JPH04202052A - Graphite manufacturing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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, and high electrical conductivity, so it occupies an important position as an industrial material and is widely used as gaskets, electrodes, heating elements, and structural materials. ing. 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, the kudzu 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,
Examples include aromatic polyimide, aromatic polyamide, polybenzimidazole, polybenzobisthiazole, polybenzoxazole, polythiazole, polyparaphenylenevinylene, and the like.

Based on these findings, the applicant has filed a patent application for the invention (Japanese Unexamined Patent Publications No. 61-275114, No. 61-27511,
275115, JP-A-61-275117, etc.).

On the other hand, an invention has also been filed in which a block-shaped graphite is created by laminating polymer films and heating them under pressure (JP-A-1-105199, JP-A-63-235).
(See Publication No. 218).

(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 products. As described in JP-A-1-105199, a plurality of films are sandwiched between two substrates,
Highly oriented block graphite cannot be obtained 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).
Therefore, each graphitized layer must firmly adhere 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 polymeric films are stacked one on top of the other, and are graphitized by pressure treatment and firing in a temperature range where almost no change in film dimensions occurs. In this case, the pressure treatment is usually performed in a temperature range of less than 2600°C and a temperature range of 2600°C or more, and the pressure of the pressure treatment in the temperature range of 2600°C or more is The temperature should be lower than 2600° C. and the pressure should be higher than the pressure in the pressure treatment.

Further, in order to solve the above problem, in the method for producing graphite according to claim 3, a plurality of polymer films or a carbonaceous film obtained from the polymer films are stacked one on top of the other, and the polymer pyrolysis temperature is In the temperature range exceeding the same thermal decomposition temperature, the treatment is performed under virtually no pressure, and in the temperature range exceeding the same thermal decomposition temperature and 2000°C (usually 1000°C to 2000°C), pressure treatment is performed, and in the temperature range of 2000 to 2600°C, It is made into graphite by performing substantially no-pressure treatment and then performing pressure treatment again in a temperature range of 2,600° C. or higher. In this case, the pressure of the pressure treatment carried out in a temperature range exceeding the polymer thermal decomposition temperature and 2000°C is usually an arbitrary value in the range of 2 to 50 kg/cm2, as described in claim 4,
The pressure of the pressure treatment carried out in a temperature range of 2600° C. or higher is usually set to an arbitrary value in the range of 50 kg/cm 2 or higher, as described in claim 5.

As the polymer film for the starting material in the present invention, for example, as described in claim 6, various polyphenylene oxadiazole (POD), polybenzothiazole (PB
T), polybenzobisthiazole (PBBT), polybenzoxazole (PBO), polybenzobisoxazole (PBBO), various aromatic polyimides (PI),
Various aromatic polyamides (PA), polyphenylenebenzimidazole (FBI), polyphenylenebenzimidazole (PPBI), polythiazole (PT),
Examples include a film made of at least one selected from 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 general formulas.

F3CH3 Examples of aromatic polyamides include polyamides represented by the following general formula.

〇 〇II II However, R3=
-■, R4=- Of course, polyimide or polyamide films other than those exemplified above may 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 manufacturing method according to the present invention, since the pressure treatment is carried out in a state where the film dimensions hardly change, wrinkles and internal distortions do not occur, and the inside of each graphitized layer forms crystals in which carbon atoms are regularly arranged in a predetermined manner. is in a highly oriented state in which the particles are properly oriented.

In the temperature range below 2600℃, the film size changes due to the progress of graphitization will occur first, and the weight of 50kg
By applying a low pressure of /am2 or less, it becomes possible to obtain graphite with high coordinating property.

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 specifically described using an example in which the polymer film is a polyimide film.

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

The drawings show 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.

This polyimide film conforms to the film dimension curve A in the drawing.
As seen in Figure 2, it only slightly elongates at 400 to 500°C, but rapidly shrinks in the polymer decomposition temperature range of 500 to 700°C, reducing to 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 shown 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 a temperature range of 2600° C. or higher, the film dimensions almost no longer change as shown 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 carried out in a temperature range where the dimensions of the film do not change. Temperature range between 2,000℃ and 2, exceeding the polymer thermal decomposition temperature
Since there is virtually no dimensional change in the film in a temperature range of 600° C. or higher, it is sufficient to carry out the pressure treatment in this temperature range so that the inside of the film is in a sufficient orientation state. Note that the pressure treatment does not need to be performed immediately after the polymer thermal decomposition temperature is exceeded or immediately after the temperature reaches 2600° C., and the pressure treatment may be performed 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 other temperature ranges exceeding the polymer thermal decomposition temperature or in the temperature range of 2,000 to 2,600°C, the film dimensions change significantly, so substantially pressureless treatment is performed. Note that "substantially no pressure treatment" as used herein means that no pressure is applied that would produce 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).
There is no problem with applying a harmless low pressure of less than cm2).

Then, in the temperature range exceeding the polymer thermal decomposition temperature and 2000°C, the film size usually still changes from 2 to 50 kg/kg depending on the number of stacked films. Apply an arbitrary pressure in a low range of about cm2, and then in a temperature range of 2600°C or higher,
The film size does not change anymore, and it is still in a soft state, so it can weigh up to 50 kg/100 lbs., depending on the number of stacked films.
High pressure exceeding cm2 (preferably 100-500
kg/cm2) to obtain a good orientation and strong adhesion.

The above is, of course, not only true for polyimide films, but generally for polymeric films that can be converted into superior graphite by heat treatment. This is because, during firing for graphitization, these polymer films must undergo a thermal decomposition process that includes film shrinkage, a process in which there is almost no expansion or contraction,
This is because the film undergoes a graphitization process in which the film stretches, and then a process in which the graphitization progresses to a considerable extent with almost no expansion or contraction.

This will be explained in more detail next.

Example 1 - Fifty polyparaphenylene-1,3,4-oxadiazole films measuring 2 cm in length, 3 cm in width, and 50 μm in thickness 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 alcon gas atmosphere. During this time, only a pressure of 100 g/cm 2 was applied to the film using the jig type (2). Next, after reaching 1200°C, a pressure of 20 kg/cm2 was applied while maintaining the same temperature increase rate until reaching 1400°C. Then the pressure is reduced and the temperature is 2600
Until the temperature rises to ℃, the pressure due to the weight of the jig is 100
Only g/cm2 was added. Temperature is 2600℃
After reaching the temperature, apply a pressure of 200 kg/cm2 and heat to 3000℃ while maintaining the pressure of 200 kg/cm2.
Block-shaped graphite was obtained by increasing the temperature to .

Example 2 - 200 aromatic polyimide films (trade name: Kapton H film, manufactured by D'upon) with a length of 2 cm, a width of 3 cm, and a thickness of 25 μm were stacked and set in a graphite jig and fired as follows. .

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 E]-00 g/cm 2 due to the weight of the jig was applied to the film. Next, after reaching 1400℃, while maintaining the same temperature increase rate, a pressure of 30kg/cm2 was applied to 1600℃.
I ran it until it reached . 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. temperature is 2
After reaching 700℃, apply a pressure of 300kg/cm2, and continue to heat it for 3 hours while maintaining the pressure of 300kg/cm2.
Block-shaped graphite was obtained by increasing the temperature to 000°C.

Example 3 - Aromatic polyimide film with a length of 2 cm, a width of 3 cm, and a thickness of 25 μm (trade name: Kapton H film manufactured by Dupon)
Carbonaceous film 200 heat-treated at a temperature of 1200°C
The sheets were stacked and set in a graphite jig, and fired as follows.

First, the temperature was raised to 1400° C. at a rate of 10° C./min in an argon gas atmosphere. During this time, only the pressure due to the weight of the jig], OOg/cm2, was applied to the film. Next, after reaching 1400°C, a pressure of 30 kg/cm2 was applied while maintaining the same temperature increase rate until reaching 1600°C. Then the pressure is reduced and the temperature is 270
Until the temperature rises to 0℃, the pressure due to the weight of the jig is 10
Only 0g/cm2 was added. temperature is 2700
After reaching the temperature of
By raising the temperature to ℃, block-shaped graphite was obtained.

Example 4 - PET film 1 with a length of 2 cm, a width of 3 cm, and a thickness of 50 μm
00 sheets 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 100 g/cm2 due to the weight of the jig was applied to the film. Next, after reaching 1500°C, a pressure of 30 kg/cm2 was applied while maintaining the same temperature increase rate until reaching 1800°C. Then the pressure is reduced and the temperature is 2800
Until the temperature rises to ℃, the pressure due to the weight of the jig is 100
Only g/cm2 was added. Temperature is 2800℃
After reaching the temperature, apply a pressure of 300 kg/cm2 and heat to 3000°C while maintaining the pressure of 300 kg/cm2.
Block-shaped graphite was obtained by increasing the temperature to .

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

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

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

Example 1 Block graphite was obtained in the same manner as in Example 4, except that FBI film was used instead of O-PET 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 PET film.

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

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

The block graphite obtained in Examples 1 to 13 was
It had a smooth surface with almost no wrinkles.

The characteristics of each graphite were measured using a Rotorflex RU-200B X-ray diffraction apparatus manufactured by Rigaku Corporation. 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 Table 1.

As shown in Table 1, the graphite of Example 19 all has excellent locking properties and is well suited for monochromators for X-rays and neutron beams. .

(Effects of the Invention) According to the method for producing graphite according to claims 1 to 6, excellent highly oriented graphite without wrinkles or internal distortion can be easily obtained.

In the method for producing graphite according to claim 2.4, 2
The pressure applied in the temperature range below 600℃ is 50kg/cm
Since it is low at 2 or less, graphite with higher orientation can be obtained.

In the method for producing graphite according to claim 2.5, 2
The pressure applied in the temperature range of 600℃ or higher is 50kg/cm
Since it is as high as 2 or more, high quality block graphite can be obtained.

In the method for producing graphite according to claim 6, 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 (6)

[Claims] (1) Multiple sheets of polymer films or carbonaceous films obtained from polymer films are stacked one on top of the other, and then pressure treated and fired at a temperature range where almost no change in film dimensions occurs, resulting in graphite formation. Characteristic graphite manufacturing method. (2) Pressure treatment in the temperature range below 2600℃ and 2600℃
2. The method for producing graphite according to claim 1, wherein the pressure treatment is carried out in each of the above temperature ranges, and the pressure of the pressure treatment in the temperature range of 2600°C or higher is lower than the pressure of the pressure treatment in the temperature range of 2600°C. (3) Multiple sheets of polymer films or carbonaceous films obtained from polymer films are stacked and treated under virtually no pressure in the temperature range up to the polymer thermal decomposition temperature, and then Pressure treatment is performed in a temperature range exceeding 2000°C, and virtually no pressure treatment is performed in the temperature range of 2000 to 2600°C, and then pressure treatment is performed again in a temperature range of 2600°C or higher to produce graphite. A method for producing graphite characterized by: (4) The method for producing graphite according to claim 3, wherein the pressure of the pressure treatment carried out in a temperature range of 2000° C. exceeding the polymer thermal decomposition temperature is in the range of 2 to 50 kg/cm^2. (5) The method for producing graphite according to claim 3, wherein the pressure of the pressure treatment performed in a temperature range of 2600° C. or higher is in a range of 50 kg/cm^2 or higher. (6) The polymer film is made of at least one of polyoxadiazole, aromatic polyimide, aromatic polyamide, polybenzimidazole, polybenzobisthiazole, polybenzoxazole, polythiazole, and polyparaphenylene vinylene. A method for producing graphite according to any one of claims 1 to 5.