JP2022083803A - Absorbent article - Google Patents

Abstract

To provide an absorbent article having practically sufficient liquid absorptivity, and having smooth touch and excellent feeling of wearing.SOLUTION: An absorbent article 1 includes an absorbent core 5 capable of absorbing and holding body fluid, and a surface sheet 3 arranged on the nearer side from the skin of a wearer than the absorbent core 5. A fiber mass layer 6 which is an aggregate of multiple fiber masses 11 is arranged on the farther side from the skin of the wearer than the absorbent core 5. The fiber mass 11 contains non-absorbent thermoplastic fibers. An average fineness of constituent fibers of the fiber mass 11 is 1 dtex or more and 2.5 dtex or less.SELECTED DRAWING: Figure 2

Description

The present invention relates to an absorbent article comprising a fiber mass layer, which is an aggregate of a plurality of fiber masses.

As absorbent articles such as disposable diapers and menstrual napkins, a front sheet arranged at a position where it can come into contact with the wearer's skin, and a back sheet arranged at a position farther from the wearer's skin than the front surface sheet. Those including an absorber interspersed between both sheets are known. The absorber is typically composed of an absorbent core containing a water-absorbent fiber such as wood pulp or a water-absorbent material such as a water-absorbent polymer, and can absorb and retain body fluids such as urine, stool, and menstrual blood. .. There are many properties required for the absorber, such as flexibility, cushioning, and shape retention, as well as liquid absorbency, and various techniques for improving the absorber have been proposed in response to these.

Patent Document 1 describes an absorber containing a thermoplastic fiber and a cellulosic water-absorbent fiber, wherein the thermoplastic fiber is a surface of the absorber on the front surface sheet side and a surface of the absorber on the back surface sheet side. What is exposed in both and is described. According to Patent Document 1, the thermoplastic fibers are arranged in this way, so that the absorber is flexible and does not easily twist.
Patent Document 2 describes an absorber in which a non-woven fabric piece having a three-dimensional structure in which heat-sealed fibers are bonded to each other and a hydrophilic fiber are mixed.

The present applicant has previously proposed an absorber containing a fiber mass containing synthetic fibers and a water-absorbent fiber, and the fiber masses or the fiber mass and the water-absorbent fiber are entangled with each other (the applicant). Patent Document 3). The fiber mass described in Patent Document 3 has a fixed shape and a flat surface in contrast to the non-woven fabric piece described in Patent Document 2, and the absorber containing the fiber mass has cushioning property and compression recovery property. It is excellent in responsiveness to external force and can be deformed flexibly.
Further, the applicant, as an absorbent article provided with an absorbent body containing a fiber mass described in Patent Document 3, has an absorbent core in a region facing the excretory portion of the wearer, rather than the non-skin facing surface side of the absorbent core. The ratio of the content mass of the fiber mass to the total content mass of the fiber mass and the water-absorbent fiber is smaller on the side facing the skin, that is, on the side farther from the wearer's skin than the absorbent core. We have proposed a structure in which a fiber mass layer, which is an aggregate of fiber masses, is arranged (Patent Document 4). The absorbent article described in Patent Document 4 is excellent in cushioning property and liquid drawing property, and has a feature that the absorbent body is not easily twisted during wearing.

Japanese Unexamined Patent Publication No. 2015-16296 Japanese Unexamined Patent Publication No. 2002-301105 JP-A-2017-63469 Japanese Unexamined Patent Publication No. 2020-96779

The surface sheet is usually a member of the absorbent article that has the most chance of coming into contact with the wearer's skin, and the touch of the surface sheet can greatly affect the quality such as the wearing feeling of the absorbent article. In general, a smooth touch is preferred as the touch of the surface sheet, but by reducing the fineness of the constituent fibers of the surface sheet (reducing the fiber diameter), the surface sheet can be given a smooth touch. However, when the constituent fibers of the surface sheet become thinner, the body fluid is easily retained in the gaps between the fibers, and the body fluid excreted on the skin-facing surface of the surface sheet is less likely to be drawn into the absorbent core side, so that the body fluid is absorbed. The liquid absorbability of the sex article is lowered, and specifically, inconveniences such as a tendency for body fluid to remain on the surface sheet and a tendency for liquid return (wet back) to occur easily occur. The liquid return is a phenomenon in which the body fluid excreted on the skin-facing surface of the surface sheet is once drawn into the surface sheet or the absorbent core and then returns to the skin-facing surface of the surface sheet again. As described above, in the prior art, there is a trade-off relationship between the improvement of the feel of the surface sheet (acquisition of a smooth feel) and the liquid absorbability. A technique for imparting a smooth feel to a surface sheet without causing a decrease in liquid absorption has not yet been provided.

An object of the present invention is to provide an absorbent article which has sufficient liquid absorbency for practical use, is smooth to the touch, and is excellent in wearing feeling.

The present invention is an absorbent article comprising an absorbent core capable of absorbing and retaining body fluid and a surface sheet arranged closer to the wearer's skin than the absorbent core, and is more than the absorbent core. On the side far from the wearer's skin, a fiber mass layer, which is an aggregate of a plurality of fiber masses, is arranged.
In one embodiment of the absorbent article of the present invention, the fiber mass preferably contains non-water-absorbent thermoplastic fibers.
In one embodiment of the absorbent article of the present invention, the average fineness of the constituent fibers of the fiber mass is preferably 1 dtex or more and 2.5 dtex or less.
Other features, effects and embodiments of the invention are described below.

According to the present invention, there is provided an absorbent article having sufficient liquid absorbency for practical use, smooth to the touch, and excellent in wearing feeling.

FIG. 1 is a plan view schematically showing the skin-facing surface side (surface sheet side) of the sanitary napkin according to the embodiment of the absorbent article of the present invention by partially breaking it. FIG. 2 is a schematic cross-sectional view of the line I-I cross section of FIG. 1 (cross section along the thickness direction and the lateral direction of the absorbent article). FIG. 3 is a simplified version of FIG. 2, and is an explanatory diagram of a state in which the absorbent article of the present invention is being worn. FIG. 3 (a) shows the skin in contact with the skin-facing surface of the surface sheet. FIG. 3 (b) shows a state in which the skin moves in the direction indicated by the arrow from the state shown in FIG. 3 (a). FIG. 4 is a view corresponding to FIG. 2 of another embodiment of the absorbent article of the present invention. FIG. 5 is a view corresponding to FIG. 2 of still another embodiment of the absorbent article of the present invention. FIG. 6 is a schematic plan view of the absorbent core shown in FIG. 5 on the non-skin facing surface side. FIG. 7 is a schematic perspective view of an example of the fiber mass according to the present invention. FIG. 8 is a diagram schematically showing an example of a fiber mass according to the present invention.

Hereinafter, the present invention will be described based on the preferred embodiment thereof with reference to the drawings. In the description of the drawings below, the same or similar parts are designated by the same or similar reference numerals. The drawings are basically schematic, and the ratio of each dimension may differ from the actual one.

1 and 2 show a menstrual napkin 1 which is an embodiment of the absorbent article of the present invention. The napkin 1 has an absorbent core 5 capable of absorbing and retaining body fluids such as menstrual blood, and a surface sheet arranged on the side closer to the wearer's skin than the absorbent core 5 (the side facing the skin of the absorbent core 5). 3 and.

In the present embodiment, as shown in FIG. 1, the napkin 1 corresponds to the front-back direction of the wearer and is orthogonal to the vertical direction X extending from the ventral side of the wearer to the dorsal side through the crotch portion and the vertical direction X. It has a lateral direction Y. Further, the napkin 1 has a vertical central region M including an excretory portion facing the excretory portion such as the wearer's vaginal opening, and an anterior region F arranged on the front side (ventral side) of the wearer from the vertical central region M. And a posterior region R arranged on the posterior side (dorsal side) of the wearer with respect to the vertical central region M.

In the present embodiment, the napkin 1 extends outward in the horizontal direction Y from each of the absorbent main body 2 having a shape long in the vertical direction X and both side portions of the absorbent main body 2 along the vertical direction X in the vertical central region M. It has a pair of wing portions 2W and 2W. The absorbent body 2 is the main part of the napkin 1, and as shown in FIG. 2, in addition to the surface sheet 3 and the absorbent core 5, the side farther from the wearer's skin than the absorbent core 5 ( A back surface sheet 4 arranged on the non-skin facing surface side of the absorbent core 5) and a fiber mass layer 6 interposed between the absorbent core 5 and the back surface sheet 4 are provided. In the form shown in FIG. 2, the absorbent core 5 and the fiber mass layer 6 are integrally covered with the liquid permeable sheet 7.

The vertical central region M is a region within a predetermined range in the vertical direction (longitudinal direction, X direction in the drawing) of the absorbent article, including the portion facing the excretion portion. As described above, when the absorbent article has a wing portion, it corresponds to the region having the wing portion in the vertical direction of the absorbent article, and in the case of the napkin 1 as an example, in the vertical direction X of one wing portion 2W. It is a region sandwiched between the root along the root and the root along the vertical direction X of the other wing portion 2W. In the napkin 1, the pair of wing portions 2W and 2W are formed symmetrically with respect to the vertical center line (not shown) extending in the vertical direction X by bisecting the napkin 1 in the horizontal direction Y. The base of one wing portion 2W on the side closer to the front region F and that of the other wing portion 2W are located at the same position in the vertical direction X. Further, the vertical central region of the absorbent article having no wing portion (for example, a disposable diaper) corresponds to, for example, a region located in the middle when the absorbent article is divided into three equal parts in the vertical direction.

In the present specification, the "skin facing surface" is a surface of the absorbent article or a component thereof (for example, the absorbent core 5) that is directed toward the wearer's skin when the absorbent article is worn, in other words, relatively. It is a surface close to the wearer's skin, and the "non-skin facing surface" is a surface opposite to the skin facing surface of the absorbent article or its constituent members (a surface relatively far from the wearer's skin). The term "when worn" as used herein means a state in which the normal proper wearing position, that is, the correct wearing position of the absorbent article is maintained.

As shown in FIG. 2, the front surface sheet 3 covers the entire surface of the absorbent core 5 facing the skin, and the back sheet 4 covers the entire non-skin facing surface of the absorbent core 5. Both sheets 3 and 4 extend outward from both ends of the absorbent core 5 in the vertical direction X, respectively. The back surface sheet 4 extends outward in the lateral direction Y from both side edges along the vertical direction X of the absorbent core 5, and forms a side flap portion 2S together with the side sheet 8 described later. As shown in FIG. 1, the side flap portion 2S has a portion protruding outward in the lateral direction Y from the peripheral portion in the vertical central region M, and this portion is a wing portion 2W. The wing portion 2W is used by being folded back to the non-skin facing surface side of the crotch portion of the clothing when the napkin 1 is attached to clothing such as shorts, and the crotch portion of the clothing in the wing portion 2W. A wing portion adhesive portion (not shown) is provided on the surface facing the non-skin facing surface as a means for fixing the wing portion 2W. Further, on the non-skin facing surface of the absorbent main body 2 (non-skin facing surface of the back sheet 4), an adhesive portion (not shown) is provided as a fixing means for fixing the napkin 1 to clothes such as shorts. The wing portion adhesive portion and the main body adhesive portion are each covered with a release sheet (not shown) made of a film, a non-woven fabric, paper, or the like before use. Further, both sides of the absorbent body 2 facing the skin (the surface of the surface sheet 3 facing the skin) along the vertical direction X are overlapped with the left and right sides of the absorbent core 5 along the vertical direction X in a plan view. , A pair of side sheets 8 and 8 are arranged over substantially the entire length of the absorbent body 2 in the vertical direction X. The pair of side sheets 8 and 8 are joined to other members such as the surface sheet 3 by a known joining means such as an adhesive at a linear joining portion (not shown) extending in the vertical direction X, respectively.

As the front surface sheet 3, the back surface sheet 4, the absorbent core 5, and the side sheet 8, various ones conventionally used for this kind of absorbent article are particularly used, provided that they do not deviate from the gist of the present invention. It can be used without limitation.
As the surface sheet 3, for example, a non-woven fabric having a single-layer or laminated structure having liquid permeability can be used, and as the non-woven fabric, a non-woven fabric manufactured by the card method (for example, an air-through nonwoven fabric), a spunbonded nonwoven fabric, or a meltblown nonwoven fabric can be used. , Spun lace non-woven fabric, needle punch non-woven fabric can be exemplified. The nonwoven fabric constituting the surface sheet 3 may be subjected to a hydrophilization treatment using a hydrophilic agent such as a surfactant.
The back surface sheet 4 and the side sheet 8 include a leak-proof sheet, that is, a liquid impermeable (property that does not allow liquid to pass through) or a liquid impervious (although not liquid impermeable). A sheet having a property of being difficult to pass through can be used, and for example, a moisture-permeable resin film can be used.

As an example of the absorbent core 5, there is a so-called stacking type absorbent core made of a fiber aggregate containing water-absorbent fibers. The fiber-stacked absorbent core is typically manufactured by stacking water-absorbent fibers using a known fiber stacking device. In the fiber-stacked absorbent core, the content of the water-absorbent fiber in the fiber aggregate is preferably 50% by mass or more, and may be 100% by mass, based on the total mass of the fiber aggregate. The fiber-stacked absorbent core may contain a water-absorbent polymer, and examples thereof include those in which particles of the water-absorbent polymer are supported inside a fiber aggregate.
Another example of the absorbent core 5 is a sheet-type absorbent core. The sheet-type absorbent core is typically a fiber sheet (paper, non-woven fabric, etc.) containing water-absorbent fibers or non-water-absorbent fibers, and a water-absorbent polymer fixed to the inside or the surface of the fiber sheet. Including materials. As a specific example of the sheet-type absorbent core, there is a structure in which particles of a water-absorbent polymer are interposed and arranged between two opposing fiber sheets. In general, the sheet-type absorbent core is thinner and more flexible than the fiber-stacked absorbent core.
The basis weight of the absorbent core 5 is not particularly limited, but is preferably 100 g / m ² or more, more preferably 200 g / m ² or more, and preferably 200 g / m 2 or more, from the viewpoint of the balance of required performance such as liquid absorption and wearing feeling. It is 800 g / m ² or less, more preferably 600 g / m ² or less.

An example of a water-absorbent fiber that can be used in the absorbent core 5 is a cellulose fiber. Examples of the cellulose fiber include wood pulp such as coniferous tree pulp and broadleaf tree pulp, natural fiber such as non-wood pulp such as cotton pulp and hemp pulp; modified pulp such as cationized pulp and marcelled pulp; regeneration of cupra, rayon and the like. Examples thereof include fibers, and one of these can be used alone or in combination of two or more.
As an example of the non-absorbent fiber that can be used in the absorbent core 5, there is a non-absorbent thermoplastic fiber that is a constituent fiber of the fiber mass 11.
Examples of the water-absorbent polymer that can be used in the absorbent core 5 include a polymer or a copolymer of acrylic acid or an alkali metal salt of acrylic acid.

As shown in FIG. 2, on the side farther from the wearer's skin than the absorbent core 5 (the non-skin facing surface side of the absorbent core 5), a fiber mass layer 6 which is an aggregate of a plurality of fiber masses 11 is provided. It is arranged. The fiber mass layer 6 can contribute to the improvement of cushioning property, compression recovery property, shape retention property and the like of the napkin 1.

The fiber mass 11 is a fiber aggregate in which a plurality of fibers are grouped together and integrated. The fiber mass 11 may be a standard fiber aggregate such as a sheet piece obtained by cutting a synthetic fiber sheet having a certain size with a cutter or the like, or a non-woven fabric mainly composed of synthetic fibers may be finely divided. It may be an amorphous fiber aggregate produced by crushing into pieces, or by peeling or tearing off. Particularly preferred as the fiber mass 11, is one consisting of a fixed fiber aggregate, which will be described in detail later.

In the fiber mass layer 6, typically, a plurality of fiber masses 11 are individually present independently, and it is possible to individually take out the fiber mass 11 from the fiber mass layer 6.
The fiber mass layer 6 may contain only the fiber mass 11 composed of a fixed fiber aggregate, may contain only the fiber mass 11 composed of an irregular fiber aggregate, or may contain both fiber masses 11. It may be included. A particularly preferable form of the fiber mass layer 6 is a form containing only the fiber mass 11 composed of a fixed fiber aggregate. In the fiber mass 11 made of an amorphous fiber aggregate, the fibers are projected from various parts of the surface due to the randomly oriented constituent fibers, and the surface roughness is relatively large. Therefore, the fiber mass layer 6 is formed. In, the fiber lumps 11 are likely to engage with each other through their surfaces, and the degree of freedom of movement of the fiber lumps 11 is likely to be limited. On the other hand, since the surface roughness of the fiber mass 11 made of a fixed fiber aggregate is smaller than that of the fiber mass 11 made of an irregular fiber aggregate, the degree of freedom of movement of the fiber mass 11 in the fiber mass layer 6 is high. Is relatively large. The large degree of freedom of movement of the fiber mass 11 in the fiber mass layer 6 is effective in improving the flexibility, cushioning property, compression recovery property, and shape retention property of the fiber mass layer 6.

As described above, the fiber mass layer 6 may be arranged on the non-skin facing surface side of the absorbent core 5, and as shown in FIG. 2, the fiber mass layer 6 may be arranged on the non-skin facing surface of the absorbent core 5. May be directly stacked, or another member may be interposed between the absorbent core 5 and the fiber mass layer 6 (see FIG. 4). However, since the fiber mass layer 6 does not usually have the leak-proof property that the back surface sheet 4 has, the fiber mass layer 6 is from the viewpoint of preventing leakage from the non-skin facing surface side of the napkin 1. Is preferably arranged on the skin-facing surface side of the back sheet 4.

The fiber mass layer 6 may be arranged in at least a part of a region overlapping the absorbent core 5 in a plan view, may be arranged in the entire region, or may be arranged laterally from the region. It may have a portion extending to.
The fiber mass layer 6 is preferably arranged at least in the vertical central region M (the region located in the middle when the napkin 1 is divided into three equal parts in the vertical direction X). Since the vertical central region M of the napkin 1 is usually sandwiched between the wearer's thighs when the napkin 1 is worn, it extends in the vertical direction X due to the movement of both thighs during the wearer's walking motion. It is easily twisted around the virtual axis of rotation, and therefore, it is more susceptible to external force than the front region F and the rear region R, and twisting (undesirable deformation) is likely to occur. By arranging the fiber mass layer 6 that can contribute to the improvement of cushioning property, compression recovery property, shape retention property, etc. in the vertical central region M, which is a portion easily affected by such an external force, twisting is effective. Can be prevented.

The basis weight of the fiber mass layer 6 is not particularly limited, but if the basis weight of the fiber mass layer 6 is too small, the action and effect of the fiber mass layer 6 is not sufficiently exhibited, and conversely, if it is too large, the napkin 1 becomes bulky. This may lead to a decrease in wearing comfort. Considering the above, the basis weight of the fiber mass layer 6 is preferably 32 g / m ² or more, more preferably 80 g / m ² or more, and preferably 640 g / m ² or less, more preferably 480 g / m ² or less. be.

The fiber mass 11 contains non-absorbent thermoplastic fibers. Since the fiber mass 11 contains non-water-absorbing thermoplastic fibers, the fiber mass layer 6 is not only in a dry state but also in a wet state due to absorption of water in a body fluid or the like. The action effect (improvement effect such as shape retention, flexibility, cushioning property, compression recovery property, and resistance to twisting) according to 6 is stably exhibited.

The non-water-absorbent and thermoplastic fiber is a synthetic fiber made of a non-water-absorbent thermoplastic resin as a forming material. Examples of the non-water-absorbent thermoplastic resin include polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate (PET); polyamides such as nylon 6 and nylon 66; polyvinylidene acid, polymethacrylic acid alkyl esters, and polyvinyl chloride. , Polyvinylidene chloride and the like, and one of these can be used alone or in combination of two or more.

In the present invention, the so-called synthetic fiber using a synthetic resin (thermoplastic resin) as a forming material, such as the non-water-absorbent and thermoplastic fiber, is a mixture of one kind of synthetic resin or two or more kinds of synthetic resins. It may be a single fiber made of a blended polymer, or it may be a composite fiber. The composite fiber referred to here is a synthetic fiber obtained by combining two or more kinds of synthetic resins having different components with a spinneret and spinning them at the same time, and has a structure in which a plurality of components are continuous in the length direction of the fiber. It means those that are mutually bonded in the fiber. The form of the composite fiber includes a core sheath type, a side-by-side type, and the like, and is not particularly limited.

The non-water-absorbent thermoplastic fiber used for the fiber mass 11 preferably has a moisture content of less than 6%, more preferably less than 4%. The water-absorbent fiber preferably used for the above-mentioned absorbent core 5 preferably has a water content of 6% or more, and more preferably 10% or more. Moisture content is measured by the following method.

<Measurement method of moisture content>
This measurement method conforms to the moisture content test method of JIS P8203. Specifically, the fiber to be measured is allowed to stand in an environment having a temperature of 40 ° C. and a relative humidity of 80% RH for 24 hours, and then the weight (W, unit: g) of the fiber before the absolute drying treatment is measured in that environment. .. After that, the fibers are allowed to stand in an electric dryer having a temperature of 105 ± 2 ° C. (for example, manufactured by Isuzu Seisakusho Co., Ltd.) for 1 hour to perform an absolute drying treatment of the fibers. After the absolute drying treatment, the fibers are wrapped in a wrap film (for example, Saran Wrap (registered trademark) manufactured by Asahi Kasei Corporation), and the fibers wrapped in the wrap film are housed together with silica gel in a glass desiccator. Is allowed to stand in an environment with a temperature of 20 ± 2 ° C. and a relative humidity of 65 ± 2%. When the temperature of the fiber reaches 20 ± 2 ° C., the constant amount of the fiber (W', unit: g) is weighed, and the water content of the fiber to be measured is calculated by the following formula.
Moisture content of fiber (%) = (W-W'/ W') x 100

The content of the non-water-absorbent thermoplastic fiber in the fiber mass 11 is preferably 90% by mass or more, more preferably 100% by mass, based on the total mass of the fiber mass 11. That is, the fiber mass 11 may contain fibers other than the non-water-absorbent thermoplastic fiber, for example, a cellulose fiber which is one of the water-absorbent fibers, but is formed only of the non-water-absorbent thermoplastic fiber. Is the most preferable.

The napkin 1 is characterized in that the average fineness of the constituent fibers of the fiber mass 11 is 1 dtex or more and 2.5 dtex or less. Due to such a characteristic configuration, the napkin 1 is excellent in both liquid absorption and wearing feeling. As described above, if the constituent fibers of the surface sheet 3 are reduced in fineness in order to smooth the touch of the surface facing the skin of the surface sheet 3, there is a concern that the liquid absorbency may be lowered. The smooth feel of the surface sheet 3 during wearing is realized without lowering the fineness of the constituent fibers, and the wearing feeling is improved without causing a decrease in liquid absorption. The reason is inferred as follows.
While wearing the napkin 1, from the state where the wearer's skin 100 is in contact with the skin facing surface of the surface sheet 3 as shown in FIG. 3 (a), the skin 100 is as shown in FIG. 3 (b). When the surface sheet 3 moves in the direction indicated by the reference numeral Y1 (to the right in FIG. 3) while maintaining the contact state with the skin facing surface of the surface sheet 3, the fiber mass layer 6 is deformed so as to follow the movement of the skin 100. At this time, since the surface sheet 3 moves in the same direction as the skin 100, friction is less likely to occur between the skin facing surface of the surface sheet 3 and the skin 100. This difficulty in generating friction is a direct cause of feeling that the surface of the surface sheet 3 facing the skin is smooth to the touch, and this difficulty in generating friction causes the fiber mass layer 6 to follow the movement of the skin 100. This is due to the deformation. That is, when the average fineness of the constituent fibers of the fiber lump 11 is within the specific range, the responsiveness of the fiber lump layer 6 to an external force is improved, and the fiber lump layer 6 can be flexibly deformed, and as a result. It is presumed that the surface of the surface sheet 3 facing the skin has a smooth feel. Further, in general, fibers having an average fineness in the specific range are classified into fibers having a fine fiber diameter, and the fiber mass 11 is formed by reducing the fiber diameter of the constituent fibers of the fiber mass 11 constituting the fiber mass layer 6. Since the surface roughness of the fiber lump layer 6 is reduced, the friction when the fiber lumps 11 come into contact with each other in the deformation of the fiber lump layer 6 is reduced, and as a result, the fiber lump layer 6 can be flexibly deformed with respect to an external force. It is presumed to be.

From the viewpoint of ensuring that the above-mentioned effects are more reliably exerted, the average fineness of the constituent fibers of the fiber mass 11 is preferably 2.5 dtex or less, more preferably 2.0 dtex or less. From the viewpoint of smoothing the feel of the surface facing the skin of the surface sheet 3 (making it possible to flexibly deform the fiber mass layer 6), it is preferable that the average fineness of the constituent fibers of the fiber mass 11 is small, but the fibers From the viewpoint of ensuring the shape-retaining property of the mass 11, the average fineness of the constituent fibers of the fiber mass 11 is preferably 1.0 dtex or more, more preferably 1.2 dtex or more.
Particularly preferred is a form in which the "fineness" of the constituent fibers of the fiber mass 11 is within the above range, not the "average fineness" of the constituent fibers of the fiber mass 11.
The fineness (average fineness) of the constituent fibers of the fiber mass 11 is measured by the following method.

<Measuring method of fineness of constituent fibers of fiber mass>
In this measurement method, the cross-sectional area of the constituent fibers of the fiber mass to be measured (cross-sectional area in the direction orthogonal to the length direction of the fibers) is measured, and information on the composition of the constituent fibers, for example, the constituent fibers are synthetic fibers. If so, information such as the type of resin that is the forming material and the content ratio of multiple types of resin if they are contained is acquired, and the composition of the fiber mass to be measured is based on the information. Calculate the fineness of the fiber.
The measurement of the cross-sectional area of the fiber can be carried out by using a known observation means such as an electron microscope (SEM). When the fiber to be measured is a fiber such as a core-sheath type composite fiber, which is divided into a plurality of components (for example, a core portion and a sheath portion) in a cross section in a direction orthogonal to the length direction of the fiber. , Measure the cross-sectional area of each of the plurality of sections.
The acquisition of information on the composition of the fiber can be carried out, for example, by specifying the type of resin using a DSC (differential thermal analyzer) and determining the specific gravity. If the fiber to be measured contains multiple types of resins, specify the approximate component ratios for them.
For example, when the constituent fiber of the fiber mass is a single fiber composed of only PET, the cross section of the fiber is observed according to a conventional method using SEM, and the cross-sectional area is calculated from the observed image. Further, the PET single fiber is composed of a single component resin by performing thermal analysis on such PET single fiber according to a conventional method using DSC and acquiring information such as the melting point and peak shape of the resin (PET). It can be seen that the single component is PET, the density of PET, and the like. The fineness is calculated by calculating the mass of the PET single fiber using the information such as the cross-sectional area of the fiber and the density of the resin (PET) obtained in this way.

The constituent fibers of the surface sheet 3 have an average fineness of the constituent fibers of the surface sheet 3 from the viewpoint of suppressing the liquid residue on the surface sheet 3, improving the liquid drawability and improving the liquid absorbency of the napkin 1. It is preferably 1.7 dtex or more, more preferably 2.0 dtex or more, and preferably 2.7 dtex or less, more preferably 3.3 dtex or less. In the present invention, the smoothness of the surface sheet 3 to the touch is realized by setting the average fineness of the constituent fibers of the fiber mass 11 of the fiber mass layer 6 within a specific range, so that the constituent fibers of the surface sheet 3 are relatively high. By increasing the fineness, the above-mentioned effect of improving liquid absorption can be realized.
The average fineness of the constituent fibers of the surface sheet 3 is measured according to the above <method for measuring the fineness of the constituent fibers of the fiber mass>. Specifically, a small piece of an appropriate size is cut out from the surface sheet 3 to make a measurement sample, and the measurement is performed by the same method as the above-mentioned measurement method.

From the viewpoint of improving the liquid absorbability of the napkin 1, the average fineness of the constituent fibers of the surface sheet 3 is preferably larger than the average fineness of the constituent fibers of the fiber mass 11. That is, it is preferable that the relationship of "average fineness of constituent fibers of surface sheet 3> average fineness of constituent fibers of fiber mass 11" is established.
The ratio of the average fineness of the constituent fibers of the surface sheet 3 to the average fineness of the constituent fibers of the fiber mass 11 is preferably 0.68 or more, more preferably 1.0 or more as the former / the latter, assuming the former> the latter. , And more preferably 3.3 or less, more preferably 2.25 or less.

In the present embodiment, as shown in FIG. 2, the fiber mass layer 6 is directly laminated on the non-skin facing surface of the absorbent core 5, and the absorbent core 5 and the fiber mass layer 6 are formed by the liquid permeable sheet 7. It is covered integrally. With such a configuration, the shape-retaining property of the fiber mass layer 6 is improved, and the fiber mass layer 6 is prevented from collapsing due to the movement of the wearer while wearing the napkin 1, so that the average fineness of the constituent fibers of the fiber mass 11 is suppressed. The action and effect by setting the above-mentioned specific range can be more reliably achieved.

The liquid permeable sheet 7 may be one continuous sheet, in which case the length (width) of the lateral Y is the absorbent core 5 and the fiber mass layer covered by the liquid permeable sheet 7. The length (width) of the lateral Y in the laminated structure of 6 may be 2 times or more and 3 times or less the width (maximum width) of the maximum portion. Such a wide liquid-permeable sheet 7 covers, for example, the entire surface of the skin-facing surface (or non-skin-facing surface) of the laminated structure, and from both side edges along the vertical direction X of the laminated structure to the horizontal direction Y. The extended portion covers the entire non-skin facing surface (or skin facing surface) of the laminated structure. Further, the liquid permeable sheet 7 may be composed of a plurality of sheets, for example, one skin side liquid permeable sheet covering the skin facing surface of the laminated structure, and the skin side liquid permeable sheet. Is a separate body, and may be configured to include two sheets of one non-skin side liquid permeable sheet covering the non-skin facing surface of the laminated structure.
The absorbent core 5 and the fiber mass layer 6 and the liquid permeable sheet 7 may be bonded by an adhesive such as a hot melt type adhesive.

As the liquid-permeable sheet 7, a sheet having liquid permeability can be used without particular limitation. For example, a non-woven fabric, paper, or the like produced by various manufacturing methods can be used, and a single-layer structure may be used, which may be of the same type or different types. A laminated structure of a plurality of sheets may be used.
The basis weight of the liquid permeable sheet 7 is preferably 5 g / m ² or more, more preferably 10 g / m ² or more, and preferably 50 g / m ² or less, more preferably 25 g / m ² or less.

It is preferable that no adhesive is arranged between the fiber mass layer 6 and the member directly overlapped with the skin facing surface of the fiber mass layer 6. For example, in the form shown in FIG. 2, since the “member directly stacked on the skin facing surface of the fiber mass layer 6” is the absorbent core 5, an adhesive is applied between the fiber mass layer 6 and the absorbent core 5. It is preferable that is not arranged. For example, in the form shown in FIG. 2, when the adhesive is arranged between the fiber mass layer 6 and the absorbent core 5, the fiber mass 11 existing on the skin-facing surface of the fiber mass layer 6 and in the vicinity thereof is said. Since it is fixed to the non-skin facing surface of the absorbent core 5 by the adhesive, the deformation of the fiber mass layer 6 that follows the movement of the wearer's skin is suppressed, and the constituent fibers of the fiber mass 11 are suppressed. When the average fineness is in the specific range, the action and effect may not be sufficiently exhibited. Therefore, it is preferable that no adhesive is arranged between the fiber mass layer 6 and the member directly overlapped with the skin facing surface of the fiber mass layer 6.
The term "adhesive" as used herein refers to all adhesives used for joining members to each other in this type of absorbent article, and specific examples thereof include hot melt type adhesives.
Further, "no adhesive is arranged" here means not only a form in which no adhesive is arranged at all, but also a very small amount of adhesive that cannot substantially function as an adhesive. Includes the arranged forms. Considering the latter form, the basis weight of the adhesive between the fiber mass layer 6 and the member directly laminated on the skin facing surface of the fiber mass layer 6 is preferably 15 g / m ² or less, more preferably 10 g / g /. It is m ² or less, most preferably zero.

In the fiber mass layer 6, a plurality of fiber masses 11 are entangled with each other, and the fiber mass 11 and the member are between the fiber mass layer 6 and the member directly overlapped with the skin facing surface of the fiber mass layer 6. It is preferable that the constituent fibers are entangled with each other. For example, in the form shown in FIG. 2, since the “member directly stacked on the skin facing surface of the fiber mass layer 6” is the absorbent core 5, the constituent fibers of the fiber mass layer 6 and the absorbent core 5 (for example, water absorption). It is preferable that the fibers are entangled with each other. The presence of such entanglement between the fibers improves the shape-retaining property of the fiber mass layer 6 and reduces the collapse of the fiber mass layer 6 due to the movement of the fiber mass 11, so that the constituent fibers of the fiber mass 11 can be reduced. Combined with the action and effect of having the average fineness in the specific range, the fiber mass layer 6 can more flexibly respond to the movement of the wearer while wearing the napkin 1, and the surface sheet 3 can be used. The smooth feel of the surface facing the skin can be obtained more reliably. Further, the average fineness of the constituent fibers of the fiber mass 11 is within the above-mentioned specific range, and the presence of entanglement between the fibers related to the fiber mass 11 causes not only the quick response to the external force of the fiber mass layer 6 but also the flexibility. Properties, cushioning properties, compression recovery properties, etc. can also be improved. That is, the fiber mass layer 6 flexibly deforms with respect to an external force (for example, the body pressure of the wearer of the napkin 1) received from various directions when the napkin 1 is worn, and the napkin 1 is closely fitted to the wearer's body with good fit. I can let you. Such excellent deformation-recovery properties of the fibrous mass layer 6 can be exhibited not only when the fibrous mass layer 6 is compressed but also when it is twisted. That is, since the fiber mass layer 6 incorporated in the napkin 1 is arranged in a state of being sandwiched between the wearer's thighs when the napkin 1 is worn, both thighs during the wearer's walking motion. Depending on the movement of the part, it may be twisted around a virtual axis of rotation extending in the vertical direction X, but even in such a case, since the fiber mass layer 6 has high deformation-recovery characteristics, both thighs. It easily deforms and recovers against an external force that promotes twisting from the body, and therefore is less likely to twist, and can impart a high fit to the wearer's body to the napkin 1.

The following forms A and B are included in the above-mentioned "entanglement between fiber masses 11 in the fiber mass layer 6" and "entanglement between the fiber mass 11 of the fiber mass layer 6 and the constituent fibers of the member in contact with the fiber mass layer 6". Included.
Form A: A form in which the fiber lumps 11 or the constituent fibers of the member in contact with the fiber lump 11 and the fiber lump layer 6 are bonded to each other by entanglement of the fibers, not by fusion.
Form B: In the natural state of the fiber mass layer 6 (in a state where no external force is applied), the fiber masses 11 are not bonded to each other or the constituent fibers of the member in contact with the fiber mass 11 and the fiber mass layer 6, but the fiber mass is not bonded. In a state where an external force is applied to the layer 6, the fiber lumps 11 or the constituent fibers of the member in contact with the fiber lump 11 and the fiber lump layer 6 can be bonded to each other by entanglement of the fibers. The term "state in which an external force is applied to the fiber mass layer 6" as used herein means, for example, that the fiber mass layer 6 is worn while wearing an absorbent article (napkin 1 in the present embodiment) to which the fiber mass layer 6 is applied. It is in a state where a deforming force is applied.

As described above, in the fiber lump layer 6, as in the form A, the fiber lump 11 is entangled with other fiber lumps 11 or constituent fibers of a member in contact with the fiber lump layer 6, that is, by "entanglement". In addition to being bonded, it also exists in a state where it can be entangled with the constituent fibers of the member in contact with the other fiber mass 11 or the fiber mass layer 6, as in the form B. The binding by entanglement of such fibers is one of the important points for more effectively expressing the action and effect of the above-mentioned fiber mass layer 6. In particular, it is preferable that the fiber mass layer 6 has the "entanglement" of the form A from the viewpoint of shape retention. Since the bond by entanglement of fibers has no adhesive component or fusion and is made only by the entanglement of fibers, the individual elements (fiber mass 11, fiber) that are entangled are compared with the bond by fusion of fibers. The degree of freedom of movement of the constituent fibers of the member in contact with the mass layer 6) is high, so that the individual elements can move to the extent that the unity as an aggregate composed of them can be maintained. As described above, the fiber lump layer 6 has a plurality of fiber lumps 11 contained therein, or the fiber lumps 11 and the constituent fibers of the member in contact with the fiber lump layer 6 are relatively loosely bonded to each other, thereby causing an external force. It has a gradual shape-retaining property that can be deformed when it receives a shock, and has both shape-retaining property, cushioning property, compression recovery property, and the like at a high level. The napkin 1 provided with such a high-quality fiber mass layer 6 has a smooth feel on the skin-facing surface of the surface sheet 3, and also has a good fit to the wearer's body and is excellent in wearing feeling. ..

The entanglement of the fibers related to the fiber mass 11 described above is mainly due to the entanglement of the ends of the constituent fibers (non-water-absorbent thermoplastic fibers) of the fiber mass 11, and the ends of the constituent fibers of the fiber mass 11. The larger the number per unit area of, the more likely it is that the fibers related to the fiber mass 11 will be entangled with each other. This point will be described in detail later.

In the present embodiment, as shown in FIG. 2, a plurality of convex portions 31 protruding toward the wearer's skin are formed on the skin-facing surface of the surface sheet 3. In the napkin 1, as described above, the average fineness of the constituent fibers of the fiber lump 11 is within the specific range, so that the responsiveness to the external force of the fiber lump layer 6 is improved, and the fiber lump layer 6 is worn by the napkin 1. In the middle, as shown in FIG. 3B, by deforming to follow the movement of the wearer's skin 100, the friction between the skin facing surface of the surface sheet 3 and the skin 100 is reduced, and as a result, the friction is reduced. Where the skin-facing surface of the surface sheet 3 is smooth to the touch, the convex portion 31 formed on the skin-facing surface of the surface sheet 3 moves the wearer's skin 100 in the same manner as the fiber mass layer 6. It is also effective to reduce the friction between the skin facing surface of the surface sheet 3 and the skin 100 that a plurality of convex portions 31 are formed on the skin facing surface of the surface sheet 3 because the surface sheet 3 can be deformed to follow the skin facing surface. It can be a means. Therefore, in addition to the average fineness of the constituent fibers of the fiber mass 11 being in the above-mentioned specific range, a plurality of convex portions 31 are formed on the skin-facing surface of the surface sheet 3, so that the skin-facing surface of the surface sheet 3 is opposed to the skin. The texture of the napkin 1 becomes smoother, and the wearing feeling of the napkin 1 can be further improved. Further, since a plurality of convex portions 31 are formed on the skin facing surface of the surface sheet 3, the skin facing surface of the surface sheet 3 is in full contact with the wearer's skin, resulting in stickiness, stuffiness, and rubbing. In addition to reducing the irritation caused by the above, the excrement is less likely to adhere to the wearer's skin and the unpleasant wet feeling is reduced, so that the wearing feeling of the napkin 1 can be improved in this respect as well.

The pattern of the convex portion 31 (shape and arrangement of the convex portion) is not particularly limited, and the pattern on the uneven surface sheet in this type of absorbent article can be appropriately adopted. Further, the convex portion 31 may be a solid structure in which fibers are filled inside, or may be a hollow structure having a space portion of a certain size in which the fibers are not filled inside.
In the present embodiment, as shown in FIG. 2, concave portions 32 are formed around each of the plurality of convex portions 31, and the surface facing the skin of the surface sheet 3 is composed of a plurality of convex portions 31 and a plurality of concave portions 32. An uneven shape is given. This uneven shape exists at least on the skin-facing surface of the surface sheet 3 at a portion that can come into contact with the wearer's skin when the napkin 1 is worn, and may be present over the entire skin-facing surface. Such an uneven surface sheet having an uneven shape on the surface can be typically manufactured by partially applying a pressing process such as embossing to a surface sheet having no unevenness. The portion of the surface sheet that has been squeezed is the concave portion 32, and the portion that has not been squeezed is the convex portion 31. The concave portion 32 has a higher density than the convex portion 31 in which the material for forming the surface sheet 3 is compacted by the pressing process and is not subjected to the pressing process.

4 and 5 show key parts of other embodiments of the absorbent article of the invention. Regarding other embodiments described later, a configuration different from that of the above-mentioned napkin 1 will be described, and the same configurations as those of the napkin 1 are designated by the same reference numerals and the description thereof will be omitted. The description of the napkin 1 is appropriately applied to the configurations not particularly described in the embodiments described later.

In the napkin 1A shown in FIG. 4, at least the non-skin facing surface of the absorbent core 5 is covered with the liquid permeable sheet 7, and the fiber mass layer 6 is directly superposed on the non-skin facing surface of the liquid permeable sheet 7. There is. More specifically, in the napkin 1A, not only the non-skin facing surface but also the entire outer surface of the absorbent core 5 is covered with the liquid permeable sheet 7, and the liquid covering the non-skin facing surface of the absorbent core 5. The fiber mass layer 6 is directly laminated on the non-skin facing surface of the permeable sheet 7. In the napkin 1A, the fiber mass layer 6 is not covered with a sheet member such as the liquid permeable sheet 7, and the fiber mass 11 constituting the fiber mass layer 6 is exposed. In the napkin 1A, the "member directly laminated on the skin facing surface of the fiber mass layer 6" is the liquid permeable sheet 7, and therefore, for the reason described above, between the fiber mass layer 6 and the liquid permeable sheet 7. It is preferable that no adhesive is arranged, and that the fiber mass layer 6 and the constituent fibers of the liquid permeable sheet 7 (for example, water-absorbent fibers or non-water-absorbent fibers) are entangled with each other.

The napkin 1A basically has the same effect as the napkin 1, but the fiber mass layer 6 is a sheet member (liquid permeable sheet 7) in that the fiber mass layer 6 is not covered with the sheet member. The shape retention of the fiber mass layer 6 is inferior to that of the covered napkin 1. With the napkin 1 having excellent shape retention of the fiber mass layer 6, even if the wearer's skin repeatedly moves in a predetermined direction while maintaining the contact state with the skin facing surface of the surface sheet 3, the fiber mass layer 6 is used. Since the shape of the above can be maintained, the action and effect of setting the average fineness of the constituent fibers of the fiber mass 11 within the above-mentioned specific range can be more stably exhibited.

In the napkin 1B shown in FIG. 5, the absorbent core 5A has a grooved recess 50 having an opening in at least one of the skin facing surface and the non-skin facing surface of the absorbent core 5A and extending in a predetermined direction. is doing. The groove-shaped recess 50 itself is a space portion in which the material for forming the absorbent core 5 does not exist. Therefore, the portion of the absorbent core 5A that overlaps the groove-shaped recess 50 in a plan view has a lower basis weight than the periphery thereof.

In the absorbent core 5A, as shown in FIG. 5, the groove-shaped recess 50 exists on the non-skin facing surface of the absorbent core 5A and does not exist on the skin facing surface of the absorbent core 5A. Further, in the absorbent core 5A, as shown in FIG. 6, the groove-shaped recess 50 includes a vertical recess 50X extending in the vertical direction X and a lateral recess 50Y extending in a direction intersecting (orthogonal) with the vertical recess 50X. The vertical recesses 50X and the horizontal recesses 50Y exist in the entire non-skin facing surface of the absorbent core 5A. On the non-skin facing surface of the absorbent core 5A, a plurality of vertical recesses 50X are intermittently arranged in the horizontal direction Y, and a plurality of horizontal recesses 50Y are intermittently arranged in the vertical direction X. The plurality of portions surrounded by the recesses 50X and 50Y on the non-skin facing surface are convex portions 51 having a larger basis weight than the portions overlapping the recesses 50X and 50Y in a plan view, respectively. In the absorbent core 5A, the portion overlapping the groove-shaped recess 50 (50X, 50Y) in a plan view is a low basis weight portion having a relatively small basis weight, and the other portion is a high basis weight portion having a relatively large basis weight. Is. Therefore, in the absorbent core 5A, the low basis weight portion and the high basis weight portion are alternately arranged in both the vertical direction X and the horizontal direction Y.

When the absorbent core 5A receives an external force in a direction intersecting the extending direction of the groove-shaped recess 50, the absorbent core 5A tends to be deformed so as to be entirely tilted in the direction in which the external force acts. Specifically, for example, when the absorbent core 5 shown in FIG. 3 is the absorbent core 5A, the skin 100 maintains the contact state with the skin facing surface of the surface sheet 3 as shown in FIG. 3 (b). However, for example, when the fiber mass layer 6 is deformed so as to follow the movement of the skin 100 in the Y1 direction when the skin 100 moves in the direction indicated by the reference numeral Y1, the absorbent core 5A also deforms at this time. It can be deformed in the same manner as the fiber mass layer 6. Specifically, in the absorbent core 5A shown in FIG. 5, the groove-shaped recess 50 exists on the non-skin facing surface of the absorbent core 5A, and the low basis weight portion is a portion that overlaps the groove-shaped recess 50 in a plan view. Is present on the skin facing surface side, for example, when an external force is applied to the vertical central region M of the napkin 1B from the lateral direction Y which is the direction intersecting the extending direction of the vertical recess 50X, the absorbent core 5A becomes The low-rigidity portion (the portion where the vertical recess 50X in the absorbent core 5A is located) where the vertical recess 50X which is a space portion and the low basis weight portion located on the skin side of the wearer overlap in the thickness direction is It is easily deformed so that it falls down greatly in the lateral direction Y. On the other hand, the fiber mass layer 6 is deformed so as to follow the movement of the skin against the same external force applied to the absorbent core 5A. Therefore, the napkin 1B can improve the deformation of the absorbent core 5A with respect to the external force applied to the vertical intermediate region M, while suppressing the breakage of the absorbent core 5A due to the external force. In the napkin 1B, when the wearer's skin moves while maintaining contact with the skin facing surface of the surface sheet 3, both the absorbent core 5A and the fiber mass layer 6 follow the movement of the skin. As compared with the napkin 1 provided with the absorbent core 5, the friction between the skin facing surface of the surface sheet 3 and the skin is further reduced, and the skin facing surface of the surface sheet 3 is further reduced. Can be smoother to the touch.
Further, as shown in FIG. 5, when the absorbent core 5A and the fiber mass layer 6 are adjacent to each other without interposing other members, the absorbent core 5A is absorbed by the groove-shaped recess 50 in the low basis weight portion. The hydrophilic fibers of the sex core 5A and the fibers of the fiber mass 11 are less likely to be entangled. Therefore, it becomes difficult for the excrement liquid to propagate to the fiber mass layer 6, and it becomes easy to sustain the deformation of the fiber mass layer 6 so as to follow the movement of the skin for a long period of time.

In the absorbent article of the present invention, as the form of the groove-shaped recess 50, a non-penetrating type that does not penetrate the absorbent core 5 in the thickness direction and a penetrating type that penetrates the absorbent core 5 in the thickness direction (not shown). There can be. The plurality of groove-shaped recesses 50 of the absorbent core 5A are all non-penetrating type, but even if the groove-shaped recesses 50 are penetrating type, basically the same effect as the non-penetrating type groove-shaped recesses 50 is obtained. You can expect it. Further, regarding the position of the groove-shaped recess 50 when the groove-shaped recess 50 is a non-penetrating type, the absorbent core 5A is present on the non-skin facing surface, but may be present on the skin facing surface. , It may be present on both sides, and in any case, the action effect (deformation promoting effect of the absorbent core, etc.) by the groove-shaped recess 50 can be expected.

Further explaining the absorbent core 5A, the plurality of groove-shaped recesses 50 of the absorbent core 5A are all non-penetrating type, have an opening on the non-skin facing surface of the absorbent core 5A, and are on the opposite side to the opening. The absorbent core 5A has a bottom on the skin-facing surface side. The skin-facing surface side of the absorbent core 5A in which the bottom of the groove-shaped recess 50 is unevenly distributed is composed of a continuous layer 52 in which the groove-shaped recess 50 does not exist, and a plurality of the continuous layer 52 and the non-skin facing surface side of the absorbent core 5A. It is integrally configured with the convex portion 51 of the above. The skin-facing surface of the absorbent core 5A is a flat surface formed by the continuous layer 52 and has substantially no unevenness, whereas the non-skin-facing surface of the absorbent core 5A is a groove-shaped recess 50 (50X, 50Y). It has a concavo-convex shape composed of a plurality of concave portions and a plurality of convex portions 51 composed of openings of the above, and is a concavo-convex surface.

Hereinafter, the fiber mass 11 will be further described. FIG. 7 shows a preferred outer shape of the fiber mass 11. The fiber mass 11 has a rectangular parallelepiped shape rather than a quadrangular prism shape. The fiber mass 11 includes two base surfaces 111 facing each other and a body surface 112 connecting the two base surfaces 111. Both the basic surface 111 and the skeleton surface 112 are at a level applied when evaluating the degree of surface unevenness in an article mainly composed of this type of fiber, and are portions where it is recognized that there is substantially no unevenness.

In the fiber mass 11, the skeleton surface 112 preferably has a larger number of fiber ends per unit area than the basic surface 111. Such a fiber mass 11 is obtained by cutting a raw material sheet with a cutter or the like, and the skeleton surface 112 thereof is a cut surface formed by cutting the raw material sheet. Due to this, on the skeleton surface 112 which is the cut surface at the time of manufacturing the fiber mass 11, the fiber end portion formed by the cut end portion of the constituent fiber 11F of the fiber mass 11 is the entire skeleton surface 112. The skeleton surface 112 has a larger number per unit area of the fiber end portion of the constituent fiber 11F than the basic surface 111 (that is, the uncut surface at the time of manufacturing the fiber mass 11).

The fiber ends existing on each surface (basic surface 111, skeleton surface 112) of the fiber mass 11 are such that the fiber mass 11 faces the skin of another fiber mass 11 contained in the fiber mass layer 6 or the fiber mass layer 6. It is useful for forming entanglements with the constituent fibers of the members directly stacked on the surface (absorbent core 5 for napkins 1 and 1B, liquid permeable sheet 7 for napkin 1A). In general, the larger the number of fiber ends per unit area, the better the entanglement. Therefore, increasing the number of fiber ends per unit area has various characteristics such as shape retention of the fiber mass layer 6. It can lead to improvement. The number of fiber ends per unit area on each surface of the fiber mass 11 is not uniform, and the number of such fiber ends per unit area is "skeleton surface 112> basic surface 111" as described above. Since the relationship is established, the entanglement with the other fiber lumps 11 or the fibers of the fiber lump 11 differs depending on the surface of the fiber lump 11, and the skeleton surface 112 has higher entanglement than the basic surface 111. That is, the bond by entanglement with another fiber mass or fiber via the skeleton surface 112 has a stronger bonding force than that through the basic surface 111, and in one fiber mass 11, the basic surface 111 And the skeleton surface 112 may have a difference in the binding force with other fibers. In general, the stronger the bonding force, the more the degree of freedom of movement of the bonded fibers is limited, and the strength (shape retention) of the entire fiber mass layer 6 is improved, but the softness tends to be decreased. .. As described above, in the fiber mass layer 6, each of the plurality of fiber masses 11 contained therein is entangled with other fiber masses 11 or fibers around the fiber mass 11 having two kinds of binding forces. As a result, the fiber mass layer 6 has both appropriate softness and strength (shape retention).

Atypical fiber lumps produced by irregularly cutting a raw material sheet with a cutting machine such as a mill cutter as described in Patent Documents 2 and 3 have a basic surface 111 and a skeleton surface 112. Since it does not have a "face" and an external force of the cutting process is applied to the entire fiber mass at the time of its manufacture, the fiber end portions of the constituent fibers are randomly formed in the entire fiber mass. Compared with such an amorphous fiber mass, the fiber mass 11 according to the present invention is more likely to sufficiently exhibit the action and effect of the fiber end portion of the constituent fiber 11F.

From the viewpoint of ensuring that the above-mentioned action and effect of the fiber end are more reliably performed, the number N1 per unit area of the fiber end of the basic surface 111 (non-cut surface) and the fiber of the skeleton surface 112 (cut surface). The ratio to the number N2 per unit area of the end is preferably N1 / N2, preferably 0 or more, more preferably 0.05 or more, and preferably 0.90 or less, on the premise of N1 <N2. Is less than or equal to 0.60. More specifically, N1 / N2 is preferably 0 or more and 0.90 or less, and more preferably 0.05 or more and 0.60 or more.
The number N1 per unit area of the fiber end of the basic surface 111 is preferably 0 pieces / mm ² or more, more preferably 3 pieces / mm ² or more, and preferably 8 pieces / mm ² or less, more preferably 6. Pieces / mm ² or less.
The number N2 per unit area of the fiber end of the skeleton surface 112 is preferably 5 pieces / mm ² or more, more preferably 8 pieces / mm ² or more, and preferably 50 pieces / mm ² or less, more preferably 40 pieces / mm 2. Pieces / mm ² or less.
The number of fiber ends of the basic surface 111 and the skeleton surface 112 per unit area is measured by the following method.

<Measuring method of the number of fiber ends per unit area on each surface of the fiber mass>
A member (fiber mass) containing a fiber to be measured is attached to a sample table using a paper double-sided tape (Nichiban Co., Ltd. Nystack NW-15). The measurement piece is then platinum coated. For coating, an ion sputtering device E-1030 (trade name) manufactured by Hitachi Naka Seiki Co., Ltd. is used, and the sputtering time is 120 seconds. The cut surface of the measurement piece is observed on the basic surface and the skeletal surface at a magnification of 100 times using a JCM-6000 type electron microscope manufactured by JEOL Ltd. In this observation screen with a magnification of 100 times, a rectangular area of 1.2 mm in length and 0.6 mm in width is set at an arbitrary position on the measurement target surface (basic surface or skeleton surface), and the area of the rectangular area is the said. After adjusting the observation angle and the like so as to occupy 90% or more of the area of the observation screen, the number of fiber ends contained in the rectangular region is measured. However, in the observation screen with a magnification of 100 times, when the measurement target surface of the fiber mass is smaller than 1.2 mm × 0.6 mm and the ratio of the area of the rectangular region to the entire observation screen is less than 90%. After increasing the observation magnification to more than 100 times, the number of fiber ends contained in the rectangular region on the measurement target surface is measured in the same manner as described above. Here, the "fiber end" to be measured is the end in the length direction of the constituent fibers of the fiber mass, and the portion other than the end in the length direction of the constituent fibers from the measurement target surface (intermediate in the length direction). Even if the part) is extended, the middle part in the length direction is not subject to the number measurement. Then, the number of fiber ends per unit area on the measurement target surface (basic surface or skeleton surface) of the fiber mass is calculated by the following formula. For each of the 10 fiber lumps, the number of fiber ends per unit area on each of the basic surface and the skeleton surface was measured according to the above procedure, and the average value of the plurality of measured values was calculated as the average value of the plurality of measured values. The number per unit area of.
Number of fiber ends per unit area on the measurement target surface (basic surface or skeleton surface) of the fiber mass (number / mm ² ) = number of fiber ends included in the rectangular region (1.2 × 0.6 mm) / Area of the rectangular area (0.72 mm ² )

It is preferable to set the dimensions and the like of each part of the fiber mass 11 as follows. The dimensions of each part of the fiber mass 11 can be measured based on an electron micrograph or the like.
When the basic surface 111 has a rectangular shape in a plan view as shown in FIG. 7, the length L1 of one side (short side) 111a is preferably 0.1 mm or more, more preferably 0.3 mm or more, still more preferably 0.5 mm. The above, preferably 10 mm or less, more preferably 6 mm or less, still more preferably 5 mm or less.
When the fiber mass 11 has a rectangular shape in a plan view, the length L2 of the other side (long side) 111b of the basic surface 111 is preferably 0.3 mm or more, more preferably 1 mm or more, still more preferably 2 mm or more. The thickness is preferably 30 mm or less, more preferably 15 mm or less, still more preferably 10 mm or less.
As shown in FIG. 7, when the basic surface 111 is the surface having the maximum area among the plurality of surfaces of the fiber mass 11, the length L2 of the other side (long side) 111b is the fiber mass 11. Matches the maximum delivery length of.
The ratio of the length L1 of one side (short side) 111a to the length L2 of the other side (long side) 111b is preferably 0.003 or more and 1 or less, more preferably 0.025 or more 1 as L1 / L2. It is as follows. Particularly preferable fiber lumps 11 include those in which the aspect ratio of the basic surface 111 is 1 or close to 1, that is, the shape of the basic surface 111 in a plan view is square or similar. When such a fiber lump 11 is used for the fiber lump layer 6, the fiber lump layer 6 tends to be bulky, and cushioning properties and the like can be improved.
The thickness T of the fiber mass 11, that is, the length T between the two opposing basic surfaces 111 is preferably 0.1 mm or more, more preferably 0.3 mm or more, and preferably 10 mm or less, more preferably 6 mm or less. be.
The size of the fiber lump 11 is not particularly limited, and can be appropriately set in consideration of the cushioning property, the liquid permeability, and the like of the fiber lump layer 6. The area of the basic surface 111, which has the largest area among the plurality of surfaces of the fiber mass 11, can be an index of the size of the fiber mass 11. The area of the basic surface 111 of the fiber mass 11 is preferably 1 mm ² or more, more preferably 5 mm ² or more, and preferably 100 mm ² or less, more preferably 50 mm ² or less.

FIG. 8 shows a diagram schematically showing an example of the fiber mass 11 according to the present invention. As shown in FIG. 8, the fiber mass 11 includes a main body portion 110 and fibers 11F extending outward from the main body portion 110, and has a lower fiber density (unit area) than the main body portion 110. Those having the extended fiber portion 113 (with a small number of per-fibers) can be included. The fiber mass layer 6 may also include a fiber mass 11 having no extended fiber portion 113, that is, a fiber mass 11 composed of only the main body portion 110. The extended fiber portion 113 may include a type of fiber end portion existing on each surface (basic surface 111, skeleton surface 112) of the fiber mass 11 described above, and is a fiber among the fiber end portions. It is a fiber end extending outward from each surface of the mass 11.

The extended fiber portion 113 is mainly composed of a plurality of fiber lumps 11 contained in the fiber lump layer 6 or members directly overlapped with the skin facing surface of the fiber lump layer 6 (absorbent core 5 in napkins 1 and 1B, In the napkin 1A, it contributes to the improvement of the entanglement with the constituent fibers of the liquid permeable sheet 7), is directly involved in the improvement of the shape retention of the fiber mass layer 6, and is uniformly dispersed in the fiber mass layer 6 of the fiber mass 11. It may indirectly reinforce the action and effect of the main body 110 by affecting the sex and the like.

As shown in FIG. 8, the fiber mass 11 includes an extended fiber bundle portion 113S including a main body portion 110, more specifically, a plurality of fibers 11F extending outward from the skeleton surface 112 as a kind of extended fiber portion 113. Have. At least one of the extended fiber portions 113 included in the fiber mass 11 may be the extended fiber bundle portion 113S. The extended fiber bundle portion 113S is formed by gathering a plurality of fibers 11F extending from the skeleton surface 112, and extends from the skeleton surface 112 of the main body portion 110 as compared with the extended fiber portion 113. Characterized by its long length. The extended fiber bundle portion 113S may also be present on the basic surface 111, but is typically present on the skeletal surface 112 as shown in FIG. 8, and is not present at all on the basic surface 111, or even if it is present. The number is less than the skeletal surface 112. The reason is the same as the reason why the extended fiber portion 113 mainly exists on the skeleton surface 112 which is the cut surface of the raw material sheet, and is as described above. Since the fiber mass 11 has such a long, thick and large extended fiber bundle portion 113S, which can be called an extended fiber bundle portion 113, the fiber masses 11 are placed on each other or on the skin facing surface of the fiber mass layer 6. The entanglement of the directly stacked members with the constituent fibers is further strengthened, and as a result, the predetermined effect of the present invention due to the presence of the fiber lump 11 is more stably exhibited. Further, when the extended fiber bundle portion 113S has a heat-sealed portion, it is entangled via the extended fiber bundle portion 113S due to the improvement in the strength of the extended fiber bundle portion 113S itself. It is preferable because the entanglement between the existing fiber lumps 11 or the constituent fibers of the member directly overlapped with the skin facing surface of the fiber lump layer 6 is further strengthened.

As described above, the fiber mass 11 contains non-water-absorbent thermoplastic fibers, and is preferably composed mainly of non-water-absorbent thermoplastic fibers. The fibers can have a three-dimensional structure in which the fibers are heat-sealed to each other, and a plurality of heat-sealed portions are three-dimensionally dispersed and arranged inside the fiber mass 11. The fiber mass 11 having such a structure exhibits excellent effects in shape retention, flexibility, cushioning property, compression recovery property, resistance to twisting, and the like regardless of whether the fiber mass layer 6 is in a dry state or a wet state. Can be. Further, as described above, it is preferable that the extended fiber bundle portion 113S has a heat-sealed portion. However, by using a thermoplastic fiber as a constituent fiber of the fiber mass 11, such an extended fiber bundle portion 113S is used. It is also possible to obtain a preferable form of. In order to obtain the fiber mass 11 in which a plurality of heat-fused portions are three-dimensionally dispersed, the raw material sheet may be similarly configured, and such a plurality of heat-fused portions may be three-dimensionally configured. As described above, the raw material sheet dispersed in the above can be produced by subjecting a web or a non-woven fabric mainly composed of thermoplastic fibers to a heat treatment such as hot air treatment.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to such Examples.

[Examples 1 and 2]
A menstrual napkin having the same basic configuration as the napkin 1 shown in FIG. 1 was prepared and used as Examples 1 and 2. Examples 1 and 2 are similarly configured except for the average fineness of the constituent fibers of the fiber mass. Details of each member in the menstrual napkins of Examples 1 and 2 are as follows.
-As the surface sheet, a concave-convex surface sheet having a basis weight of 74 g / m ² having a skin-side layer forming a skin-facing surface and a non-skin-side layer forming a non-skin facing surface was used. A non-woven fabric containing non-heat-shrinkable fibers is used as the skin-side layer, and a non-woven fabric containing heat-shrinkable fibers is used as the non-skin-side layer, according to the method described in Japanese Patent Application Laid-Open No. 2015-186543. An uneven surface sheet having a layered structure was manufactured.
A polyethylene resin film (FL-KDJ100nN, manufactured by Daika Kogyo Co., Ltd.) having a basis weight of 37 g / m ² was used as the back sheet.
-As the absorbent core, a mixed fiber-type absorbent core containing coniferous bleached kraft pulp (NBKP), which is a water-absorbent fiber, and particles of a water-absorbent polymer was used. The basis weight of the fiber is 440 g / g / portion of the excretion portion facing portion (the portion of the absorbent article facing the wearer's excretion portion) and the portion corresponding to the vicinity thereof (hereinafter, also referred to as “excretion portion facing portion area”). m ² , the peripheral part of the area facing the excretion part was 200 g / m ² . The basis weight of the water-absorbent polymer was 70 g / m ² in the area facing the excretion part and 35 g / m ² in the peripheral area facing the excretion part.
-As a raw material sheet for fiber lumps, an air-through non-woven fabric having a basis weight of 25 g / m ² containing only non-water-absorbing thermoplastic fibers made of polyethylene and polyethylene terephthalate resin as constituent fibers (fibers having a heat-sealed portion between constituent fibers). Using a sheet), the raw material sheet was cut into a grid shape to produce a rectangular fiber mass such as the fiber mass 11 shown in FIG. 7. With reference to FIG. 7, the size of the rectangular parallelepiped fiber mass was 5 mm in length L1, 5 mm in length L2, and 0.6 mm in thickness T.
-As the fiber mass layer, a fiber mass layer made only of the fiber mass produced as described above was used. The basis weight of the fiber mass layer was 140 g / m ² . The fibrous mass layer was placed only in the vertical central region of the menstrual pad (the part facing the excretory part of the wearer).
-As the liquid permeable sheet, a core wrap sheet made of tissue paper having a basis weight of 16 g / m ² was used. The absorbent core and the fibrous mass layer were integrally covered with a liquid permeable sheet.

[Comparative Examples 1 to 3]
The menstrual napkin of Comparative Example 1 is the same as the menstrual napkin of Example 1 except that it does not have a fiber mass layer.
The menstrual napkin of Comparative Example 2 is the same as the menstrual napkin of Comparative Example 1 except that the average fineness of the constituent fibers of the skin side layer forming the skin facing surface of the surface sheet was changed.
The menstrual napkin of Comparative Example 3 is the same as the menstrual napkin of Example 1 except that the average fineness of the constituent fibers of the fiber mass was changed.

[Performance evaluation]
For the menstrual napkins of each Example and Comparative Example, the friction work amount, the dynamic twist rate, and the liquid return amount were measured by the following methods, respectively. The results are shown in Table 1 below.

<Measurement method of friction work>
An acrylic plate having a smooth surface and a uniform thickness is placed on a horizontal surface, and a menstrual napkin to be measured is placed on the upper surface of the acrylic plate with the non-skin facing surface (back surface sheet) facing down. On the skin facing surface (surface sheet) which is the upper surface of this napkin, a model skin made of silicon having a square shape in a plan view with a length of 6.5 mm in the vertical direction and a length of 3.5 mm in the horizontal direction (manufactured by Imai Rubber Co., Ltd.) A weight of 0.5 mm) is placed, and a weight is placed on the model skin to apply a load of 13 gf / cm ² to the napkin. Attach a string to one end of the weight on the napkin, and use a tensile tester (manufactured by Orientec Co., Ltd., product name "TENSILON RTC-1210S") to pull this string horizontally at a tensile speed of 200 mm / min. The displacement amount Δx (unit: mm) of the weight and the tensile load F (unit: N) corresponding to the frictional force acting between the model skin and the napkin are recorded. Create a graph with the tensile load F on the vertical axis and the displacement amount Δx on the horizontal axis, and measure the area of the part between the graph and the horizontal axis Δx until the maximum static friction force Fmax is reached. The amount of friction work. The larger the value of the friction work amount, the smoother the skin-facing surface of the surface sheet of the napkin to be measured, which is highly evaluated.

<Measurement method of dynamic twist rate>
Measurements are made using a driven female lower body human body model. First, after measuring the center width of the menstrual pad to be measured, more specifically, the lateral length of the napkin in the vertical center (hereinafter, also referred to as "center width before walking"), the napkin is always used. Attach to the shorts according to the law, and then attach the shorts to the human body model according to the usual method. Next, the human body model is walked at a speed of 100 steps / minute for 30 minutes, and while the human body model is walking, 1.5 g of defibered horse blood is injected into the wearing napkin after walking for 3 minutes in 15 seconds. Repeat 6 times and inject a total of 9 g of defibered horse blood into the napkin. Then, remove the napkin from the shorts, measure its center width (hereinafter, also referred to as "center width after walking"), and use the following formula from "center width before walking" and "center width after walking". Calculate the dynamic twist rate (%).
Dynamic twist rate (%) = [{(center width before walking)-(center width after walking)} / (center width before walking)] x 100
The smaller the value of the dynamic twist rate, the more difficult it is to twist the napkin to be measured, and the higher the evaluation. The defibered horse blood to be injected into the measurement target is defibered horse blood manufactured by Japan Biotest Research Institute, and its viscosity at a liquid temperature of 25 ° C. is adjusted to 8 cp, and such viscosity is determined by Toki. This is the viscosity when measured at a rotation speed of 12 rpm with a rotor having a rotor name of L / AdP (rotor code 19) in a TVB-10M viscometer manufactured by Sangyo Co., Ltd.

<Measurement method of liquid return amount>
The menstrual napkin to be measured is spread out in a plane and placed horizontally so that the skin facing surface side (surface sheet side) faces upward, and an elliptical injection port (major diameter 50 mm, minor diameter 23 m) is placed on the napkin. ) Is placed. Weigh 3 g of defibrous blood from horses manufactured by Nippon Biotest Laboratory Co., Ltd., whose viscosity has been adjusted to 24 mPa · s, in a 10 cc injection beaker. Such a viscosity is the viscosity when measured at a rotation speed of 12 rpm with a rotor of the rotor name L / Adp (rotor code 19) in a TVB-10M type viscometer manufactured by Toki Sangyo Co., Ltd. After pouring this blood into the injection port at once, leave it for 1 minute, and then fold a piece of tissue (Nippon Paper Crecia's Kleenex (registered trademark)) in three on the part of the napkin where the blood was poured. A rectangular weight having a weight of 125 g and a bottom area of 31 cm ² is placed and allowed to stand for 5 seconds, and the amount of blood (g) sucked by the absorbent paper is calculated from the weight of the absorbent paper after 5 seconds. The measurement is performed three times, and the average value is used as the amount of liquid returned to the napkin to be measured. The smaller the value of the amount of liquid return, the better the liquid absorption of the napkin to be measured, and the higher the evaluation.

1,1A, 1B Menstrual napkins (absorbent articles)
F Front area M Vertical center area R Rear area 2 Absorbent body 3 Surface sheet 31 Convex part 32 Concave part 4 Backside sheet 5,5A Absorbent core 50, 50X, 50Y Groove-shaped concave part 51 Convex part 52 Continuous layer 6 Fiber mass layer 7 Liquid permeable sheet 8 Side sheet 11 Fiber lump 11F Fiber lump constituent Fiber 110 Main body 111 Basic surface 112 Skeleton surface 113 Extended fiber part 113S Extended fiber bundle part

Claims (7)

An absorbent article comprising an absorbent core capable of absorbing and retaining body fluids and a surface sheet disposed closer to the wearer's skin than the absorbent core.
A fiber mass layer, which is an aggregate of a plurality of fiber masses, is arranged on the side farther from the wearer's skin than the absorbent core.
The fiber mass contains non-absorbent thermoplastic fibers.
An absorbent article having an average fineness of 1 dtex or more and 2.5 dtex or less of the constituent fibers of the fiber mass. The absorbent article according to claim 1, wherein the constituent fibers of the surface sheet have an average fineness of 1.7 dtex or more. Claim 1 or 2 in which the fiber mass layer is directly superposed on the non-skin facing surface of the absorbent core, and the absorbent core and the fiber mass layer are integrally covered with a liquid permeable sheet. Absorbent article described in. The absorbent article according to any one of claims 1 to 3, wherein an adhesive is not arranged between the fiber mass layer and a member directly laminated on the skin facing surface of the fiber mass layer. A plurality of the fiber masses are entangled with each other in the fiber mass layer, and the fiber mass and the structure of the fiber mass are configured between the fiber mass layer and a member directly overlapped with the skin facing surface of the fiber mass layer. The absorbent article according to any one of claims 1 to 4, wherein the fibers are entangled with the fibers. The absorbent article according to any one of claims 1 to 5, wherein a plurality of convex portions protruding toward the wearer's skin are formed on the skin-facing surface of the surface sheet. The absorbent core has a groove-like recess having an opening in at least one of the skin-facing surface and the non-skin-facing surface of the absorbent core and extending in a predetermined direction, and the groove-shaped recess in the absorbent core. The absorbent article according to any one of claims 1 to 6, wherein the portion overlapping the recess in a plan view has a lower basis weight than the periphery thereof.

Images