JP4979424B2 - Absorbent articles - Google Patents

Description

  The present invention relates to an absorbent article.

Conventionally, in an absorbent article such as a sanitary napkin, in order to improve the fit to the wearer's body, the absorbent article is formed with a protruding part protruding to the skin contact surface side in the center in the width direction. Are known. Moreover, in order to make the protrusion fit flexibly to the wearer, an absorbent article (see Patent Document 1) in which the protrusion is given a cushioning property is known.
Moreover, the top sheet which coat | covers the primary absorption member which exists in the inside of a protrusion part, and the secondary absorption member which exists in a main-body part so that a primary absorption member may be wrapped, and the top sheet which coat | covers the upper surface of a secondary absorption member An absorbent article separated by a top sheet (see Patent Document 2) has been proposed.

Japanese Utility Model Publication No. 3-118727 Japanese National Patent Publication No. 10-504486

However, in the absorbent article described in Patent Document 1, a hydrophobic cushion material is disposed inside the protrusion in a state of being wrapped in an absorbent sheet containing a polymer absorbent, and the skin of the protrusion The absorbent sheet is located in the vicinity of the contact surface. In addition, the presence of the hydrophobic cushion material restricts the transfer of liquid from the absorbent sheet near the skin contact surface to the absorbent layer located below the cushion material. Therefore, the liquid held in the absorbent sheet in the vicinity of the skin contact surface is likely to wet back (liquid return) to the skin contact surface, and stuffiness and stickiness are likely to occur.
Moreover, in the absorbent article described in Patent Document 2, the two top sheets that are separated from the primary absorbent member and the secondary absorbent member are formed of an apertured film, and the protrusions are inferior in cushioning properties. Further, the primary absorbent member and the secondary absorbent member are separated from each other by a top sheet made of an apertured film, and the liquid is not actively transferred from the primary absorbent member to the secondary absorbent member. Therefore, the protrusion in the absorbent article described in Patent Document 2 is inferior in cushioning properties, and is less prone to stuffiness and stickiness.

  Accordingly, an object of the present invention is to have an excellent cushioning property, have a protruding portion that shows a good fit by flexibly following the movement of the wearer's skin, has a small liquid spread, and absorbs less easily. To provide an article.

  An absorbent article comprising an absorbent layer between a top sheet and a back sheet, wherein the absorbent layer is located on the top sheet side of the lower absorbent layer and the lower absorbent layer and is smaller than the lower absorbent layer An absorbent layer, and a cushion layer disposed between the lower absorbent layer and the upper absorbent layer, and the surface sheet, the upper absorbent layer, and the cushion layer at the center in the width direction of the absorbent article. A protrusion protruding to the seat side is formed, and the cushion layer is composed of a fiber assembly mainly composed of hydrophilic synthetic fibers, and has a density ρU of the upper absorbent layer under no pressure, the cushion layer The density ρC and the density ρD of the lower absorbent layer satisfy the relationship ρC <ρU <ρD, and under pressure, the density ρUP of the upper absorbent layer, the density ρCP of the cushion layer, and the density ρDP of the lower absorbent layer are ρUP ≦ ρ The object is achieved by providing an absorbent article that satisfies the relationship of CP ≦ ρDP and ρUP <ρDP.

  The absorbent article of the present invention has excellent cushioning properties, has a protruding portion that flexibly deforms following the movement of the wearer's skin and exhibits good fit, has a small liquid spread, and does not easily cause wetback.

Hereinafter, the present invention will be described based on preferred embodiments with reference to the drawings.
FIG.1 and FIG.2 is a figure which shows the sanitary napkin which is one Embodiment of the absorbent article of this invention.
The sanitary napkin 1 of the present embodiment has a vertically long shape like a normal sanitary napkin, and includes an absorbent layer 4 between the top sheet 21 and the back sheet 3 as shown in FIG. ing. The absorbent layer 4 includes a lower absorbent layer 41, an upper absorbent layer 42 that is located closer to the skin contact surface than the lower absorbent layer 41 and is smaller than the lower absorbent layer 41, and includes a lower absorbent layer 41 and an upper absorbent layer 42. A cushion layer 43 disposed therebetween is provided. At the center in the width direction of the napkin 1, a protruding portion A that protrudes toward the surface sheet 21 is formed by the surface sheet 21, the upper absorbent layer 42, and the cushion layer 43. The cushion layer 43 is made of a fiber assembly mainly composed of hydrophilic synthetic fibers, and under no pressure, the density ρU of the upper absorbent layer, the density ρC of the cushion layer, and the density ρD of the lower absorbent layer are ρC < The relationship ρU <ρD is satisfied, and the density ρUP of the upper absorbent layer, the density ρCP of the cushion layer, and the density ρDP of the lower absorbent layer under pressure satisfy the relationship ρUP ≦ ρCP ≦ ρDP and ρUP <ρDP.

The sanitary napkin 1 of the present embodiment (hereinafter simply referred to as sanitary napkin 1) will be described in detail.
The surface sheet 21 described above forms the skin contact surface P of the sanitary napkin 1 (surface directed toward the wearer's skin when worn), and the back sheet 3 is the non-skin contact surface Q of the sanitary napkin 1. (A surface that is directed to the side opposite to the wearer's skin when worn (mainly the clothing side such as shorts)). More specifically, as shown in FIG. 2, the skin contact surface P of the sanitary napkin 1 is formed from the composite surface sheet 2, and the non-skin contact surface Q is liquid-impermeable or liquid-hard. It is formed from a permeable back sheet 3. The composite topsheet 2 includes a liquid-permeable topsheet 21 and a pair of sidesheets 22 connected to both sides of the topsheet 21 via heat seal portions 23. The side sheet 22 is liquid-impermeable or liquid-impermeable, and is made of, for example, a water-repellent nonwoven fabric.

  As shown in FIG. 1, the sanitary napkin 1 has a middle-high portion (protruding portion) 5 that protrudes toward the topsheet 21 (projects toward the wearer's skin) at the center in the width direction. . The middle-high part 5 is formed in the excretion part opposing part arrange | positioned facing a wearer's liquid excretion part at the time of wear. The middle-high part 5 extends over a predetermined length in the longitudinal direction of the napkin 1 and has a length that extends from the liquid excretion part of the wearer to a little rear of the anus.

As shown in FIG. 2, the absorbent layer 4 in the sanitary napkin 1 includes a lower absorbent layer 41, an upper absorbent layer 42, and a cushion layer 43.
The lower absorbent layer 41 has a shape that is long in the same direction as the longitudinal direction of the napkin 1, and the plan view shape is a vertically long rectangular shape in which both ends in the longitudinal direction are arcuate. The lower absorbent layer 41 is disposed on the back sheet 3 that forms the non-skin contact surface Q. On the non-skin contact surface Q, an adhesive part (not shown) for fixing the napkin to clothing such as shorts is formed.

The upper absorbent layer 42 is located in the vicinity of the skin contact surface P in the middle and high portions 5, more specifically, adjacent to the lower surface of the topsheet 21 that forms the skin contact surface P in the middle and high portions 5. It is arranged. The upper absorbent layer 42 is smaller than the lower absorbent layer 41, and the length in either the longitudinal direction or the width direction of the napkin 1 is smaller than that of the lower absorbent layer 41. The width of the upper absorbent layer 42 is preferably 10 to 90%, particularly 20 to 80% of the width of the lower absorbent layer 41. The length of the upper absorbent layer 42 in the napkin longitudinal direction is approximately the same as the length in the same direction as the wing portion 6. The wing part 6 is formed of a back sheet 3 and a side sheet 22 part of the composite surface sheet 2 that extend outward from both side edges of the lower absorbent layer 41.
Both the upper absorbent layer 42 and the cushion layer 43 are formed in a rectangular shape that is long in the same direction as the longitudinal direction of the napkin 1.
The widths of the upper absorbent layer 42, the lower absorbent layer 41, and the cushion layer 43 are measured in a cross section (see FIG. 2) in the napkin width direction that passes through the highest portion of the middle-high portion 5.

The cushion layer 43 is disposed between the lower absorbent layer 41 and the upper absorbent layer 42. In the longitudinal direction of the napkin, the width of the cushion layer 43 is preferably 10 to 90%, particularly 20 to 80% of the width of the lower absorbent layer 41 in the portion where the middle and high portions 5 protrude the highest. Is preferably 80 to 130%, particularly 90 to 120% of the width of the upper absorbent layer 42.
The cushion layer 43 is configured to allow liquid to pass between the upper and lower surfaces. When the liquid can pass between the upper and lower surfaces, the liquid transfer from the upper absorbent layer 42 to the cushion layer 43 and the liquid transfer from the cushion layer 43 to the lower absorbent layer 41 do not occur simultaneously. It is.

  As shown in FIG. 2, the middle-high portion 5 is formed of a liquid-permeable surface sheet 2 portion of the composite surface sheet 2, an upper absorbent layer 42, and a cushion layer 43. The middle-high part 5 fits flexibly to the liquid excretion part of the wearer and has a function of quickly absorbing the liquid excreted from the liquid excretion part.

The cushion layer 43 in the sanitary napkin 1 is composed of a fiber assembly mainly composed of hydrophilic synthetic fibers, and the fiber density is increased by compression.
Each of the upper absorbent layer 42 and the lower absorbent layer 41 also includes a fiber material.

In the sanitary napkin 1 of the present embodiment, the density ρU of the upper absorbent layer 42, the density ρC of the cushion layer 43, and the density ρD of the lower absorbent layer 41 satisfy the relationship ρC <ρU <ρD under no pressure.
The cushion layer 43 is composed of a material whose density ρC is originally low and whose internal structure (mainly, the aggregate structure of fibers made hydrophilic, specifically, (fiber) density ρ) is easily changed by pressure. Therefore, a good cushioning property is obtained in the middle and high portions 5, and the structure ρC of the cushion layer 43 is small because there is little change in the structure of the cushion layer under no pressure to low wearing pressure (about 0 to 15 cN / cm ² ). Since the cushion layer preferentially deforms (mainly thickness decreases and density increases) under a medium mounting pressure (about 15 to 40 cN / cm ² ), which is smaller than the density ρU of the upper absorbent layer 42, the cushion layer The density ρC is slightly higher than the density ρU of the upper absorption layer 42 and lower than the density ρD of the lower absorption layer 41.
Moreover, under high mounting pressure (40 cN / cm ² or more), the density ρC of the cushion layer 43 is higher than the density ρU of the upper absorbent layer 42 and preferably has a density substantially equal to that of the lower absorbent body 41.

  The low wearing pressure is a pressure applied when a sanitary napkin 1 is attached to a dedicated underwear such as sanitary shorts or other underwear and worn by a woman. This pressure is mainly applied to the sanitary napkin during light exercise. At this low wearing pressure, the upper absorbent layer 42 and the lower absorbent layer 41 are not completely connected by the cushion layer 43. Here, the “state that is not completely connected” means that the smooth flow of liquid is interrupted by sandwiching a low-density cushion layer, while the liquid diffusibility in the upper absorbent layer is weakened. It shows a state in which the liquid can move slowly, that is, the liquid movement is permitted from the portion where the cushion layer is compressed at both the liquid reservoir portion and the width direction both ends.

  At the medium mounting pressure, the capillary force of the cushion layer is slightly higher than that of the upper absorbent layer, so that the liquid is easily transferred from the upper absorbent layer to the cushion layer. Especially when walking, pressure is applied partially, so the liquid moves when the pressure is applied, and the liquid staying in the cushion layer has a higher capillary force when the pressure is not applied (the part where the pressure is released). It is easy to be guided to the lower absorption layer.

In the actual wearing environment, the environment in which the pressure fluctuates between the low wearing pressure and the middle wearing pressure occupies the majority, but at this time, the relationship between the cushion layer 43 and the upper absorbent layer 42 is slowly as described above. An important point is that the liquid moves toward the lower absorption layer 41. This is comprehensively related to the amount of menstrual excretion per time, the absorption characteristics of the lower absorption layer 41, and the absorption capacity of the upper absorption layer 42. That is, the amount of menstrual blood excreted at one time is considered to be about 2 cc. The upper absorbent layer 42 is designed to have a capacity capable of sufficiently absorbing this one liquid excretion.
On the other hand, the lower absorbent layer 41 has a structure design having a high absorption retention capacity as will be described later, but as a result, the liquid is flowing at a stroke because the liquid is slow to penetrate into the absorbent layer. The liquid spreads on the surface of the lower absorption layer 41, and as a result, the liquid spread of the napkin becomes large. Therefore, having a so-called temporary stock function that temporarily holds the liquid by the upper absorbent layer 42 and the cushion layer 43 and slowly delivers the liquid is effective in sucking the liquid firmly without spreading.

  High wearing pressure is often in a state where a large pressure is suddenly applied, such as sitting on a chair or crossing legs. In such a high wearing pressure state, the density ρCP of the cushion layer 43 is increased as described above, and ρUP ≦ ρCP ≦ ρDP, between the density ρUP of the upper absorbent layer 42 and the density ρDP of the lower absorbent layer 41, And the relationship of ρUP <ρDP is established. In this case, since the capillary force also increases in this order, the liquid remaining in the upper absorbent layer 42 is drawn out in the order of the cushion layer 43 and the lower absorbent layer 41, and is finally stored in the lower absorbent layer 41. .

  Thus, when viewed as an absorption mechanism, the upper absorbent layer 42 quickly receives one liquid excretion, and slowly transmits the liquid to the lower absorbent layer 41 under a low mounting pressure to a medium mounting pressure. As a result, the lower absorption layer 41 can obtain time for absorption and fixation inside without spreading the liquid. When the high mounting pressure is applied from time to time, the liquid remaining in the upper absorbent layer 42 quickly moves to the lower absorbent layer 41, and the upper absorbent layer 42 regains the absorption capacity that can cope with the next liquid excretion.

The density ρU is, 0.002~0.1g / cm ^3, preferably in particular 0.008~0.06g / cm ^3, said density ρC is, 0.001~0.05g / cm ^3, particularly is preferably 0.006~0.03g / cm ^3, said density ρD is, 0.02~0.3g / cm ^3, it is particularly preferably 0.03~0.2g / cm ^3.

  Thus, according to the sanitary napkin 1 of this embodiment, the cushioning property of the middle-high part 5 is excellent, and the middle-high part 5 is flexibly deformed following the movement of the wearer's skin to obtain good fit. In addition, liquid spreading is small and wetback is unlikely to occur.

The density ρUP is preferably 0.006 to 0.12 g / cm ³ , particularly preferably 0.009 to 0.06 g / cm ³ , and the density ρCP is preferably 0.01 to 0.15 g / cm ³ , particularly is preferably 0.013~0.08g / cm ^3, said density ρDP is, 0.02~0.3g / cm ^3, it is particularly preferably 0.03~0.2g / cm ^3.

The densities ρU, ρC, and ρD of the upper absorbent layer 42, the cushion layer 43, and the lower absorbent layer 41 under no pressure are measured as follows. Further, the density ρUP, ρCP, ρDP under pressure (under load) of each layer is measured as follows.
Furthermore, the data of the compression test used for the measurement is also used when measuring the compression rate and thickness recoverability of the cushion layer.
(Method of measuring density under no pressure and under pressure)
For density measurement, the concept of JIS-P-8118 is applied mutatis mutandis, but the pressing conditions and the number of measured sheets are changed as follows according to the purpose of evaluation.
(Sampling) Cut the product into a rectangle from the center of the product according to the size of the middle and high part 5, take out the upper absorbent layer 42, the cushion layer 43, and the lower absorbent layer 41 and leave them in a 25 ° C / 55% RH environment for a whole day and night. Use a test piece.
At this time, the test piece size is set to 50 × 50 mm in the JIS regulations, but may be changed to a size that can accommodate all components such as 20 × 50 mm according to the size of the product.
In addition, when the cross-sectional shape of the middle-high portion 5 is an R shape having a large central bulge, the rectangular shape of at least 10 × 10 mm or more is cut out centering on the highest position of the bulge.

(Measuring device) Kato Tech Co., Ltd. compression tester KES-G5 and precision balance capable of weighing 4 digits after the decimal point (Measurement)
1) Weight: The weight of each test piece is measured in advance with a precision balance.
2) Thickness measurement by compression test: Set the test piece on the head of the compression tester without wrinkles and pressurize to 50 g / cm ² under standard conditions. Hold for 1 minute and return to the original head height. Hereinafter, the thickness is measured using the obtained chart.
(a) Unpressurized thickness d (0); 0.1 g / cm ² load thickness is defined as the unpressurized thickness.
(The 0.1 g / cm ² position is read by enlarging the chart and dividing the scale proportionally.)
(b) Thickness under pressure d (50): 50 g / cm ² load thickness is defined as thickness under pressure.
(density)
Calculate as follows and calculate the density.
(a) Density under no pressure; (test specimen weight) / ((test specimen area) × d (0))
(b) Density under pressure; (test specimen weight) / ((test specimen area) × d (50))

From the viewpoint of improving the transferability of the liquid from the upper absorbent layer 42 to the lower absorbent layer 41 under pressure and / or the prevention of liquid return from the lower absorbent layer 41 to the upper absorbent layer 42 under no pressure, and the liquid as described above. From the viewpoint of slowly transferring the pressure to the lower absorbent layer 41, the cushion layer 43 preferably has a Krem water absorbency of 2 to 50 mm, particularly 15 to 45 mm under no pressure, and a Klem water absorbency of 40 mm or more under pressure.
In any case, the pressure absorption of the cushion layer 43 is preferably lower than that of each of the upper absorbent layer 42 and the lower absorbent layer 41 under no pressure, and the water absorption of the upper absorbent layer 42 is preferably lower than the lower absorbent layer 41. It is preferable that it is lower than the water absorption of Klem.
In any case, the pressure absorption of the cushion layer 43 is preferably higher than that of the upper absorbent layer 42 under pressure, and the water absorption of the cushion layer 43 is preferably lower than that of the lower absorbent layer 41. preferable.

(Measurement method of Krem absorbency under no pressure and under pressure)
JIS-P-8141 is applied mutatis mutandis and physiological saline is used as a test solution.
From the napkin 1 (absorbent article), the upper absorbent layer 42, the lower absorbent layer 41, and the cushion layer 43 are respectively taken out and cut into a width of 15 mm and a length that can be taken according to the direction of the product to obtain a test piece.
When any one of the upper and lower absorbent layers 42 and 41 is configured by superposing a plurality of absorbent sheets, the Klem water absorption is measured individually for all the sheets, and the material having the highest water absorption is used as the representative value. It is preferable to do.
When cutting out the test piece, a cutting method that may crush the sheet, such as a push-off cutter, is not preferable because it has a high possibility of affecting the results. In particular, a bulky structure such as cotton-like pulp or cushion layer 43 has a great influence. In particular, when cutting out with a width of 12 mm (when the longitudinal direction of the test piece is cut out), the cut surface is cut out using a knife, cutter, razor or the like.

And a test piece is set to the jig prescribed | regulated to JISP8141, and the water absorption of Klem after 1 minute is measured using the physiological saline for a test liquid. In order to facilitate the determination of the suction height, the test solution may be appropriately colored with a dye such as Blue No. 1 or methylene blue.
Normally, the water absorption of all components can be measured by the size (length) of the test piece. If the suction height after 1 minute exceeds the total length of the test piece, two test pieces are connected vertically. It may be remeasured together. Specifically, 3 mm of test pieces are overlapped at the seam, and measurement is performed by lightly fastening with the cellophane tape from one side. At this time, the cellophane tape width is set to the width of the test piece and the same length is set to 20 mm so that the influence of sticking is minimized.
The above measurement is performed three times, and the average value is defined as the Krem water absorption (under no pressure).
Clem water absorbency under pressure (under load) is measured by measuring 50 g / cm ² thickness of the cushion material in the compression test described above, and compressing the cushion material with an appropriate jig.
Specifically, two 120-mesh metal mesh made of stainless steel and four thumbscrews are prepared so that the four corners can be fixed.
Cushion material is sandwiched between wire meshes (even if the same cushion material is opened with about 10mm gap), tighten the thumbscrew while accurately measuring the gap with calipers, and adjust to 20g / cm ² thickness. Go. Measure the clearance on the front, back, left and right of the wire mesh, and prepare carefully so that it is evenly compressed. Subsequent measurements are the same as the above-mentioned Klem water absorption, except that the suction height is measured while being sandwiched between wire meshes.

The upper absorbent layer 42 in the sanitary napkin 1 of the present embodiment has a liquid retention amount per unit area (hereinafter also referred to as a liquid retention force) smaller than the lower absorbent layer 41.
(Measurement method of liquid holding amount per unit weight)
The upper absorbent layer 42 and the lower absorbent layer 41 are taken out from the napkin (absorbent article).
If the lower absorbent layer 41 is large, it may be cut into an appropriate size to form a test piece. For example, the central portion of the absorbent layer may be cut into a width of 50 mm and a length of 150 mm to form a test piece. As will be described later, the size of the lower absorbent layer may be used as long as it can be centrifuged without folding the test piece in two.
A non-woven fabric or nylon mesh or the like is used to create a bag of a size that allows the test piece to be expanded and the bag weight is measured in advance. Let this weight be W0. Each test piece is weighed in advance. Let this weight be W1. The test piece is spread in the bag and immersed in a vat containing an excess amount of physiological saline for 1 minute. Immediately after this, the bag (with the test piece) is taken out, fixed to the inner periphery of the basket of Kokusan Co., Ltd. H-130C, centrifuged at 2000 rpm for 10 minutes, and then the bag. The test piece is taken out and the weight is measured. Let this weight be W2.
From the above measurement results, the amount of liquid retained per unit weight is
Liquid holding amount (g / g) = (W2-W1-W0) / W1
Can be calculated.

Further, from the viewpoint of reducing the state in which a large amount of liquid is present in the vicinity of the skin contact surface as much as possible, and making it difficult to cause wetback, stuffiness, and stickiness to the skin contact surface, the per unit area of the upper absorbent layer 42 The liquid holding amount is preferably 12 g / g or less, more preferably 2 to 10 g / g.
From the viewpoint of facilitating the liquid transfer from the upper absorbent layer 42 to the lower absorbent layer 41 and holding a sufficient amount of liquid in the lower absorbent layer 41 to prevent liquid leakage outside the sanitary napkin, The liquid holding amount per unit area of the absorption layer 41 is preferably 14 g / g or more, more preferably 15 to 28 g / g.

  In order to exhibit the absorption characteristics as described above, the upper absorption layer 42 needs the following characteristics. 1) The amount of liquid excreted at a time can be quickly stored, 2) The liquid transfer from the upper absorbent layer 42 to the lower absorbent layer 41 is good, and 3) The liquid from the lower absorbent layer 41 to the upper absorbent layer 42 is good. Good anti-return property, 4) The structure and absorption characteristics do not change greatly due to liquid absorption, especially after liquid transfer to the lower absorption layer. From this viewpoint, the upper absorbent layer has a thickness of 2 mm or more, preferably 2.5 to 4.5 mm, and (1) an absorbent body mainly composed of pulp fibers and synthetic fibers, and (2) crosslinked pulp. It is preferable to consist of an absorber containing fibers, or (3) an absorber containing pulp fibers bound by an adhesive resin.

As the absorbent of (1), a piled product obtained by mixing and mixing pulp fibers and synthetic fibers, an air-through nonwoven fabric (synthetic fibers (fibers made of a thermoplastic resin and subjected to hydrophilic treatment)) are deposited, Non-woven fabric bonded by hot air treatment) and sheets obtained by alternately laminating thin layers of cotton-like pulp, cotton-like pulp, or sheets obtained by mixing and mixing cotton-like pulp and synthetic fibers, a bulky air-through nonwoven fabric Alternatively, an absorbent body wrapped with an airlaid nonwoven fabric can be used. By including synthetic fibers, a bulky upper absorbent layer having a low fiber density can be obtained.
The ratio of pulp fibers and synthetic fibers in the absorbent body is preferably 15:85 to 85:15, particularly preferably 25:75 to 75:25, in terms of mass ratio (the former: latter).
Synthetic fibers include polyolefin fibers made of polyolefin resins such as polyethylene and polypropylene, polyester fibers made of polyester resins such as polyethylene phthalate, polyamide fibers such as nylon, core-sheath type made of two or more resins, or side-by-side Examples include side-type composite fibers and regenerated fibers such as rayon. These fibers can be used alone or in combination of two or more. These fibers are preferably hydrophilized by various methods known to those skilled in the art.

The synthetic fiber is preferably longer and thicker than pulp so that the absorbent of (1) can absorb the liquid quickly and has little structural change even after liquid absorption and can be restored to its original state. Specifically, the preferred fineness is 2.2 to 14 dtex, more preferably 4.0 to 11 dtex, and the preferred fiber length is 5 to 100 mm, more preferably 25 to 75 mm. Further, it is more preferable that the fiber is subjected to secondary or tertiary crimping and is three-dimensionally bent.
For the same reason, in order to prevent the flocculent pulp layer from becoming unrecoverable, among the above-mentioned various absorbents, a piled product obtained by mixing and depositing pulp and synthetic fiber is the best, but long It is difficult to mix and deposit synthetic fibers with pulp. For this reason, it is preferable to use synthetic fibers having a fiber length of 60 mm or less, more preferably 25 to 55 mm, in consideration of the process of simultaneously mixing synthetic fibers in the pulp opening process.
In a mixed fiber system of pulp and synthetic fiber, the synthetic fiber may be bonded by hot air treatment after fiber stacking.

As the absorber of (2), wet-deposited cross-linked pulp fibers (low liquid retention fibers having a centrifugal retention of 0.7 g / g or less, which have been subjected to crimping and cross-linking treatment on the pulp and subjected to three-dimensional crimping), Bulk paper obtained by drying, non-woven fabric obtained by mixing heat-bonded fibers (fibrous binders) such as fibrous polyvinyl alcohol with the crosslinked pulp, wet-depositing, and drying, the crosslinked pulp and the synthetic fibers described above Nonwoven fabric obtained by mixing and wet-depositing and drying, and a sheet in which pulp fibers are mixed and dispersed can be used. By including the crosslinked pulp fiber, a bulky upper absorbent layer having a low fiber density can be obtained.
The content ratio (% by mass) of the crosslinked pulp fiber in the absorbent body is preferably 40 to 95%, particularly preferably 50 to 92%.

As the absorber (3), a so-called dry pulp sheet obtained by spraying and infiltrating various binder (adhesive resin) solutions onto a web in which pulp fibers are air-flow deposited by the airlaid method and drying can be used. By including pulp fibers bonded with an adhesive resin, a bulky upper absorbent layer having a low fiber density can be obtained.
The content (mass%) of the pulp fiber bonded with the adhesive resin in the absorbent body is preferably 75 to 98%, particularly preferably 85 to 97%. The synthetic fiber etc. which were mentioned above may be included with such a pulp fiber.
As the binder, polyvinyl alcohol, vinyl acetate, polyacrylic acid, polyacrylamide, carboxymethylcellulose, starch, carrageenan, and a salt or derivative thereof in an aqueous solution (or an aqueous emulsion) are preferably used.

  In any composition, the upper absorbent layer 42 should not include a thin layer sheet of wet-deposited pulp fiber, such as absorbent paper or mount, and the fiber sheet for molding and transportability of the upper absorbent layer 42. When wrapping with, it is preferable that it is the structure wrapped with various nonwoven fabrics, especially an air-through nonwoven fabric or an airlaid nonwoven fabric.

From the viewpoint of improving the liquid transfer property from the upper absorbent layer 42 to the lower absorbent layer 41 under pressure and / or the liquid return prevention property from the lower absorbent layer 41 to the upper absorbent layer 42 under no pressure, the lower absorbent layer 41. (4) It is preferable to consist of an absorber containing a pulp fiber and a superabsorbent polymer. Further, from the viewpoint of improving the soft wearing feeling of the whole napkin 1, the thickness of the lower absorbent layer 41 is preferably 7 mm or less, more preferably 2 to 5 mm.
As the absorbent of (4), a superabsorbent polymer sandwiched between two fiber layers composed of a fiber product obtained by mixing and mixing pulp fibers and a superabsorbent polymer, and pulp fibers formed by wet papermaking. A superabsorbent polymer is sandwiched between two fiber layers made of the above-mentioned crosslinked pulp fibers, and these are integrally pressed and pressed, and these are pressed together. (For example, an absorbent sheet described in JP-A-8-246395), a fiber assembly containing pulp fibers and a superabsorbent polymer in a mixed state, and pressed into a thickness direction to be consolidated, Etc.

The proportion of fibers such as pulp in the lower absorbent layer 41 is preferably 40 to 75% by mass, particularly 50 to 70% by mass. Moreover, it is preferable that the ratio of the superabsorbent polymer in the lower absorption layer 41 is 25-60 mass%, especially 30-50 mass%.
As the superabsorbent polymer contained in the lower absorbent layer 41, a conventionally known polymer can be used without particular limitation. Examples thereof include starch, crosslinked carboxylmethylated cellulose, a polymer or copolymer of acrylic acid or an alkali metal acrylate salt, polyacrylic acid and a salt thereof, and a polyacrylate graft polymer. As the polyacrylic acid salt, a sodium salt can be preferably used. In addition, a comonomer such as maleic acid, itaconic acid, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, 2- (meth) acryloylethanesulfonic acid, 2-hydroxyethyl (meth) acrylate or styrenesulfonic acid is added to acrylic acid. Copolymers copolymerized within a range that does not deteriorate the performance of the superabsorbent polymer can also be preferably used. These superabsorbent polymers can be used alone or in admixture of two or more.

  The material constituting the cushion layer 43 (hereinafter also referred to as cushion material) is compressed in the thickness direction by the pressure applied by the wearer's skin when the napkin is used, and the thickness is restored when released from the pressure. As described above, it is preferable to use a material that allows liquid to pass between the upper and lower surfaces.

As a cushioning material, for example, the compression rate under a load of 50 gf / cm ² is 50% or more (more preferably 65% or more), and after being left for 1 minute under a load of 50 gf / cm ² , it is returned to the state under no load. Those having a thickness recovery rate of 80% or more (more preferably 90% or more) can be preferably used. The cushion layer preferably has a thickness (measured in a single state) under no load (before compression) that is 80 to 300% of the thickness of the upper absorbent layer 42 under no load. The lower thickness is preferably 1 mm or more, particularly 3 to 12 mm. Moreover, it is preferable that the protrusion height T (refer FIG. 2) of the middle-high part 5 is 3-30 mm, More preferably, it is 4-17 mm.

(Compression rate under 50 gf / cm ² load, thickness recovery rate when returned to no load)
Based on the chart obtained by the compression test of the cushion material, the thickness data of the following points was read and calculated as follows.
Non-pressurized cushion material thickness d (0); as described above (thickness at 0.1 g / cm ² ).
Thickness d (50) under pressure applied to the cushion material; as described above.
Cushion material recovery thickness d _f ; thickness when compressive stress (vertical axis) becomes 0 g / cm ² in the return path; compression rate under 50 gf / cm ² load; [d (50) −d (0)] / d (0) x 100 (%)
Thickness recovery rate: d _f / d (0) × 100 (%)

  As the cushion material, a fiber assembly composed mainly of hydrophilic synthetic fibers is used. The fiber assembly used as the cushion material includes single layer or multilayer nonwoven fabrics, card webs that are not nonwoven fabrics, and the like.

The preferable example of the cushion material which comprises the cushion layer 43 was shown in FIGS.
The cushion layer 43 shown in FIG. 3 includes a fiber layer laminate 43A in which high-density fiber layers 431 and 433 and low-density fiber layers 432 and 434 are alternately laminated.
The high density or low density in the high density fiber layer and the low density fiber layer means that one is higher or lower in density than the other, and is relative.
The fiber layer laminate 43A shown in FIG. 3 is a high-density fiber layer 433 and two low-density fiber layers 432 and 434 that are positioned above and below the high-density fiber layer 433 and have a lower density than the high-density fiber layer 433. And a high-density fiber layer 431 stacked on the upper side of the low-density fiber layer 432.

As shown in FIG. 3A, in the fiber layer laminate 43A, the low-density fiber layers 432 and 434 having a relatively low fiber density are bulky in an unpressurized state, and the upper absorbent layer Although the movement of the liquid between 42 and the lower absorption layer 41 is interrupted, as shown in FIG. 3B, the fiber density is higher than the high-density fiber layers 431 and 433 in the pressurized state. The lower low density fiber layers 432 and 434 are preferentially compressed. Therefore, in the pressurizing state of the protruding portion 5, the fiber density and capillary force of the low density fiber layers 432 and 434 rapidly increase, and the liquid smoothly moves from the upper absorbent layer 42 to the lower absorbent layer 41.
In such a laminated body, the density of the high-density fiber layer is made substantially equal to the density of the upper absorbent layer 42, the density of the low-density fiber layer is lowered, and the layers are thinned to make the low-density fiber layer thin. Since it is easily and evenly crushed and easily recovered, the liquid mobility on the entire surface of the cushion layer is improved at a stretch when a medium load to a large load is applied, and the liquid can be quickly transmitted to the lower absorbent layer 41.
The fiber density (apparent density) of each of the high-density fiber layers 431 and 433 under no pressure is preferably 0.002 to 0.1 g / cm ³ , particularly preferably 0.006 to 0.04 g / cm ³ , and low The fiber density (apparent density) of each of the density fiber layers 432 and 434 under no pressure is preferably 0.001 to 0.05 g / cm ³ , particularly preferably 0.006 to 0.03 g / cm ³ .

The fiber layer laminate 43A can be manufactured, for example, as follows.
First, each of the nonwoven fabric for the low-density fiber layer and the nonwoven fabric for the high-density fiber layer are produced, and the respective nonwoven fabrics are stacked one by one, and both the nonwoven fabrics are integrated by heat fusion by an air-through method, A two-layer nonwoven fabric is obtained. Then, the obtained two-layered nonwoven fabric is integrated using a hot-melt adhesive or the like to obtain a fiber layer laminate 43A. Note that the two-layered nonwoven fabric may be joined by thermal fusion or the like, or the nonwoven fabric for the low density fiber layer and the nonwoven fabric for the high density fiber layer may be joined by other joining means such as a hot melt adhesive. You can go.
The high density fiber layers 431 and 433 constituting the fiber layer laminate 43A are preferably made of fibers thicker than the low density fiber layers 432 and 434. The fineness of the constituent fibers of the high-density fiber layer is preferably 0.8 to 4.8 dtex, and the fineness of the constituent fibers of the low-density fiber layer is preferably 4 to 15 dtex. Moreover, it is preferable that the low-density fiber layers 432 and 434 in the fiber layer laminate 43A have a higher degree of crimping of the constituent fibers than the high-density fiber layers 431 and 433.

  The thickness of the entire fiber laminate 43A under no pressure is preferably 2 to 7 mm, particularly preferably 3 to 5.5 mm.

The cushion layer 43 shown in FIG. 4 is formed of an embossed nonwoven fabric 43B formed by partially forming an embossed portion 437 on the fiber assembly 436 by embossing, and the embossed nonwoven fabric 43B includes an embossed nonwoven fabric 43B as shown in FIG. In addition, the embossed portion 437 and the non-embossed portion 438 are mixed in a plan view.
As the fiber assembly 436, a bulky fiber assembly can be used. For example, an air-through nonwoven fabric made of synthetic fibers or a nonwoven fabric obtained by air-laying synthetic fibers and treating them with hot air (air-laid air-through nonwoven fabric) In addition, it is preferable to use a fiber aggregate deposited by carding synthetic fibers, a fiber aggregate deposited by airlaid fiber synthesis, and the like.
As shown in FIG. 4A, the embossed nonwoven fabric 43 </ b> B has protrusions composed of non-embossed portions 438 on both upper and lower surfaces in a non-pressurized state. As shown in FIG. 4B, in the pressurized state, the pressing force by the upper absorbent layer 42 and the lower absorbent layer 41 is concentrated on the protruding portion of the non-embossed portion 438. Is preferentially compressed.
Here, the fiber density of the embossed portion 437 is larger than that of the upper absorbent layer 42, the fiber density of the non-embossed portion 438 is smaller than that of the upper absorbent layer 42, and supports the absorbent layer in contact with the upper absorbent layer 42. Only the non-embossed portion 438 is present, and the embossed portion 437 is characterized in that it is not in contact with the upper absorbent layer at all under no pressure. In this state, liquid movement from the upper absorbent layer 42 to the cushion layer 43 is difficult to occur.
In the pressurized state of the protruding portion 5, the fiber density and capillary force in the non-embossed portion 438 are rapidly increased, and the liquid smoothly moves from the upper absorbent layer 42 to the lower absorbent layer 41.

  Thus, the non-embossed portion 438 of the embossed nonwoven fabric 43B functions as a column that elastically supports the upper absorbent layer 42 from below. Therefore, in order for the non-embossed portion 438 not to buckle easily, the non-embossed portion 438 is connected to form a continuous region as shown in FIG. 4C, or has an area of at least 20 mm 2 or more, preferably 75 mm 2 or more per region. In addition, the area ratio of the entire non-embossed portion 438 is preferably 50% or more, particularly 65 to 90%.

The area ratio of the embossed part 437 is measured as follows.
An enlarged image is output from the embossed nonwoven fabric 43 </ b> B using a KEYENCE magnification observation system (High Scope, VH-8000). The magnification can be adjusted as appropriate within the range in which the following operations can be easily performed, but in the present application, the magnification is 25 times.
A transparent film such as an OHP film is superimposed on the enlarged image, and the outer periphery of the non-embossed portion 438 is traced with magic (black). At this time, an actual scale is put on the end of the film (a gold scale scale output at the same magnification is used).
Using the transparent film, the area per one non-embossed portion 438 and the area ratio of the whole non-embossed portion 438 are calculated by an image analysis apparatus.
As an image analysis apparatus, an analysis system [NEXUS NewQube] manufactured by Nexus Co., Ltd. is used, but a similar system may be appropriately used. Further, when non-embossed regions are continuous as shown in FIG. 4C, it is described as “continuous region” (since it is possible to obtain the entire region area, but there is not much meaning), and the area calculation is not performed.
Further, the embossed nonwoven fabric 43B preferably has a thickness under no pressure (a thickness including a protruding portion of the non-embossed portion) of 2 to 7 mm, particularly 3 to 5.5 mm.

The cushion layer 43 shown in FIG. 5 is composed of a fiber assembly 43C in which coiled fibers 440 crimped in a spiral are dispersed in a fiber assembly composed of synthetic fibers 439.
In the fiber assembly 43C, as shown in FIG. 5A, in a non-pressurized state, the coiled fibers 440 are separated from each other in a relatively sparse fiber assembly composed of synthetic fibers 439. Exists. Since the coiled fiber 440 is dense, the capillary force is high and the liquid can easily flow. On the other hand, since the surrounding synthetic fibers 439 are sparse, it is difficult for the liquid to flow. The coiled fibers 440 are dispersed and fixed so as to be partially wound around the synthetic fibers 439, while the synthetic fibers 439 are also fixed to each other by the coiled fibers 440 being wound. Therefore, the cushion layers shown in FIG. 5 are fixed to each other without being subjected to a special bonding operation, and become a fiber assembly. Under no pressure, since the coiled fibers 440 that allow the liquid to flow are not connected to each other, the movement of the liquid between the upper absorbent layer 42 and the lower absorbent layer 41 is blocked, but FIG. As shown in FIG. 4, in the pressurized state, the dispersed spring fibers are continuously formed to form a liquid flow channel having a high capillary force. Therefore, in the pressurized state of the protrusion 5, the liquid permeability of the fiber assembly 43 </ b> C is rapidly increased, and the liquid smoothly moves from the upper absorbent layer 42 to the lower absorbent layer 41. Examples of the coiled fiber 440 include a coiled fiber produced by crimping a latent crimpable fiber in a spiral shape by heat treatment. The latent crimpable fiber is composed of, for example, an eccentric core-sheath type composite fiber or a side-by-side type composite fiber containing two types of thermoplastic polymer materials having different shrinkage ratios. The thing as described in -296325 gazette and patent 2759331 gazette is mentioned. As an example of two types of thermoplastic polymer materials having different shrinkage rates, for example, a combination of an ethylene-propylene random copolymer (EP) and polypropylene (PP) is preferably exemplified.

  The latent crimpable fibers (including coiled fibers that have developed crimps) are preferably contained in the cushion layer 43 in an amount of 25 to 75% by mass, and more preferably 30 to 55% by mass. . Moreover, as a coil-shaped fiber, what was shape | molded helically by methods other than a heat | fever can be used. Furthermore, the surrounding synthetic fiber 439 is preferably one having an appropriate fineness that is easily deformed under pressure but is not easily buckled. For this reason, it is preferably 2.0 to 6.7 dtex, particularly 3.5 to 4.7 dtex. preferable.

  The nonwoven fabric including the coiled fiber formed by crimping the latent crimpable fiber spirally is obtained, for example, by heat-treating a mixed product of non-heat-shrinkable fibers and latent crimpable fibers. Also, a fiber assembly (may be a non-woven fabric) made of non-heat-shrinkable fibers is laminated and partially integrated on a fiber assembly (can be a non-woven fabric) made of latent crimpable fibers. Thereafter, it may be obtained by heat treatment.

The preferable relationship between the upper absorbent layer 42, the cushion layer 43, and the lower absorbent layer 41 and the preferred combination thereof are that the upper absorbent layer 42 is bulkier than the lower absorbent layer 41 and can absorb liquid quickly, and is compressed by the cushion layer 43. Difficult and the structure is stable. The lower absorbent layer 41 can absorb and hold the liquid firmly, and does not have to be able to hold the liquid as quickly as the upper absorbent layer 42. Such a most preferable combination consists of a deposit obtained by mixing and mixing pulp fibers and synthetic fibers in the upper absorbent layer 42, the cushion layer 43, the cushion layer shown in FIG. 5, and the lower absorbent layer 41 in the form of crosslinked pulp fibers. Most preferably, a superabsorbent polymer is sandwiched between two fiber layers, and these are integrally pressed and pressed.
In order for the upper absorbent layer 42 to satisfy the above-mentioned preferable relationship, the ratio of the pulp fiber and the synthetic fiber in the absorbent body is 30:70 to 60:40, and the fineness of the synthetic fiber is 4.0 to 7.6 dtex. The fiber length is 30 to 55 mm, which is three-dimensionally crimped, and is most preferably a mixed pile deposit in which the synthetic fibers are simultaneously mixed and simultaneously opened at the time of pulp opening and air-flow deposited.
The cushion layer 43 has a preferred basis weight of 30 g / m ² or more, more preferably 40 to 200 g / m ² , most preferably because the coiled fiber is released without pressure and the liquid easily flows under pressure. Is 45 to 150 g / m ² , the ratio of the coiled fiber to the synthetic fiber is 20:80 to 70:30, and the fineness of the synthetic fiber is 3.0 to 11 dtex, more preferably 4.0 to 9.0 dtex. The fineness of the coiled fiber is 2.0 to 10 dtex, more preferably 3.0 to 8 dtex. For the same reason, the lower absorbent layer 41 is most preferably an absorbent sheet having a superabsorbent polymer amount of 30 to 50% by weight and the remainder being a pulp sheet or a crosslinked pulp sheet.

  The sanitary napkin 1 shown in FIGS. 1 and 2 will be further described. As shown in FIGS. 1 and 2, the top sheet 21 has a lower absorbent layer 41 in the embossed groove 7 formed so as to surround the middle and high portions 5. And integrated.

As mentioned above, although several embodiment of the absorbent article of this invention was described, this invention can be suitably changed suitably, without being restrict | limited to the said embodiment.
For example, the absorbent article of the present invention may be a panty liner (cage sheet), an incontinence pad, a disposable diaper or the like instead of a sanitary napkin. Further, the sanitary napkin or the like may not have the wing portion 6 or the rear flap portion 8 that extends laterally at the rear portion of the napkin. Further, a thin cushion layer made of the same material as that of the cushion layer 43 may be provided between the top sheet 21 and the upper absorbent layer 42 in the middle-high portion (projecting portion) 5.
Further, the fiber layer laminate 43A has alternately the high-density fiber layer and the low-density fiber layer in order from the upper absorbent layer 42 side, but the central high-density fiber layer 433 and the low-density fibers on both sides thereof. It may consist of only the layers 432 and 434.
Moreover, the middle-high part (protrusion part) 5 may be formed so that it may extend from the product center to the product rear end part, and may fill the dent (crack) of the hip.

FIG. 1 is a perspective view showing a sanitary napkin which is an embodiment of the absorbent article of the present invention. 2 is a cross-sectional view taken along line II-II shown in FIG. FIG. 3 is a view showing an example of a cushion material constituting the cushion layer. FIG. 3 (a) is a non-pressurized state, and FIG. 3 (b) is a cross-sectional view showing a pressurized state. FIG. 4 is a view showing another example of a cushion material constituting the cushion layer, FIG. 4 (a) is a state under no pressure, FIG. 4 (b) is a cross-sectional view showing a state under pressure, FIG. 4C is a plan view of the cushion material. The FIG. 5 is a view showing still another example of the cushion material constituting the cushion layer, FIG. 5 (a) is a state under no pressure, and FIG. 5 (b) is a cross-sectional view showing a state under pressure. .

Explanation of symbols

1 Sanitary napkin (absorbent article)
2 Composite surface sheet 21 Surface sheet 22 Side sheet 3 Back surface sheet 4 Absorbing layer 41 Upper absorbent layer 42 Lower absorbent layer 43 Cushion layers 43A to 43C Cushion material 5 Middle and high part (protruding part)
7 Embossed groove

Claims (6)

An absorbent article having an absorbent layer between the top sheet and the back sheet,
The absorbent layer includes a lower absorbent layer, an upper absorbent layer located closer to the surface sheet than the lower absorbent layer and smaller than the lower absorbent layer, and a cushion layer disposed between the lower absorbent layer and the upper absorbent layer. Equipped,
In the central portion in the width direction of the absorbent article, a protruding portion that protrudes toward the surface sheet is formed by the surface sheet, the upper absorbent layer, and the cushion layer,
The cushion layer is composed of a fiber assembly mainly composed of hydrophilic synthetic fibers,

Under no pressure, the density ρU of the upper absorbent layer, the density ρC of the cushion layer, and the density ρD of the lower absorbent layer satisfy the relationship of ρC <ρU <ρD ,
Under pressure, the density ρUP of the upper absorbent layer, the density ρCP of the cushion layer, and the density ρDP of the lower absorbent layer satisfy the relationship of ρUP ≦ ρCP ≦ ρDP and ρUP <ρDP , and
Under no pressure, the cushion layer has a lower water absorption than that of the upper absorbent layer and the lower absorbent layer .
The density ρU, ρC, ρD under no pressure is based on a thickness d (0) under a load of 0.1 g / cm ² when each test piece obtained from each layer is pressed with a compression tester . The density obtained by the following formula (a) from the weight and area of each test piece, and the densities ρUP, ρCP, ρDP under pressure are the thickness d (50) under a load of 50 g / cm ² measured in the same manner. Based on the above, an absorbent article having a density determined by the following formula (b) from the weight and area of each test piece.
(A) Density under no pressure = (test specimen weight) / ((test specimen area) × d (0))
(B) Density under pressure = (test specimen weight) / ((test specimen area) × d (50)) The upper absorbent layer is composed of an absorbent body mainly composed of pulp fibers and synthetic fibers, an absorbent body containing crosslinked pulp fibers, or an absorbent body containing pulp fibers bonded with an adhesive resin,
The absorptive article according to claim 1 in which a lower layer absorption layer consists of an absorber containing a pulp fiber and a superabsorbent polymer. Material constituting the cushion layer is 50 gf / cm ² under load compression ratio of 50% or more and allowed to stand for 1 minute under 50 gf / cm ² load was back to under a load of 0.1 g / cm ² The absorbent article of Claim 1 or 2 whose thickness recovery rate is 80% or more . The absorptive article according to any one of claims 1 to 3, wherein the cushion layer has a Krem water absorbency of 2 to 50 mm under no pressure and a Klem water absorbency of 40 mm or more under pressure. The cushion layer is composed of a dense fiber layer and a low density fibrous layer are alternately laminated fiber layers laminate absorbent article according to any one of claims 1-4. The said cushion layer consists of an embossed nonwoven fabric in which an embossed part is partially formed on the fiber assembly by embossing, and the embossed nonwoven fabric contains a mixture of an embossed part and a non-embossed part. the absorbent article according to any one of 1-4.

Images