JP4752707B2 - Electrolytic solution for electrolytic capacitors - Google Patents

Description

The present invention relates to an electrolytic solution for electrolytic capacitors, and more particularly to an electrolytic solution for electrolytic capacitors having low specific resistance characteristics.

An electrolytic capacitor is generally a strip-like high-purity aluminum foil that is chemically or electrochemically etched to enlarge the surface of the aluminum foil, and this aluminum foil is converted into a chemical conversion solution such as an ammonium borate aqueous solution. Anode electrode foil formed by chemical conversion treatment inside to form an oxide film layer on the surface, and a cathode electrode foil made of high-purity aluminum foil subjected only to etching treatment are wound through a separator made of manila paper or the like. Turn to form a capacitor element. The capacitor element is impregnated with an electrolytic solution for driving an electrolytic capacitor, and then stored in a bottomed cylindrical outer case made of aluminum or the like. A sealing body made of elastic rubber is attached to the opening of the outer case, and the outer case is sealed by drawing.

Here, as an electrolytic solution for driving an electrolytic capacitor having high conductivity impregnated in the capacitor element, γ-butyrolactone is a main solvent, and imidazolinium cation or imidazole, which are cations obtained by quaternizing a cyclic amidine compound as a solute. A solution in which a salt having a cation component as a cation component and an acid conjugate base as an anion component is dissolved is used (see Patent Documents 1 and 2). Although this electrolytic solution has excellent electrical conductivity, it has poor withstand voltage, and borodiglycolic acid has been proposed as a solute for electrolytic solution having high conductivity characteristics and high withstand voltage (Patent Document 3).

JP 08-32440 A Japanese Patent Application Laid-Open No. 08-324411 Japanese Patent Laid-Open No. 2004-134458

  Although the electrolytic solution using this borodiglycolic acid has a high withstand voltage, it has a problem of high leakage current.

Accordingly, an object of the present invention is to provide an electrolytic solution for an electrolytic capacitor having low specific resistance characteristics, a high withstand voltage, and a low leakage current.

The electrolytic solution for electrolytic capacitors of the present invention uses a borodiglycolic acid tertiary amine salt as a solute, 0.4 to 1.0 wt% of water, hydroxycarboxylic acid or a derivative thereof or a salt thereof, a sulfite group or One or more selected from compounds containing a persulfate group are added.

And, γ-butyrolactone is used as a solvent.

Further, the electrolytic solution contains 90 wt% or less of sulfolane, 3-methylsulfolane, or 2,4-dimethylsulfolane in the solvent.

The inventors of the present invention have focused on the cause of the high leakage current of the electrolytic solution using borodiglycolic acid, and that it takes time to rise in the spark voltage of the electrolytic solution. That is, when the Vt characteristic is measured, the voltage rises up to about 50 V, but the subsequent rise is bad. That is, although it is formed at the time of capacitor production, it was assumed that the subsequent chemical film dissolution and re-reaction reaction were poor, and therefore the withstand voltage was high but the leakage current was high. Therefore, as a result of studying to improve the rise, as a result, 0.4 to 3.0 wt% of water is selected, which is selected from hydroxycarboxylic acid or a derivative thereof or a salt thereof, and a compound containing a sulfite group or a persulfate group. Or it became clear that the rise of a spark voltage became high by adding 2 or more types. That is, a chemical reaction of the electrode foil occurs due to water present in the electrolytic solution, and the reaction is caused by hydroxycarboxylic acid or a derivative thereof or a salt thereof and one or more selected from compounds containing a sulfite group or a persulfate group. Is promoted, the chemical conversion of the electrolyte is improved, the rise of the spark voltage is accelerated, and as a result, the leakage current is considered to be reduced.

The electrolytic solution for an electrolytic capacitor of the present invention contains a borodiglycolic acid tertiary amine salt as a solute, a solvent, 0.4 to 1.0 wt% of water, a hydroxycarboxylic acid or a derivative thereof or a salt thereof, and a sulfite group. or it is characterized in that the addition of the one or more selected from compounds containing persulfate group. The amount of water added is 0.4 to 3.0 wt%, preferably 0.4 to 2.0 wt%, and more preferably 0.5 to 0.8 wt%. If it is less than this range, the effect is small, and if it exceeds this range, it seems to be due to hydrolysis of borodiglycolic acid, but ESR increases.

As hydroxycarboxylic acid, glycolic acid, lactic acid, 2-hydroxybutyric acid, salicylic acid, hydroxymalonic acid, malic acid, α-methylmalic acid, tartaric acid, citric acid, γ-resorcylic acid, β-resorcylic acid, hydroxyphthalic acid, Mention may be made of dihydroxyphthalic acid.

Examples of the compound containing a sulfite group or a persulfate group include sulfite, ammonium sulfite, and ammonium peroxodisulfate.

The additive amount of these additives is 0.1 to 3 wt%, preferably 0.3 to 2 wt%. If the amount is less than this range, the effect of improving the chemical conversion property is lowered. .

And the addition amount of the borodiglycolic acid in the electrolyte solution of this invention is 10-50 wt%, Preferably it is 20-30 wt%. If it is less than this range, the specific resistance will increase, and if it exceeds this range, the withstand voltage will decrease. .

As the solvent used in the electrolytic solution of the present invention, a protic polar solvent, an aprotic solvent, and a mixture thereof can be used. Protic polar solvents include monohydric alcohols (ethanol, propanol, butanol, pentanol, hexanol, cyclobutanol, cyclopentanol, cyclohexanol, benzyl alcohol, etc.), polyhydric alcohols and oxyalcohol compounds (ethylene glycol) Propylene glycol, glycerin, methyl cellosolve, ethyl cellosolve, methoxypropylene glycol, dimethoxypropanol, etc.). Examples of aprotic polar solvents include amides (N-methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N-diethylformamide, N-methylacetamide, N, N-dimethylacetamide, N-ethylacetamide, N, N-diethylacetamide, hexamethylphosphoricamide, etc.), lactones (γ-butyrolactone, δ-valerolactone, γ-valerolactone, etc.), sulfolane (sulfolane, 3-methylsulfolane) 2,4-dimethylsulfolane, etc.), cyclic amides (N-methyl-2-pyrrolidone, etc.), carbonates (ethylene carbonate, propylene carbonate, isobutylene carbonate, etc.), nitriles (acetonitrile, etc.), sulfoxides ( Dimethyl sulfoxide, etc. 2-imidazolidinone [1,3-dialkyl-2-imidazolidinone (1,3-dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidinone, 1,3-di ( n-propyl) -2-imidazolidinone), 1,3,4-trialkyl-2-imidazolidinone (1,3,4-trimethyl-2-imidazolidinone, etc.)] and the like. It is done. Among these, use of γ-butyrolactone is preferable because impedance characteristics are improved, and use of sulfolane, 3-methylsulfolane, or 2,4-dimethylsulfolane is preferable because high temperature characteristics are improved. The content of γ-butyrolactone in the solvent is 10 to 100 wt%, preferably 30 to 100 wt%. Below this range, the specific resistance increases.

The present invention will be described more specifically with reference to the following examples.

（表１）から分かるように、実施例は比較例に比べて、初期、高温寿命試験後も漏れ電流特性が改善されている。また、γ−レゾルシル酸を添加した比較例３は添加しない比較例２に比べて効果はなく、本願のヒドロキシカルボン酸またはその誘導体またはそれらの塩と、亜硫酸基または過硫酸基を含む化合物の相乗効果によって、本願の効果が得られていることがあきらかである。 In this embodiment, 25 parts of borodiglycolic acid, 0.1 part of ammonium peroxodisulfate, 1 part of γ-resorcylic acid, and 75 parts of γ-butyrolactone or γ-butyrolactone and sulfolane as the solvent were used as the electrolytic solution for the electrolytic capacitor. . In addition, an electrolytic capacitor was manufactured using an electrolytic solution not using the additive of the present application as Comparative Examples 1 and 2, and an electrolytic solution added with 1 part of γ-resorcylic acid as Comparative Example 3. These electrolytic capacitors were evaluated for high-temperature life characteristics. The test conditions are 105 ° C. and 1000 hours load. The ratio of the solvent of the electrolytic solution and the test results are shown in (Table 1).

As can be seen from (Table 1), the leakage current characteristics of the example are improved after the initial and high-temperature life test as compared with the comparative example. Further, Comparative Example 3 to which γ-resorcylic acid was added was not effective as compared to Comparative Example 2 to which γ-resorcylic acid was not added, and synergy between the hydroxycarboxylic acid of the present application or a derivative thereof or a salt thereof and a compound containing a sulfite group or persulfate group It is obvious that the effect of the present application is obtained by the effect.

Claims (4)

Borodiglycolic acid tertiary amine salt as a solute, selected from 0.4 to 3.0 wt% of water, hydroxycarboxylic acid or a derivative thereof or a salt thereof, and a compound containing a sulfite group or a persulfate group Or the electrolytic solution for electrolytic capacitors which added 2 or more types. 2. The electrolytic solution for an electrolytic capacitor according to claim 1 , wherein the hydroxycarboxylic acid is γ-resorcylic acid and the compound containing a persulfate group is ammonium peroxodisulfate. Claim 1 or 2 electrolytic capacitor electrolyte solution according with γ- butyrolactone as a solvent.   The electrolytic solution for an electrolytic capacitor according to claim 3, comprising 90 wt% or less of sulfolane, 3-methylsulfolane, or 2,4-dimethylsulfolane in the solvent.