JPH03167319A - Production of carbon fiber and graphite fiber - Google Patents

Abstract

PURPOSE:To obtain a high-performance carbon fiber and graphite fiber having high strength and modulus and good appearance by using an optically anisotropic pitch containing an optically anisotropic phase at a specific ratio and having specific changing ratio of orientation of magnetic field. CONSTITUTION:An optically anisotropic pitch containing >=95% optically anisotropic phase, being 2000-3000sec in longitudinal relax time by solid and wide <1>H-NMR, 0.20-0.50 in changing ratio of orientation of magnetic field by pyrene-added high-temperature <13>C-NMR and preferably containing >=95% content of optically anisotropic phase is melt-spun and 0.01-10wt.% lubricant is attached to the spun yarn and load is applied to the fiber bundle and then the fiber bundle is treated e.g. at <=200 deg.C in atmosphere of oxidation agent of halogen, NO2, etc., for a short time to infusibilize the fiber bundle and the infusibilized fiber bundle is subjected to preliminary carbonization under atmosphere of argon gas, etc., at 500-1000 deg.C and carbonization at 1000-2000 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing high-performance carbon fibers and graphite fibers. More specifically, the present invention relates to a method for producing high-performance carbon fibers and graphite fibers using optically anisotropic pitch having specific association properties as a raw material. [Conventional technology] There has been a demand for the development of high-performance materials with light weight, high strength, and high modulus of elasticity in various industrial fields such as automobiles and aircraft. ) are attracting attention. Currently, the mainstream carbon fibers on the market are still PAN-based carbon fibers made from polyacrylonitrile, but carbon fibers made from coal or petroleum-based pitches are also cheaper raw materials, have a high yield in the carbonization process, and have good elasticity. It is regarded as important due to its advantages such as the ability to obtain fibers with high fiber content, and active research and development efforts are being carried out. Carbon fibers obtained from optically isotropic pitch have low strength and elastic modulus, but high-performance carbon fibers can be obtained from optically anisotropic pitch obtained by heat-treating optically isotropic pitch. Regarding optically anisotropic pitch 1111 production, for example, general raw materials for pitch 12 production such as heavy hydrocarbon extraction, tar, commercially available isotropic pitch, etc. are simply heat-treated (Japanese Patent Laid-Open No. 49
-19127y, No. 57-42924), extracting the optically isotropic pitch with a solvent and heat-treating the insoluble content (Japanese Patent Application Laid-open No. 160427/1984, etc.), heating while blowing inert gas. Process (Unexamined Japanese Patent Publication No. 5 Jl-1686
No. 87), heat treatment after partial hydrogenation (Japanese Patent Application Laid-open No. 18-18421)
, The pyrolysis polycondensation is stopped in the middle and high concentration anisotropic pitch is obtained by sedimentation separation or centrifugation depending on the difference in specific gravity (Japanese Patent Publications No. 61-38755 and No. 62-24036)
Several methods have been proposed. [Problems to be Solved by the Invention] However, when carbon fibers are produced using a pitch in which the optically anisotropic phase obtained by such a method has a pitch of 95% or more, the associativity of the pitch usually decreases. It is too strong, the range of long-term stable spinning conditions is narrow, and it is difficult to control the fiber structure by spinning. Therefore, it is difficult to optimize crystal growth during carbonization and graphitization, and as a result, it is difficult to obtain high-performance carbon fibers. The problem is that it is difficult to Therefore, the object of the present invention is to overcome these problems, that is, to create a fiber structure with high spinning stability and using pitch as a raw material that has special association characteristics different from conventional optically anisotropic pitch. It is easy to control and can stably produce high-performance carbon fiber. The purpose of this invention is to provide a method for producing carbon fiber and graphite fiber. [Means for Solving the Problems] According to the present invention, containing 95% or more of an optically anisotropic phase,
Moreover, the longitudinal relaxation time measured by solid-state wide-width 2H-NMR is 2,000-3,000 tsec, and the magnetic field orientation change rate measured by pyrene-added high-temperature C-NMR is 0.20-0.50. Provided is a method for producing carbon fibers and graphite fibers, which is characterized in that a certain optically anisotropic pitch is used as a raw material, which is melt-spun, made infusible, carbonized, and optionally graphitized. In the present invention, optically anisotropic pitch refers to a pitch that shows brightness by polishing the cross section of a pitch lump solidified at room temperature and rotating crossed nicols using a reflective polarizing microscope, that is, a pitch that has substantially no optical anisotropy. This refers to a pitch in which most of the pitches are tropic, and a pitch that is optically isotropic without any brilliance is referred to as an optically isotropic pitch in this specification. The optically anisotropic pitch includes not only a pure optically anisotropic pitch but also an optically isotropic phase contained in an optically anisotropic phase in the form of a spherical or irregularly shaped island. Conversely, optically isotropic pitch also includes a small amount of optically anisotropic phase in the optically isotropic pitch. The optically anisotropic phase in is considered to be similar to the so-called mesophase, but there are two types of mesophase: one that is insoluble in quinoline or pyridine, and one that contains a large amount of components that are soluble in quinoline or pyridine. The optically anisotropic phase referred to in the book is mainly
This is the latter mesoface. In addition, the content of the optically anisotropic phase in the present invention refers to the area ratio occupied by the optically anisotropic phase in the sample obtained by photographing the sample under orthogonal polarization using a polarizing microscope. It was determined by measurement. The softening point of pitch in the present invention refers to the solid-liquid transition temperature of pitch, which is determined from the peak temperature of absorption and release of latent heat during melting or solidification of pitch using a differential scanning calorimeter. be. This temperature is suitable for other ring-and-pole methods for pitch samples,
It agrees within a range of ±10°C with that measured by the micro-melting point method. The method for producing carbon fibers and graphite fibers of the present invention will be explained in detail below. (1) Optically anisotropic pitch of H material (1) Physical properties of pitch The optically anisotropic pitch used as a raw material in the present invention contains 9 or more optically anisotropic phases and has a solid wide 1[
The longitudinal relaxation time measured by 1H-NMR is 2,0
00-3, OOOmsec (preferably 2,20
0-2,700 msec), and the magnetic field orientation change rate measured by pyrene-added high-temperature C-NMR is 0.
．． 20-0.50 (preferably 0.30-0.48). Note that the longitudinal relaxation time here refers to the environment around the hydrogen in the pitch molecule (side chain structure,
(aromatic ring skeleton structure, interactions between pitch molecules, etc.); the larger this value, the more side chains there are, the smaller the aromatic ring skeleton, and the easier the molecule as a whole is to move. Also, as this value decreases, the number of side chains decreases and the aromatic ring skeleton develops, making it difficult for the molecule as a whole to move. Therefore, the longitudinal relaxation time is a parameter that represents the association characteristics attributed to the molecular structure. It can be found as follows. Use I! :Solid wide width'H-NMR Sample: Bitch powder approx. 1006 Measurement method: Pack the sample into a 5-inch inner diameter sample tube
After vacuum degassing under 0-” torr, the tube length is 4
0 ■ Seal the tube so that it is no more than ugly. Set the sample and
801 τ - 90° pulse with acquisition time (τ) of 0. O
Measure the spectral intensity (▲τ) at 10-15 points by varying the time from 1 second to about 20 seconds. The longitudinal relaxation time (T,) is calculated from the spectral intensity at each acquisition time using the following formula (1). Aω: Spectral intensity when τ is infinite Aτ: Spectral intensity when time τ is reached The larger this value is, the stronger the interaction between pitch molecules is and the less affected by the solvent, and the smaller this value is, the weaker the interaction between pitch molecules is, which is less affected by the solvent. It shows that it is easy. Therefore, the magnetic field orientation change rate is a parameter that represents the association force between pitch molecules, and can be found as follows. Equipment: Solution "C-NMR, 13C high temperature probe Sample: Pitch approx. 1g, pyrene (reagent special grade, mp149℃, b
p3g6℃) approx. Ig measurement method: Add 10% by weight of pyrene to bitch and grind and mix in a mortar. Pack the mixture into a sample tube with an internal diameter of 5, and melt it in a block bath preheated to 300°C while purging with nitrogen to fully fill it with the sample. Separately, prepare a pitch-only sample. The sample is heated to a specified temperature in a probe. Gated-Decoupling
Obtain the spectrum using the method. The cumulative number of times is approximately 2000. Measured temperature is 200~ for pitch only
300poise, 20-30poise for pitch/pyrene system
Measure at a temperature that will result in . The magnetic field orientation change rate (R) is determined by the following formula (II). ? n. : Aromatic carbon (magnetic field oriented molecules) strength ■■,. : Aromatic carbon (free molecule) intensity Ill. ．． , : aromatic carbon (
Magnetic field orientation molecules) strength, pyrene 10 weight addition I1m. ．． , : aromatic carbon (free molecule) strength, pyrene 1
The optically anisotropic pitch used in the present invention, in which the strength of pyrene is subtracted in terms of molar ratio, has the above-mentioned specific longitudinal relaxation time and magnetic field orientation change rate, so it has appropriate associativity. has. Therefore, when this pitch is used, the spinnable range is wide and the structure control in the spinning process is easy, and as a result, carbon iI4Jlm fibers with high strength and high elastic modulus can be easily obtained. If the longitudinal relaxation time of the pitch is less than 2,000 msec, the pitch is difficult to move due to its molecular structure, and as a result, the associative properties become too strong, resulting in low spinning stability and difficulty in controlling the fiber structure by spinning. As a result, it is difficult to optimize the crystal length during carbonization and graphitization, making it difficult to obtain carbon fibers with high strength and high elasticity. Conversely, the longitudinal relaxation time is 3,000s+seC
If this value is exceeded, the molecular structure becomes more mobile, resulting in weak association, and in some cases optically isotropic phases may be included, resulting in poor spinnability. Additionally, since the number of highly reactive side chain structures increases, control during the infusibility and carbonization processes becomes difficult. On the other hand, if the pitch magnetic field orientation change rate exceeds 0.50, the association force between molecules becomes too strong, resulting in low spinning stability and difficulty in obtaining high-strength, high-elastic carbon fibers; If it is less than 0.20, the optically isotropic phase increases more than A, and the spinnability deteriorates significantly due to the viscosity difference with the optically anisotropic phase. (n) Production of pitch The optically anisotropic pitch with appropriate associativity used in the present invention is obtained by selecting a specific petroleum-based carbonaceous raw material and undergoing multi-stage heat treatment including separation and removal of the optically anisotropic phase portion. It can be produced by recovering the optically anisotropic phase portion. Specifically, the optically anisotropic pitch used in the present invention uses a petroleum-based oily or tar-like substance having a specific composition and structure as a starting material, and
The first stage heat treatment is carried out at a temperature in the range of 80 to 460°C, and the reaction is stopped when 5 to 20% of the optically anisotropic phase in the raw or bit is formed. After separating and removing the optically anisotropic phase portion, the obtained optically isotropic pitch was heated at 380 to 460°C.
It can be easily produced by carrying out a second heat treatment at a temperature in the range of Ru. In this production method, the starting material is a fraction with a boiling point of 500 to 550°C calculated at normal pressure, which is obtained by vacuum distillation of heavy residual oil that is a by-product when petroleum is catalytically cracked. An oily or tar-like substance is used which contains aromatic components and resin components which are hebutane-soluble components as main components and does not substantially contain asphaltene components which are n-hebutane-insoluble components. The starting material does not contain solid foreign matter that causes a decrease in strength or high molecular weight components that form polymer substances through heat treatment reactions. In this production method, in order to subject the carbonaceous raw material to thermal decomposition polycondensation, the raw material is subjected to two stages of heat treatment, and after the first stage of heat treatment, the optically anisotropic phase portion is separated and removed.
Further, after the second heat treatment, the optically anisotropic phase portion is separated and recovered.

Thermal decomposition polycondensation refers to a reaction in which the thermal decomposition reaction and polycondensation reaction of heavy hydrocarbons occur in parallel as main reactions, thereby changing the chemical structure of the pitch component molecules. As a result of the reaction, scission of the paraffin chain structure, dehydrogenation, ring closure, and development of a planar structure of polycyclic condensed aromatics due to polycondensation proceed. For this reaction, the carbonaceous feedstock is about 380 to about 46
Heat treatment is carried out in two stages at 0°C, preferably 400-430°C. In the heat treatment, the reaction temperature is approximately 460°C.
If the temperature exceeds 380°C, the volatilization of unreacted raw materials will increase, the softening point of the optically anisotropic phase will also increase, and coking will easily occur, making it unsuitable. This is not desirable as it takes a long time. During heat treatment, stirring is performed to prevent local overheating and ensure uniform reaction, but in addition, to quickly remove low molecular weight substances produced as a result of thermal decomposition, stirring is performed under reduced pressure or as necessary. This can be carried out by blowing inert gas into the reactor. In this case, the inert gas may be one that has sufficiently low chemical reactivity with the pitch at the reaction temperature, such as nitrogen, water vapor, carbon dioxide, light hydrocarbon gas, or a mixture thereof. It is preferable to preheat these inert gases before blowing them in without lowering the reaction temperature. The inert gas containing cracked oil and cracked gas is extracted from the upper part of the reactor and passes through a condenser, scrubber, separation tank, etc., and the cracked oil and cracked gas are removed. Thereafter, it is also possible to use the inert gas again.

This heat treatment reactor can be of any type as long as it is a liquid-phase pyrolysis device, but it is usually made of a cylindrical container, with a raw material supply port, cracked oil, cracked gas, and inert gas. The reactor is equipped with a discharge port, a pitch outlet, etc., a stirring device, etc. is installed inside the reactor, and a heater for heating the raw materials, etc. is installed outside. The reaction operation may be performed using any method such as patch, semi-patch, or continuous method. In this manufacturing method, the optically anisotropic phase is
When ~20% (preferably 7 to 15%) is recovered, the heat treatment is stopped and the optically anisotropic phase portion is separated and removed. By removing this optically anisotropic phase portion, polymers that tend to grow during the initial stage of heat treatment are removed. If this first stage heat treatment is carried out until the optically anisotropic phase exceeds 20%, the yield of pitch decreases, and conversely, if it is stopped at less than 5%, the polymer removal effect decreases. The optically anisotropic phase produced by the first heat treatment! %
= 2.0%, the method for removing the optically anisotropic phase portion from the contained pitch, that is, the method for separating the optically anisotropic phase portion and the optically isotropic phase portion, is as follows: Various known solid-liquid separation methods may be employed as appropriate, but in particular separation methods that utilize differences in specific gravity (see, Japanese Patent Publication No. 61-38755, No. 62
-24036 publications> is preferred, and particularly in industrial production, centrifugation is preferred.

In the centrifugation method, pitch containing an optically anisotropic phase generated by heat treatment is centrifuged in its molten state, whereby the optically anisotropic phase has a higher specific gravity than the optically isotropic phase. Therefore, the lower layer (
The optically anisotropic phase is approximately 80%
The lower layer is an optically anisotropic pitch that forms a continuous phase and contains a slightly optically isotropic phase in the form of islands or minute spheres, while the upper layer is an optically isotropic phase. It is an optically isotropic pitch in which the phase is the majority, and the optically anisotropic phase is dispersed in minute spherical bodies, and the interface between the upper layer and the lower layer is clear. This method takes advantage of the fact that the specific gravity of the upper layer and the lower layer in the molten state is significantly different, and separates the lower layer from the upper layer to separate the optically anisotropic pitch and the optically isotropic pitch. Note that the centrifugal separation operation is a processing operation that applies high-speed rotation to a fluid, collects a phase with a higher specific gravity in the fluid toward the bottom (in the direction of the centrifugal force), and separates this. For example, a so-called centrifugal separator is advantageously used, particularly a continuous centrifuge that continuously separates and discharges a heavy phase and a light phase.

The temperature at which the optically anisotropic phase portion is separated depends on the magnitude of the centrifugal force, but is preferably above the softening point of the pitch, preferably from 250°C to 250°C.
The temperature range is 300℃. It may be a predetermined constant temperature within this range, or it does not necessarily have to be a constant temperature. The main purpose of this process is to deposit and coalesce the optically anisotropic parts in the direction of centrifugal force, and it is necessary to avoid thermal decomposition and polycondensation reactions as much as possible. Therefore 300℃
Temperatures higher than this are not preferred, and temperatures higher than necessary make it difficult to operate the centrifugal separator continuously for a long period of time, but at the above-mentioned temperature, there is no such problem. Furthermore, at temperatures lower than the above-mentioned range, the viscosity of the entire pitch system, especially of the optically anisotropic phase, is high, making it difficult for the optically isotropic phase co-precipitated in the lower optically anisotropic phase to come off.

Further, the centrifugal force acceleration of the centrifugal separation operation may have any value, but the residence time between the optically anisotropic phase portion (heavy phase) and the optically isotropic phase portion (light phase) may be set at any value. Preferably 1,000 in order to keep it short and separate efficiently in a short time.
A range of ˜10,OOOG can be adopted.

After the optically anisotropic phase portion is separated and removed, the pitch consisting of the optically isotropic phase is subsequently subjected to a second heat treatment. In the second heat treatment, an optically anisotropic phase of 20% is formed in the pitch.
It is discontinued when the content reaches ~70%, preferably 30-65%.

This is because the pitch that has undergone the second heat treatment is then subjected to a process to separate and recover the optically anisotropic phase portion, and in this optically anisotropic pitch recovery process, a homogeneous pitch with a low softening point is In order to obtain a high yield of optically anisotropic pitch, it is necessary to have a high pitch yield after the pyrolysis polycondensation reaction, an optically anisotropic phase content of about 20 to about 70%, and a softening point of 260°C. This is because the following is preferable. If the optically anisotropic phase in the pitch after the pyrolysis polycondensation reaction is less than 20%, the yield of the optically anisotropic pitch in the subsequent separation and recovery is extremely small.
Conversely, if the optically anisotropic phase is made larger than 70%,
Separability during separation and recovery deteriorates, making it impossible to obtain high-concentration optically anisotropic pitch. The optically anisotropic phase-containing pitch obtained by the second heat treatment is one in which most or substantially all of the optically anisotropic phase has a diameter of 500 μm or less,
Preferably, those in a spherical state with a diameter of 300 μm or less are suitable. In this manufacturing method, the optically anisotropic phase-containing pitch produced by the second heat treatment is then subjected to an optically anisotropic pitch separation and recovery process, where the optically anisotropic pitch and the optically equivalent pitch are separated and recovered. It is separated into directional pitch. As for the separation method in this case, similar to the separation after the first heat treatment, various known solid-liquid separation methods are appropriately employed, and it is particularly preferable to employ a separation method that utilizes the difference in specific gravity. In industrial production, it is preferable to employ centrifugation.

However, in this optical anisotropic pitch recovery process, when centrifugation is used, the temperature is 3lO to 360°C.
The centrifugal force acceleration is preferably in the range of 5,000 to 2
A range of 0,OOOG is preferred. By this optically anisotropic pitch recovery process, optically anisotropic pitch with an optically anisotropic phase content of 95% or more can be obtained economically in a short time. In addition, in this manufacturing method, it is also possible to add an appropriate finishing heat treatment immediately after the optical anisotropic pitch recovery treatment. That is, by using a particularly short residence time in the recovery process, an optically anisotropic pitch with a sufficiently low softening point but with a slightly insufficient optically anisotropic phase content of about 80%-90% can be produced. Then, a method may be adopted in which this is subjected to a thermal weighting reaction treatment at a temperature of 300°C to 430°C to adjust the characteristics of the optically anisotropic pitch to fall within narrow quality control limits. can. The optically anisotropic pitch containing 80-90% of the optically anisotropic phase contains 10-20% of the optically isotropic phase, but this optically isotropic phase is further thermograined. It is known that the softening point can be reduced by adding a small amount of reaction treatment, and the softening point can also be gradually raised. The content of anisotropic phase can be adjusted to 95% or more.

The pitch obtained by this manufacturing method is continuously taken out of the system and is either kept in a liquid state or solidified to become a product. By this method, an optically anisotropic pitch having a sufficiently low softening point and appropriate associativity can be obtained.

(2) Production of fiber (i) Spinning The optically anisotropic pitch having the above-mentioned association properties can be spun by a known method. In such a method, for example, a spinneret having a diameter of 0.1 to 0.5 mm is used in a 1-1.
Pitch was placed in a metal spinning container with a spinneret of 0.000 spinnerets below, and the pitch was heated to 280 to 37 mL in an inert gas atmosphere.
The pitch was held at a constant temperature between 0°C and kept in a molten state, and the pressure of the inert gas was increased to several hundred μml/g to push the molten pitch out of the nozzle and let it flow down while controlling the temperature and atmosphere. The pitch fiber is wound onto a bobbin that rotates at high speed. Alternatively, it is also possible to adopt a method in which pitch fibers spun from a spinneret are collected in a can-like manner in a lower collecting case while being collected by an air current. In this case, continuous spinning is possible by supplying pitch to the spinning container using pre-melted pitch or pressurized supply using a gear pump or the like. Furthermore, in the above method, it is also possible to use a method in which pitch fibers are drawn and drawn using gas that is controlled at a constant temperature and descends at high speed in the vicinity of the die to produce long fibers on a belt conveyor below. can. Furthermore, a cylindrical yarn container with a spinneret on the peripheral wall was used. It rotates at high speed, supplies molten pitch to the continuous B&1, extrudes the pitch from the peripheral wall of the cylindrical spinner by centrifugal force, and accumulates pitch fibers that are drawn by the action of rotation. It is also possible to use the eel spinning method. (n) Bundling agent (oil agent) In the present invention, the melt-spun pitch fibers are bundled through an air sucker and guided to an oiling roller.
Add a focusing agent (oil) to further focus.

In this case, examples of the sizing agent include ethyl alcohol,
Alcohols such as isopropyl alcohol, n-propyl alcohol, butyl alcohol or viscosity 3 to 300c
St (30℃) dimethyl silicone oil, methylphenyl silicone oil, etc. diluted with a solvent such as silicone oil or paraffin oil, or dispersed in water with an emulsifier added; Similarly, graphite, polyethylene glycol, hindered Dispersed esters; Among the various oils used for other ordinary fibers, such as polyester fibers, those that do not disturb the fibers can be used. As, U
Method of application by passing through a letter-shaped guide Conventionally known application methods such as oiling roller method and spray method can be used.

Furthermore, although the sizing agent can be applied at any time between the spinning process and the infusibility process, in order to stably handle the brittle pitch fibers, it is preferable to apply the sizing agent between the spinneret and one winder.

The amount of sizing agent attached to the fibers is usually 0.01 to 10 m
%, preferably 0.05-5% by weight. (Question) Infusibility of pitch fibers The pitch fibers that have been applied with the above-mentioned sizing agent and bundled are made infusible by a known method. The temperature of the infusibility step is 15
The temperature is raised stepwise or gradually in the range of 0°C to 400°C, preferably 200°C to 350°C, and the treatment is usually carried out for 10 minutes to 5 hours. The treatment time may be as long as 1 to 3 days so that the infusibility reaction proceeds sufficiently and uniformly. Infusibility can be achieved using air, oxygen, a mixed gas of air and oxygen or nitrogen, etc. In the present invention,
Treat for a short time in an atmosphere containing oxidizing agents such as halogens, N0, ozone, etc. at a temperature of 200°C or less, or in an oxygen gas atmosphere at a temperature 30 to 50°C lower than the softening point of pitch, i.e. 150 to Hold at a temperature of 240°C for 5 minutes to 1 hour until sufficient infusibility is obtained, and then heat at a temperature of about 300°C as necessary.
A method in which infusibility is completed by raising the temperature to ℃ is preferred, and the latter method is particularly preferred because it is easy and reliable. (iv) Heat treatment process Next, this infusible carbonaceous pitch fiber is heated in a chemically inert atmosphere such as argon gas or nitrogen gas.
After preliminary carbonization by raising the temperature to 500 to 1,000℃,
Carbon fibers are obtained by carbonization by raising the temperature to a temperature in the range of 1,000 to 2,000°C;
By raising the temperature to a temperature within the range of ,000°C and proceeding to graphitization treatment, graphite fibers are obtained. In the present invention, there are no particular limitations on the method of carbonization and graphitization, and generally known methods can be used. Also, during the infusibility, carbonization, and graphitization treatments, it prevents scratches from rubbing against the furnace walls and furnace bottom, avoids shrinkage and deformation of the yarn, or produces carbon fibers and graphite fibers with good appearance and high physical properties. For such purposes, when processing fiber bundles coated with a sizing agent, it is preferable to apply a load or tension to the fiber bundles. [Effects of the Invention] The method for producing carbon fibers and graphite fibers of the present invention uses optically anisotropic pitch having the above-mentioned specific association characteristics as a raw material, so it has a wide spinnable range and high spinning stability. , It becomes easier to control the fiber structure in the spinning process, and as a result,
According to the method of the present invention, carbon fibers and graphite fibers with high strength and high elasticity can be produced stably and efficiently.

〔Example〕

The present invention will be explained in more detail below with reference to Examples, but the scope of the present invention is of course not limited thereto. Example 1 Heavy residual oil produced as a by-product in the catalytic cracking process of petroleum was distilled under reduced pressure, and residual tar at a temperature of 500 to 550° C. in terms of normal pressure was fractionated and used as a starting material. This tar-like substance contains 90.7 carbon by weight and 8.1 hydrogen by weight. It consisted of 1.1 parts by weight of sulfur, and its composition was as shown in Table 1, and it did not contain asphaltenes. Table 1: 20 kg of this tar-like substance was charged into a reaction tank with an internal volume of 35 m, and heated at 415°C for 4 hours with thorough stirring under a nitrogen stream. Thermal decomposition polycondensation of the IR eye is carried out, and when observed with a polarized light [vII mirror, an optically isotropic matrix of 200. The pitch containing the following optically anisotropic spheres was obtained at a yield of 25% based on the FM tar. Next, this pitch was loaded into a continuous centrifuge and centrifuged in the first stage under the conditions of 250°C, 1G, and OOOG in a nitrogen atmosphere. The pitch was divided into a substantially optically isotropic pitch "B" containing no more than 2% of an orthotropic phase. Next, the pitch uPr was subjected to a second stage of pyrolysis polycondensation at 415°C for 3 hours to obtain pitch #C containing about 50% of optically anisotropic spheres of 200741 or less as residual pitch.
It was obtained in 67% yield.

This pitch tlc" was subjected to a second centrifugation in a batch-type centrifuge under nitrogen flow at 350°C and 10,000 yen. A substantially optically isotropic pitch "Ell" with a sexual phase of 3% or less was obtained in a ratio of about 50:50.
D" is solid" Longitudinal relaxation time measured by H-NMR is 2
, 410 w+sec, high temperature" The magnetic field orientation change rate measured by C-NMR was 0.450. Also, the softening point was 265°C.

Next, the pitch "D" was filled into a spinning machine with a 0.3-inch nozzle, and the spinning machine was used at a spinning temperature of 320°C for 1,000 m/min.
When the fibers were taken at a high speed of 13.0 min, the average fiber diameter remained at about 13.0 mm without breaking for more than 1 hour. This pitch fiber was oxidized and infusible at 230°C for 1 hour in an oxygen atmosphere, and then heated at 100°C/in an inert gas atmosphere.
The temperature was raised to 2,500°C at a heating rate of ra in to obtain graphite fibers. The average thread diameter of the graphite fibers obtained was 10.0.
．． Average intensity 4. 60I'a, average elastic modulus 850GP
It was a. Example 2 The pitch “B” obtained in Example 1 was heated at 420°C for 2 hours.
The second stage of pyrolysis polycondensation is carried out, and the remaining pitch is 20
A pitch 'F' containing about 50% of optically anisotropic spheres of 01 or less was obtained with a yield of 63%.This pitch II F
I+ in a batch centrifuge at 350°C under a nitrogen stream for 1
A second stage of centrifugation is carried out under the conditions of 0.00000000000000000000000000000000000,000% of the optically anisotropic phase is obtained. Pitch “H”
” were obtained in a ratio of approximately 50:5G.

Pitch "G" had a longitudinal relaxation time of 2,200 ssec measured by solid-state H-NMR, and a rate of change in magnetic field orientation measured by high-temperature 13C-NMR of 0.475. In addition, its softening point was 267°C. Next, pitch "G" was charged into a spinning machine with a nozzle of 0.3 aul, and at a spinning temperature of 320 °C, 1,0
When the fibers were drawn at a high drawing speed of 00 i/win, pitch fibers with an average fiber diameter of about 13 mm could be obtained without breaking for more than 1 hour continuously.

This pitch fiber was oxidized and infusible at 230°C for 1 hour in an oxygen atmosphere, and then at 100'C/s in an inert gas atmosphere.
The temperature was raised to 2,500° C. at a temperature increase rate of 100 min to obtain graphite fibers. The graphite fibers obtained had an average thread diameter of 9.71s, an average strength of 4.3 GPa, and an average elastic modulus of 810 GPa. Example 3 The optical anisotropy pitch "D" obtained in Example 1 was set to 0.1
Fill a spinning machine with a small diameter nozzle with a diameter of 31
When the fibers were spun at a spinning temperature of 5° C., pitch fibers having an average fiber diameter of about 12 μm were obtained without breakage for more than 1 hour at a take-up speed of 1.00 m/min.

This pitch fiber was heated at 230°C in 100% oxygen gas for 1
Infusibility treatment is carried out by holding for a time of 1,500°C and 2,5°C at a heating rate of 100°C/min in an inert gas.
It was carbonized and graphitized by raising the temperature to 00℃. The average fiber diameter of the Ja fibers carbonized at 1,500°C is 9.4cm, and the tensile strength is 3.6GPa. The tensile modulus is 270 GPa, the average fiber diameter of the fibers graphitized at 2,500°C is 9.0,n, and the tensile strength is 4. 2
GPa, and the tensile modulus was 840 GPa. Comparative Example 1 The same heavy residual oil as in Example 1 was distilled under reduced pressure and a fraction of 415°C or higher was used as a starting material. This residual oil contains 89.9 carbon by weight, 8.9 hydrogen by weight, and 1 sulfur by weight.
．． 0 weight calculation, and the set or as shown in Table-2,
It contained 3.8 parts by weight of asphaltene. Table 2 This residual oil was subjected to the first stage thermal decomposition condensation and centrifugation under the same conditions as in Example 1, resulting in an optically anisotropic phase 1GG.
% of the pitch 11 I l# and the optically anisotropic phase is less than or equal to the substantially optically isotropic pitch R J 11 of about 25
:75 ratio. Pitch 11 I I1 is a solid "}L-NMR-measured longitudinal relaxation time of 2,250 tmsec. High temperature" C-NM
The m-field orientation change rate measured at }l was 0.645.

Next, the pitch "I" was filled into a spinning machine with a 0.3 mm nozzle, and the spinning speed was 500 m/s at a spinning temperature of 320°C.
When the yarn was taken at a take-up speed of 1.5 in., the average fiber diameter was approximately 12.5 without breaking for more than 1 hour.
We were able to obtain p- pitch fibers. However, 1,OO
Stable spinning was not possible at the high take-up speed of Om/win. This pitch fiber was oxidized and infusible at 230°C for 1 hour in an oxygen atmosphere, and then heated to 100°C/+ in an inert gas atmosphere.
The temperature was raised to 2,500° C. at a temperature increase rate of 100 min to obtain graphite fibers. The graphite fibers obtained had an average thread diameter of 9.3cm, an average strength of 3.7GPa, and an average modulus of elasticity. It was 70GPa.

Comparative Example 2 The pitch "J" obtained in Comparative Example 1 was... The second stage of pyrolysis polycondensation was carried out at 415°C for 4 hours, and 2
A pitch "L" containing about 50% of optically anisotropic spheres of 00 μm or less was obtained with a yield of 7.0 μm.

This pitch 14 L I1 was centrifuged in a second stage under a nitrogen stream at 350°C and 10,000 yen in a batch type centrifuge to obtain a pitch 14 L I1 with a 100% optically anisotropic phase.
A substantially optically isotropic pitch 41 N #l with an optically anisotropic phase of less than 3% was obtained in a ratio of approximately 50:50.The pitch "what" is a solid "H-NMR The longitudinal relaxation time measured at 1,960+++sec. High temperature "C-NI'l"
The magnetic field orientation change rate measured at R was 0.620. Next, the pitch "A" was filled into a spinning machine with a 0.3 mm nozzle, and 500 m/I was filled at a spinning temperature of 320°C.
When the fibers were drawn at a drawing speed of lin, the average fiber diameter was approximately 12 mm without breaking for more than 1 hour.
．． It was possible to obtain pitch fibers with a pitch of 5μ. However, 1,
Stable spinning could not be achieved at a high take-up speed of 000 m/+*in. This pitch fiber was oxidized and infusible at 230°C for 1 hour in an oxygen atmosphere, and then heated at 100°C/w in an inert gas atmosphere.
Graphite fibers were obtained by increasing the temperature to 2,500°C at a heating rate of in. The obtained graphite fibers had an average thread diameter of 9.0 μ, an average strength of 3.4 GPa, and an average elastic modulus of 750 GPa.
Comparative Example 3 Pitch 1 ICI1 obtained in Example 1 contains 50% optically anisotropic phase, has a longitudinal relaxation time of 2,900 msec measured by solid state II-NMR, and is measured by high temperature C-NMR. The magnetic field orientation change rate was 0.150. Spinning was carried out in the same manner as in Example 1 using pitch "C", but the spinnability was poor and pitch fibers could not be obtained. Comparative Example 4 Of the heavy residual oil of Example 1, 450°C converted to normal pressure
The following fractions were used as starting tars. Using the same reactor as in Example 1, pyrolysis polycondensation was carried out at 400°C for 4 hours, and pitch 11011 containing about 4% of optically anisotropic spheres of 200 μm or less as residual pitch was mixed with 2% of the remaining pitch. Obtained in yield. This pitch “0” is processed using a batch centrifuge under a nitrogen stream.
Centrifugation was carried out under the conditions of 310°C and 10,000°C, resulting in a pitch of 96% optically anisotropic phase 'P' and a substantially optically isotropic pitch 14 with an optically anisotropic phase of 3 or less.
I got Q II. Pitch IP" has a longitudinal relaxation time of 3,100 msec measured by solid-state l-1-NMR, and a height of 7113C-NM.
The magnetic field orientation change rate measured at R was 0.430.

Next, the pitch IIP'' was filled into a spinning machine with a nozzle of 0.3 opening, and the spinning machine was spun at 500 m/s at a spinning temperature of 300°C.
The average fiber diameter was approximately 12.5 in. I was able to get some bitch fiber. However, 1, OOOIl/w
It was not possible to stably spin the yarn at the high take-up speed of in. This pitch fiber was oxidized and infusible at 230°C for 1 hour in an oxygen atmosphere, and then 100°C/Il in an inert gas atmosphere.
The temperature was raised to 2,500° C. at a heating rate of lin to obtain graphite fibers. The average thread diameter of the graphite fibers obtained was 9.077 m, and the average strength was 3. 3GPa. The average elastic modulus was 720 GPa. Comparative Example 5 A pitch containing about 80% of optically anisotropic spheres with a residual pitch of 200.0% or less was obtained by subjecting the bitch gtB of Example 1 to a second stage of pyrolysis polycondensation at 440° C. for 2 hours. R
l+ was obtained in 55% yield. This Bitch II R I1 was subjected to a second centrifugation in a batch type centrifuge under a nitrogen stream at 350°C and 10,000 yen, resulting in a pitch "S" with 100% optical anisotropic phase A substantially optically isotropic pitch "Tll" with an optically anisotropic phase of less than 3% was obtained in a ratio of about 50:50.

The pitch "SIT" had a longitudinal relaxation time of 1,800 msec measured by solid-state H-NMR, and a rate of change in magnetic field orientation measured by high-temperature C-NMR of 0.491.

Next, Bitch 11 S l# was charged into a spinning machine with a nozzle of 0.3 opening, and 500
At a take-up speed of m/sin, pitch fibers with an average fiber diameter of approximately 13μ could be obtained. However, 1,000m/
Stable spinning was not possible at the take-up speed of the Otori ink. This pitch fiber was oxidized and infusible at 230°C for 1 hour in an oxygen atmosphere, and then 100°C/■i in an inert gas atmosphere.
The temperature was raised to 2,500°C at a heating rate of n to obtain graphite fibers. The average thread diameter of the graphite fibers obtained was 9.5. , average intensity 3
．． The average elastic modulus was 770 GPa. Comparative Example 6 The optical anisotropy pitch obtained in Comparative Example 2 was set to 0.1.
When the fibers were filled into a spinning machine having a small nozzle with a diameter of 5 mm and spun, stable spinning was not possible due to frequent yarn breakage at any temperature.

Claims (1)

[Claims] (1) Contains 95% or more of an optically anisotropic phase, and has a longitudinal relaxation time of 2 as measured by solid-state broad width ^2H-NMR.
000 to 3,000 msec, and the magnetic field orientation change rate measured by pyrene-added high temperature^1^3C-NMR is 0.20 to 0.50 as a raw material. Melt-spun, infusible, carbonized,
A method for producing carbon fibers and graphite fibers, which further comprises graphitizing the fibers in some cases.