JP2024063697A - Disposable diapers - Google Patents

Abstract

[Problem] To provide a paper diaper that can be efficiently recycled for materials after use. [Solution] The paper diaper 10 according to the present disclosure is a paper diaper 10 that can be washed, separated and recycled after use, and includes an exterior body 30 that forms the outer shape of the paper diaper 10 when worn, an absorbent body supported by the exterior body 30, and a plurality of elastic members 50 that impart stretchability, the plurality of elastic members 50 including elastic members 24b, 35 that are a plurality of short elastic members each having a length of 100 mm to 200 mm in a non-stretched state, the hot melt adhesive used in the paper diaper 10 includes a low softening point hot melt adhesive with a softening point of 60°C to 90°C, and the absorbent body includes a biodegradable highly absorbent polymer that is a biodegradable highly absorbent polymer. [Selected Figure] Figure 2

Description

This disclosure relates to disposable diapers.

Patent Document 1 discloses a pants-type absorbent article. The outer body of this pants-type absorbent article has a plurality of elastic members for forming waist gathers arranged in a transversely stretchable manner in the portions corresponding to the ventral side and dorsal side (waist region, iliac region, and waist region). The plurality of elastic members are fixed by adhesive between the outer layer sheet and the inner layer sheet constituting the outer body so as to be transversely stretchable, and are arranged intermittently in the vertical direction.

JP 2022-048114 A

The amount of disposable diapers used and discarded is increasing year by year as society ages. Currently, most used disposable diapers are incinerated, with some being recycled. Most of the recycled diapers are thermally recycled after being processed into RPF (Refuse derived paper and plastics densified Fuel) and the like, with only a small amount being material recycled.

In general, when recycling used paper diapers, waste is removed from the paper diapers by stirring them in water, and the constituent materials of the paper diapers are separated and washed to recover reusable raw materials. However, when stirring the paper diapers in water, the elastic material (especially the thread-like elastic material) used to give the paper diapers elasticity occasionally becomes entangled in the stirrer, drainage pump, etc. (hereinafter referred to as "stirrer, etc."), which makes it necessary to stop the stirrer, etc. and remove the entangled elastic material from the stirrer, etc., which is inefficient. In addition, the hot melt adhesive that bonds the constituent materials of the paper diapers together is difficult to peel off in water or warm water, making it difficult to separate the constituent materials. In addition, it is difficult to completely remove the superabsorbent polymer that is mixed into the absorbent body of the paper diaper from the wastewater, and the superabsorbent polymer may remain in the wastewater, which may have an adverse effect on the environment. These factors are factors that reduce the efficiency of material recycling of used paper diapers and are one of the reasons why the amount of material recycled is low.

Therefore, the purpose of this disclosure is to provide disposable diapers that can be efficiently recycled after use.

In order to solve the above problems, the first aspect of the present invention is a paper diaper that can be washed and separated after use and recycled, comprising an exterior body that forms the outer shape of the paper diaper when worn, an absorbent body supported by the exterior body, and a plurality of elastic members that impart stretchability, the plurality of elastic members including a plurality of short elastic members each having a length of 100 mm to 200 mm in a non-stretched state, the hot melt adhesive used in the paper diaper including a low softening point hot melt adhesive having a softening point of 60°C to 90°C, and the absorbent body including a biodegradable highly absorbent polymer that is a biodegradable highly absorbent polymer.

This disclosure makes it possible to efficiently recycle materials from used disposable diapers.

1 is a front external perspective view of a disposable diaper according to an embodiment of the present invention; FIG. 2 is a plan view of the disposable diaper of FIG. 1 in an unfolded state, as viewed from the skin side. 3 is a schematic cross-sectional view taken along line III-III of FIG. 2. FIG. 2 is an explanatory diagram of a rotary drum device used in the recycling process.

Below, we will explain a disposable diaper 10 according to one embodiment of the present invention with reference to the drawings.

Figure 1 is a front perspective view of the appearance of a disposable diaper according to one embodiment of the present invention. Figure 2 is a plan view of the disposable diaper of Figure 1 when unfolded, as seen from the skin side. Figure 3 is a schematic cross-sectional view taken along the line III-III of Figure 2. Note that each figure does not stipulate the relative sizes of the components of the disposable diaper 10, and the dimensions of each component can be appropriately selected from a wide range depending on the intended use of the disposable diaper 10, the age of the intended wearer, etc.

In this specification, wearing the paper diaper 10 means the state in which the paper diaper 10 is worn on the body, regardless of whether the body fluid is absorbed before, during, or after absorption. The paper diaper 10 is usually worn on the body inside clothing, but it may be worn on the body so that at least a part of it is exposed to the outside. The "front side" means the direction that is the wearer's stomach side when the paper diaper 10 is worn, and the "rear side" means the direction that is the wearer's back side. The "upper side" means the direction that is the wearer's head side when the paper diaper 10 is worn, and the "lower side" means the direction that is the wearer's foot side. The left-right direction means the left-right direction as seen from a wearer facing forward. The longitudinal direction of each component of the paper diaper 10 means the longitudinal direction (direction along the front and back) when the paper diaper 10 is unfolded (as shown in FIG. 2), and is the direction along the arrow X in FIG. 2. The width direction of each component of the disposable diaper 10 refers to the direction perpendicular to the longitudinal direction of the disposable diaper 10 when it is unfolded (the direction along the left and right), and is the direction along the arrow Y in FIG. 2. The thickness direction of each component of the disposable diaper 10 refers to the direction in which each component is stacked, and is the direction along the arrow Z in FIG. 3. The skin side of each component of the disposable diaper 10 refers to the direction in the thickness direction that faces the skin of the wearer when the disposable diaper 10 is worn, and the non-skin side refers to the direction opposite the skin side in the thickness direction. Body fluids refer to liquids discharged from the body to the outside, such as urine, blood, and water in loose stools.

[Disposable diapers]
1 to 3, the disposable diaper 10 according to this embodiment includes an absorbent main body 20 that extends in a generally band-like shape in the front-to-rear direction below the crotch area of the wearer to absorb bodily fluids, an exterior body 30 that supports the absorbent main body 20, and a plurality of elastic members 50 that impart stretchability to the disposable diaper 10. The exterior body 30 constitutes the outer shape of the disposable diaper 10 when worn. Note that in this embodiment, a pants-type disposable diaper 10 will be described as an example of a disposable diaper, but the disposable diaper is not limited to the pants-type, and may be, for example, a tape-fastened disposable diaper provided with fastening tapes and target tapes on the left and right sides.

The multiple elastic members 50 used in the disposable diaper 10 include the elastic member 24b used in the absorbent body 20 and the elastic member 35 used in the outer body 30. Details of the elastic members 24b and 35 will be described later. Note that the multiple elastic members 50 used in the disposable diaper 10 may include, in addition to the elastic members 24b and 35, other elastic members that impart stretchability to the disposable diaper 10.

The outer body 30 has a front waist region 31 located in front of the wearer's abdomen when worn, a rear waist region 32 located behind the wearer's back, and a crotch region 33 located between the wearer's legs. The absorbent body 20 is mainly disposed on the inner side of the crotch region 33 of the outer body 30, but a part of it (front and rear ends) may extend to the front waist region 31 or the rear waist region 32 of the outer body 30.

[Absorbent body]
The absorbent body 20 has a liquid-permeable top sheet 21 on the skin side, a liquid-impermeable back sheet 22 on the non-skin side, and an absorbent body 23 arranged between the top sheet 21 and the back sheet 22. Furthermore, the absorbent body 20 of this embodiment has three-dimensional gathers 24. The absorbent body 20 is arranged on the skin side mainly in the crotch region 33 of the exterior body 30 so as to extend from the front waist region 31 toward the rear waist region 32. The absorbent body 20 is fixed to the exterior body 30 by hot melt adhesive, heat fusion, ultrasonic bonding, or the like.

(Top sheet)
The top sheet 21 may be formed from a substrate having liquid permeability such that bodily fluids move to the absorbent 23. Examples of substrates include nonwoven fabrics such as thermal bonded nonwoven fabrics, composite nonwoven fabrics in which thermal bonded nonwoven fabrics/spunbonded nonwoven fabrics are laminated, perforated films such as perforated polyethylene films, foamed films such as polyethylene foams and urethane foams, or composite sheets in which these are laminated. The top sheet 21 may be embossed or perforated on the surface in order to improve liquid permeability. As a method for performing these embossing and perforation processes, known methods can be performed without limitation. In addition, in order to reduce irritation to the skin, the top sheet 21 may contain lotion, antioxidant, anti-inflammatory component, pH adjuster, antibacterial agent, moisturizer, etc. From the viewpoint of strength and processability, the basis weight of the top sheet 21 is preferably, for example, 18 g/m ² or more and 100 g/m ² or less. The shape of the top sheet 21 is not particularly limited, but may be any shape that covers the absorbent body 23 so as to guide bodily fluids to the absorbent body 23 without leakage.

(Back seat)
The back sheet 22 may be formed using a liquid-impermeable substrate so that the body fluid held by the absorbent 23 does not leak to the non-skin side, and is formed from a material such as a resin film or a composite sheet in which a resin film and a nonwoven fabric are laminated. The nonwoven fabric used in the composite sheet is not particularly limited in its manufacturing method, and examples thereof include composite nonwoven fabrics in which multiple nonwoven fabrics of the same type and/or different types are laminated, such as spunbond nonwoven fabric, meltblown nonwoven fabric, spunbond nonwoven fabric/meltblown nonwoven fabric, spunbond nonwoven fabric/meltblown nonwoven fabric/spunbond nonwoven fabric, and composite materials thereof. Examples of the resin film include polyester, polyvinyl alcohol, polyethylene, polypropylene, and composite films of polyethylene and polypropylene.

From the viewpoint of strength and processability, the basis weight of the back sheet 22 is preferably 15 g/m ² or more and 40 g/m ² or less. In addition, in order to prevent stuffiness during wearing, it is preferable that the back sheet 22 has breathability. In order to provide the back sheet 22 with breathability, for example, a filler may be blended into the resin film of the base material, or the back sheet 22 may be embossed. In addition, an example of the filler is calcium carbonate, and the blending method thereof may be any known method without any restrictions. For example, a porous (breathable) resin film can be obtained by kneading a resin and a filler, forming the resulting kneaded product into a film, and removing the filler from the resulting film.

(Absorber)
The absorbent body 23 includes a body fluid absorbing material, and preferably includes absorbent fibers as a base material and a body fluid absorbing material held by the absorbent fibers.

The absorbent fiber as the base material of the absorbent body 23 is not particularly limited as long as it is generally used in absorbent articles such as sanitary napkins, diapers, and urine pads, and is formed from materials such as fluff pulp, cotton, rayon, acetate, tissue, absorbent paper, and hydrophilic nonwoven fabric. Among these, fluff pulp is preferably used from the viewpoint of absorbency. Examples of fluff pulp include wood pulp, synthetic fiber, polymer fiber, non-wood pulp, etc., which are defibrated into a cotton-like state. In addition, the basis weight of the absorbent fiber of the absorbent body 23 is preferably 100 g/m ² or more and 500 g/m ² or less from the viewpoint of recycling. If the basis weight of the absorbent fiber of the absorbent body 23 is greater than 500 g/m ² , it is not preferable because the labor (time, cost) required for the separation process of the absorbent fiber may be large.

The body fluid absorbing material of the absorber 23 is not particularly limited as long as it absorbs and retains body fluids, and examples thereof include super absorbent polymers (SAPs). From the viewpoint of recycling, the basis weight of the super absorbent polymer is preferably 30 g/ ^m2 or more and 300 g/ ^m2 or less. If the basis weight of the super absorbent polymer is more than 300 g/ ^m2 , the labor (time, cost) required for the separation and processing of the super absorbent polymer may become large, which is not preferable.

The absorbent 23 preferably contains absorbent fibers and a superabsorbent polymer, and examples of its configuration include those formed by mixing SAP particles into absorbent fibers, and SAP sheets in which SAP particles are fixed between the fibers of the napped parts of absorbent fibers. From the viewpoint of preventing the SAP particles from falling off and stabilizing the shape of the absorbent 23, it is preferable to wrap the absorbent 23 in a carrier sheet. Also, the superabsorbent polymer may be formed into a fibrous form and mixed with the absorbent fibers as a base material. The base material of the carrier sheet may be any material that has hydrophilicity, and examples of the base material of the carrier sheet include hydrophilic nonwoven fabrics such as tissue, absorbent paper, and airlaid nonwoven fabrics. When the absorbent 23 has multiple carrier sheets, the base materials of the carrier sheets may be the same or different.

Superabsorbent polymers are capable of absorbing bodily fluids and preventing backflow. From the perspective of material recycling, the superabsorbent polymers used in the disposable diaper 10 include starch-based, cellulose-based, amino acid-based, and other biodegradable superabsorbent polymers (hereinafter sometimes referred to as "biodegradable superabsorbent polymers"). Biodegradability refers to the property of a substance being decomposed by the action of living organisms such as microorganisms, and is sometimes also called biodegradability. In other words, biodegradable superabsorbent polymers are superabsorbent polymers that have the property of being decomposed by microorganisms in soil or water.

The total weight of the biodegradable superabsorbent polymer contained in the absorbent body 23 is preferably 80% or more and 100% or less of the total weight of all superabsorbent polymers (including biodegradable superabsorbent polymers) used in the disposable diaper 10, and is most preferably 100%. In other words, the ratio of the total weight of the biodegradable superabsorbent polymers to the total weight of all superabsorbent polymers used in the disposable diaper 10 is preferably 80% or more and 100% or less, and is most preferably 100%. By setting the total weight of the biodegradable superabsorbent polymer contained in the absorbent body 23 within the above range, the impact on the environment can be greatly reduced even if superabsorbent polymer remains in the wastewater when the disposable diaper 10 is stirred with a stirrer during recycling.

(3D gathers)
The three-dimensional gathers 24 are provided, for example, to prevent side leakage of bodily fluids. The three-dimensional gathers 24 of this embodiment include a three-dimensional gather sheet 24a and a thread-like elastic member (short elastic member) 24b. For example, various nonwoven fabrics can be used for the three-dimensional gather sheet 24a. One end side of the three-dimensional gather sheet 24a in the width direction is fixed along the longitudinal direction near both ends in the width direction of the skin side of the back sheet 22, the middle part in the width direction is fixed along the longitudinal direction near both ends in the width direction of the skin side of the top sheet 21, and the other end side in the width direction is a free end. For the thread-like elastic member 24b, for example, a thread-like elastic member such as natural rubber, synthetic rubber, polyurethane, etc. can be appropriately used. The thread-like elastic member 24b is arranged along the longitudinal direction near the other end (free end) in the width direction of the three-dimensional gather sheet 24a, and gives stretchability and standing ability to the other end (free end) of the three-dimensional gather sheet 24a. The other end of the three-dimensional gathered sheet 24a, which has elasticity and standing ability, is stretchable and deformable to fit the wearer's body shape.

The thread-like elastic members 24b used in the three-dimensional gathers 24 include short elastic members. "Short elastic members" means elastic members each having a length of 100 mm or more and 200 mm or less in a non-stretched state. In this embodiment, all of the thread-like elastic members 24b used in the three-dimensional gathers 24 are short elastic members. That is, the multiple elastic members that impart stretchability to the disposable diaper 10 include the elastic members 24b, which are short elastic members. For example, in this embodiment, the absorbent body 20 is divided in the longitudinal direction into two regions separated by approximately the center in the longitudinal direction (the position indicated by the two-dot chain line A in FIG. 2), and the elastic members 24b are provided in each of the two regions, so that the length of the elastic members 24b in a non-stretched state does not exceed 200 mm. In this case, a long elastic member extending across the two regions may be adhered to the three-dimensional gather sheet 24a, and then the long elastic member may be cut at the position indicated by the two-dot chain line A to form a plurality of elastic members (short elastic members) 24b arranged in series. In this case, it is preferable to minimize the cutting of the three-dimensional gather sheet 24a. In this embodiment, all of the thread-like elastic members 24b used in the three-dimensional gather 24 are short elastic members, but this is not limited thereto, and it is sufficient that they include at least short elastic members.

The position of the elastic member 24b is not limited to the two regions on both sides of the absorbent body 20 in the longitudinal direction, with the boundary being approximately the center of the longitudinal direction (the position shown by the two-dot chain line A in Figure 2) as described above, and it is sufficient that the length of the elastic member 24b in the unstretched state is 100 mm or more and 200 mm or less. In addition, in this embodiment, the absorbent body 20 is provided with three-dimensional gathers 24, but this is not limited, and the absorbent body 20 does not need to have three-dimensional gathers 24.

[Exterior body]
1 and 2, the exterior body 30 is a member that constitutes the outer shape of the disposable diaper 10, and is formed by laminating a nonwoven fabric sheet 34 and a plurality of thread-like elastic members (short elastic members) 35. Note that a plurality of nonwoven fabric sheets 34 may be laminated.

For the nonwoven fabric sheet 34, a nonwoven fabric such as a thermal bonded nonwoven fabric, an air-through nonwoven fabric, or a spunbonded nonwoven fabric, preferably an air-through nonwoven fabric or a spunbonded nonwoven fabric made of a thermoplastic resin such as polypropylene, polyester, or polyethylene, can be used.

The outer body 30 has a front waist region 31 that is located in front of the wearer's abdomen when worn, a rear waist region 32 that is located behind the wearer's back, and a crotch region 33 that is located between the wearer's legs.

As shown in FIG. 2, the exterior body 30 in the unfolded state has a symmetrical shape. The front waist region 31 and the rear waist region 32 each have a side seal portion 36 extending along the longitudinal direction at both ends in the width direction, and are arranged at positions spaced apart from each other in the longitudinal direction. The crotch region 33 is an area located between the front waist region 31 and the rear waist region 32. By fixing both ends in the width direction of the front waist region 31 and both ends in the width direction of the rear waist region 32 to each other by the side seal portion 36, the exterior body 30 is configured as a pants-like shape as a whole, as shown in FIG. 1, with both left and right ends of the front waist region 31 and both left and right ends of the rear waist region 32 continuing. In the following description, the direction of the exterior body 30 indicates the direction when worn by a wearer.

As shown in FIG. 1, the outer body 30 has a waist opening 37 at the top of the front waist region 31 and the rear waist region 32, and leg openings 38a, 38b on both the left and right sides of the crotch region 33. The waist opening 37 is the part into which the wearer's torso passes when worn, and is formed by the upper edge portions of both the front waist region 31 and the rear waist region 32. The waist opening 37 is provided with an elastic member 35a, which will be described later, and is stretchable in the circumferential direction. The left and right leg openings 38a, 38b are the parts into which the wearer's legs pass, and are formed by both the left and right end edges of the crotch region 33. The left and right leg openings 38a, 38b are provided with an elastic member 35c, which will be described later, and are stretchable in the circumferential direction.

(Mono-material)
It is preferable to reduce the number of types of resins used in the nonwoven fabrics and films used in the disposable diaper 10 in order to facilitate material recycling into plastic raw materials. For example, it is preferable to reduce the number of types of resins used in the nonwoven fabrics used in the top sheet 21, the three-dimensional gather sheet 24a, the exterior body 30, etc. of the absorbent body 20, and the films used in the back sheet 22, etc. of the absorbent body 20. Specifically, it is preferable to limit the total number of types of resins used in the disposable diaper 10, such as polyethylene, polypropylene, polyester, and polyurethane, to four or less, more preferably three or less, and even more preferably two or less. By setting the total number of types of resins used in the disposable diaper 10 within the above range, it is possible to improve the efficiency of material recycling of the plastic content.

(Elastic member)
As shown in Figs. 1 and 2, the plurality of elastic members 35 are arranged in the front waist region 31, the rear waist region 32, and the crotch region 33, respectively, and are joined to the nonwoven fabric sheet 34. The nonwoven fabric sheet 34 and the elastic members 35 are preferably bonded to each other via a hot melt adhesive that is present only in each elastic member 35. As the thread-like elastic member 35, for example, an elastic member having elasticity such as natural rubber, synthetic rubber, polyurethane, etc. can be appropriately used, and its thickness is preferably 500 dtex or more and 2000 dtex or less. The elastic members 35 used in the front waist region 31, the rear waist region 32, and the crotch region 33 include short elastic members. In this embodiment, all of the plurality of elastic members 35 used in the front waist region 31, the rear waist region 32, and the crotch region 33 are short elastic members. That is, the plurality of elastic members that impart elasticity to the paper diaper 10 include the elastic members 35 that are short elastic members. In this embodiment, all of the multiple elastic members 35 used in the front waist region 31, the rear waist region 32, and the crotch region 33 are short elastic members, but this is not limited to this and it is sufficient that they include at least short elastic members.

Among the multiple elastic members 35, the multiple elastic members 35a provided at the upper ends of the front waist region 31 and the rear waist region 32 constitute a band-shaped first elastic region 39 extending in the circumferential direction of the waist opening 37 near the waist opening 37. The first elastic region 39 allows the waist opening 37 to be stretched in the circumferential direction. The multiple elastic members 35a of the first elastic region 39 are arranged in multiple stages spaced apart from each other up and down. For example, in this embodiment, the front waist region 31 and the rear waist region 32 are divided in the width direction into two regions separated by the center in the width direction (the position indicated by the two-dot chain line B in FIG. 2), and elastic members 35a are provided in each of the two regions, so that the length of the elastic members 35a in the unstretched state does not exceed 200 mm. In this case, a long elastic member extending across the two regions may be adhered to the nonwoven fabric sheet 34, and then the long elastic member may be cut at the position indicated by the two-dot chain line B to form a plurality of elastic members (short elastic members) 35a arranged in series. At this time, it is preferable to minimize the cutting of the nonwoven fabric sheet 34.

The multiple elastic members 35b among the multiple elastic members 35 constitute a band-shaped second elastic region 40 extending in the width direction at a position spaced downward from the first elastic region 39 of the front waist region 31 and the rear waist region 32. The second elastic region 40 allows the front waist region 31 and the rear waist region 32 to stretch in the circumferential direction. The multiple elastic members 35b of the second elastic region 40 are arranged in multiple stages spaced apart from each other vertically. For example, in this embodiment, the front waist region 31 and the rear waist region 32 are divided in the width direction into three regions separated by a predetermined position (the position shown by the two-dot chain line C in FIG. 2), and the elastic members 35b are provided in each of the three regions, so that the length of the elastic members 35b in the non-stretched state does not exceed 200 mm. In this case, after adhering a long elastic member extending across the above three regions to the nonwoven fabric sheet 34, the long elastic member may be cut at the position indicated by the two-dot chain line C to form a plurality of elastic members (short elastic members) 35b arranged in series. At this time, it is preferable to minimize the cutting of the nonwoven fabric sheet 34.

Of the multiple elastic members 35, the multiple elastic members 35c arranged in the crotch region 33 in this embodiment form a third elastic region 41 extending widthwise at the front side and a fourth elastic region 42 extending widthwise at the rear side. The left and right leg openings 38a, 38b are circumferentially stretchable by the third elastic region 41 and the fourth elastic region 42.

The third stretchable region 41 has a left region 41a (a region on the outer side of the two-dot chain line D in FIG. 2), a central region 41b (a region between the two-dot chain line D and the two-dot chain line E in FIG. 2), and a right region 41c (a region on the outer side of the two-dot chain line E in FIG. 2). The left region 41a extends downward from the left lower end of the front waist region 31 along the left leg opening 38a. The central region 41b crosses the crotch region 33 from the lower end of the left region 41a to the left and right. The right region 41c extends upward from the right end of the central region 41b along the right leg opening 38b and continues to the right lower end of the front waist region 31. The multiple elastic members 35c of the third stretchable region 41 are arranged in multiple stages spaced apart from each other vertically. For example, in this embodiment, the third stretchable region 41 is divided into four regions, a left region 41a, a right region 41c, and regions on both sides of the width center of the central region 41b (position indicated by the two-dot chain line F in FIG. 2), and elastic members 35c are provided in each of the four regions, so that the length of the elastic members 35c in the unstretched state does not exceed 200 mm. In this case, a long elastic member extending across the four regions may be bonded to the nonwoven fabric sheet 34, and then the long elastic member may be cut at the positions indicated by the two-dot chain lines D, E, and F to form a plurality of elastic members (short elastic members) 35c arranged in series. At this time, it is preferable to minimize the cutting of the nonwoven fabric sheet 34.

The fourth stretchable region 42 has a left region 42a (a region on the outer side of the two-dot chain line D shown in FIG. 2), a central region 42b (a region between the two-dot chain line D and the two-dot chain line E shown in FIG. 2), and a right region 42c (a region on the outer side of the two-dot chain line E shown in FIG. 2). The left region 42a extends downward from the left lower end of the rear waist region 32 along the left leg opening 38a. The central region 42b crosses the crotch region 33 from the lower end of the left region 42a to the left and right. The right region 42c extends upward from the right end of the central region 42b along the right leg opening 38b and continues to the right lower end of the rear waist region 32. The multiple elastic members 35c of the fourth stretchable region 42 are arranged in multiple stages spaced apart from each other vertically. For example, in this embodiment, the fourth stretchable region 42 is divided into four regions, a left region 42a, a right region 42c, and regions on both sides of the width center of the central region 42b (position indicated by the two-dot chain line F in FIG. 2), and elastic members 35c are provided in each of the four regions, so that the length of the elastic members 35c in the unstretched state does not exceed 200 mm. In this case, a long elastic member extending across the four regions may be bonded to the nonwoven fabric sheet 34, and then the long elastic member may be cut at the positions indicated by the two-dot chain lines D, E, and F to form a plurality of elastic members (short elastic members) 35c arranged in series. At this time, it is preferable to minimize the cutting of the nonwoven fabric sheet 34.

In this embodiment, the third stretchable region 41 and the fourth stretchable region 42 are provided to extend in the width direction across the crotch region 33, but this is not limited thereto. For example, left and right stretchable regions may be provided to extend along the edges of the left and right leg openings 38a, 38b without crossing the crotch region 33. In this embodiment, four stretchable regions (the first stretchable region 39 to the fourth stretchable region 42) are provided in the exterior body 30, but the number and positions of the stretchable regions are not limited thereto, and any stretchable region may be provided that can impart stretchability in a desired direction and strength to the paper diaper 10. In this embodiment, the four stretchable regions (the first stretchable region 39 to the fourth stretchable region 42) are divided at predetermined positions (positions shown by two-dot chain lines B to F in FIG. 2) and elastic members 35 are disposed in each divided region, but the positions at which the stretchable regions are divided are not limited to the above positions, and any position may be provided so that the length of the elastic member 35 in the non-stretched state does not exceed 200 mm.

When the distance between rows of elastic members formed by short elastic members (elastic members 24b, 35) is within 10 mm, it is preferable to shift the positions of the divided parts of the short elastic members in each row by 20 mm or more in the width direction. Note that a row of elastic members means a portion where the short elastic members are lined up in series.

When forming a plurality of short elastic members (elastic members 24b, 35) arranged in a line in series by cutting the long elastic member at a predetermined position after adhering the long elastic member to a sheet (including the three-dimensional gathered sheet 24a and the nonwoven fabric sheet 34), it is preferable to apply the hot melt adhesive to the sheet or long elastic member without leaving any gaps so that the elastic members do not come out from the cut places.

The total weight of the short elastic members (elastic members 24b, 35) used in the disposable diaper 10 is preferably 1% to 5% of the weight of the disposable diaper 10. In other words, the ratio of the total weight of the elastic members (elastic members 24b, 35) to the weight of the disposable diaper 10 is preferably 1% to 5%. By making the ratio of the total weight of the elastic members (elastic members 24b, 35) to the total weight of the disposable diaper 10 1% to 5%, it is possible to greatly reduce the entanglement of the elastic members in agitators, drainage pumps, etc. (hereinafter referred to as "agitators, etc.") during the recycling process, and to reduce the inclusion of the elastic members as foreign matter in recovered materials such as absorbent fibers.

(Hot melt adhesive)
A hot melt adhesive is used to bond the various constituent materials described above in the disposable diaper 10. Examples of hot melt adhesives used in the disposable diaper 10 include SBC (styrene block copolymer)-based hot melt adhesives, EVA (ethylene vinyl acetate)-based hot melt adhesives, and olefin-based hot melt adhesives. Known methods can be used to apply the hot melt adhesive, such as a curtain coat method or a spiral method in which the molten hot melt adhesive is applied from a nozzle in a non-contact manner, or a slot method in which the adhesive is applied in a contact manner.

The hot melt adhesives used in the disposable diaper 10 include hot melt adhesives with a softening point of 90°C or less (hereinafter referred to as "low softening point hot melt adhesives"). The total weight of the low softening point hot melt adhesives is preferably 70% or more and 100% or less of the total weight of all hot melt adhesives (including low softening point hot melt adhesives) used in the disposable diaper 10. In other words, the ratio of the total weight of the low softening point hot melt adhesives to the total weight of all hot melt adhesives used in the disposable diaper 10 is preferably 70% or more and 100% or less. By setting the total weight of the low softening point hot melt adhesives in the above range, the constituent materials are easily peeled off in warm water, and the constituent materials are easily separated from each other, so that the disposable diaper 10 after use can be efficiently material recycled.

The low-softening-point hot melt adhesive is preferably used at least in the portion of the absorbent body 23 where the superabsorbent polymer is fixed between the fibers of the absorbent fibers. This allows the superabsorbent polymer particles fixed between the fibers to be easily separated during separation processing. In this case, the content of the low-softening-point hot melt adhesive in the absorbent body 23 is preferably 10 g/ ^m2 or less. This allows the amount of foreign matter derived from the hot melt component to be reduced in the material recovered in the material recycling process.

(Recycling process)
Next, a description will be given of a recycling process of used paper diapers 10. Fig. 4 is an explanatory diagram of a rotary drum device used in the recycling process.

In this embodiment, the recycling process of used paper diapers 10 is carried out using an agitator, for example, a rotary drum device 100. This rotary drum device 100 can be applied to various sanitary products that have a synthetic resin film portion and a liquid-absorbent portion attached to the film portion, such as urine absorption pads.

As shown in FIG. 4, the rotary drum device 100 has a cylindrical water tank 102 as a water tank section disposed within a casing 101, a rotary drum 103 disposed within the water tank 102, and a motor 104 for rotating the rotary drum 103. A number of small holes are provided on the peripheral surface of the rotary drum 103. A blade for breaking various types of bags may be provided on the inner peripheral surface of the rotary drum 103.

An opening 105 is provided on one end surface of the casing 101, and an openable door 106 is attached to it. The water tank 102 and the rotating drum 103 are arranged with the cylinder axis direction in the horizontal direction (or in an oblique direction that is higher toward the opening 105).

The water tub 102 and the motor 104 are supported in the casing 101 by a support member (not shown). The rotating drum 103 is connected to the motor 104 by a shaft 107. The shaft 107 is supported in the water tub 102 by a bearing (not shown).

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

When using this rotary drum device 100 to process used disposable diapers 10, the door 106 is opened, the used disposable diapers 10 and processing chemicals are placed into the rotary drum 103, and then the door 106 is closed. A predetermined amount of water is supplied from the water supply pipe 108 into the water tank 102, and then the rotary drum 103 is rotated by the motor 104. In this way, the used disposable diapers 10 are processed. Note that the motor 104 may rotate in only one direction, or may rotate back and forth (forward and reverse).

After a predetermined time (e.g., 0.01 to 5 hours, particularly 0.08 to 2 hours) has elapsed and the treatment has been sufficiently performed, 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 dehydrated by centrifugal force.

If necessary, water may then be poured into the water tank 102 from the water supply pipe 108 to rinse any residue left in the rotating drum 103. This rinsing may be done by pouring water in or by storing the water in the tank.

After rinsing is complete, open door 106, remove the contents, and send them to the next processing step.

As with a rotary drum washing machine, a drying mechanism that uses hot air may be provided, in which case the contents can be dried after rinsing. The temperature of the hot air may also be increased to heat and sterilize the contents.

In this way, when recycling the paper diaper 10 according to this embodiment, the used paper diaper 10, a chemical for treating the moisture absorbent, and water are placed in the rotary drum device 100, and the used paper diaper 10 is sterilized, decomposed, and separated.

The chemicals used to treat the moisture absorbent include components that remove moisture (dehydrate) from the superabsorbent polymer (SAP) contained in the 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). As calcium sources, slaked lime, calcium chloride, etc. can be used. The chemicals may also include a disinfectant component for disinfection. There are no particular restrictions on the disinfectant component, but an inexpensive one is calcium hypochlorite (bleaching powder).

In the disposable diaper 10 configured as described above, the elastic members 24b, 35 used in the disposable diaper 10 are short elastic members each having a length of 200 mm or less in an unstretched state. Therefore, when the used disposable diaper 10 is stirred in water using a stirrer for material recycling of the used disposable diaper 10, the elastic members 24b, 35 are less likely to become entangled in the stirrer or the like (e.g., the rotary drum device 100, the drainage pump 112, etc.). This reduces the number of times the stirrer or the like needs to be stopped to remove the entangled elastic material from the stirrer or the like, improving workability.

In addition, the length of each of the elastic members 24b, 35 in the unstretched state is 100 mm or more, ensuring the elasticity of the disposable diaper 10.

The hot melt adhesive used to bond the various constituent materials of the disposable diaper 10 includes a low-softening-point hot melt adhesive with a softening point of 90°C or less. This makes it easier for the constituent materials to peel off from each other in warm water, making it easier to separate the constituent materials using a mixer, and allowing for efficient material recycling of the disposable diaper 10 after use.

The superabsorbent polymers used in the disposable diaper 10 include biodegradable superabsorbent polymers that are biodegradable, such as starch-based, cellulose-based, and amino acid-based, from the viewpoint of material recycling. Biodegradable superabsorbent polymers have the property of being decomposed by microorganisms in soil or water, so even if superabsorbent polymers remain in the wastewater after stirring with a stirrer, the impact on the environment can be suppressed.

In this way, according to this embodiment, when used paper diapers 10 are washed and separated using an agitator, the number of times the agitator etc. needs to be stopped can be reduced, the constituent materials can be easily separated, and the impact of the superabsorbent polymer on the environment can be reduced, so that used paper diapers 10 can be efficiently recycled as materials.

In addition, by setting the total weight of the biodegradable superabsorbent polymer contained in the absorbent body 23 to 80% or more and 100% or less of the total weight of all superabsorbent polymers (including biodegradable superabsorbent polymers) used in the disposable diaper 10, the impact on the environment can be significantly reduced even if superabsorbent polymer remains in the wastewater after stirring with the mixer.

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

The disposable diapers (pants-type disposable diapers (large size)) of Example 1 and Comparative Examples 1 and 2 were recycled using a rotary drum device (agitator) and evaluated for the following two items (number of times the agitator was stopped, and the rate of gather-related defects in disposable diapers).

The rotary drum device (mixer) had the following configuration.
Diameter of the tank: 180cm
Length of tank: 120cm
Rotating drum diameter: 160 cm
Length of rotating drum: 110cm
Diameter of the small holes in the rotating drum: 0.7 cm
Axial direction of the tank and rotating drum: Horizontal

The recycling process involves first putting disposable diapers and chemicals (slaked lime: 15,000 g, calcium hypochlorite: 800 g) into the rotating drum of the rotating drum device, then pouring in and storing 800 L of tap water. The rotating 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 a rotary mixing process is performed. After 0.5 hours, the rotating drum is stopped, the water is drained, and the rotating drum is rotated at 300 rpm for 4 minutes to spin-dry. After stopping the rotating drum, 800 L of tap water is poured in to store and rinse (15 minutes), and then drained and spin-dryed in the same manner as above.

The "number of times the agitator, etc. was stopped" is evaluated based on the number of times the agitator, etc. (including the drain pump) was stopped to remove the elastic member during one recycling process when approximately 300 kg of used pants-type disposable diapers (large size) were recycled. For example, if the recycling process was carried out 10 times and the agitator, etc. was stopped once to remove the elastic member, the number of times the agitator, etc. was stopped to remove the elastic member during one recycling process would be 0.1. The evaluation criteria are as follows:
○: Number of stops less than 0.1 time △: Number of stops 0.1 to less than 1 time ×: Number of stops 1 time or more

The evaluation of "gather-related defective rate of disposable diapers" is based on the gather-related defective rate in the manufacturing process inspection of pants-type disposable diapers (L size). The evaluation criteria are as follows.
○: Defective product rate less than 0.1% △: Defective product rate 0.1% to less than 1% ×: Defective product rate 1% or more

The results are shown in Table 1. In the table, "unstretched length of elastic member" indicates the unstretched length of the elastic member used in the gathers of a pants-type disposable diaper (large size). Also, "number of elastic members" indicates the number of elastic members used in the gathers of one pants-type disposable diaper (large size).

From the above, it has been confirmed that the disposable diaper of the present invention can be efficiently recycled after use.

10: Disposable diaper 20: Absorbent body 21: Top sheet 22: Back sheet 23: Absorbent body 24: Three-dimensional gathers 24b: Elastic member (short elastic member)
30: Outer body 35, 35a, 35b, 35c: Elastic member (short elastic member)
50: Plural elastic members

Claims (1)

A paper diaper that can be washed, separated and recycled after use,
An exterior body that defines the outer shape of the paper diaper when worn;
An absorber supported by the exterior body;
and a plurality of elastic members that provide stretchability;
The plurality of elastic members include a plurality of short elastic members each having a length of 100 mm or more and 200 mm or less in a non-stretched state,
The hot melt adhesive used in the disposable diaper includes a low-softening point hot melt adhesive having a softening point of 60° C. or higher and 90° C. or lower,
The disposable diaper is characterized in that the absorbent body contains a biodegradable highly absorbent polymer.