阅读说明：本技术 石墨的制造方法以及制造装置 (Method and apparatus for producing graphite ) 是由 小铁贵广 饭塚直人 木村俊彦 于 2020-01-20 设计创作，主要内容包括：在制造更高品质的石墨的石墨的制造方法中,在将加热炉内的最高温度设为2900℃以上时,加热器与石墨容器之间发生放电,无法高效地将电力转化为电加热器的热。本发明的目的在于,提供用于制造更高品质的石墨的石墨的制造方法。在石墨化工序中,将石墨容器与加热器的距离设为特定的长度范围,将加热炉内的气体设为包含氦气的气氛,将加热炉内加热而使得最高温度为2900℃以上,由此可得到热扩散率更高的石墨。(In a method for producing graphite for producing higher-quality graphite, when the maximum temperature in a heating furnace is set to 2900 ℃ or higher, electric discharge occurs between a heater and a graphite container, and electric power cannot be efficiently converted into heat of an electric heater. The purpose of the present invention is to provide a method for producing graphite of higher quality. In the graphitization step, graphite having a higher thermal diffusivity can be obtained by setting the distance between the graphite container and the heater to a specific length range, setting the gas in the heating furnace to an atmosphere containing helium, and heating the inside of the heating furnace so that the maximum temperature becomes 2900 ℃ or higher.)

1. A method of making graphite, comprising:

a graphitization step of graphitizing the carbide placed in the graphite container in a heating furnace provided with a gas supply device and a heater to obtain graphite,

in the above-mentioned graphitization step,

(i) the graphite container is disposed at a position having a shortest distance of more than 5mm and less than 50mm from the heater,

(ii) the gas in the heating furnace is made to be the following atmosphere: the helium gas content is more than 0 mol% and 100 mol% or less, assuming that the total amount is 100 mol%,

(iii) and heating the inside of the heating furnace to a maximum temperature of 2900 ℃ or higher, and heat-treating the carbide.

2. The method for producing graphite according to claim 1, wherein the graphite container is provided at a position where a shortest distance from the heater is 20mm or more and 30mm or less.

3. The method for producing graphite according to claim 1 or claim 2, wherein the gas in the heating furnace is made to be an atmosphere of: the helium gas content is 10 mol% or more and 70 mol% or less, assuming that the total amount is 100 mol%.

4. A graphite production apparatus comprising a heating furnace for graphitizing a carbide placed in a graphite container,

the heating furnace is provided with: a housing, a heating furnace main body, a power supply part made of graphite, and a heater made of graphite,

the heating furnace main body is also provided with a gas inlet pipe and a gas outlet pipe for introducing inert gas into the heating furnace main body,

the graphite container is disposed at a position where the shortest distance from the heater is greater than 5mm and less than 50 mm.

5. The graphite production apparatus according to claim 4, wherein the graphite container is provided at a position where a shortest distance from the heater is 20mm or more and 30mm or less.

6. The apparatus for producing graphite according to claim 4 or 5, wherein the gas introduction pipe and the gas discharge pipe are configured to make the gas in the heating furnace have an atmosphere of: the helium gas content is 10 mol% or more and 70 mol% or less, assuming that the total amount is 100 mol%.

Technical Field

The present invention relates to a method and an apparatus for producing graphite.

Background

Graphite is produced, for example, from a polymer material through a carbonization step and a graphitization step. In the carbonization step, a polymer material placed in a graphite container is charged into a heating furnace, and carbonized at a temperature of about 1400 ℃ under reduced pressure, vacuum or nitrogen atmosphere in the heating furnace to obtain a carbide. In the graphitization step, the graphite container containing the obtained carbide is graphitized in argon gas at a temperature of 2500 ℃ or higher at the maximum temperature to obtain graphite.

Patent document 1 describes a heating furnace in which helium gas or argon gas is used for each member of the heating furnace depending on the purpose of the member.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication "Japanese patent application laid-open No. 2004-132587"

Disclosure of Invention

Problems to be solved by the invention

It is known that in order to obtain high-quality graphite, for example, graphite having a higher thermal diffusivity and a high heat dissipation property, the highest temperature in the graphitization step is preferably high. However, the present inventors have found that a large-scale production of graphite having an internal volume of more than 2m is possible to obtain high-quality graphite³When the maximum temperature of such a large heating furnace is raised to 2900 ℃ or higher, electric discharge may occur between the heater and the graphite container, and it may be impossible to efficiently convert electric power into heat of the electric heater.

That is, the present inventors independently found the following new problems: in the conventional method for producing graphite of higher quality, when the maximum temperature in the heating furnace is set to 2900 ℃ or higher, electric discharge occurs between the heater and the graphite container, and it is sometimes impossible to efficiently convert electric power into heat of the electric heater.

The present invention aims to provide a method and an apparatus for producing graphite having a high thermal diffusivity by suppressing discharge between a heater and a graphite container in a heating furnace.

Means for solving the problems

The present invention relates to the following method for producing graphite.

[1] A method of making graphite, comprising: a graphitization step of graphitizing a carbide placed in a graphite container in a heating furnace provided with a gas supply device and a heater to obtain graphite, wherein in the graphitization step, (i) the graphite container is provided at a position where a shortest distance from the heater is more than 5mm and less than 50mm, and (ii) a gas in the heating furnace is made to be an atmosphere of: (ii) a helium gas content of more than 0 mol% and not more than 100 mol% when the total amount is 100 mol%, (iii) heating the inside of the heating furnace so that the maximum temperature is 2900 ℃ or more, and heat-treating the carbide.

[2] The method for producing graphite according to item [1], wherein the graphite container is provided at a position where a shortest distance from the heater is 20mm or more and 30mm or less.

[3] The method for producing graphite according to [1] or [2], wherein the gas in the heating furnace is made to be an atmosphere of: the helium gas content is 10 mol% or more and 70 mol% or less, assuming that the total amount is 100 mol%.

The present invention also relates to the following graphite production apparatus.

[4] A graphite production apparatus comprising a heating furnace for graphitizing a carbide placed in a graphite container, the heating furnace comprising: the heating furnace comprises a casing, a heating furnace main body, a graphite power supply part and a graphite heater, wherein the heating furnace main body is also provided with a gas inlet pipe and a gas outlet pipe for introducing inert gas into the heating furnace main body, and the graphite container is arranged at a position with the shortest distance from the heating furnace being more than 5mm and less than 50 mm.

[5] The apparatus for producing graphite as described in item [4], wherein the graphite container is provided at a position where a shortest distance from the heater is 20mm or more and 30mm or less.

[6] The apparatus for producing graphite according to [4] or [5], wherein the gas introduction pipe and the gas discharge pipe are configured such that the gas in the heating furnace is in an atmosphere of: the helium gas content is 10 mol% or more and 70 mol% or less, assuming that the total amount is 100 mol%.

ADVANTAGEOUS EFFECTS OF INVENTION

According to one embodiment of the present invention, in the heating furnace, the discharge between the heater and the graphite container is suppressed, and the maximum temperature in the heating furnace can be increased. Therefore, a method and an apparatus for producing graphite capable of obtaining graphite having high thermal diffusivity and high heat dissipation properties can be provided.

Drawings

Fig. 1 is a front view showing a schematic configuration of a heating furnace.

Fig. 2 is a front view showing a schematic configuration of a heating furnace indicating a distance between a graphite container and a heater.

Detailed Description

One embodiment of the present invention will be described in detail below. However, the present invention is not limited to this, and various modifications can be made within the scope described, and embodiments obtained by appropriately combining technical means disclosed in the respective different embodiments are also included in the technical scope of the present invention.

A method for producing graphite according to one embodiment of the present invention includes a graphitization step of graphitizing a carbide placed in a graphite container in a heating furnace provided with a gas supply device and a heater to obtain graphite, wherein in the graphitization step, (i) the graphite container is provided at a position where a shortest distance from the heater is greater than 5mm and less than 50mm, and (ii) a gas in the heating furnace is made to be in an atmosphere of: (ii) a helium gas content of more than 0 mol% and not more than 100 mol% when the total amount is 100 mol%, (iii) heating the inside of the heating furnace so that the maximum temperature is 2900 ℃ or more, and heat-treating the carbide.

< Polymer Material >

Examples of the polymer material suitably used in the method for producing graphite of the present invention include polyimide, polyamide, polyoxadiazole, polybenzothiazole, polybenzobithiazole, polybenzoxazole, polybenzobisoxazole, polyparaphenylene vinylene, polyphenylenebenzimidazole, polyphenylenebenzinebiimidazole and polythiazole. Polyimide is particularly preferable from the viewpoint of thermal diffusivity of the graphite obtained.

< carbonization step >

In the production of graphite, a carbonization step of carbonizing the polymer material is first performed, and then a graphitization step of graphitizing the obtained carbide (hereinafter also referred to as graphitization) is performed.

(highest temperature)

The carbonization step is a step of obtaining a carbide by carbonizing a polymer material by heat treatment at about 1000 ℃. The maximum temperature at the time of the heat treatment is, for example, preferably 700 to 1800 ℃, more preferably 800 to 1500 ℃, still more preferably 900 to 1200 ℃, and particularly preferably 1000 ℃.

(rate of temperature increase)

The temperature increase rate in the carbonization step is, for example, preferably 0.01 to 20 ℃/min, more preferably 0.1 to 10 ℃/min, still more preferably 0.2 to 5.0 ℃/min, and particularly preferably 0.5 to 2.0 ℃/min.

(holding time)

The holding time in the carbonization step, specifically, the holding time at the maximum temperature is preferably 1 minute to 1 hour, more preferably 5 minutes to 30 minutes, and still more preferably 8 minutes to 15 minutes.

(shape of Polymer Material)

In the carbonization step, a laminate obtained by laminating a rectangular polymer material film may be carbonized (single sheet method), or the polymer material film in a roll form may be carbonized while keeping the roll form, or the polymer material film in a roll form may be carbonized while being continuously unwound. That is, the form of the polymer material thin film in the carbonization step is not particularly limited.

< graphitization step >

In the graphitization step, the carbide obtained as described above is put into a graphite container and heat-treated at a predetermined temperature in a heating furnace.

(heating furnace)

In one embodiment of the present invention, graphite can be produced using a heating furnace such as that shown in fig. 1, for example. Fig. 1 shows a heating furnace for producing graphite, which has a heating furnace main body 2 in a casing 1, and includes a graphite power supply unit 4 and a graphite heater 3. The furnace body 2 is used in the graphitization step of firing (heat treatment) the carbide 6 placed in the graphite container 5 at a high temperature of 2900 ℃ or higher to graphitize in the method for producing graphite.

The heating furnace main body 2 may be provided with a heater at the bottom surface portion thereof as necessary, or may be provided with a gas introduction pipe and a gas discharge pipe for introducing an inert gas into the heating furnace main body 2. The structure and appearance of the heating furnace are not limited to those shown in fig. 1.

(distance between graphite Container and Heater)

In the graphitization step, from the viewpoint of suppressing electric discharge, (i) the graphite container is preferably provided at a position having a shortest distance from the heater of more than 5mm, more preferably at a position of 7mm or more, still more preferably at a position of 10mm or more, and particularly preferably at a position of 20mm or more. When the graphite container is disposed at a position at a shortest distance of 5mm or less from the heater, the heater may be energized with the graphite container, and the temperature of the graphite container may not be raised. From the viewpoint of productivity, the graphite container is preferably provided at a position where the shortest distance from the heater is less than 50mm, more preferably at a position of 40mm or less, and still more preferably at a position of 30mm or less. When the graphite container is disposed at a position at a shortest distance of 50mm or more from the heater, although discharge is less likely to occur, the volume of the graphite container must be reduced, and productivity may be deteriorated.

The distance between the graphite container and the heater is, for example, a distance 10 between the heater 3 and the graphite container 5 as shown in fig. 2.

In the graphitization step in the present invention, the graphite container and the heater are not in contact with each other, and the distance between the graphite container and the heater, that is, the distance between the outer wall of the graphite container and the portion where the distance between the outer wall of the graphite container and the heater is the smallest (also referred to as the shortest distance from the heater), is greater than 5mm and less than 50 mm. The heater in the present invention is not limited to the heating element, and when there is a member covering the heating element, the heater refers to the entire member including the member covering the heating element. In addition, the non-contact in the present invention means: the container and the heating surface of the heater are separated by a space (a gas layer or a vacuum space) (note that even if the container and a part of the heater are in contact, the present invention is determined to be non-contact when the action and effect of the present invention are exerted). If the container and the heater are not in contact with each other, uniform energization and heat generation in the heater can be performed, and heating by the heater can be performed uniformly without local unevenness in the graphite container. As a result, excellent graphite without quality variation can be obtained in the graphite container.

On the other hand, if electricity is applied to the heater in a state where the heater is in contact with the container, electricity is also applied to the graphite container in the contact region, and thus uneven heat generation occurs in the heater, and uniform heating of the graphite container cannot be achieved, and it is difficult to sufficiently achieve uniformity of graphitization of the raw material thin film (carbide). If the graphite container is close to the heater, electric discharge occurs between the graphite container and the heater, the graphite container and the heater are consumed, and the temperature rise is hindered. Therefore, the graphite container is separated from the heater by more than 5mm to prevent discharge and consumption of the graphite container and the heater. However, although the maximum temperature in the heating furnace may be raised to a temperature lower than 2900 ℃ for the above-mentioned distance, the temperature is not raised to 3000 ℃ or higher because discharge occurs more strongly when the temperature is raised to 3000 ℃ or higher. Therefore, although heating is usually performed in an argon atmosphere, in the present invention, when the total amount of gas in the heating furnace is 100 mol%, 10 mol% or more of helium gas is mixed into argon gas. This enables the temperature to be raised to a high temperature range of 3000 ℃ or higher without causing discharge.

(highest temperature in heating furnace)

In the graphitization step, the carbide is heat-treated by heating in a heating furnace so that the maximum temperature becomes 2900 ℃ or higher, preferably 3000 ℃ or higher, and particularly preferably 3100 ℃ or higher.

(graphitization step/rate of temperature rise)

The temperature increase rate in the graphitization step is, for example, preferably 0.01 to 20 ℃/min, more preferably 0.1 to 10 ℃/min, and still more preferably 0.5 to 5.0 ℃/min.

(holding time)

The holding time at the maximum temperature in the graphitization step is preferably 1 minute to 1 hour, more preferably 5 minutes to 30 minutes, and still more preferably 8 minutes to 15 minutes.

(shape of carbide)

In the graphitization step, a laminate obtained by laminating rectangular carbonaceous thin films may be graphitized, or a rolled carbonaceous thin film may be graphitized while being held in a roll, or a rolled carbonaceous thin film may be continuously drawn out to be graphitized. That is, the form of the carbonaceous thin film in the graphitization step is not particularly limited.

(pressure of gas)

The pressure of the gas (gas) in the heating furnace in the graphitization step is preferably 0.1 to 200kPa higher, more preferably 2 to 100kPa higher, and still more preferably 5 to 50kPa higher than the pressure of the gas outside the heating furnace. By making the pressure higher than the pressure of the gas outside the heating furnace, it is possible to make the members in the heating furnace such as the heater difficult to deteriorate.

(gas in graphite Container in graphitization step)

In the graphitization step, from the viewpoint of suppressing electric discharge that tends to occur in a high-temperature region, (ii) the gas in the heating furnace is preferably in an atmosphere of: the ratio of helium is 10 mol% or more and 90 mol% or less, and more preferably 20 mol% or more and 70 mol% or less, when the total amount is 100 mol%.

(graphite Container)

The shape of the graphite container used in the present invention is not particularly limited, and a box shape, a cylindrical shape, or the like can be applied. The graphite used as a material of the graphite container is a broad concept including a material mainly containing graphite as long as it can be heated to the temperature range, and includes, for example, isotropic graphite, extruded graphite, and the like. Isotropic graphite having excellent electrical and thermal conductivity and excellent homogeneity is particularly preferable as a material of the graphite container. The graphite used as the material of the graphite container used in the present invention has a thermal conductivity of 5 to 500W/(cm K), preferably 20 to 300W/(cm K), and more preferably 50 to 200W/(cm K).

(non-contact between heater and electric conductor)

In the heat treatment process for graphitization according to the present invention, it is preferable that the heater is not in contact with an electric conductor that allows electric current to flow outside the heating furnace. The conductor of the present invention means a resistivity of 10²～10⁹Omega m. When an electric conductor for passing an electric current to the outside of the heating furnace is brought into contact with the heater, there is a possibility that the electric current leaks to cause an abnormality in a device for controlling the electric power of the heater or to damage a heater constituting member. This may cause a problem such as no increase in heater temperature. In addition, electric discharge (arc) may occur near the contact portion between the heater and the conductor, and the heater or the conductor in contact therewith may be broken. Preferably, the current does not substantially flow from the heater to the graphite container through the electric conductor. When an electric current flows through the graphite container, damage such as breakage or contamination may occur to the sample (carbide) held in the graphite container.

Examples

(evaluation of discharge State)

Whether or not discharge between the heater and the graphite container occurs is evaluated based on a change in the apparent resistance value of the heater obtained from voltage-current data of the heater shown by the symbol "3" in fig. 1. Since both the current and the voltage increase as the temperature approaches the maximum temperature, the value obtained by dividing the voltage by the current, that is, the apparent resistance value of the heater becomes a predetermined value depending on the temperature. On the other hand, if discharge occurs, the current greatly increases and the voltage decreases in a high temperature region. That is, if an electric discharge occurs between the heater and the graphite container, the apparent resistance of the heater is greatly reduced to such an extent that cannot be explained by the physical properties of graphite. The reason why the apparent resistance of the heater is lowered is that argon in the atmosphere is ionized under high temperature conditions to become argon ions, and the furnace space is discharged to flow a short-circuit current, thereby lowering the apparent resistance. However, the addition of helium gas at a minimum of 10 mol% did not lower the apparent resistance, and the state was evaluated as a non-discharge state. Specifically, it is determined that discharge is generated (discharge is generated) when the apparent resistance of the heater gradually decreases as the temperature in the furnace increases, and it is determined that discharge is not generated (no discharge) when the apparent resistance of the heater does not decrease even at a high temperature.

(example 1)

2000 sheets of a single-piece polyimide film having a width of 254mm, a length of 310mm and a thickness of 50 μm were stacked and placed in a graphite container having a width of 370mm, a depth of 370mm and a height of 500mm as shown in FIG. 1. Next, the graphite container with the monolithic polyimide film placed therein was placed in a heating furnace as shown in fig. 1. At this time, the shortest distance of the graphite container from the heater was 20 mm. After the door of the heating furnace was closed, the inside of the heating furnace was made to be under a nitrogen atmosphere. The temperature in the heating furnace was raised to 1400 ℃ at a rate of 10 ℃/min, and the monolithic polyimide film was carbonized. Then, the nitrogen in the heating furnace was entirely replaced with a gas containing 10 mol% of helium and 90 mol% of argon. Subsequently, the temperature in the heating furnace was heated at a rate of 5 ℃/min to 3100 ℃, and then the temperature was maintained for 15 minutes to graphitize the carbide, thereby obtaining monolithic graphite. In the graphitization step, no discharge occurred, and the maximum temperature in the furnace was 3100 ℃.

The obtained monolithic graphite had a width of 228mm, a length of 279mm and a thickness of 25 μm and a thermal diffusivity of 10.4cm²/s。

(example 2)

Monolithic graphite was obtained in the same manner as in example 1, except that the atmosphere gas in the heating furnace in the graphitization step was changed to a gas containing 50 mol% of helium and 50% of argon. In the graphitization step, no discharge occurred, and the maximum temperature in the furnace was 3100 ℃.

The obtained monolithic graphite had a width of 228mm, a length of 279mm and a thickness of 25 μm and a thermal diffusivity of 10.4cm²/s。

(example 3)

Monolithic graphite was obtained in the same manner as in example 1, except that the atmosphere gas in the heating furnace in the graphitization step was changed to a gas containing 70 mol% helium and 30% argon. In the graphitization step, no discharge occurred, and the maximum temperature in the furnace was 3100 ℃.

The obtained monolithic graphite had a width of 228mm, a length of 279mm and a thickness of 25 μm and a thermal diffusivity of 10.4cm²/s。

Comparative example 1

Monolithic graphite was obtained in the same manner as in example 1 except that the atmosphere gas in the heating furnace in the graphitization step was changed to a gas containing 100% argon. In the graphitization step, discharge occurred, and the maximum temperature in the heating furnace was 2890 ℃.

The obtained monolithic graphite had a width of 228mm, a length of 279mm and a thickness of 25 μm and a thermal diffusivity of 8.7cm²/s。

Comparative example 2

The same procedure as in example 1 was repeated except that the shortest distance between the graphite container and the heater was set to 0mm, and as a result, the heater was in contact with the graphite container, and the graphite container was energized, so that the temperature of the graphite container could not be increased.

Comparative example 3

Discharge marks were observed on both the heater and the graphite container in the same manner as in example 2, except that the shortest distance between the graphite container and the heater was set to 5 mm.

(example 4)

The same procedure as in example 2 was repeated except that the shortest distance between the graphite container and the heater was 10mm, and discharge marks were not observed in both the heater and the graphite container.

The conditions and evaluations of the examples and comparative examples are summarized in table 1.

[ Table 1]

Industrial applicability

According to the method and apparatus for producing graphite of the present invention, higher-quality graphite can be produced.

Description of the reference numerals

1 casing

2 heating furnace body

3 heating device

4 power supply part

5 graphite container

6 carbide

10 distance of heater from graphite container