JP7520743B2 - Absorbent body and method for manufacturing the absorbent body - Google Patents

Description

The present invention relates to an absorbent body and a method for manufacturing an absorbent body.

Patent Document 1 discloses an absorbent body having an absorbent core in which an absorbent polymer is contained in an aggregate of liquid-absorbent fibers, and a core wrap sheet covering the upper and lower surfaces of the absorbent core. Patent Document 1 describes that the absorbent polymer is evenly distributed in the planar direction of the absorbent core in order to prevent a decrease in absorption performance in areas where the polymer density is low due to the movement of the absorbent polymer, and to prevent a crisp feeling in areas where the polymer density is high. Specifically, the absorbent core is divided into multiple regions (30 mm x 30 mm square regions) in the longitudinal and lateral directions of the absorbent body, and when the absorbent polymer content is measured for each divided region, the ratio (row standard deviation/row average) indicating the variation in absorbent polymer content is set to 0.20 or less for both the row of divided regions in the longitudinal direction and the row of divided regions in the lateral direction.

Patent No. 4711946

However, in Patent Document 1, among the regions into which the absorbent core is divided, those that do not overlap with the absorbent core are excluded from the measurement. Therefore, the sides in the width direction of the hourglass-shaped absorbent core are excluded from the measurement of the absorbent polymer content, and the variation in the polymer content of the sides of the absorbent core is not taken into consideration. If the absorption performance of the sides of the absorbent core is not taken into consideration in this way, the absorption performance of the sides of the absorbent core is reduced, which leads to lateral leakage of excreted liquid.
In addition, in the absorbent body of Patent Document 1, the upper and lower surfaces of the absorbent core are simply fixed to the core wrap sheet via an adhesive, so that the movement of the absorbent polymer and fibers cannot be prevented, and they may fall out of the gaps in the core wrap sheet. In particular, if the polymer or the like falls out of the side of the absorbent core, the absorption performance of the side will decrease, which may lead to side leakage of excreted liquid.

The present invention was made in consideration of the above-mentioned problems, and its purpose is to prevent the high-absorbency polymer and liquid-absorbent fibers from falling off from the lateral sides of the absorbent body, thereby maintaining the absorption performance of the sides of the absorbent body.

The main invention for achieving the above-mentioned object is an absorbent body having a vertical direction, a horizontal direction and a thickness direction, and having an absorbent core and a core wrap sheet arranged on both sides of the absorbent core in the thickness direction, wherein the absorbent core has a liquid absorbent fiber and a superabsorbent polymer, and the absorbent body has a compressed portion in which at least a pair of side portions in the horizontal direction are compressed in the thickness direction, and the portion of the compressed portion of the side portion of the absorbent body in which the liquid absorbent fiber and the superabsorbent polymer are arranged is divided into six in the vertical direction and into two regions in the horizontal direction as divided regions, and when an area ratio is calculated for each divided region by dividing the area occupied by the liquid absorbent fiber and the superabsorbent polymer when the divided region is viewed in a plane in the thickness direction by the area of the divided region, the CV value indicating the variation in the area ratio is 26% or less.
Other features of the present invention will become apparent from the following detailed description of the present invention and the accompanying drawings.

The present invention makes it possible to prevent the high-absorbency polymer and liquid-absorbent fibers from falling off from the lateral sides of the absorbent body, thereby maintaining the absorption performance of the sides of the absorbent body.

FIG. 1A is a plan view of the absorbent body 1 as viewed in the thickness direction, FIG. 1B is a side view of the absorbent body 1 as viewed in the lateral direction, and FIG. 1C is a front view of the absorbent body 1 as viewed in the longitudinal direction. 1 is an explanatory diagram of divided regions r1 to r12 of the compression section 4. FIG. 3A to 3D are diagrams showing modified examples of the absorbent body 1. FIG. 4A to 4E are explanatory diagrams of a method for measuring the occupied area ratio of the absorbent core 10. FIG. 10 is an explanatory diagram of second divided regions r1'-r12' of a compressed portion 4 at an end portion in the longitudinal direction of an absorbent body 1. FIG. 6A and 6B are explanatory diagrams of a drop-off test of the superabsorbent polymer 12 from the absorbent body 1. FIG. 3A to 3C are explanatory diagrams of a manufacturing method for the absorbent body 1. 1 is a graph showing the measurement results of Example 1 and Comparative Example 1 (high basis weight absorbent core). 1 is a graph showing the measurement results of Example 2 and Comparative Example 2 (low basis weight absorbent core).

At least the following matters will become apparent from the description of this specification and the accompanying drawings.
An absorbent body having a vertical direction, a horizontal direction, and a thickness direction, and having an absorbent core and a core wrap sheet arranged on both sides of the absorbent core in the thickness direction, wherein the absorbent core has a liquid absorbent fiber and a superabsorbent polymer, and the absorbent body has a compressed portion in which at least a pair of side portions in the horizontal direction are compressed in the thickness direction, and the portion of the compressed portion of the side portion of the absorbent body in which the liquid absorbent fiber and the superabsorbent polymer are arranged is divided into six in the vertical direction and into two regions in the horizontal direction as divided regions, and when an area ratio is calculated for each divided region by dividing the area occupied by the liquid absorbent fiber and the superabsorbent polymer when the divided region is viewed in a plane in the thickness direction by the area of the divided region, the CV value indicating the variation in the area ratio is 26% or less.

With this type of absorbent body, the planar variation of the absorbent core arranged on the side is small, and the strength of the compressed part formed on the side can be made uniform. Therefore, the entire planar area of the side of the absorbent body is firmly compressed, which prevents the absorbent core from falling off from the side, and maintains the absorption performance of the side.

The absorbent body is characterized in that the compressed portions are provided at a pair of ends 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 fiber and the superabsorbent polymer are arranged is divided into six in the transverse direction, and the region divided into two in the longitudinal direction is defined as a second divided region, and when a second area ratio is calculated for each of the second divided regions by dividing the area occupied by the liquid absorbent fiber and the superabsorbent polymer when the second divided region is viewed in a plane in the thickness direction by the area of the second divided region, a CV value indicating the variation in the second area ratio is 26% or less.

With this type of absorbent body, the planar variation of the absorbent core arranged at the longitudinal end is small, and the entire planar area of the end is firmly compressed. This prevents the absorbent core from falling off the longitudinal end of the absorbent body, and maintains the absorption performance of the end.

The absorbent body is characterized in that the superabsorbent polymer does not fall off from the absorbent body even when the absorbent body before absorption is moved back and forth between a pair of beating plates in a direction intersecting the plane of the absorbent body, and a predetermined part of the plane of the absorbent body is brought into contact with the pair of beating plates at a speed of 1000 times per minute for one minute.

With this type of absorbent body, the entire flat area of the sides and longitudinal ends is firmly compressed, so even if the absorbent body vibrates, the highly absorbent polymer is prevented from falling off, and the absorption performance of the sides and longitudinal ends is maintained.

The absorbent body is characterized in that at least in the compressed portions of the sides of the absorbent body, no adhesive is provided between the absorbent core and the core wrap sheet in the thickness direction.

With this type of absorbent, the absorption performance of the sides can be prevented from being hindered by the adhesive, and the absorption performance of the sides can be maintained. In addition, since the planar variation of the absorbent core arranged on the sides of the absorbent is small and the entire planar area of the sides is firmly compressed, peeling (opening) of the core wrap sheet can be suppressed even without the use of adhesive.

The 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 of the absorbent body.

Such an absorbent body can prevent the adhesive from impairing the absorption performance of the absorbent body over its entire flat surface.

The absorbent body is characterized in that the liquid absorbent fibers include pulp fibers, the core wrap sheet includes cellulosic fibers, and the pulp fibers are hydrogen bonded to the cellulosic fibers.

With this type of absorbent body, the liquid absorbent fiber and the core wrap sheet are firmly bonded together by hydrogen bonding. In particular, because compressed portions are formed on the sides of the absorbent body, the liquid absorbent fiber and the core wrap sheet are more strongly hydrogen bonded and this state is maintained. This further prevents the core wrap sheet from peeling (opening) on the sides of the absorbent body.

The absorbent body is characterized in that a pair of side portions in the lateral direction of the core wrap sheet arranged on one side in the thickness direction are not folded back to the other side in the thickness direction to cover the side edges of the absorbent core in the lateral direction, and a pair of side portions in the lateral direction of the core wrap sheet arranged on the other side in the thickness direction are not folded back to the one side in the thickness direction to cover the side edges of the absorbent core.

With this type of absorbent body, the planar area of the core wrap sheet can be reduced, leading to cost reduction. In addition, because the side edges of the absorbent core are exposed, the absorption performance from the side edges is improved. Furthermore, because there is little variation in the planar direction of the absorbent core arranged on the side of the absorbent body and the entire planar area of the side is firmly compressed, even if the side edges of the absorbent core are not covered with the core wrap sheet, it is possible to prevent the absorbent core from falling out of the absorbent body.

Also, a method for manufacturing an absorbent body having a longitudinal direction, a lateral direction, and a thickness direction, an absorbent core, and a first core wrap sheet and a second core wrap sheet arranged on both sides of the absorbent core in the thickness direction, the method comprising: a depositing step in which the liquid absorbent fiber and superabsorbent polymer of the absorbent core are deposited on the first core wrap sheet transported in the transport direction; a supplying step in which the second core wrap sheet is supplied onto the liquid absorbent fiber and the superabsorbent polymer deposited in the depositing step; a squeezing step in which at least the portions of the laminate of the first core wrap sheet, the liquid absorbent fiber, the superabsorbent polymer, and the second core wrap sheet that correspond to a pair of side portions in the lateral direction of the absorbent body are squeezed in the thickness direction of the laminate to form compressed portions; and a cutting step in which the laminate is cut on the compressed portions to form the outer edge of the absorbent body.

This method of manufacturing an absorbent body can reduce the planar variation of the absorbent core arranged on the side of the absorbent body compared to, for example, a manufacturing method in which the absorbent core is die-cut and transferred to a core wrap sheet. In addition, because the cut is made on the compressed part of the laminate, the side edge of the absorbent body in the lateral direction can be cut neatly.

A method for manufacturing such an absorbent body, characterized in that it includes a spraying step, which is performed after the deposition step and before the squeezing step, in which water is sprayed onto at least one of the first core wrap sheet, the liquid absorbent fiber and the superabsorbent polymer, and the second core wrap sheet.

According to this method of manufacturing an absorbent body, the materials that make up the absorbent body are hydrogen-bonded and firmly bonded to each other. In particular, because compressed parts are formed on the sides of the absorbent body, the materials are more strongly hydrogen-bonded and this state is maintained. This makes it possible to further prevent peeling (opening) of the core wrap sheet on the sides of the absorbent body.

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<<Basic configuration of absorbent body 1>>
FIG. 1A is a plan view of the absorbent body 1 as viewed in the thickness direction, FIG. 1B is a side view of the absorbent body 1 as viewed in the lateral direction, and FIG. 1C is a front view of the absorbent body 1 as viewed in the longitudinal direction.

The absorbent body 1 has a vertical direction, a horizontal direction, and a thickness direction that are perpendicular to each other, and has a rectangular planar shape when viewed in the thickness direction. The planar shape of the absorbent body 1 is not limited to a rectangle, and may be various shapes such as a square, an hourglass shape, or an ellipse. When the vertical and horizontal lengths are different as in the absorbent body 1 of this embodiment, the long direction of the absorbent body 1 is defined as the vertical direction, and the short side direction of the absorbent body 1 is defined as the horizontal direction.

The absorbent body 1 has 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 a mixture of a collection of liquid-absorbent fibers 11 and a super absorbent polymer 12 (SAP: Super Absorbent Polymer).

The core wrap sheets 2, 3 are liquid-permeable sheets. Examples of the core wrap sheets 2, 3 include tissue, nonwoven fabric, and perforated film. Examples of the liquid-absorbent fibers 11 in the absorbent core 10 include cellulosic fibers (e.g., pulp fibers, non-wood fibers such as cotton and hemp, and recycled fibers such as rayon) and thermoplastic synthetic fibers that have been hydrophilically treated (e.g., polyethylene, polypropylene, etc.).

The absorbent body 1 has a compressed portion 4 where the core wrap sheets 2, 3 and the absorbent core 10 are compressed in the thickness direction. The absorbent body 1 shown in FIG. 1A has a compressed portion 4 of a predetermined width along the outer peripheral edge of the absorbent body 1. The compressed portion 4 is a portion where the absorbent body 1 is recessed in the thickness direction compared to the surrounding area, and is thinner, and the density of the absorbent core 10 (liquid-absorbent fibers 11) is higher than the surrounding area.

The thickness of the absorbent body 1 can be compared, for example, by visually comparing it, or by using a dial thickness gauge ID-C1012C manufactured by Mitutoyo Corporation or an equivalent device to compare the values measured by applying a pressure of, for example, 3.0 gf/cm ² to a target site. In addition, the density of the absorbent core 10 can be compared, for example, by comparing images of a cross section of the absorbent body 1 cut in the thickness direction, enlarged using an electron microscope or the like.

In the compression section 4, the area of the compression section 4 may be compressed uniformly (flat), or may be compressed in a predetermined pattern. Examples of the compression section 4 compressed in a predetermined pattern include a plurality of discretely arranged dot-like compression sections, a plurality of dot-like compression sections arranged in a line, and a groove-like compression section compressed continuously in a line. The compression section 4 may also be composed of compression sections with different compression strengths (depths of depressions).

The absorbent 1 having the above configuration can be used alone, or can be incorporated into absorbent articles (e.g., disposable diapers, sanitary napkins, incontinence pads, panty liners, pet sheets, sweat pads, etc.). When the absorbent 1 is incorporated into an absorbent article, it is generally used by being disposed between a liquid-permeable sheet and a liquid-impermeable sheet.

<<Variation of absorbent core 10>>
Fig. 2 is an explanatory diagram of divided regions r1 to r12 of the compressed portion 4. Figs. 3A to 3D are diagrams showing modified examples of the absorbent body 1.

In the absorbent body 1 shown in Figures 1A to 1C, the core wrap sheets 2, 3 and the absorbent core 10 have the same planar shape and size. In other words, the absorbent core 10 exists up to a pair of side ends 1a in the horizontal direction of the absorbent body 1 and a pair of ends 1b in the vertical direction. In addition, the absorbent body 1 has a compressed portion 4 along the outer peripheral edge. Therefore, at the outer peripheral edge of the absorbent body 1, the absorbent core 10 is compressed in the thickness direction together with the core wrap sheets 2, 3.

In this way, the absorbent body 1 preferably has a compressed portion 4 in which at least a pair of lateral side portions (longitudinal side portions) are compressed in the thickness direction. In other words, the portion of the absorbent body 1 where the absorbent core 10 is located is preferably compressed in the thickness direction by the compressed portion 4.

By doing so, the core wrap sheets 2, 3 and the absorbent core 10 are firmly bonded to each other at the sides of the absorbent body 1, which prevents the core wrap sheets 2, 3 from peeling (opening up), and prevents the liquid absorbent fibers 11 and the superabsorbent polymer 12 from falling off from the peeled off parts. In addition, the liquid absorbent fibers 11 and the superabsorbent polymer 12 are entangled at high density by the compression section 4, which prevents the absorbent core 10 from moving. From this point of view, it can be said that the liquid absorbent fibers 11 and the superabsorbent polymer 12 can be prevented from falling off from the sides of the absorbent body 1.

The side portions of the absorbent body 1 in the lateral direction refer to all or part of the regions at both ends when the absorbent body 1 is divided horizontally into three. It is sufficient that the compressed portions 4 are provided in those regions (side portions) where the liquid absorbent fibers 11 and the superabsorbent polymer 12 are arranged. Therefore, as in the modified absorbent body 1 shown in Figure 3A, the compressed portions 4 do not need to reach the side ends 1a of the absorbent body 1 in the lateral direction.

Furthermore, it is preferable that the absorbent cores 10 are evenly arranged in the planar direction on a pair of lateral side portions of the absorbent 1. Specifically, as shown in FIG. 2, the compressed portion 4 on the side of the absorbent 1, where the liquid-absorbent fibers 11 and superabsorbent polymer 12 are arranged, is divided evenly into six portions in the vertical direction (longitudinal direction) and into two portions in the horizontal direction, which are defined as divided regions r. In other words, the compressed portion 4 on the side of the absorbent 1 is divided into 12 divided regions r1 to r12.

Then, for each divided region r, the occupied area ratio of the absorbent core 10 when the divided region r is viewed in a plane in the thickness direction is calculated. That is, the total occupied area of the liquid absorbent fiber 11 and the superabsorbent polymer 12 in the divided region r is divided by the area of the divided region r. In this case, the CV value, which indicates the variation in the occupied area ratio of the absorbent core 10, is set to 26% or less. The CV value is the standard deviation of the occupied area ratio of the absorbent core 10 for each of the 12 divided regions r1 to r12 divided by the average value (standard deviation/average value).

The small CV value of 26% or less and the small variation in the occupied area ratio of the absorbent core 10 when the side of the absorbent body 1 is viewed in a plane in the thickness direction means that the liquid absorbent fibers 11 and superabsorbent polymer 12 are evenly arranged in the planar direction on the side of the absorbent body 1.

The small planar variation of the absorbent cores 10 arranged on the sides of the absorbent body 1 allows the strength of the compressed parts 4 formed on the sides of the absorbent body 1 to be uniform. For example, it is possible to prevent areas from being created where strong pressure cannot be applied due to a small amount of absorbent cores 10 arranged. As a result, the entire planar area of the side of the absorbent body 1 is firmly compressed. This further prevents the liquid absorbent fibers 11 and superabsorbent polymers 12 from falling off from the sides of the absorbent body 1, and maintains the absorption performance of the sides of the absorbent body 1.

For example, when the absorbent body 1 is incorporated into an absorbent article such as a disposable diaper, the absorbent body 1 is arranged so that its vertical direction (longitudinal direction) is aligned with the longitudinal direction of the absorbent article (front-to-back direction of the wearer). This maintains the absorption performance of the sides of the absorbent body 1, thereby preventing side leakage of excrement from the absorbent article.

4A to 4E 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 fiber 11 and the superabsorbent polymer 12 when the divided region r is viewed in a plane in the thickness direction is calculated by the following method.
(1) First, an X-ray imaging device (e.g., an X-ray fluoroscopy device manufactured by Beam Sense Co., Ltd.: FLEX-M863 or equivalent) is used to X-ray the absorber 1 to be measured. The imaging conditions are a tube voltage of 35 kV, a tube current of 100 μA, a pixel size of 20×20 μm, a pixel number of 1500×1000 pixels, and a resolution of 2 μm (geometric magnification: 10 times). Images of the 12 divided regions r1 to r12 (where the absorbent core 10 is sandwiched between a pair of core wrap sheets 2, 3) defined in the absorber 1 and an area of only the pair of core wrap sheets 2, 3 are simultaneously taken. Note that, in the case where there is no area of only the core wrap sheets 2, 3 as in the absorber 1 illustrated in FIG. 1A, a sample in which the absorbent core 10 is separated from the core wrap sheets 2, 3 is prepared and photographed.
(2) Next, the captured image (FIG. 4A) is input into an image processing device (for example, a computer having installed thereon image linking software and image measurement software: UN Analyzer manufactured by Unique Corporation or equivalent analysis software).
(3) Next, the contrast of the X-rayed image is adjusted using an image processing device. The X-rayed image (FIG. 4A) is adjusted so that it becomes clearer (white areas become whiter and black areas become blacker). Specifically, the gamma correction value is set to 0.6, the brightness correction value to -21, and the contrast correction value to 13.
(4) Next, the contrast-adjusted image (FIG. 4B) is binarized by an image processing device. Specifically, the area where only the pair of core wrap sheets 2 and 3 are present is processed to be white, and the area where the absorbent core 10 is present is processed to be black. Then, the color of the binarized image (FIG. 4C) is inverted. In other words, an image (FIG. 4D) is created in which the area where the absorbent core 10 is present is white.
(5) Next, an image processing device cuts out the portions corresponding to the 12 divided regions r1 to r12 from the image created in (4) (FIG. 4D) (FIG. 4E).
(6) Finally, an image processing device (for example, a UN analyzer for measuring the degree of dispersion) is used to measure the area (A1) of each divided region r and the area (A2) of the region (white region) in which the absorbent core 10 is located within the divided region r. Then, the occupied area ratio (A2/A1) of the absorbent core 10 is calculated for each divided region r.

The configuration of the absorbent body 1 is not limited to that shown in Figures 1A to 1C. For example, as shown in Figures 3A and 3B, the absorbent core 10 may be smaller than the absorbent body 1 and may not reach the ends 1a and 1b of the absorbent body 1. In this case, the region in the compressed portion 4 on the side of the absorbent body 1 where the absorbent core 10 is present is divided into 12 regions, which are called divided regions r. The region on the side of the absorbent body 1 where the absorbent core 10 is not present may not be compressed as shown in Figure 3A, or may be compressed as shown in Figure 3B.

It is sufficient that the compressed parts 4 are provided at least on the sides of the absorbent body 1, and for example, as shown in FIG. 3C, the compressed parts 4 do not have to be provided on the ends in the longitudinal direction of the absorbent body 1. Although not shown, the compressed parts 4 may be provided not only on the outer peripheral ends of the absorbent body 1, but also in the center of the absorbent body 1. The pattern of the compressed parts 4 and the strength of compression may be varied depending on the position of the absorbent body 1 (for example, between the lateral sides and the longitudinal ends).

Furthermore, the divided regions r1 to r12 do not necessarily have to have the same shape and area. For example, in the case of an hourglass-shaped absorbent body 1 as shown in FIG. 3D, or in the case of a compressed portion 4 whose width varies depending on the vertical position (not shown), first, the length from one end of the compressed portion 4 on the side of the absorbent body 1 in the vertical direction to the other end is defined as six equal regions. Each of these six divided regions is then defined as two equal regions in the horizontal direction, resulting in twelve divided regions r1 to r12. This is also the case for the second divided regions r'1 to r'12 described below.

Figure 5 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. As in the absorbent body 1 illustrated in Figure 1A, it is preferable that the compressed portions 4 are provided not only on the lateral sides of the absorbent body 1 but also on a pair of longitudinal ends. By doing so, the core wrap sheets 2, 3 and the absorbent core 10 are firmly bonded even at the longitudinal end of the absorbent body 1, and the liquid absorbent fibers 11 and the superabsorbent polymer 12 are densely intertwined, so that the absorbent core 10 can be prevented from falling off from the longitudinal end of the absorbent body 1. The longitudinal end of the absorbent body 1 refers to a part or all of the regions at both ends when the absorbent body 1 is divided into three longitudinally.

Furthermore, it is preferable that the absorbent cores 10 are evenly arranged in the planar direction at a pair of longitudinal ends of the absorbent 1. Specifically, as shown in FIG. 5, the compressed portion 4 at the longitudinal end of the absorbent 1, where the liquid absorbent fibers 11 and the superabsorbent polymer 12 are arranged, is divided evenly into six regions in the horizontal direction, and the regions divided evenly into two regions in the vertical direction are called second divided regions r'1 to r'12.

Then, for each second divided region r', the occupied area ratio of the absorbent core 10 when the second divided region r' is viewed in a plane in the thickness direction is calculated (a second area ratio obtained by dividing the total occupied area of the liquid absorbent fiber 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 variation in the occupied area ratio of the absorbent core 10 is set to 26% or less. The occupied area ratio of the absorbent core 10 can be calculated by the method described in Figures 4A to 4E.

The small CV value of 26% or less and the small planar variation of the absorbent core 10 arranged at the longitudinal end of the absorbent body 1 allows the strength of the compressed portion 4 formed at the longitudinal end of the absorbent body 1 to be uniform. As a result, the entire planar area of the longitudinal end of the absorbent body 1 is firmly compressed, which further prevents the absorbent core 10 from falling off from the longitudinal end of the absorbent body 1, and maintains the absorption performance of the longitudinal end of the absorbent body 1. However, it is not limited to the above, and the CV value of the occupied area ratio of the absorbent core 10 at the longitudinal end of the absorbent body 1 may be greater than 26%.

It is also desirable that the absorbent body 1 has an absorption performance that allows it to be incorporated 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 relatively high, at 10% or more, preferably 30% or more, and more preferably 40% or more. It is also desirable that the mass ratio of the superabsorbent polymer 12 is as described above not only in the center of the absorbent body 1 but also in the outer peripheral end of the absorbent body 1. This improves the absorption performance of the end (side) of the absorbent body 1, and can suppress leakage of excreted liquid.

The following method can be exemplified as a method for measuring the mass of the superabsorbent polymer 12 contained in the absorbent core 10. First, an arbitrary mass of the superabsorbent polymer 12 is taken from the absorbent core 10 before absorption, neutralization titration is performed using 1 mol/L hydrochloric acid, a calibration curve is created, and the polymer coefficient of the superabsorbent polymer 12 is calculated. Next, a part to be measured is taken from the absorbent core 10 as a sample, and the mass of the sample (liquid absorbent fiber 11 + superabsorbent polymer 12) is measured. After that, the sample is placed in ion-exchanged water in which an appropriate amount of sodium chloride is dissolved, and 1 ml of 1 mol/L hydrochloric acid is injected at each time, and the amount of hydrochloric acid injected at the point when the value of the pH meter measuring the pH of the ion-exchanged water changes significantly is read. The value read is multiplied by the above-mentioned polymer coefficient to obtain the mass of SAP contained in the sample. The mass ratio of SAP can be calculated from the mass of SAP and the mass of the sample.

The superabsorbent polymer 12 in the absorbent core 10 may be either fibrous or granular, but the superabsorbent polymer 12 in this embodiment is granular. The average particle size of the granular superabsorbent polymer 12 is approximately 100 to 600 μm (microns).

The following method can be used as an example of a method for measuring the average particle size of the superabsorbent polymer 12. First, multiple (e.g., 50) superabsorbent polymers 12 are removed from the absorbent core 10 before absorption, and observed under an optical microscope or the like to measure the diameter or length of the major axis of each superabsorbent polymer 12. The average value is taken as the average particle size of the superabsorbent polymer 12.

6A and 6B are explanatory diagrams of a test for the superabsorbent polymer 12 falling off from the absorbent body 1. In the absorbent body 1 of this embodiment, the absorbent core 10 is evenly arranged in the planar direction at the side portions in the horizontal direction and the end portions in the vertical direction, and the entire planar area of the outer peripheral end portion of the absorbent body 1 is firmly compressed. Specifically, the absorbent body 1 before absorption is reciprocated between a pair of beating plates 21 and 22 in a direction intersecting the plane of the absorbent body 1 (thickness direction), and a reciprocating motion in which a predetermined part of the plane of the absorbent body 1 is abutted against the pair of beating plates 21 and 22 is performed at a speed of 1000 times per minute for one minute. Even in this case, it is preferable that the superabsorbent polymer 12 does not fall off from the absorbent body 1. In other words, it is preferable that the side portions and the end portions in the vertical direction of the absorbent body 1 are firmly compressed by the compression section 4 to such an extent that the superabsorbent polymer 12 does not fall off from the outer peripheral end portion of the absorbent body 1 even when the absorbent body 1 is vibrated. This ensures that the absorbency of the sides and longitudinal ends of the absorbent body 1 is maintained.

The shedding test of the superabsorbent polymer 12 is carried out by the following method.
(1) First, the absorbent body 1 before absorption is set on the vibrator 20 that reciprocates in a direction (thickness direction) intersecting the plane of the absorbent body 1. As shown in Fig. 6A, the absorbent body 1 is set so that its lateral direction is aligned with the vertical direction and so that the chuck portion 201 of the vibrator 20 grips the absorbent body 1 from below. At this time, in order to prevent the absorbent body 1 from sagging, the region gripped by the chuck portion 201 is set to a region that is about 30 to 50% of the length W of the end portion along the lateral direction of the absorbent body 1 and a region that is about 10 to 30% of the length L of the side portion along the vertical direction of the absorbent body 1.
(2) Next, a pair of striking plates 21, 22 (e.g., acrylic plates) are fixed and installed at a position where they abut against a part of the plane of the absorbent 1. The pair of striking plates 21, 22 are positioned with a gap in the direction of movement intersecting the plane of the absorbent. Also, as shown in FIG. 6B, the absorbent 1 is placed between the pair of striking plates 21, 22. The gap between the pair of striking plates 21, 22 may be approximately the maximum thickness of the absorbent 1 (e.g., 5 mm). Also, in order not to inhibit the dropout of the superabsorbent polymer 12 from the opening of the absorbent 1, the region struck by the striking plates 21, 22 is an area having a length of about 30 to 50% of the length W of the end portion along the lateral direction of the absorbent 1, and an area having a length of about 10 to 30% of the length L of the side portion along the longitudinal direction of the absorbent 1. Also, the striking plates 21, 22 strike the end portion of the absorbent 1 on the opposite side to the side where the chuck portion 201 is located in the longitudinal direction.
(3) Next, the vibration shaft 202 extending vertically downward from the chuck 201 of the vibrator 20 is vibrated to reciprocate the absorbent 1 between the pair of beating plates 21, 22 in a motion direction (thickness direction) intersecting the plane of the absorbent 1. Specifically, the absorbent 1 is reciprocated for one minute at a speed at which the reciprocating motion of the absorbent 1 (movement of the absorbent 1 to one side in the motion direction and movement of the absorbent 1 to the other side in the motion direction) is performed 1000 times per minute. At this time, a part of the plane of the absorbent 1 comes into contact with the pair of beating plates 21, 22, and vibration occurs in the absorbent 1.
(4) Thereafter, visual inspection is performed to see whether or not the superabsorbent polymer 12 has fallen off from the absorbent body 1. The beating plates 21, 22 may be reciprocated relative to the absorbent body 1.

As shown in FIG. 1B, it is preferable that at least in the compressed portion 4 of the side in the lateral direction of the absorbent body 1, no adhesive is provided between the absorbent core 10 and the core wrap sheets 2, 3 in the thickness direction. This prevents the absorbent core 10 from being hindered by the adhesive, and maintains the absorbent performance of the side of the absorbent body 1. In addition, in the absorbent body 1 of this embodiment, the absorbent core 10 is evenly arranged in the planar direction at the side of the absorbent body 1, and the entire planar area of the side of the absorbent body 1 is firmly compressed. Therefore, even if the absorbent core 10 and the core wrap sheets 2, 3 are not joined by adhesive at the side of the absorbent body 1, the opening of the side of the absorbent body 1 can be suppressed.

Furthermore, it is preferable that no adhesive is provided between the absorbent core 10 and the core wrap sheets 2, 3 in the thickness direction over the entire plane of the absorbent body 1. This prevents the absorbency of the absorbent core 10 from being hindered by adhesive over the entire plane of the absorbent body 1, allowing the absorbent body 1 to be used effectively. Furthermore, if the absorbent core 10 is evenly arranged in the plane even at the longitudinal ends of the absorbent body 1, the ends are firmly compressed, so that opening at the ends of the absorbent body 1 can be suppressed even if no adhesive is provided.

However, this is not limited to the above, and one or both of the pair of core wrap sheets 2, 3 may be joined to the absorbent core 10 with an adhesive (e.g., a hot melt adhesive).

The liquid absorbent fibers 11 constituting the absorbent core 10 preferably contain pulp fibers, and the core wrap sheets 2 and 3 preferably contain cellulosic fibers (e.g., pulp fibers, non-wood fibers such as cotton and hemp, regenerated fibers such as rayon, etc.). It is preferable that the pulp fibers of the liquid absorbent fibers 11 are hydrogen bonded to the cellulosic fibers of the core wrap sheets 2 and 3.

By doing so, the liquid absorbent fibers 11 and the core wrap sheets 2, 3 are firmly bonded. In particular, because compressed portions 4 are formed on the sides (and longitudinal ends) of the absorbent 1, the liquid absorbent fibers 11 and the core wrap sheets 2, 3 are more strongly hydrogen bonded and this state is maintained. This further suppresses the opening of the sides (and longitudinal ends) of the absorbent 1.

It is possible to confirm by well-known methods that the liquid absorbent fiber 11 (absorbent core 10) contains pulp fiber and that the core wrap sheets 2, 3 contain cellulose-based fiber. For example, this can be confirmed by using an identification dye to color the fiber or by observing the fiber under an optical microscope, etc.

In addition, when the pulp fibers of the liquid absorbent fibers 11 and the cellulosic fibers of the core wrap sheets 2, 3 are hydrogen bonded (but the absorbent core 10 and the core wrap sheets 2, 3 are not joined with an adhesive), the peel strength between the absorbent core 10 and the core wrap sheets 2, 3 is preferably 0.1 N/25 mm or more, and more preferably 0.3 N/25 mm or more (details will be described later in Example 4).

However, this is not limited to the above, and the liquid absorbent fiber 11 does not have to contain pulp fiber, and the core wrap sheets 2, 3 do not have to contain cellulose-based fiber.

In addition, in the absorbent body 1 of this embodiment, as shown in FIG. 1C, a pair of lateral side portions of the core wrap sheet 2 arranged on one side in the thickness direction are not folded back to the other side in the thickness direction to cover the lateral side edges (end faces along the thickness direction) of the absorbent core 10. Similarly, a pair of lateral side portions of the core wrap sheet 3 arranged on the other side in the thickness direction are not folded back to one side in the thickness direction to cover the lateral side edges (end faces along the thickness direction) of the absorbent core 10. In other words, as shown in FIG. 1B, when the absorbent body 1 is viewed from the side, the lateral side edges of the absorbent core 10 are exposed.

With this type of absorbent body 1, the area of the core wrap sheets 2 and 3 can be reduced. In addition, the number of folding steps of the core wrap sheets 2 and 3 can be reduced in the manufacturing process of the absorbent body 1. This allows the cost of the absorbent body 1 to be reduced. In addition, since the lateral side edges of the absorbent core 10 are exposed, the absorption performance from the exposed parts 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 planar 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 wrap sheets 2 and 3, the fall-off of the absorbent core 10 outside the absorbent body 1 can be suppressed.

However, this is not limited to the above, and the lateral sides of the core wrap sheets 2, 3 may be folded over to cover the side edges of the absorbent core 10. Also, the longitudinal ends of the core wrap sheets 2, 3 may or may not be folded over to cover the longitudinal edges of the absorbent core 10 (Fig. 1C).

===Method of Manufacturing Absorbent Body 1===
A typical absorbent body manufacturing device (not shown) is known to use a pattern drum. A pattern drum is a rotating drum having a plurality of molds (recesses) at predetermined intervals on the outer circumferential surface thereof, the molds corresponding to the shape of the absorbent body. Suction holes are provided on the bottom surface of the mold, and liquid absorbent fibers and superabsorbent polymers scattered from a duct facing the pattern drum are deposited in the mold. The absorbent cores deposited in the mold are sequentially released from the pattern drum and transferred to a core wrap sheet or the like, thereby producing the absorbent body.

However, in the case of manufacturing methods of absorbents using pattern drums, it may not be possible to cleanly release the absorbent core from the mold, or the liquid-absorbent fibers may fly around or the superabsorbent polymer may roll when the absorbent core is transferred to the core wrap sheet. This makes it difficult to distribute the materials evenly in the planar direction of the absorbent core, and material variation is particularly likely to be large at the outer peripheral edge of the absorbent core. This can result in insufficient absorption performance at the outer peripheral edge of the absorbent core, or it may be necessary to pile up more material than necessary to make up for the deficiency.

Figure 7 is an explanatory diagram of the manufacturing method of the absorbent body 1. The manufacturing device 30 of the absorbent body 1 in this embodiment has a supply roller 31 that supplies the core wrap sheet 3 (hereinafter also referred to as the first core wrap sheet 3), an airlaid machine 32, a supply roller 33 that supplies the core wrap sheet 2 (hereinafter also referred to as the second core wrap sheet 2), a water spray 34, a compression roller 35, and a cut roller 36. In this embodiment, the vertical direction (longitudinal direction) of the absorbent body 1 corresponds to the conveying direction (MD direction) of the manufacturing device 30, and the horizontal direction of the absorbent body 1 corresponds to the CD direction that intersects with the conveying direction of the manufacturing device 30, but is not limited to this, and the opposite direction may also correspond.

The manufacturing method of the absorbent body 1 using the above manufacturing device 30 is as follows. First, the first core wrap sheet 3 is supplied to the manufacturing line by the supply roller 31. The liquid absorbent fiber 11 and the superabsorbent polymer 12 are deposited by the airlaid machine 32 on the first core wrap sheet 3, which is transported in the transport direction by a transport device (conveyor belt, drive roller, etc.) not shown (deposition process). In detail, the liquid absorbent fiber 11 and the superabsorbent polymer 12 are supplied from the airlaid machine 32 arranged above the first core wrap sheet 3 toward the first core wrap sheet 3 below. In FIG. 7, the first core wrap sheet 3 is transported horizontally, but this is not limited thereto, and the first core wrap sheet 3 may be transported wrapped around a rotating drum.

Next, the second core wrap sheet 2 is supplied by the supply roller 33 onto the liquid absorbent fibers 11 and superabsorbent polymer 12 deposited in the deposition process (supply process).

Next, water is sprayed by the water spray 34 onto the laminate 1' of the first core wrap sheet 3, the liquid absorbent fiber 11, the superabsorbent polymer 12, and the second core wrap sheet 2 (spraying process).

Next, the compression roller 35 compresses at least the portions of the laminate 1' corresponding to a pair of lateral sides of the absorbent 1 in the thickness direction to form compressed portions 4 (compression process). Preferably, compressed portions 4 are also formed in the portions of the laminate 1' corresponding to a pair of longitudinal ends of the absorbent 1. The compression roller 35 is 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 roller 35 may be heated or unheated, but being heated allows the laminate 1' to be strongly compressed.

Finally, to form the outer edge of the absorbent body 1, the compressed portion 4 of the laminate 1' is cut by the cutting roller 36 (cutting process). The cutting roller 36 is composed of a pair of rollers, one of which is provided with a cutter blade on its outer circumferential surface corresponding to the cutting position, and the other roller is configured to receive the cutter blade of the first roller. Note that in the cutting process, only a portion of the outer edge of the absorbent body 1 (e.g., a side portion) may be cut.

According to this manufacturing method of the absorbent body 1, the liquid absorbent fiber 11 and the superabsorbent polymer 12 are deposited on the first core wrap sheet 3, so that problems that occur when using a conventional pattern drum (such as the inability to cut out the absorbent core cleanly and the occurrence of material variations when transferring the absorbent core) are unlikely to occur. Therefore, the absorbent core 10 can be evenly arranged over the entire plane of the absorbent body 1. In other words, in the absorbent body 1 manufactured by the manufacturing method of this embodiment, the planar variation of the absorbent core 10 arranged on the side (and the vertical end) is small, and the compressed part 4 is formed in which the entire plane of the side (and the vertical end) is firmly compressed. Furthermore, in the cutting process, the cut is made on the hard and stable compressed part 4, so that the side end 1a in the horizontal direction (and the end 1b in the vertical direction) of the absorbent body 1 is neatly cut.

In addition, water is sprayed onto the materials after the deposition process and before the squeezing process. Therefore, when the core wrap sheets 2, 3, the liquid absorbent fibers 11, and the superabsorbent polymer 12 are cellulose-based materials, hydrogen bonds are formed in the materials. For example, the liquid absorbent fibers 11 and the superabsorbent polymer 12 are hydrogen bonded to the core wrap sheets 2, 3, the liquid absorbent fibers 11 are hydrogen bonded to each other, and the liquid absorbent fibers 11 and the superabsorbent polymer 12 are hydrogen bonded. Thus, an absorbent body 1 in which the constituent materials are firmly bonded can be manufactured. In particular, since the compressed parts 4 are formed on the sides (and longitudinal ends) of the absorbent body 1 after the water is sprayed, the materials are more strongly hydrogen bonded and this state is maintained. Therefore, the opening of the sides (and longitudinal ends) of the absorbent body 1 can be further suppressed.

In FIG. 7, a water spray 34 is provided above the laminate 1', and water is sprayed onto the second core wrap sheet 2 located on the upper surface of the laminate 1'. In this case, the water penetrates the second core wrap sheet 2, the absorbent core 10, and the first core wrap sheet 3 in that order. This makes it easier for hydrogen bonds to form between the second core wrap sheet 2 and the absorbent core 10, and the second core wrap sheet 2 and the absorbent core 10 are more firmly bonded together.

However, this is not limited to the above, and water may be sprayed onto the first core wrap sheet 3 from the underside of the laminate 1', or from both the top and bottom of the laminate 1'. The water spraying process may also be performed before the supply process of the second core wrap sheet 2. That is, water may be sprayed onto the liquid absorbent fibers 11 and the superabsorbent polymer 12 from above, or water may be sprayed onto the first core wrap sheet 3 from below. The water spraying process may also be performed at multiple locations, such as before and after the supply process of the second core wrap sheet 2.

In addition, before the compression step of forming the compressed parts 4 corresponding to the sides of the absorbent body 1, a step of compressing the entire surface of the laminate 1' in a predetermined pattern or uniformly (flatly) over the entire surface (hereinafter also referred to as the full surface compression step). The compression in the full surface compression step is weaker than that when the compressed parts 4 are formed.

By providing a water injection process before the full surface squeezing process, the materials on the entire surface of the laminate 1' are squeezed in a hydrogen-bonded state (water-injected state), so the materials are more strongly hydrogen-bonded and this state is maintained.

After the full compression process, the laminate 1' may be wound up on a roller, and the wound laminate 1' may be set on a separate line to perform the process of forming the compressed portion 4 and the cutting process on separate lines. In this case, various absorbents 1 (e.g., absorbents 1 of different sizes) can be manufactured from the laminate 1'. In this case, it is also preferable to provide a water injection process again before the process of forming the compressed portion 4 on the separate line. By doing so, hydrogen bonding of the materials occurs again on the separate line, thereby increasing the strength of the compressed portion 4. On the other hand, as shown in FIG. 7, when the compressed portion 4 is formed on the same line as the process of manufacturing the laminate 1', it is possible to further suppress the fall-off of the absorbent core 10 during the manufacture of the absorbent 1.

==== Working Example ====
<<Examples 1 and 2>>
Ten absorbents 1 each of Examples 1 and 2 were produced by the manufacturing method of the absorbent body 1 of this embodiment. The absorbent body 1 was rectangular as illustrated in Figures 1A to 1C, and the absorbent body 1 had a horizontal length of 60 mm, a vertical length of 100 mm, and a width of the compressed portion 4 of 10 mm. The absorbent body 1 of Example 1 had a high basis weight absorbent core 10, the basis weight of the liquid absorbent fiber 11 (pulp fiber) was 260 g/m ² , and the basis weight of the superabsorbent polymer 12 was 240 g/m ^2. The absorbent body 1 of Example 2 had a low basis weight absorbent core 10, the basis weight of the liquid absorbent fiber 11 (pulp fiber) was 75 g/m ² , and the basis weight of the superabsorbent polymer 12 was 63 g/m ^2. The core wrap sheets 2 and 3 were tissue (basis weight 13 g/m ² ). 7, water was sprayed from above onto the liquid absorbent fibers 11 and the superabsorbent polymer 12 before the second core wrap sheet 2 was supplied. After the second core wrap sheet 2 was supplied, the entire surface of the laminate 1' was uniformly (flatly) squeezed with a pressure of 10 to 80 MPa using a compression roller heated to 150° C. Thereafter, water was sprayed from below onto the first core wrap sheet 3, and then a lattice-patterned compressed portion 4 was formed with a pressure of 50 to 250 MPa using a compression roller heated to 65° C.

<<Comparative Examples 1 and 2>>
Eight absorbents each of Comparative Examples 1 and 2 were produced by a manufacturing method using a pattern drum. The material of the core wrap sheet and the shape and size of the absorbent (compressed portion) were the same as those of Examples 1 and 2. The absorbent core of Comparative Example 1 was a high basis weight absorbent core the same as that of Example 1. The absorbent core of Comparative Example 2 was a low basis weight absorbent core the same as that of Example 2. The absorbent core was released from the mold of the pattern drum and transferred onto the first core wrap sheet, and then the second core wrap sheet was laminated thereon. Then, the entire surface of the laminate was uniformly (flatly) compressed with a strength of 10 to 80 MPa by a compression roller heated to 150°C. Then, as in Example 1, water was sprayed from below onto the first core wrap sheet, and a lattice pattern compressed portion was formed with a strength of 50 to 250 MPa by a compression roller heated to 65°C.

<<Measurement Results of Examples 1 and 2 and Comparative Examples 1 and 2>>
Measurements (FIGS. 4A to 4E) were carried out on the area ratio of the absorbent core 10 described above with respect to the lateral side portions of the absorbent bodies of Examples 1 and 2 and Comparative Examples 1 and 2. The measurement results are shown in Table 1.

Figure 8 is a graph showing the measurement results of Example 1 and Comparative Example 1 (high basis weight absorbent). Figure 9 is a graph showing the measurement results of Example 2 and Comparative Example 2 (low basis weight absorbent). From the graphs of Figures 8 and 9, an opening (peeling of the core wrap sheets 2 and 3) occurs in an absorbent with a CV value of 27%, but an opening does not occur in an absorbent with a CV value smaller than 27%. Therefore, as in the absorbent 1 of this embodiment, by suppressing the CV value indicating the variation in the occupied area ratio of the absorbent core in the horizontal side to 26% or less, it is possible to suppress the opening of the side of the absorbent 1 and to suppress the fall-off of the absorbent core from the side. Similarly, it can be said that the opening of the vertical end of the absorbent 1 can be suppressed by suppressing the CV value indicating the variation in the occupied area ratio of the absorbent core to 26% or less at the vertical end of the absorbent 1.

In addition, it was found that the manufacturing method of this embodiment (Examples 1 and 2) allows the manufacture of absorbent bodies with less variation in the absorbent core at the sides and less likely to open up, compared to the case where a pattern drum is used (Comparative Examples 1 and 2). All absorbent bodies 1 manufactured by the manufacturing method of this embodiment have a CV value of 26% or less.

In addition, absorbents with a high basis weight tended to have a lower CV value than absorbents with a low basis weight. This is thought to be because in absorbents with a high basis weight, pressure can be applied firmly to the absorbent core when forming the compressed parts, and because the liquid-absorbent fiber and the superabsorbent polymer are entangled at a high density, gaps through which materials can move are unlikely to occur. For this reason, some of the absorbents in Comparative Example 1 had a CV value of 26% or less. Therefore, even if a manufacturing method using a pattern drum is used, if the absorbent has a high basis weight, it may be possible to manufacture the absorbent 1 of this embodiment (an absorbent with a CV value of 26% or less), and the manufacturing method for the absorbent 1 of this embodiment is not limited to the method exemplified in FIG. 7. However, the manufacturing method for absorbent 1 exemplified in FIG. 7 can more reliably manufacture an absorbent with a CV value of 26% or less.

<<Example 3>>
An absorbent body 1 (50 mm x 95 mm) of Example 3 was produced by reducing the width of the compressed portion 4 at the outer peripheral end of the absorbent body 1 of Example 1 (Fig. 1A) from 10 mm to 5 mm. The shedding test of the superabsorbent polymer 12 described in Fig. 6A and Fig. 6B was carried out on this absorbent body 1 of Example 2. The horizontal length x vertical length of the absorbent body 1 gripped by the chuck portion 201 of the vibrator 20 was 20 mm x 20 mm. The horizontal length x vertical length of the absorbent body 1 beaten by the beater plate 21 was 20 mm x 20 mm.

Even when the absorbent body 1 of Example 3 was vibrated by reciprocating between a pair of beating plates 21, 22, no falling off of the superabsorbent polymer 12 from the absorbent body 1 was confirmed. Therefore, it was found that in the absorbent body 1 manufactured by the manufacturing method of this embodiment (Figure 7), the planar variation of the absorbent core 10 arranged on the lateral side and longitudinal end is small, and a compressed portion 4 is formed in which the entire planar area of the outer peripheral end of the absorbent body 1 is firmly compressed.

<<Example 4 and Comparative Example 3>>
Five rectangular samples (Example 4) were prepared by compressing the entire surface of a laminate in the thickness direction, in which an absorbent core 10 in which a superabsorbent polymer 12 is mixed with an aggregate of liquid-absorbent fibers 11 containing pulp fibers and core wrap sheets 2, 3 (tissue) containing cellulosic fibers are laminated. Similarly, five rectangular samples (Comparative Example 3) were prepared by compressing the entire surface of a laminate in the thickness direction, in which an absorbent core 10 identical to that in Example 4 and core wrap sheets 2, 3 (SMS nonwoven fabric containing polyolefin fibers) not containing cellulosic fibers are laminated. 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 wrap sheets 2, 3 (after hydrogen bonding was generated in the sample of Example 4). In addition, the absorbent core 10 and the core wrap sheets 2, 3 were not bonded with an adhesive. Further, a sample was produced in accordance with the manufacturing method shown in FIG. 7, having a length of 25 mm in the conveying direction (MD direction) and a length of 50 mm in the CD direction intersecting with the MD direction.

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, 3 using a tensile tester (Instron Model 5565 manufactured by Instron Japan Co., Ltd. or an equivalent device). The test was performed after leaving the sample and the tensile tester at rest in a constant temperature and humidity environment of a temperature of 20° C. (±2° C.) and a humidity of 60% (±5%). The peel test method is as follows.
(1) First, the core wrap sheets 2, 3 were peeled off from the absorbent core 10 at the CD end of the sample to be measured, and the absorbent core 10 (CD end) was held by one chuck of a tensile tester, and the core wrap sheets 2, 3 (CD end) were held by the other chuck. The length of the sample held by the chuck was about 10 mm, and the distance between the chucks was 10 mm.
(2) In the tensile tester, the distance between the two chucks was increased at a predetermined speed (e.g., 100 mm/min), and the absorbent core 10 and the core wrap sheets 2 and 3 were pulled in the CD direction until they were separated from each other. The maximum load applied between the chucks during the tensile test was read and used as the peel strength (in the CD direction) of the sample being measured.

The measurement results for the five samples of Example 4 and the five samples of Comparative Example 3 are shown in Table 2.

From the results in Table 2, it can be seen that Example 4, in which the liquid absorbent fiber 11 comprises pulp fiber and the core wrap sheets 2, 3 comprise cellulosic fiber and are hydrogen bonded, has a stronger peel strength than Comparative Example 3, in which the liquid absorbent fiber 11 and the core wrap sheets 2, 3 are not hydrogen bonded. The average peel strength of Example 4 was 0.548 N/25 mm, and the average peel strength of Comparative Example 3 was 0.093 N/25 mm. Therefore, when the above peel test is performed on the lateral side or longitudinal end of the absorbent body 1, if the peel strength is 0.1 N/25 mm or more (preferably 0.3 N/25 mm or more), it is considered that there is a high probability that hydrogen bonds are formed between the liquid absorbent fiber 11 and the core wrap sheets 2, 3.

Although the embodiments of the present invention have been described above, the above embodiments are intended to facilitate understanding of the present invention and are not intended to limit the interpretation of the present invention. Furthermore, the present invention may be modified or improved without departing from the spirit of the invention, and it goes without saying that the present invention includes equivalents thereof.

1 absorbent,
2 (second) core wrap sheet, 3 (first) core wrap sheet,
4. Compression section,
10 absorbent core, 11 liquid absorbent fiber, 12 superabsorbent polymer,
20 vibrator, 201 chuck portion, 202 rotating shaft portion,
21, 22 Beating board,
30 Manufacturing apparatus for absorbent body 1, 31 Supply roller, 32 Airlaid machine,
33 supply roller, 34 water spray,
35 squeeze roller, 36 cut roller,
r1 to r12 divided regions, r'1 to r'12 second divided regions,

Claims (9)

It has a vertical direction, a horizontal direction, and a thickness direction,
An absorbent body having an absorbent core and a core wrap sheet disposed on both sides of the absorbent core in the thickness direction,
The absorbent core comprises liquid-absorbent fibers and a superabsorbent polymer;
The absorbent body has a compressed portion in which at least a pair of side portions in the lateral direction are compressed in the thickness direction,
The compressed portion of the side of the absorbent body, in which the liquid absorbent fiber and the superabsorbent polymer are arranged, is divided into six regions in the vertical direction and two regions in the horizontal direction, which are defined as divided regions;
An absorbent body characterized in that, for each divided region, when the area occupied by the liquid absorbent fiber and the superabsorbent polymer when the divided region is viewed in a plane in the thickness direction is divided by the area of the divided region to calculate the area ratio, the CV value indicating the variation in the area ratio is 26% or less. The absorbent body according to claim 1,
The compressed portions are provided at a pair of ends of the absorbent body in the longitudinal direction,
a compressed portion at the end of the absorbent body, the portion in which the liquid absorbent fiber and the superabsorbent polymer are arranged, is divided into six in the horizontal direction and a region obtained by dividing the compressed portion into two in the vertical direction is defined as a second divided region;
An absorbent body characterized in that, for each of the second divided regions, a second area ratio is calculated by dividing the area occupied by the liquid absorbent fiber and the superabsorbent polymer when the second divided region is viewed in a plane in the thickness direction by the area of the second divided region, and the CV value indicating the variation in the second area ratio is 26% or less. The absorbent body according to claim 2,
The absorbent body is characterized in that the highly absorbent polymer does not fall off from the absorbent body even when the absorbent body before absorption is moved back and forth between a pair of striking plates in a direction intersecting the plane of the absorbent body, and a predetermined part of the plane of the absorbent body is abutted against the pair of striking plates at a speed of 1,000 times per minute for one minute. The absorbent body according to any one of claims 1 to 3,
An absorbent body, characterized in that at least in the compressed portions of the sides of the absorbent body, no adhesive is provided between the absorbent core and the core wrap sheet in the thickness direction. The absorbent body according to claim 4,
An absorbent body, characterized in that no adhesive is provided between the absorbent core and the core wrap sheet in the thickness direction over the entire plane of the absorbent body. The absorbent body according to any one of claims 1 to 5,
The liquid absorbent fibers include pulp fibers,
The core wrap sheet comprises cellulosic fibers,
The pulp fibers are hydrogen bonded to the cellulosic fibers. The absorbent body according to any one of claims 1 to 6,
A pair of side portions in the lateral direction of the core wrap sheet arranged on one side in the thickness direction is not folded back to the other side in the thickness direction so as to cover the side edges in the lateral direction of the absorbent core, and
An absorbent body characterized in that a pair of lateral side portions of the core wrap sheet arranged on the other side of the thickness direction are not folded back to the one side in the thickness direction so as to cover the side edges of the absorbent core. It has a vertical direction, a horizontal direction, and a thickness direction,
A method for manufacturing an absorbent body having an absorbent core, and a first core wrap sheet and a second core wrap sheet arranged on both sides of the absorbent core in the thickness direction, comprising:
A depositing step in which liquid-absorbent fibers and superabsorbent polymers included in the absorbent core are deposited on the first core wrap sheet transported in a transport direction;
A supplying step in which the second core wrap sheet is supplied onto the liquid absorbent fibers and the superabsorbent polymer deposited in the depositing step;
a compressing step in which at least portions of the laminate of the first core wrap sheet, the liquid absorbent fiber, the superabsorbent polymer, and the second core wrap sheet that correspond to a pair of side portions in the lateral direction of the absorbent body are compressed in the thickness direction of the laminate to form compressed portions;
a cutting step in which the laminate is cut on the compressed portion to form an outer edge of the absorbent body;
A method for producing an absorbent body, comprising the steps of: A method for producing an absorbent body according to claim 8, comprising the steps of:
After the depositing step and before the squeezing step,
A method for manufacturing an absorbent body, comprising a spraying step in which water is sprayed onto at least one of the first core wrap sheet, the liquid absorbent fiber and the superabsorbent polymer, and the second core wrap sheet.

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