JPS62184124A - Production of carbon yarn and graphite yarn - Google Patents

Abstract

PURPOSE:To produce high-quality carbon yarn efficiently without causing fusion between yarn, by doubling pitch yarn obtained by melt spinning, winding the doubled yarn around an air-permeable bobbin and making it infusible in a bobbin wound state as it is in an oxidizing atmosphere. CONSTITUTION:Carbonaceous pitch is subjected to melt spinning to give pitch yarn (number of filaments is 50-1,000), doubled (number of filaments is 200-50,000) and wound around an air-permeable bobbin. Then, the pitch yarn is subjected to infusible treatment in a bobbin wound state in an oxidizing atmosphere. Then, the infusible yarn is provided with water or a finishing oil and further subjected to first treatment wherein the infusible yarn is continuously sent through a nonoxidizing atmosphere at <=1,800 deg.C while reeling the infusible yarn. The infusible yarn is further subjected to a second treatment wherein the infusible yarn is continuously passed through an inert gas atmosphere at <=3,000 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) 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 fibers is as small as about 0.0 IGPa, and it is brittle, making it difficult to handle, and it is extremely difficult to obtain the long filament-like fibers necessary to obtain high-performance products. It was 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, with this method, when the yarn is piled up, it tends to be twisted or twisted, and paternal bending is likely to occur. This has the disadvantage that the strength of the yarn is significantly reduced, resulting in frequent yarn breakage and difficulty in producing high-quality yarn.

This disadvantage causes the curvature when depositing threads to become thicker (
It wasn't something that could really be improved.

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 the yarn, 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.

JP-A-60-173121, JP-A-60-81320
No. 60-21911 discloses 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 The disadvantage was that the variation in strength when applied was increased.

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 yarn becomes extremely difficult and unwinding (unwinding) becomes difficult, and when unwinding, the yarn tends to become fluffy, which significantly reduces the commercial value when made into carbon fiber or graphite fiber. was there. To solve these problems, the degree of agglutination and fusion is extremely low compared to pre-carbonized fibers, and after the infusibility is complete, the fibers are unwound from the bobbin and threaded continuously in a linear manner. Possible methods include preliminary carbonization, carbonization, and graphitization. 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 breaks down and deteriorates.
The convergence of the fiber bundle is disturbed and the fiber bundle becomes extremely weak and brittle, making it extremely difficult to unwind (unwind) it from the bobbin after infusibility, and it has the disadvantage that fuzz is likely to occur during unwinding. was.

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, when these infusible fibers are subjected to preliminary carbonization and carbonization processes, as disclosed in Japanese Patent Application Laid-open No. 59-15517, the temperature of the fiber bundle reaches 700 to 800°C. Since the strength of the fibers decreases 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 yarns.

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) As a result of intensive studies to solve these drawbacks, the inventor of the present invention has found that
When plied pitch fibers are used as pitch fibers wound on breathable bobbins, air permeability is improved and the winding thickness can be thicker than before, which improves production efficiency.
Due to the high strength of the yarn, it is easy to unwind the infusible fibers, and by selecting the conditions for the subsequent two-step heat treatment, we can produce long filaments of high-strength, high-elastic, and high-quality carbon fibers at low cost and efficiency. It has been discovered that it can be easily manufactured, and the present invention has been achieved.

Therefore, an object of the present invention is to provide a method for producing pitch yarn 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 yarn long filaments of carbon fibers and graphite fibers that have good appearance, high strength, and high modulus of elasticity.

(Means for Solving the Problems) The aspects of the present invention are such that carbonaceous pitch is melt-spun, the spun pitch ait'm is doubled, and the spun pitch ait'm is wound into a permeable bobbin to improve air permeability. Then, while winding the bobbin, infusible water or oil is applied in an oxidizing atmosphere, and then the infusible yarn on the bobbin is unwound and continuously exposed to a non-oxidizing atmosphere at 1800°C or less in a linear manner. This was achieved by carrying out a first heat treatment through the process, followed by a second heat treatment by continuously passing it through an inert gas atmosphere of 3000° C. or lower, and performing carbonization or graphitization treatment.

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 cracked tar pitch, catalytic cracking tar pitch, petroleum-based pitch such as atmospheric distillation residue, vacuum distillation residue, synthetic pitch obtained by decomposing synthetic resin, etc. In addition to those obtained by hydrogenating the pitch with hydrogen or a hydrogen donor, those modified by heat treatment, solvent extraction, etc. can also be used. The softening point of carbon 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. Contains about 95% or more of an optically anisotropic phase as measured by a polarizing microscope as an orthotropic carbonaceous pitch, 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. In this specification, it refers to a pitch in which the majority of pitches are optically anisotropic, and a pitch in which no brilliance is observed and is optically isotropic. It is called oriented 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.

Also, the case of substantially optical anisotropy means that optically anisotropic carbonaceous pitch and optically isotropic carbonaceous pitch coexist, but because the amount of optically isotropic pitch is small, 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 the IPs.

AP in this specification is considered to be the same as the so-called "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 several types, and in this specification, A
P is mainly in the latter "meso phase".

The above AP phase and IP phase are thick not only in optical properties but also in viscosity (because they are different, 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 foreign substances that are undesirable for spinning,
This means that particularly bad results occur if the IP phase is not homogeneously dispersed within the AP phase. Therefore, the optical anisotropic pitch used in the present invention is required to have substantial homogeneity. Such a homogeneous optically anisotropic pitch is I
The P content is 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 reflection microscope observation, and there is substantially no foaming due to volatile matter at the melt spinning temperature.

In the present invention, AP and IP are quantified by observing under a polarizing microscope with crossed Nicols, taking a photograph, and measuring the area ratio occupied by the AP or IP portion. Represents %. However, since the difference in specific gravity between AP and IP is small at about 0.05, the proximal volume%
and weight % can be treated as 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 pitch, and can be determined from the peak temperature of absorption or release of latent heat when pitch melts or solidifies using a differential scanning calorimeter needle. . 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 for melt spinning is 60°C to 100°C higher than the softening point of the material to be 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 heavy hydrocarbons, which are common raw materials for pitch production, may be used. Oil, tar, commercially available pitch, etc. are heated in a reaction tank at 380°C to 50°C.
Use a conventional method of sufficiently pyrolytic polycondensation while stirring at a temperature of 0°C and degassing with an inert gas to increase the optically anisotropic phase (hereinafter abbreviated as AP) of the residual pitch. I can do it. 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. The pitch will be . 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) Manufacture of fibers 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 to melt it. 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 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 the pitch tsm is stretched by m using a gas that is controlled at a constant temperature and descends at high speed near the die, and the long fibers are produced on the 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 (
In order to perform (unwinding), the traverse during spinning is 2 to 100
It is effective to wind the material with a large l rubber such as mm/(per bobbin rotation) and to have a winding thickness of 1 to 1100rn, preferably 5 to 50mm. The traverse is preferably about 5 to 20 mm/(one revolution of the bobbin) in consideration of the unwinding (unwinding) property of the pitch fibers from the bobbin.

In the present invention, even if spinning is performed by any known method, since carbonaceous pitch having 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 extremely low (suppressed), so the pitch fibers after spinning can maintain almost the same chemical composition as the pitch before spinning. Advantageously, the subsequent fibers 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, examples of the sizing agent include ethyl alcohol,
Alcohol order 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 or other solvent, or dispersed in water with an emulsifier added; the same Graphite, polyethylene glycol, or hindered esters are dispersed in the fiber; and other ordinary fibers, such as various oils used for polyether #a fibers, which do not damage the pitch fibers can be used. The amount of the sizing agent attached to the fibers is usually 0.01 to 10% by weight, but preferably 0.05 to 5% by weight.

ii) Pitch fiber doubling In the present invention, in order to increase the air permeability of the pitch fibers on the bobbin, doubling is performed before winding the pitch fibers onto the infusible bobbin.

The number of pitch fiber filaments spun from one melt spinning machine (one 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 to 50,000, preferably 500 to
The 0-ply yarn that is combined into 5,000 filaments is produced by winding the spun pitch fibers onto multiple bobbins, and then combining the unwound fiber bundles into one and winding them onto one bobbin. It will be done.

The winding traverse during doubling is 5 to 10 per bobbin rotation.
It is preferable that it is 0 mm.It is better to make the traverse larger in order to improve the irn temperament, 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 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 IO
A method is also used in which the book is first doubled, and then 2 to 10 pieces are recombined.

The greater the number of filaments in the pitch fibers, the better the air permeability, and the more uniform the infusibility reaction is, the more the winding thickness can be reduced.
It can be made smaller.

The winding thickness after doubling is usually 1 to 100 mm, preferably 5 mm.
If the 0-wrap thickness, which is ~50mm, becomes too thick, heat will accumulate and the reaction will progress unevenly, resulting in fusion and adhesion between filaments, causing variations in filament strength, and making it impossible to obtain high-quality filaments. So I don't like it.

In the present invention, since infusibility is performed while winding the bobbin, it is necessary to select a bobbin that can withstand these temperatures and has the necessary material and shape to perform infusibility uniformly.
In the present invention, in addition to bobbins made of metals such as iron, copper, nickel, aluminum, and their alloys, heat-resistant resins,
A bobbin made of carbon or ceramics, or a bobbin made of a composite material of heat-resistant resin, carbon ceramics, and inorganic or organic fibers can be used.

Heat-resistant resins include polyimide, polyamideimide,
Polyimide resins such as polyetherimide, polysulfone, polyetherketone, polyetherketone,
Aromatic polyether resins such as polyphenylene ether and polyphenylene sulfide, aromatic polyester resins such as fully aromatic polyarylate, polyphenylene, polytetrafluoroethylene, etc. can be used.

As the ceramic, silica, alumina, silicon carbide, etc. can be used. Carbon fiber, glass fiber, silicon carbide fiber, etc. can be used as the inorganic fiber. As the organic fiber, aramid fiber or the like can be used.

Since infusibility is performed while winding the bobbin, the outer surface of the bobbin is made of a material that is compatible with carbon fiber, absorbs the shrinkage of the fibers that occurs during heat treatment, and can prevent the fibers from being cut. For example, it is also preferable to coat with a carbon material.

The entire outer surface of the bobbin can also be covered with a material that is both elastic and breathable, such as carbon felt.

In the present invention, the bobbin used for doubling has a diameter of 100 mm.
It has a cylindrical shape of ~500 mm, and is made of a wire mesh to improve ventilation, or it is burst with holes or a porous filter medium such as sintered metal filter medium or sintered glass.

When drilling holes, it is preferable to set the void ratio (opening ratio) to 10 to 80%.If the void ratio is 80% or more, the strength of the bobbin will decrease, so it is not preferable (.10%).
Below this, the air permeability becomes insufficient and the firing during infusibility becomes uneven, which is not preferable. Further, for uniform firing, it is preferable to reduce the heat capacity of the bobbin, and therefore, it is preferable that the wall thickness of the bobbin is 5 mm or less. In the present invention, it is preferable to use a bobbin with a wire mesh layer of 5US304 or 5US316, and the wire mesh has a mesh size of 2 to 300 meshes, preferably 3 to 60 meshes.

iii) Infusibility of pitch fibers In the step of oxidizing the spun pitch fibers to make infusibility fibers, it is necessary to consider various combinations of temperature, oxidizing agent, and reaction time. In the present invention, basically known methods can be used as the conditions for infusibility, but
Since the pitch fibers are made infusible, it is necessary to start the oxidation reaction at a lower temperature than usual to prevent the pitch fibers from fusing.

The temperature of the infusibility step is 150°C to 400°C, preferably 2
The temperature is raised stepwise or gradually in the range of 00°C to 300°C, and the treatment is usually carried out for 1 to 5 hours. The treatment time may be as long as 1 to 3 days so that the infusibility reaction proceeds sufficiently and uniformly.

Infusibility can be achieved using air, oxygen, or a mixed gas of air and oxygen or air and nitrogen, but if the oxygen concentration is too high, the reaction within the bobbin may proceed rapidly and cause combustion. So I don't like it.

Also, at temperatures below 200℃, halogens, NO2, SO2,
Sufficient infusibility can be achieved by treatment for a single hour in an atmosphere containing an oxidizing agent such as SO3 or ozone, or at a temperature 30 to 50 degrees Celsius lower than the softening point of pitch, i.e., 150 to 240 degrees Celsius, in an oxygen gas atmosphere. The method may be carried out by holding the mixture for 10 minutes to 1 hour until it is obtained, and then raising the temperature to about 300° C. if necessary to complete the infusibility (the latter method is particularly preferred as it is easy and reliable).

In the present invention, it is also possible to adopt a method of leaving the pitch in air at 150 to 250°C for a long time and then raising the temperature to 300 to 400°C for a short time, depending on the softening point of the pitch, without using an oxidizing agent. can. In particular, when carbonaceous pitch having a softening point of 280°C or higher is used, it is preferable to hold it at a temperature of 230 to 250°C for about 30 minutes to 2 hours to make it infusible.

In the present invention, the infusibility is carried out while winding the bobbin, so if a sizing agent is used during spinning, the water and low boiling point oil in the sizing agent are evaporated and removed before the infusibility treatment. It is necessary to improve ventilation. Such pretreatment can reduce unevenness in the infusibility treatment.

For infusibility, it is preferable to replace the old gas by circulating fresh gas of the same type as the atmosphere at a rate of 0.1 to 5 times per minute.The gas replacement is performed using a cylindrical breathable bobbin. This can be done efficiently by blowing the replacing gas into the center of the tank.

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 titt' promotes gas penetration into the bobbin winding, eliminates temperature distribution in the infusibility furnace, and has the effect of making firing uniform.

During infusibility, pitch fibers that are infusible while wound on a bobbin are disrupted due to the decomposition and deterioration of the oil that binds the fiber bundles, making the fiber bundles extremely weak (brittle) and the fibers sticking together. It is extremely difficult to unwind (unwind) the spool after infusibility.In the present invention, since the fibers on the bobbin are doubled, water is supplied by spraying or the like to moisten the fibers on the bobbin. Alternatively, by applying an oil agent, the cohesiveness is improved, so that it can be easily unwound.

As the oil agent, those similar to those described in the section of the focusing oil agent for spinning can be used.

iv) Heat treatment process The carbonaceous pitch fibers that have become infusible due to infusibility are heated in a chemically inert nitrogen gas or argon gas atmosphere for 5 minutes.
Pre-carbonized fibers are obtained by raising the temperature to 00 to 1000°C and performing initial carbonization, and by further raising the temperature to 1000 to 2000°C and carbonizing, so-called carbon fibers are obtained.
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, a suitable furnace temperature profile (
In order to efficiently obtain a product with excellent performance by pre-carbonizing, carbonizing, and graphitizing the infusible pitch fibers under a temperature gradient), two-step heat treatment is performed. In general, it is easier to obtain an appropriate temperature profile (temperature gradient) when the length of the furnace is short. ! On the other hand, as the length of the furnace becomes longer, the slack in the fiber bundles causes the inside of the furnace to rub, increasing the degree of scratches, and as a result, product performance deteriorates.

These contradictory problems can be solved by dividing the heat treatment furnace and performing two stages of treatment: primary 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 that the actual temperature increase rate of the yarn temperature (hereinafter referred to as So, if this is the temperature increase rate of heat treatment) is constant, then
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 set in order to minimize the influence of the reaction product gas and tar-like substance generated during pre-carbonization of the infusible pitch fibers and carbonization on the product performance. , the first heat treatment temperature is 1800°C or less, preferably 600-1
The temperature is between 500°C and 500°C. The amount of gas generated is greatest at around 500°C, so it is preferably 600°C or higher.
A temperature of about 1500° C. is preferable because the reaction product gas is small.

The first heat treatment is preferably carried out while unwinding the infusible fibers, which have been infusible while wound on the bobbin, from the bobbin and, if necessary, while further doubling the fibers.

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 circulated and replaced at a rate of 0.05 to 1 time/min in order to remove exhaust gas generated from the infusible fibers. 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 of the first heat treatment is preferably 20 to 2000°C/min, in order to avoid cutting of the fiber bundle due to fusion by gradually carbonizing and raising the softening point of the fiber bundle little by little.
0-b If the heating rate is slowed down, threading becomes easier, but it is not economical.The first heat treatment temperature (maximum temperature) is 1800°C or lower, preferably 600-1500°C, for the reasons mentioned above.
Perform at °C. 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
In order to prevent damage caused by the yarn rubbing against the bottom and walls of the heat treatment furnace due to the slack of the fiber bundle, and to increase 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 by passing through a continuous heat treatment furnace in an atmosphere of an inert gas such as argon gas and/or nitrogen gas. Argon gas is particularly preferred as the atmospheric gas when producing graphite fibers. The atmospheric gas is circulated and replaced at a rate of 0.05 to 1 time/min in order to remove gas generated from the fibers. If necessary, the atmospheric gas may be recycled or purified and reused.

The second heat treatment is performed so that the maximum temperature is in the range of 1000 to 3000°C. It is also possible to hold the temperature within 30 minutes after reaching the maximum 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-b The second heat treatment can be performed without applying tension, but it is necessary to prevent damage to the yarn during passing through the furnace, and to improve the physical properties of carbon t, ais and graphite t1 fibers by treating under tension. o, oot-o per filament to improve.

It is preferable to apply a tension of 2 g.

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. No. 3,700..511, U.S. Pat. No. 3,764,662)
No. 3,900.556, No. 3,954,75
No. 0, No. 4,301,136, British Patent No. t, tt
o.

No. 791, No. 1.215.005, Special Publication No. 1979-1
No. 2540, No. 45-19415, No. 47-2673
3, 47-36463, JP-A-46-2961, JP-A-47-716, and JP-A-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.

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.

Gokamikugo Ward Buried 51 People Watari Preliminary Carbonization
Carbonization Pre-carbonization / Carbonization Carbonization Pre-carbonization Carbonization / Graphitization Pre-carbonization / Carbonization Carbonization / Graphitization Pre-carbonization / Carbonization Graphitization (Effects of the Invention) According to the method of the present invention, pitch fibers are doubled into a breathable bobbin. Since the pitch fibers are infusible after being wound up, air permeability is significantly improved, and even when pitch fibers are wound thickly on the bobbin, uniform infusibility is possible, and there is no fusion or agglutination between the filaments, resulting in a high You can get quality long filament yarn.

Furthermore, according to the method of the present invention, the cohesiveness and strength of the fiber bundle after infusibility are improved, so that the infusible fibers can be easily unwound from the bobbin, and after that, the infusible fibers can be threaded continuously in a linear manner. Heat treatment can be carried out smoothly. Furthermore, the present invention is a method in which the carbonaceous pitch fibers are wound around a bobbin after being doubled, infusible, and then rewound and carbonized, resulting in extremely high production efficiency. Furthermore, when optically anisotropic carbonaceous pitch fibers are used, carbon fibers or graphite fibers with high strength and high elasticity can be obtained.

In addition, since the fiber bundle is continuously subjected to the first heat treatment in a linear form, it is possible to obtain 1Jli fibers with uniform physical properties without firing unevenness, and the second high temperature heat treatment can be performed in a very short time. By terminating the process, graphite fibers with high strength and high modulus of elasticity can be easily obtained. The fibers obtained in this way are high-quality long filament yarns that have little fuzz when handled and have a good appearance.They are not only windable, unwindable, and doubled, but can also be used for textiles. 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 significance of the present invention is great.

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

(Example) Example 1 Contains approximately 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 the viscosity at 370°C was 2.8 poise. Contents of this pitch @
It is melted in the melting tank of 't201, controlled at 370°C, and the effective volume in the rotor f! It was sent to a 200 m1 cylindrical continuous centrifugal separator at a flow rate of 20 m11 minutes, and the centrifugal force was controlled at 30.0 OOG while controlling the rotor temperature at 370 °C.
A pitch with more optically anisotropic phase than the outlet (A pitch),
Bina (i-pitch) containing a large amount of optically isotropic phase was continuously extracted from the IP outlet.

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 having a 500-sized spinneret (nozzle hole diameter: 0.3 mm in diameter).
), extruded at 355°C under a nitrogen gas pressure of about 200 mmHH, 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 about 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 sunker and guided to an oiling roller, and a convergence oil was supplied at a ratio of about 0.5 t% to the yarn.

As the oil agent, dimethylpolysiloxane 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. The winding thickness of the thread in this case was about 15 mm.

The wire mesh bobbin-wound pitch fiber thus obtained was introduced into a fan-equipped forced hot air circulation furnace in an air atmosphere. The temperature was increased from 150°C to 230°C at a rate of 0.5°C/min, and the temperature was maintained at 250°C for 2 hours to make it infusible. During this time, the atmosphere in the furnace was replaced with fresh air at a rate of 0.5 times/minute.

The wind speed for stirring in this case was 0.7 m/sec.

After the infusibility treatment was completed, an oil agent prepared by adding an emulsifier to the same dimethylpolysiloxane used for spinning and dispersing it in water was applied using a sprayer.

The thread to which the oil was applied was placed at the entrance of a continuous firing furnace where the first heat treatment was performed. Next, the first heat treatment and the second heat treatment were performed continuously in a linear manner while unwinding the bobbin.
During this time, unwinding of the thread from the bobbin was carried out smoothly.

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 a temperature of 0°C. The temperature increase rate was 200° C./min, and the threading speed was 1 m/min. The second heat treatment is performed at a maximum temperature of 15% in a nitrogen gas atmosphere.
The heating rate was 500°C/min, and the threading speed was 1 m/min. The fiber was wound up at the exit of the second heat treatment furnace to obtain carbon fiber.The tension during the furnace was 1.
0.01 g per filament was used.

The tensile strength of the obtained carbon fiber was 2.2 GPa.

The elastic modulus was 260 GPa, and the thread diameter was 9.9 μm.

The carbon fiber thus obtained could be freely unwound, wound up, and doubled.

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. At that time, the tensile strength was 2.3 GPa, the elastic modulus was 650 GPa, and the thread diameter was 9.6 μm.

The graphite fiber thus obtained could be freely unwound, wound up, thread-paired, etc.

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 infusible pitch fiber, the threads were only slightly fused in the surface layer of the bobbin, but in the middle layer of the bobbin.
The pitch fibers were intensely fused and solidified into a thick plate shape, making it impossible to obtain infusible fibers.

Comparative Example 2 The process was carried out in the same manner as in Example 1, except that no oil was applied after infusibility. The fiber bundle of infusible fibers on the bobbin thus obtained could not be immediately cut and unwound.

Example 3 An optically isotropic precursor pitch having a softening point of 265°C was melt-spun using the same equipment as in Example 1. This pitch was subjected to doubling, infusibility, and first heat treatment in the same manner as in Example 1, and the second heat treatment was performed at a maximum temperature of 1500°C.

The carbon fiber obtained at this time had a tensile strength of 1.2 GPa, a tensile modulus of 90 GPa, and a thread diameter of 9.9 μm.

Claims (1)

[Claims] 1) Carbonaceous pitch is melt-spun, pitch fibers are doubled and wound around an air permeable bobbin, the bobbin is infusible in an oxidizing atmosphere, water or an oil agent is applied thereto, and then While unwinding the infusible yarn on the bobbin, the first heat treatment is performed by continuously passing it through a non-oxidizing gas atmosphere at 1800 ° C or less in a linear manner,
A method for producing carbon fibers and graphite fibers, which further comprises carbonizing or graphitizing the fibers by continuously passing them through an inert gas atmosphere of 3000° C. or lower to perform a second heat treatment. 2) A patent claim characterized in that the number of filaments of the pitch fibers before spinning is 50 to 1,000 filaments, and the number of filaments of the pitch fibers after spinning is 200 to 50,000 filaments. A method for producing carbon fibers and graphite fibers according to scope 1. 3) A patent characterized in that the spun pitch fibers having a predetermined number of filaments are obtained by winding the spun pitch fibers around a plurality of bobbins, and then unwinding and doubling the spun pitch fibers. A method for producing carbon fibers and graphite fibers according to claim 2. 4) Pounded pitch fibers having a predetermined number of filaments are obtained by collecting the spun pitch fibers using an air current after convergence, accumulating them in a can-like accumulation container, and then unraveling them and doubling them. The second claim characterized in that
The method for producing carbon fibers and graphite fibers as described in 2. 5) Pounded pitch fibers having a predetermined number of filaments are obtained by continuously doubling pitch fibers spun from spinnerets of a plurality of spinning machines while spinning. A method for producing carbon fibers and graphite fibers according to Scope 2. 6) Pounded pitch fibers having a predetermined number of filaments that are subjected to the first heat treatment are obtained by re-unraveling the once-spliced pitch and performing re-splitting. A method for producing carbon fibers and graphite fibers according to claim 2. 7) Traverse at the time of doubling 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). 8) The pitch fiber winding thickness on the bobbin after doubling is 1 to 10
The method for producing carbon fibers and graphite fibers according to claim 2, wherein the thickness is 0 mm. 9) Claim 1, characterized in that the infusibility treatment is carried out at a temperature range of 150°C to 400°C in an atmosphere of air, oxygen, or a mixed gas of air and oxygen or air and nitrogen. A method for producing carbon fiber and graphite fiber. 10) The method for producing carbon fibers and graphite fibers according to claim 9, characterized in that atmospheric gas is circulated and replaced at a rate of 0.1 to 5 times/minute. 11) The method for producing carbon fibers and graphite fibers according to claim 10, characterized in that atmospheric gas is blown into the center of the cylindrical bobbin. 12) The method for producing carbon fibers and graphite fibers according to claim 9, wherein the atmosphere is forcibly stirred at a wind speed of 0.1 to 10 m/sec. 13) The method for producing carbon fibers and graphite fibers according to claim 1, wherein the breathable bobbin is a porous cylindrical bobbin with a diameter of 100 to 500 mm. 14) The carbon according to claim 13, which is a metal perforated bobbin or a wire mesh bobbin in which small holes are opened throughout the entire surface so that the air permeability bobbin has a porosity of 10 to 80%. Method for producing fibers and graphite fibers. 15) The method for producing carbon fibers and graphite fibers according to claim 14, wherein the material composition of the breathable bobbin is a sintered metal material. 16) Claims characterized in that the breathable bobbin is a heat-resistant resin, carbon or ceramics, or a composite material of a heat-resistant resin, carbon or ceramics and inorganic fibers such as carbon fibers or ceramic fibers. The method for producing carbon fiber and graphite fiber according to item 13. 17) The heat-resistant resin is polyimide, polyamideimide,
Polyimide resins such as polyetherimide, polysulfone, polyethersulfone, polyetherketone,
A patent claim consisting of one or more materials selected from aromatic polyether resins such as polyphenyl ether and polyphenylene sulfide, aromatic polyester resins such as fully aromatic polyarylate, polyphenylene, and polytetrafluoroethylene. The method for producing carbon fibers and graphite fibers according to item 16. 18) The method for producing carbon fibers and graphite fibers according to claim 1, wherein the first heat treatment is performed in an atmosphere of nitrogen gas and/or argon gas. 19) Atmospheric gas for the first heat treatment 0.05 to 1 time/
19. The method for producing carbon fibers and graphite fibers according to claim 18, wherein the carbon fibers and graphite fibers are replaced by circulation at a rate of 100%. 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, and the optically anisotropic carbonaceous pitch contains 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.