JP2000315629A - Electrolyte for electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolyte for an intermediate to high voltage having a high sparking voltage. SOLUTION: An electrolyte is prepared by dissolving one or more kinds selected from among 1-methyl-3,5-dimethyl-3,5-dimethoxycarbonyl-1,11-undecan dicarboxylic acid, 7,8-dimethyl-7,8-dimethoxycarbonyl-1,14-tetradecan dicarboxylic acid, and their salts in a solvent containing ethylene glycol as the main component. Therefore, a high sparking voltage 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 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.

In the prior art of electrolytic capacitors, since a relatively high spark voltage can be obtained as an electrolytic solution for medium and high pressures, an electrolytic solution in which boric acid or ammonium borate is dissolved as a solute in a solvent composed of ethylene glycol is used. I was However, such an electrolytic solution has a low electric conductivity and a large amount of water is generated by esterification of ethylene glycol and boric acid.
If the temperature is 0 ° C. or higher, the internal pressure increases due to the evaporation of water, and there is a problem in that the internal pressure easily reacts with aluminum as an electrode, which is not suitable for use at high temperatures.

In order to solve such a drawback, organic dicarboxylic acids such as sebacic acid and azelaic acid are sometimes used. However, since these compounds have low solubility, crystals are easily precipitated at low temperatures and low temperatures of capacitors. The disadvantage of deteriorating the characteristics could not be avoided. Furthermore, Tokiko Sho 60
As disclosed in JP-A-13-13296, an example using butyloctane diacid as a solute or JP-B-63-15538.
There is an example in which 5,6-decanedicarboxylic acid is used as a solute as shown in Japanese Patent Application Laid-Open Publication No. H11-209,878. Electrolyte solutions using these dibasic acids or salts thereof have high sparking voltage and conductivity, are very slow in esterification, and generate little water, so that high-temperature stability can be obtained.

[0006]

However, in recent years,
Electronic equipment using a switching power supply has been widely used in ordinary households, and the demand for safety of aluminum electrolytic capacitors has been increasing. In order to improve the safety of the electrolytic capacitor, it is desired to improve the spark voltage of the electrolytic solution for the electrolytic capacitor to improve the overvoltage characteristic of the electrolytic capacitor.

Accordingly, an object of the present invention is to provide an electrolyte for medium and high pressures having a high spark voltage.

[0008]

In order to solve the above-mentioned problems, an electrolytic solution for an electrolytic capacitor according to the present invention is prepared by dissolving 1-methyl-3,5-dimethyl-3,5- One or more selected from dimethoxycarbonyl-1,11-undecanedicarboxylic acid, 7,8-dimethyl-7,8-dimethoxycarbonyl-1,14-tetradecanedicarboxylic acid, and salts thereof are solutes It is characterized by being used as.

Further, boric acid or a salt thereof is added to the electrolytic solution.

[0010] Further, benzoic acid or a salt thereof is added.

Further, one or more selected from hexites or polyhydric alcohols composed of polyethylene glycol, polyvinyl alcohol, polyoxyethylene glycerin, polyglycerin and glycerin are added.

Further, one or more kinds of nitro compounds selected from nitrobenzoic acid, nitrophenol and nitroanisole are added.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION In a solvent mainly comprising ethylene glycol of the present invention, 1-methyl-3,5-dimethyl-
One or two selected from 3,5-dimethoxycarbonyl-1,11-undecanedicarboxylic acid, 7,8-dimethyl-7,8-dimethoxycarbonyl-1,14-tetradecanedicarboxylic acid, or salts thereof. The electrolytic solution for the electrolytic capacitor in which the seeds or more are dissolved has a higher spark voltage than the conventional electrolytic solution.

When boric acid is added to the electrolytic solution, the spark voltage is further improved, and the withstand voltage of the electrolytic capacitor using the same is improved.

When benzoic acid is added, the conductivity of the electrolytic solution increases, and the tan δ of the electrolytic capacitor using the same increases.
Is reduced.

Further, when one or more kinds of hexites or polyhydric alcohols composed of polyethylene glycol, polyvinyl alcohol, polyoxyethylene glycerin, polyglycerin and glycerin are added, the spark voltage increases.

The hexites used herein include mannite, sorbit, dursit, xylit, pentaerythritol and the like.

When one or more nitro compounds selected from nitrobenzoic acid, nitrophenol and nitroanisole are added, an increase in the internal pressure of an electrolytic capacitor using this electrolytic solution can be reduced. The high temperature life characteristics of the electrolytic capacitor are improved.

1-methyl- used in the electrolytic solution of the present invention
3,5-dimethyl-3,5-dimethoxycarbonyl-
As the salt of 1,11-undecanedicarboxylic acid or 7,8-dimethyl-7,8-dimethoxycarbonyl-1,14-tetradecanedicarboxylic acid, an ammonium salt, a quaternary ammonium salt, or an amine salt can be used. As the quaternary ammonium constituting the quaternary ammonium salt, tetraalkylammonium (tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, methyltriethylammonium, dimethyldiethylammonium, etc.), pyridium (1-methylpyridium) , 1-ethylpyridium, 1,3-diethylpyridium, etc.). 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, etc.) and tertiary amines (trimethylamine, triethylamine, tributylamine, 1,8-diazabicyclo (5,4,0) -undecene-7, triethanolamine, etc.).

Further, a salt containing a quaternized cyclic amidinium ion as a cation component can be used. The quaternized cyclic amidinium ion serving as the cation component includes N, N,
The cyclic compound having an N'-substituted amidine group is a cation obtained by quaternizing the cyclic compound. Examples of the cyclic compound having an N, N, N'-substituted amidine group include the following compounds. Imidazole monocyclic compounds (1-methylimidazole, 1-phenylimidazole, 1,2-dimethylimidazole, 1
-Ethyl-2-methylimidazole, 1,2-dimethylimidazole, 1-ethyl-2-methylimidazole,
Imidazole homologs such as 1,2-dimethylimidazole and 1,2,4-trimethylimidazole; oxyalkyl derivatives such as 1-methyl-2-oxymethylimidazole and 1-methyl-2-oxyethylimidazole;
Nitro derivatives such as -methyl-4 (5) -nitroimidazole, amino derivatives such as 1,2-dimethyl-5 (4) -aminoimidazole, etc., benzimidazole compounds (1-methylbenzimidazole, 1-methyl-2) -Benzimidazole, 1-methyl-5 (6) -nitrobenzimidazole, etc.), compounds having a 2-imidazoline ring (1-methylimidazoline, 1,2-dimethylimidazoline, 1,2,4-trimethylimidazoline, 1- Methyl-2-phenylimidazoline, 1-ethyl-2-methyl-imidazoline, 1,4-dimethyl-2-ethylimidazoline, 1-methyl-2-ethoxymethylimidazoline, etc.), a compound having a tetrahydropyrimidine ring (1-methyl -1,4,5,6-tetrahydropyrimidine, 1,2-dimethyl 1,4,5,6-tetrahydropyrimidine, 1,5-diazabicyclo [4,3,0] nonene-5, etc.) and the like.

Of these, ammonium salts are preferred.

The solvent of the electrolytic solution of the present invention is mainly composed of ethylene glycol. In addition, a protic polar solvent, an aprotic solvent, and a mixture thereof can be used. As protic polar solvents, monohydric alcohols (ethanol, propanol, butanol, pentanol, hexanol, cyclobutanol,
Cyclopentanol, cyclohexanol, benzyl alcohol, etc.), polyhydric alcohols and oxyalcohol compounds (propylene glycol, glycerin, methyl cellosolve, ethyl cellosolve, methoxypropylene glycol, dimethoxypropanol, etc.). Examples of aprotic polar solvents include amides (N-methylformamide, N, N─dimethylformamide, N─ethylformamide, N, N─diethylformamide, N─methylacetamide, N, N─dimethylacetamide, N─ethylacetamide, N, N-diethylacetamide, hexamethylphosphoric amide, etc.), lactones (γ-butyrolactone, δ-valerolactone, γ-valerolactone, etc.), sulfolane (3-
Methylsulfolane, 2,4-dimethylsulfolane, etc.),
Cyclic amides (N-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, isobutylene carbonate, etc.), nitriles (acetonitrile, etc.),
Oxide type (dimethyl sulfoxide etc.), 2-imidazolidinone type [1,3-dialkyl-2-imidazolidinone (1,3-dimethyl-2-imidazolidinone, 1,3
-Diethyl-2-imidazolidinone, 1,3-di (n-
Propyl) -2-imidazolidinone, etc., 1,3,4-
Trialkyl-2-imidazolidinone (eg, 1,3,4-trimethyl-2-imidazolidinone)] and the like can be mentioned as representatives.

In the electrolytic capacitor for an electrolytic capacitor according to the present invention, 1-methyl-3,5-dimethyl-3,5-dimethoxycarbonyl-1,11-undecanedicarboxylic acid, 7,8-dimethyl-7,8-dimethoxycarbonyl The content of -1,14-tetradecanedicarboxylic acid or a salt thereof is usually 0.1 to 0.1 based on the weight of the electrolytic solution.
It is 30% by weight, preferably 3 to 20%.

When boric acid is added, the content is usually 1 to 30% by weight, preferably 2 to 7% by weight based on the weight of the electrolytic solution.

When benzoic acid is added, the content is usually 1 to 10% by weight, preferably 2 to 7% by weight.

Further, when the polyhydric alcohol is added, the content is usually 1 to 10% by weight, preferably 2 to 7% by weight.
%.

When the nitro compound is added, the content is usually 0.1 to 5 wt%, preferably 0.5 to 2 wt%.
wt%.

Further, the effect can be improved by adding a nonionic surfactant, colloidal silica or the like to the electrolytic solution for an electrolytic capacitor of the present invention.

Various additives such as an acidic phosphoric acid ester compound can be added for the purpose of reducing leakage current and absorbing hydrogen gas.

[0030]

Embodiments of the present invention will be described below.

Tables 1 to 3 show the composition of the electrolytic solution for the electrolytic capacitor, the spark voltage and the electric conductivity of each embodiment of the present invention. In the electrolyte composition, A is ammonium 1-methyl-3,5-dimethyl-3,5-dimethoxycarbonyl-1,11-undecanedicarboxylate, and B is 7,8-dimethyl-7,8-dimethoxycarbonyl. This represents ammonium -1,14-tetradecanedicarboxylate. The electrolytic solution is composed of a solvent and 1-methyl-
3,5-dimethyl-3,5-dimethoxycarbonyl-
After mixing an acid such as 1,11-undecanedicarboxylic acid, ammonia gas was injected, and the pH was adjusted to prepare the mixture.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

[Table 3]

As apparent from Tables 1 to 3,
In the first to twelfth examples, the electric conductivity is maintained higher and the spark voltage is higher than that of the conventional example. In Examples 3 and 5 in which boric acid was added, the spark voltage was even higher, and in Examples 7 and 10 in which mannite, which is a polyhydric alcohol, was added, the spark voltage was even higher. In Examples 4 and 6 to which benzoic acid was added, the conductivity was high.

Next, the aluminum electrolytic capacitors using the electrolytic solutions of Examples 7 to 12 and the conventional example were each used for 20 times.
Tables 4 and 5 show the results of the life test, which was prepared individually. The rating of the electrolytic capacitor used here is
In (Table 4), it is 450 WV180 μF, and (Table 5)
Then, it is 400 WV 220 μF. Then, under the conditions of 450 V and 400 V, respectively, at 105 ° C., 1
A 000 hour load test was performed.

[0037]

[Table 4]

[0038]

[Table 5]

As is clear from Table 4, the conventional example has a valve open during the test, but the electrolytic capacitors of Examples 7 and 10 to which boric acid of the present invention is added have the capacitance after the test. Both the change and the tan δ change are good, the withstand voltage of the electrolytic capacitor is improved, and the use of 450 V is realized.

As is clear from Table 5, Examples 8, 9, and 1 in which benzoic acid was added, as compared with the conventional example.
In Nos. 1 and 12, tan δ was reduced at the initial stage and after the test, and the capacitance change rate was good.

[0041]

As described above, the electrolytic solution for an electrolytic capacitor of the present invention is prepared by dissolving ethylene glycol in a solvent mainly.
1-methyl-3,5-dimethyl-3,5-dimethoxycarbonyl-1,11-undecanedicarboxylic acid, 7,8
-Dimethyl-7,8-dimethoxycarbonyl-1,14
-A solution in which one or two or more selected from tetradecanedicarboxylic acid or salts thereof are dissolved, and the spark voltage can be improved as compared with a conventional electrolytic solution.

When boric acid is added to the electrolytic solution, the spark voltage is further improved, and the withstand voltage of the electrolytic capacitor using the same is improved. Also, when benzoic acid is added, the conductivity of the electrolytic solution increases and the tan of the electrolytic capacitor increases.
δ is reduced.

Further, when one or more hexites or polyhydric alcohols composed of polyethylene glycol, polyvinyl alcohol, polyoxyethylene glycerin, polyglycerin and glycerin are added, the spark voltage increases. When one or more nitro compounds selected from nitro compounds composed of nitrobenzoic acid, nitrophenol and nitroanisole are added, the increase in the internal pressure of the electrolytic capacitor using this electrolytic solution can be reduced, so that the electrolytic capacitor High temperature life characteristics are improved.

Claims (5)

[Claims] (1) 1-methyl-3,5-dimethyl-3,5-dimethoxycarbonyl-1,11-undecanedicarboxylic acid in a solvent mainly composed of ethylene glycol;
7,8-dimethyl-7,8-dimethoxycarbonyl-
An electrolytic solution for an electrolytic capacitor in which one or two or more selected from 1,14-tetradecanedicarboxylic acid or salts thereof are dissolved. 2. A method according to claim 1, wherein boric acid or a salt thereof is added.
The electrolytic solution for an electrolytic capacitor according to the above. 3. The electrolytic solution for an electrolytic capacitor according to claim 1, wherein benzoic acid or a salt thereof is added. 4. The electrolytic capacitor according to claim 1, further comprising one or more selected from hexites or polyhydric alcohols comprising polyethylene glycol, polyvinyl alcohol, polyoxyethylene glycerin, polyglycerin, and glycerin. Electrolyte. 5. The electrolytic solution for an electrolytic capacitor according to claim 1, further comprising one or more nitro compounds selected from nitrobenzoic acid, nitrophenol and nitroanisole.