RU2724844C1 - Absorbent product - Google Patents

Abstract

FIELD: hygiene.SUBSTANCE: multilayer nonwoven material (10) according to the present invention has multilayer structure (13) of fibrous layers, which include thermoplastic fibres. Multilayer structure (13) has first surface (10a), which is surface of multilayer nonwoven material (10), and second surface (10b) as another surface of multilayer nonwoven material (10). First surface (10a) is formed by hydrophobic first layer (11). Hydrophilic second layer (12) is located on the side of first layer (11) closer to second surface (10b). Multilayer structure (13) includes interlayer fused parts (16), which are thinner than parts peripheral with respect to interlayer fused parts (16), and in which layers forming multilayer structure (13) are fused to each other. First layer (11) includes interfibre fused parts (17), which are thinner than parts peripheral with respect to interfibre fused parts (17), and in which constituent fibres of first layer (11) are fused to each other, besides interlayer fused parts (16). First surface (10a) has a share of area of fused parts which exceeds a share of area of fused parts of second surface (10a).EFFECT: multilayer nonwoven material (10) having this structure has a high capacity for absorption of a body fluid, such as sweat and urine.25 cl, 25 dwg

Description

FIELD OF THE INVENTION

[0001]

The present invention relates to an absorbent article that uses a multilayer nonwoven material having a multilayer structure in which a plurality of layers of nonwoven materials are stacked on top of each other.

State of the art

[0002]

In typical absorbent articles, such as disposable diapers and sanitary napkins, non-woven materials having a multilayer structure of two or more layers, non-woven materials, the surfaces of which are uneven, and so on are used as their components. For example, Patent Literature 1 describes that a sweat-absorbing sheet capable of absorbing a user's sweat is located on a part of a disposable diaper that is in contact with a user's skin, that a multilayer non-woven material that has a multilayer structure of a hydrophobic non-woven material and a hydrophilic non-woven material and in which these non-woven materials are joined together in a large number of depressed parts fastened by fusion, is used as a sweat-absorbing sheet, and it is also described that the multilayer non-woven material is arranged so that the hydrophobic non-woven material faces the skin of the user.

[0003]

In patent literature 2, as a multilayer nonwoven material suitable as a component of an absorbent article, a nonwoven sheet is described which is permeable in one direction, has liquid permeability in the direction of one surface and does not have liquid permeability in the opposite direction, and also describes - as an embodiment of a sheet of nonwoven fabric, permeable in one direction, a nonwoven material in which at least one layer is hydrophilic and the remaining layers are not hydrophilic. Patent Literature 2 also describes, as a method for manufacturing a multilayer nonwoven fabric, a method for performing the fusion bonding process by means of hot stamping rollers on superimposed layers of nonwoven fabric, and also describes, as another manufacturing method, a method for depositing long fibers having a predetermined fineness, directly on the spunbond nonwoven material and the subsequent execution or entanglement process using a means such as needle punching, water-jet processing or ultrasonic welding, or the fusion bonding process by means of hot stamping rollers.

[0004]

In Patent Literature 3, as a functional filter for use in the extraction of coffee and tea, a multilayer nonwoven material is described in which an inner layer of nonwoven material of hydrophobic microfibers and an outer layer of nonwoven material of synthetic fibers to which a means for imparting hydrophilicity, partially bonded together by adhesive or hot stamping.

List of links

Patent Literature

[0005]

Patent Literature 1: JP 2004-298467 A

Patent Literature 2: JP 2006-51649 A

Patent Literature 3: JP 2002-233720 A

SUMMARY OF THE INVENTION

[0006]

The present invention provides a multilayer nonwoven material having a multilayer structure of fibrous layers including thermoplastic fibers. The multilayer structure has a first surface, which is the surface of the multilayer nonwoven material, and a second surface, which is the other surface of the multilayer nonwoven material. The first surface is formed by a hydrophobic first layer. The hydrophilic second layer is located on the side of the first layer, closer to the second surface. The multilayer structure includes interlayer fused parts that are thinner than parts peripheral to the interlayer fused parts, and in which the layers forming the multilayer structure are fused to each other. The first layer includes interfiber fused parts that are thinner than parts peripheral to the interfiber fused parts, and in which the constituent fibers of the first layer are fused to each other, in addition to the interlayer fused parts. Assuming that the fraction of the total area of the interlayer fused parts and the interfiber fused parts of the first surface from the area of the first surface and the fraction of the total area of the interlayer fused parts and interfiber fused parts of the second surface from the area of the second surface are respectively the fraction of the area of the fused parts of the first surface and the fraction of the area of the fused parts of the second surface, then the fraction of the area of the fused parts of the first surface exceeds the fraction of the area of the fused parts of the second surface.

[0007] The present invention also provides a method for manufacturing a multilayer nonwoven material having a multilayer structure of fibrous layers including thermoplastic fibers, wherein the layers forming the multilayer structure are fused to each other in interlayer fused parts. The method includes: the step of producing a multilayer element by moving a hydrophobic base nonwoven material including interfiber fused parts that are thinner than parts peripheral to the interfiber fused parts, and in which the constituent fibers are fused to each other, and the deposition of fibers obtained by molding fibers from resin on a moving base nonwoven material, and the step of fusing the layers with each other, which consists in heating the multilayer element while simultaneously partially compressing the multilayer element in the thickness direction to form interlayer fused parts thereby.

[0008] According to the present invention, there is provided an absorbent article comprising a multilayer nonwoven material having a multilayer structure of fibrous layers including thermoplastic fibers. The multilayer structure has a first surface, which is the surface of the multilayer nonwoven material, and a second surface, which is the other surface of the multilayer nonwoven material. The first surface is formed by a hydrophobic first layer. The hydrophilic second layer is located on the side of the first layer, closer to the second surface. The multilayer structure includes interlayer fused parts that are thinner than parts peripheral to the interlayer fused parts, and in which the layers forming the multilayer structure are fused to each other. The first layer includes interfiber fused parts that are thinner than parts peripheral to the interfiber fused parts, and in which the constituent fibers of the first layer are fused to each other, in addition to the interlayer fused parts. Assuming that the fraction of the total area of the interlayer fused parts and the interfiber fused parts of the first surface from the area of the first surface and the fraction of the total area of the interlayer fused parts and interfiber fused parts of the second surface from the area of the second surface are respectively the fraction of the area of the fused parts of the first surface and the fraction of the area of the fused parts of the second surface, then the fraction of the area of the fused parts of the first surface exceeds the fraction of the area of the fused parts of the second surface. The multilayer nonwoven material is positioned so that the first surface faces the skin of the user.

[0009] The present invention provides an absorbent sheet having a multilayer structure of fibrous layers including thermoplastic fibers, wherein the absorbent sheet has a first surface and a second surface opposite the first surface, and the absorbent sheet is used with the first surface facing the skin user. The first surface is formed by a hydrophobic first layer. The hydrophilic second layer is located on the side of the first layer, closer to the second surface. The multilayer structure includes interlayer fused parts that are thinner than parts peripheral to the interlayer fused parts, and in which the layers forming the multilayer structure are fused to each other. The first layer includes interfiber fused parts that are thinner than parts peripheral to the interfiber fused parts, and in which the constituent fibers of the first layer are fused to each other, in addition to the interlayer fused parts. Assuming that the fraction of the total area of the interlayer fused parts and the interfiber fused parts of the first surface from the area of the first surface and the fraction of the total area of the interlayer fused parts and interfiber fused parts of the second surface from the area of the second surface are respectively the fraction of the area of the fused parts of the first surface and the fraction of the area of the fused parts of the second surface, then the fraction of the area of the fused parts of the first surface exceeds the fraction of the area of the fused parts of the second surface.

Brief Description of the Drawings

[0010]

[Fig. 1] Fig. 1 is a sectional view schematically illustrating a cross-section of an embodiment of a multilayer nonwoven material according to the present invention, made along the thickness direction.

[Fig. 2] Figs. 2 (a) to 2 (h) are views, each of which schematically illustrates a configuration of interlayer fused parts according to the present invention.

[Fig. 3] Figs. 3 (a) to 3 (h) are views, each of which schematically illustrates a configuration of interfiber fused parts according to the present invention.

[Fig. 4] Figs. 4 (a) to 4 (d) are views, each of which schematically illustrates a configuration of fused parts (interlayer fused parts and interfiber fused parts) on a first surface of a multilayer nonwoven material according to the present invention.

[Fig. 5] Fig. 5 is a schematic view of an embodiment of a method for manufacturing a multilayer nonwoven material according to the present invention.

[Fig. 6] Fig. 6 is a schematic perspective view of a pull-on disposable diaper as an embodiment of an absorbent article according to the present invention.

[Fig. 7] Fig. 7 is a detailed plan view schematically illustrating the surface of the diaper (inner surface) of the diaper illustrated in Fig. 6 in its flat, unstretched state.

[Fig. 8] Fig. 8 is a vertical sectional view schematically illustrating a cross section taken along line I – I in FIG. 7.

Description of Embodiments

[0011]

As described in Patent Literatures 1-3, in the case of a multilayer nonwoven material in which a plurality of sheets of nonwoven material are superimposed and joined together by hot stamping, it is difficult to reduce the surface density of each layer forming a multilayer structure, and especially it is difficult to reduce the surface density of the hydrophobic layer. Thus, the multilayer nonwoven material has a generally high surface density and high rigidity, and when used as a component of an absorbent article, wearing comfort may be impaired. In the case where the hydrophobic layer is located closest to the skin of the user, the multilayer non-woven material has insufficient ability to absorb the body fluid, such as sweat and urine.

[0012]

As a method of manufacturing a multilayer nonwoven material, a method was known in which the fibers are sequentially lowered and deposited from a plurality of forming heads spaced apart at intervals in the machine direction (MD) and the deposited fibers are hot stamped to connect them from the output side of the forming head located further just ahead in the direction of MD. A multilayer non-woven material obtained by a similar so-called direct spinning of fibers has a relatively low surface density and low stiffness. Thus, in the case where the hydrophobic layer is located closest to the skin of the user secreted by the body, the fluid can be absorbed into the part surrounding the embossed part of the hydrophobic layer. However, in the part surrounding the embossed part, the constituent fibers of the hydrophilic layer adjacent to the hydrophobic layer are densely arranged and the hydrophobic layer has a relatively small thickness, and therefore there is a possibility that the fluid released by the body will concentrate around the embossed part, so that there is a tendency for fluid to flow in the opposite direction.

[0013]

Thus, the present invention relates to the implementation of a multilayer non-woven material having a high ability to absorb body fluids, such as sweat and urine, to a method for manufacturing a multilayer non-woven material, an absorbent article and an absorbent sheet.

[0014]

The present invention will now be described with reference to the drawings based on preferred embodiments thereof. Figure 1 schematically illustrates a cross section of a multilayer nonwoven material 10 as one embodiment of a multilayer nonwoven material according to the present invention, made along the direction Z of its thickness. The multilayer non-woven material 10 has a multilayer structure 13 of fibrous layers including thermoplastic fibers. The fibrous layers are typically layers forming a nonwoven material, i.e., a single layer nonwoven material (e.g., spunbond nonwoven material) or a multilayer nonwoven material (e.g., nonwoven material with an SMS structure (layer (S) obtained by the spinneret method, - layer (M) melt-blown — layer (S) obtained by a spinneret method.) The multilayer structure 13 has a first surface 10a, which is the surface (outer surface) of the multilayer nonwoven material 10, and a second surface 10b, which is another surface (outer surface) of the multilayer nonwoven material 10 and is located opposite the first surface 10a.

[0015]

The main feature of the multilayer nonwoven material 10 is that the multilayer structure 13 has a gradient of the degree of hydrophilicity in the thickness direction Z. That is, in the multilayer structure 13, the first surface 10a is formed by a hydrophobic first layer 11 including hydrophobic fibers 14, and a hydrophilic second layer 12 including hydrophilic fibers 15 is located on the side of the first layer 11, closer to the second surface 10b. This configuration provides a multilayer structure 13 with a gradient of the degree of hydrophilicity, in which "the degree of hydrophilicity is relatively higher on the side closer to the first surface 10a than on the side closer to the second surface 10b".

[0016]

In the multilayer nonwoven fabric 10 illustrated in FIG. 1, the multilayer structure 13 is a two-layer structure of a hydrophobic first layer 11 and a hydrophilic second layer 12. The first surface 10a is formed by the first layer 11 and is hydrophobic. The second surface 10b is formed by the second layer 12 and is hydrophilic. In this case, the expression “the number of layers of the multilayer structure 13 is two” refers to the total number of layers representing two layers having different shapes or functions (that is, the first layer 11 and the second layer 12), and does not strictly correspond to the number of layers representing fibrous layers (nonwoven fabric). That is, as described later, each of the first layer 11 and the second layer 12 is not only a nonwoven material having a single layer structure, but also can be a nonwoven material having a multilayer structure of two or more layers (for example, a nonwoven material with a structure SMS). For example, if the first layer 11 is a nonwoven material with an SMS structure and the second layer 12 is a nonwoven material having a single layer structure, although the multilayer structure 13 is a two layer structure including the first layer 11 and the second layer 12, the actual number of nonwoven layers is a total of four, in particular three layers in the first layer 11 and one layer in the second layer 12. That is, each of the first layer 11 and the second layer 12 may consist of two or more layers.

[0017]

In the present invention, the degree of hydrophilicity of the fibrous layers (non-woven material), which are a collection / accumulation of fibers, is determined based on the contact angle with water, measured by the method described later. If the contact angle is less than 90 degrees, the fibrous layer is hydrophilic, and if the contact angle is 90 degrees or more, the fibrous layer is hydrophobic. As the angle of contact with water, as measured by the method below, decreases, the degree of hydrophilicity increases (the degree of hydrophobicity decreases), and as the angle of contact increases, the degree of hydrophilicity decreases (the degree of hydrophobicity increases). In the multilayer structure 13 of the multilayer nonwoven material 10, the contact angle measured by the method described below in the hydrophobic first layer 11 is 90 degrees or more, and the contact angle measured by the method described below in the hydrophilic second layer 12 is less than 90 degrees.

[0018]

<Method for measuring the contact angle of the fibrous layer (nonwoven material)>

A piece having a rectangular shape in plan view (150 mm in the MD direction and 70 mm in the CD direction) is cut out from the fibrous layer (nonwoven material) as an object of measurement, and this piece is used as a sample for measurements. Drops of liquid, which is ion-exchanged water, are “attached” to the contact surface intended for measuring the contact angle, and the image of liquid drops is recorded. The contact angle is measured based on the recorded images. More specifically, the VHX-1000 microscope manufactured by KEYENCE CORPORATION is used as a measuring device, and a zoom lens with a medium magnification is attached to the microscope with an angle of inclination of 90 °. The measurement sample is placed on the measuring table of the measuring device so that the predetermined measurement surface is facing up and that the measurement sample can be examined in the CD direction. After that, liquid droplets from 3 μl of ion-exchange water are “attached” to the intended surface of the measurement sample placed on the measuring table, and images of liquid droplets are recorded and captured in the measuring device. Of the many registered images, ten images are selected in which both ends or one end of the liquid droplets in the CD direction are “sharp” and the contact angle with the liquid droplets is measured for each of the ten images. The average value from these contact angles is obtained as the contact angle of the fibrous layer (non-woven material) as an object of measurement. The measurement medium has a temperature of 20 ° C and a relative humidity of 50%.

[0019]

The first layer 11 is formed mainly by hydrophobic fibers 14 and therefore is a hydrophobic layer. The second layer 12 is formed mainly by hydrophilic fibers 15 and therefore is a hydrophilic layer. The first layer 11 contains at least 70% of the mass. hydrophobic fibers 14 with respect to the total mass of the first layer 11, and the content of hydrophobic fibers 14 can be 100% of the mass. The second layer 12 contains at least 50% of the mass. hydrophilic fibers 15 relative to the total mass of the second layer 12, and the content of hydrophilic fibers 15 may be 100% of the mass.

[0020]

In the present invention, the degree of hydrophilicity of the fibers is determined based on the contact angle with water, measured by the method described later. If the contact angle is less than 90 degrees, the fibers are hydrophilic, while if the contact angle is 90 degrees or more, the fibers are hydrophobic. As the angle of contact with water, as measured by the method below, decreases, the degree of hydrophilicity increases (the degree of hydrophobicity decreases), and as the angle of contact increases, the degree of hydrophilicity decreases (the degree of hydrophobicity increases). In the multilayer nonwoven material 10, the contact angle measured by the method described below for hydrophobic fibers 14 forming the first layer 11 of the multilayer structure 13 is 90 degrees or more, and the contact angle measured by the method described below for the hydrophilic fibers 15 forming the second layer 12 is less than 90 degrees.

[0021]

<Contact Angle Measurement Method>

Fibers are taken from the measurement object (multilayer nonwoven material), and the angle of contact of the fibers with water is measured. When selecting fibers use scissors and tweezers. Fibers are selected from parts of the multilayer nonwoven material as an object of measurement, in particular, from the outermost surface (outer surface) of each of the first surface and the second surface and from the zone of the multilayer nonwoven material located between the first surface and the second surface. As the measuring device, an automatic MCA – J instrument for measuring the contact angle, manufactured by Kyowa Interface Science Co., Ltd., is used. Deionized water is used to measure the contact angle. The amount of liquid leaving the outlet of the jet type device designed to eject water droplets (a CTC-25 pulse injector manufactured by Cluster Technology Co., Ltd. and having an outlet diameter of 25 μm) is set to 15 picoliters, and drops water dripping directly onto the fibers. The state of this drop is recorded by means of a high-speed recording device connected to a camera oriented horizontally. For reasons associated with subsequent image analysis, the recording device is preferably a personal computer in which a high-speed image capture device is integrated. With this measurement, an image is recorded every 17 ms. The first image from the recorded images, on which water droplets fall onto the fibers, is subjected to image analysis using the supplied FAMAS software (software version: 2.6.2; analysis method: resting drop method; analysis method: Ɵ / 2 method; image processing algorithm: non-reflective; image type during image processing: frame; threshold level: 200, and without curvature correction), and the angle formed by the surface of water droplets in contact with air and fibers is calculated and used as the contact angle. The fibers taken from the measurement object are cut off with a fiber length of 1 mm, and the resulting fibers are placed on the sample support in a contact angle measuring device and held horizontally. For one fiber, the contact angles are measured in two different places. The contact angles N = 5 of the fibers are measured to the first decimal place, and the average value (rounded to the first decimal place) of the values measured in a total of ten places is determined as the contact angle of these fibers with water. The measurement medium has an indoor temperature of 22 ± 2 ° C and a relative humidity of 65 ± 2%. As the contact angle decreases, the degree of hydrophilicity increases.

[0022]

In the case where a measurement sample (e.g. fiber) is included in a component of an absorbent article (e.g., a top sheet or a sweat-absorbing sheet), as a method for removing / sampling a measurement sample, if a component including a measurement sample is attached to another component, for example, by adhesive or by fusion, this bond must be removed, and a method must be used to remove the component, including the measurement sample, from the absorbent article. However, if the component including the measurement sample is not attached to another component, a method for extracting / collecting a measurement sample directly from the absorbent article can be used. As a method of removing component fixation, it is preferable to use a method in which an adhesive or the like used to attach the component of the measurement object to another component in an absorbent article is “loosened” by means of a cooling agent such as cold spraying, and then the component The measurement object is carefully separated for extraction. This extraction method is used to measure the measurement object according to the present invention, for example, when measuring the interfiber distance and fineness described later. For reasons of minimizing the effect on the hydrophilicity agent applied to the component, it is preferable not to use a method that can cause the destruction or loss of an oily product, such as applying a solvent or blowing hot air using a drying device, as a method of removing the bonded part .

[0023]

The hydrophobic fibers 14 may be hydrophobic thermoplastic fibers (fibers that can be held together by fusion). Examples of the material for hydrophobic fibers 14 as hydrophobic thermoplastic fibers include: polyolefins, such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate; polyamides such as nylon 6 and nylon 66; polyacrylic acid, polyalkyl methacrylate, polyvinyl chloride and polyvinylidene chloride. Each of these materials may be used on its own, or two or more of these materials may be used in combination.

[0024]

On the other hand, the hydrophilic fibers 15 can be hydrophilic thermoplastic fibers (fibers that can be bonded by fusion). In particular, hydrophilic fibers 15 may be hydrophilic in nature, thermoplastic fibers, such as polyacrylonitrile fibers, or may be hydrophobic thermoplastic fibers suitable as hydrophobic fibers 14 and processed to give hydrophilicity. Each of these materials may be used on its own, or two or more of these materials may be used in combination. Examples of the latter, “thermoplastic fibers subjected to hydrophilicity treatment” include thermoplastic fibers that interfere with the hydrophilicity agent, thermoplastic fibers having surfaces to which the hydrophilicity agent is attached, and thermoplastic fibers subjected to plasma treatment. The hydrophilicity agent may be any typical hydrophilicity agent used for applications in hygiene products.

[0025]

The method of manufacturing a multilayer nonwoven material according to the present invention, described later, includes the step of producing a multilayer element by moving a hydrophobic base nonwoven material, which at the end should become the first layer 11, and by deposition of fibers obtained by forming fibers from resin, (fibers which at the end should become hydrophilic fibers 15) on the moving base nonwoven material and the formation of interlayer fused parts 16 in the multilayer element (see figure 5). "Thermoplastic fibers in which the hydrophilicity enhancing agent is interfered", that is, one example of the hydrophilic fibers 15, are hydrophilic fibers obtained by spinning fibers from a resin mixed with a hydrophilicity enhancing agent. “Thermoplastic fibers having surfaces to which a hydrophilicity enhancing agent is attached” and “thermoplastic fibers subjected to plasma treatment”, which are other examples of hydrophilic fibers 15, are hydrophilic fibers obtained by spinning fibers from a resin by depositing a resin on a base nonwoven material (or by forming interlayer fused portions 16) and then attaching the hydrophilicity or plasma treatment to the deposited layer (a cluster of fibers not subjected to any hydrophilicity treatment).

[0026]

Each of the hydrophobic fibers 14 and hydrophilic fibers 15 may be single-component fibers formed from a synthetic resin (thermoplastic resin) of the same type or from mixed polymers in the form of a mixture of synthetic resins of two or more types, or may be bicomponent fibers. Bicomponent fibers in this case refer to fibers that are synthetic fibers (thermoplastic fibers) obtained by combining synthetic resins (thermoplastic resins) of two or more types having different components, by means of a spinneret and simultaneously forming fibers, and which have a structure in which many components are continuous in the length direction of the fibers and are bonded to each other in separate fibers. The shape of the bicomponent fibers can be a shape with a sheath and a core or a shape with the arrangement of the components side by side and is not limited to a specific shape.

[0027]

Each of the first layer 11 and the second layer 12 may be a non-woven material formed mainly from short fibers (non-woven material from short fibers), or a non-woven material formed mainly from long fibers (non-woven material from long fibers). The expression "formed mainly from" means that the proportion of short fibers or long fibers in the total mass of non-woven material is 70% of the mass. or more, and this proportion, as a rule, is 100% of the mass.

[0028]

Examples of short fiber nonwoven fabric include nonwoven fabric bonded by passing through air, hydro-entanglement nonwoven fabric, needle-punched nonwoven fabric, and chemical bonded nonwoven fabric. The length of the fibers constituting the main constituent fibers (short fibers) of the nonwoven material is preferably 15 mm or more and 100 mm or less.

[0029]

As used herein, the term “long fibers” refers to fibers having a fiber length of 30 mm or more. In particular, so-called continuous long fibers having a fiber length of 150 mm or more are preferred since a non-woven material from long fibers having high tensile strength can be obtained. The upper limit of fiber length for “long fibers” is not particularly limited. "Non-woven material from long fibers", as a rule, refers to a non-woven material, including a collection of fibers in which long fibers are bonded at intervals by means of parts bonded by fusion. Examples of such nonwoven fabric from long fibers include a single layer nonwoven fabric such as spunbond nonwoven fabric and meltblown nonwoven fabric, multilayer nonwoven fabric in which spunbond layers or meltblown layers mainly formed by long fibers, for example, superimposed on one another, and non-woven material bonded by means of heated rollers and formed by carding. Examples of the multilayer nonwoven fabric include a multilayer nonwoven fabric with an SS structure (spunbond layer (S) - spunbond layer (S)), a multilayer nonwoven fabric with an SSf structure (spunbond layer (S) - spunbond layer (S) - spunbond layer (S)) multilayer nonwoven fabric with SMS structure (spunbond layer (S) - layer (M) obtained from the melt aerodynamically, spunbond layer (S)) and nonwoven fabric with SMMS structure (spunbond layer (S) - layer (M), obtained by the aerodynamic method from the melt, the layer (M) obtained by the aerodynamic method from the melt, the spunbond layer (S)).

[0030]

The method of manufacturing a multilayer nonwoven material according to the present invention, described later, includes the step of producing a multilayer element by moving a hydrophobic base nonwoven material, which at the end should become the first layer 11, and by deposition of fibers obtained by forming fibers from resin, (fibers which at the end must become hydrophilic fibers 15) on a relocatable base nonwoven material. In a multilayer nonwoven fabric 10 made by a manufacturing method that uses such direct fiber spinning technology, the first layer 11 may be either short fiber nonwoven fabric or long fiber nonwoven fabric, but a second layer 12 including fibers obtained direct spinning of the fibers (hydrophilic fibers 15), is a nonwoven fabric of long fibers. Generally, a nonwoven fabric of long fibers is more durable than a nonwoven fabric of short fibers.

[0031]

Another main feature of the multilayer nonwoven material 10 is the inclusion of two types of "thin fused parts", which are thinner than other peripheral parts, and in which the constituent fibers are fused with each other. That is, the multilayer structure 13 includes interlayer fused parts 16 that are thinner than the peripheral parts, and in which the layers forming the multilayer structure 13 are fused to each other. In addition to the interlayer fused parts 16, the first layer 11 forming the multilayer structure 13 further includes interfiber fused parts 17, which are thinner than the peripheral parts, and in which the constituent fibers of the first layer 11 are fused to each other. In the interlayer fused portions 16, the fiber components of the layers forming the multilayer structure 13 (i.e., the first layer 11 and the second layer 12 in the illustrated example) are bonded to each other by a fusion method, and these layers are joined together by a fusion method. In the multilayer structure 13 having such a structure, the interlayer fused portions 16 are formed with the same configuration on both the first surface 10a and the second surface 10b. On the first surface 10a, the interfiber fused parts 17 formed only in the first layer 11 are formed with a given configuration. Thin fused parts have a density higher than the density in other peripheral parts.

[0032]

The interlayer fused parts 16 and the interfiber fused parts 17 are sealed parts, wherein the constituent fibers in these parts are sealed in the thickness direction, and this compaction is generally performed by embossing with a melt aid and designed to accelerate the melting of thermoplastic fibers as constituent fibers, such as heat or ultrasonic waves, and are performed, in particular, for example by heat welding or ultrasonic welding. When considering such a manufacturing method, the interlayer fused parts 16 and the interfiber fused parts 17 can also be called, for example, embossed parts or compressed parts.

[0033]

In the multilayer nonwoven material 10, the interlayer fused parts 16 are formed by squeezing the precursor material of the multilayer structure 13 (a multilayer element from the first layer 11 as the base nonwoven material and the deposited layer of hydrophilic fibers 15) from the side of the second surface 10b towards the first surface 10a. With this method of formation, the interlayer fused parts 16 are pressed in from the side of the second surface 10b towards the first surface 10a, as illustrated in FIG. The interfiber fused portions 17 are formed by squeezing the precursor material of the first layer 11 (the canvas in the form of a deposited layer of hydrophobic fibers 14) from the side of the first surface 10a towards the second surface 10b. With this method of formation, the interfiber fused portions 17 are depressed from the side of the first surface 10a towards the second surface 10b, as illustrated in FIG. In the multilayer nonwoven material 10, a plurality of interlayer fused portions 16 are dispersed on each of the first surface 10a and the second surface 10b. Many interfiber fused parts 17 are dispersed on the first surface 10a. In the multilayer nonwoven material 10, each of the first surface 10a and the second surface 10b is not a flat surface without essentially any unevenness (recesses and protrusions), and is an uneven surface having recesses and protrusions.

[0034]

As described above, in the case where one or both of the first surface 10a and the second surface 10b of the multilayer nonwoven fabric 10 has an unevenness, when using the multilayer nonwoven fabric 10 for a component (for example, as a top sheet or absorbent sheet) in an absorbent article that can come into contact with the skin of the user when the multilayer nonwoven fabric 10 is positioned so that an uneven surface is in contact with the skin of the user, a gap is formed between the multilayer nonwoven material 10 and the skin of the user, so that moisture is generated from the body’s fluid, such as sweat and urine can be effectively diffused through this gap. Thus, the dryness of the surface of the multilayer nonwoven material 10 can be increased, which can lead to increased wearing comfort of the absorbent product.

[0035]

Figure 2 illustrates an example configuration (shape and layout in plan view) of the interlayer alloyed parts 16. On the first surface 10a or the second surface 10b, the configuration of the interlayer alloyed parts 16 is not limited to the example illustrated in figure 2, and the desired configuration can be used within the scope of the present invention.

FIGS. 2 (a) –2 (e) illustrate configurations, in each of which a plurality of interlayer fused parts 16 having a predetermined shape in a plan view are dispersed in a direction along the surface (a direction orthogonal to the thickness direction of the multilayer nonwoven material 10). The shape of the interlayer fused parts 16 in a plan view is an oval in FIG. 2 (a) and 2 (b), a circle in FIG. 2 (c), a rectangle or rhombus in FIG. 2 (d), and a cross in FIG. 2 (e). In FIG. 2 (a), the directions of the major axes of the plurality of interlayer fused parts 16 that are oval in plan view coincide with each other, while in FIG. 2 (b) the plurality of types of interlayer fused parts 16 that are oval in plan view, dispersed so that the directions of their major axes are oriented in different directions. Figure 2 (f) –2 (h) illustrates configurations, in each of which the interlayer fused portions 16, which are straight in plan view, extend in predetermined directions. In FIG. 2 (f), a plurality of continuous rectilinear interlayer fused parts 16 intersect each other so that the interlayer fused parts 16 form a generally lattice configuration. FIG. 2 (g) is a variant of the lattice configuration of FIG. 2 (f), in which the continuous rectilinear configuration of the interlayer alloyed parts 16 is replaced by a discontinuous rectilinear configuration, in particular, a configuration in which discontinuous lines (gaps with lines) are used , on each of which relatively short rectilinear interlayer fused parts 16 are located at intervals in a given direction. Figure 2 (h) is another example of a configuration of discontinuous rectilinear interlayer fused parts 16 of figure 2 (g), in particular, an example in which the interlayer fused parts 16 are arranged in the form of honeycombs.

[0036]

FIG. 3 illustrates examples of configurations of interfiber fused parts 17. On the first surface 10a, the configuration of interfiber fused parts 17 is not limited to the example illustrated in FIG. 3, and any desired configuration can be used within the spirit of the present invention.

FIGS. 3 (a) –3 (e) illustrate configurations, in each of which a plurality of inter-fiber fused parts 17 having a predetermined shape in a plan view are dispersed in a direction along the surface. The shape of the inter-fiber fused parts 17 in a plan view is an oval (long oval) in FIGS. 3 (a) and 3 (d), a circle in FIG. 3 (b), a rectangle or rhombus in FIG. 3 (c), and a cross figure 3 (e). In FIG. 3 (a), the directions of the major axes of the plurality of interfiber fused parts 17, which are oval in plan view, coincide with each other, while in FIG. 3 (d), the plurality of types of interfiber fused parts 17 that are oval in plan view, dispersed so that the directions of their major axes are oriented in different directions. In the configurations with distributed “points” illustrated in FIGS. 3 (a) –3 (e), the shapes of the interfiber fused parts 17 in a plan view can be, for example, triangles, polygons having five or more vertices, and stars in addition to the illustrated forms. 3 (f) –3 (h) illustrate configurations in each of which the interfiber fused parts 17, which are straight in plan view, extend in predetermined directions. In FIG. 3 (f), a plurality of continuous straight-line interfiber fused parts 17 intersect each other so that the interfiber fused parts 17 form a generally lattice configuration. FIG. 3 (g) is a variant of the lattice configuration of FIG. 3 (f), in which the continuous rectilinear configuration of the interfiber fused portions 17 is replaced by a discontinuous rectilinear configuration, in particular, a configuration in which discontinuous lines (gaps with lines) are used , on each of which relatively short straight-line interfiber fused parts 17 are located at intervals in a given direction. FIG. 3 (h) is another example of a configuration of discontinuous straight-line interfiber fused parts 17 of FIG. 3 (g), in particular an example in which interfiber fused parts 17, each of which has a hexagonal shape in plan view, are arranged that they partially overlap each other.

[0037]

Figure 4 illustrates examples of configurations of the interlayer fused parts 16 and the interfiber fused parts 17 on the first surface 10a of the multilayer nonwoven material 10, which is the surface on which the fused parts 16 and 17 of both types are formed. The configurations of the fused portions 16 and 17 on the first surface 10a are not limited to the configurations illustrated in FIG. 4, and any desired configuration can be used within the spirit of the present invention.

Figure 4 (a) illustrates a combination of the configuration of the interlayer fused parts 16 in the form of distributed points in figure 2 (a) and the configuration of the interlayer fused parts 17 in the form of distributed points in figure 3 (a). Figure 4 (b) illustrates a combination of the configuration of the interlayer fused parts 16 in the form of distributed points in figure 2 (c) and the configuration of the intermittent straight-line interfiber fused parts 17, which are arranged in a plurality of configurations in the form of honeycombs (not shown). FIG. 4 (c) illustrates a combination of the configuration of the interlayer fused parts 16 in the form of distributed points in FIG. 2 (c) and the configuration of the straight-line interfiber fused parts 17 in FIG. 3 (f). FIG. 4 (d) illustrates a combination of the configuration of the interlayer fused parts 16 as distributed points in FIG. 2 (d) and the configuration of the interfiber fused parts 17 as distributed points in FIG. 3 (c).

[0038]

In addition to the features described above, the multilayer nonwoven material 10 has a feature according to which in the case where the fractions of the total area of the interlayer fused parts 16 and the interfiber fused parts 17 with respect to the areas of the first surface 10a and the second surface 10b are respectively determined as the fractions of the areas of the fused parts of the first the surface 10a and the second surface 10b, in particular in the case where the fraction of the total area of the interlayer fused parts 16 and the interfiber fused parts 17 of the first surface 10a relative to the area of the first surface 10a is defined as the fraction of the area of the fused parts of the first surface 10a and the share of the total area of the interlayer fused parts 16 and interfiber fused parts 17 of the second surface 10b relative to the area of the second surface 10b is defined as the fraction of the area of the fused parts of the second surface 10b, the fraction of the area of the fused parts of the first surface 10a exceeds the area of the fused parts of the second surface 10 b (i.e., the relationship is established: the area ratio of the alloyed parts of the first surface 10a> the area ratio of the alloyed parts of the second surface 10b).

[0039]

Since in the multilayer nonwoven fabric 10 having the feature described above, the first layer 11 forming the first surface 10a includes hydrophobic fibers 14 and is hydrophobic, the first surface 10a essentially absorbs the body fluid, such as sweat and urine (aqueous fluid). However, the peripheral portions of the interlayer fused parts 16 and the interfiber fused parts 17 and their surroundings on the first surface 10a are important parts that serve as fluid retracting parts when absorbing fluid from the first surface 10a. That is, in the interlayer fused parts 16 of the first surface 10a and in their peripheral areas, not only hydrophobic fibers 14, but also hydrophilic fibers 15 of the second layer 12, which is a layer adjacent to the first layer 11, and has a higher degree of hydrophilicity, located relatively densely, and therefore the degree of hydrophilicity is higher (the contact angle measured by the above method is less) than in the remaining parts of the first surface 10a. Accordingly, the fluid secreted by the body can adhere mainly to the interlayer fused portions 16 and portions peripheral to them on the first surface 10a. Furthermore, as described above, the multilayer structure 13 has a gradient of the degree of hydrophilicity in the thickness direction Z in which "the degree of hydrophilicity is relatively higher on the side closer to the second surface 10b than on the side closer to the first surface 10a", and therefore, the multilayer nonwoven material 10 has a high ability to absorb liquid from the first surface 10a inward in the thickness direction Z and has a large capillary force. Accordingly, the fluid secreted by the body adhering to the interlayer fused parts 16 and the parts peripheral to them on the first surface 10a is quickly drawn into the multilayer nonwoven material 10 mainly through the peripheral sections of the interlayer fused parts 16 and their surroundings and is absorbed inward in the direction Z of the thickness and is held inside the hydrophilic second layer 12 while simultaneously diffusing in the direction along the surface (direction orthogonal to the direction Z of thickness) of the multilayer nonwoven material 10. On the first surface 10a, the portions into which the liquid is drawn are basically “peripheral portions” interlayer fused parts 16 and their surroundings. " As a rule, even if the shape of the interlayer fused parts 16 changes to the shape of the film due to the fact that the constituent fibers lose their shape in the central sections of the interlayer fused parts 16, the sections of the interlayer fused parts 16 except for the central sections, that is, the peripheral sections of the interlayer fused parts 16 and their surroundings (i.e., the parts around the interlayer fused parts 16) do not change to the shape of the film, and the shape of the fibers is maintained. Thus, the peripheral portions of the interlayer fused parts 16 and their surroundings serve as fluid retracting parts on the second surface 10b.

[0040]

For reasons related to the additional functioning of the peripheral sections of the interfiber fused parts 17 and their environs as parts that absorb liquids on the first surface 10a, the thickness of the interfiber fused parts 17 is preferably less than the thickness of the part of the first layer 11 except for the fused parts (interlayer fused parts 16 and interfiber fused parts 17). According to the data obtained by the authors of the present invention, since the interfiber fused parts 17 are thinner than the other parts of the first layer 11, despite the fact that the first layer 11 (first surface 10a) is hydrophobic (hydrophobic), peripheral sections can be further operated interfiber fused parts 17 and their environs as parts that absorb liquids. For reasons related to further providing this advantage, the thickness of the interfiber fused parts 17 is preferably 1/3 or less and more preferably 1/4 or less and preferably 1/30 or more and more preferably 1/20 or more of the thickness of the parts of the first layer 11 except fused parts (interlayer fused parts 16 and interfiber fused parts 17).

[0041]

For reasons related to an additional improvement in the ability to absorb liquids due to the gradient of the degree of hydrophilicity, and taking into account the initial condition that the contact angle of the component fibers (hydrophobic fibers 14) of the first layer 11 is greater than the contact angle of the component fibers (hydrophilic fibers 15) the second layer 12, the contact angle of the constituent fibers (hydrophobic fibers 14) of the first layer 11 is preferably 95 degrees or more and more preferably 100 degrees or more and preferably 150 degrees or less and more preferably 130 degrees or less. Given the initial condition that the contact angle of the constituent fibers (hydrophilic fibers 15) of the second layer 12 is less than the contact angle of the constituent fibers (hydrophobic fibers 14) of the first layer 11, the contact angle of the constituent fibers (hydrophilic fibers 15) of the second layer 12 is preferably 15 degrees or more and more preferably 20 degrees or more and preferably 88 degrees or less and more preferably 85 degrees or less. The degree of hydrophilicity of the constituent fibers can be adjusted by appropriately adjusting the degree of processing of thermoplastic fibers, which are the main constituent fibers of the multilayer nonwoven material 10, to give them hydrophilicity, in particular, for example, the type and / or content of the hydrophilicity improver.

[0042]

As described above, the interlayer fused portions 16 are important portions, the peripheral portions of which and their surroundings are fluid absorbent portions when absorbing fluid from the hydrophobic first surface 10a. However, since in the interlayer fused portions 16, the hydrophobic first layer 11 and the hydrophilic second layer 12 are joined together by squeezing the multilayer nonwoven material 10 in the thickness direction after absorption of the liquid (for example, when the multilayer nonwoven material 10 is used as a component of the absorbent article when it is the first surface 10a facing the skin of the user, and pressure from the side of the user's body is applied to the multilayer nonwoven material 10), the so-called passage of fluid in the opposite direction could occur, in particular, the liquid absorbed and retained in the second layer 12 could return to the first surface 10a through the peripheral sections of the interlayer fused parts 16 and their surroundings. However, the first layer 11 includes interfiber fused parts 17 in which only the constituent fibers (hydrophobic fibers 14) of the first layer 11 are fused to each other, in addition to the interlayer fused parts 16, and therefore, the passage of fluid in the opposite direction to the first surface can be effectively reduced. 10a. That is, unlike the interlayer fused parts 16, the interfiber fused parts 17 are formed only in the hydrophobic first layer 11 and are not fused with the hydrophilic second layer 12. Accordingly, the likelihood that the liquid once absorbed in the hydrophilic second layer 12 is reduced is returned from the peripheral sections of the interfiber fused parts 17 and their environs, and the interfiber fused parts 17 may have the function of preventing the flow of fluid in the opposite direction.

[0043]

To further provide an advantage (to achieve both the ability to absorb liquids and prevent the liquid from flowing in the opposite direction), the ratio of the area fraction of the fused parts of the first surface 10a (first value) to the area fraction of the fused parts of the second surface 10b (last value) (i.e. the ratio of the share the area of the fused parts of the first surface 10a to the fraction of the area of the fused parts of the second surface 10b), i.e. the first value / last value, is preferably 1.3 or more and more preferably 1.4 or more and preferably 3.0 or less and more preferably 2 5 or less. If this ratio is excessively small, it is not easy to prevent the fluid from flowing in the opposite direction, while if this ratio is excessively large, the comfort of the first skin surface 10a may deteriorate.

[0044]

The first surface 10a includes both interlayer fused parts 16 and interfiber fused parts 17, and these fused parts 16 and 17 may have the same configuration. Alternatively, for reasons related to providing more of the benefits described above, the fused portions 16 and 17 preferably have different configurations. More specifically, the interlayer fused parts 16 and the interfiber fused parts 17 preferably differ in at least two of the characteristics representing the arrangement, the shape of each fused part in the plane, the area of each fused part, the distance D16 and D17 between the fused parts (minimum the distance between the fused parts) (see figure 1) and steps P16 and P17 (see figure 1). In this case, each of the distances D16 and D17 between the fused parts refers to the distance between adjacent two fused parts (two of the interlayer fused parts 16 or the interfiber fused parts 17) in the direction along the surface of the multilayer nonwoven material 10. Each of steps P16 and P17 refers to the distance between the data centers of the two fused parts in a plan view.

[0045]

Both the interlayer fused parts 16 and the interfiber fused parts 17 are high density fused parts in which the constituent fibers are fused to each other with a density higher than in the peripheral parts and under certain conditions of compression and heating during their formation, for example, the fiber shape of thermoplastic fibers as constituent fibers can be lost and changed to a film shape. For reasons related to providing to a greater extent the advantages described above, the shape of at least the interlayer fused portions 16 is preferably at least partially changed to the shape of the film. On the other hand, the shape of the inter-fiber fused portions 17 may or may not change to the shape of the film. As described above, to obtain a thickness of the interfiber fused parts 17 smaller than the thickness of the other parts (preferably 1/3 or less of the thickness of the other parts) of the first layer 11, the shape of the interfiber fused parts 17 is preferably changed to the shape of the film. In particular, for example, the shape of both the interfiber fused parts 17 and the interlayer fused parts 16 is preferably at least partially changed to the shape of the film. Since the shape of the interlayer fused parts 16 is changed to a film shape, the degree of hydrophilicity of the interlayer fused parts 16 is higher (the contact angle measured by the above method is less important) than in the remaining parts of the first surface 10a, and the body emits the fluid, it can preferably stick mainly to the interlayer fused parts 16 and parts peripheral to them. In addition, since the shape of the interfiber fused parts 17 is changed to a film shape, the surface of the interfiber fused parts 17 in the form of a film, forming a part of the first surface 10a, is smooth, and despite the fact that the interfiber fused parts 17 are fused parts of hydrophobic fibers 14, the interfiber fused portions 17 preferably have a high adhesive adhesion to a liquid. The fiber shapes of the constituent fibers in the fused portions 16 and 17 depend mainly on the embossing mode during the formation of the fused portions 16 and 17. If the heat and compression during embossing are relatively strong, the fiber shape of the constituent fibers can easily turn into a film form.

[0046]

As described above, the peripheral portions of the interlayer fused portions 16 and their surroundings and the peripheral portions of the interfiber fused portions 17 and their surroundings serve as fluid retracting parts when absorbing fluid from the first surface 10a, and the likelihood of a fluid flow in the opposite direction is reduced, in particular in the interfiber fused parts 17. Thus, for reasons of increasing the dryness of the multilayer nonwoven material 10, the first surface 10a preferably has a dispersion zone of the interfiber fused parts in which a plurality of interfiber fused parts 17 are dispersed along the surface. In particular, in the case where the multilayer nonwoven material 10 is used as a sweat-absorbing sheet capable of absorbing sweat, with the first surface 10a facing the skin, the first surface 10a preferably has a dispersion zone of interfiber fused parts, which provides better sweat absorption ability and the possibility of further increasing the dryness of the first surface 10a, which is in contact with the skin. The entire area of the first surface 10a may be a dispersion zone of the interfiber fused parts, or only part of the first surface 10a may be a dispersion zone of the interfiber fused parts. The fraction of the area of the dispersion zone of the interfiber fused parts of the entire area of the first surface 10a is preferably 70% or more, and more preferably 80% or more.

[0047]

Regarding the arrangement of the interfiber fused parts 17 in the dispersion zone of the interfiber fused parts, in the case where a virtual circle with a radius of 2 mm is located anywhere in the dispersion zone of the interfiber fused parts, which is the area of the first surface 10a, at least a part one of the interfiber fused parts 17 or all of at least one of the interfiber fused parts 17 is preferably enclosed in this virtual circle. In this case, the expression "in the case where a virtual circle with a radius of 2 mm is located anywhere in the dispersion zone of the interfiber fused parts, which is the area of the first surface 10a, part of at least one of the interfiber fused parts 17 or all, at least at least one of the interfiber fused parts 17 is enclosed in this virtual circle "means that" in the case where 10 virtual circles are located in the dispersion zone of the interfiber fused parts, which is the area of the first surface 10a, the interfiber fused parts 17 may not be included at all "In one or two of ten virtual circles, and it is enough that a part of the interfiber fused parts 17 or the interfiber fused parts 17 as a whole be enclosed in at least one of the remaining eight virtual circles." Virtual circles are “based” on the assumption that the sweat-generating parts (sweat glands) are distributed over the surface of the skin of the human body, and the structure described above allows the multilayer nonwoven fabric 10 to more effectively absorb sweat. In particular, greater efficiency is achieved when the inter-fiber fused parts 17 satisfy the above condition with a radius of the virtual circle set to 1.5 mm.

[0048]

Both the peripheral portions of the interlayer fused portions 16 and their surroundings, and the peripheral portions of the interfiber fused portions 17 and their surroundings are liquid-drawing portions of the first surface 10a. Therefore, in order to ensure the absorption capacity of liquids that is sufficient in practice, a certain number of alloyed parts 16 and 17 of both types is necessary, that is, the periphery of the interlayer alloyed parts 16 and the interfiber alloyed parts 17 must have predetermined or longer lengths. However, an excessively large area of the interlayer alloyed parts 16 themselves on the first surface 10a can lead to a decrease in the amount of liquid that can be absorbed and can be retained in the first layer 11, since not only the hydrophobic second layer 12, but also the hydrophilic first layer 11 are fused together in interlayer fused parts 16. For these reasons, the fraction of the total area of the interlayer fused parts 16 (the total area of the plurality of interlayer fused parts 16 in the case where the first surface 10a has a plurality of interlayer fused parts 16) of the area of the first surface 10a, i.e., the fraction of the area of the interlayer fused parts 16 is preferably 15% or less and more preferably 12% or less. The lower limit of this fraction is preferably 5% or more, and more preferably 6% or more.

[0049]

The interlayer fused parts 16 are continuous over the entire length of the multilayer structure 13 (multilayer nonwoven material 10) in the thickness direction Z, and the configuration (shape and arrangement in plan view) of the interlayer fused parts 16 is substantially the same on the first surface 10a and the second surface 10b. Thus, the description of the configuration of the interlayer alloyed parts 16 of the first surface 10a in this document (for example, the dispersion zones of the interlayer alloyed parts and the area fraction of the interlayer alloyed parts 16) is also applicable to the second surface 10b, unless otherwise indicated.

[0050]

The pitch of the interfiber fused parts 17 is preferably shorter than the pitch of the interlayer fused parts 16. That is, as shown in FIG. 1, the ratio “pitch P17 of the interfiber fused parts 17 <pitch P16 of the interlayer fused parts 16” is preferably set. With this configuration, sweat can be absorbed from the point in time when the amount of sweat is small at the beginning of perspiration, and the second layer 12 has a large absorption capacity. Thus, the advantage described above can be more guaranteed (ensuring both the ability to absorb liquids and prevent the passage of liquid in the opposite direction).

[0051]

For similar reasons, the distance between the fused parts (the minimum distance between the fused parts) in the case of the interfiber fused parts 17 is preferably shorter than the distance between the interlayer fused parts 16. That is, as shown in FIG. 1, the ratio: “distance D17 between the fused parts, representing the interfiber fused parts 17, <the distance D16 between the fused parts, representing the interlayer fused parts 16 ". This configuration with such a distance between the fused parts is especially effective when each of the plurality of interlayer fused parts 16 and the plurality of interfiber fused parts 17 is distributed as dots in a plan view, for example, with the configurations illustrated in FIG. 2 (a) –2 (e) for interlayer fused parts 16, and the configurations illustrated in FIGS. 3 (a) –3 (e) for interfiber fused parts 17.

[0052]

Similarly, for reasons related to providing both the ability to absorb liquids and to prevent the passage of liquid in the opposite direction, the area of one interfiber fused portion 17 on the first surface 10a is preferably 0.3 mm ² or less, and preferably less than the area of one interlayer fused parts 16 on the second surface 10b. The area of one interfiber fused part 17 on the first surface 10a is preferably 0.25 mm ² or less, and the lower limit of the area of one interfiber fused part 17 is preferably 0.1 mm ² or more, and more preferably 0.15 mm ² or more. The ratio of the area of one interfiber fused part 17 on the first surface 10a (of the first value) to the area of one interlayer fused part 16 on the second surface 10b (last value) (i.e. the ratio of the area of one interfiber fused part 17 on the first surface 10a to the area of one interlayer fused part 16 on the second surface 10b), i.e., the first value / last value, is preferably 0.25 or more and more preferably 0.3 or more and preferably 0.8 or less and more preferably 0.75 or less. This configuration is particularly effective in cases where each set of a plurality of interlayer fused parts 16 and a plurality of interfiber fused parts 17 is distributed as dots in a plan view, for example, with the configurations illustrated in FIGS. 2 (a) - FIG. 2 (e ) for the interlayer fused parts 16, and the configurations illustrated in FIGS. 3 (a) –3 (e) for the interfiber fused parts 17.

[0053]

The surface density of the first layer 11 and the surface density of the second layer 12 are not limited to specific values and can be adjusted accordingly, for example, depending on the use of the multilayer nonwoven material 10. For example, in the case where the multilayer nonwoven material 10 is used as a component (for example, the top sheet or the absorbent sheet) of the absorbent article, such as a disposable diaper or sanitary napkin, for reasons related to preventing bulk while providing sufficient strength in practice, the total surface density of the first layer 11 and second layer 12 is preferably 13 g / m ² or more and more preferably 15 g / m ² or more and preferably 38 g / m ² or less and more preferably 35 g / m ² or less.

[0054]

The hydrophobic first layer 11 is typically first in contact with the liquid when a multilayer nonwoven material 10 is used to absorb liquid. If, in this case, the first layer 11 has a relatively low surface density and a relatively small thickness, the first layer 11 helps to absorb liquid through the interlayer fused parts 16 and parts peripheral to them on the first surface 10a. On the other hand, an excessively low surface density of the first layer 11 can lead to a decrease in strength and the occurrence of fluid flow in the opposite direction. In view of the foregoing, the surface density of the first layer 11 is preferably 8 g / m ² or more and more preferably 9 g / m ² or more and preferably 18 g / m ² or less and more preferably 17 g / m ² or less.

[0055]

The hydrophilic second layer 12 affects the ability of the interlayer fused parts 16 and parts peripheral to them on the first surface 10a of the first layer 11 to absorb liquid when the hydrophobic first layer 11 (first surface 10a) is in first contact with liquid to be absorbed. Typically, as the surface density of the second layer 12 increases, the absorbency increases and the strength also increases. On the other hand, if the surface density of the second layer 12 is excessively large, bulkiness occurs or stiffness increases. Therefore, if a multilayer nonwoven material 10 is used as a component of an absorbent article, wearing comfort may be impaired. In view of the foregoing, the surface density of the second layer 12 is preferably 5 g / m ² or more and more preferably 7 g / m ² or more and preferably 20 g / m ² or less and more preferably 18 g / m ² or less. If the second layer 12 has a surface density of only about 5 g / m ² , the strength of the second layer 12 is substantially insufficient, and there would be a risk of difficulties in the manufacture of the multilayer nonwoven material 10. On the other hand, in the method of manufacturing the multilayer nonwoven of the material according to the present invention described later, the second layer 12 is obtained by the technology of the so-called direct spinning of fibers, and therefore this risk can be eliminated.

[0056]

As described above, different types of fibrous layers can be used as the first layer 11 and the second layer 12. For reasons related to additionally providing the advantages described above in the case of liquid absorption, such as the case of using a multilayer nonwoven material 10 as a component of the absorbent article, it is particularly preferred if the hydrophilic second layer 12 is a layer of fibers obtained by aerodynamic method from a melt, into which a means for giving hydrophilicity is interfered, a layer of fibers obtained by a spunbond method, into which a means for giving hydrophilicity is interfered, or a multilayer fibrous " layer "(non-woven material) with the SMS structure, which includes fibers into which the means for imparting hydrophilicity is interfered.

[0057]

On the other hand, for reasons related to the separation of the liquid once soaked in the hydrophilic second layer 12 from the skin, the hydrophobic first layer 11 is preferably a spunbond nonwoven fabric, a nonwoven fabric bonded by passing air through and through, a nonwoven fabric obtained from a melt aerodynamically , or a multilayer non-woven material consisting of the above non-woven materials (for example, non-woven material with an SMS structure).

[0058]

Hydrophilic fibers 15 as the main constituent fibers of the second layer 12 are typically obtained by performing processing to impart hydrophilicity to inherently hydrophobic, thermoplastic fibers. That is, the second layer 12 is an accumulation of hydrophobic fibers (for example, thermoplastic fibers suitable as constituent fibers of the first layer 11) subjected to hydrophilicity. As described above, this hydrophilicity treatment can be a plasma treatment, as well as applying a hydrophilicity agent to the fibers or a cluster of fibers and intervening the hydrophilicity agent in the fibers, and the method of forming the fibers by interfering with the hydrophilicity agent in the fibers is suitable for a method of manufacturing a multilayer nonwoven material according to the present invention, described later.

[0059]

Another example of the second layer 12 is a hydrophilic nonwoven material including fibers into which a hydrophilicity enhancing agent is interfered. In the second layer 12 in this embodiment, the hydrophilicity enhancer is not attached to the surfaces of the hydrophilic fibers 15 as the main constituent fibers, but is included in the hydrophilic fibers 15. The second layer 12, one surface of which is coated with a hydrophilicity improver, has a gradient of the degree of hydrophilicity in the Z direction thickness, as described above, while the second layer 12 in the embodiment in which the hydrophilicity agent is interfered with the constituent fibers does not have a gradient of the degree of hydrophilicity in the Z direction of the thickness, taking into account the initial assumption that the constituent fibers of this layer evenly distributed throughout the second layer 12, and the degree of hydrophilicity is the same.

[0060]

Another example of the second layer 12 is a variant in which the side of the second layer 12, closer to the second surface 10b, is coated with a hydrophilicity agent. The method of applying the hydrophilicity enhancing agent is not limited to a specific method, and, depending on the circumstances, a known method may be used to enable the application of a coating liquid including a hydrophilicity enhancing agent. Examples of suitable coating methods preferably include coating using an engraved cylinder, contact coating, stencil coating, spray coating, reverse roller coating and extrusion coating, and among these coating methods, coating is particularly preferred using an engraved cylinder, flexographic coating and coating using an extrusion head, which enable coating on a side closer to the second surface 10b. The various types of surfactants and the like used to impart hydrophilicity to the components of absorbent articles, such as disposable diapers, can be used as hydrophilicity agents without any particular limitation.

[0061]

The ability of the multilayer nonwoven material 10 to absorb liquids is more or less affected by the density gradient of the fibers in the thickness direction. Thus, in the case where the hydrophobic first layer 11 (first surface 10a) is a layer that first contacts the liquid to be absorbed (the layer into which the liquid is drawn), to increase the ability of the multilayer nonwoven material 10 to absorb liquids, the first layer 11 (first surface 10a) preferably has a small thickness and low fiber density (long interfiber distance). That is, the first layer 11 has a relatively low fiber density (long interfiber distance), while the layer adjacent to the first layer 11 (second layer 12 in the illustrated example) has a large capillary strength and therefore can absorb water through the hydrophobic layer. For this reason, the layer adjacent to the first layer 11 preferably has a high fiber density (short interfiber distance). In the interlayer fused parts 16 and parts peripheral with respect to them, when viewed from the side of the first surface 10a, the hydrophilic fibers 15 of the second layer 12 having a relatively high fiber density (short interfiber distance) are easily opened for exposure between the hydrophobic fibers 14 of the first layer 11 (first surface 10a) having a relatively low fiber density (long interfiber distance), and therefore, the liquid is quickly drawn inward from the peripheral portions of the interlayer fused parts 16 and their environs on the first surface 10a and is absorbed and held in the hydrophilic second layer 12 more stably. For these reasons, the second layer 12 preferably has a fiber density higher than the fiber density of the first layer 11, that is, it preferably has a shorter interfiber distance between the constituent fibers than the first layer 11. The interfiber distance is measured by the following method.

[0062]

<Method for measuring the interfiber distance>

The interfiber distance for the accumulation of fibers, such as non-woven material or paper, is obtained by the following Equation (1), based on the assumption of Wrotnowski. Equation (1) is typically used to obtain the distance between fibers from a cluster of fibers. By hypothesis, Wrotnowski fibers are cylindrical and regularly spaced without crossing.

In the case where the sheet of the measurement object (the first layer 11 and the second layer 12) has a single layer structure, the interfiber distance for the sheet having a single layer structure can be obtained by Equation (1).

In the case where the sheet of the measurement object (the first layer 11 and the second layer 12) has a multilayer structure, as in the case of a nonwoven material with an SMS structure, the interfiber distance for a sheet having a multilayer structure can be obtained in accordance with the following procedure.

First, the interfiber distance for each of the fibrous layers forming the multilayer structure is calculated from the following Equation (1). In this calculation, the thicknesses t, the surface density W, the density ρ of the resin fibers and the fiber diameter D used in Equation (1) use the values used for the layers of the measurement object. Each parameter of thickness t, surface density W, and fiber diameter D is an average of values measured at a plurality of measurement locations.

The thickness t (mm) is measured as follows. First, a piece with the following dimensions —50 mm in the longitudinal direction × 50 mm in the width direction is cut out from the sheet being the object of measurement, whereby a cut piece of sheet is obtained. In the case when a cut-out piece of a given size cannot be obtained as a sheet of an object of measurement, for example, in the case when a sheet is taken from an absorbent article of a small size, a cut-out piece is obtained, which is as large as possible. After that, the cut piece is placed on the flat plate, then the flat glass plate is placed on the flat plate, and the load is evenly placed on the glass plate so that the load, including the glass plate, is 49 Pa, and the thickness of the cut piece is measured. In the measurement medium, the temperature is 20 ± 2 ° C and the relative humidity is 65 ± 5%, and the measurement equipment is a microscope (VHX-1000, manufactured by KEYENCE CORPORATION). To measure the thickness of the cut piece, an enlarged photograph of the cutting plane of the cut piece is first obtained. An enlarged photograph also includes an object having known dimensions. Next, the scale bar is aligned with the enlarged photograph of the cutting plane of the cut piece, and the thickness of the cut piece, that is, the thickness of the sheet as an object of measurement, is measured. The above process is repeated three times, and the average value for the three processes is used as the thickness t of the sheet as an object of measurement. In the case where the sheet as an object of measurement is a multilayer product, the boundaries between the layers are determined based on the difference in fiber diameter and the thickness is calculated.

The surface density W (g / m ² ) is obtained by cutting out the sheet as an object of measurement with a given size (for example, 12 cm × 6 cm) and - after measuring the mass - dividing the measured mass by the area obtained from the given size ("surface density W ( g / m ² ) = mass ÷ area obtained by a given size ”). The measurement is performed four times, and the average value is used as the surface density.

The density ρ (g / cm ³ ) of the resin fibers is determined based on the measurement method, which is a density gradient gradient pipe measurement method described in JIS L1015 Test Method for Artificial Staple Fibers ( JIS - Japanese Industrial Standard ) using a gradient pipe for density determination (URL: http://kikakurui.com/l/L1015–2010–01.html, JIS Handbook Fiber 2000, Japanese Standards Association, pp. 764–765).

The fiber diameter D (μm) is obtained in this way: the fiber cross-section for ten of the cut fibers is measured using an S-4000 field emission scanning electron microscope manufactured by Hitachi, Ltd., and the average value is used as the fiber diameter. The fiber diameter D is measured in accordance with the <Fiber Diameter Measurement Method> described later.

After that, the interfiber distance for each layer is multiplied by the fraction of the thickness of this layer in the total thickness of the multilayer structure, and the sum of the values obtained in this way for the layers is obtained. Accordingly, an inter-fiber distance is obtained for the constituent fibers of a given sheet having a multilayer structure. For example, in a nonwoven fabric with an SMS structure, which is a three-layer structure formed by two layers S and layer M, two layers S are used as one layer, and if the total thickness t of the three-layer structure is 0.11 mm, the thickness t of the layers S is 0, 1 mm, the interfiber distance LS for layers S is 47.8 μm, the thickness t of layer M is 0.01 mm, and the interfiber distance LS for layer M is 3.2 μm, the distance between the fibers representing the constituent fibers of a nonwoven material with a structure SMS is 43.8 μm [= (47.9 × 0.1 + 3.2 × 0.01) / 0.11].

[0063]

[Equation 1]

… (1)average interfiber distance (μm) =

… (1)

D: fiber diameter (μm)

ρ: resin fiber density (g / cm ³ )

t: thickness (mm)

W: surface density (g / m ² )

[0064]

The ratio of the interfiber distance for the constituent fibers (hydrophobic fibers 14) of the first layer 11 (first value) to the interfiber distance for the constituent fibers (hydrophilic fibers 15) of the second layer 12 (last value) [i.e., the ratio of the interfiber distance for constituent fibers (hydrophobic fibers 14 ) of the first layer 11 to the interfiber distance for the constituent fibers (hydrophilic fibers 15) of the second layer 12], that is, the first value / last value is preferably 1.1 or more and more preferably 10 or more and preferably 70 or less and more preferably 50 or less, given the initial condition that the first value is> the last value, as described above.

The interfiber distance for the constituent fibers (hydrophobic fibers 14) of the first layer 11 is preferably 7 μm or more and more preferably 10 μm or more and preferably 200 μm or less and more preferably 150 μm or less.

The interfiber distance for the constituent fibers (hydrophilic fibers 15) of the second layer 12 is preferably 5 μm or more and more preferably 7 μm or more and preferably 100 μm or less and more preferably 80 μm or less.

[0065]

For reasons related to increasing the ability to absorb liquids by performing a multilayer nonwoven material 10 with a fiber density gradient, in which the fiber density increases from the first layer 11 to the second layer 12 (to the side of the multilayer structure 13 that is internal in the Z direction of the thickness ), as described above, the constituent fibers (hydrophilic fibers 15) of the second layer 12 preferably have a fiber diameter that is smaller than the diameter of the constituent fibers (hydrophobic fibers 14) of the first layer 11. The diameter of the fibers is determined by the following method.

[0066]

<Method for measuring fiber diameter>

The measurement object (fiber layer, multilayer nonwoven material) is cut with a razor (for example, a single-blade razor manufactured by FEATHER SAFETY RAZOR Co., Ltd.), whereby a sample having a rectangular shape in plan view (8 mm × 4 mm) is obtained. The measurement object is cut out carefully so as not to damage the structure of the plane of cutting of the sample formed by cutting, for example, under the influence of pressure during cutting. Examples of preferred methods for cutting the measurement object include a method in which the measurement object is placed in liquid nitrogen to be sufficiently frozen before cutting the measurement object, and then the measurement object is cut. Using double-sided paper tape (NICE TACK NW – 15 manufactured by Nichiban Co., Ltd.), the sample is attached to the sample table. Next, the sample is coated with platinum. When applying the coating, an E – 1030 ion sputtering device (product name) manufactured by Hitachi Naka Seiki Kabushiki Kaisha is used and the sputtering time is 30 seconds. The cross section of the sample is examined using an S-4000 field-emission scanning electron microscope manufactured by Hitachi, Ltd., at 1000 times magnification.

[0067]

In the above-described method for measuring the diameter of the fibers in the case of measuring the diameter of the fibers representing the constituent fibers (hydrophobic fibers 14) of the first layer 11, fibers connected to the interfiber fused parts 17 are selected, while in the case of measuring the diameter of the fibers representing the constituent fibers ( hydrophilic fibers 15) of the second layer 12, select the constituent fibers (hydrophilic fibers 15) of the second layer 12, overlapping the interfiber fused parts 17, and measure the length of 10 fibers in the width direction with respect to the longitudinal direction, and the average value from these lengths is used as the diameter fibers.

In the case where the measurement object is a combined non-woven material formed by a plurality of fibrous layers having different fiber diameters, such as a non-woven material with an SMS structure or a non-woven material with an SMMS structure, the ability to absorb liquids from the first surface 10a of the first layer 11 is significantly affected a meltblown layer comprising thin fibers and having a high fiber density, and the ability to absorb liquids in the second layer 12 is significantly affected by a meltblown layer having thin fibers and a high fiber density. In view of the foregoing, in the case in which the measurement object is a combined nonwoven material formed by a plurality of fibrous layers having different fiber diameters and including a meltblown layer, when measuring the diameter of the fibers of the combined nonwoven material, the fiber diameter of the layer obtained by the aerodynamic method is measured from a melt, in this combined nonwoven material.

[0068]

The ratio of the diameter of the fibers representing the constituent fibers (hydrophobic fibers 14) of the first layer 11 (first value) and the diameter of the fibers representing the constituent fibers (hydrophilic fibers 15) of the second layer 12 (last value) [i.e., the ratio of the diameter of the fibers representing constituent fibers (hydrophilic fibers 15) of the second layer 12 to the diameter of the fibers constituting the fibers (hydrophobic fibers 14) of the first layer 11], that is, the last value / first value is preferably 0.05 or more and more preferably 0.06 or more and preferably 0.9 or less and more preferably 0.8 or less, taking into account the initial condition that the first value is> the last value, as described above.

The diameter of the fibers comprising the constituent fibers (hydrophobic fibers 14) of the first layer 11 is preferably 3 μm or more and more preferably 5 μm or more and preferably 40 μm or less and more preferably 30 μm or less.

The diameter of the fibers comprising the constituent fibers (hydrophilic fibers 15) of the second layer 12 is preferably 0.5 μm or more and more preferably 1 μm or more and preferably 30 μm or less and more preferably 20 μm or less.

[0069]

For reasons related to increasing the ability of the multilayer nonwoven material 10 to absorb liquids, the number of fibers (number of fibers) representing hydrophilic fibers 15 as the main constituent fibers of the second layer 12 per unit area preferably exceeds the number of fibers representing hydrophobic fibers 14 as main the constituent fibers of the first layer 11, per unit area. The number of fibers per unit area is determined by the method below.

[0070]

<Method for determining the number of fibers per unit area>

First, the multilayer nonwoven material 10 as an object of measurement is cut with a razor so that the razor is cut along the interfiber fused parts 17, in a manner similar to the method in <Method for measuring the diameter of fibers>, whereby a sample is obtained. The cutting plane of the sample is examined with an increase (adjusted to an increase at which cross sections of approximately 30-60 fibers can be measured: at 150-500 times magnification) using a scanning electron microscope and the number of cross sections of fibers that are cut across is counted per unit area (approximately 0.5 mm ² ). When counting the number of fiber cross-sections in the case of measuring the constituent fibers (hydrophobic fibers 14) of the first layer 11, select fibers connected to the interfiber fused parts 17. When measuring the constituent fibers (hydrophilic fibers 15) of the second layer 12, select the fibers (hydrophilic fibers 15) of the second layer 12, overlapping interfiber fused parts 17. When measuring component fibers (hydrophobic fibers 14) of the first layer 11 in the case when it is difficult to determine the fibers connected to the interfiber fused parts 17, the number obtained by subtracting the number of component fibers (hydrophilic fibers 15) of the second layer 12, overlapping the interfiber fused parts 17, from the number of cross-sections of fibers in a certain area in the direction of the entire thickness next to the interfiber fused parts 17, is used as the number of constituent fibers (hydrophobic fibers 14) of the first layer 11. The measurement is performed in three places, and the average value for they are used as the amount of fiber.

[0071]

The ratio of the number of fibers representing hydrophobic fibers 14 of the first layer 11 per unit area (first value) and the number of fibers representing hydrophilic fibers 15 of the second layer 12 per unit area (last value) (i.e. the ratio of the number of fibers representing hydrophilic fibers 15 of the second layer 12, per unit area to the number of fibers representing the hydrophobic fibers 14 of the first layer 11, per unit area), that is, the last value / first value is preferably 1.1 or more and more preferably 1.2 or more and preferably 5 or less and more preferably 4 or less, taking into account the initial condition that the first value is <the last value, as described above.

The number of fibers (number of fibers) representing the hydrophobic fibers 14 of the first layer 11 per unit area is preferably 9 / mm ² or more and more preferably 13 / mm ² or more and preferably 250 / mm ² or less and more preferably 180 / mm ² or less.

The number of fibers (number of fibers) representing the hydrophilic fibers 15 of the second layer 12 per unit area is preferably 10 / mm ² or more and more preferably 15 / mm ² or more and preferably 300 / mm ² or less and more preferably 200 / mm ² or less.

[0072]

The multilayer structure in the multilayer nonwoven material according to the present invention may include another layer in addition to the hydrophobic first layer including hydrophobic fibers and the hydrophilic second layer including hydrophilic fibers described above. In particular, for example, in the multilayer nonwoven fabric 10 illustrated in FIG. 1, a long fiber layer including long fibers can be placed on the side of the second layer 12, closer to the second surface 10b. That is, the multilayer nonwoven material 10 may have a multilayer structure of three or more layers including a first layer 11 forming a first surface 10a, a long fiber layer (not shown) forming a second surface 10b, and a second layer 12 located between these layers.

[0073]

The second layer 12 preferably has a degree of hydrophilicity higher than the degree of hydrophilicity of the layer of long fibers. With this structure, a part of the multilayer structure 13, not including the first layer 11, has a gradient of the degree of hydrophilicity, in which the degree of hydrophilicity is relatively high in the second layer 12, relatively close to the first layer 11, and is relatively low in the layer of long fibers ( on the side closer to the second surface 10b), relatively remote from the first layer 11. Accordingly, in the multilayer structure 13, the liquid absorbed from the first surface 10a can be stably absorbed and held in the hydrophilic second layer 12, it is difficult to move the liquid to the side, more close to the second surface 10b (a layer of long fibers), and it is difficult to leak liquid into another element or garment that is in contact with the side of the second surface 10b of the multilayer structure 13. To obtain this structure, a fiber spun is preferably used as a layer of long fibers layer. The surface density of the long fiber layer is not limited to a specific value and is preferably 3 g / m ² or more and more preferably 5 g / m ² or more and preferably 15 g / m ² or less and more preferably 13 g / m ² or less.

[0074]

As another embodiment of the multilayer structure in the multilayer nonwoven fabric of the present invention, an elastic element (not shown) may be placed between the first layer 11 and the second layer 12 in the multilayer nonwoven fabric 10 illustrated in FIG. In the case where the multilayer structure 13 is a multilayer structure of three or more layers, the placement of the elastic element is not limited to the placement between the first layer 11 and the second layer 12, and the elastic element can be placed between any layers. As described above, the placement of the elastic element between the layers of the multilayer structure gives elasticity to the multilayer nonwoven material, and the range of applications of the multilayer nonwoven material can be further increased.

[0075]

The elastic element can be stretched and preferably has a property (elasticity) in which, when the force is removed, in a state in which the elastic element is stretched to a length exceeding 1.3 times its original length (the elastic element has a length of 1.3 times exceeding the original length) the elastic element returns to a length that is less than 1.1 times or 1.1 times the original length. An inelastic element is an element that does not have such “elasticity,” that is, an element having the property in which, when the force is removed, in a state in which the element is stretched to a length exceeding 1.3 times the original length (the element has a length of 1.3 times the original length) the element does not return to a length that is less than 1.1 times or 1.1 times the original length. The shape of the elastic element is not limited to a specific example, and any shape, such as a filamentary shape, a sheet-like shape or a combination of elastic fibers (layer of elastic fibers) can be selected. For example, the multilayer nonwoven material 10 (multilayer structure 13) illustrated in FIG. 1 can take the form in which a plurality of elastic elements in the form of threads are placed between the first layer 11 and the second layer 12 and stretched in the same direction. In this case, the multilayer nonwoven material 10 (multilayer structure 13) is elastic in the direction in which the elastic elements are stretched.

[0076]

As the material for the elastic elements, a polymeric material such as natural rubber or a thermoplastic elastomer can be used. Examples of a polymeric material or thermoplastic elastomer include: styrene-based elastomers such as a block alternating styrene-butadiene block copolymer (SBS), a block alternating styrene-isoprene block copolymer (SIS), a styrene-ethylene butadiene block copolymer with block alternation (SEBS) and block-copolymer of styrene and ethylene-propylene with alternating blocks (SEPS); olefin-based elastomers (α-olefin elastomer based on ethylene and elastomer based on propylene, obtained, for example, by copolymerization of ethylene, butene, octene); polyester-based elastomer; and polyurethane-based elastomer.

[0077]

Next, a method of manufacturing a multilayer nonwoven material according to the present invention will be described with reference to the drawings based on a preferred embodiment. 5 schematically illustrates an example of a method for manufacturing a multilayer nonwoven fabric 10 described above, as one embodiment of a method for manufacturing a multilayer nonwoven fabric according to the present invention. As described above, the multilayer nonwoven material 10 has a multilayer structure 13 of fibrous layers including thermoplastic fibers (hydrophobic fibers 14 and hydrophilic fibers 15), and the layers forming the multilayer structure 13 are fused to each other in the interlayer fused parts 16.

[0078]

As illustrated in FIG. 5, a method of manufacturing a multilayer nonwoven material 10 includes: a step for producing a multilayer element 10P by moving the hydrophobic base nonwoven material 11P and depositing the hydrophilic fibers 15 obtained by spinning the fibers from the resin onto the movable base nonwoven material 11P and the step of fusing the layers together on the other hand, consisting in the formation of interlayer fused parts 16 by heating the multilayer element 10P while partially compressing the multilayer element 10P in the thickness direction. The base nonwoven material 11P includes interfiber fused parts 17 in which the constituent fibers (hydrophobic fibers 14) are fused to each other, with a density higher than in the peripheral part. The base nonwoven material 11P should finally become the first layer 11 in the multilayer nonwoven material 10, which is the object of manufacture in this manufacturing method.

[0079]

In this manufacturing method illustrated in FIG. 5, first, the base non-woven fabric 11P wound in a roll is unwound and moved by a conveyor 50 in one direction, indicated by the reference numeral MD, and during the movement, the hydrophilic fibers 15 exit the spinneret during molding a head 51 located above the conveyor 50 and deposited directly on the base nonwoven material 11P, whereby a multilayer element 10P is obtained. After that, the multilayer element 10P is moved to feed it between the two embossing rollers 52 and 53 and is hot stamped, whereby the interlayer fused parts 16 are formed (the step of fusing the layers together). The embossing roller 52 is located above the movable multilayer element 10P and during hot embossing is in direct contact with the deposited layer (canvas) of hydrophilic fibers 15 obtained by direct spinning. The embossing roller 53 is located under the movable laminate member 10P and is in contact with the base nonwoven fabric 11P during hot stamping. As for the outer peripheral surfaces of the rollers 52 and 53, which are in contact with the multilayer element 10P as the object of processing, the outer peripheral surface of the embossing roller 53 does not have irregularities (recesses and protrusions), while the outer peripheral surface of the embossing roller 52 has protrusions (not shown) with a configuration that matches the configuration of the interlayer fused parts 16 in the multilayer nonwoven material 10 as an object of manufacture. In the areas of the clamping zone between the rollers 52 and 53 having such a design, the multilayer element 10P is compressed in the direction of the thickness while it is heated to a temperature that is greater than or equal to the melting temperature of thermoplastic fibers (hydrophobic fibers 14 and hydrophilic fibers 15) included in the multilayer element 10P. Accordingly, the multilayer element 10P is partially compressed by the protrusions of the embossing roller 52 from the side of the deposited layer of hydrophilic fibers 15 towards the base nonwoven material 11P, whereby interlayer fused parts 16 are formed in the pressed parts. fibers 15 into a non-woven material and combining the non-woven material with the base non-woven material 11P integrally by means of the interlayer fused parts 16. In the above-described manner, a multilayer non-woven material 10 is obtained having a multilayer structure 13 formed by a first layer 11 of a base non-woven material 11P and a second layer 12 representing a deposited layer (canvas) of hydrophilic fibers 15. In the multilayer nonwoven material 10 thus obtained, the interlayer fused portions 16 are pressed from the side of the second surface 10b towards the first surface 10a.

[0080]

The main feature of this manufacturing method is that the hydrophilic fibers 15 are directly formed and deposited on the hydrophobic base non-woven fabric 11P, for example by melt spinning, whereby the canvas is formed as a deposited layer of these fibers. In this manufacturing method, which uses the technology of the so-called direct spinning of fibers, fibers (hydrophilic fibers 15) obtained by temporarily winding long fibers obtained by melt spinning using a winding device and subsequently drawing and cutting the resulting long fibers, Do not deposit on 11P base nonwoven.

[0081]

In the manufacture of a multilayer nonwoven material, such as a multilayer nonwoven material 10, the use of direct fiber spinning technology, as in this manufacturing method, can reduce the surface density of the multilayer nonwoven material compared to the method in which a plurality of nonwoven materials are stacked on top of one another and combined into one by hot stamping. In particular, the thickness of the hydrophilic second layer 12 formed by direct spinning of fibers can be easily reduced. The small thickness and low surface density of the hydrophilic second layer 12 make it possible to obtain a multilayer non-woven material providing increased diffusion of the absorbed liquid along the surface and high evaporation capacity. As a rule, it is difficult to reduce the surface density of such a layer obtained by the aerodynamic method from a melt, which must have a strength that can withstand its movement in the form of a single non-woven material. On the other hand, the use of the technology of direct spinning of fibers used in this manufacturing method allows the use of a thin layer obtained by the aerodynamic method from a melt and having a low surface density. In addition, since in this manufacturing method, the hydrophilic fibers 15 obtained by spinning the fibers are deposited directly on the hydrophobic base nonwoven material 11P to form the multilayer element 10P thereby, the hydrophilic fibers 15 easily pass into the base nonwoven material 11P, so that the adhesive bond between the first layer 11 and the second layer 12 increases. Thus, as described above, a high-quality multilayer non-woven material 10 is obtained, demonstrating a high ability to absorb liquids in the case where the interlayer fused parts 16 and parts peripheral with respect to them are used on the first surface 10a as fluid drawing parts, and having high strength.

[0082]

In the manufacturing method illustrated in FIG. 5, hydrophilic fibers 15, when formed, exit the die of the forming head 51, that is, the processing of the thermoplastic resin to impart hydrophilicity is performed by intervening the hydrophilicity agent. The hydrophilicity treatment by interfering with the hydrophilicity agent can, in particular, be carried out, for example, in such a way that the masterbatch with the hydrophilicity agent obtained by melting and interfering the hydrophilicity agent in a thermoplastic resin to obtain a predetermined concentration means for imparting hydrophilicity, and the thermoplastic resin as a material for producing a nonwoven material (second layer 12) is mixed in a predetermined ratio, and the mixture is melted, for example, by means of an extruder and extruded from the die of the forming head 51 to obtain long fibers, and long fibers are deposited on the base nonwoven fabric 11P.

[0083]

In the method of manufacturing a multilayer nonwoven material according to the present invention, the processing of the thermoplastic resin as a material for hydrophilic fibers 15 to make it hydrophilic can be performed after extrusion of the thermoplastic resin from the forming head 51 (after forming thermoplastic fibers). That is, after forming the fibers from a thermoplastic resin that does not include any means for imparting hydrophilicity and depositing them on the base nonwoven material 11P, attaching the hydrophilicity agent or plasma treatment can be performed on the deposited layer (accumulation of thermoplastic fibers not subjected to processing to give hydrophilicity). Alternatively, attachment of the hydrophilicity agent or plasma treatment may be performed after the formation of the interlayer fused parts 16 by means of two embossing rollers 52 and 53.

[0084]

That is, an embodiment of a method of manufacturing a multilayer nonwoven material according to the present invention may be a manufacturing method A described below. In the manufacturing method illustrated in FIG. 5, the processing of the thermoplastic resin to give it hydrophilicity is performed by intervening with the hydrophilicity agent, the hydrophilic fibers 15 obtained by spinning the fibers from the thermoplastic resin subjected to the hydrophilicity treatment and leaving the forming head 51 are deposited on the base nonwoven material 11P to form the multilayer element 10P, and the step of imparting hydrophilicity to the resin is performed before the step of forming the multilayer element in the manufacturing method A. In a manufacturing method in which the hydrophilicity enhancing agent is attached or the plasma treatment described above, the hydrophilicity of the resin (i.e., hydrophilicity of the deposited layer from the fibers obtained by molding) is performed after the step of forming the multilayer element or the step of fusing the layers together in method A of manufacture.

[0085]

(Method A for the manufacture of a multilayer nonwoven fabric)

A method of manufacturing a multilayer nonwoven material having a multilayer structure of fibrous layers including thermoplastic fibers, wherein the layers forming the multilayer structure are fused to each other in interlayer fused parts, includes: the step of producing a multilayer element by moving a hydrophobic base nonwoven material including inter-fiber fused parts that are thinner than parts peripheral to the inter-fiber fused parts, and in which the constituent fibers are fused to each other, and the deposition of fibers obtained by molding the fibers from the resin on a movable base nonwoven material ( a multilayer element forming step), a resin hydrophilizing step (hydrophilicity of the resin) and a layer fusion step with each other, comprising heating the multilayer element while simultaneously partially compressing the multilayer element in the thickness direction to form interlayer layers s fused parts through this.

[0086]

The multilayer nonwoven material according to the present invention includes an embodiment in which a plurality of second layers 12 are superposed, and the multilayer structure 13 includes three or more layers. In the case of manufacturing a multilayer nonwoven material in this form at the stage of obtaining the multilayer element 10P, hydrophilic fibers 15 are deposited on the base nonwoven material 11P many times. In this case, in the manufacturing method illustrated in FIG. 5, for example, a plurality of forming heads 51 are spaced apart in the MD direction of travel, and the hydrophilic fibers 15, when formed, sequentially exit each forming head 51 to deposit them directly on the base non-woven fabric 11P.

[0087]

The base nonwoven material 11P can be made in accordance with a typical method depending on the type of base nonwoven material 11P. The base non-woven material 11P, as a rule, is made by the stage of obtaining the canvas by deposition of fibers obtained by molding the fibers from the resin, and the step of fusing the fibers with each other, which consists in heating the canvas while partially compressing the canvas in the thickness direction to form interfiber fused parts 17. For example, in the case where the base nonwoven fabric 11P (first layer 11) is a spunbond nonwoven fabric, this nonwoven fabric is prepared as follows. That is, the resin composition as a material for the nonwoven material is first melted, for example, by means of an extruder and extruded from the die of the forming head, thereby forming long fibers. The long fibers obtained are cooled by a cooling fluid, and a tensile force is applied to the long fibers by drawing air so that the long fibers have a predetermined fineness and the resulting fibers are collected on a collecting tape and deposited to a predetermined thickness. After that, the long fibers are subjected to the fusion process by hot stamping, whereby the inter-fiber fused parts 17 are formed.

[0088]

At the stage of fusion of the fibers with each other, the canvas (a sheet-like object not subjected to fusion of the fibers with each other; the precursor material of the base nonwoven material 11P) is usually heated while squeezing in the direction of thickness from the side of one surface, whereby interfiber fused parts are formed 17. In the case of the manufacture of the multilayer nonwoven material 10 by using the technology of the so-called direct molding of fibers and when using the base non-woven material 11P, including interfiber fused parts 17 formed by squeezing from the side of one single surface of the canvas, the hydrophilic fibers 15 are deposited on the opposite surface in relation to the crushed surface (the surface on which the pressed interfiber fused parts 17 are formed) of the base nonwoven material 11P. In the multilayer nonwoven material 10 thus obtained, the interfiber fused parts 17 are pressed in from the side of the first surface 10a towards the second surface 10b.

[0089]

In this manufacturing method, the calendering process can be performed on the multilayer element 10P (multilayer nonwoven material 10) immediately before the step of fusing the layers with each other or immediately after the step of fusing the layers with each other, more specifically, immediately before hot stamping or immediately after hot stamping with using two rollers 52 and 53 for embossing. As is widely known, the calendering process is a process in which the accumulation of fibers, such as non-woven material, is subjected to heat and pressure through calendering rollers, so that the density of the accumulation of fibers increases. The calendering process performed on the multilayer element 10P immediately before the step of fusing the layers with each other or immediately after the step of fusing the layers with each other can further contribute to the "entry of hydrophobic fibers 15 into the base nonwoven material 11P", which is an advantage of the technology of direct spinning of fibers described above, and therefore, properties of the multilayer nonwoven material 10, such as the ability to absorb liquids and strength, can be further improved. The number and arrangement of calender rollers used for the calendering process is not limited to the illustrated example. For example, a configuration with a sequential arrangement or an inclined arrangement formed by three calender rollers, a configuration with a sequential arrangement, an arrangement in the form of an inverted letter L, a Z-shaped arrangement or an inclined Z-shaped arrangement formed by four calender rollers, a configuration with Z– can be used shaped arrangement or L-shaped arrangement formed by five calender rollers. The temperature in the calendering process is preferably less than or equal to the softening temperature of the constituent fibers of the multilayer element 10P (multilayer nonwoven material 10) as the object of processing. The calendering process, carried out at a softening temperature or a higher temperature, can lead to hardening of the nonwoven material, which causes a decrease in skin comfort.

[0090]

In this manufacturing method, the calendering process can be performed on the base nonwoven material 11P before the hydrophilic fibers 15 are deposited on the base nonwoven material 11P, more specifically, before the base nonwoven material 11P that moves on the production line of the multilayer nonwoven material 10 passes through forming head 51. Thus, the surface of the first layer 11 becomes smooth, and skin comfort is preferably improved. That is, the instant of the calendering process in this manufacturing method can be any of the moment immediately before the step of fusing the layers with each other and the moment immediately after the step of fusing the layers with each other, and the calendering process can occur before the hydrophilic fibers 15 are deposited on the base non-woven material 11P , or may correspond to both of these points.

[0091]

In addition, the manufacturing step of the base nonwoven material 11P may include the use of a calendaring process. That is, the calendering process can be performed on a canvas (a sheet-like object not fused with each other; a precursor material of the base non-woven material 11P) immediately before the step of fusing the fibers with each other or immediately after the step of fusing the fibers with each other.

[0092]

As described above, the multilayer nonwoven material according to the present invention includes an embodiment in which an elastic element, such as an elastic element in the form of threads, in the form of a sheet or in the form of a cluster of elastic fibers (layer of elastic fibers), is located between the first layer and the second layer. In the case of manufacturing a multilayer nonwoven material having such a configuration in which the elastic element is placed between the layers in the multilayer structure, the elastic element is placed on the base nonwoven material 11P before deposition of the hydrophilic fibers 15 on the base nonwoven material 11P. The method of placement of the elastic element may be appropriately selected depending, for example, on the type / shape of the elastic element. For example, if a layer of elastic fibers is placed in the form of a cluster of elastic fibers as an elastic element, elastic fibers can be obtained by direct spinning of the fibers and deposited on the base nonwoven fabric 11P in the same way as hydrophilic fibers 15.

[0093]

The following description will be directed to an absorbent article according to the present invention with reference to the drawings based on the preferred embodiment. An absorbent product according to the present invention is characterized in that it includes a multilayer nonwoven material according to the present invention described above. In particular, as described above, the multilayer nonwoven material according to the present invention has a multilayer structure of fibrous layers including thermoplastic fibers, the multilayer structure has a first surface that is the surface of the multilayer nonwoven material, and a second surface that is the other surface of the multilayer non-woven material, the first surface is formed by a hydrophobic first layer including hydrophobic fibers, and a hydrophilic second layer including hydrophilic fibers is located on the side of the first layer closer to the second surface. In the absorbent product according to the present invention, the multilayer nonwoven material is positioned so that its first surface faces the skin of the user.

[0094]

6-8 illustrate a pull-on disposable diaper 1, which is one embodiment of an absorbent article according to the present invention. The description of the diaper 1 will be directed mainly to components different from the components of the multilayer nonwoven material 10, which is an embodiment of the multilayer nonwoven material described above, and similar components are denoted by the same reference numerals, and their description will not be repeated. The description of the multilayer nonwoven fabric 10 is appropriately applied to components not specifically described.

[0095]

As illustrated in FIGS. 6 and 7, the diaper 1 includes a front zone A and a rear zone B located in the longitudinal direction X, and a crotch zone C located between zones A and B. The diaper 1 also includes an absorbent element 23, passing through the front zone A and the rear zone B, and the front waist valve FA and the rear waist valve FB, located outside respectively of the front and rear parts 23A and 23B of the absorbent element 23, end in the longitudinal direction X, and passing in the lateral direction Y. B in this case, the front zone A is a zone located on the front side of the user when the user is wearing an absorbent article, such as a disposable diaper, and rear zone B is the zone located on the back side of the user when the user is wearing an absorbent article, such as a disposable diaper . The front zone A and rear zone B are waist parts corresponding to the waist of the user when the user wears the diaper 1.

[0096]

As illustrated in FIG. 7, the front waist valve FA refers to a zone that is a combination of a zone that is located externally in the longitudinal direction X from the edge of the front portion 23A of the absorbent element 23, endwise in the longitudinal direction X and located on the side of the front zone A, and extends laterally Y, and an area that extends laterally Y from the front portion 23A of the absorbent member 23, is lateral in the longitudinal direction X and located on the front zone A. The rear waist flap FB refers to an area that is a combination of an area that is located outside in the longitudinal direction X from the edge of the rear part 23B of the absorbent element 23, endwise in the longitudinal direction X and located on the side of the rear zone B, and extends in the lateral direction Y, and the zone that extends in the lateral direction Y from the rear part 23B of the absorbent element 23, terminal in the longitudinal direction X and located on the side of the rear zone B.

[0097]

As illustrated in FIGS. 6 and 7, the diaper 1 includes an absorbent kit 2 and an outer covering member 3, which is located on the surface side of the absorbent kit 2 not facing the skin, and provides fixation to the absorbent kit 2. The outer covering member 3 includes the front waist flap FA and the rear waist flap FB, which are located outside respectively from the longitudinal end X, front and rear parts 23A and 23B of the absorbent element 23 forming the absorbent assembly 2, and extend laterally Y. In the diaper 1, the elasticized zone (waist elastic portion G1 and waist lower elastic portion G2) are formed in the front waist flap FA and the rear waist flap FB.

[0098]

As illustrated in FIG. 7, the diaper 1 is a so-called pull-on disposable diaper in which both side edge parts 3a1 and 3a1 of the front area A of the outer covering member 3 and both side edge parts 3b1 and 3b1 of the back zone B of the outer covering element 3 are connected to the formation of two side seams S and S, holes WO for the waist and two holes LO and LO for the legs (see Fig.6). When the outer covering element 3 of the diaper 1 in its flat unfolded, unstretched state is visible in the plan view illustrated in FIG. 7, the outer covering element 3 is preferably divided into a front area A located on the front side of the user when the user wears the diaper 1, the back a zone B located on the rear side of the user when the wearer is wearing the diaper 1, and a crotch zone C located between the front zone A and the rear zone B. In this case, the unfolded, unstretched state of the diaper 1 refers to a state in which the side seams S are torn so that the diaper 1 is deployed, as illustrated in Fig. 7, and the unfolded diaper 1 is stretched to the design dimensions (corresponding to the dimensions in a state where the diaper 1 is expanded in the plane in the absence of any impact of elastic elements) due to the stretching of the elastic elements of the parts of the diaper 1.

[0099]

As used herein, a “skin-facing surface” refers to the surface of the diaper 1 or a component thereof (eg, an absorbent kit 2) facing the skin of the user when the wearer is wearing the diaper 1. “The surface not facing the skin” refers to the surface the diaper 1 or its component, which is facing the side (side of the garment), opposite to the side of the skin of the user when the user wears the diaper 1. In the diaper 1, the longitudinal direction X refers to the direction that corresponds to the direction from the front of the user to the back side and passes through the crotch portion, and to the direction passing through the front zone A and the rear zone B in a state where the diaper 1 is deployed in a plane and stretched. The lateral direction Y refers to the direction orthogonal to the longitudinal direction X, and to the width direction of the diaper 1, expanded in the plane and stretched. The diaper 1 is symmetrical about the vertical center line CL1 extending in the longitudinal direction X and illustrated in FIG. 7. 7, reference numeral CL2 denotes a transverse center line extending in the lateral direction Y so that it divides the diaper 1 in half and orthogonal to the vertical center line CL1.

[0100]

When the diaper 1 is in its unfolded, unstretched state, illustrated in FIG. 7, in the diaper 1, the absorbent assembly 2 has an elongated shape that is relatively long in the longitudinal direction X. The absorbent assembly 2 includes a liquid permeable top sheet 21 forming a surface facing the skin, minimally permeable to liquids (including water repellent), a back sheet 22 forming a surface not facing the skin and holding a liquid absorbent element 23 located between these sheets 21 and 22. As illustrated in FIG. 7, the lateral parts of the absorbent assembly 2 extending in the longitudinal direction X (longitudinal direction) are provided with cuffs 24 and 24, which are leakproof, include an elastic member and are located in the longitudinal direction X in an extended state. In particular, leakage protection cuffs 24 are formed of minimally liquid permeable or water repellent breathable material, and leakage protection cuffs 25 stretched in the longitudinal direction X are adjacent to the free ends of the leakage protection cuffs 24. When the diaper is worn, the collapse of the elastic elements of the cuffs 25, which protect against leakage, causes the free end parts of the cuffs 24, which protect against leakage, to rise, so that it prevents the fluid released by the body from flowing in the lateral direction Y.

[0101]

As illustrated in FIG. 7, an absorbent kit 2 having the above configuration is attached by adhesive to fix the kit to the central part of the outer covering element 3, wherein its longitudinal direction corresponds to the longitudinal direction X of the diaper 1 in its flat unfolded, unstretched state. Thus, the outer covering element 3 is located on the side of the non-skin surface of the back sheet 22 forming the absorbent assembly 2 in the thickness direction of the disposable diaper 1 and is attached and attached to the side of the surface not facing the skin. Thus, in the diaper 1, the absorbent element 23 forming the absorbent assembly 2 is located in the front zone A and the rear zone B.

[0102]

In the diaper 1 illustrated in FIG. 7, the outer covering member 3 includes a front waist flap FA and a back waist flap FB, which are located outside respectively of the front and rear portions 23A and 23B of the absorbent member 23, endwise in the longitudinal direction X, and extend laterally Y. As illustrated in FIGS. 6-8, the outer covering member 3 includes an outer sheet 6 on a surface side not facing the skin and forming the outer surface of the diaper 1, and an inner sheet 3i located on the surface side of the outer sheet 6 facing the skin. The outer sheet 6 includes a bent portion 6R, in which a protruding portion protruding from each of the longitudinal end X, the front and rear parts of the inner sheet 3i, is bent to the side of the surface of the inner sheet 3i facing the skin. As illustrated in FIG. 7, the folded portion 6R of the outer sheet 6 has a rectangular shape elongated in the lateral direction Y. Each of the front and rear end portions 23A and 23B of the absorbent assembly 2 is covered by the folded portion 6R.

[0103]

As described above, the diaper 1 includes a front zone A and a rear zone B, which are waist parts corresponding to the waist of the user when the user wears the diaper 1, and, as illustrated in FIG. 7, zones A and B include, at least the waist elastic portion G1 and the lower elastic waist portion G2 as elastic zones and may also include elastic leg portions G3. That is, the outer covering member 3 includes, in zones A and B, a plurality of elastic elements 71 spaced at intervals in the longitudinal direction X and extending laterally Y between the outer sheet 6 and the inner sheet 3i forming the outer covering member 3, so that the waist elastic portion G1 and the waist lower elastic portion G2 are formed as elastic zones that are laterally elastic Y in zones A and B. The outer covering member 3 includes a plurality of leg elastic members 72 extending in a predetermined direction from zones A and B through the crotch zone C between the outer sheet 6 and the inner sheet 3i, and therefore may also include an elasticized leg portion G3 as an elasticized zone in zones A, B and C.

[0104]

In the diaper 1 illustrated in FIGS. 6 and 7, a waist elastic portion G1 is formed in each end valve, which is located externally in the longitudinal direction X (from the side opposite to the transverse axial line CL2) from the ends end in the longitudinal direction X, the front and rear parts 23A and 23B of the absorbent member 23 forming the absorbent assembly 2 in the longitudinal direction X. In the diaper 1, the waist lower elastic portion G2 is formed in each side valve located in the longitudinal direction X between the lower end of the waist elastic portion G1 closer to the transverse center line CL2, and the lower end of the side seam S. The rear waist flap FB and the front waist flap FA are also a combination of the end flap (waist elastic portion G1) and the side flap portion (waist lower elastic portion G2). In the diaper 1 illustrated in FIGS. 6 and 7, an elasticized leg portion G3 is formed at the periphery of the leg opening LO.

[0105]

As illustrated in FIGS. 6-8, the diaper 1 includes a sweat-absorbing sheet 10 (see FIG. 1) capable of absorbing sweat. The sweat sheet 10 is a multilayer nonwoven material 10 as an embodiment of the multilayer nonwoven material according to the present invention described above. The absorbent sheet 10 is positioned so that the first surface 10a (the outer surface of the hydrophobic first layer 11) faces the skin of the user.

[0106]

In the diaper 1, the sweat-absorbing sheet 10 is mainly used to absorb sweat around the user's waist and is located in the elasticized zone of the waist portion described above. That is, the absorbent sheet 10 has a shape elongated in one direction in a plan view illustrated in FIG. 7, in particular a rectangular shape (continuous shape). The sweat sheet 10 is located along the entire length of the front zone A and the rear zone B as waist parts in their lateral direction Y, while the longitudinal direction of the rectangle coincides with the lateral direction Y, and extends at least in the waist elastic portion G1 and the waist lower elastic parts of G2. In particular, the sweat-absorbing sheet 10 is attached to the skin surface of the bent portion 6R of the outer sheet 6 by known bonding means, such as adhesive, heat sealing or ultrasonic welding. The bent portion 6R is located in a place closer to the skin of the user than the absorbent element 23 when the user wears the diaper 1 (see Fig. 8). Thus, the sweat-absorbing sheet 10 on the skin-facing surface of the bent portion 6R is located in a place closer to the skin of the user than the absorbent element 23 when the user wears the diaper 1, and can come into contact with the skin of the user.

[0107]

In the diaper 1 having a configuration similar to that described above, the sweat-absorbing sheet 10 (multilayer non-woven fabric 10) having the function of absorbing sweat is located closest to the skin of the wearer of the diaper 1 on the skin-facing surface of each of the front zone A and the rear zone B as waist parts, and the sweat sheet 10 is located in the elastic zone, which includes the waist elastic part G1 and the waist lower elastic part G2 and is laterally elastic Y. Thus, when the wearer is wearing the diaper 1, the hydrophobic first surface 10a of the sweat sheet 10 (see FIG. 1) adheres well to the skin of the wearer under the action of the bonding force due to the pulling force created by the elastic zone, so that sweat from the skin can be quickly absorbed and released by evaporation.

[0108]

Since the sweat sheet 10 (multilayer nonwoven material 10) is located in the elastic zone in the diaper 1 described above, for reasons related to improving the fit to the skin of the user, the sweat sheet 10 is also preferably elastic in the same direction as the elastic zone, is in the lateral direction Y. For this reason, an elastic element (stretch element) that is elastic in the lateral direction Y is preferably placed between the first layer 11 and the second layer 12 in the absorbent sheet 10. This elastic element has already been described above.

[0109]

As for the materials for the parts of the diaper 1, for example, the top sheet 21, the back sheet 22, the absorbent element 23 and the cuffs 24, which protect against leakage, forming the absorbent set 2, can be made of various materials, usually used for the absorbent product such as a disposable diaper, without any particular limitation. For example, as the top sheet 21, for example, a single layer or multilayer nonwoven material or a perforated film can be used. As the back sheet 22, for example, a moisture-permeable polymer film can be used. As the absorbent element 23, an absorbent core formed by absorbent polymer particles and fibrous material coated with thin paper can be used. As cuffs 24, protecting against leakage, can be used, for example, water-repellent single-layer or multilayer non-woven material. Examples of an elastic element (for example, a leakproof cuff elastic element 25, elastic elements 71 and leg elastic elements 72) include synthetic rubbers such as styrene butadiene, butadiene, isoprene and neoprene, natural rubber, ethylene vinyl acetate copolymer (EVA), flexible polyolefin and polyurethane. The shape of the elastic element is preferably a shape of a thread (for example, rubber threads) having, for example, a rectangular, square, round, oval or polygonal cross section, or, for example, a shape similar to a cord (for example, a flat elastic). As a means for connecting the components of the diaper 1, various adhesives can be used, such as hot-melt adhesive, typically used for absorbent articles of this type.

[0110]

The present invention has been described based on an embodiment, but the present invention can be appropriately modified without any limitation of the embodiment.

For example, in the diaper 1, the multilayer nonwoven fabric 10, as an embodiment of the multilayer nonwoven fabric of the present invention, is used as the absorbent sheet 10. However, it is sufficient that the absorbent article of the present invention includes the multilayer nonwoven fabric of the present invention and that the first surface (hydrophobic surface including interlayer fused parts) of the multilayer non-woven material was located opposite the user's skin. The multilayer nonwoven material of the present invention can be used as a component of materials other than the absorbent sheet, and even in the case of using the multilayer nonwoven material as the absorbent sheet, the location of the multilayer nonwoven material is not limited to the location of the absorbent sheet 10 in the diaper 1.

Examples of another use of the multilayer nonwoven material of the present invention as a component of an absorbent article include its use as a top sheet located in a place closer to the skin of the user than the absorbent element. That is, in the diaper 1, the multilayer nonwoven material 10 can be used, for example, as the top sheet 21.

[0111]

Despite the fact that in the outer covering element 3 of the diaper 1, the elastic elements 71 are located between the outer sheet 6 and the inner sheet 3i, as illustrated in FIG. 7, the elastic elements 71 may not be placed. In the case of forming an elastic zone without elastic elements 71, an elastic nonwoven material that is laterally elastic Y can be used as a component of the outer covering element 3.

In the diaper 1, the outer covering member 3 has a continuous shape and passes through the front zone A, the crotch zone C and the rear zone B, as illustrated in FIG. Alternatively, the outer covering member 3 may have a divided shape in which the outer covering member 3 is divided into separate elements such as a front outer covering member, a rear outer covering member, and a crotch outer covering member.

The absorbent article according to the present invention is not limited to a pull-on disposable diaper, illustrated in the form of a diaper 1, and is also applicable to all articles intended for use in absorbing an excreted body fluid, in particular, for example, a disposable diaper of a disclosed type or a sanitary napkin.

In addition, the absorbent sheet according to the present invention is not limited to the use for the absorbent article described above, and is also applicable to articles other than the absorbent article. For example, a sweat-absorbing sheet according to the present invention can be used as a sheet per se intended to wipe sweat by a user. In addition, the sweat-absorbing sheet is also applicable to insoles for soles, axillary pads for absorbing sweat, eye masks, face masks and so on. When the sweat-absorbing sheet according to the present invention is placed opposite the skin of the user, sweat from the soles, from the armpits or from the faces can be quickly absorbed and released by evaporation.

With respect to the embodiment of the present invention described above, the following application is disclosed.

[0112]

<1> A multilayer nonwoven material having a multilayer structure of fibrous layers including thermoplastic fibers, in which

the multilayer structure has a first surface, which is the surface of the multilayer nonwoven material, and a second surface, which is the other surface of the multilayer nonwoven material,

the first surface is formed by a hydrophobic first layer,

a hydrophilic second layer is located on the side of the first layer closer to the second surface,

the multilayer structure includes interlayer fused parts that are thinner than parts peripheral to the interlayer fused parts, and in which the layers forming the multilayer structure are fused to each other,

the first layer includes interfiber fused parts that are thinner than parts peripheral to the interfiber fused parts, and in which the constituent fibers of the first layer are fused to each other, in addition to the interlayer fused parts, and,

if we assume that the fraction of the total area of the interlayer fused parts and the interfiber fused parts of the first surface of the first surface area and the fraction of the total area of the interlayer fused parts and interfiber fused parts of the second surface of the second surface area are respectively the fraction of the area of the fused parts of the first surface and the fraction of the area of the fused parts of the second surface, then the fraction of the area of the fused parts of the first surface exceeds the fraction of the area of the fused parts of the second surface.

[0113]

<2> The multilayer nonwoven material according to claim 1, wherein the interfiber fused parts of the first layer have a thickness that is less than or equal to 1/3 of the thickness of the parts of the first layer except fused parts.

<3> The multilayer nonwoven fabric according to claim 1 or 2, wherein the ratio of the area ratio of the alloyed parts of the first surface to the area ratio of the alloyed parts of the second surface, that is, the first value / last value, is 1.3-3.0.

<4> The multilayer non-woven material according to any one of paragraphs 1-3, in which the interlayer fused parts and the interfiber fused parts differ in at least two of the characteristics representing the layout, the shape of each of the fused parts in a plane, the area of each fused parts, the distance between the fused parts and the pitch.

<5> A multilayer nonwoven material according to any one of claims 1 to 4, wherein the interlayer fused parts are pressed from the second surface toward the first surface.

<6> A multilayer nonwoven material according to any one of claims 1 to 5, wherein the interfiber fused parts are pressed from the first surface toward the second surface.

<7> A multilayer nonwoven material according to any one of paragraphs 1-6, in which

the first surface includes a dispersion zone of the interfiber fused parts, in which the interfiber fused parts are dispersed, and

in the case where a virtual circle having a radius of 2 mm is located in some place in the dispersion zone of the interfiber fused parts, a part of at least one of the interfiber fused parts or all of at least one of the interfiber fused parts is included in given virtual circle.

<8> A multilayer nonwoven material according to any one of claims 1 to 7, wherein the area ratio of the interlayer alloyed parts of the area of the first surface or second surface is 15% or less.

<9> A multilayer nonwoven material according to any one of claims 1 to 8, wherein the interfiber fused parts have a pitch shorter than the pitch of the interlayer fused parts.

<10> A multilayer nonwoven material according to any one of claims 1 to 9, wherein the area of each of the interfiber fused parts on the first surface is 0.3 mm ² or less and less than the area of each of the interlayer fused parts on the second surface.

<11> A multilayer nonwoven material according to any one of claims 1 to 10, wherein the ratio of the area of each of the interfiber fused parts on the first surface to the area of each of the interlayer fused parts on the second surface, that is, the first value / last value, is 0.25 or more and 0.8 or less.

<12> A multilayer nonwoven material according to any one of claims 1 to 11, wherein the total surface density of the first layer and the second layer is 13 g / m ² or more and 38 g / m ² or less.

<13> A multilayer nonwoven material according to any one of paragraphs 1-12, wherein the surface density of the first layer is 8 g / m ² or more and 18 g / m ² or less.

[0114]

<14> A multilayer nonwoven material according to any one of claims 1 to 13, wherein the surface density of the second layer is 5 g / m ² or more and 20 g / m ² or less.

<15> A multilayer nonwoven material according to any one of claims 1 to 14, wherein the long fiber layer including the long fibers is located on the side of the second layer closer to the second surface.

<16> The multilayer nonwoven fabric according to claim 15, wherein the second layer has a hydrophilicity degree higher than the hydrophilicity of the long fiber layer.

<17> A multilayer nonwoven material according to any one of claims 1 to 16, wherein the second layer is a hydrophilic nonwoven material including fibers into which a hydrophilicity enhancing agent is interfered.

<18> A multilayer nonwoven fabric according to any one of claims 1-17, wherein the interfiber distance between the constituent fibers in the second layer is shorter than the interfiber distance between the constituent fibers in the first layer.

<19> A multilayer nonwoven material according to any one of paragraphs 1-18, wherein the number of fibers representing the constituent fibers of the second layer is per unit area greater than the number of fibers representing the constituent fibers of the first layer per unit area.

<20> A multilayer nonwoven material according to any one of paragraphs 1-19, wherein the constituent fibers of the second layer have a fiber diameter that is less than the diameter of the constituent fibers of the first layer.

[0115]

<21> A multilayer nonwoven material according to any one of claims 1 to 20, wherein the elastic element is located between the first layer and the second layer.

<22> A method of manufacturing a multilayer nonwoven material having a multilayer structure of fibrous layers including thermoplastic fibers, wherein the layers forming the multilayer structure are fused to each other in interlayer fused parts, the method comprising:

the step of producing a multilayer element by moving a hydrophobic base nonwoven material including interfiber fused parts that are thinner than parts peripheral to the interfiber fused parts and in which the constituent fibers are fused to each other, and the deposition of fibers formed by molding resin fibers on a movable base nonwoven fabric; and

the step of fusing the layers with each other, which consists in heating the multilayer element while simultaneously partially compressing the multilayer element in the thickness direction to form interlayer fused parts thereby.

[0116]

<23> A method of manufacturing a multilayer nonwoven material according to paragraph 22, wherein the calendaring process is performed on the multilayer element immediately before the step of fusing the layers with each other or immediately after the step of fusing the layers with each other.

<24> A method of manufacturing a multilayer nonwoven material according to paragraph 22 or 23, in which

the base non-woven material is formed by the step of making the canvas by deposition of hydrophobic fibers obtained by molding the fibers from the resin, and the step of fusing the fibers with each other, which consists in the formation of interfiber fused parts by heating the canvas while partially compressing the canvas in the thickness direction, and

the calendering process is performed on the canvas immediately before the step of fusing the fibers with each other or immediately after the step of fusing the fibers with each other.

<25> A method of manufacturing a multilayer nonwoven material according to any one of paragraphs 22-24, wherein the calendering process is performed on the base nonwoven material before the fibers are deposited on the base nonwoven material.

<26> A method of manufacturing a multilayer nonwoven material according to any one of paragraphs 22-25, in which the fibers deposited on the base nonwoven material are hydrophilic fibers obtained by forming fibers from a resin into which the hydrophilicity agent is interfered.

<27> A method of manufacturing a multilayer nonwoven material according to any one of paragraphs 22-26, in which

recesses of the base nonwoven material are formed by squeezing in the thickness direction from the side of one surface of the base nonwoven material, and

the fibers are deposited on the surface of the base nonwoven material, opposite to the pressed surface of the base nonwoven material.

<28> A method of manufacturing a multilayer nonwoven material according to any one of paragraphs 22-27, wherein in the step of producing the multilayer element, the fibers are deposited a total of many times on the base nonwoven material.

<29> A method of manufacturing a multilayer non-woven material according to any one of paragraphs 22-28, wherein the elastic element is placed on the base non-woven material before the fibers are deposited on the base non-woven material.

[0117]

<30> An absorbent article comprising a multilayer nonwoven material having a multilayer structure of fibrous layers including thermoplastic fibers in which

the multilayer structure has a first surface, which is the surface of the multilayer nonwoven material, and a second surface, which is the other surface of the multilayer nonwoven material,

the first surface is formed by a hydrophobic first layer,

a hydrophilic second layer is located on the side of the first layer closer to the second surface,

the multilayer structure includes interlayer fused parts that are thinner than parts peripheral to the interlayer fused parts, and in which the layers forming the multilayer structure are fused to each other,

the first layer includes interfiber fused parts that are thinner than parts peripheral to the interfiber fused parts, and in which the constituent fibers of the first layer are fused to each other, in addition to the interlayer fused parts,

if we assume that the fraction of the total area of the interlayer fused parts and the interfiber fused parts of the first surface of the first surface area and the fraction of the total area of the interlayer fused parts and interfiber fused parts of the second surface of the second surface area are respectively the fraction of the area of the fused parts of the first surface and the fraction of the area of the fused parts of the second surface, then the fraction of the area of the fused parts of the first surface exceeds the fraction of the area of the fused parts of the second surface, and

the multilayer nonwoven material is positioned so that the first surface faces the skin of the user.

[0118]

<31> An absorbent article according to claim 30, comprising a liquid retaining, absorbent element, wherein the multilayer nonwoven material is located in a place closer to the skin of the user than the absorbent element.

<32> An absorbent product according to paragraph 30 or 31, wherein the absorbent product includes a waist portion corresponding to a waist of the user, and a multilayer nonwoven material is disposed in the waist portion.

<33> The absorbent article of claim 32, wherein the waist portion includes an elastic zone in which a multilayer nonwoven fabric is disposed.

<34> The absorbent article of claim 33, wherein the elastic element is sandwiched between the first layer and the second layer in a multilayer nonwoven material.

<35> The absorbent article of claim 30, comprising a sweat-absorbing sheet capable of absorbing sweat, and the sweat-absorbing sheet is a multilayer non-woven material.

[0119]

<36> An absorbent sheet having a multilayer structure of fibrous layers including thermoplastic fibers, while the absorbent sheet contains

the first surface and the second surface located opposite the first surface, while

the sweat-absorbing sheet is used with the first surface facing the skin of the user,

the first surface is formed by a hydrophobic first layer,

a hydrophilic second layer is located on the side of the first layer closer to the second surface,

the multilayer structure includes interlayer fused parts that are thinner than parts peripheral to the interlayer fused parts, and in which the layers forming the multilayer structure are fused to each other,

the first layer includes interfiber fused parts that are thinner than parts peripheral to the interfiber fused parts, and in which the constituent fibers of the first layer are fused to each other, in addition to the interlayer fused parts, and,

if we assume that the fraction of the total area of the interlayer fused parts and the interfiber fused parts of the first surface of the first surface area and the fraction of the total area of the interlayer fused parts and interfiber fused parts of the second surface of the second surface area are respectively the fraction of the area of the fused parts of the first surface and the fraction of the area of the fused parts of the second surface, then the fraction of the area of the fused parts of the first surface exceeds the fraction of the area of the fused parts of the second surface.

[0120]

<37> Use of the multilayer nonwoven fabric according to any one of paragraphs 1-21 to absorb sweat.

<38> A method of absorbing sweat by using a multilayer nonwoven material according to any one of paragraphs 1-21.

Industrial applicability

[0121]

The present invention provides a multilayer nonwoven material having a high ability to absorb body fluid, such as sweat and urine, a method of manufacturing a multilayer nonwoven material, an absorbent article and an absorbent sheet.

Claims (35)

1. Absorbent product containing a waist portion corresponding to a user's waist, wherein the waist portion includes a multilayer nonwoven material having a multilayer structure of fibrous layers including thermoplastic fibers, wherein the multilayer structure has a first surface, which is the surface of the multilayer nonwoven material, and a second surface, which is the other surface of the multilayer nonwoven material, the first surface is formed by a hydrophobic first layer, a hydrophilic second layer is located on the side of the first layer, in the direction of the second surface, the multilayer structure includes interlayer fused parts that are thinner than the peripheral parts of the interlayer fused parts, and in which the layers forming the multilayer structure are fused to each other, the first layer includes interfiber fused parts, which are thinner than the peripheral parts, interfiber fused parts, and in which the constituent fibers of the first layer are fused with each other, in addition to the interlayer fused parts, Assuming that the fraction of the total area of the interlayer fused parts and the interfiber fused parts of the first surface from the area of the first surface and the fraction of the total area of the interlayer fused parts and interfiber fused parts of the second surface from the area of the second surface are, respectively, the fraction of the area of the fused parts of the first surface and the fraction of the area of the fused parts the second surface, then the fraction of the area of the fused parts of the first surface exceeds the fraction of the area of the fused parts of the second surface, and the multilayer nonwoven material is positioned so that the first surface faces the skin of the user. 2. The absorbent product according to claim 1, containing a retaining liquid, an absorbent element, while the multilayer nonwoven material is located in a place closer to the skin of the user than the absorbent element. 3. The absorbent product according to claim 1, in which the waist part includes an elasticized zone in which the multilayer non-woven material is located. 4. The absorbent product according to claim 3, in which the elastic element is placed between the first layer and the second layer in a multilayer nonwoven material. 5. Absorbent product according to claim 1, containing a sweat-absorbing sheet capable of absorbing sweat, while the sweat-absorbing sheet is a multilayer non-woven material. 6. The absorbent product according to claim 1, in which the interfiber fused parts of the first layer have a thickness that is less than or equal to 1/3 of the thickness of the parts of the first layer with the exception of the fused parts. 7. The absorbent product according to claim 1, in which the ratio of the area ratio of the alloyed parts of the first surface to the area ratio of the alloyed parts of the second surface, that is, the first / last, is 1.3-3.0. 8. The absorbent product according to claim 1, in which at least two of the placement patterns, flat shapes of each of the fused parts, the area of each of the fused parts, the distance between the fused parts and the pitch differ between the interlayer fused parts and the interfiber fused parts. 9. The absorbent product according to claim 1, in which the interlayer fused parts are pressed from the second surface towards the first surface. 10. The absorbent product according to claim 1, in which the interfiber fused parts are pressed from the first surface towards the second surface. 11. Absorbent product according to claim 1, in which the first surface includes a dispersion zone of the interfiber fused parts, in which the interfiber fused parts are dispersed, and in the case where a virtual circle having a radius of 2 mm is located in a place in the dispersion zone of the interfiber fused parts, part of at least one of the interfiber fused parts or all of at least one of the interfiber fused parts is included in this virtual circle. 12. The absorbent product according to claim 1, in which the fraction of the area of the interlayer fused parts of the area of the first surface or second surface is 15% or less. 13. The absorbent product according to claim 1, in which the interfiber fused parts have a step shorter than the step of the interlayer fused parts. 14. The absorbent product according to claim 1, in which the area of each of the interfiber fused parts on the first surface is 0.3 mm ² or less and less than the area of each of the interlayer fused parts on the second surface. 15. The absorbent product according to claim 1, in which the ratio of the area of each of the interfiber fused parts on the first surface to the area of each of the interlayer fused parts on the second surface, that is, the first value / last value, is 0.25 or more and 0.8 or less. 16. The absorbent product according to claim 1, in which the total surface density of the first layer and the second layer is 13 g / m ² or more and 38 g / m ² or less. 17. The absorbent product according to claim 1, in which the surface density of the first layer is 8 g / m ² or more and 18 g / m ² or less. 18. The absorbent article of claim 1, wherein the surface density of the second layer is 5 g / m ² or more and 20 g / m ² or less. 19. The absorbent product according to claim 1, in which the layer of long fibers, including long fibers, is located on the side of the second layer, closer to the second surface. 20. The absorbent product according to claim 19, in which the second layer has a degree of hydrophilicity higher than the degree of hydrophilicity of the layer of long fibers. 21. The absorbent product according to claim 1, in which the second layer is a hydrophilic non-woven material comprising fibers into which the means for imparting hydrophilicity is intervened. 22. The absorbent product according to claim 1, in which the interfiber distance between the constituent fibers in the second layer is shorter than the interfiber distance between the constituent fibers in the first layer. 23. The absorbent product according to claim 1, in which the number of fibers representing the constituent fibers of the second layer per unit area is greater than the number of fibers representing the constituent fibers of the first layer per unit area. 24. The absorbent article of claim 1, wherein the constituent fibers of the second layer have a fiber diameter that is less than the diameter of the constituent fibers of the first layer. 25. The absorbent product according to claim 1, in which the elastic element is located between the first layer and the second layer.

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