JP3214072B2 - Electrolyte 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 improvement in an electrolytic solution for an electrolytic capacitor, and more particularly to an electrolytic solution for a high-voltage electrolytic capacitor realizing long-term stabilization of life characteristics at high temperatures.

[0002]

2. Description of the Related Art An electrolytic solution for an electrolytic capacitor uses, as an anode, a valve metal having an insulating oxide film formed on the surface of aluminum or tantalum, and uses the oxide film layer as a dielectric material. An electrolyte for forming an electrolyte layer is brought into contact with the surface of the substrate, and a current collecting electrode usually called a cathode is arranged.

As described above, the electrolytic solution for an electrolytic capacitor directly contacts the dielectric layer and acts as a true cathode. That is, the electrolytic solution is interposed between the dielectric layer of the electrolytic capacitor and the current collecting cathode, and the resistance of the electrolytic solution is inserted in series with the electrolytic capacitor. Therefore, the characteristics of the electrolytic solution are a major factor affecting the characteristics of the electrolytic capacitor.

Conventionally, the electrolytic solution of a high-voltage electrolytic capacitor is:
Electrolyte containing an organic acid such as sebacic acid, azelaic acid, decanedicarboxylic acid as an anion source and ammonium as a cation source is used in a solvent mainly composed of ethylene glycol, but sufficient long life characteristics are obtained. Not been. In addition, a system in which an ammonium salt of boric acid is used as a main solute in a solvent mainly containing ethylene glycol is also used. Use under high temperature conditions was not possible due to the effect of the water formed when the acid ester was formed.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrolytic solution for a high-voltage electrolytic capacitor which has a long life at a high temperature.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the electrolytic solution of a high-voltage electrolytic capacitor, and have found that the electrolytic solution containing boric acid and ammonium as a main solute in a solvent mainly composed of ethylene glycol. The formation of a boric acid ester of boric acid and a polyhydric alcohol and reducing the generated water to 3% or less, it is possible to extend the life of the high-voltage electrolytic capacitor at high temperatures. As a result, the present invention has been completed.

[0007] Accordingly, ethylene glycol vs. 1,3
The weight ratio of butanediol is 6: 4 to 9.5: 0.5
An electrolyte containing boric acid and a polyhydric alcohol as an anion source and ammonium as a cation source in a solvent mainly comprising a mixture of An electrolytic solution for an electrolytic capacitor is provided.

According to the present invention, a polyhydric alcohol and boric acid are added to a mixture of ethylene glycol and 1,3-butanediol, and the mixture is stirred for 100-1 in an open state.
The mixture is heated to 30 ° C., and the heating is continued until the water generated by the formation of the borate ester becomes 3% or less, and then, after cooling, ammonia gas is injected with stirring to perform a neutralization reaction. Furthermore, a desired electrolytic solution can be obtained by adding an appropriate amount of an additive (nitro compound, acidic phosphate ester, etc.) that stabilizes the characteristics of the electrolytic capacitor, if necessary.

The weight ratio of the mixture of ethylene glycol and 1,3-butanediol is preferably from 6: 4 to 9.5: 0.5 for ethylene glycol to 1,3-butanediol.
5

The polyhydric alcohol is preferably ethylene glycol, glycerin, propylene glycol, mannitol, 1,2-butanediol, and pentaerythritol. The addition amount of the polyhydric alcohol is preferably 0.1 to 50 parts by weight based on 100 parts by weight of the mixture of ethylene glycol and 1,3-butanediol.

The amount of boric acid added is preferably 1 to 50 parts by weight based on 100 parts by weight of a mixture of ethylene glycol and 1,3-butanediol.

By using the electrolytic solution according to the present invention, the long-term stability of the high-temperature electrolytic capacitor's long-term life characteristics is improved by about 30% or more as compared with the conventional electrolytic solution.

[0013]

When a boric acid used as a solute is heated with a polyhydric alcohol to form a borate ester in the electrolytic solution of a high-voltage electrolytic capacitor, and the generated water is removed in advance by heating and evaporating, an electrolytic solution is used. In addition, the electrolytic capacitor product can be prevented from being damaged by the moisture in the electrolytic solution and the life characteristics being lowered even at a high temperature, and the life of the electrolytic capacitor product can be extended.

[0014]

The present invention will be described below in detail with reference to examples.

Example 1 and Comparative Example 1 1) Preparation of Electrolyte Solution As Comparative Example 1, a conventionally used electrolyte solution having the following composition was prepared by a conventional method and used.

Composition of electrolyte solution of Comparative Example 1 Component Weight (g) Ethylene glycol 100 Diammonium sebacate 4 Boric acid 5 Mannitol 3 Polyvinyl alcohol 3

The conductivity (30 ° C.) of this electrolyte sample was 1.
It was 00 ms / cm and the water content was 3.70%.

As Example 1, 10 g of mannitol and 1 g of boric acid were mixed in a mixture of 90 g of ethylene glycol and 10 g of 1,3-butanediol in accordance with the following raw material composition of the electrolytic solution.
Add 5 g, and 120-130 in the open state while stirring.
Heated at ° C. Heating was continued until the water generated by the formation of the borate ester was 3% or less. Then, after cooling, 1.4 liters of ammonia gas was injected with stirring to adjust the pH to 6. Further, 2 g of polyoxyethylene glyceryl monostearate was added to prepare and use an electrolytic solution.

Raw Material Composition of Electrolyte Solution of Example 1 Component Weight (g) Ethylene glycol 90 1,3-butanediol 10 Boric acid 15 Mannitol 10 Ammonia gas 1.40 liter Polyoxyethylene 2 glyceryl monostearate (POE = 40) )

The conductivity (30 ° C.) of this electrolyte solution sample is 0.5.
It was 869 ms / cm and the water content was 2.02%.

2) Measurement of product life characteristics The above electrolytic solution sample was impregnated into an element having a product rated voltage of 400 V and a product rated capacity of 22 μF, and an electrolytic capacitor product was prepared by a conventional method.

[0022] Twenty samples of this electrolytic capacitor product were placed at 130 ° C under a condition where a rated voltage of 400 V was applied.
After treating for 000 hours, the product life characteristics were examined.

With respect to the product sample of the treated electrolytic capacitor, capacitance, tangent of loss angle, and leakage current were measured as product life characteristics. The measurement was performed by a conventional method. Table 1 shows the result of calculating the average of the measured values of the 20 processed samples.

[0024]

[Table 1]

Example 1 shows a decrease in capacitance change rate of 53.5% as compared with Comparative Example 1, and an improvement of 29.2% in loss tangent and 22.4% in leakage current. From the observations, it was confirmed that the electrolytic capacitor using the electrolytic solution according to the present invention had long-term stability at high temperatures under high voltage conditions.

Example 2 and Comparative Example 2 1) Preparation of Electrolyte Solution As Comparative Example 2, a conventionally used electrolyte solution having the following composition was prepared by a conventional method and used.

Composition of electrolyte solution of Comparative Example 2 Component Weight (g) Ethylene glycol 100 Ammonium pentaborate 10 Mannitol 10 Polyoxyethylene 2 Glyceryl monostearate (POE = 40)

The conductivity (30 ° C.) of this electrolyte solution sample was 0.1.
It was 818 ms / cm and the water content was 6.59%.

In Example 2, pentaerythritol (10 g) and boric acid (10 g) were added to a mixture of ethylene glycol (85 g) and 1,3-butanediol (15 g) according to the following raw material composition of the electrolytic solution.
Heated at -130 ° C. Heating was continued until the water generated by the formation of the borate ester was 3% or less. Then, after cooling, 0.9 liter of ammonia gas was injected with stirring to adjust the pH to 6. Further, 2 g of polyoxyethylene glyceryl monostearate was added to prepare and use an electrolytic solution.

Electrolyte raw material composition of Example 2 Component Weight (g) Ethylene glycol 85 1,3-butanediol 15 Boric acid 10 Pentaerythritol 10 Ammonia gas 0.9 L Polyoxyethylene 2 glyceryl monostearate (POE = 40)

The conductivity (30 ° C.) of this electrolyte sample was 1.
02 ms / cm, and the water content was 1.83%.

2) Measurement of product life characteristics The above electrolytic solution sample was impregnated into an element having a product rated voltage of 400 V and a product rated capacity of 22 μF to prepare an electrolytic capacitor product.

This electrolytic capacitor product sample: 130 ° C. under the condition that 20 samples were applied to a rated voltage: 400 V
After 2,000 hours of treatment, the product life characteristics were examined.

With respect to the product sample of the treated electrolytic capacitor, capacitance, tangent of loss angle, and leakage current were measured as product life characteristics. The measurement was performed by a conventional method. Table 2 shows the result of calculating the average of the measured values of the treated samples: 20 samples. In addition, as for the product sample of Comparative Example 2 after the treatment at 130 ° C. for 2,000 hours, 20 out of the 20 samples were opened, so that the product life characteristics could not be measured.

[0035]

[Table 2]

The electrolytic solution of Comparative Example 2 had a high water content of 6.59%, and all of the 20 electrolytic capacitor product samples were opened during the treatment at 130 ° C. for 2,000 hours. Showed that I could not stand.

On the other hand, no damage occurred to the 20 electrolytic capacitor product samples of Example 2 using the electrolytic solution according to the present invention, and the samples exhibited resistance to long-term high temperatures. Also, the measured values of the product life characteristics were confirmed to have long-term stability at high temperatures under high voltage conditions, as in the sample of Example 1.

[0038]

According to the electrolytic solution for an electrolytic capacitor of the present invention, a borate ester of boric acid and a polyhydric alcohol is formed in a solvent mainly composed of a mixture of ethylene glycol and 1,3-butanediol. By setting the water content in the electrolytic solution to 3% or less, the life characteristics of the high-voltage electrolytic capacitor at high temperatures are remarkably stabilized over a long period of time, so that its industrial value is high.

Claims (2)

(57) [Claims] 1. A borate ester of boric acid and a polyhydric alcohol in a solvent mainly composed of a mixture having a weight ratio of ethylene glycol to 1,3-butanediol of 6: 4 to 9.5: 0.5. And an ammonium as a cation source, wherein the water content in the electrolyte is 3% or less. 2. The polyhydric alcohol is ethylene glycol,
Glycerin, propylene glycol, mannitol,
The electrolytic solution for an electrolytic capacitor according to claim 1, wherein the electrolytic solution is selected from the group consisting of 1,2-butanediol and pentaerythritol.