Laminate

Abstract

The purpose of the present invention is to provide a multilayer body which is useful for an absorbent article that exhibits excellent absorption rate and side leakage prevention performance with respect to multiple exposures to a liquid. A multilayer body which comprises: a liquid-permeable first sheet, a liquid-absorbing intermediate sheet, and a second sheet, said sheets having a shape that has a longitudinal direction; and a water-absorbing resin layer that is interposed at least between the first sheet and the intermediate sheet. With respect to this multilayer body, the intermediate sheet comprises a region A and a region B, which have a shape that has a longitudinal direction; and the region A and the region B satisfy at least one of the relations (1) and (2) described below, while satisfying the relation (3) described below. (1) The region A has a low density, and the region B has a high density; and if the density of the region B is taken as 1, the ratio of the density of the region A is 0.45 or less. (2) The region A is a projected part that protrudes toward the water-absorbing resin layer, and the region B is a recessed part; and the height of the projected part is 0.25 mm or more. (B) The region B is positioned inside the longitudinal ends of the intermediate sheet.

Description

[Technical Field]

[0001] The present invention relates to a laminate, and more particularly to a laminate having improved liquid penetration rate and side leakage prevention properties. [Background technology]

[0002] BACKGROUND ART Body fluid absorbent articles such as disposable diapers, incontinence pads, and sanitary napkins are composed of a laminate including an absorbent layer that absorbs liquid, a liquid-permeable top sheet arranged on the side that contacts the body, and a liquid-impermeable back sheet arranged on the side opposite the side that contacts the body.

[0003] Expresses the performance of body fluid absorbent products One of the essential properties is the speed of liquid absorption, and various improvements have been made to body fluid absorbent articles so that they can absorb liquid more quickly.

[0004] For example, Patent Document 1 proposes an absorbent article comprising a water-permeable front side sheet facing the body, a back side sheet facing the clothing, and an absorbent core contained between the front side sheet and the back side sheet and having the function of absorbing body fluids, in which a body fluid-permeable sheet (second sheet) is provided between the front side sheet and the absorbent core, the fiber density of the side facing the absorbent core being higher than the fiber density of the side facing the front side sheet.It is shown that with this absorbent article, body fluid that passes through the front side sheet and reaches the upper surface of the body fluid-permeable sheet moves so as to be guided to the side with a higher fiber density gradient (the side of the absorbent core), and is therefore quickly absorbed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-210523 Summary of the Invention [Problem to be solved by the invention]

[0006] Although the absorption speed of the absorbent article described in Patent Document 1 has been considered, considering the actual usage conditions in which a single absorbent article may be exposed to liquid multiple times, the absorption speed for liquids exposed thereto from the second time onwards slows down due to gel blocking, reducing absorbency and making the article more susceptible to side leakage.

[0007] Therefore, the present invention aims to provide a laminate useful for absorbent articles that exhibits an excellent absorption rate even when exposed to liquid multiple times and also has excellent properties for reducing the risk of side leakage (hereinafter, the property of reducing the risk of side leakage will also be referred to as "side leakage prevention property"). [Means for solving the problem]

[0008] The present inventors have conducted extensive research and found that by providing a liquid-absorbent sheet in the material constituting the laminate and configuring the liquid-absorbent sheet so that a narrow region that is relatively lower in density than other regions and / or that is convex toward the water-absorbent resin side is provided at a predetermined position, it is possible to achieve excellent absorption speed and side leakage prevention even when exposed to liquid multiple times. The present invention was completed through further research based on this finding.

[0009] That is, the present invention provides the following aspects. Item 1. A laminate including a liquid-permeable first sheet, a liquid-absorbent intermediate sheet, and a second sheet, each having a longitudinal shape, and a water-absorbent resin layer interposed between at least the first sheet and the intermediate sheet, The intermediate sheet includes a region A and a region B having a shape with a longitudinal direction, A laminate in which the region A and the region B satisfy at least one of the following relationships (1) and (2) and also satisfy the following relationship (3): (1) The region A has a low density and the region B has a high density, and the ratio of the density of the region A to the density of the region B is 0.45 or less. (2) The region A is a convex portion that is convex toward the water-absorbent resin layer, and the region B is a concave portion, and the height of the convex portion is 0.25 mm or more. (3) The region B is located inside the longitudinal end of the intermediate sheet. Item 2. The laminate according to Item 1, wherein the region A and the region B satisfy the relationships (1) and (2). Item 3. The laminate according to Item 1 or 2, wherein the region A includes linear portions extending in a direction including the longitudinal direction of the intermediate sheet. Item 4. The laminate according to any one of Items 1 to 3, wherein the region A includes linear portions extending substantially parallel to the longitudinal direction of the intermediate sheet. Item 5. The laminate according to Item 4, wherein the region B includes a linear portion arranged on the lateral center line of the intermediate sheet. Item 6. The laminate according to any one of Items 1 to 5, wherein a plurality of the regions A and a plurality of the regions B are alternately arranged in the short side direction of the regions. Item 7. The laminate according to Item 6, comprising a linear portion in which a plurality of the regions A and the regions B are arranged in parallel. Item 8. The laminate according to any one of Items 1 to 7, wherein the region B is located inside the short edge of the intermediate sheet. Item 9. An absorbent article comprising the laminate according to any one of items 1 to 8. [Effects of the Invention]

[0010] The present invention provides a laminate useful in absorbent articles that exhibits excellent absorption rate and side leakage resistance even after multiple liquid exposures. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic cross-sectional view of a first embodiment of a laminate of the present invention. [Figure 2] 2 is a schematic view showing the appearance of a portion (a portion including a longitudinal end) of the intermediate sheet of the laminate of FIG. 1. [Figure 3] 2 shows a schematic exploded view of the relevant portion of the laminate of FIG. 1. [Figure 4]The state in which the laminate of FIG. 1 is first exposed to a liquid during use is shown in an exploded view similar to FIG. [Figure 5] 3 is a schematic view showing the appearance of an intermediate sheet used in a second embodiment of the laminate of the present invention. FIG. [Figure 6] An exploded view of the laminated body of the second embodiment is shown in the same format as FIG. [Figure 7] The state in which the laminate 10a of FIG. 6 is first exposed to a liquid during use is shown in an exploded view similar to FIG. [Figure 8] 10 is a schematic view showing the appearance of an intermediate sheet used in a third embodiment of the laminate of the present invention. FIG. [Figure 9] 10 is a schematic view showing the appearance of an intermediate sheet used in a fourth embodiment of the laminate of the present invention. FIG. [Figure 10] 10 is a schematic view showing the appearance of a portion (a portion including a short edge) of an intermediate sheet used in a fifth embodiment of the laminate of the present invention. FIG. [Figure 11] Some examples of the shapes of region A and region B are shown schematically below. [Figure 12] Specific examples (embodiments) of the shapes of the region A and the region B are shown below. [Figure 13] Specific examples (embodiments) of the shapes of the region A and the region B are shown below. [Figure 14] Specific examples (comparative examples) of the shapes of the region A and the region B are shown below. [Figure 15] Specific examples (comparative examples) of the shapes of the region A and the region B are shown below. [Figure 16] Specific examples (comparative examples) of the shapes of the region A and the region B are shown below. DETAILED DESCRIPTION OF THE INVENTION

[0012] [1. Structure of laminate] The laminate of the present invention comprises a liquid-permeable first sheet, a liquid-absorbent intermediate sheet, and a second sheet, each of which has a longitudinal shape, and a water-absorbent resin layer interposed between at least the first sheet and the intermediate sheet; the intermediate sheet includes Region A and Region B, each of which has a longitudinal shape; Region A and Region B satisfy at least one of the following relationships (1) and (2), and also satisfy the following relationship (3): (1) Region A has a low density and Region B has a high density, and the ratio of the density of Region A to the density of Region B is 0.45 or less; (2) Region A has a convex portion that is convex toward the water-absorbent resin layer, and Region B has a concave portion, and the height of the convex portion is 0.25 mm or more; and (3) Region B is located inside the longitudinal edge of the intermediate sheet. This structure enables the laminate of the present invention to exhibit excellent absorption speed even when exposed to liquids multiple times. The laminate of the present invention is described in detail below.

[0013] [1-1. First embodiment] FIG. 1 shows a schematic cross-sectional view of a first embodiment of a laminate of the present invention. FIG. 1 shows a cross-sectional view of a laminate cut along a plane perpendicular to its longitudinal direction. FIG. 2 shows a schematic external view of a portion (a portion including a longitudinal end) of an intermediate sheet of the laminate of FIG. 1. FIG. 3 shows a schematic exploded view of the portion of the laminate of FIG. 1. The laminate 10 shown in FIGS. 1 and 3 includes a liquid-permeable first sheet 20, a liquid-absorbent intermediate sheet 30 shown in FIG. 2, and a second sheet 40, all of which have a longitudinal direction LD. The laminate 10 also includes a water-absorbent resin layer 51 interposed between at least the first sheet 20 and the intermediate sheet 30. Hereinafter, the stacking direction of the laminate 10 will also be referred to as the "stacking direction LMD10." The laminate 10 also includes another water-absorbent resin layer 52 between the intermediate sheet 30 and the second sheet 40. Although not shown, an adhesive layer may be interposed between the water-absorbent resin layer 51 and the intermediate sheet 30 and / or between the water-absorbent resin layer 52 and the second sheet 40.

[0014] In the laminate 10 of this embodiment, as shown in Figures 1 to 3, the intermediate sheet 30 has a low-density region as region A (hereinafter, the low-density region A will also be referred to as the "low-density region Al") having a shape with a longitudinal direction LD-A, and a high-density region as region B (hereinafter, the high-density region B will also be referred to as the "high-density region Bh"), and the high-density region Bh is located inside the longitudinal end LE of the intermediate sheet 30.

[0015] The low-density regions Al are configured so that the ratio of the density of the low-density regions Al to the density of the high-density regions Bh is 0.45 or less. From the viewpoint of further improving the absorption speed and / or side leakage prevention properties after several liquid exposures, the ratio is preferably 0.42 or less, more preferably 0.41 or less, even more preferably 0.4 or less, even more preferably 0.3 or less, even more preferably 0.2 or less, and particularly preferably 0.12 or less. The lower limit of the ratio range is not particularly limited and may vary depending on the material of the intermediate sheet 30 and / or treatment to change the density, but from the viewpoint of further improving the absorption speed and / or side leakage prevention properties after several liquid exposures, it is, for example, 0.05 or more, preferably 0.08 or more.

[0016] The specific density of the low-density region Al is, for example, 100 kg / m 3 From the viewpoint of further increasing the absorption rate and / or the side leakage prevention property after several exposures to liquid, the specific density of the low-density region Al is preferably 60 kg / m 3 Less than or equal to 50 kg / m 3 Less than or equal to 45 kg / m 3 or less, more preferably 40 kg / m 3 More preferably 35 kg / m or less 3 More preferably, 28 kg / m or less 3 Below 20 kg / m, particularly preferably 3 The lower limit of the specific density range of the low-density region Al is not particularly limited as long as the water retention can be ensured, but for example, it is 16.5 kg / m 3 or more, preferably 18 kg / m 3The above can be mentioned.

[0017] There are no particular limitations on the method for varying the density of the intermediate sheet 30. Since the intermediate sheet 30 is liquid-permeable and has spaces or pores that communicate in the thickness direction, any method can be used to vary the density as long as it can physically reduce the volume occupied by these spaces or pores. Specific methods include compressing the fabric of the intermediate sheet 30 in areas where the high-density regions Bh are to be formed, and preparing the fabric of the intermediate sheet 30 so that it is fine-meshed in areas where the high-density regions Bh are to be formed and coarse-meshed in areas where the low-density regions Al are to be formed.

[0018] The high-density region Bh being located inside the longitudinal ends LE of the intermediate sheet 30 means that no part of the high-density region Bh reaches the longitudinal ends LE of the intermediate sheet 30, and the entire high-density region Bh is located inside in the in-plane direction of both longitudinal ends LE of the intermediate sheet 30. In other words, the portions of both longitudinal ends LE of the intermediate sheet 30 are constituted by the low-density region Al.

[0019] By providing the low-density regions Al in a predetermined shape and at predetermined positions in the intermediate sheet 30 as described above, an excellent absorption rate is achieved even when exposed to liquid multiple times. The mechanism that is thought to be the reason for such an excellent absorption rate will be explained with reference to Figure 4. Figure 4 is a schematic exploded view, similar to Figure 3, of the laminate 10 in a state where it is first exposed to liquid during use (hereinafter, the laminate 10 in this state will also be particularly referred to as "laminate 10'").

[0020] First, in the laminate 10, the intermediate sheet 30 has spaces or pores that communicate in the thickness direction and is in direct contact with the water-absorbent resin layer 51, and therefore, it is considered that some of the water-absorbent resin particles that make up the water-absorbent resin layer 51 are embedded in the spaces or pores in the low-density regions Al of the intermediate sheet 30. Some of the water-absorbent resin particles that make up the water-absorbent resin layer 51 can also be embedded in the high-density regions Bh of the intermediate sheet 30, but due to the difference in density between the two regions, it is considered that more water-absorbent resin particles are embedded in the low-density regions Al.

[0021] When the laminate 10 is exposed to a liquid from the first sheet 20 side, the liquid moves in the lamination direction LMD10 and reaches the intermediate sheet 30. Since the intermediate sheet 30 has low-density regions Al and high-density regions Bh as described above, more water is diffused in the low-density regions Al. Therefore, more water-absorbent resin particles that have been recessed in the low-density regions Al absorb more water preferentially (i.e., at an earlier point in time after the laminate 10 is exposed to the liquid), and expand. In other words, the water-absorbent resin particles that absorb water and expand first are localized in the low-density regions Al. As a result, differences in the expansion rate of the water-absorbent resin particles occur throughout the water-absorbent resin layer 51 depending on the positions of the low-density regions Al and the high-density regions Bh of the intermediate sheet 30. 4, in the water-absorbent resin layer 51, a portion 51A corresponding to the low-density region A1 of the intermediate sheet 30 expands more than a portion 51B corresponding to the high-density region Bh (the water-absorbent resin layer 51 that absorbs the liquid to which it is exposed first is also particularly referred to as the "water-absorbent resin layer 51'"). The portion 51A that has expanded more corresponds to the shape of the low-density region A1 having the longitudinal direction LD-A, and forms a shape having the same longitudinal direction LD-A, that is, a convex portion (hereinafter, the portion 51A that has expanded more will also be referred to as the "convex portion 51A," and the portion 51B that has not expanded to the same size as the convex portion 51A and has become lower will also be referred to as the "concave portion 51B").

[0022] When the laminate 10' is exposed to a subsequent liquid, a portion of the liquid that reaches the water-absorbent resin layer 51' flows through the recesses 51B along the longitudinal direction of the protrusions 51A. In other words, after the liquid absorbed by the laminate 10' moves in the lamination direction LMD10, it spreads in the in-plane direction of the laminate 10' along the longitudinal direction LD-A of the protrusions 51A as it is absorbed into the water-absorbent resin layer 51'. In this way, the protrusions 51A formed by the first liquid exposure spread the absorbed liquid throughout the laminate 10' without concentrating it at the location where it reaches the water-absorbent resin layer 51', thereby maximizing the contact area between the water-absorbent resin layer 51' and the liquid. This is believed to improve the absorption rate. Furthermore, this property of preventing the absorbed liquid from concentrating at a specific location may also contribute to reducing the amount of liquid flowing back to that location. In addition, because the high-density region Bh is positioned inside the longitudinal end LE of the intermediate sheet 30, the recesses 51B in the water-absorbent resin layer 51' are also formed inside the longitudinal end LE. Therefore, the protrusions 51A at the longitudinal end LE act as physical barriers to block any liquid that reaches the vicinity of the longitudinal end LE. This reduces the risk of leakage from the longitudinal end LE (i.e., lateral leakage).

[0023] In the above description, the "first liquid exposure" and the "second liquid exposure" may be continuous or intermittent.

[0024] [1-2. Second embodiment] Fig. 5 shows an intermediate sheet used in a second embodiment of the laminate of the present invention in the same format as Fig. 2. Fig. 6 shows an exploded view of the laminate of the second embodiment in the same format as Fig. 3. The laminate 10a shown in Fig. 6 is similar to the laminate 10 of the first embodiment described above, except that the intermediate sheet 30 has been changed to an intermediate sheet 30a.

[0025] The intermediate sheet 30a used in this embodiment has a region A having a shape with a longitudinal direction LD-A, which is a region forming a convex portion that is convex toward the water-absorbent resin layer side (hereinafter, the convex portion region A will also be referred to as the “convex portion region A+”), and a region B forming a concave portion (i.e., a concave portion relative to the convex portion region A+) (hereinafter, the concave portion region B will also be referred to as the “convex portion region B-”), and the concave portion region B- is located inside the longitudinal end LE of the intermediate sheet 30a.

[0026] The convex region A+ is configured so that its height h (the height from the lowest point of the concave region B- on the same side as the convex region A+ to the highest point of the convex portion) is 0.25 mm or more. From the viewpoint of further improving the absorption rate and / or side leakage prevention properties after several exposures to liquid, the height h is preferably 0.35 mm or more, more preferably 0.45 mm or more, even more preferably 0.6 mm or more, and even more preferably 0.7 mm or more. There is no particular limitation on the upper limit of the height h range, but examples include 1 mm or less, preferably 0.9 mm or less.

[0027] In the present embodiment, the intermediate sheet 30a has substantially the same density in the raised region A+ and the recessed region B-.

[0028] The method for providing the convex region A+ and the concave region B- in the intermediate sheet 30a is not particularly limited. Examples include a method of producing the intermediate sheet 30a by a watermarking technique using a substrate having concave and convex portions corresponding to the convex region A+ and the concave region B-, respectively, and a method of preparing a block of material for the intermediate sheet 30a and slicing it so that the concave and convex shapes are exposed, and cutting it into the intermediate sheets 30a.

[0029] Providing the intermediate sheet 30a with the protruding regions A+ in a predetermined position and shape as described above also results in an excellent absorption rate even after multiple exposures to liquid. The mechanism that may explain why such an excellent absorption rate is obtained will be explained with reference to Figure 7. Figure 7 is a schematic exploded view, similar to Figure 6, of the laminate 10a in the state in which it is first exposed to liquid during use (hereinafter, the laminate 10a in this state will also be particularly referred to as "laminate 10a'").

[0030] First, in the laminate 10a, the intermediate sheet 30a has spaces or pores that communicate in the thickness direction and is in direct contact with the water-absorbent resin layer 51, and therefore, it is considered that the convex regions A+ of the intermediate sheet 30a bite into the water-absorbent resin layer 51, and some of the water-absorbent resin particles that make up the water-absorbent resin layer 51 are embedded in the spaces or pores. Some of the water-absorbent resin particles that make up the water-absorbent resin layer 51 can also be embedded in the concave regions B- of the intermediate sheet 30a, but due to the difference in height between the two regions, it is considered that more water-absorbent resin particles are embedded in the convex regions A+.

[0031] When the laminate 10a is exposed to a liquid from the first sheet 20 side, the liquid moves in the lamination direction LMD10 and reaches the intermediate sheet 30a. Because the intermediate sheet 30a has the raised regions A+ and the depressed regions B- as described above, the liquid comes into contact with the raised regions A+ earlier and diffuses therein more quickly. Therefore, a larger number of water-absorbent resin particles recessed within the raised regions A+ absorb more water preferentially (i.e., at an earlier point after the laminate 10a is exposed to the liquid), thereby expanding. In other words, the water-absorbent resin particles that absorb water and expand first are localized in the raised regions A+. As a result, the expansion rate of the water-absorbent resin particles varies throughout the water-absorbent resin layer 51 depending on the positions of the raised regions A+ and the depressed regions B- of the intermediate sheet 30a. Specifically, as shown in Fig. 7, in the water-absorbent resin layer 51', portions 51A corresponding to the convex regions A+ of the intermediate sheet 30a expand more than portions 51B corresponding to the concave regions B-. As a result, similar to Fig. 4 of the first embodiment, convex portions 51A having a shape extending in the longitudinal direction LD-A and concave portions 51B that do not expand to the same size as the convex portions 51A and are lower in size are formed.

[0032] Therefore, when the laminate 10a' is further exposed to a liquid, the liquid absorbed by the laminate 10' moves along the longitudinal direction LD-A of the protrusions 51A so as to spread in the in-plane direction of the laminate 10', as in FIG. 4 of the first embodiment. This maximizes the contact area between the water-absorbent resin layer 51' and the liquid, and thus improves the absorption rate. Furthermore, as in the first embodiment, this characteristic of not concentrating the absorbed liquid in a specific location may also contribute to reducing the amount of liquid returning to that location. Additionally, as in the first embodiment, the protrusions 51A closest to the longitudinal end LE act as a physical barrier, reducing the risk of leakage from the longitudinal end LE (i.e., lateral leakage).

[0033] In the above description, the "first liquid exposure" and the "next liquid exposure" may be continuous or intermittent.

[0034] [1-3. Third embodiment] Figure 8 shows an intermediate sheet 30b used in a third embodiment of the laminate of the present invention in the same format as Figure 2. The laminate of the third embodiment is similar to the laminate 10 of the first embodiment described above, except that the intermediate sheet 30 is changed to an intermediate sheet 30b.

[0035] The intermediate sheet 30b used in this embodiment has both the characteristics of the intermediate sheet 30 used in the first embodiment and the characteristics of the intermediate sheet 30a used in the second embodiment (satisfying the above relationships (1) to (3)). That is, the intermediate sheet 30b has a shape extending in the longitudinal direction LD-A, and includes a region A that is low-density and has convex portions that are convex toward the water-absorbent resin layer side (hereinafter, the low-density convex portion region A will also be referred to as the "low-density / convex portion region Al+"), and a region B that is high-density and has a concave shape (i.e., a concave portion relative to the convex portion) (hereinafter, the high-density non-convex portion region B will also be referred to as the "high-density / convex portion region Bh-"), and the high-density / convex portion region Bh- is located inside the longitudinal end LE of the intermediate sheet 30b.

[0036] The density ratio of the low-density / protruding regions Al+ when the density of the high-density / recessed regions Bh- in the intermediate sheet 30b is set to 1 is the same as the density ratio of the low-density regions Al when the density of the high-density regions Bh in the intermediate sheet 30 used in the first embodiment is set to 1. Furthermore, the height h of the low-density / protruding regions Al+ in the intermediate sheet 30b is the same as the height h of the protruding regions A+ in the intermediate sheet 30a used in the second embodiment.

[0037] Furthermore, the density of the low-density / convex regions Al+ in the intermediate sheet 30b is the same as the density of the low-density regions Al in the intermediate sheet 30 used in the first embodiment.

[0038] The method for providing the low-density, convex regions and the high-density, concave regions in the intermediate sheet 30b is not particularly limited, but a preferred method is an embossing method in which the fabric of the intermediate sheet 30b is compressed in the thickness direction from one side at the locations where the high-density, concave regions are to be provided.

[0039] The laminate of the third embodiment uses the intermediate sheet 30b having the above-mentioned characteristics, and therefore, when absorbing liquid, the water-absorbent resin layer takes on the characteristic expansion form explained in Fig. 4 of the first embodiment and Fig. 7 of the second embodiment, thereby improving the absorption rate and reducing the risk of side leakage. Since the characteristics of the intermediate sheet 30 and the characteristics of the intermediate sheet 30a each have the effect of improving the absorption rate and reducing the risk of side leakage, using the intermediate sheet 30b having these characteristics can significantly improve the absorption rate and the ability to prevent side leakage.

[0040] [1-4. Fourth embodiment] Figure 9 shows an intermediate sheet 30c used in a fourth embodiment of the laminate of the present invention in the same format as Figure 2. The laminate of the third embodiment is similar to the laminate 10 of the first embodiment described above, except that the intermediate sheet 30 is changed to an intermediate sheet 30c.

[0041] In addition, the intermediate sheet 30c is reversible, having low-density / convex regions Al+ and high-density / concave regions Bh- on both sides, similar to the intermediate sheet 30b used in the third embodiment, and the high-density / concave regions Bh- are located inside the longitudinal end LE of the intermediate sheet 30c.

[0042] The method for providing low-density, convex regions and high-density, concave regions on both sides of the intermediate sheet 30c is not particularly limited, but a preferred method is an embossing method in which the fabric of the intermediate sheet 30c is compressed in the thickness direction from both sides at the locations where the high-density, concave regions should be provided.

[0043] The laminate of the fourth embodiment, like the intermediate sheet 30b used in the third embodiment, uses an intermediate sheet 30b that combines the characteristics of both the intermediate sheet 30 used in the first embodiment and the characteristics of the intermediate sheet 30a used in the second embodiment, and therefore, like the third embodiment, can significantly improve absorption speed and side leakage prevention.

[0044] [1-5. Fifth embodiment] In the laminate of the present invention, as long as region B is located inside the longitudinal ends of the intermediate sheet, it does not matter whether region B reaches the short ends of the intermediate sheet. On the other hand, since the laminate of the present invention is configured to improve the absorption rate by promoting in-plane diffusion of absorbed liquid, region B may be located inside the short ends SE of the intermediate sheet in order to further reduce the risk of leakage from the short ends.

[0045] 10 is a schematic view of the appearance of a portion (a portion including a short edge) of an intermediate sheet used in a fifth embodiment of the laminate of the present invention. The laminate of the fifth embodiment is similar to the laminate 10 of the first embodiment, except that the intermediate sheet 30 is changed to an intermediate sheet 30d.

[0046] In the intermediate sheet 30d used in this embodiment, the high-density region Bh is located inside the short ends SE. The high-density region Bh being located inside the short ends SE means that no part of the high-density region Bh reaches the short ends SE of the intermediate sheet 30, and the entire high-density region Bh is located inside both short ends SE of the intermediate sheet 30 in the in-plane direction. In other words, the portions of both short ends SE of the intermediate sheet 30 are composed of the low-density region Al.

[0047] As a result, when liquid is absorbed, the absorbent resin layer expands to form a convex portion at the short end SE of the absorbent resin layer, just like at the long end LE, thereby forming a physical barrier, thereby reducing the risk of leakage from the short end SE (e.g., rear leakage).

[0048] Although the fifth embodiment has been described with reference to a case where region A is the same low-density region Al as in the first embodiment and region B is the same high-density region Bh as in the first embodiment, this fifth embodiment is also applicable to a case where an intermediate sheet is used in which the low-density region Al is changed to the convex region A+ in the second embodiment or the low-density / convex region Al+ in the third embodiment, and the high-density region Bh is changed to the concave region B- in the second embodiment or the high-density / convex region Bh- in the third embodiment. Furthermore, this fifth embodiment is also applicable to a case where an intermediate sheet having the cross-sectional shape described in the fourth embodiment is used.

[0049] [1-6. Modifications of Area A and Area B] The shapes of region A and region B are not limited to those shown in the first embodiment, and as long as they have a shape with a longitudinal direction, it is thought that the convex portions 51A formed by absorbing the first exposed liquid will guide the liquid absorbed thereafter to spread in the in-plane direction of the laminate 10', thereby improving the absorption speed, as explained with reference to Fig. 4. Furthermore, as long as region B is located inside the longitudinal end LE, it is thought that the convex portions 51A formed by absorbing the first exposed liquid will reduce the risk of side leakage at the longitudinal end LE, as explained with reference to Fig. 4.

[0050] Figure 11 shows a schematic diagram of several examples of the shapes of region A and region B. Figure 11 shows a plan view of the intermediate sheet as seen from the first sheet side, with the solid lines representing region B and the blank areas outside the solid lines representing region A. As described above, as long as region A has a longitudinal shape and region B is located inside the longitudinal end LE, the absorption rate can be improved and the risk of side leakage can be reduced. Therefore, even if there are only two regions A on the longitudinal end LE as shown in Figure 11(a), the laminate of the present invention can exhibit excellent absorption rate and side leakage prevention even when exposed to liquid multiple times. Note that in all of the examples shown in Figure 11, region B is located inside the short end SE, but it is also acceptable for region B to reach the short end SE.

[0051] From the viewpoint of improving the efficiency of guiding absorbed liquid so as to spread it in the in-plane direction, it is preferable that either or both of region A and region B include a portion forming a linear portion. Examples of region A having a portion forming a linear portion include Figures 11(a), 11(d), 11(e), and 11(f). Examples of region B having a portion forming a linear portion include Figures 11(a) to 11(f).

[0052] When region A includes linear portions, the linear portions preferably extend in a direction including the longitudinal direction LD of the intermediate sheet. The term "linear portions extending in a direction including the longitudinal direction LD" means that the extending direction of the linear portions includes a longitudinal direction LD component, regardless of whether it is parallel to the longitudinal direction LD. In other words, the "direction including the longitudinal direction LD" refers to any direction other than a direction perpendicular to the longitudinal direction LD. In other words, in all of the examples shown in Figures 11(a), 11(d), 11(e), and 11(f), the linear portions extend in a direction including the longitudinal direction LD of the intermediate sheet. This is preferable in that when liquid is exposed to the intermediate sheet for the second or subsequent time, it moves more efficiently in the in-plane direction of the laminate, particularly in the longitudinal direction LD, making it possible to effectively utilize the shape of the laminate.

[0053] When region A includes linear portions, it is more preferable that the linear portions extend substantially parallel to the longitudinal direction LD of the intermediate sheet. The linear portions extending substantially parallel to the longitudinal direction LD of the intermediate sheet means that the extension direction of the linear portions may be offset by ±5° from the longitudinal direction LD. Examples of such an embodiment include Figures 11(a) and 11(e). In such an embodiment, when absorbed liquid moves in the in-plane direction of the laminate, movement in the longitudinal direction LD is particularly efficient, which is preferable in that the shape of the laminate can be more effectively utilized.

[0054] When region B includes linear portions, the linear portions are preferably arranged on the short-side center line M of the intermediate sheet. When region B is composed of multiple linear portions, it is sufficient that at least one of the linear portions is arranged on the short-side center line M of the intermediate sheet. Examples of such an embodiment include Figures 11(a) and 11(e). In such an embodiment, when the absorbed liquid moves in the in-plane direction of the laminate, it can move at least through the area farthest from the longitudinal end LE, which is preferable in that it can more effectively prevent side leakage.

[0055] It is preferable that multiple regions A and multiple regions B are arranged alternately in the short-side direction SD-A of the regions, regardless of their shapes. Examples of such an embodiment include Figures 11(c), 11(d), 11(e), and 11(f). In such an embodiment, multiple groove-like recesses 42 described in Figure 4 are formed when absorbing liquid, which makes the movement of absorbed liquid in the longitudinal direction LD more efficient and allows effective use of the shape of the laminate.

[0056] Furthermore, it is more preferable that both region A and region B include linear portions, and that a plurality of linear portions in region A and a plurality of linear portions in region B are arranged in parallel. Examples of such an embodiment include Figures 11(d), 11(e), and 11(f). This embodiment is preferable in that the movement of absorbed liquid in the longitudinal direction LD becomes more efficient, and the shape of the laminate can be more effectively utilized.

[0057] The shapes of the region A and the region B shown in FIG. 11 may be applied singly or in a state where two or more shapes are combined.

[0058] The width of region A (i.e., the width that region A occupies in the short direction SD-A) is not particularly limited, but may be, for example, 0.3 to 5 cm. From the viewpoint of further improving the absorption rate and / or side leakage prevention properties after several exposures to liquid, the width of region A is preferably 0.4 to 3.5 cm, more preferably 0.6 to 3 cm, even more preferably 0.8 to 2.8 cm, even more preferably 1 to 2.3 cm, and even more preferably 1.2 to 1.8 cm. The width of region A may be constant overall along its extension direction, or may vary within the above range.

[0059] The width of region B is not particularly limited, but from the viewpoint of further improving the absorption rate and / or side leakage prevention properties after several exposures to liquid, it is preferably 1 to 15 mm, more preferably 2 to 12 mm, even more preferably 3 to 10 mm, and even more preferably 3 to 8 mm. The width of region B may be constant overall along its extension direction, or may vary within the above range.

[0060] The area ratio of region B in the intermediate sheet is not particularly limited, but from the viewpoint of further increasing the absorption speed and / or side leakage prevention properties after several liquid exposures, the lower limit is preferably 3% or more, more preferably 5% or more, even more preferably 10% or more, even more preferably 15% or more, and even more preferably 18% or more, and the upper limit is preferably 50% or less, more preferably 40% or less, even more preferably 30% or less, even more preferably 25% or less, and even more preferably 22% or less.

[0061] The modified example shown in FIG. 11 can be applied to all of the above-described embodiments.

[0062] [2. Materials and thickness of each component of the laminate] The material and thickness of each component constituting the laminate of the present invention are not particularly limited, and materials and thicknesses that allow each component to have the above-mentioned characteristics are appropriately selected. Note that, unless specifically mentioned in a specific embodiment, the following content can be commonly applied to all of the above-mentioned embodiments.

[0063] [2-1. Sheet 1] The first sheet is not particularly limited as long as it is liquid-permeable. The form of the first sheet is not particularly limited as long as it has spaces or pores that communicate in the thickness direction and the spaces or pores are of a size that does not allow the water-absorbent resin that constitutes the water-absorbent resin layer to pass through. Examples of the form of the first sheet include nonwoven fabric, woven fabric, and porous sheet. Among these forms, nonwoven fabric is preferred from the viewpoint of further improving the absorption speed after multiple liquid exposures and / or improving the side leakage prevention property, or in addition, reducing the amount of backflow.

[0064] The form of the nonwoven fabric is not particularly limited, and examples thereof include air-through nonwoven fabrics, point-bonded nonwoven fabrics, spun-bonded nonwoven fabrics, spunlace nonwoven fabrics, thermal-bonded nonwoven fabrics, melt-blown nonwoven fabrics, air-laid nonwoven fabrics, etc. Among these nonwoven fabrics, air-laid nonwoven fabrics are preferred from the viewpoint of further improving the absorption speed after multiple liquid exposures and / or improving the side leakage prevention properties, or in addition, reducing the amount of backflow.

[0065] Examples of materials for the first sheet include resins such as polyolefins such as polyethylene (PE) and polypropylene (PP), polyesters such as polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT) and polyethylene naphthalate (PEN), polyamides such as nylon, and rayon. These resins may be used alone or in combination of two or more.

[0066] Furthermore, when the first sheet is in the form of a nonwoven or woven fabric, the material of the first sheet may be, in addition to the above-mentioned fibers made of resin (synthetic resin fibers), natural fibers such as cotton, silk, hemp, pulp (cellulose), etc. These fibers may be used alone or in combination of two or more.

[0067] Among the above materials, from the viewpoint of further improving the absorption speed after multiple liquid exposures and / or improving the prevention of side leakage, or in addition, reducing the amount of backflow, a combination of resin fibers and natural fibers is preferred, and a combination of polyolefin fibers and pulp is more preferred.

[0068] The basis weight of the first sheet is not particularly limited, but is preferably 20 to 60 g / m from the viewpoint of further improving the absorption rate after multiple liquid exposures and, in addition, reducing the amount of return. 2 , more preferably 30 to 50 g / m 2 , and more preferably 35 to 45 g / m 2 Examples include:

[0069] The thickness of the first sheet is not particularly limited, but from the viewpoint of further improving the absorption rate after multiple liquid exposures, and in addition, reducing the amount of backflow, the thickness is preferably 0.1 to 0.8 mm, more preferably 0.2 to 0.6 mm, even more preferably 0.3 to 0.5 mm, and even more preferably 0.35 to 0.45 mm.

[0070] [2-2. Water-absorbing resin layer] The material of the water-absorbent resin layer (i.e., the water-absorbent resin) is not particularly limited as long as it is a resin that can absorb water and has the property of swelling when it absorbs water, that is, what is generally called a super absorbent resin (SAP).

[0071] Specific examples of the water-absorbing resin include hydrolyzates of starch-acrylonitrile graft copolymers, neutralized starch-acrylic acid graft polymers, saponified vinyl acetate-acrylic acid ester copolymers, crosslinked products of partially neutralized acrylic acid polymers, partially neutralized polyacrylic acid, etc. These water-absorbing resins may be used alone or in combination of two or more.

[0072] Among these water-absorbent resins, a crosslinked polymer of partially neutralized acrylic acid is preferred from the viewpoint of further improving the absorption rate after multiple exposures to liquid. The degree of neutralization of the crosslinked polymer of partially neutralized acrylic acid is, for example, 50 mol% or more, preferably 60 to 90 mol%, and more preferably 70 to 80 mol%. Methods for synthesizing the crosslinked polymer of partially neutralized acrylic acid are known, and specific examples include reverse phase suspension polymerization and aqueous solution polymerization.

[0073] The thickness of the water-absorbent resin layer is not particularly limited, but for example, the thickness of the layered surface of the laminate (i.e., the surface perpendicular to the lamination direction LMD10) is 1 mm. 2 For example, 25 to 600 g, preferably 50 to 450 g / m 2 , more preferably 100 to 400 g / m 2 , and more preferably 150 to 200 g / m 2 The thickness is as follows.

[0074] The physiological saline water absorption capacity of the water-absorbent resin is not particularly limited, but from the viewpoint of absorbing a larger amount of liquid and preventing the gel blocking phenomenon, it is preferably 30 to 75 g / g, more preferably 40 to 73 g / g, even more preferably 50 to 70 g / g, still more preferably 60 to 70 g / g, and particularly preferably 65 to 70 g / g.

[0075] The physiological saline water retention capacity of the water-absorbent resin is not particularly limited, but from the viewpoint of further increasing the absorption speed and / or side leakage prevention property after several exposures to liquid, it is preferably 20 to 60 g / g, more preferably 25 to 58 g / g, even more preferably 30 to 56 g / g, even more preferably 40 to 54 g / g, and even more preferably 48 to 52 g / g.

[0076] The saline water absorption rate of the water-absorbent resin is not particularly limited, but from the viewpoint of further increasing the absorption rate and / or side leakage prevention properties after multiple liquid exposures, it is preferably 25 to 80 seconds, more preferably 30 to 80 seconds, even more preferably 40 to 80 seconds, even more preferably 44 to 80 seconds, and even more preferably 47 to 80 seconds. The laminate of the present invention exhibits excellent effects of improving the absorption rate and preventing side leakage after multiple liquid exposures, and therefore can effectively exhibit excellent effects of improving the absorption rate and preventing side leakage even when the absorption rate of the water-absorbent resin itself is relatively slow. From this viewpoint, suitable examples of the saline water absorption rate of the water-absorbent resin include 25 to 70 seconds, preferably 25 to 60 seconds, and more preferably 25 to 50 seconds.

[0077] The median particle size of the water-absorbent resin is not particularly limited, but from the viewpoint of further increasing the absorption speed and / or side leakage prevention property after several exposures to liquid, it is preferably 100 to 600 μm, more preferably 200 to 500 μm, even more preferably 300 to 400 μm, and even more preferably 350 to 370 μm.

[0078] [2-3. Middle sheet] The material of the intermediate sheet is not particularly limited as long as it is liquid-absorbent. The form of the intermediate sheet is not particularly limited as long as it has spaces, holes, and / or apertures that communicate with at least the water-absorbent resin layer side. Examples of the intermediate sheet include nonwoven fabric, woven fabric, and porous sheet. Among these forms, nonwoven fabric is preferred from the viewpoint of further increasing the absorption speed and / or side leakage prevention properties after several exposures to liquid.

[0079] The form of the nonwoven fabric is not particularly limited, and examples thereof include air-through nonwoven fabrics, point-bonded nonwoven fabrics, spun-bonded nonwoven fabrics, spunlace nonwoven fabrics, thermal-bonded nonwoven fabrics, melt-blown nonwoven fabrics, air-laid nonwoven fabrics, etc. Among these nonwoven fabrics, air-through nonwoven fabrics are preferred from the viewpoint of further increasing the absorption rate and / or side leakage prevention properties after several exposures to liquid.

[0080] The basis weight of the intermediate sheet is not particularly limited, but from the viewpoint of further increasing the absorption rate and / or side leakage prevention property after several exposures to liquid, the lower limit is preferably 20 g / m 2 More preferably, 30 g / m 2 More preferably, 40 g / m 2 More preferably, 43 g / m 2 The upper limit is preferably 60 g / m 2 Less than 55 g / m 2 or less, more preferably 50 g / m 2 More preferably 47 g / m or less 2 The following are included:

[0081] The thickness t of the intermediate sheet is not particularly limited, and may be, for example, 0.7 mm or more. From the viewpoint of further increasing the absorption rate and / or side leakage prevention properties after several exposures to liquid, the thickness t is preferably 1.5 mm or more, more preferably 2 mm or more, and even more preferably 2.3 mm or more. The upper limit of the range of the thickness t of the intermediate sheet is not particularly limited, and may be, for example, 4 mm or less, preferably 3 mm or less, and more preferably 2.8 mm or less. Note that, in cases where region A forms a convex portion and region B forms a concave portion as in the second to fourth embodiments, the thickness t of the intermediate sheet refers to the thickness of the portion corresponding to region A.

[0082] [2-4. Other water-absorbent resin layers] The material of the other water-absorbent resin layer is not particularly limited, and can be selected from the water-absorbent resins listed above as the material of the water-absorbent resin layer. The water-absorbent resin used in the other water-absorbent resin layer may be the same as or different from the water-absorbent resin used in the above water-absorbent resin layer.

[0083] The thickness of the other water-absorbent resin layer is not particularly limited, and can be selected from the values ​​given above as the thickness of the water-absorbent resin layer. The thickness of the other water-absorbent resin layer and the thickness of the water-absorbent resin layer may be the same as or different from each other.

[0084] [2-3. Sheet 2] The second sheet may be a liquid-permeable sheet or a liquid-impermeable sheet. When the second sheet is a liquid-permeable sheet, the second sheet may be a sheet selected from those used as the first sheet, or a sheet of the same shape and material as the first sheet except that it does not have the predetermined high-wettability and low-wettability regions of the first sheet.

[0085] When the second sheet is a sheet selected from those used as the first sheet, the first sheet and the second sheet may be the same or different.

[0086] [2-4.Adhesive layer] The adhesive resin composition used in the adhesive layer is not limited as long as it can bond the water-absorbent resin to the intermediate sheet and / or the second sheet, and can be appropriately selected by a person skilled in the art. Since the laminate of the present invention is used to absorb aqueous liquids, a preferred adhesive composition is a hot-melt adhesive composition that is stable against aqueous solvents.

[0087] [3. Preparation of laminate] The method for producing the laminate of the present invention is not particularly limited, but it can be produced, for example, by the following method.

[0088] For example, a laminated material can be produced by laminating a water-absorbent resin layer and a first sheet on the surface of the intermediate sheet where the regions A and B are provided, and then laminating another water-absorbent resin layer and a second sheet on the intermediate sheet side of the laminated material to integrate all layers, thereby producing a laminate.

[0089] Furthermore, in the case where an adhesive layer is interposed between the water-absorbent resin layer and the intermediate sheet and between the water-absorbent resin layer and the second sheet, a laminated material is prepared by laminating the adhesive layer, the water-absorbent resin layer and the first sheet in this order on the surface of the intermediate sheet where the regions A and B are provided, and then another water-absorbent resin layer is laminated on the intermediate sheet side of the laminated material, and then a second sheet having an adhesive layer laminated on its surface is laminated so that the adhesive layer faces the other water-absorbent resin layer, and all layers are integrated to prepare a laminate.

[0090] The first and second sheets can be of the same shape and size, and the intermediate sheet can be one size smaller than the first and second sheets.In this case, after all layers are stacked, the edges of the first and second sheets can be joined together (for example, by heat pressing) to integrate all layers.

[0091] [4. Uses of laminates] The laminate of the present invention functions as an absorbent body that exhibits excellent absorption rate and side leakage prevention even when exposed to liquids multiple times. Therefore, the laminate of the present invention is useful for absorbent articles, and the present invention also provides absorbent articles including the laminate.

[0092] The absorbent article is not particularly limited, but preferably includes an absorbent article that needs to absorb liquid multiple times. The liquid may be a liquid containing water. More specific examples of the absorbent article include disposable diapers, urine pads, sanitary napkins, pet sheets, drip sheets for food, and waterproof materials for power cables. [Example]

[0093] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0094] (1) Synthesis of water-absorbent resin particles (super absorbent polymer; SAP) (1-1) Production Example 1: Synthesis of SAPa <First step polymerization reaction> A 2-L round-bottom cylindrical separable flask with an inner diameter of 11 cm and equipped with a reflux condenser, a dropping funnel, a nitrogen gas inlet, and a stirrer with a two-stage, four-paddle blade arrangement with a blade diameter of 5 cm was prepared. 293 g of n-heptane was added to the flask as a hydrocarbon dispersion medium, and 0.736 g of maleic anhydride-modified ethylene-propylene copolymer (Hiwax 1105A, Mitsui Chemicals, Inc.) was added as a polymeric dispersant. The flask was heated to 80°C with stirring to dissolve the dispersant, and then cooled to 50°C.

[0095] In a 300 mL beaker, 92.0 g (1.03 mol) of an 80.5 mass% aqueous solution of acrylic acid as a water-soluble ethylenically unsaturated monomer was placed. While cooling from the outside, 147.7 g of a 20.9 mass% aqueous solution of sodium hydroxide was added dropwise to the mixture to neutralize it to 75 mol%. Then, 0.092 g of hydroxyethyl cellulose (Sumitomo Seika Chemicals Co., Ltd., HECAW-15F) as a thickener, 0.0736 g (0.272 mmol) of potassium persulfate as a water-soluble radical polymerization initiator, and 0.010 g (0.057 mmol) of ethylene glycol diglycidyl ether as an internal crosslinking agent were added and dissolved to prepare a first-stage aqueous monomer solution.

[0096] The first-stage monomer aqueous solution prepared above was added to a separable flask and stirred for 10 minutes. A surfactant solution prepared by heating and dissolving 0.736 g of sucrose stearate with HLB3 (Ryoto Sugar Ester S-370, Mitsubishi Chemical Foods Corporation) as a surfactant in 6.62 g of n-heptane was then added. The system was thoroughly purged with nitrogen while stirring at a stirrer speed of 500 rpm, and the flask was immersed in a 70°C water bath to raise the temperature. Polymerization was carried out for 60 minutes, thereby obtaining a first-stage polymerization slurry.

[0097] <Second-stage polymerization reaction> In a 500 mL beaker, 128.8 g (1.44 mol) of an 80.5 mass% aqueous acrylic acid solution was placed as a water-soluble ethylenically unsaturated monomer, and while cooling from the outside, 159.0 g of a 27 mass% aqueous sodium hydroxide solution was added dropwise to carry out 75 mol% neutralization. After that, 0.090 g (0.333 mmol) of potassium persulfate as a water-soluble radical polymerization initiator and 0.0116 g (0.067 mmol) of ethylene glycol diglycidyl ether as an internal crosslinking agent were added and dissolved to prepare a second-stage aqueous monomer solution.

[0098] The contents of the separable flask system were cooled to 25°C while stirring at a stirrer speed of 1000 rpm, and then the entire amount of the second-stage aqueous monomer solution was added to the first-stage polymerization slurry. The atmosphere in the system was replaced with nitrogen for 30 minutes, and the flask was again immersed in a water bath at 70°C to raise the temperature, and the polymerization reaction was carried out for 60 minutes to obtain a hydrogel polymer.

[0099] After polymerization, 0.589 g of a 45% by mass aqueous solution of diethylenetriaminepentaacetic acid pentasodium was added to the resulting hydrogel polymer under stirring. The flask was then immersed in an oil bath set at 125°C, and 257.2 g of water was extracted from the system by azeotropic distillation of n-heptane and water while refluxing the n-heptane. Then, 4.42 g (0.507 mmol) of a 2% by mass aqueous solution of ethylene glycol diglycidyl ether was added to the flask as a surface cross-linking agent, and the mixture was maintained at 83°C for 2 hours.

[0100] The n-heptane and water were then evaporated and dried in an oil bath at 125°C to obtain dried polymer particles. The polymer particles were passed through a sieve with an opening of 850 µm, and 0.2% by mass of amorphous silica (Toxil NP-S, Oriental Silicas Corporation) relative to the mass of the polymer particles was mixed with the polymer particles to obtain 231.2 g of SAPa containing amorphous silica.

[0101] (1-2) Production Example 2: Synthesis of SAPb The same operations as in Production Example 1 were carried out, except that 257.2 g of water was removed from the hydrogel polymer after the second-stage polymerization by azeotropic distillation, to give 231.2 g of SAPb.

[0102] (1-3) Production Example 3: Synthesis of SAPc <First step polymerization reaction> A 2-L round-bottom cylindrical separable flask with an inner diameter of 11 cm and equipped with a reflux condenser, a dropping funnel, a nitrogen gas inlet, and a stirrer with a two-stage, four-paddle blade arrangement with a blade diameter of 5 cm was prepared. 293 g of n-heptane was added to the flask as a hydrocarbon dispersion medium, and 0.736 g of maleic anhydride-modified ethylene-propylene copolymer (Hiwax 1105A, Mitsui Chemicals, Inc.) was added as a polymeric dispersant. The flask was heated to 80°C with stirring to dissolve the dispersant, and then cooled to 50°C.

[0103] In a 300 mL beaker, 92.0 g (1.03 mol) of an 80.5 mass% aqueous solution of acrylic acid as a water-soluble ethylenically unsaturated monomer was placed. While cooling from the outside, 147.7 g of a 20.9 mass% aqueous solution of sodium hydroxide was added dropwise to the mixture to neutralize it to 75 mol%. Then, 0.092 g of hydroxyethyl cellulose (Sumitomo Seika Chemicals Co., Ltd., HECAW-15F) as a thickener, 0.0736 g (0.272 mmol) of potassium persulfate as a water-soluble radical polymerization initiator, and 0.010 g (0.057 mmol) of ethylene glycol diglycidyl ether as an internal crosslinking agent were added and dissolved to prepare a first-stage aqueous monomer solution.

[0104] The first-stage monomer aqueous solution prepared above was added to a separable flask and stirred for 10 minutes. A surfactant solution prepared by heating and dissolving 0.736 g of sucrose stearate with HLB3 (Ryoto Sugar Ester S-370, Mitsubishi Chemical Foods Corporation) as a surfactant in 6.62 g of n-heptane was then added. The system was thoroughly purged with nitrogen while stirring at a stirrer speed of 550 rpm, and the flask was immersed in a 70°C water bath to raise the temperature. Polymerization was carried out for 60 minutes, thereby obtaining a first-stage polymerization slurry.

[0105] <Second-stage polymerization reaction> In a 500 mL beaker, 128.8 g (1.44 mol) of an 80.5 mass% aqueous acrylic acid solution was placed as a water-soluble ethylenically unsaturated monomer, and while cooling from the outside, 159.0 g of a 27 mass% aqueous sodium hydroxide solution was added dropwise to carry out 75 mol% neutralization. After that, 0.090 g (0.333 mmol) of potassium persulfate as a water-soluble radical polymerization initiator and 0.0116 g (0.067 mmol) of ethylene glycol diglycidyl ether as an internal crosslinking agent were added and dissolved to prepare a second-stage aqueous monomer solution.

[0106] The contents of the separable flask system were cooled to 25°C while stirring at a stirrer speed of 1000 rpm, and then the entire amount of the second-stage aqueous monomer solution was added to the first-stage polymerization slurry. The atmosphere in the system was replaced with nitrogen for 30 minutes, and the flask was again immersed in a water bath at 70°C to raise the temperature, and the polymerization reaction was carried out for 60 minutes to obtain a hydrogel polymer.

[0107] After polymerization, 0.265 g of a 45% by mass aqueous solution of pentasodium diethylenetriamine pentacetate was added to the resulting hydrogel polymer under stirring. The flask was then immersed in an oil bath set at 125°C, and 271.4 g of water was extracted from the system by azeotropic distillation of n-heptane and water while refluxing the n-heptane. Then, 6.40 g (0.735 mmol) of a 2% by mass aqueous solution of ethylene glycol diglycidyl ether was added to the flask as a surface cross-linking agent, and the mixture was maintained at 83°C for 2 hours.

[0108] The n-heptane and water were then evaporated and dried in an oil bath at 125°C to obtain dried polymer particles. The polymer particles were passed through a sieve with an opening of 850 µm, and 0.5% by mass of amorphous silica (Toxil NP-S, Oriental Silicas Corporation) relative to the mass of the polymer particles was mixed with the polymer particles to obtain 230.6 g of SAPc containing amorphous silica.

[0109] (1-4) Production Example 4: Synthesis of SAPd <First step polymerization reaction> A 2-L round-bottom cylindrical separable flask with an inner diameter of 11 cm and equipped with a reflux condenser, a dropping funnel, a nitrogen gas inlet, and a stirrer with a two-stage, four-paddle blade arrangement with a blade diameter of 5 cm was prepared. 293 g of n-heptane was added to the flask as a hydrocarbon dispersion medium, and 0.736 g of maleic anhydride-modified ethylene-propylene copolymer (Hiwax 1105A, Mitsui Chemicals, Inc.) was added as a polymeric dispersant. The flask was heated to 80°C with stirring to dissolve the dispersant, and then cooled to 50°C.

[0110] In a 300 mL beaker, 92.0 g (1.03 mol) of an 80.5 mass% aqueous solution of acrylic acid as a water-soluble ethylenically unsaturated monomer was placed. While cooling from the outside, 147.7 g of a 20.9 mass% aqueous solution of sodium hydroxide was added dropwise to the mixture to neutralize it to 75 mol%. Then, 0.092 g of hydroxyethyl cellulose (Sumitomo Seika Chemicals Co., Ltd., HECAW-15F) as a thickener, 0.0736 g (0.272 mmol) of potassium persulfate as a water-soluble radical polymerization initiator, and 0.010 g (0.057 mmol) of ethylene glycol diglycidyl ether as an internal crosslinking agent were added and dissolved to prepare a first-stage aqueous monomer solution.

[0111] The first-stage monomer aqueous solution prepared above was added to a separable flask and stirred for 10 minutes. A surfactant solution prepared by heating and dissolving 0.736 g of sucrose stearate with HLB3 (Ryoto Sugar Ester S-370, Mitsubishi Chemical Foods Corporation) as a surfactant in 6.62 g of n-heptane was then added. The system was thoroughly purged with nitrogen while stirring at a stirrer speed of 550 rpm, and the flask was immersed in a 70°C water bath to raise the temperature. Polymerization was carried out for 60 minutes, thereby obtaining a first-stage polymerization slurry.

[0112] <Second-stage polymerization reaction> In a 500 mL beaker, 128.8 g (1.44 mol) of an 80.5 mass% aqueous acrylic acid solution was placed as a water-soluble ethylenically unsaturated monomer, and while cooling from the outside, 159.0 g of a 27 mass% aqueous sodium hydroxide solution was added dropwise to carry out 75 mol% neutralization. After that, 0.103 g (0.381 mmol) of potassium persulfate as a water-soluble radical polymerization initiator and 0.0116 g (0.067 mmol) of ethylene glycol diglycidyl ether as an internal crosslinking agent were added and dissolved to prepare a second-stage aqueous monomer solution.

[0113] The contents of the separable flask system were cooled to 25°C while stirring at a stirrer speed of 1000 rpm, and then the entire amount of the second-stage aqueous monomer solution was added to the first-stage polymerization slurry. The atmosphere in the system was replaced with nitrogen for 30 minutes, and the flask was again immersed in a water bath at 70°C to raise the temperature, and the polymerization reaction was carried out for 60 minutes to obtain a hydrogel polymer.

[0114] After polymerization, 0.589 g of a 45% by mass aqueous solution of pentasodium diethylenetriamine pentacetate was added to the resulting hydrogel polymer under stirring. The flask was then immersed in an oil bath set at 125°C, and 237.7 g of water was extracted from the system by azeotropic distillation of n-heptane and water while refluxing the n-heptane. Then, 4.42 g (0.507 mmol) of a 2% by mass aqueous solution of ethylene glycol diglycidyl ether was added as a surface cross-linking agent to the flask, and the mixture was maintained at 83°C for 2 hours.

[0115] The n-heptane and water were then evaporated and dried in an oil bath at 125°C to obtain dried polymer particles. The polymer particles were passed through a sieve with an opening of 850 µm, and 0.5% by mass of amorphous silica (Toxil NP-S, Oriental Silicas Corporation) relative to the mass of the polymer particles was mixed with the polymer particles to obtain 226.0 g of SAPd containing amorphous silica.

[0116] (1-5) Production Example 5: Synthesis of SAPe <First step polymerization reaction> A 2-L round-bottom cylindrical separable flask with an inner diameter of 11 cm and equipped with a reflux condenser, a dropping funnel, a nitrogen gas inlet, and a stirrer with a two-stage, four-paddle blade arrangement with a blade diameter of 5 cm was prepared. 293 g of n-heptane was added to the flask as a hydrocarbon dispersion medium, and 0.736 g of maleic anhydride-modified ethylene-propylene copolymer (Hiwax 1105A, Mitsui Chemicals, Inc.) was added as a polymeric dispersant. The flask was heated to 80°C with stirring to dissolve the dispersant, and then cooled to 50°C.

[0117] In a 300 mL beaker, 92.0 g (1.03 mol) of an 80.5 mass% aqueous solution of acrylic acid as a water-soluble ethylenically unsaturated monomer was placed. While cooling from the outside, 147.7 g of a 20.9 mass% aqueous solution of sodium hydroxide was added dropwise to the mixture to neutralize it to 75 mol%. Then, 0.092 g of hydroxyethyl cellulose (Sumitomo Seika Chemicals Co., Ltd., HECAW-15F) as a thickener, 0.092 g (0.339 mmol) of 2,2'-azobis(2-amidinopropane) dihydrochloride as a water-soluble radical polymerization initiator, 0.018 g (0.067 mmol) of potassium persulfate, and 0.0046 g (0.026 mmol) of ethylene glycol diglycidyl ether as an internal crosslinking agent were added and dissolved to prepare a first-stage aqueous monomer solution.

[0118] The first-stage monomer aqueous solution prepared above was added to a separable flask and stirred for 10 minutes. A surfactant solution prepared by heating and dissolving 0.736 g of sucrose stearate with HLB3 (Ryoto Sugar Ester S-370, Mitsubishi Chemical Foods Corporation) as a surfactant in 6.62 g of n-heptane was then added. The system was thoroughly purged with nitrogen while stirring at a stirrer speed of 500 rpm, and the flask was immersed in a 70°C water bath to raise the temperature. Polymerization was carried out for 60 minutes, thereby obtaining a first-stage polymerization slurry.

[0119] <Second-stage polymerization reaction> In a 500 mL beaker, 128.8 g (1.44 mol) of an 80.5 mass% aqueous solution of acrylic acid was placed as a water-soluble ethylenically unsaturated monomer. While cooling from the outside, 159.0 g of a 27 mass% aqueous solution of sodium hydroxide was added dropwise to the solution to neutralize it to 75 mol%, and then 0.129 g (0.476 mmol) of 2,2'-azobis(2-amidinopropane) dihydrochloride and 0.026 g (0.096 mmol) of potassium persulfate as water-soluble radical polymerization initiators, and 0.0116 g (0.067 mmol) of ethylene glycol diglycidyl ether as an internal crosslinking agent were added and dissolved to prepare a second-stage aqueous monomer solution.

[0120] The contents of the separable flask system were cooled to 25°C while stirring at a stirrer speed of 1000 rpm, and then the entire amount of the second-stage aqueous monomer solution was added to the first-stage polymerization slurry. The atmosphere in the system was replaced with nitrogen for 30 minutes, and the flask was again immersed in a water bath at 70°C to raise the temperature, and the polymerization reaction was carried out for 60 minutes to obtain a hydrogel polymer.

[0121] After polymerization, 0.589 g of a 45% by mass aqueous solution of diethylenetriaminepentaacetic acid pentasodium was added to the resulting hydrogel polymer under stirring. The flask was then immersed in an oil bath set at 125°C, and 201.4 g of water was extracted from the system by azeotropic distillation of n-heptane and water while refluxing the n-heptane. Then, 4.42 g (0.507 mmol) of a 2% by mass aqueous solution of ethylene glycol diglycidyl ether was added as a surface cross-linking agent to the flask, and the mixture was maintained at 83°C for 2 hours.

[0122] The n-heptane and water were then evaporated and dried in an oil bath at 125°C to obtain dried polymer particles. The polymer particles were passed through a sieve with an opening of 850 µm, and 0.2% by mass of amorphous silica (Toxil NP-S, Oriental Silicas Corporation) relative to the mass of the polymer particles was mixed with the polymer particles to obtain 231.2 g of SAPe containing amorphous silica.

[0123] (1-6) Production Example 6: Synthesis of SAPf <First step polymerization reaction> A 2-L round-bottom cylindrical separable flask with an inner diameter of 11 cm and equipped with a reflux condenser, a dropping funnel, a nitrogen gas inlet, and a stirrer with a two-stage, four-paddle blade arrangement with a blade diameter of 5 cm was prepared. 293 g of n-heptane was added to the flask as a hydrocarbon dispersion medium, and 0.736 g of maleic anhydride-modified ethylene-propylene copolymer (Hiwax 1105A, Mitsui Chemicals, Inc.) was added as a polymeric dispersant. The flask was heated to 80°C with stirring to dissolve the dispersant, and then cooled to 50°C.

[0124] In a 300 mL beaker, 92.0 g (1.03 mol) of an 80.5 mass% aqueous solution of acrylic acid as a water-soluble ethylenically unsaturated monomer was placed. While cooling from the outside, 147.7 g of a 20.9 mass% aqueous solution of sodium hydroxide was added dropwise to the mixture to neutralize it to 75 mol%. Then, 0.092 g of hydroxyethyl cellulose (Sumitomo Seika Chemicals Co., Ltd., HECAW-15F) as a thickener, 0.092 g (0.339 mmol) of 2,2'-azobis(2-amidinopropane) dihydrochloride as a water-soluble radical polymerization initiator, 0.018 g (0.067 mmol) of potassium persulfate, and 0.0046 g (0.026 mmol) of ethylene glycol diglycidyl ether as an internal crosslinking agent were added and dissolved to prepare a first-stage aqueous monomer solution.

[0125] The first-stage monomer aqueous solution prepared above was added to a separable flask and stirred for 10 minutes. A surfactant solution prepared by heating and dissolving 0.736 g of sucrose stearate with HLB3 (Ryoto Sugar Ester S-370, Mitsubishi Chemical Foods Corporation) as a surfactant in 6.62 g of n-heptane was then added. The system was thoroughly purged with nitrogen while stirring at a stirrer speed of 500 rpm, and the flask was immersed in a 70°C water bath to raise the temperature. Polymerization was carried out for 60 minutes, thereby obtaining a first-stage polymerization slurry.

[0126] <Second-stage polymerization reaction> In a 500 mL beaker, 128.8 g (1.44 mol) of an 80.5 mass% aqueous solution of acrylic acid was placed as a water-soluble ethylenically unsaturated monomer. While cooling from the outside, 159.0 g of a 27 mass% aqueous solution of sodium hydroxide was added dropwise to the solution to neutralize it to 75 mol%, and then 0.129 g (0.476 mmol) of 2,2'-azobis(2-amidinopropane) dihydrochloride and 0.026 g (0.096 mmol) of potassium persulfate as water-soluble radical polymerization initiators, and 0.0116 g (0.067 mmol) of ethylene glycol diglycidyl ether as an internal crosslinking agent were added and dissolved to prepare a second-stage aqueous monomer solution.

[0127] The contents of the separable flask system were cooled to 25°C while stirring at a stirrer speed of 1000 rpm, and then the entire amount of the second-stage aqueous monomer solution was added to the first-stage polymerization slurry. The atmosphere in the system was replaced with nitrogen for 30 minutes, and the flask was again immersed in a water bath at 70°C to raise the temperature, and the polymerization reaction was carried out for 60 minutes to obtain a hydrogel polymer.

[0128] After polymerization, 0.589 g of a 45% by mass aqueous solution of diethylenetriaminepentaacetic acid pentasodium was added to the resulting hydrogel polymer under stirring. The flask was then immersed in an oil bath set at 125°C, and 234.2 g of water was extracted from the system by azeotropic distillation of n-heptane and water while refluxing the n-heptane. Then, 4.42 g (0.507 mmol) of a 2% by mass aqueous solution of ethylene glycol diglycidyl ether was added to the flask as a surface cross-linking agent, and the mixture was maintained at 83°C for 2 hours.

[0129] The n-heptane and water were then evaporated and dried in an oil bath at 125°C to obtain dried polymer particles. The polymer particles were passed through a sieve with an opening of 850 µm, and 0.2% by mass of amorphous silica (Toxil NP-S, Oriental Silicas Corporation) relative to the mass of the polymer particles was mixed with the polymer particles to obtain 231.2 g of SAPf containing amorphous silica.

[0130] (2) Measurement of water-absorbent resin particles (2-1) Water absorption amount The water absorption measurement was performed in a room controlled at 25°C ± 1°C. 500 g of saline solution was weighed into a 500 mL beaker, and a stir bar (8 mm diameter x 30 mm, no ring) was placed in it. The beaker was placed on a magnetic stirrer and stirred at 600 r / min, while 2.0 g of water-absorbent resin particles were dispersed without forming lumps. The beaker was left in this state for 60 minutes to allow the water-absorbent resin particles to fully swell. The contents of the beaker were then filtered through a standard sieve with a 75 μm opening (mass Ma [g]). The sieve was tilted at an angle of approximately 30 degrees relative to the horizontal and left for 30 minutes to filter out excess water from the swollen gel on the sieve. The total mass Mb [g] of the sieve and the swollen gel on the sieve was then measured, and the water absorption of the water-absorbent resin particles in saline was calculated using the following formula. The results are shown in Tables 1 and 2. Water absorption [g / g]=(Mb-Ma) / 2.0

[0131] (2-2) Water retention capacity The water retention capacity was measured in a room regulated at 25°C ± 1°C. A cotton bag (membrane broadcloth No. 60, 100 mm wide x 200 mm long) containing 2.0 g of water-absorbent resin particles was placed in a 500 mL beaker. 500 g of a 0.9 mass % sodium chloride aqueous solution (physiological saline) was poured into the cotton bag containing the water-absorbent resin particles all at once, taking care not to allow the bag to become lumpy. The top of the cotton bag was then tied with a rubber band and allowed to stand for 30 minutes to allow the water-absorbent resin particles to swell. After 30 minutes, the cotton bag was dehydrated for 1 minute using a dehydrator (manufactured by Kokusan Co., Ltd., product number: H-122) set to a centrifugal force of 167 G, and the mass (Wa [g]) of the cotton bag containing the swollen gel after dehydration was measured. The same procedure was performed without adding water-absorbent resin particles, and the empty mass (Wb [g]) of the cotton bag when wet was measured. The water retention capacity of the water-absorbent resin particles in physiological saline was calculated using the following formula: The results are shown in Tables 1 and 2. Water retention amount [g / g]=(Wa-Wb) / 2.0

[0132] (2-3) Water absorption rate The water absorption rate was measured in a room adjusted to 25°C ± 1°C. 50 ± 0.1 g of saline was weighed into a 100 mL beaker, a magnetic stirrer bar (8 mmφ × 30 mm without a ring) was placed in it, and the beaker was immersed in a thermostatic water bath to adjust the liquid temperature to 25 ± 0.2°C. Next, the beaker was placed on a magnetic stirrer and rotated at a speed of 600 r / min to generate a vortex in the saline, and then 2.0 ± 0.002 g of water-absorbent resin particles were quickly added to the beaker. Using a stopwatch, the time (seconds) from the addition of the water-absorbent resin to the point at which the vortex on the liquid surface converged was measured, and this was taken as the water absorption rate of the water-absorbent resin particles. The results are shown in Tables 1 and 2.

[0133] (2-4) Median particle size JIS standard sieves were stacked in the following order from top to bottom: a 600 μm mesh sieve, a 500 μm mesh sieve, a 425 μm mesh sieve, a 300 μm mesh sieve, a 250 μm mesh sieve, a 180 μm mesh sieve, a 150 μm mesh sieve, and a tray. 50 g of water-absorbent resin particles were placed on the top sieve and shaken for 10 minutes using a rotary shaker to classify the particles. After classification, the mass of the particles remaining on each sieve was calculated as a mass percentage relative to the total mass to determine the particle size distribution. The particles remaining on the sieves were integrated in descending order of particle size, and the relationship between the sieve opening size and the integrated value of the mass percentage of the particles remaining on the sieves was plotted on logarithmic probability paper. The particle size corresponding to a cumulative mass percentage of 50% by mass was obtained as the median particle size by connecting the plots on the probability paper with a straight line. The results are shown in Tables 1 and 2.

[0134] (3) Preparation of the intermediate sheet The following nonwoven fabric was prepared and cut into a shape having a longitudinal direction (a rectangle of 10 cm x 40 cm). Air-through nonwoven fabric a (Guangzhou Jinhan Nonwovens Co., Ltd., D45-200, basis weight 45g / m 2 ) ·Air-through non-woven fabric B (Jiangsu Hualong Non-woven Fabric Co., Ltd., basis weight 32g / m 2 ) ·Air-through non-woven fabric c (Jiangsu Hualong Non-woven Fabric Co., Ltd., basis weight 45g / m 2 ) Air-through nonwoven fabric (KNH Enterprise Co., Ltd., AT025-CP49-0, basis weight 25g / m 2 ) Airlaid nonwoven fabric (KNH Enterprise Co., Ltd., 6190516-1A01, basis weight 40g / m 2 ) Spunlace nonwoven fabric (Kuraray Co., Ltd., 70% rayon; 20% PET; 10% PP / PE, basis weight 35g / m 2 )

[0135] (3-1) Processing of air-through nonwoven fabric a The air-through nonwoven fabric a was subjected to the following processing to obtain six types of nonwoven fabrics with different shapes of region A and region B.

[0136] (3-1-1) Using a heat sealer (Fuji Impulse Co., Ltd., FI-450-5, time settings 3 to 5), the air-through nonwoven fabric a was heat-seal embossed to form an embossed region (processed region) called region Bh-, and the remaining region (unprocessed region) called region Al+. Specifically, as shown in Figure 12, four linear regions Bh- (embossed regions) approximately 5 mm wide were formed at approximately 2 cm intervals in a direction parallel to the longitudinal direction of the nonwoven fabric, resulting in linear regions Al+ in a direction parallel to the longitudinal direction of the nonwoven fabric. The resulting processed air-through nonwoven fabric a had the shape of an intermediate sheet 30c shown in Figure 9.

[0137] (3-1-2) The same procedure as in (3-1-1) was repeated, except that three approximately 5 mm wide embossed regions Bh- (embossed portions) were formed at approximately 3 cm intervals to form a striated region Al+ parallel to the longitudinal direction of the nonwoven fabric. The resulting processed air-through nonwoven fabric a had the shape of an intermediate sheet 30c shown in Figure 9.

[0138] (3-1-3) The same procedure as in (3-1-1) was carried out, except that a single linear region Bh- (embossed portion) approximately 5 mm wide was formed along the short center line of the intermediate sheet, resulting in a region Al+ parallel to the longitudinal direction of the nonwoven fabric, as shown in Figure 13. The resulting processed air-through nonwoven fabric a had the shape of the intermediate sheet 30c shown in Figure 9.

[0139] (3-1-4) As shown in Figure 14, 12 linear regions Bh- (embossed portions) approximately 5 mm wide were formed at intervals of approximately 3 cm in the direction parallel to the short side of the nonwoven fabric, resulting in linear regions Al+ in the direction parallel to the short side of the nonwoven fabric. The resulting processed air-through nonwoven fabric a had the shape of the intermediate sheet 30c shown in Figure 9.

[0140] (3-1-5) As shown in Figure 15, fifteen embossed regions Bh- (approximately 5 mm wide) were formed at 45° angles to the longitudinal direction of the nonwoven fabric at intervals of approximately 3 cm, resulting in embossed regions Al+ (approximately 5 mm wide) at 45° angles to the longitudinal direction of the nonwoven fabric. The resulting processed air-through nonwoven fabric a had the shape of an intermediate sheet 30c shown in Figure 9.

[0141] (3-1-6) As shown in Fig. 16, a grid-like region Bh- (embossed portion) was formed by arranging three linear regions Bh- (embossed portions) of approximately 5 mm width in the direction parallel to the longitudinal direction of the nonwoven fabric and twelve linear regions Bh- (embossed portions) in the direction parallel to the lateral direction of the nonwoven fabric at intervals of approximately 3 cm. The obtained processed air-through nonwoven fabric a had the shape of an intermediate sheet 30c shown in Fig. 9.

[0142] (3-2) Processing of air-through nonwoven fabric b The same processing as in (3-1-1) above was carried out. The resulting processed air-through nonwoven fabric b had the form of an intermediate sheet 30c shown in FIG.

[0143] (3-3) Processing of air-through nonwoven fabric c The same processing as in (3-1-1) above was carried out. The processed air-through nonwoven fabric c obtained had the form of an intermediate sheet 30c shown in FIG.

[0144] (3-4) Processing of air-through nonwoven fabric d The same processing as in (3-1-2) was carried out. The resulting processed air-through nonwoven fabric d had the shape of an intermediate sheet 30c shown in FIG.

[0145] (3-5) Processing of airlaid nonwoven fabric The same processing as in (3-1-2) above was carried out. The resulting processed air-laid nonwoven fabric had the form of an intermediate sheet 30c shown in FIG.

[0146] (3-6) Processing of spunlace nonwoven fabric The same processing as in (3-1-2) above was carried out. The resulting processed spunlace nonwoven fabric had the form of an intermediate sheet 30c shown in FIG.

[0147] (4) Measurement of the middle sheet Thickness of area A (mm), height of area A (mm), density of area A (kg / m 3 The density of region A was measured based on the density of region B, and the area ratio (%) of region B was measured based on the density of region A when the density of region B was set to 1. The results are shown in Tables 1 and 2.

[0148] (4-1) Thickness of region A The thickness was measured by lightly pinching region A once with a thickness measuring instrument (Dial Thickness Gauge JB, manufactured by Ozaki Seisakusho Co., Ltd.).

[0149] (4-2) Height of Area A The thickness of region B was measured in the same manner as in (4-1), and the difference between the thickness of region B and that of region A was calculated. Half of this difference was taken as the height of region A.

[0150] (4-3) Density of region A (kg / m 3 ) The weight per unit area of ​​the nonwoven fabric of the intermediate sheet material was divided by the thickness of region A to calculate the weight per unit area.

[0151] (5) Fabrication of the laminate (5-1) Structure of the laminate A laminate was produced in which a first sheet, a water-absorbent resin layer, an adhesive layer, an intermediate sheet, another water-absorbent resin layer, an adhesive layer, and a second sheet were laminated in this order.

[0152] (5-2) Material Water-absorbent resin particles for water-absorbent resin layers and other water-absorbent resin layers (Examples 1 to 13 and Comparative Examples 1 to 16) SAPa synthesized in Preparation Example 1 SAPb synthesized in Preparation Example 2 SAPc synthesized in Preparation Example 3 SAPd synthesized in Preparation Example 4 SAPe synthesized in Preparation Example 5 SAPf synthesized in Preparation Example 6

[0153] Intermediate sheet (Examples 1 to 13 and Comparative Examples 7 to 9 and 15) ··Processed air-through nonwoven fabric (2cm intervals lengthwise) ··Processed air-through nonwoven fabric (3cm intervals lengthwise) ··Processed air-through nonwoven fabric (1 lengthwise direction) ··Processed air-through nonwoven fabric (short direction) ··Processed air-through nonwoven fabric (45° angle) ··Processed air-through nonwoven fabric (grid pattern) ··Processed air-through nonwoven fabric (longitudinal direction) ··Processed air-through nonwoven fabric (longitudinal direction) ··Processed air-through nonwoven fabric (longitudinal direction) ··Processed airlaid nonwoven fabric (longitudinal direction) ··Processed spunlace nonwoven fabric (longitudinal direction) Intermediate sheet (Comparative Examples 1 to 6, 10 to 14, and 16) Unprocessed air-through nonwoven fabric Unprocessed air-through nonwoven fabric Unprocessed air-through nonwoven fabric Unprocessed air-through nonwoven fabric Unprocessed airlaid nonwoven fabric ··Unprocessed spunlace nonwoven fabric

[0154] First sheet and second sheet (Examples 1 to 13 and Comparative Examples 1 to 16) Airlaid nonwoven fabric (KNH Enterprise Co., Ltd., 6190516-1A01, basis weight 40g / m 2 )

[0155] ·Adhesive layer Hot melt adhesive (Henkel Japan Co., Ltd., softening point 96°C, TECHNOMELT DM5912)

[0156] (5-3) Manufacturing method First and second sheets (both made of the same material) were prepared and cut to a size of 14 cm x 42 cm. Using a hot melt coating machine (Harries Co., Ltd., pump: Marshal 150, table: XA-DT, tank temperature setting: 150°C, hose temperature setting: 165°C, gun head temperature setting: 170°C), 0.2 g of hot melt adhesive was applied to the intermediate sheet in ten stripes at 10 mm intervals along the longitudinal direction of the intermediate sheet, as shown in Tables 1 and 2. The adhesive was applied in a spiral stripe pattern. The intermediate sheet was then placed so that the non-adhesive side was in contact with the second sheet, exposing 2 cm of the substrate for the second sheet on the front and rear (from the short edges) and 1 cm on the left and right (from the long edges). Furthermore, a total of 7.2 g of SAP for the water-absorbent resin layer, as shown in Tables 1 and 2, was uniformly sprayed onto the intermediate sheet using an airflow mixer (Autech Co., Ltd., pad former), to form the water-absorbent resin layer. Next, the first sheet was placed on the water-absorbent resin layer side of the intermediate sheet, sandwiched between release papers from above and below, and pressed together using a laminator (Hashima Corporation, Straight Linear Fussing Press, model HP-600LFS, 110°C, 0.1 MPa), and the release paper was removed to obtain a laminated material in which the first sheet, water-absorbent resin layer, and intermediate sheet were bonded together.

[0157] After the obtained laminated material was inverted vertically, the second sheet was gently peeled off from the intermediate sheet, and again, using the airflow mixer, a total of 7.2 g of SAP for the other water-absorbent resin layer shown in Tables 1 and 2 was uniformly sprayed onto the intermediate sheet of the laminated material, and the other water-absorbent resin layer was laminated. As described above, 10 rolls (total amount 0.2 g) of hot-melt adhesive were applied at 10 mm intervals to the surface of the peeled second sheet that had been in contact with the intermediate sheet. Thereafter, the second sheet was laminated so that the adhesive layer faced the other water-absorbent resin layer, and all layers were sandwiched between release papers and pressed together using a laminator. The release papers were then removed to obtain the desired laminate.

[0158] (6) Evaluation of laminate (6-1) Test solution A test solution having the following composition was prepared. Ion-exchanged water: 9865.75g NaCl: 100.0g CaCl2 2H2O: 3.0g MgCl₂·6H₂O: 6.0 g Triton X-100 (1%): 25.0g ·Food Blue No. 1 (for coloring): 0.25g

[0159] (6-2) Penetration rate In a room at a temperature of 25±2°C, the laminate was placed on a horizontal table, and an air-through nonwoven fabric (Rengo Nonwoven Products Co., Ltd., material composition: 50% PP and 50% PE, basis weight: 21 g / m) was placed on the first sheet as a top sheet. 2) was placed on the top sheet. Next, a 100 mL liquid-injection cylinder (a cylinder with both ends open) with a 3 cm inner diameter opening was placed at the center of the top sheet. Next, 80 mL of the test liquid, previously adjusted to 25±1°C, was poured into the cylinder from above in a vertical direction all at once. A stopwatch was used to measure the absorption time from the start of injection until the test liquid completely disappeared from the cylinder. This procedure was repeated two more times at 30-minute intervals (a total of three times), and the sum of the absorption times for each was calculated as the total permeation rate [seconds]. A smaller total permeation rate indicates a shorter total time required to absorb the liquids exposed to the top sheet one to three times, and therefore indicates a superior absorption rate for multiple liquid exposures. The results are shown in Tables 1 and 2.

[0160] The score (total permeation time reduction score) evaluating the effect of improving the absorption rate after multiple liquid exposures was calculated by calculating the difference between the total values ​​for Examples 1-6 and the total values ​​for Comparative Examples 1-6; the difference between the total values ​​for Examples 7-9 and Comparative Examples 7-9 and the total value for Comparative Example 10; the difference between the total values ​​for Examples 10-13 and the total values ​​for Comparative Examples 11-14; and the difference between the total values ​​for Comparative Example 15 and the total value for Comparative Example 16. Each difference was converted into a relative amount, with the total value for the corresponding Comparative Example being set at 100%. The total permeation time reduction score [%] is an evaluation value that indicates the percentage reduction in the total time required to absorb liquid after one to three exposures compared to the corresponding Comparative Example. A positive score indicates an improvement in the absorption rate after multiple liquid exposures, and the higher the score, the greater the improvement in the absorption rate after multiple liquid exposures. The results are shown in Tables 1 and 2.

[0161] (6-3) Backflow amount The laminate (with top sheet) used to measure the permeation rate was used to measure the amount of backflow according to the following procedure. Sixty minutes after the third test solution was added, a 10 cm square piece of filter paper, the mass of which (Wd (g)) had been measured in advance, was placed near the test solution addition position on the top sheet, and a 5 kg weight with a base of 10 cm x 10 cm was placed on top of it. After 5 minutes of loading, the mass of the filter paper (We (g)) was measured, and the increased mass was taken as the amount of backflow (g). The results are shown in Tables 1 and 2. Backflow amount (g) = We - Wd

[0162] (6-4) Diffusion distance After measuring the amount of backflow, the laminate (with top sheet) was turned upside down, and the longitudinal direction of the laminate into which the test liquid had penetrated (the planar direction of the absorbent body in the absorbent article) was measured from the opposite direction to the direction in which the test liquid was poured (the length of the area through which the short center line of the laminate passes within the diffusion area of ​​the test liquid; unit: cm [in other words, the length of the short center line of the laminate within the diffusion area of ​​the test liquid]). The longer the diffusion distance, the more efficient the longitudinal movement of the absorbed liquid when moving in the in-plane direction, indicating that the shape of the laminate was utilized effectively. The results are shown in Tables 1 and 2.

[0163] [Table 1]

[0164] [Table 2] [Explanation of symbols]

[0165] 10, 10a...Laminate 10', 10'a...Laminate in a liquid-absorbed state 20...1st sheet 30, 30a, 30b, 30c, 30d...Intermediate sheet 40...Second seat 51...Water absorbent resin layer 51'...water-absorbent resin layer in a water-absorbed state 52...Other water-absorbent resin layer A…Area A Al…Low density area A+...Convex area Al+…Low density / protruding area LD-A: Longitudinal direction of area A B…Area B Bh…High density area B-…recessed area Bh-…High density / recessed area LMD10...Laminate direction LD: Longitudinal direction (of laminate, first sheet, water-absorbent resin layer, intermediate sheet, second sheet) LE...long end SE…Short end M…short center line

Claims

1. A laminate comprising a liquid-permeable first sheet, a liquid-absorbent intermediate sheet, and a second sheet, each having a shape having a longitudinal direction, and a water-absorbent resin layer interposed between at least the first sheet and the intermediate sheet, the intermediate sheet includes a region A and a region B having a shape with a longitudinal direction, A laminate, wherein the region A and the region B satisfy the following relationships (1), (2), and (3): (1) The region A has a low density and the region B has a high density, and the ratio of the density of the region A to the density of the region B is 0.45 or less. (2) The region A is a convex portion that is convex toward the water-absorbent resin layer, and the region B is a concave portion, and the height of the convex portion is 0.25 mm or more. (3) The region B is located inside the longitudinal end of the intermediate sheet.

2. A laminate comprising a liquid-permeable first sheet, a liquid-absorbent intermediate sheet, and a second sheet, each having a shape with a longitudinal direction, and an absorbent resin layer interposed between at least the first sheet and the intermediate sheet (excluding those in which a fiber aggregate sheet consisting of tow, which is a bundle of continuous filaments, is arranged between the first sheet and the absorbent resin layer with the fiber direction being the longitudinal direction of the laminate), the intermediate sheet includes a region A and a region B having a shape with a longitudinal direction, A laminate, wherein the region A and the region B satisfy the following relationships (1), (2), and (3): (1) The region A has a low density and the region B has a high density, and the ratio of the density of the region A to the density of the region B is 0.45 or less. (2) The region A is a convex portion that is convex toward the water-absorbent resin layer, and the region B is a concave portion, and the height of the convex portion is 0.25 mm or more. (3) The region B is located inside the longitudinal end of the intermediate sheet.

3. The laminate according to claim 1 or 2, wherein the region A includes linear portions extending in a direction including the longitudinal direction of the intermediate sheet.

4. 4. The laminate according to claim 1, wherein the region A includes linear portions extending substantially parallel to the longitudinal direction of the intermediate sheet.

5. The laminate according to claim 4 , wherein the region B includes a linear portion arranged on a lateral center line of the intermediate sheet.

6. The laminate according to any one of claims 1 to 5, wherein a plurality of the regions A and a plurality of the regions B are arranged alternately in the lateral direction of the regions.

7. The laminate according to claim 6 , comprising a linear portion in which a plurality of the regions A and a plurality of the regions B are arranged in parallel.

8. The laminate according to any one of claims 1 to 7, wherein the region B is located inside the short edge of the intermediate sheet.

9. An absorbent article comprising the laminate according to any one of claims 1 to 8.

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