Absorbent

Abstract

[Problem] To improve retention of superabsorbent polymer particles of a hardwood pulp fiber-containing absorber. [Solution] The above problem is solved by an absorbent article, which is provided with an absorbent element 50 having an absorbent body 56 and a wrapping sheet 58 wrapping the absorbent body 56. The absorbent body 56 is formed by mixing and integrating pulp fibers and superabsorbent polymer particles. The proportion of particles having a smaller particle diameter before swelling than the average fiber length of the hardwood pulp fibers in the superabsorbent polymer particles 56p is 60 mass% or more. In the absorbent element 50, a plurality of highly compressed portions 51 are arranged at intervals, wherein the plurality of highly compressed portions 51 are compressed in the thickness direction TD so as to be recessed from the surface of the absorbent element 50 into the absorbent body 56. A portion other than the highly compressed portions 51 in a region where the plurality of highly compressed portions 51 are arranged is a non-highly compressed portion 52 that is thicker and has a lower density than the highly compressed portions 51. Each of the highly compressed portions 51 has a shortest distance to the closest other highly compressed portion 51 of 1 to 4 mm, and an area of each of the highly compressed portions 51 is 2 to 200 mm2.

Description

absorbent articles

[0001] The present invention relates to absorbent articles such as disposable diapers, sanitary napkins, incontinence pads, panty liners (panty liners), and the like.

[0002] The absorbent body (also referred to as an absorbent core, etc.) of an absorbent article generally contains pulp fibers and superabsorbent polymer particles. As the pulp fibers, softwood pulp (NBKP) fibers (pulp fibers derived from softwood) have been widely used. However, in recent years, the use of hardwood pulp (LBKP) fibers (pulp fibers derived from hardwood) has also been considered because hardwood pulp fibers are relatively cheaper than softwood pulp fibers (see, for example, Patent Documents 1 and 2).

[0003] However, absorbents made by mixing and accumulating pulp fibers containing both hardwood pulp fibers and softwood pulp fibers with superabsorbent polymer particles have the problem that they have lower retention of superabsorbent polymer particles (the superabsorbent polymer particles tend to move) compared to absorbents made by mixing and accumulating pulp fibers consisting only of softwood pulp fibers with superabsorbent polymer particles.

[0004] Japanese Patent Publication No. 2020-014646 Japanese Patent Publication No. 7293479

[0005] Therefore, a primary object of the present invention is to improve the retention of superabsorbent polymer particles in an absorbent body containing hardwood pulp fibers.

[0006] One aspect of an absorbent article that solves the above-mentioned problems is described below. <First Aspect> An absorbent article has a crotch area, and comprises an absorbent element having an absorbent body provided in a front-to-rear range including the crotch area, and a packaging sheet that wraps the absorbent body, wherein the absorbent body is formed by mixing and accumulating pulp fibers including hardwood pulp fibers and superabsorbent polymer particles, wherein the proportion of the superabsorbent polymer particles having a pre-swelling particle size smaller than the average fiber length of the hardwood pulp fibers is 60% by mass or more, wherein the absorbent element has a plurality of highly compressed portions compressed at intervals in the thickness direction so as to recess from at least one of the front and rear surfaces of the absorbent element into the absorbent body, wherein the portions other than the highly compressed portions in the area where the plurality of highly compressed portions are arranged are non-highly compressed portions that are thicker and have a lower density than the highly compressed portions, wherein the shortest distance between each of the plurality of highly compressed portions and the nearest other highly compressed portion is 1 to 4 mm, and wherein the area of ​​each highly compressed portion is 2 to 200 mm. ２ An absorbent article characterized by:

[0007] (Effects) The inventors discovered that in absorbents containing hardwood pulp fibers, the short fiber length of the hardwood pulp fibers makes it difficult for the pulp fibers to maintain entanglement, resulting in the increased mobility of superabsorbent polymer particles. Therefore, while a longer fiber length of the hardwood pulp fibers is preferable to prevent the migration of superabsorbent polymer particles, hardwood pulp fibers are naturally derived, and there are limitations to adjusting their characteristics, such as fiber length. Furthermore, reducing the amount of hardwood pulp fiber used is undesirable because it reduces cost benefits. In contrast, providing highly compressed sections with the area and spacing specified in this embodiment can improve the retention of superabsorbent polymer particles in absorbents containing hardwood pulp fibers, as is clear from the experimental results described below. In other words, the distance between pulp fibers is reduced in the highly compressed areas, which results in stronger entanglement of the pulp fibers, a reduction in the gaps between the pulp fibers that serve as paths for the movement of superabsorbent polymer particles, and an increase in the contact area between the pulp fibers and the superabsorbent polymer particles, thereby suppressing the movement of superabsorbent polymer particles within the absorbent body and the movement of superabsorbent polymer particles outside the absorbent body.

[0008] <Second Aspect> The absorbent article according to claim 1, wherein an area ratio of the highly compressed portions in an arrangement region of the plurality of highly compressed portions is 10 to 35%, and a diameter of a largest inscribed circle inscribed in an outer shape of the non-highly compressed portions is 30 mm or less.

[0009] (Effects) When the highly compressed portions are arranged particularly densely as in this embodiment, the movement of the superabsorbent polymer particles in the highly compressed portions is inhibited as described above, and the movement of the superabsorbent polymer particles in the non-highly compressed portions is blocked by the highly compressed portions, thereby suppressing uneven distribution of the superabsorbent polymer particles. This further improves the retention of the superabsorbent polymer particles. Furthermore, even in the non-highly compressed portions, the absorbent body deforms near the periphery of the highly compressed portions as if pulled by the deformation of the highly compressed portions, resulting in an advantage of a thinner absorbent body compared to a case in which the highly compressed portions are not present. From these perspectives, it is particularly preferable that the area ratio of the highly compressed portions is within the above-mentioned range, and that the diameter of the largest inscribed circle inscribed in the outer shape of the non-highly compressed portions is within the above-mentioned range so that the highly compressed portions are not sparsely arranged (so that the non-highly compressed portions do not continue for long periods in all directions). Conventionally, it has been considered undesirable to arrange the highly compressed portions densely, and therefore, adopting a dense arrangement of the highly compressed portions as in this embodiment does not fall within the scope of commonly performed optimization.

[0010] <Third Aspect> The absorbent article of the second aspect, wherein the highly compressed portion has an outer shape that does not have an inflection point or a bending point, the diameter of a largest inscribed circle inscribed in the outer shape of the highly compressed portion is 1 to 10 mm, and the circumferential length of the outer shape of the highly compressed portion is 1 to 15 times the circumferential length of the largest inscribed circle inscribed in the outer shape of the highly compressed portion.

[0011] (Effects) The dimensions and shape of the highly compressed portions can be determined as appropriate. However, because the highly compressed portions are hard, if the dimensions of the highly compressed portions are excessively large, if the shape of the highly compressed portions is excessively long in one direction, or if the shape is excessively complicated, the absorbent body as a whole may lack flexibility or may feel like a foreign object is mixed in the absorbent body (foreign body sensation). Therefore, it is preferable that the dimensions and shape of the highly compressed portions be within the range of this embodiment.

[0012] <Fourth Aspect> In an arrangement region of the plurality of highly compressed portions, first imaginary straight lines along a first direction are repeatedly arranged at first intervals in a second direction inclined by 80 to 90 degrees clockwise with respect to the first imaginary straight line in a plan view, and second imaginary straight lines along the second direction are repeatedly arranged at second intervals in the first direction to define a virtual lattice, and when a smallest virtual rectangle having vertices at intersections of the first imaginary straight line and the second imaginary straight line is defined, the highly compressed portions comprise first highly compressed portions arranged at the intersections of the first and second imaginary straight lines, second highly compressed portions arranged between adjacent first highly compressed portions on the first and second imaginary straight lines, respectively, and third highly compressed portions arranged at the intersections of diagonals of the virtual rectangle, and the first highly compressed portions form circles centered at the intersections of the first and second imaginary straight lines, The absorbent article of the second or third aspect, wherein the second highly compressed portion has a center of gravity at the midpoint of each side of the imaginary rectangle and is an ellipse or a rounded rectangle having a major axis along each side, and the third highly compressed portion has a center of gravity at the intersection of diagonals of the imaginary rectangle and is an ellipse or a rounded rectangle having a major axis along the front-to-rear direction, or a circle having a center at the intersection of diagonals of the imaginary rectangle.

[0013] (Effects) The shape and arrangement pattern of the highly compressed parts in the arrangement area of ​​the highly compressed parts may be determined as appropriate, but with the pattern of this type, the movement of the highly absorbent polymer particles in the non-highly compressed parts is restricted to the area surrounded by the highly compressed parts, so that uneven distribution of the highly absorbent polymer particles can be suppressed with fewer highly compressed parts, and since there are both parts where the non-highly compressed parts are linearly connected in the first direction and parts where the non-highly compressed parts are linearly connected in the second direction, even if the individual highly compressed parts harden, the absorbent body as a whole will be more likely to deform to fit the body surface.

[0014] <Fifth Aspect> The absorbent article of the fourth aspect, wherein the first highly compressed portion has a diameter of 1 to 4 mm, the second highly compressed portion has a major axis length of 3 to 6 mm and a minor axis length equal to the diameter of the first highly compressed portion, the third highly compressed portion has the same size and shape as the second highly compressed portion except that the major axis faces the front-to-rear direction, and the minimum distance between adjacent first and second highly compressed portions is 1 to 2 mm.

[0015] (Effects) When arranging the highly compressed portions along the virtual lattice described above, the dimensions of each highly compressed portion can be determined as appropriate, but it is preferable to set them within the range of this embodiment, as this not only improves the retention of the highly absorbent polymer particles, but also improves the ease of deformation of the absorbent body.

[0016] <Sixth Aspect> The absorbent article of the fourth or fifth aspect, wherein the virtual lattice has an oblique lattice pattern in which the first virtual straight lines are inclined by 40 to 50 degrees clockwise with respect to the front-to-rear direction in plan view, and the second virtual straight lines are inclined by 40 to 50 degrees counterclockwise with respect to the front-to-rear direction in plan view.

[0017] (Operation and Effect) When the highly compressed portions are arranged along a virtual lattice as described above, it is preferable to arrange them in a diagonal lattice pattern as in this embodiment, since this allows the absorbent body to be easily deformed when worn.

[0018] <Seventh Aspect> The basis weight of the pulp fibers in the absorbent body is 100 to 500 g / m ２ The absorbent article of any one of aspects 1 to 6, wherein the weight ratio of pulp fibers to superabsorbent polymer particles in the absorbent body is 40:60 to 65:35, the thickness of the non-highly compressed portion is 3 to 13 mm, and the thickness of the highly compressed portion is 60 to 90% of the thickness of the non-highly compressed portion.

[0019] (Effects) Generally, when improving backflow prevention, the mixing ratio of high-absorbent polymer particles with high liquid retention is often increased. In recent years, the mixing ratio of high-absorbent polymer particles is also often increased for the purpose of reducing the thickness of the absorbent body. However, increasing the mixing ratio of high-absorbent polymer particles tends to reduce the retention of the high-absorbent polymer particles. Therefore, it is preferable to set the blending ratio of pulp fibers and high-absorbent polymer particles in the absorbent body within the range of this embodiment and to perform compression formation of the highly compressed portion within the range of this embodiment.

[0020] <Eighth Aspect> The absorbent article of any one of the first to seventh aspects, wherein the proportion of particles having a particle size of 500 μm or less before swelling in the superabsorbent polymer particles is 60% by mass or more, and the proportion of pulp fibers having a fiber length of 0.5 mm or more and less than 1.1 mm is 40% by mass or more of all pulp fibers in the absorbent body, and the proportion of pulp fibers having a fiber width of 10 μm or more and less than 35 μm is 90% by mass or more.

[0021] (Effects) By combining hardwood pulp fibers with fibers having a longer average fiber length to achieve the fiber length distribution of the pulp fibers in this manner, the absorbent body can maintain its absorption capacity and absorption rate while also retaining the liquid retention ability of the fibers through capillary action, thereby improving backflow prevention. However, this alone leaves room for improvement in the retention of superabsorbent polymer particles. Therefore, it is preferable to combine it with the aforementioned highly compressed section to also improve the retention of superabsorbent polymer particles.

[0022] <Ninth Aspect> The absorbent article of the eighth aspect, wherein the pulp fibers of the absorbent body are made of softwood pulp fibers and hardwood pulp fibers, and the mass ratio of the hardwood pulp fibers to the softwood pulp fibers is 25 / 75 or more and 38 / 62 or less.

[0023] (Effects) As will be seen from the experimental examples described later, it is particularly preferable that the pulp fibers in the absorbent body be blended in this manner.

[0024] The present invention provides advantages such as improved retention of superabsorbent polymer particles in an absorbent body containing hardwood pulp fibers.

[0025] 1A is a plan view showing the inner surface of a pants-type disposable diaper in an unfolded state. FIG. 1B is a plan view showing the outer surface of a pants-type disposable diaper in an unfolded state. FIG. 2C is a cross-sectional view taken along line 2-2 of FIG. 1. FIG. 3C is a cross-sectional view taken along line 3-3 of FIG. 1. (a) A cross-sectional view taken along line 4-4 of FIG. 1, and (b) A cross-sectional view taken along line 5-5 of FIG. 1. FIG. 2C is a perspective view of a pants-type disposable diaper. FIG. 3D is a plan view showing the outer surface of an inner body in an unfolded state together with the outline of an outer body. FIG. 4D is a plan view showing the surface of an absorbent body together with the outline of a packaging sheet. FIG. 4E is a cross-sectional view of an absorbent element. FIG. 5 is a plan view of an absorbent element. FIG. 6 is a plan view showing an enlarged view of a main portion of the surface of an absorbent element. FIG. 7 is a plan view showing another example of an absorbent body. FIG. 8 is a cross-sectional view showing an absorbent element in a state before the absorbent body is wrapped in a packaging sheet. FIG. 9 is a cross-sectional view showing an absorbent element in a state after the absorbent body is wrapped in a packaging sheet and before a highly compressed portion is formed. FIG. 10 is a cross-sectional view of another absorbent element. FIG. 11 is a plan view showing an enlarged view of a main portion of the surface of an absorbent element. FIG. 12 is a plan view showing an enlarged view of a main portion of the surface of an absorbent element. FIG. 1 is a plan view showing an enlarged view of a main part of the surface of an absorbent element. FIG. 2 is a plan view showing an enlarged view of a main part of the surface of an absorbent element. FIG. 3 is a schematic view showing a manufacturing method of an absorbent element. FIG. 4 is an explanatory diagram of a method for measuring the depth of a highly compressed part. FIG. 5 is a cross-sectional view showing various absorbents. FIG. 6 is a schematic view showing an example of manufacturing equipment for an absorbent element. FIG. 7 is a schematic view showing an example of manufacturing equipment for an absorbent element. FIG. 8 is a side view showing a schematic view of a beat-up tester. FIG. 9 is a front view showing a schematic view of a beat-up tester.

[0026] A pants-type disposable diaper will be described in detail below as an example of an absorbent article, with reference to the accompanying drawings. Adjacent components in the thickness direction are fixed or joined as needed, in addition to the fixed or joined portions described below, in a manner similar to that of known diapers. The dotted patterns in the cross-sectional view indicate adhesives, such as hot melt adhesives, used as the fixing or joining means. Hot melt adhesives can be applied by known methods, such as slot coating, continuous or dotted bead coating, spiral, Z-shaped, or wavy spray coating, or pattern coating (transfer of hot melt adhesive using a relief printing method). Alternatively or in addition to this, hot melt adhesive can be applied to the outer periphery of the elastic member to fix the elastic member to an adjacent member. Hot melt adhesives include, for example, EVA-based, adhesive rubber-based (elastomer-based), polyolefin-based, and polyester / polyamide-based adhesives, but are not limited thereto. Material welding, such as heat sealing or ultrasonic sealing, can also be used to fix or join the components. In areas where liquid permeability in the thickness direction is required, adjacent components in the thickness direction are fixed or joined in an intermittent pattern. For example, when such intermittent fixing or joining is performed using a hot melt adhesive, intermittent pattern coating such as a spiral, Z-shaped, or wavy pattern can be suitably used. When coating an area greater than the coating width of a single nozzle, intermittent pattern coating such as a spiral, Z-shaped, or wavy pattern can be performed with or without a gap in the width direction. Material welding methods such as heat sealing and ultrasonic sealing can also be used to join the components.

[0027] In addition, as the nonwoven fabric in the following description, known nonwoven fabrics can be used appropriately depending on the location and purpose. The constituent fibers of the nonwoven fabric can be selected without particular limitation, for example, synthetic fibers such as polyolefins (e.g., polyethylene or polypropylene), polyesters, and polyamides (including single-component fibers and core-sheath and other composite fibers), regenerated fibers (e.g., rayon or cupra), and natural fibers (e.g., cotton), and mixtures of these can also be used. In order to increase the flexibility of the nonwoven fabric, it is preferable that the constituent fibers be crimped fibers. Furthermore, the constituent fibers of the nonwoven fabric can be hydrophilic fibers (including fibers made hydrophilic by a hydrophilizing agent), hydrophobic fibers, or water-repellent fibers (including fibers made water-repellent by a water-repellent agent). Furthermore, nonwoven fabrics are generally classified into staple fiber nonwoven fabrics, long fiber nonwoven fabrics, spunbond nonwoven fabrics, meltblown nonwoven fabrics, spunlace nonwoven fabrics, thermal bond (air-through) nonwoven fabrics, needle-punched nonwoven fabrics, point-bond nonwoven fabrics, laminated nonwoven fabrics (including SMS nonwoven fabrics and SMMS nonwoven fabrics in which a meltblown layer is sandwiched between spunbond layers), and the like, depending on the fiber length, sheet formation method, fiber bonding method, and laminated structure, and any of these nonwoven fabrics can be used.

[0028] 1 to 6 show an example of a pants-type disposable diaper. This pants-type disposable diaper includes a rectangular front outer body 12F constituting a front waist-surrounding portion, a rectangular rear outer body 12B constituting a rear waist-surrounding portion, and an inner body 200 provided inside the outer bodies 12F, 12B so as to extend from the front outer body 12F through the crotch region M to the rear outer body 12B. Side seals 12A are formed by joining both sides of the front outer body 12F and both sides of the rear outer body 12B, and thus an opening formed by the front and rear ends of the outer bodies 12F, 12B serves as a waist opening WO through which the wearer's torso passes, and the portions on both widthwise sides of the inner body 200 surrounded by the lower edges of the outer bodies 12F, 12B and the side edges of the inner body 200 serve as leg openings LO through which the legs pass. The inner body 200 is a portion that absorbs and retains excrement such as urine, and the outer bodies 12F, 12B are portions that support the inner body 200 against the wearer's body. Furthermore, the symbol Y indicates the overall length of the diaper in the unfolded state (the length in the front-to-back direction from the edge of the waist opening WO of the front body F to the edge of the waist opening WO of the back body B), and the symbol X indicates the overall width of the diaper in the unfolded state.

[0029] This pants-type disposable diaper has a waist region T, which is defined as the front-to-back range having the side seals 12A (the front-to-back range from the waist opening WO to the top ends of the leg openings LO), and an intermediate region L, which is defined as the front-to-back range of the portion forming the leg openings LO (between the front-to-back region having the side seals 12A of the front body F and the front-to-back region having the side seals 12A of the back body B). The portions of the front exterior body 12F and the rear exterior body 12B located in the waist region T, i.e., the front waist portion and the rear waist portion, can be conceptually divided into a "waist portion" W, which forms the edge of the waist opening, and a "lower waist portion" U, which is the portion below this. Typically, if the front and rear waist regions have a boundary where the stretch stress in the width direction WD changes (e.g., where the thickness or elongation rate of the elastic member changes), the waist region W is the portion closer to the waist opening WO than the boundary closest to the waist opening WO. If no such boundary exists, the waist extension portion 12E extending further toward the waist opening WO than the absorbent body 56 or inner body 200 is the waist region W. Their front-to-rear lengths vary depending on the size of the product and can be determined as appropriate. For example, the waist region W may be 15 to 40 mm, and the lower waist region U may be 65 to 120 mm. Meanwhile, both side edges of the middle region L are constricted in a U-shape or curved shape to fit around the wearer's legs, and these are the areas into which the wearer's legs are inserted. As a result, the pants-type disposable diaper in its unfolded state has a generally hourglass shape overall.

[0030] (Outer Body) As shown in the figure, the outer bodies 12F, 12B consist of a rectangular front outer body 12F, which constitutes at least the waist portion of the front body F, and a rectangular back outer body 12B, which constitutes at least the waist portion of the back body B. The front outer body 12F and the rear outer body 12B may not be continuous at the crotch side but may be spaced apart in the front-to-back direction LD (two-piece outer body type), or, as not shown, may be continuous from the front body to the back body (integrated outer body type). In the two-piece outer body type, the front-to-back separation distance 12d may be, for example, approximately 40 to 60% of the total length Y. In the illustrated example, the lower edges of the front outer body 12F and the rear outer body 12B are linear along the width direction WD, but the lower edge of at least one of the front outer body 12F and the rear outer body 12B may be curved to fit around the legs.

[0031] In a two-piece outer-casing pants-type disposable diaper, the inner body 200 is exposed between the front outer body 12F and the rear outer body 12B. Therefore, to prevent the liquid-impermeable sheet 11 from being exposed on the back surface of the inner body 200, a cover nonwoven fabric 13 is preferably provided on the back surface of the inner body 200, extending from between the front outer body 12F and the inner body 200 to between the rear outer body 12B and the inner body 200. The inner and outer surfaces of the cover nonwoven fabric 13 can be bonded to their respective opposing surfaces with a hot melt adhesive. The nonwoven fabric used for the cover nonwoven fabric 13 can be selected, for example, from a material similar to that of the outer bodies 12F and 12B. Although not shown, the outer body may be continuous from the front body F to the back body B, passing through the crotch area. In this case, the outer body has not only a portion corresponding to the waist region T but also a portion corresponding to the middle region L.

[0032] The front exterior body 12F and the rear exterior body 12B have a front waist portion and a rear waist portion that constitute the waist region T. In the example shown in Figures 1 and 2, the front exterior body 12F and the rear exterior body 12B have the same dimensions in the front-to-rear direction LD, and the front exterior body 12F and the rear exterior body 12B do not have a portion corresponding to the middle region L, but as shown in Figure 7, the rear exterior body 12B may have a longer front-to-rear dimension than the front exterior body 12F, and the front exterior body 12F does not have a portion corresponding to the middle region L, but the rear exterior body 12B may have a buttocks covering portion C extending from the waist region T toward the middle region L. Although not shown, the front exterior body 12F may also be provided with a groin covering portion extending from the waist region T toward the middle region L.

[0033] As shown in Figures 4 and 5, the outer body 12F, 12B is formed by joining an outer sheet layer and an inner sheet layer adjacent to the outer and inner sides of the elastic members 16-19 (described later) using a joining method such as a hot melt adhesive or welding. The outer sheet layer and the inner sheet layer can be formed from two sheets 12S, 12H as shown in the illustrated example, or from a single sheet material. For example, in the latter case, the inner sheet layer and the outer sheet layer are respectively formed by the inner and outer portions of a single sheet material folded back at the edge of the waist opening WO (which may be the edge on the crotch side) in part or all of the outer body 12F, 12B. The illustrated example shows the former case, in which the sheet material 12S forming the outer sheet layer in the lower waist portion is folded back around the waist opening WO side of the sheet material 12H forming the inner sheet layer in the lower waist portion, and this folded back portion 12r extends to cover the edge of the inner body 200 on the waist opening WO side. On the other hand, in the waist portion, the folded portion 12r serves as an inner sheet layer adjacent to the inside of the elastic member.

[0034] The outer shells 12F, 12B incorporate elastic members 16-19 to enhance the fit around the wearer's waist, forming a stretchable region A2 that stretches elastically in the width direction WD in response to the stretching of the elastic members 16-19. In this stretchable region A2, the outer shells 12F, 12B contract in response to the contraction of the elastic members when at their natural length, forming wrinkles or creases. When stretched in the longitudinal direction of the elastic members, the stretchable region A2 can be stretched to a predetermined stretch rate without wrinkles. The elastic members 16-19 can be elongated elastic members such as rubber threads (as shown in the figure), as well as known elastic members in strip, net, film, and other shapes, without any particular limitation. The elastic members 16-19 may be made of synthetic or natural rubber.

[0035] To explain the elastic members 16-19 in the illustrated example in more detail, a plurality of waist elastic members 17 are attached to the waist portion W of the outer body 12F, 12B at intervals in the front-to-rear direction so as to be continuous across the entire width direction WD. Furthermore, one or more of the waist elastic members 17 arranged in the region adjacent to the lower waist portion U may overlap the inner body 200, or may be provided on both sides in the width direction except for the central portion in the width direction that overlaps with the inner body 200. The waist elastic member 17 should have a thickness of 155 to 1880 dtex, particularly 470 to 1240 dtex (in the case of synthetic rubber; in the case of natural rubber, a cross-sectional area of ​​0.05 to 1.5 mm ２ , especially 0.1 to 1.0 mm ２ It is preferable to provide about 2 to 15, and especially about 4 to 10, rubber threads of about 1 / 4" thick (approximately 1 / 4" thick) at intervals of 2 to 12 mm, especially 3 to 7 mm, and the resulting elongation rate in the width direction WD of the waist portion W is preferably about 150 to 400%, especially about 220 to 320%. Furthermore, it is not necessary for the waist portion W to use elastic members of the same thickness or to have the same elongation rate all along the front-to-rear direction LD, and for example, the thickness or elongation rate may be different in some areas.

[0036] In addition, a plurality of lower waist elastic members 16, 19 made of elongated elastic members are attached to the lower waist portion U of the outer casing 12F, 12B at intervals in the front-to-rear direction to form a lower waist stretchable region (a region having the lower waist elastic members 16, 19). The lower waist elastic members 16, 19 have a thickness of 155 to 1880 dtex, particularly about 470 to 1240 dtex (in the case of synthetic rubber; in the case of natural rubber, a cross-sectional area of ​​0.05 to 1.5 mm ２ , especially 0.1 to 1.0 mm ２ It is preferable to provide about 5 to 30 rubber threads of about 1 / 2" thick (approximately 1 / 4" thick) at intervals of 1 to 15 mm, especially 3 to 8 mm, and the resulting elongation rate in the width direction WD of the waist lower portion U is preferably about 200 to 350%, especially about 240 to 300%. Furthermore, it is not necessary for the waist lower portion U to use elastic members of the same thickness or to have the same elongation rate all along the front-to-back direction LD, and thicknesses or elongation rates may be different in some areas.

[0037] When elastic members 16, 19 are provided in the front-to-back region including the absorbent body 56, as in the lower waist portion U in the illustrated example, in order to prevent contraction of the absorbent body 56 in the width direction WD in part or all of the region, it is preferable to designate a non-elastic region A1 in the widthwise middle, including part or all of the portion overlapping with the absorbent body 56 in the width direction WD, and designate stretchable regions A2 on both sides of the non-elastic region A1 (in the illustrated example, these are lower waist stretchable regions). The widthwise dimensions of the stretchable regions A2 on both sides of the non-elastic region A1 are generally constant in the front-to-back direction LD as in the illustrated example, or can vary in the front-to-back direction LD (not shown). Furthermore, the widthwise dimensions of the stretchable regions A2 on both sides of the non-elastic region A1 in the width direction WD can be generally the same in the front body portion F and the back body portion B, or can be different.

[0038] The stretchable region A2 and non-stretchable region A1 can be constructed by attaching the elastic members 16-17, 19 between the inner and outer sheet layers, and then cutting the elastic members 16, 19 into small pieces by applying pressure and heat or cutting them at one location in the middle of the width of the region that will become the non-stretchable region A1, or over almost the entire region, so that stretchability remains in the stretchable region A2 while eliminating stretchability in the non-stretchable region A1. Note that unnecessary elastic members 18 that do not substantially contribute to the formation of stretchability remain in the non-stretchable region A1.

[0039] The sheet materials 12S, 12H forming the inner and outer sheet layers can be used without any particular limitation, but nonwoven fabric is preferred. When nonwoven fabric is used, the basis weight per sheet is 10 to 30 g / m ２ It is preferable to set it to about this level.

[0040] The elastic members 16-19 can be fixed to the exterior bodies 12F, 12B by known methods. The inner sheet layer and the outer sheet layer can also be joined to each other by known methods. For example, in the portions of the exterior bodies 12F, 12B having the elastic members 16-19, a hot melt adhesive HM can be applied only to the outer peripheral surfaces of the elastic members 16-19 using an application means such as a comb gun or a SureWrap nozzle, and then the elastic members 16-19 are sandwiched between the inner sheet layer and the outer sheet layer. This allows the elastic members 16-19 to be fixed to the inner sheet layer and the outer sheet layer, and the inner sheet layer and the outer sheet layer to be fixed to each other, using only the hot melt adhesive HM applied to the outer peripheral surfaces of the elastic members 16-19.

[0041] (Inner Body Joint Portion) The inner body 200 can be joined to the outer bodies 12F, 12B by a joining means that uses material welding, such as heat sealing or ultrasonic sealing, or by a hot melt adhesive. In the illustrated example, the inner body 200 is fixed to the inner surfaces of the outer bodies 12F, 12B via a hot melt adhesive that is applied to the back surface of the inner body 200, that is, in this case, the back surface of the liquid-impermeable sheet 11 and the base portions 65 of the rising gathers 60. The inner body joint portion 20 that joins the inner body 200 and the outer bodies 12F, 12B can be provided over almost the entire overlapping area, as shown in Figure 2, and can also be provided in a portion excluding both widthwise ends of the inner body 200, for example.

[0042] (Inner body) The inner body 200 can have any shape, but in the illustrated example, it is a rectangle with its long sides along the front-to-back direction LD. As shown in Figures 3 to 5, the inner body 200 comprises a top sheet 30 that faces the body, a liquid-impermeable sheet 11, and an absorbent element 50 interposed therebetween. Reference numeral 40 denotes an intermediate sheet (second sheet) that is provided between the top sheet 30 and the absorbent element 50 in order to quickly transfer liquid that has permeated the top sheet 30 to the absorbent element 50, and reference numeral 60 denotes rising gathers 60 that extend from both sides of the inner body 200 so as to contact the wearer's legs in order to prevent excrement from leaking out the sides of the inner body 200.

[0043] (Top sheet) The top sheet 30 is liquid-permeable, and examples thereof include a perforated or non-perforated nonwoven fabric, a perforated plastic sheet, etc. The top sheet 30 may consist of a single sheet, or a laminated sheet obtained by bonding two or more sheets together. Similarly, the top sheet 30 may consist of a single sheet, or two or more sheets in the planar direction.

[0044] The side edges of the top sheet 30 may be folded back at the side edges of the absorbent element 50, or may not be folded back and may extend out to the sides beyond the side edges of the absorbent element 50.

[0045] The top sheet 30 is preferably fixed to an adjacent backside member by a material welding joining means such as heat sealing or ultrasonic sealing, or by a hot melt adhesive, in order to prevent misalignment relative to the backside member, etc. In the illustrated example, the top sheet 30 is fixed to the surface of the intermediate sheet 40 and the surface of the portion of the packaging sheet 58 that is located on the front side of the absorbent body 56 by a hot melt adhesive applied to the backside of the top sheet 30.

[0046] (Intermediate Sheet) In order to quickly transfer liquid that has permeated the top sheet 30 to the absorbent body 56, an intermediate sheet (also called a second sheet) 40, which has a faster liquid permeation rate than the top sheet 30, can be provided. This intermediate sheet 40 is intended to quickly transfer liquid to the absorbent body 56, thereby improving the absorption performance of the absorbent body 56 and reducing backflow from the absorbent body 56. The intermediate sheet 40 can also be omitted.

[0047] Examples of the intermediate sheet 40 include the same material as the top sheet 30, spunlace nonwoven fabric, spunbond nonwoven fabric, SMS nonwoven fabric, pulp nonwoven fabric, a mixed sheet of pulp and rayon, point-bond nonwoven fabric, and crepe paper. Air-through nonwoven fabric is particularly preferred because of its bulkiness. For the air-through nonwoven fabric, it is preferable to use composite fibers with a core-sheath structure, and in this case, the resin used for the core may be polypropylene (PP), but polyester (PET) with high rigidity is preferred. The basis weight is 17 to 80 g / m ２ is preferred, and 25 to 60 g / m ２ The thickness of the raw material fibers of the nonwoven fabric is preferably 2.0 to 10 dtex. In order to make the nonwoven fabric bulky, it is also preferable to use eccentric fibers, hollow fibers, or eccentric and hollow fibers as all or part of the raw material fibers.

[0048] In the illustrated example, the intermediate sheet 40 is positioned in the center and is shorter than the width of the absorbent body 56, but it may be provided across the entire width. The length of the intermediate sheet 40 in the front-to-rear direction may be the same as the entire length of the diaper, the same as the length of the absorbent element 50, or within a short length range centered on the liquid-receiving region.

[0049] In order to prevent the intermediate sheet 40 from shifting relative to the backside member, it is desirable to fix the intermediate sheet 40 to the backside adjacent member by a joining means that uses material welding such as heat sealing or ultrasonic sealing, or by a hot melt adhesive. In the illustrated example, the intermediate sheet 40 is fixed to the surface of the portion of the packaging sheet 58 that is located on the front side of the absorbent body 56 by a hot melt adhesive applied to the backside of the intermediate sheet 40.

[0050] (Liquid-impermeable sheet) The material of the liquid-impermeable sheet 11 is not particularly limited, but examples thereof include a plastic film made of a polyolefin resin such as polyethylene or polypropylene, a laminated nonwoven fabric in which a plastic film is provided on the surface of a nonwoven fabric, and a laminated sheet in which a nonwoven fabric or the like is overlaid and bonded to a plastic film. It is preferable to use a liquid-impermeable and moisture-permeable material for the liquid-impermeable sheet 11, which is preferred from the viewpoint of preventing stuffiness. As a moisture-permeable plastic film, a microporous plastic film obtained by kneading an inorganic filler into a polyolefin resin such as polyethylene or polypropylene, forming a sheet, and then stretching it uniaxially or biaxially is widely used. In addition, nonwoven fabrics using microdenier fibers, nonwoven fabrics whose leak-proofing properties have been enhanced by reducing the voids in the fibers through the application of heat or pressure, and sheets that have been made liquid-impermeable without using a plastic film by methods such as coating with a highly absorbent resin or a hydrophobic resin or a water-repellent agent can also be used as the liquid-impermeable sheet 11, but it is preferable to use a resin film in order to obtain sufficient adhesive strength when bonding with the cover nonwoven fabric 13 described below via a hot melt adhesive.

[0051] The liquid-impermeable sheet 11 is made to have a width that fits behind the absorbent element 50 as shown in the figure, and in order to improve leakproofness, it can also be made to wrap around both sides of the absorbent element 50 and extend to both sides of the absorbent element 50 on the side of the top sheet 30. The appropriate width of this extension is about 5 to 20 mm on each side.

[0052] (Absorbent Element) The absorbent element 50 has an absorbent body 56 and a packaging sheet 58 that wraps the entire absorbent body 56. The absorbent element 50 has a crotch region M and portions extending to the front and rear of the crotch region M.

[0053] (Absorbent body) The absorbent body 56 may extend across both the front and rear of the crotch region M so as to include the crotch region M. In the case of a pants-type disposable diaper such as this example, it is preferable that the absorbent body 56 extends to or near the peripheral edge of the inner body 200 in the front-to-rear direction LD and the width direction WD. The reference symbol 56X indicates the overall width of the absorbent body 56.

[0054] To ensure a sufficient absorption capacity in the crotch region M, it is preferable that the absorber 56 has a substantially rectangular shape as shown in the example of Fig. 8. Furthermore, to improve the fit in the crotch region M as shown in the example of Fig. 12(a), it is also possible to make the width of the absorber 56 in the crotch region M narrower than the front and rear sides, giving it a constricted shape. In this case, to ensure a sufficient absorption capacity in the crotch region M, it is preferable that the width n1 of the narrowest part of the absorber 56 in the crotch region M be 0.85 times or more the overall width 56X of the absorber 56.

[0055] In addition, the crotch region M refers to the range in the front-to-rear direction LD including the constricted portion 56n when the absorbent body 56 has the constricted portion 56n described below, or refers to the range in the front-to-rear direction LD including the constricted portion 56n when the absorbent body 56 does not have the constricted portion 56n but the outer shape of the diaper in the unfolded state has a constricted portion as in the illustrated example (in the illustrated example, between the front exterior body 12F and the rear exterior body 12B). In the case where there are no constricted portions, the crotch region M refers to the portion located in the center in the front-to-rear direction LD whose dimension in the front-to-rear direction LD is 20 to 30% of the overall length of the product. The portions extending forward and rearward from the crotch region M, respectively, are the front portion and the rear portion.

[0056] The absorbent body 56 may be a single layer as shown in Figures 3 and 24(a) or may be a multi-layer structure as shown in Figures 24(b) and (c). The layer of the absorbent body 56 is a layer obtained through a fiber stacking process using a predetermined fiber stacking drum and, if necessary, a compression process in the thickness direction. Therefore, for example, as shown in Figures 24(b) and (c), the absorbent body 56 may be composed of two layers: an upper layer 56a and a lower layer 56b.

[0057] The sizes of the multiple layers included in the absorbent body 56 may be the same or different from each other. The thicknesses of the multiple layers included in the absorbent body 56 may also be the same or different from each other. For example, as shown in FIG. 24( a), the widths and thicknesses of the upper layer 56a and the lower layer 56b included in the absorbent body 56 may be different. In the example shown in FIG. 24( b), the width and thickness of the upper layer 56a are smaller than those of the lower layer 56b. The sizes of the multiple layers included in the absorbent body can be set depending on the shape and purpose of the absorbent article. The number of layers is not limited to two and may be three or more.

[0058] The thickness of the absorbent body 56 (when the absorbent body is made of multiple layers, the total thickness of the multiple layers) can be 0.5 to 30 mm, preferably 1 to 15 mm. For example, in the case of a disposable diaper, the thickness of the absorbent body 56 can be 1 to 30 mm, preferably 1.5 to 15 mm, and more preferably 5 to 13 mm. In the case of a sanitary napkin, the thickness of the absorbent body 56 can be 0.3 to 30 mm, preferably 1.0 to 15 mm. The thickness of the absorbent body 56 may be uniform, or it may have regions of relatively thick or relatively thin thickness.

[0059] The absorbent body 56 is a mixture and accumulation of pulp fibers 56f and superabsorbent polymer particles 56p, and the pulp fibers 56f and superabsorbent polymer particles 56p are distributed substantially uniformly throughout the absorbent body 56, with the superabsorbent polymer particles 56p held between the pulp fibers 56f. Such an absorbent body 56 can be manufactured using a fiber stacking drum, which will be described later. It is desirable that the absorbent body 56 be a mixture and accumulation of only pulp fibers 56f and superabsorbent polymer particles 56p. However, if necessary, the absorbent body 56 may contain additives other than the pulp fibers 56f and the superabsorbent polymer particles 56p, such as fillers, pigments, sizing agents, coagulants, oil-resistant agents, aluminum sulfate, retention aids, drainage aids, dry strength agents, wet strength agents, coloring pigments, water-resistant agents, deodorizers, fragrances, etc.

[0060] (Pulp Fiber) Pulp is a collection of fibers (pulp fibers) extracted from wood, grass, or other plants by mechanical and / or chemical processing. Pulp raw materials include softwood, hardwood, bamboo, rice, kudzu, Japanese pampas grass, hemp, sugarcane, etc. Artificial cellulose such as rayon and acetate can also be used.

[0061] The pulp fibers 56f contained in the absorbent body 56 preferably contain a mixture of hardwood pulp fibers (pulp fibers derived from hardwood trees) and softwood pulp fibers (pulp fibers derived from softwood trees) having a longer average fiber length than hardwood pulp fibers, but may also contain only hardwood pulp fibers (100% hardwood pulp fibers). Hereinafter, such an absorbent body 56 will also be referred to as a hardwood pulp fiber-containing absorbent body. The hardwood pulp fibers are preferably bleached hardwood kraft pulp (LBKP) produced by the kraft method. The softwood pulp fibers are preferably bleached softwood kraft pulp (NBKP) produced by the kraft method.

[0062] The content of softwood pulp fibers and hardwood pulp fibers in the total pulp fibers 56f is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 98% by mass or more. It is also preferable that the total pulp fibers 56f consist essentially of softwood pulp fibers and hardwood pulp fibers. In this specification, the blending amount of pulp fibers 56f or its material refers to the bone-dry internal amount, i.e., the mass ratio in a bone-dry state, unless otherwise specified.

[0063] As shown in Table 1, in the case of the absorbent body 56 made of (I) softwood pulp fibers, the fiber length and fiber width of the pulp fibers 56f are relatively large, and the fiber length and fiber width also vary relatively widely. This generally results in a large distance between the pulp fibers 56f, resulting in a bulky absorbent body 56. Therefore, the absorption capacity (water absorption amount) of the pulp fibers 56f is large, and the absorption rate of the absorbent body 56 is also relatively fast. However, because the distance between the pulp fibers 56f is large, the liquid retention ability of the fibers due to capillary action is relatively low. Furthermore, the superabsorbent polymer particles (SAP) tend to fall out in the direction of gravity, resulting in a somewhat poorer retention of the superabsorbent polymer particles (SAP) between the pulp fibers 56f. As a result, compared to the absorbents 56 of (II) and (III) below, the liquid retention capacity of the absorbent body 56 is lower, and the effect of preventing liquid backflow is weaker.

[0064]

[0065] Furthermore, in the absorbent body 56 made of hardwood pulp fibers (II), the fiber length and fiber width of the pulp fibers 56f are relatively small, and the variation in fiber length and fiber width is also relatively small. This reduces the distance between the pulp fibers 56f, resulting in a high fiber density in the resulting absorbent body 56. As a result, the absorption capacity (water absorption amount) of the pulp fibers 56f is small, and the absorption rate of the absorbent body 56 or absorbent article is slow. However, because the distance between the pulp fibers 56f is small, the liquid retention capacity of the fibers due to capillary action is high. Furthermore, the retention of the superabsorbent polymer particles 56p between the pulp fibers 56f is generally good, and the liquid retention capacity of the superabsorbent polymer particles 56p is higher than that of the absorbent body 56 of (I). As a result, the liquid retention capacity of the absorbent body 56 is higher than that of the absorbent body 56 of (I), and it also has the effect of suppressing liquid backflow.

[0066] (III) The absorbent body 56 made of softwood pulp fibers and hardwood pulp fibers combines fibers with relatively long fiber lengths and wide fiber widths as described above with fibers with relatively short fiber lengths and narrow fiber widths, resulting in a fiber density intermediate between (I) and (II). This allows for a certain level of fiber absorption capacity, maintains the absorption rate of the absorbent body 56, and ensures the liquid retention capacity of the fibers through capillary action. Furthermore, the high-absorbent polymer particles 56p are retained between the pulp fibers 56f, further enhancing the liquid retention capacity of the high-absorbent polymer particles 56p compared to (I) and (II). As a result, the absorbent body 56 maintains its absorption capacity and absorption rate while also achieving liquid retention capacity. Thus, the (III) configuration can ensure both the absorption capacity, absorption rate, and liquid retention capacity, thereby improving backflow prevention.

[0067] In the above (III), the inclusion of softwood pulp fibers ensures a certain degree of bulkiness in the absorbent body 56, thereby preventing deterioration in the feel of the resulting absorbent article against the skin. Furthermore, the inclusion of softwood pulp fibers also ensures operability when producing fluff pulp from the pulp sheet (i.e., suppressing powder scattering and preventing fibers from adhering to the equipment). Good operability contributes to high overall productivity in the production of absorbent articles.

[0068] In one preferred example of the hardwood pulp fiber-containing absorbent body 56, the proportion of pulp fibers with a fiber length of 0.5 mm or more and less than 1.1 mm is 40% or more by mass, and the proportion of pulp fibers with a fiber width of 10 μm or more and less than 35 μm is 90% or more by mass. The proportion of pulp fibers with a fiber length of 0.5 mm or more and less than 1.1 mm can be preferably 42.6% or more, more preferably 43% or more, even more preferably 43.2% or more, 43.7% or more, or 45% or more. The proportion of pulp fibers with a fiber width of 10 μm or more and less than 35 μm can be preferably 90.6% or more, more preferably 91.0% or more, even more preferably 91.2% or more, or 91.4% or more. By having the absorbent body 56 contain specific pulp fiber lengths and specific pulp fiber widths within specific ranges, the advantage (III) of the absorbent body 56 (particularly, backflow prevention) can be further improved and more reliably achieved.

[0069] The upper limit of the proportion of pulp fibers 56f having a fiber length of 0.5 mm or more and less than 1.1 mm in all pulp fibers 56f of hardwood pulp fiber-containing absorbent body 56 is not particularly limited, but due to variations in fiber length resulting from pulp being a natural material, it can be 80% by mass or less, 60% by mass or less, or 55% by mass or less. Similarly, the upper limit of the proportion of pulp fibers having a fiber width of 10 μm or more and less than 35 μm is not particularly limited, but can be 98% by mass or less, 95% by mass or less, or 94% by mass or less.

[0070] The fiber length and fiber width of the pulp fibers can be measured using a measuring instrument "VALMET FS5" in accordance with JIS-P8226:2011 (ISO16065-2:2007) "Pulp - Fiber length measurement method by optical automatic analysis."

[0071] Furthermore, in the hardwood pulp fiber-containing absorbent body 56, the average fiber length when pulp fibers having a fiber length of 0.5 mm or more but less than 1.1 mm are measured at 0.02 mm intervals (with a classification width of 0.02 mm) can be 0.5 to 0.8 mm, preferably 0.6 to 0.7 mm. This suppresses variations in the distribution of voids that can occur depending on the orientation direction of the pulp fibers in the absorbent body 56, ensuring a high absorption rate.

[0072] Furthermore, in the hardwood pulp fiber-containing absorbent body 56, the standard deviation σ when pulp fibers having a fiber length of 0.5 mm or more but less than 1.1 mm are measured at 0.02 mm intervals (with a classification width of 0.02 mm) can be 0.58 mm or less, preferably 0.56 mm or less, more preferably 0.54 mm or less, and even more preferably 0.50 mm or less. Having a standard deviation within the above range can improve the absorption capacity and absorption speed of the absorbent body 56, and improve backflow prevention.

[0073] Furthermore, when pulp fibers with a fiber width of 10 μm or more but less than 35 μm are measured at 1 μm intervals (classification width of 1 μm), the average fiber width can be 15 μm or more and 30 μm or less, preferably 18 μm or more and 27 μm or less. By setting the average fiber width within the above range, it is possible to maintain an appropriate amount of interfiber space, preventing a decrease in absorption rate, and also to avoid an excessively large contact area between pulp fibers, thereby preventing an excessive increase in the bonding strength between fibers. This allows for appropriate defibration during production. Note that if the defibration ability of the pulp sheet is excessively low, over-defibration may occur during the production of fluff pulp (excessive defibration work may be performed), generating fine fibers and potentially reducing the absorption rate of the resulting absorbent.

[0074] When pulp fibers having a fiber width of 10 μm or more but less than 35 μm are measured at 1 μm intervals (classification width of 1 μm), the standard deviation σ can be 2.9 μm or less, preferably 2.8 μm or less, more preferably 2.75 μm or less, and even more preferably 2.6 μm or less, or 2.59 μm or less. By keeping the standard deviation within the above range, the absorption rate and backflow prevention effect can be improved.

[0075] As described above, the hardwood pulp fiber-containing absorbent 56, which has reduced variation in the distribution of fiber lengths within a specific range and the distribution of fiber widths within a specific range, has good backflow prevention effects while maintaining absorption capacity and absorption speed, despite the inclusion of hardwood pulp fibers.

[0076] The raw material wood for the softwood pulp fibers contained in the pulp fibers is not particularly limited, but pines such as radiata pine and various cedars are preferably used.

[0077] The raw material wood for hardwood pulp fibers is not particularly limited, but acacia, eucalyptus, and the like are preferably used. Acacia is a material characterized by low shrinkage upon drying, high impact resistance, and durability and hardness. Pulp obtained from acacia also retains its original properties, making it a useful raw material pulp with high moisture absorption and drying properties. Eucalyptus belongs to the genus Eucalyptus, and species such as Eucalyptus globulus, Eucalyptus grandis, Eucalyptus europhylla, Eucalyptus nitens, and Eucalyptus regnans have long been widely used as raw pulp materials for paper manufacturing. The resulting pulp fibers have rigid, unbreakable fiber lumens, and the incorporation of these pulp fibers can increase the bulk and reduce the density of absorbents. Acacia is preferred as a hardwood pulp fiber because it has a larger fiber width than eucalyptus, resulting in bulkiness. Even when combined with softwood pulp fibers, there is little decrease in absorption capacity and absorption rate.

[0078] The mass ratio of hardwood pulp fibers to other pulp fibers such as softwood pulp fibers in the hardwood pulp fiber-containing absorbent 56 is not limited and can be, for example, 10 / 90 to 90 / 10, but from the standpoint of operability, it is preferably 20 / 80 to 50 / 50, more preferably 25 / 75 to 38 / 62, even more preferably 25 / 75 or more but less than 38 / 62, even more preferably 26 / 74 to 36 / 64, and particularly preferably 28 / 72 to 35 / 65.

[0079] Furthermore, the content of acacia wood in the raw wood of the hardwood pulp fibers, i.e., the content of pulp fibers derived from acacia wood in the hardwood pulp fibers in the hardwood pulp fiber-containing absorbent body 56, can be preferably 5 to 95% by mass, more preferably 5% by mass or more but less than 95% by mass, and even more preferably 20 to 93% by mass, 20 to 90% by mass, 25 to 85% by mass, or 50 to 80% by mass. Even with hardwood pulp fibers that are shorter than softwood pulp fibers and tend to pack tightly together, and regardless of the direction in which the fibers are oriented (for example, in the length direction, width direction, and / or thickness direction of the resulting absorbent article), more uniform voids between the fibers can be ensured.

[0080] In addition to the above-mentioned softwood bleached kraft pulp and hardwood bleached kraft pulp, other pulp fibers may be used as the pulp fibers constituting the absorbent body 56, such as soda pulp, sulfite pulp, chemi-thermomechanical pulp, chemi-reiner mechanical pulp, and thermo-chemi-mechanical pulp. However, if the lignin in the fibers is not sufficiently removed, the absorption amount and absorption rate of the pulp fibers tend to decrease, so bleached pulp from which lignin has been sufficiently removed is preferred. When the other pulps are contained, the content of the other pulps is preferably 10% by mass or less of the total pulp raw material.

[0081] Furthermore, the pulp fibers 56f contained in the absorbent body 56 may contain recycled pulp fibers (recycled pulp fibers) regardless of the type. For example, the pulp fibers 56f may contain recycled softwood pulp fibers or recycled hardwood pulp fibers. When recycled pulp fibers are used, the amount of ash in the pulp fibers used in the absorbent body, for example, the amount of ash in fluff pulp, is preferably as small as possible. Furthermore, when recycled pulp fibers are used, when comparing pulps derived from the same raw material before and after recycling, the whiteness of the recycled pulp may be lower than or equal to the whiteness of virgin pulp (pulp that is not recycled or unrecycled pulp), but it is preferable that it be equal.

[0082] When the absorbent body 56 has multiple layers, only some of the layers may contain hardwood pulp fibers, or all of the layers may contain hardwood pulp fibers. For example, when the absorbent body 56 is composed of two layers, an upper layer 56a and a lower layer 56b, only the lower layer 56b may contain hardwood pulp fibers, or only the upper layer 56a, which may come into direct contact with the skin, may contain hardwood pulp fibers.

[0083] The basis weight of the pulp fibers 56f in the absorbent body 56 (the basis weight of the entire absorbent body made of multiple layers when the absorbent body is made of multiple layers) is 100 to 500 g / m ２ , preferably 100 to 300 g / m ２ , particularly preferably 120 to 250 g / m ２ For example, in the case of a disposable diaper, the weight of the pulp fiber can be 100 to 300 g / m ２ , preferably 120 to 200 g / m ２ In the case of a sanitary napkin, for example, the basis weight of the pulp fibers in the absorbent body 56 (the basis weight of the entire absorbent body made of multiple layers when the absorbent body is made of multiple layers) can be 150 to 500 g / m ２ , preferably 250 to 400 g / m ２ The basis weight of the pulp fibers may be uniform overall, or may have regions with relatively high or relatively low basis weight.

[0084] (Superabsorbent polymer particles) The term "superabsorbent polymer particles 56p" includes not only "particles" but also "powder." The superabsorbent polymer particles 56p used in this type of disposable diaper can be used as is. The pre-swelling particle size (particle size before absorbing liquid) of the superabsorbent polymer particles 56p is not particularly limited. However, it is preferable that the superabsorbent polymer particles 56p have a pre-swelling particle size of more than 150 μm and not more than 850 μm, and it is more preferable that the superabsorbent polymer particles 56p have a pre-swelling particle size of more than 150 μm and not more than 850 μm, and it is particularly preferable that the superabsorbent polymer particles 56p have a pre-swelling particle size shorter than the average fiber length of hardwood pulp fibers (for example, not more than 600 μm, more preferably not more than 500 μm), and it is more preferable that the superabsorbent polymer particles 56p have a pre-swelling particle size shorter than the average fiber length of hardwood pulp fibers (for example, not more than 600 μm, more preferably not more than 500 μm), and it is particularly ...).

[0085] The particle size distribution of the superabsorbent polymer particles 56p can be determined by placing standard sieves (e.g., standard sieves manufactured by Tokyo Screen Co., Ltd.) with mesh sizes of 850 μm, 600 μm, 500 μm, 355 μm, 300 μm, 250 μm, and 150 μm as specified in JIS Z 8801, and a tray in this order from top to bottom in a shaker (e.g., AS200 manufactured by Retsch Co., Ltd.), and then loading the entire amount of superabsorbent polymer particles onto the top sieve for sieving. The shaking conditions are 50 Hz, amplitude 0.5 mm, and shaking time 10 minutes. The sieving is performed in an environment with a temperature of 23±2°C and a humidity of 50±5%, and the sample is stored in the same environment for at least 24 hours before sieving before measurement. Sieving is performed three times, and the average of the three measurements is used as the sieved mass for each sieve. From the mass of the superabsorbent polymer particles on each sieve and the total mass (mass of all superabsorbent polymer particles), the content ratio (mass percentage) of the particle size ranges corresponding to each sieve (i.e., greater than 850 μm, greater than 600 μm and less than 850 μm, greater than 500 μm and less than 600 μm, greater than 355 μm and less than 500 μm, greater than 300 μm and less than 355 μm, greater than 250 μm and less than 300 μm, greater than 150 μm and less than 250 μm, and less than 150 μm) can be determined. Furthermore, if a particle size cumulative curve is determined based on this particle size distribution and the particle diameter corresponding to the median cumulative value (50%) of the cumulative curve is taken as the average particle diameter, the average particle diameter of the superabsorbent polymer particles is preferably in the range of 355 to 500 μm, and more preferably in the range of 370 to 470 μm.

[0086] The material for the superabsorbent polymer particles 56p is not particularly limited, but a material with a water absorption capacity of 40 g / g or more is preferred. Examples of the superabsorbent polymer particles 56p include starch-based, cellulose-based, and synthetic polymer-based materials (polyacrylate-based, polysulfonate-based, maleic anhydride-based), and include starch-acrylic acid (salt) graft copolymers, saponified starch-acrylonitrile copolymers, crosslinked sodium carboxymethylcellulose, and acrylic acid (salt) polymers. The shape of the superabsorbent polymer particles 56p is preferably a commonly used powder or granular form, but other shapes can also be used.

[0087] The highly absorbent polymer particles 56p preferably have a water absorption rate of 70 seconds or less, particularly 40 seconds or less. If the water absorption rate is too slow, backflow (liquid supplied into the absorber 56 flows back out of the absorber 56) is likely to occur.

[0088] Furthermore, the highly absorbent polymer particles 56p preferably have a gel strength of at least 1000 Pa. This effectively prevents the sticky feeling after absorbing liquid, even when the absorbent body 56 is bulky.

[0089] The basis weight of the superabsorbent polymer particles 56p can be determined as appropriate depending on the absorption amount required for the application of the absorbent body 56. Therefore, although it cannot be generalized, the basis weight of the superabsorbent polymer particles 56p in the absorbent body 56 (the basis weight of the entire plurality of layers when the absorbent body 56 is made up of a plurality of layers) is preferably 50 to 350 g / m ２ , preferably 100 to 300 g / m ２ For example, in the case of a disposable diaper, the basis weight of the highly absorbent polymer particles 56p can be set to 50 to 300 g / m ２ , preferably 100 to 250 g / m ２ In addition, for example, in the case of a sanitary napkin, the basis weight of the superabsorbent polymer particles 56p in the absorbent body 56 (the basis weight of the entire absorbent body 56 when the absorbent body 56 is made up of multiple layers) can be 70 to 470 g / m ２ , preferably 140 to 240. When the absorbent body 56 has two layers, the basis weight of the superabsorbent polymer particles 56p in the lower layer 56b may be different from the basis weight of the superabsorbent polymer particles 56p in the upper layer 56a. That is, the basis weight of the superabsorbent polymer particles 56p in the lower layer 56b may be greater than the basis weight of the superabsorbent polymer particles 56p in the upper layer 56a, or conversely, the basis weight of the superabsorbent polymer particles 56p in the lower layer 56b may be less than the basis weight of the superabsorbent polymer particles in the upper layer 56a.

[0090] The ratio of the pulp fibers 56f and the superabsorbent polymer particles 56p in the absorbent body 56 is not particularly limited, and can be, for example, a weight ratio of pulp fibers 56f:superabsorbent polymer particles 56p of 40:60 to 65:35.

[0091] The average particle size of the superabsorbent polymer particles 56p after swelling is preferably 2,000 to 3,000 μm, and more preferably 2,200 to 2,800 μm. The average particle size of the superabsorbent polymer particles 56p after swelling refers to the average diameter of the superabsorbent polymer particles 56p in a swollen state after immersion in physiological saline for 60 minutes and then draining for 15 minutes. This average diameter is determined by observing the swollen superabsorbent polymer particles 56p from one direction using a microscope at 50x magnification, measuring the maximum diameter of any 20 particles that are entirely visible on the surface of the superabsorbent polymer particles 56p, and taking the arithmetic mean. In particular, it is preferable for the average particle size of the superabsorbent polymer particles 56p after swelling to be greater than the average fiber length of the hardwood pulp fibers, because this facilitates the severing of entanglement between the pulp fibers 56f due to the expansion of the superabsorbent polymer particles 56p, making the expansion of the superabsorbent polymer particles 56p less likely to be inhibited (so-called gel blocking is less likely to occur).

[0092] (Low Basis Weight Portion) As shown in the examples in Figures 1 to 4, the absorbent body 56 may have elongated low basis weight portions 56L extending in the front-to-back direction LD on both sides of the width direction WD in the crotch region M, or may not have low basis weight portions 56L (not shown). The low basis weight portions 56L refer to portions with a low basis weight and do not include portions that are compressed in the thickness direction TD but do not change their basis weight, such as the highly compressed portions 51 described below. The low basis weight portions 56L can be slits that penetrate the thickness direction TD, but are preferably recesses with a low accumulation of pulp fibers and superabsorbent polymer particles, as shown in the example, because this facilitates ensuring sufficient absorption. The recesses may be formed on either the front or back surface of the absorbent body 56. Providing such low basis weight portions 56L in the absorbent body 56 encourages bending of the absorbent body 56 along the low basis weight portions 56L, improving the fit of the absorbent element 50 in the crotch region M. The total basis weight of the pulp fibers and superabsorbent polymer particles in the low basis weight portion 56L may be less than the total basis weight of the pulp fibers and superabsorbent polymer particles in the portions other than the low basis weight portion 56L, and may be, for example, 0.1 to 0.5 times the total basis weight of the pulp fibers and superabsorbent polymer particles in the portions other than the low basis weight portion 56L.

[0093] As long as the low basis weight portion 56L is elongated in the front-to-rear direction LD, it may extend linearly along the front-to-rear direction LD, or it may be curved so that it is positioned laterally as it approaches both sides in the front-to-rear direction LD, as in the illustrated example. The front and rear ends of the low basis weight portion 56L may have any suitable shape. For example, it may be linear as in the example shown in FIG. 12(a), or it may be curved (e.g., semicircular) as in the example shown in FIG. 8, or it may have rounded corners at both ends and a linear intermediate portion (not shown). The width m1 of the low basis weight portion 56L may be determined as appropriate, and may be 0.04 to 0.1 times the width n1 (meaning the overall width 56X in the case of a rectangle) of the narrowest portion of the crotch region M of the absorbent body 56. The width m1 of the low basis weight portion 56L may be constant along its length or may vary. The dimensions and arrangement of the low basis weight portion 56L in the front-to-rear direction LD may be determined as appropriate. For example, the dimension m2 of the low weight portion 56L in the front-to-rear direction LD can be 50 to 120%, and more preferably 50 to 80%, of the dimension of the crotch region M in the front-to-rear direction LD. The low weight portion 56L may be contained within the crotch region M, or may extend to the front, rear, or both the front and rear of the crotch region M.

[0094] As shown in FIG. 8, the low basis weight portions 56L may be provided on both sides of the crotch region M in the width direction WD, and one may be provided in the center of the width direction WD. Alternatively, as shown in FIG. 12(a), only one may be provided in the center, or as shown in FIG. 12(b), only one may be provided on each side of the crotch region M in the width direction WD.

[0095] (Highly Compressed Sections) As shown in Figures 3, 4, and 9 to 11, the absorbent element 50 has a plurality of highly compressed sections 51 compressed in the thickness direction TD at intervals so as to recess from the surface of the absorbent element 50 into the absorbent body 56. Furthermore, within the region where the plurality of highly compressed sections 51 are arranged (a rectangular region with sides along the front-to-rear direction LD and the width direction WD, respectively, and circumscribing all of the highly compressed sections 51), the portions other than the highly compressed sections 51 are non-highly compressed sections 52 that are thicker and lower in density than the highly compressed sections 51. The highly compressed sections 51 are high-density sections that have been compressed by pressure (direct pressure) to have approximately the same thickness, and form the bottom of the recess. On the other hand, the non-highly compressed sections 52 are thicker and lower in density than the highly compressed sections 51, but even in the non-highly compressed sections 52, the absorbent body 56 deforms in the vicinity of the highly compressed sections 51 as if pulled by the deformation of the highly compressed sections 51, resulting in an increase in density as it approaches the highly compressed sections 51. As long as the non-highly compressed portions 52 are thicker and have a lower density than the highly compressed portions 51, they may be partially or entirely compressed in the thickness direction TD simultaneously with, before, or after the formation of the highly compressed portions 51. It is preferable that the non-highly compressed portions 52 do not have depressions on either or both of the front and back surfaces of the absorbent element 50.

[0096] The highly compressed portions 51 may be provided over the entire front-rear direction and width direction of the absorbent element 50 (i.e., the entire surface of the absorbent element 50 is the arrangement area of ​​the highly compressed portions 51), or they may be provided only in a portion of the front-rear direction or a portion of the width direction of the absorbent element 50. For example, although not shown, the highly compressed portions 51 may be provided only in a middle region in the front-rear direction LD that includes the crotch region M, or conversely, the highly compressed portions 51 may not be provided in the middle region in the front-rear direction LD that includes the crotch region M, but may be provided only in regions on both the front and rear sides of that middle region. Furthermore, although the highly compressed portions 51 in the illustrated example do not recess from the surface of the sheets located on the front side of the absorbent element (in the illustrated example, the top sheet 30 and intermediate sheet 40) into the absorbent body 56, they may be recessed from the surface of the absorbent element 50 into the absorbent body 56 as a result of being pressed from the sheets located on the front side of the absorbent element 50 so as to recess into the absorbent body 56.

[0097] The density of the absorbent body 56 in the highly compressed portion 51 is not particularly limited, but is preferably 60,000 to 250,000 g / m ３It is preferable that the density is 65,000 to 200,000 g / m ３ On the other hand, the density of the absorbent body 56 in the non-highly compressed portion 52 is not particularly limited, but is preferably 50,000 to 200,000 g / m ３ It is preferable that the density is 55,000 to 150,000 g / m ３ The density of the absorbent body 56 in the highly compressed portion 51 and the non-highly compressed portion 52 is measured by the following method.

[0098] (Method for measuring the density of the absorbent body 56 in the highly compressed portions 51) (1) At least one of the sheets on the front and back sides of the absorbent element 50 is peeled off so that the surface having the highly compressed portions 51 of the absorbent element 50 is exposed, and the area of ​​the highly compressed portions 51 is measured using the method described below. (2) The basis weight of the absorbent element 50 is measured. (3) A portion of the packaging sheet 58 is cut from the absorbent element 50, and the basis weight of the packaging sheet 58 is measured. (4) The mass of the absorbent element 50 in the highly compressed portions 51 is calculated from the measurement results of (1) and (2) above, and the mass of the packaging sheet 58 in the highly compressed portions 51 is calculated from the measurement results of (1) and (3) above, and the mass of the absorbent body 56 in the highly compressed portions 51 is calculated by subtracting the latter from the former. (5) The absorbent element 50 is frozen with liquid nitrogen, and then cut in the thickness direction TD so as to cross approximately the center of the highly compressed portions 51, and the cut surface is observed under a microscope to measure the thickness of the absorbent body 56. (6) Assuming that the thickness of the absorbent body 56 in the highly compressed portion 51 is constant, the volume of the absorbent body 56 in the highly compressed portion 51 is calculated by multiplying the area of ​​the highly compressed portion 51 in (1) above by the thickness of the absorbent body 56 in (5) above. (7) The density of the absorbent body 56 in the highly compressed portion 51 is calculated by dividing (4) above by (6) above.

[0099] (Method for measuring absorbent density in non-highly compressed portions) (1) Peel off at least one of the sheets on the front and back sides of the absorbent element 50 so that the surface having the non-highly compressed portions 52 of the absorbent element 50 is exposed, and five rectangular measurement areas of predetermined dimensions are marked using a pen on the non-highly compressed portions 52. Measure the dimensions of the measurement areas to determine their area. (2) Measure the basis weight of the absorbent element 50. (3) Cut out a portion of the packaging sheet 58 from the absorbent element 50 and measure the basis weight of the packaging sheet 58. (4) Determine the mass of the absorbent element 50 in the measurement area from the results of measurements (1) and (2) above, and determine the mass of the packaging sheet 58 in the measurement area from the results of measurements (1) and (3) above, and subtract the latter from the former to determine the mass of the absorbent body 56 in the measurement area. (5) After freezing the absorbent element 50 with liquid nitrogen, cut it in the thickness direction TD so as to cross approximately the center of the measurement area, and observe the cut surface under a microscope to measure the thickness of the absorbent body 56. (6) Assuming that the thickness of the absorbent body 56 in the measurement target area is constant, the volume of the absorbent body 56 in the measurement target area is calculated by multiplying the area of ​​the measurement target area (1) above by the thickness of the absorbent body 56 in (5) above. (7) The density of the absorbent body 56 in the non-highly compressed portion 52 is calculated by dividing (4) above by (6) above.

[0100] The area of ​​each highly compressed portion 51 is not particularly limited, but is preferably 2 to 25 mm ２ It is preferable that the thickness is about 3 to 15 mm. ２ It is particularly preferable that

[0101] The highly compressed portions 51 are high-density portions compressed in the thickness direction TD by pressure (direct pressure) to a substantially uniform thickness, and are the bottoms of depressions recessed from at least one of the front and back surfaces of the absorbent element 50. Such high-density portions have the property that the intertwining of fibers is unlikely to be broken even when they expand due to liquid absorption. On the other hand, the non-highly compressed portions 52 are thicker and have a lower density than the highly compressed portions 51. However, even in the non-highly compressed portions 52, the absorbent body 56 deforms near the periphery of the highly compressed portions 51 as if pulled by the deformation of the highly compressed portions 51, resulting in an increase in density as it approaches the highly compressed portions 51. As a result, capillary action is strongly exhibited in the highly compressed portions 51, which not only increases the liquid retention capacity compared to the surrounding areas but also draws liquid toward the highly compressed portions 51. Therefore, if the individual spaced apart highly compressed portions 51 have a certain degree of density and area, in an absorbent 56 containing hardwood pulp fibers, the strength of the absorbent 56 after absorbing liquid is less likely to decrease, and the suction force due to capillary action acts on a larger amount of excrement, causing the excrement absorbed by the absorbent 56 to spread over a wider area.

[0102] Although not shown, the absorbent element 50 may be compressed in the thickness direction TD so as to recess from both the front and back sides into the absorbent body 56, or the highly compressed portions 51 may be compressed in the thickness direction TD so as to recess only the back side of the absorbent element 50 into the absorbent body 56. In this case, a recess is formed on the back side of the absorbent element 50. However, as in the illustrated example, when the highly compressed portions 51 are compressed in the thickness direction TD so as to recess from at least the front side of the absorbent element 50 into the absorbent body 56, both backflow prevention and diffusion are improved. That is, as described above, capillary action is strongly expressed in the highly compressed portions 51, which not only increases liquid retention compared to the surrounding area, but also draws liquid toward the highly compressed portions 51, and allows excreted liquid collected by the highly compressed portions 51 to be firmly retained in areas far from the skin. As a result, backflow is less likely to occur.

[0103] Furthermore, the shortest distance d4 from the nearest other highly compressed portion 51 can be approximately 1 to 4 mm, and preferably approximately 1.5 to 3.5 mm. Providing the highly compressed portions 51 at relatively close intervals in this manner makes it less likely that the strength of the absorbent body 56 will decrease after absorbing liquid, and allows capillary suction to act on a larger amount of excrement, spreading the excrement absorbed by the absorbent body 56 over a wider area. Providing highly compressed portions 51 with a certain area at such intervals reduces the distance between the pulp fibers 56f in the highly compressed portions 51, thereby strengthening the entanglement of the pulp fibers 56f, reducing the gaps between the pulp fibers 56f that serve as paths for the movement of the superabsorbent polymer particles 56p, and increasing the contact area between the pulp fibers 56f and the superabsorbent polymer particles 56p. This in turn inhibits the movement of the superabsorbent polymer particles 56p within the absorbent body 56 and the movement of the superabsorbent polymer particles 56p out of the absorbent body 56. In other words, the retention of the high-absorbent polymer particles 56p in the absorbent body 56 containing hardwood pulp fibers is improved.

[0104] The area ratio of the highly compressed portions 51 in the region where the highly compressed portions 51 are arranged (total area of ​​the highly compressed portions 51 / area of ​​the region where the highly compressed portions 51 are arranged) is preferably 10 to 35%, and more preferably 20 to 35%. Furthermore, the diameter of the largest inscribed circle 54 inscribed in the outer shape of the non-highly compressed portions 52 is preferably 30 mm or less, more preferably 10 mm or less, even more preferably 6.5 mm or less, even more preferably 6 mm or less, and particularly preferably 5 mm or less. Furthermore, the lower limit of the diameter of the largest inscribed circle 54 inscribed in the outer shape of the non-highly compressed portions 52 is preferably 2 mm, more preferably 3 mm, and particularly preferably 4 mm.

[0105] In this way, when the highly compressed portions 51 are arranged particularly densely, the aforementioned improvement in liquid diffusibility is further enhanced. Furthermore, the retention of the superabsorbent polymer particles 56p is also further enhanced. Furthermore, even in the presence of non-highly compressed portions 52, the absorbent body 56 deforms near the periphery of the highly compressed portions 51 as if pulled by the deformation of the highly compressed portions 51, resulting in the advantage of a thinner absorbent body 56 compared to a case in which the highly compressed portions 51 are not present. From these perspectives, it is particularly preferable that the area ratio of the highly compressed portions 51 be within the above-mentioned range. Furthermore, it is particularly preferable that the diameter of the largest inscribed circle 54 inscribed in the outer shape of the non-highly compressed portions 52 is small so that the highly compressed portions 51 are not arranged sparsely (so that the non-highly compressed portions 52 do not continue long in all directions).

[0106] The dimensions and shape of the highly compressed portion 51 can be determined as appropriate. However, because the highly compressed portion 51 is a hard portion, if the dimensions of the highly compressed portion 51 are excessively large, if the shape of the highly compressed portion 51 is excessively long in one direction, or if the shape of the highly compressed portion 51 is excessively intricate, the absorbent body 56 as a whole may lack flexibility or may feel like a foreign object is mixed in the absorbent body 56 (foreign body sensation). Furthermore, if the dimensions of the highly compressed portion 51 are excessively small, if the shape of the highly compressed portion 51 is excessively long in one direction, or if the shape of the highly compressed portion 51 is excessively intricate, there is also the problem that the packaging sheet 58, when made of crepe paper, may be easily torn. Therefore, the diameter of the largest inscribed circle 53 inscribed in the outer shape of the highly compressed portion 51 is preferably 1 to 10 mm, more preferably 1 to 6 mm, even more preferably 2 to 5 mm, and particularly preferably 2.5 to 3.5 mm. Furthermore, the circumferential length of the outer shape of the highly compressed portion 51 is preferably 1 to 15 times the circumferential length of the largest inscribed circle 53 inscribed in the outer shape of the highly compressed portion 51, more preferably 1 to 5 times, even more preferably 1.0 to 2.5 times, even more preferably 1.0 to 2.0 times, and particularly preferably 1.0 to 1.6 times.

[0107] For example, the major axis d1 (the length of the long side of the smallest circumscribing rectangle) of each highly compressed portion 51 can be approximately 4 to 9 mm, and the minor axis d2 (the length of the short side of the smallest circumscribing rectangle) can be approximately 2 to 5 mm. When the lengths of the four sides of the smallest circumscribing rectangle for each highly compressed portion 51 are equal, the length d3 of the sides can be approximately 2 to 5 mm.

[0108] The shortest dimension of each highly compressed portion 51 is not particularly limited, but is preferably longer than the average fiber length of the hardwood pulp fibers, more preferably at least 4 times, even more preferably 4 to 10 times, and particularly preferably 4 to 12 times. Having the shortest dimension of each highly compressed portion 51 longer than the average fiber length of the hardwood pulp fibers has the advantage of reducing pulp bias and improving the shape retention of the absorbent body. Furthermore, the shortest dimension of each highly compressed portion 51 is preferably longer than the average particle size of the superabsorbent polymer particles 56p after swelling, more preferably 1.5 times or more, even more preferably 1.5 to 6 times, and particularly preferably 1.5 to 5 times. Having the shortest dimension of each highly compressed portion 51 longer than the average particle size of the superabsorbent polymer particles 56p after swelling has the advantage of improving the retention of the superabsorbent polymer particles and reducing bias in absorption performance.

[0109] The external shape of the highly compressed portion 51 is not particularly limited, and a shape that does not have an inflection point or a bending point, such as a circle, an ellipse, or a rounded rectangle (including shapes in which one of the opposite sides is not a straight line but is a semicircle), is preferable, but it may also be a triangle, a rectangle, a cloud, an X-shape, a V-shape, a U-shape, etc.

[0110] Generally, when improving backflow prevention, the mixing ratio of high-absorbent polymer particles with high liquid retention is often increased. In recent years, the mixing ratio of high-absorbent polymer particles has also been increased in order to, for example, reduce the thickness of the absorbent body 56. However, increasing the mixing ratio of high-absorbent polymer particles not only reduces the shape retention of the highly compressed sections 51, but also makes it difficult for the absorbent body 56 to deform in the non-highly compressed sections 52 near the periphery of the highly compressed sections 51, as if pulled by the deformation of the highly compressed sections 51, which may make it difficult to improve backflow prevention and diffusion. Furthermore, the high-absorbent polymer particles that have absorbed and expanded excrement are likely to adhere to each other, which may inhibit the diffusion of excrement (gel blocking), which may make it difficult to improve diffusion. Therefore, it is recommended that the basis weight of the pulp fibers in the absorbent body 56 be 100 to 500 g / m. ２ In this case, the weight ratio of pulp fibers to superabsorbent polymer particles in the absorbent body 56 is preferably 45:55 to 65:35.

[0111] The thickness 50t of the absorbent element 50 and the thickness 51t of the highly compressed portion 51 can be determined as appropriate, but insufficient compression may make it difficult to improve low return flow and diffusion. Therefore, when the above-mentioned range of pulp fiber basis weight and range of ratio of pulp fiber to superabsorbent polymer particles are adopted, the thickness 50t of the absorbent element 50 (the thickness of the non-highly compressed portion 52) is preferably 3 to 13 mm. In this case, the thickness 51t of the highly compressed portion 51 (the minimum value if the thickness varies) can be determined as appropriate, but in general, it is preferably 60 to 90% of the thickness 50t of the absorbent element 50.

[0112] The highly compressed portions 51 can be arranged in any regular or irregular pattern. For example, the highly compressed portions 51 may be arranged in a grid pattern in which dotted high compressed portions 51 are arranged as shown in FIG. 17 , in patterns in which dotted high compressed portions 51 are arranged in a staggered or matrix pattern as shown in FIGS. 18 and 19 , or in patterns in which X-shaped high compressed portions 51 are arranged in a matrix pattern as shown in FIG. 20 . Although not shown, the highly compressed portions may also be arranged in a grid pattern in which linearly connected high compressed portions are arranged, or in patterns in which high compressed portions of different sizes and shapes are arranged at intervals to form a predetermined pattern. In particular, when the highly compressed portions 51 are arranged in a dotted line pattern or when linearly connected high compressed portions 51 are arranged in a grid pattern, the movement of the superabsorbent polymer particles 56 p in the non-highly compressed portions 52 is restricted to the area surrounded by the highly compressed portions 51, and therefore uneven distribution of the superabsorbent polymer particles 56 p can be suppressed with fewer highly compressed portions 51. For example, as shown in FIG. 21 , a pattern may be used in which a plurality of high-compression portions 51 of different areas are arranged, with the largest high-compression portion 51 having an area three or more times larger than the smallest high-compression portion 51. The pattern shown in FIG. 21 includes a plurality of linear high-compression portions 51 of the same width but different lengths, with the longest high-compression portion 51 being three or more times larger than the shortest high-compression portion 51. The pattern shown in FIG. 21 also includes a combination of high-compression portions 51 extending in the front-to-rear direction LD, high-compression portions 51 extending in diagonal directions, and high-compression portions 51 having a portion extending in the front-to-rear direction LD and portions extending diagonally from both the front and rear ends of the high-compression portion 51. While the dimensions of each portion are shown in FIGS. 17 to 21 , these dimensions are merely examples and can, of course, be individually modified as appropriate.

[0113] One preferred pattern of the highly compressed portion 51 is the example shown in FIGS. In this example, in the arrangement area of ​​the high compression section 51, first virtual straight lines 81 along a first direction are repeatedly arranged at first intervals 81d in a second direction inclined by 80 to 90 degrees clockwise relative to the first virtual straight line 81 in a planar view, and second virtual straight lines 82 along the second direction are repeatedly arranged at second intervals 82d in the first direction to define a virtual lattice. When a smallest virtual rectangle 83 having the intersections of the first virtual straight lines 81 and the second virtual straight lines 82 as vertices is defined, the high compression section 51 consists of a first high compression section 51a arranged at the intersection positions of the first virtual straight lines 81 and the second virtual straight lines 82, second high compression sections 51b arranged between adjacent first high compression sections 51a on the first virtual straight line 81 and between adjacent first high compression sections 51a on the second virtual straight line 82, and third high compression sections 51c arranged at the intersection positions of the diagonals of the virtual rectangle. The first highly compressed portion 51a is a circle centered at the intersection of the first imaginary line 81 and the second imaginary line 82, the second highly compressed portion 51b is a rounded rectangle (or may be an ellipse) having a center of gravity at the midpoint of each side of the imaginary rectangle and having a major axis along each side, and the third highly compressed portion 51c is a rounded rectangle (or may be an ellipse or a circle centered at the intersection of the diagonal of the imaginary rectangle) having a center of gravity at the intersection of the diagonal of the imaginary rectangle and having a major axis along the front-to-rear direction LD. This pattern can improve the diffusibility in the major axis direction (first direction and second direction) of the second highly compressed portion 51b, and since the non-highly compressed portions 52 have both a portion where they are linearly continuous in the first direction and a portion where they are linearly continuous in the second direction, even if each highly compressed portion 51 hardens, the absorbent body 56 as a whole will easily deform to fit the body surface.

[0114] 11 and 16, the dimensions of each highly compressed portion 51 can be determined as appropriate, but the first highly compressed portion 51a has a diameter of 1 to 4 mm, the second highly compressed portion 51b has a major axis length of 3 to 6 mm and a minor axis length equal to the diameter of the first highly compressed portion 51a, and the third highly compressed portion 51c has the same size and shape as the second highly compressed portion 51b except that its major axis is oriented along the front-to-rear direction LD. It is preferable that the shortest distance d4 between adjacent first and second highly compressed portions 51a and 51b is 1 to 2 mm, as this not only improves backflow prevention and liquid dispersibility but also improves the ease of deformation of the absorbent body 56. The ratio of the first spacing 81d:second spacing 82d is preferably in the range of 0.9:1.1 to 1.1:0.9, and it is particularly preferable that the first spacing 81d and the second spacing 82d are equal. The first gap 81d and the second gap 82d can be set to about 10 to 14 mm.

[0115] Furthermore, if the above-mentioned virtual lattice has a diagonal lattice shape in which the first virtual straight line 81 is inclined 40 to 50 degrees clockwise relative to the front-to-back direction LD in a planar view and the second virtual straight line 82 is inclined 40 to 50 degrees counterclockwise relative to the front-to-back direction LD in a planar view, this is preferable because it not only makes the absorbent body 56 more easily deformable when worn, but also provides excellent liquid diffusion properties.

[0116] Table 2 shows specific examples of the arrangement of the highly compressed portions 51.

[0117] The absorbent element can be manufactured by a known method. For example, an absorbent element 50 having a highly compressed portion 51 can be manufactured by performing the following steps: a first step of forming an absorbent body 56 by mixing and accumulating pulp fibers and superabsorbent polymer particles; a second step of forming a package 50P by wrapping the entire absorbent body 56 in a package sheet 58; and a third step of passing the package 50P between an anvil roll 90 having numerous protrusions 91 spaced apart on its outer circumferential surface in the same pattern as the highly compressed portion 51 and an opposing smooth roll 92 having a cylindrical surface (without protrusions 91), as shown in Figure 22 . The highly compressed portion 51 can be formed by pressing the portion of the package 50P sandwiched between the numerous protrusions 91 of the anvil roll 90 and the smooth roll 92. The highly compressed portion 51 may be formed while heating either the anvil roll 90 or the smooth roll 92, or without heating. In the third step, only the portion of the packaging body 50P that is sandwiched between the numerous protrusions 91 of the anvil roll 90 and the smooth roll 92 may be pressed, or the entire packaging body 50P may be pressed while the portion that is sandwiched between the numerous protrusions 91 of the anvil roll 90 and the smooth roll 92 is pressed to the deepest extent.

[0118] The dimensions, shape, and arrangement of the tip surfaces of the protrusions 91 can be, for example, the same as the dimensions, shape, and arrangement of the highly compressed portions 51. The clearance (minimum distance between the pressing positions) between the anvil roll 90 and the smooth roll 92 can be equal to or less than the thickness of the highly compressed portions 51, and can be, for example, 0.5 to 1.5 mm. The pressure used when forming the highly compressed portions 51 with the anvil roll 90 and the smooth roll 92 can be determined as appropriate, and can be, for example, 0.2 to 0.4 MPa.

[0119] (Packaging Sheet) As the packaging sheet 58, a liquid-permeable sheet such as crepe paper, nonwoven fabric, polylaminated nonwoven fabric, or a perforated sheet can be used. The nonwoven fabric used for the packaging sheet 58 is not particularly limited, but an SMS nonwoven fabric or an SSMMS nonwoven fabric, in which at least one meltblown layer is sandwiched between a pair of spunbond layers on the front and back, can be suitably used. The material of the fiber is not particularly limited, and for example, polypropylene fiber, polyethylene / polypropylene bicomponent fiber, etc. can be used. The basis weight of the packaging sheet 58 can be determined as appropriate, but is preferably 5 to 40 g / m ２ , especially 10 to 30 g / m ２ It is preferable that the following be used.

[0120] The crepe paper used for the packaging sheet is not particularly limited, but the basis weight is 13 to 20 g / m ２ , especially 14 to 18 g / m ２ Furthermore, the crepe paper preferably has an air permeability of 1 to 15 seconds as measured in accordance with JIS P 8117:2009 "Paper and paperboard - Test method for air permeability and air resistance (intermediate range) - Gurley method."

[0121] The average fiber length of the pulp constituting the crepe paper used in the packaging sheet 58 may be less than twice the average fiber length of all the pulp fibers constituting the absorbent body 56, but is preferably 1.5 to 3 times the average fiber length, which has the advantage of improving the material strength. The average fiber length of the pulp constituting the crepe paper used in the packaging sheet 58 is more preferably 1.5 to 3 times the average fiber length of all the pulp fibers constituting the absorbent body 56.

[0122] On the other hand, the crepe paper used for packaging sheet 58 generally has a tensile breaking elongation of 20 to 35% in the front-to-rear direction LD and a tensile breaking elongation of 4 to 8% (particularly 5 to 7%) in the width direction WD, as specified in JIS P 8113:2006. When packaging sheet 58 is made of such crepe paper, the crepe paper may tear at the edges of highly compressed sections 51 or between adjacent highly compressed sections 51 when forming the highly compressed sections 51. However, this can be reduced by ensuring that the outer shape of each highly compressed section 51 does not have an inflection point or bending point, that the diameter of the largest inscribed circle inscribed in the outer shape of each highly compressed section 51 is 2 to 5 mm, and that the perimeter of the outer shape of each highly compressed section 51 is 1 to 2.5 times the perimeter of the largest inscribed circle inscribed in the outer shape of each highly compressed section 51.

[0123] It is preferable for the packaging sheet 58 to be configured so that the MD direction is along the front-to-rear direction LD, as this facilitates manufacturing. In this case, the fiber orientation of the packaging sheet 58 is in the front-to-rear direction LD, and the dry tensile strength in the width direction WD is significantly weaker than the dry tensile strength in the front-to-rear direction LD. Therefore, if the dimension of the highly compressed portion 51 in the front-to-rear direction LD is more than twice, particularly more than three times, the dimension of the highly compressed portion 51 in the width direction WD (i.e., the highly compressed portion 51 is elongated in the front-to-rear direction LD), the packaging sheet 58 is prone to tearing on both sides of the width direction WD. Therefore, it is preferable for the dimension of the highly compressed portion 51 in the front-to-rear direction LD to be less than twice, particularly less than 1.5 times, the dimension of the highly compressed portion 51 in the width direction WD, as this makes the packaging sheet 58 less prone to tearing.

[0124] The packaging structure of the packaging sheet 58 can be determined as appropriate, but from the standpoint of ease of manufacturing and preventing leakage of superabsorbent polymer particles from the front and rear edges, it is preferable to wrap the sheet around the absorbent body 56 in a cylindrical shape so as to surround the front, back, and both side surfaces, as shown in the illustrated example, with the front and rear edges extending beyond the front and rear of the absorbent body 56, and to join the overlapping wound portions and the overlapping portions of the extending front and rear edges by a joining means such as a hot melt adhesive or material welding.

[0125] In particular, as shown in Figure 15, the packaging sheet 58 has a surface portion 58s located on the front side of the absorbent body 56, a first back side portion 58a that continues from the surface portion 58s, wraps around one side edge of the absorbent body 56 to reach the back side of the absorbent body 56, and a second back side portion 58b that continues from the surface portion 58s, wraps around the other side edge of the absorbent body 56 to reach the back side of the absorbent body 56.The first back side portion 58a and the second back side portion 58b have a stacked portion 58W in which they overlap each other, and if all the highly compressed portions 51 are formed in the stacked portion 58W, this is preferable because the crepe paper on the forming surface of the highly compressed portions 51 is doubled, improving strength and making them less likely to tear when the highly compressed portions 51 are formed.

[0126] The shape retention of the absorbent element 50 due to the highly compressed portions 51 is determined by the retention of the highly compressed portions 51 themselves, which in turn is determined by the bond strength between the packaging sheet 58 and the absorbent body 56 in the highly compressed portions 51 and the shape retention of the absorbent body 56 itself. When the packaging sheet 58 and the absorbent body 56 are bonded together using hot melt adhesives HM1 and HM2, the increase in surface area due to the formation of the highly compressed portions 51 requires more hot melt adhesive HM1 and HM2 than usual to sufficiently maintain the bond strength between the packaging sheet 58 and the absorbent body 56 and the shape retention of the absorbent body 56 itself. Therefore, the surface of the absorbent body 56 and the inner surface of the packaging sheet 58 should have a density of 5.0 to 20.0 g / m2 at least over the entire region having the highly compressed portions. ２ , particularly 7.5 to 15.0 g / m ２ It is preferable that the adhesive is bonded via hot melt adhesives HM1 and HM2.

[0127] For example, as shown in Figure 9, when a depression is formed on the surface of the absorbent body 56 due to the highly compressed portion 51, the above-mentioned amount of hot melt adhesive HM can be achieved by providing two layers of hot melt adhesive HM1, HM2 on the back surface of the absorbent body 56 over the entire area having the highly compressed portion 51. Such a structure can be produced by applying a first hot melt adhesive HM1 to almost the entire inner surface of the unfolded packaging sheet 58 on the surface facing the absorbent 56, as shown in Figure 13, then placing the absorbent 56 in the middle of the first hot melt adhesive HM1 on the packaging sheet 58 in the width direction WD, and bonding the back surface of the absorbent 56 to the packaging sheet 58 via the first hot melt adhesive HM1, then applying a second hot melt adhesive HM2 to almost the entire surface of the absorbent 56, and then, as shown in Figure 14, folding back the portions of the packaging sheet 58 that extend on both sides of the absorbent 56 onto the surface of the absorbent 56, respectively, and bonding the surface of the absorbent 56 to the folded-back portions of the packaging sheet 58 via the first hot melt adhesive HM1 and the second hot melt adhesive HM2, and bonding the overlapping portions of the packaging sheet 58 via the first hot melt adhesive HM1, and then forming a lattice-shaped highly compressed portion 51 by embossing, as shown in Figure 9.

[0128] In order to reduce costs, the absorbent element 50 may have no other sheet layers such as paper or nonwoven fabric (which may of course have an adhesive layer) between the packaging sheet 58 and the absorbent body 56, as shown in Figure 9, or may have other sheet layers on at least one side of the front or back of the absorbent body 56.

[0129] <Method for manufacturing absorbent body> The absorbent body 56 can be manufactured by a known method. Figure 25 is a schematic diagram of an example of an absorbent body manufacturing apparatus 100. In this absorbent body manufacturing apparatus, a pulp supply unit 111 that supplies a fibrous material that mainly contains pulp is provided upstream. The pulp supply unit 111 may be equipped with a defibrator, and a pulp sheet 110 is supplied to this defibrator.

[0130] When manufacturing an absorbent body 56 containing hardwood pulp fibers, a pulp sheet 110 containing hardwood pulp fibers is supplied to a defibrator. In the defibrator, the pulp sheet 110 is mechanically defibrated into fibers to obtain fluff pulp. The pulp sheet 110 may be in either a bale or roll form, but a roll form is preferred because it facilitates improved productivity.

[0131] Furthermore, there are no particular limitations on the device used for the mechanical treatment to defibrate the pulp sheet 110. Known defibrators used in the manufacture of absorbent articles such as disposable diapers can be used, and defibrators that utilize frictional force or shear force for mechanical treatment can be preferably used. Examples of defibrator types include hammer-type defibrators, impact-type defibrators, roll-type defibrators, and jet airflow defibrators.

[0132] The fluff pulp obtained by defibration is supplied into the duct 112. A polymer particle introduction section 113 for supplying superabsorbent polymer particles may be provided midway through the duct 112. Thus, the pulp fibers 56f (fluff pulp) and superabsorbent polymer particles 56p are mixed in the duct 112 and then supplied to the stacking drum 115. A plurality of absorbent molds 115C are arranged circumferentially spaced apart on the outer circumferential surface of the stacking drum 115. As the stacking drum 115 rotates, the absorbent molds 115C sequentially receive the mixture of pulp fibers 56f and superabsorbent polymer particles 56p. The bottom of the absorbent mold 115C is made of a perforated plate or mesh plate, and the mixture of pulp fibers and superabsorbent polymer particles can be accumulated on the bottom of the absorbent mold 115C by sucking gas through the perforations. Furthermore, by venting gas through the perforations, the absorbent 56 can be supplied to a conveying means 116 such as a belt conveyor. The fiber stacking drum 115 is provided with a negative pressure chamber and a positive pressure chamber inside, and each chamber is capable of sucking in and discharging gas, respectively.

[0133] A scuffing roll (or brush) 114 may be provided downstream within the duct 112. The scuffing roll 114 scrapes off excess stacked absorbent material, making the surface of the absorbent material accumulated in the absorbent mold 115C uniform. The absorbent 56 supplied to the conveying means 116 can be compressed in the thickness direction by compression means 117. The compression means 117 may be a pair of rolls as shown in FIG. 25, or a pair of pressing members approaching the absorbent 56 from both sides. The compression means 117 improves the shape retention of the absorbent 56.

[0134] Further downstream, the absorbent body 56 is wrapped in a wrapping sheet 58 to become the absorbent element 50. The step of wrapping the absorbent body 56 in the wrapping sheet 58 can also be carried out by a known method.

[0135] When two layers of absorbent body 56 are laminated, as shown in Figure 26, a manufacturing apparatus 120 can be used that includes single-layer manufacturing units 101 and 102 that respectively manufacture the layers included in absorbent body 56, in the illustrated example, upper layer 56a and lower layer 56b. Both single-layer manufacturing units 101 and 102 have the same configuration as manufacturing apparatus 100 (Figure 25) for manufacturing a single-layer absorbent body. The absorbent body layers 56a and 56b manufactured in the single-layer manufacturing units 101 and 102 are stacked in the thickness direction, and then the entire assembly is wrapped in packaging sheet 58 to form an absorbent element.

[0136] (Rising gathers) The rising gathers 60 have rising portions 68 that rise from the sides of the inner body 200, and these rising portions 68 come into contact with the wearer's area from the groin through the legs to the buttocks, preventing side leakage. The rising gathers 60 can be omitted as necessary. In the illustrated example, the rising gathers 60 have a base side portion 60B that rises obliquely toward the center in the width direction, and a tip side portion 60A that rises obliquely from the intermediate portion toward the outside in the width direction, but the present invention is not limited to this and can be modified as appropriate, such as to rise toward the center in the width direction as a whole.

[0137] More specifically, the rising gathers 60 in the illustrated example are formed by folding a strip-shaped gathered sheet 62, having a length equal to the longitudinal length of the inner body 200, in two by folding the leading end portion in the width direction WD, and by fixing a plurality of elongated gathered elastic members 63 between the folded portion and the sheet in the vicinity thereof in a stretched state along the longitudinal direction at intervals in the width direction WD. The base end portion of the rising gathers 60 opposite the leading end (the end portion opposite the folded portion of the sheet in the width direction WD) forms a root portion 65 fixed to the side portion of the inner body 200, and the portion other than the root portion 65 forms a main body portion 66 (the portion on the folded portion side) extending from the root portion 65. The main body portion 66 further has a root portion 60B extending toward the center in the width direction and a tip portion 60A folded back at the leading end of the root portion 60B and extending outward in the width direction. The front-to-rear end portions of the main body portion 66 are formed as fallen portions 67 which are fixed in a fallen state to the side surfaces of the top sheet 30, while the front-to-rear intermediate portion between them is formed as an unfixed raised portion 68, and a gathered elastic member 63 extending along the front-to-rear direction LD is fixed in a stretched state to at least the tip portion of this raised portion 68.

[0138] In the rising gathers 60 configured as described above, the contractile force of the gather elastic member 63 causes the rising portions 68 to rise up so as to come into contact with the skin as shown by the arrows in Fig. 3. In particular, when the root portion 65 is located on the back side of the inner body 200, the rising portions 68 rise up so as to open outward in the width direction in the crotch region and its vicinity, so that the rising gathers 60 come into contact with the surrounding legs as a whole, improving fit. The root portion 65 can also be fixed to the front side of the inner body 200, for example, to the surfaces of both side portions of the top sheet 30.

[0139] In a bent structure such as the illustrated rising gathers 60, in which the main body portion 66 is composed of a root portion 60B extending toward the center in the width direction and a tip portion 60A folded back at the tip of the root portion 60B and extending outward in the width direction, the tip portion 60A and the root portion 60B are joined in a folded state at a fallen portion 67, and the root portion 60B is joined in a folded state to the topsheet 30. To join the opposing surfaces at the fallen portion 67, at least one of various application methods of hot melt adhesive and material welding such as heat sealing and ultrasonic sealing can be used. In this case, the joining of the root portion 60B and the topsheet 30 and the joining of the tip portion 60A and the root portion 60B may be performed by the same means or by different means. For example, it is preferable to join the root portion 60B and the top sheet 30 with a hot melt adhesive, and to join the tip portion 60A and the root portion 60B with material welding.

[0140] As the gathered sheet 62, a nonwoven fabric that is soft and has excellent uniformity and hiding power, such as a spunbond nonwoven fabric (SS, SSS, etc.), an SMS nonwoven fabric (SMS, SSMMS, etc.), or a meltblown nonwoven fabric, and that has been subjected to a water-repellent treatment with silicone or the like as necessary, can be suitably used. In this case, the fiber weight of the nonwoven fabric is 10 to 30 g / m ２ Although not shown, a waterproof film may be interposed between the two folded gathered sheets 62.

[0141] The gathered elastic member 63 can be made of rubber thread or the like. When spandex rubber thread is used, the thickness is preferably 470 to 1240 dtex, more preferably 620 to 940 dtex. The elongation percentage of the gathered elastic member 63 in the attached state is preferably 150 to 350%, more preferably 200 to 300%. The number of gathered elastic members 63 is preferably 2 to 6, more preferably 3 to 5. The appropriate spacing between the gathered elastic members 63 is 3 to 10 mm. This configuration makes it easier for the gathered elastic members 63 to come into contact with the skin over their entire surface. The gathered elastic members 63 may be placed not only on the tip side but also on the base side.

[0142] In the rising portion 68 of the rising gathers 60, at least one of various application methods of hot melt adhesive and material welding, such as heat sealing or ultrasonic sealing, can be used to bond the inner and outer layers of the gathered sheet 62 together and to secure the gathered elastic member 63 sandwiched therebetween. Bonding the entire inner and outer layers of the gathered sheet 62 together reduces flexibility, so it is preferable to leave the areas other than the adhesive portion of the gathered elastic member 63 unbonded or to only weakly bond them. In the illustrated example, hot melt adhesive is applied only to the outer peripheral surface of the gathered elastic member 63 using an application means such as a comb gun or a SureWrap nozzle, and the gathered elastic member 63 is sandwiched between the inner and outer layers of the gathered sheet 62. This results in a structure in which the gathered elastic member 63 is secured to the inner and outer layers of the gathered sheet 62 and the inner and outer layers of the gathered sheet 62 are secured together solely by the hot melt adhesive applied to the outer peripheral surface of the gathered elastic member 63.

[0143] Similarly, the fallen portion 67 can be fixed by at least one of various application methods of hot melt adhesive and material welding such as heat sealing or ultrasonic sealing.

[0144] 1 to 4, etc., side flaps 70 extending out to the sides of the absorbent body 56 are provided on both sides of the inner body 200, and it is preferable that side stretchable regions SG that stretch in the front-to-rear direction are formed in these side flaps 70. The side flaps 70 in the illustrated example have one or more elongated side elastic members 73 arranged along the front-to-rear direction LD and spaced apart from one another, a first sheet layer 71 facing the outside of the side elastic member 73, and a second sheet layer 72 facing the inside of the side elastic member 73.

[0145] The sheet material forming the first sheet layer 71 and the second sheet layer 72 is not particularly limited, and any suitable nonwoven fabric can be selected, such as a nonwoven fabric that can be used for the above-described rising gathers 60 or the above-described outer bodies 12F and 12B. In the illustrated example, the first sheet layer 71 and the second sheet layer 72 are formed by extending the gathered sheet 62 of the rising gathers 60, as will be described later. In this case, the front and rear ends of the side flaps 70 coincide with the front and rear ends of the rising gathers 60 (i.e., the front and rear ends of the inner body 200 in this case).

[0146] The side elastic members 73 are not particularly limited either, and can be elongated elastic members similar to the gathered elastic members 63 described above. The extension percentage of the side elastic members 73 in the attached state is preferably 150 to 350%, more preferably 200 to 270%. The number of side elastic members 73 is preferably 2 to 16, more preferably 6 to 10. The appropriate spacing between the side elastic members 73 is 5 to 10 mm.

[0147] The side elastic members 73 are fixed to the first sheet layer 71 and the second sheet layer 72. Various application methods of hot melt adhesive HM or material welding methods such as heat sealing and ultrasonic sealing can be used to bond the first sheet layer 71 and the second sheet layer 72 together and to secure the side elastic members 73 sandwiched between them. Because a large bonded area between the first sheet layer 71 and the second sheet layer 72 reduces flexibility, it is preferable to leave the portions of the side elastic members 73 unbonded or to bond them only weakly. In the illustrated example, the hot melt adhesive HM is applied only to the outer peripheral surfaces of the side elastic members 73 using an application method such as a comb gun or a SureWrap nozzle, and the side elastic members 73 are sandwiched between the first sheet layer 71 and the second sheet layer 72. The hot melt adhesive HM applied only to the outer peripheral surfaces of the side elastic members 73 secures the side elastic members 73 to the first sheet layer 71 and the second sheet layer 72 and secures the first sheet layer 71 and the second sheet layer 72 together.

[0148] In the illustrated example, the sheet material constituting the first sheet layer 71 and the sheet material constituting the second sheet layer 72 are folded back at the side edges of the side flaps 70, and these folded back portions are fixed (closed) to the back surface of the liquid-impermeable sheet 11. This fixing can be performed with a hot melt adhesive HM as in the illustrated example, or by welding the materials together.

[0149] The side flaps 70 may be omitted.

[0150] <Production Examples of Pulp Sheets for Absorbent Body Production> Using the materials shown in Table 1, pulp sheets Nos. 1 to 20 containing hardwood pulp fibers were produced according to the following procedure.

[0151] (Cooking process) (1) Hardwood: Acacia and eucalyptus were mixed in the mass ratio shown in Table 1, and white liquor having a predetermined sulfidity was added. Cooking was carried out in a rotary autoclave at a liquor ratio of 6.0 (L / kg) and a maximum temperature of 170°C, yielding hardwood unbleached kraft pulp with a kappa number of approximately 16. (2) Softwood: White liquor having a predetermined sulfidity was added to cedar, and cooking was carried out in a rotary autoclave at a liquor ratio of 6.0 (L / kg) and a maximum temperature of 170°C, yielding softwood unbleached kraft pulp with a kappa number of approximately 30.

[0152] (Washing process) After diluting the unbleached pulp to a pulp consistency of about 2%, No. 2 filter paper (manufactured by Advantec Co., Ltd.) was placed in a Buchner funnel and dewatered to a pulp consistency of about 12%. The unbleached pulp was then sandwiched between square filter papers (manufactured by Advantec Co., Ltd.) and pressure was applied using a press to dewater it to a pulp consistency of 33%. This washing process was carried out twice.

[0153] (Bleaching Process) (1) Hardwood unbleached kraft pulp was ozone bleached for approximately 2 minutes at 45°C with 8.1% ozone gas. For the ozone bleaching, ozone gas from a laboratory ozone generator, a PSA Ozonizer SGA-01A-PSA4 manufactured by Sumitomo Precision Products Co., Ltd., was used. The pulp after ozone bleaching was further bleached with chlorine dioxide at 70°C with a chlorine dioxide addition rate of 1.5% and a pulp consistency of 10% by mass to obtain bleached hardwood kraft pulp. Between each bleaching process, the pulp was diluted to approximately 2% consistency, and then a dilution and washing process was carried out twice, using No. 2 filter paper (manufactured by ADVANTEC) in a Buchner funnel to dehydrate the pulp to approximately 12% consistency. (2) Softwood Unbleached kraft pulp was bleached with chlorine dioxide at a chlorine dioxide addition rate of 1.5% and a pulp consistency of 10% by mass at 70°C for 30 minutes. Subsequently, alkaline hydrogen peroxide bleaching was performed at 70°C for 120 minutes with an alkali addition rate of 1%, a hydrogen peroxide addition rate of 0.3%, and a pulp consistency of 10% by mass. Subsequently, alkaline treatment was performed at 70°C for 120 minutes with a sodium hydroxide addition rate of 0.2%, a pulp consistency of 10% by mass. Subsequently, chlorine dioxide bleaching was performed at 70°C for 150 minutes with a chlorine dioxide addition rate of 0.3%, a pulp consistency of 10% by mass, to obtain softwood bleached kraft pulp. Between each bleaching step, the pulp was diluted to a consistency of approximately 2%, and then a dilution and washing step was performed twice using No. 2 filter paper (manufactured by ADVANTEC) placed in a Buchner funnel to dehydrate the pulp consistency to approximately 12%.

[0154] (Papermaking process) The obtained hardwood kraft pulp and softwood kraft pulp were diluted to a consistency of about 2% without beating, and adjusted to the blending ratios shown in Table 2. Then, using the adjusted pulp slurry, a semi-automatic sheet machine (manufactured by Kumagai Riki Kogyo Co., Ltd.) was used to make a paper with a basis weight of 800 g / m ２ A hand-made sheet (pulp sheet for fluff pulp) was prepared so that the

[0155] <Preparation of absorbent articles> Each pulp sheet was used to prepare an absorbent body using the apparatus shown in Figure 25. The amount of superabsorbent polymer added to the fluff pulp was 9.3 g relative to 7.7 g of fluff pulp. Using the obtained absorbent body, disposable diapers (tape type, L size) were prepared without providing the above-mentioned highly compressed portion 51.

[0156] <Measurement of Pulp Fiber Length and Fiber Width, etc.> The fiber length and fiber width of each hardwood unbleached kraft pulp after the cooking and washing processes were measured. The fiber length and fiber width were measured using a Valmet fiber length analyzer "VALMET FS5" in accordance with JIS-P8226:2011 (ISO16065-2:2007) "Pulp - Fiber length measurement method by optical automatic analysis." The fiber analyzer "VALMET FS5" is a device that can measure the length and width of pulp fibers by image analysis of diluted pulp fibers passing through a measurement cell inside the fiber analyzer. From the obtained measurements, the mass-based proportion of pulp fibers with a fiber length of 0.5 mm or more and less than 1.1 mm and the mass-based proportion of pulp fibers with a fiber width of 10 μm or more and less than 35 μm were calculated. The average fiber length and standard deviation σ were calculated when the pulp fibers having a fiber length of 0.5 mm or more and less than 1.1 mm were measured at 0.02 mm intervals (with a classification width of 0.02 mm), and the average fiber width and standard deviation σ were calculated when the pulp fibers having a fiber width of 10 μm or more and less than 35 μm were measured at 1 μm intervals (with a classification width of 1 μm). The average values ​​(average fiber length and average fiber width values) are arithmetic means. The standard deviation was calculated from n = 10,000 or more measurements using a fiber analyzer. The calculation results are shown in Table 3.

[0157]

[0158] <Evaluation> Evaluation was carried out as follows. The evaluation results are shown in Table 4.

[0159] (Density) The density of the fluff pulp pulp sheet in each example was measured in accordance with "Paper and paperboard - Test methods for thickness, density and specific volume" described in JIS-P8118 (2014).

[0160] (Calculation of specific burst strength) The specific burst strength of the pulp sheet for fluff pulp in each example was calculated by dividing the burst strength [kPa] measured in accordance with JIS-P8131 (2009) by the basis weight [kPa m ２ / g].

[0161] (Evaluation of defibration ability) Based on the burst strength index, the defibration ability of each pulp sheet for fluff pulp was evaluated. The evaluation criteria were the following five levels. When the evaluation was A, B, C, or D, the defibration ability of the pulp sheet for fluff pulp was good, and among these, the defibration ability in the case of A was excellent. Furthermore, D was slightly inferior, but at a level that is not problematic in practical use. A: Burst strength index was 1.2 kPa m ２ / g or more 1.5kPa・m ２ B: The specific burst strength is 1.6 kPa·m / g or less. ２ / g or 1.1 kPa m ２ C: Specific burst strength is 1.7 kPa m ２ / g or 1.0 kPa m ２ D: Specific burst strength is 1.8 kPa m ２ / g or 0.9 kPa m ２ / g. E: Specific burst strength is 1.9 kPa m ２ / g or more or 0.8 kPa m ２ / g or less.

[0162] (Measurement of Klemm's Water Absorbency) The Klemm's water absorbency of each fluff pulp sheet was measured in accordance with "Paper and paperboard - Water absorbency test method - Klemm's method" described in JIS-P8141 (2004). More specifically, ２ For each fluff pulp sheet, the height [mm] was measured 1 minute after the start of measurement, and the water absorption rate [mm / min] from 1 minute to 2 minutes after the start of measurement was calculated based on the height [mm] 1 minute and 2 minutes after the start of measurement.

[0163] (Water Absorption Evaluation) Based on the height value one minute after the start of the measurement, the water absorption (absorption performance) of the flap pulp sheet was evaluated according to the following criteria: A: The height one minute after the start of the Klemm water absorbency measurement was 29 mm or more and 40 mm or less. B: The height one minute after the start of the Klemm water absorbency measurement was 27 mm or more and less than 29 mm. C: The height one minute after the start of the Klemm water absorbency measurement was 25 mm or more and less than 27 mm. D: The height one minute after the start of the Klemm water absorbency measurement was less than 25 mm.

[0164] (Evaluation of Water Absorption Rate) Based on the water absorption rate values ​​from 1 to 2 minutes after the start of the measurement, the water absorption rate of the flap pulp sheet was evaluated according to the following criteria: A: The water absorption rate from 1 to 2 minutes after the start of the Klemm water absorbency measurement was 9 mm / min or more. B: The water absorption rate from 1 to 2 minutes after the start of the Klemm water absorbency measurement was 7 mm / min or more and less than 9 mm / min. C: The water absorption rate from 1 to 2 minutes after the start of the Klemm water absorbency measurement was 5 mm / min or more and less than 7 mm / min. D: The water absorption rate from 1 to 2 minutes after the start of the Klemm water absorbency measurement was more than 3 mm / min and less than 5 mm / min. E: The water absorption rate from 1 to 2 minutes after the start of the Klemm water absorbency measurement was 3 mm / min or less.

[0165] (Evaluation of workability during production of fluff pulp) The workability during production of fluff pulp was evaluated at a basis weight of 200 g / m ２The pulp sheets for fluff pulp in each example were cut into 2 cm x 2 cm pieces and crushed in a commercially available mixer (Mixer TM856, manufactured by Tescom Co., Ltd.), and the degree of paper dust generated during crushing was examined for evaluation. The amount of paper dust accumulated during crushing increased from E to A. The evaluation was based on the following five levels. Evaluations of A, B, C, and D indicated good workability. A: Paper dust flew around when the pulp sheet was crushed, and a small amount of pulp accumulated on the mixer walls. B: Paper dust flew around when the pulp sheet was crushed, and a small amount of pulp accumulated on the mixer walls. C: Paper dust flew around when the pulp sheet was crushed, and a small amount of pulp accumulated on the mixer walls. D: Paper dust flew around when the pulp sheet was crushed, and some pulp accumulated on the mixer walls, but this was within the range of no problem. E: Paper dust flew around when the pulp sheet was crushed, and a large amount of pulp accumulated on the mixer walls, to a level that was unsuitable for practical use.

[0166] (Evaluation of Skin Rash Suppression of Absorbent Articles) A ​​total of 220 monitors were asked to use 10 of each of No. 1 to 22 disposable diapers prepared as described above for each example. That is, 10 monitors evaluated each disposable diaper of one example. The number of diapers that developed a rash was then evaluated as a percentage. The evaluation was based on the following five levels. A rating of A, B, C, or D means that the effect of suppressing skin rash is better than that of No. 20, which has the same configuration as the existing product. A: The rash incidence rate is better than that of No. 20. B: The rash incidence rate is slightly better than that of No. 20. C: The rash incidence rate is slightly better than that of No. 20. D: The rash incidence rate is slightly better than that of No. 20 and is usable. E: The rash incidence rate is the same as that of No. 20, at the same level as the existing product. The effect of suppressing rash is related to the effect of suppressing return of the absorbent body and the absorption capacity of the absorbent body.

[0167]

[0168] As can be seen from Tables 3 and 4, Nos. 1 to 19, which contain hardwood pulp fibers and softwood pulp fibers, and in which the proportion of pulp fibers with a fiber length of 0.5 mm or more and less than 1.1 mm in the total pulp fibers is 42.6% or more, and the proportion of pulp fibers with a fiber width of 10 μm or more and less than 35 μm is 90.6% or more, showed particularly good results in terms of defibration ability, workability during fluff pulp production, and rash prevention effect in absorbent articles.

[0169] <Effect Confirmation Test 1> Pant-type disposable diaper samples (having the same structure as in Figures 1 to 6) equipped with absorbent elements of the various conditions shown in Table 5 were prepared, and measurements of the thickness of the absorbent elements, a backflow test under pressure, measurements of the diffusion area, an absorbent core strength test, and a polymer dropout test were performed. Note that the basis weight of the packaging sheet, the dry tensile strength of the packaging sheet, and the tensile breaking elongation of the packaging sheet in Table 5 were measured values ​​of the material before the highly compressed portion was formed.

[0170] The dimensions of each part of Samples 1 and 3 were as follows: Length d3 of first highly compressed portion 51a: 3 mm Major diameter d1 of second highly compressed portion and third highly compressed portion: 4.82 mm Minor diameter d2 of second highly compressed portion and third highly compressed portion: 3 mm First interval 81d: 12.63 mm Second interval 82d: 12.63 mm Intersection angle between first imaginary line 81 and second imaginary line 82: 90 degrees

[0171] In Samples 1 and 3, the highly compressed portions were formed over the entire surface of the absorbent element at a pressure of 0.4 MPa. Samples 2 and 4 were comparative examples that did not have highly compressed portions. All conditions other than those shown in Table 5 were the same for all samples.

[0172] (Reverse Pressure Test) This test was conducted using a blue test solution prepared by dissolving approximately 5 g of Kiriya Food Grade Blue No. 1 (Brilliant Blue FCF) (packaged as powder) in approximately 300 ml of artificial urine. The procedure was as follows: (1) The side seals 12A of the sample were cut to open the front and back panels F and B. The sample was then placed on a horizontally placed flat plate with the front surface (the surface containing the highly compressed recess) facing up. The four corners of the sample were secured to the flat plate with adhesive tape so that the inner body 200 was held in place in a flat, unfolded position. (2) A pouring tube (consisting of an acrylic cylindrical section with an inner diameter of 23 mm, an outer diameter of 25 mm, and a height of 100 mm, and a square flange extending around the cylindrical section with dimensions of 100 mm x 100 mm x 2 mm) was placed vertically on the center of the absorbent body (the center of the width and the center of the front-to-back direction) on the surface of the sample. (3) Using a measuring cylinder, pour 50 cm of the blue test solution into the top opening of the injection tube. ３ 7cm ３ The artificial urine was poured at a rate of 1 / sec. / sec., and the test was waited from the start of the pouring until the artificial urine disappeared from the sample surface (complete absorption), and then the pouring tube was removed. (4) The test was left for 30 minutes after the pouring tube was removed. (5) Following the step (4) above, steps (2) to (4) above were repeated. (6) Following the step (5) above, steps (2) and (3) above were repeated. (7) 20 minutes after the artificial urine from the third pouring in step (6) above was completely absorbed, a 5 kg weight was placed on the artificial urine pouring point and left for 10 minutes. The weight was a square with a flat base measuring 100 mm long x 100 mm wide, and was placed on the sample surface so that the length and width of the weight were aligned with the front-to-back and width directions of the sample, and the center of the weight was located over the center of the absorbent body. (8) Advantec qualitative filter paper No. The weight (g) of 30 sheets of 2 (100 mm long x 100 mm wide square) was measured to three decimal places using an electronic balance. (9) Following the procedure in (7) above, 30 sheets of the filter paper were placed between the weight and the sample surface, with the center and orientation aligned. After 20 seconds, all the filter papers were removed and their weight (g) was measured to two decimal places. The weight measured before absorption in (5) above was subtracted from the weight measured after absorption to determine the amount of return.

[0173] (Measurement of Diffusion Area) Following the pressure-reverse test, the sample was fixed on a horizontally placed flat plate, with a ruler placed next to it. Still images of the sample and ruler were taken from directly above the sample. The captured image data was then loaded into the image analysis software "Fiji" (Fiji Is Just ImageJ), and the area of ​​the blue portion on the sample surface was measured using the following procedure. (1) Launch Fiji, select "File" and then "Open," and load the image to be measured. (2) Select the "Straight" icon and align it with two points on the ruler scale in the image. (3) Select "Analyze" and then "Set Scale," and enter the actual distance between the two points aligned in (2) above (read from the ruler scale) in "Known distance" and the unit in "Unit of length." (4) Select "Image," "Type," and then "8-bit" to convert the image to 8-bit. (5) Select "Image," "Adjust," and "Threshold" in that order to display the Threshold selection screen, set the Threshold to 150-210 (Default Red), and check "Dark background" and "Don't reset range." (6) Select "Analize" and "Set Measurements" in that order, check "Area," "Mean gray value," "Min & Max gray value," and "Limit to threshold," and select OK. (7) Select "Polygon selections," and circle the liquid diffusion range within the range displayed in red in (5) above. (8) Select "Analyze" and "Measure" in that order to display the "Results," and set the "Area" item to the diffusion area (set "Unit of length" to cm, and the unit of area is cm). ２ (We decided to do so.)

[0174] (Absorbent Body Strength Test) (1) After cutting the side seal 12A of the sample and opening the front body F and back body B, the sample was placed on a horizontally placed flat plate with the front surface (the surface having the depressions in the highly compressed areas) facing up, and the four corners of the sample were fixed to the flat plate with adhesive tape so that the inner body 200 was fixed in a flat, unfolded state. (2) A pouring tube (consisting of an acrylic cylindrical section with an inner diameter of 23 mm, an outer diameter of 25 mm, and a height of 100 mm, and a square flange section extending around the cylindrical section, measuring 100 mm long x 100 mm wide x 2 mm thick) was placed at the center of the absorbent body (the center in the width direction and the center in the front-to-back direction) and 100 mm rearward from there, and held vertically. (3) 90 cm of the above blue test liquid was poured into the upper opening of the pouring tube using a measuring cylinder. ３ 7cm ３ The test tubes were then poured at a rate of 10 ... ３ 7cm ３ The artificial urine was poured at a rate of 1 / sec. / sec, and a wait was made from the start of pouring until the artificial urine disappeared from the sample surface (complete absorption), at which point a 300 g weight was placed on the flange of the central pouring tube, and a load was applied evenly to the flange. (5) After leaving the sample for 5 minutes after the weight in (4) was placed, the sample was removed from the flat plate and attached to the rotating plate 303 of the hammering tester 300 described below, and hammering was performed repeatedly at 5-second intervals. Note that in the initial state in which the rotating plate 303 was facing vertically downward, the outer surface of the front exterior body 12F of the sample was attached to the hook member 303F of the rotating plate 303 so that the front-to-back direction of the sample 320 was aligned with the up-and-down direction. (6) During the striking in (5) above, the tester visually inspected the shape of the absorbent body of sample 320 from the front of the striking surface 301S, and after recognizing that a tear had occurred in the absorbent body, the tester stopped striking after each strike, measured the width of the tear with a ruler, and recorded the number of strikes until the width of the tear reached 3 cm as the strength of the absorbent body.

[0175] 27 and 28 show a hammer tester 300. The hammer tester 300 comprises a support 310 made of a rectangular parallelepiped frame placed on the floor, a light box 301 attached to the middle of the back surface 311 of the support 310 in the vertical direction, a first rotation shaft 302 extending in a substantially horizontal direction and spaced apart above the light box 301 on the back surface 311, and one end of the first rotation shaft 302 is fixed to the first rotation shaft 302 and is supported so as to be freely rotatable forward and backward between a state facing vertically downward and a state facing horizontally by rotating from there toward the front. The light box 301 includes a flat rotating plate 303, a second rotating shaft 304 provided concentrically with a center line obtained by extending the rotation center line of the first rotating shaft 302 in the horizontal direction, a sample gripping arm 305 extending radially from the second rotating shaft 304 and supported by the second rotating shaft 304 so as to be rotatable forward and backward, and a drive source (servo motor) 306 for rotating the sample gripping arm 305 forward and backward between a state in which the arm faces vertically downward and a state in which the arm faces substantially horizontally after being rotated toward the front. The light box 301 has a transparent striking surface 301S on the front, and light from an internal light (white LED) 301L passes through the striking surface 301S and is irradiated forward. Furthermore, the rotating plate 303 has a hook member 303F of a mechanical fastener attached over almost the entire surface that is the front side when the rotating plate 303 is initially facing vertically downward, and this hook member 303F can be used to attach the outer surface of the sample 320. The tip of the sample gripping arm 305 has a clamp unit 307 that grips the lower end of the sample 320 hanging down from the rotating plate 303 facing vertically downward, and while maintaining this position, rotates the lower end of the sample 320 toward the front side until it reaches a substantially horizontal position, and then releases the grip. A drive source (not shown) for driving the clamp unit 307 is also provided. Reference numeral 307C denotes a pair of gripping units for gripping the sample 320 from both the front and back sides of the lower end of the sample 320.

[0176] In the striking tester 300, after the sample 320 is attached to the rotating plate, in the initial state without any external force being applied, the sample 320 and the rotating plate 303 face substantially vertically downward, as shown by the solid line in FIG. 27 , and the outer surface of the sample 320 is in contact with the striking surface 301S of the light box 301. The sample gripping arm 305 also faces substantially vertically downward, with the clamp 307 at its tip open. When the test operation is initiated, the clamp 307 automatically closes to grip the lower end of the sample 320, as shown by the arrow and two-dot chain line in the enlarged portion of FIG. 27 . While maintaining this state, the sample gripping arm 305 rotates until it is substantially horizontal toward the front, as shown by the arrow and two-dot chain line in FIG. 27 , and the lower end of the sample 320 also faces substantially in the same direction. Next, as indicated by the arrow and two-dot chain line in the enlarged portion of FIG. 27 , the clamp unit 307 automatically opens, causing the sample 320 and the rotating plate 303 to lose their restraining external force and freely rotate around the first rotating shaft 302 due to their own weight, causing the back surface of the sample 320 to strike the striking surface 301S of the light box 301. The sample gripping arm 305 then returns to its initial state. During the testing operation, this striking operation of the sample 320 (gripping, rotating, releasing, and striking) is repeated at set time intervals. By stopping the testing operation, the sample 320 and the rotating plate 303 face almost vertically downward, and the sample 320 stops in a position aligned with the striking surface 301S of the light box 301. Here, a tester facing the front of the sample 320 can visually confirm the shape of the absorber by the illumination light from the light box 301 that passes through the sample 320 (depending on the amount of light transmitted). In particular, the external shape of the absorbent body that has absorbed the above-mentioned blue test liquid can be easily recognized visually.

[0177] (Polymer Shedding Test) (1) After cutting the side seal 12A of the sample to open the front body F and back body B, the rear end of the inner body was cut along the rear edge of the absorbent body to expose the rear edge of the absorbent body. Since the rear outer body 12B of this sample had a folded portion 12r that covered the inner body 200 up to the edge on the waist opening WO side, this folded portion 12r was peeled off and cut off using cold spray. (2) With the rotating plate 303 of the aforementioned striking tester 300 facing vertically downward in its initial state, the outer surface of the front outer body 12F of the sample was attached to the hook member 303F of the rotating plate 303 so that the front-to-back direction of the sample 320 was aligned with the vertical direction. A collection tray (not shown) for collecting superabsorbent polymer particles was placed 10 cm below the striking surface 301S. The striking was then repeated 30 times at 5-second intervals. (3) After the impact in (2) above, the weight of the fallen polymer in the collection tray was measured and recorded as the amount of fallen polymer.

[0178] The test results are shown in Table 5.

[0179]

[0180] Sample 1, which had an absorbent body containing hardwood pulp fibers and had highly compressed sections formed in the absorbent element, had higher absorbent body strength than Sample 2, which was identical except for not having highly compressed sections, and had absorbent body strength at the same level as Sample 3, which had an absorbent body made only of softwood pulp fibers. The diffusion area of ​​Sample 1 was significantly higher than Sample 2 and at the same level as Sample 3, which had an absorbent body made only of softwood pulp fibers. Furthermore, Sample 1 not only had a lower backflow amount than Sample 2, but also significantly the lowest of all the samples, a noteworthy result. Sample 1 also had a lower amount of shed polymer than Sample 2, and at the same level as Sample 3, which had an absorbent body made only of softwood pulp fibers. As can be seen from the comparison of Samples 1 and 2 and Samples 3 and 4, the formation of highly compressed sections reduced the thickness of the absorbent element, and as can be seen from the comparison of Samples 1 and 3, the inclusion of hardwood pulp fibers further reduced the thickness of the absorbent element.

[0181] <Explanation of Terms Used in the Specification> The following terms used in the specification have the following meanings unless otherwise specified in the specification.

[0182] The "front-to-back direction" refers to the direction indicated by the symbol LD in the figure (vertical direction), and the "width direction" refers to the direction indicated by the symbol WD in the figure (left-to-right direction), and the front-to-back direction and the width direction are perpendicular to each other.

[0183] "Front side" means the side closest to the wearer's skin when worn, and "rear side" means the side farthest from the wearer's skin when worn.

[0184] "Front" means the side closest to the wearer's skin when worn, and "back" means the side farthest from the wearer's skin when worn.

[0185] "Elongation rate" refers to a value when the natural length is 100%. For example, an elongation rate of 200% is equivalent to an elongation ratio of 2 times.

[0186] - "Artificial urine" is a mixture of 2 wt% urea, 0.8 wt% sodium chloride, 0.03 wt% calcium chloride dihydrate, 0.08 wt% magnesium sulfate heptahydrate, and 97.09 wt% ion-exchanged water.

[0187] "Gel strength" is measured as follows: 1.0 g of superabsorbent polymer is added to 49.0 g of artificial urine and stirred with a stirrer. The resulting gel is left in a thermo-hygrostat at 40°C and 60% RH for 3 hours, then returned to room temperature, and the gel strength is measured using a curd meter (Curdmeter-MAX ME-500, manufactured by I.techno Engineering).

[0188] - "Basis weight" is measured as follows. After pre-drying the sample or test piece, it is left in a test room or device under standard conditions (test location: temperature 23±1°C, relative humidity 50±2%) until it reaches a constant weight. Pre-drying refers to bringing the sample or test piece to a constant weight in an environment at a temperature of 100°C. Note that pre-drying is not necessary for fibers with an official moisture regain of 0.0%. Using a sample collection template (100mm x 100mm), a sample measuring 100mm x 100mm is cut from the test piece when it has reached a constant weight. The weight of the sample is measured and multiplied by 100 to calculate the weight per square meter, which is the basis weight.

[0189] The "thickness" of thick members such as the absorber 56 and the absorbent element 50 is measured using a thickness gauge (Peacock, Dial Thickness Gauge, Model H (measurement range: 0 to 10 mm, probe: circular pressure plane with a diameter of 10 mm, measuring force: approximately 1.7 N, pressure: approximately 21.7 kPa)) manufactured by Ozaki Seisakusho Co., Ltd., with the test member and the thickness gauge positioned horizontally. The thickness of the absorbent element 50 (non-highly compressed portion 52) is determined as follows. That is, ten regions of the non-highly compressed portion 52 of the absorbent element 50 are selected so that the inscribed circle inscribed in the outer shape of the non-highly compressed portion 52 is the largest, and the thickness measured by aligning the center of the inscribed circle of each region with the center of the probe of the thickness gauge is defined as the thickness of the absorbent element 50 (non-highly compressed portion 52).

[0190] The "thickness" of the highly compressed portion 51 is calculated by subtracting the depth of the highly compressed portion 51 from the thickness of the absorbent element 50 (non-highly compressed portion 52).

[0191] The "depth" of the highly compressed portion 51 is measured using a Keyence Corporation One-Shot 3D Measuring Macroscope VR-3200 or its equivalent, the observation application "VR-H2V," and the analysis application "VR-H2A," or their equivalent software. In principle, the measurement is performed at a magnification of 12x and with a field of view area of ​​24mm x 18mm. However, the magnification and field of view area can be changed depending on the size of the highly compressed portion 51. To measure the specific depth, the observation application is launched, a sample is placed on the microscope stage so that the highly compressed portion 51 to be measured is positioned within the field of view, and the "Measure" button is pressed. Next, the analysis application is executed, and the measured 3D information is analyzed. The analysis procedure is described below with reference to FIG. 23 . That is, using the analysis application, a depth (measured cross-sectional curve) profile is obtained along a line segment Q1 passing through the center (or center of gravity, if the shape is not circular) of one highly compressed portion 51 in the image portion (XY portion in the figure) shown from a planar viewpoint. From the cross-sectional curve of this depth profile, surface roughness components with wavelengths shorter than λc: 800 μm (where λc is the "filter defining the boundary between the roughness component and the waviness component" described in JIS-B0601, "3.1.1.2") are removed using a low-pass filter. Within the "contour curve Q2" of the image portion (XZ portion in the figure) shown from a cross-sectional viewpoint, positions where the curve is nearly flat or where the curve is most pronounced upward are designated as two boundary points P1 and P2, and the minimum height value of the range between these boundary points P1 and P2 is determined. Furthermore, the average value of the height values ​​of boundary points P1 and P2 is designated as the maximum height. The depth of the highly compressed portion 51 can then be determined by subtracting the minimum height value from the maximum height value. The two boundary points P1 and P2 are visually selected. The planar image of the highly compressed portion 51 being measured may be used as a reference for this selection. The above measurements are carried out for any 10 highly compressed portions 51 designed to have the same dimensions and shape, and the results are taken as an average value.

[0192] The dimensions of the highly compressed portions 51, such as their diameter and spacing, are measured using a Keyence Corporation One-Shot 3D Measuring Macroscope VR-3200 or its equivalent, the observation application "VR-H2V," and the analysis application "VR-H2A," or their equivalent software. In principle, the measurement is performed at a magnification of 12x and with a field of view area of ​​24mm x 18mm. However, the magnification and field of view area can be changed depending on the size of the highly compressed portions 51. Specifically, when measuring dimensions, the observation application is launched, a sample is placed on the microscope stage so that the highly compressed portions 51 to be measured are positioned within the field of view, and the "Measure" button is pressed. Next, the analysis application is executed, and the measured 3D information is analyzed. The procedure for analyzing the diameter of the highly compressed portions 51 is described below with reference to FIG. 23. That is, using the analysis application, a depth (measured cross-sectional curve) profile is obtained for a line segment Q1 passing through the highly compressed portions 51 of interest along an arbitrary diameter direction in the image area (XY portion in the figure) shown from a planar perspective. From the cross-sectional curve of this depth profile, surface roughness components with wavelengths shorter than λc: 800 μm (where λc is the "filter defining the boundary between the roughness component and the waviness component" as described in JIS-B0601, "3.1.1.2") are removed using a low-pass filter. The image portion (XZ portion in the figure) shown from a cross-sectional perspective is obtained by removing these surface roughness components with wavelengths shorter than λc: 800 μm (where λc is the "filter defining the boundary between the roughness component and the waviness component" as described in JIS-B0601, "3.1.1.2"). The intersections of the "contour curve Q2" with a line Q3 parallel to the X-axis, located +0.25 mm from the lowest point 51L, are designated as P3 and P4, and the distance X1 in the X-axis direction between these intersections P3 and P4 is designated as the diameter of the highly compressed portion 51. The above measurements are performed on any 10 highly compressed portions 51 designed to have the same dimensions and shape, and the results are taken as the average. The procedure for analyzing the spacing between adjacent highly compressed portions 51 is described below with reference to FIG. 23 . That is, using the above analysis application, a depth (measured cross-sectional curve) profile is obtained for a line segment Q1 passing through two adjacent highly compressed portions 51 along the direction of the target spacing in the image portion shown from a planar perspective.From the cross-sectional curve of this depth profile, surface roughness components with wavelengths shorter than λc: 800 μm (where λc is the "filter defining the boundary between the roughness component and the waviness component" described in JIS-B0601 "3.1.1.2") are removed using a low-pass filter to form a "contour curve Q2" of the image portion (XZ portion in the figure) shown from a cross-sectional perspective, and the intersections with a line Q3 parallel to the X axis located +0.25 mm from the lowest point 51L are designated as P3, P4, P5, and P6, and the distance X2 in the X-axis direction between the two adjacent intermediate intersection points P4 and P5 is designated as the spacing between the highly compressed portions 51. The above measurements are performed on any five pairs of adjacent highly compressed portions 51 designed to have the same dimensions and shape, and the results are taken as the average value.

[0193] The "thickness" of thin sheets such as nonwoven fabrics was measured using an automatic thickness measuring device (KES-G5 handy compression measurement program) with a load of 0.098 N / cm ２ , and pressure area: 2 cm ２ Automatic measurement is performed under the following conditions.

[0194] The "area" of the highly compressed portion 51 is measured using a Keyence Corporation One-Shot 3D Measuring Macroscope VR-3200 or its equivalent, the observation application "VR-H2V," and the analysis application "VR-H2A," or their equivalent software. Generally, the measurement is performed at a magnification of 12x and with a field of view of 24mm x 18mm. However, the magnification and field of view can be changed depending on the size of the highly compressed portion 51. Specifically, to measure the area, the observation application is launched, a sample is placed on the microscope stage so that the highly compressed portion 51 to be measured is positioned within the field of view, and the "Measure" button is pressed. Next, the analysis application is executed, and the "Volume / Area" button is pressed to move to the volume / area measurement screen to analyze the measured 3D information. On the volume / area measurement screen, the "Recess" button is pressed, followed by the "Set Measurement Area" button. Then, the "Minimum Height" button in "Auxiliary Tool 2" is pressed to specify an area that includes one highly compressed portion 51 of interest, and the lowest point within the displayed area is selected. Next, select "Auto Extraction (Level)" from the "Element Tools," then specify the lowest point as the reference point, set the intersection height to +0.25 mm, and press the "OK" button. Return to the volume / area measurement screen, and the value displayed as the area of ​​the portion from the lowest point to a height of 0.25 mm within the specified region is taken as the area of ​​the highly compressed portion 51. The above measurements are carried out for any five highly compressed portions 51 designed with the same dimensions and shape, and the result is taken as the average value.

[0195] "Area ratio" refers to the proportion of the area of ​​a target portion per unit area, and is calculated by dividing the total area of ​​the target portion (e.g., the highly compressed portion 51) in the entire target region (e.g., the back surface of the absorbent element 50) by the area of ​​the target region, and expressing it as a percentage. When calculating the area ratio of the highly compressed portions 51, a rectangular region circumscribing all of the highly compressed portions 51 is used as the target region, and the total area of ​​the highly compressed portions 51 is calculated from the area of ​​the highly compressed portions 51, as described below. That is, when five or more highly compressed portions 51 designed with the same dimensions and shape are provided, the area of ​​all of the highly compressed portions 51 in that design is the average value measured using the above-described method for measuring the area of ​​the highly compressed portions 51. On the other hand, when the dimensions and shapes of the highly compressed portions 51 are irregular, or when there are fewer than five highly compressed portions 51 designed with the same dimensions and shape, the area of ​​each of the highly compressed portions 51 is measured individually using the above-described method for measuring the area of ​​the highly compressed portions 51 (the average value is not calculated).

[0196] "Water absorption" is measured according to JIS K7223-1996 "Test method for water absorption of superabsorbent resins."

[0197] "Water absorption rate" is the "time to the end point" when 2 g of superabsorbent polymer and 50 g of physiological saline are used and the "test method for water absorption rate of superabsorbent polymers" according to JIS K7224-1996 is performed.

[0198] "Deployed state" means a state in which the device is deployed flat without contraction (including any contraction such as contraction due to an elastic member) or slack.

[0199] - Unless otherwise specified, the dimensions of each part refer to the dimensions in the unfolded state, not the natural length state.

[0200] - If there is no description of the environmental conditions for a test or measurement, the test or measurement shall be carried out in a test room or device under standard conditions (the test location shall be a temperature of 23±1°C and a relative humidity of 50±2%).

[0201] The present invention can be used in all absorbent articles having an absorbent core, including disposable diapers such as pants-type disposable diapers, tape-type disposable diapers, and pad-type disposable diapers, as well as sanitary napkins and pet diapers.

[0202] 11...liquid-impermeable sheet, 12A...side seal, 12B...rear outer body, 12E...waist extension portion, 12F, 12B...outer body, 12F...front outer body, 12S, 12H...sheet material, 13...cover nonwoven fabric, 16, 19...waist lower elastic member, 17...waist elastic member, 18...unnecessary elastic member, 20...inner body joining portion, 200...inner body, 30...top sheet, 40...intermediate sheet, 50...absorbent element, 50P...packaging body, 51...highly compressed portion, 51a...first highly compressed portion, 51b...second highly compressed portion, 51c...third highly compressed portion, 52...non-highly compressed portion, 56...absorbent body, 56f...pulp fiber, 56p...superabsorbent polymer particles, 56L...low basis weight portion, 58...packaging sheet, 60...rising gathers, 60A...tip side portion, 60B...attachment base side portion, 62...gathered sheet, 63...gathered elastic member, 67...flat portion, 68...risen portion, 70...side flap, 71...first sheet layer, 72...second sheet layer, 73...side elastic member, 81...first imaginary straight line, 82...second imaginary straight line, 90...anvil roll, 91...projection portion, 92...smooth roll, A1...non-stretchable region, A2...stretchable region, B...back body, C...buttocks covering portion, F...front body, HM...hot melt adhesive, HM1...first hot melt adhesive, HM2...second hot melt adhesive, L...middle region, LD...front and rear direction, LO...leg opening, M...crotch portion, SG...side stretchable region, T...torso region, TD...thickness direction, U...lower waist portion, W...waist portion, WD...width direction, WO...waist opening.

Claims

DEPCT691 Targeted Absorbent, consisting of: an absorbent element composed of an absorbent body arranged in a certain front-back direction including the target, and a wrapper that encloses the absorbent body. The absorbent body is made from a mixture and bundling of pulp fibers, including hardwood pulp fibers and superconducting polymer particles. The percentage of such particles whose pre-swelling particle diameter is less than the average fiber length of hardwood pulp fibers in the superconducting polymer particles is 60% by mass or more. The absorbent element is equipped with a number of spaced high-compression zones, which are compressed in the thickness direction to be concave into the absorbent body from at least one of the front and back surfaces of the absorbent element. Apart from the high-compression zones in the arrangement of these zones are non-compression zones, which are thicker and denser than the high-compression zones. The shortest distance from each high-compression zone to the nearest other high-compression zone is 1 to 4 mm.And the area of ​​each highly compressed section is 2 to 200 square millimeters.

2. Adsorbents according to claim 1, where the area ratio of the highly compressed section in the arrangement area of ​​a certain number of highly compressed sections is 10 to 35%, and the diameter of the largest attached circle attached to the boundary of the non-compressed section is 30 mm or less.

3. Adsorbents according to claim 2, where the highly compressed section has a boundary without any indentation or bending points, the diameter of the largest attached circle attached to the boundary of the highly compressed section is 1 to 10 mm, and the circumference of the boundary of the highly compressed section is 1 to 15 times the circumference of the largest attached circle attached to the boundary of the highly compressed section.

4. Adsorbents according to claim 2 or 3,Where a virtual grid formed by repeatedly arranged virtual straight lines in the first direction at the first spacing in the second direction is tilted 80 to 90 degrees clockwise in a top-down view relative to the first virtual straight line and the second repeatedly arranged virtual straight lines in the second spacing in the first direction, is defined within a region of arrangement of a number of compressed sections, and the smallest virtual square whose vertices are the intersection of the first and second virtual straight lines, the compressed section is composed of the first compressed section arranged at the intersection of the first and second virtual straight lines, the second compressed section arranged sequentially between adjacent first compressed sections on the first virtual straight line and between adjacent first compressed sections on the second virtual straight line, and the third compressed section arranged at the intersection of the diagonals of the virtual square.The first compressed section is a circle centered on the intersection of the first and second virtual straight lines; the second compressed section is an ellipsoid or rounded rectangle with its center of gravity at the midpoint of each side and its major axis along each side of the virtual square; and the third compressed section is an ellipsoid or rounded rectangle with its center of gravity at the intersection of the diagonals and major axis in the anterior-rear direction of the virtual square, or a circle centered on the intersection of the diagonals of the virtual square.

5. Under claim 4, where the first compressed section has a diameter of 1 to 4 mm, the second compressed section has a major axis length of 3 to 6 mm and a minor axis length equal to the diameter of the first compressed section, the third compressed section is of the same size and shape as the second compressed section except for the determination of the direction of the major axis, which is in the anterior-rear direction.And the minimum spacing between the first and second adjacent high-compression sections is 1 to 2 mm.6 Adsorbents under claim 4, where the virtual grid has a diagonal grid shape in which the first virtual straight line is tilted 40 to 50 degrees clockwise in a top view relative to the front-back direction and the second virtual straight line is tilted 40 to 50 degrees counterclockwise in a top view relative to the front-back direction.7 Adsorbents under claim 1 or 2, where the basic weight of the membrane fibers in the absorbent body is At a density of 100 to 500 g / m², the weight ratio of membrane fibers to superconducting polymer particles in the absorbent body is 40:60 to 65:35, the thickness of the non-compressible section is 3 to 13 mm, and the thickness of the compressible section is 60 to 90% of the thickness of the non-compressible section of the 8 absorbents according to claim 1 or 2, where the percentage of such particles, whose pre-swelling particle diameter is 500 micrometers or less, in the superconducting polymer particles is 60% by mass or more, and in the total membrane fibers of the absorbent body.The percentage of pulp fibers with a fiber length of 0.5 mm or more and less than 1.1 mm is 40% or more by mass, and the percentage of pulp fibers with a fiber width of 10 micrometers or more and less than 35 micrometers is 90% or more by mass.

9. Adsorbents under claim 8, where the pulp fibers of the absorbent body are composed of softwood pulp fibers and hardwood pulp fibers, and the ratio by mass of hardwood pulp fibers to softwood pulp fibers is 25 / 75 or higher and 38 / 62 or lower;

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