Absorbent article

Abstract

To provide an absorbent article capable of efficiently recovering a material included in an absorber.SOLUTION: The absorbent article includes a top sheet, a back sheet, and an absorber, wherein the top sheet and the back sheet are bonded via an alkali-soluble bonding part.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an absorbent article. [Background technology]

[0002] Absorbent products such as disposable diapers, sanitary napkins, and pet sheets are composed of a back sheet, a top sheet, a core wrap, super absorbent polymer (SAP), pulp, etc. Of these, pulp is a natural material, so it has a low environmental impact even when disposed of in landfills, and it can also be reused as a raw material for cardboard. In addition, development of biodegradable SAP is underway. To protect the environment, there is a demand for technology that can efficiently separate the SAP and pulp from other materials in used absorbent products.

[0003] A typical absorbent article has a structure in which an absorbent body made of SAP and pulp is placed between a liquid-permeable top sheet and a liquid-impermeable back sheet, and sealed with a hot-melt adhesive (see Patent Documents 1 and 2). To recover the SAP and pulp from such an absorbent article, the adhesive joint must be heated or physically destroyed. Patent Document 3 discloses that components of disposable sanitary products are bonded together using a biodegradable hot-melt adhesive made from a starch hydrolysate. Meanwhile, Patent Document 4 discloses a hot-melt adhesive soluble in alkaline water as an adhesive for bookbinding and packaging. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-96882 [Patent Document 2] Japanese Patent Publication No. 2023-176753 [Patent Document 3] Special Publication No. 2018-538379 [Patent Document 4] Japanese Patent Application Publication No. 9-111217 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide an absorbent article that can efficiently recover materials contained in the absorbent body. [Means for solving the problem]

[0006] The present inventors have found that the above problems can be solved by bonding the top sheet and back sheet that encase the absorbent body via an alkali-soluble adhesive, and have completed the present invention.

[0007] That is, the present invention includes the following aspects. <1> A top sheet, a back sheet, and an absorbent body, The absorbent article has the top sheet and the back sheet bonded together via an alkali-soluble adhesive. <2> Item 1. The absorbent article according to item 1, further comprising a core wrap. <3> Item 3. The absorbent article according to item 2, wherein the absorbent body and at least one selected from the group consisting of the top sheet, the back sheet, and the core wrap are bonded via an alkali-soluble adhesive. <4> Item 4. The absorbent article according to item 2 or 3, wherein the core wraps are bonded to each other or the core wrap and the backsheet are bonded via an alkali-soluble adhesive. <5> Item 5. The absorbent article according to any one of items 1 to 4, wherein the adhesive portion contains an alkali-soluble resin. <6> Item 6. The absorbent article according to any one of items 1 to 5, wherein the adhesive portion comprises a layer containing an alkali-soluble resin and adhesive layers formed on both sides of the layer. <7> Item 7. The absorbent article according to item 5 or 6, wherein the alkali-soluble resin is a thermoplastic resin or a cured product of a thermosetting resin. <8> 8. The absorbent article according to any one of items 5 to 7, wherein the alkali-soluble resin has a unit represented by formula (1). [ka] (In formula (1), A is a hydrocarbon group which may have a substituent. X 1 is an oxygen atom, a sulfur atom, or a nitrogen atom which may have a substituent. R 1 represents a hydrocarbon group or silyl group which may have a substituent, or a hydrogen atom. <9> Item 9. The absorbent article according to item 8, wherein the unit represented by formula (1) is a unit represented by formula (2), formula (3), or formula (4). [ka] (In formula (2), X 1a , X 1b are each independently an oxygen atom, a sulfur atom, or a nitrogen atom which may have a substituent. R 1a , R 1b is a hydrocarbon group or silyl group which may have a substituent, or a hydrogen atom, and R 1a and R 1b At least one of the groups is a hydrogen atom. R 2 , R 3 are each independently a hydrocarbon group or silyl group which may have a substituent, or a hydrogen atom. [ka] (In formula (3), X 1c , X 1d , X 2 , X 3 are each independently an oxygen atom, a sulfur atom, or a nitrogen atom which may have a substituent. R 1c , R 1dis a hydrocarbon group or silyl group which may have a substituent, or a hydrogen atom, and R 1c and R 1d At least one of the groups is a hydrogen atom. R 4 is a hydrocarbon group or a silyl group which may have a substituent. D is a hydrocarbon group which may have a substituent. [ka] (In formula (4), X 1 is an oxygen atom, a sulfur atom, or a nitrogen atom which may have a substituent. R 1 represents a hydrocarbon group or silyl group which may have a substituent, or a hydrogen atom. R 4 , R 5 and E are each independently a hydrocarbon group which may have a substituent. <10> Item 10. The absorbent article according to any one of items 1 to 9, wherein the absorbent body contains an absorbent resin and / or naturally derived fibers. <11> When the adhesive joint is immersed in water for 1 hour, the weight change from before immersion is -10% to 10%. Item 11. The absorbent article according to any one of items 1 to 10. <12> The top sheet and the back sheet are bonded together by a rectangular adhesive portion that surrounds the absorbent body and / or the core wrap, Two or more sides of the rectangular adhesive portion are alkali-soluble, and one or more of the sides is a long side. Item 12. The absorbent article according to any one of items 1 to 11. <13> Item 3. The absorbent article according to item 2, wherein the absorbent body is sandwiched between two or more core wraps, and the two or more core wraps are bonded together by an alkali-soluble adhesive. <14> Item 14. A method for dismantling absorbent articles, comprising the step of immersing the absorbent article according to any one of items 1 to 13 in an alkaline solution at 0 to 60°C. [Effects of the Invention]

[0008] Materials contained in the absorbent body can be efficiently recovered from the absorbent article of the present invention. [Brief explanation of the drawings]

[0009] [Figure 1A] FIG. 2 is a cross-sectional view taken along the line AA' of the absorbent article according to the first embodiment of the present invention [Figure 1B] 1 is a top view of an absorbent article according to a first embodiment of the present invention. [Figure 2A] FIG. 5 is a cross-sectional view taken along the line BB' of the absorbent article according to the second embodiment of the present invention [Figure 2B] FIG. 2 is a top view of an absorbent article according to a second embodiment of the present invention. [Figure 3A] FIG. 5 is a cross-sectional view taken along CC' line of the absorbent article according to the third embodiment of the present invention. [Figure 3B] FIG. 10 is a top view of an absorbent article according to a third embodiment of the present invention. [Figure 4A] FIG. 6 is a cross-sectional view taken along the line DD' of an absorbent article according to a fourth embodiment of the present invention [Figure 4B] FIG. 10 is a top view of an absorbent article according to a fourth embodiment of the present invention. [Figure 5A] FIG. 8 is a cross-sectional view taken along the line EE' of an absorbent article according to a fifth embodiment of the present invention [Figure 5B] FIG. 10 is a top view of an absorbent article according to a fifth embodiment of the present invention. [Figure 6A] FIG. 2 is a cross-sectional view taken along the line FF' of an absorbent article according to a sixth embodiment of the present invention [Figure 6B] FIG. 10 is a top view of an absorbent article according to a sixth embodiment of the present invention. [Figure 7A] FIG. 20 is a cross-sectional view of the absorbent article of the seventh embodiment of the present invention taken along the line GG [Figure 7B] FIG. 10 is a top view of an absorbent article according to a seventh embodiment of the present invention. [Figure 8A] FIG. 10 is a cross-sectional view taken along the line HH′ of the absorbent article according to the eighth embodiment of the [Figure 8B] FIG. 10 is a top view of an absorbent article according to an eighth embodiment of the present invention. [Figure 9A] FIG. 10 is a cross-sectional view taken along II' line of an absorbent article according to a ninth embodiment of the present [Figure 9B] FIG. 10 is a top view of an absorbent article according to a ninth embodiment of the present invention. [Figure 10] FIG. 2 is a cross-sectional view of an example of an adhesive joint. [Figure 11] FIG. 2 is a cross-sectional view of an example of an adhesive joint. [Figure 12] FIG. 2 is a cross-sectional view of an example of an adhesive joint. [Figure 13] FIG. 2 is a cross-sectional view of an example of an adhesive joint. [Figure 14] FIG. 2 is a cross-sectional view of an example of an adhesive joint. [Figure 15] FIG. 2 is a cross-sectional view of an example of an adhesive joint. DETAILED DESCRIPTION OF THE INVENTION

[0010] <<Absorbent articles>> The absorbent article of the present invention comprises a top sheet, a back sheet, and an absorbent body, and is characterized in that the top sheet and the back sheet are bonded together via an alkali-soluble adhesive. The absorbent article may further comprise a core wrap. In the absorbent article of the present invention, the top sheet and the back sheet are bonded together via an alkali-soluble adhesive, so that the adhesive dissolves when the absorbent article is immersed in an alkaline solution, allowing the absorbent body to be easily recovered. The materials contained in the recovered absorbent body can be reused.

[0011] <Sheet-shaped substrate> The top sheet, back sheet, and core wrap are all sheet-like substrates. The top sheet is placed closer to the wearer's skin than the absorbent body. The top sheet is preferably liquid-permeable to body fluids such as urine and blood. Examples of top sheets include woven fabrics, nonwoven fabrics, and porous films. Examples of materials that can be used to form top sheets include polypropylene, polyethylene, polyester, polyamide, cellulose, rayon, and cotton.

[0012] The backsheet is positioned farther from the wearer's skin than the absorbent body. The backsheet is preferably liquid-impermeable to prevent leakage of bodily fluids held by the absorbent article. Examples of the backsheet include nonwoven fabrics and films. Examples of materials for the backsheet include polyethylene, polypropylene, polyurethane, etc. When using a film as the backsheet, it is preferable to use a moisture-permeable film to prevent stuffiness when worn. Alternatively, a laminated backsheet in which a liquid-permeable sheet is bonded to a liquid-impermeable sheet with an adhesive or the like can also be used as the backsheet.

[0013] The core wrap encases the absorbent body and holds the absorbent resin and natural fibers contained in the absorbent body. Examples of core wrap include woven fabric, nonwoven fabric, porous film, and paper sheet. Materials that can be used to make the core wrap include polypropylene, polyethylene, polyester, cellulose, rayon, and cotton.

[0014] In addition to the top sheet, back sheet, and core wrap, the absorbent article may also include sheet-like substrates that are generally included in absorbent articles, such as a leak-proof guard sheet, a distribution sheet that is placed under the top sheet to promote the dispersion of body fluids into the absorbent body, a cover sheet that reinforces the back sheet and improves the feel, a deodorizing sheet that absorbs odors, an adhesive sheet for fastening to clothing, etc., and a waist stretch sheet or fastening tape for fastening to the body.

[0015] <Absorbent> Absorbents absorb and retain liquids. Examples of materials that make up absorbents include absorbent resins and fibers. Examples of absorbent resins include synthetic resins such as poly(meth)acrylic resins and polyacrylamide resins, as well as naturally derived absorbent resins. Examples of fibers include naturally derived fibers. In particular, when the absorbent resin is a biodegradable material, such as polyaspartic acid, cellulose, chitin, chitosan, starch, or a derivative thereof, even when naturally derived fibers are used in combination, they can be disposed of in landfills or used as fertilizer raw materials without separating the two. Some of these biodegradable materials are easily decomposed by acids or alkalis, and when an absorbent containing such materials is used, the naturally derived fibers can be recovered in high purity.

[0016] Examples of naturally occurring fibers that can be used include cellulose fibers such as mechanical pulp, chemical pulp, semi-chemical pulp, and dissolving pulp obtained from wood, regenerated fibers such as rayon and acetate, and cotton fibers. The absorbent body is preferably one in which an absorbent resin is held in these naturally occurring fibers.

[0017] Examples of fluids that can be absorbed by absorbents include body fluids such as blood, mucus, urine, etc. The pH of these body fluids is generally 4.0 to 8.0.

[0018] <Adhesive part> In an absorbent article, the top sheet and the back sheet are bonded via an alkali-soluble adhesive, which results in the absorbent body being fixed within the absorbent article. As long as the alkali-soluble adhesive is present between the top sheet and the back sheet, it can efficiently detach the absorbent body from the absorbent article upon contact with an alkaline solution, so the position of the alkali-soluble adhesive in the absorbent article and the combination of the adhesive bodies are not particularly limited.

[0019] In the absorbent article, the core wraps may be bonded to each other or to the back sheet via an alkali-soluble adhesive. The absorbent body may be bonded to at least one selected from the group consisting of the top sheet, the back sheet, and the core wrap via an alkali-soluble adhesive. In these embodiments, the absorbent body can be reliably fixed within the absorbent article, while being efficiently recovered by reaction with an alkaline solution.

[0020] When at least a portion of the core wrap is bonded to the core wrap via an alkali-soluble adhesive, the absorbent body may be sandwiched between two or more core wraps and then the core wraps may be bonded together, or the absorbent body may be wrapped inside a folded core wrap and then the ends of the folded core wrap may be bonded. The core wrap may be formed into a cylindrical shape and then the absorbent body may be enclosed inside, and the ends may be bonded with an alkali-soluble adhesive. When the absorbent body is wrapped in the core wrap, all four sides may be closed, or one or two sides may be open. Specific examples of absorbent articles will be described based on the following embodiments 1 to 9, but are not limited to these.

[0021] Embodiment 1 is shown in Figures 1A and 1B. Embodiment 1 is an example without a core wrap. Figure 1A is a cross-sectional view taken along the line A-A' in Figure 1B. The absorbent body 15 of the absorbent article 1 is sandwiched between the back sheet 13 and the top sheet 11. The top sheet 11 and the back sheet 13 are bonded together around the periphery of the absorbent body by adhesive sections 14, so that the absorbent body 15 is held inside. It is preferable that the adhesive sections 14 are alkali-soluble adhesive sections on at least two of the four sides.

[0022] Embodiment 2 is shown in FIGS. 2A and 2B, and Embodiment 3 is shown in FIGS. 3A and 3B. FIG. 2A is a B-B' cross-sectional view of FIG. 2B. FIG. 3A is a C-C' cross-sectional view of FIG. 3B. In Embodiments 2 and 3, the absorbent body 15 is wrapped in and held within the folded core wrap 12. In Embodiment 2, the adhesive surfaces of the core wrap 12 are on the side and backsheet 13 sides. In Embodiment 3, the adhesive surface of the core wrap 12 is on the backsheet 13 side. In Embodiments 2 and 3, the ends of the core wrap 12 are bonded via alkali-soluble adhesive parts 14 between the core wraps 12. When the absorbent body 15 is sealed by the core wrap 12 as in Embodiment 2, it is preferable that two approximately parallel sides of the core wrap 12 are bonded via alkali-soluble adhesive parts 14. When the absorbent body 15 is not sealed by the core wrap 12 as in Embodiment 3, the adhesive parts 14 do not have to be alkali-soluble. In embodiments 2 and 3, the top sheet 11 and the back sheet 13 preferably have alkali-soluble adhesive joints on at least two of the four adhesive joints 14, as in embodiment 1. The core wrap 12 and the back sheet 13 may be bonded by an alkali-soluble adhesive joint, or may be bonded by a non-alkali-soluble adhesive joint, or may not be bonded by an adhesive joint at all.

[0023] Embodiment 4 is shown in Figures 4A and 4B, and embodiment 5 is shown in Figures 5A and 5B. Figure 4A is a cross-sectional view taken along the line D-D' in Figure 4B. Figure 5A is a cross-sectional view taken along the line E-E' in Figure 5B. Embodiments 4 and 5 are examples in which an absorbent body 15 is held by a single core wrap 12. In embodiment 4, the absorbent body 15 is sealed by adhesive parts 14 in three directions, and in embodiment 5, one side of the core wrap 12 is adhesively attached and two sides are free.

[0024] Of the adhesive joints 14 between the core wraps 12 in embodiment 4, it is preferable that the adhesive joints 14 on two or more sides are alkali-soluble. In embodiment 5, the adhesive joints between the core wraps 12 do not have to be alkali-soluble. As in embodiments 1 to 3, it is preferable that the adhesive joints 14 on at least two sides of the adhesive joints 14 on the four sides between the top sheet 11 and the back sheet 13 are alkali-soluble. The core wrap 12 and the back sheet 13 may be bonded by an alkali-soluble adhesive joint, but may also be bonded by an adhesive joint that is not alkali-soluble, or may not be bonded by an adhesive joint at all.

[0025] Embodiment 6 is shown in Figures 6A and 6B, and Embodiment 7 is shown in Figures 7A and 7B. Figure 6A is a cross-sectional view taken along the line F-F' in Figure 6B. Figure 7A is a cross-sectional view taken along the line G-G' in Figure 7B. Embodiments 6 and 7 are examples in which an absorbent body 15 is held in a single cylindrically formed core wrap 12. In Embodiment 6, the cylindrical opening is sealed by a bonded joint 14 between the core wraps 12. In Embodiment 7, there is no bonded joint between the core wraps 12, leaving the core wraps 12 open. In Embodiment 6, the bonded joint 14 between the core wraps 12 is preferably an alkali-soluble bonded joint. As in Embodiments 1 to 5, the top sheet 11 and the back sheet 13 preferably have alkali-soluble bonded joints on at least two of the four bonded joints 14. The core wrap 12 and the back sheet 13 may be bonded by an alkali-soluble bonded joint, or may be bonded by a non-alkali-soluble bonded joint, or may not be bonded by any bonded joint.

[0026] Embodiment 8 is shown in Figures 8A and 8B, and Embodiment 9 is shown in Figures 9A and 9B. Figure 8A is a cross-sectional view taken along the line H-H' in Figure 8B. Figure 9A is a cross-sectional view taken along the line I-I' in Figure 9B. In Embodiments 8 and 9, an absorbent body 15 is sandwiched between two core wraps 12. In Embodiment 8, the absorbent body 15 is sealed by the bonded joints 14 between the core wraps 12, while in Embodiment 9, two sides of the core wrap 12 are open. Of the bonded joints 14 between the core wraps 12 in Embodiment 8, two or more sides are preferably alkali-soluble. In Embodiment 9, the bonded joints 14 between the core wraps 12 do not have to be alkali-soluble. As in Embodiments 1 to 7, it is preferable that at least two of the four bonded joints 14 of the top sheet 11 and the back sheet 13 are alkali-soluble. The core wrap 12 and the back sheet 13 may be bonded together by an alkali-soluble adhesive, or may be bonded together by an adhesive that is not alkali-soluble, or may not be bonded together by an adhesive at all.

[0027] In an absorbent article, when the top sheet and back sheet are overlapped, as shown in Figure 1B, the adhesive portion is arranged in a rectangular shape so as to surround the periphery of the absorbent core, and it is preferable that two or more sides of this rectangular adhesive portion are alkali-soluble. When the rectangle is rectangular, it is preferable that one or more sides of the two or more alkali-soluble adhesive portions are long sides. In this case, the absorbent core can be securely held during use of the absorbent article, and the absorbent core can be efficiently recovered when immersed in an alkaline solution.

[0028] The alkali-soluble adhesive part preferably contains an alkali-soluble resin in at least a part thereof. The alkali-soluble resin may be either a thermoplastic resin or a cured product of a thermosetting resin, but a thermoplastic resin is preferred because it can be used to manufacture absorbent articles in the same manner as conventional hot melt adhesives. Specific examples of the alkali-soluble adhesive part include (1) an adhesive part consisting of only an alkali-soluble layer, and (2) an adhesive part in which an alkali-soluble layer and an adhesive layer are laminated.

[0029] (1) In an adhesive joint consisting only of an alkali-soluble layer, the alkali-soluble layer may contain only an alkali-soluble resin, or may contain an adhesive in addition to the alkali-soluble resin. (1) Examples of an adhesive joint consisting only of an alkali-soluble layer are shown in Figures 10 to 11.

[0030] (2) An adhesive joint formed by laminating an alkali-soluble layer and an adhesive layer is formed, for example, when a resin composition without adhesive properties is used. When a laminate consisting of an alkali-soluble layer (a) and adhesive layers (b) formed on both sides of the layer is present between two adherends, sufficient adhesion can be achieved throughout the adhesive joint, even when the alkali-soluble layer is made of a resin composition without adhesive properties. Furthermore, when an absorbent article is immersed in an alkaline solution, the alkali-soluble layer dissolves, destroying the adhesive joint and releasing the adhesion between the adherends. Adhesives conventionally used in the manufacture of absorbent articles can be used as adhesives for forming the adhesive layers (b) formed on both sides of the alkali-soluble layer. Specific examples include adhesives described below as optional components of resin compositions, as well as compositions containing plasticizers, waxes, surfactants, tackifiers, stabilizers, etc. (2) Examples of adhesive joints formed by laminating an alkali-soluble layer and an adhesive layer are shown in Figures 12 to 15.

[0031] The adhesiveness of the adhesive joint can be evaluated by placing a resin composition between the top sheet and the back sheet, thermocompressing them, and then peeling the top sheet and the back sheet at 180 degrees, and visually observing the surface condition of the peeled surface. In the case of interfacial peeling between the substrate and the composition layer, the area that can be used may be limited, so peeling due to cohesive failure of the adhesive joint is preferred, and peeling due to material failure of the substrate is more preferred. It can also be evaluated by a T-peel test in accordance with JIS K6845. For example, if the peel strength at a tensile speed of 100 mm / min is 0.1 N / 25 mm or more, it is likely to be satisfactory in practical use, and if it is 0.2 N / 25 mm or more, it can be used for a wider range of applications, and if it is 0.3 N / 25 mm or more, it is even more preferable.

[0032] Specific examples of alkali-soluble adhesive parts will be described with reference to the drawings. Figure 10 shows an embodiment in which a top sheet or core wrap 101 and a back sheet or core wrap 102 are adhered by an alkali-soluble layer 103.

[0033] FIG. 11 shows an embodiment in which a topsheet or core wrap 101 and a backsheet or core wrap 102 are adhered together by an alkali-soluble layer 105 containing an adhesive.

[0034] 12 shows an embodiment in which a top sheet or core wrap 101 and a back sheet or core wrap 102 are bonded together by an alkali-soluble layer 103 and an adhesive layer 104. Even if the alkali-soluble layer only adheres to a specific sheet-like substrate, the provision of adhesive layer 104 makes it possible to bond a back sheet or core wrap 102 made of a wide variety of materials.

[0035] 13 shows an embodiment in which a top sheet or core wrap 101 and a back sheet or core wrap 102 are bonded together by an alkali-soluble layer 103 and an adhesive layer 104. Even if the alkali-soluble layer only adheres to a specific sheet-like substrate, the provision of adhesive layer 104 makes it possible to bond top sheets or core wraps 101 made of a wide variety of materials.

[0036] 14 shows an embodiment in which a top sheet or core wrap 101 and a back sheet or core wrap 102 are bonded together by two alkali-soluble layers 103 and an adhesive layer 104. Even if the alkali-soluble layer only adheres to a specific sheet-like substrate, the provision of adhesive layer 104 makes it possible to bond a top sheet or core wrap 101 made of a wide variety of materials to a back sheet or core wrap 102 made of a wide variety of materials.

[0037] FIG. 15 shows an embodiment in which a topsheet or core wrap 101 and a backsheet or core wrap 102 are bonded together by an alkali-soluble layer 103 and two adhesive layers 104 .

[0038] 10 to 15, one to three layers are formed between the top sheet or core wrap 101 and the back sheet or core wrap 102, but the number of layers is not particularly limited. Furthermore, the two alkali-soluble layers 103 in FIG. 14 may be formed of the same material or different materials. Similarly, the two adhesive layers 104 in FIG. 15 may be formed of the same material or different materials.

[0039] The structure of the alkali-soluble resin contained in the adhesive portion is not particularly limited as long as it dissolves in an alkaline solution, but it preferably has an alkali-soluble group that forms a water-soluble salt or ion in an alkaline solution. Examples of the alkali-soluble group include a carboxyl group, an acid anhydride group, and a sulfonic acid group, with a carboxyl group and an acid anhydride group being preferred. The alkali-soluble resin may have only one type of alkali-soluble group, or two or more types.

[0040] Furthermore, the alkali-soluble resin preferably has a hydrophilic structure to improve reactivity with alkaline solutions. The hydrophilic structure is preferably a polyoxyalkylene chain, and more preferably polyethylene glycol. The molecular weight of the polyethylene glycol portion is preferably 500 to 20,000, more preferably 800 to 6,000, and even more preferably 1,000 to 2,000. The hydrophilic structure can be bonded to the alkali-soluble resin via, for example, an ester with a carboxyl group or an acid anhydride group, or a sulfonate ester with a sulfonic acid group. However, the alkali-soluble resin preferably has a free alkali-soluble group, and is more preferably a partially esterified resin having a carboxyl group and a polyoxyalkylene chain.

[0041] The acid value of the alkali-soluble resin is preferably 1 to 1000 mgKOH / g, more preferably 5 to 750 mgKOH / g, and even more preferably 10 to 400 mgKOH / g. If it is less than 1 mgKOH / g, water resistance tends to be insufficient when the resin has an alkali-soluble skeleton. If it exceeds 1000 mgKOH / g, adhesion tends to be insufficient. The acid value here refers to the amount of free alkali-soluble groups contained in the resin.

[0042] Examples of the main chain structure of alkali-soluble resins include linear hydrocarbons such as methylene, ethylene, propylene, butylene, butadiene, pentylene, hexylene, heptylene, octylene, nonylene, ethers, urethanes, ureas, esters, thioethers, carbonates, and amides; branched hydrocarbons such as isopropylene, isobutylene, 2,2-dimethylpropylene, and 2-ethyl-2-methylpropylene; cyclic hydrocarbons such as cyclohexylene, cyclopentylene, norbornene, phenylene, naphthylene, and styrene; and acrylonitrile-styrene copolymers, butadiene-styrene copolymers, and acrylonitrile-butadiene-styrene copolymers. Hydrogen atoms in the main chain may be substituted with halogen atoms, amino groups, sulfo groups, cyano groups, nitro groups, or other groups. The main chain may also contain heteroatoms such as N, S, O, and P.

[0043] The alkali-soluble resin is a resin represented by the formula (1): [ka] It is preferable that the unit has the following formula:

[0044] In formula (1), A is a hydrocarbon group which may have a substituent. The hydrocarbon group preferably has 1 to 650 carbon atoms, more preferably 1 to 350 carbon atoms. The hydrocarbon group may be a saturated or unsaturated hydrocarbon group, and may have a linear, branched, or cyclic structure. Specific examples of the substituent include a carboxyl group, an alkoxy group, a phenoxy group, a halogen atom, an amino group, a sulfo group, a cyano group, a nitro group, an amide group, a hydrazide group, and an acylhydrazide group. The hydrocarbon group may contain a heteroatom such as N, S, O, or P. Examples of structures containing a heteroatom contained in the hydrocarbon group include: [ka] Examples include:

[0045] Specific examples of the hydrocarbon group include linear hydrocarbons such as methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, ether, urethane, urea, ester, thioether, carbonate, and amide; branched hydrocarbons such as isopropylene, isobutylene, 2,2-dimethylpropylene, and 2-ethyl-2-methylpropylene; cyclic hydrocarbons such as cyclohexylene, cyclopentylene, norbornenylene, phenylene, biphenylene, and naphthylene; PEG chain, succinimide, maleic acid, isoprene, and homopolymers and copolymers composed of units containing these structures.

[0046] In formula (1), X 1 is an oxygen atom, a sulfur atom, or a nitrogen atom which may have a substituent. Specific examples of the substituent include an alkyl group, a vinyl group, an allyl group, an aryl group, an alkoxy group, a cyano group, an acyl group, an amino group, and an amide group.

[0047] In formula (1), R 1is a hydrocarbon group or silyl group which may have a substituent, or a hydrogen atom. The hydrocarbon group preferably has 1 to 500 carbon atoms, more preferably 1 to 300 carbon atoms. The hydrocarbon group is a saturated or unsaturated hydrocarbon group, and may have any of a linear structure, a branched structure, and a cyclic structure. Specific examples of the substituent include an alkoxy group, a phenoxy group, a halogen atom, an amino group, an amido group, a sulfo group, a cyano group, a nitro group, a hydrazine group, and a hydrazide group. The hydrocarbon group may contain a heteroatom such as N, S, O, or P. Examples of structures containing a heteroatom contained in the hydrocarbon group include: [ka] Examples include:

[0048] Specific examples of the hydrocarbon group include linear hydrocarbons such as methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, ether, urethane, urea, ester, thioether, carbonate, and amide; branched hydrocarbons such as isopropylene, isobutylene, 2,2-dimethylpropylene, and 2-ethyl-2-methylpropylene; cyclic hydrocarbons such as cyclohexylene, cyclopentylene, norbornenylene, phenylene, biphenylene, and naphthylene; PEG chain, succinimide, maleic acid, isoprene; and homopolymers and copolymers composed of units containing these structures.

[0049] In formula (1), R 1 Specific examples of the halogen atom include fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0050] The method for producing an alkali-soluble resin having a unit represented by formula (1) is not particularly limited, but it can be obtained, for example, by an ester-forming reaction between a polycarboxylic acid containing the structure A in formula (1) and a hydrocarbon such as polyoxyalkylene. Furthermore, the carboxyl groups of the obtained alkali-soluble resin may be further reacted with a compound such as an alcohol or an amine.

[0051] Examples of the unit represented by formula (1) include units represented by formula (2), formula (3), or formula (4). [ka]

[0052] In formula (2), X 1a , X 1b are each independently an oxygen atom, a sulfur atom, or a nitrogen atom which may have a substituent. 1a , X 1b A specific example of X in formula (1) is 1 is the same as R 1a , R 1b is a hydrocarbon group or silyl group which may have a substituent, or a hydrogen atom, and R 1a and R 1b At least one of R is a hydrogen atom. 1a , R 1b A specific example of R in formula (1) 1 is the same as

[0053] In formula (2), R 2 , R 3 R are each independently a hydrocarbon group or silyl group which may have a substituent, or a hydrogen atom. 2 , R 3 A specific example of R in formula (1) 1 is the same as

[0054] The unit represented by formula (2) preferably has at least one carboxyl group. 1a is an oxygen atom and R 1a is a hydrogen atom, or X 1b is an oxygen atom and R 1b is preferably a hydrogen atom.

[0055] [ka]

[0056] In formula (3), X 1c , X1d , X 2 , X 3 are each independently an oxygen atom, a sulfur atom, or a nitrogen atom which may have a substituent. 1c , X 1d , X 2 , X 3 A specific example of X in formula (1) is 1 is the same as R 1c , R 1d is a hydrocarbon group or silyl group which may have a substituent, or a hydrogen atom, and R 1c and R 1d At least one of R is a hydrogen atom. 1c , R 1d A specific example of R in formula (1) 1 is the same as R 4 R is a hydrocarbon group or a silyl group which may have a substituent. 4 Specific examples of the substituent and hydrocarbon group are R in formula (1), 1 D is a hydrocarbon group which may have a substituent. Specific examples of the substituent and hydrocarbon group of D are the same as the substituent and hydrocarbon group of A in formula (1), respectively.

[0057] The unit represented by formula (3) preferably has at least one carboxyl group. 1c is an oxygen atom and R 1c is a hydrogen atom, or X 1d is an oxygen atom and R 1d is preferably a hydrogen atom.

[0058] As a unit represented by formula (3), formula (5): [ka] In formula (5), D is the same as in formula (3). n is an integer of 1 or more, preferably 4 to 500, and more preferably 8 to 150. The unit represented by formula (5) can be obtained, for example, by reacting pyromellitic acid or its anhydride, naphthalene-1,4,5,8-tetracarboxylic acid or its anhydride, 3,3',4,4'-benzophenonetetracarboxylic acid or its anhydride, or the like with polyethylene glycol. In the alkali-soluble resin, the number of repetitions of the unit represented by formula (5) is preferably 10 to 500, and more preferably 20 to 250.

[0059] [ka]

[0060] In formula (4), X 1 is an oxygen atom, a sulfur atom, or a nitrogen atom which may have a substituent. 1 A specific example of X in formula (1) is 1 is the same as

[0061] In formula (4), R 1 R is a hydrocarbon group or silyl group which may have a substituent, or a hydrogen atom. 1 A specific example of R in formula (1) 1 is the same as

[0062] In formula (4), R 4 , R 5 and E are each independently a hydrocarbon group which may have a substituent. 4 , R 5 Specific examples of the substituent and hydrocarbon group are R in formula (1), 1 Specific examples of the substituent and hydrocarbon group of E are the same as the substituent and hydrocarbon group of A in formula (1), respectively.

[0063] <Resin composition> The material used to form the alkali-soluble adhesive joint is not particularly limited as long as it can form the above-mentioned alkali-soluble resin by heating or drying. For example, the above-mentioned compounds having alkali-soluble groups and hydrophilic structures, or resin compositions containing such compounds, can be used.

[0064] A compound having an alkali-soluble group and a hydrophilic structure can be obtained, for example, by forming an ester bond between the alkali-soluble group of a compound having an alkali-soluble group and a hydroxyl group of an alcohol. Examples of compounds having an alkali-soluble group that can be used as a raw material include pyromellitic acid or its anhydride, naphthalene-1,4,5,8-tetracarboxylic acid or its anhydride, 3,3',4,4'-benzophenonetetracarboxylic acid or its anhydride, and 3,3',4,4'-biphenyltetracarboxylic acid or its anhydride.

[0065] The compound having an alkali-soluble group used as a raw material may also be a polymer. Examples of polymers include linear hydrocarbons such as methylene, ethylene, propylene, butylene, butadiene, pentylene, hexylene, heptylene, octylene, nonylene, ethers, urethanes, ureas, esters, thioethers, carbonates, and amides; branched hydrocarbons such as isopropylene, isobutylene, 2,2-dimethylpropylene, and 2-ethyl-2-methylpropylene; and cyclic hydrocarbons such as cyclohexylene, cyclopentylene, norbornene, phenylene, naphthylene, and styrene. Examples of such polymers include L-IR-403, L-IR-410, and ISOBAM-304 (all manufactured by Kuraray Co., Ltd.).

[0066] Examples of alcohol compounds that can be used as raw materials include 1,6-hexanediol, polyethylene glycol, polypropylene glycol, and ethylene oxide-propylene oxide copolymers.

[0067] When the compound having an alkali-soluble group and a hydrophilic structure is a thermoplastic resin, the adhesive joint can be formed using only the resin. When the adhesive joint is formed using a resin composition containing optional components in addition to the compound having an alkali-soluble group and a hydrophilic structure, the content of the compound having an alkali-soluble group and a hydrophilic structure in the resin composition is preferably 1 to 99 wt %, more preferably 20 to 95 wt %, and even more preferably 50 to 95 wt % of the total solid content. If the content is less than 1 wt %, dismantling properties tend to be reduced.

[0068] <Optional ingredients> The resin composition used to form the alkali-soluble adhesive joint can contain, in addition to an alkali-soluble group and a compound having a hydrophilic structure, a crosslinking agent, a catalyst, a binder, a solvent, a surfactant, an adhesive, a tackifier, a stabilizer, a plasticizer, a wax, etc.

[0069] <Crosslinking agent> Examples of the crosslinking agent include an isocyanate compound, an oxazoline compound, an epoxy compound, an alcohol compound, an amine compound, an alkylene carbonate compound, a haloepoxy compound, a halohydrin compound, a carbodiimide compound, a silane coupling agent, and a polyvalent metal compound.

[0070] Examples of the isocyanate compound include hexamethylene diisocyanate, 2,4-tolylene diisocyanate, etc. Examples of the oxazoline compound include 1,2-ethylenebisoxazoline, etc.

[0071] Examples of epoxy compounds include succinic acid glycidyl ester, sorbitol polyglycidyl ether, trimethylolpropane polyglycidyl ether, polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and glycidol.

[0072] Examples of the alcohol compound include ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, 1,3-propanediol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, polypropylene glycol, glycerin, polyglycerin, 2-butene-1,4-diol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,2-cyclohexanediol, trimethylolpropane, diethanolamine, triethanolamine, polyoxypropylene, oxyethylene-oxypropylene block copolymer, pentaerythritol, and sorbitol.

[0073] Examples of the amine compound include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine, inorganic salts or organic salts (such as azithinium salts) of these amine compounds, and the like.

[0074] Examples of the alkylene carbonate compound include 1,3-dioxolan-2-one, 4-methyl-1,3-dioxolan-2-one, 4,5-dimethyl-1,3-dioxolan-2-one, 4,4-dimethyl-1,3-dioxolan-2-one, 4-ethyl-1,3-dioxolan-2-one, 4-hydroxymethyl-1,3-dioxolan-2-one, 1,3-dioxan-2-one, 4-methyl-1,3-dioxan-2-one, and 4,6-dimethyl-1,3-dioxan-2-one.

[0075] Examples of haloepoxy compounds include epichlorohydrin, epibromohydrin, α-methylepichlorohydrin, and polyamine adducts thereof (eg, Kaimen (registered trademark) manufactured by Hercules).

[0076] A crosslinkable binder may be used as the crosslinking agent. Examples of crosslinkable binders include polyester resins, acrylic resins, polyurethane resins, and polyolefin resins having reactive functional groups. Examples of reactive functional groups include oxazoline rings, carboxyl groups, and carbodiimide groups. Examples of resins having an oxazoline ring in a side chain include polymers obtained by addition polymerization of oxazolines such as poly-2-methyl-2-oxazoline and poly-2-propyl-2-oxazoline, and polymers containing addition-polymerizable oxazoline groups. Commercially available products include Epocross WS-300, WS-500, WS-700, K-2010E, K-2030E, and K-2020E (manufactured by Nippon Shokubai Co., Ltd.). Examples of resins having a carboxyl group in the side chain include PLASCOAT Z-760 and Z-730 (manufactured by GOO Chemical Industry Co., Ltd.), ARROWBASE SE1200 and ARROWBASE DA-1010 (manufactured by Unitika Ltd.), ZAIKSENE A and ZAIKSENE L (manufactured by Sumitomo Seika Chemicals Co., Ltd.), etc. Examples of resins having a carbodiimide group in the side chain include Carbodilite V-02, Carbodilite SV-02 and Carbodilite E-02 (manufactured by Nisshinbo Chemical Inc.).

[0077] The amount of the crosslinking agent in the resin composition is preferably 0.1 to 100 parts by weight, more preferably 5 to 90 parts by weight, per 100 parts by weight of the compound having an alkali-soluble group and a hydrophilic structure.

[0078] <Catalyst> The catalyst is not particularly limited as long as it is a compound that can catalyze the reaction of the crosslinking agent, and compounds that generate radicals by heat, compounds that generate cations by heat, compounds that generate anions by heat, compounds that reduce the activation energy of the crosslinking reaction by coordination, etc. can be used. Specific examples include radical generators such as alkylphenone compounds, benzoin compounds, benzophenone compounds, oxime ester compounds, and phosphine compounds; base generators such as oxime ester compounds, ammonium compounds, benzoin compounds, dimethoxybenzyl urethane compounds, and orthonitrobenzyl urethane compounds; acid generators such as onium salts, halogen-containing compounds, diazomethane compounds, sulfone compounds, and sulfonic acid compounds; tin compounds such as dibutyltin dilaurate and dibutyltin diacetate; bismuth compounds such as bismuth octylate; titanium compounds such as tetraoctyl titanate and titanium ethyl acetoacetate; zirconium compounds such as zirconium monoacetylacetate and zirconium tetraacetylacetate; amines such as triethylenediamine and 1,4-diazabicyclo[2,2,2]octane (DABCO); platinum compounds such as chloroplatinic acid and alkenylsiloxane platinum complexes; iron complexes; and cobalt complexes. The amount of the catalyst in the resin composition is preferably 0.001 to 5 parts by weight, more preferably 0.01 to 3 parts by weight, per 100 parts by weight of the crosslinking agent.

[0079] <Binder> The resin composition may contain a binder that does not have a reactive functional group other than the resin having an alkali-soluble group and a hydrophilic structure. Examples of such binders include urethane resins, ester resins, acrylic resins, polyvinyl alcohol resins, cellulose resins, and olefin resins. The amount of binder in the resin composition is preferably 1 to 200 parts by weight, more preferably 5 to 20 parts by weight, per 100 parts by weight of the compound having an alkali-soluble group and a hydrophilic structure.

[0080] <Solvent> Examples of the solvent include water and organic solvents, such as ether solvents, amide solvents, hydrocarbon solvents, alcohol solvents, ester solvents, aldehyde solvents, ketone solvents, and solvents containing carbon atoms, such as solvents containing carbon atoms and hetero atoms.

[0081] Examples of ether solvents include propylene glycol monomethyl ether, anisole, 4-methylanisole, diisopropyl ether, diethyl ether, dibutyl ether, tetrahydrofuran, dimethoxyethane, cyclopentyl methyl ether, and tert-butyl methyl ether. Examples of amide solvents include dimethylformamide, dimethylacetamide, and N-methylpyrrolidone. Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, and cyclohexane, and aromatic hydrocarbon solvents such as benzene, toluene, xylene, mesitylene, ethylbenzene, tert-butylbenzene, trifluoromethylbenzene, nitrobenzene, and chlorobenzene. Examples of alcohol solvents include methanol, ethanol, propanol, butanol, ethylene glycol, and propylene glycol monomethyl ether. Examples of ester solvents include ethyl acetate, butyl acetate, and propylene glycol monomethyl ether acetate. Examples of aldehyde solvents include formaldehyde and acetaldehyde. Examples of ketone solvents include acetone, methyl ethyl ketone, and methyl isobutyl ketone. Examples of solvents containing carbon atoms and heteroatoms include acetonitrile and dimethyl sulfoxide. When the resin composition contains a solvent, the amount of the solvent is preferably 1 to 99% by weight, and more preferably 10 to 95% by weight. The resin composition may contain a solvent, but it is preferable that it does not contain one.

[0082] <Surfactant> Examples of surfactants include siloxane compounds such as polyether-modified polydimethylsiloxane, polyether-modified siloxane, polyetherester-modified hydroxyl group-containing polydimethylsiloxane, polyether-modified acrylic group-containing polydimethylsiloxane, polyester-modified acrylic group-containing polydimethylsiloxane, perfluoropolydimethylsiloxane, perfluoropolyether-modified polydimethylsiloxane, and perfluoropolyester-modified polydimethylsiloxane; polyether compounds such as polyoxyethylene alkylphenyl ether, propylene oxide polymer, and ethylene oxide polymer; carboxylic acids such as coconut oil fatty acid amine salts and gum rosin; ester compounds such as castor oil sulfates, phosphate esters, alkyl ether sulfates, sorbitan fatty acid esters, sulfonates, and succinates; and sulfonate compounds such as alkylarylsulfonic acid amine salts and dioctyl sodium sulfosuccinate. The amount of surfactant is preferably 0.01 to 10 wt % of the total solids content of the resin composition, and more preferably 0.1 to 5 wt %.

[0083] <Adhesive> Examples of adhesives include olefin-based hot-melt adhesives including polyolefins and polyolefin copolymers; polyester-based hot-melt adhesives including polyethylene terephthalate, polybutylene terephthalate, and polycaprolactone; rubber-based hot-melt adhesives made from styrene-butadiene-styrene (SBS), styrene-ethylene / butylene-styrene (SEBS), styrene-ethylene / propylene-styrene (SEPS), styrene-isoprene (SI), and styrene-isoprene-styrene (SIS); and reactive urethane hot-melt adhesives made from urethane prepolymers having isocyanate groups at their ends. The amount of adhesive is preferably 0.1 to 70% by weight of the total solids content of the resin composition.

[0084] <Tackifier> Examples of the tackifier include gum rosin, wood rosin, distilled rosin, hydrogenated rosin, polymerized rosin, etc. The amount of the tackifier is preferably 0.01 to 60% by weight of the total solid content of the resin composition.

[0085] <Stabilizer> Examples of the stabilizer include antioxidants such as hindered phenol compounds, sulfur compounds, and phosphorus compounds, and light stabilizers such as benzotriazole compounds, hindered amine compounds, and benzophenone compounds. The amount of the stabilizer in the resin composition is preferably 0.01 to 10% by weight.

[0086] <Plasticizer> Examples of plasticizers include naphthenic oils, paraffinic oils, mineral oils, phthalates, adipates, polybutene, polyisoprene, hydrogenated polyisoprene, polybutadiene, benzoates, animal oils, vegetable oils, glycerol esters of fatty acids, etc. The amount of plasticizer in the resin composition is preferably 0.01 to 40% by weight.

[0087] <Wax> Examples of waxes include paraffin wax, microcrystalline wax, polyethylene wax, and polypropylene wax.

[0088] <Method of manufacturing adhesive joint> The method for forming the adhesive portion is not particularly limited, and examples include (i) a method of disposing a resin composition on a portion of a back sheet, overlaying a top sheet, and heating or drying the resin composition; (ii) a method of disposing a resin composition on a portion of a top sheet, overlaying a back sheet, and heating or drying the resin composition; and (iii) a method of disposing a resin composition on at least a portion of a core wrap, overlaying the core wrap, and heating or drying the resin composition. Even when the resin composition does not have adhesive properties, for example, a method of disposing an alkali-insoluble adhesive layer on the back sheet, disposing a resin composition, further disposing an adhesive layer, overlaying a top sheet, and heating or drying the resin composition and adhesive composition can be used. Methods for disposing a resin composition on a back sheet or top sheet include applying or impregnating a liquid resin composition, or applying or spraying a solid resin composition. If the resin composition is adhesive, a sheet-like resin composition formed on a release film can be transferred.

[0089] The method for applying the resin composition can be appropriately selected depending on the type of resin composition, core wrap, top sheet, and back sheet, and is not particularly limited. It can be applied by a common method such as slot coater coating, roll coater coating, omega coating, spiral coating, slot spray coating, curtain spray coating, dot coating, control seam coating, bead coating, or letterpress transfer.

[0090] When the resin composition is thermoplastic, the heating temperature is preferably 50 to 160° C. When the resin composition is thermosetting, the heating temperature is preferably 30 to 160° C., more preferably 40 to 120° C. The heating time is preferably 0.5 to 180 minutes, more preferably 0.5 to 30 minutes.

[0091] The thickness of the produced adhesive joint is not particularly limited, but is preferably 0.1 to 300 μm, and more preferably 0.5 to 100 μm. Within this range, both adhesive strength and dissolution rate when immersed in an alkaline solution can be achieved.

[0092] It is preferable that an alkali-soluble adhesive joint dissolves easily when immersed in an alkaline solution, but is stable when not immersed in an alkaline solution. When an alkali-soluble adhesive joint is immersed in water for 1 hour, the weight change calculated using the following formula from the weight a before immersion and the weight b after immersion is preferably -10% to 10%, more preferably -5% to 5%, and even more preferably -3% to 3%. The pH of the water used in the test is 6.0 to 8.0, and the temperature during immersion is 25°C. Formula: Weight change (%) = ((ba) / a) * 100

[0093] <<How to disassemble absorbent articles>> The method for dismantling absorbent articles of the present invention is characterized by comprising a step of immersing the absorbent articles in an alkaline solution at 0 to 60° C. The alkaline solution used for dismantling the absorbent articles preferably has a pH of 8.5 to 14, more preferably a pH of 11 to 14, and even more preferably a pH of 12 to 14.

[0094] Examples of alkaline agents contained in the alkaline solution include sodium hydroxide, potassium hydroxide, sodium carbonate (Na2CO3), and ammonia. These may be used alone or in combination of two or more. These alkaline agents are preferably dissolved in water or an organic solvent such as ethanol, methanol, isopropanol, or tetrahydrofuran. The concentration of the alkaline agent in the alkaline solution is preferably 0.01 to 10% by weight, more preferably 0.1 to 5% by weight.

[0095] The temperature condition when the absorbent article is immersed in the alkaline solution is 0 to 60°C, preferably 15 to 50°C. The time condition is preferably 60 minutes or less, more preferably 30 minutes or less. If necessary, the absorbent article may be shaken or stirred while immersed in the alkaline solution.

[0096] There are no particular limitations on the method for evaluating the dismantling properties of an absorbent article when immersed in an alkaline solution, but it is preferable that the adhesion between the top sheet and the back sheet is released after the absorbent article is immersed in a 0.4 wt % aqueous potassium hydroxide solution at 25°C for 10 minutes.

[0097] When the adhesive portion contains an adhesive or the like that is not alkali-soluble, it is preferable to dissolve or disperse it in the solution by immersing it in an alkaline solution. This is because the reliability of dissolution of the adhesive portion can be improved. When the adhesive or the like that is not alkali-soluble does not dissolve in an alkaline solution but is dissolved or dispersed in water, an acidic aqueous solution, an oxidizing agent aqueous solution, or an organic solvent, the reliability of dissolution of the adhesive portion can be improved by the step of dissolving the alkali-soluble adhesive or the like in these solutions and the step of immersing it in an alkaline solution.

[0098] If the absorbent article is immersed in an alkaline solution to dissolve the adhesive bonds, the naturally-derived fibers and water-absorbent resin contained in the absorbent core can be separated from the absorbent article by known methods such as specific gravity difference, filtration, centrifugation, vibrating sieve, etc. When the water-absorbent resin is a derivative of polyaspartic acid, cellulose, chitin, chitosan, starch, or the like, and is made of a material that can be easily decomposed by acid or alkali, or when it is made of a material that can be decomposed by an oxidizing agent, such as polyacrylic acid having a hydrazine structure, adjusting the composition of the alkaline solution makes it easy to recover high-purity naturally-derived fibers.

[0099] On the other hand, when the water-absorbent resin is a typical synthetic resin such as poly(meth)acrylic resin or polyacrylamide resin, the separation of the naturally-derived fibers and the water-absorbent resin can be facilitated by removing a certain amount of water from the water-absorbent resin by adding calcium salts such as calcium chloride, calcium hydroxide, and calcium carbonate, or magnesium salts such as magnesium hydroxide. Such a decomposition step or dehydration step of the water-absorbent resin may be carried out before or after the step of immersing the absorbent article in an alkaline solution, or may be carried out simultaneously. When carried out simultaneously, a calcium salt or the like is added to the alkaline solution.

[0100] <<Resin composition for forming adhesive joints>> The resin composition of the present invention is a resin composition for forming the adhesive portion of the absorbent article. The resin composition is not particularly limited as long as it can form an alkali-soluble adhesive portion by heating or drying, but examples thereof include compositions containing an alkali-soluble group and a compound having a hydrophilic structure. These compositions are as described above for the absorbent article. [Example]

[0101] The present invention will be described below with reference to examples, but is not limited to these examples. Hereinafter, "parts" and "%" mean "parts by weight" and "% by weight", respectively, unless otherwise specified.

[0102] (1) Preparation of resin composition (Production example 1) Thermoplastic resin 1 96 g of 1,6-hexanediol (Tokyo Chemical Industry Co., Ltd.) and 87.3 g of pyromellitic anhydride (Daicel Corporation) were added to a 1 L separable flask and stirred at 120 °C for 24 hours. The mixture was dissolved in 300 g of ethyl acetate, and the organic layer was washed three times with 200 g of ion-exchanged water. The mixture was concentrated under reduced pressure at 60 °C and vacuum-dried overnight at room temperature to obtain 198 g of Thermoplastic Resin 1.

[0103] (Production example 2) Thermoplastic resin 2 100 g of polyester polyol (PEG-1000, manufactured by Sanyo Chemical Industry Co., Ltd.) and 34.5 g of 1,6-hexanediol (manufactured by Tokyo Chemical Industry Co., Ltd.) were mixed in a 1 L separable flask, and 87.3 g of pyromellitic anhydride (manufactured by Daicel Corporation) was added and stirred at 120 °C for 24 hours. 300 g of ethyl acetate was added, and the organic layer was washed three times with 200 g of ion-exchanged water. The mixture was concentrated under reduced pressure at 60 °C and vacuum-dried overnight at room temperature to obtain 200 g of thermoplastic resin 2.

[0104] (Production example 3) Thermoplastic resin 3 100 g of polyester polyol (PEG-1000, manufactured by Sanyo Chemical Industry Co., Ltd.) and 35.5 g of 1,6-hexanediol (manufactured by Tokyo Chemical Industry Co., Ltd.) were mixed in a 1 L separable flask, and 117.7 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride (manufactured by UBE Corporation) was added and stirred at 120 °C for 24 hours. The mixture was dissolved in 300 g of ethyl acetate, and the organic layer was washed three times with 200 g of ion-exchanged water. The mixture was concentrated under reduced pressure at 60 °C and vacuum-dried overnight at room temperature, yielding 227 g of Thermoplastic Resin 3.

[0105] (Production example 4) Thermoplastic resin 4 3.00 g of polyester polyol (polyethylene glycol 6,000, Fujifilm Wako Pure Chemical Industries, Ltd.) and 0.11 g of pyromellitic anhydride (Daicel Corporation) were added to a test tube and stirred at 120°C for 24 hours. After cooling to room temperature, 2.8 g of acetonitrile, 0.49 g of triethylamine, and 0.45 g of di(N-succinimidyl) carbonate were added and stirred at 25°C for 2 hours. 0.06 g of 4-hydroxybenzoic acid hydrazide was added and stirred overnight at 25°C. After concentration under reduced pressure at 60°C, the mixture was washed with water using chloroform as a good solvent, and the chloroform layer was dried over sodium sulfate. The filtrate obtained by vacuum filtration was concentrated under reduced pressure at 60°C and vacuum dried to obtain 2.8 g of thermoplastic resin 4.

[0106] (Production example 5) Thermoplastic resin 5 3.00 g of polyester polyol (polyethylene glycol 6,000, Fujifilm Wako Pure Chemical Industries, Ltd.) and 0.11 g of pyromellitic anhydride (Daicel Corporation) were added to a test tube and stirred at 120°C for 24 hours. After cooling to room temperature, 2.9 g of acetonitrile, 0.30 g of triethylamine, and 0.28 g of di(N-succinimidyl) carbonate were added and stirred at 25°C for 2 hours. 1.24 g of ethylene oxide propylene oxide copolymer (Sanicol H-0725, Sanyo Chemical Industries, Ltd.) was added and stirred overnight at 25°C. After concentration under reduced pressure at 60°C, the mixture was washed with water using chloroform as a good solvent, and the chloroform layer was dried over sodium sulfate. The filtrate obtained by vacuum filtration was concentrated under reduced pressure at 60°C and vacuum dried to obtain 3.1 g of Thermoplastic Resin 5.

[0107] (Production example 6) Thermoplastic resin 6 2.19 g of ethylene oxide propylene oxide copolymer (Sanicol AH-4322, manufactured by Sanyo Chemical Industry Co., Ltd.), 2.0 g of acetonitrile, and 0.61 g of triethylamine were mixed in a test tube, and 0.15 g of ISOBAM-304 (manufactured by Kuraray Co., Ltd.) was added and stirred overnight at 25°C. After concentration under reduced pressure at 60°C, the mixture was washed with water using chloroform as a good solvent, and the chloroform layer was dried over sodium sulfate. The filtrate obtained by filtration under reduced pressure was concentrated under reduced pressure at 60°C and vacuum dried to obtain 1.7 g of thermoplastic resin 6.

[0108] (Production example 7) Thermoplastic resin 7 0.94 g of ethylene oxide-propylene oxide copolymer (Newpol 50HB-5100, manufactured by Sanyo Chemical Industries, Ltd.) and 2.8 g of L-IR-403 (manufactured by Kuraray Co., Ltd.) were added to a test tube and stirred overnight at 120°C. The mixture was dissolved in ethyl acetate, and the organic layer was washed three times with 100 g of ion-exchanged water. The mixture was concentrated under reduced pressure at 60°C and vacuum-dried overnight at room temperature, yielding 2.1 g of thermoplastic resin 7.

[0109] (Production Example 8) Resin composition 8 Alkali-soluble substance A was produced by the following method. 200 g of polyester polyol (PEG-1000, manufactured by Sanyo Chemical Industries, Ltd.) and 41.4 g of pyromellitic anhydride (Daicel Corporation) were added to a 1 L separable flask and stirred at 120°C for 24 hours. The mixture was dissolved in 300 g of ethyl acetate, and the organic layer was washed three times with 200 g of ion-exchanged water. The mixture was concentrated under reduced pressure at 60°C and vacuum-dried overnight at room temperature to obtain 217 g of alkali-soluble substance A having a structure in which units represented by formula (3) are repeated. The components listed in Table 1 were mixed to obtain resin composition 8.

[0110] [Table 1]

[0111] (Production Example 9) Resin composition 9 Alkali-soluble substance B was produced by the following method. 200 g of polyester polyol (PEG-2000, manufactured by Sanyo Chemical Industries, Ltd.) and 20.7 g of pyromellitic anhydride (Daicel Corporation) were added to a 1 L separable flask and stirred at 120°C for 24 hours. The mixture was dissolved in 300 g of ethyl acetate, and the organic layer was washed three times with 200 g of ion-exchanged water. The mixture was concentrated under reduced pressure at 60°C and vacuum-dried overnight at room temperature to obtain 198 g of alkali-soluble substance B having a structure in which units represented by formula (3) are repeated. The components listed in Table 2 were mixed to obtain resin composition 9. [Table 2]

[0112] (2) Preparation of test specimens Test piece A was prepared in such a manner that an alkali-soluble adhesive area approximately 5 mm wide was placed on all four sides of a 6 cm square substrate 1 and a 6 cm square substrate 2, approximately 5 mm inward from the edge, and 1.7 g of absorbent 1 or 2 containing a mixture of the components listed in Table 3 was enclosed inside the adhesive area.

[0113] [Table 3]

[0114] Test piece B was also prepared, which had an alkali-soluble adhesive area over the entire surface of a 6 cm square substrate 2, with the 1.7 g of absorbent 1 or 2 adhered from the center of substrate 2 to approximately 5 mm inside the edge of substrate 2, and with all four sides of the area approximately 5 mm from the edge adhered to substrate 1, thereby fixing the absorbent inside. Table 5 shows the configuration of substrates 1 to 2 and the adhesive area for each test piece. The manufacturing method for each adhesive area is described below.

[0115] (2-1) Adhesion by heating of thermoplastic resin 1 (adhesion part I, Examples 1, 2, 11, and 12) Thermoplastic resin 1 heated to 70°C was applied onto substrate 2 shown in Tables 5 to 6, and then substrate 1 was attached, pressed, and allowed to cool, thereby bonding substrate 1 and substrate 2 via adhesive part I made of thermoplastic resin 1.

[0116] (2-2) Adhesion by heating of thermoplastic resin 2 (adhesion part II, Example 3) Thermoplastic resin 2 heated to 60°C was applied onto substrate 2, and then substrate 1 was attached, pressed, and allowed to cool, thereby bonding substrate 1 and substrate 2 together via adhesive part II made of thermoplastic resin 2.

[0117] (2-3) Adhesion by heating of thermoplastic resin 3 (adhesion part III, Example 4) Thermoplastic resin 3 heated to 60°C was applied onto substrate 2, and then substrate 1 was attached, pressed, and allowed to cool, thereby bonding substrate 1 and substrate 2 together via adhesive part III made of thermoplastic resin 3.

[0118] (2-4) Adhesion by curing of resin composition 8 (adhesion part IV, Example 5) Resin composition 8 was applied onto substrate 2, and then substrate 1 was attached. Thereafter, the resin composition 8 was cured by keeping the temperature at 120°C for 20 minutes. As a result, substrate 1 and substrate 2 were bonded together via adhesive part IV made of resin composition 8.

[0119] (2-5) Adhesion by curing of resin composition 9 (adhesion part V, Example 6) Resin composition 9 was applied onto substrate 2, and then substrate 1 was attached. Thereafter, the resin composition 9 was cured by keeping the temperature at 120°C for 20 minutes. As a result, substrate 1 and substrate 2 were bonded together via adhesive part V made of resin composition 9.

[0120] (2-6) Adhesion by heating of thermoplastic resin 4 (adhesion part VI, Example 7) Thermoplastic resin 4 heated to 70°C was applied onto substrate 2, and then substrate 1 was attached, pressed, and allowed to cool, thereby bonding substrate 1 and substrate 2 together via adhesive joint VI made of thermoplastic resin 4.

[0121] (2-7) Adhesion by heating of thermoplastic resin 5 (adhesion part VII, Example 8) Thermoplastic resin 5 heated to 100°C was applied onto substrate 2, and then substrate 1 was attached, pressed, and allowed to cool, thereby bonding substrate 1 and substrate 2 together via adhesive joint VII made of thermoplastic resin 5.

[0122] (2-8) Adhesion by heating of thermoplastic resin 6 (adhesion part VIII, Example 9) Thermoplastic resin 6 heated to 60°C was applied onto substrate 2, and then substrate 1 was attached, pressed, and allowed to cool, thereby bonding substrate 1 and substrate 2 together via adhesive part VIII made of thermoplastic resin 6.

[0123] (2-9) Adhesion by heating of thermoplastic resin 7 (adhesion part IX, Example 10) Thermoplastic resin 7 heated to 60°C was applied onto substrate 2, and then substrate 1 was attached, pressed, and allowed to cool, thereby bonding substrate 1 and substrate 2 together via adhesive joint IX made of thermoplastic resin 7.

[0124] (3) Disassembly test Each test piece was immersed in physiological saline for 10 minutes, and then the absorbed test piece was transferred to a beaker containing 300 ml of the alkaline solution shown in Table 4 and stirred for 30 minutes at the temperature shown in Tables 5 and 6. Substrates 1 and 2 were then recovered and dried, after which the weight of the absorbent remaining in the test piece was measured and evaluated according to the following criteria. The evaluation results are shown in Tables 5 and 6. 〇: Less than 0.3g △: 0.3g or more and less than 1.0g ×: 1.0g or more [Table 4]

[0125] (4) Adhesive strength Substrate 1 and one side of substrate 2 were bonded together using the combinations of substrates and adhesive parts shown in Tables 5 and 6. The opposite sides of the bonded edges were firmly grasped with each hand and then pulled in a straight line (at an angle of 180 degrees to each other) to separate them. The adhesive strength was evaluated by checking the peeled surfaces of substrate 1 and substrate 2. The evaluation results are shown in Tables 5 and 6. ○: Material destruction of the substrate was observed △: Cohesive failure was observed in the adhesive joint ×: Interfacial failure was observed between the adhesive part and the substrate.

[0126] (5) Weight change after immersion in water Using the combinations of substrates and adhesive joints shown in Tables 5 and 6, test pieces with alkali-soluble adhesive joints were prepared by bonding one side of substrate 1 and substrate 2 together. The weight of the alkali-soluble adhesive joint was adjusted to approximately 0.25 g. The test pieces were immersed in neutral water at 25°C for 1 hour, and the weight change (%) was calculated using the following formula from the weight a before immersion and the weight b after immersion. The results are shown in Tables 5 and 6. Formula: Weight change (%) = ((ba) / a) * 100

[0127] [Table 5]

[0128] [Table 6]

[0129] In Examples 1 to 12, sufficient adhesive strength was observed in the alkali-soluble adhesive joints. Furthermore, after the absorbent article was immersed in an alkaline solution, only a small amount of absorbent remained in the test piece, allowing for efficient recovery of the absorbent. Meanwhile, the weight change after immersing the adhesive joints in neutral water was within the range of -10% to 10%, confirming that the adhesive joints were stable even when immersed in water. [Explanation of symbols]

[0130] 10 Absorbent articles 11 Topsheet 12 Core Wrap 13 Back Seat 14 Adhesive part 15 Absorbent 101 Topsheet or Core Wrap 102 Backsheet or Core Wrap 103 Alkali-soluble layer 104 Adhesive layer 105 Alkali-soluble and adhesive-containing layer

Claims

1. A top sheet, a back sheet, and an absorbent body, The absorbent article has the top sheet and the back sheet bonded together via an alkali-soluble adhesive.

2. The absorbent article of claim 1 further comprising a core wrap.

3. The absorbent article according to claim 2, wherein the absorbent body and at least one selected from the group consisting of the top sheet, the back sheet, and the core wrap are bonded via an alkali-soluble adhesive.

4. The absorbent article according to claim 2 or 3, wherein the core wraps are bonded to each other or the core wrap and the backsheet are bonded to each other via an alkali-soluble adhesive.

5. The absorbent article according to claim 1 or 2, wherein the adhesive portion contains an alkali-soluble resin.

6. The absorbent article according to claim 1 or 2, wherein the adhesive portion comprises a layer containing an alkali-soluble resin and adhesive layers formed on both sides of the layer.

7. The absorbent article according to claim 5 , wherein the alkali-soluble resin is a thermoplastic resin or a cured product of a thermosetting resin.

8. The absorbent article according to claim 7 , wherein the alkali-soluble resin has a unit represented by formula (1): 【Chemistry 1】 (In formula (1), A is a hydrocarbon group which may have a substituent. X １ is an oxygen atom, a sulfur atom, or a nitrogen atom which may have a substituent. R １ represents a hydrocarbon group or silyl group which may have a substituent, or a hydrogen atom.

9. The absorbent article according to claim 8, wherein the unit represented by formula (1) is a unit represented by formula (2), formula (3), or formula (4). 【Chemistry 2】 (In formula (2), X １a , X １ｂ are each independently an oxygen atom, a sulfur atom, or a nitrogen atom which may have a substituent. R １a , R １ｂ represents a hydrocarbon group or a silyl group which may have a substituent, or a hydrogen atom, and R １a and R １ｂ At least one of the groups is a hydrogen atom. R ２ , R ３ are each independently a hydrocarbon group or silyl group which may have a substituent, or a hydrogen atom. 【Transformation 3】 (In formula (3), X １ｃ , X １ｄ , X ２ , X ３ are each independently an oxygen atom, a sulfur atom, or a nitrogen atom which may have a substituent. R １ｃ , R １ｄ represents a hydrocarbon group or a silyl group which may have a substituent, or a hydrogen atom, and R １ｃ and R １ｄ At least one of the groups is a hydrogen atom. R ４ is a hydrocarbon group or a silyl group which may have a substituent. D is a hydrocarbon group which may have a substituent. 【Chemistry 4】 (In formula (4), X １ is an oxygen atom, a sulfur atom, or a nitrogen atom which may have a substituent. R １ represents a hydrocarbon group or silyl group which may have a substituent, or a hydrogen atom. R ４ , R ５ and E are each independently a hydrocarbon group which may have a substituent.

10. The absorbent article according to claim 1 or 2, wherein the absorbent body comprises an absorbent resin and / or a naturally derived fiber.

11. When the adhesive joint is immersed in water for 1 hour, the weight change from before immersion is -10% to 10%. The absorbent article according to claim 1 or 2.

12. The top sheet and the back sheet are bonded together by a rectangular adhesive portion that surrounds the absorbent body and / or the core wrap, Two or more sides of the rectangular adhesive portion are alkali-soluble, and one or more of the sides are long sides. The absorbent article according to claim 1 or 2.

13. 3. The absorbent article according to claim 2, wherein the absorbent body is sandwiched between two or more core wraps, and the two or more core wraps are bonded together with an alkali-soluble adhesive.

14. A method for dismantling absorbent articles, comprising the step of immersing the absorbent article according to claim 1 or 2 in an alkaline solution at 0 to 60°C.

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