Absorber and method for producing absorber

Abstract

To provide an absorber that rapidly absorbs moisture and prevents the reverse flow of the absorbed moisture.SOLUTION: An absorber comprises: an absorbent core which comprises, in order from the skin-facing side, a first SAP layer containing SAP particles composed of superabsorbent polymers, a sheet-like base layer having liquid permeability, and a second SAP layer containing SAP particles having a high value that is calculated by dividing the average surface area by the average volume of the SAP particles included in the first SAP layer; and a liquid-permeable core wrap sheet that covers the skin-facing side and the non-skin-facing side of the absorbent core.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to an absorber and a method for manufacturing the 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] An absorbent article has an absorber and absorbs liquid generated from the human body. The absorbed liquid is retained in the absorber, but the once-absorbed liquid may flow back due to strong pressure or the like. The flowing-back liquid gives discomfort to the wearer.

[0005] An object of the present invention is to provide an absorber that is less likely to cause backflow.

Means for Solving the Problems

[0006] An absorber according to one aspect of the present invention includes an absorption core including, in order from the skin side, a first SAP layer containing SAP particles that are superabsorbent polymers, a sheet-like base layer having liquid permeability, and a second SAP layer containing SAP particles having a large value obtained by dividing the average surface area of the SAP particles contained in the first SAP layer by the average volume; and a liquid-permeable core wrap sheet covering the skin side and the non-skin side of the absorption core.

Effects of the Invention

[0007] According to the present invention, it is possible to provide an absorber that is less likely to cause backflow.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

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 this embodiment, for a tape-type disposable diaper (an example of an "absorbent article" in the present application, hereinafter simply referred to as "diaper"), the direction connecting the front body portion disposed facing the abdomen of the wearer and the back body portion disposed facing 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 (opposite to the crotch) under the crotch of the wearer. Further, in the state where the diaper is worn by the wearer (hereinafter abbreviated as "worn state"), the side facing the wearer's skin (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 corresponding to 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 corresponding to 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 corresponding to the front and rear of the wearer in the state where the diaper 1 is worn by the wearer.

[0011] FIG. 1 is a perspective view of a diaper according to this 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 has a crotch region 1B which is a portion corresponding to the crotch covering the genitals of the wearer in the worn state, a front body region 1F located on the front side of the crotch region 1B and corresponding to the front body portion of the wearer, and a back body region 1R located on the rear side of the crotch region 1B and corresponding to the back body portion 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 back body region 1R. When the tapes 2L and 2R are attached to the front patch 2F with the front body region 1F disposed on the abdominal side of the wearer and the back body region 1R disposed on the back 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] In the diaper 1, an absorber capable of absorbing and holding liquid is mainly disposed around the crotch region 1B. Further, in the diaper 1, leg gathers 3AL and 3AR are provided at a portion surrounding the wearer's leg (thigh portion) to suppress the formation of a gap serving as a liquid outflow path between the diaper 1 and the wearer's skin. Three-dimensional gathers 3BL and 3BR are provided inside the diaper 1 in the width direction relative to the leg gathers 3AL and 3AR, and a waist gather 3R is provided at a portion surrounding the wearer's abdominal circumference. The leg gathers 3AL and 3AR, the three-dimensional gathers 3BL and 3BR, and the waist gather 3R are in close contact with the wearer's skin by the contraction force (elastic force) of the elastic member. Therefore, the liquid discharged from the wearer's genitals is absorbed by the absorber of the diaper 1 without leaking from the diaper 1. As the elastic member, filamentous rubber (rubber thread), belt-like 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 when cut along the center in the longitudinal direction along the width direction. FIG. 4 is a plan view of the diaper 1 in the extended state as viewed from the skin side. In FIG. 4, the illustration of the elastic members 4C, 4SL, and 4SR is omitted. The diaper 1 has a cover sheet 4 that forms an outer surface in the worn state. The cover sheet 4 is a sheet-like member having a substantially rectangular appearance with constrictions 4KL and 4KR provided at portions corresponding to the long sides, and forms the exterior surface of the diaper 1. The constrictions 4KL and 4KR are provided at portions where the wearer's thighs are located (the leg surrounding regions 10L and 10R shown in FIG. 4). It is provided. 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 its 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 outer surface in which the front body region 1F, the crotch region 1B, and the back body region 1R are continuously provided.

[0014] And the diaper 1 has a back sheet 5 (an example of the "non-skin side sheet" of the present disclosure), an absorber 6, and a top sheet 7 (an example of the "skin side sheet" of the present disclosure), which are sequentially laminated on the skin side of the cover sheet 4. The back sheet 5, the absorber 6, and the top sheet 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 back sheet 5 is a sheet formed of a water-impermeable thermoplastic resin as a material, like the cover sheet 4. The back sheet 5 is preferably composed of a material having moisture permeability in order to suppress sweating in the worn state. Further, the top sheet 7 is a sheet-like member disposed on the skin side of the wearer. The top sheet 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 top sheet 7 that can contact 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 top sheet 7. The top sheet 7 may have hydrophilicity. Note that the basis weight of the top sheet 7 is, for example, 16~35g / m 2 It is. The top sheet 7 may have intermittent squeezing grooves. By providing the squeezing grooves, the granular feeling of the content 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 in which the backsheet 5, the absorber 6, and the topsheet 7 are laminated, both longitudinal ends 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 by the absorber 6 from the ventral side to the dorsal side of the wearer. Therefore, no matter whether the wearer discharges liquid out of the body in a posture with the abdomen facing downward or a posture with the back facing downward, the discharged liquid will contact 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 both ends of the front crotch region 1F and the rear crotch region 1R of the diaper 1.

[0016] In addition, 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 backsheet 5. The elastic members 4SL and 4SR are provided in an appropriate number (three in the present 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 surrounding regions which are the parts where the thighs of the wearer are located at both ends in the width direction of the under crotch region 1B. The leg surrounding regions 10L and 10R are arranged at both ends in the width direction of the under crotch region 1B. Further, the leg gathers 3AL and 3AR are formed in the arrangement regions of the elastic members 4SL and 4SR.

[0017] In addition, the diaper 1 has elongated strip-shaped side sheets 8L and 8R (a pair of leak-proof sheets). The side sheets 8L and 8R are sheets having non-water permeability (liquid impermeability) provided at the long side portions of the topsheet 7. The side sheets 8L and 8R are provided with constrictions 8KL and 8KR at the parts where the thighs of the wearer are located (the leg surrounding regions 10L and 10R shown in FIG. 4), similar to the cover sheet 4. And elastic members 8EL and 8ER for forming three-dimensional gathers 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 drawn longitudinally by the contracting force of the elastic members 8EL and 8ER and rise from the top sheet 7 to form three-dimensional gathers 3BL and 3BR that prevent the outflow of liquid.

[0018] In addition, the 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 rather than the elastic members 4SL and 4SR. The elastic member 4C is provided according to the elastic force (contracting force) required in the design of the diaper 1 and the like.

[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 of the absorber 6 on the back waist region 1R side, 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 non-woven fabric sheets, and the elastic member 9ER is adhered in an extended state in the width direction of the diaper 1 between the two non-woven fabric sheets. The elastic member 9ER is disposed in the waist sheet 9R with the longitudinal direction in the stretching and contracting direction being 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 make the diaper 1 adhere to the wearer and prevent 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 body region 1F side of the absorber 6, closer to the front end side of the diaper 1 (front end 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 non-woven fabric sheets, similar to the waist sheet 9R. Note that no elastic member is disposed on the waist sheet 9F, and thus the waist sheet 9F has no shrinkability. 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 .

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

[0022] <Absorber> Next, the detailed structure of the absorber 6 will be described. FIG. 5 is a diagram showing the structure of the absorber. As described above, the absorber 6 has an absorption core 6C and a core wrap sheet 6W. The core wrap sheet 6W is a water-permeable sheet. The core wrap sheet 6W covers the absorption core 6C to prevent it from collapsing and suppresses the leakage of SAP particles, which will be 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 absorption core 6C and a lower core wrap sheet 6WB that covers the non-skin side of the absorption 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 absorption core 6C (specifically, the core wrap sheet on the skin side is required to have a function of quickly passing the inflowing liquid to the absorption core 6C, and the core wrap sheet on the non-skin side is required to have a function of reinforcing the absorption core 6C to prevent it from collapsing), as shown in this figure, the core wrap sheet 6W is preferably composed of two sheets, namely 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 roles. 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" as used herein is a concept encompassing 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, those not fixed inside the absorption core 6C are included. Also, the absorption core 6C does not contain short fibers that would prevent the movement of the SAP particles. The core wrap sheet 6W has the role of suppressing the collapse of the absorption core 6C and suppressing the dissipation of the SAP particles.

[0026] The absorption core 6C includes a sheet-like base layer 6I having liquid permeability. The base layer 6I is a fiber sheet such as a non-woven fabric, for example. 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 is arranged with SAP particles having a small particle size, the surface area per volume of the SAP particles is larger in the lower SAP layer than in 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 size. 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 of the SAP particles 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 volume of the SAP, the surface area per unit volume of the SAP can be calculated. These operations are performed multiple times to calculate the average value.

[0028] Figure 6 is a table in which the particle size of the SAP particles collected in the upper SAP layer is measured, and the SAP particles are approximated as spheres to calculate the number of particles per unit volume and the surface area per unit volume. Figure 7 is a table in which the particle size of the SAP particles collected in the lower SAP layer is measured, and the SAP particles are approximated as spheres to calculate the number of particles per unit volume and the surface area per unit volume. In Figures 6 and 7, the particle size is measured and the surface area and volume are calculated for 30 SAP particles each that make up the upper SAP layer and the lower SAP layer, and the average value of each value is obtained.

[0029] Although it takes a certain amount of time for the moisture that reaches the SAP layer to be absorbed by the SAP particles, the absorption time depends on the surface area of the SAP particles. Since the surface area per unit volume of the SAP particles that make up the lower SAP layer 6B is larger than the surface area per unit volume of the SAP particles that make up the upper SAP layer 6A, the moisture that has penetrated into the lower SAP layer is absorbed earlier than the upper SAP layer. The excreted fluid generated from the human body and penetrating 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 excreted fluid from flowing back to the skin surface side. Therefore, the comfort of the wearer is maintained.

[0030] Further, when the SAP particles come into contact with moisture, they expand and gel. If the gelled SAP particles are arranged 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 arranged in the upper SAP layer 6A absorb moisture, the SAP particles arranged in the lower SAP layer 6B absorb moisture and are more likely to expand. The lower SAP layer 6B is far from the skin surface. Also, even when the SAP particles arranged in the lower SAP layer 6B absorb water, expand, and gel, the SAP particles arranged in the upper SAP layer 6A closer to the skin surface have not yet expanded. Therefore, a so-called gel blocking phenomenon in which the flow path of the discharged liquid is blocked by the SAP particles arranged 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, if 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 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 to the lower SAP layer 6B and is absorbed there, so that the overall absorption rate can be increased. The base layer 6I may be composed of, for example, a bulky air-through nonwoven fabric.

[0032] There are approximately spherical non-crushed products (pearl products) and crushed products with complex corners in the SAP particles. Either of them can be used for the absorber according to this embodiment, but it is more preferable to use the 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 the amount of short fibers contained is less than that in the prior art, and the SAP cannot be sufficiently fixed by the short fibers. Instead, by providing the 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 out of the absorber 6 by any chance, 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. In the case of Ra = (100 × Ta × da) / (Wa × Da) - Da ··· Equation (1) The numerical value obtained by this formula is more specifically 380 μm. It can be said that it is desirable for the inter-fiber void size of the base layer to have a range from this numerical value, and be 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.

[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 with a small particle size that form 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 with a small particle size can be passed through to form the lower SAP layer 6B. Also, at this time, if a crushed type is used as the SAP particles, the SAP particles are entangled with the fibers of the base layer 6I. By entangling 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 and 9R are adhered to the top sheet 7 on the skin side and adhered to the back sheet 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 fibers of the pulp 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 absorber 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 absorber 6.

[0038] Further, the diaper 1 according to the present embodiment may contain unfixed SAP particles. If no measures are 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 absorber may spread to the end portions 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 portions in the longitudinal direction of the absorber 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 absorber 6, that is, between the absorber 6 and the waist sheets 9F and 9R. More specifically, in the regions within D1 and D2 shown in FIG. 8, the topsheet 7 and the backsheet 5 are weakly adhered or non-adhered. Note that D1 is the distance between the absorber 6 and the waist sheet 9R on the rear waist region 1R side. D2 is the distance between the absorber 6 and the waist sheet 9F on the front waist region 1F side. The specific lengths of D1 and D2 are omitted. Here, the weak adhesion means an adhesive force that allows the sheets adhered to each other to be peeled off without breaking them, and is an adhesive force assumed to be naturally peeled off by, for example, the contraction force of the elastic member when the diaper 1 is worn. In the regions within D1 and D2, the topsheet By making the topsheet 7 and the backsheet 5 non - adherent or weakly adherent, the SAP particles fall off from the upper SAP layer 6A and the lower 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, 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, 9R is suppressed. Since the waist sheets 9F, 9R and the topsheet 7 and the backsheet 5 are relatively strongly adhered, 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, 9R are wider than the absorber 6, even if the SAP particles leaked into the SAP accommodation space move in the width direction, the waist sheets 9F, 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 - adherent, no hot - melt adhesive is applied between the topsheet 7 and the backsheet 5, and when the topsheet 7 and the backsheet 5 are weakly adherent, 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 easily bent. Here, when the hook portions of the tapes 2L, 2R in the worn state of the diaper 1 are adhered to the loop portion of the front patch 2F and the front (ventral) end portions of the tapes 2L, 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 portion. In this way, the diaper 1 can block the SAP particles at this 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 greater than the average particle size of the SAP particles. For example, the average particle size of the SAP particles is 350 μm, and the particle size is set to be 150 to 650 μm. The waist sheets 9F and 9R are thicker than the particle size of the SAP particles, for example, 0.8 mm or more. Even if the SAP particles move to 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 to the SAP accommodation space.

[0042] Also, when each distance D1 and D2 between the absorber 6 and the waist sheets 9F and 9R is 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 on the SAP accommodation space. In order not to give the wearer a foreign body sensation of SAP even when body pressure is applied to the diaper 1, it is preferable that the absorber 6 and the waist sheets 9F and 9R 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 wearer's skin is made to contact the absorber 6 and the waist sheets 9F and 9R, and the wearer's skin is suppressed from touching 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, each distance D1 and D2 in the longitudinal direction of the diaper 1 between the absorber 6 and the waist sheets 9F and 9R is preferably at least twice the average particle size of the SAP particles. More preferably, each distance D1 and D2 is at least ten times the average particle size 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 each distance between the absorber 6 and the waist sheets 9F and 9R as described above, the force for the SAP particles to peel off the topsheet 7 and the backsheet 5 It can prevent the action on the adhesion of the waist sheets 9F, 9R to the top sheet 7 and the back sheet 5. Therefore, the diaper 1 can prevent the waist sheets 9F, 9R from peeling off from the top sheet 7 and the back sheet 5, and can suppress the leakage of the SAP particles.

[0044] Further, the waist sheet 9F on the front body region 1F side does not have shrinkability. For this reason, 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 layer SAP layer 6A and the lower layer 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 SAP accommodation space is also formed between the crotch region side of the waist sheet 9F and the back sheet 5. When the SAP particles are accommodated in the accommodation space, since the waist sheet 9F is arranged closer to the skin side than the accommodation space, the skin contact (foreign body sensation) of the SAP particles in the accommodation space can be reduced. Also, as described above, when the top sheet 7 and the back sheet 5 are bent to the non - skin side in the region within D2 in the worn state, the skin contact of the SAP particles in the accommodation space can be further reduced.

[0046] Also, as shown in FIG. 4, the three-dimensional gathers 3BL and 3BR formed by the side sheets 8L and 8R and the stretch 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 fold lines 30L and 30R extending in the longitudinal direction, and are not adhered to the top sheet 7 inside the fold lines 30L and 30R. Therefore, in the worn state of the diaper 1, the inside of the side sheets 8L and 8R from the fold lines 30L and 30R stands up on the skin side due to the contraction force of the stretch members 8EL and 8ER provided on the side sheets 8L and 8R in the extended state in the longitudinal direction of the diaper 1, and thereby the three-dimensional gathers 3BL and 3BR are formed.

[0047] When the three-dimensional gathers 3BL and 3BR stand up, fixing portions 31L and 31R serving as the longitudinal starting points of this standing are formed. In FIG. 4, the fixing portions 31L and 31R are shown filled in. The fixing portions 31L and 31R are inside the width direction of the diaper 1 from the fold lines 30L and 30R and are formed on the longitudinal end sides of the absorber 6. The fixing portions 31L and 31R are formed on both sides of the front body region 1F and the back body region 1R, and each fixing portion 31L and 31R is arranged to straddle the absorber 6 and the waist sheets 9F and 9R in the thickness direction. The fixing portions 31L and 31R are formed by applying a hot melt adhesive between the non-skin sides 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 portions 31L and 31R.

[0048] Here, non - adhesive regions are not 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" refers to between each sheet. On the non - skin - contact side of the fixing parts 31L and 31R, the top sheet 7 and the absorber 6, and the top sheet 7 and the waist sheets 9F and 9R are adhered. 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, shrinkage of the absorber 6 on the front - body region 1F side is suppressed. Therefore, on the front side of the absorber 6, it is possible to suppress the dropping of the SAP particles from the lower SAP layer 60B and the upper SAP layer 60D. Also even if the fixing parts 31L and 31R are arranged across the waist sheet 9R having shrinkage force, the rigidity of the absorber 6 on the back - body region 1R side can be increased. Therefore, it is possible to suppress the sagging of the end part on the back side of the absorber 6. Note that 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 in order to suppress the sagging of the absorber 6.

[0049] Also, even when 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, this SAP can be accommodated in the SAP accommodation space, and leakage of the SAP particles to the outside can be suppressed by the waist sheets 9F and 9R.

[0050] Figure 9 is a diagram showing an overview of the SAP fixation rate test. Figure 9 is a device for examining the degree to which 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] In the dropping rod 30, the absorber 6 cut into two at the central portion in the longitudinal direction is arranged. 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 dropping. 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 fixing rate (%) of the SAP can be obtained by the formula (1 - DR / DF)×100.

[0052] Figure 10 is a diagram showing another example of the SAP fixing rate test. The outline of the test apparatus and the test method are the same as those shown in Figure 9. However, in the example shown in Figure 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 Figure 9, the SAP particles separated from the absorber 6 due to the impact of the dropping of the dropping rod 30 accumulate at the bottom of the bag 34 instead of the electronic balance 33. Then, after the completion of the 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 Figure 10, the absorber 6 is covered with the bag 34. Although the SAP particles may scatter to places other than below the experimental apparatus due to the impact of dropping, by covering the absorber 6 with the bag 34, the scattered SAP particles can be surely captured, and the amount of the non-fixed SAP particles in the absorber 6 can be measured more accurately. The content of the calculation formula for the fixing rate (%) of the SAP is the same as that described above.

[0054] As a result of this experiment, the fixing rate of the SAP particles was 96%. It can be seen that even in the absorber 6 containing the SAP particles with 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) to FIG. 11(D). In FIG. 11(A), first, a lower core wrap sheet 6WB, which is a non-skin-side core wrap sheet, is disposed, and a base layer 6I composed of fibers is disposed on the lower core wrap sheet 6WB. This step corresponds to the base layer placement step referred to in the present application. In FIG. 11(B), an upper SAP layer 6A is disposed on the base layer 6I. At this time, the upper SAP layer 6A contains SAP particles that constitute the lower SAP layer 6B. This step corresponds to the SAP placement step referred to in the present application. In FIG. 11(C), an upper core wrap sheet 6WA, which is a skin-side core wrap sheet, is disposed on the upper SAP layer 6A. This step corresponds to the covering step referred to in the present application.

[0056] In FIG. 11(D), the upper surface of the upper core wrap sheet 6WA and the bottom surface of the lower core wrap sheet 6WB are pressed against the completed laminate using a press roll. At this time, among the SAP particles contained in the upper SAP layer 6A, those having a small particle diameter and capable of passing through the fibers of the base layer 6I pass through the base layer 6I by 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 pressurization 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, it becomes possible to manufacture an absorber 6 having an upper SAP layer 6A with a large particle diameter and a lower SAP layer 6B containing SAP particles having a smaller particle diameter than the SAP particles contained in the upper SAP layer.

[0057] Figure 12 is a view of the pressing process as seen from the side. The completed laminate advances toward the press roll R and is pressed by the press roll R. Figure 12(A) shows the state where the laminate is advancing toward the press roll R. Figure 12(B) shows the state where the laminate is pressed by the press roll R and has 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 between press plates.

[0058] The fiber interstice 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 production, 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 penetrate and be fixed in 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] Although the embodiments have been described above, the content of the present invention is not limited to the above embodiments. In the above embodiments, the tape-type disposable diaper has been described as an example, but the present invention is not limited thereto, and the present invention is also applicable to absorbent articles such as absorbent pads and pant-type disposable diapers.

[0060] The features included in each of the embodiments disclosed above can be combined with each other.

Explanation of Reference Numerals

[0061] 1 ·· Diaper 1B ·· Inseam region 1F ·· Front body region 1R ·· Back body region 2L, 2R ·· Elastic body 3BL, 3BR ·· Elastic body 3L, 3R ·· Three-dimensional gathers 4. Cover Sheet 5. Back Sheet 6. Absorbent 6A. Upper SAP Layer 6B. Lower SAP Layer 6C. Absorbent 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 first SAP layer containing SAP particles, which are superabsorbent polymers, in order from the skin side, a sheet-like base layer having liquid permeability, and a second SAP layer containing SAP particles having a large value obtained by dividing the average surface area of the SAP particles contained in the first SAP layer by the average volume, and an absorption core; A core wrap sheet having liquid permeability and covering the skin side and the non-skin side of the absorption core; An absorber comprising:

2. 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 the same components. The absorber according to claim 1.

3. 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 2.

4. 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 1 to 3.

5. The base layer is formed of synthetic fibers. The absorber according to any one of claims 1 to 3.

6. A base layer placement step of placing a base layer composed of fibers on a non-skin side core wrap sheet covering the non-skin side of the absorber; A SAP placement step of placing SAP particles on the base layer; A covering step of placing a skin side core wrap sheet covering the skin side of the absorber on the SAP particles; A pressing step of applying pressure between the non-skin side core wrap sheet and the skin side core wrap sheet; A method for manufacturing an absorber, comprising:

7. The base layer is a fiber sheet having 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 6.

8. The SAP particles are of a crushed type. The method for manufacturing an absorber according to claim 7.

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