JPS61184811A - Electrolytic liquid for electrolytic capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to electrolytes for electrolytic capacitors.

According to the present invention, an excellent electrolyte solution for electrolytic capacitors (hereinafter sometimes simply referred to as electrolyte solution) having low specific resistance over a wide operating temperature range can be obtained.

Conventional technology Ethylene glycol (E
It is well known that boric acid, adipic acid, or their salts are dissolved as a solute in a solvent (sometimes abbreviated as C), but the ethylene glycol solvent used in this electrolyte has a high viscosity, and the freezing point is low. The specific resistance of the electrolyte increases significantly at low temperatures due to the relatively high resistance of the electrolyte, resulting in poor low-temperature characteristics of electrolytic capacitors.

In order to improve this drawback, it has been proposed to use N,N-dimethylformamide, which has a lower freezing point than ethylene glycol, as the solvent (see Japanese Patent Publication No. 33-3984). However, N,N-dimethylformamide
The solubility of ionogens such as boric acid, adipic acid, or their ammonium salts is low, making it impossible to reduce the specific resistance of the electrolytic solution.

It has also been proposed to use γ-butyrolactone (sometimes abbreviated as GBL) as a solvent, but the above-mentioned N
, has the same problems as N-dimethylformamide.

Summary of the Invention In order to find a new electrolyte solution that solves the above-mentioned problems, the present inventors conducted extensive studies on electrolytes that are combinations of various solvents and solutes, and completed the present invention.

That is, the present invention provides an electrolytic solution for an electrolytic capacitor, characterized in that ditriethylammonium pyromellitate is dissolved as a solute in a mixed solvent containing γ-butyrolactone and ethylene glycol.

Effects of the Invention The electrolytic solution for electrolytic capacitors of the present invention specifically exhibits a very low specific resistance over a wide temperature range, making it an electrolytic solution for electrolytic capacitors that can be used over a wide temperature range.

Detailed Description of the Invention The electrolytic solution of the present invention uses a mixed solvent containing γ-butyrolactone and ethylene glycol as a solvent, and ditriethylammonium pyromellitate as a solute.

The mixing ratio of γ-butyrolactone and ethylene glycol is preferably used in the range of 95:5 to 50:50 by weight, and the concentration of ditriethylammonium pyromellitate is 1 to 40% by weight, preferably 5 to 30% by weight. Used within the range of

Ditriethylammonium pyromellitate can be obtained by neutralizing pyromellitic acid with triethylamine slightly in excess of 2 equivalents, but the electrolytic solution of the present invention is obtained by adding pyromellitic acid and 2 equivalents of triethylamine to a solvent and dissolving them by heating. It can also be adjusted.

The electrolytic solution of the present invention essentially consists of the above-mentioned mixed solvent of T-butyrolactone and ethylene glycol and ditriethylammonium pyromellitate, and is used for purposes such as preventing galvanic corrosion, reducing leakage current, and absorbing hydrogen gas. Phosphoric acid, hypophosphorous acid,
Co-solutes such as phosphorous acid or its ammonium salts, phosphoric acid derivatives such as amine salts, dinitrobenzene, dinitrophenol, nitrobenzene derivatives such as hyphric acid, etc. can be added.

Further, the specific resistance can be reduced by adding a small amount of water, for example, about 1 to 7 weight water, within a range that does not adversely affect the temperature characteristics.

EXPERIMENTAL EXAMPLES The present invention will be explained in more detail with reference to Examples and Comparative Examples. The ditriethylammonium pyromellitate used in the following experimental series was obtained by adding triethylamine in a slight excess of 2 equivalents of pyromellitic acid. It was obtained by neutralizing and then heating and drying under reduced pressure.

Example 1 A mixed solvent of γ-butyrolactone and ethylene glycol with a weight ratio of 80:20 was added with 10 parts! -% ditriethylammonium throatromellitate was dissolved to prepare an electrolytic solution.

The conductivity of this electrolyte at 25°C (using conductivity tester "CM-6A" manufactured by Toa Denpa Kogyo Co., Ltd.) and sparks under the condition that a constant current of smA/- was applied to a pair of smooth aluminum foils. The generated voltage was measured. Conductivity is 3.80
ms/m, and the spark generation voltage was 120V.

Example 2 Electrolytes were obtained by dissolving 10% by weight of ditriethylammonium pyromellitate in a mixture of r-butyrolactone and ethylene glycol at various weight ratios, and the electrical conductivity of each was measured. The results are shown in Figure 1.

It is clear from Figure 1 that the conductivity of the mixed solvent electrolyte is improved, especially when the mixing ratio of γ-butyrolactone and ethylene glycol is within the range of 95:5 to 50:50. It was observed that the conductivity of the system was significantly higher than that of the single solvent system.

Example 3 In Example 1, the conductivity and spark generation voltage of the electrolytic solution in which 5% by weight of water was added were 4.75 m, respectively.
It was 87cm and 120v.

Comparative Example 1 The conductivity and spark generation voltage of an electrolytic solution in which 10% by weight of ditriethylammonium pyromellitate was dissolved in a γ-butyrolactone solvent were 2.14 ms/y+s, respectively.
, 125v.

Comparative Example 2 The conductivity and spark generation voltage of an electrolytic solution in which 10% by weight of ditriethylammonium pyrromeliftate was dissolved in an ethylene glycol solvent were 0.91 ms/lyn, respectively.
, 150v.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the correlation between the amount of EG in the GBL/EG solvent and the electrical conductivity of an electrolytic solution based on a mixed solvent of γ-butyrolactone and ethylene glycol. Patent applicant Mitsubishi Yuka Co., Ltd. agent Patent attorney Hidetoshi Furukawa Agent Patent attorney Masahisa Hase Figure 1 EG amount in a certain GBL/EG solution (wt '10) Procedural amendment 11F (voluntary) l Case Indication of 1985 Patent Application No. Koda No. 935 3
Title of the invention Electrolyte solution for electrolytic capacitors Relationship to the case of the person making the amendment Patent applicant address No. 2, Marunouchi 2-chome, Chiyoda-ku, Tokyo Name (w
5) Mitsubishi Yuka Co., Ltd. Hiro Agent Address Mitsubishi Yuka Co., Ltd., S-2, 2-chome, Marunouchi, Chiyoda-ku, Tokyo ~ Column for detailed explanation of the invention in the specification Contents of the amendment (1) Page 2 of the specification In the / line, "/~daOX*chi," is corrected to "/% by weight or more up to saturation concentration."

Claims (1)

[Claims] (1) An electrolytic solution for an electrolytic capacitor, characterized in that ditrimethylammonium pyromellitate is dissolved as a solute in a mixed solvent containing γ-butyrolactone and ethylene glycol.