JP4065637B2 - Battery separator and method for producing the same - Google Patents

Description

この表１から明らかなように、本発明のセパレータは安定して電池を製造できるものであった。また、電池を繰り返し使用しても容量が低下しにくいものであった。
【００４９】
【発明の効果】
本発明の電池用セパレータは、フィルム状の層によって極板のバリを受け止めることができ、また引張り強さに優れ、巻回するなどの際に破断しにくいものであるため、ショートしにくいものである。また、電池使用時においても、フィルム状の層によって金属結晶を受け止めることができるため、ショートしにくいものである。更に、フィルム状の層によって適度な腰があるため、電池製造時の取り扱い性にも優れるものである。
また、本発明のセパレータは繊維層を備えているため、この繊維層によって電解液を保持して、電池の起電反応を円滑に行なわせることができるものである。
【００５０】
本発明の電池用セパレータの製造方法は、前記セパレータを簡易に製造することができる。
また、微孔フィルムと繊維ウエブ又は不織布とを一体化した場合と異なり、適度な微孔（極板で発生した酸素等が通過できる程度）を有するセパレータを容易に製造できる方法である。
【図面の簡単な説明】
【図１】 オレンジ型複合熱可塑性繊維の模式的断面図
【図２】 実施例１のセパレータの断面の電子顕微鏡写真
【図３】 比較例１のセパレータの断面の電子顕微鏡写真
【符号の説明】
１ オレンジ型複合熱可塑性繊維
１１ 高密度ポリエチレン成分
１２ ポリプロピレン成分[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a battery separator and a method for producing the same.
[0002]
[Prior art]
Conventionally, a separator is used between the positive electrode and the negative electrode in order to separate the positive electrode and the negative electrode of the battery to prevent a short circuit and to keep the electrolyte solution and to smoothly perform an electromotive reaction.
In recent years, with the reduction in size and weight of electronic devices, the space occupied by batteries has become narrower. ing. For that purpose, since the amount of the active material of the electrode needs to be increased, the volume occupied by the separator is inevitably reduced. In addition, the volume occupied by the separator is inevitably reduced from the viewpoint of reducing the electrical resistance.
Conventionally, a nonwoven fabric is used as such a separator, but when the thickness of the separator (nonwoven fabric) is reduced as described above and the thickness reaches a level of 0.15 mm or less, the amount of fibers constituting the nonwoven fabric is reduced. The hole diameter tends to increase due to the decrease, and it is necessary to wind around the electrode plate group with a large tension to reduce the volume occupied by the separator. There was a tendency to become easy.
Also, for example, in the case of a secondary battery such as a nickel-hydrogen battery or a nickel-cadmium battery, a metal crystal is formed while charging and discharging are repeated, and the metal crystal penetrates the separator and shorts. There was also.
[0003]
[Problems to be solved by the invention]
The present invention has been made to solve the above-described problems, and provides a battery separator that is not easily short-circuited by a metal crystal when forming an electrode plate group or when a battery is used. An object is to provide a manufacturing method.
[0004]
[Means for Solving the Problems]
The battery separator of the present invention (hereinafter referred to as “separator”) has a film-like layer formed by pressure bonding of fibers on the entire surface in a direction perpendicular to the thickness direction of the nonwoven fabric. Both sides A non-woven fabric provided with a fiber layer containing fibers bonded to the film-like layer From the group of non-woven fabrics having a film-like layer formed by pressure-bonding fibers on one side and a fiber layer containing fibers joined to the film-like layer on the other side, in the direction perpendicular to the thickness direction of the non-woven fabric. Selected non-woven fabric Consists of. Since the film-like layer is present over the entire surface, the film-like layer can catch the burr of the electrode plate, and has excellent tensile strength and is difficult to break when wound. Therefore, it is difficult to short-circuit when forming the electrode plate group. In addition, even when the battery is used, the metal crystal can be received by the film-like layer, so that the battery can be prevented from being short-circuited. Furthermore, since an appropriate waist is imparted by the film-like layer, it is excellent in handleability during battery production. Moreover, since the separator of this invention is equipped with the fiber layer, it can hold | maintain electrolyte solution by this fiber layer and can perform an electromotive reaction smoothly.
[0005]
In the method for producing a battery separator of the present invention, after a heat treatment and a pressure treatment are performed on the entire fiber web containing thermoplastic fibers to form a pressure-bonded fiber web, one or both sides of the pressure-bonded fiber web are formed. This is a method for manufacturing a separator as described above, in which a fluid flow is applied to the substrate.
Thus, according to the manufacturing method of the present invention, the separator as described above can be easily manufactured.
Further, unlike the case where the microporous film and the fiber web or the nonwoven fabric are integrated, it is a method by which a separator having appropriate micropores (a degree that allows oxygen generated in the electrode plate to pass through) can be easily manufactured.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The separator of the present invention can receive the burrs and metal crystals of the electrode plate, and has a film-like layer formed by pressure bonding of the fibers on the entire surface in the direction perpendicular to the thickness direction so as to be excellent in tensile strength. . In the case where a film-like region obtained by pressure bonding of fibers is partially provided in a direction perpendicular to the thickness direction of the separator, the above-described effect is insufficient.
“Thickness direction of nonwoven fabric (separator)” is 1 cm. ² The direction perpendicular to the front and back virtual planes that can come into contact with the fibers constituting the surface of the nonwoven fabric (separator) when 500 g is loaded.
[0007]
The film-like layer of the separator of the present invention is a layer formed by pressure bonding of fibers. This “crimping” refers to a state in which individual fibers are deformed so as not to retain the cross-sectional shape inherent to each fiber, and are in close contact and integrated with surrounding fibers. In addition, the resin which has not been crimped | bonded in the crimped fiber may be contained. Such a film-like layer can be confirmed from, for example, an electron micrograph in a cross section of a nonwoven fabric (separator).
[0008]
Thus, since the film-like layer of the present invention is formed by pressure bonding of fibers, the nonwoven fabric (separator) of the present invention has a certain degree of air permeability. However, the high air permeability of the nonwoven fabric (separator) of the present invention means that the degree of pressure bonding of the fibers is low, and as a result, it is difficult to catch the burrs and metal crystals of the electrode plate, Since the strength becomes low, the air permeability of the nonwoven fabric (separator) of the present invention is preferably 15 cm / s or less, more preferably 10 cm / s or less. When the separator of the present invention is used for a sealed nickel-hydrogen battery or nickel-cadmium battery, oxygen generated from the positive electrode is quickly permeated to the negative electrode during overcharge to suppress an increase in battery internal pressure. It is preferable that it is 2 cm / s or more.
The “air permeability” in the present invention refers to a value obtained by measurement according to the method defined in JIS L 1096 (6.27.1 A method (Fragile method)).
[0009]
Similarly, the average pore diameter of the nonwoven fabric (separator) of the present invention is preferably 15 μm or less so that it can catch burrs and metal crystals of the electrode plate and is excellent in tensile strength, and is preferably 10 μm or less. More preferred. When the separator of the present invention is used for a sealed nickel-hydrogen battery or nickel-cadmium battery, oxygen generated from the positive electrode is quickly permeated to the negative electrode during overcharge to suppress an increase in battery internal pressure. It is preferable that the thickness is 3 μm or more.
The “average pore diameter” in the present invention refers to a value measured by a bubble point method using a porometer (manufactured by Coulter).
[0010]
The nonwoven fabric (separator) of the present invention preferably has a tensile strength in at least one direction of 150 N / 50 mm width or more, so that it does not break due to tension when forming the electrode plate group, and 170 N / 50 mm width. More preferably, it is more preferably 190 N / 50 mm width or more.
Conventionally, wet nonwoven fabrics have been used as nonwoven fabrics constituting separators from the viewpoint of uniform dispersibility of fibers, but the fiber length of fibers that can be used in this wet nonwoven fabric is about 25 mm at the maximum, and the entanglement between fibers is also weak. In some cases, it does not have a tensile strength of 150 N / 50 mm width or more.
On the other hand, the nonwoven fabric (separator) of the present invention has excellent tensile strength of 150 N / 50 mm width or more even if it is composed of fibers having a fiber length of 25 mm or less, which is excellent in uniform dispersibility of fibers.
This tensile strength is a value in at least one direction. Generally, when manufacturing a nonwoven fabric, fibers tend to be oriented in the flow direction of the nonwoven fabric, so the tensile strength in the flow direction of the nonwoven fabric (so-called vertical direction). Is the strongest.
"Tensile strength" is a non-woven fabric having a width of 50 mm fixed between chucks (distance between chucks: 10 cm) of a tensile strength tester (Orientec, Tensilon UTM-III-100), and a tensile speed of 300 mm / min. This is the value when pulled with.
[0011]
The thickness of the film-like layer is about 10 to 150 μm so that it can catch burrs and metal crystals of the electrode plate, and is excellent in tensile strength and can be increased in battery capacity. Is preferable, and it is more preferable that it is about 20-100 micrometers.
[0012]
The fiber that constitutes the film-like layer is preferably a thermoplastic fiber so that it can be easily pressure-bonded. Examples of the thermoplastic fiber include polyester resins, polyamide resins, polyolefin resins (eg, polyethylene resins, polypropylene resins, etc.), crystalline thermoplastic resins such as polyvinylidene chloride resins, and polyvinyl chloride resins. Resins, polystyrene-based resins, polyacrylonitrile-based resins, polyvinyl alcohol-based amorphous thermoplastic resins, and the like can be used.
Among these, when used for an alkaline battery, it is preferably composed of a polyolefin resin so as to be excellent in alkali resistance and oxidation resistance.
Examples of the polyolefin resin include polyethylene resins (for example, ultrahigh molecular weight polyethylene, high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, ethylene copolymer, etc.), polypropylene resins ( For example, polypropylene, a propylene copolymer, etc.), polymethylpentene resin (for example, polymethylpentene, methylpentene copolymer, etc.) etc. can be mentioned.
[0013]
It should be noted that the composite thermoplastic fiber composed of two or more types of thermoplastic resins having different pressure bonding properties can maintain fiber strength with at least one type of thermoplastic resin even when at least one type of thermoplastic resin is pressure bonded, and has a high tensile strength. Since it can be set as the more excellent nonwoven fabric (separator), it is suitable.
The cross-sectional shape of the composite thermoplastic fiber can be, for example, a core-sheath type, an eccentric type, a side-by-side type, a sea-island type, an orange type, or a multiple bimetal type.
When the separator of the present invention is used for an alkaline battery, it is preferable that the composite thermoplastic fiber is composed only of the polyolefin resin as described above so that the composite thermoplastic fiber is also excellent in alkali resistance and oxidation resistance.
Examples of the composite thermoplastic fiber composed only of such a polyolefin resin include polyethylene resins (for example, ultrahigh molecular weight polyethylene, high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, ethylene copolymer). Polymer) and a polypropylene resin, and a combination of high-density polyethylene and low-density polyethylene.
[0014]
Moreover, if the high-strength fiber having a tensile strength of 4.4 cN / dtex or more is included as the fiber that is the basis of the film-like layer, the burrs and metal crystals of the electrode plate are difficult to penetrate the separator. Therefore, it is preferable. The tensile strength of the high strength fiber is preferably 6.2 cN / dtex or more, more preferably 7.9 cN / dtex or more, and still more preferably 10.6 cN / dtex or more. In addition, although the upper limit of the tensile strength of a high strength fiber is not specifically limited, about 50 cN / dtex is suitable.
“Tensile strength” in the present invention refers to a value measured by a method defined in JIS L 1015 (chemical fiber staple test method).
When using the separator of this invention for an alkaline battery, it is preferable that resin which comprises a high strength fiber consists of polyolefin resin so that it may be excellent in alkali resistance and oxidation resistance. More specifically, for example, polyethylene resins (for example, ultrahigh molecular weight polyethylene, high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, ethylene copolymer, etc.), polypropylene resins (for example, , Polypropylene, propylene copolymer, etc.) and polymethylpentene resin (for example, polymethylpentene, methylpentene copolymer, etc.). Among these, it is preferable to consist of a polypropylene resin or a polyethylene resin.
The high-strength fiber may be composed of one type of resin component, or two or more types of resin components may be mixed or combined. This high-strength fiber is also preferably combined with two or more kinds of resin components because it can contribute to the formation of a film-like layer and can suppress burr in the electrode plate and penetration of metal crystals. The fiber cross-sectional shape of the composite high-strength fiber can be, for example, a core-sheath type, an eccentric type, a side-by-side type, a sea-island type, an orange type, or a multiple bimetal type, contributing to the formation of a film-like layer The core-sheath type, the eccentric type or the sea-island type is preferable, and the core-sheath type is particularly preferable. More specifically, a high-strength fiber having a polypropylene resin as a core component and a polyethylene resin as a sheath component, which has a large difference in terms of pressure-bonding properties, is preferable.
[0015]
Since the nonwoven fabric of the present invention includes a fiber layer containing fibers bonded to the above-mentioned film-like layer on one side or both sides (preferably both sides) of the above-described film-like layer, an electrolyte solution is formed by this fiber layer. Can be maintained to ensure a smooth electromotive reaction.
Examples of the bonding state of the fiber constituting the fiber layer with the film-like layer include pressure bonding, fusion, part of the fiber constituting the film-like layer, and the like.
The fibers constituting the fiber layer may be composed of the same resin as the fiber that is the basis of the film-like layer, or may be composed of a different resin. It is preferable that at least one kind of fiber resin which is the basis of the layer is included.
When the separator of the present invention is used for an alkaline battery, it is preferable that the fiber that is the basis of the film-like layer is composed of a polyolefin resin as described above. Is also preferably made of a polyolefin resin. More specifically, polyethylene resins (for example, ultra-high molecular weight polyethylene, high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, ethylene copolymer, etc.), polypropylene resins (for example, polypropylene) , Propylene copolymer, etc.) and polymethylpentene resin (eg, polymethylpentene, methylpentene copolymer, etc.). Among these, it is more preferable that the resin is composed of a polypropylene resin or a polyethylene resin.
[0016]
Although the fiber diameter of the fiber which comprises a fiber layer is not specifically limited, Since it is excellent in the retainability of electrolyte solution, it is suitable if the fiber diameter contains 6 micrometers or less. More preferably, it is 5 μm or less. The lower limit is not particularly limited, but about 0.1 μm is appropriate.
Since the higher the abundance ratio of such ultrafine fibers, the better the retention of the electrolyte solution, it is preferable that each fiber layer contains 10 mass% or more, and more preferably contains 20 mass% or more. Preferably, 30 mass% or more is contained.
The fiber diameter in the present invention refers to the fiber diameter when the fiber cross-sectional shape is circular, and when the fiber cross-sectional shape is non-circular, it refers to the fiber diameter when the fiber cross-sectional shape is converted to a circle.
[0017]
The fiber constituting the fiber layer has a tensile strength of 4.4 cN / dtex or more (preferably 6.2 cN / dtex or more, more preferably 7.9 cN / dtex or more, 10.6 cN / dtex or more. It is more preferable that the high-strength fibers are more preferable because the burrs and metal crystals of the electrode plate are less likely to penetrate the separator.
This high-strength fiber is preferably composed of a polyolefin resin constituting the high-strength fiber constituting the film-like layer, and more preferably composed of a polypropylene resin or a polyethylene resin.
Such high-strength fibers are preferably contained in an amount of 5 mass% or more in each fiber layer, and more preferably 10 mass% or more.
[0018]
The fiber length of the fibers constituting such a fiber layer (for example, ultrafine fibers, high strength fibers, etc.) is not particularly limited, but is preferably 25 mm or less, and 20 mm so that the dispersibility of the fibers is excellent. More preferably, it is more preferably 15 mm or less.
[0019]
Thus, although the fiber layer of the nonwoven fabric (separator) of this invention contains the fiber joined with the film-like layer, when the fiber which comprises a fiber layer is joined with the film-like layer, it will be called dropping of a fiber. Since problems are less likely to occur, the more fibers that are bonded to the film-like layer, the better. In addition, even if the fibers constituting the fiber layer are not bonded to the film-like layer, the drop-off problem is solved if the fibers are bonded to another fiber bonded to the film-like layer constituting the fiber layer. it can.
[0020]
The separator of the present invention comprises a nonwoven fabric provided with a fiber layer on one or both sides of a film-like layer, and preferably has a fiber layer on both sides. When the fiber layers are provided on both surfaces, both surfaces do not need to be composed of the same fiber layer, and may be different in terms of the resin composition of the constituent fibers, the fineness, the fiber length, the composition of the constituent fibers, and the like.
[0021]
When the separator of the present invention is used for an alkaline battery, a polyolefin resin is suitable as the resin that constitutes the fiber that forms the fiber layer and the fiber that is the basis of the film-like layer of the separator of the present invention. , Electrolyte retention tends to be poor. Therefore, hydrophilization treatment selected from sulfonation treatment, fluorine gas treatment, vinyl monomer graft polymerization treatment, surfactant treatment, discharge treatment, or hydrophilic resin application treatment so as to have excellent electrolyte retention. Is preferably applied to the nonwoven fabric. These hydrophilic treatments will be described in the manufacturing method described later.
[0022]
Next, the manufacturing method of the separator (nonwoven fabric) of the present invention will be described.
The separator (nonwoven fabric) as described above of the present invention is subjected to heat treatment and pressure treatment on the entire fiber web containing thermoplastic fibers to form a crimped fiber web, and then one side of the crimped fiber web. Or it can manufacture by making a fluid flow act on both surfaces.
According to the manufacturing method of the present invention, first, a pressure-bonded fiber web consisting only of a film-like layer having a low air permeability and a small average pore diameter is formed by heat treatment and pressure treatment, and then the film is formed by the action of a fluid flow. Since the fibers constituting the layer are unraveled to expose the fibers and form a fiber layer, the separator as described above, that is, the burrs of the electrode plates and the penetration of metal crystals can be suppressed, and the tensile strength Can be easily manufactured.
Note that the air permeability can be adjusted as appropriate by adjusting the conditions of the heat treatment, the pressure treatment, or the fluid flow, and thus can correspond to various batteries.
In addition, since the thickness can be reduced by heat treatment and pressure treatment, a separator corresponding to an increase in capacity can be easily manufactured.
Furthermore, since it is a method which can be manufactured without laminating a microporous film and a nonwoven fabric or fiber web, it is a method which can manufacture a separator simply.
[0023]
In the method for producing a separator (nonwoven fabric) of the present invention, a fiber web containing thermoplastic fibers is first produced.
Examples of this thermoplastic fiber include polyester resins, polyamide resins, polyolefin resins (eg, polyethylene resins, polypropylene resins, etc.), crystalline thermoplastic resins such as polyvinylidene chloride resins, and polyvinyl chloride. One or more types of thermoplastic fibers composed of one or more types of resins such as amorphous thermoplastic resins such as a series resin, a polystyrene type resin, a polyacrylonitrile type resin, and a polyvinyl alcohol type can be used.
When the separator of the present invention is used for an alkaline battery, it is preferable to use a fiber composed of a polyolefin-based resin so as to be excellent in alkali resistance and oxidation resistance.
Examples of the polyolefin resin include polyethylene resins (for example, ultrahigh molecular weight polyethylene, high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, ethylene copolymer, etc.), polypropylene resins ( Examples thereof include polypropylene and propylene copolymers) and polymethylpentene resins (for example, polymethylpentene and methylpentene copolymers).
[0024]
When a composite thermoplastic fiber composed of two or more types of thermoplastic resins having different pressure bonding properties is used as this thermoplastic fiber, even if at least one type of thermoplastic resin is pressure bonded, the fiber strength is increased by at least one type of thermoplastic resin. Therefore, a separator (nonwoven fabric) with more excellent tensile strength can be obtained, and at least one thermoplastic resin that has been pressure-bonded is destroyed and not pressure-bonded by the action of a fluid flow that is a subsequent process. It is preferable because fibers (preferably ultrafine fibers having a fiber diameter of 6 μm or less) made of at least one thermoplastic resin are generated to easily form a fiber layer.
The cross-sectional shape of the composite thermoplastic fiber can be, for example, a core-sheath type, an eccentric type, a side-by-side type, a sea-island type, an orange type, or a multiple bimetal type. Among these, the side-by-side type, the orange type, and the multi-bimetal type, which are easy to break down at least one thermoplastic resin that is pressure-bonded by the action of the fluid flow, are preferable, and the orange type and the multi-bimetal type that easily generate ultrafine fibers. It is more preferable that the thermoplastic resin to be pressure-bonded is an orange type that can be uniformly positioned on the fiber surface.
The fineness of such a composite thermoplastic fiber is preferably about 0.1 to 7 dtex (decitex) so as to easily generate ultrafine fibers having a fiber diameter of 6 μm or less.
Such composite thermoplastic fibers are preferably contained in the fiber web in an amount of 5 mass% or more.
“Two or more types of thermoplastic resins having different crimping properties” means a case where a heat treatment and a pressure treatment as described below are performed on a fiber web composed of fibers made of individual thermoplastic resins. And a combination of thermoplastic resins having different tensile strengths by 10% or more. A major factor affecting the crimpability is the melting point of the thermoplastic resin. If the difference in melting point of the thermoplastic resin is 10 ° C. or more (preferably 20 ° C. or more), two or more types of thermoplastic resins having different crimp properties are used. In many cases.
When used for an alkaline battery, the composite thermoplastic fiber is preferably composed only of the polyolefin resin as described above so that the composite thermoplastic fiber is also excellent in alkali resistance and oxidation resistance.
Examples of the composite thermoplastic fiber composed only of such a polyolefin resin include polyethylene resins (for example, ultrahigh molecular weight polyethylene, high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, ethylene copolymer). Polymer) and a polypropylene resin, and a combination of high-density polyethylene and low-density polyethylene.
The “melting point” in the present invention refers to a temperature giving a maximum value of a melting endothermic curve obtained by heating from room temperature at a heating rate of 10 ° C./min using a differential calorimeter.
[0025]
The thermoplastic fiber has a tensile strength of 4.4 cN / dtex or more (preferably 6.2 cN / dtex or more, more preferably 7.9 cN / dtex or more, and 10.6 cN / dtex or more. (It is even more preferable) that high-strength fibers are present in the film-like layer and / or fiber layer, so that burrs and metal crystals on the electrode plate are difficult to penetrate the separator. Therefore, it is preferable.
When the separator of the present invention is used for an alkaline battery, the resin constituting the high-strength fiber is preferably made of a polyolefin resin, more preferably a polypropylene resin or a polyethylene resin. In addition, the high-strength fiber may be composed of one type of resin component, or two or more types of resin components may be mixed or combined, but if two or more types of resin components are combined, a film This is suitable because it can contribute to the formation of a layer. Examples of the fiber cross-sectional shape of the composite high-strength fiber include a core-sheath type, an eccentric type, a side-by-side type, a sea-island type, an orange type, and a multiple bimetal type. A core-sheath type, an eccentric type, or a sea-island type that can contribute is preferable, and a core-sheath type is particularly preferable. More specifically, a high-strength fiber having a polypropylene resin having a large difference in pressure-bonding properties as a core component and a polyethylene resin as a sheath component is preferable.
When thermoplastic fibers other than high-strength fibers are included, the high-strength fibers preferably constitute the fiber layer of the separator. Therefore, when the thermoplastic fibers other than high-strength fibers are pressure bonded, It is preferable that the resin constituting the high-strength fiber includes a resin that is harder to be crimped than a resin that can be crimped with a thermoplastic fiber so as not to be crimped. From the viewpoint of the melting point, it is preferable to use a high-strength fiber containing a resin having a melting point that is 10 ° C. or more, preferably 20 ° C. or more higher than the melting point of the thermoplastic fiber-bondable resin.
For example, when the resin that can be crimped to the thermoplastic fiber is made of a polyethylene resin, it is preferable that a polypropylene resin is included as the resin constituting the high-strength fiber. In addition, when the resin which can crimp a thermoplastic fiber consists of low density polyethylene or an ethylene copolymer, ultra high molecular weight polyethylene may be included as resin which comprises a high strength fiber.
Such high-strength fibers are preferably contained in the fiber web in an amount of at least 5 mass%, more preferably at least 10 mass%.
[0026]
The fiber web of the present invention contains the thermoplastic fibers as described above. However, if the amount of the thermoplastic fibers is small, the pressure-bonding becomes insufficient by the heat treatment and pressure treatment described later, resulting in the formation of a film-like layer. The thermoplastic fiber is preferably contained in the fiber web in an amount of 60 mass% or more, more preferably 80 mass% or more, and most preferably 100 mass% thermoplastic fiber. .
In addition, when two or more types of thermoplastic fibers are included, if all of the thermoplastic fibers are pressure-bonded, there is a tendency that the fiber layer is not easily formed by the action of the fluid flow. Therefore, at least one type of thermoplastic fiber is used. The resin preferably has a lower pressure-bonding property than other thermoplastic resins. More preferably, the at least one thermoplastic fiber is a composite thermoplastic fiber, and the at least one thermoplastic resin of the composite thermoplastic fiber is more compressible than the other thermoplastic resins of the composite thermoplastic fiber. Low is preferred.
From the viewpoint of the melting point which is the largest factor, it is preferable that at least one thermoplastic resin has a melting point of 10 ° C. or higher (preferably 20 ° C. or higher) and higher melting point than other thermoplastic resins. More preferably, the at least one thermoplastic fiber is a composite thermoplastic fiber, and the at least one thermoplastic resin of the composite thermoplastic fiber is 10 ° C. or higher than other thermoplastic resins of the composite thermoplastic fiber. (Preferably 20 ° C. or higher) It is preferable that the melting point is high.
When the thermoplastic fiber is composed of two types of polyolefin fibers, for example, (1) a combination of a polyolefin-based composite thermoplastic fiber composed of a polypropylene-based resin and a polyethylene-based resin and a polypropylene-based thermoplastic fiber, (2) a polypropylene-based fiber A combination of a polyolefin-based composite thermoplastic fiber composed of a resin and a polyethylene-based resin and a polyethylene-based thermoplastic fiber; (3) a polypropylene-based composite fiber composed of a polypropylene-based resin and a polyethylene-based resin; A combination such as a combination with a polyolefin-based composite thermoplastic fiber composed of the same or different polyethylene resin as the resin is preferable.
Examples of fibers other than thermoplastic fibers include, for example, regenerated fibers such as rayon, polynosic and cupra, semi-synthetic fibers such as acetate, inorganic fibers such as glass fibers and carbon fibers, plant fibers such as cotton and hemp, wool, Animal fibers such as silk can be used.
Moreover, it is preferable that the fineness of any fiber constituting these fiber webs is about 0.1 to 7 dtex.
[0027]
The fiber web of the present invention contains the thermoplastic fiber as described above. Examples of the method for forming the fiber web include a wet method, a dry method such as a card method and an air lay method, a direct method such as a spun bond method and a melt blow method. The law can be adopted. Among these, it is preferable to form by a wet method that easily forms a film-like layer having a low air permeability and a small average pore diameter.
The fiber length of the fibers constituting the fiber web varies depending on the method of forming the fiber web, and is preferably about 1 to 25 mm when formed by a wet method, and about 25 to 160 mm when formed by a dry method. Preferably there is.
According to the production method of the present invention, a separator (nonwoven fabric) having sufficient tensile strength can be produced even when thermoplastic fibers having a short fiber length are used as in the wet method.
As this wet method, there are conventionally known methods such as a horizontal long net method, an inclined wire type short net method, a circular net method, or a long net / circular net combination method.
Note that the fiber orientation is close to one direction by adjusting the net moving speed and the slurry flow rate so that the tensile strength in at least one direction can be easily increased. Is preferred.
The fiber web may be composed of a single layer, the method of forming the fiber web, the type of fiber constituting the fiber web (especially the type of thermoplastic fiber), and the blend of fibers constituting the fiber web (particularly thermoplastic). Fiber webs that differ in terms of fiber blending), fineness of fibers constituting the fiber web (especially the fineness of thermoplastic fibers), fiber length of the fibers constituting the fiber web (particularly the fiber length of thermoplastic fibers), etc. You may be comprised from the layer or more.
For example, if a fiber web with a large amount of polyolefin-based thermoplastic fiber having a core-sheath cross section is placed between fiber webs with a large amount of polyolefin-based thermoplastic fiber having an orange-shaped cross section, the heat treatment described below is performed. In addition, it is easy to form a film-like layer having a low air permeability and a small average pore diameter in the vicinity of the center portion by pressurizing treatment, and contains a lot of ultrafine fibers having a fiber diameter of 6 μm or less by the action of fluid flow. A separator having an excellent fiber layer can be easily produced.
Further, the surface density of the fiber web is 20 to 100 g / m so that the entire fiber web can be pressure-bonded to form a film. ² Is preferably 40 to 80 g / m. ² It is more preferable that
[0028]
Subsequently, the whole fiber web is subjected to heat treatment and pressure treatment to form a pressure-bonded fiber web. As described above, since the heat treatment and the pressure treatment are performed on the entire fiber web, when the heat treatment and the pressure treatment are partially performed, or only the heat treatment is performed on the fiber web as a whole. A film-like layer, which cannot be obtained when carried out in the above, can be formed.
[0029]
Such heat treatment and pressure treatment can be performed simultaneously or separately. As an apparatus that can simultaneously perform the former heat treatment and pressure treatment, for example, there is a thermal calendar. An apparatus that can perform only the heat treatment includes a hot-air through heat treatment device, and a device that can perform only the pressure treatment includes a calendar.
In the case where the fiber web contains composite thermoplastic fibers, at least one kind of all composite thermoplastic fibers constituting the composite thermoplastic fibers so that a film-like layer can be easily formed by pressure bonding of the fibers. It is preferable to carry out the heat treatment and the pressure treatment under the condition in which the thermoplastic resin is pressure bonded.
From the viewpoint of the melting point which is the largest factor, in order to press-bond at least one kind of thermoplastic resin constituting the composite thermoplastic fiber of all the composite thermoplastic fibers, Of the thermoplastic resins having a low melting point, it is preferable to carry out the heat treatment at a temperature that is at least 10 ° C. lower than the melting point of the thermoplastic resin having the highest melting point.
For example, in the case of a fiber web containing a composite thermoplastic fiber having a melting point of 120 ° C. of the thermoplastic resin having the lowest melting point and a composite thermoplastic fiber having a melting point of 130 ° C. of the thermoplastic resin having the lowest melting point, The heat treatment is preferably performed at a temperature of 120 ° C. or higher. Further, the pressure treatment is preferably performed at a pressure of about 0.05 to 0.5 MPa so that the thermoplastic resin is sufficiently pressure-bonded.
In addition, if heat treatment and pressure treatment are performed under the condition that the entire thermoplastic fiber is pressure-bonded, it tends to be difficult to form a fiber layer due to the action of the next fluid flow. It is preferable that the heat treatment and the pressure treatment be performed under the condition that the plastic fiber is a composite thermoplastic fiber and at least one kind of the thermoplastic resin of the composite thermoplastic fiber is difficult to press.
From the viewpoint of the melting point which is the largest factor, 5 ° C. or more, preferably 8 ° C. higher than the melting point of the thermoplastic resin having the highest melting point so that the thermoplastic resin having the highest melting point of the composite thermoplastic fiber does not press. It is preferable to carry out the heat treatment at a lower temperature.
For example, in the case of a fiber web containing a composite thermoplastic fiber having a melting point of 160 ° C. of the thermoplastic resin having the highest melting point, the heat treatment is performed at a temperature of 155 ° C. or less, preferably at a temperature of 152 ° C. or less. It is preferable to do this.
For example, when a heat treatment and a pressure treatment are performed on a wet fiber web including a core-sheath type composite thermoplastic fiber and an orange type composite thermoplastic fiber, the heat treatment and the pressure treatment may cause at least the pressure-bonded fiber web. It is preferable that the pressure is sufficiently bonded to such an extent that the tensile strength in one direction is 250 N / 50 mm width or more.
[0030]
Next, the separator (nonwoven fabric) of the present invention can be produced by applying a fluid flow to one or both sides of the pressure-bonded fiber web produced as described above. By applying a fluid flow to the crimped fiber web, a fiber layer can be formed on the surface on which the fluid flow is applied. Therefore, if a fluid flow is applied to one side, the fiber layer is provided on one side. In addition, a separator (nonwoven fabric) having a film-like layer on the other side can be produced. If a fluid flow is applied to both sides, a fiber layer is provided on both sides and a film-like layer is provided near the center. It is possible to manufacture a separator (nonwoven fabric). In general, since it is preferable that an electrolyte exists around both electrodes, it is preferable to have a fiber layer on both sides of the film-like layer.
In this way, the fiber layer can be formed by releasing a fiber pressed by a fluid flow from a pressure-bonded state, or destroying and removing a thermoplastic resin pressed by a fluid flow, and a fiber made of a non-pressed thermoplastic resin. This is thought to be due to exposing the surface to the surface.
From such a viewpoint, it is preferable that all the thermoplastic fibers constituting the pressure-bonded fiber web are composite thermoplastic fibers, and at least one thermoplastic resin of all the composite thermoplastic fibers is not pressure-bonded. By being in such a state, it becomes easy to generate ultrafine fibers having a fiber diameter of 6 μm or less.
For example, when the fibers constituting the pressure-bonding fiber web are composed of two types of polyolefin-based composite thermoplastic fibers, the polyolefin-based composite thermoplastic fibers composed of a polypropylene-based resin and a polyethylene-based resin are the same as or different from the same or different polypropylene-based resins. It is preferably composed of a combination of polyolefin-based composite thermoplastic fibers composed of different polyethylene-based resins.
In addition, when making a fluid flow act on both surfaces of a crimping | compression-bonding fiber web, the action conditions may be the same or different. By adjusting the degree of action of the fluid flow, the state of the fiber layer can be changed, and as a result, the amount of electrolyte around the electrode can be adjusted.
[0031]
The fluid flow is preferably water that is easy to handle.
More specifically, for example, a fluid flow may be ejected from a nozzle plate in which nozzles are arranged in a row or in two or more rows with a diameter of 0.05 to 0.3 mm and a pitch of 0.2 to 3 mm onto a crimped fiber web. . Such a fluid flow may be ejected one or more times. As described above, it is considered that the fiber that has been crimped by the fluid flow is released from the crimped state, or the crimped thermoplastic resin is destroyed and removed. More specifically, it is preferable to eject a fluid flow of 5 MPa or more, preferably 8 MPa or more.
When the fluid flow is applied, the support material that supports the pressure-bonded fiber web may have an opening such as a net or may not have an opening. The latter, which has no opening, is preferable because it is difficult to form an opening in the pressure-bonded fiber web even when a fluid flow acts, and a separator having low air permeability, a small average pore diameter, and short-circuit can be manufactured. Support material. It should be noted that the portion that does not have an opening, that is, is nonporous, does not have to be the entire support material, and at least the portion corresponding to the fluid flow operating portion is sufficient. Examples of the shape of the nonporous support material include a roll shape and a flat plate shape.
In addition, when a non-porous support material is used in this way, there are few places where the fluid flow can be discharged like a support material having an opening, so that the fluid stays on the crimped fiber web and the fluid flow There is a tendency to reduce the effect. Therefore, it is preferable that a means (for example, a suction device) capable of sucking and removing the reflected flow of the fluid flow is installed in the vicinity (for example, the upper side) of the pressure-bonded fiber web so that the fluid does not stay on the pressure-bonded fiber web.
[0032]
A separator having a fiber layer on one side or both sides of a film-like layer can be produced by the action of the fluid flow as described above. If further tensile strength or rigidity is required, the fibers constituting the fiber layer may be fused together. In addition, since this fiber layer needs to hold | maintain electrolyte solution, when fusing the fiber which comprises a fiber layer, it is preferable not to apply a pressure.
[0033]
As described above, the separator (nonwoven fabric) of the present invention, that is, the film-like layer formed by pressure bonding of the fibers is provided on the entire surface in the direction perpendicular to the thickness direction of the nonwoven fabric, and one side or both sides of the film-like layer. Moreover, the separator (nonwoven fabric) provided with the fiber layer containing the fiber joined to the said film-like layer can be manufactured.
In addition, as a fiber constituting the fiber layer, a separator (nonwoven fabric) including an ultrafine fiber having a fiber diameter of 6 μm or less uses, for example, a fiber having a fiber diameter of 6 μm or less as a thermoplastic fiber constituting the crimped fiber web, It can be manufactured by using a composite thermoplastic fiber containing a thermoplastic resin having a diameter of 6 μm or less, which is not subjected to pressure bonding by heat treatment and pressure treatment at the time of forming a pressure-bonded fiber web.
Moreover, the separator (nonwoven fabric) in which the fiber length of the fibers constituting the fiber layer is 25 mm or less can be produced by using a fiber web (for example, wet fiber web) from fibers having a fiber length of 25 mm or less. it can.
A separator (nonwoven fabric) containing high strength fibers having a tensile strength of 4.4 cN / dtex or more as fibers constituting the fiber layer, for example, has a tensile strength of 4.4 cN / dtex as fibers constituting the fiber web. It can manufacture by including the above high strength fiber.
Furthermore, a nonwoven fabric having an air permeability of 15 cm / s or less, an average pore diameter of 15 μm or less, or a tensile strength in at least one direction of 150 N / 50 mm width or more, for example, increases the amount of thermoplastic fibers. Increasing the amount of composite thermoplastic fibers as thermoplastic fibers, forming dense fiber webs (e.g., forming by a wet method), sufficiently pressing the fiber web by heat treatment and pressure treatment, non-porous It can be manufactured by satisfying the conditions such as not to damage the film-like layer such as using a quality support material.
[0034]
Although the separator of the present invention is composed of the above-described nonwoven fabric, since it is preferable to use polyolefin fibers as thermoplastic fibers so as to be excellent in alkali resistance and oxidation resistance, the electrolytic solution retention tends to be poor. . Therefore, it is preferable to further perform a hydrophilization treatment selected from sulfonation treatment, fluorine gas treatment, vinyl monomer graft polymerization treatment, surfactant treatment, discharge treatment, or hydrophilic resin application treatment.
Hereinafter, although the aspect which implements a hydrophilic treatment with respect to a nonwoven fabric is demonstrated, after performing a hydrophilic treatment with respect to the fiber which comprises a nonwoven fabric, even when manufacturing a nonwoven fabric, a hydrophilic treatment is implemented similarly. It ’s fine.
[0035]
The sulfonation treatment is not particularly limited. For example, the nonwoven fabric as described above is immersed in a solution composed of fuming sulfuric acid, sulfuric acid, chlorosulfuric acid or sulfuryl chloride, or sulfur trioxide gas is brought into contact with the nonwoven fabric. There is a method of introducing a sulfonic acid group by applying a discharge in a state where a nonwoven fabric is arranged in the presence of sulfur monoxide gas or sulfur dioxide gas.
[0036]
The fluorine gas treatment is not particularly limited. For example, fluorine gas diluted with an inert gas (for example, nitrogen gas, argon gas, etc.), oxygen gas, carbon dioxide gas, and sulfur dioxide gas. The fiber surface of the nonwoven fabric can be hydrophilized by exposing the nonwoven fabric to a mixed gas with at least one gas selected from the above. In addition, after making sulfur dioxide gas adhere to a nonwoven fabric beforehand and making fluorine gas contact, permanent hydrophilicity can be provided more efficiently.
[0037]
In the graft polymerization of the vinyl monomer, for example, acrylic acid, methacrylic acid, acrylic ester, methacrylic ester, vinyl pyridine, vinyl pyrrolidone or styrene can be used as the vinyl monomer. When styrene is graft-polymerized, it is preferably sulfonated in order to impart affinity with the electrolytic solution. Among these, acrylic acid can be suitably used because of its excellent affinity with the electrolytic solution.
As a method for polymerizing these vinyl monomers, for example, a method in which a nonwoven fabric is dipped in a solution containing a vinyl monomer and a polymerization initiator and heated, a method in which a vinyl monomer is applied to the nonwoven fabric and radiation is applied, and a radiation is irradiated in the nonwoven fabric Then, there are a method of contacting with a vinyl monomer, a method of impregnating a nonwoven fabric with a vinyl monomer solution containing a sensitizer, and then irradiating with ultraviolet rays. If the surface of the nonwoven fabric is modified by ultraviolet irradiation, corona discharge, plasma discharge, etc. before contacting the vinyl monomer solution and the nonwoven fabric, the graft monomer can be efficiently graft-polymerized because of its high affinity with the vinyl monomer solution. .
[0038]
Examples of the surfactant treatment include an anionic surfactant (for example, an alkali metal salt of a higher fatty acid, an alkyl sulfonate, or a sulfosuccinate ester salt), or a nonionic surfactant (for example, a polyoxyethylene alkyl). The nonwoven fabric can be immersed in a solution of ether or polyoxyethylene alkylphenol ether), or this solution can be applied to or dispersed on the nonwoven fabric.
[0039]
Examples of the discharge treatment include corona discharge treatment, plasma treatment, glow discharge treatment, creeping discharge treatment, and electron beam treatment. Among these discharge treatments, under atmospheric pressure in air, a non-woven fabric is placed between a pair of electrodes each carrying a dielectric so as to be in contact with both of these dielectrics, and an AC voltage is applied between these two electrodes. When the method is applied and discharge is generated in the voids inside the nonwoven fabric, not only the outside of the nonwoven fabric but also the surface of the fibers constituting the inside of the nonwoven fabric can be treated. Therefore, it is excellent in the holding | maintenance of the electrolyte solution in the inside of a separator.
[0040]
As hydrophilic resin provision processing, hydrophilic resins, such as carboxymethylcellulose, polyvinyl alcohol, crosslinkable polyvinyl alcohol, or polyacrylic acid, can be made to adhere, for example. These hydrophilic resins can be dissolved or dispersed in a suitable solvent, and then the nonwoven fabric can be immersed in the solvent, or this solvent can be applied or dispersed on the nonwoven fabric and dried to be adhered. In addition, it is preferable that the adhesion amount of hydrophilic resin is 0.3-1 mass% of the whole separator so that air permeability may not be impaired.
Examples of the crosslinkable polyvinyl alcohol include polyvinyl alcohol in which a part of the hydroxyl group is substituted with a photosensitive group. More specifically, the photosensitive group is a styrylpyridinium type or styrylquinolinium type. And polyvinyl alcohol substituted with a styrylbenzothiazolium-based one. This crosslinkable polyvinyl alcohol can also be cross-linked by light irradiation after being attached to the nonwoven fabric in the same manner as other hydrophilic resins. Polyvinyl alcohol in which a part of such hydroxyl groups is substituted with a photosensitive group is excellent in alkali resistance and contains many hydroxyl groups that can form chelates with ions, and is dendritic on the electrode plate during discharge and / or charge. This forms a chelate with the ions before the metal is deposited, and it is difficult to cause a short circuit between the electrodes.
[0041]
The surface density of the separator of the present invention is 20 to 100 g / m. ² Is preferable, and more preferably 40 to 80 g / m. ² It is. Areal density is 20 g / m ² If it is less than 100 g / m, the tensile strength may be insufficient. ² This is because the thickness tends to be too large. Moreover, it is preferable that the thickness of a separator is 0.02-0.21 mm.
[0042]
The separator of the present invention can catch the burrs of the electrode plate with a film-like layer, has excellent tensile strength, and is difficult to break when being wound, and therefore is not easily short-circuited. Further, even when the battery is used, the metal crystal can be received by the film-like layer, so that it is difficult to cause a short circuit. Furthermore, since the film-like layer has an appropriate waist, it is excellent in handleability during battery production.
Therefore, for example, primary batteries such as alkaline manganese batteries, mercury batteries, silver oxide batteries, air batteries, secondary batteries such as nickel-cadmium batteries, silver-zinc batteries, silver-cadmium batteries, nickel-zinc batteries, nickel-hydrogen batteries, etc. It can be suitably used as a battery separator.
[0043]
Examples of the present invention will be described below, but the present invention is not limited to the following examples. Various physical properties are values measured as follows.
"Tensile strength" is a test piece with a width of 50 mm fixed between the chucks of a tensile strength tester (Orientec, Tensilon UTM-III-100) (distance between chucks: 10 cm) and pulled at a pulling speed of 300 mm / min. It is the value when.
“Air permeability” is a value measured by a method defined in JIS L 1096 (6.27.1 A method (Fragile method)).
“Average pore diameter” is a value measured by a bubble point method using a porometer (manufactured by Coulter).
[0044]
【Example】
Example 1
The core component is made of polypropylene (melting point: 160 ° C., circular in cross section), the sheath component is made of low density polyethylene (melting point: 110 ° C.), the core-sheath type composite thermoplastic fiber having a fineness of 2.2 dtex and a fiber length of 10 mm is 20 mass%. A high strength polypropylene thermoplastic fiber having a tensile strength of 10.6 cN / dtex, a fineness of 1.33 dtex, and a fiber length of 10 mm (melting point: 166 ° C., circular in cross section) 20 mass%, and a polypropylene component (see FIG. 1). Medium symbol 12, approximately triangular, 8 polypropylene ultrafine fibers (melting point: 160 ° C.) with a fineness of 0.133 dtex (diameter: 4.3 μm), and substantially circular with a fineness of 0.089 dtex (diameter: 3.5 μm) Polypropylene ultrafine fiber (melting point: 160 ° C) can be generated) and high-density polyethylene component (symbol 11 in the figure, approximately triangular shape and fineness) 0.133 dtex (diameter: 4.2 μm) high-density polyethylene ultrafine fibers (melting point: 130 ° C., 8 can be generated), orange-type composite thermoplastic fiber 60 mass% with a fineness of 2.2 dtex and a fiber length of 5 mm; The slurry obtained by mixing and dispersing is made into a fiber web (surface density: 70 g / m) by using an inclined wire type short net system. ² ) And dried. The wet fiber web had fibers oriented in the length direction.
Next, the wet fiber web is subjected to a heat treatment at a temperature of 140 ° C. and a pressure treatment at a pressure of 0.2 MPa on the whole wet fiber web by a compliant press machine (Asahi Textile Machine Industry, JR-1000LTS-E). In practice, the sheath component (low density polyethylene component) of the core-sheath type composite thermoplastic fiber and the high density polyethylene component of the orange type composite thermoplastic fiber were pressure-bonded to form a pressure-bonded fiber web. The tensile strength in the warp direction of this press-bonded fiber web was 272 N / 50 mm width.
Next, after this pressure-bonded fiber web was applied to a support plate made of a non-porous roll, a water flow having a pressure of 15 MPa from a nozzle plate arranged in a row with a nozzle diameter of 0.13 mm and a pitch of 0.6 mm was applied twice alternately on both sides. The nonwoven fabric was produced by drying. In addition, the suction apparatus was installed above the crimping | compression-bonding fiber web so that the reflected flow of a water flow could be suction-removed, and the reflected flow of the water flow was suction-removed.
From the electron micrograph (refer to FIG. 2) in the cross section of this nonwoven fabric, a film-like layer (thickness: about 45 μm) is formed on the entire surface in the direction perpendicular to the thickness direction, and this film-like layer The fiber layer containing the fiber joined to the film-like layer was provided on both sides. The fibers constituting this fiber layer are all polypropylene fibers having a fiber diameter of 12 μm (fiber length: 10 mm or less, occupying about 7 mass% in the fiber layer), and polypropylene microfibers having a fiber diameter of 4.3 μm (fiber length: 5 mm or less, occupying about 42 mass% in the fiber layer), high-density polyethylene ultrafine fiber having a fiber diameter of 4.2 μm (fiber length: 5 mm or less, occupying about 24 mass% in the fiber layer), and polypropylene having a fiber diameter of 13.7 μm It was composed of strength fibers (tensile strength: 10.6 cN / dtex, fiber length: 10 mm or less, occupying about 27 mass% in the fiber layer).
The nonwoven fabric was then treated with fuming sulfuric acid solution (15% SO _Three The solution was immersed in the solution for 2 minutes to carry out the sulfonation treatment. Next, the sulfonated nonwoven fabric was sufficiently washed with water, dried, and then subjected to a calendar treatment, whereby the separator of the present invention (surface density: 66 g / m ² , Thickness: 0.15 mm). The tensile strength in the vertical direction of this separator was 162 N / 50 mm width. The separator had an air permeability of 5.2 cm / s and an average pore diameter of 8.3 μm.
[0045]
(Comparative Example 1)
Area density of 70 g / m produced in the same manner as in Example 1. ² The whole wet fiber web is heat-treated (under no pressure) in an oven set at a temperature of 135 ° C., and the sheath component (low density polyethylene) of the core-sheath composite thermoplastic fiber and orange composite thermoplastic fiber The high-density polyethylene component was fused to form a fused fiber web. The tensile strength in the warp direction of this fused fiber web was 130 N / 50 mm width.
Next, the surface density was 70 g / m by applying a water flow in the same manner as in Example 1. ² A non-woven fabric was produced. From the electron micrograph (see FIG. 3) in the cross section of this nonwoven fabric, it was found that there was no film-like layer formed by pressure bonding of the fibers in the direction perpendicular to the thickness direction.
Subsequently, sulfonation treatment, washing with water, drying and calendar treatment were carried out in the same manner as in Example 1 to obtain a separator (surface density: 72 g / m ² , Thickness: 0.15 mm). The tensile strength in the vertical direction of this separator was 133 N / 50 mm width. The separator had an air permeability of 18 cm / s and an average pore diameter of 15.5 μm.
[0046]
(Defect rate during battery manufacturing)
As a battery current collector, a positive electrode (33 mm wide, 182 mm long) filled with nickel hydroxide in a nickel foam support, and a paste type hydrogen storage alloy negative electrode (mesh metal alloy MmNi) _Five Mold, 33 mm width, 247 mm length).
Next, the separators of Example 1 and Comparative Example 1 cut to a width of 33 mm and a length of 410 mm were sandwiched between the positive electrode and the negative electrode, respectively, and wound in a spiral shape to create an SC-type electrode group. At this time, the rate at which the battery could not be manufactured due to a short circuit due to burrs on the electrode plate was defined as the defective rate during battery manufacture. The results are shown in Table 1.
[0047]
(Measurement of capacity maintenance rate)
As a battery current collector, a positive electrode (33 mm wide, 182 mm long) filled with nickel hydroxide in a nickel foam support, and a paste type hydrogen storage alloy negative electrode (mesh metal alloy MmNi) _Five Mold, 33 mm width, 247 mm length).
Next, each separator cut to a width of 35 mm and a length of 410 mm was sandwiched between the positive electrode and the negative electrode, respectively, and wound in a spiral shape to prepare an SC-type electrode group. Next, after this electrode group was housed in an outer can, 5N-potassium hydroxide and 1N-lithium hydroxide were poured into the outer can as electrolytes, and sealed to prepare a cylindrical nickel-hydrogen battery.
Next, each cylindrical nickel-hydrogen battery was charged at a charging rate of 0.1 C and 150% of the capacity, then discharged at a discharging rate of 0.1 C, and an initial capacity (A) at a final voltage of 1.0 V. Was measured. Next, after charging 150% of the capacity at a charging rate of 0.1 C, it was left in a thermostatic chamber at a temperature of 65 ° C. for 5 days. Thereafter, the battery was discharged again at a discharge rate of 0.1 C, and the capacity (B) at a final voltage of 1.0 V was measured. From these results, the initial capacity retention ratio (Ci,%) was calculated by the following equation. This result was also as shown in Table 1.
Ci = (B / A) × 100
Here, Ci means an initial capacity maintenance ratio, A means an initial capacity, and B means a capacity after being left.
Subsequently, the same charge / discharge as described above, that is, after charging 150% of the capacity at a charging rate of 0.1 C, discharging at a discharge voltage of 0.1 C with a final voltage of 1.0 V is defined as one cycle. After 200 cycles of charge / discharge, the battery was charged 150% of the capacity at a charging rate of 0.1 C, and then left in a thermostatic chamber at a temperature of 65 ° C. for 5 days. Thereafter, the battery was discharged again at a discharge rate of 0.1 C, and the capacity (C) at a final voltage of 1.0 V was measured. From these results, the capacity retention rate after 200 cycles (C ₂₀₀ %) Was calculated. This result was also as shown in Table 1.
C ₂₀₀ = (C / A) x 100
Where C ₂₀₀ Is the capacity retention rate after 200 cycles, A is the initial capacity, and C is the capacity after 200 cycles.
Furthermore, the same charging / discharging as described above, that is, charging / discharging with one cycle of charging at a discharge rate of 0.1 C with a final voltage of 1.0 V after charging 150% of the capacity at a charge rate of 0.1 C. After 500 cycles, the battery was charged 150% of the capacity at a charging rate of 0.1 C, and then left in a thermostatic chamber at a temperature of 65 ° C. for 5 days. Thereafter, the battery was discharged again at a discharge rate of 0.1 C, and the capacity (D) at a final voltage of 1.0 V was measured. From these results, the capacity retention rate after 500 cycles (C ₅₀₀ %) Was calculated. This result was also as shown in Table 1.
C ₅₀₀ = (D / A) x 100
Where C ₅₀₀ Denotes a capacity retention rate after 500 cycles, A denotes an initial capacity, and D denotes a capacity after 500 cycles.
[0048]
[Table 1]

As apparent from Table 1, the separator of the present invention was able to produce a battery stably. Moreover, even if the battery was repeatedly used, the capacity was difficult to decrease.
[0049]
【The invention's effect】
The battery separator of the present invention can catch the burrs of the electrode plate with a film-like layer, is excellent in tensile strength, and is difficult to break when wound, so it is difficult to short-circuit. is there. Further, even when the battery is used, the metal crystal can be received by the film-like layer, so that it is difficult to cause a short circuit. Furthermore, since the film-like layer has an appropriate waist, it is excellent in handleability during battery production.
Moreover, since the separator of this invention is equipped with the fiber layer, electrolyte solution can be hold | maintained by this fiber layer, and the electromotive reaction of a battery can be performed smoothly.
[0050]
The battery separator manufacturing method of the present invention can easily manufacture the separator.
Further, unlike the case where the microporous film and the fiber web or the nonwoven fabric are integrated, it is a method by which a separator having appropriate micropores (a degree that allows oxygen generated in the electrode plate to pass through) can be easily manufactured.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of an orange type composite thermoplastic fiber.
2 is an electron micrograph of a cross section of the separator of Example 1. FIG.
3 is an electron micrograph of a cross section of the separator of Comparative Example 1. FIG.
[Explanation of symbols]
1 Orange type composite thermoplastic fiber
11 High-density polyethylene component
12 Polypropylene component

Claims (14)

A film-like layer formed by pressure bonding of fibers is provided on the entire surface in a direction perpendicular to the thickness direction of the nonwoven fabric, and a fiber layer including fibers bonded to the film-like layer is provided on both surfaces of the film-like layer. A nonwoven fabric having a film layer formed by pressure bonding of fibers on one side and a fiber layer containing fibers bonded to the film-like layer on the other surface. A battery separator comprising a nonwoven fabric selected from the group .   2. The battery separator according to claim 1, wherein the fiber constituting the fiber layer includes an ultrafine fiber having a fiber diameter of 6 [mu] m or less.   The battery separator according to claim 1 or 2, wherein the fiber length of the fibers constituting the fiber layer is 25 mm or less.   The battery separator according to any one of claims 1 to 3, wherein the fiber constituting the fiber layer includes a high-strength fiber having a tensile strength of 4.4 cN / dtex or more.   The battery separator according to any one of claims 1 to 4, wherein the air permeability is 15 cm / s or less.   The battery separator according to any one of claims 1 to 5, wherein an average pore diameter is 15 µm or less.   7. The battery separator according to claim 1, wherein the tensile strength in at least one direction is 150 N / 50 mm width or more.   It consists of a nonwoven fabric subjected to a hydrophilization treatment selected from sulfonation treatment, fluorine gas treatment, vinyl monomer graft polymerization treatment, surfactant treatment, discharge treatment, or hydrophilic resin application treatment. The battery separator according to any one of claims 1 to 7.   A heat treatment and a pressure treatment are performed on the entire fiber web containing thermoplastic fibers to form a pressure-bonded fiber web, and then a fluid flow is applied to one or both sides of the pressure-bonded fiber web. And including a fiber bonded to the film-like layer on one side or both sides of the film-like layer on a whole surface in a direction perpendicular to the thickness direction of the nonwoven fabric by a fiber pressure bonding. The manufacturing method of the battery separator which consists of a nonwoven fabric provided with the fiber layer.   The method for producing a battery separator according to claim 9, wherein the thermoplastic fiber includes composite thermoplastic fibers made of two or more types of thermoplastic resins having different crimping properties.   The method for producing a battery separator according to claim 9 or 10, wherein the fiber web comprises a wet fiber web produced by a wet method.   The heat treatment and the pressure treatment are performed under a condition in which at least one kind of thermoplastic resin constituting the composite thermoplastic fiber of all the composite thermoplastic fibers is pressure-bonded. Manufacturing method of battery separator.   The support material for supporting the pressure-bonding fiber web when the fluid flow is applied uses a support material having at least a portion corresponding to the fluid flow acting portion as non-porous material. Item 13. A method for producing a battery separator according to any one of Items 12 to 13.   After the non-woven fabric is formed, a hydrophilization treatment selected from sulfonation treatment, fluorine gas treatment, vinyl monomer graft polymerization treatment, surfactant treatment, discharge treatment, or hydrophilic resin application treatment is carried out. The method for producing a battery separator according to any one of claims 9 to 13, wherein the battery separator is characterized in that

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