JP2975099B2 - Manufacturing method of graphite - Google Patents

Description

Description: TECHNICAL FIELD 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, a neutron monochromator, and a neutron filter.

(Conventional technology) Graphite has outstanding heat resistance, chemical resistance, high electrical conductivity, etc., and therefore 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
Since it has excellent spectral and reflection characteristics for X-rays and neutrons, it is used as a radiation optical element such as a monochromator or a filter for X-rays or neutrons. It is one idea to use naturally occurring graphite for the radiation optical element, but the quality of natural graphite is very limited, and it is handled in powder or scaly form. Due to the difficulty, graphite is artificially produced, and it is desirable to use this artificial graphite.

Conventionally, as a method for producing artificial graphite, there is a method of high-temperature decomposition deposition of hydrocarbon gas in the gas phase and hot working, which is a process of re-annealing at 3400 ° C. for a long time while applying pressure. It is created by. The graphite thus produced is called highly oriented graphite (HOPG) and has excellent properties comparable to natural single crystal graphite. However, according to this manufacturing method, there is a problem that the manufacturing process is extremely complicated and the yield is extremely low. As a result, HOPG becomes extremely expensive and is not suitable for practical use.

Therefore, as a method for producing graphite that can solve such problems, a method has been developed in which a high-quality graphite is easily and inexpensively produced by firing a polymer film at a high temperature. Polymer compounds generally belong to difficult-to-graphite materials, and have not been converted to good quality graphite even if heated at a high temperature of 3000 ° C. However, recent studies have shown that some of the polymeric compounds can be converted to good quality graphite by appropriate heat treatment. Examples of the polymer compound that can be converted into high-quality graphite include polyoxadiazole, aromatic polyimide, aromatic polyamide, polybenzimidazole, polybenzobisthiazole, polybenzoxazole, polythiazole, polyparaphenylenevinylene, and the like. .

Inventions based on these findings have already been filed for patents (see Japanese Patent Application Laid-Open Nos. 61-275114, 61-275115, 61-275117, etc.).

On the other hand, a patent application has been filed for producing a block-like graphite by laminating polymer films and heating under pressure (see Japanese Patent Application Laid-Open No. 1-105199 and Japanese Patent Application No. 63-235218).

(Problems to be Solved by the Invention) However, it has been found that the above-described methods for producing graphite do not always provide completely satisfactory products. As described in JP-A-1-105199, simply interposing a plurality of films between two substrates and caulking with bolts does not lead to obtaining highly oriented block-like graphite. In order to be an excellent block-shaped highly oriented graphite, the inside of each graphitized layer is in a state in which crystals in which carbon atoms are regularly arranged in a predetermined manner are properly oriented (highly oriented state). They must be firmly bonded together to form a single block. Simply applying pressure and heat-treating the film does not produce excellent graphite due to wrinkles and internal distortion, or in extreme cases, the film is broken.

The present invention has been made in view of the above circumstances, and has as its object to provide a method capable of easily producing an excellent highly oriented graphite.

(Means for Solving the Problems) In order to achieve the above object, in the method for producing graphite according to claim 1, a polymer film having a thickness such that an internal structure is not destroyed by gas generation even by heat treatment;
Alternatively, the carbonaceous films obtained from the polymer films are stacked and subjected to a pressure treatment in a temperature range exceeding the polymer pyrolysis temperature and between 2000 ° C. (usually 1000 ° C. to 2000 ° C.) ~ 2600 ℃ between the substantially pressureless treatment, after performing the pressure treatment in the temperature range of 2600 ℃ or more, once lower to the temperature range of 1600 ℃ or less, and then returned to the temperature range of 2600 ℃ or more at least Graphite is formed by calcination at least once in the temperature range of 2600 ° C. or more. The process of once lowering to a temperature range of 1600 ° C. or less and then returning to a temperature range of 2600 ° C. or more and performing the pressure treatment at least in the temperature range of 2600 ° C. or more may be repeated a plurality of times. Usually, the pressure treatment performed at a temperature exceeding the polymer thermal decomposition temperature and between 2000 ° C. is ^{2 to} 50 kg / cm ^2.
It is preferable to carry out at an arbitrary pressure in the range of 2600 ° C.
The pressure treatment performed in the above temperature range is preferably performed at an arbitrary pressure of 50 kg / cm ² or more. It is preferable to perform the pressure treatment again in the temperature range of 2600 ° C. or more at an arbitrary pressure of 20 kg / cm ² or more. When the pressure is less than 20 kg / cm ² , the obtained block-like graphite tends to be in a foamed state. Here, the “substantially no pressure treatment” means that pressure is not applied so as to produce a pressing effect, and 2 kg / cm ² or less (more preferably 500 g / cm ² or less) by the pressing jig itself. ) Harmless low pressure is acceptable.

As the starting material polymer film in the present invention,
For example, various kinds of polyphenylene oxadiazole (POD), polybenzothiazole (PB
T), polybenzobisthiazole (PBBT), polybenzoxazole (PBO), polybenzobisoxazole (P
BBO), various aromatic polyimides (PI), various aromatic polyamides (PA), polyphenylene benzimidazole (PB
I), polyphenylene benzobisimidazole (PPB
Examples include films made of at least one selected from I), polythiazole (PT), and polyparaphenylene vinylene (PPV). Of course, not limited to these, it goes without saying that any polymer film that can be converted to high-quality graphite by heat treatment at a high temperature can be used as a starting material film.

Among the above, as the various polyoxadiazoles, polyparaphenylene-1,3,4-oxadiazole and isomers thereof are preferred. In addition, examples of various aromatic polyimides include polyimides represented by the following general formula.

However, And as an aromatic polyamide, the polyamide represented by the following general formula is mentioned.

However, Of course, a polyimide or polyamide film other than the above examples may be used.

The thickness of the polymer film as a starting material is preferably 400 μm or less. If the thickness of the film exceeds 400 μm, the internal structure of the film is destroyed by the gas generated inside the film, making it difficult to achieve high orientation.

(Function) In the production method according to claims 1 and 2, 1000 ° C. during the firing process.
Because of the above-mentioned temperature-lowering process, the inside of each graphitized layer is in a highly oriented state in which crystals in which carbon atoms are regularly arranged in a predetermined manner are properly oriented.

In addition, in this manufacturing method, substantially no pressure treatment is performed in a temperature region where the film dimensional change is large, and pressure treatment is performed in a temperature region where there is almost no film dimensional change, thereby suppressing the occurrence of wrinkles and internal structural distortion. Easy to get the status.

In the present invention, since it is sufficient to control the temperature and the pressure in the firing step, it can be implemented very easily without any difficulty.

(Example) Hereinafter, an example of the present invention will be described.

First, the present invention will be described more specifically, taking an example where the polymer film is a polyimide film.

Polyimide (trade name: Kapton, thickness 25 μm, manufactured by Dupon) was used as a polymer film as a starting material. The drawing is
The graph shows the elongation and shrinkage of the polyimide film in the plane direction as the heat treatment temperature rises, and the graphitization rate (measured using X-ray diffraction) as the heat treatment temperature rises.

As shown in the film size curve A in the drawing, this polyimide film only slightly expands at 450 to 500 ° C., but rapidly shrinks in the polymer decomposition temperature range of 500 to 700 ° C., and has an original length. It is about 75% longer. When the temperature exceeds the polymer decomposition temperature and the temperature is between 2000 ° C., the film does not expand and contract and almost no dimensional change occurs. But 2000-2600 ℃
Then the film stretches in reverse and returns to 90% of its original size. The elongation of the film in this temperature range is closely linked to the progress of graphitization, and the graphitization rate curve B
As can be seen, the graphitization rate sharply increases as the film elongates. As described above, in the temperature range of 2600 ° C. or less, a change occurs in the film dimensions. In contrast, in the temperature range above 2600 ° C, as seen in the drawing,
The film dimensions hardly change anymore.

The film which exhibits the above dimensional change with respect to the temperature change is fired as follows.

First, in a temperature range where the dimensional change accompanying the thermal decomposition is large until the temperature exceeds the polymer thermal decomposition temperature range, substantially no pressure treatment is performed. Perform pressure treatment at a pressure of about ² to 50 kg / cm2, and
Substantially no-pressure treatment is performed in a temperature range of 00 to 2600 ° C. where the dimensional change accompanying the progress of graphitization is large, and 50 ° C. in a temperature range where there is almost no dimensional change of 2600 ° C. or more after the next graphitization is almost completed
A pressure treatment of kg / cm ² is performed.

Thereafter, in the present invention, the temperature is once reduced to 1600 ° C. or less. That is, the temperature drops by 1000 ° C. or more.
The temperature may be lowered to room temperature, and the work of replacing the jig and the press ram may be performed. When lowering the temperature, it is desirable to maintain the pressure applied up to at least 2000 ° C. After 2000 ° C., the pressure may be reduced so that there is almost no adverse effect. After cooling, the temperature is raised again to 2600 ° C. In the reheating, it is desirable to increase the temperature to a temperature higher than the maximum temperature up to that time. During reheating, it is preferable to apply a lower arbitrary pressure of 20 kg / cm ² or less until 2600 ° C. And, at a temperature range of 2600 ° C or more, 20 kg / cm ²
It is desirable to apply the above arbitrary pressure. If the pressure is less than 20 kg / cm ² , a foaming state is easily caused.

In addition, the pressure treatment, immediately after exceeding the polymer thermal decomposition temperature,
It is not necessary to perform the treatment immediately after the temperature reaches 2600 ° C., and the pressure treatment may be performed while the temperature is in the predetermined temperature range. It is not necessary to perform the pressure treatment over the entire predetermined temperature range.

The above is, of course, not only true for polyimide films, but also generally for polymer films that can be converted to excellent graphite by heat treatment. Because, in the firing for graphitization, these polymer films necessarily undergo a thermal decomposition process including film shrinkage, a process with almost no expansion and contraction, a graphitization process involving film elongation, and a considerable degree of graphitization. This is because they undergo a process with almost no expansion and contraction.

 Next, a more detailed description will be given.

Example 1 Polyparaphenylene-1, 2 cm long, 3 cm wide, and 50 μm thick
Fifty 3,4-oxadiazole films were stacked, set on a graphite jig, and fired as follows.

First, in an argon gas atmosphere, at a rate of 10 ° C / min, 1200
The temperature was raised to ° C. During this time, only a pressure of 100 g / cm ² depending on the weight of the jig was applied to the film. Next, after the temperature reached 1200 ° C., a pressure of 20 kg / cm ² was applied until the temperature reached 1400 ° C. while maintaining the same heating rate. Thereafter, the pressure was reduced so that only a pressure of 100 g / cm ² depending on the weight of the jig was applied until the temperature rose to 2600 ° C. Temperature 2600
After reaching ℃, apply pressure of 200kg / cm ² and keep 200kg / cm2
The temperature was raised to 3000 ° C. while maintaining a pressure of / cm ² . Subsequently, the temperature was lowered to 1200 ° C. once while applying a pressure of 200 kg / cm ² , maintained for 30 minutes, and again raised to 2600 ° C. at a rate of 10 ° C./min at a pressure of 20 kg / cm ² . Later, 26
A pressure of 200 kg / cm ² was applied in a temperature range of 00 ° C. or higher, and the temperature was raised to 3000 ° C. to obtain block graphite.

Example 2 200 aromatic polyimide films (Kapton H film, trade name, manufactured by Dupon) having a length of 2 cm, a width of 3 cm, and a thickness of 25 μm were stacked, set on a graphite jig, and fired as follows.

First, 1400 at a rate of 10 ° C / min in an argon gas atmosphere
The temperature was raised to ° C. During this time, only a pressure of 100 g / cm ² depending on the weight of the jig was applied to the film. Next, after the temperature reached 1400 ° C., a pressure of 30 kg / cm ² was applied until the temperature reached 1600 ° C. while maintaining the same heating rate. Thereafter, the pressure was reduced so that only a pressure of 100 g / cm ² depending on the weight of the jig was applied until the temperature rose to 2700 ° C. Temperature 2700
After reaching ° C., a pressure of 300 kg / cm ^2, it 3000k
The temperature was raised to 300 ° C. while maintaining a pressure of g / cm ² . Subsequently, once the temperature was lowered to 1000 ° C. while applying a pressure of 200 kg / cm ² and maintained for 30 minutes, again, the temperature was raised to 2700 ° C. at a rate of 10 ° C./min with the pressure being 10 kg / cm ² . Thereafter, a pressure of 200 kg / cm ² was applied in a temperature range of 2700 ° C. or higher, and the temperature was raised to 3000 ° C. to obtain block graphite.

Example 3 One hundred PBT films each having a length of 2 cm, a width of 3 cm and a thickness of 50 μm were stacked, set on a graphite jig, and fired as follows.

First, in an argon gas atmosphere, at a rate of 10 ° C / min, 1500
The temperature was raised to ° C. During this time, only a pressure of 100 g / cm ² depending on the weight of the jig was applied to the film. Next, after the temperature reached 1500 ° C., a pressure of 30 kg / cm ² was applied until the temperature reached 1800 ° C. while maintaining the same heating rate. Thereafter, the pressure was reduced so that only a pressure of 100 g / cm ² depending on the weight of the jig was applied until the temperature was raised to 2800 ° C. After the temperature reached 2800 ° C., a pressure of 300 kg / cm ^2, as 300 kg / cm ²
While maintaining the pressure, the temperature was raised to 3000 ° C. Then, the temperature was lowered to once 300kg / 800 ℃ while applying a pressure of cm ²
Maintain for 30 minutes, again at 20 ° C with the pressure at 10 kg / cm ²
After the temperature was raised to 2800 ° C. at a rate of / min, a pressure of 200 kg / cm ² was applied in a temperature range of 2800 ° C. or higher, and the temperature was raised to 3000 ° C. to obtain block graphite.

Example 4 A block graphite was obtained in the same manner as in Example 3, except that a PBBT film was used instead of the PBT film.

Example 5 Block graphite was obtained in the same manner as in Example 3, except that a PBO film was used instead of the PBT film.

Example 6 A block graphite was obtained in the same manner as in Example 3, except that a PBBO film was used instead of the PBT film.

Example 7 Block graphite was obtained in the same manner as in Example 3 except that a PI film was used instead of the PBT film.

Example 8 A block graphite was obtained in the same manner as in Example 3 except that a PA film was used instead of the PBT film.

-Example 9- A block graphite was obtained in the same manner as in Example 3, except that a PBI film was used instead of the PBT film.

Example 10 Block graphite was obtained in the same manner as in Example 3 except that a PBBI film was used instead of the PBT film.

Example 11 Block graphite was obtained in the same manner as in Example 3 except that a PT film was used instead of the PBT film.

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

-Comparative Examples 1 to 12-In each of the examples, block graphite was obtained in the same manner as in each of the examples, except that the treatment after the temperature was lowered was not performed.

Block-like graphite obtained in Examples 1 to 12,
It had a smooth surface with almost no wrinkles.

The characteristics of each graphite were measured using a Rotorflex RU-200B type X-ray diffractometer manufactured by Rigaku Corporation. The evaluation was made based on the half width of the diffraction line obtained as a result of the rocking characteristic measurement at the peak position of the graphite (002) diffraction line. The measurement results are shown in Tables 1 and 2.

The graphite of the examples, as seen in Table 1,
All of them have excellent locking characteristics and are well understood to be suitable for X-ray and neutron beam monochromators and the like. It can also be clearly understood that the process of raising and lowering the temperature of 1000 ° C. or more greatly contributes to the improvement of the orientation.

(Effect of the Invention) In the method for producing graphite according to the first to third aspects, a high-temperature graphite having no wrinkles or internal distortion can be easily obtained because the temperature is raised and lowered by 1000 ° C. or more in the firing process. .

In the method for producing graphite according to the second aspect, in addition, substantially no pressure treatment is performed in a temperature region where the film dimensional change is large, and pressure treatment is performed in a temperature region where there is almost no film dimensional change. Can reliably be obtained.

In the method for producing graphite according to the third aspect, since the raw material film is suitable for graphitization, highly oriented graphite is easily obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a characteristic diagram showing temperature-film dimensions and temperature-film graphitization ratio when a polyimide film is fired. A: Film dimension curve B: Graphitization ratio curve

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Toshiharu Hoshi 3-10-1, Higashi-Mita, Tama-ku, Kawasaki-shi, Kanagawa Matsushita Giken Co., Ltd. (72) Inventor Naomi Nishiki 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Denshi Parts Co., Ltd. (72) Katsuyuki Nakamura 1006 Okadoma Kazuma Kadoma, Osaka Prefecture Matsushita Electric Parts Co. 56) References JP-A-1-203208 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C01B 31/04 101 C04B 35/52

Claims (2)

(57) [Claims] 1. A polymer film having a thickness such that its internal structure is not destroyed by the generation of gas even by heat treatment, or a carbonaceous film obtained from said polymer film is superposed on the polymer film, and the temperature exceeds the polymer thermal decomposition temperature. Pressure treatment is performed in the temperature range between 2000 ° C, pressure-free treatment is performed between 2000 and 2600 ° C, and pressure treatment is performed in the temperature range of 2600 ° C or more, and then temporarily in the temperature range of 1600 ° C or less. Down to 26 again
A method for producing graphite, comprising returning to a temperature range of at least 00 ° C. and performing a pressure treatment at least at a temperature range of at least 2600 ° C. at least once to obtain a graphite by firing. 2. The polymer film according to claim 1, wherein the polymer film comprises at least one of polyoxadiazole, aromatic polyimide, aromatic polyamide, polybenzimidazole, polybenzobisthiazole, polybenzoxazole, polythiazole, and polyparaphenylene virene. Claim 1 consisting of
A method for producing the described graphite.