JPH07211590A - Electrolytic solution for electrolytic capacitor - Google Patents

Abstract

PURPOSE:To obtain an electrolytic solution whose resistivity is lowered, which improves the characteristic of an electrolytic capacitor and whose life is made long by containing at least one kind out of cholic acid, deoxycholic acid, dehydrocholic acid and their salt. CONSTITUTION:The electrolytic solution contains at least one kind out of cholic acid, deoxycholic acid, dehydrocholic acid and their salt. Since the cholic acid, the deoxycholic acid, the dehydrocholic acid or their salt has a hydroxyl group or a carbonyl group inside molecules, it can be dissolved easily by polyhydric alcohols which are used as a solvent. As a result, the resistivity of the electrolytic solution can be lowered, and a spark starting voltage can be raised. In addition, since a substance such as the cholic acid or the like has a steric structure, it hardly forms a complex with an electrode foil. As a result, it is possible to restrain the capacitance of an electrolytic capacitor from being reduced. In addition, since the substance such as the cholic acid or the like hardly causes an esterification reaction with the polyhydric alcohol, it is possible to restrain the electrolytic capacitor from being degraded in a high-temperature atmosphere.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, an electrolytic solution for medium- and high-voltage electrolytic capacitors uses, for example, a component obtained by dissolving boric acid or ammonium borate in a polyhydric alcohol such as ethylene glycol. There is also an electrolytic solution using an organic dibasic acid such as azelaic acid or sebacic acid as a solute in order to lower the impedance of the electrolytic capacitor and prolong the life thereof.

[0003]

However, the former electrolytic solution has a drawback that it has a high specific resistance. Further, ethylene glycol and the like and boric acid undergo an esterification reaction to produce a large amount of water,
This water has a drawback that it deteriorates the oxide film of the electrode foil, which increases the leakage current (hereinafter referred to as LC) of the electrolytic capacitor. Due to this increase in LC, a large amount of gas is generated and the explosion-proof valve operates, so that the life of the electrolytic capacitor is shortened.

In addition, the latter electrolytic solution has a drawback that when the electrolytic capacitor is subjected to a high temperature load test, the capacitance is greatly decreased and tan δ is increased, and therefore the life is short.

An object of the present invention is to provide an electrolytic solution for an electrolytic capacitor, in which the above drawbacks are improved, the specific resistance is low, the characteristics of the electrolytic capacitor can be improved, and the service life can be extended.

[0006]

In order to achieve the above object, the present invention provides a cholic acid, a deoxycholic acid, a dehydrocholic acid, or a cholic acid, a deoxycholic acid or a dehydrocholic acid in an electrolytic solution for an electrolytic capacitor containing a polyhydric alcohol as a main solvent. The present invention provides an electrolytic solution for an electrolytic capacitor, which contains at least one kind of the salt.

Polyhydric alcohols include ethylene glycol, diethylene glycol, propylene glycol, 1,4
-Butanediol, trimethylethylene glycol, pentaglycerol, trimethylene glycol, isobutylene glycol (2-methyl-1,2-propanediol) and the like are used.

The cholic acid, deoxycholic acid, dehydrocholic acid or salts thereof may be contained individually or in combination of two or more kinds. As a combination, there are two or more kinds of arbitrary acids such as cholic acid, two or more kinds of arbitrary salts such as ammonium cholate, or one or more kinds of acids such as cholic acid. And any one or more salts such as ammonium cholate.

The addition amount of cholic acid, deoxycholic acid, dehydrocholic acid or their salts is preferably in the range of 1 to 30 wt%. That is, the addition amount is 1 wt%
If it is less, the effect of lowering the specific resistance and improving the life of the electrolytic capacitor is low. On the other hand, if it is more than 30 wt%, the spark generation voltage is lowered and the low temperature characteristics of the electrolytic capacitor are apt to be deteriorated.

[0010]

Since cholic acid, deoxycholic acid, dehydrocholic acid or salts thereof have a hydroxyl group or a carbonyl group in the molecule, they are easily dissolved in polyhydric alcohols used as a solvent. Therefore, the specific resistance of the electrolytic solution can be reduced and the spark generation voltage can be increased.

Moreover, since substances such as cholic acid have a three-dimensional structure, it is difficult to form a complex with the electrode foil. Therefore, it is possible to suppress the capacity of the electrolytic capacitor from decreasing.

Further, substances such as cholic acid have the property that they hardly cause an esterification reaction with polyhydric alcohols due to the effect of steric hindrance. Therefore, the amount of water produced by esterification in the electrolytic solution can be reduced. This can prevent the electrolytic capacitor from deteriorating in a high temperature atmosphere.

[0013]

EXAMPLES The present invention will be described below based on examples.
First, a polyhydric alcohol made of ethylene glycol is used as a solvent. Next, as the solute, cholic acid, dehydrocholic acid, ammonium cholic acid, ammonium deoxycholic acid, ammonium dehydrocholic acid or a combination thereof is used. Further, as the additive, ammonium borate, mannite, aqueous ammonia, or a combination thereof is used.

Next, the specific resistance and the spark generation voltage were measured for the electrolytic solutions of Examples and Conventional Examples, and the results are shown in Table 1. In this case, the measurement temperature is such that the specific resistance is 30 ° C. and the spark generation voltage is 85 ° C.

[0015]

[Table 1]

As is apparent from Table 1, the specific resistances of Examples 1 to 6 are 490 to 600 Ω · cm, and those of Conventional Example 1 to Conventional Example 3 are 650 to 1,200 Ω · cm, and the former is the latter. The size is about 41 to 92% of that of the above. The spark generation voltage is 450 to 4 in the first to sixth embodiments.
60V, Conventional Example 1 to Conventional Example 3 are 430 to 460V, and the former is higher than the latter as a whole.

Further, initial characteristics and characteristics after a high temperature load test were measured for aluminum electrolytic capacitors having a rating of 400 V and 330 μF, which were impregnated with the electrolytic solution of the components shown in Table 1. The conditions for the high temperature load test are an applied voltage of 400 V, an ambient temperature of 105 ° C. and a standing time of 2000 h. The number of samples is 20 each. The measurement results are shown in Table 2.

[0018]

[Table 2]

As is clear from Table 2, regarding the initial characteristics, Nos. 1 to N impregnated with the electrolytic solutions of Examples 1 to 6 were used.
The electrolytic capacitor of o6 is tan δ 0.051-0.06
0, LC 40-45 μA. And the electrolytic capacitors No. 7 to No. 9 impregnated with the electrolytic solutions of Conventional Example 1 to Conventional Example 3 have tan δ 0.065 to 0.089 and LC 50 to 7 respectively.
It became 8 μA. That is, in the former electrolytic capacitor, tan δ is reduced to about 57 to 92% and LC is reduced to about 51 to 90%, respectively, as compared with the latter.

After the high temperature load test, No1 to No6
The electrolytic capacitor has a capacity change rate of -0.6 to -0.9%,
tan δ 0.066 to 0.075, LC 10 to 13 μA, and the number of samples with the explosion-proof valve activated became 0. And No8 ~
The No. 9 electrolytic capacitor has a capacity change rate of −3.9 to −.
4.7%, tan δ 0.098 to 0.101, LC22 to
In 23, the number of samples operated by the explosion-proof valve was 3 to 8. Therefore,
The former has a capacity change rate of about 13 to 23 compared to the latter.
%, Tan δ is about 65 to 77%, LC is about 43 to 59.
%, Respectively. In addition, in the No. 7 electrolytic capacitor, all explosion-proof valves were activated.

[0021]

As described above, according to the present invention, since cholic acid, deoxycholic acid, dehydrocholic acid or salts thereof are contained, the specific resistance can be reduced and the spark generation voltage can be increased. It is possible to obtain an electrolytic solution for an electrolytic capacitor which can reduce tan δ and LC of the electrolytic capacitor and can prolong its life.

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] February 4, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

[0015]

[Table 1]

Claims (1)

[Claims] 1. An electrolytic capacitor for electrolytic capacitors containing polyhydric alcohol as a main solvent, which contains at least one of cholic acid, deoxycholic acid, dehydrocholic acid or salts thereof. Electrolyte.