JP2003068581A - Electrolyte for driving electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolyte or driving an electrolytic capacitor for which resistivity is low and reliability at a high temperature is improved. SOLUTION: In a solvent for which ethylene glycol and water of 10.0 to 50.0 wt.% are mixed, organic carboxylic acid or its salt and at least one kind of 2-hydroxytropone (tropolone) (chemical formula 1), 3-hydroxytropone, or 4-hydroxytropone are dissolved for 0.01 to 3.0 wt.%. Hydration of the water in the electrolyte and electrode foil is suppressed.

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 driving an electrolytic capacitor (hereinafter referred to as an electrolytic solution), and more particularly to an electrolytic solution having a low specific resistance and improved reliability at high temperatures. is there.

[0002]

2. Description of the Related Art An electrolytic capacitor has a separator interposed between an anode foil whose surface area is enlarged by etching a high-purity aluminum foil and the surface of which is anodized, and an etched cathode foil facing the anode foil. The wound and wound element is impregnated with an electrolytic solution, housed in a case, and sealed with a sealing body. In such an electrolytic capacitor, the characteristics of the electrolytic solution are a major factor in determining the performance of the electrolytic capacitor. In particular, with the recent miniaturization of electrolytic capacitors, electrode foils having a high etching rate have come to be used, and tan δ of capacitors has become high, so that an electrolytic solution having a low specific resistance is always required. Conventionally,
As an electrolytic solution having a low cost and a low specific resistance, a solution in which water is added to ethylene glycol as a main solvent and ammonium salts such as adipic acid and benzoic acid are dissolved as a solute has been used.

[0003]

However, in order to meet the demands of the market, it is necessary to further reduce the specific resistance of the electrolytic solution. For that purpose, the solute concentration must be increased or a large amount of water must be added. I have to. However, when the solute concentration is increased, the solute precipitates, and when a large amount of water is added, the water in the electrolytic solution undergoes a hydration reaction with the electrode foil at high temperature to generate gas, increasing the internal pressure of the electrolytic capacitor. Therefore, it was difficult to use at 105 ° C or higher. Due to the above problems, there has been a demand for an electrolytic solution that can suppress the hydration reaction between water and the electrode foil at high temperature even if a large amount of water is added.

[0004]

In order to solve the above-mentioned problems, the present invention suppresses the hydration reaction between water and electrode foil at high temperature by adding hydroxytropone to the electrolytic solution, so as to obtain a low ratio. It is intended to provide an electrolytic solution having high resistance and high reliability at high temperatures. That is, ethylene glycol and 10.0-5
An organic carboxylic acid or a salt thereof, and at least one of 2-hydroxytropone (Chemical Formula 1), 3-hydroxytropone, and 4-hydroxytropone, in a solvent mixed with 0.0 wt% of water. Is an electrolytic solution for driving an electrolytic capacitor, characterized in that

[0005]

[Chemical 2]

Further, the amount of hydroxytropone is
It is an electrolytic solution for driving an electrolytic capacitor, which is 0.01 to 3.0 wt%.

The above organic carboxylic acids include formic acid, acetic acid, malonic acid, acrylic acid, lactic acid, butyric acid, malic acid, valeric acid, succinic acid, adipic acid, azelaic acid, pimelic acid, suberic acid, sebacic acid, maleic acid. Acid, benzoic acid,
Examples thereof include phthalic acid, salicylic acid and borodisalicylic acid.

Examples of the organic carboxylic acid salts include ammonium salts, primary amine salts such as methylamine, ethylamine and t-butylamine, secondary amine salts such as dimethylamine, ethylmethylamine and diethylamine, trimethylamine and diethylmethyl. Examples thereof include tertiary amine salts such as amine, ethyldimethylamine and triethylamine, and quaternary ammonium salts such as tetramethylammonium, triethylmethylammonium and tetraethylammonium.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In an electrolytic solution containing water, since hydroxytropone is adsorbed on the surface of an electrode foil, the temperature is 105 ° C.
At a high temperature, the hydration reaction between water in the electrolytic solution and the electrode foil is suppressed, and even if the amount of water added increases, gas generation can be suppressed.

[0010]

EXAMPLES The present invention will be specifically described below based on examples. Electrolytic solutions were prepared with the compositions shown in Tables 1 and 2, and the specific resistance at 30 ° C. was measured.

[0011]

[Table 1]

[0012]

[Table 2]

Using the electrolytic solutions shown in Tables 1 and 2, the rated voltage is 16V.
Each of 10 aluminum electrolytic capacitors of −6800 μF (φ16 × 25 mmL) was manufactured, and the capacitance, tan
δ, initial characteristics of leakage current and high temperature load test (105 ° C
Tables 3 and 4 show the results of examining the rate of change in capacitance, tan δ, leakage current, and appearance after applying the rated voltage for 1000 hours.

[0014]

[Table 3]

[0015]

[Table 4]

Conventional Examples 1 and 2, Comparative Examples 1 to 3 and Examples 1 to 1
Comparing with 45, the aluminum electrolytic capacitors according to Examples 1 to 45 to which hydroxytropone was added are 1
Although stable characteristics were exhibited even after 1000 hours at 05 ° C., in the conventional examples 1 and 2, the explosion-proof valve operated in a short time.

The amount of hydroxytropone added is
The range of 0.01 to 3.0 wt% is preferable. 0.01w
If it is less than t%, the effect of suppressing the hydration reaction with the electrode foil cannot be sufficiently obtained, and if it exceeds 3.0 wt%, the capacity change rate and tan δ in the high temperature load test become large, which is not preferable.

The amount of water added to the electrolytic solution is 1
The range of 0.0 to 50.0 wt% is preferable. 10.0w
If it is less than t%, the adsorption of hydroxytropone on the electrode foil is insufficient, and the specific resistance of the electrolytic solution does not become low.
If it exceeds 0.0 wt%, there is a problem that the effect of preventing hydration of the electrode foil by hydroxytropone cannot be sufficiently obtained.

The coordination of the OH group of hydroxytropone is 2-position (2-hydroxytropone), 4 in this embodiment.
The 4-position (4-hydroxytropone) was used, but the 3-position OH group also has the same effect. Further, the effects of the present invention are not limited to the examples, and even if the organic carboxylic acids or salts thereof exemplified above are used alone or as a mixture of a plurality of them, the same effects as the examples are obtained.

[0020]

As described above, in the electrolytic solution of the present invention, by adding hydroxytropone such as tropolone even if a large amount of water is mixed for the purpose of lowering the specific resistance,
Since an electrolytic solution having excellent stability at high temperature and low specific resistance can be obtained, it is possible to improve the characteristics and reliability of the electrolytic capacitor at low cost.

Claims (2)

[Claims] 1. Ethylene glycol and 10.0-50.
In a solvent mixed with 0 wt% of water, organic carboxylic acid or a salt thereof, and 2-hydroxytropone (tropolone)
(Chemical formula 1), 3-hydroxytropone, or at least one of 4-hydroxytropone is dissolved, and an electrolytic solution for driving an electrolytic capacitor. [Chemical 1] 2. The electrolytic solution for driving an electrolytic capacitor, wherein the amount of hydroxytropone according to claim 1 is 0.01 to 3.0 wt%.