JPH01214107A - Electrolytic capacitor - Google Patents

Abstract

PURPOSE:To obtain an electrolytic capacitor having no improper case expansion and high temperature stability without loss of product characteristics by employing nonaqueous electrolyte of an adjusted pH in the capacitor. CONSTITUTION:A driving electrolyte which is dissolved in a sole or mixture solvent of ethylene glycol or gamma-butyrolactone is employed with tetramethylammonium maleate or tetraethylammonium maleate as a solute in an electrolytic capacitor. The electrolyte in the capacitor is adjusted to 7 or more of pH, and water content amount contained in the electrolyte is adjusted. An improper case expansion is eliminated without loss of product characteristics, and the stability at a high temperature is improved in the capacitor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrolytic capacitor using a novel driving electrolyte.

[Prior Art] Electrolytic capacitors, whose capacitor elements are made by winding a foil of a valve metal such as aluminum together with a separator, generally use a driving electrolyte (hereinafter referred to as "electrolyte") in the capacitor element.
It has a sealed structure in which the capacitor element is housed in a metal case such as aluminum or a synthetic resin case.

Conventionally, the electrolytic solution for electrolytic capacitors has generally been made of ethylene glycol, etc., in which salts such as ammonium salts of organic acids, which do not corrode metal electrodes, have been dissolved. There is. (Refer to Japanese Patent Publication No. 58-13019, etc.) In addition, as an electrolytic solution that has high conductivity (low electrical resistance) and is stable at high temperatures, an electrolytic solution in which a quaternary ammonium salt of a saturated chain dicarboxylic acid is dissolved in a polar organic solvent is used. The use of liquid is disclosed in JP-A-59-78522.

In addition, electrolytes with low resistivity have been developed using quaternary ammonium salts of chain unsaturated dicarboxylic acids as electrolytes (JP-A-62-276815; JP-A-62-276815;
(See Publication No. 145713) [Problems to be Solved by the Invention] However, in capacitors as typified by the aforementioned Japanese Patent Publication No. 58-13019, 1 to 30% of water is added to increase the conductivity. , characteristic deterioration at high temperatures due to corrosion of the cathode foil and dissociated ammonia, especially changes in loss (tan δ), and large leakage current after being left unloaded at high temperatures, making it suitable for industrial equipment that requires higher reliability. Its use had the disadvantage of being limited.

Furthermore, the capacitor as typified by the above-mentioned Japanese Patent Application Laid-open No. 59-78522 has the drawback that it is insufficient in view of the current requirements.

Furthermore, when a quaternary ammonium salt of a chain unsaturated dicarboxylic acid is used as an electrolyte, there is an inconvenient drawback in that the case bulges due to gas generation due to decomposition of the electrolytic solution.

[Means for Solving the Problems] The present inventors have conducted various research and examinations with the aim of eliminating the above-mentioned drawbacks and finding a non-aqueous electrolytic capacitor that does not cause case bulge or impair product characteristics. PH of
It has been found that the above objective can be achieved by keeping the value within a specific range.

Thus, the present invention provides an electrolytic capacitor using a driving electrolyte in which tetramethylammonium maleate or tetraethylammonium maleate is dissolved in a single or mixed solvent of ethylene glycol or γ-butyrolactone as a solute. The gist of the present invention is an electrolytic capacitor characterized in that the pH of the electrolyte in the capacitor is 7 or more.

In the present invention, as the polar organic solvent contained in the driving electrolyte, γ-butyrolactone or ethylene glycol can be used alone or as a mixed solvent. The mixing ratio of the mixed solvent can be set arbitrarily, but it is preferable that the amount of γ-butyrolactone is large because the conductivity can be increased.The preferred mixing ratio is γ-butyrolactone/ethylene glycol ratio of 80/20 to 9515. It is.

The content of the above-mentioned solute in the solvent can be selected in various ways, but preferably 5 to 40% by weight, especially 10 to 30% by weight in the electrolytic solution improves the corrosion resistance and high frequency characteristics (impedance) of the electrolytic capacitor. preferred in terms of

Furthermore, in the present invention, it is preferable that the amount of water contained in the electrolytic solution in the electrolytic capacitor (hereinafter referred to as a product) is small from the viewpoint of preventing property deterioration. If it exceeds this level, the tanδ change will increase, which is undesirable.The reason why the amount of moisture contained in the electrolyte in the product increases is due to moisture in the raw material capacitor element (mainly the separator) and moisture absorption during the product manufacturing process. Approximately 0. Since it has been found that the water content increases by 6%, it is preferable that the electrolytic solution (electrolytic solution for impregnation) with which the product is impregnated has a water content of usually less than 1%.

In the present invention, the pH of the electrolytic solution can be adjusted within a specific range by suitably mixing tetramethylammonium maleate or tetraethylammonium maleate and maleic acid in a solid state or dissolved in a solvent. It is. Thus, the preferred range is 7 or more, especially 8-12.

A typical embodiment of the electrolytic capacitor of the present invention includes an aluminum foil anode and an aluminum foil cathode separated by an appropriate separator such as paper, which are wound into a cylindrical shape to form a capacitor element. The element is impregnated with a driving electrolyte. The amount of electrolytic solution impregnated is preferably 50 to 300% by weight based on the separator. The element impregnated with the electrolytic solution is housed in a case made of corrosion-resistant metal, synthetic resin, or the like, and has a sealed structure. Examples and comparative examples of the present invention will be described below.

[Examples and Comparative Examples Examples 1 to 7. Comparative Examples 1 and 2 Each Example and Comparative Example were prepared by the method shown below. However, the preparation method shown below is not particularly limited to this.

Tetramethylammonium maleate salt or tetraethylammonium maleate salt is prepared by mixing and dissolving aqueous tetramethylammonium hydroxide solution (15% aqueous solution) or aqueous tetraethylammonium hydroxide solution (40% aqueous solution) and maleic acid at a molar ratio of 50:51. The water was removed using an evaporator to obtain a solid salt, which was then used. Dissolve the above salt as a solute in a polar organic solvent,
Furthermore, adjust the pH by appropriately mixing and dissolving maleic acid.
This was used as the electrolytic solution used in Examples and Comparative Examples.

Electrolytic capacitors (rated 6.3V-15000μF) with aluminum electrodes were manufactured using variously prepared electrolytes, and the case swelling and tan δ (25°C, 120Hz) changes in high-temperature load tests (110°C) were measured. was measured. The results are shown in Table 1.

(This page, blank space below) [Effects of the Invention] As shown above, according to the present invention, by using a non-aqueous electrolyte with adjusted pH, the product can be manufactured without deteriorating the product characteristics and without any bulging defects. An electrolytic capacitor with excellent high temperature stability can be obtained.

Agent (patent attorney) −’lξRestraint

Claims (1)

[Claims] (1) An electrolytic capacitor using a driving electrolyte in which tetramethylammonium maleate or tetraethylammonium maleate is dissolved in a single or mixed solvent of ethylene glycol or γ-butyrolactone as a solute; An electrolytic capacitor characterized in that the pH of the electrolyte is 7 or more.