Nonwoven fabric for absorbent article

Abstract

To provide a nonwoven fabric for absorbent article capable of further improving liquid absorbability and soft feeling of an absorbent article simultaneously.SOLUTION: A nonwoven fabric for absorbent article has a skin surface side and non-skin surface side on the opposite side of the skin surface side, a plurality of ridge parts protruding on the skin surface side and extending in a plane direction, and recesses between the ridge parts adjacent to each other. A plurality of fused parts to connect fibers with each other are disposed on constituent fibers. The fused parts include film-like parts stretched between fibers.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Nonwoven fabrics are used in various applications, such as components of absorbent articles such as diapers and sanitary napkins. For example, Patent Documents 1 to 4 describe nonwoven fabrics having various uneven structures from the viewpoints of texture, cushioning properties, liquid absorbency, etc. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-133574 A [Patent Document 2] Japanese Patent Application Publication No. 3-137258 [Patent Document 3] JP 2008-25081 A [Patent Document 4] JP 2020-467 A Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, the level of functionality required by users for absorbent articles has been increasing, and therefore nonwoven fabrics used in such absorbent articles are being required to have improved functions such as liquid absorbency and texture, and there is room for further improvement in this regard. In view of the above, the present invention relates to a nonwoven fabric for absorbent articles which can further improve both the liquid absorbency and the soft feel of the absorbent article at the same time. [Means for solving the problem]

[0005] The present invention provides a nonwoven fabric for absorbent articles having a skin-facing side and a non-skin-facing side opposite the skin-facing side, a plurality of ridges protruding toward the skin-facing side and extending in a planar direction, and a recess between adjacent ridges, wherein the constituent fibers have a plurality of fused portions that bond the fibers together, and the fused portions include membrane portions stretched between the fibers.

[0006] The present invention also provides a method for producing a nonwoven fabric for absorbent articles, comprising: a pushing step of placing a fibrous web on a support having an uneven shape having a plurality of protrusions and recesses between the protrusions, and pushing the fibrous web along the recesses with a pushing part of a pushing member to form a porous fibrous web having an open surface on the pushing member side, a heat flow fusion step of applying a first heated fluid to the porous fibrous web simultaneously with or after the pushing step to fuse the fibers together to obtain a porous nonwoven fabric, and a stretch fusion step of applying a second heated fluid to the porous nonwoven fabric after the heat flow fusion step while stretching it at a draw ratio of 1.05 or more and 1.2 or less as described below. Draw ratio=(pulling speed of the porous nonwoven fabric in the pulling section downstream of the second heated fluid application section) / (feed speed of the porous nonwoven fabric in the second heated fluid application section) Effect of the Invention

[0007] The nonwoven fabric for absorbent articles of the present invention can further improve both the liquid absorbency and the soft texture of the absorbent article. According to the manufacturing method of the nonwoven fabric for absorbent articles of the present invention, the above-mentioned nonwoven fabric for absorbent articles of the present invention can be suitably manufactured. [Brief description of the drawings]

[0008] [Figure 1] 1 is a plan view showing a schematic view of an example of a nonwoven fabric for absorbent articles according to the present invention, viewed from the skin side. [Diagram 2] 2 is a cross-sectional view taken along the line R1-R1 of the nonwoven fabric for absorbent articles shown in FIG. 1. [Diagram 3]Photographs (A) and (B) are drawings showing an example of a membrane portion stretched between fibers. [Figure 4] FIG. 14 is a diagram explaining the method for measuring fiber orientation. (A) is an SEM image of the fiber, (B) is an OHP fiber image, (C) is a binarized fiber image, (D) is a power spectrum, and (E) is an angular distribution diagram of the average amplitude. [Diagram 5] 2 is a cross-sectional view taken along the line R2-R2 of the nonwoven fabric for absorbent articles shown in FIG. 1. [Figure 6] FIG. 1 is a cross-sectional view showing an example of an embodiment of a nonwoven fabric of the present invention comprising a plurality of fiber layers. [Figure 7] FIG. 1 is an explanatory diagram showing a schematic diagram of a preferred embodiment of the method for producing a nonwoven fabric for absorbent articles according to the present invention, in which (A) shows a pushing process, (B) shows a heat flow fusion process in which a porous nonwoven fabric is obtained by a first heated fluid, and (C) shows a stretch fusion process in which the porous nonwoven fabric is stretched while a second heated fluid is applied. [Figure 8] FIG. [Figure 9] FIG. [Figure 10] FIG. 13 is a plan view showing a state in which the support body and the push-in member are combined. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A preferred embodiment of the nonwoven fabric for absorbent articles according to the present invention will be described below with reference to the drawings. In this specification, the nonwoven fabric for absorbent articles may be simply referred to as a nonwoven fabric.

[0010] 1 and 2, nonwoven fabric 10 has a front and back surface, that is, a skin-facing side 10T and a non-skin-facing side 10B opposite to skin-facing side 10T. Skin-facing side 10T refers to the side that faces the skin of a wearer when nonwoven fabric 10 is incorporated into an absorbent article, and non-skin-facing side 10B refers to the side opposite to the side that faces the skin of the wearer.

[0011] The nonwoven fabric 10 has a plurality of ridges 1 that protrude toward the skin-facing side 10T and extend in a planar direction, and recesses 2 provided between adjacent ridges 1, 1. This allows the nonwoven fabric 10 to have an uneven structure in the thickness direction Z. The ridges 1 are three-dimensional fiber layers that are erected in the thickness direction Z of the nonwoven fabric 10, and are located higher on the skin-facing side 10T than the bottoms 21 of the recesses 2. Each of the plurality of ridges 1 has an apex 1A and a wall 1B that supports the apex 1A. Due to the uneven structure, the nonwoven fabric 10 can exhibit good cushioning properties, dryness due to a reduced contact area with the skin on the skin-facing side 10T, liquid migration along the extension direction of the ridges 1, and quick liquid permeability due to the ridges 1 and the recesses 2.

[0012] The planar direction is a surface direction understood when the skin facing side 10T is viewed in plan. In other words, the planar direction is also a direction along the plane of the non-skin facing side 10B of the nonwoven fabric 10. For example, it corresponds to a straight line L tangent to the surface of the non-skin facing side 10B of the nonwoven fabric 10 shown in FIG. 2. In this case, the thickness direction Z of the nonwoven fabric 10 corresponds to a direction perpendicular to the straight line L. More specifically, the extension direction of the ridge portion 1 is one direction included in the plane of the planar direction. The multiple ridge portions 1 all extend in the one direction, and are arranged parallel to each other at a distance in a direction intersecting the one direction. In this embodiment, the one direction is the longitudinal direction Y of the nonwoven fabric 10, and the direction intersecting the one direction is the width direction X perpendicular to the longitudinal direction Y of the nonwoven fabric 10. However, the one direction and the direction intersecting the one direction are not limited to this embodiment, and can be appropriately set within the plane of the planar direction. In addition, the direction intersecting the one direction is not limited to a direction perpendicular to the one direction, and may be a direction intersecting at any angle.

[0013] As shown in FIG. 3, the constituent fibers of the nonwoven fabric 10 are provided with a plurality of fused parts 4 that bond the fibers together. The fused parts 4 include those that are provided at the intersections of the fibers to bond the fibers together (hereinafter, the fused parts at the intersections are designated by the reference numeral 4A). The presence of the fused parts 4A at the intersections allows the nonwoven fabric 10 to maintain its shape as a sheet. An example of such a nonwoven fabric is an air-through nonwoven fabric in which the fused fiber parts are formed by an air-through method. Therefore, the constituent fibers of the nonwoven fabric 10 include thermoplastic fibers.

[0014] Furthermore, the fused portion 4 includes a film-like portion 4B stretched between the fibers as shown in Figs. 3(A) and (B). The membrane portion 4B is a thin film formed so that the resin connects the fibers and partially fills the space between the fibers. The membrane portion 4B imparts mobility and shape recovery properties to the network structure of the constituent fibers consisting of the fusion points 4A at the intersections, in which the distance between the fibers expands and contracts within a certain range while maintaining the positional relationship between the fibers. Such a membrane portion 4B is formed by a stretch-fusion process in which a heated fluid is applied again to the nonwoven fabric after forming the nonwoven fabric including the fusion parts 4A at the intersections in the manufacturing method described below. That is, the membrane portion 4B can be said to be a thin film between the fibers obtained by melt-stretching the thermoplastic fibers of the constituent fibers. The membrane portion 4B may be formed adjacent to the fusion parts 4A at the intersections of the fiber intersections, or may be formed away from the fusion parts 4A. The shape of the membrane portion 4B may be planar or string-like. Such membrane portions 4B increase the elasticity of the network structure of the constituent fibers of the nonwoven fabric 10, starting from the fused portions 4A, and allow the fabric 10 to move (deform) more gently and gradually. This also makes it easier for the fabric 10 to exhibit more reliable recovery (cushioning properties).

[0015] As a result, the nonwoven fabric 10 has a softer feel. Furthermore, nonwoven fabric 10 also contains membrane portions 4B in rib portions 1, improving the shape retention of rib portions 1. As a result, when nonwoven fabric 10 is incorporated as a component of an absorbent article and is subjected to a load due to wearing, the function of rib portions 1 to spread received excreted liquids and the like along rib portions 1 is easily maintained, and quick liquid transfer from rib portions 1 to recesses 2 is easily sustained. In other words, nonwoven fabric 10 can further improve both the liquid absorbency and the soft texture of the absorbent article at the same time.

[0016] From the viewpoint of enhancing the soft feel of the nonwoven fabric 10 while favorably exerting the above-mentioned effects, it is preferable that the membrane portion 4B is disposed in a larger amount on the non-skin side 10B than on the skin side 10T. Also, from the viewpoint of enhancing the shape retention of the ridge portion 1 in addition to the above-mentioned soft feel, it is more preferable that the membrane portion 4B is disposed in a larger amount on the non-skin side of the ridge portion 1 than in other portions.

[0017] (Method of confirming membrane portion 4B and measuring occurrence frequency) The non-skin-facing side 10B of the nonwoven fabric 10 is observed in plan view, and five locations of the non-skin-facing side of the top 1A of the ridge portion 1 are imaged at about 50x using a scanning electron microscope (JCM-6000Plus manufactured by JEOL Ltd.). The number of membrane portions 4B within an area of ​​1 mm x 1 mm is counted, and the numbers at the five locations are averaged. The average value obtained is regarded as the occurrence frequency of the membrane portions 4B.

[0018] From the viewpoint of making the above-mentioned action more effective, the occurrence frequency of the membrane portion 4B confirmed by the above-mentioned measurement method is preferably 0.3 or more, more preferably 0.5 or more, and even more preferably 0.8 or more. From the viewpoint of maintaining the appearance of the nonwoven fabric 10, the occurrence frequency of the membrane portions 4B is preferably 30 or less, more preferably 20 or less, even more preferably 10 or less, and even more preferably 5 or less.

[0019] Furthermore, in the nonwoven fabric 10, it is preferable that the rib portion 1 has fiber orientation along the extending direction (longitudinal direction Y) of the rib portion 1. This allows the nonwoven fabric 10 to further increase the mobility of liquid (direction of liquid spreading) along the extending direction of the rib portion 1. Furthermore, the mobility of liquid along the extending direction of the rib portion 1 can be maintained even under load due to the shape retention of the rib portion 1 caused by the presence of the above-mentioned membrane portion 4B. When this nonwoven fabric 10 is incorporated as a component of an absorbent article and the rib portion 1 is arranged in the longitudinal direction of the absorbent article, the excreted liquid is highly mobile in the longitudinal direction of the absorbent article, realizing high liquid absorbency over a wider range. At the same time, the mobility of the excreted liquid in the width direction of the absorbent article is restricted, further improving prevention of side leakage.

[0020] The fiber orientation is a concept consisting of fiber orientation angle and orientation strength. The fiber orientation angle is a concept that indicates the direction in which multiple fibers with different orientation directions are oriented as a whole fiber. Therefore, it can be said to be a numerical representation of the shape of a fiber assembly. The fiber orientation strength is a concept that indicates the amount of fibers that exhibit an orientation angle. If the orientation angle is less than 1.05, it can be said that there is almost no orientation, and if it is 1.05 or more, there is orientation. The fiber orientation along the extension direction of the ridge portion 1 is specified for the fibers at the crest 1A of the ridge portion 1. When the orientation angle of the fibers along the extension direction of the crest 1 is 60° or more and 120° or less, and the orientation strength is 1.1 or more, it can be said that the ridge portion 1 has fiber orientation along its extension direction. The orientation angle and orientation strength are formed for the first time by the stretch-fusion process in the manufacturing method described below, and are extremely high compared to conventional ones.

[0021] (Method of measuring fiber orientation along the extension direction of the crest 1A of the ridge portion 1) First, the fibers of the top 1A of the ridge 1 observed in a planar view of the skin-facing side 10T of the nonwoven fabric 10 are photographed with a scanning electron microscope (JCM-6000Plus manufactured by JEOL Ltd.) to obtain an SEM image as shown in Fig. 4(A). When photographing, the magnification is adjusted (100 to 300 times) so that 10 or more fibers can be measured. The obtained SEM image is printed out and the fibers are traced onto an OHP sheet to obtain an OHP fiber image as shown in Figure 4(B). The OHP fiber image is then scanned into a personal computer. A black and white binarized fiber image is obtained from the digitized fiber image (Figure 4(C)). The binarized fiber image is Fourier transformed using a fiber orientation analysis program to obtain a power spectrum as shown in Figure 4(D). The fiber orientation analysis program used is (Surface fiber orientation analysis program FiberOri8single03.exe (published by Toshiharu Emae, Paper Science Laboratory, Department of Biomaterials Science, Graduate School of Agricultural and Life Sciences, The University of Tokyo)). This is approximated by an ellipse to obtain an angle distribution diagram of the average amplitude as shown in Figure 4(E). The orientation angle and orientation strength can be obtained from this angle distribution diagram. In the angle distribution diagram shown in Figure 4(E), α is the orientation angle, and the ratio of the major axis LA to the minor axis SA in the approximated ellipse (LA / SA) is the orientation strength.

[0022] The orientation angle of the fibers along the extension direction of the crests 1A of the ridges 1 is preferably 70° or more, more preferably 80° or more, and even more preferably 91° or more, from the viewpoint of making it easier to develop the membrane portions 4B. Also, the orientation angle of the fibers along the extension direction of the crests 1A of the ridges 1 is preferably 115° or less, and more preferably 110° or less, from the same viewpoint as above. In addition, the orientation strength of the fibers along the extension direction of the tops 1A of the ridges 1 is preferably 1.15 or more, more preferably 1.2 or more, from the same viewpoint as above. Also, the orientation strength of the fibers along the extension direction of the tops 1A of the ridges 1 is preferably 1.8 or less, more preferably 1.7 or less, from the viewpoint of maintaining the appearance (outer appearance).

[0023] In the nonwoven fabric 10, it is preferable that the openings 3 are disposed at the bottoms 21 of the recesses 2. This can increase the downward fluidity (liquid permeability) of liquid that moves along the ribs 1 in the extension direction (longitudinal direction Y). As a result, when the nonwoven fabric 10 is incorporated as a constituent member of an absorbent article, the liquid absorbency of the absorbent article can be increased. In addition, the membrane-like portions 4B stretched between the fibers are more likely to be formed on the non-skin-facing side of the ribs 1, which has a greater amount of fiber, than on the bottoms 21, where the openings 3 are located, and the above-mentioned effect of the membrane-like portions 4B can be more effectively exerted.

[0024] Unlike the fine holes formed between fibers, the openings 3 are holes formed by processing the nonwoven fabric 10, and have a much larger opening area than the fine holes formed between fibers. In FIG. 1, the entire area between adjacent ribs 1, 1 is shown as openings 3, but the size of openings 3 can be selected appropriately. For example, there may be a fiber layer extending from the lower end of wall 1B of rib 1 toward opening 3. At least 1.0 mm 2 It is preferable that the opening area is equal to or more than this. The size of the openings 3 can be measured using a microscope (for example, VHX6000 (product name, manufactured by Keyence Corporation)). Specifically, the nonwoven fabric 10 is viewed in plan from the skin-facing side 10T, the areas of the openings 3 are measured at 10 points using a microscope, and the average value is taken as the opening area of ​​each opening.

[0025] The area of ​​the opening 3 is set to 1.0 mm2 in order to enhance the liquid permeability. 2 More than 1.5mm is preferable. 2 More preferably, 2.0 mm or more 2 More preferably, the area of ​​the opening 3 is 50 mm 2 Less than 40mm is preferable 2 Less than or equal to 35mm is preferred 2 The following is even more preferred:

[0026] The planar shape of the openings 3 may be various from the viewpoint of enhancing the downward flowability in the nonwoven fabric 10, and examples thereof include a circle, an ellipse, and a rectangle. However, the planar shape of the apertures 3 is preferably an elongated ellipse having a major axis and a minor axis from the viewpoint of preventing the passage of the superabsorbent polymer material (so-called SAP (superabsorbent polymer)) contained in the absorbent article when the nonwoven fabric 10 is incorporated as a constituent member of the absorbent article, and from the viewpoint of suppressing wet-back of excreted liquid once absorbed by the absorbent body. This enhances the ability to prevent the superabsorbent polymer material from leaking out of the absorbent article, thereby enhancing the liquid absorbency of the absorbent article.

[0027] From the above viewpoints, the ratio of the major axis to the minor axis in the planar shape of the pores 3 is preferably 1.2 or more, more preferably 1.3 or more, and even more preferably 1.5 or more. From the viewpoint of maintaining the appearance of the nonwoven fabric 10, the ratio of the major axis to the minor axis is preferably 5 or less, more preferably 4 or less, and even more preferably 3.5 or less. From the viewpoint of further improving the leakage prevention property of the superabsorbent polymer material, the minor axis is preferably 3 mm or less, more preferably 2 mm or less, and even more preferably 1.8 mm or less. From the viewpoint of further improving the liquid permeability of the nonwoven fabric 10, the minor axis is preferably 0.5 mm or more, and more preferably 0.8 mm or more. The major axis is preferably 1 mm or more, more preferably 1.5 mm or more, and even more preferably 2.1 mm or more, from the viewpoint of further increasing the liquid permeability of the nonwoven fabric 10. Moreover, the major axis is preferably 5 mm or less, and more preferably 4 mm or less, from the viewpoint of maintaining the appearance of the nonwoven fabric 10. The above values ​​regarding the planar shape of the opening 3 can be measured using a microscope (for example, VHX6000 (product name, manufactured by Keyence Corporation)).

[0028] The planar shape of the apertures 3, which are elongated ellipses having the above-mentioned major and minor axes, is finely formed by enhancing the shape through the stretching and fusing step in the manufacturing method described below. By using such a manufacturing method, the apertures 3 are formed elongated, and the groove width of the recesses 2 is narrowed accordingly. As a result, in an absorbent article incorporating the nonwoven fabric 10 as a topsheet, the wearer's skin is less likely to come into contact with the absorbent body when pressure is applied, and the effect of suppressing the rewetting of excreted liquid once absorbed is also enhanced.

[0029] In the nonwoven fabric 10, the walls 1B constituting the rib portions 1 preferably extend perpendicular to the planar direction of the nonwoven fabric 10. The planar direction of the nonwoven fabric 10 is as defined above. The term "perpendicular" means the direction along the thickness direction Z of the nonwoven fabric 10. As a result, the wall 1B vertically supports the top 1A of the ridge 1. This, together with the membrane portion 4B stretched between the fibers, enhances the retention of the three-dimensional shape of the ridge 1. As a result, when the nonwoven fabric 10 is used as a top sheet of an absorbent article, the thickness of the uneven structure is easily maintained, and the recesses 1 on the skin side 10T are less likely to come into contact with the skin. That is, the skin contact area on the skin side 10T of the nonwoven fabric 10 is suppressed to the ridge 1 (mainly the top 1A), and the non-contact area between the wearer and the nonwoven fabric 10 is increased. This can improve the breathability of an absorbent article incorporating the nonwoven fabric 10 as a top sheet, and can improve the dryness of the wearer's skin surface. In addition, the liquid return path from the nonwoven fabric 10, which is the top sheet, to the wearer's skin surface is reduced, suppressing the opportunity for liquid to adhere to the skin surface, and further improving the dryness described above. Furthermore, coupled with the soft feel, shape recovery and shape retention provided by the membrane portions 4B described above in the nonwoven fabric 10, the wearing comfort of the absorbent article is further improved.

[0030] The "perpendicular" of the wall 1B means that the angle θ with respect to the plane of the non-skin facing side 10B of the nonwoven fabric 10 shown in FIG. 2 is not limited to being strictly 90°, but is between 60° and 120°. In this range, the wall 1B has a shape that extends at an angle that is substantially recognized as 90° in the thickness direction Z of the nonwoven fabric 10. The angle θ means the intersection angle between the plane of the non-skin facing side 10B of the nonwoven fabric 10 and the extension line of the wall 1B. Specifically, as shown in FIG. 2, in a cross section in the thickness direction Z including the ridge portion 1, the angle θ means the interior angle of the angle formed by the center line M of the width of the fiber layer of the wall 1B and the straight line L tangent to the surface of the non-skin facing side 10B of the nonwoven fabric 10. This angle θ can be obtained by observing a micrograph of the cross section obtained by the above-mentioned microscope.

[0031] 2, wall 1B extends linearly between top 1A and bottom 21 of recess 2, and the entire wall 1B is erected perpendicular to bottom 21 of recess 2. However, this is not limited thereto, and wall 1B may include a portion extending in a curved or wavy shape. In this case, the angle θ is specified by taking the line connecting the boundary point between top 1A and wall 1B and the end of wall 1B on the non-skin side as center line M. In addition, it is preferable that all of the multiple wall portions 1B extend perpendicular to the planar direction of the nonwoven fabric 10, but some of the wall portions 1B may not extend perpendicular to the planar direction of the nonwoven fabric 10. In the latter case, the number of perpendicular wall portions 1B is preferably 60% or more of the wall portions 1B in the entire rib portion 1, from the viewpoint of further enhancing the effect of the fiber orientation along the thickness direction Z described above.

[0032] In a cross section of the nonwoven fabric 10 in the thickness direction Z, including the ridge portions 1 and the recessed portions 2, the fiber layer of the wall portion 1B can be partitioned by the following method. That is, the nonwoven fabric 10 having a cross section in the thickness direction Z including the ridges 1 and the recesses 2 is placed on the base of the microscope with the non-skin facing side 10B facing down. Next, a flat plate (e.g., a flat acrylic plate) is placed on the skin facing side 10T of the nonwoven fabric 10, and a pressure of 4.9 mN / cm 2A load of 10 ... In specifying the boundary between top 1A and wall 1B, the thickness of top 1A in the portion without wall 1B is defined as the thickness of the end of top 1A, and the portion excluding this thickness is defined as wall 1B. Wall 1B has an end (also called base 1D) on non-skin facing side 10B, and bottom 21 of recess 2 refers to the region provided between adjacent protrusions 1, 1, including base 1D.

[0033] Furthermore, in nonwoven fabric 10, the fibers of wall portion 1B preferably have a fiber orientation along thickness direction Z with respect to the plane of non-skin facing side 10B of nonwoven fabric 10. This can further enhance the above-mentioned effect due to the vertical extension of wall portion 1B. Furthermore, the fiber orientation along the thickness direction Z in the wall portion 1B, combined with the elasticity due to the fiber structure of the fiber layer in the wall portion 1B, provides the nonwoven fabric 10 with excellent cushioning properties. That is, the nonwoven fabric 10 has an excellent softness against the skin that is further enhanced. Furthermore, when the nonwoven fabric 10 is used as a top sheet in an absorbent article, the liquid mobility along the extension direction due to the fiber orientation of the ridges and the downward liquid flowability due to the openings 3 arranged at the bottoms 21 of the recesses 2 are more likely to be sustained even under load, and the return of liquid from the absorbent body to the skin side is suppressed. This allows the nonwoven fabric 10 to simultaneously further improve the liquid absorbency and soft feel of an absorbent article incorporating the nonwoven fabric 10.

[0034] The fiber orientation along the thickness direction Z of the wall portion 1B is represented by the fiber orientation angle and orientation strength, as described above. When the fiber orientation angle is 60° or more and 120° or less and the orientation strength is 1.1 or more in a cross section of the thickness direction Z of the wall portion 1B, it can be said that the wall portion 1B has fiber orientation along the thickness direction Z.

[0035] (Method of measuring fiber orientation along the thickness direction Z of the wall portion 1B) As shown in FIG. 1, the wall portion 1B is measured in the following procedure. That is, the cross section of the fiber layer of the wall portion 1B defined in the cross section of the thickness direction Z of the nonwoven fabric 10, including the rib portions 1 and the recesses 2 of the nonwoven fabric 10, is observed at a magnification of 50 times using a scanning electron microscope (SEM). The fiber orientation angle and orientation strength are measured for the fibers of the observed wall portion 1B by applying the above-mentioned (method of measuring fiber orientation along the extending direction of the crests 1A of the rib portions 1) mutatis mutandis.

[0036] The orientation angle of the fibers in the thickness direction Z in the wall portion 1B is preferably 60° or more, more preferably 70° or more, from the viewpoint of uneven processing. Also, the orientation angle of the fibers in the thickness direction Z in the wall portion 1B is preferably 120° or less, more preferably 110° or less, from the viewpoint of uneven processing, and further preferably 99° or less, from the viewpoint of further suppressing the movement of liquid in the width direction X (liquid leakage between the crotch areas). Furthermore, by making the orientation angle of the fibers in the thickness direction Z in the wall portion 1B 99° or less, the effect of the fiber orientation of the top portion 1A of the ridge portion 1 becomes more significant, and in cooperation with this, the mobility of the liquid can be more suitably controlled. In addition, the fiber orientation strength in the thickness direction Z of the wall portion 1B is preferably 1.15 or more, more preferably 1.2 or more, from the viewpoint of uneven processing. Also, the fiber orientation strength in the thickness direction Z of the wall portion 1B is preferably 1.8 or less, more preferably 1.7 or less, from the viewpoint of appearance (outer appearance), and even more preferably 1.29 or less, from the viewpoint of further suppressing the movement of liquid in the width direction X (liquid leakage between the crotch areas). Also, by having the fiber orientation strength in the thickness direction Z of the wall portion 1B be 1.29 or less, the effect of the fiber orientation of the top portion 1A of the ridge portion 1 becomes more significant, and in cooperation with this, the mobility of the liquid can be more suitably controlled.

[0037] Furthermore, as shown in FIG. 1, the nonwoven fabric 10 preferably has, together with the ribs 1, saddle portions 15 which extend in a direction X intersecting the ribs 1 and connect adjacent ribs 1, 1 to each other. The saddle portion 15, like the rib portion 1, protrudes from the non-skin side 10B to the skin side 10T, and is a three-dimensional fiber layer standing in the thickness direction Z of the nonwoven fabric 10. More specifically, the saddle portion 15 has an apex 15A on the skin side 10T and a wall portion 15B supporting the apex 15A. As described above, the fibers of the wall portion 15B preferably have a fiber orientation along the thickness direction Z. In addition, the wall portion 15B preferably extends perpendicular to the planar direction of the nonwoven fabric 10. The "perpendicular" is synonymous with the "perpendicular" defined in the rib portion 1 described above. The fiber orientation along the thickness direction Z of wall portion 15B in saddle portion 15 and the “vertical” of wall portion 15B can be measured in a cross section perpendicular to the extension direction of saddle portion 15 (cross section in thickness direction Z at the position of line R2-R2 along one direction Y in FIG. 1) as shown in FIG. 5, in the same manner as the measurement method described above for wall portion 1B.

[0038] The above structure makes it difficult for the ridges 1 connected by the saddle 15 to approach each other, and prevents the ridges 1 from falling in one direction due to an external force such as pressure. That is, the saddle 15 supports the ridges 1 from the side, improving the shape retention of the ridges 1. This makes it easier for the thickness of the ridges 1 to remain under load, and makes it easier to maintain the soft texture of the ridges 1. In addition, for example, when the nonwoven fabric 10 is incorporated as a component of an absorbent article, the distance between the top 1A of the ridges 1 and the absorbent side of the non-skin-facing side 10B is more easily maintained even under the body pressure of the wearer when wearing the absorbent article, making it even more difficult for liquid to return to the skin-facing side 10T. Furthermore, the presence of the saddle 15 acts to block excreted liquid between the ridges 1, 1, and further improves the liquid flow prevention on the skin-facing side 10T of the nonwoven fabric 10.

[0039] In a plan view from one surface side 10T of the nonwoven fabric 10, the saddle portion 15 preferably extends in a direction intersecting the extension direction of the rib portion 1. The extension direction of the saddle portion 15 can be in various directions as long as it connects adjacent rib portions 1, and is preferably a direction perpendicular to the extension direction of the rib portion 1. For example, it is preferable that the extension direction of the rib portion 1 is the longitudinal direction Y as described above, and the extension direction of the saddle portion 15 is the width direction X of the nonwoven fabric 10. Hereinafter, these directions are also referred to as the extension direction Y of the rib portion 1 and the extension direction X of the saddle portion 15. In addition, the planar shape of each saddle portion 15 as viewed from the skin side 10T is not limited to a rectangle as shown in Fig. 1, and may be various shapes. For example, the planar shape of the saddle portion 15 as viewed from the skin side 10T may be such that the width increases toward the ridge portion 1.

[0040] In the example shown in FIG. 1, the saddle portions 15 are arranged in a plurality of band regions 16 extending parallel to the ribs 1 between the ribs 1, 1 in a plan view of the skin-facing side 10T of the nonwoven fabric 10. In each band region 16, a plurality of saddle portions 15 are arranged at intervals along the extension direction Y of the ribs 1 running in parallel. The aforementioned recesses 2 are located at the intervals between the saddle portions 15. That is, in each band region 16, the saddle portions 15 and the recesses 2 are alternately arranged. As a result, the recesses 2 are partitioned by the wall portion 1B of the rib portion 1 and the wall portion 15B of the saddle portion 15. More specifically, the region surrounded by the plurality of ribs 1 and the plurality of saddle portions 15, which are three-dimensional fiber layers erected in the thickness direction Z, is the box-shaped or cylindrical recess 2. The aforementioned opening portion 3 is arranged at the bottom 21 of the recess 2.

[0041] 1, in a plan view from the skin-facing side 10T of nonwoven fabric 10, ribs 1 and saddles 15 are arranged in a lattice pattern, and recesses 2 are arranged in a square pattern dotted within the lattice. If such square recesses 2 have the aforementioned openings 3, liquid spread in the extension direction due to the aforementioned fiber orientation of the ribs 1 can be collected into the openings 3 and allowed to descend more reliably, thereby further enhancing the downward fluidity of the liquid. This allows the nonwoven fabric 10 to simultaneously further improve the liquid absorbency and soft feel of an absorbent article incorporating the nonwoven fabric 10.

[0042] Although the saddle portion 15 has a three-dimensional fiber structure similar to that of the rib portion 1, it is preferable that the saddle portion 15 has a portion that is lower in height from the bottom 21 of the recess 2 than the rib portion 1, as shown in Figures 2 and 5. This further reduces the contact area between the skin and the skin-facing side 10T of the nonwoven fabric 10, maintaining a pleasant feel against the skin and increasing breathability to further prevent stuffiness between the skin and the saddle portion. The difference (H1-H15) between the height H1 in the thickness direction Z of the rib portion 1 and the height H15 in the thickness direction Z of the saddle portion 15 is preferably 0.5 mm or more and 7 mm or less in terms of improving the above-mentioned action. The height H1 in the thickness direction Z of the rib portion 1 is the distance in the thickness direction Z from a plane in contact with the surface of the non-skin side 10B of the nonwoven fabric 10 to the skin side 10T of the crest 1A of the rib portion 1. The height H15 in the thickness direction Z of the saddle portion 15 is the distance in the thickness direction Z from a plane in contact with the surface of the non-skin side 10B of the nonwoven fabric 10 to the skin side 10T at the lowest position of the crest 15A of the saddle portion 15.

[0043] (Method of measuring the difference between the height H1 of the ridge 1 in the thickness direction Z and the height H15 of the saddle 15 in the thickness direction Z) As shown in Fig. 5, a thickness direction Z cross section (thickness direction Z cross section at the position of line R2-R2 in Fig. 1) of nonwoven fabric 10 is prepared at the lowest position of saddle portion 15 along the extension direction of band region 16 in which saddle portions 15 are arranged, and placed on a horizontal table so that the surface of non-skin side 10B abuts it. The height H1 from the horizontal table to skin side 10T of crest 1A of ridge portion 1 and the height H15 to skin side 10T of crest 15A of saddle portion 15 are measured. The height difference (H1-H15) is calculated from these measured values. The above-mentioned microscope can be used to measure the height from the horizontal table.

[0044] The uneven structure of nonwoven fabric 10 may be composed of one fiber layer, or may be composed of two or more fiber layers. When the uneven structure of nonwoven fabric 10 is composed of multiple fiber layers, it is preferable that the multiple fiber layers have different fiber diameters from each other, from the viewpoint of a softer feel and further increasing the overall load-bearing strength, and it is preferable that the fiber layer on non-skin side 10B has a fiber diameter larger than that of the fiber layer on skin side 10T. In this case, it is preferable that the membrane portion 4B stretched between the fibers is in the fiber layer on non-skin side 10B.

[0045] As another embodiment in which nonwoven fabric 10 is composed of a plurality of fiber layers, the uneven structure described above may be composed only of the fiber layer on skin-facing side 10T. A preferred embodiment in this case will be described below with reference to an example shown in FIG. The nonwoven fabric 20 shown in Fig. 6 has a laminated structure of an upper layer M1 on the skin-facing side 20T and a lower layer M2 on the non-skin-facing side 20B. The upper layer M1 has the ridge portion 1 and the recessed portion 2 described above. The upper layer M1 and the lower layer M2 are laminated at the bottom 21 of the recessed portion 2 (this portion is called the laminated portion 25). This allows the nonwoven fabric 20 to have a thick and fluffy texture, and the lower layer M2 supports the uneven structure of the upper layer M1, making it easier to more stably achieve the above-mentioned effect of the uneven structure of the upper layer M1. In particular, the laminated portion 25 serves as the base of the uneven structure, making it easier to more stabilize the three-dimensional shape of the ridge portion 1. The nonwoven fabric 20 also contains the above-mentioned membrane portions 4B between the constituent fibers. In order to satisfactorily exert the above-mentioned effects of the membrane portions 4B, it is preferable that the membrane portions 4B are disposed in the lower layer M2.

[0046] In the nonwoven fabric 20 shown in FIG. 6, the above-mentioned openings 3 are not present. However, from the viewpoint of increasing the downward fluidity of the liquid, it is preferable that the above-mentioned openings 3 are present in the upper layer M1. When the openings 3 are present, the fiber layer of the lower layer M2 may be raised from the openings 3 to the skin side 10T. In this case, the laminated portion 25 of the upper layer M1 and the lower layer M2 is present at the position of the bottom 21 excluding the openings 3 of the recess 2 of the upper layer M1, and the laminated area of ​​the laminated portion 25 of the upper layer M1 and the lower layer M2 is narrower than when the openings 3 are not present. However, even when the openings 3 are present, the fiber layer of the lower layer M2 can be raised from the openings 3 to the skin side 10T, so that the three-dimensional shape of the ridge portion 1 can be stabilized. Furthermore, in nonwoven fabric 20, from the viewpoint of strengthening the directionality of liquid spreading, it is preferable that rib portion 1 has the above-mentioned fiber orientation.

[0047] In addition, in the nonwoven fabric 20, the inside of the rib portion 1 of the upper layer M1 preferably has a structure in which the lower layer M2 penetrates (a structure with an intrusion portion 5) (FIG. 6). This makes it easier for the lower layer M2 to actively draw in liquid even in the rib portion 1, further improving the downward fluidity of the liquid. In addition, the cushioning properties of the rib portion 1 are further improved, and the feel of the nonwoven fabric 20 is further improved. In this case, the inside of the rib portion 1 may be solid or hollow.

[0048] The fiber diameter of the fibers in the lower layer M2 is preferably larger than that of the fibers in the upper layer M1. This can increase the liquid permeability from the openings 3 when fibers thicker than those in the upper layer M1 are exposed as protuberances from the openings 3 of the upper layer M1. From this viewpoint, the ratio (D2 / D1) of the fiber diameter (D2) of the lower layer M2 to the fiber diameter (D1) of the upper layer M1 is preferably 1.2 or more, more preferably 1.5 or more, and even more preferably 2.0 or more. Moreover, from the viewpoint of improving the texture of the raised portion, the ratio (D2 / D1) is preferably 10.0 or less, more preferably 9.0 or less, and even more preferably 8.0 or less. The fiber diameter (D2) of the fibers in the lower layer M2 is preferably 15 μm or more, more preferably 20 μm or more, and even more preferably 25 μm or more, from the viewpoint of improving the liquid permeability from the openings 3. Moreover, the fiber diameter (D2) of the fibers in the lower layer M2 is preferably 80 μm or less, more preferably 70 μm or less, and even more preferably 60 μm or less, from the viewpoint of improving the texture of the protruding parts. From the viewpoint of improving the texture, the fiber diameter (D1) of the fibers in the upper layer M1 is preferably 8 μm or more, more preferably 10 μm or more, and even more preferably 12 μm or more. Also, from the viewpoint of maintaining softness, the fiber diameter (D1) of the fibers in the upper layer M1 is preferably 40 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less. The above fiber diameter means the average fiber diameter in each fiber layer.

[0049] (Method of measuring average fiber diameter in each fiber layer) The fiber diameter can be measured by observing the cross section of the fiber layer using the following method. The part to be measured (for example, the upper layer M1) is frozen in an unloaded state using cold spray or liquid nitrogen, etc., to fix the structure, and in this state, it is cut in the thickness direction Z using a cutter blade to expose the cross section of the measurement part. The cross section is observed at a magnified scale using a scanning electron microscope (JCM-5100 manufactured by JEOL Ltd.), and the magnification is adjusted to a magnification (300 times) at which the fiber cross section can be measured. Five observation photographs are taken in this state to obtain a cross-sectional observation photograph. Next, the fiber diameters of 30 fibers per photograph are measured, and the arithmetic average value is taken as the average fiber diameter of the present invention. When the fibers are not perfectly circular, the line segment that connects two points on the periphery in the cross section and has the maximum across length in the cross section is defined as the long axis, and the line segment that is perpendicular to the long axis and has the maximum length is defined as the short axis. The lengths of the long axis and the short axis of each fiber are then measured by analyzing and calculating them using image analysis software or the like, and the arithmetic mean value of the long axis length and the short axis length of a single fiber is defined as the fiber diameter of each fiber, and the arithmetic mean value of the fiber diameters of 30 fibers is defined as the average fiber diameter of the fibers in the present invention. When the nonwoven fabric to be measured is incorporated in an absorbent article, the absorbent article is sprayed with a cold spray, the hot melt adhesive is solidified, and then the nonwoven fabric to be measured is carefully peeled off. This method is common to other measurements in this specification.

[0050] The weight of the nonwoven fabric of the present invention is set to 15 g / m from the viewpoint of improving the texture of the nonwoven fabric. 2 More than 20 g / m is preferable. 2 More preferably, 25 g / m 2 The weight per unit area of ​​the nonwoven fabric of the present invention is preferably 80 g / m2 or more, from the viewpoint of not impeding the comfortable feeling of use of the wearer. 2 Less than 70 g / m is preferable. 2 Less than 60 g / m is more preferable. 2 The following is even more preferred:

[0051] (Method of measuring basis weight of nonwoven fabric 10) The area and mass of the nonwoven fabric 10 stored for 24 hours or more in an environment of 23±2° C. and a relative humidity of 50±5% are measured to determine the elasticity.

[0052] The nonwoven fabric of the present invention has a stiffness of 4.9 mN / cm 2 (0.05gf / cm 2 The thickness under load is preferably 0.8 mm or more, more preferably 1.0 mm or more, and even more preferably 1.2 mm or more. 2 The load is a load that assumes fluffing on the surface of the nonwoven fabric. 2 By having the thickness under load within the above range, the liquid backflow prevention performance is improved, making it difficult for the wearer's skin to become wet. In addition, the nonwoven fabric of the present invention has a strength of 4.9 mN / cm 2 The thickness under load is preferably 10 mm or less, more preferably 8 mm or less, and even more preferably 7 mm or less, from the viewpoint of not impeding the wearer's comfortable use.

[0053] (Method of measuring thickness of nonwoven fabric) 4.9mN / cm on nonwoven fabric 2 (0.05gf / cm2 The thickness is measured with a thickness measuring device under a load of 100 mm. A laser displacement meter manufactured by Omron Corporation is used as the thickness measuring device. Measurements are taken at 10 points, and the average value is calculated to determine the thickness.

[0054] Next, a preferred embodiment of a method for producing nonwoven fabric 10 will be described with reference to Figs. 7 to 10. The production method described below illustrates a form in which openings 3 are provided at bottoms 21 of recesses 2. In the case where openings 3 are not included, it is preferable that the tips of protrusions 121 of support 120 described below do not have peaks 122. Furthermore, when producing nonwoven fabric 20, it can be formed by laminating another fiber web after step (II) (heat flow fusion step) described below. As shown in FIG. 7, the manufacturing method of this embodiment includes the following three steps (hereinafter, each step may be referred to as step (I), step (II), and step (III)). (I) A pressing process in which a fiber web 100 is placed on a support 120 having an uneven shape with a plurality of protrusions 121 and recesses 125 between the protrusions 121, 121, and the fiber web 100 is pressed along the recesses 125 by a pressing portion 131 of a pressing member 130 to form a shape, and holes are opened at locations corresponding to the protrusions 121, thereby forming an unevenly perforated fiber web 101 having an open surface on the pressing member 130 side. (II) A heat flow fusion step of applying a first heated fluid W1 to the porous fibrous web 101 simultaneously with or after the pushing step to fuse the fibers together to obtain the porous nonwoven fabric 102. (III) A stretch-fusion step in which, after the heat flow fusion step, the porous nonwoven fabric 102 is stretched at a draw ratio of 1.05 or more and 1.2 or less while a second heated fluid W2 is being applied thereto. Draw ratio=(pulling speed of the porous nonwoven fabric 102 in the pulling section downstream of the second heated fluid application section) / (feed speed of the porous nonwoven fabric 102 in the second heated fluid application section)

[0055] The fibrous web 100 described above is a precursor to the nonwoven fabric 10 and comprises thermoplastic fibers. The "fiber web" refers to a fiber assembly in which constituent fibers, including thermoplastic fibers, are loosely entangled without being fused and fixed, and which does not have the shape retention of a sheet by itself. In other words, it is a fiber assembly before being made into a nonwoven fabric. Therefore, the mobility between fibers in the fiber web 100 is high, and the fiber web 100 is highly deformable in the pushing process. Such a fiber web 100 is supplied from a carding machine (not shown) to a predetermined thickness.

[0056] In step (I), as shown in FIG. 7(A), a pressing member 130 is used to directly press the fiber web 100 on the support 120 with mechanical pressure. This forms the uneven perforated fiber web 101 that will become the nonwoven fabric 10. This type of shaping results in stronger fiber orientation and a perpendicular orientation to the nonwoven fabric plane, compared to when the fiber web is pressed with non-mechanical pressure such as wind. Furthermore, it is not necessary to apply a large pressing force to increase the unevenness height difference formed in the fiber web 100, and the fiber web 100 can be shaped softly. Furthermore, fiber disorder can be suppressed to improve shaping properties.

[0057] The support 120 is drum-shaped as shown in FIG. 7, for example, and has protrusions 121 on the drum peripheral surface as shown in FIG. 7(A). On the drum peripheral surface of the support 120, a plurality of protrusions 121 are arranged at intervals in one direction (first direction D1) and a direction perpendicular thereto (second direction D2), as shown in FIG. 8, for example. A plurality of protrusion rows 121A, each of which is formed by arranging a plurality of protrusions 121 in the first direction D1, are arranged at a distance from each other in the second direction D2. The protrusions 121 have a spire 122 at their tips. The spire 122 forms the openings 3 in the bottoms 21 of the recesses 2 of the nonwoven fabric 10. When the openings 3 are not formed, it is preferable that the tips of the protrusions 121 of the support 120 do not have the spire 122. The planar shape of the projection 121 as viewed from the tip end side is not limited to a rectangle as shown in Fig. 8, but may be various shapes, such as a circle, an ellipse, or a diamond. The recess 125 has a first recess 125A extending in the first direction D1 between the protrusion rows 121A, 121A, and a second recess 125C located between the protrusions 121, 121 in the protrusion row 121A. The second recess 125C is connected to the adjacent first recess 125A, and extends intermittently in the second direction D2 via the first recess 125A.

[0058] In support 120, a plurality of protrusions 121 are arranged corresponding to positions where recesses 2 are to be formed in nonwoven fabric 10. Second recesses 125C between protrusions 121, 121 in protrusion row 121A are located at positions where saddle portions 15 are to be formed in nonwoven fabric 10. In other words, protrusion row 121A is located at a position that will become band regions 16 between ribs 1, 1 in nonwoven fabric 10. First recesses 125A are located at a position that will become rib portions 1 in nonwoven fabric 10. The bottom of each recess 125 has a structure that allows the heating fluid to pass through, and for example, a plurality of holes (not shown) are provided therein.

[0059] The pushing member 130 is in the form of a roll as shown in Fig. 7, for example, and has a pushing portion 131 as shown in Fig. 7(A) on the roll peripheral surface. On the roll peripheral surface of the pushing member 130, a plurality of pushing portions 131 continuing in the first direction D1 are arranged at intervals in the second direction D2 as shown in Fig. 9, for example. Between the pushing portions 131, 131, a recess 132 continuing in the first direction D1 is formed. The pushing portion 131 of the pushing member 130 corresponds to the first recess 125A of the support body 120. The recess 132 of the pushing member 130 corresponds to the protrusion row 121A of the support body 120. The bottom of the recess 132 of the pushing member 130 has a structure through which the heating fluid can pass, and for example, a plurality of holes (not shown) are provided.

[0060] The height of the pushing portion 131 of the pushing member 130 is preferably 1 mm or more so that it can be sufficiently inserted between the protrusions 121 of the support 120 .

[0061] The first direction D1 and the second direction D2 in the support 120 and the pushing member 130 are preferably a machine direction (MD) and a cross direction (CD) perpendicular to the machine direction in the manufacturing process. The machine direction and the cross direction in the manufacturing process preferably correspond to one direction and a direction crossing the one direction in the nonwoven fabric 20, and preferably correspond to a longitudinal direction Y and a cross direction X in an absorbent article including the nonwoven fabric 20. However, the first direction D1 and the second direction D2 are not limited to these.

[0062] In step (I), the protrusions 121 of the support 120 are inserted into the recesses 132 of the pushing member 130. The pushing portion 131 of the pushing member 130 is inserted into the first recesses 125A of the support 120 (FIGS. 7(A) and 10). This pushing between the support 120 (FIG. 8) and the pushing member 130 (FIG. 9) allows the uneven structure of the nonwoven fabric 10 to be suitably formed. The fiber web 100 is pressed into the position of the first recess 125A of the support 120 by the pressing portion 131 of the pressing member 130 to form a shape. This portion becomes the rib portion 1 of the nonwoven fabric 10. At this time, between the protrusions 121 of the support 120 and the pressing portion 131 of the pressing member 130, the fibers of the fiber web 100 are shaped into a vertically standing shape along the thickness direction Z. The shaped fibers are not fused and have high mobility, so they are oriented in the thickness direction Z. This portion becomes the wall portion 1B of the rib portion 1 in the nonwoven fabric 10. Meanwhile, the fibers of the fibrous web 100 are pushed up to the bottom of the recesses 132 of the pushing member 130 at the positions of the protrusions 121 of the support 120 and are opened. This portion becomes the recesses 2 including the openings 3 in the nonwoven fabric 10. The second recess 125C between the protrusions 121, 121 in the protrusion row 121A of the support 120 corresponds to the recess 132 of the pushing member 130, so the pushing portion 131 does not enter. However, the pushing force of the pushing portions 131, 131 of the pushing member 130 acts on both sides of the fibers of the fiber web 100 in the second recess 125C of the protrusion row 121A. Due to this action, the fibers of the fiber web 100 in the second recess 125C are stretched in the second direction D2 by the pushing portions 131, 131 on both sides and pushed in the thickness direction Z, so that the fibers are shaped in the thickness direction Z and the orientation of the fibers changes. This portion becomes the saddle portion 15 in the nonwoven fabric 10. The saddle portion 15 has an apex 15A and a wall portion 15B, and the wall portion 15B is similar to the wall portion 1B of the ridge portion 1. By these shaping and perforations, an unevenly perforated fiber web 101 is formed.

[0063] When the porous fibrous web 101 which becomes the nonwoven fabric 10 is made of a plurality of fibrous layers, the fibrous web 100 may be a laminate of a plurality of fibrous layers. Alternatively, the fibrous web 100 may be joined with another fibrous web to form a laminate just before the meshing position of the support 120 and the pushing member 130.

[0064] The height of the protrusions 121 of the support 120 and the height of the pushing portion 131 of the pushing member 130 are appropriately determined depending on the thickness of the nonwoven fabric to be manufactured, etc. For example, it is preferably 2 mm or more, more preferably 3 mm or more, even more preferably 5 mm or more, and preferably 25 mm or less, more preferably 23 mm or less, and even more preferably 20 mm or less. Specifically, it is preferably 2 mm or more and 25 mm or less, more preferably 3 mm or more and 23 mm or less, and even more preferably 5 mm or more and 20 mm or less.

[0065] Next, step (II) is carried out simultaneously with or after step (I). In step (II), a first heated fluid W1 is applied to the porous fibrous web 101 to fuse the fibers together. That is, fusion points 4A are formed at the intersections of the constituent fibers to form a nonwoven fabric. This results in a porous nonwoven fabric 102 (FIG. 7(B)). When step (II) is performed after step (I), step (II) is preferably performed after removing the pushing member 130 from the support 120. For example, the support 120 rotates while holding the porous fiber web 101, passes through the meshing portion between the support 120 and the pushing member 130, and the pushing member 130 inserted into the support 120 is removed when the meshing is released. The support 120 further rotates, and the first heating fluid W1 is applied to the porous fiber web 101 at the position of the first heating fluid application section 140. The support 120 preferably has a heating fluid suction section 141 at a position facing the first heating fluid application section 140 inside the drum. The heating fluid includes various fluids that can melt the thermoplastic component of the fiber to form a fused portion, such as hot air and steam. From the viewpoint of more suitably forming the fused portion and maintaining the above-mentioned uneven structure, the heating fluid is preferably hot air.

[0066] The temperature of the first heated fluid W1 is set to a temperature at which the thermoplastic fibers constituting the porous fibrous web 101 can be melted to form fused fiber portions at the intersections of the fibers. Considering typical fiber materials used in this type of product, the temperature is preferably 0°C to 70°C higher than the melting point of the thermoplastic fibers constituting the porous fibrous web 101, and more preferably 5°C to 50°C higher. From the viewpoint of effective fusion, the wind speed of the first heated fluid W1 is preferably 1 m / s or more, more preferably 2 m / s or more, and from the viewpoint of making the device scale compact, the wind speed of the first heated fluid W1 is preferably 100 m / s or less, more preferably 80 m / s or less.

[0067] Next, in the step (III), the unevenly porous nonwoven fabric 102 is stretched at a draw ratio of 1.05 or more and 1.2 or less as described below while being supplied with a second heated fluid W2. Draw ratio=(pulling speed of the porous nonwoven fabric 102 in the pulling section 153 downstream of the second heated fluid application section 150) / (feed speed of the porous nonwoven fabric 102 in the second heated fluid application section 150) In this treatment step, the thermoplastic resin component of the constituent fibers and the thermoplastic resin component of the fused portions 4A are melted and stretched again in the porous nonwoven fabric 102, which has been made into a nonwoven fabric by forming the fused portions 4A at the fiber intersections. This allows the membrane portions 4B stretched between the fibers to be well formed. As a result, the nonwoven fabric 10 is obtained.

[0068] The second heated fluid application section 150 includes a fusion furnace 151 and a conveying section 152 for the porous nonwoven fabric 102, and the feed speed is set by the conveying section 152. The conveying section 152 is a belt conveyor in FIG. 7. The pulling section 153 is a pair of conveying rolls in FIG. 7. However, the conveying section 151 and the pulling section 152 are not limited to this, and may be any that can be normally used in the manufacturing method of this type of article. In the example shown in FIG. 7, the rotation speed of the belt conveyor constituting the conveying section 152, i.e., the rotation speed of the rolls that rotate the belt of the belt conveyor, is the feed speed. Also, the rotation speed of the pair of conveying rolls constituting the pulling section 153 is the pulling speed.

[0069] By setting this ratio within the above-mentioned range, it is possible to apply an appropriate high tension to the porous nonwoven fabric 102. By applying the high tension together with the application of the second heated fluid W2, the remelted resin component can be suitably stretched between the fibers, and the membrane portion 4B can be favorably formed. The high tension is an external force applied along the longitudinal direction Y, which is the conveying direction of the porous nonwoven fabric 102, and acts to elongate the porous nonwoven fabric 102 in the longitudinal direction Y. At the same time, it acts to reduce the length of the porous nonwoven fabric 102 in the width direction X. As a result, the obtained nonwoven fabric 10 is stretched in the longitudinal direction Y more than the porous nonwoven fabric 102. The stretch ratio can be, for example, 5% to 20%.

[0070] From the above viewpoints, the draw ratio is more preferably 1.06 or more, and further preferably 1.07 or more. From the viewpoint of maintaining the appearance of the nonwoven fabric produced, the draw ratio is more preferably 1.2 or less, and even more preferably 1.15 or less. By setting the draw ratio higher than that during normal nonwoven fabric processing, slippage on the rolls is eliminated, meandering is suppressed, and running is very stable.

[0071] From the viewpoint of better exerting the action of the membrane portion 4B and from the viewpoint of maintaining the soft texture of the skin-facing side 10T, the second heated fluid W2 is preferably applied from the side that will become the non-skin-facing side 10B of the nonwoven fabric 10. When producing a nonwoven fabric 10 including open holes 3 by applying the second heated fluid W2 in this manner, it is preferable that the membrane portion 4B formed in step (III) can be formed in greater amount on the non-skin-facing side 10B of the ridge portion 1, which has a greater fiber amount than the bottom portion 21 including the open holes 3.

[0072] Taking into consideration the typical fiber materials used in this type of product, the temperature of the second heated fluid W2 is preferably 0°C to 60°C higher than the melting point of the thermoplastic fibers that make up the porous nonwoven fabric 102, and more preferably 5°C to 40°C higher. The wind speed of the second heated fluid W2 is preferably 0.3 m / s or more, and more preferably 0.4 m / s or more, from the viewpoint of fusing the fibers in the porous nonwoven fabric 102. Moreover, the wind speed of the second heated fluid W2 is preferably 20 m / s or less, and more preferably 10 m / s or less, from the viewpoint of further enhancing the softness of the nonwoven fabric 20.

[0073] As described above, the nonwoven fabric of the present invention can be suitably produced by the method for producing a nonwoven fabric of this embodiment including the above-mentioned steps (I), (II) and (III).

[0074] In the above manufacturing method, the push-in member 130 is not limited to one having push-in portions 131 that are continuous in the first direction D1 as shown in Fig. 9. For example, the push-in portions 131 may be formed in a lattice shape, and square-shaped recesses 132 may be formed between the lattice-shaped push-in portions 131.

[0075] In the method for producing the nonwoven fabric of this embodiment, it is preferable to have a cooling step after applying the first heated fluid W1. For example, as shown in Fig. 7, it is preferable to arrange a cooling section 160 having a cooling nozzle and a cooling suction section 161 inside the drum of the support 120 opposite each other at a position where the porous nonwoven fabric 102 obtained by applying the first heated fluid W1 is aligned along the outer periphery of the drum of the support 120. This makes it possible to keep the support 120 at a certain temperature or lower, and makes it easier to peel off the obtained nonwoven fabric while maintaining its shape.

[0076] The thermoplastic fibers constituting the nonwoven fabric of the present invention can be any fibers commonly used as materials for nonwoven fabrics without any particular limitations. For example, they may be fibers made of a single resin component or composite fibers made of multiple resin components. Composite fibers may have, for example, a core-sheath structure or a side-by-side structure. When using composite fibers containing a low melting point component and a high melting point component as the thermoplastic fiber (for example, composite fibers having a core-sheath structure in which the sheath is a low melting point component and the core is a high melting point component), the temperature of the heating fluid applied to the fiber web in the manufacturing process is preferably equal to or higher than the melting point of the low melting point component and lower than the melting point of the high melting point component. More preferably, the temperature is equal to or higher than the melting point of the low melting point component and 10°C lower than the melting point of the high melting point component, and even more preferably, the temperature is 5°C or higher than the melting point of the low melting point component and 20°C or lower than the melting point of the high melting point component. In terms of elasticity, the more the core of the core-sheath structure composite fibers have, the higher the elasticity. Therefore, it is preferable that the core component is larger in terms of cross-sectional area ratio. A specific example of a composite fiber having a core-sheath structure in which the sheath is a low melting point component and the core is a high melting point component is a composite fiber having a core-sheath structure in which the sheath is a polyethylene resin (hereinafter also referred to as PE) and the core is a polyethylene terephthalate resin (hereinafter also referred to as PET). Furthermore, in composite fibers with a core-sheath structure, when the resin component of the sheath has a lower glass transition point than the resin component of the core (hereinafter referred to as a low-glass transition point resin component; for example, the resin component of the core is PET and the resin component of the sheath is PE), the thickness recovery of the nonwoven fabric can be further improved by reducing the mass ratio of the low-glass transition point resin component.

[0077] The nonwoven fabric for absorbent articles of the present invention can be used as a component of various absorbent articles, which broadly include articles used to absorb liquids discharged from the body, such as diapers for adults and infants, sanitary napkins, panty liners, and urine pads.

[0078] An absorbent article having the nonwoven fabric for absorbent articles of the present invention typically comprises a top sheet, a back sheet, and a liquid-retentive absorbent interposed between the two sheets. In the absorbent article, the nonwoven fabric for absorbent articles of the present invention can be suitably used as the top sheet that comes into contact with the skin of the wearer. EXAMPLES

[0079] The present invention will be described in more detail below based on examples, but the present invention is not limited thereto. In the examples, "parts" and "%" are all based on mass unless otherwise specified. In Table 1, "←" means that the value is the same as the column on the left.

[0080] Example 1 The above-mentioned steps (I) to (III) were carried out based on the manufacturing method shown in FIG. 7 to produce the nonwoven fabric shown in FIG. 1 to FIG. 3 and FIG. 5, which was used as the nonwoven fabric sample of Example 1. In this case, a laminate of the first fiber layer and the second fiber layer shown in Table 1 was used as the fiber web 100. The surface side on which the first fiber layer was arranged was used as the skin side 10T. The constituent fibers of the fiber web 100 were core-sheath type (polyethylene terephthalate (PET) / polyethylene (PE)=5:5) thermoplastic fibers that had been subjected to hydrophilic treatment. The first heated fluid W1 had a temperature of 160° C. and a wind speed of 5 m / sec. The basis weight of the produced nonwoven fabric sample was 30 g / m 2 The second heated fluid W2 had a temperature of 160° C. and a wind speed of 2.0 m / sec. The draw ratio in the step (III) was 1.1.

[0081] Example 2 A nonwoven fabric sample of Example 2 was produced in the same manner as in Example 1, except that the draw ratio in step (III) was set to 1.07.

[0082] (Comparative Example) A nonwoven fabric sample for comparison was produced in the same manner as in Example 1, except that the draw ratio in step (III) was 1.03.

[0083] The nonwoven fabric samples of Examples 1 and 2 and the Comparative Example were confirmed with respect to the following structures. The measurement results are shown in Table 1. (1) Length and width of the opening 3 (length in the longitudinal direction Y and length in the width direction X) The measurement was carried out using the above-mentioned microscope (VHX6000 (product name, manufactured by Keyence Corporation)). (2) Frequency of occurrence of membrane portion 4B The measurement was carried out based on the above-mentioned (Method for confirming the membrane portion 4B and method for measuring the occurrence frequency). (3) Fiber orientation in ridge section 1 The measurement was performed based on the above-mentioned (method of measuring fiber orientation along the extending direction of the crests 1A of the ridges 1). (4) Fiber orientation in wall section 1B The measurement was performed based on the above-mentioned (method of measuring fiber orientation along the thickness direction Z of the wall portion 1B).

[0084] In addition, the nonwoven fabric samples of Examples 1 and 2 and the Comparative Example were tested for the following evaluation items, with the results being as shown in Table 1. The following tests were carried out by preparing evaluation diapers using each nonwoven fabric sample. That is, a commercially available baby diaper (product name "Merry's Smooth Air Through S size", Kao Corporation, manufactured in 2020) was used as an absorbent core by removing the top sheet, and nonwoven fabrics cut to 100 x 250 mm from each nonwoven fabric sample of the examples and comparative examples were laminated. The nonwoven fabric samples were laminated so that the non-skin-facing side 10B faced the absorbent core side, and the periphery of the laminated nonwoven fabric sample was fixed to prepare an evaluation diaper.

[0085] (1) Softness The softness was evaluated using a KES compression tester (KES FB-3 manufactured by Kato Tech Co., Ltd.) in normal mode, and the compression characteristics were evaluated up to 5.0 kPa, and the WC value was taken as the softness. Measurements were taken at three points and the average value was taken. This KES compression tester was used for a compressed area of ​​2 cm2. 2 The plate has a circular plane, the compression speed is 0.02 mm / s, the maximum compression pressure is 5.0 kPa, and when the maximum compression pressure is reached, the compression direction is reversed and the recovery process begins. The WC value is expressed in terms of compression energy, gf cm / cm 2 The higher the WC value, the easier it is to compress and the softer it is.

[0086] (2) Liquid absorption time In the diaper for evaluation, the nonwoven fabric test layered as the top sheet had a density of 13.6 g / cm 2 A load equal to the pressure of 1017 mm was applied evenly to the nonwoven fabric sample. 2 Artificial urine (composition: urea 1.940% by mass, sodium chloride 0.795% by mass, magnesium sulfate 0.110% by mass, calcium chloride 0.062% by mass, potassium sulfate 0.197% by mass, Red No. 2 (dye) 0.010% by mass, water 96.886% by mass) was poured through the tube. 40 g of artificial urine was poured three times at 10-minute intervals, and the time (seconds) until the entire amount was absorbed in the third pour was measured. The time when artificial urine was no longer observed inside the tube was regarded as "the entire amount was absorbed." The above operation was carried out three times, and the average of the three "times (seconds) until the entire amount was absorbed" was regarded as the liquid absorption time (seconds). The shorter the liquid absorption time, the easier it is for the liquid to penetrate into the interior. In other words, it indicates excellent liquid absorbency.

[0087] (3) Amount of wet back Ten minutes after the completion of injection for the absorption time measurement, a stack of 10 sheets of Advantec filter paper No. 4A (100 mm×100 mm, mass measurement W1) was placed on the absorbent article with the injection point at the center. A pressure of 3.5 kPa was applied through a 5 mm thick, 100 mm x 100 mm acrylic plate, and the mass of the filter paper was measured after 2 minutes (W2). The amount of liquid return was calculated using the following formula. Amount of liquid returned (g) = Mass of filter paper after pressure (W2) - Initial mass of filter paper (W1)

[0088] (4) Liquid spreading length (longitudinal direction Y and transverse direction X) After the above-mentioned wetback measurement, the width of the artificial urine spread on each nonwoven fabric sample in the longitudinal direction Y and the transverse direction X was measured and defined as the liquid spread length.

[0089] [Table 1]

[0090] As shown in Table 1, the nonwoven fabric samples of Examples 1 and 2 were superior in softness and had reduced liquid absorption time and wet-back amount compared to the nonwoven fabric sample of the Comparative Example. Moreover, the nonwoven fabric samples of Examples 1 and 2 had a longer liquid spreading length in the longitudinal direction Y and a reduced liquid spreading length in the width direction X compared to the nonwoven fabric sample of the Comparative Example, and thus could effectively utilize absorbency in the longitudinal direction by suppressing liquid leakage from the crotch when applied to an absorbent article. That is, it was found that the nonwoven fabric samples of Examples 1 and 2 were able to further improve both the liquid absorbency and the soft feel in absorbent articles, compared to the nonwoven fabric sample of Comparative Example. [Explanation of symbols]

[0091] 1 ridge 2 Recess 21 Bottom 3 Opening part 4 Fusion part 4A Fiber intersection fusion area 4B Membrane 10, 20 Nonwoven fabric 10T, 20T Skin side 10B, 20B Non-skin side

Claims

1. A nonwoven fabric for absorbent articles having a skin-facing side and a non-skin-facing side opposite the skin-facing side, comprising a plurality of ridges protruding from the skin-facing side and extending in a planar direction, and recesses between adjacent ridges, A nonwoven fabric for absorbent articles, wherein the constituent fibers have multiple fusion portions that connect the fibers together, and these fusion portions include a membrane-like portion stretched between the fibers.

2. The nonwoven fabric for absorbent articles according to claim 1, wherein the ridges have a fiber orientation along the direction of extension of the ridges.

3. The nonwoven fabric for absorbent articles according to claim 1 or 2, wherein the recess has an opening at the bottom.

4. Nonwoven fabric for absorbent articles according to claim 1 or 2, having a laminated structure of an upper layer on the skin side and a lower layer on the non-skin side, wherein the upper layer comprises the ridges and the recesses, and the upper layer and the lower layer are laminated at the bottom of the recesses.

5. The nonwoven fabric for absorbent articles according to claim 4, wherein the interior of the ridges in the upper layer has a structure in which the lower layer is embedded.

6. A pressing step is performed in which a fiber web is placed on a support having an uneven shape with multiple protrusions and recesses between the protrusions, the fiber web is pressed along the recesses by the pressing portion of a pressing member to shape it, and holes are made in the locations corresponding to the protrusions, forming an uneven, perforated fiber web having perforated surfaces on the side of the pressing member, Simultaneously with or after the pressing step, a heat flow fusion step is performed to obtain a nonwoven fabric with uneven openings by applying a first heating fluid to the uneven opening fiber web to fuse the fibers together. A method for manufacturing a nonwoven fabric for absorbent articles, comprising: a stretch-fusion step, after the heat-flow fusion step, in which a second heating fluid is applied to the uneven nonwoven fabric while it is stretched at the following draw ratio of 1.05 to 1.

2. Draw ratio = (Pulling speed of the uneven perforated nonwoven fabric in the pulling section downstream of the second heating fluid application section) / (Feeding speed of the uneven perforated nonwoven fabric in the second heating fluid application section)

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