JPH04202053A - Production of graphite - Google Patents

Abstract

PURPOSE:To easily obtain a superior highly oriented block-shaped graphite free from creases and internal strain by pressurizing laminated polymer films in two stages in which temp. and pressure are specified when the films are heated under pressure. CONSTITUTION:Plural polymer films or carbonaceous films obtd. from the polymer films are laminated and graphitized by firing in which an arbitrary pressure of >=10kg/cm<2> is applied at a constant temp. within a temp. range of <2,600 deg.C and then an arbitrary pressure of >=50kg/cm<2> is applied at a constant temp. within a temp. range of >=2,600 deg.C. Orientation hindering action due to the difference in expansion coefft. between jigs and the films is inhibited in the 1st-stage pressurization, carbon atoms are regularly arranged in each graphitized layer and the grains are accurately oriented to obtain highly oriented graphite.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing graphite that can be used as a radiation optical element such as an X-ray monochromator-1 neutron monochromator-1 neutron beam filter.

(Prior technology) Graphite has outstanding heat resistance, chemical resistance, high electrical conductivity, etc., so it occupies an important position as an industrial material, and is widely used in gaskets, electrodes, heating elements, and structural materials. Among them, highly oriented graphite is
Because it has excellent spectroscopic and reflective properties for X-rays and neutron beams, it is used as radiation optical elements such as monochromators and filters for X-rays and neutron beams. One idea is to use naturally occurring graphite for this radiation optical element, but high-quality natural graphite is produced in very limited quantities and is difficult to handle as it is in the form of powder or flakes. Graphite has been manufactured artificially, and it is desirable to use this artificial graphite.

Conventionally, artificial graphite has been produced by high-temperature decomposition deposition of hydrocarbon gas in the gas phase and hot processing, which is a process of re-annealing at 3400°C for a long time while applying pressure. It is created by

Graphite created in this way is called highly oriented graphite (HOPG) and has excellent properties comparable to natural single crystal graphite. However, this manufacturing method has the problem that the manufacturing process is extremely complicated and the yield is extremely low, resulting in the HOPG being extremely expensive and not suitable for practical use.

Therefore, as a method for producing graphite that can solve these problems, a method has been developed in which high-quality graphite is produced easily and at low cost by firing a polymer film at a high temperature. Polymer compounds generally belong to difficult-to-graphite materials, and it has been thought that they will not be converted into high-quality graphite even if heated at a high temperature of 3000°C. However, recent research has revealed that some polymer compounds can be converted into high-quality graphite through appropriate heat treatment. Examples of polymer compounds that can be converted into high-quality graphite include polyoxadiazole, aromatic polyimide, aromatic polyamide, polybenzimidazole, polybenzobisthiazole, polybenzoxazole, polythiazole, polyparaphenylene vinylene, etc. .

Based on these findings, a patent application has already been filed for the invention (Japanese Patent Laid-Open No. 61-275114, Japanese Patent Laid-Open No. 61-27).
5115, JP-A-61-275117, etc.).

On the other hand, patent applications have also been filed for an invention in which block-shaped graphite is created by laminating polymer films and heating them under pressure (JP-A-1-105199, JP-A-63-2).
(See Publication No. 35218).

(Problems to be Solved by the Invention) However, it has been found that the above-mentioned methods for producing graphite do not provide completely satisfactory results. As described in JP-A-1-105199, a plurality of films are sandwiched between two substrates,
It is not possible to obtain highly oriented block graphite simply by caulking with bolts and heat-treating. In order to have excellent block-like highly oriented graphite, each graphitized layer must have crystals in which carbon atoms are regularly arranged in a properly oriented state (highly oriented state).
The graphitized layers must be firmly adhered to each other to form a single block.

Simply applying pressure and heat treatment will not produce excellent graphite, as the film will develop wrinkles and internal distortions, and in extreme cases, the film will tear.

In view of the above circumstances, an object of the present invention is to provide a method by which excellent highly oriented graphite can be easily produced.

(Means for Solving the Problem) In order to achieve the above object, in the method for producing graphite according to claim 1, a plurality of polymer films, or
Carbonaceous films obtained from polymer films are piled up, and at least 10 kg/kg is deposited in a temperature range below 2600°C.
After performing the pressure treatment so that the temperature does not substantially change while applying an arbitrary pressure of cm2 or more, the temperature substantially changes while applying an arbitrary pressure of at least 50 kg/cm2 or more in a temperature range of 2600°C or more. In the method for producing graphite according to claim 2, a carbonaceous film obtained from a plurality of polymer films or a carbonaceous film obtained from a plurality of polymer films is The temperature range exceeds the polymer thermal decomposition temperature and is between 2000°C (usually 10008°C to 20°C).
00℃) at an arbitrary pressure of 2 to 50 kg/cm2 in such a way that the temperature does not substantially change if the arbitrary pressure exceeds at least 1 g/cm2, and then
During the application of an arbitrary pressure of at least 50 kg/cm'' in a temperature range of 600°C or higher, the temperature is kept substantially unchanged so that the graphite is formed by firing under pressure treatment.In this case, the temperature is 2000°C. Even below, it is preferable that the temperature is not substantially changed when the pressure is 2 kg/cm2 or more, and even in the temperature range of 2600°C or more, the temperature is not substantially changed when the pressure is 20 kg/cm2 or more. It is preferable to carry out substantially pressureless treatment until the polymer thermal decomposition temperature is exceeded, and to
It is desirable to carry out substantially pressureless treatment even in the temperature range of 000 to 2,600°C. Note that "substantially no pressure treatment" here means that no pressure is applied that would cause a pressurizing effect, and the pressure applied by the pressurizing jig itself is 2 kg/cm2 or less (more preferably 1 kg/cm2 or less). ), it does not matter where a harmless low pressure is applied.

=7- As the polymer film for the starting material in the present invention, for example, as described in claim 3, various polyphenylene oxadiazole (POD), polybenzothiazole (PB
T), polybenzobisthiazole (PBBT), polybenzoxazole (PBO), polybenzobisoxazole (PBBO), various aromatic polyimides (PI), various aromatic polyamides (PA), polyphenylenebenzimidazole (FBI), polyphenylene Examples include a film made of at least one selected from benzobisimidazole (PPBI), polythiazole (PT), and polyparaphenylene vinylene (PPV). Of course, the starting material film is not limited to these, and it goes without saying that any polymer film that can be converted into high-quality graphite by heat treatment at high temperatures can be used as the starting material film.

Among the various polyoxadiazoles mentioned above, polyparaphenylene-1,3,4-oxadiazole and isomers thereof are preferred. Also,
Examples of various aromatic polyimides include polyimides represented by the following formulas.

Examples of aromatic polyamides include polyamides represented by the following formula.

Of course, polyimide or polyamide films other than those exemplified above may also be used.

The thickness of the polymer film serving as the starting material is preferably 400 μm or less. Film thickness is 400μm
This is because if it exceeds this, the internal structure of the film will be destroyed due to the gas generated inside the film, making it difficult to achieve high orientation.

(Function) In the method for producing graphite according to the present invention, 10 kg
Since the temperature is not substantially changed during pressurization exceeding /cm2, the orientation inhibiting effect caused by the difference in expansion/contraction rate between the jig and the film is eliminated, and the carbon atoms inside each graphitized layer are arranged as specified. It is possible to obtain highly oriented graphite in which regularly arranged crystals are properly oriented.

In addition, in the manufacturing method according to claim 2, since the pressure treatment is carried out in a state where the film dimensions hardly change, wrinkles and internal distortions are sufficiently suppressed, and the obtained graphite becomes more highly oriented.

In the temperature range below 2600℃, the film dimensions still change due to the progress of graphitization, so 50kg
By applying a low pressure of /cm2 or less, highly oriented graphite can be obtained.

In a temperature range of 2600° C. or higher, applying a high pressure of 50 kg/cm 2 or higher will ensure that each graphitized layer is firmly adhered to each other, and a high-quality block-shaped graphite can be obtained.

The present invention can be carried out extremely easily without any difficulties, since it is sufficient to control the timing and intensity of applying pressure in the firing process.

(Example) The present invention will be explained in detail below.

First, the present invention will be explained in more detail by taking as an example the case where the polymer film is a polyimide film.

Polyimide (Dupon
A film manufactured by Kapton (product name: Kapton, thickness 25 μm) was used.

The drawing shows the expansion and contraction of this polyimide film in the plane direction as the heat treatment temperature increases, and the graphitization rate (measured using X-ray diffraction) as the heat treatment temperature increases by 1.

This polyimide film conforms to the film dimension curve A in the drawing.
As seen in Figure 2, it stretches only slightly at 450 to 500°C, but rapidly shrinks in the polymer decomposition temperature range of 500 to 700°C, reaching 75% of its original length. When the temperature exceeds this polymer decomposition temperature and reaches 2000°C, the film does not expand or contract, and almost no dimensional change occurs. However, at 2000-2600°C, the film stretches back to 90% of its original dimensions. The elongation of the film in this temperature range is closely linked to the progress of graphitization, and as seen in the graphitization rate curve B in the drawing, the graphitization rate increases rapidly as the film stretches. In this way, film dimensions change in the temperature range below 2600°C. On the other hand, in the temperature range of 2600°C or higher, the film dimensions hardly change (no longer), as seen in the drawing.

Polyimide films that exhibit the above-mentioned dimensional changes in response to temperature changes are laminated and turned into graphite by firing with pressure treatment, but in order to avoid problems such as wrinkles and internal distortion, basic Specifically, the pressure treatment may be performed in a temperature range where the film dimensions hardly change, and the pressure treatment may be performed in a temperature range where the film dimensions largely change. There is virtually no dimensional change in the film in the temperature range between 2,000°C, which exceeds the polymer thermal decomposition temperature, and in the temperature range of 2,600°C or higher, so pressure treatment is performed in this temperature range to ensure that the inside of the film is fully oriented. All you have to do is make it so. Note that it is not necessary to perform the pressure treatment immediately after the temperature exceeds the polymer thermal decomposition temperature or immediately after the temperature reaches 2600° C., but it is sufficient to perform the pressure treatment while the temperature is within a predetermined temperature range. It is not necessary to carry out the pressure treatment over the entire predetermined temperature range.

In the temperature range exceeding other polymer thermal decomposition temperatures or in the temperature range of 2000 to 2600°C, Fee 13
= Since the lume dimensions change significantly, virtually no pressure treatment should be used.

In the temperature range exceeding the polymer thermal decomposition temperature and 2000°C, the film usually undergoes a temperature range where the dimensional change is large, so depending on the number of stacked films, the After applying an arbitrary pressure in a low range and at a temperature of 2,600°C or higher, the film dimensions will no longer change and the film will be in a soft state. Preferably 100 to 400 kg/c
m2) to obtain a good alignment state and strong adhesion state.

As mentioned above, when a pressure exceeding 10 kg/cm2 is applied, the temperature is not substantially changed.

The above is, of course, not only applicable to polyimide films, but generally to polymeric films that can be converted into superior graphite by heat treatment.

This will be explained in more detail next.

Example 1 - 50 sheets of polyparaphenylene-1,3,4-oxadiazole films with a length of 2 cm, a width of 3 cm, and a thickness of 50 Hlm were stacked and set in a graphite jig, and fired as follows. .

First, the temperature was raised to 1200°C at a rate of 10'C/min in an argon gas atmosphere. During this time, only a pressure of 100 g/cm2 due to the weight of the jig was applied to the film. Next, after reaching 1200° C., the pressure of 20 kg/cm 2 was released for 20 minutes while maintaining that temperature. Thereafter, the pressure was reduced so that only a pressure of 100 g/am2 due to the weight of the jig was applied until the temperature rose to 2800'C. After the temperature reaches 2800℃, while maintaining the temperature, apply 200kg/c for 30 minutes.
After applying a pressure of m2 and reducing the pressure, 3000
Block graphite was obtained by raising the temperature to 'C.

- Comparative Example 1 - After reaching 1200°C, the temperature was increased to 140°C while maintaining the temperature increase rate.
A pressure of 20 kg/cm' was applied until the temperature reached 0°C, and after the temperature reached 2800'C, a pressure of 20 kg/cm' was applied.
Block-shaped graphite was obtained in the same manner as in Example 1, except that the temperature was raised to 3000° C. while applying a pressure of 00 kg/cm 2 .

Example 2 - Aromatic polyimide film L having a length of 2 cm, a width of 3 cm, and a thickness of 25 μm (manufactured by Dupon Co., Ltd., product name: Captofun 11) was stacked and set in a Taraphite jig, and fired as follows. did.

First, the temperature was raised to 1400° C. at a rate of 10° C./min in an argon gas atmosphere. During this time, only a pressure of long/cm2 due to the weight of the jig was applied to the film. Next, after reaching 1400° C., a pressure of 30 kg/cm 2 was applied for 30 minutes while maintaining that temperature. Thereafter, the pressure was reduced so that only 100 g/cm2 of pressure due to the weight of the jig was applied until the temperature rose to 2700°C. After the temperature reached 2700°C, a pressure of 300 kg/cm2 was applied for 30 minutes while maintaining that temperature, and then the pressure was reduced and the temperature was raised to 3000°C to obtain block graphite.

- Comparative Example 2 - After reaching 1400°C, the temperature was increased to 160°C while maintaining the temperature increase rate.
A pressure of 20 kg/Cm2 was applied until the temperature reached 0°C, and after the temperature reached 2700°C, a pressure of 30 kg/Cm2 was applied.
Block-shaped graphite was obtained in the same manner as in Example 2, except that the temperature was raised to 3000° C. while applying a pressure of 0 kg/cm 2 .

Example 3 - 200 sheets of aromatic polyimide film (product name: Kapton H film manufactured by Dupon) heat-treated at a temperature of 1000°C, measuring 2 cm in length, 3 cm in width, and 25111+11 in thickness, were stacked on top of each other in a graphite jig. set,
It was fired as follows.

First, the temperature was raised to 1400°C at a rate of Iθ°C/min in an argon gas atmosphere. During this time, only a pressure of 100 g/cn+2 due to the weight of the jig was applied to the film. Next, after reaching 1400° C., a pressure of 30 kg/cm 2 was applied for 30 minutes while maintaining that temperature. Thereafter, the pressure was reduced so that only 100 g/cm2 of pressure due to the weight of the jig was applied until the temperature rose to 2700°C. After the temperature reached 2700°C, a pressure of 300 kg/cm2 was applied for 30 minutes while maintaining that temperature, and then the pressure was reduced and the temperature was raised to 3000°C to obtain block graphite.

Example 4 - 100 PBT films measuring 2 cm long, 3 cm wide, and 5 Q (rm) thick were stacked and set in a graphite jig, and fired as follows.

First, the temperature was raised to 1500° C. at a rate of 10° C./min in an argon gas atmosphere. During this time, only a pressure of long/cm2 due to the weight of the jig was applied to the film. Next, after reaching 1500° C., a pressure of 30 kg/cm 2 was applied for 30 minutes while maintaining that temperature. after that,
The pressure was reduced so that only 100 g/cm2 of pressure due to the weight of the jig was applied until the temperature rose to 2800°C. After the temperature reached 2800°C, a pressure of 300 kg/am2 was applied for 30 minutes while maintaining the temperature, and then the pressure was reduced and the temperature was raised to 3000°C to obtain block graphite.

- Comparative Example 3 - After reaching 1500°C, the temperature increase rate was not maintained until 18-
]ll- Apply a pressure of 30 kg/cm2 until the temperature reaches 00°C, and after the temperature reaches 2800°C,
Block-shaped graphite was obtained in the same manner as in Example 4, except that the temperature was raised to 3000° C. while applying a pressure of 0 kg/cm 2 .

Example 5 - Block-shaped graphite was obtained in the same manner as in Example 4, except that a PBBT film was used instead of the PBT film.

Comparative Example 4 - Block-shaped graphite was obtained in the same manner as Comparative Example 3, except that a PBBT film was used instead of the PBT film.

Example 6 - Block-shaped graphite was obtained in the same manner as in Example 4, except that a PBO film was used instead of the PBT film.

Comparative Example 5 A blower-shaped graphite was obtained in the same manner as Comparative Example 3, except that a PBO film was used instead of the PBT film.

Example 7 - Block-shaped graphite was obtained in the same manner as in Example 4, except that a PBBO film was used instead of the PBT film.

Comparative Example 6 - Block-shaped graphite was obtained in the same manner as Comparative Example 3, except that a PBBO film was used instead of the PBT film.

Example 8 - Block-shaped graphite was obtained in the same manner as in Example 4, except that a PI film was used in place of the PBT film.

Comparative Example 7 - Block-shaped graphite was obtained in the same manner as Comparative Example 3, except that a PI film was used in place of the PBT film.

Example 9 - Block-shaped graphite was obtained in the same manner as in Example 4, except that a PA film was used in place of the PBT film.

Comparative Example 8 - Block-shaped graphite was obtained in the same manner as Comparative Example 3, except that a PA film was used instead of the PBT film.

Example 10 - Block-shaped graphite was obtained in the same manner as in Example 4, except that a PBI film was used instead of the PBT film.

Comparative Example 9 - Block-shaped graphite was obtained in the same manner as Comparative Example 3, except that an FBI film was used instead of the PBT film.

Example 1l - Block-shaped graphite was obtained in the same manner as in Example 4, except that a PBB I film was used in place of the PBT film.

Comparative Example 1 O- Block-like graphite was obtained in the same manner as Comparative Example 3, except that a PBBI film was used in place of the PBT film.

Example 12 - Block-shaped graphite was obtained in the same manner as in Example 4, except that a PT film was used instead of the PBT film.

Comparative Example 1l - Block-shaped graphite was obtained in the same manner as Comparative Example 3, except that a PT film was used in place of the PBT film.

Example 13 - Block-shaped graphite was obtained in the same manner as in Example 4, except that a PP film was used in place of the PBT film.

Comparative Example 12 - Block-shaped graphite was obtained in the same manner as Comparative Example 3, except that a PPV film was used in place of the PBT film.

The block graphite of each of the above examples had a perfectly smooth surface with almost no wrinkles.

The block graphite of the comparative example also had a smooth surface without wrinkles.

The characteristics of each graphite were measured using a loader manufactured by Rigaku Denki Co., Ltd.
Measurement was performed using a Flex RU100B X-ray diffraction device. Evaluation was made using the half-width of the diffraction line obtained as a result of rocking characteristic measurement at the peak position of the graphite (002) diffraction line. The measurement results are shown in Tables 1 and 2.

Table 1 Table 2 Comparing the rocking properties of the Examples in Table 1 and the Comparative Examples in Table 2, the graphite of the Examples has very excellent rocking properties and is resistant to X-rays. It can be clearly seen that it is suitable for neutron beam monochromators, etc.

(Effects of the Invention) In the method for producing graphite according to claims 1 to 3, excellent highly oriented graphite without wrinkles or internal distortion can be easily obtained.

In the method for producing graphite according to claim 2, since the pressure treatment is performed in a temperature range where the film dimensions hardly change,
Graphite with higher orientation can be obtained.

In the method for producing graphite according to claim 3, since the raw material film is suitable for graphitization, highly oriented graphite can be easily obtained.

[Brief explanation of the drawing]

The drawing is a characteristic diagram showing temperature-film dimensions and temperature-film dalaphite conversion rate during firing of a polyimide film. A... Film dimension curve B... Graphitization rate curve.

Claims (3)

[Claims] (1) Layer multiple polymer films or carbonaceous films obtained from polymer films, and
After performing the pressure treatment in such a manner that the temperature does not substantially change during the application of an arbitrary pressure of at least 10 kg/cm^2 in a temperature range of less than 00°C, at least 50 kg/cm^2 in a temperature range of 2600°C or more. A method for producing graphite, characterized in that the graphite is turned into graphite by firing in which the temperature is substantially unchanged while applying an arbitrary pressure of ^2 or more. (2) Multiple sheets of polymer films or carbonaceous films obtained from polymer films are stacked together and heated in a temperature range of 2 to 50 degrees Celsius exceeding the polymer thermal decomposition temperature and 2000 degrees Celsius.
After performing pressure treatment at an arbitrary pressure of kg/cm^2 in such a way that the temperature does not substantially change when the arbitrary pressure exceeds at least 10 kg/cm^2, at least a temperature range of 2600°C or higher is performed. A method for producing graphite, which is characterized in that the graphite is turned into graphite by firing in which a pressure treatment is performed so that the temperature does not substantially change while applying an arbitrary pressure of 50 kg/cm^2 or more. (3) The polymer film is made of at least one of polyoxadiazole, aromatic polyimide, aromatic polyamide, polybenzimidazole, polybenzobisthiazole, polybenzoxazole, polythiazole, and polyparaphenylene vinylene. The method for producing graphite according to claim 1 or 2.