JP7014577B2 - Absorber and absorbent article - Google Patents

Description

The present invention relates to an absorber for an absorbent article.

Absorbent articles such as disposable diapers and menstrual napkins generally include a front sheet that is placed relatively close to the wearer's skin and a back sheet that is placed relatively far from the wearer's skin. , Consists of an absorber interposed between the two sheets. This absorber is typically composed mainly of hydrophilic fibers (water-absorbent fibers) such as wood pulp and further contains water-absorbent polymer particles. For absorbers used in absorbent articles, improving various properties such as flexibility (cushioning property), compression recovery property, and shape retention property is a major issue.

As a technique for improving the absorber, for example, Patent Document 1 describes the synthesis of hydrophobic fibers having a longer fiber length than the pulp fibers, for example, polypropylene which has not been hydrophilized, in the absorber mainly composed of pulp fibers and water-absorbent polymers. It is described that the fibers are dispersed in the pulp fibers. According to Patent Document 1, such an absorber does not have a reversion phenomenon of body fluid due to the presence of hydrophobic fibers, and the strength is increased by entwining hydrophobic fibers having a long fiber length with pulp fibers. It is said that good shape retention can be maintained.

Further, in Patent Document 2, in an absorber mainly composed of pulp fiber and water-absorbent polymer, hydrophilic long fibers having a longer fiber length than pulp fibers, for example, rayon, cotton, wool, hemp, etc. are dispersed in the pulp fibers. It is stated that it should be done. According to Patent Document 2, such an absorber can stably maintain its shape before and after absorption of body fluid, and the hydrophilic filaments are dispersed without heat treatment, so that the absorber can be absorbed. It is said that the texture is appropriately maintained as a whole body, and there is little possibility of causing inhibition of body fluid absorption.

Further, Patent Document 3 describes an absorber containing heat-sealed fibers, a non-woven fabric piece in which the fibers are bonded in advance to give a three-dimensional structure, and hydrophilic fibers. This non-woven fabric piece having a three-dimensional structure is manufactured by crushing the non-woven fabric into small pieces using a crushing means such as a cutter mill method, and FIGS. 1 and 1 of the same document are produced due to such a manufacturing method. As described in No. 3, it has an indefinite shape and does not substantially have a portion that can be regarded as a flat surface. Patent Document 3 describes a preferred form of the absorber described in the same document in which non-woven fabric pieces are heat-fused together. According to the absorber described in Patent Document 3, since the non-woven fabric piece has a three-dimensional structure, voids are formed inside the absorber, and the resilience when absorbing water is improved, and as a result, the water absorption performance is improved. It is said that.

Further, Patent Document 4 describes a fine web having a relatively dense fine fiber nucleus and a fiber or a fiber bundle extending outward from the nucleus, and the fine web and wood pulp or a water-absorbing polymer. It is described that a non-woven web mixed with particles can be used as an absorber for absorbent articles. This fine web is manufactured by peeling or tearing off a raw material sheet such as a non-woven fabric, and has an irregular shape and can be regarded as a flat surface like the non-woven fabric piece described in Patent Document 3. Substantially does not have.

Japanese Unexamined Patent Publication No. 2004-73698 Japanese Unexamined Patent Publication No. 6-98909 JP-A-2002-301105 Japanese Unexamined Patent Publication No. 1-156560

Since the absorbers described in Patent Documents 1 and 2 both contain cellulose-based fibers such as pulp fibers and hydrophilic long fibers such as synthetic fibers or rayon, they contain only cellulose-based fibers as constituent fibers. It has higher rigidity than the absorbent body, and it is expected that various properties such as cushioning property and compression recovery property will be improved due to this, but multiple synthetic fibers contained therein exist independently. Since it does not form a single mass, the effect of improving these properties is not sufficient, and therefore, when applied to an absorbent article, it may be easily twisted and the fit may be insufficient. Yes, especially after absorption of body fluids such as urine and menstrual blood, the occurrence of such inconvenience is remarkable.

On the other hand, in each of the absorbers described in Patent Documents 3 and 4, since the synthetic fiber contained is a synthetic fiber aggregate called a non-woven fabric piece or a fine web, improvement in cushioning property can be expected. However, as described above, the synthetic fiber aggregate contained in the absorbers described in Patent Documents 3 and 4 is produced by crushing, stripping or tearing off the non-woven fabric mainly composed of synthetic fibers into small pieces. Therefore, the shape and size are not uniform due to the indefinite shape, and due to this, when mixed with pulp fiber or the like, it is difficult to obtain a uniform mixture of the two, and the desired effect is obtained. May not be obtained. Further, as in the preferred form of the absorber described in Patent Document 3, when all the synthetic fiber aggregates contained in the absorber are heat-sealed to each other, the movement of the absorber itself is restricted, and as a result, the absorber itself is restricted. The hardness as a whole may increase, and various properties such as flexibility may decrease.

Therefore, the subject of the present invention is an absorber that is excellent in cushioning property and compression recovery property, can be flexibly deformed with good response to an external force, and can improve the wearing feeling when applied to an absorbent article. The present invention also relates to providing an absorbent article using the absorber.

The present invention is an absorber containing a fiber mass containing synthetic fibers and a water-absorbent fiber, and a plurality of the fiber masses or the fiber mass and the water-absorbent fiber are entangled with each other. Is an absorber having a main body portion defined by two basic surfaces facing each other and a skeleton surface intersecting both basic surfaces, and the synthetic fiber contains a hydrophilic agent.
Further, the present invention is an absorbent article comprising the above-mentioned absorber of the present invention.

The absorber of the present invention is excellent in cushioning property and compression recovery property, can be flexibly deformed with good response to an external force, and can improve the wearing feeling when applied to an absorbent article. Further, the absorber of the present invention can exhibit such an excellent effect not only before the liquid is absorbed but also in a wet state in which the liquid is absorbed and retained.
Further, since the absorbent article of the present invention is provided with such a high-quality absorbent body, it is excellent in wearing feeling and leak-proof property.

FIG. 1 is a plan view schematically showing an example of a sanitary napkin according to an embodiment of the absorbent article of the present invention, with the skin facing surface side (surface sheet side) partially broken. FIG. 2 is a cross-sectional view schematically showing the I-I line cross section of FIG. FIG. 3 is a schematic perspective view of a part of the absorbent core included in the absorbent article shown in FIG. FIG. 4 is a diagram schematically showing a deformed state of the absorbent core shown in FIG. 3 during compression. 5 (a) and 5 (b) are schematic perspective views of the main body of the fiber mass according to the present invention, respectively. FIG. 6 is an explanatory diagram of a method for producing a fiber mass according to the present invention. FIG. 7 (a) is an electron micrograph (observation magnification 25 times) of an example of the fiber mass according to the present invention, and FIG. 7 (b) shows the electron as the fiber mass contained in the absorber shown in FIG. It is a figure which showed the fiber mass of a micrograph schematically.

Hereinafter, the absorber of the present invention will be described together with the absorbent article of the present invention comprising the absorber with reference to the drawings based on their preferred embodiments. 1 and 2 show a menstrual napkin 1 which is an embodiment of the absorbent article of the present invention. The napkin 1 has an absorber 4 that absorbs and retains body fluid, a liquid-permeable surface sheet 2 that is arranged on the skin-facing surface side of the absorber 4 and can come into contact with the wearer's skin, and a non-absorbent body 4. It is provided with a liquid-impermeable back sheet 3 arranged on the side facing the skin. As shown in FIG. 1, the napkin 1 has a vertical direction X extending from the ventral side of the wearer to the dorsal side via the crotch portion and a lateral direction Y orthogonal to the vertical direction X corresponding to the front-back direction of the wearer. In the vertical direction X, the vertical central region B including the excretion portion facing portion (excretion point) facing the excretion portion such as the wearer's genital region and the wearer's ventral side (anterior side) of the excretion portion facing portion. ), And the posterior region C, which is located on the back side (rear side) of the wearer from the excretory portion facing portion.

In the present specification, the "skin facing surface" is a surface of the absorbent article or its constituent members (for example, the absorbent body 4) that is directed toward the skin side of the wearer when the absorbent article is worn, that is, relatively of the wearer. The side closer to the skin, the "non-skin facing surface" is the side of the absorbent article or its constituents that is opposite to the skin side when the absorbent article is worn, that is, toward the side relatively far from the wearer's skin. It is the surface to be. The term "when worn" as used herein means a state in which a normal proper wearing position, that is, a correct wearing position of the absorbent article is maintained.

As shown in FIG. 1, the napkin 1 has an absorbent main body 5 having a shape long in the vertical direction X and both side portions of the absorbent main body 5 along the vertical direction X in the vertical central region B toward the outside in the horizontal direction Y. It has a pair of extending wing portions 5W and 5W. The absorbent main body 5 is a portion that is the main body of the napkin 1, and includes the front surface sheet 2, the back surface sheet 3, and the absorbent body 4, and has an anterior region A, a vertical central region B, and a rear region C in the vertical direction X. It is divided into three categories.

The vertical central region of the absorbent article of the present invention is a wing in the vertical direction (longitudinal direction, X direction in the figure) of the absorbent article when the absorbent article has a wing portion like the napkin 1. It means a region having a portion, and taking napkin 1 as an example, it is a region sandwiched between a root along the vertical direction X of one wing portion 5W and a root along the vertical direction X of the other wing portion 5W. Further, the vertical central region of the absorbent article having no wing portion means a region located in the middle when the absorbent article is divided into three equal parts in the vertical direction.

In the napkin 1, the absorber 4 includes a liquid-absorbing absorbent core 40 and a liquid-permeable core wrap sheet 41 that covers the outer surface of the absorbent core 40. Like the absorbent body 5, the absorbent core 40 has a long shape in the vertical direction X in a plan view as shown in FIG. 1, and the longitudinal direction of the absorbent core 40 is one with respect to the vertical direction X of the napkin 1. However, the width direction of the absorbent core 40 coincides with the lateral direction Y of the napkin 1. The absorbent core 40 and the core wrap sheet 41 may be bonded by an adhesive such as a hot melt type adhesive. The absorber 4 does not have to include the core wrap sheet 41, in which case the absorbent core 40 is used as it is as the absorber 4 in the absorbent article.

As described above, the absorber 4, which is an embodiment of the absorber of the present invention, is incorporated into an absorbent article such as a napkin 1 so as to be indirectly applied to human skin, that is, a member such as a surface sheet 2 is attached. It is used by being indirectly applied to the skin through the skin, and has a skin facing surface and a non-skin facing surface on the opposite side thereof, and corresponds to the vertical direction X corresponding to the front-back direction of the wearer of the napkin 1 and this. It has a horizontal direction Y that is orthogonal to each other, and is divided into three areas, a front area A, a vertical center area B, and a rear area C, in the vertical direction X. In addition to indirectly applying the absorber 4 to the skin of such a person, the absorber 4 can also be used by directly applying it.

In the napkin 1, the core wrap sheet 41 is one continuous sheet having a width of 2 times or more and 3 times or less the length of the lateral Y of the absorbent core 40, and as shown in FIG. 2, it absorbs. It covers the entire skin-facing surface of the sex core 40 and extends outward in the lateral direction Y from both side edges along the vertical direction X of the absorbent core 40, and the extending portion thereof is below the absorbent core 40. It is rolled down to cover the entire non-skin facing surface of the absorbent core 40. In the present invention, the core wrap sheet does not have to be such a single sheet, for example, one skin-side core wrap sheet that covers the skin-facing surface of the absorbent core 40 and the skin-side. It may be a separate body from the core wrap sheet, and may include two sheets including one non-skin side core wrap sheet that covers the non-skin facing surface of the absorbent core 40.

As shown in FIG. 2, the surface sheet 2 covers the entire surface of the absorber 4 facing the skin. On the other hand, the back surface sheet 3 covers the entire non-skin facing surface of the absorber 4, further extends outward in the lateral direction Y from both side edges along the vertical direction X of the absorber 4, and together with the side sheet 6 described later. It forms a side flap portion. The side flap portion is a portion of the napkin 1 made of a member extending outward in the lateral direction Y from the absorber 4. The back surface sheet 3 and the side sheet 6 are bonded to each other by known bonding means such as an adhesive, a heat seal, and an ultrasonic seal at the extending portions from both side edges of the absorber 4 along the vertical direction X. Each of the front surface sheet 2 and the back surface sheet 3 and the absorber 4 may be bonded by an adhesive. As the front surface sheet 2 and the back surface sheet 3, various types conventionally used for absorbent articles such as menstrual napkins can be used without particular limitation. For example, as the surface sheet 2, a non-woven fabric having a single-layer or multi-layer structure, a perforated film, or the like can be used. As the back sheet 3, a moisture-permeable resin film or the like can be used.

As shown in FIG. 1, the side flap portions greatly project outward in the horizontal direction Y in the vertical central region B, whereby a pair of side flap portions are formed on both the left and right sides of the absorbent main body 5 along the vertical direction X. Wings 5W and 5W are extended. The wing portion 5W has a substantially trapezoidal shape in which the lower base (the side longer than the upper base) is located on the side portion side of the absorbent main body 5 in a plan view as shown in FIG. 1, and the non-skin facing surface thereof. Is formed with a wing portion adhesive portion (not shown) for fixing the wing portion 5W to clothing such as shorts. The wing portion 5W is used by being folded back toward the non-skin facing surface (outer surface) side of the crotch portion of clothing such as shorts. Before its use, the adhesive portion of the wing portion is covered with a release sheet (not shown) made of a film, a non-woven fabric, paper or the like. Further, a pair of both side portions of the absorbent body 5 on the skin-facing surface, that is, the skin-facing surface of the surface sheet 2 along the vertical direction X, overlap with the left and right side portions of the absorbent body 4 along the vertical direction X in a plan view. Side sheets 6 and 6 are arranged over substantially the entire length of the absorbent body 5 in the vertical direction X. The pair of side sheets 6 and 6 are joined to another member such as the surface sheet 2 by a known joining means such as an adhesive by a joining line (not shown) extending in the vertical direction X, respectively.

One of the main characteristic portions of the napkin 1 is the absorbent body 4, particularly the absorbent core 40 which is the main body of the absorbent body 4. FIG. 3 shows a portion of the absorbent core 40. As shown in FIGS. 2 and 3, the absorber 4, more specifically, the absorbent core 40 includes a fiber mass 11 containing a plurality of fibers (synthetic fibers) 11F and a water-absorbing fiber 12F. The fiber mass 11 is a fiber aggregate in which the fibers 11F are intentionally integrated and integrated, whereas the water-absorbent fiber 12F is in a state where the fibers 12F can exist independently without being intentionally integrated. It is present in the absorbent core 40. The fiber mass 11 mainly contributes to the improvement of the flexibility, cushioning property, compression recovery property, shape retention property and the like of the absorbent core 40. On the other hand, the water-absorbent fiber 12F mainly contributes to the improvement of the liquid absorbency and the shape-retaining property of the absorbent core 40. The absorbent core 40 can be said to be substantially the absorber 4 itself, and the following description of the absorbent core 40 is appropriately applied as a description of the absorbent body 4 unless otherwise specified. That is, the present invention includes a case where the absorber is formed only of the absorbent core without containing the core wrap sheet, and in that case, the absorber and the absorbent core have the same meaning.

As used herein, the term "fiber mass" is a fiber aggregate in which a plurality of fibers are grouped together and integrated. Examples of the form of the fiber mass include a sheet piece divided from a synthetic fiber sheet having a certain size. In particular, a non-woven fabric is selected as the synthetic fiber sheet, and a non-woven fabric piece cut out from the non-woven fabric into a predetermined size and shape is preferable as the fiber mass.

As described above, the sheet piece-shaped fiber mass, which is a preferred embodiment of the fiber mass according to the present invention, is not configured to accumulate a plurality of fibers to form the sheet piece, but rather than the sheet piece. It is also manufactured by cutting a fiber sheet (preferably a non-woven fabric) having a large size (see FIG. 6). The plurality of fiber lumps contained in the absorber (absorbent core) of the present invention are a plurality of sheet piece-like fibers having higher stereotypes as compared with those produced by conventional techniques such as Patent Documents 3 and 4. It is a lump.

It is preferable that 90% by mass or more of the constituent fibers 11F of the fiber mass 11 is synthetic fibers, and 100% by mass, that is, all of the constituent fibers 11F are synthetic fibers. Further, as will be described later, it is more preferable that the constituent fiber 11F, which is a synthetic fiber, is non-absorbent.

In the absorbent core 40, a plurality of fiber lumps 11 or the fiber lumps 11 and the water-absorbent fiber 12F are entangled with each other. In the absorbent core 40 of the present embodiment, a plurality of fiber lumps 11 are entangled with the constituent fibers (fibers 11F and 12F) in the absorbent core 40 to form one fiber lump continuum. Further, the plurality of fiber lumps 11 may be entangled with each other, and the fiber lumps 11 and the water-absorbent fiber 12F may be entangled and bonded to each other. Further, usually, a plurality of water-absorbent fibers 12F are also entangled with each other. At least a part of the plurality of fiber lumps 11 contained in the absorbent core 40 is entangled with other fiber lumps 11 or the water-absorbent fiber 12F. In the absorbent core 40, all of the plurality of fiber masses 11 contained therein may be entangled with each other to form one fiber mass continuum, and the plurality of fiber mass continuums may be non-existent with each other. It may be mixed in the combined state.

Since the fiber lump 11 itself is excellent in flexibility and the like, by including it in an absorber (absorbent core), the absorber is potentially excellent in flexibility and the like. In the absorbent core 40, in addition to containing such fiber lumps 11, the fiber lumps 11 or the fiber lumps 11 and the water-absorbent fiber 12F are also entangled with each other and thus bonded to each other by entanglement. 40 is more excellent in responsiveness to external force, and is excellent in shape retention, flexibility, cushioning property, compression recovery property and the like. For example, the absorbent core 40 flexibly deforms to an external force (for example, the wearer's body pressure) received from various directions when the napkin 1 is worn, and can be brought into close contact with the wearer's body with good fit.

FIG. 4 schematically shows a deformed state when the absorbent core 40 is compressed by receiving an external force F. In the absorbent core 40 in which the fiber mass 11 which is a fiber aggregate and the water-absorbent fiber 12F which is a non-fiber aggregate coexist, the boundary between the two members 11 and 12F due to the difference in rigidity between the two members 11 and 12F. Where BL (dotted line in FIG. 24) is particularly flexible and the boundary BL functions as a bend during deformation of the absorbent core 40, the bend BL usually exists over the entire area of the absorbent core 40. Therefore, the absorbent core 40 is flexibly deformed in a responsive manner to various external forces, and when the external force is released, the absorbent core 40 is quickly restored by the compression recovery property of the fiber mass 11. Can be restored to the state of. Such deformation-recovery properties of the absorbent core 40 can be similarly manifested not only when the absorbent core 40 is compressed, but also when it is twisted. That is, since the absorbent core 40 incorporated in the napkin 1 is arranged in a state of being sandwiched between both thighs of the wearer when the napkin 1 is worn, the absorbent core 40 is the walking of the wearer. The movement of both thighs during movement may cause twisting around a virtual axis of rotation extending in the vertical direction X, but even in such cases, the absorbent core 40 has high deformation-recovery characteristics. Therefore, the napkin 1 can be easily deformed and recovered by an external force that promotes twisting from both thighs, and therefore is not easily twisted, and can impart a high fit to the wearer's body to the napkin 1.

As described above, in the absorbent core 40, the fiber lumps 11 are entangled with each other or the fiber lumps 11 and the water-absorbent fiber 12F are entangled with each other. A and B are included.
Form A: A form in which the fiber lumps 11 and the like are not fused but are bonded by the entanglement of the constituent fibers 11F of the fiber lumps 11.
Form B: In the natural state of the absorbent core 40 (a state in which no external force is applied), the fiber lumps 11 and the like are not bonded to each other, but in a state where the absorbent core 40 is subjected to an external force, the fiber lumps 11 and the like are not bonded to each other. A form that can be bonded by entanglement of constituent fibers 11F. The "state in which an external force is applied to the absorbent core 40" as used herein is, for example, a state in which a deformable force is applied to the absorbent core 40 while the absorbent article to which the absorbent core 40 is applied is being worn. ..

Thus, in the absorbent core 40, as in Form A, the fiber mass 11 is bonded to another fiber mass 11 or the water-absorbent fiber 12F by entanglement, that is, "entanglement" between the fibers, and other forms. Like B, it also exists in a state where it can be entangled with other fiber lumps 11 or water-absorbent fibers 12F, and the binding by entanglement of such fibers more effectively expresses the action and effect of the above-mentioned absorbent core 40. It is one of the important points. However, it is preferable that the absorbent core 40 has the "entanglement" of Form A from the viewpoint of shape retention. Bonding by entanglement of fibers is performed only by entanglement of fibers, not by adhesion or fusion using adhesive components, and therefore, compared to bonding by "fusion of fibers" as described in Patent Document 3, for example. , The confounding individual elements (fiber mass 11, water-absorbent fiber 12F) have a high degree of freedom of movement, so that the individual elements move to the extent that they can maintain their cohesiveness as an aggregate. obtain. As described above, the absorbent core 40 is deformed when it receives an external force because the plurality of fiber lumps 11 contained therein or the fiber lumps 11 and the water-absorbent fiber 12F are relatively loosely bonded to each other. It has a possible and gentle shape retention property, and has both shape retention property, cushioning property, compression recovery property, and the like at a high level.

It is not necessary that all of the binding modes via the fiber mass 11 in the absorbent core 40 are "entangled", and a part of the absorbent core 40 includes other binding modes other than entanglement, such as bonding with an adhesive. May be.

However, the remainder after removing "fusion via the fiber mass 11" formed in the absorbent core 40 as a result of being integrated with other members of the absorbent article such as the above-mentioned leak-proof groove from the absorbent core 40. In that part, that is, in the absorbent core 40 itself, it is desirable that the fiber lumps 11 are bonded to each other or the fiber lumps 11 and the water-absorbent fiber 12F are bonded only by "entanglement of fibers".

From the viewpoint of more reliably expressing the action and effect of the absorbable core 40 described above, the form A "fiber mass 11 bound by entanglement" and the form B "fiber mass 11 in a confoundable state" The total number of the fibers is preferably half or more, more preferably 70% or more, and more preferably 80% or more with respect to the total number of fiber lumps 11 in the absorbent core 40.
From the same viewpoint, the number of fiber lumps 11 having the “entanglement” of Form A is 70% or more, particularly 80% or more of the total number of fiber lumps 11 having a bond with another fiber lump 11 or the water-absorbent fiber 12F. Is preferable.

One of the main features of the absorbent core 40 is the outer shape of the fiber mass 11. FIG. 5 shows two typical outer shapes of the fiber mass 11. The fiber mass 11A shown in FIG. 5A has a rectangular parallelepiped shape more specifically than the prismatic shape, and the fiber mass 11B shown in FIG. 5B has a disk shape. The fiber lumps 11A and 11B are common in that they include two opposing base planes 111 and a skeleton plane 112 connecting the two base planes 111. Both the basic surface 111 and the skeleton surface 112 are at a level applied when evaluating the degree of surface unevenness in an article mainly composed of this type of fiber, and are portions where it is recognized that there is substantially no unevenness.

The rectangular parallelepiped-shaped fiber mass 11A in FIG. 5A has six flat surfaces, of which two facing surfaces having the maximum area are the basic surfaces 111, and the rest. Each of the four surfaces is a skeletal surface 112. The basic surface 111 and the skeleton surface 112 intersect each other, and more specifically, are orthogonal to each other.
The disk-shaped fiber mass 11B of FIG. 5B has two flat surfaces facing each other in a circular shape in a plan view and a curved peripheral surface connecting the two flat surfaces, where the two flat surfaces are formed. Each surface is a basic surface 111, and the peripheral surface is a skeleton surface 112.
The fiber lumps 11A and 11B are also common in that the skeleton surface 112 has a quadrangular shape, more specifically, a rectangular shape in a plan view.

The plurality of fiber lumps 11 contained in the absorbent core 40 each have two opposing basic surfaces 111 and a skeleton surface 112 connecting both basic surfaces 111, such as the fiber lumps 11A and 11B shown in FIG. It differs from the non-woven fabric pieces or fine webs described in Patent Documents 3 and 4, which are irregular fiber aggregates, in that they are provided with "standard fiber aggregates". In other words, when any one fiber mass 11 in the absorbent core 40 is seen through (for example, when observed with an electron microscope), the fluoroscopic shape of the fiber mass 11 depends on the observation angle, and one fiber. Where there are a large number of perspective shapes per mass 11, each of the plurality of fiber masses 11 in the absorbent core 40 connects two opposing basic surfaces 111 and both basic surfaces 111 as one of the many perspective shapes. It has a specific perspective shape with a skeletal surface 112. The plurality of non-woven fabric pieces or fine webs contained in the absorbers described in Patent Documents 2 and 3 substantially have a "plane" such as a basic surface 111 or a skeleton surface 112, that is, a widened portion. However, the outer shapes are different from each other and they are not "standard".

As described above, Patent Documents 3 and 4 describe that the plurality of fiber lumps 11 contained in the absorbent core 40 are "standard fiber aggregates" defined by the basic surface 111 and the skeleton surface 112. Since the uniform dispersibility of the fiber mass 11 in the absorbent core 40 is improved as compared with the case of the irregularly shaped fiber aggregate as described, the fiber aggregate such as the fiber mass 11 is blended into the absorbent core 40. As a result, the expected effects (improvement effects such as flexibility, cushioning, and compression recovery of the absorbent core) will be stably exhibited. Further, in particular, in the case of the rectangular parallelepiped fiber mass 11 as shown in FIG. 5 (a), the outer surface thereof is composed of six surfaces of two basic surfaces 111 and four skeleton surfaces 112, and thus is shown in FIG. 5 (b). Compared to the disk-shaped fiber mass 11 having three outer surfaces, it is possible to have a relatively large number of contact opportunities with other fiber mass 11 or the water-absorbent fiber 12F, and the entanglement is enhanced and the shape retention property is improved. It can also lead to improvement of such things.

In the fiber mass 11, the total area of the two basic surfaces 111 is preferably larger than the total area of the skeleton surface 112. That is, in the rectangular parallelepiped fiber mass 11A of FIG. 5 (a), the total area of each of the two basic surfaces 111 is larger than the total area of each of the four skeleton surfaces 112, and FIG. 5 (b). In the disk-shaped fiber mass 11B, the total area of each of the two basic surfaces 111 is larger than the area of the skeleton surface 112 forming the peripheral surface of the disk-shaped fiber mass 11B. In any of the fiber lumps 11A and 11B, the basic surface 111 is the surface having the largest area among the plurality of surfaces of the fiber lumps 11A and 11B.

The fiber mass 11 which is a "standard fiber aggregate" defined by the two basic surfaces 111 and the skeleton surface 112 intersecting the two basic surfaces 111 has a different manufacturing method from the prior art. It can be realized by doing so. As shown in FIG. 6, a preferable method for producing the fiber lump 11 is to cut the raw material fiber sheet 10bs (a sheet having the same composition as the fiber lump 11 and having a larger size than the fiber lump 11) as a raw material by using a cutting means such as a cutter. It is used to cut into a fixed form. The plurality of fiber lumps 11 thus produced have a more standard shape and dimensions as compared with those produced by conventional techniques such as Patent Documents 3 and 4. FIG. 6 is a diagram illustrating a method for manufacturing the rectangular parallelepiped-shaped fiber mass 11A of FIG. 5A, and the dotted line in FIG. 6 indicates a cutting line. The absorbent core 40 contains a plurality of fiber lumps 11 having uniform shapes and dimensions obtained by cutting the fiber sheet into a fixed shape. As described above, a non-woven fabric is preferable as the raw material fiber sheet 10bs.

In the rectangular parallelepiped-shaped fiber mass 11A of FIG. 5A, as shown in FIG. 6, the raw material fiber sheet 10bs intersects (more specifically, orthogonally) the first direction D1 and the first direction D1 in the second direction. It is manufactured by cutting into D2 to a predetermined length. Both directions D1 and D2 are each a predetermined direction in the plane direction of the sheet 10bs, and the sheet 10bs is cut along the thickness direction Z orthogonal to the plane direction. As described above, in a plurality of rectangular parallelepiped fiber lumps 11A obtained by cutting the raw material fiber sheet 10bs into a so-called sword pattern, the cut surface, that is, the surface that comes into contact with a cutting means such as a cutter when the sheet 10bs is cut is usually formed. The skeleton surface 112, that is, the non-cut surface, that is, the surface that does not come into contact with the cutting means, is the basic surface 111. The basic surface 111 is a front and back surface (a surface orthogonal to the thickness direction Z) of the sheet 10bs, and as described above, is the surface having the largest area among the plurality of surfaces of the fiber mass 11A.

The above description of the fiber mass 11A basically applies to the disk-shaped fiber mass 11B of FIG. 5 (b). The only substantial difference from the fiber mass 11A is the cutting pattern of the raw material fiber sheet 10bs, and when the sheet 10bs is cut into a fixed shape to obtain the fiber mass 11B, the shape of the fiber mass 11B is matched to the plan view shape. The sheet 10bs may be cut into a circular shape.

Further, the outer shape of the fiber mass 11 is not limited to that shown in FIG. 5, and the basic surface 111 and the skeleton surface 112 are both flat surfaces that are not curved as in the respective surfaces 111 and 112 of FIG. 5 (a). Alternatively, it may be a curved surface such as the skeleton surface 112 (peripheral surface of the disk-shaped fiber mass 11B) in FIG. 5 (b). Further, the basic surface 111 and the skeleton surface 112 may have the same shape and dimensions, and specifically, for example, the outer shape of the fiber mass 11A may be a cubic shape.

As described above, the two types of surfaces (basic surface 111 and skeleton surface 112) of the fiber mass 11 (11A, 11B) are used to cut the raw material fiber sheet 10bs by a cutting means such as a cutter when manufacturing the fiber mass 11. It is classified into a cut surface (skeleton surface 112) formed by the sheet 10bs and a non-cut surface (basic surface 111) that is inherently possessed by the sheet 10bs and does not come into contact with the cutting means. Due to the difference in whether or not the cut surface is used, the cut surface, the skeleton surface 112, is characterized in that the number of fiber ends per unit area is larger than that of the non-cut surface, the basic surface 111. Has. The term "fiber end" as used herein means the end in the length direction of the constituent fibers 11F of the fiber mass 11. Normally, the fiber end is also present on the basic surface 111, which is a non-cut surface, but the skeleton surface 112 is formed by cutting because it is a cut surface formed by cutting the raw material fiber sheet 10bs. A large number of fiber ends consisting of cut ends of the constituent fibers 11F are present in the entire skeleton surface 112, that is, the number of fiber ends per unit area is larger than that of the basic surface 111. ..

At the fiber ends existing on each surface (basic surface 111, skeleton surface 112) of the fiber mass 11, the fiber mass 11 is between the other fiber mass 11 included in the absorbent core 40 and the water-absorbent fiber 12F. Useful for forming entanglements. Further, in general, the larger the number of fiber ends per unit area, the better the entanglement, which may lead to the improvement of various properties such as the shape retention of the absorbent core 40. As described above, the number of fiber ends per unit area on each surface of the fiber mass 11 is not uniform, and the number of such fiber ends per unit area is "skeleton surface 112> basic surface 111". Since the magnitude relationship is established, the entanglement with other fibers (other fiber mass 11, water-absorbent fiber 12F) via the fiber mass 11 differs depending on the surface of the fiber mass 11, and the skeleton surface 112 is the basic surface 111. Highly entangled compared to. That is, the bond by entanglement with other fibers via the skeleton surface 112 has a stronger bonding force than that through the basic surface 111, and in one fiber mass 11, the basic surface 111 and the skeleton surface There may be a difference in the bonding force with other fibers from 112.

As described above, in the absorbent core 40, each of the plurality of fiber lumps 11 contained therein has two types of binding forces with respect to other fibers (other fiber lumps 11, water-absorbent fiber 12F) around the absorbent core 40. The absorbent core 40 has an appropriate softness and strength (shape retention). When the absorbent core 40 having such excellent properties is used as an absorber of the absorbent article according to a conventional method, it is possible to provide a comfortable wearing feeling to the wearer of the absorbent article. At the same time, the inconvenience that the absorbent core 40 is destroyed by an external force such as the wearer's body pressure at the time of wearing is effectively prevented.

In particular, in the fiber mass 11 (11A, 11B) shown in FIG. 5, the total area of the two basic surfaces 111 is larger than the total area of the skeleton surface 112, as described above. Therefore, the basic surface 111, which has a relatively small number of fiber ends per unit area and therefore has a relatively low entanglement with other fibers, has a skeleton surface 112 having the opposite property. It means that the total area is larger than that. Therefore, the fiber lumps 11 (11A, 11B) shown in FIG. 5 have other fibers (other fiber lumps 11, water-absorbent fibers 12F) in the vicinity as compared with the fiber lumps having fiber ends uniformly present on the entire surface. ) Is easily suppressed, and even if it is entangled with other fibers in the vicinity, it is easy to be entangled with a relatively weak binding force. Can impart sex.

On the other hand, the nonwoven fabric pieces or fine webs described in Patent Documents 3 and 4 are basically manufactured by cutting the raw material fiber sheet into an irregular shape by a cutting machine such as a mill cutter as described above. It is not a fixed-form sheet piece-like fiber mass having a "face" like the surface 111 or the skeleton surface 112, and moreover, the external force of the cutting process is applied to the entire fiber mass at the time of its manufacture, so that the constituent fibers The fiber end portion of the above is randomly formed in the entire fiber mass, and it is difficult to sufficiently exhibit the above-mentioned action and effect by the fiber end portion.

From the viewpoint of more reliably exerting the action and effect of the fiber end portion described above, the number N1 per unit area of the fiber end portion of the basic surface 111 (non _- cut surface) and the skeleton surface 112 (cut surface). The ratio of the fiber end to the number N ₂ per unit area is N ₁ / N ₂ , preferably 0 or more, more preferably 0.05 or more, and preferably 0, assuming N ₁ <N ₂ . It is .90 or less, more preferably 0.60 or less. 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 more.
The number N ₁ per unit area of the fiber end of the basic surface 111 is preferably 0 pieces / mm ² or more, more preferably 3 pieces / mm ² or more, and preferably 8 pieces / mm ² or less, still more preferably. 6 pieces / mm ² or less.
The number N ₂ per unit area of the fiber end of the skeleton surface 112 is preferably 5 pieces / mm ² or more, more preferably 8 pieces / mm ² or more, and preferably 50 pieces / mm ² or less, still more preferably. 40 pieces / mm ² or less.
The number of fiber ends of the basic surface 111 and the skeleton surface 112 per unit area is measured by the following method.

<Measuring method of the number of fiber ends per unit area on each surface of the fiber mass>
A member (fiber mass) containing a fiber to be measured is attached to a sample table using a paper double-sided tape (Nichiban Co., Ltd. Nystack NW-15). The measurement piece is then platinum coated. For coating, an ion sputtering device E-1030 (trade name) manufactured by Hitachinaka Seiki Co., Ltd. is used, and the sputtering time is 120 seconds. The cut surface of the measurement piece is observed on the basic surface and the skeletal surface at a magnification of 100 times using a JCM-6000 type electron microscope manufactured by JEOL Ltd. In this observation screen with a magnification of 100 times, a rectangular area of 1.2 mm in length and 0.6 mm in width is set at an arbitrary position on the measurement target surface (basic surface or skeleton surface), and the area of the rectangular area is the said. After adjusting the observation angle and the like so as to occupy 90% or more of the area of the observation screen, the number of fiber ends contained in the rectangular region is measured. However, in the observation screen with a magnification of 100 times, when the measurement target surface of the fiber mass is smaller than 1.2 mm × 0.6 mm and the ratio of the area of the rectangular region to the entire observation screen is less than 90%. After increasing the observation magnification to more than 100 times, the number of fiber ends contained in the rectangular region on the measurement target surface is measured in the same manner as described above. Here, the "fiber end" to be counted is the end in the length direction of the constituent fibers of the fiber mass, and the portion other than the end in the length direction of the constituent fibers from the measurement target surface (intermediate in the length direction). Even if the part) is extended, the middle part in the length direction is not subject to the number measurement. Then, the number of fiber ends per unit area on the measurement target surface (basic surface or skeleton surface) of the fiber mass is calculated by the following formula. For each of the 10 fiber lumps, the number of fiber ends per unit area on each of the basic surface and the skeleton surface was measured according to the above procedure, and the average value of the plurality of measured values was calculated as the average value of the plurality of measured values. The number per unit area of.
Number of fiber ends per unit area on the measurement target surface (basic surface or skeleton surface) of the fiber mass (number / mm ² ) = number of fiber ends included in the rectangular region (1.2 × 0.6 mm) / Area of the rectangular area (0.72 mm ² )

When the basic surface 111 of the fiber mass 11 has a rectangular shape in a plan view as in the fiber mass 11A shown in FIG. 5A, the viewpoint of improving the uniform dispersibility of the fiber mass 11 in the absorbent core 40. Therefore, it is preferable that the short side 111a of the rectangle is shorter than the thickness of the absorbent core 40 containing the fiber mass 11 (11A).
The ratio of the length of the short side 111a to the thickness of the absorbent core 40 is preferably 0.03 or more, more preferably 0.08 or more, and preferably 1 or less, still more preferably 0.5, as the former / the latter. It is as follows.
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, still more preferably 6 mm or less. The thickness of the absorbent core 40 is measured by the following method.

<Measuring method of thickness of absorber (absorbent core)>
The object to be measured (absorbent, absorbent core) is placed on a horizontal surface so as not to be wrinkled or bent, and the thickness of the object to be measured is measured under a load of 5 cN / cm ² . Specifically, for measuring the thickness, for example, a thickness meter PEACOCK DIAL UPRIGHT GAUGES R5-C (manufactured by OZAKI MFG.CO.LTD.) Is used. At this time, a plan-viewing circular or square plate (thickness) whose size is adjusted so that the load on the measurement object is 5 cN / cm ² between the tip of the thickness gauge and the cut-out object to be measured. (Acrylic plate of about 5 mm) is placed and the thickness is measured. In the thickness measurement, 10 points are measured, and the average value thereof is calculated to obtain the thickness of the object to be measured.

It is preferable to set the dimensions and the like of each part of the fiber mass 11 (11A, 11B) as follows. The dimensions of each part of the fiber mass 11 can be measured based on an electron micrograph or the like at the time of specifying the outer shape of the fiber mass 11 described later.
When the basic surface 111 has a rectangular shape in a plan view as shown in FIG. 5A, the length L1 of the short side 111a is preferably 0.1 mm or more, more preferably 0.3 mm or more, and particularly preferably 0.5 mm. The above, and preferably 10 mm or less, more preferably 6 mm or less, and particularly preferably 5 mm or less.
The length L2 of the long side 111b of the rectangular basic surface 111 in a plan view is preferably 0.3 mm or more, more preferably 1 mm or more, particularly preferably 2 mm or more, and preferably 30 mm or less, further preferably 15 mm or less. It is particularly preferably 10 mm or less.
As shown in FIG. 5, when the basic surface 111 is the surface having the maximum area among the plurality of surfaces of the fiber mass 11, the length L2 of the long side 111b is the maximum transfer length of the fiber mass 11. The maximum transfer length corresponds to the diameter of the basic surface 111 having a circular shape in a plan view in the disk-shaped fiber mass 11B.
The ratio 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, as the former L1 / the latter L2. It is preferably 0.5 or less. In the present invention, the plan view shape of the basic surface 111 is not limited to the rectangular shape as shown in FIG. 5A, but may be a square shape, that is, the ratio of the lengths L1 and L2 of the two sides orthogonal to each other is , L1 / L2 may be 1.
The thickness T of the fiber mass 11, that is, the length T between the two opposing basic surfaces 111 is preferably 0.1 mm or more, more preferably 0.3 mm or more, and preferably 10 mm or less, still more preferably 6 mm or less. be.

Further, in the absorbent core 40, it is preferable that the fiber lumps 11 are densely and uniformly distributed throughout the absorbent core 40 because the responsiveness to an external force tends to be isotropic. From such a viewpoint, it is preferable that the overlapping portion of the plurality of fiber lumps 11 is present in an arbitrary 10 mm square unit region in the two-direction projection view of the absorbent core 40 orthogonal to each other. Reference numerals 11Z in FIGS. 3 and 4 indicate overlapping portions of the plurality of fiber lumps 11. The term "projective view in two directions orthogonal to each other" as used herein is typically a projection view in the thickness direction of the absorbent core (that is, when the absorbent core is observed from its skin-facing surface or non-skin-facing surface). ) And the projection view in the direction orthogonal to the thickness direction (that is, when the absorbent core is observed from the side surface).

FIG. 7A shows an electron micrograph of an example of the fiber mass according to the present invention, and FIG. 7B shows a diagram schematically showing the fiber mass 11 according to the electron micrograph. Has been done. As shown in FIG. 7, the plurality of fiber lumps 11 included in the absorbent core 40 include a main body portion 110 and fibers 11F extending outward from the main body portion 110, and the main body portion 110 is included. The fiber density is low (the number of fibers per unit area is small), and the fiber having the extended fiber portion 113 can be included. The absorbent core 40 may also include a fiber mass 11 having no extended fiber portion 113, that is, a fiber mass 11 composed of only the main body portion 110. The extended fiber portion 113 may include a type of fiber end portion existing on each surface (basic surface 111, skeleton surface 112) of the fiber mass 11 described above, and is a fiber among the fiber end portions. It is a fiber end extending outward from each surface of the mass 11.

The main body portion 110 is a portion defined by the above-mentioned two facing basic surfaces 111 and a skeleton surface 112 connecting both basic surfaces 111. The main body 110 is a portion that forms the main body of the fiber mass 11 and forms a fixed outer shape of the fiber mass 11, and various characteristics such as high flexibility, cushioning property, and compression recovery property of the fiber mass 11 are basic. It is largely due to the main body 110. On the other hand, the extended fiber portion 113 mainly contributes to the improvement of the entanglement between the plurality of fiber lumps 11 contained in the absorbent core 40 or between the fiber lumps 11 and the water-absorbent fiber 12F, and retains the absorbent core 40. In addition to being directly related to the improvement of shape, it can also affect the uniform dispersibility of the absorbent core 40 of the fiber mass 11 and indirectly reinforce the action and effect of the main body 110.

The main body portion 110 has a higher fiber density than the extended fiber portion 113, that is, the number of fibers per unit area is large. Further, usually, the fiber density of the main body 110 itself is uniform. The ratio of the main body 110 to the total mass of the fiber mass 11 is usually at least 40% by mass or more, preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 85% by mass or more. The main body portion 110 and the extended fiber portion 113 can be distinguished by the following work of specifying the outer shape.

The work of specifying the outer shape of the main body 110 of the fiber mass 11 included in the absorbent core 40 is the work of specifying the height difference of the fiber density (the number of fibers per unit area) and the fibers in the fiber mass 11 and its peripheral portion. This can be done by paying attention to the difference in the type and fiber diameter of the main body and confirming the "boundary" between the main body 110 and the other parts. The main body portion 110 has a higher fiber density than the extended fiber portion 113 existing around the main body portion 110, and the synthetic fiber which is a constituent fiber of the main body portion 110 is usually a water-absorbent fiber 12F (typically a cellulosic fiber). Since they are qualitatively and / or dimensionally different, even in the case of the absorbent core 40 in which a large number of fiber lumps 11 and water-absorbent fibers 12F are mixed, the boundary can be easily confirmed by paying attention to the above points. The boundary thus confirmed is the peripheral edge (side) of the basic surface 111 or the skeleton surface 112, and the basic surface 111 and the skeleton surface 112 are specified by such boundary confirmation work, and the main body portion 110 is specified. Will be done. Such boundary confirmation work can be carried out by observing the object (absorbent core 40) at a plurality of observation angles as needed using an electron microscope. In particular, the fiber mass 11 contained in the absorbent core 40 is such that the fiber masses 11A and 11B shown in FIG. 5 have "the total area of the two basic surfaces 111 is larger than the total area of the skeleton surface 112". In particular, when the basic surface 111 is a surface having the maximum area of the fiber mass 11, the basic surface 111 having a large area can be relatively easily identified, so that the main body 110 can be used. The work of specifying the outer shape can be performed smoothly.

As shown in FIG. 7, the extending fiber portion 113 extends outward from at least one of the basic surface 111 and the skeleton surface 112 forming the outer surface of the main body portion 110, and is a constituent fiber of the main body portion 110. It consists of 11F. FIG. 7 is a plan view of the fiber mass 11 from the side of the basic surface 111 (the surface having the maximum area among the plurality of surfaces of the fiber mass 11), and the fibers 11F are formed from the skeleton surface 112 intersecting the basic surface 111. A large number of extended fibers are formed to form the extended fiber portion 113.

The form of the extended fiber portion 113 is not particularly limited. The extended fiber portion 113 may be composed of one fiber 11F, or may be composed of a plurality of fibers 11F as in the extended fiber bundle portion 113S described later. Further, the extended fiber portion 113 includes the end portion in the length direction of the fiber 11F extending from the main body portion 110, but the length of the fiber 11F is added to or replaced with such a fiber end portion. It may include parts other than both ends in the direction (intermediate part in the length direction). That is, in the fiber mass 11, both ends of the constituent fibers 11F in the length direction exist in the main body portion 110, and the other parts, that is, the intermediate portions in the length direction extend outward from the main body portion 110 in a loop shape ( Where there is a case of protrusion), the extended fiber portion 113 in that case is configured to include such a loop-shaped protrusion of the fiber 11F. In other words, of the extended fiber portions 113, those whose ends are exposed are one type of fiber end portions.

As described above, one of the main roles of the extended fiber portion 113 is to entangle the plurality of fiber lumps 11 contained in the absorbent core 40 with each other, or the fiber lumps 11 and the water-absorbent fiber 12F. .. Generally, the extension length of the extension fiber portion 113 from the main body portion 110 becomes longer, the thickness of the extension fiber portion 113 becomes thicker, or the number of extension fiber portions 113 contained in one fiber mass 11. When the amount of entanglement increases, the connection between the entangled objects via the extended fiber portion 113 becomes stronger and the entanglement becomes difficult to be released, so that the predetermined effect of the present invention can be more stably achieved. Become.

When the fiber mass 11 is obtained by cutting the raw material fiber sheet 10bs into a fixed shape as shown in FIG. 6, the extended fiber portion 113 is present in a relatively large amount on the skeleton surface 112 which is the cut surface thereof. On the other hand, it does not exist at all on the basic surface 111, which is a non-cut surface, or even if it exists, the number is smaller than that of the skeletal surface 112. As described above, the reason why the extended fiber portion 113 is unevenly distributed on the skeleton surface 112 which is the cut surface is that most of the extended fiber portion 113 is "fluff" generated by cutting the raw material fiber sheet. That is, since the skeleton surface 112 formed by cutting the raw material fiber sheet 10bs is entirely rubbed by a cutting means such as a cutter at the time of cutting, fluff made of the constituent fibers 11F of the sheet 10bs is likely to be formed, so-called fluffing. easy. On the other hand, since the basic surface 111, which is a non-cut surface, does not have friction with such a cutting means, it is difficult to form fluff, that is, the extended fiber portion 113.

The intervals L1a (interval in the first direction) and the intervals L2a (intervals in the second direction) of the cutting lines at the time of cutting the raw material fiber sheet 10bs are the viewpoints of promoting the formation of the extended fiber portion 113 and the fiber lumps 11 described above. From the viewpoint of ensuring the dimensions necessary for exhibiting a predetermined effect, it is preferably 0.3 mm or more, more preferably 0.5 mm or more, and preferably 30 mm or less, still more preferably 15 mm or less.

As shown in FIG. 7, the fiber mass 11 is a kind of extended fiber portion 113, and is a stretched fiber bundle portion including a plurality of fibers 11F extending outward from the main body portion 110, more specifically, the skeleton surface 112. It has 113S. At least one of the extended fiber portions 113 included in the fiber mass 11 may be the extended fiber bundle portion 113S. The extended fiber bundle portion 113S is formed by gathering a plurality of fibers 11F extending from the skeleton surface 112, and extends from the main body portion 110 (skeleton surface 112) as compared with the extended fiber portion 113. It is characterized by a long protrusion. The extended fiber bundle portion 113S may also be present on the basic surface 111, but typically exists on the skeletal surface 112 as shown in FIG. 7, and does not exist at all on the basic surface 111, or even if it exists. The number is less than the skeletal surface 112. The reason is the same as the reason why the extended fiber portion 113 mainly exists on the skeleton surface 112 which is the cut surface, and is as described above.

Since the fiber mass 11 has such an extended fiber bundle portion 113S which can be said to be a long, thick and large extended fiber portion 113, the fiber masses 11 or the fiber mass 11 and the water-absorbent fiber 12F can be connected to each other. The entanglement becomes stronger, and as a result, the predetermined effect of the present invention due to the presence of the fiber lump 11 becomes more stable. The extended fiber bundle portion 113S is easily formed by performing the above-mentioned cutting of the raw material fiber sheet 10bs under the condition of easy fluffing (see FIG. 6).

The extension length of the extension fiber bundle portion 113S from the main body portion 110, that is, the extension length from the skeleton surface 112 (cut surface) is preferably 0.2 mm or more, more preferably 0.5 mm or more, and It is preferably 7 mm or less, more preferably 4 mm or less. The extension length of the extension fiber bundle portion 113S can be measured in the work of specifying the outer shape of the fiber mass 11 (boundary confirmation work). Specifically, for example, a double-sided tape manufactured by 3M Co., Ltd. was attached to the surface of a transparent sample table made of acrylic with a KEYENCE microscope (50 magnification), and a fiber mass 11 was placed and fixed on the double-sided tape. Above, after specifying the outer shape of the fiber mass 11 according to the above-mentioned work of specifying the outer shape, the length of the extended portion of the fiber 11F extending from the outer shape is measured, and the measured extension is measured. The length of the minute is defined as the extension length of the extension fiber bundle portion 113S.

It is preferable that the plurality of constituent fibers 11F of the extended fiber bundle portion 113S are heat-sealed to each other. The heat-sealed portion of the extended fiber bundle portion 113S is usually in the length direction of the extended fiber bundle portion 113S as compared with other portions (non-heat-fused portions) of the extended fiber bundle portion 113S. The transfer length (diameter when the cross section of the heat-sealed portion is circular) is long in the direction orthogonal to. Since the extended fiber bundle portion 113S has such a heat-sealed portion that can be said to be a large-diameter portion, the strength of the extended fiber bundle portion 113S itself is increased, thereby passing through the extended fiber bundle portion 113S. The entanglement between the entangled fiber lumps 11 or between the fiber lumps 11 and the water-absorbent fiber 12F becomes stronger. Further, when the extended fiber bundle portion 113S has a heat-sealed portion, not only when the extended fiber bundle portion 113S is in a dry state but also when it is in a wet state by absorbing moisture. There is an advantage that the strength and shape retention of the extended fiber bundle portion 113S itself are enhanced. Due to such merits, when the absorbent core 40 is applied to the napkin 1, the absorbent core 40 absorbs body fluids such as urine and menstrual blood excreted by the wearer as well as when the absorbent core 40 is in a dry state. Even in the wet state, the action and effect caused by the presence of the above-mentioned fiber mass 11 can be stably exerted. Such an extended fiber bundle portion 113S having a heat-sealed portion is used as the raw material fiber sheet 10bs in the manufacturing process of the fiber mass 11 as shown in FIG. 6, that is, the cutting step of the raw material fiber sheet 10bs of the fiber mass 11. It can be manufactured by using the above-mentioned "fiber sheet having a heat-sealed portion between constituent fibers".

As described above, the fiber mass 11 is characterized in that it has a main body portion 110 (a fixed fiber aggregate) defined by a basic surface 111 and a skeleton surface 112, and the constituent fibers 11F thereof are characterized. It is also characterized by being a synthetic fiber containing a hydrophilizing agent. The "hydrophilic agent" referred to in the present invention refers to a contact angle with water measured by the following method, which improves the hydrophilicity of the fiber when the hydrophilic agent is applied to the fiber. It is an agent that reduces it.

Whether the fiber is hydrophilic or hydrophobic can be determined based on the contact angle with water measured by the following method. If this is less than 90 degrees, it is hydrophilic, and if it is 90 degrees or more, it is hydrophilic. It is hydrophobic. The smaller the contact angle with water measured by the following method, the higher the hydrophilicity (lower hydrophobicity), and the larger the contact angle, the lower the hydrophilicity (higher hydrophobicity).

<Measurement method of contact angle>
The fiber is taken out from the measurement target (absorbent core), and the contact angle of water with respect to the fiber is measured. As a measuring device, an automatic contact angle meter MCA-J manufactured by Kyowa Interface Science Co., Ltd. is used. Deionized water is used to measure the contact angle. The amount of liquid discharged from the inkjet water droplet discharge unit (Pulse injector CTC-25 manufactured by Cluster Technology Co., Ltd., having a discharge unit hole diameter of 25 μm) is set to 20 picolitres, and the water droplet is dropped directly above the fiber. The state of dripping is recorded on a high-speed recording device connected to a horizontally installed camera. From the viewpoint of image analysis later, the recording device is preferably a personal computer incorporating a high-speed capture device. In this measurement, an image is recorded every 17 msec. In the recorded video, the first image of water droplets on the fibers is the attached software FAMAS (software version is 2.6.2, analysis method is droplet method, analysis method is θ / 2, image processing algorithm. Is non-reflective, the image processing image mode is frame, the threshold level is 200, and the curvature is not corrected.) Make a corner. The fiber taken out from the object to be measured is cut into a fiber length of 1 mm, and the fiber is placed on a sample table of a contact angle meter and maintained horizontally. Measure the contact angles at two different points for each fiber. N = 5 contact angles are measured up to one digit after the decimal point, and the average value of the measured values at 10 points in total (rounded to the second digit after the decimal point) is defined as the contact angle of the fiber with water. The measurement environment is room temperature 22 ± 2 ° C. and humidity 65 ± 2% RH.

The absorber (absorbent core) to be measured is used as a constituent member of another article such as an absorbent article, and when the absorber is taken out and evaluated and measured, the absorber is an adhesive. When it is fixed to other components by fusion, etc., the adhesive force is removed from the fixed part by blowing cold air from a cold spray within the range that does not affect the contact angle of the fibers. Take out from. This procedure is common to all measurements herein.

The fact that the synthetic fiber, which is the constituent fiber 11F of the fiber mass 11, contains a hydrophilizing agent means that the fiber mass 11 has been hydrophilized. One of the effects of the hydrophilization treatment of the fiber mass 11 contained in the absorbent core 40 is that the physical characteristics of the absorbent core 40 when the absorbent core 40 absorbs and retains the liquid and is in a wet state. Improvement can be mentioned. According to the findings of the present inventor, when the degree of hydrophilization of the constituent fibers (synthetic fibers) of the fiber mass is increased (the contact angle with water is reduced), the absorbent core containing the fibers is compressed in a wet state. The amount of work (w-WC) tends to increase. Since this increase in the value of w-WC leads to the improvement of the cushioning property of the absorbent core in the wet state, it is possible to include the hydrophilic agent in the constituent fibers (synthetic fibers) of the fiber mass in the wet state of the absorbent core. It can be said that it is effective in improving the cushioning property of.

Further, in the absorbent core 40, as described above, the fiber mass 11 and the water-absorbent fiber 12F, which are the constituent members thereof, are bonded to each other by entanglement between the same species and different species, and due to this, they are fused by fusion. Where the mobility of the body fluid (liquid diffusivity in the plane direction, liquid permeability in the thickness direction) is potentially enhanced as compared with the case of being bound, the fiber mass 11 is further hydrolyzed. And, the excellent properties related to the movement of these body fluids can be further improved. For example, when the absorbent core 40 first receives the body fluid of the wearer of the napkin 1 at the excretion portion facing portion located in the central portion of the vertical central region B on the skin facing surface, the body fluid is hydrolyzed. The constituent fibers 11F of the resulting fiber mass 11, that is, the synthetic fiber fibers containing the hydrophilizing agent, and the water-absorbent fibers 12F entwined with the constituent fibers 11F are rapidly drawn into the inside of the absorbent core 40 from the excretion portion facing portion, and further. Can quickly permeate in the thickness direction toward the non-skin facing surface side (back surface sheet 3 side) while rapidly diffusing in the absorbent core 40 in the surface direction.

Further, as described above, the fiber mass 11 has a main body portion 110 defined by a basic surface 111 and a skeleton surface 112, and these surfaces 111 and 112 usually have interfiber gaps of the constituent fibers 11F. There are many. When the fiber mass 11 having a large number of interfiber voids on the surface is hydrophilized, the body fluid existing outside the fiber mass 11 (main body 110) is subjected to the capillary action of the interfiber voids to cause the fiber mass 11 to flow. As a result, the liquid absorbency of the absorbent core 40 can be improved.

Further, as described above, the fiber mass 11 has an extended fiber portion 113 extending outward from the main body portion 110, and the extended fiber portion 113 is provided with a plurality of fibers 11F extending from the main body portion 110. Where the extended fiber bundle portion 113S containing the fiber 11F may be present, if the fiber 11F contains a hydrophilic agent, the extended fiber bundle portion 113S also naturally contains the hydrophilic agent, thereby increasing the hydrophilicity. Therefore, the movement of the body fluid through the extended fiber bundle portion 113S becomes smoother. That is, when the constituent fibers 11F of the fiber lumps 11 contain a hydrophilizing agent, in addition to the effect of improving the entanglement strength between the fiber lumps 11 or between the fiber lumps 11 and the water-absorbent fibers 12F, further, in the absorbent core 40. The effect of improving the mobility of the body fluid can be expected, and even when an external force is applied to the absorbent core 40 due to the body pressure of the wearer of the napkin 1, the body fluid is rapidly transferred in the absorbent core 40. obtain.

From the viewpoint of ensuring that the above-mentioned action and effect caused by the synthetic fiber 11F, which is the constituent fiber of the fiber mass 11, containing the hydrophilic agent, are more reliably exerted, the fiber containing the hydrophilic agent. 11F is preferably a hydrophilic fiber, and the contact angle of the fiber 11F (synthetic fiber) with water is preferably 75 degrees or less, more preferably 70 degrees or less, more preferably 60 degrees or less, and particularly preferably 50 degrees. It is as follows. The contact angle of the fiber 11F with water can be adjusted by appropriately adjusting the type and content of the hydrophilic agent contained therein.

The constituent fiber 11F of the fiber mass 11, that is, the synthetic fiber containing the hydrophilizing agent is produced by incorporating the hydrophilizing agent into the raw material fiber, and the contact angle of the produced fiber 11F with water is the said. It is less than that of raw fiber. The content of the hydrophilic agent in the fiber 11F is not particularly limited, and typically, the surface layer portion of the fiber 11F is a hydrophilic agent, that is, the hydrophilic agent is attached to the surface of the raw material fiber on the thin film. However, instead of this, for example, a hydrophilic agent may be kneaded inside the raw material fiber, or a hydrophilic agent may be kneaded inside the raw material fiber, and the hydrophilic agent is further kneaded on the surface of the raw material fiber. It may be in the form of attached.

The hydrophilizing agent used in the present invention is not particularly limited as long as it is a general hydrophilizing agent used for hygienic products. Examples of the hydrophilizing agent include those containing anionic surfactants, cationic surfactants, amphoteric surfactants or nonionic surfactants, and one of these agents may be used alone or in combination of two or more thereof. be able to. Among these, a hydrophilizing agent containing at least one selected from the group consisting of anionic surfactants and nonionic surfactants is preferable because the degree of hydrophilization can be easily controlled. The amount of the hydrophilizing agent applied to the synthetic fibers constituting the fiber mass 11 is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, as the amount of the surfactant contained in the hydrophilizing agent. It is more preferably 0.05% by mass or more, preferably 10% by mass or less, still more preferably 5% by mass or less, and even more preferably 2% by mass or less.

Examples of the anionic surfactant include an alkyl sulfate, an alkyl sulfonate, an alkyl carboxylate, and an alkyl sulfosuccinate, and an anionic surfactant having a sulfonic acid group as a hydrophilic group is particularly preferable.

As the anionic surfactant in which the hydrophilic group is sulfonic acid or a salt thereof, for example, dialkyl sulfonic acid or a salt thereof can be mentioned as a preferable example showing high permeability at a low concentration. Specific examples of the dialkylsulfonic acid include a dicarboxylic acid such as dioctadecylsulfosuccinic acid, didecylsulfosuccinic acid, ditridecylsulfosuccinic acid, di2-ethylhexylsulfosuccinic acid, dialkylsulfosuccinic acid and dialkylsulfoglutaric acid, and diesters. Saturated fatty acids and unsaturated fatty acids such as compounds sulfonated from the alpha position of, 2-sulfotetradecanoic acid 1-ethyl ester (or amide) sodium salt, 2-sulfohexadecanoic acid 1-ethyl ester (or amide) sodium salt, etc. Alpha sulfo fatty acid alkyl ester (or amide) sulfonated at the α-position of the ester (or amide), dialkylalkene sulfonic acid obtained by sulfonated the internal olefin of the hydrocarbon chain or the internal olefin of the unsaturated fatty acid, etc. Can be mentioned. The number of carbon atoms of each of the two-chain alkyl groups of the dialkyl sulfonic acid is preferably 4 or more and 14 or less, and particularly preferably 6 or more and 10 or less. Examples of the dialkylsulfosuccinate include Perrex OT-P (product name) manufactured by Kao Corporation.

Examples of the cationic surfactant include alkyl (or alkenyl) trimethylammonium halides, dialkyl (or alkenyl) dimethylammonium halides, alkyl (or alkenyl) pyridinium halides, and the like, and these compounds have 6 or more carbon atoms. Those having an alkyl group or an alkenyl group of 18 or less are preferable. Examples of the halogen in the halide compound include chlorine and bromine.

Examples of the amphoteric surfactant include alkyl (1 to 30 carbon atoms) dimethyl betaine, alkyl (1 to 30 carbon atoms) amidoalkyl (1 to 4 carbon atoms) dimethyl betaine, and alkyl (1 to 30 carbon atoms) dihydroxy. Betaine-type amphoteric surfactants such as alkyl (1 to 30 carbon atoms) betaine and sulfobetaine type amphoteric surfactants, alanine type [alkyl (1 to 30 carbon atoms) aminopropionic acid type, alkyl (1 to 30 carbon atoms) 30) Iminodipropionic acid type] Amphoteric surfactant, glycine type such as alkyl betaine [alkyl (carbon number 1 to 30) aminoacetic acid type, etc.] Amino acid type amphoteric surfactant such as amphoteric surfactant, alkyl (carbon number) 1-30) Examples thereof include aminosulfonic acid-type amphoteric surfactants such as taurine-type.

Examples of the nonionic surfactant include polyhydric alcohol fatty acid esters such as glycerin fatty acid ester, poly (preferably n = 2 to 10) glycerin fatty acid ester, and sorbitan fatty acid ester (all preferably having 8 to 8 carbon atoms in the fatty acid). 60), an alkylene oxide adduct of the polyhydric fatty acid fatty acid ester (preferably 2 to 60 mol of the addition mole),
Polyoxyalkylene (additional mole number 2 to 60) alkyl (carbon number 8 to 22) amide, polyoxyalkylene (addition mole number 2 to 60) alkyl (carbon number 8 to 22) ether, polyoxyalkylene modified silicone, amino modification Examples include silicone.

As the raw material fiber of the constituent fiber 11F of the fiber mass 11, that is, the synthetic fiber not containing the hydrophilic agent, various synthetic fibers used for hygienic products can be used without particular limitation, but is preferably thermoplastic. It is a fiber. The reason why the thermoplastic fiber is preferable as the fiber 11F is that the fiber mass 11 is provided with a three-dimensional structure in which a plurality of thermoplastic fibers 11F are heat-sealed to each other, and the absorbent core 40 is in a dry state or a wet state. However, this is to enable excellent effects in shape retention, flexibility, cushioning property, compression recovery property, and resistance to twisting. Further, as described above, it is preferable that the extended fiber bundle portion 113S has a heat-sealed portion. However, since the constituent fiber 11F of the fiber mass 11 is a thermoplastic fiber, such an extended fiber bundle portion It is also possible to obtain a preferable form of 113S. In order to obtain a fiber mass 11 in which a plurality of heat-sealed portions are three-dimensionally dispersed, the raw material fiber sheets 10bs (see FIG. 6) may be similarly configured, and such a plurality of heats may be obtained. As described above, the raw material fiber sheet 10bs in which the fused portions are three-dimensionally dispersed can be manufactured by subjecting a web or a non-woven fabric mainly composed of thermoplastic fibers to a heat treatment such as hot air treatment.

Further, as described above, the constituent fibers 11F constituting the fiber mass 11 are hydrophilic so that the contact angle with water is preferably 75 degrees or less, but they are non-water-absorbent, that is, water (urine, menstrual blood, etc.). It is preferable that it has a property of being difficult to absorb (body fluid). This is in stark contrast to the water-absorbent fiber 12F used in combination with the fiber mass 11 which literally has water absorbency. Since the fiber 11F is a non-water-absorbent fiber having poor water absorption, the presence of the above-mentioned fiber mass 11 occurs not only when the absorbent core 40 is in a dry state but also when it is in a wet state by absorbing body fluid. The resulting action and effect (improvement effect such as shape retention, flexibility, cushioning property, compression recovery property, and resistance to twisting) will be stably exhibited. Therefore, the raw material fiber is preferably a non-water-absorbent synthetic fiber.

As used herein, the term "water-absorbent" is easily understood by those of skill in the art, for example, pulp is said to be water-absorbent. Similarly, it can be easily understood that thermoplastic fibers are non-absorbent. On the other hand, the degree of water absorption of fibers such as synthetic fibers can also be determined by the value of the water content measured by the following method. As the water-absorbent fiber, the water content is preferably 6% or more, more preferably 10% or more. On the other hand, the non-water-absorbent fiber preferably has such a water content of less than 6%, more preferably less than 4%. If the water content is less than 6.0%, the fiber is determined to be a non-water-absorbent fiber, and if it is 6.0% or more, the fiber is determined to be a water-absorbent fiber.

<Measurement method of moisture content>
The water content was calculated by applying the water content test method of JIS P8203 mutatis mutandis. That is, after the fiber sample was allowed to stand in a test room having a temperature of 40 ° C. and a relative humidity of 80% RH for 24 hours, the weight W (g) of the fiber sample before the absolute drying treatment was measured in the room. Then, it was allowed to stand for 1 hour in an electric dryer having a temperature of 105 ± 2 ° C. (for example, manufactured by Isuzu Seisakusho Co., Ltd.) to dry out the fiber sample. After the absolute drying treatment, Si silica gel (for example, Si silica gel (for example,) in a state where the fiber sample is covered with Saran Wrap (registered trademark) manufactured by Asahi Kasei Corporation in a test room in a standard state with a temperature of 20 ± 2 ° C. and a relative temperature of 65 ± 2%. Toyoda Kako Co., Ltd. is placed in a glass desigator (for example, manufactured by Tech Jam Co., Ltd.) and allowed to stand until the temperature of the fiber sample reaches 20 ± 2 ° C. Then, the constant amount W'(g) of the fiber sample is weighed, and the water content of the fiber sample is obtained by the following formula. Moisture content (%) = (W-W'/ W') x 100

As the raw material fiber of the constituent fiber 11F of the fiber mass 11, as described above, a synthetic fiber made of a thermoplastic and non-water-absorbent synthetic resin is preferable. Examples of such preferable synthetic resins (thermoplastic resins) include polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate; polyamides such as nylon 6 and nylon 66; polyacrylic acid, polymethacrylic acid alkyl esters, and polyvinyl chloride. Examples thereof include vinyl and polyvinylidene chloride, and one of these can be used alone or in combination of two or more. The fiber 11F may be a single fiber made of one kind of synthetic resin (thermoplastic resin) or a blend polymer in which two or more kinds of synthetic resins are mixed, or may be a composite fiber. The composite fiber referred to here is a synthetic fiber (thermoplastic fiber) obtained by compounding two or more kinds of synthetic resins having different components with a spinneret and spinning them at the same time, and a plurality of components are continuous in the length direction of the fiber. A structure that is mutually bonded within a single fiber. The form of the composite fiber includes a core sheath type, a side-by-side type, and the like, and is not particularly limited.

The content of the hydrophilizing agent in the fiber 11F may be appropriately adjusted depending on the type of the raw material fiber and the hydrophilizing agent, the desired degree of hydrophilization, and the like, and is not particularly limited. For example, the thermoplastic resin may be used as the raw material fiber. When a material is used, a general hydrophilic agent used for sanitary products is used, and the contact angle of the fiber 11F with water is 75 degrees or less, the total mass of the fiber 11F is used. On the other hand, it is preferably 0.2% by mass or more, more preferably 0.4% by mass or more, and preferably 2.0% by mass or less, still more preferably 1.5% by mass or less. If the content of the hydrophilizing agent is too small, the degree of hydrophilization of the fiber mass 11 may be low and the above-mentioned action and effect may not be sufficiently exerted. On the contrary, if the content is too large, the raw material at the manufacturing site of the fiber mass 11 There is a risk of line contamination during transport of fiber sheets.

On the other hand, as the water-absorbent fiber 12F used in combination with the fiber mass 11, hydrophilic and water-absorbent fibers conventionally used as a material for forming an absorbent core of this kind of absorbent article can be used, for example. Wood pulp such as coniferous tree pulp and broadleaf tree pulp, natural fiber such as non-wood pulp such as cotton pulp and hemp pulp; modified pulp such as cationized pulp and marcelled pulp; recycled fiber such as cupra and rayon are mentioned. Can be used alone or in combination of two or more.

The contact angle of the constituent fibers 11F (synthetic fiber 11F) of the fiber mass 11 with water is preferably equal to or larger than the contact angle of the water-absorbent fiber 12F with water. That is, it is preferable that the hydrophilicity of the synthetic fiber 11F is equal to or lower than the hydrophilicity of the water-absorbent fiber 12F. By establishing such a magnitude relationship of hydrophilicity, the movement of body fluid from the fiber mass 11 to the water-absorbent fiber 12F or the opposite direction becomes smoother, and the liquid-absorbing property of the absorbent core 40 becomes smoother. Can be expected to be further improved. In order to realize the magnitude relationship of "fiber 11F ≥ water-absorbent fiber 12F" with respect to the contact angle with water as described above, the degree of hydrophilization of the fiber 11F by the hydrophilizing agent may be appropriately adjusted. The contact angle of the water-absorbent fiber 12F with water is preferably 60 degrees or less, more preferably 40 degrees or less, assuming that the contact angle of the water-absorbent fiber 12F is less than that of the fiber 11F.

Further, it is preferable that the contact angle of the constituent fibers 11F (synthetic fiber) of the fiber mass 11 with water is smaller than the contact angle of the surface sheet 2 with water. That is, the hydrophilicity of the fiber 11F is preferably higher than that of the surface sheet 2. Due to the establishment of such a magnitude relationship of hydrophilicity, in the napkin 1, the liquid absorbed by the surface sheet 2 is quickly taken into the absorbent core 40, and the liquid in the plane direction inside the absorbent core 40 described above is also established. Due to the diffusion effect, the liquid retention amount of the surface sheet 2 and the absorbent core 40 is reduced, particularly in the excretion portion facing portion located in the central portion of the vertical central region B (see FIG. 1) of the napkin 1, and by extension, the liquid retention amount is reduced. Even after the liquid is absorbed, the effect of excellent cushioning in the portion facing the excretory portion and its vicinity is exhibited. In this way, in order to realize the magnitude relationship of "surface sheet 2> fiber 11F (fiber mass 11) ≥ water-absorbent fiber 12F" with respect to the contact angle with water, the degree of hydrophilization of the fiber 11F by the hydrophilic agent is adjusted. In addition, if necessary, the surface sheet 2 may be subjected to the same hydrophilization treatment as the fiber 11F to be appropriately adjusted.

In the absorbent core 40, the content mass ratio of the fiber mass 11 and the water-absorbent fiber 12F is not particularly limited, and the types of the constituent fibers 11F (synthetic fiber containing a hydrophilic agent) and the water-absorbent fiber 12F of the fiber mass 11 are not particularly limited. However, from the viewpoint of more reliably achieving the predetermined effect of the present invention, the content mass ratio of the fiber mass 11 and the water-absorbent fiber 12F is the former (fiber mass 11) /. The latter (water-absorbent fiber 12F) is preferably 20/80 to 80/20, more preferably 40/60 to 60/40.

The content of the fiber mass 11 in the absorbent core 40 is preferably 20% by mass or more, more preferably 40% by mass or more, and preferably 80% by mass or less with respect to the total mass of the absorbent core 40 in a dry state. , More preferably 60% by mass or less.
The content of the water-absorbent fiber 12F in the absorbent core 40 is preferably 20% by mass or more, more preferably 40% by mass or more, and preferably 80% by mass with respect to the total mass of the absorbent core 40 in a dry state. Below, it is more preferably 60% by mass or less.

The basis weight of the fiber mass 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, still more preferably 480 g / m ² or less. ..
The basis weight of the water-absorbent fiber 12F 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, further preferably 480 g / m ² or less. be.

As described above, the excellent effect exerted by the absorbent core 40, specifically, for cushioning property, compression recovery property, liquid drawing property, liquid diffusivity, etc. in both a dry state and a wet state. The excellent effect is largely due to the inclusion of the fiber lump 11 whose constituent fiber is the fiber 11F containing the hydrophilic agent, and the distribution state of the fiber lump 11 in the absorbent core 40 is due to the absorbent core 40. It can have a considerable effect on the manifestation of action and effect.

For example, when the absorbent core 40 is divided into two equal parts in the thickness direction (the direction orthogonal to the skin facing surface or the non-skin facing surface of the absorbent core 40), the side relatively close to the skin of the wearer of the napkin 1. That is, when the fiber lump 11 is present on the skin-facing surface side (surface sheet 2 side) of the absorbent core 40, the fiber lump 11 having a lower liquid retention property than the water-absorbent fiber 12F is close to the wearer's skin. As a result, the body fluid is smoothly transferred from the skin-facing surface side to the non-skin-facing surface side (back surface sheet 3 side), and the liquid draw-in property of the absorbent core 40 is improved. Since the amount of liquid remaining on the surface of the surface sheet 2 facing the skin is reduced, an unpleasant wet feeling and a sticky feeling can be suppressed, which can lead to an improvement in the wearing feeling of the napkin 1.

Further, the expression of action and effect (cushioning property, liquid absorbing property, etc.) by the absorbent core 40 is influenced not only by the distribution state of the fiber mass 11 in the absorbent core 40 but also by the orientation of the fiber mass 11. .. Basically, the plurality of fiber lumps 11 contained in the absorbent core 40 are random with respect to the thickness direction of the absorbent core 40 (the direction orthogonal to the skin facing surface or the non-skin facing surface of the absorbent core 40). When it is oriented to, it is preferable because the cushioning property, particularly the cushioning property and the compression recovery property in the wet state of the absorbent core 40 and the liquid absorbing property can be compatible at a high level. Here, "the fiber lumps 11 are randomly oriented with respect to the thickness direction of the absorbent core 40" means the longitudinal direction of each of the plurality of fiber lumps 11 (main body 110), that is, the longitudinal length of the basic surface 111. When focusing on the direction (maximum delivery length direction, radial direction), it means that the major axis directions of each of the plurality of fiber lumps 11 included in the absorbent core 40 are not uniform with each other. When the production of the absorbent core 40 is carried out according to a conventional method using a known fiber stacking device equipped with a rotating drum, the plurality of fiber lumps 11 contained in the absorbent core 40 usually have the absorbent core 40. It becomes a state of being randomly oriented with respect to the thickness direction of.

Further, at least a part of the plurality of fiber lumps 11 contained in the absorbent core 40 is oriented so that the major axis direction (longitudinal direction of the basic surface 111) is along the thickness direction of the absorbent core 40. Is preferable. The term "oriented along the thickness direction" as used herein means that the angle between the long axis direction of the fiber mass 11 and the thickness direction of the absorbent core 40 is 45 degrees or less. When the fiber mass 11 is oriented in the absorbent core 40 so that the major axis direction of the fiber mass 11 is along the thickness direction of the absorbent core 40, the fiber mass 11 is not so oriented. In this case, for example, when the long axis direction of the fiber mass 11 coincides with the direction orthogonal to the thickness direction of the absorbent core 40, that is, the fiber mass 11 is a surface facing the skin or a non-skin facing surface of the absorbent core 40. The resilience of the absorbent core 40, especially in the wet state, can be further improved as compared with the case where it is oriented along the direction. Of all the fiber lumps 11 contained in the absorbent core 40, preferably 30% by mass or more, more preferably 50% by mass or more, the major axis direction of such fiber lumps 11 is in the thickness direction of the absorbent core 40. It is preferable that the orientation is along the line.

As described above, the excellent liquid absorbency (liquid drawability, liquid diffusivity, etc.) of the absorbent core 40 is the constituent fibers 11F existing on the surface of the main body 110 of the fiber mass 11, that is, the basic surface 111 and the skeleton surface 112. It is largely due to the interfiber voids. In this regard, the constituent fibers 11F of the fiber mass 11 are preferably oriented in the plane direction of the basic surface 111. With such a configuration, since a large number of interfiber gaps of the constituent fibers 11F are formed on the basic surface 111 of the fiber mass 11 (main body portion 110), the liquid absorption property of the absorbent core 40 can be further improved. Here, "the fiber 11F is oriented in the plane direction of the basic surface 111" means a state in which the fiber 11F extends along the plane direction of the basic surface 111. It is more preferable that the fibers 11F extend along the longitudinal direction of the basic surface 111. Further, it is more preferable that the total number of fibers 11F existing on the basic surface 111 is preferably 30% or more, more preferably 50% or more, oriented in the plane direction (preferably the longitudinal direction) of the basic surface 111.

The absorbent core 40 may contain other components other than the fiber mass 11 and the water-absorbent fiber 12F, and a water-absorbent polymer can be exemplified as the other component. As the water-absorbent polymer, a particulate polymer is generally used, but a fibrous polymer may also be used. When a particulate superabsorbent polymer is used, its shape may be spherical, lumpy, bale-shaped or amorphous. The average particle size of the water-absorbent polymer is preferably 10 μm or more, more preferably 100 μm or more, and preferably 1000 μm or less, still more preferably 800 μm or less. As the water-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 salts thereof, and polymethacrylic acid and salts thereof.

The content of the water-absorbent polymer in the absorbent core 40 is preferably 5% by mass or more, more preferably 10% by mass or more, and preferably 60% by mass or less with respect to the total mass of the absorbent core 40 in a dry state. , More preferably 40% by mass or less.
The basis weight of the water-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, still more preferably 70 g / m ² or less. ..

The absorbent core 40 can be manufactured in the same manner as the absorbent core containing this type of fiber material. As described above, the fiber mass 11 is a raw material fiber sheet (a sheet having the same composition as the fiber mass 11 and having a larger size than the fiber mass 11) as a raw material, using a cutting means such as a cutter. , Can be manufactured by cutting in two directions intersecting (orthogonal) with each other, and the plurality of fiber lumps 11 thus manufactured are "standard fiber aggregates" having uniform shapes and dimensions (for example, a main body portion). 110 is a rectangular parallelepiped shape). The absorbent core 40 including the fiber mass 11 and the water-absorbent fiber 12F can be manufactured according to a conventional method using, for example, a known fiber stacking device equipped with a rotating drum. Such a fiber stacking device typically includes a rotary drum having an accumulation recess formed on the outer peripheral surface thereof.
The accumulation recess is provided with a duct having a flow path inside for transporting the raw materials (fiber mass 11, water-absorbent fiber 12F) of the absorbent core 40, and the rotating drum is placed around the rotation axis along the circumferential direction of the drum. While rotating, the raw material conveyed on the air flow (vacuum air) generated in the flow path by suction from the inside of the rotating drum is made to be stacked in the accumulation recess. The fiber stack formed in the accumulation recess by the fiber stacking process 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, still more preferably 600 g / m ² or less.

The absorbent core 40 (absorbent 4) having the above-mentioned configuration is flexible and has excellent cushioning properties, is also excellent in compression recovery, is deformed with good responsiveness to external force, and is promptly deformed when the external force is released. Return to the original state. The characteristics of such an absorbent core can be evaluated on the basis of compression work (WC) and compression recovery rate (RC). The amount of compression work is a measure of the cushioning property of the absorbent core, and it can be evaluated that the larger the WC value is, the higher the cushioning property is. The compression recovery rate is a measure showing the degree of recovery when the absorbent core is compressed and the compressed state is released, and it can be evaluated that the larger the RC value, the higher the compression recovery. Further, considering the role of the absorbent core 40 in absorbing and retaining the liquid, the absorbent core 40 has a WC value and an RC value not only in a dry state but also in a wet state by absorbing body fluid or the like. Larger is preferred. In order for the absorbent core 40 to have such characteristics in a wet state, it is effective to use a synthetic fiber containing a hydrophilic agent as the constituent fiber 11F of the fiber mass 11 as described above, and the synthetic fiber. Is even better if it is non-absorbent and thermoplastic.

<Measurement method of compression work (WC) and compression recovery rate (RC)>
It is generally known that the compression work (WC) and compression recovery rate (RC) of the absorbent core 40 can be expressed by the measured values by KES (Kawabata Evaluation System) manufactured by Katou Tech Co., Ltd. (Reference: Standardization and analysis of texture evaluation (2nd edition), author Kio Kawabata, published on July 10, 1980). Specifically, the compression work amount and the compression recovery rate can be measured by using the automated compression test apparatus KES-FB3-AUTO-A manufactured by Kato Tech Co., Ltd. The measurement procedure is as follows.
A 195 mm × 68 mm rectangular sample in plan view (absorbent not wrapped in a core wrap sheet, that is, an absorbent core) is prepared and attached to the test table of the compression test device. Next, the sample is compressed between steel plates having a circular plane with an area of 2 cm ² . The compression rate is 0.01 cm / sec, and the maximum compression load is 490.2 mN / cm ² . The recovery process is also measured at the same speed. The compression work (WC) is expressed by the following equation. In the formula, T _m , To and P are the thickness under a load of 490.2 mN / cm ^{2 (4.9 kPa), 4.902 mN / cm 2} ₍ ⁴⁹ Pa), and the load at the time of measurement (mN), respectively. / Cm ² ) is shown.
The compression recovery rate (RC) is the ratio of the compression work amount (WC) at the time of compression and the compression work amount (WC') when the compressed state is restored to the original state [WC'/ WC). ] × 100.

The "dry absorbent core" to be measured by the measurement method is prepared by leaving the absorbent core to be measured in an environment of a temperature of 23 ° C. and a relative humidity of 50 RH% for 24 hours. Further, the "wet state absorbent core" to be measured by the measurement method is adjusted as follows. The dry absorbent core is placed horizontally so that the skin facing surface side is on the upper side, and a cylindrical acrylic plate with an injection port having a diameter of 1 cm is placed on the skin facing surface of the absorbent core. 5.0 g of defibrated horse blood was injected from the injection port, and the condition was maintained for 1 minute after the injection. The defibered horse blood injected into the absorbent core to be measured was a defibered horse blood manufactured by Nippon Biotest Co., Ltd., and the viscosity at a liquid temperature of 25 ° C. was adjusted to 8 cp. The viscosity is the viscosity when measured at a rotation speed of 30 rpm with a rotor of the rotor name L / Adp (rotor code 19) in a TVB-10M type viscometer manufactured by Toki Sangyo Co., Ltd. Further, in order to prevent the measuring device from getting wet when the measuring method is carried out, the portion of the measuring device corresponding to the injection point of the defibered horse blood of the measurement target (absorbent core) and the peripheral portion thereof is provided. Saran Wrap (registered trademark) manufactured by Asahi Kasei Corporation was covered with a piece of Saran Wrap (registered trademark) cut into 4 cm × 4 cm.

Although the present invention has been described above based on the embodiment, the present invention can be appropriately modified without being limited to the embodiment.
For example, in the above embodiment, the absorber 4 is configured to include the absorbent core 40 and the core wrap sheet 41 covering the absorbent core 40, but the core wrap sheet 41 may be omitted.
Further, in the absorbent core according to the present invention, all of the fiber lumps (synthetic fiber aggregates) contained therein do not have to be a fixed-shaped fiber aggregate such as the fiber lump 11, which deviates from the gist of the present invention. As long as it does not, a very small amount of atypical fiber aggregates may be contained in addition to the fixed-form fiber aggregates.
The absorbent article of the present invention broadly includes articles used for absorbing body fluids (urine, loose stool, menstrual blood, sweat, etc.) discharged from the human body, and in addition to the above-mentioned menstrual napkins, sanitary shorts and fastenings. So-called deployable disposable diapers with tape, pants-type disposable diapers, incontinence pads and the like are included. Further, the following additional notes are disclosed with respect to the above-described embodiment of the present invention.

<1> An absorber containing a fiber mass containing synthetic fibers and a water-absorbent fiber, in which a plurality of the fiber masses or the fiber mass and the water-absorbent fiber are entangled with each other, and the fiber mass is the fiber mass. An absorber having a main body portion defined by two basic surfaces facing each other and a skeleton surface intersecting both basic surfaces, and the synthetic fiber containing a hydrophilic agent.
<2> The absorber according to <1>, wherein the contact angle of the synthetic fiber with water is 75 degrees or less, preferably 70 degrees or less, more preferably 60 degrees or less, and more preferably 50 degrees or less.
<3> The absorber according to <1> or <2>, wherein the contact angle of the synthetic fiber with water is equal to or greater than the contact angle of the water-absorbent fiber with water.
<4> The absorber according to any one of <1> to <3>, wherein the synthetic fiber is a non-water-absorbent fiber.
<5> The absorber according to any one of <1> to <4>, wherein the total area of the two basic surfaces is larger than the total area of the skeleton surface.
<6> The number of fiber ends present on each of the basic surface and the skeleton surface per unit area is set to any one of <1> to <5> in which the number of the skeleton surface is larger than that of the basic surface. The absorber described.
<7> The ratio N ₁ / N ₂ between the number N ₁ per unit area of the fiber end portion of the basic surface and the number N ₂ per unit area of the fiber end portion of the skeleton surface is 0 or more and 0. The absorber according to <6>, which is 90 or less, preferably 0.05 or more and 0.60 or more.
<8> The number of the fiber ends of the basic surface per unit area is 0 pieces / mm ² or more, 8 pieces / mm ² or less, preferably 3 pieces / mm ² or more, 6 pieces / mm ² or less. The absorber according to <6> or <7>.
<9> The number of the fiber ends of the skeleton surface per unit area is 5 pieces / mm ² or more, 50 pieces / mm ² or less, preferably 8 pieces / mm ² or more, 40 pieces / mm ² or less. The absorber according to any one of <6> to <8>.

<10> The fiber mass includes an extended fiber portion extending outward from the main body portion and has an extended fiber portion having a fiber density lower than that of the main body portion, and the extended fiber portion of the extended fiber portion. The absorber according to any one of <1> to <9>, wherein at least one of them is an extended fiber bundle portion containing a plurality of fibers extending from the main body portion.
<11> The absorber according to any one of <1> to <10>, wherein the main body portion has a rectangular parallelepiped shape.
<12> The absorber according to any one of <1> to <11>, wherein the plurality of fiber lumps contained in the absorber are randomly oriented with respect to the thickness direction of the absorber.
<13> The basic surface has a long shape in one direction, and at least a part of the plurality of fiber lumps contained in the absorber has a longitudinal direction of the basic surface along the thickness direction of the absorber. The absorber according to any one of <1> to <12>, which is oriented in.
<14> The absorber according to any one of <1> to <13>, wherein the content mass ratio of the fiber mass to the water-absorbent fiber is 20/80 to 80/20 as the former / the latter.
<15> The absorber according to any one of <1> to <14>, wherein the constituent fibers of the fiber mass are oriented in the plane direction of the basic surface.

<16> The fiber mass is present in the absorber in a state where it is entangled with another fiber mass or the water-absorbent fiber, and can also be entangled with the other fiber mass or the water-absorbent fiber. The absorber according to any one of <1> to <15>.
<17> The total number of the fiber lumps bonded by the entanglement and the fiber lumps in a state where the fiber lumps can be entangled is preferably half or more, more preferably 70%, based on the total number of the fiber lumps in the absorber. As mentioned above, the absorber according to <16>, which occupies 80% or more more preferably.
<18> preferably 70% or more, more preferably 80% or more of the total number of the fiber lumps having a bond with the other fiber lump or the water-absorbent fiber is formed by entanglement of the fibers. The absorber according to any one of <1> to <17>.
<19> The absorber according to any one of <1> to <18>, wherein the fiber mass is derived from a non-woven fabric.
<20> The above-mentioned <1> to which the hydrophilic agent contains one or more selected from the group consisting of an anionic surfactant, a cationic surfactant, an amphoteric surfactant and a nonionic surfactant. The absorber according to any one of <19>.
<21> The absorber according to <20>, wherein the hydrophilic agent contains an anionic surfactant.
<22> The absorber according to <21>, wherein the anionic surfactant contains an alkylsulfosuccinate.

<23> An absorbent article comprising the absorber according to any one of <1> to <22>.
<24> A liquid-permeable surface sheet is provided on one surface side of the absorber, and the fiber mass is present on a side relatively close to the surface sheet side when the absorber is bisected in the thickness direction. The absorbent article according to any one of <1> to <23>.
<25> The absorbent body and the surface sheet arranged on the skin facing surface side of the absorbent body are provided, and the contact angle of the synthetic fiber with water is compared with the contact angle of the surface sheet with water. The absorbent article according to <24>, which is small and has a contact angle of the water-absorbent fiber with water or more.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to such Examples.

[Examples 1 to 5]
An absorbent core was produced and used as a sample of the absorber of each example. Specifically, the fiber mass and the water-absorbent fiber were used as the fiber material of the absorbent core, and the fiber mass and the water-absorbent fiber were manufactured according to a conventional method using a known fiber stacking device. The fiber mass was produced by cutting the raw material fiber sheet into a diced pattern according to FIG.
As the raw material fiber sheet of the fiber mass, the basis weight is 21 g / m ² and the constituent fiber is a non-water-absorbent thermoplastic fiber composed of a polyethylene resin fiber and a polyethylene terephthalate resin fiber (non-water-absorbent fiber, fiber diameter 1.8 μm). An air-through non-woven fabric having a thickness of 0.6 mm (a fiber sheet having a heat-sealed portion between constituent fibers) was used. The constituent fibers of the fiber mass were in the form of a hydrophilic agent attached on a thin film on the surface of a non-water-absorbent thermoplastic fiber which is a raw material fiber. In Examples 1 to 4, the composition A having the following composition was used as the hydrophilic agent in an amount of 0.4% by mass based on the mass of the constituent fibers of the fiber mass. Further, in Example 5, the composition A and a commercially available surfactant (Perex OT-P, manufactured by Kao Corporation) are used as the hydrophilizing agent, and the amount of the hydrophilizing agent used is the mass of the constituent fibers of the fiber mass. On the other hand, the former was 0.4% by mass and the latter was 0.2% by mass. As the water-absorbent fiber, softwood bleached kraft pulp (NBKP) having a fiber diameter of 2.2 μm was used. The fiber mass (standard synthetic fiber aggregate) used for the absorbent core has a rectangular parallelepiped main body as shown in FIG. 5A, and the short side 111a of the basic surface 111 thereof is 0.8 mm and the long side. The 111b had a thickness of 3.9 mm and the thickness T had a thickness of 0.6 mm. The number of fiber ends per unit area on the basic surface 111 was 3.2 pieces / mm ² , and the number of fiber ends on the skeleton surface 112 was 19.2 pieces / mm ² . In the absorbent cores of each example, the fiber lumps were densely and evenly distributed.

(Composition of Composition A)
-Alkyl phosphate ester potassium salt (neutralized potassium hydroxide of gripper 4131 manufactured by Kao Co., Ltd.) 25% by mass
・ Dialkylsulfosuccinate sodium salt (Perex OT-P manufactured by Kao Corporation)
10% by mass
-Alkyl (stearyl) betaine (Ancitor 86B manufactured by Kao Corporation) 15% by mass
-Polyoxyethylene (additional number of moles: 2) Stearyl amide (Amizole SDE manufactured by Kawaken Fine Chemicals) 30% by mass
-Polyoxyethylene, polyoxypropylene-modified silicone (X-22-4515 manufactured by Shin-Etsu Chemical Co., Ltd.) 20% by mass

[Comparative Example 1]
The absorbent core of a commercially available menstrual napkin (manufactured by Unicharm Co., Ltd., trade name "Tanom Pew Slim 23 cm") was used as it was as the absorber of Comparative Example 1. The absorbent core of Comparative Example 1 is a mixture of synthetic fibers and cellulosic fibers (hydrophilic fibers) and does not contain fiber lumps.

[Comparative Example 2]
Examples 1 to 1 except that an amorphous non-woven fabric piece was used as the fiber mass and the absorbent core was subjected to a hot air step to heat-fuse the non-woven fabric pieces contained in the absorbent core to each other. The absorber was produced in the same manner as in 5. In the hot air process applied to the absorbent core, a mixed aggregate of non-woven fabric pieces and pulp fibers (length 210 mm × width 66 mm) is placed in an electric dryer (for example, manufactured by Isuzu Seisakusho Co., Ltd.) at a temperature of 140 ° C. The non-woven fabric pieces were allowed to stand for 30 minutes, and the pieces of the non-woven fabric were heat-sealed. The amorphous non-woven fabric piece used was manufactured by tearing the same non-woven fabric piece as the air-through nonwoven fabric used in the example in an arbitrary direction, and the transfer length in a plan view was about 25 mm. Further, in Comparative Example 2, the composition A was used as the hydrophilic agent applied to the constituent fibers of the nonwoven fabric piece.

[Performance evaluation]
For the absorbers of each Example and Comparative Example, the compression work amount in the dry state (d-WC), the compression work amount in the wet state (w-WC), and the compression recovery rate in the dry state (d) by the above method. -RC) and the compression recovery rate (w-RC) in the wet state were measured, respectively. The results are shown in Table 1 below.

As shown in Table 1, the absorber of each example was hydrophilized and contained synthetic fibers containing a hydrophilizing agent and was defined by two basic surfaces and a skeletal surface intersecting both basic surfaces. Due to the inclusion of a fixed-sized fiber mass, the amount of compression work is large in both the dry state and the wet state as compared with Comparative Examples 1 and 2 which do not contain such a fiber mass, and compression recovery is performed. The rate also showed a high value in both the dry state and the wet state. In particular, from the comparison between each example and Comparative Example 2, in order to obtain an absorber having a large compression work even in a wet state and excellent cushioning property, in addition to hydrophilizing the fiber mass in the absorber, further It can be seen that it is effective to make the fiber lumps into a fixed shape and to connect the fiber lumps by entanglement.

1 Menstrual napkin (absorbent article)
A Front area B Vertical center area C Rear area 2 Front sheet 3 Back sheet 4 Absorber 40 Absorbent core 11 Fiber mass 11F Fiber mass constituent fibers (synthetic fiber)
110 Main body 111 Basic surface 112 Skeleton surface 113 Extended fiber part 113S Extended fiber bundle part 12F Water-absorbent fiber 41 Core wrap sheet 5 Absorbent main body 6 Side sheet 10bs Raw material fiber sheet for fiber mass

Claims (9)

An absorber containing a fiber mass containing synthetic fibers and a water-absorbent fiber, and a plurality of the fiber masses or the fiber mass and the water-absorbent fiber are entangled with each other.
The fiber mass has a main body portion defined by two basic surfaces facing each other and a skeletal surface intersecting both basic surfaces.
The basic surface has a long shape in one direction, and at least a part of the plurality of fiber lumps contained in the absorber is oriented so that the longitudinal direction of the basic surface is along the thickness direction of the absorber. And
An absorber in which the synthetic fiber contains a hydrophilic agent. The absorber according to claim 1, wherein the contact angle of the synthetic fiber with water is 75 degrees or less. The absorber according to claim 1 or 2, wherein the total area of the two basic surfaces is larger than the total area of the skeletal surface. The absorber according to any one of claims 1 to 3, wherein the number of fiber ends present on each of the basic surface and the skeletal surface per unit area is larger on the skeletal surface than on the basic surface. The fiber mass has an extended fiber portion configured to include fibers extending outward from the main body portion.
The absorber according to any one of claims 1 to 4, wherein at least one of the extended fiber portions is an extended fiber bundle portion including a plurality of fibers extending from the main body portion. The absorber according to any one of claims 1 to 5 , wherein the content mass ratio of the fiber mass to the water-absorbent fiber is 20/80 to 80/20 as the former / the latter. The absorber according to any one of claims 1 to 6 , wherein the constituent fibers of the fiber mass are oriented in the plane direction of the basic surface. An absorbent article comprising the absorber according to any one of claims 1 to 7 . 8. Claim 8 in which a liquid-permeable surface sheet is provided on one surface side of the absorber, and the fiber mass is present on a side relatively close to the surface sheet side when the absorber is bisected in the thickness direction. Absorbent article described in.

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