Pulp crushing method

Abstract

To provide a pulp crushing method capable of obtaining cellulose fibers in which fibrillation and fiver shortening are suppressed.SOLUTION: A pulp crushing method is characterized in after roughly pulverizing pulp, processing, by a crusher, the pulverized pulp. The pulp crushing method satisfies the following conditions (A) and (B): (A) the crusher has beating gaps formed by a plurality of circular or similar shape of plates each having a beating function part and disposed so as to face each other, and crushes the pulp passing through the beating gaps by rotating only one of the plates or rotating the plates mutually; (B) an average fibril periphery length change rate R (%) is 100% or less, that is represented by (a pulp average fibril periphery length after crushing processing minus a pulp average fibril periphery length before the crushing processing) / (pulp average fibril periphery length before the crushing processing)×100.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for disintegrating pulp. [Background technology]

[0002] Pulp, which is mainly composed of cellulose, is used in many fields, such as raw materials for papermaking, raw materials for pulp cotton used in disposable diapers and household paper, pulp processed into clothing fibers through chemical processes, raw materials for cellulose acetate used in cigarette filter chips and triacetate films, etc. Furthermore, with the development of decarbonization technology in recent years, cellulose, a natural material, has been attracting attention as a binder component used in civil engineering and dust removal, instead of petroleum-derived materials.

[0003] Pulp for such applications is used as a cellulose raw material after being disintegrated by a crushing process. As a crushing process, for example, Patent Document 1 proposes crushing in water and drying in the presence of an organic solvent to obtain a crushed cellulose raw material.

[0004] Furthermore, Patent Document 2 discloses a method of disintegrating cellulosic crushed material by grinding it using a cutter mill or the like. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 3-197501 [Patent Document 2] Japanese Patent Application Publication No. 8-229421 Summary of the Invention [Problem to be solved by the invention]

[0006] In the conventional crushing methods described above, crushing can sometimes lead to the progression of fibrillation and a decrease in fiber length. When using the material as a binder, it is desirable to be able to crush the material while maintaining its fiber length without causing fibrillation to progress, in order to make it easier to trap soil, dust, etc.

[0007] Therefore, an object of the present invention is to provide a pulp disintegration method capable of obtaining cellulose fibers in which fibrillation and shortening are suppressed. [Means for solving the problem]

[0008] As a result of extensive investigations, the present inventors have found that the problems can be solved by the following (1) and (2). (1) A method for disintegrating pulp, comprising coarsely crushing the pulp and then treating the pulp in a disintegrator, the method being characterized in that the following conditions (A) and (B) are satisfied: (A) The crusher has a beating gap formed by opposing multiple circular or similarly shaped plates with beating function sections, and the pulp passing through the beating gap is crushed by rotating only one of the plates or by rotating the plates relative to each other. (B) The rate of change in average fibril circumference R (%), expressed as (average fibril circumference of pulp after crushing treatment - average fibril circumference of pulp before crushing treatment) / (average fibril circumference of pulp before crushing treatment) x 100, is 100% or less. (2) The method for crushing pulp according to (1), wherein the beating gap is in the range of 0.1 to 5.0 mm. Effect of the Invention

[0009] According to the present invention, a pulp disintegration method capable of obtaining cellulose fibers in which fibrillation and fiber shortening are suppressed can be provided. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] That is, the present invention is a method for crushing pulp, which comprises coarsely crushing the pulp and then treating it with a crusher, and which is characterized by satisfying the following conditions (A) and (B): (A) The crusher has a beating gap formed by opposing multiple circular or similarly shaped plates with beating function sections, and the pulp passing through the beating gap is crushed by rotating only one of the plates or by rotating the plates relative to each other. (B) The rate of change in average fibril circumference R (%), expressed as (average fibril circumference of pulp after crushing treatment - average fibril circumference of pulp before crushing treatment) / (average fibril circumference of pulp before crushing treatment) x 100, is 100% or less.

[0011] <Pulp> The pulp used in the present invention includes wood-derived pulps such as softwood unbleached kraft pulp (NUKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), hardwood bleached kraft pulp (LBKP), softwood unbleached sulfite pulp (NUSP), softwood bleached sulfite pulp (NBSP), hardwood unbleached sulfite pulp (LUSP), hardwood bleached sulfite pulp (LBSP), thermomechanical pulp (TMP), ), pressed groundwood pulp (PGW), refiner ground wood pulp (RGP), alkaline hydrogen peroxide mechanical pulp (APMP), alkaline hydrogen peroxide thermomechanical pulp (APTMP), linters, pulp derived from herbs such as jute, hemp, paper mulberry, mitsumata, and kenaf, pulp derived from bamboo, recycled pulp, and waste paper pulp. From the viewpoint of having a certain fiber length or more as a pulp raw material, wood-derived pulp is preferred, and pulp derived from conifers is more preferred.

[0012] Examples of methods for preparing wood-derived pulp include methods that include chemical pulping (cooking) treatment. By chemical pulping (cooking), lignin, a coloring substance, is dissolved and removed, and pulp with high whiteness can be obtained by combining it with oxygen delignification and bleaching. Examples of chemical pulping (cooking) methods include sulfite cooking, kraft cooking, soda-quinone cooking, and organosolv cooking, and kraft pulp is preferred from an environmental and economical perspective. In the kraft cooking method, alkaline chemicals such as sodium hydroxide, potassium hydroxide, and sodium carbonate are used in combination with sulfur-containing chemicals such as sodium sulfide and sodium sulfite, and additives such as quinone-based cooking aids and polysulfides can be used. These additives do not need to be used if cooking can be performed with alkaline chemicals alone.

[0013] In the method for preparing pulp, the pulp obtained by cooking can be subjected to oxygen delignification. The known medium or high consistency method can be used for the oxygen delignification used in the present invention as is. In the medium consistency method, the pulp consistency is preferably 8 to 15 mass%, and in the high consistency method, 20 to 35 mass%. As the alkali in the oxygen delignification, sodium hydroxide or potassium hydroxide can be used, and as the oxygen gas, oxygen from the cryogenic separation method, oxygen from PSA (Pressure Swing Adsorption), oxygen from VSA (Vacuum Swing Adsorption), etc. can be used.

[0014] The reaction conditions for the oxygen delignification treatment are not particularly limited, but the oxygen pressure is 3 to 9 kg / cm2, more preferably 4 to 7 kg / cm2, the alkali addition rate is 0.5 to 4 mass%, the temperature is 80 to 140°C, the treatment time is 20 to 180 minutes, and other conditions that are known in the art can be applied. Note that in the present invention, the oxygen delignification treatment may be carried out multiple times.

[0015] The pulp that has been subjected to the oxygen delignification treatment may then be sent to a washing step, and after washing, may be subjected to a bleaching treatment as described below. The brightness of the pulp that has been subjected to the oxygen delignification treatment is preferably 30% to 55% based on ISO 2470.

[0016] In the preparation of pulp, in addition to chemical pulping (cooking) and oxygen delignification, a bleaching treatment can also be carried out. This results in a pulp with a higher brightness. Examples of bleaching treatment methods include chlorine treatment (C), chlorine dioxide bleaching (D), alkaline extraction (E), hypochlorite bleaching (H), hydrogen peroxide bleaching (P), alkaline hydrogen peroxide treatment stage (Ep), alkaline hydrogen peroxide-oxygen treatment stage (Eop), ozone treatment (Z), chelate treatment (Q), and combinations of two or more of these treatments on pulp that has been delignified by any conventional method. Examples of combinations (sequences) of two or more treatments include DE / PD, C / DEHD, ZED-PZ / D-Ep-D, Z / D-Ep-DP, D-Ep-D, D-Ep-DP, D-Ep-PD, Z-Eop-DD, Z / D-Eop-D, and Z / D-Eop-DED (the " / " in the sequence means that the treatments before and after the " / " are performed consecutively without washing). The bleaching treatment is not limited to the above examples, and may be a commonly used method. Pulp that has been bleached is usually in a fluid state (fluid pulp). The brightness of the pulp subjected to such bleaching treatment is preferably 70% or more based on ISO 2470.

[0017] In the present invention, it is important that the pulp sheet made of the above-mentioned pulp is roughly pulverized by light cutting, crushing, etc. before being fed into the crusher. By lightly cutting or crushing, the crushability of the pulp sheet can be improved and adjusted, and the load fluctuation in the crusher can be suppressed, stabilizing the operation of the crusher.

[0018] The moisture content of the pulp of the present invention is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. Furthermore, in order to prevent the raw material fibers from being shortened before and after the disintegration of the cellulose fibers of the present invention, the moisture content is more preferably 30% by mass or more, and particularly preferably 40% by mass or more. The upper limit is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, and particularly preferably 65% ​​by mass or less. By adjusting the moisture content of the pulp within this range, the cellulose fibers in the disintegration treatment can be easily adjusted. There is no particular restriction on the moisture content treatment as long as the desired moisture content is satisfied. After forming a pulp sheet from the pulp slurry in a papermaking machine, pressing, and drying with a dryer, moisture may be added to adjust the moisture content to the desired moisture content, or the moisture content may be adjusted to the desired moisture content in the state of a wet sheet that is not dried in the papermaking machine. The moisture content of the pulp is the water content relative to the total mass of the pulp and water.

[0019] <Crusher> It is important that the crusher used in the present invention has one or more beating gaps formed by circular or similarly shaped plates with a beating function, and is characterized in that the pulp passing through the beating gaps is crushed by rotating only one of the plates or by rotating both plates.

[0020] The beating functional section preferably has a coarse crushing functional section and a fine crushing functional section, the coarse crushing functional section being disposed near the center of the plate, and the fine crushing functional section being disposed on the periphery of the coarse crushing functional section. The coarse crushing functional section is preferably formed with at least one type of teeth selected from, for example, pin tooth type, bolt tooth type, pyramidal tooth group, and linear tooth group. The fine crushing functional section is preferably formed with linear tooth group, and linear teeth as fine tooth type are preferable so that the coarsely crushed material can be finely crushed.

[0021] By arranging such a fine-disintegrating functional portion at the peripheral portion, undisintegrated pulp pieces and the like can be reduced and disintegration properties can be improved, making it easier to obtain cellulose fibers with suppressed fibrillation and a small rate of change in average fibril circumference.

[0022] The plate having a circular or similar shape may be any shape having a circular or similar planar shape, such as a disk shape or a doughnut shape with a hole in the center.

[0023] It is important that the crusher used in the present invention has two or more plates and that the plates have one or more opposing beating gaps. The beating gap is also called clearance, and the beating gap is preferably in the range of 0.05 to 10.0 mm, more preferably in the range of 0.05 to 5 mm, and even more preferably in the range of 0.10 to 5 mm.

[0024] Therefore, in the case of the crusher described above, pulp fed into the crusher is supplied from the center of the plate to the beating gap, and by rotating only one of the plates or rotating multiple plates relative to each other, the pulp is crushed in the crushing function section, while the crushed material is moved to the periphery of the plate by centrifugal force, and the crushed material is discharged from the beating gap.

[0025] By treating the pulp in this manner with the above-mentioned crusher, the pulp is easily disintegrated into cellulose fibers as it passes through the crushing functional section of the plate plane, and the stress of the mechanical treatment can be reduced, so that long-fiber cellulose that maintains its fiber length can be obtained.

[0026] Examples of such disintegrators include the Super Fibrator manufactured by Hasegawa Iron Works Ltd., the Single Disc Refiner / Double Disc Refiner manufactured by Aikawa Iron Works Ltd., the Single Disc Refiner, MR Type Recycle Refiner, CR Type Recycle Refiner manufactured by Kumagai Rikoki Kogyo Co., Ltd., and the Double runner attrition mill manufactured by Sprout, Waldron & Co., Ltd., which are generally called disc refiners, and the Conical Flaker manufactured by Asec Corp., which are generally called conical refiners, which are used together with the special plates described above.

[0027] <Cellulose fibers after crushing treatment> It is important that the cellulose fibers obtained by such a pulp crushing process have an average fibril circumference change rate R (%), expressed as (average fibril circumference of pulp after crushing process - average fibril circumference of pulp before crushing process) / (average fibril circumference of pulp before crushing process) x 100, of 100% or less.

[0028] The average fibril perimeter is an index of the degree of fluffiness of the cellulose fiber surface, and the larger the average fibril perimeter, the more fluffy (the more fibrillated) the cellulose fiber is. The larger the average fibril perimeter of the cellulose fiber (in other words, the more fluffy the fiber), the stronger the bonds between the cellulose fibers become and the more difficult they are to disentangle. The average fibril perimeter of such cellulose fibers is preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less, and even more preferably 5% or less. As a lower limit, 1% or more is preferable, and 1.5% or more is more preferable.

[0029] When the average fibril circumference change rate R is 100% or less, fibrillation is suppressed even if a crushing process is performed, and it is expected that the fiber length before and after the crushing process will be maintained at a high rate. Such an average fibril circumference change rate R is preferably 80% or less, and more preferably 60% or less. There is no particular lower limit, but it is preferably -100% or more, more preferably -80% or more, and even more preferably -60% or more.

[0030] Therefore, the average fibril circumference change rate R has an absolute value of |R|≦100, preferably |R|≦80, more preferably |R|≦60, and particularly preferably |R|≦50, |R|≦40, or |R|≦30.

[0031] The average fibril circumference of cellulose fibers can be measured, for example, by an L&W Fiber Tester Plus manufactured by ABB Ltd. Specifically, for example, it can be measured by the following method.

[0032] 300 ml of the aqueous dispersion diluted to contain 0.1 g of solid cellulose fiber is subjected to an image analysis type fiber analyzer (product name: L&W Fiber Tester Plus, manufactured by ABB) and measurements are performed for 300 seconds to obtain the fibril perimeter (average fibril perimeter) (n=2). Note that the measurement is performed after setting the Max value of Fines Limit to 0.2 and the Min value of Length class 1 to 0.2 on the Sample type screen that determines the measurement conditions.

[0033] The average fiber length of the cellulose fiber of the present invention is preferably 0.5 mm or more and 3.0 mm or less. When the average fiber length of the cellulose fiber is less than 0.5 mm, even if the fiber length can be kept high by the pulp disintegration method of the present invention, the final fiber length is short, so there is a concern that the expected binder effect due to fiber entanglement is difficult to be exhibited. Also, when the average fiber length exceeds 3.0 mm, there is a concern that the number of bundled fibers is likely to increase during the pulp disintegration process.

[0034] The average fiber amount of the cellulose fibers subjected to the crushing treatment is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more, of the average fiber length of the pulp before the crushing treatment (including pulp that has been lightly cut or crushed and loosened). When the average fiber length is within this range, the binder effect described above is easily manifested. The average fiber length retention rate (%) can be expressed as (average fiber length of the cellulose fibers subjected to the crushing treatment) / (average fiber length of the pulp before the crushing treatment)×100.

[0035] The average fiber length of cellulose fibers can be determined by an image analysis type fiber analyzer such as a fractionator manufactured by Valmet or an L&W Fiber Tester Plus manufactured by ABB. Specifically, for example, 300 ml of an aqueous dispersion diluted to contain 0.1 g of solid cellulose fibers is subjected to an image analysis type fiber analyzer (product name: L&W FiberTester Plus, manufactured by ABB), and measurement is performed for 300 seconds to determine the length-weighted fiber length (n=2). Note that the measurement is performed after setting the Max value of Fines Limit to 0.2 and the Min value of Length class 1 to 0.2 on the Sample type screen that determines the measurement conditions. EXAMPLES

[0036] The present invention will be described in more detail below by way of examples, but the present invention is not limited to these.

[0037] <Comparative Example 1> A pulp sheet (brightness 47.2%, average fibril circumference 1.6%, average fiber length 0.93 mm, solids content 53 wt% / moisture content 47 wt%) made from unbleached pulp derived from hardwood was subjected to oxygen delignification treatment. The pulp sheet was dispersed in water to obtain a 4 wt% aqueous dispersion, which was then processed in a single disc refiner (product name: 14-inch Lab Refiner (manufactured by Aikawa Iron Works Co., Ltd.), clearance 0.15 mm) and beaten until the Canadian Standard Freeness (csf) reached 0 ml, obtaining an aqueous dispersion containing beaten pulp. Thereafter, the obtained aqueous dispersion was adjusted in a centrifugal dehydrator so that the solid content was 16% by weight, and cellulose fiber A having an average fibril circumference of 29.2% and an average fiber length of 0.76 mm was obtained.

[0038] <Comparative Example 2> Beating was continued until the csf reached 400 ml, and an aqueous dispersion containing beaten pulp was obtained. Cellulose fiber B having an average fibril circumference of 3.6% and an average fiber length of 0.93 mm was obtained in the same manner as in Comparative Example 1, except that the obtained aqueous dispersion was adjusted to have a solid content of 22% by weight.

[0039] <Example 1> An unbleached pulp sheet derived from coniferous trees (brightness 22.8%, solids 45% by weight / moisture content 55% by weight) was dispersed in water to obtain a 3% by weight aqueous dispersion, which was then processed through a single disc refiner (product name: BR-300CB Lab Refiner (manufactured by Kumagai Riki Kogyo), clearance 0.1 mm) and beaten until the Canadian Standard Freeness (csf) reached 695 ml, obtaining an aqueous dispersion containing beaten pulp. Thereafter, the resulting aqueous dispersion was adjusted in a centrifugal dehydrator so that the solid content was 30% by weight, and a wet sheet-like product having an average fibril circumference of 2.7% and an average fiber length of 2.05 mm was obtained. The obtained wet sheet-like material was disintegrated by processing it in the above-mentioned single disc refiner (clearance 3.95 mm) to obtain cellulose fiber C having an average fibril circumference of 3.3% and an average fiber length of 2.06 mm.

[0040] <Example 2> An unbleached pulp sheet (brightness 22.8%, solid content 45% by weight / moisture content 55% by weight) derived from coniferous trees was dispersed in water to prepare a 3% by weight aqueous dispersion. The resulting aqueous dispersion was adjusted in a centrifugal dehydrator so that the solid content was 35% by weight, to obtain a wet sheet-like product having an average fibril circumference of 2.0% and an average fiber length of 2.07 mm. The obtained wet sheet-like material was crushed by processing it with a single disc refiner (product name: BR-300CB Lab Refiner (manufactured by Kumagai Riki Kogyo), clearance 3.95 mm) to obtain cellulose fiber D with an average fibril circumference of 1.9% and an average fiber length of 2.08 mm.

[0041] <Example 3> An unbleached pulp sheet derived from coniferous trees (brightness 22.8%, average fibril circumference 2.6%, average fiber length 2.17 mm, solids content 45 wt% / moisture content 55 wt%) was crushed by processing it with a single disc refiner (product name: BR-300CB Lab Refiner (manufactured by Kumagai Riki Kogyo), clearance 2.5 mm) to obtain cellulose fiber E with an average fibril circumference of 2.7% and an average fiber length of 2.15 mm.

[0042] <Example 4> A bleached pulp sheet derived from coniferous trees (brightness 84%, solids 80% by weight / moisture 20% by weight) was processed with a guillotine and coarsely crushed to a size of 5 cm square with an average fibril circumference of 2.1% and an average fiber length of 2.16 mm. The obtained coarsely crushed material was further crushed using a single disc refiner (product name: 14-inch Lab Refiner (Aikawa Iron Works Co., Ltd.), clearance 0.15 mm) to obtain cellulose fiber F with an average fibril circumference of 1.9% and an average fiber length of 2.05 mm.

[0043] <Example 5> A bleached pulp sheet derived from hardwood (brightness 86.2%, solids 52% by weight / moisture 48% by weight) was coarsely ground in a soft material grinder (product name: SR-360, manufactured by Horai Co., Ltd., outlet screen diameter: φ50 mm) until the average fibril circumference was 2.2% and the average fiber length was 0.69 mm. The fibers were then crushed using a single-disc refiner (clearance 1.0 mm) to obtain cellulose fiber G with an average fibril circumference of 2.3% and an average fiber length of 0.70 mm.

[0044] [Table 1]

[0045] <Evaluation of the bondability of sand and gravel> The mixture was prepared according to the composition in Table 2, and mixed by stirring using a general-purpose mixer (BL600, manufactured by Shinto Chemical Co., Ltd.) at a rotation speed of 130 rpm for 4 minutes.

[0046] [Table 2] *1: Akagi Gardening Co., Ltd., sand from the Yahagi River selected to be 1-3 mm in size

[0047] 2 g of each formulation was weighed out and molded using a tabletop tablet molding machine HANDTAB-100 (manufactured by Ichihashi Seiki Co., Ltd.) under conditions of 30 MPa / 5 seconds to obtain tablets with a diameter of 1.2 cm. The crushing strength of the obtained tablet molded product was measured at 3 m / sec using a texture analyzer FTRD-100N (manufactured by Imada Co., Ltd.) The results are shown in Table 3.

[0048] [Table 3]

[0049] As shown in Table 3, when cellulose fibers having a small rate of change in average fibril circumference obtained by the pulp disintegration method of the present invention are used, molded products having high strength can be obtained and have excellent binder performance.

Claims

1. A method for disintegrating pulp, comprising coarsely crushing pulp and then treating the pulp in a disintegrator, the method being characterized in that the following conditions (A) and (B) are satisfied: (A) The crusher has a beating gap formed by opposing multiple circular or similarly shaped plates with beating function sections, and the pulp passing through the beating gap is crushed by rotating only one of the plates or by rotating the plates relative to each other. (B) The rate of change in average fibril circumference R (%), expressed as (average fibril circumference of pulp after crushing treatment - average fibril circumference of pulp before crushing treatment) / (average fibril circumference of pulp before crushing treatment) x 100, is 100% or less.

2. 2. The method for crushing pulp according to claim 1, wherein the beating gap is in the range of 0.1 to 5.0 mm.

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