Absorbed products

Abstract

DEPCT64 The absorbent product (1) of this invention includes the absorbent assembly (4) and the top plate (2). Provided on the skin-facing side of the absorbent component (4). The absorbent component (4) includes: The liquid-absorbing core (40) and core wrap sheet (41) are stacked on top of the skin-facing surfaces of Absorption core (40) The absorption core (40) includes water-absorbing fibers (12F) and a group of fibers (11) which have Low water absorption fibers (11F) which have a lower water absorption capacity than the water absorption capacity of water-absorbing fibers. (12F) Ratio of the fluid diffusion area of ​​the absorption axis (40) to the fluid diffusion area. Core wrapping plate (41), fluid diffusion area of ​​the core absorption / fluid diffusion area of The core wrapping sheet is 0.7 or more. -----------------------------------------------------------

Description

absorbent articles

[0001] The present invention relates to absorbent articles such as sanitary napkins.

[0002] Absorbent articles such as disposable diapers and sanitary napkins generally comprise a topsheet positioned relatively close to the wearer's skin, a backsheet positioned relatively far from the wearer's skin, and an absorbent body interposed between the two sheets. This absorbent body typically comprises an absorbent core that forms the main body of the absorbent body, and a core wrap sheet that covers the surface of the absorbent core. The absorbent core is often composed primarily of absorbent fibers such as wood pulp, and further contains absorbent polymer particles. For absorbent bodies used in absorbent articles, improving various properties such as flexibility (cushioning), compression recovery, and shape retention is a major challenge.

[0003] As an improved technology for absorbents, for example, Patent Document 1 describes an absorbent body containing thermoplastic resin fibers and cellulose-based water-absorbent fibers, in which the thermoplastic resin fibers are exposed on both the surface of the absorbent body facing the top sheet and the surface of the absorbent body facing the back sheet. 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 the cellulose-based water-absorbent fibers, and therefore the absorbent body is soft and resistant to twisting.

[0004] Patent Document 2 also describes an absorbent body containing absorbent fibers and nonwoven fabric pieces that contain heat-sealed fibers and have been previously bonded to form a three-dimensional structure. These three-dimensional nonwoven fabric pieces are produced by pulverizing nonwoven fabric into small pieces using a pulverizing means such as a cutter mill. Due to this manufacturing method, the nonwoven fabric pieces have an irregular shape, as shown in Figures 1 and 3 of the same document, and do not substantially have any areas that can be considered flat. Patent Document 2 also describes a preferred form of the absorbent body described therein, in which the nonwoven fabric pieces are heat-sealed together. According to the absorbent body described in Patent Document 2, the three-dimensional structure of the nonwoven fabric pieces results in the formation of voids within the absorbent body, improving recovery upon absorbing moisture and, as a result, improving water absorption performance.

[0005] Patent Document 3 describes a fine web having a relatively dense fine fiber core and fibers or fiber bundles extending outward from the core, and also describes that a nonwoven web obtained by mixing the fine web with wood pulp or water-absorbent polymer particles can be used as an absorbent body for absorbent articles. This fine web is produced by tearing or tearing off a raw material sheet such as a nonwoven fabric, and like the nonwoven fabric piece described in Patent Document 2, it has an irregular shape and does not substantially have any parts that can be considered flat.

[0006] Furthermore, Patent Document 4 describes a problem that when an absorbent body contains a water-absorbent polymer, when the absorbent body absorbs liquid and expands, the swelling of the water-absorbent polymer is prevented by the sealing of the top sheet and back sheet arranged above and below the absorbent body, by interposing a cushion layer having high compression / compression recovery properties and liquid permeability between the top sheet and the absorbent body, and also describes that this cushion layer is formed as an assembly of small pieces of nonwoven fabric and that the thickness of the cushion layer is 10 to 40 mm. Patent Document 4 does not specifically describe the shape of the small pieces of nonwoven fabric used in the cushion layer, etc.

[0007] JP 2015-16296 A JP 2002-301105 A JP 1-156560 A JP 2003-52750 A

[0008] The present invention relates to an absorbent article having a longitudinal direction corresponding to the front-to-back direction of a wearer and a lateral direction perpendicular thereto, the absorbent article comprising an absorbent body and a topsheet disposed on the skin-facing side of the absorbent body. The absorbent body is configured to include a liquid-absorbent core and a core wrap sheet covering the skin-facing side of the absorbent core, the absorbent core including a fiber mass containing absorbent fibers and weakly absorbent fibers having lower absorbency than the absorbent fibers. The ratio of the liquid diffusion area of ​​the absorbent core measured by the following method to the liquid diffusion area of ​​the core wrap sheet measured by the following method, expressed as the former / the latter, is 0.7 or more.

[0009] <Method for measuring liquid diffusion area> The measurement object is fixed on an inclined surface at a 45° angle to the horizontal plane, with its skin-facing surface facing the inclined surface, and 1.5 g of defiberized horse blood is injected onto the skin-facing surface of the measurement object over 23 seconds. After leaving it for 3 minutes, the same amount of defiberized horse blood is again injected into the same injection site over the same time period. This injection and leaving procedure of defiberized horse blood is repeated six times, until a total of 9 g of defiberized horse blood is injected into the measurement object. After the injection procedure is complete, the diffusion area of ​​the defiberized horse blood on the skin-facing surface of the measurement object is measured, and this is taken as the liquid diffusion area of ​​the measurement object.

[0010] FIG. 1 is a partially cutaway plan view schematically showing the skin-facing side (topsheet side) of an example of a sanitary napkin, which is one embodiment of the absorbent article of the present invention. FIG. 2 is a cross-sectional view schematically showing a cross section taken along line II of FIG. 1. FIG. 3 is a schematic perspective view of a portion of an absorbent core provided in the absorbent article shown in FIG. 1. FIG. 4 is a diagram schematically showing the deformation state of the absorbent core shown in FIG. 3 upon compression. FIG. 5(a) is an electron microscope photograph (observation magnification: 25x) of an example of a fiber agglomerate according to the present invention, and FIG. 5(b) is a diagram schematically showing the fiber agglomerate in the electron microscope photograph as a fiber agglomerate contained in the absorbent body shown in FIG. 2. FIG. 6 is an explanatory diagram of a method for producing a fiber agglomerate according to the present invention. FIGS. 7(a) and 7(b) are schematic perspective views of the main body portion of a fiber agglomerate according to the present invention. FIG. 8 is an explanatory diagram of a method for measuring the liquid diffusion area. Detailed Description of the Invention

[0011] The absorbent described in Patent Document 1 contains synthetic fibers (thermoplastic resin fibers) in addition to cellulosic water-absorbent fibers, and therefore has higher rigidity than absorbents containing only cellulosic water-absorbent fibers as constituent fibers. As a result, improvements in various properties such as cushioning and compression recovery can be expected. However, because the multiple synthetic fibers contained therein exist independently and do not form a single cohesive mass, the effect of improving these various properties is not sufficient. Therefore, when applied to absorbent articles, there is a risk that the article will be prone to twisting and will not fit well. Such inconveniences are particularly noticeable after absorbing body fluids such as urine and menstrual blood.

[0012] On the other hand, the absorbents described in Patent Documents 2 to 4 all contain synthetic fibers that are synthetic fiber aggregates called nonwoven fabric pieces or fine webs, and are therefore expected to provide improved cushioning. However, according to the inventor's findings, when a large number of such weakly absorbent synthetic fiber aggregates are contained in the absorbent, the liquid permeability of the absorbent decreases, and as a result, bodily fluids that pass through the topsheet and reach the skin-facing surface (core wrap sheet) of the absorbent are less likely to be drawn into the absorbent (absorbent core), resulting in a large amount of bodily fluid remaining on the skin-facing surface of the absorbent, causing an uncomfortable stickiness or wet feeling on the skin. Patent Documents 2 to 4 do not describe the problems with absorbents caused by weakly absorbent synthetic fiber aggregates, and no technology has yet been provided that solves these problems while utilizing the advantages of synthetic fiber aggregates.

[0013] Therefore, the present invention relates to an absorbent article having an absorbent body with high liquid permeability to an absorbent core and excellent cushioning properties.

[0014] The present invention will now be described based on preferred embodiments with reference to the drawings. Figures 1 and 2 show a sanitary napkin 1, one embodiment of an absorbent article of the present invention. The napkin 1 comprises an absorbent core 4 for absorbing and retaining bodily fluids, a liquid-permeable topsheet 2 disposed on the skin-facing side of the absorbent core 4 and capable of contacting the wearer's skin, and a liquid-impermeable backsheet 3 disposed on the non-skin-facing side of the absorbent core 4. As shown in Figure 1, the napkin 1 has a longitudinal direction X, which corresponds to the front-to-rear direction of the wearer and extends from the wearer's ventral side through the crotch region to the dorsal side, and a transverse direction Y perpendicular thereto. The napkin 1 is divided into three regions in the longitudinal direction X: a longitudinal central region B including an excretory-part-facing region (excretory point) facing the wearer's excretory parts, such as the vaginal opening; a front region A disposed closer to the wearer's ventral side (front side) than the excretory-part-facing region; and a rear region C disposed closer to the wearer's dorsal side (rear side) than the excretory-part-facing region.

[0015] In this specification, the "skin-facing side" refers to the side of the absorbent article or its constituent member (e.g., the absorbent core 4) that faces the skin of the wearer when the absorbent article is worn, i.e., the side that is relatively close to the wearer's skin, and the "non-skin-facing side" refers to the side of the absorbent article or its constituent member that faces the opposite side to the skin side when the absorbent article is worn, i.e., the side that is relatively far from the wearer's skin. Note that "when worn" here refers to the normal, appropriate wearing position, i.e., a state in which the correct wearing position of the absorbent article is maintained.

[0016] 1, the napkin 1 has an absorbent main body 5 elongated in the longitudinal direction X, and a pair of wing portions 5W, 5W extending outward in the transverse direction Y from both side portions of the longitudinal central region B of the absorbent main body 5 along the longitudinal direction X. The absorbent main body 5 is the main part of the napkin 1, and comprises the topsheet 2, backsheet 3, and absorbent body 4, and is divided into three regions in the longitudinal direction X: a front region A, a longitudinal central region B, and a rear region C.

[0017] In the absorbent article of the present invention, when the absorbent article has wing portions like napkin 1, the vertical central region means the region having the wing portions in the vertical direction (longitudinal direction, X direction in the figure) of the absorbent article, and in the case of napkin 1 as an example, it is the region sandwiched between the base of one wing portion 5W along the vertical direction X and the base of the other wing portion 5W along the vertical direction X. In addition, in an absorbent article without wing portions, the vertical central region means the region located in the middle when the absorbent article is divided into three equal parts in the vertical direction.

[0018] The absorbent body 4 is configured to include a liquid-absorbent absorbent core 40 and a liquid-permeable core wrap sheet 41 that covers at least the skin-facing surface of the absorbent core 40. Like the absorbent main body 5, the absorbent core 40 has a shape that is elongated in the vertical direction X in a plan view as shown in Fig. 1, with the longitudinal direction of the absorbent core 40 coinciding with the vertical direction X of the napkin 1 and the width direction of the absorbent core 40 coinciding with the horizontal direction Y of the napkin 1. The absorbent core 40 and the core wrap sheet 41 may be joined together with an adhesive such as a hot-melt adhesive.

[0019] In the napkin 1, the core wrap sheet 41 is a single continuous sheet having a width that is two to three times the length in the transverse direction Y of the absorbent core 40, and as shown in Figure 2, it covers the entire skin-facing surface of the absorbent core 40 and extends outward in the transverse direction Y from both side edges of the absorbent core 40 along the longitudinal direction X, with these extending portions being folded down below the absorbent core 40 to cover the entire non-skin-facing surface of the absorbent core 40. In the present invention, the core wrap sheet does not have to be such a single sheet, and may be composed of two sheets, for example, one skin-side core wrap sheet that covers the skin-facing surface of the absorbent core 40 and one non-skin-side core wrap sheet that is separate from the skin-side core wrap sheet and covers the non-skin-facing surface of the absorbent core 40.

[0020] As shown in FIG. 2 , the topsheet 2 covers the entire skin-facing surface of the absorbent body 4. Meanwhile, the backsheet 3 covers the entire non-skin-facing surface of the absorbent body 4 and extends outward in the transverse direction Y from both side edges of the absorbent body 4 along the longitudinal direction X to form side flap portions (portions consisting of members extending outward in the transverse direction Y from the absorbent body 4) together with the side sheets 6 described below. The backsheet 3 and the side sheets 6 are joined to each other at their extending portions from both side edges of the absorbent body 4 along the longitudinal direction X by known joining means such as adhesives, heat sealing, or ultrasonic sealing. The topsheet 2 and the backsheet 3 may each be joined to the absorbent body 4 by an adhesive. Various materials conventionally used in absorbent articles such as sanitary napkins can be used for the topsheet 2 and the backsheet 3 without any particular restrictions. For example, the topsheet 2 can be a single-layer or multi-layer nonwoven fabric, a perforated film, or the like. The backsheet 3 can be a moisture-permeable resin film, or the like.

[0021] As shown in Fig. 1, the side flap portions significantly protrude outward in the horizontal direction Y in the vertical central region B, thereby forming a pair of wing portions 5W, 5W extending from both the left and right sides of the absorbent main body 5 along the vertical direction X. In a plan view as shown in Fig. 1, the wing portions 5W have a generally trapezoidal shape with their lower bases (longer sides than the upper bases) positioned on the sides of the absorbent main body 5, and wing adhesive portions (not shown) are formed on their non-skin-facing surfaces to secure the wing portions 5W to clothing such as shorts. The wing portions 5W are used by folding them over to the non-skin-facing surface (outer surface) of the crotch portion of clothing such as shorts. Before use, the wing adhesive portions are covered with a release sheet (not shown) made of film, nonwoven fabric, paper, or the like. Furthermore, a pair of side sheets 6, 6 are arranged over substantially the entire length of the absorbent body 5 in the longitudinal direction X on both sides of the skin-facing surface of the absorbent body 5, i.e., the skin-facing surface of the topsheet 2, so as to overlap with the left and right sides of the absorber 4 in the longitudinal direction X in a plan view. The pair of side sheets 6, 6 are joined to other members, such as the topsheet 2, by known joining means such as adhesives, at joining lines (not shown) extending in the longitudinal direction X.

[0022] As shown in Figures 1 and 2, the skin-facing surface of the absorbent body 4 partially forms a recessed portion 7, where the core wrap sheet 41 and the absorbent core are integrally recessed toward the non-skin-facing side of the absorbent body 4. The recessed portion 7 is formed by compressing the napkin 1 from its skin-facing side, i.e., the topsheet side, and can also be called a "compressed portion" based on the method of formation. Compression can be performed using known methods, such as embossing with or without heat or ultrasonic embossing. Due to the method of formation, the recessed portion 7 is formed by the topsheet 2, core wrap sheet 41, and absorbent core 40 being integrally recessed toward the non-skin-facing side of the absorbent core 40 (the backsheet 3 side). Furthermore, due to the method of formation, the recessed portion 7 has a higher density than its surrounding area (the area where the recessed portion 7 is not formed). That is, the absorbent body 5 has a high-density portion corresponding to the recessed portion 7 and a low-density portion corresponding to the non-recessed portion. At the bottom of the recess 7, the topsheet 2, the core wrap sheet 41 and the absorbent core 40 may be heat-sealed and integrated together.

[0023] As shown in FIG. 1 , the recess 7 is formed at least in the longitudinal central region B, and more specifically, it is continuous in the longitudinal direction X from a portion of the front region A near the longitudinal central region B to a portion of the rear region C near the longitudinal central region B. In the napkin 1, the recess 7 is linear in plan view as shown in FIG. 1 , and the linear recess 7 forms a closed ring in plan view. The ring-shaped recess 7 is elongated in the longitudinal direction X in plan view, and its longitudinal direction coincides with the longitudinal direction X. In each of the front region A and the rear region C, the ring-shaped recess 7 is formed in a U-shape or an arc-shape that convex outward in the longitudinal direction X, with the apex of the U-shape or arc-shape located at the center of the napkin 1 in the transverse direction Y. In the longitudinal central region B, the ring-shaped recess 7 is formed as a pair of lines extending in the longitudinal direction X. In this way, the recess 7 is formed so as to surround the center of the longitudinal central region B in the transverse direction Y.

[0024] In the napkin 1, the depth of the recesses 7 (the depth from the non-recessed skin-facing surface of the topsheet 2) is constant throughout its entire length. The depth of the recesses 7 can be set in the same range as the depth of the leakage prevention grooves in this type of absorbent article, and is usually about 1 to 10 mm. The formation of the recesses 7 can be expected to have the effect of suppressing the diffusion of liquid in the planar direction of the absorbent body 4, particularly in the lateral direction Y, and preventing the absorbent body 4 from twisting. The shape and arrangement of the linear recesses 7 are not limited to the illustrated form and can be set in the same manner as what is called a leakage prevention groove in this type of absorbent article, and the planar shape can be composed of straight lines and / or curves, and each line can be continuous or broken (i.e., two types of portions with different depths are arranged alternately in the direction of extension of the linear recesses).

[0025] One of the main characteristic features of the napkin 1 is the absorbent core 40. FIG. 3 shows a portion of the absorbent core 40 (a portion where the recessed portion 7 is not formed). As shown in FIGS. 2 and 3 , the absorbent core 40 includes fiber agglomerates 11 containing a plurality of fibers (synthetic fibers with weak water absorption) 11F and absorbent fibers 12F. The fiber agglomerates 11 are fiber aggregates in which the fibers 11F are intentionally accumulated and integrated into agglomerates, whereas the absorbent fibers 12F are present in the absorbent core 40 in a state where they can exist individually and independently without being intentionally integrated. The fiber agglomerates 11 primarily contribute to improving the softness, cushioning properties, compression recovery, shape retention, etc. of the absorbent core 40. On the other hand, the absorbent fibers 12F primarily contribute to improving the liquid absorption and shape retention of the absorbent core 40. The absorbent core 40 can essentially be said to be the absorbent body 4 itself, and unless otherwise specified, the following description of the absorbent core 40 will be appropriately applied to the description of the absorbent body 4. In other words, the present invention includes a case where the absorbent body does not include a core wrap sheet and is formed only from an absorbent core, and in that case, the absorbent body and the absorbent core have the same meaning.

[0026] In this specification, the term "fiber agglomerate" refers to a fiber aggregate in which a plurality of fibers are integrated into one body. Examples of the form of the fiber agglomerate include sheet pieces separated from a synthetic fiber sheet of a certain size. In particular, a nonwoven fabric is selected as the synthetic fiber sheet, and a nonwoven fabric piece cut from the nonwoven fabric to a predetermined size and shape is preferred as the fiber agglomerate.

[0027] Thus, the sheet-shaped fiber agglomerates, which are a preferred embodiment of the fiber agglomerates according to the present invention, are not configured to form the sheet pieces by piling up a plurality of fibers, but are produced by cutting a fiber sheet (preferably a nonwoven fabric) that is larger in size than the sheet pieces (see Figure 6). The plurality of fiber agglomerates contained in the absorbent body of the present invention are sheet-shaped fiber agglomerates with a high degree of dimensional stability compared to those produced by conventional techniques such as those described in Patent Documents 1 and 2.

[0028]

[0005] However, as described in Patent Documents 1 to 4, absorbent cores containing weakly water-absorbent synthetic fiber aggregates have low liquid permeability, as mentioned above. Therefore, absorbents using such cores tend to have body fluids remaining on the skin-facing surface of the skin-side core wrap sheet that covers the skin-facing surface of the absorbent core, which may result in an uncomfortable stickiness or wet feeling on the skin. As a result of various studies conducted by the present inventors to solve these problems caused by the use of weakly water-absorbent fibers, it was found that it is effective to set the liquid diffusibility in the plane direction of the skin-side core wrap sheet, which is usually the first to come into contact with body fluid in an absorbent body, within a specific range in relation to the liquid diffusibility in the plane direction of the absorbent core abutting the skin-side core wrap sheet.

[0029] Based on this finding, in the napkin 1, the ratio of the liquid diffusion area of ​​the absorbent core 40 measured by the above-mentioned <Method for Measuring Liquid Diffusion Area> to the liquid diffusion area of ​​the skin-side core wrap sheet 41 measured by the same method (hereinafter also referred to as the "liquid diffusion area ratio") is set to 0.7 or more. When the liquid diffusion area ratio is 0.7 or more, bodily fluids are more likely to smoothly transfer from the skin-side core wrap sheet 41 to the absorbent core 40, and bodily fluids are less likely to remain on the skin-facing surface of the skin-side core wrap sheet 41, thereby reducing unpleasant stickiness and wetness on the skin. From the perspective of ensuring smoother transfer of bodily fluids from the skin-side core wrap sheet 41 to the absorbent core 40, the liquid diffusion area ratio is preferably 0.75 or more, more preferably 0.8 or more, and preferably 1.5 or less, and even more preferably 2.0 or less.

[0030] Referring to Figure 8, the <Method for Measuring Liquid Diffusion Area> is explained in more detail below. The measurement object S (absorbent core, core wrap sheet) is a 240 mm x 75 mm rectangular shape in plan view. The measurement table 100 used for measurement has an inclined surface 100a with an angle θ of 45° with respect to the horizontal. The measurement object S is placed on the inclined surface 100a so that its skin-facing surface faces the inclined surface 100a. Furthermore, an acrylic plate 101 with a thickness of 3 mm and an area larger than that of the measurement object S is placed on the measurement object S. The defibrinated horse blood injected as simulated blood into the measurement object S has a viscosity of 8 mPa·s, measured using a B-type viscometer (Model No. TVB-10M manufactured by Toki Sangyo Co., Ltd., measurement conditions: rotor No. 19, 30 rpm, 25°C, 60 seconds). For example, defiberized horse blood manufactured by Japan Biotest Laboratory Co., Ltd. can be used as such defiberized horse blood, and the viscosity can be adjusted to the predetermined range as needed by adjusting the blood cell / plasma ratio, etc. The defiberized horse blood is injected into the measurement object S at the center of the skin-facing surface of the measurement object S (the portion indicated by the arrow in Figure 8 ) using a microtube pump (manufactured by Tokyo Rikakikai Co., Ltd., not shown). A tube (not shown) is connected to this pump, and the end of the tube opposite to the pump connection is connected to the measurement object S on the slope 100a, and the defiberized horse blood is injected into the measurement object S through the tube. The diffusion area of ​​the defiberized horse blood on the skin-facing surface of the measurement object S can be measured by copying the distribution area of ​​the defiberized horse blood on the measurement object S onto an overhead projector sheet and processing the overhead projector sheet in the usual manner using image analysis software NexusNewQube (manufactured by Nexus).

[0031] As mentioned above, in order to achieve a liquid diffusion area ratio of 0.7 or more, it is necessary to devise the composition of both or one of the absorbent core 40 and the skin-side core wrap sheet 41. Particularly effective is a technique for improving the liquid permeability of the skin-side core wrap sheet 41. From this perspective, it is preferable that the skin-side core wrap sheet 41 be a porous sheet mainly made of pulp. Unless otherwise specified, the description of the "skin-side core wrap sheet" in this specification also applies to other portions of the core wrap sheet 41, which is a single continuous sheet, such as the non-skin-side core wrap sheet that forms the non-skin-facing surface of the absorbent body 4, i.e., the non-skin-side core wrap sheet interposed between the backsheet 3 and the absorbent core 40.

[0032] An example of a suitable porous sheet for the skin-side core wrap sheet 41 is a pulp sheet primarily composed of pulp. A typical example of this pulp sheet is paper produced by a wet papermaking process. The pulp, which is the main component of the porous sheet, can be a cellulosic fiber, such as wood pulp (NBKP), hardwood bleached kraft pulp (LBKP), softwood bleached sulfite pulp (NBSP), or thermomechanical pulp (TMP); bast fibers (such as paper mulberry, mitsumata, and gampi); or non-wood pulp (such as straw, bamboo, kenaf, and hemp). These fibers can be used alone or in combination. The pulp content in the porous sheet is preferably 10% by mass or more, more preferably 50% by mass or more. The porous sheet may contain components other than pulp. Examples of the other components include fillers such as talc, dyes, color pigments, paper strength agents, antibacterial agents, pH adjusters, retention aids, water-resistant agents, and antifoaming agents, which are generally used as raw materials or additives for papermaking. These may be used alone or in combination of two or more.

[0033] In addition, from the viewpoint of increasing the liquid permeability of the skin side core wrap sheet 41 (the porous sheet), the density of the skin side core wrap sheet 41 is 0.1 g / m ３ Below 0.08 g / m ３ The density of the skin side core wrap sheet 41 is preferably 0.02 g / m or less.３ More preferably, 0.04 g / m ３ This is preferable because it is easy to maintain sufficient sheet strength.

[0034] From the viewpoint of the balance between liquid permeability and strength, the basis weight of the skin side core wrap sheet 41 (the porous sheet) is preferably 5 g / m ２ More preferably, 10 g / m ２ or more, and preferably 50 g / m ２ More preferably 30 g / m or less ２ The following is the result.

[0035] 1 and 2, the napkin 1 has a recessed portion 7 formed on the skin-facing surface of the absorbent body 4, where the core wrap sheet 41 (more specifically, the skin-side core wrap sheet 41) and the absorbent core 40 are recessed integrally on the non-skin-facing side of the absorbent body 4. This configuration makes the shape of the absorbent body 4 more stable against the body pressure and movements of the wearer of the napkin 1, and is expected to further improve the fit, etc. of the napkin 1. Furthermore, the recessed portion 7 is formed only in a part of the absorbent body 4 (absorbent core 40), and the non-formed portion of the recessed portion 7, which accounts for the majority of the absorbent core 40, is flexible and cushiony due to the shape retention provided by the entanglement of the constituent fibers, as will be described later, and therefore the napkin 1 can substantially fully exhibit the characteristics of the non-formed portion of the recessed portion 7. The ratio of the total area of ​​the recesses 7 to the total area of ​​the skin-facing surface of the absorbent body 4 (absorbent core 40) (recess occupancy rate) is preferably 3% or more, more preferably 5% or more, and preferably 97% or less, more preferably 95% or less, from the viewpoint of the balance between the shape stability and cushioning properties of the absorbent body 4.

[0036] 1, the napkin 1 is formed with a recess 7 surrounding the central portion of the longitudinal central region B in the transverse direction Y, thereby further improving the shape stability of the central portion of the longitudinal central region B. The central portion of the longitudinal central region B surrounded by the recess 7 usually includes the portion facing the excretion area (excretion point), and is an important portion that first receives and diffuses bodily fluids excreted by the wearer of the napkin 1. The high shape stability of this important portion is expected to further improve various properties such as liquid absorbency (leak prevention), fit, and wearing comfort.

[0037] The absorbent core 40 will be further described below. In the absorbent core 40, the plurality of fiber agglomerates 11 are entangled with one another or with the absorbent fibers 12F. In the absorbent core 40 of this embodiment, the plurality of fiber agglomerates 11 are bonded by entanglement with the constituent fibers (fibers 11F, 12F) in the absorbent core 40 to form a single continuous fiber agglomerate. The plurality of fiber agglomerates 11 may be entangled with one another, and the fiber agglomerates 11 may be entangled with the absorbent fibers 12F. Furthermore, typically, the plurality of absorbent fibers 12F are also entangled with one another. At least some of the plurality of fiber agglomerates 11 contained in the absorbent core 40 are entangled with other fiber agglomerates 11 or absorbent fibers 12F. In the absorbent core 40, all of the plurality of fiber agglomerates 11 contained therein may be entangled with one another to form a single continuous fiber agglomerate, or multiple continuous fiber agglomerates may be mixed together in an unbonded state. The entanglement property of the fiber agglomerates 11, i.e., the ease with which they become entangled with other fiber agglomerates 11 or absorbent fibers 12F, is largely dependent on the shape (number, size, distribution, etc.) of the extended fiber portions 113, which will be described later, possessed by the fiber agglomerates 11, and the entanglement property of the fiber agglomerates 11 can be increased by appropriately controlling the shape of the extended fiber portions 113.

[0038] The fiber agglomerates 11 have excellent flexibility, etc. In the present embodiment, as described above, the absorbent core 40 contains a plurality of fiber agglomerates 11 that are bonded to one another by entanglement, and furthermore, the fiber agglomerates 11 and the absorbent fibers 12F are also bonded to one another by entanglement, so that the absorbent core 40 has excellent shape retention, flexibility, cushioning properties, compression recovery, etc., and when incorporated into the napkin 1, it flexibly deforms in response to external forces (e.g., body pressure of the wearer of the absorbent article) applied from various directions, allowing the napkin 1 to fit closely to the body of the wearer with good fit.

[0039] Figure 4 shows a schematic diagram of the deformation of the absorbent core 40 when compressed by an external force F. The absorbent core 40, which is composed of a mixture of fiber agglomerates 11, which are fiber aggregates, and absorbent fibers 12F, which are non-fiber aggregates, is particularly prone to bending at the boundary BL (dotted line in Figure 4) between the two components 11, 12F due to the difference in rigidity between the two components 11, 12F. The boundary BL functions as a bending portion when the absorbent core 40 deforms. Since the boundary BL, which serves as the bending portion, is typically present throughout the entire absorbent core 40, the absorbent core 40 flexibly deforms in response to various external forces. Furthermore, when the external force is released, the compression recovery property of the fiber agglomerates 11 allows the absorbent core 40 to quickly return to its original state. This deformation-recovery characteristic of the absorbent core 40 is exhibited not only when the absorbent core 40 is compressed, but also when it is twisted. That is, the absorbent core 40 incorporated in the napkin 1 is positioned between the wearer's thighs when the napkin 1 is worn, and therefore the absorbent body 4 may be twisted around an imaginary axis of rotation extending in the vertical direction X due to the movement of the wearer's thighs when walking. However, even in such cases, the absorbent core 40 has high deformation-recovery properties, so it easily deforms and recovers in response to external forces that would encourage twisting from the thighs, and is therefore less likely to twist, allowing the napkin 1 to have a high fit to the wearer's body.

[0040] As described above, in the absorbent core 40, the fiber agglomerates 11 are entangled with each other or with the absorbent fibers 12F. Here, the "entanglement" of the fiber agglomerates 11 includes the following modes A and B. Mode A: The fiber agglomerates 11 are bonded together, not by fusion, but by entanglement of the constituent fibers 11F of the fiber agglomerates 11. Mode B: In the natural state of the absorbent core 40 (when no external force is applied), the fiber agglomerates 11 are not bonded together, but when an external force is applied to the absorbent core 40, the fiber agglomerates 11 can be bonded together by entanglement of the constituent fibers 11F. Here, the "state in which an external force is applied to the absorbent core 40" refers to a state in which a deforming force is applied to the absorbent core 40, for example, while an absorbent article to which the absorbent core 40 is applied is being worn.

[0041] Thus, in the absorbent core 40, the fiber agglomerates 11 are bonded to other fiber agglomerates 11 or absorbent fibers 12F by fiber entanglement, i.e., "intertwining," as in Form A, and also exist in a state in which they can be entangled with other fiber agglomerates 11 or absorbent fibers 12F, as in Form B. Such fiber entanglement is an important factor in more effectively achieving the aforementioned effects of the absorbent core 40. However, from the perspective of shape retention, the absorbent core 40 preferably has the "intertwining" of Form A. In either Form A or B, the entanglement of the constituent fibers in the absorbent core 40 is achieved solely by fiber entanglement without the use of an adhesive. Therefore, while the bonding strength itself is lower than bonding by "fiber fusion" as described in, for example, Patent Document 2, the individual entangled elements (fiber agglomerates 11, absorbent fibers 12F) have a higher degree of freedom of movement, and therefore the individual elements can move within a range in which they can maintain the integrity of their aggregate. In this way, the absorbent core 40 has a gentle shape retention that allows it to deform when subjected to external force, as the multiple fiber agglomerates 11 contained therein or the fiber agglomerates 11 and the absorbent fibers 12F are relatively loosely bonded to each other, and the absorbent core 40 has a high level of shape retention, cushioning properties, compression recovery, etc.

[0042] Furthermore, it is not necessary that all of the bonding patterns via the fiber agglomerates 11 in the absorbent core 40 be "entangled," and some of the absorbent core 40 may include bonding patterns other than entanglement, such as bonding with an adhesive.

[0043] However, in the remaining portion of the absorbent core 40, excluding the "fusion via fiber agglomerates 11" formed in the absorbent core 40 as a result of being integrated with other components of the absorbent article, such as the recessed portion 7 in the napkin 1, i.e., the absorbent core 40 itself, it is desirable that the bonding between the fiber agglomerates 11 or the bonding between the fiber agglomerates 11 and the absorbent fibers 12F be achieved only by "fiber entanglement."

[0044] From the viewpoint of more reliably achieving the aforementioned functional effects of the absorbent core 40, the total number of "fiber agglomerates 11 bonded by entanglement" of Form A and "fiber agglomerates 11 in a state where they can be entangled" of Form B is preferably at least half, more preferably at least 70%, and even more preferably at least 80% of the total number of fiber agglomerates 11 in the absorbent core 40. From the same viewpoint, it is preferable that the number of fiber agglomerates 11 having "entanglement" of Form A is at least 70%, and especially at least 80%, of the total number of fiber agglomerates 11 having bonds with other fiber agglomerates 11 or absorbent fibers 12F.

[0045] One of the main features of the absorbent core 40 is the external shape of the fiber agglomerates 11. Figure 5 shows two typical external shapes of the fiber agglomerates 11. The fiber agglomerates 11A shown in Figure 5(a) are more specifically rectangular parallelepiped-shaped than square prism-shaped, and the fiber agglomerates 11B shown in Figure 5(b) are disk-shaped. The fiber agglomerates 11A and 11B have in common the fact that they have two opposing base planes 111 and a body plane 112 connecting the two base planes 111. Both the base plane 111 and the body plane 112 are portions that are recognized as having substantially no irregularities at the level applied when evaluating the degree of surface irregularities in an article mainly composed of this type of fiber.

[0046] The rectangular parallelepiped fiber agglomerate 11A in Fig. 5(a) has six flat surfaces, of which two opposing surfaces with the largest areas are base surfaces 111, and the remaining four surfaces are skeletal surfaces 112. The base surfaces 111 and skeletal surfaces 112 intersect with each other, more specifically, are perpendicular to each other. The disk-shaped fiber agglomerate 11B in Fig. 5(b) has two opposing flat surfaces that are circular in plan view and a curved peripheral surface connecting the two flat surfaces, and the two flat surfaces are base surfaces 111, and the peripheral surface is skeletal surface 112. The fiber agglomerates 11A and 11B are also similar in that the skeletal surfaces 112 are quadrangular in plan view, more specifically, rectangular.

[0047] The plurality of fiber agglomerates 11 contained in the absorbent core 40 are each a "fixed-shape fiber aggregate" having two opposing basic surfaces 111 and a skeletal surface 112 connecting the two basic surfaces 111, such as fiber agglomerates 11A and 11B shown in Fig. 5, and are therefore different from the nonwoven fabric pieces or fine webs described in Patent Documents 2 and 3, which are irregular fiber aggregates. In other words, when any one fiber agglomerate 11 in the absorbent core 40 is viewed through (for example, when observed with an electron microscope), the perspective shape of the fiber agglomerate 11 varies depending on the observation angle, and there are multiple perspective shapes for one fiber agglomerate 11. However, each of the multiple fiber agglomerates 11 in the absorbent core 40 has, as one of the multiple perspective shapes, a specific perspective shape having two opposing basic surfaces 111 and a skeletal surface 112 connecting the two basic surfaces 111. The multiple nonwoven fabric pieces or fine webs contained in the absorbent bodies described in Patent Documents 2 and 3 do not substantially have "surfaces" such as the basic surface 111 or the skeletal surface 112, i.e., expansive parts, and have different external shapes from each other and are not "fixed shape."

[0048] In this way, when the plurality of fiber agglomerates 11 contained in the absorbent core 40 are "fixed-shaped fiber aggregates" defined by basic surfaces 111 and skeletal surfaces 112, the fiber agglomerates 11 are more uniformly dispersed in the absorbent core 40 than when the fiber agglomerates are irregular-shaped fiber aggregates as described in Patent Documents 2 and 3, and the effects expected from incorporating fiber aggregates such as the fiber agglomerates 11 into the absorbent core 40 (such as improved flexibility, cushioning, and compression recovery of the absorbent body) are more stably achieved. In particular, in the case of a rectangular parallelepiped fiber agglomerate 11 as shown in Figure 5(a), its outer surface consists of six surfaces, namely, two basic surfaces 111 and four skeletal surfaces 112. Therefore, compared to a disk-shaped fiber agglomerate 11 having three outer surfaces as shown in Figure 5(b), this allows for a relatively greater opportunity for contact with other fiber agglomerates 11 or absorbent fibers 12F, thereby increasing entanglement and potentially leading to improved shape retention, etc.

[0049] In the fiber agglomerate 11, the total area of ​​the two basic surfaces 111 is greater than the total area of ​​the skeletal surfaces 112. That is, in the rectangular parallelepiped fiber agglomerate 11A of Fig. 5(a), the sum of the areas of the two basic surfaces 111 is greater than the sum of the areas of the four skeletal surfaces 112, and in the disk-shaped fiber agglomerate 11B of Fig. 5(b), the sum of the areas of the two basic surfaces 111 is greater than the area of ​​the skeletal surfaces 112 that form the circumferential surface of the disk-shaped fiber agglomerate 11B. In both fiber agglomerates 11A and 11B, the basic surfaces 111 are the surfaces with the largest area among the multiple surfaces of the fiber agglomerates 11A and 11B.

[0050] Such fiber agglomerates 11, which are "fixed-shape fiber aggregates" defined by two basic planes 111 and skeletal planes 112 intersecting both basic planes 111, can be realized by a manufacturing method different from that of conventional techniques. A preferred method for manufacturing fiber agglomerates 11, as shown in FIG. 6, involves cutting a raw fiber sheet 10bs (a sheet having the same composition as the fiber agglomerates 11 but larger in size) into a fixed shape using a cutting device such as a cutter. The multiple fiber agglomerates 11 manufactured in this manner have a more uniform shape and size compared to those manufactured by conventional techniques such as those described in Patent Documents 2 and 3. FIG. 6 illustrates a manufacturing method for the rectangular parallelepiped-shaped fiber agglomerates 11A shown in FIG. 5(a), and the dotted lines in FIG. 6 indicate cutting lines. The absorbent core 40 contains multiple fiber agglomerates 11 with uniform shape and size obtained by cutting a fiber sheet into a fixed shape. As mentioned above, a nonwoven fabric is preferred as the raw fiber sheet 10bs.

[0051] The rectangular parallelepiped fiber agglomerates 11A shown in Fig. 5(a) are produced by cutting a raw fiber sheet 10bs to a predetermined length in a first direction D1 and a second direction D2 intersecting (more specifically, perpendicular to) the first direction D1, as shown in Fig. 6. Each of the directions D1 and D2 is a predetermined direction in the plane of the sheet 10bs, and the sheet 10bs is cut along a thickness direction Z perpendicular to the plane. In this manner, in the multiple rectangular parallelepiped fiber agglomerates 11A obtained by cutting the raw fiber sheet 10bs into a so-called dice pattern, the cut surfaces, i.e., the surfaces that come into contact with a cutting tool such as a cutter when cutting the sheet 10bs, are generally called skeletal surfaces 112, and the non-cut surfaces, i.e., the surfaces that do not come into contact with the cutting tool, are called basic surfaces 111. The basic surfaces 111 are the front and back surfaces of the sheet 10bs (surfaces perpendicular to the thickness direction Z) and, as mentioned above, are the surfaces with the largest area among the multiple surfaces of the fiber agglomerates 11A.

[0052] The above description of fiber agglomerates 11A also basically applies to the disk-shaped fiber agglomerates 11B shown in Fig. 5(b). The only substantial difference from fiber agglomerates 11A is the cutting pattern of raw fiber sheet 10bs. When fiber agglomerates 11B are obtained by cutting sheet 10bs into a fixed shape, the sheet 10bs can be cut into a circular shape that matches the planar shape of fiber agglomerates 11B.

[0053] The external shape of the fiber agglomerates 11 is not limited to that shown in Fig. 5, and both the basic surfaces 111 and the skeletal surfaces 112 may be flat, uncurved surfaces like the surfaces 111 and 112 in Fig. 5(a), or may be curved surfaces like the skeletal surface 112 (the peripheral surface of the disk-shaped fiber agglomerates 11B) in Fig. 5(b). The basic surfaces 111 and the skeletal surfaces 112 may have the same shape and dimensions. Specifically, for example, the external shape of the fiber agglomerates 11A may be a cube.

[0054] As described above, the two types of surfaces (basic surface 111 and skeletal surface 112) of the fiber agglomerates 11 (11A, 11B) are classified into cut surfaces (skeletal surface 112) formed by cutting the raw fiber sheet 10bs with a cutting means such as a cutter when producing the fiber agglomerates 11, and uncut surfaces (basic surface 111) that are inherent to the sheet 10bs and do not come into contact with the cutting means. Due to the difference between cut surfaces and uncut surfaces, the skeletal surface 112, which is a cut surface, is characterized by having a larger number of fiber ends per unit area than the basic surface 111, which is an uncut surface. Here, "fiber ends" refers to the longitudinal ends of the constituent fibers 11F of the fiber agglomerates 11. Normally, fiber ends are also present on the basic surface 111, which is an uncut surface, but since the skeletal surface 112 is a cut surface formed by cutting the raw fiber sheet 10bs, a large number of fiber ends consisting of the cut ends of the constituent fibers 11F formed by this cutting are present throughout the entire skeletal surface 112, i.e., the number of fiber ends per unit area is greater than that of the basic surface 111.

[0055] The fiber ends present on each surface (basic surface 111, skeletal surface 112) of the fiber agglomerates 11 are useful for entangling the fiber agglomerates 11 with other fiber agglomerates 11 and absorbent fibers 12F contained in the absorbent core 40. Generally, the greater the number of fiber ends per unit area, the better the entanglement, which can lead to improvements in various properties such as the shape retention of the absorbent core 40. As mentioned above, the number of fiber ends per unit area on each surface of the fiber agglomerates 11 is not uniform, and there is a magnitude relationship of "skeletal surface 112 > basic surface 111" regarding the number of such fiber ends per unit area. Therefore, the entanglement ability with other fibers (other fiber agglomerates 11, absorbent fibers 12F) via the fiber agglomerates 11 differs depending on the surface of the fiber agglomerates 11, with the skeletal surface 112 having a higher entanglement ability than the basic surface 111. That is, the bonding strength due to entanglement with other fibers via the skeletal surface 112 is stronger than that via the basic surface 111, and within one fiber mass 11, there may be a difference in the bonding strength with other fibers between the basic surface 111 and the skeletal surface 112. Generally, the stronger the bonding strength, the more restricted the degree of freedom of movement of the bonded fibers, and the strength (shape retention) of the absorbent core 40 as a whole improves, but the softness tends to decrease.

[0056] In this way, each of the plurality of fiber agglomerates 11 contained in the absorbent core 40 is entangled with the other surrounding fibers (the other fiber agglomerates 11, the absorbent fibers 12F) with two types of bonding strength, which gives the absorbent core 40 both appropriate softness and strength (shape retention). When the absorbent core 40 having such excellent properties is used in a conventional manner as an absorbent body of an absorbent article, it can provide a comfortable wearing experience to the wearer of the absorbent article and effectively prevent the absorbent core 40 from being destroyed by external forces such as the wearer's body pressure when worn.

[0057] In particular, as described above, the fiber agglomerates 11 (11A, 11B) shown in Fig. 5 have a larger total area of ​​the two basic faces 111 than the total area of ​​the skeletal faces 112. This means that the basic faces 111, which have a relatively small number of fiber ends per unit area and therefore a relatively low tendency to entangle with other fibers, have a larger total area than the skeletal faces 112, which have the opposite property. Therefore, compared to fiber agglomerates in which fiber ends are uniformly distributed over the entire surface, the fiber agglomerates 11 (11A, 11B) shown in Fig. 5 are more likely to be prevented from entangling with other surrounding fibers (other fiber agglomerates 11, absorbent fibers 12F). Even if they are entangled with other surrounding fibers, they are likely to do so with a relatively weak bond, and therefore are less likely to form large agglomerates, which can impart excellent softness to the absorbent core 40.

[0058] In contrast, the nonwoven fabric pieces or fine webs described in Patent Documents 2 and 3 are manufactured by cutting a raw fiber sheet into irregular shapes using a cutting machine such as a mill cutter, as mentioned above, and therefore are not regular sheet-shaped fiber agglomerates with "surfaces" such as the basic surface 111 or the skeletal surface 112. Furthermore, since the external force of the cutting process is applied to the entire fiber agglomerate during manufacturing, the fiber ends of the constituent fibers are formed randomly throughout the fiber agglomerate, making it difficult to fully achieve the aforementioned effects of the fiber ends.

[0059] In order to ensure the above-mentioned effect of the fiber ends, the number N of fiber ends per unit area of ​​the basic surface 111 (non-cut surface) is set to １ and the number N of fiber ends per unit area of ​​the skeleton surface 112 (cut surface). ２ The ratio of １ <N ２ Assuming that, N １ / N ２ is preferably 0 or more, more preferably 0.05 or more, and is preferably 0.90 or less, more preferably 0.60 or less. １ / N ２ is preferably 0 or more and 0.90 or less, and more preferably 0.05 or more and 0.60 or more. １ is preferably 0 pieces / mm ２ More preferably, 3 pieces / mm２ or more, and preferably 8 pieces / mm ２ More preferably, 6 pieces / mm or less ２ The number N of fiber ends per unit area of ​​the skeletal surface 112 is ２ is preferably 5 pieces / mm ２ More preferably, 8 pieces / mm ２ or more, and preferably 50 pieces / mm ２ More preferably, 40 pieces / mm ２ The number of fiber ends per unit area on the basic surface 111 and the skeletal surface 112 is measured by the following method.

[0060] <Method for measuring the number of fiber ends per unit area on each surface of a fiber mass> A test piece containing the fiber to be measured (fiber mass) is attached to a sample stage using double-sided paper tape (Nichiban Co., Ltd., Nicetack NW-15). The test piece is then platinum-coated. An ion sputtering device E-1030 (product name) manufactured by Hitachi Naka Seiki Co., Ltd. is used for the coating, and the sputtering time is 120 seconds. The cut surface of the test piece is observed at 100x magnification using a JCM-6000 electron microscope manufactured by JEOL Corporation, with the basal and skeletal surfaces. In this 100x magnification observation screen, a rectangular region measuring 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 observation angle and other factors are adjusted so that the area of ​​the rectangular region occupies 90% or more of the area of ​​the observation screen, and the number of fiber ends contained within the rectangular region is then measured. However, when the measurement surface of the fiber clump is smaller than 1.2 mm × 0.6 mm on an observation screen at 100x magnification, and the area of ​​the rectangular region occupies less than 90% of the entire observation screen, the observation magnification is increased to more than 100x, and the number of fiber ends contained within the rectangular region on the measurement surface is measured in the same manner as above. Here, the "fiber ends" to be counted are the longitudinal ends of the constituent fibers of the fiber clump, and even if a portion other than the longitudinal ends of the constituent fibers (longitudinal intermediate portions) extends from the measurement surface, this longitudinal intermediate portion is not counted. The number of fiber ends per unit area on the measurement surface (basic surface or skeletal surface) of the fiber clump is then calculated using the following formula. For each of 10 fiber clumps, the number of fiber ends per unit area on each of the basic surface and skeletal surface is measured according to the procedure described above, and the average of these multiple measurements is taken as the number of fiber ends per unit area on the measurement surface. The number of fiber ends per unit area (number / mm) on the measurement surface (basic surface or skeletal surface) of the fiber clump is calculated using the following formula. ２ ) = number of fiber ends contained in a rectangular area (1.2 × 0.6 mm) / area of ​​the rectangular area (0.72 mm ２ )

[0061] When the basic surface 111 of the fiber agglomerates 11 has a rectangular shape in plan view, as in the fiber agglomerates 11A shown in Figure 5(a), from the viewpoint of improving the uniform dispersion of the fiber agglomerates 11 in the absorbent body 4, it is preferable that the short side 111a of the rectangular shape be equal to or shorter than the thickness of the absorbent core 40 containing the fiber agglomerates 11 (11A). The ratio of the length of the short side 111a to the thickness of the absorbent core 40, as the former / the latter, is preferably 0.03 or more, more preferably 0.08 or more, and preferably 1 or less, and more preferably 0.5 or less. The thickness of the absorbent core 40 is preferably 1 mm or more, more preferably 2 mm or more, and preferably 15 mm or less, and more preferably 10 mm or less. The thickness of the absorbent core 40 is measured by the following method.

[0062] <Method for measuring the thickness of the absorbent body> The object to be measured (the absorbent core 40) was placed on a horizontal surface without wrinkles or bends, and the thickness was measured at 5 cN / cm ２ The thickness of the object to be measured is measured under a load of 5 cN / cm. Specifically, for example, a thickness gauge, PEACOCK DIAL UPRIGHT GAUGES R5-C (manufactured by OZAKI MFG.CO.LTD.), is used to measure the thickness. At this time, a load of 5 cN / cm is applied to the object to be measured between the tip of the thickness gauge and the cut-out object to be measured. ２ The thickness is measured by placing a plate (an acrylic plate with a thickness of about 5 mm) that is circular or square in plan view and has a size adjusted so that the thickness is 10 points, and the average value of these measurements is calculated to be the thickness of the object to be measured.

[0063] The dimensions of each portion of the fiber agglomerates 11 (11A, 11B) are preferably set as follows. The dimensions of each portion of the fiber agglomerates 11 can be measured based on electron microscope photographs taken during the process of specifying the external shape of the fiber agglomerates 11, which will be described later. When the basic surface 111 has a rectangular shape in plan view as shown in FIG. 5( a), the length L1 of the short side 111a is preferably 0.3 mm or more, more preferably 0.5 mm or more, and preferably 10 mm or less, and more preferably 6 mm or less. The length L2 of the long side 111b of the basic surface 111 having a rectangular shape in plan view is preferably 0.3 mm or more, more preferably 2 mm or more, and preferably 30 mm or less, and more preferably 15 mm or less. When the basic surface 111 is the surface having the largest area among the multiple surfaces of the fiber agglomerate 11 as shown in Fig. 5, the length L2 of the long side 111b corresponds to the maximum diameter of the fiber agglomerate 11, which corresponds to the diameter of the circular basic surface 111 in a disk-shaped fiber agglomerate 11B in a planar view. The ratio L1 / L2 of the length L1 of the short side 111a to the length L2 of the long side 111b is preferably 0.003 or more, more preferably 0.025 or more, and preferably 1 or less, and even 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. 5(a) and may be a square shape. That is, the ratio L1 / L2 of the lengths L1 and L2 of the two mutually perpendicular sides may be 1. The thickness T of the fiber mass 11, that is, the length T between the two opposing basic faces 111, is preferably 0.1 mm or more, more preferably 0.3 mm or more, and is preferably 10 mm or less, more preferably 6 mm or less.

[0064] Furthermore, the absorbent core 40 is preferably mechanically isotropic so that the effects resulting from the presence of the fiber agglomerates 11 can be easily achieved on all surfaces of the absorbent core 40. To this end, it is preferable that the fiber agglomerates 11 are distributed uniformly and at a high density throughout the absorbent core 40. From this perspective, it is preferable that, in two mutually orthogonal projection views of the absorbent core 40, overlapping portions of a plurality of fiber agglomerates 11 are present in any 10 mm square unit area. The reference numeral 11Z in Figures 3 and 4 indicates overlapping portions of a plurality of fiber agglomerates 11. Here, the "two mutually orthogonal projection views" typically include a projection view in the thickness direction of the absorbent core (absorbent body) (i.e., when the absorbent core is observed from its skin-facing or non-skin-facing surface) and a projection view in a direction perpendicular to the thickness direction (i.e., when the absorbent core is observed from its side).

[0065] Fig. 7(a) shows an electron microscope photograph of an example of a fiber agglomerate according to the present invention, and Fig. 7(b) shows a schematic diagram of a fiber agglomerate 11 based on the electron microscope photograph. As shown in Fig. 7, the plurality of fiber agglomerates 11 contained in the absorbent core 40 may include those having a main body portion 110 and extended fiber portions 113, which are composed of fibers 11F extending outward from the main body portion 110 and have a lower fiber density (fewer fibers per unit area) than the main body portion 110. The absorbent core 40 may also include fiber agglomerates 11 that do not have extended fiber portions 113, i.e., fiber agglomerates 11 consisting only of the main body portion 110. The extended fiber portions 113 are a type of fiber end portion present on each surface (basic surface 111, skeletal surface 112) of the fiber agglomerate 11, and are those fiber ends that extend outward from each surface of the fiber agglomerate 11.

[0066] The main body portion 110 is a portion defined by the two opposing basic surfaces 111 and the skeletal surface 112 connecting the two basic surfaces 111. The main body portion 110 constitutes the main body of the fiber agglomerates 11 and is the portion that forms the fixed external shape of the fiber agglomerates 11. The various properties of the fiber agglomerates 11, such as high flexibility, cushioning properties, and compression recovery, are essentially due to the main body portion 110. On the other hand, the extended fiber portions 113 mainly contribute to improving the entanglement of the multiple fiber agglomerates 11 contained in the absorbent core 40 with each other or between the fiber agglomerates 11 and the absorbent fibers 12F, and are not only directly involved in improving the shape retention of the absorbent core 40 but also affect the uniform dispersion of the fiber agglomerates 11 in the absorbent core 40, thereby indirectly reinforcing the effects attributable to the main body portion 110.

[0067] The main body portion 110 has a higher fiber density, i.e., a larger number of fibers per unit area, than the extended fiber portions 113. Furthermore, the fiber density of the main body portion 110 itself is usually uniform. The proportion of the main body portion 110 in the total mass of the fiber agglomeration 11 is usually at least 40% by mass or more, preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 85% by mass or more. The main body portion 110 and the extended fiber portions 113 can be distinguished by the following outer shape identification process.

[0068] The task of identifying the external shape of the main body portion 110 of the fiber agglomerates 11 contained in the absorbent core 40 can be performed by confirming the "boundary" between the main body portion 110 and other portions, focusing on differences in fiber density (the number of fibers per unit area) and differences in fiber type and fiber diameter in the absorbent core 40. The main body portion 110 has a higher fiber density than the extended fiber portions 113 present around it, and the synthetic fibers constituting the main body portion 110 are typically qualitatively and / or dimensionally different from the absorbent fibers 12F (typically cellulosic fibers). Therefore, even in an absorbent core 40 containing a mixture of numerous fiber agglomerates 11 and absorbent fibers 12F, the boundary can be easily identified by focusing on these points. The boundary thus identified is the periphery (edge) of the basic surface 111 or the skeletal surface 112. This boundary confirmation task identifies the basic surface 111 and the skeletal surface 112, and ultimately identifies the main body portion 110. Such boundary confirmation work can be performed by using an electron microscope to observe the object (absorbent core 40) from multiple observation angles as necessary. In particular, when the fiber agglomerates 11 contained in the absorbent core 40 are those in which the total area of ​​the two basic faces 111 is larger than the total area of ​​the skeletal faces 112, such as the fiber agglomerates 11A and 11B shown in Figure 5, and particularly when the basic face 111 is the face with the largest area of ​​the fiber agglomerates 11, the basic face 111 with the largest area can be identified relatively easily, and the work of identifying the external shape of the main body portion 110 can be performed smoothly.

[0069] As shown in Fig. 7, the extended fiber portion 113 is made of constituent fibers 11F of the main body portion 110, which extend outward from at least one of the basic surface 111 and the skeletal surface 112 that form the outer surface of the main body portion 110. Fig. 7 is a plan view of the fiber agglomerate 11 from the basic surface 111 side (the surface having the largest area among the multiple surfaces of the fiber agglomerate 11), and many fibers 11F extend from the skeletal surface 112 that intersects with the basic surface 111 to form the extended fiber portion 113.

[0070] The shape of the extended fiber portion 113 is not particularly limited. The extended fiber portion 113 may be composed of a single fiber 11F, or may be composed of multiple fibers 11F, such as the extended fiber bundle portion 113S described below. The extended fiber portion 113 includes the longitudinal ends of the fibers 11F extending from the main body portion 110. However, in addition to these fiber ends, the extended fiber portion 113 may also include a portion (a longitudinal intermediate portion) other than both longitudinal ends of the fibers 11F. That is, in the fiber agglomeration 11, both longitudinal ends of the constituent fibers 11F may be present in the main body portion 110, and the remaining portion, i.e., the longitudinal intermediate portion, may extend (protrude) outward from the main body portion 110 in a loop shape. In this case, the extended fiber portion 113 is composed of the loop-shaped protruding portion of the fiber 11F.

[0071] As mentioned above, one of the main roles of the extended fiber portions 113 is to entangle the multiple fiber agglomerates 11 contained in the absorbent core 40 with one another, or the fiber agglomerates 11 with the absorbent fibers 12F. Generally, as the extension length of the extended fiber portions 113 from the main body portion 110 increases, or the thickness of the extended fiber portions 113 increases, or the number of extended fiber portions 113 contained in one fiber agglomerate 11 increases, the connections between the entangled objects via the extended fiber portions 113 become stronger, making it more difficult to undo the entanglement, and the desired effect of the present invention is thereby more stably achieved.

[0072] When the fiber agglomerates 11 are obtained by cutting a raw fiber sheet 10bs into a fixed shape as shown in Figure 6, the extended fiber portions 113 are relatively abundant on the skeletal surface 112, which is the cut surface, whereas they are completely absent or, if present, fewer in number than on the basal surface 111, which is the uncut surface. The reason the extended fiber portions 113 are unevenly distributed on the skeletal surface 112, which is the cut surface, is that many of the extended fiber portions 113 are "fluff" generated by cutting the raw fiber sheet. That is, the skeletal surface 112 formed by cutting the raw fiber sheet 10bs is rubbed overall by a cutting means such as a cutter during cutting, so fluff composed of the constituent fibers 11F of the sheet 10bs is easily formed, or so-called "fuzzing." Depending on the type of raw fiber sheet, shortening the spacing between the cutting lines or slowing the cutting speed can make the extended fiber portions 113 more likely to be formed, and their length can also be adjusted. On the other hand, the basic surface 111, which is the non-cut surface, does not have friction with the cutting means, and therefore fluff, that is, the extended fiber portion 113, is unlikely to be formed.

[0073] The spacing L1a (spacing in the first direction, see Figure 6) and spacing L2a (spacing in the second direction, see Figure 6) of the cutting lines when cutting the raw fiber sheet 10bs are preferably 0.3 mm or more, more preferably 0.5 mm or more, and preferably 30 mm or less, more preferably 15 mm or less, from the viewpoint of promoting the formation of the extended fiber portions 113 described above and ensuring the dimensions necessary for the fiber agglomerates 11 to exhibit the desired effects.

[0074] As shown in FIG. 7 , the fiber agglomeration 11 has, as a type of extending fiber portion 113, an extending fiber bundle portion 113S including a plurality of fibers 11F extending outward from the main body portion 110, more specifically, the skeletal surface 112. At least one of the extending fiber portions 113 of the fiber agglomeration 11 may be this extending fiber bundle portion 113S. The extending fiber bundle portion 113S is formed by gathering together a plurality of fibers 11F extending from the skeletal surface 112 and is characterized by a longer extension length from the skeletal surface 112 compared to the extending fiber portion 113. The extending fiber bundle portion 113S may also be present on the basic surface 111, but is typically present on the skeletal surface 112 as shown in FIG. 7 , and is not present at all on the basic surface 111, or even if present, the number of extending fiber bundle portions 113S is smaller than that on the skeletal surface 112. The reason for this is the same as the reason why the extending fiber portions 113 are mainly present on the skeletal surface 112, which is the cut surface, and has been described above.

[0075] The fiber agglomerates 11 have such extended fiber bundles 113S, which may also be called long, thick, and large extended fiber portions 113, which further strengthens the entanglement of the fiber agglomerates 11 with each other or with the absorbent fibers 12F, thereby more stably achieving the desired effects of the present invention attributable to the presence of the fiber agglomerates 11. The extended fiber bundles 113S are easily formed by cutting the raw fiber sheet 10bs under the aforementioned conditions that make fuzzing likely (see FIG. 6).

[0076] The extension length of the extending fiber bundle portion 113S from the main body portion 110, i.e., the extension length from the skeletal surface 112 (cut surface), is preferably 0.05 mm or more, more preferably 0.15 mm or more, and preferably 7 mm or less, even more preferably 4 mm or less. The extension length of the extending fiber bundle portion 113S can be measured during the aforementioned work of specifying the external shape of the fiber agglomerate 11 (boundary confirmation work). Specifically, for example, using a Keyence microscope (50x magnification), double-sided tape manufactured by 3M Corporation is attached to the surface of a transparent acrylic sample stage, and the fiber agglomerate 11 is placed and fixed thereon. The external shape of the fiber agglomerate 11 is then specified according to the aforementioned work of specifying the external shape, and the length of the extending portion of the fibers 11F extending from the external shape is measured, and the measured extension length is defined as the extension length of the extending fiber bundle portion 113S.

[0077] The extending fiber bundle portion 113S preferably has a plurality of constituent fibers 11F heat-fused to one another. The heat-fused portions of the extending fiber bundle portion 113S typically have a longer span (or diameter, if the cross section of the heat-fused portion is circular) in a direction perpendicular to the longitudinal direction of the extending fiber bundle portion 113S than the other portions (non-heat-fused portions) of the extending fiber bundle portion 113S. The extending fiber bundle portion 113S having such heat-fused portions, which can also be considered large-diameter portions, increases the strength of the extending fiber bundle portion 113S itself, thereby further strengthening the entanglement of the fiber agglomerates 11 intertwined with each other via the extending fiber bundle portion 113S, or between the fiber agglomerates 11 and the water-absorbent fibers 12F. Furthermore, when the extended fiber bundle portion 113S has a heat-fused portion, there is an advantage that the strength and shape retention of the extended fiber bundle portion 113S itself are increased not only when the extended fiber bundle portion 113S is in a dry state but also when it has absorbed water and is in a wet state. Due to this advantage, when the absorbent core 40 is applied to an absorbent article, the effects resulting from the presence of the fiber agglomerates 11 described above can be stably achieved not only when the absorbent core 40 is in a dry state but also when it has absorbed bodily fluids such as urine or menstrual blood excreted by the wearer and is in a wet state. Such extended fiber bundle portions 113S having heat-fused portions can be manufactured by using the "fiber sheet having heat-fused portions between constituent fibers" as the raw fiber sheet 10bs in the manufacturing process of the fiber agglomerates 11 as shown in FIG. 6 , i.e., in the cutting process of the raw fiber sheet 10bs of the fiber agglomerates 11.

[0078] The constituent fibers 11F of the fiber agglomerates 11 include "weakly absorbent" fibers that have lower absorbency than the absorbent fibers 12F. The weakly absorbent fibers used as the fibers 11F are preferably weakly absorbent synthetic fibers. Because the constituent fibers 11F of the fiber agglomerates 11 are weakly absorbent, the aforementioned effects (such as improved shape retention, flexibility, cushioning, compression recovery, and resistance to twisting) attributable to the presence of the fiber agglomerates 11 are stably achieved not only when the absorbent core 40 is dry, but also when the absorbent core 40 is wet after absorbing moisture (body fluids such as urine or menstrual blood). The content of the weakly absorbent fibers as the constituent fibers 11F in the fiber agglomerates 11 is preferably 90% by mass or more relative to the total mass of the fiber agglomerates 11, and most preferably 100% by mass, i.e., the fiber agglomerates 11 are formed solely from weakly absorbent fibers. In particular, when the weakly absorbent fibers as the constituent fibers 11F are non-absorbent fibers, the aforementioned effects attributable to the presence of the fiber agglomerates 11 are more stably achieved.

[0079] As used herein, the term "absorbency" is readily understood by those skilled in the art, such as the fact that pulp is absorbent. Similarly, it is easily understood that thermoplastic fibers are weakly absorbent compared to pulp, but are also non-absorbent. Meanwhile, the degree of absorbency of a fiber can be measured by the moisture content measured by the following method, which allows the relative difference in absorbency (the difference between absorbent fibers and fibers with weaker absorbency) to be compared and a more preferable range to be defined. The higher the moisture content, the stronger the absorbency of the fiber. Absorbent fibers according to the present invention preferably have a moisture content of 6% or more, more preferably 10% or more. Meanwhile, weakly hydrophilic fibers according to the present invention preferably have a moisture content of less than 6%, more preferably less than 4%. A moisture content of less than 6% can be determined as a non-absorbent fiber. In other words, non-absorbent fibers are preferred as weakly hydrophilic fibers according to the present invention.

[0080] <Method for Measuring Moisture Recoveries> The moisture recoveries were calculated according to the moisture recoveries test method of JIS P8203. Specifically, a fiber sample was left standing in a test room at a temperature of 40°C and a relative humidity of 80% RH for 24 hours, and then the weight W (g) of the fiber sample before the oven-drying treatment was measured in the same room. The fiber sample was then placed in an electric dryer (e.g., manufactured by Isuzu Motors Co., Ltd.) at a temperature of 105±2°C for 1 hour to perform the oven-drying treatment. After the oven-drying treatment, the fiber sample was wrapped in Saran Wrap (registered trademark) manufactured by Asahi Kasei Corporation and placed in a glass desiccator (e.g., manufactured by Techjam Co., Ltd.) under standard conditions of a temperature of 20±2°C and a relative humidity of 65±2%. The fiber sample was then placed in a glass desiccator (e.g., manufactured by Techjam Co., Ltd.) with Si silica gel (e.g., manufactured by Toyota Chemical Industry Co., Ltd.) and allowed to stand until the temperature reached 20±2°C. The constant weight W' (g) of the fiber sample was then weighed, and the moisture recoveries of the fiber sample were calculated using the following formula: Moisture content (%) = (W-W' / W') x 100

[0081] Similarly, from the viewpoint of enabling the absorbent core 40 to exhibit excellent effects in terms of shape retention, flexibility, cushioning, compression recovery, resistance to twisting, etc. in both dry and wet states, it is preferable that the fiber mass 11 has a three-dimensional structure in which multiple thermoplastic fibers are heat-fused to each other.

[0082] Furthermore, in order to obtain such fiber agglomerates 11 in which a plurality of heat-fused portions are three-dimensionally dispersed, thermoplastic fibers are preferably used as the non-water-absorbent synthetic fibers used as the constituent fibers 11F of the fiber agglomerates 11. As described above, it is preferable that the extended fiber bundle portions 113S have heat-fused portions, and by using thermoplastic fibers as the constituent fibers 11F of the fiber agglomerates 11, it is possible to obtain a preferred form of the extended fiber bundle portions 113S.

[0083] In order to obtain a fiber agglomeration 11 in which a plurality of heat-fused portions are dispersed three-dimensionally, the raw fiber sheet 10bs (see FIG. 6) needs only to be similarly configured. Furthermore, as described above, the raw fiber sheet 10bs in which a plurality of heat-fused portions are dispersed three-dimensionally can be produced by subjecting a web or nonwoven fabric primarily made of thermoplastic fibers to a heat treatment such as hot air treatment.

[0084] Examples of suitable thermoplastic resins, which are non-absorbent synthetic resins, for the constituent fibers 11F of the fiber agglomeration 11 include polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate; polyamides such as nylon 6 and nylon 66; polyacrylic acid, polymethacrylic acid alkyl esters, polyvinyl chloride, and polyvinylidene chloride. These can be used alone or in combination. The fibers 11F may be single fibers made of a single thermoplastic resin or a blend polymer of two or more synthetic resins containing a thermoplastic resin, or may be composite fibers. The composite fiber referred to here is a synthetic fiber (thermoplastic fiber) obtained by combining two or more synthetic resins with different components in a spinneret and simultaneously spinning them. The multiple components are continuous in the fiber length direction and bonded to each other within the single fiber. The composite fiber configuration may be a core-sheath type, a side-by-side type, or the like, and is not particularly limited.

[0085] Furthermore, it is preferable that the fiber mass 11 has a contact angle with water of less than 90 degrees, particularly 70 degrees or less, as measured by the method described below, from the viewpoint of further improving the ability to draw in body fluids during initial excretion. Such fibers can be obtained by treating the above-mentioned weakly water-absorbent fibers, preferably non-water-absorbent fibers, with a hydrophilizing agent in a conventional manner. A conventional surfactant can be used as the hydrophilizing agent.

[0086] <Method for measuring contact angle> Fibers are removed from the measurement object (absorbent core, fiber mass), and the contact angle of water with the fiber is measured. An automatic contact angle meter MCA-J manufactured by Kyowa Interface Science Co., Ltd. is used as the measuring device. Deionized water is used to measure the contact angle. The amount of liquid ejected from the inkjet water droplet ejection unit (CTC-25 pulse injector with an ejection orifice diameter of 25 μm manufactured by Cluster Technology Co., Ltd.) is set to 20 picoliters, and the water droplets are dropped directly onto the fiber. The dropping behavior is recorded on a high-speed recording device connected to a horizontally placed camera. From the perspective of later image analysis, a personal computer equipped with a high-speed capture device is preferable as the recording device. In this measurement, images are recorded every 17 msec. In the recorded video, the first image of the water droplet landing on the fiber was analyzed using the accompanying software FAMAS (software version 2.6.2, analysis method: sessile drop method, analysis method: θ / 2 method, image processing algorithm: non-reflective, image processing image mode: frame, threshold level: 200, curvature correction: no), and the angle between the surface of the water droplet in contact with the air and the fiber was calculated, which was taken as the contact angle. The fiber removed from the measurement target was cut to a fiber length of 1 mm and placed on the sample stage of the contact angle meter and maintained horizontally. The contact angle was measured at two different locations for each fiber. The contact angles of N = 5 fibers were measured to one decimal place, and the average value (rounded to two decimal places) of the measured values ​​at a total of 10 locations was defined as the contact angle of the fiber with water. The measurement environment was a room temperature of 22 ± 2 °C and a humidity of 65 ± 2% RH.

[0087] When the absorbent body (absorbent core) to be measured is used as a component of another article such as an absorbent article, and the absorbent body is removed for evaluation and measurement, if the absorbent body is fixed to the other component by adhesive, fusion, etc., the adhesive force is removed from the fixed part by a method such as spraying cold air from a cold spray to an extent that does not affect the contact angle of the fibers, and then the absorbent body is removed. This procedure is common to all measurements in this specification.

[0088] The absorbent fiber 12F may be any absorbent fiber conventionally used as a material for forming the absorbent body of this type of absorbent article, and examples thereof include natural fibers such as wood pulp, such as softwood pulp or hardwood pulp, and non-wood pulp, such as cotton pulp or hemp pulp; modified pulp, such as cationized pulp or mercerized pulp; and the like. One of these fibers may be used alone, or two or more may be mixed together. Among the absorbent fibers, cellulose-based absorbent fibers are particularly preferred.

[0089] In the absorbent core 40, the mass content ratio of the fiber agglomerates 11 to the absorbent fibers 12F is not particularly limited and may be adjusted appropriately depending on the types of the constituent fibers (weakly absorbent synthetic fibers) 11F and the absorbent fibers 12F of the fiber agglomerates 11. For example, if the constituent fibers 11F of the fiber agglomerates 11 are non-absorbent thermoplastic fibers and the absorbent fibers 12F are cellulose-based absorbent fibers, the mass content ratio of the fiber agglomerates 11 to the absorbent fibers 12F, in terms of the former (fiber agglomerates 11) / the latter (absorbent fibers 12F), is preferably 20 / 80 to 80 / 20, and more preferably 40 / 60 to 60 / 40, from the viewpoint of more reliably achieving the desired effects of the present invention.

[0090] The content of fiber agglomerates 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, and more preferably 60% by mass or less, relative to the total mass of the absorbent core 40 in a dry state. The content of 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 or less, and more preferably 60% by mass or less, relative to the total mass of the absorbent core 40 in a dry state.

[0091] The basis weight of the fiber agglomerates 11 in the absorbent core 40 is preferably 32 g / m ２ More preferably, 80 g / m ２ or more, and preferably 640 g / m ２ More preferably 480 g / m or less ２ The basis weight of the water-absorbent fiber 12F in the absorbent core 40 is preferably 32 g / m ２ More preferably, 80 g / m ２or more, and preferably 640 g / m ２ More preferably 480 g / m or less ２ The following is the result.

[0092] The absorbent core 40 may contain components other than the fiber agglomerates 11 and the absorbent fibers 12F, such as absorbent polymers. Particulate absorbent polymers are generally used as absorbent polymers, but fibrous ones may also be used. When particulate superabsorbent polymers are used, they may be spherical, lumpy, bale-shaped, or irregular in shape. The average particle diameter of the absorbent polymer is preferably 10 μm or more, more preferably 100 μm or more, and preferably 1000 μm or less, and even more preferably 800 μm or less. Polymers or copolymers of acrylic acid or alkali metal acrylates can generally be used as absorbent polymers. Examples include polyacrylic acid and its salts, and polymethacrylic acid and its salts.

[0093] The content of the water-absorbent polymer in the absorbent core 40 is preferably 5% by mass or more, more preferably 10% by mass or more, and preferably 60% by mass or less, more preferably 40% by mass or less, based on the total mass of the absorbent core 40 in a dry state. The basis weight of the water-absorbent polymer in the absorbent core 40 is preferably 10 g / m ２ More preferably, 30 g / m ２ or more, and preferably 100 g / m ２ More preferably 70 g / m or less ２ The following is the result.

[0094] The basis weight of the absorbent core 40 may be adjusted as appropriate depending on the intended use, etc. For example, when the absorbent core 40 is intended for use as an absorbent body in an absorbent article such as a disposable diaper or sanitary napkin, the basis weight of the absorbent core 40 is preferably 100 g / m ２ More preferably, 200 g / m ２ or more, and preferably 800 g / m ２ More preferably 600 g / m or less ２ The following is the result.

[0095] The absorbent core 40 having the above-described configuration and an absorbent article such as a napkin 1 including the absorbent core 40 are flexible and have excellent cushioning properties, as well as excellent compression recovery properties, deforming responsively to external forces and quickly returning to their original state when the external forces are released. The characteristics of an absorbent article including such an absorbent body (absorbent core) can be evaluated using the compression work (WC) and recovery work (WC') as measures. The compression work is a measure of the cushioning properties of an absorbent article, and the higher the WC value, the higher the cushioning properties can be evaluated. The recovery work is a measure of the degree of recovery when the absorbent article is compressed and released from the compressed state, and the higher the WC' value, the higher the compression recovery properties can be evaluated. Furthermore, considering the role of the absorbent core 40 in absorbing and retaining liquid, it is preferable that the absorbent article have high WC and WC' values ​​not only in a dry state but also when it becomes wet after absorbing body fluids or the like. In order for the absorbent article to have such properties in a wet state, it is effective to use non-water-absorbent synthetic fibers such as thermoplastic fibers as the constituent fibers 11F of the fiber agglomerates 11, as described above.

[0096] The absorbent article preferably has a dry compression work (d-WC) of 80 mN cm / cm ２ More preferably, 90 mN cm / cm ２ or more, and preferably 150 mN cm / cm ２ More preferably, 110 mN cm / cm or less ２ The work of compression (w-WC) of the absorbent article in a wet state is preferably 70 mN cm / cm ２ More preferably, 80 mN cm / cm ２ or more, and preferably 150 mN cm / cm ２ More preferably, 110 mN cm / cm or less ２ The following is the result.

[0097] The recovery work (d-WC') of the absorbent article in a dry state is preferably 34 mN cm / cm ２ More preferably, 44 mN cm / cm ２ or more, and preferably 150 mN cm / cm ２More preferably 60 mN cm / cm or less ２ The work of recovery (w-WC') of the absorbent article in a wet state is preferably 15 mN cm / cm ２ More preferably, 25 mN cm / cm ２ or more, and preferably 150 mN cm / cm ２ More preferably 55 mN cm / cm or less ２ The following is the result.

[0098] <Method for measuring compression work (WC) and recovery work (WC')> It is generally known that the compression work (WC) and recovery work (WC') of an absorbent article can be expressed as measured values ​​using the KES (Kawabata Evaluation System) manufactured by Kato Tech Co., Ltd. (Reference: Standardization and Analysis of Texture Evaluation (2nd Edition), author Kawabata Toshio, published July 10, 1980). Specifically, the compression work and recovery work can be measured using an automated compression testing device KES-G5 manufactured by Kato Tech Co., Ltd. The measurement procedure is as follows. An "absorbent article (sanitary napkin) with an absorbent core" as a sample is attached to the test stand of the compression testing device. Next, the sample is placed on a surface of 2 cm2. ２ The specimen is compressed between steel plates with circular flat surfaces. The compression speed is 0.02 cm / sec, and the maximum compression load is 490 mN / cm. ２ The recovery process is also measured at the same speed. The compression work (WC) and recovery work (WC') are expressed by the following equations. ｍ , T ｏ and 490 mN / cm ２ Thickness under load: 4.9 mN / cm ２ It indicates the thickness under load. a is the load (mN / cm) during measurement (compression process) ２ ) to P b is the load (mN / cm) during measurement (recovery process) ２ ) is shown.

[0099]

[0100]

[0101] The "absorbent article with a dry absorbent body" that is the subject of the measurement method is prepared by leaving the dry absorbent article for 24 hours in an environment with a temperature of 23° C. and a relative humidity of 50% RH. The "absorbent article with a wet absorbent body" that is the subject of the measurement method is prepared by placing the dry absorbent article horizontally with the topsheet side (skin-facing side) facing up, placing an oval injection port (major axis 50 mm, minor axis 23 mm) on the topsheet, injecting 3.0 g of defibered horse blood through the injection port, leaving it to stand for 1 minute, and then injecting another 3.0 g of defibered horse blood and maintaining the state for 1 minute after injection. The defibered horse blood injected into the measurement subject was defibered horse blood manufactured by Nippon Biotest Co., Ltd. and adjusted to a viscosity of 8 cp at a liquid temperature of 25°C. This viscosity was measured using a TVB-10M viscometer manufactured by Toki Sangyo Co., Ltd., with a rotor named L / Adp (rotor code 19) at a rotation speed of 12 rpm.

[0102] The absorbent core 40 can be manufactured in the same manner as absorbent cores (absorbents) containing this type of fiber material. As described above, the fiber agglomerates 11 can be manufactured by cutting a raw fiber sheet (a sheet having the same composition as the fiber agglomerates 11 but larger in size than the fiber agglomerates 11) in two intersecting (orthogonal) directions using a cutting means such as a cutter, as shown in Figure 6. The multiple fiber agglomerates 11 manufactured in this manner are "fixed-form fiber aggregates" with uniform shapes and sizes (for example, the main body portion 110 is rectangular). The absorbent core 40 containing the fiber agglomerates 11 and absorbent fibers 12F can be manufactured in the usual manner using, for example, a known fiber stacking device equipped with a rotating drum. Such a fiber stacking device typically comprises a rotating drum having an accumulation recess formed on its outer peripheral surface, and a duct having an internal flow path for transporting the raw materials of the absorbent core 40 (fiber mass 11, absorbent fibers 12F) to the accumulation recess.The rotating drum is rotated around its rotation axis along the drum circumferential direction, and the raw materials transported on an air flow (vacuum air) generated in the flow path by suction from the inside of the rotating drum are stacked in the accumulation recess.

[0103] While the present invention has been described above based on the embodiments, it is not limited to these embodiments and can be modified as appropriate. For example, in the absorbent core of the present invention, the fiber agglomerates do not need to be uniformly dispersed throughout the absorbent core, but may be unevenly distributed. An example of an absorbent core with unevenly distributed fiber agglomerates is a laminated structure consisting of a layer primarily composed of fiber agglomerates and a layer primarily composed of absorbent fibers. Furthermore, the absorbent core of the present invention does not need to contain all of the fiber agglomerates (weakly absorbent synthetic fiber aggregates) as regular fiber aggregates like fiber agglomerates 11. Within the scope of the present invention, a small amount of irregular fiber aggregates may be included in addition to such regular fiber aggregates. The absorbent article of the present invention broadly encompasses articles used to absorb body fluids (urine, loose stool, menstrual blood, sweat, etc.) discharged from the human body, and includes, in addition to the sanitary napkin described above, sanitary shorts, so-called flat-type disposable diapers with fastening tape, pants-type disposable diapers, incontinence pads, etc. The following supplementary notes are further disclosed regarding the above-described embodiment of the present invention.

[0104] <1> An absorbent article having a longitudinal direction corresponding to the front-to-back direction of a wearer and a lateral direction perpendicular thereto, comprising an absorbent body and a topsheet arranged on the skin-facing side of the absorbent body, wherein the absorbent body is configured to include a liquid-absorbent core and a core wrap sheet covering the skin-facing side of the absorbent core, the absorbent core including a fiber mass containing absorbent fibers and weakly absorbent fibers having lower water absorption properties than the absorbent fibers, wherein the ratio of the liquid diffusion area of ​​the absorbent core measured by the method below to the liquid diffusion area of ​​the core wrap sheet measured by the method below, expressed as the former / the latter, is 0.7 or more. <Method for measuring liquid diffusion area> A measurement object is fixed on an inclined plane at an angle of 45° to the horizontal plane, with its skin-facing side facing the inclined plane, and 1.5 g of defibered horse blood is injected onto the skin-facing side of the measurement object over 23 seconds. After leaving it for 3 minutes, the same amount of defibered horse blood is again injected into the same injection site over the same period of time. This injection and leaving procedure of defibered horse blood is repeated six times, and a total of 9 g of defibered horse blood is injected into the measurement object. After completion of the injection procedure, the diffusion area of ​​the defibered horse blood on the skin-facing surface of the measurement object is measured and defined as the liquid diffusion area of ​​the measurement object. <2> The absorbent article according to <1>, wherein the core wrap sheet is a porous sheet mainly made of pulp. <3> The absorbent article according to <1> or <2>, wherein the skin-facing surface of the absorbent body is partially formed with a recessed portion, in which the core wrap sheet and the absorbent core are integrally recessed on the non-skin-facing surface side of the absorbent body. <4> The absorbent article according to <3>, wherein the absorbent article is divided in the longitudinal direction into a longitudinal central region including an excretory-part-facing portion facing the wearer's excretory part, a front region located closer to the wearer's ventral side than the excretory-part-facing portion, and a rear region located closer to the wearer's dorsal side than the excretory-part-facing portion, and the recessed portion is formed to surround the lateral center of the longitudinal central region. <5> The absorbent article according to any one of <1> to <4>, wherein the fiber mass has a rectangular parallelepiped or disc-like outer shape.

[0105] <6> The absorbent article according to any one of <1> to <5>, wherein the fiber agglomerates have a main body portion with a relatively high fiber density and extended fiber portions present around the main body portion and having a lower fiber density than the main body portion, wherein the plurality of fiber agglomerates are entangled with one another and the fiber agglomerates and the water-absorbent fibers are entangled with one another. <7> The absorbent article according to <6>, wherein the main body portion has two opposing basic surfaces and a skeletal surface connecting the two basic surfaces, and the basic surface has a quadrangular shape in a plan view. <8> The absorbent article according to <7>, wherein the total area of ​​the two basic surfaces is greater than the total area of ​​the skeletal surface. <9> The absorbent article according to <7> or <8>, wherein the fiber agglomerates have extended fiber bundle portions including a plurality of fibers extending outward from the skeletal surface. <10> The absorbent article according to <9>, wherein the extended fiber bundle portions have portions where a plurality of fibers are heat-fused to one another. <11> The absorbent article according to <9> or <10>, wherein the extension length of the extended fiber bundle portion from the main body portion, preferably the extension length from the skeletal surface, is 0.05 mm or more and 7 mm or less, preferably 0.15 mm or more and 4 mm or less. <12> The absorbent article according to any one of <7> to <11>, wherein the basic surface has a rectangular shape in a plan view, and the short side of the rectangular shape is shorter than the thickness of the absorbent body. <13> The absorbent article according to <12>, wherein the ratio of the length of the short side of the basic surface to the thickness of the absorbent body, as the former / latter, is 0.03 or more and 1 or less, preferably 0.08 or more and 0.5 or less. <14> The absorbent article according to <12> or <13>, wherein the length of the short side of the basic surface is 0.3 mm or more and 10 mm or less, preferably 0.5 mm or more and 6 mm or less. <15> The absorbent article according to any one of <12> to <14>, wherein the length of the long side of the basic surface is 0.3 mm or more and 30 mm or less, preferably 2 mm or more and 15 mm or less. <16> The number N of fiber ends present on the basic surface per unit area １ and the number N of fiber ends per unit area present on the skeletal surface. ２ Ratio to N １ / N ２<17> The absorbent article according to any one of <7> to <15>, wherein the number of fiber ends present on the basic plane per unit area is 0 pieces / mm ２ Above, 8 pieces / mm ２ Preferably 3 or less per mm ２ Above, 6 pieces / mm ２ <18> The absorbent article according to any one of <7> to <16>, wherein the number of fiber ends present on the skeletal surface per unit area is 5 / mm ２ Above, 50 pieces / mm ２ Preferably 8 pieces / mm or less ２ Above, 40 pieces / mm ２ The absorbent article according to any one of <7> to <17>, which is:

[0106] <19> The absorbent article according to any one of <1> to <18>, wherein the fiber agglomerates have a three-dimensional structure in which a plurality of thermoplastic fibers are thermally fused to one another. <20> The absorbent article according to any one of <1> to <19>, wherein the mass ratio of the fiber agglomerates to the absorbent fibers, as the former / the latter, is 20 / 80 to 80 / 20. <21> The absorbent article according to any one of <1> to <20>, wherein the fiber agglomerates are bonded to other fiber agglomerates or the absorbent fibers by entanglement in the absorbent body, and also exist in a state in which they can be entangled with other fiber agglomerates or the absorbent fibers. <22> The absorbent article according to any one of <1> to <21>, wherein 70% or more, preferably 80% or more of the total number of fiber agglomerates having bonding portions with other fiber agglomerates or the absorbent fibers, the bonding portions are formed by fiber entanglement. <23> The absorbent article according to any one of <1> to <22>, wherein the fiber agglomerates are derived from a nonwoven fabric. <24> The density of the core wrap sheet is 0.1 g / m ３ <25> The absorbent article according to any one of <1> to <23>, wherein the density of the core wrap sheet is 0.1 g / m or less. ３ or less, preferably 0.08 g / m ３ or less, and 0.02 g / m ３ or more, preferably 0.04 g / m ３<26> The absorbent article according to any one of <1> to <24>, wherein the core wrap sheet has a basis weight of 50 g / m ２ Preferably 30 g / m or less ２ and 5 g / m ２ or more, preferably 10 g / m ２ The absorbent article according to any one of <1> to <25> above.

[0107] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0108] Examples 1 and 2 Sanitary napkins were produced with the same structure as the napkin 1 shown in FIG. ２ An air-through nonwoven fabric of 37 g / m was used as the back sheet. ２ The absorbent body was manufactured in a conventional manner using a known fiber stacking device, using the fiber agglomerates and absorbent fibers as the fiber material for the absorbent core, and a separately prepared core wrap sheet. The fiber agglomerates were manufactured by cutting the raw fiber sheet into a dice pattern, as shown in Figure 7. The raw fiber sheet for the fiber agglomerates was manufactured using thermoplastic fibers (fiber diameter 18 μm) made of polyethylene resin and polyethylene terephthalate resin, with a basis weight of 21 g / m. ２ An air-through nonwoven fabric (a fiber sheet having heat-fused portions between constituent fibers) of this type was used. Softwood bleached kraft pulp (NBKP) with a fiber diameter of 22 μm was used as the absorbent fiber. The fiber mass (a fixed-shaped synthetic fiber aggregate) used in the absorber had a rectangular parallelepiped main body as shown in FIG. 5(a), with the short side 111a of its basic surface 111 being 0.8 mm, the long side 111b being 3.9 mm, and the thickness T being 0.6 mm. The number of fiber ends per unit area on the basic surface 111 was 3.2 / mm. ２ , the number of fiber ends per unit area on the skeletal surface 112 is 19.2 pieces / mm ２ The basis weight of the absorbent body was 350 g / m ２ The thickness was 5.7 mm.

[0109] Details of the core wrap sheet (the porous sheet) used in Examples 1 and 2 are as follows: (Core wrap sheet of Example 1) Made of softwood bleached kraft pulp (NBKP), basis weight: 13.5 g / m ２ , Density: 0.092g / cm ３ (Core wrap sheet of Example 2) A mercerized softwood bleached kraft pulp (NBKP) with a circularity of 0.80 and a basis weight of 16.0 g / m ２ , Density: 0.069g / cm ３ The paper used was:

[0110] Comparative Example 1 A commercially available sanitary napkin (manufactured by Unicharm Corporation, product name "Tanom Pew Slim 23 cm") was used as is as Comparative Example 1. The absorbent body in the sanitary napkin of Comparative Example 1 was a mixture of synthetic fibers (weakly absorbent fibers) and cellulosic fibers (absorbent fibers), and did not contain fiber clumps.

[0111] Comparative Example 2: A sanitary napkin was prepared in the same manner as in Example 1, except that the absorbent body was changed as follows. The absorbent body used in Comparative Example 2 was the same as that used in Example 1, except that irregular nonwoven fabric pieces were used as the fiber masses in the absorbent core, and the absorbent core was covered with a core wrap sheet and then subjected to hot air treatment to thermally fuse the nonwoven fabric pieces contained in the absorbent core to each other. In the hot air treatment applied to the absorbent body, a mixed assembly (240 mm long x 75 mm wide) of nonwoven fabric pieces and pulp fibers was left to stand in an electric dryer (e.g., manufactured by Isuzu Motors Ltd.) at 150°C for 10 minutes to thermally fuse the nonwoven fabric pieces to each other. The irregular nonwoven fabric pieces used were prepared by tearing the same air-through nonwoven fabric used in Example 1 in any direction, and their diameter in plan view was approximately 25 mm.

[0112] [Comparative Example 3] A sanitary napkin was prepared in the same manner as in Example 1, except that the absorbent body was changed to the following, and designated Comparative Example 3. The absorbent body used in Comparative Example 3 did not contain fiber agglomerates in the absorbent core, and was composed only of the water-absorbent fibers. The core wrap sheet (the porous sheet) had a basis weight of 16.0 g / m ２ , density 0.102g / cm３ Bleached softwood kraft pulp (NBKP) was used.

[0113] [Performance Evaluation] For each of the sanitary napkins of the Examples and Comparative Examples, the liquid diffusion areas of the absorbent core and the skin-side core wrap sheet were measured using the method described above, and the liquid diffusion area ratio (liquid diffusion area of ​​the absorbent core / liquid diffusion area of ​​the core wrap sheet) was calculated based on the measured values. Furthermore, the compression work (WC) and recovery work (WC') were measured using the method described above, and cushioning properties and compression recovery properties were evaluated based on these measured values. The results are shown in Table 1 below.

[0114]

[0115] As shown in Table 1, each Example has multiple fiber agglomerates that are entangled with each other and a liquid diffusion area ratio (liquid diffusion area of ​​the absorbent core / liquid diffusion area of ​​the core wrap sheet) of 0.7 or more. Compared with Comparative Examples 1 to 3, which are conventional techniques that do not satisfy these requirements, the Examples have larger values ​​for compression work (WC) and recovery work (WC') in both dry and wet states, resulting in excellent cushioning and compression recovery in both states. Furthermore, each Example has a liquid diffusion area ratio within the specified range, resulting in excellent liquid permeability from the topsheet through the skin-side core wrap sheet to the absorbent core. Therefore, each Example was less likely to retain body fluid on the skin-facing side of the absorbent body after excretion.

[0116] The absorbent article of the present invention includes an absorbent core having high cushioning properties and liquid permeability, and therefore, with the absorbent article of the present invention, body fluids are less likely to remain on the skin-facing side of the absorbent core after excretion, reducing unpleasant stickiness and wetness on the skin, and it is expected to have excellent wearing comfort and fit.

Claims

DEPCT641. An absorbent product whose longitudinal direction perfectly overlaps the wearer's front-to-back direction and whose transverse direction is perpendicular to the longitudinal direction, consisting of an absorbent element and a top sheet provided on the skin-facing surface of the absorbent element, where the absorbent element includes a liquid-absorbing core and a core wrap sheet superimposed on the skin-facing surface of the absorbent core. The absorbent core includes conductive absorbent fibers and a group of fibers containing low-water-absorbing fibers with lower water absorption than the water-absorbing fibers. The ratio of the liquid diffusion area of ​​the absorbent core to the liquid diffusion area of ​​the core wrap sheet, liquid diffusion area of ​​the absorbent core / liquid diffusion area of ​​the core wrap sheet, is 0.7 or greater, and the liquid diffusion area is determined by the method described below: <Method for measuring the liquid diffusion area> The object of measurement is fixed on a slope at an angle of 45 degrees to the horizontal plane, with the skin-facing surface of the object of measurement facing the slope from the skin-facing surface of the object of measurement, 1.5 grams of defibrinized horse blood were injected for 23 seconds; subsequently, the object of measurement was allowed to sit for 3 minutes, and 1.5 grams of defibrinized horse blood were injected from exactly the same injection site for 23 seconds; this injection and sitting operation of defibrinized horse blood was repeated 6 times, and a total of 9 grams of defibrinized horse blood was injected into the object of measurement. After the injection operation was complete, the diffusion area of ​​defibrinized horse blood on the skin-facing surface of the object of measurement was determined as the diffusion area of ​​the fluid of the object of measurement.

2. The absorbent product according to claim 1 where the core wrap is a porous sheet primarily composed of membrane.

3. The absorbent product according to claim 1 or 2 where the skin-facing surface of the absorbent component has a partial recess formed by the combined pressure of the core wrap and the absorbent core to the non-skin-facing surface of the absorbent component. 4.

4. Any absorptive product under Recourse 1 through 4 where the absorptive product is divided in the longitudinal direction into longitudinal central regions, which include an area facing the wearer's secretions, an anterior region placed closer to the wearer's abdomen than the area facing the secretions, and a posterior region placed closer to the wearer's back than the area facing the secretions, and a retractable portion is formed to enclose the transverse central region in the longitudinal central region.

5. Any absorptive product under Recourse 1 through 4 where the outer shape of the fiber mass is a rectangular parallelogram or disc shape.

6. Any absorptive product under Recourse 1 through 5 where the fiber mass has a main body with a higher fiber density and, around the main body, extended fiber portions with a lower fiber density than the fiber density of the main body; a number of fiber masses are intertwined with each other and fiber masses are intertwined with water-absorbing fibers. 7.

8. An absorbent product under claim 6 where the main body has two opposing base surfaces and the body surface is connected to the two base surfaces and the base surfaces are rectangular in planar view.

9. An absorbent product under claim 7 where the total area of ​​the two base surfaces is greater than the total area of ​​the body surface.

10. An absorbent product under claim 7 or 8 where the fiber bundle has an extended fiber bundle that extends from the body surface and contains a certain number of fibers.

11. An absorbent product under claim 9 where the extended fiber bundle has a portion where a certain number of fibers are fused together.

11. An absorbent product under claim 9 or 10 where the extended length of the fiber bundle extending from the main body is 0.05 mm or more and 7 mm or less.

12. Any one of the absorbent products under claims 7 through 11 where the base surfaces are rectangular in planar view and the short side of the rectangle is shorter than the thickness of the absorbent component. 13.

14. Absorbent products under claim 12 where the ratio of the length of the short side of the base surface to the thickness of the absorbent component, length / thickness, is 0.03 or more and 1 or less.

15. Absorbent products under claim 12 to 14 where the long side of the base surface is 0.3 mm or more and 10 mm or less.

16. Absorbent products under claim 7 to 15 where the ratio of the number of fiber ends in a unit area on the base surface, N1, to the number of fiber ends in a unit area on the body surface, N2, N1 / N2 is 0 or more and 0.90 or less.

17. Absorbent products under claim 7 to 16 where the number of fiber ends in a unit area on the base surface is 0 fiber ends / square millimeter or more and 8 fiber ends / square millimeter or less. 18.

18. Any absorbent product under claims 7 through 17 where the number of fiber ends in a unit area on the body surface is 5 fiber ends / sq mm or more and 50 fiber ends / sq mm or less.

29. Any absorbent product under claims 1 through 18 where the fiber bundles have a three-dimensional structure in which a number of thermoplastic fibers are fused together.

20. Any absorbent product under claims 1 through 19 where the mass ratio of the fiber bundles to the water-absorbing fibers, pre / post-absorbing material is 20 / 80 to 80 / 20.

21. Any absorbent product under claims 1 through 20 where in the absorbent assembly, fiber bundles are fused together or to the water-absorbing fibers by interlocking and can be interlocked with each other or with the water-absorbing fibers.

22. Any absorbent product under claims 1 through 21 where 70% or more of the fiber bundles that are fused together or with the water-absorbing fibers are fused by fiber interlocking. 23.

24. Any absorbent product under claims 1 through 23 in which the core wrap has a density of 0.1 g / m³ or less.

25. Any absorbent product under claims 1 through 24 in which the core wrap has a density of 0.02 g / m³ or more and 0.1 g / m³ or less.

26. Any absorbent product under claims 1 through 25 in which the core wrap has a base weight of 5 g / m³ or more and 50 g / m³ or less.