JPS63302512A - Electrolytic capacitor - Google Patents

Abstract

PURPOSE:To obtain a capacitor stably operating for a prolonged term at a high temperature of 100 deg.C or more and capable of reducing tan delta as withstanding voltage is left as it is kept high by using an electrolyte in which two components or more of benzoic acid or its salt and the derivative of benzoic acid or its salt are mixed and dissolved into a solvent. CONSTITUTION:An electrolyte in which two components or more of benzoic acid or its salt and the derivative of benzoic acid or its salt are mixed and dissolved into a solvent is employed. It is preferable that ammonium salt or alkylamine salt is used as said salt and benzoic acid halide alkyl benzoic acid or alkoxy benzoic acid is employed as the derivative of benzoic acid. The electrolyte such as an electrolyte for drive in which 5wt.% benzoic acid ammonium salt, 5wt.% O-pthorobenzoic acid, 0.2wt.% ammonium phosphate, 1.8wt.% aqueous ammonia, and 88wt.% ethylene glycol is mixed is employed, thus manufacturing an electrolytic capacitor at rated 250V 220muF using aluminum as an electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a long-life aluminum electrolytic capacitor.

[Prior art] Electrolytic capacitors are made by winding a foil of a valve metal such as aluminum together with a separator to form a capacitor element.Generally, the capacitor element is impregnated with a driving electrolyte, and a metal case made of aluminum or synthetic resin is used. The capacitor element is housed in a case and has a sealed structure.

Conventionally, the driving electrolyte for medium-high voltage electrolytic capacitors uses ethylene glycol as the main solvent, and a solution in which ammonium salts of chain dicarboxylic acids such as boric acid, adipine, and decanedicarboxylic acid are dissolved has been used. Ta. However, when boric acid is used, high conductivity cannot be obtained, and when chain dicarboxylic acid is used, the characteristics deteriorate significantly at high temperatures of 100° C. or higher.

Therefore, studies have been made to use aromatic carboxylic acids that are stable at high temperatures and provide high properties. Among them, benzoic acid, which provides a relatively high spark voltage, is suitable as a solute for medium-pressure electrolytes. An electrolytic solution prepared by dissolving ammonium salt of benzoic acid in ethylene glycol is well known (Japanese Patent Publication No. 1973-
However, in order to guarantee a long life at high temperatures, it is preferable to keep the PU of the electrolytic solution from 5 to 7 and the water content as low as possible. If the pn or water content is large, the electrolytic foil will be immersed and its properties will deteriorate, or gas will be generated and the safety valve may operate. However, if the water content is limited to 5 wt% or less and the pH is limited to a range of 5 to 7, high conductivity cannot be obtained with benzoic acid alone, making it difficult to obtain an electrolytic capacitor with high characteristics (low tan δ).

Furthermore, an electrolytic solution in which ammonobenzoate, boric acid, and mannitol are dissolved in ethylene glycol is also known (Japanese Patent Application Laid-Open No. 57-197).
-60829), although this system is indeed stable at high temperatures, the conductivity is not high enough to satisfy current requirements, and therefore it is not possible to obtain a capacitor with sufficiently small tan δ.

In addition, electrolytic solutions using substituted benzoic acid or nonanedicarboxylic acid alone are also known (Japanese Patent Laid-Open No. 18722-1983).
0, JP-A-61-172:123).

However, although the former is stable at high temperatures, it cannot meet the electrical conductivity currently required, and the latter has problems with stability at high temperatures and insufficient electrical conductivity.

[Problems to be Solved by the Invention] The present invention solves the above-mentioned problems, operates stably for a long time under high temperatures of 100°C or higher, and can reduce tan δ while maintaining high withstand voltage. The purpose is to provide capacitors.

[Means for Solving the Problems] Thus, the present invention uses an electrolytic solution in which two or more components of benzoic acid or its salt and a benzoic acid derivative or its salt are mixed and dissolved in a solvent. This article focuses on the characteristics of electrolytic capacitors.

In the present invention, the benzoic acid derivative is preferably selected from halogenated benzoic acids, alkylbenzoic acids and alkoxybenzoic acids.

Halogenated benzoic acids can range from monohalogenated benzoic acid to pentahalogenated benzoic acid depending on the number of hydrogen atoms substituted with halogen atoms, but from the viewpoint of solubility in solvents, monohalogenated benzoic acid to trihalogenated benzoic acid Benzoic acid is preferred. Further, as the halogen atom, a fluorine atom is particularly preferable. In the case of monohalogenated benzoic acid, the ortho form is more preferred.

The number of alkyl groups in the alkylbenzoic acid is preferably 1 to 3, and from the viewpoint of solubility in a solvent, the number of carbon atoms in the alkyl group is preferably 1 to 1o, particularly 1 to 4.

Specific examples of these alkylbenzoic acids include monomethylbenzoic acid (toluic acid), monoethylbenzoic acid,
Examples include monopropylbenzoic acid, motuptylbenzoic acid, dimethylbenzoic acid, diethylbenzoic acid, dipropylbenzoic acid, dibutylbenzoic acid, trimethylbenzoic acid, triethylbenzoic acid, tripropylbenzoic acid, and tributylbenzoic acid.

Among these, toluic acid is the most preferable from the viewpoint of solubility and electrolyte properties.Furthermore, toluic acid has three isomers: ortho form, meta form, and para form, but no matter which one is used, good results are obtained. Get results. Among them, the para form has the highest spark voltage and is preferably 0, and the number of alkoxy groups in the alkoxybenzoic acid is preferably 1 to 3, and from the viewpoint of solubility in a solvent, the number of carbon atoms in the alkoxy group is 1 to 101, particularly 1. ~
4 is preferred.

Specific examples of these alkoxybenzoic acids include monomethoxybenzoic acid (anisic acid), monoethoxybenzoic acid, monopropoxybenzoic acid, monobutoxybenzoic acid, dimethoxybenzoic acid, dimethoxybenzoic acid, dipropoxybenzoic acid, Examples include dibutoxybenzoic acid, trimethoxybenzoic acid, triethoxybenzoic acid, tripropoxybenzoic acid, and triptoxybenzoic acid.

Furthermore, methoxybenzoic acid (anisic acid) has an ortho form,
There are three types of isomers: meta and bulk, and good results can be obtained using any of them. Among them, para-methoxybenzoic acid (p-anisic acid) has the highest spark voltage and is preferred. Next, the solvent will be explained.

The solvent that can be used in the present invention is not particularly limited, but is preferably a nonaqueous solvent, and specifically, known ethylene glycol, propylene glycol, diethylene glycol, methylpyrrolidone, methylcarpitol, γ-butyrolactone, γ-valerolactone, N, N-
Dimethylformamide, N-methylformamide, N-
Methylpyrrolidone, propylene carbonate, 3-methyl-1,
3-year-old xacylidin-2-one, phenyl acetate, etc. are used as appropriate.

The concentration of each solute in these solvents is preferably 1% by weight to saturation concentration, particularly 1 to 15% by weight per component. Below this concentration, the desired sufficient conductivity cannot be obtained, and higher As the alkali source for the PH2g1 clause, which may precipitate at room temperature if the concentration is high, ammonia, alkylamine, etc. can be used as appropriate, but ammonia is most preferred since it provides high conductivity and high spark voltage.

Ammonia may be added in the form of aqueous ammonia, but it is preferable to add it in the form of ammonium benzoic acid or ammonium salt of benzoic acid derivatives in order to control the moisture content.

The lower the water content, the better from the viewpoint of longevity, especially 5wt.
% or less. If the pH is too high or too low, the electrode foil will be immersed, so it is preferable to adjust the pH within the range of 5 to 7.

In addition, additives commonly used to improve the chemical properties and stability of electrolytes, such as ammonium phosphate, boric acid, etc., and their salts, and polysaccharides such as mannitol and sorbitol are added. However, there is no adverse effect on the characteristics.

The electrolytic capacitor of the present invention includes capacitors of various embodiments. In a typical embodiment, an aluminum foil anode and an aluminum foil cathode separated by a suitable separator such as paper are used, these are wound into a cylindrical shape to form a capacitor element, and this element is impregnated with a driving electrolyte. .

The amount of electrolytic solution impregnated is preferably 50 to 300% by weight based on the separator. The element impregnated with the electrolytic solution is housed in a case made of corrosion-resistant metal, synthetic resin, or the like, and has a sealed structure.

An embodiment of the present invention will be described below.

[Function] In the present invention, it is necessary to contain two components selected from benzoic acid or a salt thereof and a benzoic acid # derivative or a salt thereof as a solute. Its effect is still not clearly understood, or if the above two components are not contained, as is clear from the examples below, the defective rate at the time of commercialization will be high, or the initial dielectric loss (tan δ) will increase. Either the value is high or tan δ becomes very large over time.

[Examples] The present invention will be specifically described below based on Examples and Comparative Examples.

As shown in Comparative Examples 1 to 5 and Examples 1 to 19, electrolytic capacitors having a rating of 250 V and 220 μF and having aluminum electrodes were manufactured using a driving electrolyte containing various components. A rated voltage was applied to this capacitor at 100° C., and changes in loss (tan δ) after 1,000 hours were measured and shown in Table 1.

Table 1 also shows the number of short bank failures due to insufficient spark voltage during capacitor manufacturing.

Comparative Example 1 Weight% Benzoic acid ammonium salt 12 Water
3 Ethylene glycol 85 Comparative example 2 Benzoic acid ammonium salt 10 Boric acid 2 Mannitol 3 Water
2 Ethylene glycol 83 Comparative example 3 p-toluic acid 10 Ammonia water 4 Ethylene glycol 86 Comparative example 4 Water
3 Ethylene glycol 90 Comparative example 5 Weight % anisic acid
10 ammonia water
4 Ethylene glycol 86 Example 1 Ammonium benzoate kMs O-toluic acid 5 Ammonia water
2 Ethylene glycol 88 Example 2 Ammonium salt of benzoate 5 m-Toluic acid 5 Aqueous ammonia 2 Ethylene glycol 88 Example 3 Ammonium salt of benzoate 5 P-Toluic acid 5 Aqueous ammonia 2 Ethylene glycol 88 Example 4 Weight, benzoic acid Ammonium salt 4 p-toluic acid 4 porium #
2 mannits
3 Ammonia water 2 Ethylene glycol 85 Example 5 Benzoic acid ammonium salt 5 t-tutylbenzoic acid 5 Ammonium phosphate 0.2 Ammonia water
1.8 Ethylene glycol 88 Example 6 Benzoic acid ammonium salt 5 p-ethoxybenzoic acid 5 Aqueous ammonia
2 Ethylene glycol 88 Example 7 Weight % ammonium salt of benzoate 5 1-anisic acid 1% 15 Aqueous ammonia 2 Ethylene glycol 88 Example 8 Ammonium salt of benzoate 5 p-anisic acid 5 Aqueous ammonia
2 Ethylene glycol 88 Example 9 Benzoic acid ammonium salt 4 p-anisic acid 4-boric acid
2 Mannite 3 Ammonia water 2 Ethylene glycol 85 Example 10 Weight % benzoic acid ammonium salt 5 p-anisic acid Penta-ammonium phosphate 0.2 Ammonia water
1.8 Ethylene glycol 88 Example 11 Benzoic acid ammonium salt 5 0-Fluorobenzoic acid 5 Aqueous ammonia
2 Ethylene glycol 88 Example 12 Benzoic acid ammonium salt 5 m-fluorobenzoic acid 5 Aqueous ammonia
2 Ethylene glycol 88 Example 13 Benzoic acid ammonium salt 5 p-chlorobenzoic acid 5 Aqueous ammonia
2 Ethylene glycol 88 Example 14 Weight % ammonium benzoate 1iA4 0-chlorobenzoic acid 4 boric acid
2 mannits
3 Ammonia water 2 Ethylene tallicol 85 Example 15 Benzoic acid ammonium salt 5 0-Fluorobenzoic acid 5 Ammonium phosphate 0.2 Ammonia water
1.8 Ethylene glycol 88 Example 16 Benzoic acid ammonium salt 5 1)-)-Ruilic acid 30-Fluorobenzoic acid 3 Aqueous ammonia
2 Ethylene glycol 87 Example 17 Weight % benzoic acid ammonium salt 5 p-)ruylic acid 3p-anisic acid
3 Ammonia water
2 Ethylene glycol 87 Example 18 m-) Ruylic acid 3p-anisic acid
3-trifluorobenzoic acid
3 Aqueous ammonia 4 Ethylene glycol 87 Example 19 Ammonium salt of benzoate 5 Trichlorobenzoic acid 5 Aqueous ammonia 2 Ethylene glycol 88 Table 1 [Effects of the invention] According to the present invention, the defective rate during production is low and 100'C
It operates stably for a long time under high temperatures above
An electrolytic capacitor with a small δ can be obtained.

Claims (7)

[Claims] (1) An electrolytic capacitor characterized by using an electrolytic solution in which two or more of benzoic acid or its salt and a benzoic acid derivative or its salt are mixed and dissolved in a solvent. (2) The electrolytic capacitor according to claim (1), wherein the salt is an ammonium salt or an alkylamine salt. (3) The electrolytic capacitor according to claim (1), wherein the benzoic acid derivative is halogenated benzoic acid, alkylbenzoic acid, or alkoxybenzoic acid. (4) The electrolytic capacitor according to claim (3), wherein the halogenated benzoic acid is mono- or trihalogenated benzoic acid. (5) The alkyl group of alkylbenzoic acid has 1 to 10 carbon atoms
An electrolytic capacitor according to claim (3). (6) The alkoxy group of alkoxybenzoic acid has 1 or more carbon atoms
10. The electrolytic capacitor according to claim (3), which is No. 10. (7) The electrolytic capacitor according to claim (1), wherein the concentration of benzoic acid or its salt and benzoic acid derivative or its salt in the electrolytic solution is from 1% by weight to a saturation concentration.