JP2012009653A - Electrolytic solution for driving electrolytic capacitor and electrolytic capacitor using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic solution for driving an electrolytic capacitor, capable of maintaining a high withstand voltage even when an electrolyte concentration is increased.SOLUTION: The electrolytic solution for driving an electrolytic capacitor comprises an electrolyte dissolved in a solvent. The electrolyte is selected from the group consisting of specific higher dibasic acids including an alkyl side chain coordinated at a predetermined position and salts of the specific higher dibasic acids. The electrolyte is preferably a tetradecanedioic acid derivative including an alkyl group with 4-10 carbon atoms coordinated at 3-position, or a tetradecanedioic acid unsaturated derivative.

Description

  The present invention relates to an improvement in an electrolytic solution for driving an electrolytic capacitor (hereinafter referred to as an electrolytic solution). In particular, by using a specific higher dibasic acid as an electrolyte, the electrolyte concentration is increased while increasing the withstand voltage. It is related with the electrolyte solution for the drive of the electrolytic capacitor which can be performed.

  An electrolytic capacitor is one of common electronic components, and is widely used in various electronic components and electrical products, mainly for power supply circuits and digital circuit noise filters.

  In general, an electrolytic capacitor is obtained by electrochemically etching a metal foil and an anode foil having an oxide film formed by anodizing the surface after the metal foil has been electrochemically etched to increase the surface area. A capacitor element obtained by inserting and winding a separator between the cathode foil is impregnated with an electrolytic solution, and then stored in an exterior case, and then the opening of the case is sealed with elastic rubber, and the sealed portion is drawn. It is constituted by.

  In such an electrolytic capacitor, the electrolytic solution is in contact with the surface of the anode foil and functions as a substantial cathode that transmits electrons from the cathode foil. In addition, the electrolytic solution is also required to have a function (chemical conversion) for repairing deterioration and damage of the insulating oxide film, which affects the leakage current and life characteristics of the electrolytic capacitor.

In addition, due to the increasing demand for safety, there is a need for an electrolyte that can realize an electrolytic capacitor with a high withstand voltage so as not to cause a short circuit or ignition under severe conditions where a voltage exceeding the rated voltage is applied. It has been.
Conventionally, an electrolytic solution in which a higher dibasic acid or a salt thereof is dissolved in a solvent containing ethylene glycol as a main component has been used for an electrolytic capacitor for high voltage (see, for example, Patent Document 1 and Patent Document 2). ). In such an electrolytic solution, a method of decreasing the electrolyte concentration is employed as a method for increasing the withstand voltage.

JP 2000-315629 A JP 2006-108158 A

However, if the electrolyte concentration is too low, there is a problem that the chemical conversion property of the electrolytic solution is lowered when the electrolytic solution is left at a high temperature for a long period of time. Such a problem is considered to occur because if the capacitor is kept at a high temperature, the electrolyte decreases due to thermal degradation, and therefore, when the electrolyte concentration is low from the beginning, it is particularly susceptible to the decrease in electrolyte.
Accordingly, development of an electrolytic solution for driving an electrolytic capacitor that can increase the electrolyte concentration while increasing the withstand voltage is desired.

  As a result of intensive studies to solve the above problems, the present inventors have found that a high withstand voltage can be maintained even when the concentration of the electrolyte is increased by using a specific higher dibasic acid as an electrolyte. completed.

That is, the present invention is an electrolytic solution for driving an electrolytic capacitor obtained by dissolving an electrolyte in a solvent, wherein the electrolyte is a group consisting of any one or more compounds of formulas I to IV and a salt of the compound. It is selected from these.

By employing at least one substance selected from the group consisting of the above-mentioned compounds of formulas I to IV and salts thereof as the electrolyte, the electrolyte concentration can be increased while maintaining a high withstand voltage.
By increasing the electrolyte concentration, it is possible to delay the decrease of the electrolyte accompanying thermal degradation when left at a high temperature for a long period of time, so that it is possible to maintain the chemical conversion properties of the electrolyte over a long period of time. Furthermore, the specific resistance of the electrolytic solution containing the above electrolyte hardly increases even when left at high temperature.

  The concentration of the electrolyte is preferably 0.080 to 0.600 mol / kg from the viewpoint of achieving both high withstand voltage and low specific resistance.

  A preferable solvent for the electrolytic solution is a mixed solvent of ethylene glycol and water.

  An electrolytic capacitor having a capacitor element impregnated with the driving electrolyte exhibits excellent withstand voltage characteristics and long-term stable chemical conversion / specific resistance characteristics.

  According to the present invention, by using the above-mentioned specific substance as an electrolyte, a high withstand voltage can be maintained even when the electrolyte concentration is increased, and an electrolytic solution for driving an electrolytic capacitor having a low specific resistance change rate even at a high temperature is obtained. Can be provided.

The electrolyte solution according to the present invention only needs to contain an electrolyte selected from the group consisting of the compounds of the above formulas I to IV and salts thereof, and includes only one kind of the electrolyte or two or more kinds. You may go out. In particular, an electrolytic solution containing a compound of formula III or a salt thereof is preferred. In addition, the compounds of Formulas II to IV have geometric isomers and exhibit properties that are easily dissolved in a solvent.
In Formulas I to IV, R ₁ represents an alkyl group having 4 to 10 carbon atoms (C ₄ H _{9 to} C ₁₀ H ₂₁ ). More preferred electrolytes are compounds of formulas I to IV where R ₁ is an alkyl group having 5 to 8 carbon atoms or salts thereof, and particularly preferred electrolytes are compounds of formulas I to IV where R ₁ is an alkyl group having 6 carbon atoms. Or a salt thereof.
In the case where R ₁ is an alkyl group having 1 to 3 carbon atoms, the bulkiness becomes small, and it becomes easy to react with other components in the electrolytic solution, which is not preferable. For example, an esterification reaction may occur between ethylene glycol, which is a suitable solvent according to the present invention, and an amidation reaction may occur between this ester compound and ammonia. On the other hand, when R ₁ is an alkyl group having 11 or more carbon atoms, the solubility in a solvent is remarkably lowered, which is not preferable.
In the compounds of formulas I-IV, R ₁ is located at the 12th carbon, counting from one carboxy terminus.
A particularly preferred compound of the present invention is a main chain having 14 carbon atoms, that is, a tetradecanedioic acid derivative or a tetradecanedioic acid unsaturated derivative, in which R ₁ is the 12th position from one carboxy terminus and the other It is coordinated to the 3rd carbon starting from the carboxy terminus.

In the compounds of formulas I to IV, R ₂ and R ₃ represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms.
When there is an alkyl group at the α-position of the carboxyl group, steric hindrance occurs due to the bulkiness of the alkyl group, and due to the adjacent electron-donating group, the esterification reaction with the OH group of ethylene glycol, which is the solvent, occurs. There is merit to be suppressed.

In the compound of the formula I, n ₁ represents an integer of ₁ to 10, and in the compound of the formula II, n ₂ represents an integer of 0 to 10. More preferably, n ₁ is a compound of formula I having ₁ to 8 and n ₂ is a compound of formula II having 0 to 8, particularly preferably a compound of formula I in which n ₁ is 1 (tetradecanedioic acid derivative) Or a compound of formula II where n ₂ is 0 (tetradecanedioic acid unsaturated derivative).

Preferred salts of the compounds of formulas I to IV include diammonium salts, primary amine salts such as methylamine, ethylamine and t-butylamine, secondary amine salts such as dimethylamine, ethylmethylamine and diethylamine, trimethylamine and diethyl Examples thereof include tertiary amine salts such as methylamine, ethyldimethylamine and triethylamine, quaternary ammonium salts such as tetramethylammonium, triethylmethylammonium and tetraethylammonium, imidazolinium salts and imidazolium salts.
Particularly preferred is the diammonium salt.

The electrolytic solution according to the present invention has a high withstand voltage with respect to the molar concentration. And by setting the said electrolyte to 0.080-0.600 mol / kg (3.0-20.0 weight%), a high withstand voltage is realizable, suppressing the raise of a specific resistance. A more preferable electrolyte concentration is 0.096 to 0.474 mol / kg (3.5 to 15.0% by weight), and a particularly preferable electrolyte concentration is 0.140 to 0.298 mol / kg (5.0 to 10. 0% by weight).
With conventional electrolytes, the withstand voltage tends to decrease when the electrolyte concentration is increased, and it is necessary to lower the electrolyte concentration. However, when the electrolyte concentration is decreased, the specific resistance increases, and the electrolyte solution is not suitable for long-term high temperature exposure. There was a problem that the chemical conversion could not be maintained for a long time.
In the electrolyte according to the present invention, the withstand voltage is unlikely to decrease even when the electrolyte concentration is increased, and it is possible to achieve high withstand voltage and long-term maintenance of chemical conversion.

As the solvent used in the present invention, ethylene glycol which is a solvent capable of obtaining an electrolytic solution having excellent temperature characteristics is preferable. Ethylene glycol can be used alone, but is preferably mixed with water in order to reduce the specific resistance.
The concentration of ethylene glycol in the electrolytic solution is preferably 80 to 97% by weight, more preferably 83 to 95% by weight. When water is used in combination, the concentration of water in the electrolytic solution is preferably 0.5 to 10.0% by weight, and more preferably 1.0 to 3.0% by weight.
Other usable solvents include one or more selected from the group consisting of alcohols, ethers, amides, oxazolidinones, lactones, nitriles, carbonates, and sulfones. Specific examples of the solvent are as follows.

  Examples of alcohols include methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, diacetone alcohol, benzyl alcohol, amyl alcohol, furfuryl alcohol, propylene glycol, diethylene glycol, hexylene glycol, glycerin and hexitol.

  Moreover, as a high molecular weight body of alcohol, polyalkylene glycols, such as polyethylene glycol and polypropylene glycol, and its copolymer (henceforth, polyalkylene glycol) etc. are mentioned.

  Ethers include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, ethylene glycol phenyl ether, tetrahydrofuran, 3-methyltetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol Examples include diethyl ether.

  Examples of amides include N-methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N-diethylformamide, N-methylacetamide, N, N-dimethylacetamide, N-ethylacetamide, N, N- Examples include diethylacetamide and hexamethylphosphoric amide.

  Examples of oxazolidinones include N-methyl-2-oxazolidinone and 3,5-dimethyl-2-oxazolidinone.

  Examples of lactones include γ-butyrolactone, α-acetyl-γ-butyrolactone, β-butyrolactone, γ-valerolactone, and δ-valerolactone.

  Examples of nitriles include acetonitrile, acrylonitrile, adiponitrile, 3-methoxypropionitrile and the like.

  Examples of carbonates include ethylene carbonate and propylene carbonate.

  Examples of the sulfones include dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, sulfolane, 3-methyl sulfolane, and 2,4-dimethyl sulfolane.

  Examples of other solvents include N-methyl-2-pyrrolidone, dimethyl sulfoxide, 1,3-dimethyl-2-imidazolidinone, toluene, xylene, paraffins and the like.

Moreover, an additive can also be contained in electrolyte solution as needed.
Additives include phosphoric acid such as orthophosphoric acid, phosphorous acid, hypophosphorous acid, pyrophosphoric acid, polyphosphoric acid, methyl phosphate, ethyl phosphate, butyl phosphate, isopropyl phosphate, dibutyl phosphate, dioctyl phosphate Compounds, boric acid compounds such as boric acid and its complex compounds, polyhydric alcohols such as mannitol, sorbitol, xylitol, pentaerythritol, polyvinyl alcohol, nitro compounds such as p-nitrobenzoic acid and m-nitroacetophenone, colloidal silica , Aluminosilicates and silicone compounds (for example, reactive silicones such as hydroxy-modified silicones, amino-modified silicones, carboxyl-modified silicones, alcohol-modified silicones, and epoxy-modified silicones) and silane coupling agents (for example, 3-glycids) Shi trimethoxysilane, vinyl trimethoxysilane, ethyl triethoxysilane) and the like, silicon compounds such as.

  Further, if necessary, the electrolyte solution may be adipic acid, azelaic acid, sebacic acid, 1,6-decanedicarboxylic acid, 5,6-decanedicarboxylic acid, 7-vinylhexadecene-1,16-dicarboxylic acid, which are higher dibasic acids. An aliphatic carboxylic acid such as an acid, an aromatic carboxylic acid such as benzoic acid, or a salt thereof can also be contained.

The electrolytic solution of the present invention can be used for, for example, a wound aluminum electrolytic capacitor.
The capacitor using the electrolytic solution according to the present invention can be manufactured by a usual method. For example, an anode foil subjected to etching treatment and oxide film formation treatment and a cathode foil subjected to etching treatment are wound through a separator. It can be manufactured by a method of turning to form a capacitor element, impregnating the capacitor element with an electrolytic solution, and then storing the capacitor element in a bottomed cylindrical outer case.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited by these Examples.

[Preparation of electrolyte]
3-hexyl-tetradecane-2,4-dienedioic acid diammonium salt (hereinafter referred to as electrolyte A), which is an ammonium salt of a compound according to formula IV (R ₁ = C ₆ H ₁₃ , R ₂ = R ₃ = H) ) Or a compound according to Formula III (R ₁ = C ₆ H ₁₃ , R ₂ = R ₃ = H), which is an ammonium salt of 3-hexyl-tetradecane-2,5-dienedioic acid diammonium (hereinafter, electrolyte B) And an electrolyte according to an embodiment of the present invention, and diammonium 1,6-decanedicarboxylate (hereinafter referred to as electrolyte C) or diammonium sebacate (hereinafter referred to as electrolyte D). An electrolytic solution according to the comparative example used was prepared.
The electrolyte solution compositions of the examples and comparative examples are as shown in Table 1.

[Measurement of withstand voltage]
About each electrolyte solution of an Example and a comparative example, the electrode foil which formed the anodic oxide film which has a withstand voltage of 600V was immersed in 105 degreeC electrolyte solution, and voltage was raised with the constant current of 0.1 mA / cm < ² >. The spark generation voltage (withstand voltage of the electrolyte) was measured.
The results are shown in Table 1.

As a result of the experiment, the electrolyte solutions of the comparative examples (electrolyte C and electrolyte D) have an electrolyte concentration of 0.093 mol / kg (2.4 wt%) (comparative example 1) and 0.086 mol / kg (2.0 wt), respectively. %) (Comparative Example 3) showed a spark voltage of 480 V or more, but the electrolyte concentrations were 0.141 mol / kg (3.6 wt%) (Comparative Example 2) and 0.140 mol / kg (3.2 wt.), Respectively. %) (Comparative Example 4), the spark voltage significantly decreased.
On the other hand, in the electrolyte solution according to the example, when the electrolyte concentration was 0.096 to 0.097 mol / kg (3.5% by weight) (Example 1 and Example 5), the spark voltage exceeded 480V. In particular, the electrolyte B exhibited a high spark voltage exceeding 490V.
When compared on the basis of the same weight molar concentration, in Comparative Example 2 (0.141 mol / kg) and Comparative Example 4 (0.140 mol / kg), the spark voltage is 461 V and 470 V, respectively. In Example 2 (0.140 mol / kg) and Example 6 (0.141 mol / kg), the spark voltages are 482 V and 490 V, respectively, and the spark voltage is higher than that of the comparative example.
When electrolyte A is used, even if the electrolyte concentration is increased to 0.295 mol / kg (Example 3) and 0.469 mol / kg (Example 4), the electrolyte concentration is 0.140 to 0.141 mol / kg. A spark voltage comparable to that of Comparative Examples 2 and 4 in kg (on the order of 3% by weight) was exhibited.
When electrolyte B was used, a high spark voltage exceeding 480 V was exhibited even when the electrolyte concentration was increased to 0.298 mol / kg (Example 7), and increased to 0.474 mol / kg (Example 8). In addition, the spark voltage of the same level as that of Comparative Example 4 having an electrolyte concentration of 0.140 mol / kg was maintained.

From the results of this experiment, the electrolytes C and D of the comparative example show a significant decrease in withstand voltage due to an increase in electrolyte concentration (molar concentration), but the electrolytes A and B of the present invention show a decrease in withstand voltage. It can be seen that the effect on the is small.
For example, when the concentration of the electrolyte C is increased from 0.093 to 0.141 mol / kg, the spark voltage is decreased from 480 to 461 V, and when the concentration of the electrolyte D is increased from 0.086 to 0.140 mol / kg, the spark is decreased. Although the voltage decreases from 485 to 470 V, the electrolytes A and B of the present invention have almost no withstand voltage even when the electrolyte concentration is increased from 0.096 to 0.140 mol / kg or from 0.097 to 0.141 mol / kg. It can be seen that this is an excellent electrolyte that does not decrease and the influence of the increase in electrolyte concentration on the decrease in withstand voltage is significantly smaller than in the comparative example.

[Measurement of resistivity change rate in high temperature storage test]
Next, the electrolytes of Comparative Example 2, Comparative Example 4, Example 2, and Example 6 having approximately the same weight molar concentration (about 0.140 mol / kg) were sealed in an ampoule tube and placed in an atmosphere at 105 ° C. The specific resistance change rate after 1000 hours was measured.
The results are shown in Table 2.

As shown in Table 2, in the standing test at 105 ° C. for 1000 hours, it can be seen that the rate of change in specific resistance after 1000 hours is smaller in the electrolytic solution of the present invention than in the comparative example. From this, it can be seen that the electrolytic solution of the present invention suppresses an increase in specific resistance and improves the long-term stability of the electrolytic solution specific resistance.
The reason for this is considered as follows. Generally, higher dibasic acids tend to have higher withstand voltage as the distance between the carboxyl groups at both ends increases, but the specific resistance increases because the degree of dissociation decreases. However, in this example, by coordinating the alkyl side chain to the 3-position (12-position from the other carboxy terminus), the structure of the compound becomes asymmetric, and the electrical bias of the molecule causes a decrease in the degree of dissociation. It is considered that even if the carboxyl group distance is increased, the increase in specific resistance can be suppressed.
Furthermore, when compared by weight%, the electrolyte solution of the example has a higher electrolyte concentration than the electrolyte solution of the comparative example, so that the decrease in the electrolyte due to thermal degradation is delayed when left at high temperature for a long time, which also changes the specific resistance. This is considered to be a factor of the rate decline.

  In addition, this invention is not restricted to the said Example, When the said solute is used individually or in multiple, the same effect as the above is acquired.

Claims (4)

An electrolytic solution for driving an electrolytic capacitor obtained by dissolving an electrolyte in a solvent, wherein the electrolyte is selected from the group consisting of any one or more compounds of Formulas I to IV and salts of the compounds Electrolytic solution for driving an electrolytic capacitor characterized by

  2. The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein the concentration of the electrolyte is 0.080 to 0.600 mol / kg.   The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein the solvent is a mixed solvent of ethylene glycol and water.   An electrolytic capacitor comprising a capacitor element impregnated with the driving electrolyte solution according to claim 1.