JP3254983B2 - Electrolyte 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 an electrolytic solution for an electrolytic capacitor.

[0002]

2. Description of the Related Art An electrolytic capacitor such as an aluminum electrolytic capacitor generally has a structure in which a capacitor element is impregnated with an electrolytic solution. This electrolytic solution has a composition in which, for example, ethylene glycol is used as a solvent and ammonium borate is used as a solute. With this composition, the spark generation voltage is high, but the specific resistance is large and the loss of the electrolytic capacitor is large. Accordingly, for the purpose of lowering the specific resistance without lowering the spark generation voltage, Japanese Patent Publication No. 62-800
As described in No. 4, there is also an electrolytic solution having a composition in which adipic acid or a salt thereof and ammonium hypophosphite are dissolved in ethylene glycol.

[0003]

However, an electrolytic solution in which adipic acid or the like is dissolved is liable to undergo esterification at a high temperature, and therefore has a drawback that the specific resistance increases. Therefore, the loss of the electrolytic capacitor increases at a high temperature.

An object of the present invention is to provide an electrolytic solution for an electrolytic capacitor which can improve the above-mentioned drawbacks, can effectively reduce the specific resistance, and can improve the tan δ characteristics and the like of the electrolytic capacitor.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides 2,2,3-trimethylglutaric acid,
2,2,4-trimethylglutaric acid, 2,3,4-tri
Methyl glutaric acid or one or more of their salts
Disclosed is an electrolytic solution for an electrolytic capacitor characterized by being dissolved by 8% or more .

[0006] 2,2,3-trimethylglutaric acid and 2,2
2,4-trimethylglutaric acid, 2,3,4-trimethyl
The structural formulas of luglutaric acid are as shown in Chemical formulas 1 to 3 , respectively.

[0007]

Embedded image

[0008]

Embedded image

[0009]

Embedded image

[0010]

[Action] 2,2,3-trimethylglutaric acid, 2,2,2
4-trimethylglutaric acid, 2,3,4-trimethylg
Rutaric acid and salts thereof are dicarboxylic acids having a side chain, and are more excellent in chemical conversion and solubility than adipic acid which is a linear dicarboxylic acid. Therefore, the spark generation voltage of the electrolyte can be increased, and the specific resistance can be reduced. Also,
This trimethylglutaric acid or the like has a methyl group at the α-position of the main chain, and is less likely to cause an esterification reaction with glycols such as ethylene glycol due to the steric hindrance. Therefore, the electrolyte exhibits a stable specific resistance even at a high temperature. And the life of the electrolytic capacitor can be extended.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.
Glycols use ethylene glycol. Then, this ethylene glycol alone or γ-butyrolactone is mixed to form a solvent. Also, in this solvent,
Ammonium 2,3-trimethylglutarate and 2,2
Ammonium 4-trimethylglutarate, 2,3,4-
Dissolve ammonium trimethylglutarate .

Incidentally, ammonium 2,2,3-trimethylglutarate, ammonium 2,2,4-trimethylglutarate, ammonium 2,3,3-trimethylglutarate, ammonium 2,3,4-trimethylglutarate, adipine Table 1 shows the solubility of ammonium acid in ethylene glycol.

[0013]

[Table 1]

As apparent from Table 1, 2,2,3-
The solubility of trimethylglutarate such as ammonium trimethylglutarate is 47-54%, while that of ammonium adipate is 14.5%. That is, the former dissolves in ethylene glycol at least three times the latter.

Next, specific resistance at a temperature of 30 ° C. and spark generation voltage at a temperature of 85 ° C. were measured for Examples , Comparative Examples and conventional electrolytes having the compositions shown in Table 2. did.

[0016]

[Table 2]

As apparent from Table 2, in Examples 1 to 3 , the specific resistance is 262 to 283 Ω · cm, and the spark generation voltage is 430 to 440 V. Further, in Conventional Examples 1 and 2, the specific resistance is 350 to 370 Ω · cm, and the spark generation voltage is 400 to 430 V. That is, the first to third examples have a specific resistance of about 7 compared to the first and second examples.
0.8 to 80.1 %, and the spark generation voltage is up to 1.
It is one time higher.

Further, each of the electrolytes of Examples 1 to 3, Comparative Example and Conventional Example 1 was placed in a heat-resistant bottle,
The sample was left in an atmosphere at a temperature of 110 ° C., and the specific resistance and the esterification ratio were measured. The measurement temperature of the specific resistance is 30 ° C.
Table 3 shows the measurement results.

[0019]

[Table 3]

As is clear from Table 3, after leaving for 1,000 hours, Examples 1 to 3 showed a specific resistance of 478 to
544 Ω · cm, and the esterification ratio is 36 to 64 %. Further, in Conventional Example 1, the specific resistance is 1,855 Ω · cm, and the esterification ratio is 98%. That is, in Examples 1 to 3 , the specific resistance is reduced to about 29.3 % or less and the esterification rate is reduced to about 65.3% or less, as compared with Conventional Example 1.

Further, the initial characteristics and the characteristics after the high-temperature load test were measured for a constant 250 V, 1,000 μF aluminum electrolytic capacitor impregnated with an electrolyte having the composition shown in Table 2. In the high temperature load test, a rated voltage of 250 V is continuously applied,
The test was carried out in an atmosphere at a temperature of 110 ° C. for 1,000 to 2,000 hours. The number of samples is 20 each. The measured values are shown in Table 4 as average values.

[0022]

[Table 4]

As is clear from Table 4, after leaving for 2,000 hours, Examples 1 to 3 showed tan δ of 4.0 to 4.0.
4.3 % and a leakage current of 5 μA. And Conventional Example 1
Has a tan δ of 13.8% and a leakage current of 9 μA. That is, Example 1 to Example 3 were compared with Conventional Example 1
The tan δ is less than about 32.1 % and the leakage current is 5/9.

[0024]

As described above, according to the present invention ,
3-trimethylglutaric acid, 2,2,4-trimethylg
Rutaric acid, 2,3,4-trimethylglutaric acid and the like
Dissolves 8% or more of its salt, it is excellent in solubility, etc., it can lower the specific resistance, has stable specific resistance even at high temperature, can improve the tan δ characteristics of electrolytic capacitors, etc., and improves its life The resulting electrolytic solution for an electrolytic capacitor is obtained.

Claims (1)

(57) [Claims] 1. An electrolytic solution for an electrolytic capacitor , comprising:
2,3-trimethylglutaric acid, 2,2,4-trimethyl
Luglutaric acid, 2,3,4-trimethylglutaric acid or
Is an electrolytic solution for electrolytic capacitors, characterized in that at least one of these salts is dissolved in 8% or more .