JP7692391B2 - Nonwoven fabric for absorbent articles and method for manufacturing the same - Google Patents

Description

The present invention relates to a nonwoven fabric for absorbent articles and a method for manufacturing the nonwoven fabric.

For example, Patent Document 1 discloses a composite nonwoven fabric for absorbent articles, which is made by laminating a cotton web and a synthetic staple fiber web containing thermally adhesive staple fibers, in which the constituent fibers of the cotton web, the constituent fibers of the cotton and synthetic staple fiber webs, and the constituent fibers of the synthetic staple fiber web are three-dimensionally entangled and integrated, and in which the intersections of the fibers are thermally bonded by fusion of the thermally adhesive component.

Patent Document 2 also discloses a nonwoven fabric for absorbent articles that includes a first fiber layer and a second fiber layer located on one main surface of the first fiber layer, the first fiber layer including a first sheath-core composite fiber, the second fiber layer including a second sheath-core composite fiber and a cellulosic fiber, the fineness of the first sheath-core composite fiber being smaller than that of the second sheath-core composite fiber, the fineness of the first sheath-core composite fiber being 1.0 to 2.8 dtex, the fineness of the second sheath-core composite fiber being 1.7 to 5.6 dtex, and the fineness of the cellulosic fiber being 1.2 to 6.0 dtex, and the second fiber layer including 5% to 40% by mass of cellulosic fiber based on the total mass of the second fiber layer.

Japanese Patent Application Publication No. 11-229256 JP 2020-171688 A

In the nonwoven fabric of Patent Document 1, the constituent fibers of the cotton web, the constituent fibers of the cotton and synthetic staple fiber webs, and the constituent fibers of the synthetic staple fiber web are three-dimensionally entangled and integrated by treating the laminated webs with a high-pressure fluid. The nonwoven fabric has a low bulk because the web is subjected to a large force in the thickness direction by the high-pressure fluid. When the nonwoven fabric is used as a top sheet for an absorbent article, the low bulk makes it difficult for liquid to penetrate in the thickness direction, and the nonwoven fabric has poor liquid permeability.

Patent Document 2 states that joining the first and second fiber layers by the air-through method (hot air penetration type heat treatment method) is preferable because it is easy to obtain a nonwoven fabric with good texture. However, there is a problem in that there are few points of contact between the fibers of the first and second fiber layers, so there are few places where they can fuse, and the first and second fiber layers are easily peeled off. The more cellulosic fibers contained in the second fiber layer, the fewer the places where the first and second fiber layers can fuse, and the easier it is for the first and second fiber layers to peel off.

The present invention aims to provide a nonwoven fabric for absorbent articles that can suppress delamination and has excellent liquid permeability, and a method for manufacturing the nonwoven fabric for absorbent articles.

The present invention is a nonwoven fabric for absorbent articles that includes a first fiber layer and a second fiber layer in order in the thickness direction, the first fiber layer has a first surface and is made of heat-sealing fibers, the second fiber layer includes absorbent fibers and heat-sealing fibers, some of the heat-sealing fibers of the first fiber layer penetrate into the second fiber layer and are fused to some of the heat-sealing fibers of the second fiber layer, and the absorbent fibers of the second fiber layer are not exposed to the first surface.

The present invention is a method for manufacturing a nonwoven fabric for absorbent articles, comprising a first step of spraying gas from the side of a first fiber web made of heat-fusible fibers and a second fiber web containing absorbent fibers and heat-fusible fibers, which are stacked in order in the thickness direction, and a second step of melting the surfaces of the heat-fusible fibers of the first fiber web and the heat-fusible fibers of the second fiber web to fuse the heat-fusible fibers together, the first step spraying the gas under conditions in which the amount of movement of the heat-fusible fibers of the first fiber web in the thickness direction is greater than the amount of movement of the heat-fusible fibers in the width direction perpendicular to the machine direction.

The nonwoven fabric for absorbent articles according to the present invention can suppress delamination and has excellent liquid permeability. The manufacturing method for nonwoven fabric for absorbent articles according to the present invention can suppress delamination and obtain a nonwoven fabric with excellent liquid permeability.

1 is a diagram showing a schematic diagram of an absorbent article according to an embodiment. 2 is an end view showing a schematic cross section taken along line II-II in FIG. 1. FIG. 4 is a partially enlarged cross-sectional view of the top sheet. 1 is a schematic diagram showing a manufacturing process of a nonwoven fabric according to an embodiment of the present invention. FIG. 11 is a partially enlarged cross-sectional view showing a schematic diagram of a nonwoven fabric according to a modified example. 1 is a micrograph of a cross section of a nonwoven fabric according to Example 1. 1 is a micrograph of a cross section of a nonwoven fabric according to Comparative Example 1. 1 is a micrograph of a cross section of a nonwoven fabric according to Comparative Example 2. 1 is a micrograph of a cross section of a nonwoven fabric according to Reference Example 1.

The present invention relates to the following aspects:

[Aspect 1]
A nonwoven fabric for absorbent articles, comprising a first fiber layer and a second fiber layer in that order in a thickness direction,
the first fiber layer has a first surface and is made of thermally adhesive fibers;
The second fiber layer includes a water-absorbent fiber and a heat-fusible fiber,
A nonwoven fabric, wherein a portion of the heat-fusible fibers of the first fiber layer penetrates into the second fiber layer and is fused to a portion of the heat-fusible fibers of the second fiber layer, and the water-absorbent fibers of the second fiber layer are not exposed to the first surface.
In the nonwoven fabric, a part of the heat-fusible fibers in the first fiber layer and a part of the heat-fusible fibers in the second fiber layer are fused to each other. That is, a part of the heat-fusible fibers in the first fiber layer penetrates into the second fiber layer and contacts and is fused to a part of the heat-fusible fibers contained in the second fiber layer. Therefore, in the nonwoven fabric, the first fiber layer and the second fiber layer are firmly bonded to each other, so that delamination between the first fiber layer and the second fiber layer can be suppressed.
The absorbent fibers of the second fiber layer are held in the second fiber layer by a part of the heat-fusible fibers of the first fiber layer and a part of the heat-fusible fibers of the second fiber layer that are fused to each other. The absorbent fibers of the second fiber layer are not exposed to the first surface and therefore are unlikely to fall off from the first surface. Therefore, the nonwoven fabric is prevented from losing the fibers of the second fiber layer.

When the nonwoven fabric is used as a topsheet of an absorbent article and the first surface is the skin-facing surface, bodily fluids supplied to the skin-facing surface migrate from the skin-facing surface into the first fiber layer. When the second surface is the skin-facing surface, bodily fluids supplied to the skin-facing surface migrate from the skin-facing surface into the second fiber layer. The nonwoven fabric is bulky and has excellent liquid permeability because it includes the first fiber layer made of heat-fusible fibers and the second fiber layer containing absorbent fibers and heat-fusible fibers.

As a result, the nonwoven fabric can suppress delamination between the first and second fiber layers and has excellent liquid permeability.

[Aspect 2]
2. The nonwoven fabric according to claim 1, wherein the first surface of the first fiber layer does not have a recess recessed in a thickness direction.
If a recess recessed in the thickness direction were formed on the first surface, the volume of that portion would be low, resulting in reduced liquid permeability.
In contrast, the nonwoven fabric of the present invention does not have any recesses formed in the thickness direction on the first surface, so that accumulation of body fluids in specific locations is suppressed, and therefore the nonwoven fabric has excellent liquid permeability.

[Aspect 3]
A nonwoven fabric according to claim 1 or 2, further comprising a third fibrous layer made of thermally adhesive fibers on the opposite side of the second fibrous layer to the first fibrous layer.
The surface of the third fiber layer disposed on the opposite side of the second fiber layer from the first fiber layer of the second fiber layer constitutes the second side of the nonwoven fabric. The second fiber layer is covered by the third fiber layer, and the water-absorbent fibers are prevented from being exposed from the second side. Therefore, the nonwoven fabric is prevented from losing the water-absorbent fibers.

[Aspect 4]
A nonwoven fabric as described in aspect 3, wherein a portion of the heat-fusible fibers of the first fiber layer that have penetrated into the second fiber layer penetrates through the second fiber layer, penetrates into the third fiber layer, and is fused to a portion of the heat-fusible fibers of the third fiber layer.

In the nonwoven fabric, a part of the heat-fusible fibers of the first fiber layer is further fused to a part of the heat-fusible fibers of the third fiber layer. That is, a part of the heat-fusible fibers of the first fiber layer penetrates into the second fiber layer, and a part of the heat-fusible fibers penetrates the second fiber layer, penetrates into the third fiber layer, and is fused to a part of the heat-fusible fibers of the third fiber layer. Therefore, the nonwoven fabric is firmly bonded not only between the first fiber layer and the second fiber layer, but also between the second fiber layer and the third fiber layer, so that delamination between layers can be suppressed.
The water-absorbent fibers of the second fiber layer are held in the second fiber layer by a part of the heat-fusible fibers of the first fiber layer and a part of the heat-fusible fibers of the second fiber layer that are fused to each other, and by a further part of the heat-fusible fibers of the first fiber layer that have penetrated the second fiber layer and a part of the heat-fusible fibers of the third fiber layer that are fused to each other, so that the nonwoven fabric is further prevented from losing fibers of the second fiber layer.

[Aspect 5]
A nonwoven fabric according to claim 4, wherein a portion of the heat-fusible fibers of the second fiber layer penetrates into the third fiber layer and is fused to a further portion of the fusible fibers of the first fiber layer and to a portion of the heat-fusible fibers of the third fiber layer.

A part of the heat-fusible fibers of the second fiber layer penetrates into the third fiber layer, and in the third fiber layer, is fused to a part of the heat-fusible fibers of the third fiber layer, and is further fused to a part of the heat-fusible fibers of the first fiber layer that penetrates through the second fiber layer into the third fiber layer. Therefore, the nonwoven fabric has a stronger bond between the second fiber layer and the third fiber layer, and can further suppress interlayer peeling.
The water-absorbent fibers of the second fiber layer are held in the second fiber layer by a part of the heat-fusible fibers of the second fiber layer and a part of the heat-fusible fibers of the third fiber layer, which are fused together, and by a further part of the heat-fusible fibers of the first fiber layer that have penetrated the second fiber layer and a part of the heat-fusible fibers of the second fiber layer, which are fused together. Therefore, the nonwoven fabric is further prevented from losing fibers of the second fiber layer.

[Aspect 6]
Aspect 6. The nonwoven fabric of any one of aspects 1 to 5, wherein the first surface of the first fibrous layer is a skin-facing surface.
When the nonwoven fabric is used as a top sheet of an absorbent article and the first surface is the skin-facing surface, the body fluid supplied to the skin-facing surface migrates from the skin-facing surface to the inside of the first fiber layer. The absorbent fibers are not exposed to the skin-facing surface, so the body fluid is less likely to remain on the skin-facing surface. The body fluid that migrates to the inside of the first fiber layer further migrates in the thickness direction and reaches the interface between the first fiber layer and the second fiber layer. The body fluid smoothly migrates to the second fiber layer because a part of the heat-fusible fibers of the first fiber layer penetrates into the second fiber layer. The body fluid that migrates to the second fiber layer is absorbed by the absorbent fibers contained in the second fiber layer. When the nonwoven fabric is used as a top sheet of an absorbent article, the body fluid absorbed by the absorbent fibers is absorbed by the absorbent body arranged on the non-skin side. In this way, the nonwoven fabric smoothly migrates the body fluid supplied to the skin-facing surface from the first fiber layer to the second fiber layer and is absorbed by the absorbent fibers of the second fiber layer, so that the nonwoven fabric has excellent liquid management properties.

[Aspect 7]
7. The nonwoven fabric of claim 6, wherein the second fibrous layer has a uniform basis weight in a plane direction.
Since the basis weight of the second fiber layer is uniform in the surface direction, bodily fluid that is supplied to the skin-facing surface and migrates in the thickness direction is absorbed uniformly regardless of the position in the surface direction, and therefore the nonwoven fabric has excellent liquid drainage properties regardless of the position in the surface direction.

[Aspect 8]
A nonwoven fabric according to claim 6 or 7, wherein the second fiber layer contains the water-absorbent fiber in an amount of 40% by mass or more and 70% by mass or less.
Since the nonwoven fabric contains 40% by mass or more and 70% by mass or less of absorbent fibers in the second fiber layer, the absorbent fibers more reliably absorb body fluids discharged from the wearer, and therefore the nonwoven fabric has excellent liquid drainage properties when body fluids are repeatedly supplied to the nonwoven fabric.

[Aspect 9]
a first step of injecting gas onto a first fiber web made of heat-fusible fibers and a second fiber web including water-absorbent fibers and heat-fusible fibers, the first fiber web being stacked in order in a thickness direction, from the side of the first fiber web;
a second step of melting surfaces of the heat-fusible fibers of the first fiber web and the heat-fusible fibers of the second fiber web to fuse the heat-fusible fibers together;
The first step is a method for manufacturing a nonwoven fabric for absorbent articles, in which the gas is sprayed under conditions in which the amount of movement of the heat-fusible fibers of the first fiber web in the thickness direction is greater than the amount of movement of the fibers in the width direction perpendicular to the machine direction.

In the first step of injecting gas from the first fiber web side onto a first fiber web made of heat-fusible fibers and a second fiber web containing absorbent fibers and heat-fusible fibers, which are stacked in the thickness direction, the gas is injected under conditions in which the amount of movement of the heat-fusible fibers of the first fiber web in the thickness direction is greater than the amount of movement of the heat-fusible fibers in the width direction perpendicular to the machine direction, so that a nonwoven fabric according to aspect 1 can be formed. That is, this manufacturing method can form a nonwoven fabric for absorbent articles that has a first fiber layer and a second fiber layer in order in the thickness direction, in which the first fiber layer is made of heat-fusible fibers and has a first surface, the second fiber layer contains absorbent fibers and heat-fusible fibers, some of the heat-fusible fibers of the first fiber layer penetrate into the second fiber layer and are fused to the heat-fusible fibers of the second fiber layer, and the absorbent fibers of the second fiber layer are not exposed to the first surface.

The nonwoven fabric for absorbent articles according to the embodiment will be described in detail below with reference to the drawings.

(Configuration of absorbent article)
FIG. 1 is a diagram showing a schematic view of an absorbent article 10 according to an embodiment, FIG. 2 is an end view showing a schematic cross section taken along line II-II in FIG. 1, and FIG. 3 is a partially enlarged cross-sectional view of the topsheet.

The absorbent article 10 shown in FIG. 1 is a sanitary napkin, and has a longitudinal direction L, a width direction W, and a thickness direction T that are perpendicular to each other. The absorbent article 10 includes a main body portion 12 extending in the longitudinal direction L, and a pair of flap portions 14 extending on both sides of the width direction W at approximately the center of the longitudinal direction L. The longitudinal direction L, width direction W, and thickness direction T of the absorbent article 10 coincide with the longitudinal direction L, width direction W, and thickness direction T of each material described below, so that the longitudinal direction L, width direction W, and thickness direction T are used commonly for the absorbent article 10 and each material thereof below. The terms "skin-facing side" and "non-skin-facing side" refer to the side relatively closer to and farther from the wearer's skin surface in the thickness direction T, respectively, when the absorbent article 10 is worn by the wearer of the absorbent article 10, and are used commonly for each material of the absorbent article 10. In this specification, the "skin-facing surface" and the "non-skin-facing surface" of the absorbent article 10 and each of the materials that make up the absorbent article 10 (e.g., top sheet, absorbent body, back sheet, etc.) are sometimes simply referred to as the "skin-facing surface" and the "non-skin-facing surface," respectively.

As shown in FIG. 2, the absorbent article 10 includes a top sheet 16, an absorbent body 18, and a back sheet 20, which are arranged in the thickness direction T from the skin-facing side. The top sheet 16 is a liquid-permeable sheet located on the skin-facing side of the wearer. The absorbent body 18 is a liquid-absorbing and liquid-retentive material located between the top sheet 16 and the back sheet 20. Examples of materials constituting the absorbent body 18 include pulp fibers, synthetic fibers, and absorbent polymers. The back sheet 20 is a liquid-impermeable sheet located on the non-skin-facing side of the wearer. Examples of the back sheet 20 include any liquid-impermeable sheet such as a liquid-impermeable nonwoven fabric or synthetic resin film, a composite sheet of these, or an SMS nonwoven fabric. An exterior sheet (not shown) that reinforces the back sheet 20 and improves the feel may be laminated on the non-skin-facing side of the back sheet 20. Examples of the exterior sheet include any water-repellent sheet such as a material similar to the back sheet 20, a water-repellent nonwoven fabric or synthetic resin film, or a composite sheet of these. The absorbent body 18, the top sheet 16, and the back sheet 20 are each bonded with an adhesive. The adhesive for bonding the top sheet 16, the absorbent body 18, and the back sheet 20 can be a known material commonly used in absorbent articles 10, such as a thermoplastic adhesive.

(Surface sheet)
The top sheet 16 will be described below with reference to Fig. 3. The top sheet 16 is made of a nonwoven fabric according to this embodiment. The top sheet 16 has a longitudinal direction L, a width direction W, and a thickness direction T, and has a first surface 22 on one side and a second surface 24 on the opposite side to the first surface 22. The first surface 22 and the second surface 24 each intersect with the thickness direction T. The first surface 22 and the second surface 24 according to this embodiment are each approximately flat. One direction of the thickness direction T is upward, and the other direction is downward.

The top sheet 16 comprises a first fiber layer 26 and a second fiber layer 28 in the above order in the thickness direction T. The first fiber layer 26 is made of heat-fusible fibers and has a first surface 22 that is the skin-facing surface of the top sheet 16 (liquid-permeable sheet). There are no particular limitations on the type of nonwoven fabric of the top sheet 16 as long as it is a nonwoven fabric that can be used for absorbent articles, but a thermally bonded nonwoven fabric in which heat-fusible fibers are fused together is preferred, and an air-through nonwoven fabric is more preferred. The thickness of the top sheet 16 is, for example, 0.5 to 3.0 mm.

The basis weight of the first fiber layer 26 is generally uniform in the surface direction, and may be, for example, 6 to 200 g/m ^2. The heat-fusible fibers contained in the first fiber layer 26 are fibers made of thermoplastic resins, for example, olefin resins such as polyethylene (PE), polypropylene (PP), and ethylene-vinyl acetate copolymer (EVA); polyester resins such as polyethylene terephthalate (PET) and polylactic acid (PLA); and polyamide resins such as 6-nylon. These resins may be used alone or in combination of two or more types of resins. The structure of such fibers made of thermoplastic resins is not particularly limited, and examples thereof include core-sheath type fibers such as PET/PE, composite fibers such as side-by-side type fibers, and island/sea type fibers; hollow type fibers; and irregular cross-section fibers such as flat, Y-shaped, and C-shaped. Fibers having these structures may be used alone or in combination of two or more types of fibers. The fineness of the heat-fusible fibers may be, for example, 1 to 20 dtex.

The second fiber layer 28 contains absorbent fibers and heat-sealable fibers, and has a second surface 24 that is the non-skin-facing surface of the top sheet 16. The second fiber layer 28 preferably contains 40% to 60% absorbent fibers by mass. The absorbent fibers are not exposed from the first surface 22.

The basis weight of the second fiber layer 28 is generally uniform in the surface direction, and may be, for example, 6 to 200 g/ ^m2 . Examples of the absorbent fibers contained in the second fiber layer 28 include natural cellulosic fibers such as pulp, cotton, and hemp; and regenerated cellulosic fibers such as rayon, lyocell, and cupra. These cellulosic fibers may be used alone or in combination of two or more types. The fineness of the absorbent fibers may be, for example, 0.5 to 5.0 dtex.

The heat-fusible fibers contained in the second fiber layer 28 can be selected from the heat-fusible fibers exemplified in the first fiber layer 26, and may be the same as or different from the heat-fusible fibers in the first fiber layer 26. The fineness of the thermoplastic resin fibers contained in the second fiber layer 28 can be, for example, 1 to 20 dtex. The fiber diameter of the heat-fusible fibers contained in the second fiber layer 28 may be the same as or different from the fiber diameter of the heat-fusible fibers contained in the first fiber layer 26.

The topsheet 16 may further include a third fiber layer 30 made of heat-fusible fibers on the second surface 24 side. That is, the topsheet 16 may include a first fiber layer 26, a second fiber layer 28, and a third fiber layer 30 in this order in the thickness direction T. The third fiber layer 30 may be made of the same material as the first fiber layer 26. The basis weight of the third fiber layer 30 is generally uniform in the surface direction, and may be, for example, 6 to 200 g/m ^2. The third fiber layer 30 may have the same configuration as the first fiber layer 26. The third fiber layer 30 is in contact with the second fiber layer 28 on the surface facing the skin. When the topsheet 16 includes the third fiber layer 30, the surface on the non-skin facing side of the third fiber layer 30 becomes the second surface 24, which is the non-skin facing surface of the topsheet 16.

The boundary between the first fiber layer 26 and the second fiber layer 28, and the boundary between the second fiber layer 28 and the third fiber layer 30 can be determined by the presence or absence of absorbent fibers. That is, in the cross section of the top sheet 16, the upper end of the thickness direction T where the absorbent fibers exist may be the boundary between the first fiber layer 26 and the second fiber layer 28, the side where the absorbent fibers exist may be the second fiber layer 28, and the side where the absorbent fibers do not exist may be the first fiber layer 26. Similarly, in the cross section of the top sheet 16, the lower end of the thickness direction T where the absorbent fibers exist may be the boundary between the second fiber layer 28 and the third fiber layer 30, the side where the absorbent fibers exist may be the second fiber layer 28, and the side where the absorbent fibers do not exist may be the third fiber layer 30. The boundary between the first fiber layer 26 and the second fiber layer 28, and the boundary between the second fiber layer 28 and the third fiber layer 30 thus determined are linear in FIG. 3, but the present invention is not limited to this, and may be somewhat undulating in the thickness direction T. The absorbent fibers can be visually identified by dyeing them using the method described below.

The thickness of the first fiber layer 26, i.e., the height from the boundary between the first fiber layer 26 and the second fiber layer 28 to the first surface 22, is, for example, 0.3 to 2.0 mm. The skin-facing surface of the first fiber layer 26 (the first surface 22 of the nonwoven fabric) does not have a recess recessed in the thickness direction T. In this specification, the recess refers to a recess intentionally formed by bending or moving the fibers by gear processing or air jet spraying, and does not include undulations formed naturally by the arrangement of fibers that are merely stacked. In the height from the boundary between the first fiber layer 26 and the second fiber layer 28 to the first surface 22, the minimum height is preferably 50% or more of the maximum height, and more preferably 70% to 95% or less. The thickness of the second fiber layer 28, i.e., the height from the boundary between the first fiber layer 26 and the second fiber layer 28 to the boundary between the second fiber layer 28 and the third fiber layer 30, is, for example, 0.2 to 1.0 mm. The thickness of the third fiber layer 30, i.e., the height from the boundary between the second fiber layer 28 and the third fiber layer 30 to the second surface 24, is, for example, 0.2 to 0.5 mm.

A portion of the heat-fusible fibers of the first fiber layer 26 is fused to a portion of the heat-fusible fibers of the second fiber layer 28 within the second fiber layer 28. That is, a portion of the heat-fusible fibers of the first fiber layer 26 bends toward the second fiber layer 28 in the thickness direction T, penetrates into the second fiber layer 28, and comes into contact with and is fused to a portion of the heat-fusible fibers contained in the second fiber layer 28.

A portion of the heat-fusible fibers of the first fiber layer 26 that have penetrated into the second fiber layer 28 is fused to a portion of the heat-fusible fibers of the third fiber layer 30 within the third fiber layer 30. That is, a portion of the heat-fusible fibers of the first fiber layer 26 bends toward the second fiber layer 28 in the thickness direction T and penetrates into the second fiber layer 28, and a portion of the heat-fusible fibers penetrates the second fiber layer 28 and penetrates into the third fiber layer 30, where they come into contact with and are fused to a portion of the heat-fusible fibers of the third fiber layer 30.

A portion of the heat-fusible fibers of the second fiber layer 28 is fused to a portion of the heat-fusible fibers of the third fiber layer 30 within the third fiber layer 30. That is, a portion of the heat-fusible fibers of the second fiber layer 28 bends toward the third fiber layer 30 in the thickness direction T, penetrates into the third fiber layer 30, and comes into contact with and is fused to a portion of the heat-fusible fibers contained in the third fiber layer 30.

(Manufacturing method)
The manufacturing method of the topsheet 16 will be described below with reference to Fig. 4. Fig. 4 is a schematic diagram showing the manufacturing process of the topsheet 16 including a first fiber layer 26 and a second fiber layer 28. The topsheet 16 is manufactured through a first step, a second step, a third step, and a fourth step. In Fig. 4, MD refers to the machine direction (conveyance direction).

In the first process, heat-fusible fibers and absorbent fibers are supplied to a first carding machine 32 to form a second fiber web 34. In the second process, heat-fusible fibers are supplied to a second carding machine 36 to form a first fiber web 38. The first fiber web 38 is layered on the second fiber web 34 to obtain a laminated web 40. The laminated web 40 is transported to the third process.

In the third step, the laminated web 40 is placed on the circumferential surface of the suction drum 42. The suction drum 42 has an inner cylinder 44 in a fixed state and an outer cylinder 46 that is concentric with the inner cylinder 44 and has air permeability and rotates in the machine direction MD. The suction drum pressure measured by a pressure gauge in the suction drum is appropriately selected depending on the basis weight of each fiber web and the flow rate of the first air and the second air described later, and is preferably 5 to 9 kPa, more preferably 5 to 8 kPa. The laminated web 40 is placed on the circumferential surface of the outer cylinder 46 and is transported together with the outer cylinder 46 in the machine direction MD at a predetermined speed, for example, a speed of 100 m/min. The inner cylinder 44 has a suction area 48. Above the suction area 48, a first manifold 50 having a plurality of nozzles aligned in a cross direction CD perpendicular to the machine direction MD and a second manifold 52 arranged parallel to the first manifold 50 and having a plurality of nozzles aligned in the cross direction CD are provided. The nozzle has a predetermined opening diameter, for example, a diameter of 1 mm. The first manifold 50 sprays the first air, which is composed of a gas heated at, for example, 200° C., toward the laminated web 40. The flow rate of the first air sprayed from the first manifold 50 is, for example, 3 to 5 m ³ /min. Subsequently, the second manifold 52 sprays the second air, which is composed of a gas heated at, for example, 200° C., toward the laminated web 40. The flow rate of the second air sprayed from the second manifold 52 is, for example, 3 to 5 m ³ /min.

In the laminated web 40, the first air and the second air are sequentially sprayed, which causes the heat-fusible fibers of the first fibrous web 38 located directly below the first manifold 50 and the second manifold 52 to move. By setting the flow rate of the first air and the second air to 3 to 5 m ³ /min, the heat-fusible fibers of the first fibrous web 38 move a greater amount in the thickness direction T than in the width direction W (cross direction CD). In other words, the first air and the second air are sprayed under conditions in which the amount of movement in the thickness direction T is greater than the amount of movement in the cross direction CD (width direction W) perpendicular to the machine direction MD. As a result, the heat-fusible fibers of the first fibrous web 38 hardly move in the width direction W, and some of them bend toward the second fibrous web 34 in the thickness direction T and enter the second fibrous web 34.

By spraying the first air and the second air under the above-mentioned specified conditions, the surface of the first fiber web 38 moves less in the width direction W and is pressed in the thickness direction T, resulting in a smoother surface structure with fewer irregularities overall. Therefore, the top sheet 16 can be formed by placing the first fiber layer 26 based on the first fiber web on the skin side.

In the fourth step, the laminated web 40 passes through a dryer 54. The dryer 54 blows heated air at a temperature capable of melting the surface of the heat-fusible fibers, for example 120°C to 150°C, onto the laminated web 40. In the laminated web 40, the heat-fusible fibers fuse together. As described above, some of the heat-fusible fibers of the first fiber web 38 penetrate into the second fiber web 34, and therefore fuse to some of the heat-fusible fibers contained in the second fiber web 34 within the second fiber web 34.

The laminated web 40 conveyed from the dryer 54 is cooled to room temperature to obtain a top sheet 16 that can be used for absorbent articles. The top sheet (nonwoven fabric) 16 obtained in the manner described above is an air-through nonwoven fabric, and therefore has excellent bulkiness.

The top sheet 16 with the third fiber layer 30 is prepared by supplying heat-fusible fibers to a carding machine (not shown) prior to the first step to form a third fiber web, overlaying the second fiber web 34 formed in the first step on the third fiber web, and then overlaying the first fiber web 38 formed in the second step to form a laminated web. The laminated web is then subjected to the third and fourth steps to obtain the top sheet 16 with the first fiber layer 26, the second fiber layer 28, and the third fiber layer 30.

(Action and Effects)
The absorbent article 10 is worn with the top sheet 16 disposed on the side facing the wearer's skin. Body fluid discharged from the wearer is supplied to the top sheet 16. The body fluid moves in the thickness direction T from the first surface 22 to the first fiber layer 26. The body fluid is drawn further inward by the absorbent fibers of the first fiber layer 26 and the second fiber layer 28, and a portion of the body fluid is absorbed by the absorbent fibers. The body fluid drawn in and absorbed by the absorbent fibers is absorbed by the top sheet 16 and the absorbent body 18 disposed on the non-skin side.

The top sheet 16 is for an absorbent article having a first fiber layer 26 and a second fiber layer 28 in order in the thickness direction T, the first fiber layer 26 has a skin-facing surface and is made of heat-sealing fibers, the second fiber layer 28 contains absorbent fibers and heat-sealing fibers, some of the heat-sealing fibers of the first fiber layer 26 penetrate into the second fiber layer 28 and are fused to some of the heat-sealing fibers of the second fiber layer 28, and the absorbent fibers of the second fiber layer 28 are not exposed to the skin-facing surface.

In the top sheet 16, a portion of the heat-fusible fibers of the first fiber layer 26 and a portion of the heat-fusible fibers of the second fiber layer 28 are fused together. That is, a portion of the heat-fusible fibers of the first fiber layer 26 bends toward the second fiber layer 28 in the thickness direction T, penetrates into the second fiber layer 28, and comes into contact with and is fused to a portion of the heat-fusible fibers contained in the second fiber layer 28. Therefore, since the first fiber layer 26 and the second fiber layer 28 are firmly bonded to each other in the top sheet 16, delamination between the first fiber layer 26 and the second fiber layer 28 can be suppressed.

The absorbent fibers of the second fiber layer 28 are held in the second fiber layer 28 by a portion of the heat-fusible fibers of the first fiber layer 26 and a portion of the heat-fusible fibers of the second fiber layer 28 that are fused together. Therefore, the top sheet 16 is prevented from losing the fibers of the second fiber layer 28.

Body fluids supplied to the skin-facing surface are transferred from the skin-facing surface to the inside of the first fiber layer 26 by the heat-fusible fibers of the first fiber layer 26, so the body fluids are less likely to remain on the skin-facing surface of the top sheet 16. Therefore, the top sheet 16 has excellent liquid permeability. The top sheet 16 is an air-through nonwoven fabric. Therefore, the top sheet 16 has excellent bulkiness and therefore excellent liquid permeability.

The body fluid that has migrated into the first fiber layer 26 further migrates in the thickness direction T and reaches the interface between the first fiber layer 26 and the second fiber layer 28, since the absorbent fibers are not exposed on the skin-facing surface. The body fluid smoothly migrates to the second fiber layer 28 because some of the heat-fusible fibers of the first fiber layer 26 penetrate into the second fiber layer 28. The body fluid that has migrated to the second fiber layer 28 is absorbed by the absorbent fibers contained in the second fiber layer 28. The body fluid absorbed by the absorbent fibers is absorbed by the absorbent body 18 arranged on the non-skin side. In this way, the top sheet 16 smoothly migrates the body fluid supplied to the skin-facing surface from the first fiber layer 26 to the second fiber layer 28 and is absorbed by the absorbent fibers of the second fiber layer 28, resulting in excellent liquid handling properties.

As a result, the top sheet 16 is able to suppress delamination between the first fiber layer 26 and the second fiber layer 28, and has excellent liquid permeability and liquid drainage properties.

In this specification, liquid permeability is evaluated as the time it takes for bodily fluids to completely penetrate from the skin-facing surface into the top sheet 16, and liquid drainage is evaluated as the time it takes for bodily fluids to drain from the skin-facing surface to the non-skin-facing surface and disappear from the top sheet 16.

If the first surface of the first fiber layer is the skin-facing surface and a recess is formed on the skin-facing surface that is recessed in the thickness direction, the distance from the skin-facing surface to the absorbent fibers contained in the second fiber layer is short. In other words, the absorbent fibers that have absorbed body fluids are located close to the skin-facing surface, so that body fluids supplied to the skin-facing surface do not migrate in the thickness direction but instead accumulate in the recess, resulting in reduced liquid permeability.

The top sheet 16 of this embodiment does not have any recesses recessed in the thickness direction T on the skin-facing surface, which prevents bodily fluids from accumulating in specific locations. Therefore, the top sheet 16 has excellent liquid permeability.

The surface sheet 16 has a uniform basis weight of the second fiber layer 28 in the surface direction. Because the basis weight of the second fiber layer 28 is uniform in the surface direction, bodily fluids supplied to the skin-facing surface and migrate in the thickness direction T are absorbed uniformly regardless of the position in the surface direction. Therefore, the surface sheet 16 has excellent liquid drainage properties regardless of the position in the surface direction.

The top sheet 16 contains 40% to 70% by mass of absorbent fibers in the second fiber layer 28, so the absorbent fibers more reliably absorb the body fluids discharged from the wearer. Therefore, the top sheet 16 has excellent liquid drainage properties when body fluids are repeatedly supplied to it.

When the third fiber layer 30 made of heat-fusible fibers is provided on the non-skin side of the second fiber layer 28, the second fiber layer 28 is covered by the third fiber layer 30, preventing the absorbent fibers from being exposed from the non-skin-facing surface. Therefore, the top sheet 16 prevents the absorbent fibers from falling out.

A part of the heat-fusible fibers of the first fiber layer 26 that has penetrated into the second fiber layer 28 may further penetrate the second fiber layer 28, penetrate into the third fiber layer 30, and fuse with a part of the heat-fusible fibers of the third fiber layer 30. That is, a part of the heat-fusible fibers of the first fiber layer 26 bends toward the second fiber layer 28 in the thickness direction T and penetrates into the second fiber layer 28, and a part of it penetrates the second fiber layer 28, penetrates into the third fiber layer 30, and fuses with a part of the heat-fusible fibers of the third fiber layer 30. Therefore, the surface sheet 16 is firmly bonded between the first fiber layer 26 and the second fiber layer 28, as well as between the second fiber layer 28 and the third fiber layer 30, so that delamination between layers can be suppressed.

The absorbent fibers of the second fiber layer 28 are held in the second fiber layer 28 by a portion of the heat-fusible fibers of the first fiber layer 26 and a portion of the heat-fusible fibers of the second fiber layer 28 that are fused together, and by a further portion of the heat-fusible fibers of the first fiber layer 26 that have penetrated the second fiber layer 28 and a portion of the heat-fusible fibers of the third fiber layer 30. Therefore, the top sheet 16 is further prevented from losing fibers of the second fiber layer 28.

A part of the heat-fusible fibers of the second fiber layer 28 may penetrate into the third fiber layer 30 and be fused to a further part of the fusible fibers of the first fiber layer 26 and to a part of the heat-fusible fibers of the third fiber layer 30. That is, a part of the heat-fusible fibers of the second fiber layer 28 bends toward the third fiber layer 30 in the thickness direction T and penetrates into the third fiber layer 30, and is fused to a part of the heat-fusible fibers of the third fiber layer 30 in the third fiber layer 30, and is further fused to a further part of the heat-fusible fibers of the first fiber layer 26 that penetrated through the second fiber layer 28 and penetrated into the third fiber layer 30. Therefore, the surface sheet 16 is more firmly bonded between the second fiber layer 28 and the third fiber layer 30, so that interlayer peeling can be more suppressed.

The absorbent fibers of the second fiber layer 28 are held in the second fiber layer 28 by a portion of the heat-fusible fibers of the second fiber layer 28 and a portion of the heat-fusible fibers of the third fiber layer 30 that are fused together, and by a further portion of the heat-fusible fibers of the first fiber layer 26 that have penetrated the second fiber layer 28 and a portion of the heat-fusible fibers of the second fiber layer 28 that are fused together. Therefore, the top sheet 16 is further prevented from losing fibers of the second fiber layer 28.

(Modification)
The present invention is not limited to the above embodiment, and can be modified as appropriate within the scope of the present invention. For example, the top sheet 60 shown in FIG. 5 may have irregularities. That is, the top sheet 60 has, on the first surface 22, a plurality of solid protrusions 62 protruding in the direction from the second surface 24 toward the first surface 22, and a plurality of recesses 64 recessed in the direction from the first surface 22 toward the second surface 24. In this specification, "solid" means that there is no space in the protrusions 62 where the fiber density is significantly lower than the surroundings, which would prevent the movement of liquid. If the difference in height between the highest part where the height of the first surface 22 is the highest and the deepest part where the height of the first surface 22 is the lowest is d, the part protruding upward from the deepest part at a height of d/2 from the deepest part can be called the protrusions 62, and the part recessed downward can be called the recesses 64. The top sheet 60 having irregularities may be formed by further undergoing a gear processing step after the fourth step in the above manufacturing method. In the gear processing process, the nonwoven fabric formed by bonding the first fiber layer 26, the second fiber layer 28, and the third fiber layer is sandwiched between a pair of gear processing rolls and locally pressed to form a plurality of recesses 64, thereby obtaining the surface sheet 60.
The topsheet 60 may have compressed portions (not shown). The compressed portions are arranged intermittently in the longitudinal direction L in the recesses 64. The compressed portions may be arranged at equal intervals in the longitudinal direction L in the recesses 64, or may be arranged at unequal intervals. In the recesses 64 adjacent to each other in the width direction W, the compressed portions may be located at the same position in the longitudinal direction L, or at different positions. The compressed portions are formed by sandwiching the first fiber layer 26 from above and the third fiber layer 30 arranged with the second fiber layer 28 in between in the thickness direction T, and join the first fiber layer 26, the second fiber layer 28, and the third fiber layer 30.

The type and use of the absorbent article 10 are not particularly limited, and examples include hygiene and sanitary products such as panty liners, disposable diapers (tape type, pants type), incontinence pads, and sweat sheets, which may be intended for humans or non-human animals such as pets. The liquids that the absorbent article 10 is intended to absorb are not particularly limited, and examples include the wearer's liquid waste, body fluids, etc.

In the above embodiment, the first fiber layer is disposed on the skin side, but the present invention is not limited to this. For example, the nonwoven fabric may be applied to a top sheet by disposing the first fiber layer on the non-skin side and disposing the second fiber layer or the third fiber layer on the skin side. In other words, the second surface is the surface facing the skin. In this case, the nonwoven fabric has a first fiber layer made of heat-fusible fibers and a second fiber layer containing absorbent fibers and heat-fusible fibers, so it is bulky and has excellent liquid permeability. The absorbent fibers of the second fiber layer are not exposed to the first surface, so they are unlikely to fall off from the first surface.

(Measurement method)
<Top sheet basis weight, thickness, fiber density and fineness>
The basis weight, thickness, fiber density and fineness of the topsheet in the above embodiment are measured by the following methods.
(1) Surface sheet basis weight: A sample is cut from the surface sheet to a suitable size, for example, 10 cm x 10 cm, and left for 24 hours in an atmosphere at a temperature of 20°C and a humidity of 65%, after which the mass is measured. The measured mass is divided by the area of the sample to calculate the sample basis weight. The average value of the basis weights of the 10 samples is regarded as the surface sheet basis weight.
(2) Surface sheet thickness: Using a thickness gauge equipped with a 15 ^cm2 gauge (model FS-60DS, manufactured by Daiei Chemical Industry Co., Ltd.), measure the thickness of the surface sheet under a measurement load of 3 gf/ ^cm2 (0.3 kPa). The thickness is measured at three points on one sample, and the average value of the three thicknesses is regarded as the thickness of the surface sheet.
(3) Fiber density of the topsheet: The fiber density of the topsheet is calculated by dividing the weight of the topsheet determined by the above method by the thickness of the topsheet determined by the above method.
(4) Fiber fineness: The fiber fineness is determined by measuring the cross-sectional area of the fiber by magnifying and observing the cross-sectional shape of the fiber using a scanning electron microscope, and calculating the fiber fineness from the cross-sectional area and the specific gravity of the fiber (i.e., the specific gravity of the components that constitute the fiber).

<Thickness of each part>
The thickness of each part of the first fiber layer, the second fiber layer, and the third fiber layer of the top sheet is measured by the following method. First, the hydrophilic fiber is dyed, and then the thickness of each part is measured. The hydrophilic fiber is dyed in the following procedure. (1) Prepare the top sheet to be measured for thickness. (2) Put 1 L of water in a pan and heat it to 60°C to 70°C. (3) Put the reagent Kayastain Q (Shikisensha Co., Ltd.) into the pan (2) and dissolve it. (4) Heat the pan to 80°C. (5) Put the top sheet into the pan (4) and leave it for 30 minutes. (5) Then, rinse the top sheet with running water. (6) Dry it in an oven at 80°C for 1 hour. As a result of the above procedure, the absorbent fiber (rayon) is dyed blue and the heat-fusible fiber (PET) is dyed yellow.
The thickness is measured by the following procedure. (1) The dyed topsheet is cut into a sample having a length of 5 mm in the machine direction (MD) and 20 mm in the cross direction (CD). (2) The sample is fixed to a jig with double-sided tape so that the CD cross section can be observed. (3) An enlarged photograph of the cross section is taken with a digital microscope VHX-7000 manufactured by Keyence Corporation, the distance between two points for planar measurement is selected, and the thickness of each of the first fiber layer, the second fiber layer, and the third fiber layer of the topsheet is measured.

<Absorbent fiber content>
The content of the water-absorbent fiber in the second fiber layer can be obtained as follows. (1) A sample of the target area is cut out from the top sheet that has been dried at 105°C for 1 hour, and the initial mass (g) of the sample is measured. (2) The sample is immersed in 70% sulfuric acid for 1 hour to dissolve the water-absorbent fiber. (3) The sample after immersion in sulfuric acid is washed with about 6 liters of water while being sucked on a Buchner funnel, and then washed with about 1 liter of pure water. (4) The washed sample is dried at 105°C for 2 hours, and the post-treatment mass (g) of the sample is measured. (5) The post-treatment mass of the sample is subtracted from the initial mass of the sample to calculate the water-absorbent fiber content (g), and the obtained water-absorbent fiber content mass is converted into a mass per unit planar area to obtain the water-absorbent fiber content.

(Example)
A nonwoven fabric corresponding to the topsheet according to the above embodiment was produced and evaluated. The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

(A) Sample According to the above-mentioned manufacturing method, a nonwoven fabric according to Example 1 was produced, which includes a first fiber layer, a second fiber layer, and a third fiber layer, using PE/PET core-sheath type fibers as the heat-fusible fibers and fibers made of rayon as the water-absorbent fibers. The flow rates of the first and second air in the third step were 5 ^m3 /min, and the suction drum pressure was 5.6 kPa. The temperature of the heated air in the fourth step was 136°C. The specific configuration is as shown in Table 1.

As a comparative example, a nonwoven fabric of Comparative Example 2 was produced in the same manner as in the above Example, except that the third and fourth steps of the above manufacturing method were not performed and instead a hydroentanglement method was used.

As a reference example, a nonwoven fabric of Reference Example 1 was produced in the same manner as in the above-mentioned Examples, except that the third step in the above-mentioned manufacturing method was not performed. A nonwoven fabric of Reference Example 2 was produced, which had a first fiber layer made of PE/PET sheath-core fibers, and a second fiber layer containing cotton as absorbent fibers and thermoplastic resin fibers of PE/PET sheath-core fibers, and had a concave-convex structure on the first surface, by spraying an air jet with a flow rate of 9 m ³ /min for the first air and the second air in the third step in the above-mentioned manufacturing method, and setting the suction drum pressure to 8.6 kPa. The nonwoven fabric of Reference Example 1 was produced through the same steps as in the above-mentioned Examples, except that the concave-convex structure was formed. Microscopic photographs of the cross sections of the obtained nonwoven fabric are shown in Figs. 6 to 9.

(B) Evaluation Method Various tests were carried out according to the following procedures.

(Liquid permeability and liquid drainage test)
(1) A sample cut to a size of 200 mm x 100 mm and an acrylic plate of the same size as the sample and having a through hole of 40 mm x 10 mm in the center were prepared.
(2) An acrylic plate was placed on the center of the surface of the sample on the side of the first fiber layer.
(3) 2 ml of horse blood was dripped using a micropipette and a stopwatch was started at the same time.
(4) The time it took for the horse blood to disappear from the sample and around the hole in the acrylic plate (permeation time) was measured.
(5) The time it took for the horse blood inside the acrylic plate to drain (liquid drainage time) was then measured.
(6) 30 seconds after the start of the measurement, a second 2 ml of horse blood was dripped (the second measurement was started even if the first horse blood had not been completely drained).
(7) The above measurements (4) and (5) were carried out in sequence.
(8) 60 seconds after the start of the measurement, the acrylic plate was removed, and 90 seconds after the start of the measurement, 10 pieces of filter paper (35 mm x 50 mm) whose weight had been measured in advance and a weight (35 mm x 50 mm, 525 g) were placed on the area where the horse blood had been dropped.
(9) After 60 seconds, the weight was removed and the weight of the filter paper was measured.

(10) The mass of the filter paper before placing it on the sample was subtracted from the mass of the filter paper after placing it on the sample to determine the rewet (g), and the percentage relative to the amount of absorbed horse blood (2 ml ≒ 2 g) was calculated.

(Fiber shedding test)
(1) The membrane filter was dried in an oven at 90° C. for 1 hour and then allowed to cool in a desiccator for 30 minutes.
(2) Five samples measuring 100 mm x 100 mm were prepared.
(3) Five 300 ml beakers containing 300 ml of tap water were prepared.
(4) A rotor was placed in the beaker and the mixture was stirred with a magnetic stirrer.
(5) The sample was folded into an inverted cone shape with the smoother surface facing outwards.
(6) The sample from (5) was gently dropped into the center of the water surface of the beaker, and the stopwatch was started when the sample touched the center of the water surface.
(7) After stirring for 10 minutes, the sample was removed.
Steps (4) to (7) were carried out for each sample.
(8) The weight of the membrane filter of (1) was measured.
(9) A membrane filter was placed on top of the suction bottle, a funnel was placed on top of it, and then secured in place with a holder.
(10) Ethanol was poured into the funnel to wet the membrane filter, and the vacuum pump was turned on to perform suction.
(11) The stirred water from the beaker was poured into the funnel and then sucked out.
(12) Once the stirred water in the beaker had been sucked up, the hose connected to the suction bottle was first removed and the vacuum pump was turned off.
(13) The funnel was removed, and the membrane filter with accumulated fibers was removed into a petri dish.
(14) The petri dish was covered with plastic wrap to allow air to enter, and the time was written on the plastic wrap.
(15) The membrane filter of (14) was dried in an oven at 90° C. for 1 hour, allowed to cool in a desiccator for 30 minutes, and then its weight was measured.
Steps (9) to (15) were carried out for each sample.
(16) The average value of the measured weights (n=5) was recorded as the amount of fiber loss (mg/m ² ).

(C) Evaluation Results As shown in Table 1, the nonwoven fabric according to Example 1 exhibited excellent results in terms of liquid permeability and liquid drainage in both the first and second tests. It was also confirmed that the nonwoven fabric according to Example 1 had excellent rewetability.

The nonwoven fabric in Comparative Example 1 was produced by the hydroentanglement method, and therefore had low bulk, leading to poor liquid permeability, and the presence of absorbent fibers on the surface is thought to have resulted in poor liquid drainage.

Compared to Example 1, Reference Example 1 had poorer liquid drainage and rewetting properties, and had a greater amount of fiber shedding. The nonwoven fabric of Reference Example 1 did not undergo the third step in the manufacturing method of the above embodiment, and it is believed that the liquid was not able to move smoothly from the first fiber layer to the second fiber layer. In addition, it is believed that the nonwoven fabric of Reference Example 1 had an increased amount of fiber shedding because the absorbent fibers were less likely to be retained in the second fiber layer.

It is believed that the nonwoven fabric of Reference Example 2, which had an uneven structure formed on the first surface by spraying an air jet, was prone to liquid pooling in the recesses, resulting in poor liquid permeability and liquid drainage.

10 Absorbent article 12 Main body portion 14 Flap portion 16 Top sheet (nonwoven fabric)
18 Absorbent body 20 Back sheet 22 First surface (skin facing surface)
24 Second surface (non-skin facing surface)
40 Laminated web 42 Suction drum 44 Inner cylinder 46 Outer cylinder 48 Suction area 54 Dryer 60 Surface sheet 62 Convex portion 64 Concave portion CD Cross direction MD Machine direction L Longitudinal direction T Thickness direction W Width direction

Claims (9)

A nonwoven fabric for absorbent articles, comprising a first fiber layer and a second fiber layer in that order in a thickness direction,
the first fiber layer has a first surface and is made of thermally adhesive fibers;
The second fiber layer includes a water-absorbent fiber and a heat-fusible fiber,
a part of the thermally adhesive fiber of the first fiber layer penetrates into the second fiber layer and is fused to a part of the thermally adhesive fiber of the second fiber layer;
the water-absorbent fibers of the second fiber layer are not exposed to the first surface,
The first fiber layer is a nonwoven fabric having no recesses formed on the first surface thereof that are recessed in the thickness direction . The nonwoven fabric according to claim 1, further comprising a third fiber layer made of heat-fusible fibers on the opposite side of the second fiber layer from the first fiber layer. 3. The nonwoven fabric according to claim 2, wherein a portion of the heat-fusible fibers of the first fiber layer that have penetrated into the second fiber layer penetrates the second fiber layer, penetrates into the third fiber layer, and is fused to a portion of the heat-fusible fibers of the third fiber layer. The nonwoven fabric according to claim 3 , wherein a portion of the heat-fusible fibers of the second fiber layer penetrates into the third fiber layer and is fused to a further portion of the fusible fibers of the first fiber layer and to a portion of the heat-fusible fibers of the third fiber layer. The nonwoven fabric according to claim 1, wherein the first surface of the first fiber layer is a surface facing the skin. The nonwoven fabric according to claim 5 , wherein the second fibrous layer has a uniform basis weight in a plane direction. The nonwoven fabric according to claim 5 , wherein the second fiber layer contains 40% by mass or more and 70% by mass or less of the water-absorbent fiber. a first step of injecting gas onto a first fiber web made of heat-fusible fibers and a second fiber web including water-absorbent fibers and heat-fusible fibers, the first fiber web being stacked in order in a thickness direction, from the side of the first fiber web;
a second step of melting surfaces of the heat-fusible fibers of the first fiber web and the heat-fusible fibers of the second fiber web to fuse the heat-fusible fibers together;
The first step is a method for producing a nonwoven fabric for absorbent articles, in which the gas is sprayed from a plurality of nozzles arranged in the width direction at a flow rate of 3 to 5 ^m3 /min, which is a condition in which the amount of movement of the heat-fusible fibers of the first fiber web in the thickness direction is greater than the amount of movement of the heat-fusible fibers in the width direction perpendicular to the machine direction . 9. The method for producing a nonwoven fabric for absorbent articles according to claim 8, wherein the first step comprises placing the first fiber web and the second fiber web stacked in order in the thickness direction on a peripheral surface of a suction drum having a suction drum pressure of 5 to 9 kPa, and injecting the gas.

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