JP2008300689A - Electrolytic solution for driving electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolytic solution for driving an electrolytic capacitor capable of improving a spark generation voltage (withstand voltage of the electrolytic solution) while suppressing an increase in specific resistance. <P>SOLUTION: The electrolytic solution is characterized in that at least higher dibasic acid or its salt, boric acid or its ammonium salt, and undecanoic γ-lactone are compounded in a solvent, the main solvent of which is ethylene glycol, and that the amount of compound of the undecanoic γ-lactone is 0.5-2.0 wt.% of the entire electrolytic solution. <P>COPYRIGHT: (C)2009,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 a driving electrolytic solution having improved withstand voltage.

Conventionally, the electrolytic solution for medium- and high-pressure aluminum electrolytic capacitors uses ethylene glycol or the like as a main solvent to dissolve higher dibasic acid or its ammonium salt and boric acid or its ammonium salt to increase the withstand voltage of the electrolytic solution. An electrolytic solution to which a polyhydric alcohol such as mannitol or sorbitol is added is used (for example, see 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, polyhydric alcohols such as mannitol and sorbitol have a slow improvement in withstand voltage with respect to the amount added, and when a large amount of polyhydric alcohol is added, it undergoes an esterification reaction with higher dibasic acid and boric acid. There is a problem that the resistance increases remarkably.

  In view of the above problems, an object of the present invention is to provide a driving electrolyte having a low specific resistance and a high withstand voltage.

  As a result of various studies to solve the above problems, the inventor of the present application has obtained a new finding that undecanoic γ-lactone has a high adsorptivity to an electrode foil as compared with a polyhydric alcohol. Based on this knowledge, the problem is solved by applying the characteristics to the driving electrolyte.

  That is, in the electrolytic solution according to the present invention, at least a higher dibasic acid or a salt thereof, boric acid or an ammonium salt thereof, and an undecanoic γ-lactone represented by the following chemical formula: It is characterized by blending.

  In this invention, it is preferable that the compounding quantity of the said undecanoic gamma-lactone is 0.5-2.0 wt% with respect to the whole electrolyte solution.

  In the present invention, examples of the higher dibasic acid include azelaic acid, sebacic acid, benzoic acid, 1,6-decanedicarboxylic acid, 5,6-decanedicarboxylic acid, 7-vinylhexadecene-1,16-dicarboxylic acid, and the like. be able to.

  As salts of higher dibasic acids, primary amine salts such as methylamine, ethylamine, t-butylamine, secondary amine salts such as dimethylamine, ethylmethylamine, diethylamine, trimethylamine, diethylmethylamine, ethyldimethylamine, triethylamine, etc. And quaternary ammonium salts such as tetramethylammonium, triethylmethylammonium, and tetraethylammonium.

  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.

  Furthermore, various additives can be added to the above electrolyte 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, polyoxyethylene polyoxypropylene glycol random copolymers and block copolymers Examples include molecular compounds and nitro compounds.

  In the present invention, undecanoic γ-lactone is added to an electrolytic solution in which a higher dibasic acid, boric acid or a salt thereof is blended in a solvent containing ethylene glycol as a main component, so that the specific resistance is low and the withstand voltage is high. An electrolytic solution can be realized.

In addition, undecanoic γ-lactone and higher dibasic can be obtained by adding undecanoic γ-lactone in a solvent containing ethylene glycol as a main component, with higher dibasic acid or salt thereof and boric acid or ammonium salt thereof as solutes. A product resulting from an esterification reaction with an acid or boric acid does not hinder the movement of ions in the electrolytic solution, and can improve the withstand voltage while suppressing an increase in the specific resistance of the electrolytic solution.
Furthermore, since undecanoic γ-lactone has a high adsorptivity to electrode foil, it can efficiently carry out esterification reaction with higher dibasic acid and boric acid on the electrode foil. Can be improved.

  Examples of the present invention will be specifically described below. Electrolytic solutions were prepared with the compositions shown in Tables 1 and 2, and the specific resistance at 30 ° C. and the spark generation voltage at 85 ° C. (withstand voltage of the electrolytic solution) were measured. The results are shown in Tables 1 and 2.

From Table 1 and Table 2, it can be seen that, in comparison with the conventional example to which mannitol was added, Examples 1 to 17 according to the present invention have improved withstand voltage while suppressing an increase in specific resistance.
However, if the amount of undecanoic γ-lactone added is less than 0.5 wt%, the improvement of the withstand voltage cannot be confirmed (Example 1), and if the amount added exceeds 2.0 wt%, the specific resistance increases remarkably. It becomes unsuitable for the use of resistance (Example 5).
From the above, it can be said that the amount of undecanoic γ-lactone added is preferably in the range of 0.5 to 2.0 wt%.

  The effects of the present invention are not limited to the examples, but an electrolytic solution in which the above-mentioned various compounds are dissolved alone or in plural, an electrolytic solution in which other additives are added, and an electrolytic solution in which a sub-solvent is mixed Even when used in the above, the same effect as in the example was obtained.

Claims (2)

It is characterized in that at least a higher dibasic acid or a salt thereof, boric acid or an ammonium salt thereof, and an undecanoic γ-lactone represented by the following chemical formula are blended in a solvent containing ethylene glycol as a main solvent. Electrolytic solution for driving electrolytic capacitors.

  2. The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein a blending amount of the undecanoic γ-lactone is 0.5 to 2.0 wt% with respect to the entire electrolytic solution.