JP5417133B2 - Absorbent articles - Google Patents

Description

  The present invention relates to an absorbent article such as a sanitary napkin.

  Absorbent articles such as sanitary napkins and disposable diapers are known that have a liquid-permeable top sheet, a liquid-impermeable back sheet, and an absorbent body interposed between both sheets and containing a water-absorbing polymer. It has been. For example, in Patent Document 1, as an absorbent article that suppresses bulging caused by swelling of a superabsorbent resin (water-absorbing polymer) in the absorbent article, the absorber is densely packed with the superabsorbent resin. It is described that has a dense layer and a space layer adjacent to the dense layer in the up-down direction and having a dotted portion.

  Further, Patent Document 2 has a second layer parallel to the first layer in a face-to-face relationship, and a continuous region in which the water-absorbing polymer is substantially uniformly distributed between both layers, and the continuous region. An absorbent structure is described having an enclosed and substantially free of water-absorbing polymer. According to the absorbent structure described in Patent Document 2, a space in which the water-absorbing polymer can expand is secured by the presence of the section, and the total fluid capacity of the absorbent structure can be efficiently used. Yes.

  Further, Patent Document 3 contains crosslinked polymer particles, a flocculant, and water-insoluble inorganic porous fine particles as absorbent resin particles (water-absorbing polymer) excellent in absorption performance, and has a water retention amount of 35. Absorptive resin particles having an absorption amount under load of ˜50 g / g and 18 to 25 g / g are described. According to the absorbent resin particles, it is difficult to cause so-called gel blocking, in which the liquid passage is blocked by the absorbent resin particles swollen by the absorption of the liquid.

JP 2008-237382 A Japanese National Patent Publication No. 11-503594 JP 2008-247949 A

  In the techniques described in Patent Documents 1 and 2, gel blocking may occur in a region where water-absorbing polymers are dense. Therefore, an absorbent article such as a sanitary napkin to which these techniques are applied is a non-skin contact surface (skin contact surface) from the skin contact surface (surface directed toward the skin side of the absorbent product wearer). The liquid on the opposite side) is poorly permeable, liquid residue is likely to occur on the surface sheet that forms the skin contact surface, and there is a risk that the excreted body fluid will be in contact with the skin for a long time, causing a load on the skin. is there.

  Moreover, although the absorptive resin particle of patent document 3 has a fixed effect in prevention of gel blocking, there exists a possibility of raise | generating gel blocking in the state to which predetermined pressure, such as body pressure, was applied. Therefore, in the absorbent article using the absorbent resin particles described in Patent Document 3, for example, when body fluid is excreted when the wearer of the absorbent article is sitting, gel blocking occurs. Since the body fluid is excreted in the body, it is difficult for the body fluid to permeate from the skin contact surface side to the non-skin contact surface side. The rest may occur.

  Accordingly, an object of the present invention is to provide an absorbent article that is excellent in liquid permeability, hardly causes liquid residue on the skin contact surface, and has an excellent dry feeling.

The present invention is an absorbent article comprising a top sheet, a back sheet, and an absorbent body interposed between both sheets and including a water-absorbing polymer and a fiber, wherein the water-absorbing polymer has an angle of repose of a swollen gel. The absorbent body has a water-absorbing polymer high concentration region in which the content of the water-absorbing polymer exceeds the average water-absorbing polymer content calculated by the following formula. The above-mentioned problems are solved by providing an absorbent article.
Water-absorbing polymer average content (% by mass) = (total mass of all water-absorbing polymers contained in the absorber / total mass of the absorber) × 100

  According to the absorbent article of the present invention, the bodily fluid excreted on the skin contact surface side is quickly transmitted to the non-skin contact surface side, and liquid residue on the surface sheet is hardly generated, and an excellent dry feeling is obtained.

FIG. 1 is a perspective view schematically showing a skin contact surface side (surface sheet side) of a sanitary napkin that is an embodiment of the absorbent article of the present invention. FIG. 2 is a cross-sectional view schematically showing a cross section taken along line II of FIG. FIG. 3 is a plan view schematically showing a distribution pattern of the water-absorbing polymer in the absorbent body included in the napkin shown in FIG. FIG. 4 is a cross-sectional view schematically showing a part of a cross section along the thickness direction of the absorbent body included in the napkin shown in FIG. 1. FIG. 5A and FIG. 5B are cross-sectional views schematically showing a part of FIG. 4 in an enlarged manner. FIG. 6 is a schematic explanatory view of a manufacturing method of an absorbent body provided in the napkin shown in FIG. FIG. 7 is a view corresponding to FIG. 3 showing another embodiment of the distribution pattern of the water-absorbing polymer in the present invention. FIG. 8A to FIG. 8C are diagrams corresponding to FIG. 3 showing still another embodiment of the distribution pattern of the water-absorbing polymer in the present invention. FIG. 9 is a schematic explanatory diagram of another method for manufacturing an absorbent body according to the present invention. FIG. 10 is a perspective view schematically showing a part of a manufacturing apparatus used in the manufacturing method shown in FIG. FIG. 11 is a cross-sectional view schematically showing a cross section of the absorbent body obtained by the manufacturing method shown in FIG. FIG. 12 is an explanatory diagram of a method for measuring the angle of repose of a swollen gel. FIG. 13 is a perspective view schematically showing one embodiment of a top sheet provided in the napkin shown in FIG. 1. 14 is a plan view schematically showing an enlarged part of the skin contact surface side of the top sheet shown in FIG. 15 is a cross-sectional view schematically showing a cross section taken along line III-III in FIG. FIG. 16 is a photomicrograph of the linear embossing and the fiber parallel standing part adjacent to the linear embossing as viewed from the skin contact surface side of the top sheet. 17 is a cross-sectional view schematically showing a cross section along the thickness direction of the napkin shown in FIG. FIG. 18 is a schematic diagram illustrating some examples in the case where individual partition regions or a plurality of types of partition regions have a dimensional ratio of golden ratio or silver ratio. FIG. 19 is a schematic explanatory view of the method for producing the top sheet shown in FIG. FIG. 20 is a cross-sectional view showing another embodiment of the top sheet according to the present invention.

  Hereinafter, the absorbent article of the present invention will be described based on its preferred embodiments with reference to the drawings. The sanitary napkin which is one Embodiment of the absorbent article of this invention is shown by FIG.1 and FIG.2. A sanitary napkin 1 (hereinafter also referred to as a napkin 1) of the present embodiment has a shape that is long in one direction in plan view, and includes a liquid-permeable top sheet 2, a liquid-impermeable back sheet 3, and both An absorbent body 10 interposed between the sheets 2 and 3 and including a water-absorbing polymer is provided. As will be described later, the napkin 1 contains a water-absorbing polymer having an angle of repose of the swollen gel of 45 ° or less as described later. The absorbent body 10 has a shape that is long in one direction in a plan view, and its longitudinal direction (the direction indicated by the symbol X in FIG. 1) coincides with the longitudinal direction of the napkin 1 so that the width direction of the napkin 1 (FIG. 1). In the middle direction).

  As shown in FIG. 2, the top sheet 2 covers the entire skin contact surface of the absorbent body 10, and the back sheet 3 covers the entire non-skin contact surface of the absorbent body 10. An adhesive is applied on the non-skin contact surface of the back sheet 3 to form a fixing portion (not shown) for fixing the napkin 1 to shorts or the like. As the back sheet 3, those usually used in the technical field can be used without particular limitation. For example, the back sheet 3 may be composed of a liquid-impermeable film sheet. It may have water vapor permeability. The top sheet 2 will be described later.

  In the present specification, the “longitudinal direction” is a direction along the long side direction of the absorbent article or its constituent member (absorber or the like), and the “width direction” is a direction orthogonal to the longitudinal direction. . In addition, the “skin contact surface” is a surface of the absorbent article or a component thereof directed to the wearer's skin when the absorbent article is worn, and the “non-skin contact surface” is the wear of the absorbent article. The surface is directed to the side opposite to the skin contact surface.

  On the skin contact surface side (surface sheet 2 side) of the napkin 1, a pair of leak-proof grooves 4 and 4 extending in the longitudinal direction of the napkin 1 are formed on both left and right sides in the longitudinal direction. The leak-proof groove 4 is formed by compacting and integrating the top sheet 2 and the absorbent body 10 from the top sheet 2 side by pressing means such as embossing. The pair of leak-proof grooves 4 and 4 are substantially symmetrical with respect to the longitudinal center line of the napkin 1, and their front and rear ends are connected to each other, thereby forming a closed shape as a whole. By forming the leak-proof grooves 4 and 4, body fluid or the like flowing outward in the napkin width direction is blocked, and leakage (lateral leakage) from the side of the napkin 1 is effectively prevented. Furthermore, it is preferable that the leak-proof grooves 4 and 4 reach the vicinity of the lower portion of the absorber 10 in terms of preventing the absorber 10 from being biased and blood remaining.

  An end seal portion 5 is formed on the periphery of the napkin 1 at a position spaced outward from the absorber 10. The end seal portion 5 is formed by joining portions extending outward from the peripheral edge of the absorbent body 10 of each of the topsheet 2 and the backsheet 3. The end seal portion 5 is formed by heat embossing with an adhesive such as hot melt disposed in a predetermined portion of the sheet material, from the viewpoint of improving and stabilizing the flexibility of the seal portion and the seal strength when wet To more preferable.

  The napkin 1 of the present embodiment has the main characteristics of the absorber 10 and the top sheet 2. These will be sequentially described below.

[Absorber]
The absorbent body 10 included in the napkin 1 of the present embodiment includes a laminated structure formed by laminating two fiber sheets 11 and 12 as a plurality of layers made of a fiber assembly, as shown in FIG. A granular water-absorbing polymer is interposed between at least one of the layers in the laminated structure (between the two fiber sheets 11 and 12). Between the two fiber sheets 11 and 12, only the water-absorbing polymer may be interposed (hereinafter, this form is also referred to as “form A”), or the water-absorbing polymer and the fiber may be interposed (hereinafter referred to as “form A”). This form is also referred to as form B). Unless otherwise specified, the water-absorbing polymer according to the present invention (the water-absorbing polymer used in the present invention) includes a water-absorbing polymer having a repose angle of a swollen gel described later of 45 ° or less.

The absorbent body 10 has a water-absorbing polymer high concentration region 13 in which the water-absorbing polymer content rate exceeds the water-absorbing polymer average content rate calculated by the following formula, and the water-absorbing polymer content rate is the water-absorbing polymer average content rate. Less water-absorbing polymer or no water-absorbing polymer. Here, the content of the water-absorbing polymer is calculated by the following formula.
Water-absorbing polymer average content (% by mass) = (total mass of all water-absorbing polymers contained in the absorber / total mass of the absorber) × 100
Content of water-absorbing polymer (% by mass) = (total mass of all water-absorbing polymers contained in the region / total mass of the region) × 100

  In the form A (a form in which only the water-absorbing polymer is interposed between at least one of the layers in the laminated structure), the distribution of the water-absorbing polymer in the absorbent body 10 is excreted if there is a light and shade as described above. The liquid is once held in the water-absorbing polymer low-concentration region 14, so that the speed of taking up the liquid into the absorbent body 10 is increased, and the liquid diffuses through the region 14 to the water-absorbing polymer high-concentration region 13. The liquid is transferred and fixed in the region 13. Thus, the absorber 10 of the said form A can use the whole efficiently, and is excellent in the absorption efficiency of a liquid.

  Further, in the form B (a form in which the water-absorbing polymer and the fiber are interposed between at least one of the layers in the laminated structure), the distribution of the water-absorbing polymer in the absorber 10 has the above-described light and shade. 1) When the excreted liquid is a low-viscosity liquid such as urine, the absorbability of the liquid in the absorbent body 10 mainly due to the action of the capillary force formed between the fibers in the low-absorbent polymer low-concentration region 14 2) When the excreted liquid is a highly viscous liquid such as menstrual blood or loose stool, the fibers of the water-absorbing polymer low concentration region 14 mainly act as a barrier against the highly viscous liquid. Therefore, the diffusibility of the liquid is lowered, and so-called side leakage is effectively prevented. The water-absorbing polymer low-concentration region 14 in the form B has a relatively high fiber content instead of a relatively low water-absorbing polymer content, and thus has an effect on such a liquid. .

  Further, in each of the forms A and B, if the distribution of the water-absorbing polymer in the absorbent body 10 has the above-described light and shade, the water-absorbing polymer low-concentration region 14 has an elastic modulus compared to the water-absorbing polymer high-concentration region 13. Since it can be bent easily at a low level, the entire absorbent body 10 becomes flexible, the uncomfortable feeling during wearing is reduced, and the region 14 is flexibly bent, so that the absorbent body 10 is not irregularly twisted, Stable absorption performance can be expressed.

  Whether or not a certain region of the absorbent body is a high water-absorbing polymer concentration region containing a water-absorbing polymer at a concentration higher than the average concentration of the water-absorbing polymer can be examined, for example, as follows. . That is, the absorber is divided into five equal parts in the longitudinal direction and the width direction, and the absorber is divided into 25 regions. And about each area | region, the content rate (mass%) of a water absorptive polymer is computed using the said formula, and when the calculated value is larger than the said water absorptive polymer average density | concentration (mass%), the said area | region is water-absorbed. When the polymer is in a high concentration region and the calculated value is smaller than the average concentration of the water absorbent polymer, the region is defined as a low concentration region of the water absorbent polymer.

  From the viewpoint of ensuring the above-described effects, the difference between the water-absorbing polymer content in the water-absorbing polymer high-concentration region 13 and the water-absorbing polymer average content is 10% by mass or more, particularly 20% by mass. % Or more is preferable. From the same viewpoint, the difference between the water-absorbing polymer content in the water-absorbing polymer low-concentration region 14 and the water-absorbing polymer average content is preferably in the same range.

The content of the water-absorbing polymer in the water-absorbing polymer high-concentration region 13 is preferably 30% by mass or more, particularly 50 to 100% by mass, based on the total mass of the region 13. Further, the basis weight of the water-absorbing polymer in the water-absorbing polymer high-concentration region 13 is 10 g / m ² or more, particularly 10 to ²⁰⁰ g / in, when the absorbent body 10 is used as an absorbent body of a sanitary napkin as in this embodiment. m ^2, especially is preferably 15 to 100 / m ^2.

In addition, when using the absorber 10 as an absorber of an incontinence pad, the basis weight of the water-absorbent polymer in the water-absorbent polymer high-concentration region 13 is 10 to 500 g / m ² , particularly 15 to 350 g / m ^2. preferable. Moreover, when using the absorber 10 as a diaper absorber for infants, the basis weight of the water-absorbent polymer in the water-absorbent polymer high-concentration region 13 is 50 to 500 g / m ² , particularly 100 to 300 g / m ^2. Is preferred.

The content of the water-absorbing polymer in the water-absorbing polymer low-concentration region 14 is preferably 50% by mass or less, particularly preferably 0 to 40% by mass, based on the total mass of the region 14. Further, the basis weight of the water-absorbing polymer in the water-absorbing polymer low-concentration region 14 is 100 g / m ² or less, particularly 0 to 50 g / m, when the absorbent body 10 is used as an absorbent body of a sanitary napkin as in this embodiment. m ² is preferable.

In addition, when using the absorber 10 as an absorber of an incontinence pad, the basis weight of the water-absorbent polymer in the water-absorbent polymer low-concentration region 14 is 10 to 200 g / m ² , particularly 15 to 150 g / m ^2. preferable. Moreover, when using the absorber 10 as a diaper absorber for infants, the basis weight of the water-absorbent polymer in the water-absorbent polymer low-concentration region 14 is 0 to 200 g / m ² , particularly 0 to 100 g / m ^2. Is preferred.

  FIG. 3 schematically shows the distribution pattern of the water-absorbing polymer in the absorbent body 10. In the present embodiment, as shown in FIG. 3, the absorbent body 10 includes a substantially rectangular water-absorbing polymer high-concentration region 13 in plan view and a substantially quadrangular water-absorbing polymer low-concentration region 14 in plan view. Are arranged alternately in both the longitudinal direction X and the width direction Y. Further, the longitudinal side edges 10 s and 10 s of the absorbent body 10 as a whole are the water-absorbing polymer low concentration region 14. As described above, in the absorbent body 10 according to the present embodiment, a large number of water-absorbing polymer high-concentration regions 13 and a large number of water-absorbing polymer low-concentration regions 14 in a region sandwiched between the longitudinal side edges 10s and 10s. Are arranged so as to form a checkerboard pattern in plan view as shown in FIG.

  The shape of the water-absorbing polymer high-concentration region 13 in plan view is not limited to a quadrangular shape as shown in FIG. 3, and can be any shape such as a circular shape, a rhombus, a circular shape, a wavy shape, etc. The visual size (area of one region 13) is preferably 1 to 60%, more preferably 5 to 40 with respect to the total area of the skin contact surface (or non-skin contact surface) of the absorbent body 10. %. Moreover, the water-absorbing polymer high concentration region 13 is preferably in a state where a large number of small regions 13 are formed in the unit region. Further, in the plan view of the absorbent body 10, the ratio (S1 / S2) of the total area S1 of the water-absorbing polymer high concentration region 13 to the total area S2 of the water-absorbing polymer low concentration region 14 is preferably 30/70 to 90. / 10, more preferably 40/60 to 80/20.

  FIG. 4 schematically shows a part of a cross section along the thickness direction of the absorbent body 10. In the water-absorbing polymer high-concentration region 13, as shown in FIG. 4, a plurality of water-absorbing polymer particles 15 overlap each other and are densely packed. In FIG. 4, for ease of explanation, the distribution state of the water-absorbing polymer particles 15 is schematically shown. However, in actuality, in the water-absorbing polymer high concentration region 13, the plurality of particles 15 are The absorbers 10 overlap with each other with a certain spread in the surface direction, and also overlap with each other in the thickness direction of the absorber 10. Further, in FIG. 4, it is described that the particles 15 do not exist in the water-absorbing polymer low concentration region 14, but actually, the amount of the particles 15 smaller than that of the water-absorbing polymer high concentration region 13 is Similar to the particles 15 in the region 13, they may be overlapped.

  In the water-absorbing polymer high concentration region 13, a plurality of water-absorbing polymer particles are in contact with each other at two or more points, and a void surrounded by the water-absorbing polymer is formed between the contact points of the particles. FIG. 5A and FIG. 5B are cross-sectional views schematically showing examples of voids formed in the water-absorbing polymer high concentration region 13, respectively. In the example shown in FIG. 5A, two water-absorbing polymer particles 15a and 15b are in contact with each other at two points indicated by reference numerals C1 and C2 in FIG. 5A, and a contact C1 between the particles 15a and 15b. , C2, a void S1 surrounded by the water-absorbing polymer 15 is formed. In the example shown in FIG. 5B, three water-absorbing polymer particles 15c, 15d, and 15e are in contact with each other at three points indicated by reference numerals C1, C2, and C3 in FIG. , 15d, 15e, a gap S2 surrounded by the water-absorbing polymer 15 is formed between the contacts C1, C2, C3.

  The “void surrounded by the water-absorbing polymer” according to the present invention is not limited to the form shown in FIG. 5, and various forms of voids exist in the high-absorbent polymer high-concentration region. Further, in FIG. 5, it is described that nothing is included in the voids S1 and S2 surrounded by the water-absorbing polymer 15, but the absorbent forming material (for example, fibers, water-absorbing properties) is included in the voids. In some cases, inorganic particles used for polymer surface treatment, water-absorbing polymer particles that are not fixed and movable, and the like are included.

  The absorbent body 10 has a space for taking in the liquid once by having a void surrounded by such a water-absorbing polymer in the water-absorbing polymer high-concentration region 13 in a dry state before liquid absorption. In addition, gel blocking is unlikely to occur, and in particular, a highly viscous liquid such as menstrual blood is less likely to block the gap between adjacent water-absorbing polymer particles. And according to the napkin 1 provided with the absorber 10 which has such a characteristic, the following effects 1) -3) are show | played.

Effect 1) Since the excretion fluid is quickly taken into the absorbent body 10 and the repetitive absorbability is good, the liquid spread on the surface of the napkin 1 (the skin contact surface of the surface sheet 2) is reduced, and the surface The dry feeling is improved and the leakage of the liquid in the width direction is suppressed.
Effect 2) It is possible to reduce the amount of fiber components such as pulp as compared with the conventional one by improving the absorbability. As a result, the absorber 10 can be made thinner, and the napkin 1 can be made thinner. And improved wearability.
Effect 3) Since it is difficult to form a solid gel mass due to the water-absorbing polymer in the absorbent body 10, the absorbent body 10 and the napkin 1 provided with the same become flexible, reducing the uncomfortable feeling of wearing and providing a comfortable feeling. can get.

Whether or not the void surrounded by the water-absorbing polymer described above is formed in the water-absorbing polymer high-concentration region 13 can be confirmed by the following <Method for measuring the size of the void surrounded by the water-absorbing polymer>. . When the pore size Spore obtained by the following measurement method is 400 μm ² or more, it can be said that a void surrounded by the water absorbent polymer is formed in the region (water absorbent polymer high concentration region). In other words, in the present invention, a void surrounded by the water-absorbing polymer is formed in the water-absorbing polymer high concentration region 13 (a void formed between the contacts of the water-absorbing polymer particles that are in contact with each other at two or more points of contact). In order to be recognized as being present, it is not sufficient that the voids are merely present in the region 13, and the size of the voids measured by the following measurement method needs to be 400 μm ² or more. The size Spore of the void is preferably 1000 μm ² or more from the viewpoint of ensuring the above-described effect.

<Measurement method of size of void surrounded by water-absorbing polymer>
Prior to the measurement, as a pretreatment, a dry absorbent body to be measured is placed on a flat table, and a load of 24.5 kPa is continuously applied over the entire absorbent body for 12 hours. By this pretreatment, the thickness of the absorber can be recovered and the influence of wrinkles and the like can be removed. For the pretreated absorber, the high-absorbent polymer high-concentration region is specified according to the method described above. The following operations are performed on the three regions identified as the water-absorbing polymer high concentration region, and the size of the void surrounded by the water-absorbing polymer in the region is measured. When there are only one or two water-absorbing polymer high concentration regions, the water-absorbing polymer high concentration region is divided into three equal parts in the length direction and / or the lateral direction. Perform the operation. The sum of the void areas for each of the three regions (portions) is obtained by the following operation, the average value of these is calculated, and this is the size Spore of the void surrounded by the water-absorbing polymer.
The cut surface in the longitudinal direction of the water-absorbing polymer high-concentration region is divided into 25-fold magnified images using a microscope (Keyence Corporation, VH-8000), and captured and captured as image data. The image data composed of a plurality of divided images thus obtained is processed using image analysis processing software (Image-Pro plus, Media Cybernetics), and a plurality of divided images are each surrounded by a void surrounded by a water-absorbing polymer ( The total area of voids formed between the contacts of the water-absorbing polymer particles that are in contact with each other at two or more points of contact is calculated. Then, the total sum of the void areas for each of the plurality of divided images is obtained.

  In the water-absorbing polymer high-concentration region 13, the ratio [= (Spore / Ssap) × 100] of the size Spore of the void surrounded by the water-absorbing polymer to the area Ssap occupied by the water-absorbing polymer is 3 to 50%. More preferably, it is in the range of 5 to 30% from the viewpoint of increasing absorbability. Here, the area Ssap occupied by the water absorbent polymer in the water absorbent polymer high concentration region 13 can be obtained as follows. That is, in the above <Method for measuring size of void surrounded by water-absorbing polymer>, the total area occupied by the water-absorbing polymer is calculated for each of a plurality of divided images, and this is calculated in the high-concentration region of the water-absorbing polymer. The area Ssap occupied by the water-absorbing polymer particles is defined.

In order to develop a state in which voids surrounded by the water-absorbing polymer are formed in the water-absorbing polymer high-concentration region 13 (that is, the void size Spore obtained by the measurement method is 400 μm ² or more) It is necessary to use a polymer having a repose angle of the swollen gel in a specific range. The water-absorbing polymer used in the present invention preferably further has predetermined physical properties such as a centrifugal holding amount, a bulk specific gravity, a liquid passing speed under pressure, and the like within a specific range. Details of the water-absorbing polymer used in the present invention will be described later.

  As the fiber sheets 11 and 12 (layers composed of fiber aggregates) constituting the absorbent body 10, a sheet-like material containing fibers can be used, and examples thereof include paper and nonwoven fabric. As the fibers contained in the fiber sheets 11 and 12, those normally used in the technical field can be appropriately used. For example, wood pulp such as conifer pulp, hardwood pulp, and non-wood pulp such as bamboo, kenaf, straw, mulberry, mitsumata, cotton, etc. (regenerated fiber such as cupra and rayon); semi-synthetic fiber such as acetate; Synthetic fibers such as polyolefins, polyamides, polyvinyl alcohols, polyesters; modified pulps obtained by chemically treating natural fibers such as crosslinked pulp and mercerized pulp, etc. Or 2 or more types can be mixed and used.

  Particularly preferred as the fiber sheets 11 and 12 include pulp fibers and fibers that are less hydrophilic than the pulp fibers (hereinafter also referred to as weakly hydrophilic fibers). A fiber sheet having such a composition (hereinafter also referred to as a weakly hydrophilic fiber-containing sheet) has a high bulk (distance between constituent fibers) and a low density, and has a feature of high liquid permeability in the thickness direction and low water retention. Therefore, when the fiber sheet is used as a constituent material of the absorbent body, the excretion fluid is quickly taken in, and the dryness of the surface is improved.

  The weakly hydrophilic fiber is a fiber that is less hydrophilic than pulp fiber. Specifically, fibers having a water absorption gradient of 0.05 g / second or less obtained by the following <Hydrophilicity evaluation method> are weakly hydrophilic fibers. The slope of water absorption of pulp fibers (for example, NBKP) is generally 0.07 to 0.09 g / sec.

<Hydrophilicity evaluation method>
A fiber is filled in an acrylic tube having an inner diameter of 15 mm, which is cylindrical and has both ends in the axial direction open to a density of 0.05 g / cm ³ . An acrylic tube filled with fibers was connected to an electronic balance (AND, GX-400), and in 200 ml of a test solution (saline colored with blue No. 1) placed in a 300 ml beaker, A portion extending 5 mm from the lower end of the tube in the axial direction of the tube is immersed in the fiber in the tube to absorb the test solution, and the increase in weight per predetermined time is monitored. Before the absorption amount reaches equilibrium, the slope of the water absorption amount with respect to the time up to 30 seconds after immersion is obtained. If the line does not become a straight line, an approximate line is obtained by the method of least squares, and the slope of the approximate line is taken as the slope of the water absorption amount. It can be judged that the fiber having a larger slope of the water absorption has higher hydrophilicity.

Examples of the weakly hydrophilic fiber include modified pulp such as crosslinked pulp and mercerized pulp;
Hydrophobic fine particles (eg, hydrophobic silica, zeolite, clay, etc.) and various modifiers on the surface of synthetic fibers (eg, polyvinyl alcohol fiber, acrylic fiber, polyester fiber, etc.) having a hydrophilic group in the structure , Hydrocarbon oils, various oils such as ester oils and silicone oils, and the like, to which fatty acids, thought alcohols, and the like are attached. These can be used alone or in admixture of two or more. Examples of the modifying agent include bulking agents described in JP-A-2008-297651, JP-A-2008-163499, JP-A-2007-177072, and the like.

  The content of weakly hydrophilic fibers (excluding those in which hydrophobic fine particles are adhered to the fiber surface) in the weakly hydrophilic fiber-containing sheet is preferably 20 to 95% by mass with respect to the total mass of the sheet, More preferably, it is 40-80 mass%. When a fiber having hydrophobic fine particles attached to the fiber surface is used as the weakly hydrophilic fiber, the content thereof is preferably 40 to 100% by mass, more preferably based on the total mass of the weakly hydrophilic fiber-containing sheet. Is 60 to 100% by mass. In addition, the mass ratio of the pulp fiber and the weakly hydrophilic fiber (pulp fiber / weakly hydrophilic fiber) in the weakly hydrophilic fiber-containing sheet is preferably 20/80 to 80/20, more preferably 30/70 to 70. / 30.

The fiber sheets 11 and 12 may contain components other than the fibers, such as a paper strength enhancer, a fixing agent for various particles, and a texture improving agent. The basis weight of the fiber sheets 11 and 12 is preferably 10 to 60 g / m ² , particularly preferably 15 to 40 g / m ² , and the thickness (thickness under no load) is 0.15 to 0.55 mm, In particular, the thickness is preferably 0.2 to 0.45 mm.

  The absorber 10 may be substantially entirely covered with a covering sheet (not shown). When substantially the entire absorbent body is covered with a covering sheet, it is particularly effective for improving the shape stability and handling properties of the absorbent body and preventing the extreme movement and falling off of the water-absorbing polymer. The form of covering the absorbent body with the covering sheet is not particularly limited. For example, the form in which the upper surface (skin contact surface) and the left and right side faces of the absorbent body are covered with the covering sheet, and in addition to these faces, the absorbent body The form by which the lower surface (non-skin contact surface) is covered with a covering sheet. When covering the absorber 10 with a coating sheet, the absorber 10 and the coating sheet may be joined by a predetermined means. Since both are joined, the rigidity as the whole of the absorbent body 10 covered with the covering sheet is increased, and thereby the handling property is further improved. As a means for joining the absorbent body and the covering sheet, for example, in addition to bonding with an adhesive or heat fusion, embossing performed on a normal sanitary napkin (absorbing body from above the covering sheet or the top sheet 2) (Thickness direction grooves reaching 10) are formed.

  As the covering sheet, a material having a sufficient strength to prevent the water-absorbing polymer from dropping off and a material that does not hinder the permeation of excreted liquid is appropriately used. As the covering sheet, for example, a hydrophilic fiber sheet, a perforated film or the like is used, and as this hydrophilic fiber sheet, for example, paper such as tissue paper or various nonwoven fabrics (spunbond nonwoven fabric, spunbond-meltblown-spunbond nonwoven fabric). Spunbond-meltblown-meltblown-spunbond nonwoven fabric, thermal bond nonwoven fabric, needle punch nonwoven fabric, spunlace nonwoven fabric, airlaid nonwoven fabric, spunlace nonwoven fabric containing hydrophilic fibers such as acrylic and rayon, etc.). These nonwoven fabrics may be subjected to a hydrophilic treatment or a hole opening treatment as necessary, and may further be formed with slits, or may be subjected to a softening process such as embossing. Examples of the constituent fibers of these nonwoven fabrics include fibers using a thermoplastic resin such as polyethylene, polypropylene, and polyethylene terephthalate alone, or composite fibers using these resins. Moreover, hydrophilic fibers, such as rayon, cotton, lyocell, tencel, acetate, and natural pulp, can coexist in these nonwoven fabrics.

  The absorber 10 can be manufactured as follows, for example. As shown in FIG. 6, the absorbent body manufacturing method according to the present embodiment, after spraying the water-absorbing polymer 15 in a predetermined pattern on one surface of the fiber sheet continuous body 11 ′, separate fiber sheets on the one surface. Including a step of superimposing the continuum 12 '. The fiber sheet continuums 11 ′ and 12 ′ are both flat sheet continuums that are substantially free of irregularities, and can be manufactured according to this type of fiber sheet manufacturing method. There is no particular limitation, and a wet method or a dry method may be used.

  It is preferable that the continuous body 11 ′ on which the water-absorbing polymer 15 is directly sprayed is impregnated with water and wet before the spraying. The water content of the continuum 11 'before spraying the water-absorbing polymer is preferably 40 to 100% by mass, more preferably 50 to 80% by mass. Although it is possible to measure the water content of the water-absorbing polymer during the production of the absorber by using a commercially available moisture sensor or the like, the continuum itself to which the water-absorbing polymer is dispersed contains water. For this reason, it is generally difficult to accurately measure the water content of the water-absorbing polymer during the production of the absorber. Therefore, in view of the water absorption amount of the water-absorbing polymer measured using <DW method for measuring the water absorption rate of the water-absorbing polymer> described below, the water-absorbing polymer is optimized so that the water content of the water-absorbing polymer is optimal. The spraying position, the distance until the continuum 11 ′ and the continuum 12 ′ merge, the pressure after the merging of both continuums, the distance to the drying process, the production speed, etc. are set.

  For spraying the water-absorbing polymer 15, a polymer spraying device as shown in FIG. 6 can be used. The polymer spraying device is disposed so as to be rotatable in the circumferential direction above one surface of the continuous body 11 ′ being conveyed, and includes a cylindrical roll 60 that sprays the water-absorbing polymer 15 on the one surface. A large number of recesses 61 that can accommodate the water-absorbing polymer 15 are formed on the peripheral surface of the roll 60. A large number of recesses 61 are formed on the peripheral surface of the roll 60 in a pattern corresponding to the distribution pattern (see FIG. 3) of the water-absorbing polymer in the absorbent body 10 finally obtained. The water-absorbing polymer 15 is once supplied into the recess 61 of the rotating roll 60, and then transferred onto one surface of the continuous body 11 '.

  After the water-absorbing polymer 15 is sprayed, water is sprayed on the water-absorbing polymer 15 on one surface of the continuum 11 ′ as necessary. Before the continuous body 11 ′ is overlaid with the continuous body 12 ′ of the fiber sheet, the water content of the water-absorbing polymer 15 dispersed on the continuous body 11 ′ is 1 to 50% by weight, particularly 5 to 20% by weight. It is preferable. In this way, the reason for adjusting the water content of the dispersed water-absorbing polymer to a specific range is that the water-absorbing polymer is swollen so that the water-absorbing polymer exhibits appropriate adhesion between the water-absorbing polymers in a predetermined position. This is for fixing between the fiber sheets and fixing the gap between the fiber sheets, and also for forming and maintaining voids between the water-absorbing polymers in the subsequent pressing / drying step. However, if the water content of the water-absorbing polymer is too high, excessive swelling may cause a decrease in absorption performance of the water-absorbing polymer after drying, so the upper limit of the water content can be set as described above. preferable.

  Next, another continuous fiber sheet 12 ′ in a dry state is superposed on the continuous body 11 ′ so as to cover the sprayed water-absorbing polymer 15, and is pressed as necessary to form a continuous body 10 ′ of the absorbent body. Get. Time from spraying the water-absorbing polymer 15 on the continuum 11 ′ to overlaying the continuum 12 ′ (when pressing after overlapping, the time from spraying the water-absorbing polymer 15 to pressing) Is preferably 1 to 10 seconds, more preferably 2 to 5 seconds. Moreover, when pressing, the pressing force becomes like this. Preferably it is 2.0-5.0 kPa, More preferably, it is 3.5-4.5 kPa. The absorbent body 10 is obtained by cutting the continuous body 10 ′ thus obtained into a predetermined shape.

  The absorber which concerns on this invention is not limited to the said embodiment, In the range which does not deviate from the meaning of this invention, it can change suitably. Below, other embodiment of the absorber which concerns on this invention is described with reference to drawings. In other embodiments to be described later, constituent parts different from the above-described embodiments will be mainly described, and the same constituent parts are denoted by the same reference numerals and description thereof will be omitted. The description of the above embodiment is applied as appropriate to components that are not particularly described.

  The distribution pattern of the water-absorbing polymer in the absorbent body according to the present invention is not limited to the staggered pattern distribution pattern as shown in FIG. 3, and may be a striped pattern distribution pattern as shown in FIG. The distribution pattern of the water-absorbing polymer shown in FIG. 7 is a band-shaped water-absorbing polymer high-concentration region 13 extending in the longitudinal direction X of the absorber 10 and a band-shaped water-absorbing polymer low-concentration region 14 that also extends in the longitudinal direction X. They are formed alternately in the width direction Y.

  FIG. 8A to FIG. 8C show other examples of the distribution pattern of the water-absorbing polymer. The distribution pattern of the water-absorbing polymer shown in FIG. 8A is such that the rectangular water-absorbing high-concentration region 13 extending in the longitudinal direction X of the absorbent body 10 matches the longitudinal direction with the longitudinal direction X of the absorbent body 10. The absorber 10 is disposed and formed at the center in the width direction.

  In the distribution pattern of the water-absorbing polymer shown in FIG. 8B, a plurality of rhombus-shaped water-absorbing polymer low-concentration regions 14 are arranged in a staggered pattern, and the water-absorbing polymer high-concentration region 13 is located between adjacent regions 14 and 14. It is arranged and formed. In the distribution pattern shown in FIG. 8B, the region 13 has a strip shape extending in the direction intersecting with the longitudinal direction X and the width direction Y of the absorber 10, and the rhombic region 14 is formed in the region 13. Besieged.

  The distribution pattern of the water-absorbing polymer shown in FIG. 8C is the same as that shown in FIG. 8B except that the water-absorbing polymer concentration in the high water-absorbing polymer high concentration region 13 is not uniform but partially different. The distribution pattern of the functional polymer is the same. In the distribution pattern shown in FIG. 8C, the overlapping portion 13A of the band-shaped water-absorbing polymer high-concentration region 13 that intersects each other has a water-absorbing polymer as compared with other portions in the region 13 other than the overlapping portion 13A. The concentration of is high. The distribution pattern shown in FIG. 8C is obtained by, for example, spraying a water-absorbing polymer so as to form a plurality of strip-like regions 13 extending diagonally upward to the right (or diagonally upward to the left), and then diagonally upward to the left (or diagonally upward to the right). ) Is obtained by spraying a water-absorbing polymer so as to form a plurality of strip-like regions 13 extending in FIG.

  Moreover, as a method of spraying the water-absorbing polymer so that the water-absorbing polymer high-concentration region and the water-absorbing polymer low-concentration region exist, in addition to the method using the polymer spraying device capable of spraying in the specific pattern described above, Examples of the sheet on which the water-absorbing polymer is directly sprayed include a method using an uneven sheet having unevenness on the surface. The above-described method using the polymer spraying device was a method of spraying the water-absorbing polymer in a specific pattern so that the distribution of the water-absorbing polymer is shaded on a flat sheet having substantially no unevenness. In the method using a sheet, since the unevenness is formed in a specific pattern in advance on the spreading surface of the sheet on which the water-absorbing polymer is directly sprayed, the unevenness can be obtained by uniformly spreading the water-absorbing polymer over the entire spreading surface. A distribution pattern of the water-absorbing polymer corresponding to this pattern is obtained. As the concavo-convex sheet, paper obtained by a wet papermaking method can be used, and the concavo-convex sheet made of such a paper is a method of manufacturing according to a conventional method using a patterned papermaking net used in wet papermaking, or It is obtained by a method of making a flat paper having substantially no unevenness and subjecting the paper to steel match embossing.

  Further, the absorbent body according to the present invention has a laminated structure formed by laminating a plurality of layers made of fiber aggregates, like the absorbent body 10, and absorbs water between at least one of the layers in the laminated structure. If the high water-absorbing polymer concentration region described above exists, the mixed product of the water-absorbing polymer and the fiber (the water-absorbing polymer and the fiber are uniformly mixed) May have been).

  FIG. 9 shows an example of a method for producing an absorbent body made of a mixed product of a water-absorbing polymer and fibers. The manufacturing method includes a step of scattering and depositing an absorbent material containing fibers and a water-absorbing polymer on the peripheral surface 71a of the rotating drum 71. In the absorbent body composed of a mixed fiber of a water-absorbing polymer and fibers, the same fibers as those contained in the fiber sheets 11 and 12 can be used as the fibers.

  FIG. 10 shows a part of the peripheral surface 71 a of the rotating drum 71. A large number of quadrangular concave portions 72 are formed on the peripheral surface 71a in plan view. A large number of the concave portions 72 are arranged at predetermined intervals in a predetermined direction, and a convex portion 73 is formed between the adjacent concave portions 72, 72. The convex portion 73 is formed in a lattice shape. Inside the rotating drum 71, suction means (not shown) such as a blower for holding the absorber material deposited on the peripheral surface 71a on the peripheral surface 71a is provided. Further, in the vicinity of the rotating drum 71, a charging mechanism (not shown) capable of charging the absorber material to the peripheral surface 71a of the rotating drum 71 at high speed by a vacuum action or the like is disposed. As the charging mechanism, for example, a mechanism constituted by a screw feeder and its rotation driving device can be cited.

  In this manufacturing method, first, a continuous body 74 of a covering sheet (sheet covering the absorber) made of paper or the like is supplied onto the peripheral surface 71a of the rotating drum 71 rotating in the circumferential direction. The continuous body 74 supplied on the peripheral surface 71a is held in a deformed state along the shape of the peripheral surface 71a by the suction means in the rotary drum 71. In addition, before supplying the continuous body 74 on the peripheral surface 71a, hot melt bonding is performed on the deposition surface of the absorbent material in the continuous body 74 (the surface opposite to the surface facing the peripheral surface 71a) by the coating device 75. Apply an adhesive such as an adhesive.

  Next, an absorber material containing fibers and a water-absorbing polymer is introduced onto the adhesive-applied surface of the continuous body 74 by the introduction mechanism, and this is deposited. The charged absorbent material enters the concave portion 72 covered with the continuum 74 and is deposited on the convex portion 73 covered with the continuum 74. The continuum 74 is ultimately completely buried by the absorbent material. Thus, a continuous body of the absorbent body 30 made of a mixed product of the water-absorbing polymer and the fibers is formed on the peripheral surface 71a of the rotating drum 71 via the continuous body of the covering sheet 74.

  In FIG. 11, a cross section along the thickness direction of the continuous body of the absorber 30 is schematically shown. In the continuum of the absorbent body 30, the portion 33 corresponding to the convex portion 73 has less absorber material than the portion 32 corresponding to the concave portion 72 by an amount corresponding to the thickness of the convex portion 73. A thin thin portion 33 is formed. The portion 32 corresponding to the recess 72 is a thick portion 32 having a thickness larger than that of the thin portion 33. When the absorber 30 is used, the thick portion 32 mainly functions as a liquid absorption region, and the thin portion 33 mainly functions as a pressure absorption region. The formation of the above-described high water-absorbing polymer concentration region (and the low water-absorbing polymer concentration region) is affected by the proportion of the water-absorbing polymer in the absorbent material put into the rotating drum 71, and the absorption. It is irrelevant whether an area of the body is thick or thin. Therefore, for example, one of the thick part 32 and the thin part 33 may be a water-absorbing polymer high concentration region, or both may be a water-absorbing polymer high concentration region.

  The distribution of the water-absorbing polymer in the absorber 30 is, for example, in a manufacturing apparatus as shown in FIG. 9, the distance from the water-absorbing polymer inlet (not shown) to the rotating drum 71, the water-absorbing polymer inlet and the rotating drum 71. Can be controlled by appropriately adjusting the height in the duct provided between the two and the suction pressure in the rotary drum 71. For example, by introducing the water-absorbing polymer from the lower side in the duct, the mixing ratio of the fibers and the water-absorbing polymer is changed in the duct, and the lower side of the duct is in a mixed state having a higher water-absorbing polymer concentration than the upper side of the duct. As a result, this portion is laminated on the rotating drum 71 earlier than the pulp, and a lot of water-absorbing polymer is present in the concave portion 72 having a stronger suction force. As a result, the meat corresponding to the concave portion 72 is present. The thick part 32 becomes a high concentration region of the water absorbent polymer.

  Subsequently, an adhesive such as a hot melt adhesive is applied to one surface of another continuous body 76 of the coating sheet by the coating device 75, and the adhesive-coated surface of the continuous body of the absorbent body 30 is the same as the continuous body. By overlapping and integrating so as to face each other and cutting them into a predetermined shape, an absorbent body 30 made of a mixed fiber of a water-absorbing polymer and fibers, which is entirely covered with a covering sheet, is obtained. The effect similar to the absorber 10 is show | played by the absorber 30 also.

The absorber according to the present invention has an excellent liquid absorbing ability even if the thickness is reduced by the action of the void surrounded by the water absorbent polymer in the high concentration region of the water absorbent polymer described above. Is possible. More specifically, the absorber according to the present invention can be a thin absorber having a thickness under a load of 7 g / cm ^2, preferably 0.2 to 5 mm, more preferably 0.3 to 2.5 mm. It is. In particular, like the absorbent body 10 described above, “having a laminated structure in which a plurality of layers made of fiber assemblies are laminated, and a water-absorbing polymer is interposed between at least one of the layers in the laminated structure. The “absorber” is an absorber that can be easily thinned.

The napkin 1 of the present embodiment can be thinned by including the absorber that can be thinned as described above. The thickness of the napkin 1 is preferably 1 to 10 mm, particularly 1 to 7 mm, and more preferably 1.5 to 5.5 mm because it does not feel strange while preventing leakage during wearing and is convenient for carrying. The thickness of the napkin here means the thickness of the napkin under a load of 7 g / cm ^{2 and} is measured by the following method.

<Method for measuring thickness>
Place the entire product to be measured (napkins) on a flat surface with the top sheet side up, without wrinkles or bending, and place 7 g / cm ^{2 on} the upper surface of the area where the absorber is placed. Apply a load and measure the thickness under that condition. Thickness meter PEACOCK DIAL UPRIGHT GAUGES R5-C (manufactured by OZAKI MFG.CO.LTD.) Is used for measuring the thickness. At this time, a plate (an acrylic plate having a thickness of about 5 mm) is disposed at the measurement portion between the tip of the thickness meter and the product, and the size of the plate is adjusted so that the load is 7 g / cm ² . The shape of the plate is circular or square. The measurement is performed at 23 ± 2 ° C. and humidity 50 ± 5%, and the sample is measured after being stored in the same environment for 24 hours or more.

  Moreover, the absorber which concerns on this invention has a high softness | flexibility in any of a dry state and a wet state. More specifically, in the absorbent body according to the present invention, at least one of “bending rigidity in the longitudinal direction” and “bending rigidity in the width direction” is preferably 10 to 50 g in both a dry state and a wet state. More preferably, it is 5-30 g. The bending stiffness of the absorber is measured as follows.

<Measurement method of bending stiffness>
The bending stiffness value can be measured with a handle-ometer. The measuring method using the handle-ometer is in accordance with Japanese Industrial Standard “JIS L-1096 (General Textile Testing Method)”. An absorbent body cut to 150 mm in the longitudinal direction and 100 mm in the width direction is arranged in a direction perpendicular to the groove on a support base having a groove with a width of 30 mm. The center of the absorbent body in the longitudinal direction is pushed with a blade having a thickness of 2 mm, and the resistance value (g) when the absorbent body is pushed in by 8 mm is measured with a load cell. As a measuring device, a texture tester (handle-of-meter method) HOM-2 manufactured by Daiei Kagaku Seisakusho can be used. The measurement is performed at 23 ± 2 ° C. and a humidity of 50 ± 5%, and the measurement is performed after storing the absorber in the same environment for 24 hours or more before the measurement. The average value of the three points is defined as “longitudinal bending stiffness in the dry state”.
In addition, the measurement was performed in the same manner as described above except that the absorbent body cut to 100 mm in the longitudinal direction and 150 mm in the width direction was rotated by 90 ° and placed in the measuring device, and the average value of the three points was calculated as “Dry state” Bending rigidity in the width direction ”.
In addition, after immersing the absorber in physiological saline in an amount that the absorber reaches a sufficient saturation for 30 minutes, the surface of the absorber is repeatedly pressed with a Kim towel, and the liquid is not returned, and the longitudinal direction is the same as described above. Measurement is performed in each of the direction and the width direction, and the average value of each of the three points is defined as “bending rigidity in the longitudinal direction in the wet state” and “bending rigidity in the width direction in the wet state”.
In either case, the measurement is performed such that the blade of the measuring device hits the high-concentration region of the water-absorbing polymer. Also, if the individual measured values in the longitudinal direction and the width direction are within the range of fluctuation, it is determined that there is no anisotropy in rigidity in the longitudinal direction and the width direction, and the average value of all measured values Is used as a representative value.

Below, the water absorbing polymer used by this invention is demonstrated.
At least a part of the water-absorbing polymer used in the present invention is preferably a water-absorbing polymer having an angle of repose of a swollen gel obtained by the following measurement method of 45 ° or less, preferably 5 to 30 °. As shown in FIG. 12, the angle of repose of the swollen gel is an angle formed by the inclined surface 91a of the cone 91 and the horizontal surface 91b formed by dropping the swollen gel 90 of the water-absorbing polymer onto the horizontal surface 91b and depositing it. This is an index of the fluidity of the water-absorbing polymer. It can be determined that the smaller the angle of repose of the swollen gel, the higher the fluidity of the water-absorbing polymer when wet. The use of a water-absorbing polymer having high fluidity when wet is effective in forming a void surrounded by particles of the water-absorbing polymer in the above-described high water-absorbing polymer concentration region. The angle of repose of the swollen gel can be adjusted by the amount retained by crosslinking, the solubilized amount, the shape, the surface treatment, and the like.

<Measurement method of repose angle of swollen gel>
0.2 g of the water-absorbing polymer as a measurement sample is placed in a glass beaker, and further, a physiological saline solution sufficient to swell the water-absorbing polymer, specifically, 5 times the saturated absorption amount of the water-absorbing polymer. Is poured into a beaker and left for 30 minutes to obtain a swollen gel 90. Then, as shown in FIG. 12, the obtained swollen gel 90 is filled into an acrylic tube 92 having an inner diameter of 15 mm that has a cylindrical shape and both ends in the axial direction are open ends. Separate from the jack so that one end (open end) in the axial direction of the pipe 92 is in contact with the horizontal surface 91b of a jack (laboratory jack, manufactured by ASONE CORPORATION) having a horizontal surface 91b movable downward. Fix with a fixing tool (not shown). Further, a weight 93 having a weight of 20 g is placed on the swollen gel in the tube, and held in that state for 5 minutes. Thereafter, the jack is operated to gradually lower the horizontal surface 91b and gradually expand the space between the fixed tube 92 and the horizontal surface 91b. Then, the cone 91 is obtained by flowing out on the horizontal surface 91b and depositing the swollen gel 90 thereon. At this time, if the swollen gel does not flow under this load, the measurement is impossible. The angle formed by the inclined surface 91a of the cone 91 and the horizontal surface 91b is measured, and the measured value is taken as the repose angle of the swollen gel. Specifically, the cone 91 is photographed from the side surface, and the repose angle is obtained by approximating the inclined surface 91a with a straight line based on the obtained photograph of the cone 91. Measurement (photographing) was carried out at 23 ± 2 ° C. and humidity of 50 ± 5%, and the average value of three points excluding the minimum and maximum values was taken as the measured value (the angle of repose of the swollen gel). In addition, it measures after measuring a sample for 24 hours or more in the same environment before weighing the water-absorbing polymer.

  In the absorbent article of the present invention, at least a part of the contained water-absorbing polymer may be a water-absorbing polymer having an angle of repose of the swollen gel of 45 ° or less, and is included in the absorbent article (absorber). It is not necessary for all the water-absorbing polymers to be a water-absorbing polymer having an angle of repose of the swollen gel of 45 ° or less, and the absorbent article of the present invention includes a water-absorbing polymer having an angle of repose of the swollen gel of 45 ° or less, One or more water-absorbing polymers may be contained. The proportion of the water-absorbing polymer having an angle of repose of the swollen gel of 45 ° or less in all the water-absorbing polymers contained in the absorbent body according to the present invention is preferably 30% by mass or more, more preferably 50% by mass or more. Preferably it is 60-100 mass%. In particular, the water-absorbing polymer high-concentration region may contain a water-absorbing polymer having an angle of repose of the swollen gel of 45 ° or less, preferably 50% by mass or more, and more preferably 70-100% by mass. The water-absorbing polymer contained in the high-concentration polymer high-concentration region is particularly preferably a water-absorbing polymer having an angle of repose of the swollen gel of 45 ° or less.

  When the swollen gel has an angle of repose of 45 ° or less and another water-absorbing polymer, for example, in an absorbent body that is long in one direction, a part or the whole of the central part in the width direction of the absorbent body Further, a water-absorbing polymer having an angle of repose of the swollen gel of 45 ° or less can be distributed, and another water-absorbing polymer can be distributed over a part or the entire area of each side of the absorbent body. By adopting such a distribution of two kinds of water-absorbing polymers, for example, when the absorbent article is a sanitary napkin, the product central part maintains the quick liquid absorbency and the dry feeling of the surface. By causing gel blocking on the side part, there is an effect of preventing the excretory liquid from penetrating into the absorbent body and leaking from the end part of the product. Furthermore, different interfaces of the water-absorbing polymer serve as inflection points, and there is an effect of improving fit.

  The water-absorbing polymer used in the present invention (including a water-absorbing polymer having an angle of repose of a swollen gel of 45 ° or less; hereinafter the same unless otherwise specified) has a centrifugal retention amount of 5 to 25 g / in accordance with JIS K 7223. g, particularly 7 to 20 g / g. The centrifugal retention amount of the water-absorbing polymer is a property related to the water absorption amount (water absorption ratio) of the water-absorbing polymer. Generally, a water-absorbing polymer having a large centrifugal retention amount has a large water absorption amount. However, a water-absorbing polymer with a large value of centrifugal retention and a large amount of water absorption has a large expansion coefficient due to liquid absorption and low gel strength in a water-containing state, so such a water-absorbing polymer is used as a constituent material of the absorber. Then, in the high water-absorbing polymer high concentration region described above, there is a possibility that voids surrounded by the water-absorbing polymer particles are not formed. The amount of centrifugal retention is measured as follows.

<Measuring method of centrifugal retention>
The measurement of the centrifugal retention amount is performed according to JIS K 7223 (1996). Nylon woven fabric (mesh opening 255, sold by Sanriku Manufacturing Co., Ltd., product name: nylon net, standard: 250 x mesh width x 30 m) is cut into a rectangle with a width of 10 cm and a length of 40 cm and folded in half at the center in the longitudinal direction. Both ends are heat-sealed to produce a nylon bag having a width of 10 cm (inner dimension: 9 cm) and a length of 20 cm. 1.00 g of the water-absorbing polymer as a measurement sample is precisely weighed and placed uniformly at the bottom of the produced nylon bag. The nylon bag containing the sample is immersed in physiological saline (0.9 mass% sodium chloride water) adjusted to 25 ° C. After 30 minutes from the start of immersion, the nylon bag is taken out from the physiological saline, suspended in a vertical state for 1 hour and drained, and then dehydrated using a centrifugal dehydrator (Kokusan Co., Ltd., model H-130C special model). The dehydration condition is 143 G (800 rpm) for 10 minutes. After dehydration, the mass of the sample is measured, and the target centrifugal retention amount is calculated according to the following formula. Centrifugal retention amount (g / g) = (a′−b−c) / c; where a ′ is the total mass (g) of the sample and the nylon bag after centrifugal dehydration, and b is before the water absorption of the nylon bag (dried) Mass) (g), c represents the mass (g) of the sample before water absorption (during drying). The measurement was performed 5 times (n = 5), the values at each of the upper and lower points were deleted, and the average value of the remaining three points was taken as the measured value. The measurement is performed at 23 ± 2 ° C. and humidity 50 ± 5%, and the sample is measured after being stored in the same environment for 24 hours or more.

  The absorbent body comprising the water-absorbing polymer having a centrifugal retention amount of 5 to 25 g / g has a high gel strength in the water-containing state, and therefore, in the production process of the absorbent body, the absorbent body is pressed or Even when heated / compressed, or mixed with a water-absorbing polymer at a high concentration, or even when the water-absorbing polymer is arranged in layers, there is little risk that the particles of the water-absorbing polymer will completely stick together, In the high water-absorbing polymer high concentration region described above, a structure having voids surrounded by water-absorbing polymer particles can be taken.

  On the other hand, many of the conventional absorbers of this type take a method of increasing the maximum absorption amount of the water-absorbing polymer contained in the absorber in order to develop a high liquid absorption capacity. The centrifugal retention amount of the water-absorbing polymer contained in the absorbent body usually exceeds 20 g / g. Such a water-absorbing polymer having a high absorption amount has a low gel strength particularly in a water-containing state, and the surface of the swollen water-absorbing polymer is easily plasticized with water. When the treatment is performed, the water-absorbing polymer particles are almost completely adhered to each other, and the water-absorbing polymer layer formed by a large number of water-absorbing polymer particles has a plate-like shape without voids. Such a plate-like water-absorbing polymer layer is particularly difficult to absorb a highly viscous liquid such as blood, and the liquid is completely blocked by the water-absorbing polymer layer. There is.

  The adjustment of the centrifugal retention amount of the water-absorbing polymer can be performed, for example, by adjusting the surface crosslinking degree of the water-absorbing polymer. Generally, when the surface cross-linking degree of the water-absorbing polymer increases (surface cross-linking treatment proceeds), the centrifugal retention amount (water absorption magnification) tends to decrease. Specifically, for example, by performing surface cross-linking treatment (post-crosslinking treatment) again on the water-absorbing polymer that has been subjected to surface cross-linking treatment manufactured by a conventional method, the centrifugal retention amount can be adjusted to the above range. Is possible. In addition, the centrifugal retention amount can be adjusted by increasing the degree of crosslinking of the entire water-absorbing polymer regardless of the presence or absence of surface crosslinking treatment. The degree of crosslinking of the water-absorbing polymer preferably used in the present invention (the degree of surface crosslinking or the degree of crosslinking of the entire water-absorbing polymer) is at a higher level than the degree of crosslinking of ordinary water-absorbing polymers. In order to realize the degree, it is preferable to take a method such as increasing the amount of the crosslinking agent, raising the reaction temperature, or taking a longer reaction time.

The water-absorbing polymer used in the present invention preferably has a bulk specific gravity of 0.5 to 0.8 g / cm ³ , particularly 0.55 to 0.7 g / cm ³ . The bulk specific gravity serves as an index of the shape of the water-absorbing polymer particles, and as a result, serves as an index of various characteristics of the water-absorbing polymer such as control of the water absorption rate and maintenance of repeated water absorption. If the bulk specific gravity is too small, irregularities on the surface of the water-absorbing polymer particles become prominent, but the irregularities are easily crushed and flattened by, for example, pressure treatment in the manufacturing process of the absorbent body. There is a possibility that voids surrounded by the above-mentioned water-absorbing polymer particles in the high-absorbent polymer high-concentration region in the obtained absorbent body are difficult to form. On the other hand, if the bulk specific gravity is too large, irregularities on the surface of the water-absorbing polymer particles are reduced, and close-packing is facilitated, which may make it difficult to form such voids. The water-absorbing polymer having a bulk specific gravity within the above range has irregularities with an appropriate height formed on the surface of the particles. Therefore, the water-absorbing polymer is closely packed to form the above-described water-absorbing polymer high-concentration region. In this case, a void surrounded by the water-absorbing polymer particles is easily formed in the region. The bulk specific gravity can be adjusted by the sp value of the solvent used in the crosslinking reaction of the water-absorbing polymer, the polymerization temperature, the dropping time (crosslinking speed and distribution) of the crosslinking agent, the type and amount of the dispersing agent, and the like. The bulk specific gravity is measured as follows.

<Method of measuring bulk specific gravity>
The bulk specific gravity was measured according to JIS K6219-2 2005. The water-absorbing polymer to be measured was poured into the center of a cylindrical container (a stainless steel container having a diameter of 100 mm, capacity 1000 ml) having a known mass and volume from a height of 50 mm or less from the lower end of the container. At this time, a sufficient amount of the water-absorbing polymer was poured into the cylindrical container so that the poured water-absorbing polymer formed a triangular pyramid above the upper end of the cylindrical container. Then, the excess water-absorbing polymer above the upper end of the cylindrical container is wiped off using a spatula, the weight of the container is measured in this state, and the weight of the container is subtracted from the measured value. Was calculated by dividing the mass by the volume of the container. The measurement is performed at 23 ± 2 ° C. and humidity 50 ± 5%, and the sample is measured after being stored in the same environment for 24 hours or more.

  Further, the water-absorbing polymer used in the present invention preferably has a water absorption rate of 2 to 20 ml / 0.3 g · 30 seconds, particularly 4 to 15 ml / 0.3 g · 30 seconds by the DW method. The water absorption rate by the DW method expresses the behavior of the water-absorbing polymer to absorb and absorb the liquid, or the behavior of taking the liquid into the gaps between the adjacent water-absorbing polymer particles. It serves as an index of shape retention, particularly the shape retention of the absorbent after absorption. If the water absorption rate of the water-absorbing polymer by the DW method is too fast (the value of the water absorption rate by the DW method is too large), the moisture content in the absorbent body becomes too high, resulting in poor drying during production of the absorbent body. While becoming easy, there exists a possibility that the space | gap enclosed with the particle | grains of the water absorbing polymer in the polymer high concentration area | region mentioned above may not be formed. On the other hand, if the water absorption rate of the water-absorbing polymer by the DW method is too slow (the value of the water absorption rate by the DW method is too small), the tackiness of the water-absorbing polymer will not work sufficiently, and sufficient interlayer adhesion will not be obtained. The absorber may delaminate due to the movement of the wearer after the line or liquid absorption, and the water-absorbing polymer may leak out of the absorber. The water absorption rate by the DW method can be adjusted by the shape, particle size, bulk specific gravity, degree of crosslinking, etc. of the water-absorbing polymer. The water absorption rate by the DW method is measured as follows.

<Measurement method of water absorption rate by DW method>
The water absorption rate by the DW method is measured by using a device (Demand Wettability Tester) generally known as a device for performing the DW method. Specifically, in the apparatus, the level of the physiological saline solution is set at the same level as the surface of the polymer spray table (70 mmφ, a table in which No. 2 filter paper is placed on the glass filter No. 1), and the polymer spray table Sprinkle 0.3 g of the water-absorbing polymer to be measured on the surface. The water absorption at the time when the water-absorbing polymer is sprayed is set to 0, and the water absorption after 30 seconds is measured. The amount of water absorption is measured by a burette scale indicating the amount of decrease in the saline water level. The value of the water absorption obtained is taken as the water absorption rate by the DW method. The measurement is performed at 23 ± 2 ° C. and humidity 50 ± 5%, and the sample is measured after being stored in the same environment for 24 hours or more.

  Further, the water-absorbing polymer used in the present invention preferably has a liquid passing rate under pressure of 2.0 kPa of 150 ml / min or more, particularly 200 to 2000 ml / min, particularly 250 to 1500 ml / min. Here, the load of 2.0 kPa substantially corresponds to the pressure applied to the absorbent body when the absorbent article is worn. The liquid passing rate under pressure serves as an index of the diffusion / permeation rate of the liquid in the absorber. That is, in absorbent articles such as sanitary napkins and disposable diapers, excreted fluid such as urine and menstrual blood is taken into the absorbent body located below through the surface sheet forming the skin contact surface, and the absorbent body In, for example, when the fiber material such as pulp is once held in a space formed and then absorbed and held by an absorption mechanism that is fixed by the water-absorbent polymer in the absorbent body, the absorption rate of excretory fluid in the absorbent article is It depends mainly on the “speed at which the water-absorbing polymer fixes the liquid” and the “diffusion / permeation speed of the liquid in the absorber”. This “speed at which the water-absorbing polymer fixes the liquid” can be evaluated by the water absorption speed by the DW method, and “the diffusion / permeation speed of the liquid in the absorber” should be evaluated by the liquid passing speed under pressure. Can do. Since a water-absorbing polymer having a slow liquid passage rate under pressure (small value of the liquid passage rate under pressure) tends to inhibit diffusion of the liquid in the absorbent body due to gel blocking, particularly in the case of repeated absorption of the liquid. Even if the speed of fixing the liquid of the water-absorbing polymer itself (water absorption speed according to the DW method) is sufficiently high, the absorption speed of the liquid in the absorbent article using the water-absorbing polymer is not sufficient and may be slow. . The liquid passing rate under pressure can be adjusted by the strength of cross-linking (internal cross-linking and surface cross-linking as necessary), shape, surface treatment, and the like.

  The liquid flow rate under pressure is measured using a measurement method and a measurement apparatus described in JP-A-2003-235889. Specifically, the flow rate under pressure at 2.0 kPa is measured by the following procedure. The following measurement is performed at 23 ± 2 ° C. and a relative humidity of 50 ± 5%. Before the measurement, the sample is stored in the same environment for 24 hours or more.

<Measurement method of liquid flow rate under pressure>
In a 100 mL glass beaker, a sufficient amount of physiological saline (0.9% by mass sodium chloride water) to swell the measurement sample water-absorbing polymer 0.32 ± 0.005 g, for example, the saturated absorption amount of the water-absorbing polymer. Immerse it in 5 times more saline and leave it for 30 minutes. Separately, at the lower end of an opening of a vertically standing cylinder (inner diameter 25.4 mm), a wire mesh (mesh opening 150 μm, biocolumn sintered stainless steel filter 30SUS sold by Sansho Co., Ltd.) and a capillary (with an inner diameter of 2 mm) ( A filtration cylindrical tube having an inner diameter of 4 mm and a length of 8 cm) is prepared, and the contents of the beaker including the swollen measurement sample are put into the cylindrical tube with the cock closed. Next, a cylindrical rod having a diameter of 2 mm with a wire mesh having an opening of 150 μm and a diameter of 25 mm is inserted into the filtration cylindrical tube so that the wire mesh and the measurement sample are in contact with each other. Place a weight so that the load of. After standing in this state for 1 minute, the cock is opened to flow the liquid, and the time until the liquid level in the filtration cylindrical tube reaches the 40 mL scale line from the 60 mL scale line (that is, 20 mL of liquid passes) (T ₁ ) (Seconds). Using the measured time T ₁ (seconds), the flow rate at 2.0 kPa is calculated from the following equation. In the equation, T ₀ (seconds) is a value obtained by measuring the time required for 20 ml of physiological saline to pass through the wire mesh without putting the measurement sample in the filtering cylindrical tube. Flow rate (ml / min) = 20 × 60 / (T ₁ −T ₀ ) The value obtained by the above formula is divided by the thickness of the swollen water-absorbing polymer layer in the cylinder, and converted to a value per 20 mm. Thus, the liquid passing speed under pressure is set. The measurement was performed 5 times (n = 5), the values at each of the upper and lower points were deleted, and the average value of the remaining three points was taken as the measured value. Incidentally, a more detailed method for measuring the flow rate under pressure is described in paragraphs [0008] and [0009] of JP-A No. 2003-235889, and the measuring device is shown in FIGS. 2.

  The particles of the water-absorbing polymer used in the present invention preferably have an average particle size of 200 to 600 μm, particularly 250 to 450 μm, and particularly 250 to 400 μm. The use of water-absorbing polymer particles having an average particle diameter in such a range is effective in forming voids surrounded by the water-absorbing polymer particles in the polymer high concentration region described above.

  In addition, among all the water-absorbing polymers contained in the absorbent body, when the content of the water-absorbing polymer having a particle size of less than 250 μm is less than 20% by mass, particularly less than 15% by mass, The absorption time is shortened and leakage is less likely to occur. Further, in addition to the content of the water-absorbing polymer having a particle size of less than 250 μm being in the above range, the content of the water-absorbing polymer having a particle size of less than 150 μm is less than 5% by mass, particularly less than 3% by mass. This is preferable because the above-described effect can be more reliably exhibited.

  The “average particle size” and the “content of water-absorbing polymer having a particle size of less than 250 μm” and “content of water-absorbing polymer having a particle size of less than 150 μm” are measured by the following <Method for measuring particle size distribution>, respectively. The As is apparent from the following measurement method, the “water-absorbing polymer having a particle size of less than 250 μm or less than 150 μm” is not limited to a water-absorbing polymer having a spherical shape or a nearly spherical shape. The shape of the water-absorbing polymer is not limited.

<Measuring method of particle size distribution>
50 g of all the water-absorbing polymer contained in the absorbent body (absorbent article) was added to a standard sieve having openings 850, 600, 500, 355, 300, 250, 150 defined by JIS Z 8801 (for example, Tokyo Screen Co., Ltd.). Using a shaker (for example, AS200 type, manufactured by Lecce), the product is sieved using a standard sieve) and a saucer. The shaking condition is 50 Hz, the amplitude is 0.5 mm, and the shaking time is 10 minutes. The measurement was performed 3 times, and the average value was defined as the mass on the sieve. The mass on each sieve obtained was divided by 50 to determine the relative frequency, and a particle size cumulative curve was drawn. The particle diameter corresponding to the central cumulative value (50%) of the cumulative curve was taken as the average particle diameter. After the sieving operation, the “water-absorbing polymer having a particle size of 250 μm or more” is placed on the sieve having an opening of 250, and the “water-absorbing polymer having a particle size of less than 250 μm” is screened under the sieve having an opening of 250, ie On the upper and lower saucers, “water-absorbing polymer having a particle size of less than 150 μm” means what is on the saucer after passing through a sieve having 150 openings. The sieving was performed 3 times, and the average value of 3 times was defined as the mass on each sieve. The mass on each obtained sieve was calculated as a mass percentage with respect to the total mass, and the abundance ratio of each particle size was calculated. The measurement is performed at 23 ± 2 ° C. and humidity 50 ± 5%, and the sample is measured after being stored in the same environment for 24 hours or more.

  The water-absorbing polymer used in the present invention preferably has a degree of neutralization of less than 75 mol%. In particular, when the water-absorbing polymer is an acrylic acid cross-linked polymer, the degree of neutralization is preferably 30% or more and less than 75 mol%, particularly 50% or more and less than 75 mol%. When the neutralization degree of the water-absorbing polymer is less than 75 mol%, the pH of the excretory liquid in contact with the water-absorbing polymer becomes weakly acidic, and ammonia or other bases generated by decomposition of urine possessed by the water-absorbing polymer The napkin is kept in a weakly acidic range or neutral range (approximately less than pH 5-8) due to its high neutralizing ability for the sex component, so even if the liquid returns and the excretory fluid adheres to the skin, Less irritation. Moreover, generation | occurrence | production of a urine odor and a rotten odor can be suppressed by the neutralization ability of such a water absorbing polymer.

  In addition, when the neutralization degree of the water-absorbing polymer is less than 75 mol%, it is suppressed that counter ions (for example, sodium and potassium) used for neutralization in excretory liquids and napkins are suppressed. Swelling inhibition due to ion agglomeration of the water-absorbing polymer due to the counter ions is less likely to occur. In order to improve the water absorption rate and control the bulk density, it is more preferably used than the reverse phase suspension polymerization method in which the shape and particle size of the water-absorbing polymer particles are easy to control. In this case, if the degree of neutralization is low, the acrylic acid monomer is easily dispersed in the organic solvent / water / surfactant mixed solution, which is the reaction field, thereby improving productivity and stabilizing the physical properties. The degree of neutralization is measured as follows.

<Method for measuring the degree of neutralization>
First, a neutralization titration curve of the main chain polymer of the water-absorbing polymer is prepared. For example, when the water absorbent polymer is an acrylic acid crosslinked polymer, the main chain polymer of the water absorbent polymer is polyacrylic acid. The case where the water-absorbing polymer is an acrylic acid crosslinked polymer will be described below as an example. A sodium hydroxide solution was appropriately added dropwise to an ion exchange aqueous solution of polyacrylic acid (Wako Pure Chemical Industries, average molecular weight 250,000), and the pH of the solution was measured using a pH meter. At this time, the degree of neutralization was calculated from the molecular weight of polyacrylic acid and the number of moles of added sodium hydroxide, and the neutralization degree was plotted on the horizontal axis and the pH was plotted on the vertical axis to draw a neutralization titration curve. The degree of neutralization was in the range of 50 to 100%. As the pH meter, Horiba pH ion meter D53 and electrode type 6583 were used. Next, 0.1 g of the water-absorbing polymer was put into 20 ml of ion-exchanged water, and after stirring for 10 minutes, the pH of the stirred solvent was measured. From the obtained pH value, the neutralization titration curve was used for the purpose. The degree of neutralization was calculated. The measurement is performed at 23 ± 2 ° C. and humidity 50 ± 5%, and the sample is measured after being stored in the same environment for 24 hours or more.

  Regarding the measurement of the degree of neutralization, instead of the above method, the amount of sodium in the water-absorbing polymer was quantified by elemental analysis, and the following theoretical structural formula (1) (theory applied to acrylic acid-based water-absorbing polymers) The target neutralization degree may be calculated based on the structural formula. Moreover, it may replace with the said method and may calculate the target neutralization degree from the value measured by the method based on JISK0113-1997. A method based on JIS K0113-1997 is a method in which a 0.1 N potassium hydroxide aqueous solution is used as a titrant to perform potentiometric titration, and an end point is determined by an inflection point method.

  The neutralization degree of the water-absorbing polymer can be adjusted, for example, by neutralizing the water-absorbing polymer with a basic compound. The neutralization treatment can be performed in the same procedure as the neutralization treatment of a conventionally known water-absorbing polymer, but the water-absorbing polymer preferably used in the present invention has a carboxy group and / or a carboxylate group and has a surface. The water-absorbing polymer that has been subjected to the crosslinking treatment is further subjected to a surface crosslinking treatment and a neutralization treatment in order. As a neutralization treatment method, for example, a method in which an aqueous solution in which a predetermined amount of a basic compound is dissolved in a water-absorbing polymer is added; a water-absorbing polymer and a predetermined amount of a powdered basic compound are mixed and water is further added And the like. Examples of the basic compound used in the neutralization treatment include water-soluble carbonate compounds such as sodium bicarbonate, sodium carbonate, potassium bicarbonate and potassium carbonate; water-soluble hydroxide compounds such as sodium hydroxide, potassium hydroxide and water glass Is mentioned.

  The water-absorbing polymer used in the present invention preferably has all of the above-mentioned physical properties in the specific range. However, a void is formed between the water-absorbing polymers in a high concentration region of the water-absorbing polymer, so that the absorber can be quickly formed. From the viewpoint of expressing liquid uptake, in addition to the angle of repose of the swollen gel being 45 ° or less, the flow rate under pressure at least at 2.0 kPa is 150 ml / min or more, particularly 200 to 2000 ml / min, In particular, it is preferably 250 to 1500 ml / min.

The water-absorbing polymer used in the present invention can be obtained, for example, by the following production methods 1) and 2).
1) A method of polymerizing a monomer containing (meth) acrylic acid and / or an alkali metal salt thereof to obtain a polymer, and crosslinking the polymer with a crosslinking agent.
2) A method of polymerizing a monomer containing (meth) acrylic acid and / or an alkali metal salt thereof in the presence of a crosslinking agent.

  The production methods 1) and 2) can be performed using a known method for producing a polyacrylic acid-based water-absorbing polymer. As this known production method, for example, (i) a reverse phase suspension polymerization method using an anionic surfactant described in Japanese Patent No. 2721658 as a dispersant, and (ii) Japanese Patent Laid-Open No. 2003-235889 And the aqueous solution polymerization method described in 1.

  In the production method of 1), a crosslinking agent may be used in the step of obtaining a polymer by polymerizing a monomer containing (meth) acrylic acid and / or an alkali metal salt thereof, and in the production method of 2), After polymerizing a monomer containing (meth) acrylic acid and / or an alkali metal salt thereof in the presence of a crosslinking agent, the polymer obtained by the polymerization may be further crosslinked with a crosslinking agent. That is, in the production methods 1) and 2), the crosslinking treatment may be performed twice or more.

  The polymer of a monomer containing (meth) acrylic acid and / or an alkali metal salt thereof prepared by the production method of 1) above is (meth) acrylic acid from the viewpoints of blood absorbability control, safety, production cost, and the like. Homopolymers, copolymers thereof, or cross-linked products thereof. Examples of the homopolymer of (meth) acrylic acid include polyacrylic acid and polymethacrylic acid. Examples of the copolymer of (meth) acrylic acid include acrylic acid or methacrylic acid, maleic acid, itaconic acid, acrylamide, Copolymers obtained by copolymerizing co-monomers such as 2-acrylamido-2-methylpropanesulfonic acid, 2- (meth) acryloylethanesulfonic acid, 2-hydroxyethyl (meth) acrylate, or styrenesulfonic acid, starch-acrylic acid Examples thereof include a graft copolymer. The amount of the comonomer of the copolymer is preferably in a range that does not deteriorate blood absorption performance. Moreover, as an alkali metal salt of (meth) acrylic acid, sodium salts, such as polyacrylic acid and polymethacrylic acid, are preferable.

  Among these, (meth) acrylic acid or an alkali metal salt homopolymer or copolymer cross-linked product thereof, starch-acrylic acid graft copolymer cross-linked product is preferable, and acrylic acid or alkali metal acrylate single salt A cross-linked polymer is more preferred. These polymers usually contain 50 mol% or more of acrylic acid monomer units, preferably 60 mol% or more, more preferably 70 mol% or more, still more preferably 80 mol% or more, and are substantially insoluble in water. Although it is a polymer having a high degree of swelling.

  The crosslinking agent used in the production methods 1) and 2) can react with two or more polymerizable unsaturated groups in the molecule, or two or more carboxy groups and / or carboxylate groups in the molecule. Any compound having a reactive group may be used, and examples thereof include a compound having two or more hydroxyl groups in the molecule, a compound having two or more polymerizable double bonds, and a compound having two or more epoxy groups.

  Examples of the “compound having two or more hydroxyl groups in the molecule” include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, polyglycerin, propylene glycol, diethanolamine, polyoxypropylene, sorbitan fatty acid ester, trimethylolpropane. , Pentaerythritol, 1,3-propanediol, sorbitol and the like.

Examples of the “compound having two or more polymerizable double bonds in the molecule” include bis (meth) acrylamide, allyl (meth) acrylamide, di- or polyester of (meth) acrylic acid by polyol (for example, diethylene glycol diacrylate). , trimethylolpropane triacrylate, and polyethylene glycol diacrylate), C ₁ -C ₁₀ derived from the reaction of a polyhydric alcohol and 2-8 C ₂ -C ₄ alkylene oxide per hydroxyl group, unsaturated with polyols Examples thereof include di- or polyester of mono- or polycarboxylic acid (for example, ethoxylated trimethylolpropane triacrylate) and the like.

  Examples of the “compound having two or more epoxy groups in the molecule” include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin triglycidyl ether, glycerol polyglycidyl ether, polyglycerol polyglycidyl ether. And polyglycidyl ethers such as trimethylolpropane polyglycidyl ether, sorbitol polyglycidyl ether, pentaerythritol polyglycidyl ether, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether, and hydrogenated bisphenol A type diglycidyl ether.

  Among these crosslinking agents, a compound having two or more polymerizable double bonds and a compound having two or more epoxy groups in the molecule are preferable, and a compound having two or more epoxy groups in the molecule is more preferable. Specifically, ethylene glycol diglycidyl ether and trimethylolpropane polyglycidyl ether are particularly preferable.

  In the production methods of 1) and 2), the amount of the crosslinking agent used is 0.15 / 100 to 40/100 in terms of the mass ratio of [crosslinking agent / monomer], and 0.2 / 100 to 30/100. Preferably, 0.3 / 100-20 / 100 is more preferable.

[Surface sheet]
As shown in FIG. 13, the topsheet 2 provided in the napkin 1 of the present embodiment is composed of a single layer non-woven fabric (three-dimensionally shaped non-woven fabric). One surface 2 b of the surface sheet 20 is substantially flat, and the other surface 2 a has a concavo-convex shape having a large number of concave portions 20 and convex portions 23. The other surface 2 a is a surface that forms a skin contact surface of the napkin 1. The convex part 23 is located between the concave parts 20. The inside of the convex part 23 is filled with the constituent fibers of the topsheet 20.

  The recessed part 20 has the linear embossing 21 as a junction part by which the component fiber is crimped | bonded or adhere | attached. Here, examples of means for crimping the fiber include embossing and ultrasonic embossing with or without heat. On the other hand, as means for adhering fibers, bonding with hot melt or various adhesives can be mentioned. The linear emboss 21 in the surface sheet 2 according to the present embodiment is formed by subjecting a fiber web formed by a card method to hot embossing. In the linear emboss 21, the heat-fusible fibers, which are constituent fibers of the top sheet 2 or the non-woven fabric constituting the top sheet 2, are integrated by heat-sealing. In the heat-fusible fiber in the linear emboss 21, the heat-fusible component is melted and the fiber form is not maintained.

  In addition, the shape of the joint is not limited to a straight line in a plan view, but includes a curved line, and each line may be a continuous line or a broken line. It may be formed intermittently. The term “intermittently” means that adjacent intervals between the dotted joints are separated by 5 mm or more. Moreover, it is not necessary to form the area | region enclosed by the junction part (linear embossing 21) like the form shown in FIG.

  The linear embosses 21 are formed in a lattice shape as shown in FIG. More specifically, as shown in FIG. 14, the topsheet 2 includes a plurality of first linear embosses 21 a formed in parallel with each other at predetermined intervals as linear embosses 21. A plurality of second linear embosses 21b formed in parallel and at predetermined intervals, and the first linear emboss 21a and the second linear emboss 21b form an angle α with each other. Crossed. The width W1 of the first linear emboss 21a and the width of the second linear emboss 21b are the same, and the interval W2 between the first linear embosses 21a and the interval between the second linear embosses 21b are also the same. The same.

  The width W1 (only one is shown) of the first and second linear embosses 21a and 21b is 0.1 to 1.5 mm, particularly 0.3 to 0, in order to securely fix the fiber in the linear embossing. Is preferably 9 mm, and the interval W2 between the first linear embosses 21a and the interval between the second linear embosses 21b are 2 to 14 mm so as to easily form a fiber parallel standing portion described later, 2 to 8 mm is particularly preferable. W1 and W2 are measured in a direction perpendicular to the line. The width of the line may change from the intersection, but W1 is measured at the intersection and the midpoint of the intersection. W2 is measured by a line connecting opposite sides of the partition region 22.

  The X direction in FIGS. 13 and 14 is the same as the sheet flow direction (MD) during the manufacture of the topsheet, and is also the same as the longitudinal direction X of the napkin 1 (see FIG. 1). Further, the Y direction in FIGS. 12 and 13 is the same direction as the direction (CD) orthogonal to the flow direction of the sheet at the time of manufacturing the surface sheet, and the same direction as the width direction Y (see FIG. 1) of the napkin 1. is there.

  Since the linear emboss 21 is formed in a lattice shape as described above, the top sheet 2 is formed with partitioned regions 22, 22... Partitioned by the linear emboss 21. Each partition area 22 is an area surrounded by a linear emboss 21 and has a rhombus shape in plan view. The central portion of each partition region 22 is raised relative to the concave portion 20 surrounding the partition region 22 to form a convex portion 23.

  Thus, the wearer of the napkin 1 by the recessed part 20 (linear embossing 21) and the convex part 23 being alternately arrange | positioned in each of one direction of the surface sheet 20, and the direction orthogonal to this one direction. The area of contact with the skin is reduced, and stuffiness and rash are effectively prevented. Moreover, when the convex part 23 (partition area | region 22) is surrounded by the recessed part 20 (linear embossing 21), and has the closed shape in planar view, the convex part 23 is not surrounded by the recessed part 20 As compared with the above, the constituent fibers in the convex portion 23 are easily stretched in the thickness direction of the surface sheet 2, so that the thickness of the convex portion 23 is increased. The contact area with the skin of the surface sheet 2 is reduced, and 2) since the convex portions 23 are formed in a regular pattern, the visual impression is improved.

  In the surface sheet 2 according to the present embodiment, as shown in FIG. 15, in the vicinity of the joint in the recess 20, that is, at the time of the linear emboss 21 (wrinkle) (joint and non-joint part adjacent to the joint A fiber parallel upright portion 24 is formed at which the constituent fibers rise in parallel in a direction away from the emboss 21 starting from the emboss 21. The fiber parallel upright portion 24 is a non-joined portion (non-embossed region) adjacent to the linear emboss 21 and is formed adjacent to each of the first linear emboss 21a and the second linear emboss 21b. ing.

  More specifically, as shown in FIG. 15, the fibers 25 of the fiber parallel upright portions 24 are arranged so as to rise from a linear emboss 21 toward a direction approaching the wearer's skin of the napkin 1. In addition, as shown in FIG. 16, the top sheet 2 is arranged in parallel in a direction P in which the linear embosses 21 extend in a plan view.

  It is preferable that the length L (refer FIG.15 and FIG.16) measured along the fiber which comprises the surface by the side of the skin contact surface 2a of the fiber parallel standing part 24 is 0.5-4.0 mm, More preferably, it is 0.5-2.0 mm, More preferably, it is 0.5-1.0 mm. Moreover, the fiber parallel standing part 24 formed adjacent to the 1st or 2nd linear embossing 21a, 21b is set to 100% when the circumference | surroundings of the division area 22 are formed over the perimeter. 70% or more, preferably 40% or more.

  FIG. 15 is a cross-sectional view, that is, a boundary between a linear emboss 21 (that is, a bonded portion to which constituent fibers are pressure-bonded or bonded) and a non-bonded portion adjacent to the emboss 21 (that is, a fiber parallel standing portion 24). That is, in a cross-sectional view along a direction orthogonal to (in the case of the linear emboss 21) (direction Q in FIG. 16), the distance r between the adjacent fibers 25 in the fiber parallel standing portion 24 is the linear emboss 21. It gradually decreases as you head toward. That is, in a cross-sectional view as shown in FIG. 15, a straw-shaped space is formed between the fibers 25 arranged in parallel in the vertical direction in the fiber parallel upright portion 24, and the space is directed toward the linear emboss 21. It has a tapered shape. In the fiber standing part 24, the inter-fiber distance r is preferably 5 to 250 μm, more preferably 40 to 200 μm. The interfiber distance r is approximately 0 μm at or near the linear emboss 21. The interfiber distance r is measured as follows. In addition, it is not necessary for the space formed by all the fibers to have a tapered shape, and it is preferable that 30% or more, more preferably 50% or more of the number of spaces has a tapered shape.

<Measurement method of distance between fibers>
First, the topsheet is cut in a direction that forms an angle α with the first linear embossed line 21a, that is, in a direction parallel to the second linear embossed line 21b. The obtained cross section is photographed using a microscope (Keyence, VH-8000). When there is a fiber that is sinking in the depth direction, 3D imaging is performed using the apparatus, and the image is projected onto a plane. Next, a straight line asymptotic to each fiber is drawn from the embossed line 21 as a base point, and the angle formed with the non-skin contact surface of the topsheet is taken as a reference line, the point of the length L of the fiber parallel upright portion 24 on the reference line When the perpendicular line was drawn, the intersection of the perpendicular line and the asymptotic line of the fiber adjacent to the fiber was determined, and the inter-fiber distance r was calculated. If the joint (emboss) has a shape other than a linear shape, such as a circular shape or a cross shape, the surface sheet is cut so as to connect the embosses between adjacent ones in the width direction of the product. Perform the operation.

  As shown in FIG. 16, the fibers 25 of the fiber parallel upright portions 24 are aligned substantially in the direction Q intersecting the embossed line direction P in the case of the linear embossing 21. That is, one end 25a in the longitudinal direction of the fiber 25 is fixed to the linear emboss 21 by melting the heat-fusible component, and the other end in the longitudinal direction is the first in the plan view of the topsheet 2. The first or second linear emboss 21a, 21b extends in a direction intersecting with the extending direction P, more specifically, in a direction (Q direction) substantially orthogonal to the direction P. By forming the emboss 21 in a linear shape, the fibers extend in parallel from the line. The linear shape is preferably a continuous straight line or curved line. In the case of a broken line, the interval between the lines may not be extremely large, but the interval between the lines is preferably 2 mm or less.

  Further, the fibers 25 of the fiber parallel standing portions 24 have extended portions 25b extending beyond the fiber parallel standing portions 24, and these extended portions 25b extend non-parallel to the convex portion 23. In the convex portion 23, particularly the central portion thereof, a fiber joining point (not shown) is formed in which intersecting constituent fibers are heat-sealed at each other intersection.

  As described above, the distance r between the adjacent fibers 25 in the fiber standing upright portion 24 is gradually decreased toward the linear emboss 21 which is a joint portion to which the constituent fibers 25 are bonded or bonded. Thus, a tapered straw-shaped space is formed between the adjacent fibers 25 toward the linear emboss 21, and the liquid is drawn toward the linear emboss 21 through the space. Further, since the fibers 25 in the vicinity of the linear emboss 21 are erected while extending in a direction intersecting with the direction in which the linear emboss 21 extends, the linear shape of the liquid reaching the boundary with the linear emboss 21 is increased. Movement along the direction in which the emboss 21 extends is relatively difficult. Therefore, as shown in FIG. 17, the liquid supplied to the skin contact surface 2 a side of the top sheet 2 smoothly moves to the absorbent body 10 via the fiber parallel upright portions 24, and the liquid is applied to the top sheet 2. The rest is unlikely to occur.

  Moreover, since the partition region 22 partitioned by the linear emboss 21 is formed and the fiber parallel upright portions 24 are formed around the partition region 22, the movement of the liquid across the partition region 22 is suppressed. Inconvenience such as liquid leakage due to the liquid flowing on the top sheet 2 is unlikely to occur.

  Moreover, as shown in FIG. 17, the joining part (linear embossing 21) of the topsheet 2 and the water-absorbing polymer high-concentration region 13 in the absorbent body 10 substantially coincide, that is, the region 13 below the joining part. The presence of the liquid has an effect of reducing the liquid residue on the top sheet 2 while maintaining a quick liquid uptake.

  Moreover, although not shown in figure, contrary to the form shown in FIG. 17, the joining part (linear embossing 21) of the surface sheet 2 and the water-absorbing polymer low concentration region 14 in the absorbent body 10 substantially coincide. That is, the presence of the region 14 below the joint is effectively prevented from leaking because the liquid diffuses throughout the product due to the high liquid diffusibility of the region 14. Further, in this case, the liquid diffused in the region 14 is fixed in the water-absorbing polymer high concentration region 13 adjacent to the region 14, and the position of the region 13 is substantially the same as the convex portion 23 that is the bulky portion of the topsheet 2. The coincidence has an effect of reducing so-called liquid return in which the liquid fixed in the region 13 returns to the surface sheet 2 side.

The area of each partition region 22 is preferably 0.25 to ² cm ² . Further, the area ratio of the linear emboss 21 (joint portion) is preferably 16% or less, and particularly preferably 14% or less because the liquid hardly remains in the surface sheet 2. If the area ratio of the joint portion is too high, the convex portion of the sheet is pressed down, and the liquid tends to remain in the surface sheet. Further, the area ratio of the joint is preferably 10% or more, particularly 11% or more from the viewpoint of improving the liquid suction property. If the area ratio of the joint portion is too low, the width of the joint portion (linear embossing 21) becomes narrow and the strength of the linear embossing cannot be ensured, so that the liquid sucking property is deteriorated. The area ratio of the joint is measured as follows.

<Method of measuring the area ratio of the joint>
The area ratio of the joint is obtained by image analysis of a real photograph. At this time, if there is a fiber defect in the joint, manual correction is performed, and measurement is performed assuming that there is a fiber.

  Further, as shown in FIG. 15, the surface sheet 2 according to the present embodiment includes a non-woven fabric constituting the surface sheet 2 in a portion overlapping the fiber parallel standing portion 24 on the non-skin contact surface side. It has the fiber parallel part 26 arranged in parallel in the direction away from the embossed 21 of the shape. By having the fiber parallel part 26 in the part which overlaps with the fiber parallel standing part 24, it is prevented that the liquid drawn in through the fiber parallel standing part 24 stays in the non-skin contact surface vicinity of the surface sheet 2, FIG. As shown, the liquid A moves more smoothly to the absorbent body 10.

  From the viewpoint of further improving the transferability of the liquid to the absorbent body 10, when the topsheet 2 is incorporated into the napkin 1, the fiber parallel part 26 is brought into contact with the absorbent body 10 substantially in parallel as shown in FIG. 17. It is preferable to arrange in. In addition, it is preferable that the fiber parallel part 26 has the same configuration as the fiber parallel stand part 24 except that the fiber parallel stand part 26 is not raised.

  When a partitioned area surrounded by linear embossing is formed on the surface sheet, each partitioned area or two types of partitioned areas with different dimensions are formed with a dimensional ratio of golden ratio or white silver ratio. Is preferred.

  The golden ratio is the most beautiful ratio since ancient times, and the approximate ratio a: b is 9:16, but the golden ratio a: b in the present invention is in the range of 9:15 to 9:17. . By forming the partition region having the golden ratio, it is possible to obtain a surface sheet or an absorbent article having a beautiful appearance as well as excellent absorption performance.

  The silver ratio is a ratio based on a traditional Japanese wood split and is said to have stable and timeless beauty, and a: b is 1: 1.414. The silver ratio a: b is in the range of 1: 1.3 to 1: 1.5. By forming the partition region having the silver ratio, it is possible to obtain a surface sheet and an absorbent article that have excellent absorption performance and give a sense of stability and security.

  As an example in which each partition region has a dimensional ratio of golden ratio or white silver ratio, as shown in FIG. 14, the ratio of the diagonal lengths L1 and L2 of the rhombus-shaped partition region 22 is set to the golden ratio or white silver. The ratio a: b is mentioned. In this case, a of golden ratio or silver ratio a: b may be L1, b may be L2, a may be L2, and b may be L1. In addition, the length starting from the center of the intersection of 21a (21) and 21b (21) shown in the figure as the starting point / ending point may be the length corresponding to L1 and L2.

  As an example of giving a dimensional ratio of golden ratio or silver ratio to a plurality of types of partitioned areas, as shown in FIG. 18, two types of partitioned areas 22A and 22B having different dimensions and shapes are parallel to each other or straight. The ratio of the lengths of the diagonal lines L3 and L4 that are aligned with each other may be the golden ratio or the silver ratio a: b. In this case, a in the golden ratio or silver ratio a: b may be L3, b may be L4, a may be L4, and b may be L3.

  In addition, when reminding the diagonal of each division area as a virtual line which comprises golden ratio or white silver ratio, the line of an absorbent article edge part and side groove embossing play an auxiliary role. Therefore, it is more effective to match the larger ratio in the longitudinal direction of the product.

  The surface sheet 2 according to the present embodiment includes a heat-extensible fiber whose length is extended by heating as a constituent fiber. The heat-extensible fiber is preferably a heat-fusible fiber. The heat-fusible fiber as the heat-extensible fiber is preferably a composite fiber comprising a heat-fusible component and a high-melting-point component having a higher melting point than the heat-fusible component, more preferably a heat-fusible component. Is a core-sheath type composite fiber having a high melting point component as a core. The heat fusion component and the high melting point component are preferably thermoplastic resins. Examples of the heat fusion component include polyethylene, polypropylene, polybutene-1, polypentene-1, or a random or block copolymer thereof. Examples of the high melting point component include polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyamides such as nylon-6 and nylon-66, and the like.

  Preferred combinations of the heat fusion component and the high melting point component include polyethylene and polyethylene terephthalate, polyethylene and polypropylene, low melting point polyethylene terephthalate and polyethylene terephthalate, polyethylene and polybutylene terephthalate, and the like. is not. The core-sheath type composite fiber may be a concentric type, an eccentric type, or a fiber having a core component exposed at a part of the entire circumference of the fiber.

  The heat-fusible fiber is preferably a heat-extensible composite fiber from the viewpoint of the formability of the fiber side-upstanding portion described later and the formability of the uneven shape. The heat-extensible conjugate fiber is a conjugate fiber whose length is extended by heating, and is a fiber that extends at a temperature of 90 ° C. or higher, preferably 110 ° C. to 130 ° C. When the heat-extensible conjugate fiber is stretched during the production of the topsheet 2, it is possible to form irregularities with large undulations and to easily generate a fiber parallel upright portion described later. Therefore, after the surface sheet 2 is completed, many of them are in an extended state, and do not mean fibers that are further extended from the state. The heat-extensible composite fiber after extension is also included in the heat-extensible composite fiber.

  Examples of the heat-stretchable composite fiber include a fiber that changes in the crystalline state of the resin by heating or is stretched, or a fiber that has been crimped and has an apparent length that is released by crimping. . As the heat-extensible composite fiber, it is 10 to 30 ° C. higher than the softening point of the heat-fusible component and 10 ° C. lower than the melting point. It is preferable from the point that a part and an uneven | corrugated shape are formed notably. Preferable examples of the heat-extensible conjugate fiber are described in paragraphs [0024] to [0040] of JP-A-2005-350836.

  The ratio of the composite fiber composed of the heat-fusible component and the high-melting-point component, particularly the heat-extensible composite fiber, is preferably 40 to 100% by mass, more preferably 70 to 100% by mass in the constituent fibers of the surface sheet 2. %, More preferably 95 to 100% by mass. Examples of fibers to be blended in addition to these composite fibers include fibers composed of thermoplastic resins (non-composite fibers).

  The manufacturing method of the surface sheet 2 mentioned above is demonstrated, referring FIG. 19 for the case where it manufactures using a heat | fever extensible composite fiber as an example. First, a web 2A serving as a raw sheet of the top sheet 2 is produced using a predetermined web forming means (not shown). The web 2A contains a heat-extensible composite fiber or is made of a heat-extensible composite fiber. Examples of the web forming means include (a) a card method in which short fibers are opened using a card machine, and (b) a method in which melt-spun continuous filaments are directly pulled by air soccer and deposited on a net (spunbond). And (c) a known method such as a method in which short fibers are transported in an air stream and deposited on a net (air array method).

  Next, the web 2 </ b> A is introduced into the heat embossing device 51. In the heat embossing device 51, the web 2A is subjected to heat embossing. The heat embossing device 51 includes a pair of rolls 52 and 53. The roll 52 is a smooth roll having a smooth peripheral surface. On the other hand, the roll 53 is a sculpture roll in which a lattice-like convex portion corresponding to the linear emboss 21 is formed on the peripheral surface thereof. Each of the rolls 52 and 53 can be heated to a predetermined temperature.

  The heat embossing is performed at a temperature at which the heat-fusible component of the heat-extensible composite fiber in the web 2A is melted. The processing temperature of the heat embossing is preferably performed at a temperature that is equal to or higher than the melting point of the heat-fusible component in the heat-extensible composite fiber in the web 2A and lower than the melting point of the high-melting point component. Moreover, it is preferable to carry out at the temperature below the elongation start temperature of a heat | fever extensible fiber.

  The nonwoven fabric 54 which has the linear embossing 21 is obtained by heat embossing. Subsequently, the nonwoven fabric 54 is conveyed to the hot air spraying device 55. In the hot air spraying device 55, the nonwoven fabric 54 is subjected to air-through processing. The hot air blowing device 55 is configured such that hot air heated to a predetermined temperature penetrates the nonwoven fabric 54. The air-through process is performed at a temperature at which the heat-extensible composite fiber in the nonwoven fabric 54 is elongated by heating. And it is performed at a temperature at which the intersections of the heat-extensible composite fibers in a free state existing in the non-woven fabric 54 other than the linear emboss 21 are thermally fused. However, it is preferable that the temperature is lower than the melting point of the high melting point component of the heat-extensible conjugate fiber.

  By such an air-through process, the heat-extensible conjugate fiber contained in the nonwoven fabric 54 is stretched at portions other than the linear emboss 21. Since a part of the thermally stretchable conjugate fiber is fixed by the linear emboss 21, it is the portion between the linear embosses 21 that extends. Since a part of the thermally stretchable conjugate fiber is fixed by the linear emboss 21, the stretched portion of the stretched thermally stretchable conjugate fiber loses its place in the plane direction of the non-woven fabric 54, so The heat stretchable conjugate fiber on the hot air blowing side moves in the thickness direction of the nonwoven fabric 54. As a result, a fiber parallel upright portion 24 is formed in the vicinity of the linear emboss 21, and a convex portion 23 is formed at the center of the partition region surrounded by the linear emboss 21. Further, the intersections of the heat-extensible composite fibers existing between the linear embosses 21 are joined by heat fusion by air-through processing, and the fiber joining points are formed in a three-dimensionally dispersed state on the convex portion 23. . In this way, the target surface sheet 2 is obtained.

  FIG. 20 is a view showing another embodiment of the top sheet according to the present invention. The napkin 1 of the present embodiment may include a top sheet 2A shown in FIG. The surface sheet 2A shown in FIG. 20 is the same as the surface sheet 2 described above except that it is not particularly described. The top sheet 2A shown in FIG. 20 has a two-layer structure in which an upper layer 27 and a lower layer 28 are laminated, and the top sheet 2A absorbs the lower layer 28 side with the upper layer 27 side facing the wearer's skin side. Used in the napkin 1 toward the body 10 side.

  The upper layer 27 is made of the heat-extensible conjugate fiber described above or includes the heat-extensible conjugate fiber, and the lower layer 28 does not contain the heat-extensible conjugate fiber or is smaller in amount than the upper layer 27. Contains composite fiber. The upper layer 27 and the lower layer 28 are joined by a lattice-like joint formed by embossing, and the joint becomes the linear emboss 21 in the topsheet 2A.

  Near the linear emboss 21 in the upper layer 27, a fiber parallel standing portion 24 similar to the fiber parallel standing portion of the surface sheet 2 described above is formed adjacent to the linear emboss 21. In the convex portion 23 formed by the above, a heat fusion point 29 is formed in which the heat-extensible conjugate fibers are heat-sealed at each other intersection. Since the top sheet 2A also has the fiber standing upright portion 24, the same function and effect as the top sheet 2 are achieved.

  When the upper layer 27 and the lower layer 28 are laminated like the surface sheet 2A, the lower layer 28 constituting the non-skin contact surface side of the surface sheet 2A is more rigid than the constituent fibers of the upper layer 27. It is preferable to use a high fiber. By using a highly rigid fiber on the non-skin contact surface side, it is possible to effectively prevent the surface sheet from being twisted. Here, the highly rigid fiber is a fiber having a higher melting point or a higher resin density than the fiber used on the skin contact surface side.

  The surface sheet according to the present invention is not limited to the embodiment described above, and can be appropriately changed without departing from the spirit of the present invention. For example, the planar view shape of the partition region is not limited to a rhombus shape, and may be an arbitrary shape such as a square, a rectangle, a parallelogram, an ellipse, or a triangle. In addition, a plurality of types of partition regions having different shapes in plan view can be provided on one surface sheet, for example, by combining diamond-shaped partition regions and parallelogram-shaped partition regions.

  The napkin 1 of the present embodiment is used by being attached to an undergarment in the same manner as a normal sanitary napkin of this type. Since the napkin 1 of the present embodiment includes the topsheet 2 that is excellent in liquid draw-in and liquid permeability, and the absorbent body 10 that can quickly and repeatedly absorb body fluid, The excreted bodily fluid is quickly transmitted to the non-skin contact surface side, so that the liquid residue in the top sheet 2 is hardly generated, and an excellent dry feeling is obtained. In addition, since the absorbent body 10 is flexible and can be thinned, the napkin 1 provided with the absorbent body 10 can be designed to have a small thickness, is not bulky, and has excellent portability and wearing feeling. It can be. The same effect can be obtained when the topsheet 2A is used instead of the topsheet 2 or when the absorber 30 is used instead of the absorber 10.

  As mentioned above, although this invention was demonstrated based on the preferable embodiment, this invention is not restrict | limited to the said embodiment. For example, the absorbent article of the present invention is not limited to sanitary napkins, but can also be applied to disposable diapers, incontinence pads, urine-absorbing pads, pet diapers, pet sheets, and the like.

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

  Hereinafter, a method for synthesizing the water-absorbing polymer used in this example (Synthesis Example 1) will be described. Synthesis Example 1 proceeded in the order of synthesis of the water-absorbing polymer and crosslinking treatment of the water-absorbing polymer as described below.

[Synthesis Example 1]
<Synthesis of water-absorbing polymer>
Polyoxyalkylene ether phosphate 0.1% (as opposed to acrylic acid mass) as a dispersant in SUS304 5L reaction vessel (using anchor blade) equipped with stirrer, reflux condenser, monomer dropping port, nitrogen gas inlet tube, thermometer , Active ingredient amount), and 1500 ml of normal heptane was added. The temperature was raised to 90 ° C. while stirring in an atmosphere of nitrogen gas. On the other hand, in a 2 L three-necked flask, acrylic acid as a monomer aqueous solution was prepared from 80% acrylic acid (manufactured by Toagosei Co., Ltd., act. 80.6%), ion-exchanged water, 48% sodium hydroxide aqueous solution (manufactured by Asahi Glass, act. 1000 g of sodium (72% neutralized product) was obtained. After adding 0.25 g of N-acylated glutamic acid soda (trade name: Amisoft PS-11) dissolved in ion-exchanged water 4.41 g to this monomer aqueous solution, 550 g (hereinafter referred to as monomer aqueous solution A). ), 250 g (hereinafter referred to as monomer aqueous solution B), and 250 g (hereinafter referred to as monomer aqueous solution C).

Next, 2,2′-azobis (2-amidinopropane) dihydrochloride (Wako Pure Chemical Industries, trade name V-50) 0.05 g, polyethylene glycol (Kao, K-PEG6000 LA) 0.5 g, citric acid 4 g of ammonium iron (III) (manufactured by Kanto Chemical) and 10 g of ion-exchanged water were mixed and dissolved to prepare an initiator (A) solution. Further, 0.6 g of sodium persulfate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 10 g of ion-exchanged water to prepare an initiator (B) solution. Further, a titanium citrate aqueous solution (50% citric acid and 7.6% (TiO ₂ ) titanyl sulfate aqueous solution mixed at a mass ratio of 20/27) was prepared. To monomer aqueous solution A, 12 g of initiator (A) solution is added to prepare monomer A. To monomer aqueous solution B, 5 g of initiator (B) solution is added to prepare monomer B. To monomer aqueous solution C, initiator ( B) Monomer C was prepared by adding 5 g of the solution and 2 g of a titanium citrate aqueous solution (citric acid / Ti molar ratio = 2, Ti amount 0.015% to acrylic acid mass).

  Subsequently, the monomer A, the monomer B, and the monomer C, which were allowed to stand for 5 minutes or more, were dropped from the monomer dropping port through the monomer dropping port in this order and polymerized. After completion of monomer dropping, azeotropic dehydration was performed using a dehydrating tube to adjust the water content of the water-absorbing polymer (hydrogel), and then ethylene glycol diglycidyl ether (manufactured by Nagase ChemteX, trade name Denacol EX- 810) A solution in which 0.5 g was dissolved in 10 g of ion-exchanged water was added. Thereafter, 2 g of a 60% 1-hydroxyethylidene-1,1′-diphosphonic acid aqueous solution (trade name Bride ADPA-60A, manufactured by Rhodia) was added. After cooling, normal heptane was removed and dried to obtain a water-absorbing polymer.

<Crosslinking treatment of water-absorbing polymer>
100 g of the water-absorbing polymer obtained in <Synthesis of water-absorbing polymer> was charged in the same reaction vessel (using anchor blade) as that used in <Synthesis of water-absorbing polymer>, and 300 ml of normal heptane was added. While stirring in a nitrogen atmosphere, the temperature was raised to 75 ° C. Thereafter, a solution obtained by dissolving 3 g of ethylene glycol diglycidyl ether (manufactured by Nagase ChemteX, trade name Denacol EX-810) as a crosslinking agent was added to 60 g of ion-exchanged water using a dropping funnel from the dropping port. After refluxing for 1.5 hours, normal heptane was removed and dried to obtain a water-absorbing polymer having a particle surface crosslinked.

[Synthesis Examples 2 and 3]
According to Synthesis Examples 2 and 3, a water-absorbing polymer having a particle surface crosslinked was obtained. Synthesis Examples 2 and 3 differed from Synthesis Example 1 only in the amount of the crosslinking agent used in <Crosslinking treatment of water-absorbing polymer>, and 5 g in Synthesis Example 2 and 1 g in Synthesis Example 3.

  The centrifugal retention amount of the water-absorbing polymer obtained in Synthesis Examples 1 to 3, the angle of repose of the swollen gel, the bulk specific gravity, the water absorption speed by the DW method, the liquid passing speed under pressure at 2.0 kPa, and the average particle diameter were described above. It measured according to the measuring method. These results are shown in Table 1 below.

[Example 1]
Cross-linked pulp having a fiber roughness of 0.32 mg / m and a fiber cross-section roundness of 0.30 (“High Bulk Additive HBA-S” manufactured by Weyerhauser Paper, slope of water absorption obtained by the above-described <Hydrophilicity evaluation method> 0.04 g / sec) 70 parts by mass and 30 parts by mass of softwood kraft pulp (Skeena Cellulose Co. “SKEENA PRIME”) having a fiber roughness of 0.18 and a fiber cross-section of roundness of 0.32 are dispersed and mixed in water. Furthermore, with respect to 100 parts by dry weight of the mixed pulp, a paper strength reinforcing agent (polyamide epichlorohydrin resin, manufactured by Nippon PMC Co., Ltd., Kaimen WS-570) is dispersed and mixed in water with a resin component, After the predetermined concentration was reached, a fiber web was formed by using this dispersed mixed solution at a forming part of a wet paper machine so that the dry basis weight was 25 g / m ² . Next, the fiber web was dehydrated with a suction box until the water content became 100 parts by mass based on 100 parts by mass of the dry fiber web. Next, immediately before the press part, the water-absorbing polymer of Synthesis Example 1 was sprayed in the pattern shown in FIG. 3 at a spraying basis weight of 30 g / m ² on the wet fiber web after dehydration. Next, a fiber sheet (basis weight 25 g / m ² ) having a blending composition similar to that of the fiber web as a fiber aggregate and having a paper composition (basis weight 25 g / m ² ) is superimposed on the surface of the fiber web. A superposed body of fiber web and fiber sheet is introduced into a dryer, dried and integrated at a temperature of 130 ° C., so that a water-absorbing polymer is interposed between two fiber sheets 90 mm long and 35 mm wide. I got an absorber.

  The absorbent body thus obtained has a structure generally shown in FIGS. Specifically, each water-absorbing polymer high-concentration region in the absorber had a quadrangular shape in plan view, a length in the absorber longitudinal direction of 20 mm, and a length in the absorber width direction of 10 mm. Further, in the plan view of the absorbent body, the ratio (S1 / S2) of the total area S1 of the high water-absorbing polymer high concentration region to the total area S2 of the low water-absorbing polymer low concentration region was 80/20. Further, the average content of the water-absorbing polymer in the absorbent is 33% by mass, the content of the water-absorbing polymer in the high water-absorbing polymer concentration region is 42% by mass, and the content of the water-absorbing polymer in the low water-absorbing polymer concentration region is substantially It was 0 mass%.

  An adhesive was applied to the non-skin contact surface side of the obtained absorber, and a back sheet was fixed on the non-skin contact surface of the absorber via the adhesive. Next, the entire surface of the skin contact surface of the absorbent is covered with a surface sheet, and the skin contact surface side of the surface sheet is embossed according to a conventional method to form a leak-proof groove, and a napkin precursor Got. Adhesive is applied to a predetermined portion of the non-skin contact surface (outer surface of the back sheet) of the napkin precursor thus obtained, and an adhesive part is formed. The end portion was subjected to end sealing according to a conventional method to obtain a napkin. In this napkin, the following were used for the top sheet, and a polyethylene film having a thickness of 25 μm was used for the back sheet. The napkin generally has the structure shown in FIGS. The napkin thus obtained was used as a sample of Example 1.

(Surface sheet used in Example 1)
A core-sheath type composite fiber (core: polypropylene, sheath: polyethylene) having a fiber diameter of 4 dtex and an elongation rate of 8% is passed through a card machine to form a web, and the web is introduced into a heat embossing device. Formed. Subsequently, the web was introduced into a hot air spraying apparatus, and hot air treatment was performed by air-through processing to obtain a surface sheet having a fiber parallel standing portion in the vicinity of the linear embossing. The formation pattern of the linear embossing of the obtained surface sheet is the pattern shown in FIG. 14, and the width W1 of each of the first and second linear embossing 21a and 21b is 0.5 mm, and the first linear embossing The distance between 21a and the distance W2 between the second linear embosses 21b were 6 mm, and the ratio of the diagonal lines L1 and L2 (L1: L2) of the formed rhombic partition region was 7:13. Moreover, the area ratio of the linear embossing was 14%.

[Example 2]
In Example 1, a napkin was produced in the same manner as in Example 1 except that the following was used as the absorber, and this was used as a sample of Example 2.

(Absorber of Example 2)
In the absorbent body of Example 1, the absorbent body was prepared in the same manner as in Example 1 except that the water-absorbing polymer spray basis weight was 36 g / m ² and the water-absorbing polymer spray pattern was as shown in FIG. This was prepared and used as the absorber of Example 2. The water-absorbing polymer high-concentration region in the absorbent body has a rectangular shape in plan view, and the length of the rectangular water-absorbing polymer high-concentration region in the longitudinal direction of the absorbent body is substantially the same as the length in the longitudinal direction of the absorbent body. Yes, the length in the width direction of the absorber was 10 mm. Further, in the plan view of the absorbent body, the ratio (S1 / S2) of the total area S1 of the high water-absorbing polymer high concentration region to the total area S2 of the low water-absorbing polymer low concentration region was 80/20. Further, the average content of the water-absorbing polymer in the absorbent is 33% by mass, the content of the water-absorbing polymer in the high water-absorbing polymer concentration region is 42% by mass, and the content of the water-absorbing polymer in the low water-absorbing polymer concentration region is substantially It was 0 mass%.

Example 3
In Example 1, a napkin was prepared in the same manner as in Example 1 except that the following was used as the absorber, and this was used as a sample of Example 3.

(Absorber of Example 3)
In the absorbent body of Example 1, an absorbent body was produced in the same manner as in Example 1 except that the dispersion pattern of the water-absorbing polymer was changed to the pattern shown in FIG. . In the plan view of the absorber, the ratio (S1 / S2) of the total area S1 of the high water-absorbing polymer high concentration region to the total area S2 of the low water-absorbing polymer concentration region was 50/50. Further, the average water-absorbing polymer content of the absorber is 37.5% by mass, the water-absorbing polymer content in the high-absorbent polymer concentration region is 54% by mass, and the water-absorbing polymer content in the low-absorbent polymer concentration region is It was substantially 0% by mass.

Example 4
In Example 1, a napkin was produced in the same manner as in Example 1 except that the following was used as the absorber, and this was used as a sample of Example 4.

(Absorber of Example 4)
Using an apparatus as shown in FIG. 9, an absorbent body made of a mixed fiber of water-absorbing polymer and fiber was produced, and this was used as the absorbent body of Example 4. On the peripheral surface of the rotating drum in the apparatus, there is provided a mold in which a large number of concave portions and lattice-shaped convex portions are formed as shown in FIG. This mold had a length of 17 cm in the rotating direction of the drum and a length (width) of 7 cm in the rotating shaft direction of the drum. In the final mixed fiber product, the portion corresponding to the concave portion of the mold is a thick portion (water absorbent polymer high concentration region), and the portion corresponding to the convex portion is a thin portion (water absorbent polymer low concentration region). Become. 100 parts by mass of defibrated pulp (fluff pulp) and 20 parts by mass of the water-absorbing polymer of Synthesis Example 1 are mixed in an air stream, and sucked into the mold from the inner surface of the metal mesh disposed on the lower side of the mold The fiber was piled up while performing. The water-absorbing polymer was introduced with the water-absorbing polymer inlet (not shown) close to the lower part of the duct as long as the entire air flow was not disturbed. The mixed fiber thus obtained generally has the structure shown in FIG. 11, the basis weight is 240 g / m ² , the length of the thick part (water-absorbing polymer high concentration region) in the longitudinal direction of the absorber, and the absorption The length in the body width direction was 10 mm. Moreover, the space | interval between adjacent thick parts (water-absorbing polymer high concentration area | region) was divided | segmented by the low concentration area | region of 5 mm in both the absorber longitudinal direction and the width direction. In addition, the average content of the water-absorbing polymer in the mixed fiber is 17% by mass, the content of the water-absorbing polymer in the thick part (water-absorbing polymer high concentration region) is 25% by mass, and the thin part (water-absorbing polymer low concentration region). ) Was 9% by mass. The obtained mixed fiber was wrapped in a tissue paper having a basis weight of 16 g / m ² spray-coated with a hot melt adhesive to obtain an absorbent body of Example 4.

Example 5
In Example 1, a napkin was prepared in the same manner as in Example 1 except that the following were used as the absorber, and this was used as a sample of Example 5.

(Absorber of Example 5)
A hot-melt adhesive (P-618B manufactured by Toyo Petrolite) was applied separately at a coating amount of 5 g / m ² , and separately prepared on the adhesive coating surface of a tissue paper (upper covering sheet) having a basis weight of 16 g / m ^2. A pulp fiber fiber web (basis weight 240 g / m ² , width 7 cm, length 17 cm) was placed. This tissue paper has larger dimensions than the fiber web. Next, from the top of the fiber web, a total of 0.45 g of the water-absorbing polymer of Synthesis Example 1 was placed on the fiber web at a width of 10 mm and a pitch of 5 mm, 3 bars (one line at the center of the fiber web and one line on each side). The amount of water-absorbing polymer was sprayed 0.15 g per muscle). Further, a tissue paper (basis weight 16 g / m ² ) as a lower covering sheet in which a hot-melt adhesive is applied at a coating amount of 5 g / m ² with the same size as the fiber web on the water-absorbing polymer spray surface of the fiber web. Are stacked so that the adhesive application surface faces the fiber web, and the portions extending from the fiber web in the upper coating sheet are wound up on the upper surface of the lower coating sheet, and then the upper and lower surfaces of the fiber web are Was inverted to obtain the absorbent body of Example 5 having a rectangular shape in plan view, in which substantially the entire absorbent body was covered with tissue paper (covering sheet). The distribution pattern of the water-absorbing polymer in the absorbent body of Example 5 is almost as shown in FIG. Further, the average water-absorbing polymer content of the absorbent body of Example 5 was 19% by mass, the water-absorbing polymer content in the high water-absorbing polymer high concentration region was 37% by mass, and the water-absorbing polymer content in the low water-absorbing polymer low concentration region. The rate was substantially 0% by weight.

Example 6
In Example 1, a napkin was produced in the same manner as in Example 1 except that the following was used as the surface sheet, and this was used as a sample of Example 6.

(Surface sheet used in Example 6)
The surface sheet was formed in the same manner as in Example 1 except that the embossing (joint portion) formation pattern of the surface sheet used in Example 1 was a pattern in which a large number of cross-shaped embosses were arranged in a staggered pattern in plan view. Got. The vertical and horizontal embossed lines in each cross-shaped emboss are composed of rectangles each having a length of 4 mm and a width of 1 mm, and the distance between the center points of the adjacent cross-shaped embosses is 8 mm in the napkin width direction, and the napkin longitudinal direction At 6 mm intervals. The area ratio of embossing was 14%.

Example 7
In Example 1, a napkin was prepared in the same manner as in Example 1 except that the water-absorbing polymer of Synthesis Example 1 was used instead of the water-absorbing polymer of Synthesis Example 1, and a napkin was produced. Samples of

Example 8
In Example 1, a napkin was prepared in the same manner as in Example 1 except that the water-absorbing polymer in Synthesis Example 3 was used instead of the water-absorbing polymer in Synthesis Example 1, and a napkin was produced. Samples of

Example 9
In Example 1, a napkin was prepared in the same manner as in Example 1 except that the top sheet was changed to an air-through non-woven fabric (a perforated sheet used for a Kao Co., Ltd. Laurier Super Slim Guard). A sample was used. Unlike the surface sheet used in Example 1, this air-through nonwoven fabric does not have a fiber parallel standing part.

[Comparative Example 1]
In Example 1, a napkin was produced in the same manner as in Example 1 except that the following was used as the absorber, and this was used as a sample of Comparative Example 1.

(Absorber of Comparative Example 1)
Using an apparatus as shown in FIG. 9, an absorbent body made of a mixed fiber of water-absorbing polymer and fiber was produced, and this was used as the absorbent body of Comparative Example 1. However, the mold provided on the peripheral surface of the rotary drum in the apparatus is not a concave or convex portion as shown in FIG. The length was 7 cm). 100 parts by mass of defibrated pulp (fluff pulp) and 20 parts by mass of the water-absorbing polymer of Synthesis Example 1 are mixed in an air stream, and sucked into the mold from the inner surface of the metal mesh disposed on the lower side of the mold The fiber was piled up while performing. The basis weight of the mixed product thus obtained was 240 g / m ² . The mixed fiber product was wrapped in a tissue paper having a basis weight of 16 g / m ² spray-coated with a hot melt adhesive to obtain an absorbent body of Comparative Example 1.

[Comparative Example 2]
A napkin was produced in the same manner as in Example 1 except that the water-absorbing polymer was changed to Nippon Catalytic CA-W4S in Example 1, and this was used as a sample of Comparative Example 2.

[Evaluation]
About the sanitary napkin of an Example and a comparative example, while measuring thickness and bending rigidity according to the said measuring method, the absorption time, the liquid return amount, and the liquid residual amount were measured with the following method.
In addition, regarding the absorbent body in each sanitary napkin, the presence or absence of a water-absorbing polymer high-concentration region, and if a water-absorbing polymer high-concentration region exists, the size of the void surrounded by the water-absorbing polymer particles in the region Spore , And the ratio (%) of Spore to the area Ssap occupied by the water-absorbing polymer particles [= (Spore / Ssap) × 100] were measured according to the measurement methods described above. These results are shown in Table 2 below. Table 1 below shows the characteristics of the water-absorbing polymer used in each sanitary napkin.

<Measurement method of absorption time>
With the sanitary napkin to be measured spread in a plane and fixed on a horizontal surface with the top sheet facing up, an acrylic plate with a cylindrical injection part is placed on the top sheet in the center of the absorber. Further, a weight is placed on the acrylic plate, and a load of 5 g / m ² is applied to the center of the absorber. The injection part provided on the acrylic plate has a cylindrical shape with an inner diameter of 10 mm, and the central axis of the cylindrical injection part coincides with the central axis in the longitudinal direction and the width direction of the acrylic plate, and the cylindrical injection part A through-hole having an inner diameter of 10 mm is formed so as to communicate between the inside and the surface sheet facing surface of the acrylic plate. Next, the acrylic plate is arranged so that the central axis of the cylindrical injection portion coincides with the central portion of the absorber in plan view, and 3 g of blood is injected from the cylindrical injection portion and absorbed by the sanitary napkin. The time (seconds) from when the blood (defibrated horse blood, manufactured by Nippon Biotest Co., Ltd.) reaches the surface of the napkin until the total amount of 3 g is absorbed by the napkin is measured, and this is the first absorption time It was. In addition, 3 minutes after the first blood injection, the above procedure is repeated until 3 g of blood is further injected (a total of 6 g of blood is injected) until the total amount of the reinjected blood is absorbed by the napkin. Time (seconds) was measured, and this was taken as the second absorption time. The smaller the value of these absorption times, the faster the absorption speed and the higher the evaluation. Table 1 below shows the absorption time for the second time (when 6 g of blood was injected). In addition, in the first time, when it exceeded 3 minutes until the total amount (3 g) of the injected blood was absorbed, the next 3 g was injected immediately after the total amount was absorbed.

<Measurement method of liquid return amount>
In <Measurement method of absorption time>, after 3 minutes from the third blood injection, the acrylic plate and the weight are removed, and the basis weight of 30 g / 7 cm × 7 cm is formed on the skin contact surface of the napkin (on the top sheet). Ten sheets of m ² absorbent paper (commercial tissue paper) were placed on top of each other, and a load of 68 g / cm ² was applied to the absorbent paper for 1 minute. After the loading, 10 sheets of absorbent paper were removed, and the weight of the 10 sheets of absorbent paper was measured. From this measured value and the measured value of the weight of 10 sheets of absorbent paper before the load obtained in advance, the mass (g) of blood absorbed in 10 sheets of absorbent paper is determined, and this mass is taken as the liquid return amount. did. The smaller the liquid return amount, the higher the napkin absorption performance and the higher the evaluation.

<Measurement method of remaining liquid amount>
Place a sanitary napkin horizontally, put an acrylic plate with a 1 cm diameter injection port on top, and inject 3 g of defibrinated horse blood (manufactured by Nippon Biotest Co., Ltd.) for 1 minute. That state was maintained. Next, the acrylic plate is removed, the surface sheet is taken out from the napkin, and its weight is measured. The weight of the surface sheet before blood injection, which is measured in advance, is subtracted from the weight, and the difference (defibrillation remaining in the surface sheet is removed). The weight of the horse blood) was taken as the remaining liquid amount. The smaller the remaining amount of liquid, the better the dry feeling and the higher the evaluation.

  As is apparent from the results shown in Table 2, all of the examples had a short absorption time, a small liquid return amount and a small liquid remaining amount, and were excellent in liquid permeability and dry feeling on the skin contact surface. On the other hand, since Comparative Example 1 did not mainly have a high water-absorbing polymer high concentration region, the result was inferior in the liquid remaining amount. In Comparative Example 2, since the size of the voids (Spore) surrounded by the water-absorbing polymer in the high water-absorbing polymer high-concentration region was small, the absorption time and the remaining liquid amount were inferior. In Comparative Example 2, since the void is too small, the size Spore cannot be measured, and a void surrounded by the water absorbent polymer is formed in the high water absorbent polymer high concentration region in Comparative Example 2. Is hard to say. As described above, the reason why the voids are not substantially formed in the high-concentration region of the water-absorbing polymer of Comparative Example 2 is mainly due to the centrifugal retention amount of the water-absorbing polymer, the angle of repose of the swollen gel, and the addition at 2.0 kPa. It is presumed that the reduction liquid passing speed, particularly the repose angle of the swollen gel, is not within the appropriate range (45 ° or less) defined in the present invention.

1 Sanitary napkin (absorbent article)
2,2A Top sheet 3 Back sheet 4 Leak-proof groove 5 End seal part 10, 30 Absorber 11, 12 Fiber sheet (layer of fiber assembly)
13 Water-absorbing polymer high-concentration region 14 Water-absorbing polymer low-concentration region 15, 15a to 15e Water-absorbing polymer 20 Recessed portion 21 Linear embossing (joint portion)
22 partition region 23 convex part 24 fiber parallel standing part 25 fiber 26 constituting fiber parallel standing part fiber parallel part C1 to C3 contact point S1, S2 of water absorbent polymer particles void surrounded by water absorbent polymer

Claims (11)

An absorbent article comprising a top sheet, a back sheet, and an absorbent body interposed between both sheets and including an absorbent polymer and fibers,
The water-absorbing polymer includes a water-absorbing polymer having an angle of repose of the swollen gel of 45 ° or less,
The absorbent body has a water-absorbing polymer high concentration region in which the content of the water-absorbing polymer exceeds the average water-absorbing polymer content calculated by the following formula :
Absorption in which a plurality of particles of the water-absorbing polymer are in contact with each other at two or more points in the high-concentration region of the water-absorbing polymer, and a void surrounded by the water- absorbing polymer is formed between the contact points of the particles . Sex goods.
Water-absorbing polymer average content (% by mass) = (total mass of all water-absorbing polymers contained in the absorber / total mass of the absorber) × 100 The absorbent article of claim 1, wherein the size of the space surrounded by the water-absorbing polymer is 400 [mu] m ² or more. The absorbent article according to claim 1 or 2 , wherein the water-absorbing polymer has a centrifugal retention amount of 5 to 25 g / g according to JIS K 7223. The absorbent article according to any one of claims 1 to 3 , wherein the water-absorbing polymer has a liquid passing rate under pressure of 2.0 kPa of 150 ml / min or more. The absorbent article as described in any one of Claims 1-4 whose neutralization degree of the said water absorbing polymer is less than 75 mol%. The absorbent article according to any one of claims 1 to 5, wherein a difference between the content of the water-absorbent polymer and the average content of the water-absorbent polymer in the high-concentration region of the water-absorbent polymer is 10% by mass or more. The absorbent body has a water-absorbing polymer low concentration region in which the water-absorbing polymer content is less than the water-absorbing polymer average content or does not contain the water-absorbing polymer,
The ratio (the former / the latter) of the total area of the water-absorbing polymer high-concentration region and the total area of the water-absorbing polymer low-concentration region in plan view of the absorber is 30/70 to 90/10. the absorbent article according to any one of 1-6. In a plan view of the absorber, the band-shaped water-absorbing polymer high concentration region extending in the longitudinal direction of the absorber and the band-shaped water-absorbing polymer low concentration region extending in the longitudinal direction are in the width direction of the absorber. The absorbent article according to claim 7 , wherein the absorbent articles are alternately arranged. The absorber has a layered structure formed by laminating a plurality of layers of fiber aggregate, according to claim 1-8 wherein the water-absorbing polymer in at least one interlayer of the layers in the laminated structure is interposed The absorbent article as described in any one of these. The surface sheet has a concave portion and a convex portion on the skin contact surface side, and the concave portion has a joint portion to which constituent fibers are pressure-bonded or bonded,
In the vicinity of the joint, a fiber parallel upright portion is formed in which the constituent fibers stand up in parallel in a direction away from the joint from the joint.
In a cross-sectional view along the direction orthogonal to the boundary between the joint and the non-joint part adjacent to the joint, the distance between the adjacent fibers in the fiber parallel standing part gradually decreases toward the joint. The absorptive article according to any one of claims 1 to 9 . The absorptive article according to claim 10 in which said surface sheet is constituted including heat extensibility textiles for which the length is prolonged by heating.