JPH043452B2 - - Google Patents

Description

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

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

However, with conventional techniques, the tensile strength of pitch fiber is as low as approximately 0.01 GPa, and it is brittle, making it difficult to handle, making it difficult to obtain the long filament-like fibers necessary to obtain high-performance products. was extremely difficult.

Conventionally, the method for producing long filament carbon fibers from pitch fibers involves dropping the spun yarn into a wire mesh basket and depositing it, making it infusible together with the wire mesh, and then subjecting it to a first heat treatment at 700°C or higher. After making the yarn have a tensile strength of 0.2 GPa or more, carbonize the carbon fiber at a temperature of about 1500℃ after or while winding it up from the basket. A method has been proposed (Special Publication No. 51-12740). However, in this method, when the yarns are piled up, they tend to be twisted or twisted, and the yarns tend to be bent, so when made into carbon fibers, the yarns have extremely uneven appearance and have a poor appearance. The strength of the yarn is significantly reduced, resulting in frequent yarn breakage and difficulty in producing high-quality yarn. These drawbacks could not be essentially improved by increasing the curvature when the threads were piled up.

On the other hand, Japanese Patent Publication No. 53-4128 discloses that a mesophasic pitch is melt-spun, wound once onto a bobbin, and some of the threads are placed on a wire mesh plate for 250 min.
A method is disclosed in which the yarn is oxidized in an oxidizing atmosphere at a temperature of 500°C to 500°C to increase the strength of the yarn and to make the yarn easier to handle before processing. However, this method is carried out in an oxidizing atmosphere at a temperature range of 400 to 500°C, and as the oxidation is carried out at too high a temperature, the strength of the final carbon fiber yarn decreases, and once wound, the yarn loses its strength. The drawback was that production efficiency was low because oxidation was carried out while taking out parts one by one.

JP-A-60-173121, JP-A-60-81320, and JP-A-60-21911 disclose a method in which the bobbin is infusible as it is wound and preliminary carbonization is performed in a non-oxidizing atmosphere at a certain temperature or lower. is disclosed. However, in these methods, when the pitch fibers on the bobbin are wound thickly, the permeability during infusibility or pre-carbonization is insufficient, which tends to cause fusion or sticking between the filaments, and after pre-carbonization, It becomes difficult to unwind (rewind) the thread on the bobbin, and when unwinding,
The disadvantage is that the threads tend to become fluffy, which significantly reduces the commercial value when made into carbon fibers or graphite fibers.

In addition, due to insufficient air permeability, there was a drawback that the degree of infusibility greatly varied, and when it was made into carbon fiber or graphite fiber, the strength varied greatly.

Japanese Unexamined Patent Publication No. 60-81320 discloses a method in which the pitch fibers are made infusible while wound on a bobbin, and then the infusible pitch fibers are unwound (unwound) from the bobbin to be carbonized and graphitized. This method makes the bobbin winding infusible,
Compared to the pre-carbonization method, it is advantageous in that it can be unwound (unwound) at a stage where the degree of adhesion and fusion between fibers and fiber bundles is significantly lower, but the strength of the fibers is still weak as that of pitch fiber. On top of that, during infusibility, the decomposition and deterioration of the oil that binds the infusible fibers is significant.
The convergence of the fiber bundle is disturbed and the fiber bundle becomes extremely weak and brittle. For this reason, there was a drawback that unwinding (unwinding) after infusibility became extremely difficult. Furthermore, there was a drawback that fluff was easily generated on the yarn during unwinding.
In addition, due to insufficient air permeability, there was a drawback that the degree of infusibility greatly varied, and when it was made into carbon fiber or graphite fiber, the strength varied greatly.

≪Problems to be solved by the invention≫ Furthermore, in Japanese Patent Application Laid-open No. 128020/1987, a yarn drawn by a godet roller after melt spinning is continuously passed through a hot air oven for infusibility at a yarn speed of 0.15 m/min. A method is disclosed in which carbon fibers are obtained by continuously passing the carbon fiber through a carbonization furnace. However, with this method, uniform infusibility can be achieved, so variations in physical properties are small, and when made into carbon fibers, yarns with a good appearance can be obtained. The anionic water-soluble surfactant used as the oil agent decomposes and the bundle becomes disordered, which causes the fiber bundle to easily break during infusibility, making operation difficult.

These drawbacks can be solved by the method of emulsifying polysiloxane (silicone oil) with a surfactant and using it as a water emulsion type oil agent (Japanese Patent Publication No. 12739/1989), or by using other known surfactants or water emulsion type oil agents (Japanese Patent Publication No. 51/1989). 12740, Japanese Patent Publication No. 53-10125, Japanese Patent Application Laid-open No. 103313-1980, etc.), the problem could not be solved. Therefore, during infusibility, the oil that binds the fibers decomposes and deteriorates, resulting in significant stickiness of the fibers, disturbance of bundles, and loss of flexibility of the fibers. For this reason, the conventional drawbacks that the fibers become tattered, the fiber bundles break, and yarn handling becomes difficult have not been solved.

On the other hand, it is also possible to use polysiloxane diluted with a solvent etc.
No. 47-36464), this method has the drawback that the thread is easily damaged due to the solubility of the solvent, and this method also has the drawback that it is prone to fusion and fluffing. In addition, since a low boiling point solvent or polysiloxane is used as a diluent, the diluent evaporates during work, which poses a major problem in terms of work and environmental protection, as well as high costs. Ta.

In addition, since the infusibility rate is slow, there is a drawback that the amount of product produced per hour is extremely small.

Therefore, there are operational and environmental issues during operation,
There is no cutting of fiber bundles during the infusibility treatment, allowing for smooth operation and a large production volume per hour.The yarn has a good appearance and is less fluffy when handled, and has high strength and elasticity, resulting in uneven yarn strength. There has been a strong need for a method for producing long filaments of high-quality pitch-based carbon fibers at low cost and efficiently.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned drawbacks of the prior art and provide a method for producing pitch-based carbon fibers that are easy to handle and have high quality.

Another object of the present invention is to have good appearance, high strength,
An object of the present invention is to provide a method for efficiently producing high-quality pitch-rate long filament carbon fibers with high elastic modulus.

≪Means for Solving the Problems≫ The objects of the present invention are to melt-spun carbonaceous pitch, combine the spun pitch fibers, apply a water emulsion-based heat-resistant oil agent, and then spin the fibers in an oxidizing atmosphere. A method for producing carbon fibers and graphite fibers, in which a fiber bundle is passed continuously in a linear manner to make it infusible, and then carbonized or graphitized in an inert gas atmosphere. This was achieved by a method for producing carbon fibers and graphite fibers, characterized in that the number of filaments is 50 to 1,000 filaments, and the number of filaments after doubling is 200 to 50,000 filaments.

(a) Carbonaceous pitch The carbonaceous pitch used in the present invention is not particularly limited, and includes coal tar pitch obtained by dry distillation of coal, coal-based pitch such as coal liquefied product, naphtha cracking tar pitch, and catalytic cracking tar pitch. , various types of pitches such as petroleum-based pitches such as atmospheric distillation residues and vacuum distillation residues, synthetic pitches obtained by decomposing synthetic resins, hydrogenation of these pitches with hydrogen or hydrogen donors, heat treatment, and solvent extraction. Modified products can also be used.

The carbonaceous pitch of the present invention may be an optically isotropic pitch or an optically anisotropic pitch, and can also be applied to pitches called neomesophase and premethophase, but in particular,
The optically anisotropic pitch described below is preferred.

(b-1) Optically anisotropic carbonaceous 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 using a reflective polarizing microscope. This refers to pitches in which glitter is observed, that is, pitches in which the majority of pitches are substantially optically anisotropic; Here, it is called optically isotropic carbonaceous pitch. Therefore, the optically anisotropic carbonaceous pitch in this specification includes not only a pure optically anisotropic carbonaceous pitch but also a spherical or optically isotropic phase in the optically anisotropic phase. This also includes cases where it is contained in an irregularly shaped island.

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

AP in this specification is the so-called "meso phase"
However, there are two types of "meso phase": one that is substantially insoluble in quinoline or pyridine, and one that contains many components that are soluble in quinoline or pyridine.
AP is mainly the latter "meso phase".

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

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

In the present invention, it is preferable that the optically anisotropic pitch used 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 during melting or solidification of pitch using a differential scanning calorimeter. I can do it. The softening point measured by this method agrees within a range of ±10°C with the temperature obtained by other measurement methods such as the ring and ball method and the micro melting point method.

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

(b-2) Method for producing optically anisotropic pitches The optically anisotropic pitches used in the present invention may be produced using any production method, but heavy carbonized pitches, which are common raw materials for pitches production, may be used. Hydrogen oil, tar, commercially available pitcher, etc. are heated to 380℃ in a reaction tank.
Conventional methods can be used, including sufficient pyrolytic polycondensation with stirring and degassing with an inert gas at a temperature of ˜500° C. to increase the residue pitch AP. However, this method
If AP manufactures 80% or more,
The thermal decomposition polycondensation reaction progresses too much, the quinoline insoluble content increases to over 70% by weight, and the softening point also reaches 330.
Not only can the temperature be higher than 0.degree. C., but also the IP is difficult to form a microspherical dispersed state, so it is not necessarily a preferable method.

Therefore, the preferred method for producing the optically anisotropic pitch used in the present invention is to stop the thermal decomposition polycondensation reaction halfway and heat the polycondensate at 350°C.
By holding the AP at a temperature in the range of ~400°C and leaving it essentially still, the lower layer of AP with higher density grows and matures and is deposited, which is then deposited with the lower layer of lower density.
This is a method of separating and extracting a portion containing a large amount of IP, and the details of this method are described in Japanese Patent Application Laid-Open No. 119984/1984.

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

(c) Production of fibers () Spinning Pitch having a high AP content and a low softening point as described above can be spun by a known method. In such a method, for example, a pitch is placed in a metal spinning container having 1 to 1,000 spinnerets with a diameter of 0.1 mm to 0.5 mm below, and the pitch is heated between 280 and 370°C under an inert gas atmosphere. The pitch is held at a constant temperature, kept in a molten state, and the pressure of the inert gas is increased to several hundred mmHg to push the molten pitch out of the nozzle, and while controlling the temperature and atmosphere, the pitch fibers flowing down are heated at high speed. It is wound onto a rotating bobbin.

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

Alternatively, it is also possible to adopt a method in which pitch fibers spun from a spinneret are collected in a can-like manner in a lower collecting case while being collected by an air current. In this case, it is possible to continuously perform spinning by supplying pitch to the spinning container by supplying pre-melted pitch under pressure using a gear pump or the like. Furthermore, in the above method, it is also possible to use a method in which pitch fibers are drawn and taken up using gas that is controlled at a constant temperature and descends at high speed in the vicinity of the die, and long fibers are produced on a belt conveyor below.

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

In addition, in the present invention, even when spinning by any known method, even though the AP content is as high as 95% or more, the softening point is as low as 230°C to 320°C. Since optically anisotropic carbonaceous pitch is used, temperatures of 280℃~
It can be spun at a lower temperature of 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 sucker, and then guided to an oiling roller where a sizing agent (oil agent) is applied and further bundled. In this case, the sizing agent is
For example, alcohols such as ethyl alcohol, isopropyl alcohol, n-propyl alcohol, butyl alcohol, or alcohols with a viscosity of 3 to 3
300cst (25℃) dimethylpolysiloxane,
Methylphenylpolysiloxane etc. diluted with a low boiling point silicone oil or paraffin oil or other solvent, or dispersed in water with an emulsifier added; Similarly, graphite, polyethylene glycol or hindered esters are dispersed. surfactants diluted with water; and other oils that do not damage pitch fibers among the various oils used for ordinary fibers such as polyester fibers.

In some cases, an antistatic agent may be added to these materials.

The amount of these oils attached to fibers is 0.01~
10% by weight, particularly preferably 0.05 to 5% by weight.

() Doubling of pitch fibers In the present invention, pitch fibers are doubled prior to infusibility in order to increase the strength of the fiber bundle and to continuously and stably pass it through the infusibility furnace during infusibility.

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

In the present invention, 2 to 20 pitch fiber bundles obtained by melt spinning are used to form 200 to 50,000, preferably 500 to 5,000 filaments.

Doubling is performed by first winding the spun pitch fibers around a plurality of bobbins, then simultaneously unwinding them, combining the fiber bundles into one, and winding them around one bobbin.

The traverse during doubling is preferably 5 to 100 mm per revolution of the bobbin. In order to improve the unwinding property from the bobbin, it is better to make the traverse larger, but if it is too large, the thread is likely to be damaged, so it is not preferable.

Pitch fibers dropped in a can shape may be pulled up from multiple baskets or cases and combined.

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

You can do 2 to 20 threads at a time, but
Pair 2 to 10 threads the first time, then tie these 2 more times.
A method of recombining ~10 threads is also used.

In order to increase the thread plubility and increase the cohesiveness during infusibility, add 0.1~
30 twists/m, preferably 1 to 5 twists/m are applied.

In the present invention, in order to ensure stable thread passing through the infusibility furnace during infusibility, a special heat-resistant water emulsion type oil agent is applied at the time of yarn doubling. As the oil agent, a water emulsion type is particularly preferable from the viewpoints of workability, environment, and manufacturing cost.

In the present invention, as a heat-resistant water emulsion-based oil agent, a distillate with a boiling point of 600℃ or less (atmospheric pressure equivalent) obtained by distilling a nonionic surfactant under reduced pressure is used as an emulsifier, and a An emulsified alkyl phenyl polysiloxane having viscosity is used.

As the nonionic surfactant, polyoxyethylene alkyl ether and polyoxyethylene alkyl ester are used.

The alkylphenyl polysiloxane preferably contains 5 to 80 mol% of phenyl groups as a component, particularly preferably 10 to 50 mol%.

Moreover, as the alkyl group, a methyl group, an ethyl group, and a propyl group are preferable. The same molecule may have two or more types of alkyl groups.

With this combination, a water emulsion-based oil can be made, and the decomposition and deterioration of the oil during infusibility is extremely low, the fiber bundles are well bundled, and the fiber bundles are not cut during infusibility, and there is no fluffing. It is possible to pass through the infusibility furnace continuously in a linear manner.

If a nonionic surfactant is used as an emulsifier without distillation and an emulsified alkyl phenyl polysiloxane is used, the oil agent that binds the fiber bundles will decompose and deteriorate during infusibility, and the bundle will be disrupted. Fiber bundles tend to break, making yarn handling difficult. In addition, dimethylpolysiloxane (dimethylsilicone oil), fatty acid ester oil, mineral oil, etc. can be emulsified with ordinary surfactants, but the decomposition and deterioration of the oil agent during infusibility is more severe than when alkylphenylpolysiloxane is used. This causes the fiber bundles to stick together, making it even more difficult to handle the yarn.

On the other hand, even if an attempt is made to emulsify dimethylpolysiloxane (dimethylsilicone oil) with a distilled nonionic surfactant, emulsification is difficult and it cannot be used as a water emulsion type oil agent.

In order to further improve the heat resistance of the oil agent, antioxidants such as amines, organic selenium compounds, and phenols may be added to the oil agent.

These antioxidants include phenyl-
α-Naphthylamine, dilauryl selenide, phenothiazine, iron octlate, etc. are used.

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

The amount of these oils attached to the fibers is 0.01 to 10% by weight, preferably 0.05 to 5% by weight.

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

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

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

In the present invention, the threads are doubled so that continuous threading can be smoothly performed, and a heat-resistant oil agent is applied to prevent the fiber bundle from breaking during the infusibility treatment.
Various known combinations of temperature, oxidizing agent, and reaction time can be used in the step of oxidizing pitch fibers to produce infusible carbonaceous fibers.

The temperature of the infusibility step in the present invention is 150°C
The temperature is raised stepwise or gradually in the range of -400°C, preferably 200°C - 300°C, and the treatment is usually carried out for 30 minutes - 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 it can be used as a method for shortening reaction time.

In the present invention, the treatment is carried out for a short time in an atmosphere containing oxidizing agents such as halogen, NO ₂ or ozone at a temperature of 200°C or less, or in an oxygen gas atmosphere that is 30 to 50°C lower than the softening point of pitch. A preferred method is to maintain the temperature at a temperature of 150 to 240°C for 10 minutes to 1 hour until sufficient infusibility is obtained, and then raise the temperature to about 300°C if necessary to complete the infusibility, and the latter method is particularly preferred. is easy and reliable and is preferred.

For infusibility, it is preferable to replace old gas by circulating a fresh gas of the same type as the atmosphere at a rate of 0.1 to 3 times per minute.

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

During the infusibility treatment, it can be done without applying tension, but in the infusibility furnace, the fiber bundles (threads) sag and rub against the bottom and walls of the furnace, resulting in drag scratches. Infusibility is carried out while applying a tension of 0.001 to 0.2 g per filament in order to improve carbon fiber physical properties such as tensile strength and tensile modulus.

The fiber bundles leaving the continuous infusibility furnace have become weak and brittle due to decomposition, evaporation, and deterioration of some of the oil in the furnace, so a heat-resistant oil is applied again and the fiber bundles are treated as threads. It is more preferable to improve the properties.

() Heat treatment process Next, this infusible carbonaceous pitch fiber is carbonized by raising the temperature to a temperature in the range of 1000 to 2000℃ in a chemically inert atmosphere such as argon or nitrogen gas. By doing so, carbon fibers are obtained, and when the temperature is raised to a temperature in the range of 2000 to 3000°C and the graphitization treatment is carried out, so-called graphite fibers are obtained.

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

≪Effects of the Invention≫ The present invention increases the strength of the fiber bundle by doubling carbonaceous pitch fibers, and further applies a heat-resistant oil to infusible the fiber bundle continuously in a linear manner. There is no cutting of fiber bundles during melting, and production speed can be increased.

In particular, since a water emulsion-based oil is used, the threads are less likely to be damaged or fused, and there are no major problems in terms of work and environmental protection such as making them infusible when doubling the threads.
Since carbonization and graphitization can be carried out continuously, it is possible to use continuous equipment, and it is also possible to obtain carbon fibers and graphite fibers with good appearance, uniform tensile strength, and high physical properties such as tensile modulus.

In particular, when optically anisotropic carbonaceous pitch fibers are used, the strength and elastic modulus are further improved.

As described above, production efficiency is extremely high, and carbon fibers and graphite fibers with high strength and high elastic modulus can be obtained efficiently.

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

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

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

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

Six bobbins wound with pitch fibers were combined at a traverse pitch of 20 mm/rotation, and wound onto a stainless steel bobbin as a 3000 filament.

At the time of yarn doubling, 40 cst methyl phenyl polysiloxane (phenyl content 25 mol%) was distilled under reduced pressure from polyoxyethylene alkyl ether with a number average molecular weight of 1000, which is a nonionic surfactant, at 25°C and A water emulsion-based oil agent was used, which was emulsified using a distillate up to ℃ as an emulsifier. The concentration of the water emulsion oil agent was 0.5% by weight, and it was applied by roller contact. The amount applied was 0.2% by weight based on the yarn.

While unwinding (unwinding) the bobbin-wound pitch fiber obtained in this way from the bobbin, the furnace inlet temperature was set at 150°C.
It was introduced continuously in a linear manner into a continuous infusibility furnace with forced hot air circulation equipped with a fan in an air atmosphere with a maximum temperature gradient of 270°C. 1℃/from temperature 150℃ to 270℃
The temperature was raised in 1 minute and held at 270°C for 30 minutes.

The treatment time was 150 minutes. During this time, the atmosphere in the furnace was replaced 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/sec.
It was per filament.

During this time, the pitch fibers were smoothly unwound from the bobbin.

After the infusibility was completed, the same oil agent used for doubling was applied by roller contact.

This infusible pitch fiber was heated to 1500°C in an inert gas atmosphere to obtain carbon fiber. The diameter of the carbon fiber is 9.9μm, and the tensile strength is
The tensile modulus was 2.7 GPa, and the tensile modulus was 260 GPa.

In addition, this carbon fiber was heated at 2500℃ in an inert gas atmosphere.
The graphite fiber obtained by raising the temperature to 2.5 GPa had a thread diameter of 2.5 GPa and a tensile modulus of 710 GPa.

Comparative Example 1 The same procedure as in Example 1 was carried out except that polyoxyethylene alkyl ether, which is a nonionic surfactant, was used as it was instead of the emulsifier in the heat-resistant water emulsion oil without being distilled under reduced pressure. This thing is
During infusibility, the oil decomposed, deteriorated, and stuck in the furnace, causing the fibers to become tattered and the fiber bundles to be cut.

Comparative Example 2 The same process as in Example 1 was carried out except that the yarns were not doubled. The fiber bundles of the thus obtained pitch fibers were cut in the furnace during infusibility, making it impossible to obtain long infusible fibers.

Comparative Example 3 The process was carried out in the same manner as in Example 1, except that no heat-resistant oil was applied during the yarn doubling. In this case, the fiber bundles were frequently cut during the continuous infusibility furnace, making it impossible to obtain long fibers.

Comparative Example 4 The same process as in Example 1 was carried out, except that methylpolysiloxane with a viscosity of 28 cst was emulsified with sodium lauroyl sulfonate, a surfactant, as the oil agent applied during yarn doubling. The amount of adhesion to the fibers was the same as in Example 1.

In this case, during infusibility, the oil agent decomposed and deteriorated in the furnace, the fibers were severely stuck together and crumbled, and the fiber bundles were cut.

Comparative Example 5 As oil agents applied at the time of yarn doubling, 3.6% by weight of carbon black, 0.8% by weight of ammonium persulfate, and ammonium laurate which is a water-soluble surfactant were added.
Example 1 except that 0.4% by weight was used.
processed in the same way.

In this product, the oil agent decomposed and the fiber bundles were cut in the furnace during infusibility.

Claims (1)

[Scope of Claims] 1 Carbonaceous pitch is melt-spun, the spun pitch fibers are combined, and then a water emulsion-based heat-resistant oil is applied, and then the fiber bundle is continuously linearized in an oxidizing atmosphere. A method for producing carbon fibers and graphite fibers, in which the fibers are infusible through the process, and then carbonized or graphitized in an inert gas atmosphere, wherein the number of filaments of the pitch fibers before doubling is 50 to 1000 filaments, The number of filaments of Pituchi fiber after doubling is
A method for producing carbon fiber and graphite fiber, characterized by having 200 to 50,000 filaments. 2. A patent claim 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 item 1. 3. Pounded pitch fibers having a predetermined number of filaments can be obtained by collecting the spun pitch fibers using an air current after convergence, accumulating them in a can-like accumulation container, and then unwinding and piling the fibers. A method for producing carbon fibers and graphite fibers according to claim 1, characterized in that: 4. Claims characterized in that the combined 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. The method for producing carbon fiber and graphite fiber according to item 1. 5. The method according to claim 1, characterized in that the spun pitch fibers having a predetermined number of filaments are obtained by re-unraveling the pitch fibers that have been spliced once and performing re-splicing. A method for producing carbon fiber and graphite fiber. 6. The method for producing carbon fibers and graphite fibers according to claim 1, characterized in that the traverse during doubling is 5 to 100 mm/(one revolution of the bobbin). 7. The method for producing carbon fibers and graphite fibers according to claim 1, characterized in that the yarns are twisted 0.1 to 30 times per meter during doubling. 8 The water emulsion-based oil agent applied to the spun fibers is made by distillation of a nonionic surfactant under reduced pressure, using a distillate with a boiling point of 600°C or less (atmospheric pressure equivalent boiling point) as an emulsifier, and boiling at 25°C for 10 Claim 1, characterized in that it is an emulsified alkyl phenyl polysiloxane having a viscosity of ~1000 cst.
The method for producing carbon fibers and graphite fibers as described in 2. 9. The method for producing carbon fibers and graphite fibers according to claim 8, wherein the alkyl phenyl polysiloxane contains 5 mol% to 80 mol% of phenyl groups. 10 A patent claim characterized in that the alkyl group of the alkyl phenylpolysiloxane contains any one of a methyl group, an ethyl group, a propyl group, or two or more groups selected from these, which are the same or different. A method for producing carbon fibers and graphite fibers according to Scope 8. 11. The method for producing carbon fibers and graphite fibers according to claim 8, wherein the nonionic surfactant is polyoxyethylene alkyl ether and/or polyoxyethylene alkyl ester. 12. The method for producing carbon fibers and graphite fibers according to claim 1, wherein the heat-resistant oil agent contains an antioxidant such as amines, organic selenium compounds, and phenols. 13 The antioxidant is phenyl-α-naphthylamine, dilaurylselenide, phenothiazine,
13. The method for producing carbon fibers and graphite fibers according to claim 12, wherein the fiber is one or a mixture of two or more selected from iron octrate. 14 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. 15. 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 such as halogen, NO ₂ or ozone. 16. 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. 17. 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 5 m/sec. 18 0.001~ per filament when infusible
The method for producing carbon fibers and graphite fibers according to claim 1, characterized in that a tension of 0.2 g is applied. 19 The carbonaceous pitch is an optically anisotropic pitch, the optically anisotropic carbonaceous pitch contains about 95% or more of an optically anisotropic phase, and has a softening point of about 230 to
The method for producing carbon fibers and graphite fibers according to claim 1, wherein the temperature is 320°C.