JP7713766B2 - Moisture-absorbing sheet, disposable wearable article, and method of manufacturing the same - Google Patents

Description

The present invention relates to a moisture-absorbing sheet, a disposable wearable article, and a method for manufacturing the same.

It has been proposed to provide disposable wearable articles such as disposable diapers and sanitary napkins with moisture-absorbing properties for a variety of reasons.

For example, disposable wearing articles such as disposable diapers and sanitary napkins have an absorbent body that absorbs excretions such as urine, and a liquid-impermeable resin film that covers the back of the absorbent body. To prevent the absorbent body from becoming stuffy when worn, the liquid-impermeable resin film has been made to be moisture-permeable in the thickness direction (see, for example, Patent Documents 1 and 2). Furthermore, in many absorbent articles, the back of the liquid-impermeable resin film has also been covered with an exterior nonwoven fabric to give the outer surface of the product a cloth-like feel and appearance (see, for example, Patent Document 2).

However, in conventional absorbent articles, the high moisture permeability of the liquid-impermeable resin film used to prevent stuffiness can be a drawback, as even after the absorbent body has absorbed excrement, the outer surface of the product or underwear can retain moisture, which can give the mistaken impression of leakage when touched with the hand.

This problem can be solved by reducing the moisture permeability of the liquid-impermeable resin film, but in that case, a decrease in the ability to prevent stuffiness cannot be avoided. Therefore, it has been proposed to provide a moisture-absorbing layer in the liquid-impermeable resin film or the outer nonwoven fabric (see, for example, Patent Document 1).

In addition, disposable wearable articles generally have poor breathability, and are known to easily become stuffy inside when worn. To prevent this, it has been proposed to attach a moisture-absorbing sheet (see, for example, Patent Document 3).

In addition, moisture-absorbing sheets are sometimes used as product packaging materials or within product packaging (see, for example, Patent Document 4).

However, in moisture-absorbing sheets, not only is the performance of the moisture-absorbing material important, but also the breathability required to allow moisture to escape and to supply moisture to the moisture-absorbing material, and conventional sheets have had room for improvement in this regard.

Patent No. 6442098 Japanese Patent Application Laid-Open No. 2017-144174 JP 2010-279621 A JP 2010-279606 A

The primary objective of the present invention is to provide a moisture-absorbing sheet, a disposable wearable article, and a method for manufacturing the same that are highly breathable to allow moisture to escape and efficiently supply moisture to a moisture-absorbing material.

The moisture-absorbing sheets and the like that solve the above problems are as follows.
<First Aspect>
a nonwoven fabric in which thin-walled portions shrunk in the thickness direction are repeatedly formed at intervals;
and a microfibrous cellulose aggregate attached within the thin-walled portion.
A moisture-absorbing sheet characterized by:

(Action and effect)
This moisture-absorbent sheet is based on a nonwoven fabric in which thin sections are repeatedly formed at intervals, and is characterized by the attachment of highly moisture-absorbent microfibrous cellulose aggregates within the thin sections. Therefore, even when this moisture-absorbent sheet is sandwiched between an object or member, ventilation gaps are formed between the object or member and the thin sections of the moisture-absorbent sheet. This ventilation gap allows moisture to escape along the surface of the moisture-absorbent sheet. Furthermore, during this process, moisture is efficiently supplied to the moisture-absorbing microfibrous cellulose aggregates, allowing them to be absorbed. Such moisture-absorbent sheets can be used alone or, as described below, can be used as components of disposable wearable articles.

<Second Aspect>
The microfibrous cellulose aggregate is not present in any portion other than the thin portion.
The moisture-absorbing sheet according to the first embodiment.

(Action and effect)
The microfibrous cellulose aggregate is hard. Therefore, it is preferable that the moisture-absorbent sheet has the microfibrous cellulose aggregate attached only to the thin-walled portion. This allows the moisture-absorbent sheet to be flexible and deformable in areas other than the thin-walled portion, and the user or wearer is less likely to touch the hard thin-walled portion or to feel its hardness on the skin.

<Third Aspect>
The thin-walled portion is provided in a striped or lattice pattern.
The moisture-absorbing sheet according to the first or second aspect.

(Action and effect)
When the thin-walled portions are arranged in a striped or lattice pattern, the continuity of the ventilation gaps is increased, thereby improving the breathability for releasing moisture and for efficiently supplying moisture to the moisture absorbent material.

<Fourth Aspect>
The nonwoven fabric constituting the moisture-absorbing sheet is a short-fiber nonwoven fabric having a fineness of 2 to 10 dtex and a basis weight of 20 to 40 g/m ² ,
The amount of the microfibrous cellulose aggregate attached to the thin-walled portion is 0.1 to 5.0 g/ ^m2 .
The moisture-absorbing sheet according to the first or second aspect.

(Action and effect)
The nonwoven fabric constituting the moisture-absorbing sheet is not particularly limited, but since it is preferable that it is bulky and has excellent shapeability, it is preferable that it is a nonwoven fabric within the above range. Furthermore, in order to improve moisture absorption, the more the amount of microfibrous cellulose aggregate attached, the better, but if it is too much, the product will become unnecessarily hard. Therefore, it is preferable that the content of microfibrous cellulose aggregate in the thin-walled portion is within the above range.

<Fifth Aspect>
An absorber;
a breathable, liquid-impermeable resin film provided on the back side of the absorbent body;
an exterior nonwoven fabric covering the back surface of the liquid-impermeable resin film;
A disposable wearing article having
a moisture-absorbing sheet provided between the liquid-impermeable resin film and the exterior nonwoven fabric,
The moisture-absorbing sheet has a nonwoven fabric in which thin-walled portions shrunk in the thickness direction are repeatedly formed at intervals, and a microfibrous cellulose aggregate attached to the thin-walled portions,
a ventilation gap is provided between the exterior nonwoven fabric and the thin portion, and between the liquid-impermeable resin film and the thin portion ,
A disposable wearing article characterized by:

(Action and effect)
The disposable wearing article has the moisture-absorbent sheet of the first aspect interposed between the liquid-impermeable resin film and the outer nonwoven fabric to form a ventilation gap, and therefore, the moisture that increases after absorbing excrement and is released from the liquid-impermeable resin film can be effectively absorbed by the moisture-absorbent sheet, making it less likely that the outer surface of the product or underwear will feel damp.

<Sixth Aspect>
a breathable skin-contacting layer in contact with the wearer's skin;
a moisture-absorbing sheet provided so as to have a portion adjacent to the back side of the skin-contact layer,
The moisture-absorbing sheet has a nonwoven fabric in which thin-walled portions shrunk in the thickness direction are repeatedly formed at intervals, and a microfibrous cellulose aggregate attached to the thin-walled portions,
A ventilation gap is provided between the skin contact layer and the thin portion.
A disposable wearing article characterized by:

(Action and effect)
In order to prevent stuffiness during wear, the disposable wearable article is provided with a moisture-absorbing sheet adjacent to the back side of the skin-contact layer, thereby efficiently absorbing moisture inside the disposable wearable article or releasing it to the outside, thereby preventing stuffiness during wear.

<Seventh Aspect>
a step of applying a dispersion of microfibrous cellulose to a nonwoven fabric in a repeating pattern at intervals and drying the dispersion to form thin-walled portions in the applied portions of the dispersion and to produce a moisture-absorbing sheet having microfibrous cellulose aggregates formed in the thin-walled portions;
and attaching the moisture-absorbent sheet between members overlapping in a thickness direction of the disposable wearing article, to manufacture the disposable wearing article having an air-permeable gap between the members and the thin-walled portion.
A method for manufacturing a disposable wearing article.

(Action and effect)
When a microfibrous cellulose dispersion is applied to a nonwoven fabric and the applied portion of the dispersion is dried, the volume of the microfibrous cellulose aggregates gradually decreases as they are formed. Accordingly, the volume of the nonwoven fabric at the applied portion of the dispersion also decreases, automatically forming a thin-walled portion. This manufacturing method utilizes this phenomenon.
For example, a thin-walled portion may be formed on the nonwoven fabric that will become the moisture-absorbing sheet by embossing, or a microfibrous cellulose aggregate may be attached to the thin-walled portion afterwards. However, according to the present manufacturing method, a moisture-absorbing sheet can be formed simply by applying a dispersion of microfibrous cellulose in a desired pattern to the nonwoven fabric that will become the moisture-absorbing sheet and drying it.
Furthermore, if the nonwoven fabric is coated with a dispersion of microfibrous cellulose and then attached to other components of the disposable wearing article before drying (i.e., before the thin-walled portion is formed), the formation of ventilation gaps may be insufficient. In contrast, the present manufacturing method uses a moisture-absorbent sheet after drying to manufacture the disposable wearing article, thereby enabling the formation of satisfactory ventilation gaps. Therefore, the present manufacturing method attaches the cover layer after the thin-walled portion is formed.

The present invention offers advantages such as excellent breathability for moisture escape and efficient supply of moisture to the moisture absorbent material.

FIG. 1 is a plan view showing the inner surface of a tape-type disposable diaper in an unfolded state. FIG. 1 is a plan view showing the outer surface of a tape-type disposable diaper in an unfolded state. This is a cross-sectional view taken along line 6-6 in Figure 1. This is a cross-sectional view taken along line 7-7 in Figure 1. This is a cross-sectional view taken along line 8-8 in Figure 1. 9 is a cross-sectional view taken along line 9-9 in FIG. 1. This is a cross-sectional view taken along line 5-5 in Figure 1. FIG. 2 is a plan view showing the essential parts of the diaper in an unfolded state. FIG. 2 is a plan view showing the essential parts of the diaper in an unfolded state. FIG. 2 is a plan view showing the essential parts of the diaper in an unfolded state. FIG. 2 is an enlarged cross-sectional view of the moisture-absorbing sheet. 1A and 1B are plan views showing various patterns of thin portions (portions of attached microfibrous cellulose).

Figures 1 to 7 show an example of a tape-type disposable diaper. In the figures, the symbol W indicates the overall width of the diaper excluding the connecting tape, and the symbol L indicates the overall length of the diaper. The dotted areas in the cross-sectional views indicate adhesive used as a joining means for joining the various components located on the front and back sides. This can be achieved by solid, bead, curtain, summit, or spiral application of hot melt adhesive, or pattern coating (transfer of hot melt adhesive using a relief printing method), or alternatively or in addition, by applying the adhesive to the outer surface of the elastic member using a comb gun or SureWrap application. Hot melt adhesives include, for example, EVA-based, adhesive rubber-based (elastomer-based), olefin-based, and polyester/polyamide-based types, but no particular limitations apply. Material welding methods such as heat sealing and ultrasonic sealing can also be used to join the various components.

This tape-type disposable diaper has an absorbent body 56, a liquid-permeable top sheet 30 covering the front side of the absorbent body 56, a liquid-impermeable resin film 11 covering the back side of the absorbent body 56, and an exterior nonwoven fabric 12 covering the back side of the liquid-impermeable resin film 11 and constituting the outer surface of the product. Reference symbol F indicates a ventral side portion located forward of the center in the front-to-rear direction, and reference symbol B indicates a dorsal side portion located rearward of the center in the front-to-rear direction.

The materials and characteristics of each part will be explained below.
(Absorbent)
The absorbent body 56 is a portion that absorbs and retains excretory fluid and can be formed from a fiber assembly. Examples of such fiber assembly include stacked staple fibers such as cotton-like pulp and synthetic fibers, as well as filament assemblies obtained by opening synthetic fiber tows (fiber bundles) such as cellulose acetate as needed. The fiber weight can be, for example, approximately 100 to 300 g/ ^m2 when stacked staple fibers such as cotton-like pulp or short fibers are used, and approximately 30 to 120 g/ ^m2 when used as a filament assembly. The fineness of the synthetic fibers is, for example, 1 to 16 dtex, preferably 1 to 10 dtex, and more preferably 1 to 5 dtex. In the case of a filament assembly, the filaments may be non-crimped, but are preferably crimped. The degree of crimp of the crimped fibers can be, for example, about 5 to 75 crimps per 2.54 cm, preferably about 10 to 50 crimps, and more preferably about 15 to 50 crimps. Uniformly crimped fibers can also be used.

(Superabsorbent polymer particles)
The absorbent body 56 may contain superabsorbent polymer particles in part or in its entirety. The term "superabsorbent polymer particles" includes not only "particles" but also "powder." The superabsorbent polymer particles used in this type of absorbent article can be used as they are. The particle size of the superabsorbent polymer particles is not particularly limited. For example, when the particles are sieved (shaken for 5 minutes) using a 500 μm standard sieve (JIS Z8801-1:2006) and the particles that fall through the sieve are then sieved (shaken for 5 minutes) using a 180 μm standard sieve (JIS Z8801-1:2006), the proportion of particles remaining on the 500 μm standard sieve is preferably 30% by weight or less, and the proportion of particles remaining on the 180 μm standard sieve is preferably 60% by weight or more.

The material for the superabsorbent polymer particles is not particularly limited, but a water absorption capacity of 30 g/g or more is preferred. Superabsorbent polymer particles include starch-based, cellulose-based, and synthetic polymer-based materials, such as starch-acrylic acid (salt) graft copolymers, saponified starch-acrylonitrile copolymers, crosslinked sodium carboxymethylcellulose, and acrylic acid (salt) polymers. The preferred shape of the superabsorbent polymer particles is the commonly used powder form, but other shapes can also be used.

Highly absorbent polymer particles with a water absorption rate of 70 seconds or less, and particularly 40 seconds or less, are preferably used. If the water absorption rate is too slow, the liquid supplied to the absorbent body 56 is more likely to return to the outside of the absorbent body 56, a phenomenon known as backflow.

Furthermore, it is preferable to use superabsorbent polymer particles with a gel strength of 1000 Pa or more. This effectively reduces the sticky feeling after absorbing liquid, even when a bulky absorbent body 56 is used.

The basis weight of the superabsorbent polymer particles can be determined appropriately depending on the absorption capacity required for the application of the absorbent body 56. Therefore, although it is not possible to generalize, it can be set to 50 to 350 g/ ^m² . If the basis weight of the polymer is less than 50 g/ ^m² , it becomes difficult to ensure the absorption capacity. If it exceeds 350 g/ ^m² , not only will the effect saturate, but the excess superabsorbent polymer particles will cause an uncomfortable, gritty feeling.

(packaging sheet)
To prevent the superabsorbent polymer particles from escaping or to improve the shape retention of the absorbent body 56, the absorbent body 56 can be incorporated as an absorbent element 50 wrapped in a wrapping sheet 58. Examples of suitable wrapping sheets 58 include tissue paper, particularly crepe paper, nonwoven fabric, polylaminated nonwoven fabric, and perforated sheets. However, it is preferable that the sheet be one that prevents the superabsorbent polymer particles from escaping. When using nonwoven fabric instead of crepe paper, hydrophilic SMMS (spunbond/meltblown/meltblown/spunbond) nonwoven fabric is particularly suitable, and polypropylene, polyethylene/polypropylene, and the like can be used. The fiber weight is preferably 5 to 40 g/m ² , and more preferably 10 to 30 g/m ² .

3, the packaging sheet 58 may be in a form in which one sheet wraps the entire absorbent body 56, or multiple sheets, such as two sheets on top and two sheets on bottom, may wrap the entire absorbent body 56. The packaging sheet 58 may also be omitted.

(Top sheet)
The top sheet 30 is liquid permeable, and may be, for example, a perforated or non-perforated nonwoven fabric, a porous plastic sheet, or the like. Furthermore, the raw fiber of the nonwoven fabric is not particularly limited. Examples include synthetic fibers such as olefins (e.g., polyethylene and polypropylene), polyesters, and polyamides; recycled fibers (e.g., rayon and cupra); natural fibers (e.g., cotton); and mixed fibers and composite fibers made from two or more of these. Furthermore, the nonwoven fabric may be manufactured by any processing method. Examples of processing methods include known methods such as spunlace, spunbond, thermal bond, meltblown, needle punch, air-through, and point bond. For example, if flexibility and drapeability are desired, the spunlace method is preferred, and if bulkiness and softness are desired, the thermal bond method is preferred.

The top sheet 30 extends from the front to the rear of the product in the front-to-back direction, and extends laterally beyond the absorbent body 56 in the width direction WD. However, if necessary, for example, when the starting point of the rising gathers 60 (described below) is located closer to the center in the width direction than the side edges of the absorbent body 56, the width of the top sheet 30 can be made shorter than the overall width of the absorbent body 56.

(middle seat)
In order to quickly transfer liquid that has permeated the top sheet 30 to the absorbent body, an intermediate sheet (also called a "second sheet") 40 can be provided, which has a faster liquid permeation rate than the top sheet 30. This intermediate sheet 40 is intended to quickly transfer liquid to the absorbent body, improving the absorption performance of the absorbent body and preventing the phenomenon of absorbed liquid "backflowing" from the absorbent body. The intermediate sheet 40 can also be omitted.

Examples of the intermediate sheet 40 include the same material as the top sheet 30, spunlace nonwoven fabric, spunbond nonwoven fabric, SMS nonwoven fabric, pulp nonwoven fabric, a mixed sheet of pulp and rayon, point-bond nonwoven fabric, and crepe paper. Air-through nonwoven fabrics are particularly preferred due to their bulkiness. For air-through nonwoven fabrics, composite fibers with a core-sheath structure are preferably used. In this case, the resin used for the core may be polypropylene (PP), but polyester (PET) with high rigidity is preferred. The basis weight is preferably 17 to 80 g/ ^m² , more preferably 25 to 60 g/ ^m² . The thickness of the raw fiber of the nonwoven fabric is preferably 2.0 to 10 dtex. To increase the bulk of the nonwoven fabric, it is also preferable to use eccentric fibers, hollow fibers, or eccentric and hollow fibers as all or part of the mixed raw fiber material.

In the illustrated example, the intermediate sheet 40 is shorter than the width of the absorbent body 56 and is positioned in the center, but it may be provided across the entire width. The intermediate sheet 40 may also be provided across the entire length of the diaper, or, as in the illustrated example, it may be provided only in the middle portion including the excretion area.

(Liquid-impermeable resin film)
The liquid-impermeable resin film 11 is not particularly limited as long as it has moisture permeability, but for example, a microporous sheet obtained by kneading an inorganic filler into an olefin resin such as polyethylene or polypropylene to form a sheet and then stretching it uniaxially or biaxially can be suitably used. Needless to say, the liquid-impermeable resin film 11 does not include those that use a nonwoven fabric as a base material to enhance waterproofness.

It is desirable for the liquid-impermeable resin film 11 to extend over the same or a wider area as the absorbent body 56 in the front-to-back direction LD and width direction WD, but if necessary, such as when other water-blocking means are present, it may be configured so that it does not cover the edges of the absorbent body 56 in the front-to-back direction LD and width direction WD.

(exterior nonwoven fabric)
The exterior nonwoven fabric 12 covers the entire back side of the liquid-impermeable resin film 11, giving the product an exterior cloth-like appearance. The exterior nonwoven fabric 12 is not particularly limited, and examples of the material fiber include synthetic fibers such as olefins (e.g., polyethylene or polypropylene), polyesters, and polyamides, as well as recycled fibers (e.g., rayon or cupra), and natural fibers (e.g., cotton). Processing methods include spunlace, spunbond, thermal bond, air-through, and needle punch. However, long-fiber nonwoven fabrics such as spunbond nonwoven fabrics, SMS nonwoven fabrics, and SMMS nonwoven fabrics are preferred because they offer both softness and strength. Nonwoven fabrics can be used singly or in layers. In the latter case, the nonwoven fabrics are preferably bonded together with a hot-melt adhesive or the like. When using nonwoven fabric, a fiber weight of 10 to 50 g/m ² , and particularly 15 to 30 g/m ^{2 ,} is desirable.

The exterior nonwoven fabric 12 can be bonded to the adjacent components on the front side, i.e., in the illustrated example, the liquid-impermeable resin film 11 or moisture-absorbent sheet 15 described below, using an adhesive such as a hot-melt adhesive applied in an appropriate pattern, or by welding the materials together.

(Get up and gather)
In order to prevent excrement from moving laterally along the top sheet 30 and to prevent so-called side leakage, it is preferable to provide rising gathers 60 that rise towards the wearer's skin on both sides of the surface in the width direction WD. Of course, the rising gathers 60 can be omitted.

When rise-up gathers 60 are used, their structure is not particularly limited, and any known structure can be used. The rise-up gathers 60 in the illustrated example are composed of a gather sheet 62 that is substantially continuous in the width direction WD, and an elongated gather elastic member 63 that is fixed to the gather sheet 62 in a stretched state along the front-to-back direction LD. A water-repellent nonwoven fabric can be used as the gather sheet 62, and rubber thread or the like can be used as the gather elastic member 63. As shown in Figures 1 and 2, multiple elastic members can be provided, or one elastic member can be provided.

The inner surface of the gathered sheet 62 has a joining start point in the width direction WD on the side of the top sheet 30, and the portion extending outward in the width direction from this joining start point is joined with a hot melt adhesive or the like to the inner surface of each side flap portion SF, that is, in the illustrated example, to the side of the liquid-impermeable resin film 11 and the side of the exterior nonwoven fabric 12 located outward in the width direction.

Around the legs, the rise-up gathers 60 are fixed to the top sheet 30 at both ends in the front-to-back direction of the product, but the area between them is an unfixed, free section that stands up due to the contractile force of the elastic members 63 and comes into close contact with the body surface.

(End flap section, side flap section)
The illustrated tape-type disposable diaper has a pair of end flap portions EF that do not have the absorbent body 56 and extend to the front and rear of the absorbent body 56, respectively, and a pair of side flap portions SF that do not have the absorbent body 56 and extend laterally beyond both side edges of the absorbent body 56.

(flat gathers)
A side elastic member 64 made of an elongated elastic member such as rubber thread is fixed to each side flap portion SF in a stretched state along the front-to-rear direction LD, thereby forming flat gathers in the leg-surrounding portions of each side flap portion SF. As shown in the illustrated example, the side elastic member 64 is provided between the gathered sheet 62 and the liquid-impermeable resin film 11 on the widthwise outer side near the joining start end of the joining portion of the gathered sheet 62, or it can also be provided between the liquid-impermeable resin film 11 and the exterior nonwoven fabric 12 in the side flap portion SF. A plurality of side elastic members 64 can be provided on each side as shown in the illustrated example, or only one can be provided on each side.

(connecting tape)
The side flap portions SF of the back portion B are each provided with a connecting tape 13 which is detachably connected to the outer surface of the abdominal portion F. When putting on the diaper, the connecting tape 13 is wrapped around the outer surface of the abdominal portion F from both sides of the waist, and the connecting portions 13A of the connecting tape 13 are connected to appropriate locations on the outer surface of the abdominal portion F.

The structure of the connecting tape 13 is not particularly limited, but in the illustrated example, it has a sheet base material that forms a tape attachment portion 13C fixed to the side flap portion SF and a tape main portion 13B that protrudes from this tape attachment portion 13C, and a connecting portion 13A that faces the ventral side and is provided in the middle of the width of the tape main portion 13B on this sheet base material, with the tip side of this connecting portion 13A forming a grip portion.

The connecting portion 13A may be provided with a hook material (male material) of a mechanical fastener (hook-and-loop fastener), or may be provided with an adhesive layer. The hook material has multiple engaging protrusions on its connecting surface, and the engaging protrusions may be shaped in various ways, including (A) a square, (B) a J-shape, (C) a mushroom, (D) a T-shape, and (E) a double J-shape (two J-shapes joined back-to-back). Any of these shapes is acceptable.

Furthermore, the sheet substrate forming the tape attachment portion 13C to the tape main body portion 13B can be made of nonwoven fabric, plastic film, polylaminated nonwoven fabric, paper, or a composite material of these, but spunbond nonwoven fabric, air-through nonwoven fabric, or spunlace nonwoven fabric with a fineness of 1.0 to 3.5 dtex, a basis weight of 20 to 100 g/ ^m2 , and a thickness of 1 mm or less is preferred.

(Target sheet)
A target sheet 20 having a target for facilitating connection is preferably provided at the connection points of the connecting tape 13 in the ventral portion F. When the connecting portion 13A is made of a hook material, the target sheet 20 can be a sheet substrate made of a plastic film or nonwoven fabric with a large number of loop threads on the surface thereof so that the engaging protrusions of the hook material can become entangled. Alternatively, when the connecting portion 13A is made of an adhesive material layer, a sheet substrate made of a smooth, adhesive plastic film with a release-treated surface can be used. Furthermore, when the connection points of the connecting tape 13 in the ventral portion F are made of a nonwoven fabric, for example, when an exterior nonwoven fabric 12 is provided as shown in the figure, the target sheet 20 can be omitted and the hook material can be entangled with the fibers of the exterior nonwoven fabric 12 for connection. In this case, the target sheet 20 can be provided as a marker between the exterior nonwoven fabric 12 and the liquid-impermeable resin film 11.

(moisture-absorbing sheet)
Characteristically, as shown in Figures 8 to 10, a moisture-absorbent sheet 15 is provided between the liquid-impermeable resin film 11 and the exterior nonwoven fabric 12. When such a moisture-absorbent sheet 15 is provided between the liquid-impermeable resin film 11 and the exterior nonwoven fabric 12, moisture that has permeated the liquid-impermeable resin film 11 is not blocked by the moisture-absorbent sheet 15, so the moisture-preventing properties when worn are unlikely to decrease. At the same time, due to the high moisture absorption properties of the microfibrous cellulose aggregate, moisture is retained more in the moisture-absorbent sheet 15 than in the exterior nonwoven fabric 12 that constitutes the exterior surface of the product or in the underwear, so the exterior surface of the product and the underwear are unlikely to feel damp.

In particular, as shown in FIG. 11 , the moisture-absorbent sheet 15 preferably comprises a nonwoven fabric 16 having thin-walled portions 16t repeatedly formed at intervals, each of which has been shrunk in the thickness direction, and microfibrous cellulose aggregates 17 attached within the thin-walled portions 16t. The thin-walled portions 16t may have depressions on both the front and back sides of the moisture-absorbent sheet 15, as shown in the example shown, or may have depressions on only one side of the moisture-absorbent sheet 15. As a result, even though the moisture-absorbent sheet 15 is sandwiched between the liquid-impermeable resin film 11 and the outer nonwoven fabric 12, ventilation gaps 18 are formed between them and the thin-walled portions 16t of the moisture-absorbent sheet 15. Therefore, this moisture-absorbent sheet 15 can release moisture along the surface of the moisture-absorbent sheet 15 through these ventilation gaps 18. Furthermore, during this process, moisture is efficiently supplied to the moisture-absorbing material, the microfibrous cellulose aggregates 17, for absorption.

The moisture-absorbent sheet 15 may have microfibrous cellulose aggregates 17 in addition to the thin portions 16t, but the microfibrous cellulose aggregates 17 are rigid. Therefore, it is preferable that the moisture-absorbent sheet 15 have the microfibrous cellulose aggregates 17 attached only to the thin portions 16t. This allows the moisture-absorbent sheet 15 to flexibly deform in areas other than the thin portions 16t, and makes it less likely for the user or wearer to touch the rigid thin portions 16t, or for their rigidity to be transmitted to the skin.

The thin-walled portions 16t may be formed in any pattern, as long as they are repeated at intervals. For example, the thin-walled portions 16t may be formed in a vertical stripe pattern, as shown in FIG. 8, in which multiple linear thin-walled portions 16t extending along the front-to-rear direction LD are spaced apart in the width direction WD, or in a horizontal stripe pattern, as shown in FIG. 9, in which multiple linear thin-walled portions 16t extending along the width direction WD are spaced apart in the front-to-rear direction LD. The thin-walled portions 16t may also be formed in a dot pattern, as shown in FIGS. 12(a)-(e), or in a diagonal grid pattern, as shown in FIG. 12(f). In particular, forming the thin-walled portions 16t in a striped or grid pattern increases the continuity of the ventilation gaps 18. This is preferable because it provides even better breathability for moisture release and efficient moisture supply to the moisture absorbent material. When the thin-walled portions 16t are formed in a linear pattern, they can be formed in a curved or wavy pattern, in addition to a straight line.

The dimensions of the thin-walled portions 16t can be determined as appropriate. When the thin-walled portions 16t are arranged in a striped pattern, the line width x1 of the thin-walled portions 16t is preferably 1.0 to 4.0 mm, particularly 2.0 to 3.0 mm, and the spacing s1 between adjacent attachment portions is preferably 5 to 30 mm, particularly 10 to 20 mm. When the thin-walled portions 16t are arranged in a dotted pattern, the diameter d (the length of the longest portion) of the thin-walled portions 16t is preferably 1.0 to 4.0 mm, particularly 2.0 to 3.0 mm, and the spacing s2, s3 between the centers (or centers of gravity) of adjacent rows in the width direction WD and the front-to-rear direction LD is preferably 5 to 25 mm, particularly 10 to 15 mm. Furthermore, when the thin portions 16t are arranged in a lattice pattern, the line width x2 of the thin portions 16t is preferably 1.0 to 4.0 mm, particularly 2.0 to 3.0 mm, and the lattice spacing s4 (the spacing between parallel thin portions 16t) is preferably 5 to 30 mm, particularly 10 to 20 mm. The dimensions of the attachment portions of the microfibrous cellulose aggregate can be the same as, smaller than, or larger than the dimensions of the thin portions 16t.

The nonwoven fabric 16 constituting the moisture-absorbing sheet 15 is not particularly limited, but since it is preferable that it is bulky and has excellent formability, it is preferable that it is a short-fiber nonwoven fabric with a fineness of 2 to 10 dtex and a basis weight of 20 to 40 g/ ^m2 .

To improve moisture absorption, the more microfibrous cellulose content the better, but if it is too much, the product becomes unnecessarily hard. Therefore, the content of microfibrous cellulose in the thin-walled portion 16t is preferably about 0.1 to 5.0 g/ ^m² , and more preferably about 0.5 to 3.0 g/ ^m² .

<Manufacturing method>
For example, the moisture-absorbing sheet 15 can be manufactured by embossing the nonwoven fabric 16 that will become the moisture-absorbing sheet 15 to form a thin portion 16t, or by subsequently attaching a microfibrous cellulose aggregate 17 to the thin portion 16t.

The moisture-absorbing sheet 15 can be manufactured by the following method. That is, when a dispersion of microfibrous cellulose is applied to the nonwoven fabric 16 that will become the moisture-absorbing sheet 15 in a repeating pattern with intervals, the dispersion penetrates between the fibers of the nonwoven fabric 16. When it dries, a thin portion 16t is formed in the applied portion of the dispersion, and a microfibrous cellulose aggregate 17 is formed within the thin portion 16t. That is, when the dispersion of microfibrous cellulose is applied to the nonwoven fabric 16 and then the applied portion of the dispersion is dried, the volume of the microfibrous cellulose aggregate 17 gradually decreases as the microfibrous cellulose aggregate 17 is formed. Then, the volume of the applied portion of the nonwoven fabric 16 also decreases, and the thin portion 16t is automatically formed. The present manufacturing method utilizes this. According to this method, the moisture-absorbing sheet 15 can be formed simply by applying a dispersion of microfibrous cellulose in a desired pattern to the nonwoven fabric 16 that will become the moisture-absorbing sheet 15 and drying it.

However, according to this manufacturing method, if another sheet is attached to the nonwoven fabric 16 before drying (i.e., before the thin portion 16t is formed) after applying the dispersion of microfibrous cellulose to the nonwoven fabric 16, the ventilation gap 18 may not be formed. Therefore, when attaching the present moisture-absorbing sheet 15 to another member, it is preferable to attach the other member after forming the thin portion 16t. For example, the thin portion 16t can be formed in principle by applying a dispersion of microfibrous cellulose to an existing nonwoven fabric 16 member such as the intermediate sheet 40 or the exterior nonwoven fabric 12. However, since it is necessary to attach another member after drying the dispersion of microfibrous cellulose, this is not suitable for manufacturing on a high-speed manufacturing line. Therefore, as shown in the example, it is preferable to manufacture a disposable wearing article by separately manufacturing a dedicated moisture-absorbing sheet 15 and attaching it between appropriate members. On the other hand, when forming the thin portion 16t by embossing, another member can be attached to the nonwoven fabric 16 that will become the moisture-absorbing sheet 15 before applying the dispersion of microfibrous cellulose.

When forming the attachment portion of the microfibrous cellulose aggregates 17 by applying a microfibrous cellulose dispersion, the concentration (mass/volume) of the microfibrous cellulose dispersion is preferably 0.1 to 10%, more preferably 1.0 to 5.0%, and particularly preferably 1.5 to 3.0%.

The B-type viscosity (60 rpm, 20°C) of the microfibrous cellulose dispersion is, for example, 700 cps or less, preferably 200 cps or less, and more preferably 50 cps or less. By keeping the B-type viscosity of the microfibrous cellulose dispersion low in this way, the microfibrous cellulose can be applied uniformly to the nonwoven fabric.

The microfibrous cellulose dispersion can be applied to the target surface by spraying, or by transfer using a letterpress or other method.

Pulp fibers that can be used to produce microfibrous cellulose include chemical pulps such as hardwood pulp (LBKP) and softwood pulp (NBKP); mechanical pulps such as bleached thermomechanical pulp (BTMP), stone ground pulp (SGP), pressed stone ground pulp (PGW), refiner ground pulp (RGP), chemi-ground pulp (CGP), thermo-ground pulp (TGP), ground pulp (GP), thermomechanical pulp (TMP), chemi-thermomechanical pulp (CTMP), and refiner mechanical pulp (RMP); waste paper pulp produced from used brown paper, used kraft envelope paper , used magazine paper, used newspaper, used flyer paper, used office paper, used cardboard, white used paper, Kent used paper, imitation used paper, used land certificate paper, and used recycled paper; and deinked pulp (DIP) obtained by deinking waste paper pulp. These may be used alone or in combination as long as the intended effect is not impaired. Furthermore, the pulp fibers may be subjected to a chemical treatment such as carboxymethylation.

Methods for producing microfibrous cellulose include mechanical methods such as the high-pressure homogenizer method, the microfluidizer method, the grinder grinding method, the bead mill freeze-pulverization method, and the ultrasonic fiberization method, but are not limited to these methods. In addition, microfibrillation is promoted by the combined use of TEMPO oxidation treatment, phosphate esterification treatment, acid treatment, etc.

＜Other＞
The moisture-absorbent sheet 15 may be used alone or attached to another part of the disposable wearable article. When used, the moisture-absorbent sheet 15 may have a non-breathable or poorly breathable member adjacent to one or both of the front and back sides, or may have a breathable material adjacent to both the front and back sides, or may have no adjacent member on one of the front and back sides.

For example, as shown in Figure 9, a moisture-absorbing sheet 15 can be provided between components in the waist portion, etc., or as shown in Figure 10, a moisture-absorbing sheet 15 can be provided on the back side of the target sheet 20 (for example, between the target sheet 20 and the exterior nonwoven fabric 12, or between the exterior nonwoven fabric 12 and the liquid-impermeable resin film 11).

In particular, to prevent stuffiness during wear, if the moisture-absorbing sheet 15 is provided so that a portion thereof is adjacent to the back side of the breathable skin-contacting layer that comes into contact with the wearer's skin (or the entirety of the sheet is adjacent to the back side of the skin-contacting layer), moisture inside the disposable wearable article can be efficiently absorbed or released to the outside during wear, thereby preventing stuffiness. For example, in the example shown in Figure 9, if the moisture-absorbing sheet 15 is provided in the waist area, the moisture-absorbing sheet 15 can be provided between the absorber 56 and the liquid-impermeable resin film 11 and between the top sheet 30 and the liquid-impermeable resin film 11.

<Explanation of terms used in the specification>
In the present specification, the following terms have the following meanings unless otherwise specified in the specification.

- The "front-rear direction" refers to the direction indicated by the symbol LD in the figure (longitudinal direction), and the "width direction" refers to the direction indicated by the symbol WD in the figure (left-right direction), with the front-rear direction and width direction being perpendicular to each other.

"MD direction" and "CD direction" refer to the flow direction (MD direction) in the manufacturing equipment and the horizontal direction (CD direction) perpendicular to it, and depending on the part of the product, one of them may be the front-to-back direction and the other the width direction. The MD direction of a nonwoven fabric is the direction of fiber orientation of the nonwoven fabric. Fiber orientation is the direction in which the fibers of the nonwoven fabric run, and can be determined, for example, by a measurement method based on the fiber orientation test method using zero-distance tensile strength in TAPPI standard method T481, or a simple measurement method that determines the fiber orientation direction from the tensile strength ratio in the front-to-back direction and the width direction.

- "Front side" means the side closest to the wearer's skin when worn, and "back side" means the side farthest from the wearer's skin when worn.

- "Front" means the side of the component that is closest to the wearer's skin when worn, and "back" means the side of the component that is farthest from the wearer's skin when worn.

- "Elongation rate" refers to the value when the natural length is 100%. For example, an elongation rate of 200% is equivalent to an elongation ratio of 2 times.

- "Gel strength" is measured as follows. 1.0 g of superabsorbent polymer is added to 49.0 g of artificial urine (a mixture of urea: 2 wt%, sodium chloride: 0.8 wt%, calcium chloride dihydrate: 0.03 wt%, magnesium sulfate heptahydrate: 0.08 wt%, and ion-exchanged water: 97.09 wt%) and stirred with a stirrer. The resulting gel is left in a thermo-hygrostat at 40°C x 60% RH for 3 hours, then returned to room temperature, and the gel strength is measured with a curd meter (I.techno Engineering: Curdmeter-MAX ME-500).

・"Basis weight" is measured as follows. After pre-drying the sample or test piece, leave it in a test room or device under standard conditions (test location: temperature 23±1°C, relative humidity 50±2%) until it reaches a constant weight. Pre-drying refers to bringing the sample or test piece to a constant weight in an environment at a temperature of 100°C. Note that pre-drying is not necessary for fibers with an official moisture regain of 0.0%. Using a sample collection template (100mm x 100mm), cut out a sample measuring 100mm x 100mm from the test piece that has reached a constant weight. Measure the weight of the sample and multiply it by 100 to calculate the weight per square meter, which is the basis weight.

"Thickness" is measured automatically using an automatic thickness measuring device (KES-G5 handy compression measurement program) under the conditions of a load of 0.098 N/ ^cm2 and a pressurized area of 2 ^cm2 . The thickness of perforated nonwoven fabrics is measured in the area excluding the holes and the surrounding protrusions.

- Water absorption is measured according to JIS K7223-1996 "Test method for water absorption of superabsorbent resins."

- The water absorption rate is the "time to the end point" when testing 2 g of superabsorbent polymer and 50 g of saline solution according to JIS K7224-1996 "Test method for water absorption rate of superabsorbent polymers."

"Microfibrous cellulose" refers to fine cellulose fibers or bundles thereof extracted from plants such as pulp, and generally refers to fibrous cellulose with an average fiber width of nano size (1 to 1000 nm or less), with those with an average fiber width (median diameter) of 100 nm or less (generally called cellulose nanofibrils (CNF)) being preferred, and those with an average fiber width (median diameter) of 10 to 60 nm being particularly preferred.

The "average fiber width" of microfibrous cellulose can be measured by the following method. That is, first, 100 ml of an aqueous dispersion of microfibrous cellulose with a solid content concentration of 0.01 to 0.1% by mass is filtered through a Teflon (registered trademark) membrane filter, and the solvent is replaced once with 100 ml of ethanol and three times with 20 ml of t-butanol. Next, the sample is freeze-dried and osmium-coated to obtain a sample. This sample is observed using an electron microscope SEM image at a magnification of 5,000 times, 10,000 times, or 30,000 times (in this embodiment, a magnification of 30,000 times) depending on the width of the fibers that make up the sample. Specifically, two diagonal lines are drawn on the observed image, and three straight lines are arbitrarily drawn that pass through the intersection of the diagonal lines. Furthermore, a total of 100 fiber rods that intersect with these three straight lines are visually measured. The median diameter of the measured values is then taken as the average fiber width.

- "Expanded state" means a flat, unfolded state without contraction or sagging.

- Unless otherwise specified, the dimensions of each part refer to the dimensions in the unfolded state, not the natural length state.

-If no specification is given regarding the environmental conditions for testing or measurement, the testing or measurement shall be performed in a test room or device under standard conditions (test location: temperature 23±1°C, relative humidity 50±2%).

The present invention can be applied to all types of disposable diapers, including not only tape-type disposable diapers like those in the above example, but also pants-type disposable diapers, pad-type disposable diapers, etc. It goes without saying that it can also be applied to other absorbent articles such as sanitary napkins.

11...liquid-impermeable resin film, 12...exterior nonwoven fabric, 13...connecting tape, 13A...connecting portion, 13B...tape main body, 13C...tape attachment portion, 15...moisture-absorbing sheet, 16...nonwoven fabric, 16t...thin portion, 17...microfibrous cellulose aggregate, 18...gap, 20...target sheet, 30...top sheet, 40...intermediate sheet, 50...absorbent element, 56...absorbent body, 58...packaging sheet, 60...rising gathers, 62...gathered sheet, B...dorsal portion, F...ventral portion, WD...width direction, LD...front-to-back direction.

Claims (6)

a nonwoven fabric in which thin-walled portions shrunk in the thickness direction are repeatedly formed at intervals;
A moisture-absorbing sheet having a dried microfibrous cellulose aggregate attached only to the fibers in the thin portion,
The nonwoven fabric constituting the moisture-absorbing sheet is a short-fiber nonwoven fabric having a fineness of 2 to 10 dtex and a basis weight of 20 to 40 g/ ^m2 ,
The amount of the microfibrous cellulose aggregate attached to the thin-walled portion is 0.1 to 5.0 g/ ^m2 ,
The depressions in the thin-walled portions are left unfilled on both the front and back sides of the moisture-absorbing sheet.
A moisture-absorbing sheet characterized by: The microfibrous cellulose aggregate is not present in any portion other than the thin portion.
The moisture-absorbing sheet according to claim 1. The thin-walled portion is provided in a striped or lattice pattern.
The moisture-absorbing sheet according to claim 1 or 2. An absorber;
a breathable, liquid-impermeable resin film provided on the back side of the absorbent body;
an exterior nonwoven fabric covering the back surface of the liquid-impermeable resin film;
A disposable wearing article having
a moisture-absorbing sheet provided between the liquid-impermeable resin film and the exterior nonwoven fabric,
The moisture-absorbing sheet has a nonwoven fabric in which thin-walled portions that have shrunk in the thickness direction are repeatedly formed at intervals, and a dried microfibrous cellulose aggregate that adheres only to the fibers within the thin-walled portions,
The depressions in the thin-walled portions are left unfilled on both the front and back sides of the moisture-absorbing sheet,
a ventilation gap is provided between the exterior nonwoven fabric and the thin portion, and between the liquid-impermeable resin film and the thin portion,
A disposable wearing article characterized by: a breathable skin-contacting layer in contact with the wearer's skin;
a moisture-absorbing sheet provided so as to have a portion adjacent to the back side of the skin-contact layer,
The moisture-absorbing sheet has a nonwoven fabric in which thin-walled portions that have shrunk in the thickness direction are repeatedly formed at intervals, and a dried microfibrous cellulose aggregate that adheres only to the fibers within the thin-walled portions,
The depressions in the thin-walled portions are left unfilled on both the front and back sides of the moisture-absorbing sheet,
a ventilation gap is provided between the skin contact layer and the thin portion, and between a member adjacent to the back side of the moisture-absorbing sheet and the thin portion ,
A disposable wearing article characterized by: a step of applying a dispersion of microfibrous cellulose to a nonwoven fabric in a repeating pattern at intervals, and drying the dispersion that has penetrated between the fibers of the nonwoven fabric, thereby forming thin-walled portions in the applied portions of the dispersion, and producing a moisture-absorbent sheet in which dried microfibrous cellulose aggregates are attached only to the fibers within the thin-walled portions, and the depressions in the thin-walled portions are left unfilled on both the front and back sides of the moisture-absorbent sheet;
and attaching the moisture-absorbent sheet, with the recesses of the thin-walled portions left unfilled on both the front and back sides, between members overlapping in the thickness direction of the disposable wearing article, to manufacture a disposable wearing article having ventilation gaps between the members and the thin-walled portions.
A method for manufacturing a disposable wearing article.