Wet Process Slurries for Linerboard

Abstract

A method for making a wet slurry containing mineral filler for a linerboard making process can include mixing mineral ore with water to form an initial slurry; sieving the initial slurry to remove agglomerates having a particle size greater than 250 microns; milling the initial slurry until the DSO 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 sieving the milled slurry to remove particles having a particle size greater than 44 microns, thereby producing a final slurry.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS The benefit of priority to U.S. Provisional Patent Application No. 63 / 488,167, filed March 2, 2023, is claimed herein, the disclosure of which is incorporated herein by reference in its entirety.

[0002] The present disclosure relates to a method for incorporating mineral fillers into linerboard using a wet slurry. [Background technology]

[0003] Linerboard is generally any grade of paper product suitable for making corrugated packaging materials and containers. Given its application in corrugated packaging, linerboard is designed to have high tensile strength, burst strength, and compression strength. Linerboard is generally made using 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 acid papermaking environments, such as the linerboard manufacturing process, is limited. Additionally, as is done in other papermaking processes, the use of mineral fillers requires the removal of fiber from the stock to maintain important properties such as bulk and basis weight. While this is advantageous for reducing the amount of costly fiber required in such processes, for linerboard production, fiber substitution is considered detrimental to maintaining the strength properties required for the linerboard. Summary of the Invention

[0004] The linerboard manufacturing industry needs an effective method for incorporating mineral fillers into linerboard without adversely affecting the strength properties of the linerboard. Fibers are becoming limited in supply and expensive to produce compared to minerals. The linerboard market is expected to grow at a CAGR of 2.3% globally (2.1% in the U.S.). The methods of the present disclosure can advantageously provide a way to expand fiber applications and reduce costs to meet this global growth.

[0005] According to an embodiment, a method for making a wet slurry containing mineral filler for a linerboard making process includes mixing a mineral ore, for example, raw or as-mined mineral ore, with water to form an initial slurry having a solids content of about 10% to about 30%, sieving the initial slurry to remove agglomerates having a particle size greater than 250 microns, and sieving the slurry. 50 The process can include grinding the initial slurry until the particle size is 10 microns or less and the weight percent of particles having a particle size of 45 microns is less than 5% by weight based on the total weight of the slurry; and sieving the ground slurry to remove particles having a particle size greater than 44 microns, thereby producing a final slurry having a solids content of about 10% to about 20%. Depending on the size of the incoming mineral ore, the process can further include sizing the mineral ore to an average particle size of about 2 cm to about 8 cm. For example, if the mineral ore is provided in as-mined or raw form of sufficient size, size adjustment may not be necessary. For example, kaolin can have an average particle size of about 2 cm to about 8 cm in raw form.

[0006] According to an embodiment, a method for making a wet slurry containing mineral filler for a linerboard making process includes mixing a mineral ore, e.g., as-mined or raw 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 agglomerates having a particle size greater than 250 microns; and screening the slurry. 50The process can include grinding the initial slurry until the particle size is 10 microns or less and the weight percent of particles having a particle size of 45 microns is less than 5% by weight based on the total weight of the slurry; and sieving the ground slurry to remove particles having a particle size greater than 44 microns, thereby producing a final slurry, the final slurry having a solids content of at least about 10%. Depending on the size of the incoming mineral ore, the process can further include sizing the mineral ore to an average particle size of about 2 cm to about 8 cm. For example, if the mineral ore is provided in as-mined or raw form of sufficient size, size adjustment may not be necessary. For example, kaolin can have an average particle size of about 2 cm to about 8 cm in raw form.

[0007] A method for making linerboard according to the present disclosure can include incorporating a final slurry formed by the method for making a wet slurry of the present disclosure into a stock containing fibers for making linerboard, wherein the stock contains about 2% to about 20% by weight of minerals, based on the total weight of the stock, and forming a linerboard from the stock.

[0008] In accordance with the present disclosure, also disclosed herein is a linerboard made by the method of the present disclosure or containing an additive made by the method of the present disclosure. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a Horiba particle size distribution graph showing particle size distribution for precursor (initial) slurry (dispersed and passed through 60M). [Figure 2] 1 is a Horiba particle size distribution graph showing the particle size distribution of the final slurry prepared by the method of the present disclosure. [Figure 3] FIG. 1 is a schematic diagram of a process flow diagram for the method of the present disclosure. [Figure 4]FIG. 1 is a schematic diagram of a distribution unit according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] The disclosed method advantageously provides the mineral as a slurry to allow for easier dispersion into existing paper stock. To be successful, it was also required that the mineral be retained in the paper product in an amount greater than 75% and not cause wear on the equipment used in forming the wet paper sheet. Furthermore, to be an economically viable process, no more than 20%, and preferably no more than 15%, of the mineral ore used in forming the slurry should be discarded in forming the slurry.

[0011] The slurries of the present disclosure can have a high solids content of about 10% to about 20%. The slurries can be used directly in linerboard manufacturing processes as an additive to stock to provide mineral filler in amounts exceeding those previously used in the linerboard industry. For example, a linerboard manufacturing process can include mineral filler in an amount of about 2% to about 20% based on the weight of the stock. Advantageously, it has been found that the methods of the present disclosure can form slurries with high mineral solids content that can utilize mineral ores received directly from the mining site, regardless of moisture content and ore size. Mineral ores can be used in the processes of the present disclosure as they are mined and without further purification before use in the process. Ore in an "as-mined" state can have a starting particle size of about 20 cm to about 45 cm. Some mineral types, for example, can have an as-mined state of sufficient size for use in the process. For example, kaolin in an as-mined state can have a particle size of about 2 cm to about 8 cm. Optionally, sizing can be performed to reduce the particle size of the mineral ore, for example, to an average particle size of about 2 cm to about 8 cm. Furthermore, the slurry produced by the disclosed method can be used directly in a papermaking process to provide an effective mineral filler content to the linerboard without adversely affecting the strength properties of the linerboard or causing harmful wear and tear to the equipment or sheet during the papermaking process. For example, linerboard produced with about 12% mineral filler has been found to have acceptable strength properties that are within 15-20% of the strength of linerboard produced without filler. This advantageously allows linerboard to be produced with a reduced fiber content without sacrificing the necessary strength.

[0012] Linerboard mills are expected to require approximately 40,000 to 75,000 tpy of mineral to meet their capacity needs. The methods of the present disclosure can advantageously meet these needs in a cost-effective manner by enabling the mineral slurry to be produced on-site, avoiding costly transportation of the slurry to the production site. However, it is also contemplated herein that the slurry can be produced in a facility remote from the linerboard mill and transported to the mill.

[0013] A method for producing a mineral filler wet slurry for a linerboard making process can optionally include sizing the mineral ore to reduce the mineral to a size of about 2 cm to about 8 cm. If the incoming mineral ore has a size of about 2 cm to about 8 cm, sizing may not be necessary. After sizing (if required), the mineral ore is mixed with water to produce a slurry. The slurry is then sieved to remove large agglomerates. The large agglomerates removed by sieving can optionally be collected and resized to reduce the amount of waste ore generated in the process. For example, the larger agglomerates can be crushed and then reintroduced into the method of the present disclosure to form the initial slurry, or the larger agglomerates can be crushed to a particle size of less than 45 microns and then introduced into the final slurry. For example, after crushing, particles that pass through a 45-micron sieve can be introduced into the final slurry.

[0014] After sieving, the slurry is milled to reduce the particle size of the minerals in the slurry to a value acceptable for abrasion and wear performance in the process. The milled slurry is then sieved to remove agglomerates. The resulting slurry can be pumped directly into a linerboard making process and used in the paper stock as a mineral filler.

[0015] Sizing the mineral ore may include reducing the particle size to pass through an 8 cm. For example, the mineral ore may be sized using a shredder.

[0016] The initial slurry formed after sizing can have a solids content of at least about 10%. For example, the initial slurry can have a solids content of about 10% to about 70%, about 30% to about 60%, about 10% to about 30%, about 15% to about 25%, or about 17% to about 20%. For example, the slurry can have a solids content of about 20%. The slurry can be formed by combining the sized mineral with water under conditions sufficient to form a slurry.

[0017] Slurries can be made while maintaining a suitable viscosity with or without the need for added dispersants. For example, it has been observed that slurries with solids contents up to 30% can be achieved without dispersants while maintaining a Brookfield 100 rpm viscosity of less than 660 cps. Optionally, the initial slurry can be formed using a dispersant. For example, for high solids contents, such as above 30% and up to about 70%, the use of a dispersant can facilitate slurry formation. 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 include sodium silicate with an NO:SiO ratio of 1:1 to 1:3.3. Examples of dispersants include, but are not limited to, sodium hexametaphospate, sodium tripolyphosphate (STPP), tetrasodium pyrophosphate (TSPP), sodium polyacrylate, sodium silicate, and combinations thereof. The dispersant may be included in an amount of about 0.1 to about 5.0 percent based on the total dry component weight of the slurry.

[0018] For example, the sized mineral, 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.

[0019] The slurry can 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. For example, the mixing speed can be about 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, 2500, 2600, 2700, 2800, 2900, 3000, 3100, 3200, 3300, 3400, 3500, 3600, 3700, 3800, 3900, 4000, 4100, 4200, 4300, 4400, 4500, 4600, 4700, 4800, 4900, or 5000 fpm, or any value therebetween, or any range defined by these values. A slurry can be formed in a dispersion system as disclosed herein. Advantageously, it has been found that the dispersion system according to the present disclosure is capable of imparting high shear to form the slurry while minimizing viscosity and blade wear.

[0020] For example, the slurry can be formed using a mixing energy of about 50 kilowatts per short ton (kw / ston) to about 150 kw / ston. Other suitable mixing energies include about 80 kw / ston to about 120 kw / ston, about 100 kw / ston to 150 kw / ston, about 50 kw / ston to about 75 kw / ston, or about 60 kw / ston to 110 kw / ston. For example, the slurry can be formed with a mixing power of about 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, or 150 kw / ston, or any value therebetween, or any range defined by these values. The mixing can impart sufficient energy to the slurry to substantially break down the minerals in the slurry to minus 60 mesh (60M), which is a slurry having a particle size substantially equal to or less than 250 microns.

[0021] The slurry can be sieved to remove larger agglomerates, thereby removing particles having a Horiba particle size greater than 250 microns. For example, sizing can be used to remove particles having a Horiba particle size greater than 250 microns up to about 595 microns. For example, sieving can be used to remove agglomerates of +30M to +60M size. Unless otherwise specified, particle sizes herein are made with reference to Horiba particle size. The larger agglomerates removed by sieving can be crushed and reintroduced into the process to reduce the amount of waste mineral generated by the process. For example, the larger agglomerates can be crushed and then reintroduced into the method of the present disclosure to form the initial slurry, or the larger agglomerates can be crushed to a particle size less than 45 microns and then introduced into the final slurry.

[0022] After sieving, the slurry is crushed to separate the minerals. 50The particle size is reduced to 10 microns or less. Milling can also be performed to reduce the amount of particles having a Horiba particle size greater than 45 microns to 1% to about 10% by weight. The slurry can be, for example, media milled. Milling can be performed with an energy input of, for example, about 20 kW / ton to about 80 kW / ton, about 30 kW / ton to about 70 kW / ton, about 40 kW / ton to about 60 kW / ton, or about 20 kW / ton to about 50 kW / ton. Other suitable milling energy inputs can be about 20, 30, 40, 50, 60, 70, or 80 kW, or any value therebetween, or any range defined by these values.

[0023] It has been observed that particles in mineral ores having a particle size greater than 45 microns can be abrasive in downstream processing. Therefore, reducing or eliminating particles in this size range and reducing the concentration of particles of this size in the slurry can help reduce or prevent both abrasive wear during processing of the slurry and abrasive wear caused by the filler during linerboard production.

[0024] After grinding, the slurry can then be sieved again to remove agglomerates. For example, particles having a Horiba particle size greater than 44 microns can be removed. For example, agglomerates having a Horiba particle size greater than 44 microns and up to 53 microns can be removed. For example, agglomerates or sand particles that are between 325 microns and 280 microns can be removed. For example, dispersion can be performed so that sieving of the final slurry has less than 1% to 20% of the agglomerates removed. For example, the final slurry can have less than 10% of the agglomerates removed during the final sieving. Larger agglomerates removed by sieving can be crushed and reintroduced into the process to reduce the amount of waste mineral generated by the process. For example, the larger agglomerates can be crushed and then reintroduced into the method of the present disclosure to form the initial slurry, or the larger agglomerates can be crushed to a size less than 44 microns, sieved, and introduced into the final slurry. Particles sieved from re-ground larger agglomerates can be introduced at an early stage in the process, for example to form an initial slurry.

[0025] The disclosed method can also include treating mineral ores to remove highly abrasive minerals, such as quartz. For example, montmorillonite ore is approximately 70% montmorillonite clay by X-ray diffraction. Other mineral species present can include quartz and mica. Removal of abrasive minerals mixed with the ore can minimize abrasion and wear from the slurry on ceramic and polymeric fabrics used in linerboard processes.

[0026] The methods of the present disclosure can also optionally include treating the mineral ore to remove highly abrasive minerals, such as quartz and / or mica. Removal of abrasive minerals mixed with the ore can minimize abrasion and wear from the slurry on ceramic and polymeric cloths used in linerboard processes.

[0027] Reduction and / or complete elimination of abrasive minerals and mineral filler particle size of less than 10 microns 50 It has been observed that limiting the amount of precursor minerals and starting ores to d results in a mineral slurry that is suitable for use in linerboard processes and avoids degradation or damage to the ceramic and polymer fabrics used in the linerboard process. Referring to Figure 1, the precursor minerals and starting ores are 50 and d 90 It was found to have a significant proportion of particles of 45 microns size, which pushes up the 50 and d 90 1 shows the mineral after treatment with the method of the present disclosure to reduce particle size. During abrasion and wear testing of these two mineral compositions, a correlation was observed between higher particle size and abrasion and wear in the untreated system.

[0028] The final slurry formed by the methods of the present disclosure may have a Brookfield 100 spd viscosity of 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 ranges defined by such values. Such a viscosity may advantageously allow the slurry to be pumped to a linerboard manufacturing process. For example, a slurry generation facility may be located on-site at a linerboard manufacturing facility, such that, for example, as-mined mineral ore can be brought to the facility for on-site generation into a slurry mineral filler and pumped directly to the linerboard manufacturing process. It is also contemplated herein that the slurry may be generated off-site at the linerboard manufacturing process and transported to the linerboard manufacturing facility.

[0029] An apparatus for producing a wet slurry of mineral filler for use in linerboard production can include a mineral ore receiving and sizing unit for sizing mineral ore to an ore size of about 2 cm to about 8 cm. The apparatus further includes a dispersing unit for mixing the sized mineral ore with water to form an initial slurry having a solids content of about 10% to about 30%. The apparatus also includes a first screening unit for screening the initial slurry to remove agglomerates having a particle size greater than 250 microns. The slurry d 50 A grinding unit is included for grinding the initial slurry until the particle size is 10 microns or less and the weight percent of particles having a particle size of 45 microns is less than 5% by weight based on the total weight of the slurry. The facility also includes a second sieving unit for sieving the ground slurry to remove particles having a particle size greater than 44 microns, thereby producing a final slurry. Figure 3 shows one possible configuration for the production facility.

[0030] This facility can be at a linerboard mill so that the slurry can be pumped or otherwise transported directly to a linerboard production unit for incorporation into the stock. For example, the wet slurry facility can include a wet slurry storage unit in fluid communication with a unit for processing the linerboard stock to pump the mineral slurry directly into the stock to provide the required mineral filler.

[0031] Alternatively, the equipment for producing the wet slurry can be separate from the linerboard production unit and a storage unit containing the wet slurry can be transported to the linerboard rolling mill for use as a mineral filler.

[0032] Any of the methods or equipment described herein can be used to process a variety of minerals into the desired wet slurry. For example, the mineral can be a clay such as montmorillonite, kaolin, feldspar, smectite, illite, etc. Mineral ores from any of these sources can contain secondary minerals such as mica, quartz, opal, and feldspar. It has been found that the wet slurry process of the present disclosure can advantageously reduce the presence of secondary minerals to a greater extent than through a dry process. For example, quartz can be included as a secondary mineral in the ore and removed in a sieving step to remove sand grains. The remaining secondary minerals can be removed / reduced through the grinding and sieving steps of the process. The final slurry can contain reduced amounts of secondary minerals compared to the mineral ore, such that the minerals present in the final slurry are greater than 80% clay species.

[0033] Dispersion systems according to the present disclosure can advantageously enable the formation of mineral slurries of the present disclosure having high shear while minimizing viscosity and blade wear. The dispersion system includes a dispersion tank having a tank height-to-diameter ratio of about 1.0 to about 2.5. For example, the dispersion tank can have a tank height-to-diameter ratio of about 1.5. It has been found that these ratios advantageously allow for a high number of contacts of the slurry components with the blades. The dispersion system further includes blades disposed 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 this sizing allows for a high number of blade collisions. Figure 4 shows one possible design for a successful disperser using the present invention.

[0034] The blades may be made from a highly wear-resistant material such as urethane or metal coated with tungsten carbide.

[0035] The dispersion system of the present disclosure is capable of sustaining a tip speed of about 2,000 to 5,000 fpm for a mixing time of up to 1 hour, for example, 10 to 20 minutes.

[0036] The foregoing description has been given for clarity of understanding only, and no unnecessary limitations should be understood therefrom, as modifications within the scope of the disclosure may be apparent to those skilled in the art.

[0037] All patents, patent applications, government publications, government regulations, and literature references cited herein are incorporated by reference in their entirety. In the case of conflict, the present description, including definitions, will control.

[0038] Throughout this specification, when a compound, composition, method, and / or process is described as comprising components, steps, or materials, it is contemplated that the compound, composition, method, and / or process can also comprise, consist essentially of, or consist of any combination of the listed components or materials, unless otherwise stated. Component concentrations may be expressed in weight concentration units unless specifically indicated otherwise. Combinations of components are contemplated to include homogeneous and / or heterogeneous mixtures, as would be understood by one of skill in the art in light of the foregoing disclosure.

[0039] References US4,797,158 US11,447,395 US5,055,161 US$8,512,850 EP 0017353 DE3306478A

Claims

1. 1. A method for making a wet slurry containing mineral filler for a linerboard making process, comprising: mixing mineral ore with water to form an initial slurry having a solids content of about 10% to about 30%, wherein the mineral ore has an average particle size of about 2 cm to about 8 cm; sieving the initial slurry to remove agglomerates having a particle size greater than 250 microns; d of the slurry ５０ milling the initial slurry until the particle size is 10 microns or less and the weight percent of particles having a particle size of 45 microns or more is less than 5 weight percent based on the total weight of the slurry; and sieving 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%.

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

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

4. 1. A method for making a wet slurry containing mineral filler for a linerboard making process, comprising: mixing a mineral ore with water and a dispersant to form an initial slurry having a solids content of at least about 10%, wherein the mineral ore has an average particle size of about 2 cm to about 8 cm; sieving the initial slurry to remove agglomerates having a particle size greater than 250 microns; d of the slurry ５０ milling the initial slurry until the particle size is 10 microns or less and the weight percent of particles having a particle size of 45 microns or more is less than 5 weight percent based on the total weight of the slurry; and sieving 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%.

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

6. 5. The method of claim 4, wherein the dispersing agent is one or more of sodium hexametaphospate, sodium tripolyphosphate (STPP), and tetrasodium pyrophosphate (TSPP), sodium polyacrylate, and sodium silicate.

7. The dispersant is N ２ O:SiO ２ 5. The method of claim 4, wherein the ratio of sodium silicate to silicate is from about 1:1 to 1:3.

3.

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

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

10. 10. The method of any one of the preceding claims, wherein no more than 20% of the mineral ore is discarded in producing the final slurry.

11. 11. The method of claim 10, wherein no more than 15% of the mineral ore is discarded in producing the final slurry.

12. 10. A method according to any one of the preceding claims, wherein the mineral is one or more of clay, kaolin, feldspar, smectite or illite.

13. 10. The method of any one of the preceding claims, further comprising sieving the mineral ore to at least partially remove sand grains, the sand grains comprising quartz.

14. 10. The method of any one of the preceding claims, wherein the mineral ore comprises one or more secondary minerals, and the final slurry comprises a reduced amount of secondary minerals compared to the mineral ore, such that the mineral content in the final slurry is greater than 80% clay type.

15. 15. The method of claim 14, wherein the secondary minerals include one or more of mica, quartz, opal, and feldspar.

16. 10. The method of any one of the preceding claims, wherein the mixing is carried out for about 5 minutes to about 1 hour.

17. 10. The method of any one of the preceding claims, wherein the mixing is carried out in a dispersion unit having a tip speed of about 1000 fpm to about 5000 fpm.

18. 10. The method of any one of the preceding claims, wherein the mixing is carried out at a mixing energy input of from about 50 kw / ston to about 150 kw / ston.

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

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

21. 10. A method according to any one of the preceding claims, wherein the mineral ore is as mined.

22. 22. The method of claim 21, wherein the mineral ore as-mined has an average particle size of about 2 cm to about 8 cm.

23. 23. The method of claim 22, wherein the as-mined mineral ore is kaolin.

24. 10. The method of any one of the preceding claims, wherein the mineral ore is sized to an average particle size of from about 2 cm to about 8 cm before mixing with water to form the initial slurry.

25. 10. The method of any one of the preceding claims, further comprising collecting the agglomerates having a particle size greater than 250 microns that are removed during sieving of the initial slurry, crushing the agglomerates, and recycling the agglomerates to a mixing step to form the initial slurry.

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

27. 10. The method of any one of the preceding claims, wherein the grinding is carried out at an energy input of from about 20 kw / ston to about 80 kw / ston.

28. 10. A method for making a linerboard, the method comprising: incorporating a final slurry formed by the method of any one of the preceding claims into a stock containing fibers for making the linerboard, the stock containing from about 2% to about 20% by weight of minerals, based on the total weight of the stock; and forming the linerboard from the stock.

29. 30. A linerboard made by the method of claim 28.

30. 1. An installation for the production of a wet slurry of mineral filler for use in linerboard production, comprising: a mineral ore receiving and sizing unit for sizing the mineral ore to a particle size of about 2 cm to about 8 cm; a dispersing unit for mixing the sized mineral ore with water to form an initial slurry having a solids content of at least about 10%; a first sieving unit for sieving the initial slurry to remove agglomerates having a particle size greater than 250 microns; d of the slurry ５０ a grinding unit for grinding the initial slurry until the particle size is 10 microns or less and the weight percentage of particles having a particle size of 45 microns or more is less than 5 wt.% based on the total weight of the slurry; a second sieving unit for sieving the milled slurry to remove particles having a particle size greater than 44 microns, thereby producing a final slurry.

31. 31. The facility of claim 30, further comprising a final slurry storage unit in fluid communication with the linerboard production unit.

32. 32. The installation of claim 30 or 31, wherein the initial slurry has a solids content of about 10% to about 30%.

33. 32. The installation of claim 30 or 31, wherein the initial slurry further comprises a dispersant and has a solids content of up to 70%.

34. 1. A dispersion system for forming a wet slurry of mineral filler for linerboard, comprising: A dispersion tank and a blade disposed in the dispersion tank, the dispersion tank has a tank height and a tank diameter, and the ratio of the tank height to the tank diameter is from about 1.0 to about 2.5; The dispersion system wherein the blade has a blade diameter, and the ratio of the tank diameter to the blade diameter is between about 1.75 and 2.

5.

35. 35. The dispersion system of claim 34, wherein the blades are formed from a high shear material.

36. 36. The dispersion system of claim 35, wherein the blades are formed from metal coated with urethane or tungsten carbide.

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