CN111093583B

CN111093583B - Absorbent body and absorbent article

Info

Publication number: CN111093583B
Application number: CN201880059620.9A
Authority: CN
Inventors: 糸井奈美江; 汤山晓; 金子将也
Original assignee: Kao Corp
Current assignee: Kao Corp
Priority date: 2017-11-28
Filing date: 2018-11-21
Publication date: 2022-03-22
Anticipated expiration: 2038-11-21
Also published as: WO2019107238A1; RU2763716C2; RU2020120379A3; RU2020120379A; CN111093583A; TWI756493B; TW201929811A

Abstract

The absorbent body (4) of the present invention comprises fiber masses (11) containing synthetic fibers (11F) and water-absorbent fibers (12F), and a plurality of 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. Regarding the mass ratio (fiber block ratio) of the fiber blocks (11) to the water-absorbent fibers (12F), the skin-facing surface side (front sheet (2) side) of the absorbent body (4) is smaller than the non-skin-facing surface side (back sheet (3) side). The fiber block (11) has a main body portion (110) defined by 2 opposing base faces (111) and a skeleton face (112) intersecting the two base faces (111).

Description

Absorbent body and absorbent article

Technical Field

The present invention relates to an absorbent body used in direct or indirect contact with the skin, and preferably used as an absorbent body for an absorbent article.

Background

Generally, an absorbent article such as a disposable diaper or a sanitary napkin includes a front sheet disposed at a position relatively close to the skin of a wearer, a back sheet disposed at a position relatively distant from the skin of the wearer, and an absorbent body interposed between the two sheets. Typically, this absorbent material mostly contains water-absorbent fibers such as wood pulp and further contains water-absorbent polymer particles. With respect to an absorbent body used in an absorbent article, improvement of various properties such as flexibility (cushioning property), compression recovery property, shape retention property, and the like is an important issue.

As a technique for improving an absorber, for example, patent document 1 describes an absorber including: a nonwoven fabric sheet containing heat-fusible fibers and having a three-dimensional structure formed by bonding fibers to each other in advance; and a water-absorbent fiber. The nonwoven fabric sheet having a three-dimensional structure is produced by pulverizing a nonwoven fabric into a fine sheet by a pulverizing means such as a chopper method, and is formed into an indefinite shape as described in fig. 1 and 3 of the document by this production method, and has substantially no portion that can be seen as a flat surface. Patent document 1 describes, as a preferred embodiment of the absorbent body described in the document, a structure in which nonwoven fabric sheets are heat-welded to each other. According to the absorbent body described in patent document 1, 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, and as a result, the water absorption performance is improved.

Patent document 2 describes that a fine fiber web having a dense fine fiber core and fibers or fiber bundles extending outward from the core is useful as an absorbent material for absorbent articles, and that a nonwoven fiber web obtained by mixing the fine fiber web with wood pulp and water-absorbent polymer particles is also useful. The microfiber web is produced by drawing or tearing a raw material sheet such as a nonwoven fabric, and is formed into an indefinite shape in the same manner as the nonwoven fabric sheet described in patent document 1, and has substantially no portion that can be seen as a flat surface.

Further, patent document 3 describes that, when an absorbent material contains a water-absorbent polymer, in order to solve the problem that swelling of the water-absorbent polymer is inhibited by sealing between a front sheet and a back sheet disposed above and below the absorbent material when the absorbent material absorbs a liquid and swells, a cushion layer having high compression/compression recovery properties and liquid permeability is provided between the front sheet and the absorbent material, and further, it describes that the cushion layer is an assembly of fine pieces of nonwoven fabric. Further, it is described that the buffer layer has a thickness of 10mm to 40 mm. Patent document 3 does not specifically describe the shape of the nonwoven fabric used for the cushion layer.

Documents of the prior art

Patent document

Patent document 1: U.S. patent application publication No. 2010/0174259 specification

Patent document 2: specification of U.S. Pat. No. 4813948

Patent document 3: japanese patent laid-open No. 2003-52750

Disclosure of Invention

The absorbent body of the present invention is used in direct or indirect contact with the skin, and has a skin-facing surface disposed at a position relatively close to the skin of the user and a non-skin-facing surface disposed at a position relatively distant from the skin of the user. The present invention includes a fiber mass containing synthetic fibers and water-absorbent fibers, and a plurality of the fiber masses are entangled with each other or the fiber mass and the water-absorbent fibers are entangled with each other. The mass ratio of the fiber mass contained in the skin-facing surface side to the water-absorbent fiber is smaller than the mass ratio of the fiber mass contained in the non-skin-facing surface side to the water-absorbent fiber.

The present invention also provides an absorbent article having the absorbent body of the present invention.

Drawings

Fig. 1 is a plan view schematically showing an example of a skin-facing surface side (topsheet side) of a catamenial napkin which is 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 an enlarged cross-sectional view of only the absorber shown in fig. 2.

Fig. 4 is a view (cross-sectional view) corresponding to fig. 3 of another embodiment of the absorbent body of the present invention.

Fig. 5(a) and 5(b) are schematic perspective views of the main body in the fiber block of the present invention, respectively.

FIG. 6 is an explanatory view of the method for producing a fiber block of the present invention.

Fig. 7(a) is an electron micrograph (observation magnification: 25 times) of an example of a fiber block of the present invention, and fig. 7(b) is a diagram schematically showing the fiber block contained in the absorbent body shown in fig. 2 as the fiber block in the electron micrograph.

Fig. 8 is an explanatory view of a method of measuring the surface diffusion area.

Detailed Description

As described above, the synthetic fiber aggregate contained in the absorbent bodies disclosed in patent documents 1 and 2 has an indefinite shape and is completely inconsistent in shape and size, and therefore, when the synthetic fiber aggregate is mixed with wood pulp or the like, it is difficult to obtain uniform mixing of the synthetic fiber aggregate and wood pulp, and the desired effect may not be obtained. Further, the synthetic fiber aggregate disclosed in these documents is produced by pulverizing a nonwoven fabric mainly composed of synthetic fibers into a fine sheet shape or by pulling or tearing, and therefore the surface is supposed to be randomly rough. In an absorbent body comprising a plurality of such synthetic fiber aggregates having a rough surface, the plurality of synthetic fiber aggregates are entangled with each other with a strong binding force over the entire surface thereof, and as a result, the degree of freedom of movement of each synthetic fiber aggregate is significantly restricted. Therefore, it is difficult to form a gap for allowing body fluid to pass therethrough, and the liquid absorption property is poor. Further, as shown in a preferred embodiment of the absorbent body disclosed in patent document 1, when all the synthetic fiber aggregates contained in the absorbent body are thermally fused to each other, their own actions are restricted, and as a result, the hardness of the entire absorbent body may increase, and the liquid absorption properties may further decrease.

Further, when a synthetic fiber aggregate is blended in an absorbent body as described in patent documents 1 and 2, the distance between fibers constituting the fiber aggregate becomes longer than that in a normal absorbent body without such a fiber aggregate, and therefore, the ease of introduction of liquid (liquid introduction property) present on the surface of the absorbent body into the absorbent body may be lowered. Further, when a cushion layer including a synthetic fiber aggregate having a considerable thickness is disposed on an absorbent body as described in patent document 3, the above-described problem of liquid absorption becomes more serious.

Accordingly, the present invention provides an absorbent body which has high cushioning properties, is less likely to be twisted, has excellent liquid-drawing properties, and can improve the wearing feeling when applied to an absorbent article, and an absorbent article using the absorbent body.

Hereinafter, an absorbent body of the present invention and an absorbent article of the present invention including the same will be described based on preferred embodiments thereof with reference to the drawings. A catamenial sanitary napkin 1 as one embodiment of the absorbent article of the present invention is shown in fig. 1 and 2. The sanitary napkin 1 comprises: an absorbent body 4 which absorbs and retains a body fluid; a liquid-permeable topsheet 2 that is disposed on the skin-facing surface side of the absorbent body 4 and that can be brought into contact with the skin of the wearer; and a liquid-impermeable back sheet 3 disposed on the non-skin-facing surface side of the absorbent body 4. As shown in fig. 1, the sanitary napkin 1 has a longitudinal direction X extending from the abdomen side to the back side of the wearer through the crotch portion, corresponding to the front-back direction of the wearer, and a transverse direction Y orthogonal thereto, and is further divided into 3 regions in the longitudinal direction X: a longitudinal central region B including a portion facing a wearer's excretory part (excretory point) such as the pudendal region; a front region A disposed closer to the abdomen (front) side of the wearer than the excretory part facing part; and a rear region C disposed closer to the back side (rear side) of the wearer than the excretory part facing portion.

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 distant from the skin of the wearer. Here, "worn" refers to a state in which a normal and appropriate wearing position, that is, an accurate 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 of a longitudinal central region B in the absorbent main body 5 in the longitudinal direction X. The absorbent main body 5 is a part constituting the main body of the sanitary napkin 1, and includes the front sheet 2, the back sheet 3, and the absorbent body 4, and is divided into 3 regions, i.e., a front region a, a longitudinal central region B, and a rear region C, in the longitudinal direction X.

In the absorbent article of the present invention, the longitudinal central region refers to a region having a flap portion in the longitudinal direction (longitudinal direction, X direction in the drawing) of the absorbent article when the absorbent article has the flap portion, such as the sanitary napkin 1, and is a region between a root portion of one flap portion 5W in the longitudinal direction X and a root portion of the other flap portion 5W in the longitudinal direction X, taking the sanitary napkin 1 as an example. Further, the longitudinal central region in the absorbent article without the wing guard portion is a middle region when the absorbent article is divided into three equal parts in the longitudinal direction.

In the sanitary napkin 1, the absorber 4 includes a liquid-absorbent core 40 and a liquid-permeable core-covering sheet 41 that covers the outer surface of the absorbent core 40. The absorbent core 40 is formed into a shape elongated in the longitudinal direction X in a plan view as shown in fig. 1, similarly to the absorbent main body 5, the longitudinal direction of the absorbent core 40 coincides with the longitudinal direction X of the sanitary napkin 1, and the width direction of the absorbent core 40 coincides with the transverse direction Y of the sanitary napkin 1. The absorbent core 40 and the core sheet 41 may be bonded to each other with an adhesive such as a hot-melt adhesive.

As described above, the absorbent body 4, which is an embodiment of the absorbent body of the present invention, is provided in an absorbent article such as a sanitary napkin 1, and is used so as to indirectly adhere to the skin of a person, that is, indirectly adhere to the skin via a member such as a backsheet 2, and has a skin-facing surface (facing surface to the topsheet 2) disposed at a position relatively close to the skin of a user (wearer of the sanitary napkin 1) and a non-skin-facing surface (facing surface to the backsheet 3) disposed at a position relatively distant from the skin of the user in use, and has a longitudinal direction X corresponding to the front-back direction of the wearer of the sanitary napkin 1 and a lateral direction Y orthogonal thereto, and is divided into 3 regions of a front region a, a longitudinal direction central region B, and a rear region C in the longitudinal direction X. In addition to the mode of using the absorbent body 4 in indirect contact with the skin, a mode of using the absorbent body 4 in direct contact with the skin without interposing a member such as a sheet may be employed.

In the sanitary napkin 1, the core-wrapped sheet 41 is a 1 continuous sheet having a width of 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. 2, wraps the entire skin-facing surface region of the absorbent core 40, and extends outward in the transverse direction Y from both side edges of the absorbent core 40 in the longitudinal direction X, and the extended portion is rolled under the absorbent core 40 to wrap the entire region of the absorbent core 40 other than the skin-facing surface. In the present invention, the core sheet may not be 1 sheet, and may include 2 sheets of, for example, 1 skin-side wrapping sheet covering the skin-facing surface of the absorbent core 40 and 1 non-skin-side wrapping sheet covering the non-skin-facing surface of the absorbent core 40 separately from the skin-side wrapping sheet.

As shown in fig. 2, the topsheet 2 covers the entire area of the skin-facing surface of the absorbent body 4. On the other hand, the back sheet 3 covers the entire region of the absorbent body 4 other than the skin-facing surface, extends outward in the lateral direction Y from both side edges of the absorbent body 4 in the longitudinal direction X, and forms side flaps together with the side sheets 6 described below. The side flaps are portions of the sanitary napkin 1 including 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 from the extending portions of 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 sheets 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 longitudinal central region B, and thus a pair of

wing portions

5W, 5W extend on both the left and right sides of the absorbent main body 5 in the longitudinal direction X. 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 the plan view shown in fig. 1, and a wing section adhesive section (not shown) for fixing the wing section 5W to a wearing article such as pants is formed on the non-skin-facing surface thereof. The wing-protector section 5W is folded back to the non-skin-facing surface (outer surface) side of the crotch section of clothing such as shorts and the like. The flap portion adhesive portion is covered with a release sheet (not shown) including a film, nonwoven fabric, paper, or the like before use. In addition, a pair of

side pieces

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

side sheets

6 and 6 are bonded to other members such as the topsheet 2 by a known bonding means such as an adhesive at bonding lines not shown extending in the longitudinal direction X.

As one of the main characteristic parts of the sanitary napkin 1, the absorbent body 4, particularly, the absorbent core 40 constituting the main body of the absorbent body 4 can be cited. As shown in fig. 2, the absorbent core 40 is characterized by containing a fiber block 11 including fibers (synthetic fibers) 11F in addition to the water-absorbent fibers 12F. In contrast to the absorbent core 40 in which the plurality of water-absorbent fibers 12F are not aggregated but are independently present, and which can be individually taken out from the absorbent core 40, the fiber mass 11 is a fiber aggregate in which the plurality of fibers 11F are intentionally aggregated into a mass and integrated, and can be present in the absorbent core 40 in a state of always maintaining the form as the fiber aggregate. The fiber block 11 mainly contributes to improvement in flexibility, cushioning property, compression recovery property, shape retention property, and the like of the absorbent core 40. On the other hand, the water-absorbent fibers 12F mainly contribute to improvement in liquid absorbency, shape retention property, and the like of the absorbent core 40. The absorbent core 40 may be substantially the absorbent body 4 itself, and the following description of the absorbent core 40 can be applied to the description of the absorbent body 4 unless otherwise specified. That is, the present invention includes a case where the absorbent body is formed only of the absorbent core without the core sheet, and in this case, the absorbent body has the same meaning as the absorbent core.

The "fiber mass" as used herein refers to a fiber aggregate in which a plurality of fibers are integrally joined together. The fiber block may be in the form of a sheet obtained by cutting a synthetic fiber sheet having a predetermined size. In particular, it is preferable to select a nonwoven fabric as the synthetic fiber sheet and to form a nonwoven fabric sheet cut out of the nonwoven fabric in a predetermined size and shape as a fiber block.

As described above, the small piece-shaped fiber mass, which is a preferred embodiment of the fiber mass of the present invention, is not configured in such a manner that a plurality of fibers are gathered to form the small piece, but is manufactured by cutting a fiber sheet (preferably, a nonwoven fabric) having a size larger than the small piece (see fig. 6). The plurality of fiber masses contained in the absorbent body of the present invention are a plurality of small piece-like fiber masses having higher shape fixability than the fiber masses produced by the prior art of patent documents 1 and 2.

Further, in the absorbent core 40, the plurality of fiber pieces 11 are entangled with each other or the fiber pieces 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 contained 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 1 fiber piece continuous body, and there may be a case where a plurality of fiber piece continuous bodies are mixedly present in a state where they are not bonded to each other.

The fiber block 11 is a member excellent in flexibility and the like. In the absorbent core 40 of the present invention, since the fiber blocks 11 or the fiber blocks 11 and the water-absorbent fibers 12F are entangled and bonded to each other in addition to the fiber blocks 11, the absorbent core 40 is more excellent in responsiveness to external force and excellent in flexibility, cushioning properties, and compression recovery properties. For example, when the absorbent core 40 of the present invention is incorporated into an absorbent article, the absorbent article can be flexibly deformed against external forces (for example, body pressure of a wearer of the absorbent article) applied from various directions, and can be made to fit the body of the wearer well. 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 the absorbent core 40 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 body 4 may be twisted around a virtual rotation axis extending in the longitudinal direction X by the movements of the thighs during the walking movement of the wearer, and even in such a case, the absorbent core 40 has high deformation-recovery characteristics, and therefore, can be easily deformed and recovered by external forces from the thighs that induce the twisting, and is therefore less likely to twist, and it is possible to impart high conformability to the body of the wearer to the sanitary napkin 1.

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 includes the following mode A.

Mode 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.

Mode B: in the natural state (state where no external force is applied) of the absorbent core 40, the fiber blocks 11 and the like are not bonded to each other, but in the state where the external force is applied to the absorbent core 40, the fiber blocks 11 and the like are bonded to each other due to entanglement of the constituent fibers 11F with each other. Here, the "state in which an external force is applied to the absorbent core 40" refers to a state in which a deforming force is applied to the absorbent core 40, for example, during wearing of an absorbent article to which the absorbent core 40 is applied.

As described above, in the absorbent core 40, in addition to the fiber block 11 and the other fiber block 11 or the water-absorbent fibers 12F being bonded by the entanglement of the fibers, that is, "entanglement", as in the case of the mode a, there is a state in which the fiber block 11 and the other fiber block 11 or the water-absorbent fibers 12F can be bonded by entanglement as in the mode B, and the bonding by the entanglement of the fibers is an important point for more effectively exhibiting the operational effect of the absorbent core 40. However, in terms of shape retention, it is preferable that the absorbent core have "entanglement" of the mode a.

The entire bonded state of the absorbent core 40 via the fiber block 11 need not be "entangled", and a part of the absorbent core 40 may include a bonded state other than entanglement, for example, bonding with an adhesive.

However, in the absorbent core 40 itself, which is the remaining portion of the absorbent core 40 excluding the absorbent core 40 "through fusion of the fiber blocks 11" formed as a result of integrating, for example, known leakage preventing grooves and the like with other members of the absorbent article, it is preferable that the bonding of the fiber blocks 11 to each other or the bonding of the fiber blocks 11 and the absorbent fibers 12F is formed only by "entanglement of fibers".

From the viewpoint of more reliably exhibiting the effects of the above-described 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 still more preferably 80% or more of the total number of the fiber masses 11 in the absorbent core 40.

From the same viewpoint, the number of the fiber masses 11 having the "entanglement" of the mode a is preferably 70% or more, particularly preferably 80% or more, of the total number of the fiber masses 11 having the bonding portions with the other fiber masses 11 or the water-absorbent fibers 12F.

The sanitary napkin 1 is characterized by containing the fiber block 11 and also by the arrangement of the fiber materials (the fiber block 11 and the water-absorbent fibers 12F) in the absorbent core 40. That is, in the absorbent core 40, as shown in fig. 2 and 3, the content mass ratio of the fiber mass 11 to the water-absorbent fibers 12F (hereinafter also referred to as "fiber mass ratio") is smaller on the skin-facing surface side (front sheet 2 side) than on the non-skin-facing surface side (back sheet 3 side). That is, in the absorbent core 40, the water-absorbent fibers 12F are present in a large amount on the skin-facing surface side, and the fiber masses 11 (synthetic fibers 11F) are present in a large amount on the non-skin-facing surface side.

In this manner, by providing the absorbent core 40 with the "superabsorbent fiber portion 12P" (see fig. 3) having a relatively low fiber bulk ratio (including a fiber bulk ratio of 0 mass%), in other words, containing a larger amount of the water-absorbent fibers 12F than the other portions of the absorbent core 40, on the side that first receives the body fluid excreted by the wearer of the sanitary napkin 1, that is, on the skin-facing surface side of the absorbent core 40, the liquid drawing force (capillary force) on the skin-facing surface of the absorbent core 40 is increased, and the liquid absorption performance of the absorbent core 40 is improved. On the other hand, the non-skin-facing surface side of the absorbent core 40 is a region having a relatively high fiber mass ratio (including a case where the absorbent core does not contain water-absorbent fibers and only fiber masses are present), in other words, a "multi-fiber-mass region 11P" containing a larger amount of fiber masses 11 than other regions of the absorbent core 40 (see fig. 3), and therefore, the absorbent core 40 can sufficiently exhibit the effects mainly exerted by the fiber masses 11, such as the effects of improving the cushioning properties and the twisting resistance. In the multi-fiber block portion 11P, it is preferable that the fiber blocks 11 be distributed uniformly and at a high density over the entire portion of the portion 11P, from the viewpoint of more reliably exhibiting the desired operational effect of the portion 11P.

The above-described fiber mass ratio, that is, the content mass ratio of the fiber mass 11 to the water-absorbent fiber 12F is calculated as follows. The fiber mass ratio at the measurement target site is obtained by measuring the content (mass) of each of the fiber masses 11 and the water-absorbent fibers 12F existing at the measurement target site (for example, the skin-facing surface side of the absorbent body 4) in the thickness direction of the absorbent body 4 (absorbent core 40), that is, in the direction perpendicular to the skin-facing surface or the non-skin-facing surface of the absorbent body 4 (absorbent core 40), and dividing the content of the fiber masses 11 thus measured by the content of the water-absorbent fibers 12F and expressing the content by 100 fractions.

The fiber mass ratio in the skin-facing surface side of the absorbent core 40, that is, in the superabsorbent fiber portion 12P, is preferably 140 mass% or less, more preferably 70 mass% or less, and even more preferably 30 mass% or less, from the viewpoint of rapidly introducing body fluid into the absorbent core 40. The lower limit of the fiber mass ratio in the superabsorbent fiber portion 12P is preferably 10 mass%, more preferably 5 mass%, and still more preferably 0 mass%.

The fiber mass ratio in the non-skin-facing surface side of the absorbent core 40, that is, the multi-fiber mass portion 11P, is preferably 70 mass% or more, more preferably 140 mass% or more, and even more preferably 170 mass% or more, on the assumption that the fiber mass ratio is larger on the skin-facing surface side. The upper limit of the fiber mass ratio on the non-skin-facing surface side of the absorbent core 40 is not particularly limited, and the content of the water-absorbent fibers 12F on the non-skin-facing surface side may be 0 mass%. In this case, the fiber block ratio becomes numerically infinite because the denominator in the calculation formula becomes zero, and in this case, the expression "only fiber blocks exist" or the fiber block occupancy described below is 100 mass% instead of the expression of the fiber block ratio.

As described above, the sanitary napkin 1 is characterized in that the absorbent fibers 12F are present in the absorbent core 40 biased on the skin-facing surface side, and the fiber masses 11 (synthetic fibers 11F) are present in the non-skin-facing surface side. As an index indicating the characteristics of the distribution of the fiber mass 11, a ratio of the contained mass of the fiber mass 11 to the total contained mass of the fiber mass 11 and the water-absorbent fibers 12F (hereinafter, also referred to as "fiber mass occupancy") may be used instead of the above-described fiber mass ratio.

The fiber block occupancy was calculated as follows. The fiber mass occupancy of the measurement target site is obtained by measuring the content (mass) of each of the fiber masses 11 and the water-absorbent fibers 12F existing in the measurement target site (for example, the skin-facing surface side of the absorbent body 4) in the thickness direction of the absorbent body 4 (absorbent core 40), that is, in the direction perpendicular to the skin-facing surface or the non-skin-facing surface of the absorbent body 4 (absorbent core 40), and by dividing the mass content of the fiber mass 11 thus measured by the total value of the mass contents of the water-absorbent fibers 12F and the fiber mass 11 and expressing the value as 100 fractions.

From the viewpoint of more reliably exhibiting the above-described effects, the fiber mass occupancy in each portion of the absorbent core 40 is preferably set as follows, on the premise that the non-skin-facing surface side is larger than the skin-facing surface side.

The fiber mass occupancy in the skin-facing surface side of the absorbent core 40, i.e., the superabsorbent fiber portion 12P, is preferably 60 mass% or less, more preferably 30 mass% or less, and still more preferably 20 mass% or less. The lower limit of the fiber block occupancy in the superabsorbent fiber site 12P is preferably 10 mass%, more preferably 5 mass%, and still more preferably 0 mass%.

The fiber mass occupancy in the non-skin-facing surface side of the absorbent core 40, i.e., the multiple fiber mass portion 11P, is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, and preferably 100% by mass or less, more preferably 95% by mass or less, and even more preferably 85% by mass or less.

The difference between the fiber block occupancy of the fibrous block portion 11P and the fiber block occupancy of the superabsorbent fiber portion 12P, when the latter is subtracted from the former, is preferably 15 mass% or more, more preferably 50 mass% or more, and still more preferably 80 mass% or more.

In addition, the ranges of the "fiber block occupancy" in the multi-fiber block portion 11P and the multi-absorbent fiber portion 12P and the ranges of the "fiber block ratio" in the multi-fiber block portion 11P and the multi-absorbent fiber portion 12P are, when the entire absorbent core 40 is integral, divided into two equal parts in the thickness direction, and the skin-facing surface side thereof is applied as the multi-fiber block portion 11P, and the non-skin-facing surface side thereof is applied as the multi-absorbent fiber portion 12P.

The phrase "the entire absorbent core is integral" as used herein means that the absorbent core is integrally formed, and a structure in which a plurality of absorbent core layers formed separately are stacked is excluded. In the latter structure, one absorbent core layer is separable from the other absorbent core layer, and the two layers are not inseparable and not integral. As a specific example of the mode in which the entire absorbent core has unity, a mode in which all the materials (the fiber block 11 and the water-absorbent fibers 12F) forming the absorbent core 40 are stacked at once can be cited. The absorbent core 40 in each of the absorbent body 4 shown in fig. 3 and the absorbent body 4A shown in fig. 4 described below has 2 regions (the multi-absorbent fiber region 12P and the multi-fiber region 11P) having different fiber block occupancy rates and fiber block ratios, but the

fibers

12F and 11F are entangled with each other at the interface between the 2

regions

12P and 11P, whereby the entire absorbent core has unity. In contrast, in the absorbent core 40 in the modification of the absorbent body 4A described below, the

constituent fibers

12F and 11F are not substantially entangled with each other at the interface of the 2

regions

12P and 11P divided into layers, and the entire absorbent core is not integrated.

In the present invention, the superabsorbent fiber sites 12P are preferably formed of only the absorbent fibers 12F, but if the fiber mass 11 is present in the superabsorbent fiber sites 12P, the absorbent core 40 as a whole is excellent in that the effect of the fiber mass 11 can be improved. In particular, in the case where the fiber block 11 and the water-absorbent fibers 12F are present in an entangled or entangled state in the superabsorbent fiber portion 12P in which the fiber block 11 and the water-absorbent fibers 12F are present in a mixed state, it is preferable that the superabsorbent fiber portion 12P first absorbs a body fluid such as menstrual blood and then supplies the body fluid to the space in the superabsorbent fiber portion 11P. Further, it is preferable that the fiber block 11 and the water-absorbent fiber 12F are entangled in the multi-fiber block portion 11P because the above-described effects are more easily exhibited.

As shown in fig. 3, the absorbent core 40 has a fiber mass occupancy and a fiber mass ratio that gradually increase from the skin-facing surface side (front sheet 2 side) to the non-skin-facing surface side (back sheet 3 side). In other words, in the absorbent core 40, the water-absorbent fibers 12F gradually decrease from the skin-facing surface side to the non-skin-facing surface side. That is, in the thickness direction of the absorbent core 40, the fiber mass 11 is not present in the skin-facing surface of the absorbent core 40 and in the vicinity thereof, or is present in the absorbent core 40 at the lowest fiber mass occupancy rate and the lowest fiber mass ratio, and in the non-skin-facing surface of the absorbent core 40 and in the vicinity thereof, the fiber mass 11 is present in the absorbent core 40 at the highest fiber mass occupancy rate and the highest fiber mass ratio.

The arrangement of the fiber materials (the fiber mass 11, the water-absorbent fibers 12F) in the absorbent core 40 is not limited to the arrangement shown in fig. 3, that is, the arrangement in which the fiber mass occupancy and the fiber mass ratio gradually change from one surface side to the other surface side in the thickness direction of the absorbent core 40, and can be appropriately modified within the range not departing from the technical idea of the present invention described above. Fig. 4 shows a view corresponding to fig. 3 of an absorbent body 4A as another embodiment of the absorbent body of the present invention. The absorbent body 4A will be mainly described with respect to the components different from the absorbent body 4, and the same components will be denoted by the same reference numerals and the description thereof will be omitted. The description of the absorbent body 4 (absorbent core 40) applies to the constituent parts not specifically described.

In the absorbent body 4A shown in fig. 4, the absorbent body 4A is divided into 2 regions (the superabsorbent fiber region 12P and the multi-fiber region 11P) having different fiber block occupancy rates and fiber block ratios in a layered manner in the thickness direction. In any of the 2 regions, the fibrous mass occupancy rate and the fibrous mass ratio may not be necessarily in the thickness direction of the absorbent body 4A in either of the superabsorbent fiber region 12P on the skin-facing surface side and the fibrous mass region 11P on the non-skin-facing surface side. The difference in fiber mass occupancy between the skin-facing side portion and the non-skin-facing side portion when each of the

portions

11P, 12P is divided into two equal parts in the thickness direction is preferably 30 mass% or less, and more preferably 10 mass% or less. In the absorbent body 4A, the fiber mass occupancy and the fiber mass ratio preferably greatly change at the interface between the superabsorbent fiber sites 12P and the multi-fiber mass sites 11P. The boundary surface between the two portions is the center of the absorbent body 4A in the thickness direction in the embodiment shown in fig. 4, that is, the absorbent body 4A is divided into 2 portions in the thickness direction, i.e., the superabsorbent fiber portion 12P and the mass portion 11P, but the position of the boundary surface can be set appropriately, and the thicknesses of the two portions may be different from each other.

In the case where the absorbent core 40 is divided into the superabsorbent fiber portion 12P and the mass portion 11P in layers as in the absorbent body 4A shown in fig. 4, the superabsorbent fiber portion 12P is preferably a portion extending over 20 to 80% of the thickness of the absorbent core 40 from the skin-facing surface of the absorbent core 40 toward the inner side in the thickness direction of the absorbent core 40, and more preferably a portion extending over 30 to 70% of the thickness. The multi-fiber block portion 11P preferably extends over 20 to 80% of the thickness of the absorbent core 40 from the non-skin-facing surface of the absorbent core 40 toward the inner side in the thickness direction of the absorbent core 40, and more preferably over 30 to 70% of the thickness.

In addition, when the absorbent core 40 is divided into the superabsorbent fiber sites 12P and the multi-fiber mass sites 11P in layers as in the absorbent body 4A shown in fig. 4, the thickness of each of the superabsorbent fiber sites 12P and the multi-fiber mass sites 11P is preferably 0.5mm or more, more preferably 1mm or more, and preferably 10mm or less, more preferably 5mm or less, and even more preferably 4mm or less.

The thickness of each portion of the absorbent core 40 was measured using 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 >

The absorbent core (absorbent body) is left standing in a horizontal position without wrinkles or curves, 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 as a measurement sample. Then, 5cN/cm of the measurement sample was measured²Thickness under load. Specifically, the thickness is measured, for example, using a thickness meter, PEACOCK DIAL UPRIGHT GAUGES R5-C (OZAKI MFG. CO. LTD.). At this time, the load between the distal end of the thickness gauge and the measurement sample was 5cN/cm²In the above-described method, a circular or square plate (acrylic plate having a thickness of about 5 mm) in a plan view, which is adjusted in size, is arranged, and the thickness is measured. The thickness measurement is taken at 10 and their average is calculated as the thickness.

In the absorbent body 4A, the superabsorbent fiber sites 12P and the multi-fiber block sites 11P are bonded to each other at their interfaces by entanglement of the constituent fibers (the constituent fibers 11F of the fiber block 11, the water-absorbent fibers 12F). That is, at the interface between the two portions, the water-absorbent fibers 12F of the multi-absorbent fiber portion 12P on the skin-facing surface side are entangled with the fiber masses 11 (fibers 11F) of the multi-fiber portion 11P on the non-skin-facing surface side, whereby the two portions are relatively loosely bonded to each other, and the entire absorbent body 4A (absorbent core 40) is integrated.

Further, as a modification of the absorbent body 4A shown in fig. 4, there can be mentioned a mode in which the superabsorbent fiber portion 12P on the skin-facing surface side is not bonded to the multi-fiber block portion 11P on the non-skin-facing surface side, and this is also included in the present invention. The absorbent body 4A according to this modification was produced as follows: first, a layer corresponding to the superabsorbent fiber portion 12P and a layer corresponding to the mass portion 11P are separately produced, and then the two layers are superposed. In the modification of the absorbent body 4A obtained by this manufacturing method, since there is almost no entanglement of the

constituent fibers

11F and 12F at both portions, the entire absorbent core 40 is not integrated, and can be easily separated into the superabsorbent fiber portion 12P and the multi-fiber mass portion 11P.

As a specific advantage of the aspect in which the fiber mass occupancy and the fiber mass ratio of the absorbent body 4 gradually change from one side to the other side in the thickness direction of the absorbent body as shown in fig. 3, 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 of the fibers passing through the fiber mass is easily maintained in the thickness direction, and the cushioning property of the absorbent body is easily maintained well during use. As an advantage unique to the mode in which the absorbent body 4A has 2 portions having different fiber block occupancy rates and fiber block ratios in the thickness direction as shown in fig. 4, the following can be mentioned: 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.

The

absorbent bodies

4 and 4A (absorbent cores 40) can be manufactured by a conventional method using a known fiber stacking apparatus having a drum, and in this case, the specific arrangement of the fiber materials (fiber mass 11, water-absorbent fibers 12F) as shown in fig. 3 or 4 can be realized by appropriately adjusting the order of stacking the fiber mass 11 and water-absorbent fibers 12F on the drum in the manufacturing method using the fiber stacking apparatus.

The absorbent core 40 may contain other components than the fiber block 11 and the water-absorbent fibers 12F, and a water-absorbent polymer may be exemplified as the other component. Reference numeral 13 in the figure is a water-absorbent polymer. The water-absorbent polymer generally has a particulate structure as shown in the figure, and may be in a fibrous form. When the particulate water-absorbent polymer is used, the shape thereof may be any of spherical, block, columnar bag or amorphous shape. The average particle diameter of the water-absorbent polymer is preferably 10 μm or more, more preferably 100 μm or more, and preferably 1000 μm or less, more preferably 800 μm or less. As the water-absorbent polymer, a polymer or copolymer of acrylic acid or an alkali metal salt of acrylic acid can be generally used. Examples thereof include polyacrylic acid and salts thereof and polymethacrylic acid and salts thereof.

In the absorbent core 40, as shown in fig. 3, since the water-absorbent polymer 13 is contained on the skin-facing surface side of the absorbent core 40, the water-absorbent polymer 13 is contained in the superabsorbent fiber portion 12P. By thus including the water-absorbent polymer 13 having excellent water absorbency on the skin-facing surface side of the absorbent core 40, which is particularly problematic in terms of the excellence of liquid-intake properties, the liquid-intake properties of the skin-facing surface of the absorbent core 40 can be further improved in addition to the technique of forming the superabsorbent fiber sites 12P on the skin-facing surface side, that is, the fiber mass occupancy and the fiber mass ratio are relatively low.

In the absorbent core 40, the water-absorbent polymer 13 may be contained in a portion other than the skin-facing surface side (the superabsorbent fiber portion 12P) of the absorbent core 40, that is, the multi-fiber block portion 11P. In particular, in view of the main purpose of providing the water-absorbent polymer 13 in the absorbent core 40 to improve the liquid intake property on the skin-facing surface side of the absorbent core 40, it can be said that it is essentially meaningless to provide the water-absorbent polymer 13 positively on the non-skin-facing surface side (the multi-fiber block portion 11P) of the absorbent core 40. Further, if the water-absorbent polymer 13 is positively provided on the non-skin-facing surface side (the multi-fiber block portion 11P) of the absorbent core 40, the expression of the action and effect (such as the effect of improving the cushioning property and the twisting resistance) by the multi-fiber block portion 11P may be inhibited. In view of the above, the absorbent core 40 preferably has a content of the water-absorbent polymer 13 in a region other than the skin-facing surface side (the multi-absorbent fiber region 12P), specifically, for example, the multi-fiber block region 11P, which is smaller than the skin-facing surface side, or may be zero.

The content of the water-absorbent polymer 13 in the absorbent core 40 is preferably 5% by mass or more, more preferably 10% by mass or more, and preferably 60% by mass or less, more preferably 40% by mass or less, with respect to the total mass of the absorbent core 40 in a dry state.

The grammage of the water-absorbent polymer 13 in the absorbent core 40 is preferably 10g/m²Above, more preferably 30g/m²Above, and preferably 100g/m²Hereinafter, more preferably 70g/m²The following.

One of the main features of the absorbent core 40 is the outer shape of the fiber block 11. Fig. 5 shows 2 typical outer shapes of the fiber block 11. The fiber block 11A shown in fig. 5(a) has a quadrangular prism shape, more specifically, a rectangular parallelepiped shape, and the fiber block 11B shown in fig. 5(B) has a disk shape. The common point of the fiber blocks 11A and 11B is that they include 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 considered to be substantially free of irregularities, based on the grade applied when evaluating the degree of irregularities on the surface of an article mainly composed of such fibers.

The rectangular parallelepiped fiber block 11A of fig. 5(a) has 6 flat surfaces, of which 2 opposite surfaces having the largest area among the 6 surfaces are base surfaces 111, respectively, and the remaining 4 surfaces are skeleton surfaces 112, respectively. 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 of fig. 5(B) has 2 opposing flat surfaces of a circular shape in plan view, each of the 2 flat surfaces being a base surface 111, and a curved peripheral surface connecting the two flat surfaces, the peripheral surface being a skeleton surface 112.

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

The plurality of fiber masses 11 contained in the absorbent core 40 are "set fiber aggregates" each including 2 opposing base surfaces 111 and a skeleton surface 112 connecting the two base surfaces 111, such as the

fiber masses

11A and 11B shown in fig. 5, unlike the nonwoven fabric sheet or the microfiber web described in patent documents 1 and 2, which are amorphous fiber aggregates. In other words, when observing any 1 fiber block 11 in the absorbent core 40 in a see-through manner (for example, observing with an electron microscope), the see-through shape of the fiber block 11 differs depending on the observation angle thereof, and a plurality of see-through shapes exist for each 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 skeleton surface 112 connecting the two base surfaces 111 as one of the plurality of see-through shapes. The plurality of nonwoven fabric sheets or fine fiber webs included in the absorbent bodies described in patent documents 1 and 2 do not have "faces" substantially like the base face 111 or the skeleton face 112, that is, portions having developed portions, and are not "set" in shape but have different shapes from each other.

As described above, if the plurality of fiber masses 11 contained in the absorbent core 40 are "set 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 amorphous fiber aggregates described in patent documents 1 and 2, and therefore, the effects (the effects of improving the flexibility, cushioning properties, compression recovery properties, and the like of the absorbent body) expected by blending the fiber aggregates such as the fiber masses 11 in the absorbent core 40 can be stably exhibited. In particular, in the case of the fiber block 11 having a rectangular parallelepiped shape as shown in fig. 5(a), since the outer surface thereof includes 6 surfaces of 2 base surfaces 111 and 4 skeleton surfaces 112, the fiber block 11 has more opportunities to come into contact with other fiber blocks 11 or water-absorbent fibers 12F than the fiber block 11 having a circular disk shape with 3 outer surfaces as shown in fig. 5(b), and thus entanglement properties are improved, which contributes to improvement of shape retention properties and the like.

In the fiber block 11, it is preferable that the total area of the 2 base surfaces 111 is larger than the total area of the skeleton surface 112. That is, in the rectangular parallelepiped fiber block 11A in fig. 5(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. 5(B), the total of the areas of the 2 base surfaces 111 is larger than the area of the skeleton surface 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.

Such a fiber mass 11 as a "set fiber aggregate" defined by 2 base planes 111 and a skeleton plane 112 intersecting the two base planes 111 can be realized by making the manufacturing method different from the prior art. As shown in fig. 6, a preferred method for producing the fiber block 11 is to cut a raw material fiber sheet 10bs (a sheet having the same composition as the fiber block 11 and a size larger than the fiber block 11) into a set shape by using a cutting mechanism such as a cutter. The shapes and sizes of the plurality of fiber blocks 11 thus manufactured are uniformly formed in a more definite form than those of the structures manufactured by the prior art techniques such as patent documents 1 and 2. Fig. 6 is a diagram illustrating a method for producing the rectangular parallelepiped fiber block 11A shown in fig. 5(a), and broken lines in fig. 6 indicate cutting lines. A plurality of fiber pieces 11 having a uniform shape and size obtained by shape-setting and cutting the fiber sheet are blended in the absorbent core 40. As described above, the raw fiber sheet 10bs is preferably a nonwoven fabric.

As shown in fig. 6, the rectangular parallelepiped fiber block 11A of fig. 5(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 and D2 are each a predetermined 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 sheet 10bs into dice (so-called dice) shapes, the cut surface, that is, the surface that comes into contact with the cutting means such as a cutter at the time of cutting the sheet 10bs is generally the skeleton surface 112, and the non-cut surface, that is, the surface that does not come into contact with the cutting means is the base 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 the 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 of fig. 5 (B). The substantial difference from the fiber block 11A is only in the cutting mode of the raw material 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 into a circular shape corresponding to the planar shape of the fiber block 11B.

The outer shape of the fiber block 11 is not limited to the configuration shown in fig. 5, and the base surface 111 and the skeleton surface 112 may be flat surfaces that are not curved as in the case of the

surfaces

111 and 112 in fig. 5(a), or may be curved surfaces as in the case of the skeleton surface 112 in fig. 5(B) (the circumferential surface of the disk-shaped fiber block 11B). The base surface 111 and the skeleton surface 112 may have the same shape and the same size.

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 by a cutting mechanism such as a cutter in the production of the fiber block 11; and a non-cut surface (base surface 111) which is a surface originally provided in the sheet 10bs and which does not come into contact with the cutting means. The skeleton surface 112 as a cut surface has the following features because of the difference in the cut surface: the number of fiber ends per unit area is larger than that of the base surface 111 which is a non-cut surface. The "fiber end" herein means the end in the longitudinal direction of the constituent fiber 11F of the fiber mass 11. In general, although the fiber ends are also present in the base surface 111 which is a non-cut surface, since the skeleton surface 112 is a cut surface formed by cutting the raw material fiber sheet 10bs, the fiber ends including the cut ends of the fibers 11F formed by the cutting are present in a large amount in the entire skeleton surface 112, that is, the number of the fiber ends per unit area 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 interlacing the fiber block 11 with other fiber blocks 11 and 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 improves, and thus the more various properties such as shape retention of the absorbent core 40 can be improved. Further, as described above, since the number of fiber ends per unit area on 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) passing through the fiber block 11 differs depending on the surface of the fiber block 11, and the entanglement of the skeleton surface 112 is higher than the entanglement with the basic surface 111. That is, the bonding force by the bonding with the other fibers by the entanglement with the skeleton surface 112 is strong via the base surface 111, and the bonding force with the other fibers may be different between the base surface 111 and the skeleton surface 112 in 1 fiber block 11. In general, the stronger the bonding force, the more the degree of freedom of movement of the bonded fibers is restricted, and the strength (shape retention) of the entire absorbent core 40 is improved, but the softness tends to decrease.

In this way, in the absorbent core 40, the plurality of fiber blocks 11 contained therein are entangled with other fibers (other fiber blocks 11, water-absorbent fibers 12F) in the periphery thereof at 2 bonding forces, whereby the absorbent core 40 has both appropriate softness and strength (shape retention property). Further, when the absorbent core 40 having such excellent characteristics is used as an absorber of an absorbent article in accordance with a usual method, it is possible to provide a comfortable wearing feeling to a wearer of the absorbent article and to effectively prevent a trouble that the absorbent core 40 is broken by an external force such as body pressure of the wearer when wearing the absorbent article.

In particular, as described above, the total area of the 2 base faces 111 of the fiber block 11(11A, 11B) shown in fig. 5 is larger than the total area of the skeleton face 112. This means that, since the number per unit area of the fiber end is relatively small, the total area of the base face 111, which has relatively low entanglement with other fibers, is larger than the skeleton face 112, which has properties opposite thereto. Therefore, the fiber mass 11(11A, 11B) shown in fig. 5 is more likely to be entangled with other fibers (other fiber mass 11, water-absorbent fibers 12F) in the periphery than a fiber mass having fiber ends 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 form large lumps, and can impart excellent flexibility to the absorbent core 40.

On the other hand, the nonwoven fabric sheets or the fine fiber webs described in patent documents 1 and 2 are produced by cutting a raw material fiber sheet into an indefinite shape or the like by a cutter such as a chopper as described above, and therefore, the raw material fiber sheet does not become a small sheet-like fiber mass having a definite shape of a "plane" such as the base plane 111 and the skeleton plane 112, and an external force for cutting treatment is applied to the entire fiber mass at the time of production thereof, and therefore, the fiber ends constituting the fibers are irregularly formed in the entire fiber mass, and it is difficult to sufficiently exhibit the above-mentioned operational effects by the fiber ends.

From the viewpoint of more reliably exhibiting the above-described action and effect by the fiber end, the number N of the fiber ends per unit area of the base surface 111 (non-cut surface)₁Number N of fiber ends per unit area of skeleton surface 112 (cut surface)₂In the ratio of N₁＜N₂On the premise of N₁/N₂In the above expression, it is preferably 0 or more, more preferably 0.05 or more, and preferably 0.90 or less, more preferably 0.60 or less. More specifically, N₁/N₂Preferably 0 or more and 0.90 or less, and more preferably 0.05 or more and 0.60 or less.

Number per unit area N of fiber ends of base surface 111₁Preferably 0 pieces/mm²Above, more preferably 3/mm²Above, and preferably 8/mm²Hereinafter, more preferably 6 pieces/mm²The following.

Number per unit area N of fiber ends of skeleton face 112₂Preferably 5 pieces/mm²Above, more preferably 8 pieces/mm²Above, and preferably 50/mm²Hereinafter, more preferably 40 pieces/mm²The following.

The number per unit area of the fiber ends of the base surface 111 and the skeleton surface 112 is measured by the following method.

< method for measuring the number of fiber ends per unit area in each side of a fiber block >

For a member (fiber block) including fibers to be measured, a measurement piece was attached to a sample table using a double-sided adhesive tape (Nicetack NW-15 manufactured by Nichiban gmbh). Next, the measurement piece was platinum-coated. An ion sputtering apparatus model E-1030 (trade name) manufactured by Nicote Seiki Co., Ltd was used for the coating, and the sputtering time was 120 seconds. For the cut surface of the measurement piece, the base surface and the skeleton surface were observed at a magnification of 100 times using a JCM-6000 type electron microscope manufactured by JEOL corporation. In the observation screen of 100 times magnification, a rectangular area of 1.2mm in vertical direction and 0.6mm in horizontal direction is set at an arbitrary position on the measurement target surface (base surface or skeleton surface), and the number of fiber ends contained in the rectangular area is measured while adjusting the observation angle so that the area of the rectangular area occupies 90% or more of the area of the observation screen. However, when the observation screen of 100 times magnification is smaller than 1.2mm × 0.6mm and the ratio of the area of the rectangular region to the entire observation screen is less than 90%, the number of fiber ends included in the rectangular region of the observation screen is measured in the same manner as described above after the observation magnification is increased to 100 times. Here, "fiber end portion" as a target of the number measurement is a longitudinal end portion of the constituent fiber of the fiber block, and even if a portion (longitudinal intermediate portion) other than the longitudinal end portion of the constituent fiber extends from the measurement target surface, the longitudinal intermediate portion is not a target of the number measurement. The number of fiber ends per unit area on the surface to be measured (base surface or skeleton surface) of the fiber mass is calculated according to the following equation. For each of the 10 fiber blocks, the number per unit area of the fiber ends of each of the base surface and the skeleton surface was measured in the above order, and the average of the plurality of measured values was taken as the number per unit area of the fiber ends of the surface to be measured.

Number per unit area (number) of fiber ends of measurement target surface (base surface or skeleton surface) of fiber blockNumber/mm²) The number of fiber ends contained in a rectangular area (1.2 × 0.6 mm)/the area of the rectangular area (0.72 mm)²)

In the case where the basic surface 111 of the fiber block 11 has a rectangular shape in plan view like the fiber block 11A shown in fig. 5(a), from the viewpoint of improving uniform dispersibility of the fiber block 11 in the absorbent core 40, the short side 111A of the rectangular shape is preferably equal to or shorter than the thickness of the absorbent core 40 including the fiber block 11 (11A). The ratio of the length of the short side 111a to the thickness of the absorbent core 40, expressed as the former/latter, is preferably 0.03 or more, more preferably 0.08 or more, and preferably 1 or less, more preferably 0.5 or less.

The thickness of the absorbent core 40 is preferably 1mm or more, more preferably 2mm or more, and preferably 15mm or less, more preferably 10mm or less, and further preferably 6mm or less. The thickness of the absorbent core 40 was measured using the method described above.

The dimensions and the like of the respective portions of the fiber block 11(11A, 11B) are preferably set as follows. The dimensions of each portion of the fiber block 11 can be measured based on an electron micrograph or the like at the time of a specific operation of the outer shape of the fiber block 11 described below.

When the base surface 111 has a rectangular shape in plan view as shown in fig. 5(a), the length L1 of the short side 111a is preferably 0.3mm or more, more preferably 0.5mm or more, and preferably 10mm or less, more preferably 6mm 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 2mm or more, and preferably 30mm or less, more preferably 15mm or less.

As shown in fig. 5, when the base surface 111 has 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 of the fiber block 11, which coincides with the diameter of the circular base surface 111 in the planar view of the disk-shaped fiber block 11B.

When the ratio of the length L1 of the short side 111a to the length L2 of the long side 111b is L1/L2, it is preferably 0.003 or more, more preferably 0.025 or more, and preferably 0.5 or less.

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.

The absorbent core 40 is preferably mechanically isotropic so that the effect of the presence of the fiber block 11 is easily exerted on all surfaces of the absorbent core 40. Therefore, the fiber pieces 11 are preferably distributed in a high density and uniformly throughout the absorbent core 40. From this viewpoint, it is preferable that the overlapping portions of the plurality of fiber blocks 11 are present in arbitrary 10mm square unit regions in the projection views of the absorbent core 40 in the 2 directions orthogonal to each other. As the "projection views in the 2 directions orthogonal to each other" here, a projection view in the thickness direction of the absorbent core (absorbent body) (that is, a projection view of the absorbent core viewed from the skin-facing surface or the non-skin-facing surface thereof) and a projection view in the direction orthogonal to the thickness direction (that is, a projection view of the absorbent core viewed from the side surface thereof) can be typically mentioned.

Fig. 7(a) shows an electron micrograph of an example of the fiber block of the present invention, and fig. 7(b) shows a view schematically showing the fiber block 11 according to the electron micrograph. As shown in fig. 7, the plurality of fiber blocks 11 included in the absorbent core 40 may have a structure including a main body portion 110 and an extended fiber portion 113 including fibers 11F extending outward from the main body portion 110 and having a fiber density lower than that of the main body portion 110 (the number ratio of fibers per unit area is small). The absorbent core 40 may include a fiber block 11 having no extending fiber part 113, that is, a fiber block 11 composed only of the main body part 110. The extended fiber portion 113 is one of fiber ends present on the respective surfaces (the base surface 111 and the skeleton surface 112) of the fiber block 11, and is a fiber end portion extending outward from the respective surfaces of the fiber block 11.

The main body 110 is a portion defined by the 2 opposing base surfaces 111 and a skeleton surface 112 connecting the two base surfaces 111. The main body portion 110 is a portion that constitutes the main body of the fiber block 11 and forms a shape of the fiber block 11, and the main body portion 110 is large because various characteristics of the fiber block 11, such as high flexibility, cushioning properties, and compression recovery properties, are basically derived from the main body portion 110. On the other hand, the extended fiber part 113 mainly contributes to improvement of the entanglement of the plurality of fiber pieces 11 or the fiber pieces 11 and the water-absorbent fibers 12F contained in the absorbent core 40, and improves the shape retention property directly acting on the absorbent core 40, and also affects uniform dispersibility of the fiber pieces 11 in the absorbent core 40, and the operational effect by the main body part 110 can be indirectly enhanced.

The main body portion 110 has a higher fiber density, i.e., a larger number of fibers per unit area, than the extended fiber portion 113. In addition, the main body 110 generally has a uniform fiber density. The ratio of the main body portion 110 to the total mass of the fiber mass 11 is usually at least 40 mass%, preferably 50 mass% or more, more preferably 60 mass% or more, and still more preferably 85 mass% or more. The main body 110 and the extended fiber portion 113 can be distinguished by the following operation for determining the external shape.

The operation of determining the outer shape of the main body portion 110 of the fiber block 11 contained in the absorbent core 40 can be performed by paying attention to the difference in fiber density (the number of fibers per unit area), the type of fibers, the difference in fiber diameter, and the like in the absorbent core 40, and confirming the "boundary" between the main body portion 110 and the other portions. The fiber density of the main body portion 110 is higher than that of the extended fiber portion 113 existing therearound, and since the synthetic fibers, which are the constituent fibers of the main body portion 110, are generally different in nature and/or size from the water-absorbent fibers 12F (typically, cellulose fibers), the above-described boundaries can be easily confirmed by focusing on the above-described points even in the absorbent core 40 in which a plurality of fiber masses 11 and water-absorbent fibers 12F are mixed. The boundary thus confirmed is the peripheral edge (side) of the base surface 111 or the skeleton surface 112, and the base surface 111 and the skeleton surface 112, and thus the body portion 110, can be specified by this boundary confirmation work. This boundary confirmation operation can be performed by observing the object (absorber 4) at a plurality of observation angles as necessary using an electron microscope. In particular, when the fiber block 11 included in the absorbent core 40 is "the total area of the 2 basic surfaces 111 is larger than the total area of the skeleton surface 112" as in the fiber blocks 11A and 11B shown in fig. 5, particularly when the basic surface 111 is the largest area of the fiber block 11, the large-area basic surface 111 can be easily identified, and thus the work of identifying the outer shape of the main body 110 can be smoothly performed.

As shown in fig. 7, the extended fiber part 113 includes the constituent fibers 11F of the main body part 110 that extend outward from at least 1 of the basic surface 111 and the skeleton surface 112 that form the outer surface of the main body part 110. Fig. 7(b) is a view of the fiber block 11 as viewed from the base surface 111 (the surface having the largest area among the plurality of surfaces of the fiber block 11) side, and a plurality of fibers 11F are extended from the skeleton surface 112 intersecting the base surface 111 to form an extended fiber portion 113.

The form of the extended fiber part 113 is not particularly limited. The extended fiber portion 113 may include 1 fiber 11F, and may include a plurality of fibers 11F as in the extended fiber bundle portion 113S described below. The extended fiber portion 113 includes the longitudinal end portions of the fibers 11F extending from the main body portion 110, but may include portions other than both the longitudinal end portions of the fibers 11F (longitudinal intermediate portions) in addition to such fiber end portions. That is, in the fiber block 11, both end portions in the longitudinal direction constituting the fibers 11F may be present in the main body portion 110, and the other portion, that is, the longitudinal direction intermediate portion may extend (protrude) annularly outward from the main body portion 110, and the extended fiber portion 113 in this case includes an annular protruding portion of the fibers 11F.

One of the main functions of the extended fiber section 113 is to entangle the plurality of fiber pieces 11 included in the absorbent core 40 or to entangle the fiber pieces 11 and the water-absorbent fibers 12F as described above. In general, when the length of the extended fiber part 113 extending from the body 110 is increased, the thickness of the extended fiber part 113 is increased, or the number of the extended fiber parts 113 included in 1 fiber block 11 is increased, the connection between the objects entangled with each other via the extended fiber part 113 is increased, and thus the entanglement is not easily released, so that the specific effects of the present invention can be exerted more stably.

In the case where the fiber block 11 is obtained by cutting the raw material fiber sheet 10bs into a set shape as shown in fig. 6, the drawn fiber portions 113 are present in a relatively large amount on the skeleton surface 112 as the cut surface, and, unlike this, are not present at all on the base surface 111 as the non-cut surface, or even if present on the base surface 111, the number thereof is smaller than the number of the skeleton surfaces 112. The reason why the elongated fiber portions 113 are unevenly present in many cases on the skeleton surface 112 as the cut surface in this way is that the elongated fiber portions 113 are often "fuzz" generated by cutting of the raw material fiber sheet. That is, since the skeleton surface 112 formed by cutting the raw fiber sheet 10bs is entirely rubbed by a cutting means such as a cutter at the time of cutting, fluff of the constituent fibers 11F of the holding sheet 10bs is easily formed, and so-called fuzz is easily generated. Although it depends on the type of the raw fiber sheet, if the interval between the cutting lines is shortened or the cutting speed is slowed, the extended fiber portions 113 can be easily formed and the length thereof can be adjusted. On the other hand, since the base surface 111 as the non-cut surface does not rub against the cutting mechanism, the pile or the extending fiber part 113 is not easily formed.

The interval L1a (interval in the 1 st direction, see fig. 6) and the interval L2a (interval in the 2 nd direction, see fig. 6) of the cutting lines at the time of cutting the raw material fiber sheet 10bs are preferably 0.3mm or more, more preferably 0.5mm or more, and preferably 30mm or less, and more preferably 15mm or less, from the viewpoint of promoting the formation of the above-described spread fiber portions 113, the viewpoint of ensuring a desired size while exhibiting a specific effect on the fiber mass 11, and the like.

As shown in fig. 7, the fiber block 11 includes an extended fiber bundle portion 113S including a plurality of fibers 11F extending outward from the main body portion 110, more specifically, from the skeleton surface 112, which is one type of the extended fiber portion 113. At least one of the extended fiber portions 113 included in the fiber block 11 may be the extended fiber bundle portion 113S. The extended fiber bundle portion 113S is formed by collecting a plurality of fibers 11F extending from the skeleton surface 112, and is characterized by having a longer extension length from the skeleton surface 112 than the extended fiber portion 113. The extended fiber bundle portions 113S may be present on the base surface 111, typically on the skeleton surface 112 as shown in fig. 7, and may be completely absent from the base surface 111 or, if present, less in number than the skeleton surface 112. The reason for this is the same as the reason why the extended fiber part 113 is mainly present on the skeleton surface 112 which is a cut surface, as described above.

Since the fiber block 11 has such a long and thick spread fiber bundle portion 113S, which is also referred to as a large-sized spread fiber portion 113, the entanglement of the fiber blocks 11 with each other or the fiber block 11 and the water-absorbent fiber 12F is further strengthened, and as a result, the specific effect of the present invention due to the presence of the fiber block 11 can be more stably exhibited. The extended fiber bundle portion 113S is easily formed by cutting the raw fiber sheet 10bs (see fig. 6) under the above-described condition that fluffing is easily caused.

The length of the extended fiber bundle portion 113S extending from the body portion 110, that is, the length of the extended fiber bundle portion extending from the skeleton surface 112 (cut surface) is preferably 0.2mm or more, more preferably 0.5mm or more, and preferably 7mm or less, more preferably 4mm or less. The extended length of the extended fiber bundle portion 113S can be measured in the work of determining the outer shape of the fiber block 11 (boundary confirmation work). Specifically, for example, a double-sided tape manufactured by 3M corporation was attached to the surface of an acrylic transparent sample holder using a microscope (50 magnification) manufactured by Keyence, the fiber block 11 was placed and fixed thereon, the outer shape of the fiber block 11 was determined in accordance with the above-described determination of the outer shape, the length of the amount of extension in the fiber 11F extending from the outer shape was measured, and the length of the amount of extension thus measured was used as the length of extension of the extended fiber bundle portion 113S.

The extended fiber bundle portion 113S is preferably formed by thermally fusing the plurality of constituent fibers 11F to each other. The heat-fused portion of the extended fiber bundle portion 113S is generally longer in radial length (span) in a direction perpendicular to the longitudinal direction of the extended fiber bundle portion 113S (diameter when the cross section of the heat-fused portion is circular) than other portions (non-heat-fused portions) of the extended fiber bundle portion 113S. By providing the extended fiber bundle portion 113S with such a heat fusion portion, which may also be referred to as a large diameter portion, the strength of the extended fiber bundle portion 113S itself is increased, and thus the entanglement of the fiber masses 11 or the entanglement of the fiber masses 11 and the water-absorbent fibers 12F, which are entangled through the extended fiber bundle portion 113S, is further enhanced. Further, if the extended fiber bundle portion 113S has a heat fusion bonded portion, the following advantages are obtained: the strength, shape retention property, and the like of the drawn fiber bundle portion 113S itself can be improved not only when the drawn fiber bundle portion 113S is in a dry state but also when the drawn fiber bundle portion 113S absorbs moisture and becomes in a wet state. By utilizing this advantage, when the absorbent core 40 is applied to an absorbent article, the above-described operational effect due to the presence of the fiber pieces 11 can be stably exhibited even when the absorbent core 40 is in a dry state and is in a wet state by absorbing body fluid such as urine or menstrual blood excreted by a wearer. The extended fiber bundle portion 113S having the heat-fusion bonded portion can be produced by using "a fiber sheet having a heat-fusion bonded portion constituting fibers" as the raw fiber sheet 10bs in the production process of the fiber block 11 shown in fig. 6, that is, in the cutting process of the raw fiber sheet 10bs of the fiber block 11.

The constituent fibers 11F of the fiber block 11 include synthetic fibers. The synthetic fibers used as the fibers 11F preferably have a water absorption property lower than that of the water-absorbent fibers 12F (weak water absorption property), and particularly preferably are non-water-absorbent synthetic fibers. The constituent fibers 11F of the fiber block 11 may contain fiber components (e.g., natural fibers) other than synthetic fibers, and by including the weakly hydrophilic fibers, preferably non-water-absorbent fibers, in the constituent fibers 11F of the fiber block 11, the above-described operational effects (improvement effects of shape retention, flexibility, cushioning properties, compression recovery properties, resistance to twisting, and the like) due to the presence of the fiber block 11 can be stably exhibited not only when the absorbent core 40 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, the above-described effects due to the presence of the fiber mass 11 can be more stably exhibited.

In the present specification, the term "water-absorbing property", for example, pulp may mean water-absorbing property, and those skilled in the art can easily understand it. Similarly, it can be easily understood that the thermoplastic fibers are weakly water-absorbent (particularly, non-water-absorbent). On the other hand, the degree of water absorption of the fibers can be compared with the relative difference in water absorption by the value of the water fraction measured by the following method, and a more preferable range can be defined. The larger the value of the water content, the stronger the water absorption of the fiber. The water content of the water-absorbent fibers is preferably 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 as 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, after a fiber sample was left to stand in a laboratory at a temperature of 40 ℃ and a relative humidity of 80% RH for 24 hours, the weight W (g) of the fiber sample before the absolute drying treatment was measured in the laboratory. Thereafter, the fiber sample was allowed to stand still for 1 hour in an electric drier (manufactured by fifty-bell manufacturing Co., Ltd., for example) at a temperature of 105. + -. 2 ℃ to thereby dry the fiber sample absolutely. After the absolute drying treatment, a silica gel (e.g., Toyota chemical Co., Ltd.) was placed in a glass dryer (e.g., Tech jam Co., Ltd.) in a state in which a fiber sample was wrapped with Saran Wrap (registered trademark) manufactured by Asahi chemical Co., Ltd.) in a laboratory in a standard state in which the temperature was 20. + -. 2 ℃ and the relative humidity was 65. + -. 2%, and the fiber sample was allowed to stand until the temperature became 20. + -. 2 ℃. Thereafter, the constant W' (g) of the fiber sample was weighed, and the water content of the fiber sample was determined according to the following equation. Water content (%) (W-W '/W') × 100.

Similarly, the fiber block 11 preferably has a three-dimensional structure in which a plurality of thermoplastic fibers are thermally fused to each other, from the viewpoint that the absorbent core 40 can exhibit excellent effects in shape retention, flexibility, cushioning properties, compression recovery properties, resistance to twisting, and the like in both the dry state and the wet state.

In order to obtain such a fiber mass 11 in which a plurality of heat fusion portions are three-dimensionally dispersed, the synthetic fibers used as the constituent fibers 11F of the fiber mass 11 are preferably thermoplastic fibers. As described above, the extended fiber bundle portion 113S preferably has the heat fusion bonded portion, and the preferable form of the extended fiber bundle portion 113S can be obtained by using the thermoplastic fiber as the constituent fiber 11F of the fiber block 11.

The raw material fiber sheet 10bs (see fig. 6) may be configured similarly 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 may be produced by subjecting a web or nonwoven fabric mainly composed of thermoplastic fibers to heat treatment such as hot air treatment as described above.

As the non-water-absorbent synthetic resin (thermoplastic resin) which is preferable as a material of the fibers 11F constituting the fiber block 11, for example, there can be mentioned: 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 kind of these may be used alone or 2 or more kinds may be used in combination. The fibers 11F may be single fibers composed of 1 kind of synthetic resin (thermoplastic resin) or blended polymers of 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 synthetic resins having different components by a spinning head, and bonding the synthetic fibers to each other in a single fiber in a structure in which the components are continuous in the longitudinal direction of the fiber. The form of the composite fiber is not particularly limited, and includes a core-sheath type, a side-by-side type, and the like.

In addition, from the viewpoint of further improving the drawing-in property of the body fluid discharged at the initial stage, 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 non-water-absorbent synthetic fibers with a hydrophilizing agent in accordance with a conventional 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 respect to the fiber was measured. An automatic contact angle meter MCA-J manufactured by covex interface science corporation was used as a measuring device. Deionized water was used in the contact angle measurement. The amount of liquid discharged from an ink-jet type water droplet discharge unit (pulse jet CTC-25 having a discharge unit hole diameter of 25 μm manufactured by Cluster Technology) was set to 20 picoliters, and water droplets were dropped directly above the fibers. The dripping was recorded in a high-speed video recording device connected to a horizontally arranged video camera. From the viewpoint of performing image analysis later, the recording device is preferably a personal computer in which a high-speed capture device is incorporated. In this measurement, images were recorded every 17 msec. In the video obtained by the video recording, the first image in which the water droplet was attached to the fiber was subjected to image analysis by attached software FAMAS (version of software is 2.6.2, analysis method is a droplet method, analysis method is a θ/2 method, image processing algorithm is no reflection, image processing image mode is a frame, threshold level (threshold level) is 200, and curvature correction is not performed), 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 to a fiber length of 1mm, and the fiber was placed on a sample stage of a contact angle meter and maintained at a horizontal state. The contact angles at 2 different sites were measured for each 1 fiber. The contact angle between the fiber and water was defined as the value obtained by measuring the contact angle of 5N atoms to 1 position after the decimal point and averaging the measured values of 10 positions (rounding off the 2 nd position after the decimal point). The measurement environment was set at room temperature 22. + -. 2 ℃ and humidity 65. + -. 2% RH.

In addition, 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 an adhesive, welding, or the like, the adhesive force is removed from the fixed portion by a method such as cold air blowing a cold spray in a range that does not affect the contact angle of the fibers, and then the absorbent body is taken out. This processing order is common throughout the measurements in this specification.

As the water-absorbent fibers 12F, those conventionally used as a material for forming an absorbent body of such an absorbent article 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. As described above, in view of the main role of the water-absorbent fibers 12F to improve the liquid absorbency of the absorbent body 4, natural fibers and regenerated fibers (cellulose fibers) are preferable as the water-absorbent fibers 12F.

In the absorbent body 4, the content mass ratio of the fiber mass 11 and the water-absorbent fibers 12F is not particularly limited, 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 mass 11, and the like. For example, when the constituent fibers 11F of the fiber mass 11 are thermoplastic fibers (non-water-absorbent synthetic fibers) and the water-absorbent fibers 12F are cellulose-based water-absorbent fibers, the mass ratio of the fibers 11 and the water-absorbent fibers 12F is preferably 20/80 to 80/20, more preferably 40/60 to 60/40, in terms of more reliably exhibiting the specific effects of the present invention, when expressed by the mass ratio of the former (fiber mass 11)/the latter (water-absorbent fibers 12F).

The content of the fiber mass 11 in the absorbent body 4 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 body 4 in a dry state.

The content of the water-absorbent fibers 12F in the absorbent body 4 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 body 4 in a dry state.

The grammage of the fiber mass 11 in the absorbent body 4 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 body 4 is preferably 32g/m²Above, more preferably 80g/m²Above, and preferably 640g/m²Hereinafter, more preferably 480g/m²The following.

The absorbent body 4 can be manufactured in the same manner as an absorbent body containing such a fibrous material. As described above, the fiber block 11 can be produced by cutting a raw material fiber piece (a piece having the same composition as the fiber block 11 and a larger size than the fiber block 11) as a raw material in 2 mutually intersecting (orthogonal) directions by using a cutting mechanism such as a cutter as shown in fig. 6, and the plurality of fiber blocks 11 thus produced are a "shaped fiber aggregate" (for example, the body portion 110 is in a rectangular parallelepiped shape) having a uniform shape and size. The absorbent body 4 containing the fiber mass 11 and the water-absorbent fibers 12F can be manufactured by a usual method using a known fiber stacking apparatus having a drum, for example. Typically, the fiber stacking apparatus includes a drum having a collecting recess formed in an outer peripheral surface thereof, and a duct having a flow path therein for conveying the raw material (the fiber mass 11 and the water-absorbent fibers 12F) of the absorbent core 40 to the collecting recess, and accumulates the raw material conveyed by an air flow (vacuum air) generated in the flow path by suction from an inner side of the drum to the collecting recess while rotating the drum around a rotation axis in a drum circumferential direction. The fiber-laminated material formed in the collecting recess by this fiber-laminating step is the absorbent core 40.

The grammage of the absorbent body 4 may be appropriately adjusted depending on the use thereof and the like. For example, when the absorbent body 4 is used as an absorbent body of an absorbent article such as a disposable diaper or a sanitary napkin, the grammage of the absorbent body 4 is preferably 100g/m²Above, more preferably 200g/m²Above, and preferably 800g/m²Hereinafter, more preferably 600g/m²The following. As described above, the grammage of the absorbent body 4 shown here can be applied directly to the absorbent core 40.

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 includes the absorbent core 40 and the core sheet 41 covering the same, but the core sheet 41 may not be included.

The absorbent core of the present invention may not be a fiber aggregate in which all of the fiber masses (synthetic fiber aggregates) contained therein are set like the fiber mass 11, and may contain a very small amount of amorphous fiber aggregates in addition to the set fiber aggregate, without departing from the scope of the present invention.

The absorbent article of the present invention widely includes articles for absorbing body fluid (urine, loose stools, menstrual blood, sweat, etc.) discharged from a human body, and includes menstrual shorts, so-called open-type disposable diapers with fastening tapes, pant-type disposable diapers, incontinence pads, and the like in addition to the above-described menstrual sanitary napkins. The following remarks are further disclosed with respect to the above embodiments of the present invention.

[ 1] an absorbent body which is used in direct or indirect contact with the skin, which has a skin-facing surface disposed at a position relatively close to the skin of a user during use and a non-skin-facing surface disposed at a position relatively far from the skin of the user, the absorbent body comprising a mass of synthetic fibers and water-absorbent fibers, and a plurality of the mass of synthetic fibers being entangled with each other or the mass of synthetic fibers being entangled with the water-absorbent fibers, wherein the mass ratio of the mass of synthetic fibers to the mass of water-absorbent fibers on the side of the skin-facing surface is smaller than the mass ratio of the mass of synthetic fibers to the mass of water-absorbent fibers on the side of the non-skin-facing surface.

< 2 > the absorbent body according to the above < 1 >, wherein the mass ratio of the fiber mass to the water-absorbent fibers increases gradually from the skin-facing surface side toward the non-skin-facing surface side.

< 3 > an absorbent body which is used in direct or indirect contact with the skin, which has a skin-facing surface disposed at a position relatively close to the skin of a user when in use, and a non-skin-facing surface disposed at a position relatively far from the skin of the user, wherein the absorbent body comprises a mass of synthetic fibers and water-absorbent fibers, and a plurality of the mass of synthetic fibers are entangled with each other or the mass of synthetic fibers and the water-absorbent fibers are entangled with each other, and wherein the ratio of the mass of synthetic fibers contained on the skin-facing surface side to the total mass of the mass of synthetic fibers and the water-absorbent fibers is smaller than the ratio of the mass of synthetic fibers contained on the non-skin-facing surface side to the total mass of the mass of synthetic fibers and the water-absorbent fibers. (that is, the non-skin-facing surface side is larger than the skin-facing surface side).

< 4 > the absorbent body according to the above < 3 >, 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 gradually increases from the skin-facing surface side to the non-skin-facing surface side.

< 5 > the absorbent body according to any one of the above < 1 > to < 4 >, 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 is 0 mass% or more and 60 mass% or less on the skin-facing surface side, 50 mass% or more and 100 mass% or less on the non-skin-facing surface side, and the difference between the mass content and the total mass content is 15 mass% or more.

< 6 > the absorbent body as described in the above < 5 >, wherein the difference is 80% by mass or more.

< 7 > the absorbent body as described in any of above < 1 > to < 6 >, wherein said fibrous mass has a main body portion defined by 2 opposing base faces and a skeleton face intersecting both of the base faces.

< 8 > the absorbent body as stated above < 7 > wherein the total area of said 2 base faces is greater than the total area of said skeleton faces.

< 9 > the absorbent article according to the above < 7 > or < 8 >, wherein said base surface has a rectangular shape in plan view, and the shorter side of the rectangular shape is equal to or shorter than the thickness of said absorbent article.

< 10 > the absorbent body according to the above < 9 >, wherein the length of the short side of the base face is 0.3mm or more, preferably 0.5mm or more, and 10mm or less, preferably 6mm or less.

[ 11 ] the absorbent body according to the above-mentioned < 9 > or < 10 ], wherein the length of the long side of the base face is 0.3mm or more, preferably 2mm or more, and 30mm or less, preferably 15mm or less.

< 12 > the absorbent body as described in any one of the above < 7 > to < 11 >, wherein the number per unit area of fiber ends present on each of the base face and the skeleton face satisfies the following relationship: the number per unit area of the fiber ends of the skeleton face is greater than the number per unit area of the fiber ends of the basic face.

< 13 > the absorbent body according to any one of the above < 7 > to < 12 >, wherein the number N per unit area of the fiber ends present in said base surface₁And the number N per unit area of fiber ends present on the skeleton surface₂Ratio N of₁/N₂Is 0 to 0.90, preferably 0.05 to 0.60.

< 14 > the absorbent body according to any one of the above < 7 > to < 13 >, wherein the number of the fiber ends per unit area present on the base surface is 0 or more and 8 or less, preferably 3 or more and 6 or less.

< 15 > the absorbent body according to any one of the above < 7 > to < 14 >, wherein the number of fiber ends per unit area present on the framework surface is 5 or more and 50 or less, preferably 8 or more and 40 or less.

< 16 > the absorbent body according to any one of the above < 7 > to < 15 >, wherein the fibrous mass has a spread fiber part comprising fibers extending outward from the main body part and having a lower fiber density than the main body part.

< 17 > the absorbent body as stated in above < 16 >, wherein at least one of said extended fiber parts is an extended fiber bundle part comprising a plurality of fibers extending outward from said chassis.

< 18 > the absorbent body according to any one of the above < 1 > to < 17 >, wherein the skin-facing surface side contains a water-absorbent polymer.

< 19 > the absorbent material according to any one of the above < 1 > to < 18 >, wherein the mass ratio of the fiber mass to the water-absorbent fiber is 20/80 to 80/20 in terms of the former/latter.

< 20 > the absorbent body according to any one of the above < 1 > to < 19 >, wherein the synthetic fibers contained in the fiber mass are non-absorbent.

< 21 > the absorbent material according to any one of the above < 1 > to < 20 >, wherein said water-absorbent fibers are cellulose-based water-absorbent fibers.

< 22 > the absorbent article according to any one of the above < 1 > to < 21 >, wherein the contact angle of the fiber mass with water is less than 90 degrees, preferably 70 degrees or less.

< 23 > the absorbent body as described in the above < 22 >, wherein the fiber mass is subjected to a treatment with a hydrophilizing agent.

< 24 > the absorbent body as described in any of above < 1 > to < 23 >, wherein the absorbent body comprises an absorbent core and a core-wrapped sheet.

< 25 > the absorbent body according to any one of the above < 1 > to < 24 >, wherein the fiber mass is present in the absorbent body in a state of being entangled with other fiber masses or the water-absorbent fibers in addition to being bonded to the other fiber masses or the water-absorbent fibers by entanglement.

< 26 > the absorbent body according to the above < 25 >, wherein the total number of the fiber mass bonded by entanglement and the fiber mass in an entangled state is preferably at least half, more preferably at least 70%, and further preferably at least 80% of the total number of the fiber masses in the absorbent body.

< 27 > the absorbent body according to any one of the above < 1 > to < 26 >, wherein the bonded portions are formed by entanglement of fibers in 70% or more, more preferably 80% or more of the total number of the fiber masses having bonded portions with other fiber masses or the water-absorbent fibers.

< 28 > the absorbent body according to any one of the above < 1 > to < 27 >, wherein the fiber mass is derived from a nonwoven fabric.

< 29 > an absorbent article comprising the absorbent body as described in any one of the above < 1 > to < 28 >.

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]

A catamenial sanitary napkin having the same basic structure as the sanitary napkin 1 shown in fig. 1 was made.

Using a grammage of 30g/m²The hot-air nonwoven fabric used as the front sheet had a grammage of 37g/m²The polyethylene resin film (FL-KDJ100nN, industrially produced for mass production) was used as a back sheet. The absorbent body uses fiber blocks and absorbent fibers as fiber materials of the absorbent core, and further uses separately prepared fiber materials with a grammage of 16g/m²And manufactured according to a general method using a known fiber accumulating apparatus. Production of fiber block the raw material fiber sheet was cut into small square blocks according to fig. 6. The arrangement of the fibrous materials (fiber mass, water-absorbent fiber) in the absorbent body of example 1 was such that the fiber mass occupancy and the fiber mass ratio gradually increased from the skin-facing surface side to the non-skin-facing surface side of the absorbent body, as in the absorbent body 4 shown in fig. 3.

As a raw material fiber sheet of the fiber block, a non-water-absorbent thermoplastic fiber comprising polyethylene and a polyethylene terephthalate resin was treated with the following composition A to obtain a fiber having a grammage of 21g/m (contact angle with water of 68 degrees) as a constituent fiber²The hot air nonwoven fabric (a fiber sheet having a heat-fused part of fibers) of (1). As the water-absorbent fiber, bleached softwood kraft pulp (NBKP) was used. The fiber block (shaped synthetic fiber aggregate) used in the absorbent body has a rectangular parallelepiped body portion as shown in fig. 5(a), and the short side 111a of the basic surface 111 is 0.8mm, the long side 111b is 3.9mm, and the thickness T is 0.6 mm. Further, the number per unit area of the fiber ends of the base surface 111 was 3.2 pieces/mm²The number of fiber ends per unit area of the skeleton face 112 was 19.2 pieces/mm²。

(composition of composition A)

Potassium alkyl phosphate (potassium hydroxide neutralized product of Gripper 4131 manufactured by queen gmbh): 25% by mass

Dialkyl sulfosuccinic acid sodium salt (Pelex OT-P, manufactured by queen gmbh): 10% by mass

Alkyl (stearyl) betaine (ampithiol 86B manufactured by queen gmbh): 15% by mass

Polyoxyethylene (addition mol number: 2) stearyl amide (Amisol SDE manufactured by Kawaken Fine Chemicals): 30% by mass

Polyoxyethylene/polyoxypropylene-modified Silicone (X-22-4515, manufactured by shin Etsu chemical Co., Ltd.) 20% by mass

[ example 2]

A catamenial napkin was produced in the same manner as in example 1 except that the arrangement of the fibrous materials (fiber masses, water-absorbent fibers) in the absorbent body was such that 2 regions having different fiber mass occupancy and fiber mass ratio in the thickness direction were arranged in the same manner as in the absorbent body 4A shown in fig. 4, and example 2 was used. That is, in the absorbent body of the catamenial napkin of example 2, the skin-facing surface side is the superabsorbent fiber portion 12P, the non-skin-facing surface side is the mass portion 11P, and the

portions

12P and 11P are bonded to each other at the interface therebetween by entanglement of the constituent fibers, and the interface is located at the center in the thickness direction of the absorbent body.

[ example 3]

In example 2, a catamenial napkin of example 3 was produced with the same absorbent body except that the fiber mass occupancy of the superabsorbent fiber portion 12P was 0 mass%, that is, the absorbent fiber content on the skin-facing surface side of the absorbent body was 100 mass%, and the fiber mass occupancy of the superabsorbent fiber portion 11P was 100 mass%, that is, the absorbent fiber occupancy on the non-skin-facing surface side of the absorbent body was 0 mass%.

[ example 4]

In example 3, the fiber block was changed to 0.8mm in the short side 111a, 5.0mm in the long side 111b, and 0.6mm in thickness of the base surface 111. In the modified fiber block, the number per unit area of the fiber ends was the same as in example 2. Except for the above points, a catamenial sanitary napkin including the same absorbent body as in example 3 was produced and assumed to be example 4.

Comparative example 1

An absorbent body of a commercially available sanitary napkin for menstrual period (manufactured by Uygur Corp., trade name "Tanom Pew Slim 23 cm") was used as it is as comparative example 1. The absorbent material of comparative example 1 was a mixture of synthetic fibers and cellulose fibers (water-absorbent fibers), and contained no fiber mass.

Comparative example 2

A catamenial napkin was produced in the same manner as in example 1 except that the absorbent body was changed to the following configuration with reference to patent document 1, and this was designated as comparative example 2.

The absorbent body used in comparative example 2 was the same as the absorbent body used in example 1, except that an amorphous nonwoven fabric sheet was used as the fiber block in the absorbent core, the absorbent core was covered with the core sheet, and then hot air processing was performed to thermally bond the nonwoven fabric sheets contained in the absorbent core to each other. In the hot air treatment step of the absorber, the mixed assembly of the nonwoven fabric sheet and the pulp fiber (length 210mm × width 66mm) was allowed to stand in an electric dryer (e.g., those manufactured by fifty-boll corporation) at a temperature of 150 ℃ for 600 seconds to thermally bond the nonwoven fabric sheets to each other. The amorphous nonwoven fabric sheet used was produced by tearing the same nonwoven fabric as the through-air nonwoven fabric used in examples 1 and 2 in any direction, and had a diametral length of approximately 25mm in plan view.

[ Performance evaluation ]

For the catamenial sanitary napkins of each example and comparative example, the compression work (w-WC), the distortion rate and the surface diffusion area in the wet state were measured by the following methods, respectively. In example 4, the recovery work in the dry state (d-WC') and the compressive strain rate in the dry state (d- Δ T/T) were also measured by the following methods₀). The results are shown in table 1 below.

< measurement method of compression Work (WC) >

Generally, it is known that the compression Work (WC) of a sample can be expressed by a measurement value obtained by KES (Kawabata Evaluation System, Chuanchuan Evaluation System) manufactured by Kato Tech Co., Ltd. (reference: standardization and analysis of texture Evaluation (2 nd edition), Kawabata Kogyo, published 7/10 th 1980). Specifically, compression Work (WC) and compression Recovery (RC) were measured using an automated compression test apparatus KES-G5 manufactured by Kato Tech corporation. The measurement sequence is as follows.

An absorbent article (sanitary napkin) including an absorbent body as a sample was attached to a test stand of a compression test apparatus. Next, the sample was measured to have an area of 2cm²The steel plates of the circular plane are compressed. The compression speed was set to 0.02cm/sec, and the maximum compressive load was set to 490mN/cm². The recovery process is also measured at the same speed. The compression Work (WC) is expressed by the following formula, and the unit is mN.cm/cm²". In the formula, T_m、T₀And P_aRespectively represent 490mN/cm²Thickness under load, 4.9mN/cm²Thickness under load and load (mN/cm) under measurement (compression process)²)。

The compression work thus calculated is the compression work (w-WC) in the wet state of the sample. The larger the value of w-WC, the higher the cushioning property, and the higher the evaluation.

[ formula 1]

The "absorbent article having an absorbent body in a wet state" as a measurement target in the above measurement method is adjusted in the following manner. First, the absorbent article before injection of the defibered horse blood was left to stand in an atmosphere of air temperature 23 ℃ and relative humidity 50% RH for 24 hours to adjust the 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 (50 mm long diameter, 23mm short diameter) was placed on the topsheet, 3.0g of defibered horse blood was injected through 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 defibered horse blood injected into the measurement object was the same as horse blood prepared in the following < method for measuring surface diffusion area >.

< method for measuring restoring Work (WC) >

The work of recovery (WC') of the sample can be measured using the KES described above. Specifically, the recovery work (WC') was measured using an automated compression test apparatus KES-G5 manufactured by Kato Tech corporation. The measurement sequence is as follows.

An "absorbent article having an absorbent body (sanitary napkin)" as a sample was attached to a test stand of a compression test apparatus. Next, the sample was measured to have an area of 2cm²The steel plates of the circular plane are compressed. The compression speed was set to 0.2cm/sec, and the maximum compression load was set to 2450mN/cm². The recovery process is also measured at the same speed. The recovery work (WC') is expressed by the following formula, and the unit is mN.cm/cm²". In the formula, T_m、T₀And P_bRespectively shows 2450mN/cm²Thickness under load, 4.9mN/cm²Thickness at load and load at measurement (recovery process) (mN/cm)²)。

[ formula 2]

The recovery work (WC ') is not displayed on the measurement result screen of the KES-G5, and the compression recovery Ratio (RC) calculated from the compression Work (WC) and the recovery work (WC') is displayed on the measurement result screen. At this time, the recovery work (WC') was calculated from the following equation using the parameters (WC, RC) displayed in the measuring device.

[ formula 3]

WC′＝RC×WC÷100

The above "recovery work in a dry state (d-WC ')" absorbent article in a dry state (sanitary napkin) "was used as a sample in the above measurement method of < recovery work (WC'). The absorbent body included in the absorbent article in the dry state is not used, and the unabsorbed liquid is in a dry state. According to the study by the present inventors, it was judged that the larger the value of d-WC', the higher the compression recovery property in the dry state of the absorbent body, and the higher the evaluation.

< compressive strain rate (DeltaT/T)₀) Method of measuring

Compressive strain rate (DeltaT/T) of test specimen₀) Can be usedThe KES described above performs the measurements. Specifically, the compressive strain rate (. DELTA.T/T) was measured using an automated compression test apparatus KES-G5 manufactured by Kato Tech corporation₀). The measurement sequence is as follows.

An absorbent article (sanitary napkin) including an absorbent body as a sample was attached to a test stand of a compression test apparatus. Next, the sample was measured to have an area of 2cm²The steel sheets are compressed between the steel sheets in a circular plane, the load during the compression is gradually increased, and the thickness (compressed thickness) T of the object to be measured at the time when the load reaches a predetermined maximum value (maximum load) is measured_m. Care was taken to prevent the object to be measured from wrinkling or bending. 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 (T) of the object is measured₀) The load was set to 103.9mN/cm²The thickness at the moment of time. The compressive strain rate (%) was calculated from the following formula.

Compressive strain rate (DeltaT/T)₀)＝{(T₀－T_m)/T₀)}×100

The above "compressive strain rate in the dry state (d- Δ T/T)₀) ", by applying < compressive strain rate (Δ T/T) as described above₀) The measurement was carried out using "absorbent article in a dry state (sanitary napkin)" as a sample. The absorbent body included in the absorbent article in the dry state is not used, and the unabsorbed liquid is in a dry state. According to the study of the present inventors, d-. DELTA.T/T₀The larger the value of (b) is, the higher the flexibility of the absorbent body in a dry state is, and the higher the evaluation is.

d-WC' and d- Δ T/T as described above₀Are set to 10 times the speed of the general condition of KES-G5, respectively. According to the study by the inventors, the measurement conditions can better reflect the actions of the wearer such as walking and sitting.

< method for measuring torsional curvature >

The distortion rate of the sanitary napkin for menstrual period was evaluated by 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 shorts 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 for 15 seconds after walking for 3 minutes, and this operation was repeated 6 times, and 9g in total of defibered horse blood was injected into the sanitary napkin. Then, the sanitary napkin was removed from the pants, the center width (center width after walking) was measured, and the distortion (%) was calculated from the center width before walking and the center width after walking according to the following equation. The smaller the value of the distortion rate, the less likely the sanitary napkin is distorted, and the higher the evaluation. The defibered horse blood injected into the measurement object was the same as horse blood prepared in the following < method for measuring surface diffusion area >.

Torsion rate [ { (center width before walking) - (center width after walking) } ÷ (center width before walking) ] × 100

< method for measuring surface diffusion area >

The measurement subject (sanitary napkin) was fixed on a slant having an angle of 45 ° with respect to the horizontal plane with its skin-facing surface facing the slant, and the following operations were performed: after 1.5g of horse blood for defibrination was injected to the skin-facing surface of the subject over 23 seconds, and after leaving for 3 minutes, the same amount of horse blood for defibrination was injected again to the same injection site over the same period of time. The procedure of injecting and leaving the defibrinated horse blood was repeated 6 times, and a total of 9g of the defibrinated horse blood was injected into the measurement object. After the injection operation is completed, the diffusion area of the defibered horse blood on the skin-facing surface of the measurement object is measured and set as the surface diffusion area of the measurement object.

The method of measuring the < surface diffusion area > described above was supplemented with reference to fig. 8, and the measurement object S (sanitary napkin) was a planar quadrangular shape of 240mm × 75 mm. The measuring table 100 for measurement has a slope 100a at an angle θ of 45 ° to the horizontal plane. The measurement object S is placed on the inclined surface 100a so that the skin-facing surface thereof faces the inclined surface 100a, and an acrylic plate 101 having an area larger than the thickness of the measurement object S by 3mm is placed on the measurement object S. The viscosity of the defibrinated horse blood injected as the dummy blood into the measurement object S was 8 mPas as measured by using a type B viscometer (model TVB-10M manufactured by Toyobo industries Co., Ltd., measurement conditions: rotor No.19, 30rpm, 25 ℃ C., 60 seconds). As such defibrinated horse blood, for example, defibrinated horse blood manufactured by Nippon Bio-test Laboratories, ltd, can be used, and the viscosity can be adjusted to the above-mentioned predetermined range by adjusting the ratio of blood cells, plasma, and the like as necessary. The injection position of the defibrinated horse blood in the measurement object S was set as the center portion (the portion indicated by the arrow in fig. 8) of the skin-facing surface of the measurement object S, and the injection was performed using a not-shown micro-tube pump (manufactured by tokyo physical and chemical instruments co. A tube, not shown, is connected to the pump, an end portion of the tube opposite to the side connected to the pump is connected to the measurement target S on the inclined surface 100a, and the defibrinated horse blood is injected into the measurement target S through the tube. The diffusion area of the defibered horse blood in the skin-facing surface of the measurement subject S can be measured as follows: an OHP sheet is processed by drawing a distribution region of defibrinated horse blood of the measurement object S thereon according to a conventional method using image analysis software nexusnewquery (manufactured by Nexus corporation).

[ Table 1]

﹡ 1: average of diameter length of unshaped fiber block

As shown in table 1, in each example, since a plurality of fiber masses are entangled with each other or a fiber mass and a water-absorbent fiber are entangled with each other and a size relationship of "non-skin-facing surface side > skin-facing surface side" is established with respect to the fiber mass occupancy, the value of compression work w — WC in a wet state is larger than in comparative examples 1 and 2 which do not satisfy this condition, and therefore, the cushioning property is excellent, and the twist rate is small, so that the twist is not easily generated, and the liquid intake property is excellent due to the size relationship. In particular, as is clear from a comparison between each example and comparative example 2, in order to obtain an absorbent body having a large compression work in a wet state and excellent cushioning properties, it is effective to set fiber masses and to bond the fiber masses to each other by entanglement.

Industrial applicability

The absorbent body of the present invention has high cushioning properties, is less likely to be twisted, has excellent liquid intake properties, and can improve the wearing feeling when applied to an absorbent article.

Further, the absorbent article of the present invention includes the high-quality absorbent body, and therefore, is excellent in wearing feeling and leakage prevention.

Claims

1. An absorbent body that is used in direct or indirect contact with the skin, and that has a skin-facing surface that is disposed at a position relatively close to the skin of a user when in use, and a non-skin-facing surface that is disposed at a position relatively far from the skin of the user, the absorbent body characterized in that:

the absorbent body comprises fiber blocks containing synthetic fibers and water-absorbent fibers, a plurality of the fiber blocks are entangled with each other or the fiber blocks are entangled with the water-absorbent fibers,

the ratio of the mass content of the fiber mass on the non-skin-facing surface side to the total mass content of the fiber mass and the water-absorbent fibers is larger than the ratio of the mass content of the fiber mass on the skin-facing surface side to the total mass content of the fiber mass and the water-absorbent fibers,

the fiber block is a shaped fiber aggregate having a main body portion defined by 2 opposing base faces and a skeleton face intersecting the two base faces,

a plurality of the fiber blocks are intertwined with each other at the base face and the skeleton face,

the number per unit area of fiber ends present in each of the base face and the skeleton face satisfies the following relationship: the number per unit area of the fiber ends of the skeleton face is greater than the number per unit area of the fiber ends of the basic face,

the fiber block is in the shape of a quadrangular prism.

2. The absorbent 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 gradually increases from the skin-facing surface side to the non-skin-facing surface side.

3. The absorbent body according to claim 1 or 2, 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 is 0 mass% or more and 60 mass% or less on the skin-facing surface side, 50 mass% or more and 100 mass% or less on the non-skin-facing surface side, and the difference between the mass content and the total mass content is 15 mass% or more.

4. An absorbent body according to claim 3, wherein:

the difference is 80 mass% or more.

5. The absorbent of claim 1, wherein:

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

6. The absorbent body according to claim 1 or 2, wherein:

the base surface has a rectangular shape in plan view, and the short side of the rectangular shape is equal to or shorter than the thickness of the absorbent body.

7. The absorbent body according to claim 1 or 2, wherein:

the number per unit area of the fiber ends present in the base surface N₁And the number N per unit area of fiber ends present on the skeleton surface₂Ratio N of₁/N₂Is 0 to 0.90 inclusive.

8. The absorbent of claim 7, wherein:

the ratio N₁/N₂Is 0.05 to 0.60 inclusive.

9. The absorbent body according to claim 1 or 2, wherein:

the number of fiber ends per unit area present on the base surface is 0 or more and 8 or less.

10. The absorbent body according to claim 1 or 2, wherein:

the number of fiber ends per unit area present on the skeleton surface is 5 or more and 50 or less.

11. The absorbent body according to claim 1 or 2, wherein:

the fiber block has an extended fiber portion including fibers extending outward from the main body portion, and having a lower fiber density than the main body portion.

12. The absorbent of claim 11, wherein:

at least one of the extended fiber portions is an extended fiber bundle portion including a plurality of fibers, which extends outward from the skeleton surface.

13. The absorbent body according to claim 1 or 2, wherein:

the skin-facing surface side contains a water-absorbent polymer.

14. The absorbent body according to claim 1 or 2, wherein:

the mass ratio of the fiber mass to the water-absorbent fiber is 20/80-80/20 in terms of the former/latter.

15. The absorbent body according to claim 1 or 2, wherein:

the synthetic fibers contained in the fiber mass are non-water-absorbent.

16. The absorbent body according to claim 1 or 2, wherein:

the water-absorbent fiber is a cellulose-based water-absorbent fiber.

17. The absorbent body according to claim 1 or 2, wherein:

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

18. The absorbent body of claim 17, wherein:

the fiber block was subjected to a treatment with a hydrophilizing agent.

19. The absorbent body according to claim 1 or 2, wherein:

the absorbent body includes an absorbent core and a core-spun sheet.

20. The absorbent body according to claim 1 or 2, wherein:

the fiber mass is bonded to another fiber mass or the water-absorbent fiber by entanglement in the absorbent body, and is also present in a state of being capable of being entangled with another fiber mass or the water-absorbent fiber.

21. The absorbent of claim 20, wherein:

the total number of the fiber pieces bonded by entanglement and the fiber pieces in an entangled state is at least half of the total number of the fiber pieces in the absorbent body.

22. The absorbent body according to claim 1 or 2, wherein:

and a fiber block having a bonding portion with the other fiber blocks or the water-absorbent fibers, the bonding portion being formed by entanglement of fibers, in which 70% or more of the total number of the fiber blocks is present.

23. The absorbent body according to claim 1 or 2, wherein:

the fiber blocks are from non-woven fabrics.

24. An absorbent article characterized by:

comprising the absorbent body according to any one of claims 1 to 23.