JPS6223083B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat treatment method for efficiently performing the infusibility and carbonization treatments necessary when producing carbon fiber using coal-based or petroleum-based pitch as a raw material, and an apparatus used therefor. be. Carbon fiber takes advantage of its excellent properties of heat insulation, heat resistance, chemical resistance, rigidity, and electrical conductivity.
Insulating materials, sealing materials, materials for electrical and mechanical parts,
It is widely used as a material for structural members and sports equipment. Conventionally, high-quality carbon fibers were mainly produced by firing fibers such as acrylonitrile and cellulose, but these raw materials are expensive and have low carbonization yields, making them difficult to use for industrial use. This is not an appropriate method for supplying large amounts of material. For this reason, as a result of active research and development into technology for producing high-strength, high-elasticity carbon fibers using various types of pituitary that are inexpensive and easily available as raw materials, a number of highly feasible methods have been proposed in recent years. has been done. By the way, in order to produce carbon fibers from pitch-based raw materials, the method generally involves melt-spinning the pitch-based raw materials, making them infusible by heating them in an oxidizing atmosphere, and then carbonizing them by firing them in an inert atmosphere. is taken. The infusibility process and the carbonization process are usually carried out by running the spun raw material fiber in a heating furnace in an oxidizing or inert atmosphere while winding it around a roller. Pitch-based raw material fibers have low strength and elongation and are brittle, so it is not possible to increase the winding speed, and there is also a limit to the curvature of the folding roller used, and it takes time and effort to repair yarn breaks. There are many problems that should be improved, such as, and the equipment tends to be large-scale, so it is inevitable that it will be inconvenient when implemented industrially. As an improved method to solve these problems, the raw material fibers that have been melt-spun are placed on a conveyor, and the fibers are transferred along with the conveyor.
Method of infusibility through heating zone
175664), a method in which the melt-spun raw material fibers are suspended from horizontal bars arranged in a tray and introduced into an infusibility chamber together with the tray to be infusible (Japanese Patent Application Laid-Open No. 1983-6547), etc. There is. However, in these methods, the raw material fibers wound on a bobbin during melt spinning are unwound and transferred to a horizontal bar by a conveyor, or they are placed on a conveyor using a special device without being wound on a bobbin. It has the disadvantage that the operation and equipment are complicated because it needs to be suspended from a horizontal bar. Also, consideration has been given to winding raw material fibers onto a bobbin during melt spinning and subjecting them to infusibility and carbonization treatment as they are. However, apart from the infusibility process, a considerable amount of tar-like decomposition products are generated in the carbonization process, which causes contamination of the fiber surface and adhesion of fibers to each other, so this is removed by purging with inert gas, etc. However, the gaps between the fibers on the bobbin are so small that it is actually very difficult to remove them. Under these circumstances, the present inventors have conducted extensive research in order to develop a method and apparatus that can efficiently perform heat treatments such as infusibility and carbonization on pitch-based raw material fibers wound around a bobbin. As a result of stacking, it was discovered that the purpose could be achieved by using a hollow drum with a porous body and heat-treating the raw material fibers wound on it while passing gas through the body. Based on this knowledge, the present invention has been made. That is, in the present invention, pitch-based raw material fibers are wound around a hollow drum having a porous body whose both sides are hermetically sealed, and the required gas is passed between the raw material fibers through the pores of the porous body. A method for heat treatment of pitch-based raw material fibers characterized by heating the fibers while forcibly passing through the fibers, and a gas preheater having a temperature control means and a gas vent hole provided at an appropriate location for use in this method. A hollow cylindrical raw fiber winding drum made of a porous material having communicating holes closed at both ends is disposed inside the heating furnace, and a drum is installed at an appropriate position at one end of the drum. The present invention provides a heat treatment apparatus characterized in that a gas conduit from the gas preheater is connected to the gas introduction hole. Next, the present invention will be explained in more detail with reference to the accompanying drawings. FIG. 1 is a partially cross-sectional explanatory diagram showing an example of the apparatus of the present invention, and raw material fiber 1 obtained by melt-spinning coal-based pitch, petroleum-based pitch, or a mixture thereof is as follows:
It is wound up on a hollow drum consisting of a porous body 2 closed on both sides by side plates 3, 3. This porous body portion 2 is made of a material having a large number of communicating holes, and each of the side plates 3, 3 is made of a dense material that does not allow gas to pass through. This hollow drum is placed in a heating furnace 4, such as an electric furnace or an infrared heating device, which is maintained at a predetermined temperature by a temperature controller 5, and is heat-treated. During this time,
The gas preheated by the gas preheater 6 is sent through the gas conduit 8 to the gas introduction hole 9 provided on one side plate of the hollow drum, and from the communication hole in the porous body 2, the raw material wound on it is sent. After being passed through the fiber layer 1, it is discharged to the outside through a gas vent provided in the upper part of the heating furnace. The gas preheater 6 is controlled to a predetermined temperature by a temperature regulator 7. The gases supplied at this time include oxidizing gases such as oxygen and air in the case of the infusible process, which needs to be oxidized, and in the case of the carbonization process, gases supplied to prevent properties from deteriorating due to oxidation during carbonization. Inert gases such as nitrogen, helium, and argon are used. The raw material fiber 1 wound onto the hollow drum is usually a so-called tow or yarn made up of about 30 single fibers obtained by melt spinning. The crisscross angle when winding up this raw fiber 1 can be arbitrarily selected within the range of 0 to 30°, but it is recommended to set it to 1.0° or more in consideration of breathability and ease of unwinding. desirable. Further, the thickness of the raw material fiber layer is preferably about 20 mm or slightly thicker, although it is preferable that it be thinner in terms of ease of reaction and thicker in terms of production efficiency. The raw material fiber layer 1 may be provided on the outside of the hollow drum body 2 as shown in FIG. 1, but it may also be provided on the inside of the hollow drum body 2 as shown in FIG. The material of the body part 2 on which the raw material fiber layer 1 is provided is one that can withstand the temperature and atmosphere during infusibility or carbonization, and the raw material fiber layer 1 provided thereon
A material that provides appropriate flow resistance is used so that the gas can be uniformly dispersed. Examples of such materials include metals, sintered bodies such as ceramics,
Examples include a sintered body of carbon, a metal mesh body and a laminate thereof, a perforated metal plate, and a composite body thereof. Further, the flow resistance of the body portion 2 is desirably at least 50% or more of the flow resistance value of the raw material fiber layer 1. If necessary, a flexible felt-like material can be laminated onto the porous material to further ensure uniform gas distribution. The treatment temperature in the method of the present invention is 200 to 400°C in the case of the infusibility step, and the preferable temperature for preheating the gas to be introduced is 100 to 400°C. On the other hand, the treatment temperature in the case of the carbonization step is 400 to 1000°C, and the gas preheating temperature is preferably 300 to 1000°C. These processing temperatures are achieved by heating at a rate of increase of 1° C./min or higher. In the infusibility process, the gas supply rate is determined by the necessity of supplying reactants for the oxidation reaction, removing reaction by-products, and removing reaction heat, and in the carbonization process, the reaction by-products are completely removed and the It is advantageous to set the linear velocity based on the surface area of the hollow drum body 2 at 5 cm/sec or more in both the infusibility process and the carbonization process. According to the method of the present invention, the raw material fibers are first heat-treated under infusibility conditions while introducing an oxidizing gas, and then the introduced gas is changed to an inert gas.
By heating under carbonization conditions, the infusibility step and the carbonization step can be performed continuously using the same device. The method of the present invention has the following advantages when implemented industrially. (1) Melt-spun raw fibers can be infusible and carbonized while being wound around a bobbin. (2) Equipment efficiency and thermal efficiency during heat treatment are extremely high. (3) Because processing conditions are easy to control, products with stable quality can be obtained. (4) It can prevent fusion between raw fibers during carbonization. Next, the present invention will be explained in more detail with reference to Examples. Example 1 Pitch obtained as a residue of ethylene bottom oil was melt-spun according to a conventional method to form a hollow drum made of ceramic sintered body with a diameter of 100 mm and a length of 300 mm (opening ratio of the body part 40%, average pore diameter 5 μm). , material thickness 5
The material was wound onto a porous bobbin (mm) to a layer thickness of 20 mm. Next, this was placed in an electric furnace and heated at 300°C for 1 hour while blowing air preheated to 300°C through the gas inlet hole on the side of the bobbin to infusible the raw material fibers. The conditions at this time include a linear velocity of 30 mm based on the surface area of the bobbin cylindrical surface as the gas supply rate.
cm/sec and 1°C/min as the heating rate. Next, the obtained infusible fibers were removed from the bobbin, samples were taken from each fiber layer, loosened into single filaments, and heated at a heating rate of 10°C/min while passing nitrogen gas through an infrared heating device. The temperature was raised to 1000°C and held at this temperature for 30 minutes to cause carbonization. As a result, no mutual adhesion between fibers was observed on the surface of the fiber layer, the intermediate layer, or the layer in contact with the bobbin surface. The physical properties of the carbon fiber thus obtained are shown in the table. Comparative Example 1 The same raw material fiber as in Example 1 was wound onto a porous bobbin under the same conditions as in Example 1, and the other conditions were the same as in Example 1, except that the material was not removed from the bobbin and no ventilation was performed during infusibility. When the resulting infusible yarn was removed from the bobbin and carbonized in an infrared heating device in the same manner as in Example 1, the fibers in the intermediate layer of the fiber layer and the layer in contact with the bobbin surface were completely melted, forming a plate. As a result, the desired carbon fiber could not be obtained. Comparative Example 2 The infusible fiber obtained in Example 1 was heated at a heating rate of 10°C/min in a nitrogen atmosphere without removing it from the bobbin.
The temperature was raised to 1000°C and maintained at this temperature for 30 minutes to carbonize. The fibers thus obtained showed mutual adhesion in each layer and had poor physical properties. The physical properties are shown in the table. Example 2 The infusible yarn obtained in Example 1 was placed in a nitrogen atmosphere without removing it from the bobbin, and nitrogen gas preheated to the same temperature as the atmosphere was injected into the bobbin at a speed of 50 cm/sec based on the bobbin surface area. While passing from
The temperature was raised to 1000°C at a heating rate of 10°C/min, and this temperature was maintained for 30 minutes for carbonization. At this time, no mutual adhesion of fibers was observed. The heat treatment conditions and physical properties of the carbon fibers thus obtained are shown in the table. 【table】

[Brief explanation of the drawing]

FIG. 1 is a partially cross-sectional explanatory view of an example of the apparatus of the present invention, and FIG. 2 is a cross-sectional view showing a raw material fiber winding drum in a different aspect from that shown in FIG. In the figure, numeral 1 is a raw material fiber layer, 2 is a porous body of a hollow drum, 3 is a side plate, 4 is a heating furnace, and 6 is a gas preheater.

Claims (1)

[Scope of Claims] 1. Pitch-based raw material fibers are wound around a hollow drum having a porous body whose both sides are hermetically sealed, and the required distance between the raw material fibers is passed through the pores of the porous body. A heat treatment method for pitch-based raw material fibers, which is characterized by heating while forcing gas through. 2. The method according to claim 1, wherein the raw fiber is wound around the outside of a hollow drum. 3. The method according to claim 1, wherein the raw fiber is wound inside a hollow drum. 4 Consisting of a gas preheater with temperature control means and a heating furnace with temperature control means and gas vent holes in appropriate places,
A hollow cylindrical raw fiber winding drum made of a porous material with communicating holes and closed at both ends is placed inside the heating furnace, and a gas introduction hole provided at an appropriate position at one end of the drum is placed inside the heating furnace. . A heat treatment apparatus for pitch-based raw material fibers, characterized in that a gas conduit from the gas preheater is connected.