JPH11186107A - Aluminum electrolytic capacitor and electrolytic solution for driving it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve high temperature heat resistance by using an imidazoline salt expressed by a specific formula as a solvent. SOLUTION: An imidazoline salt expressed by the formula is used as a solvent. In the formula, X is aromatic dicarboxylic acid or aliphatic dicarboxylic acid and R is an alkyl group having a carbon number of 1-3. As the aromatic dicarboxylic acid, phthalic acid, isophthalic acid or terephthalic acid is preferable. As the aliphatic dicarboxylic acid, maleic acid, citraconic acid and fumaric acid are preferable. As the electrolytic solution, aprotic solvent is preferably used as solvent. Other solvent may be mixed with the aprotic solvent. In such a case, glycol is preferable as the mixing solvent. The content of imidazoline acid expressed in the formula in the solvent is optimum in the status of saturated solution with the highest electric conductivity.

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 is impregnated, put into a bottomed metal case, the opening is sealed with an insulating sealing member, and the lead leads fixed to the anode foil and the cathode foil are respectively inserted into the through holes of the sealing member. It has a structure that is pulled out from the outside.

An electrolytic solution for driving an aluminum electrolytic capacitor (hereinafter referred to as “electrolytic capacitor”) (hereinafter referred to as “electrolytic solution”) is a substantially dielectric electrode foil (hereinafter referred to as “electrolytic solution”) of an electrolytic capacitor having such a structure. In contact with the oxide film of the anode foil), it functions as a true cathode and has the ability to repair the oxide film. During the energization, the oxide film always undergoes a chemical reaction of regeneration, stabilizing the capacitor characteristics. However, when used for a long period of time or when used after being stored for a long period of time, regeneration of the oxide film becomes insufficient, and the function as a capacitor is reduced.

[0004] Therefore, the ability of the electrolytic solution to repair the oxide film,
This directly affects the characteristics of the electrolytic capacitor itself. Therefore, to obtain a high-performance electrolytic capacitor,
It is indispensable to use an electrolytic solution having an excellent oxide film repairing ability.

[0005] Therefore, as the preferred electrolyte, a solution in which an aprotic solvent is used as a main solvent and a carboxylic acid or a salt thereof is dissolved is often used. In particular, an electrolytic solution in which a quaternary ammonium salt of an aromatic carboxylic acid or a tertiary amine salt is dissolved as a solute in a solvent mainly containing γ-butyrolactone is often used for a low-pressure electrolytic capacitor.

[0006]

However, in recent years, the environmental load of electronic devices has increased. For example, in an electrolytic capacitor disposed in an engine room of an automobile, 13% is required.
Although heat resistance at a high temperature exceeding 0 ° C. is required, conventional electrolytic solutions cannot withstand such a high temperature, and the performance of the capacitor is significantly deteriorated.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and provides an aluminum electrolytic capacitor having high heat resistance at high temperatures and an electrolytic solution for driving the aluminum electrolytic capacitor. That is, the present invention is characterized in that an imidazoline salt represented by the following structural formula [1] is used as a solute.

Embedded image (In the formula, X represents an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid, and R represents an alkyl group having 1 to 3 carbon atoms.)

The aromatic dicarboxylic acid used in the present invention is preferably, but not limited to, phthalic acid, isophthalic acid or terephthalic acid.

The aliphatic dicarboxylic acid used in the present invention is preferably maleic acid, citraconic acid, fumaric acid or malonic acid, but is not limited thereto.

The electrolyte of the present invention preferably uses an aprotic solvent as a solvent.
Butyrolactone, γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-
Lactones such as caprolactone, γ-heptalactone, γ-hydroxy-n-caprylic acid lactone, γ-nonalactone, δ-decalactone, and γ-undecalactone are exemplified, but not limited to lactones.

In the present invention, another solvent may be mixed with the aprotic solvent. In this case, the solvent to be mixed is preferably glycols, and examples thereof include ethylene glycol, ethylene glycol monoalkyl ether, ethylene glycol dialkyl ether, propylene glycol, diethylene glycol, diethylene glycol monoalkyl ether, diethylene glycol dialkyl ether, polyethylene glycol, and glycerin. However, the solvent mixed in the present invention is not limited to only glycols.

In the electrolytic solution according to the present invention, the content of the imidazoline salt represented by the structural formula [1] in the solvent can be variously selected, but the state of a saturated solution is most preferable because it has the highest electric conductivity. That is, the content of the imidazoline salt represented by the structural formula [1] is 1 to 60% by weight, preferably about 10 to 40% by weight in the electrolytic solution.

In the present invention, lactones and glycols can be used alone, however, when they are used in combination, higher electric conductivity is easily obtained. The mixing ratio of lactones and glycols is about 20:80 to 95: 5 by weight.

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 to 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.

Furthermore, 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 of the present invention in an amount of 0.1 to 1%.
0% 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. Also, the presence of water in the electrolyte at high temperatures causes corrosion of the aluminum foil, etc., so it is desirable that it is not present as much as possible. However, if it is about 3% by weight or less, no particular inconvenience occurs.

[0017]

EXAMPLES Examples 1 and 2 have the following compositions.
2 was prepared, and the following comparative examples 1 and 2 were prepared as comparative examples.

Example 1 Monomethylimidazoline phthalate 20.0% by weight γ-butyrolactone 74.5% by weight Ethylene glycol 5.0% by weight Water 0.5% by weight

Example 2 Monoethylimidazoline maleate 20.0% by weight γ-butyrolactone 79.0% by weight p-Nitrobenzoic acid 0.5% by weight Water 0.5% by weight

Comparative Example 1 Triethylamine phthalate 20.0% by weight γ-butyrolactone 74.5% by weight Ethylene glycol 5.0% by weight Water 0.5% by weight

Comparative Example 2 Tetramethylammonium maleate 20.0% by weight γ-butyrolactone 79.0% by weight p-Nitrobenzoic acid 0.5% by weight Water 0.5% by weight

The electric conductivity (μS / cm; at a liquid temperature of 40 ° C.) and the spark voltage (V; at a liquid temperature of 105 ° C.) of the electrolyte solutions of Examples 1 and 2 and Comparative Examples 1 and 2 were measured. Table 1 shows the results.

[0023]

[Table 1]

From these results, the electrolytic solution of Example 1 was superior to the electrolytic solution of Comparative Example 1 and the electrolytic solution of Example 2 was superior to the electrolytic solution of Comparative Example 2 in electric conductivity at a high temperature. It can be seen that the spark voltage is much higher.

Next, the electrolytes of Examples 1 and 2 and Comparative Example 1,
25 electrolytic capacitors rated at 25 V and 330 μF (product size; diameter: 8 mm, shaft length: 20 mm) were manufactured using the electrolyte solution No. 2 and subjected to a load test at a temperature of 135 ° C. for 200 times.
0 hours, the performance of the capacitor before and after the load test (initial capacitance C (μF), capacitance change rate ΔC / C
(%), Tan δ, leakage current LC (μA / 1 min))
Was measured. Table 2 shows the average value. Table 3 shows changes in appearance after the load test.

[0026]

[Table 2]

[0027]

[Table 3]

The electrolytes of Examples 1 and 2 and Comparative Example 1
25 electrolytic capacitors rated at 35 V and 1000 μF (product size; diameter: 35 mm, shaft length: 35 mm) were manufactured using the electrolyte solution No. 2 and subjected to a load test at a temperature of 150 ° C. by 1000.
And the performance of the electrolytic capacitor before and after the load test (initial capacitance C (μF), capacitance change rate ΔC / C
(%), Tan δ, leakage current LC (μA / 1 min))
Was measured. Table 4 shows the results. Table 5 shows the change in appearance after the load test.

[0029]

[Table 4]

[0030]

[Table 5]

From these results, the electrolytic capacitors of Examples 1 and 2 have a smaller capacitance change rate (ΔC / C) even after a long-time load test than the electrolytic capacitors of Comparative Examples 1 and 2. It can be seen that changes in tan δ and leakage current LC are also small. In Comparative Examples 1 and 2, remarkable case swelling occurred after the load test, while Examples 1 and 2 showed no abnormality. This seems to be basically due to the thermal stability of the imidazoline ring. Thus, it can be seen that the electrolytic solution and the electrolytic capacitor of the present invention have remarkably excellent heat resistance.

[0032]

According to the present invention, since the imidazoline salt represented by the structural formula [1] is used as a solute, it has excellent electric conductivity, high spark voltage, little change in capacitance with time, and high temperature heat resistance. An electrolytic solution for driving an aluminum electrolytic capacitor and an aluminum electrolytic capacitor having excellent characteristics can be obtained.

Claims (6)

[Claims] 1. An electrolytic solution for driving an aluminum electrolytic capacitor, comprising an imidazoline salt represented by the following structural formula [1] as a solute. Embedded image (Wherein, X represents an aromatic dicarboxylic acid, and R represents 1 carbon atom)
And represents an alkyl group of 1 to 3. ) 2. An electrolytic solution for driving an aluminum electrolytic capacitor, comprising an imidazoline salt represented by the following structural formula [1] as a solute. Embedded image (Wherein, X represents an aliphatic dicarboxylic acid, and R represents 1 carbon atom)
And represents an alkyl group of 1 to 3. ) 3. The electrolytic solution for driving an aluminum electrolytic capacitor according to claim 1, wherein an aprotic solvent is used as the solvent. 4. An aluminum electrolytic capacitor characterized by using an electrolytic solution for driving an aluminum electrolytic capacitor using an imidazoline salt represented by the following structural formula [1] as a solute. Embedded image (Wherein, X represents an aromatic dicarboxylic acid, and R represents 1 carbon atom)
And represents an alkyl group of 1 to 3. ) 5. An aluminum electrolytic capacitor using an electrolytic solution for driving an aluminum electrolytic capacitor using an imidazoline salt represented by the following structural formula [1] as a solute. Embedded image (Wherein, X represents an aliphatic dicarboxylic acid, and R represents 1 carbon atom)
And represents an alkyl group of 1 to 3. ) 6. The aluminum electrolytic capacitor according to claim 4, wherein an electrolytic solution for driving an aluminum electrolytic capacitor using an aprotic solvent as a solvent is used.