Non-woven fabric, separator for electrochemical element, and membrane support

Abstract

Provided are: a non-woven fabric which has excellent heat resistance and mechanical strength and is highly versatile, and which is suitable for use in applications requiring heat resistance; and a separator for electrochemical elements, which comprises the non-woven fabric, and a membrane support. The non-woven fabric according to the present invention contains a polymethylpentene component and a polyethylene component, the polyethylene component having been fused, and the polymethylpentene component and the polyethylene component each account for 30 vol% or more of the entire non-woven fabric constituting fibers. Another non-woven fabric according to the present invention contains core-sheath composite fibers having a polyethylene component as a sheath component and a polymethylpentene component as a core component, the polyethylene component has been fused, the polymethylpentene component and the polyethylene component each account for 30 vol% or more of the entire non-woven fabric constituting fibers, and the thickness of the non-woven fabric is 100 [mu] m or less. The core-sheath composite fiber has a direction in which the tensile strength per unit gram weight is 2.0 N / 5 cm width or more, or the ratio of the length to the fiber diameter of the core-sheath composite fiber is 350 or more.

Description

Technical Field

[0001] This invention relates to a nonwoven fabric. The nonwoven fabric of this invention exhibits excellent heat resistance and mechanical strength, making it suitable for applications requiring these properties, such as separators for electrochemical components, separator supports for batteries, and separator supports for water electrolysis.

[0002] Furthermore, the nonwoven fabric of the present invention not only has excellent heat resistance, but also excellent mechanical strength despite being relatively thin, and excellent permeability, thus making it suitable for applications requiring the above-mentioned properties, such as separator supports for batteries, separator supports for water electrolysis, and separators for electrochemical components. Background Technology

[0003] Unlike woven or knitted fabrics, nonwoven fabrics have fibers that can be randomly oriented, resulting in a wide variety of properties such as dust removal, liquid retention, wiping properties, concealment, softness, separation, isolation, and strength imparting, making them suitable for various applications. However, depending on the fibers that make up the nonwoven fabric, there may be cases where the heat resistance or mechanical strength is insufficient, making it unsuitable for applications requiring heat resistance.

[0004] For example, the liquid retention and insulating properties of nonwoven fabrics can be used as separators between the electrodes of nickel-metal hydride (NiMH) batteries. In recent years, NiMH batteries have been increasingly used in automobiles as power sources and as backup power for devices such as T-BOX, GPS, and T-CONNECT. However, due to the insufficient heat resistance or mechanical strength of nonwoven fabrics, they sometimes cannot provide reliable NiMH batteries over long periods of time.

[0005] As a nonwoven fabric capable of solving the aforementioned heat resistance technical problem, a nonwoven fabric (diaphragm) utilizing a polyolefin-based split composite fiber composed of polymethylpentene, a polyolefin resin with high heat resistance, and polypropylene has been proposed (Patent Document 1).

[0006] However, even nonwoven fabrics that utilize polyolefin-based split fibers composed of a combination of polymethylpentene and polypropylene do not possess sufficient heat resistance and mechanical strength.

[0007] The aforementioned technical problems regarding heat resistance and mechanical strength are not limited to the separators of nickel-metal hydride batteries, etc. The same problems will also occur when non-woven fabrics are used as separator supports for batteries or separator supports for water electrolysis.

[0008] For example, the strength-imparting properties of nonwoven fabrics are utilized to serve as a support for the separator between the electrodes of nickel-zinc batteries. Nickel-zinc batteries are prone to short circuits due to dendrite formation, so resin membranes are often used as separators. However, due to the insufficient mechanical strength of resin membranes, nonwoven fabrics are used as the support (Patent Document 2). This type of separator, made of resin membrane, is formed by filling the voids in the nonwoven fabric with a resin solution and then evaporating the solvent from the resin solution. However, since the resin used in the past as a support is a polyolefin resin such as polyethylene or polypropylene, it is prone to shrinkage due to the heat during evaporation or use, failing to provide the strength-imparting function of a support and exhibiting poor heat resistance.

[0009] On the other hand, polyphenylene sulfide resin is also known as a nonwoven fabric resin that is a support with excellent heat resistance. However, in order to construct a nonwoven fabric support using polyphenylene sulfide fibers, adhesive fibers are needed to fix the polyphenylene sulfide fibers. Adhesive fibers made of polyolefin fibers have poor heat resistance. In order to use unstretched polyphenylene sulfide fibers with excellent heat resistance for plasticization and fixation, heating and pressure are required. As a result, the pores of the support are reduced and the ion permeability is poor.

[0010] As a nonwoven fabric capable of solving the aforementioned heat resistance technical problem, a nonwoven fabric (diaphragm) utilizing a polyolefin-based split composite fiber composed of polymethylpentene, a polyolefin resin with high heat resistance, and polypropylene has been proposed (Patent Document 1).

[0011] However, even nonwoven fabrics that utilize polyolefin-based split composite fibers composed of a combination of polymethylpentene and polypropylene do not simultaneously possess sufficient heat resistance, mechanical strength, and permeability (ion permeability).

[0012] The aforementioned technical problems regarding heat resistance, mechanical strength, and permeability are not limited to the aforementioned battery separator support; the same problems also arise when used as a separator support for electrolysis or a separator for electrochemical elements that utilizes nonwoven fabric.

[0013] Existing technical documents

[0014] Patent documents

[0015] Patent Document 1: Japanese Patent Application Publication No. 2021-161563

[0016] Patent Document 2: Japanese Patent Application Publication No. 2019-179678 Summary of the Invention

[0017] (a) Technical problems to be solved

[0018] This invention was implemented to solve the aforementioned technical problems, and its object is to provide a highly versatile nonwoven fabric with excellent heat resistance and mechanical strength, which is also suitable for applications requiring heat resistance. Furthermore, this invention also aims to provide a diaphragm for electrochemical components with excellent heat resistance and mechanical strength.

[0019] Furthermore, an object of the present invention is to provide a nonwoven fabric with excellent heat resistance, mechanical strength, and permeability. Further, an object of the present invention is to provide a membrane support with excellent heat resistance, mechanical strength, and ion permeability.

[0020] (II) Technical Solution

[0021] The nonwoven fabric of the present invention comprises polymethylpentene and polyethylene, and is a nonwoven fabric in which the polyethylene component has been fused together, wherein the polymethylpentene component accounts for more than 30% by volume of the nonwoven fabric constituting the fiber whole, and the polyethylene component accounts for more than 30% by volume of the nonwoven fabric constituting the fiber whole.

[0022] Preferably, the nonwoven fabric comprises a core-sheath type composite fiber in which polyethylene is used as the sheath component and polymethylpentene is used as the core component. Furthermore, it is preferable to further comprise extremely fine fibers with a fiber diameter of 4.5 μm or less as the nonwoven fabric constituent fibers.

[0023] The preferred nonwoven fabric has a tensile strength of 2.5 N / 5 cm or more per unit weight in one direction. Furthermore, the preferred nonwoven fabric has a porosity of 50-80%. Further, the preferred nonwoven fabric has a liquid retention rate of 5% or more after being pressurized at 5.7 MPa.

[0024] The diaphragm for the electrochemical element of the present invention comprises the above-mentioned nonwoven fabric.

[0025] This invention relates to "(1) a nonwoven fabric comprising polymethylpentene and polyethylene, wherein the polyethylene component is fused together, wherein the polymethylpentene component accounts for more than 30% by volume of the nonwoven fabric as a whole fiber, and the polyethylene component accounts for more than 30% by volume of the nonwoven fabric as a whole fiber, wherein the thickness of the nonwoven fabric is less than 100 μm, and it has a tensile strength of more than 2.0 N / 5 cm width per unit weight in a direction."

[0026] Preferably: "(2) The nonwoven fabric according to (1) comprises a core-sheath type composite fiber in which polyethylene is used as the sheath component and polymethylpentene is used as the core component as the nonwoven fabric constituent fiber."

[0027] Preferably: "(3) The nonwoven fabric according to (2), wherein the ratio (L / D) of the length (L, unit: μm) of the core-sheath type composite fiber to the fiber diameter (D, unit: μm) is 350 or more."

[0028] Preferably: "(4) The nonwoven fabric according to (1) to (3), wherein the porosity of the nonwoven fabric is 60% or more."

[0029] Preferably: "(5) The nonwoven fabric according to (1) to (4), wherein the basis weight of the nonwoven fabric is 20 g / m²". 2 the following. ".

[0030] Another invention relates to "(6) a nonwoven fabric comprising a core-sheath type composite fiber in which polyethylene is used as a sheath component and polymethylpentene is used as a core component, wherein the polyethylene component, which is the sheath component of the core-sheath type composite fiber, has been fused together, and the polymethylpentene component accounts for more than 30% by volume of the nonwoven fabric constituting the fiber, while the polyethylene component accounts for more than 30% by volume of the nonwoven fabric constituting the fiber, wherein the thickness of the nonwoven fabric is less than 100 μm, and the ratio (L / D) of the length (L, unit: μm) of the core-sheath type composite fiber to the fiber diameter (D, unit: μm) is more than 350."

[0031] Preferably: "(7) The nonwoven fabric according to (6), wherein it has a tensile strength of 2.0 N / 5 cm width or more per unit weight in a direction."

[0032] Preferably: "(8) The nonwoven fabric according to (6) or (7), wherein the porosity of the nonwoven fabric is 60% or more."

[0033] Preferably: "(9) The nonwoven fabric according to (6)~(8), wherein the basis weight of the nonwoven fabric is 20 g / m²". 2 the following. ".

[0034] Preferred: "(10) A membrane support comprising any one of (1) to (9) a nonwoven fabric."

[0035] (III) Beneficial Effects

[0036] The nonwoven fabric of this invention exhibits excellent heat resistance because polymethylpentene constitutes more than 30% by volume of the fiber structure. Furthermore, it also possesses excellent mechanical strength because polyethylene constitutes more than 30% by volume of the fiber structure and is fused together. Therefore, it is a versatile nonwoven fabric suitable for applications requiring heat resistance.

[0037] If the nonwoven fabric is composed of core-sheath type composite fibers that use polyethylene as the sheath component and polymethylpentene as the core component, then even if it contains a large amount of polyethylene with a relatively low melting point and poor heat resistance, the heat resistance will still be excellent because the polymethylpentene component is the core component.

[0038] If the nonwoven fabric is further composed of extremely fine fibers with a fiber diameter of less than 4.5 μm, it can be a nonwoven fabric with micropores. In addition, since the nonwoven fabric has a wide surface area, it has excellent liquid retention.

[0039] If a nonwoven fabric has a tensile strength of 2.5 N / 5 cm or more per unit weight in a direction, it has excellent mechanical strength.

[0040] If the porosity of the nonwoven fabric is 50-80%, then because there is more space to hold liquid, the amount of liquid retained is greater.

[0041] If the liquid retention rate of the nonwoven fabric is above 5% after being pressurized at 5.7MPa, it can retain the liquid even when pressure is applied, thus demonstrating strong liquid retention capacity.

[0042] The diaphragm for electrochemical devices of the present invention, due to its inclusion of the nonwoven fabric, exhibits excellent heat resistance and mechanical strength. Therefore, by using the diaphragm for electrochemical devices of the present invention, it is possible to manufacture electrochemical devices suitable for applications requiring heat resistance, such as automobiles.

[0043] The nonwoven fabric of the present invention exhibits excellent heat resistance because the polymethylpentene component accounts for more than 30% by volume of the total fiber composition. Furthermore, the polyethylene component accounts for more than 30% by volume of the total fiber composition, the polyethylene component is fused together, and it has excellent mechanical strength in a direction with a tensile strength of 2.0 N / 5 cm width or more per unit weight. Moreover, because its thickness is as thin as 100 μm or less, it is a nonwoven fabric with excellent permeability.

[0044] If the nonwoven fabric is composed of core-sheath type composite fibers that use polyethylene as the sheath component and polymethylpentene as the core component, then even if it contains a large amount of polyethylene with a relatively low melting point and poor heat resistance, the heat resistance will still be excellent because the polymethylpentene component is the core component.

[0045] If the ratio (L / D) of the length (L, unit: μm) of the core-sheath composite fiber to the fiber diameter (D, unit: μm) is 350 or higher, then the fiber length is longer than the fiber diameter. Therefore, the core-sheath composite fiber is more likely to form fiber entanglement with the nonwoven fabric. In addition, if the amount is the same, there are fewer fiber roots and fewer joints between fibers, resulting in high tensile strength and excellent mechanical strength.

[0046] If the porosity of a nonwoven fabric is above 60%, it has many pores and therefore excellent permeability. For example, it has excellent ion permeability and fluid permeability.

[0047] If the weight of the nonwoven fabric is 20 g / m² 2The following fibers have a lower fiber content, resulting in excellent permeability. For example, they have excellent ion permeability and fluid permeability.

[0048] Another nonwoven fabric of the present invention exhibits excellent heat resistance because the polymethylpentene component accounts for more than 30% by volume of the total nonwoven fabric fibers. Furthermore, if the polyethylene component accounts for more than 30% by volume of the total nonwoven fabric fibers, the polyethylene component is fused together, and the core-sheath composite fiber ratio (L / D) is more than 350, the fiber length is longer than the fiber diameter. Therefore, the core-sheath composite fibers easily entangle with the nonwoven fabric fibers. Moreover, for the same amount, the number of fibers is less, resulting in fewer fiber junctions and thus higher tensile strength and excellent mechanical strength. Furthermore, because the thickness is as thin as 100 μm or less, it is a nonwoven fabric with excellent permeability.

[0049] If the nonwoven fabric has a tensile strength of 2.0 N / 5 cm or more per unit weight in any direction, it has excellent mechanical strength.

[0050] If the porosity of a nonwoven fabric is above 60%, it has many pores and therefore excellent permeability. For example, it has excellent ion permeability and fluid permeability.

[0051] If the weight of the nonwoven fabric is 20 g / m² 2 The following fibers have a lower fiber content, resulting in excellent permeability. For example, they have excellent ion permeability and fluid permeability.

[0052] The membrane support of the present invention, due to its inclusion of the nonwoven fabric, exhibits excellent heat resistance, mechanical strength, and permeability. Therefore, by using the membrane support of the present invention, it is possible to manufacture membranes with excellent heat resistance, mechanical strength, and permeability. For example, if used as a separator support for batteries or a separator support for electrolysis, it is possible to manufacture separators with excellent heat resistance, mechanical strength, and ion permeability. Attached Figure Description

[0053] Figure 1 A schematic cross-section of the split fibers that can be used to manufacture the nonwoven fabric of the present invention;

[0054] Figure 2 A schematic cross-section of another segmented fiber that can be used to manufacture the nonwoven fabric of the present invention;

[0055] Figure 3 A schematic cross-section of another segmented fiber that can be used to manufacture the nonwoven fabric of the present invention;

[0056] Figure 4 A schematic cross-section of another segmented fiber that can be used to manufacture the nonwoven fabric of the present invention;

[0057] Figure 5A schematic cross-section of another segmented fiber that can be used to manufacture the nonwoven fabric of the present invention;

[0058] Figure 6 A schematic cross-section of another segmented fiber that can be used to manufacture the nonwoven fabric of the present invention;

[0059] Figure 7 This is a schematic cross-sectional view of the plasma processing apparatus used in the embodiment.

[0060] Explanation of reference numerals in the attached figures

[0061] 1: Orange-type composite fiber; 11: Polymethylpentene component or resin component other than polymethylpentene component; 12: Resin component other than polymethylpentene component or polymethylpentene component; 1a, 1b: Electrode; 2a, 2b: Dielectric; 4: AC power supply; 5: First nonwoven fabric or second nonwoven fabric. Detailed Implementation

[0062] (Basic nonwoven fabric)

[0063] The basic nonwoven fabric of this invention comprises polymethylpentene and polyethylene components, wherein the polyethylene components are fused together. The polymethylpentene component accounts for more than 30% by volume of the total fiber composition of the basic nonwoven fabric, and the polyethylene component also accounts for more than 30% by volume of the total fiber composition of the basic nonwoven fabric. Hereinafter, the basic nonwoven fabric will be referred to simply as "nonwoven fabric".

[0064] Polymethylpentene has a melting point of approximately 220-240°C, which is higher than that of other polyolefins, and exhibits excellent heat resistance. Since this heat-resistant polymethylpentene component accounts for more than 30% by volume of the total fiber composition of the nonwoven fabric, the nonwoven fabric of the present invention exhibits excellent heat resistance. Because the higher the amount of polymethylpentene, the better the heat resistance, the polymethylpentene component preferably accounts for more than 35% by volume of the total fiber composition of the nonwoven fabric, more preferably more than 40% by volume. On the other hand, as described later, since the inclusion of more than 30% by volume of polyethylene results in excellent mechanical strength, the polymethylpentene component is 70% by volume or less, preferably 65% ​​by volume or less, more preferably 60% by volume or less.

[0065] In addition, polymethylpentene is a copolymer containing 85 mol% or more of 4-methylpentene-1, for example, it can be a copolymer of 4-methylpentene-1 with one or more α-olefins (such as ethylene, propylene, butene-1, hexene-1, octene-1, decane-1, tetradecane-1, octadecane-1, etc.). The polymethylpentene component can be one type or two or more. When there are two or more types, their total amount is 30% or more by volume of the total fiber composition of the nonwoven fabric.

[0066] Nonwoven fabrics can contain, for example, (1) a core-sheath type composite fiber in which resin components other than polymethylpentene are used as sheath components and polymethylpentene is used as a core component, (2) a core-sheath type composite fiber in which polymethylpentene is used as a sheath component and resin components other than polymethylpentene are used as a core component, and (3) an orange-shaped composite fiber in which polymethylpentene and resin components other than polymethylpentene extend radially from the center in the fiber cross-section (see reference). Figures 1-5 (4) Multilayer bimetallic composite fibers formed by alternating layers of polymethylpentene and resin components other than polymethylpentene in the fiber cross-section (refer to) Figure 6 (5) Single-component fibers consisting only of polymethylpentene.

[0067] Among them, (1) core-sheath type composite fiber that uses resin components other than polymethylpentene as sheath components and polymethylpentene components as core components can improve mechanical strength by utilizing the welding force of resin components other than polymethylpentene components, and at the same time, the polymethylpentene components as core components make the heat resistance excellent, so it is suitable.

[0068] The resin component that can constitute the sheath, excluding polymethylpentene, can be, for example, a polyolefin resin (e.g., polypropylene resin, polyethylene resin, etc.), a polyester resin (e.g., polyester copolymer), or a nylon resin (e.g., nylon copolymer). Among these, a polyolefin resin with excellent chemical resistance and versatility is preferred, and a polyethylene resin with excellent weldability is even more preferred.

[0069] When the sheath component is preferably polyethylene, the polyethylene component exhibits excellent weldability. Furthermore, although polyethylene has a low melting point and poor heat resistance, it is suitable because using polymethylpentene as the core component results in excellent heat resistance. Additionally, this polyethylene component can, for example, have a density of 0.942 g / cm³. 3 The above-mentioned 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 Low-density polyethylene, linear low-density polyethylene, ultra-high molecular weight polyethylene, or polyethylene copolymers are used. Among them, high-density polyethylene has a certain degree of hardness, stiffness, and toughness, making it suitable for use as a nonwoven fabric with excellent handling properties.

[0070] In addition, when the core-sheath type composite fiber is used, in order to make it a nonwoven fabric with excellent heat resistance and mechanical strength, the volume ratio of the resin component (sheath component, such as polyethylene component) other than the polymethylpentene 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.

[0071] Furthermore, the polymethylpentene component used as the core does not necessarily have to be a single type; it can be two or more island-type components. Additionally, in the fiber cross-section, the core and sheath components can be arranged concentrically or with the core component offset from the center; concentric arrangement is preferred for achieving excellent dimensional stability in the nonwoven fabric.

[0072] The content of the suitable core-sheath type composite fiber is only required to be such that the polymethylpentene component in the nonwoven fabric accounts for more than 30% by volume of the total fiber composition of the nonwoven fabric, and the polyethylene component accounts for more than 30% by volume of the total fiber composition of the nonwoven fabric. There is no particular limitation. In order to easily meet this volume ratio, it is preferred to contain more than 50% by volume, more preferably more than 60% by volume, further preferably more than 70% by volume, and even more preferably more than 80% by volume of the core-sheath type composite fiber in which the polyethylene component is used as the sheath component and the polymethylpentene component is used as the core component.

[0073] In addition, (3) orange-shaped composite fibers in which polymethylpentene and resin components other than polymethylpentene extend radially from the center in the fiber cross-section (see reference). Figures 1-5 (4) Multilayer bimetallic composite fibers formed by alternating layers of polymethylpentene and resin components other than polymethylpentene in the fiber cross-section (see reference) Figure 6 By applying mechanical force, it is divided into individual polymethylpentene components and resin components other than polymethylpentene components, which can produce fibers that are finer than the fiber diameter. Therefore, it can become a nonwoven fabric with micropores. In addition, since the nonwoven fabric has a wide surface area of ​​the fibers, it can become a nonwoven fabric with excellent resin or liquid retention properties, and is therefore suitable.

[0074] More specifically, by applying mechanical force to the orange-type composite fiber or multilayer bimetallic composite fiber, extremely fine fibers with a fiber diameter of less than 4.5 μm can be produced. Nonwoven fabrics containing such extremely fine fibers can become nonwoven fabrics with micropores. In addition, due to the wide fiber surface area, they can become nonwoven fabrics with excellent resin or liquid retention properties.

[0075] In addition, if mechanical external force is applied to Figure 1The orange-shaped composite fiber 1 shown will produce approximately triangular-shaped fine fibers composed of polymethylpentene component 11 and approximately triangular-shaped fine fibers composed of resin component 12 other than polymethylpentene component.

[0076] If mechanical external force is applied to Figure 2 The orange-shaped composite fiber 1 shown will produce approximately elliptical ultrafine fibers composed of polymethylpentene component 11 or resin component 11 other than polymethylpentene component, and approximately triangular ultrafine fibers composed of resin component 12 other than polymethylpentene component or polymethylpentene component 12.

[0077] If mechanical external force is applied to Figure 3 The orange-type composite fiber 1 shown will produce approximately triangular-shaped ultrafine fibers composed of polymethylpentene component 11 or resin component 11 other than polymethylpentene component, and approximately triangular and round-shaped ultrafine fibers composed of resin component 12 other than polymethylpentene component or polymethylpentene component 12.

[0078] If mechanical external force is applied to Figure 4 The orange-type composite fiber 1 shown will produce extremely fine fibers in generally elliptical and round shapes composed of polymethylpentene component 11 or resin component 11 other than polymethylpentene component, and extremely fine fibers in generally triangular shapes composed of resin component 12 other than polymethylpentene component or polymethylpentene component 12.

[0079] If mechanical external force is applied to Figure 5 The orange-shaped composite fiber 1 with a hollow portion shown will produce approximately ladder-shaped fine fibers composed of polymethylpentene component 11 or resin component 11 other than polymethylpentene component, and approximately ladder-shaped fine fibers composed of resin component 12 other than polymethylpentene component or polymethylpentene component 12.

[0080] If mechanical external force is applied to Figure 6 The multilayer bimetallic composite fiber 1 shown will produce fine fibers in generally trapezoidal and generally semi-circular shapes composed of polymethylpentene component 11, and fine fibers in generally trapezoidal and generally semi-circular shapes composed of resin component 12 other than polymethylpentene component.

[0081] Thus, the ultrafine fibers produced from orange-type composite fibers or multilayer bimetallic composite fibers have a non-circular, irregular cross-sectional shape. These ultrafine fibers with such irregular cross-sectional shapes can be arranged in a densely packed configuration, thus creating a dense nonwoven fabric with excellent separation, isolation, and concealment properties.

[0082] In addition, mechanical external forces capable of splitting such composite fibers can include fluid flows such as water, calenders, refining machines, pulpers, agitators, beaters, etc.

[0083] Furthermore, (5) the fiber diameter of a single-component fiber composed solely of polymethylpentene can be 0.1 to 30 μm, but if it is an extremely fine fiber of 4.5 μm or less, it can become a nonwoven fabric with micropores. In addition, since the surface area of ​​the nonwoven fabric fibers is wide, it can become a nonwoven fabric with excellent resin or liquid retention properties, and is therefore suitable. Such a single-component extremely fine fiber composed solely of polymethylpentene can be manufactured by applying mechanical external force to the above-mentioned orange-type composite fiber or multilayer bimetallic composite fiber, or it can be manufactured by removing only the sea component from an island-type composite fiber in which polymethylpentene is the island component. According to the latter method of using island-type composite fibers, even finer fibers can be produced, and is therefore suitable. More specifically, it can become an extremely fine fiber with a fiber diameter of 4.0 μm or less, an extremely fine fiber with a fiber diameter of 3.0 μm or less, and an extremely fine fiber with a fiber diameter of 2.0 μm or less.

[0084] To ensure excellent mechanical strength of the nonwoven fabric, the ultrafine fibers constituting the nonwoven fabric of the present invention are preferably stretched. As described above, when ultrafine fibers are made from orange-type composite fibers, multilayer bimetallic composite fibers, or island-type composite fibers, if the orange-type composite fibers, multilayer bimetallic composite fibers, or island-type composite fibers are stretched in the stage before slitting, the ultrafine fibers made from these fibers are also in a stretched state.

[0085] On the other hand, the nonwoven fabric of the present invention includes at least 30% by volume of a polyethylene component with excellent weld strength, which constitutes the entire fiber structure of the nonwoven fabric. Since part or all of this polyethylene component participates in the welding, it becomes a nonwoven fabric with excellent mechanical strength. The higher the amount of this polyethylene component, the better the weld strength, resulting in a nonwoven fabric with excellent mechanical strength. Therefore, the polyethylene component preferably accounts for at least 35% by volume of the entire fiber structure of the nonwoven fabric, more preferably at least 40% by volume. However, as described above, it is necessary to include at least 30% by volume of polymethylpentene component to achieve excellent heat resistance. Therefore, the polyethylene component is 70% by volume or less, preferably 65% ​​by volume or less, more preferably 60% by volume or less.

[0086] In addition, polyethylene can be high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, ultra-high molecular weight polyethylene, or polyethylene copolymers. Among them, high-density polyethylene has a certain degree of hardness, stiffness, and toughness, making it suitable as a nonwoven fabric with excellent handling properties. Furthermore, the polyethylene copolymer can be a copolymer with one or more α-polyolefins, such as propylene, butene-1, hexene-1, octene-1, decane-1, tetradecane-1, octadecane-1, etc. The polyethylene component can be one type or two or more types; when two or more types are used, their total volume must be 30% or more of the total volume of the nonwoven fabric fibers.

[0087] Nonwoven fabrics can contain polyethylene components in the aforementioned amounts, with the polyethylene components having been fused together, and can include, for example, (a) core-sheath type composite fibers in which polyethylene components are used as sheath components and resin components other than polyethylene components are used as core components; (b) orange-type composite fibers in which polyethylene components and resin components other than polyethylene components extend radially from the center in alternating directions in the fiber cross-section (see reference). Figures 1-5 (c) Multilayer bimetallic composite fibers formed by alternating layers of polyethylene and resin components other than polyethylene in the fiber cross-section (see reference). Figure 6 (d) Single-component fibers consisting solely of polyethylene.

[0088] Among them, (a) core-sheath type composite fiber, which uses polyethylene as the sheath component and resin components other than polyethylene as the core component, is suitable because the polyethylene component has excellent welding strength and the fiber morphology maintenance based on the resin components other than polyethylene (core component) can improve the mechanical strength of nonwoven fabric.

[0089] The resin component, other than polyethylene, that constitutes the core-sheath component of this core-sheath type composite fiber can be, for example, a polyolefin resin (e.g., polymethylpentene resin, polypropylene resin, etc.), a polyester resin (e.g., polyethylene terephthalate, etc.), or a nylon resin (e.g., nylon 6, nylon 66, etc.). Among these, a polyolefin resin with excellent chemical resistance and versatility is preferred, and a polymethylpentene resin with excellent heat resistance is even more preferred.

[0090] Furthermore, when using this core-sheath type composite fiber, in order to obtain 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, such as 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 make the weld strength brought by the polyethylene component excellent.

[0091] Furthermore, the resin component other than polyethylene used as the core component does not necessarily have to be a single type; it can be two or more island-type resins. Additionally, in the fiber cross-section, the core and sheath components can be arranged concentrically or with the core component offset from the center; concentric arrangement is preferred for achieving excellent dimensional stability in the nonwoven fabric.

[0092] The content of the suitable core-sheath type composite fiber is only required to make the polyethylene component in the nonwoven fabric account for more than 30% by volume of the total fiber composition of the nonwoven fabric, and the polymethylpentene component account for more than 30% by volume of the total fiber composition of the nonwoven fabric. There is no particular limitation. In order to easily meet this volume ratio, it is preferred to contain more than 50% by volume, more preferably more than 60% by volume, further preferably more than 70% by volume, and even more preferably more than 80% by volume of the core-sheath type composite fiber in which the polyethylene component is used as the sheath component and the polymethylpentene component is used as the core component.

[0093] The nonwoven fabric of the present invention preferably comprises a core-sheath type composite fiber in which polyethylene is used as the sheath component and polymethylpentene is used as the core component. To improve the rigidity and compression resistance of the nonwoven fabric, it can include high-strength fibers with a tensile strength of 5 cN / dtex or higher. The higher the tensile strength of the high-strength fiber, the better the effect. Therefore, when the high-strength fiber is composed 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 fiber is a composite fiber and the mechanical strength of the nonwoven fabric is improved by welding 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 the case of any high-strength fiber, the upper limit of the tensile strength is not particularly limited, but is approximately 50 cN / dtex. In this invention, "tensile strength" refers to the tensile strength measured using a constant-speed tension tensile testing machine under the conditions of a clamp interval of 20 mm and a tensile speed of 20 mm / min, in accordance with JIS L 1015: 2010 "Test method for chemical fiber stature (test method for chemical fiber short fiber)" 8.7.1 (standard time test).

[0094] The resin composition constituting this high-strength fiber is not particularly limited. For example, it can be a single polyolefin resin (e.g., polypropylene resin, polyethylene resin, polymethylpentene resin, etc.), polyester resin (e.g., polyethylene terephthalate, polyester copolymer), nylon resin (e.g., nylon 6, nylon 66, nylon copolymer), or a combination thereof. Among these, polyolefin resins with excellent chemical resistance and versatility are preferred. For example, when the high-strength fiber is formed from a single component, it can be composed of ultra-high molecular weight polyethylene, polypropylene, etc. When it is a composite fiber formed from two resin components, it can be: a core-sheath type composite fiber in which polyethylene (especially high-density polyethylene) is used as the sheath component and polypropylene is used as the core component; or a core-sheath type composite fiber in which polyethylene (especially high-density polyethylene) is used as the sheath component and polymethylpentene is used as the core component, etc.

[0095] The nonwoven fabric of the present invention preferably comprises a core-sheath type composite fiber in which polyethylene is used as the sheath component and polymethylpentene is used as the core component. In order to improve the heat resistance of the nonwoven fabric, it may contain heat-resistant fibers with a melting point or decomposition temperature of 210°C or higher. Examples of resins constituting the heat-resistant fibers include polyphenylene sulfide (PPS), polybenzimidazole (PBI), polyether ether ketone (PEEK), polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), fluorinated ethylene propylene (FEP), ethylene-chlorotrifluoroethylene (ECTFE), ethylene-tetrafluoroethylene (ETFE), polychlorotrifluoroethylene (PCTFE), polyimide (PI), and polyamide-imide (PAI). In addition, "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 test piece in an oven-dry state decreases by 5% as obtained by thermogravimetric determination as specified in JIS K 7120-1987.

[0096] The nonwoven fabric of the present invention preferably comprises a core-sheath type composite fiber in which polyethylene is used as the sheath component and polymethylpentene is used as the core component. The fiber diameter of the fibers constituting the nonwoven fabric, including the core-sheath type composite fiber, is not particularly limited. However, in order to make the fibers uniformly dispersed and of excellent quality, and to uniformly impart strength, and to make the nonwoven fabric with excellent density and resin or liquid retention, the diameter is preferably 0.1 to 35 μm, more preferably 0.5 to 28 μm, and even more preferably 1 to 20 μm.

[0097] Furthermore, as described above, it is preferable to include 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 composed, for example, of polyolefin resins such as polymethylpentene resins, polypropylene resins, and polyethylene resins; polyester resins such as polyethylene terephthalate and polyester copolymers; and nylon resins such as nylon 6, nylon 66, and nylon copolymers. Among these, ultrafine fibers composed of polyolefin resins with excellent chemical resistance and versatility are preferred, and those composed of polymethylpentene resins or polypropylene resins with excellent heat resistance are even more desirable.

[0098] In addition, as mentioned above, ultrafine fibers can be manufactured by applying mechanical external force to orange-type composite fibers or multilayer bimetallic composite fibers, or by extracting and removing the marine components from island-type composite fibers.

[0099] In this invention, the fiber diameter refers to the diameter when the cross-sectional shape of the fiber is circular. When it is non-circular, the diameter of a circle with the same area as the cross-sectional area is regarded as the fiber diameter.

[0100] Furthermore, the fiber length of the nonwoven fabric comprising core-sheath type composite fibers and ultrafine fibers is not particularly limited. The shorter the fiber length, the higher the degree of freedom of the fiber, and the more likely it is to become an excellent nonwoven fabric with uniformly dispersed fibers. Therefore, 0.1 to 160 mm is preferred, more preferably 0.5 to 105 mm, further preferably 1 to 55 mm, and even more preferably 1 to 20 mm.

[0101] In addition, the nonwoven fabric of the present invention may contain two or more core-sheath type composite fibers, ultrafine fibers and / or heat-resistant fibers that differ in resin composition, fiber diameter and / or fiber length.

[0102] The nonwoven fabric of the present invention is in a state where the fibers are bonded together by welding together with polyethylene components. In addition to welding, the fibers can also be three-dimensionally complexed. This is because the mechanical strength of the nonwoven fabric is superior through three-dimensional complexation. Such three-dimensional complexation can be formed, for example, by subjecting the fiber web to a fluid flow such as water or by needle punching.

[0103] The nonwoven fabric of the present invention exhibits excellent mechanical strength. Specifically, it is preferable to have a tensile strength of 2.5 N / 5 cm width or more per unit weight in one direction. When evaluating tensile strength using unit weight, a higher basis weight, i.e., a greater fiber content, inevitably leads to higher mechanical strength. Therefore, to objectively evaluate the mechanical strength of the nonwoven fabric, the fiber content, i.e., the amount of fiber per unit weight, is used. The stronger the tensile strength, the better the mechanical strength. Therefore, a tensile strength of 2.8 N / 5 cm width or more is more preferable, further preferably 3.0 N / 5 cm width or more, and even more preferably 3.2 N / 5 cm width or more is more desirable. Since a higher tensile strength indicates better mechanical strength, there is no particular upper limit, but it can be 10 N / 5 cm width or less.

[0104] The tensile strength of the present invention is obtained through the following steps.

[0105] 1. Take a strip of nonwoven fabric with a length of 200 mm and a width of 50 mm as the test piece.

[0106] 2. The tensile strength of a long strip test piece was determined using a tensile strength testing machine. The testing conditions were set as follows: distance between the clamps 100 mm, tensile speed 300 mm / min, and the strength at break was measured.

[0107] 3. Perform the above steps 1 to 2 three times, and calculate the arithmetic mean of the strength at the point of fracture in the three times. This arithmetic mean is taken as the tensile strength (unit: N / 50mm width).

[0108] Additionally, the following steps confirm whether there is a direction with a tensile strength of 2.5 N / 5 cm width or more per unit weight.

[0109] 1. Take three strip-shaped test pieces, each 200 mm long and 50 mm wide, along a reference direction of the nonwoven fabric (e.g., the longitudinal direction, which is the production direction of the nonwoven fabric).

[0110] 2. Take three strip-shaped test pieces, each 200 mm long and 50 mm wide, with the length direction being the direction after rotating them 10° relative to the reference direction.

[0111] 3. Similarly, for each of the 16 directions, three strip-shaped test pieces, each 200 mm long and 50 mm wide, are taken, with the direction after rotation relative to the reference direction increasing by 10° in each successive direction as the length direction. That is, including the reference direction, three strip-shaped test pieces are taken for each of the 18 directions.

[0112] 4. Use the above method to determine the tensile strength of the strip-shaped test pieces in each direction.

[0113] 5. Determine the results of the tensile strength measurements in the 18 directions, and the direction with the strongest tensile strength.

[0114] 6. The tensile strength (Tmax, unit: N / 50mm width) in the direction of strongest tensile strength is divided by the weight (M, unit: g / m²). 2 The tensile strength (Tu) per unit weight is calculated using the following formula.

[0115] Tu=Tmax / M

[0116] 7. As a result, if the tensile strength per unit weight is 2.5 N / 5 cm or more, then at least that direction corresponds to the direction in which the tensile strength per unit weight is 2.5 N / 5 cm or more.

[0117] In addition, since nonwoven fabrics are produced in a continuous nonwoven form, the fibers tend to orient themselves more or less along the production direction. Therefore, in most cases, the production direction of nonwoven fabrics is the direction with a tensile strength of 2.5 N / 5 cm width or more per unit weight.

[0118] Furthermore, even if the tensile strength per unit weight is 2.5 N / 5 cm width or more, it is sometimes impractical due to the weak absolute tensile strength. Therefore, a direction with tensile strength of 100 N / 5 cm width or more is preferred, a direction with 110 N / 5 cm width or more is more preferred, a direction with 120 N / 5 cm width or more is even more preferred, and a direction with 130 N / 5 cm width or more is even more preferred. This direction is particularly preferred in the production direction when manufacturing nonwoven fabrics.

[0119] The nonwoven fabric of the present invention preferably has a shrinkage rate of 5% or less when heated at 150°C to achieve excellent heat resistance. The lower the shrinkage rate, the better the heat resistance. Therefore, the shrinkage rate when heated at 150°C is more preferably 4.5% or less, even more preferably 4.0% or less, and even more preferably 3.5% or less.

[0120] The shrinkage rate when heated to 150°C is a value obtained using the following method.

[0121] 1. A test piece (area: Ab=10000mm²) is taken from the nonwoven fabric, with a length of 100mm in the longitudinal direction (the production direction of the nonwoven fabric) and a length of 100mm in the transverse direction (the direction orthogonal to the longitudinal direction). 2 ).

[0122] 2. Place the test piece in a dryer with the temperature set to 150°C.

[0123] 3. After 10 minutes, remove the test piece from the dryer, measure its longitudinal and transverse lengths, and calculate its area (Aa, unit: mm). 2 ).

[0124] 4. Calculate the thermal shrinkage rate (S, unit: %) using the following formula.

[0125] S=[(Ab-Aa) / Ab]×100=(10000-Aa) / 100

[0126] 5. Repeat steps 1 to 4 three times, calculate the heat shrinkage rate for the three test pieces, and take the arithmetic mean as the "shrinkage rate when heated at 150℃".

[0127] The porosity of the nonwoven fabric of the present invention is not particularly limited. In order to maximize the space for liquid retention and the amount of liquid retained, the porosity is preferably 50% or more, more preferably 53% or more, and even more preferably 56% or more. On the other hand, if the porosity is too high, there is a tendency for the mechanical strength to decrease. Therefore, it is preferably 80% or less, more preferably 75% or less, and even more preferably 70% or less.

[0128] Furthermore, the porosity (P, unit: %) of the present invention refers to the value obtained by the following calculation formula.

[0129] P = 100 - (Fr1 + Fr2 + ... + Frn)

[0130] Here, Frn represents the filling rate (unit: %) of the n-component that makes up the nonwoven fabric, which is the value obtained by the following formula.

[0131] Frn=[(M×Prn) / (T×SGn)]×100

[0132] Here, M refers to the basis weight of the nonwoven fabric (unit: g / cm³). 2 T refers to the thickness of the nonwoven fabric (unit: cm), Prn refers to the mass ratio of the n component in the nonwoven fabric, and SGn refers to the density of the n component (unit: g / cm³). 3 ).

[0133] The apparent density of the nonwoven fabric of the present invention is not particularly limited, but in order to maximize the space for liquid retention and the amount of liquid retained, the apparent density is preferably 0.57 g / cm³. 3 The preferred value is 0.53 g / cm³. 3 The following is a further preferred value: 0.50 g / cm³ 3 Below. On the other hand, if the apparent density is too low, there is a tendency for the mechanical strength to deteriorate; therefore, the apparent density is preferably 0.23 g / cm³. 3 The above, more preferably 0.28 g / cm³3 The above is further preferred to be 0.34 g / cm³. 3 The above. The apparent density is a calculated value derived from the basis weight and thickness of the nonwoven fabric; more specifically, it is the basis weight (unit: g / cm³). 2 The value obtained by dividing the thickness (in cm).

[0134] 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 can retain liquid even under pressure, making it a nonwoven fabric with strong liquid retention capacity. The higher the liquid retention rate, the stronger the liquid retention capacity; therefore, the liquid retention rate after pressurization is more preferably 6% or more, and even more preferably 7% or more. Furthermore, the upper limit of the liquid retention rate after pressurization is not particularly limited and can be 20% or less.

[0135] The liquid retention rate is a value obtained using the following method.

[0136] 1. Cut the nonwoven fabric into circles with a diameter of 30mm and take 4 circular test pieces.

[0137] 2. After the circular test piece reaches moisture equilibrium at a temperature of 20℃ and a relative humidity of 65%, its mass (M0) is measured.

[0138] 3. Soak the nonwoven fabric in a potassium hydroxide aqueous solution with a specific gravity of 1.3 (20℃) for 1 hour, keeping it in the potassium hydroxide aqueous solution to replace the air in the nonwoven fabric.

[0139] 4. Clamp the nonwoven fabric with three circular filter papers (diameter = 30mm) on the top and bottom. Use a pressure pump to apply a pressure of 5.7MPa for 30 seconds, and then measure the mass (M1) of the nonwoven fabric.

[0140] 5. Calculate the liquid retention rate (Rr, unit: %) using the following formula.

[0141] Rr=[(M1-M0) / M0]×100

[0142] 6. The liquid retention rate of the four circular test pieces was measured, and the liquid retention rate was calculated for each piece. The arithmetic mean of the four calculated liquid retention rates was taken as the liquid retention rate of the nonwoven fabric in this invention.

[0143] The basis weight of the nonwoven fabric of this invention varies depending on the application and is not particularly limited, and can be 10~200 g / m². 2 The weight is per 1m 2 The quality of the nonwoven fabric and its size are less than 1m. 2 When, it will be converted to 1m 2 The value after that is taken as the weight in grams.

[0144] The thickness of the nonwoven fabric of this invention varies depending on the application and is not particularly limited, and can be 0.03~2mm. In this invention, "thickness" refers to the arithmetic mean obtained by measuring a 5N load using an outside micrometer (0~25mm) as specified in JIS B 7502: 1994 at 10 randomly selected locations.

[0145] The nonwoven fabric of this invention utilizes polyethylene components for welding and also contains polymethylpentene components. While it has a high proportion of polyolefin resin components and excellent chemical resistance, it is sometimes not suitable for various applications. Therefore, various processing methods can be implemented to make it more suitable for diverse uses. For example, it can be colored using pigments or dyes, or charged, or patterned. Hydrophilic groups such as sulfonic acid groups, carboxyl groups, and carbonyl groups can also be introduced.

[0146] The nonwoven fabric of this invention exhibits excellent heat resistance and mechanical strength, making it suitable for a wide range of applications and highly versatile. For example, it is suitable for use as a separator for electrochemical components, a separator support for batteries such as nickel-zinc batteries, and a separator support for water electrolysis. Furthermore, as an electrochemical component, examples 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; multivalent ion batteries such as magnesium, aluminum, calcium, and zinc; lithium-sulfur batteries; lithium-zinc metal-air batteries; lithium-ion capacitors; fluoride-ion batteries; and potassium-ion batteries. In particular, even when used as a separator for alkaline secondary batteries such as nickel-cadmium and nickel-hydrogen batteries, it exhibits excellent heat resistance and mechanical strength, thus enabling the manufacture of alkaline secondary batteries suitable for automotive applications requiring heat resistance.

[0147] The membrane for suitable alkaline secondary batteries such as nickel-cadmium batteries and nickel-hydrogen batteries is described. Because it contains polymethylpentene and polyethylene components, the polyethylene component is fused together, and the polymethylpentene component accounts for more than 30% by volume of the nonwoven fabric fibers. At the same time, the polyethylene component accounts for more than 30% by volume of the nonwoven fabric fibers. Therefore, it has excellent heat resistance and mechanical strength and is suitable for use in applications that require heat resistance of more than 100°C, such as the membrane for alkaline secondary batteries used in automobiles.

[0148] Furthermore, if the product includes ultrafine fibers produced from orange-type composite fibers, multilayer bimetallic composite fibers, and ultrafine fibers made by removing sea components from island-type composite fibers, it becomes a membrane composed of a nonwoven fabric with micropores. The nonwoven fabric fibers have a wide surface area and excellent electrolyte retention, thus possessing the characteristic of being usable not only at high temperatures above 100°C but also exhibiting excellent performance at low temperatures below 60°C in alkaline secondary batteries. Additionally, if the product includes ultrafine fibers produced from orange-type composite fibers and multilayer bimetallic composite fibers, the cross-sectional shape of these ultrafine fibers has an irregular profile, resulting in a complex and long path from one side of the membrane (nonwoven fabric) to the other, thus reducing the likelihood of short circuits due to dendrites.

[0149] Furthermore, when the separator contains high-strength fibers, it is less likely to break due to electrode burrs during the manufacture of alkaline secondary batteries, thus enabling the production of alkaline secondary batteries with a good yield. In addition, due to its excellent compression resistance, the electrode spacing can be maintained after the battery is assembled, resulting in excellent electrolyte retention. It also effectively prevents physical short circuits caused by microparticles from the shedding of active material.

[0150] Furthermore, when the diaphragm contains heat-resistant fibers, it has the characteristic of being able to withstand long-term use under high-temperature conditions greater than 100°C.

[0151] When the nonwoven fabric of the present invention is used as a separator for alkaline secondary batteries, in order to achieve excellent electrolyte resistance, it is preferable to be composed only of polyolefin fibers, which are composed only of polyolefin resins. For example, it is preferable to be composed of one or more of the following polyolefin fibers: core-sheath type composite fibers in which polyethylene (especially high-density polyethylene) is used as the sheath component and polymethylpentene is used as the core component; core-sheath type composite fibers in which polyethylene (especially high-density polyethylene) is used as the sheath component and polypropylene is used as the core component; single-component fibers (very fine fibers or high-strength fibers) composed of polyethylene, polypropylene or polymethylpentene; orange-type or multilayer bimetallic composite fibers composed of polypropylene and polymethylpentene; and other polyolefin fibers composed of polyethylene and polymethylpentene.

[0152] If the porosity of the membrane of the present invention is 50-80% and / or the apparent density is 0.23-0.57 g / cm³ 3 This results in a high electrolyte retention rate and excellent mechanical strength, making it suitable for use as a separator in automotive alkaline secondary batteries.

[0153] Furthermore, if the electrolyte retention rate of the diaphragm of the present invention is 5% or more after being pressurized at 5.7 MPa, the electrolyte can be maintained even when pressure is applied during the formation of the electrode group, without impairing ion permeability, thus enabling the production of long-life alkaline secondary batteries.

[0154] The basis weight of the diaphragm of the present invention can be 10~200 g / m³. 2 It can be 20~100g / m 2 It can be 25~85g / m 2 It can be 30~70g / m 2 The thickness can be 0.01~0.30mm, 0.03~0.25mm, or 0.05~0.20mm.

[0155] As described above, the diaphragm of the present invention is preferably made of only polyolefin fibers, but there is a tendency for the injection or retention of aqueous electrolyte to deteriorate. Therefore, it is preferable to introduce hydrophilic groups such as sulfonic acid groups, carboxyl groups, and carbonyl groups to increase the affinity with the electrolyte.

[0156] Furthermore, the separator for electrochemical elements of the present invention, primarily the separator for alkaline secondary batteries, can be made solely of the nonwoven fabric described above, or it can be laminated with other nonwoven fabrics, woven fabrics, knitted fabrics, webs, membranes, etc., thereby adding various functions such as reinforcement or separation.

[0157] (First Nonwoven Fabric)

[0158] The first nonwoven fabric of the present invention is a nonwoven fabric that, in addition to its heat resistance and mechanical strength, also exhibits excellent permeability among basic nonwoven fabrics. Therefore, the following description will only focus on the differences between the first nonwoven fabric and the basic nonwoven fabric.

[0159] The ratio (L / D) of the length of the fibers comprising the core-sheath type composite fiber, the ultrafine fiber, and the heat-resistant fiber of the present invention, to the fiber diameter (D), is preferably 350 or more. This is because if the ratio (L / D) is 350 or more, the fiber length is longer compared to the fiber diameter, thus the fibers comprising the first nonwoven fabric containing the core-sheath type composite fiber are more likely to entangle with each other. Furthermore, for the same amount of fiber, the number of fibers is smaller, and the number of junctions between fibers is smaller, resulting in higher tensile strength and better mechanical strength. The larger the ratio (L / D), the stronger this tendency becomes. Therefore, the ratio (L / D) is more preferably 400 or more, further preferably 450 or more, further preferably 500 or more, further preferably 550 or more, and further preferably 600 or more. On the other hand, as mentioned above, when the ratio (L / D) is large, the fibers are prone to entanglement and tend to act in a direction that hinders the uniform dispersion of the fibers. Therefore, the ratio (L / D) is preferably 7000 or less, more preferably 2000 or less, even more preferably 1600 or less, even more preferably 1300 or less, and even more preferably 1000 or less.

[0160] The fiber diameter of the core-sheath type composite fiber of the present invention (particularly a core-sheath type composite fiber in which polyethylene resin is used as the sheath component and polymethylpentene resin is used as the core component) can be smaller than the stated ratio (L / D), and there is no particular limitation. However, in order to improve the mechanical strength and heat resistance of the first nonwoven fabric, it is preferable to have a diameter of 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. On the other hand, if the core-sheath type composite fiber is too coarse, it tends to result in a first nonwoven fabric with poor fiber dispersion. Therefore, it is preferable to have a diameter of 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.

[0161] Furthermore, the fiber length of the first nonwoven fabric constituent fibers, which includes core-sheath type composite fibers, ultrafine fibers, and heat-resistant fibers, is not particularly limited. The longer the fiber length, the easier it is for the first nonwoven fabric constituent fibers to entangle with each other, resulting in superior mechanical strength. Therefore, 6 mm or more is preferred, more preferably 8 mm or more, and even more preferably 10 mm or more. On the other hand, if the fiber length is too long, the fibers are more likely to entangle with each other, potentially hindering the uniform dispersion of the fibers. Therefore, 105 mm or less is preferred, 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, is fused, a fiber length within the aforementioned range is preferred to facilitate entanglement to a certain extent.

[0162] In addition, the first nonwoven fabric of the present invention may contain two or more core-sheath type composite fibers, high-strength fibers, ultrafine fibers, and heat-resistant fibers that differ in terms of resin composition, resin configuration in fiber cross-section, fiber diameter, ratio (L / D), and / or fiber length.

[0163] The first nonwoven fabric of the present invention exhibits excellent mechanical strength, specifically, it has a tensile strength of 2.0 N / 5 cm width or more per unit weight in one direction. When evaluating tensile strength using unit weight, a higher basis weight, i.e., a higher fiber content, inevitably results in higher mechanical strength. Therefore, to objectively evaluate the mechanical strength of the first nonwoven fabric, the fiber content, i.e., the weight per unit weight, is used. The stronger this tensile strength, the better the mechanical strength; therefore, a tensile strength of 2.2 N / 5 cm width or more is more preferred, and a tensile strength of 2.4 N / 5 cm width or more is even more preferred. While a higher tensile strength per unit weight indicates better mechanical strength, there is no particular upper limit; it can be 10 N / 5 cm width or less.

[0164] In addition, in the same manner as the aforementioned basic nonwoven fabric, the following steps are used to confirm whether there is a direction with a tensile strength of 2.0 N / 5 cm width or more per unit weight.

[0165] In addition, since the first nonwoven fabric is produced in the form of a continuous first nonwoven fabric, the fibers tend to be oriented more or less along the production direction. Therefore, in most cases, the production direction when manufacturing nonwoven fabric is the direction with a tensile strength of 2.0 N / 5 cm width or more per unit weight.

[0166] Even though the first nonwoven fabric of the present invention has a tensile strength of 2.0 N / 5 cm or more per unit weight in a direction, it is sometimes impractical due to its weak absolute tensile strength. Therefore, it is preferable to have a tensile strength of 20 N / 5 cm or more in a direction, more preferably a tensile strength of 25 N / 5 cm or more in a direction, and even more preferably a tensile strength of 30 N / 5 cm or more in a direction. This direction is particularly preferred to be the production direction during the manufacture of the first nonwoven fabric.

[0167] As described above, even if the first nonwoven fabric of the present invention has a tensile strength of 20 N / 5 cm or more in one direction, if the tensile strength in another direction is weak, it will easily break in that other direction, sometimes making it unusable. Therefore, the tensile strength in the direction orthogonal to the direction with a tensile strength of 20 N / 5 cm or more is preferably 15 N / 5 cm or more, more preferably 18 N / 5 cm or more, and even more preferably 20 N / 5 cm or more. As described above, the direction with a tensile strength of 20 N / 5 cm or more is preferably the production direction when manufacturing the first nonwoven fabric, therefore, this orthogonal direction is preferably the width direction when manufacturing the first nonwoven fabric.

[0168] The first nonwoven fabric of the present invention has a thickness of 100 μm or less, except that it has a tensile strength of 2.0 N / 5 cm width or more per unit weight. Therefore, it becomes a nonwoven fabric with excellent permeability. The thinner the fabric, the better the permeability; therefore, a thickness of 80 μm or less is preferred, more preferably 70 μm or less, further preferably 60 μm or less, and even more preferably 50 μm or less. The lower limit of the thickness is not particularly limited, but for the purpose of excellent mechanical strength, 10 μm or more is preferred.

[0169] The porosity of the first nonwoven fabric of the present invention is not particularly limited, but in order to achieve excellent permeability, it is preferably 60% or more, more preferably 65% ​​or more, and even more preferably 70% or more. On the other hand, if the porosity is too high, there is a tendency for the mechanical strength to deteriorate, so it is preferably 90% or less, more preferably 85% or less, and even more preferably 80% or less.

[0170] The basis weight of the first nonwoven fabric of the present invention varies depending on the application and is not particularly limited, but if it is 20 g / m²... 2 The following composition results in a low fiber content, allowing for the creation of a thin, nonwoven fabric with excellent permeability, making it suitable for use. For example, it can be a nonwoven fabric with excellent ion permeability and fluid permeability. The lower the basis weight, the better the effect; therefore, 18 g / m² is preferred. 2 The preferred value is 16g / m 2 Below. On the other hand, if the basis weight is too low, the mechanical strength tends to weaken; therefore, 3 g / m³ is more preferable. 2 The above is further preferred to be 5g / m 2 above.

[0171] The apparent density of the first nonwoven fabric of the present invention is not particularly limited, but in order to achieve excellent permeability, the apparent density is preferably 0.35 g / cm³. 3 The following is more preferably 0.30 g / cm³. 3 The following is a further preferred value: 0.28 g / cm³ 3 The following applies. On the other hand, if the apparent density is too low, there is a tendency for the mechanical strength to deteriorate; therefore, the apparent density is preferably 0.10 g / cm³. 3 The above, more preferably 0.15 g / cm³ 3 The above is further preferred to be 0.20 g / cm³. 3 above.

[0172] The first nonwoven fabric of the present invention contains polymethylpentene and exhibits excellent heat resistance. Regarding the degree of heat resistance, the shrinkage rate when heated to 150°C is preferably 5% or less. The lower the shrinkage rate, the better the heat resistance; therefore, the shrinkage rate when heated to 150°C is more preferably 4.5% or less. Ideally, it is 0%.

[0173] (Second nonwoven fabric)

[0174] The second nonwoven fabric of the present invention comprises a core-sheath type composite fiber in which polyethylene is used as a sheath component and polymethylpentene is used 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, has been fused together, wherein the polymethylpentene component accounts for more than 30% by volume of the fiber integral of the second nonwoven fabric, and the polyethylene component accounts for more than 30% by volume of the fiber integral of the second nonwoven fabric.

[0175] Polymethylpentene has a melting point of approximately 220-240°C, which is higher than that of other polyolefins, resulting in excellent heat resistance. Since this heat-resistant polymethylpentene component accounts for more than 30% by volume of the total fiber composition of the second nonwoven fabric, the second nonwoven fabric of the present invention exhibits excellent heat resistance. Because the higher the amount of polymethylpentene, the better the heat resistance, the polymethylpentene component preferably accounts for more than 35% by volume of the total fiber composition of the second nonwoven fabric, more preferably more than 40% by volume. On the other hand, as described later, since it contains more than 30% by volume of polyethylene, resulting in excellent mechanical strength, the polymethylpentene component is 70% by volume or less, preferably 65% ​​by volume or less, more preferably 60% by volume or less.

[0176] Furthermore, the polymethylpentene component constituting the core-sheath type composite fiber can be the same as the polymethylpentene component constituting the first nonwoven fabric, and can be one type or two or more types. When there are two or more types, their total amount is more than 30% by volume of the fiber constituting the second nonwoven fabric.

[0177] The polyethylene component, serving as the sheath component of the core-sheath type composite fiber in the second nonwoven fabric, exhibits excellent weldability. Furthermore, although the polyethylene component has a relatively low melting point and poor heat resistance, its excellent heat resistance is achieved by using polymethylpentene as the core component. Similar to the first nonwoven fabric, this polyethylene component can be high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, ultra-high molecular weight polyethylene, or a polyethylene copolymer. High-density polyethylene is particularly suitable due to its certain degree of hardness, stiffness, and toughness, making it a suitable second nonwoven fabric with excellent workability. Additionally, the polyethylene component can be one type or two or more types.

[0178] The second nonwoven fabric of the present invention includes at least 30% by volume of a polyethylene component with excellent weld strength, which constitutes 30% by volume of the fiber structure of the second nonwoven fabric. Part or all of this polyethylene component participates in the welding process, resulting in excellent mechanical strength. The higher the amount of this polyethylene component, the better the weld strength, and the more likely it is to become a second nonwoven fabric with excellent mechanical strength. Therefore, the polyethylene component preferably accounts for at least 35% by volume of the fiber structure of the second nonwoven fabric, more preferably at least 40% by volume. On the other hand, as described above, in order to achieve excellent heat resistance, it is necessary to include at least 30% by volume of a polymethylpentene component. Therefore, the polyethylene component is 70% by volume or less, preferably 65% ​​by volume or less, more preferably 60% by volume or less. Furthermore, when two or more polyethylene components are included, their total amount is at least 30% by volume of the fiber structure of the second nonwoven fabric.

[0179] In addition, in order to ensure that the second nonwoven fabric can balance heat resistance and mechanical strength, the volume ratio of polyethylene component (sheath component) to polymethylpentene component (core component) of the core-sheath type composite fiber is preferably 30:70~70:30, more preferably 35:65~65:35, and even more preferably 40:60~60:40.

[0180] Furthermore, the polymethylpentene component used as the core does not necessarily have to be a single type; it can be two or more types, and the fiber cross-section is island-shaped. Additionally, in the fiber cross-section, the core and sheath components can be arranged concentrically or with the core component offset from the center. For the purpose of creating a second nonwoven fabric with excellent dimensional stability, a concentric arrangement is preferred.

[0181] The content of the core-sheath type composite fiber is not particularly limited as long as the polymethylpentene component in the second nonwoven fabric accounts for more than 30% by volume of the total fiber composition of the second nonwoven fabric, and the polyethylene component accounts for more than 30% by volume of the total fiber composition of the second nonwoven fabric. In order to easily meet this volume ratio, it is preferred to contain more than 50% by volume, more preferably more than 60% by volume, even more preferably more than 70% by volume, and even more preferably more than 80% by volume.

[0182] The second nonwoven fabric comprises polymethylpentene and polyethylene components in the aforementioned amounts, including core-sheath type composite fibers in which polyethylene is used as the sheath component and polymethylpentene is used as the core component, but in addition, it may include, for example, (1) core-sheath type composite fibers in which resin components other than polymethylpentene and polyethylene are used as the sheath component and polymethylpentene is used as the core component; (2) core-sheath type composite fibers in which polyethylene is used as the sheath component and resin components other than polyethylene and polymethylpentene are used as the core component; (3) core-sheath type composite fibers in which polymethylpentene is used as the sheath component and resin components other than polymethylpentene are used as the core component; (4) core-sheath type composite fibers in which resin components other than polyethylene are used as the sheath component and polyethylene is used as the core component; (5) orange-shaped composite fibers in which polymethylpentene and resin components other than polymethylpentene, or polyethylene and resin components other than polyethylene, alternately extend radially from the center in the fiber cross-section (see reference). Figures 1-5 (6) Multilayer bimetallic composite fibers formed by alternating layers of polymethylpentene and resin components other than polymethylpentene, or polyethylene and resin components other than polyethylene in the fiber cross-section (refer to) Figure 6 (7) Single-component fibers consisting only of polymethylpentene; (8) Single-component fibers consisting only of polyethylene; (9) Single-component fibers consisting of resin components other than polymethylpentene and polyethylene, etc.

[0183] In addition, (5) orange-shaped composite fibers in which polymethylpentene and resin components other than polymethylpentene, or polyethylene and resin components other than polyethylene, alternately extend radially from the center in the fiber cross-section (see reference). Figures 1-5 (6) Multilayer bimetallic composite fibers formed by alternating layers of polymethylpentene and resin components other than polymethylpentene, or polyethylene and resin components other than polyethylene in the fiber cross-section (refer to) Figure 6 By applying mechanical force, it is divided into individual polymethylpentene components, polyethylene components, or resin components other than polyethylene and polymethylpentene components, thereby producing extremely fine fibers with a fiber diameter of less than 4.5 μm. Therefore, it can become a second nonwoven fabric with micropores. In addition, since the surface area of ​​the fibers constituting the second nonwoven fabric is wide, it can become a second nonwoven fabric with excellent resin and liquid retention properties.

[0184] Furthermore, if fluid flows such as water, or mechanical forces such as those from a calender, refining mill, pulper, agitator, or beater are applied to... Figures 1-5 The orange-type composite fiber 1 shown, or Figure 6The multilayer bimetallic composite fiber 1 shown will produce ultrafine fibers with the same irregular cross-sectional shape as the ultrafine fibers described in the first nonwoven fabric, and perform the same function as the first nonwoven fabric.

[0185] Furthermore, similar to the first nonwoven fabric, (7) is a single-component fiber composed only of polymethylpentene; (8) is a single-component fiber composed only of polyethylene; and (9) is a single-component fiber composed of resin components other than polymethylpentene and polyethylene. The fiber diameter can be 0.1 to 30 μm, preferably an ultrafine fiber of 4.5 μm or less, more preferably an ultrafine fiber of 4.0 μm or less, even more preferably an ultrafine fiber of 3.0 μm or less, and even more preferably an ultrafine fiber of 2.0 μm or less. Additionally, such ultrafine fibers can be manufactured in the same manner as the first nonwoven fabric. Furthermore, in order to achieve excellent mechanical strength in the second nonwoven fabric, the ultrafine fibers constituting the second nonwoven fabric are preferably stretched in the same manner as the first nonwoven fabric.

[0186] The second nonwoven fabric of the present invention comprises a core-sheath type composite fiber in which polyethylene is used as the sheath component and polymethylpentene is used as the core component. However, in order to improve the rigidity and compression resistance of the second nonwoven fabric, it can include high-strength fibers with a tensile strength of 5 cN / dtex or higher, the same as that of the first nonwoven fabric. When composed 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 fiber is a composite fiber and the mechanical strength of the second nonwoven fabric is improved by welding 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 the case of any high-strength fiber, the upper limit of the tensile strength is not particularly limited, but is about 50 cN / dtex. This high-strength fiber can be composed of the same resin component as the first nonwoven fabric.

[0187] The second nonwoven fabric of the present invention comprises a core-sheath type composite fiber in which polyethylene is used as the sheath component and polymethylpentene is used as the core component. However, in order to make the heat resistance of the second nonwoven fabric better, it can contain the same heat-resistant fibers as the first nonwoven fabric.

[0188] The second nonwoven fabric of the present invention comprises a core-sheath type composite fiber in which polyethylene is used as the sheath component and polymethylpentene is used as the core component. The fiber diameter of the fibers constituting the second nonwoven fabric, including the core-sheath type composite fiber, is not particularly limited. However, in order to enable the fibers to be uniformly dispersed and thus uniformly impart strength, and to make the second nonwoven fabric with excellent resin and liquid retention, the diameter is preferably 0.1 to 35 μm, more preferably 0.5 to 28 μm, and even more preferably 1 to 20 μm.

[0189] Furthermore, as described above, it is preferable to include 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 composed, for example, of polyolefin resins such as polymethylpentene resins, polypropylene resins, and polyethylene resins; polyester resins such as polyethylene terephthalate and polyester copolymers; and nylon resins such as nylon 6, nylon 66, and nylon copolymers. Among these, ultrafine fibers composed of polyolefin resins with excellent chemical resistance and versatility are preferred, and those composed of polymethylpentene resins or polypropylene resins with excellent heat resistance are even more desirable.

[0190] In addition, as mentioned above, ultrafine fibers can be manufactured by applying mechanical external force to orange-type composite fibers or multilayer bimetallic composite fibers, or by extracting and removing the marine components from island-type composite fibers.

[0191] The ratio (L / D) of the length (L, unit: μm) of the core-sheath type composite fiber constituting the second nonwoven fabric of the present invention to the fiber diameter (D, unit: μm) is 350 or more. If this ratio (L / D) is 350 or more, the fiber length is relatively long compared to the fiber diameter. Therefore, the fibers in the second nonwoven fabric containing the core-sheath type composite fiber are more prone to entanglement. Furthermore, for the same amount of fiber, the number of fibers is less, resulting in fewer fiber junctions and thus higher tensile strength and superior mechanical strength. The larger the ratio (L / D), the stronger this tendency becomes. Therefore, the ratio (L / D) is preferably 400 or more, more preferably 450 or more, further preferably 500 or more, further preferably 550 or more, and even more preferably 600 or more. On the other hand, as mentioned above, when the ratio (L / D) is relatively large, the fibers are more likely to entangle with each other, which tends to act in a direction that hinders the uniform dispersion of the fibers. Therefore, the ratio (L / D) is preferably 7000 or less, more preferably 2000 or less, even more preferably 1600 or less, even more preferably 1300 or less, and even more preferably 1000 or less.

[0192] The fiber diameter of the core-sheath type composite fiber constituting the second nonwoven fabric of the present invention can be less than the stated ratio (L / D), and there is no particular limitation. In order to improve the mechanical strength and heat resistance of the second nonwoven fabric, it is preferable to have a diameter of 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. On the other hand, if the core-sheath type composite fiber is too coarse, it tends to become a second nonwoven fabric with poor fiber dispersion. Therefore, it is preferable to have a diameter of 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.

[0193] Furthermore, the fiber length of the second nonwoven fabric constituent fibers, which includes core-sheath type composite fibers, ultrafine fibers, and heat-resistant fibers, is not particularly limited. The longer the fiber length, the easier it is for the second nonwoven fabric constituent fibers to entangle with each other, and the better the mechanical strength tends to be. Therefore, 6 mm or more is preferred, more preferably 8 mm or more, and even more preferably 10 mm or more. On the other hand, if the fiber length is too long, the fibers are more likely to entangle with each other, and there is a tendency for it to act in a direction that hinders the uniform dispersion of the fibers. Therefore, 105 mm or less is preferred, 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, is fused, a fiber length within the aforementioned range is preferred to facilitate a certain degree of entanglement.

[0194] In addition, the second nonwoven fabric of the present invention may contain two or more core-sheath type composite fibers, high-strength fibers, ultrafine fibers, and heat-resistant fibers that differ in terms of resin composition, resin configuration in fiber cross-section, fiber diameter, ratio (L / D), and / or fiber length.

[0195] In addition to having a ratio (L / D) of 350 or higher, the second nonwoven fabric of the present invention has a thickness of 100 μm or less. Therefore, it becomes a nonwoven fabric with excellent permeability. The thinner the fabric, the better the permeability; therefore, a thickness of 80 μm or less is preferred, more preferably 70 μm or less, even more preferably 60 μm or less, and even more preferably 50 μm or less. The lower limit of the thickness is not particularly limited, but for excellent mechanical strength, a thickness of 10 μm or more is preferred.

[0196] The second nonwoven fabric of the present invention is in a state where the fibers are bonded together by welding with polyethylene components. In addition to welding, the fibers can also be three-dimensionally complexed. This is because the mechanical strength of the second nonwoven fabric is superior due to the three-dimensional complexation. Such three-dimensional complexation can be formed, for example, by using a fluid flow such as water or by needle punching on the fiber web.

[0197] The second nonwoven fabric of the present invention exhibits excellent mechanical strength after the polyethylene component is fused together. Similar to the first nonwoven fabric, it preferably has a direction with a tensile strength of 2.0 N / 5 cm width or more per unit weight. Similar to the first nonwoven fabric, the tensile strength per unit weight is more preferably 2.2 N / 5 cm width or more, and even more preferably 2.4 N / 5 cm width or more. The higher the tensile strength per unit weight, the better the mechanical strength. There is no particular upper limit, but it can be 10 N / 5 cm width or less.

[0198] For the second nonwoven fabric, similar to the first nonwoven fabric, it is preferable that the production direction during the manufacture of the second nonwoven fabric is a direction in which the tensile strength per unit weight is 2.0 N / 5 cm width or more. Furthermore, similar to the first nonwoven fabric, it is preferable to have a direction with a tensile strength of 20 N / 5 cm width or more, more preferably a direction with a tensile strength of 25 N / 5 cm width or more, and even more preferably a direction with a tensile strength of 30 N / 5 cm width or more. This direction is particularly preferred during the manufacture of the second nonwoven fabric.

[0199] Furthermore, similar to the first nonwoven fabric, the tensile strength of the second nonwoven fabric in the direction orthogonal to the direction with a tensile strength of 20 N / 5 cm or more is preferably 15 N / 5 cm or more, more preferably 18 N / 5 cm or more, and even more preferably 20 N / 5 cm or more. The direction with a tensile strength of 20 N / 5 cm or more is preferably the production direction during the manufacture of the second nonwoven fabric; therefore, this orthogonal direction is preferably the width direction during the manufacture of the second nonwoven fabric.

[0200] Similar to the first nonwoven fabric, in order to achieve excellent permeability, 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. On the other hand, if the porosity is too high, there is a tendency for the mechanical strength to deteriorate, so it is preferably 90% or less, more preferably 85% or less, and even more preferably 80% or less.

[0201] The basis weight of the second nonwoven fabric of the present invention varies depending on the application and is not particularly limited, but it may be 20 g / m². 2 The following formula, with its low fiber content, allows for the creation of a thinner second nonwoven fabric with excellent permeability, making it suitable. For example, it can be a second nonwoven fabric with excellent ion permeability and fluid permeability. The lower the basis weight, the better the effect; therefore, 18 g / m² is preferred. 2 The preferred value is 16g / m 2 Below. On the other hand, if the basis weight is too low, there is a tendency for weak mechanical strength; therefore, 3 g / m³ is more preferable. 2 The above is further preferred to be 5g / m 2 above.

[0202] Similar to the first nonwoven fabric, in order to achieve excellent permeability, the apparent density of the second nonwoven fabric of the present invention is preferably 0.35 g / cm³. 3 The following is more preferably 0.30 g / cm³. 3 The following is a further preferred value: 0.28 g / cm³ 3 The following. Furthermore, to achieve excellent mechanical strength, a value of 0.10 g / cm³ is preferred. 3 The above, more preferably 0.15 g / cm³ 3 The above is further preferred to be 0.20 g / cm³.3 above.

[0203] The second nonwoven fabric of the present invention contains polymethylpentene and exhibits excellent heat resistance. Regarding the degree of heat resistance, the shrinkage rate when heated to 150°C is preferably 5% or less. The lower the shrinkage rate, the better the heat resistance; therefore, the shrinkage rate when heated to 150°C is more preferably 4.5% or less. Ideally, it is 0%.

[0204] The second nonwoven fabric of the present invention utilizes polyethylene components for welding and also contains polymethylpentene components. It has a high proportion of polyolefin resin components and excellent chemical resistance; however, it is sometimes not suitable for various applications. Therefore, various processing methods can be implemented to make it more suitable for various applications. For example, it can be colored with pigments or dyes, or charged, or patterned. Hydrophilic groups such as sulfonic acid groups, carboxyl groups, and carbonyl groups can also be introduced.

[0205] (Method for manufacturing the base nonwoven fabric, the first nonwoven fabric, or the second nonwoven fabric)

[0206] The suitable base nonwoven fabric, first nonwoven fabric, or second nonwoven fabric (sometimes collectively referred to as "nonwoven fabric") of the present invention can be manufactured, for example, in the following manner.

[0207] First, fibers containing polymethylpentene and fibers containing polyethylene are prepared. As described above, polymethylpentene and polyethylene components can be contained in the same fiber, similar to a core-sheath type composite fiber where polyethylene is the sheath component and polymethylpentene is the core component; this arrangement is even preferred. Orange-type composite fibers, multilayer bimetallic composite fibers, ultrafine fibers, high-strength fibers, heat-resistant fibers, etc., as described above, can be prepared as needed. Furthermore, as described above, in the case of a second nonwoven fabric, a core-sheath type composite fiber with polyethylene as the sheath component and polymethylpentene as the core component is prepared; in the case of a first nonwoven fabric, the same core-sheath type composite fiber is preferred.

[0208] Next, a fiber web is formed using the prepared fibers. At this point, the fibers are blended to ensure that the polymethylpentene component comprises at least 30% by volume of the fiber, and that the polyethylene component comprises at least 30% by volume of the fiber, and that the polyethylene component can participate in the welding process to form the fiber surface. Furthermore, when producing ultrafine fibers by applying mechanical force to orange-type composite fibers or multilayer bimetallic composite fibers, preparation can be carried out before forming the fiber web by dividing the orange-type composite fibers or multilayer bimetallic composite fibers using, for example, a refining mill, a pulper, a mixer, or a beater. Additionally, by extracting and removing the sea component from island-type composite fibers, ultrafine fibers composed of island components can be prepared.

[0209] There are no particular limitations on the method for forming the fiber web. For example, it can be formed using dry methods such as air-jet web formation or carding, wet methods such as horizontal long web formation, inclined wire short web formation, circular web formation, and long web / circular web combination formation, as well as direct methods such as spunbonding, meltblowing, and electrospinning. Among these, the wet method, which is preferred for easily forming fiber webs with excellent texture, is preferred.

[0210] Next, the fiber web can be heat-treated, and nonwoven fabric can be manufactured by welding fibers containing polyethylene components. Alternatively, water can be applied to the fiber web to further improve its mechanical strength, and / or to incorporate undivided orange-type composite fibers or multilayer bimetallic composite fibers as the fiber web constituent fibers, and to produce extremely fine fibers from these composite fibers. Furthermore, even when water is applied as described later, heat treatment is performed after the water application to weld the fibers containing polyethylene components.

[0211] For the heat treatment of the fiber web, if the fibers containing polyethylene can be fused together, the heat treatment can be carried out under no pressure, under pressure, or by melting the polyethylene component under no pressure and then applying pressure. This heat treatment can be performed, for example, by a hot calender, a hot air through-type heat treatment machine, or a cylindrical contact type heat treatment machine. Regarding the heating temperature, when heating and pressurizing are performed simultaneously, it is preferably within the range of the softening temperature to the melting point of the polyethylene component. When no pressurization is applied, it is preferably within the range of the softening temperature to 30°C higher than the melting point of the polyethylene component.

[0212] For the latter treatment using water flow through a fiber web, any conditions that allow the fibers to become fully entangled and break down unsegmented orange-type composite fibers or multilayer bimetallic composite fibers into individual resin components to produce extremely fine fibers are acceptable. These conditions vary depending on the type of fiber and are therefore not particularly limited. For example, this can be achieved by spraying water at a pressure of 1 MPa to 30 MPa onto the fiber web from a nozzle plate with one or more rows of nozzles arranged in a diameter of 0.05 to 0.3 mm and a pitch of 0.2 to 3 mm. The water flow is applied to one or both sides of the fiber web at least once. Furthermore, when manufacturing nonwoven fabrics without openings, it is preferable to use a support such as a mesh that has a fine non-opening portion (wire diameter), for example, a support with a non-opening portion (wire diameter) of 0.25 mm or less. Conversely, when manufacturing nonwoven fabrics with openings, it is preferable to use a support such as a mesh that supports the fiber web, with a coarse non-opening portion (wire diameter), for example, a support with a non-opening portion (wire diameter) greater than 0.25 mm.

[0213] Furthermore, in cases where the unsegmented orange-shaped composite fibers or multilayer bimetallic composite fibers move due to the action of water flow, making it difficult to segment these composite fibers and generate ultrafine fibers, the composite fibers can be fixed by welding with polyethylene components before the water flow is applied. Even when the composite fibers are welded and fixed in the above manner, ultrafine fibers will be generated by the action of water flow, and the weld will dissipate, with the fibers forming a three-dimensional complex.

[0214] When ultrafine fibers are generated by applying water flow in the above manner to induce three-dimensional complexation between fibers, and then fused together using fibers containing polyethylene (especially core-sheath type composite fibers), the fibers fuse together in a state with numerous junctions in a three-dimensional complex, thus resulting in a nonwoven fabric with superior mechanical strength. Furthermore, the fusion of fibers containing polyethylene can be carried out using the methods and conditions described above.

[0215] To make the nonwoven fabric of the present invention suitable for various applications, and even more easily suitable for various applications, various post-processing can be performed. For example, coloring treatment using pigments or dyes can be performed; charging treatment such as corona discharge, plasma discharge, or water charging can be performed; patterning treatment such as engraving based on embossing rollers or printing using printing resins can be performed; hydrophilic treatment such as sulfonation treatment, fluorine gas treatment, graft polymerization treatment of vinyl monomers, discharge treatment, surfactant treatment, or hydrophilic resin treatment can be performed; etc.

[0216] (Applications of the first and second nonwoven fabrics of this invention)

[0217] The first and second nonwoven fabrics of the present invention have excellent heat resistance, mechanical strength, and permeability, thus making them highly versatile and suitable for various applications. For example, they are suitable for use as membrane supports such as battery separator supports or water electrolysis separator supports, and separators for electrochemical components.

[0218] Furthermore, the membrane support or diaphragm for electrochemical elements of the present invention may be composed solely of the first or second nonwoven fabric of the present invention, or may include nonwoven fabrics, woven fabrics, knitted fabrics, webs, porous membranes, etc., other than the first or second nonwoven fabric of the present invention. Thus, if materials other than the first or second nonwoven fabric of the present invention are included, various effects such as strength imparting or separation are sometimes more superior.

[0219] Examples of batteries in which the first or second nonwoven fabric of the present invention can be used as a separator support include nickel-zinc batteries, zinc or magnesium metal-air batteries, and lithium-ion secondary batteries.

[0220] Furthermore, examples of water electrolysis diaphragms for which the first or second nonwoven fabric of the present invention can be used as diaphragm supports include fluorine-based or hydrocarbon-based proton exchange membranes for proton exchange membrane (PEM) water electrolysis devices, fully aromatic polymer anion exchange membranes for anion exchange membrane (AEM) water electrolysis devices, polyester-based porous membranes or fluorine membranes for alkaline water electrolysis devices, and electrolyte membranes such as yttrium oxide-stabilized zirconium oxide for solid oxide electrolyzers (SOEC).

[0221] Furthermore, examples of electrochemical elements for which the first or second nonwoven fabric of the present invention can be used 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; multivalent 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.

[0222] As an example of applying the first or second nonwoven fabric of the present invention as a membrane support, a support for a separator in a nickel-zinc battery will be described.

[0223] The first nonwoven fabric of the present invention has excellent heat resistance because the polymethylpentene component accounts for more than 30% by volume of the fiber composition of the first nonwoven fabric. In addition, since the polyethylene component accounts for more than 30% by volume of the fiber composition of the first nonwoven fabric, the polyethylene component is fused together, and has a tensile strength of more than 2.0 N / 5 cm width per unit weight in the direction, it has excellent mechanical strength. Furthermore, since the thickness is less than 100 μm, it has excellent permeability. Furthermore, the second nonwoven fabric of the present invention has excellent heat resistance because the polymethylpentene component accounts for more than 30% by volume of the total fiber composition of the second nonwoven fabric. In addition, if the polyethylene component accounts for more than 30% by volume of the total fiber composition of the second nonwoven fabric, the polyethylene component has been fused together, and the ratio (L / D) of the core-sheath type composite fiber is more than 350, the fiber length is longer than the fiber diameter, so the core-sheath type composite fiber is easy to entangle with the fiber composition of the second nonwoven fabric. In addition, if the amount is the same, the number of fibers is less and the number of joints between fibers is less, so the tensile strength is high and the mechanical strength is excellent. Furthermore, since the thickness is less than 100 μm, the permeability is excellent.

[0224] Therefore, a slurry containing layered double hydroxides (LDH) and / or LDH-like compounds (collectively referred to as "LDH"), which are components of the separator in nickel-zinc batteries, is coated onto a first nonwoven fabric or a second nonwoven fabric. The LDH can easily permeate the entire internal pores of the first or second nonwoven fabric. By heating to remove the dispersion medium of the LDH, a separator bearing LDH on the first or second nonwoven fabric can be manufactured. Due to the excellent permeability of the first or second nonwoven fabric, LDH can be uniformly dispersed throughout its internal pores. Heating to remove the dispersion medium of the slurry prevents the first or second nonwoven fabric from shrinking and maintains its shape, thus enabling the manufacture of a separator that maintains a uniformly dispersed state of LDH. Furthermore, in the manufactured separator, the LDH, as a constituent material, is supported by the first or second nonwoven fabric, which has excellent mechanical strength, resulting in a separator with excellent mechanical strength.

[0225] In addition, if the first nonwoven fabric or the second nonwoven fabric contains extremely fine fibers with a fiber diameter of less than 4.5 μm, then each gap in the first nonwoven fabric or the second nonwoven fabric is small and can be a uniformly sized gap. Therefore, LDH can be uniformly carried by the first nonwoven fabric or the second nonwoven fabric as a whole. Furthermore, it can be a state where the path from one side of the diaphragm to the other side is complex and long, thus having the characteristic of not easily generating short circuits caused by dendrites.

[0226] When the first or second nonwoven fabric of the present invention is used as a support for the separator of a nickel-zinc battery, in order to achieve excellent alkali resistance, the first or second nonwoven fabric is preferably composed only of polyolefin fibers, which are composed only of polyolefin resins. For example, it is preferred to be composed only of one or more of the following polyolefin fibers: core-sheath type composite fibers in which polyethylene (especially high-density polyethylene) is used as the sheath component and polymethylpentene is used as the core component; core-sheath type composite fibers in which polyethylene (especially high-density polyethylene) is used as the sheath component and polypropylene is used as the core component; single-component fibers (very fine fibers or high-strength fibers) composed of polyethylene, polypropylene, or polymethylpentene; orange-type or multilayer bimetallic composite fibers composed of polypropylene and polymethylpentene; and other polyolefin fibers composed of polyethylene and polymethylpentene.

[0227] In addition, as described above, the first or second nonwoven fabric of the present invention is preferably composed only of polyolefin fibers. Since it tends to have poor compatibility with slurries containing LDH and is difficult to uniformly carry LDH throughout the first or second nonwoven fabric, it is preferable to introduce hydrophilic groups such as sulfonic acid groups, carboxyl groups, and carbonyl groups, and to add affinity with the dispersion medium of the slurry.

[0228] Example

[0229] The following describes embodiments of the present invention, but the present invention is not limited to the following embodiments.

[0230] (Core-sheath type composite fiber)

[0231] The core component is prepared from polymethylpentene (melting point: 235℃, density: 0.82 g / cm³). 3 The sheath is composed of high-density polyethylene (melting point: 130℃, density: 0.94g / cm³). 3 The core-sheath type composite fiber is composed of (fiber diameter: 17μm, fiber length: 10mm, volume ratio of polymethylpentene to high-density polyethylene: 6:4, and one core component arranged in concentric circles).

[0232] (High-strength core-sheath type composite fiber)

[0233] The core component is prepared from polypropylene (melting point: 168℃, density: 0.91 g / cm³). 3 The sheath is composed of high-density polyethylene (melting point: 135℃, density: 0.94g / cm³). 3 The high-strength composite fiber (fiber diameter: 10μm, fiber length: 5mm, Young's modulus: 45cN / dtex, volume ratio of polypropylene to high-density polyethylene: 6:4, one core component arranged in concentric circles) is composed of a tensile strength of 6.5cN / dtex.

[0234] (High-strength fiber)

[0235] Prepare high-strength fibers composed solely of polypropylene (tensile strength: 9.5 cN / dtex, melting point: 168℃, fiber diameter: 13 μm, fiber length: 10 mm, density: 0.91 g / cm³). 3 ).

[0236] (Orange-type composite fiber)

[0237] Prepare Figure 5 The image shows polypropylene ultrafine fibers (melting point: 160℃, density: 0.91 g / cm³) produced from polypropylene components [which can produce 8 fibers marked 11 in the image, approximately trapezoidal in shape, with a fineness of 0.11 dtex (fiber diameter: 3.8 μm)]. 3 [This can produce 8 polymethylpentene ultrafine fibers (melting point: 235℃, density: 0.82g / cm³) marked 12 in the figure, roughly ladder-shaped, with a fineness of 0.11 dtex (fiber diameter: 4.1μm).] This component, along with polymethylpentene, produces 8 fibers (marked 12 in the figure), approximately ladder-shaped, with a fineness of 0.11 dtex (fiber diameter: 4.1μm). 3The fiber is a stretched orange-shaped composite fiber with a cross-sectional shape of orange and a hollow part, a fineness of 1.7 dtex and a fiber length of 5 mm (volume ratio of polypropylene to polymethylpentene: 6:4).

[0238] (Very fine fibers)

[0239] We plan to manufacture a sea-island type composite fiber (fineness: 1.65 dtex, fiber length: 2 mm) by spinning and stretching using a composite spinning method. The sea component is composed of copolyester, and the island component contains 25 island components composed of polypropylene.

[0240] Then, the island-type composite fiber was immersed in a water bath (temperature: 80℃) composed of 10% by mass sodium hydroxide aqueous solution for 30 minutes. By extracting and removing the copolyester that constitutes the sea component of the island-type composite fiber, ultrafine fibers composed of polypropylene were prepared (average fiber diameter: 2μm, melting point: 172℃, fiber length: 2mm, cross-sectional shape: circular, density: 0.91g / cm³). 3 ).

[0241] (Examples 1-3, Comparative Examples 1-2)

[0242] After the slurry is mixed and dispersed according to the proportions shown in Table 1, fiber webs are formed separately using a wet method (horizontal long web method).

[0243] Then, the fiber web was dried at 140°C without pressure, and simultaneously fused together with the high-density polyethylene component of the core-sheath composite fiber (Examples 1-3, Comparative Example 1) or the high-density polyethylene component of the high-strength core-sheath composite fiber (Comparative Example 2) to produce a nonwoven fabric.

[0244] Then, the nonwoven fabric was immersed in a fuming sulfuric acid solution (15% SO3 solution) at 60°C for 2 minutes, thoroughly washed and dried to introduce sulfonic acid groups onto the fiber surface. The thickness was then adjusted using a calender at room temperature to manufacture diaphragms. The physical properties of these diaphragms are shown in Table 1.

[0245] [Table 1]

[0246]

[0247] For the separators of Examples 1-3, where both polymethylpentene and polyethylene constitute 30% or more of the total nonwoven fabric fibers, the tensile strength per unit weight in the production direction is 2.5 N / 5 cm width or more, exhibiting excellent mechanical strength. Furthermore, the shrinkage rate upon heating at 150°C is less than 5%, demonstrating excellent heat resistance. However, for the separator of Comparative Example 1, where both polymethylpentene and polyethylene constitute less than 30% of the total nonwoven fabric fibers, not only is the tensile strength per unit weight in the production direction less than 2.5 N / 5 cm width, indicating poor mechanical strength, but the shrinkage rate upon heating at 150°C is greater than 5%, indicating poor heat resistance.

[0248] Furthermore, for the diaphragm of Comparative Example 2, where the polymethylpentene content is less than 30% by volume of the nonwoven fabric constituting the fiber as a whole, although the tensile strength per unit weight in the production direction of the diaphragm is more than 2.5 N / 5 cm width, and the mechanical strength is excellent, the shrinkage rate when heated at 150°C is 25%, and the heat resistance is significantly poor.

[0249] (Example 4, Comparative Example 3)

[0250] After the slurry is mixed and dispersed according to the proportions shown in Table 2, fiber webs are formed separately using a wet method (horizontal long web method).

[0251] Then, the fiber web is dried at 140°C without pressure, and simultaneously welded using either the high-density polyethylene component of the core-sheath composite fiber (Example 4) or the high-density polyethylene component of the high-strength core-sheath composite fiber (Comparative Example 3) to produce a welded web.

[0252] Then, the welded mesh is placed on a wire diameter of 0.15 mm, and water jets with a pressure of 8 MPa are sprayed alternately from both sides of 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 perform three-dimensional complexation of the fibers, thereby creating water flow complexing meshes.

[0253] Then, these water-flow complexed networks are dried at 140°C without pressure, and simultaneously welded again using high-density polyethylene components of core-sheath composite fibers or high-strength core-sheath composite fibers to produce welded complexed nonwoven fabrics.

[0254] Then, the welded nonwoven fabric was immersed in a fuming sulfuric acid solution (15% SO3 solution) at 60°C for 2 minutes, followed by thorough washing and drying to introduce sulfonic acid groups onto the fiber surface. The thickness was then adjusted using a room-temperature calender to manufacture diaphragms. The physical properties of these diaphragms are shown in Table 2.

[0255] [Table 2]

[0256]

[0257] For the diaphragm of Example 4, where both polymethylpentene and polyethylene components account for more than 30% by volume of the nonwoven fabric fibers, the tensile strength per unit weight in the production direction is more than 2.5 N / 5 cm width, exhibiting excellent mechanical strength. Furthermore, the shrinkage rate when heated to 150°C is less than 5%, demonstrating excellent heat resistance. It can be used not only as a diaphragm for electrochemical components in high-temperature applications, but also, due to the inclusion of extremely fine fibers produced by orange-type composite fibers, it has a high liquid retention rate under pressure and excellent electrolyte retention. Therefore, it can be used as a diaphragm for manufacturing electrochemical components with excellent workability even in low-temperature applications.

[0258] However, for the diaphragm of Comparative Example 3, where both polymethylpentene and polyethylene components are less than 30% by volume of the nonwoven fabric as a whole fiber, although the tensile strength per unit weight in the production direction of the diaphragm can be ensured to be more than 2.5 N / 5 cm width by water flow complexation, the shrinkage rate when heated at 150°C is 20%, and the heat resistance is significantly poor.

[0259] (Core-sheath type composite fiber A)

[0260] The core component is prepared from polymethylpentene (melting point: 235℃, density: 0.82 g / cm³). 3 The sheath is composed of high-density polyethylene (melting point: 130℃, density: 0.94g / cm³). 3 The core-sheath type composite fiber A (fiber diameter: 17μm, fiber length: 10mm, ratio (L / D) = 588, volume ratio of polymethylpentene to high-density polyethylene: 6:4, one core component arranged in concentric circles) is composed of a core-sheath type composite fiber.

[0261] (Core-sheath type composite fiber B)

[0262] Prepare a core-sheath composite fiber B that is identical to the core-sheath composite fiber A (fiber diameter: 17μm, fiber length: 5mm, ratio (L / D) = 294, volume ratio of polymethylpentene to high-density polyethylene: 6:4, and one core component arranged in concentric circles, except that the fiber length is shorter than that of the core-sheath composite fiber A (5mm long).

[0263] (High-strength core-sheath type composite fiber)

[0264] The core component is prepared from polypropylene (melting point: 168℃, density: 0.91 g / cm³). 3 The sheath is composed of high-density polyethylene (melting point: 135℃, density: 0.94g / cm³). 3The high-strength core-sheath composite fiber (fiber diameter: 10μm, fiber length: 5mm, ratio (L / D) = 500, volume ratio of polypropylene to high-density polyethylene: 6:4, one core component arranged in concentric circles) has a tensile strength of 6.5cN / dtex.

[0265] (Very fine fibers)

[0266] We plan to manufacture a sea-island type composite fiber (fineness: 1.65 dtex, fiber length: 2 mm) by spinning and stretching using a composite spinning method. The sea component is composed of copolyester, and the island component contains 25 island components composed of polypropylene.

[0267] Then, the island-type composite fiber was immersed in a water bath (temperature: 80℃) composed of 10% sodium hydroxide aqueous solution for 30 minutes. The copolyester, which constitutes the sea element of the island-type composite fiber, was removed by extraction to prepare ultrafine fibers composed of polypropylene (average fiber diameter: 2μm, melting point: 172℃, fiber length: 2mm, ratio (L / D) = 1000, cross-sectional shape: circular, density: 0.91g / cm³). 3 ).

[0268] (Heat-resistant fiber)

[0269] Prepare heat-resistant fibers made of polyphenylene sulfide (PPS) (fiber diameter: 9.7 μm, fiber length: 6 mm, ratio (L / D) = 619).

[0270] (Examples 11-13, Comparative Examples 11-15)

[0271] After the slurry is mixed and dispersed according to the proportions shown in Table 3, fiber webs are formed separately using a wet method (horizontal long web method).

[0272] Then, the fiber web was dried at 140°C without pressure, and simultaneously fused together 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 components of high-strength core-sheath type composite fibers (Comparative Example 15) to produce a first nonwoven fabric or a second nonwoven fabric.

[0273] Then, in having Figure 7 The schematic cross-section of the discharge treatment device shown depicts a first or second nonwoven fabric 5 sandwiched between dielectrics 2a and 2b. Under atmospheric pressure and in the presence of air (humidity: 60% RH), an AC voltage (voltage: 0.1 kVp, output: 2.8 kW, output per unit area: 1.83 W / cm²) is applied between the two electrodes 1a and 1b for 30 seconds. 2(Frequency: 25kHz, Waveform: Sine wave) Plasma treatment is performed to generate discharge inside the first or second nonwoven fabric, introducing hydrophilic groups such as carboxyl or carbonyl groups onto the fiber surface. Then, the thickness is adjusted using a room-temperature calender to manufacture supports. The physical properties of these supports are shown in Table 3.

[0274] Additionally, evaluate the "Resistance" in Table 3 by following these steps.

[0275] (1) Prepare a mixture of 28.5% by mass zirconium oxide, 1.5% by mass acrylic adhesive, and 70% by mass pure water.

[0276] (2) The coating rod is started with a gap of 50 μm between it and each of the first or second nonwoven fabrics to coat the above mixture onto one side of the first or second nonwoven fabric.

[0277] (3) Dry the coated first nonwoven fabric or second nonwoven fabric at 100°C for 10 minutes to produce inorganic particles coated on the first nonwoven fabric or second nonwoven fabric.

[0278] (4) Take three 50mm square samples coated with the first or second nonwoven fabric by each inorganic particle and determine their respective mass.

[0279] (5) Immerse each sample in an immersion solution with a density of 1.3 g / cm³. 3 (Temperature: 20℃) Potassium hydroxide aqueous solution was used to absorb 80% of the solution relative to the mass of each sample.

[0280] (6) After absorption, each sample was clamped with a 35mm square nickel plate and the resistance was measured when a current of 1kHz and 1mA was applied.

[0281] (7) The case where the arithmetic mean resistance of the three samples is less than 0.4Ω is evaluated as “〇”, the case where it is higher than 0.4Ω but less than 0.6Ω is evaluated as “△”, and the case where it is higher than 0.6Ω is evaluated as “×”.

[0282] [Table 3]

[0283]

[0284] For the support in Examples 11-13, where both polymethylpentene and polyethylene components account for 30% or more (32.5% or 42.5% by volume) of the fiber composition of the first or second nonwoven fabric, and for Example 11, which contains polymethylpentene / polyethylene core-sheath type composite fibers with a ratio (L / D) of 350 or more and where both polymethylpentene and polyethylene components account for 30% or more (32.5% or 42.5% by volume) of the fiber composition of the first or second nonwoven fabric, The support structure has a tensile strength of 2.0 N / 5 cm width or more per unit weight in the production direction (2.0~2.4 N / 5 cm width), exhibiting excellent mechanical strength. Furthermore, its shrinkage rate upon heating at 150°C is less than 5% (4.5%, 2.0%), demonstrating excellent heat resistance. The support structure is also thin (less than 100 μm, 45~50 μm) and has low electrical resistance (less than 0.4 Ω). Therefore, it is possible to produce membranes in which zirconium oxide is carried throughout the internal voids of the support structure, resulting in excellent permeability. In particular, the support structure containing polyphenylene sulfide fibers as heat-resistant fibers has a heat shrinkage rate of only 2.0% at 150°C, demonstrating excellent heat resistance.

[0285] However, the support of Comparative Example 11, which has a thickness greater than 100 μm (103 μm), has a high resistance (greater than 0.6 Ω), so it can only produce a film in which zirconium oxide is locally present in the internal voids of the support, resulting in poor permeability.

[0286] Furthermore, in Comparative Example 12, where both polymethylpentene and polyethylene components constitute less than 30% (25% by volume) of the fiber composition of the first or second nonwoven fabric, the tensile strength per unit weight in the production direction of the support is less than 2.0 N / 5 cm width (1.4 N / 5 cm width), indicating poor mechanical strength. Moreover, the shrinkage rate when heated at 150°C is greater than 5% (10.0%), indicating poor heat resistance.

[0287] Furthermore, for the supports of Comparative Examples 13 and 14, which contain a ratio (L / D) of less than 350 (294) and use polymethylpentene as the core component and high-density polyethylene as the sheath component, the tensile strength per unit weight in the production direction of the support is less than 2.0 N / 5 cm width (1.7 N / 5 cm width), indicating poor mechanical strength.

[0288] In addition, the support of Comparative Example 13 has a slightly lower porosity (61%) and a slightly higher electrical resistance (0.4~0.6Ω), so zirconium oxide tends to exist locally in the internal voids of the support, resulting in slightly poorer permeability.

[0289] Furthermore, the support of Comparative Example 15, in which the polymethylpentene content is less than 30% (0% by volume) of the fiber composition of the first or second nonwoven fabric, has a shrinkage rate greater than 5% (25.0%) when heated at 150°C, indicating poor heat resistance.

[0290] Industrial applicability

[0291] The nonwoven fabric of this invention exhibits excellent heat resistance and mechanical strength, thus possessing high versatility for various applications. For example, it is suitable for use as a separator for electrochemical components, a separator support for batteries such as nickel-zinc batteries, and a separator support for water electrolysis.

[0292] In addition, examples of electrochemical components 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; multivalent ion batteries such as magnesium, aluminum, calcium, and zinc; lithium-sulfur batteries; lithium-zinc metal-air batteries; lithium-ion capacitors; fluoride-ion batteries; and potassium-ion batteries. In particular, even when used as separators in alkaline secondary batteries such as nickel-cadmium and nickel-hydrogen batteries, they exhibit excellent heat resistance and mechanical strength, thus enabling the manufacture of alkaline secondary batteries suitable for automotive applications requiring heat resistance.

[0293] Another nonwoven fabric of the present invention has excellent heat resistance, mechanical strength and permeability, and is therefore highly versatile for various applications. For example, it is suitable for use as a membrane support for battery separators or water electrolysis separators, and as a separator for electrochemical components.

Claims

1. A nonwoven fabric comprising polymethylpentene and polyethylene components, wherein the polyethylene components are fused together, characterized in that, The polymethylpentene component accounts for more than 30% by volume of the total fiber composition of the nonwoven fabric, and the polyethylene component accounts for more than 30% by volume of the total fiber composition of the nonwoven fabric.

2. The nonwoven fabric according to claim 1, characterized in that, It comprises a core-sheath type composite fiber that uses polyethylene as the sheath component and polymethylpentene as the core component as the nonwoven fabric component.

3. The nonwoven fabric according to claim 2, characterized in that, It further includes extremely fine fibers with a fiber diameter of less than 4.5 μm as the constituent fibers of the nonwoven fabric.

4. The nonwoven fabric according to claim 1, characterized in that, It has a tensile strength of 2.5 N / 5 cm width or more per unit weight.

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

6. The nonwoven fabric according to claim 1, characterized in that, The liquid retention rate after being pressurized at 5.7 MPa is over 5%.

7. A diaphragm for an electrochemical element, characterized in that, It comprises the nonwoven fabric according to any one of claims 1 to 6.

8. A nonwoven fabric comprising polymethylpentene and polyethylene, wherein the polyethylene component is fused together, and wherein the polymethylpentene component constitutes at least 30% by volume of the nonwoven fabric fibers, and the polyethylene component constitutes at least 30% by volume of the nonwoven fabric fibers, characterized in that, The nonwoven fabric has a thickness of less than 100 μm and has a tensile strength of more than 2.0 N / 5 cm width per unit weight in a direction.

9. The nonwoven fabric according to claim 8, characterized in that, It comprises a core-sheath type composite fiber that uses polyethylene as the sheath component and polymethylpentene as the core component as the nonwoven fabric component.

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

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

12. The nonwoven fabric according to claim 8, characterized in that, 20g / m 2 the following.

13. A nonwoven fabric comprising a core-sheath type composite fiber in which polyethylene is used as a sheath component and polymethylpentene is used as a core component, wherein the polyethylene component, which is the sheath component of the core-sheath type composite fiber, has been fused together, and wherein the polymethylpentene component accounts for more than 30% by volume of the total fiber composition of the nonwoven fabric, and the polyethylene component accounts for more than 30% by volume of the total fiber composition of the nonwoven fabric, characterized in that... The thickness of the nonwoven fabric is less than 100 μm, and the ratio (L / D) of the length (L, unit: μm) of the core-sheath type composite fiber to the fiber diameter (D, unit: μm) is more than 350.

14. The nonwoven fabric according to claim 13, characterized in that, It has a tensile strength of 2.0 N / 5 cm width or more per unit weight.

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

16. The nonwoven fabric according to claim 13, characterized in that, 20g / m 2 the following.

17. A membrane support, characterized in that, It comprises the nonwoven fabric as described in any one of claims 8 to 16.

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