JPH09148194A - Electrolyte for driving electrolytic capacitors - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrolyte having a high conductivity without causing a liquid leakage by a method wherein a solute, which consists of the carboxylic acid tertiary salt of imidazoles which are shown by a specified formula, is dissolved in a solvent containing a gamma-butyrolactone as its main component. SOLUTION: An electrolyte is obtained by dissolving a solute, which consists of carboxylic acid tertiary salt of imidazoles which are shown by the formula I (In the formula, the R<1> and the R<2> show hydrogen, an alkyl group of 1 to 10 C or an alkyl group and the R<3> and the R<4> show hydrogen, an alkyl group of 1 to 10 C, a second aliphatic hydrocarbon ring or a second aromatic hudrocarbon ring.), in a solvent containing a gamma-butyrolactone as its main component. As the imidazoles, a 1-methylimidazole, a 1-ethylimidazole, a 1,2- dimethylimidazole or the like is used and as a carboxylic acid, a maleic acid, a citraconic acid, an oxalic acid, a phthalic acid, a 4-methylphythalic acid or the like is used.

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 aluminum and electrolytic capacitors, which has a high electric conductivity and does not leak.

[0002]

2. Description of the Related Art As shown in FIG. 1, an aluminum electrolytic capacitor is a capacitor element 1 in which a pair of anode and cathode foils are wound with a spacer made of kraft paper or manila paper interposed therebetween and impregnated with a driving electrolytic solution. The anode external terminal 5 and the cathode external terminal 5 and the cathode external terminal 5 which are drawn out from one end face are fixed to a sealing body 4 made of a hard resin provided with an explosion-proof valve (not shown) at arbitrary places. The capacitor element 1 in a state of being connected to the external terminal 6 via a rivet 7 is housed in a cylindrical metal case 9 made of aluminum through a vibration isolator 8 made of, for example, attack polypropylene or pitch, and The opening of the case 9 is sealed with the sealing body 4.

Conventionally, as an electrolytic solution for driving an electrolytic capacitor (hereinafter referred to as an electrolytic solution), an electrolytic solution prepared by dissolving boric acid or ammonium salts of various carboxylic acids in a solvent mainly composed of ethylene glycol has been used. (JP-A-7
-235451). Recently, an electrolytic solution in which an amine salt of an organic acid such as phthalic acid or maleic acid is dissolved in a solvent mainly composed of γ-butyrolactone is also used for the purpose of improving impedance characteristics in a high frequency region and life characteristics at high temperature. However, a capacitor using an amine salt-based electrolytic solution is still insufficient in performance, and development of an electrolytic solution having more excellent high frequency impedance characteristics is desired.

In order to improve the high frequency impedance characteristics, it is necessary to use an electrolytic solution having higher conductivity. As such an electrolytic solution, a quaternary ammonium salt such as a maleic acid mono (methyltriethylammonium) salt or a phthalic acid mono (tetraethylammonium) salt is used as a solute, and this is dissolved in a solvent containing γ-butyrolactone as a main component. A liquid has been proposed and put to practical use (Japanese Patent Application Laid-Open No. 62-62160).
No. 145713, JP-A No. 62-145715), however, since these quaternary ammonium salt-based electrolytes are alkalis locally generated near the cathode portion in the capacitor, they attack aluminum and cause a problem from the cathode sealing portion. It has been reported that it has a drawback of causing liquid leakage ("Journal of Japanese Reliability Society", "Reliability", pp. 54-55, May issue, 199).
5 years).

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrolytic solution having higher conductivity without causing liquid leakage.

[0006]

The present invention relates to a solvent containing γ-butyrolactone as a main component, and imidazoles represented by the general formula (1).

[0007]

Embedded image

(In the formula, R ¹ and R ² are hydrogen and carbon number 1
10 represents an alkyl group or an allyl group. R ³ and R ⁴
Represents hydrogen, an alkyl group having 1 to 10 carbon atoms, an allyl group, a second aliphatic hydrocarbon ring or a second aromatic hydrocarbon ring. The present invention provides an electrolytic solution for driving an electrolytic capacitor, which is obtained by dissolving a solute composed of the carboxylic acid tertiary salt of (4).

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Carboxylic Acid Tertiary Salts of Imidazoles: Carboxylic acid tertiary salts of solute imidazoles can be easily obtained by mixing imidazoles and carboxylic acids.

(1) Imidazoles Specific examples of the imidazoles represented by the general formula (1) include imidazole, 1-methylimidazole, 2-methylimidazole, 4-methylimidazole, 5-methylimidazole and 1-ethyl. Imidazole, 2-ethylimidazole, 4-ethylimidazole, 5-ethylimidazole, 1,2-dimethylimidazole, 1,4-dimethylimidazole, 1,5-dimethylimidazole,
2,4-dimethylimidazole, 2,5-dimethylimidazole, 4,5-dimethylimidazole, 1-phenylimidazole, 2-phenylimidazole, 4-phenylimidazole, 5-phenylimidazole, benzimidazole, 1-methylbenzimidazole, 2-methylbenzimidazole, 4-methylbenzimidazole, and 5-methylbenzimidazole can be mentioned.

(2) Carboxylic Acid Examples of carboxylic acid include maleic acid, citraconic acid,
Unsaturated aliphatic dicarboxylic acids such as dimethyl maleic acid and 1,2-cyclohexene dicarboxylic acid; oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid , Dodecanoic acid, tridecanoic acid, dimethylmalonic acid, diethylmalonic acid, dipropylmalonic acid, 2-methylglutaric acid, 3-methylglutaric acid, 3,3-dimethylglutaric acid, 3-methyladipic acid, 2-butyloctane Saturated aliphatic dicarboxylic acids such as diacid, 2,3-dibutylsuccinic acid and cyclohexanedicarboxylic acid; aromatic dicarboxylic acids such as phthalic acid and 4-methylphthalic acid; benzoic acid, toluic acid, cumic acid, t-butylbenzoic acid,
Aromatic monocarboxylic acids such as anisic acid can be mentioned. These carboxylic acid salts of imidazoles may be used alone or in combination of two or more.

(3) Solvent The solvent used in the present invention is a solvent mainly composed of γ-butyrolactone, and γ-butyrolactone may be used, or this may be mixed with various auxiliary solvents. Specific examples of the auxiliary solvent include N-methylformamide, N-ethylformamide, N, N-dimethylformamide, N, N-
Diethylformamide, N-ethylacetamide, N,
Amide solvents such as N-dimethylacetamide and N-methylpyrrolidinone; lactone solvents such as γ-valerolactone and δ-valerolactone; carbonate solvents such as ethylene carbonate, propylene carbonate and butylene carbonate; ethylene glycol, glycerin, methyl cellosolve and the like. Alcohol solvent; Nitrile solvent such as 3-methoxypropionitrile and glutaronitrile;
Examples thereof include phosphoric acid ester solvents such as trimethyl phosphate and triethyl phosphate; and mixtures of two or more kinds of these solvents.

(4) Electrolytic solution for driving electrolytic capacitor: The carboxylic acid electrolytic solution of imidazole as a solute is used in a proportion of 1 to 50% by weight, preferably 5 to 40% by weight, based on the electrolytic solution. The electrolyte contains various auxiliary solutes such as phosphorus compound, nitroaromatic compound, boric acid, hexites, colloidal silica, etc. for the purpose of reducing leakage current, absorbing hydrogen gas, improving withstand voltage as necessary. Can be added. Further, 1 to 5% by weight of water can be added for the purpose of improving electric conductivity and chemical conversion. Since the pH of the electrolytic solution is on the acidic side of 3 to 6.0, aluminum is not exposed and there is no risk of liquid leakage during long-term use.

[0014]

【Example】

Example 1 25 parts by weight of N-methylimidazole phthalate salt was dissolved in a mixed solvent of 67.5 parts by weight of γ-butyrolactone and 7.5 parts by weight of ethylene glycol to obtain an electrolytic solution. The electric conductivity of this electrolytic solution at 25 ° C. was 6.27 mS / cm, and 5 mA / cm was added to a pair of + and − aluminum smooth foils.
The spark generation voltage when the constant current of ² was applied was 80V. In the liquid leakage test, the capacitor shown in FIG. 1 was manufactured using an electrolytic solution, left at 85 ° C. for 2,000 hours, and then the appearance of the sealing portion was observed. There was no liquid leakage.

Examples 2 to 6 and Comparative Examples 1 to 4 Electrolyte solutions having the compositions shown in Table 1 were prepared and evaluated in the same manner as in Example 1. Table 1 shows the results.

[0016]

[Table 1]

[0017]

INDUSTRIAL APPLICABILITY The electrolytic solution for driving an aluminum electrolytic capacitor of the present invention can obtain an electrolytic solution having a higher conductivity than the conventional electrolytic solution using an amine salt. Further, the electrolytic solution of the present invention has a spark voltage sufficient to be used as a driving electrolytic solution for a low voltage electrolytic capacitor.

[Brief description of the drawings]

FIG. 1 is a perspective view of an aluminum electrolytic capacitor.

Claims (4)

[Claims] 1. An imidazole compound represented by the general formula (1) in a solvent mainly composed of γ-butyrolactone: (In the formula, R ¹ and R ² represent hydrogen, an alkyl group having 1 to 10 carbon atoms or an allyl group. R ³ and R ⁴ are hydrogen, an alkyl group having 1 to 10 carbon atoms, an allyl group, and a second group. An electrolytic solution for driving an electrolytic capacitor, which is obtained by dissolving a solute composed of a tertiary carboxylic acid salt of an aliphatic hydrocarbon ring or a second aromatic hydrocarbon ring. 2. Imidazoles are 1-methylimidazole, 2-methylimidazole, 4-methylimidazole, 5-methylimidazole, 1-ethylimidazole, 2-ethylimidazole, 4-ethylimidazole, 5-ethylimidazole, 1, 2-dimethylimidazole, 1,4-dimethylimidazole, 1,5-dimethylimidazole, 2,4-dimethylimidazole,
The electrolytic solution for driving an electrolytic capacitor according to claim 1, which is selected from 2,5-dimethylimidazole and 4,5-dimethylimidazole. 3. The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein the carboxylic acid of the carboxylic acid tertiary salt of a solute imidazole is maleic acid or phthalic acid. 4. The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein the solvent is a mixed solvent of 85 to 99% by weight of γ-butyrolactone and 15 to 1% by weight of ethylene glycol.