JPH0763047B2 - Electrolytic solution for electrolytic capacitors - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic solution for electrolytic capacitors, and more particularly to an electrolytic solution for electrolytic capacitors having improved flame retardancy for medium and high pressure.

[0002]

2. Description of the Related Art An electrolytic solution used in a conventional medium- and high-voltage aluminum electrolytic capacitor has ethylene glycol as a main solvent and boric acid or ammonium borate dissolved therein.

This ethylene glycol-boric acid type electrolytic solution has a large amount of water due to the condensed water generated by the esterification reaction and has flame retardancy.

[0004]

However, this conventional electrolytic solution has a drawback that it tends to generate a large amount of gas when used at a temperature higher than 100 ° C. Therefore, in the electrolytic capacitor using this electrolytic solution, the explosion-proof valve provided is easy to operate, and becomes defective in a short time.

In order to prevent this gas generation, an electrolytic solution of a component obtained by dissolving an organic acid in ethylene glycol is sometimes used. However, this electrolytic solution has a drawback that it is easily ignited and burned by a spark generated when an overvoltage is applied to the electrolytic capacitor or when the electrolytic capacitor is punctured.

An object of the present invention is to provide an electrolytic solution for an electrolytic capacitor, in which the above drawbacks are improved, gas generation can be suppressed, and combustion is difficult.

[0007]

In order to achieve the above-mentioned object, the present invention provides an electrolytic solution for an electrolytic capacitor in which an organic acid or a salt thereof is dissolved in a solvent containing ethylene glycol as a main component. The present invention provides an electrolytic solution for an electrolytic capacitor, which is characterized by dissolving 1.5 to 10.0 wt% of boric acid ester.

If the amount of polyvinyl alcohol-boric acid ester dissolved is less than 1.5 wt%, the flame retarding effect is reduced. Further, when the amount of dissolution exceeds 10.0 wt%, the electrolytic solution gels, the specific resistance increases, and the low temperature tan δ increases. Therefore, the dissolved amount is 1.5-10.
The range of 0 wt% is preferable.

[0009]

[Function] Since the organic acid or its salt is dissolved in ethylene glycol or the like, gas generation can be suppressed.

Further, in the polyvinyl alcohol-borate ester, the hydroxyl group of polyvinyl alcohol and boric acid react with each other, and boric acid acts as a cross-linking agent, so that it becomes three-dimensional and has a network structure. As a result, the electrolytic solution has a higher boiling point and is less likely to be vaporized, and gas generation is suppressed.

To vaporize and burn a compound which has generated a three-dimensional bond by cross-linking, the bond between the atoms of these compounds must be broken to decompose into a low molecular weight compound. Requires a lot of energy. Therefore, even if a spark or the like occurs, most of the energy is spent for this decomposition, and it is difficult to burn the vaporized substance.

Further, the polyvinyl alcohol-borate ester has the effect of increasing the flame retardancy by facilitating carbonization which decomposes the low molecular weight compound generated by thermal decomposition into carbon and water.

Since it has a three-dimensional network structure, it has little effect of hindering the movement of ions, and the specific resistance hardly increases.

Further, this electrolytic solution having a three-dimensional network structure is held by electrolytic paper even at a high temperature and is highly reliable.

[0015]

EXAMPLES The present invention will be described below based on examples.
Ethylene glycol is used as a main solvent, and ammonium benzoate, ammonium 1.6-decanedicarboxylate, ammonium azelaate, ammonium sebacate, and the like are dissolved therein as solutes. Then, polyvinyl alcohol-borate ester is dissolved in the solution composed of the solvent and the solute in an amount of 1.5 to 10 wt%.

Next, regarding the embodiment of the present invention and the conventional example,
The specific resistance and the spark voltage were measured as the electrolytic solution having the component ratios shown in Table 1.

[0017]

[Table 1]

According to Table 1, comparing Example 1 and Conventional Example 1, Example 2 and Conventional Example 2, and Example 3 and Conventional Example 3 in which the same substance was used as the solvent and the solute, respectively, the specific resistance and sparks were compared. The voltages are almost the same.

The electrolytic solutions of Example 1 and Conventional Example 1 were used as impregnating solutions for electrolytic capacitors rated at 250 V and 10,000 μF, and the electrolytic solutions of Example 2, Example 3, Conventional Example 2 and Conventional Example 3 were used. Used as an impregnating solution for an electrolytic capacitor rated at 400 V and 4,700 μF. Then, each of these electrolytic capacitors was applied with an overvoltage, and the breakdown state was investigated. The test condition is that the voltage of 400V is applied to the electrolytic capacitor with the rated voltage of 250V, and the rated voltage is 400V.
A voltage of 600 V is applied to each of them and a current of 30
A was run.

As a result, the caps of all electrolytic capacitors used in the test were broken. The electrolytic capacitors impregnated with Examples 1 to 3 generated all white smoke, but did not ignite and burn. However, all electrolytic capacitors impregnated with Conventional Example 1 to Conventional Example 3 ignited and burned.

[0021]

As described above, according to the present invention, by dissolving polyvinyl alcohol-borate ester in an amount of 1.5 to 10 wt%, an electrolytic solution for an electrolytic capacitor which can improve flame retardancy and suppress gas generation can be provided. can get.

Claims (1)

[Claims] 1. A polyvinyl alcohol-borate ester is dissolved by 1.5 to 10 wt% in an electrolytic solution for an electrolytic capacitor in which an organic acid or a salt thereof is dissolved in a solvent containing ethylene glycol as a main component. Electrolytic solution for electrolytic capacitors.