JP2836774B2 - Electrolyte for driving 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 driving an aluminum electrolytic capacitor (hereinafter referred to as an electrolytic solution).

[0002]

2. Description of the Related Art An aluminum electrolytic capacitor is used while performing a chemical reaction, but it is required that even if an overvoltage exceeding a rated voltage is applied, a short circuit or ignition due to the short circuit does not occur. To cope with this, as one method, a method using an electrolyte having a withstand voltage greatly exceeding the rated voltage has been considered. However, in general, an increase in the withstand voltage causes an increase in the specific resistance, which may impair the basic characteristics of the capacitor such as ripple absorption, which is not preferable. As another method, it is conceivable to operate the explosion-proof valve due to heat generation without increasing the specific resistance level.However, as soon as the rated temperature or the rated voltage is exceeded, the explosion-proof valve is activated. But not preferred. As means for improving the withstand voltage without increasing the specific resistance level, addition of sulfamic acid, addition of alkylphosphoric acid and the like have been proposed, but the withstand voltage cannot be sufficiently improved. In particular, aluminum electrolytic capacitors used in power electronics applications tend to accommodate a larger capacity in a larger case. The reality is that there is a strong demand for a response.

[0003]

SUMMARY OF THE INVENTION According to the present invention, by adding a specific additive, the withstand voltage can be improved without increasing the specific resistance, and the explosion-proof valve can be formed without short-circuiting even when an overvoltage is applied. An object of the present invention is to provide an electrolytic solution for an aluminum electrolytic capacitor that operates.

[0004]

In order to solve these problems, an electrolytic solution of an electrolytic capacitor using an organic polar solvent as a main solvent and an organic acid or an inorganic acid or a salt thereof as a solute is expressed by the following formula (1) or (2). It is characterized by adding the alkyl ether sulfate shown. The alkyl ether sulfate is a salt of ammonium, sodium, or potassium, and is added in an amount of 0.01 to 0.5% by weight.
An electrolytic solution for driving an electrolytic capacitor, characterized in that:

[0005]

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[0006]

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[0007]

In the present invention, the alkyl ether sulfate is
It is an ester of a sulfuric acid with a polyethylene glycol type nonionic surfactant having ethylene oxide, and is an anionic surfactant. Therefore, it is considered that the nonionic surfactant has both the activity at a low concentration and the activity of an anion at a wide temperature range. Furthermore, it is said that it is easily soluble in polar solvents and has high stability to alkalis and acids. Therefore, since the electrolytic solution is uniformly impregnated in the entire anode foil including the cut portion, the formation of a chemical conversion film in aging is made uniform. As a result, when an overvoltage is applied, current flows particularly in the entire cut portion, and heat is generated. It is considered that the valve operation is caused by the above. Even if aging results in the formation of a high-quality chemical conversion film as a whole, if there is even one place where conversion is insufficient, the current is concentrated especially at that place when overvoltage is applied, so that re-formation is performed. Needless to say, it is thought that the part was destroyed, resulting in a short circuit or a fire caused by the short circuit. Therefore, it is important how uniformly the electrolyte is impregnated in the anode foil. Further, since the anode foil is usually aged in an atmosphere of 65 ° C. to 105 ° C., the surface active action is lost even in this temperature range. It is important not to. The same applies to the case where the film is left unloaded at a high temperature of 105 ° C. where deterioration of the film easily occurs. Judging from the results, it is considered that the alkyl ether sulfate shown in the formula 1 satisfies this point in particular.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a description will be given based on specific embodiments of the present invention. The solvent is mainly a polyhydric alcohol such as ethylene glycol or diethylene glycol, and contains up to 10% by weight of water. As a solute, a higher dibasic acid such as 7-vinyl-9-hexadecene-1,16-dicarboxylic acid and boric acid or its ammonium salt;
Hexit such as sorbit is used. As an additive,
The alkyl ether sulfates according to the invention are used. Phosphoric acid or hypophosphorous acid may be used as another additive. As the alkyl ether sulfate, lauryl alcohol (ethylene oxide 4 mole addition product) sulfate ammonium salt, nonylphenol (ethylene oxide 10 mole addition product) sulfate sodium salt and the like are used.

In the composition table shown in Table 1, in the case of a straight-chain alcohol system, the number of carbon atoms is represented by Cn, and the number of moles of ethylene oxide added is represented by EOm. Similarly, in the case of phenol, the number of carbon atoms of the alkyl group added to phenol is Cj,
The number of moles of ethylene oxide added is represented by EOk. The surfactant is generally a sodium salt, but may be a potassium salt or an ammonium salt. In addition,
In this example, ammonium salts were used in Examples 1 to 6, potassium salts were used in Examples 7 and 11, and sodium salts were used in Examples 8 to 10.

The addition amount of the alkyl ether sulfate is 0.0
A range of 5% to 0.2% by weight is preferred. Although not shown in Table 1, when less than 0.01% by weight, the effect of addition was not observed, and when more than 0.5% by weight, foaming was observed during stirring of the electrolytic solution. When carboxymethyl cellulose or ammonium sulfate was added, the effect was observed when the amount of the alkyl ether sulfate was 0.1% by weight or less.

The carbon number of the alkyl group R _1- of the alkyl ether sulfate represented by the formula 1 is suitably between 8 and 18, and the mole number m of ethylene oxide is suitably 2-6. Similarly, the alkyl group R _2- of the alkyl ether sulfate represented by the formula 2 suitably has 8 to 9 carbon atoms, and the ethylene oxide preferably has 4 to 10 moles m. It is considered that hygroscopicity and ionicity are related.

In the examples, the base composition was as follows. Ethylene glycol 79.39% by weight Diethylene glycol 5% by weight Pure water 3% by weight 7-vinyl-9-hexadecene-1,16-dicarboxylic acid 4% by weight Ammonium azelate 2% by weight Ammonium benzoate 2% by weight Boric acid 3% by weight Mannit 1.5 Wt% Phosphoric acid 0.1 wt% Hypophosphorous acid 0.01 wt%

As is clear from Table 1, the spark generation voltage (also referred to as a scintillation voltage) is 5 to 5 in comparison with the conventional example.
Although the resistance is increased by 15 V, the specific resistance is almost equal.

Using the electrolyte shown in Table 1, a rating of 400
A prototype of an aluminum electrolytic capacitor of V, 330 μF was made, 550 V, 3 A was applied at room temperature, and the operation status of the explosion-proof valve was investigated. An overvoltage test was performed using 50 products as initial products for each type of electrolyte solution, and 50 overvoltage tests were carried out after leaving the batteries unloaded at 105 ° C. for 250 hours. Table 2 shows the results. Table 2
The number of median denominators is the number excluding the number of products in which the short-circuit and the explosion-proof valve did not operate in the 5-minute overvoltage test out of 50 products.

As is clear from Table 2, the NG products are greatly reduced in all the examples, and the effect of the addition of the alkyl ether sulfate is apparent.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

According to the present invention, in order to cope with overvoltage of a product by operating an explosion-proof valve without short-circuiting the product,
Although it is indispensable to study the specification of the capacitor element, as the driving electrolyte for aluminum electrolytic capacitors,
As described above, 0.01% by weight of alkyl ether sulfate was added.
By adding 0.5 to 0.5% by weight, it is possible to greatly reduce the short circuit due to the breakdown of the anode film in the overvoltage application test while keeping the specific resistance level equal, and there is an industrial value.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01G 9/035

Claims (2)

(57) [Claims] 1. An electrolytic solution for driving an electrolytic capacitor comprising an organic polar solvent as a main solvent and an organic acid or an inorganic acid or a salt thereof as a solute, comprising an alkyl ether represented by the formula (1) or (2).
An electrolytic solution for driving an electrolytic capacitor, characterized by adding tersulfate. Embedded image Embedded image 2. The alkyl ether sulfate is an ammonium or sodium or potassium salt,
An electrolytic solution for driving an electrolytic capacitor, wherein the amount of addition is 0.01 to 0.5% by weight.