JPS6369214A - Electrolytic capacitor - Google Patents

Abstract

(57) [Abstract] 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 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 then the capacitor element is impregnated with a driving electrolyte and is housed in a metal case such as aluminum or a synthetic resin case. It has a sealed structure in which the capacitor element is housed.

Conventionally, the driving electrolyte for such electrolytic capacitors uses a polar organic solvent such as ethylene glycol as the main solvent.
An electrolytic solution in which a salt, such as an ammonium salt of a saturated organic acid, which does not corrode metal electrodes, is dissolved is generally used (Japanese Patent Publication No. 130.19/1983).

(Problems to be Solved by the Invention) However, in the above electrolytic solution, in order to reduce loss (tan δ), which is an index of electrical resistance,
Although it has been done to contain % water by weight, 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 changes in loss (tan δ). The problem was that it was large. In addition, JP-A-59-78522 discloses the use of an electrolytic solution in which a quaternary ammonium salt of a saturated chain dicarboxylic acid is dissolved in a polar organic solvent as a liquid that has high conductivity (low electrical resistance) and is stable at high temperatures. has been disclosed. However, according to the example, the conductivity of this electrolytic solution is at most 9.4 IaS/cm, which is insufficient compared to the currently required level (12 to 2501 S/CI). Ta.

The present invention solves the above problems and has low electrical resistance.
The purpose of the present invention is to provide an electrolytic capacitor with excellent high-temperature stability.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides an electrolytic solution characterized in that a driving electrolyte prepared by dissolving a quaternary ammonium salt of benzoic acid in a polar organic solvent is used. It provides capacitors.

As the quaternary ammonium salt of benzoic acid used in the present invention, those having a quaternary ammonium represented by the general formula R4N+ and having an alkyl group (R) of 1 to 10 carbon atoms, particularly 1 to 4 carbon atoms, are used. Examples thereof include tetramethylammonium benzoate, tetraethylammonium benzoate, tetrapropylammonium benzoate, and tetrabutylammonium benzoate.

The reason why a quaternary ammonium salt of benzoic acid is used in the present invention is that in the case of other amine salts of benzoic acid, the electrolyte has low conductive dust and the tan δ of the product becomes large, which is undesirable. .

The content (Wolfs degree) of the quaternary ammonium salt of benzoic acid used in the present invention in the electrolytic solution 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.

As the polar organic solvent used in the present invention, any polar organic solvent commonly used in electrolytic capacitors can be used. Among these solvents, amides, lactones, glycols, sulfur compounds, or carbonates can be preferably used. Specific examples of preferred solvents include dimethylformamide, N-methylformamide, γ-butyrolactone, β-butyrolactone, γ-valerolactone, N-methylpyrrolidone, ethylene glycol, ethylene glycol monoalkyl ether, ethylene glycol dialkyl. Examples include ether, dimethyl sulfoxide, propylene carbonate, and ethylene cyanohydrin, and these solvents may be used alone or in appropriate mixtures.

In the present invention, in order 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. This quaternary ammonium salt may be produced by reacting substances that can be produced.

In the present invention, it is not necessary to include water in the electrolytic solution, but it is effective to lower the specific resistance. However, if the water content is increased beyond a certain limit, it will cause swelling of the electrolytic capacitor case and corrosion of the electrode foil, so for long-term use at high temperatures, the water content should be It is preferable to have as few as possible. Therefore, depending on the purpose of use of the capacitor, the water content is preferably in the range of 0.1 to 20%, and 0.5 to 20%.
More preferably 15% by weight.

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.

(Example) Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples.

After mixing 1 mol of a 10% aqueous solution of tetraalkylammonium hydroxide (alkyl group has 1 to 3 carbon atoms) to 2 mol of benzoic acid to dissolve the rest number, water is removed using an evaporator. This was removed to produce a quaternary ammonium salt of benzoic acid, which was used as a solute and a predetermined amount was dissolved in a polar organic solvent to obtain the electrolytes of Examples 1 to 10. The pH of the electrolytic solution was adjusted to 5-7.

Using these electrolytes, we fabricated an electrolytic capacitor (rated 10V, 1000μF) with aluminum electrodes, and conducted a high temperature load test (rated voltage applied, 125℃, 1000 hours) to determine the change in loss (tan δ). was measured and the results are shown in Table 1. In addition, Comparative Examples 1 to 4 are cases in which a solute other than the quaternary ammonium salt of benzoic acid is used.
An electrolytic capacitor was manufactured in the same manner as in the example, and a high temperature load test was conducted under the same conditions as in the example. The results are shown in Table 1.

Next, choose γ-butyrolactone as a polar organic solvent,
Tetramethylammonium benzoate (Experimental Example 1), triethylamine benzoate (Experimental Example 2), tetramethylammonium adipate (Experimental Example 3), and triethylamine maleate (Experimental Example 4) were dissolved in various concentrations as solutes, and the mixture was sealed. After being stored in a container at 125°C for 1000 hours, the specific resistance at 40°C and the spark voltage at 85°C were measured.

The results are shown in graphs 1 to 4 in FIG. 1. In FIG. 1, the results of Experimental Examples 1 to 4 showed that the higher the solute concentration, the smaller the specific resistance and spark voltage. The smaller the specific resistance and the larger the spark voltage, the more preferable the electrolytic solution is, and the one plotted at the upper left in the figure is preferable. Therefore, the electrolytic solution of Experimental Example 1 (corresponding to Example 1) is used as the electrolytic solution of Experimental Examples 2 to 2. 4 (corresponding to Comparative Examples 1 to 3) has superior high-temperature properties.

Figure 2 shows 40% of electrolyte solution containing tetramethylammonium benzoate dissolved in T-butyrolactone at various concentrations.
As is clear from this figure, which shows the value of resistivity at °C, as the concentration of solute increases, the resistivity of the electrolyte decreases, but when the concentration reaches 40-50%, it becomes saturated and precipitates form. Therefore, the resistivity cannot be lowered any further.

Table 1 (Effects of the Invention) As explained above, according to the present invention, an electrolytic capacitor with excellent high-temperature stability and small change in loss (tan δ) under high-temperature conditions can be obtained.

[Brief Description of the Drawings] Fig. 1 is a graph showing the relationship between the specific resistance of the electrolyte and the spark voltage in Experimental Examples 1 to 4, and Fig. 2 is a graph showing the relationship between the quaternary ammonium of benzoic acid used in the present invention. Salt concentration (wt%)
It is a graph which shows the relationship between and specific resistance. Patent/Applicant: Asahi Glass Co., Ltd. Figure 1 0 100 2CO Hihokuko (Q) Figure 2 '8. @4a tetramethishi 7> L Niji v1 (1f
z) Procedural amendment October 6, 1986

Claims (3)

[Claims] (1) An electrolytic capacitor characterized by using a driving electrolyte solution formed by dissolving a quaternary ammonium salt of benzoic acid in a polar organic solvent. (2) The electrolytic capacitor according to claim 1, wherein the content of the quaternary ammonium salt of benzoic acid in the electrolytic solution is 1 to 50% by weight. (3) The electrolytic capacitor 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.