JP4800527B2 - Non-woven fabric, battery using the non-woven fabric, and capacitor using the non-woven fabric - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a nonwoven fabric suitable for a variety of uses, a battery using the nonwoven fabric and a capacitor using the nonwoven fabric. SOLUTION: This nonwoven fabric comprises extra fine fiber aggregates obtained by assembling extra fine fibers having <=5 &mu;m fiber diameter and/or pulpy materials. The total number of the extra fine fiber aggregates and/or the pulpy materials on one side (A) of the nonwoven fabric is different from that of the extra fine fiber aggregates and/or the pulpy materials on the other side (B) of the nonwoven fabric. This battery using the nonwoven fabric as a separator hardly raises an internal pressure. This capacitor using the nonwoven fabric as a separator has excellent ionic conductivity and yet excellent electrical insulating properties by the existence of one side having the total number of the extra fine fiber aggregates and/or the pulpy materials smaller than that of the other side.

Description

【０１３５】
（最大孔径の測定）
実施例１のセパレータのポリプロピレン極細繊維集合体が実質的に存在していない面における最大孔径、及び比較例１のセパレータの最大孔径を、ポロメータ（コールター社製）を用いてバブルポイント法により測定した。この値は表１に示す通りであった。
【０１３６】
（（最大孔径／平均流量孔径）比の測定）
実施例１のセパレータのポリプロピレン極細繊維集合体が実質的に存在していない面における平均流量孔径、及び比較例１のセパレータの平均流量孔径を、ポロメータ（Ｐｏｌｏｍｅｔｅｒ、コールター（Ｃｏｕｌｔｅｒ）社製）を用いてミーンフローポイント法により測定した。
【０１３７】
次いで、前述のようにして得られた最大孔径値をもとに、（最大孔径／平均流量孔径）比を算出した。この結果は表１に示す通りであった。
【０１３８】
（空隙率の測定）
まず、各セパレータの目付（Ｗ）及び厚さ（Ｔ）を測定した。
【０１３９】
次いで、セパレータ構成材の樹脂の密度（ｄ）を、各構成材の密度及び質量比率から算出した。
【０１４０】
次いで、次の式から「空隙率（Ｐ）」を算出した。
空隙率（Ｐ）＝｛１−Ｗ／（Ｔ×ｄ）｝×１００
この結果は表１に示す通りであった。
【０１４１】
（長手方向における引張り強さの測定）
長手方向と直交する方向（幅方向）に長さ５ｃｍで、長手方向に長さ２０ｃｍに裁断した長方形状の各セパレータを、引張り強さ試験機（オリエンテック製、テンシロンＵＴＭ−III−１００）のチャック間（チャック間距離：１０ｃｍ）に固定し、引張り速度３００ｍｍ／ｍｉｎで各セパレータを長手方向に引張り、各セパレータを破断するために要する力を測定し、この力を長手方向における引張り強さとした。この結果は表１に示す通りであった。
【０１４２】
（ニードル式耐貫通力）
円筒状貫通孔（内径：１１ｍｍ）を有する支持台の円筒状貫通孔を覆うように各セパレータを１枚載置し、更に各セパレータ上に、円筒状貫通孔（内径：１１ｍｍ）を有する固定材を、固定材の中心が前記支持台の円筒状貫通孔の中心と一致するように載置して各セパレータを固定した後、このセパレータに対して、ハンディー圧縮試験機（カトーテック製、ＫＥＳ−Ｇ５）に取り付けられたニードル（先端部における曲率半径：０．５ｍｍ、直径：１ｍｍ、治具からの突出長さ：２ｃｍ）を、０．０１ｃｍ／ｓの速度で垂直に突き刺し、ニードルが突き抜けるのに要する力を測定し、この力をニードル式耐貫通力とした。この結果は表１に示す通りであった。
【０１４３】
（単位目付あたりのニードル式耐貫通力）
前記（ニードル式耐貫通力）と目付から、単位目付あたりのニードル式耐貫通力を算出した。この結果は表１に示す通りであった。
【０１４４】
（加圧保液率の測定）
直径３０ｍｍに裁断した各セパレータをそれぞれ、温度２０℃、相対湿度６５％の状態下で、水分平衡に至らせた後、質量（Ｍ_０）を測定した。
【０１４５】
次に、セパレータ中の空気を水酸化カリウム水溶液で置換するように、比重１．３（２０℃）の水酸化カリウム水溶液中に１時間浸漬し、水酸化カリウム水溶液を保持させた。
【０１４６】
次に、このセパレータを上下３枚づつのろ紙（直径：３０ｍｍ）で挟み、加圧ポンプにより、５．７ＭＰａの圧力を３０秒間作用させた後、セパレータの質量（Ｍ_１）を測定した。
【０１４７】
次いで、次の式により加圧保液率を求めた。なお、この測定は１つのセパレータに対して４回行ない、その平均を加圧保液率とした。この結果は表１に示す通りであった。
加圧保液率（％）＝｛（Ｍ_１−Ｍ_０）／Ｍ_０｝×１００
【０１４８】
（電池内圧試験）
電極の集電体として、発泡ニッケル基材を用いたペースト式ニッケル正極（３３ｍｍ幅、１８２ｍｍ長）と、ペースト式水素吸蔵合金負極（メッシュメタル系合金、３３ｍｍ幅、２４７ｍｍ長）とを作成した。
【０１４９】
次いで、各セパレータを３３ｍｍ幅、４１０ｍｍ長に裁断した後、それぞれを正極と負極との間に挟み込み、渦巻き状に巻回して、ＳＣ（ｓｕｂ−Ｃ）型対応の電極群を作成した。この電極群を外装缶に収納し、電解液として５Ｎ水酸化カリウム及び１Ｎ水酸化リチウムを外装缶に注液し、封緘して、容量が２０００ｍＡｈの円筒型ニッケル−水素電池を作成した。なお、実施例１のセパレータを使用した場合には、ポリプロピレン極細繊維集合体が存在する面が負極と当接するように配置した。
【０１５０】
次いで、この円筒型ニッケル−水素電池を、温度２０℃で、０．５Ｃにて充電を行い、容量の１５０％充電時における電池内圧を測定した。実施例１のセパレータを使用した電池の内圧を基準（１００）とした時の比率を、表１に示す。
【０１５１】
表１の結果から明らかなように、本発明のセパレータは薄く、機械的強度に優れ、内圧の低い電池を製造できるものであった。
【０１５２】
【発明の効果】
本発明の不織布は、繊維径が５μｍ以下の極細繊維が集合した極細繊維集合体、及び／又はパルプ状物を含む不織布であり、前記不織布の一方の面（Ａ）における前記極細繊維集合体及び／又はパルプ状物の総個数と、前記不織布の他方の面（Ｂ）における前記極細繊維集合体及び／又はパルプ状物の総個数とが異なるため、各種性能を有するものである。例えば、電池用セパレータとして使用した場合には、極細繊維集合体及び／又はパルプ状物の総個数の多い面において電解液が局在化しやすいため、この面を負極と当接するように配置すれば、酸素と負極との接触機会が増大して、酸素を充分に消費することができるため、内圧が上昇しにくい電池を製造することができる。また、濾過材として使用した場合には、極細繊維集合体及び／又はパルプ状物の総個数の少ない面の存在により、圧力損失の増大を抑制できる。更に、キャパシタ用のセパレータとして使用した場合、極細繊維集合体及び／又はパルプ状物の総個数の多い面の存在によってイオン伝導性を高めることができ、しかも極細繊維集合体及び／又はパルプ状物の総個数の少ない面の存在によって電気絶縁性に優れている。
【図面の簡単な説明】
【図１】 実施例１の不織布の極細繊維集合体の多い面の電子顕微鏡写真
【図２】 実施例１の不織布の極細繊維集合体の少ない面の電子顕微鏡写真[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a nonwoven fabric, a battery using the nonwoven fabric, and a capacitor using the nonwoven fabric.
[0002]
[Prior art]
Nonwoven fabrics can be randomly arranged, and are excellent in various properties such as separation performance, liquid retention performance, or insulation performance, and thus are applied to various applications.
[0003]
One of the applications utilizing the insulation performance and liquid retention performance of the nonwoven fabric is a battery separator application. In other words, a non-woven fabric is arranged as a separator between the positive electrode and the negative electrode so that the positive electrode and the negative electrode of the battery are separated to prevent a short circuit and the electrolysis reaction can be performed smoothly while holding the electrolytic solution. ing.
[0004]
For example, when a nonwoven fabric is used as a separator for a nickel metal hydride battery, the space occupied by the nickel metal hydride battery has become narrower as electronic devices have become smaller and lighter in recent years. Since the same or higher performance is required, it is required to increase the capacity of the nickel metal hydride battery. For that purpose, since it is necessary to increase the amount of the active material of the electrode, the volume occupied by the separator (nonwoven fabric) is inevitably reduced.
[0005]
Thus, even when the volume of the separator (nonwoven fabric) is reduced, the fibers constituting the separator (nonwoven fabric) are made thin so that the surface area of the fiber is reduced so that the insulating performance and the electrolyte holding performance are excellent. I thought it would be wide.
[0006]
One method of thinning the fibers is a method of forming by a melt blow method. However, when the nonwoven fabric formed by this method is used as a separator for a sealed nickel-metal hydride battery, there is a problem that the internal pressure of the battery rises due to oxygen generated from the positive electrode, causing liquid leakage.
[0007]
Moreover, since the nonwoven fabric formed by the melt blow method is comprised from the thin fiber and is excellent in the separation performance, it can be used conveniently as a filter material. However, there is a problem that the pressure loss tends to increase because the fibers are thin and dense.
[0008]
Furthermore, even when a nonwoven fabric formed by the melt blow method is used as a separator for a capacitor, although it has excellent liquid holding performance and insulation performance, there is a problem that the ion conductivity is low because the fibers are thin and dense. It was.
[0009]
[Problems to be solved by the invention]
The present invention has been made in order to solve the above-mentioned problems, and it is difficult to increase the internal pressure even when used as a battery separator, and the pressure loss increases even when used as a filter material. To provide a non-woven fabric that is suitable for various uses, such as being difficult or having excellent ion conductivity even when used as a capacitor separator, and to provide a battery using this non-woven fabric and a capacitor using this non-woven fabric. With the goal.
[0010]
[Means for Solving the Problems]
The present inventors have pursued the cause of the increase in the internal pressure of the battery, because the oxygen generated from the positive electrode cannot be consumed sufficiently in the negative electrode, and the oxygen cannot be consumed sufficiently in the negative electrode. It has been found that the surface of the nonwoven fabric formed by the melt-blowing method is dense, holds the electrolyte over the entire surface of the nonwoven fabric, and has a narrow contact area between oxygen and the negative electrode.
[0011]
It was also found that the pressure loss tends to be high when used as a filter material, because the surface of the nonwoven fabric formed by the melt blow method is dense. Similarly, it has been found that the low conductivity of ions when used as a capacitor separator is due to the dense surface of the nonwoven fabric formed by the melt-blowing method.
[0012]
  The present invention has been made on the basis of such findings, and the nonwoven fabric of the present invention is “a fiber cross-sectional shape formed by removing sea components of a sea-island type composite fiber, and a fiber diameter of 5 μm or less. A non-woven fabric that is fixed only by fusing, and includes the total number of the ultra-fine fiber assemblies on one surface (A) of the non-woven fabric, and the other of the non-woven fabrics. The total number of the ultrafine fiber aggregates on the surface (B) is differentThe non-woven fabric is derived from a fiber web formed by a wet method using a slurry in which individual ultrafine fibers and an aggregate of ultrafine fibers are dispersed.It is a nonwoven fabric characterized by this.
[0013]
  In this way, ultrafine fiber assemblythe body'sBecause it consists of non-woven fabrics with different total numbers on both sides, when used as a battery separator, an ultrafine fiber assemblythe body'sSince the electrolyte solution is likely to be localized on the surface with a large total number, if this surface is arranged so as to contact the negative electrode, the contact opportunity between oxygen and the negative electrode increases, and oxygen can be consumed sufficiently. Therefore, the increase in the internal pressure of the battery can be suppressed.the body'sIncreased pressure loss can be suppressed due to the presence of a small number of surfaces. When used as a separator for capacitors, an assembly of ultrafine fibersthe body'sAlthough the electrolyte solution is localized due to the presence of a large number of surfaces, it is rich, so that it is a non-woven fabric that can be adapted to various uses, such as being able to enhance ionic conductivity.
[0014]
A battery using this nonwoven fabric as a separator is difficult to increase the internal pressure.
[0015]
  Capacitors using this non-woven fabric as a separator have excellent ion conductivity and an ultra-fine fiber assemblythe body'sExcellent electrical insulation due to the presence of a small number of surfaces.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The nonwoven fabric of the present invention can be reduced in thickness, and when used as a battery separator, it can suppress an increase in internal pressure, and when used as a filter material, it can suppress an increase in pressure loss. When it is used as a separator for use, it includes an ultrafine fiber assembly in which ultrafine fibers having a fiber diameter of 5 μm or less are aggregated and / or a pulp-like material so as to be excellent in various properties such as excellent ion conductivity. Yes.
[0017]
The former “ultrafine fiber aggregate in which ultrafine fibers having a fiber diameter of 5 μm or less are aggregated” has a portion in which the fiber axes of a plurality of ultrafine fibers are substantially in the same direction. From a viewpoint, it has a portion in which a plurality of ultrafine fibers are bundled (see FIG. 1).
[0018]
Such an ultrafine fiber assembly is, for example, (1) at least one resin component (sea component) of a composite fiber (for example, sea-island type composite fiber) composed of two or more types of resin components having different solubility in a specific solvent. Can be obtained by a method that does not fully or completely solve the ultrafine fiber bundle formed by removing (2) a composite fiber composed of two or more types of resin components having different degrees of swelling with respect to a specific solvent. On the other hand, it can be obtained by a method of separating each resin component by contacting with a specific solvent, or (3) Although the splitting fiber can be split by the impact of external force, the splitting is performed. After that, it can be obtained by a method in which an external force that is not understood is applied and only the splittable fibers are split. Among these, (1) formed by removing at least one resin component (sea component) from a composite fiber (for example, sea-island type composite fiber) composed of two or more types of resin components having different solubility in a specific solvent. It is preferable that the ultrafine fiber bundle is obtained by a method that does not fully or sufficiently solve the fiber bundle because it is excellent in the dispersibility of fibers including fibers other than the ultrafine fiber aggregate and pulp-like material. In particular, if the ultrafine fiber bundle formed by removing the sea component of the sea-island type composite fiber is a method that does not fully or fully understand, it is possible to form voids between the ultrafine fibers, hold the electrolyte, In addition, it is preferable because a thin nonwoven fabric can be easily formed.
[0019]
The individual ultrafine fibers that make up this ultrafine fiber assembly have a finer fiber surface area due to their thinness, and when used as separators for batteries or capacitors, they have excellent electrolyte retention and when used as filter media. Can impart various characteristics such as excellent dust collection. Specifically, the fiber diameter of each ultrafine fiber is 5 μm or less, preferably 4 μm or less, more preferably 3 μm or less, and even more preferably 2 μm or less. The lower limit of the fiber diameter of each ultrafine fiber is not particularly limited, but about 0.01 μm is appropriate.
[0020]
The “fiber diameter” in the present invention refers to the diameter when the cross-sectional shape of the fiber is circular, and the diameter of a circle having the same cross-sectional area when the cross-sectional shape of the fiber is non-circular. Considered as fiber diameter.
[0021]
The ultrafine fiber can be composed of an organic component and / or an inorganic component, but is preferably composed of an organic component that can be reduced in weight. More specifically, it can be comprised from 1 or more types of resin, such as a polyamide-type resin, polyolefin-type resin, and polyester-type resin. In particular, it is preferably composed of a polyolefin-based resin that is excellent in chemical resistance (electrolytic solution resistance when used as a battery or capacitor separator) and can be adapted to various applications. . For example, polyethylene resin (for example, ultra high molecular weight polyethylene, high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, ethylene copolymer, etc.), polypropylene resin (for example, polypropylene, propylene copolymer) For example, polymethylpentene, methylpentene copolymer, etc., and is preferably made of polypropylene resin or polyethylene resin.
[0022]
On the other hand, the pulp-like material contains fibrillated fine fibers, and its constituent components are not particularly limited, but for the same reason as ultrafine fibers, polyamide resins, polyolefin resins, polyester resins, etc. It is preferably composed of one or more kinds of resins, and more preferably composed of polyolefin resins. This polyolefin resin can also be exactly the same as the above-mentioned ultrafine fiber, for example, a polyethylene resin (for example, ultrahigh molecular weight polyethylene, high density polyethylene, medium density polyethylene, low density polyethylene, linear low density) Polyethylene, ethylene copolymer, etc.), polypropylene resin (eg, polypropylene, propylene copolymer, etc.), and polymethylpentene resin (eg, polymethylpentene, methylpentene copolymer, etc.) It can be made of a polypropylene resin or a polyethylene resin.
[0023]
The nonwoven fabric of the present invention contains such an ultrafine fiber aggregate and / or pulp-like material, but preferably does not substantially contain a pulp-like material. That is, it is preferable to include an ultrafine fiber aggregate and other fibers (including individual ultrafine fibers). This is because the parts other than the fine fibers of the pulp-like material are thicker and the surface area is not so wide, as a result of various characteristics (for example, suppressing the increase in internal pressure when used as a battery separator). This is because the degree of improvement in the effect of suppressing the increase in pressure loss when used as a filter medium, the improvement in ion conductivity when used as a separator for capacitors, and the like is low.
[0024]
The fibers constituting the nonwoven fabric of the present invention can contain, in addition to the above-described ultrafine fiber aggregate and / or pulp-like material, ultrafine fibers, thick fibers having a fiber diameter exceeding 5 μm, and the like.
[0025]
These ultrafine fibers are aggregated and are not in the state of an ultrafine fiber aggregate, that is, the individual ultrafine fibers are in a dispersed state. Various characteristics can be imparted by being in such a dispersed state. For example, when it is used as a battery separator, it is excellent in electrical insulation, and also has excellent electrolyte retention, so that an electromotive reaction can be caused smoothly. Moreover, when used as a filter medium, the filtration performance can be improved. Furthermore, when used as a separator for capacitors, it has excellent electrical insulation.
[0026]
The dispersed ultrafine fibers (hereinafter sometimes referred to as “dispersed ultrafine fibers”) may be the same as the ultrafine fibers constituting the ultrafine fiber aggregate (hereinafter also referred to as “aggregate ultrafine fibers”). May be different.
[0027]
In addition, it is preferable that the fiber diameter of each dispersion | distribution ultrafine fiber is substantially the same so that a dispersion | distribution ultrafine fiber may disperse | distribute uniformly and various characteristics may improve. That is, the value (= σ / d) obtained by dividing the standard deviation value (σ) of the fiber diameter distribution of the dispersed ultrafine fiber by the average fiber diameter (d) of the dispersed ultrafine fiber is 0.2 or less (preferably 0.18 or less). ) Is preferred. When the fiber diameters of the dispersed ultrafine fibers are exactly the same, the standard deviation value (σ) is 0, so the lower limit of the value (σ / d) is 0.
[0028]
The “average fiber diameter (d) of the dispersed ultrafine fibers” refers to a value obtained by measuring the fiber diameters of 100 or more (n) dispersed ultrafine fibers and averaging the measured fiber diameters. The “standard deviation value (σ)” of the dispersed ultrafine fiber is a value calculated from the following equation using the measured fiber diameter (χ).
Standard deviation = {(nΣχ²-(Σχ)²) / N (n-1)}^1/2
Here, n means the number of measured dispersed ultrafine fibers, and χ means the fiber diameter of each dispersed ultrafine fiber.
[0029]
In addition, when the dispersion | distribution ultrafine fiber whose fiber diameter is 5 micrometers or less consists of a 2 or more types group from a viewpoint of fiber diameter distribution, it is preferable that the said relationship is materialized about each dispersion | distribution ultrafine fiber group.
[0030]
Also, each dispersed ultrafine fiber has substantially no change in diameter in the fiber axis direction (that is, has substantially the same diameter) so that the dispersed ultrafine fiber is uniformly dispersed and various properties are improved. Are preferred).
[0031]
Such a dispersed ultrafine fiber in which the fiber diameters of the respective dispersed ultrafine fibers are substantially the same, or a dispersed ultrafine fiber whose diameter does not substantially change in the fiber axis direction, is, for example, regulated in the sea component in the spinneret portion. Then, it can be obtained by removing the sea component of the sea-island type composite fiber obtained by the composite spinning method in which the island component is extruded and combined.
[0032]
In addition, depending on the method of removing the sea component of the sea-island type composite fiber obtained by the method of spinning after mixing the resin constituting the island component and the resin constituting the sea component, which is generally referred to as a mixed spinning method, It is difficult to obtain dispersed ultrafine fibers in which the fiber diameters of the dispersed ultrafine fibers are substantially the same, or dispersed ultrafine fibers whose diameter does not substantially change in the fiber axis direction. However, it can be used in the present invention.
[0033]
In addition, it is difficult to obtain a dispersed ultrafine fiber in which the fiber diameters of the dispersed ultrafine fibers are substantially the same, or a dispersed ultrafine fiber whose diameter does not substantially change in the fiber axis direction even by the melt blow method. However, it can be used in the present invention.
[0034]
The dispersed ultrafine fiber of the present invention may contain one or more kinds of dispersed ultrafine fibers as described above, or two or more kinds. For example, the dispersion ultrafine fiber formed from the sea-island composite fiber obtained by the composite spinning method and the dispersed ultrafine fiber formed from the sea-island composite fiber obtained by the mixed spinning method can be included.
[0035]
If the dispersed ultrafine fiber contains a resin component that can be involved in fusion (hereinafter sometimes referred to as “fused component”), the fused ultrafine fiber can be fused by the fused component, and the dispersed ultrafine fiber is reliably This is a preferred embodiment because it is fixed and the dispersed ultrafine fibers do not fall off or fluff.
[0036]
When the dispersed ultrafine fiber includes a fusion component, the dispersed ultrafine fiber can be composed of only the fusion component, or a component having a melting point higher than that of the fusion component and the fusion component (hereinafter referred to as “non- It may also be composed of two or more types of components (sometimes referred to as “fused components”). When the dispersed ultrafine fiber is composed of two or more kinds of components including a fusion component and a non-fusion component as in the latter case, the fiber form can be maintained even when fused by the fusion component. This is preferable because of its excellent shape stability.
[0037]
When the dispersed ultrafine fiber is composed of a fusion component and a non-fusion component, the fusion component preferably occupies a part or all of the surface of the dispersion ultrafine fiber so that fusion can be performed. More specifically, the cross-sectional shape of the dispersed ultrafine fiber is preferably, for example, a core-sheath type, an eccentric type, or a sea-island type. The non-fusion component preferably has a melting point that is 10 ° C. or more higher than the melting point of the fusion component so that the fiber shape can be maintained, and more preferably has a melting point that is 20 ° C. or more.
[0038]
The dispersed ultrafine fiber containing the fusion component and the non-fusion component is, for example, a cross-sectional shape as described above as a die for extruding the island component when spinning a sea-island type composite fiber by a conventional composite spinning method. (For example, a core-sheath type, an eccentric type, and a sea-island type) can be used to spin a sea-island type composite fiber to remove sea components, or spin a sea-island type composite fiber by a conventional composite spinning method. In this case, it can be obtained by supplying a resin in which a fusion component and a non-fusion component are mixed to a die for extruding the island component, spinning the sea-island type composite fiber, and removing the sea component.
[0039]
The “melting point” in the present invention refers to a temperature that gives a maximum value of a melting endothermic curve obtained by using a differential scanning calorimeter at a temperature rising temperature of 10 ° C./min and raising the temperature from room temperature. When there are two or more maximum values, the highest temperature maximum value is taken as the melting point.
[0040]
The dispersed ultrafine fibers are preferably short fibers having a high degree of freedom (fiber length of 30 mm or less) so that the dispersed ultrafine fibers can be uniformly dispersed. However, when the dispersed ultrafine fibers and sea-island type composite fibers are cut, If fibers or island components are crimped together, it is easy to form an ultrafine fiber assembly, so it is necessary to use dispersed ultrafine fibers or sea-island type composite fibers that are difficult to crimp between dispersed ultrafine fibers or island components when cutting. preferable.
[0041]
Examples of such dispersed ultrafine fibers and sea-island type composite fibers that are difficult to be crimped include, for example, dispersed ultrafine fibers and sea-island type composite fibers containing polymethylpentene, or a melting point of 166 ° C. or higher (preferably 168 ° C. or higher) And dispersed ultrafine fibers and sea-island type composite fibers.
[0042]
Moreover, it is preferable that the cross-sectional shape of the dispersed ultrafine fiber is circular so that the dispersed ultrafine fiber can be easily dispersed uniformly.
[0043]
If the nonwoven fabric of the present invention contains thick fibers having a fiber diameter exceeding 5 μm in addition to the aggregate ultrafine fibers, the nonwoven fabric can be made excellent in mechanical strength. For example, when used as a battery separator, this thick fiber can prevent the separator (nonwoven fabric) from breaking, and the thick fiber resists pressure to ensure a void, Preferably, combined with the action of the dispersed ultrafine fibers, the electrolyte retainability is excellent, and an electromotive reaction can be caused smoothly. In addition, when used as a filter medium, an appropriate gap can be secured by this thick fiber, so that an increase in pressure loss can be suppressed. Furthermore, when used as a separator for a capacitor, an appropriate gap is formed, so that ion conductivity can be improved.
[0044]
A thicker fiber diameter of the thick fiber is superior in the above-described effect, and therefore, the fiber diameter is preferably 8 μm or more, more preferably 9 μm or more, and even more preferably 10 μm or more. If the fiber diameter of the thick fiber is too large, the thickness of the nonwoven fabric increases, and various characteristics (electrical insulation performance when used as a battery separator or capacitor separator, and filtration when used as a filter material) Performance, etc.) tends to decrease, and is preferably 35 μm or less, more preferably 30 μm or less.
[0045]
When the dispersed ultrafine fibers are also included, if the average fiber diameter of the thick fibers is 5 times or more than the average fiber diameter of the dispersed ultrafine fibers, voids are secured by the thick fibers, and the dispersed ultrafine fibers are likely to exist in the voids. . That is, it is preferable because dispersed ultrafine fibers exist between the skeletons made of thick fibers, and even when pressure is applied, it is difficult to break and a void can be secured. More preferably, the average fiber diameter of the thick fibers is at least 5.5 times the average fiber diameter of the dispersed ultrafine fibers.
[0046]
The average fiber diameter of the thick fibers is a value obtained in the same manner as the average fiber diameter of the dispersed ultrafine fibers. That is, it is a value obtained by measuring the fiber diameters of 100 or more (n) thick fibers and averaging the measured fiber diameters.
[0047]
As such a thick fiber, it is preferable to include a highly elastic thick fiber having a Young's modulus of 50 cn / dtex or more. This is because the inclusion of such highly elastic thick fibers having Young's modulus makes it difficult to break due to tension, and resists pressure and facilitates securing voids. In addition, since it is excellent in such an effect, so that Young's modulus is high, it is preferable that it is 65 cn / dtex or more, and it is more preferable that it is 80 cn / dtex or more.
[0048]
This “Young's modulus” refers to the value of the apparent Young's modulus calculated from the initial tensile resistance measured by the method specified in JIS L 1015: 1999, paragraph 8.11. The initial tensile resistance is a value measured by a constant speed tension type testing machine.
[0049]
The fiber diameter of the highly elastic thick fiber is not particularly limited as long as it is a fiber diameter exceeding 5 μm, but it is preferably 7 μm or more and is preferably 8 μm or more so that it is difficult to break and a void can be secured. Is more preferable, and it is still more preferable that it is 10 micrometers or more. On the other hand, if the fiber diameter of the highly elastic thick fiber is too large, the thickness of the nonwoven fabric increases, and various properties (electrical insulation performance when used as a battery separator or capacitor separator, when used as a filter material) It is preferable that the thickness is 35 μm or less because the filtration performance tends to be reduced. A more preferable fiber diameter of the highly elastic thick fiber is 13 to 30 μm, and a more preferable fiber diameter is 13 to 25 μm.
[0050]
In addition, when the dispersed ultrafine fibers are included, the high elastic thick fibers are excellent in the performance of securing voids, so that the average fiber diameter of the highly elastic thick fibers is not less than 6 times the average fiber diameter of the dispersed ultrafine fibers. It is preferable that it is 6.5 times or more.
[0051]
Moreover, when the dispersion | distribution ultrafine fiber is included, it is preferable that the average fiber length of a highly elastic thick fiber is 2.5 times or more of the average fiber length of a dispersion | distribution ultrafine fiber. By satisfying such a relationship, it becomes easy for dispersed ultrafine fibers to be present between the skeletons made of highly elastic thick fibers. More preferably, the average fiber length of the highly elastic thick fibers is at least 3 times the average fiber length of the dispersed ultrafine fibers, more preferably at least 4 times, and most preferably at least 5 times.
[0052]
The “fiber length” in the present invention refers to the length obtained by JIS L 1015 (chemical fiber staple test method) B method (corrected staple diagram method), and “average fiber length” is 100 randomly selected. The average value of the fiber lengths of the fibers.
[0053]
Although this highly elastic thick fiber can be comprised from the organic type component and / or the inorganic type component, it is preferable that it is comprised from the organic type component which can be reduced in weight. More specifically, it can be comprised from 1 or more types of resin components, such as a polyamide-type resin, polyolefin-type resin, and polyester-type resin. In particular, it is preferably composed of a polyolefin-based resin so as to be excellent in chemical resistance (in the case of a battery separator, resistance to electrolytic solution). For example, polyethylene resin (for example, ultra high molecular weight polyethylene, high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, ethylene copolymer, etc.), polypropylene resin (for example, polypropylene, propylene copolymer) And a polymethylpentene resin (for example, polymethylpentene, methylpentene copolymer, etc.). Of these, ultra high molecular weight polyethylene and polypropylene are preferred.
[0054]
In addition, the highly elastic thick fiber of this invention may be comprised from the above resin components independently, and 2 or more types of resin components may be mixed or composited. As a cross-sectional shape of the highly elastic thick fiber composed of two or more kinds of resin components, for example, a core-sheath type, an eccentric type, and a sea-island type can be used. Thus, when comprised from 2 or more types of resin components, it can fuse | fuse by the resin component which comprises the fiber surface.
[0055]
In addition, when the dispersed ultrafine fibers are included, when the fiber diameter of the highly elastic thick fibers is 10 μm or more, the mass ratio of the highly elastic thick fibers is 1 to 4 times the mass ratio of the dispersed ultrafine fibers. preferable. This is because such a mass ratio tends to result in a state in which dispersed ultrafine fibers are present between the skeletons made of highly elastic thick fibers.
[0056]
Further, it is preferable that a thick fused fiber is included as the thick fiber, and the fused thick fiber is fused. The inclusion of such fused thick fibers is preferable because the mechanical strength can be further improved.
[0057]
The fusion component of the fused thick fiber has a melting point that does not adversely affect the constituent materials other than the fused thick fiber (for example, ultrafine fiber aggregate, pulp-like material, dispersed ultrafine fiber, highly elastic thick fiber, etc.). preferable. For example, when fibers other than fusion thick fibers include an ultrafine fiber assembly made of polypropylene resin alone, a dispersed ultrafine fiber made of polypropylene resin alone, and a highly elastic thick fiber made of polypropylene resin alone Is a polyethylene-based resin (for example, ultrahigh molecular weight polyethylene, high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, ethylene copolymer, etc.) It is preferable to contain a propylene copolymer (for example, ethylene-butene-propylene copolymer, ethylene-butadiene-propylene copolymer, ethylene-propylene copolymer, etc.). Ultrafine fiber assembly made of polypropylene resin alone, polypropylene resin alone In the case of the dispersion ultrafine fiber and the high elastic fiber made of ultrahigh molecular weight polyethylene alone, polyethylene (for example, high density polyethylene, medium density polyethylene, low density) Polyethylene, linear low density polyethylene, etc.) or ethylene copolymers.
[0058]
This fusion-bonded fiber may be composed only of the fusion component, or may contain a non-fusion component having a melting point higher than that of the fusion component in addition to the fusion component. When it is composed of a fusion component and a non-fusion component as in the latter case, the mechanical strength of the nonwoven fabric can be further improved. The cross-sectional shape of the fused thick fiber in this case can be, for example, a core-sheath type, an eccentric type, or a sea-island type. The non-fusion component is preferably made of a resin that is higher by 10 ° C. than the melting point of the fusion component, and more preferably made of a resin that is higher by 20 ° C. or more.
[0059]
The nonwoven fabric of the present invention may contain the above-described ultrafine fiber aggregate and / or pulp and other materials (for example, dispersed ultrafine fibers, highly elastic thick fibers, fusion thick fibers, etc.). (1) extra fine fiber aggregate and dispersed extra fine fiber, (2) extra fine fiber aggregate and highly elastic thick fiber, (3) extra fine fiber aggregate and fusion thick fiber, (4) extra fine fiber aggregate, dispersed extra fine fiber And (5) ultrafine fiber aggregate, dispersed ultrafine fiber, and fused thick fiber, (6) ultrafine fiber aggregate, fused thick fiber, and highly elastic thick fiber, (7) ultrafine fiber aggregate It is preferable to consist of a combination of a body, a dispersed ultrafine fiber, a highly elastic thick fiber, and a fusion thick fiber.
[0060]
The non-woven fabric constituent material of the present invention (for example, ultrafine fiber aggregate, dispersed ultrafine fiber, highly elastic thick fiber, fusion thick fiber, etc.) is composed of an organic component and / or an inorganic component as described above. However, it is preferable that any constituent material is composed of an organic component so that the nonwoven fabric can be reduced in weight. More specifically, it can be composed of one or more types such as polyamide resin, polyolefin resin, and polyester resin. In particular, it is preferable that any constituent material is substantially composed of a polyolefin-based resin so as to be excellent in chemical resistance. The phrase “substantially composed of a polyolefin-based resin” means that the surface of the constituent material is substantially composed of a polyolefin-based resin because the portion of the constituent material that is greatly affected by the chemical is the surface. For example, a fiber composed of a polyamide resin and a polyolefin-based resin and in which only the polyolefin-based resin occupies the surface of the fiber (excluding both ends of the fiber) is substantially a polyolefin-based fiber.
[0061]
If the resin constituting the surface of the constituent material of the nonwoven fabric of the present invention (for example, an ultrafine fiber aggregate, pulp-like material, dispersed extrafine fiber, thick fiber, etc.) is made of the same type of resin, the fusion force between the constituent materials is increased. It is suitable because it is strong and excellent in mechanical strength. In particular, if the surface is made of polypropylene resin, the heat resistance is excellent. In addition, even when the fusing components of the constituent materials of the nonwoven fabric (for example, ultrafine fiber aggregates, pulp-like materials, dispersed extrafine fibers, thick fibers, etc.) are all made of the same type of resin, the fusing power between the constituent materials is strong. It is suitable because of its excellent mechanical strength. In particular, it is preferable that the fusion component of the constituent material is made of a polyethylene resin.
[0062]
The fibers constituting the nonwoven fabric of the present invention (for example, dispersed ultrafine fibers, aggregated ultrafine fibers, highly elastic thick fibers, fused thick fibers, etc.) can be in an unstretched state, but seem to have excellent mechanical strength. Further, it is preferably in the stretched state.
[0063]
Further, the fiber length of the fibers constituting the nonwoven fabric of the present invention (for example, dispersed ultrafine fibers, aggregated ultrafine fibers, highly elastic thick fibers, fusion thick fibers, etc.) is not particularly limited, but the fiber length is It is preferable that it is 0.5-30 mm. More preferably, it is a fiber cut to 1 to 20 mm.
[0064]
The nonwoven fabric of the present invention contains the above-described ultrafine fiber aggregate and / or pulp-like material, but the total number of ultrafine fiber aggregates and / or pulp-like material on one surface (A) of the nonwoven fabric, and the nonwoven fabric Since the total number of ultrafine fiber aggregates and / or pulp-like materials on the other surface (B) is different, various characteristics can be imparted and can be adapted to various applications. For example, when used as a separator for a sealed battery, the electrolyte solution is likely to be localized on the surface where the total number of ultrafine fiber aggregates and / or pulp-like materials is large. If it arrange | positions, since the contact opportunity of oxygen and a negative electrode increases and oxygen can fully be consumed, the raise of the internal pressure of a battery can be suppressed. Further, when used as a filter medium, an increase in pressure loss can be suppressed due to the presence of a surface having a small total number of ultrafine fiber aggregates and / or pulp-like materials. Furthermore, when used as a separator for capacitors, the electrolyte solution is localized due to the presence of a surface having a large total number of ultrafine fiber aggregates and / or pulp-like materials, but is rich in ion conductivity. Can be increased.
[0065]
The degree of difference in the total number of the ultrafine fiber aggregates and / or pulp-like materials is not particularly limited because it varies as appropriate depending on the intended use, target performance, etc., but the ultrafine fiber aggregates and / or pulp-like materials are not particularly limited. In other words, since the presence of the non-woven fabric deteriorates the texture of the nonwoven fabric, the ultrafine fiber aggregate and / or the pulp-like material is not used in the aspect of a small total number of ultrafine fiber aggregates and / or pulp-like materials. It is preferably substantially absent. In other words, the surface with a small total number of ultrafine fiber aggregates and / or pulp-like materials is composed of at least one type of fiber selected from dispersed ultrafine fibers, highly elastic thick fibers, and fused thick fibers. Is preferred. In addition, in the surface where the total number of ultrafine fiber aggregates and / or pulp-like materials is small, there may be included splittable fibers (undivided) that can be split by the impact of external force.
[0066]
On one side of this nonwoven fabric, there is substantially no ultrafine fiber aggregate and / or pulp-like material, and an index indicating that the constituent materials (particularly fibers) are uniformly dispersed is the “geometric index”. Can be mentioned. When the value of the formation index is 0.15 or less, the constituent materials are uniformly dispersed. A more preferable formation index is 0.10 or less.
[0067]
This “geometry index” refers to a value obtained by the method described in JP-A-2001-50902. That is, the value obtained as follows.
(1) Light is irradiated from the light source to the object to be measured (nonwoven fabric), and the reflected light reflected in a predetermined region of the object to be measured is received by the light receiving element, and the luminance information is acquired. To do.
(2) A predetermined region of the object to be measured is equally divided into an image size of 3 mm square, 6 mm square, 12 mm square, and 24 mm square to obtain four divided patterns.
(3) The luminance value of each section equally divided for each obtained division pattern is calculated based on the luminance information.
(4) Based on the luminance value of each section, the average luminance (X) for each division pattern is calculated.
(5) A standard deviation (σ) for each division pattern is obtained.
(6) The coefficient of variation (CV) for each division pattern is calculated by the following equation.
Coefficient of variation (CV) = (σ / X) × 100
Here, σ indicates a standard deviation for each divided pattern, and X indicates a luminance average for each divided pattern.
(7) A coordinate group obtained as a result of taking the logarithm of each image size as the X coordinate and the coefficient of variation corresponding to the image size as the Y coordinate is regressed to a linear line by the least square method, and the inclination is calculated. The absolute value of is the formation index.
[0068]
In addition, on one side of the nonwoven fabric, there is substantially no ultrafine fiber aggregate and / or pulp-like material, and an index indicating that the constituent materials (particularly fibers) are uniformly dispersed is “maximum pore diameter”. Can be mentioned. When the maximum pore diameter is 40 μm or less, the constituent materials are uniformly dispersed. It means that the smaller the maximum pore diameter is, the more uniform the dispersibility of the constituent material. Therefore, it is more preferably 35 μm or less, and further preferably 30 μm or less. The “maximum pore diameter” refers to a value measured by a bubble point method using a porometer (manufactured by Coulter).
[0069]
Furthermore, on one side of the nonwoven fabric, an ultrafine fiber aggregate and / or pulp-like material is substantially absent, and an index indicating that the constituent materials (particularly fibers) are uniformly dispersed is “(maximum pore diameter / Average flow pore size) ratio ”. When this (maximum pore diameter / average flow pore diameter) ratio (= maximum pore diameter / average flow pore diameter) is 2 or less (more preferably 1.9 or less), the constituent materials are uniformly distributed. Ideally, the maximum hole diameter and the average flow hole diameter are the same, that is, the (maximum hole diameter / average flow hole diameter) ratio is 1. This “average flow pore size” refers to a value obtained by the method prescribed in ASTM-F316. For example, a value measured by the mean flow point method using a porometer (Polometer, manufactured by Coulter) is used. Say.
[0070]
The “nonwoven fabric surface” in the present invention refers to a nonwoven fabric surface corresponding to one of a pair of opposing surfaces having the largest area of a rectangular parallelepiped formed when the nonwoven fabric surface is smooth, and the magnification is 50 times. An area that can be recognized by taking an electron micrograph. The “total number of ultrafine fiber aggregates and / or pulp-like materials” refers to the number of ultrafine fiber aggregates and / or pulp-like materials that can be confirmed by the electron micrograph. In addition, “whether the total number of ultrafine fiber aggregates and / or pulp-like materials on both surfaces of the nonwoven fabric is different” is the number in the range of 2 mm × 2 mm of the electron micrographs for 20 locations on each surface of the nonwoven fabric. Count and judge based on the average value.
[0071]
It is preferable that the nonwoven fabric of the present invention is substantially fixed only by fusion of constituent materials (particularly fibers). Thus, it is suitable because it is excellent in the texture and excellent in various characteristics by being fixed only by fusion of the constituent materials. For example, when the constituent material is fixed by entanglement other than fusion, dispersion of the constituent material is disturbed by an action (for example, fluid flow such as water flow) for entanglement of the constituent material. In addition, various performances (electrical insulation performance when used as a battery separator or capacitor separator, filtration performance when used as a filter material) may be reduced, but if fixed only by fusion, Since the dispersion of the material is not disturbed, it has excellent properties.
[0072]
In addition, a fiber may get entangled in the stage which manufactures a nonwoven fabric. For example, even when a fiber web is formed by a carding machine or a fiber web is formed by a wet method, the shape of the fiber web can be maintained to some extent. This indicates that the fibers are more or less intertwined. However, this degree of entanglement is not an entanglement that disturbs the dispersion of the constituent materials as in the fluid flow entanglement described above, and therefore, in the present specification, it is regarded as not substantially entangled. Thus, “substantially only fusion of the constituent materials” refers to a state in which the constituent materials are fixed only by fusion after the fiber web is formed. From another viewpoint, this state is that the non-woven fabric components (for example, ultrafine fiber aggregates, pulp-like materials, dispersed ultrafine fibers, highly elastic thick fibers, fused thick fibers, etc.) are substantially two-dimensionally. It is in the state of arrangement.
[0073]
The non-woven fabric of the present invention is unevenly distributed such that the total number of ultrafine fiber aggregates and / or pulp-like materials as described above varies depending on the surface, but other constituent materials (dispersed ultrafine fibers, thick fibers, etc.) are unevenly distributed. Or may be uniformly dispersed. For example, when used as a battery separator or a capacitor separator, other constituent materials are uniformly dispersed, so that the electrolyte can be uniformly held throughout the nonwoven fabric. When it can be manufactured and used as a filter medium, it is excellent in filtration performance because other constituent materials are uniformly dispersed.
[0074]
The thickness of the nonwoven fabric of the present invention is not particularly limited. However, the thinner the nonwoven fabric is, the smaller the thickness of the nonwoven fabric can be reduced when it is applied to various applications. For example, when used as a battery separator, the battery can be reduced in size if used for the same length as in the prior art, and the capacity of the battery can be increased if used for the same amount. On the other hand, if the thickness of the nonwoven fabric is too thin, the mechanical strength of the nonwoven fabric is lowered, so that it is preferably 10 μm or more, more preferably 20 μm or more, still more preferably 30 μm or more, and 40 μm or more. Most preferably.
[0075]
This “thickness” was selected at random using an outer micrometer (0 to 25 mm) specified in JIS B 7502: 1994, measured by the measurement method of JIS C 2111 5.1 (1). The average value of 10 points.
[0076]
The nonwoven fabric of the present invention has a total surface area of 20 m per unit weight.²The above is preferable. In particular, when the thickness is 100 μm or less, the fact that the total surface area is large although it is thin means that it can be involved in various functions. For example, when it is used as a battery separator or a capacitor separator, it can be involved in the retention of the electrolyte and is also excellent in electrical insulation. Moreover, when used as a filter medium, it can participate in collection.
[0077]
Thus, the larger the total surface area, the better the effect, so the total surface area per unit weight is 22 m.²Preferably it is 25m or more.²The above is more preferable.
[0078]
Here, “weight per unit area” means a basis weight obtained based on the method specified in JIS P 8124 (paper and paperboard—basis weight measurement method), and “total surface area per unit weight” means the BET method. The value obtained by converting the surface area obtained by the above per unit area. For example, the basis weight is X (g / m²), The surface area obtained by the BET method is Y (m²/ G), XY (m²) Is the total surface area per unit weight.
[0079]
The basis weight of the nonwoven fabric of the present invention is not particularly limited, but is 10 to 300 g / m.²The degree is appropriate. As described above, when the thickness is 100 μm or less, the thickness can be set to 5 to 75 g / m so that the mechanical strength is excellent.²It is preferably 10 to 50 g / m.²It is more preferable that
[0080]
The nonwoven fabric of the present invention preferably has a tensile strength in at least one direction of 20 N / 5 cm width or more. If it has this level of tensile strength, it can be applied to various applications. More preferable tensile strength is 30 N / 5 cm width or more, and further preferably 40 N / 5 cm width or more. In addition, since tension acts on the nonwoven fabric mainly in the longitudinal direction, the tensile strength is preferably in the longitudinal direction of the nonwoven fabric.
[0081]
This “tensile strength” is a tensile strength tester (Tensilon UTM-III-, manufactured by Orientec Co., Ltd.) manufactured by cutting a rectangular non-woven fabric that is 5 cm long in a direction perpendicular to a certain direction and 20 cm long in a certain direction. 100) between chucks (distance between chucks: 10 cm), the force required to pull the nonwoven fabric at a pulling speed of 300 mm / min and break the nonwoven fabric.
[0082]
The nonwoven fabric of the present invention may be subjected to various treatments so as to suit various applications. For example, when a nonwoven fabric is used as a battery separator or a capacitor separator, it is preferably composed of a polyolefin resin so that the electrolyte solution resistance is excellent as described above. Therefore, it is preferable that hydrophilicity imparting treatment is performed. Moreover, when using a nonwoven fabric as a filter material, in order to improve collection performance, it is preferable that the electretization process is performed.
[0083]
As described above, the nonwoven fabric of the present invention has various performances due to the difference in the total number of ultrafine fiber aggregates and / or pulp-like materials on both sides, and therefore can be applied to various applications. For example, as a separator for a battery, in particular, if a non-woven fabric of ultrafine fibers and / or a surface with a large total number of pulp-like materials are in contact with the negative electrode, a battery in which the internal pressure is hardly increased can be manufactured. When used as a separator for a capacitor, ion conductivity can be increased by the presence of a surface having a large total number of ultrafine fiber aggregates and / or pulp-like materials, and the ultrafine fiber aggregates and / or pulp-like materials can be increased. Due to the presence of the surface with a small total number, it is excellent in electrical insulation, and if used as a filter medium, an increase in pressure loss can be suppressed. In addition to these uses, for example, the present invention can be applied to various uses such as cleaning cloths, medical cover cloths, moisture-permeable waterproof cloths, interlinings, clothing surface materials, synthetic leather base fabrics, and artificial leather base fabrics.
[0084]
In addition, when using the nonwoven fabric of this invention as a battery separator or a capacitor separator, the porosity of the nonwoven fabric is 45 to 70% so that the electrolyte retainability and ion permeability are excellent. Is preferable, and it is more preferable that it is 50 to 65%.
[0085]
This “porosity (P)” is a value obtained by the following equation.
Porosity (P) = {1−W / (T × d)} × 100
Here, W is a basis weight (g / m²), T means the thickness of the nonwoven fabric (μm), and d means the density of the nonwoven fabric component (g / cm³). In addition, when a nonwoven fabric constituent material consists of 2 or more types of resin, the density of a nonwoven fabric constituent material says the mass average of each resin. For example, density d₁Resin A is a (mass%) and density d₂When the resin B is composed of b (mass%), the density of the constituent material is a value obtained by the following equation.
d = d₁× a / 100 + d₂× b / 100
[0086]
Moreover, when using the nonwoven fabric of this invention as a battery separator or a capacitor separator, it is preferable that needle type penetration resistance is 500 gf or more. That is, in any case, the active material constituting the electrode does not penetrate through the separator and short circuit. A more preferable needle type penetration resistance is 600 gf or more, and a more preferable needle type penetration resistance is 700 gf or more.
[0087]
This needle type penetration resistance means the value obtained as follows.
One non-woven fabric is placed so as to cover the cylindrical through-hole of the support base having a cylindrical through-hole (inner diameter: 11 mm), and a fixing material having a cylindrical through-hole (inner diameter: 11 mm) is further formed on the non-woven fabric. The nonwoven fabric is fixed by placing the fixing material so that the center of the fixing material coincides with the center of the cylindrical through hole of the support base. Next, a needle (curvature radius at the tip: 0.5 mm, diameter: 1 mm, protrusion length from the jig: 2 cm) attached to a handy compression tester (Kato Tech, KES-G5) is applied to this nonwoven fabric. ) Is vertically stabbed at a speed of 0.01 cm / s, the force required for the needle to penetrate is measured, and this force is defined as a needle-type penetration resistance.
[0088]
When the nonwoven fabric of the present invention is used as a battery separator or a capacitor separator, the needle penetration resistance per unit weight is preferably 14 gf or more, more preferably 15 gf or more, and more preferably 16 gf or more. More preferably, it is most preferably 18 gf or more. This is because the higher this value is, the more difficult it is for the active material to penetrate the separator.
[0089]
In addition, "average needle type penetration resistance" means the value which averaged the value obtained by measuring the said needle type penetration resistance about 30 places of a nonwoven fabric. The “average needle type penetration resistance per unit weight” is the average needle type penetration resistance per unit weight (g / m²) Means the value divided by.
[0090]
When the nonwoven fabric of the present invention is used as a battery separator or a capacitor separator, oxygen and / or sulfur-containing functional groups (for example, for example, so as to impart or improve the affinity for the electrolyte solution on the surface of the nonwoven fabric constituent material) A sulfonic acid group, a sulfonic acid group, a sulfofluoride group, a carboxyl group, a carbonyl group, etc.), a hydrophilic monomer is graft-polymerized, a surfactant is added, or a hydrophilic resin is used. It is preferable that it is provided.
[0091]
The nonwoven fabric of this invention can be manufactured as follows, for example.
First, an ultrafine fiber assembly and / or a pulp-like material is prepared. Preferably, a highly elastic thick fiber or a fused thick fiber as described above is prepared. In addition, when using a dispersion | distribution ultrafine fiber, it can obtain by unraveling an ultrafine fiber aggregate | assembly with a disaggregator etc. In addition, since the microfiber assembly can be obtained by applying an external force that causes only splitting on the splittable fiber that can be split by the impact of external force, instead of or in addition to the microfiber assembly, A splittable fiber that can be split by the impact of an external force may be prepared.
[0092]
Next, a fiber web is formed using the prepared ultrafine fiber aggregate and / or pulp-like material, preferably a dispersed ultrafine fiber, a highly elastic thick fiber, a fused thick fiber, etc., and when forming this fiber web, An ultrafine fiber aggregate with a different degree of ultrafine fiber aggregation or a pulp-like material with a different degree of fibrillation is used. Since the difference in dispersion behavior is caused by using an ultrafine fiber assembly having a different degree of aggregation or a pulp-like material having a different degree of fibrillation in this way, the surface (A) and the other surface (B) are different. Further, it is possible to form fiber webs having different total numbers of ultrafine fiber aggregates and / or pulp-like materials. For example, when a fiber web is formed by a wet method, the dispersion position in the slurry is different between an ultrafine fiber aggregate with a high degree of aggregation and an ultrafine fiber aggregate with a low degree of accumulation (extremely individual ultrafine fibers). The ultrafine fiber aggregate with a high degree of aggregation is easy to disperse inside the slurry, and the ultrafine fiber aggregate with a low degree of aggregation is easy to disperse on the surface of the slurry. There are many ultrafine fiber aggregates with a high degree of aggregation on the papermaking net side, and there are many ultrafine fiber aggregates with a low degree of aggregation on the side opposite to the papermaking net side.
[0093]
In addition, the method for forming the fiber web is not limited to the wet method. Even when the fiber web is formed by the dry method, the dispersion behavior varies depending on the degree of aggregation and the degree of fibrillation, so the same fiber web is formed. be able to. However, it is preferably formed by a wet method so that fibers other than the ultrafine fiber aggregate and / or pulp can be uniformly dispersed. As this wet method, it can be formed by a conventionally known method, for example, a horizontal long net method, an inclined wire type short net method, a circular net method, or a long net / circular net combination method.
[0094]
Next, the fiber web constituent material is fixed to obtain a nonwoven fabric. When this fixing is performed by fusing the fusion component of the fiber web constituent material (for example, dispersed ultrafine fiber, high elastic thick fiber, fusion thick fiber, etc.), the dispersion of the fiber web constituent material is not disturbed and the texture is excellent. This is preferable because a nonwoven fabric can be formed.
[0095]
The fusion with the fusion component may be performed under no pressure, may be performed under pressure, or is performed after the fusion component is melted under no pressure (preferably immediately pressurized). You may do it. In any case, the heating temperature is preferably within the range from the softening temperature of the fusion component to a temperature higher by 30 ° C. than the melting point. It is preferable that the tensile strength is adjusted as appropriate so that the tensile strength is 20 N / 5 cm. The “softening temperature” refers to a temperature that gives a starting point of a melting endothermic curve obtained by using a differential calorimeter and raising the temperature from room temperature at a rate of temperature increase of 10 ° C./min.
[0096]
If the fiber web contains splittable fibers that can be split by the impact of an external force, the splittable fibers are split by applying a fluid flow such as a water flow to generate an ultrafine fiber aggregate. May be.
[0097]
Moreover, when the thickness of the nonwoven fabric is thicker than necessary, it is preferable to adjust the thickness by passing between a pair of rolls.
[0098]
The total surface area per unit weight of the present invention is 20 m.²The nonwoven fabric as described above can be produced by considering the composition of the constituent materials. That is, it can manufacture by increasing the compounding quantity of a microfiber aggregate and / or a pulp-like thing, and a dispersion | distribution microfiber.
[0099]
On one side of the nonwoven fabric of the present invention, the ultrafine fiber aggregate and / or the pulp-like material is not substantially present, and the formation index is an index indicating that the constituent materials are uniformly dispersed. A nonwoven fabric of 15 or less, a nonwoven fabric having a maximum pore diameter of 40 μm or less, or a nonwoven fabric having a (maximum pore diameter / average flow pore diameter) ratio of 2 or less increases the amount of dispersed ultrafine fibers, or forms an ultrafine fiber aggregate and / or pulp. Use fibers that are not fibrillated as components other than materials, use short fibers with a fiber length of about 1 to 20 mm, form fiber webs by wet methods, and fix fibers only by fusing It can manufacture by using these together, such as (not performing an entanglement process).
[0100]
The nonwoven fabric having a tensile strength of at least 20 N / 5 cm width in at least one direction (preferably the longitudinal direction) of the present invention has a single fiber orientation by adjusting the moving speed of the papermaking net and the slurry flow rate. It can be produced by using these in combination, such as in a state close to the direction, increasing the degree of fusion, and increasing the fiber length.
[0101]
Nonwoven fabric with a porosity of 45 to 70%, suitable as a battery separator or capacitor separator, reduces the amount of dispersed fine fibers, reduces the amount of fibers used, and adjusts the pressure when fusing It can manufacture by using these together.
[0102]
Nonwoven fabric with needle penetration resistance of 500 gf or more and nonwoven fabric with needle penetration resistance per unit weight of 14 gf or more, which is suitable as a battery separator or capacitor separator, use high elastic thick fibers with a large Young's modulus , Increase the amount of high elastic thick fibers, disperse the high elastic thick fibers uniformly, fuse firmly with the fused thick fibers, or melt the fused thick fibers immediately after pressurization. It can be manufactured by adjusting various conditions such as wearing.
[0103]
Since the nonwoven fabric of the present invention is preferably substantially composed only of a polyolefin-based resin so as to be excellent in chemical resistance, when used as a battery separator or a capacitor separator, the retention of the electrolyte is improved. Therefore, it is preferable to perform a hydrophilic treatment. Examples of the hydrophilization treatment include sulfonation treatment, fluorine gas treatment, vinyl monomer graft polymerization treatment, surfactant treatment, discharge treatment, or hydrophilic resin application treatment.
[0104]
In addition, these hydrophilic treatments may be performed on the fibers to form a nonwoven fabric, or the nonwoven fabric may be formed and then the hydrophilic treatment may be performed. However, the hydrophilic treatment is performed after the nonwoven fabric is formed. It is preferable to manufacture. Hereinafter, although the method to hydrophilize after forming a nonwoven fabric is demonstrated, when carrying out a hydrophilization treatment with respect to a fiber, it can implement similarly.
[0105]
The sulfonation treatment is not particularly limited. For example, the sulfonic acid group is introduced by immersing the nonwoven fabric as described above in a solution composed of fuming sulfuric acid, sulfuric acid, sulfur trioxide, chlorosulfuric acid, or sulfuryl chloride. And a method of introducing a sulfonic acid group into a nonwoven fabric by applying an electric discharge in the presence of sulfur monoxide gas, sulfur dioxide gas, sulfur trioxide gas, or the like.
[0106]
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 surface of the nonwoven fabric constituent material 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.
[0107]
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.
[0108]
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 in the nonwoven fabric is irradiated. 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 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. .
[0109]
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.
[0110]
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 inside a separator.
[0111]
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 0.3-5 mass% of the whole nonwoven fabric so that air permeability may not be impaired.
[0112]
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.
[0113]
Since the battery of the present invention uses the nonwoven fabric as described above as a separator, the internal pressure is unlikely to increase. In particular, if the surface of the nonwoven fabric is arranged so that the total number of the ultrafine fiber aggregates and / or pulp-like materials are in contact with the negative electrode, the electrolyte is localized and the chance of contact between oxygen and the negative electrode increases. Thus, since oxygen can be sufficiently consumed, an increase in the internal pressure of the battery can be suppressed.
[0114]
The battery of the present invention can be exactly the same as the conventional one except that the nonwoven fabric as described above is used as a separator. For example, in a cylindrical nickel-hydrogen battery, an electrode plate group in which a nickel positive electrode plate and a hydrogen storage alloy negative electrode plate are wound in a spiral shape through a nonwoven fabric (separator) as described above is inserted into a metal case. It has a structure. As the nickel positive electrode plate, for example, a sponge-like porous porous material filled with an active material made of nickel hydroxide solid solution powder can be used. As the hydrogen storage alloy negative electrode plate, for example, a nickel plated perforated steel plate, For foamed nickel or nickel net, AB₅-Based (rare earth) alloy, AB / A₂B-based (Ti / Zr-based) alloy or AB₂Those filled with a (Laves phase) -based alloy can be used. As the electrolytic solution, for example, a potassium hydroxide / lithium hydroxide two-component system or a potassium hydroxide / sodium hydroxide / lithium hydroxide three-component system can be used. The case is sealed with an insulating gasket by a sealing plate provided with a safety valve. Furthermore, a positive electrode current collector and an insulating plate are provided, and if necessary, a negative electrode current collector is provided.
[0115]
Note that the battery of the present invention does not need to be cylindrical, and may be rectangular or button-shaped. In the case of a square type, it has a laminated structure in which a nonwoven fabric (separator) is disposed between a positive electrode plate and a negative electrode plate. Further, the present invention is not limited to nickel metal hydride batteries, but includes secondary batteries such as alkaline manganese batteries, mercury batteries, silver oxide batteries, and air batteries, nickel-cadmium batteries, silver-zinc batteries, silver-cadmium batteries, nickel-zinc batteries, and the like. Can be a secondary battery.
[0116]
Since the capacitor of the present invention uses a nonwoven fabric as described above as a separator, the ion conductivity can be increased by the presence of a surface having a large total number of ultrafine fiber aggregates and / or pulp-like materials. The electrical insulation is excellent due to the presence of a surface having a small total number of fiber aggregates and / or pulp-like materials.
[0117]
The capacitor of the present invention can be exactly the same as the conventional one except that the nonwoven fabric as described above is used as a separator. For example, a sheet-like collector electrode (for example, an aluminum thin plate), an electrode (for example, an electrode obtained by mixing and pulverizing granular activated carbon, carbon black, and polytetrafluoroethylene), a nonwoven fabric (separator), an electrode, and a collector electrode in this order The capacitor of the present invention can be configured by stacking the insulating sheet on the stacked uppermost layer and / or lowermost layer and then winding the electrode group.
[0118]
The capacitor according to the present invention is suitable for both an aqueous solution capacitor in which the electrolytic solution is an aqueous sulfuric acid solution and a non-aqueous solution capacitor in which an organic solvent such as propylene carbonate and γ-butyrolactone and an electrolyte such as a quaternary ammonium salt are used. Can be used.
[0119]
Although the Example of the separator of this invention is described below, this invention is not limited to these Examples.
[0120]
【Example】
(Example 1)
As a sea-island type composite fiber, a fiber obtained by a composite spinning method in which 25 island components made of polypropylene are present in a sea component made of poly-L-lactic acid (hereinafter referred to as “PLLA”) (fineness: 1 .65 dtex, cut fiber length: 2 mm, melting point: 172 ° C.).
[0121]
Next, this sea-island type composite fiber is immersed in a bath composed of a 10 mass% sodium hydroxide aqueous solution at a temperature of 80 ° C. for 30 minutes to extract and remove PLLA, which is a sea component of the sea-island type composite fiber, to obtain a polypropylene microfiber assembly. (Fiber diameter of polypropylene extra fine fiber: 2 μm) was obtained.
[0122]
Next, half of this polypropylene ultrafine fiber assembly was supplied to an aqueous medium so that the concentration was 0.5%, and then it was melted by a disaggregator for 10 minutes to be sufficiently broken into individual polypropylene dispersed ultrafine fibers. A first slurry was prepared. This polypropylene-dispersed ultrafine fiber had the following physical properties.
Fiber diameter: 2 μm, average fiber diameter: 2 μm, ρ / d: 0.083, melting point: 172 ° C., cut fiber length: 2 mm, average fiber length: 2 mm, density: 0.91 g / cm³, Non-fibrillated, stretched, substantially unchanged in diameter in the fiber axis direction, fiber cross-sectional shape: circular
[0123]
Next, the other half of the polypropylene microfiber assembly is supplied to an aqueous medium so that the concentration is 0.5%, and then is thawed for 3 minutes by a disaggregator to completely dissolve each polypropylene-dispersed microfiber. A second slurry was prepared, in which unmixed polypropylene ultrafine fiber aggregates were mixed.
[0124]
In addition, as the fusion thick fiber, the core component (non-fusion component) is polypropylene (melting point: 168 ° C., density: 0.91 g / cm).³The sheath component (fusion component) is high density polyethylene (melting point: 135 ° C., density: 0.96 g / cm³Core-sheath type composite thick fiber (fineness: 0.8 dtex, fiber diameter: 10.5 μm, average fiber diameter: 10.5 μm, cut fiber length: 5 mm, mass ratio of core component to sheath component is 1: 1) , Not fibrillated, stretched).
[0125]
Further, as a highly elastic thick fiber, a thick fiber made of highly crystalline polypropylene (Young's modulus: 90 cN / dtex, fineness: 1.3 dtex, fiber diameter: 13.5 μm, average fiber diameter: 13.5 μm, cut fiber length: 10 mm) Average fiber length: 10 mm, density: 0.91 g / cm³, Not fibrillated, stretched).
[0126]
Next, 10 mass% of the polypropylene-dispersed ultrafine fiber in the first slurry, 10 mass% of the polypropylene ultrafine fiber aggregate that is not completely understood as the polypropylene-dispersed ultrafine fiber in the second slurry, and 50 mass% of the core-sheath type composite thick fiber Then, a fiber web was formed from the third slurry mixed and dispersed so as to have a blending ratio of 30 mass% of polypropylene high-elasticity thick fibers by a wet method (horizontal long net method).
[0127]
Next, the fiber web is left in a hot-air circulating dryer set at a temperature of 135 ° C. for 3 minutes to dry the fiber web and heat-seal the sheath component (high-density polyethylene) of the core-sheath type composite thick fiber. After fixing the fibers with each other, calender treatment is performed to adjust the thickness, and the fused nonwoven fabric (weight per unit: 40 g / m)², Thickness: 100 μm, (average fiber diameter of thick fibers) / (average fiber diameter of dispersed ultrafine fibers) = 5.5, total surface area per basis weight: 29.7 m²) Was formed.
[0128]
Electron micrographs (magnification: 50 times) on both sides of this fused nonwoven fabric were photographed. On one side (see FIG. 1), a polypropylene ultrafine fiber aggregate was present, but the other side (FIG. 2). In the reference), the polypropylene ultrafine fiber aggregate was substantially absent, and the polypropylene dispersed ultrafine fiber, the core-sheath type composite thick fiber, and the polypropylene highly elastic thick fiber were in a uniformly dispersed state.
[0129]
Next, this fused nonwoven fabric is brought into contact with a mixed gas composed of 3 vol% of fluorine gas, 5 vol% of oxygen gas, 5 vol% of sulfur dioxide gas, and 87 vol% of nitrogen gas for 120 seconds, whereby sulfonic acid groups, A carbonyl group, a carboxyl group, and a hydroxyl group were introduced to produce a fused nonwoven fabric for a separator (hereinafter referred to as a separator).
[0130]
(Comparative Example 1)
Melt blown nonwoven fabric made of polypropylene (average fiber diameter: 5 μm, unstretched, the diameter is substantially changed in the fiber axis direction, fiber cross-sectional shape: circular, basis weight: 40 g / m², Thickness: 100 μm, total surface area per unit area: 35.2 m²) Was prepared.
[0131]
When the electron micrographs on both sides of the melt blown nonwoven fabric were taken, no polypropylene microfiber aggregates existed on either side, and they were in a uniformly dispersed state.
[0132]
Next, in the same manner as in Example 1, this meltblown nonwoven fabric was introduced with a sulfonic acid group, a carbonyl group, a carboxyl group, and a hydroxyl group on the fiber surface to produce a meltblown nonwoven fabric for a separator (hereinafter referred to as a separator).
[0133]
(Measurement of formation index)
The formation index on the surface of the separator of Example 1 where the polypropylene microfiber aggregates were not substantially present and the formation index of the separator of Comparative Example 1 were measured as follows.
(1) Light is applied to the object to be measured (separator) from a light source, and luminance information is obtained by receiving reflected light reflected by a predetermined region of the object to be measured by a light receiving element. .
(2) A predetermined area of the object to be measured was equally divided into an image size of 3 mm square, 6 mm square, 12 mm square, and 24 mm square to obtain four divided patterns.
(3) The luminance value of each section equally divided for each obtained division pattern was calculated based on the luminance information.
(4) Based on the luminance value of each section, the luminance average (X) for each division pattern was calculated.
(5) The standard deviation (σ) for each divided pattern was obtained.
(6) The coefficient of variation (CV) for each divided pattern was calculated by the following equation.
Coefficient of variation (CV) = (σ / X) × 100
Here, σ indicates a standard deviation for each divided pattern, and X indicates a luminance average for each divided pattern.
(7) A coordinate group obtained as a result of taking the logarithm of each image size as the X coordinate and the coefficient of variation corresponding to the image size as the Y coordinate is regressed to a linear line by the least square method, and the inclination is calculated. The absolute value of was used as the formation index. In addition, a formation index means that the fiber is disperse | distributed uniformly, so that a number is small.
The results are shown in Table 1.
[0134]
[Table 1]

[0135]
(Maximum pore size measurement)
The maximum pore diameter in the surface of the separator of Example 1 where the polypropylene ultrafine fiber aggregates were not substantially present and the maximum pore diameter of the separator of Comparative Example 1 were measured by a bubble point method using a porometer (manufactured by Coulter). . This value was as shown in Table 1.
[0136]
(Measurement of (maximum pore diameter / average flow pore diameter) ratio)
The average flow pore diameter on the surface of the separator of Example 1 where the polypropylene microfiber aggregates are not substantially present and the average flow pore diameter of the separator of Comparative Example 1 were measured using a porometer (Polometer, manufactured by Coulter). Measured by the mean flow point method.
[0137]
Next, a (maximum pore diameter / average flow pore diameter) ratio was calculated based on the maximum pore diameter value obtained as described above. The results are shown in Table 1.
[0138]
(Measurement of porosity)
First, the basis weight (W) and thickness (T) of each separator were measured.
[0139]
Next, the density (d) of the resin of the separator constituent material was calculated from the density and mass ratio of each constituent material.
[0140]
Next, “porosity (P)” was calculated from the following equation.
Porosity (P) = {1−W / (T × d)} × 100
The results are shown in Table 1.
[0141]
(Measurement of tensile strength in the longitudinal direction)
Each rectangular separator cut to a length of 5 cm in the direction orthogonal to the longitudinal direction (width direction) and to a length of 20 cm in the longitudinal direction is obtained from a tensile strength tester (Orientec, Tensilon UTM-III-100). Fixed between chucks (distance between chucks: 10 cm), each separator was pulled in the longitudinal direction at a pulling speed of 300 mm / min, and the force required to break each separator was measured. This force was defined as the tensile strength in the longitudinal direction. . The results are shown in Table 1.
[0142]
(Needle-type penetration resistance)
One separator is mounted so as to cover the cylindrical through hole of the support base having a cylindrical through hole (inner diameter: 11 mm), and a fixing material having a cylindrical through hole (inner diameter: 11 mm) on each separator. Are fixed so that the center of the fixing material coincides with the center of the cylindrical through hole of the support base, and each separator is fixed. Then, a handy compression tester (KES-TECH, KES-) is applied to the separator. G5) Needle (curvature radius at the tip: 0.5 mm, diameter: 1 mm, protruding length from jig: 2 cm) is pierced vertically at a speed of 0.01 cm / s, and the needle penetrates The force required for this was measured, and this force was defined as the needle-type penetration resistance. The results are shown in Table 1.
[0143]
(Needle penetration resistance per unit weight)
The needle type penetration resistance per unit basis weight was calculated from the above (needle type penetration resistance) and basis weight. The results are shown in Table 1.
[0144]
(Measurement of pressure retention rate)
Each separator cut to a diameter of 30 mm was brought to a water balance at a temperature of 20 ° C. and a relative humidity of 65%.₀) Was measured.
[0145]
Next, the air in the separator was immersed in an aqueous potassium hydroxide solution having a specific gravity of 1.3 (20 ° C.) for 1 hour so that the aqueous potassium hydroxide solution was replaced, and the aqueous potassium hydroxide solution was retained.
[0146]
Next, the separator was sandwiched between three upper and lower filter papers (diameter: 30 mm), and a pressure of 5.7 MPa was applied for 30 seconds with a pressure pump, and then the mass of the separator (M₁) Was measured.
[0147]
Subsequently, the pressurization liquid retention was calculated | required by the following formula. In addition, this measurement was performed 4 times with respect to one separator, and the average was made into the pressurization liquid retention. The results are shown in Table 1.
Pressure retention ratio (%) = {(M₁-M₀) / M₀} × 100
[0148]
(Battery pressure test)
As the electrode current collector, a paste type nickel positive electrode (33 mm width, 182 mm length) using a foamed nickel base material and a paste type hydrogen storage alloy negative electrode (mesh metal alloy, 33 mm width, 247 mm length) were prepared.
[0149]
Next, each separator was cut into a width of 33 mm and a length of 410 mm, and then sandwiched between a positive electrode and a negative electrode and wound in a spiral shape to create an electrode group corresponding to SC (sub-C) type. This electrode group was housed in an outer can, and 5N potassium hydroxide and 1N lithium hydroxide as electrolytes were poured into the outer can and sealed to prepare a cylindrical nickel-hydrogen battery having a capacity of 2000 mAh. In addition, when the separator of Example 1 was used, it arrange | positioned so that the surface in which a polypropylene microfiber assembly exists may contact | abut with a negative electrode.
[0150]
Next, this cylindrical nickel-hydrogen battery was charged at a temperature of 20 ° C. at 0.5 C, and the battery internal pressure at the time of charging 150% of the capacity was measured. Table 1 shows the ratio when the internal pressure of the battery using the separator of Example 1 is defined as the reference (100).
[0151]
As is apparent from the results in Table 1, the separator of the present invention was thin, excellent in mechanical strength, and capable of producing a battery having a low internal pressure.
[0152]
【The invention's effect】
The non-woven fabric of the present invention is an ultra-fine fiber assembly in which ultra-fine fibers having a fiber diameter of 5 μm or less are aggregated and / or a non-woven fabric containing a pulp-like material, and the ultra-fine fiber assembly on one surface (A) of the non-woven fabric and Since the total number of pulp-like materials and the total number of the ultrafine fiber aggregates and / or pulp-like materials on the other surface (B) of the nonwoven fabric are different, they have various performances. For example, when used as a battery separator, the electrolyte solution is likely to be localized on the surface where the total number of ultrafine fiber aggregates and / or pulp-like materials is large. Since the contact opportunity between oxygen and the negative electrode is increased and oxygen can be sufficiently consumed, a battery in which the internal pressure is hardly increased can be manufactured. Further, when used as a filter medium, an increase in pressure loss can be suppressed due to the presence of a surface with a small total number of ultrafine fiber aggregates and / or pulp-like materials. Further, when used as a separator for a capacitor, the ion conductivity can be increased by the presence of a surface having a large total number of ultrafine fiber aggregates and / or pulp-like materials, and the ultrafine fiber aggregates and / or pulp-like materials can be enhanced. Due to the presence of a surface with a small total number, the electrical insulation is excellent.
[Brief description of the drawings]
FIG. 1 is an electron micrograph of a surface having a large number of ultrafine fiber aggregates of the nonwoven fabric of Example 1.
FIG. 2 is an electron micrograph of the surface of the nonwoven fabric of Example 1 with a small number of ultrafine fiber aggregates.

Claims (9)

Non-woven fabric fixed by fusion only, including an ultrafine fiber assembly formed by removing sea components of sea-island type composite fibers, and containing only ultrafine fibers having a circular fiber cross-sectional shape and a fiber diameter of 5 μm or less , and the the total number of the ultrafine fibrous aggregate in one face (a) of the nonwoven fabric, Ri said and are Do different total number of the ultrafine fibrous aggregate in the other surface of the nonwoven fabric (B), the nonwoven fabric is individually A non-woven fabric characterized by being derived from a fiber web formed by a wet method in which a slurry in which ultrafine fibers and ultrafine fiber aggregates are dispersed .   The nonwoven fabric according to claim 1, wherein the ultrafine fiber aggregate is substantially absent on a surface having a small total number of ultrafine fiber aggregates. The nonwoven fabric according to claim 1 or 2, wherein the nonwoven fabric has a thickness of 100 µm or less. The nonwoven fabric according to any one of claims 1 to 3, wherein a total surface area per unit weight is 20 m ² or more. The nonwoven fabric according to any one of claims 1 to 4 , wherein the nonwoven fabric is used as a battery separator. The nonwoven fabric according to any one of claims 1 to 4 , wherein the nonwoven fabric is used as a separator for a capacitor. A battery using the nonwoven fabric according to any one of claims 1 to 4 as a separator. The battery according to claim 7 , wherein a surface having a large total number of the ultrafine fiber aggregates of the nonwoven fabric is in contact with the negative electrode. A non-woven fabric according to any one of claims 1 to 4 is used as a separator.

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