JP2002100540A - Aluminum electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide electrolyte for an aluminum electrolytic capacitor with improved shelf characteristics, the manufacturing method of the electrolyte, and the electrolytic capacitor using the electrolyte. SOLUTION: The electrolyte for electrolytic capacitors contains a combination where a phosphoric acid ion is bonded to a water-soluble complex, so that an appropriate amount of phosphoric acid ions in the electrolyte can be maintained for a long time for inhibiting deterioration in electrode foil after it has been left as it is, thus improving the shelf characteristics of the electrolytic capacitor using the electrolyte.

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, a method for producing the same, and an electrolytic capacitor using the same.

[0002]

2. Description of the Related Art An electrolytic capacitor generally has the following configuration. That is, a high-purity aluminum foil formed in a belt shape is chemically or electrochemically etched to enlarge the surface, and the expanded aluminum foil is subjected to a chemical conversion treatment in a chemical conversion solution such as an ammonium borate aqueous solution. By doing so, a capacitor element is formed by winding, via a separator, an anode foil having an oxide film layer formed on the surface of an aluminum foil and a cathode foil having a high-purity aluminum foil expanded. The capacitor element is impregnated with a driving electrolyte, and is housed in a metal bottomed cylindrical outer case. Further, a sealing body made of elastic rubber is housed at the opening end of the outer case, and the opening end of the outer case is sealed by drawing to form an electrolytic capacitor.

[0003] Conventionally, as an electrolytic solution impregnated in a capacitor element of a small-sized, low-pressure electrolytic capacitor, ethylene glycol as a main solvent, adipic acid,
Known are those in which an ammonium salt such as benzoic acid is used as a solute or those in which γ-butyrolactone is used as a main solvent and a quaternized cyclic amidinium salt such as phthalic acid or maleic acid is used as a solute.

[0004]

However, when such an electrolytic capacitor is left unattended, the capacitance decreases, the leakage current characteristics deteriorate, and the safety valve may open. Such a standing characteristic, which is a characteristic after a long period of time with or without a load, has a great influence on the reliability of the electrolytic capacitor.

[0005] Then, when the electrolytic capacitor deteriorated after being left for a long time was analyzed, it was found that the pH of the electrolytic solution was high and the anion component of the solute was attached to the surface of the electrode foil. From this, aluminum on the surface of the electrode foil reacts with the anion component of the solute and adheres to the electrode foil, and further, the aluminum is dissolved to form a hydroxide and the like, and a part of the aluminum reacts with the anion component of the solute. Generates hydrogen gas. It became clear that this reaction was repeated and the pH increased, leading to deterioration of the electrode foil and valve opening.

It is well known that phosphoric acid is effective in preventing such deterioration of the electrode foil, but it is not sufficient. This is because even if this phosphoric acid is added to the electrolyte, the added phosphoric acid forms a complex with aluminum in the electrolyte and adheres to the electrode foil, and the phosphoric acid disappears from the electrolyte. Things. Further, if the amount is too large, there is a problem that the leakage current increases. However, the characteristics of the electrolytic capacitor are kept good while an appropriate amount of phosphate ions remains at the stage of disappearance. From these facts, it is an object of the present invention to provide an electrolytic solution for an electrolytic capacitor having good standing characteristics, a method for producing the same, and an electrolytic capacitor using the same.

[0007]

An electrolytic capacitor for an electrolytic capacitor according to the present invention is characterized in that a conjugate in which phosphate ions are bound to a water-soluble metal complex is added.

The method for producing an electrolytic solution for an electrolytic capacitor according to the present invention comprises preparing a solution comprising a chelating agent, a compound generating phosphate ions in a solvent, and a metal or a metal compound, and performing a chelating reaction. And a phosphate ion binding reaction is completed to form a conjugate in which a phosphate ion is bonded to a water-soluble metal complex, and then the conjugate is added to an electrolyte solution.

Here, the compound that forms phosphate ions in the solvent is a phosphorus compound represented by the general formula (Chemical Formula 2), a salt thereof, a condensate thereof, or a salt of a condensate thereof. It is characterized by.

An electrolytic capacitor according to the present invention is characterized in that the electrolytic solution for an electrolytic capacitor is used.

In the above electrolytic solution for an electrolytic capacitor, the metal complex is an aluminum complex, and the method for producing the metal complex is characterized in that the metal or the metal compound is aluminum or an aluminum compound.

Embedded image (Wherein R ₁ and R ₂ represent —H, —OH, —R ₃ , —OR
₄ : R ₃ and R ₄ are an alkyl group, an aryl group, a phenyl group, an ether group)

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The electrolytic solution for an electrolytic capacitor of the present invention contains a conjugate in which a phosphate ion is bonded to a water-soluble metal complex. Immediately after this production, the electrolytic solution for an electrolytic capacitor of the present invention has a conjugate in which a phosphate ion is bound to a water-soluble metal complex (hereinafter referred to as a water-soluble conjugate). To release phosphate ions in the electrolytic solution in an appropriate amount for a long period of time. Then, in the electrolytic capacitor using the electrolytic solution for an electrolytic capacitor, the leaving property is improved by the phosphate ion held in the appropriate amount.

The water-soluble conjugate can be obtained by dissolving a chelating agent, a metal or a metal compound and a compound capable of forming phosphate ions in a solvent in a solvent. In this solution, a complex is formed between the chelating agent and the metal ion dissolved in the solvent, and a phosphate ion binds to the complex to form a water-soluble conjugate. Then, the combined body is added to the electrolytic solution to produce the electrolytic solution for an electrolytic capacitor of the present invention. The solvent used here may be any solvent that dissolves a chelating agent, a metal or a metal compound, and a compound that generates phosphate ions in the solvent, and among them, water, ethylene glycol, γ-butyrolactone, and the like are preferable.

The chelating agent used in the present invention includes the following. That is, citric acid, tartaric acid,
Α-hydroxycarboxylic acids such as gluconic acid, malic acid, lactic acid, glycolic acid, α-hydroxybutyric acid, hydroxymalonic acid, α-methylmalic acid, dihydroxytartaric acid, γ-resorcylic acid, β-resorcylic acid, trihydroxybenzoic acid Hydroxyphthalic acid, dihydroxyphthalic acid, phenoltricarboxylic acid, aurintricarboxylic acid, aromatic hydroxycarboxylic acids such as eriochrome cyanine R, sulfocarboxylic acids such as sulfosalicylic acid, hydrolyzable tannins such as tannic acid and condensed tannins. Tannins, guanidines such as dicyandiamide, saccharides such as galactose and glucose, lignins such as lignosulfonate, and ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), glycol ether diaminetetraacetic acid (GEDTA), diethylenetriaminepentaacetic acid (DTPA), hydroxyethylethylenediaminetriacetic acid (HEDTA), aminopolycarboxylic acids such as triethylenetetraminehexaacetic acid (TTHA), and salts thereof. Among these, tannic acid, gluconic acid, DTPA, GEDTA, and TTHA are preferred. And, as these salts, ammonium salts, aluminum salts, sodium salts, potassium salts and the like can be used. Note that two or more of these chelating agents may be used.

As the metal, aluminum, iron, copper, nickel, manganese, zinc, calcium, magnesium,
Metals that form a complex with the chelating agent, such as barium, lead, titanium, niobium, and tantalum, can be used. Further, as the metal compound, oxides, hydroxides, chlorides,
In addition, compounds that generate metal ions in a solvent, such as metal salts such as sulfates and carbonates, can be used.

Then, a compound capable of generating phosphate ions in an aqueous solution (hereinafter referred to as a phosphate-forming compound) is added. Examples of the phosphoric acid-generating compound include a phosphorus compound represented by the general formula (Formula 2), a salt thereof, a condensate thereof, or a salt of a condensate thereof.

The following can be mentioned as these phosphoric acid-generating compounds. Orthophosphoric acid, phosphorous acid,
Hypophosphorous acid, their salts, and ammonium salts, aluminum salts, sodium salts, calcium salts, and potassium salts. Orthophosphoric acid and its salts decompose in aqueous solution to produce phosphate ions. Phosphorous acid, hypophosphorous acid, and salts thereof are decomposed in an aqueous solution to generate phosphite ions and hypophosphite ions, and then oxidized to phosphate ions.

Further, phosphoric compounds such as ethyl phosphate, diethyl phosphate, butyl phosphate and dibutyl phosphate, and phosphonic compounds such as 1-hydroxyethylidene-1,1-diphosphonic acid, aminotrimethylene phosphonic acid and phenylphosphonic acid Acid compounds and the like. In addition, phosphinic acid compounds such as methylphosphinic acid and butyl phosphinate are exemplified.

Furthermore, the following condensed phosphoric acids or salts thereof can be mentioned. It is a linear condensed phosphoric acid such as pyrophosphoric acid, tripolyphosphoric acid, or tetrapolyphosphoric acid, or a cyclic condensed phosphoric acid such as metaphosphoric acid or hexametaphosphoric acid, or a combination of such linear or cyclic condensed phosphoric acids. . And, as salts of these condensed phosphoric acids, ammonium salts, aluminum salts, sodium salts, calcium salts, potassium salts and the like can be used.

These are also phosphoric acid-generating compounds that generate phosphate ions in an aqueous solution, or generate phosphite ions and hypophosphite ions, and then oxidize to phosphate ions.

Of these, orthophosphoric acid or a salt thereof, a condensed phosphoric acid, or a phosphoric acid compound which easily generates a phosphate ion is preferable. Further, orthophosphoric acid which generates a lot of phosphate ions relatively quickly with respect to the amount added,
Linear condensed phosphoric acid such as pyrophosphoric acid and tripolyphosphoric acid,
Or a salt thereof is preferred. In addition, other than these compounds, the effect of the present invention can be obtained as long as the substance generates phosphate ions in an aqueous solution.

The solute contained in the electrolytic solution includes ammonium salts, amine salts, quaternary ammonium salts and cyclic amidine compounds which are usually used in electrolytic solutions for electrolytic capacitors and have an anionic component of a conjugate base of an acid. Grade salts. Primary amines (methylamine, ethylamine, propylamine,
Butylamine, ethylenediamine, etc., secondary amines (dimethylamine, diethylamine, dipropylamine, methylethylamine, diphenylamine, etc.), tertiary amines (trimethylamine, triethylamine, tripropylamine, triphenylamine, 1,8─diazabicyclo (5, 4,0) {undecene} 7 etc.). As the quaternary ammonium constituting the quaternary ammonium salt, tetraalkylammonium (tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, methyltriethylammonium, dimethyldiethylammonium, etc.), pyridium (1-methylpyridium) 1,1-ethylpyridium, 1,3-diethylpyridium, etc.). In addition, examples of the cation constituting the quaternary salt of the cyclic amidine compound include cations obtained by quaternizing the following compounds. That is, the imidazole monocyclic compound (1─
Methylimidazole, 1,2-dimethylimidazole,
Imidazole homologues such as 1,4-dimethyl-2-ethylimidazole, 1-phenylimidazole, oxyalkyl derivatives such as 1-methyl-2-oxymethylimidazole, 1-methyl-2-oxyethylimidazole, 1
-Methyl-4 (5) -nitroimidazole, nitro and amino derivatives such as 1,2-dimethyl-5 (4) -aminoimidazole, etc., benzimidazole (1-methylbenzimidazole, 1-methyl-2-benzylbenzimidazole) Etc.), compounds having a 2-imidazoline ring (1 @ -methylimidazoline, 1,2-dimethylimidazoline, 1,2,4-trimethylimidazoline, 1,4-
Dimethyl-2-ethylimidazoline, 1-methyl-2-
Phenylimidazoline, etc.), compounds having a tetrahydropyrimidine ring (1-methyl-1,4,5,6-tetrahydropyrimidine, 1,2-dimethyl-1,4,5,6)
-Tetrahydropyrimidine, 1,8-diazabicyclo [5.4.0] undecene-7, 1,5-diazabicyclo [4.3.0] nonene-5, and the like.

The anionic components include adipic acid, glutaric acid, succinic acid, benzoic acid, isophthalic acid, phthalic acid, terephthalic acid, maleic acid, toluic acid, enanthic acid, malonic acid, formic acid and 1,6-decanedicarboxylic acid ,
Decanedicarboxylic acid such as 5,6-decanedicarboxylic acid,
Octanedicarboxylic acid such as 1,7-octanedicarboxylic acid, azelaic acid, organic acid such as sebacic acid, or
Examples thereof include boric acid, a polyhydric alcohol complex compound of boric acid obtained from boric acid and a polyhydric alcohol, and conjugate bases of inorganic acids such as phosphoric acid, carbonic acid, and silicic acid. Of these, preferred are decanedicarboxylic acid, octanedicarboxylic acid, azelaic acid, sebacic acid, adipic acid, glutaric acid, succinic acid, benzoic acid, isophthalic acid, organic carboxylic acids such as formic acid, or boric acid, boric acid. It is a polyhydric alcohol complex compound.

As the solvent, a protic polar solvent, an aprotic polar solvent, water, and a mixture thereof can be used. Protic polar solvents include monohydric alcohols (methanol, ethanol, propanol, butanol, hexanol, cyclohexanol,
Cyclopentanol, benzyl alcohol, etc.), polyhydric alcohols and oxy alcohol compounds (ethylene glycol, propylene glycol, glycerin, methyl cellosolve, ethyl cellosolve, 1,3-butanediol, methoxypropylene glycol, etc.). As aprotic polar solvents, amides (N-methylformamide, N, N-dimethylformamide, N
-Ethylformamide, N, N-dimethylformamide, N-methylacetamide, hexamethylphosphoramide, etc.), lactones (γ-butyrolactone, δ-
Valerolactone), cyclic amides (N-methyl-2-
Pyrrolidone, etc.), carbonates (ethylene carbonate, propylene carbonate, etc.), nitriles (acetonitrile, etc.), oxides (dimethylsulfoxide, etc.), 2-imidazolidinone [1,3-dialkyl-
2-imidazolidinone (1,3-dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidinone, 1,3-di (n-propyl) -2-imidazolidinone, etc.), 1 , 3,4-trialkyl-2-imidazolidinone (eg, 1,3,4-trimethyl-2-imidazolidinone)] and the like.

Here, usually, when the solvent of the electrolytic solution for the electrolytic capacitor contains water, the deterioration of the electrode foil becomes remarkable,
Also in this case, since an appropriate amount of phosphate ions is released from the water-soluble conjugate, the standing characteristics of the electrolytic capacitor of the present invention are good. Furthermore, even when a solvent containing water as a main component is used, the storage characteristics do not deteriorate, and by using such a solvent, the specific resistance of the electrolytic solution for the electrolytic capacitor can be reduced. Can be reduced in impedance. Here, the content of water in the solvent is 35 to 100 wt%, preferably 35 to 100 wt%.
65 wt%. When the value is equal to or more than the lower limit, the impedance characteristics are good, and when the value is equal to or less than the upper limit, the low-temperature characteristics are good. In addition, when a solvent containing water as a main component is used, there is no problem such as ignition when the capacitor fails due to nonstandard use such as high voltage use, and the environment resistance is good.

When at least one of adipic acid or a salt thereof is used as a solute, the impedance is further reduced. The content of the adipic acid or salt thereof is 5 to 23 wt% in the electrolytic solution, preferably 8 to 18 w%.
t%. Above this range, the specific resistance decreases, and below this range, the low-temperature characteristics are good. The content of the other solutes is about 5 to 23% by weight, preferably 8 to 18% by weight of the whole electrolyte.

In order to stabilize the life characteristics of the electrolytic capacitor, nitrophenol, nitrobenzoic acid, nitroacetophenone, nitrobenzyl alcohol,
(Nitrophenoxy) ethanol, nitroanisole,
Aromatic nitro compounds such as nitrophenetol, nitrotoluene, dinitrobenzene and the like can be added.

Further, for the purpose of improving the safety of the electrolytic capacitor, a nonionic surfactant, a polyhydric alcohol, ethylene oxide and / or
Alternatively, a polyoxyalkylene polyhydric alcohol ether compound or polyvinyl alcohol obtained by addition polymerization of propylene oxide can also be added.

Further, by adding boric acid, a polysaccharide (such as mannitol, sorbite, pentaerythritol), a complex compound of boric acid and a polysaccharide, and colloidal silica, to the electrolytic solution for an electrolytic capacitor of the present invention. The voltage can be improved.

For the purpose of reducing the leakage current, an oxycarboxylic acid compound or the like can be added.

The electrolytic capacitor containing the electrolytic solution of the present invention has a standing characteristic, that is, a long-term load,
Good characteristics after no-load test.

Hereinafter, the present invention will be described. In the electrolytic solution for an electrolytic capacitor of the present invention, a binder in which phosphate ions are bound to a water-soluble metal complex is added. Can be kept in quantity. That is, the phosphate ions in the electrolyte are reduced by reacting with the aluminum eluted from the electrode foil. With this decrease, the water-soluble conjugate releases phosphate ions, and the phosphate in the electrolyte is reduced. It acts to keep ions in an appropriate amount. The appropriate amount of phosphate ions suppresses dissolution of aluminum and generation of aluminum hydroxide and the like, thereby suppressing deterioration of the electrode foil, thereby improving the leaving characteristics of the electrolytic capacitor.

That is, if only phosphate ions are added to the electrolytic solution, the phosphate ions react with the aluminum and disappear from the electrolytic solution, so that the leaving characteristics deteriorate.
Also, when a large amount is added, the leakage current characteristics are further deteriorated. However, in the electrolytic capacitor of the present invention, an appropriate amount of phosphate ions is present in the electrolytic solution without disappearing even after a long period of time, so that good leaving characteristics can be maintained, and the leakage current characteristics can also be improved. Good without deterioration.

The following experiments have demonstrated these facts. The electrolytic capacitor of the present invention was disassembled, and the electrolytic solution impregnated in the capacitor element was washed and removed. Thereafter, the capacitor element was impregnated with an electrolytic solution containing no phosphate ions to prepare an electrolytic capacitor. The standing characteristics of the electrolytic capacitor were good. Then, phosphate ions were detected from the electrolytic solution of the electrolytic capacitor, and aluminum was hardly detected. That is, the water-soluble conjugate attached to the electrode foil releases phosphate ions into the electrolyte solution containing no phosphate ions, and after that, by keeping a certain amount of phosphate ions appropriately for a long time, the capacitor is left untreated. The characteristics are improved. In addition, even when the above operation was performed several times for the electrolytic capacitor thus produced, phosphate ions were similarly detected from the electrolytic solution, and the leaving characteristics of the electrolytic capacitor were good. In addition, when the aluminum complex is not water-soluble, that is, when the aluminum complex is hardly soluble or insoluble, it is thought that there is no effect of maintaining the phosphate ion in the electrolytic solution in an appropriate amount as in the present invention, but the effect of the present invention is obtained. It is not possible. Although the description has been given of the aluminum electrolytic capacitor, the same applies to other electrolytic capacitors such as a tantalum electrolytic capacitor.

As described above, the water-soluble conjugate used in the present invention has a property of releasing phosphate ions. Here, the number of phosphate ions that can be bonded to the complex varies depending on the coordination number of the chelating agent and the metal, but it is preferable that the phosphate ions be bonded in an appropriate number to obtain desired characteristics. That is, if the phosphate ion bound to the water-soluble conjugate is not appropriate, the number of phosphate ions that can be released during standing decreases,
The desired effect cannot be obtained. Therefore, as in the present invention, a solution of a chelating agent, a phosphoric acid-generating compound and a metal or a metal compound is prepared, and a conjugate in which phosphate ions are bonded to a water-soluble metal complex in the solution is formed. Thus, the chelation reaction and the phosphate ion binding reaction can be completed, and a water-soluble conjugate having an appropriate number of phosphate ions bound thereto can be obtained. Then, the electrolytic solution for an electrolytic capacitor of the present invention can be manufactured by adding this combined substance to the electrolytic solution. On the other hand, even if a chelating agent, a phosphate ion-generating compound, a metal or a metal compound is added to the electrolytic solution, the chelating agent and the phosphate ions generated in the electrolytic solution react with the electrode foil. It is difficult to adjust the number of phosphate ions bonded to the metal complex. Therefore, the phosphate ions in the electrolyte cannot be kept properly for a long time, and the desired leaving characteristics cannot be obtained.

Furthermore, it has been found that when a chelating agent is added to an electrolytic solution to form a water-soluble conjugate in the electrolytic solution, the chelating agent dissolves the electrode foil. However, in the electrolytic solution of the present invention, since the water-soluble binder after the chelation reaction is added, the binder does not dissolve the electrode foil.

Then, it was found that the pH of the electrolytic solution of the present invention did not increase and was maintained at 5 to 7 (measured by diluting it 50 times as an aqueous solution). This is because the dissolution of the electrode foil is suppressed by the phosphate ions held in the electrolytic solution, and therefore, the anion component of the electrolyte is suppressed from reacting with the electrode foil, and the increase in pH is suppressed. I think that the.

[0038]

The present invention will be described in detail below with reference to examples. The capacitor element is formed by winding an anode foil and a cathode foil via a separator. The anode electrode foil is obtained by chemically or electrochemically etching an aluminum foil having a purity of 99.9% in an acidic solution and expanding the surface thereof, and then performing a chemical conversion treatment in an aqueous solution of ammonium adipate. Use an oxide film layer. Purity 99.
9% of aluminum foil was etched and a foil subjected to a surface expansion treatment was used.

In the capacitor element configured as described above,
Impregnate the electrolytic solution for driving the aluminum electrolytic capacitor. The capacitor element impregnated with this electrolytic solution is housed in a cylindrical outer case made of aluminum with a bottom, a butyl rubber sealing body is inserted into the open end of the outer case, and the end of the outer case is drawn. To seal the aluminum electrolytic capacitor.

The electrolyte used here was prepared as follows. First, a chelating agent, a metal compound, and ammonium dihydrogen phosphate shown in (Table 1) were added to 10 parts of water to complete the chelation reaction and the phosphate ion binding reaction, thereby preparing a water-soluble conjugate. Next, the aqueous solution of the water-soluble conjugate was added to the electrolyte shown in (Table 2) consisting of water, ethylene glycol, and ammonium adipate to prepare an electrolyte of the present invention. Further, as Comparative Example 1, an aqueous solution was prepared by adding 0.2 parts of aluminum hydroxide and 1 part of aluminum dihydrogen phosphate to 10 parts of water, and this aqueous solution was added to the electrolytic solution of (Table 1). The composition is shown in parts. The specific resistance is shown in (Table 2). As a conventional example, γ-
An electrolytic solution containing 75 parts of butyrolactone and 25 parts of ethyl dimethyl imidazolinium phthalate was used. Specific resistance is 81Ωc
m.

A high-temperature life test of the aluminum electrolytic capacitor constructed as described above was conducted. The rating of the aluminum electrolytic capacitor is 6.3 WV-5600 μF. The test conditions are
105 ° C., rated voltage load, no load, 1000 hours. Then, the capacitor after the test was disassembled, and the electrode foil was immersed in a buffer solution having a pH of 7 or more, heated to extract phosphate ions, and the concentration was measured. The measurement lower limit of the phosphate ion concentration is 1 ppm. The results are shown in Tables 3 and 4.

[0042]

[Table 1] (Note) TaA: tannic acid [CAS: 1401-55-
4] GluA: gluconic acid DTPA: diethylenetriamine hexaacetic acid AlOH: aluminum hydroxide FeSO: ferric sulfate NiSO: nickel sulfate CaCO: calcium carbonate 2PA: ammonium dihydrogen phosphate

[0043]

[Table 2] (Note) EG: Ethylene glycol AAd: Ammonium adipate

[0044]

[Table 3] (Note) Cap: capacitance (μF), tan δ: tangent of dielectric loss, LC: leakage current (μA), ΔCap: capacitance change rate (%) Phosphoric acid: phosphoric acid concentration (ppm)

[0045]

[Table 4]

As can be seen from Tables 2 to 4 and the characteristics of the conventional example, the specific resistance of the example is 18 to 68 Ωcm.
And much lower than the conventional 81 Ωcm,
nδ is also 0.060 to 0.081, which is 0.101 of the conventional example.
Lower.

As can be seen from (Table 3) and (Table 4), the phosphoric acid concentration of the example after 1000 hours has passed is 4 to 12 ppm under each test condition, and the storage characteristics at 105 ° C. are good. Met.

Further, the content of water in the solvent is 40 to 85%.
In Examples 1, 3, and 5, the phosphoric acid concentration was 4 to 12 p.
pm, and the leaving property is also good. Examples 2 to 4 in which the content of ammonium adipate is 10 to 18 parts
Has a phosphoric acid concentration of 5 to 8 ppm and good standing characteristics.

On the other hand, Comparative Examples 2 and 3, in which only diammonium hydrogen phosphate was added, respectively,
Although 50 ppm and 10000 ppm of diammonium hydrogen phosphate were added, the valve was opened, and no phosphate group was detected from the electrolyte at the time of opening the valve. This indicates that the phosphate ions in the electrolyte have disappeared. The initial leakage current of Comparative Example 3 in which 1.2 parts of diammonium hydrogen phosphate was added was high.

Further, in Comparative Example 1 in which an aqueous solution obtained by reacting aluminum hydroxide with diammonium hydrogen phosphate was added, the valve was opened. Is not detected, indicating the effect of the water-soluble conjugate of the present invention.

When the film voltage of the electrode foil was measured for an electrolytic capacitor obtained by adding only the chelating agent to the electrolytic solution, the film voltage was found to be low. This indicates that the oxide film of the electrode foil was dissolved by the chelating agent. On the other hand, in the example, such a decrease in the film voltage is not observed. Furthermore, the initial leakage current is good. From these results, it can be seen that the aqueous solution of the water-soluble conjugate prepared in advance does not contain a chelating agent and excess phosphoric acid, and the chelation reaction and the binding reaction of phosphate ions are completed.

[0052]

As described above, in the present invention, since a conjugate in which a phosphate ion is bonded to a water-soluble metal complex is added to the electrolytic solution for an electrolytic capacitor, the phosphate ion in the electrolytic solution is reduced. Can be kept in the proper amount for a long time,
By suppressing the deterioration of the electrode foil after standing, it is possible to provide an electrolytic solution for electrolytic capacitors having good standing characteristics, a method for producing the same, and an electrolytic capacitor using the same.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hisatomi Ito 1-167, Higashi-Ome, Ome-shi, Tokyo Nippon Chemi-Con Corporation (72) Inventor Tatsuki Tsuji 1-167, Higashi-Ome 1-chome, Ome-shi, Tokyo Nippon Chemi-Con Inside the corporation

Claims (6)

[Claims] 1. An electrolytic solution for an electrolytic capacitor in which a conjugate in which a phosphate ion is bonded to a water-soluble metal complex is added. 2. A solution comprising a chelating agent, a compound that forms phosphate ions in a solvent, and a metal or a metal compound is prepared, and the chelation reaction and the phosphate ion binding reaction are completed to form a solution. A method for producing an electrolytic solution for an electrolytic capacitor, comprising: forming a conjugate in which phosphate ions are bonded to a metal complex of (1), and adding the conjugate to the electrolytic solution. 3. The compound which forms phosphate ions in the solvent is a phosphorus compound represented by the general formula (1), a salt thereof, a condensate thereof, or a salt of a condensate thereof. 3. The method for producing an electrolytic solution for an electrolytic capacitor according to 2. 4. An electrolytic capacitor using the electrolytic solution for an electrolytic capacitor according to claim 1. 5. The electrolytic solution for an electrolytic capacitor according to claim 1, wherein the metal complex is an aluminum complex. 6. The method for producing an electrolytic solution for an electrolytic capacitor according to claim 2, wherein the metal or the metal compound is aluminum or an aluminum compound. Embedded image (Wherein R ₁ and R ₂ represent —H, —OH, —R ₃ , —OR
₄ : R ₃ and R ₄ are an alkyl group, an aryl group, a phenyl group, an ether group)