Nonwoven fabric for liquid permeable sheet of absorbent article, and manufacturing method of the nonwoven fabric

Abstract

To provide a nonwoven fabric for a liquid permeable sheet of a new absorbent article.SOLUTION: A nonwoven fabric 1 for a liquid permeable sheet of an absorbent article includes thermally fusible fibers 7 and cellulosic fibers 9. The thermally fusible fibers 7 are thermally fused to each other. A ratio of the cellulosic fibers 9 to the nonwoven fabric 1: x (mass ratio) and a distance among fibers in the nonwoven fabric 1: y (μm) in the nonwoven fabric 1 satisfy the following formula (1): -19x+70<y<-70x+120 formula (1), where 0<x.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a nonwoven fabric for a liquid-permeable sheet of an absorbent article and a method for manufacturing the nonwoven fabric.

Background Art

[0002] Nonwoven fabrics for absorbent articles containing cellulosic fibers have been studied. For example, Patent Document 1 discloses an absorbent sheet (Claim 1) formed by arranging heat-fusible non-hydrophilic fibers mixed with hydrophilic fibers in a crossed manner and fixing the crossed portions by heat fusion, and a method for manufacturing an absorbent sheet (Claim 2) characterized by mixing heat-fusible non-hydrophilic fibers and hydrophilic fibers, heating this to a temperature at which the surface of the non-hydrophilic fibers can be melted, and heat-fusing the crossed portions of the non-hydrophilic fibers.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Patent Document 1 does not disclose the nonwoven fabric according to the present disclosure. Therefore, an object of the present disclosure is to provide a novel nonwoven fabric for a liquid-permeable sheet of an absorbent article.

Means for Solving the Problems

[0005] The present inventors have found a nonwoven fabric for a liquid-permeable sheet of an absorbent article, which contains heat-fusible fibers and cellulose-based fibers, wherein the heat-fusible fibers are heat-fused to each other, and in the nonwoven fabric, the ratio of the cellulose-based fibers: x (mass ratio) and the fiber distance of the nonwoven fabric: y (μm) satisfy the following formula (1): -19x + 70 < y < -70x + 120 Formula (1), where 0 < x.

Advantages of the Invention

[0006] The nonwoven fabric for a liquid-permeable sheet of an absorbent article according to the present disclosure is novel.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0008] Specifically, the present disclosure relates to the following aspects. [Aspect 1] A nonwoven fabric for a liquid-permeable sheet of an absorbent article, which contains heat-fusible fibers and cellulose-based fibers, wherein the heat-fusible fibers are heat-fused to each other, and in the nonwoven fabric, the ratio of the cellulose-based fibers: x (mass ratio) and the fiber distance of the nonwoven fabric: y (μm) satisfy the following formula (1): -19x + 70 < y < -70x + 120 Formula (1) where 0 < x, and which is characterized by satisfying the above.

[0009] Examples of nonwoven fabrics containing cellulosic fibers include air-through nonwoven fabrics and spunlace nonwoven fabrics. An air-through nonwoven fabric is formed by blowing hot air onto a web to thermally bond thermally fusible fibers. Therefore, although a generally manufactured air-through nonwoven fabric (hereinafter referred to as a "general air-through nonwoven fabric") can generally contain cellulosic fibers, it is known that it is difficult to increase the content rate of cellulosic fibers. The inventor of the present application found that in an air-through nonwoven fabric, when the amount of cellulosic fibers is increased, although the fiber distance becomes smaller, the amount (number per unit volume) of the thermal fusion part by the thermally fusible fibers decreases, so that the strength of the air-through nonwoven fabric tends to be low.

[0010] A spunlace nonwoven fabric is formed by blowing a high-pressure water stream onto a web to entangle the fibers. Therefore, it is relatively easy to increase the amount of cellulosic fibers in a spunlace nonwoven fabric. However, due to the high-pressure water stream, the fiber distance of the formed nonwoven fabric becomes smaller, and due to the entanglement of the fibers, the strength of the nonwoven fabric tends to be low despite the small fiber distance.

[0011] In the above nonwoven fabric, the thermally fusible fibers are thermally bonded to each other, and the content rate of the cellulosic fibers and the fiber distance of the nonwoven fabric have a predetermined relationship. The predetermined relationship between the content rate of the cellulosic fibers and the fiber distance of the nonwoven fabric cannot be achieved in a general air-through nonwoven fabric and a general spunlace nonwoven fabric, and the above nonwoven fabric is novel. Further, the above nonwoven fabric has a smaller fiber distance and higher strength compared to a general air-through nonwoven fabric having the same content rate of the same cellulosic fibers.

[0012] [Aspect 2] The nonwoven fabric according to Aspect 1, wherein in formula (a), 0.10 ≦ x ≦ 0.50.

[0013] In the above nonwoven fabric, since the content rate of the cellulose-based fibers is within a predetermined range and the distance between the fibers is within a predetermined range, the distance between the fibers is smaller and the strength is higher compared to a general air-through nonwoven fabric having the same content rate of cellulose-based fibers. Further, when the above cellulose-based fibers include the hydrophilic cellulose-based fibers described later, the nonwoven fabric is likely to be excellent in, for example, hygroscopicity and sweat absorbency due to the hydrophilic cellulose-based fibers.

[0014] [Aspect 3] In the above nonwoven fabric, the strength z (N / 25 mm) in the conveyance direction during the production of the nonwoven fabric satisfies the following formula (2): -35x + 27 < z Formula (2) The nonwoven fabric according to Aspect 1 or 2 that satisfies the above.

[0015] Since the above nonwoven fabric has a predetermined strength, it is excellent in strength compared to a general air-through nonwoven fabric having the same content rate of cellulose-based fibers.

[0016] [Aspect 4] The nonwoven fabric according to any one of Aspects 1 to 3, which is an air-through nonwoven fabric containing short fibers. Since the above nonwoven fabric is a predetermined air-through nonwoven fabric, the effect of Aspect 1 is high.

[0017] [Aspect 5] The nonwoven fabric according to any one of Aspects 1 to 4, wherein the heat-fusible fibers are heat-fused to the cellulose-based fibers. In the above nonwoven fabric, since the heat-fusible fibers are heat-fused to the cellulose-based fibers, it is excellent in strength compared to a nonwoven fabric in which the heat-fusible fibers are not heat-fused to the cellulose-based fibers.

[0018] [Aspect 6] The nonwoven fabric according to any one of Aspects 1 to 5, wherein the cellulose-based fibers are entangled with each other. In the above nonwoven fabric, since the cellulose-based fibers are entangled with each other, it is excellent in strength compared to a nonwoven fabric in which the cellulose-based fibers are not entangled with each other.

[0019] [Aspect 7] The nonwoven fabric according to any one of Aspects 1 to 6, wherein the heat-fusible fiber is composed of a biomass raw material or a recycled raw material. In the nonwoven fabric, since the heat-fusible fiber is composed of a predetermined material, the environmental load can be reduced.

[0020] [Aspect 8] The nonwoven fabric according to any one of Aspects 1 to 7, wherein the heat-fusible fiber has biodegradability. In the nonwoven fabric, since the heat-fusible fiber has biodegradability, the environmental load can be reduced.

[0021] [Aspect 9] The nonwoven fabric according to any one of Aspects 1 to 8, wherein the cellulose-based fiber has hydrophilicity and the heat-fusible fiber has hydrophobicity.

[0022] In the nonwoven fabric, since the cellulose-based fiber has hydrophilicity and the heat-fusible fiber has hydrophobicity, when the nonwoven fabric is used as a liquid-permeable sheet, particularly as a top sheet having liquid permeability, it becomes easier to draw body fluid in the thickness direction through the cellulose-based fiber, and it becomes difficult for the body fluid to spread in the plane direction.

[0023] [Aspect 10] A method for manufacturing the nonwoven fabric according to any one of Aspects 1 to 9, A fluid application step of applying a fluid from above to a web containing the heat-fusible fiber and the cellulose-based fiber disposed on a support having a plurality of holes to form a web to which the fluid is applied, A nonwoven fabric forming step of heat-treating the web to which the fluid is applied on a support having a plurality of holes to form the nonwoven fabric. The method is characterized by comprising the above steps.

[0024] The above manufacturing method can easily manufacture the nonwoven fabric according to Aspect 1.

[0025] The nonwoven fabric for the liquid-permeable sheet of the absorbent article according to the present disclosure and the method for manufacturing the nonwoven fabric for the liquid-permeable sheet of the absorbent article according to the present disclosure will be described in detail below. In this specification, the "nonwoven fabric for the liquid-permeable sheet of the absorbent article according to the present disclosure" may be simply referred to as "the nonwoven fabric according to the present disclosure" or "the nonwoven fabric". Further, in this specification, the "method for manufacturing the nonwoven fabric for the liquid-permeable sheet of the absorbent article according to the present disclosure" may be simply referred to as "the manufacturing method according to the present disclosure".

[0026] <Nonwoven fabric> FIG. 1 is a perspective view of a nonwoven fabric according to one embodiment of the present disclosure (hereinafter referred to as "the first embodiment"), specifically, an air-through nonwoven fabric 1. The air-through nonwoven fabric 1 includes a support surface 3 and an air surface 5. The air-through nonwoven fabric 1 contains heat-sealable fibers 7 and cellulose-based fibers 9. In FIG. 1, for the sake of distinction, the heat-sealable fibers 7 are represented relatively thickly and the cellulose-based fibers 9 are represented relatively thinly, but this does not mean the fiber diameters of the heat-sealable fibers 7 and the cellulose-based fibers 9. Regarding the characteristics of the air-through nonwoven fabric 1, they will be described in general terms below.

[0027] The nonwoven fabric according to the present disclosure is a nonwoven fabric for the liquid-permeable sheet of the absorbent article. The absorbent article is not particularly limited, and examples thereof include sanitary napkins, panty liners, disposable panties, disposable diapers (for infants and adults), urine pads, incontinence pads, breast pads, etc.

[0028] As the liquid-permeable sheet, any sheet that is used as the liquid-permeable sheet of the absorbent article can be adopted without particular limitation. For example, a liquid-permeable top sheet having a skin-contact surface, a core wrap that covers the absorbent core, a liquid diffusion sheet (second sheet) disposed between the top sheet and the absorbent core, a liquid diffusion sheet (third sheet) disposed between the absorbent core and the liquid-impermeable sheet, etc. can be mentioned.

[0029] The nonwoven fabric according to the present disclosure contains heat-fusible fibers and cellulosic fibers. As the heat-fusible fibers, those used as heat-fusible fibers in the art can be adopted without limitation. Specifically, fibers containing a low-melting thermoplastic resin and a high-melting thermoplastic resin can be used. In order to fuse the heat-fusible fibers together, those containing a low-melting thermoplastic resin such as polyethylene resin and low-melting point polypropylene on at least the surface are preferred. Examples of the heat-fusible fibers include single-component fibers of polyethylene resin; single-component fibers of polypropylene resin; core-sheath type composite fibers with a core of polyethylene terephthalate resin and a sheath of polyethylene resin; core-sheath type composite fibers with a core of polypropylene resin and a sheath of polyethylene resin; core-sheath type composite fibers with a core of high-melting point polypropylene resin and a sheath of low-melting point polypropylene resin; side-by-side type composite fibers composed of polyethylene terephthalate resin and polyethylene resin; side-by-side type composite fibers composed of polypropylene resin and polyethylene resin, and the like.

[0030] The heat-fusible fibers are preferably heat-fusible fibers having biodegradability. Thereby, the nonwoven fabric is likely to have biodegradability. Examples of the low-melting thermoplastic resin constituting the biodegradable heat-fusible fibers include polybutylene succinate, poly(hydroxybutyrate / hydroxyhexanoate), polycaprolactone, poly(caprolactone / butylene succinate), poly(butylene succinate / adipate), poly(butylene succinate / carbonate), poly(butylene adipate / terephthalate), polyethylene succinate, or polylactic acid.

[0031] Examples of the high-melting thermoplastic resin constituting the biodegradable heat-fusible fibers include polylactic acid, polyhydroxybutyrate, polyglycolic acid, or cellulose acetate. The heat-fusible fibers can be biomass plastics, recycled ones, or the like.

[0032] The above heat-fusible fiber may not be hydrophilized and may be hydrophobic, or may be hydrophilic by being hydrophilized. Examples of the hydrophilization treatment include treatments using surfactants, hydrophilic agents, etc. (for example, kneading a surfactant into the inside of the heat-fusible fiber, applying a surfactant to the surface of the heat-fusible fiber, etc.), plasma processing, and the like.

[0033] The above heat-fusible fiber preferably has a fineness of 0.8 dtex or more, and more preferably 0.9 dtex or more. Also, the above heat-fusible fiber preferably has a fineness of 20 dtex or less, more preferably 10 dtex or less, and even more preferably 4 dtex or less. Thereby, the non-woven fabric according to the present disclosure is likely to have a certain thickness under pressure and has an excellent touch.

[0034] The above heat-fusible fiber preferably has an average fiber length of 20 mm or more, and more preferably 30 mm or more. Also, the above heat-fusible fiber preferably has an average fiber length of 80 mm or less, and more preferably 60 mm or less. Thereby, the non-woven fabric according to the present disclosure has less unevenness and is excellent in strength. Also, the non-woven fabric according to the present disclosure has excellent formability.

[0035] In the present disclosure, the average fiber length of the fiber is measured according to "A7.1 Method A (standard method) Measuring the length of individual fibers on a graduated glass plate" in "A7.1 Measurement of fiber length" in Appendix A of JIS L 1015:2010. Note that the above method is a test method corresponding to ISO 6989 issued in 1981.

[0036] Examples of the above cellulose-based fiber include natural cellulose fiber, regenerated cellulose fiber, purified cellulose fiber, and semi-synthetic cellulose fiber. Examples of the above natural cellulose fiber include plant fibers, such as seed hair fibers (for example, cotton fiber), bast fibers (for example, hemp), leaf vein fibers (for example, manila hemp), and fruit fibers (for example, coconut).

[0037] Examples of the cotton fiber include Gossypium hirsutum cotton fiber (e.g., upland cotton), Gossypium barbadense cotton fiber, Gossypium arboreum cotton fiber, and Gossypium herbaceum cotton fiber. Further, the cotton fiber can be organic cotton fiber or pre-organic cotton (trademark) fiber. The organic cotton fiber means cotton certified by GOTS (Global Organic Textile Standard).

[0038] Examples of the regenerated cellulose fiber include rayon, for example, viscose rayon obtained from viscose, polynosic, and modal, and fibers such as cuprammonium rayon (also referred to as "cupra") obtained from a cuprammonium solution of cellulose.

[0039] Examples of the purified cellulose fiber include lyocell. Specifically, it is obtained by dissolving pulp in an aqueous solution of N-methylmorpholine N-oxide to form a spinning dope, and extruding it into a dilute solution of N-methylmorpholine N-oxide to form fibers. The above purified cellulose is commercially available, for example, as Tencel (trademark). Examples of the semi-synthetic fiber include semi-synthetic cellulose, for example, acetate fiber, for example, fibers such as triacetate and diacetate.

[0040] Except for natural cellulose fibers, the above cellulose-based fibers preferably have a fineness of 1.0 dtex or more, and more preferably 1.4 dtex or more. Further, except for natural cellulose fibers, the above cellulose-based fibers preferably have a fineness of 10 dtex or less, and more preferably 6 dtex or less. Thereby, the nonwoven fabric according to the present disclosure is likely to have a certain thickness under dry conditions and under pressure, and has excellent touch.

[0041] The above cellulose-based fibers preferably have an average fiber length of 20 mm or more, and more preferably 30 mm or more. Also, the above cellulose-based fibers preferably have an average fiber length of 80 mm or less, and more preferably 60 mm or less. Thereby, the nonwoven fabric according to the present disclosure has less unevenness and excellent strength. Also, the nonwoven fabric according to the present disclosure has excellent formability.

[0042] Since the nonwoven fabric according to the present disclosure contains the above cellulose-based fibers (hydrophilic cellulose-based fibers described later), the nonwoven fabric according to the present disclosure is excellent in, for example, hygroscopicity, sweat absorbency, etc. Also, since the nonwoven fabric according to the present disclosure contains the above cellulose-based fibers (hydrophilic cellulose-based fibers) at a high ratio, that is, contains the above heat-fusible fibers at a low ratio, the nonwoven fabric contains fibers derived from crude oil at a low ratio, becomes an environmentally considerate nonwoven fabric, and can contribute to the achievement of sustainable development goals (SDGs).

[0043] The above cellulose-based fibers can be water-repellent cellulose-based fibers imparted with water repellency by treatment with a water repellent. In addition, in order to distinguish cellulose-based fibers not treated with a water repellent from water-repellent cellulose-based fibers, they may be referred to as hydrophilic cellulose-based fibers.

[0044] The above water-repellent cellulose-based fibers are disclosed, for example, in JP-A-2002-266241, JP-A-2003-20570, JP-A-2019-65443, JP-A-2022-58301, etc., and, for example, Eco Lipelas (trade name, water-repellent viscose rayon) manufactured by Daiwa Boreyon Co., Ltd., Olea (trade name, water-repellent viscose rayon) manufactured by Kelheim Fibres GmbH, etc. are commercially available.

[0045] Since the nonwoven fabric according to the present disclosure contains water-repellent cellulose fibers, the nonwoven fabric according to the present disclosure is excellent in dry feeling. Further, since the nonwoven fabric according to the present disclosure contains the above water-repellent cellulose fibers at a high ratio, that is, contains the above heat-fusible fibers at a low ratio, the nonwoven fabric contains fibers derived from crude oil at a low ratio, becomes an environmentally considerate nonwoven fabric, and can contribute to the achievement of sustainable development goals (SDGs).

[0046] The nonwoven fabric according to the present disclosure can further contain synthetic fibers that are not intended to be heat-fused. Examples of the synthetic fibers include those containing a single component, for example, single fibers, or those containing a plurality of components, for example, composite fibers. Further, the synthetic fibers can be biomass plastics, recycled ones, etc.

[0047] Examples of the above components include polyolefin-based polymers such as polyethylene and polypropylene; polyester-based polymers such as terephthalate-based polymers such as polyethylene terephthalate (PET), polybutylene terephthalate, and polypentylene terephthalate; polyamide-based polymers such as nylon 6 and nylon 6,6; acrylic-based polymers; polyacrylonitrile-based polymers; and modified products thereof.

[0048] The synthetic fibers preferably have a fineness of 0.8 dtex to 20 dtex and preferably have an average fiber length of 20 to 80 mm. The synthetic fibers may not be hydrophilized and may be hydrophobic, or may be hydrophilized and have hydrophilicity. Examples of the hydrophilization treatment include those described in the section of the heat-fusible fibers.

[0049] When the nonwoven fabric according to the present disclosure contains the synthetic fiber, the ratio of the synthetic fiber is preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less, even more preferably 20% by mass or less, even more preferably 10% by mass or less, and even more preferably 5% by mass or less of the heat-fusible fiber, from the viewpoint of the strength of the nonwoven fabric.

[0050] In the nonwoven fabric according to the present disclosure, as described above, the heat-fusible fiber may be hydrophilic or hydrophobic, the cellulose-based fiber may be hydrophilic or hydrophobic, and the synthetic fiber, if desired, may be hydrophilic or hydrophobic. Each of the heat-fusible fiber, the cellulose-based fiber, and the synthetic fiber, if desired, can arbitrarily select hydrophilicity and hydrophobicity according to the performance required for the liquid-permeable sheet of the absorbent article. In the nonwoven fabric according to the present disclosure, it is preferable that the cellulose-based fiber has hydrophilicity and the heat-fusible fiber has hydrophobicity, and it is preferable that the cellulose-based fiber has hydrophilicity and the heat-fusible fiber and the synthetic fiber, if desired, have hydrophobicity. Thereby, when the nonwoven fabric is used for a liquid-permeable sheet, particularly a top sheet having liquid permeability, it becomes easier to draw body fluid in the thickness direction through the cellulose-based fiber, and it becomes difficult for the body fluid to spread in the planar direction.

[0051] In the nonwoven fabric according to the present disclosure, the heat-fusible fibers are heat-fused to each other. Further, in the nonwoven fabric according to the present disclosure, it is preferable that the heat-fusible fiber and the cellulose-based fiber are heat-fused to each other. Thereby, the nonwoven fabric is excellent in strength as compared with the case where the heat-fusible fiber is not heat-fused to the cellulose-based fiber. In the nonwoven fabric according to the present disclosure, it is preferable that the cellulose-based fibers are entangled with each other. Further, in the nonwoven fabric according to the present disclosure, it is preferable that the cellulose-based fiber and the heat-fusible fiber are entangled with each other. Thereby, the nonwoven fabric is excellent in strength as compared with the case where the cellulose-based fibers are not entangled with each other.

[0052] In the nonwoven fabric according to the present disclosure, in the nonwoven fabric, the ratio of the cellulose-based fiber: x (mass ratio) and the fiber distance of the nonwoven fabric: y (μm) satisfy the following formula (1): -19x + 70 < y < -70x + 120 Formula (1) In the formula, 0 < x is satisfied. Thereby, compared with a general air-through nonwoven fabric having the same content rate of the cellulose-based fiber, the nonwoven fabric has a smaller fiber distance and thus higher strength.

[0053] In Formula (1), the fiber distance of the nonwoven fabric: y (μm) is within a range surrounded by two predetermined straight lines. The two predetermined straight lines are referred to as an upper straight line (in Formula (1), the straight line of y = -70x + 120) and a lower straight line (in Formula (1), the straight line of y = -19x + 70).

[0054] In Formula (1), x means the ratio (mass ratio) of the cellulose-based fiber to the total amount of the nonwoven fabric. In Formula (1), 0 < x, preferably 0.10 ≤ x, more preferably 0.15 ≤ x, and even more preferably 0.20 ≤ x. Also, in Formula (1), the upper limit of X is the intersection point of the upper straight line and the lower straight line. Preferably, x ≤ 0.60, more preferably x ≤ 0.50, even more preferably x ≤ 0.45, and even more preferably x ≤ 0.40. Thereby, compared with a general air-through nonwoven fabric having the same content rate of the cellulose-based fiber, the nonwoven fabric has a smaller fiber distance and thus higher strength. Further, when the cellulose-based fiber contains a hydrophilic cellulose-based fiber, the nonwoven fabric is likely to be excellent in, for example, hygroscopicity, sweat absorbency, etc. due to the hydrophilic cellulose-based fiber.

[0055] In the nonwoven fabric according to the present disclosure, the upper straight line in formula (1) is preferably y = -70x + 115, more preferably y = -70x + 110, still more preferably y = -70x + 105, and even more preferably y = -70x + 100. In the nonwoven fabric according to the present disclosure, the lower straight line in formula (1) is preferably y = -19x + 73, more preferably y = -19x + 75, and still more preferably y = -19x + 77. Thereby, the nonwoven fabric has a smaller fiber distance and thus higher strength compared to a general air-through nonwoven fabric having the same cellulose fiber content.

[0056] In the present disclosure, x is measured according to the "6.2.2 70% sulfuric acid method" of "Test method for blending ratio of textile products - Part 2: Fiber blending ratio" in JIS L 1030-2:2012.

[0057] In the present disclosure, the fiber distance: y (μm) is measured and calculated as follows.

Number

[0058] In the present disclosure, the thickness (mm, cm) of the nonwoven fabric is measured by FS-60DS manufactured by Dainichi Kagaku Seiki Co., Ltd. [measurement surface 44 mm (diameter), measurement pressure 3 g / cm 2 under standard conditions (temperature 23 ± 2 °C, relative humidity 50 ± 5%), by pressing five different parts of the nonwoven fabric, and means the average value of the five measurement values.

[0059] In the present disclosure, the basis weight (g / m 2 ) of the nonwoven fabric is measured by a direct reading balance (for example, electronic balance HF-300 manufactured by Ken Seiko Kogyo Co., Ltd.) for the masses of three test pieces (10 mm × 10 mm) cut out from the object, and is calculated from the average value of the masses of the three test pieces, which is the mass per unit area (g / m 2) means

[0060] In the nonwoven fabric according to the present disclosure, the strength in the conveying direction during the production of the nonwoven fabric: z (N / 25 mm) satisfies the following formula (2): -35x + 27 < z Formula (2) It is preferable to satisfy The range of x is the same as that in formula (1). Thereby, the nonwoven fabric is superior in strength compared to a general air-through nonwoven fabric having the same cellulose fiber content. In formula (2), the strength: z (N / 25 mm) has a value higher than a predetermined straight line. The above-mentioned predetermined straight line is z = -35x + 27, preferably z = -35x + 28.

[0061] In the present disclosure, the strength in the conveying direction during the production of the nonwoven fabric is measured by the following conveying direction strength test. [Conveying Direction Strength Test] (1) Cut the nonwoven fabric into 150 mm × 25 mm (longitudinal direction × transverse direction) to form a test sample. The test sample is cut so that the longitudinal direction coincides with the conveying direction (MD) during the production of the nonwoven fabric. (2) Using a tensile testing machine (manufactured by Shimadzu Corporation, Autograph AG-Xplus), the tensile test sample is subjected to a tensile test at a speed of 100 mm / min, and the breaking strength (N / 25 mm) of the tensile test sample is measured and adopted as the conveying direction strength (N / 25 mm).

[0062] The nonwoven fabric according to the present disclosure is not particularly limited, and examples include an air-through nonwoven fabric, an air-through nonwoven fabric containing heat-fusible fibers, a nonwoven fabric in which a web containing cellulose fibers is laminated on the air-through nonwoven fabric and water-flow entangled, etc. The nonwoven fabric is preferably an air-through nonwoven fabric, and more preferably an air-through nonwoven fabric containing short fibers. Thereby, the effects of the present disclosure are excellent. Examples of the fiber length of the short fibers include the above-mentioned average fiber lengths for the heat-fusible fibers and the cellulose fibers.

[0063] The nonwoven fabric according to the present disclosure, to function as a liquid-permeable sheet of an absorbent article, preferably has a basis weight of 10 g / m 2 or more, more preferably 15 g / m 2 or more, and even more preferably 20 g / m 2 or more. Also, for the same reason, the nonwoven fabric according to the present disclosure preferably has a basis weight of 60 g / m 2 or less, more preferably 50 g / m 2 or less, and even more preferably 40 g / m 2 or less.

[0064] The nonwoven fabric according to the present disclosure, to function as a liquid-permeable sheet of an absorbent article, preferably has a thickness of 0.1 mm or more, more preferably 0.4 mm or more, even more preferably 0.5 mm or more, and still more preferably 0.6 mm or more. Also, for the same reason, the nonwoven fabric according to the present disclosure preferably has a thickness of 3.0 mm or less, more preferably 2.5 mm or less, even more preferably 2.0 mm or less, and still more preferably 1.5 mm or less.

[0065] <Method for manufacturing nonwoven fabric> FIG. 2 is a diagram for explaining a nonwoven fabric manufacturing system 101 for carrying out a method for manufacturing a nonwoven fabric according to one embodiment of the present disclosure (hereinafter sometimes referred to as the "second embodiment"). The nonwoven fabric manufacturing system 101 manufactures the air-through nonwoven fabric 1 according to the first embodiment.

[0066] The manufacturing system 101 according to the second embodiment includes (i) a mesh belt 103 which is a support having a plurality of holes, (ii) a fluid application device 105 disposed above the mesh belt 103, (iii) a first suction device 107 disposed below the fluid application device 105 with the mesh belt 103 interposed therebetween, (iv) a second suction device 109 disposed downstream in the conveyance direction MD of the first suction device 107 and below the mesh belt 103, and (v) a heat treatment device 111 disposed downstream of the second suction device 109 and covering the mesh belt 103 from above and below.

[0067] Place a web 51 containing heat-fusible fibers on the mesh belt 103 and convey it in the conveyance direction MD. Note that the web 51 is formed by dry-opening the heat-fusible fibers.

[0068] Next, apply a fluid 113 (specifically, water) from the fluid application device 105 to the web 51, and form a web 53 to which the fluid is applied by sucking the applied fluid 113 from the first suction device 107 disposed below the fluid application device 105. Note that the fluid application device 105 supplies the fluid 113 in a curtain shape so as to extend in the orthogonal direction CD orthogonal to the conveyance direction MD. By applying a fluid from the fluid application device 105, the formed air-through nonwoven fabric 1 is likely to have a predetermined fiber spacing.

[0069] Next, use the second suction device 109 to suck the moisture remaining in the web 53 to which the fluid is applied, and form a dehydrated web 55. Next, pass the dehydrated web 55 through the heat treatment device 111 to fuse the heat-fusible fibers in the dehydrated web 55 and form the air-through nonwoven fabric 1. Note that in the heat treatment device 111, the heated air is passed from above downward through the dehydrated web 55 and the mesh belt 103 to fuse the heat-fusible fibers in the dehydrated web 55.

[0070] The method for manufacturing a nonwoven fabric according to the present disclosure includes the following steps. - A fluid application step (hereinafter referred to as the "fluid application step") of applying a fluid from above to a web containing the heat-fusible fibers and the cellulose-based fibers disposed on a support having a plurality of holes to form a web to which the fluid is applied. - A nonwoven fabric forming step (hereinafter referred to as the "nonwoven fabric forming step") of heat-treating the web to which the fluid is applied on a support having a plurality of holes to form the nonwoven fabric.

[0071] [Fluid application step] In the fluid application step, as the support having a plurality of holes, in the field of air-through nonwoven fabrics, a support commonly used can be adopted. For example, a mesh belt, a punching plate, a nickel cylinder, etc. can be mentioned. The web can have the same composition as the nonwoven fabric described in the "nonwoven fabric" section above, and includes heat-fusible fibers and cellulosic fibers.

[0072] The fluid is not particularly limited, and examples include water, steam, air, etc. From the viewpoint that the formed nonwoven fabric is likely to have a predetermined fiber spacing, it is preferable that the fluid is applied to the entire web. For example, it is preferable that the fluid is applied to the web in a curtain shape.

[0073] Also, it is preferable that the fluid does not thermally fuse the heat-fusible fibers contained in the web. For example, it is preferable that the temperature of the fluid is lower than the melting point and softening point of the heat-fusible fibers contained in the web. When the heat-fusible fiber is a composite fiber, it is preferable that the temperature of the fluid is lower than the melting point of the heat-fusible resin having a lower melting point. This is because the formed nonwoven fabric in the subsequent nonwoven fabric forming step is less likely to have a predetermined fiber spacing.

[0074] The fluid is applied to the web at a basis weight of 20 to 100 g / m 2 at a flow rate of 10 to 40 L / min per meter of length in the orthogonal direction perpendicular to the conveyance direction, which is preferable.

[0075] It is preferable that the fluid is sucked from below the support. This is because the formed nonwoven fabric is likely to have a predetermined fiber spacing. The suction pressure for sucking the fluid from below the support can be selected, for example, from the viewpoints of smoothing the support surface and air surface of the web and making it difficult for water to remain in the web. For example, suction pressures such as more than 0 KPa, 1 KPa or more, 2 KPa or more, etc., 25 KPa or less, 20 KPa or less, 15 KPa or less, 10 KPa or less, etc. can be mentioned.

[0076] [Nonwoven fabric forming step] As the support having the plurality of holes, in the field of air-through nonwoven fabrics, a support commonly used can be adopted. For example, a mesh belt, a punching plate, a nickel cylinder, etc. can be mentioned. The support having the plurality of holes may be the same as or different from the support in the fluid application step.

[0077] The conditions for heat-treating the web to which the fluid is applied are not particularly limited as long as they can fuse the heat-fusible fibers, and can be the same as the conditions for fusing the heat-fusible fibers in a general method for manufacturing an air-through nonwoven fabric. For example, when the heat-fusible fiber is a core-sheath type composite fiber, the heat treatment can be carried out at a temperature higher than the resin constituting the sheath part and lower than the resin constituting the core part.

Example

[0078] Hereinafter, the present disclosure will be described with examples, but the present disclosure is not limited to these examples. [Production Example 1] Using the apparatus shown in FIG. 2, nonwoven fabric No. 1 was manufactured. The specific configuration is as follows. 70 parts by mass of core-sheath type composite fiber A (fiber A) (core part / sheath part: PLA (polylactic acid) / PBS (polybutylene succinate), fineness: 2.4 dtex, average fiber length: 51 mm) as a heat-fusible fiber and 30 parts by mass of rayon fiber (fineness: 1.4 dtex, average fiber length: 44 mm) as a cellulose-based fiber were opened dry to form web No. 1.

[0079] Web No. 1 was placed on a mesh belt and conveyed at a speed of 5 m / min in the conveying direction. While being conveyed, curtain-shaped water (length in the direction orthogonal to the conveying direction: 600 mm) was applied from above to Web No. 1 at a speed of 19.4 L / min by free-falling, thereby implementing a fluid application step and forming Web No. 1 with the fluid applied. The applied water was sucked at a suction pressure of 5 KPa using the first suction device 107 and at a suction pressure of 2 KPa using the second suction device 109. Web No. 1 with the fluid applied was passed through a heat treatment device 111 (air temperature: 120 °C, air volume from above to below: 1.3 m / s), thereby forming Nonwoven Fabric No. 1.

[0080] [Production Example 2] Web No. 2, Web No. 2 with the fluid applied, and Nonwoven Fabric No. 2 were formed in the same manner as in Production Example 1, except that the ratios of the heat-fusible fibers and the cellulose-based fibers were as shown in Table 1.

[0081] [Comparative Production Example 3] Web No. 3, Web No. 3 with the fluid applied, and Nonwoven Fabric No. 3 were formed in the same manner as in Production Example 1, except that only heat-fusible fibers were used without including cellulose-based fibers. Nonwoven Fabric No. 3 does not include cellulose-based fibers and corresponds to the comparative example.

[0082] [Production Examples 4 and 5] Web No. 4 and No. 5, Web No. 4 and No. 5 with the fluid applied, and Nonwoven Fabric No. 4 and No. 5 were formed according to Production Example 1, except that the heat-fusible fibers were changed from "core-sheath type composite fiber A" to 'core-sheath type composite fiber B (fiber B) (core / shell: polyethylene terephthalate / polyethylene, fineness: 2.2 dtex, average fiber length: 51 mm)', the ratios of the heat-fusible fibers and the cellulose-based fibers were changed as shown in Table 1, and the air temperature of the heat treatment device was changed to 135 °C.

[0083] [Comparative Production Example 6] A web No.6, a web No.6 to which a fluid was applied, and a nonwoven fabric No.6 were formed in the same manner as in Production Example 4, except that only heat-fusible fibers were used and no cellulose-based fibers were included. Nonwoven fabric No.6 does not contain cellulose-based fibers and corresponds to a comparative example.

[0084] [Comparative Production Examples 7 to 12] Webs No.7 to No.12 and nonwoven fabrics No.7 to No.12 were formed according to Production Examples 1 and 2, Comparative Production Example 3, Production Examples 4 and 5, and Comparative Production Example 6, respectively, except that the fluid application step was omitted. Nonwoven fabrics No.7 to No.12 are general air-through nonwovens and correspond to comparative examples.

[0085] [Production Example 13] An air-through nonwoven fabric No.13 (basis weight: 35 g / m 2 ) was prepared from core-sheath composite fiber C (fiber C) as a heat-fusible fiber (core / shell: polyethylene terephthalate / polyethylene, fineness: 3.3 dtex, average fiber length: 38 mm) and core-sheath composite fiber D (fiber D) (core / shell: polyethylene terephthalate / polyethylene, fineness: 3.4 dtex, average fiber length: 44 mm). A web No.13 (basis weight: 20 g / m 2 ) containing 30 parts by mass of rayon fiber (fineness: 1.4 dtex, average fiber length: 44 mm) as a cellulose-based fiber and 70 parts by mass of synthetic fiber (single fiber of polyethylene terephthalate, fineness: 1.6 dtex, average fiber length: 44 mm) was prepared. The web No.13 was laminated on the air-through nonwoven fabric No.13 to form a laminate No.13, and the laminate No.13 was placed on a support such that the air-through nonwoven fabric No.13 was on the support side.

[0086] The laminate No.13 was subjected to water jet treatment from the web No.13 side under the following conditions and then dried to form a nonwoven fabric No.13. - Diameter of nozzle: 0.1 mm - Pitch of nozzle: 1.0 mm - Distance: 20 mm - Water pressure: 3 MPa (first time), 7 MPa (second and third times) Incidentally, the nonwoven fabric No. 13 contained 11% by mass of cellulosic fibers.

[0087] [Production Examples 14 to 16] Webs No. 14 to 16, laminates No. 14 to 16, and nonwoven fabrics No. 14 to 16 were formed in the same manner as in Production Example 13, except that the ratios of rayon fibers in Web No. 13 were adjusted so as to be as shown in Table 2 for the ratios of heat-fusible fibers and cellulosic fibers. Note that the amount of synthetic fibers is not described in Table 2.

[0088] [Comparative Production Example 17] 70 parts by mass of polyethylene terephthalate fibers (PET fibers) (fineness: 1.6 dtex, average fiber length: 44 mm) and 30 parts by mass of rayon fibers (fineness: 1.4 dtex, average fiber length: 44 mm) as cellulosic fibers were opened dry to form Web No. 17.

[0089] Web No. 17 was subjected to water jet treatment under the following conditions and dried to form nonwoven fabric No. 17. - Diameter of nozzle: 0.1 mm - Pitch of nozzle: 1.0 mm - Distance: 20 mm - Water pressure: 3 MPa × 2 (once from each of one side and the other side of the web)

[0090] [Comparative Production Examples 18 to 20] Webs No. 18 to 20, webs No. 18 to No. 20, and nonwoven fabrics No. 18 to No. 20 were formed in the same manner as in Comparative Production Example 17, except that the ratios of PET fibers and cellulosic fibers were as shown in Table 2. Nonwoven fabrics No. 17 to No. 20 are general spunlace nonwoven fabrics and correspond to the comparative examples.

[0091] [Comparative Production Example 21] A laminated web No. 21 having a three-layer structure of an upper layer, an intermediate layer, and a lower layer was prepared. The upper layer is a web (basis weight: 11 g / m 2 ) containing 60% by mass of core-sheath composite fiber C (fiber C) as a heat-sealable fiber and 40% by mass of core-sheath composite fiber D (fiber D) as a heat-sealable fiber. The intermediate layer is a web (basis weight: 12 g / m 2 ) containing 75% by mass of core-sheath composite fiber D (fiber D) as a heat-sealable fiber and 25% by mass of rayon fiber. The lower layer is a web (basis weight: 7 g / m 2 ) containing 60% by mass of core-sheath composite fiber C (fiber C) as a heat-sealable fiber and 40% by mass of core-sheath composite fiber D (fiber D) as a heat-sealable fiber. The laminated web No. 21 was passed through a heat treatment device to fuse the heat-sealable fibers together, forming nonwoven fabric No. 21.

[0092] [Comparative Production Example 22] The intermediate layer was changed from "a web (basis weight: 12 g / m 2 ) containing 75% by mass of core-sheath composite fiber D (fiber D) as a heat-sealable fiber and 25% by mass of rayon fiber" to "a web (basis weight: 12 g / m 2 ) containing 50% by mass of core-sheath composite fiber D (fiber D) as a heat-sealable fiber and 50% by mass of rayon fiber". Except for this change, laminated web No. 22 and nonwoven fabric No. 22 were formed in the same manner as Comparative Production Example 21.

[0093] [Comparative Production Example 23] The basis weight of the upper layer was changed from "11 g / m 2 " to "14 g / m 2 ". Except for this change, laminated web No. 23 and nonwoven fabric No. 23 were formed in the same manner as Comparative Production Example 21. [Comparative Production Example 24] The basis weight of the upper layer was changed from "11 g / m 2 " to "14 g / m 2 ". Except for this change, laminated web No. 24 and nonwoven fabric No. 24 were formed in the same manner as Comparative Production Example 22.

[0094] [Examples 1 to 8, and Comparative Examples 1 to 16] The types, ratios (mass ratios), and basis weights (g / m2 ) The thickness (mm) and fiber distance (μm) are shown in Tables 1 and 2. Also, the relationship between the ratio of cellulose-based fibers: x (mass ratio) and the fiber distance of the nonwoven fabric: y (μm) in the groups of nonwoven fabrics No. 1, 2, 4, 5, and 13 to 16 (the above are examples) and the groups of nonwoven fabrics No. 3, 6 to 12, and 17 to 24 (the above are comparative examples) is shown in Figure 3.

[0095] The conveying direction strength (N / 25 mm) on the air side of nonwoven fabrics No. 1 to No. 24 was measured according to the method described in this specification. The results are shown in Tables 1 and 2. The relationship between the ratio of cellulose-based fibers: x (mass ratio) and the conveying direction strength (N / 25 mm) of the nonwoven fabric in the groups of nonwoven fabrics No. 1, 2, 4, and 5 (the above are examples) and the groups of nonwoven fabrics No. 8 to 11 (the above are comparative examples) is shown in Figure 4.

[0096]

Table 1

[0097]

Table 2

Explanation of Symbols

[0098] 1 Air-through nonwoven fabric 3 Support surface 5 Air side 7 Heat-fusible fiber 9 Cellulose-based fiber 51 Web 53 Web to which fluid is applied 55 Dehydrated web 101 Manufacturing system 103 Mesh belt 105 Fluid application device 107 First suction device 109 Second suction device 111 Heat treatment device 113 Fluid

Claims

1. A nonwoven fabric for a liquid-permeable sheet of an absorbent article, comprising heat-fusible fibers and cellulosic fibers, wherein the heat-fusible fibers are heat-fused to each other, in the nonwoven fabric, the ratio of the cellulosic fibers: x (mass ratio) and the fiber distance of the nonwoven fabric: y (μm) satisfy the following formula (1): −19x + 70 < y < −70x + 120 Formula (1) wherein 0 < x, satisfying, a nonwoven fabric characterized by this.

2. The nonwoven fabric according to Claim 1, wherein in Formula (1), 0.10 ≦ x ≦ 0.

50.

3. In the nonwoven fabric, the strength in the conveying direction during the production of the nonwoven fabric: z (N / 25 mm) satisfies the following formula (2): −35x + 27 < z Formula (2) The nonwoven fabric according to Claim 1, satisfying this.

4. The nonwoven fabric according to Claim 1, wherein the nonwoven fabric is an air-through nonwoven fabric containing short fibers.

5. The nonwoven fabric according to Claim 1, wherein the heat-fusible fibers are heat-fused to the cellulosic fibers.

6. The nonwoven fabric according to Claim 1, wherein the cellulosic fibers are entangled with each other.

7. The nonwoven fabric according to Claim 1, wherein the heat-fusible fibers are composed of biomass raw materials or recycled raw materials.

8. The nonwoven fabric according to Claim 1, wherein the heat-fusible fibers have biodegradability.

9. The nonwoven fabric according to Claim 1, wherein the cellulosic fibers have hydrophilicity and the heat-fusible fibers have hydrophobicity.

10. A method for manufacturing the nonwoven fabric according to any one of Claims 1 to 9, comprising: a fluid application step of applying a fluid from above to a web containing the heat-fusible fibers and the cellulosic fibers disposed on a support having a plurality of holes to form a web to which the fluid is applied; a nonwoven fabric forming step of heat-treating the web to which the fluid is applied on a support having a plurality of holes to form the nonwoven fabric, characterized by comprising this.

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