CN112135593B

CN112135593B - Absorbent article

Info

Publication number: CN112135593B
Application number: CN201980032633.1A
Authority: CN
Inventors: 立川裕美; 金子将也; 糸井奈美江
Original assignee: Kao Corp
Current assignee: Kao Corp
Priority date: 2018-12-13
Filing date: 2019-12-12
Publication date: 2022-04-15
Anticipated expiration: 2039-12-12
Also published as: CN112135593A; WO2020122161A1

Abstract

An absorbent article (1) of the present invention comprises: a excretion part opposite region (B) which is arranged opposite to the excretion part of the user when in use; and a front region (A) and a rear region (C) which are arranged in front of and behind the longitudinal direction (X) of the region (B), and which have an absorber (4). The absorbent body (4) contains a fiber mass (11) containing synthetic fibers (11F) and water-absorbent fibers (12F). In the absorbent body (4), the ratio of the mass content of the fiber mass (11) to the total mass content of the fiber mass (11) and the water-absorbent fibers (12F) (fiber mass occupancy) is greater in the excretion portion-corresponding region (B) than in the front region (A) and the rear region (C), and is smaller in the excretion portion-corresponding region (B) on the skin-facing surface side (B1) of the absorbent body than on the non-skin-facing surface side (B2) of the absorbent body.

Description

Absorbent article

Technical Field

The present invention relates to an absorbent article.

Background

Generally, an absorbent article such as a disposable diaper or a sanitary napkin includes a front sheet disposed relatively close to the skin of a wearer, a back sheet disposed relatively far from the skin of the wearer, and an absorbent body interposed between the two sheets. Typically, the absorbent material is composed mainly of water-absorbent fibers such as wood pulp, and further contains water-absorbent polymer particles. An absorbent body used in an absorbent article has a great problem in improving various properties such as flexibility, cushioning properties, compression recovery properties, shape retention properties, and the like.

As a technique for improving an absorbent body, for example, patent document 1 describes an absorbent body containing thermoplastic resin fibers and cellulose-based water-absorbent fibers, the thermoplastic resin fibers being exposed on both the front sheet side surface and the back sheet side surface of the absorbent body. According to the absorbent body described in patent document 1, the thermoplastic resin fibers function as a skeleton for holding other components of the absorbent body such as cellulose-based water-absorbent fibers, and therefore are soft and less likely to wrinkle.

Patent document 2 describes an absorbent body comprising a nonwoven fabric sheet and water-absorbent fibers, wherein the nonwoven fabric sheet comprises heat-fusible fibers, and a three-dimensional structure is imparted by bonding fibers in advance, and the nonwoven fabric sheet is uniformly distributed over the entire absorbent body. The nonwoven fabric sheet having the three-dimensional structure is produced by pulverizing the nonwoven fabric into fine pieces by a pulverizing means such as a chopper method, and by adopting this production method, the nonwoven fabric sheet is formed into an indefinite shape as described in fig. 1 and 3 of the document, and has substantially no portion that can be regarded as a flat surface. Patent document 2 describes, as a preferred embodiment of the absorbent body described in the document, heat-sealing nonwoven fabric sheets to each other. According to the absorbent body described in patent document 2, since the nonwoven fabric sheet has a three-dimensional structure, voids are formed in the absorbent body, and the recovery property when absorbing moisture is improved, resulting in improvement of water absorption performance.

Patent documents

3 and 4 describe an absorbent article having a member which is separate from the absorbent body and has excellent cushioning properties. In the absorbent article described in patent document 3, a cushioning material made of a film having elasticity, a sheet obtained by embossing a fiber aggregate, or the like is disposed on, under, or in an absorbent body. In the absorbent article described in patent document 4, a cushion layer composed of an aggregate of fine pieces of nonwoven fabric is disposed between the topsheet and the absorbent body.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2015-16296

Patent document 2: japanese patent laid-open No. 2002-301105

Patent document 3: japanese patent laid-open No. 2000-316902

Patent document 4: japanese patent laid-open No. 2003-52750

Disclosure of Invention

The present invention provides an absorbent article having a longitudinal direction corresponding to a front-back direction of a user and a lateral direction orthogonal to the longitudinal direction, and comprising: a region opposite to the excretion part of the user when in use; a front region disposed on the front side of the region facing the drain portion in the longitudinal direction; and a rear region disposed longitudinally rearward of the region opposed to the excretion portion, the absorbent article having an absorber. The absorbent body contains a fiber mass including synthetic fibers and water-absorbent fibers. In the absorbent body, a ratio of a mass content of the fiber mass to a total mass content of the fiber mass and the water-absorbent fiber is larger in the excretion portion-corresponding region than in the front region and the rear region, and is smaller on the skin-facing surface side of the absorbent body than on the non-skin-facing surface side of the absorbent body in the excretion portion-corresponding region.

Drawings

Fig. 1 is a plan view schematically showing a skin-facing surface side (topsheet side) of a sanitary napkin as an embodiment of an absorbent article of the present invention, partially cut.

Fig. 2 is a cross-sectional view schematically showing a section I-I of fig. 1.

Fig. 3 is a plan view schematically showing the skin-facing surface side of the absorbent body of the absorbent article shown in fig. 1.

Fig. 4 (a) is a cross-sectional view schematically showing the section II-II of fig. 3, and fig. 4 (b) is a cross-sectional view schematically showing the section III-III of fig. 3.

Fig. 5 is a longitudinal sectional view schematically showing the section IV-IV of fig. 3.

Fig. 6 (a) and (b) are schematic perspective views of fiber blocks used in the present invention, respectively.

Fig. 7 is an explanatory view of a method for producing a fiber block used in the present invention.

Detailed Description

In order to improve the wearing feeling of an absorbent article, it is effective to improve the cushioning property of an absorbent body of the absorbent article, and therefore it is more effective to use an absorbent body containing fiber masses such as a nonwoven fabric sheet described in patent document 2 than an absorbent body in which constituent fibers are present independently of each other described in patent document 1. Further, as described in

patent documents

3 and 4, it is also effective to use a member having excellent cushioning properties in addition to the absorbent body for improving the wearing feeling of the absorbent article. However, even if the cushioning properties of the absorbent body are improved by using these conventional techniques, when the absorbent body is easily wrinkled by external force such as body pressure applied when the absorbent article is worn, the wearing feeling of the absorbent article cannot be improved. Further, the absorbent body is required to have liquid absorption properties at a certain level or more, but for example, if the absorbent body contains only the nonwoven fabric sheet described in patent document 2, the liquid absorption properties may be reduced. Further, for example, if a member having excellent cushioning properties is disposed between the topsheet and the absorbent body as described in

patent documents

3 and 4, the distance between the topsheet and the absorbent body becomes long, and the liquid-drawing properties may be reduced, which may still lead to a reduction in liquid-absorbing properties. An absorbent body which is less likely to wrinkle when wearing an absorbent article and is excellent in cushioning properties and liquid intake properties has not yet been provided.

Therefore, the present invention relates to an absorbent article having good wearing feeling before and after excretion and excellent absorption performance.

Hereinafter, preferred embodiments of the absorbent article according to the present invention will be described with reference to the drawings. Fig. 1 and 2 show a sanitary napkin 1 as an embodiment of an absorbent article of the present invention. The sanitary napkin 1 has: an absorbent body 4 which absorbs and retains a body fluid; a topsheet 2 that is disposed on the skin-facing surface side of the absorbent body 4, is capable of contacting the skin of the wearer, and has liquid permeability; and a back sheet 3 which is disposed on the non-skin-facing surface side of the absorbent body 4 and has liquid impermeability. As shown in fig. 1, the sanitary napkin 1 has a longitudinal direction X extending from the abdominal side to the back side of the wearer through the crotch portion, and a transverse direction Y orthogonal to the longitudinal direction X, corresponding to the front-back direction of the wearer, and has in the longitudinal direction X: a excretion portion-facing region B including excretion portion-facing portions (excretion points) arranged to face excretion portions such as the pudenda of a wearer when worn; a front region a disposed on the front side in the longitudinal direction (the abdominal side of the wearer) with respect to the excretion portion-corresponding region B; and a rear region C which is disposed on the rear side in the longitudinal direction (the back side of the wearer) of the excretion portion-corresponding region B and is divided into the three regions.

In the present specification, the "skin-facing surface" is a surface of the absorbent article or a component thereof (e.g., the absorbent body 4) that faces the skin side of the wearer when the absorbent article is worn, that is, a surface that is relatively close to the skin of the wearer, and the "non-skin-facing surface" is a surface of the absorbent article or a component thereof that faces the side opposite to the skin side when the absorbent article is worn, that is, a surface that is relatively far from the skin of the wearer. Here, "worn" means a state in which a normal proper wearing position, that is, a proper wearing position of the absorbent article is maintained.

As shown in fig. 1, the sanitary napkin 1 has: an absorbent main body 5 having a shape elongated in the longitudinal direction X; and a pair of

wing portions

5W, 5W extending outward in the transverse direction Y from both side portions in the longitudinal direction X of the excretion portion-corresponding region B of the absorbent main body 5. The absorbent main body 5 is a part constituting the main body of the sanitary napkin 1, and has the front sheet 2, the back sheet 3, and the absorbent body 4, and is divided into three regions, a front region a, a excretion portion-corresponding region B, and a rear region C in the longitudinal direction X.

When an absorbent article such as a sanitary napkin 1 has flaps, the absorbent article has the flaps in the longitudinal direction (longitudinal direction, X direction in the drawing). Taking the sanitary napkin 1 as an example, a region sandwiched by an imaginary straight line extending in the transverse direction Y through the root portions on the front side in the longitudinal direction X of each of the pair of

wing portions

5W, 5W and an imaginary straight line extending in the transverse direction Y through the root portions on the rear side in each of the pair of

wing portions

5W, 5W is the excretion portion-facing region B. In the sanitary napkin 1, the pair of

flaps

5W, 5W are formed symmetrically with respect to the longitudinal center line bisecting the sanitary napkin 1 in the transverse direction Y and extending in the longitudinal direction X, and the root portion on the front side of one flap 5W and the root portion on the front side of the other flap 5W are present at the same position in the longitudinal direction X.

The region of the absorbent article (e.g., a disposable diaper) having no flap portion facing the excretion portion corresponds to a region in which the absorbent article is positioned in the middle when the absorbent article is trisected in the longitudinal direction X.

As shown in fig. 2, the topsheet 2 covers the entire skin-facing surface of the absorbent member 4. On the other hand, the back sheet 3 covers the entire non-skin-facing surface of the absorbent body 4, extends outward in the lateral direction Y from both side edges of the absorbent body 4 in the longitudinal direction X, and forms wing portions together with the side sheets 6 described below. The side flaps are portions of the sanitary napkin 1 that are formed by members extending outward in the transverse direction Y from the absorbent body 4. The back sheet 3 and the side sheet 6 are joined to each other by a known joining means such as an adhesive, heat seal, or ultrasonic seal at extending portions extending from both side edges of the absorbent body 4 in the longitudinal direction X. The front sheet 2 and the back sheet 3 may be bonded to the absorbent body 4 with an adhesive. As the front sheet 2 and the back sheet 3, various materials conventionally used in absorbent articles such as sanitary napkins can be used without particular limitation. For example, a single-layer or multi-layer nonwoven fabric, an apertured film, or the like can be used as the front sheet 2. As the back sheet 3, a moisture-permeable resin film or the like can be used.

As shown in fig. 1, the wing portions largely extend outward in the lateral direction Y in the excretion portion-corresponding region B, and thus a pair of

wing portions

5W, 5W extend on both left and right sides of the absorbent main body 5 in the longitudinal direction X. As shown in fig. 1, the wing section 5W has a substantially trapezoidal shape with a lower base (a side longer than an upper base) located on the side of the absorbent main body 5 in a plan view, and a wing section bonding section (not shown) for fixing the wing section 5W to clothing such as shorts is formed on the non-skin-facing surface thereof. The wing part 5W is folded back toward the non-skin-facing surface (outer surface) of the crotch part of the clothing such as shorts. Further, since the wing portions 5W are folded back toward the non-skin-facing surface (outer surface) side of the crotch portion of the clothing such as pants and the like, the non-skin-facing surface of the wing portions 5W, which is the surface on which the wing portions are bonded, faces the skin of the wearer when used, and becomes a skin-facing surface. The wing part bonding part is covered with a release sheet (not shown) including a film, a nonwoven fabric, paper, or the like before use. In addition, a pair of

side sheets

6, 6 is disposed over substantially the entire length in the longitudinal direction X of the absorbent main body 5 on both side portions along the longitudinal direction X of the skin-facing surface of the topsheet 2, which is the skin-facing surface of the absorbent main body 5, so as to overlap with both side portions along the longitudinal direction X of the absorbent body 4 in plan view. The pair of

side sheets

6 and 6 are joined to the topsheet 2 or other members by known joining means such as an adhesive or hot embossing at joining lines not shown extending in the longitudinal direction X.

As shown in fig. 1, the absorbent body 4 extends from the front region a to the rear region C via the excretion portion-corresponding region B over substantially the entire length of the sanitary napkin 1 (absorbent main body 5) in the longitudinal direction X. The absorbent body 4 is used by being incorporated into an absorbent article such as a sanitary napkin 1 to indirectly contact human skin, that is, indirectly contact the skin via a member such as a backsheet 3, and includes: a skin-facing surface (a surface facing the topsheet 2) which is disposed at a position relatively close to the skin of a wearer of the sanitary napkin 1, i.e., a user, during use; and a non-skin-facing surface (a surface facing the back sheet 3) which is disposed at a relatively distant position from the skin of the user, has a longitudinal direction X corresponding to the front-back direction of the user and a lateral direction Y perpendicular to the longitudinal direction X, and has a front region a, a drain-facing region B, and a rear region C in the longitudinal direction X. The front region a of the absorbent body 4 is a portion of the absorbent body 4 located in the front region a of the sanitary napkin 1, the excretion portion-corresponding region B of the absorbent body 4 is a portion of the absorbent body 4 located in the excretion portion-corresponding region B of the sanitary napkin 1, and the rear region C of the absorbent body 4 is a portion of the absorbent body 4 located in the rear region C of the sanitary napkin 1. In addition to the mode in which the absorbent body 4 is used in indirect contact with the skin, a mode in which the absorbent body is used in direct contact with the skin without interposing a member such as a sheet may be employed.

Fig. 3 to 5 show the absorbent body 4. The absorbent body 4 in the present embodiment has a liquid-absorbent core 40 and a liquid-permeable core-covering sheet 41 covering the outer surface of the absorbent core 40. As described above, in the present embodiment, the absorbent core 40 is wrapped and integrated by the core sheet 41. The absorbent core 40 is a member constituting the main body of the absorber 4, and has a shape elongated in the longitudinal direction X in a plan view shown in fig. 3. The absorbent core 40 is disposed on the sanitary napkin 1 such that the longitudinal direction thereof coincides with the longitudinal direction X of the sanitary napkin 1. The absorbent core 40 and the core sheet 41 may be joined together by an adhesive such as a hot-melt adhesive.

In the present embodiment, the core sheet 41 is 1 continuous sheet having a width 2 times or more and 3 times or less the length of the absorbent core 40 in the transverse direction Y, and as shown in fig. 4, covers the entire skin-facing surface of the absorbent core 40, extends outward in the transverse direction Y from both side edges of the absorbent core 40 in the longitudinal direction X, and is rolled up with its extending portion downward of the absorbent core 40 to cover the entire non-skin-facing surface of the absorbent core 40. In the present invention, the core sheet may cover the entire non-skin-facing surface of the absorbent core 40, extend outward in the transverse direction Y from both side edges of the absorbent core 40 in the longitudinal direction X, and have extended portions folded over the absorbent core 40 to cover the entire skin-facing surface of the absorbent core 40. Further, the core-spun sheet may not be the 1 sheet, and for example, may include the following 2 sheets: 1 skin-side wrapping sheet covering the skin-facing surface of the absorbent core 40; and 1 non-skin-side wrapping chip which is separate from the skin-side wrapping chip and covers the non-skin-facing surface of the absorbent core 40. Further, the absorbent body 4 may not have a core sheet, and the absorbent body of the present invention includes an absorbent body composed of only an absorbent core.

The absorbent core 40 is also substantially referred to as the absorbent body 4 itself, and the following description of the absorbent core 40 is also suitable for use as a description of the absorbent body 4 unless otherwise specified. The absorbent body 4 includes a form including only the absorbent core without a core sheet, and in the absorbent body of this form, the absorbent body has the same meaning as the absorbent core.

The absorbent core 40 is mainly composed of a core-forming material, and typically, is composed of only the core-forming material. The core forming material includes at least water-absorbent fibers 12F and a fiber block 11 containing the fibers 11F. In the absorbent core 40 of the present embodiment, the water-absorbent polymer 13 is further included as a core-forming material. The constituent fibers 11F of the fiber block 11 are synthetic fibers.

In the present specification, the "fiber mass" refers to a fiber aggregate in which a plurality of fibers are aggregated and integrated. The fiber mass used in the present invention may be a fiber aggregate shaped like a small piece obtained by cutting a synthetic fiber sheet having a certain size with a cutter or the like, or an amorphous fiber aggregate produced by pulverizing a nonwoven fabric composed mainly of synthetic fibers into a fine piece, or by pulling or tearing the same, such as a nonwoven fabric sheet described in patent document 2, regardless of the production method thereof. In the present invention, the absorbent body (absorbent core) may be i) an embodiment containing only the set fiber aggregate as the fiber mass, or ii) an embodiment containing only the amorphous fiber aggregate as the fiber mass, or iii) an embodiment in which the set fiber aggregate and the amorphous fiber aggregate are mixed to form the fiber mass, but the above-described embodiment of i) is preferably used. In the amorphous fiber aggregate, since the fibers are randomly oriented, the fibers protrude from various parts of the surface and the surface is rough, and the fiber aggregates are entangled with each other over the entire surface, and as a result, the degree of freedom of movement of each fiber aggregate may be restricted, and the flexibility may be lowered. The fiber block 11 of the present embodiment is a set fiber aggregate as described below.

As described above, the fiber block 11 is a fiber aggregate in which a plurality of fibers 11F are gathered and integrated into a block, and a plurality of the fiber blocks are present in the absorbent core 40 in a state where the fiber blocks are held in this form. The fiber mass 11 mainly contributes to improvement in flexibility, cushioning properties, compression recovery properties, and shape retention of the absorbent core 40 due to the form of the fiber aggregate.

The plurality of water-absorbent fibers 12F are present in the absorbent core 40, and these plurality of water-absorbent fibers 12F can be entangled with each other, but are preferably not aggregated as in the case of the constituent fibers 11F of the fiber block 11, but are present independently of each other. The water-absorbent fibers 12F mainly contribute to the improvement of the liquid absorbency of the absorbent core 40 and also contribute to the improvement of the shape retention of the absorbent core 40.

As the water-absorbent fibers 12F, water-absorbent fibers that have been conventionally used as a material for forming the absorbent body of such absorbent articles can be used. Examples of the water-absorbent fibers include: natural fibers such as wood pulp such as softwood pulp or hardwood pulp, and non-wood pulp such as cotton pulp or hemp pulp; modified pulp such as cationized pulp and mercerized pulp; regenerated fibers such as cuprammonium fibers and rayon can be used alone or in combination of 1 or more. The water-absorbent fibers 12F mainly serve to improve the liquid absorbency of the absorbent body 4, and therefore natural fibers and regenerated fibers (cellulose fibers) are preferable as the water-absorbent fibers 12F.

The water-absorbent polymer 13 is present in the absorbent core 40 in the form of a plurality of small pieces of water-absorbent polymer, and mainly contributes to the improvement of the liquid absorbency in the absorbent core 40. The shape of the small pieces of the water-absorbent polymer 13 is not particularly limited, and may be, for example, a sphere, a block, a bag, a fiber, or an irregular shape. The average particle diameter of the water-absorbent polymer 13 is preferably 10 μm or more, more preferably 100 μm or more, and preferably 1000 μm or less, more preferably 800 μm or less. In general, as the water-absorbent polymer 13, a polymer or copolymer of acrylic acid or an alkali metal salt of acrylic acid can be used. Examples thereof include polyacrylic acid and salts thereof and polymethacrylic acid and salts thereof, and specifically include acrylic acid polymer partial sodium salts such as Aqualic CA and Aqualic cam (both manufactured by japan catalyst (stock) corporation).

In the absorbent core 40, the plurality of fiber masses 11 and the water-absorbent fibers 12F are present in a mixed state, but in the present embodiment, the fiber masses 11 are not simply mixed but the fiber masses 11 are entangled with each other or the fiber masses 11 and the water-absorbent fibers 12F are entangled with each other. In the absorbent core 40 of the present embodiment, the plurality of fiber blocks 11 are bonded by intertwining with the constituent fibers (

fibers

11F, 12F) in the absorbent core 40, thereby forming 1 fiber block continuum. Further, the plurality of fiber blocks 11 may be entangled with each other, and the fiber blocks 11 may be entangled with the water-absorbent fibers 12F to be bonded. Further, the plurality of water-absorbent fibers 12F are usually entangled with each other. At least a part of the plurality of fiber pieces 11 included in the absorbent core 40 is entangled with another fiber piece 11 or the water-absorbent fiber 12F. In the absorbent core 40, there may be a case where all of the plurality of fiber pieces 11 contained therein are entangled with each other to form a 1-piece fiber piece continuous body, and there may be a case where a plurality of fiber piece continuous bodies are mixed in a state where they are not bonded to each other.

In the absorbent core 40, in addition to the fiber blocks 11 having excellent flexibility and the like, since the fiber blocks 11 or the fiber blocks 11 and the water-absorbent fibers 12F are entangled with each other and bonded to each other, the absorbent core 40 has more excellent responsiveness to an external force and is excellent in flexibility, cushioning properties, and compression recovery properties. The absorbent core 40 is flexibly deformed against external forces (for example, body pressure of a wearer of the sanitary napkin 1) received from various directions when the sanitary napkin 1 is worn, and the sanitary napkin 1 can be brought into close contact with the body of the wearer with good fit. Such excellent deformation-recovery characteristics of the absorbent core 40 can be exhibited not only when the absorbent core 40 is compressed but also when it is twisted. That is, since the absorbent core 40 incorporated in the sanitary napkin 1 is disposed in a state of being sandwiched between the thighs of the wearer when the sanitary napkin 1 is worn, the absorbent core may be twisted around a virtual rotation axis extending in the longitudinal direction X in accordance with the movement of the thighs during walking motion of the wearer, but even in this case, the absorbent core 40 has high deformation-recovery characteristics, and therefore is easily deformed and recovered against an external force that urges the twisting to occur with the thighs, and is less likely to wrinkle, and the sanitary napkin 1 can be given high conformability to the body of the wearer.

In the absorbent core 40, the fiber masses 11 are entangled with each other or the fiber masses 11 are entangled with the water-absorbent fibers 12F, and the "entanglement" of the fiber masses 11 with each other here includes the following forms A and B.

Form A: the fiber blocks 11 are not welded to each other, but are joined by intertwining the constituent fibers 11F of the fiber blocks 11.

Form B: in a natural state (state where external force is not applied) of the absorbent core 40, the fiber blocks 11 and the like are not bonded to each other, but in a state where external force is applied to the absorbent core 40, the fiber blocks 11 and the like can be bonded to each other by winding the constituent fibers 11F around each other. Here, the "state in which the external force is applied to the absorbent core 40" is, for example, a state in which a deforming force is applied to the absorbent core 40 in a state in which an absorbent article (in the present embodiment, the sanitary napkin 1) to which the absorbent core 40 is applied is worn.

In this way, the absorbent core 40 is connected to the fiber block 11 and the other fiber blocks 11 or the water-absorbent fibers 12F by fiber entanglement, i.e., "entanglement" as in the embodiment a, and is also present in a state capable of entanglement with the other fiber blocks 11 or the water-absorbent fibers 12F as in the embodiment B. The combination of the entangled fibers is important to more effectively exhibit the effect of the absorbent core 40. In particular, from the viewpoint of shape retention, the absorbent core 40 preferably has "entanglement" of the form a. Since the bonding by the entanglement of the fibers is achieved only by the entanglement of the fibers without the need for an adhesive component or welding, the flexibility of movement of the entangled elements (the fiber block 11 and the water-absorbent fibers 12F) is higher than that of the bonding by the welding of the fibers, and therefore the elements can move within a range in which the integrity of the aggregate formed by the elements can be maintained. In this manner, the absorbent core 40 has a shape retaining property that is capable of being deformed gently when an external force is applied, by the plurality of fiber pieces 11 contained therein being relatively loosely bonded to each other or the fiber pieces 11 and the water-absorbent fibers 12F, thereby achieving a combination of shape retaining property, cushioning property, compression recovery property, and the like at a high level. The sanitary napkin 1 having the high-quality absorbent core 40 can be closely attached to the body of the wearer with good fitting properties, and is excellent in wearing feeling.

The bonding method of the absorbent core 40 by the fiber block 11 is not necessarily all "intertwined", and a part of the absorbent core 40 may be bonded by a bonding method other than intertwining, for example, bonding with an adhesive.

However, in the unprocessed absorbent core 40 itself, which is the remaining portion of the absorbent core 40 after the "fusion bonding of the fiber blocks 11" formed in the absorbent core 40 as a result of integration with other components of the absorbent article, such as known leakage preventing grooves or the like, it is preferable that the bonding of the fiber blocks 11 to each other or the bonding of the fiber blocks 11 and the water-absorbent fibers 12F is achieved only by "entanglement of fibers".

From the viewpoint of more reliably exhibiting the effects of the absorbent core 40, the total number of the "fiber masses 11 bonded by entanglement" in the form a and the "fiber masses 11 in an entangled state" in the form B is preferably half or more, more preferably 70% or more, and even more preferably 80% or more, of the total number of the fiber masses 11 in the absorbent core 40.

From the same viewpoint, "entangled" fiber masses 11 having the form a are preferably 70% or more, particularly preferably 80% or more, of the total number of fiber masses 11 having a joint with another fiber mass 11 or water-absorbent fiber 12F.

One of the characteristics of the absorbent core 40 is the arrangement of the core-forming material represented by the fiber block 11. In the absorbent core 40, as shown in fig. 3 to 5, the fiber pieces 11 are not uniformly distributed over the entire absorbent core 40, but are present in the excretion portion-facing region B relatively more than in the front region a and the rear region C, and are present in the excretion portion-facing region B relatively more than in the skin-facing surface side B1 on the non-skin-facing surface side B2.

The skin-facing surface side B1 of the excretion portion-corresponding region B of the absorbent core 40 is a portion closer to the skin-facing surface when the excretion portion-corresponding region B of the absorbent core 40 is bisected in the thickness direction, and the non-skin-facing surface side B2 is a portion closer to the non-skin-facing surface in this case. The same applies to the skin-facing surface side and the non-skin-facing surface side of the front region a and the rear region C of the absorbent core 40.

When the offset of the fiber mass 11 in the absorbent core 40 is compared with the total content mass of the water-absorbent fibers 12F used as the core forming material of the absorbent core 40 together with the fiber mass 11, and "the ratio of the content mass of the fiber mass 11 to the total content mass of the fiber mass 11 and the water-absorbent fibers 12F" (hereinafter also referred to as "fiber mass occupancy") is defined, the fiber mass occupancy of each part of the absorbent core 40 is such that the excretion part-facing region B is larger than the front region a and the rear region C, and the skin-facing surface side B1 is smaller than the non-skin-facing surface side B2 in the excretion part-facing region B.

The fiber block occupancy is a value obtained by measuring the content of each of the fiber blocks 11 and the water-absorbent fibers 12F existing in a predetermined measurement target region of the absorbent core 40 (absorbent body 4) by mass, dividing the content mass of the fiber block 11 thus measured by the total value of the content masses of the water-absorbent fibers 12F and the fiber block 11, and expressing the result by 100 fractions. That is, the fiber block occupancy (mass%) } × 100 (mass content of the fiber block 11/(mass content of the water-absorbent fiber 12F + mass content of the fiber block 11).

In general, the excretion portion-corresponding region B of the absorbent core 40 is sandwiched between the thighs of the wearer when the sanitary napkin 1 is worn, and therefore tends to twist about an imaginary rotation axis extending in the longitudinal direction X in accordance with the movement of the thighs during walking motion of the wearer, and is more likely to be subjected to a strong action of an external force than the front region a and the rear region C, and to cause wrinkles. By arranging more fiber blocks 11 contributing to improvement in cushioning properties, compression recovery properties, shape retention properties, and the like in the excretion portion-corresponding region B of the absorbent core 40, in which wrinkles are relatively more likely to occur, than in the front region a and the rear region C, that is, by setting the fiber block occupancy rate in the excretion portion-corresponding region B higher than that in the front region a and the rear region C, it is possible to effectively prevent a failure in which the absorbent body 4 is wrinkled when the sanitary napkin 1 is worn.

In particular, in the present embodiment, as described above, the absorbent body 4 includes: an absorbent core 40 containing a core-forming material represented by a fiber block 11 and an absorbent fiber 12F; and a core sheet 41 covering the outer surface of the absorbent core 40, whereby the core-forming material is integrated, and therefore, the absorbent body 4 can be more reliably prevented from being wrinkled when the sanitary napkin 1 is worn, in addition to the operational effects of the offset of the fiber pieces 11.

In addition, typically, the water-absorbent fibers 12F constitute a main body and hardly contain the fiber mass 11 on the skin-facing surface side B1 of the excretion portion-facing region B of the absorbent core 40, and the skin-facing surface side B1 having such a structure tends to have a significantly reduced shape retention property when the absorbent liquid is brought into a wet state, and thus has a problem that the absorbent core is easily wrinkled due to an unexpected deformation by external pressure in the wet state. However, the non-skin-facing surface side B2 of the absorbent core 40 adjacent to the skin-facing surface side B1 in the thickness direction is a portion where the fiber mass 11 including synthetic fibers is present in a biased manner and has excellent shape retention even in a wet state, and therefore, the absorbent core 40 can be prevented from wrinkling even when the liquid is absorbed in the region B facing the excretion portion of the absorbent core 40 and is in a wet state. The wrinkle preventing effect is more effective when the fiber mass 11 and the water-absorbent fibers 12F are entangled at the interface between the skin-facing surface side B1 and the non-skin-facing surface side B2 and the vicinity thereof.

Further, the skin-facing surface side B1 of the excretion portion-facing region B of the absorbent core 40 is a portion of the absorbent core 40 that receives body fluid excreted from the excretion portion of the wearer of the sanitary napkin 1 at first, and therefore, is excellent in liquid-drawing properties, and it is desirable to absorb body fluid into the absorbent core 40 quickly. Further, the most contributing to the improvement of the liquid drawing-in property among the core-forming materials contained in the absorbent core 40 is the water-absorbent fibers 12F, and the fiber block 11 is less contributing to the improvement of the liquid drawing-in property. In the excretion portion-facing region B of the absorbent core 40, the relationship of the size of "skin-facing surface side B1 < non-skin-facing surface side B2" is established as described above with respect to the fiber mass occupancy, and instead of making the fiber mass occupancy on the skin-facing surface side B1 smaller than the fiber mass occupancy on the non-skin-facing surface side B2, relatively many water-absorbent fibers 12F are present on the skin-facing surface side B1. This provides the absorbent core 40 with excellent liquid-drawing properties, and can quickly draw discharged body fluid into the interior for absorption and retention. Further, since the fiber block occupancy rate has a relationship of "excretion portion-corresponding region B > front and rear regions A, C", the bodily fluid received by the excretion portion-corresponding region B is easily diffused and absorbed in the longitudinal direction X in the absorbent core 40. Therefore, the absorbent core 40 is also excellent in suppressing the side leakage of bodily fluids.

From the viewpoint of more reliably achieving the operational effect of the presence of the fiber masses 11, the fiber mass occupancy of each portion of the absorbent core 40 is preferably set as follows.

The fiber mass occupancy of the non-skin-facing surface side B2 of the excretion portion-facing region B of the absorbent core 40 is preferably 50 mass% or more, more preferably 90 mass% or more, and may be 100 mass%, that is, the fiber mass 11 is contained but the water-absorbent fibers 12F are not contained at all, on the premise that the fiber mass occupancy is higher than the fiber mass occupancy of the other portions (the front region a, the rear region C, and the skin-facing surface side B1 of the excretion portion-facing region B) of the absorbent core 40.

The fiber mass occupancy on the skin-facing surface side B1 of the excretion portion-facing region B of the absorbent core 40 is preferably 50 mass% or less, more preferably 10 mass% or less, and may be 0 mass%, that is, the water-absorbent fibers 12F are contained but the fiber mass 11 is not contained at all, on the assumption that the fiber mass occupancy is lower than the fiber mass occupancy on the non-skin-facing surface side B2.

The difference between the fiber mass occupancy rate on the non-skin surface side B2 and the fiber mass occupancy rate on the skin surface side B1 in the excretion portion-facing region B of the absorbent core 40, when the former is subtracted from the latter, is preferably 50 mass% or more, more preferably 90 mass% or more, and may be 100 mass%, that is, only the fiber mass 11 is contained on the non-skin surface side B2, and the fiber mass 11 is not contained at all on the skin surface side B1.

Typically, the fiber mass occupancy of the front region a and the rear region C of the absorbent core 40 is set in the same manner as the fiber mass occupancy of the skin-facing surface side B1 of the excretion portion-facing region B of the absorbent core 40.

From the viewpoint of more reliably achieving the operational effect of the fiber masses 11 being unevenly distributed in the excretory part facing region B, it is preferable that the fiber masses 11 be present in the excretory part facing region B in an amount of 90 mass% or more, and particularly preferably 95 mass% or more, of all the fiber masses 11 contained in the absorbent core 40.

The excretory part facing region B of the absorbent core 40 may be 1) maintained in a constant state without changing the fiber mass occupancy rate in the thickness direction, or 2) gradually increasing in the fiber mass occupancy rate from the skin-facing surface side B1 toward the non-skin-facing surface side B2, on the skin-facing surface side B1 and the non-skin-facing surface side B2, respectively. In the configuration of 2) above, the fiber mass 11 is absent or present at the lowest fiber mass occupancy in the skin-facing surface of the absorbent core 40 and the vicinity thereof in the thickness direction of the absorbent core 40 in the excretion portion-facing region B of the absorbent core 40, and the fiber mass 11 is present at the highest fiber mass occupancy in the non-skin-facing surface of the absorbent core 40 and the vicinity thereof in the excretion portion-facing region B of the absorbent core 40. The front region a and the rear region C of the absorbent core 40 may have the form of 1) or 2) described above.

The following advantages can be mentioned as specific advantages of the form 1): it is easy to design the respective independent functions on the skin-facing surface side and the non-skin-facing surface side of the absorbent body (absorbent core). Further, as advantages peculiar to the form of the above 2), the following can be mentioned: since the mixing ratio of the water-absorbent fibers and the fiber mass changes gently in the thickness direction of the absorbent body, even when an external force is applied to the absorbent body, the entangled state formed by the fiber mass is easily maintained in the thickness direction, and the cushioning property of the absorbent body is easily maintained well during use.

The fiber block occupancy may gradually increase from the front region a and the rear region C of the absorbent core 40 toward the excretion portion-corresponding region B. For example, in the front region a and the rear region C, the fiber block occupancy rate gradually increases from the outer side to the inner side in the longitudinal direction X, and the excretion portion-corresponding region B may have the form of 1) or 2) described above.

In the present embodiment, as shown in fig. 4 (a), the drain-portion-opposing region B of the absorbent core 40 has, in the thickness direction: a portion 11P having a fiber mass occupancy of preferably 50 mass% or more, more preferably 90 mass% or more (hereinafter also referred to as "fiber mass-enriched portion"); and a portion (hereinafter also referred to as "water-absorbent fiber-enriched portion") 12P having a fiber mass occupancy of preferably less than 50 mass%, more preferably 10 mass% or less, more specifically, the non-skin-facing surface side B2 as a whole becomes the fiber mass-enriched portion 11P, and the skin-facing surface side B1 as a whole becomes the water-absorbent fiber-enriched portion 12P. Thus, in the excretion portion-facing region B of the absorbent core 40 shown in fig. 4 (a), the fiber block occupancy rate greatly changes at the boundary between the skin-facing surface side B1 (water-absorbent fiber-enriched portion 12P) and the non-skin-facing surface side B2 (fiber block-enriched portion 11P).

The water-absorbent fiber-rich sites 12P are sites having a water-absorbent fiber occupancy of preferably 50 mass% or more, more preferably 90 mass% or more. The "water-absorbent fiber occupancy" herein refers to the ratio of the mass content of the water-absorbent fibers 12F to the total mass content of the fiber mass 11 and the water-absorbent fibers 12F, and is calculated by replacing the molecule of the calculation formula of the fiber mass occupancy from the "mass content of the fiber mass 11" to the "mass content of the water-absorbent fibers".

As shown in fig. 4 (b) and 5, the front region a and the rear region C of the absorbent core 40 contain almost no fiber mass 11, and the fiber mass occupancy of both regions A, C is 0 mass% or close to 0 mass%, and the whole becomes the water-absorbent fiber-rich part 12P.

The fiber-block-rich region 11P is mainly composed of the fiber block 11, and typically does not substantially contain the water-absorbent fibers 12F, so that the characteristics of the fiber block 11 are strongly reflected, and mainly contributes to improvement of flexibility, cushioning properties, compression recovery properties, shape retention properties, and the like of the absorbent core 40. In the fiber cake rich part 11P, the fiber cake 11 is preferably distributed in a high density and uniformly over the whole. On the other hand, since the water-absorbent fiber-rich part 12P is mainly composed of the water-absorbent fibers 12F, typically, is substantially free of the fiber block 11, the characteristics of the water-absorbent fibers 12F are strongly reflected, and the liquid-drawing property of the absorbent core 40 is mainly improved. In the water-absorbent fiber-rich part 12P, the water-absorbent fibers 12F are preferably distributed uniformly and at a high density over the entire surface.

As described above, the fiber-block occupancy of each part of the absorbent core 40 is based on the assumption that the relationship of the sizes of the "front region a, the rear region C < the excretion portion-facing region B" and the relationship of the sizes of the "skin-facing surface side B1 < the non-skin-facing surface side B2" of the excretion portion-facing region B are established, and the positions of the fiber-block-enriched portion 11P and the water-absorbent-fiber-enriched portion 12P are not particularly limited, and the fiber-block-enriched portion 11P may be present on the skin-facing surface side B1 of the excretion portion-facing region B of the absorbent core 40, and the water-absorbent-fiber-enriched portion 12P may be present on the non-skin-facing surface side B2.

The water-absorbent fiber-enriched part 12P is preferably present in the range of 20 to 80% of the thickness of the absorbent core 40 from the skin-facing surface of the absorbent core 40 to the inside of the absorbent core 40 in the thickness direction, and more preferably in the range of 30 to 70% of the thickness.

The fiber-block-enriched portion 11P is preferably present in the range of 20 to 80% of the thickness of the absorbent core 40 from the non-skin-facing surface of the absorbent core 40 to the inside of the absorbent core 40 in the thickness direction, and more preferably in the range of 30 to 70% of the thickness.

The thickness of each of the water-absorbent fiber-rich part 12P and the fiber-lump-rich part 11P is preferably 0.5mm or more, more preferably 1mm or more, and preferably 5mm or less, more preferably 4mm or less.

The thickness of each portion of the absorbent core 40 was measured by the following method. The thickness of the entire absorbent core 40 (absorbent body 4), the thickness of the sanitary napkin 1, and the like can also be measured by the following methods.

< method for measuring thickness >

An absorbent core (absorbent body) is left standing in a horizontal position without wrinkles or folds, and a measurement target site (for example, a skin-facing surface side or a non-skin-facing surface side of the absorbent core) is cut out from the absorbent core to prepare a measurement sample. Then, 5cN/cm of the measurement sample was measured²Under load. Specifically, in measuring the thickness, for example, a thickness meter, PEACOCK DIAL UPRIGHT GAUGES R5-C (OZAKI MFG. C0.LTD. manufactured) is used. At this time, the size was adjusted so that the load became 5cN/cm²The plate (acrylic plate having a thickness of about 5 mm) in a plan view is placed between the tip of the thickness gauge and the measurement sample, and the thickness is measured. In the thickness measurement, arbitrary 10 portions in the measurement sample are measured, and the average value of the thicknesses of the 10 portions is calculated as the thickness of the measurement sample.

The thickness of the absorbent core 40 is preferably thinner in the front region a and the rear region C than in the center of the excretion portion-corresponding region B in the transverse direction Y (at a position overlapping with an imaginary straight line bisecting the absorbent core 40 in the transverse direction Y and extending in the longitudinal direction X). Thus, when the sanitary napkin 1 is worn, the front and rear regions A, C of the absorbent core 40 easily follow the clothing such as shorts with good fit, and the wearing feeling on the front body side or the hip side of the wearer can be further improved. Further, the absorbent core 40 is configured as follows: at least the center of the excretion portion-corresponding region B in the lateral direction Y and its vicinity, that is, the center portion (the position where the raised portion 15 described below is formed) is thicker than the front and rear regions A, C. Therefore, in cooperation with the fiber block occupancy being greater in the excretory section opposing region B than in the front and back regions A, C, when the sanitary napkin 1 is worn, the portion overlapping the central portion in the lateral direction Y of the excretory section opposing region B of the absorbent core 40 in plan view can be more suitably fitted to the excretory section of the wearer. As described above, the thickness difference in the longitudinal direction X of the absorbent core 40 can be achieved by making the fiber mass occupancy of the excretion portion-corresponding region B of the absorbent core 40 higher than the fiber mass occupancy of the front region a and the rear region C.

In addition, typically, the thickness of the absorbent core 40 in the widthwise direction Y in the drain portion opposing region B is uniform over the entire length (the entire width) of the widthwise direction Y, or in a high-thickness structure in which the thickness of the central portion in the widthwise direction Y is larger than the thicknesses of both side portions thereof as shown in fig. 2, and in either of these dimensions, when the relationship "the thickness of the central portion (the central portion) in the widthwise direction Y of the absorbent core 40 in the drain portion opposing region B > the thickness of the absorbent core 40 in the front region a, and the thickness of the absorbent core 40 in the rear region C" is established, the relationship "the thickness of both side portions in the widthwise direction Y of the absorbent core 40 in the drain portion opposing region B > the thickness of the absorbent core 40 in the front region a, and the thickness of the absorbent core 40 in the rear region C" is also established.

In the absorbent core 40, the ratio of the thickness of the front region a to the thickness of the center of the region B opposite to the excretion portion in the lateral direction Y (or the portion of the region B having the largest thickness) is preferably 0.1 or more, more preferably 0.3 or more, and preferably 0.9 or less, more preferably 0.8 or less, when expressed as the former/latter, on the premise that the former < the latter. The ratio of the thickness of the rear region C to the thickness of the center of the drain-opposing region B in the lateral direction Y (or the portion of the region B having the largest thickness) is also preferably set in the same manner as described above.

The thickness of the excretion portion-corresponding region B of the absorbent core 40 (the thickness does not simultaneously become the maximum thickness in the lateral direction Y) is preferably 3mm or more, more preferably 4mm or more, and is preferably 10mm or less, more preferably 8mm or less.

The thicknesses of the front region a and the rear region C of the absorbent core 40 are each preferably 1mm or more, more preferably 2mm or more, and preferably 8mm or less, more preferably 6mm or less.

From the viewpoint of more reliably achieving the operational effect by the presence of the bias of the fiber block 11, the area of the portion of the non-skin-facing surface of the absorbent core 40 located in the excretion portion-facing region B is preferably 60% or less, more preferably 50% or less, and still more preferably 40% or less of the area of the non-skin-facing surface of the absorbent core 40. The portion of the absorbent core 40 located in the excretion portion-corresponding region B is a portion having a higher fiber mass occupancy rate than the portions located in the front region a and the rear region C, and particularly the non-skin-facing surface side B2 thereof, and therefore the region B as a whole can be said to be a portion of a "cushion portion" that can strongly reflect the cushioning properties of the fiber mass 11. In particular, in the present embodiment, the non-skin-facing surface side B2 is the fiber mass enriched portion 11P mainly composed of the fiber mass 11 and containing almost no water-absorbent fibers 12F, and therefore the excretion portion-facing region B having this portion 11P can effectively function as a buffer portion. That is, the "ratio of the area of the non-skin-facing surface of the excretory section facing region B to the area of the non-skin-facing surface of the absorbent core 40" may also be referred to as "ratio of the area of the non-skin-facing surface of the cushion section (the portion of the absorbent core 40 where the fiber mass 11 is present in a biased manner on the non-skin-facing surface side of the absorbent core 40) to the area of the non-skin-facing surface of the absorbent core 40 (the absorbent body 4)" (hereinafter also referred to as "cushion section area ratio"). By setting the area ratio of the cushion portion to 60% or less, that is, the area ratio of the excretion portion facing region B in which the fiber block 11 is present in a biased manner on the non-skin facing surface side B2 to 60% or less, the effect of improving the wearing feeling on the front body portion and the hip portion side of the body in the front region a and the rear region C can be obtained. In addition, from the viewpoint of reliably improving the fit of the excretory part to the region B and improving the wearing feeling, the lower limit of the cushioning part area ratio is preferably 20% or more, more preferably 25% or more, and even more preferably 30% or more. The cushioning portion area ratio is calculated by the following equation.

Area ratio (%) of the cushion portion (area of the cushion portion on the non-skin-facing surface/area of the absorbent core on the non-skin-facing surface) × 100

As described above, although the absorbent polymer 13 is contained in the absorbent core 40, the location of the absorbent polymer 13 in the absorbent core 40 is not particularly limited, and may be distributed uniformly throughout the absorbent core 40 or may be present in a part of the absorbent core 40 in a biased manner, but is preferably present at least in the region B of the absorbent core 40 opposite to the excretion portion. This can further improve the liquid absorption property in cooperation with the action and effect (particularly, the effect of improving the liquid drawing property) of the fiber block 11 due to the presence of the bias. Further, when more water-absorbent polymer 13 is present on the skin-facing surface side B1 than on the non-skin-facing surface side B2 in the excretion portion-facing region B of the absorbent core 40, the effect is more excellent. That is, the absorbent core 40 contains the water-absorbent polymer 13 at least in the excretion portion-facing region B, and the content of the water-absorbent polymer 13 in the absorbent core 40 is preferably larger on the skin-facing surface side B1 than on the non-skin-facing surface side B2.

It is preferable that the non-skin-facing surface side B2 of the excretion portion-facing region B of the absorbent core 40 contains not only the fiber mass 11 but also the water-absorbent fibers 12F and/or the water-absorbent polymer 13. With this configuration, the body fluid can be easily introduced into the non-skin surface side B2, the body fluid can be efficiently fixed to the non-skin surface side B2, and the liquid absorption properties of the absorbent core 40 can be further improved.

In the present embodiment, as shown in fig. 5, the absorbent core 40 has a raised portion 15 raised toward the skin of the wearer (user of the absorbent body 4) of the sanitary napkin 1 than the peripheral portion in the excretion portion-corresponding region B. The core forming material of the raised portion 15 has a larger grammage than that of the peripheral portion thereof, and therefore has a larger thickness than that of the peripheral portion. The raised part 15 in the present embodiment is formed at the excretion part-corresponding portion (excretion point) of the excretion part-corresponding region B, and more specifically, the central portion in the lateral direction Y of the excretion part-corresponding region B of the absorbent core 40 where the excretion part-corresponding portion is located is formed so as to be raised convexly toward the skin side of the wearer than the peripheral portion. By the presence of the raised portion 15 in the excretion portion-corresponding region B of the absorbent core 40, as shown in fig. 2, the excretion portion-corresponding region B of the sanitary napkin 1 corresponding thereto is formed with a convex portion on the skin-facing surface toward the skin side of the wearer. In this manner, since the convex portions corresponding to the raised portions 15 of the absorbent core 40 are present on the skin-facing surface of the excretion portion-facing region B of the sanitary napkin 1, the convex portions come into close contact with the excretion portion of the wearer, and the wearing feeling and the liquid absorption properties are improved. Further, as described above, in the excretion portion-facing region B of the absorbent core 40 where the convex portions are present, the fiber block 11 is present in a biased manner on the non-skin-facing surface side B2, whereby the non-bunching property and liquid-drawing property of the absorbent core 40 can be secured at a high level, and therefore, the wearing feeling and liquid-absorbing property of the sanitary napkin 1 can be further improved in addition to the operational effects of the convex portions. The raised portion 15 may be formed over the entire length of the region B of the absorbent core 40 corresponding to the excretion portion in the lateral direction Y. The bulge portion 15 may extend from the excretion portion-corresponding region B toward the front region a and/or the rear region C.

In the absorbent core 40, the content mass ratio of the fiber block 11 to the water-absorbent fibers 12F is not particularly limited on the premise that the specific range of the fiber block occupancy is satisfied, and may be appropriately adjusted depending on the types of the constituent fibers (synthetic fibers) 11F and the water-absorbent fibers 12F of the fiber block 11, and the like. For example, when the constituent fibers 11F of the fiber mass 11 are thermoplastic fibers (non-water-absorbing synthetic fibers) and the water-absorbing fibers 12F are cellulose-based water-absorbing fibers, the mass ratio of the fibers 11 and the water-absorbing fibers 12F is preferably 20/80 to 80/20, and more preferably 40/60 to 60/40, in terms of reliably achieving the specific effects of the present invention, when expressed by the mass ratio of the former (fiber mass 11)/the latter (water-absorbing fibers 12F).

The content of the fiber block 11 in the absorbent core 40 is preferably 20% by mass or more, more preferably 40% by mass or more, and preferably 80% by mass or less, more preferably 60% by mass or less, with respect to the total mass of the absorbent core 40 in a dry state.

The content of the water-absorbent fibers 12F in the absorbent core 40 is preferably 20 mass% or more, more preferably 40 mass% or more, and preferably 80 mass% or less, more preferably 60 mass% or less, with respect to the total mass of the absorbent core 40 in a dry state.

The content of the water-absorbent polymer 13 in the absorbent core 40 is preferably 1 mass% or more, more preferably 5 mass% or more, and further preferably 80 mass% or less, more preferably 50 mass% or less, with respect to the total mass of the absorbent core 40 in a dry state.

The term "absorbent core in a dry state" as used herein means an absorbent core before absorption of body fluids.

The grammage of the fiber mass 11 in the absorbent core 40 is preferably 32g/m²Above, more preferably 80g/m²Above, and preferably 640g/m²Hereinafter, more preferably 480g/m²The following.

The grammage of the water-absorbent fibers 12F in the absorbent core 40 is preferably 32g/m²Above, more preferably 80g/m²Above, and preferably 640g/m²Hereinafter, more preferably 480g/m²The following.

The grammage of the water-absorbent polymer 13 in the absorbent core 40 is preferably 5g/m²Above, more preferably 10g/m²Above, preferably 200g/m²Hereinafter, more preferably 100g/m²The following.

The absorbent core 40 can be manufactured by a conventional method using a known fiber stacking device having a rotary drum. Typically, the fiber stacking device has: a rotary drum having a collecting recess formed on an outer circumferential surface thereof; and a duct having a flow path therein for conveying the core forming material (the fiber block 11, the water-absorbent fibers 12F, the water-absorbent polymer 13) to the collecting concave portion, the fiber accumulating device rotating the rotary drum around the rotary shaft along the circumferential direction of the drum, oneThe core forming material conveyed by the air flow generated in the flow path by the suction from the inside of the rotary drum is accumulated in the collecting recess. The fiber-laminated material formed in the collecting recess by this fiber-laminating step is the absorbent core 40. The specific arrangement of the core-forming materials in the absorbent core 40 can be achieved by appropriately adjusting the order of deposition of the core-forming materials on the rotary drum in the manufacturing method using the above-described fiber deposition apparatus. The absorbent core 40 preferably has a grammage of 100g/m²Above, more preferably 200g/m²Above, it is preferably 800g/m²Hereinafter, more preferably 600g/m²The following.

As a method for producing the absorbent body (absorbent body in which the fiber mass is present with a bias in the thickness direction) of the present invention using a known fiber stacking apparatus, for example, the following 2 methods can be mentioned.

1) A method in which a stacked body produced by one stacking apparatus is stacked and integrated with a stacked body produced by another stacking apparatus using 2 stacking apparatuses (hereinafter, also referred to as "1 st production method").

2) A method in which the timing of supplying the fiber mass to the collecting dents and the timing of supplying the water-absorbent fibers to the collecting dents were different from each other by using 1 fiber stacking apparatus (hereinafter, also referred to as "the 2 nd production method").

In the above-described production method 1, first, a water-absorbent fiber-stacked body is produced by using water-absorbent fibers and a water-absorbent polymer (if necessary) as a core-forming material and by collecting the core-forming material in the collecting depressions of the fiber-stacking device 1. The water-absorbent fiber-laminated body can correspond to the water-absorbent fiber-enriched portions 12P of the absorbent core 40. In addition, a fiber block was used as a core-forming material, and the core-forming material was collected in the collecting recess of the 2 nd fiber-collecting device to produce a fiber block-collected body. The fiber-block-integrated body can correspond to the fiber-block-enriched portion 11P of the absorbent core 40. Next, the water-absorbent fiber stacked body and the fiber block stacked body are stacked to obtain a stacked body, and the stacked body is integrated by pressing in the thickness direction. As a method of integration different from this, a known vacuum conveyor or the like is used, and the water-absorbent fiber stacked body is placed on a suction surface of the suction device, and the fiber stacked body is stacked on the water-absorbent fiber stacked body in a state where a suction force of the suction surface is exerted, and integrated. In any of the integration methods, entanglement of the water-absorbent fibers and the fiber mass occurs at the interface between the water-absorbent fiber-integrated body and the fiber mass-integrated body. The absorbent body of the present invention (excretion portion-corresponding region B of the absorbent core 40) is thus obtained.

In the above-described manufacturing method 2, a mechanism in which the suction force of the collecting dents is locally different is used as the fiber stacking device. For example, the collecting recess has a structure having a low suction recess and a high suction recess having a higher suction force than the low suction recess. The low suction recess and the high suction recess are connected in a rotation direction (circumferential direction) of a rotating drum of the fiber stacking device. The fiber accumulating device of this configuration is operated to rotate the rotary drum in the circumferential direction and convey the accumulating recess in one direction, while generating an air flow from the outside of the rotary drum to the accumulating recess by suction from the inside of the rotary drum, and the core forming material is supplied to the accumulating recess by the air flow and accumulated (accumulating step). In the collecting step, first, the fiber mass is supplied to the collecting recess and collected. At this time, the fiber masses are collected together in the high suction concave portion, and the fiber mass aggregate is formed in the high suction concave portion. Next, after or during the aggregation of the fiber mass, the water-absorbent fibers and the water-absorbent polymer (as necessary) are supplied to the aggregation depressions to aggregate them. At this time, the water-absorbent fibers (water-absorbent polymer) are gathered in the low-suction concave portion among the gathering concave portions, and also gathered in the fiber mass gathered in the high-suction concave portion, that is, the water-absorbent fiber aggregate is formed in the entire gathering concave portion. Further, since the fiber block has air permeability, even in a state where the fiber block is gathered in the high suction recess, a suction force capable of sucking the water-absorbent fibers acts on the gathered fiber block, and the water-absorbent fibers (water-absorbent polymer) can be overlapped and gathered on the fiber block gathered in the high suction recess. In this way, a laminate of the fiber block stacked body and the water-absorbent fiber stacked body is formed in the high suction recessed portion, and entanglement of the fiber block and the water-absorbent fiber occurs at the interface between the two stacked bodies. The absorbent body of the present invention (excretion portion-corresponding region B of the absorbent core 40) is thus obtained.

The fiber block 11 will be further described below. In fig. 6, 2 typical outer shapes of the fiber block 11 are shown. The fiber block 11A shown in fig. 6 (a) is formed in a quadrangular prism shape, more specifically, a rectangular parallelepiped shape, and the fiber block 11B shown in fig. 6 (B) is formed in a disk shape. The fiber blocks 11A and 11B are common in that they have 2 base planes (base planes) 111 facing each other and a skeleton plane (body plane)112 connecting the 2 base planes 111. Both the base surface 111 and the skeleton surface 112 are portions that are considered to be substantially free from irregularities, at levels applied when evaluating the degree of irregularities on the surface of such articles mainly composed of fibers.

The rectangular parallelepiped fiber block 11A in fig. 6 (a) has 6 flat surfaces, and of the 6 flat surfaces, 2 opposed surfaces having the largest areas are base surfaces 111, and the remaining 4 flat surfaces are skeleton surfaces 112. The base surface 111 and the skeleton surface 112 intersect with each other, and more specifically, are orthogonal to each other.

The disk-shaped fiber block 11B shown in fig. 6 (B) has 2 opposing flat surfaces that are circular in plan view, and a curved peripheral surface that connects the two flat surfaces, each of the 2 flat surfaces being a base surface 111 and the peripheral surface being a skeleton surface 112.

The fiber blocks 11A and 11B are also common in that the skeleton surface 112 has a quadrangular shape in plan view, more specifically, a rectangular shape.

The plurality of fiber masses 11 included in the absorbent core 40 are different from the above-described amorphous fiber aggregate in the conventional art in that they are "shaped fiber aggregates" having 2 opposing base surfaces 111 and a skeleton surface 112 connecting the two base surfaces 111, as in the

fiber masses

11A and 11B shown in fig. 6, respectively. In other words, when any 1 fiber block 11 in the absorbent core 40 is seen through (for example, when observed with an electron microscope), the see-through shape of the fiber block 11 differs depending on the observation angle, and a plurality of see-through shapes exist for 1 fiber block 11, and each of the plurality of fiber blocks 11 in the absorbent core 40 has a specific see-through shape including 2 opposing base surfaces 111 and a framework surface 112 connecting the two base surfaces 111 as one of the plurality of see-through shapes. The amorphous fiber aggregate in the above-described conventional art does not substantially have "planes" such as the base plane 111 and the skeleton plane 112, that is, portions where the extended portions exist, and is not "set" because the outer shapes are different from each other.

As described above, when the plurality of fiber masses 11 included in the absorbent core 40 are "shaped fiber aggregates" defined by the base surface 111 and the skeleton surface 112, the uniform dispersibility of the fiber masses 11 in the absorbent core 40 is improved as compared with the case where the fiber aggregates are amorphous, and therefore, the effects (effects such as improvement in flexibility, cushioning properties, and compression recovery properties of the absorbent body) that can be expected by combining fiber aggregates such as the fiber masses 11 with the absorbent core 40 can be exhibited more stably. In particular, in the case of the fiber block 11 having a rectangular parallelepiped shape as shown in fig. 6 (a), since the outer surface is constituted by 6 surfaces in total of 2 base surfaces 111 and 4 skeleton surfaces 112, there are relatively many opportunities for contact with other fiber blocks 11 or water-absorbent fibers 12F, so that the entanglement property is improved, and the shape retention property and the like are also improved.

In the fiber block 11, the total area of the 2 base surfaces 111 is preferably larger than the total area of the skeleton surface 112. That is, in the rectangular parallelepiped fiber block 11A in fig. 6 (a), the total of the areas of the 2 base surfaces 111 is larger than the total of the areas of the 4 skeleton surfaces 112, and in the disk-shaped fiber block 11B in fig. 6 (B), the total of the areas of the 2 base surfaces 111 is larger than the area of the skeleton surfaces 112 forming the peripheral surface of the disk-shaped fiber block 11B. In both of the fiber blocks 11A and 11B, the base surface 111 has the largest area among the plurality of surfaces of the fiber blocks 11A and 11B.

The fiber mass 11, which is the "set fiber aggregate" defined by the 2 base surfaces 111 and the skeleton surface 112 intersecting the two base surfaces 111, is produced by a production method different from the conventional method. A preferred method for producing the fiber block 11 includes the steps of: as shown in fig. 7, a raw fiber sheet 10bs as a raw material is cut in a set shape by a cutting device such as a cutter. The raw material fiber sheet 10bs is a sheet having the same composition as the fiber block 11 and a size larger than the fiber block 11, and is preferably a nonwoven fabric. The plurality of fiber blocks 11 manufactured through this process have a more uniform shape and size than the amorphous fiber aggregate manufactured by the prior art. Fig. 7 is a diagram illustrating a method for producing the rectangular parallelepiped fiber block 11A shown in fig. 6 (a), and broken lines in fig. 7 indicate cutting lines. The absorbent core 40 is combined with a plurality of fiber pieces 11 having a uniform shape and size obtained by shape-setting cutting of the fiber sheet.

As shown in fig. 7, the rectangular parallelepiped fiber block 11A shown in fig. 6 (a) is produced by cutting a raw fiber sheet 10bs in a 1 st direction D1 and a 2 nd direction D2 intersecting with (more specifically, orthogonal to) the 1 st direction D1 by a predetermined length. The two directions D1, D2 are each a specific one of the planar directions of the sheet 10bs, and the sheet 10bs is cut in the thickness direction Z orthogonal to the planar direction. In the plurality of rectangular parallelepiped fiber blocks 11A obtained by cutting the raw material fiber pieces 10bs in a so-called dice shape, a surface of the cut section, i.e., the cut section 10bs, which is in contact with a cutting device such as a cutter is usually a skeleton surface 112, and a non-cut section, i.e., a surface which is not in contact with the cutting device is a basic surface 111. The base surface 111 is a front surface and a back surface (surfaces orthogonal to the thickness direction Z) of the sheet 10bs, and is a surface having the largest area among the plurality of surfaces of the fiber block 11A as described above.

The above description of the fiber block 11A is basically applied to the disk-shaped fiber block 11B shown in fig. 6 (B). The substantial difference from the fiber block 11A is only in the cutting pattern of the raw fiber sheet 10bs, and when the fiber block 11B is obtained by cutting the sheet 10bs in a set shape, the sheet 10bs may be cut in a circular shape in accordance with the shape of the fiber block 11B in a plan view.

The outer shape of the fiber block 11 is not limited to the shape shown in fig. 6, and the base surface 111 and the skeleton surface 112 may be flat surfaces that are not curved, as in the

surfaces

111 and 112 in fig. 6 (a), or may be curved surfaces, as in the skeleton surface 112 in fig. 6 (B) (the circumferential surface of the disk-shaped fiber block 11B). The basic surface 111 and the skeleton surface 112 may have the same shape and the same size, and specifically, the outer shape of the fiber block 11A may be a cubic shape, for example.

The size of the fiber block 11 is not particularly limited, and may be appropriately set in consideration of the cushioning property, liquid permeability, and the like of the absorbent core 40. The area of the base surface 111, which is the largest area among the plurality of surfaces of the fiber block 11, can be an index of the size of the fiber block 11. The area of the basic surface 111 of the fiber block 11 is preferably 1mm²Above, more preferably 5mm²Above, and preferably 100mm²Hereinafter, more preferably 50mm²The following.

A preferable fiber block 11 has a configuration in which the aspect ratio of the base surface 111 is 1 or nearly 1, that is, the shape of the base surface 111 in a plan view is a square or a nearly square. When the fiber block 11 is used in the absorbent core 40, the absorbent core 40 tends to be bulky, and cushioning properties and the like can be improved.

The aspect ratio of the basic surface 111 is determined by the ratio of the lengths of 2 sides that define the rectangular basic surface 111 and are orthogonal to each other when the shape of the basic surface 111 in a plan view is a rectangle. When the 2 sides have the same length, the aspect ratio of the rectangular basic surface 111 in a plan view is 1, and when the 2 sides have different lengths, that is, when the basic surface 111 has a rectangular shape in a plan view as shown in fig. 6 (a), the aspect ratio is determined by the ratio (L2/L1) of the length L2 of the long side 111b to the length L1 of the short side 111 a. In addition, as in the fiber block 11B shown in fig. 6 (B), when the shape of the base surface 111 in plan view is not a quadrangle, the length is determined by the ratio of the lengths of 2 axes that are orthogonal to each other through the center (center of gravity) of the base surface 111. When the 2 axes have the same length, the aspect ratio of the non-rectangular basic surface 111 in plan view is 1, and when the 2 axes have different lengths, that is, when there is a short axis having a relatively short length and a long axis having a relatively long length, the aspect ratio is obtained as the ratio (the former/the latter) of the length of the long axis (the length indicated by symbol L2 in fig. 6 (b)) to the length of the short axis.

The dimensions and the like of the respective portions of the fiber block 11(11A, 11B) can be set as follows, for example. The dimensions of the respective portions of the fiber block 11 can be measured based on an electron micrograph or the like of the fiber block 11.

When the base surface 111 has a rectangular shape in a plan view as shown in fig. 6 (a), the length L1 of the short side 111a is preferably 0.1mm or more, more preferably 0.3mm or more, even more preferably 0.5mm or more, and is preferably 10mm or less, more preferably 6mm or less, even more preferably 5mm or less.

The length L2 of the long side 111b of the rectangular basic surface 111 in plan view is preferably 0.3mm or more, more preferably 1mm or more, and even more preferably 2mm or more, and is preferably 30mm or less, more preferably 15mm or less, and even more preferably 10mm or less.

As shown in fig. 6, when the base surface 111 is a surface having the largest area among the plurality of surfaces of the fiber block 11, the length L2 of the long side 111B coincides with the maximum diameter length (length of the long axis) of the fiber block 11, which coincides with the diameter of the circular base surface 111 in the plan view of the disk-shaped fiber block 11B.

The thickness T of the fiber block 11, that is, the length T between the 2 opposing base surfaces 111, is preferably 0.1mm or more, more preferably 0.3mm or more, and preferably 10mm or less, more preferably 6mm or less.

As described above, the 2 kinds of faces (the base face 111, the skeleton face 112) of the fiber block 11(11A, 11B) are classified into: a cut surface (skeleton surface 112) formed by cutting the raw fiber sheet 10bs using a cutting device such as a cutter when the fiber block 11 is manufactured; and a non-cut surface (base surface 111) which is a surface originally possessed by the sheet 10bs and which does not come into contact with the cutting device. The skeleton surface 112 as the cut surface has a characteristic that the number of fiber ends per unit area is larger than that of the base surface 111 as the non-cut surface depending on whether or not the cut surface is different. The "fiber end" herein means the longitudinal end of the constituent fiber 11F of the fiber mass 11. Normally, although the fiber ends are also present in the base surface 111 as the non-cut surface, since the skeleton surface 112 is a cut surface formed by cutting the raw material fiber sheet 10bs, many fiber ends including the cut ends of the constituent fibers 11F formed by the cutting are present in the entire skeleton surface 112, that is, the number of the fiber ends per unit area of the skeleton surface 112 is larger than the number of the fiber ends per unit area of the base surface 111.

The fiber ends present on the respective surfaces (the base surface 111 and the skeleton surface 112) of the fiber block 11 are useful for forming entanglement between the fiber block 11 and the other fiber blocks 11 and the water-absorbent fibers 12F contained in the absorbent core 40. In general, the greater the number of fiber ends per unit area, the more the entanglement can be improved, and therefore, the various properties such as the shape retention of the absorbent core 40 can be improved. As described above, since the number of fiber ends per unit area in each surface of the fiber block 11 is not uniform, and the magnitude relationship of "skeleton surface 112 > basic surface 111" holds for the number of fiber ends per unit area, the entanglement with other fibers (other fiber block 11, water-absorbent fibers 12F) via the fiber block 11 differs in different surfaces of the fiber block 11, and the entanglement of the skeleton surface 112 is higher than that of the basic surface 111. That is, the bonding force by the bonding achieved by the entanglement of the skeleton surface 112 with other fibers is stronger than the bonding achieved by the entanglement of the base surface 111 with other fibers, and the bonding force between the base surface 111 and the skeleton surface 112 with other fibers is different in 1 fiber block 11. In general, the stronger the bonding force, the more the freedom of movement of the fibers to be bonded is restricted, and the strength (shape retention) of the entire absorbent core 40 tends to be improved, but the flexibility tends to be lowered.

As described above, the plurality of fiber blocks 11 included in the absorbent core 40 are entangled with other fibers (other fiber blocks 11, water-absorbent fibers 12F) around the fiber blocks with 2 types of bonding force, whereby the absorbent core 40 has appropriate flexibility and strength (shape retention property) at the same time. When the absorbent core 40 having such excellent characteristics is used as an absorber of an absorbent article according to a usual method, it is possible to provide a comfortable wearing feeling to a wearer of the absorbent article and to effectively prevent the absorbent core 40 from being broken by external force such as body pressure of the wearer when worn.

In particular, as described above, in the fiber block 11(11A, 11B) shown in fig. 6, the total area of the 2 base surfaces 111 is larger than the total area of the skeleton surface 112. Therefore, the number per unit area of its fiber ends is relatively small, thereby implying that: the total area of the base surface 111 having relatively low intermingling with other fibers is larger than the total area of the skeleton surface 112 having the property opposite thereto. Therefore, the fiber mass 11(11A, 11B) shown in fig. 6 is more likely to be entangled with other fibers (other fiber mass 11, water-absorbent fibers 12F) in the periphery than a fiber mass in which the fiber ends are uniformly present over the entire surface, and is also more likely to be entangled with other fibers in the periphery with a relatively weak binding force, and therefore is less likely to be large lumps, and can impart excellent flexibility to the absorbent core 40.

The constituent fibers 11F of the fiber block 11 include synthetic fibers. The synthetic fibers used as the fibers 11F preferably have a lower water absorption property (weak water absorption property) than the water-absorbent fibers 12F, and particularly preferably have a non-water-absorbent property. The constituent fibers 11F of the fiber block 11 may contain fiber components other than synthetic fibers (for example, natural fibers), but when the constituent fibers 11F of the fiber block 11 contain fibers having weak hydrophilicity, preferably non-water-absorbing fibers, the absorbent core 40 can stably achieve the operational effects (effects such as improvement in shape retention, flexibility, cushioning properties, compression recovery properties, and resistance to wrinkling) due to the presence of the fiber block 11 not only when it is in a dry state but also when it is in a wet state by absorbing moisture (body fluid such as urine or menstrual blood). The content of the synthetic fibers constituting the fibers 11F in the fiber mass 11 is preferably 90 mass% or more, and most preferably 100 mass% with respect to the total mass of the fiber mass 11, that is, the fiber mass 11 is formed of only synthetic fibers. In particular, when the synthetic fibers constituting the fibers 11F are non-water-absorbent fibers, the operational effect of the presence of the fiber mass 11 can be more stably achieved.

In the present specification, the term "water-absorbing property" is, for example, a concept that can be easily understood by those skilled in the art, such as a term that pulp is water-absorbing. Also, the expression that the thermoplastic fiber has weak water absorbency (particularly, non-water absorbency) can be easily understood. On the other hand, the degree of water absorption of the fibers can be compared with the relative difference in water absorption by using the value of the water content ratio obtained by the following method, and a more preferable range can be specified. The larger the value of the water content, the stronger the water absorption of the fiber. The water-absorbent fiber preferably has a water content of 6% or more, more preferably 10% or more. On the other hand, the moisture content of the synthetic fibers is preferably less than 6%, more preferably less than 4%. When the moisture content is less than 6%, the fibers can be judged to be non-water-absorbent fibers.

< method for measuring moisture content >

The water content was calculated by the water content test method according to JIS P8203. That is, the weight W (g) of the fiber sample before the absolute drying treatment was measured in a test chamber in which the fiber sample was left standing at 40 ℃ and 80% RH for 24 hours. Thereafter, the sample was allowed to stand in an electric drier (manufactured by Isuzu Co., Ltd.) at a temperature of 105. + -. 2 ℃ for 1 hour to thereby dry the fiber sample absolutely. After the absolute drying treatment, the fiber sample was wrapped in Saran Wrap (registered trademark) manufactured by asahi chemical corporation, in a standard laboratory at a temperature of 20 ± 2 ℃ and a relative temperature of 65 ± 2%, and then, Si silica gel (e.g., manufactured by toyota chemical corporation, manufactured by Tech jam, manufactured by yota corporation, for example) was put into a glass drier and allowed to stand until the fiber sample reached a temperature of 20 ± 2 ℃. Thereafter, the constant W' (g) of the fiber sample was measured, and the water content of the fiber sample was determined by the following equation.

Water content (%) (W-W '/W') × 100

Similarly, the fiber block 11 preferably has a three-dimensional structure formed by thermally fusing a plurality of thermoplastic fibers to each other, from the viewpoint that the absorbent core 40 can exhibit excellent effects such as shape retention, flexibility, cushioning properties, compression recovery properties, and resistance to wrinkling in either of the dry state and the wet state.

The raw material fiber sheet 10bs (see fig. 7) may be configured in the same manner so as to obtain the fiber mass 11 in which the plurality of heat-fusion portions are three-dimensionally dispersed, and the raw material fiber sheet 10bs in which the plurality of heat-fusion portions are three-dimensionally dispersed can be produced by subjecting a web or a nonwoven fabric mainly composed of thermoplastic fibers to heat treatment such as hot air treatment as described above.

Examples of the non-water-absorbent synthetic resin (thermoplastic resin) suitably used as a material of the fibers 11F constituting the fiber block 11 include: polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate; polyamides such as nylon 6 and nylon 66; polyacrylic acid; polyalkylmethacrylate; polyvinyl chloride; polyvinylidene chloride, etc., and 1 of them may be used alone or 2 or more of them may be used in combination. The fibers 11F may be single fibers made of 1 kind of synthetic resin (thermoplastic resin) or a blend polymer obtained by mixing 2 or more kinds of synthetic resins, or may be composite fibers. The composite fiber herein refers to a synthetic fiber (thermoplastic fiber) obtained by simultaneously spinning 2 or more kinds of synthetic resins having different components by compounding with a spinneret, and the synthetic fiber is joined to each other within a single fiber in a structure in which the plural kinds of components are continuously present in the longitudinal direction of 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.

In addition, from the viewpoint of further improving the drawing-in property of the body fluid at the time of initial excretion, the contact angle of the fiber block 11 with water is preferably less than 90 degrees, and particularly preferably 70 degrees or less. Such fibers are obtained by treating the above-mentioned non-water-absorbent synthetic fibers with a hydrophilizing agent according to a usual method. As the hydrophilizing agent, a general surfactant can be used.

< method for measuring contact Angle >

The fiber was taken out from the measurement object (absorbent core), and the contact angle of water with the fiber was measured. An automatic contact angle meter MCA-J manufactured by covex interface science corporation was used as a measuring device. Contact angle was measured using deionized water. The amount of liquid discharged from an ink-jet type water droplet discharge unit (pulse jet CTC-25 having a discharge unit pore size of 25 μm, manufactured by Cluster Technology) was set to 20 picoliters, and water droplets were dropped directly onto the fibers. The dripping state is shot to a high-speed video device connected with a horizontally arranged camera. The recording device is preferably a personal computer incorporating a high-speed capture device from the viewpoint of performing image analysis in the later stage. In the present measurement, an image is taken every 17 msec. In the captured image, the original image of the water droplet falling down to the fiber was subjected to image analysis using attached software FAMAS (software version 2.6.2, analysis method being a droplet method, analysis method being a θ/2 method, image processing algorithm being no reflection, image processing image mode being a frame, threshold level (threshold level), no curvature correction), and the angle formed by the surface of the water droplet contacting the air and the fiber was calculated as the contact angle. The fiber taken out of the object was cut at a fiber length of 1mm, and the fiber was placed on a sample stage of a contact angle meter and maintained horizontal. The contact angle was measured at 2 different sites per 1 fiber. The contact angle of 5 fibers was measured and found to be 1 position after the decimal point, and the value obtained by averaging the measured values of 10 positions in total (rounded to 2 positions after the decimal point) was defined as the contact angle of the fiber with water. The measurement environment is 22 + -2 deg.C at room temperature and 65 + -2% RH at humidity.

In addition, when an absorbent body (absorbent core) to be measured is used as a component of another article such as an absorbent article, and when the absorbent body is taken out and evaluated, and the absorbent body is fixed to another component by means of an adhesive, welding, or the like, the bonding force is released by means of cold air blowing, or the like, within a range that does not affect the contact angle of the fibers, and then the fixed portion is taken out. This procedure is common to all measurements in the present specification.

The present invention has been described above based on embodiments thereof, but the present invention is not limited to the above embodiments and can be modified as appropriate.

For example, in the above embodiment, the absorbent body 4 has a large thickness structure in which the thickness of at least the center portion in the lateral direction Y of the excretion portion-corresponding region B is larger than the thickness of the other region A, C, but the thickness of the absorbent body 4 may be the same in the excretion portion-corresponding region B and the front-rear region A, C. In this case, for example, the absorbent body 4 having a uniform thickness as a whole can be produced by the following method: an absorbent core 40 having a uniform thickness is produced, and a material for forming at least a part of a region B corresponding to a discharged part of the absorbent core 40 having a uniform thickness is removed, and then the fiber block 11 having the removed thickness portion is immediately supplemented.

The absorbent article of the present invention widely includes articles for absorbing body fluid (urine, loose stool, menstrual blood, sweat, etc.) discharged from a human body, and includes menstrual shorts, so-called open-type disposable diapers having fastening tapes, pants-type disposable diapers, incontinence pads, and the like in addition to the above-described menstrual sanitary napkins.

Examples

The present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

[ example 1]

An absorbent body 4 shown in fig. 3 to 5 was produced as an absorbent body of example 1. Specifically, the absorbent core 40 was obtained by using the fiber block 11, the absorbent fibers 12F and the absorbent polymer 13 as core-forming materials, respectively stacking the absorbent fiber-rich part 12P and the fiber block-rich part 11P by a conventional method using 2 known stacking devices, and stacking the absorbent fiber-rich part 12P and the fiber block-rich part 11P in an overlapping manner and pressing them in the thickness direction, thereby obtaining an absorbent core 40 having a grammage of 16g/m²The absorbent core 40 is entirely covered with the core sheet 41 to produce the absorbent body 4. The fiber block 11 is produced by cutting a raw material fiber sheet into small blocks in accordance with fig. 7. Using a non-water-absorbing thermoplastic fiber composed of polyethylene resin fibers and polyethylene terephthalate resin fibers (non-water-absorbing fibers having a fiber diameter of 18 μm) as a constituent fiber, the basis weight was 18g/m²And a hot air nonwoven fabric (a fiber sheet having a heat-fused part of fibers) having a thickness of 0.6mm as a raw material fiber sheet of the fiber block. Needle-leaved sun-cured kraft pulp (NBKP) was used as the water-absorbent fibers 12F. A polyacrylic acid partial sodium salt was used as the water-absorbent polymer 13.

In the absorbent body 4 of example 1, the longitudinal length was 210mm, the lateral length was 70mm, and the lateral lengths were excluded as the front region A and the back region CExcept for the front and rear end portions in the longitudinal direction X of a part of the absorbent core 4, a constant value is maintained over the entire length in the longitudinal direction of the absorbent core 4. The absorbent body 4 of example 1 had a thickness of 3.2mm in each of the front region a and the rear region C, 5.7mm in the excretion portion-corresponding region B, and a raised portion that was raised toward the skin of the user than the peripheral portion in the excretion portion-corresponding region B. In the absorbent core 40 of example 1, the entire non-skin-facing surface side B2 of the excretion portion-facing region B was the fiber-lump-enriched region 11P (region having a fiber-lump occupancy of 100 mass%), the other regions were all the water-absorbent fiber-enriched regions 12P (region having a fiber-lump occupancy of 0.01 mass% and region having a water-absorbent fiber occupancy of 99.9 mass%), the longitudinal length of the front region a (water-absorbent fiber-enriched region 12P) was 55mm, the longitudinal length of the excretion portion-facing region B (fiber-lump-enriched region 11P) was 80mm, and the longitudinal length of the rear region C (water-absorbent fiber-enriched region 12P) was 75 mm. The absorbent body 4 of example 1 had a cushioning portion area ratio (the ratio of the area of the non-skin-facing surface of the excretion portion-facing region B to the total area of the non-skin-facing surface of the absorbent body) of 38.6%. The grammage of the fiber block of the absorbent core 40 of example 1 was 140g/m²The basis weight of the water-absorbent fiber was 210g/m². In addition, the absorbent core 40 of example 1 contained 50g/m²The water-absorbent polymer 13 is contained in the water-absorbent fiber-rich sites 12P in an amount of 90 mass% or more. Further, although the fiber lumps 11 and the water-absorbent fibers 12F are entangled with each other at the interface between the fiber-lump-rich portion 11P and the water-absorbent-fiber-rich portion 12P, the water-absorbent fibers 12F are not contained in the fiber lump layer 11P and the fiber lumps 11 are not contained in the water-absorbent fiber layer 12P except for the interface and the vicinity thereof. The value of the "fiber block occupancy" is a value of a portion other than the boundary surface region.

[ comparative example 1]

A laminate in which an elastic cushion sheet was laminated on the non-skin-facing surface side of an absorbent member having an absorbent core and a core sheet was produced as the absorbent body of comparative example 1. The absorbent body of comparative example 1 was uniformly 5.7mm thick. The absorbent member of comparative example 1 basically contained no fiber mass in the absorbent core, except thatThe structure was the same as that of the absorbent body of example 1. The absorbent member has the same shape and size as the absorbent member in plan view, and a grammage of 40g/m²The sheet-like hot-air nonwoven fabric of (3) was used as a cushion sheet, and 3 cushion sheets were stacked and fixed to the non-skin-facing surface of the absorbent member to form a cushion portion. The cushioning sheets are fixed to cover the entire area of the non-skin-facing surface of the absorbent member, and a hot-melt adhesive is used for fixing the cushioning sheets to each other and fixing the cushioning sheet to the absorbent member. In the absorbent body of comparative example 1, the entire area of the non-skin-facing surface of the absorbent body is formed as the cushion portion, and therefore the cushion portion area ratio is 100%. The grammage of the water-absorbent fiber was 210g/m²。

[ comparative example 2]

An absorbent body of comparative example 2 was produced, which had exactly the same structure as the absorbent member of comparative example 1. The absorbent body of comparative example 2 was equally 5.7mm thick. The water-absorbent fiber has a grammage of 350g/m²。

[ Performance evaluation ]

For the absorbers of the respective examples and comparative examples, the dynamic wrinkling rate, ring-type breakage rate, flexural rigidity, dynamic maximum absorption amount, compression set, and recovery work were measured by the following methods, respectively. The results are shown in Table 1 below.

When an absorbent article is used as a measurement target, a catamenial sanitary napkin having the same basic structure as the sanitary napkin 1 shown in fig. 1 is produced using the absorbent bodies of the examples and comparative examples, and the catamenial sanitary napkin is used for measurement. The gram weight of the catalyst is 30g/m²The hot air non-woven fabric is used as a front sheet of a sanitary napkin for menstrual period, and 37g/m²A polyethylene resin film (FL-KDJ100nN, industrially produced on a large scale) was used as the back sheet.

< method for measuring dynamic wrinkling Rate >

The dynamic wrinkling rate of a catamenial sanitary napkin was used as a measurement sample, and the dynamic wrinkling rate of the measurement sample was evaluated using a driven lower body manikin for women. First, the center width (the transverse length of the longitudinal center of the sanitary napkin) (the center width before walking) of the sanitary napkin to be measured was measured, and the sanitary napkin was attached to the pants and worn on the female manikin. Next, the dummy was walked at a speed of 100 steps/minute for 30 minutes, and during walking of the dummy, 1.5g of defibered horse blood was injected into the sanitary napkin in a worn state after walking for 3 minutes for 6 times and 15 seconds, and a total of 9g of defibered horse blood was injected into the sanitary napkin. Then, the sanitary napkin was detached from the pants, the center width (center width after walking) was measured, and the dynamic wrinkling rate (%) was calculated from the center width before walking and the center width after walking by the following equation. The smaller the value of the dynamic tucking ratio, the less likely the sanitary napkin is to be tucked, and the higher the evaluation. The defibrinated horse blood injected into the measurement object was defibrinated horse blood manufactured by japan biological test (gmbh) and viscosity thereof was adjusted to 8cp at a liquid temperature of 25 ℃.

Dynamic wrinkling rate (%) [ { (center width before walking) - (center width after walking) }/(center width before walking) ] × 100

< method for measuring ring-type breakage rate >

An absorbent body to be measured was brought into a wet state, the absorbent body in the wet state was bent in the longitudinal direction (longitudinal direction) so that the skin-facing surface of the absorbent body (the surface facing the topsheet of a sanitary napkin) was on the inside, and both ends in the longitudinal direction were fixed to each other by a stapler to prepare a ring-shaped measurement sample having a diameter of 45mm, as described below (method for producing an absorbent article having an absorbent body in a wet state). A small table top tester EZTest (EZ-L) manufactured by shimadzu corporation, inc, was used to mount an annular measurement sample on a test bed such that the axial direction of the ring of the measurement sample was perpendicular to the measurement sample mounting surface of the test bed, and the measurement sample was repeatedly compressed 3 times at a compression rate of 120 mm/min until the distance between the compression mechanism of the measurement sample and the measurement sample mounting surface became 30mm, and the height after compression was measured. The ring-type breakage (%) was calculated from the height of the sample before compression and the height of the sample after compression by the following equation. The smaller the value of the ring-type breakage rate, the less likely the absorbent body to wrinkle when wearing the absorbent article, and the higher the evaluation.

Ring type breakage rate (%) [ { (height before compression) - (height after compression) }/(height before compression) ] × 100

< method for measuring flexural rigidity >

The sanitary napkin at the menstrual period was used as a measurement sample and evaluated by using a texture testing machine (softness tester method, model HOM-3) manufactured by Daorhizi Seiki, Ltd. First, the sanitary napkin was set on a sample table with a slit width of 40mm so that the longitudinal direction (longitudinal direction) of the sanitary napkin was perpendicular to the blade. The measurement sample is arranged on the sample stage so that a measurement portion for measuring the flexural rigidity of the sample overlaps with the slit position of the sample stage. When measuring the bending rigidity of the front region of the menstrual sanitary napkin, a position of 35mm toward the longitudinal inner side from the longitudinal end portion of the front region (the front end portion of the sanitary napkin) was taken as a measurement portion, when measuring the bending rigidity of the rear region of the menstrual sanitary napkin, a position of 35mm toward the longitudinal inner side from the longitudinal end portion of the rear region (the rear end portion of the sanitary napkin) was taken as a measurement portion, and when measuring the bending rigidity of the excretion portion-corresponding region of the menstrual sanitary napkin, the longitudinal center of the excretion portion-corresponding region was taken as a measurement portion. Next, the blade set to be lowered to a position 10mm from the surface of the sample stage was lowered to press the measurement sample, and the peak value (mN) at this time was taken as the value of the flexural rigidity of the measurement sample. The smaller the value of the flexural rigidity, the more excellent the wearing feeling of the absorbent article incorporating the absorbent body is judged to be, and the higher the evaluation is.

< method for measuring dynamic maximum absorption >

Menstrual sanitary napkins of the subject of measurement were fixed to menstrual shorts and worn on a dynamic model of the human body. A movable female lumbar model enabling walking movement of both legs is used as a dynamic model of the human body. The dynamic model was started to perform walking, and 1 minute after the walking was started, 2g of simulated blood was injected from the liquid discharge point (1 st time). Further, 3 minutes after the 1 st liquid injection was completed, 3g of the mock blood was injected (2 nd time). Further, 3 minutes after the end of the 2 nd liquid injection, 2g of the mock blood was injected (3 rd time). After 3 rd, the operation of injecting 2g of the dummy blood after injecting the liquid for 3 minutes was repeated, and the liquid injection operation was terminated at the time when the dummy blood was oozed out from the flap portion of the sanitary napkin, and the total weight of the dummy blood injected up to this time was defined as the dynamic maximum absorption amount (g).

Blood was simulated using: a blood cell/plasma ratio of defibrinated horse blood (manufactured by Toyobo Co., Ltd., Japan Biotesting research) was prepared so that the viscosity measured by using a type B viscometer (manufactured by Toyobo industries, Ltd., model number TVB-10M, measurement conditions: spindle No.19, 30rpm, 25 ℃ C., 60 seconds) was 8 mPas. The larger the value of the dynamic maximum absorption amount, the more rapidly the body fluid migrates to the absorber and is less likely to leak, and the evaluation is high.

< method for measuring compression set (Δ T/T0) >

The compression deformation ratio (Δ T/T0) of the sample can be measured using KES. Specifically, the compression set (Δ T/T0) was measured using an automated compression test apparatus KES-G5 manufactured by Gamut technologies, Inc. The measurement sequence is as follows.

The absorbent body to be measured is brought into a wet state as follows (method for producing an absorbent article having an absorbent body in a wet state). The sample was mounted on a test bed of a compression test apparatus. Next, the sample was placed in a chamber having an area of 2cm²The round flat steel plates of (1) are compressed, the load at the time of compression is gradually increased, and the thickness (compression thickness) Tm of the object to be measured at the time when the load reaches a specific maximum value (maximum load) is measured. It is necessary to take care that the object to be measured is wrinkled or bent. The measurement conditions of the compression tester are as follows.

Compression speed: 0.2mm/sec

Maximum load: 2450mN/cm²

·SENS：10

·DEF：20

Further, the initial thickness (T0) of the object was such that the load became 103.9mN/cm²The thickness at the moment of time. The compression set was calculated by the following formula(％)。

Compression deformation ratio (Δ T/T0) { (T0-Tm)/T0) } × 100

< method for measuring compression work and recovery work >

It is known that the recovery work (hereinafter, also referred to as "WC'") of an object to be measured (absorber) can be expressed by a measurement value in KES (Kawabata Evaluation System, Chuanchi Evaluation System) manufactured by Kawabata Ltd. (reference: standardization and analysis of texture Evaluation (2 nd edition), Kawabata Kogyo, Kawabata Kawakayao, published by 7/10 th 1980). Specifically, WC' can be measured using a compression test apparatus KES-G5 manufactured by Gamut technologies, Inc. The measurement sequence is as follows. In addition, since the compression work (hereinafter, also referred to as "WC") can be measured at the same time when measuring WC ', the measurement methods of WC and WC' are described below in combination.

A240 mm × 70mm square specimen (absorbent body wrapped with a core-wrapped sheet) in a plan view was prepared and mounted on a test bed of a compression test apparatus. A measurement sample was prepared by bringing the absorbent body into a wet state as follows (method for producing an absorbent article having an absorbent body in a wet state). Next, a non-depressed portion of the measurement sample, that is, a portion to which compression processing or the like is not applied and which retains the original appearance of the measurement sample was placed to have an area of 2cm²The steel plates of the circular plane are compressed. In the compression step, the compression speed was 0.2cm/sec and the maximum compression load was 2450mN/cm². The recovery process is also measured at the same speed. WC is represented by the following formula (1), WC' is represented by the following formula (2), and the unit is mN · cm/cm²". In the following formula, Tm represents 2450mN/cm²(4.9kPa) thickness under load, TO represents 4.902mN/cm²(49Pa) thickness under load. Further, Pa in the following formula (1) and Pb in the following formula (2) represent the measured load (mN/cm) during the compression process, respectively²) And the measured load at recovery (mN/cm)²)。

[ formula 1]

[ formula 2]

In addition, WC 'is not displayed on the measurement result screen of the KES-G5, and the compression recovery rate or the compression rebound rate (hereinafter, also referred to as "RC") calculated by WC and WC' is displayed on the measurement result screen. At this time, using the parameters (WC, RC) displayed in the measuring device, WC' was calculated by the following equation.

[ formula 3]

WC′＝RC×WC÷100

(method of producing absorbent article having absorbent body in Wet State)

The absorbent article before injection of the defibered horse blood was left to stand in an environment of air temperature 23 ℃ and relative humidity 50 RH% for 24 hours to prepare an absorbent article in a dry state. The absorbent article in the dry state was horizontally placed with the topsheet side (skin-facing side) facing upward, an oval inlet (length of 50mm, short diameter of 23m) was placed on the topsheet, 3.0g of defibered horse blood was injected from the inlet, the mixture was allowed to stand for 1 minute, 3.0g of defibered horse blood was further injected, and the state was maintained for 1 minute after the injection, whereby an absorbent article having an absorbent body in a wet state was obtained. The defibrinated horse blood injected into the absorbent article was defibrinated horse blood manufactured by japanese bioassay (incorporated by reference), and the viscosity at a liquid temperature of 25 ℃ was adjusted to 8cp, and the viscosity was measured at a rotation speed of 12rpm using a TVB-10M viscometer manufactured by eastern mechanical industries, incorporated by reference, with a spindle having a spindle name of L/Adp (spindle number 19).

[ Table 1]

*1: calculated by { mass of contained fiber mass/(mass of contained fiber mass + mass of contained water-absorbent fiber) } × 100.

*2: the thickness was calculated by (area of the cushion portion of the absorbent body on the non-skin-facing surface/area of the absorbent body on the non-skin-facing surface) × 100. In example 1, the entire region of the absorbent body in which the fiber mass was unevenly distributed and which was opposed to the excretion portion was defined as the cushion portion.

*3: the measurement target (absorber) is a measurement value in a wet state.

Industrial applicability

The absorbent article of the present invention is excellent in wearing feeling before and after excretion and in absorption performance.

Claims

1. An absorbent article having a longitudinal direction corresponding to a front-rear direction of a user and a transverse direction orthogonal to the longitudinal direction, and having: a region opposite to the excretion part of the user when in use; a front region disposed on the front side of the region facing the drain portion in the longitudinal direction; and a rear region disposed on a longitudinally rear side of the region opposed to the excretion portion, the absorbent article having an absorber, the absorbent article being characterized in that:

the absorbent body contains a fiber mass comprising synthetic fibers and water-absorbent fibers,

the fiber mass is a fiber aggregate in which a plurality of fibers are gathered together to form a single body,

in the absorbent body, a ratio of a mass content of the fiber block to a total mass content of the fiber block and the water-absorbent fiber is larger in the excretion portion-corresponding region than in the front region and the rear region, and is smaller on the skin-facing surface side of the absorbent body than on the non-skin-facing surface side of the absorbent body in the excretion portion-corresponding region,

in the absorbent body, a plurality of the fiber pieces are entangled with each other or the fiber pieces are entangled with the water-absorbent fibers,

the synthetic fibers contained in the fiber block have lower water absorption than the water-absorbent fibers.

2. The absorbent article of claim 1, wherein:

the absorbent body contains the fiber mass in an amount of 90 mass% or more of the entire fiber mass contained in the absorbent body in the excretion portion-corresponding region.

3. The absorbent article of claim 1, wherein:

the thickness of the absorbent body in the front region and the rear region is smaller than the thickness of the absorbent body in the widthwise center of the excretion portion-corresponding region.

4. The absorbent article of claim 1, wherein:

an area of a portion of the non-skin-facing surface of the absorbent body located in the excretion portion-facing region is 60% or less of an area of the non-skin-facing surface of the absorbent body.

5. The absorbent article of claim 1, wherein:

the absorbent body contains a water-absorbent polymer at least in the excretion portion-facing region, and the content of the water-absorbent polymer on the skin-facing surface side is greater than the content of the water-absorbent polymer on the non-skin-facing surface side in the absorbent body.

6. The absorbent article of claim 1, wherein:

the absorbent body includes: an absorbent core containing the fiber block and the water-absorbent fiber; and a core-covering sheet covering an outer surface of the absorbent core.

7. The absorbent article of claim 1, wherein:

the absorbent body has a raised portion that is raised toward the skin of the user in a region facing the excretion portion, compared to the peripheral portion.

8. The absorbent article of claim 3, wherein:

in the absorbent body, a ratio of a thickness of the front region or the rear region to a thickness of the widthwise center of the region opposed to the excretion portion is 0.1 to 0.9 in terms of the former/latter on the premise that the former < the latter.

9. The absorbent article of claim 1, wherein:

the ratio of the mass content of the fiber mass to the total mass content of the fiber mass and the water-absorbent fiber on the non-skin-facing surface side of the excretion portion-facing region of the absorbent body is 50 mass% or more on the premise that the ratio is higher than the ratio in other regions of the absorbent body.

10. The absorbent article of claim 1, wherein:

the ratio of the mass content of the fiber mass to the total mass content of the fiber mass and the water-absorbent fiber on the skin-facing surface side of the excretion portion-facing region of the absorbent body is 50 mass% or less, on the premise that the ratio is lower than the ratio on the non-skin-facing surface side of the excretion portion-facing region of the absorbent body.

11. The absorbent article of claim 1, wherein:

the difference in the ratio of the mass content of the fiber mass to the total mass content of the fiber mass and the water-absorbent fiber between the non-skin-facing surface side of the excretion portion-facing region of the absorbent body and the skin-facing surface side of the excretion portion-facing region of the absorbent body is 50 mass% or more when the former is subtracted from the latter.

12. The absorbent article of claim 1, wherein:

the fiber block has 2 opposing base faces and a skeleton face joining the 2 base faces.

13. The absorbent article of claim 12, wherein:

in the block, the total area of 2 of the base surfaces is greater than the total area of the skeleton surfaces.

14. The absorbent article of claim 12, wherein:

the area of the basic surface is 1mm²Above and 100mm²The following.

15. The absorbent article of claim 1, wherein:

the content of the synthetic fibers contained in the fiber block is 90 mass% or more with respect to the total mass of the fiber block.

16. The absorbent article of claim 1, wherein:

the moisture content of the synthetic fibers contained in the fiber mass is less than 6%.

17. The absorbent article of claim 1, wherein:

the water content of the water-absorbent fiber is 6% or more.

18. The absorbent article of claim 1, wherein:

the contact angle of the fiber block and water is lower than 90 degrees.

19. The absorbent article of claim 1, wherein:

the absorbent article is a catamenial sanitary napkin.