JPH03167291A - Optically anisotropic pitch and its manufacture - Google Patents

Abstract

PURPOSE:To improve the stability in spinning by subjecting an asphaltene-free oily or tarry substance to two-step heat treatment under specified conditions. CONSTITUTION:An oily or tarry substance which comprises a fraction having a boiling point of 500-550 deg.C under atmospheric pressure and obtained by vacuum distillation of a heavy residual oil formed as a by-product in catalytic cracking of petroleum, which contains an n-heptanes-soluble aromatic matter and resinous material as principal components, and which does not contain an n-heptane- insoluble component comprising an asphaltene is heat-treated at 380-460 deg.C under a reduced pressure while blowing an inert gas therein until an optically anisotropic phase amounts to 5-20%. The optically anisotropic phase is then separated and removed. The obtained pitch is heat-treated at 380-460 deg.C until the optically anisotropic phase amounts to 20-70%, and the optically anisotropic phase is then separated and collected, thus giving an optically anisotropic pitch having a longitudinal relaxation time of 2,000-3,000msec as measured by the solid-state broad line <1>H-NMR and a rate of change in magnetic field orientation of 0.20 to 0.50 as measured by the pyrene-added high-temperature <13>C-NMR.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optically anisotropic pitch suitable for producing high-performance carbon fibers and a method for producing the same.

More specifically, the present invention relates to an optically anisotropic pitch suitable for producing high-performance carbon fibers with excellent spinning stability and a method for producing the same.

[Conventional technology]

BACKGROUND ART Conventionally, there has been a demand for the development of high-performance materials having light weight, high strength, high elastic modulus, etc. in various industrial fields such as automobiles, aircraft, etc., and carbon fiber has been attracting attention from these viewpoints.

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 pitches are also cheaper raw materials and have a higher yield in the carbonization process. It is regarded as important due to its advantages such as the ability to obtain fibers with high elastic modulus, and active research and development is 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 the production of optically anisotropic pitch, heavy hydrocarbon oil, which is a common raw material for pitch production,
For example, tar, commercially available isotropic pitch, etc. are simply heat treated (JP-A-49-19127, JP-A-57-42924).
JP-A-54-160427, etc.), extracting the optically isotropic pitch with a solvent and heat-treating the insoluble content (JP-A-54-160427, etc.), heat-treating while blowing an inert gas (JP-A-58-1989). -168687), heat treatment after partial hydrogenation (JP-A-57-100186, JP-A-5B-184)
21 publications) methods have been proposed. However, optically anisotropic pitch produced only by heat treatment generally has a high softening point and is difficult to stably spin. Although the pitch characteristics can be controlled to some extent, the process is complicated and the manufacturing cost is high.

In order to solve this problem, the thermal decomposition polycondensation is stopped halfway and high-concentration anisotropic pitch is obtained by sedimentation separation or centrifugation depending on the difference in specific gravity (Japanese Patent Publication No. 38755/1983).
62-24036) method has been proposed. [Problem to be solved by the invention] However, the above-mentioned Japanese Patent Publication No. 61-38755 and No. 62
-24036, when pyrolysis polycondensation is carried out by ordinary heat treatment to produce pitch with an optically anisotropic phase of 95% or more, the associative properties become too strong. The problem is that the range of long-term stable spinning conditions is narrow, making it difficult to control the fiber structure through spinning. Therefore, the object of the present invention is to overcome these problems, that is, to easily obtain high-performance carbon fibers that exhibit optical anisotropy at a low softening point and have weak associativity to some extent. The purpose of this invention is to provide a directional pitch and a method for manufacturing the same. [Means for Solving the Problems] According to the present invention, the longitudinal relaxation time measured by solid-state wide@1H-NMR is 2,000 to 3,000 msec, and the longitudinal relaxation time measured by birene-added high temperature "C-NMR" is 2,000 to 3,000 msec. 95% optically anisotropic phase suitable for carbon fiber production characterized by a magnetic field orientation change rate of 0.20 to 0.50.
An optically anisotropic pitch containing the above is provided, and has a boiling point of 500 to 550 when converted to normal pressure obtained by vacuum distillation of heavy residual oil by-produced when petroleum is catalytically cracked.
℃ fraction, which mainly contains aromatic and resin components soluble in n-heptane, and substantially does not contain asphaltene components insoluble in n-heptane, 1 at a temperature in the range of 380-460℃
Heat treatment is performed in the second stage, and the reaction is stopped when 5-20% of the optically anisotropic phase in the raw pitch is formed. After separating and removing the optically anisotropic phase portion, the resulting pitch is
A second heat treatment is performed at a temperature in the range of 460°C, and the reaction is stopped when 20 to 70% of the optically anisotropic phase is formed.
There is provided a method for producing the optically anisotropic pitch described above, which comprises separating and recovering the optically anisotropic phase portion.

In addition, optically anisotropic pitch as used in the present invention refers to a pitch in which brightness is observed by polishing the cross section of a pitch lump solidified at room temperature and rotating an orthogonal Nicol with a reverse polarizing microscope, that is, a pitch that is substantially optically anisotropic. This refers to a pitch in which most of the pitches are optically anisotropic, and a pitch that is optically isotropic without any brilliance is referred to as an optically isotropic pitch in this specification. Therefore, the optical anisotropic pitch in this specification includes:
It includes not only a pure optically anisotropic pitch but also a case where an optically isotropic phase is included in an optically anisotropic phase in the form of a sphere or an irregularly shaped island. On the contrary, optically isotropic pitch also includes a small amount of optically anisotropic phase. In addition, the optically anisotropic phase in this specification is considered to be the same as a so-called mesophase, but mesophase includes two types: one that is insoluble in quinoline or pyridine, and one that contains a large amount of components that are soluble in quinoline or pyridine. There are several types, and the optically anisotropic phase referred to herein is mainly the latter mesophase.

In addition, the content of the optically anisotropic phase as used in the present invention refers to the area ratio occupied by the optically anisotropic phase portion in the sample obtained by photographing the sample under orthogonal Nicol 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 ±1 compared to that measured by other ring and ball methods, micro melting point methods, etc. for pitch samples.
It matches within the range of 0°C.

Hereinafter, the optically anisotropic pitch of the present invention and its manufacturing method will be explained in detail.

The optically anisotropic pitch of the present invention has an optically anisotropic phase of 95
% or more, and the longitudinal relaxation time measured by solid-state wide-width 1H-NMR is 2,000 to 3,000 msec (
(preferably 2,200-2,700 msec), and the magnetic field orientation change rate measured by birene-added high temperature 13C-NMR is 0.20-0.50 (preferably 0.50 msec).
30 to 0.48).

The longitudinal relaxation time referred to here reflects the environment around hydrogen in pitch molecules (side chain structure, aromatic ring skeleton structure, interaction between pitch molecules, etc.), and the larger this value is, the more , has many side chains and a small aromatic ring skeleton, making the molecule as a whole easy to move. Furthermore, 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 representing the association characteristics attributed to the molecular structure, and it can be obtained as follows.

Equipment used: Solid wide@'H-NMR Sample: Approximately 100 mg of pitch powder Measurement method: Pack the sample into 5 inner diameter sample tubes, approximately 1
After vacuum degassing under 0”” torr, the tube length is 4
Seal the tube so that it is below 0m+a. Set the sample,
Set the acquisition time (τ) to 0 with l80°-τ-90° pulse.
．． Measure the spectral intensity (Aτ) at 10 to 15 points by varying the intensity between 0.01 seconds and about 20 seconds. The longitudinal relaxation time (T1) is calculated from the spectral intensity at each acquisition time using the following formula (1). A 00 : Spectral intensity when τ is infinite A τ : Spectral intensity at time τ On the other hand, the magnetic field orientation change rate is the change when the association state is changed by adding a solvent from the outside to the optically anisotropic pitch. The larger this value is, the stronger the interaction between pitch molecules is and the less the influence of the solvent is. It shows that it is easy to accept. 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 IEf: 1 liquid 13C-NMR, ``C high temperature probe sample: pitch approx. 1g, pyrene (reagent special grade, a+p149
℃, bPa 86℃) Approximately 0.1 g Measurement method: Add pyrene to pitch in a weight ratio of 10, and grind and mix in a mortar. Pack the mixture into a sample tube with an inner diameter of 5 minutes, and melt it in a block bath preheated to 300°C while purging with nitrogen to fully fill it with the sample. A pitch-only sample is also prepared separately. The sample is heated to a predetermined temperature in the probe, and Gated-Decoupling
Obtain the spectrum using the method. The cumulative number of times is approximately 2,000. The measured temperature is 200℃ for pitch only.
=300poise, pitch/pyrene type 20~30p
Measure at a temperature that will result in oiss. The magnetic field orientation change rate (R) is determined by the following formula (II).

■,. . : Aromatic carbon (magnetic field oriented molecules) intensity I13. :
Aromatic carbon (free molecule) intensity I111. ．． ,: aromatic carbon (magnetic field oriented molecules) strength, pyrene lO weight 2 addition I13. ．． , : aromatic carbon (free molecule) strength, pyrene 1
The optically anisotropic pitch of the present invention, which has zero weight addition but subtracts the strength of pyrene in terms of molar ratio, has appropriate associativity because it has both the above-described specific longitudinal relaxation time and magnetic field orientation change rate. Therefore, when producing carbon fibers using the pitch of the present invention, the spinnable range is wide and the structure can be easily controlled in the spinning process, and as a result, carbon fibers with high strength and high elastic modulus can be easily produced. Obtainable.

In addition, 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 property becomes 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. On the other hand, when the longitudinal relaxation time exceeds 3,000 seconds, the molecular structure becomes more mobile and the associativity becomes weaker, and in some cases an optically isotropic phase is included, resulting in poor spinning properties. It's bad. 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 to 5% or more, resulting in significantly poor spinnability due to the viscosity difference with the optically anisotropic phase. The optically anisotropic pitch having appropriate associativity of the present invention is
It can be produced by selecting a specific petroleum-based carbonaceous raw material and performing multi-stage heat treatment including separation and removal of the optically anisotropic phase portion and recovery treatment of the optically anisotropic phase portion.

That is, the method for producing optically anisotropic pitch of the present invention produces a petroleum-based oily or tar-like substance having a specific composition and structure. This is used as a starting material and subjected to a first heat treatment at a temperature in the range of 380 to 460°C, and the reaction is stopped when 5 to 20% of the optically anisotropic phase in the raw material or pitch is formed. After separating and removing the anisotropic phase portion, the optically isotropic pitch obtained is subjected to 2
It is characterized in that the heat treatment in the second stage is carried out, and the reaction is stopped when 20 to 7 degrees of optically anisotropic phase is produced, and the optically anisotropic phase portion is separated and recovered. In the method of the present invention, the starting material is a fraction having a boiling point of 500 to 550°C calculated at normal pressure, which is obtained by vacuum distillation of heavy residual oil by-produced when petroleum is catalytically cracked. An oily or tar-like substance is used which contains aromatic components and resin components which are n-heptane soluble components as main components and does not substantially contain asphaltene components which are n-heptane insoluble components. The raw material does not contain solid foreign matter that causes a decrease in strength or high molecular weight components that form high molecular substances through heat treatment reactions. In the method of the present invention, in order to carry out pyrolysis polycondensation of the carbonaceous raw material, the raw material is subjected to two stages of heat treatment, and after the first heat treatment, a portion of the optically anisotropic phase portion is removed. After the second heat treatment, the optically anisotropic phase portion is separated and recovered. Note that pyrolysis polycondensation refers to a reaction in which the pyrolysis reaction and polycondensation reaction of heavy hydrocarbons occur in parallel as the main reaction, thereby changing the chemical structure of the Pitzchi molecule. As a result of this 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. It is time consuming and undesirable.

During heat treatment, stirring is performed to prevent local overheating and to ensure a 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 when necessary. This can be carried out by blowing an inert gas into the reactor. In this case, the inert gas may be one that has sufficiently low chemical reactivity with pitch at the reaction temperature, such as nitrogen, water vapor, carbon dioxide, light hydrocarbon gas, or a mixture thereof. These inert gases should be preheated before blowing.
This is preferable without lowering the reaction temperature. The inert gas containing cracked oil and cracked gas is extracted from the top 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 recycle and use the inert gas. 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. In addition, the reaction operation may be carried out by any method such as batch, semi-patch, or continuous method. In the method of the present invention, the optically anisotropic phase is
When -20% (preferably 7-15%) is produced, the heat treatment is stopped and the optically anisotropic phase portion is separated and removed. This process for removing the optically anisotropic phase portion removes polymeric substances that are likely to be generated during the initial stage of heat treatment. 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 is
Various known methods can be used to remove the optically anisotropic phase portion from the pitch containing 20%, that is, to separate the optically anisotropic phase portion and the optically isotropic phase portion. Solid-liquid separation methods are employed as appropriate, but in particular separation methods that utilize differences in specific gravity (see Japanese Patent Publications No. 61-38755 and No. 62-24)
It is preferable to adopt the method (No. 036 publications), and especially in industrial production, it is preferable to adopt the centrifugal separation method. 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 above forms a continuous phase, and the optically anisotropic pitch containing a slightly optically isotropic phase in the form of islands or minute spheres forms the lower layer, while the upper layer is optically isotropic. This 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 and lower layers 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. 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 to a lower layer (in the direction of centrifugal force), and separates it. As a method, a so-called centrifugal separator operation, particularly a continuous type centrifugal separator that continuously separates and discharges a heavy phase and a light phase, is advantageously used.

The temperature at which the optically anisotropic phase is separated depends on the magnitude of the centrifugal force, but is preferably higher than the softening point of the pitch, preferably 250°C -
The temperature range is 300℃. It may be a predetermined constant temperature within this range, and 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 above this level are undesirable, and temperatures higher than necessary make it difficult to operate the centrifugal separator continuously for long periods 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. The centrifugal force acceleration of the centrifugation operation may be of 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.
-10,000G range 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. The tropic phase is 20
Discontinue when the content reaches ~7oz, 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°C, 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 optically anisotropic pitch in the next separation and recovery will be extremely small, and conversely, the optically anisotropic phase will increase. If the phase is larger than 70%, the separability during separation and recovery will deteriorate, making it impossible to obtain a highly concentrated 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 is in a spherical state with a diameter of 500 μm or less, preferably 300 μm or less. Appropriate. In the method of the present invention, the optically anisotropic phase-containing pitch recovered 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 anisotropic pitch are separated and recovered. isotropic 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 use centrifugation. However, in this optical anisotropic pitch recovery process, when centrifugation is used, the temperature is 310 to 360°C.
It is preferable that the centrifugal acceleration is in the range of S, Goo-2
A range of 0,000G 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 the present invention, it is also possible to add an appropriate finishing heat treatment immediately after the optical anisotropic pitch recovery treatment. That is, using a particularly short residence time in the recovery process,
The softening point is sufficiently low, but the optically anisotropic phase content is approximately 80%.
A somewhat insufficient optically anisotropic pitch of ~90% was produced, which was then subjected to a thermal weighting reaction treatment at a temperature of 300°C to 430°C. Methods can also be employed to adjust the optical anisotropy pitch properties to within narrow quality control limits. 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 90% or more. The pitch obtained by the method of the present invention is continuously taken out of the system and is either kept in a liquid state or solidified to become a product. By the method of the present invention, an optically anisotropic pitch having a sufficiently low softening point and appropriate associativity can be obtained. The pitch obtained as described above is melt-spun according to a known method, and the obtained pitch fibers are made infusible, carbonized, and optionally further graphitized, resulting in good spinnability and high performance. pitch-based carbon fibers and graphite fibers can be obtained.

〔Effect of the invention〕

Since the optically anisotropic pitch of the present invention has the above-mentioned specific association characteristics, when carbon fibers are produced using the pitch of the present invention, the spinnable range is wide and the structure can be easily controlled in the spinning process. , it is possible to easily produce carbon fibers with high strength and high modulus. In addition, according to the method for producing optically anisotropic pitch of the present invention, (a) the JJr material contains a solid foreign material and a high molecular weight component that easily forms a polymeric substance by heat treatment, and has a specific composition and structure. In addition, the polymers that tend to form at the beginning of the heat treatment are removed as an optically anisotropic phase after the first heat treatment. (c) Few impurities,
Optically anisotropic pitch with narrow molecular weight distribution, low softening point, and appropriate associativity can be produced stably and easily. [Example] The present invention will be explained in more detail with reference to Examples below, but the scope of the present invention is of course not limited thereto. Example 1 The heavy residual oil produced as a by-product in the catalytic cracking process of petroleum was distilled under reduced pressure, and the residual tar at a temperature of 500 to 550°C converted to normal pressure was fractionated and used as a starting material. This tar-like substance consisted of 90.7 parts by weight of carbon, 8.1 parts by weight of hydrogen, and 1.1 parts by weight of sulfur, and its composition was as shown in Table 1, and did not contain asphaltenes. Table 1: 20 kg of this tar-like substance was charged into a reaction tank with an internal volume of 351 cm, and the first stage of pyrolysis polycondensation was carried out at 415°C for 4 hours with sufficient stirring under a nitrogen stream. 200 for an isotropic matrix. Pitch containing approximately 8% of the following optically anisotropic spheres was added to the raw material tar by 25%.
% yield. Next, this pitch was loaded into a continuous centrifugal separator and centrifuged in the first stage at 250°C and 10,000G in a nitrogen atmosphere. The pitch was separated into a substantially optically isotropic pitch "B" containing no more than 2% of an orthotropic phase. Next, the pitch "B" was subjected to a second stage of pyrolysis polycondensation at 415°C for 3 hours. , the pitch "゛C" containing about 50% of optically anisotropic spheres of 200μ or less as residual pitch is 6
Obtained with a yield of 7%. This pitch “C” is processed under a nitrogen stream using a batch centrifuge.
A second stage of centrifugation is performed at 350°C and 1G,000G, and the optically anisotropic phase is substantially optically isotropic with a pitch of 100% ``D'' and an optically anisotropic phase of less than 100%. pitch "E" was obtained in a ratio of about 50:5G. Pitch "D" has a longitudinal relaxation time of 2,410 as measured by solid-state 1H-NMR.
msec, high temperature" The magnetic field orientation change rate measured by C-NMR was 0.450. Also, its softening point was 265 ° C.
Met. Next, the pitch "D" was filled into a spinning machine with a 0.3 sn nozzle, and 1,000 m
When the fibers were drawn at a high drawing speed of 1/min, pitch fibers with an average fiber diameter of about 13 mm could be obtained without yarn breakage 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 heated to 100"C/w in an inert gas atmosphere.
The temperature was raised to 2,500°C at a heating rate of 1.5 in to obtain graphitized fibers. The average thread diameter of the graphitized fibers obtained was 10. 〇1.The average strength was 4.6 GPa and the average elastic modulus was 850 GPa. 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
0. The following pitch "F" containing about 50% of optically anisotropic spheres was obtained with a yield of 63%. This pitch “F” is processed using a batch centrifuge under a nitrogen stream.
A second stage of centrifugation was performed at 350°C and 10,000G, and the optically anisotropic phase was substantially optically isotropic with a pitch of 100% "G" and an optically anisotropic phase of less than 100%. The pitch "H" was obtained at a ratio of approximately 50:50. Bitch゛′G”
The longitudinal relaxation time measured by solid state 1}1-NMR is 2,2
00msec. The magnetic field orientation change rate measured by high 21'' C-NMR was 0.475. Also, its softening point was 267°C. Next, a nozzle with a pitch "G" of 0.3 1,000 at a spinning temperature of 320°C.
When picked up at a high picking speed of m/sin,
The average fiber diameter was approximately 13.5 mm without breaking for more than 1 hour continuously. We were able to obtain pitch fibers. The pitch fibers were oxidized and infusible at 230°C for 1 hour in an oxygen atmosphere, and then heated at 100°C/s in an inert gas atmosphere.
The temperature was raised to 2,500°C at a heating rate of 1.5 in to obtain graphitized fibers. The average yarn diameter of the graphitized fibers obtained was 9.7p, and the average strength was 4. The average elastic modulus was 810 GPa. Comparative Example 1 Example! The same heavy residual oil was distilled under reduced pressure and the fraction above 415°C was used as the starting material. This residual oil contains 89.9 carbon by weight, 8.9 hydrogen by weight, and 1 sulfur.
．． The composition is as shown in Table 2.
It contained 3.8% by weight of asphaltene. Table 2 This residual oil was subjected to the first stage of pyrolysis condensation and centrifugation under the same conditions as in Example 1, resulting in an optically anisotropic phase of 100
% pitch "I" and a substantially optically isotropic pitch "taJ" with an optically anisotropic phase of 3z or less in a ratio of about 25:75. The longitudinal relaxation time measured by 2,250 msec was 2,250 msec, and the rate of change in magnetic field orientation measured by high temperature C-NMR was 0.645.

Next, the pitch "■" 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 I picked it up at Ilin's picking speed, it was continuous! Average fiber diameter of approximately 12 without yarn breakage over time
．． It was possible to obtain pitch fibers of 5 pm. However, 1,
Stable spinning could not be achieved at a high take-up speed of 1,000 m/sin. This pitch fiber was oxidized and infusible at 230°C for 1 hour in an oxygen atmosphere, and then at 100°C/i in an inert gas atmosphere.
The temperature was raised to z, soo°C at a heating rate of n to obtain graphitized fibers. The obtained graphitized fibers had an average thread diameter of 9.3 μ, an average strength of 3.7 GPa, and an average elastic modulus of 770 GPa. Comparative Example 2 The pitch “J” obtained in Comparative Example 1 was subjected to the second stage of pyrolysis polycondensation at 415°C for 4 hours, and the remaining pitch was 2
Pitch "shi" containing about 50% of optically anisotropic spheres of 00 pm or less was obtained with a yield of 70%. This pitch “L”
in a batch centrifuge under nitrogen flow at 350°C for 10
The second stage of centrifugation was carried out under the conditions of ,000G, and the optically anisotropic phase was 100% pitch "H" and the optically anisotropic phase was 3.
% or less of the substantially optically isotropic pitch "N". Approximately 5
Obtained at a ratio of 0:50. Pitch "H" is solid 1R-NN
The longitudinal relaxation time measured at R is 1,960+msec. The IT field orientation change rate measured by high-temperature C-NMR is 0.6.
It was 20. Next, the pitch 'Koku' was filled into a spinning machine with a 0.3 mm nozzle, and the spinning machine was used for 500 m/+ at a spinning temperature of 320°C.
When the fibers were taken at a take-up speed of *in, it was possible to obtain pitch fibers with an average JIIl diameter of approximately 12.5 without yarn breakage for over 1 hour continuously. but,
1. Stable spinning was not possible at a high take-up speed of Goos/sin. The pitch fibers were oxidized and infusible at 230'C in an oxygen atmosphere for 1 hour, and then at 100'C/in an inert gas atmosphere.
The temperature was raised to 2,500"C at a temperature increase rate of 1.5" to obtain graphitized fibers.The average yarn diameter of the obtained graphitized sui was 9.0 mm, the average strength was 3.4 GPa, and the average elastic modulus was 750 GPa. Comparative Example 3 The pitch itClj obtained in Example 1 contains 50% of an optically anisotropic phase, and has a longitudinal relaxation time of 2,900 msec measured by solid-state 'H-NMR. The measured magnetic field orientation change rate was o,tso. Pitch "C' was used for spinning in the same manner as in Example 1, but the spinnability was poor and pitch fibers could not be obtained. Comparative Example 4 Of the heavy residual oil of Example I, 450℃ converted to pressure
The following fractions were used as starting tars. Using the same reaction apparatus as in Example 1, thermal decomposition polycondensation was carried out at 400°C for 4 hours, and a pitch "10j" containing about 4 days of optically anisotropic spheres of 200 pm or less as a residual pitch was obtained. %
It was obtained with a yield of . This pitch “0” is processed using a batch centrifuge under a nitrogen stream.
Centrifugation was performed at 310°C and 1G,000G.
The optically anisotropic phase has a pitch of 96% ``P'' and the optically anisotropic phase is 3 and the following substantially optically isotropic pitch ``'Q''''
I got it. The pitch "P" had a longitudinal relaxation time of 3,100 msec as measured by solid-state I{-NMR, and a magnetic field orientation change rate of 0.430 as measured by high-temperature C-NMR.

Next, the pitch "P" was filled into a spinning machine with a nozzle opening of 0.3, and the spinning speed was 500 m/wi at a spinning temperature of 300°C.
Pitch fibers with an average fiber diameter of approximately 12.5 pm could be obtained at a take-up speed of n. However, 1,000m/mi
Stable spinning could not be achieved at a high take-up speed of n. The pitch fibers were oxidized and infusible at 230°C for 1 hour in an oxygen atmosphere, and then heated at 100°C/s in an inert gas atmosphere.
The temperature was raised to 2,500°C at a heating rate of 1.5 in to obtain graphitized fibers. The graphitized fibers obtained had an average thread diameter of 9.0 μs, an average strength of 3.3 GPa, and an average elastic modulus of 720 GPa. Comparative Example 5 Pitch "B" of Example 1 was subjected to the second pyrolysis polycondensation at 440° C. for 2 hours to produce a pitch containing about 80% of optically anisotropic spheres of 200p or less as residual pitch. ,R
” was obtained with a yield of 55%. This pitch “R” was subjected to a batch centrifuge under a nitrogen stream.
A second stage of centrifugation is carried out at 350°C and 10,000G, resulting in a pitch "S" of 100% optically anisotropic phase and a substantially optically isotropic phase with an optically anisotropic phase of 3% or less. A pitch "T'" of approximately 50:50 was obtained.

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

Next, the pitch "S" was filled into a spinning machine with 0.3 nozzles, and the spinning speed was 500 m/mi at a spinning temperature of 320°C.
Pitch fibers with an average fiber diameter of about 13 μm could be obtained at a take-up speed of n. However, 1,000Il/win
Stable spinning was not possible at this take-up speed. The pitch fibers were oxidized and infusible at 230°C for 1 hour in an oxygen atmosphere, and then heated at 100°C/s in an inert gas atmosphere.
The temperature was raised to 2,500°C at a heating rate of 1.5 in to obtain graphitized fibers. The average yarn diameter of the graphitized fibers obtained was 9.5μ, and the average strength was 3. 8 GPa, and the average elastic modulus was 770 GPa.

Claims (2)

[Claims] (1) Longitudinal relaxation time measured by solid-state wide width^1H-NMR is 2,000 to 3,000 msec, and magnetic field orientation change rate measured by pyrene-added high temperature^1^3C-NMR is 0.20 -0.50, an optically anisotropic pitch containing 95% or more of an optically anisotropic phase suitable for carbon fiber production. (2) The boiling point converted to normal pressure obtained by distilling heavy residual oil by-product when petroleum is catalytically cracked is 50.
A fraction of 0 to 550°C, containing mainly aromatic and resin components soluble in n-heptane, and substantially free of asphaltene components insoluble in n-heptane, in the form of oil or tar. The substance is subjected to a first heat treatment at a temperature in the range of 380 to 460°C, and the reaction is stopped when 5 to 20% of the optically anisotropic phase in the generated pitch is formed.
After separating and removing the optically anisotropic phase portion, the obtained pitch is subjected to a second heat treatment at a temperature in the range of 380 to 460°C, and when 20 to 70% of the optically anisotropic phase has been formed, The method for producing optically anisotropic pitch according to claim 1, characterized in that the reaction is stopped and the optically anisotropic phase portion is separated and recovered.