JP2002110470A - Electrolyte for electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolyte of electrolytic capacitor, having a good shelf characteristic. SOLUTION: The electrolyte for an aluminum electrolytic capacitor is made by adding a tannic acid to an electrolyte consisting of a solvent and solute. By adding the tannic acid, the shelf characteristic of the electrolytic capacitor can be improved and an initial electrostatic capacity can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrolytic solution for an electrolytic capacitor.

[0002]

2. Description of the Related Art An electrolytic capacitor generally has the following configuration. That is, a high-purity aluminum foil formed in a belt shape is chemically or electrochemically etched to enlarge the surface, and the expanded aluminum foil is subjected to a chemical conversion treatment in a chemical conversion solution such as an ammonium borate aqueous solution. By doing so, a capacitor element is formed by winding, via a separator, an anode foil having an oxide film layer formed on the surface of an aluminum foil and a cathode foil having a high-purity aluminum foil expanded. The capacitor element is impregnated with a driving electrolyte, and is housed in a metal bottomed cylindrical outer case. Further, a sealing body made of elastic rubber is housed at the opening end of the outer case, and the opening end of the outer case is sealed by drawing to form an electrolytic capacitor.

[0003] Conventionally, as an electrolytic solution impregnated in a capacitor element of a small-sized, low-pressure electrolytic capacitor, ethylene glycol as a main solvent, adipic acid,
Known are those in which an ammonium salt such as benzoic acid is used as a solute or those in which γ-butyrolactone is used as a main solvent and a quaternized cyclic amidinium salt such as phthalic acid or maleic acid is used as a solute.

[0004]

However, when such an electrolytic capacitor is left unattended, the capacitance decreases, the leakage current characteristics deteriorate, and the safety valve may open. Such a standing characteristic, which is a characteristic after a long period of time with or without a load, has a great influence on the reliability of the electrolytic capacitor.

Accordingly, an object of the present invention is to provide an electrolytic solution for an electrolytic capacitor having good standing characteristics.

[0006]

An electrolytic solution for an electrolytic capacitor according to the present invention is characterized in that tannic acid is added to an electrolytic solution comprising a solvent and a solute.

[0007] In the electrolytic solution for an electrolytic capacitor, a solvent containing water as a main component is used.

Further, in the electrolytic solution for an electrolytic capacitor, at least one of adipic acid and a salt thereof is used as a solute.

Further, when the content of water in the solvent is 35 to 10
0 wt%.

[0010] The electrolytic solution is characterized in that the content of adipic acid or a salt thereof is 5 to 23 wt%.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The electrolytic solution for an electrolytic capacitor of the present invention comprises a tannic acid [CAS:
1401-55-4].

The solutes contained in the electrolytic solution include ammonium salts, amine salts, quaternary ammonium salts and cyclic amidine compounds which are usually used in electrolytic solutions for electrolytic capacitors and have an anionic component of a conjugate base of an acid. Grade salts. Primary amines (methylamine, ethylamine, propylamine,
Butylamine, ethylenediamine, etc., secondary amines (dimethylamine, diethylamine, dipropylamine, methylethylamine, diphenylamine, etc.), tertiary amines (trimethylamine, triethylamine, tripropylamine, triphenylamine, 1,8-diazabicyclo (5, 4,0) {undecene} 7 etc.). As the quaternary ammonium constituting the quaternary ammonium salt, tetraalkylammonium (tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, methyltriethylammonium, dimethyldiethylammonium, etc.), pyridium (1-methylpyridium) , 1-ethylpyridium, 1,3-diethylpyridium, etc.). In addition, examples of the cation constituting the quaternary salt of the cyclic amidine compound include cations obtained by quaternizing the following compounds. That is, the imidazole monocyclic compound (1─
Methylimidazole, 1,2-dimethylimidazole,
Imidazole homologs such as 1,4-dimethyl-2-ethylimidazole and 1-phenylimidazole, oxyalkyl derivatives such as 1-methyl-2-oxymethylimidazole and 1-methyl-2-oxyethylimidazole,
-Methyl-4 (5) -nitroimidazole, nitro and amino derivatives such as 1,2-dimethyl-5 (4) -aminoimidazole, etc., benzimidazole (1-methylbenzimidazole, 1-methyl-2-benzylbenzimidazole) Etc.), compounds having a 2-imidazoline ring (1-methylimidazoline, 1,2-dimethylimidazoline, 1,2,4-trimethylimidazoline, 1,4-
Dimethyl-2-ethylimidazoline, 1-methyl-2-
Phenylimidazoline, etc.), compounds having a tetrahydropyrimidine ring (1-methyl-1,4,5,6-tetrahydropyrimidine, 1,2-dimethyl-1,4,5,6)
-Tetrahydropyrimidine, 1,8-diazabicyclo [5.4.0] undecene-7, 1,5-diazabicyclo [4.3.0] nonene-5, and the like.

The anionic components include adipic acid, glutaric acid, succinic acid, benzoic acid, isophthalic acid, phthalic acid, terephthalic acid, maleic acid, toluic acid, enanthic acid, malonic acid, formic acid and 1,6-decanedicarboxylic acid ,
Decanedicarboxylic acid such as 5,6-decanedicarboxylic acid,
Octanedicarboxylic acid such as 1,7-octanedicarboxylic acid, azelaic acid, organic acid such as sebacic acid, or
Examples thereof include boric acid, a polyhydric alcohol complex compound of boric acid obtained from boric acid and a polyhydric alcohol, and conjugate bases of inorganic acids such as phosphoric acid, carbonic acid, and silicic acid. Of these, preferred are decanedicarboxylic acid, octanedicarboxylic acid, azelaic acid, sebacic acid, adipic acid, glutaric acid, succinic acid, benzoic acid, isophthalic acid, organic carboxylic acids such as formic acid, or boric acid, boric acid. It is a polyhydric alcohol complex compound.

Among these, it is preferable to use at least one of adipic acid or a salt thereof because high conductivity and high-temperature stability can be obtained. Here, the content of adipic acid or a salt thereof in the electrolytic solution is 5 to 23 wt%, preferably 8 to 18 wt%. Above this lower limit, the conductivity increases, and below this upper limit the solubility improves.

[0015] The solvent of the electrolytic solution of the present invention includes:
Protic polar solvents, aprotic polar solvents, and mixtures thereof can be used. Examples of the protic polar solvent include water, monohydric alcohol (methanol, ethanol, propanol, butanol, hexanol, cyclohexanol, cyclopentanol, benzyl alcohol, etc.), polyhydric alcohol and oxyalcohol compounds (ethylene glycol, propylene glycol) , Glycerin, methyl cellosolve, ethyl cellosolve, 1,3
-Butanediol, methoxypropylene glycol, etc.)
And so on. Examples of aprotic polar solvents include amides (N-methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N-dimethylformamide, N-methylacetamide, hexamethylphosphoramide, etc.), lactones (Γ-butyrolactone, δ-valerolactone, etc.), cyclic amides (N-
Methyl-2-pyrrolidone, etc.), carbonates (ethylene carbonate, propylene carbonate, etc.), nitriles (acetonitrile, etc.), oxides (dimethylsulfoxide, etc.), 2-imidazolidinone [1,3-dialkyl-2-imidazo] Ridinone (1,3-dimethyl-2
-Imidazolidinone, 1,3-diethyl-2-imidazolidinone, 1,3-di (n-propyl) -2-imidazolidinone, etc., 1,3,4-trialkyl-2-imidazolidinone (1,3,4-trimethyl-2-imidazolidinone and the like)] and the like.

Among them, it is preferable to use a solvent containing water as a main component, since a high conductivity can be obtained. Here, the content of water in the solvent is 35 to 100 wt%, and when the content is 65 wt% or less, the low-temperature characteristics are good. Therefore, the content is preferably 35 to 65 wt%.

Since a certain amount of phosphate ions in the electrolytic solution is consumed by reacting with the electrode foil at the time of preparing the electrolytic capacitor, the amount added at the time of preparing the electrolytic solution is 0.002 mol% by weight.
Further, if added in an amount of 0.04 mol% or more, the initial film dissolution is severe, and the leaving characteristics of the electrolytic capacitor are deteriorated. Therefore, 0.002 to 0.04 mol% by weight is preferable, and 0.003 to 0.04 mol% is more preferable.
0.03 mol% by weight.

In order to stabilize the life characteristics of the electrolytic capacitor, nitrophenol, nitrobenzoic acid, nitroacetophenone, nitrobenzyl alcohol,
(Nitrophenoxy) ethanol, nitroanisole,
Aromatic nitro compounds such as nitrophenetol, nitrotoluene, dinitrobenzene and the like can be added.

Further, for the purpose of improving the safety of the electrolytic capacitor, a nonionic surfactant, a polyhydric alcohol, ethylene oxide and / or
Alternatively, a polyoxyalkylene polyhydric alcohol ether compound or polyvinyl alcohol obtained by addition polymerization of propylene oxide can also be added.

Further, by adding boric acid, polysaccharides (such as mannitol, sorbite, pentaerythritol), a complex compound of boric acid and polysaccharide, and colloidal silica to the electrolytic solution for an electrolytic capacitor of the present invention, the resistance is further improved. The voltage can be improved.

An oxycarboxylic acid compound or the like can be added for the purpose of reducing the leakage current.

The electrolytic capacitor containing the electrolytic solution for an electrolytic capacitor of the present invention has good standing characteristics, that is, characteristics after a long-term load and no-load test, and also improves the initial capacitance. .

Further, in the electrolytic solution for an electrolytic capacitor of the present invention, it is considered that the action of dissolving the oxide film of tannic acid causes the dielectric oxide film of the electrode foil to be dissolved during the production of the electrolytic capacitor. However, the initial capacitance is improved.

[0024]

Next, embodiments of the present invention will be described in detail. The capacitor element is formed by winding an anode foil and a cathode foil via a separator. The anode electrode foil has a purity of 9
After a 9.9% aluminum foil was chemically or electrochemically etched in an acidic solution and subjected to surface expansion treatment, a chemical conversion treatment was performed in an aqueous solution of ammonium adipate to form an anodic oxide film layer on the surface. Use something. As the cathode foil, a foil obtained by etching an aluminum foil having a purity of 99.9% and expanding the surface was used.

In the capacitor element configured as described above,
An electrolytic solution for driving an electrolytic capacitor is impregnated. The capacitor element impregnated with this electrolytic solution is housed in a cylindrical outer case made of aluminum with a bottom, a butyl rubber sealing body is inserted into the open end of the outer case, and the end of the outer case is drawn. To seal the electrolytic capacitor.

The composition of the electrolytic solution used here and its specific resistance are shown in (Table 1). Compositions are given in parts. The tannic acid used here is tannic acid specified by CAS: 1401-55-4. Further, as a conventional example, an electrolytic solution containing 75 parts of γ-butyrolactone and 25 parts of ethyl dimethyl imidazolinium phthalate was used. The specific resistance was 81 Ωcm.

A high-temperature life test of the aluminum electrolytic capacitor constructed as described above was conducted. The rating of the aluminum electrolytic capacitor is 6.3 WV-5600 μF. The test conditions are
105 ° C, rated voltage load, no load, 1000 hours. The results are shown in (Table 2) and (Table 3). The initial characteristics of the conventional example are as follows: the capacitance is 5540 μF, t
an δ was 0.101 and the leakage current was 13 μA.

[0028]

[Table 1] (Note) EG: Ethylene glycol AAd: Ammonium adipate TaA: Tannic acid

[0029]

[Table 2] (Note) Cap: capacitance (μF), tan δ: tangent of dielectric loss, LC: leakage current (μA), ΔCap: capacitance change rate (%)

[0030]

[Table 3]

As can be seen from (Tables 2) and (Table 3), the leaving characteristics of the examples are good. In comparison, in the comparative example in which tannic acid was not added, the initial specific resistance was 8
0, tan δ is 0.108 to 0.109, specific resistance, t
Both an and δ are the lowest levels of conventional products, but they have been opened, and according to the present invention, an aluminum electrolytic capacitor having unprecedented low tan δ characteristics and excellent leaving characteristics has been realized. I understand.

Further, as can be seen from Tables 1 to 3 and the characteristics of the conventional example, the specific resistance of the example is 18 to 6
8 Ωcm, which is much lower than the conventional example of 81 Ωcm, and the initial tan δ is also 0.060 to 0.081, which is lower than the conventional example of 0.101. The capacitance is 5600-56.
90 μF, which is larger than 5540 μF of the conventional example.

[0033]

As described above, according to the present invention, since tannic acid is added to the electrolytic solution comprising a solvent and a solute,
It is possible to provide an electrolytic solution for an electrolytic capacitor capable of improving good standing characteristics and improving the initial capacitance.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hisatomi Ito 1-167, Higashi-Ome, Ome-shi, Tokyo Nippon Chemi-Con Corporation (72) Inventor Tatsuki Tsuji 1-167, Higashi-Ome 1-chome, Ome-shi, Tokyo Nippon Chemi-Con Inside the corporation

Claims (5)

[Claims] 1. An electrolytic solution for an electrolytic capacitor in which tannic acid is added to an electrolytic solution comprising a solvent and a solute. 2. The method according to claim 1, wherein a solvent containing water as a main component is used.
The electrolytic solution for an electrolytic capacitor according to the above. 3. The electrolytic solution for an electrolytic capacitor according to claim 1, wherein at least one of adipic acid or a salt thereof is used as a solute. 4. A solvent having a water content of 35 to 100 wt.
%. The electrolytic solution for an electrolytic capacitor according to claim 2, wherein 5. The electrolytic solution for an electrolytic capacitor according to claim 3, wherein the content of adipic acid or a salt thereof in the electrolytic solution is 5 to 23 wt%.