Manufacturing method of absorber and absorber

Abstract

To provide a manufacturing method of an absorber for securing sheet strength without reducing a liquid absorption amount even when liquid is absorbed while being thinned before liquid absorption, and an absorber.SOLUTION: A manufacturing method of an absorber first performs the following steps: a fiber laminate step which mixes and laminates a fiber and an absorbent polymer material containing heat-weldable fiber to obtain a fiber laminate; a heat treatment step which applies to the fiber laminate heat treatment at a temperature equal to a melting point or higher of the heat-weldable fiber and obtains the heat-seal fiber laminate; and a pressurizing step which has the heat-seal fiber laminate hold water to obtain a hydrous fiber laminate, in this order, and then simultaneously or separately applies a pressurization step to the hydrous fiber laminate and a drying step which applies heat treatment at the temperature below the melting point of the heat-weldable fiber for drying.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing an absorbent core used in absorbent articles such as diapers and sanitary napkins, and to the absorbent core. [Background technology]

[0002] The absorbent body disposed in the absorbent article often contains an absorbent polymer material (a surface-crosslinked polymer material called SAP (superbsorbent polymer)) that enhances the absorption performance. Several techniques have been proposed for such absorbent bodies from the viewpoint of improving the absorbency. For example, Patent Document 1 describes an absorbent structure in which highly absorbent polymer particles are fixed to a fibrous support substrate via a binder attached to the surface of the particles. The fibrous support substrate and the binder are bonded to each other by a strong bond that does not easily dissociate even when the highly absorbent polymer particles absorb water and swell, and a weak bond that easily dissociates when the particles absorb water and swell. When the highly absorbent polymer particles absorb water and swell, the weak bonds on the surface dissociate, expanding the gap between the fibers. This is said to make it less likely that gel blocking between polymer particles, which inhibits water absorption, will occur. Patent Document 2 describes an absorbent sheet that is made of a fiber assembly and a fiber web, in which a superabsorbent polymer is dispersed in the fiber web. When the superabsorbent polymer is dispersed on the wet fiber web in the wet papermaking process during the manufacture of the absorbent sheet, it becomes sticky and is fixed between the fibers. Patent Document 3 describes an absorbent body in which a superabsorbent polymer is held in a nonwoven fabric containing heat-fusible fibers and non-heat-fusible fibers. During the manufacture of the absorbent body, particles of the superabsorbent polymer are scattered on the nonwoven fabric and held in place by being surrounded by fibers. During liquid absorption, the non-heat-fusible fibers surrounding the superabsorbent polymer move, changing the distance between the fibers, preventing inhibition of swelling of the superabsorbent polymer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2001-46434 A [Patent Document 2] Japanese Patent Application Publication No. 8-229070 [Patent Document 3] JP 2002-159533 A Summary of the Invention [Problem to be solved by the invention]

[0004] 2. Description of the Related Art Absorbents containing absorbent polymer materials are often made thin and in the form of a sheet from the standpoint of ease of wearing when an absorbent article containing the absorbent is used. However, in general, it is difficult for a sheet-shaped absorbent to maintain its sheet shape as the absorbent polymer material absorbs liquid and swells. This may cause the absorbent to lose its shape. The loss of shape may also cause a decrease in the amount of liquid absorbed. Therefore, there is room for improvement in the amount of liquid absorbed and the sheet strength of conventional sheet-shaped absorbents.

[0005] In view of the above, the present invention relates to a manufacturing method for an absorbent body, which is thinned before absorbing liquid but maintains sheet strength without reducing the amount of absorbed liquid even when absorbing liquid, and to the absorbent body. [Means for solving the problem]

[0006] The present invention provides a method for manufacturing an absorbent body, which comprises carrying out, in the order of a stacking step, of mixing and stacking fibers including heat-fusible fibers and absorbent polymer material to obtain a stack, a heat treatment step, of heat-treating the stack at a temperature equal to or higher than the melting point of the heat-fusible fibers to obtain a heat-fused stack, and a hydration step, of watering the heat-fusible stack to obtain a wet stack, and then simultaneously or separately carrying out a pressurizing step of applying pressure to the wet stack and a drying step of heat-treating the wet stack at a temperature below the melting point of the heat-fusible fibers and drying it.

[0007] The present invention also provides an absorbent comprising fibers and an absorbent polymer material, wherein the fibers comprise heat-fusible fibers and the heat-fusible fibers have fusion points at their intersections, the heat-fusible fibers account for 4% by mass or more and 30% by mass or less of the mass of the absorbent before absorbing liquid, the fusion points comprise 2 to 14 fusion points within a square field of view of 1 mm x 1 mm observed from the surface of the absorbent, and the absorbent has a composite portion in which the fibers are incorporated within the absorbent polymer material. Effect of the Invention

[0008] According to the method for producing an absorbent body of the present invention, it is possible to suitably produce an absorbent body that is thin before absorbing liquid, but that maintains sheet strength without decreasing the amount of absorbed liquid even when absorbing liquid. The absorbent body of the present invention is thin before absorbing liquid, but even when absorbing liquid, the amount of absorbed liquid is not reduced and sheet strength is ensured. [Brief description of the drawings]

[0009] [Figure 1] 1(A) to 1(E) are explanatory views showing the steps included in a preferred embodiment of a method for producing an absorbent body according to the present invention. [Diagram 2] FIG. 2 is a plan view showing a schematic diagram of an example of a composite part in which fibers are incorporated into an absorbent polymer material. [Diagram 3] 1 is a drawing-substitute SEM photograph showing an example of a 1 mm x 1 mm square field of view including a fused portion, observed from the surface of the absorbent body of this embodiment. [Figure 4] 1 is a drawing-substitute SEM photograph showing an example of a 1.5 mm×1.5 mm square field of view including a fused portion, observed from the surface of the absorbent body of this embodiment. [Diagram 5] 1 is a drawing-substitute SEM photograph showing an example of a 1.5 mm x 1.5 mm square field of view including a composite portion, observed from the surface of the absorbent body of this embodiment. [Figure 6] 1(A) to 1(F) are SEM photographs, each of which shows an image of an absorbent sample of each of the example and comparative examples 1 to 5. [Figure 7]7 is a drawing-substitute SEM photograph showing an enlarged image of FIG. 6(A) and FIG. 6(D). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, preferred embodiments of the method for producing an absorbent body of the present invention will be described with reference to the drawings. The method for producing an absorbent body according to the present embodiment includes the following steps (I) to (V) (hereinafter referred to as steps (I) to (V) respectively) as shown in Figures 1(A) to 1(E). In the production method, steps (I) to (III) are carried out in this order, and then steps (IV) and (V) are carried out simultaneously or separately. When carried out separately, steps (IV) and (V) are preferably carried out in this order. (I) A fiber-stacking process in which fibers including thermally adhesive fibers and an absorbent polymer material are mixed and stacked to obtain a fiber stack. (II) A heat treatment step of subjecting the pile to a heat treatment at a temperature equal to or higher than the melting point of the heat-fusible fibers to obtain a heat-fusible pile. (III) A hydration step in which the heat-fused laminate is hydrated to obtain a hydrated laminate. (IV) A pressurizing step of applying pressure to the water-containing stacked fiber material. (V) A drying step of subjecting the heat-fusible fiber to a heat treatment at a temperature lower than the melting point thereof and drying the same.

[0011] In the fiber-stacking step of step (I), as shown in FIG. 1(A), fibers 1 including thermally adhesive fibers 1A and absorbent polymer material 2 are mixed and stacked to obtain a fiber stack 3. This mixed fiber stacking process can be performed by various methods commonly used in the manufacture of absorbents. For example, the fibers 1 and absorbent polymer material 2 can be mixed and stacked in a predetermined fiber-stacking region by feeding them into air sucked into the region. For example, this can be performed using a device including a rotating drum having a duct and a plurality of fiber-stacking recesses on the roll circumferential surface, as described in JP 2017-047212 A and JP 2019-088415 A.

[0012] In the fiber-stacking step of step (I), the thermally fusible fibers 1A are not fused to each other and are free to move. In the obtained fiber stack 3, the fibers 1 and the absorbent polymer material 2 are mixed and stacked with air or the like as described above, and no pressure is applied for compression. Therefore, even if there is pressure due to the weight of the fibers 1 and the absorbent polymer material 2, the fiber stack 3 maintains a relatively wide inter-fiber distance and is bulky. In this state, the absorbent polymer material 2 is sandwiched between the fibers.

[0013] The heat-fusible fibers 1A may include various materials that are commonly used in this type of article. For example, the fiber may include one or more resins selected from polyolefin resins, polyester resins, polyamide resins, acrylonitrile resins, vinyl resins, vinylidene resins, and the like. The polyolefin resin may contain one or more selected from polyethylene (hereinafter, also referred to as PE), polypropylene, polybutene, and the like. The polyester-based resin may include one or more selected from polyethylene terephthalate (hereinafter, also referred to as PET), polybutylene terephthalate, and the like. The polyamide resin may contain one or more materials selected from nylon and the like. The vinyl resin may contain one or more resins selected from polyvinyl chloride and the like. The vinylidene resin may contain one or more resins selected from polyvinylidene chloride and the like. Modified products of these various resins can also be used.

[0014] The thermally adhesive fiber 1A may include a single fiber made of a single resin component, or may include a composite fiber containing multiple resin components. The composite fiber may include one or more selected from side-by-side fibers, sheath-core fibers, sheath-core fibers having an eccentric crimp, and split fibers. When the thermally adhesive fiber 1A is a composite fiber, it preferably contains a core-sheath fiber from the viewpoint of ensuring the sheet strength. When the thermally adhesive fiber 1A is a monofilament, from the viewpoint of ensuring the sheet strength, the fiber length is preferably 3 mm or more, more preferably 5 mm or more, and even more preferably 10 mm or more. When the thermally adhesive fiber 1A is a monofilament, the fiber length is preferably 60 mm or less, more preferably 50 mm or less, and even more preferably 40 mm or less, from the viewpoint of softening the sheet.

[0015] The fibers 1 may include various fibers that are normally used as constituent materials of absorbents other than the thermally adhesive fibers 1A. Among them, it is preferable to include cellulose fibers 1B. By including the cellulose fibers 1B, as described below, hydrogen bonds are generated in the cellulose fibers during the hydration step (III) to the drying step (V), which allows the distance between the fibers to be shortened, and the resulting absorbent body can be made thinner. In addition, the hydrogen bonds are released by the absorption of liquid during use of the absorbent body, which allows the thickness to be restored, and the swelling space of the absorbent polymer material 2 to be expanded. This allows the absorbent body to maintain a high absorption amount during liquid absorption without decreasing it. In this specification, "liquid absorption" does not mean absorption during the hydration step, but means absorbing objects such as urine and blood after the absorbent body is manufactured.

[0016] The cellulose fibers 1B may include various materials that are commonly used in this type of product, such as one or more selected from wood pulp, natural fibers other than wood pulp, modified pulp, regenerated fibers, etc. The wood pulp may include one or more selected from softwood bleached kraft pulp (hereinafter also referred to as NBKP), hardwood bleached kraft pulp, softwood bleached sulfite pulp, thermomechanical pulp, and the like. The natural fibers other than wood pulp may include one or more selected from cotton pulp, hemp pulp, and the like. The modified pulp may include one or more selected from cationic pulp, mercerized pulp, and the like. The regenerated fibers may include one or more selected from cupra, rayon, and the like.

[0017] The absorbent polymer material 2 is typically SAP. This absorbent polymer material 2 has the property of absorbing liquid inside the crosslinked surface, swelling, and gelling to retain the liquid inside. For example, it is preferable that the absorbent polymer material 2 is capable of absorbing and retaining liquid of 20 times or more its own weight and gelling. The absorbent polymer material 2 may include various materials used in absorbents without any particular limitations. For example, it may include a hydrogel material obtained by polymerizing a water-soluble ethylenically unsaturated monomer composed mainly of acrylic acid or an acrylic acid salt, and optionally containing a crosslinking agent. It may also include one or more materials selected from the group consisting of polyethylene oxide, polyvinylpyrrolidone, crosslinked products of sulfonated polystyrene and polyvinylpyridine, saponified products of starch-poly(meth)acrylonitrile graft copolymers, starch-poly(meth)acrylic acid graft copolymers, and hydrolyzates of starch-poly(meth)acrylic ester graft copolymers. There are no particular limitations on the shape of the absorbent polymer material 2, and various shapes used for absorbents can be used, such as spheres, granules, fibers, bales, and blocks.

[0018] Next, in the heat treatment step of step (II), as shown in Fig. 1(B), the pile 3 is heat treated at a temperature equal to or higher than the melting point of the heat fusible fiber 1A, thereby obtaining a heat fused pile 4. Note that when the heat fusible fiber 1A is a composite fiber, the "melting point of the heat fusible fiber 1A" refers to the melting point of the resin having the lower melting point.

[0019] The heat-fused piled fabric 4 has fusion points 8 at the intersections between the heat-fusible fibers 1A due to the heat treatment. In step (II), the fusion points 8 form a bulky fiber network structure while the inter-fiber distance of the piled fabric 3 remains relatively wide. Therefore, in the heat-fused piled fabric 4, an appropriate number of fusion points 8 are formed, and the relatively wide inter-fiber distance state (bulky state) is fixed in the fiber network structure (hereinafter, this fusion is referred to as "first bond"). In addition to the fusion points 8 at the intersections between the heat-fusible fibers 1A, the heat-fusible piled fabric 4 may have fusion portions between the heat-fusible fibers 1A and other constituent materials or absorbent polymer material 2. The "intersection of the heat-fusible fibers 1A" referred to here means a portion where two or more heat-fusible fibers 1A intersect with one heat-fusible fiber 1A so as to cross the fiber length of the other heat-fusible fiber 1A. The presence of the fusion points 8 at such intersections allows the mesh to be as large as possible. From this perspective, it is preferable that the overlap length of the heat-fusible fibers 1A along their fiber length is short. Specifically, it is preferable that the overlap length along the fiber length is 0.5 mm or less. Note that the "fusion points 8" referred to here does not include the composite portion 6 described below.

[0020] In the step (II), from the viewpoint of forming the thermally fused pile 4 in a bulky state, the pressure applied to the pile 3 is preferably kept to 50 Pa or less, more preferably 40 Pa or less, and even more preferably 30 Pa or less. In reality, it is 0 (zero) Pa or higher.

[0021] In the step (II), from the viewpoint of suitably controlling the pressure within the above range, the heat treatment is preferably carried out using hot air. When the heat treatment is carried out with hot air, the speed of the hot air is preferably 2 m / sec or less, more preferably 1.4 m / sec or less, and even more preferably 1 m / sec or less, from the viewpoint of suitably suppressing the pressure. Furthermore, the speed of the hot air is practically 0 m / sec or higher.

[0022] Regarding the heat treatment at the above-mentioned "temperature equal to or higher than the melting point of the heat-fusible fiber 1A," the difference (T2-T1) between the melting point (T1) of the heat-fusible fiber 1A and the heat treatment temperature (T2) is preferably 10°C or more, more preferably 20°C or more, and even more preferably 30°C or more, from the viewpoint of better forming the fusion point 8. Moreover, from the viewpoint of preventing solidification of the fibers and maintaining the texture of the heat-fused product 4, the difference (T2-T1) is preferably 80° C. or less, more preferably 70° C. or less, and even more preferably 60° C. or less.

[0023] In the water-adding step (III), as shown in Fig. 1(C), the heat-fused piled material 4 is soaked in water to obtain a water-containing piled material 5. In this step, various methods can be used to soak the heat-fused piled material 4 in water as evenly as possible, for example, a method of spraying water using a spray can be used. The temperature of the water used in this step is preferably 0 to 100°C. As a result, the absorbent polymer material 2 contained in the heat-fused laminate 4 absorbs the liquid, swells, and becomes sticky. Furthermore, when the fibers 1 contain cellulose fibers 1B, the cellulose fibers 1B also absorb the liquid.

[0024] In step (III), the amount of water contained in the heat-fused laminate 4 is preferably 100% or more of the mass of the heat-fused laminate 4, more preferably 130% or more, and even more preferably 160% or more, from the viewpoints of efficiently bringing the absorbent polymer material into contact with the water and efficiently thinning the absorbent body by the subsequent pressurizing step. In addition, the amount of water contained in the heat-sealed laminate 4 is preferably 500% or less of the mass of the heat-sealed laminate 4, more preferably 400% or less, and even more preferably 300% or less, from the viewpoint of preventing solidification of the absorbent and reducing the load in the subsequent drying process.

[0025] In the pressurizing step of step (IV), as shown in Fig. 1(D), pressure is applied to the water-containing piled fabric 5. This compresses the mesh spaces (interfiber distances) of the fiber mesh structure made of the thermally fusible fibers 1A, and the thickness of the water-containing piled fabric 5 is compressed. At the same time, the fibers 1 are taken into the absorbent polymer material 2 that has swollen and has viscous fluidity. This integrates the fibers 1 and the absorbent polymer material 2, and further compresses the mesh spaces. When the fiber 1 contains heat-fusible fibers 1A, the heat-fusible fibers 1A are incorporated into the swollen absorbent polymer material 2, resulting in a high compression effect on the mesh spaces. When the fiber 1 contains heat-fusible fibers 1A and cellulose fibers 1B, both of them are incorporated into the swollen absorbent polymer material 2. This causes compression in the entangled portions of the heat-fusible fibers 1A and the cellulose fibers 1B, further compressing the mesh spaces. Moreover, the cellulose fibers 1B absorb the liquid in the water-containing piled fabric 5 and become wet, forming hydrogen bonds due to the above-mentioned pressurization.

[0026] From the viewpoint of more effectively incorporating the fibers 1 into the absorbent polymer material 2, the pressure in the pressurizing step (IV) is preferably 16 kPa or more, more preferably 80 kPa or more, and even more preferably 160 kPa or more. Moreover, from the viewpoint of preventing solidification of the absorbent body and maintaining flexibility, the pressure is preferably 500 kPa or less, more preferably 400 kPa or less, and even more preferably 300 kPa or less. When the pressurizing step (IV) is performed separately from the drying step (V), it is preferable to perform the pressurizing step at room temperature without intentionally applying heat. Even if heat is applied, it is preferable to apply heat at a temperature lower than the melting point of the thermally fusible fiber 1A.

[0027] In the drying step of step (V), as shown in FIG. 1(E), the pressurized water-containing stack 5 is dried by heat treatment at a temperature lower than the melting point of the heat-fusible fiber 1A. At that time, the swollen absorbent polymer material 2 is dehydrated and shrunk while incorporating the fiber 1 (heat-fusible fiber 1A, or heat-fusible fiber 1A and cellulose fiber 1B) inside, forming a composite part 6. For example, as shown in FIG. 2, a part 1M (dotted line part) of the fiber length of the fiber 1 is confined inside the absorbent polymer material 2, and the remaining part 1N (solid line part) of the fiber length is fixed in a state of extending outside the absorbent polymer material 2. Note that, although only the heat-fusible fiber 1A is shown as the fiber 1 in FIG. 2, this is not limiting, and the fiber 1 may include both the heat-fusible fiber 1A and the cellulose fiber 1B. In the latter case, the composite part 6 may include both the heat-fusible fiber 1A incorporated inside the absorbent polymer material 2 and the cellulose fiber 1B incorporated inside the absorbent polymer material 2.

[0028] The above-mentioned dehydration and shrinkage of the absorbent polymer material 2 creates an anchor effect between the fiber 1 and the absorbent polymer material 2, which fixes the crushed state of the water-containing stack 5 (hereinafter, this is referred to as the "second bond"), resulting in a thin, sheet-like absorbent body 7. Furthermore, if the fiber 1 contains cellulose fibers 1B, hydrogen bonds are formed in the cellulose fibers 1B due to the above-mentioned pressure application. Specifically, hydrogen bonds are formed between the cellulose fibers 1B, 1B, and between the cellulose fibers 1B and the absorbent polymer material 2 in the composite portion 6. The action of these hydrogen bonds more firmly fixes the thin state of the absorbent body 7.

[0029] In step (V), the heat treatment can be carried out by various methods commonly used for drying treatment, for example, an electric drying oven can be used. In the step (V), the time of the heat treatment is preferably 300 seconds or more, more preferably 600 seconds or more, and even more preferably 900 seconds or more, from the viewpoint of more satisfactorily carrying out the drying. Furthermore, the heat treatment time is practically 1500 seconds or less.

[0030] With regard to the "heat treatment at a temperature below the melting point of the heat-fusible fiber 1A" in step (V), the difference (T1-T3) between the melting point (T1) of the heat-fusible fiber 1A and the heat treatment temperature (T3) is preferably 5°C or more, more preferably 10°C or more, and even more preferably 20°C or more, from the viewpoint of performing the above-mentioned drying more satisfactorily. Furthermore, from the viewpoint of reducing the thermal energy required during production and reducing the thermal effects on the absorbent polymer material 2 and other components, the difference (T1-T3) is preferably 200°C or less, more preferably 150°C or less, and even more preferably 100°C or less.

[0031] The absorbent 7 obtained through the above-mentioned steps (I) to (V) is stably thinned before absorbing liquid. On the other hand, during liquid absorption, the above-mentioned anchor effect and hydrogen bonds in the absorbent 7 are released as the absorbent polymer material 2 absorbs liquid and swells, and the bulky fiber network structure (the above-mentioned first bond state) is restored, and the fiber distance increases. That is, the thickness of the absorbent 6 is restored to the thickness of the above-mentioned heat-fused laminated fabric 4 or a thickness greater than that. As a result, a space for the absorbent polymer material 2 to swell is automatically secured in the absorbent 7 according to the liquid absorption, and the occurrence of absorption inhibition due to gel blocking of the absorbent polymer material 2 can be effectively suppressed. As a result, the absorbent 6 can fully exhibit its absorption performance without decreasing the amount of liquid absorption even during liquid absorption (for this reason, the absorbent 7 may become thicker than the above-mentioned first bond state due to the swelling of the absorbent polymer material 2). At the same time, the fiber network structure in which the heat-fusible fibers 1A are heat-fused to each other is easily maintained without being released by the liquid during liquid absorption. The fiber network structure formed by this heat fusion acts to ensure the sheet strength of the absorbent body 7 even when absorbing liquid. As a result, even if there is swelling pressure when the absorbent polymer material 2 absorbs liquid, the sheet shape of the absorbent body 7 when absorbing liquid can be maintained.

[0032] As described above, according to the manufacturing method of the absorbent body of this embodiment, it is possible to suitably manufacture an absorbent body 7 that is thinned before absorbing liquid, but that maintains sheet strength without reducing the amount of absorbed liquid even when absorbing liquid.

[0033] In the manufacturing method of the absorbent body of this embodiment, from the viewpoint of better forming the above-mentioned fiber mesh structure, it is preferable that the thermally fusible fiber 1A is contained in an amount of 4 mass% or more, more preferably 6 mass% or more, and even more preferably 8 mass% or more, relative to the mass of the stack 3 obtained in step (I). From the viewpoint of preventing solidification of the absorbent body, the thermally adhesive fiber 1A is preferably contained in the pile 3 at 30 mass % or less, more preferably 25 mass % or less, and even more preferably 20 mass % or less.

[0034] When the fibers 1 contain heat-fusible fibers 1A and cellulose fibers 1B, the ratio (M2 / M1) of the mass of the heat-fusible fibers 1A to the total mass (M1) of the fibers in the pile 3 is preferably 25% by mass or more, more preferably 35% by mass or more, and even more preferably 45% by mass or more, from the viewpoints of forming a fiber mesh structure by the heat-fusible fibers 1A while simultaneously improving the liquid absorbency of the absorbent body 7 and increasing the thinning of the absorbent body 7 due to hydrogen bonding of the cellulose fibers 1B. From the viewpoint of better forming a fiber network structure by the thermally adhesive fibers 1A, the ratio (M2 / M1) is preferably 75% by mass or less, more preferably 60% by mass or less, and even more preferably 50% by mass or less.

[0035] In the manufacturing method of the absorbent body of this embodiment, the thickness of the heat-fused laminated fabric 4 obtained in step (II) at 362.8 Pa is preferably 110% or more, more preferably 120% or more, and even more preferably 130% or more of the thickness of the absorbent body 7 obtained in step (V) at 362.8 Pa. This is expected to allow the thickness to recover after absorbing liquid. Furthermore, the thickness of the heat-fused laminated fabric 4 at 362.8 Pa is preferably 400% or less, more preferably 300% or less, and even more preferably 200% or less of the thickness of the absorbent body 7 at 362.8 Pa. This is expected to make the absorbent body 7 thinner. The load of "362.8 Pa" is based on JIS K6732 and assumes measurements using a "Constant Pressure Thickness Gauge Model PG-11" manufactured by Techclock Corporation.

[0036] In the manufacturing method of the absorbent body of this embodiment, the density of the entire fiber 1 contained in the heat-fused laminate 4 obtained in step (II) is 10 kg / m 3 More than 15kg / m is preferable. 3 More preferably, 20 kg / m 3 This is more preferable because the sheet shape can be easily maintained even after absorbing liquid. The density is 70 kg / m 3 Less than 55kg / m is preferable. 3 Less than 40kg / m is more preferable. 3 The following is even more preferable. This is expected to enable the absorbent body 7 to be made even thinner. The density is calculated by dividing the basis weight of the entire fibers 1 contained in the heat-fused pile 4 by the thickness of the pile 3 under 362.8 Pa.

[0037] Next, preferred embodiments of the absorbent body of the present invention will be described below. The absorbent body 7 of this embodiment is obtained through the above-mentioned steps and has the following structure. That is, the absorbent body 7 of this embodiment includes fibers 1 and absorbent polymer material 2. The fibers 1 include heat-fusible fibers 1A, and the heat-fusible fibers 1A, 1A have fusion points 8 at their intersections. The intersections referred to here are as defined above. Furthermore, the absorbent body 7 of this embodiment contains heat-fusible fibers 1A in an amount of 4% by mass or more and 30% by mass or less relative to the mass of the absorbent body 7 before liquid absorption, and the fusion points 8 include 2 to 14 fusion points 8 within a square field of view of 1 mm x 1 mm observed from the surface of the absorbent body 7. In addition, the absorbent body 7 of this embodiment has a composite portion 6 in which the fibers 1 are incorporated within the absorbent polymer material 2 . In addition, the term "before absorbing liquid" used here refers to the state before the absorbent 7 is used, and means the state in which the absorbent 7 is compressed into a sheet (a compressed state of the fiber network structure). It also means the state before the liquid absorbing means described below is implemented (the same applies below).

[0038] In the absorbent body 7 of this embodiment, it is preferable that the fibers 1 further contain cellulose fibers 1B from the viewpoints of reducing the thickness before liquid absorption, improving the amount of liquid absorption during liquid absorption, and further increasing the sheet strength. In order to further enhance the hydrogen bonds described above, the absorbent 7 before absorbing liquid preferably contains 2% by mass or more of cellulose fibers 1B, more preferably 3.5% by mass or more, and even more preferably 5% by mass or more. In addition, from the viewpoint of controlling the hydrogen bonds that occur and maintaining softness, it is preferable that the absorbent 7 contains 30% by mass or less of cellulose fibers 1B, more preferably 25% by mass or less, and even more preferably 20% by mass or less, of the mass of the absorbent 7 before liquid absorption.

[0039] As shown in the manufacturing method described above, the absorbent body 7 of this embodiment contains heat-fusible fibers 1A and their fusion points 8, as well as the composite part 6, and thus is thin before absorbing liquid, but maintains sheet strength without reducing the amount of liquid absorbed even during liquid absorption. In particular, by setting the content of the heat-fusible fibers 1A to be equal to or more than the above lower limit, the absorbent body 7 is less likely to collapse when absorbing liquid, the sheet strength is increased, and more fusion points 8 can be included. Furthermore, by setting the number of fusion points 8 of the heat-fusible fiber 1A to be equal to or greater than the above lower limit, the fiber network structure due to the fusion points 8 becomes more reliable, improving the recovery when absorbing liquid. In addition, by setting the content of the heat-fusible fibers 1A to be equal to or less than the above upper limit, the absorbent body 7 before absorbing liquid can be prevented from becoming too hard without becoming bulky, and flexibility can be maintained. Furthermore, by setting the number of fusion points 8 of the heat-fusible fibers 1A to the above upper limit or less, the mesh space (fiber distance) of the fibers 1 that are restored when absorbing liquid can be increased, which means that the thickness of the absorbent body 7 can be increased when absorbing liquid. Furthermore, by including the composite section 6, the state in which the inter-fiber distance before liquid absorption is reduced is fixed, and the absorbent body 7 is more reliably made thinner. During liquid absorption, the fibers 1 in the composite section 6 are released from the absorbent polymer material 2 at the timing when the absorbent polymer material 2 starts to swell, and the bulky mesh space of the fiber mesh structure is quickly restored (as a result, the thickness of the absorbent body 7 increases). In addition, the swelling pressure caused by the liquid absorption of the absorbent polymer material 2 further promotes the restoration, making it easier to expand the mesh space. This ensures a space for the absorbent polymer material 2 to absorb liquid and swell, making it easier for the absorbent polymer material 2 to effectively exhibit its absorption performance. In addition, when the absorbent 7 contains the cellulose fibers 1B together with the heat-fusible fibers 1A as the fibers 1, hydrogen bonds are generated in the cellulose fibers 1B before liquid absorption, further reducing the inter-fiber distance, and more reliably reducing the thickness of the absorbent 7. During liquid absorption, the hydrogen bonds are released together with the composite portion 6, causing the inter-fiber distance to expand more quickly, and the absorption performance of the absorbent polymer material 2 is more effectively exhibited.

[0040] (Method of measuring the number of fusion points 8 in absorber 7; in the case of a square visual field of 1 mm x 1 mm) Specifically, the number of fusion points 8 in the absorbent body 7 can be measured by the following method. That is, an image is taken of an area of ​​1 mm×1 mm on one surface of the absorbent body 7, within a range in which fusion of the heat-fusible fibers 1A can be confirmed. Whether or not the thermoplastic fibers 1A are fused can be determined by taking an image using a scanning electron microscope (SEM). A frame is added to the obtained captured image to specify a parallel field of view range of 1 mm x 1 mm, and the magnification is appropriately increased so that the fused portion can be easily confirmed. In this way, the number of points at which the thermoplastic fibers 1A are fused at the intersections is visually counted. For example, as shown in Fig. 3, within a frame K1 of a 1 mm x 1 mm square field of view marked on the captured image, the number of fusion points 8 (e.g., the portion indicated by a circle in Fig. 3) of the heat-fusible fibers 1A at the intersections defined above is visually counted.

[0041] The absorbent body 7 preferably has the following tensile strength in order to have high sheet strength. That is, the absorbent body 7 is subjected to the following [Sample Preparation Procedure] and [Liquid Absorption Procedure], and the tensile strength measured by the following [Measurement Means I] is preferably 1.0 N / 25 mm or more and 10.0 N / 25 mm or less, more preferably 1.5 N / 25 mm or more, even more preferably 2.0 N / 25 mm or more, more preferably 8.0 N / 25 mm or less, and even more preferably 5.0 N / 25 mm or less. If the tensile strength is above the lower limit, the sheet strength of the absorbent body 7 becomes stronger, and if the tensile strength is below the upper limit, the softness of the absorbent body 7 is more easily maintained.

[0042] [Sample preparation procedure] An absorbent body to be evaluated is collected from an absorbent article. Here, the absorbent body means a member containing fibers and an absorbent polymer material. Generally, in absorbent articles, the absorbent body is often covered with a sheet material such as paper or nonwoven fabric. In this specification, the absorbent body does not include these sheet materials. Herein, only the absorbent body is collected. In the case where the sheet material is bonded to the absorbent body with a hot melt adhesive, the hot melt adhesive is solidified by cold spray, and then the absorbent body is carefully peeled off from the sheet material. Hereinafter, the collected absorbent body is referred to as an evaluation sample. [Suction procedure] (1) Pour deionized water into a container large enough to contain the evaluation sample, in an amount sufficient to fully immerse the evaluation sample. (2) Immerse the evaluation sample in a container filled with deionized water. At that time, be careful that the evaluation sample does not absorb too much deionized water, and if it does, add more deionized water. (3) After immersion for 10 minutes, collect the evaluation sample.

[0043] [Measurement means I] (1) The evaluation sample that has absorbed the liquid is cut to a width of 25 mm so that it can be placed 40 mm apart between the chucks of a tensile testing machine. (2) Using a "Biaxial Tensile Test System AG-Xplus" (product name) manufactured by Shimadzu Corporation, the maximum load value at which the evaluation sample breaks is measured at a speed of 20 mm / min, and this value is regarded as the tensile strength.

[0044] Regarding the change in thickness of the absorbent body 7 before and after absorbing liquid, the difference in thickness of the absorbent body 7 under a load of 362.8 Pa before and after carrying out the above-mentioned "liquid absorbing step" is preferably 8 mm or more and 30 mm or less. By suitably increasing the thickness of the absorbent body 7 before and after liquid absorption, the space for the absorbent polymer material 2 to absorb liquid and swell due to the increased interfiber distance is increased, and a larger absorption amount can be maintained. In other words, a decrease in the amount of liquid absorbed during the liquid absorption process can be more effectively suppressed. From this perspective, the difference in thickness of the absorbent body 7 under a load of 362.8 Pa before and after carrying out the above-mentioned [liquid absorption step] is more preferably 10 mm or more, and even more preferably 15 mm or more. Moreover, the difference in thickness of the absorbent 7 under a load of 362.8 Pa before and after the liquid absorbing step is more preferably 25 mm or less, and even more preferably 20 mm or less, so that when worn as an absorbent article, the absorbent portion feels less uncomfortable.

[0045] The thickness of the absorbent 7 before absorbing liquid, when thinned into a sheet, is preferably 0.3 mm or more and 2.5 mm or less, more preferably 2.0 mm or less, and even more preferably 1.5 mm or less.

[0046] (Method of measuring difference in thickness of absorbent body 7 before and after liquid absorption) (1) Using a constant pressure thickness gauge (Model PG-11) manufactured by Techclock Corporation, measure the thickness of the evaluation sample taken according to the procedure described above in [Sample Preparation Procedure] before liquid absorption at a load of 362.8 Pa. The thickness at this time is designated as H1. (2) The evaluation sample is made to absorb liquid by the above-mentioned "liquid absorption step". (3) Using the method described in (1) above, measure the thickness of the evaluation sample after liquid absorption under a load of 362.8 Pa. The thickness at this time is designated as H2. (4) The difference in thickness before and after absorption is H2-H1.

[0047] In order to increase the sheet strength of the absorbent 7 during liquid absorption and to strengthen the fiber mesh structure formed by the fusion points 8 of the heat-fusible fibers 1A, it is more preferable for the absorbent 7 to contain 6 mass% or more of the heat-fusible fibers 1A relative to the mass of the absorbent 7 before liquid absorption, and it is even more preferable for the absorbent 7 to contain 8 mass% or more of the heat-fusible fibers 1A. In addition, from the viewpoint of better forming a compressed state of the fiber mesh space before liquid absorption, it is more preferable that the absorbent body 7 contains heat-fusible fibers 1A in an amount of 25 mass% or less, and even more preferable that the absorbent body 7 contains heat-fusible fibers 1A in an amount of 20 mass% or less, relative to the mass of the absorbent body 7 before liquid absorption.

[0048] The ratio of the mass of the heat-fusible fibers 1A to the total mass of the fibers in the absorbent body 7 is preferably the same as the ratio (M2) of the mass of the heat-fusible fibers 1A to the total mass of the fibers in the pile 3 (M1) (M2 / M1).

[0049] (Method of measuring the mass ratio of the heat-fusible fibers 1A and the cellulose fibers 1B to the mass of the absorbent body 7 before liquid absorption, and the ratio of the mass of the cellulose fibers 1B to the mass of the heat-fusible fibers 1A) (1) The absorbent is pulverized and decomposed in an organic solvent that does not dissolve the absorbent components, or in a highly concentrated salt solution that can suppress the water absorption and expansion of the absorbent polymer material, or in an acidic solution with a pH of 2.5 or less. (2) Separation based on the difference in specific gravity of the absorbent polymer material, or by mixing with a large amount of water to swell the water-absorbent polymer, and then separating the heat-fusible fiber and cellulose by filtration. (3) Calculate the dry mass of the separated heat-fusible fiber and cellulose. (4) A liquid that does not dissolve the heat-fusible fibers is selected from among ionic liquids, cuprammonium liquids, and mixtures of carbon disulfide and sodium hydroxide that can dissolve cellulose fibers, and the cellulose is dissolved and removed. (5) The remaining heat-fusible fibers are washed and dried, and the dry mass is measured and compared with the mass in (3) above to calculate M2 / M1.

[0050] The heat-fusible fibers 1A contained in the absorbent 7 may be composite fibers or single fibers as described above. When the heat-fusible fibers 1A are composite fibers, they are preferably core-sheath fibers as described above. When the heat-fusible fibers 1A are single fibers, the fiber length is preferably within the above-mentioned range.

[0051] In the absorbent body 7, it is preferable that there are 2 or more fusion points 8 within a 1 mm x 1 mm square visual field observed from the surface of the absorbent body 7, more preferably 4 or more fusion points 8, and even more preferably 6 or more fusion points 8. This ensures a more reliable fiber network structure due to the fusion points 8, and makes it possible to maintain a higher sheet strength when absorbing liquid. Furthermore, the number of fusion points 8 within a 1 mm×1 mm square field of view observed from the surface of the absorbent body 7 is preferably 14 or less, more preferably 12 or less, and even more preferably 10 or less. This allows the fiber mesh space (fiber distance) that is restored upon liquid absorption to be larger. In other words, the increase in thickness of the absorbent body 7 upon liquid absorption can be further increased. The number is measured based on the above-mentioned (method of measuring the number of fusion-bonded points 8 in absorbent body 7; in the case of a square visual field range of 1 mm×1 mm).

[0052] Furthermore, the number of fusion points 8 is preferably within the following range within a 1.5 mm x 1.5 mm square field of view observed from the surface of the absorbent 7. The size of "1.5 mm x 1.5 mm" in the "1.5 mm x 1.5 mm square field of view" means that the number of fusion points can be counted reliably and more averagely over a larger range. By observing the "1.5 mm x 1.5 mm square field of view" together with the above-mentioned "1 mm x 1 mm square field of view", the number of fusion points can be grasped more accurately. This number can be measured by applying the above-mentioned (method of measuring the number of fusion points 8 in the absorbent 7; in the case of a 1 mm x 1 mm square field of view). For example, as shown in FIG. 4, within the frame K2 of the 1.5 mm x 1.5 mm square field of view added to the captured image, the fusion points 8 of the heat-fusible fiber 1A at the intersection defined above (for example, the part indicated by a circle in FIG. 4) are visually counted.

[0053] The number of fusion points 8 is preferably 5 or more, more preferably 9 or more, and even more preferably 13 or more within a 1.5 mm × 1.5 mm square field of view observed from the surface of the absorbent body 7. This ensures a more reliable fiber network structure due to the fusion points 8, and enables the sheet strength to be maintained higher when absorbing liquid. Furthermore, the number of fusion points 8 within a square field of view of 1.5 mm×1.5 mm observed from the surface of the absorbent body 7 is preferably 32 or less, more preferably 27 or less, and even more preferably 23 or less. This makes it possible to increase the fiber mesh space (fiber distance) that is restored upon liquid absorption. In other words, it is possible to further increase the increase in thickness of the absorbent body 7 upon liquid absorption.

[0054] In addition, the composite parts 6 are desirably arranged in 20 or more places, more preferably 22 or more places, and even more preferably 24 or more places, within a square visual field of 1.5 mm × 1.5 mm observed from the surface of the absorbent body 7. This makes it possible to more reliably and satisfactorily achieve a reduction in the thickness of the absorbent body 7 due to a reduction in the interfiber distance before liquid absorption, and a rapid restoration of the fiber network structure upon liquid absorption. Moreover, the composite parts 6 are preferably arranged in 45 or less locations, more preferably in 40 or less locations, and even more preferably in 35 or less locations, within a square visual field of 1.5 mm x 1.5 mm observed from the surface of the absorbent body 7. This makes it easier to maintain the softness of the absorbent body.

[0055] (Method of measuring the location where the composite part 6 is arranged) Specifically, the location where the composite portion 6 is disposed can be measured by the following method. That is, an image is taken by SEM on one surface of the absorbent body 7 in an area of ​​1.5 mm×1.5 mm that includes a plurality of absorbent polymer materials 2 . A frame K2 is attached to the obtained captured image to specify a parallel field of view range of 1.5 mm x 1.5 mm, and the image is appropriately enlarged to a magnification that makes it easy to confirm the composite portion. This allows visual counting of composite materials 6 in which fibers 1 are incorporated into absorbent polymer material 2. Whether or not a composite portion 6 is present can be determined by observing that an end of fiber 1 is incorporated into the absorbent polymer material at the interface between absorbent polymer material 2 and fiber 1. Also, when multiple fibers 1 are incorporated into one absorbent polymer material 2, they are counted as multiple locations.

[0056] In order to further improve the absorption performance of the absorbent body 7 and to increase the number of the aforementioned composite parts 6, it is preferable that the absorbent body 7 contains 50% by mass or more of absorbent polymer material 2, more preferably 60% by mass or more, and even more preferably 70% by mass or more, of the mass of the absorbent body 7 before liquid absorption. In order to prevent the absorbent polymer material 2 from falling off, the absorbent body 7 preferably contains the absorbent polymer material 2 in an amount of 95% by mass or less relative to the mass of the absorbent body 7 before absorbing liquid.

[0057] The shedding rate of the absorbent polymer material 2, obtained by measuring the absorbent body 7 before absorbing liquid by the following [Measuring means II], is preferably 0% to 2%, more preferably 1% or less, and even more preferably 0.5% or less. This makes it possible to suppress shedding of the absorbent polymer material 2 in the absorbent body 7 before absorbing liquid, i.e., before use, and to fully exhibit the expected absorption performance during use.

[0058] [Measurement Method II] (1) Obtain an evaluation sample based on the [Sample Preparation Procedure]. (2) Cut the evaluation sample to a width of 50 mm and a length of 60 mm. The absorbent polymer contained in the evaluation sample is prone to increasing in mass when it absorbs moisture. In order to measure the shedding rate accurately, after the evaluation sample is taken, it is stored in a Unipack (product name) manufactured by Seisan Nippon Co., Ltd. (3) The shedding rate of the absorbent polymer material is measured according to the following procedure. (i) The evaluation sample is taken out of the Unipack and its mass is measured. The mass at this time is designated as W1. (ii) The evaluation sample is placed back into the Unipack, and the Unipack containing the evaluation sample is fixed to a Verder Scientific AS200 sieve shaker and shaken at an amplitude of 1 mm for 1 minute. (iii) After the shaking is completed, the evaluation sample is taken out of the Unipack again and the mass is measured. The weight at this time is designated as W2. (iv) The value calculated by (W1-W2) / W1 x 100 is the dropout rate of the absorbent polymer material.

[0059] The absorbent body of the present invention can be applied in various fields, for example, it is suitably used as a liquid retaining portion of absorbent articles used to absorb liquid discharged from the body, such as sanitary napkins, panty liners, disposable diapers, and incontinence pads.

[0060] The absorbent article including the absorbent of the present invention is typically constructed by sandwiching the absorbent between a surface sheet on the skin side and a back sheet on the non-skin side. The constituent members of the absorbent article can be made of materials commonly used in the technical field without any particular restrictions. For example, the surface sheet can be made of a liquid-permeable, soft-touch material, such as various nonwoven fabrics such as air-through nonwoven fabrics. The surface sheet can also be made of a plurality of nonwoven fabrics, or a combination of a nonwoven fabric and another material. The back sheet can be made of a liquid-impermeable or water-repellent sheet such as a thermoplastic resin film or a laminate of the film and a nonwoven fabric. The back sheet may be water vapor permeable. The absorbent article may further include various members according to the specific use of the absorbent article. For example, when the absorbent article is applied to a disposable diaper or sanitary napkin, one or more pairs of three-dimensional guards can be arranged on both the left and right sides of the surface sheet.

[0061] In relation to the above-mentioned embodiments, the present invention further discloses the following method for producing an absorbent body, an absorbent body, and an absorbent article including the absorbent body.

[0062] <1> A fiber-stacking process in which fibers including thermally adhesive fibers and an absorbent polymer material are mixed and stacked to obtain a fiber-stacking material; A heat treatment step of subjecting the stack to a heat treatment at a temperature equal to or higher than the melting point of the heat-fusible fibers to obtain a heat-fusible stack; and A hydration step of hydrating the heat-fused laminated material to obtain a hydrated laminated material is carried out in this order, A pressurizing step of applying pressure to the water-containing laminated fiber and a drying step of applying heat treatment at a temperature lower than the melting point of the heat-fusible fiber and drying the laminated fiber are carried out simultaneously or separately. A method for manufacturing an absorbent body.

[0063] <2> The fibers include cellulose fibers. <1> A method for producing the absorbent body according to claim 1. <3> The heat treatment step is performed by using hot air. <1> or <2> A method for producing the absorbent body according to claim 1.

[0064] <4> In the heat treatment step, a pressure applied to the fiber stack is set to 0 (zero) Pa or more and 50 Pa or less. <1> ~ <3> 13. A method for producing an absorbent body according to any one of claims 1 to 12. <5> The thermal adhesive fiber is contained in an amount of 4% by mass or more and 30% by mass or less, preferably 6% by mass or more and 25% by mass or less, and more preferably 8% by mass or more and 20% by mass or less, based on the mass of the stack. <1> ~ <4> 13. A method for producing an absorbent body according to any one of claims 1 to 12. <6> The amount of water added to the heat-sealed laminated fabric in the water-adding step is 100% or more and 500% or less, preferably 130% or more and 400% or less, more preferably 160% or more and 300% or less, of the mass of the heat-sealed laminated fabric. <1> ~ <5> 13. A method for producing an absorbent body according to any one of claims 1 to 12. <7> The thickness of the heat-fused laminated fabric at 362.8 Pa is 110% or more and 400% or less, preferably 120% or more and 300% or less, more preferably 130% or more and 200% or less, of the thickness of the absorbent body at 362.8 Pa. <1> ~ <6> 13. A method for producing an absorbent body according to any one of claims 1 to 12. <8> The pressure in the pressurizing step is 16 kPa or more and 500 kPa or less, preferably 80 kPa or more and 400 kPa or less, and more preferably 160 kPa or more and 300 kPa or less. <1> ~ <7> 13. A method for producing an absorbent body according to any one of claims 1 to 12. <9> The density of the entire fibers contained in the heat-sealed laminate is 10 kg / m 3 More than 70kg / m 3 Less than 15 kg / m 3 More than 55kg / m 3 Less than or equal to 20 kg / m 3 More than 40kg / m 3 The above-mentioned <1> ~ <8> 13. A method for producing an absorbent body according to any one of claims 1 to 12.

[0065] <10> The above <1> ~ <9> 1. An absorbent body obtained by the method for producing an absorbent body according to any one of the preceding claims.

[0066] <11> 1. An absorbent body comprising fibers and absorbent polymer material, The fibers include thermally adhesive fibers, and the thermally adhesive fibers have fusion points at intersections between each other, The absorbent body contains the heat-fusible fiber in an amount of 4% by mass or more and 30% by mass or less relative to the mass of the absorbent body before absorbing liquid, The fusion points include 2 to 14 points within a square field of view of 1 mm x 1 mm observed from the surface of the absorbent body, The absorbent body has a composite structure in which the fibers are entrapped within the absorbent polymer material.

[0067] <12> The absorbent is subjected to the following [Sample Preparation Procedure] and [Liquid Absorption Procedure], and the tensile strength measured by the following [Measurement Means I] is 1.0 N / 25 mm or more and 10.0 N / 25 mm or less, preferably 1.5 N / 25 mm or more and 8.0 N / 25 mm or less, more preferably 2.0 N / 25 mm or more and 5.0 N / 25 mm or less. <10> or <11> The absorbent body according to claim 1. [Sample preparation procedure] An absorbent body to be evaluated is taken from the absorbent article. If the sheet material is bonded to the absorbent body with a hot melt adhesive, the hot melt adhesive is solidified with a cold spray, and then the absorbent body is carefully peeled off from the sheet material. Hereinafter, the taken absorbent body is referred to as the evaluation sample. [Suction procedure] (1) Pour deionized water into a container large enough to contain the evaluation sample, in an amount sufficient to fully immerse the evaluation sample. (2) Immerse the evaluation sample in a container filled with deionized water for 10 minutes. At this time, pay attention to whether the evaluation sample absorbs too much deionized water and runs out of deionized water. If it does, add more deionized water. (3) After immersion for 10 minutes, collect the evaluation sample. [Measurement means I] (1) The evaluation sample that has absorbed the liquid is cut to a width of 25 mm so that it can be placed 40 mm apart between the chucks of a tensile testing machine. (2) Using a "Biaxial Tensile Test System AG-Xplus" (product name) manufactured by Shimadzu Corporation, the maximum load value at which the evaluation sample breaks is measured at a speed of 20 mm / min, and this value is regarded as the tensile strength. <13> The difference in thickness of the absorbent body under a load of 362.8 Pa before and after the liquid absorption step is 8 mm or more and 30 mm or less. <10> ~ <12> 13. The absorbent body according to claim 12 .

[0068] <14> The fibers include cellulose fibers. <10> ~ <13> 13. The absorbent body according to claim 12 .

[0069] <15> The cellulose fiber is contained in an amount of 2% by mass or more, preferably 3.5% by mass or more, and more preferably 5% by mass or more, based on the mass of the absorbent before absorbing liquid. <14> The absorbent body according to claim 1. <16> The absorbent body contains 30% by mass or less, preferably 25% by mass or less, and more preferably 20% by mass or less of the cellulose fibers relative to the mass of the absorbent body before absorbing liquid. <14> or <15> The absorbent body according to claim 1. <17> The absorbent body contains the heat-fusible fiber in an amount of 4% by mass or more, preferably 6% by mass or more, and more preferably 8% by mass or more, based on the mass of the absorbent body before absorbing liquid. <10> ~ <16> 13. The absorbent body according to claim 12 . <18> The absorbent body contains the heat-fusible fiber in an amount of 30% by mass or less, preferably 25% by mass or less, and more preferably 20% by mass or less, based on the mass of the absorbent body before absorbing liquid. <10> ~ <17> 13. The absorbent body according to claim 12 . <19> The heat-fusible fiber is a composite fiber, preferably a core-sheath fiber. <10> ~ <18> 13. The absorbent body according to claim 12 . <20> The heat-fusible fiber is a single fiber, and preferably has a fiber length of 3 mm or more and 60 mm or less. <10> ~ <19> 13. The absorbent body according to claim 12 . <21> The fusion points include 2 or more, preferably 4 or more, and more preferably 6 or more within a square visual field of 1 mm x 1 mm observed from the surface of the absorbent body. <11> ~ <20> 13. The absorbent body according to claim 12 . <22> The fusion points include 14 or less, preferably 12 or less, and more preferably 10 or less within a square visual field of 1 mm x 1 mm observed from the surface of the absorbent body. <11> ~ <21> 13. The absorbent body according to claim 12 .

[0070] <23> The fusion points include 5 to 32 points within a square visual field of 1.5 mm x 1.5 mm observed from the surface of the absorbent body. <11> ~ <22> 13. The absorbent body according to claim 12 .

[0071] <24> The fusion points include 9 or more, preferably 13 or more, within a square visual field of 1.5 mm x 1.5 mm observed from the surface of the absorbent body. <23> The absorbent body according to claim 1. <25> The fusion points are 27 or less, preferably 23 or less, within a square visual field of 1.5 mm x 1.5 mm observed from the surface of the absorbent body. <23> or <24> The absorbent body according to claim 1.

[0072] <26> The composite portion is arranged in 20 to 45 locations within a square visual field of 1.5 mm x 1.5 mm observed from the surface of the absorbent body. <11> ~ <25> 13. The absorbent body according to claim 12 .

[0073] <27> The composite portion is arranged at 22 or more locations, preferably 24 or more locations, within a square visual field of 1.5 mm×1.5 mm observed from the surface of the absorbent body. <26> The absorbent body according to claim 1. <28> The composite parts are arranged at 40 or less locations, preferably 35 or less locations, within a square visual field of 1.5 mm x 1.5 mm observed from the surface of the absorbent body. <26> or <27> The absorbent body according to claim 1. <29> The absorbent body contains the absorbent polymer material in an amount of 50% by mass or more and 95% by mass or less, preferably 60% by mass or more, and more preferably 70% by mass or more, based on the mass of the absorbent body before absorbing liquid. <10> ~ <28> 13. The absorbent body according to claim 12 . <30> The absorbent body before absorbing liquid has a dropout rate of 0% to 2%, preferably 1% or less, and more preferably 0.5% or less, as measured by the following [Measurement Method II]. <10> ~ <29> 13. The absorbent body according to claim 12 . [Measurement Method II] (1) Obtain an evaluation sample based on the [Sample Preparation Procedure]. (2) Cut the evaluation sample to a width of 50 mm and a length of 60 mm. The absorbent polymer contained in the evaluation sample is prone to increasing in mass when it absorbs moisture. In order to measure the shedding rate accurately, after the evaluation sample is taken, it is stored in a Unipack (product name) manufactured by Seisan Nippon Co., Ltd. (3) The shedding rate of the absorbent polymer material is measured according to the following procedure. (i) The evaluation sample is taken out of the Unipack and its mass is measured. The mass at this time is designated as W1. (ii) The evaluation sample is placed back into the Unipack, and the Unipack containing the evaluation sample is fixed to a Verder Scientific AS200 sieve shaker and shaken at an amplitude of 1 mm for 1 minute. (iii) After the shaking is completed, the evaluation sample is taken out of the Unipack again and the mass is measured. The weight at this time is designated as W2. (iv) The value calculated by (W1-W2) / W1 x 100 is the dropout rate of the absorbent polymer material.

[0074] <31> The above <10> ~ <30> An absorbent article comprising the absorbent body according to any one of the preceding claims. EXAMPLES

[0075] The present invention will be described in more detail below based on examples, but the present invention is not limited thereto. In the examples, "parts" and "%" are all based on mass unless otherwise specified. "←" means that the content is the same as that in the left column, and "↑" means that the content is the same as that in the upper column.

[0076] (Example) (1) Material Fiber 1: The cellulose fiber 1B was NBKP, and the thermally adhesive fiber 1A was a composite fiber with a core-sheath structure (core: PET, sheath: PE), with a mass ratio of 50:50. The basis weight of the entire fiber 1 was 40 g / m 2 It was decided. Absorbent polymer material 2: Basis weight 200g / m 2 So I prepared it.

[0077] (2) Manufacturing method Using the above materials, the steps of fiber stacking, heat treatment, hydration, pressurization, and drying were carried out in this order as shown in Table 1 to prepare absorbent samples of the examples. The heat treatment step was performed using hot air, and the temperature of the hot air was set to 132° C., which was higher than the melting point of the thermal adhesive fiber 1A (the melting point of the PE resin component). The pressure applied to the fiber stack in the heat treatment step was controlled to 0 Pa or less. In the water addition step, the amount of water added to the heat-fused laminated fabric using a spray was 1016% of the mass of the fibers. The pressurizing step was carried out at room temperature (25° C.) and the pressure was set to 2.07 MPa. The drying step was carried out at 105° C., which is lower than the melting point of the heat-fusible fiber 1A (the melting point of the PE resin component). (2) Absorber sample The absorbent sample of the example obtained above contained 50 mass% of the heat-fusible fiber 1A relative to the total mass of the fibers of the absorbent sample. The number of fusion points and the presence or absence of composite parts were as shown in Table 2. That is, the absorbent sample contained 8.3 mass% of the thermoplastic fiber 1A relative to the mass of the absorbent sample. The number of fusion points was measured based on the above-mentioned (method of measuring the number of fusion points 8 in absorbent body 7; in the case of a square visual field range of 1 mm × 1 mm). The presence or absence of the composite part 6 was confirmed based on the above-mentioned (method of measuring the location where the composite part 6 is located in the absorbent body 7).

[0078] Comparative Example 1 Using the materials shown in Table 1, an absorbent sheet (a fiber web carrying an absorbent polymer and a fiber assembly laminated together) as shown in FIG. 9 of the aforementioned Patent Document 2 (JP Patent Publication 8-229070) was produced by a papermaking process. In other words, the fiber stacking process, heat treatment process, and hydration process used in the examples were not carried out. Next, a pressurizing process and a drying process were carried out to produce an absorbent sample of Comparative Example 1. Each process was carried out under the conditions shown in Table 1.

[0079] Comparative Example 2 An absorbent sample of Comparative Example 2 was prepared in the same manner as in Comparative Example 1, except that the materials used were the same as those in the Example.

[0080] Comparative Example 3 An absorbent sample of Comparative Example 3 was produced using the same materials as in the Examples, but without the hydration and drying steps used in the Examples, and instead by carrying out the fiber-stacking step, heat treatment step, and pressurization step. Each step was carried out under the conditions shown in Table 1. In the pressurizing step, a Mini Test Press-10 (product name) manufactured by Toyo Seiki Seisakusho Co., Ltd. was used to perform heat pressing (pressure 0.207 MPa) at 200° C., which is higher than the melting point of the heat-fusible fiber 1A (melting point of the PE resin component). In the absorbent sample of Comparative Example 3 thus prepared, the fibers were merely attached to the surface of the absorbent polymer material, and no composite portion was formed.

[0081] Comparative Example 4 Using the same materials as in the examples, the fiber-stacking step and heat treatment step were carried out, followed by the pressurizing step, hydration step, and drying step in this order, to produce an absorbent sample of Comparative Example 4. Each step was carried out under the conditions shown in Table 1. In this case, in the pressurizing step, the same heat pressing was performed as in Comparative Example 3. In the drying step, heat pressing was performed at 115° C., which is lower than the melting point of the heat-fusible fiber 1A (the melting point of the PE resin component).

[0082] Comparative Example 5 Using the same materials as in the examples, the fiber-stacking step, heat treatment step, and hydration step were carried out, followed by simultaneous pressurization and drying steps (pressurized drying fusion) to produce an absorbent sample for Comparative Example 5. Each step was carried out under the conditions shown in Table 1. The pressing step and the drying step were carried out simultaneously by the same heat press as in Comparative Example 3.

[0083] (test) 1.Before liquid absorption (1) Thickness The measurement was performed based on the above-mentioned (method for measuring the difference in thickness of the absorbent body 7 before and after liquid absorption). (2) Tensile strength Measurement was carried out based on the above-mentioned [Measurement Method I].

[0084] 2. When absorbing liquid (1) Thickness After the above-mentioned [Sample preparation procedure] and [Liquid absorption procedure], the measurement was performed based on the above-mentioned (Method for measuring the difference in thickness of the absorbent body 7 before and after liquid absorption). (2) Tensile strength After the above-mentioned [Sample Preparation Procedure] and [Liquid Absorption Procedure], measurements were performed based on the above-mentioned [Measurement Method I]. (3) Saturation absorption After taking the sample according to the above-mentioned [Sample Preparation Procedure], the sample weight was measured, and then after carrying out the [Liquid Absorption Procedure], the weight of the sample that had absorbed the liquid was measured.

[0085] The results of each of the above tests are shown in Table 3 below.

[0086] [Table 1]

[0087] [Table 2]

[0088] [Table 3]

[0089] As shown in Tables 2 and 3, Figs. 6(A) to (F), and Figs. 7(A) and (B), the absorbent samples prepared in the examples contained a relatively large amount of heat-fusible fibers 1A at an equal ratio to cellulose fibers 1B, but the number of fusion points was not excessive and was appropriately arranged, and the absorbent samples contained composite parts. Therefore, the thickness was easily restored after liquid absorption, and the saturated absorption amount was large. Moreover, the rate of decrease in the tensile strength of the absorbent was suppressed before and after liquid absorption, and a certain level was ensured. In other words, the absorbent samples prepared in the examples were thinned before liquid absorption, but even when absorbing liquid, the liquid absorption amount was not decreased and the sheet strength was ensured. This is thought to be because the compressed state of the fiber network structure of the heat-fusible fibers formed by the moderate number of fusion points and the bonded state of the composite part arranged in the absorbent polymer material were released by liquid absorption, and the network space was greatly expanded, and the swelling space of the absorbent polymer material was quickly secured. In addition, since the fiber network structure of the heat-fusible fibers is formed starting from an appropriate number of fused portions, the sheet is resistant to collapse even after absorbing liquid, and the sheet strength is ensured. [Explanation of symbols]

[0090] 1. Fiber 1A Heat-sealable fiber 1B Cellulose fiber 2. Absorbent polymer material 3. Piled Fibers 4. Heat-sealed piled fabric 5 Water-containing fiber pile 6 Complex section 7 Absorber 8 Fusion point

Claims

1. a fiber-stacking step of mixing and stacking fibers including heat-fusible fibers and an absorbent polymer material to obtain a fiber stack; a heat treatment step of subjecting the pile to a heat treatment at a temperature equal to or higher than the melting point of the heat-fusible fibers to obtain a heat-fusible pile; a hydration step of hydrating the heat-fused laminated material to obtain a hydrated laminated material, and then A pressurizing step of applying pressure to the water-containing fibrous material and a drying step of applying heat treatment at a temperature below the melting point of the heat-fusible fibers and drying the material are carried out simultaneously or separately. Method for manufacturing absorbent body.

2. The method for manufacturing an absorbent body according to claim 1 , wherein the fibers include cellulose fibers.

3. The method for manufacturing an absorbent body according to claim 1 or 2, wherein the heat treatment step is carried out by using hot air.

4. An absorbent body obtained by the method for producing an absorbent body according to claim 1.

5. 1. An absorbent body comprising fibers and an absorbent polymer material, The fibers include heat-fusible fibers, and the heat-fusible fibers have fusion points at their intersections, The absorbent body contains the heat-fusible fibers in an amount of 4% by mass or more and 30% by mass or less relative to the mass of the absorbent body before absorbing liquid, The fusion points include 2 to 14 points within a square field of view of 1 mm x 1 mm observed from the surface of the absorbent body, The absorbent body has a composite portion in which the fibers are entrapped within the absorbent polymer material.

6. The absorbent article of claim 5 , wherein the fibers comprise cellulosic fibers.

7. 7. The absorbent body according to claim 5, wherein the number of the fusion-bonded points is 5 to 32 within a square field of view of 1.5 mm x 1.5 mm observed from the surface of the absorbent body.

8. 7. The absorbent body according to claim 5, wherein the composite portions are arranged in 20 to 45 locations within a square visual field of 1.5 mm x 1.5 mm observed from the surface of the absorbent body.

9. An absorbent article comprising the absorbent body according to any one of claims 4 to 6.

Images