JPS6291414A - Production of graphite film - Google Patents

Abstract

PURPOSE:To improve the mechanical strength of a graphite film by heat-treating a specified polymer film in an inert gas or in vacuum at limited temp., then impregnating the film with a binder component, and then heating the film. CONSTITUTION:At least one kind of polymer film selected from the following polymer materials is heated at >=1,800 deg.C in an inert gas or in vacuum. The film is then impregnated with the binder component and heated at <=1,400 deg.C. Polyoxaziazole, polybenzothiazole, polybenzobisthiazole, polybenzooxazole, polybenzobisoxazole, poly(pyromellitimide), poly(m-phenylene isophthalamide), poly(m-phenylene benzoimidazole), poly(m-phenylene benzobisimidazole), and polythiazole are exemplified as the above-mentioned polymer materials. Carbonaceous materials, synthetic resins, fats and oils, metals and/or inorg. compds. can be used as the binder.

Description

[Detailed description of the invention] Industrial fields of application The present invention is applicable to electrodes, heating elements, structural materials, gaskets, heat insulating materials,
Corrosion-resistant sealing materials, electrical brushes, X-ray monochromators
2 Regarding the manufacturing method of flexible and tough graphite film used as a moderator for nuclear reactors, etc., in particular, it uses a special polymer material as a raw material and performs a specific heat treatment and binder impregnation treatment. The present invention relates to a method for producing a graphitelum.

Problems to be Solved by the Prior Art and the Invention Graphite plays an important role as an industrial material due to its excellent heat resistance, chemical resistance, and high electrical conductivity. One method is to use naturally occurring graphite, but high-quality graphite is produced in very limited quantities and is difficult to handle in the form of blocks or powder, making it difficult to handle manually. (O)
It is.

The most common method for producing such artificial graphite is to heat various organic substances and carbonaceous substances at 3000° C. or higher to convert them into graphite.

This method usually uses carbonaceous materials such as coke and binders such as pitch as starting materials, and sometimes various polymers. Such raw materials are heated to 3000°
There are many types of carbon structures produced by heating to about C, ranging from those relatively close to the Grapheye 1 structure to those far removed from it. In this way, carbon whose structure changes relatively easily into a gelatite-like structure by heat treatment of 11 is called easily graphitizable carbon, and carbon that does not change into a gelatite-like structure is called difficult-to-graphitize carbon.

The reason why such a difference in structure 1- occurs is closely related to the graphitization mechanism and depends on whether or not structural defects existing in the carbon precursor are easily removed by the subsequent heat treatment. Of course, when preparing the graphite 1-heavy file 11, the raw material that is most likely to produce graphite 1-formable carbon is selected, but it is difficult to completely remove the resulting structural defects by heating. Therefore! 11. Until now, it has not been possible to create a Grapheye 1-film with properties similar to natural single crystal Grapheye 1 through heat treatment.

In other words, the above manufacturing method generally produces a complete graph eye 1.
There were 51 drawbacks when it was possible to obtain a product with a ~ structure, but without it. For example, the electrical conductivity in the a-axis direction, which is the most typical physical property of graphite 1-, has a value of 1 to 2.5 x 1. O'S/am, whereas in this manufacturing method it is generally 1 to 2 x 10']S/C
Only products with a conductivity of m can be removed. In order to overcome such shortcomings, (1,) F'e.

(2) A method of manufacturing by precipitation of carbides from a Ni/C-based melt, (2) A method of manufacturing by high-temperature decomposition deposition of gas phase hydrocarbons and its hot processing, and (3) Interlayer extraction band of natural graphite and its subsequent process. Artificial graph eye 1-
Film is being manufactured. However, all of these conventional methods have major problems in the process and the properties of the produced graphite film, so they are used only for special purposes.

In order to solve the problems of the prior art, the present inventors
We investigated various methods for creating graphite films by heat treatment of organic materials, which is the most common method, and first developed poly(p-phenylene-1,3゜4, oxadiazole) (
Japanese Patent Application No. 11541/1986 to propose a method for easily converting POD (abbreviated as POD) into graphite by heat treatment at a temperature of 1,600°C or higher in an inert gas or vacuum.
No. 5) revealed that this polymer is the one that most easily converts into graphite among conventional polymer materials, and becomes almost completely graphite when heat treated at 2500°C or higher. The present inventor also found that polybenzothiazole, polybenzobisthiazole, polybenzoxazole, polybenzobisoxazole, and polythiazole can be easily converted into graphite by heat treatment at a temperature of 18 oo'C or higher. How to
0-11-5416) and poly(pyromellitimide), poly(m-phenylene isophthalamide), poly(
Polymers such as m-phenylenebenzimidazole) and poly(m-phenylenebenzobisimidazole) are heat-treated in an inert gas at a temperature range of 400 to 700°C to prevent self-shrinkage, and then heated to a temperature of 1800°C or higher. proposed a method for producing Grapheye 1~ films with excellent properties by heat-treating them (Patent Application 1986 1..1, 5).
41.8).

Although the film obtained in this way has excellent conductivity and flexibility, it cannot be said to have sufficient mechanical strength because the original properties of Graph Eye 1 appear. Although Eye 1~ can be considered for a wide range of uses as an industrial material, the range of applications for graphite obtained by the above-mentioned manufacturing method is limited.

The purpose of the present invention is to obtain graphite which has the excellent properties of such a graphitized polymer film and also has mechanical toughness, and in order to achieve this purpose, As a result of a detailed study of the structure of heat-treated polymer films, the present inventors obtained new knowledge that all polymer films heat-treated at 1800°C or higher have a unique layer structure. Focusing on the layer structure, we conducted further intensive research to utilize the interlayers to impart toughness.We found that by impregnating a binder component between these layers and then heat-treating them at an appropriate temperature, the interlayer bond becomes stronger. The present invention was achieved by discovering that toughness can be imparted to the film.

That is, the present invention provides polyoxadiazole, polybenzothiazole, polybenzobisthiazole, polybenzoxazole, polybenzobisoxazole, poly(pyromellitimide), poly(m-phenylene isophthalamide), poly(m- phenylenebenzimidazole)
, poly(m-phenylenebenzobisimidazole), and polythiazole at 1.800°C in an inert gas or vacuum.
The present invention relates to a method for producing a graphite film, which comprises heat-treating at a temperature above, then impregnating with a binder component, and heat-treating at a temperature of 1400° C. or below.

The method of the present invention cannot be applied to all polymers, but is limited to those having a layered structure as described in item 1 above, and therefore is currently limited to the polymers of the present invention. Table 1 summarizes the names, abbreviations, and structural formulas of the starting material polymers of the present invention.

Table 1 and FIG. 1 show, as an example of the layer structure, an electron micrograph of the layer structure of a graphite film formed when a polyoxadiazole (POD) film is treated in argon at 2500°C. In the polymer of the present invention, such a layered structure is usually formed at a temperature of 1800°C or higher, so it is necessary to heat the base film to 1800°C or higher. In fact, it was not possible to impregnate the binder with the treated material at 1800° C. or lower even if the binder impregnation treatment was performed.

Binders include carbonaceous substances, synthetic resins, oils and fats, metals, and inorganic compounds. Pitch is mainly used as the carbonaceous material, but in order to control the degree of porosity, low-viscosity materials such as tar, creosote oil, acenaphthene, etc. can be mixed and used.

As the synthetic resin, epoxy resin, phenol resin, furfuryl alcohol resin, polyester, polyvinylidene chloride, polydivinylbenzene, polyvinyl butyral, etc. can be widely used. Linseed oil, tung oil, etc. can be used as the oil and fat, white metal, copper, aluminum, etc. can be used as the metal, and phosphate, alumina, water glass, etc. can be used as the inorganic compound. The amount of binder added is selected within a range that increases the strength and does not lose the original properties of the graphitized film, and the amount added varies depending on the type of binder, but it is usually 5 to 20% relative to the graphite film. Weight % weight % tube circumference is suitable. The temperature of this secondary heating varies depending on the type of binder, but is generally appropriately selected from a range of 1400° C. or lower. 1400℃ or higher 1-. Temperatures of 10 to 10% are generally unnecessary and can in some cases weaken the bond and cause the film to lose its toughness. Furthermore, when a synthetic resin is used as a binder, heat treatment at high temperatures is not necessary; for polymers such as polyvinyl butyral, polyester, and polyvinylidene chloride, drying at a temperature of 50 to 100°C after impregnation is sufficient. Provides strength.

The heating time is 10 minutes to 4 hours, preferably 30 minutes to 11 hours.

Graphite l-fill 11 obtained was converted to graphite (
To express the degree of graphitization, X-ray diffraction parameters such as lattice constant and crystallite size in the C-axis direction and the graphitization rate calculated therefrom are often used, and electrical conductivity values are also often used. The lattice constant is calculated from the position of the (002) diffraction line of X-rays, and the closer it is to the value of 6,708 people, which is the lattice constant of natural single crystal graphite, the more developed the graphite structure is. Further, the size of the crystallite in the C-axis direction is calculated from the half-width of the (OO2) diffraction line.

The larger the value, the better the planar structure of graph eye i- is developed. The crystallite size of natural single crystal graphite is 1. It is OO0Å or more. The graphitization rate is calculated from the crystal plane spacing (dooz) in the literature [Merig a
nd Maj re, Les Carbons
Vol, 1 p129 (]-965)]. Of course, it is 100% in natural single crystal graphite. The electrical conductivity value refers to the value in the a-axis direction of graphite, and is 1 to 2.5 for natural single crystal graphite.
X104S/cm. The larger the conductivity value, the closer the structure is to graphite.

Naturally, as the amount of binder added increases, the original properties of the graphitized film will be lost. Therefore, here, the properties of the graphitized film will be estimated by measuring the electrical conductivity value, which is the easiest to measure.

action POD, PBO, PBBO, PT, PBBT.

PI, PA, PBI, PBBI, PT (T-1, PBT
-2. A PBT-3 film is heat treated in an inert gas or vacuum at a temperature of 1800'C or higher to form a graphitized film, then impregnated with a binder component and reheated at a temperature of 1400'C or lower. This makes it possible to impart mechanical toughness to the graphitized film without impairing its properties.

EXAMPLES The present invention will be explained below using examples, but it goes without saying that the present invention is not limited to these examples.

The physical properties of the graphitized film were measured as follows.

1. Electrical conductivity (S/cm) A four-terminal electrode was attached to the sample using silver paste 1- and a gold wire, a constant current was passed through the outer electrode, and the voltage drop was measured at the inner electrode. sample width,
The length and thickness were determined using a microscope and the electrical conductivity value was determined.

2. Tensile strength and bending strength were measured according to JISR7222 using an Olsen type universal testing machine.

Example 1 A 25 micron thick POD film was sandwiched between graphite substrates, heated at a rate of 10°C per minute in an argon stream, and treated at 2800°C for 1 hour.

The furnace used was an electric furnace (Ultra High Temperature Furnace Model 46-1 manufactured by Shinsei Electric Furnace Co., Ltd.) using a carbon heater. The film thus obtained was once cooled to room temperature, and then a furfuryl alcohol initial polymer [Hitafuran 302, Hitachi Chemical Co., Ltd.
Co., Ltd.)] was impregnated. After the impregnated furfuryl alcohol was polymerized and cured, it was heat-treated at 1000° C. for 40 minutes using a UTF-8 type electric furnace manufactured by Sankyodenro Co., Ltd. After the heat treatment, the amount of binder component impregnated was determined by weight measurement, and then the electrical conductivity, tensile strength, and bending strength of the film were measured. The results are shown in Table 2. It can be seen that if the amount of binder is within 20% by weight based on the graphite film, the tensile strength and bending strength can be significantly improved without substantially damaging the conductive dust of the film.

Table 2 Example 2 p which was heat-treated at 2800° C. in the same manner as in Example 1.

Add acenaphthene and pitch mixture to D film at 200℃
impregnated at a temperature of After impregnating, the film was heated at a rate of 10°C per minute using a UTF-8 type electric furnace manufactured by Sankyo Denro Co., Ltd.
The temperature was raised to 00°C for 30 minutes to perform a secondary heat treatment. The amount of impregnation was varied by changing the ratio of acenaphthene to pitch. Table 3 shows the values of electrical conductivity, tensile strength, and bending strength of the film thus prepared.

When the binder is pitch, an improvement in mechanical strength similar to that in Example 1 is observed, and this effect becomes noticeable when the amount added exceeds 5% by weight, and conversely, when the amount added is 27% by weight, there is a decrease in conductive dust. It turns out that it brings about

Table 3 Example 3 POD, PBO, PBBO, PT, PBBT.

PI, PA, PBI, PBBI, PBT-1, PBT-
2. Twelve types of polymers, PBT-3, were heat-treated at 2500° C. in the same manner as in Example 1.

The resulting heat-treated film was impregnated with a mixture of acenaphthene and pitch at a temperature of 200°C, and after impregnation, the film was heated at 900°C for 30 minutes using a UTF-8 type electric furnace manufactured by Sankyo Denro Co., Ltd. Secondary heat treatment was performed. The amount of binder impregnated was varied by varying the ratio of acenaphthene to pitch. Table 4 shows the electrical conductivity and tensile strength 1 bending strength values of the films thus prepared. P.O.
It can be seen that impregnation with other polymers is possible as in the case of D, and mechanical properties such as tensile strength and bending strength can be significantly improved by impregnation with a binder component and subsequent heat treatment. It is also found that when the amount of impregnation exceeds about 20% by weight, the amount of conductive dust tends to decrease.

Table 4 1191 Example 4 p which was heat-treated at 2800° C. in the same manner as in Example 1.

Epoxy resin (manufactured by Sumitomo Chemical Co., Ltd.,
Sumie epoxy ELM-434) was impregnated in a conventional manner. After impregnation, the film was heated at 80°C for 1 hour and at 150°C for 1 hourff.
Jj: Finally, heat treatment was performed at 170° C. for 1 hour to harden the epoxy resin. Table 5 shows the electrical conductivity and tensile strength values of the films thus prepared.

Table 5 Other binders such as linseed oil, tung oil, phenolic resin, polyester, polyvinylidene chloride, polydivinylbenzene, polyvinyl butyral, white metal, phosphate, alumina, water glass, etc. were prepared using graphite in the same manner as in Example 3. Similar results were obtained by impregnating the film and then heat treating it.

In short, the present invention relates to polyoxadiazole, polybenzothiazole, polybenzobisthiazole, polybenzoxazole, polybenzobisoxazole, poly(
pyromellitimide), poly(m-phenylene isophthalamide), poly(m-phenylenebenzimidazole), poly(m-phenylenebenzobisimidazole)
, at least one kind of polymer film selected from polythiazole is heated in an inert gas or vacuum for 1800 min.
A method for producing a graphite film, characterized in that it is heat treated at a temperature of 1400°C or higher, then impregnated with a binder component, and then reheated at a temperature of 1400°C or lower, which has better electrical conductivity than the present invention and is mechanically It became possible to produce a graphite film with excellent physical properties. The graphitic film of the present invention is widely used in electrodes, heating elements, structural forests, gaskets, heat insulating materials, corrosion-resistant sealing materials, brushes for electrical equipment, moderators for X-ray monochromators-1 nuclear reactors, and the like.

[Brief explanation of drawings]

FIG. 1 is an electron micrograph of the layer structure of a graphite film formed when a POD film is treated at 2500° C. in argon.

Claims (4)

[Claims] (1) Polyoxadiazole, polybenzothiazole,
polybenzobisthiazole, polybenzoxazole,
At least one selected from polybenzobisoxazole, poly(pyromellitimide), poly(m-phenylene isophthalamide), poly(m-phenylenebenzimidazole), poly(m-phenylenebenzobisimidazole), and polythiazole A polymer film of various types is heat-treated at a temperature of 1800°C or higher in an inert gas or vacuum, and then impregnated with a binder component and heated to a temperature of 1400°C.
A method for producing a graphite film characterized by heat treatment at the following temperature. (2) The method for producing a graphite film according to claim 1, wherein the binder is a carbonaceous material, a synthetic resin, an oil or fat, a metal, and/or an inorganic compound. (3) The synthetic resin is furfuryl alcohol resin and/or epoxy resin, and the carbonaceous material is acenaphthene and/or
or pitch, the method for producing a graphite film according to claim 2. (4) Apply binder to graphite film from 5 to 50%
The method for producing a graphite film according to claim 1, 2 or 3, wherein 20% by weight is added.