JP2022122854A - Nonwoven fabric for absorbent articles and method of producing the same, and top-sheet for absorbent articles and absorbent article containing the same - Google Patents

Abstract

To provide a nonwoven fabric for absorbent articles suited for use as a top-sheet or the like, which nonwoven fabric has a smoother feel, is less prone to fluffing, and has superior liquid absorbency.CONSTITUTION: The nonwoven fabric for absorbent articles includes a first fibrous layer and a second fibrous layer, wherein one surface of the first fibrous layer forms a surface of the nonwoven fabric, the other surface is in contact with the second fibrous layer, the fiber layer includes an adhesive fiber and a first hydrophilic fiber, the second fiber layer includes a second hydrophilic fibers, the adhesive fibers in the first fiber layer allow the fibers to adhere to each other, the first fiber layer and the second fiber layer are integrated by entangling the fibers, the radius of curvature (φ1) of the fiber on the surface of the first fiber layer is 30 μm or more, the radius of curvature (φ2) of the fibers on the surface of the second fiber layer is 40 μm or less, φ1>φ2 is satisfied, and the first fiber layer is arranged closer to the user's skin.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present disclosure relates to a nonwoven fabric for absorbent articles, a method for producing the same, a topsheet for absorbent articles, and absorbent articles including the same.

One of the uses of nonwoven fabrics includes members constituting absorbent articles such as pantiliners, sanitary napkins, disposable diapers for infants, and disposable diapers for nursing care, such as top sheets (also referred to as top sheets or surface materials). . So far, nonwoven fabrics used for top sheets for absorbent articles, etc. from the viewpoint of the feel that the skin feels, the comfort when using the absorbent article, the liquid absorption when body fluid is released, and the liquid backflow prevention. have been proposed.

For example, Patent Document 1 includes cellulosic fibers and adhesive fibers, includes bonding points between the adhesive fibers and cellulosic fibers and/or adhesive fibers, cellulosic fibers and cellulosic fibers and/or adhesive A nonwoven fabric that includes entangled points with fibers and has an adhesive intersection index of 1 to 60 pieces/mm ² or a thickness reduction rate of 30 to 45% is applied to human skin such as an absorbent article. We propose to use it for applications that come in direct contact with it.

Patent Document 2 discloses a fiber sheet containing cotton fibers and two or more different synthetic fibers, wherein the two or more synthetic fibers form a nonwoven fabric, and the cotton fibers enter into the fiber network of the nonwoven fabric and the fibers A fiber sheet formed on one side of the nonwoven fabric by being entangled with a network in a state in which a cotton fiber layer partially enters the nonwoven fabric, wherein the fiber sheet comprises a specific combination of two or more synthetic fibers. Suggest. Patent Document 2 proposes incorporating this fiber sheet into an absorbent article so that the cotton fiber layer faces the user's body.

WO2019/151527 pamphlet Japanese Patent Application Laid-Open No. 2004-324038

Since the top sheet of the absorbent article is in direct contact with the user's skin, the tactile sensation is important, and the ability (absorbency) to quickly absorb blood and excrement and move it to the absorbent side is also important. be. Furthermore, since the absorbent article is used in a delicate part, it is natural that the members constituting the absorbent article should be manufactured in consideration of sanitation in a substantial aspect, and the appearance should also be clean. There is a tendency to desire to give a hygienic impression. For example, in the case of the top sheet, if the fibers become fuzzy when the top sheet is opened or during use, the user may feel unsanitary and hesitate to use the top sheet. Furthermore, when the fuzzy fibers fall off and adhere to the user's body or clothes, the user's discomfort is further increased.

INDUSTRIAL APPLICABILITY The present disclosure provides a nonwoven fabric for absorbent articles that is suitable for use as a top sheet or the like that has a smoother feel, is less prone to fluffing, and exhibits good liquid absorbency.

This disclosure is
A nonwoven fabric for absorbent articles comprising a first fiber layer and a second fiber layer,
one surface of the first fiber layer forms the surface of the nonwoven fabric, and the other surface is in contact with the second fiber layer;
The first fiber layer includes adhesive fibers and first hydrophilic fibers,
The first fiber layer contains 40% to 75% by mass of the adhesive fiber and 25% to 60% by mass of the first hydrophilic fiber, based on the total mass of the first fiber layer. ,
The second fiber layer comprises a second hydrophilic fiber,
The second fiber layer contains 70% by mass or more and 100% by mass or less of the second hydrophilic fiber based on the total mass of the second fiber layer,
In the first fiber layer, the fibers are bonded to each other by the adhesive fibers,
The first fiber layer and the second fiber layer are integrated by entangling the fibers,
The radius of curvature (φ1) of the fibers on the surface of the first fiber layer is 30 μm or more, the radius of curvature (φ2) of the fibers on the surface of the second fiber layer is 40 μm or less, and φ1>φ2 is satisfied;
wherein the first fibrous layer is positioned closer to the user's skin;
A nonwoven fabric for absorbent articles is provided.

The nonwoven fabric for absorbent articles according to the present disclosure comprises a first fiber layer containing hydrophilic fibers and adhesive fibers, and a second fiber layer in which the proportion of hydrophilic fibers is a predetermined value or more, and the first fiber layer The hydrophilic fibers and the adhesive fibers are adhered to each other, and the fibers are entangled so that the degree of entanglement of the fibers in each fiber layer is different. With this configuration, in the nonwoven fabric for absorbent articles of the present disclosure, the surface of the first fiber layer on the side closer to the user's skin provides a smooth feel, and the second fiber layer serves to draw in bodily fluids. Furthermore, since both the first fiber layer and the second fiber layer contain hydrophilic fibers and are entangled with each other, the generation of fluff is further suppressed.

4 is an electron micrograph showing the surface of the nonwoven fabric produced in Example 1 on the side of the second fiber layer.

(Circumstances leading to this embodiment)
In Patent Document 1, in order to achieve a soft texture and suppress fuzz, cellulosic fibers and adhesive fibers are used to form a web by a carding machine, and then an adhesion treatment is performed, and then a hydroentanglement treatment is performed. Therefore, techniques for manufacturing nonwoven fabrics have been proposed. The same document also describes a nonwoven fabric produced by laminating webs in which two kinds of fibers are mixed at different ratios, and performing adhesion treatment and hydroentanglement treatment. However, the nonwoven fabric described in Patent Document 1 still has room for improvement in terms of fluff suppression and liquid absorbency.

As a result of repeated studies by the present inventors, in terms of suppressing fuzz in nonwoven fabrics using hydrophilic fibers, particularly cellulose fibers, entanglement of fibers is more effective than fixation of fibers by thermal bonding or the like. It has been found to be more effective to make it stronger. In order to strengthen the entanglement between fibers, for example, it is necessary to increase the water pressure during the hydroentanglement treatment and/or increase the number of times the water jet is sprayed on the web. However, if the degree of entanglement between fibers is increased, streak-like irregularities formed on the surface of the nonwoven fabric due to jetting water become more pronounced, which reduces the smoothness of the surface of the nonwoven fabric. In addition, when hydrophilic fibers are used, the more the fibers are entangled, the more likely the softness of the nonwoven fabric as a whole is impaired, and the voids between the fibers are reduced or reduced, resulting in a decrease in liquid absorbency. There is a tendency.

Patent Document 2 proposes a configuration in which a nonwoven fabric made of thermoadhesive fibers and a cotton fiber layer are combined on the premise that the cotton fiber layer side contacts the user's skin. Therefore, when the nonwoven fabric described in this document is used as a top sheet of an absorbent article, body fluids from the user first come into contact with the cotton fiber layer and then move toward the absorbent body. Since cotton fibers have high water absorption and liquid retention properties, the nonwoven fabric described in the same document tends to retain liquid in the cotton fiber layer, resulting in increased liquid return. If the liquid backflow is large, the skin tends to become wet during use, which may cause discomfort to the user. In addition, when the cotton fiber layer retains body fluids (especially blood), the color of the body fluids tends to appear on the surface of the nonwoven fabric, which may cause discomfort to the user during or after use.

In view of these problems, the present inventors have found that in a nonwoven fabric having a laminated structure, each fiber layer contains a hydrophilic fiber in a predetermined ratio, thereby suppressing fluff due to entanglement between hydrophilic fibers and reducing the thickness. We investigated a configuration that enhances liquid absorbency by forming a hydrophilic gradient in the direction. Furthermore, adhesive fibers are contained in the fiber layer on the side that contacts the skin of the user, and the fibers in the fiber layer are bonded to each other to integrate the fibers to some extent, and the degree of entanglement of the fiber layer on the side that contacts the skin is reduced. The degree of entanglement was less than that of the fiber layer on the opposite side. As a result, according to the nonwoven fabric for absorbent articles of the present embodiment (hereinafter also simply referred to as "nonwoven fabric"), a smooth feel, improved liquid absorbency, and reduced fluff are realized. In such a configuration, the fiber layer on the side in contact with the skin contains hydrophilic fibers and adhesive fibers, is subjected to adhesion treatment, and then a fiber layer containing a higher proportion of hydrophilic fibers is laminated, It is obtained by entangling and integrating by a predetermined method.
The nonwoven fabric of this embodiment will be described below.

(First embodiment)
The nonwoven fabric of this embodiment is a nonwoven fabric for absorbent articles including a first fiber layer and a second fiber layer,
one surface of the first fiber layer forms the surface of the nonwoven fabric, and the other surface is in contact with the second fiber layer;
The first fiber layer includes adhesive fibers and first hydrophilic fibers,
The first fiber layer contains 40% to 75% by mass of the adhesive fiber and 25% to 60% by mass of the first hydrophilic fiber, based on the total mass of the first fiber layer. ,
The second fiber layer comprises a second hydrophilic fiber,
The second fiber layer contains 70% by mass or more and 100% by mass or less of the second hydrophilic fiber based on the total mass of the second fiber layer,
In the first fiber layer, the fibers are bonded to each other by the adhesive fibers,
The first fiber layer and the second fiber layer are integrated by entangling the fibers,
The radius of curvature (φ1) of the fibers on the surface of the first fiber layer is 30 μm or more, the radius of curvature (φ2) of the fibers on the surface of the second fiber layer is 40 μm or less, and φ1>φ2 is satisfied;
wherein the first fibrous layer is positioned closer to the user's skin;
It is a nonwoven fabric for absorbent articles.
First, the fibers that constitute the nonwoven fabric of the present embodiment will be described below.

(adhesive fiber)
"Adhesive fiber" means that adhesiveness is exhibited by adhesion treatment (e.g., thermal adhesion treatment, electron beam irradiation, ultrasonic welding (ultrasonic welder), etc.), and the fibers are adhered to each other to form an adhesion point. It refers to a fiber that can be used, and is not particularly limited as long as the nonwoven fabric targeted by the present disclosure can be obtained.

Adhesive fibers include, for example, synthetic fibers made of thermoplastic resin.
The thermoplastic resin is not particularly limited, for example, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polylactic acid, polybutylene succinate and copolymers thereof; polypropylene, polyethylene ( high-density polyethylene, low-density polyethylene, linear low-density polyethylene, etc.), polybutene-1, propylene copolymers containing propylene as the main component (propylene-ethylene copolymer, propylene-butene-1-ethylene copolymer polyolefin resins such as ethylene-acrylic acid copolymers and ethylene-vinyl acetate copolymers; polyamide resins such as nylon 6, nylon 12 and nylon 66; acrylic resins; polycarbonate, polyacetal, polystyrene , engineering plastics such as cyclic polyolefins, and elastomers thereof. Synthetic fibers may be produced using one or more thermoplastic resins arbitrarily selected from these.

Synthetic fibers may be single fibers composed of one or more thermoplastic resins selected from those listed above, or they may be composite fibers composed of two or more components (also referred to as "sections"). In the conjugate fiber, each component may consist of one thermoplastic resin, or may be a mixture of two or more thermoplastic resins. The conjugate fibers may be, for example, core-sheath conjugate fibers, islands-in-the-sea conjugate fibers, or side-by-side conjugate fibers. The core-sheath type conjugate fiber may be an eccentric core-sheath type conjugate fiber in which the center of the core component and the center of the sheath component do not coincide in the cross section of the fiber, and the concentric core in which the center of the core component and the center of the sheath component coincide in the cross section of the fiber. It may be a sheath type composite fiber. In this embodiment, a concentric core-sheath type conjugate fiber may be used in order to make the nonwoven fabric more smooth to the touch. The concentric core-sheath type conjugate fiber can make the nonwoven fabric more dense. The bicomponent fibers may also be split bicomponent fibers.

Synthetic fibers, whether single fibers or composite fibers, may have a circular cross-section or may have an irregular cross-section (non-circular cross-section). In the case of the core-sheath type conjugate fiber and the islands-in-sea type conjugate fiber, the core component and/or the island component may have an irregular cross section in the cross section of the fiber.
When the synthetic fiber has a modified cross-section, the cross-section may be elliptical, polygonal, star-shaped, or shaped with multiple protrusions joined at the base (eg, clover-shaped).
In this embodiment, two or more synthetic fibers may be used in combination as the synthetic fibers.

When the synthetic fiber is a bicomponent fiber, two or more components may be arranged such that the lower melting thermoplastic resin constitutes a portion of the fiber surface. A low melting point thermoplastic resin (low melting point component) melts or softens when heat is applied in the process of producing a nonwoven fabric, and becomes an adhesive component. The low melting point component may contribute to adhesion between fibers or adhesion to other members to form bond points.
When the synthetic fiber is a conjugate fiber, the low-melting-point component may be exposed in the cross section of the fiber over a length of, for example, 40% or more, particularly 50% or more, of the length of the peripheral surface of the fiber. more particularly over 60% of the length, and even more particularly over 80% of the length. Alternatively, the low melting point component may be exposed over the entire circumference of the fiber.

When the synthetic fiber is a core-sheath type composite fiber, the composite ratio of core and sheath (volume ratio, core/sheath) may be, for example, 80/20 to 20/80, particularly 60/40 to 40/60. It's okay. When the core/sheath composite ratio is within this range, the adhesion between the fibers is moderate. Further, when the composite ratio of core/sheath is within this range, when the nonwoven fabric is manufactured by carrying out the entangling process after the adhering process, excessive peeling of the bonded portions in the entangling process does not occur. Further, when the core/sheath composite ratio is within this range, the fiber shape is easily maintained by the core component, and the strength of the nonwoven fabric can be made suitable.

The adhesive component of the adhesive fiber (the low melting point component in the case of composite fibers) may be a copolymer of an olefin and an unsaturated carboxylic acid or derivative thereof. Such copolymers exhibit good adhesion to cellulosic fibers, which are an example of hydrophilic fibers. Examples of unsaturated carboxylic acids include maleic acid, acrylic acid, methacrylic acid, fumaric acid, and itaconic acid, and derivatives thereof include unsaturated carboxylic acid anhydrides, methyl methacrylate, ethyl methacrylate, and 2-hydroxy methacrylate. Ethyl, methacrylic acid esters such as dimethylaminoethyl methacrylate, or similar acrylic acid esters, glycidyl acrylate, glycidyl methacrylate, butene carboxylic acid esters, allyl glycidyl ether, 3,4-epoxybutene, 5,6-epoxy -1-hexene, vinylcyclohexene monoxide and the like. Particularly preferred is an ethylene-acrylic acid copolymer in which the olefin is ethylene and the unsaturated carboxylic acid or its derivative is acrylic acid or its derivative.

Combinations of thermoplastic resins that make up the conjugate fibers include, for example, combinations of polyolefin resins such as polyethylene/polyethylene terephthalate, polypropylene/polyethylene terephthalate, and propylene copolymer/polyethylene terephthalate, and polyester resins (polyolefin resin/polyester resins), combinations of two types of polyolefin resins such as polyethylene/polypropylene, propylene copolymer/polypropylene, ethylene-acrylic acid copolymer/polypropylene, and combinations of two types of polyester resins with different melting points. .

When the synthetic fiber is a core-sheath type conjugate fiber in which a thermoplastic resin having a lower melting point constitutes the sheath, the core/sheath combination is, for example, polyethylene terephthalate/polyethylene, polyethylene terephthalate/polypropylene, or polyethylene terephthalate/propylene. Polymers, polytrimethylene terephthalate/polyethylene, polybutylene terephthalate/polyethylene, polyethylene terephthalate/copolyester (e.g. polyethylene terephthalate copolymerized with isophthalic acid), polypropylene/ethylene-acrylic acid copolymer, polylactic acid/polybutylene Contains succinate. These combinations can also be applied to composite fibers other than core-sheath type composite fibers. A core-sheath type composite fiber whose sheath is polyethylene (e.g., high-density polyethylene, low-density polyethylene, or linear low-density polyethylene) or copolyester is heat-treated at a temperature equal to or higher than the melting point of the thermoplastic resin constituting the sheath. By doing so, the sheath melts or softens, and has the property of bonding the fibers together to form a bonding point.

The thermoplastic resin exemplified as the component of the single fiber or the composite fiber may contain other components as long as it contains 50% by mass or more of the specifically indicated thermoplastic resin. For example, in the combination of polyethylene/polyethylene terephthalate, "polyethylene" may contain other thermoplastic resins and additives as long as it contains 50% by mass or more of polyethylene. This also applies in the following examples.

When the adhesive fibers are synthetic fibers, the surface of the fibers may be coated with a hydrophilic fiber treatment agent. When the nonwoven fabric of the present embodiment is produced by a method including entangling treatment with a high-pressure fluid stream (especially water stream), by making the surface of the synthetic fiber, which is hydrophobic, hydrophilic, the entanglement between the fibers is promoted, and the texture is improved. And/or it is easy to obtain a nonwoven fabric which is advantageous in terms of mechanical properties.

The hydrophilic fiber treatment agent to be applied to the adhesive fibers is not particularly limited, and those known in the technical field of synthetic fibers or those similar thereto may be used. Hydrophilic fiber treatment agents include fiber treatment agents containing various surfactants. As surfactants, anionic, cationic, amphoteric and nonionic surfactants and the like can be used.

Examples of anionic surfactants include alkyl phosphate sodium salts, alkyl ether phosphate sodium salts, dialkyl phosphate sodium salts, dialkyl sulfosuccinate sodium salts, alkylbenzene sulfonate sodium salts, alkyl sulfonate sodium salts, and alkyl sulfate sodium salts. can be done. In the anionic surfactant, each alkyl preferably has 6 to 22 carbon atoms. Further, in these anionic surfactants, other alkali metal salts such as potassium salts or alkaline earth metal salts (for example, magnesium salts) can be used instead of sodium salts.

Examples of cationic surfactants include alkyl (or alkenyl)trimethylammonium halides, dialkyl (or alkenyl)dimethylammonium halides, alkyl (or alkenyl)pyridinium halides, and the like. The cationic surfactant preferably has an alkyl or alkenyl group with 6 to 18 carbon atoms. Halogen in the above halide compound includes chlorine, bromine and the like.

Examples of amphoteric surfactants include betaine-type amphoteric surfactants such as alkyldimethylbetaine, amino acid-type amphoteric surfactants, and aminosulfonic acid-type amphoteric surfactants.
Examples of nonionic surfactants include glycerin fatty acid esters, polyglycerin fatty acid esters, polyhydric alcohol fatty acid esters such as sorbitan fatty acid esters, alkylene oxide adducts of the above polyhydric alcohol fatty acid esters, polyoxyalkylene-modified silicones, amino-modified silicone and the like.

The hydrophilic fiber treatment applied to the adhesive fibers may be a primary hydrophilic fiber treatment. Here, the term "primary hydrophilic fiber treatment agent" refers to a treatment agent that imparts to fibers the property of significantly reducing hydrophilicity once brought into contact with water. Adhesive fibers coated with a primary hydrophilic fiber treatment agent exhibit the inherent hydrophobicity of synthetic fibers after hydroentangling. good tactile sensation, suppression of excessive liquid retention) can be utilized.

For example, when the primary hydrophilic fiber treatment agent is applied to the surface of the adhesive fiber which is a synthetic fiber, the initial settling speed of the fiber is less than 60 seconds, particularly 30 seconds or less, and the treatment is performed in warm water at 40°C for 2 minutes. The sedimentation speed of the fibers after rubbing and washing (sedimentation speed after washing) may be 60 seconds or more, particularly 90 seconds or more. The initial sedimentation velocity corresponds to the sedimentation velocity when the fiber has not been exposed to a liquid, and is the sedimentation velocity measured immediately after fiber manufacture or prior to hydroentangling, or the like. Such primary hydrophilic fiber treatment agents are, for example, C8-C12 alkyl phosphate salts.

The coating amount of the hydrophilic fiber treatment agent may be 0.1% by mass or more and 2.0% by mass or less when the fiber mass (the mass of the fiber excluding the fiber treatment agent) is 100% by mass. The coating amount of the hydrophilic fiber treatment agent may be particularly 0.15% by mass or more and 1.0% by mass or less, more particularly 0.2% by mass or more and 0.6% by mass or less.

Two or more fibers may be included as adhesive fibers. In that case, the melting points of the adhesive components of these fibers may differ from each other. For example, if two types of adhesive fibers are included, the difference in the melting points of the adhesive components of these fibers may be 10°C or more and 40°C or less, in particular 15°C or more and 30°C or less.

The fineness of the adhesive fibers is not particularly limited. not generated) is preferably used. The fineness of the adhesive fibers may specifically be between 0.3 dtex and 2.5 dtex, especially between 0.5 dtex and 2.0 dtex, more especially between 0.6 dtex and 1.5 dtex. When the fineness of the adhesive fibers is within the above range, the resulting nonwoven fabric has a smooth feel.

The fiber diameter of the adhesive fibers may be, for example, 6 μm to 19 μm, particularly 8 μm to 17 μm, more particularly 10 μm to 15 μm.
When the fiber diameter of the adhesive fibers is within the above range, the nonwoven fabric tends to have a smooth feel.

The fiber length of the adhesive fibers may be, for example, 25 mm to 100 mm, especially 28 mm to 70 mm, more especially 30 mm to 60 mm.
When the fiber length of the adhesive fibers is within the above range, the entanglement of the fibers tends to be favorable. In particular, when a nonwoven fabric is produced by the method described later, the fiber length within the above range makes it easier to control the degree of entanglement between the fibers in the first fiber layer and the second fiber layer.

(hydrophilic fiber)
The nonwoven fabric of this embodiment contains hydrophilic fibers in both the first fiber layer and the second fiber layer. In this specification, the hydrophilic fibers contained in the first fiber layer are called "first hydrophilic fibers", and the hydrophilic fibers contained in the second fiber layer are called "second hydrophilic fibers". The name is for specifying the fiber layer contained, and both are hydrophilic fibers. Therefore, in the following description, items common to the first and second hydrophilic fibers will be described as items related to "hydrophilic fibers".

Hydrophilic fibers include, for example, cellulosic fibers, protein fibers, and hydrophilic synthetic fibers. In the present embodiment, cellulosic fibers are preferably used as hydrophilic fibers from the viewpoint of maintaining hydrophilicity. The hydrophilic fibers in this embodiment do not exhibit adhesiveness under the conditions in which the adhesive fibers exhibit adhesiveness.

“Cellulosic fiber” is also called cellulose fiber, and generally refers to fiber made from cellulose.
For cellulosic fibers, for example,
(1) Natural fibers derived from plants such as cotton, hemp, linen, ramie, jute, banana, bamboo, kenaf, shell ginger, hemp and kapok;
(2) Solvent-spun cellulose fibers such as viscose-derived rayon and polynosic, cuprammonium-derived cupro, and solvent-spun Tencel® and Lyocell®, and other regenerated fiber;
(3) cellulose fibers obtained by melt spinning; and (4) semi-synthetic fibers such as acetate fibers. The type of cellulosic fiber is not particularly limited.

Protein-based fibers include, for example, natural fibers such as silk and wool.
Hydrophilic synthetic fibers include, for example, synthetic fibers composed of a hydrophilic thermoplastic resin, synthetic fibers made by kneading a hydrophilic agent into a hydrophobic thermoplastic resin, and hydrophobic synthetic fibers. Synthetic fibers coated with a hydrophilic fiber treatment agent, and synthetic fibers obtained by subjecting hydrophobic synthetic fibers to hydrophilic treatment (corona discharge treatment, sulfonation treatment, graft polymerization treatment, etc.), and the like. Examples of thermoplastic resins that make up the synthetic fibers are as described above in relation to the adhesive fibers. Since most of the thermoplastic resins exemplified above are hydrophobic, when using these, it is necessary to make them hydrophilic by kneading them with a hydrophilic agent, applying a hydrophilic fiber treatment agent, or the like.

Hydrophilic fiber treatment agents include, for example, fiber treatment agents containing surfactants. As surfactants, anionic, cationic, amphoteric and nonionic surfactants and the like can be used. Examples of surfactants are as described in connection with the adhesive fibers. The content of the hydrophilic fiber treatment agent may be 0.1% by mass or more and 2.0% by mass or less when the fiber mass (the mass of the fiber excluding the fiber treatment agent) is 100% by mass. The content of the hydrophilic fiber treatment agent may be 0.15% by mass or more and 1.0% by mass or less, and more particularly 0.2% by mass or more and 0.6% by mass or less.

Hydrophilic fibers obtained by applying a hydrophilic fiber treatment agent to the surface of synthetic fibers are hydrophobic, and the hydrophilic fiber is measured by the method described later without applying a hydrophilic fiber treatment agent. is such that the sedimentation velocity is greater than, for example, 60 seconds. In addition, in synthetic fibers coated with a hydrophilic treatment agent, the hydrophobic thermoplastic resin is exposed at the fiber end faces, and liquids (especially water) are difficult to absorb from the fiber end faces, and the fibers swell due to the liquid absorption. Hateful. On the other hand, cellulosic fibers are hydrophilic as a whole and exhibit the property of absorbing liquid and swelling, and as a result of the swelling, the stiffness of the fibers tends to decrease. Therefore, synthetic fibers coated with a hydrophilic fiber treatment agent are less likely to be entangled with each other due to high-pressure liquid flow (especially high-pressure water flow) compared to cellulosic fibers, and tend to make the nonwoven fabric bulky.

The hydrophilic fiber treatment applied to hydrophilic fibers may be a durable durable hydrophilic fiber treatment. The durable hydrophilic fiber treatment agent remains on the fiber surface to maintain the hydrophilicity of the fiber even after the entangling treatment with a high-pressure fluid stream (especially water stream) when the nonwoven fabric of this embodiment is manufactured by the manufacturing method described later. have the property Specifically, the durable hydrophilic fiber treatment agent has an initial sedimentation speed of 60 seconds or less, and the sedimentation speed after washing is 60 seconds or less after washing three times with warm water at 40 ° C. for 2 minutes. It is like The post-wash sedimentation velocity may be lower than the initial sedimentation velocity as long as it is 60 seconds or less. For example, the durable hydrophilic fiber treatment agent has an initial sedimentation rate of 30 seconds or less, particularly 20 seconds or less, more particularly 15 seconds or less, and a fiber sedimentation rate of 40 seconds or less after washing with hot water at 40°C. , in particular 30 seconds or less, more particularly 20 seconds or less. Such a durable hydrophilic fiber treatment agent is, for example, an ethylene glycol-based fiber treatment agent.

Although the fineness of the hydrophilic fibers is not particularly limited, hydrophilic fibers having a relatively small fineness are preferably used in the present embodiment. Specifically, it may be 0.3 dtex to 2.8 dtex, further 0.5 dtex to 2.3 dtex, particularly 0.6 dtex to 1.7 dtex, more particularly 0.7 dtex to 1.5 dtex. By using hydrophilic fibers having relatively small fineness as the first hydrophilic fibers, the surface on the side that comes into contact with the skin (the surface of the first fiber layer) can be made smoother and denser. In addition, by making the second hydrophilic fibers also have a relatively small fineness, even when they are exposed on the first fiber layer side, the influence on the tactile sensation can be reduced. In addition, since hydrophilic fibers with a small fineness are more strongly entangled when entangled by the method described later, when these are included as the first hydrophilic fibers and/or the second hydrophilic fibers, the resulting nonwoven fabric can be obtained. Fluff is less likely to occur in the case, and fluff is less likely to come off.

The fiber diameter of the hydrophilic fibers may be, for example, 4 μm to 15 μm, particularly 5 μm to 12 μm, more particularly 6 μm to 10 μm.
By using hydrophilic fibers having a fiber diameter within the above range as the first hydrophilic fibers, the surface on the side that contacts the skin (the surface of the first fiber layer) can be made smoother and denser. Further, by setting the fiber diameter of the second hydrophilic fiber within the above range, even when this is exposed on the first fiber layer side, the influence on the touch can be reduced. In addition, hydrophilic fibers having a fiber diameter within the above range are more strongly entangled when entangled by the method described later, so that they can be used as the first hydrophilic fiber and / or the second hydrophilic fiber. When it is contained, the resulting nonwoven fabric is less prone to fluffing and fluffing is reduced.
Here, when the cross section of the hydrophilic fiber is non-circular, the fiber diameter is the average value of the length of the major diameter of the fiber cross section and the maximum length of the span connecting two points on the fiber cross section perpendicular to the major diameter. is the fiber diameter.

The fiber length of the hydrophilic fibers may be, for example, 25-100 mm, particularly 28-70 mm, more particularly 30-60 mm.
When the fiber length of the hydrophilic fibers is within the above range, the entangling properties of the fibers tend to be favorable when producing a nonwoven fabric by the method described later (especially a method in which the entangling treatment includes a hydroentangling treatment). Further, by setting the fiber length of the first hydrophilic fiber and/or the second hydrophilic fiber within the above range, it is easier to control the degree of entanglement between the fibers in the first fiber layer and the second fiber layer. becomes.

The cross-section of the hydrophilic fibers (transverse or perpendicular to the length of the fiber) may be circular or non-circular. Non-circular shapes include, for example, elliptical, Y-shaped, X-shaped, I-shaped, multi-lobed, polygonal, star-shaped, and chrysanthemum-shaped. When the cross section of the fiber is circular, the bonding area with the adhesive fiber is relatively small, so that the nonwoven fabric can have a softer texture than when non-circular fibers are used. When the fiber has a non-circular cross-section, the bonding area with the adhesive fiber is relatively large, so that the strength of the nonwoven fabric can be increased.

Chemical fibers such as regenerated fibers or semi-synthetic fibers may be used as cellulosic fibers, which are examples of hydrophilic fibers. Variations in fineness and/or fiber diameter and fiber length of chemical fibers are smaller than those of natural fibers, making it easier to adjust the degree of entanglement of the nonwoven fabric. In addition, regenerated fibers such as rayon and solvent-spun cellulose fibers have a good balance of softness and strength when wet, and it is easier to obtain softness and strength suitable for nonwoven fabrics, which is preferable. . Solvent-spun cellulose fibers are preferable in that the strength of the nonwoven fabric is improved because the single fiber strength is relatively high. Rayon has lower monofilament strength than solvent-spun cellulose fibers, but is therefore preferred because the nonwoven fabric is soft and has high entangling properties.

Hydrophilic fibers can be used alone or in combination. For example, the first hydrophilic fibers may be one or more cellulosic fibers, or one cellulosic fiber and one hydrophilic synthetic fiber. The same is true for the second hydrophilic fiber. Also, the first hydrophilic fiber and the second hydrophilic fiber may be different from each other or may be the same.

The degree of hydrophilicity of hydrophilic fibers can be evaluated, for example, using values such as the sedimentation velocity of the fibers.
The sedimentation velocity (or sedimentation time (seconds)) of the hydrophilic fibers used in the present embodiment may be, for example, less than 60 seconds, particularly 50 seconds or less, more particularly 40 seconds or less, and further In particular it may be 30 seconds or less, even more particularly 20 seconds or less. The smaller the settling velocity (or settling time) of the hydrophilic fibers, the higher the entanglement of the hydrophilic fibers tends to be.

The sedimentation rate of fibers can be measured by the following method.
Take 17 g of fiber to measure the sedimentation velocity. The collected fibers are opened (using a parallel carding machine) to form a carded web. 5 g of the card web is weighed and filled into a copper wire (thickness: 0.55 mm) cage (cylindrical with a diameter of 5 cm and a height of 8 cm, the weight of the cage body is 3 g).
Next, a constant temperature water tank is prepared, tap water is put into the constant temperature water tank, and the water temperature is adjusted to 25° C. while stirring. When the water temperature reaches 25°C, stop stirring the constant temperature water bath and start measuring the sedimentation velocity. The basket filled with fibers according to the above procedure is gently dropped from a position of 1 cm above the water surface, and a stopwatch is started as soon as the basket falls to the water surface. The fibers are gradually hydrated and the stopwatch is stopped as soon as the 8 cm high basket is completely submerged under water. The sedimentation velocity is defined as the time from when the basket is dropped to the surface of the water until it sinks below the water surface, and the average value of two measurements is taken as the sedimentation velocity of the fiber.

In addition, natural fibers such as cotton and wool have the property of repelling water that comes into contact with the fiber surface due to the oil content attached to the fiber surface and the structure of the fiber surface. It may lower the texture when combining them. Therefore, in this embodiment, when natural fibers are used as the hydrophilic fibers, oil may be removed or the surface of the fibers may be modified.

When the hydrophilic fibers are regenerated cellulose fibers or synthetic fibers coated with a hydrophilic fiber treatment, they may contain additives that these fibers normally contain. One such additive is titanium oxide to impart opacity to the fibers. A nonwoven fabric with a first fibrous layer containing regenerated cellulose fibers with a higher titanium oxide content has a lower MMD ( In particular, it tends to show MMD in the CD direction. This is presumably because titanium oxide changes the mechanical properties of the fibers and affects the entangling properties of the fibers. More specifically, it is speculated that the higher the content of titanium oxide in the regenerated cellulose fibers, the higher the rigidity and the lower the degree of entanglement by high-pressure fluid flow (especially water flow). As a result, unevenness due to injection marks (also referred to as nozzle streaks) formed on the surface of the nonwoven fabric during submerged injection is reduced, and the surface smoothness of the nonwoven fabric is improved.

(other fibers)
The nonwoven fabric of the present embodiment may contain fibers other than hydrophilic fibers and adhesive fibers (hereinafter referred to as "other fibers"). Other fibers contained in the first fiber layer are, for example, synthetic fibers that are neither adhesive fibers nor hydrophilic fibers (for example, do not melt or soften when melting the adhesive component of the adhesive fibers and do not exhibit adhesiveness hydrophobic synthetic fibers, etc.), and is not particularly limited. Other fibers contained in the second fiber layer include adhesive fibers in addition to the fibers that are not hydrophilic fibers and the synthetic fibers that are not adhesive fibers.

Other fibers may be contained in a proportion of 30% by mass or less, particularly 25% by mass or less, more particularly 20% by mass or less, when the total amount of fibers constituting each fiber layer is 100% by mass. may be included.

(Configuration of nonwoven fabric)
The nonwoven fabric of this embodiment includes a first fiber layer and a second fiber layer, the first fiber layer forming one surface of the nonwoven fabric, and the second fiber layer being arranged in contact with the first fiber layer. In addition, the first fiber layer contains 40% by mass or more and 75% by mass or less of the adhesive fiber based on the total mass of the first fiber layer, contains 25% by mass or more and 60% by mass or less of the first hydrophilic fiber, The two fiber layers contain 70% by mass or more and 100% by mass or less of the second hydrophilic fibers based on the total mass of the second fiber layer.

The surface of the nonwoven fabric formed by the first fibrous layer is located on the skin side of the user when the nonwoven fabric is incorporated into the absorbent article, and particularly contacts the skin. Therefore, in the present embodiment, the first fiber layer contains adhesive fibers to impart a smooth feel. Since the adhesive fibers are synthetic fibers as described above, even when the fibers are entangled and integrated by the action of a high-pressure fluid (especially high-pressure water flow) by the method described later, the entanglement is relatively difficult to progress, and the high-pressure fluid injection marks are not formed. The surface of the nonwoven fabric can be made smoother by reducing unevenness caused by Therefore, it is preferable that the surface of the nonwoven fabric formed by the first fiber layer be a flat surface that does not have raised portions or depressed portions.

Moreover, in this embodiment, the first fiber layer contains the first hydrophilic fibers. This, together with the inclusion of the second hydrophilic fibers in the second fiber layer, causes stronger entanglement of the hydrophilic fibers between the first fiber layer and the second fiber layer, This is for suppressing fluffing and fluffing on the surface of the first fiber layer. Here, "fluffing" refers to the state in which single fibers stand up on the surface of the nonwoven fabric, and "fluff removal" refers to the falling off of the single fibers.

Furthermore, in the present embodiment, since the second fiber layer is positioned in contact with the first fiber layer, the entanglement of the hydrophilic fibers in both fiber layers is likely to progress, and the entanglement of the hydrophilic fibers from the first fiber layer to the second fiber layer is facilitated. It is believed that a gradient is likely to occur in the ratio of hydrophilic fibers across the layers. This gradient forms a kind of "hydrophilic gradient", which is thought to improve liquid absorbency and suppress liquid return.

The proportion of adhesive fibers contained in the first fiber layer is 40% by mass or more and 75% by mass or less, particularly 45% by mass or more and 70% by mass or less, more particularly 50% by mass or more and 65% by mass or less, and even more particularly may be 55% by mass or more and 65% by mass or less. If the proportion of the adhesive fibers is too small, it will be difficult to make the surface of the first fiber layer smooth, and liquid return tends to increase. If the proportion of adhesive fibers is too large, the liquid absorbency will be reduced, and fluffing and fluffing will tend to occur.

The proportion of the first hydrophilic fibers contained in the first fiber layer is 25% by mass or more and 60% by mass or less, particularly 30% by mass or more and 55% by mass or less, more particularly 35% by mass or more and 50% by mass or less, More particularly, it may be 35% by mass or more and 45% by mass or less. If the ratio of the first hydrophilic fibers is too small, the entanglement between the first fiber layer and the second fiber layer becomes insufficient, and fluffing and fluffing tend to occur, and liquid absorbency tends to decrease. It is in. If the ratio of the first hydrophilic fibers is too large, the smoothness of the surface of the first fiber layer tends to decrease and the amount of liquid returning tends to increase. Especially when the first hydrophilic fiber is a cellulosic fiber, the fiber itself has a greater ability to retain liquid than synthetic fibers. There is a tendency for an increase in

The proportion of the second hydrophilic fibers contained in the second fiber layer is 70% by mass or more and 100% by mass or less, particularly 80% by mass or more and 100% by mass or less, more particularly 90% by mass or more and 100% by mass or less. It's okay. Alternatively, the second fibrous layer may consist only of second hydrophilic fibers.

The second fibrous layer is in contact with the first fibrous layer, and serves to diffuse the body fluid that has reached the first fibrous layer two-dimensionally in the plane direction to some extent, while rapidly transferring it to the absorbent body. Therefore, if the ratio of the second hydrophilic fibers contained in the second fiber layer is too small, it may be difficult for body fluids to transfer smoothly, and the liquid absorption speed may decrease. In addition, the second hydrophilic fibers are entangled with the first hydrophilic fibers contained in the first fiber layer to fix the fibers contained in the first fiber layer (especially the first hydrophilic fibers). do. Therefore, if the ratio of the second hydrophilic fibers is too small, fluffing and fluffing tend to occur.

The proportion of the second hydrophilic fibers in the second fibrous layer may be greater than the proportion of the first hydrophilic fibers in the first fibrous layer. According to this configuration, a gradient of the ratio of hydrophilic fibers in the thickness direction of the nonwoven fabric (a gradient that increases from the first fiber layer to the second fiber layer) is likely to be formed, and the liquid absorption of the nonwoven fabric tends to be further improved. It is in.

In the nonwoven fabric of the present embodiment, the first fiber layer contains the adhesive fibers and the first hydrophilic fibers in the above ratio, so that the hydrophobic fibers and the hydrophilic fibers are present on the surface of the nonwoven fabric. The properties of fibers with different affinities can be exhibited in a well-balanced manner. Adhesive fibers are synthetic fibers as described above and tend to be inherently hydrophobic. When the nonwoven fabric for absorbent articles contains hydrophobic fibers that do not easily absorb liquid, the nonwoven fabric feels dry to the touch, and the amount of liquid retained by the fibers themselves that constitute the nonwoven fabric is suppressed from becoming too large. to suppress the liquid return amount. On the other hand, in absorbent articles, it is desired to absorb liquid discharged from the human body and the like in a short period of time, and hydrophilic fibers quickly attract the liquid and transfer it to the absorber. Therefore, the nonwoven fabric of this embodiment can be provided as a nonwoven fabric having a well-balanced feel and liquid absorption due to the hydrophobic fibers and hydrophilic fibers present in the first fiber layer. Together with that, it exhibits properties suitable for absorbent articles.

In the nonwoven fabric of the present embodiment, the fibers are bonded to each other by the adhesive fibers contained in the first fiber layer, and the fibers constituting the first fiber layer and the second fiber layer are entangled, so that the fibers are integrated. has been made When the nonwoven fabric is produced by the method described later, only the fibers contained in the first fiber layer may be bonded by the adhesive fibers, in which case the fibers are not bonded to each other in the second fiber layer. According to such a configuration, the bonding points are present only in the first fiber layer, and the nonwoven fabric as a whole can have a soft feel. Further, when a nonwoven fabric is produced by the method described later, the fibers constituting the first fiber layer and the second fiber layer are entangled with each other in a state where the adhesion points are present only in the first fiber layer, so that the inter-layer Entanglement between fibers can be better.

Alternatively, in the nonwoven fabric of the present embodiment, fibers may be bonded to each other in the second fiber layer as well. The adhesion between the fibers in the second fiber layer may be due to the adhesive fibers of the first fiber layer that have moved to the second fiber layer due to the entangling treatment, or due to the adhesive fibers contained in the second fiber layer. can be anything. The adhesion in the second fiber layer is obtained by performing the bonding treatment after performing the entangling treatment in the manufacturing method described below. When the fibers are bonded to each other in the second fiber layer, the strength of the nonwoven fabric increases, which is advantageous in terms of handleability of the nonwoven fabric. On the other hand, such nonwoven fabrics tend to be stiff to the touch.

At the locations where the fibers are bonded to each other, bonded portions are formed by melting or softening the adhesive components of the adhesive fibers and then solidifying them again. Further, the entangling of the fibers may be carried out, for example, by a hydroentangling treatment, as will be described later.

In the nonwoven fabric of this embodiment, the smoothness of the surface of the first fiber layer is ensured by making the degree of entanglement in the first fiber layer smaller than that in the second fiber layer. In this embodiment, the radius of curvature of the fibers included in each fiber layer after fiber entanglement is used as an index representing the degree of entanglement. In each fiber layer after fiber entanglement, fibers contained in fiber layers other than the fiber layer may enter as a result of entanglement and appear on the surface of each fiber layer, including fibers from other fiber layers. to measure the radius of curvature and evaluate the degree of entanglement in each fiber layer. Therefore, in this embodiment, for both the first fiber layer and the second fiber layer, the fibers (first hydrophilic fiber, second hydrophilic fiber, adhesive fiber, and other fiber) on each surface ) is used to assess the degree of entanglement of each fiber layer.

The radius of curvature of the fiber on the surface of each fiber layer is measured as follows.
The surface of the fiber layer to be measured is observed with a scanning electron microscope (SEM, acceleration voltage: 10.0 kV, magnification: 100 times). In the captured SEM image, a circle is drawn along the semicircle at a location where the fiber is curved in a semicircular shape in a direction substantially parallel to the image plane, and the radius of the drawn circle is the radius of curvature of the fiber. do. The radius of curvature was calculated using image analysis software "Micro Measure" (manufactured by SCARA Co., Ltd.). For each SEM image, 10 numerical values were extracted from the measured curvature radii, from the smallest value to the tenth smallest value.

Five different SEM images were subjected to this measurement and extraction, and an average value was obtained from a total of 50 numerical values, which was taken as the radius of curvature of the fiber on the surface of the fiber layer. If the number of curvature radii measurable in one SEM image is less than 10, all the numerical values of the curvature radii obtained from that one image are extracted, and the curvatures measured and extracted using other SEM images Measurement and extraction are performed by increasing the number of SEM images so that there are 50 or more points including the numerical value of the radius, and the average value is obtained.

In the SEM image, whether or not the fiber is curved in a semicircular shape in a direction substantially parallel to the image plane is confirmed by visually observing the SEM image. It was judged by observing the circle drawn on the part. Specifically, circles drawn with image analysis software that are clearly smaller than others (having a radius of curvature of less than 5 µm) are judged to be curved in a direction perpendicular to the image plane. Therefore, the object to be measured was removed from the object to be measured, and the object to be measured was the one that was curved in a direction substantially parallel to the image plane.

When measuring the curvature radius, 10 loops with a small curvature radius are selected in the SEM image because such loops are caused by the entanglement of the fibers in the region shown in the image. is a good indicator of the degree of entanglement in the region. In a nonwoven fabric, even entangled fibers may be observed in an SEM image in a substantially straight state without being curved depending on their positions. not shown. On the other hand, according to the above method, loops caused by confounding are to be measured. The inventors have confirmed that if the radii of curvature of these loops are small, the other loops tend to be small as well, and that these radii of curvature determine the degree of overall entanglement to some extent. Therefore, the degree of fiber entanglement can be evaluated more accurately from 10 loops with small curvature radii.

The smaller the radius of curvature of the fibers measured by the above method, the more pronounced the curvature of the fibers, including hydrophilic fibers, due to entanglement. It is in progress. In this embodiment, the radius of curvature (φ1) of the fibers on the surface of the first fiber layer is 30 μm or more, the radius of curvature (φ2) of the fibers on the surface of the second fiber layer is 40 μm or less, and φ1>φ2. is preferably satisfied. In such a nonwoven fabric, the degree of entanglement between fibers in the first fiber layer is smaller than that in the second fiber layer, so that the texture of the surface of the first fiber layer is smooth. If φ1 is too small, the entanglement will proceed excessively, resulting in unevenness of the entanglement or exposure of fibers with a large degree of curvature to the surface, which tends to reduce the smoothness of the surface.

On the other hand, since φ2 is 40 μm or less and φ1>φ2, the degree of entanglement between fibers in the second fiber layer is greater than that in the first fiber layer. As a result, some of the fibers of the first fiber layer are fixed in such a manner that they are entangled in the strong entanglement of the second fiber layer, and the surface of the first fiber layer is effectively prevented from becoming fuzzy.

In addition, by reducing φ2 to a certain extent, the entanglement of the fibers of the first fiber layer and the fibers of the second fiber layer, particularly the first hydrophilic fibers of the first fiber layer and the second hydrophilic fibers of the second fiber layer. The entanglement with the hydrophilic fibers progresses at the fiber layer interface, and the "connection" (or integrity) of the fibers (especially the hydrophilic fibers) between the two fiber layers is improved. As a result, a kind of gradient is formed in which the proportion of hydrophilic fibers gradually increases from the first fiber layer to the second fiber layer. Such a gradient becomes a hydrophilic gradient, and when bodily fluids such as excrement and menstrual blood come into contact with the surface of the first fibrous layer, the bodily fluids can be rapidly drawn into the second fibrous layer. , can increase the liquid absorption rate. If φ2 is too large, the entanglement between the first fiber layer and the second fiber layer will be insufficient, and fluffing and fluffing will tend to occur, and the liquid absorption rate will tend to decrease.

A nonwoven fabric having φ1 and φ2 within the above ranges and satisfying φ1>φ2 also means that a relatively large number of fibers having a relatively large radius of curvature are present on the surface of the first fiber layer. In the present embodiment, where the first fiber layer contains hydrophilic fibers and adhesive fibers, the adhesive fibers are larger than the hydrophilic fibers when subjected to the entangling treatment (especially hydroentanglement) under the same conditions. Since it tends to exhibit a radius of curvature, the proportion of adhesive fibers occupying the surface of the nonwoven fabric tends to be high. Therefore, the nonwoven fabric of the present embodiment can exhibit a smaller amount of liquid return when the first fiber layer side is used as the skin contact surface by satisfying the predetermined conditions for φ1 and φ2. Adhesive fibers, which are usually synthetic fibers, are difficult to retain liquid, so even if pressure is applied, the fibers themselves can This is due to the fact that it can release less liquid.

The predetermined ranges of φ1 and φ2 are such that the fineness or fiber diameter of the adhesive fibers, the first hydrophilic fibers and the second hydrophilic fibers constituting the first fiber layer and the second fiber layer are relatively small. is easy to obtain. Since the specific fineness and fiber diameter are as explained above, they are omitted here.

Alternatively, the predetermined ranges of φ1 and φ2 may be obtained by changing the pressure and/or number of high-pressure fluid streams (especially high-pressure water streams) when manufacturing the nonwoven fabric of the present embodiment by the method described later. .
For example, when the first fiber layer contains a relatively large proportion of hydrophilic fibers, the entanglement of the hydrophilic fibers progresses and occupies most of the fiber layer, so that the radius of curvature decreases and falls within a predetermined range. φ1 may not be obtained. In this case, the first hydrophilic fibers move to the second fiber layer by increasing the pressure of the high-pressure fluid flow jetted to the side of the fiber web serving as the first fiber layer and/or increasing the number of jets. , more adhesive fibers are exposed on the surface. As a result, φ1 measured by the above method becomes large, and φ1 within a predetermined range can be obtained.

When φ1 is 135 μm or less, the degree of entanglement is good, fluffing and fluffing are less likely to occur, and the distance between the first fiber layer and the second fiber layer and the absorbent body is shortened, resulting in a higher liquid absorption rate. tend to be higher. φ1 may in particular be less than or equal to 100 μm, more particularly less than or equal to 65 μm.
When φ2 is 5 μm or more, entangling does not proceed excessively, and it is possible to suppress the nonwoven fabric from becoming too hard. φ2 may in particular be greater than or equal to 8 μm, more particularly greater than or equal to 10 μm.

When the nonwoven fabric of the present embodiment is formed using fibers with a small fineness, the entanglement of the fibers progresses further, so that the fiber density of the nonwoven fabric increases, giving a smoother surface and a smoother surface. It can give you a tactile sensation. On the other hand, when the fiber density on the surface of the nonwoven fabric increases, the voids between the fibers decrease, so there are fewer areas where the body fluid released on the surface of the nonwoven fabric is temporarily "stored", and in this respect, the liquid absorbency decreases. However, in the nonwoven fabric of the present embodiment, the hydrophilic fibers are tightly entangled between the two fiber layers, thereby improving the integrity of the hydrophilic fibers at the interface of the layers and forming a gradient of the hydrophilic fibers. . These configurations compensate for the decrease in liquid absorbency that is caused by the trade-off between improvement in smoothness and enable the nonwoven fabric of the present embodiment to exhibit good liquid absorbency.

In this embodiment, the basis weight of the first fiber layer may be, for example, 10 g/m ² or more and 40 g/m ² or less, particularly 12 g/m ² or more and 35 g/m ² or less, more particularly 15 g/m ² or more and 25 g. /m ² or less. The first fiber layer is the surface on the side closer to the user's skin, and is mainly responsible for providing a smooth feel and suppressing liquid backflow. In addition, the first fiber layer and the second fiber layer form a gradient of the ratio of the hydrophilic fibers in the thickness direction of the nonwoven fabric, thereby improving liquid absorbency.

Therefore, if the basis weight of the first fiber layer is too small, the thickness of the first fiber layer becomes small, and the loops of the second hydrophilic fibers contained in the second fiber layer having a large degree of curvature form the surface of the first fiber layer. , and the smoothness may be impaired. In addition, the amount of liquid returning may increase due to the decrease in the amount of adhesive fibers. If the basis weight of the first fiber layer is too large, the entangling of the hydrophilic fibers between the first fiber layer and the second fiber layer becomes insufficient, and fluffing and fluffing may easily occur. In addition, due to insufficient fiber entanglement between fiber layers, the "connection" (or integrity) of hydrophilic fibers between fiber layers decreases, making it difficult to form a gradient of hydrophilic fibers, resulting in a decrease in liquid absorption. I have something to do.

The basis weight of the second fiber layer may be, for example, 10 g/m ² or more and 40 g/m ² or less, particularly 15 g/m ² or more and 37 g/m ² or less, more particularly 25 g/m ² or more and 35 g/m ² or less. It's okay. The second fiber layer has a large mixing ratio of the second hydrophilic fiber, and is well entangled with the hydrophilic fiber contained in the first fiber layer, and serves to more firmly fix the fibers constituting the first fiber layer. do. Also, the second fiber layer serves to enhance the liquid absorbency of the nonwoven fabric.

Therefore, if the basis weight of the second fiber layer is too small, the fixation of the fibers in the first fiber layer becomes weak, and fluffing and fluffing may easily occur. In addition, when the basis weight of the second fiber layer is too small, the liquid absorbency may decrease. If the basis weight of the second fibrous layer is too large, the basis weight of the first fibrous layer is correspondingly reduced, which may cause the above problems. Alternatively, if the basis weight of the second fiber layer is too large, the basis weight of the entire nonwoven fabric becomes too large and may not be suitable for use as an absorbent article, or the entanglement of the fibers becomes insufficient. It becomes difficult to form a gradient of hydrophilic fibers, and liquid absorbency may decrease.

The ratio of the basis weight of the first fiber layer to the basis weight of the second fiber layer may be, for example, 2:8 (first:second) to 8:2, particularly 3:7 to 7:3, more particularly may be from 4:6 to 6:4.

The basis weight of the entire nonwoven fabric is appropriately selected according to the type of absorbent article, the place where it is arranged in the absorbent article, and the like. The basis weight of the entire nonwoven fabric may be, for example, particularly 20 g/m ² or more and 80 g/m ² or less, particularly 30 g/m ² or more and 70 g/m ² or less, more particularly 40 g/m ² or more and 60 g/m ² or less. For example, when the nonwoven fabric is used as a top sheet for sanitary napkins or pantiliners, the basis weight may be 30 g/m ² or more and 70 g/m ² or less, particularly 40 g/m ² or more and 60 g/m ² or less.

The nonwoven fabric of the present embodiment may have a thickness of 0.20 mm or more and 1.50 mm or less (thickness measured by applying a load of 294 Pa), and particularly a thickness of 0.30 mm or more and 1.25 mm or less. More particularly, it is even more preferred to have a thickness of 0.40 mm or more and 1.00 mm or less. When the nonwoven has a thickness in the range described above, the nonwoven tends to have a smoother feel.

The nonwoven fabric of the present embodiment as a whole may have, for example, a fiber density of 0.020 g/cm ³ or more and 0.150 g/cm ³ or less, particularly 0.030 g/cm ³ or more and 0.140 g/cm ³ or less. It may have a fiber density, more particularly a fiber density of 0.040 g/cm ³ or more and 0.130 g/cm ³ or less. The fiber density of the entire nonwoven fabric can be obtained from the basis weight and thickness (thickness measured by applying a load of 294 Pa). When the nonwoven fabric has a density in the range described above, the nonwoven fabric tends to exhibit a shorter liquid absorption time (ie, a higher liquid absorption rate) and a smoother feel.

The fiber density of the nonwoven fabric tends to be lower when either or both of the first and second hydrophilic fibers are synthetic fibers containing a hydrophilic fiber treatment agent, for example 0.065 g/ It may be less than ^cm3 . Nonwoven fabrics having such fiber densities tend to be bulky and provide a soft feel.

The tensile strength in the MD direction (longitudinal direction or machine direction) of the nonwoven fabric of the present embodiment may be, for example, 20.0 N/5 cm or more and 200.0 N/5 cm or less, particularly 30.0 N/5 cm or more and 190.0 N/ It may be 5 cm or less, more particularly 40.0 N/5 cm or more and 180.0 N/5 cm or less. In addition, the nonwoven fabric of the present embodiment may have a tensile strength in the CD direction (lateral direction) of, for example, 2.5 N/5 cm or more and 50.0 N/5 cm or less, particularly 5.0 N/5 cm or more and 40.0 N/5 cm. Below, more particularly, it may be 7.5 N/5 cm or more and 35.0 N/5 cm or less. When the tensile strength of the nonwoven fabric is within the above range, the shape stability of the nonwoven fabric tends to be further improved.

The nonwoven fabric of the present embodiment may have an elongation rate in the MD direction of, for example, 10% or more and 100% or less, particularly 20% or more and 60% or less, and an elongation rate in the CD direction of, for example, 40% or more. It may be 200% or less, particularly 75% or more and 120% or less. When the elongation percentage of the nonwoven fabric is within the above range, the softness of the nonwoven fabric tends to be further improved.

The stress at 10% elongation in the MD direction of the nonwoven fabric of the present embodiment may be, for example, 16.5 N/5 cm or more and 50.0 N/5 cm or less, particularly 17.0 N/5 cm or more and 40.0 N/5 cm or less, more particularly may be 17.5 N/5 cm or more and 30.0 N/5 cm or less. In addition, the nonwoven fabric of the present embodiment may have a stress at 10% elongation in the CD direction of, for example, 0.1 N/5 cm or more and 10.0 N/5 cm or less, particularly 0.2 N/5 cm or more and 7.5 N/5 cm or less. More particularly, it may be 0.3 N/5 cm or more and 5.0 N/5 cm or less. In the nonwoven fabric of the present embodiment, the hydrophilic fibers are relatively strongly entangled between the first fiber layer and the second fiber layer, so the stress at 10% elongation in the MD direction tends to be particularly high. When the stress at 10% elongation in the MD direction and the CD direction is within the above range, the handleability of the nonwoven fabric is improved, and the workability when assembling the absorbent article and the operability when the user handles the absorbent article are improved. can have a positive impact.

In the nonwoven fabric of the present embodiment, when either or both of the first and second hydrophilic fibers are synthetic fibers containing a hydrophilic fiber treatment agent, the stress at 10% elongation in the MD direction of the nonwoven fabric is , For example, it may be 2.0 N/5 cm or more and 40.0 N/5 cm or less, particularly 2.5 N/5 cm or more and 35.0 N/5 cm or less, more particularly 3.0 N/5 cm or more and 30.0 N/5 cm or less. It's okay. In addition, the nonwoven fabric of the present embodiment may have a stress at 10% elongation in the CD direction of, for example, 0.1 N/5 cm or more and 10.0 N/5 cm or less, particularly 0.2 N/5 cm or more and 7.5 N/5 cm. 0.3 N/5 cm or more and 5.0 N/5 cm or less, more particularly 0.3 N/5 cm or less. In a nonwoven fabric using synthetic fibers containing a hydrophilic fiber treatment agent, if the stress at 10% elongation in the MD direction and the CD direction is within the above range, the nonwoven fabric tends to be bulkier and more flexible.

The nonwoven fabric of the present embodiment is provided as one in which fluffing and fluffing are suppressed as described above. Specifically, the nonwoven fabric of the present embodiment has a fluffiness amount of, for example, 3.0 mg or less, particularly 2.0 mg or less, more particularly 1.0 mg or less, measured on the surface of the first fiber layer by the following method. can be provided as being If the fluff removal amount exceeds 3.0 mg, fluff may adhere to the user's skin or clothes during use, or surface fluff may stand out when used in an absorbent article. may not be suitable for use. In addition, the smaller the amount of fluff coming off, the more strongly the fibers in the first fiber layer are entangled with each other, indicating that the surface is smoother. It is possible to know the confounding state of

(Method for measuring the amount of fluff removed)
a) Urethane foam (manufactured by Inoac Corporation, trade name Maltfilter MF-30, ester polyurethane, number of cells 30, average cell diameter 410 μm, average friction coefficient (MIU) 0.69, variation in average friction coefficient (MMD ) 0.043, thickness 5 mm), a disk (diameter 70 mm, 350 g) is attached to the rotating shaft so that the rotating shaft is shifted from the center of the disk by 20 mm.
b) The same urethane foam as above is spread, and the nonwoven fabric is fixed on the table so that the first fiber layer of the nonwoven fabric becomes an exposed surface.
c) placing the disc on top of the non-woven fabric; At this time, the only load applied to the nonwoven fabric is the weight of the disk itself.
d) Rotate the rotating shaft to rotate the disk on the nonwoven fabric. Circular motion is performed 10 sets of 2 rotations clockwise and 2 rotations counterclockwise. The rotation speed at this time is about 3 seconds per one rotation.
e) After 3 sets of circular movements, the fibers falling off from the nonwoven fabric and adhering to the surface of the urethane foam covering the disk are collected.
f) The above operations a) to e) are performed on n=3 nonwoven fabrics. For each of the three nonwoven fabrics, the mass of the fallen fibers is measured, and the average value is defined as the fluff amount (mg).
In place of the urethane foam, another urethane foam was used to measure the fluff removal amount, as long as the number of cells, average cell diameter, MIU, MMD, and thickness differed within the range of ±25%. good. If the fluff removal amount measured using such a different urethane foam is within the above range, the measured fluff removal amount is considered to have been measured using the above specific urethane foam.

The nonwoven fabric of the present embodiment exhibits a liquid absorption time of, for example, 35 seconds or less, particularly 33 seconds or less, and more particularly 30 seconds or less when the liquid absorption time of a sanitary napkin is measured by the method described in the Examples. can be anything. The lower limit of the liquid absorption time may be, for example, 5 seconds. The shorter the liquid absorption time, the less discomfort the user feels when the liquid (for example, vaginal discharge, menstrual blood) is discharged.

The nonwoven fabric of the present embodiment exhibits a liquid return amount of, for example, 0.35 g or less, particularly 0.33 g or less, more particularly 0.30 g or less when the liquid return amount of the sanitary napkin described in the examples is measured. can be anything. The lower limit of the liquid return amount may be, for example, 0 g. The smaller the amount of liquid returning, the more the user feels less wet during use.

The nonwoven fabric of the present embodiment has a mean coefficient of friction (MMD) of 0.0010 or more and 0.0090 or less, particularly 0.0020 or more and 0.0020 or more in the MD direction when the variation (MMD) of the average friction coefficient on the surface of the first fiber layer described in Examples is measured. It may exhibit an MMD of 0.0080 or less, more particularly 0.0030 or more and 0.0070 or less. In the nonwoven fabric of the present embodiment, the MMD in the CD direction of the first fiber layer surface may be 0.0010 or more and 0.0120 or less, particularly 0.0020 or more and 0.0110 or less, more particularly 0.0030 or more. It may be 0.0100 or less. In the nonwoven fabric of the present embodiment, the average value of the MMD in the MD direction and the MMD in the CD direction on the surface of the first fiber layer may be 0.0030 or more and 0.0110 or less, particularly 0.0040 or more and 0.0100. 0.0050 or more and 0.0090 or less. When the MMD value is within the above range, a smoother feel is likely to be obtained.

In the nonwoven fabric of the present embodiment, when either one or both of the first and second hydrophilic fibers are synthetic fibers containing a hydrophilic fiber treatment agent, the surface of the first fiber layer described in the examples Shows an average friction coefficient (MIU) of 0.170 or more and 0.300 or less, particularly 0.175 or more and 0.295 or less, more particularly 0.180 or more and 0.290 or less in the MD direction when measuring the average friction coefficient (MIU) can be Further, in the nonwoven fabric of the present embodiment, when either one or both of the first and second hydrophilic fibers are synthetic fibers containing a hydrophilic fiber treatment agent, in the CD direction of the first fiber layer surface MIU may be 0.180 or more and 0.300 or less, particularly 0.185 or more and 0.295 or less, more particularly 0.190 or more and 0.290 or less. Synthetic fibers containing a hydrophilic fiber treatment agent are less likely to be entangled by liquid flow (especially water flow) than cellulosic fibers, as described above. Occasionally, deformation tends to occur, which tends to result in higher MIU than nonwoven fabrics using cellulosic fibers.

(Application)
Since the nonwoven fabric described as the first embodiment is for absorbent articles, it is suitably used as a member constituting absorbent articles such as disposable diapers, sanitary napkins, incontinence pads, and panty liners. . The nonwoven fabric of the present embodiment is particularly preferably used as a member that comes into direct contact with human skin, and can be used, for example, as a top sheet for absorbent articles. Moreover, the nonwoven fabric of the present embodiment may be provided in a state incorporated into an absorbent article, for example, as a topsheet.

The second fiber layer of the nonwoven fabric of this embodiment can function as a diffusion sheet. The diffusion sheet is positioned between the top sheet and the absorbent body in the absorbent article, and plays a role of diffusing body fluids from the top sheet to the absorbent body. The second fiber layer that constitutes the nonwoven fabric of the present embodiment is positioned farther from the user's skin (that is, closer to the absorbent body) and contains a higher proportion of hydrophilic fibers, which draws in body fluids. , the body fluid is likely to diffuse in the surface direction in the second fiber layer. Therefore, if the nonwoven fabric of this embodiment is used as the top sheet, it may not be necessary to provide a diffusion sheet, and the number of parts of the absorbent article can be reduced.

(Second embodiment)
Next, a method for manufacturing the nonwoven fabric of the first embodiment will be described as a second embodiment.
The manufacturing method of this embodiment is
A nonwoven fabric for absorbent articles comprising a first fiber layer and a second fiber layer, wherein the first fiber layer forms one surface of the nonwoven fabric, and the other surface is in contact with the second fiber layer, A method for producing a nonwoven fabric for absorbent articles in which the first fiber layer is arranged closer to the user's skin,
A step of producing a first fibrous web containing 40% by mass or more and 75% by mass or less of adhesive fibers and 25% by mass or more and 60% by mass or less of first hydrophilic fibers based on the total mass of the first fibrous web. ,
A step of producing a second fibrous web containing 70% by mass or more and 100% by mass or less of the second hydrophilic fiber based on the total mass of the second fibrous web;
a bonding step of bonding the fibers of the first fibrous web with the adhesive fibers;
a lamination step of obtaining a laminated fiber web by laminating the first fiber web and the second fiber web after the bonding step;
an interlacing step of interlacing and integrating the fibers of the first fibrous web and the second fibrous web of the laminated fibrous web;
The entangling step includes a hydroentangling process in which a water stream is jetted toward the second fibrous web to entangle the fibers, and then a water stream is jetted toward the first fibrous web to entangle the fibers. In the hydroentanglement treatment, the total energy E1 of the water flow jetted to the first fiber web side is higher than the total energy E2 of the water jet jetted to the second fiber web side, and the ratio of E1 to E2 (E1 /E2) is 2.5 or more and 12.0 or less,
In the method for producing a nonwoven fabric for absorbent articles, the first fibrous web serves as the first fibrous layer and the second fibrous web serves as the second fibrous layer.

Both the first fibrous web and the second fibrous web may be manufactured by known methods. The first and second fibrous webs may be in any form such as carded webs such as parallel webs, cross webs, semi-random webs and random webs, air-laid webs, and wet papermaking webs. If the first fibrous web is a parallel web, the surface of the nonwoven tends to be smoother. When the second fibrous web is a parallel web, the fibers are oriented in one direction and are easily entangled with the constituent fibers of the first fibrous layer. Therefore, when the basis weight of the second fibrous web is small, by making the second fibrous web a parallel web, the integration of the first fibrous web and the second fibrous web is likely to be promoted. The form of the second fibrous web may be the same as or different from the form of the first fibrous web. If the form is the same, the fibers of each web have the same orientation, so that the layers are easily entangled.

In the manufacturing method of this embodiment, the first fibrous web is subjected to the bonding step, and the adhesive fibers bond the fibers of the first fibrous web together. The adhesion treatment may be, for example, heat treatment (thermal adhesion treatment). According to the heat treatment, the component having the lowest melting point (thermal bonding component) among the resin components constituting the adhesive fibers is melted or softened by heating during the heat treatment, and the fibers constituting the fiber web can be bonded to each other. . The heat treatment may be, for example, hot air processing by blowing hot air, hot roll processing (for example, hot embossing roll processing), or heat treatment using infrared rays. Hot air processing is preferable because it tends to improve the texture of the nonwoven fabric. The hot air processing treatment may be carried out using a device that blows hot air at a predetermined temperature onto the fiber web, such as a hot air penetration type heat treatment machine and a hot air blowing type heat treatment machine.

When the adhesion treatment is hot air processing, hot air may be blown multiple times. When hot air is blown a plurality of times, it is preferable that the temperature of the second hot air is higher than the temperature of the first hot air.

When the adhesion treatment is a hot air processing treatment, the wind speed of the hot air may be, for example, 0.1 m/min or more and 3.0 m/min or less, particularly 0.2 m/min or more and 2.5 m/min or less, more particularly may be 0.3 m/min or more and 2.0 m/min or less. If the air velocity of the hot air is too low, the fibers may not be well bonded to each other throughout the fiber web. sag may decrease.

The temperature of the heat treatment may be a temperature at which the component having the lowest melting point (thermal bonding component) among the resin components constituting the adhesive fiber softens or melts, for example, a temperature equal to or higher than the melting point of the component. For example, when the component with the lowest melting point among the resin components constituting the adhesive fiber is high-density polyethylene, hot air at a temperature of 130° C. or higher and 150° C. or lower may be blown when the hot air processing is performed. For example, when the component with the lowest melting point among the resin components constituting the adhesive fiber is an ethylene-acrylic acid copolymer, hot air at a temperature of 90° C. or higher and 140° C. or lower is blown when performing hot air processing. In particular, hot air at a temperature of 95° C. or higher and 130° C. or lower may be blown, and more particularly hot air at a temperature of 100° C. or higher and 120° C. or lower may be blown. In addition, the temperature of the heat treatment is preferably 0° C. or more and 5° C. or less higher than the melting point or softening point of the thermal adhesive component, considering the texture of the resulting nonwoven fabric, and is preferably 1° C. or more and 4° C. or less higher than the melting point or softening point. It is more preferable to set the temperature to 2° C. or higher and 3° C. or lower.

The bonding treatment may be by irradiation with electron beams or the like, or by ultrasonic welding. These adhesion treatments also allow the fibers to adhere to each other with the resin component that constitutes the adhesive fibers.

In the manufacturing method of the present embodiment, a lamination step is performed to obtain a laminated fiber web by laminating the first fiber web that has undergone the bonding treatment in the bonding step and the second fiber web that is separately produced. The first fibrous web that has undergone the bonding process can be called a heat-bonded nonwoven fabric because the fibers are bonded to each other and have a certain degree of integrity.

The manufacturing method of the embodiment of the present invention may include a cooling step after the bonding step and before the entangling step. That is, after the bonding step and before the lamination step is performed and/or after the first and second fibrous webs are laminated and before the entanglement step is performed. Then, a cooling step of cooling the first fibrous web and/or the laminated fibrous web may be carried out. Air cooling, water cooling, or the like can be used as a cooling treatment method. If the first fibrous web after the bonding treatment is not sufficiently cooled, the adhesive component of the adhesive fibers may be in a softened state. If the laminated fiber web is subjected to the entangling treatment in this state, the bonded portions may easily peel off, and the nonwoven fabric may become prone to fluffing.

In this embodiment, after the bonding step, the first fibrous web is subjected to the entangling step together with the second fibrous web without winding the first fibrous web onto a roll. This facilitates the progress of entanglement between the fibers. This is because, once the first fibrous web after the bonding step is wound on a roll, its bulk tends to decrease, and the larger the bulk of the first fibrous web, the more time it takes for entangling with the second fibrous web. This is because voids between fibers tend to occur and entanglement proceeds more easily.

The entangling process is, for example, a needle punching process or a high-pressure fluid flow (especially water flow) entangling process. In high pressure fluid flow processing, the high pressure fluid is, for example, a high pressure gas such as compressed air and a high pressure liquid such as high pressure water. In the production of nonwoven fabrics, hydroentangling treatment using high-pressure water as a high-pressure fluid is often used. Treatment is preferably used. In the following, the entangling process when using high-pressure water (hereinafter also simply referred to as "water flow") as the high-pressure fluid will be described.

The hydroentanglement treatment is performed by, for example, injecting a water flow at a water pressure of 1 MPa or more and 15 MPa or less from a nozzle in which orifices with a hole diameter of 0.05 mm or more and 0.5 mm or less are provided at intervals of 0.3 mm or more and 1.5 mm or less. implement. The water pressure is preferably 1 MPa or more and 10 MPa or less, more preferably 1 MPa or more and 7 MPa or less, and particularly preferably 1 MPa or more and 6 MPa or less.

In this embodiment, the hydroentangling treatment may be performed by jetting water jets onto the surfaces of the second and first fibrous webs of the laminated fibrous web (that is, both sides of the laminated fibrous web). At this time, the water pressure of the water stream jetted onto the surface of the first fibrous web may be higher than the water pressure of the water stream jetted onto the surface of the second fibrous web. Furthermore, it is preferable that the number of times of jetting the water stream to the first fibrous web is larger than the number of times of jetting the jet to the second fibrous web. According to such a hydroentangling treatment, it is easier to obtain a nonwoven fabric in which the first fiber layer and the second fiber layer have φ1 and φ2 within the predetermined ranges and the relationship of φ1>φ2.

Since both the first fibrous web and the second fibrous web contain hydrophilic fibers that are likely to be entangled when water jets are jetted, in this embodiment, the degree of entanglement of the hydrophilic fibers is controlled to obtain a desired nonwoven fabric. I'm trying Specifically, by controlling the water pressure and the number of jets, the effect of the water flow on the side of the second fiber web is made smaller than the effect of the water flow on the side of the first fiber web, that is, the water flow on the second fiber web. The degree of entanglement is controlled by reducing the input water flow energy.

Since the second fibrous web contains a higher proportion of hydrophilic fibers, if the action of the water stream on the fibrous web increases, the fibers may become too entangled. As a result, loops of the second hydrophilic fibers having a small radius of curvature appear on the surface of the first fiber layer, and the tactile sensation may deteriorate. Therefore, in the present embodiment, the effect of the water stream on the first fibrous web, in which the entanglement due to the water stream is rather difficult to progress as a whole because it contains adhesive fibers, is increased to sufficiently remove the hydrophilic fibers in the two fibrous webs. Excessive entanglement is suppressed while being entangled.

In this embodiment, the water pressure of the water stream jetted onto the second fibrous web may be, for example, 1 MPa or more and 10 MPa or less, particularly 1 MPa or more and 8 MPa or less. Also, the number of times the water stream is jetted onto the second fibrous web may be, for example, one or more and three or less. The water pressure of the water stream jetted onto the first fibrous web may be, for example, 1 MPa or more and 15 MPa or less, particularly 1 MPa or more and 10 MPa or less. Also, the number of times the water stream is jetted onto the first fiber web may be, for example, two or more and four or less.

The difference in water pressure between the water streams jetted to the second fiber web and the first fiber web may be, for example, 1 MPa or more and 10 MPa or less, and particularly 1 MPa or more and 8 MPa or less. Also, the number of times the water stream is jetted onto the first fibrous web may be, for example, one or more and four or less times more than that onto the second fibrous web, and particularly one or more and three or less times more.

The hydroentanglement treatment may be carried out by first jetting a water stream a predetermined number of times toward the second fiber web side, and then jetting a predetermined number of water streams toward the first fiber web side. According to this order, the second hydrophilic fibers in the second fibrous web form the basis for entanglement, and even if a water stream with a higher water pressure is jetted from the first fibrous web side, the fibers are scattered by the water stream. etc. are further reduced, and the occurrence of coarseness and fineness in the nonwoven fabric is suppressed.

The hydroentangling treatment may be carried out by placing the fibrous web on the support and jetting a stream of water. If the surface of the nonwoven fabric is flat and does not have irregularities, the support does not have openings with an opening area exceeding 0.2 mm ² per opening, and does not have protrusions or patterns. It is better to use a support that is not For example, a plain weave support of 80 mesh or more and 100 mesh or less may be used as the support.

The energy (E) applied to the fibrous web by the jetting water stream is determined by the following equation. Regarding the total energies E1 and E2, when jetting is performed a plurality of times under different conditions such as the number of nozzle orifices and water pressure, it is preferable to calculate E in each case and set the totals as E1 and E2.

E=W×N×T/(M/1000×U×60)/1000
E: Energy (kWh/kg/m) applied to 1 kg of fiber web per 1 m width in 1 hour
W: Power (W) of fluid (water in this embodiment) per orifice of nozzle
N: Number of orifices per 1 m width of nozzle T: Number of injections M: Weight per unit area (g/m ² ) to be subjected to hydroentanglement treatment
U: Conveyance speed (m/min)

W (work rate of fluid per nozzle orifice) in the above formula is obtained by the following formula.
W=P1×(F/100)×0.163
W: Fluid power per nozzle orifice (W)
P1: water pressure (kgf/cm ² )
F: flow rate of water discharged from one orifice of nozzle (cm ³ /min)

F (the flow rate of water discharged from one orifice of the nozzle) in the above formula is obtained by the following formula.
F=S×V
F: flow rate of water discharged from one orifice of nozzle (cm ³ /min)
S: Area of fluid ejected from one orifice of nozzle (mm ² )
V: flow velocity of fluid ejected from nozzle (m/min)

V (the flow velocity of the fluid ejected from the nozzle) in the above formula is obtained by the following formula.
V=(20×g×(P1−P2)/ρ) 1/ ² ×60
V: flow velocity of fluid ejected from nozzle (m/min)
g: gravitational acceleration, ^9.8m /s2
P1: water pressure (kgf/cm ² )
P2: atmospheric pressure (kgf/cm ² )
ρ: fluid density (g/cm ³ )
Details of the method for determining E etc. are described in Japanese Patent No. 4893256.

The value of the ratio of E1 to E2 (E1/E2) may be between 2.7 and 11.0, in particular between 3.0 and 10.0.

E1 is preferably 0.03 kWh/kg/m or more and 3.50 kWh/kg/m or less. More preferably, it is 0.05 kWh/kg/m or more and 3.30 kWh/kg/m or less. When E1 is within the above range, it promotes φ1 to be larger and φ2 to be smaller, causing the first hydrophilic fibers in the first fiber layer to migrate more toward the second fiber layer, thereby preventing fluffing and fluffing. Further, a hydrophilic gradient is formed in which the ratio of hydrophilic fibers gradually increases from the first fiber layer to the second fiber layer, and the amount of liquid returning can be further reduced.
E2 is preferably 0.01 kWh/kg/m or more and 0.50 kWh/kg/m or less. More preferably, it is 0.03 kWh/kg/m or more and 0.40 kWh/kg/m or less. When E2 is within the above range, the first fiber layer and the second fiber layer can be firmly entangled without impairing the texture of the nonwoven fabric.

When the hydroentangling treatment is performed in the entangling process, the drying process may be performed after the entangling process. The drying treatment can be performed, for example, by a hot air processing treatment in which hot air is blown. The temperature of the drying treatment may be lower than the softening or melting temperature of the adhesive component (thermal adhesive component) of the adhesive fibers contained in the first fibrous web. The temperature of the drying treatment may be, for example, 10° C. or more lower than the melting point or softening point of the thermal adhesive component, particularly 15° C. or more lower, more particularly 20° C. or lower. By not softening or melting the adhesive fibers after the entangling step, a nonwoven fabric in which the fibers are not bonded to each other in the second fiber layer is obtained. In order to obtain a nonwoven fabric having such a configuration, not only the drying process but also the processing process (for example, dyeing process) of the laminated fiber web or nonwoven fabric performed after the entangling process is performed to remove the adhesive fibers contained in the first fiber web. preferably below the temperature at which the adhesive component softens or melts.

When the second fibrous web contains adhesive fibers, the adhesive fibers of the second fibrous web after the entangling process (hereinafter, "second adhesive fibers" to distinguish from the adhesive fibers contained in the first fibrous web) (referred to as entangling) may bond the fibers together (post-entangling bonding step). In particular, the melting point of the second adhesive fibers is lower than the melting point of the adhesive component of the adhesive fibers contained in the first fibrous web ("first adhesive fibers" to distinguish them from the second adhesive fibers), It is preferable to melt the adhesive component of the second adhesive fiber at a temperature lower than the temperature at which the adhesive component of the first adhesive fiber melts to bond the fibers together. As a result, re-melting or softening and solidification of the first adhesive fibers are suppressed, and hardening of the nonwoven fabric can be prevented.

In the manufacturing method in which the hydroentangling treatment is performed, the adhesive fibers may be synthetic fibers coated with the primary hydrophilic fiber treatment agent. Such adhesive fibers exhibit hydrophilicity during hydroentangling treatment to promote entanglement between fibers, and after hydroentangling treatment, the fiber treatment agent is removed and hydrophobicity is exhibited. To provide a nonwoven fabric exhibiting the advantages of hydrophobic fibers in returning and the like. Further, in the manufacturing method in which the hydroentanglement treatment is performed, when the first and second hydrophilic fibers are synthetic fibers to which a hydrophilic fiber treatment agent is applied, a durable hydrophilic fiber treatment agent is used, and the sedimentation rate is It is preferred that the exhibited hydrophilicity should not be reduced after the hydroentangling treatment. This is because synthetic fibers coated with a hydrophilic fiber treatment agent show hydrophobicity and cannot function as hydrophilic fibers when the hydrophilic fiber treatment agent is removed.

EXAMPLES Hereinafter, the nonwoven fabric according to the present disclosure and the method for producing the same will be described with reference to examples.
The fibers used to make the nonwoven fabrics of the Examples and Comparative Examples are shown below.
<Adhesive fiber 1>
Polypropylene (melting point: about 160°C) is the core, high-density polyethylene (melting point: about 133°C) is the sheath, and the core-sheath ratio (volume ratio of core component/sheath component) is 50/50. A concentric core-sheath type composite fiber having a fineness of 1.0 dtex (fiber diameter of 11.8 μm) and a fiber length of 38 mm (NBF (H) (trade name) manufactured by Daiwabo Co., Ltd.), in which the and sheath components are arranged concentrically. )

<Adhesive fiber 2>
Polypropylene (melting point: about 160°C) is the core, high-density polyethylene (melting point: about 133°C) is the sheath, and the core-sheath ratio (volume ratio of core component/sheath component) is 50/50. A concentric core-sheath type composite fiber having a fineness of 1.0 dtex (fiber diameter of 11.8 μm) and a fiber length of 38 mm, in which the and sheath components are arranged concentrically, and an alkyl phosphate-based primary hydrophilic fiber treatment agent is applied to the fiber. Fibers coated on the surface at a rate of 0.30% by weight

<Adhesive fiber 3>
Polypropylene (melting point: about 160°C) is the core, high-density polyethylene (melting point: about 133°C) is the sheath, and the core-sheath ratio (volume ratio of core component/sheath component) is 50/50. A concentric core-sheath type composite fiber having a fineness of 2.2 dtex (fiber diameter of 17.5 μm) and a fiber length of 51 mm, in which the and sheath components are arranged concentrically, and an alkyl phosphate-based primary hydrophilic fiber treatment agent is applied to the fiber. Fibers coated on the surface at a rate of 0.30% by weight

<Hydrophilic fiber A>
A viscose rayon fiber (BH (trade name) manufactured by Daiwabo Rayon Co., Ltd.) having a fineness of 0.9 dtex (fiber diameter of 8.2 μm) and a fiber length of 38 mm, with a chrysanthemum-shaped fiber cross section and a sedimentation speed of 14 seconds.
<Hydrophilic fiber B>
A viscose rayon fiber (BH (trade name) manufactured by Daiwabo Rayon Co., Ltd.) having a fineness of 0.6 dtex (fiber diameter of 7.1 μm) and a fiber length of 32 mm has a chrysanthemum-shaped fiber cross section and a sedimentation speed of 9.1 seconds. )

<Hydrophilic fiber C>
A semi-dull viscose rayon fiber (CD manufactured by Daiwabo Rayon Co., Ltd.) having a fineness of 1.1 dtex (fiber diameter of 9.7 μm), a fiber length of 38 mm, a chrysanthemum-shaped fiber cross section, and a sedimentation speed of 7.7 seconds. Name))
<Hydrophilic fiber D>
A semi-dull viscose rayon fiber (CD (product Name))

<Hydrophilic fiber E>
A viscose with a fineness of 1.4 dtex (fiber diameter of 11.4 μm) and a fiber length of 44 mm, with a chrysanthemum-shaped fiber cross section, a higher titanium oxide content than the hydrophilic fiber D, and a sedimentation speed of 5.9 seconds. Rayon fiber (manufactured by Daiwabo Rayon Co., Ltd.)
<Hydrophilic fiber F>
A semi-dull viscose rayon fiber (CD manufactured by Daiwabo Rayon Co., Ltd.) with a fineness of 3.3 dtex (fiber diameter of 15.4 μm), a fiber length of 51 mm, a chrysanthemum-shaped fiber cross section, and a sedimentation speed of 4.8 seconds. Name))

<Hydrophilic fiber G>
Cotton with an average fineness of 2.5 dtex (average fiber diameter of 13.0 m), an average fiber length of 30 mm, and a settling velocity of 8.1 seconds (manufactured by Marusan Sangyo Co., Ltd., MSD (trade name))
<Hydrophilic fiber I>
A durable hydrophilic polyethylene terephthalate fiber (manufactured by Toray Industries, Inc.) having a fineness of 1.6 dtex (fiber diameter of 12 μm), a fiber length of 51 mm, and a sedimentation speed of 2.4 seconds.

Table 1 shows the initial sedimentation velocity and post-wash sedimentation velocity for Adhesive Fibers 2 and 3 and Hydrophilic Fiber I. The sedimentation velocity after washing is the sedimentation velocity measured after washing the fibers three times by rubbing them in hot water at 40° C. for 2 minutes.

From Table 1, it can be seen that the hydrophilic fiber treatment agent applied to adhesive fibers 2 and 3 is primary hydrophilic, and the hydrophilic fiber treatment agent applied to hydrophilic fiber I is durable. confirmed.

<Production of nonwoven fabric of Example 1>
60% by mass of adhesive fibers and 40% by mass of hydrophilic fibers A as first hydrophilic fibers were mixed to prepare a first fiber web with a target weight of about 20 g/m ² using a parallel carding machine.
This first fiber web is heated at 135° C. for about 5 seconds using a hot air penetrating heat treatment machine, and the fibers are thermally bonded (adhesion treatment) by the sheath component of the adhesive fibers to form the first fiber layer. A non-woven fabric was obtained.

Using hydrophilic fiber A as the second hydrophilic fiber, a second fiber web was produced with a target basis weight of about 30 g/m ² using a parallel carding machine. The obtained second fibrous web was laminated on the surface side (air surface side) of the first fibrous layer to which the hot air was applied to obtain a laminated fibrous web.

The above laminated fiber web was placed on a plain weave net having a warp diameter of 0.132 mm, a weft diameter of 0.132 mm and a mesh number of 90 meshes. While advancing the laminated fibrous web at a speed of 4 m/min, a water jet with a water pressure of 3.5 MPa was jetted once onto the surface of the laminated fibrous web on the side of the second fibrous web using a water feeder. As the nozzle of the water supplier, a nozzle having orifices with a hole diameter of 0.12 mm provided at intervals of 0.6 mm was used. The distance between the surface of the laminated fibrous web and the orifice was 15 mm. After that, using the same water supply device, a water flow with a water pressure of 5.0 MPa was sprayed twice onto the surface of the laminated fiber web on the first fiber layer side. The total energy E1 of the water stream jetted to the first fiber web side is 1.55 kWh/kg/m, and the total energy E2 of the water stream jetted to the second fiber web side is 0.45 kWh/kg/m. The E1 ratio value (E1/E2) was 3.4.

The laminated fiber web after the hydroentanglement treatment was dried at 80°C using a hot air penetration type heat treatment machine, and the first fiber web became the first fiber layer and the second fiber web became the second fiber layer. A nonwoven fabric having a two-layer laminate structure of Example 1 was obtained.

<Production of nonwoven fabric of Example 2>
A nonwoven fabric of Example 2 was obtained in the same manner as in Example 1, except that the fiber mixing ratio of the first fiber web was 50% by mass of adhesive fibers and 50% by mass of hydrophilic fibers A.

<Production of nonwoven fabric of Example 3>
A nonwoven fabric of Example 3 was obtained in the same manner as in Example 1, except that the fiber mixing ratio of the first fiber web was 70% by mass of adhesive fibers and 30% by mass of hydrophilic fibers A.

<Production of nonwoven fabrics of Examples 4 to 8 and 10 to 14>
Examples 4 to 8 were carried out in the same manner as in Example 1, except that the types and mixture ratios of the fibers used in the first fiber web and the types of fibers used in the second fiber web were as shown in Tables 4 to 6. , 10-16 nonwoven fabrics were obtained.

<Production of nonwoven fabric of Example 9>
The type and mixing ratio of fibers used in the first fiber web and the type of fiber used in the second fiber web are as shown in Tables 4 to 6, and a water jet with a water pressure of 5.0 MPa is sprayed four times on the first fiber web side. The procedure was the same as in Example 1, except that In the production of this nonwoven fabric, the total energy E1 of the water stream jetted to the first fiber web side was 3.10 kWh/kg/m, and the total energy E2 of the water stream jetted to the second fiber web side was 0.45 kWh/kg/m. m and the ratio of E1 to E2 (E1/E2) was 6.9.

<Production of nonwoven fabric of Comparative Example 1>
The hydroentanglement treatment is performed by spraying a water flow with a water pressure of 5.0 MPa twice on the surface of the second fiber web side of the laminated fiber web, and then spraying a water flow with a water pressure of 3.5 MPa once on the surface on the first fiber web side. A nonwoven fabric of Comparative Example 1 was obtained in the same manner as in Example 1, except that the procedure was carried out. E1 was 0.45 kWh/kg/m, E2 was 1.55 kWh/kg/m, and the ratio value of E1 to E2 (E1/E2) was 0.3.

<Production of nonwoven fabric of Comparative Example 2>
In the hydroentanglement treatment, a water stream with a water pressure of 2.0 MPa was jetted once to the surface of the second fiber web side of the laminated fiber web, and then a water stream of water pressure of 3.0 MPa was jetted to the surface of the first fiber web side once. A nonwoven fabric of Comparative Example 2 was obtained in the same manner as in Example 1, except for the above. E1 was 0.36 kWh/kg/m, E2 was 0.19 kWh/kg/m, and the ratio value of E1 to E2 (E1/E2) was 1.9.

<Production of nonwoven fabric of Comparative Example 3>
A nonwoven fabric of Comparative Example 3 was obtained in the same manner as in Example 1, except that the fiber mixing ratio of the first fibrous web was 80% by mass of adhesive fibers and 20% by mass of hydrophilic fibers A.

<Production of nonwoven fabric of Comparative Example 4>
60% by mass of adhesive fiber and 40% by mass of hydrophilic fiber A as the first hydrophilic fiber are mixed, and a parallel carding machine is used to form the first fiber layer with a target basis weight of about 20 g / m ² A fibrous web was produced.
Using hydrophilic fiber A as the second hydrophilic fiber, a second fiber web was produced with a target basis weight of about 30 g/m ² using a parallel carding machine. The obtained second fibrous web was laminated on the first fibrous web to obtain a laminated fibrous web.

The above laminated fiber web was placed on a plain weave net having a warp diameter of 0.132 mm, a weft diameter of 0.132 mm and a mesh number of 90 meshes. While advancing the laminated fibrous web at a speed of 4 m/min, a water jet with a water pressure of 3.5 MPa was jetted once onto the surface of the laminated fibrous web on the side of the second fibrous web using a water feeder. As the nozzle of the water supplier, a nozzle having orifices with a hole diameter of 0.12 mm provided at intervals of 0.6 mm was used. The distance between the surface of the laminated fibrous web and the orifice was 15 mm. After that, using the same water supply device, a water flow with a water pressure of 5.0 MPa was jetted twice onto the surface of the laminated fiber web on the side of the first fiber web. E1 was 1.55 kWh/kg/m, E2 was 0.45 kWh/kg/m, and the ratio value of E1 to E2 (E1/E2) was 3.4.

The laminated fiber web after the hydroentanglement treatment is heated at 135° C. for about 5 seconds using a hot air penetration type heat treatment machine, and at the same time, the fibers are thermally bonded (adhesion treatment) by the sheath component of the adhesive fibers. Thus, a nonwoven fabric having a two-layer laminate structure of Comparative Example 4 was obtained.

<Production of nonwoven fabric of Comparative Example 5>
24% by mass of the adhesive fiber and 76% by mass of the hydrophilic fiber A were mixed to prepare a fiber web with a target basis weight of about 50 g/m ² using a parallel carding machine.
This fiber web was heated at 135° C. for about 5 seconds using a hot air penetrating heat treatment machine, and the fibers were thermally bonded (bonded) by the sheath component of the adhesive fibers to obtain a thermally bonded nonwoven fabric.

The thermally bonded nonwoven fabric was placed on a plain weave net having a warp diameter of 0.132 mm, a weft diameter of 0.132 mm, and a mesh count of 90 meshes. While the heat-bonded nonwoven fabric was advanced at a speed of 4 m/min, a water flow with a water pressure of 3.5 MPa was jetted once using a water feeder to the surface side (air surface side) of the heat-bonded nonwoven fabric to which the hot air was applied. As the nozzle of the water supplier, a nozzle having orifices with a hole diameter of 0.12 mm provided at intervals of 0.6 mm was used. The distance between the surface of the thermally bonded nonwoven fabric and the orifice was 15 mm. After that, using the same water supply device, a water flow with a water pressure of 5.0 MPa was sprayed twice on the surface opposite to the surface on which the water flow was injected. The total energy E′ of the water flow injected on the air surface side was 0.45 kWh/kg/m, and the total energy E″ of the water flow injected on the side opposite to the air surface was 1.55 kWh/kg/m.
The thermally bonded nonwoven fabric after the hydroentanglement treatment was dried at 80° C. using a hot air penetration type heat treatment machine to obtain a nonwoven fabric of a single layer structure of Comparative Example 5.

<Production of nonwoven fabric of Comparative Example 6>
A nonwoven fabric of Comparative Example 6 was obtained in the same manner as in Comparative Example 5, except that the fiber mixture ratio of the fiber web was changed to 60% by mass of adhesive fibers and 40% by mass of hydrophilic fibers A.

<Production of nonwoven fabrics of Comparative Examples 7 and 8>
Nonwoven fabrics of Comparative Examples 7 and 8 in the same manner as in Example 1 except that the types and mixture ratios of the fibers used in the first fibrous web and the types of fibers used in the second fibrous web were as shown in Table 6. got

The following evaluations were carried out on the obtained nonwoven fabrics of each example and each comparative example. The evaluation results are shown in Tables 2-6.

<Thickness and density of nonwoven fabric>
Using a thickness measuring machine (THICKNESS GAUGE model CR-60A (trade name) manufactured by Daiei Kagaku Seiki Seisakusho Co., Ltd.), the thickness of the nonwoven fabric is measured with a load of 294 Pa or 1.96 kPa applied to the nonwoven fabric. did.
The density of the nonwoven fabric was calculated based on the basis weight of the nonwoven fabric and the thickness of the nonwoven fabric measured under a load of 294 Pa.

<Strength and Elongation>
The strength and elongation was measured according to JIS L 1913:2010 6.3. Using a constant-speed tension type tensile tester, a tensile test was performed under the conditions of a sample piece (nonwoven fabric) width of 5 cm, a grip interval of 10 cm, and a tensile speed of 30±2 cm/min. The load value (tensile strength) at break, elongation, and stress at 10% elongation were measured. The tensile test was carried out with the machine direction (MD direction) and the transverse direction (CD direction) of the nonwoven fabric as tensile directions. Each evaluation result was shown as an average of values measured for three samples.

<Smoothness (KES)>
In order to evaluate the smoothness, the change in mean coefficient of friction (MMD) was measured using a friction tester (KES-SE, Kato Tech Co., Ltd.). A nonwoven fabric of 5 cm×10 cm was prepared as a sample piece. For the sample pieces, a nonwoven fabric with long sides in the MD direction and a sample piece with a long side in the CD direction were prepared. A piano wire sensor (manufactured by Kato Tech Co., Ltd.) was used as the contact terminal of the measuring instrument. The test piece is fixed to the measurement table, and the contact terminal (25 g) is applied at a speed of 1.0 mm / sec on the surface of the first fiber layer of the test piece (the surface on which the water flow was last jetted in the case of a single layer structure) , along one direction over a distance of 30 mm, and the MMD was evaluated between points 5 mm and 25 mm from the starting point of the movement. Measurements were taken three times for the test piece with the long side in the MD direction, and three times for the test piece with the long side in the CD direction, and the average of the three measurements was taken as the MMD in each direction. Furthermore, the average value of a total of 6 measurements was obtained.

<Fluff Removal>
The shedding of fluff was evaluated by measuring the amount (mg) of fibers that fell off from the nonwoven fabric by the following method.
a) Urethane foam (manufactured by Inoac Corporation, trade name Maltfilter MF-30, ester polyurethane, number of cells 30, average cell diameter 410 μm, average friction coefficient (MIU) 0.69, variation in average friction coefficient (MMD ) 0.043, thickness 5 mm), a disk (diameter 70 mm, 350 g) is attached to the rotating shaft so that the rotating shaft is shifted from the center of the disk by 20 mm.
b) The same urethane foam as above is spread, and the nonwoven fabric is fixed on the table so that the first fiber layer of the nonwoven fabric becomes an exposed surface. In the case of the nonwoven fabric having a single-layer structure, the surface to which the water flow was last jetted is the exposed surface.
c) placing the disc on top of the non-woven fabric; At this time, the only load applied to the nonwoven fabric is the weight of the disk itself.
d) Rotate the rotating shaft to rotate the disk on the nonwoven fabric. Circular motion is performed 10 sets of 2 rotations clockwise and 2 rotations counterclockwise. The rotation speed at this time is about 3 seconds per one rotation.
e) After 3 sets of circular movements, the fibers falling off from the nonwoven fabric and adhering to the surface of the urethane foam covering the disk are collected.
f) The above operations a) to e) are performed on n=3 nonwoven fabrics. For each of the three nonwoven fabrics, the mass of the fallen fibers is measured, and the average value is defined as the fluff amount (mg).
It can be said that the nonwoven fabric having a fluff shedding amount of 3.0 mg or less effectively prevents fluff shedding.

<Liquid absorbency (liquid absorption time and liquid return amount)>
When a nonwoven fabric was used as a top sheet of a sanitary napkin, the liquid absorption performance of the nonwoven fabric was evaluated.
(1) Peel off the top sheet of a commercially available sanitary napkin (manufactured by Kao Corporation, trade name “Laurier Shiawase Suhada”) to expose the absorbent body, and place a 220 mm × 80 mm nonwoven fabric to be evaluated on the absorbent body. A sample cut in the vertical direction x horizontal direction) was placed. The nonwoven fabric was arranged so that the first fiber layer was the exposed surface. In the case of the single-layered nonwoven fabric, the surface to which the water flow was last jetted was taken as the exposed surface.

A plate with an injection cylinder (height 75 mm, inner diameter 25 mm at the top of the cylinder, inner diameter 10 mm at the bottom of the cylinder) is placed on the first fiber layer, and 5 cc of artificial liquid is placed in the injection cylinder of the plate with an injection cylinder. Menstrual blood (viscosity 8 mPa·s, temperature 37° C.) was injected. The time required for the liquid to disappear from the surface of the nonwoven fabric (liquid absorption time) (seconds) was measured.
The composition of the artificial menstrual blood is 12.61% by mass of glycerin, 84.88% by mass of distilled water, 0.45% by mass of CMC (sodium carboxymethylcellulose), 0.97% by mass of NaCl (sodium chloride), and Na ₂ CO. ₃ (sodium carbonate) 1.04% by mass and red powder 0.06% by mass.

(2) 10 minutes after injecting the artificial menstrual blood for measuring the absorption time, filter paper (manufactured by Toyo Roshi Kaisha, Ltd., trade name ADVANTEC (registered trademark) No. 2, 10 cm × 10 cm) was placed on the nonwoven fabric. ) were placed, and a weight of 1 kg (shape: square, 10 cm×10 cm) was placed on the filter paper. After 20 seconds from placing the weight, the filter paper was taken out, the mass of the filter paper that absorbed the artificial menstrual blood was measured, and the mass of the filter paper before being placed on the nonwoven fabric was subtracted to calculate the liquid return amount (g).
Five samples were prepared for the nonwoven fabric to be evaluated, and the average value of the liquid absorption time and liquid return amount measured for each of the five samples was taken as the liquid absorption time and liquid return amount of the nonwoven fabric.
When the liquid absorption time measured by the above method is 35 seconds or less, it can be said that the liquid absorption rate of the nonwoven fabric is good. In addition, when the liquid return amount is 0.35 g or less, it can be said that the nonwoven fabric satisfactorily prevents the liquid return.

<Fiber Curvature Radius>
The surface of the nonwoven fabric (fiber layer) to be measured is observed with a scanning electron microscope (SEM, acceleration voltage: 10.0 kV, magnification: 100 times). In the captured SEM image, a circle is drawn along the semicircle at a location where the fiber is curved in a semicircular shape in a direction substantially parallel to the image plane, and the radius of the drawn circle is the radius of curvature of the fiber. do. The radius of curvature was calculated using image analysis software "Micro Measure" (manufactured by SCARA Co., Ltd.). For each SEM image, 10 numerical values were extracted from the measured curvature radii, from the smallest value to the tenth smallest value.

This measurement and extraction were performed on 5 different SEM images, and the average value was obtained from a total of 50 numerical values, and this was taken as the radius of curvature of the fiber on the surface of the nonwoven fabric. If the number of curvature radii measurable in one SEM image is less than 10, all the numerical values of the curvature radii obtained from that one image are extracted, and the curvatures measured and extracted using other SEM images Measurement and extraction are performed by increasing the number of SEM images so that there are 50 or more points including the numerical value of the radius, and the average value is obtained.

FIG. 1 shows an electron micrograph (SEM image) (magnification: 100) of the surface of the nonwoven fabric produced in Example 1 on the side of the second fiber layer. In FIG. 1, for ease of understanding, the circle drawn when measuring φ1 is indicated by a white dashed line.

In Tables 2 to 6, for the single-layered nonwoven fabric, the radius of curvature measured on the surface to which the water flow was last jetted was φ1, and the radius of curvature measured on the opposite side was φ2.

As shown in Table 2, all of Examples 1 to 3 satisfied φ1≧30 μm, φ2≦40 μm, and φ1>φ2, exhibited a small MMD in the CD direction, and exhibited a smooth touch. Furthermore, these examples exhibited a relatively short liquid absorption time (that is, a high liquid absorption rate) and a relatively small amount of liquid return, indicating good liquid absorption. In Examples 1 to 3, the fiber mixing ratio of the first fiber layer is varied. No significant difference in smoothness was observed in these examples. As the proportion of adhesive fibers increased, the amount of fluff coming off tended to increase, and it was found that the entanglement of the hydrophilic fibers in the first and second fiber layers contributed to the suppression of fluff coming off. The liquid absorption time tended to become longer as the proportion of adhesive fibers increased (that is, as the proportion of hydrophilic fibers decreased).

In Comparative Example 1, the hydroentanglement treatment was carried out by injecting a water flow with a higher water pressure twice on the side of the second fiber layer, and jetting a water flow with a lower water pressure once on the side of the first fiber layer to entangle the fibers. It is what I let you do.
In the nonwoven fabric of Comparative Example 1, φ1 was less than 30 µm. This is presumed to be the result of the entanglement of the hydrophilic fibers progressing further by applying greater water flow energy to the side of the second fiber layer containing more hydrophilic fibers. Therefore, the unevenness due to the jetting of the water jet appeared more remarkably, and the MMD in the CD direction became larger.

The liquid absorption time of Comparative Example 1 was longer than that of Example 1. It is presumed that this is because the entanglement of the hydrophilic fibers further progressed, resulting in a higher fiber density and a decrease in inter-fiber voids that temporarily store the liquid.

Furthermore, Comparative Example 1 showed a larger amount of fluff coming off than Example 1, which was different only in hydroentanglement treatment conditions. This is because in Comparative Example 1, the entanglement of the fibers progressed, so that more hydrophilic fibers in the second fiber layer were exposed on the surface of the first fiber layer, and more fibers were present on the surface of the first fiber layer. Therefore, it is presumed that the number of fibers falling off as fluff increased accordingly.

In Comparative Example 2, the water pressure during the hydroentanglement treatment was made lower than the water pressure used in the production of Example 1, and the number of injections was reduced to entangle the fibers.
In the nonwoven fabric of Comparative Example 2, φ2 exceeded 40 μm and φ1 was also relatively large. This means that the degree of entanglement between fibers during the hydroentanglement treatment is smaller than that in the examples. Therefore, in Comparative Example 2, the amount of fluff coming off was large. In addition, the liquid absorption time of Comparative Example 1 was longer than the liquid absorption time of any of the examples. This is because the degree of entanglement of the hydrophilic fibers between the first fiber layer and the second fiber layer is small, and the "connection" of the hydrophilic fibers between the two fiber layers is insufficient. It is presumed that this is due to the fact that it was difficult for the liquid to be drawn into the layer.

Comparative Example 3 is an example in which the proportion of adhesive fibers contained in the first fiber layer is maximized. This nonwoven fabric had a smoothness of the first fibrous layer comparable to that of Examples, but the liquid absorption time of Comparative Example 3 was longer than that of any of the Examples. This is because the hydrophilic fibers contained in the first fiber layer play a role in transferring the liquid to the second fiber layer, and the ratio of the hydrophilic fibers in the first fiber layer was small. it is conceivable that. In Comparative Example 3, the thickness was greater than that of Examples, and the distance from the surface of the nonwoven fabric to the absorbent body was increased, making it difficult for the liquid to be drawn in. This also affects the liquid absorption time. It is speculated that

Comparative Example 4 was produced by performing the entangling process first and then performing the bonding process. In this comparative example, φ1 was less than 30 μm, and the degree of entanglement in the first fiber layer was greater than that of the example. It is presumed that this is because the laminated fiber web was subjected to the hydroentangling treatment in a state in which the fibers of the first fiber layer were not adhered to each other, so that the entanglement of the fibers progressed further. Comparative Example 4 exhibited the largest MMD in the CD direction among all Examples and Comparative Examples. It is presumed that this is because the unevenness caused by the jetting of the water stream became more conspicuous.

Comparative Examples 5 and 6 are both single-layer structures, with Comparative Example 5 containing more hydrophilic fibers and Comparative Example 6 containing more adhesive fibers.
In Comparative Example 5, both φ1 and φ2 were small. This is thought to be due to the fact that the proportion of hydrophilic fibers was high and the degree of entanglement between fibers was high. Therefore, fluff coming off did not occur. On the other hand, the liquid return amount was relatively large. This is because the viscose rayon fibers used as hydrophilic fibers in the present examples and comparative examples have liquid absorption properties and retain liquid to some extent, so that when pressure is applied, the viscose rayon fibers are released. This is considered to be one of the causes of liquid return, because the total amount of liquid released increases due to the high ratio of hydrophilic fibers.

In Comparative Example 6, adhesive fibers were included in the entire single layer, and the proportion of hydrophilic fibers was small. Therefore, φ2 is large. In addition, since the hydrophilic fibers were evenly distributed over the entire layer, it was difficult to form a gradient in the ratio of the hydrophilic fibers, so the liquid absorption time was long.

Examples 4 to 7 and Comparative Example 8 differ from Example 1 in the fiber diameter of the hydrophilic fibers used, and Example 8 differs from Example 1 in the fiber diameters of the hydrophilic fibers and the adhesive fibers. In Comparative Example 8, since the hydrophilic fibers had a large fiber diameter and increased rigidity, bending was less likely to occur during the hydroentangling treatment, resulting in larger φ1 and φ2.

From these examples, the average value (AVE) of the MMD in the MD direction and the MMD in the CD direction tended to increase as the fiber diameter of the hydrophilic fibers increased. This is probably because the larger the fiber diameter, the smaller the number of fibers constituting the fiber layer with the same basis weight, and the lower the density of the surface. However, for the nonwoven fabric of Example 4, the MMD AVE was rather large. It is considered that this is because the fiber diameter is small and thus neps are generated due to the entanglement of the fibers.

In addition, the liquid return amount tended to decrease as the fiber diameter of the hydrophilic fibers increased. It is considered that this is because the amount of liquid retained by the hydrophilic fibers is reduced as the number of constituent hydrophilic fibers is reduced. On the other hand, the greater the fiber diameter of the hydrophilic fibers, the shorter the liquid absorption time. It is considered that this is because the number of fibers was small and the inter-fiber voids increased.
Example 8, in which the fineness of the adhesive fibers is large, showed a relatively large amount of fluff coming off. This is probably because the number of adhesive fibers constituting the fiber layer decreased as the fineness of the adhesive fibers increased, and the bonding points decreased accordingly.

Comparative Example 7 had a higher ratio of hydrophilic fibers in the first fiber layer than Example 1, and φ1 was less than 30 μm. This is probably because the hydrophilic fibers, which tend to be entangled with each other due to water flow, have a relatively large "curve" due to the entanglement, and the hydrophilic fibers occupy most of the fiber surface. In addition, Comparative Example 7 showed a relatively large liquid return amount. This is thought to be due to the presence of many hydrophilic fibers on the fiber surface, which tend to retain liquid.

In Example 9, the first fiber layer contained the hydrophilic fibers in the same proportion as in Comparative Example 7, and was produced by increasing the number of jets of water jetted to the first fiber layer. In Example 9, φ1 was 30 μm or more, and the liquid return amount was small. This is probably because the hydrophilic fibers moved inside the nonwoven fabric and the adhesive fibers with a relatively large radius of curvature were exposed on the surface of the nonwoven fabric by applying greater water flow energy to the first fiber layer.

In Example 10, the hydrophilic fibers contained more titanium oxide, and compared to Example 7, the MMD in all directions was smaller, and the MMD in the CD direction was particularly lower. This is probably because the increased content of titanium oxide slightly increased the rigidity of the hydrophilic fibers and slightly decreased the entangling property, so that unevenness due to jetting water was less likely to occur.

In Example 11, cotton was used as the hydrophilic fiber, and its MMD was higher than that of Example 1, and its liquid absorption rate was lower than that of Example 1. This is probably because cotton has a more irregular fiber cross-section than rayon and has unevenness, and the unevenness creates a relatively large number of voids between fibers.

Example 124 is a nonwoven fabric using polyethylene terephthalate fibers (“hydrophilic synthetic fibers”) coated with a hydrophilic fiber treatment agent in both the first and second fiber layers. It is a nonwoven fabric using a hydrophilic synthetic fiber for one of the fiber layers. Example 12 had a low fiber density and was bulky compared to Example 1. In addition, Example 12 tends to show a higher MMD AVE compared to Example 1, and compared to other examples in which cellulosic fibers are used as the first and second hydrophilic fibers. , tended to show higher MIU. Hydrophilic synthetic fibers have greater rigidity than rayon, and the fibers are less likely to entangle than rayon.

On the other hand, Examples 13 and 14 had lower fiber densities than Example 1, but lower MMD AVE than Example 12. It is believed that this is because one of the fiber layers contains rayon, which is easily entangled by water flow, so that the entanglement is well balanced between the rayon and the hydrophilic synthetic fiber.

(Aspect 1)
A nonwoven fabric for absorbent articles comprising a first fiber layer and a second fiber layer,
one surface of the first fiber layer forms the surface of the nonwoven fabric, and the other surface is in contact with the second fiber layer;
The first fiber layer includes adhesive fibers and first hydrophilic fibers,
The first fiber layer contains 40% to 75% by mass of the adhesive fiber and 25% to 60% by mass of the first hydrophilic fiber, based on the total mass of the first fiber layer. ,
The second fiber layer comprises a second hydrophilic fiber,
The second fiber layer contains 70% by mass or more and 100% by mass or less of the second hydrophilic fiber based on the total mass of the second fiber layer,
In the first fiber layer, the fibers are bonded to each other by the adhesive fibers,
The first fiber layer and the second fiber layer are integrated by entangling the fibers,
The radius of curvature (φ1) of the fibers on the surface of the first fiber layer is 30 μm or more, the radius of curvature (φ2) of the fibers on the surface of the second fiber layer is 40 μm or less, and φ1>φ2 is satisfied;
wherein the first fibrous layer is positioned closer to the user's skin;
Nonwoven fabric for absorbent articles.
(Aspect 2)
The first hydrophilic fibers have a fiber diameter of 4 μm or more and 15 μm or less, the second hydrophilic fibers have a fiber diameter of 4 μm or more and 15 μm or less, and the adhesive fibers have a fiber diameter of 6 μm or more and 19 μm or less. , the nonwoven fabric for absorbent articles according to aspect 1.
(Aspect 3)
The nonwoven fabric for absorbent articles according to aspect 1 or 2, wherein fibers are not bonded together in the second fiber layer.
(Aspect 4)
A nonwoven fabric for absorbent articles comprising a first fiber layer and a second fiber layer,
one surface of the first fiber layer forms the surface of the nonwoven fabric, and the other surface is in contact with the second fiber layer;
The first fiber layer includes adhesive fibers and first hydrophilic fibers,
The first fiber layer contains 40% to 75% by mass of the adhesive fiber and 25% to 60% by mass of the first hydrophilic fiber, based on the total mass of the first fiber layer. ,
The second fiber layer comprises a second hydrophilic fiber,
The second fiber layer contains 70% by mass or more and 100% by mass or less of the second hydrophilic fiber based on the total mass of the second fiber layer,
In the first fiber layer, the fibers are bonded to each other by the adhesive fibers,
The first fiber layer and the second fiber layer are integrated by entangling the fibers,
The first hydrophilic fibers have a fiber diameter of 4 μm or more and 15 μm or less, the second hydrophilic fibers have a fiber diameter of 4 μm or more and 15 μm or less, and the adhesive fibers have a fiber diameter of 6 μm or more and 19 μm or less. ,
The fluff removal amount of the first fiber layer measured according to the following method is 3.0 mg or less,
Nonwoven fabric for absorbent articles.
(Method for measuring the amount of fluff removed)
a) A disc (diameter: 70 mm, 350 g) whose surface is covered with urethane foam (thickness: 5 mm) is attached to the rotary shaft so that the rotary shaft is shifted from the center of the disc by 20 mm.
b) The same urethane foam as above is spread, and the nonwoven fabric is fixed on the table so that the first fiber layer of the nonwoven fabric becomes an exposed surface.
c) placing the disc on top of the non-woven fabric; At this time, the only load applied to the nonwoven fabric is the weight of the disk itself.
d) Rotate the rotating shaft to rotate the disk on the nonwoven fabric. Circular motion is performed 10 sets of 2 rotations clockwise and 2 rotations counterclockwise. The rotation speed at this time is about 3 seconds per one rotation.
e) After 3 sets of circular movements, the fibers falling off from the nonwoven fabric and adhering to the surface of the urethane foam covering the disk are collected.
f) The above operations a) to e) are performed on n=3 nonwoven fabrics. For each of the three nonwoven fabrics, the mass of the fallen fibers is measured, and the average value is defined as the fluff amount (mg).
(Aspect 5)
The fibers are not bonded together in the second fiber layer,
The nonwoven fabric for absorbent articles according to any one of aspects 1 to 4, wherein the stress at 10% elongation in the MD direction is 16.5 N/5 cm or more and 50.0 N/5 cm or less.
Nonwoven fabric for absorbent articles.
(Aspect 6)
The first fiber layer contains 55% to 75% by mass of the adhesive fiber and 25% to 45% by mass of the first hydrophilic fiber, based on the total mass of the first fiber layer. , the nonwoven fabric for absorbent articles according to any one of aspects 1 to 5.
(Aspect 7)
Aspects 1 to 6, wherein the basis weight of the first fiber layer is 10 g/m ² or more and 40 g/m ² or less, and the basis weight of the second fiber layer is 10 g/m ² or more and 40 g/m ² or less. Nonwoven fabric for absorbent articles.
(Aspect 8)
The nonwoven fabric for absorbent articles according to any one of aspects 1 to 7, wherein the adhesive fibers are concentric sheath-core composite fibers.
(Aspect 9)
The nonwoven fabric for absorbent articles according to any one of aspects 1 to 8, wherein one or both of the first hydrophilic fibers and the second hydrophilic fibers are cellulosic fibers.
(Mode 10)
The nonwoven fabric for absorbent articles according to aspect 9, wherein the cellulosic fibers are regenerated fibers.
(Aspect 11)
The nonwoven fabric for absorbent articles according to any one of aspects 1 to 10, wherein at least one of the first hydrophilic fibers and the second hydrophilic fibers is a synthetic fiber coated with a hydrophilic fiber treatment agent.
(Aspect 12)
has a density of less than 0.065 g/ ^cm3 ;
When the variation (MMD) of the average coefficient of friction on the surface of the first fiber layer is measured, the average value of the MMD in the longitudinal direction and the MMD in the transverse direction is 0.0100 or less.
The nonwoven fabric for absorbent articles according to aspect 11.
(Aspect 13)
A top sheet for absorbent articles, comprising the nonwoven fabric for absorbent articles according to any one of aspects 1 to 12, wherein the first fiber layer is arranged closer to the user's skin.
(Aspect 14)
An absorbent article comprising the topsheet of aspect 13, wherein said first fibrous layer is positioned closer to the user's skin.
(Aspect 15)
A nonwoven fabric for absorbent articles comprising a first fiber layer and a second fiber layer, wherein the first fiber layer forms one surface of the nonwoven fabric, and the other surface is in contact with the second fiber layer, A method for producing a nonwoven fabric for absorbent articles in which the first fiber layer is arranged closer to the user's skin,
A step of producing a first fibrous web containing 40% by mass or more and 75% by mass or less of adhesive fibers and 25% by mass or more and 60% by mass or less of first hydrophilic fibers based on the total mass of the first fibrous web. ,
A step of producing a second fibrous web containing 70% by mass or more and 100% by mass or less of the second hydrophilic fiber based on the total mass of the second fibrous web;
a bonding step of bonding the fibers of the first fibrous web with the adhesive fibers;
a lamination step of obtaining a laminated fiber web by laminating the first fiber web and the second fiber web after the bonding step;
an interlacing step of interlacing and integrating the fibers of the first fibrous web and the second fibrous web of the laminated fibrous web;
The entangling step includes a hydroentangling process in which a water stream is jetted toward the second fibrous web to entangle the fibers, and then a water stream is jetted toward the first fibrous web to entangle the fibers. In the hydroentanglement treatment, the total energy E1 of the water flow jetted to the first fiber web side is higher than the total energy E2 of the water jet jetted to the second fiber web side, and the ratio of E1 to E2 (E1 /E2) is 2.5 or more and 12.0 or less,
A method for producing a nonwoven fabric for absorbent articles, wherein the first fiber web serves as the first fiber layer, and the second fiber web serves as the second fiber layer.
(Aspect 16)
The adhesive fiber is a synthetic fiber whose surface is coated with a hydrophilic fiber treatment agent, has an initial sedimentation rate of less than 60 seconds, and is washed three times with warm water at 40°C for 2 minutes. The method for producing a nonwoven fabric for absorbent articles according to aspect 15, wherein the sedimentation speed after washing is 60 seconds or more.
(Aspect 17)
17. The method for producing a nonwoven fabric for absorbent articles according to aspect 15 or 16, wherein one or both of the first hydrophilic fibers and the second hydrophilic fibers are cellulosic fibers.
(Aspect 18)
The absorbent according to any one of aspects 15 to 17, wherein one or both of the first hydrophilic fiber and the second hydrophilic fiber are synthetic fibers coated with a hydrophilic fiber treatment agent on the fiber surface. A method for producing a nonwoven fabric for articles.
(Aspect 19)
The synthetic fiber, the surface of which is coated with a hydrophilic fiber treatment agent, has an initial sedimentation rate of less than 60 seconds, and has a post-washing sedimentation rate of less than 60 seconds. The method for producing a nonwoven fabric for absorbent articles according to aspect 18, which is less than 60 seconds.

Since the nonwoven fabric for absorbent articles of the present embodiment has a smooth feel and excellent liquid absorbency, it can be used as a top sheet for disposable diapers, panty liners, sanitary napkins, and the like.

Claims (19)

A nonwoven fabric for absorbent articles comprising a first fiber layer and a second fiber layer,
one surface of the first fiber layer forms the surface of the nonwoven fabric, and the other surface is in contact with the second fiber layer;
The first fiber layer includes adhesive fibers and first hydrophilic fibers,
The first fiber layer contains 40% to 75% by mass of the adhesive fiber and 25% to 60% by mass of the first hydrophilic fiber, based on the total mass of the first fiber layer. ,
The second fiber layer comprises a second hydrophilic fiber,
The second fiber layer contains 70% by mass or more and 100% by mass or less of the second hydrophilic fiber based on the total mass of the second fiber layer,
In the first fiber layer, the fibers are bonded to each other by the adhesive fibers,
The first fiber layer and the second fiber layer are integrated by entangling the fibers,
The radius of curvature (φ1) of the fibers on the surface of the first fiber layer is 30 μm or more, the radius of curvature (φ2) of the fibers on the surface of the second fiber layer is 40 μm or less, and φ1>φ2 is satisfied;
wherein the first fibrous layer is positioned closer to the user's skin;
Nonwoven fabric for absorbent articles. The first hydrophilic fibers have a fiber diameter of 4 μm or more and 15 μm or less, the second hydrophilic fibers have a fiber diameter of 4 μm or more and 15 μm or less, and the adhesive fibers have a fiber diameter of 6 μm or more and 19 μm or less. , The nonwoven fabric for absorbent articles according to claim 1. The nonwoven fabric for absorbent articles according to claim 1 or 2, wherein fibers are not bonded together in said second fiber layer. A nonwoven fabric for absorbent articles comprising a first fiber layer and a second fiber layer,
one surface of the first fiber layer forms the surface of the nonwoven fabric, and the other surface is in contact with the second fiber layer;
The first fiber layer includes adhesive fibers and first hydrophilic fibers,
The first fiber layer contains 40% to 75% by mass of the adhesive fiber and 25% to 60% by mass of the first hydrophilic fiber, based on the total mass of the first fiber layer. ,
The second fiber layer comprises a second hydrophilic fiber,
The second fiber layer contains 70% by mass or more and 100% by mass or less of the second hydrophilic fiber based on the total mass of the second fiber layer,
In the first fiber layer, the fibers are bonded to each other by the adhesive fibers,
The first fiber layer and the second fiber layer are integrated by entangling the fibers,
The first hydrophilic fibers have a fiber diameter of 4 μm or more and 15 μm or less, the second hydrophilic fibers have a fiber diameter of 4 μm or more and 15 μm or less, and the adhesive fibers have a fiber diameter of 6 μm or more and 19 μm or less. ,
The fluff removal amount of the first fiber layer measured according to the following method is 3.0 mg or less,
Nonwoven fabric for absorbent articles.
(Method for measuring the amount of fluff removed)
a) A disc (diameter: 70 mm, 350 g) whose surface is covered with urethane foam (thickness: 5 mm) is attached to the rotary shaft so that the rotary shaft is shifted from the center of the disc by 20 mm.
b) The same urethane foam as above is spread, and the nonwoven fabric is fixed on the table so that the first fiber layer of the nonwoven fabric becomes an exposed surface.
c) placing the disc on top of the non-woven fabric; At this time, the only load applied to the nonwoven fabric is the weight of the disk itself.
d) Rotate the rotating shaft to rotate the disk on the nonwoven fabric. Circular motion is performed 10 sets of 2 rotations clockwise and 2 rotations counterclockwise. The rotation speed at this time is about 3 seconds per one rotation.
e) After 3 sets of circular movements, the fibers falling off from the nonwoven fabric and adhering to the surface of the urethane foam covering the disk are collected.
f) The above operations a) to e) are performed on n=3 nonwoven fabrics. For each of the three nonwoven fabrics, the mass of the fallen fibers is measured, and the average value is defined as the fluff amount (mg). The fibers are not bonded together in the second fiber layer,
The nonwoven fabric for absorbent articles according to any one of claims 1 to 4, wherein the stress at 10% elongation in the MD direction is 16.5 N/5 cm or more and 50.0 N/5 cm or less.
Nonwoven fabric for absorbent articles. The first fiber layer contains 55% to 75% by mass of the adhesive fiber and 25% to 45% by mass of the first hydrophilic fiber, based on the total mass of the first fiber layer. The nonwoven fabric for absorbent articles according to any one of claims 1 to 5. 7. The basis weight of the first fiber layer is 10 g/m ² or more and 40 g/m ² or less, and the basis weight of the second fiber layer is 10 g/m ² or more and 40 g/m ² or less. Nonwoven fabric for absorbent articles according to. The nonwoven fabric for absorbent articles according to any one of claims 1 to 7, wherein said adhesive fibers are concentric sheath-core composite fibers. The nonwoven fabric for absorbent articles according to any one of claims 1 to 8, wherein one or both of said first hydrophilic fibers and said second hydrophilic fibers are cellulosic fibers. The nonwoven fabric for absorbent articles according to claim 9, wherein the cellulosic fibers are regenerated fibers. The absorbent article according to any one of claims 1 to 10, wherein at least one of said first hydrophilic fibers and said second hydrophilic fibers is a synthetic fiber coated with a hydrophilic fiber treatment agent. Non-woven fabric for has a density of less than 0.065 g/ ^cm3 ;
When the variation (MMD) of the average coefficient of friction on the surface of the first fiber layer is measured, the average value of the MMD in the longitudinal direction and the MMD in the transverse direction is 0.0100 or less.
The nonwoven fabric for absorbent articles according to claim 11. A top sheet for absorbent articles, comprising the nonwoven fabric for absorbent articles according to any one of claims 1 to 12, wherein the first fiber layer is arranged closer to the user's skin. 14. An absorbent article comprising the topsheet of claim 13, wherein the first fibrous layer is positioned closer to the user's skin. A nonwoven fabric for absorbent articles comprising a first fiber layer and a second fiber layer, wherein the first fiber layer forms one surface of the nonwoven fabric, and the other surface is in contact with the second fiber layer, A method for producing a nonwoven fabric for absorbent articles in which the first fiber layer is arranged closer to the user's skin,
A step of producing a first fibrous web containing 40% by mass or more and 75% by mass or less of adhesive fibers and 25% by mass or more and 60% by mass or less of first hydrophilic fibers based on the total mass of the first fibrous web. ,
A step of producing a second fibrous web containing 70% by mass or more and 100% by mass or less of the second hydrophilic fiber based on the total mass of the second fibrous web;
a bonding step of bonding the fibers of the first fibrous web with the adhesive fibers;
a lamination step of obtaining a laminated fiber web by laminating the first fiber web and the second fiber web after the bonding step;
an interlacing step of interlacing and integrating the fibers of the first fibrous web and the second fibrous web of the laminated fibrous web;
The entangling step includes a hydroentangling process in which a water stream is jetted toward the second fibrous web to entangle the fibers, and then a water stream is jetted toward the first fibrous web to entangle the fibers. In the hydroentanglement treatment, the total energy E1 of the water flow jetted to the first fiber web side is higher than the total energy E2 of the water jet jetted to the second fiber web side, and the ratio of E1 to E2 (E1 /E2) is 2.5 or more and 12.0 or less,
A method for producing a nonwoven fabric for absorbent articles, wherein the first fiber web serves as the first fiber layer, and the second fiber web serves as the second fiber layer. The adhesive fiber is a synthetic fiber whose surface is coated with a hydrophilic fiber treatment agent, has an initial sedimentation rate of less than 60 seconds, and is washed three times with warm water at 40°C for 2 minutes. 16. The method for producing a nonwoven fabric for absorbent articles according to claim 15, wherein the sedimentation speed after washing is 60 seconds or more. 17. The method for producing a nonwoven fabric for absorbent articles according to claim 15 or 16, wherein one or both of said first hydrophilic fibers and said second hydrophilic fibers are cellulosic fibers. Any one or both of the first hydrophilic fiber and the second hydrophilic fiber are synthetic fibers having a fiber surface coated with a hydrophilic fiber treatment agent, according to any one of claims 15 to 17. Method for producing a nonwoven fabric for absorbent articles. The synthetic fiber, the surface of which is coated with a hydrophilic fiber treatment agent, has an initial sedimentation rate of less than 60 seconds, and has a post-washing sedimentation rate of less than 60 seconds. The method for producing a nonwoven fabric for absorbent articles according to claim 18, wherein the time is less than 60 seconds.

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