Method for producing absorber and absorber

Abstract

To provide an absorber with reduced occurrence of reverse flow through a simple production method.SOLUTION: A method for producing an absorber comprises: a base layer placing step of placing a base layer composed of fibers on a second liquid-permeable sheet that covers the non-skin-facing side of the absorber; a SAP placing step of placing a layer containing SAP particles, which are composed of superabsorbent polymers, on the base layer; a covering step of placing a first liquid-permeable sheet, which covers the skin-facing side of the absorber, on the SAP particles; and a pressurizing step of applying a pressure between the second liquid-permeable sheet and the first liquid-permeable sheet.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an absorber and an absorber.

Background Art

[0002] Absorbent articles such as diapers are known (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Absorbent articles have an absorber, and the absorber absorbs liquids generated from the human body. It is desirable for the absorber to have the function of quickly absorbing repeatedly flowing-in liquids and suppressing backflow. When trying to enhance such functionality, the absorber tends to have a complicated structure. And an absorber with a complicated structure increases the manufacturing cost.

[0005] An object of the present invention is to provide an absorber that is difficult to cause backflow with a simple manufacturing method.

Means for Solving the Problems

[0006] A method for manufacturing an absorber according to one aspect of the present invention includes a base layer placing step of placing a base layer composed of fibers on a second water-permeable sheet covering the non-skin surface side of the absorber, a SAP placing step of placing a layer containing SAP particles, which are superabsorbent polymers, on the base layer, a covering step of placing a first water-permeable sheet covering the skin surface side of the absorber on the SAP particles, and a pressing step of applying pressure between the second water-permeable sheet and the first water-permeable sheet.

Effects of the Invention

[0007] According to the present invention, an absorber that is difficult to reverse can be provided by a simple manufacturing method.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

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Figure 4

Figure 5

Figure 6

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Figure 8

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Figure 11

Figure 12

Modes for Carrying Out the Invention

[0009] Hereinafter, an absorbent article according to an embodiment of the present invention will be described with reference to the drawings. Note that the configurations of the following embodiments are examples, and the present invention is not limited to the configurations of these embodiments.

[0010] <Embodiment> In the present embodiment, for a tape-type disposable diaper (an example of the “absorbent article” referred to in the present application, hereinafter simply referred to as “diaper”), the direction connecting the front body portion disposed to face the abdomen of the wearer and the back body portion disposed to face the back is defined as the longitudinal direction. Between these front body portions (one side in the longitudinal direction) and the back body portions (the other side in the longitudinal direction) (the center in the longitudinal direction), there is a crotch portion disposed under the crotch of the wearer (disposed to face the crotch). Further, in the state where the diaper is worn by the wearer (hereinafter abbreviated as “worn state”), the side facing the skin of the wearer (the inner side in the worn state) is defined as the skin side, and the side opposite to the skin side (the outer side in the worn state) is defined as the non-skin side. Furthermore, the direction connecting the skin side and the non-skin side is defined as the thickness direction, and the direction orthogonal to both the longitudinal direction and the thickness direction is defined as the width direction. In addition, viewing from the thickness direction is defined as a plan view. Also, the front, rear, left, and right of the diaper 1 mean the directions that coincide with the front, rear, left, and right of the wearer in the state where the diaper 1 is worn by the wearer. For example, when referring to the left-right direction in the present application, it means the direction that coincides with the left and right of the wearer in the state where the diaper 1 is worn by the wearer, and when referring to the front-rear direction in the present application, it means the direction that coincides with the front and rear of the wearer in the state where the diaper 1 is worn by the wearer.

[0011] Figure 1 is a perspective view of the diaper according to the present embodiment. The diaper 1 has a length along the longitudinal direction and a length along the width direction orthogonal to the longitudinal direction. The diaper 1 includes a crotch region 1B that is a portion corresponding to the crotch of the wearer covering the crotch of the wearer in the worn state, a front body region 1F that is located on the front side of the crotch region 1B and corresponds to the front body of the wearer, and a rear body region 1R that is located on the rear side of the crotch region 1B and corresponds to the rear body of the wearer. Tapes 2L and 2R that can be attached to a front patch 2F provided on the non-wearer side surface of the front body region 1F are provided at the left and right edges of the rear body region 1R. When the tapes 2L and 2R are attached to the front patch 2F in a state where the front body region 1F is disposed on the ventral side of the wearer and the rear body region 1R is disposed on the dorsal side of the wearer, the diaper 1 is fixed to the body of the wearer in a state of surrounding the abdominal circumference and thighs of the wearer. Since the diaper 1 is fixed to the body of the wearer in such a form, the wearer can walk around while wearing the diaper 1.

[0012] An absorber that can absorb and hold liquid is disposed mainly around the crotch region 1B in the diaper 1. Further, in the diaper 1, leg gathers 3AL and 3AR are provided at a portion surrounding the leg circumference (thigh portion) of the wearer to suppress the formation of a gap serving as a liquid outflow path between the diaper 1 and the skin of the wearer. Leakage prevention walls 3BL and 3BR are provided inside the diaper 1 in the width direction rather than the leg gathers 3AL and 3AR, and a waist gather 3R is provided at a portion surrounding the abdominal circumference of the wearer. The leg gathers 3AL and 3AR, the leakage prevention walls 3BL and 3BR, and the waist gather 3R are in close contact with the skin of the wearer by the contraction force (elastic force) of the elastic member. Therefore, the liquid discharged from the crotch of the wearer is absorbed by the absorber of the diaper 1 without leaking from the diaper 1. As the elastic member, filamentous rubber (thread rubber), belt-shaped rubber, or the like can be appropriately selected.

[0013] FIG. 2 is an exploded perspective view of the diaper 1. FIG. 3 is a cross-sectional view of the diaper 1 in the non-worn state, taken along the width direction through the center in the longitudinal direction. FIG. 4 is a plan view of the diaper 1 in the extended state, seen from the skin side. In FIG. 4, the illustration of the expansion and contraction members 4C, 4SL, and 4SR is omitted. The diaper 1 has a cover sheet 4 that forms the outer surface in the worn state. The cover sheet 4 is a sheet-like member having a substantially rectangular appearance with gathers 4KL, 4KR provided at portions corresponding to the long sides, and forms the exterior surface of the diaper 1. The gathers 4KL, 4 KR are provided at the portions where the wearer's thighs are located (the leg-around regions 10L, 10R shown in FIG. 4). The cover sheet 4 is provided for reinforcing the back sheet 5 and improving the touch, which will be described later. For example, in order to suppress leakage of excrement, a non-woven fabric made of a liquid-impermeable thermoplastic resin can be used as the material. Examples of the liquid-impermeable thermoplastic resin include polyethylene (PE) and polypropylene (PP). The cover sheet 4 is not limited to a single-layer structure, and may have a multi-layer (two-layer) structure having an inner cover sheet and an outer cover sheet. Note that the cover sheet 4 forms the outer peripheral shape (outer shape) of the absorbent pad 1. The cover sheet 4 forms an exterior surface in which the front body region 1F, the crotch region 1B, and the back body region 1R are continuously provided.

[0014] The diaper 1 has a backsheet 5 (an example of the "non-skin-side sheet" of the present disclosure), an absorber 6, and a topsheet 7 (an example of the "skin-side sheet") that are sequentially laminated on the skin side of the cover sheet 4. The backsheet 5, the absorber 6, and the topsheet 7 are all sheet-like members having a substantially rectangular appearance, and are sequentially laminated on the cover sheet 4 in a state where the longitudinal direction coincides with the longitudinal direction of the cover sheet 4. The backsheet 5 is a sheet formed of a water-impermeable thermoplastic resin as a material in order to suppress leakage of excrement, similar to the cover sheet 4. The backsheet 5 is preferably composed of a material having moisture permeability in order to suppress stuffiness in the worn state. Further, the topsheet 7 is a sheet-like member disposed on the skin side of the wearer. The topsheet 7 has liquid permeability in part or all of it. Therefore, in the worn state of the diaper 1, the liquid excreted from the wearer enters the absorber 6 through the topsheet 7 that can come into contact with the wearer's skin and is absorbed there. For example, woven fabric, non-woven fabric, and porous film can be used as the material of the topsheet 7. The topsheet 7 may have hydrophilicity. The basis weight of the topsheet 7 is, for example, 16~35 g / m 2 2. The topsheet 7 may have intermittent squeezing grooves. By providing the squeezing grooves, the granular feeling of the contents of the absorber 6 can be reduced.

[0015] The backsheet 5, the absorber 6, and the topsheet 7 all extend from the front crotch region 1F to the rear crotch region 1R. Therefore, when the crotch of the wearer is covered with the cover sheet 4 on which the backsheet 5, the absorber 6, and the topsheet 7 are laminated, both end portions in the longitudinal direction of the backsheet 5, the absorber 6, and the topsheet 7 are in a state of being located on the ventral side and the dorsal side of the wearer. That is, the crotch of the wearer is in a state of being covered with the absorber 6 from the ventral side to the dorsal side of the wearer. Therefore, no matter whether the wearer discharges the liquid out of the body in a posture with the abdomen facing downward or a posture with the back facing downward, the discharged liquid comes into contact with the absorber 6 through the topsheet 7. Note that the topsheet 7 and the backsheet 5 are longer in the longitudinal direction than the absorber 6 and extend to each end of the front crotch region 1F and the rear crotch region 1R of the diaper 1.

[0016] Further, the diaper 1 is provided with elastic members 4SL and 4SR for forming the above-described leg gathers 3AL and 3AR so as to expand and contract in the longitudinal direction of the diaper 1 between the cover sheet 4 and the back sheet 5. The elastic members 4SL and 4SR are provided in an appropriate number (three in this embodiment) determined according to the elastic force (contracting force) required in the design of the diaper 1. As shown in FIG. 4, the leg gathers 3AL and 3AR are arranged to include the leg circumference regions which are the portions where the wearer's thighs are located at both ends in the width direction of the crotch region 1B. The leg circumference regions 10L and 10R are arranged at both ends in the width direction of the crotch region 1B. Further, the leg gathers 3AL and 3AR are formed in the arrangement regions of the elastic members 4SL and 4SR.

[0017] The diaper 1 also has long and narrow strip-shaped side sheets 8L and 8R (a pair of leakage-preventing sheets). The side sheets 8L and 8R are sheets having non-water permeability (liquid impermeability) provided at the long side portions of the top sheet 7. Similar to the cover sheet 4, the side sheets 8L and 8R are provided with constrictions 8KL and 8KR at the portions where the wearer's thighs are located (the leg circumference regions 10L and 10R shown in FIG. 4). And, elastic members 8EL and 8ER for forming leakage-preventing walls 3BL and 3BR are arranged along the longitudinal direction of the diaper 1 on the side sheets 8L and 8R. When the diaper 1 is in the worn state, that is, when the diaper 1 is in a U-shaped form in side view, the side sheets 8L and 8R are pulled in the longitudinal direction by the contracting force of the elastic members 8EL and 8ER and rise from the top sheet 7 to become leakage-preventing walls 3BL and 3BR that prevent the outflow of liquid. In addition, an elastic member 4C for preventing a gap from being formed between the diaper 1 and the wearer's abdominal circumference is provided along the longitudinal direction of the diaper 1 inside the width direction of the diaper 1 and closer to the inside than the elastic members 4SL and 4SR on the cover sheet 4. The elastic member 4C is provided according to the elastic force (contracting force) required in the design of the diaper 1.

[0018]

[0019] ​Further, the elastic member 9ER for forming the waist gather 3R described above is disposed in a waist sheet 9R provided between the back sheet 5 and the top sheet 7 at a position further dorsal than the end of the absorber 6. The waist sheet 9R is disposed at a position on the front end side (the rear end side of the diaper 1) rather than the end on the back waist region 1R side of the absorber 6, away from the absorber 6, and between the top sheet 7 and the back sheet 5, and is a sheet-like member extending wider in the width direction than the absorber 6. The waist sheet 9R is formed by laminating two nonwoven sheets, and the elastic member 9ER is adhered in an extended state in the width direction of the diaper 1 between the two nonwoven sheets. The elastic member 9ER is disposed in the waist sheet 9R with the longitudinal direction, which is the stretching and contracting direction, in the left-right direction of the diaper 1. For this reason, the waist sheet 9R has shrinkability in the width direction of the diaper 1 and functions as a belt-like elastic member together with the elastic member 9ER. When the tapes 2L and 2R provided on both the left and right sides of the waist sheet 9R are adhered to the front patch 2F on the ventral side of the wearer, the elastic member 9ER exerts a contracting force to bring the diaper 1 into close contact with the wearer, preventing a gap from being formed between the diaper 1 and the wearer's abdominal circumference.

[0020] Also, a waist sheet 9F is provided between the back sheet 5 and the top sheet 7 at a position further ventral than the end of the absorber 6. The waist sheet 9F is disposed at a position on the front end side (the front end side of the diaper 1) rather than the end on the front waist region 1F side of the absorber 6, away from the absorber 6, and between the top sheet 7 and the back sheet 5, and is a sheet-like member extending wider in the width direction than the absorber 6. The waist sheet 9F is formed by laminating two nonwoven sheets in the same manner as the waist sheet 9R. Note that no elastic member is disposed in the waist sheet 9F, and thus the waist sheet 9F has no shrinkability. Note that the basis weight of the waist sheets 9F and 9R is 7 to 20 g / m 2 and, as an example, is 15 g / m 2 is.

[0021] In the present application, the state where the sheets overlap is not limited to the form in which the overlapping sheets are in contact with each other entirely, but is a concept including the form in which a part of the sheets overlap. Further, the state where the sheets are adhered to each other is a concept including the form in which another sheet is interposed between the sheets and the sheets are adhered to each other via the other sheet.

[0022] <Absorbent body> Next, the detailed structure of the absorbent body 6 will be described. FIG. 5 is a diagram showing the structure of the absorbent body. As described above, the absorbent body 6 has an absorbent core 6C and a core wrap sheet 6W. The core wrap sheet 6W is a water-permeable sheet having liquid permeability and is an example of the water-permeable sheet in the present disclosure. The core wrap sheet 6W covers the absorbent core 6C to prevent collapse and suppresses the leakage of SAP particles described later. In the example shown in FIG. 5, the core wrap sheet 6W is composed of a separate upper core wrap sheet 6WA that covers the skin side of the absorbent core 6C and a lower core wrap sheet 6WB that covers the non-skin side of the absorbent core 6C. However, the core wrap sheet 6W can also be composed of a single sheet. Since the functions required for the core wrap sheet 6W are different on the skin side and the non-skin side of the absorbent core 6C (specifically, the core wrap sheet on the skin side is required to have a function of quickly passing the inflowing liquid through the absorbent core 6C, and the core wrap sheet on the non-skin side is required to have a function of reinforcing the absorbent core 6C to prevent collapse), it is preferable to configure the core wrap sheet 6W with two sheets, namely the upper core wrap sheet 6WA and the lower core wrap sheet 6WB, as shown in this figure. The upper core wrap sheet 6WA is an example of the first water-permeable sheet in the present disclosure, and the lower core wrap sheet 6WB is an example of the second water-permeable sheet in the present disclosure. is required to have a function of quickly passing the inflowing liquid through the absorbent core 6C, and the core wrap sheet on the non-skin side is required to have a function of reinforcing the absorbent core 6C to prevent collapse), therefore, as shown in this figure, it is preferable to configure the core wrap sheet 6W with two sheets consisting of the upper core wrap sheet 6WA and the lower core wrap sheet 6WB.

[0023] The upper core wrap sheet 6WA and the lower core wrap sheet 6WB may be made of the same material, or different materials may be used according to their respective roles. More specifically, since the upper core wrap sheet 6WA is required to be a sheet that allows the inflowing liquid to easily permeate into the absorption core 6C, for example, a fine fiber air-through nonwoven fabric can be used. Since the lower core wrap sheet 6WB is required to easily maintain the shape of the absorption core 6C against external pressure, for example, tissue paper can be used.

[0024] In this embodiment, the absorption core 6C has a SAP layer composed of SAP particles. The SAP layer contains an absorbent resin such as SAP (Super Absorbent Polymer), which is a hydrophilic polymer having a cross-linked structure capable of absorbing and retaining water. The SAP particles in this embodiment refer to those obtained by granulating a resin composition containing SAP. The "resin composition containing SAP" here is a concept that includes both a composition consisting only of SAP and a composition having SAP as the main component and containing other substances to such an extent that it does not adversely affect water absorption. Examples of the "other substances" include additives (such as surface modifiers added for the purpose of hydrophobizing the particle surface) and unreacted monomers remaining during the synthesis of SAP.

[0025] Among the SAP particles, there are those that are not fixed inside the absorption core 6C. Also, the absorption core 6C does not contain short fibers that would prevent the movement of the SAP particles. The core wrap sheet 6W also has the role of suppressing the collapse of the shape of the absorption core 6C and suppressing the dissipation of the SAP particles.

[0026] The absorbent core 6C includes a sheet-like base layer 6I having liquid permeability. The base layer 6I is a fiber sheet such as, for example, a nonwoven fabric. An upper SAP layer 6A is disposed on the skin side of the base layer 6I, and a lower SAP layer 6B is disposed on the non-skin side of the base layer 6I. The SAP particles constituting the upper SAP layer 6A and the lower SAP layer are formed of the same material by the same manufacturing method and are of the same composition, but their particle sizes are different. The SAP particles constituting the upper SAP layer are larger in particle size than the SAP particles constituting the lower SAP layer. Since the lower SAP layer has SAP particles with a small particle size, the surface area per volume of the SAP particles is larger for the SAP particles constituting the lower SAP layer than for the SAP particles constituting the upper SAP layer. In other words, the value obtained by dividing the average surface area of the SAP particles contained in the upper SAP layer 6A by the average volume is smaller than the value obtained by dividing the average surface area of the SAP particles contained in the lower SAP layer 6B by the average volume. The upper SAP layer is an example of the first SAP layer in the present disclosure, and the lower SAP layer is an example of the second SAP layer in the present disclosure.

[0027] To calculate the surface area per unit, the upper core wrap sheet 6WA and the lower core wrap sheet 6WB are removed from the absorber 6, and the SAP particles are detached from each of the upper SAP layer and the lower SAP layer using an adhesive tape. Next, the SAP particles are measured with a microscope to determine the particle diameter. Since it is difficult to measure the surface area of the SAP particles, the SAP particles are approximated as spheres to calculate the surface area and the volume of the SAP particles. From the calculated volume of the SAP particles, the number of particles per unit volume can be calculated, and from the surface area and the volume of the SAP, the surface area per volume of the SAP can be calculated. These operations are performed multiple times to calculate the average value.

[0028] FIG. 6 is a table in which the particle diameters of SAP particles collected in the upper SAP layer were measured, the SAP particles were approximated as spheres, and the number of particles per unit volume and the surface area per unit volume were calculated. FIG. 7 is a table in which the particle diameters of SAP particles collected in the lower SAP layer were measured, the SAP particles were approximated as spheres, and the number of particles per unit volume and the surface area per unit volume were calculated. In FIGS. 6 and 7, the particle diameters were measured, and the surface areas and volumes were calculated for 30 SAP particles each constituting the upper SAP layer and the lower SAP layer, and the average values of the respective values were obtained.

[0029] It takes a certain amount of time for the moisture reaching the SAP layer to be absorbed by the SAP particles, and the absorption time depends on the surface area of the SAP particles. Since the surface area per unit volume of the SAP particles constituting the lower SAP layer 6B is larger than the surface area per unit volume of the SAP particles constituting the upper SAP layer 6A, the moisture infiltrating into the lower SAP layer is absorbed earlier than the upper SAP layer. The exudate generated from the human body and infiltrating from the skin surface side is not absorbed much by the upper SAP layer 6A and reaches the lower SAP layer 6B, and is preferentially absorbed by the SAP particles with a large surface area arranged in the lower SAP layer 6B. Since the lower SAP layer 6B is far from the skin surface, even if pressure is applied due to a change in body position or the like at the timing after absorption, it is possible to suppress the reverse flow of the exudate to the skin surface side. Therefore, the comfort of the wearer is maintained.

[0030] In addition, when SAP particles come into contact with moisture, they expand and gel. If the gelled SAP particles are disposed in the liquid flow path, a so-called gel blocking phenomenon may occur where the gelled SAP particles block the liquid flow path. In the absorber according to the present embodiment, before the SAP particles disposed in the upper SAP layer 6A absorb moisture, the SAP particles disposed in the lower SAP layer 6B absorb moisture and become more likely to expand. The lower SAP layer 6B is far from the skin surface. Also, even when the SAP particles disposed in the lower SAP layer 6B absorb water and expand to form a gel, the SAP particles disposed in the upper SAP layer 6A closer to the skin surface have not yet expanded. For this reason, a so-called gel blocking phenomenon in which the flow path of the discharged liquid is blocked by the SAP particles disposed in the upper SAP layer 6A is suppressed. Further, since the upper SAP layer 6A starts to absorb water after the lower SAP layer 6B has sufficiently absorbed water, the water absorption capacity of the SAP particles contained in each SAP layer can be utilized to the maximum extent. Thus, the absorbent article having the absorber according to the present embodiment can be worn for a long time.

[0031] The base layer 6I may be composed of natural fibers such as pulp fibers, but is more preferably composed of synthetic fibers made of a thermoplastic resin. For example, when pulp fibers are used as the base layer 6I, since the base layer 6I itself absorbs and retains moisture, the discharged liquid does not flow smoothly down to the lower SAP layer 6B. Since synthetic fibers do not retain moisture as compared with natural fibers, the discharged liquid that flows into the absorber 6, passes through the upper SAP 6A, and reaches the base layer 6I flows smoothly down to the lower SAP layer 6B and is absorbed there, so that the absorption rate can be increased as a whole. The base layer 6I may be composed of, for example, a bulky air-through nonwoven fabric.

[0032] There are two types of SAP particles: substantially spherical non-crushed products (pearl products) and crushed products with complex angles. Either type can be used for the absorber according to this embodiment, but it is more preferable to use crushed products. When a sheet formed of fibers is used as the base layer 6I and crushed products are used as the SAP particles, the SAP particles penetrate into the base layer 6I. In the absorber according to this embodiment, each SAP layer does not contain short fibers or contains less short fibers than before, and the short fibers cannot sufficiently fix the SAP. Instead, by providing a base layer 6I composed of fibers and adopting crushed products as the SAP particles, the position of the SAP can be fixed. Such an absorber 6 is thin because it does not contain short fibers or contains a small amount of short fibers, and is less likely to lose its shape because the SAP particles are fixed. On the other hand, when non-crushed products are used, even if they spill outside the absorber 6, there is an advantage that they are less likely to cause irritation to the wearer's skin surface or other structures.

[0033] Here, the inter-fiber spacing Ra, which is the inter-fiber void size of the base layer 6I, is defined as follows: Let Ta be the thickness (μm) of the sheet, da be the fineness (dtex) of the fibers constituting the sheet, Wa be the basis weight (g / m 2 ) of the sheet, and Da be the average single fiber diameter (μm) of the fibers constituting the sheet. Ra = (100 × Ta × da) / (Wa × Da) - Da ··· Equation (1) The numerical value obtained by this formula is more specifically 380 μm. It is desirable that the inter-fiber void size of the base layer 6I has a range centered around this value, i.e., 330 μm to 390 μm.

[0034] In this embodiment, the average particle size of the SAP particles disposed in the upper SAP layer 6A was 427 μm as shown in FIG. 6. For the upper SAP layer, if the average particle size of the SAP particles is 381 μm to 450 μm or less, the SAP particles can appropriately penetrate into the base layer 6I. In this embodiment, the average particle size of the SAP particles disposed in the lower SAP layer 6B was 308 μm as shown in FIG. 7. For the lower SAP layer, if the average particle size of the SAP particles is 280 μm to 380 μm, the SAP particles can appropriately penetrate into the base layer 6I. Note that the average particle size of the SAP particles disposed in the upper SAP layer 6A may be 350 μm or more and 1000 μm or less. Also, the average particle size of the SAP particles disposed in the lower SAP layer 6B can be 50 μm or more and 350 μm or less.

[0035] Also, the particle size of the SAP particles disposed in the lower SAP layer 6B is smaller than the fiber-to-fiber spacing Ra of the base layer 6I. Therefore, the SAP particles disposed in the lower SAP layer 6B can pass through the base layer 6I. Due to this property, for example, SAP particles having a small particle size that constitute the lower SAP layer 6B are mixed in the upper SAP layer 6A in advance and then placed on the base layer 6I, and by applying pressure thereto, only the SAP particles having a small particle size can be passed through to form the lower SAP layer 6B. Also, in this case, when a crushed type is used as the SAP particles, the SAP particles are entangled with the fibers of the base layer 6I. By being entangled with the fibers of the base layer 6I, the SAP particles are fixed and mold collapse is suppressed.

[0036] FIG. 8 is a cross-sectional view when the center in the width direction of the diaper 1 in the non-worn state is cut along the longitudinal direction. As shown in FIG. 8, the core wrap sheet 6W is non-adhesive on the skin side and the non-skin side at the longitudinal end side of the diaper 1. The reason for this non-adhesion will be described later. Also, the waist sheets 9F, 9R are adhered to the topsheet 7 on the skin side and adhered to the backsheet 5 on the non-skin side. For this adhesion, for example, a hot melt adhesive is used.

[0037] When the absorbent core is formed of pulp, the SAP particles are entangled with the pulp fibers and are difficult to fall off from the absorbent core. However, in the present embodiment, the absorbent core 6C does not contain pulp. In the absorbent body 6 having such a configuration, the SAP particles are not entangled with fibers or the like, and the SAP particles are likely to fall off at the end portions in the width direction and the longitudinal direction of the absorbent body 6.

[0038] In addition, the diaper 1 according to the present embodiment may contain unfixed SAP particles. If no countermeasure is taken for the diaper, these SAP particles may leak to the outside of the diaper. For example, if a gap is formed between the topsheet and the backsheet, the SAP particles that have fallen off from the absorbent body may spread to the end portion side in the longitudinal direction of the diaper and may leak out from between the topsheet and the backsheet.

[0039] Therefore, the diaper 1 according to the present embodiment includes waist sheets 9F and 9R disposed on the end portion side in the longitudinal direction of the absorbent body 6. Further, the topsheet 7 and the backsheet 5 are weakly adhered or non-adhered to each other on the end portion side of the absorbent body 6, that is, between the absorbent body 6 and the waist sheets 9F and 9R. More specifically, in the regions within D1 and D2 shown in FIG. 8, the topsheet 7 The topsheet 7 and the backsheet 5 are weakly adhered or non - adhered. Here, D1 is the distance between the absorber 6 and the waist sheet 9R on the back - body region 1R side. D2 is the distance between the absorber 6 and the waist sheet 9F on the front - body region 1F side. The specific lengths of D1 and D2 are omitted. Here, weak adhesion means an adhesive force that allows the sheets adhered to each other to be peeled off without breaking them, and it is assumed to be an adhesive force that can be naturally peeled off by, for example, the contraction force of the elastic member when the diaper 1 is worn. By making the topsheet 7 and the backsheet 5 non - adhered or weakly adhered in the region within D1 and D2, the SAP particles fall off from the upper - layer SAP layer 6A and the lower - layer SAP layer 6B, enter between the topsheet 7 and the backsheet 5, and peel them off from each other, thereby forming a space (hereinafter, sometimes referred to as the "SAP accommodation space") between the topsheet 7 and the backsheet 5, and the SAP particles can be accommodated in the SAP accommodation space. Also, since the waist sheets 9F and 9R are arranged on the end - side in the longitudinal direction rather than the SAP accommodation space, the movement of the SAP particles to the end - side rather than the waist sheets 9F and 9R is suppressed. Since the waist sheets 9F and 9R are relatively strongly adhered to the topsheet 7 and the backsheet 5, it is possible to prevent the SAP accommodation space from communicating with the outside of the diaper 1 and suppress the leakage of the SAP particles to the outside. Also, since the waist sheets 9F and 9R are wider than the absorber 6, even if the SAP particles that have leaked into the SAP accommodation space move in the width direction, the waist sheets 9F and 9R can suppress the leakage of the SAP particles.

[0040] Also, in the region within D2, when the topsheet 7 and the backsheet 5 are non - adhered, no hot - melt adhesive is applied between the topsheet 7 and the backsheet 5. When the topsheet 7 and the backsheet 5 are weakly adhered, a small amount of hot - melt adhesive is applied between the topsheet 7 and the backsheet 5. Therefore, the region within D2 has relatively low rigidity and is easy to bend. Here, when the hook portions of the tapes 2L and 2R in the worn state of the diaper 1 are adhered to the loop portion of the front patch 2F and the front (ventral) ends of the tapes 2L and 2R and the region within D2 overlap in the thickness direction, the diaper 1 is more likely to bend on the non - skin - side in front of the front end. In this way, the diaper 1 can trap the SAP particles at the bent portion by the topsheet 7 and the backsheet 5 bending on the non - skin - side in the region within D2 in the worn state.

[0041] Also, the waist sheets 9F and 9R have a thickness larger than the average particle diameter of the SAP particles. For example, the average particle diameter of the SAP particles is 350 μm, and the particle diameter is made to be in the range of 150 - 650 μm. The waist sheets 9F and 9R are thicker than the particle diameter of the SAP particles, for example, 0.8 mm or more. Even if the SAP particles move into the SAP accommodation space, since the SAP accommodation space is located between the absorber 6 and the waist sheets 9F and 9R, the thickness of the absorber 6 and the waist sheets 9F and 9R can prevent the SAP particles in the SAP accommodation space from touching the wearer's skin surface through the topsheet 7. Thereby, the diaper 1 can prevent giving the wearer the thickness and foreign - body sensation of the SAP particles that have moved into the SAP accommodation space.

[0042] In addition, when the distances D1 and D2 between the absorber 6 and the waist sheets 9F and 9R are set to 10 mm or less, since the skin surfaces of the wearer's abdomen and back are curved, it is difficult for the skin to touch the topsheet 7 above the SAP accommodation space. In order not to give the wearer a foreign body sensation of SAP on the skin even when body pressure is applied to the diaper 1, the absorber 6 and the waist sheets 9F and 9R preferably have a thickness of 1 mm or more. By setting the absorber 6 and the waist sheets 9F and 9R to a thickness of 1 mm or more, the skin of the wearer comes into contact with the absorber 6 and the waist sheets 9F and 9R, and it is suppressed that the skin of the wearer touches the SAP in the SAP accommodation space. Therefore, the diaper 1 can suppress giving the wearer a discomfort caused by the contact of the SAP particles.

[0043] Also, the distances D1 and D2 in the longitudinal direction of the diaper 1 between the absorber 6 and the waist sheets 9F and 9R are preferably at least twice the average particle diameter of the SAP particles. More preferably, the distances D1 and D2 are at least 10 times the average particle diameter of the SAP particles. When the SAP particles fall off from the upper SAP layer 6A and the lower SAP layer 6B and a SAP accommodation space is formed between the topsheet 7 and the backsheet 5, by setting the distances between the absorber 6 and the waist sheets 9F and 9R as described above, the force with which the topsheet 7 and the backsheet 5 peel off the SAP particles can be prevented from acting on the adhesion between the waist sheets 9F and 9R and the topsheet 7 and the backsheet 5. Therefore, the diaper 1 can prevent the waist sheets 9F and 9R from peeling off from the topsheet 7 and the backsheet 5, and can suppress the leakage of the SAP particles.

[0044] Also, the waist sheet 9F on the front body region 1F side has no shrinkability. Therefore, on the front body region 1F side, since no shrinkage force in the width direction is applied to the core wrap sheet 6W, the core wrap sheet 6W is suppressed from opening in the thickness direction. Further, when a shrinkage force is applied to the absorber 6, the SAP particles are likely to fall off from the upper SAP layer 6A and the lower SAP layer 6B. However, on the front body region 1F side, no shrinkage force is applied to the absorber 6, and the SAP particles are less likely to fall off.

[0045] Note that the crotch region side of the waist sheet 9F and the back sheet 5 may be weakly adhered or non-adhered. Thereby, a housing space for the SAP is also formed between the crotch region side of the waist sheet 9F and the back sheet 5. When the SAP particles are housed in the housing space, the waist sheet 9F is disposed closer to the skin side than the housing space, so that the skin contact (foreign body sensation) of the SAP particles in the housing space can be reduced. Further, as described above, when the top sheet 7 and the back sheet 5 are bent toward the non-skin side in the region within D2 in the worn state, the skin contact of the SAP particles in the housing space can be further reduced.

[0046] Also, as shown in FIG. 4, the leak-proof walls 3BL and 3BR formed by the side sheets 8L and 8R and the elastic members 8EL and 8ER are arranged along the widthwise ends of the top sheet 7 and extend in the longitudinal direction of the diaper 1. The side sheets 8L and 8R are joined to the widthwise end sides of the top sheet 7. A hot melt adhesive is used for this joining. The side sheets 8L and 8R are adhered to the top sheet 7 and the cover sheet 4 outside the width direction from the folding lines 30L and 30R extending in the longitudinal direction, and are not adhered to the top sheet 7 inside the folding lines 30L and 30R. Therefore, in the worn state of the diaper 1, the inner side of the folding lines 30L and 30R of the side sheets 8L and 8R stands up toward the skin side due to the contraction force of the elastic members 8EL and 8ER provided on the side sheets 8L and 8R in a state of being extended in the longitudinal direction of the diaper 1, thereby forming the leak-proof walls 3BL and 3BR.

[0047] When the leak - proof walls 3BL and 3BR stand up, the fixing parts 31L and 31R which are the starting points of this standing in the longitudinal direction are formed. In FIG. 4, the fixing parts 31L and 31R are shown filled in color. The fixing parts 31L and 31R are inside the width direction of the diaper 1 rather than the folding lines 30L and 30R, and are formed on the end side in the longitudinal direction of the absorber 6. The fixing parts 31L and 31R are formed on both sides of the front body region 1F and the rear body region 1R, and each fixing part 31L and 31R is arranged so as to straddle the absorber 6 and the waist sheets 9F and 9R in the thickness direction. The fixing parts 31L and 31R are formed by applying a hot - melt adhesive between the non - skin - contact side of the side sheets 8L and 8R and the top sheet 7. The side sheets 8L and 8R are also fixed to the top sheet 7 by the fixing parts 31L and 31R.

[0048] Here, no non - adhesive regions are provided between the fixing parts 31L and 31R, between the top sheet 7 and the absorber 6, and between the top sheet 7 and the waist sheets 9F and 9R. "Between layers" means between each sheet. On the non - skin - contact side of the fixing parts 31L and 31R, the top sheet 7 is adhered to the absorber 6, and the top sheet 7 is adhered to the waist sheets 9F and 9R. The rigidity of the end side in the longitudinal direction of the absorber 6 is increased by the fixing parts 31L and 31R. Also, since the fixing parts 31L and 31R are arranged across the waist sheet 9F having no shrinkage force, the shrinkage of the absorber 6 on the front body region 1F side is suppressed. Therefore, it is possible to suppress the dropping of the SAP particles from the upper SAP layer 6A and the lower SAP layer 6B on the front side of the absorber 6. Further, even when the fixing parts 31L and 31R are arranged across the waist sheet 9R having shrinkage force, the rigidity of the absorber 6 on the rear body region 1R side can be increased, so that it is possible to suppress the sagging of the end part on the rear side of the absorber 6. In addition, in order to suppress the sagging of the absorber 6, the fixing parts 31L and 31R are preferably formed by overlapping the absorber 6 on the end side in the width direction of the absorber 6.

[0049] Even if the SAP particles leak outside the folding lines 30L and 30R and the SAP particles enter between the side sheets 8L and 8R and the top sheet 7 or the back sheet 5, the SAP can be contained in the SAP accommodation space, and the waist sheets 9F and 9R can prevent the SAP particles from leaking outside.

[0050] FIG. 9 is a diagram showing an overview of the SAP fixation rate test. FIG. 9 is a device for examining how much SAP particles are fixed to the absorber 6. A pole stands vertically from the base 32, and a guide rail 31 with a length of 10 cm is installed vertically above the pole. Inside the guide rail 31, a dropping rod 30 is arranged. When an experimenter lifts the dropping rod 30 to the upper end of the guide rail 31 and releases the hand, the dropping rod 30 freely falls 10 cm along the guide rail 31 and stops at the lower end of the guide rail.

[0051] The absorber 6 cut into two pieces at the central part in the longitudinal direction is arranged on the dropping rod 30. Immediately below the dropping rod 30, an electronic balance 33 for weighing the dropped SAP particles is provided. Among the SAP particles contained in the absorber 6 that are not fixed, they fall from the absorber 6 to the electronic balance 33 due to the impact of the fall. In this state, the dropping operation is repeated 20 times to weigh the non-fixed SAP particles. When the amount of the dropped SAP is DR and the amount of the SAP formulated in the absorber 6 in design is DF, the fixation rate (%) of the SAP can be obtained by the formula (1 - DR / DF) × 100.

[0052] FIG. 10 is a diagram showing another example of the SAP fixation rate test. The overview of the test apparatus and the test method are the same as those shown in FIG. 9. However, in the example shown in FIG. 10, the absorber 6 is arranged in the test apparatus in a state covered with a resin bag 34. The bag 34 is made of polyethylene, for example. In the example shown in FIG. 10, the SAP particles separated from the absorber 6 due to the impact of the fall of the dropping rod 30 accumulate at the bottom of the bag 34 instead of the electronic balance 33. Then, after the completion of 20 dropping operations, the content of the bag 34 is weighed with a separately prepared electronic balance to obtain the amount of the non-fixed SAP particles.

[0053] In the experimental method shown in FIG. 10, the absorber 6 is covered with the bag 34. Although the SAP particles may scatter to places other than under the experimental apparatus due to the impact of falling, covering the absorber 6 with the bag 34 enables the scattered SAP particles to be surely captured, and the amount of SAP particles not fixed to the absorber 6 can be measured more accurately. The content of the calculation formula for the fixing rate (%) of SAP is the same as that described above.

[0054] As a result of this experiment, the fixing rate of the SAP particles was 97%. It can be seen that even in the absorber 6 containing SAP particles at a content ratio that cannot be fixed by the short fibers due to the crushed SAP particles biting into the base layer 6I, the SAP particles can be sufficiently fixed.

[0055] FIG. 11 is a diagram showing a method for manufacturing an absorber according to an embodiment. The manufacturing process proceeds from FIG. 11(A) toward FIG. 11(D). In FIG. 11(A), first, the lower core wrap sheet 6WB, which is a non-skin-side wrap sheet, is arranged, and on the lower core wrap sheet 6WB, the base layer 6I composed of fibers is arranged. This process corresponds to the base layer placement process referred to in the present application. In FIG. 11(B), on the base layer 6I, the upper SAP layer 6A, which is a layer containing SAP particles, is arranged. At this time, the upper SAP layer 6A contains the SAP particles constituting the lower SAP layer 6B. This process corresponds to the SAP placement process referred to in the present application. In FIG. 11(C), on the upper SAP layer 6A, the upper core wrap sheet 6WA, which is a skin-side core wrap sheet, is arranged. This process corresponds to the covering process referred to in the present application. In FIG. 11(D), on the upper core wrap sheet 6WA, a non-woven fabric layer 6C is arranged. This process corresponds to the non-woven fabric layer arrangement process referred to in the present application.

[0056] In Fig. 11(D), for the completed laminate, a press roll is used to press the upper surface of the upper core wrap sheet 6WA and the bottom surface of the lower core wrap sheet 6WB at a predetermined pressure. At this time, among the SAP particles contained in the upper SAP layer 6A, those with a small particle diameter that can pass through the fibers of the base layer 6I pass through the base layer 6I due to the pressing force and form a lower SAP layer 6B between the base layer 6I and the lower core wrap sheet 6WB. This step corresponds to the pressing step referred to in the present application. Fig. 11(E) is a cross-sectional view showing the structure of the absorber 6 manufactured by these steps. By going through such steps, an absorber 6 having an upper SAP layer 6A with a large particle diameter and a lower SAP layer 6B containing SAP particles with a smaller particle diameter than the SAP particles contained in the upper SAP layer can be manufactured.

[0057] Fig. 12 is a view of the pressing step seen from the side. The completed laminate advances toward the press roll R and is pressed by the press roll R. Fig. 12(A) shows a state where the laminate is advancing toward the press roll R. Fig. 12(B) shows a state where the laminate has been pressed by the press roll R and passed through the press roll R. Among the SAP particles contained in the upper SAP layer 6A, those with a small particle diameter that can pass through the fibers of the base layer 6I pass through the base layer 6I due to the pressing of the press roll when passing through the press roll. These SAP particles with a small particle diameter form the lower SAP layer 6B. Note that the pressing does not necessarily have to be performed by a press roll and may be realized by sandwiching with a press plate.

[0058] The fiber interstitial space size of the base layer 6I is 330 μm to 390 μm as described above. When observing the particle diameter of SAP particles suitable for such manufacturing, the average particle diameter was 320 μm to 380 μm. When using SAP particles with such a particle diameter, it can be said that the SAP particles are likely to bite into and be fixed to the base layer, and a part of them is likely to move from the upper SAP layer 6A to the lower SAP layer 6B under the pressure of the press roll.

[0059] Thus, by pressing the laminate to move the SAP particles and forming the lower SAP layer, a complex-structured absorber 6 having a multi-layered SAP layer can be formed by a simple lamination process. By using this lamination process, an absorber 6 capable of suppressing backflow can be manufactured at low cost by providing a lower SAP layer 6B having SAP particles with a smaller particle size than the upper SAP layer 6A.

[0060] Although the embodiments have been described above, the content of the present invention is not limited to the above embodiments. In the above embodiments, as an example of the arrangement of the absorber, a tape-type disposable diaper has been described as an example, but the present invention is not limited to this. The present invention is also applicable to absorbent articles such as absorbent pads and pant-type disposable diapers.

[0061] The features included in each of the embodiments disclosed above can be combined with each other.

Explanation of Reference Numerals

[0062] 1 ·· Diaper 1B ·· Inseam Region 1F ·· Front Body Region 1R ·· Back Body Region 2L, 2R ·· Elastic Body 3BL, 3BR ·· Leak-Proof Wall 4 ·· Cover Sheet 5 ·· Back Sheet 6 ·· Absorber 6A ·· Upper SAP Layer 6B ·· Lower SAP Layer 6C ·· Absorbing Core 6W ·· Core Wrap Sheet 6WA ·· Upper Core Wrap Sheet 6WB ·· Lower Core Wrap Sheet 7 ·· Top Sheet 8L, 8R ·· Side Sheet 30 ·· Movable Bar 31 ·· Guide Rail 32 ·· Test Bench 33 ·· Electronic Balance 34 ·· Bag SAP··SAP

Claims

1. A base layer placement step of placing a base layer composed of fibers on a second water-permeable sheet covering the non-skin side of the absorber; A SAP placement step of placing a layer containing SAP particles, which are superabsorbent polymers, on the base layer; A covering step of placing a first water-permeable sheet covering the skin side of the absorber on the SAP particles; A pressing step of applying pressure between the second water-permeable sheet and the first water-permeable sheet; A method for manufacturing an absorber, comprising:

2. The base layer is a fiber sheet with an inter-fiber void size of 330 μm to 390 μm; The average particle size of the SAP particles is 320 μm to 380 μm; The method for manufacturing an absorber according to Claim 1.

3. The SAP particles are of a crushed type; The method for manufacturing an absorber according to Claim 2.

4. An absorption core including, in order from the skin side, a first SAP layer containing SAP particles, a sheet-like base layer having liquid permeability, and a second SAP layer containing SAP particles with a large value obtained by dividing the average surface area of the SAP particles contained in the first SAP layer by the average volume; A water-permeable sheet having liquid permeability, covering the skin side and the non-skin side of the absorption core; An absorber comprising:

5. The SAP particles constituting the first SAP layer and the SAP particles constituting the second SAP layer are formed of the same material by the same manufacturing method and are of the same composition; The absorber according to Claim 4.

6. The SAP particles contained in the first SAP layer and the second SAP layer are of a crushed type; The base layer is a fiber sheet; The absorber according to Claim 5.

7. The inter-fiber void size of the base layer is 330 μm to 390 μm; The average particle size of the SAP particles contained in the first SAP layer is 381 μm to 450 μm; The average particle size of the SAP particles contained in the second SAP layer is 280 μm to 380 μm; The absorber according to any one of Claims 4 to 6.

8. The base layer is formed of synthetic fibers; The absorber according to any one of Claims 4 to 6.

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