JP7466354B2 - Absorbent articles - Google Patents

Description

The present invention relates to an absorbent article.

Nonwoven fabrics are often used in absorbent articles such as diapers. Technologies have been developed to give nonwoven fabrics various functions.

For example, Patent Document 1 describes a method of incorporating a resin-bonded nonwoven fabric impregnated or coated with an adhesive into an absorbent article such as a diaper in order to improve the thickness recovery of the absorbent article. The resin-bonded nonwoven fabric is disposed as a member of the absorbent article that does not come into contact with the skin.
Furthermore, Patent Documents 2 to 4 describe uneven nonwoven fabrics in which a fiber web is formed into an uneven shape beforehand and then made into a nonwoven fabric, thereby improving compressive deformation properties, cushioning properties, and the like.

JP 2001-187088 A JP 2012-136791 A JP 2017-42228 A JP 2019-44320 A

Some nonwoven fabrics incorporated into absorbent articles have liquid permeability that allows them to transport excreted liquids to the liquid-retaining absorbent core. However, when such nonwoven fabrics are crushed in thickness due to load during use of the absorbent article, the fiber density increases, and the resulting capillary force can increase the ability to retain excreted liquid. As a result, there is room for improvement in the dry texture of the surface of the absorbent article.

In view of the above, the present invention relates to an absorbent article that has excellent resistance to liquid returning to the outside of the absorbent core even after a load is applied.

The present invention provides an absorbent article comprising a nonwoven fabric having a binder and an absorbent core.
It is preferred that the binder is present on the fibers or at fiber intersections of the nonwoven fabric, and that the binder is present in a greater amount on one side of the front and back surfaces of the nonwoven fabric than on the opposite side.
It is preferable that the rate of change in the amount of liquid returning to the nonwoven fabric in the absorbent article be 15% or less before and after the crush test described below.
It is preferable that the opposite surface of the nonwoven fabric is disposed on the absorbent core side.
[Crush test]
The nonwoven fabric is compressed to 0.7 mm under a load of 20 kPa, and is maintained in this compressed state for 24 hours in an atmosphere at 50° C. After that, the nonwoven fabric is released from the compressed state and allowed to stand in an atmosphere at room temperature (25° C.) for 30 minutes.

The absorbent article of the present invention has excellent resistance to liquid returning to the outside of the absorbent core even after loading.

FIG. 1A is an explanatory diagram showing a schematic diagram of a state in which a compressive force is applied to a nonwoven fabric; FIG. 1B is an explanatory diagram showing a schematic diagram of a state in which the compressive force is removed; and FIG. 1C is an explanatory diagram showing that at fiber intersections, the three-dimensional fiber intersection state is repeatedly crushed and restored in response to the compressive force. FIG. 2 is a schematic diagram showing a portion of an observation image used in a method for measuring the presence rate of binder at fiber intersections on one of the front and back surfaces of a nonwoven fabric when the nonwoven fabric is viewed in plan, together with a reference circle. 1A is a side view showing the position (line A-A) at which cross section A, which passes through the center of the thickness of a flat nonwoven fabric and is perpendicular to the fiber layer on the nonwoven fabric surface (plane), is cut out, and FIG. 1B is a side view showing the position (line B-B) at which cross section B, which is perpendicular to cross section A, is cut out at the center of the thickness. 1A is a side view showing the position (line A-A) at which cross section A of a nonwoven fabric having an uneven shape is cut, the cross section passing through the thickness center of a layered portion in which fibers are present and perpendicular to the fiber layer of the nonwoven fabric surface (the uneven surface connecting the tops of the convex portions and the bottoms of the concave portions), and FIG. 1B is a side view showing the position (line B-B) at which cross section B of the nonwoven fabric passes through the thickness center and perpendicular to cross section A. FIG. 2 is a schematic diagram showing a portion of an observation screen used in a method for measuring the longitudinal orientation degree of a nonwoven fabric, together with a square reference line. FIG. 2 is a partially sectional perspective view showing a schematic diagram of specific example 1 of the uneven shape of a nonwoven fabric. 1 is a photograph showing one side of specific example 2 of a nonwoven fabric having a concave-convex shape. 8 is a partial cross-sectional view of the nonwoven fabric shown in FIG. 7 taken along the line CC. 8 is a partial cross-sectional view of the nonwoven fabric shown in FIG. 7 along the line D-D. 8 is a photograph showing the opposite side of the nonwoven fabric shown in FIG. 7 . 11 is a partial cross-sectional view of the nonwoven fabric shown in FIG. 10 taken along line EE. 11 is a partial cross-sectional view of the nonwoven fabric shown in FIG. 10 taken along the line FF. 1 is a schematic explanation of the manufacturing process of a nonwoven fabric sample in Example 5, in which (A) is an explanatory diagram showing the process of placing a fibrous web on a male support material and pressing a female support material into the male support material from above the fibrous web, (B) is an explanatory diagram showing the process of directing a first hot air stream from above the female support material to shape the fibrous web, and (C) is an explanatory diagram showing the process of removing the female support material and blowing a second hot air stream from above the shaped fibrous web to fuse the fibers together.

Hereinafter, preferred embodiments of the absorbent article of the present invention will be described.
The absorbent article of this embodiment comprises a nonwoven fabric having a binder and an absorbent core.

The nonwoven fabric is made of hydrophilic fibers and has liquid permeability. The hydrophilic fibers include fibers that are originally hydrophobic and have been coated with a hydrophilic fiber treatment agent.
The absorbent core is a component in the absorbent article that absorbs, retains and immobilizes excreted liquid. Examples of the absorbent core include an aggregate of pulp fibers, a mixed aggregate of pulp fibers and a highly absorbent polymer material, or a highly absorbent polymer material sandwiched between sheet materials such as nonwoven fabric.

In the nonwoven fabric, the binder is present on the fibers of the nonwoven fabric or at the fiber intersections. In addition, the binder is present in greater amounts on one side of the front and back surfaces of the nonwoven fabric than on the other side.

The presence of a binder on the fibers means that the binder covers the fiber surface except at fiber intersections. Fiber intersections are the areas where two or more fibers cross.

It is preferable that the binder present at the fiber intersections covers the outer surface of the fibers where the fibers cross and overlap. It is also preferable that the binder is present at the fiber intersections while extending to the fiber surface other than the fiber intersections.

The binder is a resin component different from the constituent fibers of the nonwoven fabric, and is fixed to the surfaces of the constituent fibers. For example, the binder can be sprayed onto one side of the nonwoven fabric by a spray or the like to fix it to the fiber intersections.
The sprayed mass of the binder (content in the nonwoven fabric) is preferably 5 g/ ^m2 or less per unit area of the nonwoven fabric from the viewpoint of suppressing the sticky feeling of the nonwoven fabric and increasing the low liquid retention (liquid permeability) of the nonwoven fabric.
The sprayed mass of the binder (content in the nonwoven fabric) is preferably 0.3 g/m ² or more per unit area of the nonwoven fabric, from the viewpoint of effectively exerting the action of the binder on the fiber intersections.

Various binders can be used, such as acrylic resins, ester resins, vinyl acetate resins, styrene resins, vinyl acetate-ethylene resins, and styrene-butadiene rubber.
In particular, acrylic resins, styrene-butadiene rubber, and the like are preferred as they have the viscosity, adhesiveness, and softness to maintain and restore the three-dimensional intersection arrangement of fibers at the fiber intersections.
The binder is hydrophilic (having a contact angle of 100° or less). By being a hydrophilic binder, the binder on the fibers contributes to the absorbent performance, promoting the transfer of liquid from the nonwoven fabric to the absorbent core and suppressing wetting of the nonwoven fabric.

The fixed binder has the binding ability to adhere to the surface of the fibers or fiber intersections and not to run off. In particular, the binder has the strength to withstand the mobility of the fibers at the fiber intersections necessary for the cushioning properties of the nonwoven fabric, while also having the elasticity to restore the positional relationship between the fibers after the movement. Furthermore, from the viewpoint of further improving the above-mentioned properties, it is preferable that the binder has a larger elastic strain than the fibers.

The binder acts at the fiber intersections, for example, in the following manner.
As shown in Figures 1 (A) and (B) of the nonwoven fabric 100, a compressive force (pressing force) F is applied to one surface 1A, and then the compressive force F is removed. At this time, at the fiber intersection 6 in the nonwoven fabric 100, the three-dimensional fiber crossing shape is highly retained due to the elasticity of the binder. Even if the three-dimensional intersection of the fibers 7 is crushed by the compressive force F, when the pressing force F is removed, the three-dimensional intersection arrangement of the fibers 8 at the fiber intersection 6 is restored due to the elasticity of the binder 8 (Figure 1 (C)). Due to the action of the binder on the thickness of the nonwoven fabric, the nonwoven fabric 100 has high thickness retention and thickness recovery. It is known that liquid is easily retained on the three-dimensional intersection of the fiber intersection, and when the thickness is reduced, the phenomenon that the liquid on the three-dimensional intersection flows toward the absorbent core due to its own weight is less likely to occur, and the distance between the fibers is also reduced, so that the liquid is easily retained by capillary force. However, in the nonwoven fabric of the absorbent article of this embodiment, when the thickness is restored as described above, the liquid accumulated at the three-dimensional intersection of the fiber intersections flows toward the absorbent core side by its own weight, and the liquid is less likely to remain on the skin side, promoting the transfer of liquid to the absorbent core, and the capillary force is also less likely to increase, making it difficult to retain liquid. This can occur not only when compressed by the human body, but also when the product is subjected to compression pressure while sealed in a packaging bag, and when it is removed from the packaging bag. In addition, in Figures 1 (A) and (B), the nonwoven fabric 100 is shown as being placed on the substrate 200, but is not limited to this form.
The above-mentioned action of the binder can be effectively exerted even when the nonwoven fabric is wet, so that when the wearer excretes during use of the absorbent article of the present embodiment, the nonwoven fabric has high thickness retention and thickness recovery.

Since the binder has adhesiveness, a small amount of the binder can exert the above-mentioned effect. Therefore, the fiber intersection where the binder is present is preferably a fusion point between fibers. Compared to the intersection of non-fused fibers, the fusion point already forms a bonded intersection, so it is not necessary to form an intersection by the binder. As a result, at the fusion point between fibers, a small amount of binder is required for thickness retention and thickness recovery, compared to the non-fused fiber intersection, and the thickness recovery effect due to the elasticity of the binder can be prevented from being reduced by the adhesiveness of the binder.
When the binder is present at the fusion points between the fibers, the positional relationship (multi-level crossing relationship) between the fixed fibers can be more firmly maintained.
Furthermore, when the binder is present at the intersections between non-fused fibers, the positional relationship between the fibers (three-dimensional intersection relationship) can be restored while maintaining soft deformability when pressed.
From the viewpoint of achieving both thickness retention and thickness recovery properties of the nonwoven fabric and soft cushioning properties, it is preferable that the binder is present at both the fusion points between fibers and the intersections between non-fused fibers. In this case, it is preferable that the number of fiber intersections where the binder is present is greater than the number of fused fiber intersections.

The fusion point is a portion where the fibers fuse together at the contact points between the intersecting fibers without the interposition of the binder mentioned above. The fusion point can be formed by melting the fibers together, for example, by a heat treatment when forming a nonwoven fabric from a fiber web. Examples of heat treatment include an air-through treatment in which hot air is blown, and a heat embossing treatment. When forming a fusion point by a heat treatment, it is preferable that the constituent fibers of the nonwoven fabric contain thermoplastic fibers.

The absorbent article of the present embodiment includes the nonwoven fabric as a constituent member, and the elastic action of the binder enhances thickness retention and thickness recovery. For example, when the absorbent article is removed from a package in which multiple absorbent articles are compressed and enclosed, the original thickness is restored, and the thickness is likely to be maintained even during use.
Due to the thickness retention and thickness recovery, the nonwoven fabric is prevented from increasing in fiber density when pressed, and the amount of liquid (excreted liquid, etc.) retained within the nonwoven fabric can be reduced. That is, low liquid retention in the nonwoven fabric can be achieved. As a result, the liquid permeability of the nonwoven fabric can be maintained high even under load. Furthermore, in the case of using an absorbent article, even after it is wetted with liquid and exposed to a compressed environment, the thickness recovery can suppress adhesion of liquid to the skin, achieving good absorbency.

As described above, the nonwoven fabric of the absorbent article of the present embodiment has a front and back surface, i.e., one side and an opposite side. The "one side" and "opposite side" refer to the front and back surfaces of the nonwoven fabric, and are the surface furthest from the horizontal surface in the vertical direction relative to the horizontal surface when the nonwoven fabric is placed on the horizontal surface, and the surface closest to the horizontal surface.
In this specification, the one surface side is also referred to as a first surface side and may be designated by the symbol 1 A. The opposite surface side is also referred to as a second surface side and may be designated by the symbol 1 B. In the absorbent article of this embodiment, the opposite surface (second surface) of the nonwoven fabric is the surface side that does not come into contact with the skin during use (non-skin surface side).
In this embodiment, the opposite surface side, i.e., the second surface side, is the surface onto which the binder is sprayed.

As described above, the nonwoven fabric provided in the absorbent article of this embodiment has more binder on the opposite side (second side) than on the one side (first side). This ensures a larger path for liquid to pass through in the thickness direction of the nonwoven fabric from the one side (first side). On the other hand, since there is more binder on the opposite side (second side) than on the one side (first side), the distance between fibers is relatively shorter, increasing the capillary force and strengthening the force that draws in liquid. This, combined with the thickness retention provided by the binder, reduces the amount of liquid held by the nonwoven fabric, making it even more excellent in terms of liquid permeability.

It is also preferable that the fibers constituting the nonwoven fabric have different hydrophilicity on the fibers and at the fiber intersections. Specifically, it is preferable that a large amount of binder is present at the fiber intersections, which increases the hydrophilicity of the fiber intersections and makes it easier for liquid to migrate to the absorbent core. This makes it difficult for liquid to remain on the fibers, and the liquid flows to the fiber intersections. The liquid that flows at the fiber intersections collects and flows further to the fiber intersections in the lower layer on the absorbent side due to its own weight. By repeating this process, the liquid flows further toward the absorbent side, reducing the wetting of the nonwoven fabric.

From the viewpoint of improving the low liquid retention (liquid permeability) described above, it is preferable that the nonwoven fabric is one in which the inter-fiber distance is easily ensured. It is also preferable that the nonwoven fabric is one in which the fibers are bonded together without using a binder. This makes it possible to greatly reduce the amount of binder and improve the low liquid retention.
For example, a thermally bonded nonwoven fabric in which fibers are bonded together by heat is preferred, and among them, an air-through nonwoven fabric is more preferred. The air-through nonwoven fabric can be made soft to the touch and have a good texture. In addition, the thickness can be increased to provide cushioning properties and improve the texture.

The presence or absence of binder in the nonwoven fabric and the amount of binder present on one side (first side) and the opposite side (second side) can be determined by the following method. The amount of binder present is indicated by the area ratio (%) of binder present per unit area in a plan view of the nonwoven fabric, as shown below.

(Method of confirming the presence or absence of binder and method of measuring the amount present)
(1a) Prepare a 0.3 g nonwoven fabric sample as a measurement sample. Next, place the nonwoven fabric sample in a beaker containing 100 mL of ethyl acetate and stir for 30 minutes. Remove the nonwoven fabric sample and dry it. This washes away any components attached to the nonwoven fabric sample, such as skin care agents and hot melt adhesives.
(1b) The nonwoven fabric sample is dyed using a dyeing reagent (fiber dyeing reagent Bouken Stain II, manufactured by Bouken Quality Evaluation Organization, a general incorporated foundation) that dyes the binder adhered to the fiber surface a color different from that of the fiber to distinguish between the two.
(1c) With the nonwoven fabric sample placed on a horizontal surface, an observation image of one exposed surface is captured at 100x magnification using a digital microscope VHX-900 (product name, manufactured by Keyence Corporation. All digital microscopes in this specification refer to this type). The nonwoven fabric sample is also turned over to expose the other surface and imaged in the same manner. The captured image is the observation image. The size of the observation screen is enlarged to 2.5 mm vertically and 3.0 mm horizontally.
(1d) The observation images of one side and the opposite side are subjected to a ternary processing, and the fiber area not covered by the binder, the binder area, and other areas (such as gaps between fibers) are identified by the ternary color. Based on this, the area of the binder and the area of the fiber not covered by the binder are calculated. In order to consider the relationship in terms of size per unit area, the area ratio of the binder per unit area and the area ratio of the fiber not covered by the binder per unit area are calculated when the area of the binder and the area of the fiber not covered by the binder are added together to 100 for each of the one side and the opposite side. For the same sample, the above measurements are performed at three points on each of the measurement surfaces, and the average is used as the measured value data. From the averaged measured values, the area ratio of the binder per unit area is compared for the first side and the second side.

The dyeing process (1b) will now be described.
(1b-1) Shake the container of Bouken Stain II well to mix thoroughly.
(1b-2) Place 1.5 mL of the mixed Bouken Stain II in a beaker of approximately 200 mL size, add deionized water, and make the dye solution to a total volume of 30 mL.
(1b-3) The dye solution is heated, and when the temperature is about 90°C before boiling, the nonwoven fabric sample is added and boiled at 95°C for 2 minutes.
(1b-4) The nonwoven fabric sample is taken out, thoroughly washed with water, and then dried.
(1b-5) The color is compared with the identification color and judged. For example, a binder containing acrylic resin or styrene-butadiene rubber will be dyed red and the fiber will remain white. However, the color of the binder dye will vary depending on the binder components.

A specific example of the calculation process of (1d) above is shown below. In this example, the binder region containing acrylic resin or styrene-butadiene rubber is dyed red using the fiber identification reagent Bouken Stain II, the fiber region remains white, and other regions other than the binder region and the fiber region (such as voids between fibers) turn black.
(1d-1) The observed image is subjected to a three-value process (white, red, black). This is performed by image processing on a computer, and the red area and white area in the RGB color model are calculated.
(1d-2) Convert from the RBG color model to the HSV color model. In the HSV color model, red is defined as H: 0° to 90° and 270° to 360°, S: 30% to 100%, and V: 40% to 100%. White is defined as H: 0° to 360°, S: 0% to 20%, and V: 40% to 100%. Black is defined as any range other than the above.
(1d-3) In this way, the red area (binder) and the white area (fiber) are calculated in the HVS color model, and the process of (d) above is carried out.

In the above (method of confirming the presence or absence of binder and measuring the amount present), the adhesive strength of the adhesive or the like is weakened by cooling the absorbent article with a cold spray or other cooling means, and the nonwoven fabric is removed from the product and the above-mentioned treatment is performed. This method of removing the nonwoven fabric is also applicable to other measurements in this specification.

In the above (method of confirming the presence or absence of a binder and measuring the amount of binder present), the observation image can capture not only the captured surface but also the inside of the thickness that can be observed from there (the range in focus in the observation image is the measurement target). Note that these also apply to other measurement methods in which observation images are obtained by the above (1a) to (1c) and measurements are performed.
As a result, in the above (method of confirming the presence or absence of a binder and method of measuring the amount present), it is possible to capture not only the binder area on the surface of the nonwoven fabric but also the binder area inside the thickness of the nonwoven fabric, and to grasp the amount of binder adhered to the nonwoven fabric as a relative area ratio in comparison with the fibers.

Since the binder exhibits elasticity while also having adhesiveness, it is preferable to spray the binder onto one side of the nonwoven fabric to form the nonwoven fabric provided in the absorbent article of this embodiment.
This makes it possible to more optimally realize a non-sticky, smooth feel on the non-sprayed surfaces, thickness retention and thickness recovery throughout the nonwoven fabric resulting in a fluffy feel, and low liquid retention resulting in a dry feel.

In a plan view of the nonwoven fabric, the area ratio of the binder per unit area is preferably 0.03% or more from the viewpoint of enhancing the thickness retention and thickness recovery properties and low liquid retention properties of the nonwoven fabric.
In addition, in a plan view of the nonwoven fabric, the area ratio of the binder per unit area is preferably 0.16% or less, more preferably 0.06% or less, and even more preferably 0.05% or more, from the viewpoint of enhancing the low liquid retention of the nonwoven fabric.

It is preferable that the binder's area ratio per unit area in a plan view of the nonwoven fabric is satisfied on both the first side and the second side.

The difference (M12-M11) between the area ratio of the binder per unit area on the first surface side (M11) and the area ratio of the binder per unit area on the second surface side (M12) is preferably 0.01% points or more, more preferably 0.15% points or more, and even more preferably 0.02% points or more, from the viewpoints of increasing the permeation path of the liquid from the first surface side to the second surface side and of strengthening the capillary force on the second surface side.
In addition, the difference (M12-M11) between the binder presence area ratio per unit area on the first surface side (M11) and the binder presence area ratio per unit area on the second surface side (M12) is preferably 0.02 percentage points or less from the viewpoint of ensuring liquid permeability.

In a plan view of the nonwoven fabric, the area ratio of the binder per unit area is preferably smaller than the area ratio of the fibers not covered by the binder per unit area. This requirement is preferably satisfied on both the first side and the second side. These area ratios are values measured by the above-mentioned (method of confirming the presence or absence of the binder and method of measuring the amount of the binder).
This allows the inter-fiber distance to be maintained throughout the entire nonwoven fabric, suppressing an excessive increase in capillary force and optimizing liquid permeability.
In addition, since the area ratio of the binder per unit area is smaller than the area ratio of the fibers not covered with the binder per unit area, it is possible to suppress contact between the binders. This suppresses the effect of adhesion caused by contact between the binders, and makes it possible to more effectively exert the elasticity of the binder due to contact between the fibers and the binder. As a result, the above-mentioned action of the binder can be effectively exerted.

In a plan view of the nonwoven fabric, the difference (M2-M1) between the area ratio (M1) of the binder per unit area and the area ratio (M2) of the fibers not covered by the binder per unit area is preferably 80% points or more, more preferably 90% points or more, and even more preferably 99% points or more, from the viewpoint of effectively expressing the elasticity rather than the adhesiveness of the binder to enhance the above-mentioned effect.
Moreover, from the viewpoint of exhibiting the elastic effect of the binder, the difference (M2-M1) is preferably 99.99% or less, more preferably 99.95% or less, and even more preferably 99.9% or less.

Furthermore, in the absorbent article of this embodiment, the rate of change in the amount of liquid returning to the nonwoven fabric before and after the crushing test described below is 15% or less.
In addition, in the absorbent article of the present embodiment, the opposite surface (second surface) of the nonwoven fabric is disposed on the liquid-retentive absorbent core side.

As a result, in the absorbent article of this embodiment, the nonwoven fabric can maintain a small amount of liquid retention before and after pressing. In addition, by arranging the second surface side, where the capillary force acts, on the absorbent core side, liquid is moved away from the skin and the transfer of liquid to the absorbent body is more likely to occur. As a result, the absorbent article of this embodiment is likely to maintain a dry texture even if excretion occurs while wearing it.
Furthermore, by placing the second surface side of the nonwoven fabric on the absorbent core side, the stickiness caused by the binder can be kept away from the skin, which is preferable in terms of the feel of the absorbent article against the skin.

From the viewpoint of improving the dry feel, the rate of change in the amount of wet-back is more preferably 8% or less, and even more preferably 5% or less, before and after the crushing test.
Furthermore, the rate of change in the amount of wet-back is 1.3% or more before and after the crushing test due to an increase in fiber density caused by compression.

The amount of liquid wetback in the nonwoven fabric before the crush test is preferably 0.1 g or less per unit area, more preferably 0.08 g or less per unit area, and even more preferably 0.075 g or less per unit area, from the viewpoint of achieving excellent low liquid retention in the absorbent article. The smaller the amount of liquid wetback in the nonwoven fabric before the crush test, the better, and the lower limit is 0 g or more.
The amount of liquid wetback in the nonwoven fabric after the crush test is preferably 0.1 g or less per unit area, more preferably 0.085 g or less per unit area, and even more preferably 0.081 g or less per unit area, from the viewpoint of achieving excellent low liquid retention in the absorbent article. The smaller the amount of liquid wetback in the nonwoven fabric after the crush test, the better, and the lower limit is 0 g or more.

The above crushing test and measurement of the rate of change in the amount of liquid returning can be performed using the method shown below.

(Crush test)
The nonwoven fabric of the measurement sample is compressed to 0.7 mm under a load of 20 kPa. At this time, the nonwoven fabric is compressed to 0.7 mm by, for example, inserting a spacer. This compressed state is maintained in an atmosphere of 50° C. for 24 hours, and then released from the compressed state and left in an atmosphere of room temperature (25° C.) for 30 minutes.

(Method for measuring rate of change in amount of wet-back of nonwoven fabric in absorbent article)
(2a) For each of the nonwoven fabric before and after the crush test, the amount of remaining liquid in the nonwoven fabric in the absorbent article is measured by the method described below, and the rate of change in the amount of wetback is calculated.
The absorbent core is made by mixing 250 g of pulp and 257 g of polymer and wrapping it in a mount with a basis weight of 16 g/ ^cm2 . The absorbent core and the nonwoven fabric of the test piece are 150 mm x 350 mm. For each of the nonwoven fabric before the crush test and the nonwoven fabric after the crush test, the nonwoven fabric is placed at the skin side of the absorbent core removed from the absorbent article, and the second surface side of the nonwoven fabric faces the absorbent core, to prepare the absorbent article to be measured. 40 g of colored artificial urine is injected over 10 seconds at a position 150 mm from the ventral edge in the longitudinal direction of the absorbent article and at a position corresponding to the center in the width direction. 10 minutes after the start of injection, 40 g is injected again. This operation is repeated two more times to inject a total of 160 g of artificial urine. The temperature of the test atmosphere is room temperature (20 ± 5 ° C), and the temperature of the artificial urine is room temperature (20 ± 5 ° C).
Ten minutes after the completion of the injection, a stack of ten sheets of Advantec filter paper No. 4A (100 mm x 100 mm, mass measurement W1) is placed on the nonwoven fabric with the injection point at the center.
A pressure of 3.5 kPa is applied through an acrylic plate of 5 mm thickness and 100 mm x 100 mm, and the mass of the filter paper is measured after 2 minutes (W2), and the amount of liquid return is calculated according to the following formula (I).
Liquid return amount (g)
= Mass of filter paper after pressure (W2) - Initial mass of filter paper (W1) ... (I)
(2b) Next, based on the amounts of wet-back measured for the nonwoven fabric before and after the crush test, the rate of change (%) in the amount of wet-back is calculated according to the following formula (II).
Change in amount of liquid return (%)
= (amount of liquid wetted out of nonwoven fabric after crush test - amount of liquid wetted out of nonwoven fabric before crush test)
/ Liquid return amount of nonwoven fabric before crushing test ... (II)

The composition of artificial urine is as shown in Table 1.

In addition to the absorbent core, the absorbent article of the present embodiment preferably has a surface sheet on the skin side and a back sheet on the non-skin side. It also preferably has a core wrap sheet covering the outer surface of the absorbent core. In addition, a second sheet may be disposed between the surface sheet and the core wrap sheet on the skin side of the absorbent core. An outermost exterior material may be disposed on the non-skin side of the back sheet.
The side that comes into contact with the wearer's skin when the absorbent article is worn is called the skin-facing side or front side, and the opposite side is called the non-skin-facing side or back side. These terms are also used to indicate the relative positional relationship in the component configuration of the absorbent article with respect to members that do not have a surface that comes into contact with the wearer's skin when the absorbent article is worn.

In the absorbent article of this embodiment, the nonwoven fabric described above can be incorporated as various constituent members, so long as the second surface side is disposed on the absorbent core side.
For example, the nonwoven fabric may be incorporated as one or more of the components of the top sheet, the core wrap sheet, and the second sheet, which are on the skin side of the absorbent core. The nonwoven fabric may also be incorporated as an outer material on the non-skin side. Among these, it is particularly preferable to use the nonwoven fabric as the top sheet.

In order to effectively exert the above-mentioned effects in the absorbent article of this embodiment, it is preferable that the nonwoven fabric is disposed on the skin side of the absorbent core.

In the nonwoven fabric provided in the absorbent article of this embodiment, it is preferable that the binder is present at the fiber intersections. It is preferable that the binder is present at the fiber intersections at least on the second surface side of the nonwoven fabric. This allows the nonwoven fabric to more clearly exhibit the above-mentioned thickness retention and thickness recovery properties, ensure interfiber distance, and improve liquid permeability. In addition, the fluffy texture of the nonwoven fabric can be maintained.

The ratio of the binder present at the fiber intersections is preferably 5% to 60% per unit area of the nonwoven fabric. This allows an appropriate amount of binder to be present at the fiber intersections of the nonwoven fabric, suppressing adhesion of the fibers to each other due to the binder, and making it easier to smoothly recover the arrangement of the three-dimensional intersections of the fibers at the fiber intersections. In addition, the action of the binder improves the low liquid retention (liquid permeability) and suppresses the sticky feeling of the nonwoven fabric.
From the viewpoint of further enhancing the above-mentioned effect, the presence rate of the binder on the fiber intersections is more preferably 10% or more, and even more preferably 20% or more, per unit area of the nonwoven fabric.
The presence rate of the binder on fiber intersections is more preferably 50% or less, and even more preferably 35% or less, per unit area of the nonwoven fabric, from the viewpoint of more effectively exhibiting elasticity rather than adhesiveness of the binder.

The above-mentioned presence rate of the binder on fiber intersections is preferably satisfied on at least one of the front and back surfaces of the nonwoven fabric when viewed in plan, and more preferably satisfied on both the front and back surfaces.
The above-mentioned surface side, either the front or back surface side, is more preferably the second surface side. Here, the second surface side is the surface side disposed on the absorbent core side as described above.

Furthermore, the fiber intersections include fusion points and non-fusion points between fibers, and the fiber intersections in the binder presence rate on the fiber intersections are preferably fusion points. The binder presence rate on the fusion points is preferably in the above-mentioned numerical range. This allows the binder amount to be significantly reduced compared to when the binder itself binds the fibers together, and as a result, the formation of a coating between the fibers is suppressed, the stickiness is reduced, and thickness recovery can be more easily achieved. In addition, for the "binder presence rate on fiber intersections" at the thickness center described below, the fiber intersections are preferably fusion points for the same reason as above. In addition, the binder presence rate on the fusion points is preferably in the numerical range shown for the "binder presence rate on fiber intersections" at the thickness center described below.

(Method for measuring the proportion of binder present at fiber intersections on either the front or back side of a nonwoven fabric when viewed in a plane)
(3a) The processes (1a), (1b) and (1c) in the above (Method of confirming the presence or absence of a binder and method of measuring the amount of a binder present) are carried out.
(3b) In the observation images of the front and back surfaces of the nonwoven fabric sample, a reference circle C with a diameter of 1.0 mm (dimensions in the observation image) is drawn. The number of fiber intersections (N) in the reference circle C and the number of dyed fiber intersections (Nb) among the number of fiber intersections (N) are counted. As a result of the counting, the surface side with the larger number of dyed fiber intersections (Nb) is determined as the measurement surface side. (The range in focus in the observation image is the measurement target.) Fiber intersections are counted, including those where fibers are fused to each other and those where they are not fused to each other.
(3c) The ratio of the binder present at fiber intersections per unit area is calculated based on the following formula (S1).
H (%) = Nb ÷ N × 100 (S1)
H: Presence rate of binder on fiber intersections per unit area
Nb: Number of dyed fiber intersections within the reference circle C
N: Number of fiber intersections within the reference circle C (including Nb)
Three observation images of each of these points are prepared and measured for the same nonwoven fabric sample, and the average is used as the measurement data.
FIG. 2 shows that a plurality of fiber intersections 6 where fibers 7 intersect with each other, and dyed fiber intersections 61, are present within a reference circle C marked on the observation screen.

Furthermore, in the nonwoven fabric provided in the absorbent article of this embodiment, it is preferable that the binder is present in the thickness center of the nonwoven fabric. This allows the nonwoven fabric to more clearly exhibit the aforementioned thickness retention and thickness recovery properties, and also more strongly acts to draw liquid to the second surface side (lower layer) and away from the first surface side (upper layer).

The "center of thickness" as used herein means a portion that is located at 50% of the vertical distance between a horizontal plane and an imaginary plane that is in contact with the outermost part of the nonwoven fabric on the side opposite to the surface that is in contact with the horizontal plane when the nonwoven fabric is placed on the horizontal plane (hereinafter, the vertical direction to the horizontal plane may be simply referred to as the "vertical direction").
The vertical distance between the horizontal plane and the imaginary plane is also referred to as the apparent thickness of the nonwoven fabric. For example, when the nonwoven fabric has projections and recesses on both sides, the apparent thickness is the vertical distance between the position of the apex of the projections on one side and the position of the apex of the projections on the other side.
The apparent thickness of the nonwoven fabric can be measured by the following measurement method under a load of 50 Pa. Here, a load of 50 Pa means a load sufficient to suppress fluffing on the surface of the nonwoven fabric, and is a load necessary for properly measuring the apparent thickness of the nonwoven fabric.

(Method for measuring the apparent thickness of a nonwoven fabric under a load of 50 Pa)
The nonwoven fabric to be measured is cut to 10 cm x 10 cm to prepare a measurement sample. A laser thickness gauge (high-precision displacement sensor ZS-LD80 (product name) manufactured by Omron Corporation. All laser thickness gauges used in this specification are of this type) is used to measure the thickness of the measurement sample at a load of 50 Pa. Measurements are taken at three locations, and the average value is taken as the apparent thickness of the nonwoven fabric to be measured. A load of 50 Pa is applied to the nonwoven fabric, for example, by placing a circular plate with a diameter of 2.5 cm and a mass of 2.45 g on the nonwoven fabric.
In addition, when the nonwoven fabric to be measured is incorporated into a product, the adhesive strength of the adhesive or the like is weakened by a cooling means such as a cold spray, and the nonwoven fabric is removed from the product and the above measurement is performed. This method of removing the nonwoven fabric is similarly applied to other measurements in this specification.
If it is not possible to take out a nonwoven fabric measuring 10 cm x 10 cm, take out a piece as large as possible.

The ratio of the binder present at the fiber intersections in the thickness center is preferably 10% to 60% per unit area. The presence of the binder in the thickness direction inside the nonwoven fabric further improves the thickness retention and thickness recovery properties, and further maintains a fluffy texture.
From the viewpoint of further enhancing the above-mentioned effect, the presence rate (H) of the binder on fiber intersections at the center portion of the thickness of the nonwoven fabric is more preferably 20% or more, and even more preferably 30% or more per unit area.
In addition, the presence rate of the binder on fiber intersections at the center of the thickness of the nonwoven fabric is more preferably 50% or less, and even more preferably 45% or less, per unit area, from the viewpoint of more effectively expressing the elasticity of the binder rather than its adhesiveness.

(Method for measuring the proportion of binder at fiber intersections in the center of nonwoven fabric thickness)
(4a) The above-mentioned (Method of confirming the presence or absence of a binder and method of measuring the amount of a binder) (1a) and (1b) are carried out.
(4b) A nonwoven fabric sample is frozen with liquid nitrogen, and then cut with a razor blade to prepare two cross sections passing through the center of the thickness of the nonwoven fabric sample. One is cross section A passing through the center of the thickness of the nonwoven fabric sample (a cross section passing through the center of the thickness and perpendicular to the fiber layer that forms the nonwoven fabric surface), and the other is cross section B passing through the center of the thickness of the nonwoven fabric sample and perpendicular to cross section A.
The cross section may be any of a cross section along the MD (Machine Direction) direction (machine flow direction in the manufacturing process) in the plane of the nonwoven fabric, a cross section along the CD (Cross Direction) direction (direction perpendicular to the machine flow direction), and any cross section therebetween. It is sufficient that a cross section passing through the thickness center along at least one of the planar directions satisfies the predetermined requirements.
(4c) The sample prepared in (4b) is placed on a horizontal surface with the cross section facing upward. In the state where the sample is placed on the horizontal surface, an observation image is taken at 100 times magnification using a digital microscope.
(4d) The observation images of the above two cross sections are subjected to the process of (3b) (Method for measuring the binder presence rate at fiber intersections on either the front or back surface of a nonwoven fabric when viewed in plan) to identify the measurement surface side. When obtaining an observation image of the thickness center of cross section A, the cross section sample is adjusted to the center of the observation screen from a low magnification, and the magnification is gradually increased to identify the thickness center.
(4e) Next, based on the formula (S1) in (3c) (Method for measuring the presence rate of the binder at fiber intersections on either the front or back surface of the nonwoven fabric when viewed in a plane), the presence rate of the binder at the fiber intersections in the thickness center portion of the nonwoven fabric is calculated.
For each of these, three points on the same nonwoven fabric sample, two observation images for each, are prepared and measured, and the average is used as the measurement data.

The two cross sections A and B in (4b) above are, for example, as follows.
When the nonwoven fabric has a flat shape with no unevenness in the fiber layers that are continuous in both the planar and thickness directions, cross section A is a cross section that passes through the thickness center and is perpendicular to the fiber layers that form the nonwoven fabric surface (plane). In this case, cross section B is a cross section that passes through the thickness center and along the nonwoven fabric plane. Specifically, cross section A is a cross section taken along a vertical line A-A that passes through the thickness center 105 of the nonwoven fabric 100S as shown in Fig. 3(A). Cross section B is a cross section taken along a horizontal line B-B at the thickness center 105 of the nonwoven fabric 100S as shown in Fig. 3(B).
In addition, when the fiber layer of the nonwoven fabric meanders in the thickness direction to have an uneven shape with alternating convex and concave portions, cross section A is a cross section that passes through the thickness center and is perpendicular to the fiber layer that forms the nonwoven fabric surface (the wall surface connecting the tops of the convex portions and the bottoms of the concave portions). In this case, cross section B is a cross section along the fiber layer that passes through the thickness center and forms the nonwoven fabric surface (the wall surface connecting the tops of the convex portions and the bottoms of the concave portions). Specifically, cross section A is a cross section along line A-A that passes through the thickness center 105 of the nonwoven fabric 100W as shown in FIG. 4(A). Cross section B is a cross section along line B-B (a line perpendicular to line A-A) at the position of the thickness center 105 of the nonwoven fabric 100W as shown in FIG. 4(B).

The nonwoven fabric of the absorbent article of the present embodiment preferably has an apparent thickness of 5 mm or more, which allows liquid to more easily permeate in the thickness direction from the injection point of the liquid in the nonwoven fabric rather than spreading in the planar direction, thereby further improving the low liquid retention.
From the viewpoint of further enhancing the above-mentioned effects, the apparent thickness of the nonwoven fabric is preferably 7 mm or more, and more preferably 8 mm or more.
From the viewpoint of ensuring the strength of the nonwoven fabric, the apparent thickness of the nonwoven fabric is preferably 9 mm or less, more preferably 8.5 mm or more, and even more preferably 8.3 mm or more.

Furthermore, the nonwoven fabric of the absorbent article of the present embodiment preferably has a longitudinal orientation degree of 60% or more. This allows liquid flowing on the fibers to easily penetrate in the thickness direction. In addition, this also contributes to improving thickness retention and thickness recovery. As a result, the nonwoven fabric has better low liquid retention.
From the viewpoint of further enhancing the above-mentioned effects, the degree of longitudinal orientation of the nonwoven fabric is more preferably 65% or more, and even more preferably 70% or more.
From the viewpoint of increasing the strength of the nonwoven fabric, the degree of longitudinal orientation of the nonwoven fabric is preferably 95% or less, more preferably 90% or less, and even more preferably 85% or less.

The "degree of longitudinal orientation" referred to here is a value measured by the method described below (method for measuring the degree of longitudinal orientation of nonwoven fabric), and is a value indicating the degree to which fibers having a thickness direction component are aligned. "Fibers having a thickness direction component of a nonwoven fabric" refers to fibers that have a vertical component as a vector relative to the horizontal plane when the nonwoven fabric is placed on a horizontal plane with one of its front and back sides facing up. "Having a thickness direction component" means that the vertical component is greater than zero.

(Method for measuring the degree of longitudinal orientation of nonwoven fabric)
(6a) A nonwoven fabric sample is frozen with liquid nitrogen and placed on a horizontal plane, and then a thickness cross section (cross section in the vertical direction) of a portion of the nonwoven fabric sample that is 50% of the thickness in the vertical direction relative to the horizontal plane (the thickness center portion) is prepared by cutting the nonwoven fabric sample with a razor blade.
(6b) The thickness cross section is observed at 35x magnification using a tabletop scanning electron microscope JCM-6000Plus (product name, manufactured by JEOL Ltd.), and an observed image is taken.
(6c) A reference line L forming a square of 0.5 mm x 0.5 mm (dimensions within the observed image) is added to the observed image. Here, the reference line L is composed of an upper side L1 and a lower side L2 that are aligned in a direction along the horizontal plane, and a left side L3 and a right side L4 that are aligned in the vertical direction.
(6d) Count the total number of fibers passing through the reference lines formed by each side of the square. The total number of fibers passing through the reference lines L of the top and bottom sides L1 and L2 of the square is the "top and bottom fiber number," and the total number of fibers passing through the reference lines L of the left and right sides L3 and L4 of the square is the "left and right fiber number."
(6e) The degree of longitudinal orientation Q of the nonwoven fabric is calculated as (number of upper and lower fibers)/(number of upper and lower fibers+number of left and right fibers)×100.
Three observation images of each of these points are prepared and measured for the same nonwoven fabric sample, and the average is used as the measurement data.
5 shows an observation screen with square reference lines L. In the drawing, black dots 71 indicate positions where the fiber 7 passes through the reference lines L (L1 to L4).

When the "degree of longitudinal orientation of the nonwoven fabric" is high and the "presence rate of the binder at the fiber intersections" is high, the thickness retention and thickness recovery of the nonwoven fabric are synergistically improved. In particular, when the degree of longitudinal orientation is equal to or higher than the above lower limit and the presence rate of the binder at the fiber intersections per unit area of the nonwoven fabric is equal to or higher than the above lower limit, the intersections of the longitudinally oriented fibers are elastically reinforced by the binder, which is preferable from the viewpoint of improving the thickness retention and thickness recovery.

The nonwoven fabric preferably has an uneven shape having protrusions, recesses, and walls connecting the protrusions and the recesses in the thickness direction of the nonwoven fabric while having the above-mentioned configuration. By making the uneven shape, the nonwoven fabric of the present invention has a higher volume (thicker) and a better texture while keeping the basis weight low.
The bulky nonwoven fabric having such an uneven shape has high thickness retention and thickness recovery against a pressing force due to the action of the binder, that is, the nonwoven fabric can retain high cushioning properties even after being pressed.
In addition, unlike conventional resin-bonded nonwoven fabrics, the amount of binder attached to the nonwoven fabric is controlled to a level required for thickness retention and thickness recovery, reducing the sticky feeling. This prevents the fibers from sticking to the support when forming unevenness, thereby realizing good unevenness.
It is preferable that a binder is present in the wall portion, since the above-mentioned effects become more excellent.

The "uneven shape" refers to a shape in which the cross-sectional shape of the nonwoven fabric varies depending on the position in the vertical direction relative to a horizontal surface of the nonwoven fabric. The "wall portion" refers to a fiber layer portion in a 50% region (hereinafter referred to as a thickness intermediate layer) of the thickness (apparent thickness) of the nonwoven fabric in the vertical direction relative to the horizontal surface when the nonwoven fabric is placed on a horizontal surface, excluding 25% on one side (first side) and 25% on the opposite side (second side).
The apparent thickness referred to here is a value obtained based on the above-mentioned (method of measuring the apparent thickness of a nonwoven fabric under a load of 50 Pa).

(Method of checking for the presence of binder in the wall)
(7a) 0.3 g of a nonwoven fabric sample having an uneven surface is subjected to the dyeing treatments (1a) and (1b) described above in (Method of confirming the presence or absence of a binder and method of measuring the amount of a binder present).
(7b) With the nonwoven fabric sample placed on a horizontal surface, the wall portion at the position of the intermediate layer in the thickness direction (apparent thickness) in the vertical direction relative to the horizontal surface is observed from the horizontal direction using a digital microscope, and an observation image is taken at 160x magnification.
(7c) The observed image is subjected to the same processing as in (1d) above (Method of confirming the presence or absence of binder and measuring the amount of binder present) to calculate the area where the binder is present and the fiber area.
These are measured at three points on each sample, and the average is used as the measured value data.

As the nonwoven fabric having a concave-convex shape, various materials that are usually used as materials that come into contact with the skin can be used. For example, the concave-convex shape of the nonwoven fabric may be of various types, such as a nonwoven fabric having solid convex parts, a nonwoven fabric having hollow convex parts, a nonwoven fabric having a single fiber layer structure, a nonwoven fabric having a double fiber layer structure, a nonwoven fabric having convex parts arranged in a scattered manner in a planar direction, and a nonwoven fabric having convex parts and concave parts arranged in a ridge-like manner. In addition, the nonwoven fabric may have a concave-convex shape on both sides, not just one side.
Among these, preferred is a nonwoven fabric having a single layer structure in which the convex portions of the concave-convex shape are hollow and the concave-convex shape is present on both sides of the nonwoven fabric, for example, the following nonwoven fabric 80 (specific example 1) and nonwoven fabric 90 (specific example 2).
These are explained below.

The nonwoven fabric 80 (Specific Example 1) has a single layer structure containing thermoplastic fibers, and has the uneven shape shown below.
That is, it has outer surface fiber layers 81, 82 on the first surface (one surface) 1A side and the second surface (opposite surface) 1B side, and a plurality of connecting portions 83 disposed between the outer surface fiber layer 1 on the first surface 1A side and the outer surface fiber layer 2 on the second surface 1B side. The outer surface fiber layer 81 on the first surface 1A side and the outer surface fiber layer 82 on the second surface 1B side and the connecting portions 83 are partially fused to each other by fibers.
In addition, in the outer fiber layer 82 and the connecting portion 83 on the second surface 1B side, the binder is present at the fiber entanglement points, and the binder is attached so as to cover the fiber entanglement points.
The outer fiber layers 81, 82 and the connecting portion 83 form an uneven shape in the thickness direction of the nonwoven fabric 80, which includes hollow convex portions, concave portions, and walls connecting the convex portions and the concave portions. The uneven shape is formed on both the first surface 1A side and the second surface 1B side. Specifically, on the first surface 1A side, the convex portions 81 formed by the outer fiber layer 81 and the concave portions 88 between the outer fiber layers 81 have an uneven shape. On the second surface 1B side, the convex portions 82 formed by the outer fiber layer 82 and the concave portions 89 between the outer fiber layers 82 have an uneven shape. Both the convex portions 81 formed by the outer fiber layer 81 and the convex portions 82 formed by the outer fiber layer 82 are hollow. The connecting portion 83 forms a wall portion 83 connecting the convex portions 81 and the concave portions 88 (the convex portions 82 and the concave portions 89).
The nonwoven fabric 80 may have various configurations described in paragraphs [0010] to [0048] of JP 2019-44319 A. For example, the uneven shape of the nonwoven fabric 80 may be a shape in which the convex portions 81 formed by the outer surface fiber layer 81 and the concave portions 88 between them are arranged in a ridge-like shape on the first surface 1A side. Similarly, the convex portions 82 formed by the outer surface fiber layer 82 and the concave portions 89 between them may be arranged in a ridge-like shape on the second surface 1B side. In addition, the outer surface fiber layers 81 and 82 may have fibers oriented in the planar direction. The wall portion 83 formed by the connecting portion 83 may have fibers oriented vertically. The outer surface fiber layer 1 that becomes the convex portion on the first surface 1A side may have two types (a first outer surface fiber layer 81A and a second outer surface fiber layer 81B) having lengths extending along different directions that intersect in a plan view of the nonwoven fabric. The multiple connecting parts 83 may be arranged along different directions that intersect in a plan view of the nonwoven fabric, and may have two types (first connecting parts 83A and second connecting parts 83B) with different wall surface orientations of the connecting parts 83. In this case, the first connecting parts 83A and the second connecting parts 83B may have wall surface orientations that are different from each other, or the fibers may be oriented vertically.
This nonwoven fabric 80 typically has the shape shown in FIG.
Such a nonwoven fabric 80 can be manufactured by the method described in paragraphs [0049] to [0057] of JP 2019-44319 A.

The nonwoven fabric 90 (Specific Example 2) has a single layer structure containing thermoplastic fibers, and has the uneven shape shown below.
That is, on the first surface (one surface) 1A side, a plurality of vertical ridges 911 protruding toward the first surface 1A side in the thickness direction of the nonwoven fabric are arranged extending in one direction on the first surface 1A side in a plan view. The vertical ridges 911 are arranged side by side at intervals in another direction on the first surface 1A side in a plan view different from the one direction on the first surface 1A side. In addition, horizontal ridges 921 extending in the other direction on the first surface 1A side are arranged connecting the vertical ridges 911. The vertical ridges 911 and the horizontal ridges 921 each form a hollow convex portion. The nonwoven fabric 90 has an uneven shape in its thickness direction, which includes convex portions, concave portions, and wall portions 911W connecting the convex portions and the concave portions, by the vertical ridges 911 and the horizontal ridges 921 and the concave portions 922 between them. On the first surface 1A side, the convex portions formed by the vertical ridge portions 911 and the horizontal ridge portions 921 have lengths extending along different directions that intersect in a plan view of the nonwoven fabric 90. In this case, the uneven shape on the first surface side of the nonwoven fabric 90 may be a shape in which the convex portions formed by the vertical ridge portions 911 and the horizontal ridge portions 921 and the concave portions therebetween are arranged in a ridge-groove shape.
In addition, on the second surface (opposite surface) 1B side, a plurality of hollow convex streaks 931 are arranged, which extend in one direction on the second surface 1B side in plan view and are arranged in another direction on the second surface 1B side different from the one direction on the second surface 1B side. In addition, a concave streaks 936 sandwiched between the plurality of convex streaks 931 extends in one direction on the second surface 1B side. The uneven shape on the second surface 1B side of the nonwoven fabric 90 has a shape in which the convex streaks 931 and the concave streaks 936 are arranged in a ridge-like shape. The convex streaks 931 are formed by a plurality of convex portions 934 connected in a ridge-like shape, and narrow and wide portions are alternately connected in a plan view. Between the convex portions 934 connected in a ridge-like shape, there is a slightly low depression 935. The nonwoven fabric 90 has an uneven shape in its thickness direction, which includes protrusions, recesses, and walls 931W connecting the protrusions and recesses, formed by the protrusions 931 and the recesses 936.
Furthermore, in the convex rib portion 931, the concave rib portion 936, and the wall portion 931W, the binder is present at the fiber entanglement points, and is adhered so as to cover the fiber entanglement points.
The nonwoven fabric 90 may employ various configurations described in paragraphs [0012] to [0058] of JP 2019-44320 A. For example, the orientation direction of the fibers constituting the vertical ridge portion 911 and the fibers constituting the horizontal ridge portion 921 may be different. The height of the vertical ridge portion 911 and the height of the horizontal ridge portion 912 may be different, and the horizontal ridge portion 921 may be curved in the thickness direction of the nonwoven fabric 90 or may have an equal height. In addition, each of the two lines constituting the widthwise outline of the convex strip portion 931 when viewed in plan from the second surface 1B side may be a curve having multiple arcs. Fuzz may be arranged on the side of the convex strip portion 931.
The nonwoven fabric 90 typically has the configuration shown in Figures 7-12.
Such nonwoven fabric 90 can be produced by the method described in paragraphs [0059] to [0065] of JP 2019-44320 A.

It is preferable that the nonwoven fabric of the absorbent article of this embodiment has parts with low fiber density and parts with high fiber density. Specifically, it is preferable that the first surface side has a high fiber density and the second surface side has a low fiber density. This makes it easier for liquid to move from the first surface side, which has a low fiber density, to the second surface side, which has a high fiber density, and makes it easier for the liquid to be absorbed by the absorbent core.

Furthermore, from the viewpoint of realizing a fluffy and soft feel, the fiber diameter of the nonwoven fabric is preferably 5 dtex or less, and more preferably 3.5 dtex or less.
The fiber diameter of the nonwoven fabric is preferably 1 dtex or more, and more preferably 1.3 dtex or more, from the viewpoint of decreasing the fiber density and improving absorbency.

The absorbent article of this embodiment can be used in a variety of articles that absorb and retain excreted fluids. Examples include diapers, sanitary napkins, panty liners, incontinence pads, and urine pads.

The present invention will be explained in more detail below based on examples, but the present invention should not be construed as being limited thereto. In the examples, "parts" and "%" are all based on mass unless otherwise specified. In the tables below, "-" means that the item does not have a corresponding value, etc.

Example 1
(1) Preparation of raw nonwoven fabric Raw nonwoven fabrics having the uneven shape shown in Figures 7 to 12 were prepared by the air-through method using core-sheath type thermoplastic composite fibers (core: polyethylene terephthalate (hereinafter also referred to as PET), sheath: polyethylene (hereinafter also referred to as PE)) having the fiber diameters shown in Table 2. The size of the raw nonwoven fabric was 150 mm x 350 mm.
Specifically, the film was produced based on the manufacturing method described in paragraphs [0059] to [0065] of Patent Document 4. The first hot air blowing treatment was performed under conditions of a temperature of 160° C., a wind speed of 54 m/sec, and a blowing time of 6 seconds. The second hot air blowing treatment was performed under conditions of a temperature of 160° C., a wind speed of 6 m/sec, and a blowing time of 6 seconds.
(2) Preparation of binder coating solution A binder coating solution was prepared by mixing 10% by weight of a binder solution with a solid content of about 50% and 90% by weight of deionized water. A commercially available acrylic emulsion with high elasticity was used as the binder.
(3) Spraying of binder coating liquid Next, the binder coating liquid was evenly applied by spraying to the second surface (opposite surface) 1B of the raw nonwoven fabric on which the convex streak portion 931 and the concave streak portion 936 were arranged. The amount of the binder coating liquid applied was 3.5 g/ ^m2 .
This produced nonwoven fabric samples having the basis weights shown in Table 2. The binder was adhered to the center of the thickness of the nonwoven fabric, and was particularly abundant at the fiber intersections.
(4) Preparation of absorbent article sample 250 g of pulp fiber and 257 g of superabsorbent polymer were mixed and wrapped in a backing paper having a basis weight of 16 g/ ^cm2 to prepare an absorbent core. The size of the absorbent core was 150 mm x 350 mm. The nonwoven fabric sample A1 was placed on the absorbent core to prepare the absorbent article sample A1 of Example 1.

Example 2
An absorbent article sample A2 of Example 2 was produced in the same manner as Example 1, except that the basis weight was as shown in Table 2. The binder was adhered to the center of the thickness of the nonwoven fabric, and was present in a particularly large amount at the fiber intersections.

Example 3
An absorbent article sample A3 of Example 3 was produced in the same manner as in Example 1, except that the fiber diameter and basis weight were as shown in Table 2.

Example 4
In the preparation method described in paragraphs [0059] to [0065] of Patent Document 4, the height of the protrusions of the support was changed to 6.0 mm, thereby making the apparent thickness and basis weight of the nonwoven fabric at a load of 50 Pa as shown in Table 2, and the bulk was made lower than that of Example 1. Except for this, absorbent article sample A4 of Example 4 was prepared in the same manner as Example 1.

Example 5
An absorbent article sample A5 of Example 5 was produced in the same manner as in Example 1, except that the raw nonwoven fabric was produced by the manufacturing method described in paragraphs [0049] to [0057] of JP2019-44319A using the support shown in Figure 13. The nonwoven fabric sample in absorbent article sample A5 had the uneven shape shown in Figure 6.
In the above manufacturing method, the support male member 120 shown in FIG. 13 was a rectangular column with a height of 8 mm for the protrusion 121 and a square shape of 2 mm x 2 mm when viewed from above. The pitch of the rectangular column was 5 mm in both the MD and CD directions. The support female member 130 shown in FIG. 13 was a metal member having a lattice-shaped protrusion 131 corresponding to the recess 122 of the support male member 120, and was pressed between the protrusions 121 of the support male member 120. The adjacent protrusions 121, 121 of the support female member 130 were arranged at a pitch of 5 mm, and the space into which the fibers were inserted when the support male member 120 and the support female member 130 were pressed was 0.5 mm on one side, and 1 mm on both sides of the protrusion 120 of the support male member 120. The hot air blowing treatment was performed under conditions of a temperature of 160° C., a wind speed of 6 m/sec, and a blowing time of 6 seconds.

(Comparative Example 1)
A nonwoven fabric with an uneven shape as described in Example 1 of Patent Document 2 was produced by the air-through method using core-sheath type thermoplastic conjugate fibers having the fiber diameters shown in Table 2. The basis weight was as shown in Table 2. The nonwoven fabric was used as a nonwoven fabric sample of Comparative Example 1 without being coated with a binder coating liquid.
Using the nonwoven fabric sample, an absorbent article sample C1 of Comparative Example 1 was produced in the same manner as in Example 1.

(Comparative Example 2)
A flat nonwoven fabric without irregularities was produced by the air-through method using core-sheath type thermoplastic composite fibers having the fiber diameters shown in Table 2. The basis weight was as shown in Table 2. The nonwoven fabric was used as a nonwoven fabric sample of Comparative Example 2 without being coated with a binder coating liquid.
Using the nonwoven fabric sample, an absorbent article sample C2 of Comparative Example 2 was produced in the same manner as in Example 1.

(Comparative Example 3)
A resin-bonded nonwoven fabric described in Example 1 of Patent Document 1 was produced using fibers (PET) having the fiber diameters shown in Table 2. The resin-bonded nonwoven fabric was produced by spray coating using the resin-bonded coating solution used in Example 1. The coating amount was 16.6 g/ ^m2 . This resin-bonded nonwoven fabric was used as a nonwoven fabric sample for Comparative Example 2.
The nonwoven fabric sample had a flat shape without any irregularities.
Using the nonwoven fabric sample, an absorbent article sample C3 of Comparative Example 3 was produced in the same manner as in Example 1.

(Comparative Example 4)
A nonwoven fabric having a concavo-convex shape as described in Example 1 of Patent Document 3 was produced using fibers (PET) having the fiber diameters shown in Table 2. The basis weight was as shown in Table 2. The nonwoven fabric was used as a nonwoven fabric sample of Comparative Example 4 without being coated with a binder coating liquid.
Using the nonwoven fabric sample, an absorbent article sample C3 of Comparative Example 3 was produced in the same manner as in Example 1.

The following tests (I) and (II) were carried out for the above-mentioned Examples and Comparative Examples.
(I) Compression Recovery Property For each nonwoven fabric sample, the compression recovery rate was measured assuming a situation in which the product was subjected to compression pressure by a human body and a situation in which the product was sealed in a packaging bag.
The nonwoven fabric sample to be measured was frozen with liquid nitrogen, and then cut into 10 cm x 10 cm pieces using a razor blade to prepare a measurement sample. Using a laser thickness gauge, the thickness of the measurement sample was measured under a load of 50 Pa. Measurements were taken at three locations, and the average value was taken as the apparent thickness of the nonwoven fabric before compression.
Next, the nonwoven fabric of the measurement sample was compressed to 0.7 mm under a load of 20 kPa. This compressed state was maintained in a 50°C atmosphere for 24 hours, and then released from the compressed state and left in a 25°C atmosphere for 30 minutes. Thereafter, the thickness at a load of 50 Pa was measured using a laser thickness meter. Measurements were taken at three locations, and the average value was used as the measurement data to obtain the "apparent thickness of the nonwoven fabric after release from compression."
Finally, the recovery rate of the apparent thickness of the nonwoven fabric was calculated using the following formula.
"Recovery rate of apparent thickness of nonwoven fabric after releasing compression"
= "apparent thickness of nonwoven fabric after compression and release" ÷ "apparent thickness of nonwoven fabric before compression" × 100
(II) Amount of Liquid Wet-Back and Rate of Change in Amount of Liquid Wet-Back Based on the above-mentioned (Crushing test) and (Method for measuring rate of change in amount of liquid wet-back of nonwoven fabric in absorbent article), the amount of liquid wet-back of the nonwoven fabric sample of each absorbent article sample was measured before and after the crushing test, and the rate of change in the amount of liquid wet-back was calculated based on this.
The results are shown in Table 2 below.

As shown in Table 2, the absorbent article samples of Examples 1 to 3 were superior to the absorbent article samples of Comparative Examples 1 and 2 in terms of compression recovery of the nonwoven fabric samples. In addition, the absorbent article samples of Examples 1 to 3 had a lower rate of change in the amount of liquid return than the absorbent article samples of Comparative Examples 1 to 4. In other words, the absorbent article samples of Examples 1 to 3 were superior in preventing liquid return on the outside of the absorbent core even after loading.

6 Fiber intersection 7 Fiber 8 Binder 80, 90 Nonwoven fabric having uneven shape 81, 82, 931 Recess 88, 89, 936 Protrusion 83, 931W Wall 100 Nonwoven fabric

Claims (6)

An absorbent article comprising a nonwoven fabric having a binder and an absorbent core,
The nonwoven fabric has an apparent thickness of 5 mm or more,
the binder is present on the fibers and fiber intersections of the nonwoven fabric, and the binder is present in a greater amount on one side of the front and back surfaces of the nonwoven fabric than on the other side of the front and back surfaces of the nonwoven fabric;
The binder is present at both fiber intersections between fused fibers and fiber intersections between non-fused fibers,
The number of fiber intersections where the binder is present is such that the number of fused fiber intersections is greater than the number of non-fused fiber intersections,
The rate of change in the amount of liquid returning to the nonwoven fabric in the absorbent article is 15% or less before and after the crushing test described below,
An absorbent article in which the opposite surface of the nonwoven fabric is disposed on the absorbent core side.
[Crush test]
The nonwoven fabric is compressed to 0.7 mm under a load of 20 kPa. A spacer is inserted to compress the nonwoven fabric to 0.7 mm. This compressed state is maintained in a 50° C. atmosphere for 24 hours, after which the nonwoven fabric is released from the compressed state and left to stand in a room temperature (25° C.) atmosphere for 30 minutes. The absorbent article according to claim 1, wherein, in a plan view of the nonwoven fabric, the area ratio of the binder per unit area is smaller than the area ratio of the fibers not covered by the binder per unit area. 3. The absorbent article according to claim 1, wherein the binder is present in the center of the thickness of the nonwoven fabric. The absorbent article according to any one of claims 1 to 3 , wherein the degree of longitudinal orientation of the nonwoven fabric is 60% or more. The absorbent article according to any one of claims 1 to 4 , wherein the nonwoven fabric has an uneven shape having protrusions, recesses, and walls connecting the protrusions and the recesses in the thickness direction, and the binder is present in the walls. The absorbent article according to any one of claims 1 to 5 , wherein the nonwoven fabric is disposed on the skin side of the absorbent core.

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