JPH0722083B2 - Electrolytic solution for electrolytic capacitors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention According to the present invention, an excellent electrolytic solution for an electrolytic capacitor having high electric conductivity (hereinafter sometimes simply referred to as an electrolytic solution) can be obtained.

2. Description of the Related Art It is well known that an electrolytic solution for electrolytic capacitors, in which an ammonium salt of boric acid or adipic acid is dissolved as a solute in an ethylene glycol solvent, has a high viscosity in the ethylene glycol solvent used. Since the freezing point is relatively high, the conductivity of the electrolytic solution is significantly reduced at low temperatures, and the low temperature characteristics of the electrolytic capacitor are poor.

To improve this drawback, solvents such as N, N-dimethylformamide and γ-butyrolactone, which have a lower freezing point than ethylene glycol, are used.

Problems to be Solved by the Invention However, conventional ammonium salts have poor solubility in these aprotic solvents, and organic amine salts such as triethylamine and diethylamine are used. Is very low (Japanese Patent Publication No. 54-1024).

Means for Solving the Problems The inventors of the present invention have conducted diligent studies to find out a novel electrolytic solution having higher conductivity, and the quaternary phosphonium salt of carboxylic acid exhibits significantly higher conductivity than conventional amine salts. We have found this and completed the present invention.

That is, the present invention provides an electrolytic solution for an electrolytic capacitor, which uses a quaternary phosphonium salt of carboxylic acid as a solute.

DETAILED DESCRIPTION OF THE INVENTION The carboxylic acid in the quaternary phosphonium salt of the carboxylic acid used in the present invention is a fatty acid having 1 to 30 total carbons and an aromatic monovalent or polyvalent carboxylic acid.

Specifically, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid,
Heptadecanoic acid, stearic acid, nonadecanoic acid, arachidic acid, isobutyric acid, isovaleric acid, isocaproic acid, ethylbutyric acid, methylvaleric acid, isocaprilic acid, propylvaleric acid, ethylcaproic acid, isocapric acid, tuberculostearic acid, pivalin Acid, 2,2-dimethylbutanoic acid,
2,2-dimethylpentanoic acid, 2,2-dimethylhexanoic acid,
2,2-dimethylheptanoic acid, 2,2-dimethyloctanoic acid,
2-methyl-2-ethylbutanoic acid, 2-methyl-2-ethylpentanoic acid, 2-methyl-2-ethylhexanoic acid,
2-methyl-2-ethyl-heptanoic acid, 2-methyl-2
-Propylpentanoic acid, 2-methyl-2-propylhexanoic acid, 2-methyl-2-propylheptanoic acid, acrylic acid, crotonic acid, isocrotonic acid, 3-butenoic acid, pentenoic acid, hexenoic acid, heptenoic acid, octenoic acid , Nonenic acid, decenoic acid, undecenoic acid, dodecenoic acid, tsuzunic acid, fisterric acid, goshuyuic acid, palmitoleic acid,
Aliphatic monocarboxylic acids such as petroselinic acid, oleic acid, elaidic acid, vaccenic acid, gadoleic acid, methacrylic acid, 3-methylcrotonic acid, tiglic acid, methylpentenoic acid, cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, oxalic acid, Malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, detradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, heptadecandioic acid. Acid, octadecanedioic acid, nonadecanedioic acid, eicosanedioic acid, methylmalonic acid, ethylmalonic acid, propylmalonic acid, butylmalonic acid, pentylmalonic acid, hexylmalonic acid, dimethylmalonic acid, methylethylmalonic acid, diethylmalonic acid , Methylpropyl malonic acid Methylbutylmalonic acid, ethylpropylmalonic acid, dipropylmalonic acid, ethylbutylmalonic acid, propylbutylmalonic acid, dibutylmalonic acid, methylsuccinic acid, ethylsuccinic acid, 2,2-dimethylsuccinic acid, 2,3-dimethylsuccinic acid , 2-methyl glutaric acid, 3-methyl glutaric acid, 3-methyl-3-ethyl glutaric acid, 3,3-diethyl glutaric acid, maleic acid,
Citraconic acid, 1,5-octanedicarboxylic acid, 5,6-decanedicarboxylic acid, 1,7-decanedicarboxylic acid, 4,6-dimethyl-4-nonene-1,2-dicarboxylic acid, 4,6-dimethyl- 1,2-nonanedicarboxylic acid, 1,7-dodecanedicarboxylic acid, 5-ethyl-1,10-decanedicarboxylic acid, 6-methyl-6dodecene-1,12-dicarboxylic acid, 6-methyl-1,
12-dodecanedicarboxylic acid, 6-ethylene-1,12-dodecanedicarboxylic acid, 6-ethyl-1,12-dodecanedicarboxylic acid, 7-methyl-7-tetradecene-1,14-dicarboxylic acid, 7-methyl-1 , 14-tetradecanedicarboxylic acid, 3-hexyl-4-decene-1,2-dicarboxylic acid,
3-hexyl-1,2-decanedicarboxylic acid, 6-ethylene-9-hexadecene-1,16-dicarboxylic acid, 6-ethyl-1,16-hexadecanedicarboxylic acid, 6-phenyl-
1,12-dodecanedicarboxylic acid, 7,12-dimethyl-7,11-
Octadecadiene-1,18-dicarboxylic acid, 7,12-dimethyl-1,18-octadecanedicarboxylic acid, 6,8-diphenyl-1,14-tetradecanedicarboxylic acid, 1,1-cyclopentanedicarboxylic acid, 1, Aliphatic dicarboxylic acids such as 2-cyclopentanedicarboxylic acid, 1,1-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, and 5-norbornene-2,3-dicarboxylic acid , Benzoic acid, toluic acid, ethyl benzoic acid, propyl benzoic acid, isopropyl benzoic acid, butyl benzoic acid, isobutyl benzoic acid, secondary butyl benzoic acid, tertiary butyl benzoic acid, hydroxy benzoic acid, anisic acid, ethoxy benzoic acid, Propoxybenzoic acid, isopropoxybenzoic acid, butoxybenzoic acid, isobutoxybenzoic acid, secondary butoxybenzoic acid, tertiary butto Xybenzoic acid,
Aminobenzoic acid, N-methylaminobenzoic acid, N-ethylaminobenzoic acid, N-propylaminobenzoic acid, N-
Isopropylaminobenzoic acid, N-butylaminobenzoic acid, N-isobutylaminobenzoic acid, N-tert-butylaminobenzoic acid, N-tert-butylaminobenzoic acid, N, N-
Aromatic monocarboxylic acids such as dimethylaminobenzoic acid, N, N-diethylaminobenzoic acid, nitrobenzoic acid, resorcinic acid (including o, m, p-isomers), and phthalic acid, isophthalic acid, terephthalic acid, Examples thereof include aromatic polyvalent carboxylic acids such as nitrophthalic acid, trimellitic acid, hemimellitic acid, colimesic acid and pyromellitic acid.

The quaternary phosphonium salt, tetramethylphosphonium, tetraethylphosphonium, tetrapropylphosphonium, tetrabutylphosphonium, methyltriethylphosphonium, methyltripropylphosphonium, methyltributylphosphonium, dimethyldiethylphosphonium, dimethyldipropylphosphonium, dimethyldibutylphosphonium, trimethyl Ethylphosphonium, trimethylpropylphosphonium, trimethylbutylphosphonium, ethyltripropylphosphonium, ethyltributylphosphonium, diethyldipropylphosphonium, diethyldibutylphosphonium, triethylpropylphosphonium, triethylbutylphosphonium, propyltributylphosphonium, dipropyldibutylphosphonium, tryp Aliphatic quaternary phosphonium salts such as pills butyl phosphonium and, 1,1-dimethyl phosphorous bromide, 1-methyl-1-ethyl-phosphorous chloride, 1,1
Diethylphosphoranium, 1,1-dimethylphosphorinanium, 1-methyl-1-ethylphosphorinanium, 1,1
Examples thereof include alicyclic quaternary phosphonium salts such as -diethylphosphorinanium and 1,1-pentamethylenephosphorinanium.

As a solvent for dissolving the quaternary phosphonium salt of carboxylic acid of the present invention, N-methylformamide, N-ethylformamide, N, N-dimethylformamide, N, N-diethylformamide, N-methylacetamide, N-ethylacetamide , Amide solvents such as N, N-dimethylacetamide, N, N-dimethylacetamide, N-methylpyrrolidinone, γ-butyrolactone, γ-valerolactone, σ-
Lactone solvent such as valerolactone, carbonate solvent such as ethylene carbonate, propylene carbonate and butylene carbonate, alcohol solvent such as ethylene glycol, glycerin and methyl cellosolve, nitrile solvent such as 3-methoxypropionitrile, and phosphoric acid such as trimethyl phosphate. The ester solvent may be a single solvent or a mixed solvent. Among these, a solvent mainly composed of γ-butyrolactone is particularly preferable because it has low toxicity, and the attack of the sealing agent of the electrolytic capacitor and the mixing of halogen are small.

The amount of the quaternary phosphonium salt of carboxylic acid dissolved in the solvent is not more than the saturation concentration, preferably 5 to 40% by weight.

The dissolved salt in the electrolytic solution may be a neutral salt or an acidic salt.

The electrolytic solution of the present invention is essentially composed of a quaternary phosphonium salt of carboxylic acid and a solvent, but various co-solutes for the purpose of preventing electrolytic corrosion, reducing leakage current, absorbing hydrogen gas, etc., for example, phosphoric acid derivatives, A nitrobenzene derivative or the like 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 be added for the purpose of improving the electric conductivity, improving the chemical conversion property and the like.

Effect of the Invention The quaternary phosphonium salt of carboxylic acid used as a solute in the present invention has good solubility in a solvent, and its electrolytic solution exhibits high conductivity, and is used with a solvent having a wide boiling point range to the freezing point. It is an electrolytic solution for electrolytic capacitors with a wide temperature range.

Experimental Example The present invention will be described more specifically with reference to Examples and Comparative Examples below.

Example 1 An electrolyte solution was obtained by dissolving 20% by weight of monotetraethylphosphonium maleate in a γ-butyrolactone solvent. The conductivity of this electrolyte at 25 ° C is 12.1 mS / cm, +,
-The spark generation voltage was 93 V when a constant current of 4 mA / cm ² was applied to a set of aluminum smooth foils.

Example 2 In Example 1, the conductivity and the spark generation voltage of the electrolytic solution were 10.7 mS / cm and 88 V, respectively, when monotetramethylphosphonium maleate was used instead of monotetraethylphosphonium maleate.

Example 3 In Example 1, the electric conductivity and the spark generation voltage of the electrolytic solution were 6.6 mS / cm and 103 V, respectively, when monotetrabutylphosphonium maleate was used instead of monotetraethylphosphonium maleate.

Comparative Example γ-butyrolactone solvent containing 20% by weight of monotriethylammonium maleate dissolved in an electrolyte having a conductivity of 4.2 m.
It was S / cm.

Examples 4 to 13 In Example 1, instead of monotetraethylphosphonium maleate, tetraethylphosphonium formate (Example 4), tetraethylphosphonium stearate (Example 5), monotetraethylphosphonium adipate (Example 6), sebacin Acid monotetraethylphosphonium (Example 7), eicosane diacid monotetraethylphosphonium (Example 8), dimethylmalonate monotetraethylphosphonium (Example 9), 6-ethyl-1,16-hexadecanedicarboxylic acid monotetraethylphosphonium (Implementation) Example 10), conductivity and spark generation when using monotetraethylphosphonium cyclopentylmalonate (Example 11), tetraethylphosphonium benzoate (Example 12) or monotetraethylphosphonium phthalate (Example 13) Shows a voltage to the first table.

Examples 14 to 23 In Examples 1, 4 and 6 to 13, Table 2 shows the conductivity and the spark generation voltage when the γ-butyrolactone solvent was changed to the N, N-dimethylformamide solvent.

Examples 24 to 34 In Examples 1 and 4 to 13, Table 3 shows the electric conductivity and the spark generation voltage when the γ-butyrolactone solvent was changed to the propylene carbonate solution.

Examples 35 to 43 In Examples 1, 4 and 6 to 13, Table 4 shows the electric conductivity and the spark generation voltage when the γ-butyrolactone solvent was changed to the trimethyl phosphate solvent.

In Tables 1 to 4, the following abbreviations are used.

GBL: γ-butyrolactone DMF: N, N-dimethylformamide PC: Propylene carbonate TMP: Trimethyl phosphate

Claims (1)

[Claims] 1. An electrolytic solution for an electrolytic capacitor, wherein a quaternary phosphonium salt of carboxylic acid is dissolved and used as a solute in a solvent.