JPS6236372B2 - - 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 in particular, to reducing the internal resistance of an electrolytic capacitor.
This invention relates to an electrolytic solution for medium and high voltage electrolytic capacitors that can expand the operating temperature range. [Conventional technology] In various electronic devices such as communication equipment and measurement equipment, the electrical characteristics and life characteristics of electrolytic capacitors are greatly affected by their accuracy and reliability. Smoothing electrolytic capacitors are required to have low impedance characteristics at high frequencies and have an upper limit operating temperature of over 105°C. In general, dry electrolytic capacitors are made by impregnating an electrolytic capacitor element with an electrolytic solution, which is a wound electrolytic capacitor element in which electrode foils on the anode side and cathode side are stacked together with a separator paper interposed between the two, and this electrolytic capacitor element is enclosed in an outer case. It is something. Therefore, the electrical characteristics of an electrolytic capacitor are affected by the electrolytic foil, separator paper, etc. that make up the electrolytic capacitor element, but especially the electrical characteristics such as the resistivity of the electrolyte that is dipped into the electrolytic capacitor element and the spark voltage. It is also known that chemical properties are significantly related to the operating temperature range, impedance characteristics, etc. of electrolytic capacitors. [Problems to be Solved by the Invention] Conventionally, the electrolyte solution for medium and high voltage electrolytic capacitors with a rated voltage exceeding 160 (V) has been made of so-called ethylene glycol, which is obtained by dissolving boric acid or its ammonium salt in a solvent mainly composed of ethylene glycol. A boric acid-based electrolyte is used, but this type of electrolyte has a significantly higher specific resistance than low-pressure electrolytes, so
This has the disadvantage that it causes heat generation as well as increased loss in the electrolytic capacitor, accelerating thermal deterioration of the electrolytic capacitor. Further, this type of electrolytic solution contains a large amount of water produced by the esterification reaction between ethylene glycol and boric acid in addition to the water contained in its constituent chemicals.
That is, in the case of this type of electrolytic solution, the esterification reaction easily proceeds to produce 1 mol to 3 mol of water of boric acid, and the water content in the electrolytic solution becomes extremely large. Since this moisture significantly deteriorates the dielectric oxide film formed on the surface of the electrode foil on the anode side, it has been difficult to maintain stable electrical characteristics of the electrolytic capacitor for a long period of time. Furthermore, such moisture generates a large amount of water vapor at high temperatures exceeding 100°C, causing an abnormal increase in the internal pressure of the outer case, causing expansion of the explosion-proof valve, deformation of the external appearance of the outer case, and associated electrical characteristics. It may cause deterioration etc. For this reason, this type of electrolytic solution cannot be used at high temperatures exceeding 105°C, and the upper limit operating temperature of electrolytic capacitors has been restricted. Therefore, the present invention aims to provide an electrolytic solution for driving an electrolytic capacitor that is suitable for medium-high voltage electrolytic capacitors by reducing the specific resistance value and water content. [Means for solving the problem] The electrolytic solution for driving an electrolytic capacitor of the present invention is
3-Methyl-3-butene-1,2-dicarboxylic acid, 4-methyl-4-heptene-1,2-dicarboxylic acid, 4,6-dimethyl-4-nonene-1,2
-dicarboxylic acid, 3-(1-methylpropyl)-
4,6-dimethyl-4-heptene-1,2-dicarboxylic acid or a salt thereof is dissolved in an organic solvent. That is, 3-methyl-3-butene-1.
2-dicarboxylic acid, 4-methyl-4-heptene-
1,2-dicarboxylic acid, 4,6-dimethyl-4-
In the case of an electrolytic solution in which nonene-1,2-dicarboxylic acid, 3-(1-methylpropyl)-4,6-dimethyl-4-heptene-1,2-dicarboxylic acid or a salt thereof is dissolved in an organic solvent, conventional Similar to the ethylene glycol-boric acid electrolyte, 2 moles of water can be produced from 1 mole of organic acid through an esterification reaction between an organic solvent such as ethylene glycol and a dibasic acid, which is an organic acid. The reaction rate in this case is not as fast as in conventional ethylene glycol-boric acid electrolytes, and the amount of water produced is extremely small. In addition, in the driving electrolyte of the electrolytic capacitor of the present invention, the amount of solute is smaller than that of the ethylene glycol-boric acid electrolyte, and the molecular weight of the solute is also larger than that of boric acid, so the water content in the electrolyte is small. It is characterized by an extremely small amount. Also, 3-methyl-3-butene-1,2-dicarboxylic acid, 4-methyl-4-heptene-1,2-
Dicarboxylic acid, 4,6-dimethyl-4-nonene-
1,2-dicarboxylic acid, 3-(1-methylpropyl)-4,6-dimethyl-4-heptene-1,2
- Since the dicarboxylic acid or its salt is used as the solute, the specific resistance of the electrolytic solution can be lowered, and the spark generation voltage can be increased, so that the dielectric strength of the impregnated electrolytic capacitor element can be improved. [Examples] Examples of the present invention will be described below. In each example, 3-methyl-3-butene-1,2-
Dicarboxylic acid, 4-methyl-4-heptene-1.
2-dicarboxylic acid, 4,6-dimethyl-4-nonene-1,2-dicarboxylic acid, 3-(1-methylpropyl)-4,6-dimethyl-4-heptene-
It uses 1,2-dicarboxylic acid as the solute.
That is, the specific solute is flopylene monomer or
It is composed of a dibasic acid obtained by reacting a propylene oligomer, etc., consisting of up to four monomers, with maleic acid. In order to confirm the effect of solutes in such an electrolytic solution, an ethylene glycol-boric acid electrolytic solution containing ethylene glycol as a main component was shown as a conventional example. For each of these examples, the pH, content (%) of generated water, and specific resistance value (Ω) at 30°C for the electrolyte composition
cm) are shown in Table 1. Note that ammonia gas was injected into the electrolytes of Examples 1 to 4 to set the pH value to 7.0. According to experiments, there is a certain relationship between the PH value and specific resistance in the electrolyte solutions of Examples, and the specific resistance value is minimum in the pH range of 6 to 8, so the PH value of each Example is The pH was set to 7.0 by adjusting the amount of ammonia gas injected.

[Table] The chemical formulas of the solutes in the electrolytes of Examples 1 to 4 shown in Table 1 are shown below. 3-methyl-3-butene-1,2-dicarboxylic acid 4-Methyl-4-heptene-1,2-dicarboxylic acid 4,6-dimethyl-4-nonene-1,2-dicarboxylic acid 3-(1-methylpropyl)-4,6-dimethyl-4-heptene-1,2-dicarboxylic acid As is clear from the conventional example in Table 1 and the specific measured values of each example, 3-methyl-3-butene-1.
2-dicarboxylic acid, 4-methyl-4-heptene-
1,2-dicarboxylic acid, 4,6-dimethyl-4-
According to the electrolytic solution composed of nonene-1,2-dicarboxylic acid and 3-(1-methylpropyl)-4,6-dimethyl-4-heptene-1,2-dicarboxylic acid as solutes, water content and ratio It can be seen that the resistance value can be significantly reduced compared to conventional electrolytes. In the case of each example, 3-methyl-3-butene-1,2-dicarboxylic acid, 4-methyl-4-heptene-1,2-dicarboxylic acid, 4,6-dimethyl-4-nonene-1,2- dicarboxylic acid, 3-
(1-methylpropyl)-4,6-dimethyl-4-
Ammonia is dissolved together with heptene-1,2-dicarboxylic acid by injecting ammonia gas, and 1 mole of organic acid is converted into Although it is possible to generate mol of water, the reaction rate is not as fast as in the case of the conventional electrolyte, so the amount of generated water is extremely small. Moreover, in the case of this electrolytic solution, the amount of solute is smaller than that of the conventional example, and the molecular weight of the solute is larger than that of boric acid, which indicates that the water content in the electrolytic solution is even smaller. Also, 3-methyl-3-butene-1,2-dicarboxylic acid, 4-methyl-4-heptene-1,2-
Dicarboxylic acid, 4,6-dimethyl-4-nonene-
1,2-dicarboxylic acid, 3-(1-methylpropyl)-4,6-dimethyl-4-heptene-1,2
- When ammonia is used as a solute along with dicarboxylic acid, these solutes reduce the resistivity of the electrolyte, as is clear from the fact that the resistivity values in each example are about 1/2 that of conventional electrolytes. It turns out that it works like this. Moreover, as mentioned above, the pH of the electrolyte
The minimum specific resistance value can be obtained by adjusting the amount of ammonia gas injected and setting it to approximately 7.0. Furthermore, when measuring the spark voltage of the electrolytes of each of these Examples, extremely high voltage values of 400 to 500 (V) were obtained, and furthermore, the withstand voltage of the electrolytic capacitor element impregnated with this electrolyte was at least 350 (V). ) or more was confirmed. Next, the electrical characteristics of an electrolytic capacitor using an electrolytic solution according to the present invention will be explained in comparison with an electrolytic capacitor using a conventional electrolytic solution. The sample electrolytic capacitor was made by etching the surface of high-purity aluminum foil and then anodizing it by applying a voltage of 620 (V) to form a dielectric oxide film. The aluminum foil obtained above was used as a cathode side electrode, and a separator paper was interposed between these two electrodes and wound to form an electrolytic capacitor element. It is impregnated with water and stored in an outer case, and the opening of the outer case is sealed with an elastic sealing member. Each sample electrolytic capacitor has a rated voltage of 400 (V) and a rated capacitance of 10 (μF). Table 2 shows the initial characteristics of each sample electrolytic capacitor at 20°C.

[Table] As is clear from this measurement result, in the case of the electrolytic capacitor using the electrolytic capacitor of the example,
Loss tan compared to those using conventional electrolytes
δ is about 3/4, and equivalent series resistance (ESR) is about 1/
It can be seen that the number has been reduced to about 3. Table 3 shows the 1000 hour elapsed characteristics of each sample electrolytic capacitor based on the load life test. The load life test was performed by applying a rated voltage of 400 (V) to each sample electrolytic capacitor at a high temperature of 110°C and leaving it for 1000 hours. After this test time, measurements were made in the same manner as the initial characteristics, and the outer case was We observed changes in the external shape.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to obtain an electrolytic solution with a low resistivity value and low water content, to expand the operating temperature range with low loss, especially to increase the upper limit operating temperature, and to have low impedance characteristics and high withstand voltage. Moreover, because the water content is low, the internal pressure of the outer case does not increase abnormally due to the generation of water vapor at high temperatures, and the dielectric oxide film on the electrode foil on the anode side does not deteriorate. Not at all.

Claims (1)

[Claims] 1 3-methyl-3-butene-1,2-dicarboxylic acid, 4-methyl-4-heptene-1,2-dicarboxylic acid, 4,6-dimethyl-4-nonene-1,
2-dicarboxylic acid, 3-(1-methylpropyl)-
An electrolytic solution for driving an electrolytic capacitor, characterized in that 4,6-dimethyl-4-heptene-1,2-dicarboxylic acid or a salt thereof is dissolved in an organic solvent.