JP2998850B2 - Electrolyte for driving electrolytic capacitors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic solution for driving an electrolytic capacitor.

[0002]

2. Description of the Related Art Heretofore, so-called ethylene glycol-boric acid-based electrolyte has been used as an electrolyte for driving an electrolytic capacitor particularly for medium and high pressures. This type of electrolyte is
When heated, water is generated by the esterification reaction of ethylene glycol and boric acid, and furthermore, the water reacts with the aluminum of the electrode to generate hydrogen gas. At a high temperature exceeding 100 ° C., the internal pressure increases. There was a disadvantage that it could not be used.

In order to improve such disadvantages, azelaic acid, sebacic acid, decanedicarboxylic acid or a salt thereof is partially used, but the solubility in a solvent such as ethylene glycol is poor, and the heat is poor. Insufficient stability.

Japanese Patent Application Laid-Open No. Sho 61-116815 proposes a method for improving solubility and thermal stability by using a tertiary monocarboxylic acid, but the chemical conversion is insufficient. Similarly, JP-A-1-103821 proposes a tertiary dicarboxylic acid, but has a drawback in that since it contains an ester group in the molecule, it reacts with ethylene glycol and deteriorates.

[0005]

SUMMARY OF THE INVENTION The present invention is to improve the thermal stability and solute solubility of a conventional electrolytic solution.

[0006]

Means for Solving the Problems The present inventors have proposed a solute to be used for an electrolytic solution. (1) By introducing a branched carbon chain structure (particularly an asymmetric structure), the solubility is improved and the conductivity is improved. Let it. (2) Chemical conversion is improved by introducing two carboxyl groups. (3) In order to sterically suppress esterification with ethylene glycol, a substituent is introduced at a position adjacent to the carboxyl group. (4) Except for two carboxyl groups, no functional group causing deterioration is introduced, and a skeleton is formed only with a methylene chain. As a result, the present inventors have found a salt of a tertiary dicarboxylic acid to satisfy the requirement.

The electrolytic solution for driving an electrolytic capacitor of the present invention comprises:
It is characterized by containing a salt of a tertiary dicarboxylic acid represented by the following general formula (I).

[0008]

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(In the formula, n represents an integer of 1 to 5, r and m represent an integer of 4 or 5, and R ¹ and R ² represent a hydrogen atom or a lower alkyl group.)

Hereinafter, the present invention will be described in detail. Specific examples of the tertiary dicarboxylic acid represented by the formula (I) include, for example, 2,2-tetramethylene-4,4-tetramethyleneglutaric acid, 2,2-tetramethylene-5,5
-Tetramethylene adipic acid, 2,2-tetramethylene-6,6-tetramethylene pimelic acid, 2,2-tetramethylene-7,7-tetramethylene suberic acid, 2,2
-Tetramethylene-8,8-tetramethylene azelaic acid, 2,2-tetramethylene-4,4-pentamethylene glutaric acid,

2,2-tetramethylene-5,5-pentamethyleneadipic acid, 2,2-tetramethylene-6,6
-Pentamethylene pimelic acid, 2,2-tetramethylene-7,7-pentamethylene suberic acid, 2,2-tetramethylene-8,8-pentamethylene azelaic acid, 2,
2-pentamethylene-4,4-pentamethylene glutaric acid, 2,2-pentamethylene-5,5-pentamethylene adipic acid,

2,2-pentamethylene-6,6-pentamethylenepimelic acid, 2,2-pentamethylene-7,7
-Pentamethylene suberic acid, 2,2-pentamethylene-8,8-pentamethylene azelaic acid,

[0013]

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[0014]

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[0015]

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And the like.

These carboxylic acids can be used alone or as a mixture. A compound having a cyclopentane ring or a cyclohexane ring alkyl-substituted at the 2- or 3-position becomes a mixture of optical isomers. In addition, the solubility generally tends to deteriorate as the carbon number increases.

Examples of the salt of the tertiary dicarboxylic acid used in the present invention include the ammonium, amine, quaternary ammonium, phosphonium and sulfonium salts of the above carboxylic acid.

As the solvent for dissolving the salt of the tertiary dicarboxylic acid used in the present invention, for example, N-methylformamide, N-ethylformamide, N, N-dimethylformamide, N, N-diethylformamide, N-ethyl Amide solvents such as acetamide, N, N-dimethylacetamide, N-methylpyrrolidinone; lactone solvents such as γ-butyrolactone, γ-valerolactone, δ-valerolactone;

Carbonate solvents such as ethylene carbonate, propylene carbonate, butylene carbonate and the like;
Alcohol solvents such as ethylene glycol, glycerin and methyl cellosolve; nitrile solvents such as 3-methoxypropionitrile and glutarnitrile; phosphate ester solvents such as trimethyl phosphate and triethyl phosphate; Examples thereof include a mixture of two or more solvents.

The amount of the solute dissolved in the solvent varies depending on the conductivity of the electrolytic solution to be obtained, but is generally less than the saturation concentration, preferably 1 to 25% by weight.

The electrolytic solution of the present invention contains, in addition to the salt and solvent of the tertiary dicarboxylic acid, prevention of electrolytic corrosion, reduction of leakage current,
Various auxiliary solutes such as a phosphoric acid derivative and a nitrobenzene derivative can be added for the purpose of absorbing hydrogen gas and the like. If necessary, water of 1 to 10% by weight can be added for the purpose of improving electrical conductivity and improving chemical conversion, as long as the object of the present invention is not hindered.

[0023]

The tertiary dicarboxylic acid salt used as a solute in the present invention has good solubility in a solvent, and its electrolytic solution can maintain a relatively high conductivity and a spark voltage, Since the stability is high, a long-life medium-to-high pressure electrolytic capacitor can be obtained.

[0024]

EXAMPLES (Example 1) 2,2-pentamethylene-6,
Diammonium 6-pentamethylenepimelate was dissolved in an ethylene glycol solvent at 7% by weight to prepare an electrolytic solution. The conductivity of the electrolyte was 1.0 mS / cm at 25 ° C., and the spark voltage was 460 V when a current of 10 mA / cm ² was applied to the aluminum electrode. Next, the electrolytic solution was sealed and allowed to stand at 110 ° C. for 1000 hours, and then the conductivity of the electrolytic solution was measured. The conductivity was 1.0 mS / cm 2, and no deterioration was observed.

Comparative Example 1 An electrolyte was prepared in the same manner as in Example 1, except that the solute was changed to ammonium borate.
The conductivity and the spark voltage were measured. Conductivity is 1.1mS / cm
And the spark voltage was 450V. Next, the electrolytic solution was sealed and allowed to stand at 110 ° C. for 1000 hours, and then the conductivity of the electrolytic solution was measured. The conductivity is 0.8mS / cm,
Deterioration of the electrolyte was observed.

(Comparative Example 2)
The following formula described in the official gazette:

[0027]

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An electrolytic solution was prepared in the same manner as in Example 1 except that the diammonium salt of a tertiary dicarboxylic acid was used, and the electric conductivity and the spark voltage were measured. The conductivity was 1.0 mS / cm and the spark voltage was 495V.

Next, the electrolytic solution was sealed and sealed at 110 ° C. for 1 hour.
After standing for 000 hours, the mixture was cooled to room temperature and solidified due to deterioration. NMR analysis of the deteriorated product revealed that the ester bond in the solute molecule was completely broken.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-18921 (JP, A) JP-A-2-18920 (JP, A) JP-A-59-232410 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01G 9/035

Claims (1)

(57) [Claims] 1. An electrolytic solution for driving an electrolytic capacitor, comprising a salt of a tertiary dicarboxylic acid represented by the following general formula (I). Embedded image (Wherein, n represents an integer of 1 to 5, r and m are 4 or 5
Wherein R ¹ and R ² represent a hydrogen atom or a lower alkyl group)