JPH08302014A - Production of electroconductive aniline polymer and production of solid electrolytic condenser - Google Patents

Abstract

PURPOSE: To provide a production process for an aniline electroconductive polymer of high conductivity and high reliability and a production process for a solid electrolytic condenser of excellent high-frequency characteristics and high reliability. CONSTITUTION: In this production process for an aniline electroconductive polymer, aniline or its derivative is subjected to oxidative polymerization in a solution containing a sulfonic acid derivative, an oxidizing agent which produces a strong-acid anion in the oxidation reaction, an amine salt with an acid dissociation constant of >=4.6 (preferably amine sulfonate). This process is also applicable to the production of a solid electrolytic condenser comprising a film layer-forming metal as an anode, an oxidizable film layer formed on the metal layer as a dielectric substance and a layer of a solid electrolyte formed thereon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an aniline type conductive polymer comprising a highly reliable polymerization product of polyaniline or an aniline derivative, and a method for producing a solid electrolytic capacitor using the same as a solid electrolyte.

[0002]

2. Description of the Related Art Polyaniline or a derivative thereof is a conductive polymer that exhibits high conductivity when a protonic acid is used as a dopant, and is known to exhibit higher stability in the atmosphere than polypyrrole, polythiophene and the like. ing. Further, since polyaniline and its derivatives have excellent electric characteristics, they may be widely used industrially, and many research reports have been made. Of which
Application research of electrolytic capacitors to solid electrolytes has been particularly vigorously carried out.By using highly conductive and highly reliable polyaniline or its derivatives as the solid electrolyte of solid electrolytic capacitors, small size, large capacity and high frequency range are achieved. It is known that a solid electrolytic capacitor that can maintain good capacitor characteristics and that has excellent heat resistance can be realized.

It is known that various inorganic acids (hydrochloric acid, sulfuric acid, etc.) and organic acids (carboxylic acid, sulfonic acid, organic phosphoric acid, etc.) are used as a protonic acid which is a dopant for expressing conductivity. Among them, the sulfonic acid derivative is particularly preferable, and the use of an oxidizing agent that does not generate a strong acid anion in the process of oxidizing aniline, such as dichromate or hydrogen peroxide, is particularly preferable. It is disclosed in JP-A-6-234852 that it is possible to obtain a conductive and highly heat-resistant polyaniline or a derivative thereof. However, since dichromate contains chromium ion which is a heavy metal, it is not preferable from the viewpoint of environmental protection. Further, the conductivity of polyaniline using hydrogen peroxide as an oxidant is insufficient.

On the other hand, peroxodisulfate, iodate, etc. are also useful oxidizing agents for the synthesis of high molecular weight polyaniline and are widely used (Pron et al.
F. Genoud, C.I. Menardo, and M.M.
Nechtschein), Synthetic Metals, 1988,
24, 193-201). However, while oxidants such as peroxodisulfate and iodate are useful for synthesizing high molecular weight polyaniline, when oxidizing aniline, strong acid anions are generated from these oxidants. Has been shown to serve as a dopant for polyaniline and reduce the heat resistance of the conductivity of the obtained polyaniline.

Nevertheless, US Patent Publication No. 55
23002 and the like include ammonium disulfate as an oxidizing agent,
A method for manufacturing an electrolytic capacitor is disclosed, in which sulfuric acid is used as a protonic acid to form an electrolyte polyaniline of a solid electrolytic capacitor.

On the other hand, we use a highly reliable polyaniline having a sulfonic acid derivative (mono- and disulfonic acid derivative, etc.) as a dopant, and a capacitor using it as a solid electrolyte, using an oxidizing agent that does not generate a strong acid anion such as sulfuric acid. A manufacturing method has been developed (Japanese Patent Application Laid-Open No. 6-234852, Japanese Patent Application No. 6-192353).

[0007]

Since the conventional manufacturing method uses a strong acid such as sulfuric acid as a dopant, the thermal stability of polyaniline is insufficient, and it is necessary for moisture resistance and mounting of a capacitor on a printed circuit board. Solder heat resistance (2
There is also a problem that the heat stability at 30 to 260 ° C.) is insufficient.

An object of the present invention is to use a polyaniline having high conductivity and high heat resistance, using an oxidizing agent such as peroxodisulfate or iodate which produces a strong acid anion when oxidizing. Another object of the present invention is to provide a method for producing an aniline-based conductive polymer made of a derivative thereof, and a method for producing an electrolytic capacitor using these as a solid electrolyte.

[0009]

The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems, and as a result, by adding a specific amine salt to a polymerization solution of aniline or a derivative thereof, a strong acid generated from an oxidizing agent. It was found that the amount of anions can be reduced, and even if an oxidizing agent such as disulfate or iodate is used, polyaniline or a derivative thereof having a high molecular weight and high conductivity and high reliability can be obtained. The present invention has been completed. Further, by applying the above method to a method for forming a solid electrolyte of an electrolytic capacitor, a high performance (heat resistance, moisture resistance) solid electrolytic capacitor was successfully obtained.

That is, the present invention provides aniline or an aniline derivative in a solution containing a sulfonic acid derivative, an oxidizing agent, and a salt of an amine having an acid dissociation index of 4.6 or more, preferably an amine salt of sulfonic acid. A method for producing an aniline-based conductive polymer, which comprises oxidative polymerization. Here, the acid dissociation index is the logarithm of the reciprocal of the acid dissociation constant (pKa).
Represents

The present invention also provides a solid electrolytic device comprising a film-forming metal as an anode, an oxide film formed thereon as a dielectric, and a solid electrolyte mainly composed of an aniline-based conductive polymer formed thereon. A method of manufacturing a capacitor, comprising:
A film-forming metal, an amine salt having an acid dissociation index of 4.6 or more,
A method for producing a solid electrolytic capacitor, comprising a step of immersing in a solution containing an oxidizing agent, aniline or an aniline derivative, and a sulfonic acid derivative.

In the present invention, the amine salt, the sulfonic acid derivative and the oxidizing agent are not particularly limited, but the amine salt is various ammonium salts, aliphatic amine salts such as methylamine and ethylamine, or aromatic amine salts such as aniline. Is. Of these, amine sulfonates are particularly preferable. The concentration of the amine salt is not particularly limited, but a concentration equal to or higher than the aniline monomer concentration is preferable. Sulfonic acid derivatives include aliphatic sulfonic acids such as methylsulfonic acid and ethylsulfonic acid, benzenesulfonic acid,
Aromatic sulfonic acids such as toluene sulfonic acid, dodecylbenzene sulfonic acid, naphthalene sulfonic acid and anthracene sulfonic acid, or their disulfonic acid, trisulfonic acid and other polysulfonic acids are suitable. As the oxidizing agent, ammonium peroxodisulfate, sodium chlorate, potassium chlorate, sodium bromate, potassium bromate, sodium iodate, potassium iodate, and peracid salts thereof can be used. Of these, ammonium peroxodisulfate is particularly preferable.

In the present invention, the polyaniline derivative includes those having various substituents on the benzene skeleton of polyaniline. Examples of the substituent include an alkyl group, a phenyl group, an alkoxy group, an ester group, a thioether group and the like. The polyaniline derivative includes a copolymer having 1 to 4 substituents or 1 to 4 substituents of these substituents. Furthermore, polyaniline derivatives include those substituted at the N-position with the above substituents.

The operation of polymerizing aniline or its derivative is not particularly limited. For example, a method of dissolving aniline or a derivative thereof in a suitable solvent containing a protic acid, further dissolving a predetermined amount of the amine salt, and then conducting oxidative polymerization with an oxidizing agent, aniline or a derivative thereof in a suitable solvent containing a protic acid. A method in which a mixture of an oxidizing agent and the amine salt is added and then oxidatively polymerized, or aniline or a derivative thereof is added to a solution containing a sulfonic acid compound, an oxidizing agent and the amine salt, or vapor of aniline or a derivative thereof is added. And a method of contacting and polymerizing. Of course, the solvent to be polymerized is not particularly limited, but one having a large polarity is preferable. For example, water, acetone, ethanol, methanol, tetrahydrofuran, chloroform, dichloroethane, various halogenated ethers, various halogenated esters, cresol and the like, or a mixture thereof is used.

The solid electrolytic capacitor of the present invention has a structure in which a film-forming metal is used as an anode, an oxide film formed thereon is used as a dielectric, and polyaniline which is a solid electrolyte is further formed thereon. The film-forming metal is tantalum, aluminum, niobium, titanium, zirconium, magnesium, silicon or the like, and can be used in the form of a rolled foil, a fine powder sintered product or the like.

Further, the film-forming metal is anodized in an electrolyte solution to form an oxide film which becomes a dielectric, but the electrolyte and solvent used are not particularly limited, and conventionally known ones can be used. Further, a constant voltage method or a constant current method can be applied as a method of anodic oxidation.
The holding time after the voltage becomes constant and the temperature and the like are not limited and can be set as necessary. Further, in order to improve the capacitance appearance ratio and equivalent series resistance of the capacitor, the film metal provided with a dielectric is heat-treated at a predetermined temperature and in a predetermined atmosphere, or the film metal is subjected to various surface treatments. You can also

The method for polymerizing aniline or its derivative at the time of producing the solid electrolytic capacitor of the present invention is not particularly limited.
That is, an oxidizer and an amine salt, or a mixture of an oxidizer and a sulfonic acid compound and an amine salt is introduced as it is or after being dissolved in a suitable solvent and introduced into a porous film-forming metal film forming an oxide film. Alternatively, a method of contacting with a gas or a solution of a mixture of aniline and a sulfonic acid compound and an amine salt, or by introducing aniline or a mixture of aniline and a sulfonic acid compound and an amine salt into a porous body of a film forming metal first. After that, it is carried out by a method of bringing into contact with an oxidizing agent and an amine salt, or a mixture of the oxidizing agent and a sulfonic acid compound and an amine salt.

After the completion of the polymerization, the capacitor element is washed with water or a solvent in which the oxidizing agent is easily dissolved to remove the oxidizing agent which does not contribute to the conductivity. Each of the steps such as the polymerization operation and the washing may be repeated.

The conductivity and reliability of the electrolyte polyaniline strongly depend on the dopant concentration of polyaniline. At a high dopant concentration, the conductivity of the electrolyte is high, but the moisture resistance may decrease. On the other hand, at low dopant concentrations, the conductivity of the electrolyte is reduced and the equivalent series resistance of the capacitor is increased. Therefore, after forming the electrolyte polyaniline, the dopant concentration of the electrolyte polyaniline is adjusted according to the specifications of the capacitor. The method for adjusting the dopant concentration is not particularly limited, but re-doping in a sulfonic acid solution having an appropriate concentration is a simple method.

After forming the electrolyte polyaniline, if necessary, it is dried and then a graphite layer and a silver layer are formed, and an extraction electrode is provided in the usual way to assemble into a capacitor. In the present invention, the graphite layer and the silver layer are not particularly limited, and conventionally known ones can be used.

[0021]

EXAMPLES Examples 1 to 7 show examples of a method for producing polyaniline or a derivative thereof. Examples 8-10
Shows an example of a method for producing an electrolytic capacitor using polyaniline or a derivative thereof as a solid electrolyte. In addition, the characteristics of polyaniline or a derivative thereof manufactured by a conventional manufacturing method and the characteristics of electrolytic capacitors using these as a solid electrolyte are shown in Reference Examples 1 to 5 for comparison.

The dielectric constant of polyaniline or a derivative thereof is 4.5 × 10 ⁴ ton using an IR tableting machine.
After applying a pressure of n / m ² to produce pellets of polyaniline or its derivatives, cut into 10 mm × 1 mm strips, and use the four-terminal method, that is, apply a constant current from a stabilized power supply to the current terminals to determine the voltage between the voltage terminals. The measurement was performed by the method of measuring and determining the electrical conductivity. The measurement was performed at room temperature under reduced pressure.

The thermal stability of the electrical conductivity was confirmed by allowing the strip of polyaniline or its derivative to stand in an oven set at 125 ° C. for a predetermined time and then measuring the electrical conductivity.

The amount of sulfate ion or chloride ion contained in polyaniline or its derivative was examined by ion chromatography. That is, 1.0 g of the obtained polyaniline or its derivative was crushed, and aqueous ammonia (30%) was added.
It was dropped in a 50 ml aqueous solution in which 1.2 was dissolved and stirred for 2 hours to extract the dopant, and then filtered. The sample was collected and filtered with a sample pretreatment cartridge filter (Sep-Pak, C18) manufactured by Waters. The filtrate is diluted with pure water and the ion chromatograph (Dion
It was injected into 2010i) manufactured by ex and the sulfate ion or chloride ion was measured and quantified by a calibration curve.

The frequency characteristics of the capacitors were measured using Yokogawa Hewlett-Packard Co., Impedans Analyzer 4194A. The measurement was performed at room temperature and normal pressure.

(Example 1) In a three-necked flask (for 300 ml) equipped with a dropping load, 1.9 g of toluenesulfonic acid was added.
(10 mmol) was weighed, 150 ml of pure water was added, and while stirring this, 0.93 g (10 mmol) of aniline
Was added and melted. Further, 1.9 g (10 mmol) of ammonium toluenesulfonate was added to the above solution while stirring. While maintaining the temperature of the reaction system at 0 ° C. or lower, a solution prepared by previously dissolving 2.3 g (10 mmol) of ammonium peroxodisulfate in 30 ml of pure water was added dropwise from the dropping funnel over 1 hour. After completion of the dropping, polymerization was carried out while stirring for 2 hours.

After the completion of the polymerization, the product was filtered, washed with 11 pure water and 0.51 ethanol, and dried under reduced pressure.
Yield 1.7g. The polyaniline powder thus obtained was further re-doped by stirring in 0.5 M 300 ml of a toluenesulfonic acid aqueous solution for about 1 hour.

Example 2 In a three-necked flask (for 300 ml) equipped with a dropping load, 1.9 g of toluenesulfonic acid was added.
(10 mmol) was weighed, 150 ml of pure water was added, and while stirring this, 0.93 g (10 mmol) of aniline
Was added and melted. While maintaining the temperature of the reaction system at 0 ° C. or lower, a solution prepared by dissolving 2.3 g (10 mmol) of ammonium peroxodisulfate and 1.9 g (10 mmol) of ammonium toluenesulfonate in advance in 50 ml of pure water was taken from the dropping funnel for 1 hour. Dropped. After completion of the dropping, polymerization was carried out while stirring for 2 hours.

After completion of the polymerization, the same treatment as in Example 1 was performed.

(Example 3) Polyaniline was synthesized in the same manner as in Example 1 except that the concentration of ammonium toluenesulfonate was doubled.

(Example 4) In a three-necked flask (for 300 ml) equipped with a dropping load, 1.9 g of toluenesulfonic acid was added.
(10 mmol) was weighed, 150 ml of pure water was added, and while stirring this, 0.93 g (10 mmol) of aniline
Was added and melted. Further, 1.9 g (10 mmol) of ammonium toluenesulfonate was added to the above solution while stirring. While keeping the temperature of the reaction system below 0 ° C, 0.35 g of sodium chlorate was previously added to 30 ml of pure water.
(3.3 mmol) and 2.9 g of toluenesulfonic acid (1
A solution in which 5 mmol) was dissolved was added dropwise from the dropping funnel over 1 hour. After completion of the dropping, polymerization was carried out while stirring for 2 hours.

After completion of the polymerization, the same treatment as in Example 1 was performed.

(Example 5) Polyaniline was synthesized in the same manner as in Example 1 except that orthomethoxyaniline was used in place of the aniline monomer.

(Example 6) Polyaniline was synthesized in the same manner as in Example 1 except that a methylamine salt of toluenesulfonic acid was used in place of ammonium toluenesulfonate.

(Example 7) In a three-necked flask (for 300 ml) equipped with a dropping load, 1.4 g (5 mmol) of m-xylylenedisulfonic acid was weighed, 150 ml of pure water was added, and while stirring this, aniline was added. 0.93g (10m
(mol) was added and dissolved. To the above solution, 2 g (10 mmol) of m-xylylenedisulfonic acid diammonium salt was added.
Was added with stirring. While maintaining the temperature of the reaction system at 0 ° C. or lower, a solution prepared by previously dissolving 2.3 g (10 mmol) of ammonium peroxodisulfate in 30 ml of pure water was added dropwise from the dropping funnel over 1 hour. After the dropping is completed,
Polymerization was carried out while stirring for another 2 hours.

After completion of the polymerization, the same treatment as in Example 1 was performed.

Reference Example 1 Polyaniline was synthesized in the same manner as in Example 1 except that ammonium toluenesulfonate was not added.

Reference Example 2 Polyaniline was synthesized in the same manner as in Example 1 except that an acetylhydrazine salt of toluenesulfonic acid (pKa <4.6) was used in place of ammonium toluenesulfonate.

Reference Example 3 Polyaniline was synthesized in the same manner as in Example 4 except that ammonium toluenesulfonate was not added.

Reference Example 4 Polyaniline was synthesized in the same manner as in Example 5 except that ammonium toluenesulfonate was not added.

Initial values of electrical conductivity and thermal stability of the polyaniline or its derivatives obtained in Examples 1 to 7 and Reference Examples 1 to 4 (conductivity after 200 hours at 125 ° C.)
Is shown in Table 1. Table 2 shows the amount of sulfate ion or chloride ion contained in polyaniline or its derivative. Table 1
From Table 2 and Table 2, it is clear that the polyaniline or the derivative thereof according to the present invention has a small content of a strong acid such as sulfuric acid and is excellent in thermal stability.

[0042]

[Table 1]

[0043]

[Table 2]

(Example 8) Diameter 1.5 mm, height 2 mm, powder CV value per gram (product of capacity and formation voltage) is 30
Cylindrical tantalum fine powder pellets of kCV / g were anodized in a 0.05 wt% nitric acid aqueous solution at 60 V, and then washed and dried.

The tantalum pellets were first mixed at room temperature in an amount of 5 wt% containing aniline, m-xylylenedisulfonic acid and m-xylylenedisulfonic acid diammonium salt in equivalent amounts.
% Aniline in a water: ethanol = 1: 1 solution for 30 seconds. After 5 minutes, ammonium peroxodisulfate and m-
An oxidant aqueous solution containing diammonium xylylene disulfonate (ammonium peroxodisulfate / m-ammonium xylylene disulfonate having a molar ratio of 1: 1 and an ammonium peroxodisulfate content of 10% by weight) was added to a solution cooled to 0 ° C. Soaked for 2 seconds. The tantalum pellet was taken out and kept in air for another 10 minutes to carry out polymerization. Then, it was washed with water and ethanol and dried under reduced pressure, whereby black polyaniline could be formed on the dielectric surface.

A series of operations of filling the aniline monomer, contacting with the oxidant solution, polymerization, washing and drying was repeated 10 times. Then, a silver paste was attached, the cathode lead was pulled out, and sealed with an epoxy resin to complete a capacitor.

Example 9 A capacitor was completed in exactly the same manner as in Example 8 except that a salt of m-xylylenedisulfonic acid methylamine was used in place of the diammonium m-xylylenedisulfonate. .

(Example 10) An aluminum foil (1 cm x 0.5 cm square) having a film thickness of 150 µm whose surface area was enlarged by about 20 times by etching was anodized in a 5% ammonium borate aqueous solution at 100 V, washed and dried. . A capacitor was completed in exactly the same manner except that the aluminum foil was used in place of the tantalum fine powder sintered body pellet of Example 8.

Reference Example 5 A capacitor was completed in exactly the same manner as in Example 8 except that diammonium m-xylylenedisulfonate was not added to the monomer solution and the oxidizing agent solution.

Regarding Examples 8 to 10 and Reference Example 5, 20 minutes after the production of the obtained capacitors and under the condition of 125 ° C.
Table 3 shows changes in the frequency characteristics of the capacitor after 0 hours (capacity appearance rate, equivalent series resistance value (R, 30 kHz)). From these results, the capacitors obtained according to the examples of the present invention have a capacitance appearance ratio of about 100%, a small equivalent series resistance, and good high-frequency characteristics, and also have excellent reliability under high temperature conditions. It was recognized that it was a thing.

[0051]

[Table 3]

[0052]

As described above, according to the method for producing aniline or an aniline derivative according to the present invention, an aniline-based conductive polymer having a small content of a strong acid such as sulfuric acid and excellent thermal stability was obtained. Further, according to the method for producing a solid electrolytic capacitor of the present invention, the capacity appearance rate is almost 100%, the equivalent series resistance is small, the high frequency characteristics are good, and the reliability under high temperature conditions is excellent. Was found to be

[Brief description of drawings]

FIG. 1 is a flowchart showing a method for producing an aniline-based conductive polymer according to the present invention.

Claims (4)

[Claims] 1. An aniline or an aniline derivative is oxidatively polymerized in a solution containing a sulfonic acid derivative, an oxidizing agent that generates a strong acid anion when being oxidized, and a salt of an amine having an acid dissociation index of 4.6 or more. A method for producing an aniline-based conductive polymer, comprising: 2. The method for producing an aniline-based conductive polymer according to claim 1, wherein the solution contains an amine salt of sulfonic acid. 3. A solid electrolytic capacitor comprising a film-forming metal as an anode, an oxide film formed thereon as a dielectric, and a solid electrolyte mainly composed of an aniline-based conductive polymer formed thereon. In the method, the film-forming metal is dipped in a solution containing aniline or an aniline derivative, an oxidizing agent that produces a strong acid anion during oxidation, a sulfonic acid derivative, and a salt of an amine having an acid dissociation index of 4.6 or more. A method for producing a solid electrolytic capacitor, comprising a step of carrying out polymerization. 4. A solid electrolytic capacitor comprising a film-forming metal as an anode, an oxide film formed thereon as a dielectric, and a solid electrolyte mainly composed of an aniline-based conductive polymer formed thereon. In the method, after the film-forming metal is immersed in a monomer solution containing aniline or an aniline derivative or a sulfonic acid derivative, it is immersed in an oxidant solution containing an oxidant that produces a strong acid anion when oxidation is performed to solidify the polymerization. In the method of manufacturing an electrolytic capacitor,
A method for producing a solid electrolytic capacitor, characterized in that at least one of a monomer solution and an oxidant solution contains a salt of an amine having an acid dissociation index of 4.6 or more.