JP2002280267A - Electrolyte for drive for electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolyte for drive for electrolytic capacitor, with which the voltage resistance of an electrolytic capacitor can be improved. SOLUTION: Higher dibasic acid or salt thereof, boric acid or ammonium salt thereof and crosslinked type polyvinyl alcohol-polypropylene glycol diacrylate copolymer in 0.10 to 10.0 wt.% are dissolved in a solvent, with ethylene glycol as the main component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an electrolytic solution for driving an electrolytic capacitor (hereinafter referred to as an electrolytic solution), and more particularly to an electrolytic solution having improved withstand voltage.

[0002]

2. Description of the Related Art Conventionally, a higher dibasic acid or its ammonium salt has been added to a solvent mainly composed of ethylene glycol.
It is known that the withstand voltage of an electrolytic solution can be improved by adding a synthetic polymer such as polypropylene glycol or polyvinyl alcohol to an electrolytic solution in which boric acid or ammonium borate is dissolved.

[0003]

However, polypropylene glycol having an average molecular weight of about 1000 has high solubility in an electrolyte containing ethylene glycol as a main solvent, but a large amount of addition is required to improve the withstand voltage. However, there is a problem that the specific resistance of the electrolytic solution is increased. Further, polypropylene glycol having an average molecular weight of 2,000 or more has a higher effect of improving the withstand voltage of the electrolytic solution than that having an average molecular weight of about 1,000, but has a problem in that the specific resistance increases greatly and the solubility is low. In addition, polyvinyl alcohol has a three-dimensional network structure and is capable of easily moving ions, so that the withstand voltage can be improved without greatly increasing the specific resistance. In addition to the extremely low solubility, when dissolved near the saturation concentration, the hydroxyl groups in polyvinyl alcohol gather due to electrostatic attraction, resulting in a thread-like micellar structure, which makes it difficult to obtain the withstand voltage improving effect of the polymer. . The present invention solves the above-described problems, and can improve the withstand voltage and maintain the withstand voltage while suppressing an increase in the specific resistance of the electrolytic solution, and can also improve the solubility. Is provided.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been found as a result of various studies to solve the above-mentioned problems, and has been found to be a crosslinked polyvinyl alcohol formed by crosslinking propylene glycol diacrylate to polyvinyl alcohol. -The polypropylene glycol diacrylate copolymer has a polypropylene glycol diacrylate part having high solubility in ethylene glycol and a polyvinyl alcohol part having a high effect on withstand voltage improvement. The solubility in glycol is improved, the heat resistance is improved by the crosslinked structure, and the polyvinyl alcohol can be prevented from forming a lint-like micelle structure, so that the increase in the specific resistance of the electrolytic solution can be suppressed. , Withstand It is an attempt is made to improve. That is, in a solvent containing ethylene glycol as a main component, a higher dibasic acid or a salt thereof, boric acid or an ammonium salt thereof, and a crosslinked polyvinyl alcohol-polypropylene glycol diacrylate copolymer are dissolved. It is an electrolytic solution for driving an electrolytic capacitor.

[0005] Further, there is provided an electrolytic solution for driving an electrolytic capacitor, wherein the amount of the crosslinked polyvinyl alcohol-polypropylene glycol diacrylate copolymer is 0.10 to 10.0 wt%.

Further, the above-mentioned crosslinked polyvinyl alcohol-
The average degree of polymerization of the polyvinyl alcohol part of the polypropylene glycol diacrylate copolymer is 200 to 1500
And the average degree of polymerization of the polypropylene glycol diacrylate part is 4 to 800, and the average degree of crosslinking (average number of crosslinks / average degree of polymerization) of the polyvinyl alcohol part is 2 to 60.
% For driving an electrolytic capacitor.

The higher dibasic acids include adipic acid, azelaic acid, sebacic acid, 1,6-decanedicarboxylic acid, 5,6-decanedicarboxylic acid, 7-vinylhexadecene-1,16-dicarboxylic acid and the like. Can be exemplified.

[0008] As the salt of the higher dibasic acid,
In addition to ammonium salts, methylamine, ethylamine, t
Primary amine salts such as -butylamine, secondary amine salts such as dimethylamine, ethylmethylamine and diethylamine;
Examples thereof include tertiary amine salts such as trimethylamine, diethylmethylamine, ethyldimethylamine, and triethylamine, and quaternary ammonium salts such as tetramethylammonium, triethylmethylammonium, and tetraethylammonium.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An electrolyte in which a cross-linked polyvinyl alcohol-polypropylene glycol diacrylate copolymer in which polyvinyl alcohol is cross-linked with polypropylene glycol diacrylate has properties of both the polyvinyl alcohol portion and the polypropylene glycol diacrylate portion. Will be able to take advantage of it. That is, both portions, particularly the polyvinyl alcohol portion, are effective in improving the withstand voltage of the electrolytic solution, and the polypropylene glycol diacrylate portion having a relatively low polymerization degree (low average molecular weight) improves the solubility in ethylene glycol. In addition, the increase in specific resistance is suppressed by facilitating the movement of ions by the three-dimensional network structure of the polyvinyl alcohol portion. In addition, the crosslinked structure of acrylic acid makes it difficult for thermal decomposition to occur, and in addition to improving heat resistance, it is possible to prevent polyvinyl alcohol from becoming entangled in lint, thereby impairing the withstand voltage improving effect of the polymer. Absent.

[0010]

Embodiments of the present invention will be specifically described below. An electrolytic solution was prepared according to the composition shown in Table 1, and the specific resistance of the electrolytic solution at 30 ° C. and the spark generation voltage (withstand voltage) at 85 ° C. were measured.

[0011]

[Table 1]

[0012]

[Table 2]

First, as shown in Conventional Examples and Comparative Examples 1 and 2, when a polypropylene glycol having an average degree of polymerization of 17 is added, the spark voltage increases, but the specific resistance also increases. When the addition amount was 10.0 wt%, the spark voltage reached 435 V, but the specific resistance increased to 780 Ω · cm. As shown in Comparative Examples 3 and 4, when polyvinyl alcohol having an average degree of polymerization of 500 was added, the spark voltage increased significantly as compared with polypropylene glycol, but did not dissolve when 10.0 wt% was added. Therefore, the embodiment of the present invention in which the crosslinked polyvinyl alcohol-polypropylene glycol diacrylate copolymer is added can be completely dissolved, and it is possible to suppress an increase in specific resistance while increasing a spark voltage.

When the amount of the crosslinked polyvinyl alcohol-polypropylene glycol diacrylate copolymer dissolved is 0.05% by weight, the effect of improving the withstand voltage is not sufficient, and when the amount is 15.0% by weight, the specific resistance is too high and the specific resistance is too low. Not suitable for resistance applications. Therefore, the amount of the crosslinked polyvinyl alcohol-polypropylene glycol diacrylate copolymer dissolved is preferably in the range of 0.10 to 10.0 wt%.

After the capacitor elements were impregnated with the electrolyte solutions of Examples 2 to 4 and Comparative Example 3, they were sealed together with a sealing rubber in an aluminum outer case, and a diameter of φ35.0 × 35.0 mmL was obtained.
Ten aluminum electrolytic capacitors each having a rated voltage of 400 V and a capacitance of 390 μF were prepared and subjected to aging treatment. After measuring the initial values of these products, a rated voltage was applied in a high-temperature bath at 105 ° C.
The change in an δ was investigated and the results in Table 3 were obtained.

[0016]

[Table 3]

According to Table 3, the electrolytic capacitor using this embodiment has stable characteristics even in a high temperature load test.
It turns out that it has excellent long-term reliability.

The relationship between the average degree of polymerization of the polyvinyl alcohol part of the crosslinked polyvinyl alcohol-polypropylene diacrylate copolymer and the spark generation voltage of the electrolyte was investigated using the electrolyte composition of Example 3 and the results shown in FIG. 1 were obtained. Was. From FIG. 1, the average degree of polymerization of the polyvinyl alcohol part is 200 to 15
It can be seen that a range of 00 is preferable. Average degree of polymerization is 20
If it is less than 0, the spark generation voltage is not sufficiently improved, and
If it exceeds 00, it did not completely dissolve under these conditions.

The relationship between the average degree of polymerization of the polypropylene diacrylate portion of the crosslinked polyvinyl alcohol-polypropylene diacrylate copolymer, the specific resistance of the electrolyte, and the spark generation voltage was also investigated with the electrolyte composition of Example 3. 2
Was obtained. FIG. 2 shows that the average degree of polymerization of the polypropylene diacrylate is preferably in the range of 4 to 800. When the average degree of polymerization is less than 4, the spark generation voltage is not sufficiently improved, and when the average polymerization degree is more than 800, the spark generation voltage is sufficiently improved, but the specific resistance is increased, which is not suitable for low specific resistance applications.

Next, the relationship between the average degree of crosslinking of the polypropylene diacrylate of the crosslinked polyvinyl alcohol-polypropylene diacrylate copolymer and the solubility in the electrolyte with the composition of the electrolyte of Example 5 was described. A survey was performed and the results in Table 4 were obtained. Here, the average polymerization degree of the polyvinyl alcohol part of the crosslinked polyvinyl alcohol-polypropylene diacrylate copolymer was 1500, and the average polymerization degree of the polypropylene diacrylate was 4 used.

[0021]

[Table 4]

Table 4 shows that the average degree of crosslinking is preferably in the range of 2 to 60%. Average degree of crosslinking is less than 2% or 6
If it exceeds 0%, there is a problem that the crosslinked polyvinyl alcohol-polypropylene diacrylate copolymer is not completely dissolved.

[0023]

As described above, when the crosslinked polyvinyl alcohol-polypropylene glycol diacrylate copolymer according to the present invention is dissolved in an electrolytic solution mainly composed of ethylene glycol, the increase in the specific resistance is suppressed and the withstand voltage is improved. And stable characteristics can be obtained even at a high temperature, which is of great industrial and practical value.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram of the average polymerization degree of a polyvinyl alcohol part of a crosslinked polyvinyl alcohol-polypropylene diacrylate copolymer and the spark generation voltage of an electrolytic solution.

FIG. 2 is a characteristic diagram of an average degree of polymerization of a polypropylene diacrylate portion of a crosslinked polyvinyl alcohol-polypropylene diacrylate copolymer, a specific resistance of an electrolytic solution, and a spark generation voltage.

Claims (3)

[Claims] 1. Dissolving a higher dibasic acid or a salt thereof, boric acid or an ammonium salt thereof, and a crosslinked polyvinyl alcohol-polypropylene glycol diacrylate copolymer in a solvent containing ethylene glycol as a main component. Characteristic electrolyte for driving electrolytic capacitors. 2. An electrolytic solution for driving an electrolytic capacitor, wherein the amount of the crosslinked polyvinyl alcohol-polypropylene glycol diacrylate copolymer according to claim 1 is 0.10 to 10.0 wt%. 3. The crosslinked polyvinyl alcohol-polypropylene glycol diacrylate copolymer has an average degree of polymerization of a polyvinyl alcohol part of 200 to 1500, an average degree of polymerization of a polypropylene glycol diacrylate part of 4 to 800, and a polyvinyl alcohol. 3. The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein the average crosslinking degree of the alcohol part is 2 to 60%.