JP3324803B2 - Separator for electrolytic capacitors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a separator for an electrolytic capacitor, and more particularly to a separator having a low density and thus having excellent properties such as impedance of the capacitor.
Also, the present invention relates to a separator having a void portion covered with long entanglement of ultrafine fibrils even at a low density, thereby reducing short-circuit defects, and having excellent workability in manufacturing a capacitor because of its high strength.

[0002]

2. Description of the Related Art In general, an electrolytic capacitor is generally formed of paper or nonwoven fabric (hereinafter referred to as the complexities of describing both) between metal foils constituting both positive and negative electrodes, for example, metal foils such as aluminum and tantalum. For the sake of simplicity, a separator made of paper is simply sandwiched), which is wound and laminated to form a capacitor element, which is impregnated with an electrolytic solution and sealed in a case. In such an electrolytic capacitor, it is well known that the separator greatly affects the improvement of various characteristics of the capacitor, and it is also well known that the impedance and the tan δ of the electrolytic capacitor are reduced in order to improve the performance of the electrolytic capacitor. Have been.

[0003] In order to reduce the impedance, the conditions required for the separator are that the path of electricity passing through both poles is straight and the shortest distance, and that the fibers constituting the separator do not interfere with the current. Ideally, the separator is configured so that almost the entire area of the separator serves as a current passage. This is, more specifically, (1)
The separator has a large void cross-sectional area, (2) the separator is as thin as possible, (3) the cross-sectional shape of the fiber constituting the separator is as close as possible to a circle,
(4) The diameter of the fiber cross section is as small as possible.

[0004] However, the conditions (1) and (2) required for the separator and the conditions (3) and (4) required for the fiber constituting the separator are to satisfy both simultaneously. Really difficult. Synthetic fiber (3)
Although a material satisfying the condition (4) is obtained, it is theoretically preferable in that respect. However, a separator satisfying the conditions (1) and (2) is used to reduce the impedance by using such a synthetic fiber. Even if it is going to be manufactured, it is inevitable that the short-circuit rate will be high, and the strength will be extremely weak, which will not only cause difficulty in winding work in the capacitor manufacturing process, but also This also hinders the handling of the capacitor, which also increases the short-circuit failure rate.

[0005] Therefore, the fiber material currently used for this type of condenser separator is mainly made of natural plant fibers, and the total of manila hemp and kraft pulp is 90 to 9%.
It is said to account for 5%. Attempts have also been made to mix a part of the plant fiber with synthetic fibers such as polypropylene, polyethylene and polyester to form a separator, but the density of the separator is at most about 0.3 g / cm ³ . This also hinders the work and the subsequent handling, and lowers the product yield. Moreover, the impedance is not significantly reduced.

[0006] In addition, there is also known an invention in which a paper made of fine synthetic fibers and self-bonded together by fibers is used as a separator. However, it is difficult to produce a strong low-density paper by using the synthetic fibers themselves. Since the constituent material of the separator is a hydrophobic synthetic fiber, the affinity for the electrolyte is poor,
It is difficult to achieve the desired low impedance. In order to eliminate the disadvantage of the incompatibility, it is conceivable to attach a surfactant, but this is not a practically applicable treatment means.

Further, among the synthetic fibers, polyvinyl alcohol (hereinafter abbreviated as PVA) fibers are basically made of a hydrophilic polymer, and have a non-affinity for an electrolytic solution such as the synthetic fibers. The problem is solved and the papermaking property is good, and it is easy to obtain high strength and low density paper. However, even in this case, if ordinary PVA fiber is used, there is a limit to the reduction of the paper density while maintaining the paper strength, and it is at most about 0.28 g / cm ^3. Although it is much improved compared to the case of hemp paper, there is a certain limit (about 70% in impedance ratio).

[0008]

As will be understood from the foregoing, the present invention provides a separator for an electrolytic capacitor which maintains good product yield without difficulty in handling the capacitor during and after manufacture. To provide an excellent separator that can produce a low-density paper with unprecedented low-density paper, and therefore extremely low impedance, and thus a capacitor with extremely low impedance, while maintaining the paper strength that can be achieved. It is.

[0009]

SUMMARY OF THE INVENTION The object of the present invention is to provide a film having a wet Young's modulus of 20 g / d or more and an orientation of .DELTA.n = 42.times.10.sup.- ^3.
An electrolytic capacitor constituted by using the above fibrillated cellulose fiber as at least a part of a main fiber.
Separator, wherein the cellulose fiber comprises a cell
Spinning raw material in which loin is dissolved in an amine oxide solvent
Solvent in which cellulose is precipitated by dry-wet spinning of liquid into water
Electrolytic capacitor characterized by being spun cellulose fiber
This is achieved by using a separator for the sensor.
In addition, as such a separator, in particular, the above-described separator is used.
Fibrillated cellulose fiber and 0.4 denier or less
The fibrillated product using a PVA-based fiber as a main fiber
And the weight ratio of the PVA-based fiber is 100: 0 to 20:80.
Yes, the main fibers are bound with a PVA-based binder
And the density as a separator is 0.25 g /
for electrolytic capacitors, wherein the cm ³ or less
It is preferable to use a separator.

The cellulose fibers used in the present invention are completely different from regenerated cellulose fibers (cellulose 2) such as viscose rayon, polynosic rayon, high-strength rayon and the like obtained by regenerating cellulose 1 as a raw material via conventional viscose. It is a cellulose fiber having a high wet Young's modulus, a high degree of crystallinity, and a high degree of orientation, and has a fiber inner fibril that has been extremely well developed up to the innermost layer of the fiber. This cellulose fiber is prepared by dissolving cellulose 1 (wood pulp) or / and cellulose 2 in a solvent and spin-drying it in a water bath.
The solvent-spun cellulose fiber obtained by precipitating is the most suitable, specifically, the solvent-spun cellulose fiber sold under the trade name `` TENCEL '' by Courtes Ltd. Is satisfied.

This fiber is a cellulose fiber in which the internal fibrils of the fiber have developed extremely well as far as the innermost layer of the fiber as described above. Since the wet Young's modulus is high, there is little settling in water. It was found that it was beaten effectively by the stress at the time of beating, and that it was extremely effective as a material of the separator of the present invention. That is, when the fibers are beaten with a beater, a refiner, or the like, the fibers are not completely divided by the beating, and the fibers are not simply converted into ultrafine fibers (microfibril fibers). Whether the location becomes the main skeleton portion corresponding to the original fiber diameter, or whether the original fiber main skeleton portion remains, in any case, the fiber main skeleton portion and long microfibril fibers coming out of the main skeleton portion by beating are formed. When the beaten product (fibril-like material) in this form is wet-formed into separator paper, the wet Young's modulus, crystallinity, and orientation of the fiber material are reduced. Synergistically with the high, the separator paper is composed of fibers having a low density by the fiber main skeleton, and long fibrils extending from the fiber main skeleton are adjacent to each other. And each of the skeleton entangled with a structure for supporting the fiber main skeleton portion, respectively long fibrils voids constituted by the fiber main skeleton portion is made of a uniformly filled structures with entangled.

As described above, the separator (paper) of the present invention
First, due to the properties of the fiber used and the properties and structure of the fibril-like material obtained by beating it, firstly, because of the low density and large void cross-section, the current flow through both poles was greatly reduced. Secondly, the separator has a low density and a large void cross-sectional area, but is strong enough. Thirdly, a void formed by the main fiber skeleton is formed. Even though the voids have a structure in which long fibrils are entangled and uniformly buried, the occurrence of short-circuit as a separator is small. Fifth, the fibrils are ultrafine and round fibers, which are synergistically synergistic and have a low density. There is a strong, in which it is able to impedance extremely reduced excellent separator.

[0013] Regenerated cellulose fibers such as conventional viscose rayon, polynosic rayon and high-strength rayon can be fibrillated by beating, but their wet Young's modulus is generally low, and at most a high value is obtained.
Since the weight is about 8 g / d, there is great settling in water. In addition, these regenerated cellulose fibers are originally extremely difficult to fibrillate even when the external stress at the time of beating is increased, and the beaten material is a fibril having a short outermost layer of the fiber, and has a weak strength. Since short hairs are densely formed on the surface, even if such a beaten product (fibril-like material) is wet-processed into separator paper, first, a low-density, high-strength separator paper is used. Second, the fibrils are short, and there is no entangled structure formed by the present invention due to the entanglement between the fibrils. If a low-density structure is to be obtained, short-circuits inevitably increase. Thirdly, this also limits the reduction in density, and thirdly, the electrolyte is mainly retained only in the main fiber skeleton,
This is because the structure for holding the electrolyte is insufficient. Furthermore, even as a beaten product in which the beating degree is further increased and the fibers are finely divided into ultra-fine fibers, the separator paper obtained by wet-making using this (the strength of the material, low Young's modulus and low strength) Not only) the separator paper obtained has a high density because it uses ultra-fine fibers.
This is in a direction opposite to the basic requirement for the separator to have a large void cross-sectional area and to be as thin as possible, and the desired reduction in impedance cannot be expected.

The cellulose fibers used in the present invention are:
The wet Young's modulus is 20 g / d or more, and the orientation is Δn = 4.
It is necessary to have a value of 2 × 10 ⁻³ or more. This is an index for obtaining a microfibril in which the fiber of the present invention is sufficiently oriented and crystallized up to the inner layer portion of the fiber, and to the extent that this is not satisfied, it is strong and has been described above by beating. As described above, it is impossible to obtain a beaten product in which a large number of sufficiently long microfibrils are extended from the trunk fiber (the main fiber skeleton portion) in all directions, and therefore, it is impossible to obtain the intended low-density and high-strength separator. More preferable fibers have a wet Young's modulus of 25 g / d or more. However, those having a wet Young's modulus of 150 g / d or more are difficult to produce with current industrial technology. Further, the orientation Δn is more preferably 44 × 10 ⁻³ or more. Further, the crystallinity is preferably 50% or more. Only 55% or more is difficult to obtain with current industrial technology.

[0015] Such a solvent-spun cellulose fiber is a fiber in which fibrils that have been sufficiently oriented and crystallized to the inner layer of the fiber have grown, and thus the fiber is beaten to obtain a fibril having sufficient strength. The fibrillated product is extremely excellent in alkalinity due to its physical properties.Therefore, a separator made of the fibrillated product does not elute the fiber component into the electrolytic solution due to alkali, and the regenerated cellulose fiber having the above low physical property value The separator consisting of lacks alkali resistance,
As compared with the case where elution into the electrolytic solution cannot be prevented, a good separating property can be obtained over a long period of time.

The fineness of the cellulose fibers used in the present invention before beating is 0.4 to 3.0 denier. If it is less than 0.4 denier, when it is beaten and used as a separator, its density increases,
It is not preferable because the resistance as a current path increases. More preferably, it is 1.0 denier or more. The upper limit is a rough limit fineness in the sense that it is difficult to obtain a cellulose fiber having a fibril structure that has sufficient physical properties as defined in the present invention and has a fibril structure crystallized therein. , More preferably 2.0
Denier.

The degree of beating of the cellulose fibers used in the present invention is, as described above, a fibril-like material obtained by beating in a form in which a fiber main skeleton portion and long microfibril fibers protruding from the main skeleton portion extend in all directions. Therefore, the CSF is preferably set to 200 to 700 ml. If the CSF is larger than 700 ml, the beating is insufficient and the intended beating product is not obtained, and if the CSF is less than 200 ml, the beating becomes excessive, and in this case, the desired beating product is not obtained. The volume is more preferably 300 to 600 ml, and still more preferably 350 to 550 ml.

The diameter of the microfibril fibers of the fibrillated material after beating is preferably 5 μm or less, more preferably 3 μm or less. If it exceeds 5 μm, the fiber main skeleton portion becomes too thick, or the number of fibril fibers must be extremely small, and a separator having a large void cross-sectional area cannot be formed,
Not preferred.

The binder used in the present invention is PV
A-based binders are preferred. Examples of the form include fibrous, powdery, and solution forms. In the case of producing paper for a separator by wet papermaking, a fibrous binder is preferable. This is because when the PVA-based binder is in a powder form or a solution form, it is necessary to dissolve them in order to develop paper strength as a separator. This is because the gap between the fibers is closed, so that the internal resistance increases due to the blockage of the current path, and the electrolyte retention property decreases.

On the other hand, when a fibrous binder is used, the same phenomenon as described above occurs when the solvent is completely dissolved, that is, when it is completely dissolved. Or, by means such as lowering the drying temperature, if the binder is not completely dissolved, and if only the point of intersection of the binder fiber and the main fiber is bonded while leaving the fiber form, the above disadvantage can be solved. That's why. When the water dissolution temperature of the PVA-based binder fiber suitable for this is lower than 60 ° C., the binder is completely dissolved even if the above-mentioned use method is used, which is not preferable. 60-98 ° C, more preferably 70-90 ° C, because it is not expressed
The drying temperature at the time of papermaking is a dryer temperature of 70 to 150 ° C., preferably 80 to 120 ° C.

When the weight ratio of the PVA-based binder to all the main fibers is less than 10/90, the required strength of the separator cannot be obtained. Since the amount of the main fiber for exhibiting the effect of
It is preferably 10/90 to 20/80.

As described above, the main fiber constituting the separator of the present invention is basically a solvent-spun cellulose fiber that has been beaten, but a fiber obtained by combining this with a PVA-based fiber may also be used. preferable. Further, other cellulosic fibers, synthetic fibers and the like may be mixed as long as the performance is not significantly impaired. However, the most preferable mixed paper system is one in which only the beaten solvent-spun cellulose fibers and PVA-based fibers are the main fibers.

The reason why the PVA fiber is used as a part of the main fiber is firstly that among the various fibers, the electrolyte is extremely excellent in electrolyte resistance and the electrolyte absorption is excellent. The main reason is that it has the effect of reducing the degree of swelling of the separator. As described above, in the separator of the present invention, as described above, it is preferable to use a PVA-based binder as the binder, and this and the PVA-based fiber have a high adhesive force because the hydrogen bonding force between the two works effectively. . Therefore, PVA-based binder and PVA
This is because both of the system fibers form the skeleton of the separator and serve as a support for other main fibers including the beaten solvent-spun cellulose fibers, so that the swelling of the separator can be suppressed as a whole. When the PVA-based fiber is not used, the swelling cannot be suppressed because the adhesive force between the other main fiber and the PVA-based binder is weak. If the swelling is large, the void cross-sectional area decreases due to an increase in the thickness of the paper and an increase in the fiber diameter, so that the internal resistance increases due to the blockage of the current path. As described above, when the beaten solvent-spun cellulose fiber is used, the swelling tends to be suppressed by the entanglement force of the fibril, but when combined with the PVA-based fiber, a further lower swelling degree is obtained, which is extremely effective. It is.

The preferred denier of the PVA-based fiber is 0.1% in order to achieve a very high separation property.
The fineness is preferably 4 deniers or less. However, simply making the fibers thinner is not preferable because it increases the internal resistance of the capacitor and lowers the electrolyte retention.

As described above, due to the unique fibril structure of the fibrillated material of the solvent-spun cellulose fiber, the density of the paper structure is increased even when the fibril-like material is combined with fine fibers. Instead, it makes sense to use fine denier fibers only here. That is, in order to satisfy the decrease in the internal resistance of the capacitor and the increase in the electrolyte retention by the beaten solvent-spun cellulose fiber, the PVA-based fiber may be 0.4 denier or less, which is finer than 0.5 denier. A higher degree of separation can be obtained without deteriorating the properties and in combination with the effect of the fibrils of the beaten solvent-spun cellulose fibers. In particular, in the case of thick deniers which have been conventionally used, the effect is small because the number is small at the same blending ratio, but the effect is large at a low blending ratio by making the blending ratio thinner, and by doing so, the solvent-spun cellulose is used. The mixing ratio of fibers can be increased. Therefore, the PVA fiber used in the present invention is more preferably 0.4 denier or less. However, it is difficult to directly obtain PVA-based fibers having a density of less than 0.01 denier from the current industrial technology, but such ultrafine fibers can be obtained by a method such as fibrillation.

When the blending ratio of the beaten solvent-spun cellulose fibers used in the present invention with respect to all the main fibers is less than 20% by weight, the fiber main skeleton and the microfibril fibers emerging from the skeleton extend in all directions. Since the presence of the protruding fibril-like material is reduced, and eventually a low-impedance separator cannot be obtained, the content is preferably 100 to 20% by weight, more preferably 75 to 60% by weight, and further preferably 68%. ~ 63% by weight.

Regarding the method for producing the separator of the present invention, the solvent-spun cellulose fiber is beaten to the above-mentioned predetermined CSF, and this is used as it is, a binder is added thereto, and the mixture is dispersed in water. Alternatively, a beaten product (fibrillated product) of the cellulose fiber and 0.4
This is a method in which PVA fibers having a denier or less are mixed and wet papermaking is performed in the same manner as described above, thereby realizing a separator having excellent performance and a density of 0.25 g / cm ^3. .

According to the beating method of the solvent-spun cellulose fiber used in the present invention, according to a commonly used beater, double disc refiner or the like, since the fiber is violently rubbed by the metal, only the apparent beating proceeds. Effective fibrils are not actually produced. According to the study of the present inventors, when beating is used in combination with a pulper with a crushed blade and a fiber riser (high-speed disintegrating machine) in which the tooth spacing is adjusted to the fiber length of the solvent-spun cellulose fiber, metal-to-metal contact is avoided. Meanwhile, by performing beating by internal turbulence and shearing action, the fibrous main skeleton does not break, and long fibrils due to peeling from the surface in the axial direction of the fiber are generated, so beating with a beater, double disc refiner, etc. It became clear that it was a very effective beating method in comparison.

[0029]

The embodiments of the present invention and the effects thereof will be described in more detail with reference to the following examples. Various physical properties and methods for measuring the physical properties are as follows.

(1) Orientation Δn: The retardation of each fiber was measured using a deflection microscope and a Bellec compensator, and the thickness of the site was measured. Δn = retardation / thickness (2) Beating degree (CSF): Measured according to the method described in JIS-P8121. (3) Diameter of fibril after beating: Since the solvent-spun cellulose fiber after beating has a form in which the main fiber skeleton remains and a long fibril is formed at the binding site, the diameter of the fibril after beating is determined by an optical microscope. The thickness of ten fibrils was measured by observation, and the average value was used. (4) Wet Young's modulus: Measured by a method according to JIS L-1073. (5) Crystallinity: An X-ray diffraction intensity curve was obtained, which was separated into a crystal part and an amorphous part, and the area of each was determined. Crystallinity = 100 × (crystal part area) / (crystal part area + amorphous part area) (6) Impedance ratio: When a separator made of 100% Manila hemp having a thickness of 40 μm and a density of 0.50 g / cm ³ is used. The ratio of the impedance of each separator with respect to the case where the resistance value was 100 was determined based on the resistance value of the electrolyte solution. The specific measurement was performed using an electrolytic solution obtained by dissolving ammonium adipate in ethylene glycol (specific resistance of 100 ohms). · Centimeters) impregnated in a separator, sandwiched between platinum electrodes (5 cm ² ), placed a load of 200 g thereon, and set the resistance between the electrodes to 20 ± 0.5 ° C.
A. C. The measurement was performed at 10 V and 100 KHz using a crush bridge.

Example 1 The wet Young's modulus was 26 g / d,
Orientation Δn = 45 × 10 ⁻³ , crystallinity 58.5%,
1.5 denier solvent-spun cellulose fiber (Cointole's Tencel) was cut into 2 mm, beaten with a pulper and a fiber riser, and treated with 450 ml of CSF.
And The diameter of the fibril-like microfibril fibers after the beating was 2 μm. Using this cellulose fiber fibril-like material as a main fiber, a water dissolution temperature of 75
A slurry was prepared by using a polyvinyl alcohol-based fiber having a denier of 1.0 ° C. and a cut length of 3 mm as a binder, and the weight ratio between the two was 90/10. The slurry was made into a paper by a round paper machine and dried at a dryer temperature of 110.
C., dried at a basis weight of 9.0 g / m ² , a thickness of 40 μm,
With a density of 0.225 g / cm ³ , tensile strength when dry (vertical)
Was 2.5 kg / 15 mm. The impedance ratio of the separator containing 100% solvent-spun cellulose fibers as the main fiber to the separator made of 100% Manila hemp can be extremely reduced, which is 49. It was possible to increase the capacity by a factor of 04, and furthermore, it was extremely excellent that the occurrence rate of short-circuit when using this separator was negligible.

Example 2 The solvent-spun cellulose fiber used in Example 1 was beaten with a pulper and a fiber riser to make CSF 450 ml. The diameter of the microfibril fibers of the fibrillated material after beating is 2 μm.
m. This cellulose fiber fibril-like material and, in this example, 0.3 denier and a PVA-based fiber having a cut length of 2 mm are used as main fibers, and the former is 85% by weight and the latter is 1% by weight.
5% by weight, and all the main fibers were dissolved in water at a temperature of 75 ° C., 1.0 denier, and a cut length of 3 mm.
The slurry was adjusted so that the weight ratio of the PVA-based fibrous binder was 90/10. This slurry is made into paper by a round paper machine, and dried at a dryer temperature of 110 ° C.
Basis weight 8.8 g / m ² , thickness 40 μm, density 0.221 g
/ Cm ³ , dry tensile strength (vertical) is 2.8 kg / 1
A 5 mm separator paper was obtained. The paper separator containing the solvent-spun cellulose fiber and the PVA-based fiber as the main fibers has an extremely excellent impedance ratio of 46, and its short-circuit occurrence rate is almost negligible. Was something.

Example 3 The same solvent-spun cellulose fiber as in Example 1 was beaten with a pulper and a fiber riser.
CSF was 450 ml. The fibril diameter of the obtained fibril-like material was 2 μm. Using a fibril-like material of this fiber and a PVA-based fiber having a denier of 0.3 and a cut length of 2 mm as main fibers, in the present example, the former was mixed at 65% by weight and the latter at 35% by weight. The weight ratio of all main fibers to a PVA-based fibrous binder having a water dissolution temperature of 75 ° C., 1.0 denier and a cut length of 3 mm is 9
The slurry was adjusted to be 0/10. The slurry is made into a paper by a round paper machine, dried at a dryer temperature of 110 ° C., and has a basis weight of 7.4 g / m ² , a thickness of 40 μm, a density of 0.185 g / cm ³ , and a tensile strength (vertical) of 2.9 kg. /
A 15 mm separator paper was obtained. The separator having both the solvent-spun cellulose fiber and the PVA-based fiber as main fibers had an impedance ratio of 40 and negligible short-circuit occurrence rate, and was extremely excellent as in the above-described examples.

Example 4 The same solvent-spun cellulose fiber as in Example 1 was beaten with a pulper and a fiber riser.
CSF was 450 ml. The fibril diameter of the obtained fibril-like material was 2 μm. Using a fibril-like material of this fiber and a 0.3 denier PVA-based fiber having a cut length of 2 mm as a main fiber, in the present example, the former was mixed so as to be 20% by weight, and the latter was mixed so as to be 80% by weight. The weight ratio of all main fibers to a PVA-based fibrous binder having a water dissolution temperature of 75 ° C., 1.0 denier and a cut length of 3 mm is 9
The slurry was adjusted to be 0/10. The slurry is made into a paper by a round paper machine, dried at a dryer temperature of 110 ° C., and has a basis weight of 8.7 g / m ² , a thickness of 40 μm, a density of 0.218 g / cm ³ , and a tensile strength (vertical) of 3.0 kg. /
A 15 mm separator paper was obtained. The separator made of this paper was an excellent separator with an impedance ratio of 45 and a short-circuit occurrence rate of zero.

Example 5: The same solvent-spun cellulose fiber as in Example 1 was beaten with a pulper and a fiber riser.
In this example, the CSF was 300 ml. The fibril diameter of the obtained fibril-like material was 1 μm. Using a fibril-like material of this fiber and a 0.3 denier PVA-based fiber having a cut length of 2 mm as main fibers, the former is mixed at 65% by weight and the latter at 35% by weight, and the whole main fiber is mixed. And a weight ratio of a PVA-based fibrous binder having a water dissolution temperature of 75 ° C., 1.0 denier and a cut length of 3 mm to 9
The slurry was adjusted to be 0/10. The slurry was made into a paper by a round paper machine and dried at a dryer temperature of 110 ° C., and the basis weight was 8.0 g / m ² , the thickness was 40 μm, the density was 0.20 g / cm ³ , and the tensile strength (vertical) was 3.5 kg. / 1
A 5 mm separator paper was obtained. The separator made of this paper was an extremely excellent separator with an impedance ratio of 44 and a short-circuit occurrence rate of zero.

Example 6: The same solvent-spun cellulose fiber as in Example 1 was beaten with a pulper and a fiber riser.
In this example, the CSF was 550 ml. The fibril diameter of the obtained fibril-like material was 3 μm. Using a fibril-like material of this fiber and a 0.3 denier PVA-based fiber having a cut length of 2 mm as main fibers, the former is mixed at 65% by weight and the latter at 35% by weight, and the whole main fiber is mixed. And a weight ratio of a PVA-based fibrous binder having a water dissolution temperature of 75 ° C., 1.0 denier and a cut length of 3 mm to 9
The slurry was adjusted to be 0/10. The slurry is made into a paper by a round paper machine, dried at a dryer temperature of 110 ° C., and has a basis weight of 7.3 g / m ² , a thickness of 40 μm, a density of 0.240 g / cm ³ , and a tensile strength (vertical) of 2.9 kg. /
A 15 mm separator paper was obtained. The separator made of this paper was an extremely excellent separator having an impedance ratio of 43 and a short-circuit occurrence rate of zero.

Example 7: The same solvent-spun cellulose fiber as in Example 1 was beaten with a pulper and a fiber riser.
In this example, the CSF was 150 ml. The fibril diameter of the obtained fibril-like material was 0.5 μm. Fibril-like material of this fiber, 0.3 denier, cut length 2m
m of PVA-based fiber as a main fiber, and the former is 65
% By weight, and the latter are mixed at 35% by weight, and the weight ratio of all the main fibers to the PVA-based fibrous binder having a dissolution temperature in water of 75 ° C., 1.0 denier and a cut length of 3 mm is 90/10. The slurry was adjusted as described above. This slurry is made into a paper by a round-mesh paper machine, and dried at a dryer temperature of 11.
After drying at 0 ° C., a basis weight of 9.6 g / m ² and a thickness of 40 μm
m, density 0.240 g / cm ³ , tensile strength (vertical) 3.
An 8 kg / 15 mm separator paper was obtained. The separator made of this paper was an excellent separator with an impedance ratio of 56 and a short-circuit occurrence rate of zero.

Example 8: The same solvent-spun cellulose fiber as in Example 1 was beaten with a pulper and a fiber riser.
In this example, the CSF was 750 ml. The fibril diameter of the obtained fibril-like material was 4 μm. Using a fibril-like material of this fiber and a 0.3 denier PVA-based fiber having a cut length of 2 mm as main fibers, the former is mixed at 65% by weight and the latter at 35% by weight, and the whole main fiber is mixed. And a weight ratio of a PVA-based fibrous binder having a water dissolution temperature of 75 ° C., 1.0 denier and a cut length of 3 mm to 9
The slurry was adjusted to be 0/10. The slurry is made into paper by a round paper machine, dried at a dryer temperature of 110 ° C., and has a basis weight of 7.0 g / m ² , a thickness of 40 μm, a density of 0.175 g / cm ³ , and a tensile strength (vertical) of 2.0 kg. /
A 15 mm separator paper was obtained. The separator made of this paper was an excellent separator with an impedance ratio of 55 and a short circuit occurrence rate of 0.01%.

Example 9: In this example, the wet Young's modulus was 24
g / d, orientation Δn = 42 × 10 ⁻³ , crystallinity 56.2
%, Using a 4.0 denier solvent-spun cellulose fiber (manufactured by Coatles Co., Ltd., Tencel), cut into 2 mm, and beaten with a pulper and a fiber riser.
CSF was 550 ml. The diameter of the fibril-like microfibril fibers after the beating was 4 μm. Using a fibril-like material of this fiber and a 0.3 denier PVA-based fiber having a cut length of 2 mm as main fibers, the former is mixed at 65% by weight and the latter at 35% by weight, and the whole main fiber is mixed. The slurry was adjusted so that the weight ratio of the PVA-based fibrous binder having a water dissolution temperature of 75 ° C., 1.0 denier and a cut length of 3 mm was 90/10. This slurry was made into paper by a round paper machine, and the dryer temperature was 1
After drying at 10 ° C., a basis weight of 7.2 g / m ² and a thickness of 40 μm
m, density 0.180 g / cm ³ , tensile strength (vertical) 2.
1 kg / 15 mm separator paper was obtained. The separator made of this paper had an impedance ratio of 58 and a short-circuit occurrence rate of 0.02%, and was an excellent separator.

Example 10: The same solvent-spun cellulose fibers as in Example 1 were beaten with a pulper and a fiber riser to make CSF 450 ml. The fibril diameter of the obtained fibril-like material was 2 μm. The fibril-like material of this fiber and, in this example, Manila hemp beaten into CSF300 are used as the main fibers, and the former is mixed at 65% by weight and the latter at 35% by weight. 75 ° C, 1.0 denier, cut length 3m
The slurry was adjusted so that the weight ratio of the PVA-based fibrous binder of m was 90/10. The slurry was made into a paper by a round paper machine and dried at a dryer temperature of 110 ° C. to obtain a basis weight of 10.0 g / m ² , a thickness of 40 μm, and a density of 0.2.
50 g / cm ³ , tensile strength (vertical) 2.0 kg / 15 m
m of separator paper was obtained. The separator made of this paper was an excellent separator with an impedance ratio of 65 and a short-circuit occurrence rate of 0.05%.

Example 11 The same solvent-spun cellulose fiber as in Example 1 was beaten with a pulper and a fiber riser to make CSF 450 ml. The fibril diameter of the obtained fibril-like material was 2 μm. A fibril-like material of this fiber and, in this example, rayon fiber having a single fiber fineness of 1.5 denier are used as main fibers, and the former is mixed at 65% by weight and the latter at 35% by weight. The weight ratio of the fiber and the PVA-based fibrous binder having a dissolution temperature in water of 75 ° C., 1.0 denier and a cut length of 3 mm is 9
The slurry was adjusted to be 0/10. This slurry was made into a paper by a round paper machine and dried at a dryer temperature of 110 ° C., and the basis weight was 9.8 g / m ² , the thickness was 40 μm, the density was 0.245 g / cm ³ , and the tensile strength (vertical) was 1.8 kg. /
A 15 mm separator paper was obtained. The separator made of this paper had an impedance ratio of 60 and a short-circuit occurrence rate of 0.08%, and was an excellent separator.

Example 12 The same solvent-spun cellulose fibers as in Example 1 were beaten with a pulper and a fiber riser to make CSF 450 ml. The fibril diameter of the obtained fibril-like material was 2 μm. A fibril-like material of this fiber and a polypropylene fiber having a single fiber fineness of 1.5 denier in this example are used as main fibers, and the former is 65%.
% By weight, and the latter are mixed at 35% by weight, and the weight ratio of all the main fibers to the PVA-based fibrous binder having a dissolution temperature in water of 75 ° C., 1.0 denier and a cut length of 3 mm is 90/10. The slurry was adjusted as described above. This slurry is made into a paper by a round-mesh paper machine, and dried at a dryer temperature of 11.
It is dried at 0 ° C., and has a basis weight of 9.0 g / m ² and a thickness of 40 μm.
m, density 0.225 g / cm ³ , tensile strength (vertical)
A separator paper of 5 kg / 15 mm was obtained. The separator made of this paper had an impedance ratio of 58 and a short-circuit occurrence rate of 0.10%, and was an excellent separator.

Comparative Example 1 Manila hemp was beaten with a pulper and a fiber riser to make CSF 300 ml. The fibril diameter of the obtained fibril-like material was 6 μm. This fibril-like material and PVA-based fiber having a denier of 0.3 and a cut length of 2 mm are used as main fibers, and the former is mixed at 65% by weight and the latter at 35% by weight. Melting temperature 75 ° C,
The slurry was adjusted so that the weight ratio of the PVA-based fibrous binder having a denier of 0 and a cut length of 3 mm was 90/10. The slurry is made into a paper by a round paper machine and dried at a dryer temperature of 110 ° C., and has a basis weight of 13.2 g / m ² , a thickness of 40 μm, a density of 0.330 g / cm ³ , and a tensile strength (vertical) of 0.8 kg. / 15 mm of separator paper.
The separator made of this paper had an impedance ratio of 89 and a short-circuit occurrence rate of 2.0%, which was insufficient.

Comparative Example 2: Wood pulp was beaten with a pulper and a fiber riser to obtain a CSF of 300 ml. The fibril diameter of the obtained fibril-like material was 8 μm. This fibril-like material and PVA-based fiber having a denier of 0.3 and a cut length of 2 mm are used as main fibers, and the former is mixed at 65% by weight and the latter at 35% by weight. Melting temperature 75 ° C,
The slurry was adjusted so that the weight ratio of the PVA-based fibrous binder having a denier of 0 and a cut length of 3 mm was 90/10. The slurry is made into a paper by a round paper machine, dried at a dryer temperature of 110 ° C., and has a basis weight of 14.0 g / m ² , a thickness of 40 μm, a density of 0.350 g / cm ³ , and a tensile strength (vertical) of 1.0 kg. / 15 mm of separator paper.
The separator made of this paper had an impedance ratio of 95 and a short-circuit occurrence rate of 1.9%, which was insufficient.

The structure of each of the above Examples and Comparative Examples,
The obtained measured values (physical property values) and the evaluation of each are summarized in Tables 1 to 5 below. In each table, ○, △, and × in the evaluation column indicate that the evaluation of each item is satisfactory for the purpose and effect, は indicates satisfactory, △ indicates slightly unsatisfactory, and × indicates unsatisfactory. .

[0046]

[Table 1]

[0047]

[Table 2]

[0048]

[Table 3]

[0049]

[Table 4]

[0050]

[Table 5]

[0051]

According to the constitution of the present invention, as a separator for an electrolytic capacitor, a cellulose fiber having specific physical properties in which the internal fibrils of the fiber have developed extremely well to the innermost layer of the fiber is used, and this is defined as a specific fibril form. Since it is beaten into a fibril-like material and formed as a separator, the separator can be made to have a very low density while maintaining high strength, thereby achieving an extremely excellent low impedance and a high performance. In addition, the present invention has a great effect that a capacitor having a good workability and a small occurrence rate of short circuit can be easily and stably manufactured in industrial production.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-51619 (JP, A) JP-A-63-226020 (JP, A) JP-A-63-207114 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01G 9/02

Claims (3)

(57) [Claims] A separator for an electrolytic capacitor comprising a fibrillated cellulose fiber having a wet Young's modulus of 20 g / d or more and an orientation of Δn = 42 × 10 ⁻³ or more as at least a part of a main fiber. So,
The cellulose fiber is made of an amine oxide-based cellulose.
The spinning stock solution dissolved in the solvent of
It is a solvent-spun cellulose fiber with precipitated cellulose.
And a separator for an electrolytic capacitor. 2. The separator according to claim 1, wherein the main fiber comprises a fibrillated product of the cellulose fiber according to claim 1 and a polyvinyl alcohol-based fiber of 0.4 denier or less, wherein the fibrillated product and the polyvinyl alcohol-based fiber are used. A separator for an electrolytic capacitor, wherein the weight ratio of the fibers is from 100: 0 to 20:80, and the main fibers are bonded with a polyvinyl alcohol-based binder. 3. The separator for an electrolytic capacitor according to claim 1, wherein the separator has a density of 0.25 g / cm ³ or less.