JP2001185457A - Electrolytic solution for electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic solution for middle and high voltage, which has a high sparking voltage, a good electrical conductivity and low temperature characteristic. SOLUTION: This electrolytic solution for electrolytic capacitor composed of ethyleneglycol as its base solvent, in which 1,6-decanedicarboxylic acid and benzoic acid are dissolved and a butyl tetracarboxylic acid is added, and therefore it has a high spark voltage, a good conductivity and low temperature characteristic. By using this electrolytic solution an electrolytic capacitor with a good abnormal voltage characteristic, tanδ and low temperature characteristic is 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 electrolytic capacitors, and more particularly to an electrolytic solution for medium and high pressures.

[0002]

2. Description of the Related Art An electrolytic solution for an electrolytic capacitor uses a valve metal having an insulating oxide film formed on the surface such as aluminum or tantalum for an anode electrode, and uses the oxide film layer as a dielectric material. An electrolyte for forming an electrolyte layer is brought into contact with the surface of the substrate, and a current collecting electrode usually called a cathode is arranged.

As described above, the electrolytic solution for an electrolytic capacitor directly contacts the dielectric layer and acts as a true cathode. That is, the electrolytic solution is interposed between the dielectric of the electrolytic capacitor and the collector cathode, and the resistance of the electrolytic solution is inserted in series with the electrolytic capacitor. Therefore, the characteristics of the electrolytic solution are a major factor affecting the characteristics of the electrolytic capacitor.

[0004] As an electrolytic solution for medium and high pressures, an electrolytic solution using ethylene glycol as a solvent and benzoic acid as a solute is used because of its relatively high conductivity.

[0005]

However, in recent years,
There is an increasing demand for safety, and there is also a demand for safety when an abnormal voltage is applied to a power supply or the like using a medium-to-high voltage electrolytic capacitor. In addition, good low-temperature characteristics are required to satisfy specifications in cold regions.
On the other hand, in the above-mentioned electrolytic solution, boric acid or the like is added to improve the spark voltage, and the safety against abnormal voltage can be improved, but the electric conductivity decreases, and the low-temperature characteristics deteriorate. There was a problem that the above requirements could not be satisfied.

Accordingly, an object of the present invention is to provide an electrolyte for medium and high pressures having a high sparking voltage, sufficient electric conductivity and low temperature characteristics.

[0007]

In order to solve the above problems, an electrolytic solution for an electrolytic capacitor of the present invention is prepared by dissolving 1,6-decanedicarboxylic acid and benzoic acid in a solvent mainly composed of ethylene glycol. And butyltetracarboxylic acid.

[0008] It is also preferable that one or more polyoxyalkylene polyhydric alcohol ether compounds obtained by polymerizing ethylene oxide and / or propylene oxide with a nonionic surfactant and a polyhydric alcohol are added to the electrolytic solution. Features.

Further, one or more aromatic nitro compounds are added to the electrolytic solution.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The electrolytic solution for an electrolytic capacitor of the present invention uses a solvent mainly composed of ethylene glycol.
As the solute, a mixture of 1,6-decanedicarboxylic acid and benzoic acid is used. And butyltetracarboxylic acid is used as an additive. The electrolytic solution of the present invention has a high spark voltage, sufficient electric conductivity and low-temperature characteristics, and good high-temperature life characteristics.

The content of the above solute in the electrolyte is preferably 12 to 18% by weight. Below this range,
If the low-temperature characteristics are deteriorated, and if the temperature exceeds this range, the capacity change in the life test becomes large.

Then, a non-ionic surfactant, a polyoxyalkylene polyhydric alcohol ether compound obtained by polymerizing ethylene oxide and / or propylene oxide to a polyhydric alcohol are added to the electrolytic solution, and the electrolytic solution is further added. Spark voltage can be improved. This improves the withstand voltage characteristics of the electrolytic capacitor, and further improves the abnormal voltage characteristics. In addition, since the nonionic surfactant has a property of foaming during impregnation, considering the workability at the time of impregnation, polyoxyalkylene polyoxyalkylene obtained by polymerizing ethylene oxide and / or propylene oxide with a polyhydric alcohol is used. Dihydric alcohol ether compounds are preferred.

Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, alkyl allyl formaldehyde condensed polyoxyethylene ether, polyoxyethylene polyoxypropylene alkyl ether, and polyoxyethylene of glycerin fatty acid ester. Ether, polyoxyethylene ether of sorbitan fatty acid ester, polyoxyethylene ether of sorbitol fatty acid ester, fatty acid ester of polyethylene glycol, hydrophilic silicone oil and the like.

The polyhydric alcohol of the polyoxyalkylene polyhydric alcohol ether compound obtained by polymerizing ethylene oxide and / or propylene oxide with the polyhydric alcohol includes ethylene glycol, propylene glycol,
Glycerin, pentaerythritol, sorbit, polyglycerin, trimethylolpropane, trimethylolethane and the like can be mentioned. Of these, glycerin,
Pentaerythritol, sorbit, polyglycerin,
Trimethylolpropane and trimethylolethane are preferred. Further, of these, polyoxyethylene glycerin is preferred.

The addition amount of the nonionic surfactant and the polyoxyalkylene polyhydric alcohol ether compound is 0.1%.
-15% by weight, preferably 0.5-10% by weight. Below this range, the effect decreases, and beyond this range,
Conductivity decreases. Here, the polyoxyalkylene polyhydric alcohol ether compound has an average molecular weight of 1
In the case of 000 or more, the effect is high, so the addition amount may be small.

Further, by adding an aromatic nitro compound to the electrolytic solution, generation of gas during re-chemical formation is suppressed, and thereby tan δ of the electrolytic capacitor is reduced. Further, since the rise in the internal pressure of the capacitor can be suppressed, the life characteristics of the capacitor can be improved. This is considered to be due to a reduction reaction of the nitro group with the hydrogen gas generated inside the capacitor. The addition amount of the aromatic nitro compound is 0.01
To 7.0% by weight, preferably 0.1 to 5.0% by weight. If it is less than this range, the effect decreases, and if it exceeds this range, the conductivity of the electrolytic solution decreases.

Specific examples of the aromatic nitro compound include nitrophenol, dinitrophenol, nitrobenzoic acid, nitrotoluene, dinitrotoluene, nitroxylene, nitrobenzene, dinitrobenzene, nitrobenzyl alcohol, nitroacetophenone, nitroanisole, dimethoxynitrobenzene, and nitrobenzene. Examples include aniline, nitrophenetol, nitrophthalic acid, 2- (nitrophenoxy) ethanol and the like.

The 1,6-decanedicarboxylic acid and benzoic acid in the present invention can be used as salts. Examples of the salts include ammonium salts, amine salts, quaternary ammonium salts and quaternary ammonium salts of cyclic amidine compounds. Is raised. One or more of these salts can be used. Examples of the amine constituting the amine salt include primary amines (methylamine, ethylamine, propylamine, butylamine, ethylenediamine, monoethanolamine, etc.), and secondary amines (dimethylamine, diethylamine, dipropylamine, ethylmethylamine, diphenylamine, diethanolamine). Tertiary amines (trimethylamine, triethylamine, tributylamine, 1,8-diazabicyclo (5,
4,0) -undecene-7, triethanolamine, etc.)
Is raised. Of these, ammonium salts are preferred.

The solvent is mainly composed of ethylene glycol, but a protic polar solvent, an aprotic solvent or water may be added for the purpose of improving low-temperature characteristics and reducing specific resistance. Protic polar solvents include monohydric alcohols (methanol, ethanol, propanol,
Butanol, hexanol, cyclohexanol, cyclopentanol, benzyl alcohol, etc.), polyhydric alcohols and oxy alcohol compounds (propylene glycol, glycerin, methyl cellosolve, ethyl cellosolve, 1,3-butanediol, methoxypropylene glycol, etc.), etc. Is raised. As aprotic solvents, amides (N-methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N
-Dimethylformamide, N-methylacetamide, hexamethylphosphoric amide, etc.), lactones, cyclic amides, carbonates (γ-butyrolactone, N-
Representative examples include methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate), nitriles (acetonitrile) oxides (dimethylsulfoxide and the like).

Various additives can be added for the purpose of reducing leakage current and absorbing hydrogen gas. Examples of the additive include a phosphorus compound (phosphoric acid, phosphorous acid, polyphosphoric acid, acidic phosphoric acid ester compound), an oxycarboxylic acid compound, and the like.

As described above, the electrolytic solution of the present invention has a high spark voltage, and has sufficient electric conductivity and low-temperature characteristics. Therefore, by using the electrolytic solution of the present invention, it is possible to obtain an electrolytic capacitor having good abnormal voltage characteristics and good tan δ and low-temperature characteristics.

[0022]

Embodiments of the present invention will be described below.

Table 1 shows the composition of the electrolytic solution for the electrolytic capacitor, the spark voltage and the conductivity for the examples of the present invention and the comparative examples. Here, the electrolytic solution is prepared by a conventional method, and ammonia gas is injected to p.
H was adjusted. The spark voltage is a value measured by using a capacitor element and flowing a constant current of 10 mA at room temperature.

Table 2 shows 250 V-100 μm using the electrolyte solutions of Examples and Comparative Examples in Table 1.
5 shows the initial characteristics of the electrolytic capacitor F, the change in capacitance at −40 ° C., and the impedance ratio. (Table 3)
Shows the results of a high-temperature load test at 105 ° C. for 2,000 hours.

[0025]

[Table 1]

[0026]

[Table 2]

As is clear from (Table 1), the embodiment
Comparative Example 2 using benzoic acid as a solute and adding boric acid
The conductivity at 20 ° C. and −40 ° C. is better than that of
Further, the spark voltage is higher than that of Comparative Example 3 using benzoic acid as a solute. Further, Example 2 in which polyoxyethylene glycerin was added and Example 1 in which polyoxyethylene glycerin was not added were added.
Thus, the spark voltage is high, and the effect of polyoxyethylene glycerin is understood.

As apparent from Table 2, the initial characteristics and the high temperature load characteristics of the electrolytic capacitor are also good. In particular, Example 1 in which p-nitrophenol was added
Shows good initial tan δ, little change in product height after the life test, and the effect of suppressing gas generation of p-nitrophenol. Furthermore, in Comparative Example 1, in which butyltetracarboxylic acid was not added, the rate of change in capacitance after the life test was high, and the life characteristics could not be satisfied. As described above, the ethylene glycol of the present invention, 1,6-decanedicarboxylic acid and benzoic acid, and a synergistic effect of butyltetracarboxylic acid have an unprecedented high spark voltage, conductivity, and low-temperature characteristics. It is possible to obtain an electrolytic solution for an electrolytic capacitor that has good and high-temperature life characteristics.
Therefore, by using this electrolytic solution, it is possible to realize an electrolytic capacitor having good abnormal voltage characteristics, good tan δ, good low-temperature characteristics, and good high-temperature life characteristics.

[0029]

The electrolytic solution for an electrolytic capacitor of the present invention is prepared by dissolving 1,6-decanedicarboxylic acid and benzoic acid in a solvent mainly composed of ethylene glycol and adding butyltetracarboxylic acid. High spark voltage, conductivity,
The low-temperature characteristics are good, and the high-temperature life characteristics are also good. Therefore, by using the electrolytic solution of the present invention, it is possible to obtain an electrolytic capacitor having good abnormal voltage characteristics, good tan δ, good low-temperature characteristics, and good high-temperature life characteristics.

The spark voltage can be further reduced by adding at least one polyoxyalkylene polyhydric alcohol ether compound obtained by polymerizing ethylene oxide and / or propylene oxide with a nonionic surfactant or polyhydric alcohol. Can be enhanced.

Further, by adding one or more aromatic nitro compounds, the initial tan δ of an electrolytic capacitor using this electrolytic solution is reduced, and the high-temperature life characteristics are improved.

Claims (3)

[Claims] (1) dissolving 1,6-decanedicarboxylic acid and benzoic acid in a solvent mainly composed of ethylene glycol;
An electrolytic solution for an electrolytic capacitor to which butyltetracarboxylic acid is added. 2. The electrolysis according to claim 1, wherein at least one polyoxyalkylene polyhydric alcohol ether compound obtained by polymerizing ethylene oxide and / or propylene oxide with a nonionic surfactant or polyhydric alcohol is added. Electrolyte for capacitors. 3. The method according to claim 1, wherein one or more aromatic nitro compounds are added.
The electrolytic solution for an electrolytic capacitor according to claim 1.