JPH03257810A - Electrolyte for driving electrolytic capacitor - Google Patents

Abstract

PURPOSE:To enable a spark-generating voltage to be increased without increasing a specific resistance and prevent crystal deposition from being produced even at a low temperature by adding a specific nonionic surface-active agent to an electrolyte consisting of a solvent and a dissolved substance. CONSTITUTION:A nonionic surface-active agent which is expressed by an expression I and/or an expression II is added to an electrolyte for driving an electrolytic capacitor where a dissolved substance is dissolved in an organic solvent. In the expression I, R1 is a linear chain or a branch alkyl group with 8 and 18 carbons and l ranges from 4 to 25. In the expression II, R2 is hydrogen or linear chain or a branch alkyl group and is a copolymer with a molecular weight of 400 and 10000 where m:n ratio is 1:9 and 9:1.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to electrolytic capacitors, and particularly to an electrolytic solution for driving an electrolytic capacitor with a high spark voltage.

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

Among the above-mentioned electrolytes, it is possible to increase the spark generation voltage with a boric acid-based electrolyte, but this has the disadvantage that the viscosity and specific resistance of the electrolyte become high.

Furthermore, although the viscosity and specific resistance of organic carboxylic acid electrolytes can be lowered, the spark generation voltage is limited, making it difficult to use them in high-voltage capacitors of 450 WV or higher.

(Problem to be solved by the invention) As a method for increasing the spark generation voltage,
As shown in Japanese Patent Application Laid-Open No. 62-268121, a method to which polyethylene glycol is added is known. However, when the molecular weight is small, the effect of increasing the spark voltage is small, and when the molecular weight is large, crystals tend to precipitate at low temperatures below 0° C., which limits the temperature range in which it can be used.

A method of adding modified silicone oil has also been proposed, as disclosed in Japanese Patent Application Laid-Open No. 64-84617. However, modified silicone oil is very expensive, and it is difficult to completely remove 01- ions during the manufacturing process, which may affect the characteristics of electrolytic capacitors. Furthermore, there is also the problem that modified silicone oil is unstable to acids and alkalis.

The present invention has been made in view of the above points, and its purpose is to increase the spark generation voltage without significantly increasing the resistivity, and to provide a stable electrolytic solution without crystal precipitation even at low temperatures. There is something to do.

(Means for Solving the Problems) The present invention according to the above object is characterized in that a nonionic surfactant is added to an electrolytic solution consisting of a solvent and a solute.

The nonionic surfactant has a general formula of R10(C
zH-0)I H(A) or Rz o +cznao)-(C3H601-H(
In (A), R1 is a straight chain or branched alkyl group having 8 to 18 carbon atoms, or i is a surfactant in the range of 4 to 25; in (B), a surfactant represented by B) can be used; , R2 is hydrogen or a straight chain or branched alkyl group,
A copolymer with a molecular weight of 400 to 10,000 and a man ratio of 1=9 to 9:1 is desirable.

In addition, when the nonionic surfactant is added to the electrolytic solution, it may be a mixture of two or more substances selected from the general formula (A) or (B), or (A) and (B). Also good.

The amount added of the nonionic surfactant is 1 to 30 wt.
% is preferred.

The following substances can be used as nonionic surfactants in the present invention.

-i Those belonging to formula (A) include polyoxyethylene (l = 4 to 23) lauryl ether, polyoxyethylene (l = 7 to 13) cetyl ether, polyoxyethylene (I = 6 to 12) stearyl ether, Polyoxyethylene (ffi=13) oleyl ether, etc.
The alkyl group among these may be branched.

-i Formula (B) includes polyoxyethylene polyoxypropylene glycol (m=160, n=3
0, molecular weight approximately 8,000) and polyoxyethylene polyoxypropylene (m=4, n=30) stearyl ether.

(Function) In the present invention, in the nonionic surfactant belonging to formula (A), R is a hydrophobic group and CzHaO- is a hydrophilic group. Also, for those belonging to formula (B), −C,
H, O- are hydrophobic groups and CzHaO- is a hydrophilic group.

In addition, the anodic oxide film on the electrode foil is generally A.
It is shown as E t Os, but the hydrated oxide is Al2O, ・
, H, and O, a small amount of water is incorporated into the paste coating. In addition, in the case of composite oxide coatings for medium and high pressure applications, boiling water immersion is performed as a pretreatment for chemical formation, so hydrated oxides remain on the surface even after chemical formation.

Therefore, the surface of the electrode foil is hydrophilic, and it is thought that the hydrophilic groups of the surfactant adhere to the surface of the electrode foil, thereby suppressing dielectric breakdown of the oxide film and increasing the spark generation voltage.

In addition, in the nonionic surfactants belonging to the general formula (B), polyoxyethylene (Cz Ha 0-) and polyoxypropylene (-C3H60-) are block-shaped from the viewpoint of hydrophilic and hydrophobic groups, respectively. It is more convenient to exist in

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

Table 1 shows examples of boric acid electrolytes. Conventional Example 1 used glycerin as a subsolvent and had a very high concentration of boric acid, which caused a problem in that the specific resistance was as high as 4°000Ω0. Furthermore, since ammonia water was used, workability during electrolyte preparation was poor. In the example according to the present invention, workability was improved by not using glycerin as a solvent, and ammonium salt of boric acid was used instead of aqueous ammonia, and the spark generation voltage was increased by using a nonionic surfactant. Therefore, compared to conventional example 1, the specific resistance is about 1/4,
It was also possible to increase the spark generation voltage. In addition, Example 1
The oxyethylene group of polyoxyethylene lauryl ether is! =23, and the oxyethylene group of polyoxyethylene higher alcohol ether in Example 2 and Example 4 is! =7, higher alcohol has C of 12 and 1
It is a branched saturated alkyl group mainly composed of 4. Further, in Example 3, POE-POP32 is an oxyethylene/oxypropylene block copolymer having a molecular weight of 3.000 and a ratio of man in formula (B) of 3:2. In Example 4, POE-POP41 is also an oxyethylene oxypropylene block copolymer.
Indicates a molecular weight s, oooO, where an is 4:1.

Regarding the viscosity, Conventional Example 1 has a viscosity of about 10,000 centipoise, whereas Examples 1 to 4 each have a viscosity of about 50 centipoise.
The impregnation workability was significantly improved since the reduction was significantly reduced to 0 centipoise.

Table 2 shows examples using an electrolytic solution using azelaic acid, and the example according to the present invention was able to increase the spark generation voltage compared to conventional example 2.

Regarding electrolytes for medium and high voltages, crystals tend to precipitate at low temperatures, and if crystals precipitate, the low-temperature characteristics of the capacitor will significantly deteriorate, which is not preferable. Therefore, using the electrolytic solution shown in Table 1, a crystal precipitation test was conducted by standing at 40° C. for 124 hours. As a result, crystals precipitated in Conventional Example 1, but no crystals precipitated in Examples 1 to 4.

However, in Example 4, if 5 wt % or more of POE-POP41 is added alone, crystals will precipitate, so by combining it with other surfactants according to the present invention, crystal precipitation can be prevented.

In addition, in the case of surfactants, clouding may occur at high temperatures, so please use the electrolytes listed in Table 1 at 100℃
A test was conducted to see if clouding occurred.

As a result, no clouding occurred in Examples 1, 2 and 4, but clouding occurred only in Example 3. Therefore, POE-POP
It has been found that the copolymers are better used in combination with other surfactants of the invention than alone.

FIG. 1 shows the spark generation voltage when the amount of polyoxyethylene higher alcohol ether added was changed in Example 2 of the present invention. From FIG. 1, it can be seen that the amount added is preferably 1 wt% or more.

For the capacitor test, a 500V 100μF electrolytic capacitor was made using the electrolyte listed in Table 4, and the
A load test was conducted at a temperature of 500 V for 2000 hours. The results are shown in Table 3.

In Comparative Example 4, a large amount of leakage current flowed during the load test due to the low spark voltage, which caused the valve to operate due to gas generation.

Examples 1 to 4 according to the present invention had good characteristics.

Although the present invention has been variously explained above using preferred embodiments, the present invention is not limited to these embodiments, and can be modified in many ways without departing from the spirit of the invention. Of course.

(Effects of the Invention) As described above, according to the present invention, it is possible to provide a stable electrolytic solution that has a high spark voltage and does not cause crystal precipitation even at low temperatures without significantly increasing the specific resistance.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the amount of surfactant added and the spark generation voltage of the present invention.

Claims (4)

[Claims] 1. In an electrolytic solution for driving an electrolytic capacitor in which a solute is dissolved in an organic solvent, it is a nonionic surfactant represented by the general formula R_1-O-{C_2H_4O}_l-H, where R_1 is a linear chain having 8 to 18 carbon atoms. Alternatively, an electrolytic solution for driving an electrolytic capacitor, characterized in that a surfactant having a branched alkyl group and l in the range of 4 to 25 is added. 2. In an electrolytic solution for driving an electrolytic capacitor in which a solute is dissolved in an organic solvent, the general formula R_2-O-{C_2H_4O}_m-{C_3H_6
A nonionic surfactant represented by O}_n-H, where R_2 is hydrogen or a linear or branched alkyl group, and the m:n ratio is 1:9 to 9:1, and has a molecular weight of 400.
An electrolytic solution for driving an electrolytic capacitor, characterized in that a surfactant which is a copolymer of 10,000 to 10,000 is added. 3. In an electrolytic solution for driving an electrolytic capacitor in which a solute is dissolved in an organic solvent, it is a nonionic surfactant represented by the general formula R_1-O-{C_2H_4O}_l-H, where R_1 is a linear chain having 8 to 18 carbon atoms. Or a branched alkyl group, a surfactant in which l is within the range of 4 to 25, and a surfactant with the general formula R_2-O-{C_2H_4O}_m-{C_3H_6
A nonionic surfactant represented by O}_n-H, where R_2 is hydrogen or a linear or branched alkyl group, and the m:n ratio is 1:9 to 9:1, and has a molecular weight of 400.
An electrolytic solution for driving an electrolytic capacitor, characterized in that a surfactant which is a copolymer of 10,000 to 10,000 is added. 4. The amount of the nonionic surfactant added is 1 to 30w.
The electrolytic solution for driving an electrolytic capacitor according to claim 1, 2 or 3, wherein the electrolytic solution is t%.