Absorbent article sheet

Abstract

To provide an absorbent article sheet which is highly flexible and suppresses movement of absorbent polymer even when it is dry.SOLUTION: An absorbent article sheet 1 is provided with a first fiber sheet 11, a third fiber sheet 13, and a second fiber sheet 12 between the sheets 11, 13. The absorbent article sheet 1 is provided with a first absorbent polymer layer 14 including absorbent polymer particles 16a between the first fiber sheet 11 and the second fiber sheet 12, and with a second absorbent polymer layer 15 including absorbent polymer particles 16b between the second fiber sheet 12 and the third fiber sheet 13. The second fiber sheet 12 has: a first high fiber density region 21 including a facing surface with the first fiber sheet 11; a second high fiber density region 22 including a facing surface with the third fiber sheet 13; and a low fiber density region 23 located between both high fiber density regions 21, 22 and lower in fiber presence density than both low fiber density regions 21, 22.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sheet for absorbent articles. [Background technology]

[0002] BACKGROUND ART Various improvements have been proposed for absorbent bodies used in absorbent articles such as disposable diapers. For example, Patent Document 1 describes an absorbent body that includes a first absorbent layer containing a superabsorbent polymer, a second absorbent layer containing a superabsorbent polymer, and an intermediate layer containing fibers disposed therebetween, the intermediate layer having a low fiber density portion with a relatively low fiber density and a high fiber density portion with a relatively high fiber density. The absorbent body described in this document is also described as having excellent temporary liquid retention and liquid migration in the thickness direction.

[0003] Patent Document 2 describes an absorbent sheet having a laminated absorbent layer separated into a primary absorbent layer and a secondary absorbent layer by a breathable partition layer, the absorbent layer being sandwiched between nonwoven fabrics from above and below. The document also describes that the absorbent sheet described in this document achieves both prevention of gel blocking in the early stages of urination and efficient permeation of water to the secondary absorbent layer by providing appropriate liquid distribution and diffusion due to the breathable partition layer between the primary absorbent layer and the secondary absorbent layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Re-tabled publication No. 2011 / 043256 [Patent Document 2] Japanese Patent Publication No. 2020-108752 Summary of the Invention [Problem to be solved by the invention]

[0005] In addition to liquid absorption performance, absorbents are also required to be flexible. However, the absorbent described in Patent Document 1 and the absorbent sheet described in Patent Document 2 lack sufficient flexibility. To improve the flexibility of an absorbent, for example, the pulp content in the absorbent may be reduced and the content of highly compressible nonwoven fabric may be increased. However, reducing the pulp content can cause the absorbent polymer in the absorbent to swell and break down when it absorbs the wearer's body fluids. To prevent this, absorbent bodies have been proposed in which the absorbent polymer is entangled with the constituent fibers of the nonwoven fabric. However, in such absorbent bodies, the absorbent polymer can move freely when dry, which can prevent the absorption performance from being achieved as designed. Furthermore, when an absorbent article equipped with such an absorbent body is picked up, the absorbent polymer may move, resulting in a gritty feeling.

[0006] Therefore, an object of the present invention is to provide a sheet for absorbent articles which is highly flexible and in which the migration of absorbent polymer is suppressed even when dry. [Means for solving the problem]

[0007] The present invention relates to a sheet for absorbent articles comprising a first fibrous sheet, a third fibrous sheet, and a second fibrous sheet disposed between the first and third fibrous sheets. In one embodiment, the sheet for absorbent articles preferably includes a first absorbent polymer layer containing particles of an absorbent polymer between the first fibrous sheet and the second fibrous sheet. In one embodiment, the absorbent article sheet preferably comprises a second absorbent polymer layer between the second fibrous sheet and the third fibrous sheet, the second absorbent polymer layer containing particles of an absorbent polymer that is the same as or different from the absorbent polymer. In one embodiment, the second fibrous sheet is a first high fiber density region including a surface facing the first fiber sheet; a second high fiber density region including a surface facing the third fiber sheet; a low fiber density region located between the first high fiber density region and the second high fiber density region and having a fiber density lower than both high fiber density regions; It is preferred that the compound has the following structure: [Effects of the Invention]

[0008] According to the present invention, there is provided a sheet for absorbent articles which is highly flexible and in which the migration of absorbent polymer is suppressed even when dry. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view showing a preferred embodiment of the sheet for absorbent articles of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing another embodiment of the sheet for absorbent articles of the present invention. [Figure 3] FIG. 3 is a cross-sectional view showing still another embodiment of the sheet for absorbent articles of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will now be described based on preferred embodiments thereof with reference to the drawings. The absorbent article sheet 1 (hereinafter also referred to as "sheet 1") shown in Figure 1 comprises a first fiber sheet 11, a third fiber sheet 13, and a second fiber sheet 12 arranged between the first fiber sheet 11 and the third fiber sheet 13. The sheet 1 comprises absorbent polymer particles 16. Specifically, the sheet 1 comprises a first absorbent polymer layer 14 comprising absorbent polymer particles 16a between the first fibrous sheet 11 and the second fibrous sheet 12. Similarly, the sheet 1 comprises a second absorbent polymer layer 15 comprising absorbent polymer particles 16b, which may be the same as or different from the absorbent polymer, between the second fibrous sheet 12 and the third fibrous sheet 13.

[0011] The absorbent polymer particles 16a present in the first absorbent polymer layer 14 can be fixed between the first fiber sheet 11 and the second fiber sheet 12 by an adhesive or the like (not shown). Similarly, the absorbent polymer particles 16b present in the second absorbent polymer layer 15 can be fixed between the second fiber sheet 12 and the third fiber sheet 13 by an adhesive or the like (not shown). In this way, it is preferable that the first fiber sheet and the second fiber sheet are bonded via the particles 16a constituting the first absorbent polymer layer, and that the second fiber sheet and the third fiber sheet are bonded via the particles 16b constituting the second absorbent polymer layer. By having such a configuration for the sheet 1, the particles 16a and 16b can be more reliably fixed, thereby further suppressing the movement of the particles 16a and 16b during drying.

[0012] As shown in FIG. 1 , the second fiber sheet 12 has a layered first high fiber density region 21 including the surface facing the first fiber sheet 11, a layered second high fiber density region 22 including the surface facing the third fiber sheet 13, and a layered low fiber density region 23 located between the first high fiber density region 21 and the second high fiber density region 22 and having a lower fiber density than the high fiber density regions 21, 22. The first high fiber density region 21 and the low fiber density region 23 are preferably integrated. Similarly, the low fiber density region 23 and the second high fiber density region 22 are preferably integrated. The term "integrated" means that the first high fiber density region 21 and the low fiber density region 23, and the low fiber density region 23 and the second high fiber density region 22 are formed as a single sheet having a multilayer structure that is not joined by a joining means such as an adhesive. In the sheet 1 having such a configuration, the absorbent polymer particles 16a, 16b are sandwiched between the first fiber sheet 11 and the first high fiber density region 21, or between the second fiber sheet 12 and the second high fiber density region 22, making them less likely to move when the sheet 1 is dry. In addition, the low fiber density region 23 deforms when pressure is applied in the thickness direction of the sheet 1, making the sheet 1 highly flexible. Furthermore, even if the particles 16a, 16b swell when absorbing bodily fluids, the low fiber density region 23 deforms in response to the swelling, making it less likely that the swelling of the particles 16a, 16b will be inhibited.

[0013] In the sheet 1, a rectangular raw web having a longitudinal direction and a transverse direction perpendicular thereto is folded into thirds with a fold line along the transverse direction and with the second fiber sheet 12 positioned on the inside. When the raw web is folded into thirds, the front and rear longitudinal edges of the raw web face each other. Examples of the "facing" state include a state in which the front and rear longitudinal edges of the raw web are roughly butted together, and a state in which the front and rear edges face each other at a distance. Therefore, the first fiber sheet 11 and the third fiber sheet 13 are composed of the same fiber sheet. The first high fiber density region 21 and the second high fiber density region 22 are composed of the same constituent fibers. Furthermore, the low fiber density region 23 has a two-layer structure. Details of the two-layer structure of the low fiber density region 23 will be described later.

[0014] The fiber density of the first high fiber density region 21 may be constant regardless of position in the thickness direction, or may vary depending on position in the thickness direction. In this case, the fiber density may change, for example, continuously or stepwise. The same applies to the fiber densities of the second high fiber density region 22 and the low fiber density region 23. The boundary between the first high fiber density region 21 and the low fiber density region 23 is, for example, a region where the difference between the fiber density of the first high fiber density region 21 and the fiber density of the low fiber density region 23 is 20 fibers / mm 2The difference in fiber density is 20 fibers / mm or more. 2 If the above conditions are met, when a cross section of the sheet 1 is observed under a microscope, the boundary between the first high fiber density region 21 and the low fiber density region 23 can be clearly observed. Similarly, at the boundary between the second high fiber density region 22 and the low fiber density region 23, for example, the difference in fiber density between the second high fiber density region 22 and the low fiber density region 23 is 20 fibers / mm 2 It can be a position where the value is equal to or greater than the value. The fiber density of the first high fiber density region 21, the second high fiber density region 22, and the low fiber density region 23 can be measured by the following method.

[0015] <Method for measuring fiber density> First, the first high fiber density region 21, the second high fiber density region 22, or the low fiber density region 23 to be measured is cut out from the sheet 1, and the cut surface of each region to be measured is observed under magnification using a scanning electron microscope JCM-5100 (trade name, manufactured by JEOL Ltd.). The magnification is adjusted to a magnification (150 to 500 times) that allows measurement of 30 to 60 fiber cross sections. Next, the number of fiber cross sections and the area of ​​the field of view where the number of fiber cross sections was measured are calculated. These values ​​are then used to calculate the area of ​​1 mm 2 The number of fiber cross sections per unit area was calculated and used as the fiber density (fibers / mm 2 The measurement is carried out at three locations, and the arithmetic mean value of the fiber density at the three locations is taken as the fiber density of each region.

[0016] The fiber density of the first high fiber density region 21 and the second high fiber density region 22 is independently 10 fibers / mm 2 More preferably, 15 lines / mm 2 More preferably, 20 lines / mm 2 More preferably, 30 fibers / mm 2 More than 50 lines / mm 2 or more, and preferably 300 lines / mm 2 Less than or equal to 200 lines / mm 2 or less, more preferably 150 lines / mm 2More preferably, 120 fibers / mm or less 2 Preferably, 100 or less threads / mm 2 That is, the fiber density of the first high fiber density region 21 and the second high fiber density region 22 is preferably 10 fibers / mm or less, independently of each other. 2 Over 300 lines / mm 2 Less than or equal to 15 lines / mm, preferably 15 lines / mm 2 Over 200 lines / mm 2 More preferably, 20 pieces / mm or less 2 Over 150 lines / mm 2 More preferably, 30 fibers / mm or less 2 Over 120 lines / mm 2 Preferably, 50 fibers / mm or less 2 Over 100 lines / mm 2 The following is the result. The fiber density of the first high fiber density region 21 and the second high fiber density region 22 is set to 10 fibers / mm 2 By setting the above, the particles 16a and 16b are fixed more reliably, and the movement of the particles 16 can be further restricted. The fiber density of the first high fiber density region 21 and the second high fiber density region 22 is set to 300 fibers / mm 2 By setting the following, body fluids can be smoothly transferred from the first high fiber density region 21 to the low fiber density region 23, and further, in the second high fiber density region 22, body fluids that have transferred from the low fiber density region 23 can be smoothly transferred to the second absorbent polymer layer 15.

[0017] The fiber density of the low fiber density region 23 is preferably 130 fibers / mm 2 , provided that the fiber density is lower than the fiber density of the first high fiber density region 21 and the second high fiber density region 22. 2 Less than or equal to 100 lines / mm 2 Less than 50 / mm, more preferably 2 More preferably, 40 fibers / mm or less 2 less than 5 lines / mm 2 More preferably, 10 pieces / mm 2 More preferably, 15 lines / mm 2That is, the fiber density of the low fiber density region 23 is preferably 5 fibers / mm 2 Over 130 lines / mm 2 Less than 10 pieces / mm, preferably 10 pieces / mm 2 Over 100 lines / mm 2 or less, more preferably 15 lines / mm 2 Over 50 lines / mm 2 More preferably 15 lines / mm or less 2 Over 40 lines / mm 2 The following is the result. The fiber density of the low fiber density region 23 is 5 fibers / mm 2 By setting the above, the body fluid that has migrated from the first high fiber density region 21 can be efficiently diffused within the low fiber density region 23 in a direction perpendicular to the thickness direction of the sheet 1 (hereinafter also referred to as the "planar direction"). The fiber density of the low fiber density region 23 is set to 100 fibers / mm 2 By setting the density below, the low fiber density region 23 becomes more easily deformable when pressure is applied to the sheet 1 and when the particles 16a, 16b absorb body fluids and swell.

[0018] The ratio F1 of the fiber density of the low fiber density region 23 to the fiber density of the first high fiber density region 21 (fiber density of the low fiber density region 23 / fiber density of the first high fiber density region 21) and the ratio F2 of the fiber density of the low fiber density region 23 to the fiber density of the second high fiber density region 22 (fiber density of the low fiber density region 23 / fiber density of the second high fiber density region 22) are each independently preferably 0.2 or more, more preferably 0.3 or more, even more preferably 0.5 or more, and preferably 0.9 or less, more preferably 0.8 or less, even more preferably 0.6 or less. That is, F1 and F2 are each independently preferably 0.2 or more and 0.9 or less, more preferably 0.3 or more and 0.8 or less, even more preferably 0.5 or more and 0.6 or less. By independently setting F1 and F2 to 0.9 or less, the flexibility of the sheet 1 is improved and the movement of the particles 16a and 16b is suppressed. Furthermore, by independently setting F1 and F2 to 0.2 or more and 0.9 or less, body fluids can be smoothly transferred from the first high fiber density region 21 to the low fiber density region 23, and after the body fluids are efficiently diffused in the planar direction within the low fiber density region 23, they can be smoothly transferred to the second absorbent polymer layer 15 via the second high fiber density region 22, so that the entire sheet 1 can be effectively utilized to absorb body fluids.

[0019] The thickness of the first high fiber density region 21 and the second high fiber density region 22 is independently 0.2 mm or more, more preferably 0.4 mm or more, even more preferably 0.5 mm or more, and preferably 1.5 mm or less, more preferably 1.2 mm or less, and even more preferably 1.0 mm or less, under a load of 0.05 kPa. That is, the thickness of the first high fiber density region 21 and the second high fiber density region 22 is independently 0.2 mm or more and 1.5 mm or less, more preferably 0.4 mm or more and 1.2 mm or less, and even more preferably 0.5 mm or more and 1.0 mm or less, under a load of 0.05 kPa. By independently setting the thickness of the first high fiber density region 21 and the second high fiber density region 22 to 0.2 mm or more under a load of 0.05 kPa, the particles 16a and 16b can be fixed more reliably. Furthermore, by independently setting the thickness of the first high fiber density region 21 and the second high fiber density region 22 to 1.5 mm or less under a load of 0.05 kPa, the low fiber density region 23 is sandwiched between the first high fiber density region 21 and the second high fiber density region 22, which have appropriate thicknesses, and body fluids can be efficiently diffused in the planar direction within the sandwiched region. The thickness of the first high fiber density region 21 and the second high fiber density region 22 can be measured by the following method.

[0020] <Thickness measurement method> The sheet 1 is cut in the thickness direction to cut out a measurement sample. The thickness of the first high fiber density region 21 and the second high fiber density region 22 is measured with a load of 0.05 kPa applied to the measurement sample. Specifically, for example, a digital microscope VHX-1000 manufactured by Keyence Corporation is used. At this time, a circular or square plate (an acrylic plate with a thickness of approximately 5 mm in a plan view) whose size is adjusted so that the load is 0.05 kPa is placed between the tip of the thickness meter and the measurement sample, and the thickness is measured. In the thickness measurement, 10 arbitrary locations on the measurement sample are measured, and the average value of the thicknesses at these 10 locations is calculated to be the thickness of the measurement sample.

[0021] From the viewpoint of achieving both flexibility and crush resistance in the sheet 1, it is preferable that the average fiber diameter D3 of the fibers constituting the low fiber density region 23 be larger than both the average fiber diameter D1 of the fibers constituting the first high fiber density region and the average fiber diameter D2 of the fibers constituting the second high fiber density region. Specifically, the ratio D1 / D3 of D1 to D3 and the ratio D2 / D3 of D2 to D3 are each independently preferably 0.3 or greater, more preferably 0.4 or greater, and even more preferably 0.5 or greater. From the viewpoint of promoting diffusion of body fluids in the planar direction in the low fiber density region 23, D1 / D3 and D2 / D3 are each independently preferably 0.9 or less, more preferably 0.8 or less, and even more preferably 0.7 or less. In summary, D1 / D3 and D2 / D3 are each independently preferably 0.3 or more and 0.9 or less, more preferably 0.4 or more and 0.8 or less, and even more preferably 0.5 or more and 0.7 or less.

[0022] To prevent the sheet 1 from being crushed when pressure is applied to the sheet 1, the average fiber diameter D1 of the fibers constituting the first high fiber density region 21 and the average fiber diameter D2 of the fibers constituting the second high fiber density region 22 are each independently preferably 10 μm or more and 20 μm or less, more preferably 12 μm or more and 18 μm or less, and even more preferably 14 μm or more and 16 μm or less. Furthermore, from the viewpoint of promoting the diffusion of body fluids in the planar direction in the low fiber density region 23, the average fiber diameter D3 of the fibers constituting the low fiber density region 23 is preferably 16 μm or more and 35 μm or less, more preferably 18 μm or more and 30 μm or less, and even more preferably 20 μm or more and 28 μm or less. The average fiber diameters D1, D2 and D3 can be measured by the following method.

[0023] <Method for measuring average fiber diameters D1, D2, and D3> Ten or more fibers are arbitrarily selected from the first high fiber density region 21, the second high fiber density region 22, or the low fiber density region 23 and used as the measurement object. The length (fiber diameter) in the direction perpendicular to the longitudinal direction of the measurement object is measured at three locations per fiber. The arithmetic mean value of the fiber diameters measured in this manner is designated as the average fiber diameter D1, D2, or D3.

[0024] In the sheet 1 shown in Fig. 1, the absorbent polymer is absent in the low fiber density regions 23. This allows the body fluid that has migrated from the first high fiber density regions 21 to the low fiber density regions 23 to be more easily diffused in the planar direction. To enhance this effect, it is preferable that the sheet 1 have the absorbent polymer only between the first fiber sheet 11 and the second fiber sheet 12, and between the second fiber sheet 12 and the third fiber sheet 13. The term "absence" means that the intentional presence of absorbent polymer in the low fiber density region 23 is excluded, and that it is acceptable for a small amount of absorbent polymer to be unavoidably mixed into the low fiber density region 23 during the manufacturing of the sheet 1.

[0025] As shown in FIG. 1, the low fiber density region 23 of the sheet 1 has a two-layer structure composed of a first layer 121 adjacent to the first high fiber density region 21 and a second layer 122 adjacent to the second high fiber density region 22. Further, the low fiber density region 23 has a void portion 31 located between the first layer 121 and the second layer 122, and a joint portion 32 where the first layer 121 and the second layer 122 are joined via an adhesive. Instead of this, the first layer 121 and / or the second layer 122 may have an uneven shape, and the first layer 121 and the second layer 122 may be intermittently in direct contact in the planar direction to form the joint portion 32. Alternatively, both the joint portion 32 formed by the direct contact of the two layers 121, 122 and the joint portion 32 where the two layers 121, 122 are joined via an adhesive may be mixed. Since the low fiber density region 23 has the void portion 31, the flexibility of the sheet 1 can be further enhanced. Further, by providing the void portion 31, the liquid permeability of the sheet 1 can be enhanced.

[0026] From the viewpoint of making the above effects more remarkable, in a plan view, it is preferable that the total area S1 of the void portions 31 is larger than the total area S2 of the joint portions 32. More specifically, the ratio S1 / S2 of S1 to S2 is preferably 2 or more, more preferably 5 or more, and still more preferably 10 or more. Also, from the viewpoint of sufficiently securing the area of the joint portion 32 to prevent the first layer 121 from peeling off from the second layer 122 and destroying the layer structure of the sheet 1, S1 / S2 is preferably 20 or less, more preferably 18 or less, and still more preferably 14 or less. Summarizing the above, S1 / S2 is preferably 2 or more and 20 or less, more preferably 5 or more and 18 or less, and still more preferably 10 or more and 14 or less. S1 / S2 can be measured by the following method.

[0027] <Measurement method of S1 / S2> A 10 cm x 10 cm sample is cut from the sheet 1 to be measured. If a 10 cm x 10 cm sample cannot be obtained, cut a sample with as large an area as possible. The bonded portions 32 of the sheet 1 to be measured are solidified using a cooling method such as cold spray, and the first layer 121 of the second fiber sheet of the sheet 1 is carefully peeled off from the second layer 122. Next, the areas where the bonded portions 32 are present are visualized using ink toner or the like on the side of the second layer 122 where the bonded portions 32 are attached. In this state, the total area of ​​the areas where the bonded portions 32 are present is measured using image processing software, and this is defined as the total area S1 of the bonded portions 32. The total area S2 of the voids 31 is calculated by subtracting S1 from the area of ​​the sample, and S1 is divided by S2 to calculate S1 / S2.

[0028] When wearing an absorbent article including the sheet 1, if the first fiber sheet 11 is positioned closer to the wearer's skin and the third fiber sheet 13 is positioned farther from the wearer's skin, gravity will tend to cause the second absorbent polymer layer 15 to absorb more of the wearer's body fluid than the first absorbent polymer layer 14. Therefore, it is advantageous to place more absorbent polymer in the second absorbent polymer layer 15 than in the first absorbent polymer layer 14. From this perspective, it is preferable that the basis weight B1 of the absorbent polymer present between the first fiber sheet 11 and the second fiber sheet 12 is smaller than the basis weight B2 of the absorbent polymer present between the second fiber sheet 12 and the third fiber sheet 13. Specifically, the ratio B2 / B1 of B1 to B2 is preferably 1.2 or greater, more preferably 1.4 or greater, and even more preferably 1.6 or greater. Furthermore, from the viewpoint of further reducing the thickness of the sheet 1, B2 / B1 is preferably 3.0 or less, more preferably 2.5 or less, and even more preferably 2.0 or less. In summary, B2 / B1 is preferably 1.2 or more and 3.0 or less, more preferably 1.4 or more and 2.5 or less, and even more preferably 1.6 or more and 2.0 or less.

[0029] The basis weight B1 of the absorbent polymer present between the first fiber sheet 11 and the second fiber sheet 12 (first absorbent polymer layer 14) is 20 g / cm 2 More than 200g / cm 2 It is preferable that the density is 40 g / cm or less. 2 More than 180g / cm 2 More preferably, it is 60 g / cm or less. 2 More than 160g / cm 2 It is more preferable that: The basis weight B2 of the absorbent polymer present between the second fiber sheet 12 and the third fiber sheet 13 (second absorbent polymer layer 15) is 80 g / cm 2 More than 250g / cm 2 It is preferable that the density is 100 g / cm or less. 2 More than 230g / cm 2 More preferably, it is 120 g / cm or less. 2 More than 210g / cm 2 It is more preferable that: The basis weights B1 and B2 can be measured by the following method.

[0030] <Measuring method for basis weight B1 and B2> A 10 cm x 10 cm sample is cut out from the sheet 1 to be measured. If a 10 cm x 10 cm sample cannot be obtained, a sample with as large an area as possible is cut out. The absorbent polymer present between the first fiber sheet 11 and the second fiber sheet 12 (first absorbent polymer layer 14) and the absorbent polymer present between the second fiber sheet 12 and the third fiber sheet 13 (second absorbent polymer layer 15) are each separated from the fiber material, and the mass of the absorbent polymer present in each layer is measured using the method described below. The measured mass of the absorbent polymer is divided by the area of ​​the sample, and the resulting value is taken as the basis weight.

[0031] <Method for measuring the mass of absorbent polymer> After solidifying the bonded portion 32 of the sheet 1 to be measured using a cooling method such as cold spray, the first layer 121 is carefully peeled off from the second layer 122 to separate the two layers. Next, the absorbent polymer is separated from the fibrous material constituting the separated layers 121 and 122, and the mass of the absorbent polymer is measured. Separation of the absorbent polymer and the fibrous material can be performed using a variety of methods that can almost completely separate the absorbent polymer and the fibrous material, without particular limitation. For example, the difference in particle size can be exploited by sieving through a fine mesh, or the difference in mass can be exploited by placing the material under a wind volume that scatters only the fibrous material, and measuring the mass before and after scattering. Alternatively, each layer can be immersed in an ascorbic acid solution and exposed to sunlight to dissolve the absorbent polymer, and the remaining fiber mass after washing is determined. The mass of the remaining fiber after washing can be calculated by subtracting the mass of the separated layer from the mass of the separated layer.

[0032] From the viewpoint of promoting diffusion of bodily fluids in the planar direction in gap portion 31, the distance between first layer 121 and second layer 122 is preferably 0.5 mm or more, more preferably 1 mm or more, and even more preferably 2 mm or more. In order to improve the transfer of bodily fluids between first layer 121 and second layer 122, the distance between first layer 121 and second layer 122 is preferably 6 mm or less, more preferably 5 mm or less, and even more preferably 4 mm or less. In summary, the distance between the first layer 121 and the second layer 122 is preferably 0.5 mm or more and 6 mm or less, more preferably 1 mm or more and 5 mm or less, and even more preferably 2 mm or more and 4 mm or less. The distance between the first layer 121 and the second layer 122 is 0.05 g / cm 2 The distance measured under a load of 100 mm can be measured by the following method.

[0033] <Method of Measuring the Distance Between the First Layer 121 and the Second Layer 122> The bonded portion 32 of the sheet 1 to be measured is solidified using a cooling means such as a cold spray, and the sheet 1 is cut along the thickness direction to cut out a sample. Next, the distance between the first layer 121 and the second layer 122 in this sample is adjusted by applying 0.05 g / cm2 The measurement is performed with a load of 100 mm applied. Specifically, for example, a digital microscope VHX-1000 manufactured by Keyence Corporation is used. In measuring the distance, 10 arbitrary locations on the sheet 1 are measured, and the arithmetic mean value of the thicknesses at these 10 locations is calculated to be the distance between the first layer 121 and the second layer 122.

[0034] 1 is folded in three, so that the side edge 35 of the first layer 121 and the side edge 36 of the second layer 122 are connected by fibers to integrate the layers 121, 122. This configuration of the sheet 1 makes it easier to prevent fluid leakage caused by excessive diffusion of bodily fluids in the planar direction in the gaps 31.

[0035] The thickness of first layer 121 and the thickness of second layer 122 are each independently, under a load of 0.05 kPa, preferably 0.2 mm or more, more preferably 0.4 mm or more, even more preferably 0.5 mm or more, and preferably 1.7 mm or less, more preferably 1.0 mm or less, and even more preferably 0.7 mm or less. That is, the thickness of first layer 121 and the thickness of second layer 122 are each independently, under a load of 0.05 kPa, preferably 0.2 mm or more and 1.7 mm or less, more preferably 0.4 mm or more and 1.0 mm or less, and even more preferably 0.5 mm or more and 0.7 mm or less. By independently setting the thickness of the first layer 121 and the second layer 122 to 0.2 mm or more under a load of 0.05 kPa, the low fiber density region 23 becomes more easily deformed when pressure is applied to the sheet 1 and when the particles 16a, 16b absorb body fluids and swell. Furthermore, by independently setting the thickness of the first layer 121 and the second layer 122 to 1.7 mm or less under a load of 0.05 kPa, the migration of body fluids from the first layer 121 to the first high fiber density region 21 and from the second layer 122 to the second high fiber density region 22 can proceed more efficiently. The thicknesses of the first layer 121 and the second layer 122 can be measured in the same manner as the thicknesses of the high fiber density regions 21 and 22 .

[0036] The first fiber sheet 11 and the third fiber sheet 13 can be liquid-permeable sheets, specifically, for example, paper and nonwoven fabrics such as air-through nonwoven fabrics and spunbond nonwoven fabrics. The first fiber sheet 11 and the third fiber sheet 13 can be the same type or different types. Here, "the same type" means that the manufacturing process, type of constituent fibers, diameter and length of the constituent fibers, thickness and basis weight of the fiber sheet are all the same between the compared sheets. If even one of these is different, the compared sheets are "different types" from each other. The second fiber sheet 12 can be made of nonwoven fabrics, woven fabrics, resin films, and the like, manufactured by various methods, as long as it has high fiber density regions 21, 22 and low fiber density regions 23. Specific examples of nonwoven fabrics that can be used as the second fiber sheet 12 include air-through nonwoven fabrics, spunbond nonwoven fabrics, air-laid nonwoven fabrics, and needle-punched nonwoven fabrics. Among these, air-through nonwoven fabrics are preferred for ease of manufacturing absorbent article sheets. Air-through nonwoven fabrics are preferred because their manufacturing method makes it easy to create a fiber density gradient along the thickness direction. Specifically, in the manufacturing process of air-through nonwoven fabrics, a fiber web is placed on a breathable belt, and hot air is blown onto the fiber web using an air-through method. This blowing force presses the fibers of the fiber web closer to the breathable belt against the breathable belt. As a result, high fiber density regions 21, 22 are formed on the breathable belt side of the resulting air-through nonwoven fabric, and a low fiber density region 23 is formed on the side where the hot air is blown. The constituent fibers of the second fiber sheet 12 may be either synthetic fibers or natural fibers, but preferably contains synthetic fibers, and more preferably is made of only synthetic fibers.

[0037] Examples of absorbent polymers used in sheet 1 include various hydrogel materials made of crosslinked hydrophilic polymers that are insoluble in water. Examples of hydrophilic polymers include sodium polyacrylate, acrylic acid-vinyl alcohol copolymer, (starch-acrylic acid) graft polymer, isobutylene-maleic anhydride copolymer and its saponification product, potassium polyacrylate, and cesium polyacrylate. These may be used alone or in combination of two or more. The absorbent polymer particles 16a, 16b, and 16c may be of different shapes, such as amorphous, blocky, bale-shaped, spherical, and spherical types, and any of these may be used.

[0038] 2 and 3 show other embodiments of the present invention. In these other embodiments, the configurations that differ from the seat 1 of the above-described embodiment will be mainly described, and the same configurations as those of the seat 1 will be assigned the same reference numerals and will not be described again. For the configurations that are not specifically described in these other embodiments, the description of the seat 1 will be applied as appropriate.

[0039] Unlike the sheet 1 shown in FIG. 1, the absorbent article sheet 1A (hereinafter also referred to as "sheet 1A") shown in FIG. 2 is not folded in thirds. Therefore, the low fiber density region 23 of the sheet 1A has a single layer structure. Furthermore, the low fiber density region 23 of the sheet 1A does not have the voids 31 and joints 32 shown in FIG. 1.

[0040] The thickness of the low fiber density regions 23 in the sheet 1A is preferably 0.5 mm or more, more preferably 0.8 mm or more, even more preferably 1.0 mm or more, and preferably 3.5 mm or less, more preferably 2.0 mm or less, and even more preferably 1.5 mm or less, under a load of 0.05 kPa. That is, the thickness of the low fiber density regions 23 is independently preferably 0.5 mm or more and 3.5 mm or less, more preferably 0.8 mm or more and 2.0 mm or less, and even more preferably 1 mm or more and 1.5 mm or less, under a load of 0.05 kPa. By setting the thickness of the low fiber density region 23 to 0.4 mm or more under a load of 0.05 kPa, the low fiber density region 23 becomes more easily deformed when pressure is applied to the sheet 1 and when the particles 16a, 16b absorb body fluids and swell. Furthermore, by setting the thickness of the low fiber density region 23 to 3.0 mm or less under a load of 0.05 kPa, the migration of body fluids from the low fiber density region 23 to the first high fiber density region 21 and the second high fiber density region 22 proceeds more efficiently. The thickness of the low fiber density region can be measured in the same manner as the thickness of the high fiber density regions 21 and 22.

[0041] Unlike the sheet 1 shown in FIG. 1, the absorbent article sheet 1B shown in FIG. 3 (hereinafter also referred to as "sheet 1B") is not folded in thirds. The sheet 1B has a two-layer structure in which the low fiber density region 23 is composed of a first layer 121 adjacent to the first high fiber density region 21 and a second layer 122 adjacent to the second high fiber density region 22. While the first layer 121 and the second layer 122 of the sheet 1 are composed of the same fiber sheet, the first layer 121 of the sheet 1B is composed of a fiber sheet different from the fiber sheet constituting the second layer 122. The fibers constituting the first layer 121 and the second layer 122 of the sheet 1B may be of the same type or different types.

[0042] The sheet 1B shown in Figure 3 has absorbent polymer particles 16c in at least some of the voids 31. The absorbent polymer present in the voids 31 may be the same as or different from the absorbent polymer present in the first absorbent polymer layer 14 and the second absorbent polymer layer 15. Since the sheet 1B has absorbent polymer particles 16c in at least some of the voids 31, when the sheet 1B absorbs bodily fluids, the particles 16c absorb the fluid and expand, increasing the volume of the voids 31. This allows the sheet 1 to have even greater fluid absorbency.

[0043] However, from the viewpoint of making it difficult for a wearer of an absorbent article including the sheet 1 to feel the hardness of the sheet 1, it is preferable that the amount of absorbent polymer present in the voids 31 is not excessive. From this viewpoint, it is preferable that the basis weight B1 of the absorbent polymer present between the first fiber sheet 11 and the second fiber sheet 12 and the basis weight B2 of the absorbent polymer present between the second fiber sheet 12 and the third fiber sheet 13 are both greater than the basis weight B3 of the absorbent polymer present in the voids 31. Specifically, the ratio B1 / B3 of B1 to B3 and the ratio B2 / B3 of B2 to B3 are each independently preferably 5 or more, more preferably 8 or more, and even more preferably 10 or more. In order to ensure a sufficient volume for the voids 31, B1 / B3 and B2 / B3 are each independently preferably 20 or less, more preferably 18 or less, and even more preferably 16 or less. In summary, B1 / B3 and B2 / B3 are each independently preferably 5 or more and 20 or less, more preferably 8 or more and 18 or less, and even more preferably 10 or more and 16 or less. B3 can be measured in the same manner as B1 and B2.

[0044] In order to avoid excessively hindering the movement of body fluids that have migrated into the low fiber density region 23 in the planar direction, it is preferable that no absorbent polymer be present in the low fiber density region 23 except for the void portion 31.

[0045] Next, a preferred method for producing the sheet for absorbent articles of the present invention will be described using the method for producing the sheet 1 shown in FIG. 1 as an example.

[0046] First, a fiber web containing the constituent fibers of the second fiber sheet 12 is subjected to a process of blowing hot air onto the fiber web to form a nonwoven fabric. This process is known as an air-through process. As described above, the air-through nonwoven fabric obtained in this manner has the lowest fiber density on the side exposed to the hot air and the fiber density increases continuously toward the opposite side. Therefore, this air-through nonwoven fabric can be suitably used as the nonwoven fabric constituting the second fiber sheet 12. The fibers of the nonwoven fabric may be natural fibers or synthetic fibers. Examples of resins constituting the synthetic fibers include polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate; polyamides such as nylon 6 and nylon 66; polyacrylic acid, polymethacrylic acid alkyl esters, polyvinyl chloride, and polyvinylidene chloride. These may be used alone or in combination of two or more. The fibers of the nonwoven fabric may also be composite fibers such as core-sheath or side-by-side types. The composite fibers may be composed of multiple resin components.

[0047] Next, an adhesive such as a hot melt adhesive is applied to the high fiber density side of the air-through nonwoven fabric (the side opposite to the side to which hot air was blown), and then absorbent polymer particles 16 are sprinkled on the same side. Next, a sheet of a first fiber sheet 11 (paper, nonwoven fabric, etc.) is bonded to the side on which the particles 16 are sprinkled, to obtain an intermediate sheet. This intermediate sheet is pressed with a nip roll or the like to reliably bond the first fiber sheet 11, particles 16, and air-through nonwoven fabric. Finally, an adhesive such as a hot melt adhesive is applied to the low fiber density side of the air-through nonwoven fabric, and then the sheet intermediate is folded in three so that the low fiber density side of the air-through nonwoven fabric faces inward, thereby obtaining sheet 1.

[0048] To manufacture the second fiber sheet 12 of the sheet 1A shown in FIG. 2, for example, two sheets of the air-through nonwoven fabric are prepared and laminated together with their low fiber density sides facing each other.

[0049] The sheet thus obtained is suitable for use as an absorbent body for an absorbent article. Absorbent articles using the sheet of the present invention generally have a longitudinal direction extending from the wearer's ventral side through the crotch region to the dorsal side, and a width direction perpendicular to the longitudinal direction. The absorbent article has a crotch region located in the wearer's crotch region, and ventral and dorsal regions extending in front and behind the crotch region. The crotch region has an excretory region-facing portion that faces the wearer's excretory region when the absorbent article is worn, and the excretory region-facing portion is usually located in or near the longitudinal center of the absorbent article.

[0050] Absorbent articles generally comprise a topsheet positioned on the wearer's skin-facing side, a backsheet positioned on the non-skin-facing side, and an absorbent interposed between the two sheets. The topsheet can be a liquid-permeable sheet, such as a nonwoven fabric or perforated film. The skin-facing side of the topsheet may have an uneven surface. For example, the skin-facing side of the topsheet may have a plurality of scattered protrusions. Alternatively, the skin-facing side of the topsheet may have alternating ridges and grooves extending in one direction. For such purposes, the topsheet may be formed using two or more nonwoven fabrics.

[0051] On the other hand, the backsheet may be made of, for example, a liquid-impermeable film or a spunbond, meltblown, or spunbond laminated nonwoven fabric. A liquid-impermeable film may be provided with a plurality of micropores to impart water vapor permeability to the film. To further improve the feel of the absorbent article, a sheet with a pleasant texture, such as a nonwoven fabric, may be laminated on the outer surface of the backsheet.

[0052] In addition to the topsheet, backsheet, and absorbent body described above, depending on the specific use of the absorbent article, leakage-preventing cuffs extending along the longitudinal direction may be arranged on both longitudinal sides of the skin-facing side. The leakage-preventing cuffs generally have a base end and a free end. The base end of the leakage-preventing cuff is located on the skin-facing side of the absorbent article, and the cuffs stand upright from the skin-facing side. The leakage-preventing cuffs are made of a liquid-resistant or water-repellent, breathable material. An elastic member made of rubber thread or the like may be arranged in a stretched state at or near the free end of the leakage-preventing cuff. When the absorbent article is worn, contraction of this elastic member causes the leakage-preventing cuffs to stand up toward the wearer's body, effectively preventing fluid excreted on the topsheet from leaking along the topsheet outward in the width direction of the absorbent article.

[0053] The absorbent article may further have an adhesive layer on the non-skin-facing surface, which is used to secure the absorbent article to underwear or another absorbent article when the absorbent article is worn.

[0054] Examples of absorbent articles having the above-described configuration include, but are not limited to, flat-type disposable diapers, pants-type disposable diapers, sanitary napkins, and incontinence pads.

[0055] In the above-mentioned absorbent article, the sheet of the present invention is used as an absorbent body, and in addition to the sheet of the present invention, an absorbent body having a different structure may be placed above or below the sheet. However, from the viewpoint of reliably achieving the effects achieved by the sheet of the present invention, it is preferable that the absorbent body provided in the absorbent article is only the sheet of the present invention.

[0056] Although the present invention has been described above based on its preferred embodiments, the present invention is not limited to such embodiments. For example, the sheet 1 shown in Fig. 1 does not have an absorbent polymer in the voids 31, but instead, the sheet 1 may have an absorbent polymer in the voids 31, similar to the sheet 1B shown in Fig. 3.

[0057] Although the present invention has been described above based on its preferred embodiments, the present invention is not limited to such embodiments. For example, the sheet 1 shown in Fig. 1 does not have an absorbent polymer in the voids 31, but instead, the sheet 1 may have an absorbent polymer in the voids 31, similar to the sheet 1B shown in Fig. 3. [Explanation of symbols]

[0058] 1, 1A, 1B Sheet for absorbent article 11 First fiber sheet 12 Second fiber sheet 13 Third fiber sheet 14 First absorbent polymer layer 15 Second absorbent polymer layer 16 Absorbent polymer particles 21 First high fiber density region 22 Second high fiber density region 23 Low fiber density region

Claims

1. A sheet for absorbent articles comprising a first fiber sheet, a third fiber sheet, and a second fiber sheet disposed between the first fiber sheet and the third fiber sheet, a first absorbent polymer layer containing particles of an absorbent polymer is provided between the first fibrous sheet and the second fibrous sheet; a second absorbent polymer layer between the second fibrous sheet and the third fibrous sheet, the second absorbent polymer layer containing particles of an absorbent polymer that is the same as or different from the absorbent polymer; The second fiber sheet is a first high fiber density region including a surface facing the first fiber sheet; a second high fiber density region including a surface facing the third fiber sheet; a low fiber density region located between the first high fiber density region and the second high fiber density region and having a fiber density lower than both high fiber density regions; A sheet for absorbent articles, comprising:

2. 2. The absorbent article sheet according to claim 1, wherein the average fiber diameter of the fibers constituting the low fiber density region is larger than both the average fiber diameter of the fibers constituting the first high fiber density region and the average fiber diameter of the fibers constituting the second high fiber density region.

3. the first fiber sheet and the second fiber sheet are bonded to each other via the particles constituting the first absorbent polymer layer, The sheet for absorbent articles according to claim 1 or 2, wherein the second fibrous sheet and the third fibrous sheet are bonded together via the particles constituting the second absorbent polymer layer.

4. the low fiber density region has a two-layer structure consisting of a first layer adjacent to the first high fiber density region and a second layer adjacent to the second high fiber density region, The low fiber density region is a gap portion located between the first layer and the second layer; a joint where the first layer and the second layer are in direct contact with each other or are joined via an adhesive, or both; The sheet for absorbent articles according to claim 1 or 2, which has

5. The absorbent sheet according to claim 4 , wherein a total area of ​​the void portions is larger than a total area of ​​the joint portions in a plan view.

6. In the absorbent article sheet, a rectangular raw sheet having a longitudinal direction and a transverse direction perpendicular to the longitudinal direction is folded into thirds so as to have fold lines along the transverse direction, The absorbent sheet according to claim 1 or 2, wherein a front end edge and a rear end edge in the longitudinal direction of the raw web face each other when the raw web is folded in thirds.

7. The sheet for absorbent articles according to claim 4 , wherein particles of an absorbent polymer are provided in at least some of the voids.

8. 8. The absorbent article sheet according to claim 7, wherein the basis weight B1 of the absorbent polymer present between the first fiber sheet and the second fiber sheet and the basis weight B2 of the absorbent polymer present between the second fiber sheet and the third fiber sheet are both greater than the basis weight B3 of the absorbent polymer present in the void portions.

9. 3. The absorbent article sheet according to claim 1, wherein the basis weight B1 of the absorbent polymer present between the first fiber sheet and the second fiber sheet is smaller than the basis weight B2 of the absorbent polymer present between the second fiber sheet and the third fiber sheet.

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