Laminate and absorbent article

Abstract

The purpose of the present invention is to provide a laminate useful for an absorbent article that exhibits an excellent absorption rate even with a plurality of liquid exposures. This laminate includes a liquid-permeable first sheet, a second sheet, and a water-absorbent resin layer interposed between the first sheet and second sheet, wherein the surface of the first sheet on the side of the water-absorbent resin layer includes a high wettability region and a low wettability region with a shape having a longitudinal direction, and a laminate having a contact angle with formamide in the high wettability region smaller than the contact angle with formamide in the low wettability region by 10° or more exhibits an excellent absorption rate even with a plurality of liquid exposures.

Description

[Technical Field]

[0001] The present invention relates to a laminate and an absorbent article. More specifically, the present invention relates to a laminate having an improved liquid permeation rate and an absorbent article using the same. [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] One of the essential characteristics that indicates the performance of a body fluid absorbent article is its liquid absorption rate. To date, 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 rate of the absorbent article described in Patent Document 1 has been considered, in consideration of the actual usage conditions in which a single absorbent article may be exposed to liquid multiple times, gel blocking will slow down the absorption rate for liquids exposed to it from the second time onwards, reducing absorbency.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a laminate useful for absorbent articles that exhibits an excellent absorption rate even after repeated exposure to liquids. [Means for solving the problem]

[0008] The present inventors have conducted extensive research and found that by providing a long, narrow region with higher wettability than other regions on the absorbent-side surface of the liquid-permeable sheet, which is the first material to allow liquid to permeate, among the materials constituting the laminate, it is possible to achieve an excellent absorption rate 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 second sheet, and a water-absorbent resin layer interposed between the first sheet and the second sheet, A laminate, wherein a surface of the first sheet facing the water-absorbent resin layer includes a high-wettability region and a low-wettability region, each having a shape with a longitudinal direction, and the contact angle of the high-wettability region with formamide is 10° or more smaller than the contact angle of the low-wettability region with formamide. Item 2. The laminate according to Item 1, wherein the high-wettability regions form recessed stripes. Item 3. The laminate according to Item 1, wherein the high-wettability region and the low-wettability region are flush with each other. Item 4. The laminate according to any one of Items 1 to 3, wherein the low-wettability region has a shape having a longitudinal direction, and the high-wettability region and the low-wettability region are arranged alternately in the lateral direction of the region. Item 5. The laminate according to Item 4, wherein a plurality of the high-wettability regions and the low-wettability regions are arranged in parallel. Item 6. The laminate has a shape having a longitudinal direction, Item 6. The laminate according to any one of items 1 to 5, wherein the high-wettability region extends in a direction including the longitudinal direction of the laminate. Item 7. The laminate according to Item 6, wherein the high-wettability regions extend substantially parallel to the longitudinal direction of the laminate. Item 8. The laminate according to any one of Items 1 to 7, wherein the water-absorbent resin layer is a multilayer having a first water-absorbent resin layer, a liquid-permeable intermediate layer, and a second water-absorbent resin layer in this order. Item 9. The laminate according to any one of Items 1 to 8, wherein the first sheet is made of resin fiber. Item 10. The laminate according to Item 9, wherein the resin is a polyolefin. Item 11. An absorbent article comprising the laminate according to any one of items 1 to 10. [Effects of the Invention]

[0010] The present invention provides a laminate useful in absorbent articles that exhibits excellent absorption rates 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 exploded view of a portion of the laminate of FIG. 1; [Figure 3] 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 4] Schematic diagrams show some examples of shapes of highly wettable regions. [Figure 5] 10A to 10C are schematic diagrams showing some examples of the shape of the high-wettability region when the laminate has a shape having a longitudinal direction. [Figure 6] 3 is a schematic diagram showing a liquid-permeable first sheet in a second embodiment of the laminate of the present invention. [Figure 7]3 is a schematic diagram showing a liquid-permeable first sheet in a third embodiment of the laminate of the present invention. [Figure 8] 10 is a schematic cross-sectional view of an example of a fourth embodiment of the laminate of the present invention. FIG. [Figure 9] 10 is a schematic cross-sectional view of a fifth embodiment of the laminate of the present invention. FIG. [Figure 10] Specific examples of the shape of the high wettability region are shown below. [Figure 11] Specific examples of the shape of the high wettability region are shown below. [Figure 12] Specific examples of the shape of the high wettability region are shown below. DETAILED DESCRIPTION OF THE INVENTION

[0012] [1. Structure of laminate] The laminate of the present invention includes a liquid-permeable first sheet, a second sheet, and a water-absorbent resin layer interposed between the first and second sheets, wherein the surface of the first sheet facing the water-absorbent resin layer includes a high-wettability region and a low-wettability region shaped in the longitudinal direction, and the contact angle with formamide in the high-wettability region is at least 10° smaller than the contact angle with formamide in the low-wettability region. This structure enables the laminate of the present invention to exhibit an excellent absorption rate even when exposed to liquids multiple times. The laminate of the present invention will be described in detail below.

[0013] [1-1. First embodiment] Fig. 1 shows a schematic cross-sectional view of a first embodiment of the laminate of the present invention. The laminate 10 shown in Fig. 1 includes a liquid-permeable first sheet 20, a second sheet 30, and a water-absorbent resin layer 40 interposed between the first sheet 20 and the second sheet 30. Hereinafter, the lamination direction of the laminate 10 will also be referred to as the "lamination direction LMD10." Although not shown, an adhesive layer may be interposed between the first sheet 20 and the water-absorbent resin layer 40 and / or between the water-absorbent resin layer 40 and the second sheet 30.

[0014] Fig. 2 is a schematic exploded view of a portion of the laminate 10. As shown in Fig. 2, the surface S2 of the first sheet 20 on the water-absorbent resin layer 40 side includes a high-wettability region 21 and a low-wettability region 22, each having a shape in the longitudinal direction LD21. In this embodiment, the high-wettability region 21 is recessed, and therefore forms a recess extending in the longitudinal direction LD21.

[0015] The high-wettability region 21 has relatively higher wettability than the low-wettability region 22. Specifically, the contact angle of the high-wettability region 21 with formamide is configured to be 10° or more smaller than the contact angle of the low-wettability region 22 with formamide. From the viewpoint of further improving the absorption rate after multiple liquid exposures, the difference between the contact angle of the low-wettability region 22 with formamide and the contact angle of the high-wettability region 21 with formamide is preferably 15° or more, more preferably 20° or more, even more preferably 25° or more, still more preferably 30° or more, and even more preferably 35° or more. The upper limit of the range of this difference is not particularly limited and may vary depending on the material of the first sheet 20 and / or the treatment for varying the wettability, but may be, for example, 60° or less, 50° or less, or 40° or less.

[0016] A specific example of the contact angle of the high-wettability region 21 with formamide is, for example, 95° or less, and from the viewpoint of further improving the absorption rate after multiple liquid exposures, is preferably 93° or less, more preferably 90° or less, even more preferably 80° or less, even more preferably 76° or less, and even more preferably 73° or less. The lower limit of the range of the contact angle of the high-wettability region 21 with formamide is not particularly limited, and the lower the better, and may vary depending on the material of the first sheet 20 and / or the treatment for varying the wettability, but is, for example, 50° or more, 60° or more, or 65° or more.

[0017] Specific examples of the contact angle of the low-wettability region 22 with formamide include, for example, 105° or more, and from the viewpoint of further improving the absorption rate after multiple liquid exposure, preferably 110° or more, and from the viewpoint of providing excellent liquid permeability to the first sheet 20, preferably 125° or less, more preferably 120° or less, and even more preferably 115° or less.

[0018] The treatment for varying the wettability of the surface S2 of the first sheet 20 may be a physical treatment or a chemical treatment, and is not particularly limited. For example, a physical treatment for increasing wettability may be a surface smoothing treatment, such as melt-solidification. A chemical treatment for increasing wettability may be the application and / or impregnation of a hydrophilic component. These treatments may be performed singly or in combination of two or more treatments (e.g., physical and chemical treatments). Among these treatments, in this embodiment, from the viewpoint of further improving the absorption rate after multiple liquid exposures, a physical treatment is preferred, a surface smoothing treatment is more preferred, and melt-solidification is even more preferred. In other words, the high-wettability regions 21 forming the recesses in this embodiment preferably form melt-solidified portions. The high-wettability regions 21 forming the recesses in this embodiment can be formed by using a heat-seal embossing technique to melt and press the areas where the high-wettability regions should be formed against the surface S2 of the first sheet 20 before treatment.

[0019] By providing a high-wettability region 21 of a predetermined shape on the surface S2 of the liquid-permeable first sheet 20 on the water-absorbent resin layer 40 side, an excellent absorption rate is exhibited even when exposed to liquid multiple times. A possible mechanism for achieving such an excellent absorption rate will be explained with reference to Fig. 3. Fig. 3 is a schematic exploded view similar to Fig. 2 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] The laminate 10 is exposed to a liquid from the surface opposite to the surface S2 of the first sheet 20. The liquid moves in the lamination direction LMD10, passes through the liquid-permeable first sheet 20, reaches the water-absorbent resin layer 40, and is absorbed by the water-absorbent resin that constitutes the water-absorbent resin layer 40 (hereinafter, the water-absorbent resin layer 40 that absorbs the liquid that it is first exposed to will also be particularly referred to as the “water-absorbent resin layer 40′”). At this time, the liquid that passes through the first sheet 20 and reaches the surface S2 is more concentrated in the high-wettability region 21 than in the low-wettability region 22 due to the difference in wettability between the high-wettability region 21 and the low-wettability region 22. Therefore, the portion 41 of the water-absorbent resin layer 40 facing the high-wettability region 21 absorbs more liquid than the portion 42 facing the low-wettability region 22. As a result, the portion 41 facing the high-wettability region 21 expands more than the portion 42 facing the low-wettability region 22 in accordance with the amount of liquid absorbed. The more expanded portion 41 corresponds to the shape having the longitudinal direction LD21 of the high wettability region 21, and forms a shape having a similar longitudinal direction LD21, i.e., a convex rib (hereinafter, the more expanded portion 41 will also be referred to as a "convex rib 41," and the lower portion 42 that has not expanded to the same size as the convex rib 41 will also be referred to as a "recess 42").

[0021] When the laminate 10' is exposed to a subsequent liquid, the liquid that passes through the liquid-permeable first sheet 20 and reaches the water-absorbent resin layer 40' flows through the recesses 42 along the longitudinal direction of the ridges 41. 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 LD21 of the ridges 41 as it is absorbed into the water-absorbent resin layer 40'. In this way, the ridges 41 formed by the first liquid exposure spread the subsequently absorbed liquid throughout the laminate 10' without concentrating it at the point where it reaches the water-absorbent resin layer 40', thereby maximizing the contact area between the water-absorbent resin layer 40' 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 backflow at that location.

[0022] In the above description, the "first liquid exposure" and the "second liquid exposure" may be continuous or intermittent.

[0023] [1-2. Modified examples of high wettability region] FIG. 4 shows schematic diagrams of several examples of the shape of the high-wettability region 21. In FIG. 4, solid lines represent the high-wettability region 21, and the blank areas outside the solid lines represent the low-wettability region 22. The shape of the high-wettability region 21 is not limited to that shown in the first embodiment. As long as it has a shape with a longitudinal direction, it is considered that the convex ridges 41 formed by absorption of the first exposed liquid can guide the liquid absorbed thereafter to spread in the in-plane direction of the laminate 10′, as described with reference to FIG. 3. In other words, as long as the shape of the high-wettability region 21 has a longitudinal direction, even if there is only one high-wettability region 21 as shown in FIG. 4(A), the laminate of the present invention can exhibit an excellent absorption rate even when exposed to a liquid multiple times.

[0024] The shape of the high-wettability regions 21 may be such that their extending directions (i.e., longitudinal directions) intersect. Examples of high-wettability regions 21 in such an intersecting configuration include those shown in Figures 4(B) and 4(C) in which two high-wettability regions 21 intersect with each other, and those shown in Figure 4(G) in which a plurality of high-wettability regions 21 intersect with each other. The angle of intersection is not limited to that shown in the figures and is arbitrary. In such an intersecting configuration, the liquid exposed for the second or subsequent times is guided to spread in multiple directions in the in-plane direction of the laminate, which is preferable in that it further improves the contact efficiency between the water-absorbent resin layer 40' and the liquid.

[0025] In addition to the shape of the high-wettability region 21, the shape of the low-wettability region 22 may also have a shape having a longitudinal direction. Furthermore, in this case, a plurality of high-wettability regions 21 and low-wettability regions 22 may be arranged alternately in the short-side direction SD21 of these regions. Examples of combinations of high-wettability regions 21 and low-wettability regions 22 forming such a plurality of alternating patterns include FIG. 4(A) in which one high-wettability region 21 is provided, FIG. 4(D) in which the high-wettability region 21 is arranged in a zigzag pattern, FIG. 4(E) in which the high-wettability region 21 is arranged in a spiral pattern, FIG. 4(F) in which a plurality of linear high-wettability regions 21 are arranged in parallel, and FIG. 4(H) in which a plurality of wavy high-wettability regions 21 are arranged in parallel. In such a plurality of alternating patterns, the water-absorbent resin layer 40′ that absorbs the liquid first exposed to it deforms so that the ridges 41 are arranged on both sides of the recesses 42 described in FIG. 3, and the recesses 42 become groove-like and can function as flow paths. Therefore, the liquid exposed for the second time and thereafter moves through the groove-like recesses 42 along the longitudinal direction of the ridges 41 as flow paths, which is preferable in that it allows for more efficient diffusion in the in-plane direction of the laminate.

[0026] In the case of the above-mentioned multiple alternating mode, a plurality of high wettability regions 21 and low wettability regions 22 may be arranged in parallel. Examples of combinations of high wettability regions 21 and low wettability regions 22 forming such a parallel mode include FIG. 4(E) in which the high wettability regions 21 are arranged in a spiral shape, FIG. 4(F) in which a plurality of linear high wettability regions 21 are arranged in parallel, and FIG. 4(H) in which a plurality of wavy high wettability regions 21 are arranged in parallel. Such a parallel mode is preferable in that, in the water-absorbent resin layer 40′ that has absorbed the liquid to which it has been initially exposed, the groove-like recesses 42 extend with approximately the same width, allowing the liquid exposed thereto for the second or subsequent times to move more quickly and allowing the liquid to diffuse more efficiently in the in-plane direction of the laminate.

[0027] The shapes of the high-wettability region 21 shown in FIG. 4 may be applied singly or in combination of two or more shapes.

[0028] Figure 5 shows schematic diagrams of several examples of the shape of the high-wettability region 21 when the laminate has a shape having a longitudinal direction LD10. In Figure 5, the solid lines also represent the high-wettability region 21, and the blank areas other than the solid lines represent low-wettability regions 22, although no reference numerals are shown. Figures 5(DD), 5(FF), 5(GG), and 5(HH) are modified examples of the embodiments shown in Figures 4(D), 4(F), 4(G), and 4(H), respectively, when the laminate has a shape having a longitudinal direction LD10.

[0029] When the laminate has a shape having a longitudinal direction LD10, the high-wettability region 21 preferably extends in a direction including the longitudinal direction LD10 of the laminate, as shown in Figures 5(DD), 5(FF), 5(GG), and 5(HH). The "high-wettability region 21 extending in a direction including the longitudinal direction LD10" means that the extension direction of the high-wettability region 21 includes a longitudinal direction LD10 component, regardless of whether it is parallel to the longitudinal direction LD10. The "direction including the longitudinal direction LD10" refers to any direction other than a direction perpendicular to the longitudinal direction LD10. This embodiment is preferable in that when the liquid exposed for the second or subsequent time moves in the in-plane direction of the laminate, it moves more efficiently, particularly in the longitudinal direction LD10, making it possible to effectively utilize the shape of the laminate.

[0030] Furthermore, among the embodiments shown in FIG. 5, it is more preferable that the high-wettability regions 21 (the entire region in FIG. 5(FF) and a portion thereof in FIG. 5(GG)) extend substantially parallel to the longitudinal direction LD10 of the laminate, as shown in FIG. 5(FF) and FIG. 5(GG). The high-wettability regions 21 extending substantially parallel to the longitudinal direction LD10 of the laminate means that the extension direction of the high-wettability regions 21 may be shifted by ±5° with respect to the longitudinal direction LD10. When there are multiple high-wettability regions 21, the multiple parallel high-wettability regions 21 may be arranged so as to merge (intersect) with each other, but are preferably arranged so as not to merge with each other, as shown in FIG. 5(FF). In such an embodiment, when the liquid exposed for the second time or later moves in the in-plane direction of the laminate, the movement in the longitudinal direction LD10 is particularly efficient, which is preferable in that the shape of the laminate can be utilized more effectively.

[0031] The width of the high wettability region 21 (i.e., the width that the high wettability region 21 occupies in the short direction SD21) is not particularly limited, but from the viewpoint of further improving the absorption rate and additionally reducing the amount of backflow, its lower limit is preferably 1 mm or more, more preferably 2 mm or more, even more preferably 3 mm or more, still more preferably 3.5 mm or more, and even more preferably 4 mm or more, and its upper limit is preferably 10 mm or less, more preferably 9 mm or less, even more preferably 8 mm or less, still more preferably 7 mm or less, and even more preferably 6 mm or less. The width of the high wettability region 21 may be constant overall along its extension direction, or may vary within the above range.

[0032] Furthermore, in the embodiments exemplified in Figures 4(E), 4(F), 4(G), 4(H), 5(FF), 5(GG), and 5(HH), in which multiple high-wettability regions 21 and low-wettability regions 22 are arranged in parallel, the spacing between the high-wettability regions 21 (i.e., the width of the low-wettability regions 22) is not particularly limited, but from the viewpoint of further improving the absorption rate, or additionally reducing the amount of backflow, the lower limit is preferably 0.2 cm or more, more preferably 0.3 cm or more, and even more preferably 0.5 cm or more, and the upper limit is preferably 3 cm or less, more preferably 2 cm or less, and even more preferably 1.5 cm or less.

[0033] The area occupied by the high-wettability region 21 on the surface S2 of the first sheet is not particularly limited, but from the viewpoint of further improving the absorption rate after multiple liquid exposures, or in addition, reducing the amount of backflow, the lower limit is preferably 30% or more, more preferably 35% or more, even more preferably 40% or more, and even more preferably 43% or more, and the upper limit is preferably 60% or less, more preferably 55% or less, even more preferably 50% or less, and even more preferably 47% or less.

[0034] The modifications shown in FIGS. 4 and 5 can be applied not only to the first embodiment described above, but also to all of the embodiments described below.

[0035] [1-3. Second embodiment] 6 is a schematic diagram showing a liquid-permeable first sheet 20a in a second embodiment of the laminate of the present invention. The laminate of the second embodiment is similar to the laminate 10 of the first embodiment described above, except that the first sheet 20 is replaced with the first sheet 20a.

[0036] As shown in FIG. 6, the first sheet 20a includes a surface S2 on the water-absorbent resin layer 40 (see FIG. 3) side, which includes a high-wettability region 21 and a low-wettability region 22, each having a shape with a longitudinal direction LD21. Unlike the first sheet 20 used in the first embodiment, the first sheet 20a used in this embodiment is configured so that the high-wettability region 21 and the low-wettability region 22 are flush with each other. The difference in relative wettability between the high-wettability region 21 and the low-wettability region 22 is the same as in the first embodiment. The treatment for differentiating the wettability between the high-wettability region 21 and the low-wettability region 22 may be the same as in the first embodiment. The mechanism that may be considered to provide an excellent absorption rate even after multiple liquid exposures is also the same as in the first embodiment.

[0037] [1-4. Third embodiment] 7 is a schematic diagram showing a liquid-permeable first sheet 20b in a third embodiment of the laminate of the present invention. The laminate of the second embodiment is similar to the laminate 10 of the first embodiment described above, except that the first sheet 20 is replaced with the first sheet 20b.

[0038] 7, the first sheet 20b has a surface S2 on the water-absorbent resin layer 40 (see FIG. 3) side on which the high-wettability region 21 and low-wettability region 22 are formed, similar to those of the first sheet 20 of the first embodiment, but further has a reversible design with a similar configuration on the surface opposite to surface S2. The first sheet 20b of this embodiment can be formed by using a heat-seal embossing technique to melt and press the areas where the high-wettability regions are to be formed on both sides of the untreated first sheet 20b.

[0039] [1-5. Fourth embodiment] In the fourth embodiment of the present invention, the second sheet is a liquid-permeable sheet similar to the liquid-permeable first sheet described above, including a high-wettability region and a low-wettability region shaped in the longitudinal direction, and configured so that the contact angle with formamide in the high-wettability region is 10° or more smaller than the contact angle with formamide in the low-wettability region. All of the features of the cross-sectional shape and the shape of the high-wettability region 21 described above for the liquid-permeable first sheet also apply to the second sheet 30c used in this embodiment.

[0040] Fig. 8 is a schematic cross-sectional view of an example of a fourth embodiment of the laminate of the present invention. The laminate 10c shown in Fig. 8 is reversible, in which the same sheet as the first sheet 20 is used as the second sheet 30c, and the shape and position of the high wettability region in the second sheet 30c corresponds to the shape and position of the high wettability region in the first sheet 20.

[0041] In a modified example of the laminate 10c, the shape and position of the high wettability region in the second sheet 30c do not have to correspond to the shape and position of the high wettability region in the first sheet 20. In another modified example of the laminate 10c, the first sheet 20a, 20b shown in Figures 6 and 7, respectively, may be used instead of the first sheet 20. Furthermore, in yet another modified example of the laminate 10c, the second sheet 30c may be a sheet whose cross-sectional shape and / or the shape of the high wettability region 21 is different from that of the first sheet 20, as long as it has the characteristics described above for the first sheet.

[0042] [1-6. Fifth embodiment] A cross-sectional view of a fifth embodiment of the laminate of the present invention is shown schematically in Fig. 9. The laminate 10d shown in Fig. 9 is a multilayer structure having a first water-absorbent resin layer 45, a liquid-permeable intermediate layer 50, and a second water-absorbent resin layer 46 in this order, obtained by further including a liquid-permeable intermediate layer in the water-absorbent resin layer 40 of the laminate 10c shown in Fig. 8.

[0043] Furthermore, when the fifth embodiment has the aforementioned adhesive layer (not shown), the adhesive layer can be interposed between the first sheet 20 and the first water-absorbent resin layer 45, and between the second sheet 30c and the second water-absorbent resin layer 46.

[0044] It should be noted that all of the above-mentioned variations of the laminate 10c can also be applied to the laminate 10d as variations.

[0045] [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.

[0046] [2-1. Sheet 1] The first sheet is not particularly limited as long as it is liquid-permeable and can have the above-mentioned predetermined high-wettability region and low-wettability region.

[0047] 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 easily allow the water-absorbent resin that constitutes the water-absorbent resin layer to pass through. Examples of the form of the first sheet include a nonwoven fabric, a woven fabric, and a porous sheet. Among these forms, nonwoven fabrics are preferred from the viewpoint of further improving the absorption rate after multiple exposures to liquids, and also from the viewpoint of reducing the amount of return.

[0048] 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, etc. Among these nonwoven fabrics, air-through nonwoven fabrics are preferred from the viewpoint of further improving the absorption rate after multiple liquid exposures and, in addition, reducing the amount of return.

[0049] 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.

[0050] 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.

[0051] Among the above materials, from the viewpoint of further improving the absorption rate after multiple liquid exposures and, in addition, reducing the amount of return, resin fibers are preferred, and polyolefin fibers are more preferred. When the first sheet is made of resin fiber, all of the constituent materials of the first sheet (100% by mass) may be resin, but it may also contain 20% by mass or less, 10% by mass or less, or 5% by mass or less of other constituent materials (e.g., cotton or silk).

[0052] The basis weight 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 return, the lower limit is preferably 10 g / m 2 More preferably, 15 g / m 2 More preferably, 20 g / m 2 More preferably, 24 g / m 2 The upper limit is preferably 30 g / m 2 or less, more preferably 15 to 28 g / m 2 , and more preferably 20 to 28 g / m 2 , more preferably 24 to 26 g / m 2 is.

[0053] 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 lower limit is preferably 0.04 mm or more, more preferably 0.1 mm or more, even more preferably 0.2 mm or more, and particularly preferably 0.25 mm or more, and the upper limit is preferably 0.6 mm or less, more preferably 0.45 mm or less, even more preferably 0.4 mm or less, and particularly preferably 0.35 mm or less. Note that, when the high wettability region of the first sheet forms recesses as in the first and third to fifth embodiments, the thickness of the first sheet refers to the thickness of the portion corresponding to the low wettability region.

[0054] Furthermore, when the high wettability region of the first sheet has a concave stripe shape as in the first and third to fifth embodiments, the ratio of the thickness of the portion corresponding to the high wettability region to the thickness of the portion corresponding to the low wettability region of the first sheet, when taken as 1, is preferably 0.5 or less, more preferably 0.4 or less, even more preferably 0.38 or less, and even more preferably 0.35 or less, from the viewpoint of further improving the absorption rate after multiple liquid exposures and, in addition, reducing the amount of backflow. The lower limit of this ratio range is not particularly limited, but may be, for example, 0.2 or more or 0.3 or more.

[0055] [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).

[0056] 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.

[0057] Furthermore, when the water-absorbent resin layer includes a first water-absorbent resin layer 45 and a second water-absorbent resin layer 46 as in the fifth embodiment, the first water-absorbent resin layer 45 and the second water-absorbent resin layer 46 may use the same water-absorbent resin or different water-absorbent resins.

[0058] 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.

[0059] 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 per unit, e.g. 50-1200g / m 2 , preferably 100 to 900 g / m 2 , more preferably 150 to 500 g / m 2 , and more preferably 200 to 400 g / m 2 , more preferably 250 to 350 g / m 2 The thickness of the water-absorbent resin layer mentioned above refers to the thickness of the water-absorbent resin layer 40 when the water-absorbent resin layer is a single layer (i.e., the water-absorbent resin layer 40) as shown in the first and fourth embodiments, and refers to the sum of the thicknesses of the first water-absorbent resin layer 45 and the second water-absorbent resin layer 46 when the water-absorbent resin layer is a multilayer (e.g., a first water-absorbent resin layer 45 and a second water-absorbent resin layer 46) as shown in the fifth embodiment.

[0060] Furthermore, the mass ratio of the water-absorbent resins used in the first water-absorbent resin layer 45 and the second water-absorbent resin layer 46 of the fifth embodiment (first water-absorbent resin layer 45 / second water-absorbent resin layer 46) is, for example, 90 / 10 to 30 / 70, and preferably 80 / 20 to 40 / 60.

[0061] 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 70 g / g, even more preferably 50 to 65 g / g, and even more preferably 60 to 63 g / g.

[0062] The saline water retention 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 55 g / g, more preferably 35 to 50 g / g, and even more preferably 40 to 45 g / g.

[0063] The physiological saline absorption speed of the water-absorbent resin is not particularly limited, but from the viewpoint of further improving the absorption speed after multiple exposures to liquid, or in addition, reducing the amount of backflow, the speed is preferably 25 to 80 seconds, more preferably 28 to 70 seconds, even more preferably 30 to 60 seconds, even more preferably 35 to 50 seconds, still more preferably 38 to 45 seconds, and particularly preferably 40 to 42 seconds.

[0064] The median particle size of the water-absorbent resin is not particularly limited, but from the viewpoint of further improving the absorption speed after multiple liquid exposures, or in addition, reducing the amount of backflow, 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 380 μm.

[0065] [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.

[0066] 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.

[0067] [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 and the first 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.

[0068] [2-5. Liquid permeable intermediate layer] The liquid-permeable intermediate layer 50 used in the fifth embodiment divides the first water-absorbent resin layer 45 and the second water-absorbent resin layer 46, helps the layer 10d to diffuse the liquid absorbed by the layered product 10d, and can be provided for the purpose of providing a temporary water-retaining effect until the water-absorbent resin absorbs the liquid. The material of the liquid-permeable intermediate layer is not particularly limited as long as it is liquid-permeable.

[0069] The form of the liquid-permeable intermediate layer is not particularly limited as long as it has spaces or pores that communicate in the thickness direction and are of a size that does not easily allow the water-absorbent resin that constitutes the water-absorbent resin layer to pass through. Examples of the liquid-permeable intermediate layer include nonwoven fabrics, woven fabrics, and porous sheets. Among these forms, nonwoven fabrics are preferred from the viewpoint of further improving the absorption rate after multiple liquid exposures and, in addition, reducing the amount of backflow.

[0070] 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, etc. Among these nonwoven fabrics, air-through nonwoven fabrics are preferred from the viewpoint of further improving the absorption rate after multiple liquid exposures and, in addition, reducing the amount of return.

[0071] The liquid-permeable intermediate layer may be made of the same materials as those listed as the materials for the first sheet.

[0072] The basis weight of the liquid-permeable intermediate layer 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 55 g / m 2 , and more preferably 40 to 50 g / m 2 , more preferably 43 to 47 g / m 2 Examples include:

[0073] The thickness of the liquid-permeable intermediate layer is not particularly limited, but is preferably 0.5 to 5 mm, more preferably 1 to 4 mm, and even more preferably 2 to 3 mm, from the viewpoint of further improving the absorption rate after multiple liquid exposures and, in addition, reducing the amount of backflow.

[0074] [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.

[0075] For example, in the case of laminates 10, 10c that do not have a liquid-permeable intermediate layer as in the first and fourth embodiments, the laminates can be produced by spraying a water-absorbent resin on either the surface S2 of the first sheet or the surface of the second sheet to laminate a water-absorbent resin layer, and then laminating the other of the surface S2 of the first sheet or the surface of the second sheet, and joining the peripheries of the first sheet and the second sheet as necessary (for example, by heat pressing, etc.).

[0076] When laminates 10, 10c have adhesive layers (not shown) and the adhesive layers are laminated on both the surface S2 of the first sheet and the surface of the second sheet, they can be produced by applying an adhesive to the surface S2 of the first sheet and the surface of the second sheet to laminate the adhesive layers, spraying a water-absorbent resin onto either the adhesive layer on the first sheet or the adhesive layer on the second sheet to laminate the water-absorbent resin layer, further laminating the other of the adhesive layer on the first sheet or the adhesive layer on the second sheet, and joining the peripheries of the first sheet and the second sheet as necessary (for example, by heat and pressure bonding, etc.). When laminates 10, 10c have an adhesive layer laminated on either the surface S2 of the first sheet or the surface of the second sheet, they can be produced in the same manner as above, except that an adhesive layer is not laminated on either the surface S2 of the first sheet or the surface of the second sheet.

[0077] In the case of a laminate 10d having a liquid-permeable intermediate layer as in the fifth embodiment, the laminate 10d can be produced by spraying a water-absorbent resin on either the surface S2 of the first sheet 20 or the surface of the second sheet 30c, laminating either the first water-absorbent resin layer 45 or the second water-absorbent resin layer 46, and further laminating a liquid-permeable intermediate layer 50 to produce a laminate material A, and spraying a water-absorbent resin on the other of the surface S2 of the first sheet or the surface of the second sheet, laminating the other of the first water-absorbent resin layer 45 or the second water-absorbent resin layer 46, laminating the laminate material A on the laminate material B, and, if necessary, bonding the peripheral edges of the first sheet, the liquid-permeable intermediate layer 50, and the second sheet together (for example, by heat pressing, etc.).

[0078] When the laminate 10d has an adhesive layer (not shown), the laminate can be produced by applying an adhesive to either the surface S2 of the first sheet 20 or the surface of the second sheet 30c to form an adhesive layer, spraying a water-absorbent resin to form either the first water-absorbent resin layer 45 or the second water-absorbent resin layer 46, and further laminating a liquid-permeable intermediate layer to produce a laminate material A, and applying an adhesive to the other of the surface S2 of the first sheet or the surface of the second sheet to form an adhesive layer, and further spraying a water-absorbent resin to form the other of the first water-absorbent resin layer 45 or the second water-absorbent resin layer 46, laminating the laminate material A on the laminate material B, and, if necessary, bonding the peripheries of the first sheet, the liquid-permeable intermediate layer 50, and the second sheet together (for example, by heat-pressing).

[0079] [4. Uses of laminates] The laminate of the present invention functions as an absorbent body that exhibits an excellent absorption rate 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.

[0080] 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 absorbent articles include disposable diapers, urine pads, sanitary napkins, pet sheets, drip sheets for food, and waterproof materials for power cables. [Example]

[0081] 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.

[0082] (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 two 5-cm-diameter four-paddle inclined blades 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 mixture was heated to 80°C with stirring to dissolve the dispersant, and then cooled to 50°C.

[0083] 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.

[0084] 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, yielding a first-stage polymerization slurry.

[0085] <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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] (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.

[0090] (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 two 5-cm-diameter four-paddle inclined blades 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 mixture was heated to 80°C with stirring to dissolve the dispersant, and then cooled to 50°C.

[0091] 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.

[0092] 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, yielding a first-stage polymerization slurry.

[0093] <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.

[0094] 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.

[0095] 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.

[0096] 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 SAPc containing amorphous silica.

[0097] (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. 500g ± 0.1g of saline solution was weighed into a 500mL beaker, a magnetic stirrer bar (8mmφ × 30mm without ring) was added, and the rotation speed was adjusted to 600 r / min. Next, 2.0g of water-absorbent resin particles was added and stirred at room temperature (25°C). After stirring for 60 minutes, the mixture was filtered using a JIS Z 8801-1 standard sieve with a mass Wb [g] and a mesh size of 75μm. The filtered material was left on the sieve for 30 minutes with the sieve tilted at an angle of approximately 30 degrees relative to the horizontal. The total mass Wa [g] of the absorbed water-absorbent resin particles and the sieve was measured, and the water absorption of the saline solution by the water-absorbent resin particles was calculated using the following formula. The results are shown in Table 1. Water absorption [g / g]=(Wa-Wb) / 2.0

[0098] (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 saline solution 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. The mass Wc [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 Wd [g] of the cotton bag when wet was measured. The water retention capacity of the water-absorbent resin particles in saline solution was calculated using the following formula. The results are shown in Table 1. Water retention amount [g / g]=(Wc-Wd) / 2.0

[0099] (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 the magnetic stirrer, and a rotation speed of 600 r / min was set to generate a vortex in the saline. 2.0 ± 0.002 g of water-absorbent resin particles were then quickly added to the beaker, and a stopwatch was used to measure the time (seconds) from the addition of the water-absorbent resin to the point at which the vortex on the liquid surface converged, which was taken as the water absorption rate of the water-absorbent resin particles. The results are shown in Table 1.

[0100] (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 Table 1.

[0101] (3) Preparation of the first and second sheets The following nonwoven fabric was prepared and cut into a shape having a longitudinal direction (a rectangle of 12 cm x 32 cm). Air-through nonwoven fabric a (KNH Enterprise Co., Ltd., AT025-CP49-0, material composition: PP and PE, basis weight: 25 g / m 2 ) Air-through nonwoven fabric b (Rengo Nonwoven Products Co., Ltd., material composition: 50% PP and 50% PE, basis weight: 21 g / m 2 ) Spunbond nonwoven fabric (Asahi Kasei Corporation, SMMS, Material composition: 100% PP, Weight: 12 g / m 2 ) Airlaid nonwoven fabric (KNH Enterprise Co., Ltd., 6190516-1A01, material composition: PP, PE and pulp, basis weight: 40g / m 2 ) Spunlace nonwoven fabric (Unicharm Kokko Nonwoven Co., Ltd., Soflon E, material composition: rayon, PET, PP and PE, basis weight: 33 g / m 2 )

[0102] (3-1) Processing of air-through nonwoven fabric a A heat sealer (Fuji Impulse Co., Ltd., FI-450-5, time settings 3 to 6) was used to form melt-solidified portions (embossed portions) as high-wettability regions on the air-through nonwoven fabric a by heat-seal embossing. Specifically, as shown in FIG. 10, eleven high-wettability regions (embossed portions), each approximately 5 mm wide, were formed extending at approximately 5 mm intervals in a direction parallel to the longitudinal direction of the nonwoven fabric. In FIG. 10, the shaded portions indicate high-wettability regions, and the non-shaded portions indicate low-wettability regions. The resulting processed air-through nonwoven fabric a had the shape of the first sheet 20b shown in FIG. 7.

[0103] (3-2) Processing of air-through nonwoven fabric b Highly wettable regions (embossed portions) were provided in the air-through nonwoven fabric b in the same manner as in (3-1) above. The resulting processed air-through nonwoven fabric b had the form of a first sheet 20b shown in FIG.

[0104] (3-3) Processing of spunbond nonwoven fabric The following processing was carried out on the spunbond nonwoven fabric to obtain three types of nonwoven fabric with different shapes of high-wettability regions.

[0105] (3-3-1) A high-wettability region was provided in the spunbonded nonwoven fabric in the same manner as in (3-1) above. The resulting processed spunbonded nonwoven fabric a had the high-wettability region and the low-wettability region flush with each other, as in the first sheet 20a shown in Figure 6. (3-3-2) Using the method described in (3-1) above, high-wettability regions, each approximately 5 mm wide, were formed in a grid pattern on a spunbond nonwoven fabric, extending at intervals of approximately 1.5 cm in directions parallel to the longitudinal and lateral directions of the nonwoven fabric, as shown in Figure 11. In Figure 11, the shaded areas indicate high-wettability regions, and the non-shaded areas indicate low-wettability regions. The resulting processed spunbond nonwoven fabric b had flush high-wettability regions and low-wettability regions, as in the first sheet 20a shown in Figure 6. (3-3-3) Using the method described in (3-1) above, 31 high-wettability regions, each approximately 5 mm wide, were formed on a spunbond nonwoven fabric, extending at intervals of approximately 5 mm in a direction parallel to the short direction of the nonwoven fabric, as shown in Figure 12. In Figure 12, the shaded areas indicate high-wettability regions, and the non-shaded areas indicate low-wettability regions. The resulting processed spunbond nonwoven fabric c had flush high-wettability regions and low-wettability regions, as in the first sheet 20a shown in Figure 6.

[0106] (3-4) Processing of airlaid nonwoven fabric Highly wettable regions (embossed portions) were provided on the air-laid nonwoven fabric in the same manner as in (3-1) above. The resulting processed air-laid nonwoven fabric had the form of a first sheet 20b shown in FIG.

[0107] (3-5) Processing of spunlace nonwoven fabric Highly wettable regions (embossed portions) were provided on the spunlace nonwoven fabric in the same manner as in (3-1) above. The resulting processed spunlace nonwoven fabric had the form of a first sheet 20b shown in FIG.

[0108] (4) Measurement of the first and second sheets The thickness (mm) of the low-wettability region, the thickness (mm) of the high-wettability region, the area ratio (%) of the high-wettability region to the surface area of ​​the nonwoven fabric (excluding the surface constituting the thickness), the contact angle (°), and the contact angle difference (°) were measured. The results are shown in Table 1.

[0109] (4-1) Thickness The low wettability region or high wettability region to be measured was lightly clamped once between a thickness measuring device (Dial Thickness Gauge JB, manufactured by Ozaki Seisakusho Co., Ltd.) to measure the thickness.

[0110] (4-2) Contact angle The contact angle was measured in an environment with a temperature of 25±2°C and a humidity of 50±10%. Double-sided tape (Nitto Denko's re-peelable strong double-sided tape No. 5000NS) was attached to a stainless steel metal plate (30 mm x 70 mm, 1 mm thick). The nonwoven fabric to be measured for the contact angle was cut to a size of 25 mm x 50 mm and attached to the metal plate with the double-sided tape, taking care not to create wrinkles, to prepare a measurement sample.

[0111] The automatic contact angle meter (Kyowa Interface Chemical: DMo-601) consists of a sample stage that can be moved up and down, a syringe unit installed above the stage, and a scope unit that allows for horizontal observation of the stage. Contact angles were measured using this contact angle meter using the following procedure. First, formamide was drawn into the syringe (1 mL capacity), and the measurement sample was placed on a stage vertically below the syringe. The stage was then moved upward, and a droplet of formamide (2.0 μL) was placed on a smooth surface of the sample, allowing the droplet to land on the sample. The contact angle between the formamide droplet and the sample surface 1 second after landing was determined by the θ / 2 method.

[0112] (5) Fabrication of the laminate (5-1) Structure of the laminate A laminate was produced in which a first sheet, an adhesive layer, a first water-absorbent resin layer, a liquid-permeable intermediate layer, a second water-absorbent resin layer, an adhesive layer, and a second sheet were laminated in this order.

[0113] (5-2) Material Water-absorbent resin particles for the first water-absorbent resin layer (Examples 1 to 7 and Comparative Examples 1 to 11) SAPa synthesized in Preparation Example 1 SAPb synthesized in Preparation Example 2 SAPc synthesized in Preparation Example 3 Water-absorbent resin particles for the second water-absorbent resin layer (Examples 1 to 7 and Comparative Examples 1 to 11) In all Examples and Comparative Examples, SAPa synthesized in Production Example 1 was used.

[0114] First sheet (Examples 1 to 7 and Comparative Examples 8 and 10) ··Processed air-through nonwoven fabric (longitudinal direction) ··Processed air-through nonwoven fabric (longitudinal direction) ··Processed spunbond nonwoven fabric a (longitudinal direction) ··Processed spunbond nonwoven fabric b (grid pattern) ··Processed spunbond nonwoven fabric c (transverse direction) ··Processed airlaid nonwoven fabric (longitudinal direction) ··Processed spunlace nonwoven fabric (longitudinal direction) First sheet (Comparative Examples 1 to 7, 9, and 11) Unprocessed air-through nonwoven fabric Unprocessed air-through nonwoven fabric ··Unprocessed spunbond nonwoven fabric ··Unprocessed spunbond nonwoven fabric ··Unprocessed spunbond nonwoven fabric Unprocessed airlaid nonwoven fabric ··Unprocessed spunlace nonwoven fabric

[0115] Second sheet (Examples 1 to 7 and Comparative Examples 1 to 11) In each example and comparative example, the same nonwoven fabric as the first sheet

[0116] ·Liquid permeable middle layer Air-through nonwoven fabric (Guangzhou Jinhan Nonwovens Co., Ltd., D45-200, basis weight 45g / m 2 , 2.42mm)

[0117] ·Adhesive layer Hot melt adhesive (Henkel Japan Co., Ltd., softening point 96°C, TECHNOMELT DM5912)

[0118] (5-3) Manufacturing method Using a hot melt coating machine (Harries Co., Ltd., pump: Marshal 150, table: XA-DT, tank set temperature: 150°C, hose internal set temperature: 165°C, gun head set temperature: 170°C), a total amount of 0.2 g of hot melt adhesive was applied in 10 stripes at 10 mm intervals along the longitudinal direction of the first sheet shown in Table 1 in an area excluding a 1 cm outer periphery on both ends of the short side and longitudinal direction, to form an adhesive layer. The adhesive application pattern was a spiral stripe. 4.5 g of water-absorbent resin particles shown in Table 1 were uniformly sprayed on the area where the adhesive layer was formed, and a first water-absorbent resin layer was laminated thereon. An air-through nonwoven fabric to serve as a liquid-permeable intermediate layer was placed on the first water-absorbent resin layer. The first sheet, adhesive layer, first water-absorbent resin layer, and liquid-permeable intermediate layer were sandwiched together with release paper and pressed 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 laminate A consisting of the first sheet, adhesive layer, first water-absorbent resin layer, and liquid-permeable intermediate layer.

[0119] A total of 0.2 g of hot melt adhesive was applied to a second sheet (made of the same material as the first sheet) in the same manner as above, and 4.5 g of SAPa obtained in Production Example 1 was uniformly scattered thereon, followed by laminating a second water-absorbent resin layer thereon, thereby obtaining a laminate B of a laminate of the second sheet and the second water-absorbent resin layer.

[0120] Laminate A was laminated so that the liquid-permeable intermediate layer of laminate A was in contact with the second water-absorbent resin layer of laminate B, and the laminates were pressed together using a laminator in the same manner as above to obtain the desired laminate.

[0121] (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

[0122] (6-2) Penetration rate In a room at a temperature of 25±2°C, the laminate was placed on a horizontal table with the first sheet facing up, and a rectangular (12 cm x 32 cm) air-through nonwoven fabric (Rengo Nonwoven Products Co., Ltd., material composition: 50% PP and 50% PE, basis weight: 21 g / m) was placed on top of it as a top sheet. 2 ) was placed on the laminate. Next, a 100 mL liquid-injection cylinder (a cylinder with both ends open) with an inlet having an inner diameter of 3 cm was placed at the center of the top sheet. Next, 80 mL of the test liquid, previously adjusted to 25±1°C, was injected into the cylinder from above in a vertical direction all at once. Using a stopwatch, the absorption time from the start of injection until the test liquid completely disappeared from the cylinder was measured. This operation was repeated two more times at 30-minute intervals (a total of three times), and the absorption time for each injection and the sum of the absorption times were calculated as the permeation rate [seconds]. Based on the obtained permeation rate values, three scores were calculated to evaluate the effect of improving the absorption rate after multiple exposures to liquid. Hereinafter, Examples 1 to 7 and Comparative Examples 8 and 10 were prepared using a first sheet with a high-wettability region, and Comparative Examples 1 to 7, 9, and 11, which were prepared under the same conditions except for not having a high-wettability region, are referred to as the "corresponding comparative example."

[0123] (6-2-1) Score: 1 The total value of the penetration rate [seconds] after one to three exposures was calculated, and the difference between this total value for Examples 1 to 7 and Comparative Examples 8 and 10 and that of the corresponding Comparative Example was calculated. Each of the obtained differences was converted into a relative amount, with the total value for the corresponding Comparative Example being set to 100%, and the value (%) thus obtained was designated as Score 1. Score 1 is an evaluation value that indicates the percentage reduction in the total time required to absorb the liquid after one to three exposures compared to the corresponding Comparative Example, and it can be evaluated that the higher the Score 1, the greater the effect of improving the absorption rate after multiple exposures to liquid. The results are shown in Table 1.

[0124] (6-2-2) Score: 2 The relative value of the second penetration rate [seconds] when the first penetration rate [seconds] was set to 1 was calculated as the second extension rate of the relative rate. The second extension rate of the corresponding comparative example was set to 1, and the relative value of the second extension rate for Examples 1 to 7 and Comparative Examples 8 and 10 was calculated and given a score of 2. The second extension rate of the relative rate indicates how much extra time it took to absorb the liquid exposed the second time compared to the first time. Score 2 indicates the extent to which the extra time required to absorb the liquid exposed the second time was suppressed. A score of 2 less than 1 can be evaluated as having a suppressing effect during the second liquid absorption, and the smaller the score 2, the greater the suppressing effect during the second liquid absorption. The results are shown in Table 1.

[0125] (6-2-3) Score: 3 The relative value of the penetration rate [seconds] at the third time, when the penetration rate [seconds] at the first time was set to 1, was calculated as the third extension rate of the relative rate. The relative value of the third extension rate for Examples 1 to 7 and Comparative Examples 8 and 10 was calculated when the third extension rate for the corresponding Comparative Example was set to 1, and this was assigned a score of 3. The third extension rate of the relative rate indicates how much extra time it took to absorb the liquid exposed to the third time compared to the first time. The score 3 indicates the extent to which the extra time required to absorb the liquid exposed to the third time was suppressed. A score 3 of less than 1 can be evaluated as having a suppression effect even at the third liquid absorption, and the smaller the score 3, the greater the suppression effect at the third liquid absorption. A laminate with a score 3 of less than 1 can be evaluated as having an exceptionally excellent effect of improving the absorption rate after multiple liquid exposures. The results are shown in Table 1.

[0126] (6-3) Backflow amount The laminate used to measure the permeation rate was used to measure the amount of backflow using the following procedure. Sixty minutes after the third application of the test liquid, a 10 cm square piece of filter paper, the mass of which (Wf [g]) had been measured in advance, was placed near the test liquid application 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 increase in mass was recorded as the amount of backflow [g]. The backflow test was conducted in a room conditioned to 25°C and 50% humidity (RH). The smaller the value of the backflow, the better the backflow suppression effect. The results are shown in Table 1. Backflow amount [g] = We - Wf

[0127] [Table 1] [Explanation of symbols]

[0128] 10, 10c, 10d...Laminate 10'...Laminate in a liquid-absorbed state 20, 20a, 20b...liquid-permeable first sheet 21...High wettability region 22...Low wettability area 30,30c...2nd sheet 40...Water absorbent resin layer 40'...Water-absorbent resin layer in a water-absorbed state 45...First water-absorbent resin layer 46...Second water-absorbent resin layer 50...Liquid permeable intermediate layer S2: The surface of the first sheet facing the water-absorbent resin layer LD21...Longitudinal direction (high wettability area) SD21: Short direction of high wettability area (and low wettability area) LD10...longitudinal direction (of laminate) LMD10...Lamination direction (of laminate)

Claims

1. A laminate comprising a liquid-permeable first sheet, a second sheet, and a water-absorbent resin layer interposed between the first sheet and the second sheet, a surface of the first sheet on the side of the water-absorbent resin layer includes a high-wettability region and a low-wettability region having a shape with a longitudinal direction, the contact angle of the high-wettability region with formamide being smaller by 10° or more than the contact angle of the low-wettability region with formamide, and [i] Combination of the following configurations (A) and (C) [ii] A combination of the following configurations (B) and (C), or [iii] A combination of the following configurations (A) and (D): Configuration (A) The high wettability region is a physically treated portion of the first sheet Configuration (B) The high-wettability region and the low-wettability region are flush with each other Structure (C) The width of the high wettability region is 1 to 10 mm Configuration (D) The high wettability region forms a groove A laminate comprising:

2. A laminate comprising a liquid-permeable first sheet, a second sheet, and a water-absorbent resin layer interposed between the first sheet and the second sheet, a surface of the first sheet on the side of the water-absorbent resin layer includes a high-wettability region (excluding those containing a styrene-based elastomer, a hydrocarbon-based oil, and a surfactant) and a low-wettability region having a shape having a longitudinal direction, and a contact angle of the high-wettability region with formamide is smaller by 10° or more than a contact angle of the low-wettability region with formamide, and [iv] The following configuration (C) and / or [v] The following configuration (D): Structure (C) The width of the high wettability region is 1 to 10 mm Configuration (D) The high wettability region forms a groove A laminate comprising:

3. A laminate as described in claim 1, wherein the physical processing portion of the configuration (A) is a melt-solidification portion.

4. The laminate according to any one of claims 1 to 3, wherein the low wettability region has a shape having a longitudinal direction, and the high wettability region and the low wettability region are arranged alternately in the short direction of the region.

5. The laminate according to claim 4 , wherein a plurality of the high-wettability regions and the low-wettability regions are arranged in parallel.

6. The laminate has a shape having a longitudinal direction, The laminate according to any one of claims 1 to 5, wherein the high-wettability region extends in a direction including the longitudinal direction of the laminate.

7. The laminate of claim 6 , wherein the high-wettability regions extend generally parallel to the longitudinal direction of the laminate.

8. The laminate according to any one of claims 1 to 7, wherein the water-absorbent resin layer is a multilayer having a first water-absorbent resin layer, a liquid-permeable intermediate layer, and a second water-absorbent resin layer in this order.

9. The laminate according to any one of claims 1 to 8, wherein the first sheet is made of resin fiber.

10. The laminate of claim 9, wherein the resin is a polyolefin.

11. An absorbent article comprising the laminate according to any one of claims 1 to 10.

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