JPH11297572A - Aluminium electrolytic capacitor and electrolyte for driving aluminum electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to obtain a superior low temp. characteristic with a high withstand voltage, without bulging the case at a high temp. load by using γ-butilolactone as a solvent and 2,2-dimethyl succinic acid or its salt as a solute. SOLUTION: An electrolyte contg. γ-butilolactone as a solvent and 2,2- dimethyl succinic acid or its salt as a solute for driving an aluminium electrolytic capacitor is used. The solvent is pref. mixed with glycols besides γ- butilolactone, and in the case of the mixture of γ-butilolactone with glycols, the mix wt. ratio is about 5.0:5 to 9.5:0.5. The content of 2,2-dimethyl succinic acid or its salt as a solute is pref. 8-30 wt.% and salt of 2,2-dimethyl succinic acid uses an ammonium salt or first-third amine salt of 2,2-dimethyl succinic acid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum electrolytic capacitor using an electrolytic solution for driving an electrolytic capacitor.

[0002]

2. Description of the Related Art An aluminum electrolytic capacitor is used for driving an electrolytic capacitor on a capacitor element formed by winding an aluminum anode foil and an aluminum cathode foil each having an oxide film formed on the surface of an etched aluminum foil by electrolytic oxidation or the like through a separator. The electrolytic solution was impregnated, put into a bottomed cylindrical metal case, and the opening was sealed with an insulating sealing member. The lead wires fixed to the anode foil and the cathode foil were respectively connected to the sealing member. It has a structure drawn out from the through hole.

As an electrolytic solution for driving a low-pressure aluminum electrolytic capacitor (hereinafter referred to as "electrolytic capacitor") (hereinafter referred to as "electrolytic solution"), there is widely used an electrolytic solution containing γ-butyrolactone or ethylene glycol as a main solvent. In this case, a solute containing, for example, triethylammonium citraconic acid as a main solute is used.

[0004]

However, since an electrolytic solution containing triethylammonium citraconic acid as a main solute has a low spark voltage, an aluminum electrolytic capacitor using the electrolytic solution has a low withstand voltage and causes case swelling at a high temperature load. Likely to happen. Further, there is a disadvantage that low-temperature characteristics are poor, such as a large decrease in capacitance at low temperatures.

Further, an aluminum electrolytic capacitor using an electrolytic solution containing 2,3-dimethylsuccinic acid or a salt thereof as a main solute has also been proposed (JP-A-6-29099).
No. 8, JP-A-7-45482) does not solve the above-mentioned disadvantages.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrolytic solution for driving an aluminum electrolytic capacitor which has a high withstand voltage, does not cause case swelling at a high temperature load, and has excellent low temperature characteristics, and an aluminum electrolytic capacitor using the same.

[0007]

The electrolytic solution for driving an aluminum electrolytic capacitor of the present invention is characterized in that γ-butyrolactone is used as a solvent and 2,2-dimethylsuccinic acid or a salt thereof is used as a solute.

Further, the aluminum electrolytic capacitor of the present invention is characterized in that an electrolytic solution for driving an aluminum electrolytic capacitor using γ-butyrolactone as a solvent and 2,2-dimethylsuccinic acid or a salt thereof as a solute is used.

In the present invention, in addition to γ-butyrolactone, the solvent is, for example, ethylene glycol, ethylene glycol monoalkyl ether, ethylene glycol dialkyl ether, propylene glycol, diethylene glycol, diethylene glycol monoalkyl ether, diethylene glycol dialkyl ether, polyethylene glycol, glycerin, etc. May be mixed, and it is particularly preferable to mix ethylene glycol. The solvent to be mixed is not limited to only glycols.

When γ-butyrolactone and glycols are mixed and used, the mixing ratio can be about 5.0 to 5.0 to 9.5 to 0.5 by weight, but 7: 3 is the highest spark voltage. Is preferable because electrical conductivity can be obtained.

On the other hand, in the present invention, the solute contains 2,2-dimethylsuccinic acid or a salt thereof, and the salt of 2,2-dimethylsuccinic acid includes an ammonium salt of 2,2-dimethylsuccinic acid, Tertiary amine salts are exemplified.

Specific examples of the primary amine include monoalkylamines such as methylamine, ethylamine, monoethanolamine, n-propylamine and isopropylamine.

Specific examples of the secondary amine include dimethylamine, diethylamine, diethanolamine, and di-n-amine.
Examples include dialkylamines such as propylamine or diisopropylamine or cyclic amines such as pyrrolidine.

The tertiary amine includes trialkylamines such as trimethylamine, triethylamine, N, N-dimethylethylamine, triethanolamine, tri-n-propylamine and triisopropylamine, and cyclic amines such as N-alkylpyrrolidine. No.

The content of the solute 2,2-dimethylsuccinic acid and its salt is preferably from 8 to 30% by weight. Outside this range, the electric conductivity of the electrolytic solution decreases.

In the present invention, an inorganic acid such as boric acid, phosphoric acid, tungstic acid or heteropoly acid or a salt thereof or a polysaccharide such as mannitol or sorbite is used in order to further improve the spark voltage of the electrolytic solution according to the present invention. 0.1 to 10% by weight, preferably 0.1 to 5% by weight may be added.

Further, in order to improve the tangent (tan δ) of the initial loss angle of the electrolytic capacitor, a ketone, a nitro compound or a salt thereof is added to the electrolytic solution according to the present invention in an amount of 0.1 to 0.1.
10% by weight, preferably 0.1 to 5% by weight, may be added.

The pH of the electrolytic solution according to the present invention is adjusted to 4 to 12, preferably 5 to 7, by adding a desired pH adjuster as required. Further, the presence of water in the electrolytic solution may cause corrosion of the aluminum foil. Therefore, it is preferable that the moisture is not present as much as possible. However, if it is about 5% by weight or less, no particular inconvenience occurs. May be added to increase the

[0019]

EXAMPLES Examples 1 to 3 having the following compositions were used.
8 were prepared, and the following comparative examples 1 and 2 were prepared as comparative examples.

Example 1 N, N-dimethylethylamine 2,2-dimethylsuccinate 20.0% by weight γ-butyrolactone 56.0% by weight Ethylene glycol 24.0% by weight

Example 2 N, N-dimethylethylamine 2,2-dimethylsuccinate 20.0% by weight γ-butyrolactone 80.0% by weight

Example 3 N, N-dimethylethylamine 2,2-dimethylsuccinate 20.0% by weight γ-butyrolactone 40.0% by weight Ethylene glycol 40.0% by weight

Example 4 N, N-dimethylethylamine 2,2-dimethylsuccinate 20.0% by weight γ-butyrolactone 70.0% by weight Ethylene glycol 10.0% by weight

Example 5 N, N-dimethylethylamine 2,2-dimethylsuccinate 10.0% by weight γ-butyrolactone 63.0% by weight Ethylene glycol 27.0% by weight

Example 6 Diethylamine 2,2-dimethylsuccinate 20.0% by weight γ-butyrolactone 56.0% by weight Ethylene glycol 24.0% by weight

Example 7 Pyrrolidine 2,2-dimethylsuccinate 20.0% by weight γ-butyrolactone 56.0% by weight Ethylene glycol 24.0% by weight

Example 8 Ethanolamine 2,2-dimethylsuccinate 20.0% by weight γ-butyrolactone 56.0% by weight Ethylene glycol 24.0% by weight

Comparative Example 1 Triethylamine citraconic acid 20.0% by weight γ-butyrolactone 56.0% by weight Ethylene glycol 24.0% by weight

Comparative Example 2 N, N-dimethylethylamine 2,3-dimethylsuccinate 20.0 wt% γ-butyrolactone 56.0 wt% Ethylene glycol 24.0 wt%

The electric conductivity (μS / cm; at a liquid temperature of 40 ° C.) and the spark voltage (V; at a liquid temperature of 85 ° C.) of the electrolyte solutions of Examples 1 to 8 and Comparative Examples 1 and 2 were measured. Table 1 shows the results.

[0031]

[Table 1]

From these results, it can be seen that the electrolytes of Examples 1 to 8 have higher electric conductivity and higher spark voltage than the electrolytes of Comparative Examples 1 and 2.

Next, the electrolytes of Examples 1 to 8 and Comparative Example 1,
Using the electrolyte solution of No. 2, 2000 electrolytic capacitors each having a rating of 100 V and 47 μF (product size; diameter: 10 mm, shaft length: 16 mm) were manufactured. When the initial characteristics of these electrolytic capacitors were measured, the average values were as shown in Table 2.

[0034]

[Table 2]

A high-temperature load test (temperature: 105 ° C., rated voltage: 100 V) was applied to all of these electrolytic capacitors for 2,000 hours, and the electrolytic capacitors whose metal case bottoms were swollen by 0.2 mm or more were visually confirmed. Table 3 shows the results.

[0036]

[Table 3]

From these results, it can be seen that the electrolytic solutions of Examples 1 to 8 have less case swelling than the electrolytic solutions of Comparative Examples 1 and 2.

The low-temperature characteristics of the electrolytic capacitors using the electrolytic solutions of Example 1 and Comparative Examples 1 and 2 were measured. This test measured the rate of change of capacitance between -55 ° C and 20 ° C. The result is shown in FIG.

FIG. 1 shows that the electrolytic capacitor of Example 1 has a lower rate of change in capacitance at low temperatures than the electrolytic capacitors of Comparative Examples 1 and 2.

[0040]

According to the present invention, it is possible to obtain an electrolytic solution for driving an aluminum electrolytic capacitor and an aluminum electrolytic capacitor having high withstand voltage, no case swelling under high temperature load, and excellent in low temperature characteristics.

[Brief description of the drawings]

FIG. 1 is a diagram showing low-temperature characteristics of an electrolytic capacitor.

Claims (6)

[Claims] (1) a method comprising using γ-butyrolactone as a solvent,
An electrolytic solution for driving an aluminum electrolytic capacitor, comprising dimethylsuccinic acid or a salt thereof as a solute. 2. An electrolytic solution for driving an aluminum electrolytic capacitor, wherein γ-butyrolactone and glycols are mixed to form a solvent, and 2,2-dimethylsuccinic acid or a salt thereof is used as a solute. 3. The electrolytic solution for driving an aluminum electrolytic capacitor according to claim 1, wherein the content of 2,2-dimethylsuccinic acid or a salt thereof is 8 to 30% by weight. 4. A method according to claim 2, wherein γ-butyrolactone is used as a solvent and 2,2-
An aluminum electrolytic capacitor using an electrolytic solution for driving an aluminum electrolytic capacitor using dimethylsuccinic acid or a salt thereof as a solute. 5. An aluminum characterized in that γ-butyrolactone and glycols are mixed and used as a solvent, and an electrolytic solution for driving an aluminum electrolytic capacitor using 2,2-dimethylsuccinic acid or a salt thereof as a solute is used. Electrolytic capacitor. 6. The aluminum electrolytic capacitor according to claim 4, wherein the content of 2,2-dimethylsuccinic acid or a salt thereof, which is a solute of the electrolytic solution for driving an aluminum electrolytic capacitor, is 8 to 30% by weight.