JP2001189239A - Electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic capacitor where breakdown voltage and over-voltage are improved, and further electrolytic solution leakage at a service life test and coming-out of a rubber are prevented when abnormal voltage is applied. SOLUTION: With a separator that is formed by coating an electrolytic paper, containing a high density electrolytic paper whose density is 0.6-0.9 g/cm3, with a prescribed quantity of PVA, or a separator that is formed by constituting an electrolytic paper, piling a high density electrolytic paper whose density 0.6-0.9 g/cm3 and a low density electrolytic paper of less than 0.6 g/cm3, and then sticking a prescribed quantity of polyvinyl alcohol on the side of the low density electrolytic paper in between, a cathode foil and an anode foil to which an electrode lead-out terminal is joined are piled and wound to form a capacitor element. The capacitor element is soaked in electrolytic solution containing boric acid and is put in a case, and sealing is performed with the use of a sealing material formed of peroxide partially crosslinked butyl rubber, that is formed by adding peroxide as crosslinking agent to butyl rubber polymer formed of copolymer of isobutylene, isoprene and divinylbenzene, and re-formation is performed to manufacture an electrolytic capacitor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic capacitor.

[0002]

2. Description of the Related Art In a conventional electrolytic capacitor, the surface area of a valve metal foil made of aluminum or the like is enlarged by etching, a dielectric layer is formed as an anode, and a foil of the same or another metal subjected to etching is used. It has a structure in which a cathode (electrolytic paper) is arranged between both electrodes as a cathode. This separator prevents the anode foil and the cathode foil from being short-circuited and holds the electrolytic solution, and thin, low-density paper such as kraft paper or manila paper is used. Then, the anode foil and the cathode foil, to which the electrode lead terminals are bonded, are laminated via a separator, and wound to form a capacitor element.The capacitor element is impregnated with an electrolytic solution, placed in a case, sealed, and re-formed. Thus, an electrolytic capacitor is manufactured.

However, in such a conventional electrolytic capacitor, since the electrolytic solution is in a liquid state, if the electrolytic solution is used for a long time or at a high temperature, the electrolytic solution permeates through the sealing material and evaporates, thereby lowering the capacitance and reducing tan δ. Deterioration of characteristics such as rise.

Therefore, as a method for solving the above-mentioned problems of the liquid electrolyte, a method of gelling the electrolyte has been proposed. In addition, as this gelling agent, in addition to natural products such as gelatin and cellulose, synthetic polymers such as polyvinyl alcohol, polymethyl methacrylate, and polyethylene oxide are known.

However, the present inventors prepared an electrolytic solution to which PVA was added as a gelling agent, superposed an anode foil and a cathode foil via a separator, and impregnated the wound capacitor element with the electrolyte. After enclosing in a case, heating and gelling the electrolytic solution to create an electrolytic capacitor,
When the various characteristics were investigated, the capacitance was low and tan
The result was that δ was high and the withstand voltage was not improved.

The present inventors have considered that the above phenomenon is caused by the fact that the gelled electrolyte is not adhered to the dielectric film in a good state, and have made intensive studies and have made studies as disclosed in JP-A-10-22.
No. 3481 has proposed an electrolytic capacitor. That is, the electrolytic capacitor proposed earlier
A capacitor element is formed by winding a cathode foil and an anode foil having a pit diameter of at least 0.1 μm formed on the surface thereof through a separator to which PVA is adhered to form a capacitor element. The above-mentioned problem is intended to be solved by impregnating with the electrolytic solution described above.

[0007]

However, in recent years,
2. Description of the Related Art Electronic devices using a switching power supply have been widely used in ordinary households, and a wide range of requirements for safety of electrolytic capacitors have been increasing. That is, although an electrolytic capacitor is used for such a switching power supply, in a use environment where the power supply is unstable, an overvoltage may be applied to the electrolytic capacitor, and the overvoltage characteristic that can withstand such an overvoltage may be applied. There is a growing demand for highly safe electrolytic capacitors having good withstand voltage characteristics.

In a conventional electrolytic capacitor,
As a sealing rubber, a quinoid cross-linked butyl rubber obtained by adding a quinoid as a cross-linking agent to a butyl rubber polymer made of a copolymer of isobutylene and isoprene is used.
However, in a conventional electrolytic capacitor using a quinoid crosslinked butyl rubber as a sealing rubber, when a long-term life test is performed, at the end of the life test, electrolyte leakage occurs from the insertion hole of the lead wire of the sealing rubber. There was something. Further, when an abnormal voltage is applied, there is a problem that the internal pressure of the capacitor rises and rubber comes off.

The present invention has been proposed to solve the above-mentioned problems of the prior art. It is an object of the present invention to make it possible to further improve the withstand voltage characteristic and the overvoltage characteristic, and to further improve the life test. It is an object of the present invention to provide an electrolytic capacitor capable of preventing leakage of an electrolyte and removal of rubber when an abnormal voltage is applied.

[0010]

In order to solve the above-mentioned problems, the present inventors have made it possible to further improve the withstand voltage characteristics and the overvoltage characteristics, and to prevent the leakage of the electrolytic solution during the life test and the rubber when the abnormal voltage is applied. As a result of intensive studies on an electrolytic capacitor capable of preventing disconnection, the present invention has been completed.

That is, the electrolytic capacitor according to the present invention is a separator formed by applying a predetermined amount of PVA to electrolytic paper containing high-density electrolytic paper having a density of 0.6 to 0.9 g / cm ³ , There constitute a dense electrolyte paper 0.6~0.9g / cm ^3, an electrolytic paper density superimposed low density electrolytic paper of less than 0.6 g / cm ^3, Tokoro the low-density electrolytic paper side Through a separator to which a fixed amount of polyvinyl alcohol is adhered, a cathode foil and an anode foil are overlapped and wound to form a capacitor element, and the capacitor element is impregnated with an electrolytic solution containing boric acid, and put in a case. It was sealed and re-formed. In this case, as the sealing rubber, a partially crosslinked peroxide butyl rubber obtained by adding a peroxide as a crosslinking agent to a butyl rubber polymer composed of a copolymer of isobutylene, isoprene and divinylbenzene is used.

Further, when the electrolytic capacitor according to the present invention manufactured as described above was subjected to a high temperature life test and an overvoltage test, the withstand voltage characteristic and the overvoltage characteristic were further improved as compared with the conventional electrolytic capacitor. It was found that it was possible to prevent leakage of the electrolytic solution in the life test and to prevent the rubber from slipping when an abnormal voltage was applied. Hereinafter, the configuration of the present invention will be described in detail.

[1. Separator] As the electrolytic paper constituting the separator, nonwoven fabric, manila paper, kraft paper, cellulose paper, or the like is used, and glass or synthetic polymer fiber can also be used. The separator according to the present invention has a density of 0.6 as electrolytic paper as shown below.
Single sheet made of high-density electrolytic paper of 0.9 g / cm ^3, or density low density electrolysis of dense electrolyte sheet and density of less than 0.6 g / cm ³ of 0.6~0.9g / cm ³ A certain amount of PV is applied to these electrolytic papers using double paper
A is attached. The thickness of the electrolytic paper is 2
It is desirably 0 to 150 μm, preferably 20 to 90 μm. If the thickness of the electrolytic paper is smaller than this range, the withstand voltage characteristics and the overvoltage characteristics deteriorate, and if the thickness exceeds this range, the tan δ of the capacitor increases.

(PVA) Commercially available PVA can be used as the PVA to be attached to the electrolytic paper.
With a saponification degree of from 00 to 3500, a partially saponified material having a saponification degree of 75 mol% or more and 99.5 mol% or more can be used. When the degree of polymerization is smaller than this range, the effect is reduced, and when it exceeds this range, the coating property and the solubility of PVA in the electrolytic solution are reduced, and the characteristics are deteriorated.

The coating amount of PVA is 0.1 to 20 g.
/ M ² . If the coating amount of PVA is less than this range, the effect decreases, and if it exceeds this range, tan δ of the electrolytic capacitor increases. In addition, PV
As a method of attaching A, a method of dipping the separator in a PVA solution, or applying and spraying the PVA solution, followed by drying by heating, reduced pressure, or the like (coating) can be used.

(Separator using single-layer paper)
The first separator according to the present invention can be formed by applying a predetermined amount of PVA to electrolytic paper made of high density electrolytic paper of 6 to 0.9 g / cm ^3. It has been found that in an electrolytic capacitor using, the withstand voltage characteristic and the overvoltage characteristic can be improved.

(Separator using double paper) As described above, by using electrolytic paper having high density, the withstand voltage characteristic and the overvoltage characteristic of the electrolytic capacitor can be improved.
In order to prevent short-circuits due to burrs on the electrode foil, a certain distance is required between the anode foil and the cathode foil. However, when using a high-density electrolytic paper alone, if the thickness is increased to secure the interval between the electrode foils, the withstand voltage characteristics and the overvoltage characteristics are improved, but there is a limit to the reduction of the tan δ of the capacitor. .

Therefore, the present inventors have further studied and found that a high density electrolytic paper capable of improving withstand voltage characteristics and overvoltage characteristics and a low density electrolytic paper are overlapped to form a double paper. The second separator according to the present invention can be formed by applying a predetermined amount of PVA to the obtained electrolytic paper. In the electrolytic capacitor using the second separator, the withstand voltage characteristic and the overvoltage characteristic are also obtained. It was found that tan δ could be reduced, and that tan δ could be reduced.

That is, the density is 0.6 to 0.9 g / cm
³ of the dense electrolyte sheet, in which density is a double sheet by superposing the low-density electrolytic paper of less than 0.6 g / cm ^3, was coated with a predetermined amount of PVA in the low-density electrolytic paper side. The PVA may be applied on the high-density paper side or the low-density paper side,
Considering the ease of application of PVA, it is desirable to apply it on the low density paper side. In addition, the same effect was obtained when the PVA-coated side was wound so as to be in contact with the anode foil or when wound so as to be in contact with the cathode foil.

[2. Sealing Rubber] The inventors of the present invention have conducted various studies on sealing rubber in order to prevent electrolyte leakage in a life test and rubber removal when an abnormal voltage is applied. As a result, isobutylene, isoprene and divinyl were used as sealing rubber. It has been found that good results can be obtained when a peroxide partially crosslinked butyl rubber obtained by adding a peroxide as a crosslinking agent to a butyl rubber polymer composed of a copolymer with benzene is used. In addition, the addition amount of the peroxide in the peroxide partially crosslinked butyl rubber is desirably 1 to 20 parts.

As described above, it is possible to prevent the electrolyte from leaking from the insertion hole of the lead wire of the sealing rubber.
The peroxide partially cross-linked butyl rubber has a small elastic deterioration when subjected to a heat treatment, and further, when PVA coated paper is used as a separator, the electrolyte is gelled or in a gel state, and the fluidity of the electrolyte is reduced. Therefore, it is considered that these synergistic effects are caused. In addition, it is possible to prevent the rubber from slipping out when an abnormal voltage is applied, because the elastic degradation of the partially crosslinked peroxide butyl rubber is small and the state of gas generation when PVA coated paper is used as the separator. It is thought to be due to.

[3. Anode Foil] Also, an anode foil prepared as follows is used. The metal foil for an electrolytic capacitor is subjected to an electric current treatment in an acidic solution to generate pits on the surface of the metal foil, and thereafter, the diameter of the pits is increased by chemical dissolution in a high-temperature acidic solution to increase the surface area. Perform etching. Next, the etching foil is pre-treated, and a voltage is applied in an aqueous solution of an acid such as boric acid or phosphoric acid or a salt thereof until the voltage reaches a predetermined voltage. After that, a depolarization process is performed, and a voltage is applied again to form a dielectric oxide film on the metal foil. At this time, since an oxide film is formed on the surface of the metal foil enlarged by the etching, the oxide film is also formed inside the pit. Therefore, the diameter of the pit of the anode foil after forming the oxide film is smaller than the diameter of the pit of the metal foil after etching. In the present invention, it is desirable to use an anode foil having a pit diameter of 0.1 μm or more after forming an oxide film.

[4. Cathode foil] The cathode foil used in the present invention is:
Any metal foil such as aluminum used for ordinary electrolytic capacitors may be used.

[5. Electrolyte] As the electrolyte, an electrolytic solution for driving an electrolytic capacitor containing 0.1 to 40 parts of boric acid is used. If the boric acid content is less than this range, P
Since the gelation of VA does not proceed in a favorable state, the withstand voltage characteristics and the overvoltage characteristics are reduced. If the range exceeds this range, the tan δ of the capacitor increases. In this electrolyte,
Ethylene glycol may be contained. It is more preferable that ethylene glycol is contained in the electrolyte because PVA is easily dissolved and the effect of the present invention is enhanced.

It goes without saying that other solvents may be used in combination. Examples of the solvent include protic organic polar solvents such as monohydric alcohols (ethanol, propanol, butanol, pentanol, hexanol, cyclobutanol, cyclopentanol, cyclohexanol, benzyl alcohol, etc.), polyhydric alcohols and oxy alcohols. Alcohol compounds (propylene glycol, glycerin, methyl cellosolve, ethyl cellosolve, methoxypropylene glycol, dimethoxypropanol, etc.) and the like.

Examples of the aprotic organic polar solvent include amides (N-methylformamide, N, N─dimethylformamide, N─ethylformamide, N, N─).
Diethylformamide, N-methylacetamide, N,
N─dimethylacetamide, N─ethylacetamide,
N, N-diethylacetamide, hexamethylphosphoramide, lactones, cyclic amides (γ-butyrolactone, N-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, isobutylene carbonate, isobutylene carbonate, etc. ), Nitriles (such as acetonitrile), and oxides (such as dimethylsulfoxide).

As the solute contained in the electrolytic solution, ammonium salts, amine salts, quaternary ammonium salts and quaternary cyclic amidine compounds which are usually used in electrolytic solutions for driving electrolytic capacitors and have an anionic component of a conjugate base of an acid are used. Salts. Examples of the amine constituting the amine salt include primary amines (methylamine, ethylamine, propylamine, butylamine, ethylenediamine, etc.), secondary amines (dimethylamine, diethylamine, dipropylamine, methylethylamine, diphenylamine, etc.), tertiary amines ( Trimethylamine, triethylamine, tripropylamine, triphenylamine, 1,8-diazabicyclo (5,4,0) undecene7 and the like. As the quaternary ammonium constituting the quaternary ammonium salt, tetraalkylammonium (tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, methyltriethylammonium, dimethyldiethylammonium, etc.), pyridium (1-methylpyridium) 1,1-ethylpyridium, 1,3-diethylpyridium, etc.). Examples of the cation constituting the quaternary salt of the cyclic amidine compound include cations obtained by quaternizing the following compounds. That is, the imidazole monocyclic compound (1─
Methylimidazole, 1,2-dimethylimidazole,
1,4-dimethyl-2-ethylimidazole, imidazole homologues such as 1-phenylimidazole, oxyalkyl derivatives such as 1-methyl-2-oxymethylimidazole, 1-methyl-2-oxyethylimidazole,
Nitro and amino derivatives such as -methyl-4 (5) -nitroimidazole, 1,2-dimethyl-4 (5) -nitroimidazole, etc., benzimidazole (1-methylbenzimidazole, 1-methyl-2-benzylbenzimidazole) Etc.), a compound having a 2-imidazoline ring (1
{Methylimidazoline, 1,2-dimethylimidazoline, 1,2,4-trimethylimidazoline, 1,4-dimethyl-2-ethylimidazoline, 1-methyl-2-phenylimidazoline, etc.), and a compound having a tetrahydropyrimidine ring (1) -Methyl-1,4,5,6-tetrahydropyrimidine, 1,2-dimethyl-1,4,5,6-
Tetrahydropyrimidine, 1,8-diazabicyclo [5.4.0] undecene-7, 1,5-diazabicyclo [4.3.0] nonene, and the like. Examples of the anion component include conjugate bases of acids such as carboxylic acids, phenols, phosphoric acid, carbonic acid, and silicic acid.

[6. Manufacturing method of electrolytic capacitor]
The method for manufacturing the electrolytic capacitor of the present invention will be described. That is, a cathode foil, an anode foil, and a separator to which a predetermined amount of PVA is adhered are cut into prescribed dimensions, and lead wires are joined to the cathode foil and the anode foil. Then, a separator is interposed between the cathode foil and the anode foil and wound to form a capacitor element. Next, the capacitor element is impregnated with an electrolytic solution containing boric acid, placed in a case, sealed with a sealing material, and subjected to re-chemical formation by applying a direct current at a high temperature.

As the sealing material, a partially crosslinked peroxide butyl rubber obtained by adding a peroxide as a crosslinking agent to a butyl rubber polymer composed of a copolymer of isobutylene, isoprene and divinylbenzene is used. Further, in the electrolytic capacitor of the present invention, gelation by boric acid and PVA in the electrolytic solution partially progresses, and a gel electrolyte having good adhesion to the dielectric film is obtained, and the withstand voltage characteristics are improved. I think that the. Here, when the saponification degree of PVA is 90 mol% or more, the withstand voltage characteristics are further improved.

The behavior of this partial gelation is presumed as follows. By bringing the capacitor element according to the present invention into contact with the electrolytic solution, the electrolytic solution first impregnates the pits of the anode foil. After that, the impregnated electrolytic solution comes into contact with the PVA attached to the separator, and the gelation by boric acid and PVA in the electrolytic solution partially progresses, and the gel electrolyte having good adhesion to the dielectric film is formed. Is obtained.

When the diameter of the pits of the anode foil is 0.1 μm or more, the electrolyte and PVA easily penetrate into the pits, so that a good gel is formed inside the pits.
Thereby, it is considered that better characteristics can be obtained for both the capacitance and tan δ. In addition, the gel portion and the liquid electrolyte are in a mixed state, the viscosity of the electrolyte increases, and the gel electrolyte has good adhesiveness with the dielectric film, so that it is considered that the overvoltage characteristic is also improved. .

[0032]

The present invention will be described more specifically with reference to the following examples. In addition, the configuration requirements of the example, the comparative example, and the conventional example are as shown in Table 1 below.

[Table 1]

Example 1 PVA (Saponification degree: 98.5 m)
ol%, a polymerization degree of 200) was dissolved in an aqueous solution containing 10% of an aqueous solution of electrolytic paper (kraft paper, density 0.70) made of high-density electrolytic paper.
g / cm ³ , thickness 40 μm) and dried by heating to obtain a separator to which PVA is attached. The attached amount of PVA was 5 g / m ² . This separator is a cathode foil,
The pit formed on the surface was sandwiched and wound between anode foils having a diameter of 0.1 μm or more to form a capacitor element of 500 V to 50 μF. Also, ethylene glycol 88
, 3 parts of boric acid, and 9 parts of 1,6-decanedicarboxylic acid. Then, this electrolytic solution was impregnated into a capacitor element, placed in an aluminum case, sealed with rubber, and then subjected to 525 V for 2 hours at 85 ° C. to form an aluminum electrolytic capacitor. As the sealing rubber, a partially crosslinked peroxide butyl rubber obtained by adding 3 parts of a peroxide as a crosslinking agent to a butyl rubber polymer composed of a copolymer of isobutylene, isoprene and divinylbenzene was used.

Example 2 PVA (Saponification degree 98.5 m)
ol%, a polymerization degree of 200) dissolved in an electrolytic solution (kraft paper, high-density paper having a density of 0.85 g / cm ³ and a density of 0.1%). Low-density paper having a thickness of less than 6 g / cm ³ was adhered in a paper making process to a thickness of 60 μm) and dried by heating to obtain a separator to which PVA was attached. The attached amount of PVA was 5 g / m ² . This separator was sandwiched between a cathode foil and an anode foil having pits formed on the surface having a diameter of 0.1 μm or more, and wound to form a capacitor element of 500 V to 50 μF. In addition, an electrolytic solution containing 88 parts of ethylene glycol, 3 parts of boric acid, and 9 parts of 1,6-decanedicarboxylic acid was prepared. Then, this electrolytic solution was impregnated into a capacitor element, placed in an aluminum case, sealed with the same sealing rubber as in Example 1, and then heated at 85 ° C. for 2 hours.
525 V was applied for a time to re-form to form an aluminum electrolytic capacitor.

Comparative Example 1 PVA (degree of saponification 98.5 m)
ol%, the degree of polymerization 200) was applied to the same electrolytic paper as used in Example 2 and dried by heating.
A separator to which PVA was attached was obtained. The attached amount of PVA was 5 g / m ² . This separator was sandwiched between a cathode foil and an anode foil having pits formed on the surface having a diameter of 0.1 μm or more, and wound to form a capacitor element of 500 V to 50 μF. In addition, ethylene glycol 91
And 9 parts of ammonium 1,6-decanedicarboxylate. Then, this electrolytic solution was impregnated into a capacitor element, placed in an aluminum case, sealed with the same sealing rubber as in Example 1, and then subjected to 525 V for 2 hours at 85 ° C. to be re-formed to form aluminum. An electrolytic capacitor was made.

Comparative Example 2 PVA (degree of saponification 98.5 m)
ol%, the degree of polymerization 200) was applied to the same electrolytic paper as used in Example 2 and dried by heating.
A separator to which PVA was attached was obtained. The attached amount of PVA was 5 g / m ² . This separator was sandwiched between a cathode foil and an anode foil having pits formed on the surface having a diameter of 0.1 μm or more, and wound to form a capacitor element of 500 V to 50 μF. Also, ethylene glycol 88
, 3 parts of boric acid and 9 parts of ammonium 1,6-decanedicarboxylate were prepared. Then, this electrolytic solution was impregnated into a capacitor element, placed in an aluminum case, sealed with rubber, and then subjected to 525 V for 2 hours at 85 ° C. to form an aluminum electrolytic capacitor. As the sealing rubber, a quinoid crosslinked butyl rubber obtained by adding 3 parts of a quinoid as a crosslinker to a butyl rubber polymer composed of a copolymer of isobutylene and isoprene was used.

Comparative Example 3 Kraft paper (density 0.75 g)
/ Cm ³ , and a thickness of 70 μm) were sandwiched between a cathode foil and an anode foil having pits having a diameter of 0.1 μm or more formed on the surface thereof, and wound to form a capacitor element of 500 V-50 μF. 85 parts of ethylene glycol, 3 parts of boric acid, 9 parts of 1,6-decanedicarboxylic acid,
PVA (degree of saponification 98.5 mol%, degree of polymerization 200) 3
A part of the electrolyte was prepared. Then, this electrolytic solution was impregnated into a capacitor element, placed in an aluminum case, sealed with the same sealing rubber as in Comparative Example 2, and then heated to 85 ° C.
Then, 525 V was applied for 2 hours to re-form to form an aluminum electrolytic capacitor.

[High temperature load test] A voltage of 500 V was applied to these aluminum electrolytic capacitors,
A time high temperature load test was performed. Table 2 shows the test results. Assuming that the number of tests was 10, the characteristics were indicated by the average value of the 10 capacitors, and the number of leaks was indicated in the table.

[Table 2]

As is clear from Table 2, in both Examples 1 and 2, good results were obtained in both the initial characteristics and the high-temperature load test, and a high-voltage electrolytic capacitor rated at 500 V was realized. On the other hand, in Comparative Example 1 in which the same separator as in Example 2 was used and the same sealing rubber was used, in Comparative Example 1 in which the electrolytic solution containing no boric acid was impregnated, short-circuit occurred during re-chemical formation. The reason is that, in Comparative Example 1, since boric acid was not added to the electrolyte solution, the dissolution of PVA applied to the separator did not proceed, and the effect of PVA was reduced, and a withstand voltage of a rated 500 V could not be obtained. It is considered to be.

In Comparative Example 3 in which kraft paper not coated with PVA was used as the separator and quinoid cross-linked butyl rubber was used as the sealing rubber, PVA was used as the electrolyte.
Is added to increase the withstand voltage of the electrolyte.
Electrical properties are maintained for up to 4000 hours at 5 ° C,
Since the conductivity of the electrolytic solution is low, tan δ increases. Furthermore, in Comparative Example 3, the leakage of the internal electrolytic solution occurred in five out of ten through the insertion hole of the sealing rubber through which the external electrode terminal was inserted, satisfying the high-temperature life characteristics of 105 ° C. and 4000 hours. Turned out not to.

[Overvoltage Test] Next, 600 V was applied to the aluminum electrolytic capacitors of Examples 1, 2 and Comparative Examples 2 and 3, and an overvoltage test was performed at 105 ° C. for 100 hours. Table 3 shows the test results. Assuming that the number of tests was 20, the number of occurrences of short circuits is shown in the table.

[Table 3]

As is clear from Table 3, in Examples 1 and 2, in the overvoltage test at 600 V for 100 hours, there was no occurrence of short-circuit and rubber loss, and 6
It was found to have an overvoltage characteristic of 00V.

On the other hand, in Comparative Example 2, which showed good results in the high-temperature load test, 600 V-100
In the time overvoltage test, although 15 short-circuits did not occur, rubber loss occurred in 15 out of 20 rubbers. The reason is considered as follows. That is, in Comparative Example 2, although the same separator as in Example 2 was used and the same electrolytic solution was used, but the quinoid crosslinked butyl rubber was used, when an overvoltage of 600 V was applied,
It is considered that the leakage current increased, gas was generated, and the pressure inside the capacitor was increased. At the same time, heat was generated and the elasticity of the rubber was reduced, so that rubber loss occurred.

In Comparative Example 3 using kraft paper to which PVA was not applied as a separator,
Although the electrical characteristics were maintained in the high-temperature load test of V, 18 out of 20 short-circuits occurred in the 600 V overvoltage test, and it was found that there was no 600 V overvoltage characteristic.

As described above, the electrolytic capacitors according to the first and second embodiments according to the present invention satisfy not only the rated voltage of 500 V but also the overvoltage characteristic, and furthermore, the electrolyte leakage and the abnormal voltage in the life test. It has been clarified that rubber release during application can be prevented.

[0046]

As described above, according to the present invention, the withstand voltage characteristic and the overvoltage characteristic can be further improved, and furthermore, the leakage of the electrolyte in the life test and the rubber detachment at the time of abnormal voltage application can be prevented. An electrolytic capacitor that can be provided.

Claims (8)

[Claims] 1. A cathode foil in which an electrode lead-out terminal is joined via a separator formed by attaching a predetermined amount of polyvinyl alcohol to electrolytic paper containing high-density electrolytic paper having a density of 0.6 to 0.9 g / cm ^3. And an anode foil are overlapped and wound to form a capacitor element, and the capacitor element is impregnated with an electrolytic solution containing boric acid, and as a sealing rubber, a butyl rubber polymer composed of a copolymer of isobutylene, isoprene, and divinylbenzene. Wherein a partially crosslinked peroxide butyl rubber to which a peroxide is added as a crosslinking agent is used. A dense electrolyte paper wherein density 0.6~0.9g / cm ^3, densities constitutes the electrolytic paper by superimposing a low-density electrolytic paper of less than 0.6 g / cm ^3, the low A cathode foil and an anode foil to which an electrode lead terminal is joined are laminated and wound through a separator formed by attaching a predetermined amount of polyvinyl alcohol to the density electrolytic paper side to form a capacitor element, and boric acid is added to the capacitor element. And impregnated with an electrolyte solution containing, as a sealing rubber, a butyl rubber polymer composed of a copolymer of isobutylene, isoprene, and divinylbenzene, and a peroxide partially cross-linked butyl rubber obtained by adding a peroxide as a cross-linking agent. Characteristic electrolytic capacitor. 3. The electrolytic capacitor according to claim 1, wherein the peroxide is added in the peroxide partially crosslinked butyl rubber in an amount of 1 to 20 parts. 4. The electrolytic capacitor according to claim 1, wherein the amount of polyvinyl alcohol attached to the electrolytic paper is 0.1 to 20 g / m ² . 5. The electrolytic capacitor according to claim 1, wherein the degree of polymerization of the polyvinyl alcohol attached to the electrolytic paper is 200 to 3,500. 6. The thickness of the electrolytic paper is 20 to 150 μm.
The electrolytic capacitor according to claim 1 or 2, wherein 7. The electrolyte according to claim 1, wherein the content of boric acid is 0.1 part or more.
The electrolytic capacitor according to claim 1 or 2, wherein the number is 40 parts. 8. The pit formed on the surface of the anode foil has a diameter of 0.1 μm or more.
Or the electrolytic capacitor according to claim 2.