JP2002043182A - Electrolyte for electrolytic capacitor, and electrolytic capacitor using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolyte for electrolytic capacitor, which has high electric conductivity and high withstanding voltage, and has a superior thermal stability, and also provide an electrolytic capacitor using the electrolyte. SOLUTION: The electrolyte for electrolytic capacitor contains quaternary amidinium salt of a hydroxy substituted aromatic monocarboxylic acid, and this electrolyte is used in the electrolytic capacitor.

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 an electrolytic capacitor and an electrolytic capacitor using the same. More specifically, the present invention relates to an electrolytic solution for an electrolytic capacitor characterized by containing a monocarboxylic 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 often used for low-frequency filters and bypasses. An electrolytic capacitor generally has a structure in which an anode foil and a cathode foil are wound through a separator, and the foil is housed in a case and sealed.
(Fig. 2). For the anode foil, valve metal such as aluminum or tantalum with an insulating oxide film formed as a dielectric layer is used,
As the cathode foil, an aluminum foil subjected to an etching treatment is generally used. 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,
Electrolyte is an important component that greatly affects the characteristics of electrolytic capacitors.

[0003] Among the properties of the electrolyte, the electric conductivity is directly related to the energy loss and impedance characteristics of the electrolytic capacitor. Therefore, the development of an electrolyte having a high electric conductivity has been actively carried out. For example, International Publication WO9
JP-A-5 / 15572 and JP-A-9-283379 propose an electrolytic solution in which a quaternary amidinium salt such as phthalic acid or maleic acid is dissolved in an aprotic solvent such as γ-butyrolactone. However, this type of electrolytic solution has high electric conductivity, but does not have sufficient withstand voltage, and an electrolytic solution having higher withstand voltage is required.

To solve this problem, Japanese Patent Laid-Open No.
Japanese Patent Publication No. 0-135081 proposes an electrolytic solution using a quaternary amidinium salt of benzoic acid as a solute. Although this electrolytic solution has both high electric conductivity and high withstand voltage, this electrolytic solution also has a problem in stability at a high temperature of 125 ° C.

[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 having both high electrical conductivity and high withstand voltage and excellent thermal stability, and an electrolytic capacitor using the same. Another object of the present invention is to provide an electrolytic solution for an electrolytic capacitor which can be stably supplied industrially and can be manufactured at low cost, and an electrolytic capacitor using the same.

[0006]

As a result of intensive studies to solve these problems, the present inventors have found that by using monocarboxylic acids having a specific structure, an excellent electrolytic solution having a desired effect can be obtained. They have found that a liquid can be obtained, and have completed the present invention.

That is, the present invention provides an electrolytic solution for an electrolytic capacitor containing a solvent and a quaternary amidinium salt of a hydroxy-substituted aromatic monocarboxylic acid. In a preferred embodiment of the present invention, the content of the quaternary amidinium salt of the hydroxy-substituted aromatic monocarboxylic acid is 5 to 40% by weight based on the total weight of the salt and the solvent.

The hydroxy-substituted aromatic monocarboxylic acids include salicylic acid, 4-hydroxybenzoic acid and 3-hydroxybenzoic acid.
One or more compounds selected from the group consisting of hydroxy-2-naphthoic acids are preferably used, and as the quaternary amidinium, 1-ethyl-2,3-dimethylimidazolinium or 1,2,3,4-tetra Methyl imidazolinium is preferably used. In the present invention, γ-butyrolactone is preferably used as a solvent, and ethylene glycol can be used as a secondary solvent of 40 parts by weight or less per 100 parts by weight of γ-butyrolactone.

Further, the present invention provides an electrolytic capacitor using the above-mentioned electrolytic solution, in particular, an anode electrode having an electrically insulating oxide film on the electrode surface, and a cathode electrode disposed opposite to the anode electrode with a separator interposed therebetween. An electrolytic capacitor having the same is also provided. In addition, in this specification, “to” is a range including numerical values described before and after it as a minimum value and a maximum value.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an electrolytic solution for an electrolytic capacitor and an electrolytic capacitor according to the present invention will be described in detail. The electrolytic solution for an electrolytic capacitor of the present invention is characterized by containing a quaternary amidinium salt of a hydroxy-substituted aromatic monocarboxylic acid. In the electrolytic solution for an electrolytic capacitor of the present invention, by using a hydroxy-substituted aromatic monocarboxylic acid as the anion component, both the electrical conductivity and the withstand voltage are high, and the electrolytic solution for the electrolytic capacitor having excellent thermal stability is obtained. Can be provided.

The term "hydroxy-substituted aromatic monocarboxylic acid" as used herein refers to a compound in which at least one hydroxy group is directly bonded to a carbon atom constituting an aromatic ring of the aromatic monocarboxylic acid. The number of hydroxy groups is preferably 3 or less, more preferably 2 or less, and even more preferably 1. The type of the aromatic ring is not particularly limited, but is preferably a benzene ring or a naphthalene ring. Preferred specific examples of the hydroxy-substituted aromatic monocarboxylic acid include salicylic acid, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, 1-hydroxy-2-naphthoic acid, 3-hydroxy-2-naphthoic acid, 6-hydroxy -2-naphthoic acid and the like, and mixtures thereof. Among them, salicylic acid, 4-hydroxybenzoic acid, 3-hydroxy-2-naphthoic acid,
And mixtures thereof.

In the electrolytic solution for an electrolytic capacitor of the present invention, a quaternary amidinium ion is used as a cation component.
Preferred specific examples of the quaternary amidinium salt include 1,3-
Dimethyl imidazolinium salt, 1-ethyl-3-methyl imidazolinium salt, 1,2,3-trimethyl imidazolinium salt, 1-ethyl-2,3-dimethyl imidazolinium salt, 1,2,3 4-tetramethylimidazolinium salt, 1-ethyl-2,3,4-trimethylimidazolinium salt, 1,3,4-trimethyl-2-ethylimidazolinium salt, and the like, and mixtures thereof. Among them, 1-ethyl-2,3-dimethylimidazolinium or 1,2,3,4-tetramethylimidazolinium is preferable, and 1-ethyl-2,3-dimethylimidazolinium salt is particularly preferable.

As a method for producing a quaternary amidinium salt of a hydroxy-substituted aromatic monocarboxylic acid, for example, an amidine, specifically, 1-ethyl-2-methyl-1-imidazoline is reacted with dimethyl carbonate in methanol. (Quaternization reaction), the resulting amidinium methyl carbonate,
As a specific example, a methanol solution of methyl 1-ethyl-2,3-dimethyl-imidazolinium carbonate is reacted with an equimolar amount of a hydroxy-substituted aromatic monocarboxylic acid (neutralization decarboxylation reaction). A method of distilling off methanol is exemplified.

The electrolytic solution for an electrolytic capacitor of the present invention contains at least a quaternary amidinium salt of a hydroxy-substituted aromatic monocarboxylic acid and a solvent. The content of the quaternary amidinium salt of the hydroxy-substituted aromatic monocarboxylic acid is preferably 5 to 40% by weight, more preferably 10 to 25% by weight, based on the total weight of the solvent and the salt. Although it does not specifically limit as a solvent, For example, organic polar solvents, such as (gamma) -butyrolactone, ethylene glycol, methyl cellosolve, dimethylformamide, sulfolane, and 3-methylsulfolane, can be used. Among them, γ-
A solvent mainly containing butyrolactone is preferably used. By selecting a solvent mainly composed of γ-butyrolactone, the temperature range in which the obtained electrolytic solution can be used is widened. Specifically, based on 100 parts by weight of γ-butyrolactone, the content of the solvent other than γ-butyrolactone is preferably 40 parts by weight or less, more preferably 1 to 30 parts by weight.
Parts by weight. When the content of the solvent other than γ-butyrolactone exceeds 40 parts by weight, the electric conductivity tends to be remarkably reduced.

The electrolytic solution for an electrolytic capacitor of the present invention contains other known solute components, for example, other quaternary ammonium salt-based solutes, specifically tetraalkyl carboxylic acids, as long as the effects of the present invention are not impaired. An ammonium salt or the like can be used in combination.

If necessary, components other than the above-mentioned solute and solvent can be added to the electrolytic solution for an electrolytic capacitor of the present invention. The electrolytic solution for an electrolytic capacitor of the present invention is obtained by stirring and mixing the above-mentioned components.

The present invention also provides an electrolytic capacitor using the electrolytic solution for an electrolytic capacitor. The structure and material of the electrolytic capacitor of the present invention are not particularly limited as long as the electrolytic solution for the electrolytic capacitor is used. Therefore, all cases where the electrolytic solution for an electrolytic capacitor of the present invention is used for a conventionally used electrolytic capacitor or a newly proposed electrolytic capacitor are 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 FIGS. 1 and 2 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 into an outer case made of aluminum (6), 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. This makes it an electrolytic capacitor. The electrolytic solution for an electrolytic capacitor of the present invention is used for a separator (3) sandwiched between an anode foil and a cathode foil. Kraft paper, manila paper, or the like is generally used for the separator, but the separator is not particularly limited thereto.

The electrolytic capacitor of the present invention has both high electric conductivity and withstand voltage and excellent stability at high temperatures.

[0020]

The present invention will be described more specifically with reference to the following examples. The materials, amounts, proportions,
The operation 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.

(Examples 1 to 6, Comparative Examples 1 to 4) The compositions shown in Table 1 below were mixed, and solid components were dissolved to prepare an electrolyte solution. In the table, the amounts of each component are shown in parts by weight.

The obtained electrolytic solution was evaluated for electric conductivity, withstand voltage and thermal stability. First, the electric conductivity at 25 ° C. was measured. Next, an electrolytic solution was impregnated into the wound-type element shown in FIG. 1, and an aluminum electrolytic capacitor having a structure in which the wound-type element was housed in an aluminum outer case and sealed with butyl rubber was produced. The voltage value at which spikes or scintillations were first observed in the voltage-time rise curve when applied at ° C was taken as the withstand voltage value. The specifications of the used aluminum electrolytic capacitor element are case size 10φ × 20L, rated voltage 200W
V, and the capacitance was 20 μF. Table 1 shows the measurement results of the electric conductivity and the withstand voltage.

[0023]

[Table 1]

In Example 1 of Table 1, salicylic acid was used as the hydroxy-substituted aromatic carboxylic acid. When this is compared with the conventional electrolyte solution, the voltage resistance is superior to the electrolyte solution using maleic acid (Comparative Example 1), and even when compared with the electrolyte solution using phthalic acid (Comparative Example 2). Are preferred because they have the same but somewhat higher electrical conductivity. In Example 2, the characteristics when ethylene glycol was added as the auxiliary solvent to the electrolytic solution of Example 1 were shown. High withstand voltage is exhibited by the effect of the additive, and the electric conductivity is also 8 mS.
/ Cm was maintained at a sufficiently high level.

[0025]

The results in Table 1 show that the electrolytic capacitor of the present invention has high electric conductivity and high withstand voltage.
Therefore, by utilizing the present invention, it is possible to provide an electrolytic capacitor having low loss and low impedance characteristics.

[Brief description of the drawings]

FIG. 1 is a perspective view of a wound element of an electrolytic capacitor.

FIG. 2 is a sectional view of an electrolytic capacitor.

[Explanation of symbols]

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

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Makoto Ue 8-3-1 Chuo, Ami-cho, Inashiki-gun, Ibaraki Prefecture Inside the Tsukuba Research Laboratory, Mitsubishi Chemical Corporation (72) Inventor Tatsunori Tsuji 1-167 Higashi-Ome, Ome-shi, Tokyo (1) Nippon Chemi-Con Corporation (72) Inventor Tadashi Ozawa 1-167, Higashi-Ome, Ome-shi, Tokyo, Japan

Claims (9)

[Claims] 1. An electrolytic solution for an electrolytic capacitor, comprising a solvent and a quaternary amidinium salt of a hydroxy-substituted aromatic monocarboxylic acid. 2. The composition according to claim 1, wherein the content of the quaternary amidinium salt of the hydroxy-substituted aromatic monocarboxylic acid is 5 to 40% by weight based on the total weight of the quaternary amidinium salt and the solvent. Electrolyte for electrolytic capacitors. 3. The method of claim 1, wherein said hydroxy-substituted aromatic monocarboxylic acid is salicylic acid, 4-hydroxybenzoic acid and 3-hydroxybenzoic acid.
The electrolytic solution for an electrolytic capacitor according to claim 1 or 2, which is one or more compounds selected from the group consisting of hydroxy-2-naphthoic acid. 4. The method according to claim 1, wherein the quaternary amidinium is 1-ethyl-
2,3-dimethylimidazolinium or 1,2,3
4. It is 4-tetramethylimidazolinium.
The electrolytic solution for an electrolytic capacitor according to any one of the above. 5. The electrolytic solution for an electrolytic capacitor according to claim 1, wherein the solvent is γ-butyrolactone. 6. The electrolytic solution for an electrolytic capacitor according to claim 5, wherein the content of the solvent other than γ-butyrolactone is 40 parts by weight or less per 100 parts by weight of the γ-butyrolactone. 7. The electrolytic solution for an electrolytic capacitor according to claim 6, further comprising 40 parts by weight or less of ethylene glycol per 100 parts by weight of the γ-butyrolactone. 8. An electrolytic capacitor using the electrolytic solution for an electrolytic capacitor according to claim 1. 9. An electrolytic capacitor comprising an anode electrode having an electrically insulating oxide film on an electrode surface and a cathode electrode disposed opposite to the anode electrode with a separator interposed therebetween.
An electrolytic capacitor, wherein the electrolytic solution held by the separator is the electrolytic solution for an electrolytic capacitor according to any one of claims 1 to 7.