JPH08162370A - Electrolyte solution for electrolytic capacitor - Google Patents

Abstract

PURPOSE: To obtain electrolyte solution for an electrolytic capacitor high in conductivity and dielectric strength by a method wherein the electrolyte solution is made to contain a specific amount of specific acid or its quaternary ammonium salt as solute. CONSTITUTION: Electrolyte solution is made to contain 5 to 50% by weight of specific acid represented by a general formula (X denotes -SH, -SCH2 COOH or -SCH2 CH2 COOH) or its quaternary ammonium salt as solute. γ-butyrolactone as main solvent and amide solvent, carbonate solvent, and alcohol solvent are used as solvent. Auxiliary solute such as phosphoric dielectric and nitrobenzene used for preventing galvanic corrosion and lessening a leakage current is added. A small amount of water may be added so as to improve an electrolyte solution in conductivity. By this setup, an electrolyte solution high and well balanced in conductivity and dielectric strength can be obtained.

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, and more particularly to a comparatively low voltage electrolytic solution for consumer use.

[0002]

2. Description of the Related Art As an electrolytic solution for electrolytic capacitors, there is known an electrolytic solution obtained by dissolving an ammonium salt of boric acid or adipic acid as a solute in a solvent such as ethylene glycol, N, N-dimethylformamide or .gamma.-butyrolactone. .
Further, as an electrolyte having a high electric conductivity, a quaternary ammonium salt of maleic acid or citraconic acid (Japanese Patent Publication No. 3-6646) or a salt of an aromatic carboxylic acid is used as a solute (Japanese Patent Publication No. 3-8092). Etc. have been proposed. However, as the impedance of the electrolytic capacitor is lowered, a high-performance electrolytic solution having higher conductivity is desired.
At present, it is not enough.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a high-performance electrolytic solution for electrolytic capacitors having high electric conductivity and withstand voltage characteristics.

[0004]

The present invention contains an electrolyte represented by the following general formula (1) or its quaternary ammonium salt as a solute in an amount of 5 to 50% by weight. Is.

[0005]

Embedded image

(In the formula, X is --SH, --SCH ₂ COOH.
Or an -SCH ₂ CH ₂ COOH. ) As the compound represented by the general formula (1) used in the present invention,
Specific examples thereof include thiomalic acid, carboxymethylmercaptosuccinic acid and carboxyethylmercaptosuccinic acid. These acids are maleic anhydride, hydrogen sulfide,
Thioglycolic acid or 3-mercaptopropionic acid can be produced by Michael addition by a conventional method and hydrolysis thereof.

Typical examples of the quaternary ammonium salts of the above acids include quaternary ammonium salts of aliphatic alkyl groups such as tetramethylammonium, tetraethylammonium, tetrapropylammonium and tetrabutylammonium, N, N-. Dimethylpyrrolidinium, N, N-
Examples thereof include alicyclic quaternary ammonium salts such as dimethylpiperidinium and aromatic quaternary ammonium salts such as N-ethylpyridinium. Specifically, tetramethylammonium thiomalate, tetraethylammonium thiomalate, tetrapropylammonium thiomalate,
Tetramethylammonium carboxymethylmercaptosuccinate, Tetraethylammonium carboxymethylmercaptosuccinate, Tetrapropylammonium carboxymethylmercaptosuccinate, Tetramethylammonium carboxyethylmercaptosuccinate, Tetraethylammonium carboxyethylmercaptosuccinate, Tetrapropylammonium carboxyethylmercaptosuccinate Examples thereof include ammonium.

The quaternary ammonium salt of the acid used in the present invention is obtained by, for example, neutralizing the carboxylic acid with an aqueous quaternary ammonium hydroxide solution, distilling off water, and recrystallizing the obtained product in methanol. It is manufactured by As a solvent of the electrolytic solution for an electrolytic capacitor of the present invention, that is, a solvent for dissolving an acid or a quaternary ammonium salt thereof, γ-butyrolactone is used as a main solvent from the viewpoint of solubility, handleability and safety and hygiene, and N-methylformamide, In addition to amide-based solvents such as N, N-dimethylformamide, carbonate-based solvents such as diethyl carbonate and diethyl carbonate, alcohol-based solvents such as ethylene glycol, ethyl cellosolve and diethylene glycol ethyl ether, nitrile and phosphate ester-based solvents, etc. It can be used in combination. The composition of the solvent is γ-in terms of performance as an electrolytic solution.
Butyrolactone may be 100% by volume, but γ-butyrolactone is 60 to 98% by volume, and other solvents are 2 to 40% by volume.
Is preferable in terms of solubility.

The proportion of the acid or its quaternary ammonium salt to be dissolved in the above-mentioned solvent is 5 to 50% by weight, particularly preferably 10 to 30%, which is not more than the solubility saturation. If it is less than 5% by weight, the electric conductivity is lowered, which is not preferable. On the other hand, if it exceeds 50% by weight, precipitation may occur or handling may be unfavorable. In addition, various known co-solutes such as phosphoric acid derivatives and nitrobenzene derivatives are added to the electrolytic solution of the present invention for the purpose of preventing electrolytic corrosion and reduction of leakage current, and a small amount of water is added for the purpose of improving electric conductivity. It doesn't matter.

[0010]

Since the electrolytic solution for electrolytic capacitors of the present invention contains the acid represented by the general formula (1) or its quaternary ammonium salt as a solute, it has a good balance between high conductivity and withstand voltage characteristics. It has excellent performance.

[0011]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. Example 1 20% by weight of tetraethylammonium salt of carboxyethylmercaptosuccinic acid was dissolved in a γ-butyrolactone solvent to prepare an electrolytic solution for an electrolytic capacitor. The conductivity and the spark generation voltage of this electrolytic solution were measured. The results are shown in Table 1. However, the conductivity was measured by impregnating an element having a rated voltage of 160 V and a rated capacity of 22 μF with the electrolytic solution at 30 ° C. and using a constant voltage power source under the condition of DC 5 mA. The value of the spark generation voltage is the spark generation voltage when a low current of ² mA / cm ² was applied to a pair of positive and negative aluminum smooth foils.

Examples 2 to 6 Electrolyte solutions for electrolytic capacitors were prepared in the same manner as in Example 1 except that the type of solvent, the type of solute and the blending amount were changed as shown in Table 1. It was used to measure the electrical conductivity and spark generation voltage. The results are also shown in Table 1. Comparative Examples 1 to 3 Electrolytic solutions for electrolytic capacitors were prepared using the solvents and solutes shown in Table 1, and the electrical conductivity and the spark generation voltage were measured by the method according to Example 1. The results are shown in Table 1.

[0013]

[Table 1]

* Volumes of solvents are shown in volume%. ** Solutes represent weight% of solvent. Abbreviations in the table GBL: γ-butyrolactone DMF: N, N-dimethylformamide EG: Ethylene glycol ECS: Ethyl cellosolve KEEN: Carboxyethyl mercaptosuccinate tetraethylammonium KEMN: Carboxyethyl mercaptosuccinate tetramethylammonium KEAA: Carboxyethyl mercaptosuccinate Acid KMEN: Tetraethylammonium carboxymethyl mercaptosuccinate TMEN: Tetraethylammonium thiomalate TMMN: Tetramethylammonium thiomalate MEN: Tetraethylammonium maleate FMN: Tetramethylammonium fumarate PDN: Tetramethylammonium phthalate As is clear from Table 1. The electrolytic solution of the present invention shown in Examples has higher conductivity than the electrolytic solutions of Comparative Examples. It can be seen that it has a well-balanced withstand voltage characteristic.

Claims (1)

[Claims] 1. An electrolytic solution for an electrolytic capacitor, containing 5 to 50% by weight of an acid represented by the following general formula (1) or a quaternary ammonium salt thereof as a solute. Embedded image (In the formula, X is —SH, —SCH ₂ COOH or —SCH ₂
Represents CH ₂ COOH. )