Separators for nonwoven fabrics and electrochemical elements, and membrane supports.

Abstract

To provide a highly versatile nonwoven fabric that is excellent in heat resistance and mechanical strength and can be applied to applications requiring heat resistance, or a nonwoven fabric that is excellent in heat resistance, mechanical strength, and permeability. [Solution] The nonwoven fabric of the present invention contains core-sheath type composite fibers having a polyethylene component as a sheath component and a polymethylpentene component as a core component, and the polyethylene component, which is the sheath component of the core-sheath type composite fiber, is fused to the nonwoven fabric, wherein the polymethylpentene component accounts for 30% or more by volume of the total nonwoven fabric constituent fibers, and the polyethylene component accounts for 30% or more by volume of the total nonwoven fabric constituent fibers. In particular, the thickness of the nonwoven fabric is 100 μm or less, and the tensile strength per unit basis weight is 2.0 N / 5 cm width or more in a direction, or the ratio of the fiber diameter (D, unit: μm) of the core-sheath type composite fiber to the length (L, unit: μm) (L / D) is 350 or more.

Description

[Technical Field]

[0001] This invention relates to a nonwoven fabric. Because the nonwoven fabric of this invention has excellent heat resistance and mechanical strength, it can be suitably used in applications requiring these properties, such as separators for electrochemical elements, diaphragm supports for batteries, and diaphragm supports for water electrolysis. Furthermore, the nonwoven fabric of the present invention not only has excellent heat resistance, but also excellent mechanical strength despite its thinness, and excellent permeability. Therefore, it can be suitably used in applications requiring these properties, such as diaphragm supports for batteries, diaphragm supports for water electrolysis, and separators for electrochemical elements. [Background technology]

[0002] Unlike woven or knitted fabrics, nonwoven fabrics can have randomly oriented fibers and possess various properties such as dust removal, liquid retention, wipeability, concealment, flexibility, separation, isolation, and strength-granting properties, making them suitable for a wide range of applications. However, depending on the fibers constituting the nonwoven fabric, there have been cases where the heat resistance or mechanical strength was insufficient, making them unsuitable for applications requiring heat resistance.

[0003] For example, nonwoven fabrics are used as separators to isolate electrodes in nickel-metal hydride batteries, taking advantage of their liquid-retaining and insulating properties. In recent years, nickel-metal hydride batteries have increasingly been installed in automobiles as a power source and as backup power for systems such as T-BOX, GPS, and T-CONNECT. However, due to insufficient heat resistance or mechanical strength of nonwoven fabrics, it has sometimes been impossible to provide nickel-metal hydride batteries that are reliable over long periods.

[0004] To solve these heat resistance problems, a nonwoven fabric (separator) has been proposed that utilizes polyolefin-based split-type composite fibers, which combine polymethylpentene, a highly heat-resistant polyolefin resin, with polypropylene (Patent Document 1).

[0005] However, even a non-woven fabric made of such a polyolefin-based separable fiber composed of a combination of polymethylpentene and polypropylene did not have sufficient heat resistance and mechanical strength.

[0006] Such problems with heat resistance and mechanical strength were not limited to the separators such as the nickel-metal hydride batteries described above, but also occurred in the same way when non-woven fabrics were used as separator supports for batteries or electrolysis diaphragms for water electrolysis.

[0007] For example, it is used as a support for a separator that isolates between electrodes of a nickel-zinc battery by utilizing the strength-imparting property of a non-woven fabric. Since a nickel-zinc battery is likely to short-circuit due to dendrites, a resin film is often used as a separator. However, because the mechanical strength of the resin film is insufficient, a non-woven fabric is used as a support (Patent Document 2). Such a separator made of a resin film is formed into a film as a separator by filling a resin solution into the voids of the non-woven fabric and volatilizing and removing the solvent of the resin solution. However, since the non-woven fabric constituent resin, which is the conventional support, was a polyolefin-based resin such as polyethylene or polypropylene, it was likely to shrink due to the heat during volatilization removal or the heat during use, and was inferior in heat resistance and unable to exhibit the strength-imparting effect as a support.

[0008] On the other hand, polyphenylene sulfide resin is also known as a non-woven fabric constituent resin with excellent heat resistance. However, in order to form a non-woven fabric support using polyphenylene sulfide fibers, adhesive fibers for fixing the polyphenylene sulfide fibers are required. Adhesive fibers made of polyolefin-based fibers are inferior in heat resistance, and in order to plastically fix them with unstretched polyphenylene sulfide fibers with excellent heat resistance, heating and pressurization are required, resulting in fewer voids in the support and inferior ion permeability.

[0009] As a non-woven fabric capable of solving such heat resistance problems, a non-woven fabric (separator) using a polyolefin-based split composite fiber obtained by combining polymethylpentene, which is a polyolefin resin with high heat resistance, and polypropylene has been proposed (Patent Document 1).

[0010] However, even a non-woven fabric using a polyolefin-based split fiber composed of a combination of polymethylpentene and polypropylene as described above did not have sufficient heat resistance, mechanical strength, and permeability (ion permeability).

[0011] Such problems of heat resistance, mechanical strength, and permeability were not limited to the above-described separator for a battery, but also occurred similarly when used as a separator for electrolysis or a separator for an electrochemical device using a non-woven fabric.

Prior Art Documents

Patent Documents

[0012]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0013] The present invention has been made to solve the above-described conventional problems, and an object thereof is to provide a highly versatile non-woven fabric that is excellent in heat resistance and mechanical strength and can be applied to applications that require heat resistance. Another object is to provide a separator for an electrochemical device that is excellent in heat resistance and mechanical strength.

[0014] Another object of the present invention is to provide a non-woven fabric that is excellent in heat resistance, mechanical strength, and permeability. Furthermore, an object is to provide a membrane support that is excellent in heat resistance, mechanical strength, and ion permeability.

Means for Solving the Problems

[0015] The nonwoven fabric of the present invention contains a polymethylpentene component and a polyethylene component, wherein the polyethylene component is fused to the nonwoven fabric, and the polymethylpentene component accounts for 30% or more by volume of the total nonwoven fabric constituent fibers, and the polyethylene component accounts for 30% or more by volume of the total nonwoven fabric constituent fibers.

[0016] It is preferable that the nonwoven fabric contains core-sheath type composite fibers, in which polyethylene is the sheath component and polymethylpentene is the core component. Furthermore, it is preferable that the nonwoven fabric contains ultrafine fibers with a fiber diameter of 4.5 μm or less.

[0017] The nonwoven fabric preferably has a tensile strength of 2.5 N / 5 cm width or more per unit basis weight. Furthermore, the nonwoven fabric preferably has a porosity of 50-80%. In addition, the nonwoven fabric preferably has a liquid retention rate of 5% or more after being pressurized at 5.7 MPa.

[0018] The separator for electrochemical elements of the present invention includes the nonwoven fabric.

[0019] The present invention also relates to "(1) a nonwoven fabric comprising a polymethylpentene component and a polyethylene component, wherein the polyethylene component is fused, wherein the polymethylpentene component accounts for 30% or more by volume of the total nonwoven fabric constituent fibers, and the polyethylene component accounts for 30% or more by volume of the total nonwoven fabric constituent fibers, wherein the thickness of the nonwoven fabric is 100 μm or less, and the tensile strength per unit basis weight is 2.0 N / 5 cm width or more in a direction."

[0020] (2) The nonwoven fabric of (1) is preferably a nonwoven fabric comprising a core-sheath type composite fiber in which the polyethylene component is the sheath component and the polymethylpentene component is the core component.

[0021] It is preferable that (3) the nonwoven fabric of (2) has a ratio (L / D) of the fiber diameter (D, unit: μm) of the core-sheath type composite fiber to the length (L, unit: μm) of 350 or more.

[0022] It is preferable that (4) the nonwoven fabric (1) to (3) has a void ratio of 60% or more.

[0023] (5) The basis weight is 20g / m 2 The following nonwoven fabrics (1) to (4) are preferred.

[0024] Another aspect of the present invention relates to "(6) a nonwoven fabric comprising a core-sheath type composite fiber having a polyethylene component as a sheath component and a polymethylpentene component as a core component, wherein the polyethylene component which is the sheath component of the core-sheath type composite fiber is fused, wherein the polymethylpentene component accounts for 30 volume percent or more of the total nonwoven fabric constituent fibers, and the polyethylene component accounts for 30 volume percent or more of the total nonwoven fabric constituent fibers, wherein the thickness of the nonwoven fabric is 100 μm or less, and the ratio (L / D) of the fiber diameter (D, unit: μm) of the core-sheath type composite fiber to the length (L, unit: μm) is 350 or more."

[0025] It is preferable that (7) the nonwoven fabric of (6) has a direction in which the tensile strength per unit basis weight is 2.0 N / 5 cm width or more.

[0026] It is preferable that (8) the nonwoven fabric of (6) or (7) has a porosity of 60% or more.

[0027] (9) The basis weight is 20g / m 2 The following nonwoven fabrics (6) to (8) are preferred.

[0028] "(10), a membrane support containing any of the nonwoven fabrics described in (1) to (9)." [Effects of the Invention]

[0029] The nonwoven fabric of the present invention has excellent heat resistance because polymethylpentene accounts for 30% or more by volume of the total nonwoven fabric fibers. Furthermore, because polyethylene accounts for 30% or more by volume of the total nonwoven fabric fibers and the polyethylene components are fused together, it also has excellent mechanical strength. Therefore, it is a highly versatile nonwoven fabric that can be applied to applications requiring heat resistance.

[0030] If the nonwoven fabric contains core-sheath type composite fibers, where polyethylene is the sheath component and polymethylpentene is the core component, even if it contains a large amount of polyethylene, which has a relatively low melting point and poor heat resistance, the polymethylpentene component acts as the core component, resulting in excellent heat resistance.

[0031] If the nonwoven fabric further contains ultrafine fibers with a fiber diameter of 4.5 μm or less as constituent fibers, it can be a nonwoven fabric with micropores, and because the surface area of ​​the nonwoven fabric constituent fibers is large, it has excellent liquid retention properties.

[0032] Nonwoven fabrics exhibit superior mechanical strength if they have a tensile strength of 2.5 N / 5 cm width or more per unit basis weight in a particular direction.

[0033] When the porosity of a nonwoven fabric is between 50% and 80%, there are many spaces that can hold liquid, resulting in a large liquid retention capacity.

[0034] If a nonwoven fabric retains 5% or more liquid after being pressurized at 5.7 MPa, it can hold liquid even under pressure, indicating strong liquid retention.

[0035] Because the electrochemical element separator of the present invention contains the aforementioned nonwoven fabric, it exhibits excellent heat resistance and mechanical strength. Therefore, by using the electrochemical element separator of the present invention, it is possible to manufacture electrochemical elements that can be applied to applications requiring heat resistance, such as automobiles.

[0036] The nonwoven fabric of the present invention has excellent heat resistance because polymethylpentene accounts for 30% or more by volume of the total nonwoven fabric fibers. Furthermore, polyethylene accounts for 30% or more by volume of the total nonwoven fabric fibers, and the polyethylene components are fused together, resulting in excellent mechanical strength with a tensile strength of 2.0 N / 5 cm width or more per unit basis weight. Moreover, because it is thin, with a thickness of 100 μm or less, it is a nonwoven fabric with excellent permeability.

[0037] If the nonwoven fabric contains core-sheath type composite fibers, where polyethylene is the sheath component and polymethylpentene is the core component, even if it contains a large amount of polyethylene, which has a relatively low melting point and poor heat resistance, the polymethylpentene component acts as the core component, resulting in excellent heat resistance.

[0038] When the ratio of fiber diameter (D, in μm) to length (L, in μm) (L / D) of core-sheath composite fibers is 350 or greater, the fiber length is longer than the fiber diameter, making it easier for the core-sheath composite fibers to intertwine with the nonwoven fabric fibers. Furthermore, for the same quantity, there are fewer fibers and fewer bonding points between fibers, resulting in high tensile strength and excellent mechanical strength.

[0039] Nonwoven fabrics with a porosity of 60% or more exhibit excellent permeability due to their high void ratio. For example, they have excellent ion permeability and fluid permeability.

[0040] Nonwoven fabric with a basis weight of 20g / m² 2 The following characteristics result in excellent permeability due to the low fiber content. For example, they exhibit excellent ion permeability and fluid permeability.

[0041] Another nonwoven fabric of the present invention has excellent heat resistance because the polymethylpentene component accounts for 30% or more by volume of the total nonwoven fabric fibers. Furthermore, the polyethylene component accounts for 30% or more by volume of the total nonwoven fabric fibers, and the polyethylene component is fused. In addition, the ratio of core-sheath type composite fibers (L / D) is 350 or more, meaning that the fiber length is long compared to the fiber diameter. As a result, the core-sheath type composite fibers easily intertwine with the nonwoven fabric fibers. Moreover, for the same amount, there are fewer fibers and fewer bonding points between fibers, resulting in high tensile strength and excellent mechanical strength. Furthermore, because it is thin, with a thickness of 100 μm or less, it is a nonwoven fabric with excellent permeability.

[0042] This nonwoven fabric exhibits excellent mechanical strength if it has a tensile strength of 2.0 N / 5 cm width or more per unit basis weight in a particular direction.

[0043] Nonwoven fabrics with a porosity of 60% or more exhibit excellent permeability due to their high void ratio. For example, they have excellent ion permeability and fluid permeability.

[0044] Nonwoven fabric with a basis weight of 20g / m² 2 The following characteristics result in excellent permeability due to the low fiber content. For example, they exhibit excellent ion permeability and fluid permeability.

[0045] Because the membrane support of the present invention includes the nonwoven fabric, it exhibits excellent heat resistance, mechanical strength, and permeability. Therefore, by using the membrane support of the present invention, a membrane with excellent heat resistance, mechanical strength, and permeability can be manufactured. For example, when used as a diaphragm support for batteries or electrolysis, a diaphragm with excellent heat resistance, mechanical strength, and ion permeability can be manufactured. [Brief explanation of the drawing]

[0046] [Figure 1] schematic cross-section of a splittable fiber that can be used in the production of the nonwoven fabric of the present invention. [Figure 2] A schematic cross-section of another splittable fiber that can be used in the manufacture of the nonwoven fabric of the present invention. [Figure 3] Schematic cross-section of yet another splittable fiber that can be used in the manufacture of the nonwoven fabric of the present invention [Figure 4] Schematic cross-section of yet another splittable fiber that can be used in the manufacture of the nonwoven fabric of the present invention [Figure 5] Schematic cross-section of yet another splittable fiber that can be used in the manufacture of the nonwoven fabric of the present invention [Figure 6] Schematic cross-section of yet another splittable fiber that can be used in the manufacture of the nonwoven fabric of the present invention [Figure 7] Schematic cross-sectional view of the plasma processing apparatus used in the example. [Modes for carrying out the invention]

[0047] (Basic nonwoven fabric) The basic nonwoven fabric of the present invention contains a polymethylpentene component and a polyethylene component, with the polyethylene component being fused, and the polymethylpentene component accounting for 30% or more by volume of the total constituent fibers of the basic nonwoven fabric, while the polyethylene component also accounts for 30% or more by volume of the total constituent fibers of the basic nonwoven fabric. Hereinafter, the basic nonwoven fabric will be simply referred to as "nonwoven fabric".

[0048] Polymethylpentene has a melting point of approximately 220-240°C, which is higher than other polyolefins, giving it excellent heat resistance. Because this heat-resistant polymethylpentene component accounts for 30% or more by volume of the total nonwoven fabric fibers, the nonwoven fabric of the present invention has excellent heat resistance. The higher the amount of polymethylpentene component, the better the heat resistance; therefore, it is preferable that the polymethylpentene component accounts for 35% or more by volume of the total nonwoven fabric fibers, and more preferably 40% or more by volume. On the other hand, as described later, in order to have excellent mechanical strength, the nonwoven fabric also contains 30% or more by volume of polyethylene component; therefore, the polymethylpentene component is 70% or less by volume, preferably 65% ​​or less by volume, and more preferably 60% or less by volume.

[0049] Polymethylpentene is a copolymer containing 85 mol% or more of 4-methylpentene-1. For example, it can be a copolymer of 4-methylpentene-1 and one or more α-olefins (e.g., ethylene, propylene, butene-1, hexene-1, octene-1, decane-1, tetradecane-1, octadecane-1, etc.). The polymethylpentene component may be one type or two or more types. If there are two or more types, their total amount shall be 30 volume percent or more of the total nonwoven fabric fibers.

[0050] The nonwoven fabric may contain polymethylpentene in such quantities, and the nonwoven fabric constituent fibers may include, for example, (1) core-sheath composite fibers in which a resin component other than polymethylpentene is used as the sheath component and the polymethylpentene is used as the core component, (2) core-sheath composite fibers in which the polymethylpentene is used as the sheath component and a resin component other than polymethylpentene is used as the core component, (3) orange-type composite fibers in which the polymethylpentene and resin components other than polymethylpentene radiate alternately from the center in the fiber cross-section (see Figures 1 to 5), (4) multi-bimetallic composite fibers in which the polymethylpentene and resin components other than polymethylpentene are laminated alternately in the fiber cross-section (see Figure 6), and (5) single-component fibers consisting only of polymethylpentene.

[0051] Among these, (1) core-sheath type composite fibers, in which a resin component other than polymethylpentene is used as the sheath component and the polymethylpentene component is used as the core component, are preferred because they can increase mechanical strength by utilizing the fusion force of the resin component other than polymethylpentene, and also have excellent heat resistance due to the polymethylpentene component which is the core component.

[0052] Other resin components that can constitute this sheath component include, for example, polyolefin resins (e.g., polypropylene resins, polyethylene resins, etc.), polyester resins (e.g., polyester copolymers), and nylon resins (e.g., nylon copolymers). Among these, polyolefin resins, which have excellent chemical resistance and versatility, are preferred, and polyethylene resins, which have excellent fusion strength, are preferred.

[0053] When the sheath component is a preferred polyethylene component, the polyethylene component exhibits excellent fusion strength. Furthermore, although polyethylene components generally have a relatively low melting point and poor heat resistance, the presence of a polymethylpentene component as the core component provides excellent heat resistance, making it preferable. This polyethylene component, for example, has a density of 0.942 g / cm³. 3 The above high-density polyethylene has a density of 0.930-0.942 g / cm³. 3 Medium-density polyethylene, with a density of 0.910-0.930 g / cm³ 3 This can be low-density polyethylene, linear low-density polyethylene, ultra-high molecular weight polyethylene, or ethylene copolymer. Among these, high-density polyethylene is preferred because it can be a nonwoven fabric that is somewhat rigid, has good stiffness and body, and is easy to handle.

[0054] In the case of this core-sheath type composite fiber, in order to produce a nonwoven fabric with excellent heat resistance and mechanical strength, the volume ratio of resin components other than the polymethylpentene component (sheath component, for example, polyethylene component) to the polymethylpentene component (core component) is preferably 30:70 to 70:30, more preferably 35:65 to 65:35, and even more preferably 40:60 to 60:40.

[0055] Furthermore, the core component, which is polymethylpentene, does not need to be just one; it may be two or more sea-island type components. Also, in the fiber cross-section, the core component and sheath component may be arranged concentrically, or the core component may be arranged eccentrically, but it is preferable that they be arranged concentrically so that the nonwoven fabric has excellent dimensional stability.

[0056] The content of this suitable core-sheath type composite fiber is not particularly limited, as long as the polymethylpentene component accounts for 30% or more by volume of the total nonwoven fabric constituent fibers, and the polyethylene component accounts for 30% or more by volume of the total nonwoven fabric constituent fibers. However, to easily satisfy this volume ratio, it is preferable that the core-sheath type composite fiber, in which the polyethylene component is the sheath component and the polymethylpentene component is the core component, contains 50% or more by volume, more preferably 60% or more by volume, even more preferably 70% or more by volume, and still more preferably 80% or more by volume.

[0057] Furthermore, (3) orange-shaped composite fibers (see Figures 1 to 5) in which polymethylpentene components and resin components other than polymethylpentene components radiate alternately from the center in the fiber cross-section, and (4) multi-bimetallic composite fibers (see Figure 6) in which polymethylpentene components and resin components other than polymethylpentene components are stacked alternately in the fiber cross-section, can be separated into individual polymethylpentene components and resin components other than polymethylpentene components by applying mechanical external force, thereby generating fibers with a finer fiber diameter. As a result, they can be nonwoven fabrics with fine pores, and because the surface area of ​​the nonwoven fabric constituent fibers is large, they can be nonwoven fabrics with excellent resin and liquid retention properties, making them suitable.

[0058] More specifically, by applying mechanical force to the orange-type composite fiber or multi-bimetal fiber, ultrafine fibers with a diameter of 4.5 μm or less can be generated. A nonwoven fabric containing such ultrafine fibers can be a nonwoven fabric with micropores, and because of its large fiber surface area, it can be a nonwoven fabric with excellent resin and liquid retention properties.

[0059] When a mechanical external force is applied to the orange-shaped composite fiber 1 shown in Figure 1, approximately triangular ultrafine fibers made of polymethylpentene component 11 and approximately triangular ultrafine fibers made of resin component 12 other than polymethylpentene component are generated.

[0060] When a mechanical external force is applied to the orange-shaped composite fiber 1 shown in Figure 2, approximately elliptical ultrafine fibers made of polymethylpentene component 11 or resin component 11 other than polymethylpentene component, and approximately triangular ultrafine fibers made of resin component 12 other than polymethylpentene component or polymethylpentene component 12 are generated.

[0061] When a mechanical external force is applied to the orange-shaped composite fiber 1 shown in Figure 3, approximately triangular ultrafine fibers made of polymethylpentene component 11 or resin component 11 other than polymethylpentene component, and approximately triangular and circular ultrafine fibers made of resin component 12 other than polymethylpentene component or polymethylpentene component 12 are generated.

[0062] When a mechanical external force is applied to the orange-shaped composite fiber 1 shown in Figure 4, approximately elliptical and circular ultrafine fibers made of polymethylpentene component 11 or resin component 11 other than polymethylpentene, and approximately triangular ultrafine fibers made of resin component 12 other than polymethylpentene or polymethylpentene component 12 are generated.

[0063] When a mechanical external force is applied to the orange-shaped composite fiber 1 having a hollow portion, as shown in Figure 5, approximately trapezoidal ultrafine fibers made of polymethylpentene component 11 or resin component 11 other than polymethylpentene component, and approximately trapezoidal ultrafine fibers made of resin component 12 other than polymethylpentene component or polymethylpentene component 12 are generated.

[0064] When a mechanical external force is applied to the multi-bimetallic composite fiber 1 shown in Figure 6, approximately trapezoidal and approximately semicircular ultrafine fibers made of polymethylpentene component 11, and approximately trapezoidal and approximately semicircular ultrafine fibers made of resin component 11 other than polymethylpentene component are generated.

[0065] Thus, the ultrafine fibers generated from orange-type composite fibers and multi-bimetallic composite fibers have a non-circular, irregular cross-sectional shape. Because these ultrafine fibers with irregular cross-sectional shapes can be arranged in a densely packed state, a nonwoven fabric can be formed that is dense and has excellent separability, isolation, and concealment properties.

[0066] Examples of mechanical forces that can divide such composite fibers include fluid flows such as water, calenders, refiners, pulpers, mixers, and beaters.

[0067] Furthermore, (5) single-component fibers consisting only of polymethylpentene can have a fiber diameter of 0.1 to 30 μm, but ultrafine fibers of 4.5 μm or less can be used to make nonwoven fabrics with micropores, and because the surface area of ​​the nonwoven fabric constituent fibers is large, they can be made into nonwoven fabrics with excellent resin and liquid retention properties, which is preferable. Such single-component ultrafine fibers consisting only of polymethylpentene can be made by applying mechanical external force to the orange-type composite fibers or multi-bimetallic composite fibers as described above, or by extracting and removing only the marine component from sea-island type composite fibers in which polymethylpentene is the island component. The latter method using sea-island type composite fibers is preferable because it can produce even finer ultrafine fibers. More specifically, the fibers can be ultrafine fibers with a fiber diameter of 4.0 μm or less, ultrafine fibers with a fiber diameter of 3.0 μm or less, and ultrafine fibers with a fiber diameter of 2.0 μm or less.

[0068] The ultrafine fibers that can constitute the nonwoven fabric of the present invention are preferably stretched so that the nonwoven fabric has excellent mechanical strength. As mentioned above, when ultrafine fibers are made from orange-type composite fibers, multi-bimetallic composite fibers, or sea-island type composite fibers, if the orange-type composite fibers, multi-bimetallic composite fibers, or sea-island type composite fibers are stretched at the stage before splitting, then the ultrafine fibers made from these fibers are also in a stretched state.

[0069] On the other hand, the nonwoven fabric of the present invention contains polyethylene components with excellent fusion strength in an amount of 30% or more by volume of the total nonwoven fabric constituent fibers, and since some or all of these polyethylene components are involved in fusion, the nonwoven fabric has excellent mechanical strength. The more polyethylene components there are, the better the fusion strength and mechanical strength of the nonwoven fabric, so it is preferable that the polyethylene components account for 35% or more by volume of the total nonwoven fabric constituent fibers, and more preferably 40% or more by volume. On the other hand, as mentioned above, in order to have excellent heat resistance, it is necessary to contain 30% or more by volume of polymethylpentene components, so the polyethylene components are 70% or less by volume, preferably 65% ​​or less by volume, and more preferably 60% or less by volume.

[0070] The polyethylene can be high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, ultra-high molecular weight polyethylene, or an ethylene copolymer. Among these, high-density polyethylene is preferred because it can be a nonwoven fabric that is somewhat hard, has good stiffness and resilience, and is easy to handle. The polyethylene copolymer can be a copolymer of one or more α-polyolefins such as propylene, butene-1, hexene-1, octene-1, decane-1, tetradecane-1, or octadecane-1. The polyethylene component may be one type or two or more types. If there are two or more types, their total amount shall be 30% or more by volume of the total nonwoven fabric fibers.

[0071] Nonwoven fabrics contain polyethylene components in such quantities, and the polyethylene components are fused together. The nonwoven fabric constituent fibers may include, for example, (a) core-sheath type composite fibers in which polyethylene components are used as the sheath component and resin components other than polyethylene components are used as the core component; (b) orange type composite fibers in which polyethylene components and resin components other than polyethylene components radiate alternately from the center in the fiber cross-section (see Figures 1 to 5); (c) multi-bimetal type composite fibers in which polyethylene components and resin components other than polyethylene components are laminated alternately in the fiber cross-section (see Figure 6); and (d) single-component fibers consisting only of polyethylene components.

[0072] Among these, (i) core-sheath type composite fibers, in which polyethylene is used as the sheath component and resin components other than polyethylene are used as the core component, are preferable because they have excellent fusion strength due to the polyethylene component and excellent fiber shape retention due to resin components other than polyethylene (core component), and can increase the mechanical strength of the nonwoven fabric.

[0073] Other resin components besides polyethylene that can constitute the core-sheath component of this core-sheath type composite fiber include, for example, polyolefin resins (e.g., polymethylpentene resin, polypropylene resin, etc.), polyester resins (e.g., polyethylene terephthalate, etc.), and nylon resins (e.g., nylon 6, nylon 66, etc.). Among these, polyolefin resins, which have excellent chemical resistance and versatility, are preferred, and polymethylpentene resins, which have excellent heat resistance, are preferred.

[0074] In the case of this core-sheath type composite fiber, in order to produce a nonwoven fabric with excellent heat resistance and mechanical strength, the volume ratio of the polyethylene component to the resin component other than polyethylene (core component, for example, polymethylpentene component) is preferably 30:70 to 70:30, more preferably 35:65 to 65:35, and even more preferably 40:60 to 60:40, so as to provide excellent bonding strength from the polyethylene component.

[0075] Furthermore, the resin components other than the polyethylene core component do not need to be just one; they may be two or more sea-island type. Also, in the fiber cross-section, the core component and sheath component may be arranged concentrically, or the core component may be arranged eccentrically; however, concentric arrangement is preferable to ensure a nonwoven fabric with excellent dimensional stability.

[0076] The content of this suitable core-sheath type composite fiber is not particularly limited, as long as the polyethylene component in the nonwoven fabric accounts for 30% or more by volume of the total nonwoven fabric constituent fibers, and the polymethylpentene component accounts for 30% or more by volume of the total nonwoven fabric constituent fibers. However, to easily satisfy this volume ratio, it is preferable that the core-sheath type composite fiber, in which the polyethylene component is the sheath component and the polymethylpentene component is the core component, contains 50% or more by volume, more preferably 60% or more by volume, even more preferably 70% or more by volume, and still more preferably 80% or more by volume.

[0077] The nonwoven fabric of the present invention preferably contains core-sheath type composite fibers having a polyethylene component as the sheath component and a polymethylpentene component as the core component. However, in order to increase the rigidity and compressive resistance of the nonwoven fabric, it may also contain high-strength fibers with a tensile strength of 5 cN / dtex or higher. The stronger the tensile strength of these high-strength fibers, the better the aforementioned effect. Therefore, when the high-strength fibers consist of a single component, the tensile strength is preferably 8.5 cN / dtex or higher, more preferably 8.9 cN / dtex or higher, and even more preferably 9.5 cN / dtex or higher. On the other hand, when the high-strength fibers are composite fibers and the mechanical strength of the nonwoven fabric is also increased by the fusion of the high-strength fibers, the tensile strength is preferably 5.5 cN / dtex or higher, more preferably 6.0 cN / dtex or higher, and even more preferably 6.2 cN / dtex or higher. In any case of high-strength fibers, there is no particular upper limit to the tensile strength, but it is approximately 50 cN / dtex. In this invention, "tensile strength" refers to the tensile strength measured in accordance with JIS L 1015:2010 "Test Method for Chemical Fiber Staples" 8.7.1 (Standard Time Test), using a constant-speed tension tensile testing machine under conditions of a gripping distance of 20 mm and a tensile speed of 20 mm / min.

[0078] The resin components constituting these high-strength fibers are not particularly limited, but can be composed of, for example, polyolefin resins (e.g., polypropylene resins, polyethylene resins, polymethylpentene resins, etc.), polyester resins (e.g., polyethylene terephthalate, polyester copolymers), nylon resins (e.g., nylon 6, nylon 66, nylon copolymers), etc., either individually or in combination thereof. Among these, polyolefin resins, which have excellent chemical resistance and versatility, are preferred. For example, when the high-strength fiber consists of a single component, it can be made of ultra-high molecular weight polyethylene, polypropylene, etc., and when it is a composite fiber consisting of two types of resin components, it can be a core-sheath type composite fiber in which the polyethylene component (especially high-density polyethylene component) is the sheath component and the polypropylene component is the core component, or a core-sheath type composite fiber in which the polyethylene component (especially high-density polyethylene component) is the sheath component and the polymethylpentene component is the core component.

[0079] The nonwoven fabric of the present invention preferably contains core-sheath type composite fibers having a polyethylene component as the sheath component and a polymethylpentene component as the core component. However, to further improve the heat resistance of the nonwoven fabric, it may also contain heat-resistant fibers having a melting point or decomposition temperature of 210°C or higher. Examples of resins constituting these heat-resistant fibers include polyphenylene sulfide (PPS), polybenzimidazole (PBI), polyetheretherketone (PEEK), polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), fluoroethylene propylene (FEP), ethylene chlorotrifluoroethylene (ECTFE), ethylene tetrafluoroethylene (ETFE), polychlorotrifluoroethylene (PCTFE), polyimide (PI), and polyamideimide (PAI). Note that "melting point" refers to the melting temperature obtained from the differential thermal analysis curve (DTA curve) obtained by differential thermal analysis as specified in JIS K 7121-1987, and "decomposition temperature" refers to the temperature at which the mass of the completely dry test specimen decreases by 5%, as determined by thermogravimetric analysis as specified in JIS K 7120-1987.

[0080] The nonwoven fabric of the present invention preferably contains core-sheath type composite fibers having a polyethylene component as the sheath component and a polymethylpentene component as the core component. The fiber diameter of the fibers constituting the nonwoven fabric, including these core-sheath type composite fibers, is not particularly limited, but is preferably 0.1 to 35 μm, more preferably 0.5 to 28 μm, and even more preferably 1 to 20 μm, in order to produce a nonwoven fabric in which the fibers are uniformly dispersed, has excellent texture, can be uniformly given strength, and has excellent density and resin and liquid retention properties.

[0081] As mentioned above, it is preferable that the material contains ultrafine fibers with a fiber diameter of 4.5 μm or less (preferably 4.0 μm or less, more preferably 3.0 μm or less, and even more preferably 2.0 μm or less). These ultrafine fibers can be made from, for example, polyolefin resins such as polymethylpentene resin, polypropylene resin, and polyethylene resin; polyester resins such as polyethylene terephthalate and polyester copolymer; and nylon resins such as nylon 6, nylon 66, and nylon copolymer. Among these, it is preferable that the ultrafine fibers be made from polyolefin resins, which have excellent chemical resistance and versatility, and it is preferable that they be made from polymethylpentene resin or polypropylene resins, which have excellent heat resistance.

[0082] As mentioned above, ultrafine fibers can be produced by applying mechanical external force to orange-type composite fibers or multi-bimetallic composite fibers, or by extracting and removing the marine component from sea-island type composite fibers.

[0083] In this invention, the fiber diameter refers to the diameter of the fiber's cross-sectional shape if it is circular, and if it is not circular, the diameter of a circle having the same area as the cross-sectional area is considered to be the fiber diameter.

[0084] Furthermore, the fiber length of the nonwoven fabric constituent fibers, including core-sheath type composite fibers and ultrafine fibers, is not particularly limited, but the shorter the fiber length, the greater the degree of freedom of the fibers, and the more uniformly dispersed the fibers become, resulting in a nonwoven fabric with excellent texture. Therefore, it is preferable that the fiber length is 0.1 to 160 mm, more preferably 0.5 to 105 mm, even more preferably 1 to 55 mm, and even more preferably 1 to 20 mm.

[0085] Furthermore, the nonwoven fabric of the present invention may include two or more core-sheath composite fibers, ultrafine fibers, and / or heat-resistant fibers that differ in terms of resin composition, fiber diameter, and / or fiber length.

[0086] The nonwoven fabric of the present invention is in a state where the fibers are bonded together by the fusion of polyethylene components, but in addition to fusion, the fibers may also be three-dimensionally entangled. This is because the mechanical strength of the nonwoven fabric is further improved by the three-dimensional entanglement. Such three-dimensional entanglement can be formed, for example, by applying a fluid flow such as a water stream or a needle to the fiber web.

[0087] The nonwoven fabric of the present invention has excellent mechanical strength, and more specifically, it is preferable that the tensile strength per unit basis weight is 2.5 N / 5 cm width or higher. Tensile strength is evaluated per unit basis weight because a higher basis weight, i.e., a larger fiber content, inevitably leads to higher mechanical strength. Therefore, in order to objectively evaluate the mechanical strength of the nonwoven fabric, it is evaluated per unit basis weight, which represents the fiber content. The higher this tensile strength, the better the mechanical strength, so it is more preferable that the tensile strength per unit basis weight be 2.8 N / 5 cm width or higher, even more preferable that be 3.0 N / 5 cm width or higher, and even more preferable that be 3.2 N / 5 cm width or higher. The higher this tensile strength, the better the mechanical strength, so there is no particular upper limit, but it can be 10 N / 5 cm width or less.

[0088] The tensile strength of the present invention is a value obtained by the following procedure. 1. Take a strip-shaped test piece measuring 200 mm in length and 50 mm in width from the nonwoven fabric. 2. The tensile strength of the strip-shaped test specimens is measured using a tensile strength testing machine. The measurement conditions are a chuck distance of 100 mm and a tensile speed of 300 mm / min., and the strength at fracture is measured. 3. Repeat steps 1 and 2 three times, calculate the arithmetic mean of the strengths at the time of fracture, and define this as the tensile strength (unit: N / 50mm width).

[0089] Furthermore, to confirm whether there is a direction in which the tensile strength per unit weight is 2.5 N / 5 cm width or more, the following procedure is performed. 1. Take three strip-shaped test pieces, each 200 mm long and 50 mm wide, in a reference direction of the nonwoven fabric (for example, the longitudinal direction which is the production direction of the nonwoven fabric). 2. Three strip-shaped test pieces, each 200 mm long and 50 mm wide, are taken, with the longitudinal direction being the direction rotated at a 10° angle with respect to the aforementioned reference direction. 3. Similarly, three strip-shaped test pieces, each 200 mm long and 50 mm wide, are taken for each of the 16 directions, with the length direction being the direction rotated by an angle increasing by 10° with respect to the reference direction. In other words, three strip-shaped test pieces are taken for each of the 18 directions, including the reference direction. 4. Measure the tensile strength of the strip-shaped test specimens in each direction using the method described above. 5. Based on the results of measuring the tensile strength in the 18 directions, identify the direction with the strongest tensile strength. 6. The tensile strength in the direction of the strongest tensile strength (Tmax, unit: N / 50mm width) is used as the basis weight (M, unit: g / m). 2 Divide by ), that is, calculate the tensile strength (Tu) per unit weight using the following formula. Tu = Tmax / M 7. As a result, if the tensile strength per unit weight is 2.5 N / 5 cm width or more, then at least that direction corresponds to a direction in which the tensile strength per unit weight is 2.5 N / 5 cm width or more.

[0090] Furthermore, nonwoven fabrics are produced as continuous nonwovens during manufacturing, and because the fibers tend to orient more or less in the direction of production, the direction of production during nonwoven fabric manufacturing is often the direction in which the tensile strength per unit basis weight is 2.5 N / 5 cm width or higher.

[0091] Also, even if the tensile strength per unit basis weight is 2.5 N / 5 cm width or more, if the absolute tensile strength is weak and may not be practical, the tensile strength preferably has a direction of 100 N / 5 cm width or more, more preferably has a direction of 110 N / 5 cm width or more, still more preferably has a direction of 120 N / 5 cm width or more, and still more preferably has a direction of 130 N / 5 cm width or more. This direction is particularly preferably the production direction during non-woven fabric production.

[0092] The non-woven fabric of the present invention preferably has a shrinkage rate of 5% or less when heated at 150 °C so as to have excellent heat resistance. The lower this shrinkage rate, the more excellent the heat resistance. Therefore, the shrinkage rate when heated at 150 °C is more preferably 4.5% or less, still more preferably 4.0% or less, and still more preferably 3.5% or less.

[0093] The shrinkage rate when heated at 150 °C is a value obtained by the following method. 1. From the non-woven fabric, a test piece (area: Ab = 10,000 mm 2 ) with a length of 100 mm in the longitudinal direction (production direction of the non-woven fabric) and a length of 100 mm in the lateral direction (direction perpendicular to the longitudinal direction) is taken. 2. The test piece is left in a dryer set at a temperature of 150 °C. 3. After 10 minutes, the test piece is taken out from the dryer, the lengths in the longitudinal and lateral directions of the test piece are measured, and the area (Aa, unit: mm 2 ) is calculated. 4. The heat shrinkage rate (S, unit: %) is calculated from the following formula. S = [(Ab - Aa) / Ab] × 100 = (10,000 - Aa) / 100 5. The operations of 1 to 4 are repeated 3 times, the heat shrinkage rates are calculated for 3 test pieces, and the arithmetic mean value thereof is taken as the "shrinkage rate when heated at 150 °C".

[0094] The porosity of the nonwoven fabric of the present invention is not particularly limited, but it is preferable that the porosity be 50% or more, more preferably 53% or more, and even more preferably 56% or more, in order to have many spaces that can hold liquid and to have a large liquid holding capacity. On the other hand, if the porosity is too high, the mechanical strength tends to be inferior, so it is preferable that it be 80% or less, more preferably 75% or less, and even more preferably 70% or less.

[0095] In this invention, the porosity (P, unit: %) refers to the value obtained from the following formula. P = 100 - (Fr1 + Fr2 + ... + Frn) Here, Frn represents the packing density (in %) of the n component that makes up the nonwoven fabric, and is the value obtained from the following formula. Frn = [(M × Prn) / (T × SGn)] × 100 Here, M is the basis weight of the nonwoven fabric (unit: g / cm²). 2 ), T is the thickness of the nonwoven fabric (unit: cm), Prn is the mass ratio of the n component in the nonwoven fabric, and SGn is the density of the n component (unit: g / cm³). 3 These each mean the following:

[0096] The apparent density of the nonwoven fabric of the present invention is not particularly limited, but to ensure that there are many spaces that can hold liquid and that the liquid holding capacity is large, the apparent density is 0.57 g / cm³. 3 Preferably, it is 0.53 g / cm³. 3 It is more preferable that it be less than 0.50 g / cm³ 3 It is even more preferable that the apparent density is as follows. On the other hand, if the apparent density is too low, the mechanical strength tends to be inferior, so the apparent density should be 0.23 g / cm³. 3 Preferably, it is 0.28 g / cm³ or more. 3 It is more preferable that it be greater than or equal to 0.34 g / cm³. 3 It is even more preferable that the above conditions are met. This apparent density is a calculated value obtained from the basis weight and thickness of the nonwoven fabric, and more specifically, the basis weight (unit: g / cm²). 2 This is the value obtained by dividing ) by the thickness (unit: cm).

[0097] The nonwoven fabric of the present invention preferably has a liquid retention rate of 5% or more after being pressurized at 5.7 MPa. This is because it is a nonwoven fabric that can retain liquid even when pressure is applied and has strong liquid retention capabilities. The higher this liquid retention rate value, the stronger the liquid retention capability, so it is more preferable that the liquid retention rate after pressurization be 6% or more, and even more preferable that it be 7% or more. There is no particular upper limit to the liquid retention rate after pressurization, but it can be 20% or less.

[0098] This liquid retention rate is obtained by the following method. 1. Cut the nonwoven fabric into circles with a diameter of 30 mm and take four circular test pieces. 2. After allowing the circular test specimen to reach moisture equilibrium at a temperature of 20°C and a relative humidity of 65%, measure its mass (M0). 3. Immerse the nonwoven fabric in a potassium hydroxide solution with a specific gravity of 1.3 (at 20°C) for 1 hour to replace the air inside the fabric with the potassium hydroxide solution, thereby retaining the potassium hydroxide solution. 4. The nonwoven fabric is sandwiched between three circular filter papers (diameter = 30 mm) on the top and bottom, and a pressure of 5.7 MPa is applied for 30 seconds using a pressure pump. After that, the mass (M1) of the nonwoven fabric is measured. 5. Calculate the hydrate retention rate (Rr, in %) using the following formula. Rr = [(M1 - M0) / M0] × 100 6. The liquid retention rate is measured for four circular test pieces, and the liquid retention rate is calculated for each. The four calculated liquid retention rates are arithmetically averaged to obtain the liquid retention rate of the nonwoven fabric in this invention.

[0099] The basis weight of the nonwoven fabric of the present invention varies depending on the application and is not particularly limited, but is generally between 10 and 200 g / m². 2 It can be. The measurement is 1m 2 This is the mass per unit area, and the size of the nonwoven fabric is 1 m². 2 If it is less than 1m 2 The converted value will be used as the basis.

[0100] The thickness of the nonwoven fabric of the present invention varies depending on the application and is not particularly limited, but can be between 0.03 and 2 mm. In this invention, "thickness" refers to the arithmetic mean of measurements taken at 10 randomly selected points using an outside micrometer (0-25 mm) as specified in JIS B 7502:1994 under a 5N load.

[0101] The nonwoven fabric of the present invention is fused with polyethylene components and also contains polymethylpentene components, has a high proportion of polyolefin resin components, and exhibits excellent chemical resistance. However, it may be difficult to apply to various uses, so it may be subjected to various processing to make it easier to apply to various uses. For example, it may be colored with pigments or dyes, electrostatically charged, have patterns added, or have hydrophilic groups such as sulfonic acid groups, carboxyl groups, or carbonyl groups introduced.

[0102] The nonwoven fabric of the present invention has excellent heat resistance and mechanical strength, making it highly versatile and applicable to various uses. For example, it can be suitably used as a separator for electrochemical elements, a diaphragm support for batteries such as nickel-zinc batteries, and a diaphragm support for water electrolysis. Examples of electrochemical elements include alkaline primary batteries such as alkaline manganese batteries, mercury batteries, silver oxide batteries, or air batteries; alkaline secondary batteries such as nickel-cadmium batteries, silver-zinc batteries, silver-cadmium batteries, nickel-zinc batteries, nickel-metal hydride batteries, and lead-acid batteries; lithium-ion secondary batteries; sodium-ion batteries; polyvalent ion batteries such as magnesium, aluminum, calcium, and zinc; lithium-sulfur batteries; metal-air batteries such as lithium and zinc; lithium-ion capacitors; fluoride ion batteries; and potassium-ion batteries. In particular, when used as a separator for alkaline secondary batteries such as nickel-cadmium batteries and nickel-metal hydride batteries, its excellent heat resistance and mechanical strength allow for the production of alkaline secondary batteries that can be suitably used in automotive applications requiring heat resistance.

[0103] The separator for alkaline secondary batteries such as nickel-cadmium batteries and nickel-metal hydride batteries, which is suitable for this purpose, contains a polymethylpentene component and a polyethylene component, with the polyethylene component being fused. The polymethylpentene component accounts for 30% or more by volume of the total nonwoven fabric fibers, and the polyethylene component also accounts for 30% or more by volume of the total nonwoven fabric fibers. As a result, it has excellent heat resistance and mechanical strength and can be suitably used in applications requiring heat resistance of 100°C or higher, such as as a separator for automotive alkaline secondary batteries.

[0104] Furthermore, if the material contains ultrafine fibers generated from orange-type composite fibers, ultrafine fibers generated from multi-bimetallic composite fibers, and ultrafine fibers produced by extracting and removing the marine component from sea-island type composite fibers, it has the characteristic of being able to produce alkaline secondary batteries that are excellent not only for use in high-temperature conditions exceeding 100°C but also in low-temperature conditions below 60°C, due to the large surface area of ​​the nonwoven fabric constituent fibers and excellent electrolyte retention. Moreover, if the material contains ultrafine fibers generated from orange-type composite fibers and multi-bimetallic composite fibers, the cross-sectional shape of these ultrafine fibers has an irregular shape, and the path from one side of the separator (nonwoven fabric) to the other side is complex and long, so short circuits due to dendrites are less likely to occur.

[0105] Furthermore, when the separator contains high-strength fibers, it is less likely for burrs to penetrate the electrodes during alkaline secondary battery manufacturing, and less likely for the electrodes to break due to these burrs, resulting in a higher yield of alkaline secondary batteries. In addition, it has excellent compression resistance and can maintain the distance between electrodes even after battery construction, resulting in excellent electrolyte retention and also making it easier to prevent physical short circuits caused by fine powder when the active material falls out.

[0106] Furthermore, if the separator contains heat-resistant fibers, it has the advantage of being able to withstand use in high-temperature conditions exceeding 100°C for extended periods.

[0107] When the nonwoven fabric of the present invention is used as a separator for alkaline secondary batteries, it is preferable that it is composed only of polyolefin fibers made solely of polyolefin resin so as to have excellent electrolyte resistance. For example, it is preferable that it is composed of one or more types of polyolefin fibers such as: core-sheath type composite fibers in which polyethylene component (especially high-density polyethylene component) is the sheath component and polymethylpentene component is the core component; core-sheath type composite fibers in which polyethylene component (especially high-density polyethylene component) is the sheath component and polypropylene component is the core component; single-component fibers (ultrafine fibers or high-strength fibers) made of polyethylene, polypropylene or polymethylpentene; orange-type or multi-bimetallic type composite fibers made of polypropylene component and polymethylpentene component; orange-type or multi-bimetallic type composite fibers made of polyethylene component and polymethylpentene component.

[0108] The separator of the present invention has a porosity of 50-80% and / or an apparent density of 0.23-0.57 g / cm³. 3 Therefore, because it has a large electrolyte capacity and excellent mechanical strength, it can be suitably used as a separator for automotive alkaline secondary batteries.

[0109] Furthermore, if the separator of the present invention has a liquid retention rate of 5% or more after pressurization at 5.7 MPa, it can retain the electrolyte even when pressure is applied during electrode formation, and ion permeability is not impaired, thus enabling the production of alkaline secondary batteries with a long lifespan.

[0110] The basis weight of the separator of this invention is 10 to 200 g / m². 2 It can be 20-100g / m 2 It can be 25-85 g / m 2 It can be 30-70g / m 2 It can be as follows: The thickness can be 0.01 to 0.30 mm, 0.03 to 0.25 mm, or 0.05 to 0.20 mm.

[0111] As mentioned above, the separator of the present invention is preferably composed solely of polyolefin fibers. However, since this tends to result in poor pourability and retention of aqueous electrolytes, it is preferable that hydrophilic groups such as sulfonic acid groups, carboxyl groups, and carbonyl groups are introduced to enhance affinity with the electrolyte.

[0112] Furthermore, the separators for electrochemical elements, including the alkaline secondary battery separator of the present invention, may consist solely of the nonwoven fabric described above, or they may be laminated with other nonwoven fabrics, woven fabrics, knitted fabrics, nets, films, etc., to add various functions such as reinforcement and separation.

[0113] (1st nonwoven fabric) The first nonwoven fabric of the present invention is a nonwoven fabric that, in addition to heat resistance and mechanical strength, also has excellent permeability among basic nonwoven fabrics. Therefore, only the differences between the first nonwoven fabric and the basic nonwoven fabric will be explained below.

[0114] It is preferable that the ratio (L / D) of the fiber diameter (D, unit: μm) to the length (L, unit: μm) of the first nonwoven fabric constituent fibers, including the core-sheath type composite fiber, ultrafine fiber, and heat-resistant fiber of the present invention, is 350 or more. When this ratio (L / D) is 350 or more, the fiber length is longer than the fiber diameter, so the first nonwoven fabric constituent fibers, including the core-sheath type composite fiber, tend to intertwine with each other. Also, for the same amount of fiber, there are fewer fibers and fewer joints between fibers, resulting in high tensile strength and excellent mechanical strength. The larger the ratio (L / D), the stronger this tendency becomes, so it is more preferable that the ratio (L / D) is 400 or more, even more preferable that it is 450 or more, even more preferable that it is 500 or more, even more preferable that it is 550 or more, and even more preferable that it is 600 or more. On the other hand, as mentioned above, a large ratio (L / D) tends to cause fibers to entangle easily and inhibit the uniform dispersion of fibers. Therefore, a ratio (L / D) of 7000 or less is preferable, more preferably 2000 or less, even more preferably 1600 or less, even more preferably 1300 or less, and even more preferably 1000 or less.

[0115] The fiber diameter of the core-sheath type composite fiber of the present invention (particularly, a core-sheath type composite fiber having a polyethylene resin as the sheath component and a polymethylpentene resin as the core component) is not particularly limited as long as it satisfies the above ratio (L / D), but it is preferably 10 μm or more, more preferably 11 μm or more, even more preferably 12 μm or more, even more preferably 13 μm or more, even more preferably 14 μm or more, and even more preferably 15 μm or more, so that the mechanical strength and heat resistance of the first nonwoven fabric are excellent. On the other hand, if the core-sheath type composite fiber is too thick, the first nonwoven fabric tends to have poor fiber dispersibility, so it is preferably 35 μm or less, more preferably 22 μm or less, even more preferably 20 μm or less, and even more preferably 19 μm or less.

[0116] Furthermore, the fiber length of the first nonwoven fabric constituent fibers, which include core-sheath type composite fibers, ultrafine fibers, and heat-resistant fibers, is not particularly limited, but the longer the fiber length, the easier it is for the first nonwoven fabric constituent fibers to intertwine with each other, and the better the mechanical strength tends to be. Therefore, it is preferably 6 mm or longer, more preferably 8 mm or longer, and even more preferably 10 mm or longer. On the other hand, if the fiber length is long, the fibers tend to intertwine with each other, which tends to hinder the uniform dispersion of the fibers. Therefore, it is preferably 105 mm or less, more preferably 55 mm or less, and even more preferably 20 mm or less. In particular, since the polyethylene component, which is the sheath component of the core-sheath type composite fiber, fuses together, it is preferable that the fiber length be within the above range so that it intertwines to a certain extent.

[0117] Furthermore, the first nonwoven fabric of the present invention may include two or more types of core-sheath composite fibers, high-strength fibers, ultrafine fibers, and heat-resistant fibers that differ in terms of resin composition, resin arrangement in the fiber cross-section, fiber diameter, ratio (L / D), and / or fiber length.

[0118] The first nonwoven fabric of the present invention has excellent mechanical strength, specifically, a tensile strength of 2.0 N / 5 cm width or more per unit basis weight. Tensile strength is evaluated per unit basis weight because a higher basis weight, i.e., a larger fiber content, inevitably leads to higher mechanical strength. Therefore, in order to objectively evaluate the mechanical strength of the first nonwoven fabric, it is evaluated per unit basis weight, which represents the fiber content. The higher this tensile strength, the better the mechanical strength, so it is more preferable that the tensile strength per unit basis weight be 2.2 N / 5 cm width or more, and even more preferable that be 2.4 N / 5 cm width or more. The higher this tensile strength per unit basis weight, the better the mechanical strength, so there is no particular upper limit, but it can be 10 N / 5 cm width or less.

[0119] Furthermore, the confirmation of whether the tensile strength per unit basis weight is 2.0 N / 5 cm width or higher in any direction is performed in the same manner as described above for the basic nonwoven fabric.

[0120] Furthermore, the first nonwoven fabric is produced as a continuous piece during manufacturing, and since the fibers tend to orient more or less in the direction of production, the direction of production during the manufacturing of the first nonwoven fabric is often in the direction in which the tensile strength per unit basis weight is 2.0 N / 5 cm width or higher.

[0121] Even if the first nonwoven fabric of the present invention has a direction in which the tensile strength per unit basis weight is 2.0 N / 5 cm width or more, its absolute tensile strength may be weak and impractical. Therefore, it is preferable that it has a direction in which the tensile strength is 20 N / 5 cm width or more, more preferably 25 N / 5 cm width or more, and even more preferably 30 N / 5 cm width or more. This direction is particularly preferably the production direction during the manufacturing of the first nonwoven fabric.

[0122] As described above, even if the first nonwoven fabric of the present invention has a tensile strength of 20 N / 5 cm width or more in one direction, if the tensile strength in other directions is weak, it may be prone to breaking in those directions and may not be practical. Therefore, it is preferable that the tensile strength in the direction perpendicular to the direction in which the tensile strength is 20 N / 5 cm width or more is 15 N / 5 cm width or more, more preferably 18 N / 5 cm width or more, and even more preferably 20 N / 5 cm width or more. As described above, it is preferable that the direction in which the tensile strength is 20 N / 5 cm width or more is the production direction during the manufacturing of the first nonwoven fabric, so it is preferable that the perpendicular direction is the width direction during the manufacturing of the first nonwoven fabric.

[0123] The first nonwoven fabric of the present invention has a tensile strength of 2.0 N / 5 cm width or more per unit basis weight in one direction, and the thickness of the first nonwoven fabric is 100 μm or less. Therefore, it is a nonwoven fabric with excellent permeability. The thinner the thickness, the better the permeability, so the thickness is preferably 80 μm or less, more preferably 70 μm or less, even more preferably 60 μm or less, and even more preferably 50 μm or less. There is no particular lower limit to the thickness, but it is preferably 10 μm or more so that the mechanical strength is excellent.

[0124] The porosity of the first nonwoven fabric of the present invention is not particularly limited, but is preferably 60% or more, more preferably 65% ​​or more, and even more preferably 70% or more, in order to have excellent permeability. On the other hand, if the porosity is too high, the mechanical strength tends to be poor, so it is preferably 90% or less, more preferably 85% or less, and even more preferably 80% or less.

[0125] The basis weight of the first nonwoven fabric of the present invention varies depending on the application and is not particularly limited, but is 20 g / m². 2 The following is preferable because, due to the low fiber content, it can be a thin first nonwoven fabric with excellent permeability. For example, a first nonwoven fabric with excellent ion permeability and fluid permeability. The smaller the basis weight, the better the above effect, so 18 g / m² is preferable. 2 Preferably, it is 16 g / m 2The following is preferable. On the other hand, if the basis weight is too small, the mechanical strength tends to be weak, so 3g / m 2 It is more preferable to have a value of 5 g / m² or more. 2 It is even more preferable if the above conditions are met.

[0126] The apparent density of the first nonwoven fabric of the present invention is not particularly limited, but to ensure excellent permeability, the apparent density is 0.35 g / cm³. 3 Preferably, it is 0.30 g / cm³. 3 It is more preferable that it be less than 0.28 g / cm³ 3 It is even more preferable that the apparent density is as follows. On the other hand, if the apparent density is too low, the mechanical strength tends to be inferior, so the apparent density should be 0.10 g / cm³. 3 Preferably, it is 0.15 g / cm³ or more. 3 It is more preferable that the amount be greater than or equal to 0.20 g / cm³. 3 It is even more preferable if the above conditions are met.

[0127] The first nonwoven fabric of the present invention contains a polymethylpentene component and has excellent heat resistance, preferably with a shrinkage rate of 5% or less when heated to 150°C. The lower the shrinkage rate, the better the heat resistance, so a shrinkage rate of 4.5% or less when heated to 150°C is more preferable. Ideally, it is 0%.

[0128] (Second nonwoven fabric) The second nonwoven fabric of the present invention contains core-sheath type composite fibers having a polyethylene component as a sheath component and a polymethylpentene component as a core component, and is a nonwoven fabric in which the polyethylene component, which is the sheath component of the core-sheath type composite fiber, is fused, wherein the polymethylpentene component accounts for 30% or more by volume of the total nonwoven fabric constituent fibers, and the polyethylene component accounts for 30% or more by volume of the total nonwoven fabric constituent fibers.

[0129] Polymethylpentene has a melting point of approximately 220-240°C, which is higher than other polyolefins, and exhibits excellent heat resistance. Since this heat-resistant polymethylpentene component accounts for 30% or more by volume of the total fibers constituting the second nonwoven fabric, the second nonwoven fabric of the present invention exhibits excellent heat resistance. The higher the amount of polymethylpentene component, the better the heat resistance; therefore, it is preferable that the polymethylpentene component accounts for 35% or more by volume of the total fibers constituting the second nonwoven fabric, and more preferably 40% or more by volume. On the other hand, as described later, since it also contains 30% or more by volume of polyethylene component to provide excellent mechanical strength, the polymethylpentene component is 70% or less by volume, preferably 65% ​​or less by volume, and more preferably 60% or less by volume.

[0130] Furthermore, the polymethylpentene component constituting the core-sheath type composite fiber can be the same as the polymethylpentene component that can constitute the first nonwoven fabric, and may be one type or two or more types. If there are two or more types, their total amount shall be 30% by volume or more of the total fibers constituting the second nonwoven fabric.

[0131] The polyethylene component, which is the sheath component of the core-sheath composite fiber in the second nonwoven fabric, has excellent fusion strength. Although the polyethylene component has a relatively low melting point and poor heat resistance, the presence of the polymethylpentene component as the core component provides excellent heat resistance. This polyethylene component can be high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, ultra-high molecular weight polyethylene, or ethylene copolymer, similar to the first nonwoven fabric. Among these, high-density polyethylene is preferred because it is somewhat hard, has good stiffness and resilience, and can be used to produce a second nonwoven fabric with excellent handling properties. The polyethylene component may be one type or two or more types.

[0132] In the second nonwoven fabric of the present invention, a polyethylene component with excellent fusion strength is contained in an amount of 30% or more by volume of the total constituent fibers of the second nonwoven fabric, and since some or all of this polyethylene component is involved in fusion, the mechanical strength is excellent. The more polyethylene component there is, the better the fusion strength and mechanical strength of the second nonwoven fabric; therefore, it is preferable that the polyethylene component accounts for 35% or more by volume of the total constituent fibers of the second nonwoven fabric, and more preferably 40% or more by volume. On the other hand, as mentioned above, in order to have excellent heat resistance, it is necessary to contain 30% or more by volume of polymethylpentene component, so the polyethylene component is 70% or less by volume, preferably 65% ​​or less by volume, and more preferably 60% or less by volume. If two or more types of polyethylene components are included, their total amount is 30% or more by volume of the total constituent fibers of the second nonwoven fabric.

[0133] Furthermore, the volume ratio of the polyethylene component (sheath component) and the polymethylpentene component (core component) of this core-sheath type composite fiber is preferably 30:70 to 70:30, more preferably 35:65 to 65:35, and even more preferably 40:60 to 60:40, so that the second nonwoven fabric can achieve both heat resistance and mechanical strength.

[0134] Furthermore, the core component, which is polymethylpentene, does not need to be just one; two or more fiber cross-sections may be of the sea-island type. In addition, in the fiber cross-section, the core component and sheath component may be arranged concentrically, or the core component may be arranged eccentrically, but it is preferable that they be arranged concentrically to ensure the second nonwoven fabric has excellent dimensional stability.

[0135] The content of this core-sheath type composite fiber is not particularly limited, as long as the polymethylpentene component in the second nonwoven fabric accounts for 30% or more by volume of the total constituent fibers of the second nonwoven fabric, and the polyethylene component accounts for 30% or more by volume of the total constituent fibers of the second nonwoven fabric. However, to make it easier to satisfy this volume ratio, it is preferable to contain 50% or more by volume, more preferably 60% or more by volume, even more preferably 70% or more by volume, and even more preferably 80% or more by volume.

[0136] The second nonwoven fabric contains polymethylpentene and polyethylene components in such amounts, and as constituent fibers of the second nonwoven fabric, it includes core-sheath type composite fibers in which the polyethylene component is the sheath component and the polymethylpentene component is the core component. In addition, for example, (1) core-sheath type composite fibers in which resin components other than polymethylpentene and polyethylene components are the sheath components and the polymethylpentene component is the core component, (2) core-sheath type composite fibers in which polyethylene components are the sheath component and resin components other than polyethylene and polymethylpentene components are the core components, (3) core-sheath type composite fibers in which polymethylpentene components are the sheath component and resin components other than polymethylpentene components are the core components, (4) core-sheath type composite fibers in which resin components other than polyethylene components are the sheath component and the polyethylene component is the core component The materials may include: (5) an orange-shaped composite fiber in which polymethylpentene and resin components other than polymethylpentene, or polyethylene and resin components other than polyethylene, radiate alternately from the center in the fiber cross-section (see Figures 1 to 5); (6) a multi-layer bimetallic composite fiber in which polymethylpentene and resin components other than polymethylpentene, or polyethylene and resin components other than polyethylene, are stacked alternately in the fiber cross-section (see Figure 6); (7) a single-component fiber consisting only of polymethylpentene; (8) a single-component fiber consisting only of polyethylene; (9) a single-component fiber consisting of polymethylpentene and resin components other than polyethylene.

[0137] Furthermore, (5) an orange-shaped composite fiber in which polymethylpentene components and resin components other than polymethylpentene components, or polyethylene components and resin components other than polyethylene components, extend alternately radially from the center in the fiber cross-section (see Figures 1 to 5), and (6) a multi-bimetallic composite fiber in which polymethylpentene components and resin components other than polymethylpentene components, or polyethylene components and resin components other than polyethylene components, are stacked alternately in the fiber cross-section (see Figure 6) can be separated into individual polymethylpentene components, polyethylene components, or polyethylene components and resin components other than polymethylpentene components by applying mechanical external force, thereby generating ultrafine fibers with a fiber diameter of 4.5 μm or less, and thus can be a second nonwoven fabric having fine pores, and also a second nonwoven fabric with excellent resin and liquid retention due to the large surface area of ​​the constituent fibers of the second nonwoven fabric.

[0138] Furthermore, when an orange-type composite fiber 1 as shown in Figures 1 to 5, or a multi-bimetallic composite fiber 1 as shown in Figure 6, is subjected to a fluid flow such as water, or a mechanical external force such as a calender, refiner, pulper, mixer, or beater, ultrafine fibers having a similar irregular cross-sectional shape to the ultrafine fibers described for the first nonwoven fabric are generated, and they exhibit the same effects as the first nonwoven fabric.

[0139] Furthermore, (7) single-component fibers consisting only of polymethylpentene, (8) single-component fibers consisting only of polyethylene, and (9) single-component fibers consisting of resin components other than polymethylpentene and polyethylene can have a fiber diameter of 0.1 to 30 μm, preferably ultrafine fibers of 4.5 μm or less, more preferably ultrafine fibers of 4.0 μm or less, even more preferably ultrafine fibers of 3.0 μm or less, and even more preferably ultrafine fibers of 2.0 μm or less. Such ultrafine fibers can be manufactured in the same manner as for the first nonwoven fabric. In addition, the ultrafine fibers that can constitute the second nonwoven fabric are preferably stretched, similar to the first nonwoven fabric, so that the mechanical strength of the second nonwoven fabric is excellent.

[0140] The second nonwoven fabric of the present invention contains core-sheath type composite fibers with a polyethylene component as the sheath component and a polymethylpentene component as the core component. However, in order to increase the rigidity and compressive resistance of the second nonwoven fabric, it may contain high-strength fibers with a tensile strength of 5 cN / dtex or more, similar to the first nonwoven fabric. When composed of a single component, the tensile strength is preferably 8.5 cN / dtex or more, more preferably 8.9 cN / dtex or more, and even more preferably 9.5 cN / dtex or more. On the other hand, when the high-strength fibers are composite fibers and the mechanical strength of the second nonwoven fabric is also increased by the fusion of the high-strength fibers, the tensile strength is preferably 5.5 cN / dtex or more, more preferably 6.0 cN / dtex or more, and even more preferably 6.2 cN / dtex or more. In any case of high-strength fibers, there is no particular upper limit to the tensile strength, but it is approximately 50 cN / dtex. These high-strength fibers can be composed of the same resin components as the first nonwoven fabric.

[0141] The second nonwoven fabric of the present invention contains a core-sheath type composite fiber having a polyethylene component as the sheath component and a polymethylpentene component as the core component. However, to further improve the heat resistance of the second nonwoven fabric, it may also contain heat-resistant fibers similar to those of the first nonwoven fabric.

[0142] The second nonwoven fabric of the present invention contains core-sheath type composite fibers having a polyethylene component as a sheath component and a polymethylpentene component as a core component. The fiber diameter of the fibers constituting the second nonwoven fabric, including these core-sheath type composite fibers, is not particularly limited, but is preferably 0.1 to 35 μm, more preferably 0.5 to 28 μm, and even more preferably 1 to 20 μm, so that the fibers are uniformly dispersed, uniform strength can be imparted, and the second nonwoven fabric has excellent resin and liquid retention properties.

[0143] As mentioned above, it is preferable that the material contains ultrafine fibers with a fiber diameter of 4.5 μm or less (preferably 4.0 μm or less, more preferably 3.0 μm or less, and even more preferably 2.0 μm or less). These ultrafine fibers can be made from, for example, polyolefin resins such as polymethylpentene resin, polypropylene resin, and polyethylene resin; polyester resins such as polyethylene terephthalate and polyester copolymer; and nylon resins such as nylon 6, nylon 66, and nylon copolymer. Among these, it is preferable that the ultrafine fibers be made from polyolefin resins, which have excellent chemical resistance and versatility, and it is preferable that they be made from polymethylpentene resin or polypropylene resins, which have excellent heat resistance.

[0144] As mentioned above, ultrafine fibers can be produced by applying mechanical external force to orange-type composite fibers or multi-bimetallic composite fibers, or by extracting and removing the marine component from sea-island type composite fibers.

[0145] The ratio (L / D) of the fiber diameter (D, unit: μm) to the length (L, unit: μm) of the core-sheath type composite fibers constituting the second nonwoven fabric of the present invention is 350 or more. When this ratio (L / D) is 350 or more, the fiber length is longer than the fiber diameter, so the fibers constituting the second nonwoven fabric, including the core-sheath type composite fibers, tend to intertwine with each other. Also, for the same amount of fiber, there are fewer fibers and fewer joints between fibers, resulting in high tensile strength and excellent mechanical strength. This tendency becomes stronger as the ratio (L / D) increases, so it is preferable that the ratio (L / D) be 400 or more, more preferably 450 or more, even more preferably 500 or more, even more preferably 550 or more, and even more preferably 600 or more. On the other hand, as mentioned above, a large ratio (L / D) tends to cause fibers to entangle easily and inhibit the uniform dispersion of fibers. Therefore, a ratio (L / D) of 7000 or less is preferable, more preferably 2000 or less, even more preferably 1600 or less, even more preferably 1300 or less, and even more preferably 1000 or less.

[0146] The fiber diameter of the core-sheath type composite fiber constituting the second nonwoven fabric of the present invention is not particularly limited as long as it satisfies the above ratio (L / D), but it is preferably 10 μm or more, more preferably 11 μm or more, even more preferably 12 μm or more, even more preferably 13 μm or more, even more preferably 14 μm or more, and even more preferably 15 μm or more, so that the second nonwoven fabric has excellent mechanical strength and heat resistance. On the other hand, if the core-sheath type composite fiber is too thick, the second nonwoven fabric tends to have poor fiber dispersion, so it is preferably 35 μm or less, more preferably 22 μm or less, even more preferably 20 μm or less, and even more preferably 19 μm or less.

[0147] Furthermore, the fiber length of the second nonwoven fabric constituent fibers, including core-sheath type composite fibers, ultrafine fibers, and heat-resistant fibers, is not particularly limited. However, longer fiber lengths tend to result in better entanglement among the second nonwoven fabric constituent fibers and superior mechanical strength. Therefore, a fiber length of 6 mm or more is preferable, 8 mm or more is preferable, and 10 mm or more is even preferable. On the other hand, longer fiber lengths tend to cause entanglement among the fibers, which can hinder uniform dispersion of the fibers. Therefore, a fiber length of 105 mm or less is preferable, 55 mm or less is preferable, and 20 mm or less is even preferable. In particular, since the polyethylene component, which is the sheath component of the core-sheath type composite fiber, fuses together, it is preferable that the fiber length be within the above range to allow for some degree of entanglement.

[0148] Furthermore, the second nonwoven fabric of the present invention may include two or more types of core-sheath composite fibers, high-strength fibers, ultrafine fibers, and heat-resistant fibers that differ in terms of resin composition, resin arrangement in the fiber cross-section, fiber diameter, ratio (L / D), and / or fiber length.

[0149] The second nonwoven fabric of the present invention has a ratio (L / D) of 350 or more, and a thickness of 100 μm or less. Therefore, it is a nonwoven fabric with excellent permeability. The thinner the thickness, the better the permeability, so the thickness is preferably 80 μm or less, more preferably 70 μm or less, even more preferably 60 μm or less, and even more preferably 50 μm or less. There is no particular lower limit to the thickness, but it is preferably 10 μm or more so that the mechanical strength is excellent.

[0150] In the second nonwoven fabric of the present invention, the fibers are bonded together by the fusion of polyethylene components, but in addition to fusion, the fibers may also be three-dimensionally entangled. This is because the mechanical strength of the second nonwoven fabric is further improved by the three-dimensional entanglement. Such three-dimensional entanglement can be formed, for example, by applying a fluid flow such as a water stream or a needle to the fiber web.

[0151] The second nonwoven fabric of the present invention has excellent mechanical strength due to the fusion of polyethylene components, but, similar to the first nonwoven fabric, it is preferable that it has a tensile strength of 2.0 N / 5 cm width or more per unit basis weight. Similar to the first nonwoven fabric, it is more preferable that the tensile strength per unit basis weight is 2.2 N / 5 cm width or more, and even more preferable that it is 2.4 N / 5 cm width or more. The stronger the tensile strength per unit basis weight, the better the mechanical strength, so there is no particular upper limit, but it can be 10 N / 5 cm width or less.

[0152] Similar to the first nonwoven fabric, the production direction of the second nonwoven fabric is preferably in a direction where the tensile strength per unit basis weight is 2.0 N / 5 cm width or more. Furthermore, similar to the first nonwoven fabric, it is preferable that there is a direction in which the tensile strength is 20 N / 5 cm width or more, more preferably 25 N / 5 cm width or more, and even more preferably 30 N / 5 cm width or more. This direction is particularly preferably the production direction during the manufacturing of the second nonwoven fabric.

[0153] Furthermore, similar to the first nonwoven fabric, the second nonwoven fabric preferably has a tensile strength of 15 N / 5 cm width or more in the direction perpendicular to the direction in which the tensile strength is 20 N / 5 cm width or more, more preferably 18 N / 5 cm width or more, and even more preferably 20 N / 5 cm width or more. Since the direction in which the tensile strength is 20 N / 5 cm width or more is preferably the production direction during the manufacturing of the second nonwoven fabric, this perpendicular direction is preferably the width direction during the manufacturing of the second nonwoven fabric.

[0154] The porosity of the second nonwoven fabric of the present invention is preferably 60% or more, more preferably 65% ​​or more, and even more preferably 70% or more, so as to be excellent in permeability, similar to the first nonwoven fabric. On the other hand, if the porosity is too high, the mechanical strength tends to be poor, so it is preferably 90% or less, more preferably 85% or less, and even more preferably 80% or less.

[0155] The basis weight of the second nonwoven fabric of the present invention varies depending on the application and is not particularly limited, but is 20 g / m². 2 The following is preferable because, due to the low fiber content, it can be a thin second nonwoven fabric with excellent permeability. For example, a second nonwoven fabric with excellent ion permeability and fluid permeability. The smaller the basis weight, the better the above effect, so 18 g / m² is preferable. 2 Preferably, it is 16 g / m 2 The following is preferable. On the other hand, if the basis weight is too small, the mechanical strength tends to be weak, so 3g / m 2 It is more preferable to have a value of 5 g / m² or more. 2 It is even more preferable if the above conditions are met.

[0156] The apparent density of the second nonwoven fabric of the present invention is 0.35 g / cm³, similar to that of the first nonwoven fabric, so as to have excellent permeability. 3 Preferably, it is 0.30 g / cm³. 3 It is more preferable that it be less than 0.28 g / cm³ 3 It is even more preferable that the following conditions are met. Furthermore, to ensure excellent mechanical strength, 0.10 g / cm³ 3 Preferably, it is 0.15 g / cm³ or more. 3It is more preferable that the amount be greater than or equal to 0.20 g / cm³. 3 It is even more preferable if the above conditions are met.

[0157] The second nonwoven fabric of the present invention contains a polymethylpentene component and has excellent heat resistance, preferably with a shrinkage rate of 5% or less when heated to 150°C. The lower the shrinkage rate, the better the heat resistance, so a shrinkage rate of 4.5% or less when heated to 150°C is more preferable. Ideally, it is 0%.

[0158] The second nonwoven fabric of the present invention is fused with polyethylene components and also contains polymethylpentene components, has a high proportion of polyolefin resin components, and exhibits excellent chemical resistance. However, it may be difficult to apply to various uses, so it may be subjected to various processing to make it easier to apply to various uses. For example, it may be colored with pigments or dyes, electrostatically charged, have patterns added, or have hydrophilic groups such as sulfonic acid groups, carboxyl groups, or carbonyl groups introduced.

[0159] (Method for manufacturing basic nonwoven fabric, first nonwoven fabric, or second nonwoven fabric) A preferred basic nonwoven fabric, first nonwoven fabric, or second nonwoven fabric (collectively referred to as "nonwoven fabric") of the present invention can be manufactured, for example, as follows.

[0160] First, prepare fibers containing polymethylpentene and polyethylene. As mentioned above, it is also preferable, and even preferable, for the same fiber to contain both polymethylpentene and polyethylene components, such as a core-sheath composite fiber in which the polyethylene component is the sheath component and the polymethylpentene component is the core component. If necessary, prepare orange-type composite fibers, multi-bimetallic composite fibers, ultrafine fibers, high-strength fibers, heat-resistant fibers, etc. as described above. As mentioned above, in the case of the second nonwoven fabric, it is preferable to prepare a core-sheath composite fiber in which the polyethylene component is the sheath component and the polymethylpentene component is the core component, and in the case of the first nonwoven fabric, it is preferable to prepare a similar core-sheath composite fiber.

[0161] Next, a fiber web is formed using the prepared fibers. At this time, the fibers are blended considering that the polymethylpentene component accounts for 30% or more by volume of the total fiber, the polyethylene component accounts for 30% or more by volume of the total fiber, and the polyethylene component is involved in the fusion process on the fiber surface. When ultrafine fibers are produced by applying mechanical external force to orange-type composite fibers or multi-bimetallic composite fibers, the orange-type composite fibers or multi-bimetallic composite fibers can be prepared by dividing them using, for example, a refiner, pulper, mixer, or beater before forming the fiber web. Alternatively, ultrafine fibers consisting of island components can be prepared by extracting and removing the sea component from sea-island type composite fibers.

[0162] The method for forming the fiber web is not particularly limited, but it can be formed by dry methods such as the air-lay method or the carding method, wet methods such as the horizontal long net method, the inclined wire short net method, the circular net method, and the long net / circular net combination method, or direct methods such as the spunbond method, the melt-blown method, and the electrospinning method. Among these, a wet method is preferred as it is easier to form a fiber web with excellent texture.

[0163] Next, the fiber web is heat-treated to produce a nonwoven fabric by fusing the polyethylene-containing fibers. Furthermore, to increase mechanical strength and / or to include undivided orange-type composite fibers or multi-bimetallic composite fibers as constituent fibers of the fiber web, a water stream can be applied to the fiber web to generate ultrafine fibers from these composite fibers. Even when a water stream is applied as in the latter case, a heat treatment is performed after the water stream to fuse the polyethylene-containing fibers.

[0164] The heat treatment of the former fiber web can be performed under no pressure, under pressure, or by melting the polyethylene component under no pressure and then applying pressure, as long as it can fuse the polyethylene component. Such heat treatment can be carried out, for example, with a heat calender, a hot air through-heat treatment machine, or a cylinder contact type heat treatment machine. When heating and pressurizing are performed simultaneously, the heating temperature is preferably within the range from the softening temperature of the polyethylene component to its melting point, and when pressurizing is not performed, it is preferably within the range from the softening temperature of the polyethylene component to a temperature 30°C higher than its melting point.

[0165] The latter method of treating the fiber web with a water stream is possible as long as the conditions allow the fibers to intertwine sufficiently and the undivided orange-type composite fibers or multi-bimetallic composite fibers to be separated into individual resin components to generate ultrafine fibers. This varies depending on the type of fiber and is not particularly limited, but for example, it can be carried out by spraying a water stream at a pressure of 1 MPa to 30 MPa onto the fiber web from a nozzle plate with nozzles arranged in one or more rows with a diameter of 0.05 to 0.3 mm and a pitch of 0.2 to 3 mm. This water stream treatment is performed on one or both sides of the fiber web at least once. When manufacturing a nonwoven fabric without openings, it is preferable to use a support such as a net that supports the fiber web, which has a thin non-opening (wire diameter), for example, a support with a non-opening (wire diameter) of 0.25 mm or less. Conversely, when manufacturing a nonwoven fabric with openings, it is preferable to use a support with a thick non-opening (wire diameter), such as a net or other support that supports the fiber web, for example, a support with a non-opening (wire diameter) of 0.25 mm or more.

[0166] Furthermore, if the undivided orange-type composite fibers or multi-bimetallic composite fibers move due to the action of the water flow, making it difficult to divide these composite fibers and thus difficult to generate ultrafine fibers, the composite fibers may be fused with polyethylene components and fixed before the water flow is applied. Even when the composite fibers are fused and fixed in this manner, the action of the water flow will generate ultrafine fibers, and the fusion will dissolve, causing the fibers to intertwine in three dimensions.

[0167] By applying a water flow in this manner to intertwine the fibers three-dimensionally, and in some cases generating ultrafine fibers, then fusing them with polyethylene-containing fibers (especially core-sheath type composite fibers), a nonwoven fabric with superior mechanical strength can be produced because the fibers are fused together in a state where there are many contact points between the three-dimensionally intertwined fibers. The fusion with polyethylene-containing fibers can be carried out using the method and conditions described above.

[0168] Various post-treatments can be performed to make the nonwoven fabric of the present invention suitable for various applications, or to make it easier to suit various applications. For example, coloring treatments using pigments or dyes; electrostatic treatments such as corona discharge, plasma discharge, and water-based charging; patterning treatments such as embossing with an embossing roll or printing with a printing resin; hydrophilicity-imparting treatments such as sulfonation treatment, fluorine gas treatment, vinyl monomer graft polymerization treatment, discharge treatment, surfactant treatment, and hydrophilic resin imparting treatment can be performed.

[0169] (Uses of the first and second nonwoven fabrics of the present invention) The first and second nonwoven fabrics of the present invention have excellent heat resistance, mechanical strength, and permeability, making them highly versatile and applicable to various uses. For example, they can be suitably used as membrane supports such as diaphragm supports for batteries and diaphragm supports for water electrolysis, and as separators for electrochemical elements.

[0170] Furthermore, the membrane support and electrochemical element separator of the present invention may be composed solely of the first or second nonwoven fabric of the present invention, or it may also include nonwoven fabrics other than the first or second nonwoven fabric of the present invention, such as woven fabrics, knitted fabrics, nets, porous films, etc. In this way, including materials other than the first or second nonwoven fabric of the present invention may result in even better performance in various aspects, such as strength-granting and separation effects.

[0171] Examples of batteries to which the first nonwoven fabric or the second nonwoven fabric of the present invention can be applied as a diaphragm support include nickel-zinc batteries, metal-air batteries such as zinc or magnesium batteries, and lithium-ion secondary batteries.

[0172] Furthermore, examples of water electrolysis diaphragms to which the first nonwoven fabric or the second nonwoven fabric of the present invention can be applied as a diaphragm support include fluorine-based or hydrocarbon-based proton exchange membranes in proton exchange membrane (PEM) water electrolysis devices, anion exchange membranes such as all-aromatic polymer types in anion exchange membrane (AEM) water electrolysis devices, polyester-based porous membranes or fluorine membranes in alkaline water electrolysis devices, and electrolyte membranes such as yttria-stabilized zirconia in solid oxide electrolytic cells (SOEC).

[0173] Furthermore, examples of electrochemical elements to which the first or second nonwoven fabric of the present invention can be applied as a separator include alkaline primary batteries such as alkaline manganese batteries, mercury batteries, silver oxide batteries, or air batteries; alkaline secondary batteries such as nickel-cadmium batteries, silver-zinc batteries, silver-cadmium batteries, nickel-zinc batteries, nickel-hydrogen batteries, and lead-acid batteries; lithium-ion secondary batteries; sodium-ion batteries; polyvalent ion batteries such as magnesium, aluminum, calcium, and zinc; lithium-sulfur batteries; metal-air batteries such as lithium and zinc; lithium-ion capacitors; fluoride-ion batteries; potassium-ion batteries, and the like.

[0174] Among these, as an example in which the first nonwoven fabric or the second nonwoven fabric of the present invention can be suitably used as a membrane support, a support for a diaphragm in a nickel-zinc battery will be described.

[0175] The first nonwoven fabric of the present invention has excellent heat resistance because the polymethylpentene component accounts for 30% or more by volume of the total constituent fibers of the first nonwoven fabric. Furthermore, the polyethylene component accounts for 30% or more by volume of the total constituent fibers of the first nonwoven fabric, and the polyethylene component is fused, resulting in a tensile strength of 2.0 N / 5 cm width or more per unit basis weight in a direction, thus providing excellent mechanical strength. Moreover, it has excellent permeability because it is thin, with a thickness of 100 μm or less. Furthermore, the second nonwoven fabric of the present invention has excellent heat resistance because the polymethylpentene component accounts for 30% or more by volume of the total fibers constituting the second nonwoven fabric. In addition, the polyethylene component accounts for 30% or more by volume of the total fibers constituting the second nonwoven fabric, and the polyethylene component is fused. Moreover, the ratio of core-sheath type composite fibers (L / D) is 350 or more, meaning that the fiber length is long compared to the fiber diameter, so the core-sheath type composite fibers easily intertwine with the fibers constituting the second nonwoven fabric. Furthermore, for the same amount, there are fewer fibers and fewer bonding points between fibers, resulting in high tensile strength and excellent mechanical strength. In addition, it has excellent permeability because it is thin, with a thickness of 100 μm or less.

[0176] Therefore, by applying a slurry containing layered double hydroxide (LDH) and / or LDH-like compounds (collectively referred to as "LDH"), which are diaphragm components of nickel-zinc batteries, to a first nonwoven fabric or a second nonwoven fabric, the LDH can easily penetrate into the entire internal void of the first or second nonwoven fabric. By removing the LDH dispersion medium by heating, a diaphragm supporting LDH can be manufactured using the first or second nonwoven fabric. Because the first or second nonwoven fabric has excellent permeability, the LDH can be uniformly dispersed throughout the entire internal void of the first or second nonwoven fabric. Furthermore, the first or second nonwoven fabric does not shrink easily even when heated to remove the slurry dispersion medium, and maintains its shape, thus enabling the manufacture of a diaphragm that maintains a uniform dispersion state of LDH. In addition, because the manufactured diaphragm's constituent LDH is supported by the first or second nonwoven fabric, which has excellent mechanical strength, the diaphragm has excellent mechanical strength.

[0177] Furthermore, if the first or second nonwoven fabric contains ultrafine fibers with a fiber diameter of 4.5 μm or less, the individual voids in the first or second nonwoven fabric can be small and uniform in size. This allows the LDH to be more uniformly supported throughout the first or second nonwoven fabric, and the path from one side of the diaphragm to the other can be complex and long, which makes short circuits caused by dendrites less likely to occur.

[0178] When the first nonwoven fabric or the second nonwoven fabric of the present invention is used as a support for the diaphragm of a nickel-zinc battery, it is preferable that the first nonwoven fabric or the second nonwoven fabric is composed only of polyolefin fibers made solely of polyolefin resin so as to have excellent alkali resistance. For example, it is preferable that it is composed of only one or more types of polyolefin fibers, such as: core-sheath composite fibers with polyethylene (especially high-density polyethylene) as the sheath component and polymethylpentene as the core component; core-sheath composite fibers with polyethylene (especially high-density polyethylene) as the sheath component and polypropylene as the core component; single-component fibers (ultrafine fibers or high-strength fibers) made of polyethylene, polypropylene or polymethylpentene; orange-type or multi-bimetallic composite fibers made of polypropylene and polymethylpentene; or orange-type or multi-bimetallic composite fibers made of polyethylene and polymethylpentene.

[0179] As mentioned above, it is preferable that the first or second nonwoven fabric of the present invention is composed solely of polyolefin fibers. However, because it tends to have poor affinity with slurries containing LDH and is difficult to uniformly support LDH throughout the first or second nonwoven fabric, it is preferable that hydrophilic groups such as sulfonic acid groups, carboxyl groups, and carbonyl groups are introduced to enhance affinity with the dispersion medium of the slurry. [Examples]

[0180] Examples of the present invention are described below, but the present invention is not limited to these examples.

[0181] (Core-sheath type composite fiber) The core component is polymethylpentene (melting point: 235℃, density: 0.82 g / cm³). 3 ) consists of a sheath component made of high-density polyethylene (melting point: 130℃, density: 0.94 g / cm³) 3 A core-sheath type composite fiber (fiber diameter: 17 μm, fiber length: 10 mm, volume ratio of polymethylpentene component to high-density polyethylene component: 6:4, one core component arranged concentrically) was prepared.

[0182] (High-strength core-sheath composite fiber) The core component is polypropylene (melting point: 168℃, density: 0.91 g / cm³). 3 ) consists of a sheath component which is high-density polyethylene (melting point: 135℃, density: 0.94 g / cm³). 3 A high-strength composite fiber with a tensile strength of 6.5 cN / dtex was prepared (fiber diameter: 10 μm, fiber length: 5 mm, Young's modulus: 45 cN / dtex, volume ratio of polypropylene component to high-density polyethylene component: 6:4, one core component arranged concentrically).

[0183] (High-strength fiber) High-strength fiber composed solely of polypropylene (tensile strength: 9.5 cN / dtex, melting point: 168°C, fiber diameter: 13 μm, fiber length: 10 mm, density: 0.91 g / cm³) 3 I prepared ).

[0184] (Orange-type composite fiber) As shown in Figure 5, the polypropylene component [symbol 11 in the figure, roughly trapezoidal, with a fineness of 0.11 dtex (fiber diameter: 3.8 μm) polypropylene ultrafine fibers (melting point: 160°C, density: 0.91 g / cm³)] 3 ) can be generated in 8 strands, and polymethylpentene component [symbol 12 in the figure, roughly trapezoidal polymethylpentene ultrafine fiber with a fineness of 0.11 dtex (fiber diameter: 4.1 μm) (melting point 235℃, density 0.82 g / cm³) 3A stretched orange-shaped composite fiber (volume ratio of polypropylene component to polymethylpentene component: 6:4) was prepared, having an orange-shaped cross-section and a hollow portion, with a fineness of 1.7 dtex and a fiber length of 5 mm, consisting of eight strands of [a certain material].

[0185] (Ultrafine fibers) A sea-island type composite fiber (fineness: 1.65 dtex, fiber length: 2 mm) was prepared by spinning using a composite spinning method and then stretching, resulting in a sea component made of copolymerized polyester containing 25 island components made of polypropylene.

[0186] Next, the sea-island composite fiber is immersed for 30 minutes in a bath (temperature: 80°C) consisting of a 10 mass% sodium hydroxide aqueous solution to extract and remove the copolymerized polyester, which is the marine component of the sea-island composite fiber, and obtain ultrafine polypropylene fibers (average fiber diameter: 2 μm, melting point: 172°C, fiber length: 2 mm, cross-sectional shape: circular, density: 0.91 g / cm³). 3 ) was prepared.

[0187] (Examples 1-3, Comparative Examples 1-2) After forming a slurry by mixing and dispersing the materials according to the formulations shown in Table 1, fiber webs were formed from each material using a wet method (horizontal mesh method).

[0188] Next, this fiber web was dried at 140°C without pressure, and at the same time, it was fused with a high-density polyethylene component of a core-sheath type composite fiber (Examples 1-3, Comparative Example 1) or a high-density polyethylene component of a high-strength core-sheath type composite fiber (Comparative Example 2) to produce a nonwoven fabric.

[0189] Subsequently, the nonwoven fabric was immersed in a fuming sulfuric acid solution (15% SO3 solution) at 60°C for 2 minutes, then thoroughly washed with water and dried to introduce sulfonic acid groups to the fiber surface. The thickness was then adjusted using a calender at room temperature to produce the separators. The physical properties of these separators are shown in Table 1.

[0190] [Table 1]

[0191] In Examples 1-3, the separators, in which both the polymethylpentene component and the polyethylene component accounted for 30% or more by volume of the total nonwoven fabric fibers, exhibited excellent mechanical strength, with a tensile strength of 2.5 N / 5 cm width or more per unit basis weight in the production direction of the separator, and also exhibited excellent heat resistance, with a shrinkage rate of 5% or less when heated to 150°C. In contrast, the separator of Comparative Example 1, in which both the polymethylpentene component and the polyethylene component accounted for less than 30% by volume of the total nonwoven fabric fibers, not only had inferior mechanical strength, with a tensile strength of less than 2.5 N / 5 cm width per unit basis weight in the production direction of the separator, but also inferior heat resistance, with a shrinkage rate exceeding 5% when heated to 150°C.

[0192] Furthermore, the separator in Comparative Example 2, in which the polymethylpentene component was less than 30% by volume of the total nonwoven fabric fibers, had excellent mechanical strength, with a tensile strength of 2.5 N / 5 cm width or more per unit basis weight in the production direction of the separator. However, its heat resistance was significantly poor, with a shrinkage rate of 25% when heated to 150°C.

[0193] (Example 4, Comparative Example 3) After forming a slurry by mixing and dispersing the materials according to the formulations shown in Table 2, fiber webs were formed from each material using a wet method (horizontal mesh method).

[0194] Next, this fiber web was dried at 140°C without pressure, and at the same time, it was fused with a high-density polyethylene component of a core-sheath type composite fiber (Example 4) or a high-density polyethylene component of a high-strength core-sheath type composite fiber (Comparative Example 3) to produce a fused web.

[0195] Next, this fused web was placed on a net with a wire diameter of 0.15 mm, and a water stream at a pressure of 8 MPa was sprayed twice alternately from both sides from a nozzle plate with a nozzle diameter of 0.13 mm and a pitch of 0.6 mm to split the orange-shaped composite fibers and cause three-dimensional entanglement of the fibers, thereby producing water-entangled webs.

[0196] Next, these water-entangled webs were dried at 140°C under no pressure, and simultaneously fused again with the high-density polyethylene component of core-sheath type composite fibers or high-strength core-sheath type composite fibers to produce fused-entangled nonwoven fabrics.

[0197] Next, the fused entangled nonwoven fabric was immersed in a fuming sulfuric acid solution (15% SO3 solution) at 60°C for 2 minutes, then thoroughly washed with water and dried to introduce sulfonic acid groups to the fiber surface. The thickness was then adjusted using a calender at room temperature to produce the separators. The physical properties of these separators are shown in Table 2.

[0198] [Table 2]

[0199] The separator of Example 4, in which both polymethylpentene and polyethylene components account for 30% or more of the total volume of nonwoven fabric fibers, exhibits excellent mechanical strength, with a tensile strength of 2.5 N / 5 cm width or more per unit basis weight in the separator's production direction. Furthermore, it also exhibits excellent heat resistance, with a shrinkage rate of 5% or less when heated to 150°C. This makes it suitable for use as a separator for electrochemical elements in high-temperature regions. Moreover, because it contains ultrafine fibers generated from orange-type composite fibers, it has a high liquid retention rate after pressurization and excellent electrolyte retention, making it a separator that can be used to manufacture electrochemical elements with excellent operability even in low-temperature regions.

[0200] On the other hand, in Comparative Example 3, the separator in which both the polymethylpentene component and the polyethylene component were less than 30% by volume of the total nonwoven fabric fibers, was able to secure a tensile strength of 2.5 N / 5 cm width or more per unit basis weight in the production direction of the separator through water entanglement, but the shrinkage rate when heated to 150°C was 20%, indicating significantly poor heat resistance.

[0201] (Core-sheath type composite fiber A) The core component is polymethylpentene (melting point: 235℃, density: 0.82 g / cm³). 3 ) consists of a sheath component made of high-density polyethylene (melting point: 130℃, density: 0.94 g / cm³)3 A core-sheath type composite fiber A (fiber diameter: 17 μm, fiber length: 10 mm, ratio (L / D) = 588, volume ratio of polymethylpentene component to high-density polyethylene component: 6:4, one core component arranged concentrically) was prepared.

[0202] (Core-sheath type composite fiber B) Core-sheath composite fiber B was prepared, which is identical to core-sheath composite fiber A except that its fiber length is shorter (5 mm). (Fiber diameter: 17 μm, fiber length: 5 mm, ratio (L / D) = 294, volume ratio of polymethylpentene component to high-density polyethylene component: 6:4, one core component arranged concentrically.)

[0203] (High-strength core-sheath composite fiber) The core component is polypropylene (melting point: 168℃, density: 0.91 g / cm³). 3 ) consists of a sheath component which is high-density polyethylene (melting point: 135℃, density: 0.94 g / cm³). 3 A high-strength core-sheath composite fiber with a tensile strength of 6.5 cN / dtex was prepared (fiber diameter: 10 μm, fiber length: 5 mm, ratio (L / D) = 500, volume ratio of polypropylene component to high-density polyethylene component: 6:4, one core component arranged concentrically).

[0204] (Ultrafine fibers) A sea-island type composite fiber (fineness: 1.65 dtex, fiber length: 2 mm) was prepared by spinning using a composite spinning method and then stretching, resulting in a sea component made of copolymerized polyester containing 25 island components made of polypropylene.

[0205] Next, the sea-island composite fiber is immersed for 30 minutes in a bath (temperature: 80°C) consisting of a 10 mass% sodium hydroxide aqueous solution to extract and remove the copolymerized polyester, which is the marine component of the sea-island composite fiber, and obtain ultrafine polypropylene fibers (average fiber diameter: 2 μm, melting point: 172°C, fiber length: 2 mm, ratio (L / D) = 1000, cross-sectional shape: circular, density: 0.91 g / cm³). 3 ) was prepared.

[0206] (Heat-resistant fiber) A heat-resistant fiber made of polyphenylene sulfide (PPS) was prepared (fiber diameter: 9.7 μm, fiber length: 6 mm, ratio (L / D) = 619).

[0207] (Examples 11-13, Comparative Examples 11-15) After forming a slurry by mixing and dispersing the materials according to the formulations shown in Table 3, fiber webs were formed from each material using a wet method (horizontal mesh method).

[0208] Next, these fiber webs were dried at 140°C without pressure, and simultaneously fused with the high-density polyethylene components of core-sheath type composite fibers A and B (Examples 11-13, Comparative Examples 11-14) or the high-density polyethylene component of high-strength core-sheath type composite fiber (Comparative Example 15) to produce the first nonwoven fabric or the second nonwoven fabric, respectively.

[0209] Subsequently, the first or second nonwoven fabric 5 is placed between the dielectrics 2a and 2b of the discharge apparatus having a schematic cross-section as shown in Figure 7, and an AC voltage is applied between the two electrodes 1a and 1b for 30 seconds under atmospheric pressure and in the presence of air (humidity: 60 RH%) (voltage: 0.1 kVp, output: 2.8 kW, output per unit area: 1.83 W / cm²). 2 Plasma treatment was performed to generate a discharge within the first or second nonwoven fabric (frequency: 25 kHz, waveform: sine wave) to introduce hydrophilic groups such as carboxyl groups and carbonyl groups onto the fiber surface. Furthermore, the thickness was adjusted using a calender at room temperature to produce the respective supports. The physical properties of these supports are shown in Table 3.

[0210] The "electrical resistance" in Table 3 was evaluated using the following procedure. (1) A mixture was prepared by mixing 28.5 mass% zirconium oxide, 1.5 mass% acrylic binder, and 70 mass% pure water. (2) The coating bar was operated with a gap of 50 μm between each of the first or second nonwoven fabrics to coat one side of the first or second nonwoven fabric with the above mixture. (3) The coated first nonwoven fabric or second nonwoven fabric was dried at a temperature of 100°C for 10 minutes to obtain the inorganic particle coated first nonwoven fabric or second nonwoven fabric. (4) Three 50 mm square samples were taken from each inorganic particle coated nonwoven fabric (first or second nonwoven fabric) and the mass of each was measured. (5) Each sample has a density of 1.3 g / cm³ 3 Each sample was immersed in a potassium hydroxide aqueous solution (at 20°C) and absorbed 80 mass% of its mass. (6) Each absorbed sample was sandwiched between 35 mm square nickel plates, and the electrical resistance was measured when a current of 1 kHz and 1 mA was applied, respectively. (7) If the arithmetic mean electrical resistance of the three samples was 0.4 Ω or less, it was evaluated as "○"; if it was higher than 0.4 Ω but 0.6 Ω or less, it was evaluated as "△"; and if it was higher than 0.6 Ω, it was evaluated as "×".

[0211] [Table 3]

[0212] Examples 11-13 include a support in which both the polymethylpentene component and the polyethylene component constitute 30% or more by volume (32.5% or 42.5% by volume) of the total constituent fibers of the first or second nonwoven fabric, and also includes a polymethylpentene / polyethylene core-sheath type composite fiber with a ratio (L / D) of 350 or more, in which both the polymethylpentene component and the polyethylene component constitute 30% or more by volume (32.5% or 42.5% by volume) of the total constituent fibers of the first or second nonwoven fabric. The 13 supports exhibited excellent mechanical strength, with a tensile strength of 2.0 N / 5 cm width or more (2.0 to 2.4 N / 5 cm width) in the production direction of the support, as well as excellent heat resistance, with a shrinkage rate of 5% or less (4.5%, 2.0%) when heated to 150°C. Furthermore, the supports were thin, with a thickness of 100 μm or less (45 to 50 μm), and had low electrical resistance (0.4 Ω or less), allowing for the creation of films in which zirconium oxide is supported throughout the internal voids of the support, and exhibiting excellent permeability. In particular, supports containing polyphenylene sulfide fibers, which are heat-resistant fibers, showed excellent heat resistance, with a heat shrinkage rate of 2.0% at 150°C.

[0213] In contrast, the support of Comparative Example 11, which had a thickness exceeding 100 μm (103 μm), had high electrical resistance (over 0.6 Ω), resulting in a film with poor permeability where zirconium oxide was unevenly distributed within the internal voids of the support.

[0214] Furthermore, the support material of Comparative Example 12, in which both the polymethylpentene component and the polyethylene component accounted for less than 30 volume percent (25 volume percent) of the total constituent fibers of the first or second nonwoven fabric, not only had inferior mechanical strength, with a tensile strength per unit basis weight in the separator production direction of less than 2.0 N / 5 cm width (1.4 N / 5 cm width), but also inferior heat resistance, with a shrinkage rate exceeding 5% (10.0%) when heated to 150°C.

[0215] Furthermore, the supports of Comparative Examples 13 and 14, which included core-sheath type composite fiber B having a ratio (L / D) of less than 350 (294), with a polymethylpentene component as the core component and a high-density polyethylene component as the sheath component, exhibited inferior mechanical strength, with a tensile strength per unit basis weight in the separator production direction being less than 2.0 N / 5 cm width (1.7 N / 5 cm width).

[0216] Furthermore, the support in Comparative Example 13 had a slightly lower porosity (61%), resulting in a slightly higher electrical resistance (0.4-0.6Ω). This meant that zirconium oxide tended to be unevenly distributed within the internal voids of the support, and its permeability was slightly inferior.

[0217] Furthermore, the support material of Comparative Example 15, in which the polymethylpentene component was less than 30% by volume (0% by volume) of the total constituent fibers of the first or second nonwoven fabric, exhibited poor heat resistance, with a shrinkage rate exceeding 5% (25.0%) when heated to 150°C. [Industrial applicability]

[0218] The nonwoven fabric of the present invention is highly versatile and can be applied to various uses because it exhibits excellent heat resistance and mechanical strength. For example, it can be suitably used as a separator for electrochemical elements, a diaphragm support for batteries such as nickel-zinc batteries, and a diaphragm support for water electrolysis.

[0219] Examples of electrochemical elements include alkaline primary batteries such as alkaline manganese batteries, mercury batteries, silver oxide batteries, or air batteries; alkaline secondary batteries such as nickel-cadmium batteries, silver-zinc batteries, silver-cadmium batteries, nickel-zinc batteries, nickel-metal hydride batteries, and lead-acid batteries; lithium-ion secondary batteries; sodium-ion batteries; polyvalent ion batteries such as magnesium, aluminum, calcium, and zinc; lithium-sulfur batteries; metal-air batteries such as lithium and zinc; lithium-ion capacitors; fluoride ion batteries; potassium-ion batteries; and more. In particular, when used as a separator in alkaline secondary batteries such as nickel-cadmium batteries and nickel-metal hydride batteries, its excellent heat resistance and mechanical strength make it suitable for use in automotive applications requiring heat resistance, enabling the creation of suitable alkaline secondary batteries.

[0220] Another nonwoven fabric of the present invention has excellent heat resistance, mechanical strength, and permeability, making it highly versatile and applicable to various uses. For example, it can be suitably used as a membrane support such as a diaphragm support for batteries or a diaphragm support for water electrolysis, or as a separator for electrochemical elements. [Explanation of Symbols]

[0221] 1. Orange-type composite fiber 11. Polymethylpentene component or resin component other than polymethylpentene component 12 Resin components other than polymethylpentene components or polymethylpentene components 1a, 1b electrode 2a, 2b Dielectrics 4 AC power supply 5. First nonwoven fabric or second nonwoven fabric

Claims

1. A nonwoven fabric comprising a polymethylpentene component and a polyethylene component, wherein the polyethylene component is fused, characterized in that the polymethylpentene component accounts for 30% or more by volume of the total nonwoven fabric constituent fibers, and the polyethylene component accounts for 30% or more by volume of the total nonwoven fabric constituent fibers.

2. The nonwoven fabric according to claim 1, characterized in that it contains a core-sheath type composite fiber as a nonwoven fabric constituent fiber, wherein the polyethylene component is the sheath component and the polymethylpentene component is the core component.

3. The nonwoven fabric according to claim 2, further comprising ultrafine fibers with a fiber diameter of 4.5 μm or less as nonwoven fabric constituent fibers.

4. The nonwoven fabric according to claim 1, characterized in that it has a direction in which the tensile strength per unit basis weight is 2.5 N / 5 cm width or more.

5. The nonwoven fabric according to claim 1, characterized in that the porosity is 50 to 80%.

6. The nonwoven fabric according to claim 1, characterized in that the liquid retention rate after pressurizing at 5.7 MPa is 5% or more.

7. A separator for an electrochemical element, characterized by comprising any of the nonwoven fabrics described in claims 1 to 6.

8. A nonwoven fabric comprising a polymethylpentene component and a polyethylene component, wherein the polyethylene component is fused, wherein the polymethylpentene component accounts for 30% or more by volume of the total nonwoven fabric constituent fibers, and the polyethylene component accounts for 30% or more by volume of the total nonwoven fabric constituent fibers, and the nonwoven fabric is characterized in that the thickness of the nonwoven fabric is 100 μm or less, and the tensile strength per unit basis weight is 2.0 N / 5 cm width or more in a direction.

9. The nonwoven fabric according to claim 8, characterized in that it contains a core-sheath type composite fiber as a nonwoven fabric constituent fiber, wherein the polyethylene component is the sheath component and the polymethylpentene component is the core component.

10. The nonwoven fabric according to claim 9, characterized in that the ratio (L / D) of the fiber diameter (D, unit: μm) of the core-sheath type composite fiber to the length (L, unit: μm) is 350 or more.

11. The nonwoven fabric according to claim 8, characterized in that the porosity is 60% or more.

12. Weight: 20 g / m ２ The nonwoven fabric according to claim 8, characterized in that it is as follows.

13. A nonwoven fabric comprising core-sheath type composite fibers having a polyethylene component as a sheath component and a polymethylpentene component as a core component, wherein the polyethylene component, which is the sheath component of the core-sheath type composite fiber, is fused, wherein the polymethylpentene component accounts for 30% or more by volume of the total nonwoven fabric constituent fibers, and the polyethylene component accounts for 30% or more by volume of the total nonwoven fabric constituent fibers, and the thickness of the nonwoven fabric is 100 μm or less, and the ratio (L / D) of the fiber diameter (D, unit: μm) of the core-sheath type composite fiber to the length (L, unit: μm) is 350 or more.

14. The nonwoven fabric according to claim 13, characterized in that it has a direction in which the tensile strength per unit basis weight is 2.0 N / 5 cm width or more.

15. The nonwoven fabric according to claim 13, characterized in that the porosity is 60% or more.

16. Weight: 20 g / m ２ The nonwoven fabric according to claim 13, characterized in that it is as follows.

17. A membrane support characterized by comprising any of the nonwoven fabrics described in claims 8 to 16.

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