JPH10284350A - Solid electrolyte for solid state electrolytic capacitor, its manufacture and solid state electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the doped state soluble, by using specified conductive polymer composition soluble in the doped state which contains at least polyaniline and/or its derivative and protonic acid dopant and has conductivity higher than or equal to a specified value. SOLUTION: Dedoped polyaniline and suifonic acid type diesterified compound whose molecular weight is about 534 are added to THF, and a homogeneous dark green solution is obtained by ultrasonic irradiation. The obtained doped polyaniline THF solution is spread on an aluminum anode foil and dried. By repeating this treatment, a thin film is obtained. In order to make polyaniline soluble in the doped state, protonic acid dopant satisfies the following; the value of (molecular weight of dopant)/(the number of protonic acid groups in a molecule wherein the acid dissociation constant pKa is at most 4.0) is 350-2000, and the conductivity is at least 10<-9> S/cm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive organic polymer composition containing polyaniline and / or a derivative thereof soluble in a general-purpose organic solvent and / or an aqueous solvent in a state in which a dopant coexists (hereinafter referred to as a doped state). The present invention relates to a solid electrolytic capacitor using a conductive film obtained from a product.
Since the organic polymer composition used in the present invention is soluble in a solvent or water in a doped state, a solution of the composition can be directly applied to a metal surface and dried to form a solid electrolyte.

[0002]

2. Description of the Related Art Since polyaniline, which is a conductive polymer, is generally infusible and insoluble, a method of forming a polyaniline film on a base material is a method of electrolytic polymerization (J. Elec.
tro-chem. Soc., 132, 1022, (1988)), but it has been difficult to apply it to a large-area metal surface, so that a method for solubilizing polyaniline has been desired.

Further, a method has been proposed in which undoped polyaniline can be processed because it is soluble in a certain kind of polar organic solvent (JP-A-3-28229). There is a problem that two steps of a step of molding a doped polyaniline and a step of doping with a protonic acid are required.

[0004] A method for solubilizing polyaniline in a doped state (WO92-22911) has also been proposed. However, polyaniline is industrially used, for example, by using a harmful solvent or by using an excess of a protonic acid dopant. Has many problems.

A method of dissolving doped polyaniline in a polar organic solvent to which ammonia or a volatile amine has been added (Japanese Patent Application Laid-Open No. 3-285983) has been proposed. There is a problem that amine gas is generated.

A self-doping type water-soluble polyaniline in which a sulfonic acid group serving as a dopant is directly bonded to a polymer skeleton (Japanese Patent Application Laid-Open No. 5-178889) has been proposed, but the production process is complicated and there is a problem in cost.

As a method for forming a polyaniline film on a substrate, a method is known in which aniline or a derivative thereof is chemically oxidatively polymerized in the presence of a target substrate (JP-A-2-695).
25) has been proposed, but is not suitable for industrial large-scale production.

[0008]

SUMMARY OF THE INVENTION The present inventors have made intensive studies to develop inexpensive conductive polyaniline which is soluble in a general-purpose organic solvent and / or aqueous solvent in a doped state, and as a result, a specific dopant is polyaniline or polyaniline. It has been found that the derivative can be made solvent-soluble in a doped state. Simple application using this soluble polyaniline,
As a result of intensive studies to develop an excellent solid electrolyte for a capacitor that can be coated, the present invention has been achieved.

[0009]

That is, the present invention comprises at least polyaniline and / or a derivative thereof (A) and a protonic acid dopant (B), and has a conductivity of 10 ^-9 S / cm or more; And a conductive organic polymer composition which is soluble in a doped state, wherein (proton molecular weight) / (dopant molecular weight) /
A solid electrolyte for a solid electrolytic capacitor, wherein a conductive organic polymer composition having a value of (the number of proton acid groups having an acid dissociation constant pKa of 4.0 or less in one molecule) of 350 to 2,000 is used. It is. Further, a preferable dopant used in the conductive organic polymer composition is at least one selected from the following formulas (I) and (II). The present invention relates to an electrolytic capacitor, and is further characterized in that a dispersion or solution of at least one or a mixture of conductive organic polymer compositions using the preferred dopant is applied on an oxide film-forming metal and dried. The present invention relates to a method for producing a solid electrolyte for a solid electrolytic capacitor.

[0010]

Embedded image In the formula, R ¹ is hydrogen or an alkyl group, alkenyl group, alkylthioalkyl group, aryl group, alkylaryl group, arylalkyl group, alkoxyalkyl group, aryloxyalkyl having 1 to 15, preferably 2 to 12 carbon atoms. Represents a group, and when a plurality of groups are present, they may be the same or different. R ¹ ′ is hydrogen, alkyl, alkenyl, alkoxy, alkylthio, alkylthioalkyl, aryl, alkylaryl, arylalkyl, alkylsulfinyl, alkoxyalkyl, aryloxyalkyl, alkylsulfonyl, It represents an alkoxycarbonyl group, a carboxyl group, a nitrile group, a hydroxy group, a nitro group or a halogen. When a plurality of groups are present, they may be the same or different.

Preferred R ¹ 'is hydrogen, an alkyl group, an alkoxy group, an alkylthio group, an alkylthioalkyl group, an aryl group, an alkylsulfinyl group, an alkoxyalkyl group, an alkoxycarbonyl group, a carboxyl group, a nitrile group, or a hydroxy group. More preferably hydrogen, alkoxy group, alkylthio group, alkylthioalkyl group, alkylsulfinyl group, alkoxyalkyl group, alkoxycarbonyl group, carboxyl group,
They are a nitrile group and a hydroxy group. k represents an integer of 1 to 5 and preferably an integer of 2 to 4. k ′ represents an integer of 0 to 4, and k + k ′ = 5.

[0012]

Embedded image

In the formula, R ² represents an alkyl group having 5 to 20 carbon atoms, an alkenyl group, an alkylthioalkyl group, an aryl group, an alkylaryl group, an arylalkyl group, an alkoxyalkyl group, or an aryloxyalkyl group. It represents an alkyl group, an alkylthioalkyl group, an alkoxyalkyl group, and an aryloxyalkyl group represented by Formulas 7 to 20. p represents an integer of 1 to 5, preferably an integer of 2 to 5.

In order to solubilize polyaniline in a doped state, it is important to select a proton acid dopant. Suitable dopants must have a high solvent affinity partial structure that has some spatial extent in addition to the protonic acid groups. The formula weight of one unit of polyaniline when protonated by the dopant is 181. In order to dissolve the polyaniline main chain having low solubility by doping, it is estimated that the formula weight per proton acid group of the dopant is required to be 181 or more.

In view of the above problems, the present inventors have conducted intensive studies on dopants and found that the molecular weight of the dopant was as follows.
It has been found that a dopant having a value of / (the number of protonic acid groups having an acid dissociation constant pKa of 4.0 or less in one molecule) of 350 to 2,000 is suitable. The value of 350 is approximately twice that of 181 for polyaniline. On the other hand, when the value is 2,000 or more, electron conduction between the main chains of polyaniline is hindered due to steric hindrance caused by the dopant, and the conductivity is reduced. Proton acid groups having an acid dissociation constant pKa exceeding 4.0 have insufficient protonation to polyaniline,
The conductivity of the resulting composition is low.

The value of (the molecular weight of the dopant) / (the number of proton acid groups having an acid dissociation constant pKa of 4.0 or less in one molecule) is preferably from 400 to 2,000, more preferably from 460 to 2,000, More preferably 520 to
2000, the polyaniline in the doped state is easily dispersed or dissolved in the solvent in this order.

Specific examples of suitable dopants include protonic acid compounds represented by the above formula (I) or (II). These are all organic sulfonic acids having a molecular weight of several hundreds. The dopant represented by the formula (I) is
R ¹ is an organic group having a relatively low polarity, and is useful for dissolving polyaniline mainly in a general-purpose organic solvent. The dopants of formula (II) have a sulfonate moiety of a hydrophilic group and are useful mainly for dissolving in aqueous solvents.

The aniline or its derivative used in the oxidative polymerization may be one kind or two or more kinds, and has a structure represented by the following formula (III).

[0019]

Embedded image

In the formula, r represents an integer from 0 to 5. R ³
May be the same or different, and each represents a hydrogen alkyl group, an alkenyl group, an alkoxy group, an alkanoyl group,
Alkylthio group aryloxy group, alkylthioalkyl group, aryl group, alkylaryl group, arylalkyl group, alkylsulfinyl group, alkoxyalkyl group, alkylsulfonyl group, alkoxycarbonyl group, amino group, alkylamino group, dialkylamino group, arylthio group , Arylsulfinyl, arylsulfonyl, carboxyl, halogen, cyano, haloalkyl, nitroalkyl, and cyanoalkyl groups.

Specific examples include aniline, o-toluidine, m-toluidine, o-ethylaniline, m-toluidine,
Ethylaniline, o-ethoxyaniline, m-butylaniline, m-hexylaniline, m-octylaniline, 2,3-dimethylaniline, 2,5-dimethylaniline, 2,5-dimethoxyaniline, o-cyanoaniline, , 5-dichloroaniline, 2-bromoaniline,
5-chloro-2-methoxyaniline, 3-phenoxyaniline and the like.

As the oxidizing agent, ammonium peroxodisulfate, hydrogen peroxide, ferric chloride and the like are used, and preferably, ammonium peroxodisulfate is used, but it is not particularly limited thereto.

The method for obtaining the polyaniline of the present invention includes a method in which an oxidizing agent and a solution of a protonic acid or a solution of an oxidizing agent are added to a solution or suspension of aniline or an aniline derivative and a protonic acid. For polymerization, polymerization conditions usually performed are applied. For example, the reaction temperature is between -10 ° C and 40 ° C, and the reaction time is between 30 minutes and 48 ° C.
The reaction mixture is stirred under normal pressure for a period of time.

The protonic acid added during the oxidative polymerization is not limited as long as the acid dissociation constant pKa is 4.0 or less. For example, inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid and perchloric acid, and benzene sulfone Acid, p-toluenesulfonic acid, m
Organic acids such as nitrobenzoic acid and trichloroacetic acid; and polymer acids such as polystyrene sulfonic acid, polyvinyl sulfonic acid and polyvinyl sulfuric acid.

The resulting polyaniline is de-doped into a undoped polyaniline by treating it with a base such as aqueous ammonia, but can be treated again with a desired protonic acid to obtain a doped polyaniline. At the time of oxidative polymerization, doping may be performed by adding a desired protonic acid, or may be added to undoped polyaniline to obtain doped polyaniline.

The dopant is preferably one equivalent to polyaniline. Excessive dopants are undesirable because they can induce corrosion of the substrate.

The organic solvent in which the polyaniline composition of the present invention can be dissolved can be used without any particular limitation as long as it is generally used as a general-purpose solvent. For example, tetrahydrofuran, ethers such as dioxane, methanol, ethanol, isopropyl alcohol, alcohols such as 2-n-butoxyethanol, nitriles such as acetonitrile, ketones such as acetone, carboxylic acids such as formic acid, acetic acid, and propionic acid; Aromatic hydrocarbons such as xylene and toluene, halogenated hydrocarbons such as chloroform,
Polar solvents such as N-methylpyrrolidone, dimethylformamide, dimethylsulfoxide and the like can be used.

Further, the aqueous solvent in which the polyaniline composition of the present invention can be dissolved means water or a mixed solvent with water and an organic solvent miscible with water. The ratio between water and the organic solvent is not particularly limited. As the organic solvent, for example, tetrahydrofuran, ethers such as dioxane, methanol,
Alcohols such as ethanol, isopropyl alcohol and 2-n-butoxyethanol, nitriles such as acetonitrile, ketones such as acetone, carboxylic acids such as formic acid, acetic acid and propionic acid, N-methylpyrrolidone, dimethylformamide, dimethyl sulfoxide and the like Polar solvents can be used. In any case, those having low corrosiveness and toxicity are preferable.

There is no particular limitation on the method of forming a film on the metal surface, and it is easily possible by applying a method of dipping, brushing, spray coating, roller coating, etc. with a polyaniline solution and drying. And can be applied to large-area metal surfaces.

[0030]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited by these examples.

<Synthesis Example 1> 15 g of aniline and 27 of distilled water
0 g and 36 g of concentrated hydrochloric acid were added, and a solution of 24.5 g of ammonium persulfate dissolved in 70 g of distilled water was added dropwise over 1 hour while maintaining the temperature at 0 ° C., and the mixture was further stirred for 4 hours. After filtration, washing with water, washing with methanol and ether,
Vacuum drying yielded 12.4 g of polyaniline. 10 g of the obtained polyaniline is 3% aqueous ammonia 1000
g, followed by stirring at room temperature for 2 hours, followed by filtration, washing with water, washing with methanol and washing with ether. Vacuum drying,
6.5 g of undoped polyaniline (emeraldine base) were obtained. GPC is dissolved in N-methylpyrrolidone
Is measured, the number average molecular weight is 270 in terms of polystyrene.
00, and the weight average molecular weight was 99000.

<Synthesis Example 2> A 5-necked flask (300 ml) equipped with a stirrer, a distillate extraction tube and a thermometer was charged with 5-
27.8 g of dimethyl sulfosodium isophthalate, diethylene glycol-mono-n-butyl ether 20
7.8 g and 0.02 zinc acetate as the esterification catalyst.
67 g was added and reacted at 210 ° C. for 8 hours. As the reaction progressed, the white suspension became a transparent homogeneous liquid, and the calculated amount of methanol was distilled off. Further, unreacted diethylene glycol mono-n-butyl ether was distilled off at 220 ° C. and 70 mmHg in 2 hours.

<Synthesis Example 3> To 30 ml of a THF solution of 1 g of the diester compound obtained in Synthesis Example 2 was added 20 g of an ion-exchange resin (Amberlyst 15, manufactured by Organo), and the mixture was stirred at room temperature for 15 minutes. After filtration through a glass filter, the ion exchange resin was washed again with 30 ml of THF and combined with the filtrate. Titrate with 0.02N aqueous sodium hydroxide solution,
It was confirmed quantitatively that the sulfo sodium group was converted to a sulfonic acid group. THF was distilled off, the residue was dried, and the structure of formula (IV) was confirmed by 1H-NMR and IR.

[0034]

Embedded image

0.10 g of the undoped polyaniline obtained in Synthesis Example 1 and 0.30 g of the above sulfonic acid type diester compound (molecular weight: 534) were added to 8 ml of THF, and the mixture was irradiated with ultrasonic waves for 3 hours to give a uniform dark green solution. was gotten. When this solution was filtered through a glass filter, the amount of insolubles remaining on the filter was extremely small. This doped polyaniline THF solution was applied on a polyethylene terephthalate film and dried at 120 ° C. for 1 hour to obtain a thin film having a thickness of 1 mm. When the obtained thin film was measured by a two-terminal method, the conductivity σ was 13 (S / cm). In a similar manner, the doped polyaniline was dissolved in 2-n-butoxyethanol to form a thin film. Conductivity σ = 9
(S / cm).

<Example 1> The coating and drying of the doped polyaniline THF solution obtained in Synthesis Example 3 on an aluminum anode foil was repeated to obtain a thin film having a thickness of 15 µm. After that, a capacitor was prototyped between the cathode foils. The capacitance of the obtained capacitor at 120 Hz is 1.4.
μF.

<Synthesis Example 4> 8.34 g of the diester compound obtained in Synthesis Example 2 was dissolved in 80 g of deionized water.
022 g and 1.863 g of aniline were added, and the mixture was cooled to 0 ° C. A solution prepared by dissolving 4.564 g of ammonium peroxodisulfate in 20 g of deionized water was previously cooled to 0 ° C., and added dropwise over 20 minutes. The reaction mixture is at 0 ° C.
And stirred for 20 hours. The generated doped polyaniline was precipitated, and was filtered off with a G4 glass filter, washed with water and dried. This doped polyaniline was added to MEK /
It was dissolved in a toluene (1: 1 (v / v)) solution to prepare a solid concentration of 3.0%.

<Example 2> The coating and drying of the doped polyaniline MEK / TOL solution obtained in Synthesis Example 4 on an aluminum anode foil was repeated to give a film thickness of 15 μm.
Was obtained. After that, a capacitor was prototyped between the cathode foils. The capacitance at 120 Hz of the obtained capacitor was 14.7 μF.

<Synthesis Example 5> Aqueous solution 4 of compound of formula (V)
1436 g of deionized water was added to 44.85 g, and sulfuric acid was added to the mixture.
22 g and 11.97 g of aniline were added and cooled to 0 ° C. A solution prepared by dissolving 29.33 g of ammonium peroxodisulfate in 140 g of deionized water was cooled to 0 ° C. in advance and added dropwise over 2 hours. The reaction mixture was kept at 0 ° C. and stirred for 18 hours. The resulting doped polyaniline was dispersed in water. After adding 8% by volume of methanol and centrifuging, the supernatant was removed by decantation, deionized water was added, and the mixture was redispersed in an ultrasonic bath.

[0040]

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<Example 3> The coating and drying of the aqueous dispersion of doped polyaniline obtained in Synthesis Example 5 on an aluminum anode foil was repeated to obtain a thin film having a thickness of 13 µm. Thereafter, the capacitor was sandwiched between cathode foils to produce a prototype capacitor. The capacitance at 120 Hz of the obtained capacitor was 6.2.
μF.

[0042]

The characteristics of the solid electrolytic capacitor of the present invention are as follows.
It contains a solvent-soluble polyaniline in a dope state, and can easily form a film on a metal surface by coating and drying. The polyaniline of the present invention can be easily coated even with a large-area metal material.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Keiichi Uno 2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo Co., Ltd. Research Laboratory

Claims (5)

[Claims] 1. A conductive material comprising at least polyaniline and / or a derivative thereof (A) and a protonic acid dopant (B), having a conductivity of at least 10 ^-9 S / cm and being soluble in a doped state. A functional organic polymer composition, wherein the proton acid dopant (B) has a value of (molecular weight of dopant) / (number of proton acid groups having an acid dissociation constant pKa of 4.0 or less per molecule) of 350 to 200
A solid electrolyte for a solid electrolytic capacitor, characterized by using a conductive organic polymer composition of 0. 2. A solid electrolyte for a solid electrolytic capacitor using the conductive organic polymer composition according to claim 1, wherein the dopant is represented by the formula (I). Embedded image In the formula, R ¹ represents hydrogen or an alkyl group having 1 to 15 carbon atoms, an alkenyl group, an alkylthioalkyl group, an aryl group, an alkylaryl group, an arylalkyl group, an alkoxyalkyl group, an aryloxyalkyl group,
When there are a plurality, they may be the same or different. R
¹ 'is hydrogen, an alkyl group, an alkenyl group, an alkoxy group,
Alkylthio group, alkylthioalkyl group, aryl group, alkylaryl group, arylalkyl group, alkylsulfinyl group, alkoxyalkyl group, aryloxyalkyl group, alkylsulfonyl group, alkoxycarbonyl group, carboxyl group, nitrile group, hydroxy group, nitro group Or a halogen, and when two or more are present, they may be the same or different. k is an integer of 1 to 5,
k ′ represents an integer of 0 to 4, and k + k ′ = 5. 3. A solid electrolyte for a solid electrolytic capacitor using the conductive organic polymer composition according to claim 1, wherein the dopant is represented by the formula (II). Embedded image In the formula, R ² represents an alkyl group having 5 to 20 carbon atoms, an alkenyl group, an alkylthioalkyl group, an aryl group, an alkylaryl group, an arylalkyl group, an alkoxyalkyl group, an aryloxyalkyl group, and p represents 1 to 5 Indicates an integer. 4. A solution containing at least one kind of the conductive organic polymer composition according to claim 1,
A method for producing a solid electrolyte for a solid electrolytic capacitor, wherein the method is applied on a metal having a dielectric oxide film formed thereon and dried. 5. A solid electrolytic capacitor using the solid electrolyte for a solid electrolytic capacitor according to claim 1.