manufacturing process can include a calcium bentonite filler in an amount of about 2 wt% to about 20 wt% based on the weight of the furnish. It has been advantageously discovered that the process disclosed herein can form a slurry having a high calcium bentonite solids content, which can utilize calcium bentonite ore received directly from a mining site, regardless of moisture content and ore size. Calcium bentonite ore can be used directly in the process disclosed herein, as it is mined and requires no further refining prior to use in the process. The starting particle size of the ore in its "as mined" state is typically about 20 cm to about 45 cm. The ore can be sized as part of the process disclosed herein. Alternatively, if the ore is processed, mined, or otherwise obtained in a size range of about 2 cm to about 8 cm, the sizing step can be omitted. Furthermore, the slurry produced by the disclosed method can be used directly in the papermaking process and provides an effective calcium bentonite filler content to linerboard without adversely affecting the linerboard's strength properties or causing harmful wear on equipment or paper during the papermaking process. For example, linerboard produced with approximately 12% calcium bentonite filler exhibits acceptable strength properties that are 15% to 20% of the strength of linerboard produced without filler. This advantageously allows linerboard to be produced with reduced fiber content without sacrificing desired strength.

[0018] It has been determined that containerboard mills require approximately 40,000 to 75,000 tpy of calcium bentonite to meet production capacity demands. The disclosed method can advantageously meet these demands in a cost-effective manner by allowing on-site production of calcium bentonite slurry and avoiding the costly transportation of the slurry to the production site. However, it is also contemplated that the slurry could be produced in facilities removed from the containerboard mill and transported to the mill.

[0019] A method for producing a wet slurry of calcium bentonite filler for use in a containerboard manufacturing process may include sizing calcium bentonite ore to reduce the calcium bentonite to an average particle size of about 2 cm to about 8 cm. After sizing, the calcium bentonite ore is mixed with water to produce a slurry. The slurry is then screened to remove large aggregate. If the ore provided or otherwise obtained has an average particle size of about 2 cm to about 8 cm, sizing the calcium bentonite may be omitted. In such cases, the obtained ore may be screened to remove large aggregate before being mixed with water to produce the initial slurry. The large aggregate removed by screening may optionally be collected and resized to reduce the amount of waste ore generated in the process. For example, the larger aggregate may be ground and then reintroduced into the disclosed method to form the initial slurry, or the larger aggregate may be ground to a particle size of less than 45 microns before being introduced into the final slurry. For example, after grinding, particles that pass through a 45-micron screen may be added to the final slurry.

[0020] After screening, the slurry is ground to reduce the particle size of the calcium bentonite in the slurry to a value that is acceptable for the abrasion and wear performance of the process. The ground slurry is then screened to remove aggregate. The resulting slurry can be directly pumped into the containerboard manufacturing process and used as a calcium bentonite filler in the slurry mix.

[0021] Sizing the calcium bentonite ore may include reducing the particle size to through 8 cm.For example, the calcium bentonite ore may be sized using a crusher.

[0022] The solids content of the initial slurry formed after sizing can be at least about 10%. For example, the solids content of the initial slurry can be about 10% to about 70%, about 30% to about 60%, about 10% to about 30% solids content, about 15% to about 25%, or about 17% to about 20%. For example, the solids content of the slurry can be about 20%. The slurry can be formed by mixing the sized calcium bentonite with water under conditions sufficient to form a slurry.

[0023] The slurry can be made with or without the addition of a dispersant while maintaining a suitable viscosity. For example, it has been observed that slurries with solids contents up to 30% can be obtained without a dispersant while maintaining a Brookfield 100 rpm viscosity of less than 660 cps.

[0024] Optionally, a dispersant can be used to form the initial slurry. For example, for high solids contents above 30% up to about 70%, the use of a dispersant can facilitate the formation of the slurry. For example, the dispersant can be or include a phosphate. For example, the dispersant can be or include sodium silicate. For example, the dispersant can include or be sodium silicate, wherein the N2O:SiO2 ratio is 1:1 to 1:3.3. Examples of dispersants include, but are not limited to, sodium hexametaphosphate, sodium tripolyphosphate (STPP) and tetrasodium pyrophosphate (TSPP), sodium polyacrylate, sodium silicate, and combinations thereof. The dispersant can be included in an amount of about 0.1% to about 5.0%, based on the total dry component weight of the slurry.

[0025] For example, the sized calcium bentonite, water, and optional dispersant can be mixed for about 5 minutes to about 1 hour, about 10 minutes to about 20 minutes, about 15 minutes to about 30 minutes, or about 20 minutes to about 45 minutes. Other suitable mixing times include about 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60 minutes, or any value therebetween, or a range defined by any of these values.

[0026] The slurry may be formed by mixing at a speed of about 1000 fpm to about 5000 fpm, about 3000 fpm to about 4000 fpm, or about 3500 fpm to about 4500 fpm. 400, 4500, 4600, 4700, 4800, 4900, or 5000 fpm, or any value therebetween or any range bounded by these values. The slurry can be formed in a dispersed system as disclosed herein. It has been advantageously discovered that dispersion systems according to the present disclosure can apply high shear to form a slurry while minimizing viscosity and blade wear.

[0027] In some embodiments, the present invention provides the slurry of the present invention.For example, about 50 kilowatts / short tons (kw / ston) can be used to form slurry with about 150kw / ston mixing energy.Other suitable mixing energy comprises that about 80kw / ston is about 120kw / ston, about 100kw / ston to 150kw / ston, about 50kw / ston to about 75kw / ston or about 60kw / ston to 110.For example, slurry can be formed with the mixing power of about 50,60,70,80,90,100,110,120,130,140,150kw / ston or any value therebetween or any scope limited by these values.Mixing can give the enough energy of slurry, the mineral decomposition in the slurry is to -60 orders (60M) basically, that is, granularity is 250 microns or less slurry basically.

[0028] The slurry can be screened to remove larger aggregates, thereby removing particles with a Horiba particle size greater than 250 microns. For example, sizing can remove particles with a Horiba particle size greater than 250 microns to as high as about 595 microns. For example, screening can be used to remove aggregates of +30M to +60M size. Unless otherwise indicated, the particle size herein will be with reference to the Horiba particle size. The larger aggregate removed by screening can be ground and reintroduced into the process to reduce the amount of waste minerals produced in the process. For example, the larger aggregate can be ground and then reintroduced into the method of the present disclosure to form an initial slurry, or the larger aggregate can be ground to a particle size less than 45 microns and then introduced into the final slurry. The particles screened out from the reground larger aggregate can be introduced in the initial stage of the method, for example, to form an initial slurry.

[0029] After screening, the slurry is ground to reduce the d 50 The granularity of the present invention can be reduced to 10 microns or less.Grinding can also be carried out so that the amount of the particle of Horiba granularity greater than 45 microns is reduced to about 10wt% from 1wt%.For example, medium grinding can be carried out to slurry.For example, grinding can be carried out with the energy input of about 20kw / ton to about 80kw / ton, about 30kw / ton to about 70kw / ton, about 40kw / ton to about 60kw / ton or about 20kw / ton to about 50kw / ton.Other suitable grinding energy input can be about 20,30,40,50,60,70 or 80kw / ston or any value therebetween or by any scope limited by these values.

[0030] It has been observed that particles in calcium bentonite ore with a particle size greater than 45 microns can be abrasive during downstream processing. Therefore, reducing or eliminating particles in this size range and lowering the concentration of particles of this size in the slurry can help reduce or prevent filler-induced abrasive wear during slurry processing and during linerboard manufacturing.

[0031] After grinding, the slurry can be screened again to remove aggregate. For example, particles with a Horiba particle size greater than 44 microns can be removed. For example, aggregate with a Horiba particle size greater than 44 microns up to 53 microns can be removed. For example, aggregate or gravel with a size of +325M to +280M can be removed. For example, dispersion can be performed so that less than 1% to 20% of the aggregate is removed in the final slurry screening. For example, the final slurry can have less than 10% of the aggregate removed during the final screening. The larger aggregate removed by screening can be ground and reintroduced into the process to reduce the amount of waste minerals generated in the process. For example, the larger aggregate can be ground and then reintroduced into the method of the present disclosure to form the initial slurry. For example, the larger aggregate can be ground into particles with a size less than 44 microns, screened, and introduced into the final slurry.

[0032] The disclosed method may also include processing the calcium bentonite ore to remove highly abrasive minerals, such as quartz. For example, the calcium bentonite ore may be approximately 70% montmorillonite clay as determined by X-ray diffraction. Other mineral species present may include quartz and mica. Removing abrasive minerals mixed with the ore can minimize the abrasiveness of the slurry on ceramic and polymer cloth used in the linerboard process.

[0033] It has been observed that reducing and / or completely eliminating abrasive minerals and limiting the mineral filler particle size to d 50 Smaller than 10 microns creates a mineral slurry suitable for use in linerboard processing and avoids degradation or damage to ceramic and polymer cloth used in linerboard processing. Figure 1 It was found that the precursor calcium bentonite as well as the starting ore had a significant proportion of particles sized 45 μm, which increased the d 50 and d 90 . Figure 2 The method of the present disclosure is used to reduce the 50 and d 90 Calcium bentonite after particle size. During the abrasion and wear testing of both mineral compositions, a correlation was observed between larger particle size in the unprocessed system and abrasion and wear.

[0034] The Brookfield 100 spd viscosity of the final slurry formed by the method of the present disclosure can be about 50 cps to about 600 cps, about 200 cps to about 600 cps, or about 50 cps to about 150 cps and any value therebetween and the range defined by such values. Such a viscosity can facilitate the pumping of the slurry into the linerboard manufacturing process. For example, a slurry production facility can be provided on-site at the linerboard manufacturing facility so that calcium bentonite ore, for example, mined from a raw mine, can be transported to the facility to be produced on-site into a calcium bentonite filler slurry and directly pumped into the linerboard manufacturing process. It is also contemplated herein that the slurry is manufactured off-site at the linerboard manufacturing process and transported to the linerboard manufacturing facility.

[0035] A facility for producing a wet slurry of calcium bentonite filler for use in containerboard production may include a calcium bentonite ore receiving and sizing unit for sizing the calcium bentonite ore to an ore size of about 2 cm to about 8 cm. The facility further includes a dispersion unit for mixing the sized calcium bentonite ore with water to form an initial slurry having a solids content of about 10% to about 30%. The facility also includes a first screening unit for screening the initial slurry to remove aggregate having a particle size greater than 250 microns. The facility also includes a grinding unit for grinding the initial slurry until the d 50 The milled slurry is further processed by a second screening unit configured to screen the milled slurry to remove particles having a particle size greater than 44 microns, thereby producing a final slurry. Figure 3 One possible configuration of a production facility is shown.

[0036] The facility may be located at a linerboard mill so that the slurry can be pumped or otherwise transported directly to a linerboard manufacturing unit for incorporation into the furnish. For example, the wet slurry facility may include a wet slurry storage unit that is in fluid communication with a unit for processing linerboard furnish to pump the calcium bentonite slurry directly into the furnish, thereby supplying the required calcium bentonite filler.

[0037] Alternatively, the facility for producing the wet slurry may be separate from the linerboard manufacturing unit, and the storage unit containing the wet slurry may be transported to the linerboard plant for use as calcium bentonite filler.

[0038] Calcium bentonite ore may contain accessory minerals such as mica, quartz, opal, and feldspar. It has been found that, advantageously, the wet slurry process of the present disclosure can significantly reduce the presence of accessory minerals compared to dry processes. For example, quartz can be included as a accessory mineral in the ore and can be removed in the screening step to remove grit. The remaining accessory minerals can be removed / reduced by the grinding and screening steps of the process. The final slurry can include reduced amounts of accessory minerals compared to the calcium bentonite ore, such that the minerals present in the final slurry are greater than 80% calcium bentonite.

[0039] The dispersion system according to the present disclosure can advantageously allow the formation of the calcium bentonite slurry of the present disclosure at high shear while minimizing viscosity and blade wear. The dispersion system includes a dispersion tank having a ratio of tank height to diameter of about 1.0 to about 2.5. For example, the ratio of tank height to diameter can be about 1.5. It has been found that such a ratio is conducive to a large amount of contact between the slurry components and the blades. The dispersion system also includes blades arranged inside the tank. The blades are sized so that the ratio of the dispersion tank diameter to the blade diameter is about 1.75 to 2.5. It has been observed that such sizing allows for a large amount of blade impact. Figure 4 One possible design of a successful disperser using the present invention is shown.

[0040] The blades can be made of highly wear-resistant materials such as polyurethane or tungsten carbide-coated metal.

[0041] The dispersing system of the present disclosure is capable of maintaining a tip speed of about 2,000 to 5,000 fpm for a mixing time of up to 1 hour, such as 10 to 20 minutes.

[0042] Examples

[0043] Calcium bentonite slurries for use as mineral fillers in containerboard processes were produced by the method of the present disclosure for different loadings of raw mined calcium bentonite ore. The resulting wet slurry properties are shown in Table 1. For each of these samples, the ore was processed as follows: the ore was sized to -3 inches using a crusher, the sized ore was combined with sufficient water to produce a 20% solids slurry using the dispersion system of the present disclosure. The slurry was mixed at 4000 fpm for 10 minutes. The slurry was then screened to remove +60M aggregate. The resulting slurry was media milled until the 45 micron particle size peak of the particle size distribution was less than 5 wt% and the d 50 The particle size is kept below 10 microns. A final screening is performed to remove the +325M aggregate.

[0044] Table 1 shows the reduction in particle size where each unit operation ultimately results in a successful end product.

[0045]

[0046] Handsheets were formed using the slurry of the present disclosure and exhibited acceptable strength loss at a 10% ash target, similar to the loss of standard clay products produced by conventional means. The handsheets were produced in an 8" Box and Noble former using a standard containerboard formulation with 2# / ton of alum and 4# / ton of retention aid. The retention of the calcium bentonite product was over 75% and was the best among the clays. Figure 5 shows that the present invention performs equally well in key strength properties of the handsheets when compared to other, more expensive clay products.

[0047] It was observed that due to the high surface area of ​​calcium bentonite, its particle size of 8-10 microns 50 Without intending to be bound by theory, it is believed that the specific surface area of ​​calcium bentonite in this particle size range is about 60 m 2 / g, which allows it to interact well with polymer retention aids in the slurry.

[0048] The foregoing description has been given for clearness of understanding only, and no unnecessary limitations are to be understood therefrom, since modifications within the scope of the disclosure may be obvious to those skilled in the art.

[0049] All patents, patent applications, government publications, government regulations, and references cited in this specification are hereby incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control.

[0050] Throughout this specification, unless otherwise described, when compounds, compositions, methods and / or processes are described as comprising components, steps or materials, it is contemplated that the compounds, compositions, methods and / or processes may also comprise, consist essentially of, or consist of any combination of said components or materials. Unless expressly stated otherwise, component concentrations may be expressed as weight concentrations. In view of the foregoing disclosure, as will be understood by one of ordinary skill in the art, it is contemplated that combinations of components include homogeneous and / or heterogeneous mixtures.

[0051] References

[0052] US4,797,158

[0053] US11,447,395

[0054] US5,055,161

[0055] US8,512,850

[0056] EP 0017353

[0057] <h2 style=";text-align:left;direction:ltr">DE3306478A

Claims

1. A method for producing a wet slurry containing calcium bentonite filler for use in a linerboard manufacturing process, the method comprising: mixing calcium bentonite ore with water to form an initial slurry having a solids content of about 10% to about 30%, wherein the calcium bentonite ore has an average particle size of about 2 cm to about 8 cm; screening the initial slurry to remove aggregate having a particle size greater than 250 microns; Grind the initial slurry until the d 50 The particle size is 10 microns or less and the weight percentage of particles having a particle size of 45 microns or greater is less than 5 wt% based on the total weight of the slurry; as well as The milled slurry is screened to remove particles having a size greater than 44 microns, thereby producing a final slurry having a solids content of about 10% to about 20%.

2. The method of claim 1, wherein the initial slurry does not contain a dispersant.

3. The method according to claim 1 or 2, wherein the final slurry does not contain a dispersant.

4. A method for producing a wet slurry containing calcium bentonite filler for use in a containerboard manufacturing process, the method comprising: mixing calcium bentonite ore with water and a dispersant to form an initial slurry having a solids content of at least about 10%, wherein the calcium bentonite ore has an average particle size of about 2 cm to about 8 cm; screening the initial slurry to remove aggregate having a particle size greater than 250 microns; Grind the initial slurry until the d 50 The particle size is 10 microns or less and the weight percentage of particles having a particle size of 45 microns or greater is less than 5 wt% based on the total weight of the slurry; as well as The milled slurry is screened to remove particles having a size greater than 44 microns, thereby producing a final slurry, wherein the final slurry has a solids content of at least about 10%.

5. The method of claim 4, wherein the dispersant comprises a phosphate.

6. The method according to claim 4, wherein the dispersant is one or more of sodium hexametaphosphate, sodium tripolyphosphate (STPP), tetrasodium pyrophosphate (TSPP), sodium polyacrylate, and sodium silicate.

7. The method of claim 4, wherein the dispersant comprises sodium silicate, wherein the ratio of N2O:SiO2 is about 1:1 to 1:3.

3.

8. The method of claim 4 or 5, wherein the dispersant is present in the initial slurry in an amount of about 0.1% to about 5.0% based on the total dry component weight of the initial slurry.

9. The method according to any one of the preceding claims, wherein the initial slurry is milled by media milling.

10. A method according to any one of the preceding claims, wherein 20% or less of the calcium bentonite ore is discarded in producing the final slurry.

11. The method of claim 10, wherein 15% or less of the calcium bentonite ore is discarded when producing the final slurry.

12. The method of any one of the preceding claims, further comprising screening the calcium bentonite ore to at least partially remove grit, wherein the grit comprises quartz.

13. A method according to any one of the preceding claims, wherein the calcium bentonite ore comprises one or more accessory minerals and the final slurry comprises reduced amounts of accessory minerals compared to the calcium bentonite ore such that the mineral content present in the final slurry is greater than 80% calcium bentonite.

14. The method of claim 13, wherein the accessory minerals comprise one or more of mica, quartz, opal, and feldspar.

15. The method of any one of the preceding claims, wherein mixing is performed for about 5 minutes to about 1 hour.

16. The method of any one of the preceding claims, wherein mixing is performed in the dispersion unit at a tip speed of about 1000 fpm to about 5000 fpm.

17. according to the method described in any one of the preceding claims, wherein mixing is carried out under the mixing energy input of about 50kw / ston to about 150kw / ston.

18. The method of any one of the preceding claims, wherein the initial slurry has a Brookfield viscosity of about 100 cps to about 800 cps at 100 spd.

19. The method of any one of the preceding claims, wherein the final slurry has a Brookfield viscosity of about 50 cps to about 600 cps at 100 spd.

20. The method of any preceding claim, further comprising sizing the calcium bentonite ore to an average particle size of about 2 cm to 8 cm prior to mixing with water to form the initial slurry.

21. A method according to any one of the preceding claims, wherein the calcium bentonite is mined from a quarry.

22. The method of any one of the preceding claims, further comprising collecting the aggregate having a particle size greater than 250 microns removed during screening of the initial slurry, grinding the aggregate, and recycling the aggregate to the mixing step to form the initial slurry.

23. The method of any one of the preceding claims, further comprising collecting particles greater than 44 microns removed from the milled slurry, milling the particles greater than 44 microns to a particle size less than 44 microns, and mixing with the final slurry.

24. according to the method described in any one of the preceding claims, wherein grinding is carried out under the energy input of about 20kw / ston to about 80kw / ston.

25. A method for making linerboard, the method comprising: incorporating the final pulp produced by the method of any one of the preceding claims into a fiber-containing furnish for making linerboard, wherein the furnish comprises from about 2 wt% to about 20 wt% calcium bentonite, based on the total weight of the furnish; and forming the linerboard from the furnish.

26. Containerboard produced by the method according to claim 25.

27. A plant for producing a wet slurry of calcium bentonite filler for use in containerboard production, the plant comprising: a calcium bentonite ore receiving sizing unit for sizing the calcium bentonite ore to a particle size of about 2 cm to about 8 cm; a dispersion unit for mixing the sized calcium bentonite ore with water to form an initial slurry having a solids content of at least about 10%; a first screening unit, the first screening unit being used to screen the initial slurry to remove aggregate having a particle size greater than 250 microns; A grinding unit for grinding the initial slurry until the d 50 The particle size is 10 microns or less and the weight percentage of particles having a particle size of 45 microns is less than 5 wt% based on the total weight of the slurry; as well as A second screening unit is used to screen the ground slurry to remove particles with a particle size greater than 44 microns, thereby producing a final slurry.

28. The facility of claim 27, further comprising a final slurry storage unit in fluid communication with the linerboard manufacturing unit.

29. The plant of claim 27 or 28, wherein the solids content of the initial slurry is from about 10% to about 30%.

30. The plant of claim 27 or 28, wherein the initial slurry further comprises a dispersant and the solids content of the initial slurry is up to 70%.

31. A dispersion system for forming a wet slurry of calcium bentonite filler for containerboard, the dispersion system comprising: A dispersion tank and a blade arranged in the dispersion tank, wherein The dispersion tank has a tank height and a tank diameter, and a ratio of the tank height to the tank diameter is from about 1.0 to about 2.5, and The blade has a blade diameter, and a ratio of the tank diameter to the blade diameter is about 1.75 to 2.

5.

32. The dispersion system of claim 31 , wherein the blades are formed from a high shear material.

33. The dispersion system of claim 32, wherein the blades are formed of polyurethane or tungsten carbide coated metal.

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