JP2002151040A - Separator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separator superior in mechanical performance, separability and various performances such as flexibility or the like, and used for a battery or capacitor having a high production efficiency. SOLUTION: This is the separator used for the battery or the capacitor and comprised that it is using a nonwoven fabric, and 30 wt.% or more of the nonwoven fabric is constituted by flat plate-formed fibers with the flatness of 2-30 and thickness of 0.1 to 30 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a separator used for a battery or a capacitor which is excellent in various performances such as mechanical performance, flexibility and separation property, and which is excellent in production efficiency, and an electric double layer using the same. Related to capacitors.

[0002]

2. Description of the Related Art Conventionally, porous films and nonwoven fabrics have been widely used as separators for batteries and capacitors. However, since the membrane film has low elongation and poor flexibility, it must be installed on a battery or capacitor (when wound).
However, there is a problem that the workability is poor, and a large winding tension is applied at the time of winding or a crack is easily generated when an impact is applied. On the other hand, it is also known to use a non-woven fabric using cellulose fibers or various synthetic fibers as the separator.However, when the fiber diameter is reduced or the fiber density is increased to maintain the separation property, the internal resistance increases. However, when the fiber diameter is increased or the fiber density is increased in order to reduce the internal resistance, the pore size of the nonwoven fabric becomes large, and the separation property and the mechanical performance become insufficient.
If the pore size of the nonwoven fabric is too large, there is an increased risk of a short circuit due to, for example, a peeled product of the electrode penetrating the separator.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a separator for batteries or capacitors which is excellent in various performances such as mechanical performance, separation properties and flexibility, and which has high production efficiency, and for electric double layer capacitors. It is to propose a separator and an electric double layer capacitor using the separator.

[0004]

The present invention relates to (1) a separator used for a battery or a capacitor and using a nonwoven fabric, wherein 30% by mass or more of the nonwoven fabric has a flatness of 3 to 20 and a thickness of 3 to 20; (2) a separator comprising a flattened fiber having a thickness of 0.1 to 30 μm;
(1) The separator according to (1), wherein the slab-shaped fibers are fibers obtained by splitting layered split fibers in which polyester-based resins and polyamide-based resins are alternately arranged. The separator according to (1) or (2), which is used for a multilayer capacitor,
(4) An electric double-layer capacitor using the separator according to (3).

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In order to obtain a high-performance separator, the present invention uses a specific nonwoven fabric, specifically, a nonwoven fabric using ultrafine flat plate-like fibers (fiber A).
In general, the use of ultrafine fibers increases the flexibility and separation properties, but it is necessary to increase the fiber density in order to obtain mechanical performance and separation properties. However, when the basis weight is increased to enhance the performance, the volume occupied by the separator increases, the electric capacity per battery or capacitor decreases, and the internal resistance increases because the through-holes for transmitting ions become redundant. It gets bigger.

[0006] In order to solve the above problems, the present invention provides:
A specific flat plate fiber is used. By using the flat-plate-shaped fibers, the fibers can be easily oriented two-dimensionally and the contact area between the fibers increases, so that the fibers can be firmly bonded to each other and the mechanical performance of the nonwoven fabric improves. Moreover, the pore size formed in the nonwoven fabric is reduced. Therefore, sufficient mechanical performance and separation properties can be secured without increasing the thickness and basis weight. In general, when the pore size is reduced, there arises a problem that the ion permeability decreases and the internal resistance increases. That is, for example, when fibers are entangled in a three-dimensional random state, the ion flow becomes complicated and the curvature is increased, so that the internal resistance is increased. However, in the present invention, since flat fibrous fibers which are easily two-dimensionally oriented are used, through holes are easily formed in the nonwoven fabric, and the ion flow path is straight and the curvature is small, so that the internal resistance is reduced. Is suppressed. In particular, in electric double layer capacitors, which are widely used as capacitors, fine activated carbon and activated carbon fibers are used as electrodes, so it is more important to control the pore size, and at the same time it is necessary to increase the capacitance per volume Therefore, it is more highly required to reduce the occupied area of the separator. Therefore, when the separator of the present invention is applied to an electric double layer capacitor, more remarkable effects can be obtained.

Further, when such through holes are formed, the time required for infiltrating the electrolytic solution is remarkably reduced as compared with the nonwoven fabric formed by the fibers having a very fine circular cross section, and the production efficiency is further improved. In particular, since the separator of the present invention can be made thinner, the permeation time of the electrolytic solution can be significantly reduced, and a remarkable effect can be obtained. In addition, when using an organic solvent-based electrolyte, it is necessary to dry the separator sufficiently before installing it in a battery or capacitor. Since small through-holes are easily formed, drying of water is promoted and efficiency is improved.

The flatness of the flat fiber A must be 3 or more, preferably 4 or more, more preferably 8 or more, and particularly preferably 10 or more. If the flatness of the flat-plate shaped fibers A is too small, the contact area between the fibers becomes small and the mechanical performance of the nonwoven fabric becomes insufficient, and the pore size becomes large, making it difficult to obtain a thin separator. Moreover, since the fibers are unlikely to be two-dimensionally oriented, it is difficult to form a through-hole having a small curvature ratio, thereby increasing the internal resistance. However, if the flatness of the flat-plate fibers A is too large, the processability during the production of the nonwoven fabric is deteriorated. As the flat plate-like fiber A, a plate-like fiber having a specific flatness can be used, but a fiber having a cross section of an elliptical shape, a rectangular shape, or a shape similar to the shape can be preferably used. In particular, fibers having a substantially square cross-sectional shape have a large mutual contact area,
Further, it can be more preferably used because it is easier to orient in two dimensions. In addition, the cross section referred to in the present invention refers to a cross section formed when the fiber is cut perpendicularly to the length direction of the fiber and in the thickness direction. In addition, the flatness referred to in the present invention is the long diameter (diameter of the minimum circumscribed circle) in the cross section of the fiber A.
Divided by the thickness (diameter of the largest inscribed circle = minor axis).

In the present invention, the thickness of the fiber A must be 30 μm or less, preferably 10 μm or less, more preferably 5 μm or less, and particularly preferably 3 μm or less. By having such a thickness, the nonwoven fabric can be made thinner, and the fibers A can be easily oriented in the two-dimensional direction. Therefore, the contact area between the fibers A increases, and the mechanical performance of the nonwoven fabric improves. Since the through-hole size is reduced, a high degree of separation can be achieved without increasing the thickness.
In general, when the fiber diameter is reduced, the separation property is improved, but there is a problem that the internal pressure is increased. However, in the present invention, since the through hole is linear and the curvature is reduced at the same time, the internal pressure is reduced. Can be effectively suppressed.

However, if the thickness of the fiber A is too small, the manufacturing process of the nonwoven fabric is reduced, and the mechanical performance tends to be insufficient. Therefore, the thickness of the fiber A is 0.1 μm or more, particularly 0.5 μm or more, and more preferably 0.1 μm or more.
It is preferably at least 8 μm. The major axis (width) of the flattened fiber may be determined based on the thickness and flatness.
It is preferably about 60 μm. Further, from the viewpoint of increasing the entanglement between the flat plate fibers and securing the mechanical performance of the separator, the length of the plate fibers A is preferably 0.5 mm or more, particularly preferably 1 mm or more. From the viewpoint of maintaining the homogeneity of the nonwoven fabric, the length is preferably 20 mm or less, particularly 10 mm or less, and more preferably 5 mm or less.

The type of the plate-like fiber A is not particularly limited. For example, a fiber composed of at least one resin selected from a polyester resin, a polyamide resin, a polyolefin resin, an acrylic resin, a polyvinyl alcohol resin and the like can be used. However, in the present invention, it is more preferable that at least a part of the fiber A is a fiber composed of a polyester resin and / or a polyamide resin. Since such a resin has good lyophilicity as compared with a polyolefin-based resin or the like, it is possible to easily apply an electrolytic solution. In particular, when using an organic solvent-based electrolyte, it is necessary to dry sufficiently before immersion in the electrolyte, but since the resin has a high melting point, it can be dried at a high temperature, and the drying efficiency is increased. Can be. Examples of the polyester resin that can be used in the present invention include polyesters such as polyethylene terephthalate, polybutylene terephthalate, polytetramethylene terephthalate, and polyethylene oxybenzoate, and copolymers thereof. As the polyamide resin, for example, nylon 6, nylon 66, nylon 6
And polyamides such as 10, nylon 11, and nylon 12, and copolymers thereof. Among them, polyethylene terephthalate is more preferable as the polyester resin and nylon 6 is more preferable as the polyamide resin from the viewpoint of heat resistance and cost.

When an organic solvent-based electrolyte is used, it is preferable to use plate-like fibers made of a thermoplastic resin having a melting point of 205 ° C. or higher, particularly 210 ° C. or higher. When using an organic solvent-based electrolyte, it is necessary to dry sufficiently before installing the battery or capacitor.However, in the case of fibers made of a thermoplastic resin having a high melting point, the drying temperature should be increased and It becomes possible to dry. In particular, in the present invention, since the flat fibers are used, a through-hole having a small curvature ratio is easily formed and the thickness can be reduced, so that a more remarkable effect can be obtained in terms of drying efficiency. For example, when fiber A made of a thermoplastic resin having a melting point of 240 ° C. is used, a melting point of 160
Drying can be performed in about 2/3 to 1/2 of the time when a polypropylene-based fiber having a temperature of not more than ° C is used.

The method of obtaining the fiber A is not particularly limited, and a method of extruding (for example, spinning) the above resin from a slit-shaped die may be employed. However, in this method, there is a limit in reducing the diameter of the fiber A, and in order to obtain a resin having a high degree of flatness, it is necessary to increase the ratio of the major axis / minor axis of the slit of the die. It is difficult to stably obtain the fiber A from the viewpoint of process passability. From the above, composite spinning is performed using a plurality of types of resins, and the obtained composite fiber is divided at the time of drawing, cutting, papermaking, etc. in the spinning process, so that the flatness is high and the flatness is fine. Preferably, it is a fiber. In particular, it is more preferable that the resin be a layered splittable fiber alternately arranged.By splitting such a layered splittable fiber, it is possible to efficiently obtain a highly flat flattened fiber having a high flatness, In addition, since the thickness of the fiber can be homogenized, it is possible to obtain a separator having a higher degree of formation and homogeneity. For example, even when the basis weight is as low as about 60 g / m ² or less, a separator having a difference between the maximum pore size and the average pore size of 15 μm or less, particularly 13 μm or less can be obtained. Fineness of the layered splittable conjugate fiber, number of layers,
The mixing ratio of the resin and the like may be appropriately set, but the fineness is 1 to
It is preferable that the number of layers is about 5 dtex and the number of layers is about 5 to 20, especially about 7 to 15, and when two kinds of resins are used, the mixing ratio is preferably 10:90 to 90:10 (mass ratio). By controlling the number of layers, the thickness and flatness of the fiber A can be adjusted.

The method of division is not particularly limited, and examples thereof include various methods such as a method using a chemical, a high-pressure fluid injection method, a method of performing false twisting, a needle punching method, and a heat treatment method. For example, in the case of a dividing method using drugs,
The polyester part is partially dissolved with an alkaline aqueous solution and divided into a joint part between the polyester part and the polyamide part.
A method in which separation is caused by peeling, a method in which a polyamide portion is swollen using an emulsified aqueous solution of a solvent capable of swelling and dissolving polyamide such as benzyl alcohol, and the interface is peeled to perform separation, and the like. However, if such a fiber is made into a drawn yarn, the dry heat shrinkage stress becomes large, so that the interface portion is peeled off, so that the fiber can be easily divided and thinned. It is preferable that the interface portion is substantially completely divided, but a portion that is not partially divided may remain as long as the effect of the present invention is not impaired.

As the resin constituting the splittable fiber, a polyester resin and / or a polyamide resin is suitably used as described above. Above all, it is more preferable to use, as the fiber A, a plate-like resin obtained by dividing a layered split fiber in which a polyester-based resin and a polyamide-based resin are alternately arranged. Polyester-based resins and polyamide-based resins are suitable for the present invention because they have excellent affinity with the electrolytic solution, mechanical performance, cost, and heat resistance, and the composite fibers obtained using both resins have good splitting properties. Used for By alternately arranging the polyester-based resin and the polyamide-based resin and performing a composite spinning, and dividing this, the flat-plate-like fiber A can be efficiently produced.

By using such a fiber A, it is possible to obtain a separator used for a high-performance battery or capacitor. Non-woven fabrics have excellent mechanical performance compared to porous films, and are flexible, have high elongation, and are excellent in bending resistance, so they have good winding and impact resistance and are also excellent in durability. Performance is achieved. In order to obtain the effect of the present invention, the mixing ratio of the fiber A is 30% by mass or more / non-woven fabric or more, preferably 40% by mass or more / non-woven fabric, more preferably 60% by mass or more.
% By mass or more / nonwoven fabric. Of course, a fiber other than the fiber A, a resin, an additive, and the like may be blended as long as the effects of the present invention are not impaired. A nonwoven fabric may be produced using only the fiber A, but from the viewpoint of improving the mechanical performance of the nonwoven fabric, it is preferable to incorporate a binder, particularly a binder fiber. As the binder, one that exhibits a binder function at a lower temperature than the fiber A is suitably used. For example, a resin composed of a resin having a lower melting point than the resin constituting the fiber A, or a fiber which exhibits a binder function at a low temperature because it is low-stretched or substantially undrawn can be used. However, from the viewpoint of increasing the drying efficiency of the nonwoven fabric, it is preferable to use a binder having a melting point of 205 ° C. or higher.
The mixing ratio of the binder is preferably 10% by mass or more / nonwoven fabric, particularly preferably 20% by mass or more / nonwoven fabric, and 60% by mass from the viewpoint of securing the ion permeability of the separator.
Or less, preferably 40% by mass or less / nonwoven fabric.

Although the specific constitution of the binder is not particularly limited, in the present invention, it is more preferable to use a polyester-based undrawn yarn which is low drawn, preferably substantially undrawn as compared with the fiber A. The fibers are excellent in heat resistance and at the same time have sufficient performance as a binder. The fiber is blended to produce a sheet, and then subjected to a calendering process under a condition that does not impair the performance of the fiber A (for example, the melting point of the fiber A or less). It becomes possible to manufacture a separator with high performance. The blending ratio of the binder is 10% by mass or more / nonwoven fabric, particularly 20% by mass or more /
It is preferable to use a nonwoven fabric. However, from the viewpoint of the separation property, the ratio is preferably 50% by mass or less / non-woven fabric, more preferably 45% by mass or less / non-woven fabric, particularly preferably 40% by mass or less / non-woven fabric.

The nonwoven fabric used in the present invention may be a wet-laid nonwoven fabric manufactured by a papermaking method, or spunlace.
Thermal bond, chemical bond, melt blown, including dry non-woven fabric such as spun bond,
From the viewpoint that fibers such as fiber A are easily two-dimensionally oriented and mechanical performance and ion permeability are easily improved, a wet-laid nonwoven fabric is preferably used.

The wet-laid nonwoven fabric is usually produced by dispersing a stock such as fiber and fiber A in water to produce a slurry, making the slurry with a paper machine and drying. At this time, a slurry is prepared so that the solid content concentration is about 0.1 to 5% by mass, and further diluted with water by adding water to the solid content concentration to be 0.01 to 0.5% by mass. It is mentioned as a more preferable method that papermaking is performed after forming a diluted aqueous slurry. At this time, it is preferable to adjust the viscosity and dispersibility of the slurry by using a dispersing aid, a thickener and the like. In the case of using the splittable conjugate fiber, papermaking may be performed after previously splitting into flat-plate-shaped fibers, but from the viewpoint of simplifying the manufacturing process and further dispersing the ultrafine flat fibers uniformly in the slurry, It is preferable that the slurry is divided with a pulper or the like in a state of being dispersed in water and used as a slurry for papermaking. As the paper machine, a fourdrinier paper machine, a round paper machine, an inclined type paper machine, a combination machine including a combination thereof, and the like are preferably used. As a dryer,
A Yankee type, a multi-cylinder type, or the like may be used, and the lamination may be performed. Next, it is more preferable to adjust the thickness to a desired value by a calendering process. At this time,

A separator may be obtained by using such a nonwoven fabric. Of course, a plurality of nonwoven fabrics may be laminated in order to enhance the homogeneity, or another sheet may be laminated within a range not to impair the effects of the present invention. , Surface treatment or the like may be performed. However, from the viewpoint of efficiently obtaining the effects of the present invention, it is preferable to obtain a separator using only the nonwoven fabric described above. The thickness of the separator is 200 μm or less, especially 10 μm.
It is preferably 0 μm or less, more preferably 70 μm or less.
By making the separator as thin as possible, the capacity of the electrolytic solution can be increased, and an excellent effect can be obtained from the viewpoint of ion permeability. In addition, the drying treatment and the electrolytic solution immersion treatment can be performed efficiently. When the thickness of the separator is reduced, the short-circuit prevention ability and the mechanical performance are likely to be impaired. However, when the fiber A is used, even if the thickness of the separator is reduced, the above effects are hardly impaired, so that a remarkable effect is obtained. . However, from the viewpoint of ensuring the function as a separator, the thickness is preferably 30 μm or more.
From the viewpoint of the mechanical performance, ion permeability, short-circuit prevention property, etc. of the separator, the basis weight of the separator is 10 to 70 g / m.
^The density is preferably about ² , particularly 15 to 35 g / m ² , and the density is preferably about 0.3 to 1.0 g / cm ³ .

Such a separator can be suitably used for a battery or a capacitor. The battery / capacitor to which the separator of the present invention is applied is not particularly limited. For example, alkaline manganese batteries, mercury batteries, primary batteries such as silver oxide batteries, nickel-cadmium batteries, silver-zinc batteries,
Silver-cadmium battery, nickel-hydrogen battery, nickel-
Secondary batteries such as zinc ionization and lithium batteries, as well as electrolytic capacitors (electrolytic capacitors) and electric double-layer capacitors (electric double-layer capacitors) are exemplified. Since the separator of the present invention has good drying efficiency, it can be suitably used for batteries and capacitors using an organic solvent-based electrolyte. Among them, the separator of the present invention has excellent performance especially for electric double layer capacitors. Electric double layer capacitors (hereinafter sometimes abbreviated as EDLC) are widely used as backups for memories, actuators and the like.

The configuration of the electric double layer capacitor is not particularly limited, but may be, for example, an electric double layer capacitor as shown in FIG. At this time, the electrode used is not particularly limited. For example, activated carbon or the like may be used as the electrode material.
When the activated carbon is a powder, it is mixed with a conductive material such as carbon black, a binder, a solvent or a dispersant to form a paste, and then applied to a current collector to form a polarizable electrode, or a sheet. It is molded and used as a polarizable electrode. When the activated carbon is in a fibrous form, it can be pulverized to produce an electrode like a powder, and can be used as it is. Activated carbon to be used includes steam, carbon dioxide, air, or an oxidizing gas such as a combustion gas such as LPG, or a mixture thereof, zinc chloride, potassium hydroxide, sodium hydroxide, phosphoric acid, calcium chloride, potassium sulfide. Activated carbon activated by adding a chemical such as sulfuric acid can be used.

Examples of the solvent for the electrolyte constituting the capacitor include carbonates such as dimethyl carbonate, diethyl carbonate, ethylene carbonate, and propylene carbonate; nitriles such as acetonitrile and propionitrile; γ-butyrolactone;
Lactones such as methyl-γ-butyrolactone, β-methyl-γ-butyrolactone, γ-valerolactone, 3-methyl-γ-valerolactone, dimethyl sulfoxide, sulfoxides such as diethyl sulfoxide,
Examples include amides such as dimethylformamide and diethylformamide, ethers such as tetrahydrofuran and dimethoxyethane, and organic solvents such as dimethylsulfolane and sulfolane. These organic solvents can be used as one kind or as a mixed solvent of two or more kinds.

As the electrolyte to be dissolved in these organic solvents, tetraethylammonium tetrafluoroborate, tetramethylammonium tetrafluoroborate,
Tetrapropylammonium tetrafluoroborate, tetrabutylammonium tetrafluoroborate, trimethylethyltetrafluoroborate, triethylmethylammonium tetrafluoroborate, diethyldiethylammonium tetrafluoroborate, N-ethyl-N-methylpyrrolidinium tetrafluoroborate, N, N-tetramethylenepyrrolidinium tetrafluoroborate, 1
Ammonium tetrafluoroborate such as -ethyl-3-methylimidazolium tetrafluoroborate, tetraethylammonium perchlorate, tetramethylammonium perchlorate, tetrapropylammonium perchlorate, tetrabutylammonium perchlorate, trimethylethylperchlorate, triethylmethyl Ammonium perchlorate, diethyldiethylammonium perchlorate, N-ethyl-N-methylpyrrolidinium perchlorate, N, N-tetramethylenepyrrolidinium perchlorate, 1-ethyl-3-
Ammonium perchlorates such as methyl imidazolium perchlorate, tetraethylammonium hexafluorophosphate, tetramethylammonium hexafluorophosphate, tetrapropylammonium hexafluorophosphate, tetrabutylammonium hexafluorophosphate, trimethylethylhexafluorophosphate, triethylmethylammonium Examples include ammonium hexafluorophosphates such as hexafluorophosphate and diethyldiethylammonium hexafluorophosphate. The electrolyte concentration is
0.5-5 (mol / liter = M / L), especially 1-2.
It is preferably 5 (M / L).

A desired capacitor may be manufactured using such electrodes, electrolytes, separators and the like. The method for manufacturing the capacitor is not particularly limited, and for example, a conventionally known method may be employed. The electric double layer capacitor is classified into a coin type, a wound type, and a stack type depending on the sealing mode, and the type may be determined as desired. The capacitor of the present invention can be used for any purpose. For example, it can be used for backup of memories, actuators, etc., VTRs, cameras, wristwatches, wall clocks, as well as in-vehicle applications and backup power supplies.

[0026]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[Degree of flatness] A micrograph of the fiber cross section was taken, and the flatness was calculated from (major diameter in fiber cross section) / thickness. The averaging was defined as the flatness. In the present invention, the flatness of the flattened fiber is obtained by excluding fibers having a flatness smaller than 0.7 times the flatness specified in the present invention. [Fiber thickness μm] Take a micrograph of the fiber cross section, measure the diameter (thickness) of the largest inscribed circle in the fiber cross section for any 10 or more fibers, and determine the average value as the fiber thickness (Μm). [Melting point ° C] The melting point of the resin constituting the fiber was measured using "DTG-50" manufactured by Shimadzu Corporation.

[Thickness of nonwoven fabric mm Density g / c
m ³ ] Measured according to JIS P 8118 “Test method for thickness and density of paper and paperboard”. [Basic weight g / m ² ] Measured according to JIS P 8124 “Measurement of metric basis weight of paper”. [Tear length N · m / g] Measured according to JIS P 8113 “Testing method for tensile strength of paper and paperboard”.

[Pore size μm] manufactured by Coulter Electronics Co., Ltd .: colter POROMETER II
Was measured by [Capacitance F / cm ³ , Internal resistance Ω] Charge voltage 2.5
After charging the capacitor at 4 V and a charging current of 4 mA, supplementary charging was performed at a constant voltage of 2.5 V until the current reached 1 mA, and then discharging was repeated at a constant current of 2 mA.
The capacitance was determined from the slope of 2-1.0V. The internal resistance was calculated from the voltage drop caused by opening the circuit after charging.

Reference Example 1 The first component was polyethylene terephthalate (melting point: 260 ° C.), and the second component was nylon 6.
(Melting point 220 ° C.), and polyethylene terephthalate: nylon 6 =
At a ratio of 2: 1, the spinning temperature is 285 ° C., and the single hole discharge amount is 0.8.
It was spun at 0 g / min and wound up at 1100 m / min to obtain a spun yarn. After bundling the spun yarn, 2.50
After drawing twice and applying an oil agent, it was cut to a length of 3 mm to obtain a 2.9 dtex polyester / polyamide layered splittable fiber. Incidentally, when the layered splittable fiber was substantially completely split by a pulper, the single fiber fineness was 0.2
Flat plate-like fibers composed of a polyester resin and / or a polyamide resin having 6 dtex, a thickness of 1.5 μm, and a flatness of 13.3 were obtained. The cross-sectional shape of such fibers was substantially rectangular.

Reference Example 2 Using the same polyethylene terephthalate and nylon 6 as in Reference Example 1, using a layered split slit nozzle having 11 layers, at a ratio of polyethylene terephthalate: nylon 6 = 2: 1 and a spinning temperature. 28
Spin at 5 ° C, 0.80 g / min single hole discharge rate, 10
Winding was performed at 00 m / min to obtain a spun yarn. After bundling the spun yarn, stretching it 2.30 times and applying an oil agent,
mm and 3.47 dtex polyester /
A polyamide layered split fiber was obtained. When the layered split fiber was substantially completely split by a pulper, the single fiber fineness was 0.32 dtex, the thickness was 4.2 μm, and the flatness was 2.6.
Of the polyester-based resin and / or polydamide-based resin was obtained. The cross-sectional shape of the fiber was substantially rectangular.

REFERENCE EXAMPLE 3 Polyethylene terephthalate was spun at a spinning temperature of 300 ° C. and a single hole discharge rate of 0.19 g / min, and was wound at 1320 m / min. After the convergence, only the oil treatment was performed without performing the stretching treatment, and the resultant was cut into 5 mm to obtain a polyester undrawn yarn (“EP101 × 5” manufactured by Kuraray Co., Ltd.). The resin constituting the fiber had a melting point of 260 ° C. and was substantially undrawn, so that it exhibited a binder function at a lower temperature than the fibers obtained in Reference Examples 1 and 2.

Example 1 70% by mass of the layered split fiber (main fiber) obtained in Reference Example 1, 30% of the undrawn polyester fiber (binder fiber) obtained in Reference Example 3
The slurry was prepared by putting the mixture into a pulper at a ratio of% by mass and stirring to substantially completely split the layered split fibers, and at the same time, dispersing and mixing the fibers. The obtained slurry was subjected to papermaking with a wet papermaking machine comprising a tilted papermaking machine and a Yankee dryer to produce a wet-laid nonwoven fabric having a basis weight of 25 g / m ² . In a state where two layers of this wet papermaking nonwoven fabric are stacked, a temperature of 1
Perform a calendering process at 80 ° C and a pressure of 20 kg / cm.
An EDLC separator having a basis weight of about 50 g / m ² and a thickness of 95 μm was obtained.

Separately, activated carbon ("BP" manufactured by Kuraray Chemical Co., Ltd.)
-20 "), by weight of tetrafluoroethylene (Mitsui
After adding 10% by mass of a conductive filler ("Denka Black" manufactured by Denki Kagaku Co., Ltd.), 10% by mass of "Teflon 6J" manufactured by Dupont Chemicals Co., Ltd., kneading, forming a sheet, punching out, and punching a circular polarizable electrode having a diameter of 11 mm I got Such a polarizable electrode, a separator punched to a diameter of 13 mm, and a thickness of 50 μm punched to a diameter of 11 mm as a current collecting member.
Aluminum mesh (Sunk Co., Ltd. 04) at 200 ° C
After vacuum drying for 3 days, the dew point was shifted to a temperature of -80 ° C or lower in a glove box, and the subsequent work related to cell production was performed in the glove box. A 1 M / L solution of tetraethylammonium tetrafluoroborate in propylene carbonate was used as the electrolyte, and the polarizable electrode and the separator were impregnated with the electrolyte for 30 minutes under vacuum. Using these materials, an EDLC was assembled as shown in FIG.

The separator obtained in this example is:
The dimensional change during drying at 200 ° C. for 3 days was small, and drying was efficient at high temperatures, and the permeability to the electrolyte was good, and the capacitor could be manufactured efficiently. In addition, it has excellent mechanical performance and flexibility, withstands winding tension at the time of winding, etc., and has a small curvature ratio and a small-sized through hole because it is mainly composed of flat fiber (fiber A). As a result, the internal resistance was small and excellent separation performance was achieved. Furthermore, since the thickness of such flat fibers has a small variation among single fibers and is uniform, the separator has good formation and is uniform, and the difference between the average pore size and the maximum pore size is small and the variation in separator performance is small. Was. Table 1 shows the results
Shown in

[Example 2] Polyester / polyamide layer splitting fiber (main fiber) 90 obtained in Reference Example 1
A nonwoven fabric was manufactured in the same manner as in Example 1 except that a slurry was prepared by charging the unstretched yarn (binder fiber) obtained in Reference Example 3 into the pulper at a ratio of 10% by mass. This nonwoven fabric was calendered at 180 ° C. and a pressure of 20 kg / cm without being formed into two layers to produce a separator, and an EDLC was produced in the same manner as in Example 1. The separator obtained in this example has a small dimensional change upon drying at 200 ° C. for 3 days and can be dried efficiently at a high temperature. It could be manufactured. In addition, it has excellent mechanical performance and flexibility despite its low basis weight, withstands winding tension at the time of winding, etc., and has a small curvature ratio and small size due to the main component of flat fiber (fiber A). Since small through holes were formed, the internal resistance was small and excellent separation properties were achieved. Further, since the thickness of such flat fibers is small and uniform among single fibers, the formation is good and uniform even though the basis weight is small, the difference between the average pore size and the maximum pore size is small, and the separator is small. A separator with small variations in performance was obtained. Table 1 shows the results.

Comparative Example 1 An EDLC was produced in the same manner as in Example 2 except that the layer split fiber obtained in Reference Example 2 was used instead of the layer split fiber obtained in Reference Example 1. Although the separator obtained in the comparative example was flexible and excellent in mechanical performance, the pore size became large due to the small flatness of the fiber, and the separator was insufficient in homogeneity, so that the separator was not enough. Had no function. Table 1 shows the results.

[Comparative Example 2] 70% by mass of the layered split fiber (main fiber) obtained in Reference Example 2 and 30% by mass of the polyester undrawn yarn (undrawn fiber) obtained in Reference Example 3 were applied to a pulper. By adding and stirring, the lamellar split fibers are substantially completely split, and
The slurry was adjusted by mixing. The obtained slurry was subjected to papermaking with a wet papermaking machine comprising a tilted papermaking machine and a Yankee dryer to produce a wet-laid nonwoven fabric having a basis weight of 50 g / m ² . 180 ° C. in a state where two layers of this wet-laid nonwoven fabric are stacked,
Perform a calendering process at a pressure of 20 kg / cm.
An EDLC separator of 00 g / m ² and a thickness of 220 μm was obtained. An EDLC was assembled in the same manner as in Example 1 using the obtained separator. The separator obtained in the comparative example is excellent in mechanical performance and flexibility, withstands winding tension at the time of winding, has a small dimensional change upon drying at 200 ° C. for 3 days, and has a high temperature. And could be dried efficiently. Moreover, the permeability to the electrolyte was good, and the capacitor could be manufactured efficiently. However, since the basis weight and the thickness are large, the ratio occupied by the separator in the EDLC is large, and the EDLC is not satisfactory in terms of capacitance and internal resistance. Table 1 shows the results.

[0039]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of a configuration of an electric double layer capacitor of the present invention.

[Explanation of symbols]

 1 current collecting member 2 current collecting member 3 polarizable electrode 4 polarizable electrode 5 separator 6 gasket 7 case 8 pressure adjusting spring 9 holding plate

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Nozomu Sango 1621 Sakurazu, Kurashiki-shi, Okayama Prefecture Kuraray Co., Ltd. (72) Inventor Hideharu Iwasaki 1621 Sakurazu, Kurashiki-shi, Okayama Prefecture Kuraray Co., Ltd. F-term (reference) 4L055 AF33 AF35 AF46 AF47 AJ01 BE20 EA04 EA15 EA16 FA11 FA13 FA16 FA22 GA01 GA39 5H021 CC01 CC02 EE07 EE08 HH00 HH01 HH03

Claims (4)

[Claims] 1. A separator used for a battery or a capacitor and using a non-woven fabric, wherein the separator is made of a non-woven fabric.
Mass% or more, flatness 3 to 20, thickness 0.1 to 30 μm
The separator characterized by being comprised by the flat plate-shaped fiber of the above. 2. The fiber according to claim 1, wherein the flattened fibers are obtained by splitting layered split fibers in which a polyester resin and a polyamide resin are alternately arranged.
The separator according to 1. 3. The separator according to claim 1, wherein the separator is used for an electric double layer capacitor. 4. An electric double-layer capacitor using the separator according to claim 3.