JPS62241321A - Electrolyte 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 [Industrial Field of Application] The present invention relates to an electrolytic solution for an electrolytic capacitor, and particularly to improvement of electrical characteristics such as specific resistance.

[Conventional technology]

In general, electrolytic capacitors are made by winding anode and cathode electrode foils made of a film-forming metal such as aluminum together with a separator to form an electrolytic capacitor element, and after impregnating the inside with an electrolytic solution as a driving solution, It is sealed in a case.

Electrolytic capacitors are broadly classified into low-voltage capacitors and high-voltage capacitors depending on the allowable voltage, and boric acid is used as an electrolyte constituting the electrolytic solution in high-voltage capacitors.

[Problem that the invention seeks to solve]

By the way, in an electrolytic solution using boric acid as an electrolyte, a large amount of condensed water (ester water) is generated by the boric acid itself or the combination of boric acid and a solvent, so when the temperature exceeds 100°C, the internal pressure of the case increases due to vaporization of the condensed water. It is difficult to use the product at temperatures above 100°C, as it causes the explosion-proof valve to open due to an abnormal rise in temperature.In addition, it exhibits a high voltage resistance of 1Ω or more, and its capacitance changes significantly depending on the temperature, resulting in poor temperature characteristics. It has disadvantages such as extremely poor performance.

Therefore, the present invention aims at lowering the specific resistance and improving the temperature characteristics.

[Means for solving problems]

The electrolytic solution for an electrolytic capacitor of the present invention is obtained by dissolving enandic acid or its salt as a solute in a solvent containing ethylene glycol.

[For production]

In the electrolytic solution for electrolytic capacitors of the present invention, when enandic acid or its salt is dissolved in a solvent containing ethylene glycol, the solubility of enandic acid or its salt in the solvent is high, and its degree of ionization is also increased. The resistance is reduced.

Furthermore, since the electrolytic solution for an electrolytic capacitor of the present invention hardly generates condensed water, the usable temperature range can be expanded and the rate of change in capacity due to temperature can be reduced.

When γ-butyrolactone is used as the main solvent, the solubility of enandic acid or its salt in T-butyrolactone is high, and the degree of ionization is high at low temperatures, making it particularly possible to use it at low temperatures. Therefore, the usable temperature range is expanded and the rate of change in capacity due to temperature can be reduced.

〔Example〕

Examples of the present invention will be described below by comparison with conventional examples.

The composition and weight ratio (IVT%) of the most conventional electrolytic solution (hereinafter referred to as conventional example) using boric acid are: ethylene glycol 67-t% boric acid
16.5 wt% ammonium borate
16.5 wt%, and in such an electrolytic solution, specific resistance Rs: 1Ω, withstand voltage VS: 400V
, water content, I (H, O): 26.0%.

On the other hand, the composition and weight ratio of an example of the electrolytic solution for an electrolytic capacitor of the present invention are shown below.

(Example 1) Ethylene glycol 90 wt% Ammonium enandate 10-t% The electrolytic solution of Example 1 contains ethylene glycol as the main solvent, and this electrolytic solution has a specific resistance Rs: 38
0Ω, withstand voltage Vs: 400V, water content (H, O) 7
0.5%, and the specific resistance R is 0.5% compared to the conventional electrolyte.
s was 40% or less, and the water content was extremely small.

(Example 2) T-butyrolactone 78.3 wt% Ethylene glycol 8.7 wt% Enandic acid (linear monocarboxylic acid) 13.0 wt% In this case, for example, a trace amount of triethylamine was added as a neutralizing agent. In addition, tributylamine, trimethylamine, diethylamine, dimethylamine, etc. can be used as other neutralizing agents.

The electrolytic solution of Example 2 contains ethylene glycol using T-butyrolactone as the main solvent, and this electrolytic solution has a specific resistance R3 of 930Ω and a withstand voltage Vs:
400V, contains water! (H2O): 0.5%, the specific resistance Rs was reduced to about 7%, and the water content was also very small compared to the conventional electrolytic solution.

Table 1 shows the initial characteristics of each electrolytic capacitor at room temperature when electrolytic capacitors were made using the electrolytes of the conventional example and Example 1.2.

The electrolytic capacitor used in this experiment has a rated voltage of 400W.
V, rated capacity 110 μF, diameter 161-1, length 301 m in appearance.

Table 1 For each electrolytic capacitor exhibiting the above initial characteristics, Table 2 shows the measured values after 1000 hours had elapsed after a voltage of 400 V was applied between the terminals of each electrolytic capacitor in an atmosphere of 110°C. .

(Margins below this page) Table 2 As is clear from Table 2, the rate of change in capacity and the tangent of the loss angle when the electrolyte of Example 1.2 is used.
The change in δ) is extremely small (
, the leakage current value also hardly changes and is below the initial characteristic. In addition, the occurrence of appearance defects is limited to 1 in the conventional example.
In contrast, in Example 1.2, there were no such cases.

This is because the water content of Example 1.2 is extremely low compared to the conventional example, so no vaporized gas is generated, and no deformation of the external appearance due to an increase in the internal pressure of the case occurs.

Next, the electrical characteristics of the conventional example and Examples 1.2 will be explained.

FIG. 1 shows the rate of change of capacitance versus temperature. 1st
In the figure, A1 represents the characteristics of Example 2, A2 represents the characteristics of Example 2, and B represents the characteristics of the conventional example. was measured. As is clear from this measurement result, the conventional example exhibits a rapid decrease in capacity when the temperature drops below -25°C, whereas the example exhibits a gradual decrease in capacity as the temperature decreases. It can be seen that the capacitance change with respect to temperature is small and the temperature characteristics are good.

FIG. 2 shows changes in the tangent (tan δ) of the loss angle with respect to temperature for the conventional example and Example 1.2.

In Fig. 2, AI shows the characteristics of Example 1, A2 shows the characteristics of Example 2, and B shows the characteristics of the conventional example.
The tangent of the loss angle (tan δ
) shows similar changes in both the conventional example and Example 1.2, but the value in Example 1.2 is lower than that in the conventional example in response to temperature changes. .

FIG. 3 shows the relationship between the specific resistance value and the weight ratio of the solute to the electrolytic solution. As is clear from FIG. 3, as the weight ratio of the solute increases from 5 wt % to 20-t %, the specific resistance value of the electrolyte decreases from about 700 Ω·min to about 200 Ω·min. Therefore, in the electrolytic solution for electrolytic capacitors of this invention, when setting the resistivity value to a value slightly exceeding 200 Ω, the solute weight ratio is
It turns out that it is sufficient to set it to about 0%.

〔Effect of the invention〕

As explained above, according to the present invention, when enandic acid or its salt is dissolved as a solute in a solvent containing ethylene glycol, the solubility of enandic acid or its salt in the solvent increases, and the degree of ionization at low temperatures decreases. This makes it possible to reduce the specific resistance, and since ethylene glycol and T-butyrolactone do not produce large amounts of condensed water as they do when boric acid is used, they can be used in high-temperature ranges. In addition, since the capacitance change in the low temperature range can be reduced, the usable temperature range can be expanded.

[Brief explanation of drawings]

Fig. 1 shows the change in capacitance with respect to temperature of electrolytic capacitors using the electrolytic solution for electrolytic capacitors of the present invention and the conventional electrolytic solution, and Fig. 2 shows the change in capacitance with respect to temperature of electrolytic capacitors using the electrolytic solution for electrolytic capacitors of the present invention and the conventional electrolytic solution. Figure 3 showing the change in the capacitance of the tangent of the loss angle with respect to the temperature of an electrolytic capacitor using a liquid.
The figure is a diagram showing the specific resistance of the electrolytic solution for an electrolytic capacitor of the present invention with respect to the solute weight.

Claims (2)

[Claims] (1) An electrolytic solution for electrolytic capacitors, which is obtained by dissolving enandic acid or its salt as a solute in a solvent containing ethylene glycol. (2) The electrolytic solution for an electrolytic capacitor according to claim 1, wherein the solvent contains γ-butyrolactone.