JP2020185319A - Absorbent article - Google Patents

Abstract

To provide an absorbent article comprising high fitness and leakage prevention property.SOLUTION: An absorbent article comprises: a liquid permeable top sheet (3) which has a longitudinal direction, a width direction and a thickness direction orthogonal each other; a liquid impermeable back sheet (5); and an absorbent core (10) provided between the top sheet and the back sheet. The absorbent article comprises folded parts (F1, F2) along a width direction, and on at least a part of the folded part, the absorbent core is arranged, in the absorbent article (1). The absorbent core has at least water holding fibers, and a density of the absorbent core on the folded part is 0.04 g/cm3 or greater and less than 0.3 g/cm3, and an average fiber length of the water holding fiber is less than 2 mm, and an evaluation result of flexure repulsion evaluation is 180 degree or greater and 270 degree or smaller.SELECTED DRAWING: Figure 10

Description

The present invention relates to an absorbent article.

As an example of an absorbable article, a sanitary napkin that absorbs excrement such as menstrual blood is known. Such sanitary napkins are provided with an absorber (absorbent core), which contains water-retaining fibers. Usually, softwood pulp fiber having a long fiber length is used as the water-retaining fiber. Further, Patent Document 1 also discloses a water-retaining fiber using a broad-leaved pulp fiber having a fiber length shorter than that of a softwood pulp fiber.

Japanese Patent Publication No. 2004-538024

Since sanitary napkins are individually wrapped in a folded state (for example, in a tri-folded state), they often have strong folding habits when used. If such a crease or wrinkles occur on the skin contact surface, the fit may be deteriorated, which may cause the wearer to feel uncomfortable or the leak prevention property may be deteriorated. In particular, in softwood pulp fibers, since the fiber length is long, the number of fibers in which one fiber is entangled with each other increases, so that the interaction between the pulp fibers is strong. Therefore, it is difficult for the pulp fibers to move and the confounding between the fibers to be released, which is necessary for releasing the folding habit, and as a result, the folding habit tends to remain. On the other hand, if the number of confounding fibers per fiber is reduced by reducing the density of the number of fibers, it is possible to make it difficult for creases to remain, but this is accompanied by deterioration of body fluid diffusivity due to a decrease in the capillary effect. There was a risk that the leakage prevention property would decrease.

Further, in the absorbent article of Patent Document 1, hardwood pulp fiber is used, but it is formed by the same manufacturing method (airlaid method) as the non-woven fabric, and a binder is added. For this reason, the rigidity of the binder may become too high, and folding habits may easily remain.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an absorbent article capable of improving fit and leakage prevention.

The main invention for achieving the above object has a longitudinal direction, a width direction, and a thickness direction orthogonal to each other, and a liquid permeable top sheet, a liquid impermeable back sheet, the top sheet, and the above. An absorbent article provided with an absorbent core provided between the back sheet, having a folded portion along the width direction, and having the absorbent core arranged in at least a part of the folded portion. The absorbent core has at least water-retaining fibers, and the density of the absorbent core at the folded portion is 0.04 g / cm ³ or more and less than 0.3 g / cm ³ , and the water-retaining core is present. It is an absorbent article characterized in that the average fiber length of the fibers is less than 2 mm and the evaluation result of the bending repulsion evaluation is 180 degrees or more and 270 degrees or less.

Other features of the present invention will be clarified by the description in the present specification and the accompanying drawings.

According to the present invention, it is possible to provide an absorbent article having high fit and leakage prevention property.

It is a schematic plan view which looked at the napkin 1 from the skin side in the thickness direction. It is a schematic plan view which looked at the napkin 1 from the non-skin side in the thickness direction. It is a schematic cross section shown by the arrow AA in FIG. It is a figure which shows the napkin 1 in the individually wrapped state. It is a figure which shows the distribution of the fiber length of a hardwood pulp fiber and a softwood pulp fiber. It is a figure for demonstrating the manufacturing method of the absorber 10. 7A to 7C are schematic explanatory views of an evaluation method for evaluation of bending repulsion. It is a figure (Table 1) which shows the average interfiber distance Dp of a fiber. It is a figure (Table 2) which shows the fiber number density of a fiber. It is a figure (Table 3) which shows the evaluation result of each sample.

The description of this specification and the accompanying drawings will clarify at least the following matters.
Absorbency provided between a liquid-permeable top sheet, a liquid-impermeable back sheet, and the top sheet and the back sheet, which have a longitudinal direction, a width direction, and a thickness direction orthogonal to each other. An absorbent article comprising a core, having a folded portion along the width direction, and having the absorbent core arranged in at least a part of the folded portion, wherein the absorbent core retains at least water. It has sex fibers, the density of the absorbent core at the fold is 0.04 g / cm ³ or more and less than 0.3 g / cm ³ , and the average fiber length of the water-retaining fibers is less than 2 mm. It is an absorbent article characterized in that the evaluation result of the bending repulsion evaluation is 180 degrees or more and 270 degrees or less.

According to such an absorbent article, it is possible to prevent the folding habit at the folded portion of the product from remaining, and it is possible to diffuse the excrement liquid such as menstrual blood without delay. Therefore, the fit and the leakage prevention property can be improved.

It is desirable that the water-retaining fibers include fibers having a fiber length of 3 mm or more in such an absorbent article.

According to such an absorbent article, kinking can be suppressed.

In such an absorbent article, it is desirable that the absorbent core also has a material other than the water-retaining fiber.

According to such an absorbent article, the rigidity can be increased.

It is desirable that the average number of water-retaining fibers per unit area of such an absorbent article is 300 fibers / mm ² or more and less than 2500 fibers / mm ² .

According to such an absorbent article, it is possible to make it difficult for the crease to remain and to improve the absorbency.

In such an absorbent article, it is desirable that the average interfiber distance of the water-retaining fibers is 5 μm or more and less than 40 μm.

According to such an absorbent article, it is possible to make it difficult for the crease to remain and to improve the absorbency.

In such an absorbent article, the absorbent core has a high-density fiber region having a fiber density higher than that of both end portions in the thickness direction at a central portion in the thickness direction, and the high-density fiber. It is desirable that the maximum length of the region in the longitudinal direction is shorter than the length of the folded portion in the longitudinal direction.

According to such an absorbent article, the absorbency can be further enhanced while making it difficult for the crease to remain.

In such an absorbent article, it is desirable that the average fiber length of the water-retaining fiber is shorter than the length of the folded portion in the thickness direction and the length in the longitudinal direction.

According to such an absorbent article, creases are less likely to remain.

Such an absorbent article having a thermoplastic resin fiber as the material, and the average number of crimps per unit length of the thermoplastic resin fiber is the average number of crimps per unit length of the water-retaining fiber. Is desirable.

According to such an absorbent article, the entanglement between the thermoplastic resin fiber and the water-retaining fiber can be reduced. As a result, it is possible to prevent creases from remaining, improve the wearing feeling, and improve the leakage prevention property.

=== Embodiment ===
<< Basic configuration of sanitary napkins >>
A sanitary napkin 1 (hereinafter, also simply referred to as a napkin 1) will be described as an example of the absorbent article according to the present embodiment. In the following description, a sanitary napkin will be described as an example of an absorbent article, but the absorbent article of the present embodiment also includes a so-called vaginal discharge sheet (for example, a panty liner), a light incontinence pad, and the like. It is not limited to sanitary napkins.

FIG. 1 is a schematic plan view of the napkin 1 as viewed from the skin side in the thickness direction. FIG. 2 is a schematic plan view of the napkin 1 as viewed from the non-skin side in the thickness direction. FIG. 3 is a schematic cross section shown by arrow AA in FIG. FIG. 4 is a diagram showing a napkin 1 in an individually wrapped state. For convenience, the separator 50 and the packaging sheet 60 are not shown in FIGS. 1, 3, and 4. Further, in the following description, each direction is defined as shown in FIGS. 1 to 4. That is, the "longitudinal direction" along the product longitudinal direction of the napkin 1, the "width direction" orthogonal to the longitudinal direction along the product short direction of the napkin 1, and the "thickness" orthogonal to the longitudinal direction and the width direction, respectively. "Direction" is defined. Of the longitudinal directions, the direction that is the ventral side of the wearer when the napkin 1 is used is defined as the "front side", and the direction that is the dorsal side of the wearer is defined as the "rear side". In the thickness direction, the side that comes into contact with the wearer's skin when the napkin 1 is worn is referred to as the "skin side (upper side)", and the opposite side is referred to as the "non-skin side (lower side)".

The napkin 1 is a vertically elongated sheet-like member in a plan view, and the pair of side sheets 2, the top sheet 3, the second sheet 4, the absorber 10, the carrier sheet 6, and the back sheet 5 are in the thickness direction. It is formed by laminating in order from the skin side to the non-skin side (see FIG. 3). Then, each of these members is joined to a member adjacent in the thickness direction with an adhesive such as a hot melt adhesive (HMA). Examples of the adhesive application pattern include an Ω pattern, a spiral pattern, and a stripe pattern.

Further, the napkin 1 has a napkin main body 20 provided with an absorber 10 and a pair of wing portions 30 extending outward from the central region in the longitudinal direction of the napkin main body 20 in the width direction. The central region in the longitudinal direction in which the wing portion 30 is provided is a region that comes into contact with the wearer's excretion port (lower crotch) when the napkin 1 is used.

The top sheet 3 is a member that comes into contact with the wearer's skin when the napkin 1 is used, and allows a liquid such as menstrual blood to permeate from the skin side to the non-skin side in the thickness direction and move it to the absorber 10. Therefore, for the top sheet 3, an appropriate liquid-permeable flexible sheet such as an air-through non-woven fabric is used.

The second sheet 4 is a liquid permeable sheet, and the same air-through non-woven fabric as the top sheet 3 can be exemplified. The second sheet 4 is provided on the skin side surface of the absorber 10 and plays a role of preventing the reversion of excrement such as menstrual blood, improving the diffusion of excrement, and improving the cushioning property. However, the napkin 1 does not have to have the second sheet 4.

The carrier sheet 6 may be a liquid-permeable sheet or a liquid-impermeable sheet, and examples thereof include tissue paper and SMS (spun bond / melt blown / spun bond) non-woven fabric. The carrier sheet 6 is provided between the absorber 10 and the back sheet 5. However, the napkin 1 does not have to have the carrier sheet 6.

The back sheet 5 prevents the liquid that has passed through the top sheet 3 and absorbed by the absorber 10 from seeping out to the clothing side (non-skin side) such as underwear when the napkin 1 is used. As the back sheet 5, an appropriate liquid-impermeable flexible sheet such as a polyethylene (PE) resin film is used. The plane size of the top sheet 3 and the back sheet 5 is larger than that of the absorber 10.

The side sheet 2 may be a liquid-permeable sheet or a liquid-impermeable sheet, and the same air-through non-woven fabric as the top sheet 3 can be exemplified.

Then, as shown in FIGS. 1 and 2, the outer peripheral edges of the side sheet 2 and the top sheet 3 and the back sheet 5 are bonded to each other by adhesion or welding, so that the sheets are absorbed between the sheets. Body 10 is held. Further, the pair of side sheets 2 extend outward from both side portions in the width direction of the top sheet 3 in the width direction, and form a pair of wing portions 30 together with the back sheet 5.

On the non-skin side surface of the napkin body 20 in the thickness direction (that is, the non-skin side surface of the back sheet 5), an appropriate adhesive (for example, hot melt adhesive) is applied to a plurality of strip-shaped regions along the longitudinal direction. The adhesive portion 21 for the main body formed by this is provided (see FIGS. 2 and 3). When the napkin 1 is used, the adhesive portion 21 for the main body is attached to the side surface of the skin such as underwear, whereby the napkin 1 is fixed to the underwear or the like. If the adhesive portion 21 for the main body crosses the folded portion in the longitudinal direction in the entire width direction of the folded portion (front folded portion F1 and rear folded portion F2), the adhesive extends at the folded portion. Since it is in a squeezed state, there is a risk that it will be stretched during use, and creases will easily remain. Therefore, in the present embodiment, the adhesive portion 21 for the main body portion does not cross the folded portion in the longitudinal direction in the entire width direction of the folded portion (front folded portion F1 and rear folded portion F2). As a result, it is possible to prevent the adhesive from being stretched, and it is difficult for creases to remain (a feeling of wearing can be improved and leakage prevention can be further improved). However, the present invention is not limited to this, and for example, the adhesive portion 21 for the main body portion may be provided along the width direction. In this case, for the same reason as described above, it is preferable to arrange the adhesive portion 21 for the main body portion so as not to overlap with at least a part (preferably the whole) of each folded portion. As a result, the adhesive portion 21 for the main body portion can be prevented from crossing the folded portion in the longitudinal direction in the entire width direction of the folded portion.

Similarly, a wing portion adhesive portion 31 is provided on the non-skin side surface of each wing portion 30 in the thickness direction (that is, the non-skin side surface of the back sheet 5) (see FIG. 3). When the napkin 1 is used, the wing portion 30 is bent toward the non-skin side, and the adhesive portion 31 for the wing portion is attached to the non-skin side surface of the underwear or the like, whereby the napkin 1 is fixed to the underwear or the like.

The absorber 10 (corresponding to an absorbent core) is a vertically long member that is long along the longitudinal direction, and absorbs a liquid (excretion) such as menstrual blood and holds it inside. Details of the absorber 10 will be described later. The second sheet 4, the absorber 10, and the carrier sheet 6 have the same planar shape and are laminated in the thickness direction. In the present embodiment, the respective members are bonded to each other by a hot melt adhesive (HMA), but they may not be bonded to each other.

Further, the napkin 1 is provided with a plurality of pressing portions 40 (recesses) (see FIG. 1). The squeezed portion 40 is a portion recessed from the skin side to the non-skin side in the thickness direction, and is a portion having a higher density of water-retaining fibers than an adjacent portion. In the squeezing portion 40, at least the entire area of the top sheet 3, the second sheet 4, and the absorber 10 in the thickness direction is squeezed (embossed) from the skin side in the thickness direction and joined and integrated. This makes it difficult for the napkin 1 to twist. However, not limited to the above, the pressing portion 40 may be provided only on the absorber 10, the pressing portion 40 may be provided only from the top sheet 3 to a part of the absorber 10 on the skin side in the thickness direction, or from the back sheet 5. The squeezing portion 40 may be provided on the absorber 10. Further, the arrangement pattern of the pressing portion 40 is not limited to that shown in FIG.

Further, when the napkin 1 is shipped, the separator 50 and the packaging sheet 60 are attached as shown in FIG.

The wrapping sheet 60 is a sheet member that individually wraps the napkin 1. The packaging sheet 60 is joined to the napkin 1 in a state of being overlapped with the napkin 1 in the thickness direction before the use of the napkin 1, and is removed when the napkin 1 is used. In the present embodiment, the packaging sheet 60 is a substantially rectangular sheet member having long sides in the longitudinal direction (longitudinal direction), and the napkin 1 and the packaging sheet 60 are joined via a separator 50. At the time of shipment of the napkin 1, the packaging sheet 60 is folded in the longitudinal direction together with the absorber 10 and the separator 50, and both ends of the packaging sheet 60 in the width direction are adhered (sealed) to each other in the folded state. Has been done. Further, a lead tape 62 for fixing the packaging state is provided at the center of the front end portion of the packaging sheet 60 in the width direction.

The separator 50 is a sheet member arranged between the back sheet 5 of the napkin 1 and the packaging sheet 60 (see FIG. 2). The skin-side surface of the separator 50 is peeled off using a silicone resin or the like, and is detachably attached to the main body adhesive portion 21 provided on the non-skin side surface of the napkin main body 20. Since the peeling process is known, the description thereof will be omitted. On the other hand, the non-skin side surface of the separator 50 is fixed (joined) to the packaging sheet 60 by a packaging sheet joining portion provided between the separator 50 and the packaging sheet 60. By arranging such a separator 50, the adhesive forming the adhesive portion 21 for the main body portion adheres to the packaging sheet 60 before the use of the napkin 1, and the adhesiveness of the adhesive portion 21 for the main body portion is weakened. The adhesive portion 21 for the main body portion is protected while being suppressed from becoming. When the napkin 1 is used, the separator 50 is peeled off from the main body adhesive portion 21 together with the packaging sheet 60, and the napkin 1 is fixed to the wearer's underwear or the like by the adhesive force of the main body adhesive portion 21. Will be. A separator 50 and a packaging sheet 60 may also be used. Specifically, as the packaging sheet 60, a film having a skin side surface treated with silicon and having the same function as the separator 50 may be used.

In the present embodiment, the individually wrapped napkin 1 is folded in the longitudinal direction by a plurality of creases along the width direction, as shown in FIG. Specifically, the napkin 1 is folded by two folding portions (front folding portion F1 and rear folding portion F2) so as to be folded in three in the longitudinal direction. The front folded portion F1 is located on the front side of the central position of the napkin 1 in the longitudinal direction, and the rear folded portion F2 is located on the rear side of the central position of the napkin 1 in the longitudinal direction. Further, an absorber 10 (absorbable core) is arranged in at least a part of the front folded portion F1 and at least a part of the rear folded portion F2, respectively. The front folded portion F1 has the thickness of the absorber 10 (the portion indicated by t in FIG. 1) on both sides in the longitudinal direction, centering on one end P1 in the longitudinal direction when the napkin 1 is folded (FIG. 4). The area. Further, the rear folded portion F2 is a region corresponding to the thickness of the absorber 10 on both sides in the longitudinal direction with the other end P2 in the longitudinal direction as the center in the state where the napkin 1 is folded (FIG. 4).

The number and positions of the folded portions provided on the napkin 1 are not necessarily limited to this. For example, a folding portion may be further provided on the rear side of the rear folding portion F2.

As described above, the napkin 1 is shipped to the market as a product in a state of being folded in three in the front folding portion F1 and the rear folding portion F2 together with the packaging sheet 60 (and the separator 50).

Then, when the wearer uses the napkin 1, the napkin 1 is unfolded from the folded state. At this time, folding habits often remain at the folded positions (front folding portion F1 and rear folding portion F2). If such a crease remains, the fit may be deteriorated and the leakage prevention property may be deteriorated.

Therefore, in the present embodiment, by examining the material of the absorber 10, it is possible to suppress the remaining creases and improve the fit and the leakage prevention property.

<< About absorber 10 >>
The absorber 10 has water-retaining fibers that absorb liquid, and is formed into a vertically elongated shape in a plan view. Further, the absorber 10 may contain a material other than the water-retaining fiber (for example, a thermoplastic resin fiber). When the water-retaining fiber and the thermoplastic resin fiber are provided, the absorber 10 is formed in a state where these fibers are mixed with each other.

As the water-retaining fiber, pulp, for example, wood pulp obtained from coniferous or broadleaf tree, non-wood pulp such as bagas, kenaf, bamboo, hemp, cotton (for example, cotton linter); regenerated cellulose fiber such as rayon fiber; Examples thereof include semi-synthetic fibers such as acetate fibers. Usually, softwood pulp having a long fiber length is often used as the water-retaining fiber.

FIG. 5 is a diagram showing the distribution of fiber lengths of hardwood pulp fibers (hereinafter, also referred to as hardwood pulp) and softwood pulp fibers (hereinafter, also referred to as softwood pulp). The horizontal axis shows the fiber length (mm), and the vertical axis shows the frequency (%). As shown in the figure, the average fiber length of softwood pulp is 2.5 mm, and the distribution width of the fiber length is wide (including fibers of 3 mm or more). On the other hand, the average fiber length of hardwood pulp is 0.8 mm, and the distribution width of the fiber length is narrow. The definition of the average fiber length will be described later. As described above, hardwood pulp has a shorter fiber length than softwood pulp. In the napkin 1 of the present embodiment, hardwood pulp is used as the absorber 10. As a result, the average fiber length of the water-retaining fibers is short (specifically, less than 2 mm) (see FIG. 10), and folding habits are less likely to remain (described later). If the average fiber length is shorter than the length (thickness t) in the thickness direction of the folded portion (front folded portion F1 and the rear folded portion F2) and the length in the longitudinal direction, the entire length of the folded portion is extended. Since there are no fibers, folding habits are less likely to remain.

Further, the density of the absorber 10 in the folded portion (front folded portion F1 and rear folded portion F2) is 0.04 to 0.3 (g / cm ³ ) (described later). As a result, the body fluid can be diffused without delay, and the absorbability can be ensured.

Examples of the thermoplastic resin fiber include a single fiber made of polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), etc., a fiber obtained by polymerizing PP and PE, or PP and PE. Examples thereof include composite fibers having a core-sheath structure composed of. Further, with the thermoplastic resin fiber, the degree of crimping can be adjusted. For example, as the thermoplastic resin fiber, the fiber can be crimped by using a core-sheath type or eccentric type composite fiber composed of two synthetic fiber components having different melting points. In the present embodiment, the average number of crimps per unit length of the thermoplastic resin fiber is set to be smaller than the average number of crimps per unit length of the water-retaining fiber. As a result, the entanglement between the thermoplastic resin fiber and the water-retaining fiber is reduced, and the crease is less likely to remain. Therefore, even when the thermoplastic resin fiber is contained, the wearing feeling can be improved and the leakage prevention property can be improved. As a method for measuring the average number of crimps, for example, a plurality of test pieces (for example, 5 cm square test pieces) are sampled in the width direction, and a Keyence microscope VH-Z450 or the like is used in the test pieces. The number of crimps per inch (2.54 cm) may be measured several times with no load applied to the fibers. The number of crimps (average number of crimps per unit length) can be calculated from the average value.

Further, the absorber 10 may contain fibers other than the above, and may contain natural fibers such as cellulose, for example.

Further, a liquid absorbent granular material such as a highly absorbent polymer (so-called SAP) may be added.

As a method for producing the absorber 10, a method of accumulating crushed pulp, a highly absorbent polymer, or the like is known.

FIG. 6 is a diagram for explaining a method of manufacturing the absorber 10. Here, a case where the absorber 10 includes a water-retaining fiber, a thermoplastic resin fiber, and a highly absorbent polymer (SAP) will be described.

The rotary drum 70 is a hollow cylindrical drum, and a plurality of recesses 71 are formed at a predetermined pitch on the peripheral surface as a mold for filling an absorber material. When the rotary drum 70 rotates and the recess 71 enters the material supply section 80, the absorber material supplied from the material supply section 80 is deposited (accumulated) in the recess 71 by the suction of the suction section 72.

The material supply unit 80 with the hood 80a is formed so as to cover the upper part of the rotary drum 70, and the material supply unit 80 is a crushed pulp (coniferous pulp, hardwood pulp) obtained by crushing a pulp sheet with a crusher (not shown). ) And the thermoplastic resin are supplied to the recess 71 by air transportation. Further, the material supply unit 80 includes a particle supply unit 81 for supplying superabsorbent polymer particles, and supplies superabsorbent polymer particles to the recess 71. The mixture of the water-absorbent fiber and the thermoplastic resin fiber and the superabsorbent polymer particles are deposited in the recess 71 in a mixed state, and the absorber 10 is formed in the recess 71.

When the recess 71 accommodating the absorber 10 reaches the bottom of the drum due to the further rotation of the rotating drum 70, the absorber 10 is disengaged from the recess 71, and the base material (carrier sheet 6, etc.) conveyed by the conveyor. It will be placed on top and handed over to the next process.

When the pulp sheet is crushed by the crusher, the pulp sheet may not be completely crushed and the fibers may remain in a ball shape. As a result, regions (referred to as high-density fiber regions) in which pulp is densely packed like fluff are scattered in the absorber 10. In this high-density fiber region, unlike the pressed portion 40, the fiber density is higher in the central portion in the thickness direction than in the end portions on both sides in the thickness direction. It is desirable that the maximum length of the high-density fiber region in the longitudinal direction is shorter than the length of the folded portion (front folded portion F1 and rear folded portion F2) in the longitudinal direction. As a result, the high-density fiber region does not straddle the portion where the load is applied and the portion where the load is not applied, so that the folding habit can be less likely to remain. In addition, the presence of the high density fiber region can further enhance the absorbency.

Further, as a comparative example of the absorber 10 (described later), a pulp fiber, a thermoplastic resin fiber, a powder, or the like formed into a sheet by the same manufacturing method as the non-woven fabric (airlaid method) was used. A binder is added to the airlaid, and the rigidity is higher than that manufactured by the manufacturing method shown in FIG.

=== Evaluation of napkin 1 ==
Samples (napkins 1) having different fiber components and manufacturing methods for the absorber 10 were prepared and evaluated such as bending repulsion evaluation.

<< Sample >>
See FIG. 10 for sample conditions.

Example: A sample in which hardwood pulp is contained in the absorber 10 and is produced by the production method of FIG. Here, hardwood pulp and thermoplastic resin fibers having an average fiber length of 6 to 70 mm are mixed in a predetermined ratio (Examples 1 and 2), and hardwood pulp and coniferous pulp are mixed in a predetermined ratio (Example 3). 4) and only hardwood pulp (Example 5) were evaluated.

Comparative Examples: Samples in which the absorber 10 does not contain hardwood pulp (Comparative Examples 1, 2 and 4) and samples in which the absorber 10 is produced by the airlaid method (Comparative Examples 3 and 4). Although hardwood pulp is contained in Comparative Example 3, it is produced by the airlaid method (a binder is added).

A plurality of samples under each condition were prepared, and the following evaluations (for bending repulsion evaluation, absorbent body thickness evaluation, etc.) were performed.

<< Evaluation method >>
<Bending repulsion evaluation method>
(Preparation)
The adhesive portions (seal portions) at both ends of the individual packaging (packaging sheet 60) in the width direction were cut off so as not to cut the product (napkin 1). This is to avoid touching the napkin 1 as much as possible. Then, the napkin 1 was taken out so as not to touch the fold portion to be evaluated while maintaining the state where the fold angle of the fold portion (front fold portion F1 and rear fold portion F2) was 90 degrees or less (that is,). The separator 50 and the packaging sheet 60 were peeled off from the napkin 1). After that, while maintaining the same state (the state in which the folding angle of the folded portion is 90 degrees or less), only the adhesive (adhesive portion 21 for the main body portion) of the napkin 1 is washed with toluene, and the pair of wing portions 30 It was excised and used as a measurement sample (excision is unnecessary when the wing portion 30 does not exist). When the product contains an elastic member, it should be cut at intervals of 5 mm in the longitudinal direction over the entire length of all the elastic members while keeping the folding angle of the product folding portion at 90 degrees or less. At that time, cutting of the member around the elastic member should be limited to the minimum necessary for cutting the elastic member. After cleaning, the sample is held so that the folded portion to be evaluated has the thickness at the time of individual packaging (for example, the front folded portion F1 is sandwiched between plate materials having a gap corresponding to the thickness of the two folds). The sample was placed) and the toluene was dried at room temperature.

(Bending repulsion evaluation)
7A to 7C are schematic explanatory views of an evaluation method for evaluation of bending repulsion.

First, as shown in FIG. 7A, a product folding line (a regular hexahedral transparent acrylic box having a side of 50 cm is used in this embodiment) is placed on the top surface of a jig 100 having a top surface and side surfaces whose corners are right angles. Here, the sample was arranged so that the line along the width direction of the front folding portion F1) and the end edge of the jig 100 overlap in the thickness direction. Then, a fixing member (not shown) such as a gum tape was attached to the entire width direction at a portion 20 mm away from the front folding portion F1 on the central side in the longitudinal direction, and the product sample was fixed on the jig 100. At that time, for products having folds along the longitudinal direction, all of them should be in the unfolded state.

Next, as shown in FIG. 7B, an L-shaped member 120 (in this embodiment, a 150 g L-shaped acrylic plate with a surface of 30 cm × 30 cm is used) is placed on the sample (napkin 1), and the product folding line is formed. With (here, the front folding portion F1) as a base point, the portion protruding from the top surface edge of the jig 100 was bent downward in the vertical direction (270 degrees with respect to the top surface of the jig 100). Then, the L-shaped member 120 was pressed against the sample for 3 seconds without a gap and allowed to stand.

Then, as shown in FIG. 7C, after the L-shaped member 120 is removed and allowed to stand for 1 minute, the plane from the folded portion (here, the end P1 of the front folded portion F1) to the end (here, the front end) of the product. The angle (θ) formed by the virtual straight line and the top surface of the jig 100 was measured.

<Absorbent thickness evaluation method>
First, the product (napkin 1) was taken out from the individual packaging materials (packaging sheet 60 and separator 50).

Next, the napkin 1 is frozen in liquid nitrogen, the folded portion (front folded portion F1 or rear folded portion F2) in the central portion in the width direction is cut by 50 mm in the longitudinal direction, and the folded portion is directed outward in the width direction from the cut end portion. The measurement sample was obtained by cutting all the members. If there is a squeeze groove in the center of the width direction, the same part in the width direction without the squeeze groove should be measured.

Next, the folded portion (front folded portion F1 or rear folded portion F2) is fixed in a state of being refracted 90 degrees toward the skin surface side along the folding line, and a digital microscope VHX-100 (lens) manufactured by KEYENCE CORPORATION is fixed. Using the VH-Z20R + variable illumination attachment VH-K20), an image of the cross section of the folded portion of the measurement sample was taken at a measurement area: length 20 mm × width 20 mm, and the thickness of the absorber 10 containing the water-retaining fiber was determined. It was measured. The portions of the folded portion (front folded portion F1 or rear folded portion F2) divided into approximately 10 equal parts in a range of 10 mm were measured, and the average value was taken as the thickness of the absorber 10.

<Evaluation method for absorber basis weight>
First, cut out 10 mm in the longitudinal direction around the folded portion (front folded portion F1 or rear folded portion F2) and 40 mm in the width direction centered on the central portion in the width direction, and measure the weight directly on a balance (for example, Kensei Kogyo Co., Ltd.). It was measured with an electronic balance manufactured by HF-300).

Next, the adhesive of the sample whose weight was measured was washed with toluene and dried, and then the weight of the member containing no water-retaining fiber was measured, subtracted from the weight measured above, and the cut area (this implementation). In the form, it was divided by 10 mm × 40 mm).

<Measurement method of absorber density of folded part>
The absorber density (g / cm ³ ) of the folded portion was calculated from the absorber basis weight and the absorber thickness measured above.

<Fiber length evaluation method>
The fiber length was measured at the same part as the absorber basis weight evaluation.
The average fiber length of pulp fibers means the weight-weighted average fiber length. The weight-weighted average fiber length is measured as an L (w) value by Kajaani FiberLab Fiber Properties (offline) [kajaani FiberLab fiber products (off-line)] manufactured by metso automation. The significance and measurement method of the average fiber length in Examples and Comparative Examples are also the same.

The average fiber length of fibers other than pulp fibers is the glass with the scale of "A7.1.1 A method (standard method)" in "A7.1 Fiber length measurement" of Annex A of JIS L 1015: 2010. It is measured according to "Method for measuring the length of individual fibers on a plate". The above method is a test method corresponding to ISO 6989 published in 1981.

<Average interfiber distance evaluation method>
3D image connection of a microscope (VHX-2000 manufactured by KEYENCE, lens VH-Z20W aperture open) using a sample obtained by cutting out the part corresponding to the folded part of the sample to be measured into a square shape (cut in the thickness direction). Using the function, a magnified image (for example, a 100x image for hardwoods and a 500x image for conifers) that is in focus from the surface of the sample to a depth of 100 μm is obtained, and the focal points are matched based on the enlarged image. The outside of the existing fiber was extracted. The surface formed there is used as a fiber space. The diameter of the maximum inscribed circle of the fiber space was defined as the fiber space distance, and the average value of 100 fiber spaces was defined as the average interfiber distance (Dp).

FIG. 8 is a diagram (Table 1) showing the average interfiber distance Dp of the fibers. In the figure, the fiber ratio (%) is the weight ratio of the fibers constituting the absorber 10. When the absorber 10 has a core wrap sheet, the weight ratio of the portion excluding the core wrap sheet, and when there is no core wrap sheet, it remains as it is. It is a weight ratio (the same applies to FIGS. 9 and 10).

As shown in FIG. 8, hardwood pulp has a smaller average interfiber distance Dp than softwood pulp. Further, when thermoplastic resin fibers having an average fiber length of 6 to 70 mm are mixed, the average interfiber distance Dp changes according to the mixing ratio. For example, in coniferous pulp, the average interfiber distance Dp is reduced by mixing thermoplastic resin fibers, and in hardwood pulp, the average by mixing thermoplastic resin fibers (the more thermoplastic resin fibers). The interfiber distance Dp is large.

The average interfiber distance Dp is preferably 5 μm or more and less than 40 μm. As a result, the appropriate spacing between the fibers can be maintained, the capillary effect is likely to act, and the absorbability is improved. Therefore, it is possible to make it difficult for the crease to remain and to improve the absorbability. If the average interfiber distance Dp is too small (less than 5 μm), the time required for the liquid to pass becomes long, and if the average interfiber distance Dp is too large (40 μm or more), the capillary phenomenon occurs. Is less likely to occur, and absorbency is reduced. More preferably, it is less than 20 μm. As the proportion of hardwoods increases, the capillary effect can be increased and the absorption rate can be improved.

FIG. 9 is a diagram (Table 2) showing the fiber number density of the fibers. The fiber number density (corresponding to the average number of fibers per unit area) is a value obtained by calculating the number of fibers included per unit area in the case of a finely packed structure by the fiber thickness + the average distance between fibers. ..

As shown in FIG. 9, hardwood pulp is thinner and has a shorter interfiber distance than softwood pulp, and therefore has a high fiber number density. For example, the fiber number density of hardwood pulp is 1182.2 fibers / mm ^2, which is about 6 times the fiber number density of softwood pulp (200.3 fibers / mm ² ). Therefore, when hardwood pulp is used, the density can be increased as compared with the case where softwood pulp is used. Also, here as well, the fiber number density differs depending on the mixing ratio of the thermoplastic resin fibers having an average fiber length of 6 to 70 mm.

Fiber number density is desirably 2500 lines / mm less than ² 300 lines / mm ² or more. If the fiber number density is less than 300 fibers / mm ² , folding habits are less likely to remain, but the absorber 10 becomes faint and twists during use, resulting in a decrease in the absorber area and easy leakage. .. If the density of the number of fibers is 2500 fibers / mm ² or more, folding habits tend to remain, and the absorber 10 is finished too hard, which increases the discomfort during use. If the number of fibers density 300 lines / mm ² or more 2,500 / mm ² under a, it is possible to enhance the capillary effect, also allows thinner and softening. Therefore, it is possible to make it difficult for the crease to remain and to improve the absorbability.

In the case of hardwood pulp alone, the short fiber length may make it easy to twist, but in addition to hardwood pulp, coniferous pulp (fibers with a fiber length of 3 mm or more) and heat with an average fiber length of 6 to 70 mm. By containing the plastic resin fiber, the twist can be suppressed.

<< Evaluation Results >>
FIG. 10 is a diagram (Table 3) showing the evaluation results of each sample. Here, bending repulsion evaluation. The evaluation results of the absorber density of the folded portion, the weight of the absorber, and the average fiber length of the water-retaining fiber are shown.

In Examples 1 to 5 using hardwood pulp, the evaluation result of the bending repulsion evaluation was 180 degrees or more and 270 degrees or less. It is considered that this is because the average fiber length of the water-retaining fiber in the absorber 10 is short (less than 2 mm), so that the degree of freedom of the fiber itself is large and the friction is small. As described above, in Examples 1 to 5, it can be said that folding habits are unlikely to remain in the folded portions (front folded portion F1 and rear folded portion F2). In Examples 3 and 4, softwood pulp is also contained (fibers having a fiber length of 3 mm or more are also included), but the average fiber length is less than 2 mm due to mixing with hardwood pulp. (The evaluation result of the bending repulsion evaluation is 180 degrees or more and 270 degrees or less).

Further, in Examples 1 to 5, the absorber density of the folded portion is 0.04 to 0.3 (g / cm ³ ), the body fluid can be diffused smoothly, and the absorbability can be ensured. .. That is, in Examples 1 to 5, the fit and the leakage prevention property can be improved.

On the other hand, in Comparative Example 1, Comparative Example 2, and Comparative Example 4, since hardwood pulp was not used, the average fiber length was 2.5 mm, which was longer than that of Examples 1 to 5. As a result, the evaluation result of the bending repulsion evaluation is less than 180 degrees, and folding habits tend to remain. Also in these comparative examples, it is possible to make the bending repulsion evaluation 180 degrees or more by, for example, reducing the basis weight of the absorber. However, in this case, the absorbency is lowered, so that the product may not function as an absorbent article.

Further, in Comparative Example 3, the ratio of hardwood pulp to softwood pulp is the same as that of Example 3, and the average fiber length is less than 2 mm, but it is air-laid and a binder is added. For this reason, the rigidity is high, and even if hardwood pulp is used, folding habits are likely to remain (the evaluation result of the bending repulsion evaluation is less than 180 degrees).

=== Other embodiments ===
Although the embodiments of the present invention have been described above, the above-described embodiments are for facilitating the understanding of the present invention, and are not for limiting the interpretation of the present invention. Further, it goes without saying that the present invention can be changed or improved without departing from the gist thereof, and the present invention includes an equivalent thereof.

In the above-described embodiment, the sanitary napkin 1 as an example of the absorbent article has a pair of wing portions 30, but is not limited to this. That is, the wing portion 30 may be omitted.

Further, in the above-described embodiment, the absorber 10 is covered with two sheets, a second sheet 4 and a carrier sheet 6, but the present invention is not limited to this. For example, the skin side surface and the non-skin side surface of the absorber 10 may be covered with a single sheet.

1 Sanitary napkin (absorbent article),
2 side seats, 3 top seats, 4 second seats,
5 back seats, 6 carrier seats,
10 Absorbent (absorbent core),
20 Napkin main body, 21 Adhesive part for main body 30 Wing part, 31 Adhesive part for wing 40 Squeezing part,
50 separator,
60 packaging sheet,
70 rotating drum, 71 recess, 72 suction part,
80 material supply, 80a hood,
81 Particle supply unit,
F1 front fold, F2 rear fold

The main invention for achieving the above object is
It has a longitudinal direction, a width direction, and a thickness direction that are orthogonal to each other.
With a liquid permeable top sheet,
With a liquid-impermeable back sheet,
An absorbent core provided between the top sheet and the back sheet,
An absorbent article having a folded portion along the width direction and having the absorbent core arranged in at least a part of the folded portion.
The absorbent core has at least water-retaining fibers and
The density of the absorbent core in the folded portion is 0.04 g / cm ³ or more and less than 0.3 g / cm ³ .
The average fiber length of the water-retaining fiber is less than 2 mm.
The evaluation result of the bending repulsion evaluation is 180 degrees or more and 270 degrees or less .
The absorbent core has a high-density fiber region in the central portion in the thickness direction, which has a higher fiber density than the end portions on both sides in the thickness direction.
It is an absorbent article characterized by the above.

Claims (8)

It has a longitudinal direction, a width direction, and a thickness direction that are orthogonal to each other.
With a liquid permeable top sheet,
With a liquid-impermeable back sheet,
An absorbent core provided between the top sheet and the back sheet,
An absorbent article having a folded portion along the width direction and having the absorbent core arranged in at least a part of the folded portion.
The absorbent core has at least water-retaining fibers and
The density of the absorbent core in the folded portion is 0.04 g / cm ³ or more and less than 0.3 g / cm ³ .
The average fiber length of the water-retaining fiber is less than 2 mm.
The evaluation result of the bending repulsion evaluation is 180 degrees or more and 270 degrees or less.
An absorbent article characterized by that. The absorbent article according to claim 1.
The water-retaining fiber also includes a fiber having a fiber length of 3 mm or more.
An absorbent article characterized by that. The absorbent article according to claim 1 or 2.
The absorbent core also has a material other than the water-retaining fiber.
An absorbent article characterized by that. The absorbent article according to any one of claims 1 to 3.
The average number of water-retaining fibers per unit area is 300 fibers / mm ² or more and less than 2500 fibers / mm ² .
An absorbent article characterized by that. The absorbent article according to any one of claims 1 to 4.
The average interfiber distance of the water-retaining fibers is 5 μm or more and less than 40 μm.
An absorbent article characterized by that. The absorbent article according to any one of claims 1 to 5.
The absorbent core has a high-density fiber region in the central portion in the thickness direction, which has a higher fiber density than the end portions on both sides in the thickness direction.
The maximum length of the high-density fiber region in the longitudinal direction is shorter than the length of the folded portion in the longitudinal direction.
An absorbent article characterized by that. The absorbent article according to any one of claims 1 to 6.
The average fiber length of the water-retaining fiber is shorter than the length of the folded portion in the thickness direction and the length in the longitudinal direction.
An absorbent article characterized by that. The absorbent article according to claim 3.
It has thermoplastic resin fibers as the material,
The average number of crimps per unit length of the thermoplastic resin fiber is smaller than the average number of crimps per unit length of the water-retaining fiber.
An absorbent article characterized by that.

Images