RU2769865C2 - Absorbing element and absorbing product - Google Patents

Abstract

FIELD: absorbing products.SUBSTANCE: absorbing element (4), according to the present invention, includes: fiber accumulations (11) containing synthetic fibers (11F) and absorbing fibers (12F). Multiple fiber accumulations (11) are mixed with each other, or fiber accumulations (11) and absorbing fibers (12F) are mixed. Each of fiber accumulations (11) includes main part (110) formed by means of two opposite base surfaces (111) and that surface (112) of the main part that crosses two base surfaces (111). Synthetic fibers (11F) contain a hydrophilizing agent. In addition, absorbing product (1), according to the present invention, includes above-described absorbing element (4), according to the present invention.EFFECT: obtaining an absorbing product.24 cl, 7 dwg

Description

The field of technology to which the invention belongs

[0001]

The present invention relates to an absorbent element for use in an absorbent article.

Prior Art

[0002]

An absorbent article, such as a disposable diaper or sanitary napkin, typically consists of a topsheet positioned relatively close to the wearer's skin, a backsheet positioned relatively far from the wearer's skin, and an absorbent member, located between the top sheet and the back sheet. As a rule, the absorbent body consists mainly of hydrophilic fibers (absorbent fibers), such as wood pulp fibers, and often also includes absorbent polymer particles. An absorbent body for use in an absorbent article has major problems in terms of improving various properties such as resiliency (springiness), resilience and shape retention.

[0003]

A technical solution for improving an absorbent body is disclosed in, for example, Patent Literature 1. Patent Literature 1 discloses an absorbent body that is composed primarily of cellulose fibers and absorbent polymers, with hydrophobic fibers that have a fiber length that is greater than that of cellulose fibers, for example, synthetic fibers made from polypropylene, which are not hydrophilized, are dispersed in cellulose fibers. According to Patent Literature 1, in the absorbent element, due to the presence of hydrophobic fibers, there is no flow of body fluid in the opposite direction. In addition, hydrophobic fibers, which have longer fibers, are entangled with cellulose fibers, and therefore strength is improved and good shape retention can be maintained.

[0004]

In addition, Patent Literature 2 discloses an absorbent body which is mainly composed of cellulose fibers and absorbent polymers, wherein hydrophilic long fibers having a fiber length that is greater than the length of cellulose fibers, such as rayon, cotton, wool, hemp, or the like. similar, dispersed in cellulose fibers. According to Patent Literature 2, in the absorbent member, the shape can be stably maintained before and after absorption of body fluid. Because the hydrophilic long fibers are dispersed without being subjected to heat treatment, a suitable texture is maintained throughout the absorbent member and the likelihood of bodily fluid absorption is less likely to be obstructed.

[0005]

In addition, Patent Literature 3 discloses an absorbent member including pieces of nonwoven fabric that are formed from thermofusible fibers and have a three-dimensional structure formed by bonding the fibers in advance, and hydrophilic fibers. 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. Due to this manufacturing method, the absorbent body has an indefinite shape like that shown in FIGS. 1 and 3 of Patent Literature 3 and essentially has no part that can be considered as a flat surface. Patent Literature 3 discloses an absorbent member according to a preferred embodiment in which pieces of nonwoven material are heat-fused. In the absorbent body disclosed in Patent Literature 3, the nonwoven pieces have a three-dimensional structure, empty spaces are formed inside the absorbent body, and moisture-absorption recovery property is improved. As a result, moisture absorption is improved.

[0006]

In addition, Patent Literature 4 discloses a small size lap that includes a relatively dense core of fine fibers and fibers or fiber bundles protruding outward from the core, wherein a nonwoven web obtained by bonding the small size lap with wood pulp and particles absorbent polymer, can be used as an absorbent element intended for use in an absorbent article. A web of small size is obtained by fraying or tearing a sheet of starting material, such as a nonwoven fabric. Accordingly, as with the nonwoven pieces disclosed in Patent Literature 3, it has an indefinite shape and essentially no part that can be considered as a flat surface.

Link List

Patent Literature

[0007]

Patent Literature 1: JP 2004-73698A

Patent Literature 2: JP H6-98909A

Patent Literature 3: JP 2002-301105A

Patent Literature 4: JP H1-156560A

The essence of the invention

[0008]

The present invention relates to an absorbent member including: fiber bundles containing synthetic fibers and absorbent fibers, wherein a plurality of fiber bundles are entangled with each other, or fiber bundles and absorbent fibers are entangled. Each of the fiber clusters includes a body formed by two opposing base surfaces and a body surface that intersects the two base surfaces. Synthetic fibers contain a hydrophilizing agent.

The present invention also relates to an absorbent article including an absorbent element according to the present invention.

Brief description of the drawings

[0009]

[Fig. 1] Fig. 1 is a partially cut away, schematic plan view of a skin-facing surface side (top sheet side) of an example of a sanitary napkin, which is an embodiment of an absorbent article according to the present invention.

[FIG. 2] FIG. 2 is a schematic cross section taken along line I-I shown in FIG.

[FIG. 3] FIG. 3 is a schematic perspective view of a portion of an absorbent core included in the absorbent article shown in FIG.

[Figure 4] Figure 4 is a schematic representation of the absorbent core shown in Figure 3 in a deformed state under compression.

[FIG. 5] FIGS. 5(a) and 5(b) are schematic perspective views of main parts of fiber bundles according to the present invention.

[Fig. 6] Fig. 6 is a schematic diagram illustrating a method for producing fiber aggregations according to the present invention.

[Fig. 7] Fig. 7(a) is an electron microscope image (acquired at 25× magnification) of an example of a fiber aggregation according to the present invention, and Fig. 7(b) is a schematic image schematically showing a aggregation of fibers shown in the image obtained by means of an electron microscope, as a cluster of fibers included in the absorbent element shown in Fig.2.

Description of Embodiments

[0010]

Both absorbent elements disclosed in Patent Literature 1 and 2 contain, in addition to cellulose fibers such as wood pulp fibers, synthetic fibers or hydrophilic long fibers such as rayon. Accordingly, they are stiffer than an absorbent that only includes cellulose fibers as a constituent fiber, whereby improvements in various properties such as resilience and compression recovery can be expected. However, each of the plurality of synthetic fibers included in the absorbent body is present independently, and therefore they do not form one separate, common agglomeration. Accordingly, the effect of improving various properties is insufficient. For this reason, when an absorbent is used in an absorbent article, it may soon become curled up and may not fit well, and such problems occur especially after absorption of bodily fluid such as urine or menstrual blood.

[0011]

On the other hand, in both absorbent members disclosed in Patent Literature 3 and 4, the synthetic fibers contained therein are accumulations of synthetic fibers called nonwoven pieces, small size laps, and so on. Accordingly, improvement in springback property and the like can be expected. However, as described above, the clumps of synthetic fibers included in the absorbent members disclosed in Patent Literature 3 and 4 are obtained by cutting a nonwoven fabric composed mainly of synthetic fibers into small pieces or by fraying or tearing the nonwoven fabric. Accordingly, the shape is indefinite, and the shape and dimensions are not the same. For this reason, when synthetic fiber aggregations are used together with cellulose fibers or the like, it is difficult to uniformly mix synthetic fiber aggregations and cellulose fibers, and a desired effect may not be achieved. In addition, when all of the synthetic fiber agglomerates included in the absorbent are thermally bonded, as in the preferred embodiment of the absorbent of Patent Literature 3, movement of the aggregations of synthetic fibers is limited, resulting in an increase in the hardness of the absorbent as a whole, and may deteriorate various characteristics such as elasticity.

[0012]

Accordingly, the present invention relates to an absorbent body which has very good resilience and resilience, is capable of being elastically deformed by an external force, and can provide improved wearing comfort when the absorbent body is applied to an absorbent article, and to an absorbent article. , which includes this absorbent element.

[0013]

Hereinafter, the absorbent according to the present invention and the absorbent article according to the present invention, which includes this absorbent element, will be described by means of a preferred embodiment with reference to the drawings. 1 and 2 show a sanitary napkin 1 which is an embodiment of an absorbent article according to the present invention. The liner 1 includes an absorbent member 4 that absorbs and retains a body fluid permeable to liquids, a topsheet 2 that is located on the skin side of the absorbent member 4 and can come into contact with the wearer's skin, and a liquid-impermeable backsheet 3 which is located on the non-skin side of the surface of the absorbent member 4. As shown in FIG. 1, the pad 1 has a longitudinal direction X, which corresponds to the direction from the front side to the back side of the wearer and extends from the abdominal side to the back side of the wearer through the crotch portion, and a lateral direction Y, which is orthogonal to the longitudinal direction X, and can be divided into three zones: zone B, central in the longitudinal direction, which includes a part facing the excretory part (excretion site), while the part facing the excretory part faces the excretory part, such as the external female genital organs carrier, in the longitudinal direction X; an anterior zone A, which is located on the abdominal side (front side) of the wearer with respect to the part facing the excretory part, and a rear zone C, which is located on the back side (rear side) of the wearer with respect to the part facing the excretory part.

[0014]

In the description of the present application, the term "skin-facing surface" refers to the surface of an absorbent article or its constituent element (for example, absorbent element 4), which is provided to face the wearer's skin when the absorbent article is worn, or, in other words, to a surface that is relatively close to the wearer's skin. The term "non-skin-facing surface" refers to the surface of an absorbent article, or a constituent thereof, that is provided to face away from the wearer's skin when the absorbent article is worn, or in other words, to a surface that is relatively away from the wearer's skin. In the context of this document, the expression "when wearing an absorbent article" means the normal and proper position when worn, or, in other words, the state in which the correct position of the absorbent article is maintained when worn.

[0015]

As shown in FIG. 1, the napkin 1 includes an absorbent body 5 which has a shape elongated in the longitudinal direction X, and two wings 5W and 5W which protrude outward in the lateral direction Y, respectively, from opposite sides of that area B of the absorbent of the main body 5 which is central in the longitudinal direction X. The absorbent body 5 is the body part of the napkin 1 and includes the topsheet 2, the backsheet 3 and the absorbent 4 described above, and can be divided into three zones in the longitudinal direction X: the front zone A, the zone B, the center in the longitudinal direction, and the rear zone C.

[0016]

The zone of the absorbent article according to the present invention, centered in the longitudinal direction, in the case where the absorbent article has winged parts, as in the napkin 1, is the zone that has winged parts in the longitudinal direction (length direction, X direction in the diagram) of the absorbent article , and, taking the gasket 1 as an example, is the area between the attachment area of one wing portion 5W extending in the longitudinal direction X and the attachment area of the other wing portion 5W extending in the longitudinal direction X. In the case where the absorbent article does not have wings, the area centered in the longitudinal direction is the zone located in the middle when the absorbent article is divided into three equal parts in the longitudinal direction.

[0017]

In the napkin 1, the absorbent member 4 includes a liquid-absorbing core 40 and a liquid-pervious core wrap sheet 41 that covers the outer surface of the absorbent core 40. As seen in the plan view of FIG. 1, the absorbent core 40 has shape elongated in the longitudinal direction X, as is the absorbent body 5. The longitudinal direction of the absorbent core 40 coincides with the longitudinal direction X of the pad 1, and the width direction of the absorbent core 40 coincides with the lateral direction Y of the pad 1. The absorbent core 40 and the wrap sheet 41 the cores may be joined by an adhesive such as a hot melt adhesive. The absorbent member 4 optionally includes a core wrap sheet 41 . In this case, the absorbent core 40 is used in the absorbent article as the absorbent element 4.

[0018]

As described above, the absorbent 4, which is an embodiment of the absorbent according to the present invention, is included in an absorbent article such as a napkin 1, and is used by bringing it into indirect contact with human skin, or in other words, by bringing it into indirect contact. contact with human skin through a member such as a top sheet 2. The absorbent member 4 has a skin-facing surface and a non-skin-facing surface which is located on the opposite side, has a longitudinal direction X, which corresponds to the direction from the front side to the back side of the pad wearer 1 and a lateral direction Y orthogonal to the longitudinal direction X, and can be divided into three zones in the longitudinal direction X, these three zones being the front zone A, the zone B, the center in the longitudinal direction, and the rear zone C. Absorbent element 4 can be used by putting it in direct contact act with human skin instead of putting into indirect contact with human skin.

[0019]

In the napkin 1, the core wrap sheet 41 is one continuous sheet with a width that is two times or more and three times or less the length of the absorbent core 40 in the lateral Y direction. As shown in FIG. 2, the core wrap sheet 41 covers the skin-facing surface of the absorbent core 40 throughout its entire length and extends outward in a lateral Y direction from two side edges of the absorbent core 40 that extend in the longitudinal X direction. core 40 along its entire length. In the present invention, the core wrap sheet is optionally a single sheet as described above and may consist of two sheets: for example, one skin-side core wrap sheet that covers the skin-facing surface of the absorbent core 40, and one a non-skin side core wrap sheet that is separate from the skin side core wrap sheet and covers the non-skin side surface of the absorbent core 40.

[0020]

As shown in FIG. 2, the top sheet 2 covers the skin-facing surface of the absorbent member 4 throughout its entire length. On the other hand, the backsheet 3 covers the non-skin surface of the absorbent member 4 along its entire length, protrudes outward in the lateral direction Y from the two side edges of the absorbent member 4 extending in the longitudinal direction X, and forms parts in the form of side flaps together with side sheets 6, which will be described later. The side flap portions are portions formed from members which protrude outward in the lateral Y direction from the absorbent member 4 of the pad 1. The back sheet 3 and the side sheets 6 are connected to each other at portions protruding from the two side edges of the absorbent member 4, extending in the longitudinal direction X by using a known means of connection such as adhesive, heat sealing or ultrasonic welding. Each of the topsheet 2 and the backsheet 3 can be attached to the absorbent 4 by using an adhesive. Any type of sheet that is commonly used in an absorbent article such as a sanitary napkin can be used as the top sheet 2 and back sheet 3 without limitation. For example, as the top sheet 2, a single-layer or multi-layer structure nonwoven fabric, a perforated film, or the like can be used. As the backsheet 3, a liquid-permeable resin film or the like can be used.

[0021]

As shown in FIG. 1, the side flap portions protrude largely outward in the lateral Y direction in the region B centered in the longitudinal direction, whereby two wing portions 5W and 5W are formed on the right and left sides of the absorbent body 5 in in the longitudinal direction X. As shown in the plan view of FIG. A surface of each wing portion 5W that is not facing the skin is formed with a wing portion (not shown) provided with a pressure-sensitive adhesive for attaching the wing portion 5W to a garment such as a pair of panties. The wing portions 5W are used by folding them toward the non-skin-facing surface (outer surface) side of the crotch portion of a garment such as a pair of underpants. Parts of the wings provided with a pressure-sensitive adhesive are covered with a release sheet (not shown) such as a film, a non-woven fabric or a piece of paper before use. In addition, on the two side portions of the skin-facing surface of the absorbent body 5, extending in the longitudinal direction X, or in other words, on the skin-facing surface of the top sheet 2, as seen in the plan view, two side sheets 6 and 6 are provided substantially the entire length of the absorbent body 5 in the longitudinal direction X so that they overlap the right and left side portions of the absorbent body 4 extending in the longitudinal direction X. Each of the two side sheets 6 and 6 is attached to an additional element such as a top sheet 2 along a bonding line (not shown) that extends in the longitudinal direction X by using a known bonding agent such as an adhesive.

[0022]

The main element of the napkin 1 is the absorbent 4, more specifically the absorbent core 40, which is the main part of the absorbent core 4. FIG. 2 and 3, fiber aggregations 11, each including a plurality of fibers (synthetic fibers) 11F, and absorbent fibers 12F. Each of the fiber clusters 11 is a collection of fibers formed by intentionally accumulating fibers 11F as a single piece, while the absorbent fibers 12F are not deliberately formed as a single piece and are present in the absorbent core 40 independently of each other. The fiber clusters 11 mainly contribute to improving flexibility, resilience, compression recovery, improving shape retention, and the like of the absorbent core 40. On the other hand, the 12F absorbent fibers mainly contribute to improving liquid absorption, improving shape retention, and the like. characteristics of the absorbent core 40. The absorbent core 40 may be referred to per se as the absorbent member 4. Unless otherwise stated, the description of the absorbent core 40 below is also considered to be the description of the absorbent member 4, if appropriate. That is, the present invention covers the case in which the absorbent member consists of only an absorbent core and does not include a core wrapping sheet. In this case, the absorbent element and the absorbent core mean the same thing.

[0023]

In the description of the present application, the term "cluster of fibers" refers to the collection of fibers formed by joining together a plurality of fibers. The accumulation of fibers may take the form of a piece of sheet, obtained, for example, by cutting a piece from a sheet of a certain size, formed from synthetic fibers. In particular, it is preferable to select a nonwoven fabric as a sheet of synthetic fibers, and a piece of nonwoven fabric with predetermined dimensions and shape obtained by cutting a piece of nonwoven fabric is preferably used as a fiber agglomeration.

[0024]

As described above, a fiber bundle in the form of a sheet piece, which is a preferred embodiment of the fiber bundle of the present invention, is obtained by cutting a piece from a fibrous sheet (preferably a nonwoven fabric) that has a size larger than the sheet piece, rather than by collecting a plurality of fibers and giving them the shape of a piece of sheet (see Fig.6). The plurality of fiber aggregations included in the absorbent core of the present invention are aggregations of fibers in the form of a plurality of sheet pieces which have a higher level of shape retention than those obtained by conventional methods such as in Patent Literature 3 and 4.

[0025]

Synthetic fibers preferably make up 90% of the mass. or more of the constituent fibers 11F forming the cluster 11 fibers, and more preferably 100 wt. -%, or, in other words, all constituent fibers 11F are synthetic fibers. In addition, as will be described later, it is even more preferable that the constituent fibers 11F, which are synthetic fibers, are non-absorbent fibers.

[0026]

In the absorbent core 40, a plurality of fiber clusters 11 are entangled with each other, or fiber clusters 11 and absorbent fibers 12F are entangled. In the absorbent core 40 according to the present embodiment, a plurality of fiber bundles 11 are connected due to the entanglement of the component fibers (fibers 11F and 12F) of the absorbent core 40, whereby one continuous fiber bundle is formed. In addition, a configuration is possible in which a plurality of fiber bundles 11 are entangled with each other, and the fiber bundles 11 and the absorbent fibers 12F are also connected through entanglement. In addition, the plurality of 12F absorbent fibers are also commonly entangled with each other. At least some of the many fiber aggregations 11 included in the absorbent core 40 are entangled with other fiber aggregations 11 or absorbent fibers 12F. In the absorbent core 40, all of the plurality of fiber aggregations 11 included in the absorbent core 40 may be entangled with each other, resulting in a single continuous aggregation of fibers, or a plurality of continuous aggregations of fibers may exist together in an unattached state.

[0027]

The fiber clusters 11 themselves have very good resilience and the like. Accordingly, by incorporating the fiber bundles 11 into the absorbent core (absorbent core), the resulting absorbent will inherently have very good resilience and the like. Since the absorbent core 40 contains such fiber agglomerations 11 and the fiber aggregations 11 are connected to each other due to entanglement, or the fiber aggregations 11 and the absorbent fibers 12F are connected to each other due to entanglement, the response to an external force is further improved, and the absorbent core 40 has very good shape retention, resilience, resilience, compression recovery, and the like. For example, the absorbent core 40 can be elastically deformed by an external force (eg, the pressure of the wearer's body) received from different directions when the pad 1 is worn, and can adhere well to the wearer's body.

[0028]

4 schematically shows the deformed state of the absorbent core 40 when the absorbent core 40 is compressed by an external force F. fibers are present in a mixed state, due to the difference in stiffness between the fiber clusters 11 and the absorbent fibers 12F, the absorbent core 40 bends, in particular at the BL boundaries (dashed lines shown in FIG. 4) between the fiber clusters 11 and the absorbent fibers 12F. Boundaries BL, which serve as bending portions when the absorbent core 40 is deformed, are generally present in the entire area of the absorbent core 40, and therefore the absorbent core 40 can deform elastically in response to any external force and can also rapidly recover its original shape by restoring the shape of the clusters of 11 fibers after compression, when the external force is removed. This ability of the absorbent core 40 to recover from deformation is manifested not only when the absorbent core 40 is compressed, but also when the absorbent core 40 is twisted. wearing it. Accordingly, the absorbent core 40 can be twisted around an imaginary axis of rotation extending in the longitudinal direction X due to the movement of the two hips when the wearer walks. Because the absorbent core 40 has a high ability to recover from deformation, even in such a case, the absorbent core 40 can easily recover from a deformed state caused by an external force that causes twisting and acts from the side of the two thighs. Accordingly, the liner 1 is unlikely to curl, and thus the liner 1 can be well fitted to the wearer's body.

[0029]

As described above, in the absorbent core 40, the fiber clusters 11 are entangled with each other, or the fiber clusters 11 and the absorbent fibers 12F are entangled with each other. In the context of this document, the terms "entangled" and other relevant terms used to express that the clusters of 11 fibers or the like are entangled, encompass the following configurations A and B.

Configuration A: A configuration in which the fiber bundles 11 or the like are bonded to each other by intertwining the component fibers 11F forming the fiber bundles 11 with each other rather than by fusion with each other.

Configuration B: a configuration in which the fiber clusters 11 are not connected to each other when the absorbent core 40 is in a natural state (a state in which an external force is not applied), but when an external force is applied to the absorbent core 40 of the fiber clusters 11 or the like are connected to each other by entanglement of the constituent fibers 11F with each other. In the context of this document, the expression "an external force is applied to the absorbent core 40" refers, for example, to a state in which a deforming force is applied to the absorbent core 40 while wearing an absorbent article in which the absorbent core 40 is used.

[0030]

As described above, the absorbent core 40 may have configuration A, in which the fiber clusters 11 are connected to other fiber clusters 11 or absorbent fibers 12F as a result of fiber entanglement, or configuration B, in which the fiber clusters 11 are capable of being tangled with other fiber clusters 11 or absorbent fibers. fibers 12F. The entanglement bonding is an important factor in terms of more effectively exhibiting the above-described beneficial effects of the absorbent core 40. However, the absorbent core 40 is preferably "tangled" according to configuration A for shape retention reasons. The entanglement bonding is carried out only by fiber entanglement without bonding through the use of an adhesive component or a fusion, and thus, for example, compared to a “fiber fusion” bonding as in Patent Literature 3, the degree of freedom of movement of the individual tangled members ( clumps 11 fibers and absorbent fibers 12F) is high. Accordingly, the individual elements can move within the zone in which the accumulation formed by the individual elements can maintain its integrity. As described above, since the plurality of fiber aggregations 11 included in the absorbent core 40 are relatively loosely bonded to each other, or the fiber aggregations 11 and absorbent fibers 12F included in the absorbent core 40 are relatively loosely bonded, the absorbent core 40 has moderate shape retention. and can deform in response to an external force. Accordingly, high levels of shape retention, resilience and compression recovery are achieved.

[0031]

It is not necessary that all bonds be provided by "entanglement" of the fiber bundles 11 in the absorbent core 40, and other bonds or the like may be partially provided in the absorbent core 40, such as bonding through the use of an adhesive.

[0032]

However, it is desirable that in the remainder obtained by removing - from the absorbent core 40 - those "parts fused by fiber clusters 11" that are formed in the absorbent core 40 as a result of providing the absorbent element 4 with an additional element of the absorbent article, such like the leakage prevention grooves described above, or, in other words, making them in the absorbent core 40 itself, the connection between the fiber bundles 11 or the connection between the fiber bundles 11 and the absorbent fibers 12F was made only by "fiber entanglement".

[0033]

For reasons related to the more reliable manifestation of the above-described preferred effects from the absorbent core 40, the total number of "clumps of 11 fibers that are connected by entanglement" that correspond to configuration A, and "clumps of 11 fibers that can be tangled" that correspond to configuration B, 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 that have "entanglement" according to configuration A is preferably 70% or more and particularly preferably 80% or more of the total number of fiber clusters 11 that have connected parts that are connected to other clusters 11 fibers or 12F absorbent fibers.

[0034]

The main feature of the absorbent core 40 is the outer shape of the fiber cluster 11 . Fig. 5 shows two exemplary outer shapes of fiber bundles 11. The fiber cluster 11A shown in FIG. 5(a) has the shape of a quadrangular prism, more specifically, the shape of a rectangular parallelepiped. The fiber cluster 11B shown in FIG. 5(b) is disc-shaped. The fiber clusters 11A and 11B are identical in that they have two opposite base surfaces (base planes) 111 and a body surface 112 (body side surface 112) connecting the two base surfaces 111. Both base surfaces 111 and body surface 112 parts are areas that are defined as having a flat surface essentially without any irregularities when assessing the degree of surface irregularity of the product, consisting mainly of fibers of this type.

[0035]

The cuboid fiber bundle 11A shown in FIG. 5(a) has six flat surfaces. The two opposite surfaces of these six surfaces having the largest area correspond to the base surfaces 111, and the remaining four surfaces correspond to the surfaces 112 of the body. The base surfaces 111 and the body surfaces 112 intersect with each other, more specifically, they are orthogonal to each other.

The disk-shaped fiber aggregation 11B shown in FIG. 5(b) has two opposite circular flat surfaces as seen in plan view and a curved peripheral surface that connects the two flat surfaces. The two flat surfaces correspond to the base surfaces 111, and the peripheral surface corresponds to the surface 112 of the body.

The fiber clusters 11A and 11B are also similar in that the body surface 112 has a quadrangular shape as seen in the plan view, more specifically a rectangular shape.

[0036]

The plurality of fiber agglomerations 11 contained in the absorbent core 40 differ from the nonwoven pieces disclosed in Patent Literature 3 and the small size lap disclosed in Patent Literature 4, which are aggregations of fibers having an indeterminate shape, in that each fiber aggregation 11 is a "shaped aggregation/aggregation of fibers" that has two opposing base surfaces 111 and a body surface 112 connecting the two base surfaces 111, as in fiber aggregations 11A and 11B shown in Fig.5. In other words, when viewing a fiber cluster 11 randomly selected from the fiber clusters 11 contained in the absorbent core 40 (when viewed using, for example, an electron microscope), for one fiber cluster 11, a plurality of perceptible perspective shapes will be obtained, since the perceived shape of the cluster 11 fibers in perspective changes depending on the viewing angle. Accordingly, each of the plurality of fiber aggregations 11 contained in the absorbent core 40 has a particular perspective shape having two opposing reference surfaces 111 and a body surface 112 connecting the two reference surfaces 111 as one of the plurality of perspective shapes. The plurality of nonwoven pieces and the small size lap contained in the absorbent members disclosed in Patent Literature 3 and 4, respectively, do not substantially have "surfaces" such as base surfaces 111 and body surface 112, or in other words, do not have wide parts, and therefore they have different external shapes and thus do not have a "defined shape".

[0037]

As described above, when each of the plurality of fiber agglomerations 11 contained in the absorbent core 40 is a "shaped aggregation of fibers" formed by the base surfaces 111 and the body surface 112, the ability of the fiber aggregations 11 to be uniformly distributed in the absorbent core 40 is improved compared to the indeterminate-shaped fiber assemblies like those disclosed in Patent Literature 3 and 4. Accordingly, the effects (effects of increasing flexibility, resilience, resilience and improving the like properties of the absorbent core) are stably exhibited. expected to be obtained by incorporating fiber aggregations, such as fiber aggregations 11, into the absorbent core 40. Further, in particular in the case of a cuboid-shaped fiber aggregation 11 shown in FIG. 5(a), the outer surface consists of six powers khnosti, including two base surfaces 111 and four surfaces 112 of the main body. Accordingly, the cuboid-shaped fiber aggregation 11 shown in FIG. 5(b), and thus the entanglement property is increased, which can lead to improved shape retention and the like.

[0038]

In the fiber bundle 11, the total area of the two base surfaces 111 is preferably greater than the total surface area 112 of the body. That is, in the cuboid-shaped fiber bundle 11A shown in FIG. 5(a), the sum of the respective areas of the two base surfaces 111 is greater than the sum of the respective areas of the four body surfaces 112. In addition, in the disk-shaped fiber aggregation 11B shown in FIG. 5(b), the sum of the respective areas of the two base surfaces 111 is larger than the area of that body surface 112 that forms the peripheral surface of the disk-shaped aggregation 11B. In both fiber clusters 11A and 11B, the base surfaces 111 are the surfaces that have the largest area of the plurality of surfaces of each of the fiber clusters 11A and 11B.

[0039]

The fiber agglomeration 11, which is a "collection of fibers having a certain shape" formed by two base surfaces 111 and that body surface 112 that intersects the two base surfaces 111 described above, can be obtained by using a production method different from conventional ways. A preferred method for producing fiber aggregations 11 includes, as shown in FIG. starting material, into elements with a certain shape through the use of a cutting means, such as a cutter/knife. The plurality of fiber aggregations 11 obtained as described above have the same defined shape and dimensions, unlike those obtained by the conventional methods disclosed in Patent Literature 3 and 4. FIG. fibers having the shape of a rectangular parallelepiped and shown in Fig.5(a), and the dotted lines shown in Fig.6 show cutting lines. The absorbent core 40 contains a plurality of aggregations 11 of fibers with the same shape and size, which are obtained with a certain shape by cutting the fibrous sheet in the manner described above. As described above, the nonwoven fabric is preferably used as the raw material fibrous sheet 10bs.

[0040]

The cuboid-shaped fiber clusters 11A shown in FIG. 5(a) are obtained, as shown in FIG. the first direction D1 (more specifically, orthogonal to the first direction D1). Each of the directions D1 and D2 is a predetermined direction extending in the surface direction of the sheet 10bs, and the sheet 10bs is cut along the thickness direction Z, which is orthogonal to the surface direction. As described above, in the plurality of cuboid-shaped fiber bundles 11A obtained by cutting the raw material fibrous sheet 10bs into so-called cubes, surfaces formed by cutting, or in other words, surfaces that come into contact with a cutting means such as the cutter/knife, when cutting the sheet 10bs, generally correspond to the surfaces 112 of the body, and the surfaces not formed by cutting, or in other words, the surfaces that do not come into contact with the cutting means, correspond to the base surfaces 111. The base surfaces 111 represent the front and back surfaces of the sheet 10bs (surfaces that are orthogonal to the thickness direction Z), and as described above, base surfaces 111 are surfaces that have the largest area of the plurality of fiber cluster surfaces 11A.

[0041]

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

[0042]

In addition, the outer shape of the fiber bundle 11 is not limited to the outer shapes shown in FIG. ), or curved surfaces, as in the case of the body surface 112 (peripheral surface of the disc-shaped fiber bundle 11B) shown in FIG. 5(b). In addition, the base surfaces 111 and the body surface 112 may have the same shape and the same dimensions. Specifically, for example, the outer shape of the fiber bundle 11A may be a cubic shape.

[0043]

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 raw material fibrous sheet 10bs at using a cutting tool such as a cutter/knife to produce a fiber cluster 11, and a non-cutting surface (base surface 111) which is the surface of the sheet 10bs and does not come into contact with the cutting tool. Due to the difference determined by whether the surface is a cut surface or not, the body surface 112, which is a cut surface, has the feature that the number of fiber ends per unit area of this surface 112 is greater than the number end portions of the fibers per unit area of the base surface 111, which is the surface not formed by cutting. In the context of this document, the term "fiber end" refers to the end of the constituent fiber 11F, forming a cluster of 11 fibers, in the direction of its length. Generally, there are fiber ends on the base surface 111, which is a surface not formed by cutting, but since the body surface 112 is a cutting surface, which is formed by cutting the raw material fiber sheet 10bs, the plurality of fiber ends formed by the ends of the components fibers 11F formed by cutting, which are formed by cutting, are present on the entire surface 112 of the body, or in other words, the number of end portions of fibers per unit area is greater than that of the base surface 111.

[0044]

The fiber ends provided on each surface of the fiber cluster 11 (base surfaces 111 and body surface 112) are useful for forming entanglements between the fiber cluster 11 and the other fiber clusters 11 and the absorbent fibers 12F included in the absorbent core 40. In addition, , in general, the entanglement property can be further improved by increasing the number of fiber ends per unit area, resulting in an improvement in various properties of the absorbent core 40, such as shape retention. In addition, as described above, the number of fiber ends on each surface of the fiber bundle 11 is not the same. The number of fiber ends per unit area can satisfy the following relationship: “body surface 112 > base surface 111”, entanglement with other fibers (other fiber clusters 11 and absorbent fibers 12F) through the fiber cluster 11 varies depending on the surface of the fiber cluster 11 , and the entanglement capability of the body surface 112 is better than that of the base surface 111. That is, the adhesion force caused by entanglement with other fibers through the body surface 112 is greater than the adhesion force caused by entanglement with other fibers through the base surface 111, and within a single fiber cluster 11, a difference can occur between the adhesive force caused by entanglement with other fibers through the base surface 111 and the adhesive force caused by entanglement with other fibers through the body surface 112.

[0045]

As described above, the plurality of fiber clusters 11 included in the absorbent core 40 are entangled with other fibers (other fiber clusters 11 and absorbent fibers 12F) that are present at their periphery by two types of adhesive forces. With this configuration, the absorbent core 40 has both adequate softness and adequate strength (shape retention). When the absorbent core 40, which has the very good characteristics described above, is used as an absorbent to be used in an absorbent article in accordance with a conventional method, great wearing comfort can be provided to the wearer of the absorbent article, and the problem can be effectively prevented. associated with damage to the absorbent core 40 by an external force, such as body pressure of the wearer of the absorbent article while wearing the absorbent article.

[0046]

Specifically, as described above, in the fiber bundle 11 (11A or 11B) shown in FIG. 5, the total area of the two base surfaces 111 is greater than the total area of the body surface 112. This means that the total area of the base surfaces 111, in which the number of fiber ends per unit area is relatively smaller and therefore the entanglement with other fibers is relatively weaker, is greater than the area of that body surface 112, which has the opposite properties base surfaces 111. Accordingly, in the fiber agglomeration 11 (11A or 11B) shown in FIG. fibers are evenly distributed over the entire surface. In addition, even when the fiber agglomeration 11 is entangled with other peripheral fibers, the fiber aggregation 11 is entangled with other peripheral fibers with a relatively low cohesive force, and therefore a large agglomeration is unlikely to occur, whereby the absorbent core 40 can be imparted very good resilience.

[0047]

On the contrary, as described above, the nonwoven fabric pieces disclosed in Patent Literature 3 and the small size lap disclosed in Patent Literature 4 are obtained by cutting a fibrous raw material sheet into elements with indefinite shapes using a cutting machine such as a cutting machine. mill. For this reason, they are not bundles of fibers in the form of pieces of a sheet having a certain shape with such "surfaces" as the base surfaces 111 and the surface 112 of the body. In addition, during the production of fiber bundles, an external force will be applied to all fiber bundles during cutting. Accordingly, the end portions of fibers constituting the constituent fibers are randomly formed on the entire surface of the fiber bundles, and therefore the above-described advantageous effects provided by the end portions of the fibers are not sufficiently exhibited.

[0048]

For reasons related to providing the above-described advantageous effects achieved by fiber ends, the ratio (N ₁ /N ₂₎ of the number N ₁ , which is the number of fiber ends per unit area of the base surfaces 111 (surface not formed by cutting), to the number of N ₂ , which is the number of fiber ends 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, based on the assumption 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 base surfaces 111 is preferably 0 fiber ends per ¹ mm2 or more, and more preferably 3 fiber ends per ¹ mm2 or more, and preferably 8 fiber ends per ¹ mm2 or less and more preferably 6 fiber ends per mm ² or less.

The N ₂ number of fiber ends per unit area of body surface 112 is preferably 5 fiber ends/ ^mm2 or more, and more preferably 8 fiber ends/ ^mm2 or more, and preferably 50 fiber ends/ ^mm2 or more. less and more preferably 40 fiber ends per mm ² or less.

The number of fiber ends per unit area of the body surface 112 and the number of fiber ends per unit area of the base surfaces 111 are determined using the method below.

[0049]

Method for determining the number of fiber ends per unit area on each surface of a fiber cluster

The measurement sample, which is an element (fiber cluster) containing fibers and serving as a measurement object, is attached to the stage using a piece of paper double-sided adhesive tape (NICE TACK NW-15 supplied by Nichiban Co., Ltd.). Next, the measurement sample is subjected to a platinum coating. Coating was performed using an E-1030 (product name) ion sputtering apparatus supplied by Hitachinaka Seiki Co., Ltd., and the sputtering time was set to 120 seconds. The cut surface (base surface or body surface) of the measurement sample was examined at 100× magnification using a JCM-6000 electron microscope supplied by JEOL. In the image captured at 100 times magnification, a rectangular area with a length of 1.2 mm and a width of 0.6 mm is set at an arbitrary location on the surface of the measurement object (base surface or body surface), and the viewing angle and the like are adjusted as so that the area of the rectangular area is 90% or more of the captured image. The number of fiber ends in this rectangular area is then counted. However, in the case when, in an image captured at 100x magnification, the surface of the fiber cluster that is the object of measurement is smaller than 1.2 mm × 0.6 mm, and the area of the rectangular zone is less than 90% of the captured image, the image capture magnification is set to a larger one. Than 100 times. Then, the number of fiber ends present in the rectangular area on the surface of the measurement object is counted in the manner described above. In the context of this document, "fiber end portions" to be counted refer to the ends of the constituent fibers forming a cluster of fibers in the length direction, and when the portions (parts mid-length in the length direction) are different from the ends of the constituent fibers in the length direction , protrude from the surface of the measurement object, the parts averaged in the length direction are not counted. Thereafter, the number of fiber ends per unit area of the surface (basic surface or main body surface) of the fiber bundle measurement object was calculated using the following expression. For every ten fiber aggregations, the number of fiber ends per unit area of the base surface and the number of fiber ends per unit area of the main body surface are calculated according to the procedure described above, and the average of the multiple calculated values is determined as the number of fiber ends per unit area surface of the measurement object.

Number of fiber ends per unit area of surface (basic surface or body surface) of the measurement object, which is a cluster of fibers, (fiber ends per 1 mm ² ) = number of fiber ends in a rectangular zone (1.2 × 0.6 mm ) / area of a rectangular zone (0.72 mm ² )

[0050]

In the case where the base surface 111 of the fiber cluster 11 has a rectangular shape, as seen in the plan view in the case of the fiber cluster 11A shown in FIG. core 40, each short side 111a of the rectangular-shaped cluster preferably has a size that is smaller than the thickness of the absorbent core 40 containing the fiber cluster 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, more preferably 2 mm or more, and preferably 10 mm or less, and more preferably 6 mm or less. The thickness of the absorbent core 40 is measured using the following method.

[0051]

Method for measuring the thickness of an absorbent member (absorbent core)

The measurement object (absorbent body or absorbent core) is carefully placed on a horizontal surface so that wrinkles and bulges do not occur, and then the thickness of the measurement object is measured under a load of 5 cN/cm ² . In particular, the thickness measurement is performed using, for example, a PEACOCK DIAL UPRIGHT GAUGES R5-C thickness gauge (supplied by OZAKI MFG. CO. LTD.). Wherein, a plate (an acrylic plate with a thickness of approximately 5 mm), which is round or square in plan view and has dimensions such that the load on the object to be measured is 5 cN/cm ² , is placed between the working end of the thickness gauge and the cut object. measurements, and then the thickness measurement is performed. The thickness measurement is performed at ten points, and the average of the measured values is calculated and determined as the thickness of the measurement object.

[0052]

The dimensions and the like of each portion of the fiber bundle 11 (11A or 11B) are preferably set as described below. The dimensions of each part of the fiber cluster 11 can be measured based on an image obtained by means of an electron microscope or the like, which is obtained during the outer shape identification operation of the fiber cluster 11 to be described later.

In the case where 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 0.1 mm or more, more preferably 0.3 mm or more, and even more. preferably 0.5 mm or more, and preferably 10 mm or less, more preferably 6 mm or less, and even more preferably 5 mm or less.

The length L2 of the long side 111b of the rectangular base surface 111 in plan view is preferably 0.3 mm or more, more preferably 1 mm or more, and even more preferably 2 mm or more, and preferably 30 mm or less, more preferably 15 mm or less and even more preferably 10 mm or less.

When the base surface 111 is the surface which has the largest area among the plurality of surfaces of the fiber cluster 11 shown in FIG. fiber that is circular in shape as seen in the plan view.

The ratio (first value L1/second value 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, more preferably 0.025 or more, and preferably 1 or less, and more preferably 0.5 or less. In the present invention, the shape of the base surface 111 seen in plan view is not limited to the rectangular shape shown in FIG. two sides that are orthogonal to each other can be 1.

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

[0053]

In addition, it is preferable that in the absorbent core 40, the clumps of 11 fibers are distributed densely and evenly throughout the absorbent core 40, since the response to an external force is likely to be isotropic. For this reason, it is preferable that the images of the absorbent core 40 projected in two directions, which are orthogonal to each other, have overlapping portions of a plurality of fiber clusters 11 in a single square zone with a side of a square equal to 10 mm. Reference numerals 11Z in FIGS. 3 and 4 denote overlapping portions of a plurality of fiber clusters 11. In the context of this document, the expression "images projected in two directions that are orthogonal to each other" generally covers an image projected in the direction of the thickness of the absorbent core (or, in other words, in the case when the absorbent core is viewed from that surface of the absorbent core that faces the skin, or from the side of that surface of the absorbent core that does not face the skin), and an image projected in a direction orthogonal to the thickness direction (or, in other words, in the case when the absorbent core is viewed from the side side surface).

[0054]

Fig. 7(a) is an electron microscope image of a fiber cluster according to an embodiment of the present invention, and FIG. As shown in FIG. 7, each of the plurality of fiber aggregations 11 included in the absorbent core 40 may be composed of a main body 110 and a protruding fiber part 113, which includes a fiber 11F protruding outward from the main body 110, and has a density an arrangement of fibers lower than the density of the fibers of the main body 110 (the number of fibers per unit area is small). The absorbent core 40 may comprise fiber aggregations 11 having no raised fiber portions 113, or, in other words, fiber aggregations 11 consisting of main portions 110 only. on each surface (base surface 111 or body surface 112) of the fiber cluster 11 described above and protrude outward from the surface of the fiber cluster 11.

[0055]

The main body 110 is a part formed as described above by two opposite base surfaces 111 and that main body surface 112 that connects the two base surfaces 111. The main body 110 is a part that is the main part of the fiber cluster 11 and forms the outer the shape of a cluster of 11 fibers having a certain shape. Various properties of the fiber bundle 11, such as high resilience, springability, and compression recovery property, are substantially dependent on the main body 110 to a large extent. of the absorbent core 40 or the entanglement between the fiber aggregations 11 and the absorbent fibers 12F of the absorbent core 40 has a direct effect on improving the shape retention ability of the absorbent core 40 and affects the ability of the agglomerations 11 to be evenly distributed in the absorbent core 40, and therefore indirectly enhances the preferred effects provided by the body 110.

[0056]

The main body 110 has a higher fiber density than the raised fiber portion 113, or in other words, has a higher number of fibers per unit area. In addition, the fiber density of the main body 110 itself is generally uniform. The proportion of the main part 110 in relation to the total mass of the accumulation of 11 fibers is usually 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 body 110 and the protruding fiber portion 113 can be distinguished from each other by the following outer shape identification operation.

[0057]

The operation of identifying the outer shape of the main body 110 of the fiber aggregation 11 in the absorbent core 40 can be performed by checking the "boundaries" between the main body 110 and the other parts while focusing on differences in fiber density (differences in the number of fibers per unit area) between the aggregation 11 fibers and parts peripheral to it, differences in fiber type and fiber diameter, and the like. The body 110 has a fiber density that is higher than the fiber density of the raised fiber portion 113 present in the area surrounding the body 110, and the synthetic fibers that are the constituent fibers of the body 110 are generally different from the 12F absorbent fibers (which are typically cellulose fibers) in terms of quality and/or dimensions. Accordingly, even in the absorbent core 40 in which the plurality of fiber bundles 11 and the absorbent fibers 12F are in a mixed state, boundaries like those described above can be easily established by focusing on the above points. The boundaries identified in the above manner correspond to the peripheries (sides) of the base surface 111 and the body surface 112. The base surface 111 and the body surface 112 are identified through the boundary check operation, and finally the main body 110 is identified. The boundary check operation can be performed by inspecting a predetermined object (absorbent core 40) from multiple viewing angles using an electron microscope if necessary. In particular, in the case where the fiber agglomerations 11 included in the absorbent core 40 are fiber aggregations like the fiber aggregations 11A and 11B shown in FIG. part", in particular, in the case where the base surfaces 111 have the largest area in the fiber cluster 11, the base surfaces 111, which have the largest area, can be identified relatively easily, and therefore the outer shape identification operation of the main body 110 can be performed without problems. .

[0058]

As shown in FIG. 7, the projecting fiber portion 113 is composed of a constituent fiber 11F of the main body 110 projecting outwardly from at least one of the base surfaces 111 and the body surface 112, which form the outer surface of the main body 110. FIG. 7 shows the fiber cluster 11 in plan view as viewed from the side of the base surface 111 (the surface having the largest area of the plurality of fiber cluster surfaces 11), and the projecting fiber portion 113 is formed by the plurality of fibers 11F projecting from that body surface 112 , which intersects the base surface 111.

[0059]

There is no particular restriction on the shape of the raised fiber part 113 . The raised fiber portion 113 may be composed of only one fiber 11F or may be composed of a plurality of fibers 11F, for example, like the raised fiber bundle portion 113S to be described later. Further, the protruding fiber portion 113 includes a fiber portion 11F protruding from the main portion 110 and terminating in the length direction. However, in addition to or instead of such a fiber end portion, the projecting fiber portion 113 may include a portion (length-middle portion) other than the opposite length-terminal portions of fiber 11F. That is, in the fiber cluster 11, the opposite parts of the constituent fiber 11F end in the length direction are in the main part 110, and the part other than the opposite end parts, or in other words, the part middle in the length direction, can pass (protrude) looped outward from the main body 110. In this case, the fiber projecting portion 113 includes the loop-shaped fiber projecting portion 11F. In other words, those fiber projection portions 113 of the fiber projection portions 113 whose ends are exposed are end portions of fibers of the same type.

[0060]

As described above, the main function of the projecting fiber portion 113 is to cause the plurality of fiber clusters 11 included in the absorbent core 40 to become entangled with each other, or to cause the fiber clusters 11 and absorbent fibers 12F to be entangled with each other. In general, when the protrusion length of the fiber projection portion 113 from the main body 110 is increased, or the thickness of the fiber projection portion 113 is increased, or the number of fiber projection portions 113 in one fiber cluster 11 is increased, the adhesion between objects that are entangled by the fiber portion 113 is increased. with protruding fibers, and therefore the separation of tangled objects is unlikely. Accordingly, the intended effects of the present invention are more stable.

[0061]

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 obtained 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. As described above, the reason why the fiber projection portions 113 are unevenly distributed on the main portion surface 112, which is the surface formed by cutting, is that most of the fiber projection portions 113 form a fluff created by cutting the fibrous sheet. source material. That is, the entire body surface 112 formed by cutting the raw material fibrous sheet 10bs is subjected to friction by a cutting means such as a cutter/knife when cutting the raw material fibrous sheet, and therefore there is a possibility that the constituent fibers 11f of the raw material sheet 10bs will be fluffed. , or, in other words, there is a possibility of chaffing. On the other hand, the base surface 111, which is not a cutting surface, is not subjected to friction by the cutting means, and therefore fluff or, in other words, fiber protruding portions 113 are unlikely to be formed.

[0062]

The distance L1a (distance in the first direction) and the distance L2a (distance in the second direction) between the cutting lines when cutting the raw material fiber sheet 10bs is preferably 0.3 mm or more, and more preferably 0.5 mm or more, and preferably 30 mm or more. less and more preferably 15 mm or less for reasons related to facilitating the formation of the raised fiber portions 113 described above and for reasons related to providing the dimensions necessary for the fiber cluster 11 to produce a desired effect.

[0063]

As shown in FIG. 7, the fiber agglomeration 11 has a raised fiber bundle portion 113S comprising a plurality of fibers 11F projecting outwardly from the body portion 110, more specifically, from the body surface 112, as one type of the raised fiber portion 113. At least one raised fiber portion 113 of the fiber cluster 11 is a raised fiber bundle portion 113S. The protruding fiber bundle part 113S is formed from the combined plurality of fibers 11F protruding from the body surface 112, and is characterized in that the protrusion length from the main part 110 (main body surface 112) is longer than the length of the protruding fiber part 113. The raised fiber bundle part 113S may be provided on the base surface 111, but generally, as shown in FIG. base surface 111, or in the case of such parts on the base surface 111, the number of portions 113S in the form of bundles of protruding fibers on the base surface 111 is less than on the surface 112 of the body. The reason is the same as the reason why the fiber protruding portions 113 are mainly provided on the main body surface 112, which is the surface formed by cutting and which has been described above.

[0064]

Since each fiber clump 11 includes a raised fiber bundle portion 113S as described above, which is a raised filament portion 113 having a large size, which is long and thick, entanglement between fiber clumps 11 or entanglement between clumps is further improved. 11 fibers and 12F absorbent fibers. As a result, the intended effect of the present invention, provided by the presence of fiber clusters 11, is achieved more stably. The protruding fiber bundle part 113S is easily formed by performing the above-described operation of cutting the raw material fibrous sheet 10bs under conditions where fluff is likely to form (see FIG. 6).

[0065]

The protrusion length of the protruding fiber bundle part 113S from the main part 110, or in other words, 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 preferably 7 mm or less, and more preferably 4 mm or less. The protrusion length of the protruding fiber bundle part 113S can be measured in the operation of identifying the outer shape of the fiber cluster 11 (boundary inspection operation) described above. Specifically, for example, the fiber cluster 11 is placed on a transparent acrylic microscope stage supplied by Keyence Corporation (at 50x magnification) and attached to it with a piece of double-sided adhesive tape supplied by 3M Company, and the outer shape of the fiber cluster 11 is identified in according to the outer shape identification operation. Thereafter, the protrusion length of the fiber 11F protruding from the outer shape member is measured, and the measured protrusion length is determined as the protrusion length of the protruding fiber bundle portion 113S.

[0066]

Preferably, in the projecting fiber bundle portion 113S, a plurality of constituent fibers 11F are bonded to each other by thermal fusion. Such a heat-melted portion of the raised fiber bundle portion 113S generally has an overall length (diameter in the case where the cross-section of the thermofused portion is round) in a direction orthogonal to the length direction of the raised fiber bundle portion 113S that is greater than the length other parts (parts not subjected to thermofusion) in part 113S in the form of a bundle of protruding fibers. Since the protruding fiber bundle part 113S has a thermally melted part as described above, which is also referred to as the "large diameter part", the strength of the protruding fiber bundle part 113S itself is increased, thereby further increasing the entanglement between the fiber clusters 11 through the raised fiber bundle portion 113S, or the entanglement between the fiber clusters 11 and the absorbent fibers 12F through the raised fiber bundle portion 113S. In addition, the configuration in which the protruding fiber bundle part 113S has a heat-melted part is preferable because the protruding fiber bundle part 113S absorbs moisture not only when it is in a dry state, but also when it is in a wet state, and therefore, the strength, shape retention, and the like characteristics of the protruding fiber bundle part 113S itself are improved. In addition, with this advantage, in the case where the absorbent core 40 is used in the napkin 1, the advantageous effects provided by the fiber bundles 11 as described above can be stably exhibited not only when the absorbent core 40 is in a dry state, but and also when the absorbent core 40 is in a wet state, by absorbing bodily fluid such as urine or menstrual blood of the wearer. The protruding fiber bundle portion 113S which has a thermofused portion can be obtained by using "a fibrous sheet which has a thermofused portion of constituent fibers" as the raw material fibrous sheet 10bs in the step of obtaining fiber clusters 11 shown in 6, or, in other words, at the stage of cutting the fibrous sheet 10bs of the source material to obtain clusters 11 of fibers.

[0067]

As described above, the fiber clumps 11 can be characterized by the feature that each fiber clump 11 has a main body 110 (a collection of fibers having a certain shape) formed by the base surfaces 111 and the main body surface 112, and can also be characterized by the feature that the constituent fibers 11F of the fiber bundles 11 are synthetic fibers that contain a hydrophilizing agent. The hydrophilizing agent used in the present invention refers to an agent that increases the hydrophilicity of fibers to which the hydrophilizing agent has been added, more specifically, an agent that reduces the water contact angle measured by using the following method.

[0068]

Whether the fibers are hydrophilic or hydrophobic can be determined based on the water contact angle measured using the method below. If the water contact angle is less than 90 degrees, the fibers can be determined to be hydrophilic. If the water contact angle is greater than or equal to 90 degrees, the fibers can be determined to be hydrophobic. The smaller the water contact angle measured using the method below, the higher the hydrophilicity (the lower the hydrophobicity). The larger the contact angle, the lower the hydrophilicity (the higher the hydrophobicity).

[0069]

Method for determining the contact angle

Fibers are taken from the measurement object (absorbent core) and the contact angle of the fibers with water is measured. As the measuring device, an MCA-J automatic contact angle measuring instrument supplied by Kyowa Interface Science Co., Ltd. is used. Deionized water is used to measure the contact angle. The amount of liquid exiting from the outlet of the jet-type device for ejecting water droplets (CTC-25 pulse injector supplied by Cluster Technology Co., Ltd. and having an outlet pore diameter of 25 µm) is set to 20 picoliters, and drops of water drip directly from above onto the fiber. The state in which the drop of water descends is captured by capturing an image using a high-speed recording device connected to a camera mounted horizontally. For reasons related to the subsequent performance of image analysis, it is preferable to use a personal computer in which a high-speed image capture device is included as a recording device. When measuring, an image is recorded every 17 ms. Image analysis is performed on the first image, which is the first image of the recorded video images in which the water drop reaches the fiber, by using the accompanying FAMAS software (version 2.6.2 of the software, resting drop method and Ɵ/2 method used for analysis, wherein the image processing algorithm is set to non-reflective, the image processing image view is set to a frame, the threshold level is set to 200, and no curvature correction is set), and the angle formed between the air-contacting water droplet surface and the fiber is calculated, and the result is defined as the contact angle. The fiber taken from the measurement object is cut with a fiber length of 1 mm. The fiber is placed horizontally on the sample table in the contact angle measuring instrument and maintained in a horizontal state. The contact angle is measured at two different locations for each of the five fibers to the first decimal place. The average of the measured values (rounded to the second decimal place) obtained at a total of ten locations is determined as the contact angle of the fiber with water. The measurement environment is set with an indoor temperature of 22±2°C and a relative humidity of 65±2%.

[0070]

In the case where an absorbent body (absorbent core) used as a measurement object is used as a constituent element of an article such as an absorbent article, and the absorbent element is removed and subjected to evaluation and measurement when the absorbent element is attached to another constituent element by adhesive, by fusion or the like, the bonded portion is removed after the adhesive bonding force is eliminated by using a method such as blowing cold air with a cooling spray within a range that does not affect the contact angle of the fiber. This procedure applies equally to all measurements performed in accordance with the description of this application.

[0071]

The fact that the synthetic fibers which are the constituent fibers 11F forming the fiber clusters 11 contain a hydrophilizing agent means that the fiber clusters 11 have been hydrophilized. One of the effects achieved by hydrophilizing the fiber bundles 11 in the absorbent core 40 is to improve the physical properties when the absorbent core 40 is wet due to the absorption and retention of liquid. According to the results obtained by the present inventors, if the degree of hydrophilization of the constituent fibers (synthetic fibers) forming fiber clusters increases (if the water contact angle decreases), there is a possibility of an increase in the compression workload/wet compression force (w-WC) an absorbent core that contains constituent fibers that form clusters of fibers. Increasing the w-WC value results in an improvement in the wet springback property of the absorbent core, and therefore it can be argued that the incorporation of a hydrophilizing agent into the constituent fibers (synthetic fibers) forming fiber aggregations is effective in improving the springback property of the absorbent core in wet conditions. wet condition.

[0072]

In addition, as described above, in the absorbent core 40, the fiber aggregations 11 or absorbent fibers 12F, which are the constituent fibers of the absorbent core 40, are connected to each other by entanglement, or the fiber aggregations 11 and absorbent fibers 12F are connected to each other by entanglement, whereby the mobility of the body-exuded fluid (liquid diffusion capability in the surface direction, fluid permeability in the thickness direction) inevitably increases compared with the case when they are connected by fusion to each other. In addition, when the fiber bundles 11 are hydrophilized, the very good mobility characteristics of the body fluid can be further improved. For example, when the absorbent core 40 receives the bodily exhaled fluid exiting the napkin wearer 1 in the portion facing the release portion and located in the center of the region B, longitudinally centered, on the surface facing the skin, the exuded fluid , is rapidly absorbed into the absorbent core 40 from the portion facing the discharge portion by means of the hydrophilized constituent fibers 11F forming fiber clusters 11, or in other words, synthetic fibers containing a hydrophilizing agent and the absorbent fibers 12F entangled with synthetic fibers, and quickly moves toward the non-skin surface side (backsheet side 3) in the thickness direction while rapidly diffusing in the absorbent core 40 in the surface direction.

[0073]

In addition, as described above, each of the fiber bundles 11 includes a body 110 formed by base surfaces 111 and body surface 112. Typically, there are many void spaces between the constituent fibers 11F on these surfaces 111 and 112. ) can be absorbed into the fiber clusters 11 by capillary action of the void spaces between the fibers, whereby the ability of the absorbent core 40 to absorb liquids can be improved.

[0074]

In addition, as described above, each of the fiber clusters 11 has raised fiber portions 113 protruding outward from the main body 110. The raised fiber portions 113 may include a raised fiber bundle portion 113S composed of a plurality of fibers 11F projecting from the main body 110. part 110. When the fibers 11F contain a hydrophilizing agent, the projecting fiber bundle portion 113S also contains a hydrophilizing agent, and thereby the hydrophilicity is increased. Accordingly, body fluid can move more smoothly through the projecting fiber bundle portion 113S. That is, as a result of the fact that the constituent fibers 11F forming the fiber clusters 11 contain a hydrophilizing agent, in addition to the effect of increasing the entanglement strength between the fiber clusters 11 or between the fiber clusters 11 and the absorbent fibers 12F, one can also expect the effect of increasing the mobility of body excreted fluid fluid in the absorbent core 40. Thus, body fluid can move quickly in the absorbent core 40 even when an external force, such as body pressure of the wearer of the pad 1, is applied to the absorbent core 40.

[0075]

For reasons related to more reliable manifestation of the above-described preferred effects provided by synthetic fibers that serve as constituent fibers 11F forming fiber clusters 11 and containing a hydrophilizing agent, the 11F fibers that contain a hydrophilizing agent are preferably hydrophilic fibers. The 11F fibers (synthetic fibers) have a water contact angle preferably 75 degrees or less, more preferably 70 degrees or less, even more preferably 60 degrees or less, and particularly preferably 50 degrees or less. The contact angle of the fibers 11F with water can be adjusted on a case-by-case basis according to the type of hydrophilizing agent contained in the fibers 11F, the amount of hydrophilizing agent, or the like.

[0076]

The constituting fibers 11F forming fiber clusters 11, or, in other words, synthetic fibers that contain a hydrophilizing agent, are obtained by adding a hydrophilizing agent to the fibers of the starting material. The contact angle of the 11F fibers obtained by the above method with water is smaller than the contact angle of the raw material fibers with water. There is no particular limitation as to how the hydrophilizing agent will be contained in the 11F fibers. Generally, the hydrophilizing agent is contained in a portion of the surface layer of the 11F fibers, or in other words, the hydrophilizing agent is attached to the surface of the fibers of the raw material in the form of a thin film. However, instead of this option, the hydrophilizing agent, for example, can be mixed into the fibers of the source material. Alternatively, a hydrophilizing agent may be mixed into the fibers of the parent material and the hydrophilizing agent may also be attached to the surface of the fibers of the parent material.

[0077]

There is no particular limitation on the hydrophilizing agent used in the present invention, as long as a conventional hydrophilizing agent intended for use in hygiene products is used. Examples of the hydrophilizing agent include an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant. They may be used singly or in combination of two or more. Among them, it is preferable to use a hydrophilizing agent which contains one or more substances selected from the group consisting of an anionic surfactant and a nonionic surfactant, since the degree of hydrophilization can be easily controlled. The amount of hydrophilizing agent used for synthetic fibers forming a cluster of 11 fibers is preferably 0.001% of the mass. or more, more preferably 0.01% of the mass. or more and even more preferably 0.05% of the mass. or more, and preferably 10% of the mass. or less, more preferably 5% of the mass. or less and even more preferably 2% of the mass. or less as the amount of surfactant contained in the hydrophilizing agent.

[0078]

Examples of the anionic surfactant include alkyl sulfate, alkyl sulfonate, alkyl carbonate, and alkyl sulfosuccinate. In particular, it is preferable to use an anionic surfactant which has a sulfonic acid group as a hydrophilic group.

[0079]

A preferred example of an anionic surfactant in which the hydrophilic group is a sulfonic acid or a salt thereof may be a dialkyl sulfonic acid or a salt thereof, since it has a high permeability at a low concentration. Specific examples of dialkyl sulfonic acid include: compounds obtained by esterifying a dibasic carboxylic acid such as sulfosuccinic acid dialkyl ester or sulfosuccinic acid dialkyl ester and sulfonating the alpha position of a diester such as sulfosuccinic acid dioctadecyl ester, sulfosuccinic acid dodecyl ester, sulfosuccinic acid ditridecyl ester and di -2-ethylhexyl ester of sulfosuccinic acid; an alkyl ester (or amide) of an alpha-sulfonic acid fatty acid obtained by sulfonating the b-position of an ester (or amide) of a saturated fatty acid or an unsaturated fatty acid such as the sodium salt of the 1-ethyl ester (or amide) of 2-sulfotetradecanoic acid or sodium 1-ethyl ester (or amide) salt of 2-sulfohexadecanoic acid; a dialkylalkenesulfonate obtained by sulfonating a hydrocarbon chain internal olefin or an unsaturated fatty acid internal olefin, and the like. The number of carbon atoms of each of the double-chain alkyl groups of the sulfonic acid dialkyl ester is preferably 4 or more and 14 or less, and particularly preferably 6 or more and 10 or less. As the dialkyl sulfosuccinate, for example, PELEX OT-P (product name) supplied by Kao Corporation can be used.

[0080]

Examples of the cationic surfactant include alkyl (or alkenyl) trimethylammonium halide, dialkyl (or alkenyl) dimethylammonium halide, alkyl (or alkenyl) pyridinium halide, and the like. These compounds preferably have an alkyl group or an alkenyl group having 6-18 carbon atoms. Examples of the halogen in the halide compound include chlorine, bromine, and the like.

[0081]

Examples of the amphoteric surfactant include alkyl (1-30 carbons)-dimethylbetaine, alkyl (1-30 carbons)-amide-alkyl (1-4 carbons)-dimethylbetaine, alkyl (1-30 carbons)-dihydroxy -alkyl (1-30 carbon atoms)-betaine, betaine-type amphoteric surfactants such as sulfobetaine-type amphoteric surfactant; alanine-type amphoteric surfactants [alkyl (1-30 carbons)-aminopropionic acid type, alkyl (1-30 carbons)-iminodipropionic acid type], amphoteric surfactants of the amino acid type, such as amphoteric surfactants glycine type [type alkyl (1-30 carbon atoms)-aminoacetic acid, etc.] such as alkyl betaine, and amphoteric surfactants of the amino sulfonic acid type, such as surfactant type alkyl (1-30 carbon atoms )-aminoethylsulfonic acid.

[0082]

Examples of the nonionic surfactant include esters of a polyhydric alcohol and a fatty acid (preferably a C8-60 fatty acid) such as a fatty acid glycerol ester, a poly(preferably n=2-10)-glycerol fatty acid ester, and sorbitan fatty acid ester, alkylene oxide adducts (preferably 2-60 moles added) of polyhydric alcohol fatty acid esters, polyoxyalkylene (2-60 moles added)-alkyl (8-22 carbon atoms) )-amide, polyoxyalkylene (wherein the number of moles added is 2-60) alkyl (8-22 carbon atoms) ether, polyoxyalkylene-modified silicone, amino group-modified silicone, and the like.

[0083]

Any type of synthetic fibers intended for use in hygiene products can be used without any limitation as fibers of the starting material for the production of constituent fibers 11F forming clusters of 11 fibers, or, in other words, synthetic fibers that do not contain a hydrophilizing agent. It is preferable to use thermoplastic fibers. The reason why it is preferable to use thermoplastic fibers as 11F fibers is to give - fiber clusters - a three-dimensional structure in which a plurality of 11F thermoplastic fibers are thermofused to each other, so that very good shape retention effects can be achieved. , resiliency, springback characteristics, compression recovery, and anti-torsion, whether the absorbent core 40 is in a dry state or a wet state. Further, as described above, the protruding fiber bundle part 113S preferably has a heat-melted part. By using thermoplastic fibers as the constituent fibers 11F, forming clusters 11 of fibers, it is also possible to obtain a preferred embodiment of the portion 113S in the form of a bundle of protruding fibers. In order to obtain a fiber bundle 11 in which a plurality of thermofused parts are distributed in a three-dimensional structure, it is sufficient that the raw material fiber sheet 10bs (see FIG. 6) for the fiber bundles 11 have the same configuration. In addition, the raw material fibrous sheet 10bs in which a plurality of thermofused portions are distributed in a three-dimensional structure can be obtained as described above by performing a heat treatment such as treating a canvas or a non-woven fabric formed mainly from thermoplastic fibers with hot air.

[0084]

In addition, as described above, the constituent fibers 11F, which form the fiber clusters 11, are hydrophilic with a water contact angle of about 75 degrees or less, but the constituent fibers 11F preferably do not absorb moisture, or in other words, there is preferably little chance of that they will absorb moisture (excreted by the body, a fluid such as urine or menstrual blood). This is in complete contrast to the 11F absorbent fibers, which are literally absorbent and are used in conjunction with 11 fiber bundles. Since non-absorbent fibers which have little moisture absorption capacity are used as the 11F fibers, the above-described preferred effects provided by the 11 fiber clusters (effects of improving shape retention, resilience, resilience, resilience, curl resistance) and the like) are stably exhibited not only when the absorbent core 40 is in a dry state, but also when the absorbent core 40 is in a wet state due to absorption of bodily fluid. Accordingly, the raw material fibers are preferably non-absorbent synthetic fibers.

[0085]

Those skilled in the art will readily appreciate that the term "moisture absorption" as used herein means the ability to absorb moisture, such as, for example, the ability of cellulose to absorb moisture. Likewise, those skilled in the art will also readily appreciate that thermoplastic fibers do not absorb moisture. On the other hand, the level of ability of fibers such as synthetic fibers to absorb moisture can be determined based on the moisture content determined by using the following method. The moisture content of the absorbent fibers is preferably 6% or more, and more preferably 10% or more. On the other hand, the moisture content of the non-absorbent fibers is preferably less than 6% and more preferably less than 4%. When the moisture content is less than 6.0%, the fibers are defined as non-absorbent fibers. When the moisture content is 6.0% or more, the fibers are defined as absorbent fibers.

[0086]

Method for determining moisture content

The moisture content was calculated based on the moisture content control method according to JIS P8203 ( JIS - Japanese Industrial Standard ). Specifically, the fiber sample was kept in the testing laboratory at 40° C. and 80% relative humidity for 24 hours. Thereafter, the mass W (g) of the fiber sample was measured in the testing laboratory before being dried to a completely dry state. Thereafter, the fiber sample was placed in an electric dryer (for example, supplied by Isuzu Seisakusho, Co., Ltd.) at 105 ± 2°C for one hour to dry the fiber sample completely dry. After drying to a completely dry state, in a test lab that maintains a standard state of 20 ± 2°C and a relative temperature of 65 ± 2%, a sample of fibers wrapped in Saran Wrap plastic wrap (registered trademark ) supplied by Asahi Kasei Corporation was placed in a glass desiccator (supplied by, for example, Tech-Jam) containing Si-silica gel (supplied by, for example, Toyota Kako Co., Ltd.) and left to stand until the temperature of the fiber sample did not reach 20 ± 2°C. Thereafter, the constant mass W' (g) of the fiber sample was measured, and the moisture content of the fiber sample was determined using the following expression:

Moisture content (%) = (W-W’/W’) H 100.

[0087]

As described above, it is preferable to use synthetic fibers formed from thermoplastic and non-absorbent synthetic resin as the raw material fiber for producing the constituent fibers 11F forming the fiber clusters 11. Preferred examples of synthetic resin (thermoplastic resin) include: polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate; polyamides such as nylon 6 and nylon 66; polyacrylic acid, alkyl polymethacrylate, polyvinyl chloride, polyvinylidene chloride and the like. They may be used by themselves or in combination of two or more. The 11F fiber may be a single-component fiber formed from one type of synthetic resin (thermoplastic resin) or a polymer blend in which two or more types of synthetic resins are mixed, or may be a multi-component fiber. In the context of this document, a multicomponent fiber refers to a synthetic fiber (thermoplastic fiber) obtained by joining and molding two or more types of synthetic resins of different components with a spinneret, wherein the synthetic fibers have a structure in which a plurality of components are continuous in the length direction of the fibers and connected to each other in one fiber. The multicomponent fiber may be in the form of a sheath-and-core fiber or a side-by-side fiber, and there is no particular restriction on the form of the multicomponent fiber.

[0088]

There is no particular limitation on the amount of hydrophilizing agent in the 11F fibers, and the amount of hydrophilizing agent in the 11F fibers can be adjusted on a case-by-case basis according to the type of raw material fibers, type of hydrophilizing agent, predetermined degree of hydrophilization, or the like. For example, in the case where fibers formed from the above-described thermoplastic resin are used as raw material fibers, a conventional hydrophilizing agent intended for use in hygiene products is used as a hydrophilizing agent, and the contact angle of the 11F fibers with water is set to 75 degrees or less. , the amount of hydrophilizing agent in the fibers 11F is preferably 0.2% of the mass. or more, more preferably 0.4% of the mass. or more and preferably 2.0% of the mass. or less and more preferably 1.5% of the mass. or less relative to the total weight of the 11F fibers. If the amount of hydrophilizing agent is too small, the degree of hydrophilization of the fiber bundles 11 is low, and the advantageous effects described above may not be sufficiently exhibited. On the contrary, if the amount of the hydrophilizing agent is too large, line fouling may occur during the movement of the fiber sheet of the starting material at the location where the fiber clusters 11 are formed.

[0089]

On the other hand, as the absorbent fibers 12F used together with the fiber bundles 11, hydrophilic and absorbent fibers, which are commonly used as a material for forming the absorbent cores of this type of absorbent article, can be used. Examples include: natural fibers, including wood pulp fibers such as softwood pulp and hardwood pulp, and non-wood vegetable pulp fibers such as cotton pulp and hemp pulp; modified cellulose fibers such as cationized cellulose and mercerized cellulose; regenerated fibers such as ammonium copper and rayon fibers, and the like. They may be used by themselves or in combination of two or more.

[0090]

The angle of contact of the constituent fibers 11F (synthetic fibers 11F) forming the clusters 11 of fibers with water is preferably greater than or equal to the angle of contact of the absorbent fibers 12F with water. That is, the hydrophilicity of the 11F synthetic fibers is preferably equal to or lower than the hydrophilicity of the 12F absorbent fibers. When this ratio of body hydrophilicity is achieved, the fluid can move even more smoothly from the fiber clusters 11 to the absorbent fibers 12F or in the opposite direction, and further improvement in the ability of the absorbent core 40 to absorb liquids can be expected. As described above with respect to the water contact angle, in order to achieve the ratio of 11F fiber water contact angle≥12F absorbent fiber water contact angle, the degree of hydrophilization of the 11F fibers can be adjusted appropriately by using a hydrophilizing agent. The contact angle of the 12F absorbent fibers with water is preferably 60 degrees or less, and more preferably 40 degrees or less, assuming that the contact angle of the 12F absorbent fibers with water is less than or equal to the contact angle of the 11F fibers with water.

[0091]

In addition, the contact angle of the component fibers 11F (synthetic fibers) forming the fiber clusters 11 with water is preferably smaller than the contact angle of the top sheet 2 with water. That is, the hydrophilicity of the 11F fibers is preferably higher than the hydrophilicity of the topsheet 2. When this ratio of hydrophilicity values is achieved, in the liner 1, the liquid absorbed by the topsheet 2 is quickly absorbed by the absorbent core 40. In addition, due to the effect of diffusion of the liquid towards the flat surface in the absorbent core 40 described above, in particular in the part facing the release part and located in the center of the zone B, the center in the longitudinal direction (see figure 1) in the gasket 1, the amount of liquid retained in the top sheet 2 and the absorbent core 40 is reduced , and finally, the effect of providing a very good springability in the part facing the release part and in the area surrounding it, even after the liquid has been absorbed, is exhibited. As described above with respect to the water contact angle, in order to ensure the ratio of the values: topsheet 2 water contact angle > 11F fiber (cluster 11 fibers) water contact angle≥12F absorbent fiber water contact angle, the degree of hydrophilization of the 11F fibers can be adjusted accordingly. way by using a hydrophilizing agent, or can be adjusted accordingly by subjecting the top sheet 2 to the same hydrophilic treatment as that performed for the 11F fibers, if necessary.

[0092]

In the absorbent core 40, there is no particular limitation on the weight ratio of fiber bundles 11 and 12F absorbent fibers, and the weight ratio can be adjusted on a case-by-case basis according to the type of constituent 11F fibers (synthetic fibers that contain a hydrophilizing agent ), forming clusters of 11 fibers, and the type of absorbent fibers 12F. However, for reasons related to a more reliable manifestation of the desired effects of the present invention, the ratio of the mass fractions of fiber clumps 11 and 12F absorbent fibers (first value (11 fiber clumps) / second value (12F absorbent fibers)) is preferably from 20/ 80 to 80/20 and more preferably 40/60 to 60/40.

[0093]

The number of clusters 11 fibers in the absorbent core 40 is preferably 20% of the mass. or more and more preferably 40% of the mass or more, and preferably 80% of the mass. or less and more preferably 60% of the mass. or less based on the total dry weight of the absorbent core 40.

The amount of 12F absorbent fibers in the absorbent core 40 is preferably 20% by weight. or more and more preferably 40% of the mass or more, and preferably 80% of the mass. or less and more preferably 60% of the mass. or less based on the total dry weight of the absorbent core 40.

[0094]

The areal density of the fiber bundle 11 in the absorbent core 40 is preferably 32 g/m ² or more, 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.

The basis weight of the 12F absorbent fibers in the absorbent core 40 is preferably 32 g/m ² or more, 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.

[0095]

As described above, very good effects provided by the absorbent core 40, in particular, for example, very good springback property, compression recovery property, liquid absorption property, liquid diffusion property and the like, regardless of whether whether the absorbent core 40 is dry or wet is largely due to the inclusion of fiber aggregations 11 in which 11F fibers containing a hydrophilizing agent are used as constituent fibers, and the distribution of the 11 fiber aggregations in the absorbent core 40 can significantly affect the development preferred effects provided by the absorbent core 40.

[0096]

When fiber clumps 11 are present, for example, on the skin side of the absorbent core 40 (top sheet 2 side), which is the side relatively close to the skin of the wearer of the pad 1, and which is one of the two equal parts on which the absorbent core 40 is divided in the thickness direction (the direction that is orthogonal to the skin-facing surface or the non-skin-facing surface of the absorbent core 40), because the fiber clusters 11, which have a lower liquid holding capacity compared to the absorbent fibers 12F, are close to the skin of the wearer, excreted by the body, the fluid can thus move smoothly from the side of the surface facing the skin to the side of the surface not facing the skin (the side of the backsheet 3), which improves the ability of the absorbent core 40 to absorb liquids. Therefore, the amount of excess liquid remaining on the skin-facing surface of the topsheet 2 is reduced, and moisture and stickiness causing discomfort are suppressed, which can lead to an increase in wearing comfort of the liner 1.

[0097]

In addition, not only the distribution of the fiber clusters 11 in the absorbent core 40, but also the orientation of the fiber clusters 11 also influences to a large extent the preferred effects (springability, liquid absorption capacity, and the like) provided by the absorbent core 40. As such, when the plurality of fiber clumps 11 contained in the absorbent core 40 are randomly oriented with respect to the thickness direction of the absorbent core 40 (the direction that is orthogonal to the skin-facing surface or the non-skin-facing surface of the absorbent core 40), high levels of resilience, in particular resilience when the absorbent core 40 is in a wet state, resilience after compression, and ability to absorb liquids, and thus this configuration is preferable. In the context of this document, the expression "fiber clumps 11 randomly oriented with respect to the thickness direction of the absorbent core 40" means that in case the longer axis direction of each of the plurality of fiber clumps 11 (main parts 110) is taken into account, or in other words, the longitudinal direction (maximum overall length direction or diameter direction) of the base surface 111, it will be seen that the directions of the longer axes of the plurality of fiber clusters 11 contained in the absorbent core 40 are not the same. In the case where the absorbent core 40 is manufactured in a conventional manner using a conventional fiber depositor that includes a rotating drum, the plurality of fiber bundles 11 contained in the absorbent core 40 will be randomly oriented with respect to the thickness direction of the absorbent core 40.

[0098]

Furthermore, at least a portion of the plurality of fiber clumps 11 contained in the absorbent core 40 are preferably oriented such that their longer axis direction (longitudinal direction of the base surfaces 111) is along the thickness direction of the absorbent core 40. In the context of this document, the expression " fiber aggregations are oriented so that their longer axis direction is along the thickness direction of the absorbent core" means that the fiber aggregations 11 are oriented such that the angle formed by the longer axis direction of the fiber aggregations 11 and the thickness direction of the absorbent core 40 is 45 degrees or less . When the fiber agglomerations 11 are oriented in the absorbent core 40 such that the longer axis direction of the fiber aggregations 11 runs along the thickness direction of the absorbent core 40, in particular, wet recovery of the absorbent core 40 can be improved to an even greater extent compared to the case when the fiber clusters 11 are otherwise oriented, for example, when the direction of the longer axis of the fiber clusters 11 is in a direction that is orthogonal to the thickness direction of the absorbent core 40, or, in other words, when the fiber clusters 11 are oriented along the direction of the skin-facing surface surface or non-skin-facing surface of the absorbent core 40. Preferably 30% of the mass. or more and more preferably 50% of the mass. or more of all the fiber aggregations 11 contained in the absorbent core 40 are oriented such that the longer axis direction of the aggregations 11 is along the thickness direction of the absorbent core 40.

[0099]

As described above, the very good liquid absorption characteristics (liquid absorption capacity, liquid diffusion capacity, and the like) of the absorbent core 40 are largely due to the presence of empty spaces between the constituent fibers 11F, which are on the surface of the body 110 of the fiber clusters 11 or, in other words, on the base surfaces 111 and the surface 112 of the body. In this regard, the constituent fibers 11F forming the fiber clusters 11 are preferably oriented in the direction of the surface constituting the base surface 111. Since, in this configuration, a plurality of empty spaces between the constituent fibers 11F are formed on the base surface 111 of the fiber clusters 11 (main parts 110), the characteristics the absorption of liquids by the absorbent core 40 can be further improved. In the context of this document, the expression "11F fibers are oriented in the direction of the surface constituting the base surface 111" means a state in which the 11F fibers run along the direction of the surface constituting the base surface 111. More preferably, the 11F fibers run along the longitudinal direction of the base surface 111 Even more preferably, preferably 30% or more and more preferably 50% or more of the total number of 11F fibers present on the base surface 111 are oriented in the direction of the surface (preferably in the longitudinal direction of the surface) constituting the base surface 111.

[0100]

The absorbent core 40 may comprise a component other than the fiber clusters 11 and absorbent fibers 12F. The component other than the fiber clusters 11 and the absorbent fibers 12F may be, for example, an absorbent polymer. The absorbent polymer is generally a particulate absorbent polymer, but a fibrous absorbent polymer may be used. In the case of using the superabsorbent particulate polymer, the shape may be any of a spherical shape, a cluster shape, a rice bean shape, and an indeterminate shape. The average particle size of the absorbent polymer is preferably 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 absorbent polymer, a polymer or copolymer of acrylic acid or an alkali metal salt of acrylic acid can generally be used. Examples thereof include polyacrylic acid and its salts and polymethacrylic acid and its salts.

[0101]

The amount of absorbent polymer in the absorbent core 40 is preferably 5% by weight. or more and more preferably 10% of the mass or more, and preferably 60% of the mass. or less and more preferably 40% of the mass. or less based on the total dry weight of the absorbent core 40.

The surface density of the absorbent polymer in the absorbent core 40 is preferably 10 g/m ² or more, 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.

[0102]

The absorbent core 40 can be made in the same way as an absorbent core that contains this type of fibrous material. As described above and as shown in FIG. 6, the fiber clusters 11 can be obtained by cutting a fibrous sheet of raw material (a sheet that has the same composition as the composition of the fiber clusters 11 and is larger than the fiber clusters 11) which is a starting material, in two directions that intersect each other (orthogonal to each other), using a cutting means such as a cutter/knife. Each of the plurality of fiber bundles 11 obtained by the above method has a "fiber bundle having a specific shape" (for example, each of the main parts 110 has the shape of a cuboid), and these fiber bundles have the same shape and dimensions. The absorbent core 40, which includes the fiber bundles 11 and the absorbent fibers 12F, can be manufactured, for example, in a conventional manner by using a known fiber depositor that includes a rotating drum. The fiber depositing device generally includes a rotating drum in which a storage recess is formed on an outer peripheral surface and a box inside which there is a flow channel for moving the raw material (fiber clusters 11 and absorbent fibers 12F) of the absorbent core 40 k storage recessed part. The starting material moved by the air flow (intake air) generated in the flow channel under the action of the suction force acting from the inside of the rotating drum while rotating the rotating drum around the rotation axis along the direction along the circumference of the drum, is subjected to stacking of fibers in a storage recessed parts. The fiber stack material formed in the storage recess by the fiber stacking step is the absorbent core 40. The basis weight of the absorbent core 40 is preferably 100 g/m ² or more, more preferably 200 g/m ² or more, and preferably 800 g /m ² or less, and more preferably 600 g/m ² or less.

[0103]

The absorbent core 40 (absorbent member 4), which has the configuration described above, is resilient, and has very good resilience and very good compression recovery, can be quickly deformed by an external force and can quickly return to its (his) original state when the external force is removed. The properties of the absorbent core described above can be evaluated by using the compression workload (WC)/compression force and compression recovery ratio (RC) as an index. The compressive working load is a measure of the springback capability of the absorbent core. The larger the WC value, the better the springback capability. The compression recovery rate is a measure that characterizes the recovery rate when the absorbent core is subjected to compression and then the compressive load is released. The larger the RC value, the higher the compression recovery capability. In addition, in view of the function of absorbing and holding liquids performed by the absorbent core 40, the WC value and the RC value are preferably high not only when the absorbent core 40 is in a dry state, but also when the absorbent core 40 is in a wet state. due to absorption of body exudate, fluid, or the like. In order for the absorbent core 40 to have such properties when it is wet as described above, it is advantageous to use synthetic fibers which contain a hydrophilizing agent like the constituting fibers 11F that form the fiber clusters 11 . More preferably, the synthetic fibers do not absorb moisture and are thermoplastic.

[0104]

Method for determining the workload (WC) in compression / compression force and the degree (RC) of recovery after compression

It is widely known that the compression workload (WC) and compression recovery ratio (RC) of the absorbent core 40 can be represented as measured values obtained by using the KES (Kawabata scoring system) supplied by Kato Tech Co., Ltd. (Regulatory document: Standardization and Analysis of Texture Evaluation (second edition), written by Sueo Kawabata, published on July 10, 1980). In particular, compression workload/compression force and compression recovery ratio can be measured by using the KES-FB3 AUTO-A automatic compression test machine supplied by Kato Tech Co., Ltd. The measurement technique is as follows.

A sample with dimensions of 195 mm x 68 mm, which has a quadrangular shape in plan view (an absorbent member that is not wrapped with a core wrap sheet, or in other words, an absorbent core) is prepared and attached to the test table provided in the testing machine for compression. Next, the sample is compressed between steel plates that have an area of 2 cm ² and a round flat surface. The compression rate is set to 0.01 cm/s and the maximum compressive load is set to 490.2 mN/cm ² . In the recovery process, the measurement is also performed at the same speed. The compression workload (WC)/compression force is represented by (-o) by the equation below. In the equation, T _m is the thickness under load of 490.2 mN/cm ² (4.9 kPa), T ₀ is the thickness under load of 4.902 mN/cm ² (49 Pa), and P is the load/force at the time of measurement (mN/ ^cm2 ).

In addition, the degree (RC) of recovery after compression is represented by the expression [WC'/WC] × 100, which is the ratio between the work load (WC) in compression/compression force when the sample is compressed and the work load (WC') in compression / compression force when the sample is restored from the compressed state to its original state.

[0105]

[Math expression 1]

[0106]

In this case, the "dry absorbent core" which is the measurement object in the above measurement method is prepared by keeping the absorbent core as the measurement object in an environment of 23° C. and 50% relative humidity for 24 hours. Similarly, the “wet absorbent core”, which is the object of measurement in the above measurement method, is prepared as described below. The preparation is carried out by placing the absorbent core in a dry state in a horizontal position so that the side of the surface facing the skin is facing up, placing an acrylic plate provided with a cylinder, which has an inlet with a diameter of 1 cm in the lower part, on top of the skin facing surface of the absorbent core, injecting 5.0 g of defibrinated horse blood from the inlet and maintaining this condition for one minute after injecting defibrinated horse blood. The defibrinated horse blood introduced into the absorbent core serving as the measurement object is defibrinated horse blood supplied by Nippon Bio-Test Laboratories Inc. and has a viscosity adjusted to 8 cP at a liquid temperature of 25°C. Viscosity is the viscosity measured by using the L/Adp rotor (rotor code 19) at a rotation speed of 30 rpm in a TVB-10M viscometer supplied by Toki Sangyo Co., Ltd. In addition, when performing the measurement method, in order to prevent the measuring instrument from getting wet, the insertion site in the measurement object (absorbent core) into which defibrinated horse blood is injected and the portion corresponding to the periphery of the insertion site in the measuring instrument is covered with a piece of Saran Wrap (registered trade mark) plastic wrapping film. mark) supplied by Asahi Kasei Corporation, which was cut to a size of 4 cm × 4 cm.

[0107]

The present invention has been described above by means of an embodiment thereof, but the present invention is not limited to the embodiment described above and may be changed depending on the specific case.

For example, in the embodiment described above, the absorbent member 4 includes an absorbent core 40 and a core wrap sheet 41 that covers the absorbent core 40, but the core wrap sheet 41 may be omitted.

In addition, in the absorbent core of the present invention, all of the fiber aggregations (synthetic fiber aggregates) in the absorbent core are not necessarily shaped as aggregations of 11 fibers. A very small number of such shaped fiber assemblies may be contained in an absorbent core other than as shaped fiber assemblies without departing from the spirit of the present invention.

The absorbent article of the present invention broadly encompasses articles that are used to absorb bodily fluid (urine, soft feces, menstrual blood, sweat, and the like) discharged from the human body, such as sanitary napkins such as those described above, sanitary underpants, a disposable diaper of the so-called unfolding type with fastening tape, a disposable underpants type diaper and an urological pad. The following additional statements are also disclosed in relation to an embodiment of the present invention.

[0108]

<1> An absorbent member comprising: fiber aggregations containing synthetic fibers and absorbent fibers, wherein a plurality of fiber aggregations are entangled with each other, or fiber aggregations and absorbent fibers are entangled, each of the fiber aggregations includes a body formed by two opposite base surfaces and that surface of the body which intersects the two base surfaces, and the synthetic fibers contain a hydrophilizing agent.

<2> The absorbent body of claim 1, wherein the synthetic fibers have a water contact angle of 75 degrees or less, preferably 70 degrees or less, more preferably 60 degrees or less, and even more preferably 50 degrees or less.

<3> The absorbent body according to 1 or 2, wherein the synthetic fibers have a water contact angle that is greater than or equal to the water contact angle of the absorbent fibers.

<4> The absorbent member according to any one of 1 to 3, wherein the synthetic fibers are non-absorbent fibers.

<5> An absorbent body according to any one of 1 to 4, wherein the total area of these two base surfaces is greater than the total area of this surface of the body.

<6> The absorbent body according to any one of 1 to 5, 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.

<7> The absorbent member according to claim 6, wherein the ratio N ₁ /N ₂ of the number of N ₁ fiber ends per unit area on the base surfaces to the number N ₂ of fiber ends per unit area on a given body surface is 0 or more and 0 .90 or less, and preferably 0.05 or more and 0.60 or less.

<8> The absorbent member according to 6 or 7, wherein the number of fiber ends per unit area on the base surfaces is 0 fiber ends per ¹ mm2 or more and 8 fiber ends per ¹ mm2 or less, and preferably 3 fiber ends fibers per 1 mm ² or more; and 6 fiber ends per 1 mm ² or less.

<9> The absorbent member according to any one of 6 to 8, wherein the number of fiber ends per unit area on a given surface of the body is 5 fiber ends/ ^mm2 or more and 50 fiber ends/ ^mm2 or less, and preferably 8 fiber ends per 1 mm ² or more and 40 fiber ends per 1 mm ² or less.

[0109]

<10> The absorbent member according to any one of 1 to 9, wherein each of the fiber bundles includes raised fiber portions including fiber protruding outward from the body and having a fiber density that is lower than the fiber density of the body part, and at least one of the protruding fiber parts is a protruding fiber bundle part that includes a plurality of fibers protruding from the main part.

<11> An absorbent body according to any one of 1 to 10, wherein the main body is in the shape of a cuboid.

<12> The absorbent member according to any one of 1 to 11, wherein the plurality of fiber bundles contained in the absorbent member are randomly oriented with respect to the thickness direction of the absorbent member.

<13> An absorbent member according to any one of 1 to 12, wherein each of the base surfaces has a shape elongated in one direction, and at least a portion of the plurality of fiber aggregations contained in the absorbent member are oriented so that the longitudinal direction of the base surfaces surfaces extends along the thickness direction of the absorbent element.

<14> An absorbent member according to any one of 1 to 13, wherein the weight ratio of fiber clumps and absorbent fibers (first value/second value) is 20/80 to 80/20.

<15> An absorbent body according to any one of 1 to 14, wherein the component fibers forming the fiber clusters are oriented in a surface direction corresponding to the base surfaces.

[0110]

<16> An absorbent member as claimed in any one of 1 to 15, wherein in the absorbent member, the fiber agglomerations are entangled with other fiber aggregations or absorbent fibers or capable of being entangled with other fiber aggregations or absorbent fibers.

<17> The absorbent body of claim 16, wherein the total number of tangle-bonded fiber aggregations and tangle-able fiber aggregations is preferably 50% or more, more preferably 70% or more, and even more preferably 80% or more of the total the number of fiber clumps in the absorbent body.

<18> The absorbent member according to any one of 1 to 17, wherein the fiber agglomerations having parts bonded to other fiber aggregations or absorbent fibers due to fiber entanglement account for preferably 70% or more and more preferably 80% or more of the total aggregation fibers having portions connected to other fiber aggregations or absorbent fibers.

<19> The absorbent member according to any one of 1 to 18, wherein the fiber aggregations are made from a nonwoven fabric.

<20> The absorbent body of any one of 1 to 19, wherein the hydrophilizing agent comprises one or more substances selected from the group consisting of an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant. active substance.

<21> The absorbent body of claim 20, wherein the hydrophilizing agent contains an anionic surfactant.

<22> The absorbent body of claim 21, wherein the anionic surfactant contains an alkyl sulfosuccinate.

[0111]

<23> An absorbent article comprising an absorbent member according to any one of 1-22.

<24> The absorbent article of claim 23, comprising a liquid-permeable topsheet on one surface of the absorbent member, with fiber clumps present on the side relatively close to the topsheet, which is one of two equal portions into which the absorbent member is divided in the direction of its thickness.

<25> The absorbent article of claim 23 or 24, comprising an absorbent member and a topsheet provided on the skin side of the absorbent member, wherein the synthetic fibers have a water contact angle that is less than the topsheet water contact angle and greater than or equal to the contact angle of absorbent fibers with water.

Examples

[0112]

Hereinafter, the present invention will be described in further detail by way of examples, but the present invention is not limited to the examples below.

[0113]

Examples 1-5

In each example, an absorbent core was made and used as a sample absorbent. In particular, the absorbent core was manufactured in a conventional manner using a known fiber stacker and fiber aggregator and absorbent fibers as the fibrous material of the absorbent core. Clumps of fibers were obtained by cutting the fibrous sheet of starting material into cubes, as shown in Fig.6.

As the fibrous sheet of the raw material for forming fiber clusters, a through-air-bonded nonwoven fabric (a fibrous sheet that has a thermally fused part of constituent fibers) containing, as constituent fibers, thermoplastic fibers that do not absorb moisture and is formed from polyethylene resin fibers and polyethylene terephthalate resin fibers (non-absorbent fibers with a fiber diameter of 1.8 µm), and has a surface density of 21 g/m ² and a thickness of 0.6 mm. The constituting fibers forming the fiber clusters had a configuration in which a hydrophilizing agent was attached to the surface of non-absorbent thermoplastic fibers, which were raw material fibers, in the form of a thin film. In examples 1-4, composition A having the following composition was used as a hydrophilizing agent in an amount of 0.4% of the mass. from the mass of the constituent fibers forming clusters of fibers. In addition, in Example 5, Composition A and a commercially available and commercially available surfactant (PELEX OT-P supplied by Kao Corporation) were used as a hydrophilizing agent. The amounts of composition A and surfactant used as a hydrophilizing agent were respectively 0.4% of the mass. and 0.2% of the mass. from the mass of the constituent fibers forming clusters of fibers. Bleached softwood kraft pulp (NBKP) fibers with a fiber diameter of 2.2 µm were used as absorbent fibers. Each of the fiber agglomerations (collections of synthetic fibers with a specific shape) used in the absorbent core had a cuboid-shaped main body like that shown in FIG. mm, a long side 111b with a length of 3.9 mm, and a thickness T of 0.6 mm. In addition, the number of fiber ends per unit area on the base surface 111 was 3.2 fiber ends per mm ² , and the number of fiber ends per unit area on the body surface 112 was 19.2 fiber ends per mm ² . In the absorbent cores of these examples, the clumps of fibers were distributed at a high density and evenly.

[0114]

Composition A

- 25% of the mass. alkyl phosphate ether potassium salt (neutralized product Gripper 4131 prepared using potassium hydroxide and supplied by Kao Corporation);

- 10% of the mass. sodium salt of dialkyl sulfosuccinate (PELEX OT-P, supplied by Kao Corporation);

- 15% of the mass. alkyl (stearyl) betaine (AMPHITOL 86B, available from Kao Corporation);

- 30% of the mass. polyoxyethylene (moles added: 2)-stearylamide (Amisol SDE supplied by Kawaken Fine Chemicals Co., Ltd.);

- 20% of the mass. silicone modified with polyoxyethylene, polyoxypropylene (X-22-4515, supplied by Shin-Etsu Chemical Co., Ltd.).

[0115]

Comparative Example 1

The absorbent core of a commercially available and commercially available sanitary napkin (product name: Tanom Pew Slim 23 cm supplied by Unicharm Corporation) was used as the absorbent core of Comparative Example 1. The absorbent core of Comparative Example 1 was made from a mixture of synthetic fibers and cellulose fibers (hydrophilic fibers) and, therefore, did not contain accumulations of fibers.

[0116]

Comparative Example 2

The absorbent body was made in the same manner as in Examples 1-5, except that non-woven fabric pieces with an indefinite shape were used as fiber aggregations, and a hot air treatment step was performed on the absorbent core to thermally fuse the nonwoven fabric pieces in the absorbent core to each other. with friend. In the hot air treatment step performed on the absorbent core, a set (length 210 mm × width 66 mm) of a mixture of nonwoven pieces and cellulose fibers was left to stand in an electric dryer (for example, supplied by Isuzu Seisakusho, Co., Ltd.) at a temperature 140°C for 30 minutes to heat-fuse the non-woven pieces together. The indefinitely shaped nonwoven pieces used in this case were obtained by tearing the nonwoven fabric bonded by passing air through, which was the same nonwoven fabric as used in the Examples, in all directions, and the nonwoven pieces had an overall length in view. in plan view, approximately 25 mm. In addition, in Comparative Example 2, Composition A was used as a hydrophilizing agent used in the constituent fibers forming the nonwoven pieces.

[0117]

Performance evaluation

For each of the absorbent members obtained in Examples and Comparative Examples, compression workload/dry compression force (d-WC), compression workload/wet compression force (w-WC), compression recovery ratio in dry state (d-RC), the degree of recovery after wet compression (w-RC) were determined using the methods described above. The results are shown in Table 1 below.

[0118]

Example Comparative Example one 2 3 4 5 one 2 Presence or absence of fiber accumulations Available Available Available Available Available Missing Available Method for joining bundles of fibers tangle tangle tangle tangle tangle - thermofusion Outer form of fiber clusters definite form definite shape definite shape definite shape definite form - indefinite form Fiber Cluster Dimensions (mm) 0.8 x 3.9 0.8 x 3.9 0.8 x 3.9 0.8 x 3.9 0.8 x 3.9 - 25 ^*1 Angle of contact of synthetic fibers with water (degree) 68 68 68 68 thirty 83 68 Surface density of fiber clusters (g/m ² ) fifty 100 100 150 100 116 ^*2 100 The amount of hydrophilizing agent in synthetic fibers (% wt.) 0.4 0.4 0.4 0.4 0.6 N.D. 0.4 Surface density of absorbent fibers (g/m ² ) 150 100 100 fifty 100 116 100 Absorbent thickness (mm) 2.8 2.8 2.8 2.8 2.8 2.8 2.8 Absorbent element when dry dWC
( ^mN⋅cm /cm2) 32.84 36.76 35.78 39.22 37.25 19.12 24.02 d-RC (%) 43 45 47 fifty 45 40 fifty Absorbent pad when wet w-WC
( ^mN⋅cm /cm2) 29.41 32.35 31.37 36.27 36.27 15.20 19.61 w-RC (%) 40 42 43 48 42 25 45

*1: Total length of fiber bundle

*2: The basis weight of the synthetic fibers contained in the absorbent is shown because the absorbent does not contain fiber clumps.

[0119]

As shown in Table 1, the absorbent members of the Examples comprised hydrophilized and shaped fiber aggregations that contained synthetic fibers containing a hydrophilizing agent and were formed by two base surfaces and that body surface that intersects the two base surfaces, and therefore, the compression workload/compression force was (-o) greater whether they were dry or wet, compared to the absorbent members of Comparative Examples 1 and 2, which did not contain such fiber clumps. In addition, the absorbent members of the Examples exhibited large compression recovery numbers regardless of whether they were in a dry state or a wet state. In particular, from a comparison between the Examples and Comparative Example 2, it can be seen that in order to obtain an absorbent member having a high compression workload/high compression force and having a very good resilience even when wet, it is advantageous to use fiber aggregations , having a certain shape, and to connect the clusters of fibers with each other by tangling in addition to performing a treatment to impart hydrophilicity to the clusters of fibers contained in the absorbent element.

Industrial Applicability

[0120]

The absorbent body of the present invention has a very good resilience and a very good compression recovery property, is elastically deformable under an external force, and can provide improved wearing comfort when used in an absorbent article. In addition, the absorbent body of the present invention can exhibit the above-described very good effects not only before it absorbs liquid, but also when it is in a wet state due to liquid absorption and retention.

In addition, the absorbent article of the present invention contains a high-quality absorbent member, and therefore can provide very good wearing comfort and very good leakage prevention performance.

Claims (57)

1. Absorbent element containing: fiber aggregations containing synthetic fibers; and absorbent fibers, wherein the plurality of fiber bundles are entangled with each other, or the fiber bundles and absorbent fibers are entangled, each of the fiber clusters includes a body formed by two opposing base surfaces and a body surface that intersects the two base surfaces, the main part has the shape of a quadrangular prism, and synthetic fibers contain a hydrophilizing agent, with each of the base surfaces having a shape elongated in one direction, and at least a portion of the plurality of clumps of fibers contained in the absorbent element are oriented so that the longitudinal direction of the base surfaces extends along the thickness direction of the absorbent element. 2. Absorbent element according to claim 1, wherein the synthetic fibers have a water contact angle of 75 degrees or less. 3. Absorbent element according to claim 1, wherein the synthetic fibers have a water contact angle that is greater than or equal to the water contact angle of the absorbent fibers. 4. Absorbent element according to claim 1, wherein the synthetic fibers are non-absorbent fibers. 5. Absorbent element according to claim 1, in which the total area of these two base surfaces is greater than the total area of this surface of the main part. 6. Absorbent element according to claim 1, wherein the number of fiber ends per unit area on a given base body surface is greater than the number of fiber ends per unit area on each of the base surfaces. 7. Absorbent element according to claim 6, wherein the ratio N ₁ /N ₂ of the number N ₁ of fiber ends per unit area on base surfaces to the number N ₂ of fiber ends per unit area on a given body surface is 0 or more and 0.90 or less. 8. Absorbent element according to claim 6, wherein the number of fiber ends per unit area on the base surfaces is 0 fiber ends per 1 mm ² or more and 8 fiber ends per 1 mm ² or less. 9. Absorbent element according to claim 6, wherein the number of fiber ends per unit area on a given surface of the body is 5 fiber ends/ ^mm2 or more and 50 fiber ends/ ^mm2 or less. 10. Absorbent element according to claim 1, wherein each of the fiber bundles includes raised fiber portions including fiber projecting outward from the body and having a fiber density that is lower than the fiber density of the body, and at least one of the raised fiber portions is a raised fiber bundle portion that includes a plurality of fibers projecting from the body. 11. Absorbent element according to claim 1, in which the main part has the shape of a rectangular parallelepiped. 12. Absorbent element according to claim 1, wherein the plurality of fiber clumps contained in the absorbent are randomly oriented with respect to the thickness direction of the absorbent. 13. Absorbent element according to claim 1, in which the ratio of mass fractions of clusters of fibers and absorbent fibers (first value/second value) is from 20/80 to 80/20. 14. Absorbent element according to claim 1, wherein the component fibers forming the fiber clusters are oriented in a surface direction corresponding to the reference surfaces. 15. Absorbent element according to claim 1, wherein, in the absorbent element, the fiber agglomerations are entangled with other fiber aggregations or absorbent fibers or capable of being entangled with other fiber aggregations or absorbent fibers. 16. Absorbent element according to claim 15, in which the total number of clumps of fibers connected due to entanglement and clumps of fibers capable of tangling is 50% or more of the total number of clumps of fibers in the absorbent element. 17. Absorbent element according to claim 1, in which the clumps of fibers having parts connected to other clumps of fibers or absorbent fibers due to entanglement of the fibers are 70% or more of the total number of clumps of fibers having parts connected to other clumps of fibers or absorbent fibers. 18. Absorbent element according to claim 1, in which the clusters of fibers are obtained from a non-woven material. 19. Absorbent element according to claim 1, wherein the hydrophilizing agent contains one or more substances selected from the group consisting of an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant. 20. Absorbent element according to claim 19, wherein the hydrophilizing agent contains an anionic surfactant. 21. Absorbent element according to claim 20, wherein the anionic surfactant contains an alkyl sulfosuccinate. 22. Absorbent article containing the absorbent element according to claim 1. 23. The absorbent article according to claim 22, comprising a liquid-pervious top sheet on one surface of the absorbent element, wherein the fiber clumps are present on the side close to the top sheet, which is one of two equal parts into which the absorbent element is divided in its thickness direction. 24. The absorbent article according to claim 22, comprising: absorbent and a topsheet provided on the side of the surface of the absorbent member facing the skin, wherein the synthetic fibers have a water contact angle which is less than the water contact angle of the topsheet and greater than or equal to the water contact angle of the absorbent fibers.

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