HK1250760B - Fiber sheet - Google Patents

Description

fiber sheets

Technical Field

The present invention relates to a fiber sheet that can be suitably used as a bandage or the like.

Background Art

Bandages are not only used to directly protect the affected area or to secure other protective materials (such as gauze) to the affected area, but also, if they are stretchable, can be used to stop bleeding from the wound by applying pressure when wrapped, or to improve blood flow and relieve edema. Bandages are also suitable for compression therapy, such as treating and improving varicose veins in the lower limbs.

Currently known methods for imparting stretchability to bandages include: 1) weaving yarn made of a stretchable raw material such as an elastomer represented by rubber into a fabric; 2) combining a layer formed of a stretchable raw material such as an elastomer with a non-stretchable fabric, or impregnating a non-stretchable fabric with a stretchable raw material. Many stretchable bandages using these methods are on the market.

For example, Japanese Patent No. 3743966 (Patent Document 1) describes a stretchable bandage that is imparted with stretchability in the longitudinal direction by using elastic yarns in the warp. Furthermore, Japanese Patent No. 5600119 (Patent Document 2) describes an elastic nonwoven web that is imparted with stretchability by entwining nonwoven fibers with elastic filaments in an elongated state and then relaxing the elongated state of the elastic filaments. Japanese Patent Publication No. 2014-515320 (Patent Document 3) describes a composite product having stretchability and self-adhesiveness obtained by impregnating an elastic polymer binder into an elastic composite product, the composite product comprising a nonwoven fibrous cover web, a woven scrim, and a plurality of elastic filaments disposed therebetween.

Prior art literature

Patent Literature

Patent Document 1: Japanese Patent No. 3743966

Patent Document 2: Japanese Patent No. 5600119

Patent Document 3: Japanese Patent Application No. 2014-515320

Summary of the Invention

Problems to be solved by the invention

Conventional stretchable bandages made from elastomeric materials such as rubber filaments can cause blood circulation obstruction and pain when wrapped around the application site for extended periods. These problems can be mitigated by reducing the tensile stress of the bandage's material. However, bandages with low tensile stress tend to be strongly stretched and wrapped around the application site to secure it securely, potentially exacerbating these problems.

Furthermore, when bandages are applied to areas that bend and stretch, such as joints, the bandage's elasticity is certainly beneficial in improving the flexibility (ease of movement) of the joints. However, the flexibility of joints, particularly small joints such as fingers, still has room for improvement.

Furthermore, although bandages can be applied to all parts of the body, conventional bandages, even if they possess stretchability, can, when wrapped around areas with uneven surfaces, such as joints, follow the surface well near the tops of the convex portions. However, the bandage wrapped around these areas (the concave portions) does not adhere sufficiently to the surface and may sometimes lift from the surface. In this specification, the ability of a bandage, such as a sheet, to follow the shape of the surface when wrapped around an area with uneven surfaces is referred to as "concave-convex conformability."

If the bandage has poor conformability to the surface, it may float, becoming loose and easily unraveling, or failing to achieve the desired compression force. Furthermore, if the bandage is tightly wound to conform to the surface, blood circulation may be obstructed or pain may occur.

A first object of the present invention is to provide an extensible fiber sheet that can suppress undesirable effects such as obstruction of blood circulation and pain even when wrapped around an application site for a long time, and a bandage using the extensible fiber sheet.

A second object of the present invention is to provide a fiber sheet that is unlikely to hinder the bending motion of a part that flexes and stretches even when wrapped around the part such as a joint, and a bandage using the fiber sheet.

A third object of the present invention is to provide a fiber sheet having excellent conformability to irregularities, which can be wrapped along the irregular shape of the surface even when wrapped with an appropriate strength, and a bandage using the fiber sheet.

Solutions to Problems

In order to achieve the above-mentioned first object, the present invention provides the fiber sheet and bandage described below.

[1] A fiber sheet wherein, when the initial elongation stress S ₀ [N/50 mm] is the elongation stress immediately after elongation at 50% in a first direction within a plane, and the elongation stress after elongation at 50% in the first direction for 5 minutes is the elongation stress after 5 minutes S ₅ [N/50 mm], the stress relaxation rate defined by the following formula is 85% or less:

Stress relaxation rate [%] = (elongation stress S ₅ after 5 minutes / initial elongation stress S ₀ )×100.

[2] The fiber sheet described in [1] above, wherein the stress relaxation rate is 65% or more.

[3] The fiber sheet according to [1] or [2], wherein the initial tensile stress _S0 is 2 to 30 N/50 mm or less.

[4] The fiber sheet according to any one of [1] to [3] above, wherein the curved surface sliding stress is 5 to 30 N/50 mm.

[5] The fiber sheet according to any one of [1] to [4], which has a longitudinal direction and a width direction, wherein

The first direction is the longitudinal direction.

[6] The fiber sheet according to any one of [1] to [5] above, which is a nonwoven fabric sheet.

[7] The fiber sheet according to any one of [1] to [6] above, which is a bandage.

In order to achieve the above-mentioned second object, the present invention provides the fiber sheet and bandage described below.

[8] A fiber sheet, wherein:

When the thickness of one sheet measured according to Method A of JIS L 1913 is defined as T ₁ [mm] and the thickness of three sheets stacked together measured under the same conditions is defined as T ₃ [mm], the following formula is satisfied:

{T ₃ /(3×T ₁ )}×100≤85〔%〕.

[9] The fiber sheet according to [8], wherein the following equation is satisfied when the elongation stress when the sheet is stretched at 50% in a first direction within the plane is denoted as 50% elongation stress S ₁ [N/50 mm], and the elongation stress when the sheet is stretched at 50% in a second direction within the plane perpendicular to the first direction is denoted as 50% elongation stress S ₂ [N/50 mm]:

S ₂ /S ₁ ≥3.

[10] The fiber sheet described in [9] above, having a length direction and a width direction, wherein

The first direction is the width direction.

[11] The fiber sheet according to any one of [8] to [10] above, having a basis weight of 50 g/ ^m2 or more.

[12] The fiber sheet according to any one of [8] to [11] above, wherein the compressive elastic modulus measured in accordance with JIS L 1913 is 85% or less.

[13] The fiber sheet according to any one of [8] to [12] above, wherein the curved surface sliding stress is 3 to 30 N/50 mm.

[14] The fiber sheet according to any one of [8] to [13] above, which is a nonwoven fabric sheet.

[15] The fiber sheet described in [14] above, comprising crimped fibers.

[16] The fiber sheet according to any one of [8] to [15] above, which is a bandage.

In order to achieve the third object, the present invention provides the following fiber sheet and bandage.

[17] A fiber sheet having a length direction and a width direction,

The stiffness in the width direction measured by a Handle-O-Meter method according to JIS L 1913 is 300 mN/50 mm or less.

[18] The fiber sheet described in [17] above, wherein the stiffness in the width direction is smaller than the stiffness in the length direction.

[19] The fiber sheet according to [17] or [18], wherein the compressive elastic modulus measured according to JIS L 1913 is 85% or less.

[20] The fiber sheet according to any one of [17] to [19] above, wherein the curved surface sliding stress is 3 to 30 N/50 mm.

[21] The fiber sheet according to any one of [17] to [20] above, which is a nonwoven fabric sheet.

[22] The fiber sheet described in [21] above, wherein the average fineness of the fibers constituting the nonwoven fabric sheet is 20 dtex or less.

[23] The fiber sheet described in [21] or [22] above, comprising crimped fibers.

[24] The fiber sheet according to any one of [17] to [23] above, which is a bandage.

Effects of the Invention

According to the present invention, there are provided an extensible fiber sheet capable of suppressing undesirable effects such as obstruction of blood circulation and pain even when wrapped around an application site for a long time, and a bandage using the extensible fiber sheet.

According to the present invention, it is possible to provide a fiber sheet that is unlikely to hinder the bending motion of a part that flexes and stretches, such as a joint, even when wrapped around the part, and a bandage using the fiber sheet.

According to the present invention, a fiber sheet having excellent conformability to uneven surfaces and a bandage using the fiber sheet can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating a method for preparing a sample for measuring sliding stress of a curved surface.

FIG2 is a schematic cross-sectional view showing a sample used for measuring the sliding stress of a curved surface.

FIG. 3 is a schematic diagram illustrating a method for measuring sliding stress on a curved surface.

Explanation of symbols

1 sample

2 single-sided adhesive tape

3 cores

4 alligator clips

5 weights

6 basis points

7 Half a circle from the base point

8. Cutting

9. Fixture

10 chuck

DETAILED DESCRIPTION

<First embodiment>

(1) Characteristics of fiber sheets

The fiber sheet of this embodiment (hereinafter referred to as the "fiber sheet") is an extensible fiber sheet. In addition to being suitable for use as a general bandage, it is also suitable for use as a medical device such as a compression bandage used for hemostasis, compression therapy, and the like. As used herein, "extensible" means exhibiting a 50% elongation stress in at least one direction (the first direction) within the plane of the sheet. This 50% elongation stress is preferably 0.1 N/50 mm or greater, more preferably 0.5 N/50 mm or greater, and even more preferably 1 N/50 mm or greater.

The 50% elongation stress mentioned above refers to the elongation stress immediately after stretching in the first direction at an elongation of 50%, and is also referred to herein as the "initial elongation stress S ₀ " [unit: N/50mm]. The initial elongation stress S ₀ can be measured by a tensile test in accordance with JIS L 1913, "Test methods for general nonwoven fabrics." The initial elongation stress S ₀ is preferably 30 N/50 mm or less, more preferably 20 N/50 mm or less, and even more preferably 15 N/50 mm or less. An initial elongation stress S ₀ of 30 N/50 mm or less is advantageous in preventing undesirable effects such as obstruction of blood circulation and pain caused by prolonged wrapping around the application site.

The first direction of the fiber sheet can be the direction of travel (MD) of the fiber sheet during the manufacturing process. When the fiber sheet has a length direction and a width direction, such as a bandage, the first direction is preferably the length direction of the fiber sheet. In this case, the fiber sheet as a bandage is stretched along its length direction and wrapped around the application site. When the fiber sheet has a length direction and a width direction, the CD direction, which is perpendicular to the MD direction, is preferably the width direction.

The 50% elongation stress in directions other than the first direction (e.g., CD direction, width direction when the fiber sheet has longitudinal and width directions like a bandage) of the fiber sheet is, for example, 0.5 to 50 N/50 mm, preferably 1 to 30 N/50 mm.

When the fiber sheet is stretched in the first direction at 50% for 5 minutes as elongation stress after 5 minutes S ₅ [N/50 mm], the stress relaxation rate defined by the following formula is 85% or less.

Stress relaxation rate (%) = (elongation stress S ₅ after 5 minutes / initial elongation stress S ₀ ) × 100

"The tensile stress when stretched in the first direction at an elongation of 50% for 5 minutes" refers to the tensile stress when the fabric is stretched in the first direction at an elongation of 50% and maintained in this state for 5 minutes. This is the same as the initial tensile stress _S0 and can be measured by a tensile test based on JIS L 1913 "General Nonwoven Fabric Test Methods."

A fiber sheet with a stress relaxation rate of 85% or less effectively prevents problems such as blood circulation obstruction and pain caused by prolonged wrapping around the application site. Specifically, when wrapped around the application site, the tensile stress of the fiber sheet relaxes appropriately over time, making the aforementioned problems caused by tight wrapping less likely to occur. The stress relaxation rate is preferably 84% or less, and more preferably 83% or less.

The stress relaxation rate is preferably 65% or higher, more preferably 70% or higher, and even more preferably 75% or higher. When the stress relaxation rate is within this range, the wrapped state gradually relaxes after being wound around the application area, which can prevent the wound fiber sheet from being displaced or peeled off.

The fiber sheet preferably exhibits self-adhesive properties. As used herein, "self-adhesive properties" refer to the ability of the fibers on the surface of the fiber sheet to overlap (contact) with each other, thereby interlocking, sealing, or securing the fibers. Self-adhesive properties are advantageous when the fiber sheet is a bandage, for example. For example, when the fiber sheet is a bandage, after wrapping the bandage around the application area, the bandage's ends are overlapped with the underlying bandage surface (or torn and overlapped), causing the wrapped fiber sheets to be stretched and pressed against each other, causing the fiber sheets to be joined and secured, thereby exhibiting self-adhesive properties.

By making the fiber sheet itself self-adhesive, there is no need to form a layer formed of a self-adhesive such as an elastomer or adhesive on the surface of the fiber sheet, and there is no need to prepare a separate fastening device for fixing the front end after winding. The fiber sheet is preferably composed only of non-elastomer raw materials, and more specifically, preferably composed only of fibers. For example, Japanese Patent Publication No. 2005-095381 (Patent Document 4) describes attaching an acrylic polymer (claim 1) or latex (paragraphs [0004] to [0006]) as a self-adhesive to at least one side of a bandage base material. However, forming a layer formed of such an elastomer on the surface of the fiber sheet may sometimes cause adverse conditions such as obstruction of blood circulation and pain when it is wrapped around the application area for a long time. In addition, the layer formed of the elastomer also has the potential risk of inducing skin irritation and allergies when it is wrapped around the application area.

The self-adhesiveness of a fiber sheet can be evaluated using the curved sliding stress. From the perspective of self-adhesiveness, the curved sliding stress of the fiber sheet is, for example, 3 N/50 mm or greater, preferably 5 N/50 mm or greater. Furthermore, the curved sliding stress is preferably greater than the breaking strength. Furthermore, from the perspective of making it easier to untangle the entangled fiber sheet when necessary, the curved sliding stress is preferably 30 N/50 mm or less, more preferably 25 N/50 mm or less. The curved sliding stress is measured using a tensile testing machine according to the method described in the Examples (Figures 1 to 3).

The fiber sheet is preferably hand-tearable. In this specification, "hand-tearable" refers to the property of being able to be broken (cut) by stretching it by hand. The hand-tearability of the fiber sheet can be evaluated by the breaking strength. From the perspective of hand-tearability, the breaking strength of the fiber sheet in at least one direction within the sheet surface is preferably 5 to 100 N/50 mm, more preferably 8 to 60 N/50 mm, and even more preferably 10 to 40 N/50 mm. By setting the breaking strength to the above range, good hand-tearability that can be torn (cut) relatively easily by hand can be imparted. When the breaking strength is too high, the hand-tearability is reduced, for example, it becomes difficult to tear the fiber sheet with one hand. In addition, when the breaking strength is too low, the strength of the fiber sheet is insufficient, it is easy to break, and the durability and handleability are reduced. The breaking strength can be measured by a tensile test based on JIS L 1913 "General nonwoven fabric test methods".

At least one direction within the sheet surface is the direction in which the fiber sheet is stretched when torn manually, and is preferably the first direction described above. This first direction may be the MD direction, but when the fiber sheet has a longitudinal direction and a width direction, such as in a bandage, the longitudinal direction is preferably the first direction. Specifically, when the fiber sheet is used as a bandage, the bandage is typically stretched along its longitudinal direction, wrapped around the application site, and then torn in the longitudinal direction. Therefore, the first direction is preferably the longitudinal direction, which serves as the stretching direction.

The breaking strength in a direction other than at least one direction within the sheet surface, such as the CD direction or the width direction when the fiber sheet has a length direction and a width direction like a bandage, is, for example, 0.1 to 300 N/50 mm, preferably 0.5 to 100 N/50 mm, and more preferably 1 to 20 N/50 mm.

From the viewpoint of hand-tearability, the fiber sheet is preferably composed only of a non-elastomer material, more specifically, preferably composed only of fibers. If a layer composed of an elastomer is formed on the surface of the fiber sheet, the hand-tearability will be reduced.

The fiber sheet has an elongation at break in at least one direction within the sheet surface of, for example, 50% or greater, preferably 60% or greater, and more preferably 80% or greater. This elongation at break range is advantageous in improving the stretchability of the fiber sheet. Furthermore, when the fiber sheet is used as a bandage, it can improve its ability to follow movements of areas subject to high mobility, such as joints. The elongation at break in at least one direction within the sheet surface is typically 300% or less, preferably 250% or less. The elongation at break can also be measured by a tensile test in accordance with JIS L 1913, "Testing Methods for General Nonwoven Fabrics."

The at least one direction within the sheet surface is preferably the first direction. The first direction may be the MD direction, and when the fiber sheet has a longitudinal direction and a width direction, such as a bandage, the first direction is preferably the longitudinal direction of the fiber sheet.

The breaking elongation in directions other than at least one direction in the sheet surface, for example, the CD direction or the width direction when the fiber sheet has a longitudinal direction and a width direction like a bandage, is, for example, 10 to 500%, preferably 100 to 350%.

The recovery rate after 50% elongation in at least one direction within the sheet surface (50% elongation recovery rate) is preferably 70% or greater (less than 100%), more preferably 80% or greater, and even more preferably 90% or greater. A 50% elongation recovery rate within this range improves elongation compliance. For example, when used as a bandage, it not only adequately conforms to the shape of the area of application but also helps improve the self-adhesion resulting from friction between the stacked fiber sheets. If the elongation recovery rate is too low, the nonwoven fabric will not be able to follow the complex shape of the area of application or movement during use. Furthermore, areas deformed by body movements will not recover, and the fixed hold of the wrapped fiber sheets will be weakened.

The at least one direction within the sheet surface is preferably the first direction. The first direction may be the MD direction, and when the fiber sheet has a longitudinal direction and a width direction, such as a bandage, the first direction is preferably the longitudinal direction of the fiber sheet.

The recovery rate after 50% elongation is defined by the following formula, where X is the residual strain (%) after the test when the load is removed immediately after the elongation reaches 50% in a tensile test based on JIS L 1913 "General nonwoven fabric testing methods."

Recovery rate after 50% elongation (%) = 100 - X

The recovery rate after 50% elongation in a direction other than at least one direction within the sheet surface, such as the CD direction or the width direction when the fiber sheet has a length direction and a width direction like a bandage, is, for example, 70% or more (less than 100%), preferably 80% or more.

The fiber sheet preferably has a basis weight of 30 to 300 g/ ^m² , more preferably 50 to 200 g/ ^m² . The thickness of the fiber sheet is, for example, 0.2 to 5 mm, preferably 0.3 to 3 mm, and more preferably 0.4 to 2 mm. When the basis weight and thickness are within this range, the fiber sheet exhibits a good balance between stretchability, softness, hand feel, and cushioning properties. The density (bulk density) of the fiber sheet can be a value corresponding to the basis weight and thickness, for example, 0.03 to 0.5 g/ ^cm³ , preferably 0.04 to 0.4 g/ ^cm³ , and more preferably 0.05 to 0.2 g/ ^cm³ .

The air permeability of the fiber sheet obtained by the Frazier method is preferably 0.1 cm ³ /(cm ² ·sec) or higher, more preferably 1 to 500 ^{cm 3} /(cm ² ·sec), further preferably 5 to 300 ^{cm 3} /(cm ² ·sec), and particularly preferably 10 to 200 cm ³ /(cm ² ·sec). When the air permeability falls within this range, the fiber sheet exhibits excellent breathability and is less likely to cause stuffiness, making it more suitable for applications such as bandages on the human body.

(2) Structure and manufacturing method of fiber sheet

The fiber sheet of this embodiment is not particularly limited as long as it is composed of fibers, and may be, for example, a woven fabric, a nonwoven fabric, a knitted fabric, or the like. The shape of the fiber sheet can be selected depending on the intended use, but is preferably a rectangular sheet having a longitudinal direction and a width direction, such as a tape or a strip. The fiber sheet may have a single-layer structure or a multilayer structure consisting of two or more fiber layers.

Examples of methods for imparting stretchability and extensibility to fiber sheets include: 1) pleating a fiber sheet substrate such as a woven fabric, nonwoven fabric, or knitted fabric; and 2) using coiled fibers as at least a portion of the fibers constituting a nonwoven fabric. As described above, methods involving weaving fibers made of stretchable materials such as elastomers, typically rubber, into a fiber sheet, combining a layer made of a stretchable material such as an elastomer with a non-stretchable fiber sheet substrate, or impregnating the fiber sheet with the stretchable material can lead to problems such as obstructed blood circulation and pain when wrapped around the application site for extended periods of time.

From the perspectives of self-adhesion, hand-tearability, joint flexibility when wrapped around a joint, and the ability to conform to uneven surfaces (fitting properties) when wrapped around uneven surfaces such as joints, the fiber sheet is preferably composed of a nonwoven fabric. Specifically, it is preferably a nonwoven fabric sheet, more preferably a nonwoven fabric comprising crimped fibers curled into a coil shape, and even more preferably a nonwoven fabric comprising such crimped fibers and not subjected to pleating. It is particularly preferred that the nonwoven fabric sheet be composed solely of such crimped fibers.

A fiber sheet composed of a nonwoven fabric containing crimped fibers preferably has a structure in which the individual fibers constituting the sheet are substantially non-fusion-bonded, and the crimped fibers are primarily restrained or locked by the mutual entanglement of their crimped coils. Furthermore, it is preferred that the majority (most) of the crimped fibers (with their axial direction) are oriented substantially parallel to the sheet surface. As used herein, "substantially parallel to the surface direction" means a state in which a plurality of crimped fibers (with their axial direction) are locally oriented in the thickness direction, such as by entanglement through needle punching, without repeated portions.

In a fiber sheet composed of a nonwoven fabric containing crimped fibers, the crimped fibers are preferably oriented in a certain direction within the sheet plane (e.g., the first direction described above, preferably the longitudinal direction), with adjacent or intersecting crimped fibers entangled with each other via their crimp loops. Furthermore, the crimped fibers are preferably slightly entangled with each other in the thickness direction (or oblique direction) of the fiber sheet. Entanglement of the crimped fibers may occur during the shrinkage of the fiber web serving as a precursor to the fiber sheet.

A nonwoven fabric in which the curly fibers (the axial direction of the curly fibers) are oriented and intertwined in a certain direction within the sheet surface shows good elasticity (including elongation) in that direction. When the aforementioned certain direction is, for example, the longitudinal direction, the stretchable nonwoven fabric is subjected to tension in the longitudinal direction, and the intertwined curly coils stretch and want to return to their original coils, thereby showing high elasticity in the longitudinal direction. In addition, by slightly intertwining the curly fibers in the thickness direction of the nonwoven fabric, cushioning and softness in the thickness direction can be exhibited, thereby giving the nonwoven fabric a good touch and feel. In addition, the curly coils can easily intertwine with other curly coils through contact under a certain degree of pressure. Self-adhesion can be exhibited by the intertwining of the curly coils.

In a fiber sheet composed of a nonwoven fabric containing crimped fibers, when tension is applied in the orientation direction of the crimped fibers (e.g., the first direction described above, preferably the longitudinal direction), the entangled crimped coils are elastically deformed and stretched, and when further tension is applied, they are finally untied, thereby providing good cuttability (hand-tearability).

As described above, the nonwoven fabric that can form the fiber sheet preferably includes crimped fibers that are curled into coils. The crimped fibers are preferably oriented primarily in the plane direction of the nonwoven fabric and are preferably substantially uniformly curled in the thickness direction. The crimped fibers can be composed of composite fibers formed from a phase structure of multiple resins having different thermal shrinkage rates (or thermal expansion coefficients).

The composite fibers that form the crimped fibers are fibers (latent crimped fibers) with an asymmetric or layered (so-called bimetallic) structure that crimps when heated due to the different thermal shrinkage rates (or thermal expansion coefficients) of multiple resins. These resins typically have different softening or melting points. The various resins can be selected from, for example, polyolefin resins (poly _C2-4 olefin resins such as low-density, medium-density or high-density polyethylene and polypropylene); acrylic resins (acrylonitrile resins having acrylonitrile units such as acrylonitrile-vinyl chloride copolymers); polyvinyl acetal resins (polyvinyl acetal resins); polyvinyl chloride resins (polyvinyl chloride, vinyl chloride-vinyl acetate copolymers, vinyl chloride-acrylonitrile copolymers); polyvinylidene chloride resins (vinylidene chloride-vinyl chloride copolymers, vinylidene chloride-vinyl acetate copolymers); styrene resins (heat-resistant polystyrene); polyester resins (polyethylene terephthalate resins, polypropylene terephthalate resins, polybutylene terephthalate resins, polyethylene naphthalate resins); Thermoplastic resins include _polyamides (polyamides 6, 66, 11, 12, 610, and 612, aliphatic polyamides; semi-aromatic polyamides; aromatic polyamides; polyphenylene isophthalamide, polyhexamethylene terephthalamide, and polyparaphenylene terephthalamide); polycarbonate resins (bisphenol A polycarbonate); polyparaphenylene benzobisazole resins; polyphenylene sulfide resins; polyurethane resins; and cellulose resins (cellulose esters). The above thermoplastic resins may also contain other copolymerizable units.

Among these, the various resins are preferably non-heat-wet adhesive resins (or heat-resistant hydrophobic resins or non-aqueous resins) having a softening or melting point of 100°C or higher, such as polypropylene resins, polyester resins, and polyamide resins, from the viewpoint of preventing the fibers from fusing even when melted or softened by heat treatment with high-temperature steam. Examples of these resins include polypropylene resins, polyester resins, and polyamide resins. In particular, aromatic polyester resins and polyamide resins are preferred from the viewpoint of achieving an excellent balance between heat resistance and fiber forming properties. At least the resin exposed on the surface of the conjugated fibers is preferably non-heat-wet adhesive fiber, so that the conjugated fibers (latently crimped fibers) constituting the nonwoven fabric do not fuse even when treated in high-temperature steam.

The plurality of resins constituting the conjugated fibers may be a combination of resins of the same type or a combination of resins of different types as long as they have different thermal shrinkage rates.

From the viewpoint of adhesion, the multiple resins constituting the composite fiber are preferably a combination of resins of the same type. In the case of a combination of resins of the same type, a combination of component (A) forming a homopolymer (essential component) and component (B) forming a modified polymer (copolymer) can generally be used. That is, relative to the homopolymer as an essential component, for example, by copolymerizing a copolymerizable monomer that reduces crystallinity, melting point or softening point, etc., the crystallinity can be lower than that of the homopolymer, or the melting point or softening point can be lower than that of the homopolymer by becoming amorphous. Thus, by changing the crystallinity, melting point or softening point, a difference can be set in the thermal shrinkage. The difference in melting point or softening point can be, for example, 5 to 150°C, preferably 40 to 130°C, and more preferably 60 to 120°C. The ratio of the copolymerizable monomer used for modification is, for example, 1 to 50 mol% relative to all monomers, preferably 2 to 40 mol%, and more preferably 3 to 30 mol% (particularly 5 to 20 mol%). The mass ratio of the component forming the homopolymer to the component forming the modified polymer can be selected according to the structure of the fiber, for example, homopolymer component (A)/modified polymer component (B) = 90/10 to 10/90, preferably 70/30 to 30/70, and more preferably 60/40 to 40/60.

From the perspective of easily producing latently crimped conjugate fibers, the conjugate fibers are preferably a combination of aromatic polyester resins, particularly a combination of a polyalkylene arylate resin (a) and a modified polyalkylene arylate resin (b). The polyalkylene arylate resin (a) can be a homopolymer of an aromatic dicarboxylic acid (e.g., a symmetrical aromatic dicarboxylic acid such as terephthalic acid and naphthalene-2,6-dicarboxylic acid) and an alkanediol component (e.g., a C _2-6 alkanediol such as ethylene glycol and butanediol). Specifically, poly(C _2-4 alkylene terephthalate) resins such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) can be used. PET, which is commonly used for PET fibers, has an intrinsic viscosity of 0.6 to 0.7.

On the other hand, in the modified polyalkylene arylate resin (b), examples of copolymer components that lower the melting point, softening point, or crystallinity of the essential component, polyalkylene arylate resin (a), include dicarboxylic acid components such as asymmetric aromatic dicarboxylic acids, alicyclic dicarboxylic acids, and aliphatic dicarboxylic acids, alkanediol components having a longer chain length than the alkanediol in the polyalkylene arylate resin (a), and/or diol components having an ether bond. The copolymer components may be used alone or in combination of two or more. Among these components, a wide range of usable dicarboxylic acid components include asymmetric aromatic dicarboxylic acids (such as isophthalic acid, phthalic acid, and sodium 5-sulfoisophthalate), aliphatic dicarboxylic acids (C _6-12 aliphatic dicarboxylic acids such as adipic acid), and a wide range of usable diol components include alkanediols (such as 1,3-propylene glycol, _1,4 -butanediol, 1,6-hexanediol, and neopentyl glycol), polyoxyalkylene glycols (such as diethylene glycol, triethylene glycol, polyethylene glycol, and polyoxy C _2-4 alkylene glycols). Among these, asymmetric aromatic dicarboxylic acids such as isophthalic acid and polyoxy C _2-4 alkylene glycols such as diethylene glycol are preferred. Alternatively, the modified polyalkylene arylate resin (b) may be an elastomer having a C _2-4 alkylene arylate (such as ethylene terephthalate and butylene terephthalate) as a hard segment and a (poly)oxyalkylene glycol as a soft segment.

In the modified polyalkylene arylate resin (b), the ratio of the dicarboxylic acid component (e.g., isophthalic acid) for lowering the melting point or softening point is, for example, 1 to 50 mol%, preferably 5 to 50 mol%, and more preferably 15 to 40 mol%, relative to the total amount of the dicarboxylic acid components constituting the modified polyalkylene arylate resin (b). Furthermore, the ratio of the diol component (e.g., diethylene glycol) for lowering the melting point or softening point is, for example, 30 mol% or less, preferably 10 mol% or less (e.g., 0.1 to 10 mol%) relative to the total amount of the diol components constituting the modified polyalkylene arylate resin (b). If the ratio of the copolymer component is too low, sufficient crimping is not achieved, and the morphological stability and stretchability of the crimped nonwoven fabric are reduced. On the other hand, if the ratio of the copolymer component is too high, the crimping performance is improved, but stable spinning becomes difficult.

The modified polyalkylene arylate resin (b) may contain, as monomer components, polycarboxylic acid components such as trimellitic acid and pyromellitic acid, and polyol components such as glycerin, trimethylolpropane, trimethylolethane, and pentaerythritol.

The cross-sectional shape of the composite fiber (the cross-sectional shape perpendicular to the longitudinal direction of the fiber) is not limited to a conventional solid cross-sectional shape such as a circular cross-section or a special cross-sectional shape [flat, elliptical, polygonal, 3-14 petal, T-shaped, H-shaped, V-shaped, dog-bone (I-shaped) shape, etc.], and may also be a hollow cross-sectional shape, but is generally a circular cross-sectional shape.

Examples of the cross-sectional structure of the composite fiber include phase structures formed from multiple resins, such as core-sheath, island-in-the-sea, hybrid, side-by-side (side-by-side or multi-layer laminated), radial (radially laminated), hollow radial, block, and random composite structures. Of these, structures in which phases are partially adjacent (so-called bimetallic structures) and structures with asymmetric phase structures, such as eccentric core-sheath and side-by-side structures, are preferred because they facilitate spontaneous crimping upon heating.

It should be noted that in the case where the composite fiber has a core-sheath type structure such as an eccentric core-sheath type, the core portion can be composed of a wet heat adhesive resin (for example, a vinyl alcohol polymer such as ethylene-vinyl alcohol copolymer or polyvinyl alcohol) or a thermoplastic resin with a low melting point or softening point (for example, polystyrene, low-density polyethylene, etc.) as long as it has a thermal shrinkage difference with the non-wet heat adhesive resin of the sheath portion located on the surface and can be curled.

The average fineness of the composite fiber is, for example, 0.1 to 50 dtex, preferably 0.5 to 10 dtex, and more preferably 1 to 5 dtex. If the fineness is too small, the fiber itself is difficult to manufacture and it is difficult to ensure fiber strength. Furthermore, during the crimping process, it is difficult to develop a good coil crimp. On the other hand, if the fineness is too large, the fiber becomes rigid and it is difficult to develop a sufficient crimp.

The average fiber length of the composite fiber is, for example, 10 to 100 mm, preferably 20 to 80 mm, and more preferably 25 to 75 mm. When the average fiber length is too short, it is difficult to form a fiber web, and the curled fibers are not sufficiently entangled with each other when curling, making it difficult to ensure the strength and elasticity of the nonwoven fabric. When the average fiber length is too long, it is difficult to form a fiber web with a uniform weight per unit area, and the fibers are more entangled with each other when forming the web, and when curling, they interfere with each other and are difficult to exhibit elasticity. When the average fiber length is within the above range, since a portion of the curled fibers on the surface of the nonwoven fabric are moderately exposed on the surface of the nonwoven fabric, the self-adhesiveness of the nonwoven fabric can be improved. In addition, the average fiber length within the above range is also advantageous in obtaining good hand-tearability.

The composite fiber is a latent crimped fiber, which develops (or manifests) crimps by heat treatment, and becomes a fiber having three-dimensional crimps in a substantially coil shape (helical shape or helical spring shape).

The number of crimps before heating (mechanical crimps) is, for example, 0 to 30/25 mm, preferably 1 to 25/25 mm, and more preferably 5 to 20/25 mm. The number of crimps after heating is, for example, 30 or more/25 mm (e.g., 30 to 200/25 mm), and preferably 35 to 150/25 mm.

As described above, the crimped fibers constituting the nonwoven fabric have curls that are essentially coil-shaped after being curled. The average radius of curvature of the circle formed by the coils of the crimped fibers is, for example, 10 to 250 μm, preferably 20 to 200 μm, and more preferably 50 to 160 μm. The average radius of curvature is an indicator of the average size of the circle formed by the coils of the crimped fibers. It means that when this value is large, the coils formed have a loose shape, that is, a shape with a small number of crimps. In addition, when the number of crimps is small, the crimped fibers are less intertwined with each other, making it difficult to recover the shape of the coils after deformation, which is disadvantageous in terms of exhibiting sufficient stretchability. When the average radius of curvature is too small, the crimped fibers are not fully intertwined with each other, making it difficult to ensure the strength of the web. In addition, the stress when the coils are deformed is too large, the breaking strength is excessively increased, and it is difficult to obtain appropriate stretchability.

The average pitch between the coils in the crimped fibers (average crimp pitch) is, for example, 0.03 to 0.5 mm, preferably 0.03 to 0.3 mm, and more preferably 0.05 to 0.2 mm. If the average pitch is too large, the number of crimps per fiber decreases, and sufficient stretchability cannot be achieved. If the average pitch is too small, the crimped fibers are not sufficiently entangled, making it difficult to ensure the strength of the nonwoven fabric.

In addition to the above-mentioned composite fibers, non-woven fabrics (fiber webs) may also contain other fibers (non-composite fibers). Specific examples of non-composite fibers include fibers composed of cellulose fibers [for example, natural fibers (kapok, wool, silk, hemp, etc.), semi-synthetic fibers (acetate fibers such as triacetate fibers, etc.), regenerated fibers (rayon, Polynosic, Cupra fibers, lyocell fibers (for example, registered trademark name: "Tencel", etc.)] in addition to the fibers composed of the above-mentioned non-heat-wet adhesive resins or heat-wet adhesive resins. The average fineness and average fiber length of the non-composite fibers may be the same as those of the composite fibers. Non-composite fibers may be used alone or in combination of two or more.

The ratio (mass ratio) of conjugate fibers to non-conjugate fibers is preferably adjusted so that the stress relaxation rate of the fiber sheet falls within the above-mentioned range. For example, the ratio is conjugate fibers/non-conjugate fibers = 50/50 to 100/0, preferably 60/40 to 100/0, more preferably 70/30 to 100/0, further preferably 80/20 to 100/0, and particularly preferably 90/10 to 100/0. The balance between the strength and stretchability or softness of the nonwoven fabric can be adjusted by blending non-conjugate fibers.

The nonwoven fabric (fiber web) may contain conventional additives, such as stabilizers (heat stabilizers, ultraviolet absorbers, light stabilizers, antioxidants, etc.), antibacterial agents, deodorants, fragrances, colorants (dyes, pigments, etc.), fillers, antistatic agents, flame retardants, plasticizers, lubricants, crystallization rate retardants, etc. The additives may be used alone or in combination of two or more. The additives may be either loaded on the fiber surface or contained within the fiber.

A fiber sheet composed of a nonwoven fabric containing crimped fibers can be preferably produced by a method comprising the steps of forming a web of fibers containing the above-mentioned conjugated fibers (latently crimped fibers) (web forming step), and heating the fiber web to crimp the conjugated fibers (heating step).

Conventional methods can be used to form the fiber web in the web-forming step, including direct methods such as spunbonding and meltblowing, carding methods using meltblown fibers and staple fibers, and dry methods such as air-laying. Carding methods using meltblown fibers and staple fibers are widely used, with carding methods using staple fibers being particularly popular. Examples of webs obtained using staple fibers include random webs, semi-random webs, parallel-laid webs, and cross-laid webs.

Before the heating process, an entangling process for entangling at least a part of the fibers in the fiber web can be implemented. By implementing this entangling process, a nonwoven fabric in which the curled fibers are appropriately entangled can be obtained in the subsequent heating process. The entangling method can be a mechanical entangling method, preferably a method of entangling by spraying or jetting (blowing) water. Entangling the fibers by water flow is advantageous in increasing the density of entangling by utilizing the curling in the heating process. The sprayed or jetted water can be blown from one side of the fiber web or from both sides. From the viewpoint of efficiently and firmly entangling, it is preferably blown from both sides.

The water spray pressure in the entanglement step is set to an appropriate range so that the fibers are entangled, for example, 2 MPa or more, preferably 3 to 12 MPa, more preferably 4 to 10 MPa. The temperature of the sprayed or injected water is, for example, 5 to 50°C, preferably 10 to 40°C.

For simplicity and other reasons, water spraying or jetting is preferably performed using a nozzle with a regular spray area or pattern. Specifically, for a fiber web being transported by a conveyor belt, such as an endless conveyor, water can be sprayed while the web is placed on the conveyor belt. The conveyor belt can be water-permeable, so water can be passed through the permeable conveyor belt from the back side of the fiber web and sprayed onto the fiber web. It should be noted that to prevent fiber scattering caused by the water jet, the fiber web can be pre-moistened with a small amount of water.

The nozzles for spraying or jetting water can be a plate or die head having predetermined nozzles arranged continuously in the width direction, and the plate or die head can be arranged so that the nozzles are arranged in the width direction of the supplied fiber web. The nozzle array can be more than one row, or multiple rows can be arranged in parallel. In addition, multiple nozzle dies each having a single nozzle array can be arranged in parallel.

Before the above-mentioned entangling step, a step of making the fibers in the fiber web uneven in the surface (an unevenness step) can be performed. This step can form areas in the fiber web where the fiber density is sparse. Therefore, when the entangling step is water entangling, water can be efficiently sprayed into the interior of the fiber web, making it easier to achieve appropriate entangling not only on the surface of the fiber web but also inside the fiber web.

The non-uniformization step can be performed by spraying or jetting low-pressure water onto the fiber web. Spraying or jetting low-pressure water onto the fiber web can be continuous, but is preferably performed intermittently or periodically. By spraying water onto the fiber web intermittently or periodically, a plurality of low-density portions and a plurality of high-density portions can be periodically and alternately formed.

The water spraying pressure in the non-uniformization step is preferably as low as possible, for example, 0.1 to 1.5 MPa, preferably 0.3 to 1.2 MPa, more preferably 0.6 to 1.0 MPa. The temperature of the sprayed or injected water is, for example, 5 to 50°C, preferably 10 to 40°C.

The method of spraying or injecting water intermittently or periodically is not particularly limited as long as it is a method that can periodically and alternately form a density gradient in the fiber web. From the perspective of simplicity, it is preferred to use a method of injecting water through a plate-like object (porous plate, etc.) having a regular spray area or spray pattern formed by multiple holes.

During the heating process, the fiber web is heated by high-temperature steam, causing it to curl. In this method, the fiber web is exposed to a stream of high-temperature or superheated steam (high-pressure steam), which creates coil crimps in the composite fibers (latently crimped fibers). Because the fiber web is air-permeable, even when treated from one direction, the high-temperature steam penetrates deep into the web, creating a substantially uniform crimp across the thickness, resulting in uniform fiber entanglement.

The fiber web shrinks during high-temperature steam treatment. Therefore, it is preferable to overfeed the supplied fiber web immediately before exposure to high-temperature steam, based on the target area shrinkage of the nonwoven fabric. The overfeed ratio should be 110-300%, preferably 120-250%, relative to the target nonwoven fabric length.

To supply water vapor to the fiber web, a conventional water vapor injection device can be used. The water vapor injection device is preferably capable of injecting water vapor substantially uniformly across the entire width of the fiber web at the desired pressure and volume. The water vapor injection device may be installed only on one side of the fiber web, or may be installed on the other side as well, thereby simultaneously steaming both the front and back sides of the fiber web.

Because the high-temperature steam ejected from the steam jet device is an air stream, unlike water jet encapsulation and needling treatments, it does not significantly displace the fibers within the web and penetrate into the web. The steam's penetration into the web effectively covers the surface of each fiber, achieving uniform heat curling. Furthermore, compared to dry heat treatment, sufficient heat transfer is achieved within the web, resulting in a substantially uniform curl across the web and thickness.

The nozzles for ejecting high-temperature steam, similar to the nozzles for engaging the water stream, can be a plate or die head with predetermined nozzles arranged continuously across the width of the fiber web. This plate or die head can be configured so that the nozzles are aligned across the width of the fiber web being fed. The nozzle array can be one or more rows, or multiple rows can be arranged in parallel. Furthermore, multiple nozzle dies each having a single nozzle array can be arranged in parallel.

The pressure of the high-temperature water vapor used can be selected in the range of 0.1 to 2 MPa (for example, 0.2 to 1.5 MPa). When the water vapor pressure is too high, the fibers forming the fiber web sometimes move too much and the texture becomes messy, and sometimes the fibers are excessively entangled. When the pressure is too weak, the fiber web cannot be given the heat required to show fiber curling, and the water vapor cannot pass through the fiber web, which easily makes the fiber curling in the thickness direction uneven. The temperature of the high-temperature water vapor depends on the material of the fiber, etc., and can be selected from the range of 70 to 180°C (for example, 80 to 150°C). The processing speed of the high-temperature water vapor can be selected from the range of 200 m/min or less (for example, 0.1 to 100 m/min).

After the crimping of the composite fibers in the fiber web is achieved as described above, moisture may remain in the nonwoven fabric. Therefore, a drying step may be performed as needed to dry the nonwoven fabric. Examples of drying methods include methods using drying equipment such as a drum dryer or a tenter frame; non-contact methods such as far-infrared irradiation, microwave irradiation, and electron beam irradiation; and methods such as blowing hot air and passing the nonwoven fabric through the hot air.

Examples of methods for adjusting the stress relaxation rate to the above range in the above-mentioned fiber sheet production method include adjusting the content ratio of the composite fiber to the non-composite fiber; adjusting the conditions (particularly the temperature and/or pressure) of the high-temperature steam used in the heating step; and adjusting the drying temperature in the drying step.

<Second embodiment>

(1) Characteristics of fiber sheets

The fiber sheet of this embodiment (hereinafter also referred to as "fiber sheet") can be used not only as a general bandage but also as a medical article such as a compression bandage used for hemostasis, compression therapy, etc. The fiber sheet satisfies the following formula [A], where the thickness of a single sheet measured by method A (load: 0.5 kPa) in accordance with JIS L1913 is T ₁ [mm] and the thickness of three sheets stacked together measured under this condition is T ₃ [mm].

{T ₃ /(3×T ₁ )}×100≤85〔%〕 [A]

A fiber sheet satisfying the above formula [A] is not likely to hinder the bending movement of a part of the body, even when it is wrapped around a part that is subject to bending and stretching, such as a joint. When the part is a small joint, such as a finger, the difficulty of movement becomes particularly obvious when a bandage is wrapped around it. However, by using a fiber sheet satisfying the above formula [A], even when it is wrapped around such a small joint, it is possible to effectively prevent the bending movement from being hindered. From the perspective of the bendability of the part when it is wrapped around a part that is subject to bending and stretching, the left side of the above formula [A] is preferably 84% or less, and more preferably 83% or less. The left side of the above formula [A] is usually 50% or more, and more typically 60% or more.

Another method for suppressing bending hindrance is to reduce the basis weight of the fiber sheet. However, reducing the basis weight reduces the strength of the fiber sheet. For example, the wear resistance of the exposed portion when wrapped around the application area is reduced, and the sheet is more susceptible to breakage during stretching, making it difficult to achieve sufficient durability. In contrast, using a fiber sheet that satisfies the above formula [A] can suppress bending hindrance regardless of whether the basis weight is adjusted. Therefore, the invention according to this embodiment can provide a fiber sheet that suppresses bending hindrance and has excellent durability.

From the perspective of ensuring the flexibility of a portion when wrapped around a portion that is bent and stretched, the fiber sheet preferably exhibits extensibility. As described above, in this specification, "extensibility" means exhibiting a 50% elongation stress in at least one direction (the first direction) within the sheet's plane. The 50% elongation stress refers to the elongation stress at 50% elongation (immediately after elongation) and can be measured by a tensile test in accordance with JIS L 1913, "Testing Methods for General Nonwoven Fabrics."

For example, a fiber sheet is a bandage having a length direction and a width direction. If the bandage is intended to be wrapped around a joint such as a finger, the bandage is typically wrapped so that its width direction is parallel or substantially parallel to the length direction of the finger. In this case, to improve the flexibility of the finger joint, the bandage preferably has good extensibility in at least the width direction. From this perspective, when a fiber sheet has a length direction and a width direction, such as a bandage, the first direction is preferably the width direction of the fiber sheet. This width direction can be a direction perpendicular to the direction of travel (MD direction) of the fiber sheet during the manufacturing process, i.e., the CD direction.

Therefore, the fiber sheet preferably has excellent elongation in at least one direction (first direction) within the sheet plane, more preferably in the width direction. Specifically, when the elongation stress when stretched at 50% in the first direction is set as 50% elongation stress S ₁ [N/50 mm], and the elongation stress when stretched at 50% in a second direction perpendicular to the first direction within the plane is set as 50% elongation stress S ₂ [N/50 mm], the following formula [B] is preferably satisfied.

S ₂ /S ₁ ≥3 [B]

The left side of formula [B] is preferably 5 or more. The left side of formula [B] is usually 20 or less. By using a fiber sheet having a first direction that satisfies formula [B], when the fiber sheet is wound with its first direction parallel or substantially parallel to the longitudinal direction of a finger, for example, interference with bending can be more effectively suppressed. From the perspective of imparting good extensibility in the second direction, the left side of formula [B] is preferably 10 or less.

The 50% elongation stress _S1 in the first direction is preferably 0.1 to 20 N/50 mm, more preferably 0.5 to 15 N/50 mm, and even more preferably 1 to 12 N/50 mm.

When the fiber sheet has a longitudinal direction and a width direction, the second direction perpendicular to the first direction in the plane is preferably the longitudinal direction. The longitudinal direction may be the traveling direction (MD direction) of the fiber sheet during the manufacturing process. The 50% elongation stress _S2 in the second direction and the 50% elongation stress in directions other than the first direction are preferably 0.5 to 60 N/50 mm, more preferably 1 to 45 N/50 mm, and even more preferably 2 to 40 N/50 mm.

The fiber sheet preferably exhibits self-adhesive properties. As described above, in this specification, "self-adhesive properties" refer to the property of being locked or fixed by overlapping (contacting) the fibers on the surface of the fiber sheet, thereby interlocking or adhering to each other. Self-adhesive properties are advantageous when the fiber sheet is a bandage, for example. For example, when the fiber sheet is a bandage, after wrapping the bandage around the application area, the end of the bandage is overlapped (or torn and overlapped) with the underlying bandage surface. This stretches and presses the wrapped fiber sheets, causing the fiber sheets to be joined and fixed, thereby exhibiting self-adhesive properties.

By making the fiber sheet inherently self-adhesive, there's no need to form a layer of a self-adhesive agent, such as an elastomer or adhesive, on the fiber sheet surface, nor is there a need for a separate fastener to secure the front end after wrapping. For example, Japanese Patent Application Laid-Open No. 2005-095381 (Patent Document 4) describes attaching an acrylic polymer (Claim 1) or latex (paragraphs [0004] to [0006]) as a self-adhesive to at least one side of a bandage base material. Forming a layer of an elastomer, such as latex, on the fiber sheet surface is effective in improving self-adhesion.

However, the fiber sheet of this embodiment is preferably composed solely of a non-elastomer material, more specifically, solely of fibers. When such an elastomer layer is formed on the surface of the fiber sheet, the gaps on the fiber sheet surface are sealed by the elastomer, making it difficult for the fibers to mesh when the fiber sheets are stacked. Consequently, the thickness _T3 of the stacked fiber sheets is not sufficiently reduced, resulting in a tendency to make it difficult to satisfy the above-mentioned formula [A]. Furthermore, the elastomer layer also poses the risk of causing skin irritation or allergies when wrapped around the application site.

The self-adhesiveness of a fiber sheet can be evaluated by the curved surface sliding stress. From the perspective of self-adhesiveness, the curved surface sliding stress of the fiber sheet is, for example, 3 N/50 mm or greater, preferably 5 N/50 mm or greater. Furthermore, the curved surface sliding stress is preferably greater than the breaking strength. Furthermore, from the perspective of making it easier to untangle the entangled fiber sheet when necessary, the curved surface sliding stress is preferably 30 N/50 mm or less, more preferably 25 N/50 mm or less. The curved surface sliding stress is measured using a tensile testing machine according to the method described in the Examples (Figures 1 to 3).

The fiber sheet is preferably hand-tearable. As mentioned above, in this specification, "hand-tearable" refers to the property of being able to be broken (cut) by stretching by hand. The hand-tearability of the fiber sheet can be evaluated by the breaking strength. From the perspective of hand-tearability, the breaking strength of the fiber sheet in at least one direction within the sheet surface is preferably 5 to 100 N/50 mm, more preferably 8 to 60 N/50 mm, and even more preferably 10 to 40 N/50 mm. By setting the breaking strength to the above range, good hand-tearability that can be relatively easily torn (cut) by hand can be imparted. When the breaking strength is too high, the hand-tearability is reduced, for example, it becomes difficult to tear the fiber sheet with one hand. On the other hand, when the breaking strength is too low, the strength of the fiber sheet is insufficient, it is easy to break, and the durability and handleability are reduced. The breaking strength can be measured by a tensile test based on JIS L 1913 "General nonwoven fabric test methods".

At least one direction within the sheet surface is the direction in which the fiber sheet is stretched when torn manually, and is preferably the aforementioned second direction. This second direction may be the MD direction, and when the fiber sheet has a longitudinal direction and a width direction, such as in a bandage, the longitudinal direction is preferably the longitudinal direction of the fiber sheet. Specifically, when the fiber sheet is used as a bandage, the bandage is typically stretched along its longitudinal direction, wrapped around the application site, and then torn in the longitudinal direction. Therefore, the second direction is preferably the longitudinal direction, which serves as the stretching direction.

The breaking strength in a direction other than at least one direction within the sheet surface (e.g., the first direction (CD direction), the width direction when the fiber sheet has a length direction and a width direction like a bandage) is, for example, 0.1 to 300 N/50 mm, preferably 0.5 to 100 N/50 mm, and more preferably 1 to 20 N/50 mm.

From the viewpoint of hand-tearability, the fiber sheet is preferably composed only of a non-elastomer material, more specifically, preferably composed only of fibers. When a layer composed of an elastomer is formed on the surface of the fiber sheet, the hand-tearability may be reduced.

The fiber sheet has an elongation at break in at least one direction within the sheet plane of, for example, 50% or greater, preferably 60% or greater, and more preferably 80% or greater. An elongation at break within this range is advantageous in improving the stretchability of the fiber sheet. The elongation at break in at least one direction within the sheet plane is typically 300% or less, preferably 250% or less. The elongation at break can also be measured by a tensile test in accordance with JIS L1913, "Testing Methods for General Nonwoven Fabrics."

From the perspective of improving the flexibility of a portion that is subject to bending and stretching when wrapped around a joint, the at least one direction within the sheet surface is preferably the first direction. The first direction may be the CD direction. When the fiber sheet has a longitudinal direction and a width direction, such as a bandage, the first direction is preferably the width direction of the fiber sheet.

The breaking elongation in a direction other than at least one direction within the sheet surface (e.g., the second direction (MD direction), the longitudinal direction when the fiber sheet has a longitudinal direction and a width direction like a bandage) is, for example, 10 to 500%, preferably 100 to 350%.

The recovery rate after 50% elongation in at least one direction within the sheet surface (50% elongation recovery rate) is preferably 70% or greater (less than 100%), more preferably 80% or greater, and even more preferably 90% or greater. A 50% elongation recovery rate within this range improves elongation compliance. For example, when wrapped around a flexing and stretching area such as a joint, the sheet not only fully follows the bending motion and shape of the area but also helps improve the self-adhesion caused by friction between the stacked fiber sheets. If the elongation recovery rate is too low, the sheet will not follow the bending motion of the area, and the deformation of the fiber sheet caused by this motion will not be restored, resulting in a weakened fixation of the wrapped fiber sheet.

The at least one direction within the surface of the sheet is preferably the first direction, which is particularly required to follow the bending motion of the portion when the sheet is wrapped around a portion that flexes and stretches, such as a joint. The first direction may be the CD direction. When the fiber sheet has a longitudinal direction and a width direction, such as a bandage, the width direction of the fiber sheet is preferably the first direction.

The recovery rate after 50% elongation is defined by the following formula, where X is the residual strain (%) after the test when the load is removed immediately after the elongation reaches 50% in a tensile test based on JIS L 1913 "General nonwoven fabric testing methods."

Recovery rate after 50% elongation (%) = 100 - X

The recovery rate after 50% elongation in a direction other than at least one direction within the above-mentioned sheet surface (for example, the second direction (MD direction), the width direction when the fiber sheet has a length direction and a width direction like a bandage) is, for example, greater than 70% (less than 100%), preferably greater than 80%.

The compressive modulus Pe of the fiber sheet is preferably 85% or less, more preferably 80% or less. A compressive modulus Pe within this range is advantageous in satisfying the aforementioned formula [A] and, in turn, in achieving a fiber sheet that is less likely to interfere with bending motions of joints, etc. The lower limit of the compressive modulus Pe is not particularly limited, but is, for example, 50%. The compressive modulus Pe can be calculated according to the following formula [C] based on JIS L 1913 "General Test Methods for Nonwoven Fabrics."

Pe＝{(T ₁ '-T)/(T ₁ -T)}×100 [C]

_T1 is the thickness when the initial load (0.5 kPa) is applied (mm), and has the same meaning as _T1 in the above formula [A]. T is the thickness when a load of 30 kPa is applied (mm), and _T1 ' is the thickness when the initial load is restored (mm).

The fiber sheet preferably has a basis weight of 30 to 300 g/m ² , more preferably 50 to 200 g/m ² . From the perspective of more effectively suppressing interference with bending motion, the basis weight is further preferably 180 g/m ² or less. According to the fiber sheet of this embodiment, even when the basis weight is high (e.g., 50 g/m ² or greater, 70 g/m ² or greater, 90 g/m ² or greater, 110 g/m ² or greater, or 130 g/m ² or greater), interference with bending motion of joints, etc. can be effectively suppressed.

The thickness T ₁ of the fiber sheet (this thickness T ₁ has the same meaning as T ₁ in formula [A]) is, for example, 0.2 to 5 mm, preferably 0.3 to 3 mm, and more preferably 0.4 to 2 mm. When the basis weight and thickness are within this range, a good balance is achieved in bendability, elongation, softness, hand feel, and cushioning properties when the fiber sheet is wound. The density (bulk density) of the fiber sheet can be a value corresponding to the basis weight and thickness, for example, 0.03 to 0.5 g/cm ³ , preferably 0.04 to 0.4 g/cm ³ , and more preferably 0.05 to 0.2 g/cm ³ . From the perspective of more effectively suppressing interference with bending motion, the density is more preferably 0.15 g/cm ³ or less.

The difference ΔT between the thickness _T1 of the fiber sheet when an initial load (0.5 kPa) is applied and the thickness T when a load of 30 kPa is applied is preferably 0.05 mm or greater, more preferably 0.1 mm or greater. The thickness difference ΔT falling within this range is advantageous in satisfying the above-mentioned formula [A] and, in turn, is advantageous in achieving a fiber sheet that is less likely to interfere with bending movements of joints, etc. The thickness difference ΔT corresponds to ( _T1 - T) in the above-mentioned formula [C]. The upper limit of the thickness difference ΔT is not particularly limited, but is, for example, 0.8 mm.

The air permeability of the fiber sheet obtained by the Frazier method is preferably 0.1 cm ³ /(cm ² ·sec) or higher, more preferably 1 to 500 ^{cm 3} /(cm ² ·sec), even more preferably 5 to 300 ^{cm 3} /(cm ² ·sec), and particularly preferably 10 to 200 cm ³ /(cm ² ·sec). When the air permeability falls within this range, the fiber sheet exhibits excellent breathability and is less likely to cause stuffiness, making it more suitable for applications such as bandages on the human body.

(2) Structure and manufacturing method of fiber sheet

The fiber sheet of this embodiment is not particularly limited as long as it is composed of fibers, and may be, for example, a woven fabric, a nonwoven fabric, a knitted fabric, or the like. The shape of the fiber sheet can be selected depending on the intended use, but is preferably a rectangular sheet having a longitudinal direction and a width direction, such as a tape or a strip. The fiber sheet may have a single-layer structure or a multilayer structure consisting of two or more fiber layers.

Examples of methods for imparting stretchability and extensibility to fiber sheets include: 1) pleating a fiber sheet substrate such as a woven fabric, nonwoven fabric, or knitted fabric; 2) weaving yarns made of a stretchable material such as an elastomer represented by rubber into a fiber sheet; 3) combining a layer made of a stretchable material such as an elastomer with a non-stretchable fiber sheet substrate, or impregnating the fiber sheet with a stretchable material; and 4) using crimped fibers wound into coils as at least a portion of the fibers constituting a nonwoven fabric.

Among the above, the fiber sheet of this embodiment preferably has the structure of 4). The pleating process of 1) is effective in imparting stretchability, but the undulating shape of the pleats makes it difficult to obtain a fiber sheet that satisfies the above formula [A]. The method of 2) can easily impart stretchability, but there is a risk of reduced flexibility when wrapping the fiber sheet due to the incorporation of rubber threads, etc. As mentioned above, the method of 3) tends to make it difficult to satisfy the above formula [A] by sealing the fiber sheet surface with an elastomer.

From the perspectives of joint flexibility, self-adhesion, hand-tearability when wrapped around a joint, and the ability to conform to uneven surfaces (fitting properties) when wrapped around uneven surfaces such as joints, the fiber sheet is preferably composed of a nonwoven fabric. Specifically, it is preferably a nonwoven fabric sheet, more preferably a nonwoven fabric comprising crimped fibers wound into coils, and even more preferably a nonwoven fabric comprising such crimped fibers and not subjected to any one or more (preferably none) of the treatments 1) to 3) above. It is particularly preferred that the nonwoven fabric sheet be composed solely of such crimped fibers.

A fiber sheet composed of a nonwoven fabric containing crimped fibers preferably has a structure in which the individual fibers constituting the sheet are substantially non-fusion-bonded, and the crimped fibers are primarily restrained or locked by the intertwining of these crimped loops. Furthermore, it is preferred that the majority (most) of the crimped fibers (with their axial direction) be oriented substantially parallel to the sheet surface. As described above, in this specification, "substantially parallel to the surface direction" means a state in which a plurality of crimped fibers (with their axial direction) are locally oriented in the thickness direction, such as by entanglement through needle punching, without overlapping portions.

In a fiber sheet composed of a nonwoven fabric containing crimped fibers, the crimped fibers are preferably oriented in a certain direction within the sheet plane (e.g., the second direction described above, preferably the longitudinal direction), with adjacent or intersecting crimped fibers entangled with each other through these crimped loops. Furthermore, the crimped fibers are preferably slightly entangled with each other in the thickness direction (or oblique direction) of the fiber sheet. Entanglement of the crimped fibers may occur during the shrinkage of the fiber web serving as a precursor to the fiber sheet.

A nonwoven fabric in which the crimped fibers (the axial direction of the crimped fibers) are oriented and intertwined in a certain direction within the sheet surface exhibits good stretchability (including elongation) in that direction. When tension is applied to the stretchable nonwoven fabric in the longitudinal direction, the intertwined crimped coils stretch and attempt to return to their original coils, thereby exhibiting high stretchability in the longitudinal direction. The stretchable nonwoven fabric can exhibit excellent elongation in a direction orthogonal to the certain direction within the sheet surface (e.g., the width direction). In addition, the slight intertwining of the crimped fibers in the thickness direction of the nonwoven fabric can exhibit cushioning and softness in the thickness direction, thereby providing the nonwoven fabric with a good touch and feel. In addition, the crimped coils can easily intertwine with other crimped coils through contact under a certain degree of pressure. The intertwining of the crimped coils can exhibit self-adhesion.

In a fiber sheet composed of a nonwoven fabric containing crimped fibers, when tension is applied in the orientation direction of the crimped fibers (e.g., the second direction described above, preferably the longitudinal direction), the entangled crimped coils are elastically deformed and stretched, and when further tension is applied, they are finally untied, thereby providing good cuttability (hand-tearability).

As described above, the nonwoven fabric that can form the fiber sheet preferably includes crimped fibers that are curled into coils. The crimped fibers are preferably oriented primarily in the plane direction of the nonwoven fabric and are preferably curled substantially uniformly in the thickness direction. The crimped fibers can be composed of composite fibers formed from a phase structure of multiple resins having different thermal shrinkage rates (or thermal expansion coefficients).

The composite fibers that form the crimped fibers are fibers (latent crimped fibers) with an asymmetric or layered (so-called bimetallic) structure that crimps when heated due to the different thermal shrinkage rates (or thermal expansion coefficients) of multiple resins. These resins typically have different softening or melting points. The various resins can be selected from, for example, polyolefin resins (poly _C2-4 olefin resins such as low-density, medium-density or high-density polyethylene and polypropylene); acrylic resins (acrylonitrile resins having acrylonitrile units such as acrylonitrile-vinyl chloride copolymers); polyvinyl acetal resins (polyvinyl acetal resins); polyvinyl chloride resins (polyvinyl chloride, vinyl chloride-vinyl acetate copolymers, vinyl chloride-acrylonitrile copolymers); polyvinylidene chloride resins (vinylidene chloride-vinyl chloride copolymers, vinylidene chloride-vinyl acetate copolymers); styrene resins (heat-resistant polystyrene); polyester resins (polyethylene terephthalate resins, polypropylene terephthalate resins, polybutylene terephthalate resins, polyethylene naphthalate resins); Thermoplastic resins include _polyamides (polyamides 6, 66, 11, 12, 610, and 612, aliphatic polyamides; semi-aromatic polyamides; aromatic polyamides; polyphenylene isophthalamide, polyhexamethylene terephthalamide, and polyparaphenylene terephthalamide); polycarbonate resins (bisphenol A polycarbonate); polyparaphenylene benzobisazole resins; polyphenylene sulfide resins; polyurethane resins; and cellulose resins (cellulose esters). The above thermoplastic resins may also contain other copolymerizable units.

Among these, the various resins are preferably non-heat-wet adhesive resins (or heat-resistant hydrophobic resins or non-aqueous resins) having a softening or melting point of 100°C or higher, from the perspective of preventing the fibers from fusing even when heated with high-temperature steam and melting or softening. Examples thereof include polypropylene resins, polyester resins, and polyamide resins. In particular, aromatic polyester resins and polyamide resins are preferred from the perspective of achieving an excellent balance between heat resistance and fiber forming properties. At least the resin exposed on the surface of the conjugated fibers is preferably non-heat-wet adhesive fiber, so that the conjugated fibers (latently crimped fibers) constituting the nonwoven fabric do not fuse even when treated in high-temperature steam.

The plurality of resins constituting the conjugated fibers may be a combination of resins of the same type or a combination of resins of different types as long as they have different thermal shrinkage rates.

From the viewpoint of adhesion, the multiple resins constituting the composite fiber are preferably a combination of the same type of resins. In the case of a combination of the same type of resins, a combination of component (A) forming a homopolymer (essential component) and component (B) forming a modified polymer (copolymer) can generally be used. That is, relative to the homopolymer as an essential component, for example, by copolymerizing and modifying a copolymerizable monomer that reduces crystallinity, melting point or softening point, the crystallinity can be lower than that of the homopolymer, or the melting point or softening point can be lower than that of the homopolymer by becoming amorphous. Thus, by changing the crystallinity, melting point or softening point, a difference can be set in the thermal shrinkage. The difference in melting point or softening point can be, for example, 5 to 150°C, preferably 40 to 130°C, and more preferably 60 to 120°C. The proportion of the copolymerizable monomer used for modification is, for example, 1 to 50 mol% relative to all monomers, preferably 2 to 40 mol%, and more preferably 3 to 30 mol% (particularly 5 to 20 mol%). The mass ratio of the component forming the homopolymer to the component forming the modified polymer can be selected according to the structure of the fiber, for example, homopolymer component (A)/modified polymer component (B) = 90/10 to 10/90, preferably 70/30 to 30/70, and more preferably 60/40 to 40/60.

From the perspective of easily producing latently crimped conjugate fibers, the conjugate fibers are preferably a combination of aromatic polyester resins, particularly a combination of a polyalkylene arylate resin (a) and a modified polyalkylene arylate resin (b). The polyalkylene arylate resin (a) can be a homopolymer of an aromatic dicarboxylic acid (e.g., a symmetrical aromatic dicarboxylic acid such as terephthalic acid and naphthalene-2,6-dicarboxylic acid) and an alkanediol component (e.g., a C _2-6 alkanediol such as ethylene glycol and butanediol). Specifically, poly(C _2-4 alkylene terephthalate) resins such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) can be used. Generally, PET, which is commonly used for PET fibers, has an intrinsic viscosity of 0.6 to 0.7.

On the other hand, in the modified polyalkylene arylate resin (b), examples of copolymer components that lower the melting point, softening point, or crystallinity of the essential component, polyalkylene arylate resin (a), include dicarboxylic acid components such as asymmetric aromatic dicarboxylic acids, alicyclic dicarboxylic acids, and aliphatic dicarboxylic acids, alkanediol components having a longer chain length than the alkanediol in the polyalkylene arylate resin (a), and/or diol components having an ether bond. The copolymer components may be used alone or in combination of two or more. Among these components, a wide range of usable dicarboxylic acid components include asymmetric aromatic dicarboxylic acids (such as isophthalic acid, phthalic acid, and sodium 5-sulfoisophthalate), aliphatic dicarboxylic acids (C _6-12 aliphatic dicarboxylic acids such as adipic acid), and a wide range of usable diol components include alkanediols (such as 1,3-propylene glycol, _1,4 -butanediol, 1,6-hexanediol, and neopentyl glycol), polyoxyalkylene glycols (such as diethylene glycol, triethylene glycol, polyethylene glycol, and polyoxy C _2-4 alkylene glycols). Among these, asymmetric aromatic dicarboxylic acids such as isophthalic acid and polyoxy C _2-4 alkylene glycols such as diethylene glycol are preferred. Alternatively, the modified polyalkylene arylate resin (b) may be an elastomer having a C _2-4 alkylene arylate (such as ethylene terephthalate and butylene terephthalate) as a hard segment and a (poly)oxyalkylene glycol as a soft segment.

In the modified polyalkylene arylate resin (b), the ratio of the dicarboxylic acid component (e.g., isophthalic acid) for lowering the melting point or softening point is, for example, 1 to 50 mol%, preferably 5 to 50 mol%, and more preferably 15 to 40 mol%, relative to the total amount of the dicarboxylic acid components constituting the modified polyalkylene arylate resin (b). Furthermore, the ratio of the diol component (e.g., diethylene glycol) for lowering the melting point or softening point is, for example, 30 mol% or less, preferably 10 mol% or less (e.g., 0.1 to 10 mol%) relative to the total amount of the diol components constituting the modified polyalkylene arylate resin (b). If the ratio of the copolymer component is too low, sufficient crimping is not achieved, and the morphological stability and stretchability of the crimped nonwoven fabric are reduced. On the other hand, if the ratio of the copolymer component is too high, the crimping performance is improved, but stable spinning becomes difficult.

The modified polyalkylene arylate resin (b) may contain, as monomer components, polycarboxylic acid components such as trimellitic acid and pyromellitic acid, and polyol components such as glycerin, trimethylolpropane, trimethylolethane, and pentaerythritol.

The cross-sectional shape of the composite fiber (the cross-sectional shape perpendicular to the longitudinal direction of the fiber) is not limited to a conventional solid cross-sectional shape such as a circular cross-section or a special cross-sectional shape [flat, elliptical, polygonal, 3-14 petal, T-shaped, H-shaped, V-shaped, dog-bone (I-shaped) shape, etc.], and may also be a hollow cross-sectional shape, but is generally a circular cross-sectional shape.

Examples of the cross-sectional structure of the composite fiber include phase structures formed from multiple resins, such as core-sheath, island-in-the-sea, hybrid, side-by-side (side-by-side or multi-layer laminated), radial (radially laminated), hollow radial, block, and random composite structures. Of these, structures in which phases are partially adjacent (so-called bimetallic structures) and structures with asymmetric phase structures, such as eccentric core-sheath and side-by-side structures, are preferred because they facilitate spontaneous crimping upon heating.

It should be noted that in the case where the composite fiber has a core-sheath type structure such as an eccentric core-sheath type, the core portion can be composed of a wet heat adhesive resin (for example, a vinyl alcohol polymer such as ethylene-vinyl alcohol copolymer or polyvinyl alcohol) or a thermoplastic resin with a low melting point or softening point (for example, polystyrene, low-density polyethylene, etc.) as long as it has a thermal shrinkage difference with the non-wet heat adhesive resin of the sheath portion located on the surface and can be curled.

The average fineness of the composite fiber is, for example, 0.1 to 50 dtex, preferably 0.5 to 10 dtex, and more preferably 1 to 5 dtex. If the fineness is too small, the fiber itself is difficult to manufacture and it is difficult to ensure fiber strength. Furthermore, during the crimping process, it is difficult to develop a good coil crimp. On the other hand, if the fineness is too large, the fiber becomes rigid and it is difficult to develop a sufficient crimp.

The average fiber length of the composite fiber is, for example, 10 to 100 mm, preferably 20 to 80 mm, and more preferably 25 to 75 mm. When the average fiber length is too short, it is difficult to form a fiber web, and the curled fibers are not sufficiently entangled with each other when curling, making it difficult to ensure the strength and elasticity of the nonwoven fabric. When the average fiber length is too long, it is difficult to form a fiber web with a uniform weight per unit area, and the fibers are more entangled with each other when forming the web, and when curling, they interfere with each other and are difficult to exhibit elasticity. When the average fiber length is within the above range, since a portion of the curled fibers on the surface of the nonwoven fabric are moderately exposed on the surface of the nonwoven fabric, the self-adhesiveness of the nonwoven fabric can be improved. In addition, the average fiber length within the above range is also advantageous in obtaining good hand-tearability.

The composite fiber is a latently crimped fiber, which develops (or manifests) crimps by heat treatment, and becomes a fiber having three-dimensional crimps that are substantially coil-shaped (helical or coil spring-shaped).

The number of crimps before heating (mechanical crimps) is, for example, 0 to 30/25 mm, preferably 1 to 25/25 mm, and more preferably 5 to 20/25 mm. The number of crimps after heating is, for example, 30 or more/25 mm (e.g., 30 to 200/25 mm), and preferably 35 to 150/25 mm.

As described above, the crimped fibers constituting the nonwoven fabric have curls that are essentially coil-shaped after being curled. The average radius of curvature of the circle formed by the coils of the crimped fibers is, for example, 10 to 250 μm, preferably 20 to 200 μm, and more preferably 50 to 160 μm. The average radius of curvature is an indicator of the average size of the circle formed by the coils of the crimped fibers. It means that when this value is large, the coils formed have a loose shape, that is, a shape with a small number of crimps. In addition, when the number of crimps is small, the crimped fibers are less intertwined with each other, making it difficult to recover the shape of the coils after deformation, which is disadvantageous in terms of exhibiting sufficient stretchability. When the average radius of curvature is too small, the crimped fibers are not fully intertwined with each other, making it difficult to ensure the strength of the web. In addition, the stress when the coils are deformed is too large, the breaking strength is excessively increased, and it is difficult to obtain appropriate stretchability.

The average pitch between the coils in the crimped fibers (average crimp pitch) is, for example, 0.03 to 0.5 mm, preferably 0.03 to 0.3 mm, and more preferably 0.05 to 0.2 mm. If the average pitch is too large, the number of crimps per fiber decreases, and sufficient stretchability cannot be achieved. If the average pitch is too small, the crimped fibers are not sufficiently entangled, making it difficult to ensure the strength of the nonwoven fabric.

In addition to the above-mentioned composite fibers, non-woven fabrics (fiber webs) may also contain other fibers (non-composite fibers). Specific examples of non-composite fibers include fibers composed of cellulose fibers [for example, natural fibers (kapok, wool, silk, hemp, etc.), semi-synthetic fibers (acetate fibers such as triacetate fibers, etc.), regenerated fibers (rayon, Polynosic, Cupra fibers, lyocell fibers (for example, registered trademark name: "Tencel", etc.)] in addition to the fibers composed of the above-mentioned non-heat-wet adhesive resins or heat-wet adhesive resins. The average fineness and average fiber length of the non-composite fibers may be the same as those of the composite fibers. The non-composite fibers may be used alone or in combination of two or more.

The ratio (mass ratio) of the conjugate fiber to the non-conjugate fiber is preferably adjusted so that the fiber sheet satisfies the above formula [A]. For example, the ratio is conjugate fiber/non-conjugate fiber = 50/50 to 100/0, preferably 60/40 to 100/0, more preferably 70/30 to 100/0, further preferably 80/20 to 100/0, and particularly preferably 90/10 to 100/0. The balance between the strength and stretchability or softness of the nonwoven fabric can be adjusted by blending the non-conjugate fiber.

The nonwoven fabric (fiber web) may contain conventional additives, such as stabilizers (heat stabilizers, ultraviolet absorbers, light stabilizers, antioxidants, etc.), antibacterial agents, deodorants, fragrances, colorants (dyes, pigments, etc.), fillers, antistatic agents, flame retardants, plasticizers, lubricants, crystallization rate retardants, etc. The additives may be used alone or in combination of two or more. The additives may be either loaded on the fiber surface or contained within the fiber.

A fiber sheet composed of a nonwoven fabric containing crimped fibers can be preferably produced by a method comprising the steps of forming a web of fibers containing the above-mentioned conjugated fibers (latently crimped fibers) (web forming step), and heating the fiber web to crimp the conjugated fibers (heating step).

Conventional methods can be used to form the fiber web in the web-forming step, including direct methods such as spunbonding and meltblowing, carding methods using meltblown fibers and staple fibers, and dry methods such as air-laying. Carding methods using meltblown fibers and staple fibers are widely used, with carding methods using staple fibers being particularly popular. Examples of webs obtained using staple fibers include random webs, semi-random webs, parallel-laid webs, and cross-laid webs.

Before the heating process, an entangling process for entangling at least a part of the fibers in the fiber web can be implemented. By implementing this entangling process, a nonwoven fabric in which the curled fibers are appropriately entangled can be obtained in the subsequent heating process. The entangling method can be a mechanical entangling method, preferably a method of entangling by spraying or jetting (blowing) water. Entangling the fibers by water flow is advantageous in increasing the density of entangling by utilizing the curling in the heating process. The sprayed or jetted water can be blown from one side of the fiber web or from both sides. From the viewpoint of efficiently and firmly entangling, it is preferably blown from both sides.

The water spray pressure in the entanglement step is set to an appropriate range so that the fibers are entangled, for example, 2 MPa or more, preferably 3 to 12 MPa, more preferably 4 to 10 MPa. The temperature of the sprayed or injected water is, for example, 5 to 50°C, preferably 10 to 40°C.

For simplicity and other reasons, water spraying or jetting is preferably performed using a nozzle with a regular spray area or pattern. Specifically, for a fiber web being transported by a conveyor belt, such as an endless conveyor, water can be sprayed while the web is placed on the conveyor belt. The conveyor belt can be water-permeable, so water can be passed through the permeable conveyor belt from the back side of the fiber web and sprayed onto the fiber web. It should be noted that to prevent fiber scattering caused by the water jet, the fiber web can be pre-moistened with a small amount of water.

The nozzles for spraying or jetting water can be a plate or die head having predetermined nozzles arranged continuously in the width direction, and the plate or die head can be arranged so that the nozzles are arranged in the width direction of the supplied fiber web. The nozzle array can be more than one row, or multiple rows can be arranged in parallel. In addition, multiple nozzle dies each having a single nozzle array can be arranged in parallel.

Before the above-mentioned entangling step, a step of making the fibers in the fiber web uneven in the surface (an unevenness step) can be performed. This step can form areas in the fiber web where the fiber density is sparse. Therefore, when the entangling step is water entangling, water can be efficiently sprayed into the interior of the fiber web, making it easier to achieve appropriate entangling not only on the surface of the fiber web but also inside the fiber web.

The non-uniformization step can be performed by spraying or jetting low-pressure water onto the fiber web. Spraying or jetting low-pressure water onto the fiber web can be continuous, but is preferably performed intermittently or periodically. By spraying water onto the fiber web intermittently or periodically, a plurality of low-density portions and a plurality of high-density portions can be periodically and alternately formed.

The water spraying pressure in the non-uniformization step is preferably as low as possible, for example, 0.1 to 1.5 MPa, preferably 0.3 to 1.2 MPa, more preferably 0.6 to 1.0 MPa. The temperature of the sprayed or injected water is, for example, 5 to 50°C, preferably 10 to 40°C.

The method of spraying or injecting water intermittently or periodically is not particularly limited as long as it is a method that can periodically and alternately form a density gradient in the fiber web. From the perspective of simplicity, it is preferred to use a method of injecting water through a plate-like object (porous plate, etc.) having a regular spray area or spray pattern formed by multiple holes.

During the heating process, the fiber web is heated by high-temperature steam, causing it to curl. In this method, the fiber web is exposed to a stream of high-temperature or superheated steam (high-pressure steam), which creates coil crimps in the composite fibers (latently crimped fibers). Because the fiber web is air-permeable, even when treated from one direction, the high-temperature steam penetrates deep into the web, creating a substantially uniform crimp across the thickness, resulting in uniform fiber entanglement.

The fiber web shrinks during high-temperature steam treatment. Therefore, it is preferable to overfeed the supplied fiber web immediately before exposure to high-temperature steam, based on the target area shrinkage of the nonwoven fabric. The overfeed ratio should be 110-300%, preferably 120-250%, relative to the target nonwoven fabric length.

To supply water vapor to the fiber web, a conventional water vapor injection device can be used. The water vapor injection device is preferably capable of injecting water vapor substantially uniformly across the entire width of the fiber web at the desired pressure and volume. The water vapor injection device may be installed only on one side of the fiber web, or may be installed on the other side as well, thereby simultaneously steaming both the front and back sides of the fiber web.

Because the high-temperature steam ejected from the steam jet device is an air stream, unlike water jet encapsulation and needling treatments, it does not significantly displace the fibers within the web and penetrate into the web. The steam's penetration into the web effectively covers the surface of each fiber, achieving uniform heat curling. Furthermore, compared to dry heat treatment, sufficient heat transfer is achieved within the web, resulting in a substantially uniform curl across the web and thickness.

The nozzles for ejecting high-temperature steam, similar to the nozzles for engaging the water stream, can be a plate or die head with predetermined nozzles arranged continuously across the width of the fiber web. This plate or die head can be configured so that the nozzles are aligned across the width of the fiber web being fed. The nozzle array can be one or more rows, or multiple rows can be arranged in parallel. Furthermore, multiple nozzle dies each having a single nozzle array can be arranged in parallel.

The pressure of the high-temperature water vapor used can be selected in the range of 0.1 to 2 MPa (for example, 0.2 to 1.5 MPa). When the water vapor pressure is too high, the fibers forming the fiber web sometimes move too much and the texture becomes messy, and sometimes the fibers are excessively entangled. When the pressure is too weak, the fiber web cannot be given the heat required to show fiber curling, and the water vapor cannot pass through the fiber web, which easily makes the fiber curling in the thickness direction become uneven. The temperature of the high-temperature water vapor depends on the material of the fiber, etc., and can be selected from the range of 70 to 180°C (for example, 80 to 150°C). The processing speed of the high-temperature water vapor can be selected from the range of 200 m/min or less (for example, 0.1 to 100 m/min).

After the crimping of the composite fibers in the fiber web is achieved as described above, moisture may remain in the nonwoven fabric. Therefore, a drying step may be performed as needed to dry the nonwoven fabric. Examples of drying methods include methods using drying equipment such as a drum dryer or a tenter frame; non-contact methods such as far-infrared irradiation, microwave irradiation, and electron beam irradiation; and methods such as blowing hot air and passing the nonwoven fabric through the hot air.

Examples of methods for satisfying the above-mentioned formula [A] in the above-mentioned method for producing a fiber sheet include adjusting the content ratio of the composite fiber to the non-composite fiber; adjusting the conditions (particularly the temperature and/or pressure) of the high-temperature steam used in the heating step; and adjusting the drying temperature in the drying step.

<Third embodiment>

(1) Characteristics of fiber sheets

The fiber sheet of this embodiment (hereinafter referred to as "fiber sheet") can be used not only as a general bandage but also as a medical product such as a compression bandage used for hemostasis, compression therapy, etc. The fiber sheet is in the form of a rectangular sheet having a length direction and a width direction, such as a tape or a strip (long strip).

The stiffness of the fiber sheet in the width direction is 300 mN/200 mm or less, preferably 290 mN/200 mm or less, and more preferably 280 mN/200 mm or less. For example, when a fiber sheet with a stiffness of 300 mN/200 mm or less in the width direction is wound with its longitudinal direction as the winding direction, it can be wound with appropriate strength around a portion having a concave and convex surface (such as a portion protruding due to internal bone, such as a joint), and the sheet can be wound along the shape of the concave and convex surface, resulting in excellent conformability to the concave and convex surface. From the perspective of the strength of the fiber sheet, the stiffness in the width direction is generally 30 mN/200 mm or more, preferably 50 mN/200 mm or more.

It should be noted that "wrapping with the length direction as the winding direction" refers to the usual way of wrapping a long object such as a bandage around the wrapped object. For example, taking the case where the wrapped object is a finger as an example, it means wrapping the long bandage around the finger in a way that the width direction of the bandage is parallel or basically parallel to the length direction of the finger.

Bandages that have been made stretchable in the longitudinal direction using various methods are currently known. However, the present inventors' research has revealed that simply increasing the stretchability in the longitudinal direction alone does not fully improve conformability to uneven surfaces. The present invention is based on the insight that stiffness in the width direction, rather than the length direction, unexpectedly becomes a key factor in improving conformability to uneven surfaces.

Reducing the stiffness in the width direction to fall within the above range while increasing the stiffness in the longitudinal direction to a greater value than the stiffness in the width direction is effective in achieving a good balance between the fiber sheet's conformability to uneven surfaces, strength, and durability. The difference between the stiffnesses is, for example, 10 mN/200 mm or greater, preferably 30 mN/200 mm or greater, and more preferably 50 mN/200 mm or greater. The stiffness in the longitudinal direction of the fiber sheet is, for example, 40 to 400 mN/200 mm, and preferably 60 to 300 mN/200 mm.

The stiffness of the fiber sheet can be measured by the softness tester method of JIS L 1913. According to this JIS standard, a fiber sheet with a width of 200 mm can be used as a test sample.

The compressive modulus Pe of the fiber sheet is preferably 85% or less, more preferably 80% or less. A compressive modulus Pe within this range is advantageous in improving conformability to uneven surfaces and, in turn, in achieving a fiber sheet that is less likely to interfere with bending movements of joints, etc. The lower limit of the compressive modulus Pe is not particularly limited, but is, for example, 50%. The compressive modulus Pe can be calculated using the following formula [C] based on JIS L 1913 "Test Methods for General Nonwoven Fabrics."

Pe＝{(T ₁ '-T)/(T ₁ -T)}×100 [C]

_T1 is the thickness [mm] when the initial load (0.5 kPa) is applied, T is the thickness [mm] when a load of 30 kPa is applied, and _T1 ' is the thickness [mm] when the initial load is restored.

When a fiber sheet has extensibility, its functionality, for example, can be enhanced when used as a bandage. For example, when using a fiber sheet to secure a protective material such as gauze to an application site, the extensibility of the fiber sheet can improve the securing force, or when using a fiber sheet to apply pressure to an application site by wrapping it around the application site, the compressive force can be increased. Furthermore, when a fiber sheet is applied to a site that flexes and stretches, such as a joint, the extensibility of the fiber sheet facilitates the flexing and stretching action. Furthermore, the extensibility of the fiber sheet is also beneficial for improving the conformability of the sheet to uneven surfaces.

From the above perspectives, the fiber sheet preferably exhibits extensibility. As described above, in this specification, "extensibility" means exhibiting a 50% elongation stress in at least one direction (the first direction) within the sheet's plane. The 50% elongation stress refers to the elongation stress at 50% elongation (immediately after stretching) and can be measured by a tensile test in accordance with JIS L 1913, "Testing Methods for General Nonwoven Fabrics."

From the perspectives of uneven conformability and ease of bending and stretching, the fiber sheet preferably has good extensibility at least in the width direction, which is the first direction. This width direction can be perpendicular to the direction of travel (MD) of the fiber sheet during the manufacturing process, that is, the CD direction. The 50% elongation stress in the transverse direction of the fiber sheet is preferably 0.1 to 20 N/50 mm, more preferably 0.5 to 15 N/50 mm, and even more preferably 1 to 12 N/50 mm.

On the other hand, in order to improve the holding force and compressive force of the fiber sheet, it is preferable that the fiber sheet have good elongation in the longitudinal direction. The 50% elongation stress in the longitudinal direction of the fiber sheet is preferably 0.1 to 50 N/50 mm, more preferably 0.5 to 30 N/50 mm, and even more preferably 1 to 20 N/50 mm. Increasing the 50% elongation stress in the longitudinal direction is beneficial for improving the uneven conformability. The longitudinal direction of the fiber sheet can be the direction of travel of the fiber sheet during the manufacturing process (MD direction). The 50% elongation stress in the width direction and directions other than the longitudinal direction is preferably 0.5 to 60 N/50 mm, more preferably 1 to 45 N/50 mm, and even more preferably 2 to 40 N/50 mm.

The fiber sheet preferably exhibits self-adhesive properties. As described above, in this specification, "self-adhesive properties" refer to the property of being locked or fixed by overlapping (contacting) the fibers on the surface of the fiber sheet, thereby interlocking or adhering to each other. Self-adhesive properties are advantageous when the fiber sheet is a bandage, for example. For example, when the fiber sheet is a bandage, after wrapping the bandage around the application area, the end of the bandage is overlapped (or torn and overlapped) with the underlying bandage surface. This stretches and presses the wrapped fiber sheets, causing the fiber sheets to be joined and fixed, thereby exhibiting self-adhesive properties.

By making the fiber sheet inherently self-adhesive, there's no need to form a layer of a self-adhesive agent, such as an elastomer or adhesive, on the fiber sheet surface, nor is there a need for a separate fastener to secure the front end after wrapping. For example, Japanese Patent Application Laid-Open No. 2005-095381 (Patent Document 4) describes attaching an acrylic polymer (Claim 1) or latex (paragraphs [0004] to [0006]) as a self-adhesive to at least one side of a bandage base material. Forming a layer of an elastomer, such as latex, on the fiber sheet surface is effective in improving self-adhesion.

However, the fiber sheet of this embodiment is preferably composed solely of a non-elastomer material, more specifically, solely of fibers. When a layer composed of such an elastomer is formed on the surface of the fiber sheet, or when the fiber base material is impregnated with the elastomer, it tends to be difficult to achieve the stiffness in the width direction within the above-mentioned range. Furthermore, the elastomer layer also has the potential to cause skin irritation or allergies when wrapped around the application site.

The self-adhesiveness of a fiber sheet can be evaluated by the curved surface sliding stress. From the perspective of self-adhesiveness, the curved surface sliding stress of the fiber sheet is, for example, 3 N/50 mm or greater, preferably 5 N/50 mm or greater. Furthermore, the curved surface sliding stress is preferably greater than the breaking strength. Furthermore, from the perspective of making it easier to untangle the entangled fiber sheet when necessary, the curved surface sliding stress is preferably 30 N/50 mm or less, more preferably 25 N/50 mm or less. The curved surface sliding stress is measured using a tensile testing machine according to the method described in the Examples (Figures 1 to 3).

The fiber sheet is preferably hand-tearable. As mentioned above, in this specification, "hand-tearable" refers to the property of being able to be torn (cut) by stretching it by hand. The hand-tearability of the fiber sheet can be evaluated by the breaking strength. From the perspective of hand-tearability, the breaking strength of the fiber sheet in at least one direction within the sheet surface is preferably 5 to 100 N/50 mm, more preferably 8 to 60 N/50 mm, and even more preferably 10 to 40 N/50 mm. By setting the breaking strength to the above range, good hand-tearability that can be torn (cut) relatively easily by hand can be imparted. If the breaking strength is too high, the hand-tearability is reduced, for example, it becomes difficult to tear the fiber sheet with one hand. On the other hand, if the breaking strength is too low, the strength of the fiber sheet is insufficient, it is easy to break, and the durability and handleability are reduced. The breaking strength can be measured by a tensile test based on JIS L 1913 "General nonwoven fabric test methods".

At least one direction within the sheet surface is the direction of stretching when the fiber sheet is torn by hand, preferably the longitudinal direction. This longitudinal direction may be the MD direction. Specifically, when the fiber sheet is used as a bandage, the bandage is typically stretched along its longitudinal direction, wrapped around the application site, and then broken in the longitudinal direction. Therefore, the direction in which the breaking strength falls within the above-mentioned range is preferably the longitudinal direction serving as the stretching direction.

The breaking strength in directions other than at least one in-plane direction of the sheet (eg, width direction, CD direction) is, for example, 0.1 to 300 N/50 mm, preferably 0.5 to 100 N/50 mm, and more preferably 1 to 20 N/50 mm.

From the viewpoint of hand-tearability, the fiber sheet is preferably composed only of a non-elastomer material, more specifically, preferably composed only of fibers. If a layer composed of an elastomer is formed on the surface of the fiber sheet, the hand-tearability will be reduced.

The fiber sheet has an elongation at break in at least one direction within the sheet plane of, for example, 50% or greater, preferably 60% or greater, and more preferably 80% or greater. An elongation at break within this range is advantageous in improving the stretchability of the fiber sheet. The elongation at break in at least one direction within the sheet plane is typically 300% or less, preferably 250% or less. The elongation at break can also be measured by a tensile test in accordance with JIS L1913, "Testing Methods for General Nonwoven Fabrics."

From the perspective of uneven conformability and ease of bending and stretching, the at least one direction within the sheet surface is preferably the width direction. Furthermore, from the perspective of longitudinal extensibility (e.g., the aforementioned fixing force and compressive force), the longitudinal direction is preferred. The elongation at break in directions other than the at least one direction within the sheet surface is, for example, 10 to 500%, preferably 100 to 350%.

The recovery rate after 50% elongation in at least one direction within the sheet surface (50% elongation recovery rate) is preferably 70% or greater (less than 100%), more preferably 80% or greater, and even more preferably 90% or greater. When the 50% elongation recovery rate is within this range, the fiber sheet can easily follow the surface irregularities and bending motion of the portion when wrapped around a portion with irregularities or bending and stretching, such as a joint, thereby improving the conformability to the irregularities and the ease of bending and stretching. It also helps to improve the self-adhesion caused by friction between the stacked fiber sheets. If the elongation recovery rate is too low, the fiber sheet cannot follow the bending motion of the portion, and the deformation caused by the bending motion will not be restored, resulting in a weakened fixation of the wrapped fiber sheet.

Consider from the viewpoint of the easiness of concavo-convex conformability and bending stretching action, at least one direction in the above-mentioned sheet face is preferably width direction.In addition, consider from the viewpoint of the elongation of length direction (for example, the viewpoint of above-mentioned fixing force, compressive force), be preferably length direction.

The recovery rate after 50% elongation is defined by the following formula, where X is the residual strain (%) after the test when the load is removed immediately after the elongation reaches 50% in a tensile test based on JIS L 1913 "General nonwoven fabric testing methods."

Recovery rate after 50% elongation (%) = 100 - X

The recovery rate after 50% elongation in a direction other than at least one direction in the sheet plane is, for example, 70% or more (100% or less), preferably 80% or more.

The fiber sheet preferably has a basis weight of 30 to 300 g/m ² , more preferably 50 to 200 g/m ² . To further improve the conformability to uneven surfaces, the basis weight is preferably reduced. In this case, the basis weight is preferably 160 g/m ² or less. Excessively low basis weights reduce the strength and durability of the fiber sheet.

The thickness of the fiber sheet is, for example, 0.2 to 5 mm, preferably 0.3 to 3 mm, and more preferably 0.4 to 2 mm. When the basis weight and thickness are within this range, a good balance is achieved in terms of conformability to uneven surfaces, flexibility during winding, elongation, softness, feel, and cushioning properties. The density (bulk density) of the fiber sheet can be a value corresponding to the basis weight and thickness, for example, 0.03 to 0.5 g/cm ³ , preferably 0.04 to 0.4 g/cm ³ , and more preferably 0.05 to 0.25 g/cm ³ . To further improve conformability to uneven surfaces, the density is more preferably 0.2 g/cm ³ or less.

The fiber sheet's air permeability as determined by the Frazier method is preferably 0.1 ^cm³ /( ^cm² ·sec) or greater, more preferably 1 to 500 ^cm³ /( ^cm² ·sec), even more preferably 5 to 300 ^cm³ /( ^cm² ·sec), and particularly preferably 10 to 200 ^cm³ /( ^cm² ·sec). Air permeabilities within this range provide excellent breathability and are less likely to cause stuffiness, making them more suitable for applications such as bandages on the human body.

(2) Structure and manufacturing method of fiber sheet

The fiber sheet of this embodiment is not particularly limited as long as it is composed of fibers, and may be, for example, a woven fabric, a nonwoven fabric, a knitted fabric, or the like. As described above, the fiber sheet is in the form of a rectangular sheet having a longitudinal direction and a width direction, such as a tape or a strip. The fiber sheet may have a single-layer structure or a multi-layer structure consisting of two or more fiber layers.

As described above, the fiber sheet preferably has extensibility. Examples of methods for imparting stretchability and extensibility to the fiber sheet include: 1) pleating a fiber sheet substrate such as a woven fabric, nonwoven fabric, or knitted fabric; 2) weaving yarns made of a stretchable material such as an elastomer, typically rubber, into the fiber sheet; 3) combining a layer made of a stretchable material such as an elastomer with a non-stretchable fiber sheet substrate and impregnating the sheet with the stretchable material; and 4) using crimped fibers wound into coils as at least a portion of the fibers constituting the nonwoven fabric.

Among the above, the fiber sheet of this embodiment preferably has the structure of 4). The pleating process of 1) is effective in imparting stretchability, but the undulating shape of the pleats makes it difficult to obtain a fiber sheet having a stiffness in the width direction within the above range. The methods of 2) and 3) can easily impart stretchability, but the softness is reduced, making it difficult to obtain a fiber sheet having a stiffness in the width direction within the above range.

From the viewpoints of the concave-convex fit, the bendability of the joint when wrapped around the joint, self-adhesion, and hand-tearability, the fiber sheet is preferably composed of a non-woven fabric, that is, preferably a non-woven fabric sheet, more preferably composed of a non-woven fabric comprising curly fibers curled into coils, and further preferably composed of a non-woven fabric comprising the above-mentioned curly fibers and not subjected to any one or more (preferably not all) of the above-mentioned 1) to 3) treatments. It is particularly preferred that the non-woven fabric sheet consists only of the above-mentioned curly fibers. The fiber sheet can be composed of a fabric or a knitted fabric (knitted fabric). Since the fineness of the silk (twisted yarn) constituting them is large, it is more difficult to obtain a fiber sheet having a stiffness in the width direction within the above-mentioned range. In this regard, if a non-woven fabric is used, the sheet can be composed of fibers with a smaller fineness, thereby further improving the concave-convex fit.

From the perspective of uneven conformability, the average fineness of the fibers constituting the nonwoven fabric sheet is preferably 20 dtex or less, more preferably 15 dtex or less. From the perspective of the strength and durability of the fiber sheet, the average fineness is preferably 0.5 dtex or more, more preferably 1.0 dtex or more.

A fiber sheet composed of a nonwoven fabric containing crimped fibers preferably has a structure in which the individual fibers constituting the sheet are substantially non-fused, and the crimped fibers are primarily restrained or locked by the intertwining of these crimped loops. Furthermore, it is preferred that the majority (most) of the crimped fibers (with their axial direction) be oriented substantially parallel to the sheet surface. As described above, in this specification, "substantially parallel to the surface direction" means a state in which a plurality of crimped fibers (with their axial direction) are locally oriented in the thickness direction, such as by entanglement through needle punching, without overlapping portions.

In a fiber sheet composed of a nonwoven fabric containing crimped fibers, the crimped fibers are preferably oriented in a certain direction (preferably the longitudinal direction) within the sheet surface, with adjacent or intersecting crimped fibers entangled with each other through these crimped loops. Furthermore, the crimped fibers are preferably slightly entangled with each other in the thickness direction (or oblique direction) of the fiber sheet. Entanglement of the crimped fibers may occur during the shrinkage of the fiber web serving as a precursor to the fiber sheet.

A nonwoven fabric in which the crimped fibers (the axial direction of the crimped fibers) are oriented and intertwined in a certain direction within the sheet surface exhibits good stretchability (including elongation) in that direction. When tension is applied to the stretchable nonwoven fabric in the longitudinal direction, the intertwined crimped coils stretch and attempt to return to their original coils, thereby exhibiting high stretchability in the longitudinal direction. The stretchable nonwoven fabric can exhibit excellent elongation in a direction orthogonal to the certain direction within the sheet surface (e.g., the width direction). In addition, the slight intertwining of the crimped fibers in the thickness direction of the nonwoven fabric can exhibit cushioning and softness in the thickness direction, thereby providing the nonwoven fabric with a good touch and feel. In addition, the crimped coils can easily intertwine with other crimped coils through contact under a certain degree of pressure. The intertwining of the crimped coils can exhibit self-adhesion.

In a fiber sheet composed of a nonwoven fabric containing crimped fibers, when tension is applied in the orientation direction (preferably the longitudinal direction) of the crimped fibers, the entangled crimped coils are elastically deformed and stretched, and when further tension is applied, they are finally untied, thereby having good cuttability (hand-tearability).

As described above, the nonwoven fabric that can form the fiber sheet preferably includes crimped fibers that are curled into coils. The crimped fibers are preferably oriented primarily in the plane direction of the nonwoven fabric and are preferably substantially uniformly curled in the thickness direction. The crimped fibers can be composed of composite fibers formed from a phase structure of multiple resins having different thermal shrinkage rates (or thermal expansion coefficients).

The composite fibers that form the crimped fibers are fibers (latent crimped fibers) with an asymmetric or layered (so-called bimetallic) structure that crimps when heated due to the different thermal shrinkage rates (or thermal expansion coefficients) of multiple resins. These resins typically have different softening or melting points. The various resins can be selected from, for example, polyolefin resins (poly _C2-4 olefin resins such as low-density, medium-density or high-density polyethylene and polypropylene); acrylic resins (acrylonitrile resins having acrylonitrile units such as acrylonitrile-vinyl chloride copolymers); polyvinyl acetal resins (polyvinyl acetal resins); polyvinyl chloride resins (polyvinyl chloride, vinyl chloride-vinyl acetate copolymers, vinyl chloride-acrylonitrile copolymers); polyvinylidene chloride resins (vinylidene chloride-vinyl chloride copolymers, vinylidene chloride-vinyl acetate copolymers); styrene resins (heat-resistant polystyrene); polyester resins (polyethylene terephthalate resins, polypropylene terephthalate resins, polybutylene terephthalate resins, polyethylene naphthalate resins); Thermoplastic resins include polyamides (polyamide 6, polyamide 66, polyamide 11, polyamide 12, polyamide 610, polyamide 612, aliphatic polyamides, semi-aromatic polyamides, aromatic polyamides, polyphenylene isophthalamide, polyhexamethylene terephthalamide, polyparaphenylene terephthalamide, etc.); polycarbonate resins ( _bisphenol A polycarbonate, etc.); polyparaphenylene benzobisazole resins; polyphenylene sulfide resins; polyurethane resins; and cellulose resins (cellulose esters, etc.). These various thermoplastic resins may also contain other copolymerizable units.

Among these, the various resins are preferably non-heat-wet adhesive resins (or heat-resistant hydrophobic resins or non-aqueous resins) having a softening or melting point of 100°C or higher, from the perspective of preventing the fibers from fusing even when melted or softened by heat treatment with high-temperature steam. Examples thereof include polypropylene resins, polyester resins, and polyamide resins. In particular, aromatic polyester resins and polyamide resins are preferred from the perspective of achieving an excellent balance between heat resistance and fiber forming properties. At least the resin exposed on the surface of the conjugated fibers is preferably non-heat-wet adhesive fiber, so that the conjugated fibers (latently crimped fibers) constituting the nonwoven fabric do not fuse even when treated in high-temperature steam.

The plurality of resins constituting the conjugated fibers may be a combination of resins of the same type or a combination of resins of different types as long as they have different thermal shrinkage rates.

From the viewpoint of adhesion, the multiple resins constituting the composite fiber are preferably a combination of the same type of resins. In the case of a combination of the same type of resins, a combination of component (A) forming a homopolymer (essential component) and component (B) forming a modified polymer (copolymer) can generally be used. That is, relative to the homopolymer as an essential component, for example, by copolymerizing and modifying a copolymerizable monomer that reduces crystallinity, melting point or softening point, the crystallinity can be lower than that of the homopolymer, or the melting point or softening point can be lower than that of the homopolymer by becoming amorphous. Thus, by changing the crystallinity, melting point or softening point, a difference can be set in the thermal shrinkage. The difference in melting point or softening point can be, for example, 5 to 150°C, preferably 40 to 130°C, and more preferably 60 to 120°C. The proportion of the copolymerizable monomer used for modification is, for example, 1 to 50 mol% relative to all monomers, preferably 2 to 40 mol%, and more preferably 3 to 30 mol% (particularly 5 to 20 mol%). The mass ratio of the component forming the homopolymer to the component forming the modified polymer can be selected according to the structure of the fiber, for example, homopolymer component (A)/modified polymer component (B) = 90/10 to 10/90, preferably 70/30 to 30/70, and more preferably 60/40 to 40/60.

From the perspective of easily producing latently crimped conjugate fibers, the conjugate fibers are preferably a combination of aromatic polyester resins, particularly a combination of a polyalkylene arylate resin (a) and a modified polyalkylene arylate resin (b). The polyalkylene arylate resin (a) can be a homopolymer of an aromatic dicarboxylic acid (e.g., a symmetrical aromatic dicarboxylic acid such as terephthalic acid and naphthalene-2,6-dicarboxylic acid) and an alkanediol component (e.g., a C _2-6 alkanediol such as ethylene glycol and butanediol). Specifically, poly(C _2-4 alkylene terephthalate) resins such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) can be used. PET, which is suitable for conventional PET fibers and has an intrinsic viscosity of 0.6 to 0.7, is typically used.

On the other hand, in the modified polyalkylene arylate resin (b), examples of copolymer components that lower the melting point, softening point, or crystallinity of the essential component, polyalkylene arylate resin (a), include dicarboxylic acid components such as asymmetric aromatic dicarboxylic acids, alicyclic dicarboxylic acids, and aliphatic dicarboxylic acids, alkanediol components having a longer chain length than the alkanediol in the polyalkylene arylate resin (a), and/or diol components having an ether bond. The copolymer components may be used alone or in combination of two or more. Among these components, a wide range of usable dicarboxylic acid components include asymmetric aromatic dicarboxylic acids (such as isophthalic acid, phthalic acid, and sodium 5-sulfoisophthalate), aliphatic dicarboxylic acids (C _6-12 aliphatic dicarboxylic acids such as adipic acid), and a wide range of usable diol components include alkanediols (such as 1,3-propylene glycol, _1,4 -butanediol, 1,6-hexanediol, and neopentyl glycol), polyoxyalkylene glycols (such as diethylene glycol, triethylene glycol, polyethylene glycol, and polyoxy C _2-4 alkylene glycols). Among these, asymmetric aromatic dicarboxylic acids such as isophthalic acid and polyoxy C _2-4 alkylene glycols such as diethylene glycol are preferred. Alternatively, the modified polyalkylene arylate resin (b) may be an elastomer having a C _2-4 alkylene arylate (such as ethylene terephthalate and butylene terephthalate) as a hard segment and a (poly)oxyalkylene glycol as a soft segment.

In the modified polyalkylene arylate resin (b), the ratio of the dicarboxylic acid component (e.g., isophthalic acid) for lowering the melting point or softening point is, for example, 1 to 50 mol%, preferably 5 to 50 mol%, and more preferably 15 to 40 mol%, relative to the total amount of the dicarboxylic acid components constituting the modified polyalkylene arylate resin (b). Furthermore, the ratio of the diol component (e.g., diethylene glycol) for lowering the melting point or softening point is, for example, 30 mol% or less, preferably 10 mol% or less (e.g., 0.1 to 10 mol%) relative to the total amount of the diol components constituting the modified polyalkylene arylate resin (b). If the ratio of the copolymer component is too low, sufficient crimping is not achieved, and the morphological stability and stretchability of the crimped nonwoven fabric are reduced. On the other hand, if the ratio of the copolymer component is too high, the crimping performance is improved, but stable spinning becomes difficult.

The modified polyalkylene arylate resin (b) may contain, as monomer components, polycarboxylic acid components such as trimellitic acid and pyromellitic acid, and polyol components such as glycerin, trimethylolpropane, trimethylolethane, and pentaerythritol.

The cross-sectional shape of the composite fiber (the cross-sectional shape perpendicular to the longitudinal direction of the fiber) is not limited to a conventional solid cross-sectional shape such as a circular cross-section or a special cross-sectional shape [flat, elliptical, polygonal, 3-14 petal, T-shaped, H-shaped, V-shaped, dog-bone (I-shaped) shape, etc.], and may also be a hollow cross-sectional shape, but is generally a circular cross-sectional shape.

Examples of the cross-sectional structure of the composite fiber include phase structures formed from multiple resins, such as core-sheath, island-in-the-sea, hybrid, side-by-side (side-by-side or multi-layer laminated), radial (radially laminated), hollow radial, block, and random composite structures. Of these, structures in which phases are partially adjacent (so-called bimetallic structures) and structures with asymmetric phase structures, such as eccentric core-sheath and side-by-side structures, are preferred because they facilitate spontaneous crimping upon heating.

It should be noted that in the case where the composite fiber has a core-sheath type structure such as an eccentric core-sheath type, the core portion can be composed of a wet heat adhesive resin (for example, a vinyl alcohol polymer such as ethylene-vinyl alcohol copolymer or polyvinyl alcohol) or a thermoplastic resin with a low melting point or softening point (for example, polystyrene, low-density polyethylene, etc.) as long as it has a thermal shrinkage difference with the non-wet heat adhesive resin of the sheath portion located on the surface and can be curled.

The average fineness of the composite fiber is, for example, 0.1 to 20 dtex, preferably 0.5 to 10 dtex, and more preferably 1 to 5 dtex. If the fineness is too small, the fiber itself is difficult to manufacture and it is difficult to ensure fiber strength. Furthermore, it is difficult to achieve good coil crimping during the crimping process. On the other hand, if the fineness is too large, it is difficult to adjust the stiffness in the width direction to the above range, and it is difficult to achieve sufficient crimping.

The average fiber length of the composite fiber is, for example, 10 to 100 mm, preferably 20 to 80 mm, and more preferably 25 to 75 mm. When the average fiber length is too short, it is difficult to form a fiber web, and the curled fibers are not sufficiently entangled with each other when curling, making it difficult to ensure the strength and elasticity of the nonwoven fabric. When the average fiber length is too long, it is difficult to form a fiber web with a uniform weight per unit area, and the fibers are more entangled with each other when forming the web, and when curling, they interfere with each other and are difficult to exhibit elasticity. When the average fiber length is within the above range, since a portion of the curled fibers on the surface of the nonwoven fabric are moderately exposed on the surface of the nonwoven fabric, the self-adhesiveness of the nonwoven fabric can be improved. In addition, the average fiber length within the above range is also advantageous in obtaining good hand-tearability.

The composite fiber is a latently crimped fiber, which develops (or manifests) crimps by heat treatment, and becomes a fiber having three-dimensional crimps that are substantially coil-shaped (helical or coil spring-shaped).

The number of crimps before heating (mechanical crimps) is, for example, 0 to 30/25 mm, preferably 1 to 25/25 mm, and more preferably 5 to 20/25 mm. The number of crimps after heating is, for example, 30 or more/25 mm (e.g., 30 to 200/25 mm), and preferably 35 to 150/25 mm.

As described above, the crimped fibers constituting the nonwoven fabric have curls that are essentially coil-shaped after being curled. The average radius of curvature of the circle formed by the coils of the crimped fibers is, for example, 10 to 250 μm, preferably 20 to 200 μm, and more preferably 50 to 160 μm. The average radius of curvature is an indicator of the average size of the circle formed by the coils of the crimped fibers. It means that when this value is large, the coils formed have a loose shape, that is, a shape with a small number of crimps. In addition, when the number of crimps is small, the crimped fibers are less intertwined with each other, making it difficult to recover the shape of the coils after deformation, which is disadvantageous in terms of exhibiting sufficient stretchability. When the average radius of curvature is too small, the crimped fibers are not fully intertwined with each other, making it difficult to ensure the strength of the web. In addition, the stress during the deformation of the coil shape is too high, the breaking strength is excessively increased, and it is difficult to obtain appropriate stretchability.

The average pitch between the coils in the crimped fibers (average crimp pitch) is, for example, 0.03 to 0.5 mm, preferably 0.03 to 0.3 mm, and more preferably 0.05 to 0.2 mm. If the average pitch is too large, the number of crimps per fiber decreases, and sufficient stretchability cannot be achieved. If the average pitch is too small, the crimped fibers are not sufficiently entangled, making it difficult to ensure the strength of the nonwoven fabric.

In addition to the above-mentioned composite fibers, non-woven fabrics (fiber webs) may also contain other fibers (non-composite fibers). Specific examples of non-composite fibers include fibers composed of cellulose fibers [for example, natural fibers (kapok, wool, silk, hemp, etc.), semi-synthetic fibers (acetate fibers such as triacetate fibers, etc.), regenerated fibers (rayon, Polynosic, Cupra fibers, lyocell fibers (for example, registered trademark name: "Tencel", etc.)] in addition to the fibers composed of the above-mentioned non-heat-wet adhesive resins or heat-wet adhesive resins. The average fineness and average fiber length of the non-composite fibers may be the same as those of the composite fibers. The non-composite fibers may be used alone or in combination of two or more.

The ratio (mass ratio) of conjugate fibers to non-conjugate fibers is preferably adjusted appropriately so that the stiffness in the width direction falls within the above range. For example, the ratio is conjugate fibers/non-conjugate fibers = 50/50 to 100/0, preferably 60/40 to 100/0, more preferably 70/30 to 100/0, further preferably 80/20 to 100/0, and particularly preferably 90/10 to 100/0. The balance between the strength and stretchability or softness of the nonwoven fabric can be adjusted by blending non-conjugate fibers.

The nonwoven fabric (fiber web) may contain conventional additives, such as stabilizers (heat stabilizers, ultraviolet absorbers, light stabilizers, antioxidants, etc.), antibacterial agents, deodorants, fragrances, colorants (dyes, pigments, etc.), fillers, antistatic agents, flame retardants, plasticizers, lubricants, crystallization rate retardants, etc. The additives may be used alone or in combination of two or more. The additives may be either loaded on the fiber surface or contained within the fiber.

A fiber sheet composed of a nonwoven fabric containing crimped fibers can be preferably produced by a method comprising the steps of forming a web of fibers containing the above-mentioned conjugated fibers (latently crimped fibers) (web forming step), and heating the fiber web to crimp the conjugated fibers (heating step).

Conventional methods can be used to form the fiber web in the web-forming step, including direct methods such as spunbonding and meltblowing, carding methods using meltblown fibers and staple fibers, and dry methods such as air-laying. Carding methods using meltblown fibers and staple fibers are widely used, with carding methods using staple fibers being particularly popular. Examples of webs obtained using staple fibers include random webs, semi-random webs, parallel-laid webs, and cross-laid webs.

Before the heating process, an entangling process for entangling at least a part of the fibers in the fiber web can be implemented. By implementing this entangling process, a nonwoven fabric in which the curled fibers are appropriately entangled can be obtained in the subsequent heating process. The entangling method can be a mechanical entangling method, preferably a method of entangling by spraying or jetting (blowing) water. Entangling the fibers by water flow is advantageous in increasing the density of entangling by utilizing the curling in the heating process. The sprayed or jetted water can be blown from one side of the fiber web or from both sides. From the viewpoint of efficiently and firmly entangling, it is preferably blown from both sides.

The water spray pressure in the entanglement step is set to an appropriate range so that the fibers are entangled, for example, 2 MPa or more, preferably 3 to 12 MPa, more preferably 4 to 10 MPa. The temperature of the sprayed or injected water is, for example, 5 to 50°C, preferably 10 to 40°C.

For simplicity and other reasons, water spraying or jetting is preferably performed using a nozzle with a regular spray area or pattern. Specifically, for a fiber web being transported by a conveyor belt, such as an endless conveyor, water can be sprayed while the web is placed on the conveyor belt. The conveyor belt can be water-permeable, so water can be passed through the permeable conveyor belt from the back side of the fiber web and sprayed onto the fiber web. It should be noted that to prevent fiber scattering caused by the water jet, the fiber web can be pre-moistened with a small amount of water.

The nozzles for spraying or jetting water can be a plate or die head having predetermined nozzles arranged continuously in the width direction, and the plate or die head can be arranged so that the nozzles are arranged in the width direction of the supplied fiber web. The nozzle array can be more than one row, or multiple rows can be arranged in parallel. In addition, multiple nozzle dies each having a single nozzle array can be arranged in parallel.

Before the above-mentioned entangling step, a step of making the fibers in the fiber web uneven in the surface (an unevenness step) can be performed. This step can form areas in the fiber web where the fiber density is sparse. Therefore, when the entangling step is water entangling, water can be efficiently sprayed into the interior of the fiber web, making it easier to achieve appropriate entangling not only on the surface of the fiber web but also inside the fiber web.

The non-uniformization step can be performed by spraying or jetting low-pressure water onto the fiber web. Spraying or jetting low-pressure water onto the fiber web can be continuous, but is preferably performed intermittently or periodically. By spraying water onto the fiber web intermittently or periodically, a plurality of low-density portions and a plurality of high-density portions can be periodically and alternately formed.

The water spraying pressure in the non-uniformization step is preferably as low as possible, for example, 0.1 to 1.5 MPa, preferably 0.3 to 1.2 MPa, more preferably 0.6 to 1.0 MPa. The temperature of the sprayed or injected water is, for example, 5 to 50°C, preferably 10 to 40°C.

The method of spraying or injecting water intermittently or periodically is not particularly limited as long as it is a method that can periodically and alternately form a density gradient in the fiber web. From the perspective of simplicity, it is preferred to use a method of injecting water through a plate-like object (porous plate, etc.) having a regular spray area or spray pattern formed by multiple holes.

During the heating process, the fiber web is heated by high-temperature steam, causing it to curl. In this method, the fiber web is exposed to a stream of high-temperature or superheated steam (high-pressure steam), which creates coil crimps in the composite fibers (latently crimped fibers). Because the fiber web is air-permeable, even when treated from one direction, the high-temperature steam penetrates deep into the web, creating a substantially uniform crimp across the thickness, resulting in uniform fiber entanglement.

The fiber web shrinks during high-temperature steam treatment. Therefore, it is preferable to overfeed the supplied fiber web immediately before exposure to high-temperature steam, based on the target area shrinkage of the nonwoven fabric. The overfeed ratio should be 110-300%, preferably 120-250%, relative to the target nonwoven fabric length.

To supply water vapor to the fiber web, a conventional water vapor injection device can be used. The water vapor injection device is preferably capable of injecting water vapor substantially uniformly across the entire width of the fiber web at the desired pressure and volume. The water vapor injection device may be installed only on one side of the fiber web, or may be installed on the other side as well, thereby simultaneously steaming both the front and back sides of the fiber web.

Because the high-temperature steam ejected from the steam jet device is an air stream, unlike water jet encapsulation and needling treatments, it does not significantly displace the fibers within the web and penetrate into the web. The steam jet's penetration into the web effectively covers the surface of each fiber, achieving uniform heat curling. Furthermore, compared to dry heat treatment, this allows for more efficient heat transfer into the web, resulting in a substantially uniform degree of curling across the web and thickness.

The nozzles for ejecting high-temperature steam, similar to the nozzles for engaging the water stream, can be a plate or die head with predetermined nozzles arranged continuously across the width of the fiber web. This plate or die head can be configured so that the nozzles are aligned across the width of the fiber web being fed. The nozzle array can be one or more rows, or multiple rows can be arranged in parallel. Furthermore, multiple nozzle dies each having a single nozzle array can be arranged in parallel.

The pressure of the high-temperature water vapor used can be selected in the range of 0.1 to 2 MPa (for example, 0.2 to 1.5 MPa). When the water vapor pressure is too high, the fibers forming the fiber web sometimes move too much and the texture becomes messy, and sometimes the fibers are excessively entangled. When the pressure is too weak, the fiber web cannot be given the heat required to show fiber curling, and the water vapor cannot pass through the fiber web, which easily makes the fiber curling in the thickness direction become uneven. The temperature of the high-temperature water vapor depends on the material of the fiber, etc., and can be selected from the range of 70 to 180°C (for example, 80 to 150°C). The processing speed of the high-temperature water vapor can be selected from the range of 200 m/min or less (for example, 0.1 to 100 m/min).

After the crimping of the composite fibers in the fiber web is achieved as described above, moisture may remain in the nonwoven fabric. Therefore, a drying step may be performed as needed to dry the nonwoven fabric. Examples of drying methods include methods using drying equipment such as a drum dryer or a tenter frame; non-contact methods such as far-infrared irradiation, microwave irradiation, and electron beam irradiation; and methods such as blowing hot air and passing the nonwoven fabric through the hot air.

In the above-mentioned method for producing a fiber sheet, methods for adjusting the stiffness in the width direction to the above-mentioned range include, for example, adjusting the content ratio of the composite fiber to the non-composite fiber; adjusting the conditions (particularly the temperature and/or pressure) of the high-temperature steam used in the heating step; and adjusting the drying temperature in the drying step.

Example

The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples. It should be noted that the physical properties of the fiber sheets (bandages) obtained in the following Examples and Comparative Examples were measured by the following methods.

〔1〕Number of mechanical curls (pieces/25mm)

The measurement was carried out in accordance with JIS L 1015 "Test methods for chemical staple fibers (Chemical staple fiber testing methods)" (8.12.1).

〔2〕Average number of coil turns (pcs/mm)

The crimped fibers (conjugate fibers) were extracted from the fiber sheet, and the coil crimps were not stretched, and the number of crimps was measured in accordance with JIS L 1015 "Testing methods for chemical staple fibers" (8.12.1) in the same manner as the measurement of the mechanical crimp number.

〔3〕Average curl spacing (μm)

When measuring the average number of coil windings, the distance between consecutive and adjacent coils was measured and the average value of n=100 was measured.

〔4〕Average radius of curvature (μm)

A scanning electron microscope (SEM) is used to take a photograph of any cross section of the fiber sheet at a magnification of 100 times. Among the fibers shown in the cross-sectional photograph, for fibers that have formed a spiral (coil) of more than one turn, the radius of the circle when the spiral is drawn (the radius of the circle when the curled fiber is observed from the coil axis direction) is obtained and used as the radius of curvature (μm). It should be noted that when the fiber draws a spiral in the shape of an ellipse, 1/2 of the sum of the major diameter and minor diameter of the ellipse is used as the radius of curvature. However, in order to exclude the situation where the curled fiber does not show sufficient coil curling and the situation where the spiral shape of the fiber appears elliptical due to oblique observation, only the ellipse whose major diameter to minor diameter ratio falls within the range of 0.8 to 1.2 is used as the measurement object. The average radius of curvature (μm) is obtained as the average value of n number = 100.

〔5〕Weight per unit area (g/m ² )

The measurement was carried out in accordance with JIS L 1913 "Test methods for general nonwoven fabrics".

〔6〕Thickness (mm) and density (g/cm ³ )

For the examples and comparative examples of the first embodiment (Examples 1 to 4, Comparative Example 1) and the examples and comparative examples of the third embodiment (Examples 7 to 8, Comparative Examples 5 to 6), the thickness of the fiber sheet was measured in accordance with JIS L 1913 "Test methods for general nonwoven fabrics", and the density was calculated based on this value and the weight per unit area measured by the method [5].

For the examples and comparative examples (Examples 5-6, Comparative Examples 2-4) of the second embodiment, the thickness T ₁ of a single sheet was measured using Method A of JIS L 1913 (load: 0.5 kPa). Furthermore, the thickness T ₃ of three sheets stacked together was measured under the same conditions. Based on these measured values, the left side of the above formula [A] was calculated as {T ₃ /(3×T ₁ )}×100. The density (g/cm ³ ) was calculated from the basis weight measured using the method in [5] and the thickness T ₁ measured using the above method.

[7] Stiffness (mN/200mm) in Examples and Comparative Examples (Examples 7 and 8, Comparative Examples 5 and 6) of the Third Embodiment

The softness tester method was used in accordance with JIS L 1913 "General Nonwoven Fabric Test Methods." The width of the test specimen was set to 200 mm. The fiber sheet was measured in both the longitudinal direction (MD) and the width direction (CD).

〔8〕Breaking strength (N/50mm) and elongation at break (%)

The measurement was conducted in accordance with JIS L 1913 "General nonwoven fabric test methods." The measurement was conducted in both the longitudinal direction (MD direction) and the width direction (CD direction) of the fiber sheet.

[9] Initial elongation stress S ₀ (N/50 mm), elongation stress S ₅ (N/50 mm) after 5 minutes, and stress relaxation rate (%) in Examples and Comparative Examples (Examples 1 to 4, Comparative Example 1) of the first embodiment

In accordance with JIS L 1913 "General Nonwoven Fabric Test Methods", the initial elongation stress _S0 and the elongation stress _S5 after 5 minutes were measured, and the stress relaxation rate was calculated according to the above definition formula. The initial elongation stress _S0 is the elongation stress immediately after the fabric is stretched to 50% in the longitudinal direction (MD direction), and the elongation stress _S5 after 5 minutes is the elongation stress when the fabric is stretched to 50% in the longitudinal direction (MD direction) and maintained in this state for 5 minutes.

[10] 50% elongation stress (N/50 mm) in the examples and comparative examples of the second embodiment (Examples 5-6, Comparative Examples 2-4), and the examples and comparative examples of the third embodiment (Examples 7-8, Comparative Examples 5-6)

Measurements were made in accordance with JIS L 1913, "General Nonwoven Fabric Test Methods." Measurements were made in both the longitudinal direction (MD) and the width direction (CD) of the fiber sheet. In the Examples and Comparative Examples (Examples 5-6, Comparative Examples 2-4) of the second embodiment, the 50% elongation stress in the width direction (first direction, CD) of the fiber sheet was designated S ₁ , and the 50% elongation stress in the longitudinal direction (second direction, MD) was designated S ₂ .

〔11〕Recovery rate after 50% elongation

A tensile test was performed in accordance with JIS L 1913 "Test methods for general nonwoven fabrics", and the recovery rate after 50% elongation was determined based on the following formula.

Recovery rate after 50% elongation (%) = 100 - X

Where X is the residual strain (%) after the test when the load is removed immediately after the elongation reaches 50% in the tensile test. The recovery rate after 50% elongation was measured in the longitudinal direction (MD direction) and the width direction (CD direction) of the fiber sheet.

[12] Compressive elastic modulus Pe (%) in Examples and Comparative Examples of the Second Embodiment (Examples 5 and 6, Comparative Examples 2 and 4), and Examples and Comparative Examples of the Third Embodiment (Examples 7 and 8, Comparative Examples 5 and 6)

Calculation was performed based on the above formula [C] in accordance with JIS L 1913 "General nonwoven fabric test methods".

[13] Thickness difference ΔT (mm) in the examples and comparative examples (Examples 5 to 6, Comparative Examples 2 to 4) of the second embodiment

The thickness difference ΔT is calculated as (T ₁ −T) in the above formula [C].

〔14〕Curved surface sliding stress (N/50mm)

First, a fiber sheet was cut into a size of 50 mm wide by 600 mm long, with the MD direction as the longitudinal direction, to prepare Sample 1. Next, as shown in FIG1(a), one end of Sample 1 was secured to a core 3 (a polypropylene resin tubular roll having an outer diameter of 30 mm and a length of 150 mm) using single-sided adhesive tape 2. Then, a 150 g weight 5 was placed on the other end of Sample 1 using an alligator clip 4 (with a clamping width of 50 mm and a 0.5 mm thick rubber sheet secured to the inside of the clip with double-sided tape) so that a load was applied uniformly across the entire width of Sample 1.

Next, while the core 3, holding the sample 1, is lifted so that the sample 1 and weight 5 are suspended, the core 3 is rotated five times without causing the weight 5 to swing significantly, winding up the sample 1 and lifting the weight 5 (see Figure 1(b)). In this state, the point of intersection between the outermost cylindrical portion of the sample 1 wound around the core 3 and the flat portion of the sample 1 not wound around the core 3 (the boundary between the portion of the sample 1 wound around the core 3 and the portion of the sample 1 held perpendicular by the weight of the weight 5) is defined as reference point 6. The alligator clip 4 and weight 5 are slowly removed without causing the base point 6 to shift. Next, at position 7, half a turn (180°) from reference point 6 along the sample 1 wound around the core 3, the outermost portion of the sample 1 is cut with a razor blade, creating a slit 8 (see Figure 2) without damaging the inner layer of the sample.

The curved surface sliding stress between the outermost layer of this sample 1 and the inner layer wrapped around the tubular roller 3 below (inner layer) was measured. A tensile testing machine ("Autograph" manufactured by Shimadzu Corporation) was used for this measurement. The winding core 3 was fixed to a clamp 9 mounted on the fixed-side clamp base of the tensile testing machine (see Figure 3). The end of the sample 1 (the end with the alligator clip 4) was clamped by the clamp 10 on the load cell side and stretched at a rate of 200 mm/min. The value (tensile strength) measured when the sample 1 fell (separated) at the slit 8 was used as the curved surface sliding stress.

1. Preparation of Fiber Sheet (First Embodiment)

<Example 1>

As latent crimped fibers, side-by-side conjugated staple fibers ("SOFITPN780," manufactured by Kuraray Co., Ltd., 1.7 dtex x 51 mm long, 12 mechanical crimps/25 mm, 62 crimps/25 mm after heat treatment at 130°C for 1 minute) were prepared. These fibers, 100% by mass, were combined with a polyethylene terephthalate resin (component (A)) having an intrinsic viscosity of 0.65 and a modified polyethylene terephthalate resin (component (B)) copolymerized with 20 mol% isophthalic acid and 5 mol% diethylene glycol. A carded web having a basis weight of 30 g/ ^m² was prepared using a carding process.

The carded web is moved on a conveying net and passed between a porous plate drum having serrated openings (circular shape) with a diameter of 2mmφ and a pitch of 2mm. A water stream is sprayed from the inside of the porous plate drum toward the web and the conveying net in a spray form at 0.8MPa to implement an uneven process of periodically forming low-density and high-density areas of fibers.

Next, the carded web is conveyed to the heating step while being overfed by about 200% so as not to hinder shrinkage in the subsequent heating step with steam.

Next, the carded web was introduced into a steam jet device attached to a conveyor. Steam was then applied vertically to the web by jetting water vapor at a pressure of approximately 160°C at a pressure of 0.5 MPa. This steam jet device imparted a coil crimp to the latently crimped fibers and simultaneously entangled the fibers. This steam jet device consisted of nozzles positioned within a conveyor to spray water vapor onto the carded web across the conveyor. The steam jet nozzles had an aperture of 0.3 mm and were arranged in a row at 2 mm intervals across the width of the conveyor. The processing speed was 8.5 m/min, and the distance between the nozzles and the conveyor on the suction side was 7.5 mm. Finally, the web was dried with hot air at 120°C for one minute to produce a stretchable fiber sheet.

Observation of the surface and thickness-direction cross-section of the obtained fiber sheet using an electron microscope (100x magnification) revealed that the fibers were oriented substantially parallel to the surface direction of the fiber sheet and curled substantially uniformly in the thickness direction.

<Example 2>

A stretchable fiber sheet was produced in the same manner as in Example 1, except that the hot air drying temperature was set at 140°C. Electron microscopic observation of the surface and thickness-direction cross-section of the resulting fiber sheet (100x magnification) revealed that the fibers were oriented substantially parallel to the plane of the fiber sheet and had substantially uniform curls in the thickness direction. The carded webs used in Examples 1 and 2, as well as Comparative Example 1 described below, had the same basis weight (30 g/ ^m² ).

<Example 3>

A commercially available polyurethane meltblown nonwoven fabric ("Meltblown UC0060" manufactured by Kuraray Kura Fusion Co., Ltd.) was stretched to 1.5 times and heat-embossed at a treatment temperature of 130°C onto one side of a commercially available polyester spunbond nonwoven fabric ("ECULE 3201A" manufactured by Toyobo Co., Ltd.) having a three-layer structure consisting of a spunbond nonwoven fiber layer/meltblown nonwoven fiber layer/spunbond nonwoven fiber layer. The stretched fabric was then relaxed and pleated to produce a stretchable fiber sheet.

<Example 4>

A carded web having a basis weight of 30 g/m2 was prepared in the same manner as in Example 1, except that 80% by mass of the latent crimping fibers used in Example 1 and 20% by mass of hot-melt adhesive fibers ("Sofista ^S220 " manufactured by Kuraray Co., Ltd., 3.3 dtex × 51 mm long) were used as the fibers constituting the carded web. A stretchable fiber sheet was prepared in the same manner as in Example 1, except that this carded web was used.

<Comparative Example 1>

A stretchable fiber sheet was produced in the same manner as in Example 1, except that the hot air drying temperature was set at 160°C. Observation of the surface and thickness-direction cross-section of the resulting fiber sheet using an electron microscope (100x magnification) revealed that the fibers were oriented substantially parallel to the plane of the fiber sheet and curled substantially uniformly in the thickness direction.

2. Evaluation of Fiber Sheet (First Embodiment)

The obtained fiber sheets were subjected to the following evaluation tests.

(1) Tightness evaluation test

A 2.5 cm wide fiber sheet was stretched 30% and wrapped around the second joint of the index finger three times. After 5 minutes, the fingertip was visually observed for color change and for pain.

(2) Winding stability evaluation test

A 2.5 cm wide fiber sheet was stretched 30% and wrapped around the second joint of the index finger three times. After 5 minutes, the index finger was flexed and extended 10 times to check for loosening (dislocation or peeling) of the fiber sheet.

[Table 1]

3. Preparation of Fiber Sheet (Second Embodiment)

<Example 5>

As latent crimped fibers, side-by-side conjugated staple fibers ("SOFITPN780," manufactured by Kuraray Co., Ltd., 1.7 dtex x 51 mm long, 12 mechanical crimps/25 mm, 62 crimps/25 mm after heat treatment at 130°C for 1 minute) were prepared. These fibers, 100% by mass, were combined with a polyethylene terephthalate resin (component (A)) having an intrinsic viscosity of 0.65 and a modified polyethylene terephthalate resin (component (B)) copolymerized with 20 mol% isophthalic acid and 5 mol% diethylene glycol. A carded web having a basis weight of 30 g/ ^m² was prepared using a carding process.

The carded web is moved on a conveying net and passed between a porous plate drum having serrated openings (circular shape) with a diameter of 2mmφ and a pitch of 2mm. A water stream is sprayed from the inside of the porous plate drum toward the web and the conveying net in a spray form at 0.8MPa to implement an uneven process of periodically forming low-density and high-density areas of fibers.

Next, the carded web is conveyed to the heating step while being overfed by about 200% so as not to hinder shrinkage in the subsequent heating step with steam.

Next, the carded web was introduced into a steam jet device attached to a conveyor. Steam was then applied vertically to the web by jetting water vapor at a pressure of approximately 160°C at a pressure of 0.5 MPa. This steam jet device imparted a water vapor treatment to the web, causing the latently crimped fibers to develop coil crimps and entangle the fibers. The steam jet device consisted of nozzles installed within a conveyor to spray water vapor onto the web across the conveyor. The steam jet nozzles had an aperture of 0.3 mm and were arranged in a row at 2 mm intervals across the width of the conveyor. The processing speed was 8.5 m/min, and the distance between the nozzles and the conveyor on the suction side was 7.5 mm. Finally, the web was dried with hot air at 120°C for one minute to produce a stretchable fiber sheet.

Observation of the surface and thickness-direction cross-section of the obtained fiber sheet using an electron microscope (100x magnification) revealed that the fibers were oriented substantially parallel to the surface direction of the fiber sheet and curled substantially uniformly in the thickness direction.

<Example 6>

A stretchable fiber sheet was produced in the same manner as in Example 5, except that the hot air drying temperature was set at 140°C. Electron microscopic observation of the surface and thickness-direction cross-section of the resulting fiber sheet (100x magnification) revealed that the fibers were oriented substantially parallel to the plane of the fiber sheet and had substantially uniform curls in the thickness direction. The carded webs used in Examples 5 and 6, as well as Comparative Example 2 described below, had the same basis weight (30 g/ ^m² ).

Comparative Example 2

A stretchable fiber sheet was produced in the same manner as in Example 5, except that the hot air drying temperature was set at 160°C. Observation of the surface and thickness-direction cross-section of the resulting fiber sheet using an electron microscope (100x magnification) revealed that the fibers were oriented substantially parallel to the plane of the fiber sheet and had substantially uniform curls in the thickness direction.

Comparative Example 3

A stretchable fiber sheet was produced in the same manner as in Example 5, except that 80% by mass of the latent crimping fibers used in Example 5 and 20% by mass of hot-melt adhesive fibers ("Sofista S220" manufactured by Kuraray Co., Ltd., 3.3 dtex × 51 mm long) were used as the fibers constituting the carded web. A carded web having a basis weight of 30 g/ ^m2 was produced in the same manner as in Example 5, and this carded web was used.

<Comparative Example 4>

A commercially available polyurethane meltblown nonwoven fabric ("Meltblown UC0060" manufactured by Kuraray Kura Fusion Co., Ltd.) was stretched to 1.5 times and heat-embossed at a treatment temperature of 130°C onto one side of a commercially available polyester spunbond nonwoven fabric ("ECULE 3201A" manufactured by Toyobo Co., Ltd.) having a three-layer structure consisting of a spunbond nonwoven fiber layer/meltblown nonwoven fiber layer/spunbond nonwoven fiber layer. The stretched fabric was then relaxed and pleated to produce a stretchable fiber sheet.

4. Evaluation of Fiber Sheet (Second Embodiment)

The obtained fiber sheets were subjected to the following evaluation tests.

(Flexibility of the joints after fiber sheet winding)

A 5 cm wide fiber sheet was stretched 30% and wrapped three times around the second joint of the index finger. The support and firmness provided to the finger when the second joint was bent were evaluated on a 5-point scale, and the average score of the five subjects was calculated. Of Comparative Examples 2 to 4, in Comparative Example 4, when the second joint was bent, the fiber sheet on the inside of the joint folded into a wrinkled (undulating) shape, making it appear difficult to bend.

Rating 5: No sense of support or hardness at all

Rating 4: Basically no sense of support or hardness

Rating 3: Slightly supportive and firm

Rating 2: Feeling strong support and hardness

Rating 1: Feeling extremely strong support and hardness

[Table 2]

5. Preparation of Fiber Sheet (Third Embodiment)

<Example 7>

As latent crimped fibers, side-by-side conjugated staple fibers ("SOFITPN780," manufactured by Kuraray Co., Ltd., 1.7 dtex x 51 mm long, 12 mechanical crimps/25 mm, 62 crimps/25 mm after heat treatment at 130°C for 1 minute) were prepared. These fibers, 100% by mass, were combined with a polyethylene terephthalate resin (component (A)) having an intrinsic viscosity of 0.65 and a modified polyethylene terephthalate resin (component (B)) copolymerized with 20 mol% isophthalic acid and 5 mol% diethylene glycol. A carded web having a basis weight of 30 g/ ^m² was prepared using a carding process.

The carded web is moved on a conveying net and passed between a porous plate drum having serrated openings (circular shape) with a diameter of 2mmφ and a pitch of 2mm. A water stream is sprayed from the inside of the porous plate drum toward the web and the conveying net in a spray form at 0.8MPa to implement an uneven process of periodically forming low-density and high-density areas of fibers.

Next, the carded web is conveyed to the heating step while being overfed by about 200% so as not to hinder shrinkage in the subsequent heating step with steam.

Next, the carded web was introduced into a steam jet device attached to a conveyor. Steam was then applied vertically to the web by jetting water vapor at a pressure of approximately 160°C at a pressure of 0.5 MPa. This steam jet device imparted a water vapor treatment to the web, causing the latently crimped fibers to develop coil crimps and entangle the fibers. The steam jet device consisted of nozzles installed within a conveyor to spray water vapor onto the web across the conveyor. The steam jet nozzles had an aperture of 0.3 mm and were arranged in a row at 2 mm intervals across the width of the conveyor. The processing speed was 8.5 m/min, and the distance between the nozzles and the conveyor on the suction side was 7.5 mm. Finally, the web was dried with hot air at 120°C for one minute to produce a stretchable fiber sheet.

Observation of the surface and thickness-direction cross-section of the obtained fiber sheet using an electron microscope (100x magnification) revealed that the fibers were oriented substantially parallel to the surface direction of the fiber sheet and curled substantially uniformly in the thickness direction.

<Example 8>

A stretchable fiber sheet was produced in the same manner as in Example 7, except that the hot air drying temperature was set at 140°C. Electron microscopic observation of the surface and thickness-direction cross-section of the resulting fiber sheet (100x magnification) revealed that the fibers were oriented substantially parallel to the plane of the fiber sheet and had substantially uniform curls in the thickness direction. The carded webs used in Examples 7 and 8, as well as Comparative Example 5 described below, had the same basis weight (30 g/ ^m² ).

<Comparative Example 5>

A stretchable fiber sheet was produced in the same manner as in Example 7, except that the hot air drying temperature was set at 160°C. Observation of the surface and thickness-direction cross-section of the resulting fiber sheet using an electron microscope (100x magnification) revealed that the fibers were oriented substantially parallel to the plane of the fiber sheet and had substantially uniform curls in the thickness direction.

<Comparative Example 6>

A commercially available polyurethane meltblown nonwoven fabric ("Meltblown UC0060" manufactured by Kuraray Kura Fusion Co., Ltd.) was stretched to 1.5 times and heat-embossed at a treatment temperature of 130°C onto one side of a commercially available polyester spunbond nonwoven fabric ("ECULE 3201A" manufactured by Toyobo Co., Ltd.) having a three-layer structure consisting of a spunbond nonwoven fiber layer/meltblown nonwoven fiber layer/spunbond nonwoven fiber layer. The stretched fabric was then relaxed and pleated to produce a stretchable fiber sheet.

6. Evaluation of Fiber Sheet (Third Embodiment)

The obtained fiber sheets were subjected to the following evaluation tests.

(Concave-convex fit)

A 5 cm wide fiber sheet was stretched 30% and wrapped three times around the index finger, wrist, and ankle. The fit to the surface irregularities of these joints was evaluated using the following 5-point scale, and the average score of the five subjects was calculated.

Rating 5: No lifting of the fiber sheet was felt even in the concave part.

Rating 4: The fiber sheet was not lifted.

Rating 3: The fiber sheet is slightly lifted.

Rating 2: The fiber sheet is felt to be more severely lifted.

Rating 1: The fiber sheet is extremely lifted up.

[Table 3]

Claims (8)

1. A fiber sheet, wherein, when the elongation stress immediately after elongation at a rate of 50% in a first direction in the plane is set as the initial elongation stress S _₀ , and the elongation stress after elongation at a rate of 50% for 5 minutes in the first direction is set as the elongation stress after 5 minutes S_₅, the stress relaxation rate, as defined by the following formula, is 85% or less. Stress relaxation rate = (Elongation stress after 5 minutes _S5 / Initial elongation stress _S0 ) × 100 The units for the initial elongation stress _S0 and the elongation stress _S5 after 5 minutes are N/50mm, and the unit for the stress relaxation rate is %. The fiber sheet is manufactured by the following method, which includes the following steps: A web-forming process that involves forming fibers containing composite fibers, i.e., potentially crimped fibers, into a web. A heating process that causes the composite fibers to curl by heating the fiber web; and Drying process, In the heating process, the fiber web is heated and curled by high-temperature steam, and the pressure and temperature of the high-temperature steam are 0.1-2 MPa and 70-180°C. 2. The fiber sheet according to claim 1, wherein the stress relaxation rate is 65% or more. 3. The fiber sheet according to claim 1 or 2, wherein the initial elongation stress _S0 is less than 2 to 30 N/50 mm. 4. The fiber sheet according to claim 1 or 2, wherein it has a length direction and a width direction, wherein, The first direction is the length direction. 5. The fiber sheet according to claim 1 or 2, wherein it is a nonwoven fabric sheet. 6. The fiber sheet according to claim 5, comprising crimped fibers. 7. The fiber sheet according to claim 1 or 2, wherein the surface sliding stress is 3 to 30 N/50 mm. 8. The fiber sheet according to claim 1 or 2, wherein it is a bandage.