JP4226123B2 - Electrolytic solution for driving aluminum electrolytic capacitors - Google Patents

Description

【０００６】
また、上記の有機酸がアジピン酸、フタル酸、マレイン酸、安息香酸、アゼライン酸、セバシン酸、ギ酸であることを特徴とする電解液である。
【０００７】
【発明の実施の形態】
上記のナフタレン化合物を、溶媒に水を混合してなる電解液に添加する。
上記のナフタレン系化合物の水酸基の作用により、金属と安定なキレート化合物が形成され、腐食を防止することができる。すなわち、上記のナフタレン化合物はアルミニウム電極箔表面に吸着して安定な金属錯体を形成し、陰極電極箔表面を水和劣化から保護する。
【０００８】
【実施例】
以下、実施例の具体的内容について説明する。
表１のとおり、エチレングリコールを主溶媒とし、水を副溶媒として混合してなる溶媒に、アジピン酸二アンモニウムを溶質として溶解し、１位と３位、１位と４位、１位と５位、１位と６位、１位と７位、２位と６位、２位と７位に水酸基を有するナフタレン系化合物（ナフタレンジオール）を各々０．２ｗｔ％添加したものを実施例１〜７とし、０．５〜５．０ｗｔ％添加したものを実施例８〜１２とした。また、１０．０ｗｔ％添加したものを各々比較例１、２とした。また、上記ナフタレン系化合物を添加しない従来例も併記した。これらの液組成と３０℃における比抵抗値を表１に示した。
【０００９】
【表１】

【００１０】
これらの電解液を用いて、定格６．３ＷＶ、３９０μＦのアルミニウム電解コンデンサを作製し、１０５℃ ２０００時間定格印加試験に供した結果を表２に示す。
【００１１】
【表２】

【００１２】
実施例８〜１２から明らかなように、上記ナフタレン系化合物を０．１〜０．５ｗｔ％添加することによって、１０５℃ ２０００時間後の静電容量低下を抑えることが可能である。ただし、ナフタレン系化合物は、０．１％未満では、静電容量低下防止に効果がなく、また、５．０ｗｔ％を超えて添加しても電解液に溶解しないため、０．１〜５．０ｗｔ％の範囲が適当である。
また、上記実施例では、アジピン酸アンモニウムを溶質として用いたが、これ以外にもフタル酸、マレイン酸、安息香酸、アゼライン酸、セバシン酸、ギ酸の塩またはこれらの塩と酸を組合せて用いることもできる。
これらの塩は解離度が大きく、電解液の初期の比抵抗を下げることが可能であるばかりでなく、ナフタレン系化合物の溶解能を５．０ｗｔ％程度まで上げる働きがあると考えられ、これらの塩とナフタレン化合物を併用することにより、電解液比抵抗の高温安定化に大きく寄与する。
【００１３】
【発明の効果】
上記の水酸基を有するナフタレン系化合物（ナフタレンジオール）を添加した電解液は、陰極電極箔表面の水和劣化を防止することで静電容量の低下を抑制することが可能であり、工業的価値大なるものである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrolytic solution for driving an aluminum electrolytic capacitor (hereinafter referred to as an electrolytic solution), and in particular, prevents a decrease in capacitance due to hydration deterioration of a cathode electrode foil.
[0002]
[Prior art]
Conventionally, as an electrolytic solution for an aluminum electrolytic capacitor for low pressure, an electrolytic solution obtained by dissolving a salt of a carboxylic acid such as phthalic acid or maleic acid and an amine such as triethylamine as a main solute in a solvent mainly composed of γ-butyrolactone. Is used.
[0003]
[Problems to be solved by the invention]
In recent years, aluminum electrolytic capacitors are required to have low impedance, small size, and high reliability due to market demands, and electrolytes used have low specific resistance and are required to be stable in a wide temperature range.
However, the specific resistance obtained with electrolytes using γ-butyrolactone as the main solvent so far is becoming unable to meet market demands, and from a “global environmental protection standpoint”, from a solvent such as γ-butyrolactone. An electrolytic solution using a solvent obtained by mixing ethylene glycol as a main component with water is beginning to attract attention again.
However, in order to satisfy the market demand with an electrolytic solution using a solvent obtained by mixing water with ethylene glycol, it is necessary to mix a large amount of water. Therefore, the cathode electrode foil is deteriorated by hydration. There was a problem that the capacitance was greatly reduced.
JP-A-3-69107 discloses that a naphthalene compound having a hydroxyl group at the 1-position, 2-position, 1-position, 8-position, 2-position, and 3-position is added.
However, the above compound could not be added in a large amount due to the short distance between both hydroxyl groups and poor solubility due to steric hindrance.
[0004]
[Means for Solving the Problems]
1st and 3rd, 1st and 4th, 1st and 5th, 1st and 6th, 1st and 7th, 2nd and 6th, 2nd and 7th, which produce chelate compounds Attention is focused on naphthalene-based compounds having a hydroxyl group, and the characteristics are applied to an electrolytic solution to solve the above problems.
That is, in a mixed solvent containing ethylene glycol as a main solvent and water as a sub-solvent, at least one of boric acid, an organic acid, or a salt thereof, the 1st position, the 3rd position, the 1st position, and the 4th shown in Chemical Formula 2 1 or more of naphthalene compounds having hydroxyl groups at the 1st and 5th positions, the 1st and 6th positions, the 1st and 7th positions, the 2nd and 6th positions, the 2nd and 7th positions, and 0.1 to 5.0 wt. % Electrolyte solution.
[0005]
[Chemical formula 2]

[0006]
The organic acid is an electrolytic solution characterized in that it is adipic acid, phthalic acid, maleic acid, benzoic acid, azelaic acid, sebacic acid, or formic acid.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The naphthalene compound is added to an electrolytic solution obtained by mixing water with a solvent.
By the action of the hydroxyl group of the naphthalene compound, a stable chelate compound is formed with the metal, and corrosion can be prevented. That is, the naphthalene compound is adsorbed on the aluminum electrode foil surface to form a stable metal complex, and protects the cathode electrode foil surface from hydration deterioration.
[0008]
【Example】
Hereinafter, specific contents of the embodiment will be described.
As shown in Table 1, diammonium adipate is dissolved as a solute in a solvent obtained by mixing ethylene glycol as a main solvent and water as a sub-solvent, and the 1st, 3rd, 1st, 4th, 1st and 5th Examples 1 to 6 and 1 to 7 and 2 to 6 and 2 and 7 to which naphthalene-based compounds having a hydroxyl group (naphthalene diol) were added in an amount of 0.2 wt%. 7 and those added with 0.5 to 5.0 wt% were designated as Examples 8 to 12. Moreover, what added 10.0 wt% was made into Comparative Examples 1 and 2, respectively. A conventional example in which the naphthalene compound is not added is also shown. These liquid compositions and specific resistance values at 30 ° C. are shown in Table 1.
[0009]
[Table 1]

[0010]
Table 2 shows the results of producing an aluminum electrolytic capacitor having a rating of 6.3 WV and 390 μF using these electrolytic solutions and subjected to a rated application test at 105 ° C. for 2000 hours.
[0011]
[Table 2]

[0012]
As is apparent from Examples 8 to 12, it is possible to suppress a decrease in capacitance after 2000 hours at 105 ° C. by adding 0.1 to 0.5 wt% of the naphthalene compound. However, if the naphthalene-based compound is less than 0.1%, there is no effect in preventing the decrease in the capacitance, and even if it is added in an amount exceeding 5.0 wt%, it does not dissolve in the electrolytic solution. A range of 0 wt% is appropriate.
In the above examples, ammonium adipate was used as a solute. In addition, phthalic acid, maleic acid, benzoic acid, azelaic acid, sebacic acid, formic acid salts, or a combination of these salts and acids may be used. You can also.
These salts have a high degree of dissociation and are not only capable of lowering the initial specific resistance of the electrolytic solution, but are thought to have a function of increasing the solubility of naphthalene compounds to about 5.0 wt%. The combined use of the salt and the naphthalene compound greatly contributes to the stabilization of the electrolyte resistivity at high temperatures.
[0013]
【The invention's effect】
The electrolyte solution to which the naphthalene-based compound (naphthalene diol) having a hydroxyl group is added can suppress a decrease in capacitance by preventing hydration deterioration on the surface of the cathode electrode foil. It will be.

Claims (2)

In a mixed solvent containing ethylene glycol as a main solvent and water as a sub-solvent, at least one of boric acid, organic acid, or a salt thereof, 1st and 3rd positions, 1st and 4th positions shown in Chemical Formula 1, 0.1-5.0 wt% of one or more naphthalene compounds having hydroxyl groups at the 1st and 5th, 1st and 6th, 1st and 7th, 2nd and 6th, 2nd and 7th positions An electrolytic solution for driving an aluminum electrolytic capacitor.

2. The electrolytic solution for driving an aluminum electrolytic capacitor according to claim 1, wherein the organic acid is adipic acid, phthalic acid, maleic acid, benzoic acid, azelaic acid, sebacic acid, or formic acid.