JPH09293643A - Electrolytic solution for electrolytic capacitor drive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an electrolytic solution from leaking out from an electrolytic capacitor by a method wherein quaternary ammonium salt is dissolved in a solvent containing an ethylene glycol or γ-butyrolactone as its main component as the main solute of the solvent and a specified amount of 4- hydroxyazobenzene is added to the electrolytic solution. SOLUTION: A solute containing o-tetraethyl phthalate ammonium as its main component is mixed in a solvent containing γ-butyrolactone as its main component and an electrolytic solution is prepared. 0.1 to 3.0wt.% of 4-0 hydroxyazobenzene is added to this electrolytic solution. A capacitor element 5 is impregnated with these electrolytic solutions, the element 5 is housed in an enclosure case 6 made of aluminum, the case 6 is sealed with a butyl rubber sealing material 3, aging is made and an electrolytic capacitor is manufactured. Thereby, as what is adsorbed in the vicinity of the round rod part of a cathode tab terminal 2 out of the 4-hydroxyazobenzene added to the electrolytic solution is bonded with aluminum and chelate insoluble to the solvent is formed, the electrolytic solution can be prevented from leaking out from the electrolytic capacitor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an electrolytic solution for driving an aluminum electrolytic capacitor (hereinafter simply referred to as an electrolytic solution), and more particularly to an electrolytic solution which is stable at high temperatures.

[0002]

2. Description of the Related Art In an aluminum electrolytic capacitor, a capacitor element formed by winding an aluminum anode foil and an aluminum cathode foil via separator paper is impregnated with an electrolytic solution, and the capacitor element is placed in an aluminum outer case together with a rubber sealing body. It has a closed structure by being assembled and the outer case being sealed.

FIG. 2 shows a metal (aluminum) case 6 for accommodating a capacitor element 5 in which an anode foil and a cathode tab terminal 2 to which an anode tab terminal 1 and a cathode tab terminal 2 are attached are wound with a separator sandwiched therebetween. An exploded view in which a rubber sealing body 3 for sealing the opening of the metal case 6 is disassembled is shown.

As the internal electrolytic solution impregnated in the capacitor element, those having high conductivity and those having stability when used at high temperatures are used in order to improve the characteristics of the capacitor.

For example, a solution obtained by dissolving a quaternary ammonium salt of o-phthalic acid or maleic acid as a solute in a solvent such as γ-butyrolactone or ethylene glycol is used as an electrolytic solution.

[0006]

Such an electrolytic solution has a low viscosity and is active, and liquid leakage is likely to occur from a minute gap between the terminal insertion hole of the rubber sealing body and the round bar portion of the tab terminal. It was a thing. When electricity is applied at a higher temperature, the electrolytic solution near the cathode undergoes an electrolytic reaction with the water in the electrolytic solution to locally become a strong alkali, which causes the round bar of the tab terminal to dissolve, albeit slightly. There has been a problem that the liquid leakage further progresses and the alkaline substance causes the inner surface of the terminal insertion hole of the rubber sealing body to be roughened.

[0007]

[Means for Solving the Problems] After considering the above-mentioned problems, an experimenter dissolved a quaternary ammonium salt as a main solute in a solvent containing ethylene glycol or γ-butyrolactone as a main component to prepare 4-hydroxyazobenzene. We have found that when a capacitor element is impregnated with an electrolyte solution containing the product, the leakage of the electrolyte solution from the gap between the terminal insertion hole of the rubber sealing body and the round bar of the tab terminal is extremely reduced. It was That is, the present invention relates to ethylene glycol or γ
-Electrolysis for driving an aluminum electrolytic capacitor, characterized in that a quaternary ammonium salt is dissolved as a main solute in a solvent containing butyrolactone as a main component, and 0.1-3.0% by weight of 4-hydroxyazobenzene is added. It is a liquid.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION A substance leaking from a gap between a terminal insertion hole of a rubber sealing body of a capacitor and a round bar portion of a tab terminal has a strong alkalinity. Although the details of the reaction mechanism are not clear, it is known that a basic substance is attracted to the cathode side due to a polarization reaction inside the capacitor during energization, and a strong alkali is formed in the vicinity of the cathode. Therefore, it is considered that the round bar portion of the tab terminal is melted and the gap between the rubber sealing body and the terminal insertion hole is widened to leak the electrolyte solution. 4-Hydroxyazobenzene is a strong chelating agent, forms an insoluble chelate with aluminum, and has a function of protecting the surface of aluminum particularly under strong alkali. Of the 4-hydroxyazobenzene dissolved in the electrolytic solution, what was adsorbed near the round bar of the cathode tab terminal formed an insoluble chelate, which hindered the dissolution of the round bar by the alkali generated during energization, resulting in electrolysis. Presumed to prevent leakage of liquid.

[0009]

[Example] In a solvent containing γ-butyrolactone as a main component,
A solute containing o-tetraethylammonium phthalate as a main component was mixed to prepare an electrolytic solution. 4-Hydroxyazobenzene was added to this electrolyte at the concentration shown in Table 1. The electrolytic solution was impregnated with a capacitor element, housed in an aluminum outer case, sealed with a butyl rubber sealing body, and aged to have a diameter of 10 mm and a length of 12.5.
mm, a rated voltage of 25 V, and an electrolytic capacitor having a capacitance of 220 μF, 100 electrolytic capacitors were prototyped. [Comparative Example] A product similar to that of the Example was prepared by using the above electrolytic solution without adding 4-hydroxyazobenzene.
A prototype was made and used as a comparative example.

After applying the rated voltage to the above-mentioned capacitor in a high temperature tank at 105 ° C. for 4000 hours, the capacitor was taken out, the electrolyte leaked and the product D. F. (%)investigated. The results are shown in Table 1 and FIG.

[0011]

[Table 1]

As can be seen from the above results, the electrolyte solution containing 4-hydroxyazobenzene suppresses leakage of the electrolyte solution. Further, 4-hydroxyazobenzene is less effective if less than 0.1% by weight, and if added over 3.0% by weight, the specific resistance of the electrolytic solution increases, resulting in a DF of the product.
Since the value increases, the above concentration range is suitable. Further, the additive used must be one that forms an aluminum chelate insoluble in the solvent, and EDTA or the like that forms a soluble chelate is not effective.
In addition, in the above-mentioned Examples, the use of a quaternary ammonium salt as a main solute in which leakage of the electrolyte appears remarkably, but other than that, the tertiary, secondary, and primary ammonium salts also have the same effect. Needless to say, can be obtained.

[0013]

As described above, 4-added to the electrolytic solution
Of the hydroxyazobenzene, what is adsorbed in the vicinity of the round bar of the cathode tab terminal binds with aluminum to form an insoluble chelate in the solvent, so the round bar is protected from the alkali generated at the time of energization. It is possible to prevent leakage of the electrolytic solution from the gap between the terminal round bar portion and the terminal insertion hole of the rubber sealing body.

[Brief description of drawings]

FIG. 1 shows the amount of 4-hydroxyazobenzene added and the liquid leakage occurrence rate (%) and the product D.I. F. It is a figure showing the relationship of (%).

FIG. 2 is an exploded view showing an aluminum electrolytic capacitor by disassembling it into its constituent elements.

[Explanation of symbols]

 1 Anode tab terminal 2 Cathode tab terminal 3 Rubber sealing body 4 Terminal insertion hole 5 Capacitor element 6 Metal case

Claims (4)

[Claims] 1. A quaternary ammonium salt as a main solute is dissolved in a solvent containing ethylene glycol or γ-butyrolactone as a main component, and 0.1 to 3.0% by weight of 4-hydroxyazobenzene is added. An electrolytic solution for driving aluminum electrolytic capacitors. 2. The electrolytic solution for driving an aluminum electrolytic capacitor according to claim 1, wherein the main solute is a tertiary ammonium salt. 3. The electrolytic solution for driving an aluminum electrolytic capacitor according to claim 1, wherein the main solute is a secondary ammonium salt. 4. The electrolytic solution for driving an aluminum electrolytic capacitor according to claim 1, wherein the main solute is a primary ammonium salt.