JP2003147055A - Method for producing polypyrrole and solid electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a polypyrrole by which an electroconductive polymer material exhibiting high electroconductivity and excellent heat resistance can be obtained and to provide a solid electrolytic capacitor having small impedance in resonance frequency, good high-frequency property and little deterioration of properties at high temperature by using the electroconductive polymer material as a cathode electroconductive material for solid electrolytic capacitor. SOLUTION: Chemical oxidative polymerization of pyrrole is carried out by using an oxidizing agent composed of a ferric salt of an aromatic sulfonic acid and a cupric salt of an aromatic sulfonic acid, and optionally an antioxidant. This solid electrolytic capacitor is obtained by using the resultant polypyrrole as the cathode electroconductive material.

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 polypyrrole and a solid electrolytic capacitor, and more particularly to a method for producing polypyrrole having high conductivity and heat resistance, and high conductivity of polypyrrole obtained thereby. The present invention relates to a solid electrolytic capacitor in which the polypyrrole is applied to the cathode conductive material of the electrode by utilizing its high heat resistance and heat resistance.

[0002]

2. Description of the Related Art In recent years, with the development of electronics, new materials for electronic parts have been developed.
Significant progress has been made in functional polymer materials. Even with regard to conductive materials, electron-conjugated polymer substances such as polypyrrole, polyaniline, and polythiophene and electron-accepting compounds (dopants) have been developed and put into practical use as capacitor electrode materials, battery electrode materials, antistatic materials, etc. There are also examples. When the conductive polymer substances such as polypyrrole, polyaniline, and polythiophene described above are used as the cathode of the capacitor, these conductive polymer substances have a higher dielectric constant than manganese dioxide, and also tetracyanoquinodimethane (TCNQ). It has been found that it has better heat resistance than complex salts. Paying attention to this characteristic, for example, JP-A-64-74711 and JP-A-64-7411
-74712 and JP-A-64-74713 disclose a method for producing a capacitor in which a conductive polymer is formed on an oxide film by a chemical oxidative polymerization method using an oxidizing agent. The oxidative polymerization method is a method of obtaining a polymer by mixing a monomer of a conductive polymer and an oxidizing agent. Generally, a ferric salt such as an organic acid is dissolved in various solvents as the oxidizing agent. Is often used. However, since the conductive polymer substance thus obtained is in a highly oxidized state in which anions are doped, the conductivity decreases due to heat and the like, and it is difficult to maintain the conductivity stably for a long period of time. Came. In particular, it is known that polypyrrole is apt to be oxidized, so that the electric conductivity is remarkably reduced, and the initial electric conductivity is not so high as compared with thiophene derivatives and the like. Therefore, the solid electrolytic capacitor using polypyrrole as the cathode conductive material,
It is known that impedance characteristics and heat resistance are inferior to solid capacitors using thiophene derivatives, etc., and there are examples that have been put to practical use despite the price being cheaper than thiophene derivatives. The current situation is that there are not so many.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a technique capable of solving the drawbacks of the prior art. The above and other objects and novel features of the present invention will be apparent from the description of the present specification and the accompanying drawings.

[0004]

According to the present invention, when a pyrrole is chemically oxidatively polymerized to obtain polypyrrole, an oxidizer comprising a ferric salt of an aromatic sulfonic acid and a cupric salt of an aromatic sulfonic acid is used. In a preferred embodiment, the aromatic sulfonic acid is paratoluenesulfonic acid, which is characterized in that the aromatic sulfonic acid is paratoluenesulfonic acid. Further, the present invention relates to a method for producing polypyrrole, characterized in that, when a polypyrrole is obtained by chemically oxidatively polymerizing pyrrole, an oxidizing agent is used, and an antioxidant is added to polymerize the polypyrrole. The oxidizing agent is characterized by comprising a ferric aromatic sulfonic acid salt and a cupric aromatic sulfonic acid salt. Further, the present invention, the polypyrrole obtained above,
The present invention relates to a solid electrolytic capacitor characterized by being used as a cathode conductive material.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

The pyrrole used in the present invention is a compound represented by the following general formula (1).

[0007]

[Chemical 1] (In the formula, R ₁ and R ₂ are each independently a hydrogen atom, C
_{1 to 6} linear or branched saturated or unsaturated hydrocarbon group, C _{1 to 6} linear or branched saturated or unsaturated alkoxy group, hydroxyl group, halogen atom,
It represents a nitro group, a cyano group, a trihalomethyl group, a phenyl group or a substituted phenyl group, and R ₁ and R ₂ are bonded to each other at any position to form at least one or more 5 to 7
You may form the bivalent group which forms the saturated or unsaturated cyclic structure of a member ring. )

The above-mentioned chemical oxidative polymerization method has a transition metal complex having a conjugated base of aromatic sulfonic acid as a ligand and a repeating unit forming a polymer compound having an electron conjugated system molecular structure. It can be carried out by contacting another monomer, ie, pyrrole, in a solvent. In the present invention, iron and copper are selected as the central metal constituting the transition metal complex, and Fe (III) salt of aromatic sulfonic acid and Cu are selected.
(II) A salt is used together. Aromatic sulfonic acid Fe (II
A mixed solution of I) salt and Cu (II) salt may be used.
The transition metal complex is usually used in an amount of 0.5 to 10 mol based on 1 mol of the monomer, that is, pyrrole. The solvent used in the reaction may be any solvent that can dissolve the above transition metal complex and the monomer, and examples thereof include water, methanol, ethanol, n-propanol, n-butanol, nitromethane dimethylformamide, acetonitrile and propylene carbonate. Etc. can be mentioned. The polymerization temperature is preferably 0 ° C to 50 ° C, and the reaction time is preferably 0.1 to 24 hours. Further, it is desirable that the polymerization be carried out in an inert atmosphere.

The aromatic sulfonic acid F used in the present invention
Para-toluene sulfonic acid is mentioned as an example of the aromatic sulfonic acid which comprises e (III) salt and Cu (II) salt.

The polypyrrole of the present invention comprises a structural unit represented by the following general formula (2).

[0011]

[Chemical 2] (R ₁ and R ₂ in the formula are the same as those in the general formula (1).)

It has been found that polypyrrole having good heat resistance can be obtained by using an oxidizing agent and polymerizing by adding an antioxidant in obtaining polypyrrole by chemically oxidatively polymerizing pyrrole in the present invention. As the example of the antioxidant, an antioxidant generally used for plastics can be used. For example, phenol-based antioxidants (monophenol-based, bisphenol-based, various polymer-type phenols) can be used. (Including a system antioxidant) can be used. Specific examples of the phenolic antioxidant include butylated hydroxyanisole (BHA), 2,
6-di-t-butyl-p-cresol, p-methoxyphenol, hydroquinone, 2,2-methylenebis (4-
Methyl-6-butylphenol), 2,2-methylenebis (4-ethyl-6-t-butylphenol), 1,
1,3-trismethyl-2,4,6-tris (3,5-
Di-t-butyl-4-hydroxybenzyl) benzene and the like can be mentioned. The addition amount of the antioxidant can be arbitrarily selected, but it is preferable to add it in a concentration range of 1 ppm to 10% by weight. If it is less than 1 ppm, the heat resistance improving effect is small, while if it exceeds 10% by weight, the effect is saturated and it is not economical. As the oxidizing agent in the above case, in addition to the combined use of Fe (III) salt and Cu (II) salt of aromatic sulfonic acid, a conjugate base of various aromatic sulfonic acids containing iron, ruthenium or the like as a transition metal is used. A transition metal complex having a ligand can be used.

The polypyrrole obtained by the chemical oxidative polymerization of pyrrole is a polypyrrole having the above structural unit,
The anion of aromatic sulfonic acid is contained as a dopant. Fe (III) salt of aromatic sulfonic acid and Cu
(II) By using a salt together or adding an antioxidant to an oxidant, a conductive material having high conductivity and excellent heat resistance can be obtained. Further, when the conductive polymer material is used as a cathode conductive material for an electrode, it is possible to obtain a solid electrolytic capacitor having excellent impedance characteristics up to a high frequency region and having excellent heat resistance. A solid electrolytic capacitor generally has a basic structure in which an anode metal and a cathode conductive material are joined via a dielectric layer, and an electrode lead is attached to each anode metal and the cathode conductive material. As the metal that constitutes the anode metal, aluminum, tantalum,
Niobium and the like can be mentioned, and it is usually used in the state of foil. Moreover, the surface may be etched. The dielectric layer usually consists of an oxide layer of anodic metal. The solid electrolytic capacitor in which the cathode and the anode are arranged may have any shape such as a cylindrical type or a dip type.

In the present invention, other compounds conventionally known as dopant materials can be coexisted in the polymerization system to the extent of not impairing the purpose of the polymerization.

[0015]

EXAMPLES The present invention will be further described below based on examples.

Example 1 40 g of ferric p-toluenesulfonate and 10 g of cupric p-toluenesulfonate were dissolved in ethanol to give 40% ferric p-toluenesulfonate, and p-toluenesulfonic acid ferric acid. An oxidizer of 10% was prepared as dicopper. 23.6 g of a mixed solution of 40% ferric iron p-toluenesulfonate + cupric acid 10% p-toluenesulfonate was placed in a beaker, and while stirring well using a stirrer, 0.6 g was obtained. Was added little by little, and chemical oxidative polymerization was performed. The obtained polypyrrole was thoroughly washed with methanol and then dried. Gain 0.93
g. The obtained polymer was compression-molded to form a disk, and the initial electrical conductivity was measured by the four-point probe method.
An electrical conductivity of 2.1 S / cm was obtained. Also, 105 ℃
The sample was stored in a constant temperature bath of 200, and the electric conductivity after 200 hours was measured in the same manner, and the conductivity retention rate was calculated based on the initial electric conductivity. The results are shown in Table 1.

Example 2 40 g of ferric p-toluenesulfonate and 10 g of cupric p-toluenesulfonate were dissolved in ethanol to give 40% ferric p-toluenesulfonate, p-toluenesulfonic acid ferric acid. An oxidizer of 10% was prepared as dicopper. 1000 ppm of p-methoxyphenol was added to the mixed solution of 40% ferric iron p-toluenesulfonate + cupric acid 10% p-toluenesulfonate and completely dissolved by stirring well. 23.6 g of the solution was placed in a beaker and stirred well by using a stirrer.
6 g of pyrrole was added little by little to carry out chemical oxidative polymerization. The obtained polypyrrole was thoroughly washed with methanol and then dried. Yield 0.73g. The obtained polymer was compression-molded into a disk, and the initial electrical conductivity thereof was measured by the four-point probe method. The result was 15.6 S / c.
An electrical conductivity of m was obtained. Further, the sample was stored in a constant temperature bath at 105 ° C., the electric conductivity after 200 hours was measured in the same manner, and the conductivity retention rate was calculated based on the initial electric conductivity. The results are shown in Table 1.

Example 3 To a 40% ferric ethanolic p-toluenesulfonate solution in ethanol, 1000 ppm of p-methoxyphenol was added.
This was thoroughly stirred and completely dissolved. 31.8 g of the product was placed in a beaker, and while well stirred using a stirrer, 0.6 g of pyrrole was added little by little to carry out chemical oxidative polymerization. The obtained polypyrrole was thoroughly washed with methanol and then dried. Obtained amount 0.81g. The obtained polymer was compression-molded to form a disk, and the initial electric conductivity thereof was measured by the four-point probe method. As a result, an electric conductivity of 2.3 S / cm was obtained. Again 1
The sample was stored in a constant temperature bath at 05 ° C., the electric conductivity after 200 hours was measured in the same manner, and the conductivity retention rate was calculated based on the initial electric conductivity. The results are shown in Table 1.

[0019]

Comparative Example A comparative example will be described below.

Comparative Example 1 Chemical oxidation polymerization was carried out in the same manner as in Example 1 except that 40% p-toluenesulfonic acid ferric ethanol solution was used as the oxidizing agent to obtain 1.08 g of polypyrrole. The obtained polymer was compression-molded in the same manner as in Example 1 to mold a disk, and the initial electric conductivity thereof was measured by the four-point probe method. As a result, an electric conductivity of 4.7 S / cm was obtained. . Also, the sample was stored in a constant temperature bath at 105 ° C., the electric conductivity after 200 hours was measured in the same manner, and the conductivity retention rate was calculated based on the initial electric conductivity. The results are shown in Table 1.

Comparative Example 2 A chemical oxidative polymerization was carried out in the same manner as in Example 1 using 40% p-toluenesulfonic acid cupric ethanol solution as an oxidizing agent, but polypyrrole enough to form a disk was obtained. I couldn't.

[0022]

[Table 1]

[0023]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows. That is, according to the present invention, polypyrrole having high conductivity could be obtained by using Fe (III) salt and Cu (II) salt of aromatic sulfonic acid as oxidants. Further, by adding an antioxidant to the oxidizing agent, polypyrrole having high heat resistance could be obtained. Furthermore, by adding an antioxidant to the oxidizing agent composed of the Fe (III) salt and Cu (II) salt of the aromatic sulfonic acid, a polypyrrole having high conductivity and high heat resistance could be obtained. When a conductive polymer material made of the polypyrrole is used as a cathode conductive material of a solid electrolytic capacitor, it is possible to obtain a solid electrolytic capacitor having a small impedance at resonance frequency, good high frequency characteristics, and less deterioration in characteristics at high temperatures. You can

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Minoru Nakano             3-11-1, Mizutanihigashi, Fujimi-shi, Saitama Toyamayaku             Shinki Co., Ltd. Shiki Factory F term (reference) 4J032 BA13 BA14 BC03 BC12 BD02                       BD05 CG01

Claims (5)

[Claims] 1. When polypyrrole is obtained by chemically oxidatively polymerizing pyrrole, the polymerization is carried out by using an oxidant composed of a ferric aromatic sulfonic acid salt and an aromatic sulfonic acid cupric salt. Method for producing polypyrrole. 2. The method for producing polypyrrole according to claim 1, wherein the aromatic sulfonic acid is paratoluene sulfonic acid. 3. A process for producing polypyrrole, which comprises using an oxidizing agent and adding an antioxidant when the pyrrole is chemically oxidatively polymerized to obtain polypyrrole. 4. The method for producing polypyrrole according to claim 3, wherein the oxidizing agent comprises a ferric aromatic sulfonic acid salt and an aromatic sulfonic acid cupric acid. 5. A solid electrolytic capacitor using the polypyrrole obtained in any one of claims 1, 2, 3 and 4 as a cathode conductive material.