JPH03120808A - 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 polyglycerol fatty ester having a specified general formula 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, polyglycerol 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, R1-R5 are identical or different hydrogen atom or fatty acid residue, at least one of them is fatty acid residue, and (n) is an integer larger than or equal to 1. 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 2 pts.wt. of polyglycerol oleate (n=8, R=2) 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 cellosolve.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to improvement of an electrolytic solution for electrolytic capacitors, and more specifically, to provide an electrolytic capacitor with improved voltage resistance 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 that has been oxidized to an oxide film as an anode, and using this oxide film as a dielectric with an electrolyte interposed between it and a current collecting 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 a chemical reaction is occurring, their characteristics depend largely on the properties of the electrolyte. It is important to properly maintain the aluminum oxide film used as a dielectric for stable performance.If the chemical steady state is disturbed due to incorrect usage, for example due to excessive high voltage load, the aluminum oxide film This will eventually lead to the insulation breaking.

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, f1
The voltage can be conveniently measured by immersing an appropriately sized unformed aluminum foil 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 maintained high to avoid physical and chemical changes in the dielectric material during use. The loss angle tangent, or dielectric loss tangent, which is the difference between the phase of the charging current and the phase of the external electric field, is used as a guideline for the power consumption of a capacitor, and a small value indicates low power consumption; it remains constant after charging starts. Leakage current, which is the current that flows when a value is reached, is due to the steady movement of charge carriers in the dielectric.
It is thought that charge carriers mainly consist of ions generated by the resolution of impurities in the dielectric, 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); However, it was not always 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 organic polar solvent is used as a main solvent, an organic acid,
In an electrolytic solution containing an inorganic acid or a salt thereof as a solute, the following general formula: In formula 0, which provides an electrolytic solution for an electrolytic capacitor characterized by adding a polyglycerin fatty acid ester having a polyglycerol fatty acid ester having a polyglycerol fatty acid ester (n is an integer of 1 or more), b is preferably about 1 to 8.

As specific examples of the fatty acid moiety of the polyglycerin fatty acid ester of the present invention, the following fatty acids can be exemplified: As undecylic acid (n=9),
Lauric acid (n=10), tridecylic acid (n=11),
myristic acid (n=12>, pentadecyl acid (n,=1
3), palmitic acid (n=14), heptadecylic acid (n
= 15), stearin im (n = 16), nonadecanoic acid (rho 17), arachidic acid (n = 18>, behenic acid (n
= 20), lignoceric acid < n = 22), cerotic acid <
Saturated fatty acids such as n=24), heptacanoic acid (n=25), montanic acid (n=27), melisic acid (n=28), and lafcelic acid (n=30), undecyl acid CHz "CH(CH2)a C00H oleic acid C1□H,3COOH (CiS) <9> Elaidic acid CI7833COOH (trans) <9
> Cetoleic acid C21H41COOH <11> Erucic acid C21H41COOH (CiS) <13> Brassidic acid C21H41COOH (jrans) <13> Linoleic acid C,7H,, COOH <9.12> Rirunic acid Cl7829COOH <9.12.15> Arachidonic acid C19H31COOH<5. 8. 11. 14>Stearolic acid Cl7831COOH<3 type packing, 9> (However, <>
The inside indicates the position of the unsaturated bond) Unsaturated fatty acids in the cap.

Specific examples of solvents that can be used alone or in combination as the organic or polar solvent of the electrolytic solution include the following: Protic polar/silane solvent ethanol, propatool, butanol, pentanol, hexanol. , cyclobutanol, cyclopentanol, cyclohexanol, and monohydric alcohols such as benzyl alcohol, ethylene glycol, propylene glycol, glycerin, methoxyethanol, ethoxyethanol, methoxypropylene glycol, dimethoxypropanol, methyl cellosolve, and ethyl cellosolve. Polyhydric alcohols and alcohol ethers such as toproton, polar solvent tomethylformamide,! (, N-dimethylformamide, tomethylformamide, N,N-diethylformamide, tomethylacetamide, N,N-dimethylacetamide
~Amide solvents such as amide, toethylacetamide, N,N-diethylacetamide, and hexamethylphosphoric amide, γ-butyrolactone, N-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, imbutylene carbonate, etc. Lactones, cyclic amide solvents, nitrile solvents such as acetonitrile, oxide solvents such as dimethyl sulfoxide.

Specific examples of electrolytes that can be used alone or in combination in the electrolyte of the electrolytic solution, which is an ammonium salt of an organic acid or an inorganic acid, include the following electrolytes: 1. Formic acid, acetic acid, propionic acid, enanthic acid. Aliphatic monocarboxylic acids such as malonic acid, succinic acid, glutaric 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, I-ruylic acid, aromatic carbonic acids such as pyromellitic acid, 1st base boric acid, phosphoric acid, silicic acid, HBF, HPF6, etc.! ! Ii organic acid, ammonium ammonium (NH,), monoalkylammonium such as methylammonium, ethylammonium, and propylammonium, dialkylammonium such as dimethylammonium, diethylammonium, ethylmethylammonium, and dibutylammonium, trimethylammonium, triethylammonium, Additionally, trialkylammoniums such as tributylammonium, tetramethylammonium, triethylmethylammonium, tributylammonium, tetraethylammonium, quaternary ammoniums such as N,N-dimethylpyrrolidinium, and 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 may be mixed. It is preferable that 1 to 30 parts by weight of an organic acid, an inorganic acid, or a salt thereof to be used as a solute be dissolved in such a solvent system.

Preferably, the above-mentioned polyglycerin fatty acid ester is added to an electrolytic solution consisting of such a solute-solvent system in an amount of 0.1 to
By adding 20 parts by weight, more preferably 0.5 to 5 parts 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 polyglycerol fatty acid ester having a unique wI structure, which is added to the electrolytic solution for electrolytic capacitors disclosed by the present invention,
The main solvent is an organic polar solvent including a protic polar solvent,
The mechanism of action is not clear as to how it acts in an electrolytic solution containing an ammonium salt of an organic or inorganic acid as a solute. However, the electrolytic solution for electrolytic capacitors according to the present invention can It is presumed that this contributes in some way to stabilizing the chemical steady state of the electrochemical reaction system consisting of the cathode, aluminum oxide film dielectric, and electrolyte.

As mentioned above, since electrolytic capacitors are used while undergoing chemical reactions, their characteristics largely depend on the properties of the electrolyte. Maintaining a steady state and maintaining the aluminum oxide film used as the dielectric well is important for stabilizing performance.

In the present invention, by adding a polyglycerol 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] 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. 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.

・1 Mataoka Gotan 1 As shown below, an organic polar solvent containing a protic polar solvent is used as the main solvent, water is added as necessary, and a solute and a polyglycerin fatty acid ester are added to produce the inventive solution according to the present invention. Electrolytic solutions for electrolytic capacitors (Examples 1 to 8) were prepared. Controls (Comparative Examples 1 to 8) having the same composition except that no polyglycerin fatty acid ester was added were also prepared. Each composition is shown in parts by weight in parentheses.

The polyglycerin fatty acid ester used was polyglycerin oleate (n=8.R
= 2) is indicated by A, polyglycerol oleate (n = 6, R = 3) is indicated by B, and polyglycerin stearate (n = 8. R = 5) is indicated by A. C, and polyglycerin palmitate (n=5.R=3
) is indicated by D, where R represents the number of moles of fatty acid ester added per mole of polyglycerol fatty acid ester.

'Example 1 and above A example 1 solvent: Ethylene glycol (80) water (7) Methyl cell solve <20) Solute: Diammonium adipate (20) Adipic acid (3) Polyglycerin fatty acid ester: A(2) (Example 1 only).

G'' (Example 12 and Comparative Example 2 solvent: Ethylene glycol (100) water (5) Solute: Yasu, Tada, ammonium fragrant (15) Polyglycerin fatty acid ester: A(2) (Example 2 only).

1cm3 and above comparative example 3 Molten a: Ethylene glycol (100) water (7) Solute: Ammonium sebacate (17) Polyglycerin fatty acid ester: B(3) (Example 3 only).

Example 4 and comparison r? 14 Solvent: γ-butyrolactone (60) Methyl cellosolve (15) Ethylene glycol (10) Solute: Monotetramethylammonium phthalate (15) Boric acid (2) Mannitol (2) Polyglycerin fatty acid ester: C (3) (Example 4 only).

Φ side 5 and upper example 5 solvent; γ-butyrolactone <60) Methyl cell solve (15) Ethylene glycol (10) Solute: Tetraethylammonium benzoate Boric acid 2) Mannit (2) Polyglycerin fatty acid ester: D(3) (Example 5 only).

h Example 6 and Comparative Example 6 Solvent: γ-butyrolactone (60) Ethylene glycol (20) Solute: Mohariethylammonium maleate (20) Boron a
(2) Mannitol (2) Polyglycerin fatty acid ester: D(4) (Example 6 only).

Example 7 and above Example 7 Solvent: N,N-dimethylformamide (60) Ethylene glycol (20) (15) Solute: Maleic shark mohaliethylammonium (20) Polyglycerol fatty acid ester: C (3) (Example 7 only) ).

mm8 and 1 Example 8 Solvent a: N,N-dimethylformamide (65) Ethylene glycol (20) Solute: Tetramethylammonium benzoate (15) Polyglycerin fatty acid ester: D (3) (Example 8 only).

Table 1 shows the electrical conductivity and withstand voltage at 30°C of the electrolytes of Examples 1 to 8 and Comparative Examples 1 to 8. Although a trend was observed, the withstand voltage did not improve significantly.

Table 1 ! AJ” (n+s, 4-mark upper salmon 3J mini-hito! Work 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 4.39 4.95 4.23 4.44 3.95 4.59 8.09 8.62 5.59 6.45 7.29 7.81 11.0 13.3 8.25 8.93 50 50 80 50 4゛80 50 00 5 35 0 25 00 10 5 30 5

Claims (1)

[Claims] (1) In the electrolytic solution for driving an aluminum electrolytic capacitor, the electrolytic solution has an organic polar solvent as the main solvent and an organic acid, inorganic acid, or its salt as the solute, and contains the following general formula: ▲ Numerical formula, chemical formula, table, etc. ▼ (In the formula, R_1 to R_5 are the same or different hydrogen atoms or fatty acid residues, at least one of them is a fatty acid residue, and n is an integer of 1 or more) An electrolytic solution for electrolytic capacitors characterized by the addition of ester.