JP2720550B2 - Highly conductive carbon and its composition - Google Patents

Description

The present invention relates to a highly conductive composition with highly conductive carbon and a dopant.

<Related Art> In recent years, it has been discovered that a complex compound of natural or artificial high-purity graphite and an electron acceptor or an electron donor (hereinafter referred to as a dopant) exhibits a conductivity as high as that of a metal. Has come to attract attention as a highly conductive material. This type of highly conductive carbon material has a highly developed graphite structure, and exhibits higher conductivity by forming a complex compound with a dopant.

On the other hand, from this viewpoint, attempts have been made to obtain a highly conductive carbon material which has been carbonized and further graphitized by heat treatment of a polymer.

Poly-p-phenylene vinylene (JP-A-60-11215,
JP-A-61-10016), aromatic poimide (JP-A-60-100)
-181129) is heat-treated at 2000 ° C or higher in an inert atmosphere, and the graphitization proceeds easily.
It is known that it becomes a highly conductive material exceeding 10 ⁴ S / cm, and further shows high conductivity exceeding 10 ⁵ S / cm by doping.

As described above, only polymers containing hydrocarbon, oxygen, and nitrogen have been known to be graphitized. These elements only desorb from the fired material during graphitization, and their actions are not known. In addition, treatment at about 3000 ° C. is required for graphitization.

<Problems to be Solved by the Invention> Graphitization of a sulfur-containing polymer having a catalytic action for graphitization has not been known.
In particular, polythienylenevinylene is known as a conductive polymer, but carbonization and graphitization are not known at all.

That is, the present invention diligently studied carbonization and graphitization of polythienylenevinylene and its derivative, and found that polythienylenevinylene and its derivative were graphitized, and reached the present invention.

<Means for Solving the Problems> The present invention provides a compound represented by the general formula (1): (R ₁ , R ₂ : hydrogen or a hydrocarbon group having 1 to 21 carbon atoms) High conductivity obtained by baking a conjugated polymer having a repeating unit represented by the formula below at a temperature of 400 ° C. or more in an inert atmosphere. Provided is a highly conductive composition containing carbon, and the highly conductive carbon and a dopant as essential components.

 Hereinafter, the present invention will be described in detail.

The method for synthesizing the polythierylenevinylene derivative represented by the general formula (1) used in the present invention is not particularly limited, but a sulfonium salt polymer intermediate which is a synthetic method capable of shaping into a useful form such as a film or a fiber. It is preferable to use a compound or via an intermediate of an alkoxy group polymer. In the method via a sulfonium salt polymer intermediate,
General formula (2) R ₃ , R ₄ : hydrogen or a hydrocarbon group having 1 to 20 carbon atoms, R ⁵ : a bifunctional hydrocarbon group having 4 to 20 carbon atoms, X ₁ ⁻ : a counter ion, and a disulfonium salt monomer represented by the following formula: Polymerized by the general formula (3) An intermediate polymer represented by the following formula is obtained. Further, in the method via an alkoxy group polymer intermediate, the sulfonium salt polymer intermediate represented by the general formula (3) is converted to an alcohol (R ₆
OH), and reacted with the general formula (4) To obtain an alkoxy group polymer intermediate represented by the formula: By subjecting the obtained polymer intermediate to desulfonium salt treatment or dealcoholation treatment in an inert atmosphere, a polythienylenevinylene derivative can be obtained.

In the formula, R ₁ and R ₂ are hydrogen or a hydrocarbon group having 1 to 20 carbon atoms, preferably hydrogen or an alkyl group having 1 to 6 carbon atoms, and specifically, hydrogen, methyl, ethyl and the like are preferable.

R ₃ and R ₄ are a hydrocarbon group having 1 to 10 carbon atoms, for example, methyl,
Ethyl, propyl, isopropyl, n-butyl, 2-ethylhexyl, phenyl, cyclohexyl, benzyl and the like are exemplified, and a hydrocarbon group having 1 to 6 carbon atoms, particularly methyl and ethyl, is preferred.

R ₅ is a bifunctional hydrocarbon group having 4 to 10 carbon atoms, for example, tetramethylene, pentamethylene, hexamethylene group and the like, and a hydrocarbon group having 4 to 6 carbon atoms, particularly tetramethylene, hexamethylene group is preferable. preferable.

Counterion X ₁ of sulfonium salts ^- can be used any of the conventional methods. For example, halogen, hydroxyl group, boron tetrafluoride, perchloric acid, carboxylic acid, sulfonic acid ion and the like can be used. Among them, chlorine, bromine,
Halogen ions such as iodine are preferred.

Examples of R ₆ of alcohol R ₆ OH used for converting the sulfonium salt polymer intermediate to the alkoxy group polymer intermediate include hydrocarbon groups having 1 to 10 carbon atoms, preferably hydrocarbons having 1 to 4 carbon atoms. Group.

By post-treating the polymer intermediate thus obtained, a polythienylenevinylene derivative can be produced.
The post-treatment of the polymer intermediate here is performed by applying conditions such as heat, light, ultraviolet light, strong base or acid treatment,
It means that a sulfonium salt side chain or a side chain substituted with a nucleophilic substituent is eliminated to form a conjugated structure, and heat treatment is particularly preferable.

The treatment of the polymer intermediate is preferably performed in an inert atmosphere. The term "inert atmosphere" used herein refers to an atmosphere that does not cause deterioration of the polymer during the treatment, and is generally performed using an inert gas such as nitrogen, argon, or helium. May be performed.

When performing post-treatment of the polymer intermediate by heat, treatment at an excessively high temperature results in decomposition of the conjugated polymer produced,
Since the formation reaction is slow and impractical at low temperatures, the heat treatment temperature is usually 0 to 400 ° C, preferably 100 to 320 ° C. The processing time can be appropriately selected depending on the processing temperature, but the range of 1 minute to 10 hours is industrially practical.

When the obtained polythienylenevinylene derivative is calcined at 400 ° C. or higher in an inert atmosphere, a highly inductive carbon material is obtained. The form of the polythienylenevinylene derivative may be a powder, a sheet, a film, a thread, or another molded product, but a film or a thread is preferred. Further, in these polymer molded articles, an oriented product subjected to an orientation treatment, more preferably a plane orientation treatment is preferred, and a polymer film substantially subjected to a biaxial stretching treatment is particularly preferred. The thickness of these polymer films is not particularly limited, but is usually 50 μm or less, more preferably 30 μm or less.

In the present invention, the heat treatment is performed at 400 ° C. or higher. Preferably 400 ~ 3500 ℃, more preferably 400 ~ 3300 ℃
It is. For graphitization, treatment at 2000 to 3300 ° C is preferred.

Although the treatment time is not particularly limited, it is preferable to appropriately select such that the carbonization of the polythienylenevinylene derivative and graphitization are sufficiently achieved in consideration of the heat treatment temperature,
Usually, 5 minutes to 10 hours are exemplified, but 5 minutes to 2 hours are industrially preferable.

These polythienylenevinylene derivatives can be subjected to heat treatment as they are, but before heat treatment at 1500 ° C. or higher, heat treatment (hereinafter referred to as pretreatment) may be performed in advance under specific conditions. The pretreatment is performed by heating polythienylenevinylene in an inert atmosphere such as nitrogen or argon
It is carried out at a temperature of 11500 ° C., more preferably 700-1500 ° C.

Further, in the pretreatment, when the temperature of the polythienylenevinylene is raised to the temperature of the pretreatment, the temperature is higher than the temperature at which the polymer starts to decompose, for example, at about 400 ° C or higher, 1 ° C / minute or higher, preferably 5 ° C / minute. Preferably, the temperature is raised to the temperature of the pretreatment at the above-mentioned high speed, and if the temperature is raised at a rate of 1 ° C./min or less, the fired product is likely to be foamed.

The inert atmosphere referred to in the present invention refers to an atmosphere that does not react with the fired material in the process of carbonization and graphitization, and examples thereof include a gas such as nitrogen, argon, and helium and a vacuum. Preferably, nitrogen or vacuum is used at 1500 ° C or lower, and argon gas is used at 1500 ° C or higher.

The conductivity of the calcined product is further improved by doping treatment with an electron acceptor or an electron donor, and 10 ³ to 10 ⁵
Reaches S / cm or more. The dopant is not particularly limited, but a compound in which high conductivity has been found in conventional conjugated polymers such as graphite or polyacetylene or polypyrrole can be used effectively.

The doping method can be implemented by a known method, that is, a method of directly contacting a dopant with a dopant in a gas phase or a liquid phase, an electrochemical method, ion implantation, or the like.

Specifically, examples of electron acceptors include halogens such as bromine and iodine, and Lewis acids such as iron trichloride, arsenic pentafluoride, antimony pentafluoride, boron trifluoride, sulfur trioxide, aluminum trichloride, and antimony pentachloride. , Nitric acid, sulfuric acid, chlorosulfonic acid and other protic acids, and electron acceptors such as alkali metals such as lithium, potassium, rubidium and cesium; alkaline earth metals such as calcium, strontium and barium; and other rare earth metals ( Sm, Eu, Yb), metal amides such as potassium amide and calcium amide. Although the amount of doping is not particularly limited, a preferable content is 0.1% to 150%, particularly 10% by weight of the heat-treated product.
% To 100%.

<Effect of the Invention> As described above, according to the present invention, a high-quality high-conductivity carbon material can be obtained, and according to the present invention, a high-conductivity high-conductivity carbon material having various shapes applicable to electric and electronic materials. A carbonaceous material is provided.

<Examples> The present invention will be described in more detail in the following examples, but the present invention is not limited thereto.

Example 1 2,5-thienylene-bis (methylenedimethylsulfonium)
75 g of ion-exchanged water and methanol mixed solvent
(Volume ratio 1: 1) After dissolving in 1600 ml, 1N NaOH
A mixed solution of 110 ml and methanol 800 ml is −40 ° C. to −30 ° C.
At -40 ° C to -30 ° C for 90 minutes.
Stirring was continued. After neutralizing the reaction solution, quickly dialyze
(Cello tube , Molecular weight fractionation 8000, union carbide
Ice-cooled water-methanol mixed solvent (1:
0.2) dialysis treatment for 1 day
A yellow precipitate formed within. The precipitate is separated and
After dissolving in luacetamide, cast and under a nitrogen stream
To obtain a precursor film. Cut this into 4cm x 4cm
And fix it to a metal frame, and use a horizontal tubular electric furnace in an atmosphere of nitrogen gas.
Heat treatment was performed in the air at 250 ° C. for 2 hours. The resulting film structure
From the infrared absorption spectrum, poly-2,5-thienylene
It was confirmed to be vinylene.

The obtained poly-2,5-thienylene vinylene film was heated to 950 ° C. at a rate of 10 ° C./min in a nitrogen gas atmosphere in a horizontal tubular electric furnace, and pre-baked for one hour. After cooling to room temperature, the temperature was raised from room temperature to 2900 ° C. over 1.5 hours in an argon gas atmosphere using a graphite heating element Tamman furnace, and kept at 2900 ° C. for 30 minutes to perform heat treatment. The resulting heat-treated product was a film having a thickness of about 9 μm, and the surface had a metallic luster. The Raman spectrum of this film was measured using an argon laser (wavelength: 514.5 nm) as a light source and a JASCO R-800 type Raman spectrophotometer. The Raman spectrum of this film showed strong scattering at 1590 cm ^{-1 due} to the graphite structure. The electric conductivity of the obtained heat-treated film was 7 × 10 ³ S / cm. Doping with nitric acid showed an electrical conductivity of 1.1 × 10 ⁵ S / cm.

Example 2 When the heat-treated film obtained in Example 1 was doped with SO ₃ from a gas phase by a conventional method, an electric conductivity of 1.0 × 10 ⁵ S / cm was exhibited.

Example 3 The poly-2,5-thienylenevinylene film obtained in Example 1 was placed in a horizontal tubular electric furnace at 10 ° C. in an atmosphere of nitrogen gas.
The temperature was raised to 730 ° C. at a heating rate of / min, and calcination was performed at that temperature for 10 minutes. After cooling to room temperature, using a graphite heating element Tamman furnace, 1050 ° C, 80
The temperature was raised to 2200 ° C. for 2 minutes, 2800 ° C. for 90 minutes, and 2900 ° C. for 20 minutes, followed by baking at 2900 ° C. for 30 minutes. The obtained heat-treated product was a film having a thickness of about 8 μm, and the surface had a metallic luster. The electric conductivity of the obtained heat-treated film is 7.8 × 10 ³ S /
cm. When this is doped with nitric acid, 1.1 × 10 ⁵ S /
cm conductivity.

Example 4 The poly-2,5-thienylenevinylene film obtained in Example 1 was placed in a horizontal tubular electric furnace at 10 ° C. in an atmosphere of nitrogen gas.
The temperature was raised to 910 ° C. at a heating rate of / min, followed by firing at 910 ° C. for 10 minutes. The resulting heat-treated product was a film having a thickness of about 5 μm, and the surface had a metallic luster. The electric conductivity of the obtained heat-treated film was 4.1 × 10 ¹ S / cm.

Example 5 The poly-2,5-thienylenevinylene precursor film obtained in Example 1 was heated in a horizontal tubular electric furnace in a nitrogen gas atmosphere to a heating rate of 10 ° C./min, and then heated at 730 ° C. Pre-baked for 10 minutes. After cooling to room temperature, using a graphite heating element Tamman furnace, 1050 from room temperature in 55 minutes in an argon gas atmosphere.
The temperature was raised to 2200 ° C. for 80 minutes, 2800 ° C. for 90 minutes, and 2900 ° C. for 20 minutes, followed by baking at 2900 ° C. for 30 minutes. The obtained heat-treated product was a film having a thickness of about 120 μm, and the surface had a metallic luster. The electrical conductivity of the obtained heat-treated film was 3.1.
× 10 ² S / cm.

Claims (2)

(57) [Claims] (1) General formula (R ₁ , R ₂ : hydrogen or a hydrocarbon group having 1 to 21 carbon atoms) High conductivity obtained by baking a conjugated polymer having a repeating unit represented by the formula below at a temperature of 400 ° C. or more in an inert atmosphere. carbon. 2. The general formula (R ₁ , R ₂ : hydrogen or a hydrocarbon group having 1 to 21 carbon atoms) High conductivity obtained by baking a conjugated polymer having a repeating unit represented by the formula below at a temperature of 400 ° C. or more in an inert atmosphere. A highly conductive composition containing carbon and a dopant as essential components.