RU2763716C2 - Absorbent element and absorbent product - Google Patents

Abstract

FIELD: absorbent products.

SUBSTANCE: absorbent element (4) according to the present invention includes fibre clusters (11) containing synthetic fibres (11F), and includes water-absorbing fibres (12F), and the multiple fibre clusters (11) are twisted with each other or with the water-absorbing fibres (12F). The ratio of the mass fraction of fibre clusters (11) to the mass fraction of water-absorbing fibres (12F) (the proportion of fibre clusters) is smaller on the side of the skin-facing surface (on the side of the upper sheet (2)) than on the side of the non-skin-facing surface (on the side of the back sheet (3)) of the absorbent element (4). A fibre cluster (11) includes the main part (110) formed by means of two opposing base surfaces (111) and the surface (112) of the main part crossing the base surfaces (111).

EFFECT: creation of an absorbent element containing synthetic fibre clusters.

28 cl, 10 dwg

Description

The field of technology to which the invention belongs

[0001]

The present invention relates to an absorbent element that is used in direct or indirect contact with the skin and is suitable as an absorbent element for absorbent articles.

Prior Art

[0002]

An absorbent article, such as disposable diapers and sanitary napkins, typically includes a topsheet designed to be placed relatively close to the wearer's skin, a backsheet designed to be placed relatively far from the wearer's skin, and an absorbent member between those sheets. The absorbent body typically includes water-absorbent fibers such as wood pulp fibers as a main component, and in many cases further includes water-absorbent polymer particles. The absorbent used in absorbent articles has major problems in improving various properties, including resilience (springiness), compression recovery, and shape retention.

[0003]

As a technical solution for improving absorbent members, for example, Patent Literature 1 discloses an absorbent member that includes pieces of nonwoven material including hot-melt fibers and having a three-dimensional structure that has been formed by bonding the fibers together, and includes water absorbent fibres. Pieces of nonwoven material having a three-dimensional structure are obtained by cutting the nonwoven material into pieces of small size by using a cutting means, such as a cutting mill system, while they have such an indefinite shape as shown in Fig.1 and Fig.3 in this literature source, due to the production method, and essentially do not have a part considered as flat. Patent Literature 1 discloses heat-melted nonwoven pieces as a preferred embodiment of the absorbent according to this literature. In the absorbent body according to Patent Literature 1, the nonwoven pieces have a three-dimensional structure, so that empty spaces are formed in the absorbent body and the resilience after water absorption is improved. It is believed that as a result, the ability to absorb water is improved.

[0004]

Patent Literature 2 discloses a microweb including relatively densely spaced microfiber cores and fibers or fiber bundles projecting outward from the cores, and further discloses that a nonwoven web comprising a blend of microscrim and wood pulp or particles of water-absorbing polymer, can be used as an absorbent element for absorbent products. This microweb is produced by tearing or tearing a sheet of material, such as a non-woven material, whereby it has an indefinite shape, as in the case of non-woven material pieces according to Patent Literature 1, and has essentially no part considered as flat.

[0005]

When an absorbent member containing a water-absorbent polymer located between the topsheet and the backsheet absorbs liquid to cause expansion, such closed water-absorbent polymer is prevented from swelling. To overcome this shortcoming, Patent Literature 3 discloses that an elastic layer having high compressibility/recovery after compression and liquid permeability is interposed between the topsheet and the absorbent, and further discloses that the elastic layer includes a collection of small pieces of nonwoven fabric. This literature also discloses that the elastic layer has a thickness of 10 to 40 mm. However, Patent Literature 3 does not specifically disclose the shape and the like of the small pieces of nonwoven material used in the elastic layer.

Link List

Patent Literature

[0006]

Patent Literature 1: US 2010/0174259 A

Patent Literature 2: US 4813948 B

Patent Literature 3: JP 2003-52750 A

The essence of the invention

[0007]

The present invention relates to an absorbent element that is used in direct or indirect contact with the skin and includes a surface that faces the skin and is to be placed relatively close to the user's skin during use, and a surface that is not facing the skin and to be placed relatively far from the user's skin. The absorbent body of the present invention includes fiber aggregations containing synthetic fibers and includes water-absorbent fibers, and a plurality of fiber aggregations are interwoven with each other or with water-absorbent fibers. The ratio of the mass fraction of fiber accumulations to the mass fraction of water-absorbing fibers is less on the side of the surface facing the skin than on the side of the surface not facing the skin.

The present invention is also an absorbent article incorporating the absorbent element of the present invention.

Brief description of the drawings

[0008]

[Fig. 1] Fig. 1 is a partially broken plan view schematically showing the skin-facing surface (top sheet) side of an exemplary sanitary napkin as an embodiment of the absorbent article of the present invention.

[Fig.2] Fig.2 is a schematic sectional view showing a section taken along the line I-I shown in Fig.1.

[Figure 3] Figure 3 is an enlarged sectional view of the absorbent member shown in Figure 2 only.

[Figure 4] Figure 4 is a sectional view of another embodiment of the absorbent of the present invention corresponding to Figure 3.

[Fig. 5] Fig. 5(a) and Fig. 5(b) are schematic perspective views of the main part in the fiber bundle of the present invention.

[Fig. 6] Fig. 6 is an illustrative representation of the method for producing fiber aggregations of the present invention.

[Fig. 7] Fig. 7(a) is an electron microscope photograph (obtained at a 25× inspection magnification) of an example of a fiber aggregation of the present invention, and Fig. 7(b) is an image schematically showing a aggregation fibers in an electron microscope photograph as a collection of fibers included in the absorbent shown in FIG.

[Fig. 8] Fig. 8 is an exemplary view of a method for determining the surface diffusion area.

Description of Embodiments

[0009]

Absorbent members according to Patent Literature 1 and 2 include aggregations of synthetic fibers having indefinite shapes as described above and varying in shape and size. Therefore, when such aggregates are mixed with wood pulp or the like, it is difficult to obtain a homogeneous mixture, and the intended effects may not be achieved. In addition, the accumulations of synthetic fibers disclosed in these literature sources are obtained by cutting a nonwoven fabric containing mainly synthetic fibers into small pieces or tearing and tearing such a nonwoven fabric, and therefore they are expected to have a surface with irregular roughness. . In an absorbent body containing a plurality of synthetic fiber agglomerates having such a completely rough surface, the plurality of synthetic fiber aggregations are entangled with each other over the entire surface by a relatively large adhesive force, and hence the degree of freedom of movement of the synthetic fiber aggregations is noticeably limited. With this in mind, it is unlikely that there is such a gap in the absorbent element through which body fluid passes, and the absorbent element has insufficient ability to absorb liquids. When all the aggregations of synthetic fibers included in the absorbent are bonded to each other by fusion, as in the preferred embodiment of the absorbent according to Patent Literature 1, the movement of the aggregations of fibers is limited, thus the absorbent as a whole has a higher hardness, and the ability to to the absorption of liquids may further deteriorate.

[0010]

By including such agglomerations of synthetic fibers as described in Patent Literature 1 and 2, the absorbent body has a greater spacing between constituent fibers than in a conventional absorbent body without such agglomerations of fibers, and therefore, the ability to draw liquid present on the surface may be impaired. absorbent element, into the absorbent element (ability to draw liquids). Unfortunately, by placing such an elastic layer including accumulations of synthetic fibers and having a considerable thickness as described in Patent Literature 3, the aforementioned ability to absorb liquids is further degraded on the absorbent body.

[0011]

Therefore, the present invention is intended to provide an absorbent member that has a high springback capability, is unlikely to curl, has a very good liquid draw-in capacity, and can provide an increase in wearing comfort when included in an absorbent article, and is intended to provide an absorbent article. including this absorbent element.

[0012]

The absorbent body of the present invention and the absorbent article including the absorbent body of the present invention will now be described based on their preferred embodiments with reference to the drawings. 1 and 2 show a sanitary napkin 1 as an embodiment of an absorbent article of the present invention. The liner 1 includes an absorbent member 4 that is designed to absorb and retain body fluid, liquid permeable topsheet 2 that is located on the skin side of the absorbent member 4 and is designed to come into contact with the skin carrier, and minimally permeable to liquids, the back sheet 3, which is located on the side of the surface of the absorbent element 4, not facing the skin. As shown in figure 1, the pad 1 has a longitudinal direction X, coinciding with the direction from the front side to the rear side of the wearer and extending from the abdominal side of the wearer through the crotch to the dorsal side, and a lateral direction Y, orthogonal to the longitudinal direction X, and is divided into longitudinal direction X into three zones: zone B, central in the longitudinal direction and including a zone facing the excretory part (discharge site) and designed to face the excretory part, such as the external female genital organs of the wearer, the anterior zone A, located closer to the abdominal side (front side) of the wearer than the area facing the excretory part, and the back zone C, located closer to the dorsal side (back side) of the wearer than the area facing the excretory part.

[0013]

In the present description, the "skin-facing surface" is one surface of the absorbent article or its constituent element (for example, absorbent element 4) and faces the skin of the wearer during wearing of the absorbent article, or is a surface relatively close to the wearer's skin, and "non-skin-facing surface" is another surface of the absorbent article or a constituent thereof and is a surface opposite the wearer's skin while the absorbent article is being worn, or is a surface relatively distant from the wearer's skin. In the present description, the term "during wearing" means a state in which the typical proper wearing position or normal wearing position of the absorbent article is maintained.

[0014]

As shown in FIG. 1, the napkin 1 includes an absorbent body 5 elongated in the longitudinal direction X and two flaps 5W and 5W projecting outward in the lateral direction Y from respective sides extending along the longitudinal direction X of that zone B in absorbent body 5, which is central in the longitudinal direction. The absorbent body 5 is the body of the pad 1, includes a top sheet 2, a back sheet 3, and an absorbent body 4, and is divided in the longitudinal direction X into three zones: a front zone A, a zone B, a center in the longitudinal direction, and a back zone. WITH.

[0015]

When the absorbent article has wings, as in liner 1, the area in the absorbent article of the present invention, longitudinally centered, means the area having wings in the longitudinal direction (length direction, X direction in the figure) of the absorbent article. In the exemplary pad 1, the longitudinal direction center zone is the zone between the base of one flaplet 5W extending along the longitudinal direction X and the base of the other flaplet 5W extending along the longitudinal direction X. In an absorbent article without wings, the zone central in the longitudinal direction direction, means the middle zone when the absorbent article is divided into three parts in the longitudinal direction.

[0016]

In the napkin 1, the absorbent member 4 includes an absorbent core 40 for absorbing liquids and a liquid-pervious core wrap sheet 41 enclosing the outer surface of the absorbent core 40. As with the absorbent body 5, the absorbent core 40 has a shape elongated in In the longitudinal direction X, in a plan view as shown in FIG. 1, the length direction of the absorbent core 40 is aligned with the longitudinal X direction of the pad 1, and the width direction of the absorbent core 40 is aligned with the lateral Y direction of the pad 1. Absorbent core 40 and sheet 41 for wrapping, the cores may be bonded with an adhesive such as a hot melt adhesive.

[0017]

As described above, when the absorbent 4, as an embodiment of the absorbent of the present invention, is included in an absorbent article such as a liner 1, the absorbent is used while it is in indirect contact with the human skin or when it is in indirect contact with the skin through such of the element as backsheet 2. The absorbent body has a skin-facing surface (the surface facing the topsheet 2) to be placed relatively close to the skin of the wearer (wearer wearing the pad 1) during use, and a non-skin-facing surface ( the surface facing the back sheet 3), which should be placed relatively far from the wearer's skin. The absorbent body also has a longitudinal direction X coinciding with the direction from the front side to the back side of the wearer wearing the pad 1 and a lateral direction Y orthogonal to the longitudinal direction X, and is divided in the longitudinal direction X into three zones, namely the front zone A, zone B, longitudinally central, and back zone C. Absorbent member 4 may be used in indirect contact with the skin as described above, or may be used in direct contact with the skin in the absence of any element such as like a sheet, between the absorbent 4 and the skin.

[0018]

In the napkin 1, the core wrap sheet 41 is one continuous sheet having a width that is two times or more and three times or less the size of the absorbent core 40 in the lateral Y direction. As shown in FIG. 2, the core wrap sheet overlaps the skin-facing surface of the absorbent core 40 throughout its entire length and extends outward in the lateral Y direction from respective side edges of the absorbent core 40 extending along the longitudinal direction X, and the projections are folded under the absorbent core 40 and overlap the non-skin-facing surface of the absorbent core 40 throughout its length. In the present invention, the core wrap sheet is not limited to such a single sheet. For example, the core wrap sheet may include two sheets, namely one core wrap sheet on the skin-side that overlaps the skin-facing surface of the absorbent core 40, and one core wrap sheet on the non-skin side. which is separate from the skin-side core wrapping sheet and overlaps the non-skin-facing surface of the absorbent core 40.

[0019]

As shown in FIG. 2, the top sheet 2 overlaps the skin-facing surface of the absorbent member 4 throughout its entire length. The backsheet 3 overlaps the non-skin-facing surface of the absorbent 4 along its entire length and extends outward in the lateral Y direction from respective side edges of the absorbent 4 extending along the longitudinal direction X to form side flaps together with the side sheets 6 described later. In the napkin 1, the side flap includes an element protruding outward in the lateral direction Y from the absorbent element 4. The back sheet 3 and each side sheet 6 are connected together in a part protruding from the respective side edge of the absorbent element 4 extending along the longitudinal direction X, by means of known means of connection, such as adhesive, heat sealing and ultrasonic welding. Each of the topsheet 2 and the backsheet 3 can be attached to the absorbent 4 with an adhesive. Various materials commonly used in absorbent articles such as sanitary napkins can be used as the topsheet 2 or backsheet 3 without any limitation. For example, as the top sheet 2, a single-layer or multi-layer nonwoven fabric, a porous film, or the like can be used. As the back sheet 3, a liquid-permeable resin film or the like can be used.

[0020]

As shown in FIG. 1, the side flaps protrude substantially outward in the lateral direction Y in the area B centered in the longitudinal direction, and accordingly, two protruding wings 5W, 5W are provided on both sides of the absorbent body 5 extending along the longitudinal direction. X direction. In a plan view as shown in FIG. 1, each flap 5W has a substantially trapezoidal shape, and a bottom base (a base longer than the top base) is located on the corresponding side of the absorbent body 5. The surface of the flap , not facing the skin, has a winglet adhesive portion (not shown in the drawings) for attaching the 5W winglet to a garment such as underpants. The wings 5W are used by folding them toward the non-skin surface (outer surface) side of the crotch portion of a garment such as a pant. The adhesive portions of the wings are covered with release sheets (not shown in the drawings) formed from film, non-woven material, paper, or the like before use. On both sides of the skin-facing surface of the absorbent body 5 or the skin-facing surface of the top sheet 2 extending along the longitudinal direction X, two side sheets 6, 6 are provided for substantially the entire length of the absorbent body 5 in the longitudinal direction X so that they overlap both sides of the absorbent member 4 extending along the longitudinal direction X in plan view. The two side sheets 6, 6 are attached to the other members, including the top sheet 2, by a known means of connection such as adhesive, along connection lines (not shown in the drawings), each of which extends in the longitudinal direction X.

[0021]

The main feature component of the napkin 1 is, for example, the absorbent 4, in particular the absorbent core 40 as the main component of the absorbent 4. The absorbent core 40 is characterized in that it includes fiber clusters 11 containing fibers (synthetic fibers) 11F, in addition to the water absorbent fibers 12F as shown in FIG. In the absorbent core 40, a plurality of water-absorbent fibers 12 do not form clusters, but each of them is included independently, and each fiber can be taken out separately from the absorbent core 40, while each fiber cluster 11 is an integrated collection of fibers, in which a plurality of 11F intentionally collected in a cluster, and can be included in the absorbent core 40, while constantly maintaining the form of this collection in the form of a cluster of fibers. The fiber clusters 11 contribute mainly to improving the flexibility, resilience, resilience, shape retention and the like of the absorbent core 40. similar characteristics of the absorbent core 40. The absorbent core 40 is considered essentially the absorbent element 4 itself, and the absorbent core 40 will be described as the absorbent element 4 in the description below, unless otherwise indicated. In other words, the present invention covers an absorbent member not including any core wrap sheet but including only an absorbent core, in which case the absorbent member means an absorbent core.

[0022]

As used herein, a "fiber aggregation" is a collection of fibers in which a plurality of fibers are connected together as a single element. Examples of the fiber aggregation shape include a sheet piece obtained by separating a synthetic fiber sheet having a certain size. In particular, the agglomeration of fibers is preferably a piece of nonwoven material obtained by cutting the nonwoven material selected as a sheet of synthetic fibers into predetermined sizes and shapes.

[0023]

As described above, a fiber aggregation like a piece of sheet as a preferred embodiment of the fiber aggregation of the present invention is not obtained by collecting a plurality of fibers into a piece of sheet, but is obtained by cutting a fibrous sheet (preferably a non-woven fabric) having a larger size compared to a piece sheet (see Fig.6). The plurality of fiber aggregations included in the absorbent of the present invention are a plurality of fiber aggregations similar to pieces of sheet and having a more defined shape than those obtained by the conventional art, as in Patent Literature 1 and 2.

[0024]

In the absorbent core 40, a plurality of fiber clusters 11 are intertwined with each other or with water-absorbent fibers 12F. In the absorbent core 40 of the present embodiment, a plurality of fiber bundles 11 are connected by intertwining constituent fibers (fibers 11F, 12F) in the absorbent core 40 to form one continuous fiber bundle. Together with the interweaving of the plurality of fiber bundles 11, the fiber bundles 11 can be intertwined with the 12F water-absorbent fibers and bonded together. Typically, a plurality of 12F water absorbent fibers are also intertwined with each other. At least some of the plurality of fiber aggregations 11 included in the absorbent core 40 are intertwined with other fiber aggregations 11 or water-absorbent fibers 12F. In the absorbent core 40, all of the plurality of fiber aggregations 11 included therein may be intertwined with each other to form one continuous element of the aggregations of fibers in some cases, and in some cases, the plurality of continuous elements of the aggregations of fibers may be mixed in an unbonded state.

[0025]

The fiber clusters 11 have very good resilience or the like. The absorbent core 40 of the present invention includes such fiber clusters 11, and the fiber clusters 11 are connected to each other or to the water absorbent fibers 12F by weaving. Therefore, the absorbent core 40 has a better ability to respond to an external force and has very good resilience, resilience, and resilience. For example, when incorporated into an absorbent article, the absorbent core 40 of the present invention deforms resiliently in response to external forces (eg, body pressure of the wearer wearing the absorbent article) applied in different directions and allows the absorbent article to come into intimate contact with body of the wearer with a satisfactory fit. This very good warp/recovery ability of the absorbent core 40 can be exhibited not only when the absorbent core 40 is compressed, but also when the absorbent core is warped. In other words, the absorbent core 40 included in the pad 1 is placed in a position where it is between the thighs of the wearer wearing the pad 1, and therefore the absorbent 4 can bend about a virtual axis of rotation extending in the longitudinal direction X due to movement hips when the wearer walks. Even in such a case, the absorbent core 40, which has a high deformability/recovery property, is easily deformed/recovered when subjected to such an external force that promotes the deformation caused by the thighs, whereby the absorbent core 40 is unlikely to twist, and it can give the pad 1 high ability to fit to the wearer's body.

[0026]

In the absorbent core 40, the clusters 11 of fibers are intertwined with each other or with water-absorbent fibers 12F. In the description, the "weave" of fiber bundles 11 and the like encompasses the following configuration A.

Configuration A: Fiber clusters 11 and the like are connected without fusion, but by entanglement of constituent 11F fibers forming fiber clusters 11.

Configuration B: When the absorbent core 40 is in a natural state (without any external force), the fiber clusters 11 and the like are not connected, but when an external force is applied to the absorbent core 40, the fiber clusters 11 and the like can be connected by tangling constituent fibers 11F. In this configuration, "an external force applied to the absorbent core 40" means, for example, that a deforming force is applied to the absorbent core 40 while wearing an absorbent article including the absorbent core 40.

[0027]

As described above, in the absorbent core 40, fiber aggregations 11 are connected to others with other aggregations 11 of fibers or with water-absorbent fibers 12F by intertwining or "weaving" the fibers, as in configuration A, and the aggregations 11 of fibers can be connected with other aggregations 11 of fibers or with 12F water-absorbent fibers by weaving, as in configuration B. This weaving of fibers is an important factor in terms of more effectively manifesting the above preferred effects from the absorbent core 40. The absorbent core preferably has a "weave" in configuration A for reasons associated with the ability to retain shape.

[0028]

In the absorbent core 40, all bonding methods by fiber bundles 11 are not necessarily limited to "weave", and the absorbent core 40 may in some parts have additional bonds obtained by methods other than weaving, such as adhesive bonding.

[0029]

However, in the remainder of the absorbent core 40, with the exception of the "portions fused by fiber clusters 11" and formed in the absorbent core 40 by combining with other features, such as the absorbent article's known leakage protection grooves, or, in other words, in the absorbent core 40 itself, the connection between the fiber bundles 11 or the connection between the fiber bundles 11 and the water-absorbent fibers 12F is preferably only formed by "fiber entanglement".

[0030]

For reasons related to more specific enabling of the above preferred effects from the absorbent core 40, the total number of "clumps of 11 fibers connected by interweaving" in configuration A and "clumps of 11 fibers that can be interlaced" in configuration B is preferably 50 % or more, more preferably 70% or more, and even more preferably 80% or more of the total number of fiber clusters 11 in the absorbent core 40.

For the same reasons, the number of fiber clusters 11 "interlaced" in configuration A is preferably 70% or more, in particular 80% or more of the total number of fiber clusters 11 connected to other fiber clusters 11 or to 12F water-absorbent fibers.

[0031]

The pad 1 is also characterized by the placement of fibrous materials (fiber clusters 11, water-absorbent fibers 12F) in the absorbent core 40 in addition to the fiber clusters 11 included therein. In other words, in the absorbent core 40, the ratio of the mass fraction of fiber agglomerations 11 to the mass fraction of 12F water-absorbent fibers (hereinafter also referred to as “fiber agglomeration ratio”) is smaller on the skin-facing surface side (top sheet 2 side) than on the surface side. , not facing the skin (from the side of the back sheet 3), as shown in Fig.2 and Fig.3. In other words, in the absorbent core 40, the water-absorbent fibers 12F are localized on the skin-facing side, and the fiber clusters 11 (synthetic fibers 11F) are localized on the non-skin-facing surface.

[0032]

As described above, in the absorbent core 40, the side of that surface of the absorbent core 40 that faces the skin, as the side that first receives the body fluid released from the wearer wearing the pad 1, is a part having a lower blocking ratio. fibers (including 0 wt % fiber clumps), i.e., the “high water-absorbent fiber portion 12P” containing more 12F water-absorbent fibers than other parts of the absorbent core 40 (see FIG. 3). Therefore, the skin-facing surface of the absorbent core 40 has a larger liquid-absorbing force (capillary force), and the absorbent core 40 has a satisfactory ability to absorb liquids. On the contrary, the side of that surface of the absorbent core 40 that is not facing the skin is the part having a higher proportion of fiber accumulations (including the case where it does not contain any water-absorbent fibers, but only contains fiber accumulations), that is, "part 11P with increased content of fiber clumps", containing more clumps 11 of fibers than in other parts of the absorbent core 40 (see figure 3). Therefore, the absorbent core 40 can sufficiently exhibit the advantageous effects mainly due to the fiber clusters 11, such as the effects of improving springback property and anti-curl property. In the high fiber clump portion 11P, the fiber clumps 11 are preferably evenly distributed at a high density throughout the 11P portion for reasons related to allowing the intended beneficial effects of the 11P portion to be more certain.

[0033]

The fiber agglomeration ratio, that is, the ratio of the mass fraction of fiber agglomerations 11 to the mass fraction of 12F water-absorbent fibers, is calculated as follows. In the part to be measured and determined in the thickness direction of the absorbent 4 (absorbent core 40) or in the direction orthogonal to the surface of the absorbent 4 (absorbent core 40) facing the skin, or to the surface of the absorbent 4 (absorbent core 40), not facing the skin, (for example, from the side of the surface of the absorbent element 4 facing the skin) determine the content (mass) of fiber clusters 11 and water-absorbent fibers 12F contained in the part to be measured, then the resulting content of fiber clusters 11 is divided by the content of water-absorbent fibers 12F, and the result, expressed as a percentage, is the proportion of fiber accumulations in the part to be measured.

[0034]

The proportion of fiber accumulations on the side of that surface of the absorbent core 40 that faces the skin, or in the part 12P with a high content of water-absorbing fibers, is preferably 140% of the mass. or less, more preferably 70% of the mass. or less and even more preferably 30% of the mass. or less for reasons related to the rapid absorption of bodily fluid into the absorbent core 40. The lower limit of the proportion of fiber accumulations in the part 12P with a high content of water-absorbent fibers is preferably 10 wt. -%, more preferably 5 wt. or even more preferably 0% of the mass.

The proportion of fiber accumulations on the non-skin side of the absorbent core 40, or in the fiber accumulation portion 11P, is preferably 70% by weight. or more, more preferably 140% of the mass. or more and even more preferably 170% of the mass. or more, provided that the proportion of fiber accumulations is greater than the proportion of fiber accumulations on the side of the surface facing the skin. The upper limit of the proportion of fiber accumulations on the non-skin side of the absorbent core 40 is not particularly limited, and the content of the 12F water-absorbent fibers on the non-skin side of the surface may be 0 mass%. In this case, the proportion of fiber clumps is an infinite value because the denominator in the calculation formula is 0, but in the present description, this case can be expressed as "only clumps of fibers" or as a degree of filling of clumps of fibers, which is 100 wt.%, as described later , instead of the proportion of fiber clusters.

[0035]

As described above, the napkin 1 is characterized by an absorbent core 40 in which water-absorbent fibers 12F are localized on the skin-facing side and fiber clusters 11 (synthetic fibers 11F) are localized on the non-skin-facing surface. Instead of the proportion of fiber clumps as an indicator characterizing such a specific distribution of clumps 11 of fibers, the weight ratio of clumps 11 of the total mass of clumps 11 of fibers and water-absorbent fibers 12F (hereinafter also referred to as "degree of filling of clumps of fibers") can be used.

[0036]

The degree of filling with accumulations of fibers is calculated as follows. In the part to be measured and determined in the thickness direction of the absorbent 4 (absorbent core 40) or in the direction orthogonal to the surface of the absorbent 4 (absorbent core 40) facing the skin, or to the surface of the absorbent 4 (absorbent core 40), not facing the skin, (for example, from the side of the surface of the absorbent element 4 facing the skin) determine the content (mass) of fiber clusters 11 and water-absorbing fibers 12F contained in the part to be measured, then the resulting mass of fiber clusters 11 is divided by the total the weight of the water-absorbent fibers 12F and the fiber clusters 11, and the result, expressed as a percentage, is the degree of filling of the part to be measured with the fiber clusters.

[0037]

For reasons related to the more specific manifestation of the above preferred effects, the degree of filling of each part of the absorbent core 40 with clumps of fibers is preferably set as follows, provided that this degree of filling is greater on the side of the surface not facing the skin than on the side of the surface facing the skin .

The degree of filling with accumulations of fibers from the side of the surface of the absorbent core 40, which faces the skin, or in the part 12P with a high content of water-absorbing fibers is preferably 60% of the mass. or less, more preferably 30% of the mass. or less and even more preferably 20% of the mass. or less. The lower limit of the degree of filling with accumulations of fibers in the part 12P with a high content of water-absorbing fibers is preferably 10% by mass, more preferably 5% by mass. and even more preferably 0% of the mass.

The degree of fiber accumulation on the side of that surface of the absorbent core 40 that is not facing the skin, or in the part 11P with a high content of fiber accumulations, is preferably 50% of the mass. or more, more preferably 60% of the mass. or more and even more preferably 70% of the mass. or more and preferably is 100% of the mass. or less, more preferably 95% of the mass. or less and even more preferably 85% of the mass. or less.

The difference in fiber clump density between the clump-rich portion 11P and the water-absorbent fiber-rich portion 12P, when the fiber clump density of the last-mentioned portion 12P is subtracted from the fiber clump-fill of the first-mentioned portion 11P, is preferably 15 % wt. or more, more preferably 50% of the mass. or more and even more preferably 80% of the mass. or more.

[0038]

With regard to the range of values of the "degree of fiber accumulation" in the part 11P with increased content of fiber accumulations or the part 12P with increased content of water-absorbing fibers and the range of values of the "proportion of fiber accumulations" in the part 11P with increased content of fiber accumulations or the part 12P with increased content of water-absorbing fibers in the absorbent core 40 being a single unit as a whole, the absorbent core 40 is halved in the thickness direction, and the surface side part facing the skin is considered as the clump-increased part 11P, while the surface side part , not facing the skin, is considered part of the 12P with a high content of water-absorbing fibers.

[0039]

In the description, the term "absorbent core constituting a whole unit" means that the absorbent core is formed in one piece, and the structure in which a plurality of absorbent core layers formed separately is superimposed on each other is excluded. In the last mentioned structure, one layer of absorbent core can be separated from another layer of absorbent core, and the layers do not form an inseparable integral element and are not combined into one. Specific examples of an absorbent core that is generally one piece include an absorbent core in which all of the materials (fiber clusters 11, 12F water absorbent fibers) forming the absorbent core 40 are stacked in one operation/at a time. Each absorbent core 40 in the absorbent member 4 shown in FIG. 3 and the absorbent member 4A shown in FIG. fibers) having different degrees of fiber aggregation or fiber aggregation proportions, but the constituent fibers 12F, 11F are intertwined with each other at the interface between the two parts 12P, 11P, and therefore the absorbent core as a whole is a single element. In contrast, in the absorbent core 40 in the modified embodiment of the absorbent member 4A described later, the constituent fibers 12F, 11F are not substantially intertwined with each other at the interface between the two portions 12P, 11P as separate layers, and therefore the absorbent core as a whole is not is a single element.

[0040]

In the present invention, the water-absorbent fiber portion 12P preferably contains only the water-absorbent fibers 12F, but in the case where the water-absorbent fiber portion 12P also contains fiber clumps 11, such an absorbent core 40 can substantially improve the effect obtained from the clumps 11 fibers and is therefore preferred. Specifically, when the water-absorbent fiber portion 12P comprises fiber clumps 11 and the water-absorbent fibers 12F as a mixture, and the fiber clumps 11 are intertwined or can be intertwined with the water-absorbent fibers 12F, the water-absorbent fibers 12F in the water-absorbent fiber-rich portion 12P are the first to absorb the exhaled by the body, a fluid such as menstrual blood, and thereafter excreted by the body, the fluid is supplied to the space in the portion 11P with an increased content of fiber clusters. Therefore, such a structure is preferred. In addition, in the high fiber clump portion 11P, the fiber clumps 11 are preferably intertwined with the water absorbent fibers 12F since such a structure is likely to exhibit the above effects.

[0041]

In the absorbent core 40, the degree of fiber accumulation or the percentage of fiber accumulation gradually increases from the skin-facing surface (top sheet 2) to the non-skin-facing surface (back sheet 3) as shown in FIG. In other words, in the absorbent core 40, the water-absorbent fibers 12F gradually decrease from the skin-facing surface to the non-skin-facing surface. Briefly, it can be stated that in the thickness direction of the absorbent core 40, on or near that surface of the absorbent core 40 that faces the skin, there are no fiber clumps 11 or there is a minimum fiber clump density or a minimum fiber clump ratio in the absorbent core. 40, while on or near that surface of the absorbent core 40 that is not facing the skin, fiber clumps 11 are present at the maximum clump density or the maximum fiber clump ratio in the absorbent core 40.

[0042]

The arrangement of fibrous materials (fiber clumps 11, water-absorbent fibers 12F) in a certain order in the absorbent core 40 is not limited to such an arrangement as shown in Fig. 3, that is, an arrangement in which the degree of fiber clump filling or the proportion of fiber clumps gradually changes from one surface. , defined in the direction of the thickness of the absorbent core 40, to another surface, can be modified accordingly without departing from the technical essence of the present invention. FIG. 4 shows an absorbent 4A as another embodiment of the absorbent of the present invention, different from the embodiment corresponding to FIG. The absorbent member 4A will be described mainly with respect to components different from the above absorbent member 4, and a similar component is designated with the same reference numeral and is not described. For components not specifically described, the description for the absorbent 4 (absorbent core 40) applies accordingly.

[0043] The absorbent member 4A shown in FIG. 4 is divided in the thickness direction into two layered parts (water-absorbent fiber enhanced portion 12P, fiber clump enhanced portion 11P) having different degrees of fiber clump coverage or different proportions. fiber accumulations. In these two parts, or in each of the water-absorbent fiber enhanced portion 12P as the skin-facing surface side and the fiber-enhanced portion 11P as the non-skin-facing surface, the degree of fiber accumulation filling or fiber accumulation proportion is optionally constant in the thickness direction of the absorbent member 4A. For each of the portions 11P, 12P, the difference in the degree of fiber accumulation filling between the skin-side surface side portion and the non-skin-side surface portion, which are obtained by halving in the thickness direction, is preferably 30% by mass. or less and more preferably 10% of the mass. or less. In the absorbent body 4A, the degree of clump filling or the proportion of clumps of fibers preferably changes significantly at the interface between the water-absorbent fiber rich portion 12P and the clump rich portion 11P. In the embodiment shown in FIG. 4, the interface between the parts is the center of the absorbent 4A in the thickness direction, i.e. the absorbent 4A is bisected in the thickness direction into a portion 12P with an increased content of water-absorbent fibers and a portion 11P with an increased content of fiber clusters. , but the location of the interface may be set on a case-by-case basis, and these portions may have different thicknesses.

[0044] When the absorbent core 40 is divided into the increased water-absorbent fiber portion 12P and the increased layered fiber portion 11P, as in the absorbent member 4A shown in FIG. of that surface of the absorbent core 40 that faces the skin, inward in the thickness direction of the absorbent core 40 at a distance of 20 to 80% of the thickness, more preferably 30 to 70% of the thickness of the absorbent core 40. Part 11P with increased content of fiber clusters preferably extends from that non-skin facing surface of the absorbent core 40 inward in the thickness direction of the absorbent core 40 at a distance of 20 to 80% of the thickness, more preferably 30 to 70% of the thickness of the absorbent core 40.

When the absorbent core 40 is divided into the increased water-absorbent fiber portion 12P and the layered fiber-enhanced portion 11P, as in the absorbent body 4A shown in FIG. The clump-enhanced 11P is preferably 0.5 mm or more, and more preferably 1 mm or more, and preferably 10 mm or less, more preferably 5 mm or less, and even more preferably 4 mm or less.

The thickness of each portion of the absorbent core 40 is determined by the method below. The total thickness of the absorbent core 40 (absorbent member 4), the thickness of the liner 1 and the like can also be determined according to the method below.

[0045]

<Thickness measurement method>

The absorbent core (absorbent body) is allowed to stand on a horizontal surface so that there are no wrinkles or folds, and the part to be measured (for example, the side of the skin-facing surface or the side of the non-skin-facing surface of the absorbent core) is cut out from the absorbent core, as sample for measurements. The thickness of the sample for measurements is determined under a load of 5 cN/cm ² . Specifically, the thickness is determined by using, for example, a PEACOCK DIAL UPRIGHT GAUGES R5-C thickness gauge (manufactured by OZAKI MFG. CO. LTD.). When measuring, a plate having a round or square shape in plan view (an acrylic plate having a thickness of approximately 5 mm) is placed between the working end of the thickness gauge and the measurement specimen, adjusted so that it generates a load of 5 cN/cm ² , and measure thickness. The thickness is measured at 10 points and the average value is calculated to give the thickness.

[0046]

In the absorbent body 4A, the increased water-absorbent fiber portion 12P is bonded to the increased fiber aggregation portion 11P at the interface therebetween by weaving constituent fibers (constituent fibers 11F, agglomerates 11 fibers, water-absorbent fibers 12F). In other words, at the interface between the parts, the water-absorbent fibers 12F present in the water-absorbent fiber-rich portion 12P as the skin-facing surface side are intertwined with the fiber clumps 11 (fibers 11F) present in the clump-rich portion 11P as the side. surface not facing the skin; accordingly, these parts are relatively loosely connected to each other, and therefore the absorbent member 4A (absorbent core 40) is a single member as a whole.

[0047]

Modified embodiments of the absorbent member 4A shown in FIG. to the skin, and this absorbent element is also covered by the present invention. To obtain a modified embodiment of the absorbent element 4A, first, a layer corresponding to the increased content of water-absorbent fibers 12P and a layer corresponding to the increased content of fiber clumps 11P are separately obtained, and these layers are superimposed on each other to create an absorbent element. In a modified embodiment of the absorbent body 4A made by the above method, the constituent fibers 11F and 12F in these parts hardly intertwine with each other, therefore, the absorbent core 40 is not a single element as a whole, and the part 12P with a high content of water-absorbent fibers can be easily separated from the part 11P with a high content of clusters of fibers.

[0048]

An absorbent body 4 as shown in FIG. 3, in which the degree of fiber agglomeration filling or the proportion of fiber agglomerations gradually changes in the thickness direction of the absorbent from one surface to another surface, in particular, has the following advantages: the ratio of water-absorbent fibers and fiber agglomerations gradually varies in the thickness direction of the absorbent, therefore, the weave of the clumps of fibers is likely to be maintained in the thickness direction even when an external force is applied to the absorbent, and the springback capability of the absorbent is likely to be maintained satisfactorily during use. An absorbent member 4A as shown in FIG. 4, which includes two parts in the thickness direction having different degrees of fiber accumulation or fiber accumulation proportions, in particular, has the following advantages: the skin side of the surface of the absorbent element, and the non-skin side of the surface of the absorbent body are easily created with independent functions.

[0049]

The absorbent body 4 or 4A (absorbent core 40) can be made (a) by using a known fiber depositor having a rotating drum in a well-known manner. The specific arrangement of fibrous materials (fiber aggregations 11, water-absorbent fibers 12F) shown in Fig. 3 or 4 can be achieved, for example, by appropriately setting the stacking order of fiber aggregations 11 and water-absorbing fibers 12F on a rotating drum in a manufacturing method, in in which the fiber stacking device is used.

[0050]

The absorbent core 40 may include additional components other than the fiber clusters 11 and water-absorbent fibers 12F, and examples of the additional component include a water-absorbent polymer. Reference numeral 13 in the drawings denotes a water-absorbent polymer. As the water-absorbent polymer, a particulate polymer such as shown in the figures is generally used, and a fibrous polymer may be used. In use, the particulate water-absorbent polymer may be any shape from a spherical shape, a cluster shape, an ellipsoid shape, and an indeterminate shape. The water-absorbent polymer preferably has an average particle size of 10 µm or more, and more preferably 100 µm or more, and preferably 1000 µm or less, and more preferably 800 µm or less. As the water-absorbing polymer, a polymer or copolymer of acrylic acid or an alkali metal acrylate can generally be used. Examples thereof include polyacrylic acid, its salts, polymethacrylic acid and its salts.

[0051]

In the absorbent core 40, the water-absorbent polymer 13 is contained on the side of that surface of the absorbent core 40 facing the skin, and is accordingly contained in the water-absorbent fiber portion 12P as shown in FIG. As described above, the side of that surface of the absorbent core 40 which faces the skin and which is provided particularly with very good liquid-absorbing ability, contains a water-absorbent polymer 13 which has very good water-absorbing ability and therefore liquid-absorbing ability on that skin-facing surface of the absorbent core 40 can be further increased in combination with the increased water-absorbent fiber portion 12P as the skin-facing surface side, i.e., in combination with a relatively low fiber clump or fiber clump proportion.

[0052]

In the absorbent core 40, the water-absorbent polymer 13 may be contained in a portion other than the side (high water-absorbent fiber portion 12P) of the skin-facing surface of the absorbent core 40, or in the high fiber clump portion 11P. Considering that the water-absorbent polymer 13 is contained in the absorbent core 40 mainly to increase the ability to draw liquids on the side of that surface of the absorbent core 40 that faces the skin, it may not be very important that the side (the part 11P with a high content of accumulations fibers) of the non-skin-facing surface of the absorbent core 40 intentionally contained the water-absorbent polymer 13. In addition, when the side (high fiber-clump portion 11P) of the non-skin-facing surface of the absorbent core 40 intentionally contains the water-absorbent polymer 13, the advantageous effects (such as the effects of increasing the springback property and anti-curl property) provided by the increased fiber clump portion 11P may not be exhibited satisfactorily. In view of the foregoing, the portion other than the side (high water-absorbent fiber portion 12P) of that surface of the absorbent core 40 facing the skin, in particular, for example, the high fiber clump portion 11P preferably has a lower content of water-absorbent polymer 13 compared to with the side of the surface facing the skin, and this content may be zero.

[0053]

In the absorbent core 40, the content of the water-absorbing polymer 13 is preferably 5% by weight. or more and more preferably 10% of the mass. or more and preferably is 60% of the mass. or less and more preferably 40% of the mass. or less based on the total weight of the dry absorbent core 40.

In the absorbent core 40, the surface density of the water-absorbent resin 13 is preferably 10 g/m ² or more, and more preferably 30 g/m ² or more, and preferably 100 g/m ² or less, and more preferably 70 g/m ² or less.

[0054]

The main feature of the absorbent core 40 is the outer shape of the fiber cluster 11 . 5 shows two exemplary outer shapes of the fiber bundle 11. The fiber aggregation 11A shown in FIG. 5(a) is in the shape of a quadrangular prism, more specifically, a cuboid shape, while the fiber aggregation 11B shown in FIG. 5(b) is in the shape of a disk. The fiber clusters 11A and 11B share the common feature of having two opposing base surfaces 111 and body surfaces 112 connecting the two base surfaces 111. Each of the base surfaces 111 and body surfaces 112 is substantially free of roughness in terms of evaluating surface roughness. products containing mainly fibers of this type.

[0055]

Cluster 11A of fibers, having the shape of a rectangular parallelepiped in Fig.5(a), has six flat surfaces. The two opposite surfaces of these six surfaces having the maximum area are the base surfaces 111, and the other four surfaces are the main body surfaces 112. The base surfaces 111 intersect with the surfaces 112 of the body, more specifically orthogonal to the surfaces 112 of the body.

The disk-shaped fiber aggregation 11B of FIG. 5(b) has two opposite flat surfaces having a circular shape in plan view and a curved circumferential peripheral surface connecting the flat surfaces. The two flat surfaces are the base surfaces 111, and the circumferential peripheral surface is the body surface 112.

The fiber clusters 11A and 11B share a common feature in that the body surfaces 112 are quadrangular in plan view, more specifically, a rectangular shape.

[0056]

The plurality of fiber aggregations 11 contained in the absorbent core 40 differ from the nonwoven or microweb pieces of Patent Literature 1 and 2 as indefinitely shaped fiber aggregations in that each aggregation of fibers is a "shaped aggregation of fibers" that has two opposing base surfaces 111 and body surfaces 112 connecting base surfaces 111 as in the fiber clusters 11A and 11B shown in FIG. In other words, when viewing a fiber cluster 11 randomly selected from the fiber cluster 11 contained in the absorbent core 40 (for example, when viewed under an electron microscope), the perspective shape of the fiber cluster 11 changes with viewing angles, and one fiber cluster 11 gives a large number of shapes in perspective. Each of the plurality of fiber clusters 11 in the absorbent core 40 has, as one of a plurality of perspective shapes, a specific perspective shape with two opposing base surfaces 111 and body surfaces 112 connecting the base surfaces 111. The plurality of pieces of nonwoven fabric or microweb contained in absorbent body according to Patent Literature 1 and 2, essentially do not have such a "surface" as the base surface 111 or the surface 112 of the body, which is the distribution part, have different outer shapes and do not have a "defined shape".

[0057]

As described above, when the plurality of fiber agglomerations 11 contained in the absorbent core 40 are "shaped fiber aggregations" formed by the base surfaces 111 and the body surfaces 112, the ability of the fiber agglomerations 11 to be uniformly distributed in the absorbent core 40 is improved. compared with such assemblies of fibers having an indeterminate shape as described in Patent Literature 1 and 2. Therefore, effects (effects of increasing flexibility, resilience, resilience and improving the like characteristics of an absorbent member) are stably achieved, which should appear when fiber clusters 11 such as fiber clusters 11 are contained in the absorbent core 40. In particular, a cuboid-shaped fiber cluster 11 as shown in FIG. 5(b ). Accordingly, the weaving property is improved, and the shape retention property or the like can be improved.

[0058]

In the fiber bundle 11, the total area of the two base surfaces 111 is preferably greater than the total area of the body surfaces 112. In other words, in the cuboid-shaped fiber aggregation 11A in FIG. two base surfaces 111 is greater than the area of that surface 112 of the main part, which forms the circumferential peripheral surface of the disk-shaped accumulation of fibers 11B. In each of the fiber clusters 11A and 11B, the base surface 111 has the largest area of the plurality of fiber cluster surfaces 11A or 11B.

[0059]

Such a fiber agglomeration 11 as "a collection of fibers having a certain shape" formed by two base surfaces 111 and main body surfaces 112 intersecting with base surfaces 111 can be obtained by a production method different from conventional methods. The preferred method for producing the fiber aggregation 11 is, as shown in FIG. 6, by cutting a fibrous material sheet 10bs (a sheet having the same composition as the fiber aggregation 11 but having a larger size than the fiber aggregation 11) as a material into elements with a certain shape through the use of a cutting means such as a cutter/knife. The plurality of resulting fiber clusters 11 have more defined shapes and sizes than those obtained by the conventional methods described in Patent Literature 1 and 2. FIG. (a) and the dotted lines in Fig. 6 show cutting lines. The absorbent core 40 includes a plurality of fiber aggregations 11 having the same shape and dimensions and obtained with a certain shape by cutting the fibrous sheet as described above. The fibrous material sheet 10bs is preferably a nonwoven material as described above.

[0060]

The fiber agglomeration 11A having the shape of a cuboid in FIG. 5(a) is obtained by cutting the fibrous material sheet 10bs into predetermined lengths in a first direction D1 and a second direction D2 intersecting the first direction D1 (more specifically, orthogonal to the first direction D1 ) as shown in Fig.6. Each of the directions D1 and D2 is a certain direction extending in the surface direction of the sheet 10bs, and the sheet 10bs is cut along the Z thickness direction orthogonal to the surface direction. In the plurality of cuboid fiber clusters 11A obtained by cutting the fibrous sheet 10bs of material into so-called cubes in this way, generally the surface formed by the cutting, i.e. the surface in contact with the cutting means such as a cutter/knife, when cutting the sheet 10bs, is the surface 112 of the main part, and the non-cutting surface, that is, the surface not in contact with the cutting means, is the base surface 111. The base surface 111 is the top or back surface (surface orthogonal to the Z direction of thickness) of the sheet 10bs and has the largest area of the plurality of fiber accumulation surfaces 11A as described above.

[0061]

The above description of the fiber aggregation 11A can be generally applied to the disc-shaped fiber aggregation 11B shown in FIG. 5(b). The essential difference from the fiber aggregation 11A is only in the pattern of cutting the fibrous material sheet 10bs, and in order to cut the sheet 10bs to obtain certain shapes of fiber aggregations 11B, the sheet 10bs can be cut into elements with a circular shape corresponding to the shape of the fiber aggregation 11B in plan view.

[0062]

The outer shape of the fiber bundle 11 is not limited to the outer shapes shown in FIG. 5, and each of the base surface 111 and the body surface 112 may be a flat surface without curvature, similar to the surfaces 111 and 112 in FIG. 5(a), or may be a curved surface similar to the body surface 112 (circumferential peripheral surface of the disk-like fiber bundle 11B) in FIG. 5(b). The base surface 111 and the body surface 112 may have the same shape and the same dimensions.

[0063]

As described above, the two types of surfaces (base surface 111 and body surface 112) of the fiber clumps 11 (11A or 11B) can be described as a cutting surface (body surface 112) which is formed by cutting the fibrous material sheet 10bs with a cutting means. , such as a cutter/knife, when producing fiber clusters 11, and a non-cut surface (base surface 111), which is the original surface of the sheet 10bs and is not in contact with the cutting agent. Due to the difference between the cut surface and the non-cut surface, the body surface 112 as a cut surface has a higher number of fiber ends per unit area as a feature compared to the base surface 111 as a non-cut surface. In the description, “fiber end” means the end of the 11F constituting fiber constituting the fiber cluster 11 in its length direction. Although the base surface 111 as a non-cut surface generally includes fiber ends, the body surface 112, which is a cut surface formed by cutting the fibrous material sheet 10bs, includes the entire of the body surface 112 a large number of fiber ends as cut ends of the component fiber ends 11F which are formed by cutting, and therefore has more fiber ends per unit area than the base surface 111.

[0044]

The fiber ends on each surface (base surface 111 and body surface 112) of the fiber clusters 11 are advantageous when the fiber cluster 11 forms an interweaving area with other fiber clusters 11 or 12F water-absorbent fibers contained in the absorbent core 40. A high number of fiber ends per unit area generally provides an improvement in weaveability and therefore may provide an improvement in various characteristics such as the shape retention ability of the absorbent core 40. As described above, the fiber agglomeration surfaces 11 have different numbers of fiber ends per unit area, and the number of fiber ends per unit area satisfies the relationship: "body surface 112 > base surface 111". Therefore, the ability of the fiber cluster 11 to intertwine with other fibers (other fiber clusters 11 and water-absorbent fibers 12F) varies depending on the surfaces of the fiber cluster 11, and the body surface 112 has a higher weaving ability compared to the base surface 111. In other words, the entanglement with other fibers through the body surface 112 is stronger than through the base surface 111, and the single fiber bundle 11 has an adhesive strength different between the base surface 111 and the body surface 112. In general, fibers bonded with greater cohesive force have a lower degree of freedom of movement, and the resulting absorbent core 40 has overall higher strength (shape retention) but is likely to have less softness.

[0065]

As described above, each of the plurality of fiber agglomerations 11 contained in the absorbent core 40 is intertwined with other peripheral fibers (other fiber aggregations 11 and water absorbent fibers 12F) through two types of adhesive forces, and accordingly, the absorbent core 40 simultaneously possesses appropriate softness and strength (ability to retain shape). Further, when an absorbent core 40 having such very good characteristics is used as an absorbent member in an absorbent article in a conventional manner, the absorbent article can provide wearing comfort to its wearer and can effectively prevent the disadvantage that the absorbent core 40 is torn. under the influence of external forces, including the pressure of the wearer's body while wearing.

[0066]

Specifically, as described above, in the fiber aggregation 11 (11A or 11B) shown in FIG. 5, the two base surfaces 111 have a total area that is greater than the total area of the body surfaces 112. This means that the base surfaces 111, having a relatively small number of fiber ends per unit area and, accordingly, having a relatively low ability to interweave with other fibers, have a total area that is greater than the total area of the main body surfaces 112, which have opposite characteristics to the base surfaces 111. Therefore, there is a possibility that the fiber bundle 11 (11A or 11B) shown in FIG. evenly over the entire surface. Even when intertwined with other peripheral fibers, the fiber agglomeration 11 is likely to be intertwined with a relatively low cohesive force, hence it is unlikely to form a large agglomeration, and this can provide very good resilience/flexibility to the absorbent core 40.

[0067]

In contrast, a piece of non-woven fabric or micro-web according to Patent Literature 1 and 2, which is obtained, for example, by cutting a fibrous sheet of material into elements with indefinite shapes with a cutting device such as a cutting mill, as described above, is not a collection of fibers like a piece a sheet having a certain shape with such "surfaces" as the base surface 111 and the surface 112 of the body. In addition, when fiber bundles are produced, the external force generated by cutting will be applied to the entire fiber bundle, therefore, the ends of the fibers constituting the fibers are formed randomly in the entire fiber bundle, and it is unlikely that the above-described advantageous effects provided by the count of the ends of the fibers will be achieved sufficiently.

[0068]

For reasons related to more reliable provision of the above preferred effects achieved by the ends of the fibers, the ratio (N ₁ /N _{2) of the} number N _{1 of the} ends of the fibers per unit area of the base surface 111 (surface not formed by cutting), to the number N _{2 of the} ends of the fibers per unit area of the surface 112 of the main part (surface formed by cutting) is preferably 0 or more, and more preferably 0.05 or more, and preferably 0.90 or less, and more preferably 0.60 or less, provided that N ₁ < N ₂ . More specifically, N ₁ /N _{2 is} preferably 0 or more and 0.90 or less, and more preferably 0.05 or more and 0.60 or less.

The number N ₁ of fiber ends per unit area of the base surface 111 is preferably 0 end portions of the fibers per 1 mm ² or more and more preferably 3 to the end parts of fibers per 1 mm ² or more and preferably 8 the end portions of the fibers per 1 mm ² or less and more preferably 6 fiber ends per mm ² or less.

The number N ₂ of fiber ends per unit area of surface 112 of the main body is preferably 5 end portions of the fibers per 1 mm ² or more and more preferably 8 the end portions of the fibers per 1 mm ² or more and preferably 50 end portions of the fibers per 1 mm ² or less and more preferably 40 fiber ends per mm ² or less.

The number of fiber ends per unit area of base surface 111 or body surface 112 is determined by the method below.

[0069]

<Method for determining the number of fiber ends per unit area of each fiber cluster surface>

The element (fiber cluster) containing fibers to be measured (measurement sample) is attached to the sample table with a double-sided sticky paper tape (NICETACK NW-15, manufactured by Nichiban Co., Ltd.). Next, the measurement sample is coated with platinum. An E-1030 (trade name) ion sputtering apparatus manufactured by Hitachinaka Seiki Co., Ltd. was used for coating, and the sputtering time was set to 120 seconds. The cut surfaces (base surface and body surface) of the measurement specimen were examined under a JEOL JCM-6000 electron microscope at 100× magnification. In the 100X viewing image, a rectangular area with a length of 1.2 mm and a width of 0.6 mm is set anywhere on the surface to be measured (base surface or body surface), and the viewing angle, etc. the characteristics are adjusted so that the area of the rectangular area is 90% or more of the area of the observed image. After that, the number of fiber ends in this rectangular zone is counted. When the area of fiber accumulation to be measured has dimensions that are less than 1.2 mm × 0.6 mm in the image observed at 100x magnification, and the proportion of the area of the rectangular zone is less than 90% of the total area of the observed image, the viewing magnification is set to a larger one. than 100 times, and the number of fiber ends in a rectangular area on the surface to be measured is counted in the same way. In the description, the "fiber ends" to be counted are the ends of the constituent fibers forming the fiber cluster in the length direction, and even when parts (parts intermediate in the length direction) other than the ends of the constituent fibers in the length direction protrude from the surface to be measured, parts intermediate in the length direction are excluded from the count. Thereafter, the number of fiber ends per unit area of the measured surface (base surface or body surface) of the fiber cluster is calculated according to the formula below. For each of the 10 fiber clusters, the number of fiber ends per unit area of each of the base surface and the body surface is counted according to the above procedure, and the average value of the plurality of counted values is determined as the number of fiber ends per unit area of the surface to be measured.

The number of fiber ends per unit area of the measured surface (base surface or body surface) of the fiber agglomeration, (number/mm ² ) = number of fiber ends contained in a rectangular area (1.2 × 0.6 mm) / area of the rectangular area (0 .72 mm ² )

[0070]

When the base surface 111 of the fiber cluster 11 has a rectangular shape in plan view, as in the fiber cluster 11A shown in FIG. The rectangular shaped clump 111a preferably has a size equal to or less than the thickness of the absorbent core 40 containing the fiber clump 11 (11A). The ratio of the length of the short side 111a to the thickness of the absorbent core 40, first value/second value, is preferably 0.03 or more, and more preferably 0.08 or more, and preferably 1 or less, and more preferably 0.5 or less.

The thickness of the absorbent core 40 is preferably 1 mm or more, and more preferably 2 mm or more, and preferably 15 mm or less, more preferably 10 mm or less, and even more preferably 6 mm or less. The thickness of the absorbent core 40 is determined by the method described above.

[0071]

The dimensions and the like of each portion of the fiber bundle 11 (11A or 11B) are preferably set to the following values. The dimensions of each part of the fiber bundle 11 can be determined based on a photograph taken with an electron microscope or the like during the outer shape determination operation of the fiber bundle 11 described later.

When the base surface 111 is rectangular in plan view as shown in FIG. 5(a), the length L1 of the short side 111a is preferably 0.3 mm or more, and more preferably 0.5 mm or more, and preferably 10 mm or more. less and more preferably 6 mm or less. The length L2 of the long side 111b of the base surface 111 having a rectangular shape in plan view is preferably 0.3 mm or more, and more preferably 2 mm or more, and preferably 30 mm or less, and more preferably 15 mm or less.

When the base surface 111 has the largest area of the plurality of fiber cluster surfaces 11 shown in FIG. in respect of.

The ratio L1/L2 of the length L1 of the short side 111a to the length L2 of the long side 111b is preferably 0.003 or more, and more preferably 0.025 or more, and preferably 0.5 or less.

The thickness T of the fiber bundle 11, that is, the distance T between two opposite base surfaces 111, is preferably 0.1 mm or more, and more preferably 0.3 mm or more, and preferably 10 mm or less, and more preferably 6 mm or less.

[0072]

The absorbent core 40 is preferably dynamically isotropic to promote the beneficial effects of fiber clusters 11 on each surface of the absorbent core 40. To achieve these effects, the fiber clusters 11 are preferably evenly distributed at a high density throughout the absorbent core 40. For this reason, in any single square area absorbent core 40 with a square side length of 10 mm, in images projected in two directions orthogonal to each other, the plurality of fiber clusters 11 preferably overlap each other. In the description, the expression "images projected in two directions orthogonal to each other" generally includes an image of the absorbent core (absorbent member) projected in the thickness direction (i.e., when the absorbent core is viewed from the side of its surface facing the skin , or non-skin-facing surface), and an image projected in a direction orthogonal to the thickness direction (ie, when the absorbent core is viewed from the side surface).

[0073]

Fig. 7(a) is an electron microscope photograph of an example of a fiber aggregation of the present invention, and Fig. 7(b) is an image schematically showing a fiber aggregation 11 in an electron microscope photograph. The plurality of fiber agglomerations 11 contained in the absorbent core 40 may include, as shown in FIG. low fiber density (fewer fibers per unit area) than the body 110. The absorbent core 40 may include a fiber aggregation 11 having no raised fiber portion 113, i.e. a fiber aggregation 11 having only the main body 110 The projecting fiber portion 113 is something like the fiber ends on each surface (base surface 111 or body surface 112) of the fiber cluster 11 described above, and is those fiber ends of the fiber ends that protrude outward from the surfaces of the fiber cluster 11 .

[0074]

The main body 110 is formed by the above-described two opposite base surfaces 111 and the main body surfaces 112 connecting the base surfaces 111. The main body 110 basically forms the fiber aggregation 11 and defines a certain outer shape of the fiber aggregation 11, and various properties of the fiber aggregation 11, such as high resilience/flexibility, resilience, and resilience are essentially provided mainly by the main body 110. Meanwhile, the protruding fiber portion 113 mainly contributes to improving the weaving ability between a plurality of fiber clusters 11 or between fiber clusters 11 and water-absorbent 12F fibers contained in the absorbent core 40 to directly improve the shape retention ability of the absorbent core 40 and affect the uniform distribution ability of the fiber clumps 11 in the absorbent core 40 or the like for indirect enhancement of the preferred effects provided by the body 110.

[0075]

The main body 110 has a higher fiber density or more fibers per unit area than the protruding fiber portion 113. The body 110 itself generally has a uniform fiber density. The proportion of the main part 110 in the total mass of the cluster 11 fibers, as a rule, is at least 40% of the mass. or more, preferably 50% of the mass. or more, more preferably 60% of the mass. or more and even more preferably 85% of the mass. or more. The main part 110 and the protruding fiber part 113 can be distinguished from each other by the following operation of determining the outer shapes.

[0076]

The operation of determining the outer shape of the main body 110 of the aggregation 11 of fibers contained in the absorbent core 40 can be performed by identifying the "border" between the main body 110 and the remaining parts, in particular, the difference in the density of the fibers of the absorbent core 40 is established by observation. (difference in number of fibers per unit area) or difference in fiber type or diameter. The main body 110 has a higher fiber density compared to the peripheral portions 113 with protruding fibers. In addition, the synthetic fibers as constituent fibers of the body 110 generally differ in quality and/or size from the 12F water-absorbent fibers (generally cellulose fibers). Therefore, even when the absorbent core 40 contains a large number of fiber clusters 11 and water-absorbent fibers 12F as a mixture, the boundary can be easily identified by specifically examining the above locations. The boundary identified by the above method is the edge of the base surface 111 or the body surface 112, and the base surface 111 and the body surface 112 are determined by the boundary identification operation. Therefore, the main body 110 can be determined. Such an edge identification operation can be performed by examining the object (absorbent member 4) under an electron microscope at multiple viewing angles if necessary. In particular, when the fiber aggregation 11 contained in the absorbent core 40 is the fiber aggregation 11A or 11B shown in FIG. the base surface 111 has the largest area in the fiber cluster 11, the base surface 111 having the largest area can be determined relatively easily, and therefore the outer shape of the main body 110 can be determined without problems.

[0077]

As shown in FIG. 7, the projecting fiber portion 113 includes component fibers 11F of the main body 110, and these component fibers protrude outward from at least one surface of base surfaces 111 and surfaces 112 of the main body forming the outer surface of the main body. part 110. Fig.7(b) is an image of the surface of the accumulation of 11 fibers, when viewed from the side of the base surface 111 (the surface having the largest area of the plurality of surfaces of the accumulation of 11 fibers), and a large number of fibers 11F protrude from that surface 112 of the main part , which intersects the base surface 111 to form a portion 113 with protruding fibers.

[0078]

The raised fiber portion 113 may be of any shape. The raised fiber portion 113 may be composed of a single fiber 11F or may be composed of a plurality of fibers 11F like the raised fiber bundle 113S described later. The protruding fiber portion 113 includes a fiber end 11F in the length direction protruding from the main body 110, and in addition to such a fiber end, may include a portion different from the ends of the fiber 11F in the length direction (length direction intermediate portion). In other words, in the fiber agglomeration 11, the ends of the constituent fiber 11F in the length direction may be in the main body 110, and another part or a part intermediate in the length direction may extend (protrude) in a loop shape outward from the main body 110. In such a case, the part 113 with projecting fibers includes a loop-shaped projecting part of the fiber 11F.

[0079]

As described above, the main role of the projecting fiber portion 113 is to intertwine the plurality of fiber bundles 11 contained in the absorbent core 40 with each other, or to intertwine the fiber bundles 11 with the 12F water absorbent fibers. Generally, when the protruding fiber portion 113 has a longer protruding length from the main body 110, the protruding fiber portion 113 has a greater thickness, or one fiber cluster 11 has a larger number of protruding fiber portions 113, the objects interlaced by the protruding fiber portion 113 , connect more firmly, and it is unlikely that the weave will be eliminated. Therefore, the intended effects of the present invention are more stable.

[0080]

In the case where the fiber agglomeration 11 is a fiber aggregation obtained by cutting the raw material fibrous sheet 10bs into shaped pieces as shown in FIG. surface of the fiber cluster 11 obtained by cutting, but on the base surface 111, which is not the surface formed by cutting, there are no projecting fiber parts 113, or in the case of such parts, the number of projecting fiber parts 113 is less than on the surface 112 of the main part. The reason why the raised fibers 113 are located on the main body surfaces 112 as cutting surfaces is because many of the raised fibers 113 are fluff created by cutting the fibrous sheet of material. In other words, the body surface 112 formed by cutting the fibrous material sheet 10bs has been completely rubbed by a cutting means such as a cutter/knife at the time of cutting, and therefore there is a possibility that the constituent fibers 11f of the sheet 10bs may be fluffed, and the surface of the main parts are more likely to have fluff. When there are small intervals between the cutting lines or the cutting speed is set low, there is a possibility that the raised fiber portions 113 are formed depending on the types of fibrous sheet material, and the length of the raised fiber portions 113 can be adjusted. On the contrary, the base surfaces 111, as non-cutting surfaces, are not subjected to friction by such a cutting means, and therefore fluff or fiber protruding portions 113 are unlikely to be formed.

[0081]

The intervals L1a (intervals in the first direction, see Fig. 6) and the intervals L2a (intervals in the second direction, see Fig. 6) between cutting lines at the time of cutting the fibrous material sheet 10bs are preferably 0.3 mm or more, and more preferably 0.5 mm or more, and preferably 30 mm or less, and more preferably 15 mm or less, to promote the formation of the projecting fiber portions 113 described above and to obtain fiber clusters 11 having such a necessary size to exhibit the intended effects.

[0082]

As shown in FIG. 7, the fiber agglomeration 11 has, as a protruding fiber portion 113, a protruding fiber bundle 113S projecting outwardly from the main body 110, more specifically from the body surface 112, and containing a plurality of fibers 11F. At least one of the raised fiber portions 113 of the fiber cluster 11 may be a raised fiber bundle 113S. The projecting fiber bundle 113S includes a plurality of fibers 11F gathered together and projecting from the body surface 112, and is characterized by having a longer projection length from the body surface 112 compared to the projection length of the projection fiber portion 113. The protruding fiber bundle 113S may be on the base surface 111, but typically it is on the body surface 112 as shown in FIG. surface 112 of the main body, even when the observation reveals bunches of protruding fibers. The reason is the same as the reason why the fiber protruding portions 113 are mainly provided on the surface 112 of the main body as a cutting surface, which is described above.

[0083]

When the fiber cluster 11 has such a raised fiber bundle 113S, which can be called a long, thick raised fiber portion 113 having a large size, the weave between the fiber clusters 11 or between the fiber clusters 11 and the water absorbent fibers 12F is further improved. As a result, the intended effects of the present invention provided by the presence of fiber clusters 11 are more stable. The protruding fiber bundle 113S is likely to be generated by cutting the fibrous material sheet 10bs under the above conditions where fluff is likely to form (see FIG. 6).

[0084]

The protrusion length of the protruding fiber bundle 113S from the main body 110, that is, the protrusion length from the surface 112 of the main part (surface formed by cutting), is preferably 0.2 mm or more, and more preferably 0.5 mm or more, and is preferably 7 mm or less and more preferably 4 mm or less. The protrusion length of the protruding fiber bundle 113S can be determined by the outer shape determination operation of the fiber cluster 11 (boundary identification operation) described above. Specifically, for example, a double-sided adhesive tape manufactured by 3M Company is attached to the surface of a transparent acrylic microscope stage manufactured by Keyence Corporation (at 50x magnification), and a cluster of 11 fibers is placed and attached to the tape. The outer shape of the fiber bundle 11 is determined in accordance with the above outer shape determination operation, then the protrusion length of the fiber 11F protruding from the outer shape member is measured, and the measured protrusion length is considered as the protrusion length of the protruding fiber bundle 113S.

[0085]

In the projecting fiber bundle 113S, the plurality of fibers 11F constituting it are preferably bonded to each other by a fusion method. The fusion bonded portion of the 113S raised fiber bundle generally has a larger size (diameter when the fused portion has a circular cross section) in a direction orthogonal to the length direction of the 113S raised fiber bundle compared to other portions of the 113S bundle protruding fibers (parts not connected by fusion). When the protruding fiber bundle 113S has such a fusion-bonded part called the large diameter part, the protruding fiber bundle 113S itself has a higher strength, and this structure further enhances the weave between the fiber clusters 11 or between the fiber clusters 11 and the water-absorbent fibers 12F, entwined by a bundle of 113S protruding fibers. The protruding fiber bundle 113S having the fusion-bonded portion has the advantage that the protruding fiber bundle 113S itself has higher strength, shape retention, and the like, not only when the protruding fiber bundle 113S is in a dry condition, but also when the protruding fiber bundle 113S absorbs water and is wet. Due to such advantages, the advantageous effects provided by the presence of fiber clusters 11 can be stably exhibited not only when the absorbent core 40 is in a dry state, but also when the absorbent core 40 absorbs bodily fluids released from the wearer, such as urine and menstrual blood, and is in a wet state. Such a protruding fiber bundle 113S having a fused portion can be obtained in the process for producing fiber bundles 11 shown in FIG. having portions of constituent fibers bonded by fusion" as a fibrous material sheet 10bs.

[0086]

The constituent fibers 11F forming the fiber cluster 11 include synthetic fibers. The synthetic fibers used as the 11F fibers preferably have a lower water absorbency (weak water absorbency) than the 12F water absorbent fibers, and are particularly preferred as non-water absorbent synthetic fibers. The constituent fibers 11F forming the fiber cluster 11 may include fibrous components (eg, natural fibers) other than synthetic fibers. When the constituent fibers 11F constituting the fiber cluster 11 include fibers with low hydrophilicity, preferably fibers that do not absorb water, the preferred effects (effects of improving shape retention, flexibility/resilience, resilience, rebound ability, anti-curl and the like) due to the accumulation of 11 fibers stably appear not only when the absorbent core 40 is in a dry state, but also when the absorbent core 40 absorbs water (body fluids, fluids such as urine and menstrual blood ) and is wet. In the cluster 11 fibers, the content of synthetic fibers as constituent fibers 11F is preferably 90% of the mass. or more and more preferably 100% of the mass. relative to the total weight of the fiber bundle 11, that is, the fiber bundle 11 more preferably includes only synthetic fibers. In particular, when the synthetic fibers constituting the 11F fibers are non-absorbent fibers, the advantageous effects due to the accumulation of fibers 11 are even more stable.

[0087]

The term "water absorbency" in the present description can be easily understood by a person skilled in the art in such a way that, for example, cellulose has the ability to absorb water. Similarly, it can also be easily understood that thermoplastic fibers have low water absorption capacity (in particular, no water absorption capacity). Meanwhile, with regard to the level of water-absorbing ability of the fibers, the relative difference in the water-absorbing ability of the fibers can be determined based on the comparison of the moisture content determined by the method described later, and a more preferable range thereof can also be determined. Fibers having a higher moisture content have a higher water absorption capacity. The water absorbent fibers preferably have a moisture content of 6% or more, and more preferably 10% or more. Meanwhile, the synthetic fibers preferably have a moisture content of less than 6% and more preferably less than 4%. Fibers having a moisture content of less than 6% can be defined as fibers that do not absorb water.

[0088]

<Moisture content determination method>

The moisture content was determined according to the moisture content test method in JIS P8203 ( JIS-Japanese Industrial Standard ). In other words, the fiber sample was allowed to stand in the testing laboratory at 40° C. and 80% relative humidity for 24 hours, and then the mass W (g) of the fiber sample was determined in the laboratory before it was processed to dry to a completely dry state. Thereafter, the fiber sample was allowed to be kept in an electric dryer (for example, manufactured by Isuzu Seisakusho, Co., Ltd.) at a temperature of 105 ± 2°C for 1 hour to complete the drying treatment of the fiber sample until completely dry. After being dried to a completely dry state, in a test laboratory in a standard state of 20 ± 2°C and a relative humidity of 65 ± 2%, a fiber sample wrapped in Saran Wrap (registered trademark) material, manufactured by Asahi Kasei Corporation, placed in a glass desiccator (manufactured by, for example, Tech-Jam) containing silica gel (supplied by, for example, Toyotakako Co., Ltd.), and allowed to stand until the temperature of the fiber sample reaches 20±2°C. Thereafter, the constant mass W' (g) of the fiber sample is determined, and the moisture content of the fiber sample is calculated according to the following expression. Moisture content (%) = (W - W'/W') H 100.

[0089]

For reasons related to enabling the absorbent core 40 to perform very well in terms of shape retention, flexibility/resilience, resilience, compression recovery, anti-curl, and the like, similarly in each of the dry state and the wet state, the fiber bundle 11 preferably has a three-dimensional structure in which a plurality of thermoplastic fibers are fused to each other.

[0090]

In order to obtain such a fiber bundle 11 in which a plurality of fused parts are distributed in a three-dimensional structure, the synthetic fibers used as the constituent fibers 11F forming the fiber bundles 11 are preferably thermoplastic fibers. As described above, the protruding fiber bundle 113S preferably has a fused portion. When the constituent fibers 11F forming the fiber clusters 11 are thermoplastic fibers, the projecting fiber bundle 113S may have such a preferred structure.

[0091]

In order to obtain a fiber bundle 11 in which a plurality of fused parts are distributed in a three-dimensional structure, the fibrous material sheet 10bs (see FIG. 6) may have a similar structure. Such a fibrous material sheet 10bs in which a plurality of fusion-bonded parts are distributed in a three-dimensional structure can be obtained by subjecting a web or non-woven fabric containing mainly thermoplastic fibers to a heat treatment such as hot air treatment. as described above.

[0092]

Examples of the water-repellent synthetic resin (thermoplastic resin) preferred as the material of the constituent fibers 11F forming the fiber cluster 11 include polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate; polyamides such as nylon 6 and nylon 66; and polyacrylic acid, polyalkyl methacrylate, polyvinyl chloride and polyvinylidene chloride, and these resins may be used alone or in combination of two or more of them. The 11F fiber may be a one-component fiber of one synthetic resin (thermoplastic resin) or a polymer blend of two or more synthetic resins, or may be a two-component fiber. In the description, the bicomponent fiber is a synthetic fiber (thermoplastic fiber) obtained by joining two or more synthetic resins containing different components in a spinneret and molding the synthetic resins at the same time, and has a structure in which a plurality of components are continuous in the length direction of the respective fibers and connected to each other in one fiber. The bicomponent fiber structure includes a core-clad structure, a side-by-side structure, and the like, and is not limited to a specific structure.

[0093]

The fiber cluster 11 preferably has a water contact angle of less than 90 degrees and in particular less than 70 degrees for reasons related to further increasing the receptivity of body fluid upon initial discharge. Such fibers can be obtained by treating the above-described non-absorbent synthetic fibers with a hydrophilizing agent in a conventional procedure. As a hydrophilizing agent, an ordinary surfactant can be used.

[0094]

<Contact Angle Method>

A fiber sample is taken from the measurement object (absorbent core) and the contact angle of the fiber with water is measured. As the measuring device, an MCA-J automatic contact angle measuring instrument manufactured by Kyowa Interface Science Co., Ltd. is used. Deionized water is used to measure the contact angle. The amount of liquid exiting from the jet-type ejector for ejecting water droplets (CTC-25 pulse injector manufactured by Cluster Technology Co., Ltd. and having an ejector pore size of 25 µm) is set to 20 picoliters, and a drop of water is dripped directly on top of the fiber. The dripping state is recorded by a high-speed video recorder connected to a camera mounted horizontally. For reasons related to subsequent image analysis, the DVR is preferably a personal computer combined with a high-speed image capture device. When measuring, images are recorded every 17 ms. The first image of the registered images, in which the water drop reaches the fiber, is subjected to image analysis using the accompanying FAMAS software (version 2.6.2; analysis method: resting drop method; analysis method: Ɵ/2; image processing algorithm: non-reflective; image view processing: frame; threshold level: 200; no curvature correction) to calculate the angle between the surface of the water droplet in contact with air and the fiber, resulting in a contact angle. The fiber taken from the measurement object was cut with a fiber length of 1 mm, and the cut fiber was placed on the sample table in the contact angle measuring instrument and held horizontally. For one fiber, the contact angles are measured at two different locations. The contact angles of the five fibers are measured to the first decimal place, and the average of the measured values (rounded to the second decimal place) obtained at a total of 10 locations is determined as the contact angle of the fibers with water. The measurement environment is set with an indoor temperature of 22±2°C and a relative humidity of 65±2%.

[0095]

When an absorbent body (absorbent core) as a measurement object is used as a constituent member of another article such as an absorbent article, and is attached to the other constituent member by adhesive, fusion or the like, and the absorbent member is removed for evaluation, the strength of the adhesive adhesion of the fixing part is removed by cooling spray or other methods within such limits as not to affect the contact angle of the fibers, and then the absorbent article is removed. The procedure is common to all measurements in the present description.

[0096]

As the water-absorbent fibers 12F, water-absorbent fibers commonly used as a material constituting an absorbent in this kind of absorbent article can be used. Examples of water-absorbent fibers include natural fibers such as wood pulp fibers, including softwood pulp and hardwood pulp, and non-wood vegetable pulp fibers, including cotton pulp and hemp pulp; modified cellulose fibers such as cationized cellulose and mercerized cellulose; and regenerated fibers such as copper ammonium and rayon, and they can be used alone or as a mixture of two or more of them. As described above, in view of the fact that the main role of the 12F water absorbent fibers is to enhance the ability of the absorbent 4 to absorb liquids, the 12F water absorbent fibers are preferably natural fibers or regenerated fibers (cellulose fibers).

[0097]

In the absorbent body 4, the weight ratio of the fiber bundles 11 and the water-absorbent fibers 12F is not limited to a specific value, and can be appropriately adjusted depending on the types of constituent fibers (synthetic fibers) 11F in the fiber bundles 11 and the water-absorbent fibers 12F and the like. For example, when the constituent fibers 11F in the fiber bundles 11 are thermoplastic fibers (non-water-absorbent, synthetic fibers) and the water-absorbent fibers 12F are water-absorbent cellulose fibers, for reasons related to more certain manifestation of the intended effects of the present invention, the mass fraction ratio of the clusters 11 fibers and 12F water absorbent fibers, the first value (11 fiber clusters)/second value (12F water absorbent fibers) is preferably 20/80 to 80/20, and more preferably 40/60 to 60/40.

[0098]

In the absorbent element 4, the content of fiber clusters 11 is preferably 20% by weight. or more and more preferably 40% of the mass. or more and preferably is 80% of the mass. or less and more preferably 60% of the mass. or less relative to the total dry weight of the absorbent 4.

In the absorbent element 4, the content of water-absorbent fibers 12F is preferably 20% of the mass. or more and more preferably 40% of the mass. or more and preferably is 80% of the mass. or less and more preferably 60% of the mass. or less relative to the total dry weight of the absorbent 4.

[0099]

In the absorbent body 4, the areal density of the fiber bundles 11 is preferably 32 g/m ² or more, and more preferably 80 g/m ² or more, and preferably 640 g/m ² or less, and more preferably 480 g/m ² or less.

In the absorbent body 4, the basis weight of the 12F water absorbent fibers is preferably 32 g/m ² or more, and more preferably 80 g/m ² or more, and preferably 640 g/m ² or less, and more preferably 480 g/m ² or less.

[0100]

The absorbent element 4 can be manufactured in a manner similar to that of an absorbent element containing this type of fibrous material. The fiber aggregation 11 can be obtained as described above by cutting a fibrous material sheet (a sheet having the same composition as the fiber aggregation 11 and having a larger size than the fiber aggregation 11) as a material in two directions that intersect with each other. another (orthogonal to each other) using a cutting means such as a cutter/knife as shown in FIG. The plurality of fiber bundles 11 obtained by the above-described method are "shape-shaped fiber bundles" that have the same shape and size (for example, the main body 110 has the shape of a cuboid). The absorbent body 4 containing the fiber bundles 11 and the water-absorbent fibers 12F can be manufactured, for example, in a conventional manner by using a known fiber depositor having a rotating drum. Such a fiber depositing device typically includes a rotating drum, on the outer peripheral surface of which there is a storage recess, and includes a box having a flow channel for moving raw materials (clusters 11 of fibers, water-absorbent fibers 12F) of an absorbent core 40 k storage recess. When the rotary drum is rotated about the rotation axis in the circumferential direction of the drum, the raw materials conveyed in the air flow (suction air) generated in the flow path by the suction force from the interior of the rotary drum are subjected to stacking of fibers in the storage cavity. . The product in the form of a stack of fibers formed in a storage recess by such a fiber stacking process is an absorbent core 40.

[0101]

The surface density of the absorbent 4 can be adjusted appropriately depending on its intended use or the like. For example, when the absorbent 4 is to be used as the absorbent of an absorbent article such as disposable diapers and sanitary napkins, the absorbent 4 is preferably 100 g/m ² or more, and more preferably 200 g/m ² or more, and is preferably 800 g/m ² or less, and more preferably 600 g/m ² or less. As described above, the above basis weight of the absorbent 4 can be applied to the absorbent core 40 as such.

[0102]

The present invention has been described based on the embodiments, but the present invention can be modified accordingly without being limited to the embodiments.

For example, in the above embodiments, the absorbent member 4 includes an absorbent core 40 and a core wrap sheet 41 covering the absorbent core, but the inclusion of a core wrap sheet 41 is optional.

In the absorbent core according to the present invention, all the fiber bundles (synthetic fiber bundles) contained are optionally shaped fiber bundles such as 11 fiber bundles, and in addition to the shaped fiber bundles, an extremely small amount of fiber bundles can be contained which have an indefinite shape, without departing from the scope of the present invention.

The absorbent article of the present invention covers, in a broad sense, articles used to absorb bodily fluids discharged from the human body (such as urine, liquid feces, menstrual blood and sweat), and includes, in addition to the above-described sanitary napkin, sanitary pants, the so-called disposable open-type diapers with fastening tapes, pull-on disposable diapers, urological pads, and the like. In view of the above embodiments of the present invention, the following aspects are further disclosed.

[0103]

<1> The absorbent body is used when it is in direct or indirect contact with the skin, has a surface that faces the skin and is to be placed relatively close to the skin of the user using the absorbent body, and a surface that is not facing the skin and is to be placed relatively far away from the user's skin, includes fiber aggregations containing synthetic fibers, and includes water-absorbent fibers. In an absorbent member, a plurality of fiber agglomerations are intertwined with each other or with water-absorbent fibers, and the ratio of the mass fraction of fiber aggregations to the mass fraction of water-absorbent fibers is less on the skin-facing side than on the non-skin-facing surface.

<2> The absorbent body according to <1>, wherein the ratio of the mass fraction of fiber accumulations to the mass fraction of water-absorbent fibers gradually increases from the side of the surface facing the skin to the side of the surface not facing the skin.

[0104]

<3> The absorbent body is used when it is in direct or indirect contact with the skin, has a surface that faces the skin and is to be placed relatively close to the skin of the user using the absorbent body, and a surface that is not facing the skin and is to be placed relatively far away from the user's skin, includes fiber aggregations containing synthetic fibers, and includes water-absorbent fibers. In an absorbent member, a plurality of fiber bundles are intertwined with each other or with water-absorbent fibers, and the weight ratio of fiber bundles to the total mass of fiber bundles and water-absorbent fibers is less on the skin-facing side than on the non-skin-facing side (i.e., more on the side of the surface not facing the skin than on the side of the surface facing the skin).

<4> The absorbent member according to <3>, wherein the proportion of the mass of the fiber accumulations of the total mass of the fiber accumulations and the water-absorbent fibers gradually increases from the skin-facing side of the surface to the non-skin-facing surface side.

<5> The absorbent member according to any one of <1> to <4>, in which the proportion of the mass of fiber clusters of the total mass of fiber clusters and water-absorbent fibers is 0% of the mass. or more and 60% of the mass. or less from the side of the surface facing the skin, and the proportion of the mass of accumulations of fibers from the total mass of accumulations of fibers and water-absorbing fibers is 50% of the mass. or more and 100% of the mass. or less from the side of the surface not facing the skin, and the difference between these proportions is 15% of the mass. or more.

<6> Absorbent element according to item <5>, in which this difference is 80% of the mass. or more.

[0105]

<7> The absorbent member according to any one of <1> to <6>, wherein the fiber agglomeration includes a body formed by two opposing base surfaces and a body surface that intersects the base surfaces.

<8> The absorbent member of <7>, wherein the total area of these two base surfaces is larger than the total area of this surface of the body.

<9> The absorbent member as in <7> or <8>, wherein the base surfaces are rectangular in plan view and the length of the short side of the rectangle is equal to or less than the thickness of the absorbent member.

<10> The absorbent member of <9>, wherein the short side length of the base surface is 0.3 mm or more, and preferably 0.5 mm or more, and is 10 mm or less, and preferably 6 mm or less.

<11> The absorbent body according to <9> or <10>, wherein the long side length of the base surface is 0.3 mm or more, and preferably 2 mm or more, and is 30 mm or less, and preferably 15 mm or less.

<12> The absorbent member according to any one of <7> to <11>, wherein the number of fiber ends per unit area on a given body surface is greater than the number of fiber ends per unit area on each of the base surfaces.

<13> The absorbent member according to any one of <7> to <12>, wherein the ratio N ₁ /N _{2 of the} number of N ₁ fiber ends per unit area on the base surface to the number N _{2 of} fiber ends per unit area on that surface of the body is 0 or more and 0.90 or less, and preferably 0.05 or more and 0.60 or less.

<14> The absorbent body according to any one of <7> to <13>, wherein the number of fiber ends per unit area on the base surface is 0 or more and 8 or less, and preferably 3 or more and 6 or less.

<15> An absorbent body according to any one of <7> to <14>, wherein the number of fiber ends per unit area on a given body surface is 5 or more and 50 or less, and preferably 8 or more and 40 or less.

<16> The absorbent member according to any one of <7> to <15>, wherein the fiber agglomeration includes a raised fiber portion that contains fiber protruding outward from the body and has a fiber density that is lower than the fiber density main part.

<17> The absorbent member of <16>, wherein at least one of the raised fiber portions is a raised fiber bundle protruding outward from a given surface of the body and containing a plurality of fibers.

[0106]

<18> The absorbent body according to any one of <1> to <17>, wherein the skin-facing side of the surface contains a water-absorbent polymer.

<19> The absorbent member according to any one of <1> to <18>, wherein the first value/second value weight ratio of fiber clumps and water absorbent fibers is 20/80 to 80/20.

<20> The absorbent member according to any one of <1> to <19>, wherein the synthetic fibers contained in the fiber aggregations are non-absorbent fibers.

<21> The absorbent member according to any one of <1> to <20>, wherein the water-absorbent fibers are water-absorbent cellulose fibers.

<22> An absorbent member according to any one of <1> to <21>, wherein the fiber aggregations have a water contact angle of less than 90 degrees and preferably 70 degrees or less.

<23> The absorbent body of <22>, in which the fiber aggregations have been treated with a hydrophilizing agent.

<24> The absorbent member according to any one of <1> to <23>, wherein the absorbent member includes an absorbent core and a core wrap sheet.

<25> An absorbent member according to any one of <1> to <24>, wherein in the absorbent member, the clumps of fibers are connected to each other or to the water-absorbent fibers by means of weaving, and capable of being intertwined with each other or with the water-absorbent fibers.

<26> The absorbent body according to <25>, wherein the total amount of fiber bundles connected by weaving and fiber bundles capable of being weaved is preferably 50% or more, more preferably 70% or more, and even more preferably 80% or more of the total number of fiber accumulations in the absorbent element.

<27> An absorbent member according to any one of <1> to <26>, wherein preferably 70% or more, more preferably 80% or more of the fiber bundles having a portion in which they are bonded to each other or to the water-absorbent fibers are bonded through fiber interlacing.

<28> The absorbent member according to any one of <1> to <27>, wherein the fiber aggregations are made from a nonwoven fabric.

<29> An absorbent article comprising an absorbent according to any one of <1> to <28>.

Examples

[0107]

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

[Example 1]

A sanitary napkin having substantially the same basic configuration as the napkin 1 shown in FIG. 1 was prepared.

As the top sheet, a through-air-bonded non-woven fabric having a basis weight of 30 g/m ^{2 was used} , and as a back sheet, a polyethylene film having a ^{basis weight of 37 g/m 2} (FL-KDJ100nN manufactured by Daika Kogyo) was used. Co., Ltd.). The absorbent body was manufactured in a conventional manner by a known fiber stacker using fiber aggregations and water absorbent fibers as the fibrous materials of the absorbent core and using a separately prepared tissue paper sheet to wrap the core and having a basis weight of 16 g/m ² . The fibrous sheet of material was cut into cubes in accordance with FIG. 6 to obtain fiber agglomerations. The arrangement of the fibrous materials (fiber aggregates, water-absorbent fibers) in the absorbent body of Example 1 was such that the degree of fiber accumulation or the proportion of fiber accumulations gradually increased from the skin-facing side of the absorbent surface to the non-skin-facing side of the surface, as in the case of the absorbent element 4 shown in Fig.3.

As the fiber sheet material for fibers clusters was used a nonwoven fabric bonded by passing air through, having a weight of 21 g / m ² (fibrous sheet having a part of the constituent fibers, fusion bonding), containing as constituent thermoplastic fiber filaments, not absorbent water, which were formed from polyethylene and polyethylene terephthalate resins and treated with composition A, described below (with a water contact angle of 68 degrees). Bleached softwood kraft pulp (NBKP) fibers were used as water-absorbing fibers. The fiber agglomerations (collections of synthetic fibers having a specific shape) used in the absorbent body had a main body having a cuboid shape as shown in FIG. 5(a). The length of the short side 111a of the base surface 111 was 0.8 mm, the length of the long side 111b was 3.9 mm, and the thickness T was 0.6 mm. At base surface 111, the number of fiber ends per unit area was 3.2 fiber ends per mm ² , and at base surface 112, the number of fiber ends per unit area was 19.2 fiber ends per mm ² .

[0108]

(Composition composition A)

- Potassium salt of alkyl phosphate (obtained by neutralizing Gripper 4131 manufactured by Kao Corporation with potassium hydroxide): 25 wt.

- Sodium salt of dialkyl sulfosuccinate (Pelex OT-P, manufactured by Kao Corporation): 10 wt.

- Alkyl (stearyl) betaine (Amphitol 86B, manufactured by Kao Corporation): 15% wt.

- Polyoxyethylene (number of moles added: 2)-stearylamide (Amisol SDE, manufactured by Kawaken Fine Chemicals Co., Ltd.): 30 wt.

- Polyoxyethylene-polyoxypropylene modified silicone (X-22-4515, manufactured by Shin-Etsu Chemical Co., Ltd.): 20 wt.

[0109]

[Example 2]

The same procedure was followed as in Example 1, except that the arrangement of the fibrous materials (fiber clumps, water-absorbent fibers) in the absorbent body was such that two parts differing in the degree of fiber clump filling or the proportion of fiber clumps were placed in thickness direction as in the case of the absorbent 4A shown in FIG. 4, resulting in the sanitary napkin of Example 2. as the side of the surface facing the skin, and the portion 11P with increased fiber accumulations as the side of the surface not facing the skin. Parts 12P and 11P were connected to each other at the interface between them by weaving constituent fibers, and the interface is at the center of the absorbent member, defined in the thickness direction.

[0110]

[Example 3]

The same procedure was followed as in Example 2, except that in the absorbent element, the portion 12P with increased content of water-absorbent fibers had a fiber clump density of 0% by mass, or the skin side of the surface of the absorbent element had a content of of water-absorbent fibers of 100 wt. wt., resulting in a sanitary napkin according to Example 3.

[0111]

[Example 4]

The fiber agglomeration of Example 3 was modified to have a base surface 111 having a short side 111a with a length of 0.8 mm and a long side 111b with a length of 5.0 mm, and had a thickness of 0.6 mm. In this modified fiber agglomeration, the number of fiber ends per unit area was the same as in Example 2. The same absorbent as in Example 3, except for the above points, was used to make the sanitary napkin as Example 4.

[0112]

[Comparative Example 1]

An absorbent body of a commercially available and commercially available sanitary napkin (manufactured by Unicharm Corporation, trade name “Tanom Pew Slim 23 cm”) was used as Comparative Example 1. The absorbent body of Comparative Example 1 is a mixture of synthetic fibers and cellulose fibers ( water-absorbing fibers) and does not contain clumps of fibers.

[0113]

[Comparative Example 2]

The same procedure as in Example 1 was carried out, except that the absorbent member was changed to the following member according to Patent Literature 1, resulting in a sanitary napkin as Comparative Example 2.

The absorbent member used in Comparative Example 2 was the same as the absorbent member used in Example 1, except that pieces of nonwoven material having an indefinite shape were used as fiber agglomerations in the absorbent core, and the absorbent core was closed sheet to wrap the core, and thereafter was treated with hot air to bond the pieces of nonwoven material contained in the absorbent core to each other by fusion. During the hot air treatment to which the absorbent body was subjected, it was possible to keep the accumulation (length 210 mm x width 66 mm), which is a mixture of pieces of non-woven material and cellulose fibers, in an electric dryer (for example, manufactured by Isuzu Seisakusho) at a temperature of 150 ° C for 600 seconds, and the pieces of non-woven fabric were subjected to bonding to each other by fusion. The used nonwoven fabric pieces having an undefined shape were obtained by tearing the same nonwoven fabric bonded by passing air through as the nonwoven fabrics used in Examples 1 and 2 in all directions, and the nonwoven fabric pieces had a plan view size of approximately 25 mm.

[0114]

[Performance Rating]

The compressive working load/wet compressive force (w-WC), curl degree, and surface diffusion area for each sanitary napkin of the Examples and Comparative Examples were determined by the following methods. For Example 4, the dry recovery workload (d-WC') and dry compression strain (d-DT/T ₀ ) were also determined by the methods below. The results are shown in Table 1.

[0115]

<Compression Workload (WC) Determination Method/Compression Force>

It is widely known that the compressive working load (WC) of a sample can be represented by a value measured with a Kawabata scoring system (KES) manufactured by Kato Tech Co., Ltd. (reference literature: The Standardization and Analysis of Texture Evaluation (2nd edition), by Sueo Kawabata, July 10, 1980). In particular, the KES-G5 automatic compression testing machine manufactured by Kato Tech Co., Ltd. was used to determine the compression workload (WC)/compression force and compression recovery ratio (RC). Measurement techniques are as described below.

"Absorbent article with absorbent body (sanitary napkin)" as a sample is attached to a test stand provided in the compression testing machine. Next, the sample is pressed between steel plates, each of which has a round flat surface with an area of 2 cm ² . The compression rate is set to 0.02 cm/s and the maximum compressive load is set to 490 mN/cm ² . During the recovery process, the measurement was performed at the same speed. The compression workload (WC)/compression force is represented by (-o) by the equation below, and the unit is "mN⋅cm/cm ² ". In the equation, T _m , T ₀ and P _a are respectively the thickness under load of 490 mN/cm ² , the thickness under load of 4.9 mN/cm ² and the load (mN/cm ² ) during the measurement (compression process).

The compressive workload calculated in the above manner is the wet compressive workload/force of the specimen (w-WC). A sample with a higher w-WC value is considered to have a higher springback capability and is highly rated.

[0116]

[Math expression 1]

[0117]

"Absorbent article with absorbent body in wet state" as the object of measurement in the measurement method is prepared in accordance with the following procedure. First, the absorbent article is allowed to stand before the introduction of defibrinated horse blood in an environment with a temperature of 23°C and a relative humidity of 50% for 24 hours, and the absorbent article is prepared in a dry state. The absorbent article in the dry state is placed horizontally so that the top sheet (surface facing the skin) is (s) facing up, and on the top sheet is placed an elliptical inlet element (with a major axis length of 50 mm and a length minor axis, which is 23 mm). 3.0 g of defibrinated horse blood is injected from the inlet element, after which the product is allowed to stand for 1 minute, and then 3.0 g of defibrinated horse blood is additionally injected. After injection, this state is maintained for 1 minute to obtain an absorbent article with an absorbent member in a wet state. The defibrinated horse blood injected into the measurement object is the same as that prepared in the <Surface Diffusion Area Determination Method> described later.

[0118]

<Workload Detection Method (WC’) in Recovery>

The workload (WC') at sample recovery can be determined by using the KES described above. In particular, the KES-G5 Automatic Compression Testing Machine manufactured by Kato Tech Co., Ltd. was used to determine the working load (WC') in reconditioning. The measurement procedure is as described below.

"Absorbent article with absorbent body (sanitary napkin)" as a sample is attached to a test stand provided in the compression testing machine. Next, the sample is pressed between steel plates, each of which has a round flat surface with an area of 2 cm ² . The compression rate is set to 0.2 cm/s and the maximum compressive load is set to 2450 mN/cm ² . During the recovery process, the measurement was performed at the same speed. The working load (WC') in recovery is represented by the equation below, and the unit is "mN∙cm/cm ² ". In the equation, T _m , T ₀ and P _b are respectively the thickness under load of 2450 mN/cm ² , the thickness under load of 4.9 mN/cm ² and the load (mN/cm ² ) during the measurement (recovery process).

[0119]

[Math expression 2]

[0120]

The recoil workload (WC') is not displayed on the test results screen of the KES-G5 machine, and the compression recovery rate (RC) calculated from the compressive workload (WC)/thrust is displayed on the test results screen compression and workload (WC') on recovery. In such a case, the parameters (WC, RC) displayed by the measuring device are used to calculate the recovery workload (WC') according to the expression below.

[0121]

[Math expression 3]

[0122]

"Dry Recovery Working Load (d-WC')" is determined using "Dry Absorbent Article (sanitary napkin)" as a reference in <Recovery Working Load (WC') Method>. An absorbent body included in an absorbent article in a dry state is an unused absorbent element, does not absorb any liquid and is in a dry state. According to the studies performed by the present inventors, an absorbent body in a dry state having a higher d-WC' value is regarded as having a higher compression recovery capability and is highly rated.

[0123]

<Method for determining the degree (DT/T ₀ ) of compression deformation>

The degree (DT/T ₀ ) of deformation under compression of the sample can be determined by using the KES described above. In particular, the KES-G5 automatic compression testing machine manufactured by Kato Tech Co., Ltd. was used to determine the degree (DT/T ₀ ) of compression deformation. The measurement procedure is as described below.

"Absorbent article with absorbent body (sanitary napkin)" as a sample is attached to a test stand provided in the compression testing machine. Next, the sample is compressed between steel plates, each having a round flat surface with an area of 2 cm ² , and the compressive load is gradually increased. When the load reaches a predetermined maximum value (maximum load), the thickness T _m (compressive thickness) of the object to be measured is determined. It should be noted that the measurement object does not have wrinkles or folds. The measurement conditions in the compression test machine are as described below.

- Compression speed: 0.2 mm/s

- Maximum load of 2450 mN / cm ²

- SENS: 10

- DEF: 20

The initial thickness (T ₀ ) of the measurement object is determined at a load of 103.9 mN/cm ² . The compression strain rate (%) is calculated according to the following expression.

The degree of deformation during compression (DT / T ₀ ) \u003d {(T ₀ - T _m ) / T ₀ )} H 100

[0124]

The “dry compression deformation degree (d-DT/T ₀ )” is determined using the “dry absorbent article (sanitary napkin)” as a reference in the <Compression deformation degree (DT/T ₀ ) determination method>. An absorbent member included in an absorbent article in a dry state is an unused absorbent member, does not absorb any liquid, and is in a dry state. According to the studies performed by the present inventors, an absorbent element in the dry state having a higher d-DT/T ₀ value is considered to have a higher resiliency and is highly rated.

[0125]

In the measurement mode for determining d-WC' and d-DT/T _{0, the} speed was 10 times faster than in the normal mode of the KES-G5 machine. According to research carried out by the present inventors, this measurement mode more accurately mimics the wearer's movement, such as walking and sitting down.

[0126]

<Twisting Degree Method>

The degree of curling of the sanitary napkin was evaluated using a driven human body model corresponding to the lower half of the female body. First, the center width (lateral direction dimension at the center of the pad determined in the longitudinal direction) (width at the center before walking) was determined for the pad as the object of measurement, and the pad was attached to the underpants that were attached to the female body model. Further, the human body model was allowed to walk at a speed of 100 steps per minute for 30 minutes. After walking for 3 minutes, 1.5 g of defibrinated horse blood was injected into the attached pad over 15 seconds. This operation was repeated 6 times while walking the human body model, and defibrinated horse blood with a total of 9 g was injected into the pad. Thereafter, the pad was detached from the underpants, and the width at the center (width at the center after walking) was determined. The degree (%) of twisting was calculated from the width at the center before walking and the width at the center after walking according to the following expression. A gasket having a lower curl degree value is unlikely to curl, and such a gasket is highly rated. The defibrinated horse blood injected into the measurement object is the same as that prepared in the <Surface Diffusion Area Determination Method> described later.

Degree of twist = [{(width at center before stepping) -(width at center after stepping)}/(width at center before stepping)] × 100

[0127]

<Surface diffusion area determination method>

On an inclined surface located at an angle of 45° relative to the horizontal plane, the measurement object (sanitary napkin) is fixed, while its surface facing the skin is facing the inclined surface. From the side of the surface of the measurement object facing the skin, 1.5 g of defibrinated horse blood is injected in 23 seconds, after which the measurement object is allowed to stand for 3 minutes, and the same amount of defibrinated horse blood is injected from the same place for the same time . This operation of injecting defibrinated horse blood and standing is repeated 6 times, and defibrinated horse blood with a total amount of 9 g is injected into the measurement object. measurement object.

[0128]

The above <Surface diffusion area determination method> will be specifically described with reference to FIG. The measurement object S (sanitary napkin) has a quadrangular shape with dimensions of 240 mm x 75 mm in plan view. The measurement table 100 used for measurement has an inclined surface 100a at an angle Ɵ of 45° with respect to the horizontal plane. The measurement object S is placed on the inclined surface 100a so that its skin-facing surface faces the inclined surface 100a, and an acrylic plate 101 having a thickness of 3 mm and an area larger than the area of the measurement object S is placed on the measurement object S. The defibrinated horse blood injected as pseudo-blood into the measurement object S has a viscosity of 8 mPa·s determined by using a Brookfield viscometer (manufactured by Toki Sangyo, type TVB-10M, measurement conditions: No. 19 rotor, 30 rpm, 25° C, within 60 seconds). As such defibrinated horse blood, for example, defibrinated horse blood manufactured by Nippon Bio-test Laboratories Inc. can be used, and the viscosity can be adjusted to the above predetermined range, if necessary, by adjusting the ratio of cells to blood to plasma. The injection site of the defibrinated horse blood on the measurement object S is the center of the surface of the measurement object S facing the skin (this position is indicated by an arrow in Fig. 8), and the injection is performed using a micro-tubing pump (manufactured by TOKYO RIKAKIKAI Co., Ltd.) (not shown). A tube (not shown) is connected to the pump, and the end of the tube opposite the end connected to the pump is connected to the measurement object S on the inclined surface 100a. Defibrinated horse blood is injected through the tube into the measurement object S. The diffusion area of the defibrinated horse blood on the skin-facing surface of the measurement object S can be determined as follows: the distribution area of the defibrinated horse blood on the measurement object S is copied on an overhead projector (OHP) film sheet, and the OHP film sheet is processed in a well-known manner through the NexusNewQube image analysis software (manufactured by Nexus).

[0129]

[Table 1]

Example Comparative Example one 2 3 4 one 2 Presence or absence of fiber accumulations Availability Availability Availability Availability Absence Availability Method of connection between clusters of fibers weave weave weave weave - Fusion connection The outer form of the accumulation of fibers definite shape definite shape definite shape definite shape - indefinite form Fiber Cluster Dimensions (mm)
(short side × long side of reference surface) 0.8×3.9 0.8×3.9 0.8×3.9 0.8×5 - 25 ^*1 The state of distribution of fiber clusters in the absorbent element Localized from the side of the surface, not facing the skin (figure 3) Localized from the side of the surface, not facing the skin (figure 4) Localized from the side of the surface, not facing the skin (figure 4) Localized from the side of the surface, not facing the skin (figure 4) Evenly distributed in the absorbent element Evenly distributed in the absorbent element The degree A of the filling of the accumulations of fibers from the side of the surface of the absorbent element facing the skin (% wt.) 10 10 0 0 0 50 Degree B of fiber accumulation on the non-skin side of the absorbent body (wt. %) one hundred 90 one hundred one hundred 0 50 Degree B filled with accumulations of fibers -
degree A of fiber accumulation (wt. %) 90 80 one hundred one hundred 0 0 Surface density of fiber clusters (g/m ² ) 175 175 175 175 116 175 Surface density of water-absorbing fibers (g/m ² ) 175 175 175 175 116 175 Absorbent thickness (mm) 5.7 5.7 5.7 5.7 2.8 5.7 Grade w-WC (mN⋅cm/cm ² ) 90.2 85.3 90.2 90.3 22.1 64.7 Twisting degree (%) nineteen 23 nineteen 23 40 25 Surface diffusion area (cm ² ) 34.4 34.4 34.4 30.5 34.7 62.0 d-WC' (mN⋅cm/cm ² ) / / / 225.4 / / d-DT/T ₀ (%) / / / 64.6 / /

*1: Average size of fiber clusters with indeterminate shape

[0130]

As shown in Table 1, each example in which a plurality of fiber bundles are interwoven with each other or with water-absorbent fibers and the filling degree of the fiber bundles satisfies the non-skin surface side > skin-facing surface side ratio has a larger working load w-WC in wet compression than the products of Comparative Examples 1 and 2, which do not meet these conditions, and therefore have a very good resilience. In addition, each example has a small degree of twisting, therefore, it is unlikely to curl, and it has a very good ability to draw liquids due to the above value ratio. In particular, a comparison of each example with Comparative Example 2 shows that, in order to obtain an absorbent body having a high compressive workload and a very good resiliency even when wet, it is advantageous to use fiber bundles having a certain shape and connect the fiber bundles to each other. another through weaving.

Industrial Applicability

[0131]

The absorbent body of the present invention has a high resiliency, is unlikely to curl, has a very good ability to draw liquids, and can provide an increase in wearing comfort when included in an absorbent article.

The absorbent article of the present invention includes such a high-quality absorbent member and therefore provides very good wearing comfort and very good leakage protection performance.

Claims (36)

1. Absorbent element used in direct or indirect contact with the skin and having a surface that faces the skin and is to be placed relatively close to the skin of the user using the absorbent element, and a surface that is not facing the skin and is to be placed relatively far away from the skin of the user, while the absorbent element contains: fiber aggregations containing synthetic fibers; and water-absorbing fibers a plurality of clumps of fibers are intertwined with each other or with water-absorbent fibers, and the ratio of the mass fraction of fiber accumulations to the mass fraction of water-absorbing fibers is less on the side of the surface facing the skin than on the side of the surface not facing the skin. 2. An absorbent body according to claim 1, wherein the ratio of the mass fraction of fiber accumulations to the mass fraction of water-absorbent fibers gradually increases from the skin-facing side of the surface to the non-skin-facing side of the surface. 3. Absorbent element used in direct or indirect contact with the skin and having a surface that faces the skin and is to be placed relatively close to the skin of the user using the absorbent element, and a surface that is not facing the skin and is to be placed relatively far away from the skin of the user, while the absorbent element contains: fiber aggregations containing synthetic fibers; and water-absorbing fibers a plurality of clumps of fibers are intertwined with each other or with water-absorbent fibers, and the proportion of the mass of fiber aggregations to the total mass of agglomerations of fibers and water-absorbing fibers is greater on the side of the surface not facing the skin than on the side of the surface facing the skin. 4. An absorbent body according to claim 3, wherein the proportion of the weight of the fiber aggregations to the total mass of the aggregations of fibers and the water-absorbent fibers gradually increases from the skin-facing side of the surface to the non-skin-facing side of the surface. 5. Absorbent element according to claim. 1 or 3, in which the proportion of the mass of clusters of fibers from the total mass of clusters of fibers and water-absorbing fibers is 0% of the mass. or more and 60% of the mass. or less from the side of the surface facing the skin, and the proportion of the mass of fiber clusters of the total mass of fiber clusters and water-absorbing fibers is 50% of the mass. or more and 100% of the mass. or less from the side of the surface not facing the skin, and the difference between these shares is 15% of the mass. or more. 6. Absorbent element according to claim 5, in which the difference is 80% of the mass. or more. 7. Absorbent body according to claim 1 or 3, wherein the collection of fibers includes a body formed by two opposing base surfaces and a body surface that intersects the base surfaces. 8. An absorbent body according to claim 7, wherein the total area of the two base surfaces is greater than the total surface area of the body. 9. An absorbent member as claimed in claim 7, wherein the base surfaces are rectangular in planar form and the short side of the rectangle is equal to or less than the thickness of the absorbent member. 10. An absorbent member as claimed in claim 7, wherein the number of fiber ends per unit area on the body surface is greater than the number of fiber ends per unit area on each of the base surfaces. 11. Absorbent element according to claim 7, in which the ratio N ₁ /N _{2 of the} number of N ₁ fiber ends per unit area on the base surface to the number N ₂ fiber ends per unit area on the body surface is 0 or more and 0.90 or less. 12. An absorbent body according to claim 11, wherein the N ₁ /N ₂ ratio is 0.05 or more and 0.60 or less. 13. An absorbent member according to claim 7, wherein the number of fiber ends per unit area on the base surface is 0 or more and 8 or less. 14. An absorbent body according to claim 7, wherein the number of fiber ends per unit area on the body surface is 5 or more and 50 or less. 15. The absorbent body of claim 7, wherein the fiber aggregation includes a raised fiber portion that contains fiber projecting outward from the body and has a lower fiber density than the body body. 16. The absorbent member of claim 15, wherein at least one of the raised fiber portions is a bundle of raised fibers projecting outward from the surface of the body and comprising a plurality of fibers. 17. An absorbent body according to claim 1 or 3, wherein the skin side of the surface contains a water-absorbent polymer. 18. Absorbent body according to claim 1 or 3, wherein the first/last weight ratio of fiber clumps and water-absorbent fibers is between 20/80 and 80/20. 19. An absorbent body according to claim 1 or 3, wherein the synthetic fibers contained in the fiber bundles are non-absorbent fibers. 20. An absorbent body according to claim 1 or 3, wherein the water-absorbent fibers are water-absorbent cellulose fibers. 21. Absorbent body according to claim 1 or 3, wherein the fiber aggregations have a water contact angle of less than 90 degrees. 22. An absorbent body according to claim 21, wherein the fiber aggregations have been treated with a hydrophilizing agent. 23. An absorbent member according to claim 1 or 3, wherein the absorbent member includes an absorbent core and a core wrap sheet. 24. Absorbent element according to claim 1 or 3, wherein in the absorbent element, the clumps of fibers are connected to each other or to the water-absorbent fibers by means of weaving and are able to intertwine with each other or with the water-absorbent fibers. 25. The absorbent body of claim 24, wherein the total amount of tangled fiber aggregations and tangle-able aggregations is 50% or more of the total amount of tangled fiber aggregations in the absorbent element. 26. An absorbent body according to claim 1 or 3, wherein 70% or more of the fiber bundles having a portion in which they are bonded to each other or to the water-absorbent fibers are bonded by weaving the fibers. 27. Absorbent element according to claim 1 or 3, in which the clusters of fibers are obtained from a nonwoven material. 28. An absorbent article comprising an absorbent element according to any one of claims 1 or 3.

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