JPH038092B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to an electrolytic solution for electrolytic capacitors. According to the present invention, an excellent electrolytic solution for electrolytic capacitors (hereinafter sometimes simply referred to as electrolytic solution) with high conductivity can be obtained. BACKGROUND ART A well-known electrolytic solution for electrolytic capacitors is one in which an ammonium salt of boric acid or adipic acid is dissolved as a solute in an ethylene glycol solvent. Further, as an electrolytic solution having excellent low-temperature characteristics, one in which an adipic acid or an amino acid such as maleic acid is dissolved in a solvent such as N,N-dimethylformamide or -butyrolactone, which has an even lower freezing point, is known. Problems to be Solved by the Invention However, as the impedance of electrolytic capacitors becomes lower, an electrolytic solution with even higher conductivity is desired, and JP-A-59-78522 discloses dibasic carboxylic acid HOOC-( _CH2 )n-COOH(4n
Although an electrolytic solution with high electrical conductivity in which the quaternary ammonium salt (8) is dissolved in an amide solvent containing 2 to 10% by weight of water has been disclosed, it cannot be said to be sufficient. Means for Solving the Problems The present inventors have conducted intensive studies to find a new electrolytic solution with even higher conductivity, and found that quaternary ammonium salts of aromatic carboxylic acids are The present invention was completed based on the discovery that the present invention shows higher conductivity than quaternary ammonium salts of dibasic carboxylic acids. That is, the present invention provides an electrolytic solution for an electrolytic capacitor characterized by using a quaternary ammonium salt of an aromatic carboxylic acid as a solute. Effects of the Invention The quaternary ammonium salt of aromatic carboxylic acid used as a solute in the present invention has good solubility in solvents, and also exhibits high electrical conductivity. An excellent electrolyte for electrolytic capacitors with a wide range of applications. Detailed Description of the Invention The aromatic carboxylic acid of the quaternary ammonium salt of aromatic carboxylic acid used in the present invention has the following general formula: (wherein, X, Y and Z are hydrogen atoms or alkyl groups, hydroxyl groups, alkoxy groups, amino groups, monoalkylamino groups, dialkylamino groups, nitro groups,
and carboxyl groups, which may be the same or different from each other. ) is a compound represented by The total number of carbon atoms in the aromatic carboxylic acid ranges from 7 to 30, preferably from 7 to 12. Specifically, benzoic acid, toluic acid, ethylbenzoic acid, propylbenzoic acid, isopropylbenzoic acid, butylbenzoic acid, isobutylbenzoic acid, sec-butylbenzoic acid, tertiary-butylbenzoic acid, hydroxybenzoic acid, anisic acid, Ethoxybenzoic acid, propoxybenzoic acid, isopropoxybenzoic acid, butoxybenzoic acid, isobutoxybenzoic acid, sec-butoxybenzoic acid, tertiary-butoxybenzoic acid, aminobenzoic acid, N-methylaminobenzoic acid, N-ethylaminobenzoic acid , N-propylaminobenzoic acid,
N-isopropylbenzoic acid, N-butylaminobenzoic acid, N-isobutylaminobenzoic acid, N-sec-butylaminobenzoic acid, N-tert-butylaminobenzoic acid, N,N-dimethylaminobenzoic acid,
Aromatic monocarboxylic acids (including o, m, p-isomers) such as N,N-diethylaminobenzoic acid, nitrobenzoic acid, resorcinic acid, phthalic acid, isophthalic acid, terephthalic acid, nitrophthalic acid, trimellitic acid , hemimellitic acid, pyromellitic acid, and other aromatic polyhydric carboxylic acids. Examples of quaternary ammonium salts include aliphatic quaternary ammonium salts such as tetraethylammonium, tetrapropylammonium, tetrabutylammonium, methyltrinitylammonium, N,N-
Alicyclic quaternary ammonium salts such as dimethylpyrrolidinium, N,N-dimethylpiperidinium, N,N-pentamethylenepiperidinium, and N-
Examples include aromatic quaternary ammonium salts such as ethylpyridinium. Examples of the solvent for dissolving the quaternary ammonium salt of aromatic carboxylic acid of the present invention include N-methylformamide, N-ethylformamide, N,N-dimethylformamide, N,N-diethylformamide, N-methylacetamide, N- Ethylacetamide, N,N-dimethylacetamide, N,N
- Amide solvents such as diethylacetamide and N-methylpyrrolidinone, lactone solvents such as γ-butyrolactone, γ-valerolactone, and δ-valerolactone, carbonate solvents such as ethylene carbonate, propylene carbonate, butylene carbonate, ethylene glycol, glycerin, methyl Examples include alcohol solvents such as cellosolve, nitrile solvents such as 3-methoxypropionitrile, and phosphoric acid ester solvents such as trimethyl phosphate, either alone or in combination. Among these, a solvent mainly composed of γ-butyrolactone is particularly preferred because it has low toxicity, is less likely to attack the sealing agent of an electrolytic capacitor, and is less likely to be contaminated with halogen. The amount of the quaternary ammonium salt of aromatic carboxylic acid dissolved in the above solvent is below the saturation concentration, preferably in the range of 5 to 40% by weight. Further, the electrolytic salt in the electrolytic solution does not need to be a neutral salt, and may be an acidic salt. The quaternary ammonium salt of an aromatic carboxylic acid can be produced, for example, by neutralizing the aromatic carboxylic acid with an aqueous solution of quaternary ammonium hydroxide, distilling off water under reduced pressure, recrystallizing the obtained product from methanol, and drying it under vacuum. Although obtained by drying, the electrolytic solution of the present invention can also be prepared by adding an aromatic carboxylic acid and an aqueous quaternary ammonium hydroxide solution to a solvent, dissolving the solution, and then dehydrating the solution. The electrolytic solution of the present invention essentially consists of a quaternary ammonium salt of an aromatic carboxylic acid and a solvent, but it also contains various co-solutes for the purpose of preventing galvanic corrosion, reducing leakage current, absorbing hydrogen gas, etc. Phosphoric acid derivatives, nitrobenzene derivatives, etc. can be added. The solvent used in the present invention can be used in a substantially anhydrous state, but 1 to 10% by weight of water can also be added for the purpose of improving electrical conductivity, improving chemical formability, etc. EXPERIMENTAL EXAMPLE The present invention will be described in more detail below with reference to Examples and Comparative Examples. Example 1 An electrolytic solution was obtained by dissolving 20% by weight of benzoic acid tetraethylammonium salt in a γ-butyrolactone solvent. The conductivity of this electrolyte at 25℃ is
The voltage was 8.4 mS/cm, and the spark generation voltage was 133 V when a constant current of 2 mA/cm ² was applied to a pair of smooth aluminum foils. Examples 2 to 4 In Example 1, monotetraethylammonium salt of phthalic acid (Example 2), monotetraethylammonium salt of trimellitic acid (Example 3), monotetraethylammonium salt of pyromellitic acid was used instead of tetraethylammonium salt of benzoic acid. The conductivity and spark generation voltage of an electrolytic solution using tetraethylammonium salt (Example 4) were measured. The results are shown in Table 1. Examples 5 to 7 In Example 1, N,N-dimethylformamide (Example 5), 3-methoxypropionitrile (Example 6), and trimethyl phosphate (Example 7) were used instead of γ-butyrolactone. The conductivity of the electrolyte used was measured. The results are shown in Table 1. Comparative Example 1 Table 1 shows the conductivity and spark generation voltage of an electrolytic solution in which monotetraethylammonium salt of adipic acid was used instead of tetraethylammonium salt of benzoic acid in Example 1. Comparative Examples 2-4 Monotetraethylammonium salt of adipic acid
An electrolytic solution was obtained by dissolving 20% by weight of N,N-dimethylformamide (Comparative Example 2), 3-methoxypropionitrile (Comparative Example 3), and trimethyl phosphate (Comparative Example 4) as solvents. The conductivity and spark generation voltage of the electrolyte are shown in Table 1. Comparative Example 5 In Example 1, the conductivity of the electrolytic solution using triethylammonium salt of benzoic acid instead of tetraethylammonium salt of benzoic acid was 0.8.
The temperature was mS/cm. Examples 8 to 13 In Example 1, salicylic acid (Example 8), p-nitrobenzoic acid (Example 9), o-nitrobenzoic acid (Example 10), and o-toluic acid (Example 10) were used instead of benzoic acid. Example 11), o-anisic acid (Example 12),
The conductivity of an electrolytic solution using the tetraethylammonium salt of γ-resorcinic acid (Example 13) was measured. The results are shown in Table 2. In addition, the following abbreviations were used in Tables 1 and 2. GBL: γ-Butyrolactone DMF: N,N-dimethylformamide MPN: 3-methoxypropionitrile TMP: Trimethyl phosphate

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Claims (1)

[Claims] 1. An electrolytic solution for an electrolytic capacitor, characterized in that a quaternary ammonium salt of an aromatic carboxylic acid is used as a solute.