JP2021188212A - Water-disintegrable nonwoven fabric, wet water-disintegrable nonwoven fabric, and manufacturing method of water-disintegrable nonwoven fabric - Google Patents

Abstract

To provide a water-disintegrable nonwoven fabric which has excellent impregnation tensile strength and water disintegrability.SOLUTION: Disclosed is a water-disintegrable nonwoven fabric involving a pulp fiber interlaced together with a regenerated cellulose fiber. The regenerated cellulose fiber involves a flat rayon fiber and a round-shaped rayon fiber. The mean fiber length of the regenerated cellulose fiber is 2 mm or over and 20 mm or under.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a water-decomposable non-woven fabric, a wet water-decomposable non-woven fabric, and a water-decomposable non-woven fabric.

Conventionally, cleaning products such as cleaning wipers for toilets and wipes have been used. Some cleaning products can be flushed to a flush toilet after use, in which case they can be easily disposed of after use and can be treated hygienically. As such cleaning products, cleaning products in which water-melted paper is impregnated with water or chemicals are on the market.

While water-melting paper is required to have the property of easily disintegrating when washed with water, it is also required to have strength enough to withstand work such as cleaning. Therefore, in order to improve the strength of hydrolyzed paper, it is being studied to contain a paper strength enhancer and a resin component. For example, Patent Document 1 describes a hydrolyzed paper containing a water-soluble binder having a carboxyl group selected from the group consisting of carboxymethyl cellulose, carboxyethyl cellulose and carboxymethylated starch. Here, it is studied that the carboxyl group of the water-soluble binder forms an intramolecular mixed salt with a specific polyvalent metal to increase the strength of the hydrolyzed paper. Further, Patent Document 2 describes a water-decomposable nonwoven fabric in which a water-insoluble resin is partially provided on at least one surface layer of the water-decomposable nonwoven fabric base material, and a cut is provided in the surface layer provided with the water-insoluble resin. Has been described. Here, a thermoplastic resin is used as the water-insoluble resin, thereby increasing the strength of the nonwoven fabric.

In addition, hydrolyzable non-woven fabrics mixed with synthetic fibers have also been developed. For example, Patent Document 3 discloses a fiber composite material containing natural fibers and / or synthetic fibers. Here, it is considered to use regenerated cellulose fiber (viscose fiber) as a synthetic fiber. In Example 3 of Patent Document 3, a fleece structure is produced using a round viscose fiber having a fiber length of 38 mm and a viscose flat fiber having a length of 38 mm.

Japanese Unexamined Patent Publication No. 6-184984 Japanese Unexamined Patent Publication No. 62-184193 Japanese Patent Publication No. 2008-546917

In recent years, more excellent hydrolyzability has been required for hydrolyzed paper, and there are cases where hydrolyzability is required at a higher level than before.

Further, when the water-dissolved paper is impregnated with water to bring it into a wet state, a series of impregnation operations such as impregnating the water-dissolved paper with water and then pulling up the water-dissolved paper to remove excess water are performed. When performing such an operation, the water-containing hydrolyzed paper needs to have sufficient strength, and the hydrolyzed paper is required to have sufficient impregnation tensile strength.

Therefore, in order to solve the problems of the prior art, the present inventors have proceeded with studies for the purpose of providing a water-decomposable nonwoven fabric having both excellent impregnation tensile strength and water-decomposability.

As a result of diligent studies to solve the above problems, the present inventors have used flat rayon fibers and round rayon fibers in combination as regenerated cellulose fibers in a water-decomposable non-woven fabric containing pulp fibers and regenerated cellulose fibers. Furthermore, it has been found that by keeping the average fiber length of the regenerated cellulose fiber within a predetermined range, a water-decomposable non-woven fabric having excellent impregnation tensile strength and water-decomposability can be obtained.
Specifically, the present invention has the following configurations.

[1] A water-decomposable non-woven fabric in which pulp fibers and regenerated cellulose fibers are entangled.
Regenerated cellulose fibers include flat rayon fibers and round rayon fibers.
A water-decomposable non-woven fabric having an average fiber length of 2 mm or more and 20 mm or less.
[2] When the content of the flat rayon fiber with respect to the total mass of the regenerated cellulose fiber is P (parts by mass) and the content of the round rayon fiber with respect to the total mass of the regenerated cellulose fiber is Q (parts by mass), P: The water-decomposable nonwoven fabric according to [1], wherein Q = 1: 9 to 9: 1.
[3] The content of the pulp fiber is 30 to 90% by mass and the content of the regenerated cellulose fiber is 10 to 50% by mass with respect to the total mass of the water-decomposable nonwoven fabric [1] or [2]. The water-decomposable non-woven fabric described in.
[4] The water-decomposable nonwoven fabric according to any one of [1] to [3], wherein the flat rayon fiber is a hollow flat rayon fiber.
[5] The water-decomposable nonwoven fabric according to any one of [1] to [4], wherein the ratio of the outer edge width to the outer edge length of the cross section of the flat rayon fiber is 1: 2 to 1:30.
[6] The water-decomposable nonwoven fabric according to any one of [1] to [5], wherein the average fiber length of the pulp fiber is 1.5 mm or more.
[7] The water-decomposable nonwoven fabric according to any one of [1] to [6], wherein the pulp fiber contains softwood pulp fiber, and the content of broad-leaved tree pulp fiber with respect to the total mass of the pulp fiber is 50% by mass or less.
[8] A wet water-decomposable nonwoven fabric obtained by impregnating the water-decomposable nonwoven fabric according to any one of [1] to [7] with water.
[9] A method for producing a water-decomposable nonwoven fabric, which comprises a step of applying a high-pressure water jet flow treatment to a nonwoven fabric sheet containing pulp fibers and regenerated cellulose fibers formed by a wet papermaking method.
Regenerated cellulose fibers include flat rayon fibers and round rayon fibers.
A method for producing a water-decomposable nonwoven fabric, wherein the average fiber length of the regenerated cellulose fiber is 2 mm or more and 20 mm or less.

According to the present invention, it is possible to obtain a water-decomposable nonwoven fabric having both excellent impregnation tensile strength and water-decomposability.

Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be based on typical embodiments and specific examples, but the present invention is not limited to such embodiments. In the present specification, the numerical range represented by using "~" means a range including the numerical values before and after "~" as the lower limit value and the upper limit value.

(Water-decomposable non-woven fabric)
The present invention relates to a water-decomposable nonwoven fabric in which pulp fibers and regenerated cellulose fibers are entangled. Here, the regenerated cellulose fiber includes a flat rayon fiber and a round rayon fiber. The average fiber length of the regenerated cellulose fiber is 2 mm or more and 20 mm or less.

Since the water-decomposable nonwoven fabric of the present invention has the above-mentioned structure, it has both excellent impregnation tensile strength and water-decomposability. Conventionally, in a water-decomposable non-woven fabric, impregnation tensile strength and water-decomposability are contradictory properties, and it has been difficult to achieve both at a high level. However, the present inventors have achieved both impregnation tensile strength and water solubility by using flat rayon fibers and round rayon fibers as the regenerated cellulose fibers and keeping the average fiber length of the regenerated cellulose fibers within a predetermined range. succeeded in.

Since the water-decomposable nonwoven fabric of the present invention is excellent in impregnation tensile strength, it is possible to improve the production efficiency when the water-decomposable nonwoven fabric is impregnated with water or a chemical solution to produce a wet water-decomposable nonwoven fabric. When producing a wet water-decomposable nonwoven fabric, an operation of impregnating the water-decomposable nonwoven fabric with water or a chemical solution and then withdrawing the hydrolyzable nonwoven fabric in a water-containing state from the impregnating solution is performed. Such a series of operations may be performed using, for example, an impregnation machine. Conventionally, if sufficient impregnation tensile strength cannot be obtained, the hydrolyzable nonwoven fabric may be broken or damaged during the impregnation operation, so that the wet water-decomposable nonwoven fabric cannot be manufactured or its manufacturing efficiency is lowered. was there. However, in the water-decomposable nonwoven fabric of the present invention, since the impregnated tensile strength has been successfully increased, the production efficiency of the wet water-decomposable nonwoven fabric can be improved.

The impregnation tensile strength is a geometric mean of the longitudinal and lateral tensile strengths measured 5 seconds after impregnating the water-decomposable nonwoven fabric with the chemical solution under the following conditions. Specifically, the central portion of the hydrolyzable nonwoven fabric having a width of 25 mm and a length of 114 mm is impregnated with the chemical solution for 3 seconds. Then, it is set in a tensile tester so that the measurement is started after 5 seconds, set in a vertical air chuck with a span length of 100 mm, and the conditional tensile strength at a tensile speed of 300 mm / min is measured. In the measurement, the impregnated tensile strength in the parallel and vertical directions with the water jet mark of the water-decomposable non-woven fabric is measured, and then the geometric mean is calculated to obtain the impregnated tensile strength. The chemical solution impregnated with the water-decomposable non-woven fabric contains water as the main component and is used in various cosmetic materials (water-soluble solvent, antibacterial agent, fungicide, fragrance, surfactant, etc.) in a proportion of about 10% by mass or less of the whole. It may contain a preservative, a wetting agent, a drug having a desired medicinal effect, etc.). For example, as a chemical solution, dipropylene glycol: polyaminopropyl biguanide: phosphoric acid 2Na: benzoic acid: cetylpyridinium chloride: water in mass ratio of 1.00: 0.20: 0.15: 0.15: 0.05 :. A drug solution of 98.45 can be used. The impregnated tensile strength of the water-decomposable nonwoven fabric is preferably 35 N / m or more, more preferably 37 N / m or more, and further preferably 40 N / m or more. The upper limit of the impregnated tensile strength of the water-decomposable nonwoven fabric is not particularly limited, but is preferably 200 N / m or less.

Further, since the water-decomposable nonwoven fabric of the present invention is excellent in water-decomposability, it easily disintegrates due to a water flow or a large amount of water, and the disintegrated state is maintained. Therefore, when the water-decomposable nonwoven fabric of the present invention is poured into a flush toilet or the like, the drainage port of the flush toilet or the like is not clogged with the water-decomposable nonwoven fabric. In recent years, the demand for water-saving flush toilets and the like has been increasing, but since the water-decomposable non-woven fabric of the present invention is easily hydrolyzed even in a water-saving flush toilet, it can be flushed to any flush toilet. Here, the water-decomposability of the water-decomposable non-woven fabric is such that the water-decomposable non-woven fabric is impregnated with pure water so that the mass ratio of water to the water-decomposable non-woven fabric in the absolutely dry state is 1: 2 (nonwoven fabric: water). After leaving the non-woven fabric in a sealed state in a normal temperature environment for 2 days, the measurement is carried out in accordance with "4.5 Ease of loosening" of JIS P 4501: 1993. In the present specification, the water-decomposable nonwoven fabric in an absolutely dry state is a nonwoven fabric having a water content of 1% by mass or less with respect to the total mass of the water-decomposable nonwoven fabric. The hydrolyzability of the water-decomposable nonwoven fabric is preferably 100 seconds or less, more preferably 80 seconds or less, further preferably 70 seconds or less, further preferably 67 seconds or less, and 65 seconds or less. It is particularly preferable to have. The lower limit of the water-decomposability of the water-decomposable nonwoven fabric is not particularly limited, but is preferably 15 seconds or longer.
In addition, the hydrolyzability of the hydrolyzable non-woven fabric is the same as above, and the hydrolyzable non-woven fabric is impregnated with pure water so that the mass ratio of water to the hydrolyzable non-woven fabric in the absolutely dry state is 1: 2 (non-woven fabric: water) in a wet state. After leaving the hydrolyzable non-woven fabric in a sealed state for 2 days in a normal temperature environment, it can be flushed to the world sewer toilet. When the rate) is measured, the hydrolyzability (sieving passage rate) is preferably 95% or more, and more preferably 99% or more.

Further, the water-decomposable nonwoven fabric of the present invention has excellent wet tensile strength. Therefore, when the water-decomposable non-woven fabric is impregnated with water or a chemical solution to form a wet water-decomposable non-woven fabric, it can exhibit sufficient strength to withstand cleaning work and the like. Therefore, the wet water-decomposable nonwoven fabric does not unintentionally break during the cleaning operation, and the fibers of the wet water-decomposable nonwoven fabric do not come off during use.

The wet tensile strength of the water-decomposable non-woven fabric is such that the water-decomposable non-woven fabric is impregnated with the chemical solution so that the mass ratio of the water-decomposable non-woven fabric in the absolutely dry state to the chemical solution is 1: 2 (nonwoven fabric: chemical solution). The tensile strength in the vertical and horizontal directions was measured, and the synergistic average value of the tensile strength in the vertical direction and the tensile strength in the horizontal direction was calculated. Specifically, the longitudinal and lateral tensile strengths of the wet water-decomposable nonwoven fabric are measured under the conditions of a sample width of 30 mm, a span length of 114 mm, and a tensile speed of 300 mm / min. As the tensile tester used for measuring the wet tensile strength, for example, a TENSILON universal material tester manufactured by A & D Co., Ltd. can be used. The chemical solution impregnated with the water-decomposable non-woven fabric contains water as the main component and is used in various cosmetic materials (water-soluble solvent, antibacterial agent, fungicide, fragrance, surfactant, etc.) in a proportion of about 10% by mass or less of the whole. It may contain a preservative, a wetting agent, a drug having a desired medicinal effect, etc.). For example, as a chemical solution, dipropylene glycol: polyaminopropyl biguanide: phosphoric acid 2Na: benzoic acid: cetylpyridinium chloride: water in mass ratio of 1.00: 0.20: 0.15: 0.15: 0.05 :. A drug solution of 98.45 can be used. The wet tensile strength of the water-decomposable nonwoven fabric is preferably 30 N / m or more, more preferably 40 N / m or more, and further preferably 50 N / m or more. The upper limit of the wet tensile strength of the water-decomposable nonwoven fabric is not particularly limited, but is preferably 300 N / m or less.

Hydrolyzable non-woven fabrics include pulp fibers and regenerated cellulose fibers. In the water-decomposable non-woven fabric, the pulp fiber and the regenerated cellulose fiber are entangled, whereby the pulp fiber and the regenerated cellulose fiber are integrated. Such a structure is formed by subjecting a non-woven fabric sheet containing pulp fibers and regenerated cellulose fibers formed by a wet papermaking method to a high-pressure water jet flow treatment. By applying the high-pressure water jet flow treatment, the pulp fiber and the regenerated cellulose fiber are twisted, bent, and turned into a state, so that the fibers are entangled and integrated with each other. That is, it can be said that the water-decomposable non-woven fabric is a non-woven fabric in which pulp fibers and regenerated cellulose fibers are entangled and integrated by high-pressure water jet flow treatment.

In the hydrolyzable non-woven fabric, the appearance of the pulp fibers and the regenerated cellulose fibers entwined and integrated can be seen from the magnified observation of the surface of the non-woven fabric and the appearance of the fibers being randomly oriented and entangled. Further, since the water-decomposable non-woven fabric of the present invention is a non-woven fabric in which pulp fibers and regenerated cellulose fibers are entangled and integrated by high-pressure water jet flow treatment, the water-decomposable non-woven fabric has streaks in the flow direction (MD direction) of the non-woven fabric. Jet traces are continuously formed. That is, in the present invention, it can be determined that the pulp fiber and the regenerated cellulose fiber are entangled by the presence of such a jet trace. The jet trace is a fine trace where the high-pressure water jet flow is applied, and the density of the fibers constituting the water-decomposable nonwoven fabric is higher in the jet trace than in the place where the high-pressure water jet flow is not applied.

The basis weight of the water-decomposable nonwoven fabric of the present invention ^{is preferably 15 g / m 2} or more, more preferably 20 g / m ² or more, and even more preferably 30 g / m ² or more. The basis weight of the water-decomposable nonwoven fabric ^{is preferably 100 g / m 2} or less, more preferably 80 g / m ² or less, and even more preferably 60 g / m ² or less. By setting the basis weight of the water-decomposable non-woven fabric within the above range, the impregnation tensile strength and the water-decomposability can be more effectively improved. In this specification, the basis weight of the water-decomposable nonwoven fabric is measured in accordance with JIS P 8124.

The thickness of the water-decomposable nonwoven fabric of the present invention is preferably 100 μm or more, more preferably 150 μm or more. The thickness of the water-decomposable nonwoven fabric is preferably 400 μm or less, more preferably 350 μm or less.

In the present specification, the water-decomposable non-woven fabric is a non-woven fabric in a dry state (absolutely dry state), and is a non-woven fabric that can be impregnated with water or a chemical. The present invention also relates to a wet water-decomposable nonwoven fabric obtained by impregnating a water-decomposable nonwoven fabric with water or a chemical. In addition to water, the wet water-decomposable non-woven fabric may further contain a wetting agent such as propylene glycol, an antibacterial agent, an antifungal agent, a fragrance, and a drug having a desired medicinal effect such as alcohol and parabenzoic acid esters. good. The wet water-decomposable non-woven fabric is preferably used as a wet product such as a wet tissue, a wipe, and a wiper.

The wet thickness of the water-decomposable nonwoven fabric of the present invention (thickness of the wet water-decomposable nonwoven fabric) is preferably 100 μm or more, more preferably 150 μm or more, further preferably 200 μm or more, and 250 μm or more. It is more preferably present, and particularly preferably 270 μm or more. The wet thickness of the water-decomposable nonwoven fabric (thickness of the wet water-decomposable nonwoven fabric) is preferably 1000 μm or less, more preferably 800 μm or less, and further preferably 600 μm or less. By setting the wet thickness of the water-decomposable nonwoven fabric within the above range, it is possible to further enhance the usability when using the wet water-decomposable nonwoven fabric. Specifically, it is possible to enhance the feel and softness. In addition, the cleaning effect of the wet water-decomposable non-woven fabric can be enhanced.

<Pulp fiber>
The water-decomposable nonwoven fabric of the present invention contains pulp fibers. Examples of the pulp fiber include fibers made of wood pulp, non-wood pulp, and deinked pulp. Examples of wood pulp include broadleaf pulp (blightwood kraft pulp (LBKP)), coniferous tree pulp (coniferous kraft pulp (NBKP)), sulfite pulp (SP), dissolved pulp (DP), soda pulp (AP), and unbleached craft. Examples thereof include chemical pulp such as pulp (UKP) and oxygen bleached kraft pulp (OKP). Further, semi-chemical pulp such as semi-chemical pulp (SCP) and chemiground wood pulp (CGP), mechanical pulp such as crushed wood pulp (GP) and thermomechanical pulp (TMP, BCTMP) can also be used. Examples of the non-wood pulp include cotton pulp such as cotton linter and cotton lint, non-wood pulp such as hemp, straw and bagasse, and cellulose, chitin and chitosan isolated from sea squirts and seaweed. Examples of the deinked pulp include deinked pulp made from used paper. As the pulp, one of the above types may be used alone, or two or more types may be mixed and used.

Among them, as the pulp fiber, it is preferable to use at least one selected from broadleaf pulp (blightwood kraft pulp (LBKP)) and softwood pulp (coniferous kraft pulp (NBKP)), and it is preferable to use coniferous pulp (coniferous kraft pulp (NBKP)). ) Is particularly preferable. By using softwood pulp (softwood kraft pulp (NBKP)), it becomes easy to suppress the falling off of pulp fibers when producing a water-decomposable nonwoven fabric, and the production efficiency can be improved. Further, by using softwood pulp (coniferous kraft pulp (NBKP)) as the pulp fiber, the thickness of the water-decomposable non-woven fabric at the time of wetting can be increased, and the usability and cleaning effect when using the wet water-decomposable non-woven fabric can be improved. Can be enhanced.

In the present invention, coniferous pulp and broadleaf pulp may be used in combination as the pulp fiber, but in this case, the content of the broadleaf pulp fiber with respect to the total mass of the pulp fiber is preferably 50% by mass or less, preferably 40% by mass. It is more preferably less than or equal to, more preferably 30% by mass or less, further preferably 20% by mass or less, and particularly preferably 10% by mass or less. The pulp fiber may not contain hardwood pulp, and the content of the hardwood pulp fiber may be 0% by mass with respect to the total mass of the pulp fiber.

The average fiber length of the pulp fiber is preferably 1.5 mm or more, more preferably 1.8 mm or more, and further preferably 2.0 mm or more. The average fiber length of the pulp fibers is preferably 20.0 mm or less, more preferably 10.0 mm or less, and even more preferably 7.0 mm or less. Here, in the present specification, the average fiber length of pulp fibers means a length-weighted average fiber length. The length-weighted average fiber length of the pulp fiber is the fiber length calculated by the following measuring method. First, a fiber-dispersed slurry obtained by dissociating a water-decomposable nonwoven fabric into water is produced. This is filtered through a nylon mesh screen and separated into a residue (rayon) and a filtrate (pulp dispersion). The pulp dispersion is treated with a disintegrator at 4500 rpm and sufficiently dissociated to obtain a fiber dispersion slurry. The obtained fiber-dispersed slurry is diluted to be 0.01% by mass or more and 0.02% by mass or less to prepare a diluted solution. The projected length of the fiber component contained in 10 ml of this diluted solution is measured using a fiber length measuring device (Kayani Fiber Lab Ver4.0, manufactured by Mezzo Automation), and the length-weighted average value of the disintegrated fibers is calculated.

The upper limit and the lower limit of the freeness of the pulp fiber are not particularly limited, but it is preferably 350 ml or more, more preferably 400 ml or more, and further preferably 450 ml or more. Further, it is also preferable that the freeness is about 700 ml.
Freeness is a value indicated by the Canadian standard freeness (CSF) specified in JIS P 8121, and is a value indicating the degree of beating of fibers. The beating of the fibers can be carried out by using a known beating machine such as a beader or a disc refiner for the paper material (slurry) in which the fibers are dispersed. Generally, the smaller the freeness value of the fiber, the stronger the degree of beating, the greater the damage of the fiber due to beating, and the more fibrillation is progressing. As the fibrilization of the fibers progresses, the number of bonding points between the fibers increases, so that the strength is improved. In the present invention, it is also preferable to appropriately adjust the freeness in order to keep the wet strength and the water solubility in a preferable range.

The content of the pulp fiber with respect to the total mass of the hydrolyzable nonwoven fabric is preferably 30% by mass or more, more preferably 40% by mass or more, and further preferably 50% by mass or more. The content of the pulp fiber with respect to the total mass of the water-decomposable nonwoven fabric is preferably 90% by mass or less, and more preferably 80% by mass or less. By setting the content of the pulp fiber within the above range, the impregnated tensile strength and the water-decomposability of the hydrolyzable nonwoven fabric can be more effectively enhanced.

<Regenerated cellulose fiber>
The water-decomposable nonwoven fabric of the present invention contains regenerated cellulose fibers. The average fiber length of the regenerated cellulose fiber may be 2 mm or more, preferably 3 mm or more, and more preferably 5 mm or more. The average fiber length of the regenerated cellulose fiber may be 20 mm or less, preferably 15 mm or less, more preferably 10 mm or less, and further preferably 6 mm or less. The average fiber length is the total fiber length of the flat rayon fiber and the round rayon fiber. The average fiber length of the regenerated cellulose fiber is based on the measurement method of JIS L-1015 8.4.1 average fiber length. By setting the fiber length of the regenerated cellulose fiber within the above range, both wet strength and water solubility can be achieved. In particular, by setting the fiber length of the regenerated cellulose fiber to the above upper limit value or less, it becomes easy to obtain a hydrolyzable non-woven fabric that can maintain a bulky state even in a wet state, and by setting it to the above lower limit value or more, the wet strength is high. It becomes easy to obtain a water-decomposable non-woven fabric.

Regenerated cellulose fibers include flat rayon fibers and round rayon fibers. When the content of the flat rayon fiber with respect to the total mass of the regenerated cellulose fiber is P (parts by mass) and the content of the round rayon fiber with respect to the total mass of the regenerated cellulose fiber is Q (parts by mass), P: Q = 1. : 9 to 9: 1, more preferably 3: 7 to 9: 1, more preferably 3: 7 to 8: 2, and 3: 7 to 7: 3. Is particularly preferable.

The flat rayon fiber has a flat cross-sectional shape. The cross-sectional shape of the fiber means the shape of the cut surface in the direction perpendicular to the length direction of the rayon fiber. As used herein, the flat shape means a shape in which the cross-sectional shape of a fiber has a major axis defined by a maximum length passing through a center point and a minor axis defined by a minimum length passing through a center point. The ratio of the outer edge length to the outer edge width (outer edge length / outer edge width) of the cross section of the rayon fiber is 2 or more. The ratio of the outer edge width to the outer edge length of the cross section of the flat rayon fiber is preferably 1: 2 to 1:30, more preferably 1: 2 to 1:20. Here, the ratio of the outer edge width to the outer edge length of the cross section of the flat rayon fiber can be measured by observing the flat cross section of 10 different flat rayon fibers from the vertical direction with a microscope and using the microscale as a reference. As the flat shape, for example, an eyebrows type, an oval shape, an elliptical shape, or the like can be exemplified.

As the flat rayon fiber, a dense flat rayon fiber or a hollow flat rayon fiber can be used. Above all, the flat rayon fiber is preferably a hollow flat rayon fiber. As the hollow flat rayon fiber, a commercially available product can be used, and for example, SBH manufactured by Daiwabo Rayon Masashi Co., Ltd. can be used.

The fineness of the flat rayon fiber is preferably 1.2 dtex or more and 7.0 dtex or less, more preferably 1.2 dtex or more and 5.0 dtex or less, and further preferably 1.2 dtex or more and 2.0 dtex or less. .. By setting the fineness of the flat rayon fiber within the above range, it is possible to suppress the reaggregation of the fiber component after hydrolysis, which makes it possible to more effectively enhance the water solubility.

The round rayon fiber has a round cross-sectional shape. Here, the round shape is a shape in which the cross-sectional shape of the fiber has substantially no major axis and minor axis, and the ratio of the outer edge length to the outer edge width of the cross section of the rayon fiber (outer edge length / outer edge width) is Say less than two. That is, the round rayon fiber includes a fiber having an elliptical cross section in which the ratio of the outer edge length to the outer edge width of the cross section of the rayon fiber is small. In addition, fibers having a chrysanthemum-shaped or polygonal cross section are also included in the round rayon fiber. In the present invention, it is preferable to use chrysanthemum-shaped rayon fiber as the round rayon fiber. As the chrysanthemum-shaped rayon fiber, a commercially available product can be used, and for example, Corona SB manufactured by Daiwabo Rayon Co., Ltd. can be used.

The content of the regenerated cellulose fiber with respect to the total mass of the water-decomposable nonwoven fabric is preferably 10% by mass or more, more preferably 15% by mass or more, and further preferably 20% by mass or more. The content of the regenerated cellulose fiber with respect to the total mass of the water-decomposable nonwoven fabric is preferably 50% by mass or less, and more preferably 45% by mass or less. By setting the content of the regenerated cellulose fiber within the above range, the wet strength and water solubility of the water-decomposable nonwoven fabric can be more effectively enhanced.

The regenerated cellulose fiber may contain, for example, cupra fiber, lyocell fiber, or the like, in addition to the above-mentioned flat rayon fiber or round rayon fiber.

<Arbitrary ingredient>
The water-decomposable nonwoven fabric of the present invention may contain other optional components. Examples of the optional component include a dry paper strength agent, a wet paper strength agent, a softener, and the like. Examples of the dry paper strength agent include cationized starch, polyacrylamide (PAM), carboxymethyl cellulose (CMC) and the like. Examples of the wet paper strength agent include polyamide epichlorohydrin, urea, melamine, and heat-crosslinkable polyacrylamide. Examples of the softener include anionic surfactants, nonionic surfactants, cationic surfactants and the like. The above optional components may be used alone or in combination of two or more.

However, the content of the heat-meltable resin in the water-decomposable nonwoven fabric of the present invention is preferably 5% by mass or less, more preferably 1% by mass or less, based on the total mass of the water-decomposable nonwoven fabric. The water-decomposable nonwoven fabric of the present invention preferably contains substantially no heat-meltable resin, and the content of the resin component is particularly preferably 0% by mass. In the present specification, the heat-meltable resin is at least one selected from, for example, polyethylene, polypropylene, polyamide, thermoplastic polyester and ethylene-vinyl acetate copolymer.

(Manufacturing method of water-decomposable non-woven fabric)
The method for producing a water-decomposable nonwoven fabric of the present invention includes a step of applying a high-pressure water jet flow treatment to a nonwoven fabric sheet containing pulp fibers and regenerated cellulose fibers formed by a wet papermaking method. Here, the regenerated cellulose fiber includes a flat rayon fiber and a round rayon fiber. The average fiber length of the regenerated cellulose fiber is 2 mm or more and 20 mm or less.

In the process of producing a water-decomposable nonwoven fabric, first, a slurry containing pulp fibers and regenerated cellulose fibers is obtained. Then, the slurry is wet-made using a known paper machine such as a circular net paper machine, a short net paper machine, an inclined wire paper machine, and a long net paper machine to form a non-woven fabric sheet (wet web). The fiber orientation of the nonwoven fabric sheet (wet web) can be controlled by adding a viscous agent such as polyethylene oxide to the slurry or adjusting the ratio of the papermaking liquid speed to the wire speed in the wire part of the papermaking process.

In the step of applying the high-pressure water jet flow treatment to the nonwoven fabric sheet, the obtained nonwoven fabric sheet (wet web) is subjected to the high-pressure water jet flow treatment. The high-pressure water jet flow treatment can be performed by a known method. Specifically, a nonwoven fabric sheet (wet web) was placed on a porous support, and a large number of pores having a pore diameter of about 0.08 to 0.30 mm were arranged from the upper surface of the nonwoven fabric sheet (wet web). High-pressure water is sprayed through a nozzle at a water pressure of 15 to 150 kg / cm ² , and the fibers constituting the non-woven fabric sheet (wet web) are entangled with each other. The energy applied to the nonwoven fabric sheet (wet web) by the high-pressure water jet flow treatment is represented by the high-pressure water jet flow energy of the following formula (iii). The high-pressure water jet flow energy is preferably 0.01 kWh / kg / m or more, more preferably 0.015 kWh / kg / m or more, and further preferably 0.02 kWh / kg / m or more. Further, the high-pressure water jet flow energy is preferably 0.50 kWh / kg / m or less, more preferably 0.40 kWh / kg / m or less, and further preferably 0.30 kWh / kg / m or less. preferable. By setting the high-pressure water jet flow energy within the above range, the water-decomposability can be enhanced while increasing the wet strength of the water-decomposable nonwoven fabric.
V = (2 x g x (P-Ap) x 10000 / (ρ x 1000)) ^1/2 x 60 ... (i)
V: Flow velocity of water discharged from the nozzle (m / min)
g: Gravitational acceleration = 9.8 m / s ²
P: Water pressure at the nozzle (kgf / cm ² )
A: Area of 1 nozzle hole (mm ² )
p: Atmospheric pressure (kgf / cm ² )
ρ: Water density (g / cm ³ )
F = (A / 100) x V x 100 ... (ii)
F: Flow rate of water discharged from one hole of the nozzle (cm ³ / min)
A: Area of 1 nozzle hole (mm ² )
V: Flow velocity of water discharged from the nozzle (m / min)
E = P × (F / 100) × 0.163 ... (iii)
E: High pressure water jet flow energy (kWh / kg / m)

The high-pressure water jet flow treatment may be performed online immediately after the wet papermaking is performed to form the web, or the wet papermaking web may be dried once and then the high-pressure water jet flow treatment may be performed online or offline. good.

The non-woven fabric sheet subjected to the high-pressure water jet flow treatment is pressed and dried in the subsequent steps.

(Use)
The water-decomposable non-woven fabric of the present invention is impregnated with a wetting agent such as water or propylene glycol, an antibacterial agent such as alcohol or parabenzoic acid ester, an antibacterial agent, a fragrance, or a drug having a desired medicinal effect. Used as wet products such as wipes and wipers. Further, the water-decomposable nonwoven fabric of the present invention may be used as a surface material for sanitary materials. In this case, if desired, the nonwoven fabric may be treated to increase hydrophilicity and water repellency.

Hereinafter, the features of the present invention will be described in more detail with reference to Examples and Comparative Examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention should not be construed as limiting by the specific examples shown below.

(Example 1)
Hollow flat rayon fiber with a fineness of 1.7 dtex and an average fiber length of 7 mm (trade name: Corona SBH, manufactured by Daiwa Bow Rayon Co., Ltd., ratio of outer edge width to outer edge length (flatness), 1:15) 11% by mass, fineness 1 .1 dtex, chrysanthemum-shaped rayon fiber with an average fiber length of 7 mm (trade name: Corona SB, manufactured by Daiwa Bow Rayon Co., Ltd.) 22% by mass, measured according to unbeaten coniferous kraft pulp (NBKP, JIS P 811-2: 2012) The fiber raw materials were mixed so that the resulting freeness was 673 ml and the average fiber length: 2.33 mm) 67% by mass, and the fiber raw materials were dispersed in water to obtain a pulp slurry having a solid content concentration of 1.0% by mass. A non-woven fabric sheet was prepared from a pulp slurry with a jet wire ratio of 1.04 and a papermaking speed of 105 m / min using an inclined wire type long net paper machine. Next, using a water jet device (high pressure water jet flow processing device) installed at the rear of the wire, a high pressure water jet flow is applied to the non-woven fabric sheet so that the load energy becomes 0.022kWh / kg / m. It was sprayed. The nonwoven fabric sheet treated with the high-pressure water jet flow treatment was dried to obtain a water-decomposable nonwoven fabric having ^{a basis weight of 43.0 g / m 2 after drying.}

(Example 2)
In Example 1, a hollow flat rayon fiber having a fineness of 1.7 dtex and an average fiber length of 7 mm (trade name: Corona SBH, manufactured by Daiwa Bow Rayon Co., Ltd.) 16.5 mass%, a fineness of 1.1 dtex, and a chrysanthemum type having an average fiber length of 7 mm. Rayon fiber (trade name: Corona SB, manufactured by Daiwa Bow Rayon Co., Ltd.) 16.5% by mass, unbeaten coniferous kraft pulp (NBKP, JIS P 811-2: 2012, freeness measured according to 2012 is 673 ml) 67 mass The water-decomposable rayon of Example 2 was obtained by the same method as in Example 1 except that the fiber raw materials were mixed so as to be%.

(Example 3)
In Example 1, instead of a hollow flat rayon fiber having a fineness of 1.7 dtex and an average fiber length of 7 mm (trade name: Corona SBH, manufactured by Daiwa Bow Rayon Co., Ltd.), a dense flat rayon fiber having a fineness of 2.4 dtex and an average fiber length of 10 mm is used. A water-decomposable nonwoven fabric of Example 3 was obtained by the same method as in Example 1 except that (trade name: Corona HP, manufactured by Daiwa Bow Rayon Co., Ltd.) was used.

(Example 4)
In Example 1, a hollow flat rayon fiber having a fineness of 1.7 dtex and an average fiber length of 7 mm (trade name: Corona SBH, manufactured by Daiwa Bow Rayon Co., Ltd.) 33.5% by mass, a fineness of 1.1 dtex, and a chrysanthemum type having an average fiber length of 7 mm. Rayon fiber (trade name: Corona SB, manufactured by Daiwa Bow Rayon Co., Ltd.) 16.5% by mass, unbeaten coniferous kraft pulp (NBKP, JIS P 811-2: 2012, freeness measured according to 2012 is 673 ml) 50 mass The water-decomposable rayon of Example 4 was obtained by the same method as in Example 1 except that the fiber raw materials were mixed so as to be%.

(Example 5)
In Example 1, a hollow flat rayon fiber having a fineness of 1.7 dtex and an average fiber length of 7 mm (trade name: Corona SBH, manufactured by Daiwa Bow Rayon Co., Ltd.) 16.5 mass%, a fineness of 1.1 dtex, and a chrysanthemum type having an average fiber length of 10 mm. Rayon fiber (trade name: Corona SB, manufactured by Daiwa Bow Rayon Co., Ltd.) 10.0% by mass, unbeaten coniferous kraft pulp (NBKP, JIS P 811-2: 2012, freeness measured according to 673 ml) 73. The water-decomposable rayon of Example 5 was obtained by the same method as in Example 1 except that the fiber raw materials were mixed so as to be 5% by mass.

(Example 6)
In Example 1, a hollow flat rayon fiber having a fineness of 1.7 dtex and an average fiber length of 7 mm (trade name: Corona SBH, manufactured by Daiwa Bow Rayon Co., Ltd.) 16.5 mass%, a fineness of 1.1 dtex, and a chrysanthemum type having an average fiber length of 10 mm. Rayon fiber (trade name: Corona SB, manufactured by Daiwa Bow Rayon Co., Ltd.) 10.0% by mass, unbeaten coniferous kraft pulp (NBKP, JIS P 811-2: 2012 with 673 ml of freeness) 68. Performed except that the fiber raw materials were mixed so as to be 5% by mass and 5.0% by mass of unbeaten rayon kraft pulp (LBKP, JIS P 811-2: 2012, freeness measured according to 2012 was 485 ml). The water-decomposable rayon of Example 6 was obtained by the same method as in Example 1.

(Example 7)
In Example 1, a chrysanthemum-shaped rayon fiber having a fineness of 1.1 dtex and an average fiber length of 7 mm (trade name: Corona SB, manufactured by Daiwa Bow Rayon Co., Ltd.) instead of 22% by mass has a fineness of 1.1 dtex and an average fiber length of 5 mm. The water-decomposable nonwoven fabric of Example 7 was obtained by the same method as in Example 1 except that 22% by mass of rayon fiber (trade name: Corona SB, manufactured by Daiwa Bow Rayon Co., Ltd.) was used.

(Comparative Example 1)
In Example 1, the composition of hollow flat rayon fiber (trade name: Corona SBH, manufactured by Daiwa Bow Rayon Co., Ltd.) having a fineness of 1.7 dtex and an average fiber length of 7 mm was changed to 33% by mass, and no chrysanthemum-shaped rayon fiber was used. A water-decomposable nonwoven fabric of Comparative Example 1 was obtained by the same method as in Example 1 except for the above.

(Comparative Example 2)
In Comparative Example 1, unbeaten hardwood kraft pulp (LBKP, JIS P 811-2: 2012) instead of unbeaten softwood kraft pulp (NBKP, JIS P 811-2: 2012 with a freeness of 673 ml): A water-decomposable nonwoven fabric of Comparative Example 2 was obtained in the same manner as in Comparative Example 1 except that the freeness measured according to 2012 was 485 ml).

(Comparative Example 3)
In Example 1, a hollow flat rayon fiber having a fineness of 1.7 dtex and an average fiber length of 7 mm (trade name: Corona SBH, manufactured by Daiwa Bow Rayon Co., Ltd.) was replaced with a dense flat rayon having a fineness of 2.4 dtex and an average fiber length of 35 mm (a solid flat rayon having a fineness of 2.4 dtex and an average fiber length of 35 mm). Product name: Corona HP, manufactured by Daiwa Bow Rayon Co., Ltd., a chrysanthemum-shaped rayon fiber that uses the ratio of outer edge width to outer edge length (flatness), 1: 6.3), has a fineness of 1.1 dtex, and has an average fiber length of 7 mm. Example 1 except that a chrysanthemum-shaped rayon (trade name: Corona SB, manufactured by Daiwa Bowrayon Co., Ltd.) having a fineness of 2.2 dtex and an average fiber length of 35 mm was used instead of (trade name: Corona SB, manufactured by Daiwa Bowrayon Co., Ltd.). The water-decomposable rayon of Comparative Example 3 was obtained by the same method as above.

(evaluation)
(Hydrolytic property 1)
The water-decomposable non-woven fabrics obtained in Examples and Comparative Examples were placed in an absolutely dry state, and the water-decomposable non-woven fabric was impregnated with pure water so that the mass ratio of water to the non-woven fabric in the absolutely dry state was 1: 2 (nonwoven fabric: water). The non-woven fabric in a wet state (wet water-decomposable non-woven fabric) was sealed and left for 2 days. Then, the water-decomposability of the water-decomposable non-woven fabric in a wet state was measured according to "4.5 Ease of loosening" of JIS P 4501: 1993.

(Hydrolytic 2)
A plurality of water-decomposable nonwoven fabrics obtained in Examples and Comparative Examples were cut into a size of 110 mm × 200 mm, and the mass after drying was measured. After that, the water-decomposable non-woven fabric is impregnated with pure water so that the mass ratio of the dried water-decomposable non-woven fabric and water is 1: 2 (nonwoven fabric: water), and the wet water-decomposable non-woven fabric (wet water-decomposable non-woven fabric) is sealed. And left it for 2 days. After that, the water solubility of the wet water-decomposable non-woven fabric was described in the public specification "PAS 1:2018 Certification Criteria for Products That Can Be Discharged in the Toilet" published by IWSFG. It was measured according to the "test method". Specifically, after the wet water-decomposable non-woven fabric is hydrolyzed in a slush box for 30 minutes, the test piece and water in the water tank are poured into a sieve with a mesh opening of 25 mm, and the sieve is rinsed with a shower for 1 minute. , The test piece remaining on the sieve was collected. Then, the passing rate of the sieve with respect to the initial dry weight was calculated.

(Wet tensile strength)
Dipropylene glycol: polyaminopropyl biguanide: phosphoric acid 2Na: benzoic acid: cetylpyridinium chloride: water in a mass ratio of 1.00: 0.20: 0.15: 0 to the water-decomposable non-woven fabrics obtained in Examples and Comparative Examples. A wet chemical solution was impregnated with a chemical solution having a mass ratio of .15: 0.05: 98.45 so as to have a mass ratio of 1: 2 (non-woven fabric: chemical solution) to obtain a wet water-decomposable non-woven fabric. Then, the sample was cut into a sample width of 30 mm and a sample length of 114 mm to obtain a test piece. Set the test piece on a tensile tester (TENSILON universal material tester manufactured by A & D Co., Ltd.), and under the conditions of a span length of 100 mm and a tensile speed of 300 mm / min, in parallel and perpendicular to the water jet marks of the water-decomposable non-woven fabric. The wet tensile strength in the direction was measured, and the synergistic average was calculated and used as the wet tensile strength.

(Impregnated tensile strength)
The water-decomposable nonwoven fabrics obtained in Examples and Comparative Examples were put into an absolutely dry state, and cut into a sample width of 25 mm and a sample length of 114 mm to obtain test pieces. Hold both ends in the length direction of the test piece and center it with dipropylene glycol: polyaminopropyl biguanide: phosphoric acid 2Na: benzoic acid: cetylpyridinium chloride: water in mass ratio of 1.00: 0.20: 0.15. A tensile tester (TENSILON universal material tester manufactured by A & D Co., Ltd.) so that the measurement is started after 5 seconds after being soaked in a chemical solution of 0.15: 0.05: 98.45 for 3 seconds. I set it to. Set on the upper and lower air chucks with a span length of 100 mm, measure the impregnation tensile strength in the parallel and vertical directions with the water jet marks of the water-decomposable non-woven fabric under the condition of a tensile speed of 300 mm / min, calculate the geometric mean, and impregnate tensile strength. And said.

(Thickness when wet)
The water-decomposable non-woven fabric obtained in Examples and Comparative Examples was impregnated with pure water so that the mass ratio of water to the water-decomposable non-woven fabric was 1: 2 (nonwoven fabric: water) to obtain a wet water-decomposable non-woven fabric, and its thickness was increased. JIS L 1913: 2010 General non-woven fabric test method Measured according to the 6-1-1A method. At that time, 10 points were measured with a precision thickness measuring machine (peacock manufactured by Ozaki Seisakusho, measuring element diameter 58 mm), and the average value was taken as the thickness at the time of wetting.

In the examples, a hydrolyzable non-woven fabric having high impregnation tensile strength and excellent hydrolyzability was obtained. In the examples, the processability in the impregnation step in producing the water-decomposable nonwoven fabric was improved.

Claims (9)

A hydrolyzable non-woven fabric in which pulp fibers and regenerated cellulose fibers are entangled.
The regenerated cellulose fiber contains flat rayon fiber and round rayon fiber, and contains.
A water-decomposable nonwoven fabric having an average fiber length of 2 mm or more and 20 mm or less of the regenerated cellulose fiber. When the content of the flat rayon fiber with respect to the total mass of the regenerated cellulose fiber is P (parts by mass) and the content of the round rayon fiber with respect to the total mass of the regenerated cellulose fiber is Q (parts by mass), P. : The water-decomposable nonwoven fabric according to claim 1, wherein Q = 1: 9 to 9: 1. The first or second claim, wherein the content of the pulp fiber is 30 to 90% by mass and the content of the regenerated cellulose fiber is 10 to 50% by mass with respect to the total mass of the water-decomposable nonwoven fabric. Water-decomposable non-woven fabric. The water-decomposable nonwoven fabric according to any one of claims 1 to 3, wherein the flat rayon fiber is a hollow flat rayon fiber. The water-decomposable nonwoven fabric according to any one of claims 1 to 4, wherein the ratio of the outer edge width to the outer edge length of the cross section of the flat rayon fiber is 1: 2 to 1:30. The water-decomposable nonwoven fabric according to any one of claims 1 to 5, wherein the average fiber length of the pulp fibers is 1.5 mm or more. The water-decomposable nonwoven fabric according to any one of claims 1 to 6, wherein the pulp fiber contains softwood pulp fiber, and the content of broad-leaved tree pulp fiber with respect to the total mass of the pulp fiber is 50% by mass or less. A wet water-decomposable nonwoven fabric obtained by impregnating the water-decomposable nonwoven fabric according to any one of claims 1 to 7 with water. A method for producing a water-decomposable nonwoven fabric, which comprises a step of applying a high-pressure water jet flow treatment to a nonwoven fabric sheet containing pulp fibers and regenerated cellulose fibers formed by a wet papermaking method.
The regenerated cellulose fiber contains flat rayon fiber and round rayon fiber, and contains.
A method for producing a water-decomposable nonwoven fabric, wherein the average fiber length of the regenerated cellulose fiber is 2 mm or more and 20 mm or less.