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

Abstract

The purpose of the present disclosure is to provide a new nonwoven fabric for a liquid-permeable sheet of an absorbent article.　A nonwoven fabric 1 for a liquid-permeable sheet of an absorbent article comprises heat-fusible fibers 7 and cellulose-based fibers 9, and is characterized in that the heat-fusible fibers 7 are thermally fused to each other, and the ratio of the cellulose-based fibers 9 to the nonwoven fabric 1, which is defined as x (mass ratio), and the interfiber distance of the nonwoven fabric 1, which is defined as y (μm), satisfy the following formula (1): -19x+70<y<-70x+120 (wherein 0<x).

Description

Nonwoven fabric for liquid-permeable sheet of absorbent article and method for manufacturing said nonwoven fabric

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

[0002] Nonwoven fabrics containing cellulosic fibers for absorbent articles have been studied. For example, Patent Document 1 discloses an absorbent sheet (claim 1) formed by intersecting heat-fusible non-hydrophilic fibers mixed with hydrophilic fibers and fixing the intersections by heat fusion, and a method for producing an absorbent sheet (claim 2) characterized by intermixing heat-fusible non-hydrophilic fibers with hydrophilic fibers and heating the mixture to a temperature at which the surfaces of the non-hydrophilic fibers can melt, thereby heat-fusible the intersections of the non-hydrophilic fibers.

[0003] Japanese Patent Application Publication No. 9-188949

[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.

[0005] The present inventors have discovered 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 together, and wherein the ratio x (mass ratio) of the cellulosic fibers in the nonwoven fabric and the inter-fiber distance y (μm) in the nonwoven fabric satisfy the following formula (1): −19x + 70<y<−70x + 120, where 0<x.

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

[0007] Fig. 1 is a diagram illustrating an air-through nonwoven fabric 1 according to a first embodiment. Fig. 2 is a diagram illustrating a manufacturing system 101 for an air-through nonwoven fabric according to a second embodiment. Fig. 3 is a diagram illustrating examples and comparative examples. Fig. 4 is a diagram illustrating examples and comparative examples.

[0008] Specifically, the present disclosure relates to the following aspects: [Aspect 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-fusible to each other, and wherein a ratio x (mass ratio) of the cellulosic fibers in the nonwoven fabric and a fiber-to-fiber distance y (μm) in the nonwoven fabric satisfy the following formula (1): −19x+70<y<−70x+120 Formula (1), where 0<x.

[0009] Examples of nonwoven fabrics containing cellulosic fibers include air-through nonwoven fabrics and spunlace nonwoven fabrics. Air-through nonwoven fabrics are formed by blowing hot air onto a web to heat-seal the heat-sealable fibers. Therefore, air-through nonwoven fabrics manufactured by conventional manufacturing methods (hereinafter referred to as "conventional air-through nonwoven fabrics") can generally contain cellulosic fibers, but it is known that it is difficult to increase the cellulosic fiber content. The present inventors have found that increasing the amount of cellulosic fibers in air-through nonwoven fabrics reduces the interfiber distance, but decreases the number of heat-sealed portions (number per unit volume) formed by the heat-sealable fibers, which tends to reduce the strength of the air-through nonwoven fabric.

[0010] Spunlace nonwoven fabrics are formed by spraying a high-pressure water stream onto a web to entangle the fibers. Therefore, it is relatively easy to increase the amount of cellulosic fiber in spunlace nonwoven fabrics, but the high-pressure water stream reduces the interfiber distance in the resulting nonwoven fabric, and the entanglement of the fibers tends to result in a nonwoven fabric with low strength despite the small interfiber distance.

[0011] In the nonwoven fabric, the heat-fusible fibers are heat-fused together, and a predetermined relationship exists between the cellulosic fiber content and the inter-fiber distance of the nonwoven fabric. This predetermined relationship between the cellulosic fiber content and the inter-fiber distance of the nonwoven fabric cannot be achieved with general air-through nonwoven fabrics or general spunlace nonwoven fabrics, making the nonwoven fabric novel. Furthermore, the nonwoven fabric has a smaller inter-fiber distance and higher strength than a general air-through nonwoven fabric having the same cellulosic fiber content.

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

[0013] In the nonwoven fabric, the cellulosic fiber content is within a predetermined range and the inter-fiber distance is within a predetermined range, so the inter-fiber distance is smaller and the strength is higher than that of a general air-through nonwoven fabric having the same cellulosic fiber content. Furthermore, when the cellulosic fibers include hydrophilic cellulosic fibers described below, the nonwoven fabric is likely to have excellent moisture absorption, sweat absorption, etc. due to the hydrophilic cellulosic fibers.

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

[0015] The nonwoven fabric has a predetermined strength and is therefore superior in strength to a general air-through nonwoven fabric having the same cellulosic fiber content.

[0016] [Aspect 4] The nonwoven fabric according to any one of Aspects 1 to 3, wherein the nonwoven fabric is an air-through nonwoven fabric containing short fibers. Since the nonwoven fabric is a predetermined air-through nonwoven fabric, the effects of Aspect 1 are enhanced.

[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 cellulosic fibers. In the nonwoven fabric, since the heat-fusible fibers are heat-fused to the cellulosic fibers, the strength is superior to that of a nonwoven fabric in which the heat-fusible fibers are not heat-fused to the cellulosic fibers.

[0018] [Aspect 6] The nonwoven fabric according to any one of Aspects 1 to 5, wherein the cellulosic fibers are entangled with each other. In the nonwoven fabric, since the cellulosic fibers are entangled with each other, the strength is superior to that of a nonwoven fabric in which the cellulosic fibers are not entangled with each other.

[0019] [Aspect 7] The nonwoven fabric according to any one of Aspects 1 to 6, wherein the thermally adhesive fibers are made from a biomass material or a recycled material. In the nonwoven fabric, the thermally adhesive fibers are made from a predetermined material, which reduces the environmental impact.

[0020] [Aspect 8] The nonwoven fabric according to any one of Aspects 1 to 7, wherein the thermally adhesive fibers are biodegradable. In the nonwoven fabric, the thermally adhesive fibers are biodegradable, which reduces the environmental impact.

[0021] [Aspect 9] The nonwoven fabric according to any one of aspects 1 to 8, wherein the cellulosic fibers are hydrophilic and the heat-fusible fibers are hydrophobic.

[0022] In the nonwoven fabric, the cellulosic fibers are hydrophilic and the heat-fusible fibers are hydrophobic. Therefore, when the nonwoven fabric is used as a liquid-permeable sheet, particularly a liquid-permeable top sheet, body fluids are easily drawn in the thickness direction through the cellulosic fibers, and the body fluids are less likely to spread in the planar direction.

[0023] Aspect 10 is a method for producing the nonwoven fabric according to any one of Aspects 1 to 9, comprising: a fluid applying step of applying a fluid from above to a web comprising the heat-fusible fibers and the cellulosic fibers, the web being disposed on a support having a plurality of holes, to form a fluid-applied web; and a nonwoven fabric forming step of heat-treating the fluid-applied web on a support having a plurality of holes, to form the nonwoven fabric.

[0024] The above-described manufacturing method allows the nonwoven fabric according to the first aspect to be easily manufactured.

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

[0026] <Nonwoven Fabric> Figure 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 has a support surface 3 and an air surface 5. The air-through nonwoven fabric 1 contains heat-fusible fibers 7 and cellulosic fibers 9. Note that in Figure 1, the heat-fusible fibers 7 are depicted as relatively thick and the cellulosic fibers 9 are depicted as relatively thin for the purpose of distinction, but this does not refer to the fiber diameters of the heat-fusible fibers 7 and the cellulosic fibers 9. Note that the properties of the air-through nonwoven fabric 1 will be described in general terms below.

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

[0028] The liquid-permeable sheet can be any liquid-permeable sheet used in absorbent articles without any particular restrictions, and examples include a liquid-permeable top sheet having a skin-contacting surface, a core wrap covering an absorbent core, a liquid-diffusion sheet (second sheet) disposed between the top sheet and the absorbent core, and a liquid-diffusion sheet (third sheet) disposed between the absorbent core and a liquid-impermeable sheet.

[0029] The nonwoven fabric according to the present disclosure comprises a heat-fusible fiber and a cellulosic fiber. The heat-fusible fiber may be any fiber commonly used in the art, specifically, a fiber containing a low-melting thermoplastic resin and a high-melting thermoplastic resin, without limitation. Preferably, the heat-fusible fiber contains a low-melting thermoplastic resin, such as a polyethylene resin or a low-melting polypropylene, at least on the surface to fuse the heat-fusible fibers together. Examples of the heat-fusible fiber include monocomponent fibers of polyethylene resin; monocomponent fibers of polypropylene resin; sheath-and-core composite fibers having a polyethylene terephthalate resin core and a polyethylene resin sheath; sheath-and-core composite fibers having a polypropylene resin core and a polyethylene resin sheath; sheath-and-core composite fibers having a high-melting polypropylene resin core and a low-melting polypropylene resin sheath; side-by-side composite fibers made of polyethylene terephthalate resin and polyethylene resin; and side-by-side composite fibers made of polypropylene resin and polyethylene resin.

[0030] The heat-fusible fibers are preferably biodegradable, which makes the nonwoven fabric more biodegradable. Examples of the low-melting-point 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, and polylactic acid.

[0031] Examples of the high-melting thermoplastic resin constituting the biodegradable heat-fusible fiber include polylactic acid, polyhydroxybutyrate, polyglycolic acid, and cellulose acetate. The heat-fusible fiber may be a biomass plastic or a recycled fiber.

[0032] The heat-fusible fibers may be hydrophobic without being hydrophilized, or may be hydrophilic through hydrophilization. Examples of the hydrophilization treatment include treatments using surfactants, hydrophilic agents, etc. (e.g., kneading a surfactant into the interior of the heat-fusible fibers, applying a surfactant to the surface of the heat-fusible fibers, etc.), plasma processing, etc.

[0033] The thermally adhesive fibers preferably have a fineness of 0.8 dtex or more, more preferably 0.9 dtex or more. The thermally adhesive fibers preferably have a fineness of 20 dtex or less, more preferably 10 dtex or less, and even more preferably 4 dtex or less. This allows the nonwoven fabric according to the present disclosure to easily maintain a constant thickness under pressure and to have an excellent feel against the skin.

[0034] The thermally adhesive fibers preferably have an average fiber length of 20 mm or more, and more preferably 30 mm or more. The thermally adhesive fibers preferably have an average fiber length of 80 mm or less, and more preferably 60 mm or less. This results in a nonwoven fabric with less unevenness and excellent strength. Furthermore, the nonwoven fabric of the present disclosure has excellent formability.

[0035] In the present disclosure, the average fiber length of the fibers is measured in accordance with "A7.1.1 Method A (standard method) - measuring the length of individual fibers on a graduated glass plate" in "A7.1 Measurement of fiber length" of Annex A of JIS L 1015:2010. This method is a test method equivalent to ISO 6989 published in 1981.

[0036] Examples of the cellulosic fibers include natural cellulose fibers, regenerated cellulose fibers, refined cellulose fibers, and semi-synthetic cellulose fibers. Examples of the natural cellulose fibers include plant fibers such as seed hair fibers (e.g., cotton fibers), bast fibers (e.g., hemp), leaf vein fibers (e.g., Manila hemp), and fruit fibers (e.g., palm).

[0037] The cotton fiber includes Hirsutum cotton fiber (e.g., upland cotton), Barbadense cotton fiber, Arboreum cotton fiber, and Helbaceum cotton fiber. The cotton fiber may also be organic cotton fiber or Pre-Organic Cotton (trademark) fiber. Organic cotton fiber refers to cotton certified by GOTS (Global Organic Textile Standard).

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

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

[0040] The cellulosic fibers, excluding natural cellulosic fibers, preferably have a fineness of 1.0 dtex or more, and more preferably 1.4 dtex or more. Furthermore, the cellulosic fibers, excluding natural cellulosic fibers, preferably have a fineness of 10 dtex or less, and more preferably 6 dtex or less. This allows the nonwoven fabric according to the present disclosure to easily maintain a consistent thickness under dry conditions and pressure, resulting in excellent feel against the skin.

[0041] The cellulosic fibers preferably have an average fiber length of 20 mm or more, more preferably 30 mm or more. The cellulosic fibers preferably have an average fiber length of 80 mm or less, more preferably 60 mm or less. This results in a nonwoven fabric with less unevenness and excellent strength. Furthermore, the nonwoven fabric of the present disclosure has excellent formability.

[0042] By including the cellulosic fibers (hydrophilic cellulosic fibers described below) in the nonwoven fabric according to the present disclosure, the nonwoven fabric according to the present disclosure has, for example, excellent moisture absorption, sweat absorption, etc. Furthermore, by including a high proportion of the cellulosic fibers (hydrophilic cellulosic fibers) in the nonwoven fabric according to the present disclosure, i.e., a low proportion of the heat-fusible fibers, the nonwoven fabric contains a low proportion of fibers derived from crude oil, making it an environmentally friendly nonwoven fabric and enabling it to further contribute to the achievement of the Sustainable Development Goals (SDGs).

[0043] The cellulose-based fibers may be water-repellent cellulose-based fibers that have been treated with a water-repellent agent to impart water repellency. Cellulosic fibers that have not been treated with a water-repellent agent may be referred to as hydrophilic cellulose-based fibers to distinguish them from water-repellent cellulose-based fibers.

[0044] The water-repellent cellulose fibers are disclosed in, for example, JP 2002-266241 A, JP 2003-20570 A, JP 2019-65443 A, JP 2022-58301 A, and the like. For example, Ecorepellent (trade name, water-repellent viscose rayon) manufactured by Daiwabo Rayon Co., Ltd., and Olea (trade name, water-repellent viscose rayon) manufactured by Kelheim Fibres GmbH, and the like are commercially available.

[0045] The nonwoven fabric according to the present disclosure contains water-repellent cellulosic fibers, which result in an excellent dry feel. Furthermore, the nonwoven fabric according to the present disclosure contains a high proportion of the water-repellent cellulosic fibers, i.e., a low proportion of the heat-fusible fibers, which results in a low proportion of fibers derived from crude oil, making the nonwoven fabric environmentally friendly and contributing to the achievement of the Sustainable Development Goals (SDGs).

[0046] The nonwoven fabric according to the present disclosure may further comprise synthetic fibers that are not intended to be heat-sealed. The synthetic fibers may be those containing a single component, such as a monofilament, or those containing multiple components, such as a composite fiber. The synthetic fibers may also be biomass plastics, recycled materials, 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 an average fiber length of 20 to 80 mm. The synthetic fibers may be hydrophobic without being hydrophilized, or may be hydrophilic after being hydrophilized. Examples of hydrophilization treatments include those described above for heat-fusible fibers.

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

[0050] In the nonwoven fabric according to the present disclosure, as described above, the heat-fusible fibers can be hydrophilic or hydrophobic, the cellulosic fibers can be hydrophilic or hydrophobic, and the optional synthetic fibers can be hydrophilic or hydrophobic. The hydrophilicity and hydrophobicity of the heat-fusible fibers, cellulosic fibers, and optional synthetic fibers can be selected as desired depending on the performance required of the liquid-permeable sheet of the absorbent article. In the nonwoven fabric according to the present disclosure, it is preferable that the cellulosic fibers are hydrophilic and the heat-fusible fibers are hydrophobic, and it is preferable that the cellulosic fibers are hydrophilic and the heat-fusible fibers and optional synthetic fibers are hydrophobic. As a result, when the nonwoven fabric is used in a liquid-permeable sheet, particularly a liquid-permeable top sheet, body fluids are easily drawn in the thickness direction via the cellulosic fibers, and body fluids are less likely 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. Furthermore, in the nonwoven fabric according to the present disclosure, it is preferable that the heat-fusible fibers and the cellulosic fibers are heat-fused to each other. This results in a nonwoven fabric with superior strength compared to a fabric in which the heat-fusible fibers are not heat-fused to the cellulosic fibers. In the nonwoven fabric according to the present disclosure, it is preferable that the cellulosic fibers are entangled with each other. Furthermore, in the nonwoven fabric according to the present disclosure, it is preferable that the cellulosic fibers and the heat-fusible fibers are entangled with each other. This results in a nonwoven fabric with superior strength compared to a fabric in which the cellulosic fibers are not entangled with each other.

[0052] In the nonwoven fabric according to the present disclosure, the ratio x (mass ratio) of the cellulosic fibers and the inter-fiber distance y (μm) of the nonwoven fabric satisfy the following formula (1): −19x + 70<y<−70x + 120 Formula (1), where 0<x. As a result, the nonwoven fabric has a smaller inter-fiber distance and therefore higher strength than a typical air-through nonwoven fabric having the same cellulosic fiber content.

[0053] In formula (1), the inter-fiber distance y (μm) of the nonwoven fabric is within the range surrounded by two predetermined straight lines. These two predetermined straight lines are called the upper straight line (in formula (1), the straight line y = -70x + 120) and the lower straight line (in formula (1), the straight line y = -19x + 70).

[0054] In formula (1), x represents the ratio (mass ratio) of cellulosic fibers to the total amount of the nonwoven fabric. In formula (1), x is 0<x, preferably 0.10≦x, more preferably 0.15≦x, and even more preferably 0.20≦x. Furthermore, in formula (1), the upper limit of X is the intersection of the upper and lower straight lines. x is preferably x≦0.60, more preferably x≦0.50, even more preferably x≦0.45, and even more preferably x≦0.40. This results in a smaller interfiber distance and therefore higher strength compared to a typical air-through nonwoven fabric having the same cellulosic fiber content. Furthermore, when the cellulosic fibers contain hydrophilic cellulosic fibers, the nonwoven fabric is more likely to have excellent moisture absorption, sweat absorption, and other properties due to the hydrophilic cellulosic fibers.

[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, even 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 even more preferably y = -19x + 77. As a result, the nonwoven fabric has a smaller interfiber distance and therefore higher strength than a typical air-through nonwoven fabric having the same cellulosic fiber content.

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

[0057] In the present disclosure, the inter-fiber distance: y (μm) is measured and calculated as follows: In the formula, T means the thickness (cm) of the nonwoven fabric, and B means the basis weight (g / m2 ), and α i means the ratio (mass%) of the i-th fiber, and Dt i represents the fineness (dtex) of the i-th fiber.

[0058] In the present disclosure, the thickness (mm, cm) of the nonwoven fabric is measured using an FS-60DS (measurement surface 44 mm (diameter), measurement pressure 3 g / cm) manufactured by Daiei Scientific Instruments Co., Ltd. 2 Five different points of the nonwoven fabric are pressed under standard conditions (temperature 23±2°C, relative humidity 50±5%), and the average of five measured values ​​is taken.

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

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

[0061] In the present disclosure, the strength of a nonwoven fabric in the machine direction during production is measured by the following machine direction strength test. [Machine Direction Strength Test] (1) A nonwoven fabric is cut into a size of 150 mm x 25 mm (longitudinal direction x transverse direction) to form a test sample. The test sample is cut so that the longitudinal direction coincides with the machine direction (MD) of the nonwoven fabric during production. (2) Using a tensile tester (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 used as the machine direction strength (N / 25 mm).

[0062] The nonwoven fabric according to the present disclosure is not particularly limited, and examples thereof include air-through nonwoven fabrics, and nonwoven fabrics obtained by laminating a web containing cellulosic fibers onto an air-through nonwoven fabric containing heat-fusible fibers and hydroentangling the laminate. The nonwoven fabric is preferably an air-through nonwoven fabric, and more preferably an air-through nonwoven fabric containing staple fibers. This provides excellent effects of the present disclosure. The fiber length of the staple fibers may be the average fiber length described above for heat-fusible fibers and cellulosic fibers.

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

[0064] In order to function as a liquid-permeable sheet in an absorbent article, the nonwoven fabric according to the present disclosure 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 even more preferably 0.6 mm or more. For the same reasons, 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 even 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, may be referred to as "second embodiment"). Note that the nonwoven fabric manufacturing system 101 is for manufacturing the through-air 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 arranged above the mesh belt 103, (iii) a first suction device 107 arranged below the fluid application device 105 with the mesh belt 103 sandwiched therebetween, (iv) a second suction device 109 arranged below the mesh belt 103 and downstream of the first suction device 107 in the conveying direction MD, and (v) a heat treatment device 111 arranged downstream of the second suction device 109 and covering the mesh belt 103 from above and below.

[0067] A web 51 containing heat-fusible fibers is placed on a mesh belt 103 and transported in the machine direction MD. The web 51 is formed by dry-spreading the heat-fusible fibers.

[0068] Next, a fluid 113 (specifically, water) is applied to the web 51 from the fluid application device 105, and the applied fluid 113 is sucked from a first suction device 107 disposed below the fluid application device 105, thereby forming a fluid-applied web 53. The fluid application device 105 supplies the fluid 113 in a curtain-like manner so as to extend in the cross direction CD perpendicular to the machine direction MD. By applying the fluid from the fluid application device 105, the formed air-through nonwoven fabric 1 is more likely to have a predetermined inter-fiber distance.

[0069] Next, the second suction device 109 is used to suck out the moisture remaining in the web 53 to which the fluid has been applied, thereby forming a dehydrated web 55. Next, the dehydrated web 55 is passed through a heat treatment device 111 to fuse the heat-fusible fibers in the dehydrated web 55, thereby forming the through-air nonwoven fabric 1. In the heat treatment device 111, heated air is passed from above to below through the dehydrated web 55 and the mesh belt 103, thereby fusing the heat-fusible fibers in the dehydrated web 55.

[0070] The method for producing a nonwoven fabric according to the present disclosure includes the following steps: - a fluid application step of applying a fluid from above to a web containing the heat-fusible fibers and the cellulosic fibers, which is placed on a support having a plurality of holes, to form a fluid-applied web (hereinafter referred to as the "fluid application step"); - a nonwoven fabric formation step of heat-treating the fluid-applied web on a support having a plurality of holes, to form the nonwoven fabric (hereinafter referred to as the "nonwoven fabric formation step").

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

[0072] The fluid is not particularly limited and examples thereof include water, steam, air, etc. The fluid is preferably applied to the entire web, from the viewpoint that the formed nonwoven fabric is likely to have a predetermined inter-fiber distance, and for example, the fluid is preferably applied to the web in the form of a curtain.

[0073] Furthermore, it is preferable that the fluid does not heat-seal the heat-fusible fibers contained in the web, and for example, the temperature of the fluid is preferably lower than the melting point or softening point of the heat-fusible fibers contained in the web. When the heat-fusible fibers are composite fibers, the temperature of the fluid is preferably lower than the melting point of the heat-fusible resin with a low melting point. This is because the nonwoven fabric formed in the subsequent nonwoven fabric formation step will be less likely to have the specified inter-fiber distance.

[0074] The fluid has a basis weight of 20 to 100 g / m 2 It is preferable that the flow rate per meter of length in the direction perpendicular to the conveying direction is 10 to 40 L / min.

[0075] The fluid is preferably sucked from below the support, because this makes it easier for the formed nonwoven fabric to have a predetermined inter-fiber distance. The suction pressure for sucking the fluid from below the support can be selected, for example, from the viewpoint of smoothing the support surface and the air surface of the web, making it difficult for water to remain on the web, etc., and examples of the suction pressure include more than 0 KPa, 1 KPa or more, 2 KPa or more, 25 KPa or less, 20 KPa or less, 15 KPa or less, and 10 KPa or less.

[0076] [Nonwoven Fabric Formation Step] The support having a plurality of holes may be a support commonly used in the field of air-through nonwoven fabrics, such as a mesh belt, a punching plate, a nickel cylinder, etc. The support having a 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 has been applied are not particularly limited as long as they are capable of fusing the heat-fusible fibers, and can be the same as the conditions for fusing heat-fusible fibers in a general method for producing an air-through nonwoven fabric. For example, when the heat-fusible fibers are core-sheath type composite fibers, the heat treatment can be carried out at a temperature higher than that of the resin constituting the sheath and lower than that of the resin constituting the core.

[0078] The present disclosure will be described below using examples, but the present disclosure is not limited to these examples. [Production Example 1] Nonwoven fabric No. 1 was produced using the apparatus shown in Figure 2. The specific configuration is as follows. Web No. 1 was formed by dry-spreading 70 parts by mass of core-sheath composite fiber A (fiber A) (core / sheath: 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 cellulosic fiber.

[0079] Web No. 1 was placed on a mesh belt and conveyed in the conveying direction at a speed of 5 m / min. A fluid application step was performed by applying a curtain of water (length in the direction perpendicular to the conveying direction: 600 mm) from above to Web No. 1 by free-fall at a rate of 19.4 L / min onto Web No. 1, thereby forming Web No. 1 to which the fluid had been applied. The applied water was sucked using a first suction device 107 at a suction pressure of 5 KPa and a second suction device 109 at a suction pressure of 2 KPa. Web No. 1 to which the fluid had been applied was passed through a heat treatment device 111 (air temperature: 120°C, air flow rate from above to below: 1.3 m / sec) to form nonwoven fabric No. 1.

[0080] [Production Example 2] Web No. 2, fluid-applied web No. 2, 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 cellulosic fibers were as shown in Table 1.

[0081] Comparative Production Example 3 Web No. 3, fluid-applied web No. 3, and nonwoven fabric No. 3 were formed in the same manner as Production Example 1, except that no cellulosic fibers were included and only heat-fusible fibers were used. Nonwoven fabric No. 3 did not include cellulosic fibers and corresponds to a comparative example.

[0082] [Production Examples 4 and 5] Webs No. 4 and No. 5, fluid-applied Webs No. 4 and No. 5, and nonwoven fabrics No. 4 and No. 5 were formed in accordance with Production Example 1, except that the heat-fusible fiber was changed from "core-sheath type composite fiber A" to "core-sheath type composite fiber B (fiber B) (core / sheath: polyethylene terephthalate / polyethylene, fineness: 2.2 dtex, average fiber length: 51 mm)," the ratio of the heat-fusible fiber to the cellulosic fiber was 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 Web No. 6, fluid-applied web No. 6, and nonwoven fabric No. 6 were prepared in the same manner as in Production Example 4, except that no cellulosic fibers were used and only heat-fusible fibers were used. Nonwoven fabric No. 6 did not contain cellulosic 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 Examples 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 were general air-through nonwoven fabrics and correspond to comparative examples.

[0085] [Production Example 13] An air-through nonwoven fabric No. 13 (basis weight: 35 g / m) was prepared from a core-sheath type composite fiber C (fiber C) (core / sheath: polyethylene terephthalate / polyethylene, fineness: 3.3 dtex, average fiber length: 38 mm) as a heat-fusible fiber and a core-sheath type composite fiber D (fiber D) (core / sheath: polyethylene terephthalate / polyethylene, fineness: 3.4 dtex, average fiber length: 44 mm). 2Web No. 13 (basis weight: 20 g / m) 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. 2 ) was prepared. Web No. 13 was laminated on air-through nonwoven fabric No. 13 to form laminate No. 13, and laminate No. 13 was placed on a support so that air-through nonwoven fabric No. 13 faced the support.

[0086] Laminate No. 13 was subjected to a water jet treatment from the side of Web No. 13 under the following conditions, followed by drying, to form Nonwoven Fabric No. 13: Nozzle diameter: 0.1 mm Nozzle pitch: 1.0 mm Distance: 20 mm Water pressure: 3 MPa (first pass), 7 MPa (second and third passes) Nonwoven Fabric No. 13 contained 11% by mass of cellulosic fibers.

[0087] [Production Examples 14 to 16] Webs Nos. 14 to 16, laminates Nos. 14 to 16, and nonwoven fabrics Nos. 14 to 16 were formed in the same manner as in Production Example 13, except that the ratio of rayon fiber in Web No. 13 was adjusted so that the ratios of heat-fusible fiber and cellulosic fiber were as shown in Table 2. Table 2 does not list the amount of synthetic fiber.

[0088] Comparative Production Example 17 Web No. 17 was formed by dry-spreading 70 parts by mass of polyethylene terephthalate fiber (PET fiber) (fineness: 1.6 dtex, average fiber length: 44 mm) and 30 parts by mass of rayon fiber (fineness: 1.4 dtex, average fiber length: 44 mm) as a cellulose-based fiber.

[0089] Web No. 17 was subjected to a water jet treatment under the following conditions, followed by drying, to form nonwoven fabric No. 17: nozzle diameter: 0.1 mm, nozzle pitch: 1.0 mm, distance: 20 mm, water pressure: 3 MPa x 2 (once from one side and once from the other side of the web).

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

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

[0092] Comparative Production Example 22: The intermediate layer was formed from a web (basis weight: 12 g / m) containing 75% by mass of core-sheath type composite fiber D (fiber D) as a heat-fusible fiber and 25% by mass of rayon fiber. 2 "A web (basis weight: 12 g / m) containing 50% by mass of core-sheath type composite fiber D (fiber D) as a heat-fusible fiber and 50% by mass of rayon fiber. 2 Laminated web No. 22 and nonwoven fabric No. 22 were formed in the same manner as in Comparative Production Example 21, except that the above-mentioned "

[0093] Comparative Production Example 23: The basis weight of the upper layer was set to "11 g / m 2 " to "14 g / m 2 Laminated web No. 23 and nonwoven fabric No. 23 were prepared in the same manner as in Comparative Production Example 21, except that the basis weight of the upper layer was changed to "11 g / m2." 2 " to "14 g / m 2Laminated web No. 24 and nonwoven fabric No. 24 were formed in the same manner as in Comparative Production Example 22, except that the above-mentioned step (1) was changed to "."

[0094] [Examples 1 to 8 and Comparative Examples 1 to 16] Types, ratios (mass ratios), and basis weights (g / m) of thermal adhesive fibers and cellulosic fibers of nonwoven fabrics No. 1 to No. 24 2 The thickness (mm) and inter-fiber distance (μm) of the nonwoven fabric are shown in Tables 1 and 2. The relationship between the ratio of cellulosic fibers x (mass ratio) and the inter-fiber distance y (μm) of the nonwoven fabric for Nonwoven Fabrics Nos. 1, 2, 4, 5, and 13 to 16 (all of which are Examples) and Nonwoven Fabrics Nos. 3, 6 to 12, and 17 to 24 (all of which are Comparative Examples) is shown in Figure 3.

[0095] The machine direction strength (N / 25 mm) of the air side of nonwoven fabrics No. 1 to No. 24 was measured according to the method described herein. The results are shown in Tables 1 and 2. The relationship between the cellulosic fiber ratio x (mass ratio) and the machine direction strength (N / 25 mm) of the nonwoven fabrics for Nonwoven Fabrics No. 1, 2, 4, and 5 (all of which are Examples) and Nonwoven Fabrics No. 8 to 11 (all of which are Comparative Examples) is shown in Figure 4.

[0096]

[0097]

[0098] REFERENCE SIGNS LIST 1 Air-through nonwoven fabric 3 Support surface 5 Air surface 7 Heat-fusible fiber 9 Cellulosic fiber 51 Web 53 Fluid-applied web 55 Dewatered 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 a heat-fusible fiber and a cellulose-based fiber, wherein the heat-fusible fibers are heat-fused to each other, and 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) where 0 < x, characterized nonwoven fabric.

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 or 2.

4. The nonwoven fabric according to any one of claims 1 to 3, wherein the nonwoven fabric is an air-through nonwoven fabric containing short fibers.

5. The nonwoven fabric according to any one of claims 1 to 4, wherein the heat-fusible fiber is heat-fused to the cellulose-based fiber.

6. The nonwoven fabric according to any one of claims 1 to 5, wherein the cellulose-based fibers are entangled with each other.

7. The nonwoven fabric according to any one of claims 1 to 6, wherein the heat-fusible fiber is composed of a biomass raw material or a recycled raw material.

8. The nonwoven fabric according to any one of claims 1 to 7, wherein the heat-fusible fiber has biodegradability.

9. The nonwoven fabric according to any one of claims 1 to 8, wherein the cellulose-based fiber has hydrophilicity and the heat-fusible fiber has 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 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. Characterized by the above method.

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