JP3391196B2 - Electrolyte for electrolytic capacitors - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic solution for an electrolytic capacitor. 2. Description of the Related Art An electrolytic solution used for an electrolytic capacitor such as an aluminum electrolytic capacitor for medium and high pressures is, for example, a solvent containing polyhydric alcohol such as ethylene glycol as a main component, a boric acid or a higher dibasic acid. Is a component in which sebacic acid, 1,6-decanedicarboxylic acid and the like are dissolved. But,
The practical rated voltage of an electrolytic capacitor using this electrolytic solution is a maximum of about 450 WV. If the rated voltage is higher than this voltage, a withstand voltage failure occurs and reliability is reduced. For this reason,
In order to increase the spark generation voltage and improve the pressure resistance of the electrolytic capacitor, there is an electrolytic solution using a polymer compound such as polyethylene oxide, an ester thereof, or an ethylene / propylene block polymer as an additive. [0003] However, the electrolytic solution using these additives has a drawback that the specific resistance is increased. Therefore, the impedance of the electrolytic capacitor impregnated with the electrolytic solution increases. An object of the present invention is to provide an electrolytic solution for an electrolytic capacitor which can improve the above disadvantages, has a low specific resistance, and can improve the withstand voltage of the electrolytic capacitor. [0005] In order to solve the above-mentioned problems, the present invention provides an electrolytic solution for an electrolytic capacitor containing a polyhydric alcohol as a main solvent. Wherein, in the formula, n is the degree of polymerization, R is one of hydrogen, an alkyl group, and an oxyalkylene group. Poly (1-hydroxymethyl-5-phenyl-3,4-hexanedicarboxylic acid) derivative represented by the following formula: The present invention provides an electrolytic solution for an electrolytic capacitor, characterized in that: The poly (1-hydroxymethyl-
Even if the (5-phenyl-3,4-hexanedicarboxylic acid) derivative is dissolved in the electrolytic solution, the specific resistance does not increase. Then, the electrolytic solution in which this derivative is dissolved forms a film-like complex on the surface of the anode foil constituting the capacitor element of the electrolytic capacitor. For this reason, the withstand voltage of the electrolytic capacitor is improved,
The condition can be maintained for a long time. Further, the deterioration of the oxide film formed on the surface of the anode foil can be suppressed by the film-like complex. Therefore, an increase in the leakage current of the electrolytic capacitor can be suppressed. An embodiment of the present invention will be described below. As the solvent, one or more polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, glycerin, 1,4-butanediol, and 1,3-butanediol are used as a main component. As the solute, at least one kind of boric acid or a salt thereof, an organic acid, an organic acid salt, or the like is used. Organic acids include adipic acid, benzoic acid, azelaic acid, sebacic acid, caprylic acid, 1,6
-Decane dicarboxylic acid, 5,6-decane dicarboxylic acid or the like is used. As the organic acid salt, salts of these organic acids are used. Then, in a solution comprising the above solvent and solute,
Poly (1-hydroxymethyl-5-phenyl-)
Dissolve 3,4-hexanedicarboxylic acid) derivative. The degree of polymerization n of this derivative is preferably in the range of 5 to 5000, particularly preferably about 500. That is, when the polymerization degree n is less than 5, the effect of increasing the spark generation voltage of the electrolytic solution is low. And when the polymerization degree n is larger than 5000,
It is difficult to dissolve in polyhydric alcohols, and because of its high viscosity, the viscosity of the electrolytic solution becomes high, and it becomes difficult to impregnate the capacitor element. The amount of the derivative added is preferably in the range of 0.1 to 40% by weight. That is, if the amount is less than 0.1 wt%, the effect of increasing the spark generation voltage is low. And the addition amount is 40
If the content is more than wt%, the temperature approaches the saturation state, and the low-temperature characteristics of the electrolytic capacitor deteriorate. In addition, mannite, sorbite, or the like is used as an additive. Next, an embodiment of the present invention will be described. The electrolytes of the examples have compositions as shown in Table 1. Similarly, the specific resistance and the spark generation voltage were measured together with the electrolyte solution of the comparative example having no composition containing poly (1-hydroxymethyl-5-phenyl-3,4-hexanedicarboxylic acid) shown in Table 2. Shown in The specific resistance is a temperature measured at 30 ° C., and the spark generation voltage is a value measured at a temperature of 85 ° C. [Table 1] [Table 2] As apparent from Table 1, in Examples 1 to 7, the specific resistance is 1,020 to 1,800 Ω · cm, and the spark generation voltage is 530 to 540 V. Table 2
As is clear from Comparative Examples 1 to 3, Comparative Examples 1 to 3 have a specific resistance of 1
000 ~ 1,780Ωcm and spark generation voltage is 480
It becomes 490V. Therefore, in Examples 1 to 7, the specific resistance is almost the same as in Comparative Examples 1 to 3, but the spark generation voltage is increased about 1.08 to 1.13 times. Further, an electrolytic solution shown in Table 1 is impregnated into a capacitor element to produce an aluminum electrolytic capacitor having a rated voltage of 500 V and 270 μF. The aging process at the time of manufacturing each sample is performed as follows. That is, Example 1 and Comparative Example 1
Is impregnated with a voltage of 510 VDC in an atmosphere at a temperature of 85 ° C. for 8 hours continuously. Then, a voltage of 510 VDC is continuously applied for 8 hours in an atmosphere at a temperature of 105 ° C. to the one impregnated with another electrolytic solution. The number of samples is 20 each. As a result of this aging treatment, all the samples impregnated with the electrolytic solutions of Examples 1 to 7 could be normally aged, and an aluminum electrolytic capacitor having a predetermined rating could be manufactured. However, all of the samples impregnated with the electrolytic solutions of Comparative Examples 1 to 3 were flat, so that an aluminum electrolytic capacitor could not be manufactured. From this, it is clear that the impregnation with the electrolytic solutions of Examples 1 to 7 increases the breakdown voltage of the aluminum electrolytic capacitor as compared with the electrolytic solutions of Comparative Examples 1 to 3. With respect to the manufactured aluminum electrolytic capacitor, initial characteristics and characteristics after a high-temperature load test were measured and the appearance was observed. Table 3 shows the results. The high-temperature load test is performed by leaving each sample in a high-temperature atmosphere and continuously applying a rated voltage of 500 V for 4000 hours. The temperature in the atmosphere was 8 for NO1 impregnated with the electrolytic solution of Example 1.
The temperature of NO2 to NO7 impregnated with 5 ° C and other electrolyte is 105 ° C. Each characteristic is a value at a temperature of 20 ° C. [Table 3] As is clear from Table 3, even after standing for 4000 hours, the capacitance change rate is -0.8 to 0.5.
% And tan δ are as small as 0.060 to 0.098. Moreover, the leakage current is 27.3 to 75% of the initial value.
To decline. Also, there were no abnormalities such as the case expanding or the explosion-proof valve being operated. As described above, according to the present invention, poly (1-hydroxymethyl-5-phenyl-3,4)
-Hexanedicarboxylic acid) derivative,
Thus, an electrolytic solution for an electrolytic capacitor that has a high spark generation voltage, a high withstand voltage of the electrolytic capacitor and a long life can be obtained without an increase in specific resistance.

Claims (1)

(57) [Claim 1] In an electrolytic solution for an electrolytic capacitor using a polyhydric alcohol as a main solvent, a compound represented by the formula: Wherein, in the formula, n is the degree of polymerization, R is one of hydrogen, an alkyl group, and an oxyalkylene group. Poly (1-hydroxymethyl-5-phenyl-3,4-hexanedicarboxylic acid) derivative represented by the following formula: An electrolytic solution for an electrolytic capacitor, characterized in that: