JPH0770443B2 - Electrolytic solution for driving electrolytic capacitors - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrolytic solution for driving an electrolytic capacitor, and more specifically to an electrolytic solution for driving an aluminum electrolytic capacitor.

2. Description of the Related Art Heretofore, as an electrolytic solution for driving an electrolytic capacitor of this type, particularly an electrolytic solution for medium and high pressure, an electrolytic solution in which boric acid or ammonium borate is dissolved as an electrolyte in ethylene glycol has been used.

However, in such an electrolytic solution, a large amount of water is generated in the electrolytic solution due to the crystallization water directly released from boric acid and the condensed water generated by the esterification reaction between ethylene glycol and boric acid. The electrolytic capacitors using various kinds of electrolytes showed large changes in characteristics at high temperatures.

In order to solve such a problem, an organic carboxylic acid such as adipic acid or benzoic acid or a salt thereof, which has a slow esterification reaction with ethylene glycol, has been studied as an electrolyte. If
The discharge voltage is low, and there is a drawback that the electrolytic capacitor for medium and high voltage has poor short-circuit property.

Therefore, as disclosed in JP-B-60-176218, there is an example in which polyoxyethylene dicarboxylic acid is added to an electrolytic solution to improve the discharge voltage and to improve the short-circuit property of the electrolytic capacitor.

However, as a problem of such an electrolytic solution, when polyoxyethylene dicarboxylic acid is added to the electrolytic solution,
Polyoxyethylene dicarboxylic acid has a poor solubility, and there is a problem in that it is precipitated particularly at a low temperature of -25 ° C and remarkably lowers the electric conductivity of the electrolytic solution.

The present invention improves the above problems and provides an electrolytic solution capable of improving the short-circuit property without lowering the electric power especially at low temperatures.

Means for Solving the Problems The present invention is an electrolytic solution for driving an electrolytic capacitor, wherein polyglycerol is added to an electrolytic solution containing a solvent and a solute in order to achieve the above object.

The molecular weight of polyglycerin is preferably 300 to 6000, and particularly preferably 300 to 1500. This is 300
If it is less than 1, the effect on the short-circuit property is small, and if it exceeds 1500, the electric conductivity is lowered.

The amount of polyglycerin added is preferably 0.5 to 50 wt%,
Particularly preferred is 0.5 to 20 wt%. This is 0.5wt
This is because if it is less than 20% by weight, there is no effect on the short-circuit property, and if it exceeds 20% by weight, the electrical conductivity is lowered.

As the solvent, amides, lactones, glycols, sulfur compounds and carbonates can be used alone or in combination, and preferable examples of the solvent are propyl carbonate, dimethylformamide, N-methylformamide, γ-butyrolactone. , N-methylpyrrolidone, dimethyl sulfoxide,
Examples thereof include ethylene cyanohydrin, ethylene glycol, ethylene glycol mono or dialkyl ether.

Further, the solute is an organic acid or a salt thereof, preferably azelaic acid, adipic acid, glutaric acid, phthalic acid, maleic acid, benzoic acid, or a salt thereof.

As the above-mentioned acid salt, ammonium acid, amine acid, and quaternary ammonium salt can be used.

Action Since the electrolytic solution of the present invention as described above contains polyglycerin, it is possible to obtain an electrolytic solution capable of improving the short-circuit property without lowering the conductivity particularly at a low temperature.

The reason why the decrease in electric conductivity at low temperature is not observed is that the solubility of polyglycerin is good and the viscosity does not increase due to precipitation.

Example One example according to the present invention will be described below.

Table 1 shows examples of the present invention and conventional electrolytic solution compositions, as well as the electric conductivity at room temperature and the specific electric conductivity at -25 ° C.

As is clear from comparison between the conventional example of Table 1 and the example 1, in the example using polyglycerin, at a low temperature of −25 ° C., about 10% more than the electrolytic solution containing polyoxyethylene dicarboxylic acid was used. It can be seen that the double specific conductivity is high and the decrease in specific conductivity is small.

Further, Table 2 shows the occurrence status of short circuit during aging of the aluminum electrolytic capacitors using the electrolytic solution of Table 1. The aluminum electrolytic capacitor used in the test has a well-known structure and is rated at 200V68 consisting of an anode foil, a separator, and a cathode foil.
A winding unit of 0 μF was impregnated with an electrolytic solution, placed in an aluminum case, and sealed with rubber. The aging was performed by applying a constant voltage of 250 V for 1 hour.

As is clear from Table 1, the aluminum electrolytic capacitor using the electrolytic solution of the present invention does not cause a short circuit during aging and has a great effect of suppressing a short circuit.

The relationship between the specific conductivity and the amount of addition of polyglycerin having a molecular weight of 500 is shown in FIG. 1 when the polyglycerin was added to the electrolytic solution containing ethylene glycol and ammonium adipate. From FIG. 1, it can be seen that when the addition amount exceeds 20 wt%, the specific electric conductivity is drastically reduced, and the addition amount is preferably 20 wt% or less.

In addition, polyglycerin of each molecular weight was added to the electrolytic solution consisting of ethylene glycol and ammonium adipate.
The relation between the specific conductivity and the molecular weight of polyglycerin when 10 wt% is added is shown in FIG. From FIG. 2, it can be seen that when the molecular weight of polyglycerin exceeds 1500, the specific conductivity is rapidly reduced, and the molecular weight is preferably 1500 or less.

EFFECTS OF THE INVENTION As described above, according to the present invention, it is possible to provide a highly reliable capacitor by providing an electrolytic solution having a higher specific electric conductivity than that of a conventional electrolytic solution and excellent in short-circuit property. , Of great industrial value.

[Brief description of drawings]

Fig. 1 is a characteristic diagram showing changes in the addition amount and specific electric conductivity when polyglycerin having a molecular weight of 500 is added to an electrolytic solution containing ethylene glycol and ammonium adipate. Fig. 2 shows ethylene glycol and adipic acid. FIG. 3 is a characteristic diagram showing changes in the addition amount and the specific conductivity when 10 wt% of polyglycerin having various molecular weights is added to an electrolytic solution made of ammonium.

Claims (4)

[Claims] 1. An electrolytic solution for driving an electrolytic capacitor, wherein polyglycerin is added to an electrolytic solution containing a solvent and a solute. 2. The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein an organic acid, an inorganic acid, or a salt thereof is used as the solute. 3. The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein the polyglycerin has a molecular weight of 300 to 1500. 4. The amount of polyglycerin added is 0.5 wt% to 20 wt.
%, The electrolytic solution for driving an electrolytic capacitor according to claim 1.