JP4571017B2 - Electrolytic solution for driving electrolytic capacitors - Google Patents

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 more particularly to an electrolytic solution with improved leakage current at high temperature and no load.

Along with the recent miniaturization of aluminum electrolytic capacitors, the anode foil of aluminum electrolytic capacitors has come to be used with a high etching magnification, and an electrolytic solution having a low specific resistance is required. Conventionally, electrolytes of medium- and high-pressure aluminum electrolytic capacitors contain ethylene glycol as the main solvent, organic carboxylic acid, boric acid or its ammonium salt, etc., and mannitol to increase the withstand voltage of the electrolyte. In addition, an electrolytic solution to which a polyhydric alcohol such as sorbitol is added has been proposed (see, for example, Patent Documents 1 to 3).
Japanese Examined Patent Publication No. 7-48459 (page 1-4) Japanese Examined Patent Publication No. 7-48460 (page 1-3) Japanese Examined Patent Publication No. 7-63047 (page 1-4)

  However, in order to obtain an electrolyte solution with low specific resistance, it is necessary to increase the concentration of the electrolyte or to mix a large amount of water. However, if the electrolyte concentration is increased, the deposition of the electrolyte and the withstand voltage decrease. When a large amount of water is mixed, the leakage current increases remarkably when the aluminum electrolytic capacitor is left unloaded at a high temperature. For this reason, it is the present condition that the electrolytic solution has a low specific resistance, and an aluminum electrolytic capacitor with a small increase in leakage current at high temperature and no load has not been realized.

  In view of the above problems, an object of the present invention is to provide an electrolytic solution capable of suppressing an increase in leakage current at high temperature and no load even when water is added to reduce specific resistance.

  The present invention has been discovered as a result of various studies in order to solve the above-mentioned problems, and focuses on choline phosphoric acid and intends to apply the characteristics to an electrolytic solution.

  That is, in the electrolytic solution for driving an aluminum electrolytic capacitor according to the present invention, at least an organic carboxylic acid or a salt thereof and choline phosphoric acid represented by the following chemical formula with respect to a mixed solvent containing at least ethylene glycol and water. It is characterized by being blended.

  In this invention, it is preferable that the compounding quantity of choline phosphate is 0.1-1.0 wt% with respect to the whole electrolyte solution.

  In this invention, it is preferable that the compounding quantity of water is 2.0-10.0 wt% with respect to the whole electrolyte solution.

In the present invention, the organic carboxylic acid includes polycarboxylic acids azelaic acid, 2-methyl azelaic acid, sebacic acid, 1,6-decanedicarboxylic acid, 5,6-decanedicarboxylic acid, 7-vinylhexadecene- Examples thereof include 1,16-dicarboxylic acid. In the case of the rated voltage of the aluminum electrolytic capacitor, that is, low or medium pressure, the organic carboxylic acid is oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, maleic acid, fumaric acid. Acid, itaconic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, thiodipropionic acid, etc., as oxycarboxylic acid, glycolic acid, lactic acid, tartaric acid, salicylic acid, mandelic acid, etc. Monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, lauric acid, myristic acid, stearic acid, behenic acid, acrylic acid, methacrylic acid, Oleic acid, benzoic acid, p-nitrobenzoic acid, anisic acid, cumic acid, cinnamic acid, Etc. may be used Futoe acid.
Further, borodisoxalic acid, borodiglycolic acid, borodisalicylic acid, ethylene glycol borate ester and the like may be used in combination.

  In addition to ammonium salts, organic carboxylic acid salts include primary amine salts such as methylamine, ethylamine and t-butylamine, secondary amine salts such as dimethylamine, ethylmethylamine and diethylamine, trimethylamine, diethylmethylamine, Examples thereof include tertiary amine salts such as ethyldimethylamine, triethylamine and N, N-dimethyl-N- (2-methoxyethyl) amine, and quaternary ammonium salts such as tetramethylammonium and triethylmethylammonium.

  In addition, various additives can be further added to the electrolytic solution according to the present invention 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. Examples include molecular compounds and nitro compounds.

  Since the electrolyte solution according to the present invention contains choline phosphate, it is possible to suppress an increase in leakage current at high temperature and no load even when a specific resistance is reduced using a solvent containing water. The reliability of the aluminum electrolytic capacitor can be improved. In addition, the withstand voltage is high because there is no need to increase the electrolyte concentration even when the specific resistance is lowered. Furthermore, since choline phosphoric acid is easily dissolved in a mixed solvent of ethylene glycol and water, there is no problem such as precipitation.

  In the electrolytic solution for driving an aluminum electrolytic capacitor according to the present invention, at least an organic carboxylic acid or a salt thereof and choline phosphoric acid are blended with a mixed solvent containing at least ethylene glycol and water. For this reason, even when the specific resistance is reduced using a solvent containing water, an increase in leakage current at high temperature and no load can be suppressed, and the reliability of the aluminum electrolytic capacitor can be improved. The reason is that choline phosphoric acid is adsorbed on the surface of the electrode foil to protect the electrode foil, so that even if the amount of water is high, the hydration reaction between water and the electrode foil at a high temperature of 105 ° C. is suppressed. it is conceivable that.

  In this invention, the compounding quantity of choline phosphate is 0.1-1.0 wt% with respect to the whole electrolyte solution, for example, and the compounding quantity of water is 2.0-10. 0 wt%.

  Hereinafter, based on an Example, this invention is demonstrated more concretely. First, after preparing electrolyte solution with the composition shown in Table 1, the specific resistance in 30 degreeC was measured. The results are shown in Table 1.

  First, as the conventional examples 1 to 3 and examples 1 to 17, using the electrolytic solution shown in Table 1, ten aluminum electrolytic capacitors each having a rating of 400V-22 μF (φ16 × 25 mmL) were produced, and tan δ, leakage current After measuring initial characteristics, a high temperature no-load test (left at 105 ° C. for 1000 hours) was performed, and tan δ and leakage current after the test were measured. The results are shown in Table 2.

  First, Examples 1 to 15 using ammonium 1,6-decanedicarboxylate as the organic carboxylate will be described.

  As shown in Table 2, the aluminum electrolytic capacitor using the electrolytic solutions according to Examples 1 to 15 of the present invention is a high-temperature no-load test, although water is mixed to reduce the specific resistance of the electrolytic solution. The increase in leakage current is small. More specifically, when Comparative Example 2 and Examples 3, 5, and 7 having the same water content, for example, 5% by weight of water are compared with Examples 3, 5, and 7, Examples 3, 5, and 7 containing choline phosphate are used. The aluminum electrolytic capacitor using the electrolytic solution according to the present invention exhibits superior characteristics because the increase in leakage current in the high temperature no-load test is suppressed.

  However, when the compounding amount of choline phosphate is less than 0.1 wt% (Example 1), the effect of suppressing increase in leakage current is not sufficient, and the compounding amount exceeds 1.0 wt% (Example 9). Since the specific resistance increases, it can be seen that it is not suitable for low specific resistance applications. Therefore, the amount of choline phosphoric acid is preferably in the range of 0.1 to 1.0 wt%. In addition, when the moisture content is less than 2.0 wt%, the specific resistance is high (Example 11), and when it exceeds 10.0% (Example 15), the effect of choline phosphate tends to decrease. Therefore, the amount of water is preferably in the range of 2.0 to 10.0 wt%.

  Such an effect is the same when ammonium sebacate is used as the organic carboxylic acid (Example 16) or when ammonium azelaate is used (Example 17).

  The effect of blending choline phosphoric acid is not limited to the above-mentioned examples, and the same effect was obtained even when used in an electrolytic solution containing one or more organic carboxylic acids or salts thereof described above. .

Claims (3)

An electrolytic solution for driving an electrolytic capacitor, characterized in that at least an organic carboxylic acid or a salt thereof and choline phosphoric acid represented by the following chemical formula are blended with a mixed solvent containing at least ethylene glycol and water. .

  The electrolytic solution for driving an electrolytic capacitor, wherein the amount of choline phosphoric acid according to claim 1 is 0.1 to 1.0 wt% with respect to the entire electrolytic solution.   3. The electrolytic solution for driving an electrolytic capacitor, wherein the amount of water according to claim 1 or 2 is 2.0 to 10.0 wt% with respect to the entire electrolytic solution.