JPS62271411A - 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 3. 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 are made by winding a foil of a valve metal such as aluminum together with a separator to form a capacitor element.Generally, the capacitor element is impregnated with a driving electrolyte, and the capacitor element is impregnated with a driving electrolyte, and a metal case such as aluminum or a case made of synthetic resin is used. It has a sealed structure in which the capacitor element is housed.

Conventionally, the driving electrolyte for such electrolytic capacitors is
Generally used is an electrolytic solution in which ethylene glycol or the like is used as the main solvent, and a salt that does not corrode metal electrodes, such as an ammonium salt of a saturated organic acid, is dissolved therein as an electrolyte.

(Refer to Japanese Patent Publication No. 5g-13019, etc.) However, the above electrolyte solution does not cause corrosion of the cathode foil or dissociated ammonia (
There was a drawback that characteristics deteriorated significantly at high temperatures due to evaporation of NH3). Among these, the leakage current increases significantly after being left unloaded at high temperatures.

[Problems to be Solved by the Invention] An object of the present invention is to eliminate the above-mentioned drawbacks and to provide an electrolytic capacitor that has excellent high-temperature stability and in particular exhibits a small increase in leakage current even after being left unloaded at high temperatures. do.

[Means for Solving the Problems] The present invention satisfactorily achieves the above objects. The present invention provides an electrolytic capacitor characterized in that a driving electrolyte is used.

Tetrahydrophthalic acid or tetrahydrophthalic anhydride constituting the driving electrolyte.

Δl to Δ4-tetrahydrophthalic acid, i.e. cyclohexene-1,2-dicarboxylic acid, cyclohexene-1,8-dicarboxylic acid, cyclohexene-3,4-dicarboxylic acid and cyclohexene-4,5-dicarboxylic acid or anhydride thereof, respectively All are included. Among them, Δ4−
Tetrahydrophthal (IJ, i.e. cyclohexene-4
, 5-dicarboxylic acid anhydride or its anhydride is preferred because it has low conductivity, and tetrahydrophthalic acid or its anhydride may have an appropriate substituent to the extent that the object of the present invention is not impaired.

Salts of tetrahydrophthalic acid or tetrahydrophthalic anhydride include ammonium salts, amine salts, quaternary ammonium salts, or alkali metal salts. As the amine salt, preferably used are primary to tertiary alkylamine salts having 1 to 4 carbon atoms, especially trimethylamine salt and triethylamine salt.

The quaternary ammonium salt preferably has the general formula R4N
', in which case R is an alkyl group having 1 to 10 carbon atoms, particularly 1 to 3 carbon atoms, which may have an aromatic substituent. Further, as the alkali metal salt, it is preferable to use potassium or sodium salt.

As the polar organic solvent, any polar organic solvent commonly used in electrolytic capacitors can be used. As preferred solvents, amides, lactones, glycols, sulfur compounds and/or carbonates can be used. Preferred specific examples include propyl carbonate, dimethylformamide, N-methylformamide, butyrolactone, N
- Methylpyrrolidone, dimethyl sulfoxide, ethylene cyanohydrin, ethylene glycol, ethylene glycol mono- or dialkyl ethers, and the like.

Although the content of the carboxylic acid quaternary ammonium salt in the polar organic solvent can be selected variously, the resistivity is the lowest in the state of a saturated solution.

Thus, the content (concentration) of the aromatic carboxylic acid quaternary ammonium salt in the electrolytic solution is preferably 1 to 50% by weight, particularly 5 to 40% by weight.

In the present invention, when obtaining a driving electrolyte containing tetrahydrophthalic acid, its anhydride, or its salt, these substances can be added to an organic polar solvent, but precursors that form these substances in the solvent It can also be formed in a solvent by adding it separately to the solvent.

In the present invention, water is not necessarily contained in the electrolytic solution, but it is preferable if water is contained because the specific resistance can be further reduced. However, if the water content is excessively increased, it increases the swelling of the case and the corrosion of the electrode foil, so the water content in the electrolyte is preferably 0.1 to 2.
0% by weight, especially 0.5-15% by weight is preferred. Further, the pH of the electrolytic solution is preferably controlled to 4 to 8, particularly 5 to 7, by adding an appropriate pH adjuster as necessary.

The electrolytic capacitor of the present invention includes various types of capacitors. In a typical embodiment, an aluminum foil anode and an aluminum foil cathode separated by a suitable separator such as paper are used, these are wound into a cylindrical shape to form a capacitor element, and this 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 of the present invention will be described below.

[Example Each example contains tetrahydrophthalic acid shown in Table 1,
The anhydride or its salt was dissolved as a solute in a polar organic solvent, and if necessary, the pH was adjusted by adding a carboxylic acid to prepare an electrolytic solution.

Electrolytic capacitors (100V, 47μF) with aluminum electrodes were manufactured using variously prepared electrolytes, and changes in leakage current were measured in a high temperature no-load test (125°C). The results are shown in Table 1 together with comparative examples. In Table 0, the numbers in parentheses indicate weight %.

Table 1 [Effects of the invention] The electrolytic capacitor of the invention was tested in a high temperature no-load test (125°
An electrolytic capacitor with excellent high temperature stability and small change in leakage current in C) can be obtained.

Claims (3)

[Claims] (1) An electrolytic capacitor characterized in that a driving electrolyte comprising an organic polar solvent in which tetrahydrophthalic acid, tetrahydrophthalic anhydride, or a salt thereof is dissolved is used. (2) The electrolytic capacitor according to claim (1), wherein the salt of tetrahydrophthalic acid or tetrahydrophthalic anhydride is an ammonium salt, an amine salt, or a quaternary ammonium salt. (3) The electrolytic capacitor according to claim (1) or (2), wherein 1 to 50% by weight of tetrahydrophthalic acid, tetrahydrophthalic anhydride, or a salt thereof is dissolved in an organic polar solvent.