JPH0418126A - Production of carbon fiber and graphite fiber - Google Patents

Abstract

PURPOSE:To obtain the subject fiber in good spinnability by separating a mesophase pitch into a mesophase component and a non-mesophase component, directly spinning the separated mesophase pitch in molten state and, in the case of storage, solidifying a part of the pitch. CONSTITUTION:A mesophase-containing pitch is produced by heat-treating a carbonaceous pitch obtained from a catalytic cracking residue oil of petroleum, etc. The mesophase-containing pitch is centrifuged under heating and separated into a mesophase component and a non-mesophase component. The mesophase pitch separated into the above two components is preferably subjected to thermal polymerization reaction to increase the content of the mesophase component and is directly spun in molten state followed by carbonization and graphitization to obtain the objective fiber. In the case of storing the pitch over a long period, it is preferable to solidify a part of the pitch without keeping the whole pitch in molten state and melt the solidified pitch before spinning.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing, storing, and melt-spinning carbonaceous pitch in a method for producing pitch-based high-performance carbon fibers and graphite fibers.

[Conventional technology]

Traditionally, 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, aircraft, etc., and carbon fibers (including graphite fibers) have been attracting attention from these viewpoints. ing.

Currently, commercially available carbon fibers are still PAN-based carbon fibers made from polyacrylonitrile, but pitch-based carbon fibers made from coal or petroleum-based pitches are also cheap raw materials and have a high 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.

Pitch-based carbon fibers are obtained by first adjusting carbonaceous pitch to a preferable state as a spinning raw material (pitch for spinning), then converting it into a fibrous form by melt spinning, and then infusible and carbonizing it. Carbon fibers obtained from optically isotropic pitches (i.e., non-mesophase pitches) have low strength and elastic modulus, but optically anisotropic pitches obtained by heat-treating optically isotropic pitches ( Since high-performance carbon fibers can be obtained from mesoface pitch, the production, storage, and spinning methods of spinning pitch made of mesoface pitch are very important.

Therefore, many proposals have been made regarding the production of mesoface pitch, but the usual method of heat-treating tar, commercially available optically isotropic pitch, etc. softens when the mesoface content approaches 100%. On the other hand, if the softening point is suppressed, the amount of non-mesophase components in the pitch will increase, making it heterogeneous, and the spinnability will deteriorate. In addition to deterioration, high-performance carbon fibers cannot be obtained.

In addition, the mesoface pitch obtained in this way is
Normally, after being taken out of the heat treatment reactor, the material is returned to room temperature to solidify and stored, and then melted again during spinning and subjected to the spinning process. Therefore, mesoface pitch is oxidized by solidification/remelting.

It has problems such as the generation of pyrolysis gas and changes in the mesophase structure, and furthermore, energy loss due to reheating and melting cannot be ignored.

In order to solve this problem, we developed a method of heat-treating carbonaceous pitch (pitch or its precursor) in a solution or molten state and then melt-spinning it without solidifying it (Japanese Patent Laid-Open No. 59-17
No. 3309) has been proposed.

However, if pitch is heat-treated and then melt-spun without being solidified, although the aforementioned drawbacks due to solidification/re-melting are eliminated, the aforementioned problem of poor spinnability still remains.

[Problem to be solved by the invention]

As mentioned above, in the conventional production of carbon fibers and graphite fibers from mesoface pitch, it is difficult to obtain mesoface pitch with good spinnability, so it is difficult to obtain high-performance carbon fibers and graphite fibers. The problem is that it is difficult.

In order to solve these problems, the present inventors obtained high-performance carbon fiber by directly spinning mesophase pitch separated from mesophase-containing pitch in a molten state without solidifying it and carbonizing it. A separate application was filed for the method. However, in this method, if the entire amount of molten pitch is not spun immediately and is stored in a molten state for a long period of about 7 to 30 days, the quality of the pitch deteriorates and spinnability deteriorates. There was a problem in that the physical properties of the yarn after firing deteriorated.

Therefore, the purpose of the present invention is to overcome such problems and
An object of the present invention is to provide a method for producing carbon fibers and graphite fibers with improved spinnability and yarn properties.

[Means to solve the problem]

According to the present invention, in a method for producing carbon fibers and graphite fibers in which mesophase pitch is spun, carbonized, and optionally graphitized, mesophase-containing pitch produced from carbonaceous pitch is divided into mesophase components and non-mesophase components. A carbon material characterized in that the separated mesophase pitch is directly spun in a molten state without being solidified, and a part of the mesophase pitch is solidified, and when necessary, the mesophase pitch is remelted and spun. A method of manufacturing fibers and graphite fibers is provided.

That is, the method for producing carbon fibers and graphite fibers of the present invention involves subjecting mesoface-containing pitch produced from carbonaceous pitch to a mesoface pitch separation treatment that separates mesoface components and non-mesoface components. The feature is that mesoface pitch is directly spun in a molten state without being solidified, and with this structure, mesoface pitch suitable for spinning is formed, and the solidification of mesoface pitch is prevented. / Since oxidation, thermal decomposition gas generation, mesophase structure change, etc. due to remelting are prevented, spinnability and yarn physical properties are significantly improved, and energy for remelting mesophase pitch is also saved.

Furthermore, the method of the present invention is characterized in that a part of the mesoface pitch is solidified and remelted when necessary for spinning. Although the spinnability and yarn physical properties are somewhat inferior, it also brings about the effects of increasing the ability to absorb operational fluctuations of the equipment and improving the flexibility of the manufacturing plan.

Note that the mesoface pitch (i.e., 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 the orthogonal nicols with a reflective polarizing microscope. In other words, it means a pitch in which the majority is substantially an optically anisotropic phase (referred to as a mesophase component in this specification), and a pitch in which no brilliance is observed and a pitch in which a substantially optically isotropic phase (referred to as a non-mesophase component in this specification) is present. In this specification, a pitch consisting of a non-mesophase pitch (optically isotropic pitch) is referred to as a non-mesophase pitch (optically isotropic pitch). Therefore, in this specification, mesophase pitch includes not only pure mesophase pitch but also cases where non-mesophase components are included in the mesophase pitch in the form of a sphere or an irregularly shaped island.

Conversely, non-mesophase pitches also include those that contain small amounts of mesophase components.

Furthermore, there are two types of mesoface pitch: 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 term mesoface pitch used herein mainly refers to the latter.

The mesophase content in the present invention is determined by observing and photographing a sample under crossed Nicols using a polarizing microscope and measuring the area ratio occupied by mesophase components in the sample. In addition, the softening point of pitch in the present invention refers to the same-liquid transition temperature of pitch, but using a differential scanning calorimeter, the absorption or release of latent heat when pitch melts or solidifies shows a peak. It is calculated from temperature.

This temperature is 5 or less, which agrees within a range of ±10°C with those measured by other ring and ball methods, micromelting point methods, etc. The method for producing carbon fibers and graphite fibers of the present invention will be described in detail.

(1) Carbonaceous Pitch As the carbonaceous pitch for producing the mesophase-containing pitch used in the present invention, known starting materials such as so-called heavy hydrocarbon oil, tar, or pitch can be used. Examples of starting materials include various types of petroleum-based heavy oils, pyrolysis tar, catalytic cracking residue oil, heavy oil obtained by carbonization of stone return, tar, pitch, and aromatic hydrocarbons. Suitable examples include catalytic cracking residual oil of petroleum. These can be filtered, if necessary.
It is used after undergoing preliminary treatments such as distillation and solvent extraction.

Furthermore, in order to stabilize the quality of the mesoface pitch produced, carbonaceous pitch that already contains a small amount of mesoface pitch can also be used as a raw material.

(2) Production of mesophase-containing pitch Mesophase-containing pitch is produced using carbonaceous pitch as a raw material, and the production method thereof is not specified. For example, it can also be produced by a heat treatment process in which carbonaceous pitch is subjected to a menization reaction (defined as a reaction that produces mesophase) through a pyrolysis polycondensation reaction. The term pyrolysis polycondensation reaction refers to a reaction in which a pyrolysis reaction of a heavy hydrocarbon and a polycondensation reaction occur in parallel as main reactions, thereby changing the chemical structure of pitch component molecules. As a result of this reaction, scission of the paraffin chain structure, dehydrogenation, ring closure, development of a planar structure of polycyclic condensed aromatics due to polycondensation, etc. proceed.

For this reaction, the carbonaceous pitch is about 380 to about 460
℃, preferably 400-430℃. If the reaction temperature exceeds about 460°C, the volatilization of unreacted substances in the raw materials will increase, the softening point of the carbonaceous pitch will also increase, and coking will easily occur, which is unsuitable.
If the temperature is below 0°C, the reaction will take a long time, which is not preferable.

In the heat treatment process, stirring is performed to prevent local overheating and to ensure uniform reaction, but in addition, stirring is performed under reduced pressure or as necessary to quickly remove low molecular weight substances generated as a result of thermal decomposition. This can be carried out while blowing an 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 mixed gas thereof.

It is preferable to preheat these inert gases before blowing them in, since this will not lower the reaction temperature.

In this heat treatment step, the mesophase component is brought to a state of containing about 30 to about 80%, preferably about 380 to about 70%, in the pitch that is substantially free of low molecular weight decomposition products and unreacted products. The reason for this is that in order to obtain homogeneous mesophase pitch with a low softening point in a high yield in the mesophase pitch separation process, it is preferable to stop the process and transfer to the next mesophase pitch separation process. This is because it is preferable that the content of the mesophase component in the produced pitch is about 20 to about 8, the softening point is 260° C. or less, and the pitch yield is high. Mesophase component in generated pitch is 20%
If it is less than
If it is made larger or has a softening point higher than 260°C, the separability in the separation process will be poor, making it impossible to obtain mesoface pitch with a high concentration, and the obtained mesoface pitch will have a high softening point. Become. The mesophase-containing pitch obtained in this step is suitably one in which most or substantially all of the mesophase components are in a spherical state with a diameter of 500 μm or less, preferably 300 μm or less.

(3) Separation of mesoface pitch In the present invention, mesoface-containing pitch produced from carbonaceous pitch is sent to the first mesoface pitch separation step, where it is separated into mesoface components and non-mesoface components. Various known solid-liquid separation methods are appropriately employed to separate mesoface pitch and non-mesoface pitch, but in particular, a separation method that utilizes the difference in specific gravity (reference: Japanese Patent Publication No. 38755/1983) , JP-A No. 58-180585, and JP-A-60-34619) are preferably employed, and particularly in industrial production, centrifugation is preferably employed.

In the centrifugal separation method, mesophase-containing pitch is centrifuged in its molten state. Mesophase components have a higher specific gravity than non-mesophase components, so they quickly settle, coalesce, grow, and form the lower layer (in the direction of centrifugal force). The mesophase pitch is the lower layer, in which about 80% or more of the mesophase component forms a continuous phase, and a small amount of non-mesophase components are included in the form of islands or minute spheres. The upper layer has a non-mesoface pitch in which the majority of the non-mesoface components are dispersed in the form of small spherical bodies, and the interface between the upper layer and the lower layer is clear. This method utilizes the fact that the specific gravity of the lower layer in a molten state is significantly different, and separates the lower layer from the upper layer to separate mesoface pitch and non-mesoface pitch. Note that centrifugal separation 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 this, and is one of its embodiments. As such, operation using a so-called centrifugal separator, particularly a continuous type centrifugal separator that continuously separates and discharges a heavy phase and a light phase, is advantageously used.

The temperature in the centrifugation operation depends on the magnitude of the centrifugal force, but is preferably a temperature higher than the softening point of the mesophase-containing pitch, preferably 280°C to 400°C, more preferably 320°C.
It is in the range of -380°C. A predetermined constant temperature within this range may be used, and the temperature does not necessarily have to be constant.

In this step, the main purpose is to deposit and coalesce most of the mesophase components in the direction of centrifugal force, and it is necessary to avoid thermal decomposition and polycondensation reactions as much as possible. Therefore, a temperature higher than 400° C. is not preferable, and a temperature higher than necessary makes it difficult to operate the centrifugal separator continuously for a long time, but there is no such problem at the above-mentioned temperature. Furthermore, at lower temperatures than the above range, the viscosity of pitch, especially mesoface pitch, is high, so non-mesoface components co-precipitate with mesoface components into the underlying mesoface pitch, resulting in long-term and extremely large centrifugal acceleration. Even if given, separation becomes difficult.

The centrifugal force of the centrifugation operation may be of any value, but it is possible to efficiently separate mesophase components (heavy phase) and non-mesophase components (light phase) in a short time by shortening the residence time. In order to do so, preferably 1.0OOG or more,
In particular, a range of 10,000 to 40,000 OOG can be adopted. Note that when the pitch is 50,000 OOG or more, there are limitations in terms of equipment.9 From this process, a mesoface pitch having a content of mesoface components of 90% or more, especially 95% or more can be obtained economically in a short time.

In addition, when producing mesoface-containing pitch by heat treating carbonaceous pitch, the non-mesoface pitch separated in this process can be heat-treated again to
Since it can be converted to mesophase-containing pitch,
In a preferred embodiment, this non-mesoface pitch is recycled to the heat treatment step at a specific point in time. This circulation of non-mesoface pitch causes it to undergo heat treatment again, improving the final pitch yield.

In the present invention, it is also possible to add an appropriate finishing heat treatment step immediately after the mesoface pitch separation step. That is, by using a particularly short residence time in the separation step, a mesophase pitch with a sufficiently low softening point but with a slightly insufficient content of mesophase components of about 80%-90% is produced, and then this is It is also possible to adopt a method of adding a thermogravid reaction treatment at a temperature of 300° C. to 430° C. to adjust the properties of the mesoface pitch to within narrow quality control limits. Mesophase pitch containing 80-90% mesophase components has 10% non-mesophase components.
It contains ~20%, but this non-mesophase component can be further reduced by adding a small amount of thermal weighting reaction treatment.
It is also known that the softening point gradually increases, so
The mesophase component content can be adjusted to 90% or more, preferably 95% or more, by thermograviding the separated pitch at an appropriately controlled temperature and treatment time.

In addition, in the present invention, after the mesophase pitch separation step, a solvent extraction step for removing quinoline soluble components or n-heptane soluble components, a non-oxidizing gas blowing treatment for completely removing light substances, or/ It is also possible to provide a vacuum degassing treatment process, etc., and when the above-mentioned finishing heat treatment process is provided, a mild hydrogenation treatment process may be provided immediately after to adjust the excessive rise in the softening point of the pitch. You can also do it.

In the present invention, the mesoface pitch separated in the mesoface pitch separation step (or the mesoface pitch that has undergone the final heat treatment, etc., if the above-mentioned final heat treatment, etc., is applied) is sent, for example, to a storage tank, where the softening point is lowered. It is heated and kept warm to keep it in a molten state. In this case, it is preferable to stir the pitch.

In the present invention, the mesophase pitch required for the current spinning is taken out of the system, solidified, and stored, for example, in the form of pellets. This solidified mesophase pitch is remelted when necessary and sent to the spinning process.

(4) Spinning The mesoface pitch maintained in a molten state can be directly spun by a known method after removing solid content by filtration if desired. Such a method, for example, uses a spinneret with a diameter of 0.1 mm to 0.5++u++ for 1 to 2.0 mm.
Pitch was placed in a metal spinning container having a spinneret of 0.000000000000000000000000 pitch below, and the pitch was 280 to 370 in an inert gas atmosphere.
The pitch is held at a constant temperature between 10°C and molten, and the pressure of the inert gas is increased to several 100 mmHg to extrude the molten pitch from the nozzle, and the pitch fibers flow down while controlling the temperature and atmosphere. It 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 by supplying pre-melted pitch under pressure 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 spinning vessel having a spinneret on the peripheral wall is rotated at high speed, molten pitch is continuously supplied to the spinning vessel, the pitch is pushed out from the peripheral wall of the cylindrical spinner by centrifugal force, and the spinning vessel is drawn by the action of rotation. It is also possible to adopt a spinning method that accumulates pitch fibers.

(5) Adding a sizing agent (oil) The melt-spun pitch fibers are bundled through an air sucker and guided to an oiling roller, where a sizing agent (oil) is applied and further bundled.

In this case, examples of the sizing agent include ethyl alcohol,
Alcohols such as isopropyl alcohol, n-propyl alcohol, butyl alcohol or viscosity 3-300c
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 Those in which esters are dispersed; and other ordinary fibers, such as those that do not damage pitch fibers among the various oils used for polyester fibers, can be used.

Methods of applying the sizing agent to the pitch fibers include a method of applying it through a 0-shaped guide, an oiling roller method,
Conventionally known application methods such as a spray method can be employed.

Further, although the sizing agent can be applied at any time between the spinning process and the infusibility process, it is preferable to apply the sizing agent between the spinneret and the winder in order to stably handle the pitch fibers with a weak pitch of 11. .

The amount of sizing agent attached to the fibers is usually 0.01 to 10% by weight.
and preferably 0.05 to 5 weight 2.

(6) Infusibility of pitch fibers The pitch fibers to which the above-mentioned sizing agent has been applied and are bundled are 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.

The infusibility can be achieved using air, oxygen, a mixed gas of air and oxygen or nitrogen, or a mixed gas containing an oxidizing agent such as NO2, ozone, or halogen.

(7) Carbonization and graphitization 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℃,
1. Carbon fibers are obtained by carbonizing by raising the temperature to a temperature in the range of 2,000 to 2,000 °C.
By raising the temperature to a temperature within the range of 3,000°C and proceeding to graphitization treatment, graphite fibers are obtained.

In the present invention, the details of the carbonization and graphitization methods are not particularly limited, and generally known methods can be used.

Also, during 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 these purposes, when processing a fiber bundle coated with a sizing agent, it is preferable to apply a load or tension to the fiber bundle.

〔Effect of the invention〕

The method for producing carbon fibers and graphite fibers of the present invention includes subjecting mesoface-containing pitch produced from carbonaceous pitch to a mesoface pitch separation treatment to separate mesoface components and non-mesoface components, and then subjecting the obtained mesoface pitch to Spun directly in the molten state without solidifying it,
In addition, since a part of the mesoface pitch is solidified and remelted when necessary for spinning, (a) the mesoface pitch separation process makes it possible to form a mesoface pitch suitable for spinning. (b) Therefore, spinnability and yarn physical properties are improved. (c) By spinning mesoface pitch in a molten state, oxidation and thermal decomposition due to solidification/remelting are reduced compared to the case where the entire pitch is solidified. Gas generation and mesophase structure changes are avoided, and remelting energy is saved. (d) By solidifying and preserving a portion of the mesophase pitch, the ability to absorb operating fluctuations of the equipment is increased and production planning is improved. It has the outstanding effect of improving the flexibility of
As a result, according to the present invention, high-strength, high-modulus carbon fibers and graphite fibers with good yarn quality can be stably produced.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the scope of the present invention is of course not limited thereto.

Example 1 Residual oil by-produced in catalytic cracking of petroleum, converted to normal pressure, is 4
Distilled under reduced pressure to 50℃, and further distilled the obtained tar to 100℃
The tar obtained by centrifuging at 10,0 OOG and then using an electrostatic precipitator and a filtration device to remove solids such as catalyst fine particles and solid carbon from the tar was used as a starting material.

After the solid content had been removed, the raw material tar was heated to 350° C. with a preheater, and then 100 kg was poured into a heat treatment reactor equipped with a stirrer (equipped with a peripheral heater) having a diameter of 40 cm and an internal capacity of 150 Q.

Heat treatment was performed at 415°C for 4 hours while blowing nitrogen gas from the bottom of the reactor, and the content of mesophase components was 49.
% mesophase-containing pitch was obtained.

The pitch yield was 34 wt.

Immediately after the heat treatment reaction in the reactor was completed, extraction of mesophase-containing pitch from the bottom of the reactor was started, and the mesophase-containing pitch was sent to a mesophase-containing pitch tank.

The mesophase-containing pitch produced by the above heat treatment had a softening point of 231°C, contained 16.8% by weight of quinolinated content, and had a viscosity of 2.7 voids in a molten state at 370°C.

The pitch in the mesophase-containing pitch tank is sent in a molten state to a cylindrical continuous centrifugal separator, and is subjected to centrifugal forces io, o while controlling the rotor temperature at 350°C.

It was continuously separated into molten mesoface pitch (A pitch) and non-mesoface pitch (Epitch) using OG.

The entire amount of Evitch after separation was recycled and injected again as a raw material for the heat treatment reactor.

Under the above centrifugation conditions, the yield of A pitch was approximately 48% by weight.
Met. The softening point of pitch A was approximately 263°C, the quinolinated content was 29.0 to 30.0% by weight, and the content of mesophase components was approximately 98%.

Next, a part of the A pitch just obtained was directly applied in a molten state to a spinner having a nozzle with a diameter of 0.31, and extruded at a temperature of 355°C and a nitrogen pressure of about 200 mmHg.
It is wound onto a bobbin that rotates at high speed located at the bottom of the nozzle.
When the yarn was spun at a take-up speed of approximately 500 m/min, the frequency of yarn breakage was low, less than once per hour, and there was almost no increase in pressure loss over time in the spinning nozzle.
The spinnability was extremely good.

Next, the spun pitch fibers were heated at 230°C in an oxygen atmosphere.
to infusible by leaving it for 1 hour at 25℃/N2 gas.
Carbon fibers were obtained by heating to 1,500° C. at a heating rate of 1.5 min and allowing to cool. Furthermore, some of this carbon fiber.

The graphite fibers were heated in an argon stream at a heating rate of 50°C/min up to 1,100°C, and at a heating rate of 100°C/min from 1,100°C to 2,400°C, and left to cool. I got it.

The characteristics of carbon fiber are fiber diameter, tensile strength, and tensile modulus of 10.0 m, 3.3 GPa, and 260 GPa, and the characteristics of graphite fiber are fiber diameter, tensile strength, and tensile modulus of 9.7 m, respectively. , 3, 8GPa, 590G
It was Pa.

Example 2 In Example 1, the temperature was 350°C and the centrifugal force was 10.0OOG.
A part of the A pitch obtained under the conditions was cooled and solidified to a length of about 8
■ When the pellets with a diameter of approximately 2.5 ■ were stored and remelted after 10 days, the mesophase component content remained at approximately 98%, but the quinoline soluble content was 31.5% by weight. and the softening point had risen to 267°C.

When 1 kg of this pitch was taken and spun in the same manner as in Example 1 (however, the spinning temperature was 357°C), the frequency of yarn breakage was 1 to 2 times per hour.

This pitch fiber was subjected to infusibility treatment, carbonization and graphitization treatment in the same manner as in Example 1 to produce carbon fiber and graphite fiber. The characteristics of the carbon fiber were fiber diameter, tensile strength,
Tensile modulus of elasticity is 10, On, 2.9GPa,
250GPa, the characteristics of graphite fiber are fiber diameter, tensile strength,
The tensile modulus of elasticity is 9.7, 3.6 GPa, and 5, respectively.
It was 70GPa.

Comparative Example 1 The same heat treatment reaction as in Example 1 was carried out, only the reaction time was increased to 10 hours, and the mesophase component content was 9.
A mesophase-containing pitch with a softening point of about 328° C. and a quinoline solubility of 65% by weight was obtained.

When 1 kg of this pitch was taken and spun in the same manner as in Example 1 (but at a spinning temperature of 420°C) without separating the mesophase and non-mesophase components, the frequency of yarn breakage was 3 to 5 times per 10 minutes. In many cases, spinnability was poor.

This pitch fiber was subjected to infusibility treatment, carbonization and graphitization treatment in the same manner as in Example 1 to produce carbon fiber and graphite fiber. The characteristics of the carbon fiber were fiber diameter, tensile strength,
The tensile modulus of elasticity is 10, OIlm, and 2.2GP, respectively.
a, 250GPa, the characteristics of graphite fiber are fiber diameter, tensile strength, and tensile modulus of 9.7-12 and 3GP, respectively.
a, 530 GPa, and the physical properties were worse than those of the Examples.

Comparative Example 2 When a part of the A pitch obtained in Example 1 was stored in a molten state for 10 days, its softening point was about 321°C.
The quinoline dissolved content had increased to 43.6% by weight.

When 1 kg of this pitch was taken and spun in the same manner as in Example 1 (however, the spinning temperature was 410°C), the frequency of yarn breakage was as high as 1 to 2 times per 10 minutes, and the spinnability was also reduced.

The pitch fibers were subjected to infusibility treatment, carbonization and graphitization treatment in the same manner as in Example 1 to produce carbon fibers and graphite fibers. Each is 10, ba, 2.5GPa
, 250 GPa, and the characteristics of graphite fiber: fiber diameter, tensile strength, and tensile modulus of force 19.8 μs and 2.9 G, respectively.
Pa, 550GPa.

Claims (1)

[Claims] (1) In a method for producing carbon fibers and graphite fibers in which mesoface pitch is spun, carbonized, and optionally graphitized, mesoface-containing pitch produced from carbonaceous pitch is separated into mesoface components and non-mesoface components. Carbon fiber and graphite, characterized in that the separated mesophase pitch is directly spun in a molten state without solidifying, and a part of the mesophase pitch is solidified, and when necessary, it is remelted and spun. Fiber manufacturing method.