JPH04282815A - Electrolyte for electrolytic capacitor - Google Patents

Abstract

PURPOSE:To provide electrolyte for an electrolytic capacitor in which life of the capacitor can be improved without reducing a withstand voltage. CONSTITUTION:Electrolyte for an electrolytic capacitor in which benzoyl compound such as beta-benzoyl acrylate, dibenzoylmethane, benzoylacetone, etc., and condensation polymer of phosphoric acid such as polyphosphoric acid, etc., are dissolved in electrolyte for the capacitor containing polyvalent alcohols such as ethylene glycol, etc., as main solvent and one type or more of organic acids such as butyl octanedioic acid or its salt, boric acid or its salt as solute. The benzoyl compound does not lower its withstand voltage, can effectively absorb hydrogen gas, the polymer of the phosphoric acid can suppress generation of hydrogen, and hence extend a time up to operation of an explosion preventive valve of the capacitor, thereby prolonging its life.

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.

0002

BACKGROUND OF THE INVENTION In recent years, as communication equipment, measuring equipment, etc. have become more sophisticated, there has been a strong demand for electrolytic capacitors incorporated into these equipment to have improved electrical characteristics and a longer lifespan.

[0003] Electrolytic capacitors generally use an electrolytic solution in which a solute such as an organic acid or an inorganic acid is dissolved in a polyhydric alcohol such as ethylene glycol as a solvent. For example, in order to extend the life of electrolytic capacitors, gas absorbents such as aromatic nitro compounds and phosphoric acid, which can suppress gas generation, are added to the electrolytic solution.

0004

However, aromatic nitro compounds have the disadvantage that the withstand voltage of the capacitor decreases when the amount added is large. In addition, aromatic nitro compounds have the property of absorbing generated hydrogen gas and producing amino compounds, but some amino compounds promote hydrogen gas generation and are therefore less effective as gas absorbents. If the content increases, it tends to increase the amount of gas generated, which has the disadvantage of having the opposite effect. In addition, phosphoric acid has the drawback that its effect of suppressing hydrogen gas generation is relatively low, and its effect does not last for a long time.

An object of the present invention is to provide an electrolytic solution for electrolytic capacitors which can improve the above-mentioned drawbacks and improve the life of electrolytic capacitors without reducing the withstand voltage.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention uses a polyhydric alcohol as a main solvent and uses one or more of organic acids or salts thereof, boric acid or salts thereof as a solute. The present invention provides an electrolytic solution for an electrolytic capacitor characterized by containing a benzoyl compound and a condensation polymer of phosphoric acid.

[0007]

[Operation] Usually, aluminum hydroxide exists on the surface of the aluminum cathode foil. However, this aluminum hydroxide is unstable in the electrolytic solution, and therefore the aluminum of the cathode is easily eluted into the electrolytic solution, and hydrogen gas is generated at this time.

The benzoyl compound in the electrolyte of the present invention is
It has the effect of absorbing hydrogen through the reduction reaction of carbonyl groups, suppressing gas generation. Unlike aromatic nitro compounds, this benzoyl compound does not lower its pressure resistance even when its content increases, and does not generate amino compounds, so it does not promote gas generation.

Further, the condensation polymer of phosphoric acid combines with the aluminum of the cathode to form a dense film on the surface of the cathode foil. This film has properties that are more stable against electrolytes than aluminum hydroxide. Therefore, when a condensation polymer of phosphoric acid is dissolved in an electrolytic solution, it is possible to suppress the elution of aluminum from the cathode and the generation of hydrogen gas accompanying it. The effect of this condensation polymer of phosphoric acid in suppressing the generation of hydrogen gas is greater than that of conventional phosphoric acid and lasts for a long time.

0010

EXAMPLES The present invention will be explained below based on examples. Polyhydric alcohols such as ethylene glycol are used as the solvent. As the solute, one or more of organic acids such as butyl octanedioic acid, ammonium salts thereof, boric acid, and ammonium borate are used. As the benzoyl compound, β-benzoyl acrylic acid, dibenzoylmethane, benzoylacetone, benzoylanthranyl, benzoylpyridine, benzophenone, and dibenzoyl having the structural formulas shown in Chemical Formulas 1 to 7 are used.

[0011]

[Chemical formula 1]

0012

[Case 2]

[0013]

[Chemical formula 3]

[0014]

[C4]

[0015]

[C5]

[0016]

[C6]

[0017]

[C7]

[0018] As a conjugate of phosphoric acid, the average molecular weight is 340.
using polyphosphoric acid.

Next, a cathode foil (40 mm x 200 m
m) was immersed and left at high temperature to measure the amount of hydrogen gas generated. The leaving temperature is 130° C. when organic acid ammonium is mainly used as the solute, and 110° C. when ammonium borate is used. Further, the standing time is 500 hours. The amount of hydrogen gas generated was measured in an atmosphere at a temperature of 20°C.

[0020]

[Table 1]

[0021]

[Table 2]

As is clear from Tables 1 and 2, the amount of gas generated was 0.2 ml to 1.3 m in Examples 1 to 15.
1, and in conventional examples 1 to 4, 3.5 ml to 18
．． 5 ml, and the former is reduced to about 1% to 37% of the latter.

[0023] The content of the benzoyl compound is 0.0
A good range is 1wt% to 3.0wt%, and 0.01wt%
If it is less than 3.0 wt %, the hydrogen gas absorption effect is low, and if it exceeds 3.0 wt %, it becomes difficult to dissolve and may precipitate, or the hydrogen gas absorption effect becomes low.

Further, in order to measure the withstand voltage, a capacitor element with a rating of 500 V and 330 μF was impregnated with the electrolytic solution shown in Table 3, and the voltage was increased with a constant current of 6 mA. Then, during this boosting process, the voltage at the point where the voltage significantly decreased was measured as the withstand voltage (device breakdown voltage).

[0025]

[Table 3]

As is clear from Table 3, the element breakdown voltage is
Examples 16 to 20 are 550 V to 570 V, and Conventional Examples 5 to 7 are 490 V to 520 V, with the former being 30 V to 50 V higher than the latter.

[0027]

As described above, according to the present invention, since it contains a benzoyl compound and a condensation polymer of phosphoric acid, the generation of hydrogen gas can be suppressed and the generated hydrogen gas can be effectively absorbed. An electrolytic solution for electrolytic capacitors that can improve the life of electrolytic capacitors without reducing the withstand voltage can be obtained.

Claims (1)

[Claims] Claim 1: An electrolytic solution for an electrolytic capacitor containing a polyhydric alcohol as a main solvent and one or more of organic acids or salts thereof, boric acid or salts thereof as a solute, comprising a benzoyl compound and a degenerate phosphoric acid. An electrolytic solution for an electrolytic capacitor, characterized by containing: