JPH11340099A - Electrolyte for electrolytic capacitor and electrolytic capacitor using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase spark voltage and electric conductivity so as to mitigate deterioration at a high temperature by containing one or more compounds which are selected from a dicarboxylic acid compound and its salt represented by a specific formula and a group consisting of a tricarboxylic acid compound and its salt. SOLUTION: An electrolyte for electrolytic capacitor contains one or more compounds which are selected from the group consisting of a dicarboxylic acid compound and its salt represented by formula I (R<1> is H or an alkyl group of 1-5C which may have a branch; R<2> is an alkyl group which may have a branch of 1-5C; and X is an alkylene group which may have a branches of 3-13C) and compounds and salts of tricarboxylic acid represented by formula II (R<1> is H or an alkyl group of 1-5C which may have a branch; R<2> is an alkyl group of 1-5C which may have a branch; X<1> and X<2> are independently an alkylene group of 3-13C which may have a branch.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrolytic solution for an electrolytic capacitor and an electrolytic capacitor. More specifically,
The present invention relates to an electrolytic solution for an electrolytic capacitor, which contains a polycarboxylic acid having a specific structure, and an electrolytic capacitor using the same.

[0002]

2. Description of the Related Art Electrolytic capacitors are characterized by having a large capacitance while being small, and are frequently used for low-frequency filters and bypasses. Generally, an electrolytic capacitor has a structure in which an anode foil and a cathode foil are wound via a separator, and this is housed in a case and sealed (FIG. 1).
A valve metal such as aluminum or tantalum having an insulating oxide film formed thereon as a dielectric layer is used for the anode foil, and an etched aluminum foil is generally used for the cathode foil. The separator interposed between the anode and the cathode is impregnated with an electrolytic solution to prevent a short circuit between the two electrodes, and functions as a true cathode. For this reason, the electrolytic solution is an important component that greatly affects the characteristics of the electrolytic capacitor.

[0003] Various electrolytic solutions have been proposed and used in the past. For example, an electrolytic solution in which boric acid or ammonium borate as an electrolyte is dissolved in ethylene glycol or the like is used particularly for capacitors such as capacitors for medium and high pressure. However, this type of electrolyte has a problem that ethylene glycol and boric acid cause an esterification reaction to generate water. For this reason, when the temperature is 100 ° C. or higher, the water vapor pressure becomes extremely high, and the aluminum of the electrode easily reacts.

[0004] In order to improve such disadvantages, as a solute, azelaic acid, sebacic acid, 1,10-decanedicarboxylic acid, 1,6-decanedicarboxylic acid (JP-B-60-1985)
No. 13293), dibasic acids such as 5,6-decanedicarboxylic acid (JP-B-63-15738) and 1,7-octanedicarboxylic acid (JP-A-2-224217) or salts thereof were used as solutes. Electrolytes have been proposed.
However, since these solutes have low solubility in ethylene glycol and the like, they have a problem that crystals are precipitated at a low temperature and esterification cannot be sufficiently suppressed. For this reason, it was not possible to provide an electrolytic capacitor having high electric conductivity even by using these solutes.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve these problems of the prior art. That is, an object of the present invention is to provide an electrolytic solution for an electrolytic capacitor which has a high spark voltage and high electric conductivity and is less deteriorated at high temperatures, and an electrolytic capacitor using the same. In particular, it is an object of the present invention to provide an electrolytic solution for an electrolytic capacitor which achieves a long life of a medium-to-high voltage electrolytic capacitor. Another object of the present invention is to provide an electrolytic solution for an electrolytic capacitor and an electrolytic capacitor that can be industrially stably supplied and can be manufactured at low cost.

[0006]

As a result of intensive studies to solve these problems, the present inventors have found that the use of novel polycarboxylic acids having a specific structure provides an excellent effect having an expected effect. The inventors have found that an electrolytic solution can be obtained, and have completed the present invention.

That is, the present invention provides the following general formula (1):

Embedded image (Wherein, R ¹ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms which may have a branch, R ² is an alkyl group which may have 1 to 5 carbon atoms and may have a branch, and X is 3 carbon atoms. Which represents an alkylene group which may have up to 13 branches) and salts thereof, and the following general formula (2):

Embedded image (Wherein, R ¹ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms which may have a branch, R ² is an alkyl group having 1 to 5 carbon atoms which may have a branch, X ¹ and X ² Each independently represents an alkylene group having 3 to 13 carbon atoms which may have a branch)) and an electrolytic solution for an electrolytic capacitor containing at least one compound selected from the group consisting of tricarboxylic acid compounds and salts thereof. I will provide a.

In a preferred embodiment of the present invention, the weight ratio of the dicarboxylic acid compound and its salt to the tricarboxylic acid compound and its salt in the electrolyte is from 1:30 to 1:
It is in the range of 1.5. Further, it is preferable to use one or more solvents selected from the group consisting of ethylene glycol and γ-butyrolactone as the solvent. The present invention also provides an electrolytic capacitor using the above-mentioned electrolytic solution. The electrolytic capacitor of the present invention is particularly useful for medium and high pressure.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The electrolytic solution for an electrolytic capacitor of the present invention includes a dicarboxylic acid compound having a structure represented by the general formula (1) and a salt thereof (hereinafter, referred to as “dicarboxylic acids”);
And a group consisting of a tricarboxylic acid compound having a structure represented by the general formula (2) and a salt thereof (hereinafter, referred to as “tricarboxylic acids”) (hereinafter, “polycarboxylic acids”).
). These polycarboxylic acids are new compounds provided for the first time by the present inventors.

General formula (1) representing a dicarboxylic acid compound
In the formula, R ¹ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms which may have a branch. Specific examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, and a tert-amyl group. Desirable R ¹ is a hydrogen atom, a methyl group or an ethyl group. R ² represents an alkyl group having 1 to 5 carbon atoms which may have a branch. Specific examples of the alkyl group are the same as those for R ^1. Preferred R ² is a methyl group.

X represents an alkylene group having 3 to 13 carbon atoms which may have a branch. X is preferably an alkylene group of 4 to 8 carbon atoms, particularly preferred is - (CH _{2) n} - or

Embedded image Wherein n is an integer of 5 to 7, and R ⁴ is an alkyl group having 4 to 6 carbon atoms.

[0012] Preferred substituents and specific examples of R ¹ and R ² in the general formula (2) representing the tricarboxylic acid compound are the same as R ¹ and R ² in the general formula (1). Preferred structures of X ¹ and X ^{2 in} the general formula (2) are the same as X in the general formula (1).

The polycarboxylic acids used in the present invention are all excellent in chemical stability. For this reason, it exists stably even during long-term storage or high temperature, and its chemical and physical properties can be maintained. The polycarboxylic acids used in the present invention have high solubility in alcoholic solvents such as ethylene glycol. Furthermore, when used as an electrolytic solution for an electrolytic capacitor, there is an excellent advantage that spark voltage and electric conductivity are increased. Therefore, polycarboxylic acids are electrolytic solutions that can provide an electrolytic capacitor with low loss, high rated voltage, and little deterioration at high temperatures. In particular, it is useful as an electrolytic solution that can achieve a long life of a medium-to-high pressure electrolytic capacitor.

The polycarboxylic acids used in the present invention can be synthesized by appropriately combining synthesis reactions known to those skilled in the art. Further, the polycarboxylic acids used in the present invention may be extracted from a suitable natural resource or artificial material.

As a preferred method for producing the polycarboxylic acid used in the present invention, a method comprising the following two main steps can be mentioned. The first step is represented by the general formula (3):

In the alcohol represented by R ¹ OH (3) (wherein R ¹ represents an alkyl group having 1 to 5 carbon atoms which may have a branch), the alcohol having 4 to 4 carbon atoms may be used.
This is a step of reacting 14 cycloalkanone with hydrogen peroxide. Examples of the alcohol represented by the general formula (3) include methanol, ethanol, isopropanol, n-
It is preferable to use butanol, tert-butanol and the like. The most preferred alcohol is methanol. These alcohols are preferably anhydrous.

The cycloalkanone having 4 to 14 carbon atoms includes cyclobutanone, 2-methylcyclobutanone, 3-methylcyclobutanone, 2-ethylcyclobutanone, 3-ethylcyclobutanone, 2-n-propylcyclobutanone, 3-n- Propylcyclobutanone, 2-
Isopropylcyclobutanone, 3-isopropylcyclobutanone, 2-n-butylcyclobutanone, 3-n-butylcyclobutanone, 2-isobutylcyclobutanone,
3-isobutylcyclobutanone, 2-tert-butylcyclobutanone, 3-tert-butylcyclobutanone, 2-n-pentylcyclobutanone, 3-n-pentylcyclobutanone, 2-tert-amylcyclobutanone, 3-tert-amylcyclobutanone, cyclopentanone , 2-methylcyclopentanone, 3-methylcyclopentanone, 2-ethylcyclopentanone, 3-ethylcyclopentanone, 2-n-propylcyclopentanone, 3-n-propylcyclopentanone, 2-isopropyl Cyclopentanone, 3-isopropylcyclopentanone, 2-n-butylcyclopentanone, 3-n-butylcyclopentanone, 2-isobutylcyclopentanone, 3-isobutylcyclopentanone, 2-tert-
Butylcyclopentanone, 3-tert-butylcyclopentanone, 2-n-pentylcyclopentanone, 3-
n-pentylcyclopentanone, 2-tert-amylcyclopentanone, 3-tert-amylcyclopentanone, cyclohexanone, 2-methylcyclohexanone, 3-methylcyclohexanone, 4-methylcyclohexanone, 2-ethylcyclohexanone, 3-ethyl Cyclohexanone, 4-ethylcyclohexanone, 2-n
-Propylcyclohexanone, 3-n-propylcyclohexanone, 4-n-propylcyclohexanone, 2-
Isopropylcyclohexanone, 3-isopropylcyclohexanone, 4-isopropylcyclohexanone, 2
-N-butylcyclohexanone, 3-n-butylcyclohexanone, 4-n-butylcyclohexanone, 2-isobutylcyclohexanone, 3-isobutylcyclohexanone, 4-isobutylcyclohexanone, 2-ter
t-butylcyclohexanone, 3-tert-butylcyclohexanone, 4-tert-butylcyclohexanone, 2-n-pentylcyclohexanone, 3-n-pentylcyclohexanone, 4-n-pentylcyclohexanone, 2-tert-amylcyclohexanone, 3-t
ert-amylcyclohexanone, 4-tert-amylcyclohexanone, 2,3-dimethylcyclohexanone, 2,4-dimethylcyclohexanone, 2,5-dimethylcyclohexanone, 3,4-dimethylcyclohexanone, 3,5-dimethylcyclohexanone, 2,3 -Diethylcyclohexanone, 2,4-diethylcyclohexanone, 2,5-diethylcyclohexanone, 3,4-
Diethylcyclohexanone, 3,5-diethylcyclohexanone, 2,3,4-trimethylcyclohexanone,
2,3,5-trimethylcyclohexanone, 3,4,5
-Trimethylcyclohexanone, 3,3,5-trimethylcyclohexanone, 2,4,5-trimethylcyclohexanone, 2,3,4-triethylcyclohexanone,
2,3,5-triethylcyclohexanone, 3,4,5
-Triethylcyclohexanone, 2,4,5-triethylcyclohexanone, 2,3,4,5-tetramethylcyclohexanone, 2,3,4,5-tetraethylcyclohexanone, cycloheptanone, 2-methylcycloheptanone, 3-methyl Cycloheptanone, 4-methylcycloheptanone, 2-ethylcycloheptanone, 3-ethylcycloheptanone, 4-ethylcycloheptanone, 2
-N-propylcycloheptanone, 3-n-propylcycloheptanone, 4-n-propylcycloheptanone,
2-isopropylcycloheptanone, 3-isopropylcycloheptanone, 4-isopropylcycloheptanone, 2-n-butylcycloheptanone, 3-n-butylcycloheptanone, 4-n-butylcycloheptanone,
2-isobutylcycloheptanone, 3-isobutylcycloheptanone, 4-isobutylcycloheptanone, 2-
tert-butylcycloheptanone, 3-tert-butylcycloheptanone, 4-tert-butylcycloheptanone, 2-n-pentylcycloheptanone, 3-n
-Pentylcycloheptanone, 4-n-pentylcycloheptanone, 2-tert-amylcycloheptanone,
3-tert-amylcycloheptanone, 4-tert
-Amylcycloheptanone, and cyclohexanone and alkyl-substituted cyclohexanone are particularly preferred.

The reaction of the first step is preferably carried out in an acid catalyst. Examples of the acid catalyst include sulfuric acid, hydrochloric acid, phosphoric acid, trifluoroacetic acid and the like. Among them, it is preferable to use sulfuric acid or phosphoric acid. The amount of hydrogen peroxide used in the first step is preferably 0.1 to 1 mol of cycloalkanone.
The amount is from 8 to 1.3 mol, more preferably from 0.9 to 1.2 mol, most preferably from 1.0 to 1.1 mol. The use amount of the alcohol represented by the general formula (3) is preferably 1 to 70 mol, more preferably 5 to 40 mol, per 1 mol of cycloalkanone. The amount of the acid catalyst used is preferably 0.04 to 0.1 per mole of cycloalkanone.
Mole, more preferably 0.05 to 0.08 mole.

The reaction in the first step is preferably carried out under cooling, particularly preferably at a temperature in the range of -20 to 10 ° C. Although not wishing to be bound by any theory, it is believed that the reaction in the first step produces an alkoxycycloalkane peroxide and becomes a reactant in the next second step. It is preferable that the alkoxycycloalkane peroxide generated by the reaction of the first step is subjected to the reaction of the second step without isolation.

In the second step, the product of the first step is converted to a compound of the general formula (4):

[Image Omitted] R ² —CH−CH—COOR ³ (4) wherein R ² and R ³ each independently represent an alkyl group having 1 to 5 carbon atoms which may have a branch. In this step, the unsaturated carboxylic acid ester compound is reacted.
The unsaturated carboxylic acid ester compound represented by the general formula (4) may be in a cis form or a trans form,
A mixture of the cis form and the trans form can also be used.
Examples of the unsaturated carboxylic acid ester compound represented by the general formula (4) include methyl crotonate, ethyl crotonate, n-propyl crotonate, isopropyl crotonate, n-butyl crotonate, isobutyl crotonate, and tert-crotonate. Butyl, n-pentyl crotonate,
Tert-amyl crotonic acid, methyl 2-pentenoate,
Ethyl 2-pentenoate, n-propyl 2-pentenoate,
2-isopropyl pentenoate, n-butyl 2-pentenoate, isobutyl 2-pentenoate, tert-pentenoate
t-butyl, n-pentyl 2-pentenoate, tert-amyl 2-pentenoate, methyl 2-hexenoate, ethyl 2-hexenoate, n-propyl 2-hexenoate, isopropyl 2-hexenoate, 2-hexenoic acid n-butyl, 2
-Isobutyl hexenoate, tert-butyl 2-hexenoate, n-pentyl 2-hexenoate, t-hexene 2-hexenoate
ert-amyl. Among them, it is preferable to use a crotonic acid alkyl ester.

The reaction in the second step is preferably carried out in the presence of a metal catalyst. Examples of the metal catalyst include sulfates, chlorides, ammonium salts and hydrates of metals such as iron, copper, cobalt, titanium and tin, and among them, ferrous salts are preferred. Examples of the ferrous salt include ferrous sulfate, ferrous chloride, ammonium ferrous sulfate, and hydrates thereof. Among them, ferrous sulfate is particularly preferable because it can be recovered by reduction with sulfuric acid and iron after the reaction, and can be advantageously reused. In the second step, two or more metal catalysts may be used in combination.

The amount of the unsaturated carboxylic acid ester compound used in the second step is preferably 1 to 10 mol, more preferably 2 to 8 mol, per 1 mol of cycloalkanone. The amount of the metal catalyst to be used is preferably 0.8 to 1.3 mol, more preferably 0.9 to 1.2 mol, most preferably 1.0 to 1.1 mol per mol of cycloalkanone.

In the reaction of the second step, an unsaturated carboxylic acid ester compound is added to the reaction solution of the first step, and the metal catalyst is added as it is under stirring, or an alcohol such as an alcohol represented by the general formula (3). It is preferably carried out by dropping into a suspension or a homogeneous solution as much as possible. The suspension or homogeneous solution is preferably prepared by suspending or dissolving in 2 to 4 times the amount of alcohol relative to the metal salt. If nitrogen gas is present in the preparation, the reaction of the second step can be performed efficiently. The reaction in the second step is preferably performed under cooling, more preferably at a temperature in the range of -20 to 10 ° C, and particularly preferably at a temperature in the range of -10 to 5 ° C. The reaction time is preferably 0.1 to 5 hours, more preferably 0.3 to 2 hours.

The reaction solution after the completion of the reaction in the second step contains R ¹
Is a dicarboxylic acid ester of the general formula (1), which is an alkyl group having 1 to 5 carbon atoms which may have a branch, and R ¹ is an alkyl group having 1 to 5 carbon atoms which may have a branch. Both tricarboxylic acid esters of the general formula (2) are included. The ratio of the dicarboxylic acid ester to the tricarboxylic acid ester in the reaction solution is from 1:30 to 1: 1.5 by weight.
It is.

When it is desired to obtain a dicarboxylic acid or tricarboxylic acid in which R ¹ is a hydrogen atom, ester hydrolysis is carried out as a third step. The method of ester hydrolysis is performed using any of the methods well known to those skilled in the art. For example, hydrolysis can be performed by adding an acid or an alkali.

The reaction solution after the completion of the second step and the reaction solution after the completion of the third step can be purified by performing post-treatments as necessary. By appropriately selecting purification conditions, a single compound may be isolated, or a mixture of a plurality of compounds may be obtained. When a mixture of a plurality of compounds is obtained, the component ratio can also be adjusted by utilizing the chemical or physical properties of each component. However, in the present invention,
The mixture of dicarboxylic acids and tricarboxylic acids obtained at the above weight ratio is used for the electrolyte at the same ratio,
It is preferable in terms of spark voltage and solubility.

The dicarboxylic acid compound and tricarboxylic acid compound thus obtained can be subjected to salt formation in the fourth step, if necessary. Salt formation is performed according to methods well known to those skilled in the art. Usually, it is an ammonium salt. For example, triethylmethylammonium salt, diethyldimethylammonium salt, triisopropylmethylammonium salt, dimethyldiisopropylammonium salt, dibutyldimethylammonium salt, ethyldimethylisopropylammonium salt, dimethylallylammonium salt, diallylmethylammonium salt and the like can be used. In addition, as salts other than ammonium salts, for example, quaternary salts of cyclic amidine compounds, quaternary phosphonium salts, and N, N-alkylenetetrahydrooxazinium compound salts can be used.

The method for producing polycarboxylic acids used in the present invention is not limited to those produced by the above-mentioned production method, but the above-mentioned production method is useful in that it is easy to control and has good reproducibility. . For this reason, it can be utilized as a production method capable of industrial stable supply.

In the electrolyte of the present invention, in addition to the compounds represented by the general formulas (1) and (2), a solute that can be used in the electrolyte is used in a range not to impair the intended effect of the present invention. You can also. As such a solute, boric acid,
Benzoic, malonic, succinic, glutaric, adipic, pimelic, cornic, azelaic, sebacic, methylmalonic, ethylmalonic, propylmalonic, isopropylmalonic, butylmalonic, isobutylmalonic , Ethyl methyl malonic acid, diethyl malonic acid, methyl succinic acid, dimethyl succinic acid, trimethyl succinic acid, tetramethyl succinic acid, ethyl succinic acid, diethyl succinic acid, propyl succinic acid, methyl glutaric acid,
Examples thereof include dimethylglutaric acid, ethylglutaric acid, diethylglutaric acid, maleic acid, citraconic acid, glutaconic acid, itaconic acid, allylmalonic acid, terraconic acid, fumaric acid, mesaconic acid, and muconic acid.

The solvent used in the electrolytic solution of the present invention can be selected and used without particular limitation as long as it can dissolve the compounds represented by the general formulas (1) and (2). Solvents that can be used in the electrolytic solution of the present invention include, for example, ethylene glycol, diethylene glycol, propylene glycol, glycerin, 1,4
Alcohols such as butanediol, methylcellosolve and ethylcellosolve; lactones such as γ-butyrolactone; carbonates such as ethylene carbonate and propylene carbonate; methylformamide, dimethylformamide, ethylformamide, diethylformamide, methylacetamide, dimethyl Acetamide,
Amides such as ethylacetamide and diethylacetamide; nitriles such as acetonitrile; oxides such as dimethylsulfoxide; sulfolane and N-methylpyrrolidone. Among them, ethylene glycol and γ-butyrolactone are preferred. One of these solvents may be used alone, or two or more thereof may be used in combination as a mixed solvent. Further, the electrolyte solution of the present invention may contain water, but when water is used, it is 30% by weight or less, preferably 1% by weight of the electrolyte solution.
0% by weight or less.

The composition ratio of the solute and the solvent in the electrolytic solution of the present invention is not particularly limited, but is 5:95 to 30: 7 by weight.
It is particularly preferred that it is in the range of 0. Components other than the above-mentioned solute and solvent can be added to the electrolytic solution of the present invention as needed.

The present invention also provides an electrolytic capacitor using the above-mentioned electrolytic solution of the present invention. The structure and material of the electrolytic capacitor of the present invention are not particularly limited as long as the electrolytic solution is used. Therefore, any use of the electrolytic solution of the present invention for a conventionally used electrolytic capacitor or a newly proposed electrolytic capacitor is included in the scope of the present invention. As a typical configuration example of the electrolytic capacitor of the present invention, a wound element structure shown in FIG. 1 can be exemplified. In this example, a cathode foil (2) is arranged so as to face the anode foil (1), and is wound with a separator (3) interposed therebetween. This is put in an exterior case (6) made of aluminum, and the case is sealed with a sealing material (5) such as a phenol laminate, polypropylene, or polyphenylene sulfide through packing such as butyl rubber, ethylene propylene rubber, or silicone rubber. To make an electrolytic capacitor. The electrolyte of the present invention is used for a separator (3) sandwiched between an anode foil and a cathode foil. Kraft paper, Manila paper, etc. are generally used for the separator,
It is not particularly limited to these.

The electrolytic capacitor of the present invention has a high spark voltage and a high electrical conductivity, and has little deterioration at high temperatures. For this reason, the present invention can be effectively used as an electrolytic capacitor for medium and high voltage having a particularly long life.

[0033]

The present invention will be described more specifically with reference to the following examples. The materials, amounts, proportions,
Operations and the like can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the following specific examples.

Example 1 800 ml of anhydrous methanol was placed in a flask equipped with a stirrer, cooled to 5 ° C., and 98 g of cyclohexanone and 5 g of concentrated sulfuric acid were added. While stirring this mixture, 113.4 g of 30% aqueous hydrogen peroxide was added dropwise, and the mixture was further stirred for 10 minutes while keeping the temperature at 8 ° C. to react. In this reaction solution, 500.6 g of methyl crotonate was dissolved, and 294.8 g of ferrous sulfate (heptahydrate) was gradually added thereto while maintaining the reaction temperature at -20 to -5 ° C under a nitrogen stream to carry out the reaction. I let it. After the reaction, 50% sulfuric acid aqueous solution 200ml
Was added, and methanol was distilled off, followed by extraction with diethyl ether. The diethyl ether layer was washed with water and dried, and the diethyl ether was distilled off to obtain 168 g of a polycarboxylic acid methyl ester mixture.

As a result of analyzing the obtained polycarboxylic acid methyl ester by gas chromatography, a dicarboxylic acid methyl ester mixture [R in the general formula (1) was used.
Compound in which ¹ and R ² are a methyl group and X is an alkylene group having 5 carbon atoms] (11.4%, Mass: molecular weight 23)
0) and a tricarboxylic acid methyl ester mixture [compound of formula (2) wherein R ¹ and R ² are methyl groups, and X ¹ and X ² are alkylene groups having 5 carbon atoms] (56
%, Mass: molecular weight 358). This mixture of polycarboxylic acid methyl esters was dissolved in 500 ml of methyl alcohol, and a 50% aqueous solution of 170 g of sodium hydroxide was added thereto and hydrolyzed by stirring to obtain a liquid polycarboxylic acid mixture (mixture 1).
132 g were obtained.

This mixture 1 was mixed with ethylene glycol 528
The mixture was dissolved in g and blown with ammonia to obtain a solution of the ammonium salt of the mixture 1 (20% by weight) in ethylene glycol. The pH of the resulting solution was 6.02. The water concentration of this solution was adjusted to about 1%, and the performance as an electrolyte was evaluated. First, the conductivity at 25 ° C. was measured. Next, the wound element shown in FIG. 1 was impregnated with an electrolytic solution, and a voltage value at which a spike or scintillation was first observed in a voltage-time rising curve when a constant current of 3 mA was applied was recorded as a spark voltage. The specification of the used aluminum electrolytic capacitor element is rated voltage 550W
V, and the capacitance was 10 μF. Table 1 shows the measurement results of the conductivity and the spark voltage.

Example 2 820 ml of anhydrous methanol was placed in a flask equipped with a stirrer, cooled to 5 ° C., and 103 g of 4-ethylcyclohexanone and 4.76 g of concentrated sulfuric acid were added. While stirring this mixture, 30% hydrogen peroxide 9
3.79 g was added dropwise, and stirring was continued for another 10 minutes while keeping the temperature at 8 ° C. to cause a reaction. In this reaction solution, 410.46 g of methyl crotonate was dissolved, and the reaction temperature was lowered under a nitrogen stream.
Ferrous sulfate (heptahydrate) 24 while maintaining at 20 to -5 ° C
1.73 g was gradually added and reacted. 50% after reaction
165 ml of a sulfuric acid aqueous solution was added, methanol was distilled off, and the mixture was extracted with diethyl ether. The diethyl ether layer was washed with water and dried, and the diethyl ether was distilled off to obtain 165 g of a polycarboxylic acid methyl ester mixture.

As a result of analyzing the obtained polycarboxylic acid methyl ester by gas chromatography, a dicarboxylic acid methyl ester mixture [R in the general formula (1)
Compound in which ¹ and R ² are a methyl group and X is an alkylene group having 7 carbon atoms] (6.3%, Mass: molecular weight: 258)
And a tricarboxylic acid methyl ester mixture [a compound in which R ¹ and R ² in the general formula (2) are methyl groups and X ¹ and X ² are alkylene groups having 7 carbon atoms] (60.
It was confirmed that the mixture was a mixture of 7%, Mass: molecular weight 414). The mixture of the polycarboxylic acid methyl esters was dissolved in 500 ml of methyl alcohol, and a 50% aqueous solution of 170 g of sodium hydroxide was added thereto and hydrolyzed by stirring to obtain 140 g of a liquid polycarboxylic acid mixture (mixture 2). The mixture 2 was dissolved in 560 g of ethylene glycol, and ammonia was blown into the solution to obtain a solution of the ammonium salt of the mixture 2 (20% by weight) in ethylene glycol. The pH of the resulting solution was 6.1.
It was 8. An electrolytic solution was prepared in the same manner as in Example 1, and the results of measuring the electric conductivity and the spark voltage are shown in Table 1.

Example 3 Mixture 1 prepared in Example 1
Was made into an ethylene glycol solution having a concentration of 10% by weight. Using this, an electrolytic solution was prepared in the same manner as in Example 1, and the results of measuring the electric conductivity and the spark voltage are shown in Table 1.

Example 4 Mixture 2 prepared in Example 2
Was made into an ethylene glycol solution having a concentration of 10% by weight. Using this, an electrolytic solution was prepared in the same manner as in Example 1, and the results of measuring the electric conductivity and the spark voltage are shown in Table 1.

Example 5 200 ml of anhydrous methanol was placed in a flask equipped with a stirrer, cooled to 5 ° C., and 22.43 g of 4-methylcyclohexanone and 1.16 g of concentrated sulfuric acid were added. While stirring the mixture, 22.88 g of 30% aqueous hydrogen peroxide was added dropwise, and the mixture was further stirred for 10 minutes while keeping the temperature at 8 ° C. to react. 100.12 g of methyl crotonate was dissolved in the reaction solution, and ferrous sulfate (heptahydrate) 5 was dissolved in a nitrogen stream while maintaining the reaction temperature at -20 to -5 ° C.
8.96 g was gradually added and reacted. 50% after reaction
40 ml of a sulfuric acid aqueous solution was added, methanol was distilled off, and the mixture was extracted with diethyl ether. The diethyl ether layer was washed with water and dried, and the diethyl ether was distilled off to obtain 40.0 g of a polycarboxylic acid methyl ester mixture.

As a result of analyzing the obtained polycarboxylic acid methyl ester by gas chromatography, a dicarboxylic acid methyl ester mixture [R in the general formula (1)
Compound in which ¹ and R ² are a methyl group and X is an alkylene group having 6 carbon atoms] (3.8%, Mass: molecular weight 244)
And a tricarboxylic acid methyl ester mixture [a compound in which R ¹ and R ² in the general formula (2) are methyl groups and X ¹ and X ² are alkylene groups having 6 carbon atoms] (65.
It was confirmed that the mixture was 2%, Mass: a molecular weight of 386). This mixture of polycarboxylic acid methyl esters is dissolved in 120 ml of methyl alcohol, hydrolyzed by adding a 50% aqueous solution of 40 g of sodium hydroxide and stirring to obtain a liquid polycarboxylic acid mixture (mixture 3).
34.85 g were obtained. The mixture 3 was dissolved in 139.4 g of ethylene glycol, and ammonia was blown into the solution to obtain a solution of the ammonium salt of the mixture 3 (20% by weight) in ethylene glycol. The pH of the resulting solution was 6.11. An electrolytic solution was prepared in the same manner as in Example 1, and the results of measuring the electric conductivity and the spark voltage are shown in Table 1.

Example 6 166 ml of anhydrous methanol was placed in a flask equipped with a stirrer, cooled to 5 ° C., and 18.6 g of 2-methylcyclohexanone and 0.96 g of concentrated sulfuric acid were added. While stirring this mixture, 18.99 g of 30% aqueous hydrogen peroxide was added dropwise thereto, and the mixture was further stirred for 10 minutes while keeping the temperature at 8 ° C. to cause a reaction. 83.1 g of methyl crotonate was dissolved in the reaction solution, and the reaction temperature was reduced to -2 under a nitrogen stream.
Ferrous sulfate (heptahydrate) while maintaining the temperature at 0 to -5 ° C.
94 g was gradually added and reacted. After the reaction, 33 ml of a 50% aqueous sulfuric acid solution was added, methanol was distilled off, and the mixture was extracted with diethyl ether. The diethyl ether layer was washed with water and dried, and diethyl ether was distilled off to obtain 16.72 g of a polycarboxylic acid methyl ester mixture.

As a result of analyzing the obtained polycarboxylic acid methyl ester by gas chromatography, a dicarboxylic acid methyl ester mixture [R in the general formula (1)
¹ and R ² are a methyl group and X is an alkylene group having 6 carbon atoms] (10.6%, Mass: molecular weight 24)
4) and a mixture of tricarboxylic acid methyl esters [compound in which R ¹ and R ² in the general formula (2) are methyl groups, and X ¹ and X ² are alkylene groups having 6 carbon atoms] (48.
9%, Mass: molecular weight 386). This mixture of polycarboxylic acid methyl esters was dissolved in 50 ml of methyl alcohol, and sodium hydroxide 17
g of a 50% aqueous solution and hydrolyzed by stirring to obtain a liquid polycarboxylic acid mixture (mixture 4) 13.73.
g was obtained. This mixture 4 was mixed with ethylene glycol 54.9.
By dissolving in 2 g and blowing ammonia, an ethylene glycol solution of the ammonium salt of mixture 4 (20% by weight) was obtained. The pH of the resulting solution was 5.75. An electrolytic solution was prepared in the same manner as in Example 1, and the results of measuring the electric conductivity and the spark voltage are shown in Table 1.

Example 7 50 ml of anhydrous methanol was placed in a flask equipped with a stirrer, cooled to 5 ° C., and 6.31 g of 2,5-dimethylcyclohexanone and 0.29 g of concentrated sulfuric acid were added.
Was added. While stirring the mixture, 5.72 g of 30% aqueous hydrogen peroxide was added dropwise, and the mixture was kept at 8 ° C. for 10 minutes.
The reaction was continued by stirring for minutes. 25.03 g of methyl crotonate was dissolved in this reaction solution, and ferrous sulfate (heptahydrate) 2 was dissolved in a nitrogen stream while maintaining the reaction temperature at -20 to -5 ° C.
5.03 g was gradually added and reacted. 50% after reaction
10 ml of a sulfuric acid aqueous solution was added, methanol was distilled off, and the mixture was extracted with diethyl ether. The diethyl ether layer was washed with water, dried, and distilled to remove diethyl ether.
7.93 g of a polycarboxylic acid methyl ester mixture was obtained.

As a result of analyzing the obtained polycarboxylic acid methyl ester by gas chromatography, a dicarboxylic acid methyl ester mixture [R in the general formula (1) was used.
Compounds in which ¹ and R ² are a methyl group and X is an alkylene group having 7 carbon atoms] (20%, Mass: molecular weight: 258)
And a tricarboxylic acid methyl ester mixture [a compound in which R ¹ and R ² in the general formula (2) are methyl groups and X ¹ and X ² are alkylene groups having 7 carbon atoms] (40.
It was confirmed that the mixture was 1%, Mass: a molecular weight of 414). This mixture of polycarboxylic acid methyl esters was dissolved in 25 ml of methyl alcohol, and hydrolyzed by adding a 50% aqueous solution of 8 g of sodium hydroxide and stirring to obtain a liquid polycarboxylic acid mixture (mixture 5).
05 g were obtained. This mixture 5 is mixed with ethylene glycol 2
By dissolving in 0.2 g and blowing ammonia, a solution of the ammonium salt of the mixture 5 (20% by weight) in ethylene glycol was obtained. The pH of the resulting solution was 6.0.
It was 2. An electrolytic solution was prepared in the same manner as in Example 1, and the results of measuring the electric conductivity and the spark voltage are shown in Table 1.

Comparative Example An electrolytic solution was prepared in the same manner as in Example 1 using an ethylene glycol solution of an ammonium salt of 1,7-octanedicarboxylic acid (10% by weight), and the electric conductivity and the spark voltage were measured. Table 1 shows the results.

[0048]

[Table 1]

[0049]

The results in Table 1 show that the electrolytic capacitor of the present invention has high electric conductivity and high spark voltage. Therefore, by using the present invention, it is possible to provide an electrolytic capacitor having a lower loss and a higher rated voltage. The electrolytic capacitor of the present invention also has an advantage that deterioration at high temperatures is small. Therefore, it can be effectively used as a medium-high voltage electrolytic capacitor having a particularly long life.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structural example of an electrolytic capacitor.

[Explanation of symbols]

 1: Anode foil 2: Cathode foil 3: Separator 4: Lead wire 5: Sealing material 6: Outer case

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Shuji Ichikawa 8-3-1 Chuo, Ami-cho, Inashiki-gun, Ibaraki Prefecture Inside the Tsukuba Research Laboratory, Mitsubishi Chemical Corporation (72) Inventor Kyoko Fukui 1-1167 Higashi-Ome, Ome-shi, Tokyo １ Inside Nippon Chemi-Con Corporation

Claims (5)

[Claims] 1. The following general formula (1): (Wherein, R ¹ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms which may have a branch, R ² is an alkyl group which may have 1 to 5 carbon atoms and may have a branch, and X is 3 carbon atoms. Which represents an alkylene group which may have up to 13 branches) and salts thereof, and the following general formula (2): (Wherein, R ¹ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms which may have a branch, R ² is an alkyl group having 1 to 5 carbon atoms which may have a branch, X ¹ and X ² Each independently represents an alkylene group having 3 to 13 carbon atoms which may have a branch)) and an electrolytic solution for an electrolytic capacitor containing at least one compound selected from the group consisting of tricarboxylic acid compounds and salts thereof. . 2. The electrolytic solution for an electrolytic capacitor according to claim 1, wherein the dicarboxylic acid compound and its salt and the tricarboxylic acid compound and its salt are contained in a weight ratio of 1:30 to 1: 1.5. 3. The electrolytic solution for an electrolytic capacitor according to claim 1, comprising one or more solvents selected from the group consisting of ethylene glycol and γ-butyrolactone. 4. An electrolytic capacitor using the electrolytic solution for an electrolytic capacitor according to claim 1. 5. The electrolytic capacitor according to claim 4, which is used for medium and high pressure.