Nonwoven fabric for absorbent article, absorbent article provided therewith, and method for producing nonwoven fabric for absorbent article

Abstract

To provide a nonwoven fabric for absorbent articles and the like, capable of preventing skin troubles through suppression of skin contact with excretions.SOLUTION: A nonwoven fabric for absorbent articles according to one embodiment of the present invention exhibits shrinkage on water absorption, and comprises a first fiber layer, a second fiber layer, and recesses. The first fiber layer contains more than 90 mass% of water-absorbing shrinkable fibers. The second fiber layer is laminated on the first fiber layer and contains thermally fusible fibers as a main component. The recesses are joined through compression and bonding of the first fiber layer and the second fiber layer in the thickness direction. Each of the recesses further includes a bottom part in which the water-absorbing shrinkable fibers and the thermally fusible fibers are fused together.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a nonwoven fabric for absorbent articles having water-absorbing shrinkage properties, a manufacturing method thereof, and an absorbent article using the same. [Background technology]

[0002] Water-absorption shrinkable fiber F1 is known, which contains polyvinyl alcohol or the like and shrinks when it absorbs water under a certain temperature condition. For example, Patent Document 1 discloses a nonwoven fabric having a first fiber layer in which the content of water-absorption shrinkable fiber, which is polyvinyl alcohol fiber, is 50% by mass to 90% by mass and the content of heat-fusible fiber is 10% by mass to 50% by mass, and the thickness change rate when absorbing water during use is 1.5 times or more. In this nonwoven fabric, the fibers are bonded by the fusion force of the heat-fusible fiber, and the air-through method is adopted from the viewpoint of obtaining a bulkier nonwoven fabric. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6978062 Summary of the Invention [Problem to be solved by the invention]

[0004] On the other hand, the objective of Patent Document 1 is to provide a nonwoven fabric that becomes bulky when it absorbs water, and the prevention of skin troubles caused by excrement when the fabric is used as a top sheet of an absorbent article, etc., has not been sufficiently considered.

[0005] The present invention relates to a nonwoven fabric for absorbent articles that can prevent skin troubles by suppressing contact of excrement with the skin, a manufacturing method thereof, and an absorbent article using the same. [Means for solving the problem]

[0006] A nonwoven fabric for absorbent articles according to one embodiment of the present invention has water-absorbing shrinkability and includes a first fiber layer, a second fiber layer, and recesses. The first fibrous layer contains more than 90% by mass of water-shrinkable fibers. The second fiber layer is laminated on the first fiber layer and mainly contains heat-fusible fibers. In the recess, the first fiber layer and the second fiber layer are compressed in a thickness direction and bonded to each other. The recess further includes a bottom portion to which the water-absorbing shrinkable fiber and the heat-fusible fiber are fused.

[0007] A method for producing a nonwoven fabric for absorbent articles according to another embodiment of the present invention is a method for producing a nonwoven fabric for absorbent articles having water absorption shrinkage properties, comprising the steps of: forming a first web containing more than 90% by mass of water-shrinkable fibers; forming a second web mainly containing heat fusible fibers; The method includes heating and bonding the laminated first web and second web at a temperature capable of fusing the heat-fusible fibers and the water-absorbing shrinkable fibers while pressing the laminated first web and second web in the thickness direction with a pressing member having a convex portion. Effect of the Invention

[0008] According to the nonwoven fabric for absorbent articles according to one embodiment of the present invention, it is possible to prevent skin troubles by suppressing contact of excrement with the skin. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a plan view of a nonwoven fabric for absorbent articles (nonwoven fabric) according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a partial cross-sectional view showing a cross section along line II-II in FIG. [Diagram 3] FIG. 2 is a cross-sectional view of an absorbent article using the nonwoven fabric as a top sheet. [Figure 4] 5A to 5C are schematic cross-sectional views illustrating the effects of the absorbent article. [Diagram 5] 4 is a flowchart showing a method for producing the nonwoven fabric. [Figure 6] FIG. 2 is a schematic diagram of a manufacturing apparatus used in the manufacturing process of the nonwoven fabric. [Figure 7] FIG. 7 is a partially enlarged view of FIG. [Figure 8] FIG. 4 is a plan view of a nonwoven fabric according to a second embodiment of the present invention. [Figure 9] 9 is a partial cross-sectional view showing a cross section along line IX-IX in FIG. 8. [Figure 10] FIG. 2 is a schematic cross-sectional view illustrating the function and effect of an absorbent article using the above nonwoven fabric as a topsheet. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] First Embodiment [Nonwoven fabric overview] 1 and 2 show a nonwoven fabric 10 for absorbent articles according to a first embodiment of the present invention. The nonwoven fabric 10 for absorbent articles is a nonwoven fabric used in absorbent articles, and will be referred to as nonwoven fabric 10 hereinafter.

[0012] In this specification, an absorbent article is an article capable of absorbing excretory fluid from a wearer, such as a disposable diaper, a sanitary napkin, a panty liner (discharge sheet), or a urine pad. In this specification, excretory fluid refers to liquid excretory material from a wearer, such as urine, watery stool, menstrual blood, vaginal discharge, etc. In this embodiment, an example in which the absorbent article is a disposable diaper will be described.

[0013] In each figure, the thickness direction Z indicates the thickness direction of the nonwoven fabric 10, and the first planar direction X and the second planar direction Y indicate directions perpendicular to the thickness direction Z and intersect with each other. In this embodiment, the first planar direction X corresponds to the conveying direction (MD direction) of the manufacturing device for the nonwoven fabric 10, and is, for example, the fiber orientation direction in which the fibers are most oriented. The second planar direction Y is a direction perpendicular to the first planar direction X and corresponds to the CD direction perpendicular to the MD direction. A method for determining the fiber orientation direction will be described later. The upper side of the thickness direction Z is the direction approaching the skin when the nonwoven fabric 10 is used in an absorbent article. The lower side of the thickness direction Z is the direction away from the skin when the nonwoven fabric 10 is used in an absorbent article. "Planar view" refers to a planar view from the thickness direction Z. "Planar shape" refers to a shape in a planar view. "Area" refers to the area of ​​the planar shape.

[0014] [Nonwoven fabric composition] In this embodiment, the nonwoven fabric 10 includes a first fiber layer 11, a second fiber layer 12 laminated on the first fiber layer 11, and recesses 13 that join the first fiber layer 11 and the second fiber layer 12. Each component of the nonwoven fabric 10 will be described below.

[0015] (First fiber layer) The first fiber layer 11 contains more than 90% by mass of water-absorption shrinkable fiber F1. In the example shown in Fig. 2, the first fiber layer 11 is located downward in the thickness direction Z, and is preferably disposed on the non-skin side when used in an absorbent article. The first fiber layer 11 is a nonwoven fabric layer, and may be composed of various nonwoven fabrics such as thermal bonded nonwoven fabric, chemical bonded nonwoven fabric, and needle punched nonwoven fabric. Of these, from the viewpoint of obtaining flexibility and deformability when absorbing water, the first fiber layer 11 is preferably a thermal bonded nonwoven fabric.

[0016] Water-absorption shrinkable fiber F1 is a fiber having water-absorption shrinkability. In this specification, water-absorption shrinkability refers to the property of shrinking by 10% or more when immersed in 35°C warm water for 1 minute. The water-absorption shrinkage rate of a fiber refers to the ratio of the fiber length reduced after immersion in warm water, assuming that the fiber length before immersion in warm water is 100%, and is expressed by the following formula. Fiber shrinkage rate (%) = {(L1-L2) / L1} x 100 L1: Fiber length before immersion in hot water L2: Fiber length after immersion in hot water

[0017] Specifically, the water-absorbing shrinkable fiber F1 includes one or more types selected from synthetic fibers containing resins such as polyvinyl alcohol, polyvinylpyrrolidone, and pullulan.

[0018] The water-absorption shrinkable fiber F1 preferably contains a resin having a melting point of more than 140° C. in order to impart desired physical properties such as water-absorption shrinkage and strength. Specifically, the water-absorption shrinkable fiber F1 preferably contains polyvinyl alcohol. In polyvinyl alcohol, physical properties such as water-absorption shrinkage can be relatively easily controlled by adjusting the molecular weight, degree of saponification, etc. The polyvinyl alcohol may be modified with maleic acid, itaconic acid, etc.

[0019] The resin having the highest melting point among the constituent resins of the water-absorption shrinkable fiber F1 is preferably higher than 140° C., more preferably 160° C. or higher, from the viewpoint of imparting desired physical properties such as shrinkability and strength. Moreover, the melting point is preferably 230° C. or lower, more preferably 200° C. or lower, from the viewpoint of minimizing the difference in melting point with the heat-fusible fiber F2.

[0020] As described above, the content of the water-absorption shrinkable fiber F1 in the first fiber layer 11 is greater than 90% by mass, more preferably 95% by mass or more, and even more preferably 100% by mass. In other words, it is particularly preferable that the first fiber layer 11 is composed of the water-absorption shrinkable fiber F1. By making the content of the water-absorption shrinkable fiber F1 in the first fiber layer 11 greater than 90% by mass, the water-absorption shrinkability of the first fiber layer 11 can be improved.

[0021] In addition, the content of water-absorbing shrinkable fiber F1 in the entire nonwoven fabric 10 is preferably 15 mass% or more, and more preferably 30 mass% or more, from the viewpoint of increasing the water-absorbing shrinkability of the nonwoven fabric 10, and is preferably 80 mass% or less, and more preferably 70 mass% or less, from the viewpoint of ensuring fusion properties in the recesses 13 described below.

[0022] The first fiber layer 11 may contain one or more types of fibers that do not have water-absorption-shrinkability in addition to the water-absorption-shrinkable fiber F1. Examples of the fibers that do not have water-absorption-shrinkability include hydrophilic fibers, such as heat-fusible fibers described below.

[0023] (Second fiber layer) The second fiber layer 12 is a layer mainly containing heat-fusible fibers F2. In the example shown in Fig. 2, the second fiber layer 12 is located above the first fiber layer 11 in the thickness direction Z, and is preferably disposed on the skin side when used in an absorbent article from the viewpoint of suppressing the wet feeling caused by the water-absorbing shrinkable fibers F1. The second fiber layer 12 is a nonwoven fabric layer, and various nonwoven fabrics such as thermal bonded nonwoven fabric, chemical bonded nonwoven fabric, and needle punched nonwoven fabric can be used. Of these, from the viewpoint of obtaining flexibility and deformability when absorbing water, the second fiber layer 12 is preferably a thermal bonded nonwoven fabric.

[0024] The heat-fusible fiber F2 is a fiber that fuses together by the action of heat, and is made of a thermoplastic resin. The thermoplastic resin constituting the heat-fusible fiber includes, for example, one or more selected from polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate, acrylic resins such as polyacrylic acid and polymethacrylic acid, vinyl resins such as polyvinyl chloride, and polyamide resins such as nylon. In addition, as a fiber made of a thermoplastic resin, a composite fiber (core-sheath type composite fiber or side-by-side type composite fiber) made of a combination of two types of resins among these various resins can also be used. The heat-fusible fiber F2 may be one type of fiber, or may include two or more types of fibers.

[0025] The heat-fusible fiber F2 used in the second fiber layer 12 preferably contains one or more types selected from polyesters such as polyethylene, polypropylene, and polyethylene terephthalate, from the viewpoints of ease of processing and soft feel, and is more preferably a composite core-sheath fiber that combines two of these types.

[0026] Moreover, from the viewpoint of enhancing thermal fusion properties, the thermal fusion fiber F2 preferably contains a resin having a melting point of 140° C. or less. From this viewpoint, the thermal fusion fiber F2 preferably contains, for example, polyethylene. Moreover, from the viewpoint of enhancing thermal fusion properties, the melting point of the resin having the lowest melting point among the constituent resins of the thermal fusion fiber F2 is preferably 140° C. or less, more preferably 135° C. or less. Moreover, from the viewpoint of having stable physical properties and suppressing the difference in melting point with the water-absorbing and shrinkable fiber F1, the melting point is preferably 120° C. or more, more preferably 125° C. or more.

[0027] In this specification, "the second fiber layer 12 mainly contains the heat-fusible fiber F2" means that the second fiber layer 12 contains 50 mass % or more of the heat-fusible fiber F2. From the viewpoint of sufficiently bonding the first fiber layer 11 by the embossing process described later, the content of the heat-fusible fiber F2 in the second fiber layer 12 is preferably 70 mass % or more, more preferably 90 mass % or more, and even more preferably 100 mass %. In other words, it is particularly preferable that the second fiber layer 12 is composed of the heat-fusible fiber F2.

[0028] The second fiber layer 12 may contain one or more types of fibers other than the heat-fusible fibers F2. Examples of the other fibers include non-heat-fusible fibers that do not fuse to each other by heat, such as cellulosic fibers such as pulp.

[0029] Moreover, it is preferable that the second fiber layer 12 does not contain the water-absorption shrinkable fiber F1. This prevents the absorbed water-absorption shrinkable fiber F1 from directly touching the skin when the nonwoven fabric 10 comes into contact with excrement, thereby preventing discomfort when worn, such as a wet feeling.

[0030] (recess) The recesses 13 are provided to join the first fiber layer 11 and the second fiber layer 12, and are configured as embossed portions formed by compressing and fusing the first fiber layer 11 and the second fiber layer 12 in the thickness direction Z. The recesses 13 are configured as portions recessed inward in the thickness direction Z from at least one of the lower surface 11a of the first fiber layer 11 and the upper surface 12a of the second fiber layer 12. In the example shown in Fig. 2, the recesses 13 are configured as portions recessed inward in the thickness direction Z from both the lower surface 11a of the first fiber layer 11 and the upper surface 12a of the second fiber layer 12.

[0031] The recess 13 includes a bottom 14 where the water-absorbent shrinkable fiber F1 and the heat-fusible fiber F2 are fused. In the bottom 14, the water-absorbent shrinkable fiber F1 and the heat-fusible fiber F2 may be deformed flat and fused. Alternatively, the bottom 14 may be a portion where the water-absorbent shrinkable fiber F1 and the heat-fusible fiber F2 are completely fused to form a film. In the example shown in FIG. 2, the recess 13 is illustrated diagrammatically as a portion where these fibers are fused to form a film. The recess 13 is formed, for example, by embossing a laminate of webs corresponding to the first fiber layer 11 and the second fiber layer 12, as will be described in detail later.

[0032] The planar shape of the recess 13 is not particularly limited, and can be appropriately selected from, for example, a linear shape, a circular shape, an elliptical shape, an oval shape, a polygonal shape, shapes similar thereto, and other shapes. In the example shown in Fig. 1, the recess 13 is configured in a linear shape. The term "linear" here includes a straight line shape and a curved line shape.

[0033] In this embodiment, when the recesses 13 are linearly configured, as shown in FIG. 1, it is preferable that the recesses 13 extend in a direction intersecting the fiber orientation direction (first planar direction X shown in FIG. 1). By having the recesses 13 extend so as to intersect the fiber orientation direction, more fibers can be bonded. This allows more shrinkage starting points for the water-absorption shrinkable fiber F1 to be formed, and the water-absorption shrinkability of the nonwoven fabric 10 to be improved. From the viewpoint of effectively obtaining the above-mentioned effects, the smallest angle (angle α shown in FIG. 1) between the fiber orientation direction and the extension direction of the recesses 13 is preferably 10 degrees or more, more preferably 20 degrees or more, and is preferably 60 degrees or less, more preferably 50 degrees or less.

[0034] In the example shown in FIG. 1, the nonwoven fabric 10 includes a first linear recess group 13a and a second linear recess group 13b that intersect with each other. The first linear recess group 13a and the second linear recess group 13b each include a plurality of linear recesses 13 that extend in parallel and are arranged at regular intervals. In the example shown in FIG. 1, each recess 13 included in the first linear recess group 13a and the second linear recess group 13b extends at an acute angle with the fiber orientation direction (first planar direction X). The intersecting angle of the recesses 13 in the first linear recess group 13a and the second linear recess group 13b may be an acute angle (obtuse angle) or 90 degrees, and is not particularly limited.

[0035] The distance between adjacent recesses 13 belonging to the first linear recess group 13a is preferably 3 mm or more, more preferably 5 mm or more, from the viewpoint of preventing the material from having a hard texture, and is preferably 15 mm or less, more preferably 13 mm or less, from the viewpoint of obtaining isotropic and sufficient shrinkage. The same applies to the suitable range of the distance between adjacent recesses 13 belonging to the second linear recess group 13b. The distance between adjacent recesses 13 is the average value of distances measured at five or more points.

[0036] The bottoms 14 of the recesses 13 are formed to a size that can reliably bond the first fiber layer 11 and the second fiber layer 12. When the recesses 13 are linear, the width of each bottom 14 (the dimension in the direction perpendicular to the extending direction of the recesses 13) is preferably 0.1 mm or more, more preferably 0.3 mm or more, from the viewpoint of reliably bonding the first fiber layer 11 and the second fiber layer 12 to obtain isotropic and sufficient shrinkability, and is preferably 5 mm or less, more preferably 3 mm or less, from the viewpoint of preventing a hard texture. The width of the bottoms 14 is the average value of widths measured at five or more points.

[0037] The ratio of the area of ​​the bottom portion 14 to the nonwoven fabric 10 is preferably 5% or more, more preferably 10% or more, from the viewpoint of reliably bonding the first fiber layer 11 and the second fiber layer 12 to obtain isotropic and sufficient water absorption and shrinkage properties, and is preferably 60% or less, more preferably 40% or less, and even more preferably 30% or less, from the viewpoint of preventing the fabric from becoming hard. The ratio of the area of ​​the bottom portion 14 to the nonwoven fabric 10 can be calculated by analyzing an image of a sample obtained by cutting the nonwoven fabric 10 to a predetermined size (e.g., 5 cm x 5 cm) and calculating the ratio of the area of ​​the bottom portion 14 to the entire sample.

[0038] [Effects of nonwoven fabric] In the nonwoven fabric 10 of this embodiment, the first fiber layer 11 containing the water-absorption shrinkable fiber F1 shrinks due to contact with warm water such as excreted liquid. Furthermore, the nonwoven fabric 10 has a recess 13 in which the first fiber layer 11 and the second fiber layer 12 are compressed and bonded in the thickness direction Z. Therefore, the water-absorption shrinkable fiber F1 and the heat-fusible fiber F2 contained in the entire thickness direction Z of the bottom portion 14 are fused while being compressed, and as a result, these fibers are fixed. Here, in the nonwoven fabric 10, although most of the fibers are oriented in the fiber orientation direction (first planar direction X), the nonwoven fabric 10 also contains fibers oriented in a direction other than the fiber orientation direction (first planar direction X). Therefore, the recess 13 can bond a plurality of water-absorption shrinkable fibers F1 and heat-fusible fibers F2 with various orientations arranged in the formation region of the bottom portion 14 in a planar view. Therefore, the water-absorption shrinkable fiber F1 with various orientations shrinks from the recess 13 as a starting point, and the nonwoven fabric 10 can shrink isotropically as a whole. Furthermore, since the first fiber layer 11 contains more than 90% by mass of the water-absorption shrinkable fiber F1, this, together with the fact that the starting point of shrinkage is clearly defined, can enhance the water-absorption shrinkage of the nonwoven fabric 10.

[0039] When such a nonwoven fabric 10 is used in an absorbent article, the nonwoven fabric 10 isotropically and sufficiently shrinks from the recesses 13 that come into contact with the excreted liquid. This makes it possible to suppress the diffusion of the excreted liquid in the nonwoven fabric 10 and reduce the contact area between the excreted liquid and the skin. Furthermore, as the first fiber layer 11 shrinks, the second fiber layer 12, which has low water absorption and shrinkability, deforms so as to rise upward in the thickness direction Z from the recesses 13. This forms clear irregularities on the upper surface 12a of the nonwoven fabric 10, which makes it possible to further suppress the diffusion of the excreted liquid and more effectively reduce the contact area between the excreted liquid and the skin. In addition, by using the nonwoven fabric 10 in an absorbent article having the following configuration, it is possible to suppress the return of the excreted liquid and reduce skin troubles of the wearer, as will be described in detail later.

[0040] [Configuration of absorbent articles] The absorbent article according to this embodiment includes the above-mentioned nonwoven fabric for absorbent articles (nonwoven fabric 10) and an absorbent body 4 disposed on the non-skin side of the nonwoven fabric 10. Fig. 3 shows an example in which the absorbent article is a disposable diaper (diaper 1).

[0041] 3, the diaper 1 includes a topsheet 2, an absorbent 4, a backsheet 3, and an exterior body 6. In the crotch portion of the diaper 1, the exterior body 6, the backsheet 3, the absorbent 4, and the topsheet 2 are laminated in a thickness direction Z. In the diaper 1, a first planar direction X of the nonwoven fabric 10 coincides with a longitudinal direction extending from the ventral side to the back side of the diaper 1, and a second planar direction Y of the nonwoven fabric 10 coincides with a width direction that is perpendicular to the longitudinal direction of the diaper 1 and corresponds to the left-right direction of a wearer.

[0042] In this embodiment, the topsheet 2 is made of a nonwoven fabric 10. The skin side 2a of the topsheet 2 is made of the upper surface 12a of the second fiber layer 12, and is placed so as to contact the wearer's skin. Note that detailed configuration of the nonwoven fabric 10 is omitted in Fig. 3.

[0043] The absorbent body 4 is disposed on the non-skin side of the top sheet 2, and is disposed between the top sheet 2 and the back sheet 3. The absorbent body 4 absorbs moisture from the wearer's excrement, such as urine, from the surface facing the top sheet 2, and retains the moisture from the excrement by diffusing it internally. The absorbent body 4 includes an absorbent material capable of retaining moisture as a core material. The core material may be, for example, a hydrophilic fiber stack, a structure in which an absorbent polymer is supported on the stack, or a laminate of absorbent sheets supporting an absorbent polymer. The absorbent body 4 may further include a covering material that covers the core material, as necessary.

[0044] The absorbent body 4 may or may not be bonded to the nonwoven fabric 10 (top sheet 2). Examples of a method for bonding the absorbent body 4 and the top sheet 2 (nonwoven fabric 10) include an adhesive such as a hot melt adhesive. Even if the absorbent body 4 is bonded to the nonwoven fabric 10 (top sheet 2) with an adhesive, the penetration of excreted liquid and contraction of the top sheet 2 (nonwoven fabric 10) can cause the adhesive to peel off, forming a space as described below.

[0045] The back sheet 3 is disposed on the non-skin side of the absorbent body 4. The back sheet 3 is preferably leak-proof, and is made of a sheet material having functions such as poor liquid permeability and water repellency. Examples of such sheet materials include a sheet material made of a thermoplastic resin film, a laminate of such a film and a nonwoven fabric, and the like.

[0046] The exterior body 6 is disposed on the non-skin side of the backsheet 3 and forms part of the non-skin side of the diaper 1. From the viewpoints of realizing moisture permeability, breathability, and a good feel against the skin, the exterior body 6 is preferably made of a nonwoven fabric, and further from the viewpoint of imparting leak prevention properties, it is preferable that the exterior body 6 has functions such as low liquid permeability and water repellency.

[0047] Furthermore, the diaper 1 preferably includes a pair of side sheets 5. The pair of side sheets 5 are arranged on the skin side of the widthwise lateral portions of the topsheet 2, and form, for example, three-dimensional gathers 50. The three-dimensional gathers 50 are formed by attaching thread-like or band-like elastic members 51 in a stretched state to the vicinity of the inner ends of the side sheets 5 in the widthwise direction.

[0048] In addition, the diaper 1 may have elastic members such as leg elastic members 52 that form leg gathers to improve the fit around the legs, and a waist elastic member (not shown) that forms waist gathers to improve the fit around the torso.

[0049] In the diaper 1 in which the topsheet 2 is made of nonwoven fabric 10, the contact area between the excreted liquid and the skin can be reduced by the above-mentioned action of the nonwoven fabric 10. For example, when the excreted liquid WL comes into contact with the diaper 1 when worn as shown in Fig. 4(A) as shown in Fig. 4(B), the nonwoven fabric 10 (topsheet 2) will shrink as shown in Fig. 4(C), thereby reducing the contact area of ​​the excreted liquid WL on the nonwoven fabric 10 (topsheet 2).

[0050] As shown in FIG. 4C, the nonwoven fabric 10 (top sheet 2) shrinks significantly relative to the absorbent 4, which has low water-absorption shrinkage, and this makes it easier for a space S to be formed between the absorbent 4 and the nonwoven fabric 10 (top sheet 2). The excreted liquid WL that has permeated the nonwoven fabric 10 (top sheet 2) can be accommodated in this space S and gradually absorbed by the absorbent 4. This space S can promote the permeation of the excreted liquid WL to the nonskin side of the nonwoven fabric 10 (top sheet 2), and can isolate the excreted liquid WL, thereby suppressing the liquid returning to the nonwoven fabric 10 (top sheet 2). Therefore, the absorbent article (diaper 1) having the above configuration can effectively reduce contact between the excreted liquid WL and the skin, thereby suppressing skin troubles.

[0051] [Method of manufacturing nonwoven fabric for absorbent articles] In this embodiment, the method for producing nonwoven fabric 10 includes a step S1 of forming a first web 21, a step S2 of forming a second web 22, a step S3 of joining the laminated first web 21 and second web 22 (laminate web 23), and a step S4 of forming fusion points in at least some of the fibers of the laminate web 23. An example of this process is shown in the flowchart of FIG.

[0052] 6 shows an example of an apparatus 100 for manufacturing nonwoven fabric 10. This apparatus 100 includes a first carding machine 101, a second carding machine 102, a pressing device 103, a hot air treatment device 104, and a winder 105. In this example, the material for forming nonwoven fabric 10 is transported along a transport direction MD by a transport mechanism (not shown). Note that the transport direction MD corresponds to the fiber orientation direction (first planar direction X) of nonwoven fabric 10.

[0053] (First web forming step S1) In this step, a first web 21 containing more than 90 mass % of the water-absorbent shrinkable fiber F1 is formed. The first web 21 is a web corresponding to the first fiber layer 11. The first web 21 can be formed by any appropriate web forming method such as a carding method or an airlaid method.

[0054] 6, the first web 21 is formed by a first carding machine 101. The first carding machine 101 forms the first web 21 by carding raw material fibers supplied from a raw material fiber supply unit (not shown). Since the first web 21 is carded in the machine direction MD by the first carding machine 101, the water-absorbing shrinkable fiber F1 tends to be oriented in the machine direction MD.

[0055] (Second web forming process S2) In this step, a second web 22 containing thermally adhesive fibers F2 is formed. The second web 22 is a web corresponding to the second fiber layer 12. To form the second web 22, similar to the first web 21, a web forming method such as a carding method or an airlaid method can be used.

[0056] 6, the second web 22 is formed by a second carding machine 102. The second carding machine 102 forms the second web 22 by carding raw material fibers supplied from a raw material fiber supply unit (not shown). Since the second web 22 is carded in the second carding machine 102 along the conveying direction MD, the heat-fusible fibers F2 tend to be oriented in the conveying direction MD.

[0057] In the example shown in the figure, the second web 22 is transported and laminated on the first web 21 transported by the transport mechanism. In this way, a laminated web 23 is formed in which the second web 22 is laminated on the first web 21.

[0058] (Joining process S3) In this process, the laminated first web 21 and second web 22 (laminate web 23) are heated and bonded at a temperature at which the water-absorption shrinkable fiber F1 and the heat-fusible fiber F2 can be fused while being pressed in the thickness direction Z by a pressing member having a convex portion. As a result, the portion pressed by the convex portion is depressed, and the water-absorption shrinkable fiber F1 and the heat-fusible fiber F2 are fused by the heat and pressure, thereby forming the recess 13.

[0059] 6, the pressing member is configured as a part of a pressing device 103 capable of embossing the nonwoven fabric, and is configured as, for example, an embossing roll or a mold. From the viewpoint of embossing while transporting the laminated web 23 in the transport direction MD, it is preferable that the pressing member is configured as an embossing roll. Also, from the viewpoint of efficiently heating the laminated web 23, it is preferable that the convex portion of the pressing member is heated by a heating device (not shown).

[0060] In this embodiment, the melting point of the water-absorption shrinkable fiber F1 can be higher than the melting point of the heat-fusible fiber F2. For this reason, from the viewpoint of reliably bonding the first web 21 and the second web 22 while maintaining the soft texture of the nonwoven fabric 10, it is preferable that the heating temperature of the first web 21 is higher than the heating temperature of the second web 22. For example, it is preferable that the heating temperature of the first web is higher than the heating temperature of the second web 22 by 30° C. or more and 80° C. or less.

[0061] More specifically, from the viewpoint of achieving both flexibility and bondability, the heating temperature of the first web 21 is preferably at least 50°C lower than the melting point of the resin having the highest melting point among the constituent resins of the water-absorption shrinkable fiber F1 and at most 20°C higher than the melting point, and more preferably at least 30°C lower than the melting point and at most 10°C higher than the melting point. The heating temperature of the second web 22 is preferably at least 20°C lower than the melting point of the resin having the lowest melting point among the constituent resins of the heat-fusible fiber F2 and at most 60°C higher than the melting point, and more preferably at least 5°C higher than the melting point and at most 40°C higher than the melting point.

[0062] 6, the pressing device 103 includes, as pressing members, a first roll 103a and a second roll 103b arranged opposite each other. In this example, the first roll 103a is arranged on the first web 21 side, and the second roll 103b is arranged on the second web 22 side. The peripheral surfaces of the first roll 103a and the second roll 103b are preferably heated to temperatures in the above-mentioned ranges by a heating device (not shown).

[0063] As shown in the enlarged view of Fig. 7, in the pressing device 103, the first roll 103a may be a flat roll, and the second roll 103b may be an embossing roll having convex portions 103c. Alternatively, the first roll 103a may be an embossing roll, and the second roll 103b may be a flat roll. Moreover, both the first roll 103a and the second roll 103b may be embossing rolls, and the convex portions may be arranged so as to face each other.

[0064] 7, the laminated web 23 transported by the transport mechanism is pressed between the first roll 103a and the second roll 103b while being heated by the convex portions 103c. In the laminated web 23, the fibers in the portions pressed by the convex portions 103c are fused to form the concave portions 13. As a result, the first web 21 and the second web 22 of the laminated web 23 are joined by the concave portions 13. Note that even when one of the rolls is a flat roll, both the upper surface 12a and the lower surface 11a of the nonwoven fabric 10 can be formed to be concave by adjusting the shape of the convex portions 103c, the pressing force, etc.

[0065] (Fusion point formation step S4) In this step, after the joining step S3, hot air is blown onto the laminated first web 21 and second web 22 (laminate web 23) to fuse at least some of the fiber intersections. As a result, a plurality of fusion points are formed in at least a portion of the laminate web 23, and nonwoven fabric 10 is formed. This step can increase the strength of nonwoven fabric 10. Note that in this step, it is preferable that fusion points are formed in second web 22, which contains heat-fusible fibers F2 with a low melting point.

[0066] The hot air is preferably blown in the thickness direction Z. The temperature of the hot air is set based on the melting points of the constituent resins of the heat-fusible fiber F2, and is preferably at least 1° C. higher than the melting point of the resin having the lowest melting point among the constituent resins of the heat-fusible fiber F2 and not more than 30° C. higher than the melting point, and more preferably at least 3° C. higher than the melting point and not more than 20° C. higher than the melting point.

[0067] In this step, as illustrated in FIG. 6, the hot air treatment device 104 can be used for the treatment. The hot air treatment device 104 includes, for example, a blower 104a for blowing hot air onto the laminated web 23, a suction box 104b for sucking the hot air, and a conveying device 104c for conveying the laminated web 23. The conveying device 104c includes a breathable conveying member 104d made of a breathable material such as a resin net (plastic mesh, etc.), and a plurality of conveying rolls 104e for conveying the breathable conveying member 104d, and is configured in the form of a belt conveyor in which the breathable conveying member 104d is conveyed in the conveying direction MD. The laminated web 23 on the breathable conveying member 104d is conveyed in the conveying direction MD while being blown with hot air from the blower 104a from above to below in the thickness direction Z. The hot air fuses the intersections of the fibers in the laminated web 23. The hot air blown onto the laminated web 23 is sucked and collected by the suction box 104b.

[0068] As shown in FIG. 6, the nonwoven fabric 10 produced through the fusion-bonding point forming step S4 is wound up by a winder 105, and then cut by a cutting device (not shown) such as a slitter, as necessary.

[0069] The above-described method for producing the nonwoven fabric 10 includes a bonding step S3 in which the laminated web 23 is pressed in the thickness direction Z by a pressing member having a protrusion, and is heated and bonded at a temperature capable of fusing the water-absorption shrinkable fiber F1 and the heat-fusible fiber F2. This allows the production of the nonwoven fabric 10 having the recesses 13.

[0070] If the nonwoven fabric is formed by performing the fusion point forming step S4 without performing the joining step S3, more fusion points can be formed between the fibers along the transport direction MD corresponding to the fiber orientation direction than between the fibers along other directions. In such a nonwoven fabric, since a clear starting point of shrinkage such as the concave portion 13 is not formed, water absorption shrinkage is likely to be exhibited along the transport direction MD in which a plurality of water-absorbing and shrinkable fibers F1 are connected in a long manner. Therefore, in this case, the water absorption shrinkage rate of the nonwoven fabric along the fiber orientation direction (the first plane direction X) is likely to be higher than the water absorption shrinkage rate along other directions, and it becomes difficult to obtain a nonwoven fabric that can shrink isotropically.

[0071] On the other hand, in the present embodiment, by forming the concave portion 13 in the joining step S3, a plurality of water-absorbing and shrinkable fibers F1 and heat-fusible fibers F2 arranged in the formation region of the bottom portion 14 in plan view are joined. As a result, not only the fibers oriented in the fiber orientation direction (the first plane direction X) but also the fibers oriented in a direction intersecting the fiber orientation direction (the first plane direction X) are easily joined, and a starting point of shrinkage including the water-absorbing and shrinkable fibers F1 oriented in multiple directions can be formed. Therefore, a nonwoven fabric 10 that can shrink isotropically can be manufactured by the manufacturing method including the joining step S3.

[0072] Moreover, the water-absorption shrinkable fiber F1 has a higher melting point than the heat-fusible fiber F2 and is difficult to fuse. For this reason, only in the fusion point forming step S4, it is difficult to form fusion points between the water-absorption shrinkable fiber F1 and the heat-fusible fiber F2, and it is difficult to bond the first web 21 and the second web 22, which contain more than 90% of the water-absorption shrinkable fiber F1. In contrast, in the bonding step S3 of this embodiment, the heat-fusible fiber F2 is sufficiently melted while the laminated web 23 is pressure-bonded, so that the molten resin of the heat-fusible fiber F2 penetrates into the first web 21 and is bonded sufficiently. As a result, in this embodiment, the bonding step S3 can sufficiently bond the first web 21 and the second web 22, which contain more than 90% of the water-absorption shrinkable fiber F1. In this way, in this embodiment, the content of the water-absorption shrinkable fiber F1 in the first web 21 (first fiber layer 11) can be made higher than 90% by mass, and the water-absorption shrinkability of the nonwoven fabric 10 can be improved.

[0073] [Supplementary explanation of this embodiment] The above-mentioned fiber orientation direction can be determined by the following method. First, the nonwoven fabric is placed on a scanning electron microscope JCM-5100 (trade name) manufactured by JEOL Ltd., and a planar image (adjusted to a magnification that can measure 10 or more fibers to be measured; 70 times or more and 300 times or less) is printed, and the fibers are traced on a transparent PET sheet. The image is imported into a personal computer, and the image is binarized using nexusNewQube (trade name) (standalone version) image processing software manufactured by Nexus Co., Ltd. Next, the binarized image is Fourier transformed using Fiber Orientation Analysis 8.13 Single software (trade name), which is a fiber orientation analysis program, to obtain a power spectrum, and the orientation angle is obtained from an elliptical approximation distribution diagram. The orientation angle indicates the angle at which the fibers are most oriented, and the angle direction is defined as the "fiber orientation direction".

[0074] The basis weight of the first fiber layer 11 is preferably 5 g / m from the viewpoint of obtaining sufficient water absorption and shrinkage in the nonwoven fabric 10. 2 More preferably, 10 g / m 2 From the viewpoint of obtaining a soft feel, it is preferably 40 g / m2 Less than or equal to 35 g / m 2 The following is the result.

[0075] The basis weight of the second fiber layer 12 is preferably 5 g / m2 from the viewpoints of providing sufficient heat fusion and reducing discomfort when absorbing water. 2 More preferably, 8 g / m 2 From the viewpoint of obtaining a soft feel, it is preferably 40 g / m 2 Less than or equal to 35 g / m 2 The following is the result.

[0076] The ratio of the basis weight of the first fiber layer 11 to the basis weight of the second fiber layer 12 (basis weight of the first fiber layer 11 / basis weight of the second fiber layer 12) is preferably 0.5 or more, more preferably 1.0 or more, from the viewpoint of obtaining sufficient water absorption shrinkage in the nonwoven fabric 10. Moreover, from the viewpoints of imparting sufficient heat fusion bonding and mitigating discomfort upon water absorption, the basis weight ratio is preferably 4.0 or less, more preferably 3.0 or less.

[0077] The average fiber length of the water-absorption shrinkable fiber F1 in the first fiber layer 11 is preferably 10 mm or more, and more preferably 20 mm or more, from the viewpoint of isotropically and sufficiently shrinking the nonwoven fabric 10. Moreover, from the viewpoint of obtaining a soft texture, the average fiber length is preferably 70 mm or less, and more preferably 60 mm or less.

[0078] The average fiber length of the thermally fusible fibers F2 in the second fiber layer 12 is preferably 10 mm or more, more preferably 20 mm or more, from the viewpoint of obtaining sufficient fusibility and strength. Moreover, from the viewpoint of obtaining a soft texture, the average fiber length is preferably 70 mm or less, more preferably 60 mm or less. The average fiber length of each fiber can be measured based on the average fiber length measurement method (method C) of JIS L1015.

[0079] The fineness of the water-absorbing shrinkable fiber F1 in the first fiber layer 11 is preferably 0.5 dtex or more, more preferably 1.0 dtex or more, and preferably 7.0 dtex or less, more preferably 6.0 dtex or less. The fineness of the heat-fusible fiber F2 in the second fiber layer 12 is preferably 0.3 dtex or more, more preferably 0.5 dtex or more, and preferably 5.0 dtex or less, more preferably 4.0 dtex or less.

[0080] The fiber fineness can be measured by the following method. 2 ) to prepare a measurement sample. Next, the measurement sample is viewed in cross section, and the fiber thicknesses of 10 standard water-absorption shrinkable fibers F1 at positions spaced 0.05 mm apart in the thickness direction from one side of the two main surfaces of the measurement sample are photographed at a magnification of 200 times using a scanning electron microscope, and the average fiber thickness Dn (μm) is calculated. Next, the constituent resins of the standard water-absorption shrinkable fibers F1 at positions spaced 0.05 mm apart in the thickness direction from the one surface side of the measurement sample are identified, and the theoretical fiber presence density Pn (g / cm) is calculated using a differential scanning calorimeter (DSC). 3 The average fiber thickness Dn (μm) and theoretical fiber density Pn (g / cm 3 ) to calculate the weight (g) per 10,000 m of fiber length, and this calculated value is the fineness (dtex) of the water-absorption shrinkable fiber F1. The fineness of the heat-fusible fiber F2 can also be determined in the same manner as the fineness of the water-absorption shrinkable fiber F1.

[0081] <Second embodiment> [Configuration of nonwoven fabric for absorbent articles] A nonwoven fabric 10A according to the second embodiment of the present invention further comprises openings 15 in addition to a first fiber layer 11, a second fiber layer 12, and recesses 13. This example is shown in Figures 8 and 9. In this embodiment, the same components as those in the first embodiment described above are denoted by the same reference numerals and will not be described.

[0082] The openings 15 are openings formed in the nonwoven fabric 10A in the thickness direction Z, and are preferably configured as through-holes. The openings 15 are formed, for example, after the fusion point forming step S4, by hole forming means such as a hot needle hole forming process, a punching process using a punch, or a melt-hole forming process by irradiating energy rays.

[0083] The planar shape of the openings 15 is not particularly limited, and can be appropriately selected from, for example, a circle, an ellipse, an oval, a polygon, shapes similar thereto, and other shapes. In the example shown in Fig. 8, the openings 15 are configured in an ellipse. The planar shapes of the openings 15 may be the same as shown in Fig. 1, or may be different.

[0084] The arrangement of the openings 15 is also not particularly limited, and the openings 15 may be arranged based on the arrangement of the recesses 13, or may be arranged regardless of the arrangement of the recesses 13. In the example shown in Fig. 8, the openings 15 are arranged in a pattern that is not dependent on the arrangement of the recesses 13. Specific examples of the arrangement of the openings 15 will be described later. The openings 15 may be arranged in a part of the nonwoven fabric 10A, or may be arranged throughout the entire nonwoven fabric 10A.

[0085] As shown in FIG. 10(A), the nonwoven fabric 10A allows the excreted liquid WL to easily permeate through the openings 15, and the diffusion of the excreted liquid WL can be suppressed. This can more effectively suppress the contact area between the excreted liquid WL and the skin. In addition, when the excreted liquid WL comes into contact with the first fiber layer 11, the nonwoven fabric 10A can shrink isotropically. This causes the openings 15 to shrink, as shown in FIG. 10(B), and the area of ​​the openings 15 can be reduced. Therefore, in the diaper 1A using the nonwoven fabric 10A, the excreted liquid WL that has migrated to the absorbent 4 or the like on the non-skin side of the nonwoven fabric 10A (top sheet 2) can be suppressed from migrating back to the skin side of the nonwoven fabric 10A (top sheet 2). This can suppress the excreted liquid WL from returning to the skin side 2a of the nonwoven fabric 10A (top sheet 2), and can suppress discomfort and skin troubles caused by the return of the excreted liquid. Note that the recesses 13 are not shown in FIG. 10.

[0086] [Example of aperture placement] The openings 15 may be arranged in consideration of the permeability of excreted liquid. In the example shown in FIG. 8, the openings 15 are arranged in a first opening row 15x along the first planar direction X and a second opening row 15y along the second planar direction Y perpendicular to the thickness direction Z and intersecting with the first planar direction X. In the example shown in FIG. 8, the first planar direction X is assumed to coincide with the fiber orientation direction. The phrase "the first opening row 15x is along the first planar direction X" is not limited to a state in which a line connecting the center points of the openings 15 is linear, and it is sufficient that the openings 15 are arranged at intervals along any one direction in the XY plane. Similarly, the phrase "the second opening row 15y is along the second planar direction Y" is not limited to a state in which a line connecting the center points of the openings 15 is linear, and it is sufficient that the openings 15 are arranged at intervals along a direction intersecting with the first opening row 15x in the XY plane.

[0087] In this case, as shown in Fig. 8, the openings 15 belonging to adjacent first opening rows 15x may be arranged to be shifted from each other in the first planar direction X. Alternatively, the openings 15 may be arranged at the positions where the first opening row 15x and the second opening row 15y intersect, and the openings 15 may be arranged in a lattice pattern. By regularly arranging the openings 15 in this manner, it is possible to suppress the variation in liquid permeability in the XY plane of the nonwoven fabric 10A. Therefore, the openings 15 can suppress the diffusion and return of excreted liquid regardless of the wearer's excretion position.

[0088] From the viewpoint of arranging the apertures 15 more regularly, it is preferable that the interval between adjacent apertures 15 in the first aperture row 15x is substantially constant. Similarly, it is preferable that the interval between adjacent apertures 15 in the second aperture row 15y is substantially constant. "Substantially constant interval" means that, when the intervals between apertures 15 at any three locations in each row are measured and the narrowest interval is taken as 100%, the difference between the widest interval and the narrowest interval is within 20%.

[0089] In addition, in the area where the openings 15 of the nonwoven fabric 10A are formed, a 10 cm×10 cm (100 cm 2 From the viewpoints of obtaining good liquid permeability and maintaining the shape of nonwoven fabric 10A, the ratio of the area of ​​open holes 15 to the area of ​​open holes 15 is preferably 3% or more, more preferably 10% or more, and preferably 50% or less, more preferably 40% or less. Note that the multiple open holes 15 are not limited to being distributed over the entire nonwoven fabric 10A, and may be disposed only in a part of nonwoven fabric 10A. When the area in which open holes 15 are formed is smaller than the above-mentioned 10 cm × 10 cm area, the ratio of the area of ​​open holes 15 to the area in which open holes 15 are formed is preferably within the above-mentioned range.

[0090] <Other embodiments> Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the spirit of the present invention.

[0091] For example, in the manufacturing method of nonwoven fabric 10 described in the first embodiment, fusion point forming step S4 may be performed before joining step S3. This also makes it possible to form recesses 13 that serve as starting points for shrinkage in joining step S3, and to obtain the above-mentioned effects. Note that if the joining step S3 is sufficient to produce a nonwoven fabric, fusion point forming step S4 may be omitted.

[0092] In addition, in this manufacturing method, the order of the first web forming step S1 and the second web forming step S2 is not particularly limited. Furthermore, when the first web 21 and the second web 22 are formed by an airlaid method or the like, the second web 22 may be formed directly on the formed first web 21. EXAMPLES

[0093] [Production of nonwoven fabric for absorbent articles] Example 1 A nonwoven fabric sample according to Example 1 was obtained using a nonwoven fabric manufacturing apparatus 100 as shown in FIG. 6. First, polyvinyl alcohol (PVA) fibers were prepared as water-absorbing and shrinkable fibers. The PVA fibers had a fiber diameter of 1.8 dtex, a fiber length of 51.0 mm, and a melting point of 200°C. The PVA fibers were then fed to a raw fiber feed section connected to a first carding machine 101, and the raw fiber was fed to the first carding machine 101 to form a first web 21 (basis weight 20 g / m 2 ) was formed.

[0094] As the heat-fusible fibers, core-sheath type composite fibers (hereinafter referred to as "PET / PE fibers") consisting of a core component of polyethylene terephthalate (PET) and a sheath component of polyethylene (PE) were prepared. The PET / PE fibers had a fiber diameter of 1.8 dtex, a fiber length of 38.0 mm, and the melting point of the resin (PE) that had the lowest melting point among the resins that constituted them was 130°C. The PET / PE fibers were then supplied to a raw fiber supply section connected to the second carding machine 102, and the raw fiber was supplied to the second carding machine 102 to form a second web 22 (basis weight 10 g / m 2 Then, a second web 22 was laminated on the first web 21 to form a laminated web 23.

[0095] Next, the laminated web 23 was pressed by a pressing device 103 having a first roll 103a and a second roll 103b, and the first web 21 and the second web 22 were joined. Here, the first roll 103a was a flat roll, and the second roll 103b was an embossing roll having a convex portion 103c having a shape corresponding to the concave portion 13 shown in FIG. 1. The temperature of the first roll 103a located on the first web 21 side was 190°C, and the temperature of the second roll 103b located on the second web 22 side was 150°C. As a result, the concave portions 13 having the shape and arrangement shown in FIG. 1 were formed. Note that the two adjacent concave portions 13 in the first linear concave portion group 13a and the two adjacent concave portions 13 in the second linear concave portion group 13b constituted a rhombus, and the size of this rhombus along the fiber orientation direction (first planar direction X) was 18 mm, the size along the second planar direction Y perpendicular to the fiber orientation direction was 9 mm, and the angle α was about 27 degrees.

[0096] Next, hot air was blown onto the laminated web 23 using the hot air treatment device 104 to form fusion points in the second web 22. The temperature of the hot air was set to 139° C. In this way, a sample of the nonwoven fabric according to Example 1 was produced.

[0097] Example 2 A sample of the nonwoven fabric according to Example 2 was produced in the same manner as in Example 1, except that the openings 15 were formed. The openings 15 were formed by piercing using a piercing pin. As shown in FIG. 8, the multiple openings 15 included first opening rows 15x and second opening rows 15y, and were arranged such that adjacent first opening rows 15x were shifted in the first planar direction X and adjacent second opening rows 15y were shifted in the second planar direction Y. Each opening 15 had an elliptical shape, with a dimension of 5 mm in the first planar direction X (fiber orientation direction) and a dimension of 3 mm in the second planar direction Y.

[0098] Comparative Example 1 A sample of a nonwoven fabric according to Comparative Example 1 was produced in the same manner as in Example 1, except that the composition of the first web 21 was 50% by mass of PVA fiber and 50% by mass of PET / PE fiber, and no bonding process was performed and no recesses 13 were formed.

[0099] Comparative Example 2 A sample of the nonwoven fabric according to Comparative Example 2 was produced in the same manner as in Example 1, except that no joining treatment was performed and no recesses 13 were formed.

[0100] Comparative Example 3 A nonwoven fabric sample according to Comparative Example 3 was produced in the same manner as in Example 1, except that in the pressing device 103, the temperatures of the first roll 103a and the second roll 103b were both set to 120° C. In the sample of Comparative Example 3, the first fiber layer 11 and the second fiber layer 12 were not bonded in the bonding step S3, and no recesses 13 were formed. Table 1 shows the manufacturing conditions for each sample.

[0101] [Table 1]

[0102] [Evaluation of shrinkage rate of nonwoven fabric] Each of the nonwoven fabric samples of Examples 1-2 and Comparative Examples 1-3 was cut into a 5 cm rectangle in the first planar direction X and the second planar direction Y to form a measurement sample. Each measurement sample was placed in a petri dish containing hot water at 35°C, and removed from the hot water after 1 minute. The shrinkage rate of each sample in the first planar direction X and the second planar direction Y was calculated by the following formula. The results are shown in Table 1. Shrinkage rate of nonwoven sample (%) = {(5cm-L3) / 5cm} x 100 L3: Length of the measurement sample after immersion in hot water

[0103] As shown in Table 1, in the samples of Example 1 and Example 2, the shrinkage rates in the first planar direction X and the second planar direction Y were almost the same value. On the other hand, the shrinkage rate in the second planar direction Y of the sample of Comparative Example 1 was significantly lower than the shrinkage rate in the first planar direction X, and both the first planar direction X and the second planar direction Y were lower than those of Examples 1 and 2. Furthermore, in the samples of Comparative Example 2 and Comparative Example 3, the shrinkage rates in the first planar direction X and the second planar direction Y were both 0%, and no shrinkage occurred. From these results, it was found that the samples of Examples 1 and 2 had higher shrinkage rates than the samples of Comparative Examples 1 to 3, and in addition, there was no difference between the shrinkage rates in the first planar direction X and the second planar direction Y. In other words, it was found that the samples of Examples 1 and 2 could be isotropically and sufficiently shrunk by immersion in warm water.

[0104] [Manufacture of absorbent articles] The nonwoven fabric samples of Examples 1-2 and Comparative Examples 1-3 were laminated as topsheets on the backsheet and absorbent body so that the first fiber layer was placed on the non-skin side and the second fiber layer was placed on the skin side, to obtain diaper (absorbent article) samples. The absorbent body used was a Merrys (product name) absorbent body manufactured by Kao Corporation, and the backsheet used was a Merrys (product name) backsheet manufactured by Kao Corporation.

[0105] [Evaluation of diffusion area] 40 g of colored artificial urine having the composition shown in Table 2 was poured into the diaper sample equipped with each nonwoven fabric sample of Examples 1-2 and Comparative Examples 1-3 while maintaining the height at 10 mm. The pouring point was 150 mm from the abdominal end of the diaper sample toward the center in the longitudinal direction, and the center in the width direction. 10 minutes after the start of pouring, 40 g was poured again. The same operation was repeated two more times to pour a total of 160 g of artificial urine. The temperature of the test environment was room temperature (20±5°C), and the temperature of the artificial urine was 35±5°C, which is close to body temperature. 10 minutes after the completion of pouring, the area of ​​the colored part of the top sheet was measured and defined as the diffusion area.

[0106] [Table 2]

[0107] As shown in Table 1, the diaper samples of Examples 1 and 2 had a smaller diffusion area of ​​artificial urine than the diaper samples of Comparative Examples 1 to 3. This shows that the nonwoven fabric samples of Examples 1 and 2 can suppress the diffusion of excrement and reduce the contact area between the excrement and the skin.

[0108] [Evaluation of the amount of liquid returning] 40 g of artificial urine having the above composition was poured into the diaper sample loaded with each nonwoven fabric sample of Examples 1-2 and Comparative Examples 1-3 while maintaining the height at 10 mm. The pouring point was 150 mm from the abdominal end of the diaper sample toward the center in the longitudinal direction, and was the center in the width direction. 10 minutes after the completion of the pouring, 10 sheets of ADVANTEC hard filter paper No. 4A (manufactured by Toyo Roshi Kaisha, Ltd.) (100 mm x 100 mm) were stacked and placed on the diaper sample with the pouring point at the center. Before placing on the diaper sample, the mass W1 of the 10 sheets of filter paper was measured. Next, a pressure of 3 kPa was applied to the diaper sample through an acrylic plate having a thickness of 5 mm and a size of 100 mm x 100 mm, and the mass W2 of the 10 sheets of filter paper was measured after 2 minutes, and the amount of liquid return was calculated according to the following formula. The results are shown in Table 1. Amount of liquid returned (g) = Mass of filter paper after pressure application (W2) - Mass of filter paper before test (W1)

[0109] As shown in Table 1, the diaper samples of Examples 1 and 2 had a smaller amount of wetback than the diaper samples of Comparative Examples 1 to 3. This demonstrates that the nonwoven fabric samples of Examples 1 and 2 can effectively suppress wetback. [Explanation of symbols]

[0110] 1,1A…Absorbent articles (disposable diapers, diapers) 10, 10A...Nonwoven fabric for absorbent articles (nonwoven fabric) 11...First fiber layer 12...Second fiber layer 13…Recess 14...Bottom 15...Opening part

Claims

1. A nonwoven fabric for absorbent articles having water absorption shrinkage properties, A first fiber layer containing more than 90% by mass of water-absorbing and shrinkable fibers; a second fiber layer laminated on the first fiber layer and mainly containing heat-fusible fibers; a recess in which the first fiber layer and the second fiber layer are compressed and joined in a thickness direction, The recess includes a bottom portion to which the water-absorbing shrinkable fiber and the heat-fusible fiber are fused. Nonwoven fabric for absorbent articles.

2. Further comprising one or more apertures. The nonwoven fabric for absorbent articles according to claim 1.

3. The thermally adhesive fiber contains a resin having a melting point of 140° C. or less. The nonwoven fabric for absorbent articles according to claim 1.

4. The water-absorbing shrinkable fiber contains a resin having a melting point of more than 140°C. The nonwoven fabric for absorbent articles according to claim 3.

5. The water-absorbing shrinkable fiber contains polyvinyl alcohol. The nonwoven fabric for absorbent articles according to claim 4.

6. The nonwoven fabric for absorbent articles according to any one of claims 1 to 5, An absorbent body disposed on the non-skin side of the nonwoven fabric for absorbent articles; Equipped with The second fiber layer is disposed on the skin side, and the first fiber layer is disposed on the non-skin side. Absorbent articles.

7. A method for producing a nonwoven fabric for absorbent articles having water-absorbing shrinkage properties, comprising the steps of: forming a first web containing more than 90% by weight of water-shrinkable fibers; forming a second web mainly containing heat-fusible fibers; The laminated first web and second web are pressed in the thickness direction by a pressing member having a protrusion, and are heated at a temperature at which the heat-fusible fiber and the water-absorption shrinkable fiber can be fused to each other to bond them together. A method for producing a nonwoven fabric for absorbent articles.

Images