JPH03120809A - Electrolyte for electrolytic capacitor - Google Patents

Abstract

PURPOSE:To improve breakdown strength while characteristics of electrolyte are kept satisfactory, and obtain stable characteristics even in the case of long term use, by adding specified polyoxyethylene glycerol fatty ester to electrolyte wherein organic polar solvent is used as the main solvent, and organic acid or inorganic acid or its salt is used as the solute. CONSTITUTION:As for electrolyte for driving an aluminum electrolytic capacitor, wherein an organic polar solvent is a main solvent, polyoxyethylene glycerol fatty ester having a shown general formula is added to the electrolyte whose solute is organic acid or inorganic acid or its salt. In the formula, (n) and (m) are identical or different integers larger than or equal to zero, at least one of them is larger than or equal to 1, and R is fatty acid residue. For example, the electrolyte is prepared as follow; solute composed of 20 pts.wt. of adipic acid diammonium and 3 pts.wt. of adipic acid, and 3 pts.wt. of polyoxyethylene glycerol oleate (n+m=40) in the above general formula are added to solvent composed of 80 pts.wt. of ethylene glycol, 7 pts.wt, of water and 20 pts.wt. of methyl celleosolve.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvement of an electrolytic solution for electrolytic capacitors, and more specifically, provides an electrolytic capacitor with improved m-voltage characteristics by adding specific additives. This invention relates to possible improvements in electrolyte solutions for electrolytic capacitors.

[Prior Art] Electrolytic capacitors are small, large-capacity, inexpensive, and exhibit excellent characteristics such as smoothing rectified output, and are one of the important components of various electrical and electronic devices. It is produced by using an aluminum film converted into an oxide film by electrolytic oxidation as an anode, and using this oxide film as a dielectric with an electrolyte interposed between it and the cathode. During use, the oxide film is constantly regenerated, so it is stable, but if it is not used for a long time, for example, regeneration becomes insufficient and it deteriorates.

Since electrolytic capacitors are used while undergoing chemical reactions, their characteristics largely depend on the properties of the electrolyte. Maintaining a steady state of the chemical reaction that occurs between the aluminum electrode, which has an oxide film on its surface, and the electrolyte, and maintaining the aluminum oxide film, which serves as a dielectric, in good condition is important for stabilizing performance. If the chemical steady state is disturbed due to an incorrect method, for example, due to an excessively high voltage load, the aluminum oxide film will be destroyed and eventually the insulation will be broken.

In the chemical reactions that occur during the use of electrolytic capacitors,
The electrolyte forms an ionic conductor that is a medium for ion movement. Charges move at the interface between the electrolyte and the electrode as the electrode reaction progresses, an oxidation reaction progresses at the anode surface, a reduction reaction progresses at the cathode surface, and at the same time, ions move through the electrolyte, which is an ionic conductor. Current flows.

Therefore, the electrical type conductivity of the electrolyte reflects the characteristics of the electrolyte as an ionic conductor in the chemical reactions that occur during use of the electrolytic capacitor, and is one of the important indicators for evaluating the overall performance of the capacitor.

Scintillation is a phenomenon in which the electrochemical state fluctuates as a result of a change in the physical properties of the dielectric due to the high voltage load that occurs when the load voltage of the capacitor increases, resulting in a temporal change in dielectric constant.The voltage at which this phenomenon is observed is The scintillation voltage (withstand voltage) can be used as a measure of the withstand voltage property of a capacitor, and the higher the scintillation voltage (withstand voltage), the greater the withstand voltage property of the capacitor. It is possible to measure unformed aluminum foil of a certain size by immersing it in the electrolyte to be measured without assembling the final capacitor product.

The capacitance of a capacitor is proportional to the dielectric constant of the dielectric material, so a dielectric material with a high dielectric constant should be used, and the dielectric constant should be kept high (charged) to avoid physical and chemical changes in the dielectric material during use. The loss angle tangent, which is the difference between the phase of the current and the phase of the external electric field, or the dielectric loss tangent, is used as a guideline for the power consumption of a capacitor, and a small value indicates low power consumption; it is a constant value after charging starts. The leakage current, which is the current that flows when the
Ions generated by dissociation of impurities in the dielectric are thought to be the main charge carriers, and the magnitude of change in leakage current reflects the stability of the electrochemical state of the dielectric.

In conventional general electrolyte solutions for electrolytic capacitors, acids such as boric acid or salts thereof are added to the electrolyte solution as a main solute in order to obtain high voltage resistance. In addition to these, attempts have been made to improve the electrolytic solution for electrolytic capacitors and obtain high voltage resistance by adding various additives.

Additives for obtaining high voltage resistance include, for example, the addition of sulfamic acid (Japanese Unexamined Patent Publication No. 49-82963), the addition of superric acid (Japanese Unexamined Patent Publication No. 49-133860), and the addition of dodecyl phosphate (Unexamined Japanese Patent Publication No. 49-133860). 1987-73659), addition of alkyl phosphoric acid (JP 52-153154), addition of sialic acid (JP 57-141913), use of boric acid-mannitol-polyvinyl alcohol system (JP 52-153154); No. 59-177915) and the like have been proposed, but it has not always been possible to sufficiently improve the withstand voltage while maintaining high conductivity.

[Problems to be Solved by the Invention] The present invention provides an electrolytic solution for electrolytic capacitors that maintains the properties of the electrolytic solution for electrolytic capacitors well, has improved voltage resistance, and has stable properties even when used at high temperatures for long periods of time. The purpose is to provide

[Means for Solving the Problems] According to the present invention, in an electrolytic solution for driving an aluminum electrolytic capacitor, an electrolytic solution containing an RFII solvent as a main solvent and an organic acid, an inorganic acid, or a salt thereof as a solute,
Polyoxyethylene glycerin having the following general formula: (wherein n and m are each the same or different integers of 0 or more, at least one is an integer of 1 or more, and R represents a fatty acid residue) Formula 0 provides an electrolytic solution for an electrolytic capacitor characterized by adding a fatty acid ester,
The sum of n and m is preferably about 1 to 100.

Specific examples of the fatty acid moiety of the polyoxyethylene glycerin fatty acid ester of the present invention include the following fatty acids: General formula CHs (CH2), COOH (n is an integer of 9 or more) undecylic acid (n=9),
Lauric acid < n = 10), tridecylic acid (n = 1
1), myristic e4 (n=12>, pentadecyl acid (n=13), valmitic acid (n=14), heptadecyl acid (n=15>, stearic acid (n=16), nonadecanoic acid (n=17) , arachic acid (n=18), behenic acid (n=20), lignoceric acid (n=22), cerotic acid (n=24), heptacanoic acid (n=25), montanic acid (n=27), melisin acid (n=28), as well as saturated fatty acids such as lafcel acid (n=30>) undecylic acid CH2=CH (CH2), COOH oleic acid C17HssCOOH (CiS) <9> elaidic acid C17H3sc OOH ( trans) <9>
Cetoleic acid C21H41c 00 H<11> Erucic acid C21H41COOH (cis) (13) Brassidic acid C21H41COOH (tranS) (13> Linoleic acid C,,H,,C0OH<9, 12>Linolic acid C1□H29COOH<9.12. 15>Arachidonic acid Cl9831cOOH<5.8, tl, 14) Unsaturated fatty acids such as stearolic acid C+7HxlCOOH<3-type packing, 9> (however, the position in brackets indicates the position of the unsaturated bond).

Specific examples of solvents that can be used alone or in combination as the organic polar solvent of the electrolyte include the following: proton-polar di-solvent ethanol, propatool, butanol, pentanol, hexanol, cyclo Monohydric alcohols such as butanol, cyclopentanol, cyclohexanol, and benzyl alcohol, ethylene glycol, propylene glycol, glycerin, methoxyethanol, ethoxyethanol, methoxypropylene glycol, dimethoxypropanol, methyl cellosolve, and ethyl cellosolve, etc. Polyhydric alcohols and alcohol ethers, -protic polar solvents N-methylformamide, N,N-dimethylformamide, toethylformamide, N,N-diethylformamide, tomethylacetamide, N,N-dimethylacetamide, tomethylacetamide , N,N-diethylacetamide, and amide solvents such as hexamethylphosporizamide, lactones such as γ-butyrolactone, tomethyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, and isobutylene carbonate, cyclic amide solvents, acetonitrile, etc. Nitrile solvents, oxide solvents such as dimethyl sulfoxide.

Specific examples of electrolytes that can be used alone or in combination in the electrolyte of organic acids, inorganic acids, or salts thereof include the following electrolytes: 1. Formic acid, acetic acid, propionic acid, enanthic acid. Aliphatic monocarboxylic acids such as malonic acid, succinic acid, curtaric acid, adipic acid, methylmalonic acid, pimelic acid, superric acid, azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid, citraconic acid, and itaconic acid, etc. aliphatic dicarboxylic acids, benzoic acid, phthalic acid, salicylic acid, toluic acid, and aromatic carboxylic acids such as pyromellitic acid, inorganic acids such as boric acid, phosphoric acid, silicic acid, HBF4, HPF, and ammonium ammonium. (NH4), monoalkylammoniums such as methylammonium, ethylammonium, and propylammonium; dialkylammoniums such as dimethylammonium, diethylammonium, ethylmethylammonium, and dibutylammonium; Quaternary ammoniums such as realkylammonium, tetramethylammonium, triethylmethylammonium, tributylammonium, tetraethylammonium, and N,N-dimethylpyrrolidinium, as well as other phosphoniums and arsoniums, can also be used.

The organic polar solvent of the electrolytic solution for an electrolytic capacitor according to the present invention can be the above-mentioned protic polar solvent alone, but preferably 0 to 50 parts by weight of the protic polar solvent and 100 to 50 parts by weight of the aprotic polar solvent. Prepare by mixing. If necessary, about 0 to 30 parts by weight of water can be mixed. In such a solvent system, it is preferable to dissolve 1 to 30 parts by weight of an inorganic acid or a salt thereof, such as an organic acid as a solute.

Preferably, 0.1 to 20 parts by weight, more preferably 0.5 to 5 parts by weight of the above-mentioned polyoxyethylene glycerin fatty acid ester is added to the electrolytic solution consisting of such a solute-solvent system.
By adding part by weight, it is possible to provide an electrolytic solution for an electrolytic capacitor that can realize high voltage resistance while maintaining good capacitor characteristics.

[Function] The polyoxyethylene glycerin fatty acid ester having a unique structure that is added to the electrolytic solution for electrolytic capacitors disclosed in the present invention uses an organic polar solvent as the main solvent and an organic acid or R-free acid or a salt thereof as the solute. How it acts in the electrolyte and its mechanism of action are not clear. However, the electrolyte for electrolytic capacitors according to the present invention is composed of the anode, cathode, aluminum oxide film dielectric, and electrolyte of the electrolytic capacitor. It is presumed that this contributes in some way to stabilizing the chemical steady state of the electrochemical reaction system.

As described above, since an electrolytic capacitor is used while undergoing a chemical reaction, its characteristics largely depend on the properties of the electrolyte. It is important to maintain a steady state of the chemical reaction that occurs between the aluminum electrode, which has an oxide film on its surface, and the electrolyte, and to maintain the aluminum oxide film, which serves as a dielectric, in a good condition to stabilize performance.

In the present invention, by adding a polyoxyethylene glycerin fatty acid ester having a unique structure, the oxide film is protected from hydration deterioration by the surfactant action of the additive, thereby providing good capacitor characteristics.

[Effects of the Invention] According to the present invention, there is provided an electrolytic solution for electrolytic capacitors that maintains the characteristics of electrolytic waves for electrolytic capacitors well, has improved voltage resistance, and has stable characteristics even when used at high temperatures for long periods of time. be done.

[Examples] The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited only to the following Examples.

As shown below, an electrolytic solution for an electrolytic capacitor according to the present invention is prepared by using an organic polar solvent as the main solvent, adding water as necessary, and adding a solute and a polyoxyethylene glycerin fatty acid ester. (Examples 1 to 8) were prepared. Controls (Comparative Examples 1 to 8) having the same composition except that polyoxyethylene glycerin fatty acid ester was not added were also prepared. Each composition is shown in parts by weight in parentheses.

In addition, the polyoxyethylene glycerin fatty acid ester used is represented by A for polyoxyethylene glycerin oleate (n+m, = 40) in the above general formula, and polyoxyethylene glycerin stearate (n
+m=30) is indicated by B, polyoxyethylene glycerin stearate (n±m=10) is indicated by C, and polyoxyethylene glycerin laurate (n+m=60) is indicated by C. is indicated by D.

Hexagonal side 1 and comparative example 1 Solvent: Ethylene glycol (80) Water (7) Methyl cellosolve (20) Solute: Diammonium adipate (20) Adipic acid (3) Polyoxyethylene glycerin In ester: A (3
) (Example 1 only).

Turning 2 and Comparative Example 2 Solvent: Ethylene glycol (100) Water (5) Solute: Ammonium benzoate (15) Polyoxyethylene glycerin In ester: A (2
) (Example 2 only).

Example 3 and Proportion 3 Solvent: Ethylene glycol (100) Water (7) Solute: Ammonium sebacate (17) Polyoxyethylene glycerin In ester: B(
3) (Example 3 only).

Example 4 and Comparative Example 4 Solvent: γ-butyrolactone (60) Methylcellosolve (15) Ethylene glycol (10) 2 Volumes: Phthalmonotetramethylammonium (15) Boric acid (2) Mannitol (2) Polyoxyethylene glycerin In ester: C(4
) (Example 4 only).

Turning 5 and Comparative Example 5 2 Vehicle: γ-butyrolactone (60) Methyl cellosolve (15) Ethylene glycol (10) Solute: Tetraethylammonium benzoate boric acid (2) Mannitol (2) Polyoxyethylene glycerol ! Late Esther :C(
3) (Example 5 only).

Φ Example 6 and Comparative Example 6 Solvent: γ-butyrolactone (60) Ethylene glycol (20) Solute: Monotriethylammonium maleate (20) Boric acid (2) Mannitol (2) Polyoxyethylene glycerin ■ acid ester: D (4
) (Example 6 only).

Turning 7 and Comparative Example 7 (15) Solvent: N,N-dimethylpolamide (60) Ethylene glycol (20) Solute: Maleinyl mohaliethylammonium (20) Polyoxyethylene glycerin fatty acid ester: D (2) (
Example 7 only).

Turning 8 and Ratio j8 Solvent: N,N-dimethylformamide (65) Ethylene glycol (20) Solute: Tetramethylammonium benzoate (15) Polyoxyethylene glycerin fatty acid ester: C (3) (Example 8 only).

Electrical conductivity and voltage of the electrolytic solution The electrical conductivity and withstand voltage at 30°C of the electrolytic solutions of Examples 1 to 8 and Comparative Examples 1 to 8 are shown in Table 1. Although a tendency to decrease was observed, the withstand voltage was significantly improved.

Example 1 Comparative example 1 Example 2 Comparative example 2 Example 3 Comparative example 3 Example 4 Comparative example 4 Example 5 Comparative example 5 Example 6 Comparative example 6 Example 7 Comparative example 7 Example 8 Comparative example 8 4.21 4.95 4.09 4.44 3.98 4.59 7.57 8.62 5.60 6.45 7.05 7.81 11.5 13.3 8.30 8.93 50 50 60 50 20 50 8 5 30 0 30 00 10 5 20 5

Claims (1)

[Claims] (1) In an electrolytic solution for driving an aluminum electrolytic capacitor, an electrolytic solution containing an organic polar solvent as the main solvent and an organic acid or an inorganic acid or a salt thereof as a solute contains the following general formula: ▲ Numerical formula, chemical formula, table, etc. ▼ (In the formula, n and m are the same or different integers of 0 or more, and at least one is an integer of 1 or more, and R
represents a fatty acid residue).