JPS63219119A - 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 Industrial Application The present invention relates to an electrolytic capacitor, and more particularly to an electrolytic capacitor using a novel driving electrolyte.

``Prior art'' Electrolytic capacitors are made by winding an anode foil and a cathode foil made of a valve metal such as aluminum together with a separator to create a capacitor element.Generally, the capacitor element is impregnated with a driving electrolyte, The capacitor element is housed in a case or synthetic resin case and has a sealed structure.

Conventionally, the driving electrolyte for such electrolytic capacitors uses a polar organic solvent such as ethylene glycol as the main solvent, and a salt that does not corrode the metal electrodes, such as an ammonium salt of a saturated organic acid, is dissolved in this. An electrolytic solution is commonly used (Japanese Patent Publication No. 13019/1983). It is also known to use a mixed solvent of γ-butyrolactone and ethylene glycol-1 as a solvent for the electrolyte.

(Japanese Unexamined Patent Publication No. 54-7564).

[Problems to be Solved by the Invention] However, in the electrolytic solution disclosed in Japanese Patent Publication No. 58-13019, in order to lower the tangent of the loss angle (an δ), which is an index of the electrical resistance It is common practice to include water in a wide range of percentages, but in this case, the characteristics of the capacitor deteriorate at high temperatures due to corrosion of the cathode foil and transpiration of dissociated ammonia (NH3), especially the tangent of the loss angle (t). There was a problem that the change in a n δ) was large. In addition, as an electrolytic solution that has high conductivity (low electrical resistance) and is stable at high temperatures, the use of an electrolytic solution in which a quaternary ammonium salt of a saturated chain dicarboxylic acid is dissolved in a polar 41 solvent has been disclosed in JP-A-59-78522. It has been disclosed in the publication No. However, according to the examples in the same publication, the conductivity of this electrolyte is at most 9.4 mS/cm, which is insufficient compared to the currently required C level (12 to 25 mS/cm). There was a problem. moreover,
When γ-butyrolactone and ethylene glycol are used as a mixed solvent as seen in the double series of JP-A-54-7564, the viscosity of ethylene glycol increases at low temperatures, which improves the low humidity characteristics of the capacitor. The problem was that it was small.

The present invention solves these problems and provides an electrolytic capacitor that uses a driving electrolyte that has a low ℃ pile (high conductivity), excellent low-temperature characteristics, and excellent high-temperature stability. The purpose is to provide.

Means for Solving Problem E] In order to solve the above problem, the present invention is characterized in that a driving electrolyte C, which is obtained by dissolving a quaternary ammonium salt of benzoic acid in a polar organic solvent, is used.・Provides Vru electrolytic capacitors.

The quaternary ammonium salt of benzoic acid used in the present invention is preferably a quaternary ammonium having the general formula R,,,N'' having 1 to 10 prime numbers in the argyl group (R), especially 1 to 10. -4 can be suitably used, for example, detramethylammonium benzoate, tetraethylammonium benzoate, tetrapropylammonium benzoate, butrabutylammonium benzoate, etc. Can be done.

In the present invention, it is not preferable to use a quaternary ammonium salt of benzoic acid because, in the case of benzoic acid or other amine salts, the electrolyte has a low conductivity and the tan δ of the product becomes large. It is from.

The content (concentration) of the quaternary ammonium salt of benzoic acid used in the present invention in the electrolyte composition can be selected as appropriate, but considering that the specific resistance is the lowest in the state of a saturated solution, it is 1 to 50%. % is suitable, and in particular, 5 to 40% by weight is suitable in order to obtain good high temperature stability.

In order to solve the above problems, the polar organic solvent used in the present invention includes at least γ-butyrolactone and 3-alkyl-1,3-oxazolidin-2-one (hereinafter referred to as 7').
(referred to as A, O,).

Here, examples of the alkyl group include methyl, ethyl, propyl, etc., among which methyl and ethyl are preferred from the viewpoint of improving low-temperature properties. Further, as the solvent to be mixed, any polar organic solvent commonly used in electrolytic capacitors can be used, and amides, lactones, glycols, sulfur compounds, or carbon salts are preferably used. Specific examples of preferred miscible solvents include 'C is N, N-dimethylformamide, N-methylformamide, β-butyrolactone, γ-valerolactone, N-methylpyro-1,7done, ethylene glycol, ethylene glycol. Examples include monoalkyl ether, ethylene glycol sialyl ether, dimethyl sulfoxide, propylene carbonate, and ethylene cyanohydrin.

In the present invention, to obtain a driving electrolyte containing a quaternary ammonium salt of benzoic acid, the quaternary ammonium salt may be added to a polar organic solvent, or the quaternary ammonium salt of benzoic acid may be added to a polar organic solvent. This quaternary ammonium salt may be produced by reacting substances that can be produced.

In the present invention, it is not absolutely necessary to include water in the electrolyte, but it is effective to lower the specific resistance. However, if the water content is increased beyond a certain limit, it will increase the swelling of the electrolytic capacitor's case due to the generation of internal scum and the corrosion of the electrode foil. In order to achieve this, it is preferable that the water content h' be as small as possible. Therefore, depending on the purpose of use of the C1 electrolytic capacitor, the amount of water contained in the electrolytic solution is preferably in the range of 0.1 to 20% by weight, and 0.5 to [5% by weight.
A range of -7% is more preferred.

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 are separated by a suitable separator such as paper, and these are wound into a cylindrical shape to form a capacitor element, and this element is impregnated with a driving electrolyte. let The amount of N immersed in the electrolytic solution is preferably 50 to 300% by weight based on the separator. The element r- impregnated with the electrolytic solution is housed in a case made of corrosion-resistant metal or synthetic resin, and is sealed.

[Examples] The present invention will be specifically described below based on Examples and Comparative Examples.

A 10% aqueous solution of tetraalkylammonium hydroxide (alkyl group has 1 to 3 carbon atoms) and benzoic acid are mixed to have an equimolar number to dissolve the benzoic acid, and then the evaporator removes the water. A quaternary ammonium salt of benzoic acid was produced at 1°C, and a certain amount was dissolved in a polar organic solvent using these as solutes to prepare the electrolytes of Examples 1 to 8 at °C. The pH of the electrolyte was adjusted to 5-7.

Using these electrolytes, we manufactured an electrolytic capacitor (rated 16V, 1000μF) with aluminum electrodes,
A high-temperature load test (rated voltage applied, 125° C., 1000 hours) was conducted to measure the change in the 1F tangent (tan δ) of the loss angle, and the results are shown in Table 1. In addition, Comparative Example 1 shows the case where a solute other than the quaternary ammonium salt of benzoic acid is used.
-4, electrolytic capacitors were manufactured in the same manner as in the examples, and a high temperature load test was conducted under the same conditions as in the examples.The results are shown in Table 1.

In Table 1, M, 0. and E, 0. is the above-mentioned A, 0. represents the alkyl group of methyl and ethyl, respectively.

Next, Table 2 shows the low temperature characteristics of electrolytic capacitors. The electrolytic capacitors were the same as those described above, and the number of samples was 10 each. The measurement frequency is 120Hz. 80/C20°C in the table is the capacity change rate at 20°C. /Z
20°C indicates the impedance ratio with respect to 20°C.

As can be seen from Table 1, the average value of n-10, in the comparative example, the change in the tangent of the loss angle is large in the high temperature load test, whereas in the example, this change can be kept small. .

Furthermore, as can be seen from Table 2, in the comparative example, the rate of change in △C/C20℃ and Z/Z 20℃ is large in the low-temperature characteristics, whereas in the example, it is possible to reduce this rate of change. It is possible.

[Effects of the Invention As explained in the sidebar, the present invention provides an electrolytic capacitor with excellent low-temperature characteristics and excellent high-temperature stability with small change in tangent of loss angle (tan δ) under high-temperature conditions. can be provided.

Claims (3)

[Claims] (1) A driving electrolyte is used, which is obtained by dissolving a quaternary ammonium salt of benzoic acid in a polar organic solvent consisting of γ-butyrolactone and 3-alkyl-1,3-oxazolidin-2-one. electrolytic capacitor. (2) The electrolytic capacitor according to claim 1, wherein the content of the quaternary ammonium salt of benzoic acid in the driving electrolyte is 1 to 50% by weight. (3) The electrolysis according to claim 1 or 2, wherein the alkyl group (R) of the quaternary ammonium represented by the general formula R_4N^+ has 1 to 10 carbon atoms. capacitor.