Absorbent body and method for manufacturing absorbent body

Abstract

An absorbent body comprises an absorbent core (10) and core wrapping sheets (2, 3), wherein the absorbent core (10) comprises liquid-absorbent fibers (11) and superabsorbent polymers (12), and the absorbent body (1) comprises a compressed portion (3) obtained by compressing a pair of lateral portions. A portion of the compressed portion (4) on the side of the absorbent body (1) where the liquid-absorbent fibers (11) and superabsorbent polymers (12) are arranged is divided into six parts in the longitudinal direction and two parts in the lateral direction to obtain divided areas. When an area ratio is calculated for each divided area, a CV value indicating a deviation in the area ratio is less than 26%, the area ratio being obtained by dividing the area occupied by the liquid-absorbent fibers (11) and superabsorbent polymers (12) when the divided area is viewed from above in the thickness direction by the area of ​​the divided area.

Description

Technical Field

[0001] The present invention relates to an absorbent body and a method for producing the absorbent body. Background Art

[0002] Patent Document 1 discloses an absorbent body comprising: an absorbent core formed by incorporating an absorbent polymer into an aggregate of liquid-absorbent fibers; and a core wrap sheet covering the upper and lower surfaces of the absorbent core. In Patent Document 1, the absorbent polymer is evenly dispersed in the plane of the absorbent core to prevent the absorption performance of areas with low polymer density from deteriorating due to the movement of the absorbent polymer and the resulting brittleness in areas with high polymer density. Specifically, the absorbent core is divided into multiple regions (30 mm x 30 mm square regions) in the longitudinal and width directions of the absorbent body. When the absorbent polymer content is measured for each divided region, the ratio (column standard deviation / column average) representing the deviation in the absorbent polymer content is less than 0.20 for both the columns of the longitudinal divided regions and the columns of the width divided regions.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent document: Japanese Patent No. 4711946 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] However, in Patent Document 1, areas obtained by dividing the absorbent core, including those that do not overlap with the core, are excluded from measurement. Consequently, the side portions of the hourglass-shaped absorbent core in the width direction are excluded from the absorbent polymer content measurement, and variations in the polymer content along the side portions of the absorbent core are not considered. Therefore, if the absorption performance of the side portions of the absorbent core is not considered, side leakage of excrement may occur if the absorption performance of the side portions of the absorbent core is reduced.

[0008] Furthermore, in the absorbent body of Patent Document 1, since only the upper and lower surfaces of the absorbent core are fixed to the core wrap sheet via adhesive, the movement of the absorbent polymer or fibers cannot be suppressed, and there is a possibility that the absorbent polymer and fibers will fall out from the gaps in the core wrap sheet. In particular, if the polymer and the like fall out from the side portions of the absorbent core, the absorption performance of the side portions will be reduced, resulting in side leakage of excrement.

[0009] The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to suppress the loss of superabsorbent polymer and liquid-absorbent fibers from the lateral portions of an absorbent body in the transverse direction, thereby maintaining the absorption performance of the lateral portions of the absorbent body.

[0010] Solutions to Problems

[0011] The main invention for achieving the above-mentioned purpose is an absorbent body having longitudinal, transverse and thickness directions, and comprising an absorbent core and core wrapping sheets arranged on both sides of the absorbent core in the thickness direction, characterized in that the absorbent core comprises liquid-absorbent fibers and superabsorbent polymer, the absorbent body comprises a compressed portion obtained by compressing at least a pair of side portions in the transverse direction in the thickness direction, and the portion of the compressed portion of the side portion of the absorbent body where the liquid-absorbent fibers and the superabsorbent polymer are arranged is divided into 6 parts in the longitudinal direction and 2 parts in the transverse direction as a divided area, and when an area ratio is calculated for each of the divided areas, a CV value indicating a deviation in the area ratio is 26% or less, the area ratio being obtained by dividing the area occupied by the liquid-absorbent fibers and the superabsorbent polymer when the divided area is viewed from above in the thickness direction by the area of ​​the divided area.

[0012] Other features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[0013] Effects of the Invention

[0014] According to the present invention, it is possible to suppress the superabsorbent polymer and the liquid-absorbent fibers from falling out from the side portions in the transverse direction of the absorbent body, and to maintain the absorption performance of the side portions of the absorbent body. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1A This is a top view of the absorbent body 1 viewed in the thickness direction. Figure 1B This is a side view of the absorber 1 viewed in the horizontal direction. Figure 1C This is a front view of the absorber 1 as viewed in the longitudinal direction.

[0016] Figure 2 It is an explanatory diagram of the divided regions r1 to r12 of the compression section 4 .

[0017] Figures 3A to 3D It is a figure which shows the modification of the absorber 1.

[0018] Figures 4A to 4E It is an explanatory diagram of the measurement method of the occupied area ratio of the absorbent core 10.

[0019] Figure 5 It is an explanatory diagram of the second divided regions r1 ′ to r12 ′ of the compressed portion 4 at the end portion in the longitudinal direction of the absorbent body 1 .

[0020] Figure 6A as well as Figure 6B It is an explanatory diagram of a shedding test in which the superabsorbent polymer 12 falls off from the absorbent body 1.

[0021] Figure 7 It is an explanatory diagram of the manufacturing method of the absorbent body 1.

[0022] Figure 8 It is a graph showing the measurement results of Example 1 and Comparative Example 1 (absorbent body with a high basis weight).

[0023] Figure 9 It is a graph showing the measurement results of Example 2 and Comparative Example 2 (absorbent body with low basis weight). DETAILED DESCRIPTION

[0024] At least the following matters will be apparent from the description of this specification and the accompanying drawings.

[0025] An absorbent body having longitudinal, transverse and thickness directions, and comprising an absorbent core and core wrapping sheets arranged on both sides of the absorbent core in the thickness direction, characterized in that the absorbent core comprises liquid-absorbent fibers and superabsorbent polymer, the absorbent body comprises a compressed portion obtained by compressing at least a pair of side portions in the transverse direction in the thickness direction, the portion of the compressed portion of the side portion of the absorbent body where the liquid-absorbent fibers and the superabsorbent polymer are arranged being divided into six parts in the longitudinal direction and two parts in the transverse direction as divided regions, and when an area ratio is calculated for each of the divided regions, a CV value indicating a deviation in the area ratio is 26% or less, the area ratio being calculated by dividing an area occupied by the liquid-absorbent fibers and the superabsorbent polymer when the divided region is viewed from above in the thickness direction by the area of ​​the divided region.

[0026] According to this absorbent body, the planar deviation of the absorbent cores arranged on the side portions is small, and the strength of the compressed portions formed on the side portions can be made uniform. As a result, the entire planar area of ​​the side portions of the absorbent body is firmly compressed, which can prevent the absorbent cores from falling out of the side portions and maintain the absorption performance of the side portions.

[0027] In this absorbent body, it is characterized in that the compressed portions are provided at a pair of end portions in the longitudinal direction of the absorbent body, and the portion of the compressed portion at the end portion of the absorbent body in which the liquid-absorbent fibers and the superabsorbent polymer are arranged is divided into 6 parts in the transverse direction and into 2 parts in the longitudinal direction, and the area obtained by dividing the portion into 6 parts in the transverse direction and into 2 parts in the longitudinal direction is set as the second divided area. When a second area ratio is calculated for each of the second divided areas, a CV value indicating a deviation in the second area ratio is not more than 26%, and the second area ratio is obtained by dividing the area occupied by the liquid-absorbent fibers and the superabsorbent polymer when the second divided area is viewed from above in the thickness direction by the area of ​​the second divided area.

[0028] According to such an absorbent body, the absorptive core disposed at the longitudinal end has less deviation in the plane direction, and the entire plane area of ​​the end is firmly compressed. Therefore, the absorptive core can be prevented from falling out of the longitudinal end of the absorbent body, and the absorption performance of the end can be maintained.

[0029] In this absorbent body, it is characterized in that the above-mentioned superabsorbent polymer does not fall off from the absorbent body even when it is subjected to a reciprocating motion at a speed of 1000 times per minute for 1 minute. The reciprocating motion refers to causing the above-mentioned absorbent body before absorption to reciprocate relatively between a pair of knocking plates in a direction intersecting the plane of the above-mentioned absorbent body so that a specified position in the plane of the above-mentioned absorbent body abuts against the above-mentioned pair of knocking plates.

[0030] According to such an absorbent body, since the entire planar area of ​​the side portions and the longitudinal end portions is firmly compressed, even if the absorbent body vibrates, the superabsorbent polymer is suppressed from falling off, and the absorption performance of the side portions and the longitudinal end portions can be maintained.

[0031] In this absorbent body, it is characterized in that, at least in the compressed portion of the side portion of the absorbent body, no adhesive is provided between the absorbent core and the core wrap sheet in the thickness direction.

[0032] According to such an absorbent body, the absorption performance of the side portions can be prevented from being impeded by the adhesive, and the absorption performance of the side portions can be maintained. In addition, the absorptive cores arranged on the side portions of the absorbent body have little deviation in the plane direction, and the entire plane area of ​​the side portions is firmly compressed. Therefore, even without the use of an adhesive, the core wrap sheet can be prevented from peeling (opening).

[0033] This absorbent body is characterized in that no adhesive is provided between the absorbent core and the core wrap sheet in the thickness direction over the entire plane area of ​​the absorbent body.

[0034] According to such an absorbent body, it is possible to suppress the adhesive from hindering the absorption performance of the entire plane of the absorbent body.

[0035] In this absorbent core, the liquid-absorbent fibers include pulp fibers, the core wrap sheet includes cellulose fibers, and the pulp fibers and the cellulose fibers are hydrogen-bonded.

[0036] With this absorbent core, the liquid-absorbent fibers and the core wrap sheet are firmly bonded together by hydrogen bonding. In particular, since compressed portions are formed on the sides of the absorbent core, the liquid-absorbent fibers and the core wrap sheet are more firmly hydrogen-bonded and this bond is maintained. This further prevents the core wrap sheet from peeling off (opening) on ​​the sides of the absorbent core.

[0037] In the absorbent body, it is characterized in that a pair of side portions in the transverse direction of the core covering sheet arranged on one side in the thickness direction are not folded back to the other side in the thickness direction in a manner that covers the side edges in the transverse direction of the absorbent core, and a pair of side portions in the transverse direction of the core covering sheet arranged on the other side in the thickness direction are not folded back to the one side in the thickness direction in a manner that covers the side edges of the absorbent core.

[0038] With this absorbent body, the planar area of ​​the core wrap sheet can be reduced, leading to cost reduction. Furthermore, since the side edges of the absorbent core are exposed, absorption performance from the side edges is improved. Furthermore, the absorbent core disposed on the side of the absorbent body has minimal deviation in the planar direction, and the entire plane of the side is firmly compressed. Therefore, even if the side edges of the absorbent core are not covered by the core wrap sheet, the absorbent core is prevented from falling out of the absorbent body.

[0039] In addition, a method for manufacturing an absorbent body, which has longitudinal, lateral and thickness directions, and has an absorbent core and core wrapping sheets arranged on both sides of the absorbent core in the above-mentioned thickness direction, is characterized in that the manufacturing method of the above-mentioned absorbent body comprises: a stacking process, in which the liquid-absorbent fibers and superabsorbent polymers possessed by the above-mentioned absorbent core are stacked on the above-mentioned first core wrapping sheet conveyed in the conveying direction; a supply process, in which the above-mentioned second core wrapping sheet is supplied to the above-mentioned liquid-absorbent fibers and superabsorbent polymers stacked in the above-mentioned stacking process; a compression process, in which, in a laminate of the above-mentioned first core wrapping sheet, the above-mentioned liquid-absorbent fibers, the above-mentioned superabsorbent polymers, and the above-mentioned second core wrapping sheet, at least a portion corresponding to a pair of side portions in the above-mentioned lateral direction of the above-mentioned absorbent body is compressed in the thickness direction of the above-mentioned laminate to form a compressed portion; and a cutting process, in order to form the outer edge of the above-mentioned absorbent body, the above-mentioned compressed portion of the above-mentioned laminate is cut.

[0040] This method of manufacturing an absorbent body can reduce the planar deviation of the absorbent core disposed on the side of the absorbent body, compared to, for example, a manufacturing method in which the absorbent core is demolded and then transferred to a core wrap sheet. Furthermore, since the laminate is cut at the compressed portion, the lateral ends of the absorbent body can be cut cleanly.

[0041] The method for manufacturing the absorbent body is characterized in that a spraying step is provided after the stacking step and before the compressing step, wherein water is sprayed on at least one of the first core wrapping sheet, the liquid-absorbent fibers, the superabsorbent polymer, and the second core wrapping sheet.

[0042] According to this absorbent manufacturing method, the materials constituting the absorbent are firmly bonded to each other through hydrogen bonding. In particular, since compressed portions are formed on the sides of the absorbent, the materials are more firmly hydrogen-bonded, and this state is maintained. This further prevents the core wrap sheet from peeling (opening) on ​​the sides of the absorbent.

[0043] ===Implementation Method===

[0044] <<Basic Structure of Absorber 1>>

[0045] Figure 1A This is a top view of the absorbent body 1 viewed in the thickness direction. Figure 1B This is a side view of the absorber 1 viewed in the horizontal direction. Figure 1C This is a front view of the absorber 1 as viewed in the longitudinal direction.

[0046] The absorbent body 1 has mutually orthogonal longitudinal, transverse, and thickness directions, and its planar shape when viewed in the thickness direction is a rectangle. The planar shape of the absorbent body 1 is not limited to a rectangle and may also be a variety of shapes, such as a square, an hourglass, or an ellipse. In cases where the longitudinal and transverse lengths of the absorbent body 1 are different, as in the present embodiment, the longitudinal direction of the absorbent body 1 is referred to as the longitudinal direction, and the width direction of the absorbent body 1 is referred to as the transverse direction.

[0047] The absorbent body 1 includes an absorbent core 10 and core wrap sheets 2 and 3 arranged on both sides of the absorbent core 10 in the thickness direction. The absorbent core 10 is composed of an aggregate of liquid-absorbent fibers 11 mixed with a super absorbent polymer 12 (SAP).

[0048] The core wrap sheets 2 and 3 are liquid-permeable sheets. Examples of the core wrap sheets 2 and 3 include tissue paper, nonwoven fabrics, and perforated films. Examples of the liquid-absorbent fibers 11 included in the absorbent core 10 include cellulose fibers (e.g., pulp fibers, non-wood fibers such as cotton and linen, and regenerated fibers such as rayon) or hydrophilically treated thermoplastic synthetic fibers (e.g., polyethylene and polypropylene).

[0049] The absorbent body 1 has a compressed portion 4 formed by compressing the core wrap sheets 2 and 3 and the absorbent core 10 in the thickness direction. Figure 1A The illustrated absorbent body 1 has a compression portion 4 of a predetermined width along the outer peripheral edge of the absorbent body 1. The compression portion 4 is a portion of the absorbent body 1 that is recessed in the thickness direction compared to the surrounding area and is thinner, and has a higher density of the absorbent core 10 (liquid-absorbent fibers 11) than the surrounding area.

[0050] The thickness of the absorbent body 1 can be compared by visual comparison or by using a dial thickness gauge ID-C1012C manufactured by Mitutoyo (KK) or an equivalent method based on a thickness of 3.0 gf / cm 2 Method for comparing values ​​measured by applying pressure to a target site. Alternatively, the density of the absorbent core 10 can be compared by comparing an image obtained by enlarging a cross section of the absorber 1 in the thickness direction using an electron microscope or the like.

[0051] The compressed portion 4 may be compressed uniformly (flatly) or in a predetermined pattern. Examples of the compressed portion 4 compressed in a predetermined pattern include a structure in which a plurality of dot-shaped compressed portions are discretely arranged, a structure in which a plurality of dot-shaped compressed portions are arranged in a line, and a groove-shaped compressed portion compressed continuously in a line. Furthermore, the compressed portion 4 may be composed of compressed portions having different compression strengths (deepness of the depressions).

[0052] The absorbent body 1 having the above-described structure can be used alone or incorporated into an absorbent article (e.g., disposable diapers, sanitary napkins, incontinence pads, panty liners, pet sheets, sweat-absorbing pads, etc.). When incorporated into an absorbent article, the absorbent body 1 is generally placed between a liquid-permeable sheet and a liquid-impermeable sheet.

[0053] <<Deviation of Absorbent Core 10>>

[0054] Figure 2 It is an explanatory diagram of the divided regions r1 to r12 of the compression section 4 . Figures 3A to 3D It is a figure which shows the modification of the absorber 1.

[0055] exist Figures 1A to 1C In the absorbent body 1 shown, the core wrap sheets 2 and 3 and the absorbent core 10 have the same planar shape and size. That is, the absorbent core 10 extends to a pair of lateral ends 1a and a pair of longitudinal ends 1b of the absorbent body 1. Furthermore, the absorbent body 1 has compressed portions 4 along the outer peripheral ends. Thus, at the outer peripheral ends of the absorbent body 1, the absorbent core 10 is compressed in the thickness direction along with the core wrap sheets 2 and 3.

[0056] Thus, the absorbent body 1 may have at least a pair of transverse side portions (side portions along the longitudinal direction) compressed in the thickness direction. In other words, the portion of the side portion of the absorbent body 1 where the absorbent core 10 is disposed may be compressed in the thickness direction at the compressed portion 4.

[0057] With this configuration, the core wrap sheets 2 and 3 are firmly bonded to the absorbent core 10 at the side portions of the absorbent body 1, preventing the core wrap sheets 2 and 3 from peeling (opening), and thus preventing the liquid-absorbent fibers 11 and superabsorbent polymer 12 from falling out of the peeled-off portions. Furthermore, since the compressed portion 4 entangles the liquid-absorbent fibers 11 and superabsorbent polymer 12 at a high density, movement of the absorbent core 10 is suppressed. From this perspective, it can also be said that the liquid-absorbent fibers 11 and superabsorbent polymer 12 are prevented from falling out of the side portions of the absorbent body 1.

[0058] The side portions of the absorbent body 1 in the transverse direction refer to a part or the entire region of the two end regions when the absorbent body 1 is divided into three in the transverse direction. It is sufficient as long as the compressed portion 4 is provided in the region (side portion) where the liquid-absorbent fibers 11 and the superabsorbent polymer 12 are arranged. Figure 3A As in the absorbent core 1 of the illustrated modified example, the compressed portion 4 does not reach the side end portion 1 a of the absorbent core 1 in the lateral direction.

[0059] Furthermore, the absorbent cores 10 may be evenly arranged in the planar direction on a pair of side portions in the lateral direction of the absorbent body 1. Specifically, Figure 2 As shown, the area where the liquid-absorbent fibers 11 and superabsorbent polymer 12 are arranged in the compressed portion 4 of the side portion of the absorbent body 1 is divided into six equal parts in the longitudinal direction (longitudinal direction) and two equal parts in the transverse direction, and is referred to as the divided area r. In other words, the compressed portion 4 of the side portion of the absorbent body 1 is divided into 12 divided areas r1 to r12.

[0060] For each segmented region r, the occupied area ratio of the absorbent core 10 when viewed from above in the thickness direction of the segmented region r was calculated. Specifically, the total occupied area of ​​the liquid-absorbent fibers 11 and superabsorbent polymer 12 in the segmented region r was divided by the area of ​​the segmented region r. In this case, the CV value, which indicates the variation in the occupied area ratio of the absorbent core 10, was 26% or less. The CV value is the standard deviation of the occupied area ratios of the absorbent core 10 for each of the 12 segmented regions r1 to r12 divided by the average value (standard deviation / average value).

[0061] The fact that the CV value is as small as 26% or less and the variation in the occupied area ratio of the absorbent core 10 when viewing the side portion of the absorbent body 1 in the thickness direction is small means that the liquid-absorbent fibers 11 and the superabsorbent polymer 12 are evenly arranged in the planar direction on the side portion of the absorbent body 1.

[0062] By minimizing the planar deviation of the absorbent cores 10 arranged on the side portions of the absorbent body 1, the strength of the compressed portions 4 formed on the side portions of the absorbent body 1 can be made uniform. For example, this prevents the occurrence of areas where strong pressure cannot be applied due to a small amount of absorbent cores 10. Consequently, the entire planar area of ​​the side portions of the absorbent body 1 is firmly compressed. This further prevents the liquid-absorbent fibers 11 and superabsorbent polymer 12 from falling off the side portions of the absorbent body 1, maintaining the absorbent performance of the side portions of the absorbent body 1.

[0063] For example, when the absorbent body 1 is incorporated into an absorbent article such as a disposable diaper, the absorbent body 1 is positioned so that its longitudinal direction (lengthwise direction) is aligned with the longitudinal direction of the absorbent article (the wearer's front-to-back direction). Thus, by maintaining the absorptive performance of the side portions of the absorbent body 1, side leakage of excrement from the absorbent article can be suppressed.

[0064] Figures 4A to 4E 1 and 2 are explanatory diagrams of a method for measuring the occupied area ratio of the absorbent core 10. The occupied area ratio of the liquid-absorbent fibers 11 and the superabsorbent polymer 12 when viewed from above in the thickness direction of the divided region r is calculated by the following method.

[0065] (1) First, use an X-ray imaging device (for example, an X-ray fluoroscopy device manufactured by Beamsense (company): FLEX-M863 or an equivalent means) to perform X-ray imaging of the absorbent body 1 to be measured. As imaging conditions, the tube voltage is set to 35 kV, the tube current is set to 100 μA, the pixel size is set to 20 × 20 μm, the number of pixels is set to 1500 × 1000 pixels, and the resolution is set to 2 μm (geometric magnification 10 times). At the same time, the 12 divided areas r1 to r12 specified in the absorbent body 1 (the state in which the absorbent core 10 is sandwiched by a pair of core wrapping sheets 2 and 3) and the area with only a pair of core wrapping sheets 2 and 3 are photographed. In addition, in the case of Figure 1A When there is no region consisting solely of the core wrap sheets 2 and 3 as in the absorbent body 1 illustrated, a sample is prepared in which the absorbent core 10 is separated from the core wrap sheets 2 and 3 and photographed.

[0066] (2) Next, the captured image ( Figure 4A ) is input into an image processing device (for example, a computer installed with image linking software and image measurement software manufactured by Unique (company), namely UN Analyzer or equivalent analysis software).

[0067] (3) Next, the image processing device performs contrast adjustment on the image captured by the X-ray. Adjustment is performed so that the image captured by the X-ray ( Figure 4A) becomes vivid (white parts become whiter, black parts become blacker). Specifically, set the gamma correction value to 0.6, the brightness correction value to -21, and the contrast correction value to 13.

[0068] (4) Next, the image processing device processes the contrast-adjusted image ( Figure 4B Specifically, the image is processed so that only the area where the pair of core wrap sheets 2 and 3 are present becomes white and the area where the absorbent core 10 is present becomes black. Figure 4C ) is inverted. That is, an image is produced in which the region where the absorbent core 10 is present is whitened ( Figure 4D ).

[0069] (5) Next, the image ( Figure 4D ) to divide the parts corresponding to the 12 segmented regions r1 to r12 ( Figure 4E ).

[0070] (6) Finally, using an image processing device (e.g., scatter measurement using UN Analyzer), the area (A1) of each divided region r and the area (A2) of the region (white region) within the divided region r where the absorbent core 10 is located are measured. Furthermore, the area occupied by the absorbent core 10 (A2 / A1) is calculated for each divided region r.

[0071] In addition, the structure of the absorbent body 1 is not limited to Figures 1A to 1C For example, it is also possible to Figure 3A as well as Figure 3B As shown in FIG. 1 , the absorbent core 10 is smaller than the absorbent body 1 and does not reach the side end 1a and the end 1b of the absorbent body 1. In this case, the area where the absorbent core 10 exists in the compressed portion 4 of the side of the absorbent body 1 is divided into 12 parts, and the area is referred to as the divided area r. In addition, the area where the absorbent core 10 does not exist in the side of the absorbent body 1 can be divided into 12 parts. Figure 3A It is not compressed as shown, or it can be Figure 3B Compressed as shown.

[0072] In addition, it is sufficient to provide the compressed portion 4 at least on the side of the absorbent body 1. For example, Figure 3C As shown in the figure, the compressed portions 4 are not provided at the longitudinal ends of the absorbent body 1. Furthermore, although not shown, the compressed portions 4 may be provided not only at the peripheral ends of the absorbent body 1 but also at the center of the absorbent body 1. Furthermore, the pattern or compression strength of the compressed portions 4 may be varied depending on the position of the absorbent body 1 (e.g., at the transverse side portions and at the longitudinal ends).

[0073] In addition, the shapes and areas of the divided regions r1 to r12 are not limited to be the same. Figure 3D In the case of the hourglass-shaped absorbent core 1 shown, or in the case where the width of the compressed portion 4 varies depending on the longitudinal position (not shown), first, a region is defined by dividing the longitudinal length of the compressed portion 4 on the side of the absorbent core 1 into six equal parts. Within each of these six-part regions, a region is defined by dividing each of these six-part regions into two equal parts in the transverse direction, forming twelve divided regions r1 to r12. This also applies to the second divided regions r'1 to r'12 described later.

[0074] Figure 5 1 is an explanatory diagram of the second divided regions r1' to r12' of the compressed portion 4 at the longitudinal end of the absorbent body 1. Figure 1A As shown in the example absorbent body 1, compressed portions 4 are provided not only on the lateral sides of the absorbent body 1 but also at a pair of longitudinal end portions. This configuration secures the core wrap sheets 2 and 3 and the absorbent core 10 at the longitudinal end portions of the absorbent body 1, and allows the liquid-absorbent fibers 11 and superabsorbent polymer 12 to be densely entangled. This prevents the absorbent core 10 from falling from the longitudinal end portions of the absorbent body 1. The longitudinal end portions of the absorbent body 1 refer to a portion or all of the regions at the ends when the absorbent body 1 is divided into three longitudinal sections.

[0075] Furthermore, the absorbent cores 10 may be evenly arranged in the plane direction at a pair of longitudinal end portions of the absorbent body 1. Specifically, Figure 5 As shown, the portion of the compressed portion 4 at the longitudinal end of the absorbent body 1 where the liquid-absorbent fibers 11 and the superabsorbent polymer 12 are arranged is divided into six equal parts in the transverse direction and two equal parts in the longitudinal direction, and is referred to as second divided regions r'1 to r'12.

[0076] Furthermore, for each second divided region r', the occupied area ratio of the absorbent core 10 when looking down at the second divided region r' in the thickness direction is calculated (the second area ratio obtained by dividing the total occupied area of ​​the liquid-absorbent fibers 11 and the superabsorbent polymer 12 in the second divided region r' by the area of ​​the second divided region r'). In this case, the CV value (standard deviation / average value) indicating the deviation of the occupied area ratio of the absorbent core 10 is 26% or less. The occupied area ratio of the absorbent core 10 can be calculated by Figures 4A to 4E Calculated by the described method.

[0077] By reducing the CV value to 26% or less, the planar deviation of the absorbent core 10 disposed at the longitudinal ends of the absorbent body 1 is minimized, and the strength of the compressed portion 4 formed at the longitudinal ends of the absorbent body 1 is made uniform. As a result, the entire planar area of ​​the longitudinal ends of the absorbent body 1 is firmly compressed, further preventing the absorbent core 10 from falling out of the longitudinal ends of the absorbent body 1, thereby maintaining the absorptive performance of the longitudinal ends of the absorbent body 1. However, this is not limited to the above; the CV value of the area occupied by the absorbent core 10 at the longitudinal ends of the absorbent body 1 may be greater than 26%.

[0078] Furthermore, the absorbent body 1 preferably has absorptive performance sufficient for incorporation into absorbent articles such as diapers. Therefore, in the absorbent body 1 of this embodiment, the mass ratio of the superabsorbent polymer 12 in the absorbent core 10 (mass of superabsorbent polymer 12 / mass of absorbent core 10) is set relatively high, at 10% or higher, preferably 30% or higher, and more preferably 40% or higher. Furthermore, it is preferable that the mass ratio of the superabsorbent polymer 12 remain the same not only in the center of the absorbent body 1 but also at the outer edges of the absorbent body 1. This configuration improves the absorptive performance at the ends (sides) of the absorbent body 1, thereby suppressing leakage of excrement.

[0079] The following method can be used to measure the mass of the superabsorbent polymer 12 contained in the absorbent core 10. First, an arbitrary mass of superabsorbent polymer 12 is removed from the absorbent core 10 before absorption and neutralized and titrated with 1 mol / L hydrochloric acid to create a calibration curve, allowing the polymer coefficient of the superabsorbent polymer 12 to be calculated. Next, a sample is taken from the absorbent core 10 to be measured, and the mass of the sample (liquid-absorbent fibers 11 + superabsorbent polymer 12) is measured. The sample is then added to ion-exchange water containing an appropriate amount of sodium chloride, and 1 mol / L hydrochloric acid is injected 1 ml at a time. The amount of hydrochloric acid injected is measured at the point at which the pH value of the ion-exchange water shows a significant change. The product of this read value and the polymer coefficient is the mass of the SAP contained in the sample. The mass of the SAP and the mass of the sample can be used to calculate the mass ratio of the SAP.

[0080] The superabsorbent polymer 12 included in the absorbent core 10 may be fibrous or granular, but the superabsorbent polymer 12 of this embodiment is granular. The average particle diameter of the granular superabsorbent polymer 12 is approximately 100 to 600 μm (micrometers).

[0081] The following method can be used as an example of a method for measuring the average particle diameter of the superabsorbent polymer 12. First, a plurality (e.g., 50) of superabsorbent polymers 12 are removed from the absorbent core 10 before absorption and observed using an optical microscope or the like. The diameter or major axis length of each superabsorbent polymer 12 is measured. The average value is defined as the average particle diameter of the superabsorbent polymer 12.

[0082] Figure 6A as well as Figure 6B This is an illustration of a dropout test in which the superabsorbent polymer 12 falls off the absorbent body 1. In this embodiment, the absorbent cores 10 are evenly arranged in the planar direction on the lateral sides and longitudinal ends of the absorbent body 1, and the entire planar area of ​​the peripheral ends of the absorbent body 1 is firmly compressed. Specifically, a reciprocating motion is performed at a rate of 1,000 times per minute for one minute. This reciprocating motion involves the absorbent body 1 before absorption being moved back and forth relative to each other between a pair of knocking plates 21 and 22 in a direction intersecting the plane of the absorbent body 1 (the thickness direction), so that a predetermined portion of the plane of the absorbent body 1 abuts against the pair of knocking plates 21 and 22. In this case, it is also preferable that the superabsorbent polymer 12 does not fall off the absorbent body 1. In other words, the side portions and longitudinal ends of the absorbent body 1 can be firmly compressed in the compression section 4 to such an extent that the superabsorbent polymer 12 does not fall off the peripheral ends of the absorbent body 1 even if vibration is applied to the absorbent body 1. This configuration allows the absorptive performance of the side portions and longitudinal ends of the absorbent body 1 to be more reliably maintained.

[0083] The shedding test of the superabsorbent polymer 12 was performed by the following method.

[0084] (1) First, the absorbent body 1 before absorption is placed on a vibrating machine 20 that reciprocates in a direction (thickness direction) that intersects the plane of the absorbent body 1. Figure 6A As shown, the absorbent body 1 is placed so that its transverse direction is along the vertical direction, and the chuck portion 201 of the vibrator 20 grips the absorbent body 1 from below. At this time, the area gripped by the chuck portion 201 is set to be approximately 30 to 50% of the length W of the end portion of the absorbent body 1 along the transverse direction and approximately 10 to 30% of the length L of the side portion of the absorbent body 1 along the longitudinal direction so that the absorbent body 1 does not sag.

[0085] (2) Next, a pair of knocking plates 21 and 22 (for example, acrylic plates) are fixedly installed at positions contacting a portion of the plane of the absorber 1. The pair of knocking plates 21 and 22 are positioned at intervals in the direction of movement intersecting the plane of the absorber. Figure 6BAs shown, the absorbent body 1 is arranged between a pair of knocking plates 21 and 22. The spacing between the knocking plates 21 and 22 can be approximately equal to the maximum thickness of the absorbent body 1 (e.g., 5 mm). Furthermore, the knocking plates 21 and 22 knock over an area approximately 30 to 50% of the length W of the end portion of the absorbent body 1 in the transverse direction and approximately 10 to 30% of the length L of the side portion of the absorbent body 1 in the longitudinal direction, so as not to hinder the superabsorbent polymer 12 from falling out of the opening of the absorbent body 1. Furthermore, the knocking plates 21 and 22 knock over the end portion of the absorbent body 1 in the longitudinal direction opposite to the side where the chuck portion 201 is located.

[0086] (3) Next, the vibration shaft portion 202 extending vertically downward from the chuck portion 201 of the vibrator 20 is vibrated, causing the absorbent body 1 to reciprocate between the pair of knocking plates 21 and 22 in a direction of motion (thickness direction) intersecting the plane of the absorbent body 1. Specifically, the reciprocating motion of the absorbent body 1 (movement of the absorbent body 1 toward one side of the motion direction and movement of the absorbent body 1 toward the other side of the motion direction) is performed at a rate of 1000 times per minute for 1 minute. At this time, a portion of the plane of the absorbent body 1 contacts the pair of knocking plates 21 and 22, causing vibrations to be generated in the absorbent body 1.

[0087] (4) Thereafter, it is visually observed whether the superabsorbent polymer 12 has not fallen off the absorbent body 1. Alternatively, the knocking plates 21 and 22 may be reciprocated relative to the absorbent body 1.

[0088] In addition, if Figure 1B As shown, it is preferred that, at least in the compressed portions 4 on the lateral sides of the absorbent body 1, no adhesive is provided between the absorbent core 10 and the core wrap sheets 2 and 3 in the thickness direction. This configuration prevents the absorbent core 10's absorption performance from being impaired by the adhesive, maintaining the absorption performance of the side portions of the absorbent body 1. Furthermore, in the absorbent body 1 of this embodiment, the absorbent cores 10 are evenly arranged in the planar direction on the side portions of the absorbent body 1, and the entire planar area of ​​the side portions of the absorbent body 1 is firmly compressed. Therefore, even without adhesive bonding between the absorbent core 10 and the core wrap sheets 2 and 3 on the side portions of the absorbent body 1, opening of the side portions of the absorbent body 1 can be suppressed.

[0089] Furthermore, it is preferred that no adhesive be provided between the absorbent core 10 and the core wrap sheets 2 and 3 in the thickness direction throughout the entire planar area of ​​the absorbent body 1. This configuration prevents the absorbent core 10's absorption performance from being impaired by the adhesive throughout the planar area of ​​the absorbent body 1, allowing for effective utilization of the absorbent body 1. Furthermore, when the absorbent cores 10 are evenly arranged in the planar direction at the longitudinal ends of the absorbent body 1, the ends are firmly compressed, thereby preventing the ends of the absorbent body 1 from opening even without adhesive.

[0090] However, the present invention is not limited to the above-mentioned configuration, and one or both of the pair of core wrap sheets 2 and 3 may be bonded to the absorbent core 10 via an adhesive (for example, a hot-melt adhesive).

[0091] The liquid-absorbent fibers 11 constituting the absorbent core 10 may include pulp fibers, and the core wrap sheets 2 and 3 may include cellulosic fibers (e.g., pulp fibers, non-wood fibers such as cotton or linen, or regenerated fibers such as rayon). Furthermore, it is preferred that the pulp fibers of the liquid-absorbent fibers 11 and the cellulosic fibers of the core wrap sheets 2 and 3 are hydrogen-bonded.

[0092] This structure securely bonds the liquid-absorbent fibers 11 to the core wrap sheets 2 and 3. In particular, the compressed portions 4 formed on the sides (and longitudinal ends) of the absorbent core 1 further securely hydrogen-bond the liquid-absorbent fibers 11 to the core wrap sheets 2 and 3, maintaining this bond. This further reduces the risk of openings on the sides (and longitudinal ends) of the absorbent core 1.

[0093] The fact that the liquid-absorbent fibers 11 (absorbent core 10) contain pulp fibers and that the core wrap sheets 2 and 3 contain cellulose fibers can be confirmed by known methods, such as by using an identification dye that stains the fibers or by observing the fibers under an optical microscope.

[0094] In addition, when the pulp fibers of the liquid-absorbent fibers 11 and the cellulose fibers of the core wrapping sheets 2 and 3 are hydrogen-bonded (wherein the absorbent core 10 and the core wrapping sheets 2 and 3 are not joined by an adhesive), the peel strength between the absorbent core 10 and the core wrapping sheets 2 and 3 is preferably greater than 0.1N / 25mm, and more preferably greater than 0.3N / 25mm (details will be described later in Example 4).

[0095] However, the present invention is not limited to the above-mentioned configuration, and the liquid-absorbent fibers 11 may not contain pulp fibers, and the core wrap sheets 2 and 3 may not contain cellulose fibers.

[0096] In addition, in the absorbent body 1 of this embodiment, as Figure 1C As shown in FIG. 1 , a pair of lateral sides of the core wrapping sheet 2 disposed on one side in the thickness direction are not folded back toward the other side in the thickness direction in a manner that covers the lateral side edges (end faces along the thickness direction) of the absorbent core 10. Similarly, a pair of lateral sides of the core wrapping sheet 3 disposed on the other side in the thickness direction are not folded back toward one side in the thickness direction in a manner that covers the lateral side edges (end faces along the thickness direction) of the absorbent core 10. In other words, as Figure 1B As shown, when the absorbent body 1 is viewed from the lateral direction, the side edges of the absorbent core 10 in the lateral direction are exposed.

[0097] According to such an absorbent body 1, the area of ​​the core wrapping sheets 2 and 3 can be reduced. In addition, the folding process of the core wrapping sheets 2 and 3 can be reduced in the manufacturing process of the absorbent body 1. Therefore, the cost of the absorbent body 1 can be reduced. In addition, since the side edges of the absorbent core 10 in the lateral direction are exposed, the absorption performance from the exposed portion is improved. In addition, in the absorbent body 1 of this embodiment, the absorbent core 10 is evenly arranged in the planar direction on the side of the absorbent body 1, and the entire plane area of ​​the side of the absorbent body 1 is firmly compressed. Therefore, even if the side edges of the absorbent core 10 are not covered by the core wrapping sheets 2 and 3, the absorbent core 10 can be prevented from falling out of the absorbent body 1.

[0098] However, the present invention is not limited to the above-mentioned structure, and the side portions of the core wrap sheets 2 and 3 in the transverse direction may be folded back in a manner that covers the side edges of the absorbent core 10. In addition, the longitudinal ends of the core wrap sheets 2 and 3 may be folded back in a manner that covers the longitudinal end edges of the absorbent core 10, or may not be folded back ( Figure 1C ).

[0099] ===Method for Manufacturing Absorbent Body 1===

[0100] A common absorbent manufacturing apparatus (not shown) utilizes a patterned drum. A patterned drum is a rotating drum with multiple forming dies corresponding to the shape of the absorbent at regular intervals on its outer circumference. Suction holes are provided on the bottom of the forming dies, allowing liquid-absorbent fibers and superabsorbent polymers released from a duct facing the patterned drum to accumulate in the forming dies. The absorbent cores accumulated in the forming dies are sequentially demolded from the patterned drum and transferred to a core wrap sheet, etc., to produce the absorbent.

[0101] However, in absorbent manufacturing methods utilizing a patterned roller, the absorbent core may not be cleanly released from the mold, or the liquid-absorbent fibers may scatter or the superabsorbent polymer may roll when the absorbent core is transferred to the core wrap sheet. Consequently, it is difficult to evenly distribute the material along the plane of the absorbent core, and material dispersion tends to increase significantly at the outer edges of the absorbent core. Consequently, the absorbent core's outer edges lack sufficient absorption capacity, requiring the accumulation of more material than necessary to compensate for this shortfall.

[0102] Figure 7This is an explanatory diagram of a method for manufacturing an absorbent body 1. The manufacturing apparatus 30 for the absorbent body 1 in this embodiment includes: a supply roller 31 for supplying a core wrap sheet 3 (hereinafter also referred to as the first core wrap sheet 3); an air lay machine 32; a supply roller 33 for supplying a core wrap sheet 2 (hereinafter also referred to as the second core wrap sheet 2); a water sprayer 34; a compression roller 35; and a cutting roller 36. In this embodiment, the longitudinal direction (lengthwise direction) of the absorbent body 1 corresponds to the conveying direction (MD direction) of the manufacturing apparatus 30, and the transverse direction of the absorbent body 1 corresponds to the CD direction intersecting the conveying direction of the manufacturing apparatus 30. However, this is not limiting and the directions may be reversed.

[0103] The manufacturing method of the absorbent body 1 using the above-mentioned manufacturing device 30 is as follows. First, the first core wrapping sheet 3 is supplied to the manufacturing production line by using a supply roller 31. On the first core wrapping sheet 3 conveyed in the conveying direction by a conveying device (conveyor belt, drive roller, etc.) not shown in the figure, the liquid-absorbent fibers 11 and the superabsorbent polymer 12 are stacked by using an air-laid machine 32 (stacking process). In detail, the liquid-absorbent fibers 11 and the superabsorbent polymer 12 are supplied from the air-laid machine 32 arranged above the first core wrapping sheet 3 to the first core wrapping sheet 3 below. In addition, Figure 7 In the embodiment, the first core wrap sheet 3 is conveyed horizontally, but the present invention is not limited thereto. The first core wrap sheet 3 may be conveyed while being wound around a rotating drum.

[0104] Next, the second core wrap sheet 2 is supplied by the supply roller 33 onto the liquid-absorbent fibers 11 and the superabsorbent polymer 12 accumulated in the accumulation step (supply step).

[0105] Next, water is sprayed by the water sprayer 34 onto the laminate 1' of the first core wrap sheet 3, the liquid-absorbent fibers 11 and the superabsorbent polymer 12, and the second core wrap sheet 2 (spraying step).

[0106] Next, using compression rollers 35, at least the portion of the laminate 1' corresponding to a pair of lateral side portions of the absorbent body 1 is compressed in the thickness direction to form compressed portions 4 (compression step). Preferably, compressed portions 4 can also be formed in portions of the laminate 1' corresponding to a pair of longitudinal end portions of the absorbent body 1. The compression rollers 35 are composed of a pair of rollers, and a convex portion corresponding to the shape of the compressed portion 4 is formed on the outer peripheral surface of one or both of the pair of rollers. The compression rollers 35 can be heated or unheated, and heating can strongly compress the laminate 1'.

[0107] Finally, to form the outer edge of the absorbent body 1, the laminate 1' is cut at the compressed portion 4 using a cutting roller 36 (cutting step). The cutting roller 36 comprises a pair of rollers, one of which is provided with a cutting edge corresponding to the cutting position on its outer circumference, while the other roller receives the cutting edge of the first roller. Alternatively, the cutting step may be performed to cut only a portion of the outer edge of the absorbent body 1 (e.g., the side portion).

[0108] According to this method for manufacturing an absorbent body 1, since the liquid-absorbent fibers 11 and the superabsorbent polymer 12 are deposited on the first core wrap sheet 3, problems encountered in conventional applications using a patterned roller (such as difficulty in cleanly demolding the absorbent core and material deviation during transfer) are less likely to occur. Consequently, the absorbent cores 10 can be evenly arranged across the entire planar area of ​​the absorbent body 1. Specifically, in the absorbent body 1 manufactured using the manufacturing method of this embodiment, the absorbent cores 10 arranged at the side portions (and longitudinal ends) exhibit minimal planar deviation, forming compressed portions 4 where the entire planar area of ​​the side portions (and longitudinal ends) is firmly compressed. Furthermore, in the cutting process, since cutting is performed at the hard and stable compressed portions 4, the lateral end portions 1a (and longitudinal end portions 1b) of the absorbent body 1 can be cut cleanly.

[0109] Furthermore, water is sprayed onto the material after the stacking process and before the compression process. Therefore, when the core wrap sheets 2 and 3, the liquid-absorbent fibers 11, and the superabsorbent polymer 12 are made of cellulose-based materials, hydrogen bonding occurs between the materials. For example, the liquid-absorbent fibers 11 and the superabsorbent polymer 12 hydrogen bond with the core wrap sheets 2 and 3, or the liquid-absorbent fibers 11 hydrogen bond with each other, or the liquid-absorbent fibers 11 and the superabsorbent polymer 12 hydrogen bond. Thus, an absorbent body 1 can be manufactured in which the constituent materials are firmly bonded. In particular, compressed portions 4 are formed on the sides (and longitudinal ends) of the absorbent body 1 after water spraying, so that the materials are more firmly hydrogen-bonded and this state can be maintained. Consequently, opening of the sides (and longitudinal ends) of the absorbent body 1 can be further suppressed.

[0110] exist Figure 7 In the embodiment, a water sprayer 34 is provided above the laminate 1' to spray water onto the second core wrap sheet 2 located on the upper surface of the laminate 1'. In this embodiment, water sequentially permeates the second core wrap sheet 2, the absorbent core 10, and the first core wrap sheet 3. This facilitates hydrogen bonding between the second core wrap sheet 2 and the absorbent core 10, further securing the second core wrap sheet 2 and the absorbent core 10.

[0111] However, the present invention is not limited to the above configuration. Water may be sprayed onto the first core wrap sheet 3 from the bottom side of the laminate 1', or from both the top and bottom sides of the laminate 1'. Furthermore, the water spraying step may be performed before the second core wrap sheet 2 is supplied. In other words, water may be sprayed from above the liquid-absorbent fibers 11 and superabsorbent polymer 12, or from below the first core wrap sheet 3. Furthermore, the water spraying step may be performed at multiple locations, such as before and after the second core wrap sheet 2 is supplied.

[0112] Furthermore, a step (hereinafter also referred to as a whole-surface compression step) of compressing the entire surface of the laminate 1' in a predetermined pattern or uniformly (flatly) may be performed before the compression step of forming the compressed portions 4 corresponding to the side portions of the absorbent body 1. The compression in the whole-surface compression step is weaker than the compression performed when forming the compressed portions 4.

[0113] By providing the water spraying step before the entire surface compression step, the materials in the entire planar area of ​​the laminate 1' are compressed in a hydrogen-bonded state (in a water-sprayed state), thereby more firmly hydrogen-bonding the materials and maintaining this state.

[0114] Alternatively, the laminate 1' may be wound into a roll after the entire surface compression process, and the wound laminate 1' may be placed on another production line, and the process of forming the compression portion 4 and the cutting process may be performed by the other production line. In this case, various absorbent bodies 1 (for example, absorbent bodies 1 of different sizes) can be manufactured from the laminate 1'. In this case, in the other production line, a water spraying process may be set again before the process of forming the compression portion 4. With this configuration, since hydrogen bonding of the material is generated again in the other production line, the strength of the compression portion 4 becomes higher. On the other hand, as Figure 7 As shown, when the compressed portion 4 is formed in the same production line as the process for producing the laminate 1 ′, it is possible to further suppress the absorptive core 10 from falling off during the production of the absorbent body 1 .

[0115] ===Example===

[0116] <<Examples 1 and 2>>

[0117] Ten absorbent bodies 1 of Examples 1 and 2 were produced using the method for producing the absorbent body 1 of this embodiment. Figures 1A to 1C The rectangular absorbent body 1 shown in the example has a transverse length of 60 mm, a longitudinal length of 100 mm, and a width of 10 mm at the compressed portion 4. The absorbent body 1 of Example 1 has an absorbent core 10 having a high basis weight, and the basis weight of the liquid-absorbent fibers 11 (pulp fibers) is 260 g / m 2, the unit area weight of the superabsorbent polymer 12 is set to 240 g / m 2 The absorbent body 1 of Example 2 has an absorbent core 10 with a low basis weight, and the basis weight of the liquid-absorbent fibers 11 (pulp fibers) is set to 75 g / m 2 , the unit area weight of the superabsorbent polymer 12 is set to 63g / m 2 In addition, the core wrapping sheets 2 and 3 are thin paper (weight per unit area 13g / m 2 ). In addition, part of Figure 7 Unlike the manufacturing method, water is sprayed from above onto the liquid-absorbent fibers 11 and superabsorbent polymer 12 before the second core wrap sheet 2 is supplied. Furthermore, after the second core wrap sheet 2 is supplied, the entire surface of the laminate 1' is uniformly (flattened) compressed using a compression roll heated to 150°C at a strength of 10 to 80 MPa. Subsequently, water is sprayed from below onto the first core wrap sheet 3, and then a compression roll heated to 65°C is used to form a lattice-patterned compressed portion 4 at a strength of 50 to 250 MPa.

[0118] <<Comparative Examples 1 and 2>>

[0119] Eight absorbent bodies of Comparative Examples 1 and 2 were produced by a manufacturing method using a patterned roller. The material of the core wrapping sheet, the shape of the absorbent body (compressed portion), and the size were the same as those of Examples 1 and 2. In addition, the absorbent core of the absorbent body of Comparative Example 1 was the same absorbent core with a high unit area weight as that of Example 1. The absorbent core of the absorbent body of Comparative Example 2 was the same absorbent core with a low unit area weight as that of Example 2. After the absorbent core was demolded from the forming mold of the patterned roller and transferred to the first core wrapping sheet, the second core wrapping sheet was laminated thereon. Then, the entire surface of the laminate was uniformly (flatly) compressed at a strength of 10 to 80 MPa using a compression roller heated to 150°C. Then, as in Example 1, water was sprayed from below relative to the first core wrapping sheet, and then a compression portion with a checkered pattern was formed at a strength of 50 to 250 MPa using a compression roller heated to 65°C.

[0120] <<Measurement Results of Examples 1 and 2 and Comparative Examples 1 and 2>>

[0121] The measurement of the occupied area ratio of the absorbent core 10 was performed on the lateral side portions of the absorbent bodies of Examples 1 and 2 and Comparative Examples 1 and 2 ( Figures 4A to 4E The measurement results are shown in Table 1.

[0122] [Table 1]

[0123]

[0124] Figure 8It is a graph showing the measurement results of Example 1 and Comparative Example 1 (absorbent body with a high basis weight). Figure 9 Graph showing the measurement results of Example 2 and Comparative Example 2 (low basis weight absorbent). Figure 8 、 Figure 9 As can be seen from the graph, in the absorbent with a CV value of 27%, opening (separation of the core wrap sheets 2 and 3) occurred, while in the absorbent with a CV value of less than 27%, no opening occurred. Therefore, by suppressing the CV value, which represents the deviation in the ratio of the occupied area of ​​the absorbent core at the lateral side portion, to 26% or less, as in the absorbent 1 of this embodiment, opening of the side portion of the absorbent 1 can be suppressed, and the absorption core can be suppressed from falling off the side portion. Similarly, in the longitudinal end portion of the absorbent 1, by suppressing the CV value, which represents the deviation in the ratio of the occupied area of ​​the absorbent core, to 26% or less, opening of the longitudinal end portion of the absorbent 1 can be suppressed.

[0125] Furthermore, the manufacturing method of this embodiment (Examples 1 and 2) shows that, compared to the case of using a patterned roller (Comparative Examples 1 and 2), it is possible to manufacture an absorbent body with less deviation in the absorbent core at the side portions and less likelihood of gaping. In all absorbent bodies 1 manufactured using the manufacturing method of this embodiment, the CV value was set to 26% or less.

[0126] In addition, absorbents with a high unit area weight tend to have a lower CV value than absorbents with a low unit area weight. This is considered to be because in absorbents with a high unit area weight, pressure can be firmly applied to the absorbent core when forming the compression portion, and since the liquid-absorbent fibers and the superabsorbent polymer are entangled at a high density, it is difficult to produce gaps for material movement. Therefore, among the absorbents of Comparative Example 1, there are absorbents with a CV value of less than 26%. Therefore, even if the manufacturing method using a patterned roller is used, if the absorbent has a high unit area weight, the absorbent 1 of this embodiment (an absorbent with a CV value of less than 26%) can sometimes be manufactured, and the manufacturing method of the absorbent 1 of this embodiment is not limited to Figure 7 However, according to the method shown in Figure 7 The manufacturing method of the absorbent body 1 exemplified above can more reliably manufacture an absorbent body having a CV value of 26% or less.

[0127] <<Example 3>>

[0128] Make Example 1 ( Figure 1A ) of the absorbent body 1 of Example 3, in which the width of the compressed portion 4 at the outer peripheral end portion of the absorbent body 1 is reduced from 10 mm to 5 mm (50 mm × 95 mm). Figure 6A as well as Figure 6BThe superabsorbent polymer 12 is tested for shedding. The absorbent body 1 held by the chuck portion 201 of the vibrator 20 has a horizontal length and a vertical length of 20 mm x 20 mm. Furthermore, the absorbent body 1 struck by the striking plate 21 has a horizontal length and a vertical length of 20 mm x 20 mm.

[0129] When the absorbent body 1 of Example 3 was vibrated by reciprocating between a pair of knocking plates 21 and 22, no drop of the superabsorbent polymer 12 from the absorbent body 1 was observed. Figure 7 ) in the absorbent body 1 manufactured by the present invention, the deviation in the planar direction of the absorbent core 10 arranged at the lateral side and the longitudinal end is small, forming a compressed portion 4 in which the entire plane area of ​​the outer peripheral end of the absorbent body 1 is firmly compressed.

[0130] <<Example 4 and Comparative Example 3>>

[0131] Five rectangular samples (Example 4) were prepared, each of which was formed by compressing and stacking the entire surface of a laminate of an absorbent core 10 in which a superabsorbent polymer 12 was mixed in an aggregate of liquid-absorbent fibers 11 containing pulp fibers and core wrapping sheets 2, 3 (thin paper) containing cellulose fibers in the thickness direction to form a compressed portion 4. Similarly, five rectangular samples (Comparative Example 3) were prepared, each of which was formed by compressing and stacking the entire surface of a laminate of the same absorbent core 10 as in Example 4 and core wrapping sheets 2, 3 (SMS nonwoven fabric containing polyolefin fibers) that do not contain cellulose fibers in the thickness direction to form a compressed portion 4. In addition, both samples were manufactured by the same manufacturing method as in Example 1. That is, the compressed portion 4 was formed after water was sprayed on the absorbent core 10 and the core wrapping sheets 2, 3 (after hydrogen bonding was generated in the sample of Example 4). In addition, the absorbent core 10 and the core wrapping sheets 2, 3 were not bonded by an adhesive. In addition, a Figure 7 The length of the sample in the conveying direction (MD direction) according to the manufacturing method is 25 mm and the length in the CD direction intersecting the MD direction is 50 mm.

[0132] For each sample of Example 4 and Comparative Example 3, a peel test was performed between the absorbent core 10 and the core wrap sheets 2 and 3 using a tensile testing machine (Instron Model 5565 manufactured by Instron Japan Co., Ltd. or an equivalent). The test was performed after the sample and the tensile testing machine were allowed to stand in a constant temperature and humidity environment of 20°C (±2°C) and 60% (±5%). The peel test method is as follows.

[0133] (1) First, the core wrap sheets 2 and 3 are peeled off from the absorbent core 10 at the CD end of the sample to be measured. One chuck of the tensile testing machine is used to hold the absorbent core 10 (CD end), while the other chuck is used to hold the core wrap sheets 2 and 3 (CD end). The length of the sample held by the chucks is set to approximately 10 mm, and the distance between the chucks is set to 10 mm.

[0134] (2) Using a tensile testing machine, expand the distance between the two chucks at a predetermined speed (e.g., 100 mm / min) and stretch the absorbent core 10 and the core wrap sheets 2 and 3 in the CD direction. This stretching is continued until the absorbent core 10 and the core wrap sheets 2 and 3 separate. The maximum load applied between the chucks during the tensile test is read and used as the peel strength (in the CD direction) of the sample being measured.

[0135] Table 2 shows the measurement results of the five samples of Example 4 and the five samples of Comparative Example 3.

[0136] [Table 2]

[0137]

[0138] The results in Table 2 show that Example 4, in which the liquid-absorbent fiber 11 comprises pulp fibers and the core wrap sheets 2 and 3 comprise cellulosic fibers, and these are hydrogen-bonded, exhibits greater peel strength than Comparative Example 3, in which the liquid-absorbent fiber 11 and the core wrap sheets 2 and 3 are not hydrogen-bonded. The average peel strength for Example 4 is 0.548 N / 25 mm, while the average peel strength for Comparative Example 3 is 0.093 N / 25 mm. Therefore, it is believed that when the peel strength is 0.1 N / 25 mm or greater (preferably 0.3 N / 25 mm or greater) when the aforementioned peel test is performed on the transverse side or longitudinal end of the absorbent body 1, hydrogen bonding is likely to occur between the liquid-absorbent fiber 11 and the core wrap sheets 2 and 3.

[0139] The embodiments of the present invention have been described above, but the above embodiments are examples for facilitating understanding of the present invention and are not intended to limit the present invention. In addition, the present invention may be modified and improved without departing from its concept, and the present invention naturally also includes equivalent structures.

[0140] Description of Reference Signs

[0141] 1 Absorbent body, 2 (second) core wrapping sheet, 3 (first) core wrapping sheet, 4 Compression unit, 10 Absorbent core, 11 Liquid-absorbent fiber, 12 Superabsorbent polymer, 20 Vibrator, 201 Chuck unit, 202 Rotating shaft unit, 21, 22 Tapping plates, 30 Apparatus for manufacturing absorbent body 1, 31 Supply roller, 32 Air-laid machine, 33 Supply roller, 34 Water sprayer, 35 Compression roller, 36 Cutting roller, r1 to r12 dividing areas, r'1 to r'12 second dividing areas.

Claims

1. An absorbent body having longitudinal, transverse and thickness directions, and comprising an absorbent core and core wrap sheets arranged on both sides of the absorbent core in the thickness direction, characterized in that: The absorbent core comprises liquid-absorbent fibers and superabsorbent polymers. The absorbent body has a compressed portion formed by compressing at least a pair of side portions in the transverse direction in the thickness direction. The portion of the compressed portion of the side portion of the absorbent body where the liquid-absorbent fibers and the superabsorbent polymer are arranged is divided into six parts in the longitudinal direction and two parts in the transverse direction as a divided region. When calculating the area ratio for each of the divided regions, a CV value indicating a variation in the area ratio, obtained by dividing the area occupied by the liquid-absorbent fibers and the superabsorbent polymer when viewing the divided region in the thickness direction by the area of ​​the divided region, is 26% or less.

2. The absorbent body according to claim 1, wherein The compressed portion is provided at a pair of end portions of the absorbent body in the longitudinal direction. The portion of the compressed portion at the end of the absorbent body where the liquid-absorbent fibers and the superabsorbent polymer are arranged is divided into six parts in the transverse direction and into two parts in the longitudinal direction as a second divided region. When a second area ratio is calculated for each of the second divided regions, a CV value indicating a deviation in the second area ratio is 26% or less. The second area ratio is obtained by dividing the area occupied by the liquid-absorbent fibers and the superabsorbent polymer when viewing the second divided region in the thickness direction by the area of ​​the second divided region.

3. The absorbent body according to claim 2, wherein The superabsorbent polymer does not fall off from the absorbent body when the absorbent body is subjected to a reciprocating motion at a speed of 1000 times per minute for 1 minute. The reciprocating motion refers to the absorbent body before absorption being relatively reciprocated between a pair of knocking plates in a direction intersecting the plane of the absorbent body so that a specified position in the plane of the absorbent body abuts against the pair of knocking plates.

4. The absorbent core according to any one of claims 1 to 3, wherein At least in the compressed portion of the side portion of the absorbent body, no adhesive is provided between the absorbent core and the core wrap sheet in the thickness direction.

5. The absorbent body according to claim 4, wherein No adhesive is provided between the absorbent core and the core wrap sheet in the thickness direction over the entire planar area of ​​the absorbent body.

6. The absorbent core according to any one of claims 1 to 3, wherein The liquid-absorbing fibers include pulp fibers. The core wrap sheet comprises cellulose fibers, The pulp fibers are hydrogen-bonded to the cellulose fibers.

7. The absorbent core according to any one of claims 1 to 3, wherein The pair of side portions in the transverse direction of the core wrap sheet disposed on one side in the thickness direction are not folded back toward the other side in the thickness direction so as to cover the side edges in the transverse direction of the absorbent core, and The pair of side portions in the transverse direction of the core wrap sheet disposed on the other side in the thickness direction are not folded back toward the one side in the thickness direction so as to cover the side edge of the absorbent core.

8. A method for producing an absorbent body having longitudinal, transverse and thickness directions, and comprising an absorbent core and a first core wrapping sheet and a second core wrapping sheet arranged on both sides of the absorbent core in the thickness direction, characterized in that: The method for manufacturing the absorbent body comprises: A stacking step of stacking the liquid-absorbent fibers and the superabsorbent polymer of the absorbent core onto the first core wrapping sheet being transported in the transport direction; a supplying step of supplying the second core wrapping sheet onto the liquid-absorbent fibers and the superabsorbent polymer deposited in the depositing step; a compressing step of compressing, in a laminate of the first core wrap sheet, the liquid-absorbent fibers, the superabsorbent polymer, and the second core wrap sheet, at least portions corresponding to the pair of lateral sides of the absorbent body in a thickness direction of the laminate to form compressed portions; as well as The cutting step is a step of cutting the compressed portion of the laminate to form an outer edge of the absorbent body.

9. The method for producing an absorbent body according to claim 8, wherein: A spraying step of spraying water onto at least one of the first core wrap sheet, the liquid-absorbent fibers, the superabsorbent polymer, and the second core wrap sheet is performed after the stacking step and before the compressing step.

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