JP2945697B2 - Electrolyte for electrolytic capacitors - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in an electrolytic solution for an electrolytic capacitor, and more specifically, to an electrolytic capacitor having improved withstand voltage by adding a specific additive. The present invention relates to an improvement in an electrolytic solution for an electrolytic capacitor which can be performed.

[Prior Art] Electrolytic capacitors are small, large-capacity, inexpensive and have excellent characteristics such as smoothing of rectified output, and are one of the important components of various electric and electronic devices. An aluminum film converted into an oxide film by oxidation is used as an anode, and this oxide film is used as a dielectric material and an electrolytic solution is interposed between the current collector and the collector. During use, the oxide film is constantly regenerated, so that the oxide film is stable.

Since the electrolytic capacitor is used while performing a chemical reaction, its characteristics greatly depend on the properties of the electrolytic solution. It is important to maintain the steady state of the chemical reaction between the aluminum electrode with the oxide film on the surface and the electrolytic solution and the aluminum oxide film as the dielectric to stabilize the performance. If the chemical steady state is disturbed by, for example, an excessively high voltage load or the like by mistake in the method, the aluminum oxide film is destroyed, and eventually the insulation is broken.

A phenomenon in which the electrochemical state fluctuates as a result of a change in the physical properties of a dielectric material due to an increase in the load voltage of a capacitor and a high voltage load resulting in a temporal change in dielectric constant is called scintillation. Can be used as a scintillation voltage (withstand voltage) as a measure of the withstand voltage of the capacitor, and the scintillation voltage (withstand voltage)
The higher the value, the higher the withstand voltage of the capacitor. The withstand voltage can be simply measured without assembling a final capacitor product in a state where an unformed aluminum foil of an appropriate size is immersed in the electrolytic solution to be measured.

In the conventional general electrolytic solution for electrolytic capacitors,
An acid such as boric acid or a salt thereof is added to the electrolyte as a main solute in order to obtain a high withstand voltage. Attempts have also been made to improve the electrolytic solution for electrolytic capacitors to obtain high withstand voltage by adding various additives other than these.

Examples of additives for obtaining high withstand voltage include addition of sulfamic acid (JP-A-49-82963), addition of suberic acid (JP-A-49-133860), and addition of dodecyl phosphate (JP-A-49-133860). JP-A-49-7365), addition of alkyl phosphoric acid (JP-A-52-153154), addition of diphosphorous acid (JP-A-57-1419).
No. 13), the use of a boric acid-mannitol-polyvinyl alcohol system (JP-A-59-177915) has been proposed.
It was not always possible to sufficiently improve the withstand voltage while maintaining high conductivity.

[Problems to be Solved by the Invention] It is an object of the present invention to provide an electrolytic solution for an electrolytic capacitor which has improved withstand voltage while maintaining good characteristics of the electrolytic solution for an electrolytic capacitor and provides stable characteristics. I do.

[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, and an organic acid or an inorganic acid or a salt thereof is used as a solute.
The following general formula: However, [Where l, n, p are integers whose sum is 1 or more, and m, o, q are 0
And poly and co are copolymers having an arbitrary sequence, and X ₁ , X ₂ , and X ₃ are the same or different hydro groups (—H), higher hydrocarbyl groups (—R), and higher hydrocarbyl groups. Which represents a royl group (O = R-)]. An electrolytic solution for an electrolytic capacitor is provided.

In the formula, l, n, p are preferably about 1 to 100, and m, o, q are 0
It is preferable that the sum of l, m, n, o, p, and q is not more than 100.

Tri polypropylene glycol of the present invention (polyethylene glycol) phosphate ester as X ₁ to X ₃ parts of (tri - polypropylene glycol - - polyethylene glycol phosphate esters), for example, can be exemplified the following compounds.

Unsaturated acid (n = 9), lauric acid (n = 10), tridecylic acid (n = 11), and myristin as saturated fatty acids having the general formula CH ₃ (CH ₂ ) _n COOH (n is an integer of 9 or more) Acid (n = 12), pentadecylic acid (n = 13), palmitic acid (n = 14), heptadecylic acid (n = 15), stearic acid (n = 16), nonadecanoic acid (n = 17), arachiic acid ( n = 18), behenic acid (n = 20), lignoceric acid (n = 22), serotinic acid (n = 24), heptacosanoic acid (n = 25), montanic acid (n = 27), melicic acid (n = 28), saturated fatty acids such as lacceric acid (n = 30).

Unsaturated fatty acid undecylenic acid CH ₂ CHCH (CH ₂ ) ₈ COOH oleic acid C ₁₇ H ₃₃ COOH (cis) <9> elaidic acid C ₁₇ H ₃₃ COOH (trans) <9> Cetreic acid C ₂₁ H ₄₁ COOH <11 > Erucic acid C ₂₁ H ₄₁ COOH (cis) <13> Brassic acid C ₂₁ H ₄₁ COOH (trans) <13> Linoleic acid C ₁₇ H ₃₁ COOH <9,12> Linolenic acid C ₁₇ H ₂₉ COOH <9,12 , 15> Arachidonic acid C ₁₉ H ₃₁ COOH <5,8,11,14> Stearolic acid C ₁₇ H ₃₁ COOH <triple bond, 9> (However, <> indicates the position of unsaturated bond) etc. Unsaturated fatty acids.

Higher alcohols hexyl alcohol, heptyl alcohol, octyl alcohol, caprylic alcohol, nonyl alcohol,
Decyl alcohol, undecyl alcohol, lauryl alcohol, tridecyl alcohol, myristyl alcohol, pentadecyl alcohol, cetyl alcohol, heptadecyl alcohol, stearyl alcohol, nonadecyl alcohol, eicosyl alcohol, seryl alcohol, merisyl alcohol, oleyl alcohol, and Higher alcohols such as phytol. The higher alcohol is a general term for alcohols having 6 or more carbon atoms.

Specific examples of the solvent that can be used alone or in combination with the organic polar solvent of the electrolytic solution include the following solvents: Protic polar solvent: ethanol, propanol, butanol, pentanol, hexanol, cyclobutanol, cyclobutane Pentanol, cyclohexanol, and monohydric alcohols such as benzyl alcohol, ethylene glycol, propylene glycol, glycerin, methoxyethanol, ethoxyethanol, methoxypropylene glycol, dimethoxypropanol,
Polyhydric alcohols and alcohol ethers such as methyl cellosolve and ethyl cellosolve.

Aprotic polar solvent N-methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N-diethylformamide, N-methylacetamide, N, N-dimethylacetamide, N-ethylacetamide, N, N- Amide solvents such as diethylacetamide and hexamethylphosphoric amide, γ-butyrolactone, N-methyl-2-pyrrolidone,
Lactones such as ethylene carbonate, propylene carbonate and isobutylene carbonate; cyclic amide solvents; nitrile solvents such as acetonitrile; and oxide solvents such as dimethyl sulfoxide.

Specific examples of electrolytes that can be used alone or in combination with the electrolytes of the organic or inorganic acids or salts thereof include the following electrolytes: organic acids formic acid, acetic acid, propionic acid, enanthic acid, etc. Of aliphatic monocarboxylic acids, malonic acid, succinic acid, glutaric acid, adipic acid, methylmalonic acid, pimelic acid, suberic acid, azelaic acid,
Aliphatic dicarboxylic acids such as sebacic acid, decanedicarboxylic acid, maleic acid, citraconic acid, and itaconic acid; aromatic carboxylic acids such as benzoic acid, phthalic acid, salicylic acid, toluic acid, and pyromellitic acid; inorganic acids boric acid; and phosphorus acid, silicic acid, HBF _4, inorganic acids, ammonium ammonium such as HPF ₆ (NH ₄ ^+), methylammonium, ethylammonium, and mono-alkyl ammonium, such as propyl ammonium, dimethyl ammonium, diethyl ammonium, methyl ammonium, and dibutyl Dialkyl ammonium such as ammonium, trimethyl ammonium, triethyl ammonium,
Also, quaternary ammoniums such as trialkylammonium such as tributylammonium, tetramethylammonium, triethylmethylammonium, tributylammonium, tetraethylammonium and N, N-dimethylpyrrolidinium, and other phosphoniums and arsoniums can be used.

Organic polar solvent of the electrolytic solution for an electrolytic capacitor according to the present invention, the protic polar solvent or the aprotic polar solvent alone, or 100 parts by weight of an arbitrary mixed solvent, as required, about 0.1 to 30 parts by weight. By mixing the water, the electric conductivity can be reduced and the chemical conversion (oxide film forming property) can be improved. For such a solvent system, an organic or inorganic acid or a salt thereof as a solute is added.
It is preferable to dissolve 0.5 to 40 parts by weight.

Preferably 0.1 to 20 parts by weight of the above-mentioned tripolypropylene glycol (polyethylene glycol) phosphate with respect to the electrolyte comprising such a solute-solvent system,
More preferably, by adding 0.5 to 5 parts by weight, it is possible to provide an electrolytic solution for an electrolytic capacitor which can realize high withstand voltage while maintaining good capacitor characteristics.

[Action] Tripolypropylene glycol (polyethylene glycol) phosphate having a unique structure to be added to the electrolytic solution for an electrolytic capacitor disclosed in the present invention comprises an organic polar solvent containing a protic polar solvent as a main solvent, and an organic acid or The action mechanism itself is not clear what action it takes in an electrolytic solution containing an inorganic acid or a salt thereof as a solute. However, the electrolytic solution for an electrolytic capacitor according to the present invention has some contribution to stabilization of a chemical steady state of an electrochemical reaction system composed of an anode, a cathode, an aluminum oxide film dielectric and an electrolytic solution of an electrolytic capacitor. It is estimated that there is.

As described above, since the electrolytic capacitor is used while performing a chemical reaction, its characteristics greatly depend on the properties of the electrolytic solution. It is important for the stabilization of the performance to maintain the steady state of the chemical reaction occurring between the aluminum electrode having the oxide film on the surface and the electrolyte and the aluminum oxide film serving as the dielectric in good condition.

According to the present invention, a tripolypropylene glycol (polyethylene glycol) phosphate having a unique structure is added, whereby an oxide film is protected from hydration deterioration by the surface active action of the additive, and good capacitor characteristics are provided. It is estimated to be.

[Effects of the Invention] According to the present invention, there is provided an electrolytic solution for an electrolytic capacitor which has improved withstand voltage while maintaining good characteristics of the electrolytic solution for an electrolytic capacitor and provides stable characteristics.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples.
The present invention is not limited only to the following examples.

Composition of electrolytic solution As shown below, an organic polar solvent including a protic polar solvent is used as a main solvent, water is added as necessary, and a solute and tripolypropylene glycol (polyethylene glycol) phosphate are added. An electrolytic solution for an electrolytic capacitor according to the present invention (Examples 1 to 8) was prepared. Controls (Comparative Examples 1 to 8) each having the same composition except that triphosphate glycol (polyethylene glycol) phosphate (phosphate triester) was not added.
Was also prepared. Each composition is given in parts by weight in parentheses.

In addition, the tripolypropylene glycol (polyethylene glycol) phosphate used in the above-mentioned general formula has R ₁ , R ₂ , and R ₃ of the following structure, which are represented by symbols A, B, C, and D, respectively. .

What is indicated by the symbol A However, -C ₁₈ H ₃₅ is an oleyl group, and l ₁ + l ₂ + l ₃ = 20.

What is indicated by symbol B However, this is an ethylene oxide, propylene oxide block polymer, and l ₁ + l ₂ + l ₃ = 10, m ₁ + m ₂ + m ₃ = 20, Represents an oleic acid group.

Indicated by symbol C Here, R ₁ and R ₂ are random copolymers of propylene oxide and ethylene oxide, where l ₁ + l ₂ = 20 and m ₁ + m ₂ = 10.

What is indicated by the symbol D However, this is an ethylene oxide, propylene oxide block polymer, and l ₁ + l ₂ = 10, m ₁ + m ₂ = 20, Is a palmitic acid group.

Example 1 and Comparative Example 1 Solvent: Ethylene glycol (80) Water (7) Methylcellosolve (20) Solute: Diammonium adipate (20) Adipic acid (3) Triester phosphate: A (3) (Example) 1 only).

Example 2 and Comparative Example 2 Solvent: Ethylene glycol (100) Water (5) Solute: Ammonium benzoate (15) Triester phosphate: A (2) (Example 2 only).

Example 3 and Comparative Example 3 Solvent: Ethylene glycol (100) Water (7) Solute: Diammonium sebacate (17) Triester phosphate: B (4) (Example 3 only).

Example 4 and Comparative Example 4 Solvent: γ-butyrolactone (60) Methylcellosolve (15) Ethylene glycol (10) Solute: Monotetramethylammonium phthalate (15) Boric acid (2) Mannit (2) Triphosphate Ester: B (3) (Example 4 only).

Example 5 and Comparative Example 5 Solvent: γ-butyrolactone (60) Methylcellosolve (15) Ethylene glycol (10) Solute: Tetraethylammonium benzoate (15) Boric acid (2) Mannit (2) Triester phosphate: C (3) (Example 5 only).

Example 6 and Comparative Example 6 Solvent: γ-butyrolactone (60) Ethylene glycol (20) Solute: Monotriethylammonium maleate (20) Boric acid (2) Mannit (2) Phosphate triester: C (3) ( (Example 6 only).

Example 7 and Comparative Example 7 Solvent: N, N-dimethylformamide (60) Ethylene glycol (20) Solute: Monotriethylammonium maleate (20) Phosphate triester: D (4) (Example 7 only).

Example 8 and Comparative Example 8 Solvent: N, N-dimethylformamide (65) Ethylene glycol (20) Solute: Tetramethylammonium benzoate (15) Phosphoric triester: D (4) (Example 8 only).

Conductivity and Withstand Voltage of Electrolyte Solution The conductivity and withstand voltage at 30 ° C. of the electrolyte solutions of Examples 1 to 8 and Comparative Examples 1 to 8 are shown in Table 1. Although the electrical conductivity tended to slightly decrease with the addition of the phosphoric acid triester, the withstand voltage was significantly improved.

Table 1 Conductivity (ms / cm) Withstand voltage (V) Example 1 4.20 230 Comparative example 1 4.95 150 Example 2 4.10 320 Comparative example 2 4.44 250 Example 3 3.75 425 Comparative example 3 4.59 350 Example 4 4.85 95 Comparative Example 4 8.62 85 Example 5 5.74 110 Comparative Example 5 6.45 90 Example 6 7.53 120 Comparative Example 6 7.81 100 Example 7 9.6 100 Comparative Example 7 13.3 75 Example 8 8.01 115 Comparative Example 8 8.93 75

Claims (1)

(57) [Claims] 1. An electrolytic solution for driving an aluminum electrolytic capacitor in which an organic polar solvent is used as a main solvent and an organic acid or an inorganic acid or a salt thereof is used as a solute. However, [Where l, n, p are integers whose sum is 1 or more, and m, o, q are 0
And poly and co each represent a copolymer having an arbitrary sequence, and X ₁ , X ₂ , and X ₃ each represent the same or different hydro group (—H), higher hydrocarbyl group (—R), or higher hydrocarbyl. Which represents a royl group (O = R-)]. An electrolytic solution for electrolytic capacitors, comprising: