JPH0689140B2 - Method for manufacturing conductive composite material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a conductive composite material, and more specifically,
The present invention relates to a method for producing a conductive composite material containing a conductive organic polymer as a chemically oxidized polymer of aniline or a derivative thereof and carbon black.

2. Description of the Related Art A group of electrically conductive organic polymers known as organic semiconductors have been attracting attention in recent years. However, most of them are chemically unstable, which hinders practical applications.

Therefore, as a result of intensive studies on the oxidative polymerization of aniline or a derivative thereof in order to obtain a stable and highly conductive organic polymer, the present inventors have selected a reaction condition for the oxidative polymerization. Then, since it has a high molecular weight and is already doped in the oxidative polymerization stage, it is possible to obtain a stable and highly conductive organic polymer without requiring a new doping operation. Heading (JP-A-60-197728, JP-A-60-148012, etc.), and thereafter, the conductive organic polymer has a substantially linear high molecular weight polymer having a quinonediimine structure as a main repeating unit. It has been found that
-198873).

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present inventors have earnestly studied to obtain a material having higher conductivity containing the above-mentioned conductive organic polymer, and as a result, aniline,
By coexisting with carbon black when chemically oxidatively polymerizing a derivative or a salt thereof with an oxidizing agent, a novel conductive composite material having a higher conductivity than the conductivity of each of them can be obtained. The present invention has been made by discovering that the above can be achieved.

Therefore, it is an object of the present invention to provide a method for manufacturing a novel conductive composite material.

Means for Solving the Problems A method for manufacturing a conductive composite material according to the present invention is
The derivative or a salt thereof is oxidatively polymerized with an oxidizing agent in the presence of carbon black in a solvent, contains an electron acceptor as a dopant, and has a conductivity of 10 ^-6 S / cm or more. It is characterized by precipitating coalescence.

As the aniline derivative used in the present invention, alkylaniline such as o-methylaniline, m-methylaniline, o-ethylaniline and m-ethylaniline is preferably used. The salt of aniline and its derivative is not particularly limited as long as it dissolves in the solvent used. For example, when the solvent is water, a water-soluble salt of an inorganic acid is preferably used. Usually, mineral acid salts such as hydrochloric acid and sulfuric acid are suitable, but not limited to these. Among aniline and these alkylanilines, aniline which gives a highly conductive polymer is particularly preferably used.

In the method of the present invention, the oxidizing agent is an oxidizing agent having a standard electrode potential of 0.6 V or more determined by a reduction process as a standard hydrogen electrode so that a highly conductive high molecular weight organic polymer can be obtained. A proton donor is used, if necessary.

Generally, the standard electrode potential is known as an index showing the strength of the oxidizing power of an oxidant. This standard electrode potential is defined as a half-cell composed of electrodes that accept electrons from an external circuit when the oxidant obtains electrons from the oxidant and is reduced by itself. Refers to the magnitude of electromotive force, and thus the standard electrode potential can be used to quantify the oxidizing power of the oxidant. As is well known in the field of electrochemistry, as a reference electrode for such a standard electrode potential, the hydrogen pressure is 1 atm, and the hydrogen ion activity in the solution is the unit activity. A standard hydrogen electrode is used, and the standard electrode potential is determined by setting the potential of the standard hydrogen electrode to 0V.

In the present invention, this standard electrode potential is defined as the electromotive force in the reduction half-cell reaction based on the standard hydrogen electrode.

That is, in general, the oxidant Ox obtains an electron e ⁻ and the oxidant itself becomes a reducing agent.
The electrode reaction E for red, Ox + ne ⁻¹ → Red, is given by the following Nernst equation, where the standard electrode potential is E ⁰ .

(However, F is the Faraday constant, n is the number of electrons involved in the reaction, a is the activity, R is the gas constant, and T is the absolute temperature.) Here, the standard state in which all the activities a are 1. In, the logarithmic term in the above equation is 0, and E = E ⁰ . That is, the electrode potential E is equal to the standard electrode potential E ⁰ .

Strictly speaking, the potential of the oxidizing agent in the reaction system under the actual oxidative polymerization condition needs to be calculated in consideration of the logarithmic term including the activity according to the above Nernst equation, but the method of the present invention is used. In order to select an oxidant, since the order of the oxidizing power of the oxidant substantially matches the order of this standard electrode potential, the standard state potential not including the activity term, that is, the standard electrode potential is used. However, there is practically no problem.

In the method of the present invention, the standard electrode potential is Cr ₂ O ₇
^In the case where protons participate in the reduction half-cell reaction as in ^2-, the standard electrode potential in the reactions involving protons shall be used, and in the reaction of oxidative polymerization of aniline or a derivative thereof, the required amount or A proton donor that supplies more protons, typically a protic acid such as sulfuric acid or hydrochloric acid, is allowed to exist. On the contrary, peroxosulfates and cerium (IV) salts do not involve protons in their reduction half-cell reactions. Therefore, when these are used as an oxidizing agent in the method of the present invention, it is not necessary to allow a proton donor to be present in the reaction system, however, there is no problem in allowing a proton donor to be present in the reaction system, and In order to impart high conductivity to the organic polymer obtained by the reaction, it may be preferable to allow a proton donor to be present.

Such a standard electrode potential is, for example, "CRC Handbook of Chemistry and Physics" (CRC
C Press Co.) D-155 to D-160 and "Electrochemical Handbook" edited by The Electrochemical Society of Japan (Maruzen Co., Ltd.), pp. 71-74.

Further, in the method of the present invention, when an oxidizing agent having a high standard electrode potential is used, it is desirable to select and use a protonic acid. For example, when using an oxidizing agent having a standard electrode potential higher than that of chlorine and bromine whose standard electrode potentials are 1.36 V and 1.09 V, respectively, when using hydrochloric acid or hydrobromic acid as a protic acid, 2 Cl _{^{- → Cl 2 + 2e - 2Br}} - → Br 2 + 2e - made reaction occurs in preference to the oxidation of aniline and its derivatives, since conductivity and yield of the obtained conductive organic polymer is low, as a proton acid It is preferable to use sulfuric acid.

Table 1 shows the reduction half-cell reaction of various oxidizing agents at 25 ° C. and its standard electrode potential, applicability in the method of the present invention, and the conductivity of the obtained conductive organic polymer by oxidative polymerization of aniline. In the oxidative polymerization shown in Table 1, it is easier to obtain a highly conductive polymer when a protic acid is present in the reaction system. Prepare an aqueous solution and use this aniline hydrochloride Is oxidatively polymerized with an oxidizing agent shown in the table in the absence of carbon black, to obtain a molded product obtained by compression-molding the powdery conductive organic polymer thus obtained. Each was measured.

From the above results, it is understood that a conductive organic polymer having an electric conductivity of 10 ⁻⁶ S / cm or more can be obtained by using an oxidizing agent having a standard electrode potential of 0.6 V or more.

In the present invention, a particularly preferred method is to dissolve aniline, a derivative thereof or a salt thereof in a solvent, add carbon black to this solution and mix them uniformly, and then gradually add a solution of an oxidant to this mixture. Then, the aniline or the like is oxidatively polymerized. However, the solution of the oxidizing agent may be added at once to the mixture containing aniline and the like and carbon black. Further, a solution in which aniline, a derivative thereof or a salt thereof is dissolved in a mixture containing an oxidizing agent and carbon black may be added. As described above, when it is necessary to allow a proton donor to be present in the reaction system,
It may be contained in a solution of aniline or a derivative thereof and / or an oxidant solution.

The deposition rate or polymerization rate of the conductive organic polymer based on the oxidative polymerization of aniline or the like varies depending on the oxidizing agent. Generally, the higher the standard electrode potential of the oxidant used, the faster the polymerization rate and the shorter the induction period. However, strictly speaking, the order of the standard electrode potential does not match. That is, even if the standard electrode potential is high, some oxidants have a long induction period,
Despite the high standard electrode potential, the oxidant alone is unlikely to cause oxidative polymerization of aniline or its derivatives,
In some oxidants, the addition of a small amount of catalyst initiates the polymerization immediately and the reaction rate is significantly faster. Examples of such an oxidizing agent include chlorate and hydrogen peroxide. When the oxidizing agent is a perchlorate, suitable catalysts are, for example, cupric chloride, vanadium trichloride, ammonium metavanadate and the like.

Examples of the oxidizing agent having a relatively long induction period, that is, a period before the oxidative polymer of aniline or a derivative thereof is substantially precipitated include peroxosulfate.
This oxidant has a relatively long induction period,
After the polymerization is started, the production rate of the polymer is high, and the polymerization is completed in a short time. Therefore, it is one of the oxidizing agents that can be preferably used in the present invention.

In the method of the present invention, the deposition rate of the conductive organic polymer also depends on the concentration of aniline or its derivative as a monomer and the concentration of an oxidizing agent. In general, the higher their concentration, the higher the deposition rate. Generally, the concentration of the solution of aniline or its derivative is 0.1 to 90% by weight, preferably 0.5 to 50% by weight, particularly preferably 1 to 20% by weight.
% By weight. The same applies to the concentration of the oxidant solution.

In the method of the present invention, the carbon black is usually used in the range of 1 to 200 parts by weight with respect to 100 parts by weight of aniline, a derivative thereof or a salt thereof, but is not limited thereto. Absent. Further, the carbon black is not particularly limited, and any carbon black can be used. For example, as commercially available carbon black, acetylene black (manufactured by Denki Kagaku Co., Ltd.), Vulcan XC-
Examples include 72 (manufactured by Cabobot), Ketchien Brack (manufactured by Akzo), Condite Tex # 975 (manufactured by Colombian Carbon Co.), and Seast-S (manufactured by Tokai Carbon Co., Ltd.).

In the method of the present invention, the solvent may be water, a water-miscible organic solvent, or a mixture of two or more water-immiscible organic solvents, and a water-soluble salt of aniline or alkylaniline is used. At this time, water, a water-miscible organic solvent, or a mixture thereof is usually used as the solvent. In this case, the oxidizing agent used is also preferably dissolved in these solvents. When aniline or alkylaniline itself is used, as the solvent, a water-miscible organic solvent or a water-immiscible organic solvent that dissolves them is used. In addition, it is necessary that none of the above organic solvents is oxidized by the oxidizing agent used.
For example, as the water-miscible organic solvent, acetone, tetrahydrofuran, ketones such as acetic acid, ethers, glycols, cellosolves, nitriles such as acetonitrile, or organic acids are used, and water-immiscible organic solvent. As the solvent, chloroform, carbon tetrachloride, hydrocarbon or the like is used. In the present invention, as described above, the solvent preferably dissolves both aniline or a derivative thereof and the oxidizing agent, but the present invention does not exclude the reaction in a heterogeneous system.

The reaction temperature is not particularly limited as long as it is equal to or lower than the boiling point of the solvent, but as the reaction temperature becomes higher, the conductivity of the resulting oxidized polymer tends to decrease, so from the viewpoint of obtaining a polymer having high conductivity. It is preferably at room temperature or lower.

In the method of the present invention, the conductive organic polymer is usually precipitated after the induction period of about several minutes to several hours after the initiation of the reaction. After completion of the reaction, the mixture may be stirred for a few minutes to several hours for aging. Then, the reaction product containing the conductive organic polymer and the carbon black is filtered off, washed with water, washed with an organic solvent such as acetone if necessary, and vacuum dried to obtain a conductive composite material according to the present invention. Can be obtained.

The conductive organic polymer contained in the conductive composite material according to the present invention has the general formula (Wherein R represents hydrogen or an alkyl group), which is a substantially linear polymer having a quinonediimine structure represented by the following as a main repeating unit and polymerized by an electron acceptor present in the reaction system. A polymer which has already been doped, and a conductive organic polymer containing such an electron acceptor as a dopant has a conductivity of 10 ^-6 S / cm.
That is all.

The conductive organic polymer itself, in the dry state, usually exhibits a green to black green, generally higher conductivity,
It has a bright green color. However, when the powder is pressed, it usually exhibits a glossy blue color.

The conductive organic polymer is insoluble in water and most organic solvents, but usually contains a part that is slightly soluble in concentrated sulfuric acid or that is soluble therein. The solubility in concentrated sulfuric acid varies depending on the reaction method and reaction conditions for producing a polymer, but as will be described later, aniline, a derivative thereof or a salt thereof is oxidatively polymerized with a predetermined chemical oxidizing agent. The conductive organic polymer obtained is usually in the range of 0.2 to 10% by weight, and in most cases in the range of 0.25 to 5% by weight. However, this solubility should be understood as including a portion having a solubility in the above range, particularly in the case of a high molecular weight polymer.

Furthermore, the above conductive organic polymer is 0.5 g / dl of 97% concentrated sulfuric acid.
The solution has an inherent viscosity in the range of 0.1 to 1.0 at 30 ° C,
In most cases, it is 0.2 to 0.6. In this case as well, especially in the case of high molecular weight polymers, it should be understood that the portion soluble in concentrated sulfuric acid has a logarithmic viscosity in the above range.

In addition, the conductive organic polymer is doped with an electron acceptor existing in the system at the stage of oxidative polymerization of aniline or a derivative thereof, and as a result, has high conductivity. That is, charge transfer from the polymer to the electron acceptor occurs, forming a charge transfer complex between the polymer and the electron acceptor.

As the dopant contained in the conductive organic polymer, for example, halogen such as chlorine, bromine, iodine, ferric chloride, tin tetrachloride, Lewis acid such as copper dichloride, hydrogen chloride, hydrogen bromide, sulfuric acid, nitric acid. Examples thereof include inorganic acids such as, and organic acids such as picric acid and p-toluenesulfonic acid, but are not limited thereto.

In the method of the present invention, when aniline, a derivative thereof or a salt thereof is oxidatively polymerized in a solvent with an oxidizing agent, aniline or the like is oxidized by the oxidizing agent to generate a cation radical, which is radical coupled. It is believed to form a conductive organic polymer. On the other hand, it is known that the surface of the carbon black particles has phenolic hydroxyl group, quinone type oxygen, carboxyl group, lactone ring and the like, and among these functional groups, the phenolic hydroxyl group and quinone type oxygen are In general, when radical polymerization of a vinyl monomer is prohibited or delayed, and when the vinyl monomer is radically polymerized in the presence of carbon black, the growing radicals of the vinyl monomer cause the radicals of the surface of the carbon black to grow. It is also known to carry out chain transfer by chain transfer to a functional group or a radical derived therefrom.

Therefore, the present invention is not limited by any theory, but when carbon black is present in the reaction system, the growing cation radical is a functional group on the carbon black or a radical and a radical derived therefrom. Reacting, the growth radical undergoes a grafting reaction on the carbon black, as a result of forming a complex of at least a part of the resulting conductive organic polymer and carbon black,
According to the present invention, it is possible to obtain a conductive composite material having higher conductivity than both carbon black and oxidized polymer. However, in the present invention, it is acceptable that the resulting conductive composite material contains a free conductive organic polymer or a free carbon black.

In the conductive composite material according to the present invention, it is considered to be the result of chain transfer reaction or grafting reaction of such growing radicals to carbon black. In the absence of carbon black, aniline, a derivative thereof or a salt thereof is chemically oxidized and polymerized. It was observed that the degree of polymerization of the conductive organic polymer in the composite material was somewhat lower than that of the resulting conductive organic polymer, while the composite material had a high conductivity.

The degree of polymerization of the conductive organic polymer in the conductive composite material obtained by the method of the present invention, the degree of polymerization of the conductive organic polymer obtained by oxidative polymerization of aniline and the like in the absence of carbon black, In their infrared absorption spectra, a qualitative comparison can be made from the absorbance ratio of 740 cm ^-1 to 810 cm ^-1 . That is, the conductive organic polymer as an oxidative polymer of aniline has an absorption at 810 cm ^-1 based on the C-H out-of-plane bending vibration of para-substituted benzene in the infrared absorption spectrum and the C- of mono-substituted benzene. It has absorption at 740 cm ^-1 due to the out-of-plane bending vibration. Therefore, 810
absorbance ratio of 740 cm ^-1 with respect cm ^-1 can be used as an index of the polymerization degree of the conductive composite material of the conductive organic polymer or conductive obtained in the absence of carbon black organic polymer, The larger the above ratio, the smaller the degree of polymerization of the conductive organic polymer.

Generally, for a conductive composite material according to the method of the present invention,
740 for 810 cm ^-1 in the infrared absorption spectrum
The absorbance ratio at cm ⁻¹ is 0.02 to 2, preferably 0.04 to ¹ , and the electrical conductivity is 5 S / cm or more.

In particular, according to the method of the present invention, the carbon black to be used is treated with an oxidizing agent in advance to increase the amount of radicals contained in the carbon black, whereby the conductive organic polymer is grafted onto the carbon black. However, it is possible to obtain a conductive composite material having a higher conductivity.

Effects of the Invention As described above, according to the present invention, by conducting oxidative polymerization of aniline, a derivative thereof, or a salt thereof in the presence of carbon black, a conductive organic polymer composed of an oxidative polymer such as aniline is obtained. It is possible to obtain a conductive material containing a coalesce and a carbon black and having an electric conductivity higher than that of both the polymer and the carbon black.

The electroconductive material thus obtained has high electroconductivity without requiring a new doping operation, and even if it is left in the air for a long period of time, its electroconductivity does not change at all. In contrast, it has a particularly high stability as compared with the conventionally known conductive materials.

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

(Production of conductive composite material) 52 g of distilled water was put into a glass reaction vessel with a capacity of 200 ml, and while cooling with ice water, 97% sulfuric acid 15% with stirring with a magnetic stirrer.
g was added. Next, when 52 g of acetic acid was added thereto and 2.79 g of aniline was added thereto, a white solid of aniline sulfate was temporarily precipitated, but it was dissolved by continuing stirring. After adding 0.29 g (10 parts by weight to 100 parts by weight of aniline) of Ketjenblack EC (manufactured by Akzo) as a carbon black to the aqueous solution of aniline salt, the reaction vessel was placed in an ultrasonic cleaner bath for 10 minutes. Ultrasonic dispersion was performed.

Then, while stirring the inside of the reaction vessel with a magnetic stirrer, the temperature of the mixture in the vessel was maintained at 5 to 8 ° C. in an ice water bath, and 6.85 g of ammonium peroxodisulfate powder was added little by little to this. The reaction mixture initially remained colorless except for the carbon black, but after about 8 minutes it turned black-green, 2 minutes later it turned blue and 2 minutes later it turned black-green, then Exhibited the same color.

After this, stirring was continued for another hour and the reaction mixture was adjusted to 400 m.
It was put into 1 l of acetone with stirring, and a solid substance was separated by suction filtration. Evaporation of acetone from this solid gave a bright green solid. No black color of carbon black was observed. After repeating washing with water and washing with acetone, the resultant was vacuum dried over phosphorus pentoxide.

Next, 0.87 g of the same carbon black as above (30 parts by weight to 100 parts by weight of aniline) was added to the oxidative polymerization system of aniline, or aniline was oxidatively polymerized by the same method as above without adding carbon black. Then, when each carbon black is present in an amount of 30 parts by weight with respect to aniline,
Also, samples of the conductive composite material and the conductive organic polymer alone in the absence of carbon black were obtained.

(Hydrogen peroxide treatment of carbon black) Next, the amount of radicals measured by ESR (electron spin resonance)
The hydrogen peroxide treatment of a carbon black (Ketchien Black EC) of 4.2 × 10 ¹⁶ spins / g will be described.

50 ml of acetic acid and 50 ml of 35% hydrogen peroxide in a 200 ml flask.
After adding 1.5 g of Ketjenbruck EC under stirring with a magnetic stirrer, 5 g of 97% sulfuric acid was added little by little to this. Upon the addition of this sulfuric acid, the reaction mixture began to bubble and exotherm, raising the temperature to about 40 ° C. After cooling the reaction mixture on a water bath, stirring was continued for 2 hours and then left overnight. Then, the solid matter was filtered off, washed with water and washed with acetone repeatedly, and then dried in vacuum.

As a result of ESR measurement, the carbon black treated with hydrogen peroxide had a radical amount of 2.4 × 10 ¹⁹ spins / g.

Using this hydrogen peroxide-treated carbon black, aniline was oxidatively polymerized by the same method as described above.

(Measurement of Physical Properties and Spectra) With respect to each conductive composite material according to the present invention obtained as described above, the electric conductivity and the infrared absorption spectrum were measured.

Conductivity measurement The pressure of the sample was 6000 Kg / cm ^{2 with a} tableting machine for infrared spectrophotometer.
Was formed into a disk having a diameter of 13 mm, and four copper foils having a width of about 1 mm were adhered to the four corners of the disk with silver paste, and the measurement was performed in air according to the Juan der Pauw method.

Infrared absorption spectrum Measured by the KBr method.

Measurement of ESR spectrum The sample powder was put into a quartz sample tube having an inner diameter of 4 mm, and measurement was performed using an electron spin resonance device JES-FE1XG manufactured by JEOL Ltd.

Measurement of spin concentration ESR peak area and ESR of sample containing 10 μl of 4-hydroxy-2,2,6,6-tetramethylpiperidinooxyl (10 ^-4 mol / l) with known spin number ESR data processor ES-FM11 manufactured by JEOL Ltd. based on peak area ratio
Was calculated using. The ESR peak area was obtained by double integration of the differential ESR spectrum using a data processor.

The results obtained as described above will be described below.

First, Table 2 shows the conductivity of the conductive composite material or conductive organic polymer alone obtained by oxidatively polymerizing aniline in the presence or absence of carbon black.
By conducting oxidative polymerization of aniline in the presence of carbon black, it is possible to obtain a conductive composite material having higher conductivity than both of the conductive organic polymer obtained by oxidative polymerization of carbon black and aniline.

Next, in Table 3, the conductive composite material or the conductive organic polymer according to the present invention obtained by oxidatively polymerizing aniline in the presence or absence of carbon black is 740 cm against 810 cm ^-1 in the infrared absorption spectrum of the conductive organic polymer alone. The absorbance ratio of ^-1 is shown.

As shown in Table 3, in the oxidative polymerization of aniline, the larger the amount of carbon black present, the larger the absorbance ratio, and the degree of polymerization of the conductive organic polymer. Is shown to be small. Therefore, it is considered that, in the presence of carbon black, the oxidized polymer radical of aniline causes a chain transfer reaction to carbon black.

Next, the Ketchien Black EC is treated with hydrogen peroxide to increase the amount of radicals, Aniline was reinforced and polymerized in the presence of a blank to obtain a conductive composite material according to the present invention. In Table 4, the amount of radicals contained in the carbon black, the conductivity of the obtained conductive composite material, and the above-mentioned 810 cm in the infrared absorption spectrum are shown.
The absorbance ratio of 740 cm ^-1 to ^-1 is shown. The radical amount of carbon black is shown by the spin concentration measured by ESR.

From the results shown in Table 4, it is recognized that as the radical amount of the carbon black increases, the conductivity of the conductive composite material obtained increases and at the same time, the polymerization degree of the conductive organic polymer decreases. Therefore, it is shown that as the carbon black used has a larger amount of radicals, the reaction between the cation radical and the carbon black is promoted by the oxidation of aniline, and the grafting of the conductive organic polymer to the carbon black is increased.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nao Ichise 1-2-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto Denki Kogyo Co., Ltd. (56) Reference JP-A-59-75943 (JP, A)

Claims (3)

[Claims] 1. An aniline, a derivative thereof, or a salt thereof is oxidatively polymerized in a solvent in the presence of carbon black with an oxidizing agent to contain an electron acceptor as a dopant.
A method for producing a conductive composite material, which comprises depositing a conductive organic polymer having an electric conductivity of 10 ^-6 S / cm or more. 2. The method for producing a conductive composite material according to claim 1, wherein the carbon black is previously treated with an oxidizing agent. 3. The infrared absorption spectrum of the conductive composite material, wherein the absorbance ratio of 740 cm ⁻¹ to 810 cm ⁻¹ is 0.02 to 2, and the electrical conductivity is 5 S / cm or more. A method for producing a conductive composite material according to item 1.