JPH08264388A - Electrolyte for driving electrolytic capacitor - Google Patents

Abstract

PURPOSE: To increase the voltage withholding strength of an electrolyte by making the number of carbons on the side chain including a carboxyl group which is attached to a benzene ring larger than that of a benzoic acid. CONSTITUTION: This is an electrolyte for driving an electrolytic capacitor wherein polyhydric alcohol is used as a main solvent and monocarboxylic acid which has a benzyl group as shown by the formula I or a salt of it is dissolved in the solvent. In more specific, a solvent, chief of which are ethylene glycol and 1,3-propanediol, is used and at least one kind of the acid shown by the formula I or the salt of it (an ammonium salt is generally used as a salt) is dissolved as a salute in this electrolyte. With this electrolyte, a capacitor for medium and high voltages can be obtained wherein an initial value of tanδ can be held low and the change in the capacity and the increase in the value of tanδ can be held small over a long period of time at high temperatures and a voltage withholding strength is increased.

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, in particular, an electrolytic solution for an aluminum electrolytic capacitor for medium and high voltage, which has improved withstand voltage and long-term stability of life characteristics at high temperature. The present invention relates to an electrolytic solution for driving an electrolytic capacitor (hereinafter referred to as an electrolytic solution).

[0002]

2. Description of the Related Art Conventionally, a so-called ethylene glycol boric acid-based electrolytic solution prepared by dissolving boric acid or ammonium borate in ethylene glycol has been used as an electrolytic solution for an aluminum electrolytic capacitor for medium- and high-voltages. It is used a lot. This type of electrolytic solution has an excellent property of being flame retardant, but on the other hand, due to the generation of esterified water due to the esterification reaction of boric acid and ethylene glycol and the resulting generation of hydrogen gas, an electrolytic capacitor for 105 ° C. Was difficult to deal with. on the other hand,
Also known is an electrolytic solution using an ammonium salt of a dibasic acid having 8 to 22 carbon atoms for the purpose of improving the withstand voltage property at high temperature. In the latter, it is used in combination with benzoic acid or a salt thereof, which is a monocarboxylic acid but has excellent chemical conversion properties and has a benzene ring and is stable at high temperatures. In the electrolytic solution in which benzoic acid or its salt is combined with the ammonium salt of dibasic acid and dissolved in ethylene glycol, although a significant improvement effect in terms of heat resistance is observed, it undergoes esterification at high temperature. It was unavoidable to reduce the capacity and increase tan δ due to the amidated precipitate covering the electrode surface. Although benzoic acid has excellent thermal stability, it has a limited withstand voltage.

[0003]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention improves the electrolytic solution to improve the initial
While keeping the tan δ value low,
It is an object of the present invention to provide a medium- and high-voltage capacitor which can suppress an increase in tanδ to be small over a long period of time and has improved withstand voltage.

[0004]

In order to solve the above-mentioned problems, the present invention provides a monocarboxylic acid having a benzene group represented by Chemical formula 2 in an electrolytic solution for an electrolytic capacitor using a polyhydric alcohol as a main solvent, or a compound thereof. It is characterized by dissolving salt. That is, ethylene glycol, 1,3-
This is an electrolytic solution obtained by dissolving one or more of the acid shown in Chemical formula 1 or a salt thereof (ammonium salt is generally used as a salt) as a solute in a solvent containing propanediol as a main component.

[0005]

Embedded image

[0006]

Function: The side chain containing a carboxyl group added to the benzene ring has a carbon number larger than that of benzoic acid, so that the withstand voltage of the electrolytic solution is improved. Further, since the benzene ring is formed by the π-electron bond, the stability of the electrolytic solution at high temperature is maintained. Furthermore, since the esterification reaction of ammonium salt of dibasic acid is more relaxed than that by benzoic acid,
A decrease in capacity and an increase in tan δ due to amidated precipitates can be suppressed.

[0007]

EXAMPLES Specific examples of the present invention will be described below.
Table 1 shows the results of comparison of the composition, the specific resistance and the spark generation voltage of the medium and high voltage electrolytic solutions of the examples of the present invention and the conventional example. In Table 1, electrolyte sample symbol A is a conventional example, B,
C, D and E are examples of the present invention, and F is a reference example.

[0008]

[Table 1]

As is apparent from Table 1, when the ammonium benzoate used in the conventional example and the ammonium salt shown in Chemical formula 1 in an approximately equimolar amount are used, the change in the specific resistance is very small, while the withstand voltage is small. Is greatly improved.

As described above, the preferred embodiment of the present invention is such that a solvent mainly containing ethylene glycol for medium pressure and containing 1 wt% to 8 wt% of water is used, and a salt of azelaic acid or a higher dibasic acid such as sebacic acid is used. It is an electrolytic solution in which the acid shown in Chemical formula 1 according to the present invention or its ammonium salt is dissolved together with the salts of. Also, if necessary,
The properties can be further improved by adding boric acid, mannite, phosphorous acid, hypophosphorous acid or a salt thereof.

The amount of the acid or its salt shown in Chemical formula 1 dissolved is preferably in the range of 0.5 wt% to 10 wt%. 0.5
If it is less than wt%, the effect of improving the withstand voltage is not exerted, and if it exceeds 10 wt%, the spark generation voltage is reduced.

In addition to these examples, there are many branches such as mixing with other solutes or substituting 2-ethyl-1,3-hexanediol for a part of ethylene glycol in order to improve low temperature characteristics. It can be applied.

[0012]

INDUSTRIAL APPLICABILITY As described above, in the electrolytic solution for electrolytic capacitors using a polyhydric alcohol as a main solvent, the monocarboxylic acid having a benzyl group represented by the above general formula according to the present invention or a salt thereof is used as a solute. Since the electrolytic solution can improve the withstand voltage of the electrolytic solution and can maintain the stability of the electrolytic solution at high temperature, it has great industrial and practical value.

Claims (1)

[Claims] 1. An electrolysis solution for driving an electrolytic capacitor, wherein a monocarboxylic acid having a benzyl group represented by Chemical formula 1 or a salt thereof is dissolved in an electrolytic solution for driving an electrolysis capacitor using a polyhydric alcohol as a main solvent. liquid. Embedded image