Pants-type disposable diapers

Abstract

We provide a pull-up style disposable diaper that maintains absorbency while improving the recyclability of the plastic, resulting in superior material recycling. [Solution] This disclosure provides a pant-type disposable diaper comprising an outer casing made of laminated nonwoven fabric and an absorbent body 30 disposed on the skin side of the outer casing, wherein the absorbent body 30 has a liquid-permeable top sheet 31, a liquid-impermeable back sheet 32, and an absorbent material 33 disposed between the top sheet 31 and the back sheet 32, the absorbent material 33 containing a superabsorbent polymer, the proportion of the superabsorbent polymer in the absorbent material 33 being 60% by weight or more and 100% by weight or less.

Description

Technical Field

[0001] The present disclosure relates to disposable diapers.

Background Art

[0002] Patent Document 1 discloses a disposable diaper. In this disposable diaper, two folding lines that extend in the longitudinal direction and are spaced apart in the width direction are formed in an absorber disposed within the crotch region of the disposable diaper, and a plurality of squeezing lines that extend in the width direction and are spaced apart in the longitudinal direction are formed within a predetermined region of the absorber. The predetermined region includes the folding lines and is a region that extends in the width direction from one side edge of the absorber to the other side edge. The angle formed by the center line in the width direction within the squeezing lines and the width direction is configured to fall within the range of 0° to 45°, and two adjacent squeezing lines in the longitudinal direction are configured to approach each other at a predetermined location.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, currently, used disposable diapers are collected as combustible waste by each local government and incinerated in an incinerator, or are landfilled as they are in local governments without an incinerator. Incinerating disposable diapers containing a large amount of moisture requires a lot of energy and cost. In addition, there is a limit to the area of land for landfilling.

[0005] Disposable diapers for adults tend to increase year by year due to the aging of the population, and the development of disposable diapers that are easy to recycle (environmentally friendly) is desired. Until now, thermal recycling has been the mainstream of recycling, and there are few materials that have been recycled materially.

[0006] Disposable diapers use a variety of materials, including elastic threads, absorbent material, nonwoven fabric, and tissue, and hot melt adhesive is used to bond these materials together. Currently, the absorbent material in pull-up style disposable diapers is mainly made of SAP / fluff pulp. When adult pull-up style disposable diapers are separated using a separation processing system as a means of recycling, they are larger than children's disposable diapers and tend to get tangled during decomposition, making it difficult to separate the plastic from the pulp. In addition, if a large amount of absorbent pulp remains in the recovered plastic, it negatively impacts material recycling.

[0007] Therefore, this disclosure aims to provide a pant-type disposable diaper that is superior in material recycling, by improving the recyclability of the plastic while maintaining absorption performance. [Means for solving the problem]

[0008] The inventor diligently conducted research to solve the above problems. Upon separating existing pull-up diapers using a separation system, the inventor found that the plastic fluidity (MFR), necessary for injection molding—one method of recycling recovered plastic—was poor. Therefore, the inventor created two types of pull-up diapers: one with a reduced amount of fluff pulp in the SAP / fluff pulp ratio compared to existing pull-up diapers, and another with only SAP absorbent material (no fluff pulp). These were separated using a separation system, and the MFR of the recovered plastic was evaluated. The results showed that the MFR value of the recovered plastic from the pull-up diaper without fluff pulp was high, and that the MFR decreased as the fluff pulp content increased. Thus, through diligent research, the inventor discovered that for the recycling of pull-up diapers, the ratio of SAP that maintains the absorbency of the absorbent material while maintaining the fluidity of the recovered plastic is crucial, leading to the completion of the present invention. In other words, the present invention provides the following:

[0009] A first aspect of the present invention is a pant-type disposable diaper comprising an outer casing made of laminated nonwoven fabrics and an absorbent body disposed on the skin-facing side of the outer casing, wherein the absorbent body has a liquid-permeable top sheet, a liquid-impermeable back sheet, and an absorbent material disposed between the top sheet and the back sheet, the absorbent material containing a superabsorbent polymer, and the proportion of the superabsorbent polymer in the absorbent material is 60% by weight or more and 100% by weight or less.

[0010] A second aspect of the present invention is a pant-type disposable diaper according to the first aspect, wherein the absorbent material is located in the center in the width direction and has a slit extending along the longitudinal direction.

[0011] A third aspect of the present invention is a pant-type disposable diaper according to the first or second aspect, wherein the absorbent body has a liquid-permeable liquid-diffusing sheet disposed between the top sheet and the absorbent body. [Effects of the Invention]

[0012] According to this disclosure, it is possible to provide a pant-type disposable diaper that maintains absorbency while improving the recyclability of the plastic, resulting in superior material recycling. [Brief explanation of the drawing]

[0013] [Figure 1] This is a front view perspective of a pull-up type disposable diaper according to one embodiment of the present invention. [Figure 2] Figure 1 is a plan view from the skin side showing the unfolded state of the pull-up style disposable diaper. [Figure 3] This is a plan view of the absorbent material from the skin side. [Figure 4] This is a cross-sectional view taken along the line VI-VI in Figure 3. [Figure 5] This is an explanatory diagram of a rotary drum device used for recycling. [Figure 6] This figure shows a test apparatus for evaluating absorption performance. [Modes for carrying out the invention]

[0014] The following describes a pant-type disposable diaper according to one embodiment of the present invention, with reference to the drawings.

[0015] Figure 1 is a front perspective view of a pull-up type disposable diaper according to one embodiment of the present invention. Figure 2 is a plan view from the skin side showing the pull-up type disposable diaper of Figure 1 in an unfolded state. Figure 3 is a plan view from the skin side of the absorbent main body. Figure 4 is a cross-sectional view taken along the line VI-VI in Figure 3. Note that Figure 3 shows a schematic cross-section. Furthermore, each figure does not specify the relative sizes of the components of the pull-up type disposable diaper, and the dimensions of each component can be appropriately selected from a wide range depending on the intended use of the pull-up type disposable diaper, the age of the wearer, etc.

[0016] In this specification, wearing a pull-up diaper means the state in which the pull-up diaper is attached to the body, regardless of whether it is before, during, or after the absorption of bodily fluids. Furthermore, "front" means the direction that is the wearer's abdomen when the pull-up diaper is worn, and "back" means the direction that is the wearer's back. Furthermore, "top" means the direction that is the wearer's head when the pull-up diaper is worn, and "bottom" means the direction that is the wearer's feet. Furthermore, the left and right directions mean the left and right directions as viewed from the wearer when facing forward. Furthermore, the longitudinal direction of each component of the pull-up diaper means the longitudinal direction (direction along the front and back) when the pull-up diaper is unfolded (as shown in Figure 2), and is the direction along arrow X in each figure. Furthermore, the width direction of each component of the pull-up diaper means the direction perpendicular to the longitudinal direction (direction along the left and right) when the pull-up diaper is unfolded, and is the direction along arrow Y in each figure. Furthermore, the thickness direction of each component of a pull-up type disposable diaper refers to the direction in which each component is stacked, and is the direction along the arrow Z in each diagram. Also, the skin side of each component of a pull-up type disposable diaper refers to the direction of the thickness direction toward the wearer's skin when the pull-up type disposable diaper is worn, and the non-skin side refers to the direction of the thickness direction opposite to the skin side. Furthermore, body fluids refer to liquids that are expelled from the body to the outside, such as urine, blood, and water in loose stools.

[0017] <Pants-shaped disposable diaper> As shown in FIGS. 1 and 2, the pants-shaped disposable diaper 10 according to the present embodiment is a pants-shaped disposable diaper 10 that can be washed, separated, and recycled after use, and includes an exterior body 20 that constitutes the outer shape of the pants-shaped disposable diaper 10, and an absorbent body 30 that is supported by the exterior body 20 and mainly absorbs body fluids.

[0018] <Exterior body> As shown in FIGS. 1 and 2, the exterior body 20 is a member that constitutes the outer shape of the pants-shaped disposable diaper 10, and has a front torso region 21 located in front of the wearer's abdomen when worn, a rear torso region 22 located behind the wearer's back, and a crotch region 23 located under the wearer's crotch. The absorbent body 30 is mainly disposed on the inner surface side (skin side) of the crotch region 23 of the exterior body 20, but a part (front and rear ends) thereof may extend to the front torso region 21 or the rear torso region 22 of the exterior body 20.

[0019] The exterior body 20 is formed by laminating a plurality of non-woven fabric sheets (non-woven fabrics) 24. The non-woven fabric sheet 24 can be a non-woven fabric such as a thermal bond non-woven fabric, an air-through non-woven fabric, or a spunbond non-woven fabric, preferably an air-through non-woven fabric or a spunbond non-woven fabric, and made of a thermoplastic resin such as polypropylene, polyester, or polyethylene. The number of non-woven fabric sheets 24 laminated is not particularly limited as long as it is two or more.

[0020] As shown in Fig. 2, the exterior body 20 in the unfolded state has a bilaterally symmetric shape. The front torso region 21 and the rear torso region 22 each have side seal portions 25 extending along the longitudinal direction at both ends in the width direction. The front torso region 21 and the rear torso region 22 are arranged at positions spaced apart from each other in the longitudinal direction. The crotch region 23 is a region located between the front torso region 21 and the rear torso region 22. By fixing both ends in the width direction of the front torso region 21 and both ends in the width direction of the rear torso region 22 to each other by the side seal portions 25, as shown in Fig. 1, the exterior body 20 is formed in a panty shape as a whole, with both left and right ends of the front torso region 21 and both left and right ends of the rear torso region 22 being continuous.

[0021] <Absorbent body> As shown in Figs. 2 to 4, the absorbent body 30 has a liquid-permeable topsheet 31 on the skin side, a liquid-impermeable backsheet 32 on the non-skin side, and an absorber 33 disposed between the topsheet 31 and the backsheet 32. Further, the absorbent body 30 of the present embodiment has absorbent paper 34 and a liquid diffusion sheet 35. Note that the absorbent body 30 may have other configurations (for example, three-dimensional gathers on the left and right, etc.) in addition to these.

[0022] As shown in Fig. 2, the absorbent body 30 is disposed on the skin side surface of the main crotch region 23 of the exterior body 20 so as to extend from the front torso region 21 toward the rear torso region 22. The absorbent body 30 is adhered to the skin side surface of the exterior body 20 by a hot melt adhesive.

[0023] (Topsheet) The top sheet 31 is formed from a substrate that has liquid permeability to allow bodily fluids to move to the absorbent material 33. Examples of substrates include nonwoven fabrics such as thermal bond nonwoven fabric, composite nonwoven fabrics formed by laminating thermal bond nonwoven fabric / spunbond nonwoven fabric, open films such as open polyethylene film, foamed films such as polyethylene foam and urethane foam, or composite sheets formed by laminating these. The top sheet 31 may be embossed or perforated on its surface to improve liquid permeability. Any known method can be used to perform these embossing or perforating processes without limitation. In addition, to reduce skin irritation, the top sheet 31 may contain lotions, antioxidants, anti-inflammatory components, pH adjusters, antibacterial agents, moisturizers, etc. The shape of the top sheet 31 is not particularly limited, but it should be a shape that covers the absorbent material 33 in order to guide bodily fluids to the absorbent material 33 without leakage.

[0024] (Back seat) The backsheet 32 ​​is formed using a liquid-impermeable substrate so as to prevent leakage of bodily fluids held by the absorbent 33 to the non-skin side, and is formed from materials such as a resin film or a composite sheet formed by laminating a resin film and a nonwoven fabric. The nonwoven fabric used in the composite sheet is not particularly limited in its manufacturing method and can include, for example, spunbond nonwoven fabric, meltblown nonwoven fabric, spunbond nonwoven fabric / meltblown nonwoven fabric, spunbond nonwoven fabric / meltblown nonwoven fabric / spunbond nonwoven fabric, and composite nonwoven fabrics and composite materials thereof, which are formed by laminating multiple identical and / or different types of nonwoven fabrics. The resin film can be, for example, polyester, polyvinyl alcohol, polyethylene, polypropylene, or a composite film of polyethylene and polypropylene.

[0025] The back sheet 32 ​​is preferably made breathable to prevent stuffiness during wear. To make the back sheet 32 ​​breathable, for example, a filler can be compounded into the resin film of the base material, or the back sheet 32 ​​can be embossed. Calcium carbonate can be used as a filler, and the compounding method can be any known method without limitation. For example, a porous (breathable) resin film can be obtained by kneading a resin and a filler, forming the resulting mixture into a film, and then removing the filler from the resulting film.

[0026] (Absorbent) The absorbent body 33 of this embodiment includes a superabsorbent polymer (hereinafter referred to as "SAP") as a body fluid absorbent material. The absorbent body 33 may also include absorbent fibers as a base material and SAP held by the absorbent fibers. Examples of materials containing absorbent fibers and SAP include those formed by mixing SAP particles into absorbent fibers, or SAP sheets in which SAP particles are fixed between the fibers of the napped portion of the absorbent fibers.

[0027] The absorbent body 33 in this embodiment is a two-layered absorbent body having an upper absorbent body 33a and a lower absorbent body 33b. An intermediate sheet 36 is placed between the upper absorbent body 33a and the lower absorbent body 33b. Although the absorbent body 33 in this embodiment is a two-layered absorbent body having an upper absorbent body 33a and a lower absorbent body 33b, it is not limited to this and may be a single-layered absorbent body 33.

[0028] (Upper absorber) The upper absorbent layer 33a is composed of pulp fibers as a base material and SAP. The pulp fibers are not particularly limited as long as they are generally used in absorbent articles such as sanitary napkins, diapers, and urine absorbent pads, and can be formed from materials such as fluff pulp, cotton, rayon, acetate, tissue, absorbent paper, and hydrophilic nonwoven fabric. Among these, fluff pulp is preferred from the viewpoint of absorbency. Examples of such fluff pulp include wood pulp and non-wood pulp such as synthetic fibers and polymer fibers that have been defibrated into a cotton-like form.

[0029] The SAP contained in the upper absorbent layer 33a is not particularly limited as long as it can absorb body fluids and prevent backflow, and is formed from materials such as sodium polyacrylate, polyaspartic acid, (starch-acrylic acid) graft copolymer, (acrylic acid-vinyl alcohol) copolymer, (isobutylene-maleic anhydride) copolymer and its saponified products. Among these, sodium polyacrylate is preferred from the viewpoint of absorption per unit weight.

[0030] (Lower layer absorber) The lower absorbent layer 33b contains only SAP. The SAP contained in the lower absorbent layer 33b is not particularly limited as long as it can absorb body fluids and prevent backflow, and is formed from materials such as sodium polyacrylate, polyaspartic acid, (starch-acrylic acid) graft copolymer, (acrylic acid-vinyl alcohol) copolymer, (isobutylene-maleic anhydride) copolymer and its saponified product. Among these, sodium polyacrylate is preferred from the viewpoint of absorption per unit weight. The SAP constituting the lower absorbent layer 33b may be held by being adhered to, for example, the absorbent paper 34 or intermediate sheet 36 described later.

[0031] The proportion of SAP in the absorbent material 33 (upper absorbent material 33a and lower absorbent material 33b in this embodiment) is 60% by weight or more and 100% by weight or less. If the proportion of SAP in the absorbent material 33 is less than 60% by weight, the value of the melt mass flow rate (hereinafter referred to as "MFR") of the plastic, which is generally required for injection molding, will decrease, and the recyclability of the plastic will decrease.

[0032] (slit) The absorbent material 33 preferably has a slit 37 positioned in the center in the width direction and extending along the longitudinal direction. If the absorbent material 33 is made only of SAP, as in the lower absorbent material 33b of this embodiment, the absorption rate tends to be slow. However, by providing the slit 37, the diffusivity during urine absorption can be improved, and the absorption rate can be maintained.

[0033] In this embodiment, the slit 37 is positioned in the center of the width direction of both the upper absorbent layer 33a and the lower absorbent layer 33b and extends along the longitudinal direction. The slit 37 penetrates both the upper absorbent layer 33a and the lower absorbent layer 33b in the thickness direction. The slits 37 in both the upper absorbent layer 33a and the lower absorbent layer 33b are positioned to overlap each other in the thickness direction, defining the space where no absorbent layer 33 exists. By having these slits 37, bodily fluids can quickly flow to the underside of the upper absorbent layer 33a and the upper and lower sides of the lower absorbent layer 33b, resulting in a high water absorption rate.

[0034] (Intermediate sheet) The intermediate sheet 36 is a liquid-permeable sheet used to interpose between the upper absorbent layer 33a and the lower absorbent layer 33b. This intermediate sheet 36 can quickly diffuse bodily fluids that cannot be absorbed by the upper absorbent layer 33a to the lower absorbent layer 33b. The base material of the intermediate sheet 36 can be any material that is hydrophilic, such as tissue, absorbent paper, or hydrophilic nonwoven fabric. Among these, a material with less pulp is preferable from the viewpoint of recyclability, so a hydrophilic nonwoven fabric is preferable to tissue, and an air-through nonwoven fabric is preferable from the viewpoint of absorbency and wearing comfort.

[0035] (Absorbent paper) The absorbent paper 34 encloses the entire absorbent body 33 to prevent SAP particles from falling off and to stabilize the shape of the absorbent body 33. The base material of the absorbent paper 34 should be hydrophilic, have a faster rate of permeation of bodily fluids than the top sheet 31, and allow bodily fluids to quickly diffuse into the absorbent body 33. Examples of absorbent paper 34 include tissue, absorbent paper, and hydrophilic nonwoven fabric. Among these, a lower pulp content is preferable from the viewpoint of recyclability, so hydrophilic nonwoven fabric is preferable to tissue, and air-through nonwoven fabric is preferable from the viewpoint of absorbency and wearing comfort.

[0036] (Liquid diffusion sheet) The absorbent body 30 preferably has a liquid-permeable liquid diffusion sheet 35 placed between the top sheet 31 and the absorbent body 33. The liquid diffusion sheet 35 is a liquid-permeable sheet for diffusing bodily fluids from the top sheet 31 side and guiding them to the absorbent body 33 side. Examples of the liquid diffusion sheet 35 include nonwoven fabrics such as air-through nonwoven fabric, point-bonded nonwoven fabric, spunbond nonwoven fabric, and melt-blown nonwoven fabric, as well as composite nonwoven fabrics made by laminating spunbond / melt-blown or spunbond / melt-blown / spunbond. Among these, air-through nonwoven fabric is preferred from the viewpoint of absorbency and wearing comfort. The shape of the liquid diffusion sheet 35 is not particularly limited, but in order to suitably diffuse liquid from the top sheet 31 side to the absorbent body 33, it is preferable that the shape completely covers the surface of the absorbent body 33, or, in order to reduce costs, it is preferable that the shape covers a part of the surface of the absorbent body 33 but does not completely cover it.

[0037] (Recycling process) Next, we will explain the recycling process for used pull-up style disposable diapers 10. Figure 5 is an explanatory diagram of the rotary drum device used for recycling.

[0038] In this embodiment, the recycling of used pull-up style disposable diapers 10 is carried out using an agitator, for example, a rotary drum device 100. This rotary drum device 100 is applicable to various sanitary products having a synthetic resin film portion and an absorbent portion attached to the film portion, such as urine absorption pads.

[0039] As shown in Figure 5, the rotary drum device 100 includes a cylindrical water tank 102 as a water tank section located within the casing 101, a rotary drum 103 located within the water tank 102, and a motor 104 for rotating the rotary drum 103. Numerous small holes are provided on the circumferential surface of the rotary drum 103. Blades for tearing various bags may be installed on the inner circumferential surface of the rotary drum 103.

[0040] An opening 105 is provided on one end face of the casing 101, and an openable door 106 that can open and close the opening 105 is attached to the casing 101. The water tank 102 and the rotating drum 103 are arranged with their cylindrical axis in the horizontal direction (or diagonal direction, with the opening 105 side being higher).

[0041] The water tank 102 and motor 104 are supported by the casing 101 by support members (not shown). The rotating drum 103 is connected to the motor 104 by a shaft 107. The shaft 107 is supported by the water tank 102 by bearings (not shown).

[0042] A water supply pipe 108 for supplying clean water such as tap water is connected to the top of the water tank 102. A drain pit 109 is provided at the bottom of the water tank 102, and a drain pipe 110 is connected to the drain pit 109. A drain valve 111 and a drain pump 112 are provided on the drain pipe 110. By closing the drain valve 111, water can be stored in the water tank 102, and by opening it, water can be drained from the water tank 102.

[0043] When processing used pull-up style disposable diapers 10 using this rotary drum device 100, the door 106 is opened, the used pull-up style disposable diapers 10 and processing chemicals are placed into the rotary drum 103, and then the door 106 is closed. After supplying a predetermined amount of water to the water tank 102 from the water supply pipe 108, the rotary drum 103 is rotated by the motor 104. This processes the used pull-up style disposable diapers 10. The motor 104 may rotate in only one direction, or it may rotate back and forth (forward and reverse).

[0044] After a predetermined time (for example, 0.01 hours to 5 hours, especially 0.08 hours to 2 hours) has elapsed and the processing is sufficiently completed, the drain valve 111 is opened to drain the water. At this time, the motor 104 may be used to rotate the rotating drum 103 at high speed, and the water may be dewatered by centrifugal force.

[0045] Afterward, if necessary, water may be poured into the water tank 102 from the water supply pipe 108 to rinse out any residue in the rotating drum 103. This rinsing may be done by pouring water in or by rinsing in a basin.

[0046] After rinsing is complete, open door 106 to remove the contents (recycled plastic) and send it to the next processing step.

[0047] Furthermore, a hot air drying mechanism may be provided, similar to a rotary drum washing machine, in which case the contents can be dried after rinsing. Alternatively, the temperature of the hot air may be increased to heat-sterilize the contents.

[0048] As described above, when recycling the pull-up type disposable diaper 10 according to this embodiment, the used pull-up type disposable diaper 10, a chemical for treating the moisture absorbent, and water are put into a rotary drum device 100, and the used pull-up type disposable diaper 10 is sterilized, decomposed, and separated.

[0049] The chemical used to treat the moisture absorbent contains components that remove moisture (dehydrate) from the superabsorbent polymer (SAP) contained in the pull-up type disposable diaper 10. These components preferably include cations (sodium, calcium, magnesium), organic acids (citric acid, oxalic acid), and inorganic acids (nitric acid, sulfuric acid, hydrochloric acid). Slaked lime and calcium chloride can be used as calcium sources. The chemical may also contain disinfectant components for sterilization. There are no particular restrictions on the disinfectant components, but inexpensive options include calcium hypochlorite (bleaching powder).

[0050] Although the present invention has been described above based on the above embodiments, the present invention is not limited to the contents of the above embodiments, and can naturally be modified as appropriate without departing from the present invention. In other words, all other embodiments, examples, and operational techniques made by those skilled in the art based on these embodiments are of course included in the scope of the present invention. [Examples]

[0051] The present invention will be described in more detail below with reference to examples and comparative examples. However, the present invention is not limited in any way by the following examples.

[0052] (Examples 1-4 and Comparative Examples 1-4) Under the conditions shown in Table 1, each of the pull-up style disposable diapers for Examples 1-4 and Comparative Examples 1-4 was manufactured. The absorbent material of each pull-up style disposable diaper consisted of two layers (upper absorbent layer and lower absorbent layer), similar to the embodiments described above. The upper absorbent layer was composed solely of fluff pulp. The lower absorbent layer was composed solely of SAP. The following three evaluations were then performed on each pull-up style disposable diaper: evaluation of "absorbent performance," evaluation of "total absorbency," and evaluation of "plastic recyclability."

[0053] (Absorption performance) The "absorption performance" evaluation is based on the results of measuring the absorption rate of each type of pull-up diaper.

[0054] The absorption rate of pull-up style disposable diapers is measured as follows. Figure 6 shows a test apparatus for evaluating absorption performance.

[0055] As shown in Figure 6, a jig (hereinafter referred to as the "absorption rate jig") 200 is used as a test apparatus for measuring the absorption rate. The absorption rate jig 200 has an acrylic plate 201, a cylindrical part for water injection 202, and two weights 203. The acrylic plate 201 is 100 mm x 140 mm in size and has a through hole (not shown) with a diameter of 35 mm in the center. The cylindrical part for water injection 202 is a cylindrical body with an inner diameter of 35 mm and an outer diameter of 40 mm, and is fixed to the upper surface of the acrylic plate 201 with its inner diameter communicating with the through hole in the acrylic plate 201.

[0056] To measure the absorption rate of a pull-up type disposable diaper, first, unfold the pull-up type disposable diaper (indicated as A in the figure) and lay it flat on a horizontal, smooth surface, then fix it in place. Place the acrylic plate 201 of the absorption rate jig 200 on top of the absorbent body (not shown). At this time, the through-hole of the acrylic plate 201 should be positioned in the center of the absorbent body. Next, two weights 203 weighing 687g each are placed symmetrically on the acrylic plate 201, sandwiching the water injection cylindrical part 202 in the longitudinal direction. Then, 150ml of physiological saline solution is injected from the upper end into the inner diameter of the water injection cylindrical part 202, and the time until it is completely absorbed is measured as the absorption rate. The physiological saline solution should be adjusted to a concentration of 0.9% and at 36±3℃.

[0057] The "absorption performance" will be evaluated based on the absorption rate of each pull-up type disposable diaper measured as described above, according to the following criteria. ×: Absorption rate of 45 seconds or more △: Absorption rate less than 35-45 seconds ○: Absorption rate less than 25-35 seconds ◎: Absorption rate less than 25 seconds

[0058] (Total absorption) The evaluation of "total absorption" is based on the results measured using the following method. To measure "total absorption," first prepare an electronic top-loading balance (accuracy: ±0.1 digits), a stopwatch (accuracy: ±0.0008%), a container (e.g., a bucket; capacity: 20 liters), a wire mesh, and physiological saline solution (concentration: 0.9%) as a total absorption measurement jig.

[0059] Next, measure the weight (A(g)) of the pull-up diaper (sample) using an electronic balance, and cut open both sides of the pull-up diaper with scissors. Next, pour saline solution into a container and immerse the sample in the saline solution for 5 minutes (measured with a stopwatch). Next, gently lift the waist openings on both sides of the pull-up diaper with both hands, and gently place it on a wire mesh with the top sheet facing downwards (towards the wire mesh). Leave it for 30 seconds (measured with a stopwatch) to drain the water. Next, place the drained sample into the container that has been tared, and measure its weight (B(g)) using an electronic balance. Finally, subtract weight A(g) from weight B(g) to find the "total absorbency (g)".

[0060] (Plastic recyclability) The evaluation of "plastic recyclability" is based on the MFR value measured using the contents (recovered plastic) extracted from each pull-up type disposable diaper (size L) after recycling using a rotary drum device (agitator). The MFR value is measured in accordance with the JIS standard (JIS K 7210: Method A).

[0061] The rotary drum device (agitator) had the following configuration: Aquarium diameter: 180cm Tank length: 120cm Rotating drum diameter: 160cm Rotating drum length: 110cm Diameter of the small hole in the rotating drum: 0.7 cm Axial direction of the tank and rotating drum: horizontal

[0062] The recycling process involves first placing disposable diapers and chemicals (15,000g of slaked lime and 800g of calcium hypochlorite) into the rotating drum of a rotary drum device, then adding 800L of tap water to fill it. The drum is then rotated at 30 rpm, with the rotation direction switched every 120 seconds. After rotation begins, steam is injected to raise the water temperature to 80°C, and the rotating mixing process is carried out. After 0.5 hours (30 minutes), the drum is stopped, the water is drained, and the drum is rotated at 300 rpm for 4 minutes to dewater. After stopping the drum, 800L of tap water is added and the drum is filled and rinsed for 15 minutes, after which the same draining and dewatering process is carried out as described above. Finally, the contents (recovered plastic) are removed.

[0063] The evaluation of "plastic recyclability" is based on the MFR value measured as described above, and is evaluated according to the following criteria as an assessment of the fluidity required for injection molding. ×: MFR value less than 15g / 10min ○: MFR value is 15g / 10min or higher and less than 25g / 10min ◎: MFR value of 25g / 10min or higher

[0064] The results obtained are shown in Table 1.

[0065] [Table 1]

[0066] As shown in Table 1, it has been confirmed that, according to this disclosure, it is possible to provide a pant-type disposable diaper that is excellent in material recycling, with improved plastic recyclability while maintaining absorbency. [Explanation of symbols]

[0067] 10: Pull-up style disposable diapers 20: Exterior 24: Nonwoven fabric sheet (nonwoven fabric) 30: Absorbent body 31: Top sheet 32: Back seat 33: Absorbent material 35: Liquid diffusion sheet 37: Slit

Claims

1. A pant-type disposable diaper comprising an outer casing made of laminated nonwoven fabric and an absorbent body positioned on the skin-facing side of the outer casing, The absorbent body comprises a liquid-permeable top sheet, a liquid-impermeable back sheet, and an absorbent material disposed between the top sheet and the back sheet. The absorbent material comprises a superabsorbent polymer, The proportion of the superabsorbent polymer in the absorbent material is 60% by weight or more and 100% by weight or less. A pant-type disposable diaper characterized by the following features.

2. The absorbent body has a slit located in the center in the width direction and extending along the longitudinal direction. The pant-type disposable diaper according to feature 1.

3. The absorbent body has a liquid-permeable liquid diffusion sheet disposed between the top sheet and the absorbent material. A pant-type disposable diaper according to claim 1 or 2.

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