JPH0754787B2 - Electrolytic capacitor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic capacitor obtained by impregnating a separator interposed between an anode foil and a cathode foil with a predetermined electrolytic solution, and particularly, it affects a short circuit failure rate. In order to improve the impedance characteristics and the life of the electrolytic capacitor without giving it, the separator is formed by a film or a non-woven fabric, and the separator contains cellulose having an organic substituent introduced by a chemical reaction, and the degree of swelling of the separator with respect to the electrolytic solution. Is significantly increased.

Conventional Technology Generally, electrolytic capacitors, especially aluminum electrolytic capacitors,
It is formed by winding electrolytic paper as a separator between an anode aluminum foil and a cathode aluminum foil, winding it, immersing it in a predetermined electrolytic solution, impregnating the electrolytic solution with the electrolytic solution, and sealing it. . The electrolytic solution is usually ethylene glycol, dimethylformamide, etc. as a solvent, and organic acid salts such as boric acid or ammonium adipate, ammonium hydrogen maleate are dissolved in these solvents to make it permeate from both ends of the capacitor. is doing.

The electrolytic paper as the separator must have a predetermined density and thickness selected in advance so as to reduce the short circuit defect rate during the element winding process. Has impedance characteristics,
Especially, there is a problem that the equivalent series resistance (hereinafter referred to as ESR) becomes high. That is, in order to reduce short circuit defects during the element winding process, the density of the electrolytic paper may be increased and the thickness may be increased, but the effect on the ESR of these items is that the ESR increases linearly when the electrolytic paper is thickened. As the density deteriorates and the density increases, the ESR deteriorates quadratically. Therefore, in order to reduce the ESR, it is necessary to reduce the density and the thickness of the electrolytic paper, in contrast to the improvement of the short circuit defect rate. On the other hand, the CSF value according to JIS P 8121, which indicates the degree of beating of pulp, has almost no effect on the ESR, but a smaller CSF value inevitably increases the density. Therefore, it is difficult to effectively reduce the ESR without affecting the short circuit failure.

Therefore, in order to improve the ESR without affecting the short-circuit defect rate, the present applicant has previously incorporated electrolytic fibers into the electrolysis paper by introducing organic substituents by a chemical reaction, thereby increasing the degree of swelling in an electrolytic solution. We provide electrolytic paper for capacitors (Japanese Patent Application No. 61-250479).

According to this electrolytic paper, the element is wound without causing a short circuit failure by keeping the density and thickness so that no short circuit failure occurs during the element winding process, and after impregnating with the electrolytic solution, the electrolytic solution of the electrolytic paper is used. Since the degree of swelling is significantly higher than that of conventional swelling, the fibers that make up the electrolytic paper expand,
Further, the gap between the fibers becomes large, and the density of the electrolytic paper can be substantially reduced, and the ESR can be reduced.
Moreover, since it is after the element winding step, short-circuit defects are not increased. Since it has low viscosity and low toxicity, it is used instead of an electrolyte solution that uses ethylene glycol, which has poor electrical properties at low temperatures, or dimethylformamide, which is highly toxic, as a solvent. Since there is no ESR, the degree of swelling can be remarkably increased even for an electrolytic solution using γ-butyrolactone as a solvent, and the substantial density of electrolytic paper after impregnation with the electrolytic solution is reduced to reduce the ESR. Can be improved.

On the other hand, as a separator to improve the ESR, wood kraft pulp, manila hemp pulp, instead of electrolytic paper made from natural cellulosic pulp fiber such as esparto pulp, the cross-sectional shape of the fiber is close to a perfect circle, Further, it is provided that it is formed by a non-woven fabric such as rayon fiber, vinylon fiber (polyvinyl alcohol fiber), polypropylene fiber, polyester fiber, etc., which can have a low density (Japanese Patent Application Nos. 49-29177 and 50). -81707 etc.).

In addition, as a measure to substantially improve short-circuit failure, several μ
The use of a polypropylene or polyethylene porous film having a pore size of m or less as a separator is also provided (Japanese Patent Application No. 58-33467, etc.).

Problems to be Solved by the Invention However, when the nonwoven fabric such as the rayon fiber is used as the separator, the ESR is improved, but it is more dense than the electrolytic paper made of natural cellulosic pulp fiber such as Manila hemp pulp. Since it is chipped, a short circuit defect occurs several to several tens of times, which is far from an allowable range.
Therefore, if the density is increased by calendering or the like to reduce short-circuit defects and the denseness is improved, there is no lyophilicity to the electrolytic solution and the degree of swelling is poor, so the secondary formula is the same as for so-called high-density electrolytic paper. ESR will increase. Further, it lacks liquid retention and impregnates the electrolytic solution, and thus the life of the electrolytic capacitor is shortened, resulting in impracticality.

On the other hand, when a polypropylene or polyethylene porous film or cellophane film is used as a separator, it is effective in substantially preventing short defects, but the tensile strength is too weak and the impregnation of the electrolyte is poor, making it lyophilic to the electrolyte. Since it lacks in swelling property and liquid retention, it has a large ESR and is not practical.

In particular, when using γ-butyrolactone as a solvent for the electrolytic solution, γ-butyrolactone has good low-temperature properties and workability but is poor in hydrophilicity, so the above-mentioned drawbacks are remarkable, and a nonwoven fabric or a porous film is used as a separator. It could not be used.

Therefore, in the case of using the non-woven fabric or film as the separator, the non-woven fabric is provided with denseness and wound with an element without causing a short circuit defect and impregnated with an electrolytic solution. After impregnation with the electrolyte, if the degree of swelling with respect to each electrolyte can be increased, the fiber and film layers expand and the gaps between the fibers widen, so that the density of the separator can be substantially reduced and short-circuit failure and ESR can be reduced at the same time. Can be made. Moreover, since the device is wound, short-circuit defects are not increased. It can also be used in an electrolytic solution containing γ-butyrolactone and a solvent.

Therefore, the present invention eliminates the problems that such non-woven fabrics and films as conventional separators have, and various electrolytic solutions, particularly γ-butyrolactone, in order to improve ESR without affecting the short-circuit failure rate. An object of the present invention is to provide an electrolytic capacitor capable of remarkably increasing the degree of swelling of a nonwoven fabric or a film when an electrolytic solution containing a solvent is used.

Means for Solving the Problems In order to achieve the above object, the present invention provides an electrolytic capacitor obtained by impregnating a separator interposed between an anode foil and a cathode foil with a predetermined electrolytic solution, wherein the separator is a film. Alternatively, it is formed of a non-woven fabric and is characterized in that the swelling degree with respect to the electrolytic solution is increased by containing cellulose having an organic substituent introduced by etherification reaction, esterification reaction or acetalization reaction of hydroxyl groups in the separator. An electrolytic capacitor is provided. The electrolytic solution is an electrolytic solution containing one or more selected from γ-butyrolactone, dimethylformamide, ethylene glycol, etc. as a solvent,
Particularly preferably, it has a swelling degree of 5% or more when immersed in γ-butyrolactone which is a solvent of the electrolytic solution.

According to the present invention having the above-described structure, the swelling degree of the separator made of a nonwoven fabric or a porous film is significantly increased at the time of impregnation with the electrolytic solution after the element winding step, and the fibers and the film layers constituting the separator expand, Since the gap between them becomes large, the density of the separator can be substantially reduced and the ES
R can be reduced. Moreover, since it is after the element winding step, short-circuit defects are not increased. Therefore, a non-woven fabric or a film can be used as a separator by taking advantage of its characteristics, and an electrolytic capacitor in which both the short-circuit defect rate and the ESR are reduced below desired values can be obtained. Further, according to the present invention, the amount of impregnated liquid holding the electrolytic solution is inevitably increased, so that the dry-up of the electrolytic solution can be prevented and a long-life electrolytic capacitor can be obtained.

Embodiments Hereinafter, the structure and various embodiments of the electrolytic capacitor according to the present invention will be described.

The separator used in the present invention is formed of a porous film such as polypropylene or polyester or a film such as cellophane film or rayon fiber, or a nonwoven fabric such as polyester fiber, and cellulose having an organic substituent introduced into this separator by a chemical reaction. It is included.

As the chemical reaction for introducing the organic substituent, an etherification reaction, an esterification reaction or an acetalization reaction of the hydroxyl group contained in the cellulose fiber is used to facilitate the reaction.

Chlorine CL, bromine as organic substituents introduced into cellulose
Any substituent such as Br or iodine I that does not contain an element that causes corrosion of the electrolytic capacitor may be used, but a carboxyl group (-COO
H), a sulfonic acid group (—SO ₃ H) or other substituent having a dissociative polar group is introduced, which is not preferable because the swelling property is reduced. Therefore, it is necessary to select an organic substituent to be introduced according to the degree of polarity or hydrophilicity of the electrolytic solution. Preferably a hydroxyl group to an alkyl group, an ether group,
An organic substituent having one or more kinds such as an amino group, a nitrile group, an amide group, an imide group or a carbonyl group bonded thereto, and a substituent having an appropriate polarity is desirable. Further, it is preferable that the substituent consisting of only an alkyl group has 5 or less carbon atoms. The particularly preferable chemical reaction examples are shown below.

(A) Esterification reaction (1) Reaction with acid chloride (2) Reaction with acid anhydride (3) Reaction with isocyanate (Note) R indicates any of CH ₃ , C ₂ H ₅ , and C ₃ H ₇ .

CELL indicates a cellulose chain.

(B) Etherification reaction (4) Reaction with alkyl halide CELL-OH + RCL → CELL-OR (5) Reaction with dialkyl sulfuric acid (Note) R indicates any of CH ₃ , C ₂ H ₅ , and C ₃ H ₇ .

CELL indicates a cellulose chain.

(6) Reaction with alkylene oxide (Note) R indicates any of H, CH ₃ , and C ₂ H ₅ . n represents an integer of 1 or more. CELL indicates a cellulose chain.

(7) Reaction with vinyl compounds (Note) R indicates any of CN, CONH ₂ , OC ₂ H ₅ , COCH ₃ , and COC ₂ H ₅ .

CELL indicates a cellulose chain.

(C) Acetalization reaction (8) Reaction with aldecht (Note) R represents any one of CH ₃ , C ₂ H ₅ , C ₃ H ₇ , and C ₄ H ₉ .

CELL indicates a cellulose chain.

As described above, it is preferable that a part of the hydroxyl group (OH) in the cellulose is substituted with the above-mentioned substituent by utilizing the esterification reaction (A), the etherification reaction (B) and the acetalization reaction (C).
Further, the separator used in the present invention does not need to be a film or a non-woven fabric composed only of cellulose having an organic substituent introduced therein, and may be a composite of natural cellulose or other natural resin or synthetic resin such as polyethylene, polypropylene, polyester or vinylon. It may be a film or a non-woven fabric. That is, it suffices that the film or nonwoven fabric substantially contains cellulose having an organic substituent introduced therein.

Then, in the production of the film as the separator according to the present invention, the viscose solution of cellulose introduced organic substituents, copper ammonia solution or dimethylacetamide, a solution dissolved in an organic solvent such as dimethyl sulfoxide. After casting on a substrate such as glass, metal, ceramic, synthetic resin, etc., water, a method of immersing in a non-solvent such as methanol for coagulation regeneration, further washing with water, and a method for producing by drying,
Alternatively, a method in which a thermoplastic synthetic resin such as polyethylene or polypropylene is mixed with cellulose powder having the organic substituent introduced therein to form a film by a usual extrusion molding method, further, synthetic pulp such as polyethylene or polypropylene and the organic substituent are introduced. For example, a method may be applied in which the cellulose powder thus prepared is dispersed in water, and a web is formed by an ordinary papermaking method, and then heat treatment is performed to form a film. Further, the film may be prepared by mixing inorganic powder of alumina, silica, glass, various ceramics or inorganic fibers as a filler. The thickness and porosity (porosity) of the produced film are not particularly limited, but in order to maintain good mechanical strength and ESR of the obtained electrolytic capacitor, in the case of a membranous film, a thickness of 10 ~ 30 μm is desirable. In the case of a porous film, the thickness is preferably 10 to 60 μm, the porosity is preferably 40 to 95%, and the pore size is 0.01 to 5 μ to prevent a short circuit defect.
It is desirable to set m. In order to adjust the porosity and the pore diameter, inorganic or organic powders that can be eluted in the non-solvent, for example, inorganic electrolytes such as borax and sodium sulfate, and starch, polyvinyl alcohol, and the particle size of water-soluble organic substance powders such as carboxymethylcellulose. It is also possible to adjust the mixing amount and the mixture before mixing the porous film in advance, and elute during the porous film production process or after the film is formed to adjust the pore size and the porosity. If the thickness of the film is less than 10 μm, the tensile strength will be significantly reduced and it is not practical for winding an element in the process of manufacturing an ordinary electrolytic capacitor. Therefore, a film-like film or a porous film should be directly formed on the electrode aluminum foil. It can also be molded and used as a separator.

On the other hand, in the production of the non-woven fabric according to the present invention, a wet spunbond method or an organic substituent to form a web on a wire mesh cylinder after spinning a copper ammonia solution of cellulose having an organic substituent introduced into dilute sulfuric acid. The copper-ammonium solution or viscose solution of cellulose into which is introduced is spun into dilute sulfuric acid to obtain regenerated fibers, and then cut fibers of 3 to 20 mm are formed, and then a web is formed by a dry method or a wet method to form an adhesive. A dipping adhesion method using a solution or a fusion bonding method of heating and fusion with powders or fibers of polyethylene, polypropylene, polyester or the like mixed at the time of forming the pre-wetted web is applied. When applying the wet method, especially the papermaking method, to the cut fibers, the ordinary vinylon binder fibers are mixed into the cut fibers having the organic substituent introduced therein, or the polyethylene synthetic pulp is mixed into the cut fibers, and further polyethylene fibers, polypropylene fibers, When thermoplastic fibers such as polyester binder fibers are mixed and mixed, it is preferable that the mixed fibers can be heat-sealed in the drying section during the paper making process. Further, the non-woven fabric according to the present invention may be any non-woven fabric as long as it substantially contains cellulose having an organic substituent introduced, and it is a non-woven fabric produced by mixing or mixing with ordinary rayon, polyethylene, polypropylene, polyester, vinylon. The rayon fiber may be a normal rayon fiber alone or a non-woven fabric containing other fibers with an organic substituent introduced. Although the thickness and density of the non-woven fabric are not particularly limited, the short-circuit failure of the electrolytic capacitor can be prevented and
To maintain good ESR, thickness 30-60μm, density 0.3-
0.7 g / cm ³ is preferred.

Incidentally, a film-nonwoven fabric composite obtained by coating and impregnating a cellulose solution in which an organic substituent is introduced into a non-woven fabric into which the organic substituent is introduced or a normal non-woven fabric is also applicable to the present invention. is there.

As described above, the separator according to the present invention remarkably swells in the electrolytic solution and can substantially reduce the density of the separator, so that the ESR of the obtained electrolytic capacitor can be reduced. Further, the introduced organic substituent improves the wettability and retention of the separator with respect to the electrolytic solution, and since the electrolytic solution can be sufficiently impregnated by swelling, it is possible to prevent the electrolytic solution from drying up and achieve a long service life. be able to. If the degree of swelling is extremely increased, a part of the film or the non-woven fabric will be dissolved in the electrolytic solution at the time of impregnation, and the viscosity of the electrolytic solution will increase, so if the viscosity of the electrolytic solution adversely affects the ESR. In addition, as a preferred range in which the ESR can be effectively reduced by substantially lowering the density of the film or nonwoven fabric after impregnation with the electrolytic solution, the film or nonwoven fabric is 5% or more with respect to γ-butyrolactone as a solvent. The swelling degree and the solubility of 15% or less are desirable.

Below, various examples for obtaining the electrolytic capacitor according to the present invention and the results of measuring the swelling degree, the solubility, the short circuit failure rate and the ESR of the used separator are shown. Each measured value of each sample was measured by the following measuring method and apparatus.

(1) Thickness, density and tensile strength Thickness, density and tensile strength were measured by the method specified in JIS C 2301 (electrolytic capacitor paper).

(2) Swelling degree The swelling degree is obtained by stacking 10 separators into a test piece, measuring its thickness with a micrometer (A μm), and then the test piece is immersed in γ-butyrolactone or a predetermined solvent for exactly 15 minutes. Soak. After that, the test piece was taken out, and the thickness was measured with a micrometer in a wet state (B μm). A micrometer specified in JIS C 2301 (electrolytic capacitor paper) was used, and the swelling degree was calculated by the following formula.

(3) Solubility About 2 g of the separator was used as a test piece, and the weight was accurately measured by drying to a constant weight at 105 ° C (Sg), and then the test piece was immersed in γ-butyrolactone at 25 ° C for 24 hours. To do. Thereafter, the test piece is filtered with a 200-mesh wire net and taken out, and washed on the wire net with ion-exchanged water. This test piece was dried again at 105 ° C. until it became a constant temperature, its weight was accurately measured (Tg), and the solubility was determined by the following formula.

(4) Short-circuit defect rate Separator width 18 mm, aluminum foil width 15 mm, diameter 10
After manufacturing the mm electrolytic capacitor element, the presence or absence of continuity was tested by a tester, and the one with continuity was shown as P (%) as defective.

(5) ESR (Equivalent Series Resistance) ESR is 50 WV x 220 using the specified separator and electrolyte.
A μF electrolytic capacitor was manufactured and measured with an LCR meter at a temperature of −40 ° C. and a frequency of 1000 Hz.

(6) Accelerated life test Fabricate an electrolytic capacitor of 50WV × 220μF and measure the capacitance accurately (CμF). Then, after leaving it in a constant temperature bath at 85 ° C. for 1000 hours, the capacitance was accurately measured (C′μF), and the rate of change in capacitance (%) was shown by the following formula.

(Example 1) 100 g of softwood wood pulp was thoroughly mixed with 250 ml of 2.5% NaOH aqueous solution to give alkali cellulose, then 100 g of acrylonitrile was added, and the mixture was allowed to react for 2 hours at room temperature with slow stirring to carry out cyanoethylation, and then 2 Carbon sulfide
30 g was added and the mixture was reacted under reduced pressure at 30 ° C. for 2 hours to obtain cellulose zanthate in which some of the hydroxyl groups of cellulose were cyanoethylated. Next, add water and alkali to dissolve and make viscose of 10% cellulose and 3% alkali, and age for 10 hours, and add 20 g of alumina fine powder (average particle size 1 μm) and 10 g of mirabilite (average particle size 1 μm). After stirring, the mixture is cast on a glass substrate and immediately solidified and regenerated in dilute sulfuric acid. Next, after scouring in hot water containing 2% sulfuric acid at 90 ° C. under tension, the sodium sulfate, the alkaline component and the acid component were completely extracted and washed with ion-exchanged water, and then pre-dried at 90 ° C. for 1 hour and further 120 After drying at ℃ for 1 hour, thickness 50.6μm, porosity 68.7%, average pore size 1.7μm, degree of swelling for γ-butyrolactone 60.5
%, And a tensile strength of 1.8 kg / 15 mm to obtain a porous film.

This porous film is used as a separator, and γ is used as an electrolytic solution.
An ammonium borodisalicylate was dissolved in a solvent of butyrolactone and adjusted to have a specific resistance of 200 Ω · cm (20 ° C.), and a 50 WV × 220 μF electrolytic capacitor was manufactured.

(Example 2) 3% of commercially available rayon fiber 1 kg (fiber diameter 2d, fiber length 5 mm)
After soaking in NaOH aqueous solution for 1 hour, the excess soaking solution was removed, mixed with a reaction solution consisting of 1 part of acrylonitrile and 5 parts of xylene, reacted at room temperature for 10 hours, then neutralized with a 5% acetic acid solution, and then pure. It was washed with water to obtain cyanoethylated rayon fiber. 1 kg of this cyanoethylated rayon fiber and 100 g of vinylon binder fiber (fiber diameter 1.5 d, fiber length 4 mm) are uniformly dispersed in pure water, and a cylinder test paper machine (papermaking width 360 mm,
Paper making at a speed of 4.8 m / min), thickness 93.7 μm, density 0.247 g
A web of / cm ³ was obtained. Next, calender roll processing is performed to a thickness of 50.2 μm, a density of 0.461 g / cm ³ , and a tensile strength of 2.2 kg /.
A wet non-woven fabric having a swelling degree of 94.8% with respect to 15 mm and γ-butyrolactone was obtained, and then 50 WV × 220 in the same manner as in Example 1.
A μF electrolytic capacitor was manufactured.

Example 3 100 g of rayon spunbonded non-woven fabric having a thickness of 120 μm and a density of 0.18 g / cm ³ was immersed in a reaction solution containing 100 parts of acetic anhydride, 400 parts of acetic acid and 0.5 part of sulfuric acid, and reacted at 50 ° C. for 15 minutes. After that, it is sandwiched between saran nets and thoroughly washed with pure water. Then, it was passed through a steam heating cylinder and dried, and then heat calendered at 140 ° C. to obtain an acetylated rayon nonwoven fabric having a thickness of 50.3 μm and a density of 0.429 g / cm ³ . Using this non-woven fabric as a separator, ammonium hydrogen maleate was dissolved in a solvent of dimethylformamide and adjusted to have a specific resistance of 200 Ω · cm (20 ° C.), and a 50 WV × 220 μF electrolytic capacitor was manufactured.

(Example 4) 5% of commercially available rayon fiber 1 kg (fiber diameter 2d, fiber length 5 mm)
It was immersed in an aqueous solution of NaOH, subjected to cold alkali treatment, and then centrifuged to remove excess aqueous solution of NaOH so that the amount of the immersion liquid was 40%. After this fiber was finely disentangled, it was put in a closed stainless steel container, and the air in the container was replaced with nitrogen gas. Then 1,2
-Put 500 ml of butylene oxide in a container and seal tightly.
The mixture was reacted at 0 ° C. for 60 minutes, taken out of the container, neutralized with a 5% aqueous acetic acid solution, and then washed with pure water to obtain hydroxybutylated rayon fiber. 1 kg of this hydroxyl butylated rayon fiber and 120 g of vinylon binder fiber (fiber diameter
1.5d, fiber length 5mm) is uniformly dispersed in pure water, and paper is made with a cylinder test paper machine (papermaking width 360mm, papermaking speed 5.1m / min).
A web having a thickness of 89.5 μm and a density of 0.214 g / cm ³ was obtained. Next, calender roll processing is performed to a thickness of 49.9 μm and a density of 0.
A non-woven fabric having a tensile strength of 431 g / cm ³ , an initial strength of 2.6 kg / 15 mm and a swelling degree of 6.8% with respect to γ-butyrolactone was obtained. Next, using this non-woven fabric as a separator, ammonium hydrogen maleate was dissolved in a solvent in which dimethylformamide and ethylene glycol were mixed at a weight ratio of 1: 1 as an electrolytic solution to obtain a specific resistance of 200Ω.
・ Used after adjusting to cm (20 ℃), 50WV × 220μF
The electrolytic capacitor of

(Example 5) Commercially available cellophane film (nominal thickness 20 μm) was added to 5% Na.
After immersing in an OH aqueous solution for 1 hour, the excess immersion fluid is removed, mixed with a reaction solution consisting of 1 part of acrylonitrile and 5 parts of xylene, reacted at room temperature for 6 hours, and then neutralized with a 5% aqueous solution of acetic acid.
Then, after washing with pure water, sticking it on a steam drying cylinder and drying it, thickness 21.4 μm, density 1.39 g / cm ³ , tensile strength 4.2 kg / 1
A 5 mm cyanoethylated cellophane film was obtained. Using this film as a separator, an electrolyte prepared by dissolving ammonium borodisalicylate in a solvent of γ-butyrolactone and adjusting the specific resistance to 200 Ω · cm (20 ° C) was used.
A 0WV × 220μF electrolytic capacitor was manufactured.

In addition to the above Examples 1 to 5, in order to compare the electrolytic capacitor according to the present invention with a conventional electrolytic capacitor, electrolysis using a film or non-woven fabric not introducing an organic substituent and Manila hemp electrolytic paper as a separator. A capacitor was manufactured as a comparative example as follows.

Comparative Example 1 An electrolytic capacitor was manufactured using the same electrolytic solution as in Example 1 with a commercially available polypropylene porous film (manufactured by Polyplastics Co., Ltd., nominal thickness 25 μm) as a separator.

(Comparative Example 2) 100 parts by weight of commercially available rayon fiber (fiber diameter 2d, fiber length 5 m
m), 10 parts by weight of vinylon binder fiber (fiber diameter 1.5d,
(Fiber length 4 mm) is dispersed in pure water and paper is made with a cylinder paper machine.
A web having a thickness of 83.2 μm and a density of 0.281 g / cm ³ was obtained. Next, calender roll processing is performed to a thickness of 51.1 μm and a density of 0.
A rayon non-woven fabric of 458 g / cm ³ was obtained. Using this non-woven fabric as a separator, ammonium hydrogen maleate was dissolved in a solvent in which dimethylformamide and ethylene glycol were mixed at a weight ratio of 1: 1 as an electrolytic solution to obtain a specific resistance of 200 Ω · cm (2
A 50WV x 220μF electrolytic capacitor was manufactured by using the one adjusted to 0 ° C.

Comparative Example 3 Conventionally used Manila hemp electrolytic paper (thickness 50.3 μm, density 0.45 g /
cm ³ ) was used as a separator, and other conditions were the same as in Example 1 to manufacture an electrolytic capacitor.

Comparative Example 4 An electrolytic capacitor was manufactured in the same manner as in Example 5, except that a commercially available cellophane film (nominal thickness 20 μm) was used as the separator.

The characteristics of the separators according to Examples 1 to 5 and Comparative Examples 1 to 4 obtained as described above, such as thickness, density, tensile strength, and degree of swelling in a solvent such as γ-butyrolactone, and the obtained electrolytic capacitors. The characteristics such as ESR, short circuit failure rate and capacity change rate were measured. The results are shown in Tables 1 and 2.

As shown in the measurement results of Table 1, the separator formed of the film or the nonwoven fabric according to the present invention and containing the cellulose having the organic substituent introduced therein has γ-butyrolactone and various other types as compared with the conventional separator. The degree of swelling with respect to the solvent is remarkably increased, and as a result, the density of the separator after impregnation with the electrolytic solution is substantially decreased, and as shown in Table 2, the characteristics of the electrolytic capacitor such as ESR are remarkably improved and reduced. For example, Example 1 is a porous film containing cyanoethylated cellulose, which corresponds to Comparative Example 1 which is a conventional porous film in which no organic substituent is introduced, but is swollen with γ-butyrolactone. The degree of swelling in Example 1 was 60.5%, whereas the degree of swelling in Comparative Example 1 was 0.1%, and the degree of swelling was 60.5%. it can. Therefore, the ESR of the obtained electrolytic capacitor is 6.76Ω in Comparative Example 1.
In contrast, in Example 1, the value is 1.35Ω, which is a large decrease. Also, the short circuit defect rate is 0% in Example 1, which is improved and reduced from 1.2% in Comparative Example 1. Furthermore, the rate of change in capacity has decreased from -18.3% to -2.5%, resulting in a long service life. Further, the tensile strength has practically no problem. The swelling degree with respect to other solvents, such as ethylene glycol, was 0.1% in Comparative Example 1 and hardly swelled, whereas in Example 1 it was significantly increased to 33.4%.

Further, even when compared with Comparative Example 3 which is a separator using Manila hemp pulp having substantially the same thickness and density as those of Example 1,
Swelling degree against γ-butyrolactone from 0.2% to 60.5%
As a result, the ESR is improved from 2.36Ω to 1.35Ω, and the short-circuit failure rate is also reduced.

Next, Example 2 is a non-woven fabric made of cyanoethylated rayon fiber as a raw material, and is swollen with γ-butyrolactone as compared with Comparative Example 2 which is a conventional non-woven fabric made of rayon fiber into which no organic substituent is introduced. Comparative example 2
In contrast to 1.2%, the swelling degree in Example 2 was 94.8%, and it can be clearly confirmed that the swelling degree of the nonwoven fabric was significantly increased. As a result, ESR is also 6.25Ω to 1.14Ω
Has decreased significantly. The short-circuit defect rate was 0.9% in Example 2 as well, which is an improvement compared with 1.3% in Comparative Example 2. The rate of change in capacity has also decreased from -8.2% to -2.0%, prolonging service life.

Next, Example 5 is a cyanoethylated cellophane film, and the ESR of Comparative Example 4 which is a conventional cellophane film in which no organic substituent is introduced is 35.72Ω, whereas Example 5 is remarkably 4.36Ω. Has decreased to a value that can be fully used. This is also because the degree of swelling in a solvent such as γ-butyrolactone is significantly increased from 1.1% to 92.7%, and as a result, the density of the separator after impregnation with the electrolytic solution is substantially reduced.

Further focusing on the solubility, the solubilities of Examples 1, 2, and 4 are single-digit numerical values in the range of 2.5% to 3.6%, but as described above, the ESR is greatly improved and reduced as compared with the conventional example. The results also clearly show that the viscosity does not increase to the extent that it adversely affects the ESR and that the viscosity does not adversely affect the ESR even if the swelling degree is increased according to the present invention. Further, in Example 3, the solubility was increased to 12.8% as compared with the other Examples, but the ESR showed a good value of 1.06Ω, which was comparable to the other Examples, and the comparison was made. It is greatly improved compared to the example. Therefore, it can be said that a preferable embodiment having a solubility of about 15% exerts a remarkable effect on the improvement and reduction of ESR.

Focusing on the degree of swelling, Example 4 has a degree of swelling to γ-butyrolactone of 6.8% and is less swelling than other Examples, but has an ESR of 2.45Ω and is improved as compared with Comparative Example 2. Has been done. That is, as shown in Example 4, when the degree of swelling is about 5% with respect to γ-butyrolactone, it is sufficiently effective in improving and reducing ESR.

Further, depending on the type of organic substituent or the amount of introduction thereof, the tensile strength of the electrolytic paper decreases, which may cause paper breakage of the electrolytic capacitor.In the case of the present invention, the electrolytic paper has a tensile strength of at least 0.5 kg or more. It is preferable to have

Effects of the Invention As described in detail above, the electrolytic capacitor according to the present invention uses a film or nonwoven fabric containing cellulose having an organic substituent introduced by an etherification reaction of a hydroxyl group, an esterification reaction or an acetalization reaction as a separator, The feature is that the degree of swelling in the electrolytic solution is increased, and the following operational effects are brought about. That is, after performing the element winding step using a separator formed of a film or a nonwoven fabric containing a cellulose having an organic substituent introduced by a chemical reaction, since the separator swells significantly when the impregnation step is performed, Even if the predetermined thickness and density are maintained so as not to cause a short circuit defect during the winding process, the fibers or film layers constituting the separator expand due to swelling after impregnation, and the gap between the fibers becomes large. Therefore, the density of the separator can be substantially reduced, and the equivalent series resistance (ESR) can be reduced. Moreover, since it is after the element winding step, short-circuit defects are not increased. Therefore, the ESR can be improved without affecting the short circuit defect rate. Therefore, it can be used as a separator by taking advantage of the characteristics of a film or a non-woven fabric, and an electrolytic capacitor in which both the ESR and the short circuit defect rate are reduced below desired values can be obtained. In particular, low-temperature characteristics and workability are good, but even when γ-butyrolactone having poor hydrophilicity and extremely poor ESR is used as a solvent, it is possible to significantly swell the separator, thus reducing ESR. The use range of γ-butyrolactone can be expanded.

Therefore, even when creating a desired high-voltage capacitor, the separator has a desired thickness and density to improve the withstand voltage performance and prevent the occurrence of short-circuit defects. It can be reduced and the effect is particularly large.

Further, since the introduced organic substituent improves the wettability and retention of the separator to the electrolytic solution and also increases the amount of the electrolytic solution impregnated by the swelling, the electrolytic solution is prevented from being dried up and the electrolytic capacitor The life can be improved.

Claims (3)

[Claims] 1. An electrolytic capacitor comprising a separator interposed between an anode foil and a cathode foil impregnated with a predetermined electrolytic solution, wherein the separator is formed of a film or a non-woven fabric, and hydroxyl groups are etherified into the separator. An electrolytic capacitor comprising a cellulose having an organic substituent introduced therein by a reaction, an esterification reaction, or an acetalization reaction to increase the degree of swelling with respect to the electrolytic solution. 2. The electrolytic solution comprises an electrolytic solution containing, as a solvent, one or more selected from γ-butyrolactone, dimethylformamide, ethylene glycol, methylcellosolve, propylene glycol and propylene carbonate. The electrolytic capacitor according to claim 1. 3. The electrolytic capacitor according to claim 1, wherein the swelling degree is 5% or more when immersed in γ-butyrolactone which is a solvent of the electrolytic solution.