JP2008266813A - Method for producing nonwoven fabric - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a nonwoven fabric wherein a liquid-drawing property is good and the liquid is hardly remains. <P>SOLUTION: The method for producing the nonwoven fabric includes the step of subjecting a fiber web including a heat-shrinkable fiber having heat fusability and arranged so that the surface may have an uneven shape after heat treatment and so that the fiber density in the region of a convex part may be thickened than the fiber density in the region of a concave part, to heat treatment at a temperature at which the heat shrinkable fiber can be melted and can be shrunk; and the step of pressing the resultant fiber web in the thickness direction so that the convex part in the uneven shape formed in the step of carrying out the heat treatment may be flattened out. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

  Conventionally, in order to improve the liquid drawability of the nonwoven fabric and to prevent the liquid from remaining, various ideas have been made on the types of fibers blended into the nonwoven fabric and the structure of the nonwoven fabric.

  For example, if the absorbent article is a non-woven fabric as a second sheet and is arranged between a liquid-permeable surface sheet and a liquid-retaining absorbent, the liquid on the surface sheet can be easily drawn into the second sheet (liquid drawing property). However, it is a problem that the drawn liquid does not remain in the second sheet, but moves to the absorber (inhibition of liquid remaining).

  Therefore, the second sheet (liquid permeable sheet) has a multilayer structure, and the first layer located on the absorber side includes high heat-shrinkable fibers (coiled fibers), and the second sheet located on the top sheet side. An absorbent article has been proposed in which the average fiber density of the first layer is higher than the average fiber density of the layer. (See Patent Document 1).

JP 2004-33236 A

  However, in the second sheet described in Patent Document 1, when the coiled fibers are arranged unevenly, for example, the coiled fibers are present in the first layer in the vicinity of the boundary between the first layer and the second layer. Otherwise, the fiber density between the second layer and the first layer does not differ, and the liquid of the second layer may not be drawn into the first layer. As a result, the liquid remains in the second layer (in the second sheet).

  Then, an object of this invention is to provide the manufacturing method of the nonwoven fabric with which liquid draw-in property is good and a liquid does not remain easily.

  In order to solve the above-described problems, the main present invention is that the surface after the heat treatment has a concavo-convex shape, and heat fusion is performed so that the region where the convex portion is formed is denser than the region where the concave portion is formed. The heat-shrinkable fiber web in which the heat-shrinkable fibers are disposed is heat-treated at a temperature at which the heat-shrinkable fibers can be melted and heat-shrinkable, and the uneven shape formed by the heat-treating step. A step of pressing the fiber web in the thickness direction so that the projections of the sheet are crushed.

  Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to provide the manufacturing method of the nonwoven fabric which liquid drawability is good and a liquid does not remain easily.

  This specification and the drawings disclose at least the following matters.

That is, the fiber web on which the heat-shrinkable fibers having heat-fusibility are arranged so that the surface after the heat treatment has a concavo-convex shape and the fibers in the region that is the convex portion are denser than the region that is the concave portion. The step of heat-treating at a temperature at which the heat-shrinkable fibers can be melted and heat-shrinkable, and the thickness of the fiber web so that the concavo-convex convex portions formed by the heat-treatment step are crushed. And a step of pressing in the vertical direction.
According to such a nonwoven fabric manufacturing method, for example, the nonwoven fabric has a high density region having a fiber density higher than the average fiber density and a low density region having a fiber density lower than the average fiber density, and the high density A nonwoven fabric in which the density region and the low density region communicate from one side to the other side in the thickness direction of the nonwoven fabric can be produced.

In this non-woven fabric manufacturing method, in the heat treatment step, the fiber web is heat-treated in a state of being supported by a support member from one side in the thickness direction.
According to such a nonwoven fabric manufacturing method, unevenness is formed on the surface opposite to the supported side, and conversely, since the movement of the heat-shrinkable fibers is restricted on the supported side, the unevenness is not formed. That is, in order to press the convex portion formed only on one side of the fiber web, the fiber density on the opposite side of the supported side is made higher than the fiber density on the supported side in the high density region formed on the nonwoven fabric. be able to.

In this nonwoven fabric manufacturing method, in the pressing step, the fiber web is pressed in a state of being heated at the temperature.
According to such a nonwoven fabric manufacturing method, it becomes easy to crush a convex part.

In this nonwoven fabric manufacturing method, in the pressing step, the fiber web is pressed such that the thickness of the fiber web is equal to or less than the thickness of the recess.
According to such a nonwoven fabric manufacturing method, a nonwoven fabric having a substantially uniform thickness can be manufactured.

In this nonwoven fabric manufacturing method, the amount of fibers in the region that is the convex portion is twice or more the amount of fibers in the region that is the concave portion.
According to such a nonwoven fabric manufacturing method, the high-density area | region formed in a nonwoven fabric is easy to communicate from the one side of the thickness direction of a nonwoven fabric to the other side.

In this nonwoven fabric manufacturing method, in the heat treatment step, the fiber web is heat treated so that hot air at the temperature is blown from both sides in the thickness direction.
According to such a nonwoven fabric manufacturing method, since irregularities are formed on both sides of the fiber web, the fiber density on either side of the nonwoven fabric is not increased in the high density region of the nonwoven fabric. Each fiber density can be made comparable.

=== About non-woven fabric ===
<Nonwoven fabric of comparative example>
First, the nonwoven fabric 1 of the comparative example different from the nonwoven fabric manufactured by the nonwoven fabric manufacturing method of this embodiment is demonstrated. FIG. 1 is a cross-sectional view of a nonwoven fabric 1 of a comparative example. The nonwoven fabric 1 of the comparative example is composed of an upper layer 2 (corresponding to the second layer) and a lower layer 3 (corresponding to the first layer), and for the purpose of facilitating liquid transfer from the upper layer 2 to the lower layer 3, The average fiber density of 3 is higher than the average fiber density of the upper layer 2.

  Here, the lower layer 3 of the nonwoven fabric 1 of the comparative example is formed by a fiber web containing highly heat-shrinkable fibers having heat-fusibility (before the fibers are fused, and the fibers have a degree of freedom). The The lower layer 3 is formed by heat-treating the fiber web in a state where tension is not so much applied in the thickness direction and the surface direction, and heat-sealing the fibers. When the shrinkage ratio due to heat treatment is high like high heat shrinkable fibers (for example, the shrinkage ratio with respect to the temperature during the heat treatment is 70% or more), the high heat shrinkable fibers are coiled while taking in the surrounding fibers by heat treatment. Shrink. On the other hand, the upper layer 2 of the nonwoven fabric 1 of the comparative example is formed by heat-treating a fiber web that does not contain high heat-shrinkable fibers having heat-fusibility (or a smaller amount than the lower layer 3). Therefore, the average fiber density of the lower layer 3 having the fibers (coiled fibers A) crimped in a coil shape while the high heat-shrinkable fibers take in the surrounding fibers is higher than the average fiber density of the upper layer 2.

  However, in the lower layer 3 of the nonwoven fabric 1 of the comparative example, the coiled fibers A are not necessarily evenly present, and the coiled fibers A may be unevenly present. In particular, since the lower layer 3 is manufactured in a state where tension is not so much applied, the lower layer 3 is thick (bulky) in the thickness direction. Therefore, for example, as shown in FIG. 1, the coiled fiber A may not exist in the region X on the upper surface side of the lower layer 3 that is in contact with the upper layer 2. Then, there is no difference between the fiber density of the upper layer 2 and the fiber density of the region X (lower layer 3), and the liquid in the upper layer 2 cannot be drawn into the region X of the lower layer 3 by capillary force.

  Conversely, when a large number of coiled fibers A are gathered as in the region Y of FIG. 1, the fiber density in the region Y becomes too high. As a result, a large amount of liquid or high-viscosity liquid cannot permeate between fibers, so that the liquid remains in the nonwoven fabric 1 or the liquid diffuses in the surface direction.

  Therefore, for example, it is assumed that the nonwoven fabric 1 of the comparative example is disposed as the second sheet of the absorbent article so that the upper layer 2 is on the surface sheet side between the liquid-permeable surface sheet and the liquid-retaining absorbent. However, the liquid may remain in the top sheet or the second sheet. If it does so, an unpleasant feeling (sticky feeling) will be given to a user and a wearer's skin will also be soiled.

  Therefore, it is an object of the present embodiment to provide a method for producing a nonwoven fabric that has good liquid drawability and is unlikely to retain liquid. Hereinafter, the nonwoven fabric 10 manufactured by the nonwoven fabric manufacturing method of this embodiment is demonstrated.

<Outline of the nonwoven fabric 10 produced by the nonwoven fabric production method of the present embodiment>
FIG. 2A is a top view of the nonwoven fabric 10 of the present embodiment, and FIG. 2B is a perspective view of the nonwoven fabric 10 of the present embodiment. FIG. 3A is a cross-sectional view of the nonwoven fabric 10 of the present embodiment, and FIG. 3B is an enlarged view of the cross section.

  The nonwoven fabric 10 of this embodiment has the high density area | region 11 which is a fiber density higher than the average fiber density of the nonwoven fabric 10 whole, and the low density area | region 12 which is a fiber density lower than an average fiber density. And the high density area | region 11 and the low density area | region 12 are disperse | distributed and formed in the surface direction of the nonwoven fabric 10, as shown to FIG. 2A.

  As shown in FIG. 3A, the nonwoven fabric 10 of the present embodiment has a substantially uniform thickness, and the high-density region 11 communicates from one side (upper surface) to the other side (lower surface) in the thickness direction of the nonwoven fabric 10. ing. Similarly, the low density region 12 communicates from one side to the other side. Further, in the high density region 11, as shown in FIG. 3B, the fiber density on the other side is higher than the fiber density on the one side.

  FIG. 4 is a diagram illustrating a state of liquid permeation of the nonwoven fabric 10 of the present embodiment. A state in which an absorbent body (not shown) having a higher density than the high density region 11 is arranged on the lower surface of the nonwoven fabric 10 and the liquid dropped on the upper surface of the nonwoven fabric 10 passes through the nonwoven fabric 10 and moves to the absorbent body. This will be described below.

  When a large amount of liquid is dropped on the nonwoven fabric 10, the liquid first moves to the absorbent body through the low density region 12 where there is not much fiber and resistance to permeation is low. Even when a large amount of liquid is dropped, the low density region 12 communicates in the thickness direction, so that most of the liquid can quickly move to the absorber. As a result, it is possible to prevent the liquid from diffusing on the upper surface (surface direction) of the nonwoven fabric 10.

  Then, after most of the liquid has been transferred, a small amount of liquid remaining on the upper surface of the nonwoven fabric 10 can be drawn into the nonwoven fabric 10 (inside the high density region 11) by the capillary force of the high density region 11. And in the high density area | region 11, since the fiber density of the lower surface is higher than an upper surface, the liquid drawn into the high density area | region can be reliably transferred to an absorber with capillary force.

  In addition, the liquid remaining in the low density region 12 after most of the liquid has permeated is drawn into the high density region 11 by capillary force, and finally the liquid is transferred to the absorber. Can be migrated. Even when only a small amount of liquid is dropped on the nonwoven fabric 10, the liquid can be drawn into the high density region 11 and transferred to the absorbent body by the capillary force of the high density region 11.

  In addition, in the case of a highly viscous liquid, a large number of fibers cannot resist and pass through the high density region 11, but if the liquid is in the low density region 12, even if it is a highly viscous liquid, It can move to an absorber without being inhibited.

  That is, in the nonwoven fabric 10 of this embodiment, the high-density region 11 and the low-density region 12 that are communicated from the upper surface to the lower surface of the nonwoven fabric 10 are dispersed in the surface direction of the nonwoven fabric 10. Regardless, the liquid can be transmitted without being diffused, and the liquid can be prevented from remaining on the upper surface of the nonwoven fabric 10 or inside the nonwoven fabric 10. That is, the nonwoven fabric 10 of the present embodiment is a nonwoven fabric that has low diffusibility and low persistence and good liquid drawability.

In addition, it is not necessary that all of the high density region having a fiber density higher than the average fiber density in the nonwoven fabric 10 and the low density region having a fiber density lower than the average fiber density communicate from one side of the nonwoven fabric to the other side, If at least one high-density region 11 and one low-density region 12 communicate from one side to the other side, the above effect can be obtained.
Further, not only in the high density region 11 but also in the low density region 12, the fiber density may be higher on the other side than on one side. In this case, the liquid can permeate using the capillary force in the low density region.

Here, a specific fiber density will be described. However, since the fiber density is difficult to measure, “average fiber space area” is used as an alternative numerical value of the fiber density (details will be described later).
The average space area of the high-density region 11 is 300 μm ² or more and 1000 μm ² or less, preferably 400 μm ² or more and 800 μm ² or less. When there is a difference in fiber density between the upper surface and the lower surface of the high-density region, the difference between the average space area on the upper surface side and the average space area on the lower surface side is 50 μm ² or more and 200 μm ² or less, preferably 60 μm ² or more. It is assumed that it is ˜100 μm ² or less.
The inter-fiber area in the low density region is 600 μm ² or more and 8000 μm ² or less, preferably 800 μm ² or more and 1000 μm ² or less. When there is a difference in fiber density between the upper surface and the lower surface of the low density region, the difference between the average space area on the upper surface side and the average space area on the lower surface side is 50 μm ² or more and 200 μm ² or less, preferably 60 μm ² or more. It is assumed that it is 100 μm ² or less.
Then, the difference between the average open area between the low density regions 12 and the high-density regions 11, and is is 7000Myuemu ² or less 150 [mu] m ² or more, preferably, to be 200 [mu] m ² or more 1000 .mu.m ² or less.
In addition, “interfiber distance” can be used as an alternative numerical value of the fiber density. The interfiber distance in the high density region 11 is, for example, 15 μm or more and 95 μm or less, and the interfiber distance in the low density region 12. Is, for example, 85 μm or more and 390 μm.

<Manufacturing method and constituent fibers>
The fiber web on which the heat-shrinkable fibers having heat-fusibility are arranged is heated so that the surface after the heat treatment has a concavo-convex shape, and the fibers in the convex region are denser than the concave region. Heat treatment is performed at a temperature at which the shrinkable fiber can be melted and heat-shrinkable, and the fiber web is pressed in the thickness direction so that the convex and concave portions formed by the heat treatment are crushed. Such a nonwoven fabric 10 can be obtained.

  In addition, you may mix | blend not only one type but the heat shrinkable fiber which has multiple types of heat-fusibility to a fiber web. Here, examples of the heat-shrinkable fiber include an eccentric core-sheath type composite fiber or a side-by-side type composite fiber containing two types of thermoplastic polymer materials having different shrinkage rates as components. Examples of thermoplastic polymer materials having different shrinkage rates include a combination of ethylene-propylene random copolymer and polypropylene, a combination of polyethylene and ethylene-propylene random copolymer, a combination of polyethylene and polyethylene terephthalate, and the like. Among these, an eccentric core-sheath composite fiber that does not excessively increase the shrinkage ratio with respect to the temperature during the heat treatment (for example, 145 ° C.) and is easy to control is preferable. The shrinkage rate can be controlled by adjusting the distance (eccentricity) that shifts the position of the core of the eccentric core-sheath composite fiber from the center.

  Hereinafter, the nonwoven fabric manufacturing method which heat-processes in the state supported by the supporting member from the lower side of the thickness direction is demonstrated. 5A to 5D are diagrams showing the nonwoven fabric manufacturing method of the present embodiment. First, a fiber web 21 having a predetermined thickness is continuously formed by opening a raw material obtained by mixing heat-shrinkable fibers 22 having heat-fusibility and heat-fusible fibers 23 by a card device (not shown). Form. Further, in the molded fiber web, the heat-shrinkable fibers 22 and the heat-fusible fibers 23 do not necessarily exist evenly, and regions where the heat-shrinkable fibers 22 are gathered and regions where they are not formed are formed. . A fiber web may be formed from a plurality of types of heat-shrinkable fibers. Further, the fiber web may be formed not only by the card method but also by the airlaid method.

Then, as shown in FIG. 5A, the fiber web 21 is placed on a breathable net 20 (a plate-like support member having a flat surface or a mesh structure) with a predetermined temperature. Heat treatment. That is, the fiber web 21 is heat-treated while being supported from the lower side.
In addition, as a specific example, there is a method of performing heat treatment by blowing hot air at a predetermined temperature from the upper surface side while conveying the fiber web 21 by a conveyor (described later). The predetermined temperature is a temperature at which the heat-shrinkable fibers 22 melt and heat shrink. For example, the temperature of the hot air blown to the fiber web 21 is in the range of 138 ° C. to 152 ° C., preferably 142 ° C. to 150 ° C. The wind speed of the hot air from the upper surface side direction is preferably about 0.7 m / s.

  As a result, as shown in FIG. 5B, each fiber in the fiber web 21 is melted and fused with other fibers, and the fiber cloth 24 in which the fibers are heat-sealed (here, distinguished from the fiber web before heat treatment). Therefore, a fiber cloth 24 is formed. Further, an uneven structure (sea-island structure) is formed on the surface (free surface) of the fiber cloth 24 opposite to the side supported by the breathable net 20. On the other hand, the surface (support surface) on which the fiber cloth 24 is supported is substantially flat along the surface of the breathable net 20.

  During the heat treatment, the heat-shrinkable fibers 22 on the free surface side of the fiber web 21 are not shrunk, so the surrounding fibers (such as the heat-fusible fiber 23) are freely shrunk in the surface direction. To do. That is, the convex portion 25 in the concavo-convex structure is a region where the heat-shrinkable fibers are gathered, and has a large number of fibers taken into the heat-shrinkable fibers 22 by multiplying the heat-shrinkable fibers 22 by heat shrinkage. Therefore, the basis weight (corresponding to the amount of fibers) of the region that is the convex portion 25 is higher than the average basis weight of the fiber cloth 24. On the other hand, the recess 26 is an area where the heat-shrinkable fiber 22 originally does not exist so much and the heat-fusible fiber 23 has been taken in and moved by the surrounding heat-shrinkable fiber 22. The basis weight is lower than the average basis weight. That is, the fibers are denser in the region that is the convex portion than in the region that is the concave portion. Moreover, since the fiber which existed in the recessed part 26 moves to the convex part 25 by heat processing, the convex part 25 and the recessed part 26 are formed adjacently.

  Then, as shown to FIG. 5C, the free surface side in which the uneven structure of the fiber cloth 24 is formed is pressed so that the convex part 25 may be crushed in the thickness direction. At this time, when the sheet is pressed to a thickness equal to or less than the thickness of the concave portion 26, the nonwoven fabric 10 having a substantially uniform thickness is obtained as shown in FIG. 5D. Further, when pressing, if the fiber cloth 24 is heated at a predetermined temperature, the convex portions are easily crushed, and the free surface side which has been uneven can be made more planar. The region where the convex portion 25 is crushed becomes the high-density region 11, and the region that was the concave portion 26 becomes the low-density region 12. Further, since the convex portion 25 and the concave portion 26 are formed adjacent to each other, it can be said that the high-density region 11 and the low-density region 12 are adjacent to each other in the plane direction.

  Moreover, since the high density area | region 11 is formed by pressing the convex part 25 of the free surface side of the fiber cloth 24, the fiber density of the free surface side is higher than the fiber density of the support surface side. . That is, the free surface in FIG. 5D corresponds to the lower surface of the nonwoven fabric 10 shown in FIG. 3B, and the support surface in FIG. 5D corresponds to the upper surface of the nonwoven fabric 10 shown in FIG. 3B.

  By producing a nonwoven fabric as described above, a high-density region having a high-density region having a fiber density higher than the average fiber density in the nonwoven fabric 10 and a low-density region having a fiber density lower than the average fiber density is obtained. And the nonwoven fabric which the low density area | region connected from the one side in the thickness direction of the nonwoven fabric 10 to the other side can be obtained. That is, according to the above production method, a nonwoven fabric that has good liquid drawability and hardly retains liquid can be obtained.

  Moreover, since the uneven shape is formed only on one side (free surface side) of the fiber web by performing the heat treatment in a state where the fiber web is supported from the lower side, the fiber density of the free surface side is increased in the high density region 11. The nonwoven fabric 10 can be manufactured so that the direction becomes higher than the fiber density on the support surface side.

In addition, since the high-density region 11 and the low-density region 12 are dispersed in the plane direction, and the non-woven fabric in which the high-density region 11 is communicated in the thickness direction of the non-woven fabric is suitably manufactured, the fiber web 21 is heat-treated. The basis weight (2Xg / m ² ) of the convex portion 25 at the time (FIG. 5B) may be set to be twice or more the basis weight (Xg / m ² ) of the concave portion 26. Therefore, if the “fiber physical properties” and “manufacturing conditions” are controlled, it is possible to form an uneven structure of a desired fiber.

As specific fiber properties, when the predetermined temperature by heat treatment is 145 ° C., the heat shrink rate of the heat-shrinkable fibers used at 145 ° C. is 10% or more and 60% or less, preferably 15% or more and 40% or less. .
In addition, as a measuring method of thermal contraction rate, for example, (1) Create a fiber web of 200 g / m ² with 100% of fibers to be measured with a card machine, (2) Cut to a size of 250 × 250 mm, (3) (4) Leave in a 145 ° C oven for 5 minutes, (5) Length after heat shrinkage (Because hot air is not directly hit, and the fibers are slippery and heat shrinkable) By measuring the dimensions and (6) calculating the length dimensional difference before and after heat shrinkage, the heat shrinkage rate can be calculated.

  The shorter the fiber length of the heat-shrinkable fiber 22, the easier it is to move, but if it moves too much, the difference in density between the high-density region 11 and the low-density region 12 becomes too large, so the fiber length is 25 mm or more and 70 mm or less. And preferably 25 mm or more and 40 mm or less. Therefore, the fiber web is preferably formed by a card method using relatively long fibers. The fiber thickness of the heat-shrinkable fiber 22 is preferably about 1 Dtex or more and 11 Dtex or less.

  The amount of heat-shrinkable fibers in the nonwoven fabric 10 is 30% by weight to 100% by weight, preferably 70% by weight to 100% by weight. When the heat-shrinkable fibers 22 are blended at the above ratio, the high-density regions 11 and the low-density regions 12 can be dispersed in the surface direction of the nonwoven fabric 10.

  For example, if the hot air pressure (wind speed) at the time of the heat treatment is increased, the fiber web 21 is pressed against the air-permeable net 20 so that the fibers are difficult to move, and the hot air pressure (wind speed) is controlled. If it is lowered, the fibers will move more easily. Further, the thermal contraction rate can be changed depending on the temperature, and the wind speed and temperature can be adjusted depending on the moving state of the fiber.

Hereinafter, a method for producing the nonwoven fabric 10 from the fiber web 21 in which two kinds of heat-shrinkable fibers are mixed will be described in detail. FIG. 6 is a diagram illustrating an example of a nonwoven fabric manufacturing apparatus. First, the nonwoven fabric manufacturing apparatus continuously opens the fiber web 21 having a predetermined thickness by opening a raw material in which the first heat-shrinkable fiber 51A and the second heat-shrinkable fiber 51B are mixed by the card device 50 in the opening process. Form. In addition, the fiber web 21 can also be formed only with any one kind of heat-shrinkable fiber of the 1st heat-shrinkable fiber 51A or the 2nd heat-shrinkable fiber 51B.
And the fiber web 21 is conveyed by the conveyors 52 and 53 to the entrance of the heating apparatus 54 in a 1st conveyance process. The fiber web 21 on the first conveying step is in a state in which the degree of freedom between the fibers is maintained.

Next, the fiber web 21 is heat-treated while being conveyed at the speed S <b> 1 by the conveyor 55 inside the heating device 54. Specifically, a hot air of a predetermined temperature is blown from the upper surface side of the fiber web 21 being conveyed by the conveyor 55 and heat treatment is performed. The predetermined temperature is a temperature at which the first heat-shrinkable fiber 51A and the second heat-shrinkable fiber 51B are melted and heat-shrinked, and the fiber web 21 is pressed against the support member 20 by the hot air. Heated. Therefore, heat shrinkage of the heat-shrinkable fibers of the fiber web 21 on the side on which the support member 20 abuts is suppressed by friction or the like.
Thus, the support member 20 side of the fiber web 21 has a planar shape, and the free surface side opposite to the support member 20 side has an uneven shape. In addition, the fiber web 21 (fiber cloth 24) is in a state where the fibers are fused together by the heat treatment.

  Thereafter, the fiber web 21 is pressed so that the convex portion is crushed by the roll 56. The roll 56 is arrange | positioned so that it may contact | abut with the free surface of the fiber web 21 located between 57 A of 1st conveyance rolls, and the 2nd conveyance roll 57B. And the fiber web 21 is pressed by the roll 56 with fixed strength, and the nonwoven fabric 10 of substantially uniform thickness is formed. Here, the roll 56 is preferably heated to a predetermined temperature, and the convex portion is suitably crushed in the thickness direction by the roll 56 heated to the predetermined temperature coming into contact with the free surface of the fiber web 21. . The nonwoven fabric 10 thus formed is finally wound around the winding portion 58.

  Next, a pressing method different from FIG. 6 will be described. FIG. 7 differs from FIG. 6 in the arrangement of the transport rolls 57A and 57B. In FIG. 6, the fiber web 21 between the first transport roll 57 </ b> A and the second transport roll 57 </ b> B contacts the roll 56. On the other hand, the first transport roll 57A in FIG. 7 is not arranged so that the fiber web 21 is sandwiched between the first transport roll 57A and the roll 56, and the fiber web 21 in FIG. Compared with the web 21, the distance which contacts | abuts the roll 56 is short, and the nonwoven fabric 10 of FIG. 7 will be pressed with a weaker force than the nonwoven fabric 10 of FIG. That is, the force which presses the fiber web 21 can be adjusted by adjusting arrangement | positioning of the conveyance rolls 57A and 57B.

  In FIG. 8, the roll 59 is disposed in the vicinity of the outlet of the heating device 54, and the roll 59 is brought into contact with the free surface of the fiber web 21 that has just been subjected to the heat treatment and maintains a predetermined temperature. Thereby, a convex part can be crushed suitably. Further, as shown in FIG. 9, the fiber web 21 may be heat-treated again by the heating device 60 before the fiber web 21 is pressed by the roll 61.

  In addition, as shown in FIG. 10, the free surface of the fiber web 21 can be obtained by winding the nonwoven fabric 10 (fiber web 21) in the radial direction by the winding portion 58 without pressing with a roll or the like. It is also possible to crush the protrusions formed in the thickness direction. In particular, since the winding is performed so that the support surface side of the fiber web 21 having a planar shape and the free surface side of the fiber web 21 having an uneven shape are opposed to each other, the free surface side of the fiber web 21 is uniformly pressed. Can do.

  Further, in FIG. 11, in the first half of the heating device 54, the breathable upper support member 62 is arranged at a predetermined angle with respect to the horizontal direction, and the fiber web 21 and the upper support member 62 do not come into contact with each other. Like that. On the other hand, in the latter half portion of the heating device 54, the upper support member 62 is arranged in parallel to the horizontal direction so that the upper surface of the fiber web 21 and the upper support member 62 come into contact with each other. The lower support member 63 is arranged in parallel to the horizontal direction, and supports the fiber web 21 from the lower surface side from the inlet to the outlet of the heating device 54.

  The fiber web 21 carried into such a heating device 54 is blown with hot air that has passed through the upper support member 62 in a state where the lower surface side is supported in the first half of the heating device 54, and as a result, the fiber web An uneven shape is formed on the upper surface side of 21. Thereafter, in the latter half portion of the heating device 54, the fiber web 21 is conveyed so as to be sandwiched between the lower support member 63 and the upper support member 62, and the convex portions formed on the upper surface side of the fiber web 21 are crushed. Pressed.

<Variation of non-woven fabric manufacturing method>
Unlike the nonwoven fabric manufacturing method described above, in this modification, the fiber web 21 is heated so that hot air of a predetermined temperature is blown from both sides in the thickness direction. For example, in the heating device (not shown), air-permeable support members are respectively arranged on the upper side and the lower side of the fiber web 21, and hot air of a predetermined temperature is blown against the fiber web 21 from the lower side. The fiber web 21 is heated by blowing hot air of a predetermined temperature from above. That is, the fiber web 21 in the heating device is heat-treated in a state where it is separated from the lower support member and also from the upper support member. In addition, you may blow a hot air with respect to the fiber web 21 alternately from the upper side and the lower side.

  That is, in the above-described nonwoven fabric manufacturing method, an uneven shape is formed only on the free surface side by heat treatment, whereas in this modification, the lower side of the fiber web 21 is not supported by the support member. Therefore, an uneven shape is formed on both surfaces of the fiber web 21. And by pressing the fiber web 21 in which the concavo-convex shape is formed on both surfaces, the fiber density on the free surface side becomes higher than the fiber density on the support surface side as in the high density region 11 of the nonwoven fabric described above. A region having a high fiber density in the high-density region is not formed so as to be biased toward one side (free surface side). That is, in the non-woven fabric manufactured by the modification, there is a high density region where the fiber density on one side in the thickness direction is higher than the fiber density on the other side, and conversely, the fiber density on the other side. However, there is also a high density region where the fiber density is higher than the fiber density on one side, and regions of the high density region where the fiber density is high are formed uniformly on both sides of the nonwoven fabric.

<About dispersion index (standard deviation of mean absorbance)>
In the nonwoven fabric 10 manufactured by the nonwoven fabric manufacturing method of this embodiment, the high density area | region 11 and the low density area | region 12 are disperse | distributed and formed in a surface direction. This degree of dispersion can be represented by, for example, a dispersion index (standard deviation of average absorbance).
The “standard deviation of average absorbance”, which is a “dispersion index”, is a value indicating the unevenness of light and darkness (variation) of the nonwoven fabric when irradiated from below the nonwoven fabric 10. Measurement and calculation can be performed by using a predetermined measuring instrument (for example, a formation tester (product number: FMT-MIII, manufactured by Nomura Corporation)). For example, the camera correction sensitivity is 100%, the binarization threshold ±%: 0.0, the moving pixel is 1, the effective size is 25 × 18 cm, and the surface supported by the support member in the manufacturing process is the front side. Can be measured. The dispersion index can also be measured by other known measurement methods.
And the dispersion index in the nonwoven fabric 10 of this embodiment shall be 250 or more and 450 or less, Preferably it is 280 or more and 410 or less.

  If the dispersion index is smaller than 250, the high-density region 11 and the low-density region 12 are too close to each other, that is, the density difference between the high-density region 11 and the low-density region 12 is reduced. There is a possibility that the effects (the low diffusibility of the low density region 12, the liquid drawability and the low residual property of the high density region 11) cannot be obtained. On the contrary, when the dispersion index is larger than 450, the density unevenness of the fibers becomes too large, and for example, the density of the high-density region 11 may become extremely high. Then, the liquid drawn into the nonwoven fabric 10 may remain in the high-density region 11. On the other hand, in the low density region, the number of fibers becomes extremely small, and a small amount of liquid may remain in the low density region. Then, for example, in an absorbent article in which a non-woven fabric having a dispersion index greater than 450 is disposed between the top sheet and the absorbent, the liquid drawn from the top sheet remains in the high-density region, and the liquid does not migrate to the absorbent. . And if the liquid in the high density area overflows, the capillary force due to the density difference will not work, and if it is excreted in large quantities or repeatedly excreted, the liquid will spread widely and remain on the second sheet or top sheet. Resulting in.

  Therefore, the nonwoven fabric 10 of this embodiment has a dispersion index of 250 or more and 450 or less, and the nonwoven fabric in which the high-density region 11 and the low-density region 12 are not formed without the fibers moving during the heat treatment of the fiber web. The nonwoven fabric in which the extremely high density region has been formed can be excluded. In other words, since the fibers have been appropriately moved in the surface direction during the heat treatment of the fiber web, the high-density region 11 and the low-density region 12 are dispersed in the surface direction, and the high-density region 11 and the low-density region are formed. The nonwoven fabric 10 having a suitable density difference of 12 can be obtained as the nonwoven fabric 10 of the present embodiment.

=== About Absorbent Articles ===
<Outline of absorbent article>
Hereinafter, the absorbent article using the nonwoven fabric manufactured by the nonwoven fabric manufacturing method of this embodiment is demonstrated. FIG. 12A is a perspective view of a sanitary napkin 30 that is an example of an absorbent article, and FIG. 12B is a cross-sectional view of the sanitary napkin 30.
The absorbent article (sanitary napkin) 30 of the present embodiment is arranged between a top sheet 31 that is at least partially liquid permeable, a back sheet 33 that is liquid impermeable, and between the top sheet 31 and the back sheet 33. And the second sheet 10 disposed between the top sheet 31 and the absorber 32.

  Moreover, the above-mentioned nonwoven fabric 10 is used as the second sheet 10 of the absorbent article 30 of the present embodiment. That is, the second sheet 10 of the absorbent article 30 is formed with a high density region 11 having a fiber density higher than the average fiber density in the second sheet 10 and a low density region 12 having a fiber density lower than the average fiber density. The high-density region 11 and the low-density region 12 are both communicated from the topsheet 31 side to the absorber 32 side. The high density region 11 and the low density region 12 are formed so as to be dispersed in the plane direction of the second sheet 10.

  Furthermore, in the high density region 11 of the nonwoven fabric 10 described above, the fiber density is higher on the other side than on one side (FIG. 3), and the fiber density in the high density region 11 is higher. The nonwoven fabric 10 (second sheet) is disposed between the top sheet 31 and the absorber 32 so that the side (the other side, the anti-net surface) faces the absorber 32 side. That is, in the high density region 11 of the second sheet 10 of the absorbent article, the capillary force is higher on the absorbent body 32 side than on the top sheet 31 side.

<Sanitary napkin>
The absorbent article 30 of the present embodiment can be used as a sanitary napkin, panty liner, diaper, incontinence pad, interlabial pad, and the like. Hereinafter, the sanitary napkin 30 will be described as an example. The sanitary napkin 30 is mounted such that the top sheet 31 is on the skin side of the human body and the back sheet 33 is on the underwear side. As shown in FIG. 12B, in the second sheet 10 (nonwoven fabric), the high density region 11 and the low density region 12 communicating from the top sheet 31 side to the absorber 32 side are dispersed in the plane direction of the second sheet 10. It is formed as follows. Further, it is assumed that the fiber density increases in the order of the top sheet 31, the second sheet 10, and the absorber 32. Therefore, the liquid on the surface sheet 31 moves to the second sheet 10 by capillary force, and further moves from the second sheet 10 to the absorber 32. The liquid is finally held in the absorber 32.

  13A to 13D are diagrams illustrating the absorption behavior of the liquid 40 excreted toward the top sheet 31. In the sanitary napkin 30 of the present embodiment, it is assumed that irregularities are formed on the upper surface side of the top sheet 31.

  As shown in FIG. 13A, it is assumed that liquid 40 such as menstrual blood is excreted on the top sheet 31 of the sanitary napkin 30. At this time, since the liquid 40 of the top sheet 31 accumulates in the recess (groove), diffusion of the liquid 40 in the surface direction is suppressed. Then, the liquid 40 moves to the second sheet 10 having a fiber density higher than that of the top sheet 31. At this time, when a large amount of liquid having a high flow rate is excreted in the top sheet 31, first, most of the liquid 40 passes through the low density region 12 where the resistance by the fibers is small and moves to the absorber 32. To do. For this reason, as shown in FIG. 13B, even when a large amount of liquid is excreted, the low density region 12 communicates in the thickness direction, so that the liquid 40 can be quickly transferred to the absorber 32, and the liquid 40 Can be prevented from diffusing laterally in the top sheet 31 and the second sheet 10. That is, the sanitary napkin 30 of the present embodiment suppresses the diffusion of the liquid 40 (good spot property). Moreover, you may form an opening part in the recessed part of the surface sheet 31. FIG. In this way, the liquid can be more suitably transferred from the top sheet 31 to the second sheet 10.

  As shown in FIG. 13C, after most of the liquid has moved to the absorber 32, the liquid 40 remaining in the top sheet 31 is removed from the second sheet 10 (high by the capillary force of the high-density region 11 of the second sheet 10. It can be drawn into the density region 11). And also in the high-density area | region 11, since the fiber density is higher on the absorber 32 side than on the surface sheet 31 side, the drawn liquid can be transferred to the absorber 32 by capillary force. . In addition, suppose that the fiber density of the absorber 32 is higher than the region (region on the absorber 32 side) where the fiber density is the highest in the high-density region 11 of the second sheet 10. If it does so, the liquid which reached the lowermost surface (boundary part with the absorber 32) of the second sheet | seat 10 can also transfer to the absorber 32, without remaining in the second sheet | seat 10. FIG.

  Further, most of the liquid 40 passes through the low density region 12 of the second sheet 10 and moves to the absorber 32 immediately after the liquid 40 is excreted, but the amount of liquid transferred from the top sheet 31 is small. If it decreases, the momentum of the liquid from the surface sheet 31 is lost (the flow rate is reduced), and the liquid 40 may remain between the fibers in the low density region 12. However, in the second sheet 10 (nonwoven fabric) of the sanitary napkin 30 of the present embodiment, the high density region 11 and the low density region 12 are formed adjacent to each other, and some of the fibers are entangled with each other. A small amount of the liquid 40 remaining in the region 12 can be drawn by the capillary force of the high-density region 11. The drawn liquid 40 is transferred to the absorber 32 by the capillary force of the high-density region 11.

  Summarizing the above, the absorbent article of this embodiment (sanitary napkin 30) is suppressed from diffusing in the surface direction the liquid excreted on the surface sheet 31 by the convex portion of the surface sheet 31, In addition, since most of the liquid from the top sheet 31 can be quickly transferred to the absorber 32 by the low density region communicating from the top sheet 31 to the absorber 32, the liquid diffuses in the surface direction. Can be suppressed.

  Then, after most of the liquid has moved to the absorber 32, a small amount of liquid remaining in the topsheet 31 and the low density region 12 is drawn into the high density region 11. Then, the drawn liquid can be transferred to the absorber 32 by the capillary force due to the density difference in the high-density region 11 and the density difference between the high-density region 11 and the absorber 32. That is, the liquid 40 is absorbed by the absorber 32 without remaining in the top sheet 31 or the second sheet 10.

  That is, the absorbent article (sanitary napkin 30) of the present embodiment is an absorbent article that allows liquid to permeate without diffusing, has good liquid drawability, and does not easily retain liquid. And since a liquid transfers to the absorber 32 reliably, the surface sheet 31 and the second sheet | seat 10 can be dried to a predetermined state after liquid excretion. As a result, it is possible to prevent the user's skin from being soiled by the liquid or to give the user an unpleasant feeling (sticky feeling), and even if the liquid is repeatedly excreted, the surface sheet 31 The liquid is again absorbed by the absorber 32 without overflowing the liquid (diffusing in the surface direction).

  Even when only a small amount of liquid is excreted, the liquid can be reliably transferred to the absorber 32 by the high-density region 11. Moreover, even if it is a highly viscous liquid, a liquid can be transferred to the absorber 32 by permeating through the low density region 12 with less resistance caused by the fibers. That is, in the absorbent article (sanitary napkin 30) of the present embodiment, the liquid can be absorbed by the absorber 32 regardless of the viscosity and the amount of liquid excreted in the top sheet 31.

  Although the fiber used for a nonwoven fabric was shown previously, it is preferable that the fiber itself is a fiber with high opacity, especially whitening property. By making it opaque, even when a dark body fluid such as menstrual blood is absorbed, the color of the body fluid itself can be concealed, so that a visually clean feeling is easily maintained. Furthermore, when the surface sheet 31 is provided with an opening, menstrual blood spread from the opening to the absorber can be easily seen. However, if the second sheet itself has a high whitening property, it is also concealed from the opening. Sex can be obtained.

  Specifically, the nonwoven fabric is made of fibers containing a particulate light transmission inhibitor that suppresses light transmission. An example of the light transmission inhibitor to be made opaque is an inorganic filler. As this inorganic filler, for example, titanium oxide, calcium carbonate, talc, clay, kaolin, silica, diatomaceous earth, magnesium carbonate, barium carbonate, magnesium sulfate, barium sulfate, calcium sulfate, aluminum hydroxide, magnesium hydroxide, zinc oxide, oxidation Examples include calcium, alumina, mica, glass powder, shirasu balloon, zeolite, and silicate clay. You may contain these in combination of 2 or more types. In particular, titanium dioxide is generally preferred from the standpoint of processability at the fiber production stage. The average particle diameter of the light transmission inhibitor is preferably in the range of, for example, 0.1 μm to 2 μm, and more preferably 0.2 μm to 1 μm. In order to obtain sufficient concealability (whiteness), the content of titanium dioxide as a light transmission inhibitor in the fiber weight is preferably 1% by weight or more, and more preferably 2% by weight or more.

  Moreover, when the fiber which comprises a nonwoven fabric is a core-sheath-type composite fiber, it is preferable that the content rate of the light transmission inhibitor in a core part is 2 to 10 weight%, for example. If it is less than 2% by weight, it is difficult to obtain concealability, and if it is more than 10% by weight, the fiber itself becomes too soft and it is difficult to obtain bulk.

  In the sanitary napkin 30, the above-described single nonwoven fabric 10 is used as the second sheet. However, the present invention is not limited to this, and a plurality of second sheets (nonwoven fabric 10) are arranged between the top sheet and the absorbent body. It doesn't matter. At this time, it is assumed that a plurality of second sheets (nonwoven fabrics 10) are stacked so that at least one of the high density region 11 and the low density region 12 communicates from the top sheet 31 side to the absorber 32 side. . Further, for example, when the nonwoven fabrics 10 having different fiber densities in the low density region 12 and the high density region 11 are laminated and used, a density difference is generated in the thickness direction. ).

  Moreover, the nonwoven fabric 10 (second sheet) is provided between the top sheet 31 and the absorbent body 32 so that the fiber density side (free surface, anti-net surface) in the high density region 11 faces the absorbent body 32 side. ) Is arranged, but is not limited to this. Here, on the free surface side of the nonwoven fabric 10 (FIG. 5D), a high-density region not communicating in the thickness direction is also formed, so the free surface side is compared to the support surface side (net surface), It can be said that the high density region is formed unevenly. Conversely, it can be said that the support surface side is formed with a lower density region than the free surface side.

  As described above, when the surface (support surface side) in which the low density region of the second sheet (nonwoven fabric 10) is formed unevenly is disposed on the surface sheet 31 side, the liquid in the surface sheet 31 is promptly moved to the absorber 32 side. It is possible to migrate. On the contrary, when the surface in which the low-density area | region is formed unevenly is arrange | positioned at the absorber 32 side, the liquid contained in the surface sheet 31 can be drawn in suitably and can be made to transfer to the absorber 32 side. Moreover, when many areas where fibers (heat-shrinkable fibers) are densely in contact with the topsheet 31, the friction between the topsheet 31 and the second sheet increases, and the amount of adhesive used for joining may be reduced. is there. In addition, the fibers of the top sheet 31 and the second sheet are easily entangled, and even when twisting occurs in the absorbent article, the top sheet 31 and the second sheet may be difficult to shift. Thus, by adjusting the arrangement direction of the nonwoven fabric 10, different functions can be exhibited while being the same nonwoven fabric 10.

  Moreover, it can be used as a second sheet in a state in which the nonwoven fabric 10 is folded. At this time, it is assumed that the nonwoven fabric 10 is folded so that at least one of the high-density region 11 and the low-density region 12 communicates from the topsheet 31 side to the absorber 32 side. In this case, for example, by folding the surface in which the high-density region 11 is formed in an inward direction, the surface in which the high-density region is formed in an uneven state comes to face each other. A holdable region can be formed.

  Hereinafter, components other than the nonwoven fabric (second sheet) of the absorbent article of the present embodiment will be described in detail.

<Surface sheet>
The liquid permeable region of the top sheet 31 is formed of, for example, a resin film having a large number of liquid permeable holes, a net-like sheet having a large number of meshes, a liquid permeable nonwoven fabric, or a woven fabric. Examples of the resin film and the net-like sheet include polypropylene (PP), polyethylene (PE), and polyethylene terephthalate (PET).

  The opening diameter (liquid permeation hole diameter) is in the range of 0.05 mm to 3 mm, the pitch is in the range of 0.2 mm to 10 mm, and the opening area ratio is in the range of 3% to 30%. preferable. A plurality of apertures can be formed integrally with the low-density region 12 of the second sheet 10, and the array of apertures is not particularly limited, such as a staggered pattern, a lattice pattern, or a wavy pattern. Examples of the shape of the opening include a round shape, an elliptical shape, a square shape, and the like, and a valve may be provided at the periphery of the opening. In addition, a large number of liquid-permeable holes may be formed, and a silicone-based or fluorine-based water-repellent oil agent may be applied to make it difficult for body fluids to adhere to the outer surface.

When the liquid permeable region of the top sheet 31 is a nonwoven fabric, a cellulose fiber such as rayon, a spunlace nonwoven fabric formed from a synthetic resin fiber, an air-through nonwoven fabric formed from the synthetic resin fiber, or the like can be used.
In addition, as a material, a natural product capable of biodegradability such as polylactic acid, chitosan, polyalginic acid and the like can be used.

Topsheet basis weight is preferably 15 g / ^{m 2} or more 100 g / ^{m 2} or less, 20 g / ^{m 2} or more 50 g / ^{m 2,} more preferably less, 30 g / ^{m 2} or more 40 g / ^{m 2} or less is particularly preferred. If the basis weight is less than 15 g / m ² , the surface strength cannot be sufficiently obtained, and there is a risk of breaking during use. Moreover, when larger than 100 g / m < ² >, excessive wrinkle will express and it will produce discomfort during use. Furthermore, in the case of using for a long time, when it exceeds 40 g / m ² , the liquid is held by the top sheet 31 and is kept in a solid state, which makes it uncomfortable. Further, the density is not particularly limited as long as it is 0.12 g / cm ³ or less and liquid permeable. When the density is higher than this, it is difficult to smoothly transmit between the fibers of the surface sheet. In the case of menstrual blood, those having a low density are preferable because they are more viscous than urine and the like.

<Back sheet>
The back sheet 33 is a liquid-impermeable sheet, and a material that can prevent excrement absorbed by the absorber 32 from leaking outside is used. In addition, by using a moisture-permeable material, it is possible to reduce stuffiness at the time of wearing, and to reduce discomfort at the time of wearing.
Examples of such materials include a liquid-impermeable film mainly composed of polyethylene (PE), polypropylene (PP), etc., a composite in which a liquid-impermeable film is laminated on one side of a nonwoven fabric such as a breathable film or a spunbond. A sheet etc. are mentioned. Preferably, a hydrophobic nonwoven fabric, a water-impermeable plastic film, a laminate sheet of a nonwoven fabric and a water-impermeable plastic film, or the like can be used. Alternatively, an SMS nonwoven fabric in which a melt-blown nonwoven fabric having high water resistance is sandwiched between strong spunbond nonwoven fabrics may be used.

<Absorber>
The absorber 32 has a function of absorbing and holding a liquid such as menstrual blood, and is preferably bulky, hardly deformed, and has little chemical stimulation. For example, the absorber material which consists of a fluffy pulp or an airlaid nonwoven fabric and a superabsorbent polymer can be illustrated.
In place of the fluffy pulp, for example, artificial cellulose fibers such as chemical pulp, cellulose fiber, rayon, and acetate can be exemplified. The pulp has a basis weight of 500 g / m 2 and the polymer has a basis weight of 20 g / m 2 (the polymer is dispersed throughout). Can be mentioned.
As an airlaid nonwoven fabric, for example, a nonwoven fabric in which pulp and synthetic fibers are thermally fused or fixed with a binder can be exemplified. Examples of the superabsorbent polymer (SAP) include starch-based, acrylic acid-based, and amino acid-based particulate or fibrous polymers. Although the shape and structure of the absorber 32 can be changed as necessary, the total absorption amount of the absorber 32 needs to correspond to the design insertion amount and desired application as the absorbent article. In addition, the size and absorption capacity of the absorber 32 are changed according to the application.

=== Evaluation of Nonwoven Fabric ===
<Method for evaluating absorbability by artificial menstrual blood>
In order to evaluate the absorbability of the sample, the liquid persistence, diffusibility and rewetting can be evaluated by artificial menstrual blood.
Here, the composition of artificial menstrual blood is as follows.
The following is blended with 1 liter of ion-exchanged water. (1) Glycerin 80 g (2) Sodium carboxymethylcellulose (NaCMC) 8 g (3) Sodium chloride (NaCl) 10 g (4) Sodium bicarbonate (NaHCO3) 4 g (5) Dye Red No. 102 8 g (6) Dye Red No. 2 2 g (7) Dye Yellow No.5 2g
As a measuring instrument, for example, 1) Auto Bullet (Metrohm, Inc. Model 725), 2) SKICON, 3) Colorimeter, 4) Perforated acrylic plate (40 mm × 10 mm hole in the center, length × width = 200 mm) × 100 mm, weight 130 g), 5) scale, 6) ruler, 7) artificial menstrual blood, 8) stopwatch, 9) filter paper.

  An evaluation sample is prepared as follows. The surface sheet is cut into length × width = 100 mm × 60 mm (arbitrary), and the basis weight and thickness are measured. Subsequently, the nonwoven fabric which is a measurement sample is cut into length × width = 100 mm × 60 mm (arbitrary), and the basis weight and thickness are measured. As an absorbent body, an NB pulp absorbent body is wrapped with a 15 gsm tissue and cut into 100 mm × 60 mm. And a surface sheet, a nonwoven fabric, and an absorber are joined by embossing. Hinge embossing (38mm inside).

  The evaluation procedure is as follows. 1) Stack the acrylic plates so that the center of the hole matches the center of the sample. 2) Set the nozzle of the auto burette at a position 10 mm above the acrylic plate. 3) First artificial menstrual blood is dripped under the following conditions (rate: 95 ml / min, dripping amount: 3 ml). 4) Start the stopwatch from the start of dripping, and stop most of the artificial menstrual blood from the surface (when movement stops) and measure the absorption rate (A). 5) Simultaneously with the stop, another stopwatch is started. When the artificial menstrual blood in the surface sheet disappears (when the movement stops), the stopwatch is stopped and the total dry speed is measured (B). 6) Remove the acrylic board. 7) One minute after the start of dropping, the diffusion range, SKICON value (surface dryness) and color meter (whiteness) were measured (C, D, E). 8) The second artificial menstrual blood is dropped (rate: 95 ml / min, drop amount: 4 ml). 9) Start the stopwatch from the beginning of dripping, and stop most of the artificial menstrual blood from the surface (when movement stops) and measure the absorption rate (F). 10) At the same time as the stop, another stopwatch is started. When artificial menstrual blood disappears in the surface sheet (when the movement stops), stop and measure the total dry speed (G). 11) Remove the acrylic plate. 12) One minute after the start of dropping, the diffusion range, SKICON value (surface dryness), and color meter (whiteness) were measured (H, I, J). 13) A filter paper and an acrylic plate are placed on the sample, and a 50 g / cm 2 weight is further placed thereon and left for 1.5 minutes. 14) After 1.5 minutes, the weight of the filter paper was measured, and the first rewet rate measurement (K). 15) A filter paper and an acrylic plate are placed on the sample, and a 100 g / cm 2 weight is further placed thereon and left for 1.5 minutes. 16) After 1.5 minutes, the weight of the filter paper was measured, and the second rewet rate measurement (L).

From the measurement results in the above A to L, the following evaluation results can be obtained.
1) First time (3 ml dripping): Absorption rate [sec] (A), Total dry rate [sec] (B), Diffusion range (MD × CD) [mm] (C), SKICON value [μS] (D) , Whiteness (E) [-] (E)
2) Second time (4 ml dripping (total 7 ml)): absorption rate [sec] (F), total drying rate [sec] (G), diffusion range (MD × CD) [mm] (H), SKICON value [μS ] (I), whiteness (E) [-] (J)
3) (1) Rewetting rate 1st time (under 50 g / cm2) (K), (2) Rewetting rate 2nd time (under 100 g / cm2) (L)

<Method for evaluating absorbability with artificial urine>
In order to evaluate the absorbability of the sample, the absorption rate, surface drying rate, diffusion state and rewet can be evaluated with artificial urine.
Examples of measuring instruments include (1) artificial urine, (2) burette and funnel (adjust the burette so that the dropping speed is 80 ml / 10 sec), (3) burette stand, (4) cylinder (diameter 60 mm, 550 g) ), (5) Filter paper (for example, Advantech No. 2, 100 mm × 100 mm), (6) 3.5 kg / 100 cm 2 weight, (7) Stopwatch, (8) Electronic balance, (9) Ruler, (10) Use scissors.

  The composition of the artificial urine is (I), 200 g (II) of urea, sodium chloride (salt) (III), 8 g (IV) of magnesium sulfate, 3 g (V) of calcium chloride for 10 liters of ion-exchanged water, Dye: Prepared by blending about 1 g of Blue No. 1. The sample for evaluation removes the nonwoven fabric of a commercially available disposable diaper (trade name; Mooney L size, manufactured by Unicharm Co., Ltd.), and a predetermined top sheet and a nonwoven fabric as a second sheet (for example, a high-density region is biased). The free surface side to be formed is arranged so as to face the top sheet.

  The evaluation procedure is as follows. For example, the evaluation in the following procedure can be repeated three times as one cycle for 10 minutes). (1) Mark the rewet dripping position with magic. (2) Measure the weight of the sample and the thickness of the rewetting position (confirm that the sample weight is correct). (3) The burette is fixed at a position 10 mm above the dropping position. (4) Place the burette at the dropping position (center of the cylinder) and drop artificial urine. At the same time, the measurement of the absorption rate is started with a stopwatch. (5) When the artificial urine in the cylinder is completely absorbed and disappears from the surface, stop the stopwatch. (6) When the liquid remaining on the top sheet completely moves to the intermediate sheet side, the stopwatch is temporarily stopped again. (7) Measure and fill the weight (A) of the filter paper around 50g. (8) Five minutes after the start of dropping, the weight-measured filter paper of (7) is placed on the sample with the center position of the filter paper and the dropping position aligned, and a weight is stacked thereon. (9) Eight minutes after the start of dropping (3 minutes after placing the weight), remove the weight and measure and fill in the weight (B) of the filter paper. (10) If there is a second time or later, the next measurement is started 10 minutes after the start of dropping. (11) Repeat the measurement three times. (12) When all the times of measurement are completed, the diffusion length of each time is measured.

  The diffusion length is measured by applying a ruler in parallel with the absorbent body at the longest part in the longitudinal direction that is diffused on the skin surface side. The rewetting amount is measured by “rewetting back paper weight (B) −filter paper weight (A)”.

<Evaluation of Nonwoven Fabric of this Embodiment>
A non-woven fabric was actually manufactured and the dispersion index and absorbency were evaluated. The manufacturing conditions and evaluation results of the nonwoven fabric will be described below. FIG. 14 is a table for explaining the measurement results of the structure and average absorbance of the nonwoven fabric in the examples, and FIG. 15 is a table for explaining the measurement results of average absorbance when the nonwoven fabrics in Example D are overlapped. FIG. 16 is a table for explaining the results of evaluation of the absorbability of the nonwoven fabric by artificial urine in the example, and FIG. 17 is a table for explaining the results of the evaluation of the absorbency by artificial menstrual blood of the nonwoven fabric in the example. 18 is a table for explaining the measurement results of the average space area between fibers in Example D. FIG.

The nonwoven fabric in this invention was manufactured on condition of the following.
(1) Fiber configuration The nonwoven fabrics of Examples A to E and Comparative Examples A and B were manufactured according to the fiber configuration shown in the table of FIG.

(2) Manufacturing method (a) The fiber structure shown in the table of FIG. 14 is opened using a card machine at a speed of 20 m / min to create a fiber web. Then, the fiber web is cut so that the width is 450 mm.
(B) The fiber web is cut on MD300 mm × CD300 mm and placed on a 20 mesh breathable net, conveyed at a speed of 3 m / min, temperature 145 ° C. (418.15 K), wind speed 0.7 m / s, length It transports while heating in a 1.5m heating device (oven) in about 30 seconds.
(C) Press the unevenness of the anti-net surface.

(3) Measurement of mixing ratio (dispersion degree) of high density region and low density region As described in the table shown in FIG. 14, the dispersion index in various nonwoven fabrics was measured. The measurement result of the dispersion index is also as shown in the table of FIG.
The dispersion index in Examples A to E was in the range of 287 to 396. It was 250 or more and 450 or less which is the range of the dispersion index described above. Here, Comparative Example A is an ultra-low-density sheet that is composed only of heat-fusible fibers and has substantially uniform density in the plane direction. The dispersion index in this comparative example A was 204. Comparative Example B is also an ultra-high density sheet composed only of heat-fusible fibers and uniform in density in the plane direction. The dispersion index in this comparative example B was 206.
Further, as shown in the table of FIG. 15, the dispersion index of the nonwoven fabric obtained by superimposing the nonwoven fabric of Example D was measured. From the measurement results in the table of FIG. 15, the dispersion index in Example D2, which is a nonwoven fabric in which Example D and Example D are stacked two times, and in Example D3, which is a nonwoven fabric in which three nonwoven fabrics in Example D are stacked, is The values were in the approximate range with no significant difference. Thereby, the nonwoven fabric which piled up the multiple nonwoven fabric in this invention is anticipated to have the absorptivity similar to one nonwoven fabric.

(4) Absorption evaluation A Absorption evaluation by artificial urine According to the above-described evaluation method, Examples A and E and Comparative Examples A and B were evaluated for absorption by artificial urine. From the evaluation results shown in the table of FIG. 16, the absorbent article using Examples A and E as the second sheet has a high absorption rate and the liquid transfer from the top sheet to the absorber (liquid brushing rate). fast. Compared with this, although the comparative example A has a high absorption speed, the transfer of the liquid from a surface sheet to an absorber is slow. In Comparative Example B, although the liquid transfer from the top sheet to the absorber is fast, the absorption speed is slow.
From the above, the absorbent articles using the non-woven fabrics of Examples A and E as the second sheet have a high absorption rate and a fast liquid transfer from the top sheet to the absorbent body. That is, the nonwoven fabrics of Examples A and E have low diffusibility when the liquid permeates, and do not hinder the transfer of the liquid from the top sheet to the absorber.

B. Evaluation of absorbability by artificial menstrual blood
In accordance with the evaluation method described above, Examples D1 and D2 and Comparative Examples A and B were evaluated for absorbability by artificial menstrual blood. That is, the absorptive evaluation of the absorptive article which used Examples D1 and D2 and comparative examples A and B as a second sheet in an absorptive article was performed. Here, Example D1 is a non-woven fabric folded with the free surface in Example D (an anti-net surface, a surface where the high-density region is biased) inside, and Example D2 is Example D Is a non-woven fabric that is folded with the free surface (anti-net surface, surface on which the high-density region is biased) outside. The following surface sheets were used as the surface sheets in the samples for absorption evaluation.

<Fiber structure of surface sheet>
High-density polyethylene and polyethylene terephthalate core-sheath structure on the upper layer, average fineness 3.3dtex, average fiber length 51mm, fiber A coated with a hydrophilic oil agent on the lower layer side, high-density polyethylene and polypropylene core-sheath structure, average fineness 3.3 dtex, average fiber length 51 mm, fiber B coated with hydrophilic oil, and core-sheath structure of high-density polyethylene and polyethylene terephthalate, average fineness 2.2 dtex, average fiber length 51 mm, fiber C coated with hydrophilic oil Were mixed at a ratio of 50/50. The ratio of the upper and lower layers is 16: 9 and the total basis weight is 30 gsm.

<Method for producing surface sheet>
A fiber web is created by opening with a card machine at a speed of 20 m / min, and the fiber web is cut so that the width is 450 mm. The fiber web is placed on a sleeve and conveyed onto a 20 mesh breathable net at a speed of 3 m / min (the upper layer side faces the mesh). Thereafter, the inside of the oven set at a temperature of 125 ° C. and a hot air flow rate of 10 Hz is transported in about 30 seconds while being transported through the breathable net.

<Sample preparation for evaluation>
The trial production contents of the sample for absorption evaluation are obtained by cutting each of the top sheet, Examples D1 and D2, and Comparative Examples A and B into a length of 100 mm and a width of 70 mm. Then, 500g / m2 fluff pulp adjusted to a thickness of 5mm is stacked on an absorbent core sandwiched between 16g / m2 tissue, and the core is absorbed by hinge embossing so that the narrowest part is 38mm. The above-mentioned nonwoven fabrics, which are a top sheet and a second sheet, were joined to prepare a sample for evaluation.

<Measurement method and measurement result>
About each prepared said sample, absorptivity was evaluated along the procedure as described in description of the above-mentioned evaluation method. The measurement results are as described in the table of FIG. As shown in the table of FIG. 17, the sample for evaluating absorbency using the non-woven fabric in Examples D1 and D2 as a second sheet is compared with the sample for evaluating absorbency using the non-woven fabric in Comparative Examples A and B as the second sheet. In general, the permeation time is short, the total drying time is short, and the surface diffusion area is small.

  In particular, the absorbent article sample using the nonwoven fabric in Examples D1 and D2 as the second sheet is particularly shorter in total drying time than the absorbent evaluation sample using the nonwoven fabric in Comparative Examples A and B as the second sheet. The surface diffusion area is narrow. From these things, the sample for absorptive evaluation using the nonwoven fabric of an example as a 2nd sheet has low diffusibility at the time of liquid permeation, and does not prevent the movement of the liquid from a surface sheet to an absorber.

  Moreover, it can be said that it is excellent in the dryness of the surface, and it can be said that it has a dryness repeatedly. Furthermore, as shown in the table, the sample for evaluating absorbency using the nonwoven fabric in Examples D1 and D2 as the second sheet is used as compared with the sample for evaluating absorbency using the nonwoven fabric in Comparative Examples A and B as the second sheet. The rewetting rate is low. The absorbent article using the nonwoven fabric in the present invention as the second sheet can be an absorbent article having a low rewet rate. It can be said that the liquid from the top sheet is suitably transferred to the absorber side.

  Here, the uniform low-density nonwoven fabric as in Comparative Example A has a high absorption rate, but has a low drying rate after the liquid enters the surface sheet. Moreover, since it is low density, a capillary phenomenon does not occur easily and a liquid tends to be left on the surface sheet. Therefore, the drying property of the surface sheet is poor. Moreover, a uniform high-density nonwoven fabric like the comparative example B becomes slow in an absorption rate, and becomes difficult for a liquid to enter into a surface sheet. By using the nonwoven fabric in the examples, it is possible to prevent the liquid from being transferred from the topsheet to the absorbent body due to the absorption speed in the low density region and the liquid drawing property in the high density region.

(5) Evaluation of fiber density (average space area of fibers) The average space area of fibers in the high-density region and low-density region of Example D was measured. 1) Place the sample product (Example D) on the observation table with the observation surface facing up. 2) Using a predetermined measuring instrument (for example, digital microscope, product number: VHX-100, manufactured by Keyence Corporation), the fiber surface is photographed to obtain a binarized image of the fiber. 3) The value obtained by dividing the spatial area in the binarized image (area of the region where no fiber is present: μm ² ) by the number of spaces present in the binarized image is the average spatial area of fibers (= spatial area) / Space number).

  As shown in the table of FIG. 18, the average space area of the high-density region of Example D is smaller than the average space area of the low-density region, and each average space area is included in the above-described preferable value range. Yes. Moreover, the difference of the average space area of a high density area | region and a low density area | region is also contained in the above-mentioned preferable range. The average space area on the support surface side (one side) is larger than the average space area on the free surface side (the other side), and the fiber density is higher on the free surface side (the other side) than on the support surface side (the one side). It turns out that it becomes high.

  That is, Example D manufactured based on the above-described manufacturing method and fiber configuration has a high density region and a low density region, the high density region and the low density region communicate from one side to the other side, and high In the density region, the other side is a nonwoven fabric having a higher fiber density than the one side. Therefore, Example D is a non-woven fabric that combines the properties of the high-density region and the low-density region, as can be seen from the above evaluation test.

  As mentioned above, the above-mentioned embodiment is for making an understanding of this invention easy, and is not for limiting and interpreting this invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof.

It is a figure which shows sectional drawing of the nonwoven fabric of a comparative example. FIG. 2A is a diagram showing a top view of the nonwoven fabric of this embodiment, and FIG. 2B is a diagram showing a perspective view of the nonwoven fabric of this embodiment. FIG. 3A is a cross-sectional view of the nonwoven fabric of the present embodiment, and FIG. 3B is an enlarged view of the cross section. It is a figure which shows the mode of the liquid permeation | transmission of the nonwoven fabric of this embodiment. FIG. 5A to FIG. 5D are views for explaining the outline of the method for producing a nonwoven fabric according to this embodiment. It is a figure which shows an example of the nonwoven fabric manufacturing apparatus of this embodiment. It is a figure which shows the different pressing method from FIG. It is a figure which shows the different pressing method from FIG. It is a figure which shows the different pressing method from FIG. It is a figure which shows the different pressing method from FIG. It is a figure which shows the different pressing method from FIG. FIG. 12A is a perspective view of the sanitary napkin of the present embodiment, and FIG. 12B is a cross-sectional view of the absorbent article of the present embodiment. 13A to 13D are diagrams showing the absorption behavior of the liquid excreted toward the top sheet. It is a table | surface explaining the structure of a nonwoven fabric in an Example, and the measurement result of an average light absorbency. It is a table | surface explaining the measurement result of the average light absorbency when the nonwoven fabric in Example D was piled up. It is a table | surface explaining the evaluation result of the absorptivity by artificial urine of the nonwoven fabric in an Example. It is a table | surface explaining the evaluation result of the absorbency by the artificial menstrual blood of the nonwoven fabric in an Example. It is a table | surface explaining the measurement result of the average space area between the fibers in Example D.

Explanation of symbols

1 non-woven fabric of comparative example, 2 upper layer, 3 lower layer, A coiled fiber,
10 Nonwoven fabric, 11 High density region, 12 Low density region,
20 support member, 21 fiber web, 22 heat-shrinkable fiber,
23 heat-fusible fiber, 24 fiber cloth, 30 sanitary napkin,
31 surface sheet, 32 absorber, 33 back sheet, 40 liquid,
50 card device, 51A first heat-shrinkable fiber, 51B second heat-shrinkable fiber,
52 conveyor, 53 conveyor, 54 heating device, 55 conveyor,
56 rolls, 57A first transport roll, 57B second transport roll,
58 winding part, 59 roll, 60 heating device, 61 roll,
62 Upper support member, 63 Lower support member

Claims (6)

The fiber web in which the heat-shrinkable fibers having heat-fusibility are arranged so that the surface after the heat treatment has a concavo-convex shape and the fibers are denser in the region that is the convex portion than the region that is the concave portion, Heat-treating at a temperature at which the heat-shrinkable fiber is meltable and heat-shrinkable;
Pressing the fiber web in the thickness direction so that the concavo-convex convex portion formed by the heat treatment step is crushed;
A method for producing a nonwoven fabric, comprising: It is a nonwoven fabric manufacturing method of Claim 1, Comprising:
In the heat treatment step, the fiber web is heat treated in a state of being supported by a support member from one side in the thickness direction. It is a nonwoven fabric manufacturing method of Claim 1 or Claim 2,
In the pressing step, the fibrous web is pressed in a state of being heated at the temperature. It is a nonwoven fabric manufacturing method in any one of Claims 1-3,
In the pressing step, the fibrous web is pressed such that the thickness of the fibrous web is equal to or less than the thickness of the concave portion. The method for producing a nonwoven fabric according to any one of claims 1 to 4,
The method for producing a nonwoven fabric, wherein the amount of fibers in the region that is the convex portion is twice or more the amount of fibers in the region that is the concave portion. It is a nonwoven fabric manufacturing method of Claim 1, Comprising:
In the heat treatment step, the fibrous web is heat-treated so that hot air at the temperature is blown from both sides in the thickness direction.