JPH0325005B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an electrolytic solution for driving an electrolytic capacitor, and by significantly lowering the specific resistance of the electrolytic solution, the tangent of the loss angle and high frequency characteristics of the electrolytic capacitor are improved. The present invention provides an electrolytic capacitor that has a long life and high reliability at high temperatures and can suppress changes in capacitance and increases in leakage current. [Prior Art and Problems] Conventionally, so-called ethylene glycol/boric acid ester-based electrolytes have been used as electrolytes for driving medium-high voltage aluminum electrolytic capacitors. When this type of electrolyte is heated, the esterification reaction between ethylene glycol and boric acid progresses, and water is generated at this time.This water reacts with the aluminum foil that is the material of the capacitor element in the electrolytic capacitor. Electrolytic capacitors using this electrolyte could not be used for higher temperature purposes because it would dissolve and generate hydrogen gas, causing an increase in the internal pressure of the capacitor. In addition, in order to solve the above-mentioned problem, an electrolytic solution of the same type that promotes esterification and removes the produced water has been proposed, but although the reaction with water is suppressed, the viscosity of the electrolytic solution increases. The electrolytic capacitor using this electrolyte has a significantly increased resistivity, and the loss angle tangent and impedance at high frequencies have significantly increased, making it impossible to meet the demands for high characteristics. For these reasons, electrolytic capacitors for high temperatures do not use ethylene glycol/boric acid ester electrolytes, but rather organic acid electrolytes containing relatively large molecular weight organic acids or their salts as solutes. It is being considered. Dibasic acids with a total carbon number of 16 to 22 and side chains (JP-A-Show
No. 58-27320 "Electrolytic Solution for Driving Electrolytic Capacitors") is well known, but in electrolytic capacitors using such an electrolytic solution containing a dibasic acid, the solute itself reacts with the aluminum foil forming the capacitor element. The initial capacitance is low due to complex formation, and in high-temperature load tests and high-temperature load tests, an extreme decrease in capacitance and a significant increase in leakage current are observed. It was something I couldn't do. [Improvements and Summary of the Invention] However, the present invention can eliminate the above-mentioned drawbacks, and specifically, by using 1,10-decanedicarboxylic acid or a salt thereof as an additive, By preventing the formation of complexes between the main solute, a dibasic acid with side chains, and aluminum foil, it suppresses changes in capacitance and increases in leakage current of electrolytic capacitors, and further lowers the specific resistance of the electrolyte, reducing the loss angle. By reducing the tangent of and impedance at high frequencies, we can provide electrolytic capacitors with higher performance and reliability. [Example] Next, a dibasic acid having a vinyl group in the side chain having a total number of carbon atoms of 16 to 20, such as 6-vinyl-1,12-dodecanedicarboxylic acid or a salt thereof or 6-vinyl-9-hexadecene -1,16-dicarboxylic acid dissolved in ethylene glycol electrolyte
Examples of the electrolytic solution according to the present invention in which -decanedicarboxylic acid or a salt thereof is added are shown in Table 1 together with conventional examples. The electrolyte composition is wt%, and the specific resistance (Ω cm) is at a liquid temperature of 20°C. Also, the spark voltage is at 85°C. Here, the structural formula of 6-vinyl-1,12-dodecanedicarboxylic acid is the following formula [], and the structural formula of 6-vinyl-9-hexadecene-1,16-dicarboxylic acid is the following formula [], Further, the structural formula of 1,10-decanedicarboxylic acid is shown in the following formula []. HOOC−(CH ₂ ) ₁₀ −COOH []

【table】

【table】

【table】

[Table] Next, among the electrolytes shown in Table 1, the temperature 105 for each of 20 electrolytic capacitors (rated 400V, 10μF) using the electrolytes of Conventional Example 2, Example 1, and Example 10 Table 2 shows the results of a high-temperature load test at 1000 hours of rated voltage applied at ℃. Table 3 also shows the results of a high temperature no-load test (105°C, 1000 hours) on an electrolytic capacitor (rated 400V, 220μF). (Each value of the initial and post-test characteristics is the average value of each 20 electrolytic capacitors.)

【table】

[Table] [Effect of the invention] As can be seen from Tables 2 and 3, Conventional Example 2
In this case, the initial capacitance is approximately 10% lower than the rated value, and the rate of change is large even after testing. Further, as can be seen from Table 3, in Conventional Example 2, the leakage current is 30 times or more. The phenomenon in the conventional example shown in Tables 2 and 3 is caused by the dibasic acid, which is the main solute in the driving electrolyte, reacting with the aluminum foil forming the capacitor element, as described above. As the surface area is significantly reduced, the capacitance, which is proportional to the surface area, is reduced, and the increase in leakage current is caused by the reaction of this dibasic acid with the dielectric aluminum anodic oxide film, making it unstable. The leakage current increases because an aluminum complex film is formed, which dissolves in the driving electrolyte at high temperatures. On the other hand, the present invention uses 1,10-decanedicarboxylic acid or its salt as an additive.
Such a phenomenon can be prevented by suppressing the complex formation of the dibasic acid. Furthermore, by lowering the specific resistance, the tangent of the loss angle and the impedance at high frequencies can be kept low. Next, we will discuss the effect on product properties caused by suppressing complex formation by adding 1,10-decanedicarboxylic acid or its salt, for example, 6-vinyl-9-hexadecene-1,16-dicarboxylic acid. Figure 1 shows, as an example, the change in the initial capacitance ratio to the rated capacitance when 1,10-decanedicarboxylic acid isopropylamine salt is added to an electrolytic solution containing 10 wt% acid. Also
Figure 2 shows the change in leakage current value during a high temperature no-load test at 105°C for 1000 hours. The electrolytic capacitors used here all have a rating of 400V and 10μF, and each value is the average value of 20 capacitors. As can be seen from FIG. 1, when the concentration of 1,10-decanedicarboxylic acid isopropylamine salt added is low, the initial capacitance value is low. Addition of 0.5wt% has little effect, but addition of 1wt% produces a sufficient effect. Therefore, addition of 1 wt% or more is preferable.
As can be seen from FIG. 2, when the concentration of 1,10-decanedicarboxylic acid isopropylamine salt added is low, the leakage current value increases, and decreases in the order of addition of 0.5 wt% and 1 wt%. The effect is small when added at 0.5 wt%, but the effect becomes sufficiently clear when added at 1 wt%. Therefore, by using the driving electrolyte according to the present invention, it is possible to provide an electrolytic capacitor with higher performance and higher reliability. [Scope of practical application of the invention] In the components of the electrolytic solution according to the present invention, 1,10-
The amount of decanedicarboxylic acid or its salt added is
A range of 1wt% to 10wt% is preferable; if it is less than 1wt%, the product characteristics will deteriorate significantly, and if it is more than 10wt%, the spark voltage of the electrolyte will drop, so that neither can be put to practical use.

[Brief explanation of drawings]

Figure 1 shows 6-vinyl-9-hexadecene-1,
A characteristic diagram showing the relationship between the concentration of 1,10-decanedicarboxylic acid isopropylamine salt added to 16-dicarboxylic acid and the ratio between the initial capacitance and the rated capacitance of an electrolytic capacitor. -1, for hexadecene-1,16-dicarboxylic acid
FIG. 2 is a characteristic diagram showing the relationship between the addition concentration of 10-decanedicarboxylic acid isopropylamine salt and the leakage current of an electrolytic capacitor.

Claims (1)

[Claims] 1 6-vinyl-1,12-dodecanedicarboxylic acid or its salt or 6-vinyl-9-hexadecene-1,16-dicarboxylic acid as a solute and 1 as an additive in an electrolytic solution using ethylene glycol as the main solvent. , 10-decanedicarboxylic acid or a salt thereof is added thereto.An electrolytic solution for driving an electrolytic capacitor.