JP2003031442A - Electrolyte for electrolytic capacitor and electrolytic capacitor using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a medium/high class electrolyte for prolonging the lifetime of an electrolytic capacitor in which drop rate of the specific conductivity is suppressed under high temperature while increasing the specific conductivity and the spark voltage. SOLUTION: The electrolyte for electroytic capacitor is produced by dissolving polycarboxylic acid (A) and/or its salt (B) into an organic polar solvent (C) wherein at least one carboxyl group is bonded to an aromatic ring through an alkylidene group. An electroytic capacitor using that electrolyte is also provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic solution used for an electrolytic capacitor and an electrolytic capacitor using the electrolytic solution. More specifically, the present invention relates to an electrolytic solution for medium and high pressure class and an electrolytic capacitor using the electrolytic solution.

[0002]

2. Description of the Related Art With the recent increase in the temperature of the environment in which capacitors are used, there has been a demand for an electrolytic solution having a long service life at high temperatures. On the other hand, a tertiary monocarboxylic acid (JP-A-61-116815), a tertiary dicarboxylic acid (JP-A-4-273421), a secondary and / or a tertiary carboxyl group in total. Molecular weight of 2 or more 2
An electrolytic solution using 60 or more polycarboxylic acids (JP-A-1-103821) is known.

[0003]

[Problems to be Solved by the Invention]
With the electrolytic solution using a tertiary carboxylic acid, the esterification reaction at high temperature is suppressed, but an electrolytic solution having both high spark voltage and high specific electric conductivity cannot be obtained. That is, when a secondary carboxylic acid having a small molecular weight is used and the specific electric conductivity is to be obtained, the spark voltage is reduced, and when the molecular weight is adjusted to obtain the spark voltage, the specific electric conductivity is decreased. The degree is insufficient.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that at least one of the carboxyl groups is a polycarboxylic acid bonded to an aromatic ring via a methylene group or an alkylidene group. The present invention has been accomplished by finding that the electrolytic solution using the acid (A) and / or its salt (B) shows a small decrease in the specific electric conductivity at high temperatures and has both high spark voltage and high specific electric conductivity. That is, the present invention comprises a polycarboxylic acid (A) and / or its salt (B) dissolved in an organic polar solvent (C), wherein at least one of the carboxyl groups of (A) is a methylene group or an alkylidene group. An electrolytic solution for an electrolytic capacitor, which is characterized in that it is bonded to an aromatic ring via the same, and an electrolytic capacitor using the electrolytic solution.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The electrolytic solution of the present invention comprises a polycarboxylic acid (A) in which at least one carboxyl group is bonded to an aromatic ring through a methylene group or an alkylidene group.
And / or one or more salts (B) thereof are dissolved. Since (A) has a phenyl group bonded to the α-position to the carboxyl group or a derivative thereof as a substituent, it has a large steric hindrance and can suppress the esterification reaction with a solvent to the same degree as or higher than the tertiary carboxylic acid. The decrease in specific electric conductivity at (100 to 180 ° C.) is small. Further, the electron withdrawing effect of the phenyl group or its derivative bonded to the α-position increases the acidity of the carboxylic acid and improves the degree of dissociation in the solvent, so that high specific electric conductivity is exhibited.
Therefore, even if the molecular weight is adjusted to obtain the spark voltage, a sufficient specific electric conductivity can be obtained.

The polycarboxylic acid (A) used in the present invention is a polycarboxylic acid in which at least one of the carboxyl groups is bonded to the aromatic ring via a methylene group or an alkylidene group. As (A), a polycarboxylic acid in which all carboxyl groups are bonded to an aromatic ring via a methylene group or an alkylidene group is preferable.
Furthermore, the polycarboxylic acid represented by the following general formula (1) is preferable, and the polycarboxylic acid represented by the following general formula (2) is most preferable.

[0007]

[Chemical 3]

X is a group represented by --CHR'CO2H, Z is fluorine, an alkyl group having 1 to 8 carbon atoms, a hydroxyl group,
At least one group selected from the group consisting of a hydrocarbon group having a hydroxyl group, a hydrocarbon group having a carbonyl group, a hydrocarbon group having an ether group, and a hydrocarbon group having a fluorine group, and R is a direct bond or a carbon atom. Alkylene groups, alkylidene groups, cycloalkylene groups, cycloalkylidene groups of the numbers 1 to 10, O, S, SO, SO2, CO, CF2,
C (CF3) 2, R'is hydrogen or 1 to 8 carbon atoms
X and Z may be the same as or different from each other and may form a ring. r is 0 or 1, a is an integer of 0 to 6, b, c, and d are all integers of 0 to 5, and a + b ≧ 2.

Examples of the alkyl group having 1 to 8 carbon atoms of Z include methyl group, ethyl group, n-propyl group, i-
Examples of the hydrocarbon group having a propyl group, n-butyl group and hydroxyl group include a hydroxymethyl group, a hydroxyethyl group and a hydrocarbon group having a carbonyl group such as an acetyl group, a methyloxycarbonyl group, an ethyloxycarbonyl group, As the hydrocarbon group having an ether group, for example, an alkoxyl group having an alkyl group having 1 to 8 carbon atoms (methoxyl group, ethoxyl group, etc.), a benzyloxyl group, and a hydrocarbon group having a fluorine group are, for example, perfluoromethyl. Group, perfluoroethyl group and the like. Examples of the alkylene group having 1 to 10 carbon atoms of R include an ethylene group, a propylene group, and an alkylidene group such as an ethylidene group, a propylidene group, and a cycloalkylene group such as a cyclohexylene group and a cycloalkylidene group. For example, a cyclohexylidene group and the like can be mentioned.

[0010]

[Chemical 4]

X'is a group represented by --CH2CO2H, and n is an integer having 1 to 8 carbon atoms.

In (A), examples of the alkylidene group include an alkylidene group having 1 to 10 carbon atoms and have the formula:
An alkylidene group represented by -CHR'- is preferable. Examples of R ′ of the alkylidene group include an alkyl group having 1 to 8 carbon atoms, which may form a ring. Specifically, examples thereof include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, and a cyclohexyl group. Aromatic rings include monocycles, fused polycycles, and ring assemblies. Specific examples include a benzene ring as a monocycle, a naphthalene ring as a condensed polycycle, and a biphenyl ring as a ring assembly. In (A), the number of carboxyl groups bonded to the aromatic ring is at least 1, preferably 2 to 4, and more preferably 2.

Specific examples of (A) include the following compounds (1) to (3), and among these, compounds and are preferable.

[Chemical 5]

The number or weight molecular weight of (A) can be used in an appropriate range according to the desired spark voltage and specific electric conductivity, but the spark voltage exceeds 400 V and the specific electric conductivity is also high. In order to obtain an electrolytic solution suitable for medium and high pressure class, one having a molecular weight of 100 to 1000 is preferable. Molecular weight is 10
If it exceeds 00, the specific electric conductivity becomes low. It is more preferable that the molecular weight is in the range of 100 to 400 in terms of a good balance between the spark voltage and the specific electric conductivity.

(A) can be obtained, for example, by the method described in JP-A-52-46057. For example, after converting a predetermined aromatic compound into an alkyl ketone and heating it with sulfur and a secondary amine to form an aryl alkyl thioamide,
A method of hydrolysis can be mentioned by a conventional method.

Examples of (B) include ammonium salts,
And amine salts. Examples of amines (bases) constituting the amine salt include primary amines (methylamine,
Ethylamine, ethylenediamine, etc.), secondary amines (dimethylamine, diethylamine, etc.), tertiary amines [trimethylamine, triethylamine, dimethylethylamine, dimethylisopropylamine, 1,8-diazabicyclo (5,4,0) -undecene-7, etc.] Is mentioned. Of these, ammonium salts and triethylamine salts are preferable, and ammonium salts are particularly preferable.

The molar ratio of the carboxyl group of (A) and the amino group of (B) forming a salt is (1: 2) to (1: 0.
5) is preferable, and more preferably (1: 1.2)-
(1: 0.8).

As the organic polar solvent (C) used as the electrolytic solution for the electrolytic capacitor of the present invention, one of alcohols, ethers, amides, lactones, nitriles, carbonates and other organic polar solvents or Two or more types may be mentioned. The following are specific examples of (C). Alcohols; monohydric alcohols; monohydric alcohols having 1 to 6 carbon atoms (methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, diacetone alcohol, furfuryl alcohol, etc.), monohydric alcohols having 7 or more carbon atoms (benzyl alcohol) , Octanol), dihydric alcohol; dihydric alcohol having 1 to 6 carbon atoms (ethylene glycol, propylene glycol, diethylene glycol, hexylene glycol, etc.), dihydric alcohol having 7 or more carbon atoms (octylene glycol, etc.), trihydric alcohol Alcohol: C1 to C6 trihydric alcohol (glycerin, etc.), C4 to C6 or higher alcohol; C1 to C4 to C6 or higher alcohol (hexitol, etc.), ethers ; Monoether (ethylene glycol Cole monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, ethylene glycol monophenyl ether, tetrahydrofuran, 3-methyltetrahydrofuran, etc., diether (ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether) Ether etc.) etc. Amides; formamides (N-methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N-diethylformamide, etc.), acetamides (N-methylacetamide, N, N-dimethylacetamide, N-ethyl) Acetamide, N, N-diethylacetamide, etc., propionamides (N, N
-Dimethylpropionamide, hexamethylphosphorylamide, etc.), oxazolidinones (N-methyl-2-
Oxazolidinone, 3,5-dimethyl-2-oxazolidinone, etc.). Lactones; α-acetyl-γ-butyrolactone, β
-Butyrolactone, γ-valerolactone, δ-valerolactone and the like. Nitriles; acetonitrile, acrylonitrile, etc. Carbonates; ethylene carbonate, propylene carbonate, etc. Other organic polar solvents; dimethyl sulfoxide, sulfolane, 1,3-dimethyl-2-imidazolidinone, N
-Methylpyrrolidone etc. Among the above, dihydric alcohols having 1 to 6 carbon atoms (ethylene glycol, propylene glycol, diethylene glycol, hexylene glycol, etc.) are preferable, and ethylene glycol is more preferable.

The weight of (C) is preferably 5 to 95% by weight, and 60 to 95% by weight based on the total weight of the electrolytic solution.
More preferably, it is wt%.

As a solvent used as the electrolytic solution for the electrolytic capacitor, if necessary, a non-polar solvent such as the organic polar solvent (C), for example, an aromatic solvent (toluene, xylene, etc.), a paraffinic solvent (normal paraffin, isoparaffin) is used. ) Etc. can be used together. The content of the non-polar solvent is 20% by weight or less based on the total weight of the electrolytic solution. The electrolytic solution for the electrolytic capacitor may contain water, if necessary. The content is 10% by weight or less based on the total weight of the electrolytic solution.

The total weight of (A) and (B) is preferably 1 to 70% by weight, more preferably 5 to 40% by weight, based on the total weight of the electrolytic solution.

If desired, various additives commonly used in electrolytic solutions can be added to the electrolytic solution of the present invention.
Examples of the additive include phosphoric acid derivatives (for example, phosphoric acid, phosphoric acid esters, etc.), boric acid derivatives (for example, boric acid,
A complex compound of boric acid and a polysaccharide [mannite, sorbite, etc.], a complex compound of boric acid and a polyhydric alcohol [ethylene glycol, glycerin, etc.), and a nitro compound (eg, o-nitrobenzoic acid, p- Nitrobenzoic acid, m-nitrobenzoic acid, o-nitrophenol, p-
Nitrophenol, etc.) and the like. In addition, if necessary, a carboxylic acid having a primary carboxyl group for the purpose of improving the chemical conversion property or further improving the specific electric conductivity,
A small amount of carboxylic acid having an aromatic carboxyl group can be mixed. Examples of materials that can be mixed include adipic acid, azelaic acid, 1,6 decanedicarboxylic acid, 2-butylhexanedioic acid, and benzoic acid. The amount of the above additive added is based on the total weight of (A) and (B).
It is preferably 10% by weight or less.

The pH of the electrolytic solution of the present invention is preferably 3 to 12, and more preferably 6 to 11. When producing the polycarboxylic acid salt (B), conditions are selected such that the pH of the electrolytic solution falls within this range. The pH of the electrolytic solution is an analytical value at 25 ° C. of the electrolytic solution stock solution.

The electrolytic solution used in the present invention has a spark voltage of 100.
Used for medium and high voltage class electrolytic capacitors of V or higher.

[0025]

EXAMPLES Next, specific examples of the present invention will be described, but the present invention is not limited thereto.

Production Example 1 To a suspension of 238 g of aluminum chloride in 260 ml of carbon disulfide, a solution of 73 g of 1,1-diphenylmethane dissolved in 260 ml of carbon disulfide was added at 25 ° C., and then 140 g of acetyl chloride was added dropwise. did. After aging for 2 hours,
Recrystallization gave a diacetylated product. The obtained compound was dissolved in 217 ml of morpholine, and 31 g of sulfur was added and reacted. 1200 ml of ethanol was added to form a precipitate, which was treated with 10N potassium hydroxide and 6N hydrochloric acid to obtain 65 g of dicarboxylic acid (A) 1 shown in Table 1 below.

Production Example 2 The same procedure as in Production Example 1 was carried out except that 98 g of 1,5-diphenylpentane was used instead of 73 g of 1,1-diphenylmethane in Production Example 1, and dicarboxylic acid (A) shown in Table 1 below was used.
78 g of 2 was obtained.

Production Example 3 In the same manner as Production Example 1 except that 190 g of isobutyl chloride was used instead of 140 g of acetyl chloride in Production Example 1, 78 g of dicarboxylic acid (A) 3 shown in Table 1 below was obtained.

Production Example 4 The procedure of Production Example 1 was repeated except that 98 g of 1,1-bis- (2,5-dimethyldiphenyl) methane was used instead of 73 g of 1,1-diphenylmethane used in Production Example 1. 78 g of dicarboxylic acid (A) 4 shown in Table 1 below was obtained.

Examples 1 to 5 and Comparative Examples 1 to 3 Table 1 shows the electrolytic solution compositions of Examples 1 to 5 and Comparative Examples 1 to 3 of the present invention.

[0031]

[Table 1]

[0032]

[Chemical 6]

Using the electrolytic solutions of Examples 1 to 5 and Comparative Examples 1 to 3, the specific electric conductivity, the spark voltage and the rate of decrease in the specific electric conductivity were measured, and the results are shown in Table 2. Specific conductivity: Toa Denpa Kogyo Co., Ltd. conductivity meter CM-40
The specific conductivity at 30 ° C. was measured using S. Spark voltage: Using an etched aluminum foil of 10 cm ² , the discharge voltage of the electrolytic solution when the constant current method (2 mA) was applied was measured. Specific conductivity decrease rate: The specific conductivity before the heat resistance test and the specific conductivity after the heat resistance test were measured, and the rate of change [= 100
× {(specific electric conductivity before heat resistance test)-(specific electric conductivity after heat resistance test)} / (specific electric conductivity before heat resistance test)] (unit:%) was calculated. Heat resistance test: Electrolyte solution in stainless steel container 15
It was sealed at 0 ° C. for 10 hours.

[0034]

[Table 2]

As is clear from Table 2, Example 1 of the present invention
The electrolytic solutions of Nos. 5 to 5 have a smaller specific electric conductivity decrease rate, and a higher specific electric conductivity and spark voltage than the electrolytic solutions of Comparative Examples 1 to 3.

[0036]

As described above, the electrolytic solution for electrolytic capacitors of the present invention has a small decrease rate of the specific electric conductivity at high temperature, and has a high spark voltage and a high specific electric conductivity. When used in a capacitor, the electrolytic capacitor can have a long service life and high reliability, which is of great industrial value.

Claims (8)

[Claims] 1. A polycarboxylic acid (A) and / or its salt (B) is dissolved in an organic polar solvent (C),
At least one of the carboxyl groups of (A) is bonded to an aromatic ring via a methylene group or an alkylidene group, and an electrolytic solution for an electrolytic capacitor. 2. The electrolytic solution for an electrolytic capacitor according to claim 1, wherein all the carboxyl groups of (A) are bonded to the aromatic ring via a methylene group or an alkylidene group. 3. The electrolytic solution for an electrolytic capacitor according to claim 1, wherein (A) is represented by the general formula (1). [Chemical 1] [X is a group represented by -CHR'CO2H, Z is fluorine, an alkyl group having 1 to 8 carbon atoms, a hydroxyl group, a hydrocarbon group having a hydroxyl group, a hydrocarbon group having a carbonyl group, a hydrocarbon having an ether group. Group, at least one group selected from the group consisting of hydrocarbon groups having a fluorine group, R is a direct bond, an alkylene group having 1 to 10 carbon atoms, an alkylidene group, a cycloalkylene group, a cycloalkylidene group, O, S, SO, SO2, CO, CF2, C (CF
3) 2, R ′ is hydrogen or an alkyl group having 1 to 8 carbon atoms and may form a ring, and X and Z may be the same or different. r is 0 or 1, and a
Is an integer of 0 to 6, b, c, and d are all integers of 0 to 5, and a + b ≧ 2. ] 4. The electrolytic solution for an electrolytic capacitor according to claim 1, wherein (A) is represented by the general formula (2). [X 'is a group represented by -CH2CO2H, and n is 1
Is an integer of ~ 8. ] 5. The electrolytic solution for an electrolytic capacitor according to claim 1, wherein (B) is an ammonium salt and / or an amine salt. 6. An electrolytic solution for an electrolytic capacitor, wherein the amine salt of claim 5 is a triethylamine salt. 7. The electrolytic solution for an electrolytic capacitor according to claim 1, wherein (C) is ethylene glycol. 8. An electrolytic capacitor using the electrolytic solution for an electrolytic capacitor according to claim 1.