JP2007059478A - Electrolyte for driving electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte which can ensure high breakdown voltage and suppress the increase in tanδ, by preventing reaction between an electrode foil and a water content in an electrolyte over a long time. <P>SOLUTION: A solvent made mainly of ethylene glycol is mixed with azelaic acid, carboxylic acid, such as benzoic acid, ammonium salt of boric acid, and triacrylformal indicated by a chemical Formula (1). The mixing quantity of triacrylformal is 0.10-5.0 wt.% with respect to the electrolyte as a whole, for example. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an improvement in an electrolytic solution for driving an electrolytic capacitor (hereinafter referred to as an electrolytic solution).

Conventionally, in an aluminum electrolytic capacitor, orthophosphoric acid is mixed with a solvent mainly composed of ethylene glycol, carboxylic acid, boric acid, or ammonium salt thereof to further suppress the reaction between the electrode foil and moisture in the electrolytic solution. An electrolytic solution containing an additive such as an acid is used (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, orthophosphoric acid is a strong acid and its action on the electrode foil is too strong, so that a large amount of addition reduces the withstand voltage of the electrolyte. Therefore, since orthophosphoric acid can be blended very little in the electrolytic solution, there is a problem that the reaction between the electrode foil and the water in the electrolytic solution cannot be sufficiently suppressed for a long period of time.

  In view of the above problems, an object of the present invention is to secure a high withstand voltage and to suppress an increase in tan δ by suppressing the reaction between the electrode foil and moisture in the electrolyte over a long period of time. It is in providing the electrolyte solution which can be performed.

The present invention has been found as a result of various studies to solve the above problems, and triacryl formal has a slower effect on electrode foil when it is added than orthophosphoric acid. The knowledge that the withstand voltage is not greatly reduced was obtained. Therefore, an amount sufficient to suppress the reaction between the electrode foil and moisture in the electrolytic solution over a long period of time can be blended, and an increase in tan δ in the reliability test can be suppressed.
That is, in the present invention, in an electrolytic solution for driving an electrolytic capacitor in which at least one of an organic carboxylic acid and boric acid is blended as an acid or salt in a solvent mainly composed of ethylene glycol, the following chemical formula The triacryl formal shown is blended.

In the present invention, when an electrolytic solution having a low specific resistance and a high withstand voltage is constituted, it is more preferable that both the organic carboxylic acid and boric acid are blended as an acid or a salt.

  In this invention, it is preferable that the compounding quantity of a triacryl formal is 0.10 to 5.0 weight% with respect to the whole electrolyte solution. When the blending amount of triacryl formal is less than 0.10% by weight with respect to the whole electrolyte solution, it is unsuitable for applications that require high reliability over a long period of time. Since the specific resistance of the liquid is increased, the blending amount of triacryl formal is preferably in the range of 0.10 to 5.0% by weight with respect to the entire electrolytic solution.

  In the present invention, as a co-solvent to be mixed with ethylene glycol, water, glycols such as propylene glycol, lactones such as γ-butyrolactone, γ-valerolactone, δ-valerolactone, N-methyl-2-pyrrolidone, etc. N-methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N-diethylformamide, N-methylacetamide, N, N-dimethylacetamide, N-ethylacetamide, N, N-diethylacetamide, hexa Examples include amides such as methylphosphoric amide, carbonates such as ethylene carbonate, propylene carbonate, and isobutylene carbonate, nitriles such as acetonitrile, oxides such as dimethyl sulfoxide, ethers, ketones, esters, and sulfolanes. It can be.

  In addition to azelaic acid, the organic carboxylic acid includes formic acid, acetic acid, acrylic acid, propionic acid, lactic acid, butyric acid, valeric acid, gluconic acid, benzoic acid, p-nitrobenzoic acid, anthranilic acid, salicylic acid, gentisic acid, Gallic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, decanedicarboxylic acid, oxalic acid, tolutronic acid, fumaric acid, maleic acid, citraconic acid, malic acid, tartaric acid, phthalic acid , Borodisalicylic acid, citric acid, pyromellitic acid, naphthoic acid and the like.

  Further, as an organic carboxylic acid salt, in addition to ammonium salt, monomethylamine, monoethylamine, monoethanolamine, isopropylamine, n-propylamine, dimethylamine, diethylamine, diethanolamine, di-n-propylamine, diisopropylamine, triisopropylamine -N-propylamine, trimethylamine, triethylamine, triethanolamine, tri-n-butylamine, dimethylethylamine, naphthalenediamine, benzylamine and the like.

  In the electrolytic solution to which the present invention is applied, the triacryl formal has a slower withstanding voltage drop than the phosphoric acid when added, and suppresses the reaction between the electrode foil and moisture in the electrolytic solution over a long period of time. Therefore, an increase in tan δ in the reliability test can be suppressed.

  Hereinafter, based on an Example, this invention is demonstrated more concretely. First, an electrolyte solution was prepared with the composition shown in Table 1, and the specific resistance at 30 ° C. was measured. The results are shown in Table 1.

  In addition, a capacitor element in which an aluminum anode foil and an aluminum cathode foil are wound through electrolytic paper is impregnated with an electrolytic solution having the composition shown in Table 1, and an aluminum electrolytic capacitor having a rated voltage of 250 V / 68 μF (φ16 × 25 mmL). Was made. Next, after performing an aging process at a rated voltage, a rated voltage application test was performed at 105 ° C. for 7000 hours, and tan δ at each time was measured. The results are shown in Table 1.

As shown in Table 1, the electrolytes according to Examples 1 to 14 of the present invention blended with triacryl formal had higher withstand voltage than the electrolytes according to Conventional Examples 2 to 5 to which orthophosphoric acid was added. In the case of using an electrolyte solution containing 0.5% by weight and 1.0% by weight of acid (conventional examples 4 and 5), a short puncture occurred during aging or a rated voltage application test. When the electrolytic solutions according to 1 to 14 were used, such a short puncture did not occur.
Further, in Examples 1 to 14, there is no operation of the pressure valve during the rated voltage application test as compared with the conventional example 1, and as compared with the conventional examples 2 and 3, the increase in tan δ during the rated voltage application test is suppressed. The effect was obtained.

  Here, when the blending amount of triacryl formal is less than 0.10% by weight with respect to the entire electrolyte (for example, Example 1), the increase in tan δ during the reliability test tends to be large, and the long term It is unsuitable for applications that require high reliability over a wide range. Moreover, when the compounding quantity of triacryl formal exceeds 5.0 weight% (for example, Example 12), there exists a tendency for the specific resistance of electrolyte solution to be high and initial tan-delta to be high. Therefore, the blending amount of triacryl formal is preferably in the range of 0.10 to 5.0% by weight with respect to the entire electrolyte solution.

  In addition, the effect of the triacryl formal according to the present invention is not limited to the examples, and the examples may be used even in an electrolytic solution in which the above-described various compounds are singly or plurally dissolved or an auxiliary solvent is mixed. Had the same effect. In addition, the same effect was obtained in an electrolytic solution in which either one of organic carboxylic acid and boric acid was blended as an acid or a salt.

Claims (3)

In an electrolytic solution for driving an electrolytic capacitor in which at least one of an organic carboxylic acid and boric acid is blended as an acid or salt in a solvent containing ethylene glycol as a main component,
Further, an electrolytic solution for driving an electrolytic capacitor, characterized in that a triacryl formal represented by the following chemical formula is blended.

  2. The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein both the organic carboxylic acid and boric acid are blended as an acid or a salt.   3. The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein the blending amount of triacryl formal is 0.10 to 5.0% by weight with respect to the whole electrolytic solution.