JPH0817147B2 - Electrolytic solution for driving electrolytic capacitors - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrolytic capacitor, and in particular, has a low specific resistance.
The present invention relates to an electrolytic solution for driving an electrolytic capacitor, which has stable characteristics at high temperatures.

(Prior Art) Generally, as an electrolytic solution for driving an electrolytic capacitor for medium and high voltage (hereinafter referred to as an electrolytic solution), ethylene glycol is used as a main solvent, and boric acid or an organic carboxylic acid and ammonia water or an ammonium salt of the acid is mainly used. The solute is used.

Among the above-mentioned electrolytes, the spark generation voltage can be increased for boric acid-based electrolytes, but there is a drawback that the resistivity is high and the high temperature characteristics are unstable due to the water produced by esterification. .

Further, as the organic carboxylic acid-based electrolyte, fatty acid dicarboxylic acids such as adipic acid, azelaic acid, and decanedicarboxylic acid are widely used, but in order to increase the spark generation voltage, the dissolved amount of the acid is reduced. As a result, deterioration of the electrolytic solution due to esterification or amidation reaction occurs in the high temperature load test, which causes a large increase in loss and the occurrence of corrosion.

(Problems to be Solved by the Invention) Since aromatic carboxylic acids such as benzoic acid are thermally stable, it is known that an increase rate of loss in a high temperature load test is small and an electrolytic solution resistant to corrosion can be obtained. Although it is
Due to its low spark voltage, it could not be used in high voltage capacitors.

The present invention has been made in view of the above points, and an object thereof is to provide an electrolytic solution having a low loss and a small change in characteristics at a high voltage such as a rated voltage of 400 V or more and having good corrosion resistance. It is in.

(Means for Solving the Problems) The present invention according to the above object is characterized in that ethylene glycol is used as a main solvent, benzoic acid or a salt thereof is contained as a solute, and a polyalkylene block copolymer is further added.

It is preferable that the dissolved amount of benzoic acid or its salt is 1 to 15 wt% and the added amount of polyalkylene block copolymer is 1 to 30 wt%.

As the polyalkylene block copolymer, a polyoxyethylene / polyoxypropylene block copolymer having an average molecular weight of 1,000 to 10,000 and an oxyethylene content of 10 to 90% is particularly preferable.

(Function) Since the electrolytic solution using benzoic acid is stable at high temperature, there is little change in the specific resistance when left at high temperature, and therefore the ability to form an oxide film (formability) does not decrease, so it is resistant to corrosion by chlorine ions, etc. The resistance is high.

Since the polyalkylene block copolymer can increase the spark generation voltage by adding it to an electrolytic solution containing ethylene glycol as a main solvent, the spark generation voltage can be increased by combining benzoic acid and the polyalkylene block copolymer. It is possible to obtain an electrolyte that is high and resistant to corrosion.

(Examples) Hereinafter, the present invention will be described in detail based on Examples.

Table 1 shows the composition, specific resistance and spark generation voltage of the electrolytic solution for the rated voltage of 450V. Conventional Example 1 is an example of a boric acid-based electrolytic solution, and Conventional Example 2 is an example of an organic acid-based electrolytic solution. On the other hand, Examples 1 to 3 are examples in which benzoic acid or ammonium benzoate and a polyoxyethylene / polyoxypropylene block copolymer were used to adjust the spark generation voltage to the same level as the conventional example.

In these Examples 1 to 3, the melt mass can be increased as compared with the Conventional Example 2, so that the specific resistance can be lowered. The details of the block copolymer used are shown in Table 3. There are various types of block copolymers other than those shown in Table 3, and it is of course possible to obtain the effect even if one of them is used, but it is also possible to use two or more types in combination depending on the purpose.

Table 2 shows the composition, specific resistance and spark generation voltage of the electrolytic solution for the rated voltage of 400V. As in Table 1, since the amount of dissolution can be increased as compared with Conventional Example 3, the specific resistance can be lowered.

In addition, in Examples 1 to 6, boric acid or an aliphatic carboxylic acid was added in addition to benzoic acid or a salt thereof. Since it takes time, it was added for the purpose of improving the chemical conversion property.

Table 4 shows the results of carrying out a life test at 450 ° C. for 5000 hours on a 450 V 330 μF (φ30 × 50 L) capacitor manufactured using the electrolytic solution shown in Table 1 by applying 450 V. It can be seen that the one using the electrolytic solution according to this example is superior to the conventional example in the tan δ change rate and the leakage current.

Table 5 shows the results of a life test of 400 hours at 105 ° C. for 5000 hours on a 400 V 180 μF (φ30 × 35 L) capacitor manufactured using the electrolytic solution shown in Table 2. Similar to Table 4, the one using the electrolytic solution according to the present example shows superior characteristics to the conventional example in the tan δ change rate and the leakage current.

Next, 10 ppm of chlorine ions were added to the electrolytic solution shown in Table 1 to fabricate a 450V 3.3μF (φ10 × 20L) capacitor, and a load test at 105 ° C and 450V was carried out. It was In Comparative Examples 1 and 2, corrosion occurred in 1000 hours, but in Examples 1 to 3 of the present invention, no abnormality was observed up to 5000 hours.

Table 7 shows the test results at 105 ° C and 400V for the capacitors of 450V 3.3μF (φ10 × 20L) with 10ppm of chlorine ions added to the electrolytic solution shown in Table 2, and the examples of the present invention are still 5000 hours. No abnormalities were seen.

(Effects of the Invention) As described above, according to the present invention, it is possible to provide an electrolytic solution with low loss, little change in characteristics, and good corrosion resistance.

Claims (3)

[Claims] 1. An electrolytic solution for driving an electrolytic capacitor, comprising ethylene glycol as a main solvent, benzoic acid or a salt thereof as a solute, and a polyalkylene block copolymer added thereto. 2. The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein 1 to 15 wt% of benzoic acid or a salt thereof and 1 to 30 wt% of a polyalkylene block copolymer are added. 3. The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein the polyalkylene block copolymer is a polyoxyethylene / polyoxypropylene block copolymer.