JPS6227166B2 - - Google Patents

Description

[Detailed description of the invention]

a. Field of Industrial Application The present invention relates to a method for producing carbonaceous fibers used as materials for conductors, resistors, heating elements, electrodes, or as reinforcing materials for composite materials such as FRP and FRM. b. Prior Art Conventionally, as a method for producing carbonaceous fibers, the following methods have been widely used: (1) making fibers from polyacrylonitrile, cellulose, pitch, etc., making them infusible, and then firing them. Apart from this method, (2) benzene,
A method of directly producing fibers by thermally decomposing hydrocarbon gases such as methane and ethane and performing a gas phase reaction is also known. Fibers produced by this method are called vapor-grown carbon fibers, and have superior properties in terms of modulus of elasticity, tensile strength, electrical conductivity, etc., compared to carbon fibers produced by the method (1) above. However, the conventional method for producing vapor-grown carbon fibers using a hydrocarbon gas such as benzene as a raw material has the following drawbacks. (1) Vapor-grown carbon fibers are difficult to obtain as continuous long fibers; they are short fibers and often have defects, making it difficult to obtain uniform fibers. (2) The thickness of the fibers is approximately 5 to 50 μm, which is highly variable and non-uniform. Thin fibers are preferred when used as reinforcing materials because they generally have higher strength and modulus of elasticity. However, 5 μm
It is difficult to stably obtain fibers with diameters below. (3) The reaction temperature is high, generally requiring a temperature of 1100°C or higher. (4) To promote the growth reaction, catalysts such as
Requires ultrafine powder such as Fe, Ni, Co, etc. When a catalyst is not used, it is difficult to control the reaction and fibers may not be obtained. The present inventors conducted research to resolve the drawbacks of conventional vapor-grown carbon fibers, and found that when benzene is used as a raw material, carbon fibers are produced through a dehydrogenation reaction on the catalyst surface, so Requires high temperature. Therefore, we conducted research to generate carbon fibers using reactions other than this reaction. As a result, when aromatic dianhydride is used as a raw material, the carbonyl group part cleaves, and the resulting aromatic hydrocarbon radicals associate in the gas phase and grow, forming a fibrous product. He discovered this and invented a way to produce carbonaceous fibers. That is, an aromatic diacid anhydride or a compound that generates an aromatic diacid anhydride by heating is heated and vaporized in a gas atmosphere selected from argon, nitrogen, helium, hydrogen, and a mixed gas thereof or in a vacuum. We have invented a method for producing carbonaceous fibers characterized by vapor phase growth. (Special application filed in 1982)
issue). The carbonaceous fibers obtained in this way are shown in the table below.
As shown in 1, carbonaceous fibers obtained from conventional polyacrylonitrile-based (abbreviated as PAN-based)
It also has superior tensile strength, elastic modulus, and electrical resistivity compared to vapor-grown carbon fibers made from benzene.

[Table] Although it has such excellent physical properties, on the other hand, the thickness of the fiber is about 0.1 to 4 μm in diameter, and there is a problem that it is not possible to obtain fibers that are very thick. c. Purpose of the Invention The purpose of the present invention is to provide carbonaceous fibers made from aromatic diacid anhydrides and having the excellent properties of carbonaceous fibers grown in the vapor phase and having increased fiber thickness. be. d Structure of the Invention The present inventor uses hydrocarbons such as benzene, methane, ethane, and propane on carbon fibers grown in the vapor phase using aromatic dianhydride as a raw material, and grows fibers grown in the vapor phase. and that the fiber diameter can be easily increased to about 50 μm. It was also found that the obtained carbonaceous fiber possesses high tensile strength and electrical conductivity, which are characteristics of vapor-grown carbon fiber from aromatic dianhydride present inside. The present invention was completed based on this knowledge. e Summary of the Invention The summary of the present invention is that an aromatic diacid anhydride or a compound that produces an aromatic diacid anhydride upon heating is heated in a gas atmosphere selected from argon, nitrogen, helium, hydrogen, and a mixed gas thereof. Hydrocarbons are added onto the carbonaceous fibers, which are heated and vaporized in an inert gas atmosphere or in a vacuum to produce a vapor phase, and then heated and vaporized in an inert gas atmosphere or in a vacuum to grow in a vapor phase to increase the fiber thickness. A method for producing carbonaceous fibers characterized by increasing the . Representative compounds of aromatic diacid anhydrides used in the present invention include the following compounds. Pyromellitic acid dianhydride (abbreviated as BTCD);
1,4,5,8, naphthalenetetracarboxylic acid 2
Anhydride (NTCD-1); 2,3,6,7, naphthalenetetracarboxylic dianhydride (NTCD-2);
1,2,5,6, naphthalenetetracarboxylic acid 2
Anhydride (NTCD-3); 3,4,9,10 perylenetetracarboxylic dianhydride (PTCD-1); 1,
12,6,7 perylenetetracarboxylic dianhydride (PTCD-2); 3,4,8,9 anthracenetetracarboxylic dianhydride (ATCD); 3,4,
8,9, pyrenetetracarboxylic dianhydride; 3,
3',4,4'biphenyltetracarboxylic dianhydride;2,2',3,3'biphenyltetracarboxylic dianhydride;2,2-bis(3,4-benzophenonetetracarboxylic acid) 2 anhydride; bis(3,4-dicarboxyphenyl) sulfone 2 anhydride; bis(3,4-dicarboxyphenyl) ether 2 acid anhydride, 2,3,4,5 thiophenetetracarboxylic acid 2 Anhydrides; There are also isomers of these dianhydrides and dianhydrides such as phenanthrene, acridine, pyrrole, quinoline, and colomene.However, the compound is not limited to these exemplified compounds.Furthermore, Starting materials in the present invention include:
Compounds that produce the aromatic diacid anhydride when heated, such as tetraaromatic carboxylic acids that produce aromatic diacid anhydrides when heated, can also be used. The mechanism for growing vapor-phase grown carbon fibers using aromatic diacid anhydride as a raw material essentially does not require a catalyst for growth promotion. In fact, many aromatic dianhydrides can be made into fibrous products simply by heating. However, in the case of a compound with a relatively low melting point such as BTCD (melting point 283-286°C), the presence of a catalyst is preferred since the presence of a catalyst promotes the cleavage reaction of the carbonyl group. Catalysts used in such cases include Fe, Co, Ni, V, Nb, Ta, or compounds such as their carbides and nitrides, which are commonly used in the production of vapor-grown carbon fibers. Catalysts can also be used. These catalysts are placed in the heating zone where the carbonaceous fibers are precipitated, and are particularly effective when they are in the form of ultrafine powders. The growth reaction is carried out in a gas atmosphere selected from argon, nitrogen, helium, hydrogen, and mixed gases thereof, or in vacuum. Particularly when using raw materials whose vaporization temperature is high, it is effective to carry out the process in a vacuum. On the other hand, when using a raw material with a low vaporization temperature, it is effective to use an autoclave and pressurize the gas. The presence of hydrogen generally tends to slow down growth reactions. Furthermore, when the growth reaction is carried out in the presence of a catalyst, it is preferable to have hydrogen present. In this case, hydrogen is considered to work effectively to maintain the activity of the catalyst. The presence of a small amount of oxygen has the effect of promoting the growth reaction, but the presence of 10% or more of oxygen inhibits the growth reaction. It is thought that the presence of a large amount of oxygen causes combustion and generates sooty carbon, which inhibits the growth reaction. Examples of producing carbonaceous fibers using aromatic diacid anhydrides as raw materials are as follows. Various aromatic dianhydrides pressed into pellets (pellet diameter: 13 mm, thickness: 1 mm) were set in a heating furnace and heated at a rate of 10°C/min to a preset temperature between 200 and 1000°C. After heating and holding at that temperature for 1 hour, the temperature was lowered at a rate of 40°C/min. All reactions were carried out in an argon atmosphere, and after the reaction was completed, the pellet surface was observed to confirm the presence or absence of products. The lowest temperature at which the presence of the product was recognized was defined as the formation temperature, and the general shape (diameter and length) of the fibers formed between this formation temperature and 1000°C was measured using an electron microscope. The results were as shown in Table-2.

【table】

【table】

[Table] When carbonaceous fibers grown in a vapor phase on a substrate such as a ceramic plate in this manner are passed through a hydrocarbon gas such as benzene or propane at 1100°C in argon gas or vacuum, the carbonaceous fibers are grown in a vapor phase. The fibers grow in the vapor phase and become fibers with a thick diameter. The thickness can be adjusted to any desired thickness by controlling the supply amount of benzene, etc., temperature, and reaction time. The physical properties of the fibers obtained in this way retain well the physical properties of fibers made from aromatic dianhydride as a starting material, and are better than those of carbon fibers obtained by the usual vapor phase growth method. Excellent elastic modulus, tensile strength,
It has electrical conductivity. Of course, as the diameter becomes thicker, the above-mentioned physical property values approach those of carbon fiber obtained by a normal vapor phase growth method. However, in experiments conducted by the present inventors, it is possible to obtain fibers with sufficiently excellent physical properties even when the fiber diameter is increased to about 10 times that of fibers made from aromatic dianhydride as a starting material. e Examples Example 1 PTCD-1 was heated to 600℃ in argon gas.
Carbon fibers were grown on a ceramic substrate.
The thickness of the fiber was 0.2 μm. This is mixed with benzene gas in a mixed gas of argon gas and hydrogen.
Passed at temperatures above 1100℃. The reaction time, temperature, and amount of benzene gas supplied were varied. The results were as follows.

【table】

[Table] As shown by the above results, the fiber thickness increases when the benzene gas supply amount is increased, the reaction temperature is increased, and the reaction time is prolonged. Benzene supply amount 5c.c./
The tensile strength of carbon fiber grown to a thickness of 5 μm at a reaction time of 30 minutes and a temperature of 1100°C is 32 tons/cm ² ,
Elastic modulus is 4100ton/cm ² , electrical resistivity is 1.50×10 ^-3
It was Ωcm. In other words, the physical properties of the carbon fiber obtained in this way are based on the starting PTCD fiber (0.2 μm
The physical properties of PTCD fibers are almost the same as those of φ) and maintain the excellent properties of PTCD fibers. However, as the fiber obtained by the method of the present invention becomes larger in thickness, its physical properties approach those of conventional carbon fiber grown in a vapor phase using a hydrocarbon gas such as benzene gas. . In experiments conducted by the present inventors, when the fiber diameter exceeds 30 μmφ, its physical properties are almost equal to those of conventional vapor-grown carbon fibers having the same diameter. The above uses PTCD-1 as a raw material, but other aromatic compounds 2
The fiber thickness can be similarly increased when acid anhydrides are used as raw materials, or when hydrocarbons such as methane and propane are used instead of benzene. Example 2 In the same manner as in Example 1, the diameter of carbonaceous fibers made from PTCD-1 was increased using propane gas. Although the obtained fibers were denser than those obtained when benzene gas was used, the physical properties were almost unchanged. Example 3 Using the same method as Example 1, NTCD-1, P _y TCD
The diameter of the carbonaceous fiber made using the raw material was increased. The diameter of the carbon fiber used is 0.5 for NTCD-1.
μm, P _y TCD is 0.6 μm. The diameter of such fibers is increased using benzene gas.
The fiber diameter of NTCD-1 was 15 μmφ, and the fiber diameter of P _y TCD was 10 μmφ. The physical properties of the former were a tensile strength of 28 ton/cm ² , an elastic modulus of 3900 ton/cm ² , and an electrical resistivity of 1.6×10 ⁻³ Ωcm. The physical properties of the latter were 32 ton/cm ² in tensile strength, 4000 ton/cm ² in elastic modulus, and 1.75×10 ⁻³ Ωcm in electrical resistivity. f Effects of the Invention According to the present invention, carbon fibers obtained by vapor phase growth using aromatic diacid anhydrides as raw materials have excellent tensile strength, elastic modulus, and electrical conductivity, and the fiber thickness can be reduced. It has an excellent effect of improving small defects and thereby widening the scope of handling and utilization.

Claims (1)

[Claims] 1 Aromatic 2 acid anhydride or aromatic 2 by heating
A compound that generates an acid anhydride is heated and vaporized in a gas atmosphere selected from argon, nitrogen, helium, hydrogen, and a mixed gas of these gases or in a vacuum to form a vapor phase on the carbonaceous fiber, which is further carbonized. A method for producing carbonaceous fibers, which uses hydrogen and heats and vaporizes it in an inert gas atmosphere or in a vacuum to cause vapor phase growth and increase the fiber thickness.