JPS62145714A - Electrolyte for electrolytic capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Industrial applications 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 OF THE INVENTION 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 amine salt of adipic acid or maleic acid is dissolved in a solvent such as N,N-dimethylformamide or γ-butyrolactone, which has an even lower freezing point, is known.

Problems to be Solved by the Invention However, as the impedance of electrolytic capacitors has become lower, an electrolytic solution with even higher conductivity has been desired. (2)n C00H(4<n<8
Although an electrolytic solution with high conductivity in which a quaternary ammonium salt of ) 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 conducted intensive studies to find a new electrolytic solution with even higher conductivity, and found that a highly acidic quaternary ammonium salt of alkylmalonic acid was better than the conventional adipic acid. The present invention has been completed based on the discovery that the present invention exhibits higher conductivity than quaternary ammonium salts of linear dibasic carboxylic acids such as the following.

That is, the present invention provides an electrolytic solution for an electrolytic capacitor characterized by using a quaternary ammonium salt of alkylmalonic acid as a solute.

Effects of the Invention The quaternary ammonium salt of alkylmalonic acid used as a solute in the present invention has good solubility in solvents and high conductivity, and can be used in a wide temperature range by being used with a solvent having a wide freezing point to boiling point range. It is an excellent electrolyte for a wide range of electrolytic capacitors.

Detailed Description of the Invention The alkylmalonic acid of the alkylmalonic acid quaternary ammonium salt used in the present invention has the following general formula, (wherein R1 and R2 are hydrogen atoms or alkyl groups such as methyl, ethyl, propyl, butyl, etc.) (wherein either R1 or R2 is necessarily an alkyl group).

The total number of carbon atoms in the alkylmalonic acid ranges from 4 to 3 carbon atoms, preferably from 4 to 12 carbon atoms. In addition, malonic acid in which both R□ and & are hydrogen atoms has a problem in chemical stability and lifespan because methylene hydrogen is active.

Specifically, methylmalonic acid, ethylmalonic acid, propylmalonic acid, isopropylmalonic acid, methylmalonic acid,
Isobutylmalonic acid, nibutylmalonic acid, tertiary butylmalonic acid, pentylmalonic acid, isopentylmalonic acid,
Monoalkylmalonic acids such as neopentylmalonic acid, hexylmalonic acid, octylmalonic acid and dimethylmalonic acid, methylethylmalonic acid, diethylmalonic acid, methylpropylmalonic acid, methylbutylmalonic acid, ethylpropylmalonic acid, dipropylmalonic acid Examples include ethylbutylmalonic acid, propylbutylmalonic acid, siftylmalonic acid, and the like.

Examples of quaternary ammonium salts include aliphatic quaternary ammonium salts such as tetraethylammonium, tetrapropylammonium, tetrabutylammonium, and methyltriethylammonium; N,N-dimethylpyrrolidinium;
, N-dimethylpiperidinium, N,N-hentamethylenepiperidinium, and other alicyclic quaternary ammonium salts; and N-ethylpyridinium and other aromatic quaternary ammonium salts.

Examples of the solvent for dissolving the quaternary ammonium salt of alkylmalonic 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-diethylacetamide, amide solvents such as N-methylpyrrolidinone, γ-butyrolactone, γ-valerolactone, δ- lactone solvents such as valerolactone,
Examples include carbonate solvents such as ethylene carbonate, propylene carbonate, and butylene carbonate, alcohol solvents such as ethylene glycol, glycerin, and methyl cellosol, nitrile solvents such as 3-methoxypropionitrile, and phosphate ester solvents such as trimethyl phosphate, either alone or in combination. can do. Among these, a solvent mainly composed of γ-butyrolactone is particularly preferable because it has low toxicity and is less likely to attack the sealing agent of an electrolytic capacitor and less likely to be contaminated with halogen.

The amount of quaternary ammonium salt of alkylmalonic acid dissolved in the above solvent is below the saturation concentration, preferably 5 to 40% by weight.
is within the range of Further, the molar ratio of acid to base in the dissolved salt in the electrolytic solution is in the range of 1:2 to 2:1, and in terms of conductivity, the molar ratio is most preferably 1:1.

For example, quaternary ammonium salts of alkylmalonic acids can be prepared by neutralizing 1 mol of alkylmalonic acid with 1 mol of an aqueous solution of quaternary ammonium hydroxide, distilling off water under reduced pressure, and recycling the resulting product from methanol. The electrolytic solution of the present invention can be obtained by crystallizing and vacuum drying, but it can also be prepared by adding alkylmalonic acid and an aqueous quaternary ammonium hydroxide solution to a solvent, dissolving and dehydrating the solution.

The electrolytic solution of the present invention essentially consists of a quaternary ammonium salt of alkylmalonic acid and a solvent, but it also contains various co-solutes, such as phosphoric acid derivatives, for the purpose of preventing galvanic corrosion, reducing leakage current, absorbing water bulk gas, etc. , nitropenzene derivatives, etc. can be added. In addition, 1 to 10 parts per weight can be added for the purpose of improving conductive dust, improving chemical conversion properties, etc.

EXPERIMENTAL EXAMPLES The present invention will be explained in more detail below with reference to Examples and Comparative Examples.

Example 1 An electrolytic solution was obtained by dissolving 20 parts by weight of monotetraethylammonium salt of dimethylmalonic acid in a γ-butyrolactone solvent. The conductive dust of this electrolyte at 25°C is 10.
72 IIS/(7), and the spark generation voltage was 116 V when a constant current of 2 tJtAZ was applied to a pair of smooth aluminum foils.

Example 2.3 Conductive dust and spark generation in electrolyte solution using monotetraethylammonium salt of diethylmalonic acid (Example 2) and dipropylmalonic acid (Example 3) instead of dimethylmalonic acid salt in Example 1 The voltage was measured. The results are shown in Table 1.

Examples 4 to 6 In Example 1, instead of γ-butyrolactone, N
, N-dimethylformamide (Example 4), 3-methoxypropionitrile (Example 5), and trimethyl phosphate (Example 6) were used to measure conductive dust and spark generation voltage of electrolytes. The results are shown in Table 1.

Comparative Example 1 Table 1 shows the conductive dust and spark generation voltage of the electrolytic solution in which monotetraethylammonium salt of adipic acid was used instead of dimethylmalonate in Example 1.

Comparative Examples 2 to 4 20% by weight of monotetraethylammonium salt of adipic acid was added to N,N-dimethylformamide (Comparative Example 2), 3
-Methoxypropionitrile (Comparative Example 3) and trimethyl phosphate (Comparative Example 4) were dissolved in a solvent to obtain an electrolytic solution.The conductive dust and spark generation voltage of the electrolytic solution are shown in Table 1.Table 1 From this, it can be seen that the quaternary ammonium salt of alkylmalonic acid of the present invention has a higher conductive dust and is excellent in A, even though it has more carbon atoms than the adipate.

In Table 1, the following abbreviations were used.

GBL: γ-Butyrolactone DMF: N,N-dimethylformamide MPN: 3-methoxypropionitrile TMP: ) Limethyl phosphate (margin above) Table 1

Claims (1)

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