Method for manufacturing absorbent sheets

Abstract

The present invention provides a method for manufacturing an absorbent sheet that prevents excretory fluids from being easily exposed to the outside. [Solution] A method for manufacturing an absorbent sheet having an absorbent core, a surface sheet, and a back sheet, comprising the steps of forming a continuous laminate by stacking a continuous surface sheet, a continuous absorbent core, and a continuous back sheet while transporting them in the transport direction, and cutting the continuous laminate while transporting it in the transport direction so that the length of the continuous laminate in the transport direction becomes the length of the absorbent sheet in the longitudinal or transverse direction.

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing absorbent sheets, etc. [Background technology]

[0002] As absorbent sheets, pet absorbent sheets used for handling pet waste are known. Patent Document 1 discloses a pet absorbent sheet comprising a liquid-permeable surface sheet, a liquid-impermeable back sheet, and a rectangular absorbent body placed between the two sheets. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2018-153144 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, in the absorbent sheet for pets disclosed in Patent Document 1, the surface sheet and back sheet extend in all directions from the periphery of the absorbent material, and are joined to each other at the extended portion. Therefore, there is no absorbent material around the entire periphery of the absorbent sheet. Consequently, when excretion occurs at the periphery of the absorbent sheet, the excretory fluid is received in the area where there is no absorbent material, and the excretory fluid leaks out of the absorbent sheet. In addition, areas of the absorbent sheet that consist only of the sheet and do not contain absorbent material, such as the periphery, have low rigidity and are easily peeled up. When the periphery of the absorbent sheet peels up, the absorbent surface is easily covered by the peeled sheet, and when excretion occurs in the area where the absorbent surface is covered by the sheet, the excretory fluid is not absorbed and leaks out of the absorbent sheet.

[0005] The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a method for manufacturing an absorbent sheet that prevents excretory fluid from leaking to the outside. [Means for solving the problem]

[0006] The main invention for achieving the above objective is a method for manufacturing an absorbent sheet, comprising: an absorbent core having a vertical direction, a horizontal direction, and a thickness direction, and comprising liquid absorbent fibers and a superabsorbent polymer; a liquid permeable surface sheet disposed on the front side of the absorbent core in the thickness direction; and a back sheet disposed on the back side of the absorbent core in the thickness direction, the method comprising: forming a continuous laminate by stacking a continuous surface sheet, a continuous absorbent core, and a continuous back sheet while transporting them in the transport direction; and cutting the continuous laminate while transporting it in the transport direction such that the length of the continuous laminate in the transport direction becomes the length of the absorbent sheet in the vertical or horizontal direction. Other features of the present invention will be made apparent by description in this specification and the accompanying drawings. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a method for manufacturing an absorbent sheet that prevents excretory fluid from leaking to the outside. [Brief explanation of the drawing]

[0008] [Figure 1] This is a plan view of absorbent sheet 1 as seen in the thickness direction. [Figure 2] Figures 2A and 2B are side views of the absorbent sheet 1 along the thickness direction. [Figure 3] This is a schematic cross-sectional view illustrating a modified example of the absorbent sheet 1 of the first embodiment. [Figure 4] Figures 4A and 4B show modified examples of the compression section 20. [Figure 5] This is an explanatory diagram for the manufacturing method of the absorbent continuum 2. [Figure 6] This is an explanatory diagram of the manufacturing method for absorbent sheet 1. [Figure 7]FIG. 7A is an explanatory diagram of a method for measuring the weight variation of the absorbent sheet 1, and FIG. 7B is a diagram showing the measurement results of the weight variation of the absorbent sheet 1. [Figure 8] FIGS. 8A and 8B are explanatory diagrams of the percussion test. [Figure 9] It is a diagram showing the results of the percussion test. [Figure 10] FIGS. 10A and 10B are explanatory diagrams of the absorbent sheet 1 of the second embodiment.

Embodiments for Carrying Out the Invention

[0009] From the description in this specification and the accompanying drawings, at least the following matters become clear. An absorbent sheet having a longitudinal direction, a transverse direction, and a thickness direction, an absorbent core including liquid-absorbent fibers and a superabsorbent polymer, a liquid-permeable surface sheet disposed on the front side in the thickness direction of the absorbent core, and a back surface sheet disposed on the back side in the thickness direction of the absorbent core, wherein when a region from a side edge in the longitudinal direction or the transverse direction of the absorbent sheet to a position inward by the length of the average thickness of the absorbent sheet is defined as a side edge portion, the absorbent core exists up to the side edge portion of the absorbent sheet in the longitudinal direction and also exists up to the side edge portion of the absorbent sheet in the transverse direction.

[0010] According to such an absorbent sheet, even when excreted at the peripheral portion of the absorbent sheet, the excreted liquid can be received by the absorbent core. Also, it is possible to suppress covering the absorption surface of the absorbent sheet with a sheet extending from the absorbent core. Therefore, leakage of the excreted liquid to the outside of the absorbent sheet can be suppressed.

[0011] Also, an absorbent sheet having a longitudinal direction, a lateral direction, and a thickness direction, comprising an absorbent core having liquid-absorbent fibers and a superabsorbent polymer, a liquid-permeable surface sheet disposed on the front side in the thickness direction of the absorbent core, and a back sheet disposed on the back side in the thickness direction of the absorbent core, wherein the absorbent core is exposed on each side surface along the thickness direction of a pair of side edges of the absorbent sheet in at least one of the longitudinal direction and the lateral direction.

[0012] According to such an absorbent sheet, excreted liquid can be absorbed from the side surface of the absorbent sheet where the absorbent core is exposed, and leakage of excreted liquid to the outside of the absorbent sheet can be suppressed. Further, the fact that the absorbent core is exposed on the side surface of the absorbent sheet means that the absorbent core exists up to the side edge portion of the absorbent sheet or a position close thereto. Therefore, even when excreted at the peripheral portion of the absorbent sheet, the excreted liquid can be received by the absorbent core, and it is possible to suppress covering the absorption surface of the absorbent sheet with a sheet extending from the absorbent core.

[0013] An absorbent sheet characterized in that the absorbent core is exposed on each side surface along the thickness direction of a pair of side edges of the absorbent sheet in both the longitudinal direction and the lateral direction.

[0014] According to such an absorbent sheet, excreted liquid can be absorbed from all side surfaces in four directions of the absorbent sheet. Further, the absorbent core exists up to all side edge portions in four directions or positions close thereto. Therefore, leakage of excreted liquid to the outside of the absorbent sheet can be further suppressed.

[0015] An absorbent sheet characterized in that, in a non-squeezed portion of the absorbent sheet where the absorbent sheet is not squeezed in the thickness direction, the thickness is uniform.

[0016] Such an absorbent sheet prevents a portion of its surface from protruding in the thickness direction, thus preventing, for example, animals from mischievously biting or tripping over the protruding part.

[0017] An absorbent sheet wherein the absorbent core has a pair of sides along the thickness direction of a pair of side edges in at least one of the longitudinal and transverse directions, and these sides are covered from the outside with a sheet.

[0018] With such an absorbent sheet, the sides of the absorbent core are covered by the sheet, which suppresses the shedding of the absorbent core (especially the superabsorbent polymer) from the absorbent sheet, thus ensuring the absorbent performance of the absorbent sheet.

[0019] An absorbent sheet, wherein the absorbent sheet has a pair of compressed portions along a pair of side edges of the absorbent sheet in at least one of the longitudinal and transverse directions, wherein at least the absorbent core is compressed in the thickness direction, and when the maximum length of the absorbent sheet in one direction is X mm, the compressed portions are provided in a region from the side edge to a position inward in one direction by a length of 1 / 4 of X mm.

[0020] With this type of absorbent sheet, the wastewater can be contained and diffused at the compression point, thus suppressing leakage of wastewater to the outside of the absorbent sheet. In addition, the absorbent sheet can be effectively utilized over a wide area in the planar direction.

[0021] An absorbent sheet characterized in that the compressed portion is provided in a region that is located inward from the side edge in one direction.

[0022] With this type of absorbent sheet, the internal compression section can block and diffuse the excrement, making it difficult for the excrement to reach the side edges of the absorbent sheet. Therefore, it is possible to suppress the swelling and tendency for the absorbent core (especially the superabsorbent polymer) located at the side edges of the absorbent sheet to detach after absorbing the excrement.

[0023] The absorbent sheet is characterized in that it is provided with a gap inward in one direction from the compressed portion and has at least one other compressed portion along the side edge.

[0024] With this type of absorbent sheet, the internal compression section can block and diffuse the excrement, making it difficult for the excrement to reach the side edges of the absorbent sheet, thus suppressing the tendency for the absorbent core, which has swollen with the excrement, to detach. In addition, the external compression section strongly bonds the absorbent core near the side edges of the absorbent sheet in the thickness direction, further suppressing the detachment of the absorbent core.

[0025] An absorbent sheet having a core wrap sheet that covers the front surface of the absorbent core in the thickness direction, and wherein no adhesive is provided between the absorbent core and the core wrap sheet.

[0026] Such an absorbent sheet prevents the adhesive from inhibiting the absorption of excretory fluid into the absorbent core. Therefore, the absorbent performance of the absorbent sheet can be ensured.

[0027] An absorbent sheet wherein the absorbent sheet has a core wrap sheet covering at least one side of the absorbent core in the thickness direction, the liquid absorbent fibers include pulp fibers, the core wrap sheet includes cellulose fibers, and the pulp fibers are hydrogen-bonded to the cellulose fibers.

[0028] With such an absorbent sheet, the absorbent core (pulp fibers) and the core wrap sheet (cellulose fibers) are firmly bonded together by hydrogen bonds, which suppresses the shedding of the absorbent core from the absorbent sheet.

[0029] An absorbent sheet characterized in that, when the absorbent sheet is subjected to a tapping test in which the absorbent sheet is moved back and forth between a pair of tapping plates in a direction intersecting the plane of the absorbent sheet, causing a predetermined portion of the plane of the absorbent sheet to come into contact with the pair of tapping plates, at a speed of 1,000 times per minute for one minute, the amount of shedding obtained by subtracting the weight of the absorbent sheet after the tapping test from the weight of the absorbent sheet before the tapping test is 0.5% or less, and the value obtained by dividing the amount of shedding by the weight of the absorbent sheet before the tapping test is 0.5% or less.

[0030] With such an absorbent sheet, the absorbent performance of the sheet can be maintained compared to when the amount of shedding divided by the weight of the absorbent sheet before the tapping test is greater than 0.5%.

[0031] An absorbent sheet characterized in that, when a tapping test is performed in which the absorbent sheet, before absorption, is moved back and forth between a pair of tapping plates in a direction intersecting the plane of the absorbent sheet, and a predetermined portion of the plane of the absorbent sheet is brought into contact with the pair of tapping plates, the superabsorbent polymer does not fall off the absorbent sheet at a speed of 1,000 times per minute for one minute.

[0032] Such an absorbent sheet can maintain its absorbent performance.

[0033] An absorbent sheet characterized in that, when the absorbent sheet is divided into regions having a length of 40 mm in the vertical direction and a length of 40 mm in the horizontal direction, and the regions where the absorbent core is present throughout the entire region are defined as divided regions, and the weight of each divided region is measured, the CV value of the weight variation of the divided regions is 10% or less.

[0034] With such an absorbent sheet, the absorbent core (especially the superabsorbent polymer) is more evenly distributed in the planar direction of the absorbent sheet compared to cases where the CV value of the weight variation in the divided region is greater than 10%. Therefore, during the manufacturing of the absorbent sheet, force can be applied evenly in the thickness direction, increasing the bonding strength in the thickness direction of the absorbent sheet. Consequently, the detachment of the absorbent core from the absorbent sheet can be suppressed.

[0035] Furthermore, a method for manufacturing an absorbent sheet having an absorbent core having a vertical direction, a horizontal direction and a thickness direction and comprising liquid absorbent fibers and a superabsorbent polymer; a liquid permeable surface sheet disposed on the front side in the thickness direction of the absorbent core; and a back sheet disposed on the back side in the thickness direction of the absorbent core, the method comprising the steps of forming a continuous laminate by stacking a continuous surface sheet, a continuous absorbent core, and a continuous back sheet while transporting them in the transport direction; and cutting the continuous laminate while transporting it in the transport direction such that the length of the continuous laminate in the transport direction becomes the length of the absorbent sheet in the vertical or horizontal direction.

[0036] According to this method for manufacturing absorbent sheets, it is possible to produce absorbent sheets in which the absorbent core extends to the side edge in the direction corresponding to the conveying direction, or absorbent sheets in which the absorbent core is exposed on the side surface of the side edge in the direction corresponding to the conveying direction.

[0037] ===Implementation Method=== The following describes embodiments of the absorbent sheet according to the present invention. The absorbent sheet according to the present invention can be used, for example, as an absorbent sheet for animals to handle the excrement of animals such as pets. In this case, the absorbent sheet can be used on its own, or it can be installed in an animal toilet. In addition, the absorbent sheet according to the present invention can be used for various purposes such as a childcare sheet, a nursing care sheet used during diaper changes or to prevent soiling of bedding, and a medical sheet.

[0038] ===First Embodiment=== <<Basic configuration of absorbent sheet 1>> Figure 1 is a plan view of the absorbent sheet 1 as seen in the thickness direction. Figures 2A and 2B are side views of the absorbent sheet 1 along the thickness direction. Figure 2A is a side view of the lateral side edges 1c and 1d of the absorbent sheet 1, and Figure 2B is a side view of the longitudinal side edges 1a and 1b of the absorbent sheet 1. Note that Figure 2A is a common diagram showing the side view of one lateral side edge 1c and the side view of the other lateral side edge 1d. Figure 2B is a common diagram showing the side view of one longitudinal side edge 1a and the side view of the other longitudinal side edge 1b.

[0039] The absorbent sheet 1 has a longitudinal direction, a transverse direction, and a thickness direction that are all perpendicular to each other, and its planar shape when viewed in the thickness direction is rectangular. The planar shape of the absorbent sheet 1 is not limited to a rectangle, and may be various shapes such as a square, a roughly quadrilateral (for example, a quadrilateral with rounded corners or a quadrilateral with convexly curved side edges), a polygon, or an ellipse. When the length of the longitudinal and transverse directions are different, as in the absorbent sheet 1 of this embodiment, the longitudinal direction of the absorbent sheet 1 is defined as the longitudinal direction, and the transverse direction is defined as the transverse direction. Furthermore, when the absorbent sheet 1 is a shape other than a quadrilateral, the straight line along the longest part of the absorbent sheet 1 is defined as the longitudinal direction, and the direction perpendicular to that direction is defined as the transverse direction.

[0040] The absorbent sheet 1 comprises an absorbent core 10, a liquid-permeable surface sheet 11 positioned on the front side of the absorbent core 10 in the thickness direction, and a back sheet 12 positioned on the back side of the absorbent core 10 in the thickness direction. The absorbent core 10 is an aggregate of liquid-absorbing fibers 101 mixed with a super absorbent polymer 102 (SAP). Examples of liquid-absorbing fibers 101 include cellulose fibers (e.g., pulp fibers, non-wood fibers such as cotton and hemp, regenerated fibers such as rayon, etc.) and hydrophilically treated thermoplastic synthetic fibers (e.g., polyethylene, polypropylene, etc.). Examples of the liquid-permeable surface sheet 11 include nonwoven fabrics and perforated films. Examples of the back sheet 12 include liquid-impermeable sheets (e.g., resin films, etc.) and poorly liquid-impermeable sheets (e.g., SMS nonwoven fabrics, water-repellent treated nonwoven fabrics, etc.).

[0041] Furthermore, the absorbent sheet 1 may be a sheet that can absorb on both sides, and the back sheet 12 may be a liquid-permeable sheet similar to the front sheet 11. Such an absorbent sheet 1 is best used in combination with other absorbent articles or absorbent sheets as an item that supplements the absorption of excretory fluid.

[0042] Furthermore, the absorbent sheet 1 includes a core wrap sheet 13 (also referred to as the first core wrap sheet 13) that covers the front surface of the absorbent core 10 in the thickness direction, and a core wrap sheet 14 (also referred to as the second core wrap sheet 14) that covers the back surface of the absorbent core 10. The core wrap sheets 13 and 14 are permeable to liquids. Examples of core wrap sheets 13 and 14 include tissue paper, nonwoven fabric, perforated film, etc.

[0043] Furthermore, the absorbent sheet 1 has a compressed portion 20 in a part of its plane where at least the absorbent core 10 is compressed in the thickness direction. The compressed portion 20 is a part in which the absorbent core 10 is recessed in the thickness direction compared to the surrounding area, and is thinner, and has a higher density of absorbent core 10 (liquid absorbent fiber 11) compared to the surrounding area.

[0044] In the compression section 20 illustrated in Figure 2A, the entire absorbent sheet 1 is compressed from the surface sheet 11 side. However, the compression section 20 is not limited to this, and for example, only the absorbent core 10 may be compressed, or only the absorbent core 10 and core wrap sheets 13, 14 may be compressed, or the absorbent sheet 1 may be compressed from the back sheet 12 side.

[0045] Furthermore, the compression section 20 may be uniformly compressed (in a groove-like manner) within its area, or it may be compressed in a predetermined pattern. Examples of areas in which the compression section 20 is compressed in a predetermined pattern include multiple small compression sections arranged discretely, or multiple small compression sections arranged linearly. In addition, the compression section 20 may be provided with multiple types of compression sections with different compression strengths (depths of indentations).

[0046] <<About Absorbent Core 10>> In the absorbent sheet 1 of the first embodiment, the planar shape and planar area of ​​the absorbent sheet 1 and the absorbent core 10 are the same, and the absorbent sheet 1 and the absorbent core 10 are overlapped so that their outer edges are aligned. Therefore, as shown in Figure 1, the side edges 1a and 1b of the absorbent sheet 1 in the vertical direction coincide with the side edges 10a and 10b of the absorbent core 10 in the vertical direction, and the side edges 1c and 1d of the absorbent sheet 1 in the horizontal direction coincide with the side edges 10c and 10d of the absorbent core 10 in the horizontal direction.

[0047] In this way, the absorbent core 10 is preferably present up to the side edge 1ab of the absorbent sheet 1 in the vertical direction and up to the side edge 1cd of the absorbent sheet 1 in the horizontal direction. This way, even if waste is excreted on the outer edge of the absorbent sheet 1, the excreted liquid can be received by the absorbent core 10 and absorbed and retained by the absorbent core 10. Thus, leakage of the excreted liquid to the outside of the absorbent sheet 1 can be suppressed.

[0048] Furthermore, if the surface sheet 11 or back sheet 12 extends significantly beyond the absorbent core 10, the portion consisting only of the sheet will have low rigidity and be prone to peeling. For example, an animal might peel off the sheet portion while playing, or the sheet portion might peel off if the absorbent sheet 1 is larger than the tray of the animal's litter box. Therefore, by having the absorbent core 10 extend to the side edges 1ab, 1cd, as in the absorbent sheet 1 of the first embodiment, the portion consisting only of the sheet extending beyond the absorbent core 10 can be eliminated or shortened. As a result, it is possible to prevent the sheet from peeling off and covering the absorbent surface of the absorbent sheet 1, to draw the excrement into the interior of the absorbent sheet 1, and to suppress the leakage of excrement to the outside of the absorbent sheet 1.

[0049] Furthermore, the region extending inward from the longitudinal or transverse side edges 1a to 1d of the absorbent sheet 1 by the length of the average thickness of the absorbent sheet 1 is defined as the "side edge portion 1ab, 1cd". By doing so, the length of the backing sheet 12 extending beyond the absorbent core 10 is shorter than the average thickness of the absorbent sheet 1, so that the backing sheet 12 does not peel back and fold over onto the surface sheet 11, and the absorbent surface does not become covered by the backing sheet 12.

[0050] The average thickness of absorbent sheet 1 is measured using an Ozaki Seisakusho Dial Thickness Gauge Large Type JB, or an equivalent. To define the measurement points, first, the central part of the absorbent sheet 1 is divided into three sections along its maximum width in the horizontal direction. Next, this central part is divided into three sections along its maximum length in the vertical direction, defining three regions (both ends and the center in the vertical direction). One, preferably multiple, measurement points are set for each of the three regions. The measurement points are in the non-compressed area and away from the packaging fold. The set measurement points are then measured at 3.0 gf / cm². 2 The absorbent sheet 1 is then compressed, and its thickness is measured at each location. The average of the thicknesses of the absorbent sheet 1 obtained at all measurement locations is calculated, and this average value is taken as the average thickness of the absorbent sheet.

[0051] Furthermore, it is preferable that the absorbent core 10 be exposed on each side surface along the thickness direction at the positions of the pair of side edges 1c and 1d of the absorbent sheet 1 in the lateral direction, as shown in Figure 2A. Similarly, it is preferable that the absorbent core 10 be exposed on each side surface along the thickness direction at the positions of the pair of side edges 1a and 1b of the absorbent sheet 1 in the vertical direction, as shown in Figure 2B.

[0052] The statement that the absorbent core 10 is exposed on the side surface of the absorbent sheet 1 means that the absorbent core 10 is visible when the side surface of the absorbent sheet 1 is visually inspected. Specifically, it is desirable that the absorbent core 10 be visible when the side surface of the absorbent sheet 1 is visually inspected, or that the absorbent core 10 be visible in an image of the side surface of the absorbent sheet 1 magnified using an electron microscope or the like.

[0053] In this case, the excrement is more easily absorbed from the sides of the absorbent sheet 1. Therefore, even if the excrement flows out from the surface of the absorbent sheet 1, it will be absorbed from the sides of the absorbent sheet 1, reducing the amount of excrement that leaks outside the absorbent sheet 1. For example, if the absorbent sheet 1 is placed in a tray of an animal toilet, the excrement that flows into the tray will be more easily absorbed from the sides of the absorbent sheet 1.

[0054] Furthermore, since the folding process of the sheet covering the absorbent core 10 is unnecessary during the manufacturing of the absorbent sheet 1, manufacturing becomes easier. Also, since the area of ​​the sheet covering the sides of the absorbent core 10 is unnecessary, sheet consumption can be reduced, leading to lower costs.

[0055] Furthermore, the fact that the absorbent core 10 is visible from the side of the absorbent sheet 1 means that the absorbent core 10 extends to or near the side edges 1a to 1d of the absorbent sheet 1. Therefore, the aforementioned effects can be obtained. In other words, the excreted liquid can be absorbed from the outer edge of the absorbent sheet 1, and the absorption surface can be prevented from being covered by a peeled-up sheet.

[0056] In particular, in the absorbent sheet 1 illustrated in Figure 1, the absorbent core 10 is exposed on each side surface along the thickness direction of a pair of side edges 1a to 1d of the absorbent sheet 1 in both the longitudinal and transverse directions. Therefore, excrement is easily absorbed from all four sides of the absorbent sheet 1, and it is difficult for excrement to leak out of the absorbent sheet 1.

[0057] Figure 3 is a schematic cross-sectional view illustrating a modified example of the absorbent sheet 1 of the first embodiment. The invention is not limited to the above, and the absorbent core 10 may be exposed only on one of the sides of the absorbent sheet 1 in either the vertical or horizontal direction, or the absorbent core 10 may not be exposed at all on the sides of the absorbent sheet 1.

[0058] In other words, as shown in Figure 3, the absorbent core 10 may have a pair of side edges in at least one of the longitudinal and transverse directions, each side 10S along the thickness direction, which are covered from the outside by a sheet. In Figure 3, the back sheet 12 extending beyond the absorbent core 10 is folded back while covering the side 10S of the absorbent core 10 and is positioned on the surface sheet 11. However, it is not limited to this, and the sheet covering the side 10S of the absorbent core 10 may be the surface sheet 11 or core wrap sheets 13, 14.

[0059] In this case, since the side surface 10S of the absorbent core 10 is covered with the sheet, the detachment of the absorbent core 10 from the side surface of the absorbent sheet 1 can be suppressed. Therefore, the absorption performance of the absorbent sheet 1 (especially the side edges 1ab, 1cd) is ensured, and leakage of excretory fluid to the outside of the absorbent sheet 1 can be suppressed. In addition, the excretory fluid absorbed by the absorbent core 10 can be prevented from seeping out from the side surface of the absorbent sheet 1.

[0060] Furthermore, as shown in Figures 2A and 2B, it is desirable that the thickness T of the absorbent sheet 1 be uniform in the uncompressed portion of the absorbent sheet 1 where the absorbent sheet 1 is not compressed in the thickness direction. The uncompressed portion is defined as the part of the absorbent sheet 1 other than the compressed portion 20 where the flat surface is partially compressed, and the portion where the entire flat surface of the absorbent sheet 1 is uniformly flat-pressed is included in the uncompressed portion. Moreover, uniform thickness T of the absorbent sheet 1 means substantially uniform, excluding errors that occur during the manufacturing process.

[0061] The uniform thickness T of the absorbent sheet 1 prevents a portion of the surface of the absorbent sheet 1 from protruding in the thickness direction when the absorbent sheet 1 is placed on a surface such as a floor. If a portion of the surface of the absorbent sheet 1 protrudes upward, there is a risk that an animal may bite that protruding portion and damage the absorbent sheet 1. Also, if the surface of the side edge of the absorbent sheet 1 protrudes in the thickness direction compared to the surface of the central part, there is a risk that an animal may trip over it. Therefore, as shown in Figures 2A and 2B, it is preferable that the height (position in the thickness direction) of the surface of the absorbent sheet 1 (uncompressed portion) is the same when the absorbent sheet 1 is placed on a surface.

[0062] Furthermore, by making the thickness T of the absorbent sheet 1 (uncompressed portion) uniform, the material composition laminated in the thickness direction can be made the same across the entire plane of the absorbent sheet 1. As a result, as shown in Figures 2A and 2B, the absorbent core 10 can be present up to the side edges 1a to 1d of the absorbent sheet 1, and the absorbent core 10 can be exposed on the side surface of the absorbent sheet 1 (the back sheet 12 is not folded back as shown in Figure 3). In addition, by making the thickness T of the absorbent sheet 1 uniform, the basis weight of the absorbent core 10 can be kept constant across the entire plane of the absorbent sheet 1. As a result, absorption performance is ensured across the entire plane of the absorbent sheet 1. Furthermore, since the sheet folding process is unnecessary, the manufacturing of the absorbent sheet 1 becomes easier.

[0063] Furthermore, as shown in Figure 1, the absorbent sheet 1 has a pair of lateral compression sections 21 along a pair of side edges 1a and 1b of the absorbent sheet 1 in the longitudinal direction (one direction). When the maximum length of the absorbent sheet 1 in the longitudinal direction (one direction) is Xl (X mm), the lateral compression sections 21 are preferably provided in a region extending from the lateral side edges 1a and 1b to a position that is 1 / 4 of the maximum length Xl inward in the longitudinal direction.

[0064] Similarly, the absorbent sheet 1 has a pair of longitudinal compression sections 22 along a pair of side edges 1c, 1d of the absorbent sheet 1 in the transverse direction (one direction). When the maximum length of the absorbent sheet 1 in the transverse direction (one direction) is Xw (X mm), the longitudinal compression sections 22 are preferably provided in a region extending from the longitudinally extending side edges 1c, 1d to a position that is 1 / 4 of the maximum length Xw inward in the transverse direction.

[0065] By doing so, the excrement can be diffused horizontally and vertically in the horizontal compression section 21 and the vertical compression section 22, thereby suppressing leakage of the excrement from the absorbent sheet 1. In addition, the diffusion of the excrement allows the absorbent sheet 1 to be effectively utilized over a wide area in the planar direction.

[0066] Furthermore, in the compression section 20, the absorbent cores 10 are strongly intertwined with each other, and the absorbent cores 10 and the sheet, which are stacked in the thickness direction, are strongly bonded and integrated. Therefore, even when the absorbent cores 10 extend to the side edges 1ab, 1cd, as in the absorbent sheet 1 of the first embodiment, the lateral compression section 21 and longitudinal compression section 22 near the side edges 1ab, 1cd can suppress the detachment of the absorbent cores 10 from the absorbent sheet 1. Thus, the absorption performance of the absorbent sheet 1 (especially the side edges 1ab, 1cd) can be ensured, and leakage of excretory fluid from the absorbent sheet 1 can be suppressed.

[0067] Preferably, the lateral compression section 21 is provided in a region that extends inward in the vertical direction from the laterally extending side edges 1a and 1b, that is, at a distance from the side edges 1a and 1b. Similarly, the longitudinal compression section 22 is provided in a region that extends inward in the horizontal direction from the vertically extending side edges 1c and 1d, that is, at a distance from the side edges 1c and 1d.

[0068] By doing so, the wastewater can be contained and diffused at the lateral compression section 21 and the longitudinal compression section 22, thereby reducing the amount of wastewater that reaches the side edges 1a to 1d beyond the lateral compression section 21 and the longitudinal compression section 22. Therefore, leakage of wastewater from the absorbent sheet 1 can be suppressed. In addition, the absorbent cores 10 present at the side edges 1ab and 1cd of the absorbent sheet 1 will absorb the wastewater and swell, which can prevent the absorbent cores 10 (especially the superabsorbent polymer 102) from easily falling off.

[0069] The compressed portion 20 along the side edges 1a to 1d of the absorbent sheet 1 is a compressed portion 20 that extends long in the direction in which the side edges 1a to 1d extend. Therefore, it is not limited to a compressed portion 20 that extends in a straight line parallel to the vertical or horizontal direction, but may, for example, be a compressed portion that extends in a meandering manner. Also, the length of the compressed portion 20 may be shorter than the side edges 1a to 1d of the absorbent sheet 1.

[0070] Furthermore, the compression section 20 is not limited to being provided along the four side edges 1a to 1d; for example, the compression section 20 may be provided on the absorbent sheet 1 only in one direction, either vertical or horizontal. For example, the compression section 20 may be provided only on the side of the absorbent sheet 1 where the absorbent core 10 is exposed. In this way, even if the absorbent core 10 is exposed, the compression section 20 can suppress the detachment of the absorbent core 10 and suppress the seepage of excretory fluid from the absorbent core 10.

[0071] Figures 4A and 4B show modified examples of the compression section 20. As shown in Figure 4A, the absorbent sheet 1 may have at least one other lateral compression section 211 located longitudinally inward from the lateral compression section 21, along the same side edges 1a, 1b. Similarly, the absorbent sheet 1 may have at least one other longitudinal compression section 221 located longitudinally inward from the longitudinal compression section 22, along the same side edges 1c, 1d. Figure 4A illustrates a case where the compression sections 20 are arranged in a double row, but there may be three or more lateral compression sections 21 or longitudinal compression sections 22 arranged at intervals.

[0072] In this case, the excrement can be contained and diffused by the inner lateral compression sections 211 and longitudinal compression sections 221, thereby suppressing leakage of excrement from the absorbent sheet 1. Furthermore, it is possible to suppress the absorption core 10 (especially the superabsorbent polymer 102) from easily falling off as it absorbs excrement and swells at the side edges 1ab and 1cd of the absorbent sheet 1. In addition, even if the excrement flows beyond the inner lateral compression sections 211 and longitudinal compression sections 221, it can be contained and diffused by the outer lateral compression sections 21 and longitudinal compression sections 22. Moreover, even if the absorbent core 10 extends to the side edges 1ab and 1cd, as in the absorbent sheet 1 of the first embodiment, the outer lateral compression sections 21 and longitudinal compression sections 22 can suppress the detachment of the absorbent core 10 from the absorbent sheet 1.

[0073] Furthermore, as shown in Figure 4B, multiple compression sections 20 may be arranged at intervals along a pair of side edges of the absorbent sheet 1 in either the vertical or horizontal direction. For example, by providing multiple compression sections 20 on the side of the absorbent sheet 1 where the absorbent core 10 is exposed, it is possible to suppress the detachment of the absorbent core 10 and the seepage of excretory fluid from the absorbent core 10.

[0074] The compression section 20 has been described above, but it is not limited to the above. For example, the absorbent sheet 1 does not have to have compression sections 21 and 22 along its side edges 1a to 1d, and may have point-shaped compression sections dispersed therein. Also, the absorbent sheet 1 does not have to have compression sections 20.

[0075] Furthermore, it is preferable that no adhesive is provided between the absorbent core 10 and the first core wrap sheet 13 located on the surface side of the absorbent core 10. This prevents absorption inhibition by adhesive on the surface of the absorbent core 10, and allows the excretory fluid to be drawn into the interior of the absorbent core 10. Thus, the absorption performance of the absorbent core 10 is ensured, and leakage of excretory fluid from the absorbent sheet 1 can be suppressed.

[0076] Furthermore, if the absorbent sheet 1 is a sheet that can absorb liquid on both sides and the back sheet 12 is a liquid-permeable sheet, it is preferable that no adhesive is provided between the absorbent core 10 and the second core wrap sheet 14 located on its back side. However, the above is not limited to the case, and the absorbent core 10 may be bonded to the core wrap sheets 13 and 14 with an adhesive.

[0077] Furthermore, the liquid absorbent fibers 101 constituting the absorbent core 10 may contain pulp fibers, and the core wrap sheets 13 and 14 may contain cellulosic fibers (for example, pulp fibers, non-wood fibers such as cotton or hemp, or regenerated fibers such as rayon). Preferably, the pulp fibers of the liquid absorbent fibers 101 are hydrogen-bonded to the cellulosic fibers of the core wrap sheets 13 and 14.

[0078] This ensures that the liquid absorbent fiber 101 and the core wrap sheets 13 and 14 are firmly bonded together. Therefore, even if an adhesive cannot be provided between the absorbent core 10 and the core wrap sheets 13 and 14 as described above, peeling of the core wrap sheets 13 and 14 and detachment of the absorbent core 10 from between the core wrap sheets 13 and 14 can be suppressed.

[0079] In particular, when a compressed portion 20 is formed on the absorbent sheet 1, the liquid absorbent fibers 101 and the core wrap sheets 13 and 14 are more strongly hydrogen-bonded at the compressed portion 20, and this state is maintained. Furthermore, the liquid absorbent fibers 101 also hydrogen-bond to each other, making it easier to maintain an intertwined state. Therefore, even when the absorbent core 10 extends to the side edges 1ab and 1cd of the absorbent sheet 1, as in the absorbent sheet 1 of the first embodiment, or when the absorbent core 10 is exposed from the side of the absorbent sheet 1, the detachment of the absorbent core 10 from the absorbent sheet 1 can be suppressed, and the absorption performance of the absorbent sheet 1 can be maintained.

[0080] Furthermore, the presence of pulp fibers in the liquid absorbent fiber 101 (absorbent core 10) and the presence of cellulose fibers in the core wrap sheets 13 and 14 can be confirmed by well-known methods. For example, this can be confirmed by using identification dyes to color the fibers or by observing the fibers with an optical microscope. However, the method is not limited to the above; the liquid absorbent fiber 101 does not need to contain pulp fibers, and the core wrap sheets 13 and 14 do not need to contain cellulose fibers.

[0081] <<Manufacturing method for absorbent sheet 1>> Figure 5 is an explanatory diagram of the manufacturing method for the absorbent continuum 2. Figure 6 is an explanatory diagram of the manufacturing method for the absorbent sheet 1. Next, an example of the manufacturing method for the absorbent sheet 1 will be described. In the manufacturing apparatus 40 and 50 shown in Figures 5 and 6, the longitudinal direction (longitudinal direction) of the absorbent sheet 1 (absorbent core 10) corresponds to the transport direction (MD direction) of the manufacturing apparatus 40 and 50, and the transverse direction of the absorbent sheet 1 corresponds to the CD direction which intersects the transport direction of the manufacturing apparatus 40 and 50. However, this is not limited to this, and the opposite direction may also be used.

[0082] Figure 5 shows the manufacturing apparatus 40 for the absorbent continuum 2. The absorbent continuum 2 is formed by laminating the first core wrap sheet continuum 13', the absorbent core continuum 10', and the second core wrap sheet continuum 14'. The manufacturing apparatus 40 has supply rollers 41 and 43 for supplying materials, an air laid machine 42, a water spray 44, a press roller 45, and a winding roller 46.

[0083] In the manufacturing method for the absorbent continuous 2, a continuous 14' of the second core wrap sheet is supplied to the manufacturing line by a supply roller 41. Absorbent cores 10 (liquid absorbent fibers 101 and superabsorbent polymer 102) are deposited on the continuous 14' of the second core wrap sheet, which is conveyed in the conveying direction by a conveying device (such as a conveyor belt or drive roller) not shown, by an air-laid machine 42. Absorbent cores 10 are continuously supplied from the air-laid machine 42. In Figure 5, the continuous 14' of the second core wrap sheet is conveyed horizontally, but the method is not limited to this, and the continuous 14' of the second core wrap sheet may be conveyed while wrapped around a rotating drum.

[0084] Next, the supply roller 43 supplies the continuous first core wrap sheet 13' onto the continuous 10' of the absorbent core. Then, the water spray 44 sprays water onto the laminate of the continuous first core wrap sheet 13', the continuous absorbent core 10', and the continuous second core wrap sheet 14'. After that, the press roller 45 evenly presses the entire surface of the laminate in the thickness direction. The press roller 45 consists of a pair of rollers and may or may not be heated, but heating allows for stronger pressing of the laminate.

[0085] This makes it possible to manufacture an absorbent sheet 1 in which the absorbent core 10 and the core wrap sheets 13 and 14 are hydrogen-bonded and the hydrogen-bonded state is easily maintained. Note that the position of the water spray 44 is not limited to the position shown in Figure 5, and for example, it may be before the supply of the continuous body 13' of the first core wrap sheet, or it may be provided at multiple locations, or water may be sprayed from below or from both the top and bottom.

[0086] In this way, a continuous block of absorbent material 2 is manufactured, and the continuous block of absorbent material 2 is wound up by a winding roller 46. The roll of the continuous block of absorbent material 2 is set in the manufacturing apparatus 50 of the absorbent sheet 1 shown in Figure 6.

[0087] The manufacturing apparatus 50 for the absorbent sheet 1 includes supply rollers 51, 53, and 55, adhesive dispensing sections 52 and 54 for dispensing hot melt adhesive, a water spray 56, compression rollers 57 and 58, and a cutting roller 59.

[0088] The manufacturing method for the absorbent sheet 1 is as follows. First, adhesive is applied to the upper surface of the continuous back sheet 12' supplied from the supply roller 51 by the adhesive discharge unit 52, and then the continuous absorbent material 2 supplied from the supply roller 53 is laminated on top of it. Furthermore, adhesive is applied to the upper surface of the continuous absorbent material 2 by the adhesive discharge unit 54, and then the continuous surface sheet 11' supplied from the supply roller 55 is laminated on top of it. In this way, a continuous laminate 1' is formed by laminating a continuous surface sheet 11' that is continuous in the transport direction, a continuous absorbent core 2 that is continuous in the transport direction, and a continuous back sheet 12' that is continuous in the transport direction.

[0089] Next, water is sprayed onto the continuous laminate 1' by the water spray 56. This creates hydrogen bonds between the cellulose-based materials. As a result, an absorbent sheet 1 can be manufactured in which the constituent materials are strongly bonded together. Note that the position and number of water sprays 56 are not limited to those shown in Figure 6.

[0090] Next, a vertical compression section 22 is formed by the compression roller 57, and a horizontal compression section 22 is formed by the compression roller 58. Each compression roller 57, 58 consists of a pair of rollers, and a protrusion corresponding to the shape of the compression section 20 is formed on the outer surface of one or both of the rollers. The compression rollers 57, 58 may or may not be heated, but heating them allows for stronger compression of the laminate.

[0091] Finally, the continuous laminate 1' is cut by the cutting roller 59. The cutting roller 59 consists of a pair of rollers, with a cutter blade provided on the outer surface of one roller according to the cutting position, and the other roller receiving the cutter blade of the other roller.

[0092] At this time, while the continuous laminate 1' is conveyed in the conveying direction, it is cut so that the length of the continuous laminate 1' in the conveying direction matches the length of the absorbent sheet 1 in the longitudinal or transverse direction. In this embodiment, the continuous laminate 1' is intermittently cut in the conveying direction at intervals of the longitudinal length Xl of the absorbent sheet 1. If the conveying direction corresponds to the transverse direction of the absorbent sheet 1, the continuous laminate 1' is intermittently cut in the conveying direction at intervals of the transverse length Xw of the absorbent sheet 1.

[0093] This makes it possible to manufacture an absorbent sheet 1 in which the absorbent core 10 extends to a pair of side edges 1a and 1b of the absorbent sheet 1 in the direction corresponding to the conveying direction (in this case, the longitudinal direction). Furthermore, it is possible to manufacture an absorbent sheet 1 in which the absorbent core 10 is exposed on the side surface of the absorbent sheet 1 in the direction corresponding to the conveying direction.

[0094] Furthermore, in the above manufacturing method, it is preferable to make the length of the continuous section 11' to 14' of each sheet the same in the CD direction (lateral direction), and deposit the absorbent core 10 across the entire width of the continuous section 11' to 14' of the sheet. By doing so, the absorbent core 10 is present up to the pair of side edges 1c, 1d of the absorbent sheet 1 in the direction corresponding to the CD direction (in this case, the lateral direction), and an absorbent sheet 1 can be manufactured in which the absorbent core 10 is exposed on the side surface of the absorbent sheet 1 in the direction corresponding to the CD direction.

[0095] When manufacturing a rectangular absorbent sheet 1 as shown in Figure 1, it is preferable to cut the continuous laminate 1' along a straight cutting line aligned with the CD direction. If the absorbent sheet 1 is not rectangular, for example, the continuous laminate 1' may be cut using the same mold as the shape of the absorbent sheet 1. In this case as well, the absorbent core 10 will be exposed on the side surface of the absorbent sheet 1 in the direction corresponding to the transport direction.

[0096] Here, a common manufacturing apparatus for absorbent cores (not shown) is known to utilize a pattern drum. A pattern drum is a rotating drum on which multiple molds (recesses) corresponding to the shape of the absorbent core are provided at predetermined intervals on the outer surface. Suction holes are provided on the bottom surface of the molds, and liquid absorbent fibers or superabsorbent polymers scattered from a duct opposite the pattern drum are deposited into the molds. The absorbent cores deposited in the molds are sequentially released from the pattern drum and transferred to a core wrap sheet or the like.

[0097] However, in manufacturing absorbent cores using pattern drums, it can be difficult to cleanly release the absorbent core from the mold, and when transferring the absorbent core to the core wrap sheet, liquid absorbent fibers may become airborne or superabsorbent polymers may roll around. As a result, it is difficult to distribute the material evenly in the planar direction of the absorbent core, and material variation tends to be particularly large at the outer edge of the absorbent core. Consequently, the absorption performance at the outer edge of the absorbent core may be insufficient, or it may be necessary to pile up more material than necessary to compensate for this deficiency.

[0098] In contrast, according to the manufacturing method of the absorbent core 10 illustrated in Figure 5, since the liquid absorbent fibers 101 and the superabsorbent polymer 102 are deposited on the core wrap sheet (continuum), problems that occur when using a conventional pattern drum (such as inability to neatly cut out the absorbent core and variations in the material when transferring the absorbent core) are less likely to occur. Therefore, compared to the case where a pattern drum is used, the absorbent core 10 can be evenly distributed across the entire plane of the absorbent sheet 1.

[0099] Therefore, when pressure is applied to the absorbent core 10 in the thickness direction by the press roller 45 shown in Figure 5 or the compression rollers 57, 58 shown in Figure 6, the force is easily applied evenly. As a result, the absorbent core 10 and the sheet member can be firmly joined in the thickness direction. Therefore, even if the absorbent core 10 extends to the side edges 1ab, 1cd of the absorbent sheet 1, as in the absorbent sheet 1 of the first embodiment, or if the absorbent core 10 is exposed on the side surface of the absorbent sheet 1, the detachment of the absorbent core 10 from the absorbent sheet 1 can be suppressed. However, the above manufacturing method is just one example and is not limited thereto; for example, the absorbent core 10 may be manufactured using a pattern drum.

[0100] <<Example of absorbent sheet 1: Measurement of weight variation>> Figure 7A is an explanatory diagram of the method for measuring the weight variation of absorbent sheet 1, and Figure 7B shows the measurement results of the weight variation of absorbent sheet 1. Samples of absorbent sheet 1 (examples and comparative examples) were actually prepared, and the weight variation of absorbent sheet 1 was measured.

[0101] The samples in the examples were manufactured using the manufacturing methods shown in Figures 5 and 6. The planar shape of the samples in the examples was a rectangle, with a vertical length Xl (440 mm) and a horizontal length Xw (320 mm). The absorbent core 10 was manufactured using an airlaid machine, with a basis weight of 75 g / m² for the liquid absorbent fibers (pulp fibers). 2 The basis weight of the superabsorbent polymer is 63 g / m². 2 As shown in Figures 2A and 2B, the absorbent core 10 is located along the four side edges 1a to 1d of the absorbent sheet 1 and is exposed on all four sides of the absorbent sheet 1. In addition, the core wrap sheets 13 and 14 are made of tissue paper (basis weight 13 g / m2), and the surface sheet 11 is made of air-through nonwoven fabric (basis weight 22 g / m2). 2 ) and the back sheet 12 is made of resin film (basis weight 18 g / m²). 2 )

[0102] Also, as shown in Fig. 5, the sample of the embodiment was flat-pressed with a pressing roller heated to 180°C for the absorbent core 10 and the core wrap sheets 13 and 14. Then, as shown in Fig. 6, after all the materials were laminated, water was sprayed onto the materials, and a squeezing portion 20 was formed with a squeezing roller heated to 65°C. Similar to Fig. 1, a horizontal squeezing portion 21 with a width of 5 mm and a vertical squeezing portion 22 were formed at positions 7 mm inside from the side edges 1a to 1d of the absorbent sheet 1. Although no adhesive was provided between the absorbent core 10 and the core wrap sheets 13 and 14, an adhesive was provided between the surface sheet 11 and the core wrap sheet 13, and between the back sheet 13 and the core wrap sheet 14.

[0103] The sample of the comparative example has the same shape and the same size (440 mm × 320 mm) as the sample of the embodiment. However, unlike the sample of the embodiment (Fig. 1), the horizontal squeezing portion 21 and the vertical squeezing portion 22 are not formed. Also, the basis weight of the liquid-absorbent fiber (pulp fiber) constituting the absorbent core 10 (75 g / m 2 ), and the basis weight of the superabsorbent polymer 102 (63 g / m 2 ) are the same as those of the embodiment. However, in the comparative example, an absorbent core was manufactured using a patterned drum. Specifically, a part of the absorbent core manufactured with the molding die of the patterned drum (liquid-absorbent fiber: 75 g / m 2 , superabsorbent polymer: 18 g / m 2 ) was used as the absorbent core 10 by spraying a superabsorbent polymer (45 g / m 2 ) on its surface to form a layer of the superabsorbent polymer. Also, in the sample of the comparative example, the absorbent core is smaller than the absorbent sheet 1, and a region where the absorbent core 10 does not exist was provided at the outer peripheral edge portion of the absorbent sheet 1 (width: 25 to 30 mm). In addition, the core wrap sheets 13 and 14 were made of tissue (basis weight of the front side: 13.5 g / m 2 , basis weight of the back side: 13 g / m 2 ), the surface sheet 11 was made of an air-through nonwoven fabric (basis weight: 22 g / m 2 ), and the back sheet 12 was made of a resin film (basis weight: 18 g / m 2 ).

[0104] In addition, in the comparative example sample, the core wrap sheets 13 and 14 and the absorbent core 10 were joined with adhesive, and no flat pressing was performed. The surface sheet 11 and the core wrap sheet 13, and the core wrap sheet 14 and the back sheet 12 were also joined with adhesive. Furthermore, in the comparative example, no water spraying was performed before flat pressing or the formation of the compressed sections 21 and 22.

[0105] Next, the weight variation of the absorbent sheet of the example and the absorbent sheet of the comparative example was measured. The measurement method was as follows. First, as shown in Figure 7A, the rectangular absorbent sheet was divided into square regions with a vertical length of 40 mm and a horizontal length of 40 mm. The region where the absorbent core 10 is present throughout the entire square region was defined as the "divided region". The absorbent sheets of the example and comparative example had a vertical length of 440 mm and a horizontal length of 320 mm. Therefore, the absorbent sheet was divided into 11 vertical sections and 8 horizontal sections, resulting in 88 regions (A1~A11, B1~B11...H1~H11).

[0106] In the example sample, the absorbent core 10 is present from the side edges 1a to 1d of the absorbent sheet 1, so all 88 regions become divided regions. In the comparative example sample, the absorbent core 10 is slightly smaller than the absorbent sheet 1, so 54 regions (B2 to B10, C2 to C10...G2 to G10), excluding the outer periphery of the absorbent sheet 1, become divided regions.

[0107] For the absorbent sheet (rectangular), it is recommended to set a certain vertex as the origin, and then divide the sheet into sections of 40mm length along one vertical direction from the origin, and also divide the sheet into sections of 40mm length along one horizontal direction from the origin. If the side lengths of the absorbent sheet are not multiples of 40, areas smaller than 40mm x 40mm should be excluded from the measurement. If the absorbent sheet is not rectangular, it is recommended to form a virtual rectangle with the longest vertical length of the absorbent sheet as one side and the longest horizontal length as one side, and then divide it into 40mm x 40mm areas as described above.

[0108] After cutting out divided regions from absorbent sheet 1, the weight (g) of each divided region is measured. Then, for each sample, the average weight (g) and standard deviation of the divided region are calculated, and the CV value (standard deviation / average value) is calculated by dividing the standard deviation by the average value. The results are shown in Figure 7B.

[0109] As shown in Figure 7B, in the comparative example sample, the average weight of each of the 54 divided regions was 0.33283 (g), and the standard deviation was 0.03615, resulting in a CV value of 10.86%. In contrast, in the example sample, the average weight of each of the 88 divided regions was 0.34942 (g), and the standard deviation was 0.02846, resulting in a CV value of 8.15%.

[0110] From the above results, it was found that the absorbent sheet 1 of the example in which the absorbent core 10 was manufactured using an airlaid machine had a smaller CV value indicating variation and smaller weight variation compared to the absorbent sheet of the comparative example in which the absorbent core 10 was manufactured using a pattern drum. Smaller weight variation in absorbent sheet 1 means that the variation in absorbent core 10 is also small. Therefore, in the absorbent sheet 1 of the example, force is more easily applied evenly to the material in the thickness direction during flat pressing and when forming the compressed section 20, and the material is bonded more firmly in the thickness direction.

[0111] Therefore, it is preferable to make the CV value, which indicates the weight variation of the divided region, 10% or less in the absorbent sheet 1 (i.e., smaller than the CV value when the absorbent core 10 is manufactured using a pattern drum). By doing so, the materials constituting the absorbent sheet 1 are more firmly bonded in the thickness direction compared to when the CV value, which indicates the weight variation of the divided region, is greater than 10%. Thus, even when the absorbent core 10 extends to the side edges 1ab,1cd of the absorbent sheet 1, as in the absorbent sheet 1 of the first embodiment, or when the absorbent core 10 is exposed on the side surface of the absorbent sheet 1, the detachment of the absorbent core 10 from the absorbent sheet 1 can be suppressed.

[0112] <<Example of absorbent sheet 1: tapping test>> Figures 8A and 8B are explanatory diagrams of the tapping test of absorbent sheet 1. Figure 9 shows the results of the tapping test. Samples of absorbent sheet 1 (Examples 1-4, Comparative Example) were actually prepared, and the tapping test was performed on the samples.

[0113] The composition and manufacturing method of the samples were generally the same as those used for measuring weight variation. However, the sample size was set to 100 mm in the vertical direction and 60 mm in the horizontal direction. In the comparative example samples as well, the absorbent core 10 was present along the four side edges 1a to 1d of the absorbent sheet 1, so that the absorbent core 10 was exposed on all four sides of the absorbent sheet 1. In all samples, as in Figure 1, horizontal and vertical compression sections 21 and 22, each 5 mm wide, were formed 7 mm inward from the side edges 1a to 1d of the absorbent sheet 1. In addition, in the samples of Examples 1 to 4, the basis weight of the superabsorbent polymer (SAP) was varied, as shown in Figure 9.

[0114] The tapping test will be conducted using the following method. (1) First, the absorbent sheet 1 (sample) before absorption (dry state) is set on a vibrator 60 that reciprocates in a direction (thickness direction) perpendicular to the plane of the absorbent sheet 1. As shown in Figure 8A, the absorbent sheet 1 is set so that its lateral direction is aligned with the vertical direction, and the chuck portion 601 of the vibrator 60 grips the absorbent sheet 1 from below. At this time, in order to prevent the absorbent sheet 1 from sagging, the area gripped by the chuck portion 601 is set to be an area with a length of about 30-50% of the length Xw of the lateral edge of the absorbent sheet 1, and an area with a length of about 10-30% of the length Xl of the lateral edge of the absorbent sheet 1.

[0115] (2) Next, a pair of striking plates 61 and 62 (for example, acrylic plates) are fixed and installed at a position that contacts a part of the plane of the absorbent sheet 1. The pair of striking plates 61 and 62 are spaced apart in the direction of motion that intersects the plane of the absorbent sheet 1. Also, as shown in Figure 8B, the absorbent sheet 1 is placed between the pair of striking plates 61 and 62. The spacing between the pair of striking plates 61 and 62 should be approximately the maximum thickness of the absorbent sheet 1 (for example, 5 mm). Furthermore, in order to prevent the detachment of the absorbent core 10 (especially the superabsorbent polymer 102) from the absorbent sheet 1 from being hindered, the area struck by the striking plates 61 and 62 should be an area with a length of approximately 30-50% of the length Xw of the lateral edge of the absorbent sheet 1 and an area with a length of approximately 10-30% of the length Xl of the lateral edge of the absorbent sheet 1. Furthermore, the striking plates 61 and 62 are designed to strike the end of the absorbent sheet 1 in the longitudinal direction, on the side opposite to the side where the chuck portion 601 is located.

[0116] (3) Next, the vibrating shaft portion 602 extending vertically downward from the chuck portion 601 of the vibrator 60 is vibrated to cause the absorbent sheet 1 to reciprocate between the pair of striking plates 61 and 62 in the direction of motion (thickness direction) that intersects the plane of the absorbent sheet 1. Specifically, the absorbent sheet 1 is reciprocated for one minute at a speed at which the reciprocating motion of the absorbent sheet 1 (movement of the absorbent sheet 1 in one direction of motion and movement of the absorbent sheet 1 in the other direction of motion) occurs 1000 times per minute. At this time, a part of the plane of the absorbent sheet 1 comes into contact with the pair of striking plates 61 and 62, and vibration occurs in the absorbent sheet 1. Alternatively, the striking plates 61 and 62 may be reciprocated relative to the absorbent sheet 1.

[0117] After the tapping test, the superabsorbent polymer (SAP) was visually inspected to see if it had detached from the sample, and the results are shown in Figure 9. Figure 9 also shows the weight (g) of the sample before the tapping test. The weight of the sample after the tapping test was also measured, and the "detachment amount (g)" was calculated by subtracting the weight of the sample after the test from the weight of the sample before the test. Furthermore, the "detachment rate (%)" was calculated by dividing this detachment amount (g) by the weight of the sample before the tapping test. These results are also shown in Figure 9. In this example, three samples were prepared for each type of sample, and the average value of the results of the tapping test performed on these three samples is shown in Figure 9.

[0118] As shown in Figure 9, the shedding rate of the comparative example sample (1.33%) was higher than that of the samples from Examples 1-4 (0.13-0.45%). Furthermore, shedding of the superabsorbent polymer was observed in the comparative example sample, but not in the samples from Examples 1-4.

[0119] This is likely because, compared to the comparative example sample in which the absorbent core 10 was manufactured using a pattern drum, the samples from Examples 1 to 4, in which the absorbent core 10 was manufactured using an airlaid machine, showed less weight variation. This makes it easier to apply force uniformly to the material in the thickness direction when forming the compressed sections 21 and 22, resulting in a stronger bond between the materials in the thickness direction.

[0120] Therefore, it is preferable that the detachment rate when the absorbent sheet 1 is subjected to a tapping test is 0.5% or less (similar to the detachment rate in Examples 1 to 4 where the SAP did not detach). By doing so, the detachment of the absorbent core 10 from the absorbent sheet 1 can be suppressed compared to when the detachment rate when the tapping test is greater than 0.5%. Furthermore, it is preferable that no detachment of the superabsorbent polymer occurs when the absorbent sheet 1 is subjected to a tapping test.

[0121] By doing so, even when the absorbent core 10 extends to the side edges 1ab, 1cd of the absorbent sheet 1, as in the absorbent sheet 1 of the first embodiment, or when the absorbent core 10 is exposed on the side surface of the absorbent sheet 1, the detachment of the absorbent core 10 from the absorbent sheet 1 can be suppressed. The absorption performance of the absorbent sheet 1 (especially the side edges 1ab, 1cd) is ensured.

[0122] ===Second Embodiment=== Figures 10A and 10B are explanatory diagrams of the absorbent sheet 1 of the second embodiment. In the absorbent sheet 1 of the first embodiment, the absorbent core 10 is present up to the four side edges 1ab, 1cd of the absorbent sheet 1 in the longitudinal and transverse directions. In contrast, in the absorbent sheet 1 of the second embodiment, it is sufficient that the absorbent core 10 is exposed on each side surface along the thickness direction of at least one of the pair of side edges of the absorbent sheet 1 in the longitudinal and transverse directions, as shown in Figure 10B.

[0123] Therefore, as long as the absorbent core 10 is visible from the side of the absorbent sheet 1, the absorbent core 10 may be located inside the side edges 1ab, 1cd of the absorbent sheet 1. Also, as shown in Figure 10A, the absorbent core 10 does not have to be exposed on each side of the pair of side edges 1a, 1b in one of the directions (here, the vertical direction). For example, the pair of side surfaces of the absorbent core 10 in the vertical direction may be covered with a sheet as shown in Figure 3 above. Alternatively, as shown in Figure 10A, the absorbent core 10 may be located relatively far inside from the side edges 1a, 1b of the absorbent sheet 1, and the surface sheet 11 and back sheet 12 extending from the absorbent core 10 may be joined together.

[0124] In the above case as well, the excrement is more easily absorbed from the side of the absorbent sheet 1 where the absorbent core 10 is exposed. Also, since the absorbent core 10 is visible from the side of the absorbent sheet 1, the absorbent core 10 extends to the side edges 1a to 1d or close to them. Therefore, it can absorb excrement excreted on the outer edge of the absorbent sheet 1, and it can prevent the absorbent surface from being covered by a peeled-over sheet. Thus, the amount of excrement leaking outside the absorbent sheet 1 can be reduced. In addition, the folding process of the sheet covering the absorbent core 10 is unnecessary or reduced, making manufacturing easier. Furthermore, since the area of ​​the sheet used to cover the sides of the absorbent core 10 is reduced or not required, sheet consumption can be reduced, and costs can be lowered.

[0125] While embodiments of the present invention have been described above, these embodiments are intended to facilitate understanding of the present invention and are not intended to limit its interpretation. Furthermore, the present invention can be modified or improved without departing from its spirit, and it goes without saying that the present invention includes equivalents thereof. [Explanation of symbols]

[0126] 1. Absorbent sheet, 10 absorbent cores, 101 Liquid absorbent fiber, 102 Superabsorbent polymer, 11 Front sheet, 12 Back sheet, 13,14 Core wrap sheet, 20 Compression section, 21 Horizontal compression section, 22 Vertical compression section, 40 Manufacturing equipment, 41, 43 Feeding rollers, 42 Air raiding machine, 44 Water spray, 45 Press roller, 46 Winding roller 50 Manufacturing equipment, 51, 53, 55 Feeding rollers, 52, 54 Adhesive dispensing part, 56 Water spray, 57, 58 Compression roller, 59 Cutting roller, 60 Vibrator, 61, 62 Beating boards,

Claims

1. It has a vertical direction, a horizontal direction, and a thickness direction, An absorbent core comprising liquid-absorbing fibers and a superabsorbent polymer, A liquid-permeable surface sheet disposed on the surface side in the thickness direction of the absorbent core, A back sheet disposed on the back side in the thickness direction of the absorbent core, A method for manufacturing an absorbent sheet having, A step of forming a continuous laminate by stacking a continuous surface sheet, a continuous absorbent core, and a continuous back sheet, all of which are continuous in the transport direction, while transporting them in the transport direction. A step of transporting the continuous laminate in the transport direction and cutting it so that the length of the continuous laminate in the transport direction is equal to the length of the absorbent sheet in the longitudinal or transverse direction, A method for manufacturing an absorbent sheet, characterized by having the following:

2. It has a vertical direction, a horizontal direction, and a thickness direction, An absorbent core comprising liquid-absorbing fibers and a superabsorbent polymer, A liquid-permeable surface sheet disposed on the surface side in the thickness direction of the absorbent core, A back sheet disposed on the back side in the thickness direction of the absorbent core, A method for manufacturing an absorbent sheet having, A step of forming a continuous laminate by stacking a continuous surface sheet, a continuous absorbent core, and a continuous back sheet, all of which are continuous in the transport direction, while transporting them in the transport direction. The process of cutting the laminate at intervals of the length of the absorbent sheet in the longitudinal or transverse direction while conveying the continuous laminate in the conveying direction, A method for manufacturing an absorbent sheet, characterized by having the following:

3. A method for manufacturing an absorbent sheet according to claim 1 or 2, A method for manufacturing an absorbent sheet, characterized in that, in the cutting step, the laminate is cut such that the absorbent core is exposed on the side surface of the absorbent sheet.

4. A method for manufacturing an absorbent sheet according to any one of claims 1 to 3, A method for producing an absorbent sheet, characterized in that the liquid absorbent fibers constituting the absorbent core are cellulose fibers or hydrophilically treated thermoplastic synthetic fibers.

5. A method for manufacturing an absorbent sheet according to any one of claims 1 to 4, The absorbent sheet has a rectangular or substantially rectangular shape when viewed in the thickness direction. When the region extending inward from the longitudinal or transverse side edge of the absorbent sheet by a length equal to the average thickness of the absorbent sheet is defined as the side edge portion, A method for manufacturing an absorbent sheet, characterized in that, in the cutting step, the laminate is cut such that the absorbent core exists continuously from the center of the absorbent sheet in the longitudinal direction to a position beyond the inner edge of the side edge, and also exists continuously from the center of the absorbent sheet in the transverse direction to a position beyond the inner edge of the side edge.

Images