JPH06290996A - Electrolyte for electrolytic capacitor - Google Patents

Abstract

PURPOSE:To provide a liquid electrolyte for high- and medium-voltage capacitors, which prevents the increase in pressure within capacitors at high temperature and increases the flash-over voltage without increasing its resistivity. CONSTITUTION:A liquid electrolyte comprises a solvent composed mainly of ethylene glycol, and a solute containing a salt of octanedicarboxylic acid, which may or may not have an alkyl on its side chain. The electrolyte additionally comprises silicic acid anhidride and a nitro compound.

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 driving an electrolytic capacitor, and more particularly to improving the characteristics of a medium- and high-voltage electrolytic capacitor.

[0002]

2. Description of the Related Art Generally, an electrolytic solution for driving an electrolytic capacitor has been used for medium and high pressure, in which ethylene glycol is used as a solvent and boric acid or ammonium borate is a solute. However, since this kind of driving electrolyte is water generated by the esterification reaction between ethylene glycol and boric acid, when used in an electrolytic capacitor having a temperature above 100 ° C, the water in the driving electrolyte becomes water vapor, There is a problem in that the package internal pressure of the electrolytic capacitor rises and destroys it.

Therefore, in order to solve such a problem, it has been attempted to use a salt of an organic carboxylic acid such as azelaic acid, octanedicarboxylic acid or butyloctanedioic acid for ethylene glycol.

However, although the generation of water due to esterification can be suppressed in the driving electrolytic solution using these salts, it has a drawback that low specific resistance cannot be obtained due to its low solubility and the chemical conversion is poor. Was there.

Further, solutes having an alkyl group in the side chain of an organic carboxylic acid have been devised in order to increase the solubility, but although the specific resistance is lowered, the spark generation voltage is also lowered, which is a problem for medium and high pressure applications. was there.

[0006]

As described above, the driving electrolyte using boric acid or ammonium borate as a solute in ethylene glycol has a problem in chemical stability at a high temperature exceeding 100 ° C. , Azelaic acid,
A driving electrolyte solution using a salt of an organic carboxylic acid such as octanedicarboxylic acid or butyloctanedioic acid or a salt of an organic carboxylic acid in the side chain has poor chemical conversion and has a drawback that the spark voltage at high temperature is not sufficient. , Had a problem to be solved practically.

The present invention has been made to solve the above problems, suppresses an increase in the internal pressure of an electrolytic capacitor at high temperatures, and increases the spark generation voltage without increasing the specific resistance, and It is an object of the present invention to provide an electrolytic solution for driving an electrolytic capacitor, which is suitable for medium and high voltage and has improved chemical conversion.

[0008]

The electrolytic solution for driving an electrolytic capacitor according to the present invention is prepared by dissolving octanedicarboxylic acid or a salt of octanedicarboxylic acid having an alkyl group in its side chain as a solute in a solvent mainly composed of ethylene glycol. ,
Moreover, it is characterized in that silicic acid anhydride and a nitro compound are added.

The salt is characterized in that it is an ammonium salt, a secondary amine salt, a tertiary amine salt or a quaternary ammonium salt.

Further, the side chain alkyl group is a methyl group or an ethyl group.

The nitro compound is para-nitrophenol or para-nitrobenzoic acid.

[0012]

According to the electrolytic capacitor driving electrolytic solution configured as described above, the solubility is increased by adding an alkyl group to the side chain of octanedicarboxylic acid, and the specific resistance is increased by the presence of silicic acid anhydride and a nitro compound. Without raising
It greatly increases the spark voltage, improves the chemical conversion, and suppresses the generation of hydrogen gas.

[0013]

EXAMPLES Examples of the present invention will be described below. That is, the driving electrolytic solution according to the present invention, in a solvent mainly composed of ethylene glycol, octanedicarboxylic acid or a salt of octanedicarboxylic acid having an alkyl group in the side chain as a solute, and silicic anhydride and a nitro compound. The octanedicarboxylic acid having an alkyl group in the side chain is 1-methyl-1,8-octanedicarboxylic acid, 1-ethyl-1,8-octanedicarboxylic acid, 2-methyl-1. , 8-octanedicarboxylic acid, 2-
Ethyl-1,8-octanedicarboxylic acid, 3-methyl-
1,8-octanedicarboxylic acid, 3-ethyl-1,8-
Octanedicarboxylic acid, 4-methyl-1,8-octanedicarboxylic acid, and 4-ethyl-1,8-octanedicarboxylic acid. In this case, when the side chain alkyl group becomes a propyl group or a butyl group which is an ethyl group or more, The side chain is preferably a methyl group or an ethyl group because the solubility decreases.

The above-mentioned salts include ammonium salts, secondary amine salts, tertiary amine salts and quaternary ammonium salts, and specific examples of the secondary amine salts include dimethylamine salt and diethylamine salt. Specific examples of the tertiary amine salt include trimethylamine salt and triethylamine salt, and specific examples of the quaternary ammonium salt include tetramethylammonium salt and tetraethylammonium salt. Silicic anhydride is used to increase the spark voltage and improve the chemical conversion, and its concentration is 0.1
10% by weight is desirable. The nitro compound is para-nitrophenol or para-nitrobenzoic acid, which is used to oxidize hydrogen and suppress gas generation, and preferably 0.1 to 5% by weight.

According to the driving electrolyte solution constructed as described above, the solubility as a solute is increased by adding octanedicarboxylic acid or a salt of octanedicarboxylic acid having an alkyl group in the side chain as a solute. The presence of silicic acid anhydride and nitro compounds greatly contributes to the increase of spark generation voltage, the improvement of chemical conversion, and the suppression of hydrogen gas generation without increasing the specific resistance, and electrolytic capacitors using these driving electrolytes Also, it has an excellent effect that it is suitable for medium and high voltage and at the same time, it can suppress an increase in internal pressure of the electrolytic capacitor at high temperature.

The characteristic comparison between the present invention and the conventional example will be described below based on specific examples. First, Table 1 shows the composition configurations of Examples 1 to 9 of the driving electrolyte solution according to the present invention and Conventional Examples 1 to 3 of the driving electrolyte solution according to the related art, the specific resistance at 25 ° C., and the spark generation voltage. Indicates.

As is apparent from Table 1, the spark generation voltage of the conventional examples 1 and 2 is low, and the spark generation voltage of the conventional example 3 is low, but the spark generation voltage is low. In the example, it can be seen that a high spark generation voltage can be obtained without increasing the specific resistance.

Next, the initial values and high temperature load test (105 ° C.) of aluminum electrolytic capacitors manufactured using the conventional electrolytic solutions 1 to 3 shown in Table 1 and the driving electrolytic solutions of Examples 1 to 9 were performed.
As a result of comparing the characteristics after 1000 hours, the results are shown in Tables 2 and 3.

The rating is 400 in both the embodiment and the conventional example.
V-150 μF.

[0020]

[Table 1]

[0021]

[0022]

[0023]

[Table 2]

[0024]

[Table 3]

As is clear from Tables 2 and 3, Examples 1 to 9 using the driving electrolytic solution of the present invention are compared with Conventional Examples 1 to 2 using the conventional driving electrolytic solution. Although there is not much characteristic difference in the initial stage, after the high temperature load test, the capacitance change rate, tan δ change, and leakage current change are significantly small, and the conventional examples 1 and 2 are bulged. On the other hand, in all the examples, there was no blistering phenomenon, demonstrating the remarkable effect of the present invention.

It was found that the conventional example 3 has a practical problem because the explosion-proof valve operates during aging.

[0027]

As described above, the electrolytic solution for driving an electrolytic capacitor of the present invention can increase the spark voltage without increasing the specific resistance in the presence of silicic acid anhydride, and can increase the nitro compound content. Since it is added, gas generation at high temperature is suppressed, and an electrolytic capacitor having a long life at high temperature can be obtained.

Claims (4)

[Claims] 1. A solvent comprising mainly ethylene glycol, wherein octanedicarboxylic acid or a salt of octanedicarboxylic acid having an alkyl group in a side chain is dissolved as a solute, and silicic anhydride and a nitro compound are added. An electrolytic solution for driving electrolytic capacitors. 2. The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein the salt is an ammonium salt, a secondary amine salt, a tertiary amine salt or a quaternary ammonium salt. 3. The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein the alkyl group of the side chain is a methyl group or an ethyl group. 4. The nitro compound is para-nitrophenol or para-nitrobenzoic acid.
The electrolytic solution for driving the electrolytic capacitor described.