JP2007081135A - Electrolyte for driving electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte for driving an electrolytic capacitor that can reduce specific resistance and increase a withstand voltage. <P>SOLUTION: In the electrolyte for driving an electrolytic capacitor, a carboxylic acid such as a benzoic acid, a formic acid, an adipic acid, and a sebacic acid, its salt such as ammonium and dimethylamine, and a ferulic acid expressed by a chemical expression are blended to a solvent with ethyleneglycol or the like as a main constituent. The amount of the blend of the ferulic acid is preferably in a range of 0.1 to 5.0 wt.% to the entire electrolyte. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an improvement of an electrolytic solution for driving an electrolytic capacitor (hereinafter referred to as an electrolytic solution), and particularly relates to an electrolytic solution having improved withstand voltage.

Conventionally, electrolytic solutions for medium- and high-pressure aluminum electrolytic capacitors are prepared by mixing higher dibasic acid or its ammonium salt, boric acid or its ammonium salt, and polyhydric alcohols such as mannitol in a solvent such as ethylene glycol. It has been. In this type of electrolytic solution, it is known that boric acid and polyhydric alcohols form an ester compound, and the withstand voltage of the electrolytic solution is improved due to its structural characteristics. Furthermore, blending polyvinyl alcohol, which is a synthetic polymer, has also been proposed (see, for example, Patent Documents 1 to 3).
Japanese Examined Patent Publication No. 7-48459 (page 1-4) Japanese Patent Publication No. 7-48460 (page 1-3) Japanese Examined Patent Publication No. 7-63047 (page 1-4)

  However, mannitol, sorbitol, etc. having about 6 carbon atoms are slow to improve the withstand voltage of the electrolyte even if the addition amount is increased, so it is necessary to add a large amount to greatly improve the withstand voltage. As a result, there is a problem that the resistivity is significantly increased.

  On the other hand, polyvinyl alcohol can improve the withstand voltage of the electrolytic solution by adding a smaller amount than mannitol, but it cannot be added in a large amount because it has extremely low solubility in a solvent containing ethylene glycol as a main component. Moreover, since long time heating and stirring are required in order to prepare electrolyte solution, there exists a problem that preparation takes much effort.

  Furthermore, polyhydric alcohols may cause an ester reaction with a higher dibasic acid that is a main solute, so that there has been a problem that the characteristic change of the electrolytic solution itself becomes large.

  In view of the above problems, an object of the present invention is to provide a driving electrolytic solution for an electrolytic capacitor that can achieve both a reduction in specific resistance and an increase in withstand voltage.

  The present invention has been found as a result of various studies to solve the above-mentioned problems, and has been found that ferulic acid has a carbonyl group, and this structure suppresses the chemical reaction between the electrolytic solution and the electrode foil. However, it is intended to increase the withstand voltage.

  That is, the driving electrolytic solution for an electrolytic capacitor according to the present invention is characterized in that at least a carboxylic acid or a salt thereof and ferulic acid represented by the following chemical formula are blended in a solvent mainly composed of ethylene glycol. And

  In this invention, it is preferable that the compounding quantity of ferulic acid is 0.1-5.0 wt% with respect to the whole electrolyte solution.

  In the present invention, examples of carboxylic acids include formic acid, acetic acid, lauric acid, stearic acid, decanoic acid, benzoic acid, salicylic acid, maleic acid, phthalic acid, fumaric acid, succinic acid, glutaric acid, azelaic acid, sebacic acid, 2 -Methyl azelaic acid, 1,6-decanedicarboxylic acid, 5,6-decanedicarboxylic acid, 7-vinylhexadecene-1,16-dicarboxylic acid.

  Examples of carboxylic acid salts include ammonium salts, primary amine salts such as methylamine, ethylamine, and t-butylamine, secondary amine salts such as dimethylamine, ethylmethylamine, and diethylamine, trimethylamine, diethylmethylamine, and ethyldimethylamine. And tertiary amine salts such as triethylamine, quaternary ammonium salts such as tetramethylammonium, triethylmethylammonium and tetraethylammonium, and molten salts such as imidazolinium salts.

  As a co-solvent mixed with ethylene glycol, glycols such as propylene glycol, lactones such as γ-butyrolactone and N-methyl-2-pyrrolidone, N-methylformamide, N, N-dimethylformamide, N-ethylformamide, Amides such as N, N-diethylformamide, N-methylacetamide, N, N-dimethylacetamide, N-ethylacetamide, N, N-diethylacetamide, hexamethylphosphoricamide, ethylene carbonate, propylene carbonate, isobutylene carbonate, etc. Examples thereof include carbonic acids, nitriles such as acetonitrile, oxides such as dimethyl sulfoxide, ethers, ketones, esters, sulfolane, sulfolane derivatives, water and the like. These solvents can be used not only in one kind but also in a mixture of two or more kinds.

  Various additives can be added to the electrolytic solution for the purpose of reducing leakage current, improving withstand voltage, and absorbing gas. Examples of additives include phosphoric acid compounds, boric acid compounds, polyhydric alcohols, polyvinyl alcohol, polyethylene glycol, polypropylene glycol, and polyoxyethylene polyoxypropylene glycol random copolymers and block copolymers. A molecular compound, a nitro compound, etc. are mentioned.

When an electrolytic capacitor is configured using the electrolytic solution according to the present invention, the chemical reaction between the electrolytic solution and the electrode foil can be suppressed with the addition of a small amount of ferulic acid, thereby reducing the specific resistance of the electrolytic solution and improving the withstand voltage. Can be planned. The reason is considered to be that the carbonyl group portion of ferulic acid reacts with the oxide film of the aluminum electrode foil in the electrolytic solution to form a water-resistant film.
Ferulic acid is highly soluble in solvents based on ethylene glycol and has little esterification reaction with the main solute carboxylic acid, which increases the specific resistance over time in a high-temperature atmosphere. Can be prevented.

  Hereinafter, the present invention will be described more specifically based on examples. First, an electrolyte solution was prepared according to the composition shown in Tables 1 and 2, and the specific resistance of the electrolyte solution at 30 ° C. and the spark generation voltage at 85 ° C. (withstand voltage of the electrolyte solution) were measured. The results are shown in Tables 1 and 2.

  From Table 1 and Table 2, it can be seen that the electrolytic solution according to the example in which ferulic acid is dissolved has a lower specific resistance and an improved withstand voltage than the electrolytic solution according to the conventional example. Here, when the blending amount of ferulic acid is less than 0.1 wt% (Example 1) with respect to the entire electrolyte (Example 1), the effect of improving the withstand voltage is not sufficient, and when it exceeds 5.0 wt% (Example 5), This is not preferable because the specific resistance increases greatly. Therefore, the blending amount of ferulic acid is preferably in the range of 0.1 to 5.0 wt% with respect to the entire electrolytic solution.

  In addition, this invention is not limited to an Example, The electrolyte solution which added the additive for the purpose of the electrolytic solution which melt | dissolved the various solutes illustrated previously single or plurally, and other objectives, and a cosolvent The mixed electrolyte solution had the same effect as the example.

Claims (2)

An electrolytic solution for driving an electrolytic capacitor, wherein a solvent containing ethylene glycol as a main component contains at least carboxylic acid or a salt thereof and ferulic acid represented by the following chemical formula.

  2. The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein the blending amount of ferulic acid is 0.1 to 5.0 wt% with respect to the entire electrolytic solution.