JP6554524B2 - Absorbent articles - Google Patents

Description

  The present invention relates to absorbent articles such as sanitary napkins.

  Absorbent articles such as disposable diapers and sanitary napkins are generally a top sheet that is relatively disposed near the wearer's skin and a back sheet that is relatively distant from the wearer's skin. And the absorber interposed between both sheets. The absorbent body typically comprises an absorbent core which is the main component of the absorbent body, and a core wrap sheet which covers the surface of the absorbent core, and the absorbent core is made of a water absorbent material such as wood pulp. In many cases, it is mainly composed of fibers and further contains water-absorbing polymer particles. As for the absorbent body used for the absorbent article, improvement of various properties such as flexibility (cushioning property), compression recovery property, and shape retention property is a major issue.

  As an improvement technique of the absorber, for example, Patent Document 1 discloses an absorber comprising a thermoplastic resin fiber and a cellulose-based water-absorbent fiber, wherein the thermoplastic resin fiber has a surface on the surface sheet side of the absorber. What is exposed on both the surface of the back sheet side of this and an absorber is described. According to the absorbent body described in Patent Document 1, since the thermoplastic resin fiber functions as a skeleton for holding other components of the absorbent body such as a cellulose-based water absorbent fiber, it is soft and difficult to twist. .

  Further, Patent Document 2 describes an absorbent body containing non-woven fabric pieces to which a three-dimensional structure has been imparted by bonding between fibers in advance, which contains heat-fusion fibers, and water-absorbent fibers. The non-woven fabric piece of this 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 due to such a manufacturing method, FIGS. 3 has an indefinite shape and does not substantially have a portion that can be regarded as a flat surface. Patent Document 2 describes, as a preferred form of the absorbent body described in the document, a non-woven fabric piece that is heat-sealed. According to the absorbent body described in Patent Document 2, since the non-woven fabric piece has a three-dimensional structure, a void is formed inside the absorbent body, and the restorability when absorbing water is improved, and as a result, the water absorption performance is improved. It is supposed to be.

  Further, Patent Document 3 describes a fine web having relatively dense fine fiber nuclei and fibers or fiber bundles extending outward from the nuclei, and the fine web and wood pulp or a water absorbing polymer. It is described that non-woven webs mixed with particles can be used as an absorbent for absorbent articles. This fine web is manufactured by peeling or tearing off a raw material sheet such as a non-woven fabric. Like the non-woven fabric piece described in Patent Document 2, the fine web has an indefinite shape and can be regarded as a flat surface. It does not have substantially.

  Further, in Patent Document 4, when a water-absorbing polymer is contained in the absorbent body, when the absorbent body absorbs the liquid and expands, sealing of the top sheet and the back sheet disposed above and below the absorbent body In order to solve the problem that the swelling of the water-absorbing polymer is prevented by the above, it is described that a cushioning layer having high compression / compression recovery and liquid permeability is interposed between the surface sheet and the absorbent. In addition, it is described that the cushion layer is formed as an aggregate of non-woven fabric strips and that the thickness of the cushion layer is 10 to 40 mm. Patent Document 4 does not specifically describe the shape and the like of the non-woven fabric pieces used for the cushion layer.

JP, 2015-16296, A JP 2002-301105 A Unexamined-Japanese-Patent No. 1-156560 JP 2003-52750 A

  The absorbent body described in Patent Document 1 contains synthetic fibers (thermoplastic resin fibers) in addition to the cellulose-based water-absorbing fibers, so that the absorbent body contains only cellulose-based water-absorbing fibers as a constituent fiber. It has high rigidity and can be expected to improve various properties such as cushioning and compression recovery properties. However, a plurality of synthetic fibers contained in it exist independently. The effect of improving the properties is not sufficient, and therefore, when applied to an absorbent article, there is a risk of easy fit and inadequate fit, particularly urine, After absorption of body fluid such as menstrual blood, the occurrence of such inconvenience is remarkable.

  On the other hand, in any of the absorbers described in Patent Documents 2 to 4, since the synthetic fibers contained therein are synthetic fiber aggregates called non-woven fabric pieces or fine webs, improvement in cushioning properties and the like can be expected. However, according to the findings of the present inventor, when a large number of such weakly water-absorbing synthetic fiber aggregates are contained in the absorber, the liquid permeability of the absorber is reduced, and as a result, the surface sheet is permeated. The body fluid reaching the skin-facing surface (core wrap sheet) of the absorbent is less likely to be drawn into the absorbent (absorbent core), and a large amount of fluid remains on the skin-facing surface of the absorbent, causing unpleasant skin. It causes stickiness and a feeling of getting wet. Patent Documents 2 to 4 do not describe the problem of the absorbent caused by the weakly water-absorptive synthetic fiber assembly, and while utilizing the advantages of the synthetic fiber assembly, a technique for solving such problems is still provided. It has not been.

  Therefore, the subject of this invention is related to providing an absorbent article provided with the absorber which has the high liquid permeability to an absorptive core, and is excellent in cushioning properties.

  The present invention is an absorbent which has a longitudinal direction corresponding to the front and rear direction of the wearer and a lateral direction orthogonal thereto, and comprises an absorbent body and a surface sheet disposed on the skin facing surface side of the absorbent body. The absorbent body includes a liquid-absorbent absorbent core and a core wrap sheet that covers the skin-facing surface of the absorbent core, and the absorbent core includes water-absorbing fibers. And a fiber lump containing weakly water-absorbing fibers having a lower water absorption than the water-absorbing fibers, the liquid diffusion area of the absorbent core measured by the following method, and the core wrap sheet measured by the following method The ratio of the liquid diffusion area to the liquid diffusion area is 0.7 or more as the former / the latter.

<Method of measuring liquid diffusion area>
A measurement object is fixed on a slope having an angle of 45 ° with respect to a horizontal plane with the skin facing surface facing the slope, and 1.5 g of defibrinated horse blood is applied to the skin facing surface of the measurement object for 23 seconds. After injection and leaving for 3 minutes, the same amount of defibrillated horse blood is injected again into the same injection site for the same time. This defibrinated horse blood injection and leaving operation is repeated 6 times, and a total of 9 g of defibrinated horse blood is injected into the measurement object. After completion of the injection operation, the diffusion area of the defibrillated horse blood on the skin-facing surface to be measured is measured, and this is taken as the liquid diffusion area to be measured.

The absorbent article of the present invention comprises an absorbent body having high cushioning properties and liquid permeability. For this reason, according to the absorbent article of the present invention, it is difficult for the body fluid to remain on the side facing the skin of the absorber after body fluid excretion, and the unpleasant stickiness and wet feeling of the skin are reduced, and the wearing feeling and fit are excellent. Can be expected.

FIG. 1 is a plan view schematically showing a skin facing surface side (surface sheet side) of an example of a sanitary napkin which is an embodiment of the absorbent article according to the present invention with a part broken. FIG. 2 is a cross-sectional view schematically showing a cross section taken along line II of FIG. FIG. 3 is a schematic perspective view of a portion of the absorbent core included in the absorbent article shown in FIG. FIG. 4 is a view schematically showing a deformed state of the absorbent core shown in FIG. 3 at the time of compression. FIG. 5 (a) is an electron micrograph (observation magnification 25 ×) of an example of the fiber mass according to the present invention, and FIG. 5 (b) is the fiber mass contained in the absorber shown in FIG. It is the figure which showed typically the fiber lump of the microscope picture. FIG. 6 is an explanatory diagram of the fiber lump manufacturing method according to the present invention. FIG. 7A and FIG. 7B are schematic perspective views of the main body in the fiber mass according to the present invention. FIG. 8 is an explanatory view of a method of measuring the liquid diffusion area.

  Hereinafter, the present invention will be described based on its preferred embodiments with reference to the drawings. The sanitary napkin 1 which is one Embodiment of the absorbent article of this invention is shown by FIG.1 and FIG.2. The napkin 1 includes an absorbent body 4 for absorbing and holding a body fluid, a liquid-permeable surface sheet 2 disposed on the skin-facing side of the absorbent body 4 and capable of contacting the wearer's skin, and a non-absorbent absorbent body 4. And a back sheet 3 having low liquid permeability that is disposed on the side facing the skin. As shown in FIG. 1, the napkin 1 has a longitudinal direction X corresponding to the wearer's front-rear direction, extending from the wearer's abdomen side to the back side via the crotch portion, and a transverse direction Y orthogonal thereto. Also, in the longitudinal direction X, a longitudinal central area B including an excretory part opposing part (excretion point) facing the excretory part such as the vaginal opening of the wearer, and a ventral side of the wearer (the anterior side of the excretory part opposing part ) And a rear region C which is disposed on the back side (rear side) of the wearer with respect to the excretory part facing portion.

  In the present specification, the "skin-facing surface" is a surface of an absorbent article or a component thereof (for example, the absorbent body 4) that is directed to the skin side of the wearer when wearing the absorbent article, The side close to the skin, and the “non-skin facing surface” is directed toward the side opposite to the skin side when the absorbent article is worn, that is, the side relatively distant from the wearer's skin. It is a face to be In addition, "at the time of wearing" here means the state in which the normal proper wearing position, that is, the correct wearing position of the absorbent article is maintained.

  The napkin 1 is, as shown in FIG. 1, outward in the transverse direction Y from the absorbent main body 5 having a shape long in the longitudinal direction X and both side portions along the longitudinal direction X of the longitudinal central region B in the absorbent main body 5. It has a pair of wing portions 5W, 5W extending. The absorbent main body 5 is a main part of the napkin 1 and includes the front sheet 2, the back sheet 3 and the absorbent body 4 described above, and in the longitudinal direction X, the front area A, the longitudinal central area B and the rear area C It is divided into three.

  When the absorbent article has wings as in the case of the napkin 1, the longitudinal central area in the absorbent article of the present invention is a wing in the longitudinal direction (longitudinal direction, X direction in the figure) of the absorbent article. If the napkin 1 is taken as an example, it is a region sandwiched between the root along the vertical direction X of one wing portion 5W and the root along the vertical direction X of the other wing portion 5W. Moreover, the vertical center area | region in the absorbent article which does not have a wing part means the area | region located in the middle when an absorbent article is equally divided into 3 in the vertical direction.

  The absorbent body 4 includes a liquid-absorbent absorbent core 40 and a liquid-permeable core wrap sheet 41 that covers at least the skin-facing surface of the absorbent core 40. The absorbent core 40 has a long shape in the longitudinal direction X in plan view as shown in FIG. 1 like the absorbent main body 5, and the longitudinal direction of the absorbent core 40 is one in the longitudinal direction X of the napkin 1. 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 joined by an adhesive such as a hot-melt adhesive.

  In the napkin 1, the core wrap sheet 41 is one continuous sheet having a width that is not less than 2 times and not more than 3 times the length of the absorbent core 40 in the transverse direction Y. As shown in FIG. Covering the entire skin facing surface of the absorbent core 40 and extending outward from both side edges along the longitudinal direction X of the absorbent core 40 in the lateral direction Y. 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 may not be such a single sheet, for example, one skin side core wrap sheet for covering the skin facing surface of the absorbent core 40, and the skin side. The core wrap sheet may be separate from the core wrap sheet, and may include two sheets of one non-skin side core wrap sheet covering the non-skin facing surface of the absorbent core 40.

  As shown in FIG. 2, the top sheet 2 covers the entire area of the skin facing surface of the absorber 4. On the other hand, the back sheet 3 covers the whole area of the non-skin facing surface of the absorbent body 4 and extends outward from both side edges along the longitudinal direction X of the absorbent body 4 in the lateral direction Y, together with side sheets 6 described later A side flap portion (a portion formed of a member extending outward in the lateral direction Y from the absorber 4) is formed. The back sheet 3 and the side sheet 6 are bonded to each other at the extension from the side edges along the longitudinal direction X of the absorber 4 by a known bonding means such as an adhesive, heat seal, ultrasonic seal or the like. Each of the top sheet 2 and the back sheet 3 may be bonded to the absorber 4 by an adhesive. As the top sheet 2 and the back sheet 3, various types conventionally used for absorbent articles such as sanitary napkins can be used without particular limitation. For example, as the surface sheet 2, nonwoven fabric of a single layer or a multilayer structure, an apertured film, etc. 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 flaps largely project outward in the longitudinal central area B in the lateral direction Y, whereby a pair of left and right sides along the longitudinal direction X of the absorbent main body 5 are provided. 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 of the absorbent main body 5 in a plan view as shown in FIG. The wing part adhesion part (not shown) which fixes this wing part 5W to clothes, such as shorts, is formed. The wing portion 5W is used by being folded back to the non-skin facing surface (outer surface) side of the crotch portion of clothes such as shorts. The wing adhesive section is covered with a release sheet (not shown) made of a film, nonwoven fabric, paper, or the like before use. Further, on the skin opposing surface of the absorbent main body 5, that is, on both sides along the longitudinal direction X in the skin opposing surface of the surface sheet 2, a pair is provided so as to overlap the left and right sides along the longitudinal direction X of the absorber 4 in plan view. The side sheets 6, 6 are disposed over substantially the entire length of the absorbent main body 5 in the longitudinal direction X. The pair of side sheets 6 and 6 are joined to other members such as the surface sheet 2 by a known joining means such as an adhesive at joining lines (not shown) extending in the longitudinal direction X.

On the skin facing surface of the absorbent body 4, as shown in FIGS. 1 and 2, there is a recessed portion 7 in which a core wrap sheet 41 and an absorbent core are integrally recessed on the non-skin facing surface side of the absorbent body 4. It is partially formed. The recessed portion 7 is formed by subjecting the napkin 1 to a pressing process from the side facing the skin, that is, the surface sheet side, and it can also be referred to as a "pressed portion" from the forming method. A known method can be used as the pressing process, and examples thereof include embossing with or without heat, or ultrasonic embossing. Due to the formation method of the recessed portion 7, the top sheet 2, the core wrap sheet 41, and the absorbent core 40 are integrated toward the non-skin facing surface side (the back sheet 3 side) of the absorbent core 40. Is recessed. Moreover, the recessed part 7 has a high density compared with the peripheral part (non-formed part of the recessed part 7) according to the formation method. That is, the absorbent main body 5 has a high density portion corresponding to the recessed portion 7 and a low density portion corresponding to the non-recessed portion. In the bottom part of the recessed part 7, the surface sheet 2, the core wrap sheet | seat 41, and the absorptive core 40 may be heat-sealed and integrated.

  As shown in FIG. 1, the recessed portion 7 is formed at least in the vertical central region B, and more specifically, from the portion of the front region A near the vertical central region B to the vertical region B of the rear region C. Is continuous in the vertical direction X over the portion. In the napkin 1, the recess 7 is linear in a plan view as shown in FIG. 1, and the linear recess 7 has a closed annular shape in a plan view. The annular recess 7 has a shape that is long in the longitudinal direction X in plan view, and the longitudinal direction thereof coincides with the longitudinal direction X. The annular recess 7 is formed in a U-shape or an arc shape that protrudes outward in the longitudinal direction X in each of the front area A and the rear area C, and the U-shaped or arc-shaped top portion is a napkin. 1 in the center of the horizontal direction Y. The annular recess 7 is formed in a pair of left and right lines extending in the longitudinal direction X in the longitudinal center region B. Thus, the recess 7 is formed so as to surround the central portion in the horizontal direction Y of the vertical central area B.

  In the napkin 1, the depth of the recessed portion 7 (the depth from the facing surface of the surface sheet 2 which is not recessed) is constant over the entire length in the length direction. The depth of the recessed portion 7 can be set in the same range as the depth of the leak-proof groove in this type of absorbent article, and is usually about 1 to 10 mm. Examples of the effects that can be expected by forming the recessed portion 7 include suppression of liquid diffusion in the planar direction, particularly in the lateral direction Y of the absorber 4, and prevention of twisting of the absorber 4. In addition, the shape, arrangement and the like of the linear concave portion 7 are not limited to the illustrated form, and can be set in the same manner as what is called leak-proof groove etc. in this type of absorbent article. Each line may be a continuous line or a broken line (a form in which two types of portions having different depths are alternately arranged in the extending direction of the linear recess).

  One of the main features of the napkin 1 is an absorbent core 40. In FIG. 3, a part of the absorbent core 40 (the non-formed part of the recess 7) is shown. As shown in FIGS. 2 and 3, the absorbent core 40 includes a fiber mass 11 including a plurality of fibers (weakly water-absorbing synthetic fibers) 11F and water-absorbing fibers 12F. The fiber mass 11 is a fiber aggregate in which the fibers 11F are intentionally aggregated in a lump and integrated, while the water-absorbent fibers 12F can be present independently without being intentionally integrated. 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 fibers 12F mainly contribute to the improvement of the liquid absorbability and shape retention of the absorbent core 40. The absorbent core 40 can be substantially referred to as the absorbent 4 itself, and the description of the absorbent core 40 below is appropriately applied as the description of the absorbent 4 unless otherwise specified. That is, the present invention includes the case where the absorbent does not include the core wrap sheet and is formed only of the absorbent core, in which case the absorbent and the absorbent core have the same meaning.

  As used herein, “fiber mass” refers to a fiber assembly in which a plurality of fibers are united. As a form of a fiber lump, the sheet piece divided | segmented from the synthetic fiber sheet which has a fixed magnitude | size, for example is mentioned. In particular, a nonwoven fabric piece selected from a nonwoven fabric as the synthetic fiber sheet and cut into a predetermined size and shape from the nonwoven fabric is preferred as the fiber mass.

Thus, a sheet piece-like fiber lump which is a preferred embodiment of the fiber lump according to the present invention is not configured to accumulate a plurality of fibers to form the sheet piece, but from the sheet piece. Also, it is manufactured by cutting a large size fiber sheet (preferably non-woven fabric) (see FIG. 6). The plurality of fiber masses contained in the absorbent according to the present invention are a plurality of sheet-shaped fiber masses having high formability as compared with those produced by the prior art such as Patent Documents 1 and 2.

  By the way, the absorbent core containing the synthetic fiber aggregate which is weakly water-absorbent as described in patent documents 1-4 has low liquid permeability as mentioned above, therefore, the absorber using it The body fluid tends to remain on the skin-facing surface of the skin-side core wrap sheet that covers the skin-facing surface of the absorbent core, and as a result, uncomfortable skin stickiness and wetness may occur. As a result of various investigations by the present inventors in order to solve the problems resulting from the use of such weakly water-absorptive fibers, the liquid diffusivity in the surface direction of the skin-side core wrap sheet which normally contacts the body fluid in the absorber first. In relation to the liquid diffusibility in the surface direction of the absorbent core that comes into contact with the skin-side core wrap sheet, it has been found that setting a specific range is effective.

  Based on the above findings, in the napkin 1, the liquid diffusion area of the absorbent core 40 measured by the above <Method of measuring liquid diffusion area> and the liquid diffusion area of the skin-side core wrap sheet 41 measured by the same measurement method Ratio (hereinafter also referred to as “liquid diffusion area ratio”) is set to 0.7 or more as the former / the latter. When the liquid diffusion area ratio is 0.7 or more, the body fluid is easily transferred from the skin-side core wrap sheet 41 to the absorbent core 40, and the body fluid hardly remains on the skin-facing surface of the skin-side core wrap sheet 41. Uncomfortable skin stickiness and wetness can be reduced. The liquid diffusion area ratio is preferably 0.75 or more, more preferably 0.8 or more, and preferably 1. from the viewpoint of more smoothly transferring the body fluid from the skin side core wrap sheet 41 to the absorbent core 40. It is 5 or less, more preferably 2.0 or less.

  Referring to FIG. 8, the measurement object S (absorbent core, core wrap sheet) has a square shape of 240 mm × 75 mm in a plan view, supplementarily to <Method of measuring liquid diffusion area>. The measurement stand 100 used for measurement has a slope 100 a having an angle θ of 45 ° with respect to the horizontal plane. Place the measurement target S on the slope 100a so that the skin-facing surface faces the slope 100a, and further, on the measurement target S, the acrylic plate 101 with a thickness of 3 mm larger than the measurement target S. Put it on. Defibrillated horse blood injected as simulated blood to the measurement target S is a B-type viscometer (manufactured by Toki Sangyo Co., Ltd. Model No. TVB-10M, measurement conditions: rotor No. 19, 30 rpm, 25 ° C., 60 seconds) The measured viscosity is 8 mPa · s. As such defibrillation horse blood, for example, defibrillation horse blood manufactured by Japan BioTest Laboratories, Inc. can be used, and the above-mentioned predetermined viscosity can be adjusted by adjusting the blood cell / plasma ratio and the like as necessary. It can be adjusted to the range. The injection position of the defibrinated horse blood in the measuring object S is the central part (the part indicated by the arrow in FIG. 8) of the skin facing surface of the measuring object S, and a micro tube pump (manufactured by Tokyo Rika Kikai Co., Ltd.) Use to inject. A tube (not shown) is connected to the pump, and the end of the tube opposite to the connection side with the pump is connected to the measurement target S on the slope 100a, and the defibrillated horse blood is It is injected into the measuring object S through. The diffusion area of the defibrinated horse blood on the skin facing surface of the measuring object S is obtained by copying the distribution area of the defibrinated horse blood in the measuring object S with an OHP sheet, and using the image analysis software NexusNewQube (manufactured by Nexus). It can be measured by using and treating according to a conventional method.

  As described above, in order to set the liquid diffusion area ratio to 0.7 or more, it is necessary to devise the composition or the like of both or one of the absorbent core 40 and the skin-side core wrap sheet 41. What is particularly effective is a device for improving the liquid permeability of the skin side core wrap sheet 41. From that point of view, the skin-side core wrap sheet 41 is preferably a porous sheet mainly made of pulp. In the present specification, the description of the “skin-side core wrap sheet” refers to the other part of the core wrap sheet 41 which is a continuous sheet, for example, the non-skin facing surface of the absorber 4 unless otherwise specified. It is also applied to the non-skin-side core wrap sheet that is formed, that is, interposed between the back sheet 3 and the absorbent core 40.

  Examples of the porous sheet suitable as the skin-side core wrap sheet 41 include a pulp sheet mainly composed of pulp. Typical of this pulp sheet is a paper produced by a wet papermaking process. Cellulose fibers can be used as the pulp as the main component of the porous sheet. For example, softwood bleached kraft pulp (NBKP), hardwood bleached kraft pulp (LBKP), softwood bleached sulfite pulp (NBSP), thermomechanical. Wood pulp such as pulp (TMP); bast fibers such as cocoon, cocoon, husk, etc .; non-wood pulp such as cocoon, bamboo, kenaf, hemp, etc., and one of these may be used alone or in combination of two or more. It can be used. The content of pulp in the porous sheet is preferably 10% by mass or more, more preferably 50% by mass or more. The porous sheet may contain other components other than pulp. Examples of the other components include fillers such as talc, dyes, color pigments, paper strength enhancers, antibacterial agents, and pH adjustments. Commonly used as papermaking raw materials and additives, such as agents, yield improvers, water resistance agents, antifoaming agents, etc., one of these may be used alone or in combination of two or more Can do.

Further, from the viewpoint of enhancing the liquid permeability of the skin-side core wrap sheet 41 (the porous sheet), the density of the skin-side core wrap sheet 41 is 0.1 g / m ³ or less, particularly 0.08 g / m ³ or less. It is preferable to do. In addition, since the density of the skin side core wrap sheet | seat 41 becomes like this. Preferably it is 0.02 g / m < ³ > or more, More preferably, it is 0.04 g / m < ³ > or more, since it is easy to maintain sufficient sheet | seat strength.

Further, from the viewpoint of balance between liquid permeability and strength, the basis weight of the skin-side core wrap sheet 41 (the porous sheet) is preferably 5 g / m ² or more, more preferably 10 g / m ² or more, and Preferably it is 30 g / m < ² > or less, More preferably, it is 50 g / m < ² > or less.

  In the napkin 1, as described above, as shown in FIGS. 1 and 2, the core wrap sheet 41 (more specifically, the skin side core wrap sheet 41) and the absorbent core 40 are formed on the skin-facing surface of the absorber 4. When the recessed part 7 which was recessed integrally in the non-skin opposing surface side of the absorber 4 is formed, the shape of the absorber 4 with respect to the body pressure and operation | movement of the wearer of the napkin 1 by this structure is formed. It becomes more stable, and further improvement of the fit of the napkin 1 can be expected. Moreover, it is only a part of the absorber 4 (the absorbent core 40) that the recessed part 7 is formed, and the non-formed part of the recessed part 7 which occupies most of the absorbent core 40 will be described later. In addition, since the component fibers are flexible and have cushioning properties due to the shape retaining property due to the entanglement of constituent fibers, etc., the napkin 1 substantially expresses the features of the non-forming portion of the recessed portion 7 as it is Can do. The ratio of the total area of the recessed portion 7 (occupied portion occupancy ratio) in the entire area of the skin facing surface of the absorbent 4 (absorbent core 40) is the balance of the shape stability of the absorbent 4 and cushioning property etc. From the viewpoint, it is preferably 3% or more, more preferably 5% or more, and preferably 97% or less, more preferably 95% or less.

  Further, in the napkin 1, as shown in FIG. 1, the concave portion 7 is formed to surround the central portion in the horizontal direction Y of the longitudinal central region B, so that the shape of the central portion of the longitudinal central region B Stability is further enhanced. The central part of the longitudinal central region B surrounded by the recessed part 7 is usually a part including the excretory part facing part (excretion point), and it is important that the body fluid excreted by the wearer of the napkin 1 is first received and diffused. However, since the shape stability of the important part is high, further improvements in various properties such as liquid absorbency (leakage prevention), fit, and wearing feeling can be expected.

Hereinafter, the absorbent core 40 will be further described.
In the absorbent core 40, the plurality of fiber masses 11 or the fiber mass 11 and the water absorbent fibers 12F are mutually entangled. In the absorbent core 40 of the present embodiment, a plurality of fiber masses 11 are joined by entanglement with constituent fibers (fibers 11 F and 12 F) in the absorbent core 40 to form one fiber mass continuum. In addition, the plurality of fiber masses 11 may be entangled, and the fiber masses 11 and the water absorbent fibers 12F may be entangled and bonded. Furthermore, usually, the plurality of water absorbent fibers 12F are also entangled with each other. At least some of the plurality of fiber masses 11 contained in the absorbent core 40 are entangled with the other fiber masses 11 or the water absorbent fibers 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, or the plurality of fiber mass continuums are not mutually There may be cases where they are mixed together. The entanglement property of the fiber mass 11, that is, the ease of entanglement with the other fiber mass 11 or the water-absorbing fiber 12F, is the form (number, size, distribution state, etc.) of the extended fiber portion 113 which the fiber mass 11 has later. The entanglement of the fiber mass 11 can be enhanced by appropriately controlling the form of the extension fiber portion 113.

  The fiber mass 11 is excellent in flexibility and the like. In the present embodiment, as described above, in the absorbent core 40, a plurality of fiber masses 11 contained in the absorbent core 40 are joined together by entanglement, and furthermore, between the fiber masses 11 and the water absorbing fibers 12F are also entangled with each other External force, which is excellent in shape retention, flexibility, cushioning property, compression recovery property, etc., and is incorporated into the napkin 1 from external forces (eg, body pressure of the absorbent article wearer) It can be deformed flexibly, and the napkin 1 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 the 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 are mixed, the boundary between both members 11 and 12F is caused due to the difference in rigidity between the both members 11 and 12F. Particularly easy to bend in BL (dotted line in FIG. 4), where the boundary BL functions as a bend during deformation of the absorbent core 40, the boundary BL serving as the bend is generally present over the entire area of the absorbent core 40. Therefore, the absorbent core 40 is deformed flexibly with various responsiveness to various external forces, and when the external force is released, the absorbent core 40 is quickly restored to the original by the compression recovery property of the fiber mass 11. It can be restored to the state. Such a deformation-recovery characteristic of the absorbent core 40 can be exhibited not only when the absorbent core 40 is compressed but also when it is twisted. That is, since the absorptive core 40 incorporated in the napkin 1 is disposed in a state of being sandwiched between the thighs of the wearer when the napkin 1 is worn, the absorbent body 4 is a walking motion of the wearer. Motions of the two thighs may cause it to twist about an imaginary rotational axis extending in the longitudinal direction X, but even in such a case, the absorbent core 40 has high deformation-recovery characteristics Therefore, it can be easily deformed and recovered against an external force that promotes twisting from both the thighs, and therefore, it is difficult to cause the napkin 1 to have a high fit to the wearer's body.

As described above, in the absorbent core 40, while the fiber mass 11 or the fiber mass 11 and the water-absorbent fiber 12F are entangled, the “interlacing” of the fiber mass 11 or the like referred to here is as follows: Forms A and B are included.
Form A: A form in which the fiber masses 11 are joined not by fusion but by entanglement of constituent fibers 11 F of the fiber mass 11.
Form B: In the natural state of the absorbent core 40 (no external force is applied), the fiber masses 11 and the like are not coupled, but in the state where an external force is applied to the absorbent core 40, the fiber masses 11 and the like are The form which can be couple | bonded by the entanglement of constituent fibers 11F. Here, the “state in which an external force is applied to the absorbent core 40” refers to a state in which a deforming force is applied to the absorbent core 40 during wearing of the absorbent article to which the absorbent core 40 is applied, for example. .

Thus, in the absorbent core 40, as in the form A, the fiber mass 11 is bonded to the other fiber mass 11 or the water-absorbent fibers 12F by entanglement or “interlacing” of the fibers with each other, and the form Like B, they are also present in a state in which they can be entangled with other fiber masses 11 or water-absorbent fibers 12F, and such entanglement of fibers causes the above-described effects of the absorbent core 40 to be more effectively exhibited. It is one of the important points. However, the absorbent core 40 preferably has “entanglement” of form A from the viewpoint of shape retention. In either of the form A or B, since the entanglement of constituent fibers in the absorbent core 40 is achieved only by the entanglement of the fibers without the adhesive component, as described in, for example, Patent Document 2, Compared to bonding by fusion, the bonding force itself is low, but the interlaced individual elements (fiber mass 11, water absorbent fiber 12F) have a high degree of freedom of movement. It can move within a range that can maintain the integrity as a group of As described above, the absorbent core 40 has a plurality of fiber masses 11 contained in each other or the fiber mass 11 and the water-absorbent fibers 12F which are relatively loosely bonded to each other, so that they are deformed when receiving an external force. Possible shape retention is moderate, and shape retention and cushioning properties, compression recovery, etc. are compatible at a high level.

  It is not necessary that all of the bonding modes through the fiber mass 11 in the absorbent core 40 be "entangled", and a bonding mode other than the confounding on a part of the absorbent core 40, such as bonding with an adhesive, etc. It may be included.

  However, for example, the “fusion through fiber mass 11” formed on the absorbent core 40 as a result of being integrated with other members of the absorbent article such as the recess 7 in the napkin 1 is excluded from the absorbent core 40 In the remaining portion, that is, in the absorbent core 40 itself, it is desirable that the bonding between the fiber masses 11 or the bonding between the fiber masses 11 and the water absorbing fibers 12F be made only by “fiber interlacing”.

From the viewpoint of more reliably expressing the function and effect of the absorbent core 40 described above, the “fiber lump 11 bonded by interlacing” which is Form A and the “fiber lump 11 in a state capable of being entangled” which is Form B The total number is preferably half or more, more preferably 70% or more, and more preferably 80% or more with respect to the total number of fiber masses 11 in the absorbent core 40.
From the same point of view, the number of fiber masses 11 having “entanglement” of form A is 70% or more, particularly 80% or more of the total number of fiber masses 11 having a bonding portion with other fiber masses 11 or water absorbent fibers 12F. It is preferable that

  One of the main features of the absorbent core 40 is the outer shape of the fiber mass 11. In FIG. 5, two typical outer shapes of the fiber mass 11 are shown. The fiber lump 11A shown in FIG. 5 (a) is more specifically a rectangular parallelepiped shape than the quadrangular prism shape, and the fiber lump 11B shown in FIG. 5 (b) has a disk shape. The fiber mass 11A, 11B is common in that it includes two opposing base planes 111 and a body plane 112 connecting the two basic planes 111. Each of the basic surface 111 and the skeletal surface 112 is a portion which is recognized to be substantially non-uniform at a level applied when evaluating the degree of surface irregularity in an article mainly composed of this type of fiber.

The rectangular parallelepiped-shaped fiber lump 11A in FIG. 5A has six flat surfaces, and among the six surfaces, two opposing surfaces having the maximum area are the basic surfaces 111, and the remaining The four faces are skeletal faces 112 respectively. The basic surface 111 and the skeletal surface 112 intersect with each other, more specifically, are orthogonal to each other.
The disc-shaped fiber mass 11B shown in FIG. 5 (b) has two flat surfaces facing each other in a circular shape in plan view and a curved peripheral surface connecting the two flat surfaces. Each surface is a basic surface 111, and the circumferential surface is a skeletal surface 112.
The fiber masses 11A and 11B are common in that the skeleton surface 112 has a quadrangular shape in plan view, more specifically, a rectangular shape.

Each of the plurality of fiber masses 11 contained in the absorbent core 40 includes two opposing basic surfaces 111 and a skeleton surface 112 that connects the two basic surfaces 111, such as the fiber masses 11A and 11B shown in FIG. It differs from the non-woven fabric pieces or fine webs described in Patent Documents 2 and 3 which are indeterminate shaped fiber aggregates in that they are "formed 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 see-through shape of the fiber mass 11 differs depending on the observation angle, and one fiber Where there are multiple fluoroscopic shapes per mass 11, each of the plurality of fiber masses 11 in the absorbent core 40, as one of its multiple fluoroscopic shapes, connects two opposing base surfaces 111 and two base surfaces 111. And a specific perspective shape having a skeleton surface 112. The plurality of non-woven fabric pieces or fine webs contained in the absorbent bodies described in Patent Documents 2 and 3 substantially have "surfaces" such as the basic surface 111 and the skeletal surface 112, that is, an enlarged portion. In addition, the external shapes are different from each other and not “fixed”.

  As described above, Patent Documents 2 and 3 describe that the plurality of fiber masses 11 included in the absorbent core 40 are “shaped fiber aggregates” defined by the basic surface 111 and the skeletal surface 112. Since the uniform dispersion of the fiber mass 11 in the absorbent core 40 is improved as compared with the case of the irregular-shaped fiber assembly as described, the fiber assembly such as the fiber mass 11 is blended in the absorbent core 40 Thus, the expected effects (improvement effects such as the flexibility, cushioning property, and compression recovery property of the absorbent body) are stably expressed. In particular, in the case of the rectangular parallelepiped fiber lump 11 as shown in FIG. 5A, the outer surface is composed of six surfaces of two basic surfaces 111 and four skeleton surfaces 112, and therefore, as shown in FIG. 5B. As compared with the disk-shaped fiber mass 11 having three outer surfaces as described above, it is possible to have a relatively large opportunity for contact with the other fiber mass 11 or the water absorbent fiber 12F, and the entanglement is enhanced, and the shape retention is improved. It can also lead to the improvement of

  In the fiber mass 11, the total area of the two basic surfaces 111 is larger than the total area of the skeletal surface 112. That is, in the rectangular parallelepiped fiber mass 11A of FIG. 5A, the sum of the areas of the two basic surfaces 111 is larger than the sum of the areas of the four skeletal surfaces 112, and FIG. In the disk-shaped fiber mass 11B, the sum of the areas of the two basic surfaces 111 is larger than the area of the skeletal surface 112 forming the circumferential surface of the disk-shaped fiber mass 11B. In any of the fiber masses 11A and 11B, the basic surface 111 is a surface having the largest area among the plurality of surfaces of the fiber masses 11A and 11B.

  Such a fiber mass 11 which is a “shaped fiber aggregate” defined by two basic surfaces 111 and a skeletal surface 112 intersecting both basic surfaces 111 differs from the prior art in the manufacturing method. Can be realized by A preferable method for producing the fiber mass 11 is, as shown in FIG. 6, a cutting means such as a cutter or the like as a raw material fiber sheet 10bs (sheet having the same composition as the fiber mass 11 and having a size larger than the fiber mass 11). It is used to cut into a fixed shape. The plurality of fiber masses 11 manufactured in this way have a more uniform shape and dimensions than those manufactured by the conventional techniques such as Patent Documents 2 and 3. FIG. 6 is a diagram illustrating a method of manufacturing the rectangular parallelepiped fiber lump 11A of FIG. 5A, and the dotted line in FIG. 6 indicates a cutting line. The absorbent core 40 is blended with a plurality of fiber masses 11 having a uniform shape and size obtained by cutting the fiber sheet into a regular shape in this way. As mentioned above, a nonwoven fabric is preferable as the raw fiber sheet 10bs.

  As shown in FIG. 6, the rectangular fiber-shaped fiber mass 11A of FIG. 5 (a) has a raw fiber sheet 10bs in a second direction intersecting (more specifically, orthogonal to) the first direction D1 and the first direction D1. It is manufactured by cutting into a predetermined length to D2. Both directions D1 and D2 are each a predetermined direction in the surface direction of the sheet 10bs, and the sheet 10bs is cut along a thickness direction Z orthogonal to the surface direction. As described above, in a plurality of rectangular parallelepiped fiber masses 11A obtained by cutting the raw fiber sheet 10bs into a so-called ridge shape, the cut surface, that is, a surface that comes into contact with a cutting means such as a cutter when cutting the sheet 10bs is usually provided. , The non-cutting surface, ie, the surface not in contact with the cutting means, is the basic surface 111. The basic surface 111 is the front and back surface (surface orthogonal to the thickness direction Z) in 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 is basically applicable to the disk-shaped fiber mass 11B of FIG. The substantial difference from the fiber mass 11A is only the cutting pattern of the raw fiber sheet 10bs, and when the sheet 10bs is cut into a fixed shape to obtain the fiber mass 11B, it is matched to the planar view shape of the fiber mass 11B 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 both the basic surface 111 and the skeletal surface 112 are flat surfaces which are not curved as in the respective surfaces 111 and 112 of FIG. Alternatively, it may be a curved surface such as the skeleton surface 112 (the peripheral surface of the disk-shaped fiber lump 11B) in FIG. In addition, 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 skeletal surface 112) possessed by the fiber mass 11 (11A, 11B) are cut of the raw fiber sheet 10bs by cutting means such as a cutter at the time of manufacturing the fiber mass 11. And a non-cut surface (basic surface 111) that the sheet 10bs inherently has and does not come into contact with the cutting means. Then, due to the difference between the cut surface and the cut surface, the skeletal surface 112, which is the cut surface, has a feature that the number per unit area of the fiber end is larger than the basic surface 111, which is the non-cut surface. Have The term "fiber end" as used herein means the end in the lengthwise direction of the constituent fibers 11F of the fiber mass 11. Usually, fiber ends are also present in the base surface 111 which is a non-cut surface, but the skeletal surface 112 is formed by cutting the raw fiber sheet 10 bs due to being a cut surface formed by cutting. A large number of fiber ends consisting of the cut ends of the constituent fibers 11F exist in the entire skeletal surface 112, that is, the number of fiber ends per unit area is larger than that of the basic surface 111. .

  The fiber end portion present on each surface (basic surface 111, skeletal surface 112) of the fiber mass 11 is between the fiber mass 11 and the other fiber masses 11 contained in the absorbent core 40 or the water-absorbent fibers 12F. Useful for forming confounds. In general, the greater the number of fiber ends per unit area, the better the confounding property, which can lead to improvements in various properties such as shape retention of the absorbent core 40. As described above, the number of fiber end portions per unit area on each surface of the fiber mass 11 is not uniform, and the number of the fiber end portions 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 varies depending on the surface of the fiber mass 11, and the skeleton surface 112 is the basic surface 111. Confoundability is higher than. That is, the bonding by interlacing with other fibers through the skeletal surface 112 has a stronger bonding force than that through the basic surface 111, and the basic surface 111 and the skeletal surface in one fiber mass 11 At 112, there may be a difference in bonding strength with other fibers. Generally, the stronger the bonding strength, the more the freedom of movement of the bonded fibers is limited, and the strength (shape retention) of the absorbent core 40 as a whole is improved, but the softness tends to be reduced. .

  Thus, in the absorbent core 40, each of the plurality of fiber masses 11 contained therein has two types of bonding power with respect to the other fibers (the other fiber masses 11 and the water absorbent fibers 12F) in the periphery thereof. As a result, the absorbent core 40 has moderate softness and strength (shape retention). And when the absorptive core 40 which has such an outstanding characteristic is used according to a conventional method as an absorber of an absorptive article, the wearer of the absorptive article can be provided with a comfortable wearing feeling. At the same time, the inconvenience that the absorbent core 40 is broken by an external force such as the body pressure of the wearer when worn 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. For this reason, the number of the fiber area per unit area is relatively small, and hence the basic surface 111 having relatively low interlacing property with other fibers has the opposite property to the skeletal surface 112. Means that the total area is larger. Therefore, the fiber mass 11 (11A, 11B) shown in FIG. 5 has the other fibers in the periphery (other fiber masses 11, water-absorbent fibers 12F, as compared to the fiber mass in which the fiber end uniformly exists on the entire surface. Entanglement) is easily suppressed, and even if it is entangled with other fibers in the periphery, it is easy to entangle with relatively weak bonding power, and therefore, it is difficult to become large lumps and the softness excellent in the absorbent core 40 Can impart sex.

  On the other hand, since the non-woven fabric pieces or fine webs described in Patent Documents 2 and 3 are manufactured by, for example, cutting the raw fiber sheet into an irregular shape with a cutter such as a mill cutter as described above, It is not a piece of sheet-like shaped fiber lump having a "face" like the face 111 or the skeletal face 112, and furthermore, the external force of the cutting process is applied to the entire fiber lump at the time of its production. The fiber ends are randomly formed on the entire fiber mass, and the above-described functions and effects of the fiber ends are not sufficiently exhibited.

From the viewpoint of more reliably achieving the function and effect by the fiber end portion described above, the number N ₁ per unit area of the fiber end portion of the basic surface 111 (non-cut surface) and the skeletal surface 112 (cut surface) The ratio of the fiber end to the number N ₂ per unit area is preferably 0 or more, more preferably 0.05 or more, and preferably 0 as N ₁ / N ₂ on the premise that N ₁ <N _2. .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 ends of the basic surface 111 is preferably 0 piece / mm ² or more, more preferably 3 pieces / mm ² or more, and preferably 8 pieces / mm ² or less, more preferably It is 6 pieces / mm ² or less.
The number N ₂ per unit area of the fiber end portion 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, more preferably It is 40 pieces / mm ² or less.
The number per unit area of the fiber end of the basic surface 111 and the skeletal surface 112 is measured by the following method.

<Method of measuring the number of fiber ends per unit area on each surface of a fiber mass>
Using a double-sided paper tape (Nystack NW-15 manufactured by Nichiban Co., Ltd.), the measurement piece is attached to the sample stage using a member (fiber lump) containing the fiber to be measured. The measurement piece is then coated with platinum. The coating is performed using an ion sputtering apparatus E-1030 (trade name) manufactured by Hitachi Naka Seiki Co., Ltd., and the sputtering time is 120 seconds. The basic surface and the skeleton surface of the cut surface of the measurement piece are observed at a magnification of 100 using a JCM-6000 type electron microscope manufactured by JEOL Co., Ltd. In the observation screen with a magnification of 100 times, a rectangular region 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 region is After adjusting the observation angle or the like so as to occupy 90% or more of the area of the observation screen, the number of fiber ends included in the rectangular region is measured. However, in the observation screen with a magnification of 100 times, the measurement target surface of the fiber mass is smaller than 1.2 mm × 0.6 mm, and the proportion of the area of the rectangular region in the entire observation screen is less than 90% After increasing the observation magnification to 100 times, the number of fiber ends included in the rectangular area in the measurement target surface is measured in the same manner as described above. Here, the “fiber end portion” to be subjected to the number measurement is the length direction end portion of the constituent fibers of the fiber lump, and the portion other than the length direction end portion of the constituent fibers from the measurement target surface (intermediate length direction) Even if the part) is extended, the longitudinal middle part is not targeted for the number measurement. And the number per unit area of the fiber end part in the measurement object surface (basic surface or skeleton surface) of the fiber mass is calculated by the following formula. For each of the 10 fiber masses, the number per unit area of the fiber end portion in each of the basic surface and the skeleton surface is measured according to the above procedure, and the average value of the plurality of measured values is determined as the fiber end portion in the measurement target surface. The number per unit area of
Number of fiber ends per unit area in the measurement target surface (basic surface or skeletal surface) of the fiber mass (number / mm ² ) = number of fiber ends included in rectangular area (1.2 × 0.6 mm) Area of the rectangular area (0.72 mm ² )

When the basic surface 111 of the fiber lump 11 has a rectangular shape in plan view like the fiber lump 11A shown in FIG. 5A, from the viewpoint of improving the uniform dispersibility of the fiber lump 11 in the absorbent body 10. The rectangular short side 111a is preferably equal to or 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, 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 15 mm or less, more preferably 10 mm or less. The thickness of the absorbent core 40 is measured by the following method.

<Method of measuring thickness of absorber>
The object to be measured (absorbent core 40) is left at a horizontal place without wrinkles or bending, and the thickness of the object to be measured under a load of 5 cN / cm ² is measured. Specifically, for example, a thickness gauge PEACOCK DIAL UPRIGHT GAUGES R5-C (manufactured by OZAKI MFG.CO.LTD.) Is used for measuring the thickness.
At this time, between the tip of the thickness meter and the object to be measured, the plate is circular or square in plan view, the size of which is adjusted so that the load on the object to be measured is 5 cN / cm ² An acrylic plate (about 5 mm) is placed and the thickness is measured. The thickness is measured at 10 points, and their average value is calculated to be the thickness of the object to be measured.

The dimensions and the like of each part of the fiber mass 11 (11A, 11B) are preferably set as follows. The dimension of each part of the fiber lump 11 can be measured based on, for example, an electron micrograph at the time of specifying the outer shape of the fiber lump 11 described later.
When the basic surface 111 has a rectangular shape in plan view as shown in FIG. 5A, the length L1 of the short side 111a is preferably 0.3 mm or more, more preferably 0.5 mm or more, and preferably 10 mm or less. More preferably, it is 6 mm or less. The length L2 of the long side 111b of the basic surface 111 having a rectangular shape in plan view is preferably 0.3 mm or more, more preferably 2 mm or more, and preferably 30 mm or less, more preferably 15 mm or less.
In the case where the basic surface 111 is the surface having the largest area among the plurality of surfaces of the fiber mass 11 as shown in FIG. 5, the length L2 of the long side 111 b is the maximum passing length of the fiber mass 11. , And the maximum delivery length matches the diameter of the basic surface 111 having a circular shape in 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, still more preferably, as L1 / L2. 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 lengths L1 and L2 of two sides orthogonal to each other is , L1 / L2 may be one.
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, more preferably 6 mm or less. is there.

In addition, it is preferable that the absorbent core 40 be mechanically isotropic so that effects and effects resulting from the presence of the fiber mass 11 can be easily exhibited on all surfaces of the absorbent core 40. For this purpose, it is preferable that the fiber mass 11 is uniformly distributed in the entire absorbent core 40. From such a point of view, in the projection view of the absorbent core 40 in two directions orthogonal to each other, it is preferable that an overlapping portion of the plurality of fiber masses 11 exist in an arbitrary 10 mm square unit area. The code | symbol 11Z in FIG.3 and FIG.4 has shown the overlapping part of the some fiber mass 11. In FIG. As used herein, “projection view in two directions orthogonal to each other” typically represents a projection view in the thickness direction of the absorbent core (absorber) (that is, the absorbent core is a skin facing surface or a non-skin facing surface). And the projection view in the direction orthogonal to the thickness direction (ie, the case where the absorbent core is observed from the side surface).

  FIG. 7 (a) shows an electron micrograph of an example of the fiber mass according to the present invention, and FIG. 7 (b) shows a schematic view of the fiber mass 11 in accordance with the electron micrograph. It is done. As shown in FIG. 7, the plurality of fiber masses 11 included in the absorbent core 40 include a main body 110 and fibers 11 </ b> F extending outward from the main body 110, and the main body 110. The fiber density is low (the number of fibers per unit area is small), and the extending fiber portion 113 may be included. The absorbent core 40 can also include a fiber lump 11 that does not have the extended fiber portion 113, that is, a fiber lump 11 that includes only the main body 110. The extended fiber portion 113 is a kind of fiber end portion existing on each surface (basic surface 111, skeleton surface 112) of the fiber mass 11 described above, and from each surface of the fiber mass 11 among the fiber end portions. It is the fiber end part extended outward.

  The main body 110 is a portion defined by the two opposing basic surfaces 111 and the skeleton surface 112 that connects the two basic surfaces 111. The main body 110 is a portion that forms the main body of the fiber lump 11 and forms a fixed outer shape of the fiber lump 11, and various characteristics such as high flexibility, cushioning properties, and compression recovery properties of the fiber lump 11 are fundamental. However, the location of the main body 110 is large. On the other hand, the extended fiber portion 113 mainly contributes to the improvement of the confounding property between the plurality of fiber masses 11 contained in the absorbent core 40 or between the fiber mass 11 and the water absorbent fibers 12F. In addition to being directly involved in improving the formability, the effect of the main body 110 can be indirectly reinforced by affecting the uniform dispersibility of the fiber mass 11 in the absorbent core 40.

  The main body portion 110 has a higher fiber density than the extension fiber portion 113, that is, the number of fibers per unit area is large. Also, usually, the fiber density of the main body 110 itself is uniform. The proportion of the main body portion 110 in 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 extension fiber portion 113 can be distinguished by the following specific operation of the outer shape.

  The operation of specifying the external shape of the main body portion 110 of the fiber mass 11 contained in the absorbent core 40 is the difference in height of the fiber density in the absorbent core 40 (more or less of the number of fibers per unit area) Focusing on the difference in fiber diameter and the like, this can be done by confirming the “boundary” between the main body 110 and the other parts. The main body portion 110 has a fiber density higher than that of the extension fiber portion 113 present around the main body portion 110, and usually, the synthetic fiber which is a constituent fiber of the main body portion 110 is a water absorbing fiber 12F (typically a cellulose fiber) Since the qualitative and / or dimensionally different ones, even in the absorbent core 40 in which a large number of fiber lumps 11 and water absorbent fibers 12 F are mixed, the boundary can be easily confirmed by paying attention to the above point. The boundary thus confirmed is the peripheral edge (side) of the basic surface 111 or the skeletal surface 112, and the boundary confirmation operation identifies the basic surface 111 and the skeletal surface 112, and thus the main body 110 is specified. Is done. Such boundary confirmation work can be performed by observing the object (absorbent core 40) at a plurality of observation angles as necessary using an electron microscope. In particular, the fiber mass 11 contained in the absorbent core 40 is such that “the total area of the two basic surfaces 111 is larger than the total area of the skeletal surface 112” such as the fiber masses 11A and 11B shown in FIG. In the case where the basic surface 111 is the surface having the largest area of the fiber mass 11, it is possible to relatively easily identify the large surface of the basic surface 111, The external shape can be specified smoothly.

As shown in FIG. 7, the extension fiber portion 113 extends outward from at least one of the basic surface 111 and the skeletal surface 112 forming the outer surface of the main portion 110, and is a component fiber of the main portion 110. 11F. FIG. 7 is a plan view of the fiber mass 11 viewed from the basic surface 111 side (surface having the largest area among the plurality of surfaces of the fiber mass 11), and the fibers 11F from the skeletal surface 112 intersecting the basic surface 111 are shown. A large number of extended fiber portions 113 are formed.

  The form of the extension fiber portion 113 is not particularly limited. The extended fiber portion 113 may be composed of a single fiber 11F, or may be composed of a plurality of fibers 11F as in an extended fiber bundle portion 113S described later. Further, although the extension fiber portion 113 includes the longitudinal direction end portion of the fiber 11F extending from the main body portion 110, in addition to such a fiber end portion, a portion other than the longitudinal direction end portion of the fiber 11F (length In some cases, it may include an intermediate portion in the vertical direction. That is, in the fiber mass 11, both ends in the longitudinal direction of the constituent fiber 11F exist in the main body 110, and the other parts, that is, the longitudinal intermediate portions extend outward from the main body 110 in a loop The extension fiber portion 113 in that case is configured to include a loop-like protrusion portion of the fiber 11F.

  One of the main roles of the extended fiber portion 113 is, as described above, to entangle the plurality of fiber masses 11 contained in the absorbent core 40 with each other, or the fiber mass 11 and the water absorbent fibers 12F. . Generally, the extension length from the main body part 110 of the extension fiber part 113 becomes long, or the thickness of the extension fiber part 113 becomes thick, or the number of the extension fiber parts 113 which one fiber mass 11 has When the amount of entanglement increases, the connection between the objects being entangled via the extension fiber portion 113 becomes strong and it becomes difficult to release the entanglement, so that the predetermined effect of the present invention is exhibited more stably. 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 relatively abundant in the skeletal surface 112 which is the cut surface. On the other hand, the basic surface 111 that is a non-cut surface does not exist at all, or even if it exists, the number thereof is smaller than that of the skeleton surface 112. As described above, the reason why the extension fiber portion 113 is unevenly distributed on the skeletal surface 112 which is the cut surface is that most of the extension fiber portions 113 are “fluffs” generated by cutting of the raw material fiber sheet. That is, since the skeleton surface 112 formed by cutting the raw 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 fuzzing. easy. Although depending on the type of the raw fiber sheet, if the interval between the cutting lines is shortened or the cutting speed is decreased, the extended fiber portion 113 is easily formed, and the length thereof can be adjusted. On the other hand, since the basic surface 111 which is a non-cut surface has no friction with such cutting means, the fluff, that is, the extended fiber portion 113 is difficult to be formed.

  The spacing L1a (the spacing in the first direction, see FIG. 6) and the spacing L2a (the spacing in the second direction, see FIG. 6) of the cutting line at the time of cutting the raw fiber sheet 10bs From the viewpoint of securing the dimensions necessary for the fiber mass 11 to exhibit a predetermined effect, etc., preferably 0.3 mm or more, more preferably 0.5 mm or more, and preferably 30 mm or less, more preferably Is less than 15 mm.

  As shown in FIG. 7, the fiber mass 11 is an extension fiber bundle portion including a plurality of fibers 11F extending outward from the main body portion 110, more specifically, the skeletal surface 112, as one type of the extension fiber portion 113. It has 113S. At least one of the extension fiber portions 113 included in the fiber mass 11 may be this extension fiber bundle portion 113S. The extended fiber bundle portion 113S is configured by gathering together a plurality of fibers 11F extending from the skeletal surface 112, and the extended length from the skeletal surface 112 is longer than the extended fiber portion 113. It is characterized by points. The extended fiber bundle portion 113S may be present also on the basic surface 111, but is typically present on the skeletal surface 112 as shown in FIG. 7 and may or may not be present on the basic surface 111 at all. The number is smaller than that of the skeleton surface 112. The reason is the same as the reason why the extended fiber portion 113 is mainly present on the skeleton surface 112 that is a cut surface, as described above.

  Since the fiber mass 11 has such an extended fiber bundle portion 113S which should be also referred to as a long and thick large-sized extended fiber portion 113, the fiber mass 11 or the fiber mass 11 and the water absorbing fiber 12F The entanglement is further enhanced, and as a result, the predetermined effect of the present invention due to the presence of the fiber mass 11 is more stably achieved. The extended fiber bundle portion 113S is easily formed by performing the above-described cutting (see FIG. 6) of the raw fiber sheet 10bs under conditions that facilitate fuzz.

  The extension length of the extension fiber bundle portion 113S from the main body portion 110, ie, the extension length from the skeletal surface 112 (cut surface) is preferably 0.05 mm or more, more preferably 0.15 mm or more, and Preferably it is 7 mm or less, More preferably, it is 4 mm or less. The extended length of the extended fiber bundle portion 113S can be measured in the specific work (boundary confirmation work) of the outer shape of the fiber mass 11. Specifically, for example, using a microscope (50 magnification) made of Keyence, a double-sided tape made by 3M Co., Ltd. was attached to the surface of a transparent sample stand made of acrylic, and the fiber mass 11 was placed thereon and fixed Above, after identifying the outer shape of the fiber mass 11 according to the specific operation of the outer shape described above, the length of the extension in the fiber 11F extended from the outer shape is measured, and the measured extension The length of the minute is defined as the extended length of the extended fiber bundle portion 113S.

  In the extended fiber bundle portion 113S, it is preferable that the plurality of constituent fibers 11F be thermally fused to each other. The heat-sealed portion of such an extended fiber bundle portion 113S is generally in the longitudinal direction of the extended fiber bundle portion 113S as compared with the other portion (non-heat-sealed portion) of the extended fiber bundle portion 113S. The crosswise length (in the case where the cross section of the heat-sealed portion is circular, the diameter) is long in the direction orthogonal to Since the extension fiber bundle portion 113S has a heat-sealed portion that can be said to be such a large diameter portion, the strength of the extension fiber bundle portion 113S itself is enhanced, and thereby, via the extension fiber bundle portion 113S. As a result, the entanglement between the tangled fiber masses 11 or between the fiber lumps 11 and the water absorbent fibers 12F is further enhanced. Further, when the extension fiber bundle portion 113S has a heat fusion bonding portion, not only when the extension fiber bundle portion 113S is in a dry state but also when it is in a wet state by absorbing water, There is an advantage that the strength, shape retention property, and the like of the extended fiber bundle portion 113S itself are enhanced. And by such merit, when the absorptive core 40 is applied to an absorptive article, not only when the absorptive core 40 is in a dry state, but also body fluid such as urine and menstrual blood excreted by the wearer. Even when it is absorbed and becomes wet, the effects due to the presence of the fiber mass 11 described above can be stably achieved. Such an extended fiber bundle portion 113S having a heat-sealing portion is used as the raw fiber sheet 10bs in the manufacturing process of the fiber lump 11 as shown in FIG. 6, that is, in the cutting process of the raw fiber sheet 10bs of the fiber lump 11. It can be manufactured by using the above-mentioned "fiber sheet having a heat-sealed portion between constituent fibers".

  The constituent fibers 11F of the fiber mass 11 include “weakly water-absorbing” fibers that have lower water absorption than the water-absorbing fibers 12F. The weakly water-absorbing fiber used as the fiber 11F is preferably a weakly water-absorbing synthetic fiber. Not only when the absorbent core 40 is in a dry state, but also in a wet state by absorbing water (body fluid such as urine or menstrual blood) because the constituent fiber 11F of the fiber mass 11 is a weakly water-absorbing fiber Even in such a case, the effects (the effects of improving shape retention, flexibility, cushioning, compression recovery, stiffness of the roll, etc.) resulting from the presence of the fiber mass 11 described above are stably exhibited. The content of weakly water-absorbing fibers as constituent fibers 11F in the fiber mass 11 is preferably 90% by mass or more with respect to the total mass of the fiber mass 11, and 100 mass%, that is, the fiber mass 11 is weakly water-absorbent Most preferably, it is formed only from fibers. In particular, when the weakly water-absorptive fiber as the constituent fiber 11F is a non-water-absorptive fiber, the above-described effects due to the presence of the fiber mass 11 can be exhibited more stably.

In the present specification, the term “water absorption” can be easily understood by those skilled in the art, for example, pulp is water absorption. Similarly, it can be easily understood that the thermoplastic fiber is a weakly absorbent fiber as compared to the pulp and a non-absorbent fiber. On the other hand, the degree of water absorbency of the fiber can be compared with the relative water absorbency difference (difference between the water absorbent fiber and the fiber having a weaker water absorbability) by the value of the moisture content measured by the following method. A more preferable range can also be defined. The higher the value of such moisture content, the stronger the water absorbability of the fiber. As the water-absorbing fiber according to the present invention, the moisture content is preferably 6% or more, and more preferably 10% or more. On the other hand, it is preferable that the moisture content of the weakly hydrophilic fiber according to the present invention is less than 6%, and more preferably less than 4%. When the water content is less than 6%, the fiber can be determined as a non-water absorbent fiber. That is, as the weakly hydrophilic fibers according to the present invention, non-water absorbent fibers are preferable.

<Measuring method of moisture content>
The moisture content was calculated by applying the moisture content test method of JIS P 8203 correspondingly. That is, the fiber sample was allowed to stand in a test chamber at a temperature of 40 ° C. and a relative humidity of 80% RH for 24 hours, and the weight W (g) of the fiber sample before the absolutely dry treatment was measured in the chamber. Thereafter, the fiber sample was left to stand in an electric dryer (for example, manufactured by Isuzu Seisakusho Co., Ltd.) at a temperature of 105 ± 2 ° C. for 1 hour, and the fiber sample was completely dried. After drying, Si silica gel (e.g., silica gel) is covered with a fiber sample with Saran wrap (registered trademark) manufactured by Asahi Kasei Co., Ltd. in a test room with a temperature of 20 ± 2 ° C. and a relative temperature of 65 ± 2%. Toyota Chemical Industries, Ltd.) is placed in a glass desiccator (for example, manufactured by Techjam Corporation) and allowed to stand until the fiber sample reaches a temperature of 20 ± 2 ° C. Thereafter, the constant weight W ′ (g) of the fiber sample is weighed, and the moisture content of the fiber sample is obtained by the following equation. Moisture content (%) = (W−W ′ / W ′) × 100

  Similarly, from the viewpoint of allowing the absorbent core 40 to exhibit excellent effects in shape retention, flexibility, cushioning properties, compression recovery properties, harshness, etc. in both dry and wet states. The fiber mass 11 preferably has a three-dimensional structure in which a plurality of thermoplastic fibers are heat-sealed to one another.

  In addition, synthetic fibers as non-water absorbent fibers, which are used as constituent fibers 11 F of the fiber mass 11 in order to obtain such a fiber mass 11 in which a plurality of heat fusion bonds are three-dimensionally dispersed, are thermoplastic Fiber is preferred. Further, as described above, although it is preferable that the extension fiber bundle portion 113S has a heat fusion bonding portion, the component fiber 11F of the fiber mass 11 is a thermoplastic fiber, such an extension fiber bundle portion It is also possible to obtain a preferred form of 113S.

  In order to obtain a fiber lump 11 in which a plurality of heat-sealed portions are three-dimensionally dispersed, the raw fiber sheet 10bs (see FIG. 6) may be configured similarly, and such a plurality of heat As described above, the raw fiber sheet 10bs in which the fused portions are three-dimensionally dispersed can be manufactured by subjecting a web or nonwoven fabric mainly composed of thermoplastic fibers to a heat treatment such as hot air treatment.

  Examples of the thermoplastic resin that is a non-water-absorbing synthetic resin suitable as a material for the constituent fibers 11F of the fiber mass 11 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 ester, polyvinyl chloride, polyvinylidene chloride and the like can be mentioned, and one of these can be used alone or in combination of two or more. In addition, the fiber 11F may be a single fiber made of a blend polymer obtained by mixing one kind of thermoplastic resin or two or more kinds of synthetic resins including a thermoplastic resin, or may be a composite fiber. The composite fiber here is a synthetic fiber (thermoplastic fiber) obtained by combining two or more types of synthetic resins having different components with a spinneret and simultaneously spinning them, and a plurality of components are continuous in the longitudinal direction of the fiber. In a single fiber, which has the same structure. The form of the composite fiber includes a core-sheath type, a side-by-side type, and the like, and is not particularly limited.

  Further, the fiber mass 11 preferably has a contact angle with water measured by the following method of less than 90 degrees, particularly 70 degrees or less, from the viewpoint of further improving the drawability of the body fluid in the initial excretion. Such a fiber can be obtained by treating the aforementioned weakly water-absorbing fiber, preferably a non-water-absorbing fiber, with a hydrophilizing agent according to a conventional method. Conventional surfactants can be used as the hydrophilizing agent.

<Method of measuring contact angle>
The fiber is taken out of the object to be measured (absorbent core, fiber mass), and the contact angle of water on 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 an inkjet type water droplet discharge unit (manufactured by Cluster Technology, pulse injector CTC-25 having a discharge diameter of 25 μm) is set to 20 picoliter, and the water droplets are dropped right above the fibers. The state of dropping is recorded on a high-speed recording device connected to a camera installed horizontally. The recording device is preferably a personal computer incorporating a high-speed capture device from the viewpoint of image analysis later. In this measurement, an image is recorded every 17 msec. In the recorded video, the first image of water droplets on the fiber is attached to the attached software FAMAS (software version is 2.6.2, analysis method is droplet method, analysis method is θ / 2 method, image processing algorithm Is non-reflective, the image processing image mode is frame, the threshold level is 200, and the curvature is not corrected)), and the angle between the surface of the water droplet that touches the air and the fiber is calculated and contacted. A corner. The fiber removed from the object to be measured is cut into a fiber length of 1 mm, and the fiber is placed on the sample table of the contact angle meter and kept horizontal. Two different contact angles are measured per fiber. A contact angle of N = 5 is measured to one decimal place, and a value obtained by averaging a total of ten measured values (rounded to the second decimal place) 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.

  In addition, when the absorber (absorbent core) of measurement object is used as a component of other articles | goods, such as an absorbent article, and this absorber is taken out and evaluated and measured, this absorber is an adhesive agent, If it is fixed to another component by fusion bonding etc., remove the adhesive force by a method such as blowing cold air of the cold spray within the range that does not affect the contact angle of the fiber. Take out from. This procedure is common to all measurements herein.

  As the water absorbent fiber 12F, water absorbent fibers conventionally used as a material for forming an absorbent body of this type of absorbent article can be used. For example, wood pulp such as softwood pulp and hardwood pulp, cotton pulp, hemp Natural fibers such as non-wood pulp such as pulp; modified pulp such as cationized pulp, mercerized pulp and the like can be mentioned, and one of these may be used alone, or two or more may be mixed and used. Among water-absorbent fibers, cellulose-based water-absorbent fibers are particularly preferred.

  In the absorbent core 40, the mass ratio of the fiber lump 11 and the water absorbent fiber 12F is not particularly limited, depending on the types of constituent fibers (weakly water absorbent synthetic fibers) 11F and water absorbent fibers 12F of the fiber lump 11 and the like. Adjustment may be made accordingly. For example, when the constituent fiber 11F of the fiber lump 11 is a thermoplastic fiber that is a non-water-absorbing fiber and the water-absorbing fiber 12F is a cellulosic water-absorbing fiber, the predetermined effect of the present invention is more reliably exhibited. From the viewpoint, the content mass ratio of the fiber mass 11 to the water absorbent fiber 12F is preferably 20/80 to 80/20, more preferably 40/60 as the former (fiber mass 11) / the latter (water absorbent fiber 12F). 60 to 40/40.

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 based on the total mass of the absorbent core 40 in a dry state. More preferably, it is 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, with respect to the total mass of the absorbent core 40 in a dry state.
Preferably it is 80 mass% or less, More preferably, it is 60 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, 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, more preferably 480 g / m ² or less is there.

  The absorptive 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 illustrated as another component. As a water absorbing polymer, although generally a particulate thing is used, a fibrous thing may be used. When the particulate superabsorbent polymer is used, the shape thereof may be any of a spherical shape, a block shape, a bowl shape, and an amorphous shape. The average particle size of the water-absorbing polymer is preferably 10 μm or more, more preferably 100 μm or more, and preferably 1000 μm or less, more preferably 800 μm or less. Generally, polymers or copolymers of acrylic acid or alkali metal acrylates can be used as the water-absorbing polymer. Examples thereof include polyacrylic acid and salts thereof and polymethacrylic acid and salts thereof.

The content of the water-absorbing 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 based on the total mass of the absorbent core 40 in a dry state. More preferably, it is 40% by mass or less.
The basis weight of the water-absorbing 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, more preferably 70 g / m ² or less. .

The basis weight of the absorbent core 40 may be appropriately adjusted depending on the application and the like. For example, when the application of the absorbent core 40 is an absorbent of an absorbent article such as a disposable diaper or a sanitary napkin, the basis weight of the absorbent core 40 is preferably 100 g / m ² or more, more preferably 200 g / m 2 ^{It is 2} or more, and preferably 800 g / m ² or less, more preferably 600 g / m ² or less.

  The absorbent core 40 having the above-described configuration and the absorbent article such as the napkin 1 having the absorbent core 40 are flexible and excellent in cushioning properties, excellent in compression recovery, and deformed with high responsiveness to external force. When the external force is released, it quickly returns to its original state. The characteristics of an absorbent article including such an absorbent body (absorbent core) can be evaluated using the compression work (WC) and the recovery work (WC ′) as a scale. The compression work is a measure of the cushioning property of the absorbent article, and it can be evaluated that the cushioning property is higher as the WC value is larger. The recovery work amount is a measure indicating the degree of recovery when the absorbent article is compressed and the compressed state is released, and it can be evaluated that the higher the WC ′ value, the higher the compression recovery property. Further, in consideration of the role of the absorbent core 40 for absorbing and holding the liquid, the absorbent article has a WC value and a WC ′ value not only in a dry state but also in a wet state by absorbing a body fluid or the like. Larger is preferred. In order for the absorbent article to have such properties in the wet state, it is effective to use a non-water absorbent synthetic fiber such as a thermoplastic fiber as the constituent fiber 11 F of the fiber mass 11 as described above.

Compression work amount in the dry state of the absorbent article (d-WC) is preferably 80mN · cm / cm ² or more, more preferably 90mN · cm / cm ² or more, and, preferably 150mN · cm / cm ² or less More preferably, it is 110 mN · cm / cm ² or less.
The compressive work (w-WC) in a wet state of the absorbent article is preferably 70 mN · cm / cm ² or more, more preferably 80 mN · cm / cm ² or more, and preferably 150 m.
It is N · cm / cm ² or less, more preferably 110 mN · cm / cm ² or less.

The dry recovery work weight (d-WC ') of the absorbent article is preferably 34 mN · cm / cm ² or more, more preferably 44 mN · cm / cm ² or more, and preferably 150 mN · cm / cm ² Hereinafter, it is more preferably 60 mN · cm / cm ² or less.
Recovery work load in a wet state of the absorbent article (w-WC ') is preferably 15mN · cm / cm ² or more, more preferably 25mN · cm / cm ² or more, and, preferably 150mN · cm / cm ² Hereinafter, it is more preferably 55 mN · cm / cm ² or less.

<Method of measuring compression work (WC) and recovery work (WC ')>
It is generally known that the amount of compressed work (WC) and the amount of recovered work (WC ') of absorbent articles can be expressed as measurements on KES (Kawabata Evaluation System) manufactured by Kato Tech Co., Ltd. (Reference: Standardization and analysis of texture evaluation (2nd edition), author Kukio Kawabata, issued July 10, 1980). Specifically, the compression work and the recovery work can be measured using an automated compression test apparatus KES-G5 manufactured by Kato Tech Co., Ltd. The measurement procedure is as follows.
The "absorbent article (absorber-equipped sanitary napkin)" as a sample is attached to the test stand of the compression test apparatus. Next, the sample is compressed between steel plates having a circular flat surface of 2 cm ² in area. The compression rate is 0.02 cm / sec, and the maximum compression load is 490 mN / cm ² . The recovery process is also measured at the same speed. The compression work amount (WC) and the recovery work amount (WC ′) are respectively expressed by the following equations. _Wherein, T m, _{T o} is respectively 490 mN / cm ² load at a thickness, the thickness at 4.9 mN / cm ² load. Also, P _a is the load (mN / cm ² ) at the time of measurement (compression process)
And P _b represents the load (mN / cm ² ) at the time of measurement (recovery process).

  The “absorbent article provided with the absorbent in the dry state”, which is the measurement object of the measurement method, is obtained by leaving the absorbent article in the dry state for 24 hours under an environment of 23 ° C. in air temperature and 50 RH% relative humidity. Prepare. In addition, the “absorbent article provided with a wet absorbent”, which is a measurement target of the measurement method, is such that the absorbent article in a dry state is horizontal with the top sheet side (skin facing side) facing upward. Place an oval inlet (50 mm long, 23 m short) on the surface sheet, inject 3.0 g of defibrillated horse blood from the inlet, and allow to stand still for 1 minute. Inject 3.0 g and keep the condition for 1 minute after injection. The defibrillated horse blood injected into the measurement target is a defibrillated horse blood manufactured by Nippon Biotest Co., Ltd., and the viscosity at a liquid temperature of 25 ° C. is adjusted to 8 cp. In the TVB-10M type viscometer manufactured by Kikai Sangyo Co., Ltd., the viscosity is measured when measured at a rotational speed of 12 rpm with a rotor having a rotor name L / Adp (rotor code 19).

The absorbent core 40 can be manufactured in the same manner as an absorbent core (absorber) containing this type of fiber material. As described above, as shown in FIG. 6, the fiber mass 11 is a raw material fiber sheet (a sheet having the same composition as the fiber mass 11 and having a size larger than that of the fiber mass 11) as a raw material using a cutting means such as a cutter. Can be manufactured by cutting in two directions crossing each other (orthogonal), and the plurality of fiber masses 11 manufactured in this way are “shaped fiber aggregates” (for example, body portions having uniform shape and size) 110 is a rectangular parallelepiped shape). The absorbent core 40 including the fiber mass 11 and the water absorbing fibers 12F can be manufactured, for example, according to a conventional method using a known fiber stacking device equipped with a rotating drum. Such a fiber-stacking device typically conveys a rotating drum having a recess for accumulation formed on the outer peripheral surface, and the raw material of the absorbent core 40 (fiber mass 11, water-absorbent fiber 12F) to the recess for accumulation. A duct having a flow path therein, and an air flow (vacuum) generated in the flow path by suction from the inner side of the rotary drum while rotating the rotary drum around the rotation axis along the circumferential direction of the drum. The raw material carried on the air) is stacked in the accumulation recess.

As mentioned above, although this invention was demonstrated based on the embodiment, this invention can be suitably changed, without being restrict | limited to the said embodiment.
For example, in the absorbent core according to the present invention, the fiber mass may not be uniformly dispersed throughout the absorbent core, and may be unevenly distributed. As an embodiment in which the fiber mass is unevenly distributed, an absorbent core having a laminated structure of a layer mainly composed of the fiber mass and a layer mainly composed of the water-absorbing fibers can be exemplified.
Further, in the absorbent core according to the present invention, not all of the fiber mass (the weakly absorbent synthetic fiber aggregate) contained in the absorbent core may be a shaped fiber aggregate such as the fiber mass 11 according to the present invention If it is a range which does not deviate from the above, in addition to such a regular fiber aggregate, a very small amount of an irregular fiber aggregate may be contained.
The absorbent article of the present invention widely includes articles used for absorbing body fluid (urine, soft feces, menstrual blood, sweat, etc.) discharged from the human body, and in addition to the above-described sanitary napkins, sanitary shorts and fastenings The so-called unfolded disposable diaper having a tape, the pants-type disposable diaper, the incontinence pad and the like are included. Further, the following appendices will be disclosed regarding the embodiment of the present invention described above.

<1> An absorbent article having a longitudinal direction corresponding to the wearer's front-rear direction and a lateral direction perpendicular thereto, and comprising an absorbent body and a surface sheet disposed on the skin facing surface side of the absorbent body. The absorbent body includes a liquid absorbent absorbent core, and a core wrap sheet covering the skin-facing surface of the absorbent core, the absorbent core comprising a water absorbent fiber, A fiber lump containing weakly water-absorbing fibers having a lower water absorption than the water-absorbing fibers, and the liquid diffusion area of the absorbent core measured by the following method, and the core wrap sheet measured by the following method The absorbent article whose ratio with a liquid diffusion area is 0.7 or more as the former / latter.
<Method of measuring liquid diffusion area>
A measurement object is fixed on a slope having an angle of 45 ° with respect to a horizontal plane with the skin facing surface facing the slope, and 1.5 g of defibrinated horse blood is applied to the skin facing surface of the measurement object for 23 seconds. After injection and leaving for 3 minutes, the same amount of defibrillated horse blood is injected again into the same injection site for the same time. This defibrinated horse blood injection and leaving operation is repeated 6 times, and a total of 9 g of defibrinated horse blood is injected into the measurement object. After completion of the injection operation, the diffusion area of the defibrillated horse blood on the skin-facing surface to be measured is measured, and this is taken as the liquid diffusion area to be measured.
<2> The absorbent article according to <1>, wherein the core wrap sheet is a porous sheet mainly composed of pulp.
<3> The recessed part is integrally formed on the non-skin opposing surface side of the absorbent, wherein the core wrap sheet and the absorbent core are integrally formed on the non-skin opposing surface of the absorbent. Absorbent article as described in 1> or <2>.
<4> In the longitudinal direction, the absorbent article includes a longitudinal central area including an excretory part facing part facing the wearer's excretory part, and a front area disposed closer to the wearer's belly than the excretory part facing part The <3> divided into a rear area disposed on the dorsal side of the wearer rather than the excretory part opposing part, and the recessed part is formed to surround a lateral central part of the longitudinal central area The absorbent article as described in.
<5> The absorbent article according to any one of <1> to <4>, wherein the outer shape of the fiber mass is a rectangular solid or a disc.

<6> The fiber mass includes a main body portion having a relatively high fiber density, and an extended fiber portion that is present around the main body portion and has a lower fiber density than the main body portion, The absorbent article according to any one of <1> to <5>, wherein the fiber masses are mutually entangled, and the fiber mass and the water-absorbent fibers are mutually entangled.
<7> The main body portion includes two opposing basic surfaces and a skeleton surface that connects the two basic surfaces, and the basic surface has a rectangular shape in plan view. The absorbent article as described.
<8> The absorbent article according to <7>, wherein the total area of the two basic surfaces is larger than the total area of the skeletal surface.
<9> The absorbent article according to <7> or <8>, wherein the fiber mass has an extended fiber bundle portion including a plurality of fibers extending outward from the skeleton surface.
<10> The absorbent article according to <9>, wherein the extended fiber bundle portion has a portion where a plurality of fibers are heat-fused to one another.
<11> The extension length from the main body of the extension fiber bundle portion, preferably the extension length from the skeletal surface, is 0.05 mm or more and 7 mm or less, preferably 0.15 mm or more and 4 mm or less The absorbent article according to <9> or <10>, wherein
<12> The absorptivity according to any one of <7> to <11>, wherein the basic surface has a rectangular shape in plan view, and a short side of the rectangular shape is shorter than a thickness of the absorber. Goods.
The ratio of the length of the short side of the <13> basic surface to the thickness of the absorber is 0.03 or more and 1 or less, preferably 0.08 or more and 0.5 or less as the former / the latter. The absorbent article as described in 12>.
<14> The absorbent article according to <12> or <13>, wherein the length of the short side of the basic surface is 0.3 mm or more and 10 mm or less, preferably 0.5 mm or more and 6 mm or less.
<15> The absorbent article according to any one of <12> to <14>, wherein the length of the long side of the basic surface is 0.3 mm or more and 30 mm or less, preferably 2 mm or more and 15 mm or less. <16> the number N ₁ per unit area of the fiber ends existing in the primary surface, the ratio N _{1 /} N ₂ of the number N ₂ per unit area of the fiber ends existing in the skeleton surface of 0 or more The absorbent article according to any one of <7> to <15>, which is 0.90 or less, preferably 0.05 or more and 0.60 or more.
<17> The number of fiber ends per unit area present in the basic surface is 0 / mm ² or more and 8 / mm ² or less, preferably 3 / mm ² or more and 6 / mm ² or less The absorbent article according to any one of the above <7> to <16>.
<18> The number of fiber end portions present on the skeleton surface per unit area is 5 / mm ² or more and 50 / mm ² or less, preferably 8 / mm ² or more and 40 / mm ² or less. The absorbent article as described in any one of said <7>-<17>.

<19> The absorbent article according to any one of <1> to <18>, wherein the fiber mass has a three-dimensional structure in which a plurality of thermoplastic fibers are heat-sealed to each other.
<20> The absorbent article according to any one of <1> to <19>, wherein the mass ratio of the fiber mass to the water-absorbing fiber is 20/80 to 80/20 as the former / the latter. .
<21> The fiber mass is entangled with other fiber mass or the water absorbent fiber in the absorbent body, and also present in a state capable of being entangled with another fiber mass or the water absorbent fiber The absorbent article as described in any one of said <1>-<20>.
<22> 70% or more, preferably 80% or more, of the total number of the fiber masses having joint portions with other fiber masses or the water-absorbing fibers, wherein the joint portions are formed by entanglement of fibers. The absorbent article any one of said <1>-<21>.
<23> The absorbent article according to any one of <1> to <22>, wherein the fiber mass is derived from a nonwoven fabric.
<24> The absorbent article according to any one of <1> to <23>, wherein the density of the core wrap sheet is 0.1 g / m ³ or less.
<25> The density of the core wrap sheet is 0.1 g / m ³ or less, preferably 0.08 g / m ³ or less, and 0.02 g / m ³ or more, preferably 0.04 g / m ³ or more The absorbent article as described in any one of said <1>-<24>.
<26> The basis weight of the core wrap sheet is 50 g / m ² or less, preferably 30 g / m ² or less, and 5 g / m ² or more, preferably 10 g / m ² or more. The absorbent article according to any one of 25>.

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

[Examples 1-2]
A sanitary napkin having the same configuration as the napkin 1 shown in FIG. 1 was produced.
An air-through nonwoven fabric having a basis weight of 30 g / m ² was used as the top sheet, and a 37 g / m ² polyethylene resin film was used as the back sheet. The absorbent body was manufactured according to a conventional method using a fiber stack and a water absorbent fiber as a fiber material of the absorbent core and further using a separately prepared core wrap sheet using a known fiber stacking device. The fiber lump was manufactured according to FIG. 7 by cutting the raw fiber sheet into a square shape.
An air-through non-woven fabric having a basis weight of 21 g / m ² (having a heat-sealed portion between constituent fibers) having as its constituent fibers thermoplastic fibers (fiber diameter 18 μm) consisting of polyethylene resin and polyethylene terephthalate resin as raw material fiber sheets of fiber mass Fiber sheet). As water-absorbing fiber, softwood bleached kraft pulp (NBKP) having a fiber diameter of 22 μm was used. The fiber mass used for the absorber (a synthetic fiber aggregate of a fixed shape) has a rectangular parallelepiped main body as shown in FIG. 5 (a), the short side 111a of the basic surface 111 is 0.8 mm, and the long side 111b Was 3.9 mm and the thickness T was 0.6 mm. Further, the number per unit area of the fiber end portion in the basic surface 111 was 3.2 pieces / mm ² , and the number per unit area of the fiber end portion in the skeleton surface 112 was 19.2 pieces / mm ² . The basis weight of the absorber was 350 g / m ² and the thickness was 5.7 mm.

The details of the core wrap sheet (the porous sheet) used in Examples 1 and 2 are as follows. (Core wrap sheet of Example 1)
A paper made of softwood bleached kraft pulp (NBKP) and having a basis weight of 13.5 g / m ² and a density of 0.092 g / cm ³ was used.
(Core wrap sheet of Example 2)
A softwood bleached kraft pulp (NBKP) having a roundness of 0.80 and a mercerizing treatment, and a paper having a basis weight of 16.0 g / m ² and a density of 0.069 g / cm ³ was used.

Comparative Example 1
A commercially available sanitary napkin (manufactured by Unicharm Co., Ltd., trade name "Tanom Pew Slim 23 cm") was used as Comparative Example 1 as it was. The absorbent body in the sanitary napkin of Comparative Example 1 is a mixture of synthetic fibers (weakly water-absorbing fibers) and cellulosic fibers (water-absorbing fibers), and does not contain fiber mass.

Comparative Example 2
A sanitary napkin was produced in the same manner as in Example 1 except that the absorber was changed to the following, and this was taken as Comparative Example 2.
The absorbent used in Comparative Example 2 includes an irregularly shaped non-woven fabric piece as the fiber mass in the absorbent core, and the absorbent core is coated with a core wrap sheet and then subjected to hot air treatment to be contained in the absorbent core. The absorbent body used in Example 1 is the same as that of Example 1 except that the non-woven fabric pieces are thermally fused to each other. In the hot air treatment applied to the above-mentioned absorber, a mixed aggregate of non-woven fabric pieces and pulp fibers (length 240 mm × width 75 mm) is used in an electric dryer (for example, Isuzu Co., Ltd.) at a temperature of 150 ° C. It was left to stand for 10 minutes, and the non-woven fabric pieces were heat-fused to each other. The amorphous nonwoven fabric piece used was manufactured by tearing off the same air through nonwoven fabric used in Example 1 in any direction, and the crossover length in plan view was about 25 mm.

Comparative Example 3
A sanitary napkin was produced in the same manner as in Example 1 except that the absorber was changed to the following, and this was taken as Comparative Example 3. The absorbent used in Comparative Example 3 does not contain fiber lumps in the absorbent core, and is composed of only the water absorbent fibers. As the core wrap sheet (the porous sheet), softwood bleached kraft pulp (NBKP) having a basis weight of 16.0 g / m ² and a density of 0.102 g / cm ³ was used.

[Performance evaluation]
About the sanitary napkin of each Example and a comparative example, the liquid diffusion area of each of an absorptive core and a skin side core wrap sheet | seat was measured with the said method, and a liquid diffusion area ratio (liquid of an absorptive core was measured based on the measured value. (Diffusion area / Liquid diffusion area of core wrap sheet) was calculated. Further, the amount of compression work (WC) and the amount of recovery work (WC ') were measured by the above method, and the cushioning property and the compression recovery were evaluated based on the measured values. The results are shown in Table 1 below.

As shown in Table 1, in each example, the plurality of fiber masses are entangled with each other, and the liquid diffusion area ratio (liquid diffusion area of the absorbent core / liquid diffusion area of the core wrap sheet) is 0.7 or more. In comparison with Comparative Examples 1 to 3 of the prior art which do not satisfy the above, the values of the amount of compressed work (WC) and the amount of recovered work (WC ') in both the dry state and the wet state Is excellent in cushioning and compression recovery in both states. In each example, since the liquid diffusion area ratio is in the specific range, the liquid permeability from the surface sheet to the absorbent core through the skin-side core wrap sheet is excellent. Therefore, in each of the examples, the body fluid hardly remains on the skin facing surface side of the absorber after body fluid excretion.

1 Sanitary napkin (absorbent article)
A Front area B Vertical center area C Rear area 2 Top sheet 3 Back sheet 4 Absorbent body 40 Absorbent core 11 Fiber mass 11F Constituent fiber of the fiber mass (weakly water-absorbing fiber)
DESCRIPTION OF SYMBOLS 110 Main body part 111 Basic surface 112 Frame | skeleton surface 113 Extension fiber part 113S Extension fiber bundle part 12F Water absorbing fiber 41 Core wrap sheet 5 Absorbent main body 6 Side sheet 7 Recessed part 10bs Raw material fiber sheet of fiber lump

Claims (9)

An absorbent article having a longitudinal direction corresponding to the longitudinal direction of the wearer and a lateral direction perpendicular thereto, comprising an absorbent body and a surface sheet disposed on the skin-facing surface side of the absorbent body. ,
The absorbent body comprises a liquid-absorbent absorbent core and a core wrap sheet for covering the skin-facing surface of the absorbent core, the absorbent core comprising a water-absorbent fiber, and the water-absorbent fiber And a fiber mass containing a weakly absorbent fiber having lower water absorbability,
The absorbent article whose ratio of the liquid diffusion area of the said absorptive core measured by the following method and the liquid diffusion area of the said core wrap sheet | seat measured by the following method is 0.7 or more as the former / latter.
<Method of measuring liquid diffusion area>
A measurement object is fixed on a slope having an angle of 45 ° with respect to a horizontal plane with the skin facing surface facing the slope, and 1.5 g of defibrinated horse blood is applied to the skin facing surface of the measurement object for 23 seconds. After injection and leaving for 3 minutes, the same amount of defibrillated horse blood is injected again into the same injection site for the same time. This defibrinated horse blood injection and leaving operation is repeated 6 times, and a total of 9 g of defibrinated horse blood is injected into the measurement object. After completion of the injection operation, the diffusion area of the defibrillated horse blood on the skin-facing surface to be measured is measured, and this is taken as the liquid diffusion area to be measured.   The absorbent article according to claim 1, wherein the core wrap sheet is a porous sheet mainly comprising pulp.   The recessed part which the said core-lap sheet | seat and the said absorptive core integrally dented in the non-skin opposing surface side of this absorber is partially formed in the skin opposing surface of the said absorber. The absorbent article as described in. The absorbent article has a longitudinal central area including an excretory part opposing part facing the wearer's excretory part in the longitudinal direction, a front area disposed closer to the wearer's belly than the excretory part opposing part, and the excrement Divided into the rear area located on the dorsal side of the wearer rather than the part facing part,
The absorbent article according to claim 3, wherein the recessed portion is formed to surround a transversely central portion of the longitudinal central area. The fiber mass has a main body portion having a relatively high fiber density, and an extending fiber portion that is present around the main body portion and has a lower fiber density than the main body portion,
The absorbent article according to any one of claims 1 to 4, wherein the plurality of fiber masses are entangled with each other, and the fiber mass and the water-absorbent fibers are entangled with each other.   The absorptivity according to claim 5, wherein the main body portion has two opposing basic surfaces and a skeleton surface that connects the two basic surfaces, and the basic surfaces have a quadrangular shape in plan view. Goods.   The absorbent article according to any one of claims 1 to 6, wherein the fiber mass has a three-dimensional structure in which a plurality of thermoplastic fibers are thermally fused to each other.   The absorbent article according to any one of claims 1 to 7, wherein the mass ratio of the fiber mass and the water-absorbing fiber is 20/80 to 80/20 as the former / the latter. The absorbent article according to any one of the preceding claims density of the core wrap sheets is not more than 0.02 g / ^{m 3} or more 0.1 g / ^{m 3.}