JPH06120085A - Electrolytic solution for electrolytic capacitor - Google Patents

Abstract

PURPOSE:To enable a electrolytic capacitor to be enhanced in sparking voltage, elongated in service life at high temperatures, and enhanced in reliability by a method wherein at least either 3, 6-endomethylene-DELTA<4>-tetrahydrophthalic acid or its salt is dissolved into solvent. CONSTITUTION:At least either 3,6-endomethylene-DELTA<4>-tetrahydrophthalic acid or its salt is dissolved into electrolytic capacitor electrolytic solution whose main solvent is polyhydric alcohol. By this setup, an electrolytic capacitor can be increased in sparking voltage and lessened in resistivity, tandelta, and leakage current. Even if a high voltage is applied to an electrolytic capacitor in an atmosphere of high temperature, a capacitor case is prevented from expanding or a safety valve is restrained from being actuated, and the capacitor can be set stable in characteristics such as capacity change, tandelta, leakage current, and others to operate stably.

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 Among electrolytic solutions, those used for medium and high voltage electrolytic capacitors are required to have a high spark generation voltage. For this reason, the conventional medium- and high-voltage electrolytes generally have a composition in which a polyhydric alcohol such as ethylene glycol is used as a solvent and boric acid or ammonium borate is dissolved therein. However, this electrolytic solution causes an esterification reaction between ethylene glycol or the like and boric acid or the like to generate a large amount of water.
Therefore, the electrolytic capacitor impregnated with this electrolytic solution is 100
When it is used at a temperature of ℃ or more, the vapor pressure becomes high, and it becomes easy to react with the electrode such as aluminum, and hydrogen gas is generated. Then, when the vapor pressure rises and hydrogen gas is generated to reach a predetermined pressure, the safety valve of the electrolytic capacitor operates, there is a problem that the electrolytic solution leaks and the other electronic parts incorporated in the device are damaged.

In order to improve this point, conventionally, butyloctanedioic acid or a salt thereof is used as a solute in an electrolytic solution (Japanese Patent Publication No. 60-13293), or 5,6-decanedicarboxylic acid or a salt thereof is used as a solute. It has been published (Japanese Patent Publication No. 63-15738). These solutes are dibasic acids and the like, and the esterification reaction becomes very slow. Therefore, less water is generated in the electrified liquid. And it can suppress that the internal pressure of an electrolytic capacitor rises at high temperature.

[0004]

However, the electrolytic solution containing such a dibasic acid as a solute has a low spark generation voltage, so that the life of the electrolytic capacitor does not extend so much at high temperature and reliability is improved. There is a difficult drawback.

An object of the present invention is to provide an electrolytic solution for an electrolytic capacitor, which is capable of improving the above-mentioned drawbacks, increasing the spark generation voltage, prolonging the life of the electrolytic capacitor at high temperatures, and improving its reliability. Is.

[0006]

In order to achieve the above-mentioned object, the present invention provides a solvent containing a polyhydric alcohol as a main component with 3,6-endomethylene-Δ ⁴ -tetrahydrophthalic acid or a salt thereof. The present invention provides an electrolytic solution for an electrolytic capacitor, characterized in that at least one of them is dissolved.

Ethylene glycol or the like is used as the polyhydric alcohol.

The structural formula of 3,6-endomethylene-Δ ⁴ -tetrahydrophthalic acid (hereinafter abbreviated as compound A) is as follows.

[0009]

[Chemical 1]

[0010]

EXAMPLES The present invention will be described below based on examples.
Ethylene glycol or the like is used as the solvent. Then, the compound A and its salt are dissolved in this solvent. As a solute,
In addition to the compound A, butyloctanedioic acid or a salt thereof, azelaic acid or a salt thereof, sebacic acid or a salt thereof, P-nitrobenzoic acid or a salt thereof may be used together.

Next, the compositions of the example and the conventional example were changed, and the specific resistance at a temperature of 30 ° C. and the spark voltage at a temperature of 85 ° C. were measured. In addition, together, these electrolytic solutions were impregnated into an element of an aluminum electrolytic capacitor having an aluminum electrode formation voltage of 680 V and a capacity of 100 μF, and the withstand voltage of this element was measured. The measurement results are shown in Table 1.

[0013]

[Table 1]

As is clear from Table 1, according to Examples 1 to 5, the specific resistance was reduced to about 22 to 94% and the spark voltage was about to be lower than those of Conventional Example 1 and Conventional Example 2. 1.1-
1.12 times higher. In addition, the element breakdown voltage of the former is about 1.06 to 1.09 times that of the conventional example 2.

The initial characteristics and the characteristics after the high temperature load test were measured for the aluminum electrolytic capacitors rated at 400 V and 270 μF impregnated with the electrolytic solution shown in Table 1, and shown in Table 2. In the high temperature load test, applying the rated voltage to the sample,
It is performed by leaving it in an atmosphere at a temperature of 125 ° C. for 2000 hours.
The number of samples is 10, respectively. The measured value shall be the average value.

[0016]

[Table 2]

As is clear from Table 2, No. 1 to 5 using the electrolytic solutions of Examples 1 to 5 in the initial characteristics
In comparison with Nos. 6 and 7 using Conventional Example 1 and Conventional Example 2, tan δ is reduced to about 30.8% to 93.3%, and leakage current is about 17.1% to 84.6. It has fallen to%. Even when the high temperature load test was performed, No. 1 to 5 did not cause defects such as the case swelling and the safety valve operating. In contrast, Nos. 6 and 7 had 10 and 3 safety valves, respectively. In addition, No. 1 to 5 are compared to No. 7,
The capacity change rate is about 9.6 to 16.2% and tan δ is about 4
8.2-57.1% and leakage current about 40-50%
To each of them.

[0018]

As described above, according to the present invention, compound A
The high spark generation voltage and low specific resistance can reduce the tan δ and leakage current of the electrolytic capacitor, and the case swells even when a high voltage is applied in a high temperature atmosphere. It is possible to obtain an electrolytic solution for an electrolytic capacitor which can suppress the operation of the safety valve and can operate with stable characteristics such as capacity change, tan δ, and leakage current.

Claims (1)

[Claims] 1. An electrolytic solution for an electrolytic capacitor containing a polyhydric alcohol as a main solvent, wherein 3,6-endmethylene-
An electrolytic solution for an electrolytic capacitor, wherein at least one of Δ ⁴ -tetrahydrophthalic acid or a salt thereof is dissolved.