JP2023066700A - Nonwoven fabric and production method thereof - Google Patents

Abstract

To provide a nonwoven fabric that has a soft and good cushioning property and is composed of a bulky and thick fiber structure so that the thickness can be retained and is hard to be crushed when used under pressure.SOLUTION: A nonwoven fabric is formed by laminating two or more fiber layers in a thickness direction. A first fiber layer on one surface side has convex parts and concave parts. A second fiber layer adjacent to the first fiber layer on the other surface side in the thickness direction has convex parts entering inside on the other surface side of the convex part of the first fiber layer. Fused parts of interlaminar fiber intersection points are included at least in an interface between a wall part in the convex part on the first fiber layer and a wall part in the convex part of the second fiber layer. Wall part fiber orientation in the wall part of the convex part of the first fiber layer is 0.70 to 0.99. A ratio of the wall part fiber orientation in the convex part of the first fiber layer to the wall part fiber orientation in the convex part of the second fiber layer (former/latter) is 1.1 to 1.5.SELECTED DRAWING: Figure 1

Description

The present invention relates to a nonwoven fabric and a method for producing the same.

Conventionally, there are non-woven fabrics provided with uneven shapes of various modes, and manufacturing methods for providing such uneven shapes have been developed.
For example, Patent Literature 1 discloses a technique of forming a composite sheet by bonding a first sheet and a second sheet made of a nonwoven fabric containing a resin material while shaping them by meshing together uneven rolls with heating. Are listed. In the composite sheet obtained by this technique, the second sheet has a protrusion only in the central portion of the area corresponding to the curved portion of the first sheet, and has a flat portion surrounding it.

Patent Literatures 2 and 3 describe techniques for shaping an unfused web into unevenness by blowing hot air. In the non-woven fabric obtained by this, the fiber orientation in the thickness direction is obtained in the concave-convex shaped portion of the non-fused web.

Patent Literature 4 describes a technique of laminating a non-woven fabric on an unfused web that has been unevenly shaped by meshing rolls having unevenness, and further shaping the unevenness. As a three-dimensional shaped nonwoven fabric obtained by this, a two-layer structure and a closed hollow structure in which the inside of the convex part of the surface fiber layer is hollow and the back surface fiber layer is laminated on the back surface side of the surface fiber layer is described. ing.
Further, Patent Document 5 describes a method for producing a non-woven fabric in which an unfused fiber web is shaped by pressing an indentation portion into an unfused fiber web on an uneven support, and the unfused fiber web is further laminated. It is The resulting nonwoven fabric has an uneven structure with height differences.

Patent Literature 6 describes a technique in which, after a preheating step, a nonwoven fabric formed by heat-sealing thermoplastic resin fibers is shaped unevenly by a pair of upper and lower drawing rolls that mesh and rotate.
In Patent Document 7, a nonwoven fabric obtained by hot air treatment by an air-through method is subjected to uneven shaping, and a laminated sheet having a lower layer containing heat-shrinkable fibers and an upper layer containing non-heat-shrinkable fibers is laminated and heat-shrunk. describes a technique for performing hot air treatment for In the sheet obtained by this method, the upper layer of the laminated sheet rises due to the heat shrinkage of the heat-shrinkable fibers in the lower layer, while the uneven nonwoven fabric has ridges, forming a solid inside of the ridges. .

JP 2019-063581 A JP 2016-089289 A JP 2014-012913 A JP 2021-037057 A JP 2019-112747 A JP 2016-220986 A JP 2017-038838 A

In the sheet having the concave-convex structure described in Patent Document 1, the protrusions of the second sheet are not joined to the curved portions (convex portions) of the first sheet, and the fibers oriented in the thickness direction that contribute to the anti-collapse property. The number of components is small due to the fact that it consists only of the first sheet. As a result, the space between the two sheets is easily crushed.
The non-woven fabrics described in Patent Documents 2 and 3 are provided with fiber orientation in the thickness direction by blowing hot air onto an unfused web to shape the unevenness. However, from the viewpoint of further improving cushioning properties and thickness retention properties, there is room for improvement in the fiber orientation. In addition, fibers that are not fused during the manufacturing process tend to move when hot air is blown, and there is room for improvement in order to maintain a sufficient thickness of the fiber layer of the shaped nonwoven fabric.
The non-woven fabrics described in Patent Documents 4 and 5 have a portion where the unfused web is shaped unevenly by mechanical pressing, and by controlling the amount of pressing in that portion, the fiber orientation is higher than that of the hot air blowing method. , the thickness of the fiber layer is easily obtained. On the other hand, in the nonwoven fabrics described in Patent Documents 4 and 5, there is room for improvement regarding the fiber structure between the upper and lower layers provided in the convex portions from the viewpoint of further increasing the thickness retention under pressure. Patent Documents 6 and 7 do not specifically describe this point either.

In view of the above points, the present invention relates to a nonwoven fabric that has a soft and good cushioning property, has a bulky and thick fiber structure, can maintain the thickness under pressure, and is resistant to crushing.

The present invention relates to a nonwoven fabric in which two or more fiber layers are laminated in the thickness direction, wherein the first fiber layer on one side has a convex portion and a concave portion, and the first fiber layer A second fiber layer adjacent to the other surface in the thickness direction has a convex portion extending into the other surface side of the convex portion of the first fiber layer, and at least the first fiber The interface between the wall portion of the convex portion of the layer and the wall portion of the convex portion of the second fiber layer includes an interlayer fiber intersection fused portion, and the wall portion of the convex portion of the first fiber layer includes a wall portion The fiber orientation degree is 0.70 or more and 0.99 or less, and the ratio of the wall portion fiber orientation degree in the convex portion of the first fiber layer to the wall portion fiber orientation degree in the convex portion of the second fiber layer (former / The latter) is 1.1 or more and 1.5 or less.

In addition, the present invention provides a first unfused web composed of an assembly containing fibers, a support having convex portions or concave portions and a first pushing member having a pushing portion capable of meshing with the support. a first shaping step of shaping by intermeshing; and laminating a second unfused web on the shaped first unfused web on the support, and forming the second unfused web on the side of the second unfused web. and a second shaping step of forming a shape by meshing with a second pressing member having a pressing portion that can be meshed with the support, wherein the meshing amount of the first pressing member with respect to the support , the ratio of the meshing amount of the second pushing member to the support (former/latter) is set to 1.2 or more, and in the second shaping step or after the second shaping step, the fibers are heated by the heated fluid Provided is a method for producing a nonwoven fabric that performs a heat treatment step for fusion bonding, embossing compression bonding, or embossing fusion bonding.

The nonwoven fabric of the present invention has a soft and good cushioning property, and has a bulky and thick fiber structure. Moreover, according to the manufacturing method of the nonwoven fabric of this invention, the nonwoven fabric of this invention can be manufactured suitably.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows typically one preferable embodiment of the nonwoven fabric of this invention. Fig. 2 is a cross-sectional view schematically showing another preferred embodiment of the nonwoven fabric of the present invention; FIG. 2 is a partially enlarged view of a cross section of the nonwoven fabric shown in FIG. 1; It is explanatory drawing which shows the measurement position of the wall part fiber orientation degree. It is a sectional view showing typically various area ratios in the nonwoven fabric of the present invention. (A) and (B) are explanatory diagrams schematically showing two-step intermeshing shaping in the method for producing a nonwoven fabric of the present invention. FIG. 7 is a cross-sectional view schematically showing the stacked state of the first unfused web and the second unfused web after the two-stage meshing shaping shown in FIG. be. FIG. 5 is a plan view showing a pattern in which the positions of engagement between the pushing portion of the first pushing member and the pushing portion of the second pushing member are different in the plane direction of the support. FIG. 9 is a cross-sectional view showing the relationship between the support shown in FIG. 8 and the pushing portion of the first pushing member and the pushing portion of the second pushing member; BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic which shows one example (specific example 1) of the preferable manufacturing apparatus used for the manufacturing method of the nonwoven fabric of this invention. It is a schematic diagram showing another example (specific example 2) of a preferred manufacturing apparatus used in the method for manufacturing a nonwoven fabric of the present invention. (A) to (G) show the state of the fiber layer observed when measuring the "total thickness under 0.5 gf/cm ² load" of each nonwoven fabric sample of Examples 1 to 4 and Comparative Examples 1 to 3. It is a drawing substitute photograph.

A preferred embodiment of the nonwoven fabric according to the present invention will be described below with reference to the drawings.
The nonwoven fabric of the present invention is formed by laminating two or more fiber layers in the thickness direction, and has at least a two-layer structure such as the nonwoven fabric 10 and the nonwoven fabric 20 shown in FIGS. 1 and 2, for example. The nonwoven fabric 20 shown in FIG. 2 differs from the nonwoven fabric shown in FIG. 1 only in that it has embossed portions 6 at the bottom of the recesses, and the other fiber structures are common. The following detailed description of the nonwoven fabric 10 shown in FIG. 1 also applies to the nonwoven fabric 20 shown in FIG.

The nonwoven fabric 10 of the embodiment shown in FIG. 1 has a first fiber layer 1 on one surface side 10A and a second fiber layer 2 adjacent to the first fiber layer 1 on the other surface side 10B in the thickness direction. . In addition, the other surface side 10B means the surface of the first fiber layer 1 opposite to the one surface side 10A. The one surface side 10A and the other surface side 10B are also referred to as the front surface side 10A and the rear surface side 10B. The front side 10A and the back side 10B mean the front and back sides of the nonwoven fabric 10, and also mean the front and back sides of each fiber layer. In addition, the surface side 10A of the nonwoven fabric 10 can also be the surface side (skin surface side) that comes into contact with the skin.
Although the nonwoven fabric 10 shown in FIG. 1 is a two-layer laminate of the first fiber layer 1 and the second fiber layer 2, the non-woven fabric 10 is not limited to this and may be a laminate of three or more layers. For example, another fiber layer may be laminated on the back side 10B of the second fiber layer 2 or the front side 10A of the first fiber layer 1 .

In the nonwoven fabric 10 of this embodiment, the first fiber layer 1 has convex portions 14 and concave portions 15 . The second fiber layer 2 has protrusions 24 that enter the interior of the other surface side 10B of the protrusions 14 of the first fiber layer 1 . More specifically, the rear surface side 10B of the protrusions 14 of the first fiber layer 1 has a recessed shape toward the front surface side 10A, and the protrusions 24 of the second fiber layer 2 enter the recesses. Both the convex portion 14 and the convex portion 24 have an arch shape in which the back surface side 10B is recessed toward the front surface side 10A. The convex portions 14 and the convex portions 24 overlap in the thickness direction to form the arch-shaped convex portions 4 of the nonwoven fabric 10 .
In addition, in the nonwoven fabric 10 of the present embodiment, the recesses 15 of the first fiber layer 1 are arranged so as to overlap the recesses 25 of the second fiber layer 2 in the thickness direction. Thereby, the recesses 5 of the nonwoven fabric 10 are formed.
In the nonwoven fabric 10, the convex portions 4 and the concave portions 5 formed by overlapping the first fiber layer 1 and the second fiber layer 2 in the thickness direction are arranged alternately in the plane direction. The nonwoven fabric 10 as a whole has a structure in which the apparent thickness of the whole is increased by having an uneven structure on the upper and lower sides connecting the front side 10A and the back side 10B of the laminated fiber layers 1 and 2. As long as the nonwoven fabric 10 has such a concave-convex structure, the first fiber layer 1 and the second fiber layer 2 have intermediate ridges (intermediate height portions connecting the convex portions, etc.) in addition to the above-described convex portions and concave portions. ) may be included.

Such a nonwoven fabric 10 has two thicknesses, an actual thickness and a total thickness.
"Actual thickness" means the shortest distance between points on the front side 10A and the back side 10B of each fiber layer, and means the thickness of the layer region filled with fibers for each fiber layer. The direction of the straight line connecting the shortest distance is not always perpendicular to the planar direction of the nonwoven fabric 10 . It can also be said that this is typically the thickness of each shaped fiber layer along the direction perpendicular to the extending direction V of the fiber layer. In FIG. 1, the actual thickness D1 of the first fiber layer 1 and the actual thickness D2 of the second fiber layer 2 are shown.
The “total thickness” is also referred to as apparent thickness, and means the thickness between the front and back surfaces measured with the nonwoven fabric 10 sandwiched between flat plates. The “total thickness” includes both the nonwoven fabric 10 as a whole and the fiber layers 1 and 2 as the thickness between flat plates. FIG. 1 shows the total thickness T0 of the nonwoven fabric 10, the total thickness T1 of the first fiber layer 1, and the total thickness T2 of the second fiber layer 2 in the initial state before pressing.
The "total thickness" in the initial state before pressing is measured using a flat plate with a load of 0.5 gf/cm ² applied from the surface side 10A. The “0.5 gf/cm ² load” means a load that suppresses fluffing on the surface of the nonwoven fabric, and is a light load that is necessary to properly measure the total thickness of the nonwoven fabric 10 (a load that crushes the thickness of the nonwoven fabric). It is a light load not worth the compressive force). A load of 0.5 gf/cm ² (load of 0.05 kPa) is, for example, a circular plate having a diameter of 2.5 cm and a mass of 2.45 g.

(Method for measuring total thickness of nonwoven fabric under 0.5 gf/cm ² load)
A nonwoven fabric to be measured is cut into 10 cm×10 cm to prepare a measurement sample. A laser thickness gauge (manufactured by Omron Corporation, high-precision displacement sensor ZS-LD80 (trade name)) is used, and a flat plate is used to apply a 0.5 gf / cm ^load (0.05 kPa of (load) is applied to the first surface side, and the thickness is measured in that state. The thickness is measured at three points, and the average value is taken as the total thickness of the nonwoven fabric to be measured.
In addition, when the nonwoven fabric to be measured is incorporated in the product, the adhesive force of the adhesive is weakened by cooling means such as cold spray, and the nonwoven fabric is removed from the product and the above measurement is performed. This method of taking out the nonwoven fabric is similarly applied to other measurements in this specification.
If a nonwoven fabric measuring 10 cm x 10 cm cannot be taken out, a size as large as possible is taken out.
Further, the total thickness under a high load (50 gf/cm ² load) described later can be measured by changing the load from 0.5 gf/cm ² to 50 gf/cm ² (5 kPa) in the above measuring method.

The thickness direction Z of the nonwoven fabric 10 is the direction of the thickness indicated by the above-mentioned "total thickness", and is a direction perpendicular to the planar direction N when the nonwoven fabric 10 is viewed in plan. This is also referred to as a direction that vertically connects the flat plate in contact with the top of the projection 4 and the flat plate in contact with the back surface of the bottom of the recess 5 .
Further, the extending direction V of the fiber layers is the direction in which each fiber layer continues as a layer, and is the direction in which the tops of the convex portions and the bottom portions of the concave portions are connected along the fiber layers. This means a direction that rises at an angle with respect to the planar direction N.

In the overlap in the thickness direction of the protrusions 14 of the first fiber layer 1 and the protrusions 24 of the second fiber layer 2, at least the wall portions 12 of the protrusions 14 of the first fiber layer 1 and the protrusions of the second fiber layer 2 An inter-layer fiber intersection fused portion P, which exists at the interface with the wall portion 22 in the portion 24 and where the fibers between the layers are joined, is included. In the cross section of the nonwoven fabric 10 under a load of 0.5 gf/cm ² in the thickness direction Z, as shown in FIG. Let F be the length in the thickness direction Z between the lowest point E4 on the surface side 10A of the concave portion 25 and the lowest point E4. Let G be the length in the thickness direction Z of the interface between the layers where the inter-layer fiber intersection fused portion P where the fibers are joined is G (the length in the thickness direction between the points E5 and E4). These values are obtained by a method similar to the method for measuring the void ratio (the area ratio of the void portions 3), which will be described later.

The "wall portion" refers to a fiber layer specified as follows when viewed along the vertical direction (thickness direction Z) connecting the flat plates of the nonwoven fabric 10 under a load of 0.5 gf/ ^cm2 . part.
That is, as shown in FIG. 3, the thickness direction Z between the lowest points E3 and E4 on the front side 10A of each recess 15 and 25 and the highest points E1 and E2 on the back side 10B of each protrusion 14 and 24 The fiber layer portion within the range of lengths H1 and H2 of is called a "wall portion". According to the above criteria, the wall portion 12 of the convex portion 14 of the first fiber layer 1 and the wall portion 22 of the convex portion 24 of the second fiber layer 2 are specified. In other words, the wall portion 12 of the convex portion 14 of the first fiber layer 1 and the wall portion 22 of the convex portion 24 of the second fiber layer 2 are located in the portion I where the lengths H1 and H2 in the thickness direction Z overlap in the thickness direction. At least a part or all of the inter-layer fiber cross-point fused parts P where the fibers between the layers are joined are included.

As shown in FIG. 3, the first fiber layer 1 on the front side 10A of the wall 12, which is divided according to the above criteria, is called the top portion 11, and the first fiber layer 1 on the back side 10B of the wall portion 12 is called the bottom portion 13. . The bottom 13 comprises a fiber layer arranged at the bottom of the recess 15 of the first fiber layer 1 . Similarly, the second fiber layer 2 on the surface side 10A of the wall portion 22 divided according to the above criteria is referred to as the top portion 21, and the second fiber layer 2 on the back surface side 10B of the wall portion 22 is referred to as the bottom portion 23. The bottom portion 23 includes a fiber layer arranged at the bottom portion of the recesses 25 of the second fiber layer 2 .

The above-mentioned "interlayer fiber intersection fused portion P" refers to a portion thermally fused at the intersection of fibers by a fluid (hot air, steam, etc.). Such an inter-layer fiber intersection fused part is formed by the fact that the first fiber layer 1 and the second fiber layer 2 have thermoplastic fibers, and the thermoplastic fibers present at the interfaces between the layers are melted and bonded by the fluid. formed by In addition, in the first fiber layer 1 or the second fiber layer 2, the cross-point fused portion of fibers in the layer is referred to as an "intra-layer fiber cross-point fused portion Q".

This inter-layer fiber cross-point fused portion P is included in the interface portion between the wall portion 12 of the convex portion 14 of the first fiber layer 1 and the wall portion 22 of the convex portion 24 of the second fiber layer 2 . As a result, the walls 12 and 22 are firmly joined and fixed to each other, and when the protrusions 4 of the nonwoven fabric 10 are deformed by pressure, they interfere with each other and support each other, making it difficult for them to collapse. That is, the protrusions 4 of the nonwoven fabric 10 have high pressure resistance due to the interlaminar heat intersection fused portions P. As shown in FIG. For the reason described above, the highest point E1 on the back side of the projections 14 of the first fiber layer 1 of the length G in the thickness direction Z of the interfaces between the layers where the inter-layer fiber intersection fused portions P where the fibers are joined is present. and the lowest point E4 on the surface side of the concave portion 25 of the second fiber layer 2 to the length F in the thickness direction Z (former/latter) is 0.2 or more and 0.9 or less. It is preferably 0.4 or more and 0.8 or less.
In the nonwoven fabric 10 shown in FIG. 1, the interface between the bottom portion 13 of the first fiber layer 1 and the bottom portion 23 of the second fiber layer 2 forming the bottom portion of the recess 5 also includes the inter-layer fiber intersection fused portion P. This further enhances the aforementioned resistance to pressure.

In addition, the wall portion fiber orientation degree of the wall portion 12 of the convex portion 14 of the first fiber layer 1 is 0.70 or more and 0.99 or less. The degree of fiber orientation in the wall portion is a value measured based on the method described later on the cross section of the convex portion in the thickness direction Z. As shown in FIG. The greater the degree of fiber orientation in the wall portion obtained by this measurement method, the greater the number of fibers extending along the extending direction V toward the top portion 11 of the wall portion 12 (see FIG. 4).
When the wall portion fiber orientation degree is 0.7 or more, the wall portion 12 connecting the top portion 11 and the bottom portion 13 of the convex portion 14 has high resistance to pressure from the top portion 11. there is Thereby, the thickness shape retention property of the convex part 4 of the nonwoven fabric 10 is improved. Moreover, when the wall portion fiber orientation degree is 1, the fibers are arranged in one direction, so the probability of the fibers crossing each other is reduced. That is, the density of fiber fusion points is reduced. When the degree of fiber orientation in the wall portion is high, the fibers are aligned in the extending direction V, and the rigidity component due to the fibers themselves in the extending direction V increases. Conversely, however, the density of the heat intersection fused portions of each layer decreases due to the decrease in the probability of crossing of the fibers. On the other hand, in the present embodiment, in order to increase the total rigidity of the nonwoven fabric, by setting the wall portion fiber orientation degree in the wall portion 12 to 0.99 or less, the orientation in the extending direction V of the fibers and the fiber The probability of crossing each other is increased, and the density per unit volume of the heat intersection fused parts of each layer is preferably increased. Thereby, the wall portion 12 has high deformability and high rigidity when the convex portion 14 is compressed. The convex portions 14 of the first fiber layer 1 supported by the wall portion 12 have both a soft touch without being too hard and thickness and shape retention. That is, the protrusions 14 of the first fiber layer 1 can feel a firm presence and a stable thickness in the softness provided by the arch shape of the fiber network structure.
From this point of view, the wall portion fiber orientation degree in the wall portions 12 of the protrusions 14 of the first fiber layer 1 is preferably 0.73 or more, more preferably 0.75 or more, and even more preferably 0.78 or more. Moreover, the wall portion fiber orientation degree of the wall portions 12 of the protrusions 14 of the first fiber layer 1 is preferably 0.95 or less, more preferably 0.90 or less, and even more preferably 0.81 or less.

In addition, the ratio (former/latter) of the degree of wall fiber orientation in the protrusions 14 of the first fiber layer 1 to the degree of wall fiber orientation in the protrusions 24 of the second fiber layer 2 is 1.1 or more. 5 or less. This is because the fibers of the walls 12 of the projections 14 of the first fiber layer 1 are more aligned in the extending direction V than the walls 22 of the projections 24 of the second fiber layer 2. means Since the ratio to the wall portion fiber orientation degree is as high as 1.1 or more, the first fiber layer 1 deforms softly with a low load in the initial deformation when pressure is applied. Further, by setting the ratio to the wall portion fiber orientation degree to 1.5 or less, the second fiber layer 2 is compressed while rebounding with high rigidity when pushed. In other words, while the convex portions 14 of the first fiber layer 1 are soft to the touch and have enhanced thickness and shape retention, the convex portions 24 of the second fiber layer 2 have relatively diverse fiber orientation directions. and provide thickness recovery power. The protrusions 24 of the second fiber layer 2 provide elasticity while supporting the shape of the protrusions 14 of the first fiber layer 1 from the inside, and serve as a cushion for the protrusions 4 (the protrusions 14 + the protrusions 24). Fulfill. In particular, when the wall portion fiber orientation ratio is 1.1 or more, the hardness of the nonwoven fabric 10 can be suppressed and soft cushioning properties can be enhanced. Further, when the ratio of the wall portion fiber orientation degree is 1.5 or less, the thickness of the nonwoven fabric 10 is easily maintained, and the nonwoven fabric 10 is less likely to be crushed.
From this point of view, the aforementioned ratio is preferably 1.2 or more. Moreover, the aforementioned ratio is preferably 1.4 or less.

The nonwoven fabric 10 having the fiber structure described above has a feature that the thickness and shape can be easily maintained under pressure while having the soft deformability of the fiber layer. Moreover, at the time of manufacturing the nonwoven fabric 10, the first fiber layer 1 is shaped by meshing, which will be described later. As a result of this shaping, an excessive compressive force is not applied to the unfused web, and a network structure in which the fibers are appropriately spaced apart is formed without excessively increasing the fiber density in each layer. The nonwoven fabric 10 becomes bulky and thick by having such a network structure on the surface side 10A. That is, the nonwoven fabric 10 has a bulky and thick fiber structure while having a soft and good cushioning property, and the thickness can be maintained under pressure and is hard to collapse.
In addition, the nonwoven fabric 10 is likely to be deformed by the weak force of the first fiber layer 1 as described above. From this, while the second fiber layer 2 maintains the unevenness of the nonwoven fabric 10, the first fiber layer 1 absorbs the unevenness by its deformation, so that the surface side 10A of the nonwoven fabric 10 feels bumpy when touched. At the same time, smoothness when the surface of the projection 14 is stroked is enhanced. As a result, the nonwoven fabric 10 has both the thickness shape retention property and the smoothness in the concavo-convex structure, which are conventionally difficult to achieve at the same time.

(Method for Measuring Wall Fiber Orientation Degree and Wall Fiber Orientation Angle)
The wall fiber orientation degree of the protrusions 14 of the first fiber layer 1, the wall fiber orientation degree of the protrusions 24 of the second fiber layer 2, and the wall orientation angle described later can be measured by the following method. can.
(1) Cut a sample in an arbitrary plane direction using sharp scissors. The cutting position passes through the top of the convex portion 4 and the center of the concave portion 5 adjacent to the convex portion 4 on the sample. When the sample is cut in the direction parallel to the CD direction, it is the cross section in the CD direction. In addition, MD is a machine direction (Machine Direction) in the manufacturing process of a nonwoven fabric, and CD is a direction orthogonal to MD (Cross Direction).
(2) A cross-sectional sample is prepared by cutting a sample into a rectangle and including at least 5 or more protrusions per side. The object unevenness is observed at a portion that is one unevenness or more inside the cut position of the sample corner. If the target nonwoven fabric is bonded to another layer, observe it while it is bonded to the other layer.
(3) A cross-sectional sample is placed on a flat plate so that the convex surface (surface side) faces upward, and another flat plate is placed on the cross-sectional sample so as to obtain 0.5 gf/cm ² . Place the cross-section sample so that the cross-section is aligned with the end faces of both flat plates.
(4) Next, the cross section of the cross section sample is observed from the side. A microscope is used at an observation magnification of 100x to 400x, quick synthesis (depth up, quick synthesis & 3D) is performed, the sample is moved from the back to the front, observed, and an image is captured. As an example of a microscope, VHX-6000 (trade name) manufactured by Keyence Corporation is used.
(5) Perform the following measurements using the images obtained by observation.
In the wall portion of the convex portion to be observed in the image, an intermediate position L1 of the direction of the actual thickness of each fiber layer (the direction orthogonal to the extending direction V of each fiber layer in the wall portion) S, and each concave portion 15, Intermediate height positions (M1 , M2) with a square E (see FIGS. 3 and 4). The size of the square E is smaller than the actual thickness, and the size is such that 5 or more fibers can fit in the square. The size of the square E may be different between the first fiber layer 1 and the second fiber layer 2 . The square E is tilted so that one side is parallel to the extension direction V (perpendicular to the actual thickness) in each fiber layer.
The fibers in the square E are traced to extract fibers extending from side to side. At this time, fibers that intersect only one side and are interrupted in the middle are excluded.
In the square E, the number of fibers A (adding two sides) crossing the side EA perpendicular to the extending direction V of the fiber layer, the number B of fibers crossing the side EB parallel to the extending direction V of the fiber layer (two sides plus), A/(A+B) is calculated. This value is defined as the wall portion fiber orientation degree in the convex portion of each fiber layer. The higher the degree of fiber orientation in the wall portion, the more fibers are oriented in the extending direction V of the fiber layer.
In addition, the angle of inclination of the side EB parallel to the extension direction V in the fiber layer in the square E is determined with the direction perpendicular to the plane of the nonwoven fabric (the direction of the total thickness) being 90 degrees and the plane direction being 0 degrees. This value is defined as the orientation angle of the fiber layer in the wall portion (hereinafter also referred to as the wall portion fiber orientation angle).
Each value is an average of 5 locations using a different sample edge.
(6) The boundary between the laminated first fiber layer 1 and the second fiber layer 2 has a difference in layer structure, for example, a difference in fiber diameter, a difference in fiber orientation, a difference in fiber cross-sectional shape, a layer and a layer. It can be grasped by the intervening voids, the difference in fiber density, the difference in the number of fibers per unit area, the difference in basis weight, and the like.
(7) The total thickness of each fiber layer is determined by: First, the boundaries between the front side and the back side of each fiber layer are determined based on the above differences. For example, in the case of using the number of fibers, the boundary between the number of fibers in each fiber layer at the interface between the fiber layers (or spaces) is drawn as a contour, where the number of fibers in each fiber layer is 1/2 of the central portion of the fiber layer. As the resolution at this time, draw a square lattice in which one pitch is 1/50 of the total thickness of the nonwoven fabric, and count the number of fibers in the square. A border is defined by smoothing and connecting squares in which the number of fibers is 1/2 or more and less than 1/2 of the average number of fibers in the central portion of each fiber layer. If there is a portion where the number of fibers is less than 1/2 in the fiber layer, it is excluded from the boundary line. A region formed between the boundary between the first fiber layer 1 and the second fiber layer 2 is defined as a void portion 3 .
Next, in the cross section of the sample, two straight lines on the sample surface side of the upper plate and the lower plate of the sample are obtained. The average distance in the thickness direction of the nonwoven fabric is determined for the distance between the two straight lines, and this is defined as the total thickness T0 of the nonwoven fabric 10 .

The nonwoven fabric 10 of the present embodiment having the fiber structure described above can only be obtained by the manufacturing method described later, and cannot be obtained by the conventional irregular forming technique. In particular, the degree of wall fiber orientation in the walls 12 of the protrusions 14 of the first fiber layer 1 cannot be as high as in the conventional hot air blowing. In addition, it is difficult to achieve the above wall fiber orientation ratio by stretching and shaping after laminating two layers as in the conventional art, or by shaping two layers with the same meshing amount. In addition, if the second fiber layer 2 is simply laminated without being shaped, the ratio of the wall orientation degrees exceeds 1.6, and the nonwoven fabric 10 of the present embodiment cannot be obtained.
The wall orientation ratio in the nonwoven fabric 10 of the present embodiment can be obtained by mechanically pressing the nonwoven fabric 10 with different engagement amounts with a specific difference in the manufacturing method described later. The difference in the amount of meshing becomes the difference in draw ratio with respect to the unfused web to be processed, and the higher the draw ratio, the more irregular the unfused web is shaped, and the higher the degree of fiber orientation in the wall portion. Moreover, in the shaping process by such mechanical meshing, in addition to the difference in the draw ratio, the difference in the return amount of the fibrous structure after shaping by meshing occurs between the unfused webs. That is, the higher the draw ratio, the less the amount of return of the fiber structure after shaping. Therefore, the second unfused web 200 that forms the second fibrous layer 2 follows the first unfused web 100 that forms the first fibrous layer 1, but the degree of fiber orientation is lowered due to this return. In consideration of these relationships, in the manufacturing method described later, the ratio of the wall orientation degree in the nonwoven fabric 10 of the present embodiment is imparted by mechanically pressing with different meshing amounts with a specific difference. be able to.

The total thickness (T0) of the nonwoven fabric 10 in the initial state before pressing (under a load of 0.5 gf/cm ² ) is 1 mm or more from the viewpoint of increasing the amount of deformation due to pressurization so that a softer touch can be felt. It is preferably 2 mm or more, more preferably 3 mm or more. In addition, if the total thickness (T0) of the nonwoven fabric 10 under a load of 0.5 gf/cm ² is too high, the partial basis weight of each fiber layer tends to be low and it tends to be easily crushed when pressurized. 15 mm or less is preferable, 10 mm or less is more preferable, and 6 mm or less is still more preferable from the viewpoint of preventing this.

In addition, since the nonwoven fabric 10 has the first fiber layer 1 and the second fiber layer 2, the total thickness (TM) under a high load (under a load of 50 gf/cm ² ) assumed for use is kept thicker. easy to be As a result, the nonwoven fabric 10 is suppressed from being crushed even under a high load, and it is felt that there is little plastic deformation (settling). In addition, together with the total thickness (T0) in the initial state before pressing (under a load of 0.5 gf/cm ² ), the thickness and cushioning properties can be felt with a sense of stability, and the texture is excellent. becomes.
From this point of view, the total thickness (TM) of the nonwoven fabric 10 under a high load (50 gf/cm ² load) is preferably 0.5 mm or more, more preferably 0.7 mm or more, and even more preferably 1.0 mm or more.
In addition, the total thickness (TM) of the nonwoven fabric 10 under a high load (under a load of 50 gf/cm ² ) is such that the amount of deformation due to pressure (T0-TM) is increased so that a softer touch can be obtained. It is preferably smaller than the total thickness (T0) in the initial state (under a load of 0.5 gf/cm ² ) before pressing. From this viewpoint, the total thickness (TM) is preferably 10 mm or less, more preferably 6 mm or less, and even more preferably 3 mm or less.

In the nonwoven fabric 10 of the present embodiment, appropriate gaps 3 are interposed between the first fiber layer 1 and the second fiber layer 2 in the protrusions 4 having a unique structure related to the degree of fiber orientation in the wall portion. is preferred. The void portion 3 referred to here is a portion in which the amount of fiber is extremely small compared to the first fiber layer 1 and the second fiber layer 2, and in the convex portion (further central portion in the thickness direction) of each fiber layer When the fiber density of the lower one of the fiber densities is taken as 100%, it can be defined as a region where the fiber density of the void portion 3 is 10% or less, and it is preferably a space without fibers.
As a result, a primary stock space for bodily fluids or the like is formed within the convex portion 4 . For example, when the nonwoven fabric 10 is used as a surface sheet in contact with the skin in an absorbent article, the absorbency of the absorbent article can be increased and the dryness of the skin surface can be improved. In addition, when the voids 3 are interposed with an appropriate size, the nonwoven fabric 10 is soft under a low load (for example, a range of 0.5 gf/cm ² load to 10 gf/cm ² load) at the initial stage of deformation, and is soft under a high load. (For example, in the range from 10 gf/cm ² load to 50 gf/cm ² load), the second fiber layer 2, which is the lower layer, contributes to make it difficult to collapse.
From the above viewpoint, in a cross section in the thickness direction on a line containing the center of the protrusion (the top of the protrusion) and the center of the recess adjacent to the protrusion obtained by the following (method for measuring the void ratio), the first fiber layer The ratio of voids between the first and second fiber layers 2 (area ratio of the voids 3) is preferably 4% or more from the viewpoint of increasing the deformability of the nonwoven fabric 10 under pressure and making it feel softer. 6% or more is more preferable, and 8% or more is even more preferable. Moreover, the void ratio is preferably 13% or less, more preferably 10% or less, from the viewpoint of making the total thickness of the nonwoven fabric 10 less likely to be crushed under a high load. In addition, in the nonwoven fabric 10, it is preferable that the space|gap part 3 does not interpose in this intermediate|middle ridge part when the above-mentioned intermediate|middle ridge part exists.

The above void ratio can be set appropriately by controlling the meshing amount in the manufacturing process described later. In other words, the nonwoven fabric 10 is a wall of the protrusions 14 of the first fiber layer 1 described above also from the viewpoint of interposing the appropriate voids 3 between the first fiber layer 1 and the second fiber layer 2. It is preferable to have a ratio of the degree of fiber orientation of the second fiber layer 2 to the degree of fiber orientation of the wall portion in the protrusions 24 of the second fiber layer 2 .

(Method for measuring void ratio)
(1) Sample the nonwoven fabric to be measured by cutting it with scissors or the like. When the nonwoven fabric is joined to other members (for example, when it is incorporated as a constituent member of an absorbent article), the nonwoven fabric is sampled while joined to the other members. This nonwoven fabric is placed in a non-loaded state with the projections facing upward, and stored at a temperature of 23±2° C. and a humidity of 65±5% RH for 48 hours or more and 72 hours or less.
(2) The above-mentioned samples are prepared into a rectangular shape having a size of 5 times the projection pitch (cut line 1 side)×5 times the projection pitch. At this time, in the planar view of the nonwoven fabric, one side is on a line that includes the center of the convex portion to be observed (the top of the convex portion) and the center of the concave portion adjacent to the convex portion, and the convex portion is the center with sharp scissors. Cut in the thickness direction (cut line 1). The direction of the cutting line 1 can be MD direction, CD direction, or oblique direction. The section of the cut line 1 is colored with a marker or the like.
(3) Observe the cross section of the unevenness from the cross section sample along the cut line 1 . A cross-sectional sample is placed on a flat flat plate with the convex portion 4 facing up, and a weight of the flat plate is placed thereon so as to give a load of 0.5 gf/cm ² . At this time, the position of the sample cross section and the end surface of each flat plate are matched.
(4) Using a microscope (for example, VHX-6000 (trade name) manufactured by KEYENCE CORPORATION), the cross section of the sample is observed from the side. Among the samples, three protrusions 4 and four recesses 5 located in the center along the cut line 1 are observed at a magnification of 50 to 300 times.
(5) Using the observed image, the boundaries between the first fiber layer 1 and the second fiber layer 2 are drawn using the colored portion as a guideline. If it is difficult to distinguish each fiber layer, the boundary line is determined by the method described in (Method for Measuring Wall Fiber Orientation Degree and Wall Fiber Orientation Angle).
(6) In the observed image, the inside of the boundary of each fiber layer is filled with black, and the other portions are made white. Using image analysis software (for example, Image-Pro Plus (version: 6.2.0.424) as image analysis software), between the upper plate (plate) and the lower plate (stage) within the observation image width area A (observation range) of (for example, the area defined by the two-dot chain line frame indicated by symbol A in the cross section shown in FIG. 5). The image analysis software has a resolution of 300 pixels/inch, and the size of the observed image is adjusted so that the area A is 100,000 to 200,000 ^pixels2 .
(7) In the cross-sectional area corresponding to the area A, similarly, the gap 3 formed between the back side boundary line of the first fiber layer 1 and the front side boundary line of the second fiber layer 2, the first fiber layer 1, the second fiber layer 2, the gap 18 between the front side boundary line of the first fiber layer 1 and the upper plate, the gap 28 formed between the back side boundary line of the second fiber layer 2 and the stage are calculated for each area (see, for example, FIG. 5).
(8) The ratio of voids (area ratio of voids 3) is obtained as "area of voids 3/area A×100 (%)". Similarly, the area ratios of the gap 18, the first fiber layer 1, the second fiber layer 2, and the gap 28 are obtained.
(9) Each value is the average of 5 locations using a different sample edge.

When the nonwoven fabric 10 of the present embodiment has a total thickness of 0.5 mm or more under a high load (50 gf/cm ² load) and has an appropriate void portion 3 with an area ratio of 4% or more and 13% or less, Under a low load (for example, under a load of 10 gf/cm ² ), the protrusion 4 is deformed by a soft force. On the other hand, under a high load, the voids 3 are crushed and the second fiber layer 2 compensates for the second fiber layer 1, making the entire protrusion 4 less likely to be crushed. In other words, the nonwoven fabric 10 can maintain its thickness under pressure and is less likely to collapse. As a result, the nonwoven fabric 10 has softness at the initial stage of pressurization due to the deformation behavior described above, and after that, the second fiber layer 2 compensates for the first fiber layer 1 so that the second fiber layer 2 is less likely to be crushed, so that the texture is excellent. In addition, due to the above-mentioned difference in the degree of fiber orientation in the wall portion between the first fiber layer 1 and the second fiber layer 2, it has a soft and good cushioning property accompanied by thickness recovery after pressurization.

Regarding the void ratio (area ratio of void portion 3) measured by the above (method for measuring void ratio), "void ratio (area ratio of void portion 3)/(area ratio of gap 18, void portion 3 and gap 28) total)” is preferably 0.08 or more and 0.20 or less. As a result, when the protrusions 4 of the nonwoven fabric 10 are crushed under a high load, the gaps 3 are the first to be crushed. The whole becomes even more difficult to collapse. When the above value is 0.08 or more, it is possible to secure a portion that is softly deformed by a force in the interval from the start of pressurization until the gap 3 disappears, which is preferable. Further, when the value is 0.20 or less, the stiffness of the first fiber layer 1 does not become too low, and it is preferable in that a cushioning property with a sense of security can be obtained.
From this point of view, the value of the "gap ratio (area ratio of gap 3)/(total area ratio of gap 18, gap 3, and gap 28)" is more preferably 0.10 or more.
Further, the value of the above-mentioned "gap ratio (area ratio of gap 3)/(total area ratio of gap 18, gap 3, and gap 28)" is more preferably 0.16 or less.

In addition, the nonwoven fabric 10 of the present embodiment has a thickness of the fiber layer itself in the thickness direction (the direction of the total thickness) by undergoing a manufacturing method described later that imparts a unique structure related to the degree of fiber orientation in the wall portion. . That is, the area ratio of the fiber layer in the thickness direction cross-section of the concave-convex structure is increased, and the area ratio of the above-described gaps 18, gaps 28, and voids 3 is suitably suppressed. As a result, the nonwoven fabric 10 becomes bulky and thick in the regions where the fibers exist, and the cushioning properties and thickness retention properties are further enhanced.
The above-mentioned area ratio of the fiber layer is indicated as "the area ratio of the first fiber layer 1 + the area ratio of the second fiber layer 2" measured by the above-mentioned (method for measuring void ratio). If the basis weight of the entire nonwoven fabric and the total thickness T0 are the same, the larger the area ratio, the closer to a flat shape there is no unevenness, and the lower the bulk density of each fiber layer. A lower bulk density means a higher bulk. Conversely, the smaller this value, the more irregularities there are and the higher the bulk density of each fiber layer. That is, the larger the area ratio of the first fiber layer 1 + the area ratio of the second fiber layer 2 , the bulkier the area occupied by the fibers while the nonwoven fabric 10 has the uneven structure.
The larger the "area ratio of the first fiber layer 1 + the area ratio of the second fiber layer 2", the bulkier the nonwoven fabric 10 becomes, and the cushioning property is improved by adjusting the ratio within a specific range. From this point of view, "the area ratio of the first fiber layer 1 + the area ratio of the second fiber layer 2" is preferably 36% or more, more preferably 40% or more.
In addition, "the area ratio of the first fiber layer 1 + the area ratio of the second fiber layer 2" means that the laminate of the first fiber layer 1 and the second fiber layer 2 is bulky in the area occupied by the fibers while having an uneven structure. It is preferably 60% or less, more preferably 50% or less, from the viewpoint of increasing the density and preventing crushing.

In the nonwoven fabric 10 of the present embodiment, the ratio (former/latter) of the fiber density of the tops of the protrusions 24 of the second fiber layer 2 to the fiber density of the tops of the protrusions 14 of the first fiber layer 1 is the surface side 10A 0.8 or more is preferable, and 1.0 or more is more preferable from the viewpoint of improving the soft feel of the skin and the viewpoint of improving liquid absorption due to the difference in density. As a result, the inter-fiber distance of the first fiber layer 1 can be widened without changing the fiber diameter, and the liquid permeability can be enhanced. Therefore, it is not necessary to increase the fiber diameter in order to form coarseness and fineness, and the touch can be improved. This is because in the manufacturing method described below, the higher the draw ratio due to meshing, the longer the inter-fiber distance and the lower the fiber density. That is, the meshing amount with respect to the first unfused web 100 forming the first fiber layer 1 is larger than the meshing amount with respect to the second unfused web 200 forming the second fiber layer 2, and the draw ratio is increased. As a result, the obtained first fiber layer 1 has a longer interfiber distance and a lower fiber density than the second fiber layer 2 .
The ratio is preferably 1.8 or less, more preferably 1.5 or less, from the viewpoint of preventing the first fiber layer 1 from becoming too sparse and suppressing the occurrence of fluff on the surface side 10A.

(Method for measuring fiber density)
Using a scanning electron microscope (SEM), the sample is subjected to a minimal gold sputter deposition. The observation magnification is 100 times to 700 times.
In the cross section prepared by the above (method for measuring void ratio), the number of cut end faces of the fiber is counted at the center position of the actual thickness of each layer and at the convex position of each fiber layer. The measurement range is a square with one side of 50% to 80% of the actual thickness of each layer. The fiber density (fibers/mm ² ) is determined by dividing the fiber cross section by the area of the square.
Each value is the average of 5 locations using different sample sides.

In the nonwoven fabric 10 of the present embodiment, the wall fiber orientation angle of the protrusions 14 of the first fiber layer 1 is preferably larger than the wall fiber orientation angle of the protrusions 24 of the second fiber layer 2 . As a result, in the concave-convex structure of the nonwoven fabric 10, the portion where the fibers rise from the bottom portion of the concave portion 5 to the top portion of the convex portion 4 becomes more difficult to collapse.
From this point of view, the difference (former-latter) between the wall fiber orientation angle of the protrusions 14 of the first fiber layer 1 and the wall fiber orientation angle of the protrusions 24 of the second fiber layer 2 is preferably 0 degrees or more. 12 degrees or more is more preferable, and 25 degrees or more is still more preferable. When this difference is moderate, it becomes easy to appropriately provide the above-described void 3 . Further, by increasing this difference, the gap 28 on the back surface side 10B of the second fiber layer 2 can be reduced. As a result, the compression energy in the nonwoven fabric 10 becomes smaller, the nonwoven fabric 10 becomes softer, and hardness is less likely to be felt.
In addition, the difference between the wall fiber orientation angle of the protrusions 14 of the first fiber layer 1 and the wall fiber orientation angle of the protrusions 24 of the second fiber layer 2 (the former minus the latter) is preferably 50 degrees or less, and 45 degrees. degree or less is more preferable, and 40 degree or less is even more preferable. By reducing this difference, it is possible to provide the above-mentioned gap portion 3 with a suitable size, and to reduce the gap 18 on the surface side 10A of the first fiber layer 1 . In addition, the number of inter-layer fiber intersection fused portions P at the boundary between the first fiber layer 1 and the second fiber layer 2 also increases. As a result, the compression energy in the nonwoven fabric 10 does not become too small and the nonwoven fabric 10 has an appropriate hardness in a low load region in the range of 0.5 gf/cm ² load to 10 gf/cm ² load.
The wall fiber orientation angle is measured by the method for measuring the wall fiber orientation degree and the wall fiber orientation angle described above.

In the nonwoven fabric 10 of the present embodiment, from the viewpoint of making it bulky and thick, making it difficult to crush in the thickness direction, interposing the voids 3 with an appropriate size, and having soft and good cushioning properties. , The basis weights of the first fiber layer 1 and the second fiber layer 2 are preferably within the following ranges.
The basis weight of the first fiber layer 1 is preferably 5 g/m ² or more, more preferably 10 g/m ² or more, and even more preferably 15 g/m ² or more. Moreover, the basis weight of the first fiber layer 1 is preferably 50 g/m ² or less, more preferably 40 g/m ² or less, and even more preferably 30 g/m ² or less.
The basis weight of the second fiber layer 2 is preferably 5 g/m ² or more, more preferably 7 g/m ² or more, and even more preferably 10 g/m ² or more. Also, the basis weight of the second fiber layer 2 is preferably 45 g/m ² or less, more preferably 35 g/m ² or less, and even more preferably 25 g/m ² or less.

(Method for measuring basis weight of each fiber layer)
Measure the area of the sample (the area of the sample in plan view) in advance, peel it off into each fiber layer, measure the mass of each fiber layer, and divide the mass by the area of the sample to obtain the basis weight of each fiber layer. can ask.

Such a nonwoven fabric 10 of the present embodiment has the excellent friction properties, roughness properties, and compression properties shown below due to the structure described above.

[Friction characteristics]
The nonwoven fabric 10 can be felt to have a good touch by having moderate friction. From this point of view, the average coefficient of friction (MIU) is preferably 0.1 or more, more preferably 0.2 or more. As a result, it is possible to obtain the soft feel of fibers rather than the smooth feel of a film. Moreover, from the viewpoint of not feeling sticky to the skin and not damaging the skin, the average coefficient of friction (MIU) is preferably 0.5 or less, more preferably 0.4 or less.

If the nonwoven fabric 10 has moderate smoothness, it can be felt to be pleasant to the touch. When the mean coefficient of friction (MIU) is within the moderate range and the mean deviation (MMD) of the coefficient of surface friction is small, there is a tendency to feel moderate smoothness. From this point of view, the mean deviation (MMD) of the surface friction coefficient is preferably 0.001 or more, more preferably 0.002 or more. In addition, the smaller the friction, the less the friction coefficient fluctuates and the smoother the feel even if the surface has irregularities. From this point of view, the mean deviation (MMD) of the surface friction coefficient is preferably 0.01 or less, more preferably 0.008 or less.

(Method for measuring friction characteristics)
The mean coefficient of friction (MIU) and the mean deviation value (MMD) of the coefficient of surface friction can be measured by the following methods. That is, using an automatic surface tester (KES FB4-AUTO-A manufactured by Kato Tech Co., Ltd.), a probe using a STEEL piano wire with a diameter of 0.5 mm was used to measure a probe area of 1 cm ² and a load of 50 gf/cm ² . , at a speed of 1 mm/s, and measure the friction force when reciprocating a length of 30 mm. The analysis distance is set to 20 mm length by cutting 5 mm data at both ends. MIU is the surface friction coefficient, and MMD is the average deviation value of the surface friction coefficient. The surface side of the measurement surface faces the probe side, and the X and Y directions are used as the measurement directions, and the measured values are averaged. The initial sample tension is 10 gf/cm. Each measured value is an average value obtained by measuring 5 points on the sheet.

[Roughness characteristics]
The nonwoven fabric 10 has an appropriate surface roughness on the apexes 11 of the projections 14 on the surface side 10A, so that when touched with a hand, the nonwoven fabric 10 can feel unevenness and the soft feel of the fibers in the nonwoven fabric. From this point of view, the surface roughness mean deviation (SMD) is preferably 0.1 μm or more, more preferably 0.2 μm or more, and even more preferably 0.3 μm or more. Also, the lower the surface roughness, the more skin-friendly contact can be maintained. From this point of view, the surface roughness mean deviation (SMD) is preferably 4 μm or less, more preferably 3.5 μm or less, and even more preferably 3.0 μm or less.

(Method for measuring roughness characteristics)
The surface roughness mean deviation (SMD) can be measured by the following method. That is, using the above-described automatic surface tester, a 5 mm wide probe made of a single STEEL piano wire with a diameter of 0.5 mm was used to measure a length of 30 mm under the conditions of a load of 10 gf/cm ² and a speed of 1 mm/s. Roughness is measured when reciprocating. As with the friction characteristics, the surface roughness average deviation value within the analysis distance is obtained as SMD. The surface side of the measurement surface faces the probe side, and the X and Y directions are used as the measurement directions, and the measured values are averaged. The initial sample tension is 10 gf/cm. Each measured value is an average value obtained by measuring 5 points on the sheet.

[Compression characteristics]
The greater the linearity (LC) of the compression characteristics of the convex portions 4 of the nonwoven fabric 10, the more likely it is to remain thick when pressed. From this point of view, the linearity (LC) of the compression characteristics of the projections 4 is preferably 0.4 or more, more preferably 0.5 or more. In addition, since there is a tendency to feel that it is better to deform with a soft force at the beginning and increase the repulsive force as the amount of compression increases, the linearity (LC) of the compression characteristics in the convex portion 4 is 0.8 or less. is preferred, and 0.7 or less is more preferred.

In the nonwoven fabric 10, the compressive energy (WC) of the protrusions 4 is neither too high nor too low, so that the nonwoven fabric 10 has a moderate resistance to the amount of deformation when pressed by hand, and has a soft texture. From this point of view, the compression energy (WC) in the projections 4 is preferably 3 gfcm/cm ² or more, more preferably 4.5 gfcm/cm ² or more. In addition, from the viewpoint of suppressing the repulsive force and maintaining an appropriate texture, the compression energy (WC) in the projections 4 is preferably 10 gfcm/cm ² or less, more preferably 8 gfcm/cm ² or less.

Furthermore, when the recovery energy (WC') of the convex portions 4 is large, the nonwoven fabric 10 has an appropriate resilience when pushed by the skin of a hand or the like, that is, a moderate cushioning property and excellent texture. From this point of view, the recovery energy (WC') in the projections 4 is preferably 1.7 gfcm/cm ² or more, more preferably 2 gfcm/cm ² or more. Moreover, from the viewpoint of suppressing the repulsive force and maintaining an appropriate texture, the recovery energy (WC') in the projections 1 is preferably 10 gfcm/cm ² or less, more preferably 8 gfcm/cm ² or less.

Compression resilience RC (WC'/WC×100) is obtained from these compression energy (WC) and recovery energy (WC').
When the amount of deformation described below is large, the nonwoven fabric 10 feels that the larger the RC value, the smaller the hysteresis in the elastic stress of compression and recovery, and the better the cushioning properties, and the nonwoven fabric 10 has appropriate elasticity. That is, it can be felt that the nonwoven fabric 10 undergoes little plastic deformation (settling) during compression. From this point of view, the RC value is preferably 42% or more, more preferably 44% or more. Also, the closer the RC value is to 100%, the better the elasticity. From this point of view, the RC value is preferably 100% or less, more preferably 100%.

In addition, since the total thickness (T0) of the nonwoven fabric 10 in the initial state before pressing (under a load of 0.5 gf/cm ² ) is within the above range, it is possible to increase the amount of deformation during pressing. You can feel the soft touch.

The nonwoven fabric 10 has a total thickness (TM) under a high load (50 gf/cm ² pressed) within the above range, so that it is suppressed from being crushed even under a high load, and has little plastic deformation (settling). can feel.

The nonwoven fabric 10 has a softer feel as the thickness deformation amount (T0-TM) increases. From this point of view, the thickness deformation amount (T0-TM) is preferably 0.5 mm or more, more preferably 2.5 mm or more, and even more preferably 3.5 mm or more. There is no particular upper limit to the amount of deformation in thickness (T0-TM), but when the basis weight is 100 g/m ² or less, a smaller amount of deformation prevents the distance between fibers from becoming too wide, resulting in improved cushioning properties and strength. 10 mm or less is preferable, 7 mm or less is more preferable, and 5 mm or less is even more preferable, from the viewpoint of providing excellent ductility. The larger the amount of deformation when a load is applied, the softer it feels.

(Method for measuring compression characteristics)
These compression properties can be measured by the following method. That is, using the automatic compression tester described above, at a speed of 0.05 mm / s, a probe area of 2 cm ² , and a compressive load of 0.5 gf / cm ² or more and 50 gf / cm ² or less, the sheet is compressed by the probe. Then, immediately after applying the maximum load, the thickness and the load at that time are measured when it is moved in the recovery direction. The thickness of the nonwoven fabric under a load of 0.5 gf/cm ² is defined as T0, and the thickness of the nonwoven fabric under a load of 50 gf/cm ² is defined as TM. The linearity of the compression characteristic is determined as LC, the compression energy as WC, the recovery energy as WC', the compression resilience as RC (WC'/WC×100), and the deformation amount as "TO-TM". The surface to be measured should face the stylus side. Each measured value is an average value obtained by measuring 5 points on the sheet.

[Preparation of measurement sample]
In each measurement described above, when preparing the nonwoven fabric 10 (sample) from the absorbent article, cold spray or the like is used for those bonded with a hot melt adhesive so as not to damage the nonwoven fabric 10 (sample). Then, the nonwoven fabric 10 (sample) is peeled off from the absorbent article and prepared. In addition, unless otherwise specified in each measurement, randomly selected points are measured.

Next, a preferred embodiment of the nonwoven fabric manufacturing method of the present invention will be described.

Various terms used in the nonwoven fabric manufacturing method of the present invention are defined as follows.
A "support" has an uneven shape, can be engaged with a pushing member, and temporarily holds a nonwoven fabric or an unfused web. The convex portion and concave portion described above refer to portions having a relationship of having a relative height difference with respect to the substrate, and for example, a portion protruding higher than the substrate constituting the support is the convex portion. . In this case, it can also be said that the portion of the substrate sandwiched between the convex portions is the concave portion. In addition, when the substrate constituting the support has a partially recessed portion, that portion becomes the recessed portion. In this case, it can also be said that the portion of the substrate sandwiched between the concave portions is the convex portion. The support may be flexible, such as in the form of a conveyor or net, or non-flexible, such as in the form of a drum roll or plate. Various materials can be used for the support. Examples include resins, metals, carbon, and ceramics. A non-flexible embossing roll is preferable in that embossing heat-sealing or embossing pressure bonding can be performed on the support.
A "push member" has an uneven shape and can be pushed (engaged) into a support. The pushing member may be flexible or non-flexible, and includes, for example, ring rolls, uneven rolls, nets, belts, chains, leaf springs (elastic plate-like bodies), and movable load plates. Various materials can be used for the pressing member, and examples thereof include resin, metal, carbon, and ceramic.

The term “engagement” refers to an arrangement in which the concave portion of the support and the pushing portion of the pushing member correspond to each other, and a gap is provided between the convex portion of the supporting member and the pushing portion of the pushing member to the extent that the web can enter. It means that the push-in portion enters into the concave portion while having the recessed portion. In other words, it means that the contoured shape of the support and the concave-convex shape of the pushing member are matingly matched. At this time, in order to reduce wear and deformation of the support and the pushing member, it is preferable that the support and the pushing member do not come into direct contact with each other.

A "web" is a sheet-like fiber assembly including non-woven fabrics and unfused webs. The web preferably contains thermoplastic fibers as constituent fibers.
"Nonwoven fabric" means a sheet in which a fiber assembly is formed by thermal fusion, mechanical entanglement, or chemical bonding (adhesive, chemical bond, etc.). In the nonwoven fabric of the present invention, the nonwoven fabric has the above-mentioned interlayer fiber intersection fused portion in the internal fiber structure.
"Unfused web" means an aggregate of unfused fibers that can be fused by heat (hot air, steam, heat embossing, ultrasonic embossing, etc.), and is subjected to hydroentangling or needle punching before the fusion treatment step. Nonwoven fabrics that have been mechanically entangled such as are excluded. More specifically, a web that does not have the strength of a nonwoven fabric and has a maximum tensile strength of 100 cN/50 mm or less in the MD and CD directions is defined as an unfused web. For example carded webs are included.

The "thermally fused" state means that the constituent fibers of the web in the thermally fused portion no longer have the fiber form before the fusion treatment due to the melting of the unfused web. Having a fiber shape means that the ratio (former/latter) of the length of the fiber and the diameter (calculated as a perfect circle) obtained from the cross-sectional area of the fiber is 300 times or more. For example, in the "thermally fused" state, at least a portion of the outer peripheral surface of the constituent fibers of the web is melted, making it impossible to discriminate the boundary with the outer peripheral surface of other fibers, and the fiber loses its shape before the fusion treatment. When the constituent fibers such as composite fibers are composed of two or more types of resin, even if a specific resin does not melt and maintains the fiber form, other resins melt and the boundary between the outer peripheral surfaces of the constituent fibers can be distinguished. It will not have the fiber morphology it had before the fusion process. These can be obtained by observing the cross section of the fiber fused portion with a scanning electron microscope (SEM).

"Embossed fusion" means that fibers are thermally fused together by external pressure and heat by an uneven member such as emboss. More specifically, it means that the resin of at least one of the fibers at the bonding interface between the fibers is melted by pressure and heat (due to self-heating due to intermolecular friction or compression or external heating) and bonded to the other fiber.
"Embossed pressure bonding" means that fibers are pressure-bonded to each other by external pressure or heat by an uneven member such as an emboss. More specifically, it means that one fiber adheres to another without the resin being melted by heat or pressure.

Any general fiber and thermally stretched fiber can be used for the fiber material constituting the web. The fibrous material is preferably a continuous fiber from the viewpoint of fluffing and strength, but is not limited to this, and may be a long fiber or a short fiber.
A continuous fiber is a fiber that is substantially continuous except for fiber cuts on the end face of the product member and some fiber cuts in the fluffy portion, and is seen in the spunbond method.
Long fibers are those having a fiber length of effective length (80 mm or more) and are found in meltblown processes.
Short fibers are fibers with a length of 77 mm or less, and are used in air-through nonwoven fabrics, spunlace nonwoven fabrics, and air-laid nonwoven fabrics.

Methods for supplying unfused web include spunbond method (before embossing, continuous fiber), electrospinning method (continuous fiber), spunmelt method (method combining hot air stretching and cold air stretching, long fiber), meltblown method. (long fibers), card method (short fibers), and airlaid method (short fibers). In particular, the spunbond method and the card method are preferable because a bulky three-dimensional shaped nonwoven fabric can be obtained. It is also possible to combine these supply methods.

The fiber material preferably contains thermoplastic fibers, for example, polyethylene (hereinafter also referred to as PE) fibers, polyolefin fibers such as polypropylene (hereinafter also referred to as PP) fibers, polyethylene terephthalate (hereinafter also referred to as PET), polyamide fibers obtained by using a thermoplastic resin alone such as It is also possible to use a composite fiber having a structure such as a core-sheath type or a side-by-side type. Composite fibers are preferably used in the present invention. The conjugate fibers referred to here include core-sheath fibers in which the high melting point component is the core portion and the low melting point component is the sheath portion, and side-by-side fibers in which the high melting point component and the low melting point component are arranged side by side. Preferable examples thereof include core-sheath structure fibers in which the sheath component is polyethylene or low-melting-point polypropylene. Representative examples of the core-sheath structure fibers include PET (core), PE (sheath), and PP (core). and PE (sheath), PP (core) and low melting point PP (sheath). More specifically, the constituent fibers preferably include polyolefin fibers such as polyethylene fibers and polypropylene fibers, polyethylene conjugate fibers, and polypropylene conjugate fibers. Here, the composite composition of the polyethylene conjugate fiber is polyethylene terephthalate and polyethylene, and the composite composition of the polypropylene conjugate fiber is preferably polyethylene terephthalate and low melting point polypropylene, more specifically, PET (core) and PE (sheath), PET (core) and low melting point PP (sheath). The melting point of the resin used means the melting point measured under atmospheric pressure (in _N2 gas atmosphere) unless otherwise specified.

These fibers can be used alone or in combination of two or more to form the web. The web may also contain fibers other than thermoplastic fibers, such as natural fibers such as cotton and pulp, and regenerated fibers such as rayon and cupra. Therefore, the nonwoven fabric produced by the production method of the present invention preferably contains the above fibers.

The method for producing a nonwoven fabric of the present invention has the following steps (hereinafter also referred to as step (I), step (II) and step (III)).
(I) A first unfused web consisting of an assembly containing fibers is meshed with a support having convex or concave portions and a first pushing member having a pushing portion capable of meshing with the support. First shaping step to shape.
(II) Laminating a second unfused web on the shaped first unfused web on the support, and being able to mesh with the support from the second unfused web side A second shaping step of shaping by engagement with a second pressing member having a pressing portion.
(III) In or after the second shaping step, a heat treatment step of fiber fusion using a heating fluid, or embossed pressure bonding or embossed fusion.

In the two-stage meshing shaping by the above step (I) and step (II), the ratio of the amount of meshing of the first pressing member with respect to the support to the amount of meshing of the second pressing member with respect to the support (former/latter) is 1.2 or more. That is, the pushing amount for the first unfused web due to meshing is made 1.2 or more larger than the pushing amount for the second unfused web. The first unfused web becomes the first fiber layer in the nonwoven fabric of the present invention, and the second unfused web becomes the second fiber layer.

This two-step mesh shaping process is a shaping process as shown in FIGS. 6(A) and 6(B), for example.
FIG. 6(A) shows the first shaping step of step (I). In this step, the first unfused web 100 to be the first fiber layer 1 is supported by the convex portions 111 of the support 110, and the first unfused web in the concave portions 112 between the convex portions 111, 111 is The pushing portion 121 of the first pushing member 120A pushes against 100 with an engagement amount K1. As a result, the pressed portion of the first unfused web 100 is stretched and formed into a convex shape toward the support. After peeling the first pressing member 120A from the first unfused web 100, the shaped first unfused web 100 is held on the support 110 side. As a holding method, suction is performed from the back side of the support 110 where there is no convex portion 111, the surface roughness of the side surface of the convex portion 111 of the support 110 is increased, and the surface of the side surface of the pushing portion 121 of the pushing member 120A. There is a method of reducing roughness. Although the support 110 is positioned on the upper side in FIG. 6A, the support 110 may be positioned on the lower side and the first pushing member 120A may be positioned on the upper side.
FIG. 6(B) shows the second shaping step of step (II). In this step, the second unfused web 200 that will become the second fiber layer 2 is laminated on the shaped first unfused web 100 . Next, from the side of the second unfused web 200 , the laminate of the first unfused web 100 and the second unfused web 200 in the concave portion 112 between the convex portions 111 and 111 of the support 110 is The pushing portion 122 of the second pushing member 120B pushes in with an engagement amount K2. As a result, the pushed-in portion of the second unfused web 200 is stretched and formed into a convex shape toward the support. The second unfused web 200 is shaped based on the aforementioned meshing ratio. At this time, the meshing amount K1, the meshing amount K2, and the thickness of the second unfused web 200 with respect to the first unfused web 100 cause the top portion of the first unfused web 100 to be second unfused. There are cases in which it is pressed into contact with the web 200 and cases in which it is shaped with voids. In the former case, by setting the ratio (K1/K2) to the amount of meshing to be 1.2 or more, the top of the first unfused web 100 is not pushed too strongly by the second unfused web 200. can be As a result, the thickness of the first unfused web 100 is maintained without excessive shaping.

In steps (I) and (II), as shown in FIGS. 6A and 6B, the first unfused web 100 and the second unfused web 200 are directly pushed in by mechanical pressure. As a result, both the unfused webs 100 and 200 are shaped into irregularities along the shape of the support 110 . This makes it possible to obtain a nonwoven fabric in which the fibers are oriented more strongly than in the case of pressing with a non-mechanical pressure such as wind, and which has many oriented components perpendicular to the plane of the nonwoven fabric. In addition, it is not necessary to increase the pressing force so much to increase the height difference of the unevenness to be shaped with respect to both the unfused webs 100 and 200, and the fiber webs can be softly shaped. In addition, it is possible to suppress the disorder of the fibers and improve the formability. In these steps (I) and (II), by appropriately setting the depth of indentation, the wall fiber orientation degree and wall fiber orientation angle of the nonwoven fabric of the present invention can be formed. In addition, it is preferable that the concave portion 112 of the support 110 has an opening 113 through which the heated fluid in step (III) passes. In FIG. 6, a two-stage meshing shaping process is shown, but three or more stages of meshing shaping process may be performed. At this time, the number of laminations may be two, or may be the number of laminations corresponding to the number of shaping operations of meshing.

As shown in FIG. 7, the first unfused web 100 has a larger meshing amount (K1/K2≧1.2) than the second unfused web 200, and has a higher draw ratio. The fiber orientation degree and the wall fiber orientation angle can be increased. In addition, due to the difference in meshing amount (K1/K2≧1.2), the first unfused web 100 has a higher stretch ratio at the wall than the second unfused web 200, and shaping with different stretch ratios. Therefore, the return amount B2 of the fiber structure after shaping of the second unfused web 200 is larger than the return amount B1 of the fiber structure after shaping of the first unfused web 100 (B1<B2 ). As a result, the fiber structure of the second unfused web 200 after shaping is easily restored, and the wall portion fiber orientation degree and the wall portion fiber orientation angle of the second unfused web 200 become relatively smaller.

After going through steps (I) and (II), in the heat treatment step of step (III), the laminated body of the formed first unfused web 100 and second unfused web 200 is formed on the support 110. By performing the heat treatment, the fiber cross-point fused P is formed, and the nonwoven fabric of the present invention is produced.
The heat treatment step of step (III) may be performed not only once but also multiple times. For example, the fiber fusion bonding with the heating fluid may be performed multiple times, or the fiber heat fusion bonding with the heating fluid and the embossing pressure bonding or the embossing fusion bonding may be performed in combination.

The nonwoven fabric of the present invention can be suitably produced by the method for producing the nonwoven fabric of the present invention including the steps (I) to (III) described above.
Specifically, the fiber orientation of the two unfused webs 100 and 200 can be suitably controlled. By this control, the nonwoven fabric of the present invention can be suitably formed with the above-described specific wall fiber orientation degree, specific wall fiber orientation angle, various area ratios including appropriate voids, and the like. In addition, by performing mesh shaping in two or more stages with different amounts of meshing, it is possible to widen the spaces between the fibers in the unfused web and retain large areas filled with fibers to form a bulky structure. . In this regard, the more the unfused webs 100 and 200 are stretched by meshing and shaping, the more the fiber orientation increases, while the distance between fibers increases and the fiber density decreases, so that the fiber bulk density tends to decrease. . Based on this, it is possible to simultaneously form a suitable fiber orientation and bulk density (bulk height) by controlling the meshing amount of the two stages.
As a result, it is possible to suitably produce the nonwoven fabric of the present invention that has a soft and good cushioning property, has a bulky and thick fiber structure, can maintain the thickness under pressure, and is resistant to crushing.

In particular, by setting the meshing amount ratio to 1.2 or more, the nonwoven fabric of the present invention produced has high total thickness (TM) retention under high load (under 50 gf/cm ² ). , it is possible to make it difficult to crush without lowering the texture. The reason for this is that the thickness of each layer of the unbonded web can be kept thick by pressing in two stages at the above ratio.
When two layers are superimposed and pushed in at the same time as in the conventional method, the first unfused web is pushed through the second unfused web and compressed in the thickness direction. Furthermore, when two layers are simultaneously shaped by a single-stage meshing shaping process, the voids are not formed. In this case, the wall portion fiber orientation degree and the wall portion fiber orientation angle of each layer are approximately the same, and the resulting nonwoven fabric tends to have a high compression energy when pressurized and a hard texture.
On the other hand, in the nonwoven fabric production method of the present invention, the first fiber layer 1 and the second fiber layer 2 are formed independently by performing the meshing forming step of pressing in two stages at the above ratio. The nonwoven fabric of the present invention can be suitably produced.

Thus, by setting the meshing amount ratio as described above, in addition to being able to impart the above-described specific degree of fiber orientation, the first unfused web can be shaped while suitably retaining the entire thickness.
From the above viewpoint, the meshing amount ratio is preferably 1.2 or more, more preferably 1.5 or more. From the same point of view, the ratio of meshing amounts is preferably 5.0 or less, more preferably 3.0 or less.

The meshing amount may be appropriately set within the above range according to the basis weight and thickness of the unfused web.
The basis weight and thickness of the non-fused web are within the range normally used in this type of article, and can be appropriately set according to the purpose of the nonwoven fabric to be produced. For example, the basis weight is in the range shown for the nonwoven fabric 10 described above. Further, it is practical that the thickness of each layer in the meshed state of the unfused webs is, for example, 1 mm or less.

The non-woven fabric production method of the present invention is not limited to the form in which only two types of unfused webs 100 and 200 are laminated. For example, a step of laminating another unfused web or nonwoven after step (II) may be included. In this case, the heat treatment step (III) is performed after this. As a result, the nonwoven fabric of the present invention has a flat lower layer, which suppresses the protrusions from being stretched in the width direction and being crushed when rolled and crushed.

In the method for producing a nonwoven fabric of the present invention, the pushing portion 122 of the second pushing member 120B has a top area larger than that of the pushing portion 121 of the first pushing member 120A used in steps (I) and (II). Large is preferred. For example, as shown in FIG. 7, it is preferable that the area of the top portion of the pushing portion 122 of the second pushing member 120B is larger than the area of the top portion of the pushing portion 121 of the first pushing member 120A.
In this case, after shaping, the radius of curvature of the region of the second unfused web 200 pushed by the pushing portion 122 is greater than the radius of curvature of the region pushed by the pushing portion 121 of the first unfused web 100. growing. Therefore, even after the pushing portion 122 is peeled off, the formed shape of the second unfused web 200 tends to be stable along the radius of curvature. In addition, the contact interface between the first unfused web 100 and the second unfused web 200 at the wall tends to increase, and more inter-layer fiber intersection fused portions P can be formed. In addition, the area of the top of the pushing portion 121 that pushes the first unfused web 100 is limited to be smaller than the area of the top of the pushing portion 122 that pushes the second unfused web 200 . The region where the fused web 100 is not directly pushed by the pushing portion 121 is relatively increased. This makes the first unfused web 100 and the first fiber layer 1 relatively bulkier and thicker.

From the above viewpoint, the ratio (former/latter) of the area of the top of the pushing portion 122 of the second pushing member 120B to the area of the top of the pushing portion 121 of the first pushing member 120A is preferably 1.0 or more. , is more preferably 1.2 or more, and more preferably 1.4 or more.
In addition, the ratio (former/latter) of the area of the top of the pushing portion 122 of the second pushing member 120B to the area of the top of the pushing portion 121 of the first pushing member 120A is 4.0 or less is preferable, 3.0 or less is more preferable, and 2.0 or less is preferable in order to sufficiently secure a gap with the top portion of the pressing portion 122 (to prevent contact or interference between the support and the pressing member). is more preferred.

In the nonwoven fabric manufacturing method of the present invention, in the plane direction of the laminate of the first unfused web 100 and the second unfused web 200, the pushing position of the pushing portion 121 of the first pushing member and the pushing position of the second pushing member may include a region that does not overlap with the pushing position of the pushing portion 122 .
For example, in FIG. 8A, on a plane in which rectangular convex portions 111 of the support are arranged in a grid at equal intervals, a plurality of concave portions running in parallel between a plurality of rows of convex portions 111 arranged in one direction are shown. The pushing portion 121 of the first pushing member is pushed into the portion at three points. On the other hand, in FIG. 8B, the pushing portion 122 of the second pushing member is pushed into one of them. As a result, as shown in FIG. 9, the shaping patterns of the first unfused web 100 and the second unfused web 200 are different, and the first unfused web 100 and the second unfused web 200 have different shaping patterns. The voids 3 formed in the above can be made large at some locations to create softness. However, in this case, it is preferable that the region where the pushing position of the pushing portion 121 of the first pushing member and the pushing position of the pushing portion 122 of the second pushing member overlap is 50% or more of the pushed region. In addition, in FIGS. 8A and 8B, for understanding the relationship between the pushing portion 121 of the first pushing member and the pushing portion 122 of the second pushing member in the plane direction of the support, the intervening first non The fused web 100 and the second unfused web 200 are omitted.

Next, specific examples (Specific Example 1 and Specific Example 2) of a preferred manufacturing apparatus used in the method for manufacturing a nonwoven fabric of the present invention will be described with reference to the drawings.

A nonwoven fabric manufacturing apparatus 900 of Specific Example 1 shown in FIG. 10 uses a drum-shaped support 110 having an uneven peripheral surface as a support for two-stage mesh shaping. A first pushing member 120A and a second pushing member 120B are arranged on the peripheral surface of the support 110 so as to be able to mesh with each other. The first pushing member 120A and the second pushing member 120B are roll-shaped.
First, the first unfused web 100 is fed between the support 110 and the first pushing member 120A, and the above step (I) is performed by engaging the support 110 and the first pushing member 120A.
Next, the second unfused web 200 is supplied to the uneven first unfused web 100 along the peripheral surface of the support 110, and the engagement between the support 110 and the second pushing member 120B The above step (II) is performed.

The convex or concave portions of the support 110 preferably extend in the direction of machine flow (direction of rotation of the drum). Furthermore, it is preferable that the convex portion or concave portion also extends in the width direction (the rotation axis direction of the drum shape) orthogonal to the machine flow direction. Moreover, it is preferable that the support body 110 applies a negative pressure from the peripheral surface to the inside. As a result, the first unfused web 100 and the second unfused web 200 along the peripheral surface of the support 110 are sucked, and the state of being aligned is better maintained before proceeding to the next step. can do.

Next, while holding the laminated body of the first unfused web 100 and the second unfused web 200 made uneven on the peripheral surface of the support 110, hot air W1 is blown at the position of the hot air blowing section 140, The fibers are fused with a heated fluid in step (III) described above. Thereby, the nonwoven fabric 10 which concerns on this invention is manufactured.

When the hot air W1 is blown, it is preferable to hold down the entire laminate with the net 130 from the second unfused web 200 side. Thereby, it is possible to prevent the fibers from scattering when the hot air W1 is blown. Moreover, it is preferable to have a hot air suction part 141 at a position facing the hot air blowing part 140 inside the drum of the support 110 .

The temperature of the hot air W1 is preferably 140.degree. C. or higher, more preferably 145.degree. In addition, the temperature of the hot air W1 is preferably 180° C. or lower, more preferably 175° C. or lower, and even more preferably 170° C. or lower from the viewpoint of suppressing excessive heat fusion of the thermoplastic fibers and improving the softness of the nonwoven fabric. .
In addition, the wind speed of the hot air W1 is preferably 15 m/sec or less, more preferably 12 m/sec or less, and even more preferably 10 m/sec or less, from the viewpoint of improving the cushioning properties and enhancing the retention of the entire thickness of the nonwoven fabric 10. . The wind speed of the hot air W1 is preferably 2 m/sec or more, more preferably 3 m/sec or more, and even more preferably 4/sec or more, from the viewpoint of heat-sealing the thermoplastic fibers and stabilizing the shape of the nonwoven fabric.

In addition, in the nonwoven fabric manufacturing apparatus 900 of Specific Example 1, at a position where the nonwoven fabric 10 obtained by blowing the hot air W1 is placed along the outer periphery of the drum of the support 110, the cooling unit 150 having a cooling nozzle and the support 110 It is preferable to arrange the cooling suction part 151 inside the drum so as to face it. Thereby, as described above, the support 1 can be kept below a certain temperature, and the obtained nonwoven fabric can be peeled off while maintaining its shape, and good cushioning properties can be maintained.

The above steps (I), (II) and (III) can be carried out under various conditions. For example, various conditions described in paragraphs [0010] to [0067] of the specification of JP-A-2019-112747 can be appropriately adopted and implemented.
Various forms can also be used for the support 110 and the pushing members 120A and 120B used in the steps (I) and (II). For example, the support shown in FIG. 2 described in the above document and the pressing member shown in FIGS. 3, 7 and 8 described in the above document can be used. The support shown in FIG. 2 is a drum-type support having convex portions, concave portions and apertures on its peripheral surface. A plurality of convex portions are arranged on the peripheral surface of the support so as to be spaced apart from each other in the direction of rotation and the direction of the axis of rotation. Thereby, the recess extends at least in the direction of rotation of the support. Furthermore, the concave portion also extends in the rotation axis direction. The push-in member shown in FIG. 3 has a push-in portion on the drum-shaped peripheral surface to be inserted along the concave portion of the support. As a result, the indentation portions are arranged in a grid pattern. A hollow space is formed between the indentation portions, and has a grid-like space. The pushing member shown in FIG. 8 is formed into a belt shape by weaving a string-like pushing portion in a grid pattern. The pushing member shown in FIG. 9 has a drum shape in which a plurality of rings are combined in the direction of the rotation axis, and the ring portion forms a pushing portion extending in the direction of rotation.

Further, the nonwoven fabric manufacturing apparatus 900 of the specific example 1 may have a mechanism for laminating another unfused web or nonwoven fabric (web 300) after peeling the nonwoven fabric 10 from the peripheral surface of the support 110. FIG. In this case, it is preferable to have another mechanism for performing the aforementioned step (III) after this as well.

A non-woven fabric manufacturing apparatus 910 of Concrete Example 2 shown in FIG. and a nip roller 106 that presses the first unfused web 100 conveyed by the conveyor belt 104 . Downstream thereof, a pair of rolls (support 110 and first pressing member 120A) for engaging and forming irregularities on the first unfused web 100; A roll (second pressing member 120B) is provided for joining the second unfused web 200 to the unfused web 100 and performing meshing and uneven shaping processing. Further downstream, point joining means for fusing some or all of the fibers at the bottom of the concave portion of the laminate of the first unfused web 100 and the second unfused web 200 pulled by the support 110. 130 and a cooling roll 114 for cooling the fused portion (embossed portion) fused by the point bonding means 130 . Furthermore, downstream of the cooling roll 114, there is provided a heat flow section 118 for blowing a heated fluid to fuse the fiber intersections, that is, to form a non-woven fabric.

Web supply 102, conveyor belt 104, and nip rollers 106 are configured to feed and convey first unfused web 100 toward support 110 and first pusher member 120A. In addition, the cooling roll 114 is configured to cool the layered body of the first unfused web 100 and the second unfused web 200 on which the embossed portions 6 are formed by the point bonding means 130 while conveying it toward the downstream side. It is Although the conveyor belt 104, the nip roller 106, and the cooling roll 114 may not be used as appropriate, it is preferable to provide them for stable production. As the web supply section 102, the conveyor belt 104, the nip roller 106 and the cooling roll 114, various commonly used configurations can be employed.

In the manufacturing apparatus 910 having the above configuration, first, the unfused web 100 is supplied from the web supply section 102 onto the conveyor belt 104, and while the nip roller 106 presses the unfused web 100, the conveyor belt 104 feeds the support body. 110 and the first pushing member 120A. Here, the nip roller 106 does not firmly bond the fibers, but presses the fibers together to the extent that the unfused web 100 can be transported. At this time, most of the crimped portions tend to separate due to the tensile tension when the support 110 and the first pressing member 120A mesh. In this way, the number of crimped portions is reduced by peeling, which is preferable because the degree of freedom of the fibers is increased and the texture is excellent. Further, even if a portion of the crimped portion remains, since the crimped portion is not a fused portion, there is almost no deterioration in texture due to catching.

In addition, in the nonwoven fabric manufacturing apparatus 910 of Specific Example 2, the web supply unit 102 is shown as supplying the single-layer unfused web 100, but the present invention is not limited to this. For example, the web supply section 102 may include two or more devices so as to supply an unfused web 100 having a thickness of two or more layers. When the first unfused web 100 is supplied onto the conveyor belt 104 as a laminate of two or more layers, in the manufacturing apparatus 910, uneven shaping is performed on the entire laminate by the support 110 and the first pressing member 120A. done.

In the nonwoven fabric manufacturing apparatus 910 of Specific Example 2, similarly to the nonwoven fabric manufacturing apparatus 900 of Specific Example 1 described above, the engagement between the support 110 and the first pushing member 120A and the second pushing member 120B causes the above-described Step (I) and step (II) are performed. As a result, a laminate of the first unfused web 100 and the second unfused web 200 having irregularities is obtained.
A laminate of the first unfused web 100 and the second unfused web 200 having irregularities is brought into close contact with the peripheral surface of the support 110 by frictional force, suction, or the like with the support 110 . , the substrate is conveyed to the position of the point bonding means 130 while the uneven shape is maintained. By sandwiching the point bonding means 130 and the convex or concave portions of the support 110, the fibers at the bottom of the concave portions of the laminate are embossed and crimped or embossed and fused. Thereby, the embossed portion 6 is formed in a predetermined pattern. After that, the laminated body is transferred to a cooling roll 114 to be cooled, conveyed by a downstream second conveyor belt 117, and the fiber intersection points are fused at a heat flow portion 118 (step (III)).
As a result, it is possible to suitably produce the nonwoven fabric of the present invention that has a soft and good cushioning property, has a bulky and thick fiber structure, can maintain the thickness under pressure, and is resistant to crushing.

Furthermore, the nonwoven fabric manufacturing apparatus 910 of Specific Example 2 joins the uneven first unfused web 100 and the second unfused web 200 laminate with another unfused web or nonwoven fabric (web 300). It may also have a mechanism for stacking by pressing. In this case, the embossed portions are formed by the point bonding means 130 in a state in which the laminate and the web 300 are laminated.

The nonwoven fabric of the present invention can be used for various purposes.
For example, the nonwoven fabric of the present invention can be used for absorbent articles such as diapers, sanitary napkins, panty liners, and incontinence pads. Absorbent articles typically have a liquid-permeable topsheet, a backsheet, and an absorbent body sandwiched between them. Among them, the nonwoven fabric of the present invention can be suitably used as a surface sheet. Furthermore, there is also a form in which it is used as a sheet for gathers, an exterior sheet, and a sheet for wing portions of an absorbent article.
In addition, the nonwoven fabric of the present invention can be used as a sweat absorbent sheet, or as a constituent member of an eye mask or a mask.

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention should not be construed as being limited thereto. In the examples, "parts" and "%" are based on mass unless otherwise specified. In Table 1 below, "-" means that there is no item or value corresponding to the item.

(Example 1)
A first unfused web 100 and a second unfused web 200 were prepared as described below.
The first unfused web 100 has a core-sheath type (polyethylene terephthalate (PET) (core): polyethylene (PE) (sheath) = 5:5 (mass ratio)) thermoplastic concentric core with a fineness of 1.1 dtex. type composite short fibers were used. The second unfused web 200 has a core-sheath type (polyethylene terephthalate (PET) (core): polyethylene (PE) (sheath) = 5:5 (mass ratio)) thermoplastic concentric core with a fineness of 3.3 dtex. type composite short fibers were used. Both were coated with a hydrophilic oil.
A first unfused web 100 (15 g/m ² basis weight) and a second unfused web 200 (15 g/m ² basis weight) were formed by a carding machine. The first unfused web 100 was meshed and shaped by the first pressing member shown in FIG. 6(A) and the support to form an uneven shape. After that, as shown in FIG. 6(B), a second unfused web 200 is layered on the first unfused web 100 that has been shaped in advance, and the laminated web is placed on the same support as a second pressing member. It was shaped by meshing with the support. Each condition was as shown in the table. The ratio (former/latter) of the area of the top of the pushing portion 122 of the second pushing member to the area of the top of the pushing portion 121 of the first pushing member was 1.0.
Fiber cross-point fusion treatment is performed by blowing hot air (temperature: 160°C, wind speed: 4.3 m/s, blowing time: 1.5 seconds) onto the meshed and shaped laminate on the support from the side of the second unfused web. did After that, the laminated web that has undergone meshing and shaping is peeled off from the support, and then on a conveyor net from the back surface (second fiber layer) side with a hot air temperature of 136 ° C., a wind speed of 1.5 m / s, and a blowing time of 6 s. A hot air treatment was performed on the fiber to form a fiber intersection fused portion. Thus, a nonwoven fabric sample of Example 1 was produced.

(Examples 2 and 3)
Nonwoven fabric samples of Examples 2 and 3 were produced in the same manner as in Example 1, except that the meshing amounts of the first pushing member and the second pushing member were as shown in Table 1.

(Example 4)
A second unfused web 200 is laminated on the shaped first unfused web 100, and after the laminated web is meshed and shaped on the same support by the second pushing member and the support, A flat third unfused web 300 (basis weight: 15 g/m ² ) is further laminated. Hot air (temperature: 160° C., wind speed: 4.3 m/s, blowing time: 1.5 seconds) was blown from the side of the fused web to carry out fiber cross-point fusion. A nonwoven fabric sample of Example 4 was produced in the same manner as in Example 1 except for the above. The third unfused web 300 includes a core-sheath type (polyethylene terephthalate (PET) (core): polyethylene (PE) (sheath) = 5:5 (mass ratio)) thermoplastic material having a fineness of 3.3 dtex. Concentric type composite short fibers were used.

(Comparative example 1)
A nonwoven fabric sample of Comparative Example 1 was produced in the same manner as in Example 1, except that the meshing amounts of the first pressing member and the second pressing member were as shown in Table 1 and the meshing amount ratio was set to 1.1.

(Comparative example 2)
A nonwoven fabric sample of Comparative Example 2 was produced in the same manner as in Example 1, except that the second unfused web was laminated in a flat shape without being interlocked and shaped.

(Comparative Example 3)
A non-woven fabric sample of Comparative Example 3 was produced by shaping the first unfused web and the second unfused web used in Example 1 by two-stage hot air blowing without performing intermeshing shaping. The two steps of hot air blowing were carried out as follows. That is, the first unfused web 100 is placed on the support shown in FIG. A first fused web was obtained by performing shaping and fiber intersection fusion processing. After that, the second unfused web 200 is laminated thereon, and the second unfused web 200 is applied to the laminate of the first fused web and the second unfused web 200 placed on the support. Hot air was blown from the side at a temperature of 160° C., a wind speed of 2 m/s, and a blowing time of 1.5 seconds to perform hot-air shaping and fiber cross-point fusion treatment. A nonwoven fabric sample of Comparative Example 3 was produced in the same manner as in Example 1 except for the above.

The following tests were performed on the nonwoven fabric samples of each example and each comparative example. Each test (1) to (3) below was measured based on each of the above-described measurement methods.
(1) Wall Fiber Orientation Degree, Wall Fiber Orientation Angle, and Fiber Density Measured based on the above-mentioned (measurement method for wall fiber orientation degree and wall fiber orientation angle) and (measurement method for fiber density).
(2) Area Ratio of Gap 18, First Fiber Layer 1, Gap 3, Second Fiber Layer 2, and Gap 28 Measured based on the above-mentioned (Method for Measuring Void Ratio).
(3) Friction characteristics, roughness characteristics and compression characteristics The above-mentioned (method for measuring friction characteristics), (method for measuring roughness characteristics), (method for measuring compression characteristics), (nonwoven fabric under a load of 0.5 gf / cm ² Total thickness measurement method).
(4) Texture Based on sensory evaluation based on multiple factors such as cushioning properties, amount of deformation when pressed by hand, and smoothness, one nonwoven fabric of Comparative Example 1 was evaluated as M size (Mary's tape type diaper manufactured by Kao Corporation) (2019). A three-dimensional shaped nonwoven fabric obtained by peeling off the surface material from a product manufactured in Japan in 2003 was given 3 points, and the higher the score, the better the texture. The evaluation was conducted blindly by 3 male and 3 female researchers. The obtained value was the value obtained by rounding off the decimal point of the average value.
It should be noted that the greater the value of the amount of deformation when pressed by hand, the softer the material tends to be felt. When the amount of deformation is large, the greater the compression resilience (RC), the smaller the hysteresis in the elastic stress of compression and recovery, and the better the cushioning properties tend to be. Furthermore, when the average coefficient of friction (MIU) is within the above-mentioned moderate range and the mean deviation value (MMD) of the surface friction coefficient is small, there is a tendency to feel moderate smoothness. There is no catching, etc., and there is a tendency to feel smooth with small fluctuations in the coefficient of friction.

The above evaluation results were as shown in Tables 1 and 2 below. 12(A) to 12(D) show the states of the fiber layers observed when measuring the "total thickness under 0.5 gf/cm ² load" of the nonwoven fabric samples of Examples 1 to 4. rice field. The fiber states of the fiber layers observed when measuring the "thickness under 0.5 gf/cm ² load" of the nonwoven fabric samples of Comparative Examples 1 to 3 were as shown in Figs.

As shown in Tables 1 and 2, the nonwoven fabric samples of Examples 1 to 4 had a wall portion fiber orientation degree of 0.70 or more and 0.95 or less in the first fiber layer, and the wall portion fiber orientation of the first fiber layer The ratio of the degree of fiber orientation to the wall portion fiber orientation of the second fiber layer is 1.1 or more and 1.5 or less. Therefore, it had thickness characteristics as shown below.
That is, the nonwoven fabric samples of Examples 1 to 4 have higher WC' values (cushioning properties), which are shown as compression characteristics, than those of the nonwoven fabric samples of Comparative Examples 2 and 3, and the WC values (resistance to deformation) are compared. It was neither too high nor too low compared to the nonwoven fabrics of Examples 1-3. The nonwoven fabric samples of Examples 1-4 had sufficiently high RC values (elasticity). Therefore, the nonwoven fabric samples of Examples 1 to 4 had good cushioning properties, which were fluffy and soft, compared to those of Comparative Examples 1 to 3.
In addition, the nonwoven fabric samples of Examples 1 to 4 were thicker than the nonwoven fabric sample of Comparative Example 3 in "total thickness T0 under a load of 0.5 gf/cm ² " (the thickness in the initial state before pressing). . In addition, the nonwoven fabric samples of Examples 1 to 4 were maintained in a state where the "total thickness TM under a load of 50 gf/ ^cm2 " (total thickness at high load) was thicker than those of the nonwoven fabric samples of Comparative Examples 2 and 3. It had been. Therefore, the nonwoven fabric samples of Examples 1 to 4, while having the above-mentioned soft and good cushioning properties, are bulkier and thicker than those of Comparative Examples 1 to 3, and the thickness is increased under pressure. It could be held and was hard to be crushed. Among them, the nonwoven fabric sample of Example 2 had a thickness under a low load, had a large amount of deformation, and was felt to be slightly softer than the nonwoven fabric sample of Example 1.

In addition, the nonwoven fabric samples of Examples 1 to 3 have softness at the initial stage of pressurization, and after that, the second fiber layer 2 compensates for the first fiber layer 1 so that it is difficult to crush, so the texture is excellent. (texture evaluation 4 or 5). Further, among the nonwoven fabric samples of Examples 1 to 3, the nonwoven fabric sample of Example 1 had the above-mentioned sufficient "ratio of the wall portion fiber orientation degree of the first fiber layer to the wall portion fiber orientation degree of the second fiber layer". In addition, "the wall fiber orientation angle of the first fiber layer - the wall fiber orientation angle of the second fiber layer" is high. Therefore, the nonwoven fabric sample of Example 1 has a well-balanced area ratio of the gaps 18, the first fiber layer 1, the gaps 3, the second fiber layer 2, and the gaps 28 in the cross section as shown in FIG. Compared to Examples ² and 3, which have a high total thickness T0 under a load of 5 gf/ ^cm2 , the "total thickness TM under a load of 50 gf/cm2" is high, and among the nonwoven fabric samples of Examples 1 to 3 The texture was the most excellent (texture evaluation 5).
On the other hand, in the nonwoven fabric sample of Comparative Example 1, the difference in meshing amount between the two stages was small in the manufacturing process, and the ratio of the wall portion fiber orientation was too small, so that the nonwoven fabric sample felt relatively hard. In addition, since voids were not formed, the WC value (resistance against deformation) was too high, and it felt a little harder than in Example 1 and had a poor texture. The standard deviation MMD of the coefficient of friction was also relatively high. When the nonwoven fabric has a hard uneven shape, the convex part of the nonwoven fabric tends to be difficult to follow the stylus, so this value tends to be high. Therefore, when the standard deviation MMD is high, the texture tends to be inferior (texture evaluation 2).
Although the nonwoven fabric sample of Comparative Example 2 has a "total thickness under a load of 0.5 gf/ ^cm2 ", it has excessive voids between the first fiber layer and the second fiber layer, and the lower second layer Since the fiber layer was almost flat, the ratio of the fiber orientation in the wall portion was too large, and the layer easily collapsed without compensating for the collapse of the upper layer (the "total thickness under a load of 50 gf/ ^cm2 " was insufficient). Therefore, the nonwoven fabric sample of Comparative Example 2 compared to the nonwoven fabric samples of Examples 1 to 3 in all of the LC value (cushioning property), WC value (resistance to deformation), and WC' value (cushioning property). was inferior. For these reasons, the nonwoven fabric sample of Comparative Example 2 had a poor texture (texture evaluation 1).
The nonwoven fabric sample of Comparative Example 3 was shaped only by hot air blowing, so it could not be stretched sufficiently, the amount of unevenness was small (the area ratio of the gaps 18 on the surface side 10A of the first fiber layer 1 was small), and the wall part The ratio of fiber orientation was too small, and relatively hard was felt. In addition, the "total thickness under a load of 0.5 gf/ ^cm2 " was relatively thin due to the above shaping, and the amount of deformation was reduced accordingly. For these reasons, the nonwoven fabric sample of Comparative Example 3 felt hard and had poor texture (texture evaluation 2).

As described above, the nonwoven fabrics of Examples 1 to 3 have a bulky and thick fiber structure while having soft and good cushioning properties. , and further excellent in texture.

1 first fiber layer 11 top 12 wall 13 bottom 14 protrusion 15 recess 2 second fiber layer 21 top 22 wall 23 bottom 24 protrusion 25 recess 3 void 4 protrusion 5 recess 6 embossed portion 10 nonwoven fabric T0 no load Total thickness T1 of the lower nonwoven fabric Total thickness T2 of the first fiber layer Total thickness D1 of the second fiber layer Actual thickness D2 of the first fiber layer Actual thickness M1 of the second fiber layer Intermediate height position M2 of the first fiber layer Intermediate height position P of two fiber layers Inter-layer fiber intersection fused portion Q Intra-layer fiber intersection fused portion N Planar direction V Extending direction Z of fiber layer Thickness direction (total thickness direction)
S Direction of actual thickness E Square EA, EB Square side L1 Intermediate position 18, 28 in the actual thickness direction of each fiber layer Gap 100 First unfused web 200 Second unfused web 110 Support 111 Support Convex part 120A First pushing member 121 Pushing part 120B of first pushing member Second pushing member 122 Pushing parts K1, K2 of second pushing member K1, K2 Engagement amount B1, B2 Return amount 130 Net 140 Hot air blowing part 141 Hot air suction part 150 Cooling nozzle 151 Cooling suction unit 300 Webs 900, 910 Manufacturing apparatus W1 Hot air

Claims (7)

A nonwoven fabric in which two or more fiber layers are laminated in the thickness direction,
The first fiber layer on one side has a convex portion and a concave portion, and the second fiber layer adjacent to the first fiber layer on the other side in the thickness direction is the first fiber layer. having a convex portion entering the inside of the other surface side of the convex portion;
At least an inter-layer fiber intersection fused portion is included in an interface between a wall portion of the convex portion of the first fiber layer and a wall portion of the convex portion of the second fiber layer,
In the wall portion of the projections of the first fiber layer, the wall portion fiber orientation degree is 0.70 or more and 0.99 or less, and the wall portion fiber orientation degree in the projection portion of the first fiber layer is the second fiber A nonwoven fabric having a ratio (former/latter) to the degree of fiber orientation in the wall portion of the convex portion of the layer of 1.1 or more and 1.5 or less. The ratio (former/latter) of the fiber density of the peaks of the protrusions of the second fiber layer to the fiber density of the peaks of the protrusions of the first fiber layer is 0.8 or more and 1.8 or less. 1. The nonwoven fabric according to 1. 2. A difference (former-latter) between the wall fiber orientation angle of the projections of the first fiber layer and the wall fiber orientation angle of the projections of the second fiber layer is 0 degrees or more and 50 degrees or less. Or the nonwoven fabric according to 2. An absorbent article using the nonwoven fabric according to any one of claims 1 to 3. A first unfused web consisting of an assembly containing fibers is formed by meshing a support having convex or concave portions with a first pushing member having a pushing portion capable of meshing with the support. a first shaping step;
On the support, a second unfused web is laminated on the shaped first unfused web, and from the second unfused web side, a pushing portion capable of meshing with the support is formed. a second shaping step of shaping by engagement with the second pressing member having,
The ratio (former/latter) of the amount of meshing of the first pushing member with respect to the support to the amount of meshing of the second pushing member with respect to the support is 1.2 or more,
A method for producing a nonwoven fabric, wherein in the second shaping step or after the second shaping step, a heat treatment step of fiber fusion bonding with a heating fluid, or embossed pressure bonding or embossed fusion bonding is performed. 6. The method for producing a nonwoven fabric according to claim 5, comprising a step of laminating another unfused web or nonwoven fabric after the second shaping step. The method for producing a nonwoven fabric according to claim 5 or 6, wherein the pressing portion of the second pressing member has a larger top area than the pressing portion of the first pressing member.

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