JP7594080B2 - Nonwoven fabric for absorbent articles and manufacturing method thereof - Google Patents

Description

The present invention relates to a nonwoven fabric for absorbent articles, and more specifically, to a nonwoven fabric for absorbent articles that can be used as a top sheet and a diffusion layer of an absorbent article.

Absorbent articles (e.g., diapers, incontinence pads, napkins, panty liners, etc.) are composed of a top sheet, a diffusion layer, an absorbent body, etc. The top sheet is required to quickly draw moisture that comes into contact with the absorbent article into the absorbent article, to provide a pleasant feel to human skin, and to prevent the drawn moisture from returning to the top sheet surface. The diffusion layer is required to diffuse the moisture drawn in by the top sheet and quickly pass it through, transferring it to the absorbent body, etc. The absorbent body is required to firmly retain the absorbed moisture, etc.

For example, Patent Document 1 discloses a surface sheet for absorbent articles comprising a first fiber layer that contacts the skin and a second fiber layer adjacent to the first fiber layer, the first fiber layer being a fiber layer containing 50% by mass or more of first core-sheath composite short fibers whose core component contains polypropylene and whose sheath component contains a thermoplastic resin having a melting point 5°C or more lower than the melting point of the polypropylene, the second fiber layer being a fiber layer containing 50% by mass or more of first core-sheath composite short fibers whose core component contains polyester resin and whose sheath component contains a thermoplastic resin having a melting point 50°C or more lower than the melting point of the polyester resin, A nonwoven fabric usable as a top sheet for absorbent articles is disclosed, which is a fiber layer containing 50% by mass or more of second sheath-core composite staple fibers whose center of gravity is shifted from the center of gravity of the fiber, the first sheath-core composite staple fibers have a fineness of 0.5 dtex or more and 2.1 dtex or less, the second sheath-core composite staple fibers have a fineness of 2.2 dtex or more and 5.2 dtex or less, and at least a portion of the first sheath-core composite staple fibers and the second sheath-core composite staple fibers are thermally bonded by the sheath component of the first sheath-core composite staple fibers and the second sheath-core composite staple fibers. Patent Document 1 discloses that the nonwoven fabric has the advantageous effects of having a smooth feel and good liquid absorption properties such as runoff and liquid absorption speed.

For example, Patent Document 2 discloses a sheet that can be used as a diffusion layer for absorbent articles, which is composed of fibers containing cellulose fibers that have intrafiber crosslinks and are deformed and fixed by adding a crosslinking agent to cellulose fibers and subjecting them to mechanical stirring, fluffing, and heat treatment. Patent Document 2 discloses that the sheet has the advantageous effect of quickly absorbing liquids such as urine and body fluids on the top sheet even under pressure compression, and quickly diffusing and releasing the absorbed liquid to the absorbent without retaining much of it.

JP 2015-204983 A Japanese Patent Application Publication No. 08-308873

Conventionally, in order to manufacture an absorbent article, it was necessary to bond a top sheet nonwoven fabric and a diffusion layer nonwoven fabric that were manufactured separately. In particular, when the top sheet nonwoven fabric or the diffusion layer nonwoven fabric contains cellulosic fibers, a method of using an adhesive is adopted for bonding the two fabrics. However, this method may result in gaps between the top sheet nonwoven fabric and the diffusion layer nonwoven fabric, or the amount of adhesive may be unstable, resulting in a failure to achieve stable liquid absorption performance. Furthermore, in recent years, absorbent articles have come to be required to have the property of making the color of the liquid that adheres to them less noticeable (also known as "masking properties").

On the other hand, there is a continuous demand for cost reductions in absorbent articles, and because the use of adhesives leads to increased costs, it was necessary to investigate a method of bonding without using adhesives.

After extensive research, the inventors have discovered that if a nonwoven fabric having the properties of both a top sheet nonwoven fabric and a diffusion layer nonwoven fabric can be manufactured in a single manufacturing process, the manufacturing of absorbent articles can be simplified and stable liquid absorption performance can be achieved. Furthermore, they have discovered that such a nonwoven fabric is suitable for use in absorbent articles, which has led to the completion of the present invention.

The present disclosure provides, as one aspect, a nonwoven fabric for absorbent articles, which comprises:
A nonwoven fabric comprising a first fiber layer and a second fiber layer located on one main surface of the first fiber layer,
the first fibrous layer comprises adhesive fibers;
the first fiber layer contains 60 mass% or more and 100 mass% or less of the adhesive fiber based on the total mass of the first fiber layer;
the second fibrous layer comprises cellulosic fibers;
the second fiber layer contains 60% by mass or more and 100% by mass or less of the cellulosic fibers based on the total mass of the second fiber layer;
The first fiber layer has fibers bonded to each other by the adhesive fibers,
the first fiber layer and the second fiber layer are integrated by entanglement of the fibers,
the first fibrous layer being disposed closer to the user's skin;
Satisfy either of the following (i) and (ii):
(i) The nonwoven fabric has a thickness change rate of 16% or more as measured by the following measurement method; and (ii) the fibers contained in the second fiber layer are not bonded by the adhesive fibers. This nonwoven fabric is for absorbent articles.
[Thickness change rate]
Using a thickness measuring device, the thickness of the nonwoven fabric is measured while a load of 294 Pa or 1.96 kPa is applied to the nonwoven fabric, and the thickness is calculated based on the thickness (P1) at a load of 294 Pa and the thickness (P2) at a load of 1.96 kPa according to the following formula.
Thickness change rate (%) = [(P1 - P2) / P1] x 100

In still another aspect, the present disclosure provides a method for producing a nonwoven fabric for an absorbent article, the method comprising the steps of:
A method for manufacturing a nonwoven fabric for absorbent articles, the nonwoven fabric comprising a first fiber layer and a second fiber layer located on one main surface of the first fiber layer, the first fiber layer being disposed closer to a user's skin, the method comprising the steps of:
preparing a first fiber web containing from 60% by weight to 100% by weight of adhesive fibers based on the total weight of the web;
a bonding step of bonding fibers of the first fiber web together with the adhesive fibers;
preparing a second fiber web containing 60% by weight or more and 100% by weight or less of cellulosic fibers based on the total weight of the web;
a lamination step of laminating the first fiber web and the second fiber web to obtain a laminated fiber web;
The laminated fiber web includes an entanglement step of entangling the fibers of the first fiber web and the second fiber web to integrate them,
The method for producing a nonwoven fabric for an absorbent article includes the first fiber layer and the second fiber layer includes the second fiber web.

The nonwoven fabric for absorbent articles according to the embodiment of the present invention can be used as a nonwoven fabric that has the properties of both a top sheet and a diffusion layer. Therefore, the nonwoven fabric for absorbent articles according to the present invention can be suitably used to manufacture absorbent articles, and the manufacturing method thereof can be simplified.

1 is a photograph of the surface of the nonwoven fabric sample having the smallest area with a color intensity equivalent to that of artificial menstrual blood after the second measurement of the liquid absorption time for the five nonwoven fabric samples of Example 7. In the nonwoven fabric of Example 7, there was substantially no area with a color intensity equivalent to that of artificial menstrual blood. 2 is a photograph of the surface of the nonwoven fabric sample having the smallest area with a color intensity equivalent to that of artificial menstrual blood after the second measurement of the liquid absorption time for the five nonwoven fabric samples of Comparative Example 3. In the nonwoven fabric of Comparative Example 3, areas with a color intensity equivalent to that of artificial menstrual blood were clearly present even after the first measurement of the liquid absorption time.

In one aspect, the present disclosure provides a new nonwoven fabric for absorbent articles.
The nonwoven fabric according to the embodiment of the present invention is
A nonwoven fabric comprising a first fiber layer and a second fiber layer located on one main surface of the first fiber layer,
the first fibrous layer comprises adhesive fibers;
the first fiber layer contains 60 mass% or more and 100 mass% or less of the adhesive fiber based on the total mass of the first fiber layer;
the second fibrous layer comprises cellulosic fibers;
the second fiber layer contains 60% by mass or more and 100% by mass or less of the cellulosic fibers based on the total mass of the second fiber layer;
The first fiber layer has fibers bonded to each other by the adhesive fibers,
the first fiber layer and the second fiber layer are integrated by entanglement of the fibers,
the first fibrous layer being disposed closer to the user's skin;
Satisfy either of the following (i) and (ii):
(i) The nonwoven fabric has a thickness change rate of 16% or more as measured by the following measurement method; and (ii) the fibers contained in the second fiber layer are not bonded by the adhesive fibers. This nonwoven fabric is for absorbent articles.
[Thickness change rate]
Using a thickness measuring device, the thickness of the nonwoven fabric is measured while a load of 294 Pa or 1.96 kPa is applied to the nonwoven fabric, and the thickness is calculated based on the thickness (P1) at a load of 294 Pa and the thickness (P2) at a load of 1.96 kPa according to the following formula.
Thickness change rate (%) = [(P1 - P2) / P1] x 100

The nonwoven fabric for absorbent articles according to the embodiment of the present invention can be used in absorbent articles (e.g., diapers, incontinence pads, napkins, panty liners, etc.) that come into direct contact with human skin (e.g., top sheets for absorbent articles, preferably also having the function of a diffusion layer).

The nonwoven fabric according to an embodiment of the present invention includes a first fiber layer and a second fiber layer located on one of the main surfaces of the first fiber layer, the first fiber layer includes adhesive fibers, the first fiber layer includes 60% by mass or more and 100% by mass or less of the adhesive fibers based on the total mass of the first fiber layer, and the fibers of the first fiber layer are bonded to each other by the adhesive fibers.

(Adhesive Fiber)
In the nonwoven fabric of the embodiment of the present invention, the term "adhesive fiber" refers to a fiber that exhibits adhesiveness through a bonding process (e.g., thermal bonding process, electron beam irradiation, ultrasonic welding (ultrasonic welder), etc.) and can be bonded together to form bonded portions, and is not particularly limited as long as the nonwoven fabric intended by the present disclosure can be obtained.

The adhesive fibers include, for example, synthetic fibers made of thermoplastic resin.
The thermoplastic resin is not particularly limited as long as it can produce the nonwoven fabric intended by the present disclosure, and examples thereof include polyester-based resins such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polylactic acid, polybutylene succinate, and copolymers thereof; polyolefin-based resins such as polypropylene, polyethylene (including high-density polyethylene, low-density polyethylene, linear low-density polyethylene, and the like), polybutene-1, propylene copolymers having propylene as the main component (including propylene-ethylene copolymer, propylene-butene-1-ethylene copolymer), ethylene-acrylic acid copolymer, and ethylene-vinyl acetate copolymer; polyamide-based resins such as nylon 6, nylon 12, and nylon 66; acrylic-based resins; engineering plastics such as polycarbonate, polyacetal, polystyrene, and cyclic polyolefin, as well as elastomers thereof, and the like can be exemplified, and any one of these can be selected.

The synthetic fiber may be a single fiber made of one or more thermoplastic resins selected from the above, or may be a composite fiber made of two or more components (also called "sections"). In the composite fiber, each component may be made of one thermoplastic resin, or may be a mixture of two or more thermoplastic resins. The composite fiber may be, for example, a sheath-core composite fiber, a split composite fiber, an islands-in-the-sea composite fiber, or a side-by-side composite fiber. The sheath-core composite fiber may be an eccentric sheath-core composite fiber in which the center of the core component does not coincide with the center of the sheath component in the fiber cross section, or a concentric sheath-core composite fiber in which the center of the core component coincides with the center of the sheath component in the fiber cross section. The adhesive fiber preferably includes a sheath-core composite fiber, and more preferably includes an eccentric sheath-core composite fiber.

Synthetic fibers, whether single or composite, may have a modified cross section. In the case of sheath-core and islands-in-sea composite fibers, the core and/or island components may have a modified cross section in the fiber cross section.
When the synthetic fibers have a non-circular cross section, the cross section may be elliptical, polygonal, star-shaped, or have multiple peaks joined at their bases (eg, cloverleaf shape).
In this embodiment, the synthetic fibers may be a combination of two or more synthetic fibers.

When the synthetic fiber is a composite fiber, two or more components may be arranged so that the thermoplastic resin with a lower melting point constitutes a part of the fiber surface. The thermoplastic resin with a low melting point (low melting point component) melts or softens when heat is applied in the process of producing the nonwoven fabric, and becomes an adhesive component. The low melting point component contributes to adhesion between fibers or to adhesion to other members, and can form adhesive sites.
When the synthetic fiber is a composite fiber, the low-melting point component is preferably exposed over 50% or more of the circumferential length of the fiber in the cross section of the fiber, more preferably over 60% or more, even more preferably over 80% or more, and particularly preferably over the entire circumferential length of the fiber.

In an embodiment of the present invention, the first fibrous layer has fibers bonded together by adhesive fibers.
Since the low melting point component of the adhesive fiber is not too small in the cross section of the fiber, there is a more appropriate area where the fibers can be bonded, the number of bonding points between the fibers is more appropriate, and the adhesive strength of the bonding points between the fibers is more appropriate, so that the adhesive fibers can bond more sufficiently. This makes it possible to more appropriately suppress the fluff of the nonwoven fabric and to improve the strength of the nonwoven fabric. Furthermore, in the subsequent entanglement, the degree to which the adhesion between the fibers is eliminated is more appropriate, so that the fluff of the nonwoven fabric can be more appropriately suppressed and the strength of the nonwoven fabric can be more sufficiently improved.
As described below, in the nonwoven fabric according to an embodiment of the present invention, the second fibrous layer contains cellulosic fibers, and the first fibrous layer and the second fibrous layer are integrated by entanglement.

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

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

When the adhesive fiber is a core-sheath type composite fiber in which a thermoplastic resin with a lower melting point constitutes the sheath, the core/sheath combination includes, for example, polyethylene terephthalate/polyethylene, polyethylene terephthalate/polypropylene, polyethylene terephthalate/propylene copolymer, polytrimethylene terephthalate/polyethylene, polybutylene terephthalate/polyethylene, polyethylene terephthalate/copolymerized polyester (for example, polyethylene terephthalate copolymerized with isophthalic acid), polylactic acid/polybutylene succinate, and polypropylene/ethylene-acrylic acid copolymer. Core-sheath type composite fibers in which the sheath is polyethylene (for example, high-density polyethylene, low-density polyethylene, or linear low-density polyethylene) or copolymerized polyester have the property that the sheath melts or softens when heat-treated at a temperature equal to or higher than the melting point of the thermoplastic resin constituting the sheath, bonding the fibers together and forming bonding points.

When the adhesive fiber includes a core-sheath type composite fiber, the composite ratio of the core to the sheath (volume ratio, core/sheath) of the core-sheath type composite fiber may be, for example, 80/20 to 20/80, and particularly 60/40 to 40/60.
If the ratio of the sheath is not too small, the adhesion between the fibers is more sufficient, the fuzzing can be more appropriately suppressed, or the strength of the nonwoven fabric can be more appropriate. If the ratio of the sheath is not too large, the ratio of the core component that maintains the fiber shape is more sufficient, and the strength of the nonwoven fabric can be more appropriate.

The adhesive fiber may contain two or more fibers, and the melting points of the adhesive components of those fibers may be different from each other. For example, the adhesive fiber may contain two fibers, and the difference in melting points of the adhesive components of those fibers may be 10°C or more and 40°C or less, or even 15°C or more and 30°C or less.

The fineness of the adhesive fiber is preferably from 1.0 dtex to 5.0 dtex, more preferably from 1.2 dtex to 4.8 dtex, even more preferably from 1.3 dtex to 4.5 dtex, and particularly preferably from 1.5 dtex to 3.5 dtex.
When the fineness of the adhesive fiber is within the above-mentioned range, the strength of the nonwoven fabric is improved and the texture of the nonwoven fabric is softer, which is preferable. Also, when the fineness of the adhesive fiber is within the above-mentioned range, the liquid absorption time is short and the wet-back prevention property is good, which is preferable.
When the adhesive fiber contains a splittable conjugate fiber, the adhesive fiber may contain an adhesive fiber having a fineness of 0.1 dtex or more and less than 1.0 dtex.

The fiber diameter of the adhesive fiber is preferably 10 μm or more and 33 μm or less, more preferably 12 μm or more and 30 μm or less, even more preferably 14 μm or more and 25 μm or less, and particularly preferably 16 μm or more and 22 μm or less.
When the fiber diameter of the adhesive fiber is within the above-mentioned range, the strength of the nonwoven fabric is improved and the texture of the nonwoven fabric is softer, which is preferable. Also, when the fiber diameter of the adhesive fiber is within the above-mentioned range, the liquid absorption time can be shortened and the wet-back prevention property can be improved, which is preferable.
When the adhesive fiber includes a splittable conjugate fiber, the adhesive fiber may include an adhesive fiber having a fiber diameter of 3 μm or more and less than 10 μm.

The fiber length of the adhesive fiber is preferably 25 mm or more and 100 mm or less, more preferably 30 mm or more and 70 mm or less, and even more preferably 35 mm or more and 60 mm or less.
When the fiber length of the adhesive fiber is within the above-mentioned range, the fiber entanglement is more favorable, which is preferable. In particular, the nonwoven fabric of the present disclosure can be manufactured by first bonding the constituent fibers together with the adhesive fiber and then performing an entanglement treatment. Therefore, when the fiber length is not too long, the number of bonding points on one fiber becomes more appropriate, and the entanglement with the constituent fibers of the second fiber layer can be more favorable. Also, when the fiber length is not too short, the number of bonding points on one fiber becomes more appropriate, and the entanglement of the fibers can be more favorable to the extent that the texture of the nonwoven fabric can be made sufficiently soft.

The adhesive fiber preferably has a three-dimensional crimp. In this specification, the term "three-dimensional crimp" is used to distinguish it from mechanical crimp, in which the crimp peaks (or crests) are acute. Three-dimensional crimp refers to, for example, crimp with curved peaks (wave crimp), crimp with spirally curved peaks (spiral crimp), crimp with a mixture of wave crimp and spiral crimp, and crimp with acute mechanical crimp and at least one of wave crimp and spiral crimp. The adhesive fiber may have a mechanical crimp.
When the adhesive fiber is a composite fiber, it may be a visibly crimped composite fiber. The term "visibly crimped composite fiber" refers to a fiber that exhibits three-dimensional crimp at the fiber stage. A visibly crimped composite fiber is different from a latent crimped composite fiber that exhibits three-dimensional crimp by heat treatment accompanied by fiber shrinkage.

When the adhesive fiber is an eccentric sheath-core type composite fiber, the eccentricity is preferably 5% or more and 50% or less, and more preferably 7% or more and 30% or less. The eccentricity here is defined by the following formula.
Eccentricity (%) = (distance between the center of the single fiber and the center of the core component) x 100 / (single fiber radius)
When the adhesive fiber has three-dimensional crimping, the first fiber layer has a high bulk, which prevents the liquid from coming out to the surface of the first fiber layer due to liquid return, and the masking property can be improved. When the adhesive fiber has three-dimensional crimping, the first fiber layer has a cushioning property, which improves the wearing comfort. The adhesive fibers can be used alone or in combination.

It is preferable that the adhesive fiber has a lower hydrophilicity than the cellulosic fiber contained in the second fiber layer. The hydrophilicity of the fiber can be known, for example, by the contact angle. Here, the contact angle refers to the angle between the water surface and the fiber surface where the free surface of the water contacts the fiber (taking the angle inside the water). Since the adhesive fiber has a lower hydrophilicity than the cellulosic fiber contained in the second fiber layer, it is possible to prevent liquid from coming out onto the surface of the first fiber layer due to liquid backflow, and it is also preferable because it is easy to draw liquid from the first fiber layer to the second fiber layer.

The adhesive fiber may be a fiber containing a hydrophilic fiber treatment agent. The form of inclusion of the hydrophilic fiber treatment agent is not particularly limited. The hydrophilic fiber treatment agent may be attached to the surface of the adhesive fiber or may be dispersed in the fiber. The hydrophilic fiber treatment agent can be attached to the surface of the adhesive fiber by spraying it onto the surface of the adhesive fiber with a spray or the like, or by applying it to the surface of the adhesive fiber by any method. The hydrophilic fiber treatment agent can be dispersed in the fiber by melt spinning a thermoplastic resin kneaded with the hydrophilic fiber treatment agent. The type of hydrophilic fiber treatment agent is not particularly limited. The hydrophilic fiber treatment agent may be a known one. Examples of hydrophilic fiber treatment agents include fiber treatment agents containing a surfactant. Examples of surfactants that can be used include anionic, cationic, zwitterionic and nonionic surfactants.

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 taken as 100% by mass. The content of the hydrophilic fiber treatment agent may particularly be 0.15% by mass or more and 1.0% by mass or less, and more particularly may be 0.2% by mass or more and 0.6% by mass or less.

The first fiber layer contains 60% to 100% by mass of the adhesive fiber based on the total mass of the first fiber layer, preferably 70% to 100% by mass of the adhesive fiber, more preferably 80% to 100% by mass of the adhesive fiber, and even more preferably 90% to 100% by mass of the adhesive fiber. The first fiber layer contains 60% to 100% by mass of the adhesive fiber based on the total mass of the first fiber layer, which is preferable because it can suppress fuzzing on the surface of the nonwoven fabric and improve the shape stability of the nonwoven fabric.

The first fiber layer may contain fibers other than adhesive fibers. Fibers other than adhesive fibers include, for example, cellulosic fibers, natural fibers that are not cellulosic fibers (e.g., wool, silk, etc.), and synthetic fibers that are not adhesive fibers (e.g., synthetic fibers that do not melt or soften when the adhesive component of the adhesive fiber is melted and do not exhibit adhesiveness), and are not particularly limited as long as the nonwoven fabric intended by the present invention can be obtained.

The fibers other than the adhesive fibers may be contained in a proportion of 40% by mass or less, particularly 30% by mass or less, more particularly 20% by mass or less, and even more particularly 10% by mass or less, and are not particularly limited as long as the nonwoven fabric intended by the present invention can be obtained. In an embodiment of the present invention, the first fiber layer may be a nonwoven fabric made of adhesive fibers and cellulosic fibers, or may be a nonwoven fabric made of adhesive fibers.

In an embodiment of the present invention, the fibers of the first fiber layer are bonded together by adhesive fibers. That is, the first fiber layer of an embodiment of the present invention includes bonded locations. This ensures both the strength of the nonwoven fabric and the suppression of fuzzing, improving handleability. Bonding by adhesive fibers can be achieved by melting or softening or altering a portion of the adhesive fiber to exhibit adhesiveness, and fixing the fibers that cross or come into contact with it. Bonding between fibers specifically refers to bonding between adhesive fibers and adhesive fibers, and when other fibers are further included, it also refers to bonding between adhesive fibers and other fibers. Bonding may be by thermal bonding, in which heat is applied to melt or soften a portion of the adhesive fiber, or by irradiation with an electron beam or the like or ultrasonic welding.

The first fiber layer preferably has a basis weight of 10 g/m2 or ^more and 50 g/m2 or ^less , more preferably has a basis weight of 15 g/m2 or ^more and 45 g/m2 or ^less , even more preferably has a basis weight of 20 g/m2 or ^more and 40 g/m2 or ^less , and particularly preferably has a basis weight of 20 g/ ^m2 or more and 35 g/m2 ^{or less} . When the first fiber layer has a basis weight in the above-mentioned range, the first fiber layer becomes bulky, which is preferable because it can suppress liquid from coming out to the surface of the first fiber layer due to liquid return and can improve masking properties.

In an embodiment of the present invention, the second fibrous layer comprises cellulosic fibers,
The second fiber layer contains 60% by mass or more and 100% by mass or less of the cellulosic fibers based on the total mass of the second fiber layer, and the first fiber layer and the second fiber layer are integrated by entanglement of the fibers.

Further, in an embodiment of the present invention, the first fiber layer is disposed closer to the skin of a user,
Either the following (i) or (ii) is satisfied:
(i) The thickness change rate of the nonwoven fabric measured by the following measurement method is 16% or more; and (ii) the fibers contained in the second fiber layer are not bonded by the adhesive fiber [Thickness change rate]
Using a thickness measuring device, the thickness of the nonwoven fabric is measured while a load of 294 Pa or 1.96 kPa is applied to the nonwoven fabric, and the thickness is calculated based on the thickness (P1) at a load of 294 Pa and the thickness (P2) at a load of 1.96 kPa according to the following formula.
Thickness change rate (%) = [(P1 - P2) / P1] x 100

(Cellulosic fiber)
In the nonwoven fabric according to the embodiment of the present invention, the term "cellulosic fiber" is also called cellulose fiber, and generally refers to a fiber made from cellulose as a raw material.
Cellulosic fibers include, for example, natural fibers derived from plants such as cotton, flax, flax (linen), ramie, jute, banana, bamboo, kenaf, shell ginger, hemp, and kapok; regenerated fibers such as rayon (viscose rayon) and polynosic rayon obtained by the viscose process, cupra obtained by the cuprammonium process, and Tencel (registered trademark) and Lyocell (registered trademark) obtained by a solvent spinning process; cellulose fibers obtained by a melt spinning process; and semi-synthetic fibers such as acetate fibers, and are not particularly limited as long as the nonwoven fabric intended by the present invention can be obtained.

The fineness of the cellulosic fibers is preferably 1.0 dtex or more and 5.0 dtex or less, more preferably 1.0 dtex or more and 4.0 dtex or less, and even more preferably 1.0 dtex or more and 3.5 dtex or less.
When the fineness of the cellulosic fiber is within the above-mentioned range, it is preferable that the fineness is not too small, so that voids are formed in the second fiber layer, which makes it easier to draw in liquid from the first fiber layer, and that the fineness is not too large, so that the second fiber layer has a good texture, and the surface of the second fiber layer can be flattened and uniformly contacted with the absorbent. Also, when the fineness of the cellulosic fiber is within the above-mentioned range, it is preferable that the entanglement of the fiber is more suitable, the entanglement of the nonwoven fabric is not too low, so that the strength of the nonwoven fabric and the integration of the first fiber layer and the second fiber layer are more suitable, and the entanglement of the nonwoven fabric is not too high, so that the voids of the second fiber layer are more suitable.

The fiber diameter of the cellulose-based fibers is preferably 5 μm or more and 25 μm or less, more preferably 8 μm or more and 20 μm or less, and even more preferably 10 μm or more and 17 μm or less.
When the fiber diameter of the cellulosic fiber is within the above-mentioned range, it is preferable because the fiber diameter is not too small, so that voids are formed in the second fiber layer, which makes it easier to draw in liquid from the first fiber layer, and the fiber diameter is not too large, so that the second fiber layer is well formed, and the surface of the second fiber layer is flat and can be uniformly contacted with the absorbent. Also, when the fiber diameter of the cellulosic fiber is within the above-mentioned range, it is preferable because the entanglement of the fiber is more suitable, the entanglement of the nonwoven fabric is not too low, so that the strength of the nonwoven fabric and the integration of the first fiber layer and the second fiber layer are more suitable, and the entanglement of the nonwoven fabric is not too high, so that the voids of the second fiber layer are more suitable.

The fiber length of the cellulosic fibers is preferably 25 mm or more and 100 mm or less, more preferably 30 mm or more and 70 mm or less, and even more preferably 35 mm or more and 60 mm or less.
When the fiber length of the cellulosic fiber is within the above-mentioned range, it is preferable that the fiber entanglement is favorable. When the fiber length is not too long, it is preferable that the strength of the nonwoven fabric is favorable. Also, when the fiber length is not too short, it is preferable that the voids in the second fiber layer are favorable and the integration of the first fiber layer and the second fiber layer is favorable.

The cross section of the cellulosic fibers (transverse section, or cross section perpendicular to the length of the fiber) may be circular or noncircular, and examples of noncircular shapes include ellipse, Y-shape, X-shape, well-shape, multi-lobed shape, polygonal shape, star shape, chrysanthemum shape, etc. If the cross section of the fiber is noncircular, it is preferable because it forms voids in the second fiber layer and makes it easier to draw in liquid from the first fiber layer.

The cellulosic fibers preferably include cellulosic fibers having a multi-leaf cross section, and when the fiber includes cellulosic fibers having a multi-leaf cross section, this has the advantageous effect of forming voids in the second fiber layer and facilitating the drawing of liquid from the first fiber layer. It is more preferable that the fiber includes cellulosic fibers having a multi-leaf cross section with three or more leaves. When the fiber includes cellulosic fibers having a multi-leaf cross section with three or more leaves, this has the advantageous effect of forming voids in the second fiber layer and facilitating the drawing of liquid from the first fiber layer.

The cellulosic fibers are preferably chemical fibers such as regenerated fibers and semi-synthetic fibers. Chemical fibers are more preferable because they can reduce the variation in fineness and/or fiber diameter and fiber length compared to natural fibers, and can make the size of the voids in the second fiber layer relatively uniform, making it difficult for the second fiber layer to retain liquid.
The cellulosic fibers can be used alone or in combination.

The second fiber layer contains 60% to 100% by mass of the cellulosic fibers based on the total mass of the second fiber layer, preferably 70% to 100% by mass of the cellulosic fibers, more preferably 80% to 100% by mass of the cellulosic fibers, and even more preferably 90% to 100% by mass of the cellulosic fibers. When the second fiber layer contains 60% to 100% by mass of the cellulosic fibers based on the total mass of the second fiber layer, it is preferable because it is easy to draw liquid from the first fiber layer to the second fiber layer and easy to diffuse the liquid in the second fiber layer.

The second fiber layer may contain fibers other than cellulosic fibers. Examples of fibers other than cellulosic fibers include natural fibers that are not cellulosic fibers (e.g., wool, silk, etc.), adhesive fibers, and synthetic fibers that are not adhesive fibers (e.g., synthetic fibers that do not melt or soften when the adhesive component of the adhesive fiber is melted and do not exhibit adhesiveness), and are not particularly limited as long as the nonwoven fabric intended by the present invention can be obtained.

The fibers other than the cellulosic fibers may be contained in a proportion of 40% by mass or less, particularly 30% by mass or less, more particularly 20% by mass or less, and even more particularly 10% by mass or less, and are not particularly limited as long as the nonwoven fabric of the present invention is obtained. In an embodiment of the present invention, the second fiber layer may be a nonwoven fabric made of adhesive fibers and cellulosic fibers, or may be a nonwoven fabric made of cellulosic fibers. When the second fiber layer contains adhesive fibers, it is preferable that the melting point of the adhesive component of the adhesive fibers contained in the second fiber layer is lower than the melting point of the adhesive component of the adhesive fibers contained in the first fiber layer. In particular, when the second fiber layer contains adhesive fibers, it is preferable that the adhesive component of the adhesive fibers contained in the first fiber layer is an adhesive component that does not melt at the temperature at which the adhesive component of the adhesive fibers contained in the second fiber layer melts.

In an embodiment of the present invention, the fibers of the second fiber layer are entangled. That is, the nonwoven fabric of the embodiment of the present invention includes entangled portions. This can improve the strength of the nonwoven fabric, and can also make the thickness of the second fiber layer uniform and contact the absorbent body uniformly. The entanglement of the fibers can be achieved by subjecting the nonwoven fabric to a flow of material, for example, to entangle the fibers. Specifically, the entanglement of the fibers refers to the entanglement of cellulosic fibers with cellulosic fibers, and when other fibers are further included, it also refers to the entanglement of cellulosic fibers with other fibers (e.g., adhesive fibers). The entanglement may be achieved by a needle punch method or by a fluid flow, and the fluid flow may be a water flow, an air flow, a water vapor flow, or the like. In an embodiment of the present invention, the entanglement of the cellulosic fibers is preferably achieved by a water flow or a water vapor flow.

The second fiber layer preferably has a basis weight of 10 g/m2 or ^more and 50 g/m2 or ^less , more preferably has a basis weight of 15 g/m2 or ^more and 45 g/m2 or ^less , even more preferably has a basis weight of 20 g/m2 or ^more and 40 g/m2 or ^less , and particularly preferably has a basis weight of 20 g/ ^m2 or more and 35 g/m2 ^{or less} . When the second fiber layer has a basis weight in the above-mentioned range, it is preferable because the second fiber layer does not hold too much liquid and can transfer the liquid to the absorbent while diffusing it.

The nonwoven fabric according to the embodiment of the present invention has a laminated structure in which a first fiber layer and a second fiber layer are laminated, and the first fiber layer and the second fiber layer are integrated by entangling the fibers of the first fiber layer and the fibers of the second fiber layer. The entanglement of the fibers can be achieved by, for example, subjecting the nonwoven fabric to a material flow, thereby entangling the fibers. Specifically, the entanglement of the fibers refers to the entanglement of cellulosic fibers and adhesive fibers, and when other fibers are further included, it also refers to the entanglement of cellulosic fibers and other fibers, the entanglement of adhesive fibers and other fibers, etc. The entanglement may be achieved by a needle punch method or by a fluid flow, and the fluid flow may be a water flow, an air flow, a water vapor flow, or the like. In the embodiment of the present invention, it is preferable to use a water flow or a water vapor flow to entangle the cellulosic fibers.

In the nonwoven fabric of the embodiment of the present invention, (ii) the fibers contained in the second fiber layer are preferably not bonded by the adhesive fibers contained in the first fiber layer. By not bonding the fibers contained in the second fiber layer by the adhesive fibers contained in the first fiber layer, the wettability of the nonwoven fabric surface is good, and the masking property is good, which is preferable. The fact that the fibers contained in the second fiber layer are not bonded by the adhesive fibers contained in the first fiber layer can be confirmed by the presence or absence of deformation, since the adhesive fibers exhibit adhesiveness, for example, by melting the adhesive components, at the locations where the adhesive fibers are bonded, and the like. A nonwoven fabric in which the fibers contained in the second fiber layer are bonded by the adhesive fibers contained in the first fiber layer can be obtained, for example, by integrating the fibers of the first fiber layer and the fibers of the second fiber layer by entanglement, and then bonding the fibers together with the adhesive fibers, but in that case, the bulk of the first fiber layer may be insufficient, or the texture of the first fiber layer may become hard.

In the nonwoven fabric according to the embodiment of the present invention, when the second fiber layer contains adhesive fibers, the fibers contained in the first fiber layer may be bonded by the adhesive fibers contained in the second fiber layer. In particular, when the melting point of the adhesive component of the adhesive fiber contained in the second fiber layer is lower than the melting point of the adhesive component of the adhesive fiber contained in the first fiber layer, this is preferable because it is possible to maintain the bulk of the first fiber layer well while maintaining the texture of the first fiber layer well while improving the integration of the first fiber layer and the second fiber layer.

In the nonwoven fabric according to the embodiment of the present invention, it is preferable that no openings are formed in the first and second fiber layers. If openings are formed in the first and second fiber layers, the masking properties may be poor.

The nonwoven fabric according to the embodiment of the present invention preferably has a basis weight of 30 g/m ² or more and 100 g/m ² or less, more preferably has a basis weight of 30 g/m ² or more and 80 g/m ² or less, even more preferably has a basis weight of 30 g/m ² or more and 70 g/m ² or less, and particularly preferably has a basis weight of 30 g/m ² or more and 65 g/m ² or less. When the nonwoven fabric has a basis weight within the above-mentioned range, the nonwoven fabric has advantageous effects of being bulky, having a short liquid absorption time and good wetback prevention properties, and having good masking properties.

The nonwoven fabric according to the embodiment of the present invention preferably has a thickness (measured by applying a load of 294 Pa) of 0.20 mm or more and 5.0 mm or less, more preferably 0.50 mm or more and 4.0 mm or less, and even more preferably 1.25 mm or more and 3.60 mm or less. When the nonwoven fabric has a thickness within the above-mentioned range, the nonwoven fabric has the advantageous effects of a short liquid absorption time, good wet-back prevention, good masking properties, and a comfortable fit.

The nonwoven fabric of this embodiment may have a fiber density of, for example, 0.0100 g/cm ³ or more and 0.100 g/cm ³ or less, preferably 0.0125 g/cm ³ or more and 0.0600 g/cm ³ or less, and more preferably 0.0180 g/cm ³ or more and 0.0400 g/cm ³ or less. The fiber density of the entire nonwoven fabric can be determined from the basis weight and thickness (thickness measured by applying a load of 294 Pa). When the nonwoven fabric has a density in the above-mentioned range, the nonwoven fabric has the advantageous effects of a short liquid absorption time and good wetback prevention, good masking properties, and good wearing comfort.

In the nonwoven fabric according to the embodiment of the present invention, (i) the thickness change rate of the nonwoven fabric is preferably 16% or more, more preferably 16% to 70% or less, even more preferably 16% to 65% or less, and particularly preferably 16% to 60% or less. The thickness change rate of the nonwoven fabric will be described in detail in the Examples.
When the thickness change rate of the nonwoven fabric of the present invention is within the above-mentioned range, the wettability of the surface of the nonwoven fabric is good, and the masking property is good, which is preferable.

Regarding the strength and elongation of the nonwoven fabric of the embodiment of the present invention, the tensile strength in the MD direction is preferably 25 N/5 cm or more and 125 N/5 cm or less, more preferably 25 N/5 cm or more and 100 N/5 cm or less, and the tensile strength in the CD direction is preferably 3 N/5 cm or more and 30 N/5 cm or less, more preferably 3 N/5 cm or more and 25 N/5 cm or less. When the tensile strength of the nonwoven fabric of the embodiment of the present invention is within the above-mentioned range, the shape stability of the nonwoven fabric is further improved, which is preferable.
The nonwoven fabric according to the embodiment of the present invention has a strength and elongation in the MD direction, which is described in the following examples, of preferably 20% to 100%, more preferably 23% to 90%, and preferably 20% to 120%, more preferably 28% to 110%. When the elongation of the nonwoven fabric according to the embodiment of the present invention is within the above-mentioned range, the flexibility of the nonwoven fabric is further improved, which is preferable.

In the nonwoven fabric of the embodiment of the present invention, the average value of the first absorption time and the second absorption time, which will be described in the following examples, is preferably less than 50 seconds, more preferably less than 40 seconds, and even more preferably less than 25 seconds. In the nonwoven fabric of the embodiment of the present invention, when the average value of the first absorption time and the second absorption time is within the above-mentioned range, the feeling of use is favorable, and it is preferable.

In the nonwoven fabric of the embodiment of the present invention, the average value of the first wetback amount and the second wetback amount described in the following examples is preferably 0.7 g or less, and more preferably 0.5 g or less. In the nonwoven fabric of the embodiment of the present invention, when the average value of the first wetback amount and the second wetback amount is within the above-mentioned range, the feeling of use is favorable, and it is preferable.

The nonwoven fabric for absorbent articles according to the embodiment of the present invention preferably functions as both a top sheet and a diffusion layer of the absorbent article.
In an embodiment of the present invention, an absorbent article including a nonwoven fabric for absorbent articles can be provided. Examples of such absorbent articles include diapers, incontinence pads, napkins, panty liners, and the like. The nonwoven fabric for absorbent articles of the embodiment of the present invention is disposed in an absorbent article with the first fiber layer disposed closer to the skin of the user. The nonwoven fabric for absorbent articles of the embodiment of the present invention can have the functions of both the top sheet and the diffusion layer of the absorbent article, and therefore can provide an absorbent article that can exhibit more stable liquid absorption performance and can be manufactured more easily.

In another aspect, the present disclosure provides a new method for producing a nonwoven fabric for an absorbent article.
The manufacturing method according to the embodiment of the present invention includes the steps of:
A method for manufacturing a nonwoven fabric for absorbent articles, the nonwoven fabric comprising a first fiber layer and a second fiber layer located on one main surface of the first fiber layer, the first fiber layer being disposed closer to a user's skin, the method comprising the steps of:
A step of producing a first fiber web containing 60% by mass or more and 100% by mass or less of adhesive fibers based on the total mass of the first fiber web;
a bonding step of bonding fibers of the first fiber web together with the adhesive fibers;
producing a second fiber web containing 60% by mass or more and 100% by mass or less of cellulosic fibers based on the total mass of the second fiber web;
a lamination step of laminating the first fiber web and the second fiber web to obtain a laminated fiber web;
The laminated fiber web includes an entanglement step of entangling the fibers of the first fiber web and the second fiber web to integrate them,
The method for producing a nonwoven fabric for absorbent articles includes laminating the first fiber layer including the first fiber web and the second fiber layer including the second fiber web.

The manufacturing method according to the embodiment of the present invention includes the steps of:
The method includes a step of producing a first fiber web containing 60 mass% or more and 100 mass% or less of adhesive fibers based on the total mass of the first fiber web, and a bonding step of bonding the fibers of the first fiber web together with the adhesive fibers.

The first fiber web can be manufactured by a known method using fibers containing 60% by mass or more and 100% by mass or less of adhesive fibers based on the total mass of the first fiber web. The form of the first fiber web may be any form such as a parallel web, a cross web, a card web such as a semi-random web or a random web, an air-laid web, or a wet-laid paper web. The first fiber web is preferably a parallel web form because the surface of the nonwoven fabric becomes smoother. The first fiber web preferably contains 60% by mass or more and 100% by mass or less of adhesive fibers based on the total mass of the first fiber web, because this improves the processability of the first fiber web, such as transportation, after the adhesion process.

The first fiber web is subjected to an adhesive treatment (or adhesive step). The adhesive treatment may be, for example, a heat treatment (thermal adhesive treatment). According to the heat treatment, the component (thermal adhesive component) with the lowest melting point among the resin components constituting the adhesive fiber melts or softens by heating during the heat treatment, and the fibers constituting the fiber web can be bonded together. The heat treatment may be, for example, a hot air processing treatment in which hot air is blown, a heat roll processing (for example, a hot embossing roll processing), or a heat treatment using infrared rays, but it is preferable to include a hot air processing treatment in order to improve the texture of the nonwoven fabric. The hot air processing treatment may be performed using a device that blows hot air of a predetermined temperature onto the fiber web, for example, a hot air penetration type heat treatment machine and a hot air blowing type heat treatment machine.

When the bonding process is a hot air processing process, the hot air may be blown multiple times. When blowing hot air multiple times, it is preferable that the temperature of the second hot air is higher than the temperature of the first hot air.

When the adhesive treatment is a hot air processing treatment, the speed of the hot air is preferably 0.1 m/min or more and 3.0 m/min or less, more preferably 0.2 m/min or more and 2.5 m/min or less, and even more preferably 0.3 m/min or more and 2.0 m/min or less, from the viewpoint of suppressing pilling and improving the softness of the texture.

The temperature of the heat treatment may be the temperature at which the component (thermal adhesive component) with the lowest melting point among the resin components constituting the adhesive fiber softens or melts, and may be, 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 performing hot air processing. 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 may be blown when performing hot air processing, particularly 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, from the viewpoint of suppressing fuzzing and improving the softness of the texture, the heat treatment temperature is preferably 0°C to 5°C higher than the melting point or softening point of the thermal adhesive component, more preferably 1°C to 4°C higher, and even more preferably 2°C to 3°C higher.

The adhesive treatment may be by irradiation with an electron beam or ultrasonic welding. These adhesive treatments can also bond the fibers together with the resin components that make up the adhesive fibers.

The manufacturing method according to the embodiment of the present invention includes the steps of:
producing a second fiber web containing 60% by mass or more and 100% by mass or less of cellulosic fibers based on the total mass of the second fiber web;
a lamination step of laminating the first fiber web and the second fiber web to obtain a laminated fiber web;
and an entangling step for entangling the fibers of the first fiber web and the second fiber web with respect to the laminated fiber web to integrate them.

The second fiber web can be manufactured by a known method using fibers containing 60% by mass or more and 100% by mass or less of cellulosic fibers based on the total mass of the second fiber web. The second fiber web may be in any form such as a parallel web, a cross web, a card web such as a semi-random web or a random web, an air-laid web, or a wet-laid paper web. The second fiber web is preferably in the form of a parallel web, since the fibers are oriented in one direction and are easily entangled with the constituent fibers of the first fiber layer, and even if the basis weight of the second fiber layer is low, it is easily integrated with the first fiber layer. The form of the second fiber web may be the same as or different from the form of the first fiber web, but it is preferable that the second fiber web is the same as the form of the first fiber web.

The second fiber web produced is laminated onto the first fiber web to produce a laminated fiber web.

The laminated fiber web is subjected to an entanglement treatment (or entanglement process). Examples of the entanglement treatment include a water flow entanglement treatment and a water vapor flow entanglement treatment, and it is preferable that the entanglement process includes either of these. It is preferable that the entanglement process includes a water flow entanglement treatment. These entanglement treatments facilitate entanglement with the cellulosic fibers of the second fiber web, and a nonwoven fabric having the desired physical properties can be obtained.

The manufacturing method according to the embodiment of the present invention preferably includes a cooling process (or a cooling step) after the bonding process (or bonding step) and before the entangling process (or entangling step). In other words, after the first fiber web is subjected to the bonding process and before it is subjected to the lamination process, and/or after the first fiber web and the second fiber web are subjected to the lamination process and before the laminated fiber web is subjected to the entangling process, the first fiber web and/or the laminated fiber web are preferably subjected to a cooling process (or a cooling step). The cooling process may be air cooling or water cooling. If the first fiber web is not sufficiently cooled after the bonding process, the adhesive component of the adhesive fiber may be in a softened state. If the first fiber web is subjected to the entangling process in this state, the bonded parts may be easily peeled off, and the fuzzing of the nonwoven fabric may not be sufficiently suppressed.

The hydroentanglement treatment of the laminated fiber web can be carried out by placing the laminated fiber web on a support and spraying a columnar water stream onto the support. If the surface of the laminated fiber web is to be flat and free of irregularities, the support should have no openings with an opening area of more than 0.2 ^mm2 each and no protrusions or patterns. For example, the support should have a plain weave of 80 mesh or more and 100 mesh or less.

The hydroentanglement treatment can be carried out, for example, by spraying a water stream with a water pressure of 1 MPa to 15 MPa from a nozzle having orifices with a hole diameter of 0.05 mm to 0.5 mm spaced at intervals of 0.3 mm to 1.5 mm onto each of the front and back surfaces of the fiber web, from one to five times. The water pressure is preferably 1 MPa to 10 MPa, more preferably 1 MPa to 7 MPa.

The hydroentanglement process may be performed by using a nozzle in which minute orifices from which a water stream is ejected are arranged at intervals of, for example, several mm to form highly entangled sections in the nonwoven fabric, in which the degree of entanglement between fibers is higher, and less entangled sections, in which the degree of entanglement between fibers is lower than that of the highly entangled sections, so that the highly entangled sections and less entangled sections are arranged alternately in a plan view of the nonwoven fabric. When such a nozzle is used, the areas where the water stream from the orifice hits form streaks to form highly entangled sections, and the areas where the water stream does not hit form less entangled sections. The thickness of the highly entangled sections tends to be smaller than the thickness of the less entangled sections. By forming highly entangled sections and less entangled sections in the nonwoven fabric, the liquid absorption time is shortened and wetback prevention is improved, and the integration of the first fiber layer and the second fiber layer can be strengthened.

When such a nozzle is used, the nozzle may have an orifice diameter of, for example, 0.05 mm or more and 0.5 mm or less, and the spacing between the orifices may be 2 mm or more and 20 mm or less, particularly 3 mm or more and 15 mm or less, and more particularly 4 mm or more and 10 mm or less. If the spacing between the orifices is too narrow, the distance between the highly entangled parts will be narrow, i.e., the width of the less entangled parts will be narrow, and the short liquid absorption time and wetback prevention properties may not be good. The water pressure of the water flow may be, for example, 1 MPa or more and 10 MPa or less, particularly 2 MPa or more and 8 MPa or less.

When using such a nozzle, it is preferable to spray the water stream only once onto one side of the laminated fiber web. If the water stream is sprayed multiple times onto one side or onto both sides, the width of the less entangled portion may become narrow, and the liquid absorption time and wetback prevention properties may not be good.

The support used in the hydroentanglement treatment may be a plate-shaped or roll-shaped support, and is preferably a roll-shaped support. When the support is in the form of a roll, the laminated fiber web is curved, and the fiber density becomes smaller in the thickness direction of the laminated fiber web (or in the outward direction of the usually curved web). When the columnar water flow is sprayed from the outside, entanglement by the columnar water flow is relatively easy to proceed. In the nonwoven fabric according to the embodiment of the present invention, the first fiber web is subjected to an adhesive treatment, and the laminated fiber web of the first fiber web and the second fiber web is subjected to an entanglement treatment.

The hydroentanglement treatment preferably includes spraying a columnar water stream from the second fiber web side of the laminated fiber web. This allows the energy of the water stream to be applied efficiently to the second fiber web, resulting in good entanglement, and is preferable because it allows the first fiber web and the second fiber web to be more strongly integrated while maintaining the bulkiness of the first fiber web.

When the entanglement treatment is a hydroentanglement treatment, it is preferable that the laminated fiber web is subjected to a drying treatment (drying step) after the entanglement treatment. The drying treatment can be performed by a hot air processing treatment in which hot air is blown. The temperature of the drying treatment is preferably lower than the softening or melting temperature of the adhesive component (thermal adhesive component) of the adhesive fiber contained in the first fiber web. The temperature of the drying treatment is preferably 10°C or more lower than the melting point or softening point of the thermal adhesive component, more preferably 15°C or more lower, and even more preferably 20°C or less lower. If the adhesive component is not softened or melted again after the entanglement treatment, the bulk of the nonwoven fabric is unlikely to collapse, and the texture of the nonwoven fabric is unlikely to become hard. It is preferable that the processing performed on the laminated fiber web after the entanglement treatment, not limited to the drying treatment, is performed at a temperature lower than the melting temperature of the adhesive component of the adhesive fiber contained in the first fiber web.

When the second fiber web contains adhesive fibers, the laminated fiber web may be subjected to a process of bonding the fibers together using the adhesive fibers of the second fiber web after the laminated fiber web has been subjected to the entanglement process. In particular, it is preferable to make the melting point of the adhesive fibers contained in the second fiber web lower than the melting point of the adhesive component of the adhesive fibers contained in the first fiber web, and to melt the adhesive component of the adhesive fibers contained in the second fiber web at a temperature lower than the temperature at which the adhesive component of the adhesive fibers contained in the first fiber web melts to bond the fibers together.

After the bonding process, the first fiber web can be wound up on a roll. The first fiber web may be unwound and sent to the lamination process. After the lamination process, the laminated fiber web can be wound up on a roll. The laminated fiber web may be unwound and sent to the entanglement process. However, both the first fiber web and the laminated fiber web can be subjected to the entanglement process without being wound up. This is preferable because it maintains the bulk of the first fiber web, increases the bulk of the first fiber layer, and prevents liquid from coming out onto the surface of the first fiber layer due to liquid return, and also improves masking properties.

In addition, the manufacturing method according to the embodiment of the present invention includes the steps of:
The bonding step includes a hot air processing treatment of applying hot air to one surface of the first fiber web,
The entanglement step includes a hydroentanglement treatment,
The second fiber web is laminated on the surface of the first fiber web that has been exposed to hot air,
The hydroentanglement treatment may include spraying a water stream from the side of the second fiber web first, which is preferable because the energy of the water stream can be applied efficiently to the second fiber web, resulting in good entanglement and stronger integration of the first fiber web and the second fiber web while maintaining the bulkiness of the first fiber web.

The nonwoven fabric of the present invention can be suitably used in absorbent articles such as disposable diapers, sanitary napkins, incontinence pads, and panty liners. Furthermore, it has an excellent balance of overall properties and can be used in applications that directly contact human skin, such as top sheets and diffusion layers for absorbent articles. In addition, it has excellent masking properties for the color of the liquid it absorbs, making it particularly suitable for use in sanitary napkins.

The present invention will be described in detail below with reference to examples and comparative examples. However, these examples are merely one aspect of the present invention, and the present invention is not limited to these examples.

The fibers used to manufacture the nonwoven fabrics in the Examples and Comparative Examples are shown below.
<Adhesive Fiber>
Fiber 11: An eccentric core-sheath type composite fiber having a polyethylene terephthalate core and a high-density polyethylene (melting point: about 133° C.) sheath, a fineness of 2.6 dtex, a fiber length of 51 mm, and a three-dimensional crimp with an eccentricity of 25% (NBF(SH)V (product name) manufactured by Daiwabo Polytec Co., Ltd.)
Fiber 12: A concentric core-sheath type composite fiber having a core of polylactic acid and a sheath of polybutylene succinate (melting point: about 115° C.) with a fineness of 2.4 dtex and a fiber length of 51 mm (NBF(KK)PL (product name) manufactured by Daiwabo Polytec Co., Ltd.)
Fiber 13: A concentric core-sheath type composite fiber having a core of polyethylene terephthalate and a sheath of high-density polyethylene (melting point: about 133° C.) with a fineness of 2.0 dtex and a fiber length of 45 mm (NBF (SH) (product name) manufactured by Daiwabo Polytec Co., Ltd.)
Fiber 14: A concentric core-sheath type composite fiber having a core of polyethylene terephthalate and a sheath of high-density polyethylene (melting point: about 133° C.) with a fineness of 1.35 dtex and a fiber length of 30 mm (NBF (SH) (product name) manufactured by Daiwabo Polytec Co., Ltd.)
Fiber 15: A concentric core-sheath type composite fiber having a core of polyethylene terephthalate and a sheath of high-density polyethylene (melting point: about 133° C.) with a fineness of 4.4 dtex and a fiber length of 51 mm (NBF (SH) (product name) manufactured by Daiwabo Polytec Co., Ltd.)
Fiber 16: An eccentric core-sheath type composite fiber having a polyethylene terephthalate core and a high-density polyethylene (melting point: about 133° C.) sheath, a fineness of 3.3 dtex, a fiber length of 51 mm, and a three-dimensional crimp with an eccentricity of 25% (NBF(SH)V (product name) manufactured by Daiwabo Polytec Co., Ltd.)
Fiber 17: Splittable composite fiber made of a combination of polypropylene and high-density polyethylene, with 8 divisions, a fineness of 1.8 dtex, and a fiber length of 45 mm (the smallest fineness of the fibers formed by splitting is 0.275 dtex) (DFS-7 (product name) manufactured by Daiwabo Polytec Co., Ltd.)

<Cellulosic fibers>
Fiber 21: Viscose rayon fiber having a fineness of 2.2 dtex, a fiber length of 38 mm, and a trilobal (Y-shaped) fiber cross section (Corona RBA (product name) manufactured by Daiwabo Rayon Co., Ltd.)
Fiber 22: Viscose rayon fiber having a fineness of 2.2 dtex, a fiber length of 51 mm, and a chrysanthemum-shaped fiber cross section (Corona CD (product name) manufactured by Daiwabo Rayon Co., Ltd.)
Fiber 23: Viscose rayon fiber having a fineness of 3.3 dtex, a fiber length of 51 mm, and a chrysanthemum-shaped fiber cross section (Corona CD (product name) manufactured by Daiwabo Rayon Co., Ltd.)

<Production of nonwoven fabric of Example 1>
A fiber web was produced using a parallel carding machine using only fiber 11. The basis weight of this fiber web was about 30 g/ ^m2 .
This fiber web was heated at 135° C. for about 5 seconds using a hot air penetration type heat treatment machine, and the fibers were thermally bonded (bonded) to each other by the sheath component of the fibers 11 to obtain an air-through nonwoven fabric that would become the first fiber layer.
A fiber web having a basis weight of about 30 g/ ^m2 was produced as the second fiber layer using only the fiber 21 and a parallel carding machine, and the second fiber layer was laminated on the air-through nonwoven fabric to form a laminate.
The above-mentioned laminate was placed on a plain weave net with a warp diameter of 0.132 mm, a weft diameter of 0.132 mm, and a mesh number of 90 meshes. While the laminate was advanced at a speed of 4 m/min, a columnar water flow with a water pressure of 3.0 MPa was sprayed onto the surface of the laminate on the side of the fiber web (second fiber layer) using a water supply device. The nozzle of the water supply device had orifices with a hole diameter of 0.12 mm provided at intervals of 0.6 mm. The distance between the surface of the laminate and the orifices was 15 mm. Then, a columnar water flow with a water pressure of 3.0 MPa was sprayed onto the surface of the laminate on the side of the air-through nonwoven fabric (first fiber layer) using a water supply device in the same manner.
This laminate was dried at 80° C. using a hot air penetration type heat treatment machine to obtain a nonwoven fabric of Example 1. The first fibrous layer and the second fibrous layer were integrated by entanglement of the fibers, and no open pores were formed in the first fibrous layer and the second fibrous layer.

<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 fibers 21 in Example 1 were changed to the fibers 22.

<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 fibers 21 in Example 1 were changed to the fibers 23.

<Production of nonwoven fabric of Example 4>
The nonwoven fabric of Example 4 was obtained in the same manner as in Example 1, except that in Example 1, fiber 11 was changed to fiber 12, and the temperature of the hot air penetration type heat treatment machine was changed to 128°C in the process of obtaining the air-through nonwoven fabric to be the first fiber layer.

<Production of nonwoven fabric of Example 5>
A nonwoven fabric of Example 5 was obtained in the same manner as in Example 1, except that the fibers 11 in Example 1 were changed to the fibers 13.

<Production of nonwoven fabric of Example 6>
A nonwoven fabric of Example 6 was obtained in the same manner as in Example 1, except that the fiber 11 in Example 1 was changed to the fiber 14.

<Production of nonwoven fabric of Example 7>
A nonwoven fabric of Example 7 was obtained in the same manner as in Example 1, except that the fiber 11 in Example 1 was changed to the fiber 15.

<Production of nonwoven fabric of Example 8>
A nonwoven fabric of Example 8 was obtained in the same manner as in Example 1, except that the fibers 11 in Example 1 were changed to the fibers 16.

<Production of nonwoven fabric of Example 9>
A nonwoven fabric of Example 9 was obtained in the same manner as in Example 1, except that the fiber 11 in Example 1 was changed to the fiber 17.

<Production of nonwoven fabric of Example 10>
A nonwoven fabric of Example 10 was obtained in the same manner as in Example 1, except that the water pressure of the columnar water stream sprayed against the surface of the laminate on the fiber web (second fiber layer) side was changed to 2.0 MPa, and then, when spraying the columnar water stream against the surface of the laminate on the air-through nonwoven fabric (first fiber layer) side, the nozzle of the water supplier was changed to a water supplier having orifices with a hole diameter of 0.2 mm provided at 7.0 mm intervals, and the water pressure of the columnar water stream was changed to 6.0 MPa.

<Production of nonwoven fabric of Example 11>
A nonwoven fabric of Example 11 was obtained in the same manner as in Example 10, except that the fibers 11 in Example 10 were changed to the fibers 14.

<Production of nonwoven fabric of Example 12>
A nonwoven fabric of Example 12 was obtained in the same manner as in Example 10, except that the fiber 11 in Example 10 was changed to the fiber 15.

<Production of nonwoven fabric of Example 13>
A nonwoven fabric of Example 13 was obtained in the same manner as in Example 10, except that the fiber 11 in Example 10 was changed to the fiber 13.

<Production of nonwoven fabric of Example 14>
A nonwoven fabric of Example 14 was obtained in the same manner as in Example 1, except that, instead of spraying a columnar water stream onto the surface of the laminate on the air-through nonwoven fabric (first fiber layer) side in Example 1, a columnar water stream was sprayed again onto the surface of the laminate on the fiber web (second fiber layer) side.

<Production of nonwoven fabric of Example 15>
A nonwoven fabric of Example 15 was obtained in the same manner as in Example 1, except that the basis weight of the first fiber layer was changed to about 40 g/ ^m2 and the basis weight of the second fiber layer was changed to about 20 g/ ^m2 .

<Production of nonwoven fabric of Example 16>
A nonwoven fabric of Example 16 was obtained in the same manner as in Example 1, except that in Example 1, the fiber 11 was changed to the fiber ¹³ , the basis weight of the first fiber layer was changed to about 20 g/ ^m2 , and the basis weight of the second fiber layer was changed to about 40 g/m2.

<Production of Nonwoven Fabric of Comparative Example 1>
A fiber web to be the first fiber layer was produced using a parallel carding machine using only the fiber 11. The basis weight of this fiber web was about 30 g/ ^m2 .
A fiber web having a basis weight of about 30 g/ ^m2 was produced as the second fiber layer using only fiber 21 and a parallel carding machine, and the second fiber layer was laminated on the fiber web having the first fiber layer to form a laminate.
The above-mentioned laminate was placed on a plain weave net with a warp diameter of 0.132 mm, a weft diameter of 0.132 mm, and a mesh number of 90 meshes. While the laminate was advanced at a speed of 4 m/min, a columnar water flow with a water pressure of 3.0 MPa was sprayed onto the surface of the laminate on the side of the second fiber layer using a water supplying device. The nozzle of the water supplying device had orifices with a hole diameter of 0.12 mm provided at intervals of 0.6 mm. The distance between the surface of the laminate and the orifices was 15 mm. Then, a columnar water flow with a water pressure of 3.0 MPa was sprayed onto the surface of the laminate on the side of the first fiber layer using the water supplying device in the same manner.
This laminate was heated at 135°C for approximately 5 seconds using a hot air penetration type heat treatment machine to perform a drying treatment and thermal bonding (adhesive treatment) between the fibers by the sheath component of fiber 11, thereby obtaining a nonwoven fabric of Comparative Example 1.

<Production of nonwoven fabric of Comparative Example 2>
A fiber web was produced using a parallel carding machine using only fiber 11. The basis weight of this fiber web was about 30 g/ ^m2 .
This fiber web was heated at 135° C. for about 5 seconds using a hot air penetration type heat treatment machine, and the fibers were thermally bonded (bonded) to each other by the sheath component of the fibers 11 to obtain an air-through nonwoven fabric.
The above-mentioned air-through nonwoven fabric was placed on a plain weave net with a warp diameter of 0.132 mm, a weft diameter of 0.132 mm, and a mesh number of 90 meshes. While the air-through nonwoven fabric was advanced at a speed of 4 m/min, a columnar water flow with a water pressure of 3.0 MPa was sprayed onto the surface of the air-through nonwoven fabric using a water supplying device. The nozzle of the water supplying device had orifices with a hole diameter of 0.12 mm arranged at intervals of 0.6 mm. The distance between the surface of the air-through nonwoven fabric and the orifice was 15 mm. Then, a columnar water flow with a water pressure of 3.0 MPa was sprayed onto the opposite surface of the air-through nonwoven fabric using a water supplying device in the same manner, and a drying treatment was performed at 80 ° C. using a hot air penetration type heat treatment machine to obtain a nonwoven fabric that becomes the first fiber layer.
Next, a fiber web having a basis weight of about 30 g/ ^m2 was produced using only the fiber 21 using a parallel carding machine.
The above-mentioned fiber web was placed on a plain weave net with a warp diameter of 0.132 mm, a weft diameter of 0.132 mm, and a mesh number of 90 meshes. While the fiber web was advanced at a speed of 4 m/min, a columnar water flow with a water pressure of 3.0 MPa was sprayed onto the surface of the fiber web using a water supply device. The nozzle of the water supply device had orifices with a hole diameter of 0.12 mm at intervals of 0.6 mm. The distance between the surface of the fiber web and the orifice was 15 mm. Then, a columnar water flow with a water pressure of 3.0 MPa was sprayed onto the opposite surface of the fiber web using the water supply device in the same manner, and a drying treatment was performed at 80 ° C. using a hot air penetration type heat treatment machine to obtain a nonwoven fabric that would become the second fiber layer.
A nonwoven fabric that would become the first fibrous layer was laminated on top of this nonwoven fabric that would become the second fibrous layer, to obtain a nonwoven fabric (laminate) of Comparative Example 2 in which the nonwoven fabrics were not integrated with each other.

<Production of nonwoven fabric of Comparative Example 3>
A fiber web was produced using a parallel carding machine using only fiber 11. The basis weight of this fiber web was about 60 g/ ^m2 .
This fiber web was heated at 135° C. for about 5 seconds using a hot air penetration type heat treatment machine to thermally bond (bond) the fibers together by the sheath component of the fiber 11, thereby obtaining an air-through nonwoven fabric of Comparative Example 3. Note that Comparative Example 3 is not a laminated nonwoven fabric, but a nonwoven fabric consisting of only the first fiber layer.

The nonwoven fabric was evaluated as follows.
<Thickness, thickness change rate, and density of nonwoven fabric>
The thickness of the nonwoven fabric was measured using a thickness gauge (THICKNESS GAUGE Model CR-60A (product name) manufactured by Daiei Scientific Instruments Co., Ltd.) while a load of 294 Pa or 1.96 kPa was applied to the nonwoven fabric.
The thickness change rate was calculated from the thickness (P1) at a load of 294 Pa and the thickness (P2) at a load of 1.96 kPa based on the following formula.
Thickness change rate (%) = [(P1 - P2) / P1] x 100
The density of the nonwoven fabric was calculated based on the basis weight of the nonwoven fabric and the thickness of the nonwoven fabric obtained by applying a load of 294 Pa.

<Strength and elongation>
The strength and elongation were measured according to JIS L 1913:2010 6.3. A constant-speed tension tensile tester was used to perform a tensile test under the conditions of a width of 5 cm for the sample piece (nonwoven fabric), a gripping distance of 10 cm, and a tensile speed of 30±2 cm/min. The load value at break (tensile strength), elongation, and stress at 10% elongation were measured. The tensile test was performed with the longitudinal direction (MD direction) and transverse direction (CD direction) of the nonwoven fabric as the tensile direction. The evaluation results were all shown as the average of the values measured for three samples.

<Liquid absorption time, wetback amount, masking ability>
The liquid absorption performance was evaluated using sanitary napkins that are actually on the market.
(1) The top sheet of a sanitary napkin (manufactured by P&G, product name "Whisper Pure Skin (Super Slim, normal daytime use, 22 cm)") and the two sheets located under the top sheet were peeled off to expose the absorbent body, and a nonwoven fabric (nonwoven fabric of the Example or Comparative Example) cut to 220 mm x 80 mm (longitudinal x transverse) was placed on the absorbent body. The nonwoven fabric was arranged so that the second fiber layer was in contact with the absorbent body. A plate with an injection tube (two-stage cylindrical shape with a height of 75 mm, an inner diameter of the upper part of the tube of 25 mm, and an inner diameter of the lower part of the tube of 10 mm) was placed on the first fiber layer, and 5.0 cc of artificial menstrual blood (viscosity 8 mPa s, temperature 37°C) was injected into the injection tube of the plate with the injection tube. The time required for the liquid to disappear from the surface of the nonwoven fabric (liquid absorption time) was measured. It can be said that the shorter the liquid absorption time, the higher the liquid absorption speed. The composition of the artificial menstrual blood was 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), 1.04% by mass of Na2CO3 (sodium carbonate), and 0.06% by mass of red powder.

(2) When measuring the above absorption time, 10 minutes after the injection of the artificial menstrual blood, 10 sheets of filter paper (manufactured by Toyo Roshi Kaisha, Ltd., product name ADVANTEC (registered trademark) No. 2, 10 cm x 10 cm) were placed on the nonwoven fabric of the example, and a weight of 1 kg (shape: square, 10 cm x 10 cm) was placed on the filter paper. 20 seconds after the weight was placed on the filter paper, the filter paper was removed and the weight of the filter paper that had absorbed the artificial menstrual blood was measured, and the weight of the filter paper before it was placed on the nonwoven fabric was subtracted to calculate the amount of wetback. It can be said that the smaller the amount of wetback, the less likely it is that wetback will occur.

(3) The second absorption time was measured by injecting artificial menstrual blood 25 minutes after the first injection. The amount of artificial menstrual blood was measured under the same conditions as the first injection. The second wetback amount was measured 10 minutes after the second injection of artificial menstrual blood, in the same manner as the first wetback amount.

To measure the liquid absorption time (wetback amount), five samples were prepared for each nonwoven fabric of an example or comparative example, and the average of the liquid absorption times (wetback amounts) measured for each of the five samples was used as the liquid absorption time (wetback amount) for that example or comparative example.

The liquid absorption time was evaluated on a four-level scale according to the following numerical criteria.
◎: The average value of the first and second measurements is less than 25 seconds. ○: The average value of the first and second measurements is 25 seconds or more and less than 40 seconds. △: The average value of the first and second measurements is 40 seconds or more and less than 50 seconds. ×: The average value of the first and second measurements is 50 seconds or more.

The amount of wet back was evaluated in three stages according to the following numerical criteria.
◎: The average value of the first and second measurements is 0.5 g or less. ○: The average value of the first and second measurements is greater than 0.5 g and less than 0.7 g. ×: The average value of the first and second measurements is greater than 0.7 g.

The masking property was evaluated based on the following criteria for the color intensity of the artificial menstrual blood visible on the nonwoven fabric surface from one photograph of the nonwoven fabric surface taken between the first measurement of the liquid absorption time and the measurement of the wetback amount, and one photograph of the nonwoven fabric surface taken between the second measurement of the liquid absorption time and the measurement of the wetback amount. There were a total of 10 photographs of five samples for one example or comparative example nonwoven fabric, and one photograph in which the color of the artificial menstrual blood looked the lightest (the artificial menstrual blood was concealed) was selected from the five photographs taken during the first and second measurements of liquid absorption performance. More specifically, one photograph in which the area of the dark colored part of the artificial menstrual blood visible from the nonwoven fabric surface was the smallest was selected. A photograph of the surface of the nonwoven fabric sample of Example 7 is shown in FIG. 1. A photograph of the surface of the nonwoven fabric sample of Comparative Example 3 is shown in FIG. 2.
○: In both the first and second times, there was no part with the same darkness as the artificial menstrual blood used. △: In both the first and second times, there was a part with the same darkness as the artificial menstrual blood used. ×: In both the first and second times, there was a part with the same darkness as the artificial menstrual blood used.

<Fluff>
The fluff was evaluated by observing the surface (first fiber layer side) of the nonwoven fabric and evaluating it according to the following criteria.
○: Good (very little fluff)
△: Normal (some fluff is not noticeable)
×: Bad (some fuzz is noticeable)

＊）比較例２の実測目付、密度、厚さ、強伸度については、第１繊維層及び第２繊維層それぞれの数値を記載している。前の数値が第１繊維層の数値であり、後の数値が第２繊維層の数値である。比較例２では第１繊維層と第２繊維層とは交絡によって一体化されていない。

*) The measured basis weight, density, thickness, and strength/elongation of Comparative Example 2 are the values of the first fiber layer and the second fiber layer. The first value is the value of the first fiber layer, and the second value is the value of the second fiber layer. In Comparative Example 2, the first fiber layer and the second fiber layer are not integrated by entanglement.

The nonwoven fabrics for absorbent articles of Examples 1 to 16 are nonwoven fabrics including a first fiber layer and a second fiber layer located on one main surface of the first fiber layer,
the first fibrous layer comprises adhesive fibers;
the first fiber layer contains 60 mass% or more and 100 mass% or less of the adhesive fiber based on the total mass of the first fiber layer;
the second fibrous layer comprises cellulosic fibers;
the second fiber layer contains 60% by mass or more and 100% by mass or less of the cellulosic fibers based on the total mass of the second fiber layer;
The first fiber layer has fibers bonded to each other by the adhesive fibers,
the first fiber layer and the second fiber layer are integrated by entanglement of the fibers,
The thickness change rate of the nonwoven fabric is 16% or more,
Since the first fiber layer is disposed closer to the user's skin,
Excellent in fluffiness, liquid absorption time, wetback amount, and masking properties.
The nonwoven fabric can be used as a nonwoven fabric having the properties of both a top sheet and a diffusion layer. Therefore, the nonwoven fabrics for absorbent articles of Examples 1 to 16 can be suitably used for manufacturing absorbent articles, and the manufacturing method thereof can be simplified.

In Comparative Example 1, the thickness change rate of the nonwoven fabric is not 16% or more, and the adhesive fiber contained in the first fiber layer and the cellulosic fiber contained in the second fiber layer are bonded to each other, so that the masking property is poor. In the nonwoven fabric with poor masking property, a relatively large amount of artificial menstrual blood is present on the surface of the nonwoven fabric on the first fiber layer side, so that the skin feels wet when it touches the nonwoven fabric, and the feeling of use is poor.
In Comparative Example 2, the adhesive fiber in the first fibrous layer has bonded portions and is entangled, but is not integrated with the second fibrous layer, and the liquid absorption time is poor.
Comparative Example 3 does not have a second fibrous layer containing cellulose fibers, and is inferior in the amount of wetback and masking properties.

The nonwoven fabric for absorbent articles according to the embodiment of the present invention can be used as a nonwoven fabric that has the properties of both a top sheet and a diffusion layer. Therefore, the nonwoven fabric for absorbent articles according to the present invention can be suitably used to manufacture absorbent articles, and the manufacturing method thereof can be simplified.

Claims (8)

A nonwoven fabric comprising a first fiber layer and a second fiber layer located on one main surface of the first fiber layer,
the first fibrous layer comprises adhesive fibers;
the first fiber layer contains 60 mass% or more and 100 mass% or less of the adhesive fiber based on the total mass of the first fiber layer;
the adhesive fiber includes a core-sheath type composite fiber, and the composite ratio of the core and the sheath of the core-sheath type composite fiber (volume ratio, core/sheath) is 80/20 to 20/80;
the second fibrous layer comprises cellulosic fibers;
the second fiber layer contains 60% by mass or more and 100% by mass or less of the cellulosic fibers based on the total mass of the second fiber layer;
The first fiber layer has fibers bonded to each other by the adhesive fibers,
the first fiber layer and the second fiber layer are integrated by entanglement of the fibers,
the first fibrous layer being disposed closer to the user's skin;
Satisfy either of the following (i) and (ii):
(i) The thickness change rate of the nonwoven fabric measured by the following measurement method is 16% or more; and (ii) the fibers contained in the second fiber layer are not bonded by the adhesive fibers.
[Thickness change rate]
Using a thickness measuring device, the thickness of the nonwoven fabric is measured while a load of 294 Pa or 1.96 kPa is applied to the nonwoven fabric, and the thickness is calculated based on the thickness (P1) at a load of 294 Pa and the thickness (P2) at a load of 1.96 kPa according to the following formula.
Thickness change rate (%) = [(P1 - P2) / P1] x 100 A nonwoven fabric comprising a first fiber layer and a second fiber layer located on one main surface of the first fiber layer,
the first fibrous layer comprises adhesive fibers;
the first fiber layer contains 60 mass% or more and 100 mass% or less of the adhesive fiber based on the total mass of the first fiber layer;
the second fibrous layer comprises cellulosic fibers;
the second fiber layer contains 60% by mass or more and 100% by mass or less of the cellulosic fibers based on the total mass of the second fiber layer;
The first fiber layer has fibers bonded to each other by the adhesive fibers,
the first fiber layer and the second fiber layer are integrated by entanglement of the fibers,
The first fiber layer is disposed so as to be in direct contact with the skin of a user;
Either of the following (i) and (ii) is satisfied:
(i) The thickness change rate of the nonwoven fabric measured by the measurement method below is 16% or more; and (ii) the fibers contained in the second fiber layer are not bonded by the adhesive fiber. A nonwoven fabric for a top sheet of an absorbent article.
[Thickness change rate]
Using a thickness measuring device, the thickness of the nonwoven fabric is measured while a load of 294 Pa or 1.96 kPa is applied to the nonwoven fabric, and the thickness is calculated based on the thickness (P1) at a load of 294 Pa and the thickness (P2) at a load of 1.96 kPa according to the following formula.
Thickness change rate (%) = [(P1 - P2) / P1] x 100 3. The nonwoven fabric for absorbent articles according to claim 1 or 2 , wherein the adhesive fiber has a fineness of 1.0 dtex or more and 5.0 dtex or less. The nonwoven fabric for absorbent articles according to any one of claims 1 to 3, wherein the adhesive fibers include eccentric core-sheath type composite fibers. The nonwoven fabric for absorbent articles according to any one of claims 1 to 4, wherein the fineness of the cellulosic fibers is 1.0 dtex or more and 5.0 dtex or less. The nonwoven fabric for absorbent articles according to any one of claims 1 to 5, wherein the cellulosic fibers include cellulosic fibers having a multi-lobed fiber cross section with three or more lobes. A nonwoven fabric for absorbent articles according to any one of claims 1 to 6, which has the functions of both a top sheet and a diffusion layer of an absorbent article. An absorbent article comprising the nonwoven fabric for absorbent articles according to claim 7.