JPH043453B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <<Industrial Application Field>> The present invention relates to a method for producing carbon fibers and graphite fibers from carbonaceous pitch fibers. More specifically, the present invention relates to a method for producing carbon fibers and graphite fibers suitable for obtaining long filaments by spinning optically anisotropic carbonaceous pitch and subjecting it to infusibility, carbonization, and graphitization.

<<Conventional technology>> In the past, there has been a demand for the development of high-performance materials with properties such as light weight, high strength, and high modulus of elasticity in a wide range of technical fields related to automobiles, aircraft, and various other industrial fields. Carbon fiber or molded carbon materials are attracting attention. In particular, the method of producing carbon fiber from carbonaceous pitch is considered important as a method that can produce carbon fiber with low cost and high performance.

However, with conventional techniques, the tensile strength of infusible fibers is as low as approximately 0.01 GPa, and the fibers are brittle, making them difficult to handle. This was extremely difficult.

Conventionally, the method for producing long filament carbon fibers from pitch fibers involves dropping the spun yarn into a wire mesh basket and depositing it, making it infusible together with the wire mesh, and then subjecting it to a first heat treatment at 700°C or higher. (preliminary carbonization) to increase the tensile strength of the yarn.
A method has been proposed in which carbon fibers are obtained by making the fibers have a strength of 0.2 GPa or higher, and then carbonizing the fibers at a temperature of about 1500°C after or while winding them up from the basket. −12740).
However, in this method, when the yarns are piled up, they tend to be twisted or twisted, and the yarns tend to be bent, so when made into carbon fibers, the yarns have extremely uneven appearance and have a poor appearance. This has the disadvantage that the strength of the yarn is significantly reduced, resulting in frequent yarn breakage, making it difficult to produce high-quality yarn. These drawbacks could not be essentially improved by increasing the curvature when the threads were piled up.

On the other hand, Japanese Patent Publication No. 53-4128 discloses that a mesophase pitch is melt-spun, wound once around a bobbin,
Place some of the threads on a wire mesh plate and heat to 250℃~
A method is disclosed in which the yarn is oxidized in an oxidizing atmosphere at 500° C. to increase the strength of the yarn, making it easier to handle the yarn, and then processing the yarn. However, this method has the disadvantage that the strength of the carbon fiber yarn as the final product is reduced, and that the production efficiency is poor because the yarn is oxidized while being taken out one by one after it has been wound.

In order to improve the above-mentioned problems in production efficiency, Japanese Patent Application Laid-Open No. 60-81320 and Japanese Patent Application Laid-Open No. 60-21911 discloses that the bobbin is made infusible as it is and prepared in a non-oxidizing atmosphere below a certain temperature. A method of performing carbonization is disclosed. However, in these methods, when the thickness of pitch fiber on the bobbin increases, the degree of infusibility increases due to insufficient air permeability during infusibility or pre-carbonization, and the carbon fiber or graphite fiber becomes The drawback was that the variation in strength was extremely large when it was applied.

Additionally, if you attempt to unwind the fiber after it has been infusible as it is wound on the bobbin and has undergone preliminary carbonization, the strength of the fiber will be approximately
Although it is strong at 0.2GPa, due to insufficient air permeability, agglutination and fusion between fibers and fiber bundles are noticeable, making unwinding (unwinding) extremely difficult, and fluffing of the yarn occurs when unwinding. It has the disadvantage that it is easy to process, and when it is made into carbon fiber or graphite fiber, its commercial value is significantly lowered. In order to solve these problems, the degree of adhesion and fusion is extremely low compared to pre-carbonized fibers. At the stage of infusibility, the fibers are unwound from the bobbin and threaded continuously in a linear manner. Possible methods include preliminary carbonization, carbonization, and graphitization. However, with this method, the strength of the infusible fibers is still as weak as that of pitch fibers, and during infusibility, the oil that binds the fibers decomposes and deteriorates, causing the fiber bundles to become disorganized and become extremely fragile. Because it becomes weak and brittle,
Unwinding (unwinding) from the bobbin after infusibility is extremely difficult, and fuzz is likely to occur during unwinding.

Furthermore, when the thickness of the pitch fiber on the bobbin increases, the air permeability during infusibility is insufficient, so the degree of infusibility increases, and when it is made into carbon fiber or graphite fiber, the strength variation becomes extremely large. There was a drawback.

Furthermore, when these infusible fibers are subjected to preliminary carbonization and carbonization processes, as disclosed in Japanese Patent Application Laid-Open No. 59-15517, the fiber bundle is Since the strength of the yarn is reduced to about 1/4 of the strength at room temperature, the fiber bundles tend to break during heat treatment, making it difficult to handle the yarn.

Although these drawbacks were greatly improved by the method using an air permeable bobbin disclosed in Japanese Patent Application Laid-Open No. 173121/1982, the production efficiency was still insufficient and further improvements were required.

≪Problems to be solved by the invention≫ On the other hand, as a method of obtaining a yarn that can be uniformly infusible, has small variations in physical properties, and has a good appearance when made into carbon fiber, it is possible to infusible yarn drawn with a godet roller. A method is disclosed in which carbon fibers are obtained by continuously threading the thread through a hot air oven at a speed of 0.15 m/min, and then passing it continuously through a carbonization furnace (Japanese Patent Application Laid-Open No.
55-128020). However, this method has the drawback that during the infusibility treatment, as the infusibility progresses, the bundle of yarns becomes disordered and the fiber bundles are easily cut, making operation difficult. Another drawback was that the amount of product produced per hour was extremely small.

Furthermore, when these infusible fibers are subjected to a preliminary carbonization process, the temperature of the fiber bundle decreases to about 1/4 of the strength at room temperature, as disclosed in Japanese Patent Application Laid-Open No. 59-15517. However, there was a drawback that the fiber bundles were easily cut during heat treatment.

Therefore, during the infusibility treatment, there is no breakage of fiber bundles due to disturbance of the bundle of fiber bundles, and the product output per hour is large.Also, the yarn has a good appearance, has little fuzz when handled, and has high strength and high elasticity. Therefore, there has been a strong need for a method for producing long filaments of high-quality pitch carbon fibers with uniform strength at low cost and efficiently.

Therefore, an object of the present invention is to provide a method for producing pitch-based carbon fibers and graphite fibers that are easy to handle and have high quality.

Another object of the present invention is to have good appearance, high strength,
An object of the present invention is to provide a method for efficiently producing high-quality pitch-type long filament carbon fibers and graphite fibers having a high modulus of elasticity.

<<Means for Solving the Problems>> The objects of the present invention are to melt-spun carbonaceous pitch, combine the spun pitch fibers, and thread the fiber bundle continuously in a linear manner in an oxidizing atmosphere. When performing carbonization or graphitization treatment, the first heat treatment is performed in a non-oxidizing gas atmosphere at 1800℃ or less, and then the second heat treatment is performed in an inert gas atmosphere at 3000℃ or less. A method for producing carbon fibers and graphite fibers in which a heat-resistant oil agent is applied to fibers before melting, wherein the number of filaments of the pitch fiber after spinning is 50 to 1000 filaments, and the number of filaments of the pitch fiber after spinning is 50 to 1000 filaments. This was achieved by a method for producing carbon fibers and graphite fibers characterized by 200 to 50,000 filaments.

(a) Carbonaceous pitch The carbonaceous pitch used in the present invention is not particularly limited, and includes coal tar pitch obtained by dry distillation of coal, coal-based pitch such as coal liquefied product, naphtha cracking tar pitch, and catalytic cracking tar pitch. , various types of pitches such as petroleum-based pitches such as atmospheric distillation residues and hydraulic distillation residues, synthetic pitches obtained by decomposing synthetic resins, hydrogenated pitches of these pitches with hydrogen or hydrogen donors, heat treatment, Those modified by solvent extraction etc. can also be used. The softening point of carbonaceous pitch is 230℃~320℃
Preferably it is ℃.

These carbonaceous pitches may be isotropic pitches or optically anisotropic pitches, or may be pitches called neomesophase or premethophase, but in particular, optically anisotropic pitches may be used. As a carbonaceous pitch, approximately
It is preferable to use a material containing 95% or more of an optically anisotropic phase and having a softening point of 230 to 320° C. from the viewpoint of spinning and quality of the final product.

(b-1) Optically anisotropic pitch The optically anisotropic carbonaceous pitch used in the present invention is obtained by polishing the cross section of a pitch lump solidified at room temperature and rotating crossed nicols using a reflective polarizing microscope. In this specification, pitches in which glitter is observed, that is, pitches in which the majority of pitches are substantially optically anisotropic, are referred to as pitches in which glitter is not observed and are optically isotropic. It is called isotropic carbonaceous pitch. Therefore, the optically anisotropic carbonaceous pitch in this specification includes not only a pure optically anisotropic carbonaceous pitch but also a spherical or optically isotropic phase in the optically anisotropic phase. This also includes cases where it is contained in an amorphous island.

In addition, the case of substantially optical anisotropy means that optically anisotropic carbonaceous pitches and optically isotropic carbonaceous pitches coexist, but because the amount of optically isotropic pitches is small, Depending on the polarizing microscope mentioned above, optically isotropic phase (hereinafter referred to as IP)
This is a case where only the optically anisotropic phase (hereinafter referred to as AP) is observed. In general, a clear boundary is observed between AP and IP.

AP in this specification is the so-called "meso phase"
However, the "meso phase" includes a substance that is substantially insoluble in quinoline or pyridine, and
There are two types: those containing a large amount of components soluble in quinoline or pyridine, and those referred to in this specification.
AP is mainly the latter "meso phase".

Since the AP phase and the IP phase are significantly different not only in optical properties but also in viscosity, it is generally undesirable to spin a pitch in which both phases coexist, as this may cause yarn breakage or uneven thickness of the yarn. This means that even if the optically isotropic pitch does not contain undesirable contaminants for spinning, it will give particularly bad results if the IP phase is not homogeneously dispersed within the AP phase. . Therefore, the optically anisotropic pitch used in the present invention is required to have substantial homogeneity. Such a homogeneous optically anisotropic pitch has an IP content of 20% or less, and solid particles with a diameter of 1 μm or more cannot be detected in the cross section of the pitch by reflection microscopy, and they do not volatilize at the melt spinning temperature. There is virtually no foaming caused by substances.

In the present invention, AP and IP are quantified by observing under crossed nicols with a polarizing microscope, taking photographs, and measuring the area ratio occupied by the AP or IP portion, but statistically this area ratio is substantially equal to the volume %
represents. However, the difference in specific gravity between AP and IP is
Since it is small at about 0.05, volume % and weight % can be approximately treated as equal.

The optically anisotropic pitch used in the present invention is
Preferably, its softening point is low. Here,
The softening point of pitch is the transition temperature between the solid phase and liquid phase of pitch, and can be determined from the peak temperature of absorption or release of latent heat during melting or solidification of pitch using a differential scanning calorimeter.
The softening point measured by this method agrees within a range of ±10°C with the temperature obtained by other measurement methods such as the ring and ball method and the micro melting point method.

Ordinary spinning techniques can be used for spinning in the present invention. Generally, the spinning temperature suitable for melt spinning is 60°C to 100°C higher than the softening point of the material to be spun. On the other hand, in the optically anisotropic pitch used in the present invention, thermal decomposition polycondensation occurs at temperatures above 380° C., which may generate decomposed gas or produce unmelted substances. Therefore, the softening point of the optically anisotropic pitch used in the present invention is preferably 320°C or lower,
The temperature is preferably 230° C. or higher in the infusibility treatment step described below.

(b-2) Method for producing optically anisotropic pitches The optically anisotropic pitches used in the present invention may be produced using any production method, but heavy carbonized pitches, which are common raw materials for pitches production, may be used. Hydrogen oil, tar, commercially available pitcher, etc. are heated to 380℃ in a reaction tank.
A conventional method is used to increase the optically anisotropic phase (hereinafter abbreviated as AP) of the residual pitch by sufficiently performing pyrolytic polycondensation while stirring at a temperature of ~500°C and degassing with an inert gas. be able to.
However, this method reduces AP by 80%.
When the above products are manufactured, the thermal decomposition polycondensation reaction proceeds too much, and the quinoline insoluble content increases to over 70% by weight, and the softening point may exceed 330°C, as well as optical isotropy. The phase (hereinafter abbreviated as IP) is also difficult to form a microspherical dispersed state, so this method cannot necessarily be said to be preferable.

Therefore, the preferred method for producing the optically anisotropic pitch used in the present invention is to stop the thermal decomposition polycondensation reaction halfway and heat the polycondensate at 350°C.
This is a method in which AP is kept at a temperature in the range of ~400°C and allowed to stand essentially still, allowing dense AP to grow and mature in the lower layer, and then being separated from the upper layer, which has a large amount of low-density IP. The details of this method are described in JP-A-57-119984.

A more preferable method for producing the optically anisotropic pitch used in the present invention is as described in JP-A No. 58-180585, in which a carbonaceous pitch containing an appropriate amount of AP and not yet excessively heavy is used. In this method, the AP portion is rapidly precipitated by centrifuging it while it is in a molten state. According to this method, the AP phase coalesces and grows, accumulating in the lower layer (layer in the direction of centrifugal force), and the AP is approximately 80
% or more, forming a continuous layer, with a small amount of IP in it.
The lower layer consists of pitches in which IP is dispersed in the form of crystals or minute spherules, while the upper layer consists mostly of IP, with AP dispersed therein in the form of minute spheres. In this case, the boundary between both layers is clear, and only the lower layer can be separated and taken out from the upper layer, making it possible to easily produce an optically anisotropic pitch with a high AP content and easy spinning. According to this method, the AP content is 95% or more and the softening point is 230℃~
Carbonaceous pitch at 320°C can be obtained economically in a short time. Such optically anisotropic carbonaceous pitch has excellent melt-spinning properties, and due to its homogeneity and high orientation, the tensile strength and tensile strength of carbon fibers and graphite fibers obtained by spinning it are improved. The elastic modulus is extremely excellent.

(c) Production of fiber () Spinning Carbonaceous pitch can be spun by a known method. For example, in this method, 1 to 1000 spinnerets with a diameter of 0.1 mm to 0.5 mm are used.
A pitcher is placed in a spinning container with a spinneret below it, and the spinneret is placed under an inert gas atmosphere.
The pitch is held at a constant temperature between 280 and 370 degrees Celsius, and the pressure of the inert gas is increased to several hundred mmHg while maintaining it in a molten state, and the molten pitch is pushed out of the mouthpiece and allowed to flow down while controlling the temperature and atmosphere. The pitch fibers are 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 under pressure using pre-melted pitch or 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 taken up using gas that is controlled at a constant temperature and descends at high speed in the vicinity of the die, and long fibers are produced on a belt conveyor below.

Furthermore, a cylindrical spinning container having a spinneret on the peripheral wall is rotated at high speed, and molten pitch is continuously supplied to the spinning container, and the pitch is pushed out from the peripheral wall of the cylindrical spinning device by centrifugal force, and the spinning container is rotated at high speed. It is also possible to adopt a spinning method in which pitch fibers that are drawn together are accumulated.

In the present invention, in order to unwind (unwind) uniformly from the state wound on the bobbin, the traverse during spinning is a large traverse of 2 to 100 mm/(per bobbin rotation). Thickness: 1-100mm, preferably 5-50mm
It is effective to do so. The traverse is preferably about 5 to 20 mm/(one revolution of the bobbin) in consideration of the unwinding (unwinding) property of pitch fibers from the bobbin.

In the present invention, carbonaceous pitch with a low softening point is used, regardless of which known method is used for spinning.
It can be spun at a lower temperature than conventional methods, which is ℃. When spinning at such temperatures, thermal decomposition and thermal polymerization are kept extremely low, so
The pitch fibers after spinning can maintain almost the same chemical composition as the pitch before spinning.
Therefore, it is convenient that the fibers after spinning can be remelted and spun again.

In the present invention, the melt-spun pitch fibers are bundled through an air sucker, and then guided to an oiling roller where a sizing agent (oil agent) is applied and further bundled. In this case, the sizing agent is
For example, alcohols such as ethyl alcohol, isopropyl alcohol, n-propyl alcohol, butyl alcohol, or alcohols with a viscosity of 3 to 3
300cst (25℃) dimethylpolysiloxane,
Methylphenylpolysiloxane etc. diluted with a low boiling point silicone oil (polysiloxane) or a solvent such as paraffin oil, or dispersed in water with an emulsifier added; Similarly, graphite, polyethylene glycol or hindered ester Dispersions of surfactants; surfactants diluted with water; and various oils used for ordinary fibers, such as polyester fibers, which do not damage pitch fibers can be used. The amount of sizing agent attached to the fibers is usually 0.01 to 10% by weight, but especially 0.05 to 10% by weight.
Preferably it is 5% by weight.

() Doubling of pitch fibers In the present invention, doubling is performed prior to infusibility in order to thread the yarn stably and continuously during infusibility.

The number of filaments of pitch fiber spun from one melt spinning machine (one spinneret) is limited due to melt spinning, and is usually 1 to 2000.
Preferably 50 to 1000 filaments.

In the present invention, 2 to 20 pitch fiber bundles obtained by melt spinning are used to form 200 to 50,000 filaments, preferably 500 to 5,000 filaments. The yarn doubling is performed by winding the spun pitch fibers around a plurality of bobbins, and then simultaneously unwinding the fiber bundles, combining the fiber bundles into one, and winding them around one bobbin. Winding traverse during doubling is bobbin 1
Preferably, it is 5 to 100 mm per rotation.
In order to improve the unwinding property from the bobbin, it is better to make the traverse larger, but if it is too large, the thread is likely to be damaged, so it is not preferable.

Pitch fibers dropped into cans may be pulled up from multiple baskets or cases and spliced.

For doubling, it is possible not only to unwind from a bobbin, but also to collect and double pitch fibers spun simultaneously from a plurality of spinning machines or spinnerets.

It is possible to double 2 to 20 threads at a time, but 2 to 10 threads may be multiplied at the first time, and then 2 to 20 threads may be multiplied at a time.
A method in which 10 sutures are recombined is also used.

The winding thickness after doubling is usually 1 to 100 mm, preferably 5 to 50 mm.

In the present invention, a heat-resistant oil agent is applied during and/or after the yarn doubling in order to ensure stable threadability to the infusibility furnace during infusibility.

As a heat-resistant oil, the viscosity at 25℃ is
Dilute 10 to 1000 cst of alkyl phenyl polysiloxane, dialkyl polysiloxane, or hindered ester oil with silicone oil, paraffin oil, or alcohol with a boiling point of 160°C or lower to form a 0.01 to 10% solution, preferably 0.1 to 2%.
Use as a solution.

In particular, alkylphenyl polysiloxanes are preferred because they have excellent heat resistance.

The alkylphenyl polysiloxane has a phenyl group content of 5 mol% to 80 mol%, preferably 5 mol% to 50 mol%, and the alkyl group is preferably a methyl group, an ethyl group, or a propyl group. A method in which antioxidants such as amines, organic selenium compounds, and phenols are included in the heat-resistant oil agent is also used. As the antioxidant, phenylalphanaphthylamine, dilaurylselenide, phenothiazine, iron octolate, etc. are used.

Most of the components used to dilute the heat-resistant base stock must be evaporated before entering the continuous infusible furnace, so they must have a boiling point of 160°C or lower, do not dissolve the pitch fibers, and must be diluted with the base stock. Those that can dissolve certain dimethylpolysiloxanes, methylphenylpolysiloxanes, etc. are preferred.

These diluting components include _C2 to _C8 alkanol-1, alkanol-2, unsaturated primary alcohol, hexamethyldisiloxane,
Preferably, octamethyltrisiloxane or the like is used.

The oil may be applied by any method such as spraying or roller contact.

The winding pressure after doubling can be set arbitrarily, but from the viewpoint of workability and operability, it is preferably 10 to 100 mm.

The threads may be combined before being passed through the infusibility furnace, but the infusibility may be performed while the threads are being combined.

() Infusibility of pitch fibers In the present invention, the fiber bundle is continuously passed through an oxidizing atmosphere to make it infusible.

In the present invention, the threads are doubled to ensure smooth continuous threading, a heat-resistant oil is applied, and the fiber bundles are not broken during the infusibility treatment. Various known combinations of temperature, oxidizing agent, and reaction time in the step of producing carbonaceous fibers can be used. The temperature of the infusibility step in the present invention is 150 to 400°C, preferably 200 to 300°C, and the temperature is increased stepwise or gradually, and the treatment is usually carried out for 30 minutes to 5 hours. Infusible is air,
This can be carried out using oxygen, a mixed gas of air and oxygen, or air and nitrogen, or the like. In the present invention, even if the oxygen concentration is increased, there is no fear of combustion due to the accumulation of reaction heat within the fiber bundle, so the oxygen concentration can be increased as a method of shortening the reaction time.

In the present invention, the softening point of pitch is treated at a temperature of 200°C or less in an atmosphere containing an oxidizing agent such as halogen, NO ₂ , SO ₂ , SO ₃ or ozone, or in an oxygen gas atmosphere. Than
The process is carried out by holding at a temperature 30 to 50 degrees Celsius lower, i.e., 150 to 240 degrees Celsius, for 5 minutes to one hour until sufficient infusibility is achieved, and then raising the temperature to approximately 300 degrees Celsius to complete infusibility if necessary. The latter method is particularly preferred as it is easy and reliable.

For infusibility, it is preferable to replace the old gas by circulating a fresh gas of the same type as the atmosphere at a rate of 0.1 to 5 times per minute.

It is preferable to forcibly stir the atmosphere during the infusibility treatment using a fan, and the wind speed is
0.1-10 m/sec, preferably 0.5-5 m/sec. Such forced stirring promotes gas penetration into the fiber bundle, eliminates temperature distribution in the infusibility furnace, and has the effect of making firing uniform.

Infusibility treatment can be performed without applying tension to the fibers, but it is usually done to prevent drag scratches caused by the fiber bundles (threads) sagging in the infusibility furnace and rub against the bottom of the furnace, and to improve the appearance of the fibers. In order to improve carbon fiber physical properties such as tensile strength and tensile modulus, it is preferable to perform the infusibility while applying a tension of 0.001 to 0.2 g per filament.

The thread leaving the continuous infusibility furnace is once wound onto a bobbin, then subjected to first heat treatment, then second heat treatment.
It is then subjected to the following heat treatment. Further, the first and second heat treatments may be performed as they are without being wound up.

The yarn leaving the continuous infusibility furnace is brittle and weak due to decomposition, evaporation, deterioration, etc. of a part of the oil in the furnace, so it is necessary to remove the yarn before winding it or moving on to the next primary heat treatment process. It is preferable to add the above-mentioned heat-resistant oil to the fibers to improve the yarn handling properties of the fibers.

() Heat treatment process The carbonaceous pitch fibers, which have become infusible through continuous infusibility, are heated to 500 to 1000°C in a chemically inert nitrogen gas or argon gas atmosphere to perform initial carbonization. A pre-carbonized fiber is obtained by heating the fiber to 1000-2000°C.
So-called carbon fibers are obtained by carbonization, and graphite fibers are obtained by increasing the temperature to 2000°C to 3000°C and graphitizing it. Next, these methods will be explained in detail.

In the present invention, heat treatment is performed by continuously passing the fiber to be heat treated in a linear manner through a continuous heat treatment furnace.

In particular, in the present invention, products with excellent performance can be efficiently obtained by pre-carbonizing, carbonizing, and graphitizing infusible pitch fibers under an appropriate furnace temperature profile (temperature gradient). For this purpose, a two-step heat treatment is performed. In general, if the length of the furnace is short, it is difficult to obtain an appropriate temperature profile (temperature gradient), but on the other hand, if the length of the furnace is long, the fiber bundles will sag and rub against the inside of the furnace, causing scratches. The degree of adhesion increases, resulting in a decrease in product performance. These conflicting problems can be solved by dividing the heat treatment furnace and performing two stages of treatment: first heat treatment and second heat treatment. By dividing the fiber bundle into two, it becomes easier to create an appropriate temperature profile, and it is also possible to reduce the occurrence of scratches due to slack in the fiber bundle.

In addition, by performing such two-stage treatment, the length of the furnace including the first heat treatment and the second heat treatment can be increased, so the actual temperature increase rate (the main rate) of the yarn temperature can be increased. In the specification, this is referred to as the temperature increase rate of heat treatment) if it is constant, it is advantageous because the threading speed to the furnace can be increased and the production amount per hour can be increased.

The separation temperature of the heat treatment in the two-step heat treatment in the present invention is determined by the preliminary carbonization of the infusible pitch fibers and the product performance due to the primary and secondary effects of reaction product gas and tar-like substances generated during carbonization. In order to minimize the effect on
The temperature is 1800°C or lower, preferably 600 to 1500°C. The amount of gas generated is greatest at around 500℃, so it is preferable that the temperature is 600℃ or higher, and around 500℃.
A temperature of 1500°C is preferable because the reaction product gas is small.

Although the first heat treatment can be carried out while the bobbin is being wound, it is particularly preferable to perform the first heat treatment while unwinding the infusible infusible fibers from the bobbin and, if necessary, further doubling the yarns.

The first heat treatment is performed by continuous linear passage under a non-oxidizing gas atmosphere such as nitrogen gas and/or argon gas. The atmospheric gas is
In order to remove the exhaust gas generated from the infusible fibers, circulation is performed at a rate of 0.05 to 1 time/minute.
It is also possible to recycle some of these gases or to purify them and use them all again.

If the first heat treatment is performed suddenly at a high temperature, the fiber bundles will be cut or the fibers will be partially broken due to melting and/or fusing of the fibers. To avoid this, heat treatment is started at 400°C or lower, preferably at 300°C or lower. The temperature increase rate in the first heat treatment is preferably 20-2000℃/min, preferably 50-500℃, in order to gradually carbonize the fiber bundle and increase the softening point of the fiber bundle little by little to avoid cutting the fiber bundle due to fusion. /minute.

If the heating rate is made slower, threading becomes easier, but this is not economical. The first heat treatment temperature (maximum temperature) is 1800°C or lower, preferably 600 to 1500°C, for the reasons mentioned above. After the maximum temperature is reached, it may be held for less than one hour.

The first heat treatment can be performed without applying tension, but the fiber bundle may become slack.
In order to prevent damage caused by thread rubbing on the bottom and walls of the heat treatment furnace, and to increase the physical properties of carbon fiber or graphite fiber by firing the thread under tension,
It is preferable to apply a tension of 0.001 to 0.2 g. The first heat treatment is usually 0.1~20m/
Run through the kiln continuously at a rate of 1 minute.

The second heat treatment is performed through a continuous heat treatment furnace in an inert gas atmosphere such as argon gas and/or nitrogen gas. Argon gas is particularly preferable as the atmospheric gas when producing graphite fibers.
The atmospheric gas is circulated and replaced at a rate of 0.05 to 1 time/minute in order to remove gas generated from the fibers. If necessary, the atmospheric gas may be recycled or purified and reused.

The maximum temperature of the second heat treatment is 1000 to 3000.
Do this so that the temperature is within the range of ℃. After reaching maximum temperature
Holding for up to 30 minutes is also done.

The starting temperature of the second heat treatment is 1000°C or less, and the temperature increase rate from there to the maximum temperature of the second heat treatment is 100 to 2000°C/min.

The second heat treatment can be performed without applying tension, but in order to prevent damage to the yarn during passing through the furnace and to improve the physical properties of carbon fibers and graphite fibers by processing under tension, it is necessary to It is preferable to apply a tension of ~0.2 g.

In the second heat treatment, since the first heat treatment has already turned into carbon fibers or fibers with similar strength, firing is performed using the already known firing method for polyacrylonitrile carbon fibers. (For example, U.S. Pat. No. 3700511, U.S. Pat. No. 3764662, U.S. Pat.
No. 3900556, No. 3954750, No. 4301136,
British Patent No. 1110791, British Patent No. 1215005, Special Publication No. 12540, British Patent No. 45-19415, British Patent No. 47-
No. 26733, No. 47-36463, JP-A-46-2961
No. 47-716, No. 60-99010).

The yarn leaving the second heat treatment furnace is treated with a sizing agent, a sizing agent, etc. as necessary, and then wound onto a bobbin.

In addition, the first heat treatment and the second heat treatment in the present invention
The results of the secondary heat treatment can be expressed in terms of preliminary carbonization, carbonization, and graphitization as follows.

First heat treatment Second heat treatment Pre-carbonization Carbonization Pre-carbonization/carbonization Carbonization Pre-carbonization Carbonization/graphitization Pre-carbonization/carbonization Carbonization/graphitization Pre-carbonization/carbonization Graphitization <<Effects of the Invention>> The present invention provides carbonaceous pitch fibers. After doubling to increase the strength of the fiber bundle and adding a heat-resistant oil,
Since the fiber bundle is continuously infusible in a linear form, there is no cutting of the fiber bundle during infusibility, and since the fiber bundles are doubled, the production speed can be increased.

Since the fiber bundle is continuously passed through the infusibility furnace in a linear manner, it is possible not only to obtain fibers with good appearance, but also to obtain uniform fibers with no unevenness during infusibility. Carbon fibers and graphite fibers with high strength and tensile elasticity can be obtained.

The first heat treatment at 1,800℃ or less and the second heat treatment at 3,000℃ or less allow fiber bundles to be fired continuously in a linear form, making it possible to use continuous equipment, and to produce a uniform product with a good appearance. Carbon fibers and graphite fibers with high physical properties such as tensile strength and tensile modulus can be obtained.

Further, by completing the second high-temperature heat treatment in a very short time, graphite fibers with high strength and high modulus of elasticity can be easily obtained. In addition, the carbon fibers and graphite fibers obtained in this way are high-quality long filament yarns that have little fuzz when handled and have a good appearance.
It can be made into yarns, woven fabrics, or knitted fabrics, and can be used for filament winding in the production of composite materials, production of prepregs, etc. Therefore, the scope of its application is wide, and the significance of the present invention is great.

<<Example>> The present invention will be explained in more detail below with reference to Examples, but the present invention is not limited thereto.

Example 1 A carbonaceous pitch containing approximately 55% optically anisotropic phase (AP) and having a softening point of 232° C. was used as a precursor pitch. This precursor pitch contained 16.1% by weight of quinoline insoluble matter and 0.26% by weight of ash, and had a viscosity of 2.8 poise at 370°C. This pitch is melted in a melting tank with an internal volume of 20,
The temperature is controlled at 370°C and sent at a flow rate of 20 ml/min to a cylindrical continuous centrifugal separator with an effective volume of 200 ml in the rotor.
Centrifugal force is reduced while controlling the rotor temperature to 370℃.
At 30,000G, a pitch with more optical anisotropy than the AP outlet (A pitch) and a pitch with more optical isotropy than the IP outlet (I pitch) were successively extracted.

The obtained optically anisotropic pitch contains 98% optically anisotropic phase, has a softening point of 265°C, and has a quinoline insoluble content.
It was 29.5%.

Next, the obtained optically anisotropic pitch was passed through a melt spinning machine with a 500-hole spinneret (nozzle hole size: diameter 0.3 mm), extruded at 355°C with a nitrogen gas pressure of about 200 mmHg, and The fibers were wound onto a stainless steel wire mesh bobbin with a diameter of 210 mm and a width of 200 mm that rotated at high speed, and spun for 10 minutes at a winding speed of about 500 m/min. The traverse pitch per one revolution of the bobbin was 10 mm/one revolution. There was no yarn breakage during spinning. At this time, the spun yarn was approximately converged with an air spooler and guided to an oiling roller, and a converging oil was supplied at a ratio of about 0.5% to the yarn. As an oil agent, the viscosity at 25℃ is
14cst dimethylpolysiloxane was used.

Six bobbins wound with pitch fibers were combined with a traverse pitch of 20 mm/rotation, and wound as a 3000 filament onto a stainless steel wire mesh bobbin with 10 meshes (55% void ratio).

At the time of yarn doubling, an oil agent containing 0.5% by weight of 40 cst methylphenyl polysiloxane and 99.5% by weight of isopropyl alcohol was applied at 25°C.

While unwinding (unwinding) the bobbin-wound pitch fiber obtained in this way from the bobbin, the furnace inlet temperature was set at 150°C.
It was introduced into a continuous infusibility furnace with forced hot air circulation equipped with a fan in an air atmosphere with a maximum temperature of 270°C. Temperature from 150℃
The temperature was raised to 270°C at a rate of 10°C/min and held at 270°C for 30 minutes. The treatment time was 150 minutes. During this time, the atmosphere in the furnace was replaced with fresh air at a rate of 0.5 times/minute.

The wind speed during infusibility was 0.7 m/sec, and the tension applied to the fiber bundle was 0.007 g/filament.

After the infusibility treatment was completed, the same oil agent used for doubling was applied, and the yarn was once wound onto a bobbin. This bobbin was set in front of a continuous firing furnace for performing the first heat treatment.

While unwinding this bobbin, the first
The next heat treatment, the second heat treatment, was carried out, and during this time the thread was unwound from the bobbin smoothly.

The first heat treatment was performed in a continuous firing furnace in a nitrogen gas atmosphere with a furnace inlet temperature of 300°C and a maximum temperature of 800°C.
The temperature increase rate was 200° C./min, and the threading speed was 1 m/min. The second heat treatment is performed in a nitrogen gas atmosphere at a maximum temperature of 1500℃, and the temperature increase rate at this time is 500℃.
The threading speed was 1 m/min. It was wound up at the exit of the second heat treatment furnace to obtain carbon fiber. The tension during threading was 0.01 g per filament. The obtained carbon fiber had a tensile strength of 2.5 GPa, a tensile modulus of 260 GPa, and a thread diameter of 9.9 μm.

Example 2 Graphite fibers were obtained in the same manner as in Example 1, except that the second heat treatment was performed at 2500° C. in an argon gas atmosphere. The tensile strength of the graphite fiber obtained is 2.4GPa,
The tensile elasticity was 650 GPa, and the thread diameter was 9.7 μm.

The carbon fibers and graphite fibers obtained in this way could be unwound, wound up, doubled, etc. as desired.

Comparative Example 1 The same process as in Example 1 was carried out except that the yarns were not doubled. The fiber bundles of the thus obtained pitch fibers were cut in the furnace during infusibility, making it impossible to obtain long infusible fibers.

Comparative Example 2 The same process as in Example 1 was carried out except that no heat-resistant oil was applied during the yarn doubling. In this case, the fiber bundles were frequently cut in the continuous infusibility furnace, making it impossible to obtain long fibers.

Claims (1)

[Scope of Claims] 1. Carbonaceous pitch is melt-spun, the spun pitch fibers are combined, and the fiber bundle is passed continuously in a linear manner in an oxidizing atmosphere to make it infusible. The first heat treatment is performed in a toxic gas atmosphere, and then
A method for producing carbon fibers and graphite fibers, in which a heat-resistant oil agent is applied to fibers before infusibility during carbonization or graphitization treatment by performing a second heat treatment in an inert gas atmosphere at 3000 ° C. or less, A method for producing carbon fibers and graphite fibers, characterized in that the pitch fibers after spinning have a filament number of 50 to 1000 filaments, and the pitch fibers after spinning have a filament number of 200 to 50,000 filaments. 2. The method for producing carbon fibers and graphite fibers according to claim 1, characterized in that the traverse during doubling is 5 to 100 mm/(one rotation of the bobbin). 3. The method for producing carbon fibers and graphite fibers according to claim 1, characterized in that the yarns are twisted 0.1 to 30 times per meter during doubling. 4 The heat-resistant oil agent applied to the doubled Pituchi fibers
A patent claim characterized in that it is a mixture of an alkylphenyl polysiloxane and/or a dialkyl polysiloxane having a viscosity of 10 to 1000 cst at 25°C, and a low-boiling silicone oil and/or an alcohol having a boiling point of 160°C or less. A method for producing carbon fibers and graphite fibers according to scope 1. 5. The method for producing carbon fibers and graphite fibers according to claim 4, wherein the alkyl phenyl polysiloxane contains 5 mol% to 80 mol% of phenyl groups. 6 Claim 4 or 5 in which the alkyl group is any of methyl, ethyl, and propyl groups
The method for producing carbon fibers and graphite fibers as described in 2. 7. Claim 4, characterized in that the alcohol is at least one alcohol selected from alkanol-1, alkanol-2, and unsaturated primary alcohols having 2 to 8 carbon atoms. The method for producing carbon fiber and graphite fiber described in . 8. According to any one of claims 4 to 7, the heat-resistant oil agent contains at least one antioxidant selected from amines, organic selenium compounds, and phenols. A method for producing carbon fiber and graphite fiber. 9. Claim 8, characterized in that the antioxidant is one or a mixture of two or more selected from phenyl-α-naphthylamine, dilaurylselenide, phenothiazine, and iron octolate. The method for producing carbon fiber and graphite fiber described in . 10 Infusibility treatment at a temperature range of 150°C to 400°C,
The method for producing carbon fibers and graphite fibers according to claim 1, wherein the method is carried out in an atmosphere of air, oxygen, or a mixed gas of air and oxygen or air and nitrogen. 11. The method for producing carbon fibers and graphite fibers according to claim 1, wherein the infusibility is carried out in an atmosphere containing an oxidizing gas. 12 The oxidizing gas is halogen, NO ₂ , SO ₂ ,
At least one selected from SO ₃ and ozone
The method for producing carbon fibers and graphite fibers according to claim 1, wherein the carbon fibers and graphite fibers are seeds. 13. The method for producing carbon fibers and graphite fibers according to claim 1, characterized in that the infusible atmosphere gas is circulated and replaced at a rate of 0.1 to 5 times/minute. 14. The method for producing carbon fibers and graphite fibers according to claim 1, wherein the infusible atmosphere is forcibly stirred at a wind speed of 0.1 to 10 m/sec. 15. The method for producing carbon fibers and graphite fibers according to claim 1, which comprises applying tension to the fibers during infusibility. 16. The method for producing carbon fibers and graphite fibers according to claim 1, which comprises applying a heat-resistant oil to the infusible pitch fibers and then heat-treating them. 17. The method for producing carbon fibers and graphite fibers according to any one of claims 1 to 16, characterized in that the first heat treatment is performed in an atmosphere of nitrogen gas and/or argon gas. . 18 Claim 17, characterized in that atmospheric gas is circulated and replaced at a rate of 0.05 to 1 time/min.
The method for producing carbon fibers and graphite fibers as described in 2. 19 The maximum temperature in the first heat treatment is 600
The method for producing carbon fibers and graphite fibers according to claim 1, wherein the temperature is 1500°C. 20 The first heat treatment start temperature is 400°C or less, and the temperature increase rate from the start temperature to the maximum temperature of the first heat treatment is 20 to 2000°C/min. A method for producing carbon fibers and graphite fibers according to scope 1. 21 The temperature increase rate of the first heat treatment is 50 to 5000℃/
Claim 20, characterized in that
The method for producing carbon fibers and graphite fibers as described in 2. 22 First heat treatment per filament
The method for producing carbon fibers and graphite fibers according to claim 1, characterized in that firing is performed while applying a tension of 0.001 to 0.2 g. 23. The method for producing carbon fibers and graphite fibers according to claim 1, wherein the second heat treatment is performed in an atmosphere of argon gas and/or nitrogen gas. 24 Adjust the atmospheric gas for the second heat treatment to 0.05 to 1
24. The method for producing carbon fibers and graphite fibers according to claim 23, characterized in that the exchange is carried out at a rate of times/minute. 25 The maximum temperature in the second heat treatment is 1000
The method for producing carbon fibers and graphite fibers according to claim 1, wherein the temperature is 3000°C. 26 A patent claim characterized in that the start temperature of the second heat treatment is 1000°C or less, and the temperature increase rate from the start temperature to the maximum temperature of the second heat treatment is 100 to 2000°C/min. A method for producing carbon fibers and graphite fibers according to scope 1. 27 Second heat treatment per filament
The method for producing carbon fibers and graphite fibers according to claim 1, characterized in that firing is performed while applying a tension of 0.001 to 0.2 g. 28 The carbonaceous pitch is an optically anisotropic pitch containing about 95% or more of an optically anisotropic phase, and has a softening point of about 230 to 320.
The method for producing carbon fibers and graphite fibers according to claim 1, wherein the temperature is .degree.