JP7257220B2 - absorbent article - Google Patents

Description

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

Absorbent articles such as disposable diapers and sanitary napkins generally have a topsheet that is relatively close to the wearer's skin and a backsheet that is relatively far from the wearer's skin. , and an absorbent body interposed between the two sheets. The absorbent body typically comprises an absorbent core containing water absorbent fibers such as wood pulp and water absorbent materials such as water absorbent polymers, and furthermore, a core wrap sheet covering the outer surface of the absorbent core. It is often configured including Improvement of various properties such as flexibility, cushioning properties, compression recovery properties, and shape retention properties is a major issue for absorbent bodies used in absorbent articles.

As a technique for improving the absorbent, for example, Patent Document 1 discloses an absorbent containing thermoplastic resin fibers and cellulose-based water-absorbing fibers, wherein the thermoplastic resin fibers cover the surface of the absorbent on the surface sheet side. and the backsheet-side surface of the absorbent body. According to the absorbent body described in Patent Document 1, the thermoplastic resin fibers function as a skeleton for holding other components of the absorbent body, such as cellulose-based water-absorbing fibers, so it is said to be soft and resistant to twisting. . Further, Patent Document 1 describes an absorbent article having this absorbent body, which has a recessed embossed portion formed by embossing from the surface sheet side, and further, in the embossed portion, a thermoplastic resin It is described that the fibers are preferably fused with other fibers. The embossed part described in Patent Document 1 is a well-known part called a leak-proof groove or the like in this technical field, and is adopted in absorbent articles for the purpose of improving liquid diffusibility and shape retention in the surface direction. It is

Patent Document 2 describes an absorbent body containing a nonwoven fabric piece that includes heat-fusible fibers and is preliminarily bonded to give a three-dimensional structure, and water-absorbing fibers, and the nonwoven fabric piece absorbs Evenly distributed throughout the body. This three-dimensional nonwoven fabric piece is produced by pulverizing the nonwoven fabric into small pieces using a pulverizing means such as a cutter mill method. 3, it has an irregular shape and does not substantially have a portion that can be regarded as a plane. Patent Document 2 describes a preferred form of the absorbent described in the same document, in which pieces of nonwoven fabric are heat-sealed together. According to the absorbent body described in Patent Document 2, since the nonwoven fabric pieces have a three-dimensional structure, voids are formed inside the absorbent body, and the resilience is improved when water is absorbed. As a result, the water absorption performance is improved. It is said that

In Patent Document 3, an absorbent core in an absorbent article has an opening on the non-skin-facing surface side of the absorbent core and has a groove-shaped recess extending in both the longitudinal direction and the lateral direction, and the recess A recessed absorbent part containing pulp fibers is provided at the bottom of the skin-facing surface side, and the area surrounded by the recessed part and the recessed absorbent part is a block-shaped protruding absorbent part that protrudes to the non-skin facing surface side, It is described that the protruding absorbent portion contains pulp fibers and a water absorbent polymer. In the absorbent article described in Patent Document 3, since the absorbent core is divided into a plurality of block-shaped protruding absorbent portions by mutually intersecting groove-shaped recessed portions, body fluid excreted by the wearer is While diffusing in the surface direction of the skin-facing surface side, the absorbent core is quickly drawn into the absorbent core, and is absorbed and held by the block-shaped protruding absorbent portion. Therefore, according to the absorbent article described in Patent Document 3, it is said that liquid remaining on the top sheet and liquid returning to the surface sheet are suppressed due to its excellent liquid absorbency.

JP 2015-16296 A Japanese Patent Application Laid-Open No. 2002-301105 JP 2012-130363 A

The absorbent described in Patent Document 1 further contains synthetic fibers (thermoplastic resin fibers) in addition to cellulose-based water-absorbent fibers, but the plurality of contained synthetic fibers exist independently, It does not form a cohesive mass. Therefore, the absorbent described in Patent Document 1 does not have sufficient cushioning properties, compression recovery properties, etc., and therefore, when applied to absorbent articles, it is likely to be twisted and the fit may be insufficient. After absorption of body fluids such as urine and menstrual blood, such inconveniences occur significantly.

On the other hand, in the absorber described in Patent Document 2, the synthetic fibers contained therein are aggregates of synthetic fibers called nonwoven fabric pieces. Alternatively, since it is manufactured by tearing off or tearing off, it has an irregular shape and the shape and size are not uniform. It is difficult to obtain a uniform mixture, and the desired effects may not be obtained.

Further, from the viewpoint of improving the shape retention of the absorbent body, as described in Patent Document 2, when all the synthetic fiber aggregates contained in the absorbent body are heat-sealed, the flexibility of the absorbent body can be improved. This impairs the strength, cushioning properties, etc. of the absorbent article, resulting in an insufficient improvement in the fitting property of the absorbent article. An absorbent article having an absorbent body containing a synthetic fiber assembly, which is less likely to be twisted when worn, has a good wearing feeling, and is excellent in liquid absorption has not yet been provided.

Accordingly, an object of the present invention is to provide an absorbent article that is less likely to be twisted when worn, has a good wearing feeling, and is excellent in liquid absorption.

The present invention has a vertical direction corresponding to the front-rear direction of the user and a horizontal direction perpendicular to the vertical direction. An absorbent article comprising an absorbent core that absorbs and retains bodily fluids, and has a front region arranged on the front side in the longitudinal direction and a rear region arranged on the rear side in the longitudinal direction of the longitudinal center region. The absorbent core is formed with groove-shaped recesses having openings in at least one of the skin-facing surface and the non-skin-facing surface of the absorbent core and extending in a predetermined direction. A portion of the core that overlaps with the groove-shaped recess in plan view has a lower basis weight than the surrounding area, and the absorbent core contains a fiber mass containing synthetic fibers and water-absorbing fibers. is.

The absorbent article of the present invention is less likely to be twisted when worn, has a good wearing feeling, and is excellent in liquid absorption.

FIG. 1 is a plan view schematically showing a partly broken surface of a sanitary napkin that is an embodiment of the absorbent article of the present invention, facing the skin (surface sheet side). FIG. 2 is a schematic cross-sectional view taken along line II of FIG. FIG. 3 is a schematic perspective view of one embodiment of the topsheet included in the absorbent article shown in FIG. 1. FIG. FIG. 4 is a schematic plan view of the skin-facing surface side of the absorbent body included in the absorbent article shown in FIG. 5 is a schematic cross-sectional view taken along the line II-II of FIG. 4. FIG. FIG. 6 is a schematic cross-sectional view (equivalent to FIG. 5) of another embodiment of the absorbent body according to the present invention. FIG. 7 is a schematic cross-sectional view (equivalent to FIG. 5) of still another embodiment of the absorbent body according to the present invention. FIG. 8 is a schematic cross-sectional view (equivalent to FIG. 5) of still another embodiment of the absorbent body according to the present invention. FIG. 9 is a schematic plan view (equivalent to FIG. 4) of the side facing the skin of still another embodiment of the absorbent body according to the present invention. FIG. 10 is a schematic plan view (equivalent to FIG. 4) of the skin facing surface side of still another embodiment of the absorbent body according to the present invention. FIG. 11 is a schematic plan view (equivalent to FIG. 4) of the side facing the skin of still another embodiment of the absorbent body according to the present invention. 12(a) and 12(b) are schematic perspective views of fiber masses according to the present invention. FIG. 13 is an explanatory diagram of a method for producing a fiber mass according to the present invention. FIG. 14(a) is an electron micrograph (observation magnification of 25 times) of a fiber clump according to the present invention, and FIG. 14(b) is a diagram schematically showing the fiber clump in the electron micrograph.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described based on its preferred embodiments with reference to the drawings. In addition, in the following description of the drawings, the same or similar reference numerals are given to the same or similar parts. The drawings are basically schematic, and the ratio of each dimension may differ from the actual one.

1 and 2 show a sanitary napkin 1 which is one embodiment of the absorbent article of the present invention. The napkin 1 is an article used to absorb bodily fluids such as menstrual blood excreted by its user, that is, the wearer, and comprises an absorbent body 4 having an absorbent core 40 for absorbing and retaining bodily fluids, and the absorbent body 4 . The absorbent body 4 comprises a liquid-permeable topsheet 2 that is arranged on the skin-facing side of the absorbent body 4 and can come into contact with the wearer's skin, and a leak-proof backsheet 3 that is arranged on the non-skin-facing side of the absorbent body 4. do. As shown in FIG. 1, the napkin 1 has a longitudinal direction X corresponding to the wearer's front-back direction and extending from the wearer's abdomen to the dorsal side through the crotch, and a lateral direction Y orthogonal thereto. In addition, in the longitudinal direction X, a longitudinal central region M including an excretory part facing part (excretion point) facing the wearer's excretory part such as the vaginal opening, and the wearer's ventral side (front side) from the excretory part facing part ) and a rear region R located on the back side (rear side) of the wearer from the portion facing the excretory part.

As used herein, the term “skin-facing surface” refers to the surface of the absorbent article or its constituent members (for example, the absorbent body 4) that faces the wearer's skin when the absorbent article is worn, i.e. The "non-skin facing surface", which is the side close to the skin, is the side of the absorbent article or its constituent members opposite to the skin side when the absorbent article is worn, that is, the side relatively far from the wearer's skin. It is an aspect that can be It should be noted that the term "when worn" as used herein means a state in which the absorbent article is maintained in a normal and appropriate wearing position, that is, in a correct wearing position of the absorbent article.

The napkin 1, as shown in FIG. It has a pair of extending wing portions 5W, 5W. The absorbent main body 5 is a main part of the napkin 1, comprises the topsheet 2, the backsheet 3 and the absorbent body 4, and has a front region F, a longitudinal central region M and a rear region R in the longitudinal direction X. It is divided into three.

When the absorbent article has wings such as the napkin 1, the longitudinal central region of the absorbent article of the present invention has wings in the longitudinal direction (longitudinal direction, X direction in the drawing) of the absorbent article. Taking the napkin 1 as an example, it is a region sandwiched between the root of one wing 5W along the longitudinal direction X and the root of the other wing 5W along the longitudinal direction X. In addition, in the napkin 1, the pair of wing portions 5W, 5W are formed symmetrically with respect to the longitudinal center line extending in the longitudinal direction X by dividing the napkin 1 in the lateral direction Y. One wing portion 5W The root on the side closer to the front region F of the wing and that of the other wing portion 5W are located at the same position in the longitudinal direction X. As shown in FIG. In addition, the longitudinal central region of an absorbent article having no wing portions (for example, a disposable diaper) corresponds to a region located in the middle when the absorbent article is vertically divided into three equal parts.

In the napkin 1 , the absorbent body 4 includes a liquid absorbent core 40 and a liquid permeable core wrap sheet 41 covering the outer surface of the absorbent core 40 . Like the absorbent main body 5 , the absorbent core 40 has a shape elongated in the longitudinal direction X in plan view as shown in FIG. , and the width direction of the absorbent core 40 coincides with the lateral direction Y of the napkin 1 . As shown in FIG. 1, the absorbent body 4 (absorbent core 40) extends over substantially the entire length of the napkin 1 (absorbent main body 5) in the longitudinal direction X, and extends from the front region F to the rear region R via the longitudinal central region M. extends across. The absorbent core 40 and the core wrap sheet 41 may be joined with an adhesive such as a hot-melt adhesive.

The core wrap sheet 41 may be 1) composed of only one sheet, or 2) may be composed of a plurality of sheets. The core wrap sheet 41 of 1) is, for example, one continuous sheet having a width of two to three times the length of the absorbent core 40 in the lateral direction Y, and the absorbent core 40 faces the skin. It covers the entire surface and extends outward in the lateral direction Y from both side edges along the longitudinal direction X of the absorbent core 40, and the extending portion is rolled down below the absorbent core 40 to absorb It covers the entire non-skin facing surface of the core 40 . The core wrap sheet 41 of 2) is, for example, one skin-side core wrap sheet that covers the skin-facing surface of the absorbent core 40, and a skin-side core wrap sheet that is separate from the absorbent core 40. It is composed of two sheets, one of which is a non-skin side core wrap sheet covering the non-skin facing surface.

As shown in FIG. 2, the surface sheet 2 covers the entire skin-facing surface of the absorbent body 4 . On the other hand, the back sheet 3 covers the entire non-skin-facing surface of the absorbent body 4, and further extends outward in the lateral direction Y from both side edges along the longitudinal direction X of the absorbent body 4, together with side sheets 6 to be described later. It forms a side flap part. The side flap portion is a portion of the napkin 1 made of a member extending outward in the horizontal direction Y from the absorbent body 4 . The back sheet 3 and the side sheets 6 are joined to each other at the extending portions from both side edges along the longitudinal direction X of the absorbent body 4 by a known joining means such as adhesive, heat sealing, ultrasonic sealing, or the like. Each of the top sheet 2 and the back sheet 3 and the absorbent body 4 may be joined with an adhesive. As the surface sheet 2 and the back sheet 3, various materials conventionally used for absorbent articles such as sanitary napkins can be used without particular limitation. As the surface sheet 2, for example, a liquid-permeable single-layer or multi-layer nonwoven fabric can be used, and examples of the nonwoven fabric include carded nonwoven fabrics, spunbond nonwoven fabrics, meltblown nonwoven fabrics, spunlaced nonwoven fabrics, and needles. A punched nonwoven fabric can be exemplified. The nonwoven fabric forming the surface sheet 2 may be subjected to hydrophilization treatment using a hydrophilizing agent such as a surfactant. The back sheet 3 is a sheet having a leakproof property, that is, a liquid-impermeable (liquid-impermeable property) or a liquid-impermeable (liquid-impermeable property, although not liquid-impermeable). can be used, for example, a moisture-permeable resin film can be used.

In this embodiment, as shown in FIG. 2, the surface sheet 2 has a plurality of protrusions 21 projecting toward the wearer's skin on its skin facing surface. Concave portions 22 are formed around the convex portions 21 , and the skin-facing surface of the topsheet 2 is provided with an uneven shape composed of a plurality of convex portions 21 and concave portions 22 . The uneven shape of the skin-facing surface is present at least on the skin-facing surface of the topsheet 2 where it can come into contact with the wearer's skin when the napkin 1 is worn, and may be present over the entire skin-facing surface. . Such a surface sheet having an uneven shape on the surface (uneven surface sheet) is typically obtained by subjecting a raw sheet (a production intermediate of a surface sheet to which unevenness is not imparted) to a pressing process such as embossing. It can be manufactured by partial application, and the pressed portions of the uneven surface sheet are the concave portions 22 and the portions not pressed are the convex portions 21 . The concave portions 22 are formed by compressing the material forming the surface sheet 2 by pressing, and have a higher density than the convex portions 21 that are not pressed.

The surface sheet 2, which is an uneven surface sheet, has a skin-facing surface on which a plurality of protrusions 21 protruding toward the wearer's skin are formed, and the uneven skin-facing surface of the napkin 1 conforms to the wearer's skin. When it comes into contact with the skin, the apex of the projections 21 and the areas in the vicinity thereof partially come into contact with each other. The resulting irritation is reduced. In addition, the liquid excreted by the wearer is less likely to adhere to the wearer's skin, thereby reducing the uncomfortable feeling of wetness.

The formation pattern (shape and arrangement of the protrusions) of the protrusions 21 on the skin-facing surface of the topsheet 2 is not particularly limited, and the pattern of the uneven topsheet in this type of absorbent article can be appropriately adopted. FIG. 3 shows a surface sheet 2A, which is one embodiment of the uneven surface sheet applicable to the present invention.

As shown in FIG. 3, the topsheet 2A has two layers, a skin-side fiber layer 23 positioned closer to the wearer's skin and a non-skin-side fiber layer 24 positioned farther from the wearer's skin. It is a nonwoven fabric with a structure, both fiber layers 23 and 24 are integrated in the thickness direction Z by a large number of partially formed joints 25, and are positioned between the plurality of joints 25 in the skin-side fiber layer 23. The part that contacts the skin bulges in a convex shape to form a solid protrusion 21 on the side facing the skin, and the part other than the protrusion 21 including the joint 25 is a recess 22 . The convex portion 21 having a solid structure includes two types of convex portions 21A and 21B having different sizes. The large convex portion 21A has a higher height and a larger area in plan view than the small convex portion 21B. Both of the convex portions 21A and 21B have a circular shape in plan view, and have a shape having a top portion in a cross section in either the vertical direction X or the horizontal direction Y. As shown in FIG. Both convex portions 21A and 21B are alternately arranged in a direction crossing both the vertical direction X and the horizontal direction Y. As shown in FIG. A plurality of large projections 21A are intermittently arranged at predetermined intervals in the horizontal direction Y to form a row of large projections, and a plurality of small projections 21B are intermittently arranged at predetermined intervals in the horizontal direction Y. They are arranged to form rows of small and large projections, and the row of large projections and the row of small projections are alternately arranged in the vertical direction X. The joint portion 25 is formed by embossing with heat and has an X-shape or a Y-shape in plan view.

In the surface sheet 2A, the skin-side fiber layer 23 is a non-woven fabric mainly composed of non-heat-shrinkable fibers, and the non-skin-side fiber layer 24 is a non-woven fabric mainly composed of heat-shrinkable fibers. As the non-heat-shrinkable fiber that is the main component of the skin-side fiber layer 23, it is possible to use a fiber that does not substantially have heat-shrinkability or a fiber that has a higher heat-shrinkable temperature than the heat-shrinkable fiber. As the heat-shrinkable fiber that constitutes the main component of the non-skin-side fiber layer 24, a heat-shrinkable fiber made of a thermoplastic polymer material is preferably used. Examples of such fibers include latently crimpable fibers. Before being heated, the latent crimpable fibers can be handled in the same manner as fibers for conventional nonwoven fabrics, and when heated at a predetermined temperature, the latently crimpable fibers have the property of developing helical crimps and shrinking. It is a fiber with The content of the heat-shrinkable fiber in the non-skin-side fiber layer 24 is preferably 40% by mass or more and 100% by mass or less. The latently crimpable fibers are, for example, eccentric core-sheath or side-by-side conjugate fibers composed of two types of thermoplastic polymer materials having different shrinkage rates. Examples thereof include those described in Japanese Patent Application Laid-Open No. 9-296325 and Japanese Patent No. 2759331. The non-skin-side fibrous layer 24 is formed by heating the latently-crimpable fibers at the time of heat-sealing the fiber layer containing the latently-crimpable fibers to the skin-side fiber layer 23 or after the heat-sealing. It is formed by expressing contraction and contracting it. As the uneven nonwoven fabric having two or more types of protrusions of different sizes on the surface facing the skin, such as the topsheet 2A, those described in JP-A-2015-186543, for example, can be used.

As shown in FIG. 1 , the side flap portions protrude greatly outward in the lateral direction Y in the longitudinal central region M, so that a pair of side flap portions are provided on both left and right sides along the longitudinal direction X of the absorbent body 5 . Wing portions 5W, 5W are extended. The wing portion 5W has a substantially trapezoidal shape in which the lower base (longer side than the upper base) is located on the side portion side of the absorbent main body 5 in plan view as shown in FIG. is provided with a wing adhesive portion (not shown) as fixing means for fixing the wing portion 5W to clothing such as shorts. In addition, since the wing portion 5W is folded back to the non-skin facing surface (outer surface) side of the crotch portion of clothing such as shorts, the non-skin facing surface of the wing portion 5W, which is the surface on which the wing adhesive portion is formed, is , when in use, is oriented toward the wearer's skin and forms a skin-facing surface. In addition, on the non-skin facing surface of the absorbent body 5, that is, the non-skin facing surface of the back sheet 3, a body adhesive portion (not shown) is provided as a fixing means for fixing the napkin 1 (absorbent body 5) to clothes such as shorts. ) is provided. The wing adhesive portion and the main body adhesive portion are each covered with a release sheet (not shown) made of film, nonwoven fabric, paper, or the like before use. In addition, on both sides along the longitudinal direction X of the skin-facing surface of the absorbent main body 5, that is, the surface facing the skin of the topsheet 2, a pair of absorbents are provided so as to overlap the left and right sides along the longitudinal direction X of the absorbent body 4 in plan view. are arranged over substantially the entire length of the absorbent main body 5 in the longitudinal direction X. As shown in FIG. The pair of side sheets 6, 6 are joined to other members such as the topsheet 2 by a known joining means such as an adhesive at joining lines (not shown) extending in the longitudinal direction X, respectively.

4 and 5 show the absorbent body 4 that the napkin 1 has. The absorbent core 40 included in the absorbent body 4 has groove-shaped recesses 42 that have openings in at least one of the skin-facing surface 45 and the non-skin-facing surface 46 of the absorbent core 40 and extend in a predetermined direction. formed. The groove-shaped recess 42 is preferably a space portion in which no material (core-forming material) constituting the absorbent core 40 is present, but a small amount of core-forming material may be present to the extent that the space portion can be recognized. .

The groove-shaped recess 42 has a non-penetrating type that does not penetrate the absorbent core 40 in the thickness direction (see FIGS. 5 to 7) and a penetrating type that penetrates the absorbent core 40 in the thickness direction (see FIG. 8). is included. The groove-like recess 42 in the absorbent body 4 is the former, and as shown in FIG. 5, has an opening on the non-skin-facing surface 46 of the absorbent core 40 and a bottom on the side opposite to the opening. The bottom of the groove-shaped recess 42 is a portion that overlaps with the groove-shaped recess 42 in plan view of the absorbent core 40 (projected view in the thickness direction of the absorbent core 40), and includes a core-forming material. On the other hand, the through-type groove-shaped recess 42 does not have a bottom, and the portion of the absorbent core 40 that overlaps with the through-type groove-shaped recess 42 in a plan view is a space, which is a so-called through hole.

In the absorbent core 40, the portion overlapping the groove-shaped recess 42 in plan view has a lower basis weight than its surroundings (specifically, the small absorbent portion 43 described later), that is, the unit of the core-forming material compared to the surroundings. Less mass per area. The term "low grammage" as used herein means that there is no core-forming material in a portion that overlaps with the groove-shaped recess 42 in plan view, such as the through-type groove-shaped recess 42, and the grammage of this portion is zero. Including cases.

In the absorbent body 4, the groove-shaped recess 42 has, as shown in FIG. The surface side of 40 where the opening of the vertical recess 42X and the opening of the horizontal recess 42Y are formed is divided into a plurality of small absorbent portions 43. As shown in FIG. More specifically, in the absorber 4, a plurality of vertical recesses 42X are intermittently arranged in the horizontal direction Y, and a plurality of horizontal recesses 42Y are intermittently arranged in the vertical direction X. and the plurality of lateral recesses 42Y are orthogonal to each other. The plurality of vertical recesses 42X are continuous from one end to the other end in the vertical direction X of the absorbent core 40, and the plurality of horizontal recesses 42Y are continuous from one end to the other end in the horizontal direction Y of the absorbent core 40. are doing. All groove-shaped recesses 42 (vertical recesses 42X, horizontal recesses 42Y) formed in the absorbent core 40 have openings on the non-skin-facing surface 46 of the absorbent core 40 . Therefore, in the absorbent body 4, the non-skin facing surface 46 side of the absorbent core 40 is divided into a plurality of small absorbent portions 43 by a plurality of vertical concave portions 42X and horizontal concave portions 42Y orthogonal to each other. It has a quadrangular shape in plan view as shown in FIG.

In the absorbent body 4, as shown in FIG. It has a continuous layer 44 over which the groove-like recesses 42 are not formed. A portion of the continuous layer 44 that overlaps with the groove-shaped recess 42 (vertical recess 42X, horizontal recess 42Y) in a plan view (that is, a projection view in the thickness direction of the absorber 4) constitutes the bottom of the non-penetrating groove-shaped recess 42. do. The plurality of small absorbent portions 43 are integrated via the continuous layer 44 .

In addition, in the absorbent body 4, the continuous layer 44 is unevenly distributed on the side of the skin-facing surface 45 of the absorbent core 40, as shown in FIG. As a result, the skin-facing surface 45 of the absorbent core 40 is formed by the continuous layer 44 and is a substantially flat surface without irregularities. On the other hand, the non-skin facing surface 46 of the absorbent core 40 is an uneven surface having an uneven shape composed of concave portions formed by openings of the groove-shaped concave portions 42 and convex portions formed by small absorbent portions 43 .

Since the groove-shaped recesses 42 in the absorbent core 40 have no or only a small amount of core-forming material, they are likely to become starting points for bending. Furthermore, in a portion overlapping the groove-shaped recess 42 in a plan view (hereinafter also referred to as "a portion where the groove-shaped recess 42 exists"), when the groove-shaped recess 42 is non-penetrating, the core forming material is larger than that of the surrounding area. When the groove-shaped recessed portion 42 is of the penetrating type, it is a space where no core-forming material exists. 43), and therefore, when the napkin 1 is worn, it easily becomes a flexible axis when the absorbent core 40 is bent, and can act as a bending guide. Therefore, when the napkin 1 is worn, the absorbent body 4 (absorbent core 40) can be deformed so as to conform to the shape of the wearer's body using the groove-shaped concave portion 42 as a bending guide. Therefore, the napkin 1 has excellent fitting properties, gives the wearer a good wearing feeling, and can effectively suppress leakage of bodily fluids such as menstrual blood. In addition, since the groove-shaped recesses 42 extend in the longitudinal direction X and the horizontal direction Y in the absorbent core 40, the body fluid absorption time is shortened compared to the case where the groove-shaped recesses 42 are not formed. is achieved, the diffusibility of body fluid in the surface direction is improved, and the liquid absorbency of the napkin 1 can be improved.

As described above, the groove-shaped recess 42 may have an opening in at least one of the skin-facing surface 45 and the non-skin-facing surface 46 of the absorbent core 40 and extend in a predetermined direction. 4 and FIG. 5 are not restrictive. 6 to 8 show other embodiments of absorbent bodies that can be employed in the present invention. Regarding other embodiments to be described later, constituent parts different from those of the above-described embodiment (absorbent body 4) will be mainly explained, and the same constituent parts will be denoted by the same reference numerals, and the explanation thereof will be omitted. The description of the above embodiment is appropriately applied to components that are not particularly described. In addition, hereinafter, the absorbent bodies according to the embodiments of the present invention, such as the absorbent bodies 4A to 4F, are collectively referred to as the "absorbent body 4".

In the absorbent body 4A shown in FIG. 6, the groove-shaped concave portion 42 is a non-penetrating type that does not penetrate the absorbent core 40 in the thickness direction, and has an opening in the skin-facing surface 45 of the absorbent core 40. It has a bottom opposite the opening. In addition, in the absorbent body 4A, the continuous layer 44 is unevenly distributed on the non-skin facing surface 46 side of the absorbent core 40 . Therefore, in the absorbent body 4A, the skin-facing surface 45 has an uneven shape composed of recesses formed by the openings of the groove-shaped recesses 42 and protrusions formed by the small absorbent portions 43, and is an uneven surface and a non-skin-facing surface. 46 is formed by the continuous layer 44 and is a substantially flat surface without irregularities.

In the absorbent body 4B shown in FIG. 7, the groove-shaped recessed portion 42 is a non-penetrating type that does not penetrate the absorbent core 40 in the thickness direction, and the skin-facing surface 45 and the non-skin-facing surface 46 of the absorbent core 40 are It has openings on both sides and a bottom on the side opposite to the openings. In addition, in the absorbent body 4B, the continuous layer 44 is unevenly distributed in the central portion of the absorbent core 40 in the thickness direction. Therefore, in the absorbent body 4B, the skin-facing surface 45 and the non-skin-facing surface 46 both have an uneven shape composed of concave portions formed by the openings of the groove-shaped concave portions 42 and convex portions formed by the small absorbent portions 43. It is the surface. In the absorbent body 4B, the groove-shaped recessed part 42 having an opening on the skin-facing surface 45 and the groove-shaped recessed part 42 having an opening on the non-skin-facing surface 46 overlap in plan view (projection view in the thickness direction of the absorbent body 4B). . Similarly, the small absorbent portion 43 on the skin facing surface 45 side and the small absorbent portion 43 on the non-skin facing surface 46 side overlap in plan view.

In 4 C of absorbers shown in FIG. 8, the groove-shaped recessed part 42 is a penetration type which penetrates the absorptive core 40 in the thickness direction, and does not have a bottom part. Therefore, the absorbent body 4C does not have the continuous layer 44, and the plurality of small absorbent portions 43 exist independently and separably. In addition, in the absorbent body 4C, the plurality of small absorbent portions 43 are joined to the core wrap sheet 41 via joining means such as an adhesive, thereby maintaining a predetermined arrangement.

In the absorber 4D shown in FIG. 9, a plurality (3 ) are intermittently arranged in the vertical direction X. A small absorbent portion 43 is positioned between two groove-shaped concave portions 42 adjacent to each other in the longitudinal direction X. As shown in FIG. Each of the plurality of groove-shaped recesses 42 has a convex shape curved toward one end of the rear region R side in the longitudinal direction X in plan view, and the top of the protrusion is positioned at the center in the lateral direction Y. . In the absorber 4D, the groove-shaped concave portion 42 may have an opening on the non-skin facing surface 46 (see FIG. 5), or may have an opening on the skin facing surface 45 (see FIG. 6). Both the skin-facing surface 45 and the non-skin-facing surface 46 may have openings (see FIG. 7), or may penetrate the absorbent core 40 in the thickness direction (see FIG. 8).

In the absorber 4E shown in FIG. 10, a plurality (two) of groove-shaped recesses 42 extending in the vertical direction X are intermittently arranged in the horizontal direction Y, and each groove-shaped recess 42 extends in the horizontal direction Y of the absorbent core 40. It cuts through the central part in the vertical direction X. A small absorbent portion 43 is positioned between two groove-shaped concave portions 42 adjacent to each other in the horizontal direction Y. As shown in FIG. Each of the plurality of groove-shaped recesses 42 has a continuous linear shape extending in the vertical direction X in plan view. In the absorbent body 4E, the groove-like recessed portion 42 may have an opening on the non-skin facing surface 46 (see FIG. 5), or may have an opening on the skin facing surface 45 (see FIG. 6). Both the skin-facing surface 45 and the non-skin-facing surface 46 may have openings (see FIG. 7), or may penetrate the absorbent core 40 in the thickness direction (see FIG. 8).

The absorbent core 40 in the absorbent body 4 (4A to 4E) described above, that is, the absorbent core 40 having the groove-like recessed portion 42, can be produced by a known fiber stacking method similar to the method for manufacturing the absorbent core of this type of absorbent article. It can be manufactured using an apparatus. A fiber stacking device typically includes a rotating drum having an accumulating concave portion on its outer peripheral surface, and while rotating the rotating drum, the core forming material is supplied to the outer peripheral surface in a scattering state, and the core forming material is accumulated. The fibers are stacked in the accumulating recessed portion by suction from the bottom surface of the accumulating recessed portion, and the piled materials in the accumulating recessed portion are released from the accumulating recessed portion by suction from a suction means arranged opposite to the accumulating recessed portion. , a device for transferring onto a suction means. In the fiber stacking device having such a configuration, by placing a non- or impermeable air-permeable member on a part of the air-permeable bottom surface of the stacking recessed portion to make a part of the bottom surface a non- or impermeable air-permeable part , when the core forming material is stacked, it becomes difficult to stack the core forming material in the non- or air-impermeable part, and the amount of the core-forming material stacked in the non-air-permeable part or the air-impermeable part is smaller than that in other parts of the bottom surface. less. Therefore, by manufacturing an absorbent core according to a conventional method using such a fiber stacking device equipped with a rotating drum in which a part of the bottom surface of the accumulating recess is a non-breathable or impermeable part, The portion corresponding to the air-permeable portion becomes the groove-shaped recess 42, and the portion corresponding to the other portion of the bottom surface becomes the small absorbent portion 43, whereby the absorbent core 40 having the groove-shaped recess 42 is obtained.

In this way, the absorbent core 40 formed by partially varying the suction force when the core forming material is sucked into the accumulating recessed portion has a partially different piled amount of the core forming material. In addition, the existing portion of the groove-shaped recess 42 (the portion overlapping the groove-shaped recess 42 in the absorbent core 40 in plan view) has a relatively small mass (basis weight) per unit area of the core forming material (basis weight zero), and the non-existent portion of the groove-shaped concave portion 42, ie, the small absorbent portion 43, has a relatively large basis weight.

From the viewpoint of ensuring that the absorbent core 40 has the groove-shaped concave portion 42 and the small absorbent portion 43, the dimensions of each portion of the absorbent core 40 are set as follows. is preferred.
The length (width) in the direction orthogonal to the length direction of the groove-shaped recess 42, for example, in the case of the vertical recess 42X extending in the vertical direction X, the length (width) in the horizontal direction Y is preferably 1.0 mm or more. , more preferably 3.0 mm or more, and preferably 10.0 mm or less, more preferably 5.0 mm or less.
Small absorbent portions 43 as shown in FIG. 4, that is, “small absorbent portions 43 separated by groove-shaped recessed portions 42X and 42Y crossing (perpendicularly) to each other”, in other words, “small absorbent portions 43 surrounded by groove-shaped recessed portions 42” is preferably 25 mm ² or more, more preferably 50 mm ² or more, and preferably 1000 mm ² or less, more preferably 500 mm ² or less.
The number of small absorbent portions 43 per unit area of 2500 mm ² is preferably 2 or more, more preferably 5 or more, and preferably 100 or less, more preferably 50 or less.
The basis weight of the small absorbent portion 43 (the portion of the absorbent core 40 that overlaps the small absorbent portion 43 in plan view) is greater than the basis weight of the surrounding “part of the absorbent core 40 that overlaps the groove-shaped recess 42 in plan view”. is preferably 150 g/m ² or more, more preferably 200 g/m ² or more, and preferably 800 g/m ² or less, more preferably 750 g/m ² or less.
The mass (basis weight) per unit area of the continuous layer 44 is preferably 30 g/m ² or more, more preferably 50 g/m ² or more, and preferably 160 g/m ² or less, more preferably 150 g/m ² or less. is.

The absorbent core 40 is mainly composed of a core-forming material, and typically composed of only the core-forming material. The core-forming material includes at least water-absorbing fibers 12F and fiber masses 11 containing fibers 11F. The constituent fibers 11F of the fiber mass 11 are typically synthetic fibers. The absorbent core 40 shown in FIG. 2 further contains the particulate water-absorbing polymer 13 in addition to the fiber mass 11 and the water-absorbing fibers 12F.

One of the main features of the napkin 1 is that the absorbent core 40 that forms the main body of the absorbent body 4 contains the fiber lumps 11 . Below, the absorbent core 40 will be mainly described, but the absorbent core 40 can be said to be substantially the absorbent body 4 itself. Appropriately applied as a description of the absorbent body 4 . The absorbent body according to the present invention includes a form composed only of an absorbent core without a core wrap sheet, and in such a form, the absorbent body and the absorbent core have the same meaning. .

As used herein, the term "fiber mass" refers to a fiber aggregate in which a plurality of fibers are bundled together. The fiber mass used in the present invention may be a fiber aggregate of a fixed shape, such as a sheet piece obtained by cutting a synthetic fiber sheet having a certain size with a cutter or the like, regardless of its manufacturing method, or An irregular-shaped fiber aggregate produced by pulverizing a nonwoven fabric mainly composed of synthetic fibers into small pieces, or by tearing off or tearing off, such as the nonwoven fabric pieces described in Patent Document 2, may also be used. In the present invention, the absorbent body (absorbent core) may i) include only fixed-shaped fiber aggregates as fiber aggregates, or ii) include only irregular-shaped fiber aggregates as fiber aggregates, or iii. ) The fiber mass may be in the form of a mixture of fixed-shaped fiber aggregates and irregular-shaped fiber aggregates, but the above-described form i) is preferably used. In the irregularly shaped fiber assembly, since the constituent fibers are randomly oriented, the surface is rough such that the fibers protrude from here and there on the surface. There is a risk of entanglement, and as a result, the degree of freedom of movement of each fiber assembly is restricted, resulting in reduced flexibility. The fiber clump 11 of this embodiment is a fixed-shaped fiber aggregate as described later.

As described above, the fiber mass 11 is a fiber assembly in which a plurality of fibers 11F are aggregated and integrated, and a plurality of the fiber masses 11 are present in the absorbent core 40 while maintaining their shape. The fiber mass 11 mainly contributes to improvement of the flexibility, cushioning properties, compression recovery properties, and shape retention properties of the absorbent core 40 due to the form of the fiber assembly.

A plurality of water-absorbent fibers 12F are present in the absorbent core 40, and although the plurality of water-absorbent fibers 12F can be entangled with each other, they are not aggregated like the constituent fibers 11F of the fiber mass 11, and are individually independent. preferably present in The water absorbent fibers 12F mainly contribute to improving the liquid absorbency of the absorbent core 40 and also contributes to improving the shape retention of the absorbent core 40 .

As the water-absorbing fibers 12F, water-absorbing fibers conventionally used as a material for forming the absorbent body of this type of absorbent article can be used. Examples of water-absorbing fibers include natural fibers such as wood pulp such as softwood pulp and hardwood pulp, non-wood pulp such as cotton pulp and hemp pulp; modified pulp such as cationized pulp and mercerized pulp; cupra, rayon, etc. and the like, and these can be used alone or in combination of two or more. Considering that the main role of the absorbent fibers 12F is to improve the liquid absorbency of the absorbent body 4, natural fibers and regenerated fibers (cellulosic fibers) are preferable as the absorbent fibers 12F.

A plurality of water-absorbing polymers 13 are present in the absorbent core 40 as small pieces of water-absorbing polymer, and mainly contribute to the improvement of the liquid absorbency in the absorbent core 40 . The shape of the pieces of the water-absorbent polymer 13 is not particularly limited, and may be, for example, spherical, massive, bale-shaped, fibrous, or irregular. The average particle size of the water absorbing polymer 13 is preferably 10 μm or more, more preferably 100 μm or more, and preferably 1000 μm or less, more preferably 800 μm or less. As the water absorbing polymer 13, generally, a polymer or copolymer of acrylic acid or an alkali metal salt of acrylic acid can be used. Examples thereof include polyacrylic acid and its salts and polymethacrylic acid and its salts. Specifically, acrylic acid polymers such as Aqualic CA and Aqualic CAW (both manufactured by Nippon Shokubai Co., Ltd.) Partial sodium salts are included.

In the absorbent core 40, not only are the plurality of fiber clumps 11 and the water absorbent fibers 12F mixed together, but also the fiber clumps 11 or the fiber clumps 11 and the water absorbent fibers 12F are entangled with each other. In addition, as will be described later, in the napkin 1, the concave portions 7 and 8 are formed on the skin-facing surface and the non-skin-facing surface of the absorbent body 4 (see FIG. 2 etc.), and the following fiber lumps 11 Unless otherwise specified, the description of "entanglement" in 1) applies to the portions (low-density portions 9) of the absorbent core 40 where the concave portions 7 and 8 are not formed. In the absorbent core 40 where the recesses 7 and 8 are formed, the fiber clumps 11 and the like may be entangled with each other. may not have.

In the absorbent core 40, a plurality of fiber lumps 11 are bound by entanglement with constituent fibers (fibers 11F, 12F) in the absorbent core 40 to form one fiber lump continuum. Further, the plurality of fiber clumps 11 may be entangled with each other, and the fiber clumps 11 and the absorbent fibers 12F may be entangled and bonded. Furthermore, usually, a plurality of water absorbent fibers 12F are also entangled with each other. At least some of the plurality of fiber lumps 11 contained in the absorbent core 40 are entangled with other fiber lumps 11 or water absorbent fibers 12F. In the absorbent core 40, all of the plurality of fiber lumps 11 contained therein may be entangled with each other to form one fiber lump continuum. It is possible that they are mixed in the state of combination.

In the absorbent core 40, in addition to containing the fiber clumps 11 capable of increasing the flexibility of the absorbent core 40, the fiber clumps 11 are entangled with each other or between the fiber clumps 11 and the water absorbent fibers 12F. Since the absorbent core 40 is bonded, the absorbent core 40 is more excellent in responsiveness to external force, and is excellent in flexibility, cushioning property, and compression recovery property. The absorbent core 40 deforms flexibly against external forces received from various directions when the napkin 1 is worn (for example, the body pressure of the wearer of the napkin 1), and the napkin 1 can be brought into close contact with the wearer's body with good fit. . Such excellent deformation-recovery characteristics of the absorbent core 40 can be exhibited not only when the absorbent core 40 is compressed but also when twisted. That is, since the absorbent core 40 incorporated in the napkin 1 is sandwiched between the thighs of the wearer when the napkin 1 is worn, it is Movement of the thighs may cause twisting around a virtual axis of rotation extending in the longitudinal direction X. The napkin 1 can be easily deformed and recovered from an external force that promotes twisting from the body, and therefore, it is difficult to twist, and the napkin 1 can be given a high fit to the wearer's body.

In the absorbent core 40, the fiber lumps 11 or the fiber lumps 11 and the water-absorbing fibers 12F are entangled. be done.
Form A: A form in which the fiber clumps 11 and the like are bonded by entanglement of the constituent fibers 11F of the fiber clumps 11 rather than fusion bonding.
Mode B: In the natural state of the absorbent core 40 (the state in which no external force is applied), the fiber clumps 11 and the like are not bonded together, but in the state in which the absorbent core 40 is subjected to an external force, the fiber clumps 11 and the like are bonded together. A configuration in which the constituent fibers 11F can be bound by entanglement with each other. Here, "a state in which an external force is applied to the absorbent core 40" means, for example, that the absorbent core 40 has It is in a state where deformation force is applied.

As described above, in the absorbent core 40, the fiber clumps 11 are connected to other fiber clumps 11 or the water-absorbing fibers 12F by entanglement, ie, "entangling", as in the form A. Like B, it also exists in a state where it can be entangled with other fiber clumps 11 or water absorbent fibers 12F. Such binding by entangling the fibers is one of the important points for more effectively exhibiting the function and effect of the absorbent core 40 described above. In particular, the absorbent core 40 preferably has form A of "entanglement" in terms of shape retention. Bonding by fiber entanglement does not have an adhesive component or fusion, and is made only by entanglement of fibers. The degree of freedom of movement of the fiber 12F) is high, so that its individual elements can move within a range that maintains their integrity as an assembly composed of them. In this way, the absorbent core 40 is deformed when receiving an external force because the plurality of fiber clumps 11 contained therein or the fiber clumps 11 and the absorbent fibers 12F are relatively loosely connected. It has a gentle shape retention that is possible, and has a high level of shape retention, cushioning property, compression recovery property, and the like. The napkin 1 having such a high-quality absorbent core 40 fits tightly to the wearer's body and is comfortable to wear.

It is not necessary that all the binding modes via the fiber clumps 11 in the absorbent core 40 are "entangled", and a part of the absorbent core 40 includes other binding modes other than entangling, such as bonding with an adhesive. may be However, the absorbent core 40 is excluded from the "fusion through the fiber clumps 11" formed in the absorbent core 40 as a result of being integrated with other members of the absorbent article, such as known leak-proof grooves. In the remaining portion, that is, the unprocessed absorbent core 40 itself, it is desirable that the fiber clumps 11 are bonded together or the fiber clumps 11 and the absorbent fibers 12F are bonded only by "fiber entanglement".

The napkin 1 has the above-described structure, that is, 1) the absorbent core 40 is formed with the groove-shaped recess 42, and 2) the absorbent core 40 is formed with the fiber mass 11 containing the synthetic fiber 11F. By containing the water-absorbent fibers 12F, it is difficult to get twisted when worn, and has a good wearing feeling and is excellent in liquid absorption.

More specifically, as described above, the absorbent core 40 has groove-shaped recesses 42 that can act as bending guides (flexible shafts), so that when the napkin 1 is worn, it conforms to the shape of the wearer's body. The napkin 1 is easy to deform along the contour, so that the napkin 1 is excellent in fit and wearing feeling. In addition, the groove-shaped concave portion 42 functions as a stock layer that temporarily retains bodily fluid such as menstrual blood excreted by the wearer of the napkin 1, and also diffuses it in the surface direction of the absorbent core 40, so that the napkin 1 can absorb the fluid. It is also highly absorbent. In addition, the absorbent core 40 having such excellent properties resulting from the groove-shaped recesses 42 has a fiber mass that can contribute to improving the flexibility, cushioning property, compression recovery property, and shape retention property of the absorbent core 40. 11 is contained, the functions and effects of the groove-shaped recesses 42, especially the feeling of wearing and fit, are further improved, and the wearer is less likely to become twisted. In addition, since the constituent fibers 11F of the fiber mass 11 typically contain hydrophobic synthetic fibers, they have excellent shape retention even after they absorb body fluids and get wet. Also, the effect of the fiber mass 11 can be exhibited.

In addition, in the absorbent core 40, the plurality of fiber lumps 11 or the fiber lumps 11 and the water absorbent fibers 12F are entangled with each other. Not only does it absorb body fluids and become wet, but it does not get twisted easily.

From the viewpoint of ensuring the effects of the napkin 1 described above, the continuous layer 44 (see FIGS. 5 to 7) of the absorbent core 40 has the fiber lumps 11 and the water absorbent fibers 12F. is preferred.

Further, in addition to the existence of the fiber lumps 11 and the absorbent fibers 12F in the continuous layer 44, the continuous layer 44 is unevenly distributed on the skin-facing surface 45 side of the absorbent core 40 as shown in FIG. As shown in FIG. 6, if the absorbent core 40 is unevenly distributed on the side of the non-skin facing surface 46, it is preferable because the action and effect of the napkin 1 described above can be exhibited more reliably. In this case, the side opposite to the continuous layer 44 side of the absorbent core 40 is the side on which the openings of the groove-like recesses 42 are located, and there is less core-forming material such as fiber lumps 11 than on the continuous layer 44 side. That is, the continuous layer 44 side of the absorbent core 40 (the skin-facing surface 45 side in the absorbent body 4 shown in FIG. 5) is more Many fiber clumps 11 may exist.

In this way, when the continuous layer 44 containing the fiber clumps 11 and the absorbent fibers 12F is unevenly distributed on the skin-facing surface 45 side or the non-skin-facing surface 46 side of the absorbent core 40, the depth of the groove-shaped recessed portion 42 D (see FIG. 5) is preferably 40% or more, more preferably 50% or more, and preferably 98% or less, more preferably 80% of the thickness T (see FIG. 5) of the absorbent core 40 It is below.

The thickness T of the absorbent core 40, that is, the thickness of the non-existent portion (small absorbent portion 43) of the groove-shaped recess 42 is preferably 2.0 mm or more, more preferably 3.0 mm or more, and preferably 10.0 mm or less. , more preferably 8.0 mm or less.
The thickness of each part of the absorbent core 40 is measured by the following method. The thickness of the entire absorbent core 40 (absorbent body 4), the thickness of the napkin 1, and the like can also be measured according to the following methods.

<Method for measuring thickness>
The absorbent core (absorbent body) is placed on a horizontal surface without any wrinkles or bends, and the site to be measured (for example, the skin facing side or the non-skin facing side of the absorbent core) is measured from the absorbent core. Cut out and use as a measurement sample. Then, the thickness of the measurement sample is measured under a load of 5 cN/cm ² . Specifically, a thickness gauge PEACOCK DIAL UPRIGHT GAUGES R5-C (manufactured by OZAKI MFG.CO.LTD.), for example, is used to measure the thickness. At this time, between the tip of the thickness gauge and the sample to be measured, a circular or square plate (acrylic plate with a thickness of about 5 mm), whose size is adjusted so that the load is 5 cN/cm ² in plan view, is placed. and measure the thickness. In the thickness measurement, arbitrary 10 points in the measurement sample are measured, and the average value of the thicknesses of those 10 points is calculated to be the thickness of the measurement sample.

In the absorbent core 40, the fiber lumps 11 may be distributed in any way. good. In the latter case, the fiber clumps 11 may be unevenly distributed in a part of the absorbent core 40 in the plane direction (for example, any one or two of the front area F, the longitudinal central area M and the rear area R). , may be unevenly distributed in a part of the thickness direction of the absorbent core 40 (for example, the side of the skin-facing surface 45 or the side of the non-skin-facing surface 46). It should be noted that the “skin-facing surface 45 side” referred to here is the skin-facing surface when the absorbent core 40 in the relevant region (for example, the front region F, the longitudinal central region M, or the rear region R) is divided into two equal parts in the thickness direction. The portion near the surface 45, and the “non-skin facing surface 46 side” is the portion near the non-skin facing surface 46 in such a case.

At least in the longitudinal central region M, the non-skin facing surface 46 side of the absorbent core 40 preferably has a larger mass (basis weight) per unit area of the fiber mass 11 than the skin facing surface 45 side. With such a configuration, the effects mainly due to the fiber mass 11, such as the effect of improving the cushioning property and the resistance to twisting, are enhanced. Further, in this case, the mass (basis weight) per unit area of the absorbent fibers 12F can be larger on the side of the skin-facing surface 45 of the absorbent core 40 in the longitudinal central region M than on the side of the non-skin-facing surface 46. , the absorbent fiber 12F having excellent water absorption is placed on the side of the skin-facing surface 45 of the absorbent core 40 in the longitudinal central region M, which is the portion of the absorbent core 40 that first receives body fluid excreted by the wearer of the napkin 1. Since it is contained in a relatively large amount, the liquid drawing power (capillary force) of this portion is improved, and the liquid absorbency of the absorbent core 40 is improved. Therefore, in the absorbent core 40 in the longitudinal central region M, the size relationship of "the basis weight of the fiber lumps 11 on the non-skin facing surface 46 side>the basis weight of the fiber lumps 11 on the skin facing surface 45 side" is established. The possibility that the napkin 1 will be less likely to be twisted when worn, comfortable to wear, and excellent in liquid absorbency can be further improved. It is more preferable that the magnitude relationship is established not only in the longitudinal central region M but also in the entire absorbent core 40 .

In the front region F and the rear region R, as in the longitudinal central region M, in the absorbent core 40, "the basis weight of the fiber clumps 11 on the non-skin facing surface 46 side > the basis weight of the fiber clumps 11 on the skin facing surface 45 side. It is preferable that the magnitude relationship of "amount" is established.

The ratio of the basis weight of the fiber clumps 11 on the non-skin-facing surface 46 side of the absorbent core 40 to that on the skin-facing surface 45 side is preferably 1.1 or more, more preferably 10 or more, as the former/latter.
On the premise that the basis weight of the fiber clumps 11 on the non-skin facing surface 46 side of the absorbent core 40 is larger than that on the skin facing surface 45 side, it is preferably 32 g/m ² or more, more preferably 80 g/m ^{2 .} above, and preferably 640 g/m ² or less, more preferably 480 g/m ² or less.
Assuming that the basis weight of the fiber clumps 11 on the skin-facing surface 45 side of the absorbent core 40 is smaller than that on the non-skin-facing surface 46 side, it is preferably 320 g/m ² or less, more preferably 240 g/m ^{2 .} or less, and may be 0 g/m ² .

In the absorbent core 40, the longitudinal central region M preferably has a larger mass (basis weight) per unit area of the fiber lumps 11 than the front region F and the rear region R. Since the absorbent core 40 in the longitudinal central region M is usually sandwiched between the thighs of the wearer when the napkin 1 is worn, the movement of the thighs during the wearer's walking motion causes the vertical direction X It is likely to be twisted around a virtual rotation axis extending in the direction of the arrow, and compared to the front region F and the rear region R, the external force is likely to act strongly, and twisting is likely to occur. Here, in the absorptive core 40, the above-described magnitude relationship "the basis weight of the fiber lumps 11 in the longitudinal central region M>the basis weights of the fiber lumps 11 in the front region F and the rear region R" is established, and relatively twist occurs. In the absorbent core 40 in the longitudinal central region M, which is easy to absorb, the fiber clumps 11 that can contribute to improving cushioning properties, compression recovery, shape retention, etc. are contained more than the front region F and the rear region R. , the inconvenience that the absorbent body 4 is twisted when wearing the napkin 1 can be effectively prevented, and the feeling of wearing can be further improved.

The ratio of the basis weight of the fiber clumps 11 of the absorbent core 40 in the longitudinal central region M to that in each of the front region F and the rear region R is preferably 1.1 or more, more preferably 10 or more as the former/latter. .
On the premise that the basis weight of the fiber clumps 11 of the absorbent core 40 in the longitudinal central region M is larger than that of each of the front region F and the rear region R, it is preferably 32 g/m2 or ^more , more preferably 80 g/m2. ² or more, and preferably 640 g/m ² or less, more preferably 480 g/m ² or less.
On the premise that the basis weight of the fiber clumps 11 in each of the front region F and the rear region R is smaller than that of the longitudinal central region M, it is preferably 320 g/m ² or less, more preferably 240 g/m ² or less, It may be 0 g/ ^m2 .

The above-mentioned size relationship "the basis weight of the fiber lumps 11 in the longitudinal central region M > the basis weights of the fiber lumps 11 in the front region F and the rear region R" is established, so that the effect can be exhibited more reliably. From the viewpoint, the absorbent core 40 preferably contains 90% by mass or more of all the fiber lumps 11 contained in the absorbent core 40 in the longitudinal central region M, and more preferably 95% by mass or more. Preferably, 100% by mass, that is, all of the fiber lumps 11 contained in the absorbent core 40 may be present in the longitudinal central region M.

The above-described uneven distribution of the fiber lumps 11 in the absorbent core 40 is determined by using the total content mass of the fiber lumps 11 and the water-absorbent fibers 12F used as the core forming material of the absorbent core 40 together with the "fiber lumps 11 and water absorption It can also be defined as the ratio of the mass content of the fiber lumps 11 to the total mass content of the fibrous fibers 12F" (hereinafter also referred to as the "fibrous mass occupancy ratio").
That is, in relation to the magnitude relationship of "the basis weight of the fiber lumps 11 on the non-skin facing surface 46 side>the basis weight of the fiber lumps 11 on the skin facing surface 45 side", "the fiber lumps on the non-skin facing surface 46 side It is preferable that the size relationship of "occupancy rate>fiber mass occupancy rate on the side of the skin-facing surface 45" is established.
Further, in relation to the magnitude relationship of "the basis weight of the fiber lumps 11 in the longitudinal central region M > the basis weights of the fiber lumps 11 in the front region F and the rear region R", the "fiber lump occupancy of the longitudinal central region M It is preferable to establish a magnitude relation of ratio>fibrous clump occupancy ratio of front area F and rear area R".

The fiber clump occupancy rate is obtained by measuring the content of each of the fiber clumps 11 and the water-absorbent fibers 12F existing in the predetermined measurement target portion of the absorbent core 40 by mass, and then measuring the fiber clump occupancy rate. 11 is divided by the sum of the masses contained in the water-absorbing fibers 12F and the fiber lumps 11, and expressed as a percentage of 100. That is, fiber lump occupation ratio (% by mass)={mass content of fiber lumps 11/(mass content of water-absorbing fibers 12F+mass content of fiber lumps 11)}×100.

On the premise that the fiber clump occupancy on the non-skin-facing surface 46 side of the absorbent core 40 is higher than that on the skin-facing surface 45 side of the absorbent core 40, it is preferably 50% by mass or more, more preferably 90% by mass. % or more, and 100% by mass, that is, the non-skin facing surface 46 side may not contain the water-absorbing fibers 12F at all instead of containing the fiber lumps 11 .
Further, on the premise that the fiber clump occupancy of the absorbent core 40 in the longitudinal central region M is higher than that in each of the front region F and the rear region R, it is preferably 50% by mass or more, more preferably 90% by mass or more. , and 100% by mass, that is, the absorbent core 40 in the longitudinal central region M may not contain the water absorbent fibers 12F at all instead of containing the fiber lumps 11 .

For example, in the absorbent core 40 in the longitudinal central region M, when the above-described magnitude relationship of "fiber mass occupation rate on the non-skin facing surface 46 side>fiber mass occupation rate on the skin facing surface 45 side" is established, 1) the skin On each of the facing surface 45 side and the non-skin facing surface 46 side, the fiber mass occupancy may be constant without changing in the thickness direction, or 2) the fiber mass may increase from the skin facing surface 45 side toward the non-skin facing surface 46 side. Lump occupancy may increase gradually. In the above-mentioned form 2), in the thickness direction of the absorbent core 40, the fiber lumps 11 do not exist on the skin-facing surface 45 of the absorbent core 40 and its vicinity, or the minimum At the non-skin-facing surface 46 of the absorbent core 40 and its vicinity, the fiber lumps 11 exist at the highest fiber lump occupation rate in the absorbent core 40 in the longitudinal central region M. The front region F and the rear region R of the absorbent core 40 may also have the form of 1) or 2).

As an advantage peculiar to the above-described form 1), it is easy to design independent functions on the skin-facing side and the non-skin-facing side of the absorbent core. In addition, as an advantage peculiar to the above-mentioned form 2), the mixing ratio of the water-absorbing fibers and the fiber clumps gradually changes in the thickness direction of the absorbent body, so that even when an external force is applied to the absorbent core, the fiber clumps intervene. The entangled state is easily maintained over the thickness direction, and good cushioning properties of the absorbent core are easily maintained during use.

In addition, the fiber clump occupancy rate may gradually increase from each of the front region F and the rear region R of the absorbent core 40 toward the longitudinal central region M. For example, in each of the front region F and the rear region R, the fiber mass occupancy gradually increases from the outer side to the inner side in the longitudinal direction X, and the longitudinal central region M is in the form of 1) or 2) above. good too.

In the napkin 1 of the present embodiment, as shown in FIGS. 1 and 2, the absorbent body 5 is provided with a surface sheet 2, a core wrap sheet 41 (skin side core wrap sheet), and an absorbent body 4 (absorbent core 40). A surface recessed portion 7 integrally recessed on the non-skin facing surface side (backsheet 3 side) of the absorbent body 4 is formed at least in the longitudinal central region M. As shown in FIG. The recessed surface portion 7 does not penetrate the absorbent body 4 (absorbent core 40), has an opening on the skin-facing surface of the topsheet 2, and has a bottom on the opposite side of the opening. The recessed surface 7 formed on the skin-facing surface of the napkin 1 has a function of inhibiting movement of body fluids such as menstrual blood in the planar direction.

In the napkin 1, the surface recesses 7 extend in the longitudinal direction X in the longitudinal central region M, as shown in FIGS. More specifically, the surface recess 7 includes a pair of left and right surface vertical recesses 7X, 7X extending in the vertical direction X and a pair of front and rear horizontal surface recesses 7Y, 7Y extending in the horizontal direction Y. ing.

The pair of surface vertical recesses 7X, 7X each extend over the entire length of the longitudinal center region M in the longitudinal direction X, further extend to the front region F and the rear region R, and form a continuous line as a whole. there is
At least a portion of one of the pair of surface lateral recesses 7Y, 7Y is located in the front region F, and at least a portion of the other is located in the rear region R, both of which extend in the vertical direction X in plan view. A U-shaped or arcuate continuous line projecting outward is formed, and the top of the U-shaped or arcuate portion is positioned at the center in the lateral direction Y of the napkin 1A.
The recessed portions 7X and 7Y forming the surface recessed portion 7 are connected to each other at their lengthwise ends, and the surface recessed portion 7 as a whole has a closed annular shape, more specifically a long shape, in plan view. It has an elliptical shape. A region surrounded by the pair of surface vertical recesses 7X, 7X in the longitudinal central region M is located in the central portion of the longitudinal central region M and includes the excretory part facing portion (excretion point).

In the napkin 1, as shown in FIG. 2, a core wrap sheet 41 (non-skin side core wrap sheet) and an absorbent core 40 are positioned so as to overlap the surface recessed portion 7 in a plan view so that the absorbent core 40 faces the skin. A rear surface recessed portion 8 integrally recessed on the surface side (the surface sheet 2 side) is formed at least in the longitudinal central region M. As shown in FIG. The back concave portion 8 does not penetrate the absorbent body 4 (absorbent core 40), has an opening on the non-skin-facing surface of the absorbent body 4, and has a bottom on the side opposite to the opening. The front surface recessed portion 7 and the rear surface recessed portion 8 share a bottom portion.

In this embodiment, the back surface recessed portion 8 has substantially the same shape and the same dimensions as the front surface recessed portion 7 in plan view, and forms a closed annular shape similar to the front surface recessed portion 7 . That is, the back surface recessed portion 8 extends in the vertical direction X, and extends in the horizontal direction Y along with a pair of left and right back surface vertical recessed portions 8X, 8X that overlap the front surface vertical recess portion 7X in plan view and have the same shape as the front surface vertical recess portion 7X in plan view. , and a pair of front and rear lateral recesses 8Y, 8Y (not shown) overlapping the front lateral recess 7Y in plan view and having the same shape in plan view as the front lateral recess 7Y. They are connected at the ends in the length direction, and form a closed annular shape (oblong elliptical shape) in plan view as a whole of the back recessed portion 8 .

The surface recessed portion 7 is formed by compressing the absorbent body 5 from the napkin 1, specifically from the side of the skin facing surface (the side of the surface sheet 2). ' can be said. In addition, the back concave portion 8 is formed by compressing the absorbent body 4 from the non-skin facing surface side (non-skin side core wrap sheet side), and is also called a "pressing portion". can. Both recessed portions 7 and 8, which are compressed portions, have a higher density than peripheral portions of both recessed portions 7 and 8 in absorbent body 4. As shown in FIG. That is, the absorbent main body 5 has a high-density portion corresponding to the recessed portions 7 and 8 and a low-density portion 9 in which the recessed portions 7 and 8 are not formed. ing.

The pressing process for forming both concave portions 7 and 8 melts the core-forming material contained in the absorbent body 4 (absorbent core 40), particularly melts thermoplastic fibers preferably used as constituent fibers of the fiber mass 11. A method that involves melting may be used, or a method that does not involve melting of the core-forming material may be used. Specific examples of the pressing process involving melting of the core-forming material include known embossing processes such as embossing processes involving heat and ultrasonic embossing. At the bottom of the surface recessed portion 7 formed by pressing with melting of the core forming material, that is, at the portion overlapping the surface recessed portion 7 which is a space portion in plan view, the surface sheet 2, the core wrap sheet 41 (skin side core wrap sheet) and the absorbent core 40 may be heat-sealed together. In addition, the core wrap sheet 41 (non-skin side core wrap sheet ) and the absorbent core 40 may be heat-sealed together. As described above, since the bottom portion is shared by the back recessed portion 8 and the front recessed portion 7, the bottom portion common to both the recessed portions 7 and 8 includes the top sheet 2 and the skin side in order from the front recessed portion 7 side. The core wrap sheet, the absorbent core 40 and the non-skin side core wrap sheet may exist in a state of being heat-sealed and integrated with each other.

The width of the surface recessed portion 7 (the length in the direction perpendicular to the length direction of the recessed portion) is not particularly limited, but is preferably 0.1 mm or more, more preferably 0.5 mm or more, and preferably 10 mm or less. It is preferably 5 mm or less. The width of the back recessed portion 8 can also be set within the same range.

As shown in FIGS. 1, 2 and 4, the napkin 1, more specifically, the absorbent body 5 is a portion where neither the front recessed portion 7 nor the back recessed portion 8 is formed. , 8 is present. In the present embodiment, as described above, both recessed portions 7 and 8 have substantially the same shape and the same size in plan view, and form a closed ring (elliptical shape). It exists both inside and outside the closed ring of recesses 7,8. At least the peripheral portion of the absorbent main body 5 and the central portion of the longitudinal central region M (the portion facing the excretory portion and its vicinity) are low-density portions 9 .

In addition, the low-density portion 9, in particular, is sandwiched between a pair of front vertical recesses 7X, 7X (rear vertical recesses 8X, 8X) extending in the vertical direction X through both sides of the vertical center region M in the horizontal direction Y. A pressed portion formed by a pressing process such as embossing may partially exist in the region (the central portion in the horizontal direction Y of the vertical central region M). In that case, the area of all the compressed parts present in the low-density portion 9, which occupies the total area of the low-density portion 9 (specifically, for example, the region sandwiched between the pair of surface vertical recesses 7X, 7X) The total ratio is preferably 5% or less, more preferably 3% or less. In addition, in the napkin 1 of this embodiment, there is no compressed portion in the low-density portion 9 sandwiched between the pair of surface vertical concave portions 7X, 7X.

Since the absorbent core 40 contains the fiber lumps 11, the characteristics such as shape retention and cushioning properties are improved compared to the normal absorbent core 40 that does not contain it. Having the depressed densities 7 compressed and densified further enhances such properties, e.g. the strong compressive force in the lateral direction Y exerted by the thighs of the wearer of the napkin 1. It does not easily lose its shape even when subjected to such an external force, it deforms with good responsiveness to the external force, and can quickly restore itself when the external force is released.

In addition, in the napkin 1, due to the relatively high density recessed portions 7 and 8 and the relatively low density low density portion 9 coexisting in the plane direction, there is a density difference in the plane direction. Due to the difference in density, the body fluid is easily diffused in the plane direction. That is, the napkin 1 can quickly diffuse the bodily fluid excreted by the wearer in the surface direction, and therefore effectively utilizes the absorption performance inherent in the absorbent core 40 to exhibit high liquid leakage prevention. can.

In particular, the napkin 1, as shown in FIGS. 1 and 4, has surface recesses 7 not only in the longitudinal central region M, but also in the front region F and the rear region R, so that the overall shape retention of the napkin 1 and the liquid diffusibility in the surface direction are enhanced.

In addition, in the low-density portion 9, the plurality of fiber lumps 11 exist in a state in which their original outer shape is substantially maintained. A large number of space portions are present, and the large number of space portions contribute to the expression of the excellent cushioning properties of the low-density portion 9, and can also function as a temporary stock portion for body fluids. Since the napkin 1 has the low-density portion 9 that can function as a temporary storage portion for bodily fluids in the central longitudinal region M where excreted bodily fluids tend to concentrate, the napkin 1 has excellent fluid absorption capacity. and can exhibit high liquid-leakage-proof property, and the high liquid-drawing property can reduce liquid residue on the surface of the topsheet 2 facing the skin, thereby suppressing unpleasant wet feeling and sticky feeling.

In addition, the presence of the low-density portion 9 having excellent cushioning properties and the like in the longitudinal central region M where the excretory part facing portion exists allows the longitudinal central region M to be in a dry state before absorption of body fluids as well as after absorption of body fluids. Even in a wet state, the low-density portion 9 provides flexibility and cushioning properties.

As described above, in the longitudinal central region M, if the mass (basis weight) per unit area of the fiber lumps 11 differs between the skin-facing surface 45 side and the non-skin-facing surface 46 side of the absorbent core 40, surface depressions occur. It is preferable that the portion 7 overlaps the fiber lumps 11 in plan view, and in the longitudinal central region M, the fiber lumps 11 have a basis weight different from that of the skin-facing surface 45 of the absorbent core 40 . More specifically, for example, in the absorptive core 40 in the longitudinal central region M, the above-mentioned "basis weight of the fiber lumps 11 on the non-skin facing surface 46 side > basis weight of the fiber lumps 11 on the skin facing surface 45 side" is large or small. When the relationship is established, the surface recesses 7 (surface vertical recesses 7X, surface horizontal recesses 7Y) overlap the fiber mass 11 in plan view, and extend to the non-skin facing surface 46 side in the vertical central region M. preferably reached. In addition, as described above, the side of the skin-facing surface 45 of the absorbent core 40 in the longitudinal central region M referred to here is the skin-facing surface 45 when the absorbent core 40 in the longitudinal central region M is bisected in the thickness direction. The non-skin facing surface 46 side, which is a side portion, is a portion near the non-skin facing surface 46 in such a case. With such a configuration, the effects of the recessed portions 7 and 8 and the low-density portion 9 (improvement of shape retention, improvement of liquid diffusion in the surface direction, etc.) are further improved, and absorption during wearing is further improved. The twisting of the body 4 can be prevented more reliably. Such a configuration can also be applied when the fiber clump occupancy is different between the skin-facing surface 45 side and the non-skin-facing surface 46 side of the absorbent core 40 . That is, for example, in the absorptive core 40 in the longitudinal central region M, when the size relationship of "the fiber mass occupation rate on the non-skin facing surface 46 side>the fiber mass occupation rate on the skin facing surface 45 side" is established, the surface It is preferable that the concave portions 7 (surface vertical concave portions 7X, surface horizontal concave portions 7Y) overlap the fiber lumps 11 in a plan view, and extend to the non-skin facing surface 46 side in the vertical central region M.

In the longitudinal central region M, the surface recessed portions 7 on both sides in the lateral direction Y (more specifically, the pair of surface longitudinal recessed portions 7X, 7X) and the regions sandwiched therebetween (hereinafter referred to as “horizontally inward ) of the fiber mass 11 compared to the outer side of the surface recessed portion 7 (the laterally inner region) in the lateral direction Y (hereinafter also referred to as the “laterally outer region”). It is preferable that the mass (basis weight) per unit area is large. In the napkin 1, the laterally inner region is the low density portion 9, as shown in FIGS. With such a configuration, it is possible to promote liquid diffusion in the longitudinal direction X while ensuring the liquid absorption speed in the surface recessed portion 7 (surface vertical recessed portion 7X) in the longitudinal central region M. Leakage can be effectively suppressed. The basis weight ratio of the fiber mass 11 between the laterally outer region and the laterally inner region is the former (laterally outer region)/the latter (laterally inner region) on the premise that the former < the latter. , preferably 0 or more, more preferably 0.1 or more, and preferably less than 1.0, more preferably 0.9 or less.

The surface recessed portion 7 (surface vertical recessed portion 7X), which is the boundary between the laterally inner region and the laterally outer region in the longitudinal central region M, extends in the longitudinal direction X, The term “extension” used herein includes not only the case where the surface recessed portion 7 extends in a continuous line in the vertical direction X as shown in FIG. 1, but also a plurality of surface recessed portions 7 as shown in FIG. are intermittently arranged in the longitudinal direction X, and the plurality of surface recessed portions 7 extend in the longitudinal direction X as a whole. In the latter case, the distance in the longitudinal direction X between the two surface recesses 7 closest to each other in the longitudinal direction X is preferably 30 mm or less, more preferably 20 mm or less. The same applies to the plurality of rear surface recessed portions 8 intermittently arranged in the longitudinal direction X. As shown in FIG.

From the viewpoint of ensuring the effects of the concave portions 7 and 8 and the low-density portion 9 described above, it is preferable to set the dimensions of each portion of the napkin 1 as follows.
A separation distance W1 in the lateral direction Y between the side edges along the longitudinal direction X of the absorbent body 4 (absorbent core 40) and the concave portions 7 and 8 (vertical concave portions 7X and 8X) in the longitudinal central region M (see FIG. 1 ) is preferably 5 mm or more, more preferably 10 mm or more, and preferably 25 mm or less, more preferably 20 mm or less. If the length (width) of the absorber 4 in the horizontal direction Y is not constant, the separation distance W1 is the measured value at the widest part of the absorber 4 .
The length in the horizontal direction Y, that is, the width W2 (see FIG. 1) of the low-density portion 9 in the longitudinal central region M is preferably 20 mm or more, more preferably 25 mm or more, and preferably 70 mm or less, more preferably 65 mm or less. be.

The ratio of the total area of the surface recesses 7 to the total area of the skin-facing surface of the absorbent body 4 (absorbent core 40) (recess occupancy) is preferably 0.02% or more, more preferably 0.1%. % or more, preferably 15% or less, more preferably 10% or less. The ratio of the total area of the back recessed portions 8 to the total area of the non-skin facing surface of the absorbent body 4 (absorbent core 40) (recessed portion occupancy) may be the same as that of the front recessed portions 7 described above.
The depth of the surface recessed portions 7 (7X, 7Y) (the depth based on the non-recessed portion of the surface facing the skin of the top sheet 2) is preferably 0.1 mm or more, more preferably 0.2 mm or more, And it is preferably 2.0 mm or less, more preferably 1.0 mm or less.
The depth of the back concave portion 8 (8X, 8Y) (the depth based on the non-concave portion of the non-skin facing surface of the absorbent body 4) is preferably 0.1 mm or more, more preferably 0.2 mm or more. , and preferably 2.0 mm or less, more preferably 1.0 mm or less.

In the napkin 1, the depths of the recesses 7, 8 may be constant over the entire length of the napkin 1, or partially different. Further, the shape, arrangement, etc. of the linear recesses 7 and 8 are not limited to the illustrated form, and can be set in the same manner as what is called a leak-proof groove or the like in this type of absorbent article. The linear recesses 7 and 8 may be configured to include straight lines and/or curved lines in plan view, and each line may be a continuous line or a dashed line (two types of portions with different depths may be a line). alternately arranged in the extending direction of the recesses).

In addition, in the absorbent article of the present invention, the pattern (shape and arrangement in a plan view) of the recesses 7 and 8 is not limited to a line-of-sight pattern such as the recesses 7 and 8 shown in FIG. It may be circular, elliptical, rectangular, triangular, star-shaped, heart-shaped, or the like (dot-shaped). In the absorber 4F shown in FIG. 11, surface recessed portions 7 that are circular in plan view are formed in the longitudinal central region M in a scattered pattern. are arranged intermittently to form a row of recessed portions extending in the longitudinal direction X, and the rows of recessed portions are arranged in a pair in the lateral direction Y with a gap therebetween. Although not shown, a back recessed portion 8 is formed in the same pattern as the front recessed portion 7 on the non-skin facing side of the absorbent body 4 . The absorber 4F is configured in the same manner as the absorber 4 described above except for the pattern of the concave portions 7 and 8, and the description of the absorber 4 applies appropriately to the structure of the absorber 4F that is not particularly described.

In the absorbent core 40, the content mass ratio of the fiber clumps 11 and the water-absorbent fibers 12F is not particularly limited, and may be appropriately adjusted according to the types of the constituent fibers (synthetic fibers) 11F and the water-absorbent fibers 12F of the fiber clumps 11. Just do it. For example, when the constituent fibers 11F of the fiber mass 11 are thermoplastic fibers (non-water-absorbing synthetic fibers) and the water-absorbing fibers 12F are cellulose-based water-absorbing fibers, the predetermined effects of the present invention can be obtained more reliably. From the viewpoint of the above, the content mass ratio of the fiber mass 11 and the water-absorbent fiber 12F is preferably 20/80 to 80/20, more preferably 40, as the former (fiber mass 11) / the latter (water-absorbent fiber 12F). /60 to 60/40.

The content of the fiber lumps 11 in the absorbent core 40 is preferably 20% by mass or more, more preferably 40% by mass or more, and preferably 80% by mass or less with respect to the total mass of the absorbent core 40 in a dry state. , more preferably 60% by mass or less.
The content of the water absorbent fibers 12F in the absorbent core 40 is preferably 20% by mass or more, more preferably 40% by mass or more, and preferably 80% by mass with respect to the total mass of the absorbent core 40 in a dry state. 60% by mass or less, more preferably 60% by mass or less.
The content of the water-absorbent polymer 13 in the absorbent core 40 is preferably 1% by mass or more, more preferably 5% by mass or more, and preferably 80% by mass with respect to the total mass of the absorbent core 40 in a dry state. 50% by mass or less, more preferably 50% by mass or less.
As used herein, the term "dry absorbent core" means an absorbent core before it absorbs bodily fluids.

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 fibers 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. be.
The basis weight of the water absorbent polymer 13 in the absorbent core 40 is preferably 5 g/m ² or more, more preferably 10 g/m ² or more, and preferably 200 g/m ² or less, more preferably 100 g/m ² or less. be.

As described above, the absorbent body 4 (absorbent core 40) can be manufactured according to a conventional method using a known fiber stacking device equipped with a rotating drum. As described above, the absorbent body 4 has a form in which the core-forming materials (the fiber mass 11, the water-absorbent fibers 12F, and the water-absorbent polymer 13) are uniformly distributed throughout the absorbent core 40, and the fibers in a part of the absorbent core 40. Although both forms include a form in which lumps 11 (water-absorbent fibers 12F) are unevenly distributed, any form can be manufactured according to a conventional method using a known fiber stacking device. In particular, the latter form in which the fiber clumps 11 (water-absorbing fibers 12F) are unevenly distributed in a part of the absorbent core 40 can be achieved by It is possible to manufacture by appropriately adjusting the stacking order on the rotating drum.

The fiber mass 11 will be further described below. FIG. 12 shows two typical outer shapes of the fiber clump 11 . More specifically, the fiber mass 11A shown in FIG. 12(a) has a rectangular parallelepiped shape rather than a quadrangular prism shape, and the fiber mass 11B shown in FIG. 12(b) has a disk shape. The fiber clumps 11A and 11B are common in that they have two base planes 111 facing each other and a body plane 112 connecting the two base planes 111 . Both the basic surface 111 and the skeletal surface 112 are portions that are recognized to have substantially no unevenness at the level applied when evaluating the degree of unevenness of the surface of an article mainly composed of this type of fiber.

The rectangular parallelepiped fiber mass 11A shown in FIG. 12(a) has six flat surfaces. Each of the four surfaces is the skeletal surface 112 . The basic plane 111 and the skeletal plane 112 intersect each other, more specifically, perpendicular to each other.
The disk-shaped fiber mass 11B shown in FIG. 12(b) has two opposing flat surfaces that are circular in plan view and a curved peripheral surface that connects the two flat surfaces. Each of the surfaces is the basic surface 111 and the peripheral surface is the skeletal surface 112 .
The fiber clumps 11A and 11B are also common in that the skeletal surface 112 has a quadrangular shape, more specifically a rectangular shape in plan view.

Examples of the form of the fiber clump 11 include sheet pieces obtained by dividing a synthetic fiber sheet having a certain size. That is, the sheet piece-like fiber mass, which is a preferred embodiment of the fiber mass 11, is not constructed to form the sheet piece by accumulating a plurality of fibers, but rather, the fiber mass is larger than the sheet piece. It is produced by cutting a sheet (see FIG. 13), and is a plurality of sheet piece-like fiber clumps with higher regularity than those produced by the above-described prior art.

The fiber clump 11, which is a "fixed-form fiber assembly" defined by two basic planes 111 and a skeletal plane 112 intersecting both basic planes 111, is produced by a method different from that of the prior art. This can be achieved by As described above, a preferred method for manufacturing the fiber mass 11 is, as shown in FIG. The cutting means is used to cut into a fixed shape. The plurality of fiber clumps 11 thus manufactured have more regular shapes and sizes than those manufactured by the above-described prior art. 13A and 13B are diagrams for explaining a method of manufacturing the cuboid fiber mass 11A shown in FIG. 12A, and dotted lines in FIG. 13 indicate cutting lines. The absorptive core 40 contains a plurality of fiber clumps 11 having uniform shape and size, which are obtained by cutting the fiber sheet into a regular shape.

As shown in FIG. 13, the cuboid-shaped fiber clump 11A of FIG. 12(a) has a raw material fiber sheet 10bs in a first direction D1 and a second direction intersecting (more specifically, perpendicular to) the first direction D1. It is manufactured by cutting D2 to a predetermined length. Both directions D1 and D2 are respectively predetermined one directions in the surface direction of the raw material fiber sheet 10bs, and the raw material fiber sheet 10bs is cut along the thickness direction Z perpendicular to the surface direction. In this way, the plurality of rectangular parallelepiped fiber clumps 11A obtained by cutting the raw fiber sheet 10bs into a so-called diced pattern usually come into contact with a cutting means such as a cutter when cutting the raw fiber sheet 10bs. The surface is the skeletal surface 112 and the non-cutting surface, that is, the surface that does not contact the cutting means, is the basic surface 111 . The basic surface 111 is the front and rear surfaces (surfaces orthogonal to the thickness direction Z) of the raw fiber sheet 10bs, and as described above, is the surface having the largest area among the plurality of surfaces of the fiber mass 11A.

The above description of the fiber mass 11A basically applies to the disk-shaped fiber mass 11B shown in FIG. 12(b). The only substantial difference from the fiber clump 11A is the cutting pattern of the raw fiber sheet 10bs. and cut the raw material fiber sheet 10bs into a circular shape.

In this way, the above-mentioned patent document describes that the plurality of fiber clumps 11 contained in the absorbent core 40 is a "fixed-shaped fiber assembly" defined by the basic surface 111 and the skeletal surface 112. Since the uniform dispersibility of the fiber lumps 11 in the absorbent core 40 is improved compared to the case of an amorphous fiber aggregate such as Therefore, the expected effects (improving effects such as the flexibility, cushioning properties, and compression recovery properties of the absorbent body) are exhibited more stably. In particular, in the case of a rectangular parallelepiped body portion 110 as shown in FIG. 12(a), the outer surface is composed of six surfaces, ie, two basic surfaces 111 and four skeletal surfaces 112. It becomes possible to have a relatively large number of contact opportunities with the fibers 12F, which increases the entanglement, which can lead to an improvement in shape retention and the like.

The raw fiber sheet 10bs used here is preferably a nonwoven fabric containing synthetic fibers from the viewpoint of further enhancing the cushioning properties, compression recovery properties, and shape retention properties of the absorbent core 40, and nonwoven fabrics having heat-sealed portions between synthetic fibers. is more preferred. Further, an air-through nonwoven fabric in which synthetic fibers have heat-sealed portions and a plurality of heat-sealed portions are dispersed three-dimensionally is particularly preferable.

Note that the outer shape of the body portion 110 is not limited to that shown in FIG. 12, and both the basic surface 111 and the skeletal surface 112 are flat surfaces that are not curved like the surfaces 111 and 112 in FIG. 12(a). Alternatively, it may be a curved surface like the skeletal surface 112 in FIG. 12(b). Further, the basic surface 111 and the skeletal surface 112 may have the same shape and the same size. Specifically, for example, the outer shape of the main body 110 may be a cubic shape.

Thus, the two types of surfaces (basic surface 111, skeleton surface 112) of the fiber mass 11 (11A, 11B) are formed by cutting the raw fiber sheet 10bs with a cutting means such as a cutter when manufacturing the fiber mass 11. It is classified into a cut surface (skeletal surface 112) to be formed and a non-cut surface (basic surface 111) which is a surface inherent to the sheet 10bs and does not come into contact with the cutting means. And, due to the difference between whether or not it is a cut surface, the skeletal surface 112, which is a cut surface, has more fiber ends per unit area than the basic surface 111, which is a non-cut surface. have The term “fiber ends” as used herein means ends in the longitudinal direction of the constituent fibers 11</b>F of the fiber mass 11 . Normally, fiber ends are also present on the basic surface 111 which is a non-cut surface, but the skeleton surface 112 is formed by cutting the raw fiber sheet 10bs because it is a cut surface formed by cutting. A large number of fiber ends, which are cut ends of the constituent fibers 11F, are present throughout the skeletal surface 112. In other words, the number of fiber ends per unit area is greater than that of the basic surface 111. .

Fiber ends present on each surface (basic surface 111, skeletal surface 112) of the fiber mass 11 are located between the fiber mass 11 and other fiber masses 11 contained in the absorbent core 40 and the absorbent fibers 12F. Useful for forming entanglements. In general, the greater the number of fiber ends per unit area, the better the entanglement, which can lead to the improvement of various properties of the absorbent core 40 such as shape retention. The number of fiber end portions per unit area on each surface of the fiber mass 11 is not uniform, and the number of such fiber end portions per unit area has a size relationship of “skeletal surface 112>basic surface 111”. Therefore, the entanglement with other fibers (other fiber lumps 11, water-absorbing fibers 12F) via the fiber lumps 11 differs depending on the surface of the fiber lumps 11, and the skeletal surface 112 is different from the basic surface 111. Highly confounding. That is, the binding force by entangling with other fibers via the skeletal surface 112 is stronger than that via the basal surface 111, and in one fiber mass 11, the basal surface 111 and the skeletal surface 112 may cause a difference in bonding strength with other fibers. In general, the stronger the binding force, the more restricted the freedom of movement of the bound fibers, and the strength (shape retention) of the absorbent core 40 as a whole improves, but the softness tends to decrease. .

In this way, each of the plurality of fiber clumps 11 contained in the absorbent core 40 exerts two types of bonding strength with respect to other surrounding fibers (other fiber clumps 11, water absorbent fibers 12F). The absorbent core 40 thus has both moderate softness and strength (shape retention). When the absorbent core 40 having such excellent properties is used as an absorbent body of an absorbent article according to a conventional method, it is possible to provide a comfortable wearing feeling to the wearer of the absorbent article. At the same time, the inconvenience of the absorbent core 40 being destroyed by an external force such as body pressure of the wearer when worn is effectively prevented.

On the other hand, the nonwoven fabric piece described in the above-mentioned patent document is manufactured by cutting the raw material fiber sheet into an irregular shape with a cutting machine such as a mill cutter, as described above. It is not a fixed sheet piece-like fiber clump with a "face" like 112, and moreover, the external force of the cutting process is applied to the entire fiber clump during its production, so the fiber ends of the constituent fibers are cut. It is randomly formed in the entire fiber mass, and the above-described effect due to the fiber ends is difficult to be sufficiently exhibited.

From the viewpoint of ensuring the effects of the fiber ends described above, the number N1 of fiber ends per unit area on the basic surface 111 (non-cut surface) and the number of fibers on the skeleton surface 112 (cut surface) Assuming that N1<N2, the ratio of N2 to the number of edges per unit area is preferably 0 or more, more preferably 0.05 or more, and more preferably 0.90 or less as N1/N2. is 0.60 or less. More specifically, N1/N2 is preferably 0 or more and 0.90 or less, more preferably 0.05 or more and 0.60 or more.
The number N1 of fiber ends per unit area of the basic surface 111 is preferably 0/mm ² or more, more preferably 3/mm ² or more, and preferably 8/mm ² or less, more preferably 6. pcs/mm ² or less.
The number N2 of fiber ends per unit area of the skeletal surface 112 is preferably 5/mm ² or more, more preferably 8/mm ² or more, and preferably 50/mm ² or less, more preferably 40. pcs/mm ² or less.
The number of fiber ends per unit area of the basic surface 111 and the skeletal surface 112 is measured by the following method.

<Method for measuring the number of fiber ends per unit area on each surface of the fiber mass>
A member (fiber mass) containing fibers to be measured is attached to a sample table using a double-sided paper tape (Nichiban Co., Ltd., Nicetac NW-15). The measuring piece is then platinum coated. An ion sputtering apparatus E-1030 (trade name) manufactured by Hitachi Naka Seiki Co., Ltd. is used for coating, and the sputtering time is 120 seconds. Using a JCM-6000 type electron microscope manufactured by JEOL Co., Ltd., the basal plane and skeletal plane of the cut surface of the measurement piece are observed at a magnification of 100 times. In this observation screen with a magnification of 100 times, a rectangular area of 1.2 mm in length and 0.6 mm in width is set at an arbitrary position on the surface to be measured (basic surface or skeletal surface), and the area of the rectangular area is After adjusting the observation angle and the like so that 90% or more of the area of the observation screen is occupied, the number of fiber ends included in the rectangular area is measured. However, in the observation screen with a magnification of 100 times, when the measurement target surface of the fiber mass is smaller than 1.2 mm × 0.6 mm and the ratio of the area of the rectangular region to the entire observation screen is less than 90% After increasing the observation magnification to 100 times or more, the number of fiber ends included in the rectangular area on the measurement target surface is measured in the same manner as described above. Here, the "fiber ends" to be measured are the ends in the length direction of the constituent fibers of the fiber mass, and the portions other than the ends in the length direction of the constituent fibers from the surface to be measured (middle in the length direction) part) is extended, the intermediate part in the length direction shall not be counted. Then, the number of fiber ends per unit area on the measurement target surface (basic surface or skeletal surface) of the fiber clump is calculated by the following formula. For each of the 10 fiber clumps, according to the above procedure, measure the number of fiber ends per unit area on each of the basic plane and the skeletal plane, and take the average value of these multiple measured values as the fiber end on the measurement target plane. number per unit area.
The number of fiber ends per unit area (number/mm ² ) on the measurement target surface (basic surface or skeletal surface) of the fiber mass = the number of fiber ends included in the rectangular area (1.2 × 0.6 mm)/ Area of said rectangular region (0.72 mm ² )

When the basic surface 111 of the fiber clump 11 has a rectangular shape in plan view like the fiber clump 11A shown in FIG. Therefore, the short side 111a of the rectangular shape is preferably equal to or shorter than the thickness of the absorbent body 4 containing the fiber lumps 11 (11A).
The ratio of the length of the short side 111a to the thickness of the absorbent body 4 is preferably 0.03 or more, more preferably 0.08 or more, and preferably 1 or less, more preferably 0.5 or less as the former/latter. is.
The thickness of the absorbent body 4 (absorbent core 40) is preferably 1 mm or more, more preferably 2 mm or more, and preferably 10 mm or less, more preferably 6 mm or less.

It is preferable to set the dimensions of each part of the fiber mass 11 (11A, 11B) as follows. The dimensions of each part of the fiber mass 11 can be measured based on an electron micrograph or the like during the later-described operation of specifying the outer shape of the fiber mass 11 .
When the basic surface 111 has a rectangular shape in plan view as shown in FIG. 12(a), the length L1 of the short side 111a is preferably 0.1 mm or more, more preferably 0.3 mm or more, and still more preferably 0.5 mm. and preferably 10 mm or less, more preferably 6 mm or less, and even more preferably 5 mm or less.
The length L2 of the long side 111b of the basic surface 111 having a rectangular shape in plan view is preferably 0.3 mm or more, more preferably 1 mm or more, still more preferably 2 mm or more, and preferably 30 mm or less, more preferably 15 mm or less, More preferably, it is 10 mm or less.
12, when the basic surface 111 is the surface having the largest area among the plurality of surfaces of the fiber mass 11, the length L2 of the long side 111b is the maximum span length of the fiber mass 11. , and the maximum span length matches the diameter of the circular basic surface 111 in the disk-shaped fiber mass 11B in plan view.
The ratio of the length L1 of the short side 111a to the length L2 of the long side 111b is, as L1/L2, preferably 0.003 or more, more preferably 0.025 or more, and preferably 1 or less, more preferably 0.5 or less. In the present invention, the planar shape of the basic surface 111 is not limited to a rectangular shape as shown in FIG. 8A, but may be a square shape. , L1/L2 may be 1.
The thickness T of the fiber mass 11, that is, the length T between the two opposing basic surfaces 111 is preferably 0.1 mm or more, more preferably 0.3 mm or more, and preferably 10 mm or less, more preferably 6 mm or less. be.

FIG. 14(a) shows an electron micrograph of one embodiment of the fiber clump 11, and FIG. 14(b) shows a diagram schematically showing the fiber clump 11 based on this electron micrograph. there is As shown in FIG. 14, the fiber mass 11 includes a main body portion 110 and fibers 11F extending outward from the main body portion 110, and has a lower fiber density (per unit area) than the main body portion 110. (lower number of fibers per fiber), and those with extended fiber portions 113 may be included. Note that the absorbent core 40 may also include fiber clumps 11 that do not have extended fiber portions 113 , that is, fiber clumps 11 that are composed only of main body portions 110 . The extended fiber portion 113 can include one type of fiber end portion present on each surface (the basic surface 111 and the skeletal surface 112) of the fiber mass 11 described above, and it is one of the fiber ends. Extending outwardly from each face of mass 11 are fiber ends.

The main body portion 110 is defined by the above-described two opposing basic surfaces 111 and a skeleton surface 112 connecting the two basic surfaces 111 . The body portion 110 is the main body of the fiber mass 11 and is a portion that forms the fixed outer shape of the fiber mass 11. Various properties of the fiber mass 11 such as high flexibility, cushioning properties, and compression recovery are basically This is largely due to the main body portion 110 . On the other hand, the extended fiber portion 113 mainly contributes to improving the entanglement between the plurality of fiber lumps 11 contained in the absorbent core 40 or between the fiber lumps 11 and the water absorbent fibers 12F, thereby preserving the absorbent core 40. In addition to directly improving the formability, it also influences the uniform distribution of the fiber lumps 11 in the absorbent core 40 and indirectly reinforces the effects of the main body 110 .

The main body portion 110 has a higher fiber density than the extended fiber portion 113, that is, the number of fibers per unit area is large. Moreover, the fiber density of the main body portion 110 itself is generally uniform. The ratio of the main body 110 to the total mass of the fiber mass 11 is usually at least 40% by mass, preferably 50% by mass or more, more preferably 60% by mass or more, and still more preferably 85% by mass or more. The main body portion 110 and the extended fiber portion 113 can be distinguished from each other by specifying the outer shape, which will be described later.

The task of specifying the outer shape of the main body portion 110 of the fiber mass 11 contained in the absorbent core 40 is the difference in fiber density between the fiber mass 11 and its peripheral portion (the number of fibers per unit area) and the fiber density. This can be done by checking the "boundary" between the main body part 110 and other parts, paying attention to the difference in the type and fiber diameter of the fiber. The main body portion 110 has a higher fiber density than the extending fiber portion 113 existing around it, and normally, the synthetic fibers (typically thermoplastic fibers) constituting the main body portion 110 are water absorbent fibers 12F (typically Since it is qualitatively and/or dimensionally different from cellulosic fibers), even in the absorbent body 4 in which a large number of fiber lumps 11 and water-absorbent fibers 12F are mixed, by paying attention to the above points, the above-mentioned Boundaries can be easily identified. The boundary thus confirmed is the peripheral edge (side) of the basic surface 111 or the skeletal surface 112, and the basic surface 111 and the skeletal surface 112 are identified by such boundary confirmation work, and the main body 110 is identified. be done. Such boundary confirmation work can be performed by observing the object (absorbent body 4) at a plurality of observation angles as necessary using an electron microscope.

As shown in FIG. 14 , at least one extending fiber portion 113 exists around the main body portion 110 and extends outward from at least one of the basic surface 111 and the skeletal surface 112 that are the outer surfaces of the main body portion 110 . It consists of the constituent fibers 11F of the main body portion 110 extending to the . In the fiber mass 11 shown in FIG. 10, the plurality of constituent fibers 11F protrude outward from the four sides 112a and 112b of the skeleton surface 112 which is rectangular in plan view. All of the portions are extending fiber portions 113 .

The shape of the extending fiber portion 113 is not particularly limited. The extending fiber portion 113 may be composed of one fiber 11F, or may be composed of a plurality of fibers 11F like an extending fiber bundle portion 113S described later. In addition, the extended fiber portion 113 typically includes longitudinal ends of the fibers 11F extending from the main body portion 110. In addition to or instead of such fiber ends, In some cases, the fibers F may include portions other than both ends in the longitudinal direction (intermediate portions in the longitudinal direction). That is, in the fiber mass 11, both ends in the length direction of the constituent fibers 11F are present in the main body portion 110, and the other portion, that is, the middle portion in the length direction, extends outward from the main body portion 110 in a loop shape ( In such a case, the extending fiber portion 113 is configured to include a loop-like protrusion of the fiber 11F. In other words, among the extending fiber portions 113, those whose ends are exposed are one type of fiber ends.

One of the main roles of the extended fiber portion 113 is, as described above, to entangle the plurality of fiber lumps 11 contained in the absorbent body 4 or the fiber lumps 11 and the absorbent fibers 12F. In general, the extension length of the extended fiber portion 113 from the main body portion 110 is increased, the thickness of the extended fiber portion 113 is increased, or the number of extended fiber portions 113 included in one fiber mass 11 is increased. increases, the connection between the objects entangled via the extended fiber portion 113 becomes stronger and the entanglement becomes difficult to be released. Become.

When the fiber clump 11 is obtained by cutting the raw fiber sheet 10bs into a regular shape as shown in FIG. On the other hand, the basic plane 111 which is a non-cutting plane does not exist at all, or even if it exists, the number thereof is less than that of the skeletal plane 112 . The reason why the extended fiber portions 113 are unevenly distributed on the skeletal surface 112, which is the cut surface, is that most of the extended fiber portions 113 are "fluff" generated by cutting the raw material fiber sheet. That is, since the skeletal surface 112 formed by cutting the raw fiber sheet 10bs is entirely scraped by a cutting means such as a cutter at the time of cutting, fluff composed of the constituent fibers 11F of the sheet 10bs is likely to be formed. easy. On the other hand, the basic surface 111, which is a non-cut surface, does not have friction with such a cutting means, so fluff, that is, the extended fiber portion 113 is less likely to be formed.

Intervals L1a (intervals in the first direction D1, see FIG. 13) and intervals L2a (intervals in the second direction D2, see FIG. 13) of the cutting lines when cutting the raw fiber sheet 10bs correspond to the formation of the extending fiber portions 113 described above. From the viewpoint of acceleration, etc., and from the viewpoint of ensuring the dimensions necessary for the fiber mass 11 to exhibit a predetermined effect, it is preferably 0.3 mm or more, more preferably 0.5 mm or more, and preferably 30 mm or less. More preferably, it is 15 mm or less.

As shown in FIG. 14, the fiber mass 11 includes, as a kind of the extended fiber portion 113, the main body portion 110, more specifically, the extended fiber bundle portion 113S including a plurality of fibers 11F extending outward from the skeletal surface 112. can be included. At least one of the extended fiber portions 113 included in the fiber clump 11 may be the extended fiber bundle portion 113S. The extending fiber bundle portion 113S is configured by gathering a plurality of fibers 11F extending from the skeletal surface 112, and compared to the extending fiber portion 113, the extension length of the main body portion 110 from the skeletal surface 112 is large. characterized by a long point. Although the extending fiber bundle portion 113S may exist on the basic surface 111, it is typically present on the skeleton surface 112 as shown in FIG. The number is less than the skeletal surface 112 . The reason for this is the same as the reason that the extending fiber portions 113 are mainly present on the skeletal surface 112, which is the cut surface, as described above.

Since the fiber clump 11 has such extended fiber bundle portions 113S, which can be called long and thick large-sized extended fiber portions 113, the fiber clumps 11 and the absorbent fibers 12F can be separated from each other. The entanglement is further strengthened, and as a result, the predetermined effects of the present invention due to the presence of the fiber clumps 11 are exhibited more stably. The extending fiber bundle portion 113S is easily formed by cutting the raw material fiber sheet 10bs under the above-described condition where the raw fiber sheet 10bs is prone to fluffing (see FIG. 13).

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

The plurality of constituent fibers 11F of the extending fiber bundle portion 113S are preferably heat-sealed to each other. The heat-sealed portion of the extending fiber bundle portion 113S is generally more elongated in the length direction of the extending fiber bundle portion 113S than other portions (non-heat-sealed portions) of the extending fiber bundle portion 113S. The crossing length in the direction orthogonal to the . Since the extending fiber bundle portion 113S has such a heat-sealed portion, which can be said to be a large diameter portion, the strength of the extending fiber bundle portion 113S itself is increased, thereby allowing the extending fiber bundle portion 113S to pass through the extending fiber bundle portion 113S. The entanglement between the entangled fiber lumps 11 or between the fiber lumps 11 and the absorbent fibers 12F is further strengthened. Further, when the extending fiber bundle portion 113S has a heat-sealed portion, not only when the extending fiber bundle portion 113S is in a dry state but also when it is in a wet state by absorbing moisture, There is an advantage that the strength, shape retention, etc. of the extending fiber bundle portion 113S itself are enhanced. Due to such advantages, when the absorbent core 40 is applied to an absorbent article, not only when the absorbent core 40 is in a dry state, but also body fluids such as urine and menstrual blood excreted by the wearer can be absorbed. Even when the fiber mass 11 is absorbed and becomes wet, the effect due to the presence of the fiber clumps 11 described above can be stably exhibited. Such an extended fiber bundle portion 113S having a heat-sealed portion is used as the raw fiber sheet 10bs in the manufacturing process of the fiber lump 11 as shown in FIG. It can be produced by using the above-mentioned "nonwoven fabric having heat-sealed portions of synthetic fibers".

As the constituent fibers 11F of the fiber mass 11, synthetic fibers are used. In addition, from the viewpoint that the absorber 4 can exhibit excellent effects in shape retention, flexibility, cushioning, compression recovery, resistance to twisting, etc. in both dry and wet conditions, the fiber mass 11 preferably has a three-dimensional structure in which a plurality of thermoplastic fibers are heat-sealed to each other. Further, in order to obtain such a fiber mass 11 in which a plurality of heat-sealed portions are three-dimensionally dispersed, the constituent fibers 11F of the fiber mass 11 are preferably synthetic fibers having heat-sealability. Thermoplastic fibers can be exemplified as such heat-fusible synthetic fibers, and non-water-absorbent thermoplastic fibers are particularly preferred. As described above, it is preferable that the extended fiber bundle portion 113S has a heat-sealed portion. It is also possible to obtain the preferred form of In order to obtain the fiber clump 11 in which a plurality of heat-sealed portions are three-dimensionally dispersed, the raw fiber sheet 10bs (see FIG. 13) should be similarly configured. The raw fiber sheet 10bs in which the fused portions are three-dimensionally dispersed can be produced by subjecting a web or nonwoven fabric mainly composed of thermoplastic fibers to heat treatment such as hot air treatment, as described above.

Examples of non-water-absorbing thermoplastic resins suitable as materials 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; Examples include polymethacrylic acid alkyl esters, polyvinyl chloride, polyvinylidene chloride, and the like, and these can be used alone or in combination of two or more. The fiber 11F may be a single fiber made of one kind of synthetic resin (thermoplastic resin) or a blend polymer obtained by mixing two or more kinds of synthetic resins, or may be a composite fiber. The composite fiber referred to here is a synthetic fiber (thermoplastic fiber) obtained by combining two or more types of synthetic resins with different components with a spinneret and simultaneously spinning them, and multiple components are continuous in the length direction of the fiber. It is a structure that is bonded to each other within a single fiber. The form of the composite fiber includes core-sheath type, side-by-side type, etc., and is not particularly limited.

In addition, when the absorbent body (absorbent core) to be measured is used as a constituent member of other articles such as absorbent articles, and the absorbent body is taken out and evaluated and measured, the absorbent body is used as an adhesive, If the fiber is fixed to another component by fusion bonding or the like, the adhesive strength of the fixed portion is removed by a method such as blowing cold air from a cold spray to the extent that the contact angle of the fiber is not affected. take out from This procedure is common to all measurements in this specification.

In addition, it is preferable that the constituent fibers 11F constituting the fiber mass 11 have a property of being non-absorbent, ie, having a property of hardly absorbing water (bodily fluids such as urine and menstrual blood). This is in stark contrast to the fact that the absorbent fibers 12F used in combination with the fiber mass 11 are literally absorbent. Since the fibers 11F are non-absorbent fibers with poor water absorbency, the presence of the above-described fiber lumps 11 is suppressed not only when the absorbent core 40 is in a dry state, but also when it is in a wet state after absorbing body fluids. Resulting effects (improvements in shape retention, flexibility, cushioning, compression recovery, resistance to twisting, etc.) are stably exhibited. Therefore, the raw material fibers are preferably non-water-absorbing synthetic fibers.

As used herein, the term "water absorbent" can be easily understood by those skilled in the art, for example, pulp is water absorbent. Likewise, it can be readily appreciated that thermoplastic fibers are non-absorbent. On the other hand, regarding the degree of water absorbency of fibers, relative differences in water absorbency can be compared and a more preferable range can be defined by the value of moisture content measured by the method described below. The moisture content of the absorbent fibers is preferably 6% or more, more preferably 10% or more. Non-absorbent fibers, on the other hand, preferably have such a moisture content of less than 6%, more preferably less than 4%.

<Method for measuring moisture content>
The moisture content was calculated according to the moisture content test method of JIS P8203. That is, after the fiber sample was allowed to stand in a test room at a temperature of 40° C. and a relative humidity of 80% RH for 24 hours, the weight W (g) of the fiber sample before absolutely dry treatment was measured in the room. After that, the fiber sample was completely dried by allowing it to stand for 1 hour in an electric dryer (manufactured by Isuzu Manufacturing Co., Ltd.) at a temperature of 105±2°C. After the absolute dry treatment, in a standard test room at a temperature of 20 ± 2 ° C. and a relative temperature of 65 ± 2%, Si silica gel (for example, (Toyota Kako Co., Ltd.) is placed in a glass desiccator (for example, manufactured by TechJam Co., Ltd.) and allowed to stand until the temperature of the fiber sample reaches 20±2°C. After that, the constant weight W' (g) of the fiber sample is weighed, and the moisture content of the fiber sample is obtained by the following formula. Moisture content (%) = (WW'/W') x 100

As the water-absorbing fibers 12F, water-absorbing fibers conventionally used as materials for forming the absorbent body of this type of absorbent article can be used. natural fibers such as non-wood pulp such as pulp; modified pulp such as cationized pulp and mercerized pulp; Considering that the main role of the water absorbent fibers 12F is to improve the liquid absorbency of the absorbent body 4, cellulosic fibers are particularly preferable as the water absorbent fibers 12F.

Although the present invention has been described based on the embodiments, the present invention is not limited to the above embodiments and can be modified as appropriate.
For example, in the napkin 1 shown in FIG. 1, the surface vertical recessed portion 7X and the surface horizontal recessed portion 7Y that constitute the surface recessed portion 7 are connected at their longitudinal ends, and the surface recessed portion 7 is closed as a whole. However, the recessed portions forming the surface recessed portion 7 may not be connected to each other, and the surface vertical recessed portion 7X and the surface lateral recessed portion 7Y are arranged close to each other with a gap therebetween. may The same applies to the back recessed portion 8 overlapping the front recessed portion 7 in a plan view.
The absorbent article of the present invention broadly includes articles used for absorbing bodily fluids (urine, loose stool, menstrual blood, sweat, etc.) discharged from the human body. So-called unfolded disposable diapers with tapes, underpants-type disposable diapers, incontinence pads and the like are included.

1 sanitary napkin (absorbent article)
F Front region M Vertical central region R Rear region 2, 2A Top sheet 21 Protruding part 22 Recessed part 3 Back sheet 4, 4A, 4B, 4C, 4D, 4E, 4F Absorbent body 40 Absorbent core 41 Core wrap sheet 42 Grooved recessed part 42X Vertical recess 42Y Horizontal recess 43 Small absorbent part 44 Continuous layer 45 Skin-facing surface of absorbent body or absorbent core 46 Non-skin-facing surface of absorbent body or absorbent core 5 Absorbent body 6 Side sheet 7, 7X, 7Y Surface depressions Part 8, 8X, 8Y Back concave part 9 Low density part 11 Fiber mass 11F Constituent fiber (synthetic fiber) of fiber mass
REFERENCE SIGNS LIST 110 body portion 111 basic surface 112 skeletal surface 113 extended fiber portion 113S extended fiber bundle portion 12F water absorbent fiber 13 water absorbent polymer

Claims (10)

It has a vertical direction corresponding to the front-rear direction of the user and a horizontal direction orthogonal thereto, and with respect to the vertical direction, a longitudinal central region arranged opposite to the excretory part of the user, and a longitudinal direction greater than the longitudinal central region. An absorbent article comprising an absorbent core that has a front region arranged on the front side and a rear region arranged on the rear side in the longitudinal direction from the longitudinal central region, and that absorbs and retains body fluids,
The absorbent core is formed with a groove-shaped recess having an opening in at least one of the skin-facing surface and the non-skin-facing surface of the absorbent core and extending in a predetermined direction. The portion that overlaps with the groove-shaped recess in plan view has a lower basis weight than its surroundings,
The absorbent core contains a fiber mass containing synthetic fibers and water absorbent fibers ,
An absorbent article, wherein at least in the longitudinal central region, the non-skin-facing surface side of the absorbent core has a greater mass per unit area of the fiber mass than the skin-facing surface side of the absorbent core. 2. Even in the front region and the rear region, the non-skin-facing surface side of the absorbent core has a larger mass per unit area of the fiber mass than the skin-facing surface side of the absorbent core . Absorbent article according to. It has a vertical direction corresponding to the front-rear direction of the user and a horizontal direction orthogonal thereto, and with respect to the vertical direction, a longitudinal central region arranged opposite to the excretory part of the user, and a longitudinal direction greater than the longitudinal central region. An absorbent article comprising an absorbent core that has a front region arranged on the front side and a rear region arranged on the rear side in the longitudinal direction from the longitudinal central region, and that absorbs and retains body fluids,
The absorbent core is formed with a groove-shaped recess having an opening in at least one of the skin-facing surface and the non-skin-facing surface of the absorbent core and extending in a predetermined direction. The portion that overlaps with the groove-shaped recess in plan view has a lower basis weight than its surroundings,
The absorbent core contains a fiber mass containing synthetic fibers and water absorbent fibers ,
In the absorbent core, the longitudinal central region has a larger mass per unit area of the fiber mass than the front region and the rear region. The absorbent article according to any one of claims 1 to 3 , wherein the absorbent core contains, in the longitudinal central region, 90% by mass or more of all the fiber lumps contained in the absorbent core. It has a vertical direction corresponding to the front-rear direction of the user and a horizontal direction orthogonal thereto, and with respect to the vertical direction, a longitudinal central region arranged opposite to the excretory part of the user, and a longitudinal direction greater than the longitudinal central region. An absorbent article comprising an absorbent core that has a front region arranged on the front side and a rear region arranged on the rear side in the longitudinal direction from the longitudinal central region, and that absorbs and retains body fluids,
The absorbent core is formed with a groove-shaped recess having an opening in at least one of the skin-facing surface and the non-skin-facing surface of the absorbent core and extending in a predetermined direction. The portion that overlaps with the groove-shaped recess in plan view has a lower basis weight than its surroundings,
The absorbent core contains a fiber mass containing synthetic fibers and water absorbent fibers ,
A topsheet is provided on the skin-facing side of the absorbent core, and the surface recessed portion in which the topsheet and the absorbent core are integrally recessed on the non-skin-facing side of the absorbent core is at least the Formed in the longitudinal central region,
In the longitudinal central region, the mass per unit area of the fiber mass differs between the skin-facing surface side and the non-skin-facing surface side of the absorbent core,
The surface recessed portion overlaps the fiber mass in plan view, and in the longitudinal central region, the mass per unit area of the fiber mass is different from the skin facing side of the absorbent core. absorbent article. The surface recess extends longitudinally through both lateral sides of the longitudinal central region,
In the longitudinal central region, the surface recessed portions on both sides in the lateral direction and the regions sandwiched therebetween have a higher density per unit area of the fiber mass than the surface recessed portions on the lateral sides in the lateral direction outside the surface recessed portions on the lateral sides. 6. The absorbent article of claim 5 , having a high mass. The absorbent core has a continuous layer in which the groove-shaped concave portion is not formed over the entire surface direction of the absorbent core in a part of the absorbent core in the thickness direction, and the continuous layer includes the fibers Absorbent article according to any one of the preceding claims, wherein a mass and said absorbent fibers are present. The continuous layer is unevenly distributed on the skin-facing surface side or the non-skin-facing surface side of the absorbent core, and the depth of the groove-shaped concave portion is 40% or more and 98% or less of the thickness of the absorbent core. Item 8. The absorbent article according to item 7 . The fiber mass has two opposing basic surfaces and a skeletal surface connecting the two basic surfaces,
The absorbent according to any one of claims 1 to 8 , wherein the number of fiber ends per unit area present on each of the basic surface and the skeletal surface is larger in the skeletal surface than in the basic surface. Goods. The groove-shaped recess has a vertical recess extending in the vertical direction and a horizontal recess extending in a direction intersecting the vertical recess,
The absorbent according to any one of claims 1 to 9 , wherein the side of the absorbent core on which the openings of the vertical recesses and the openings of the lateral recesses are formed is divided into a plurality of small absorbent portions. sexual goods.

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