JP2964710B2 - Manufacturing method of graphite - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing highly oriented block-like graphite used as a radiation optical element such as an X-ray monochromator, a neutron monochromator and a neutron filter.

[0002]

2. Description of the Related Art Graphite occupies an important position as an industrial material because of its excellent heat resistance, chemical resistance, high electrical conductivity and the like, and is widely used as a gasket, an electrode, a heating element and a structural material. Among them, highly oriented graphite has excellent spectral and reflection characteristics for X-rays and neutron rays, and is therefore widely used as a monochromator or filter for X-rays and neutron rays.

[0003] As one of the graphites used for such a purpose, naturally occurring graphite is used, but the quality of graphite is very limited and the handling is difficult. Since it is in the form of powder or scale, graphite is artificially produced.

Conventionally, as a method for producing such artificial graphite, there is a method in which a hydrocarbon gas is deposited at a high temperature in a gas phase at a high temperature and hot working is performed. According to this method, pressure is applied. By re-annealing at 3400 ° C. for a long time, graphite is produced.

[0005] The graphite thus produced is called highly oriented graphite (HOPG) and has excellent properties as compared with natural single crystal graphite. However, this manufacturing method has a very complicated manufacturing process and a remarkably low yield, and as a result, the manufactured highly oriented graphite is extremely expensive.

In recent years, the above-mentioned problems of the conventional method for producing high-quality graphite have been solved, and high-quality graphite can be easily produced, and the cost can be reduced. As a method, a method of firing a polymer film at a high temperature was developed. Polymeric materials generally belong to non-graphitic materials, such as 3000
It is not converted to good quality graphite when heated to a high temperature of ° C.

However, recent studies have shown that some polymeric materials can be converted to good quality graphite by appropriate heat treatment. These polymers include polyoxadiazole, aromatic polyimide, aromatic polyamide, polybenzimidazole, polybenzobisthiazole, polybenzoxazole, polythiazole, polyparaphenylenevinylene, and the like.

Based on these findings, the present inventors have filed patent applications, which are disclosed in Japanese Patent Application Laid-Open No. 61-275114.
JP, JP-A-61-275115, JP-A-61-275115
-275117. Based on these inventions, studies have been made on laminating polymer films and firing them under pressure to produce block-like graphite. These examples are described in JP-A-1-105199 and JP-A-63-105199.
No. 235218. However,
A number of measures are required to laminate multiple polymer films and obtain a block-shaped graphite with excellent orientation.Simply sintering under pressure simply produces the desired highly oriented graphite. I can't. In order to obtain highly oriented graphite, it is important that each film is properly oriented inside the block, that the graphite crystals are well arranged inside the film, and that the films adhere to each other. .

However, for example, any of the above polymer films undergoes thermal decomposition in a temperature range of 300 to 600 ° C., and the films rapidly shrink. Further, these polymers are hard and brittle in a temperature range from about 1000 ° C. to about 2000 ° C., that is, in a so-called hard carbon state. Therefore, by laminating these polymer films,
Even when heat treatment is performed while applying pressure, wrinkles and distortion of the internal structure usually occur due to shrinkage and deformation of the film, and in extreme cases, breakage.

Therefore, the point of the technology for producing a highly oriented block-like graphite from a plurality of polymer films is that it is generated during the process of thermal decomposition, carbonization and graphitization due to the expansion and contraction of the polymer film. Is how to keep the strain in the final block of graphite. For this reason, for example, essentially no pressure is applied in the thermal decomposition temperature range,
A technique of applying a pressure of 2 to 50 kg / cm ² in a temperature range of 00 ° C. and applying a pressure of 50 kg / cm ² or more at 2600 ° C. or more is adopted. The reason that no pressure is applied in the pyrolysis temperature range is that when pressure is applied in this range, the films fuse together, preventing the smooth release of decomposition gas generated from inside, and eventually causing the destruction of carbonized materials by the generated gas. Because it leads. The pressure operation between the decomposition temperature or higher and 2000 ° C. is a step of firing the carbonized product (in a state of hard carbon) so as not to break it and removing internal strain generated in the decomposition temperature range. 2600 ° C
The above pressure operation is a step of bonding the films while promoting the formation of graphite.

[0011] Pyrolysis, carbonization,
By controlling the steps of graphitization and bonding, highly oriented block-like graphite having a mosaic spread value of about 0.7 ° has been obtained.

[0012]

However, in order to realize block-like graphite having more excellent orientation, it is important to reduce the strain generated during the thermal decomposition process. For this purpose, it is desirable to apply pressure while preventing the polymer films from adhering to each other and releasing the decomposition gas smoothly in the thermal decomposition process. However, usually, the polymer film is charged during casting, adheres to each other when the films are laminated, and fusion occurs between the films due to pressure during the thermal decomposition process, so that the pressure cannot be applied.

The present inventors have studied to solve the problems in a method of manufacturing graphite by laminating a plurality of polymer films as described above, and applying pressure and heat treatment, and as a result, have previously removed charge from the surface. By using the treated polymer film as a raw material, it was possible to perform pressure calcination to reduce distortion during the thermal decomposition process, and it was possible to produce highly oriented block-shaped graphite. An object of the present invention is to provide a method for producing graphite, which can produce highly oriented block-shaped graphite at a low cost at a low cost.

[0014]

In order to achieve the above object, the technical solution of the present invention is to stack a plurality of polymer films, press and heat-treat them to produce graphite. The film is preliminarily subjected to a charge removal treatment, and is then subjected to pressure and heat treatment.

The above polymer film may be subjected to a charge removal treatment before lamination, or may be subjected to a charge removal treatment after lamination.

Various types of polyphenylene oxadiazole (POD), polybenzothiazole (PBT), polybenzobisthiazole (PBBT), polybenzoxazole (PBO), polybenzobisoxazole (PBBO), Various aromatic polyimides (PI), various aromatic polyamides (PA), poly (phenylenebenzimidazole) (PBI), poly (phenylenebenzobisimidazole) (PBBI),
At least one of polythiazole (PT) and poly (paraphenylenevinylene) (PPV) can be used.

Here, various polyoxadiazoles refer to polyparaphenylene-1.3.4-oxadiazole and isomers thereof. Various aromatic polyimides are polyimides represented by the following general formula.

[0018]

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The aromatic polyamide is a polyamide represented by the following general formula.

[0020]

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In the present invention, these polyimides,
It is not limited to polyamide.

The raw material polymer film of the present invention includes the above-mentioned POD, PBT, PBBT, PBO, PBBO, PB
I, PA, PBI, PBBI, PT, PPV, etc., but the production method of the present invention is similarly applicable to a polymer film from which a high-quality graphite can be obtained by heat treatment at a high temperature. It is possible to apply.

In the production method of the present invention, 4
It is desirable to use a film having a thickness of not more than 00 μm. When a polymer film having a thickness of 400 μm or more is used, the internal structure of the film is destroyed due to the gas generated from the inside of the film by the production method of the present invention, and a highly oriented block-shaped This is because it becomes difficult to obtain graphite.

As a method for removing charge from the polymer film in the present invention, corona discharge in air or glow discharge under reduced pressure is used. For example, taking an aromatic polyimide as an example, a polyimide film (Dupont Corporation)
(Kapton: trade name, 25 μm) is cut into an appropriate size, and then charged by corona discharge using a corona discharge device. Alternatively, a corona discharge is performed in a state where the polyimide films are laminated to remove the charge.

In the case of a polyimide film that has not been subjected to a charge removal treatment, in order to carbonize while preventing the films from fusing and wrinkling from occurring, the pressure is essentially increased in a temperature range where the film expands and contracts. It is necessary not to apply. Here, the fact that no pressure is applied essentially means that a minute pressure such as the weight of a jig for pressurization may be applied. The magnitude of the allowable pressure at this time is generally 2 kg / cm ² or less,
Particularly preferably, it is 1 kg / cm ² or less. In contrast, in the case of the polyimide film that has been subjected to the above-described charge removal treatment,
10 kg / cm ² max.
Can be pressurized. Therefore, the obtained carbonized product is
Wrinkles could be reduced much as compared with the case of using a raw material which had not been charged and removed. Then, graphitization was performed using the carbonized material thus obtained, and as a result, an improvement in the locking property of 0.2 ° on average was observed.

The above-mentioned method of pressurizing and heat treatment is not necessarily limited to a polyimide film, but can be generally applied to a polymer film converted into excellent graphite by heat treatment.

[0027]

Therefore, according to the present invention, the polymer films are not adhered to each other in the thermal decomposition process by the charge removal treatment, and the decomposition gas can be smoothly diffused to the outside through the space between the polymer films. . Also,
Since the polymer films do not adhere to each other, it is possible to apply a certain amount of pressure, and it is possible to prevent the polymer film from being wrinkled or distorted by the pressure.
The carbonized block obtained in this way is treated and graphitized, but each polymer film is properly oriented inside the block and, furthermore, the crystal is well arranged inside the polymer film. Oriented block-like graphite can be obtained.

[0028]

The present invention will be described more specifically with reference to the following examples.

(Example 1) First, a polymer having a thickness of 50 μm was prepared.
Laphenylene-1.3.4-oxadiazole film
Voltage 2KV (voltage varies with film size)
To discharge the corona, thereby performing a charge removal treatment. Next
The processed 300 films (5 × 5 cm ^TwoLaminated)
And set it in a graphite jig,
In an atmosphere, the temperature was raised to 1200 ° C at a rate of 10 ° C / min.
Was. During this time, 5kg / cm^TwoSo that the pressure of
did. After reaching 1200 ° C, the same heating rate as above
20kg / cm while keeping^TwoPressure becomes 1400 ℃
Was applied. Thereafter, the pressure is reduced and the temperature is reduced to 300
Until the temperature rises to 0 ° C, a pressure equivalent to the weight of the jig
Only the voltage was applied. The temperature reaches 3000 ° C
After that, pressure was applied again. Applied pressure is 200kg / cm^Twoso
there were. The heat treatment was completed while maintaining this pressure. this
The block-like graphite obtained in this way is almost
It had no wrinkles and a uniform surface.

The characteristics of the graphite of the present example obtained as described above were measured using an X-ray diffractometer manufactured by Rigaku Denki Co., Ltd., and the diffraction line of the rocking characteristic measurement at the peak position of the graphite (002) diffraction line was measured. Was evaluated with a half width of As a result of the measurement, the locking characteristic was 0.55.
°, which is an excellent characteristic as a monochromator for X-rays and neutrons.

(Comparative Example 1) As a comparative example, the same treatment as described above was performed using a film that had not been subjected to the charge removal treatment. However, in the process of raising the temperature to 1200 ° C., the films fused together, and It was destroyed by the generated gas. In order to prevent this destruction, in the firing step up to 1200 ° C., the processing was carried out at a pressure substantially depending on the weight of the jig, and the subsequent processing was the same as in this example. The locking characteristic of the obtained block-like graphite was 0.8 °.
As is clear from these results, it was found that the manufacturing method of this example was very effective in improving the locking characteristics.

Example 2 First, a 25 μm-thick polyimide film (Kapton H film, manufactured by Dupont Co., Ltd.) was subjected to a charge removal treatment by glow discharge (discharge voltage 300 V) under reduced pressure. Next, 300 films (5 × 5 cm ² ) after the treatment were laminated, set on a graphite jig, and then placed in an argon gas atmosphere at a rate of 10 ° C./min.
The temperature was raised to 400 ° C. During this time, a pressure of 5 kg / cm ² was applied to the sample. After the temperature reached 1400 ° C., a pressure of 20 kg / cm ² was applied until the temperature reached 1600 ° C. while maintaining the same heating rate as described above. Thereafter, the pressure was reduced so that only the pressure corresponding to the weight of the jig was applied until the temperature was raised to 2700 ° C. After the temperature reached 2700 ° C., pressure was applied again. The applied pressure was 200 kg / cm ² . While maintaining this pressure, the temperature was raised to 3000 ° C. to complete the heat treatment. The block-like graphite thus obtained had almost no wrinkles and a uniform surface.

The characteristics of the graphite of the present example obtained as described above were measured using an X-ray diffractometer manufactured by Rigaku Denki Co., Ltd., and the diffraction line of the rocking characteristic measurement at the peak position of the graphite (002) diffraction line was measured. Was evaluated with a half width of As a result of the measurement, the locking characteristic was 0.52.
°, which is an excellent characteristic as a monochromator for X-rays and neutrons.

(Comparative Example 2) As a comparative example, the same treatment as described above was performed using a film that was not subjected to the glow discharge treatment. It was destroyed by the generated gas. In order to prevent this destruction, in the firing process up to 1400 ° C., the treatment is performed at a pressure substantially due to the weight of the jig,
Subsequent processes were the same as in the present embodiment. The locking characteristics of the obtained block-like graphite were 0.75 °. As is clear from these results, it was found that the manufacturing method of this example was very effective in improving the locking characteristics.

Example 3 First, a PB having a thickness of 50 μm was used.
T, PBBT, PBO, PBBO, PA, PBI, PP
One hundred films of BI, PT, and PPV were each laminated, and a corona discharge at a voltage of 1 KV was generated in each of the films to perform a charge removal treatment. Next, the laminated film after the treatment was set on a graphite jig, and placed in an argon gas atmosphere.
The temperature was raised to 1200 ° C. at a rate of 0 ° C./min. During this time, a pressure of ² kg / cm ² was applied to the sample. 1
After the temperature reached 200 ° C., a pressure of 10 kg / cm ² was applied until the temperature reached 2000 ° C. while maintaining the same heating rate as described above. Thereafter, the pressure was reduced so that only the pressure corresponding to the weight of the jig was applied until the temperature rose to 2800 ° C. After the temperature reached 2800 ° C., pressure was applied again. The applied pressure was 150 kg / cm ² .
While maintaining this pressure, the temperature was raised to 3000 ° C. to complete the heat treatment. The block-like graphite thus obtained had almost no wrinkles and a uniform surface.

The characteristics of the graphite obtained as described above were measured using an X-ray diffractometer manufactured by Rigaku Corporation, and the half-width of the diffraction line for rocking characteristic measurement at the peak position of the graphite (002) diffraction line was measured. evaluated. The results of the measurement are shown in (Table 1).

[0037]

[Table 1]

As is clear from these results, it was found that all of the block-like graphites obtained from the above-mentioned polymers had excellent characteristics as X-ray and neutron beam monochromators.

[0039]

As described above, according to the present invention, the polymer films are prevented from adhering to each other in the thermal decomposition process due to the charge removal treatment, and the decomposed gas passes smoothly between the polymer films to the outside. Can spread. Further, since the polymer films do not adhere to each other, it is possible to apply a certain pressure, and it is possible to prevent the polymer film from being wrinkled or distorted by the pressure. As a result, it is possible to obtain a highly oriented block-like graphite in which the respective polymer films are properly oriented inside the block and the crystals are arranged neatly inside the polymer film. Therefore, it is possible to obtain a block-like graphite having a high orientation at a low cost by a simple method.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C04B 35/52 C01B 31/04 101

Claims (2)

(57) [Claims] (1) heat treatment and internal gas generation
Multiple polymer filters with a thickness that does not destroy the structure
In order to produce graphite by heat-treating while laminating and applying a pressure treatment , the polymer film is previously subjected to a charge removal treatment and the heat treatment is performed while the pressure treatment is performed.
A method for producing graphite. 2. The polymer film is at least one selected from polyoxadiazole, aromatic polyimide, aromatic polyamide, polybenzimidazole, polybenzobisthiazole, polybenzoxazole, polythiazole, and polyparaphenylenevinylene. The method for producing graphite according to claim 1, which is of a kind.