JPS62184125A - Production of carbon yarn and graphite yarn - Google Patents

Abstract

PURPOSE:To produce high-quality, uniform yarn securing stable passage of pitch yarn to an infusible treatment furnace, by adding a heat-resistant finishing oil to pitch yarn obtained by melt spinning and subjecting the yarn to infusible treatment. CONSTITUTION:Carbonaceous pitch is subjected to melt spinning to give pitch yarn (number of filament is 50-1,000), which is doubled (number of filaments is changed to 200-50,000). The prepared yarn bundle is passed through an oxidizing atmosphere, made infusible, subjected to a first heat treatment in a nonoxidizing atmosphere at <=1,800 deg.C and then to a second heat treatment in an inert gas atmosphere at <=3,000 deg.C to give carbon yarn. In the operation, the yarn before the infusible treatment is provided with a heat-resistant finishing oil. Addition of the heat-resistant finishing oil is carried out during yarn doubling and/or after yarn doubling. An alkylphenylpolysiloxane is especially preferable as the heat-resistant finishing oil.

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 by spinning optically anisotropic carbonaceous pitch, subjecting it to infusibility, carbonization, and graphitization to obtain long filaments.

(Prior art) 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 manufacturing carbon fiber from carbonaceous pitch is regarded as important as a method that can manufacture carbon fiber with low cost and high performance.

However, depending on the conventional technology, the tensile strength of the infusible fiber is as small as about 0.0 IGPa, and it is brittle, making it difficult to handle, and it is difficult to obtain the long filament-like fibers necessary for obtaining high-performance patient products. It was extremely difficult.

Conventionally, as a method for producing long filament carbon fibers from pitch fibers, the spun yarn is dropped into a wire mesh basket and deposited, the wire mesh is made infusible, and then the wire mesh is infusible.
After carrying out the first heat treatment (preliminary carbonization) at 00°C or higher so that the tensile strength of the yarn is 0°2GPa or higher, the yarn is pulled up from the basket and wound up, or after being wound up, 1500°C. A method of obtaining carbon fiber by carbonization at a temperature of about ℃ has been proposed (Japanese Patent Publication No. 51-1274
No. 0). However, in this method, when the yarn is piled up, it tends to be twisted or twisted, and paternal bending is likely to occur.As a result, when it is made into carbon fiber, the yarn has extremely uneven appearance and has a poor appearance. The disadvantage is that the strength is significantly reduced, resulting in frequent yarn breakage and difficulty in producing high quality yarn.

These drawbacks cannot be essentially improved even if the curvature is increased when the threads are piled up.

On the other hand, Japanese Patent Publication No. 53-4128 discloses that mesoface pitch is melt-spun, wound once onto a bobbin, some of the threads are placed in a net tray, and then heated in an oxidizing atmosphere at 250°C to 500°C. A method is disclosed in which the yarn is oxidized to increase the strength of the yarn, making it easier to handle, and then processing the yarn. However, this method has the disadvantage that the strength of the carbon fiber yarn that is the final product decreases, 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 production efficiency problem,
No. 81320 and Japanese Unexamined Patent Publication No. 60-21911 disclose a method in which the bobbin winding is infusible and preliminary carbonization is performed in a non-oxidizing atmosphere at a certain temperature or lower. However, in these methods, when the winding thickness of the 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 There was a drawback that the variation in strength became extremely large when it was applied.

Furthermore, if the fibers are made infusible while wound on a bobbin and then unwound after being pre-carbonized, the strength of the fibers will be as strong as approximately 0°2 GPa, but the air permeability will be insufficient, causing damage between the fibers and fiber bundles. The disadvantage is that the sticking and fusion of the fibers is very noticeable and it becomes extremely difficult to unwind (unwind), and when unwinding, the yarn tends to become fluffy, which significantly reduces the commercial value when it is made into charcoal Awh fiber or graphite fiber. there were. In order to solve these problems, the degree of adhesion and fusion is much lower than that of pre-carbonized uh fibers, and it is necessary to unwind them from the bobbin at the stage of infusibility, which is lower than that of pre-carbonized uh fibers, and to continuously form a wire. A possible method is to perform preliminary carbonization, carbonization, and graphitization while threading. However, in 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 thin. Since it becomes weak and brittle, it becomes extremely difficult to unwind (unwind) it from the bobbin after it has been made infusible, and it has the disadvantage that 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 varies greatly. There was a drawback.

Furthermore, as disclosed in Japanese Patent Application Laid-Open No. 15517/1984, the time required for these infusible fibers to be subjected to preliminary carbonization and carbonization processes is such that the temperature of the fiber bundle reaches a temperature of 700 to 800°C. Since the strength of the yarn decreases to about 1/4 of the strength at room temperature, it has the disadvantage that uIi ITO is easily cut during heat treatment and is difficult to handle as a yarn.

Although these drawbacks have been greatly improved by the method using a breathable bobbin disclosed in JP-A-60-173121, the production efficiency is still insufficient and further improvements are required.

(Problems to be Solved by the Invention) On the other hand, as a method for obtaining 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 has been disclosed in which carbon fibers are obtained by continuously passing the yarn through a hot-blast stove at a speed of 0.15 m/min and then continuously passing it through a carbonization furnace (Japanese Patent Laid-Open No. 128020/1983). However, in this method, during the infusibility treatment, as the infusibility progresses, the bundle of yarns becomes disordered, and the fiber bundle is likely to be cut.
The drawback was that it was difficult to operate. Another drawback was that the amount of product produced per hour was extremely small.

Also, these are infusible! When subjecting the 6-fiber to the preliminary carbonization process,
As disclosed in Japanese Unexamined Patent Publication No. 59-15517, the temperature of the fiber bundle decreases to about 1/4 of the strength at room temperature, so the disadvantage that the fiber bundle is easily cut during heat treatment has become apparent. .

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 pitch-based carbon fibers of high quality 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 provide a method for efficiently producing high-quality pitch-based long filament carbon fibers and graphite fibers that have good appearance, high strength, and high elastic modulus.

(Means for Solving the Problems) The aspects of the present invention include melt spinning carbonaceous pitch,
The spun pitch fibers are doubled, the fiber bundle is passed continuously in a linear manner in an oxidizing atmosphere to make it infusible, a first heat treatment is performed in a non-oxidizing gas atmosphere at 1800°C or less, and then 3
A method for producing carbon fibers and graphite fibers in which carbonization or graphitization treatment is performed by performing a secondary heat treatment in an inert gas atmosphere of 000°C or less, the fibers being imparted with a heat-resistant oil agent before infusibility. This was achieved by a method for producing carbon fibers and graphite fibers characterized by the following.

a) Carbonaceous pitch The carbonaceous pitch used in the present invention is not particularly limited, and includes coal tar pitch obtained by dry distilling coal;
Various pitches such as coal-based pitch such as coal liquefied products, naphtha cracking tar pitch, catalytic cracking tar pitch, petroleum-based pitch such as atmospheric distillation residue, vacuum distillation residue, synthetic pitch obtained by decomposing synthetic resin, In addition to those obtained by hydrogenating these pitches with hydrogen or a hydrogen donor, those modified by heat treatment, solvent extraction, etc. can also be used. The softening point of the carbonaceous pitch is preferably 230°C to 320°C.

These carbonaceous pitches may be isotropic pitches or optically anisotropic pitches, or may be pitches called neomesofaces or premesofaces, but especially optically anisotropic pitches. As an orthotropic carbonaceous pitch, it contains about 95% or more of an optically anisotropic phase as measured by a trace amount of polarized light a, and
It is preferable to use one 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 orthogonal nicols with a reflective polarizing microscope to make it shine. This means a pitch in which most of the pitches are observed to be optically anisotropic; 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 an optically isotropic phase in which the optically anisotropic phase is spherical or non-spherical. This also includes cases where it is contained in a fixed island shape.

In addition, the case of substantially optical anisotropy means that optically anisotropic carbonaceous pitch and optically isotropic carbonaceous pitch coexist, but the optically isotropic pitch is less dominant. This is a case where the optically isotropic phase (hereinafter referred to as IP) cannot be observed depending on the polarizing microscope described above, and only the optically anisotropic phase (hereinafter referred to as AP) is observed. Incidentally, in general, AP
A clear boundary is observed between and tp.

Honmei! AP in Book I is considered to be the same as the so-called 1-meso phase, but the "meso phase" includes two types: one that is substantially insoluble in quinoline or pyridine, and one that contains a large amount of components that are soluble in quinoline or pyridine. There are different types, and the main
The AP referred to in the book is mainly the latter ``meso phase''.

Since the above-mentioned AP phase and IP phase differ greatly not only in optical properties but also in viscosity, it is generally undesirable to spin a pitch in which both are mixed, as it may cause yarn breakage or uneven yarn thickness. □ 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 uniformly dispersed within the AP phase. do. Therefore, substantial homogeneity is required for the optically anisotropic pitch used in the present invention. Such a homogeneous optically anisotropic pitch has an IP content of 20% or less, solid particles with a particle size of 1 μm or more cannot be detected in the cross section of the pitch by reflective g-fine observation, and it is difficult to detect solid particles with a particle size of 1 μm or more at the melt spinning temperature. There is substantially no foaming due to abrasive 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 AP or 18 parts. However, the difference in specific gravity between AP and IP is about 0.05, which is small, so it can be approximated as volume %.
and Tpi1% can be treated as being equal.

The optically anisotropic pitch used in the present invention preferably has a low softening point. Here, the softening point of pitch is the transition temperature between the solid phase and liquid phase of Vinona, 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 is ±10°C higher than the temperature obtained by other measurement methods such as the ring and ball method or the trace melting point method.
Match within the range.

Ordinary spinning techniques can be used for spinning in the present invention. Generally, the spinning temperature leading to melt spinning is 60°C to 100°C higher than the softening point of the material being spun. On the other hand, the optical anisotropy pitch used in the present invention is 380
If the temperature is higher than 0.degree. C., thermal decomposition polycondensation may occur and decomposition gas may be generated or unmelted substances may be produced. Therefore, the softening point of the optically anisotropic pitch used in the present invention is preferably 320°C or lower, and the softening point of the optically anisotropic pitch used in the present invention is preferably 320°C or lower, and the
Preferably, the temperature is 30°C or higher.

b-2) Method for producing optically anisotropic pitch The optically anisotropic pitch used in the present invention may be produced using any production method, but it may be produced using the general raw materials of the Pi-Sochi manufacturing field. A certain side yi
j Hydrocarbon oil, tar, commercially available pitch, etc. are heated to 380 ml 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 pyrolysis polycondensation while stirring at a temperature of ℃ to 500℃ and degassing with an inert gas. can do. However, when a product with an AP content of 80% or more is produced by this method, the thermal decomposition polycondensation reaction proceeds too much, and the quinolinated content increases to 70% or more by weight, and the softening point may reach 330°C or more. In addition, the optically isotropic phase (hereinafter abbreviated as IP) is also difficult to form a microspherical dispersed state, which is not necessarily a preferable method.

Therefore, a preferred method for producing the optically anisotropic pitch used in the present invention is to terminate the pyrolysis polycondensation reaction halfway and maintain the polycondensate at a temperature in the range of 350°C to 400°C to substantially This is a method in which AP is allowed to stand still and deposited in the lower layer while growing and ripening, and this is separated and taken out from the upper layer where there is a large amount of IP with low density. It is stated in the specification.

A more preferable method for producing the optically anisotropic pitch used in the present invention is a carbonaceous pitch that contains an appropriate amount of AP and is not yet excessively heavy, as described in JP-A-58-180585. In this method, the AP portion is rapidly precipitated by centrifuging it in a molten state. According to this method, the AP phase accumulates in the lower layer (layer in the direction of centrifugal force) while coalescing and growing, forming a continuous layer with about 80% or more of AP,
The lower layer has a pitch in which a small amount of IP is dispersed in the form of crystals or minute spherical bodies, while the upper layer is mostly composed of IP with AP dispersed in the form of minute spheres. pitch. In this case, the boundary between both layers is clear;
Only the lower layer can be separated and taken out from the upper layer, and optically anisotropic pitch that has a large AP content and is easy to spin can be easily produced. According to this method, carbonaceous pitch having an AP content of 95% or more and a softening point of 230°C to 320°C can be obtained economically in a short time. Such optically anisotropic carbonaceous pitch has excellent melt spinning processing properties, and due to its homogeneity and high orientation, the tensile strength and elastic modulus of carbon fibers and graphite fibers obtained by spinning it are excellent. will be extremely excellent.

C)i! Production of Fiber i) Spinning Carbonaceous pitch can be spun by a known method. Such a method is applicable, for example, to a diameter of 0.1 mm to
Pitch is placed in a spinning vessel having 1 to 1,000 0.5 mm spinnerets below, and the pitch is maintained at a constant temperature between 280 and 370°C under an inert gas atmosphere until melted. While maintaining this condition, the pressure of the inert gas is increased to several hundred mmHH to force the molten pitch out of the die, and while controlling the temperature and atmosphere, the pitch fibers that flow down are wound onto a bobbin that rotates at high speed.

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 or 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 taken up using gas that is controlled at a constant temperature near the die and descends at high speed, and long fibers are produced on a belt conveyor below.

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.

In the present invention, uniform unwinding (
2 to 100 traverses during spinning
It is wound with a large traverse such as mm/(per revolution of the bobbin), and the winding thickness is 1 to 100 mm, preferably 5 mm.
It is effective to set the distance to 50 mm. The traverse is 5, considering the unwinding (unwinding) of the pitch fiber from the bobbin.
Approximately 20 mm/(one rotation of the bobbin) is preferable.

In the present invention, even if spinning is performed by any known method, since carbonaceous pitch with a low softening point is used, spinning can be performed at a lower temperature of 280° C. to 370° C. than conventional methods. When spinning at such temperatures, thermal decomposition and thermal polymerization are kept to an extremely low level, so that 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 thunker and then guided to an oiling roller where a sizing agent (oil agent) 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 (25℃) dimethylpolysiloxane, methylphenylpolysiloxane, etc., diluted with a low boiling point silicone oil (polysiloxane) or paraffin oil, etc., or dispersed in water with an emulsifier added; Dispersed with graphite, polyethylene glycol, or hindered esters; diluted surfactants with water; and other oils used for ordinary fibers, such as polyester fibers, that do not harm pitch fibers. can be used. The amount of the sizing agent attached to the fibers is usually 0.01-10% by weight, and preferably 0.05-5% by weight.

ii) Pitch fiber doubling In the present invention, doubling is performed prior to infusibility in order to stably and continuously thread the fibers during infusibility.

The number of pitch fibers spun from one melt spinning machine (l spinneret) is limited due to melt spinning, and is usually 1 to 2,000, preferably 50 to 1,000.
It is a filament.

In the present invention, the pitch fiber bundle obtained by melt spinning is
Using 0, 200~so, ooo preferably 500~
The 0-ply yarn that is combined into 5,000 filaments is performed by winding the spun pitch fibers onto multiple bobbins, and then simultaneously unwinding the fiber bundles, combining them into one, and winding them onto a single bobbin. be exposed.

The winding traverse during doubling is 5 to 10 per bobbin rotation.
The traverse is preferably 0 mm. 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 this is not preferable.

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

The doubling can be performed not only by unwinding from a bobbin, but also by gathering and doubling pitch fibers spun simultaneously from a plurality of spinning machines or spinnerets.

You may combine 2 to 20 yarns at a time, but 2 to 10 yarns may be combined at a time.
A method is also used in which the book is first doubled and then 2 to 10 pieces are doubled again.

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

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.

The heat-resistant oil has a viscosity of 10 to 10 at 25°C.
00cst alkylphenylpolysiloxane, dialkylpolysiloxane, or hindered sultyl oil is diluted with silicone oil, paraffin oil, or alcohol having a boiling point of 160°C or lower to form a 0.01 to 10% solution, preferably 0.0cst.
Use as a 1-2% solution.

In particular, alkylphenylpolysiloxane is preferred because it has 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, phenyl alpha naphthylamine, dilauryl selenide, phenothiazine, iron octlate, etc. are used.

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

As these diluent components, 02 to C8 alkanol-
1, alkanol-2, unsaturated primary alcohols, hexamethyldisiloxane, octamethyltrisiloxane, etc. are preferably used.

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

Although the spinal pressure after thread doubling can be set arbitrarily, it is preferably 10 to 109 mm in terms of workability and operability.

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

iii) Infusibility of pitch fibers In the present invention, infusibility is achieved by continuously passing the fiber bundle through an oxidizing atmosphere.

In the present invention, the threads are doubled so that continuous threading can be smoothly performed, a heat-resistant oil is applied, and the fiber bundle is not broken during the infusibility treatment, so the pitch fibers are oxidized and become infusible. Regarding the temperature, oxidizing agent, and reaction time in the step of forming carbonaceous fibers, various known combinations can be used.6 The temperature of the infusibility step in the present invention is in the range of 150 to 400°C, preferably 200 to 300°C. The temperature is generally increased stepwise or gradually for 30 minutes to 5 hours. Infusibility can be performed using air, 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 accumulation of reaction heat within the fiber bundle, so the r1&element concentration can be increased as a method of shortening the reaction time.

In the present invention, halogen and N
Treatment is performed for one hour in an atmosphere containing an oxidizing agent such as O2, SO2.303, or ozone, or at a temperature 30 to 50 degrees Celsius lower than the softening point of pitch in an oxygen gas atmosphere, i.e., 150 to 50 degrees Celsius.
It may be carried out by holding the temperature at 240°C for 5 minutes to 1 hour until sufficient infusibility is obtained, and then raising the temperature to about 300°C to complete the infusibility if necessary. The latter method is particularly easy. Moreover, it is reliable and preferable.

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

The atmosphere during the infusibility treatment is preferably forcibly stirred by a fan, and the wind speed is 0.1 to 10 m/sec, preferably 0.5 to 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. 0.0 per filament in order to improve carbon fiber physical properties such as tensile strength and tensile modulus.
It is preferable to perform infusibility while applying a tension of 0.01 to 0.2 g.

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

The yarn that leaves the continuous infusibility furnace undergoes some decomposition of the oil in the furnace,
Since the fibers have become brittle and weak due to evaporation, deterioration, etc., it is recommended to apply the above-mentioned heat-resistant oil before winding or moving on to the next first heat treatment process to improve the yarn handling properties of the fibers. preferable.

iv) Heat treatment process The carbonaceous pitch fibers that 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. Carbonized fiber is obtained, and further 1000 to 2000
So-called carbon fibers are obtained by raising the temperature to 2000°C to 3000°C and carbonizing, and graphite fibers are obtained by raising the temperature to 2000°C to 3000°C and graphitizing. 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, a suitable furnace temperature profile (
In order to efficiently obtain products with excellent performance by pre-carbonizing, carbonizing, and graphitizing the infusible pitch fibers under a temperature gradient, two-step heat treatment is generally performed. 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, rubbing the inside of the furnace and causing more scratches. As a result, product performance deteriorates.

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 of the yarn In this book, this is the temperature increase rate of heat treatment) is constant,
This 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 primary and secondary effects of the pre-carbonization of the infusible pitch fibers and the reaction product gas and tar-like substances generated during carbonization. In order to minimize the impact on
The next heat treatment temperature is 1800°C or less, preferably 600 to 1500°C, taking into consideration the fiber bundle strength.The amount of gas generated is highest at around 500°C, so it is preferably 600°C or higher, and about 1500°C or higher. ℃ 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 continuously passing through a non-oxidizing gas atmosphere such as nitrogen gas and/or argon gas in a linear manner. Flow replacement is performed at a rate of 0.05 to 1 time/min. 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, the start of heat treatment was
Start at a temperature below 300°C, preferably below 300°C. The temperature increase rate in the first heat treatment is set to 20 to 20 b minutes in order to gradually carbonize the fiber bundle and raise the softening point of the fiber bundle little by little to avoid cutting the fiber bundle due to fusion.

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.
It is also carried out at °C and held within 1 hour after reaching the maximum temperature.

The first heat treatment can be performed without applying tension, but
In order to prevent damage caused by yarn rubbing on the bottom and furnace wall of the heat treatment furnace due to slack in the fiber bundle, and to improve the physical properties of carbon fiber or graphite fiber by firing the yarn under tension, 0.001 to 0.00 per filament.
The first heat treatment, which is preferably carried out under a tension of 2 g, is carried out continuously through a firing furnace at a speed of usually 0.1 to 20 m/min.

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.The atmospheric gas is preferably argon gas, especially when making graphite fibers. In order to remove the gas generated from the gas, the gas is circulated and replaced at a rate of 0.05 to 1 time/min. If necessary, the atmospheric gas may be recycled or purified and reused.

The second heat treatment is performed such that the maximum temperature is in the range of 1000 to 3000°C, and is also held within 30 minutes after reaching the J2 & high temperature.

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 10
0 to b 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 the carbon fiber and graphite fiber by treating it under tension. It is preferable to apply a tension of 0.001 to 0.2 g per filament.

In the second heat treatment, since the first heat treatment has already turned into carbon fiber or a fiber with a strength similar to that, it can be fired using the already known firing method for polyacrylonitrile carbon fiber. (e.g., U.S. Pat. Nos. 3,700.511, 3,764,662, 3,900.556, 3,954,750)
No. 4,301.136, British Patent No. 1,110
No. 791, No. 1,215,005, Special Publication No. 1979-
No. 12540, No. 45-19415, No. 47-267
No. 33, No. 47-36463, JP-A No. 46-2961
No. 47-716, No. 6O-99QIQ).

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.

Note that the results of the first heat treatment and the second heat treatment in the present invention can be expressed in terms of preliminary carbonization, carbonization, and graphitization as follows.

Odo Kyugo treatment 11 Kyugo treatment preliminary 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 increases the strength of fiber bundles by doubling carbonaceous pitch fibers. Furthermore, since the fiber bundle is linearly and continuously infusible after being applied with a heat-resistant oil agent, there is no cutting of the fiber bundle during infusibility, and the production speed can be increased because the fiber bundles are doubled.

Since the fiber bundle is continuously passed through the infusibility furnace in a linear manner, it is possible to not only obtain fibers with good appearance (but also to obtain uniform fibers without any unevenness during infusibility). Carbon fibers and graphite fibers with high tensile strength and tensile elasticity can be obtained.

The first heat treatment at 1,800℃ or lower and the second heat treatment at 3,000℃ or lower allow fiber bundles to be fired continuously in a linear form, making it possible to use continuous equipment and producing a good (and uniform) 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), and can be used for winding, unwinding, doubling, fabrics, etc. It can also be made into a knitted fabric, and can be used for filament winding in the production of composite materials, prepreg production, etc., so the scope of its application is wide and the present invention has great loyalty.

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

Example 1 Contains about 55% optically anisotropic phase (AP) and has a softening point of 2
Carbonaceous pitch at 32°C was used as precursor pitch. This precursor pitch contained 16.1% by weight of quinoline solubility and 0.26% by weight of ash, and had a viscosity of 2.8 voids at 370°C. This pitch was melted in a melting tank with an internal volume of 20ffi, controlled at 370°C, and sent to a cylindrical continuous centrifugal separator with an effective internal volume of 200ml at a flow rate of 20ml/t/min, and the rotor temperature was controlled at 370°C. At the same time, the centrifugal force is AP at 30.0000
A pitch with more optically anisotropic phase than the outlet (A pitch),
Pitch with more optical isotropy than IP outlet (■ pitch)
were extracted consecutively.

The optically anisotropic pitch obtained is 98 times the optically anisotropic phase.
%, softening point 265℃, quinoline solubility 29.5%
Met.

Next, the obtained optically anisotropic pitch was transferred to a melt spinning machine with a 500-sized spinneret (nozzle hole diameter: 0.3 mm in diameter).
), extruded at 355°C with a nitrogen gas pressure of approximately 200 mmHg, and wound onto a stainless steel wire mesh bobbin with a diameter of 210 mm and a width of 200 mm that rotates at high speed provided at the bottom of the nozzle at a winding speed of approximately 500 m/min. Spinning was carried out for 10 minutes. The pitch of the traverse per revolution of the bobbin was 10 mm/rotation. There was no yarn breakage during spinning. At this time, the spun yarn was approximately converged by an air sucker and guided to an oiling roller, and a converging oil was supplied at a ratio of about 0.5% to the yarn. As the oil agent, dimethyl polycloxane having a viscosity of 14 cst at 25° C. was used.

Six bobbins wound with pitch fibers were combined at a traverse pitch of 20 mm/rotation, and wound into a 3°,000 filament around a 10-mesh (porosity: 55%) stainless steel wire mesh bobbin.

At the time of yarn doubling, 0.5% by weight of methylphenylpolysiloxane of 40 cst at 25°C and 99% of isopropyl alcohol were added.
．． An oil agent mixed with 5% by weight was applied.

While unwinding (unwinding) the bobbin-wound pitch fiber obtained in this way from the bobbin, the furnace inlet temperature was 150°C, and the maximum temperature was 2.
It was introduced into a continuous infusibility furnace with forced hot air circulation equipped with a fan in an air atmosphere of 70°C. Temperature 150℃ to 270″C 10
It was brought to ambient temperature at a rate of 0.degree. C./min and held at 270.degree. 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/min.

The wind speed during infusibility was 0.7 m/sec, and the tension applied to the fiber bundle was 0.007 g/l per 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 where the first heat treatment was performed.

While unwinding this spool, a first heat treatment and a second heat treatment were continuously performed in a linear manner. During this time, the spool was smoothly unwound from the bobbin.

The first heat treatment was performed at a furnace inlet temperature of 300°C and a maximum temperature of 80°C.
The firing was carried out in a continuous firing furnace in a nitrogen gas atmosphere at 0°C. The temperature increase rate was 200° C./min, and the threading speed was 1 m/min. The second heat treatment was performed in a nitrogen gas atmosphere at a maximum temperature of 1500°C, at a temperature increase rate of 500°C/min and a threading speed of 1.
m/min. It is rolled up at the exit of the second heat treatment furnace,
Carbon fiber was obtained. The tension during threading is per 1 filament,
The test was carried out using 0.01 g. The tensile strength of the obtained carbon fiber is 2
．． 50 Pa, tensile modulus was 260 GPa, and thread diameter was 9.9 μm.

Example 2 Graphite fibers were obtained in the same manner as in Example 1, except that the second heat treatment was carried out at 2500° C. in an argon gas atmosphere. The obtained graphite fiber had a tensile strength of 2.4 GPa and a tensile elasticity of 6.
It was 50 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 process was carried out in the same manner as in Example 1, except that the yarns were not doubled.

In the thus obtained pitch fibers, the fiber bundles were cut in the furnace during infusibility, making it impossible to obtain long infusible fibers.

Comparative Example 2 The process was carried out in the same manner as in Example 1, except that no heat-resistant oil was applied during 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 doubled, and the fiber bundle is passed continuously in a linear manner in an oxidizing atmosphere to make it infusible. A method for producing carbon-based fibers and graphite fibers, comprising a first heat treatment in an oxidizing gas atmosphere, and then a second heat treatment in an inert gas atmosphere at 3000°C or less to carbonize or graphitize the fibers. , a method for producing carbon fibers and graphite fibers, characterized in that the fibers before being infusible are provided with a heat-resistant oil agent. 2) The number of filaments of the pitch fiber after spinning is 50 to 1,
000 filaments, and the number of filaments of the pitch fibers to be infusible is 200 to 50,000 filaments. Time traverse of 5 to 100 mm/(Bobbin 1
3. The method for producing carbon fibers and graphite fibers according to claim 2, wherein the method comprises: rotation). 4) The method for manufacturing carbon fibers and graphite fibers according to claim 2, characterized in that the yarns are twisted 0.1 to 30 times per meter during doubling. 5) The heat-resistant oil agent applied to the doubled pitch fibers is heated to 25°C.
Claims characterized in that it is a mixture of alkylphenylpolysiloxane and/or dialkylpolysiloxane having a viscosity of 10 to 1,000 cst, and a low-boiling silicone oil and/or alcohol having a boiling point of 160°C or less The method for producing carbon fiber and graphite fiber according to item 1. 6) Alkylphenylpolysiloxane has 5 phenyl groups
The method for producing carbon fibers and graphite fibers according to claim 5, characterized in that the carbon fibers and graphite fibers contain from mol% to 80 mol%. 7) The method for producing carbon fibers and graphite fibers according to claim 5 or 6, wherein the alkyl group is a methyl group, an ethyl group, or a propyl group. 8) The alcohol is an alkanol having 2 to 8 carbon atoms.
6. The method for producing carbon fibers and graphite fibers according to claim 5, wherein the alcohol is at least one type of alcohol selected from 1, alkanol 2, and unsaturated primary alcohol. 9) Claims 5 to 8, characterized in that the heat-resistant oil agent contains at least one antioxidant selected from amines, organic selenium compounds, and phenols.
A method for producing carbon fibers and graphite fibers according to any one of paragraphs. 10) The antioxidant is phenyl-α-naphthylamine,
The method for producing carbon fibers and graphite fibers according to claim 9, wherein the method is one or a mixture of two or more selected from dilauryl selenide, phenothiazine, and iron octolate. 11) 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. 12) 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. 13) The oxidizing gas is halogen, NO_2, SO_2,
The method for producing carbon fibers and graphite fibers according to claim 12, characterized in that at least one selected from SO_3 and ozone is used. 14) 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. 15) 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. 16) The method for producing carbon fibers and graphite fibers according to claim 1, which comprises applying tension to the fibers during infusibility. 17) The method for producing carbon fibers and graphite fibers according to claim 1, characterized in that heat treatment is carried out after applying a heat-resistant oil to the infusible pitch fibers. 18) Production of carbon fibers and graphite fibers according to any one of claims 1 to 17, wherein the first heat treatment is performed in an atmosphere of nitrogen gas and/or argon gas. Method. 19) The method for producing carbon fibers and graphite fibers according to claim 18, characterized in that atmospheric gas is circulated and replaced at a rate of 0.05 to 1 time/min. 20) The maximum temperature in the first heat treatment is 600 to 1
The method for producing carbon fibers and graphite fibers according to claim 1, wherein the temperature is 500°C. 21) A patent claim characterized in that 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 item 1. 22) The method for producing carbon fibers and graphite fibers according to claim 21, wherein the temperature increase rate in the first heat treatment is 50 to 500°C/min. 23) The first heat treatment was performed at 0.00% per filament.
The method for producing carbon fibers and graphite fibers according to claim 1, wherein the firing is performed while applying a tension of 1 to 0.2 g. 24) 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. 25) Atmospheric gas for the second heat treatment 0.05 to 1 time/
25. The method for producing carbon fibers and graphite fibers according to claim 24, wherein the carbon fibers and graphite fibers are replaced by circulation at a rate of 100%. 26) The maximum temperature in the second heat treatment is 1000~
Claim 1 characterized in that the temperature is 3000°C.
The method for producing carbon fibers and graphite fibers as described in 2. 27) 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 item 1. 28) The second heat treatment was performed at a rate of 0.00 per filament.
The method for producing carbon fibers and graphite fibers according to claim 1, wherein the firing is performed while applying a tension of 1 to 0.2 g. 29) 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°C. A method for producing carbon fibers and graphite fibers according to claim 1.