Cellulose pulp with excellent particle trapping property and binding property and its producing method

Abstract

To provide a cellulose pulp excellent in both particle trapping property and binder property, and to provide a method for producing the cellulose pulp, since beaten fibers are used in a variety of fields due to their excellent ability to capture functional particles, but there are also applications that require not only particle trapping property but also binder property, pulp-like acrylonitrile fibers are known as beaten fibers that combine these properties, but in recent years the environmental impact of plastic waste has become an issue and there has been a demand for a shift to bio-based materials, while conventional bio-based materials containing cellulose have not necessarily been satisfactory in terms of combining the above-mentioned properties.SOLUTION: The cellulose pulp according to the present invention is characterized in that the cellulose pulp fibril area is 15% or more and the fibril area(%) / 100×fine(%) / 100 is 0.05 or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to cellulose pulp having excellent particle-trapping properties and binder properties, and a method for producing the same. In the present invention, particle-trapping properties refer to the property of capturing and retaining particles, and binder properties refer to the property of binding together fibers that constitute a fiber structure, thereby increasing the strength of the fiber structure. [Background technology]

[0002] Beaten fibers are characterized by their hyperbranched structure and high specific surface area, and are excellent in adhesive properties and in capturing functional particles such as activated carbon. As a result, they are used in a variety of fields, including papermaking, packaging materials, paints, building materials, industrial materials, beauty products, and health care.

[0003] Furthermore, there are applications in which beaten fibers are required to have not only particle-capturing properties but also binder properties. For example, Patent Document 1 discloses pulp-like acrylonitrile fibers as beaten fibers that have both particle-capturing properties and binder properties.

[0004] On the other hand, in recent years, the environmental impact of plastic waste has become a problem, and there is a demand for a shift to bio-based materials. However, conventional bio-based materials containing cellulose have not necessarily been satisfactory in terms of achieving both the particle capture and binder properties mentioned above. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-181669 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the current state of the prior art, and its object is to provide a cellulose pulp having excellent particle trapping and binder properties, and a method for producing the same. [Means for solving the problem]

[0007] As a result of extensive research to achieve the above-mentioned object, the inventors discovered that cellulose pulp characterized by a fibril area of ​​15% or more and a fibril area (%) / 100 × fine (%) / 100 of 0.05 or more has excellent particle capture properties and excellent binder properties, and thus arrived at the present invention.

[0008] That is, the present invention is achieved by the following means. (1) Cellulose pulp characterized in that the fibril area is 15% or more and the fibril area (%) / 100×fine (%) / 100 is 0.05 or more. (2) Cellulose pulp according to (1), characterized in that the fine content is 85% or less. (3) The cellulose pulp according to (1), which is used for capturing particles. (4) The cellulose pulp according to (1), which is used as a binder. (5) A structure using the cellulose pulp described in (1). (6) A wet-laid nonwoven fabric using the cellulose pulp described in (1). (7) A method for producing cellulose pulp according to (1), characterized in that it comprises beating a cellulosic raw material with a refiner. [Effects of the Invention]

[0009] The cellulose pulp of the present invention has excellent particle capturing properties and binder properties, and can therefore be suitably used as a material for forming functional filters carrying functional particles. DETAILED DESCRIPTION OF THE INVENTION

[0010] The raw material for the cellulose pulp of the present invention is not limited as long as it is a material commonly used as a cellulose pulp raw material, and examples thereof include cellulose-based raw materials such as coniferous trees, broad-leaved trees, bamboo, etc., but raw materials derived from coniferous trees with good binding properties are preferred. In particular, bleached kraft pulp (NBKP) made from coniferous trees is preferred in consideration of its binding properties and ease of processing into cellulose pulp having the properties described below.

[0011] Furthermore, the cellulose pulp of the present invention preferably has a fibril area (%) / 100×fine (%) / 100 ratio of 0.05 or more, more preferably 0.06 or more. If it is less than 0.05, the particle capturing ability and binder property become insufficient.

[0012] Here, "fibril area" is a property measured by the method described below and is an index showing the degree of branching of pulp fibers. Although not precise, "fibril area" can be thought of as the ratio of the area occupied by branched portions to the planar area of ​​pulp fibers in pulp after removing the components corresponding to "fine" (also called "fine components") described below. Similarly, "fine" is a property measured by the method described below and refers to the proportion of pulp fibers with a fiber length of less than 0.2 mm in pulp, and is an index of the amount of fine pulp fibers in pulp.

[0013] In the present invention, the fibril area is preferably 15% or more, more preferably 20% or more. There is no upper limit to the fibril area, but considering the time required for beating the cellulose pulp raw material, it is preferably 30% or less.

[0014] In the present invention, the above-mentioned fines are preferably 30% or more, more preferably 35% or more. The upper limit of the fines is preferably 85% or less, more preferably 80% or less. If the fines are below the lower limit, the formation of the primary composite described below does not proceed. If the fines are above the upper limit, the fibril area decreases, and the formation of the secondary composite described below does not proceed. As a result, the balance between the fines and fibril area required for composite formation is lost, and satisfactory particle capture and binding properties may not be obtained.

[0015] The inventors have found that the larger the product of the fibril area (%) and the fines (%), the better the particle-trapping ability and binder properties. Although the reason for this is unclear, it is speculated that the fine components with a large specific surface area first trap particles, forming a primary composite of a certain size, and then the components with a large fibril area bind this primary composite to form a secondary and tertiary composite, stabilizing it and improving the particle-trapping ability.

[0016] The cellulose pulp of the present invention is obtained by beating a cellulosic raw material. The beating method is not limited, and a beating machine such as a beater, refiner, or high-pressure homogenizer can be used. Among these, beating with a refiner is preferred. Refiner beating easily increases the fibril area while suppressing an excessive increase in fines, making it possible to produce cellulose pulp with a fibril area of ​​15% or more and a fibril area (%) / 100 × fines (%) / 100 ratio of 0.05 or more with high productivity. In the present invention, it is not necessary to treat the cellulose raw material with an enzyme such as cellulase to promote beating before beating.

[0017] There are no restrictions on the conditions for beating with a refiner, but it is necessary to adjust the shape of the refiner blades, processing flow rate, clearance, etc. so that fibril area (%) / 100 × fine (%) / 100 is 0.05 or more.

[0018] The cellulose pulp of the present invention described above has excellent particle capture properties and binder properties, and can be used alone or in combination with other materials to form structures useful for many applications. In such structures, it is desirable to use the cellulose pulp of the present invention in an amount of preferably 5% by weight or more, more preferably 10% by weight or more, and even more preferably 20% by weight or more, from the viewpoint of obtaining the effects of the cellulose pulp of the present invention.

[0019] The external appearance of the structure may be a paper-like material, a sheet-like material, a laminate, a spherical or cylindrical molded body, etc. The cellulose pulp of the present invention may be contained in the structure in such a manner that it is substantially uniformly distributed by mixing with other materials such as fibers or resin compositions, or in the case of a structure having multiple layers, it may be concentrated in one of the layers (which may be single or multiple), or it may be distributed in each layer at a specific ratio.

[0020] The external appearance and content of the structures exemplified above, the other materials constituting the structures, and the other members to be combined with the structures are determined as appropriate, taking into consideration the functions, properties, and shapes required for the type of final product (for example, diffusion layers or absorption layers in hygiene products (diapers, urine absorption pads, sanitary napkins, etc.), carbon sheets for fuel cell diffusion membranes, water purification filters, activated carbon support sheets and filters, papermaking binders, paper products, wet friction materials, etc.), and the manner in which the cellulose pulp of the present invention contributes to the realization of such functions.

[0021] The properties of the cellulose pulp of the present invention can be effectively utilized in the above-mentioned applications. For example, in applications such as absorbent layers in hygiene products and activated carbon-carrying sheets, the particle-trapping properties can be utilized to fix water-absorbent resins or activated carbon particles. In applications such as diffusion layers in hygiene products, the hydrophilicity of the fibrils can also improve the diffusibility of urine and other substances. [Example]

[0022] Examples are given below to facilitate understanding of the present invention, but these are merely illustrative and the gist of the present invention is not limited thereto. In the examples, parts and percentages are by weight unless otherwise specified. Furthermore, each property was measured by the following methods.

[0023] <Binding properties> A water slurry was prepared with a weight ratio of beaten sample / acrylic short fiber (fineness 0.4 dtex, fiber length 3.0 mm) = 30 / 70, and the slurry was spread on a square sheet machine manufactured by Kumagai Riki Kogyo Co., Ltd. at a basis weight of 50 g / m 2 The paper was made to the required thickness and dried using a thermal calendar to prepare the paper for evaluation. The resulting paper was cut into pieces measuring 2 cm (W) x 10 cm (L), and the breaking strength was measured using a tensile tester (A&D RTA500 (U-1573)) at a pulling rate of 2 cm / min. The higher the breaking strength, the better the adhesiveness. Note that a binding strength of 20 N or more is considered to be sufficient.

[0024] <Particle capture ability> Add 1 g of the beaten sample (equivalent to 1 g of solids) to 1 L of pure water and stir. Add 6 g of powdered activated carbon (Taihei Chemical Industry Co., Ltd., Brocol B brand activated carbon, average particle size 90 μm) and stir for 30 minutes. Then, pass the sample through a 173 μm mesh sieve (area 200 cm). 2 The weight (A [g]) of the residue after sieving was measured after drying at 105°C for 5 hours, and the amount of activated carbon captured per 1 g of sample was calculated using the following formula. Note that a particle capture capacity of 30% or more is considered to be sufficient. Particle trapping ability (%)=A / 6×100

[0025] <Fibril area, fine> Measurements were carried out using a Lorentzen & Wettre Fiber Tester Plus.

[0026] <Examples 1 to 5, Comparative Examples 1 to 4> The NBKP was beaten using a refiner by adjusting the number of passes and clearance of the refiner, to obtain cellulose pulps of Examples 1 to 5 and Comparative Examples 1 to 4, which differ in fibril area and fineness.

[0027] <Comparative Example 5> The NBKP used above was evaluated.

[0028] Table 1 shows the evaluation results of the cellulose pulp obtained in the above-mentioned Examples and Comparative Examples.

[0029] [Table 1]

[0030] As shown in Table 1, it is clear that Examples 1 to 5 have good binding properties and particle trapping properties. On the other hand, it is clear that none of Comparative Examples 1 to 5 can achieve both binding properties and particle trapping properties.

Claims

1. A cellulose pulp characterized in that the fibril area is 15% or more and the fibril area (%) / 100×fine (%) / 100 is 0.05 or more.

2. 2. The cellulose pulp according to claim 1, wherein the fines content is 85% or less.

3. 2. The cellulose pulp according to claim 1, which is used for particle capture.

4. 2. The cellulose pulp according to claim 1, which is used as a binder.

5. A structure using the cellulose pulp according to claim 1.

6. A wetlaid nonwoven fabric using the cellulose pulp according to claim 1.

7. 2. The method for producing cellulose pulp according to claim 1, further comprising beating the cellulosic raw material with a refiner.

Images