Pulp crushing method and cellulose fiber manufacturing method using the same

Abstract

To provide cellulose fibers that are excellent in binder effect and the like without being subjected to chemical modification treatment or pulverizing treatment and maintain fiber length.SOLUTION: A pulp crushing method is characterized in after performing a water-containing treatment on a pulp so that a water content thereof becomes 30 to 90 mass%, feeding the water containing pulp to a crusher. A pulp crushing method is also characterized in that the crusher has one or more beating gaps formed by circular or similar shape of plates each having a beating function part and crushes the pulp passing through the beating gaps by rotating only one of the plates or rotating the plates mutually.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for disintegrating pulp and a method for producing cellulose fibers using the same. [Background technology]

[0002] With the recent development of decarbonization technology, pulp, which is mainly composed of cellulose, is expected to be applied to various uses as a natural material. For example, cellulose fibers that have been subjected to a microfabrication process are expected to have an excellent binder effect because the effects of entanglement of fibers and hydrogen bonding become more pronounced (for example, Patent Document 1).

[0003] On the other hand, in order to carry out the fine refining process, the pulp must be chemically modified to make it easier to defibrate, or mechanical processing must be repeated using a large amount of energy. Therefore, in order to advance decarbonization technology, a simpler method for obtaining cellulose fibers with a high binding effect is desired.

[0004] It is assumed that cellulose fibers having a high binder effect without such a micronizing treatment can be obtained by maintaining long fibers so that the fibers are more easily entangled. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-206521 A Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, an object of the present invention is to provide cellulose fibers which are excellent in binder effect and maintain their fiber length without being subjected to chemical modification treatment or micronization treatment. [Means for solving the problem]

[0007] As a result of extensive investigations, the present inventors have found that the problems can be solved by the following (1) to (4). (1) A method for disintegrating pulp, comprising the steps of: subjecting pulp to a moisture treatment so that the moisture content of the pulp is 30 to 90 mass %; and then supplying the water-containing pulp to a disintegrator. (2) The method for crushing pulp described in (1), characterized in that the crusher has one or more beating gaps formed by circular or similarly shaped plates with a beating function section, and the pulp passing through the beating gaps is crushed by rotating only one of the plates or by rotating both of the plates. (3) The method for crushing pulp according to (2), wherein the beating gap is in the range of 0.1 to 5.0 mm. (4) A method for producing cellulose fibers obtained by the pulp disintegration method described in any one of (1) to (3), characterized in that the cellulose fibers have an average fiber length in the range of 0.5 mm to 3.0 mm and an average fibril circumference of 10% or less. Effect of the Invention

[0008] According to the present invention, it is possible to provide cellulose fibers that have excellent binder effects and maintain their fiber length without being subjected to chemical modification treatment or micronization treatment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] That is, the present invention provides a method for crushing pulp, which comprises subjecting pulp to a moisture treatment so that the moisture content of the pulp is 30 to 90 mass %, and then supplying the water-containing pulp to a crusher.

[0010] <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.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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).

[0016] The brightness of the pulp subjected to such bleaching treatment is preferably 70% or more based on ISO 2470.

[0017] In the present invention, the pulp sheet made of the above-mentioned pulp may be used as is, but may be subjected to a light cutting or crushing treatment before being fed into the crusher. By performing a light cutting or crushing treatment, the crushability of the pulp sheet can be improved or adjusted, and the load fluctuation in the crusher can be suppressed, stabilizing the operation of the crusher.

[0018] It is important that the pulp of the present invention is subjected to a moisture impregnation treatment so that the moisture content of the pulp is in the range of 30 to 90% by mass before being fed into a crusher. The moisture impregnation treatment is not particularly limited as long as it satisfies the target moisture content. After forming a pulp sheet from the pulp slurry in a papermaking machine and pressing it, the papermaking machine may dry the pulp to a moisture content of 20% or less, and then add moisture to adjust the moisture content to the target moisture content. Alternatively, the papermaking machine may adjust the moisture content to the target moisture content in the form of a wet sheet that is not dried in the papermaking machine. The moisture content of the present invention refers to the moisture content ratio of water to the total mass of pulp and water. By performing the moisture impregnation treatment in the above-mentioned range, the hydrogen bonds between the cellulose fibers are appropriately weakened, so that when the papermaking machine performs the crushing treatment described below, the pulp begins to loosen before the cellulose fibers are cut, and cellulose fibers that maintain their fiber length can be obtained. If the moisture content of the pulp is less than 30% by mass, the reduction in the bonding strength between the fibers will be insufficient, and the amount of bundled fibers will increase due to drying shrinkage when the moisture is removed, which is undesirable. On the other hand, if the moisture content exceeds 90% by mass, there will be too much free water and the pulp will not be able to be disintegrated by a crusher, which is undesirable.

[0019] The moisture content of such pulp of the present invention is more preferably 40% by mass or more, more preferably 80% by mass or less, and even more preferably 70% by mass or less.

[0020] <Crusher> The crusher used in the present invention is not particularly limited as long as it is capable of performing a crushing treatment on the hydrated pulp. For example, the crusher is preferably a crusher having one or more beating gaps formed by circular or similarly shaped plates equipped with a beating function section, and characterized in that the pulp passing through the beating gaps is crushed by rotating only one of the plates or by rotating both of the plates.

[0021] 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.

[0022] By disposing such a fine-disintegrating functional portion on 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 that maintain long fibers.

[0023] The plate having a circular or similar shape may be any plate having a circular or similar planar shape, such as a disk shape or a doughnut shape with a hole in the center.

[0024] It is important that the crusher used in the present invention has two or more of the above plates, and that the plates have one or more opposing beating gaps.

[0025] The beating gap is also called clearance, and is preferably in the range of 0.1 to 5.0 mm, more preferably in the range of 0.3 to 4.5 mm, and further preferably in the range of 0.4 to 4.2 mm.

[0026] Therefore, in the case of the crusher described above, the water-treated 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 crushed material is moved to the periphery of the plate by centrifugal force, and the crushed material is discharged from the beating gap.

[0027] By treating the water-containing treated pulp in this manner with the crusher described above, 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, making it possible to obtain long-fiber cellulose that maintains its fiber length.

[0028] 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.

[0029] <Cellulose fibers after crushing treatment> The cellulose fibers obtained by such a pulp crushing treatment preferably have an average fiber length in the range of 0.5 mm to 3.0 mm and a fibril circumference of 10% or less.

[0030] 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.

[0031] When the average fiber length of the cellulose fibers is less than 0.5 mm, even if the fiber length can be kept high by the pulp crushing 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 manifest. 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 crushing process.

[0032] 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 achieved. The average fiber length maintenance 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.

[0033] 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.

[0034] 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.

[0035] The average fibril circumference is an index of the degree of fluffiness of the cellulose fiber surface, and the larger the average fibril circumference, the fluffier the cellulose fiber. The larger the average fibril circumference of the cellulose fiber (in other words, the fluffier the fiber), the stronger the bonds between the cellulose fibers become and the more difficult they are to disentangle, making it more difficult to obtain the expected binder effect. Therefore, the average fibril circumference is preferably 10% or less, more preferably 8% or less, and even more preferably 5% or less. 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] <Example 1> The pulp sheet (brightness 47.2%, solid content 53% by mass / moisture content 47% by mass) made from unbleached pulp derived from hardwood and subjected to oxygen delignification was dispersed in water to obtain a 4% by mass 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 400 ml. The average fiber length after beating was 0.93 mm. Thereafter, the obtained aqueous dispersion was adjusted in a centrifugal dehydrator so that the solid content was 30% by mass, to obtain a wet sheet-like product. The obtained wet sheet-like material was further disintegrated by processing it in a single disc refiner (product name: BR-300CB Lab Refiner (manufactured by Kumagai Riki Kogyo), clearance 3.95 mm) to obtain cellulose fiber A with an average fiber length of 0.92 mm and an average fibril circumference of 3.7%.

[0038] <Example 2> An unbleached pulp sheet derived from coniferous trees (whiteness 22.8%, solids content 45% by mass / moisture content 55% by mass) was dispersed in water to obtain a 3% by mass aqueous dispersion, and cellulose fiber B having an average fiber length of 1.89 mm and an average fibril circumference of 10.0% was obtained in the same manner as in Example 1, except that the average fiber length after beating was 1.95 mm.

[0039] <Example 3> An unbleached pulp sheet derived from coniferous trees (whiteness 22.8%, solids 45% by mass / moisture 55% by mass, average fiber length 2.17 mm) was disintegrated by processing it directly in a single disc refiner (product name: BR-300CB Lab Refiner (manufactured by Kumagai Riki Kogyo), clearance 2.5 mm) without being made into an aqueous dispersion, to obtain cellulose fiber C with an average fiber length of 2.15 mm and an average fibril circumference of 2.7%.

[0040] <Example 4> The pulp sheet was coarsely pulverized to an average fiber length of 1.99 mm using a soft material pulverizer (product name: SR-360, manufactured by Horai Co., Ltd., outlet screen diameter: φ50 mm) without preparing an aqueous dispersion as in Example 3. Thereafter, the pulp sheet was disintegrated by processing with a single disc refiner (clearance 0.5 mm) to obtain cellulose fiber D having an average fiber length of 1.96 mm and an average fibril circumference of 2.1%.

[0041] <Example 5> A bleached pulp sheet derived from coniferous trees (whiteness 79.0%, solids 44% by mass / moisture content 56% by mass, average fiber length 2.04 mm) was coarsely crushed manually to approximately 5 cm squares and disintegrated by processing with a single disc refiner (clearance 3 mm) to obtain cellulose fiber E with an average fiber length of 2.03 mm and an average fibril circumference of 1.9%.

[0042] <Example 6> A bleached pulp sheet derived from hardwood (whiteness 86.2%, solids 52% by mass / moisture 48% by mass, average fiber length 0.72 mm) was used, and the clearance of the single disc refiner was changed to 1.0 mm. In the same manner as in Example 4, except that, cellulose fiber F was obtained with an average fiber length of 7.0 mm after coarse grinding, an average fiber length of 0.7 mm after disintegration, and an average fibril circumference of 2.3%.

[0043] <Example 7> A pulp sheet (brightness 38.0%, solids 46% by mass / moisture 54% by mass) made from unbleached pulp derived from coniferous trees that had been subjected to oxygen delignification treatment was used, and the aqueous dispersion was beaten until the Canadian Standard Freeness (csf) reached 200 ml. Cellulose fiber G with an average fiber length of 1.78 mm and an average fibril circumference of 11.0% was obtained in the same manner as in Example 2, except that the average fiber length after beating was adjusted to 1.83 mm and the solids content to 28% by mass.

[0044] <Example 8> The aqueous dispersion was beaten until the Canadian standard freeness (csf) was 0 ml, and the average fiber length after beating was adjusted to 0.76 mm and the solid content to 23 mass %. Cellulose fiber H having an average fiber length of 0.74 mm and an average fibril circumference of 28.7% was obtained in the same manner as in Example 1, except that the aqueous dispersion was beaten until the Canadian standard freeness (csf) was 0 ml, and the average fiber length after beating was adjusted to 0.76 mm and the solid content to 23 mass %.

[0045] <Example 9> The aqueous dispersion was beaten until the Canadian standard freeness (csf) was 400 ml, and the average fiber length after beating was adjusted to 1.03 mm and the solid content to 23 mass%. In the same manner as in Example 7, however, cellulose fiber I having an average fiber length of 0.99 mm and an average fibril circumference of 34.1% was obtained.

[0046] <Comparative Example 1> A bleached pulp sheet derived from coniferous trees (brightness 85%, solid content 85% by mass / moisture content 15% by mass, average fiber length 1.77 mm) was coarsely crushed to an average fiber length of 1.22 mm using a soft material crusher (product name: SR-360, manufactured by Horai Co., Ltd., outlet screen diameter: φ50 mm). The pulverized material was then processed in a single disc refiner (clearance 0.15 mm) to obtain cellulose fiber J with an average fiber length of 0.86 mm and an average fibril circumference of 2.1%.

[0047] [Table 1]

[0048] <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.

[0049] [Table 2] *1: Akagi Gardening Co., Ltd., sand from the Yahagi River selected to be 1-3 mm in size

[0050] 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.

[0051] 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.

[0052] [Table 3]

[0053] As shown in Table 3, when the cellulose fibers having a high average fiber length retention rate obtained by the pulp disintegration method of the present invention are used, molded products having high strength can be obtained, and the binder performance is excellent. On the other hand, the cellulose fibers of the comparative examples having a poor average fiber length retention rate were shown to have a weak effect on improving strength.

Claims

1. A method for disintegrating pulp, comprising the steps of: subjecting pulp to a water-imparting treatment so that the water content of the pulp is 30 to 90 mass %; and then supplying the water-imparted pulp to a disintegrator.

2. The method for crushing pulp according to claim 1, characterized in that the crusher has one or more beating gaps formed by circular or similarly shaped plates with a beating function portion, and the pulp passing through the beating gaps is crushed by rotating only one of the plates or by rotating both of the plates.

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

4. A method for producing cellulose fibers, characterized in that the cellulose fibers are obtained by the pulp disintegration method described in any one of claims 1 to 3, and have an average fiber length in the range of 0.5 mm to 3.0 mm and an average fibril circumference of 10% or less.

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