KR102070167B1 - Raw Material Pitch for Carbon Fiber Manufacturing - Google Patents

Abstract

An object of this invention is to provide the raw material pitch for carbon fiber manufacture which can manufacture the carbon fiber excellent in tensile strength comparatively cheaply. The raw material pitch for carbon fiber manufacture of this invention is a pitch obtained from coal, and is a pitch for manufacturing carbon fiber by melt spinning, and the content rate of oxygen is 1.0 mass% or more, and the content rate of toluene soluble content is 20 mass% or more, It is characterized by the above-mentioned. It is done. The coal may be bituminous coal or sub-bituminous coal. The raw material pitch for the carbon fiber production may be one obtained by thermally treating a soluble component separated from a thermal decomposition product in a solvent of coal by a solvent extraction treatment at a temperature of less than 300 ° C.

Description

Raw Material Pitch for Carbon Fiber Manufacturing

This invention relates to the raw material pitch for carbon fiber manufacture.

Carbon fiber is widely used as a reinforcing material for structural materials, such as resin, concrete, and ceramics, for example. In addition, the carbon fiber is also used as a heat insulating material, an activated carbon raw material, a conductive material, a heat transfer material, or the like, for example.

Carbon fibers are generally produced by molding a pitch obtained from synthetic resins such as polyacrylonitrile, petroleum or coal into a fibrous form by spinning, and impregnating (air oxidation) and carbonizing the yarn. Coal pitch is a residue after taking out volatile components, such as naphthalene, by distillation from the coal tar which is a by-product liquid substance at the time of distilling coal and manufacturing coke among the said raw materials, and is a black material. Such coal pitch is a mixture of many compounds containing many aromatic compounds containing many benzene rings in the skeleton.

In more detail, since coal pitch is heated to about 1000 degreeC at the time of coke manufacture, the polycyclic aromatic compound with high ring condensation degree is a main component, For example, alkyl side chains, such as a methyl group, an ethyl group, and a propyl group, For example, The content rate of the structure containing oxygen, such as an ether bond and a phenol group, is extremely small. Although the oxygen content rate can be used as an index of the content rate of these structures, the oxygen content rate of coal pitch is generally 1 mass% or less, and in many cases is 0.5 mass% or less.

When the coal pitch is heated at about 100 ° C. to about 200 ° C., the coal pitch melts and becomes a charged liquid. Thus, the coal pitch can be spun by extruding it from the nozzle. However, as described above, the coal pitch is a by-product during coke production and is recovered as a residue, and thus, for example, various components that inhibit spinning and subsequent incompatibility and carbonization of metal impurities or solid carbon powder, etc. It is included. For this reason, it is difficult to manufacture carbon fiber stably and efficiently from coal pitch. In addition, these impurities may cause the defect of the carbon fibers produced, and thus lower the tensile strength of the carbon fibers obtained.

Moreover, it is preferable that the raw material pitch used for manufacture of carbon fiber melt | dissolves uniformly at a fixed temperature at the time of spinning. The softening point of the raw material pitch is preferably 150 ° C. or more so as to increase the efficiency of the incompatibility treatment for fixing the shape of the fiber spun with the raw material pitch, and to perform spinning at a temperature at which pyrolysis reaction does not occur during spinning. 350 ℃ or less is preferable so that.

In order to satisfy these demands, it is proposed to modify the pitch of coal by, for example, adjusting components, removing impurities, etc., on the pitch obtained by the solvent extraction treatment of coal (for example, Japanese Patent Publication No. See publication 7-15099).

However, the reforming treatment of coal pitch as described above becomes a factor that boosts the production cost of carbon fibers.

Japanese Patent Publication Hei 7-15099

In view of the above problems, it is an object of the present invention to provide a raw material pitch for producing carbon fibers which can produce carbon fibers having excellent tensile strength at a relatively low cost.

Invention made in order to solve the said subject is a pitch obtained from coal, and is a pitch for manufacturing carbon fiber by melt spinning, content of oxygen is 1.0 mass% or more, and content of toluene soluble matter is 20 mass It is% or more, It is a raw material pitch for carbon fiber manufacture.

As for the raw material pitch for carbon fiber manufacture, since content rate of oxygen is 1.0 mass% or more, oxygen forms bridge | crosslinking between molecules in a carbonization process. For this reason, the said raw material pitch for carbon fiber manufacture inhibits the lamination formation of an aromatic ring, and can suppress the development of a crystal | crystallization. As a result, the stress concentration between the microcrystals when stress acts on the carbon fiber can be alleviated, so that the tensile strength of the carbon fiber obtained is improved. Moreover, since the content rate of the toluene soluble component comprised from the compound with a comparatively small molecular weight is 20 mass% or more, the raw material pitch for carbon fiber manufacture is excellent in meltability and spinning property in a melt spinning process. Therefore, by using the said raw material pitch for carbon fiber manufacture, the carbon fiber excellent in tensile strength can be manufactured comparatively cheaply.

The coal may be bituminous coal or sub-bituminous coal. As described above, since the coal is bituminous coal or sub-bituminous coal, the yield of the raw material pitch for producing the carbon fiber is relatively high. As a result, the raw material pitch for producing the carbon fiber, and moreover, the carbon fiber can be produced relatively inexpensively.

The said raw material pitch for carbon fiber manufacture should just heat-process the soluble component isolate | separated by the solvent extraction process at the temperature below 300 degreeC from the thermal decomposition product in the solvent of coal. Thus, since the raw material pitch for carbon fiber manufacture heat-processes the soluble component isolate | separated by the solvent extraction process at the temperature below 300 degreeC from the thermal decomposition product in the solvent of coal, it is a thing of oxygen The content rate and content rate of the toluene soluble content can be easily and reliably within the said range. As a result, the raw material pitch for carbon fiber manufacture, and also the carbon fiber excellent in tensile strength can be manufactured comparatively cheaply.

Here, "the oxygen content rate" means the content rate of the oxygen atom containing not only oxygen molecule but the atom couple | bonded with another atom, and specifically means the value measured based on JIS-M8813 (2004). In addition, "the content rate of toluene soluble content" is a value measured based on JIS-K2207 (1996). In addition, "bituminous coal" and "sub-bituminous coal" refer to coal having coal quality as defined in JIS-M1002 (1978).

As mentioned above, carbon fiber can be manufactured inexpensively by using the raw material pitch for carbon fiber manufacture of this invention.

BRIEF DESCRIPTION OF THE DRAWINGS It is a flowchart which shows the procedure of the manufacturing method of the raw material pitch for carbon fiber manufacture of one Embodiment of this invention.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail, referring drawings suitably.

[Raw pitch for carbon fiber manufacturing]

The raw material pitch for carbon fiber manufacture which concerns on one Embodiment of this invention is obtained from coal, and is a raw material pitch for producing carbon fiber by melt spinning.

It is preferable that the raw material pitch for carbon fiber manufacture is obtained from a thermal decomposition product in the solvent of coal. Coal contains many structures containing oxygen, such as an alkyl side chain, compared with the coal tar and petroleum residue which are processed at comparatively high temperature, and also contains many toluene soluble components. For this reason, the said raw material pitch for carbon fiber manufacture obtained from the thermal decomposition product in the solvent of coal can have the characteristics as demonstrated below.

As a minimum of the content rate of oxygen in the raw material pitch for carbon fiber manufacture, it is 1.0 mass%, 1.5 mass% is preferable, and 1.7 mass% is more preferable. On the other hand, as an upper limit of the content rate of oxygen, 5.0 mass% is preferable, 4.0 mass% is more preferable, 3.0 mass% is more preferable. When the content of oxygen does not fall below the lower limit, there is a possibility that the crystal development at the time of carbonization cannot be sufficiently suppressed, and the carbon fiber obtained is easily broken by stress concentration. On the contrary, when the oxygen content exceeds the above upper limit, the mass reduction rate at the time of carbonization is large, and there is a fear that the production cost of the carbon fiber may increase because the yield of the carbon fiber is lowered.

As a minimum of the content rate of the toluene soluble content in the raw material pitch for carbon fiber manufacture, it is 20 mass%, 30 mass% is preferable, and 35 mass% is more preferable. On the other hand, as an upper limit of the content rate of toluene soluble content, 80 mass% is preferable, 60 mass% is more preferable, 50 mass% is further more preferable. When the content rate of toluene soluble content does not reach the said minimum, there exists a possibility that the meltability and radioactivity at the time of melt spinning may become inadequate. On the contrary, when the content rate of toluene soluble content exceeds the said upper limit, there exists a possibility that the manufacturing cost of carbon fiber may rise because the yield of carbon fiber falls.

As coal used as a raw material of the raw material pitch for carbon fiber manufacture, anthracite coal, bituminous coal, sub-bituminous coal, lignite, etc. are mentioned in order of high coalization degree, Among them, bituminous coal or sub-bituminous coal which has moderate coal degree is preferable. . Since bituminous coal and sub-bituminous coal have a relatively high content of toluene soluble and have a suitable oxygen content, the raw material pitch for producing carbon fiber in which oxygen content and toluene soluble content is within the above range by using bituminous coal and sub-bituminous coal as raw material coal. The yield can be increased. In addition, lignite having a lower degree of coalification than sub-bituminous coal has a drawback that the oxygen content is too large and the yield of carbon fibers from the raw material pitch is lowered. In addition, anthracite coal having a higher degree of coalification than bituminous coal has a drawback that melt spinning of the raw material pitch is not easy because the oxygen content rate and the toluene soluble content content rate are small.

[Method for Producing Raw Material Pitch for Carbon Fiber Production]

Then, the manufacturing method of the raw material pitch for carbon fiber manufacture is demonstrated.

The said raw material pitch for carbon fiber manufacture can be manufactured by the manufacturing method shown in FIG. The manufacturing method of the raw material pitch for carbon fiber manufacture is a process of forming ashless coal which is a thermal decomposition product of coal by the thermal decomposition and extraction process in the solvent of a coal (thermal decomposition product formation process: step S1), and this thermal decomposition product formation process Step (Separation step: step S2) and the step of heat treating the soluble component obtained in this separation step (heat treatment step: step S3) Equipped.

Thermal decomposition product forming process

In the thermal decomposition product formation process of step S1, the slurry which mixed the raw material coal and the solvent is heated above the thermal decomposition temperature of the raw material coal, the soluble component of the thermally decomposed raw coal is extracted to a solvent, and at this thermal decomposition temperature Anthracite is obtained by separating insoluble components of. In addition, "ashless coal" is a modified coal which reformed coal, and it means that ash content is 5% or less, Preferably it is 3% or less, More preferably, it is 1% or less. In addition, "ash" means the value measured based on JIS-M8812 (2004).

The solvent is not particularly limited as long as it has a property of dissolving raw coal, and examples thereof include monocyclic aromatic compounds such as benzene, toluene, and xylene, bicyclic aromatic compounds such as naphthalene, methylnaphthalene, dimethylnaphthalene, and trimethylnaphthalene, and anthracene. Tricyclic aromatic compounds, such as these, can be used. The bicyclic aromatic compound includes naphthalenes having aliphatic chains and biphenyls having long chain aliphatic chains.

Among the above solvents, a bicyclic to tricyclic aromatic compound which is a coal derivative purified from coal dry distillation products is preferable. The bicyclic aromatic compound of a coal derivative is stable also in a heated state, and is excellent in affinity with coal. Therefore, by using such a bicyclic aromatic compound as a solvent, the ratio of the coal component extracted to a solvent can be raised, and a solvent can be easily collect | recovered and circulated for use by methods, such as distillation.

As a minimum of the heating temperature (pyrolysis extraction temperature) of a slurry, 300 degreeC is preferable, 350 degreeC is more preferable, and 380 degreeC is more preferable. On the other hand, as an upper limit of the heating temperature of a slurry, 450 degreeC is preferable and 420 degreeC is more preferable. If the heating temperature of the slurry does not reach the lower limit, the bonds between the molecules constituting the coal cannot be sufficiently weakened, and thus, when, for example, low-grade coal is used as the raw coal, the inventory temperature of the ashless coal to be extracted is changed. There is a fear that it cannot be increased or the yield may be low and uneconomical. On the contrary, when the heating temperature of the slurry exceeds the above upper limit, the thermal decomposition reaction of coal becomes very active, so that the oxygen content of ashless coal may become insufficient, or the recombination of the produced pyrolysis radicals may occur, resulting in the extraction rate of ashless coal. This may fall.

The extraction rate to coal in the pyrolysate forming step (yield of ashless coal) varies depending on the quality of the coal used as the raw material, but in the case of bituminous coal or sub-bituminous coal, for example, 20 mass% or more and 60 mass% or less.

<Separation process>

In the separation step of step S2, by applying the ashless coal obtained in the thermal decomposition product forming step of step S1 to the low temperature solvent extraction treatment, a relatively low molecular weight soluble component that is solvent extracted at low temperature and a relatively high molecular weight insoluble that is not solvent extracted. Separate into components. As a result, a soluble component capable of melt spinning is obtained.

More specifically, a slurry obtained by dispersing pulverized anthracite in a solvent is prepared, and the slurry is maintained within a predetermined temperature range for a predetermined time, and then solid content, that is, an insoluble component, and a liquid, that is, a soluble component, in the slurry are eluted. Separate the solvent.

As a minimum of the average particle diameter of the ashless coal disperse | distributed in a solvent, 50 micrometers is preferable and 100 micrometers is more preferable. On the other hand, as an upper limit of the average particle diameter of the ashless coal disperse | distributing in a solvent, 3 mm is preferable and 1 mm is more preferable. When the average particle diameter of the ashless coal disperse | distributed in a solvent does not reach the said minimum, there exists a possibility that it may become difficult to separate the liquid containing the extracted soluble component and the solid content which is an insoluble component. On the contrary, when the average particle diameter of the ashless coal dispersed in a solvent exceeds the said upper limit, there exists a possibility that the extraction efficiency of a soluble component may fall. In addition, an "average particle diameter" means the particle diameter which turns into a volume integrated value 50% in the particle size distribution measured by the laser diffraction scattering method.

As a minimum of the mixing ratio of the ashless coal with respect to the solvent of the said slurry, 3 mass% is preferable and 5 mass% is more preferable. On the other hand, as an upper limit of the mixing ratio of the ashless coal with respect to a solvent, 40 mass% is preferable and 30 mass% is more preferable. If the mixing ratio of the ashless coal to the solvent does not fall below the lower limit, the production efficiency is low and there is a risk of becoming uneconomical. On the contrary, when the mixing ratio of ashless coal to the solvent exceeds the above upper limit, there is a possibility that handling of the slurry and separation of insoluble components may become difficult.

The separation method of the solvent and the insoluble component in which the soluble component elutes is not particularly limited, and known separation methods such as filtration, centrifugal separation, gravity sedimentation, or a combination of two methods thereof can be employed. Among these, the combination of the centrifugal separation method and the filtration method which can continuously operate a fluid, is suitable for a large amount of processing at low cost, and can remove an insoluble component reliably is preferable.

In this way, by removing the solvent from the liquid (supernatant) from which the insoluble component is separated, the soluble component of ashless coal is separated and recovered, and the insoluble component of the ashless coal is separated and recovered by removing the solvent from the solid content concentrate. The method of removing the solvent from the supernatant and the solid concentrate is not particularly limited, and a general distillation method or an evaporation method can be used. In particular, the removal of the solvent from the insoluble component is preferably by distillation in order to recover and reuse the solvent.

As a solvent used at the said separation process, what is necessary is just to be able to elute the low molecular weight component of ashless coal, and the same thing as the solvent used for the said thermal decomposition product formation process can be used. As a solvent for a separation process, the solvent from which a sufficient extraction rate is obtained at low temperature, Preferably normal temperature is preferable, and as such a preferable solvent, pyridine, methylnaphthalene, tetrahydrofuran, anthracene, etc. are mentioned, for example.

The solvent extraction process temperature in a separation process differs in the optimal temperature according to the kind of solvent. However, generally as solvent extraction process temperature, less than 300 degreeC is preferable, 200 degrees C or less is more preferable, 150 degrees C or less is further more preferable. In addition, as a minimum of a solvent extraction process temperature, although it does not specifically limit, Normal temperature, for example, 20 degreeC is preferable. When the solvent extraction treatment temperature exceeds the above upper limit, the molecular weight of the soluble component to be extracted increases, so that the softening temperature is too high and the spinning efficiency may be lowered during melt spinning. On the contrary, when solvent extraction process temperature does not reach the said minimum, cooling may be needed and a cost may increase unnecessarily.

As a minimum of the extraction time in a separation process, ie, the time hold | maintained at the said solvent extraction process temperature, 10 minutes are preferable and 15 minutes are more preferable. On the other hand, as an upper limit of extraction time, 120 minutes are preferable and 90 minutes are more preferable. When extraction time does not reach the said minimum, there exists a possibility that it may not fully elute the low molecular weight component of ashless coal. On the contrary, when extraction time exceeds the said upper limit, there exists a possibility that manufacturing cost may increase unnecessarily.

As a minimum of the extraction rate of the soluble component from ashless coal in a separation process, 10 mass% is preferable, 20 mass% is more preferable, 30 mass% is further more preferable. On the other hand, as an upper limit of the extraction rate of the soluble component from ashless coal, 90 mass% is preferable, 70 mass% is more preferable, 50 mass% is further more preferable. When the extraction rate of the soluble component from ashless coal in a separation process does not reach the said lower limit, a yield is low and there exists a possibility that the manufacturing cost of the raw material pitch for carbon fiber manufacture may increase. On the contrary, when the extraction rate of the soluble component from the ashless coal in the separation process exceeds the above upper limit, the softening temperature of the soluble component may be high and the spinning efficiency may be lowered.

<Heat treatment process>

In the heat treatment step of step S3, the soluble component obtained in the separation step of step S2 is heated to volatilize the low molecular weight component, and the raw material pitch for carbon fiber production is obtained by decomposing and removing the component thermally decomposed at low temperature in advance. . Thus, by removing the volatile component and the decomposable component which may inhibit melt spinning in advance, the raw material pitch for producing the carbon fiber facilitates melt spinning and enables the production of carbon fibers excellent in tensile strength at a relatively low cost. .

It is preferable to heat the said heat processing in non-oxidizing gas atmosphere. In this way, problems such as an increase in softening temperature can be prevented by heating in a non-oxidizing gas atmosphere to prevent oxidative crosslinking. The non-oxidizing gas is not particularly limited as long as the oxidation of the pitch can be suppressed, but nitrogen gas is more preferable from an economic point of view.

In addition, it is preferable to perform the said heat processing in a reduced pressure state. By heat-processing in the pressure reduction state in this way, the vapor of the volatile component and the gas of a thermal decomposition product can be efficiently removed from a pitch.

As a minimum of the heat processing temperature in the said heat processing process, 150 degreeC is preferable, 170 degreeC is more preferable, and 200 degreeC is still more preferable. On the other hand, as an upper limit of the said heat processing temperature, 350 degreeC is preferable, 320 degreeC is more preferable, 280 degreeC is more preferable. When the said heat processing temperature does not reach the said minimum, the volatile component in a soluble component cannot fully be removed, there is a possibility that the sharpness of the raw material pitch for carbon fiber manufacture becomes inadequate, and spin efficiency may fall. On the contrary, when the heat treatment temperature exceeds the upper limit, the energy cost may be unnecessarily increased, the useful component may be thermally decomposed to reduce the production efficiency of the carbon fiber, and carbonization may be progressed to reduce the radioactivity. There is concern.

Moreover, it is preferable that the heat processing temperature in a heat processing process is higher than the solvent extraction process temperature in the separation process of step S2. In this way, when the heat treatment temperature is higher than the solvent extraction treatment temperature, the volatile component having a boiling point higher than the solvent extraction treatment temperature can be removed from the pitch. As a result, the volatile components escape from the raw material pitch for producing carbon fiber at the time of spinning, thereby preventing the formation of pores or disconnection of the yarn.

In addition, the heat treatment temperature in the heat treatment step is more preferably higher than the melt spinning temperature. As described above, since the heat treatment temperature is higher than the melt spinning temperature, components that can be thermally decomposed at the time of melt spinning can be thermally decomposed and removed in advance in this heat treatment step. Thereby, it can prevent that the thermal decomposition product produced | generated at the time of spinning cut | disconnects the yarn shape which radiated the pitch, or forms these defects in the carbon fiber finally obtained by these thermal decomposition products.

As a minimum of the heat processing time (time maintained by the said heat processing temperature) in the said heat processing process, 10 minutes are preferable and 15 minutes are more preferable. On the other hand, as an upper limit of the heat processing time in the said heat processing process, 120 minutes are preferable and 90 minutes are more preferable. When the heat treatment time in the heat treatment step is less than the lower limit, there is a fear that the low molecular weight component cannot be sufficiently removed. On the contrary, when the heat treatment time in the heat treatment step exceeds the upper limit, there is a fear that the treatment cost unnecessarily increases.

As a minimum of the softening temperature of the raw material pitch for carbon fiber manufacture obtained by heat-processing a soluble component, 150 degreeC is preferable and 170 degreeC is more preferable. On the other hand, as an upper limit of the softening temperature of the raw material pitch for carbon fiber manufacture, 280 degreeC is preferable and 250 degreeC is more preferable. When the softening temperature of the said raw material pitch for carbon fiber manufacture does not fall below the said minimum, an incompatible process temperature cannot be raised and there exists a possibility that an incompatible process may become inefficient. On the contrary, when the softening temperature of the raw material pitch for carbon fiber production exceeds the upper limit, it is necessary to increase the melt spinning temperature, and there is a fear that the spinning may become unstable or the cost may increase. In addition, "softening temperature" is a value measured by the ring-and-ball method based on ASTM-D36.

As a lower limit of the yield of the said raw material pitch for carbon fiber manufacture from the soluble component obtained at the said separation process in this heat processing process, 80 mass% is preferable and 85 mass% is more preferable. On the other hand, as an upper limit of the yield of the raw material pitch for carbon fiber manufacture from the soluble component in a heat processing process, 98 mass% is preferable and 96 mass% is more preferable. If the yield of the raw material pitch for producing carbon fiber from the soluble component in the heat treatment step does not reach the lower limit, there is a possibility that the yield of the raw material pitch for producing carbon fiber may be unnecessarily reduced. On the contrary, when the yield of the said raw material pitch for carbon fiber manufacture from a soluble component in a heat processing process exceeds the said upper limit, the pitch will remain by the remainder of the volatile component and the component thermally decomposed at low temperature in the said raw material pitch for carbon fiber manufacture. There is a possibility that the sharpness of the resin may be insufficient, and the radiation efficiency may decrease.

[Method of producing carbon fiber]

Moreover, the method to manufacture carbon fiber using the raw material pitch for carbon fiber manufacture is demonstrated.

The manufacturing method of the carbon fiber using the raw material pitch for carbon fiber manufacture includes the process of melt spinning the said raw material pitch for carbon fiber manufacture, the process of infusifying the yarn-shaped body obtained by this melt spinning, and the unfused yarn form. It is equipped with the process of carbonizing an upper body.

Melt Spinning Process

In the melt spinning step, the raw material pitch for producing the carbon fiber is melt spun using a known spinning device. That is, the raw material pitch in the molten state is formed into a thread shape by passing through a nozzle (detention), and the shape of the raw material pitch is fixed to the thread shape by cooling.

What is necessary is just to use a well-known thing as a nozzle used for this melt spinning, For example, the thing of diameter 0.1mm or more and 0.5mm or less, length 0.2mm or more and 1mm or less can be used. The yarn-shaped body which melt-spun the raw material pitch is wound up by the drum of about 100 mm or more and about 300 mm or less in diameter, for example.

As a minimum of melt spinning temperature, 180 degreeC is preferable and 200 degreeC is more preferable. On the other hand, as an upper limit of melt spinning temperature, 350 degreeC is preferable and 300 degreeC is more preferable. When melt spinning temperature does not reach the said minimum, there exists a possibility that melting of a raw material pitch may become inadequate and stable spinning may not be possible. On the contrary, when melt spinning temperature exceeds the said upper limit, there exists a possibility that the thread-shaped body which the component in the raw material pitch thermally decomposed and radiated may be disconnected.

Although it does not specifically limit as a minimum of the linear velocity of melt spinning, 100 m / min is preferable and 150 m / min is more preferable. On the other hand, as an upper limit of the linear velocity of melt spinning, 500 m / min is preferable and 400 m / min is more preferable. When the linear velocity of melt spinning does not reach the said minimum, there exists a possibility that manufacturing efficiency may be low and carbon fiber may become expensive. On the contrary, when the linear velocity of melt spinning exceeds the said upper limit, spinning will become unstable and manufacturing efficiency will fall, and carbon fiber may also become expensive.

As a minimum of the average diameter of the yarn-shaped object spun in melt spinning, 5 micrometers is preferable and 7 micrometers is more preferable. On the other hand, as an upper limit of the average diameter of the yarn-shaped object spun in melt spinning, 20 micrometers is preferable and 15 micrometers is more preferable. When the average diameter of a yarn is less than the said minimum, there exists a possibility that it may be unable to stably spin. On the contrary, when the average diameter of a yarn body exceeds the said upper limit, there exists a possibility that the flexibility of a yarn body may become inadequate.

<Incompatibility Process>

In the infusible process, the yarn-like body obtained in the melt spinning process is crosslinked and infusified by heating in an atmosphere containing oxygen. As an atmosphere containing oxygen, air is generally used.

As a minimum of incompatibility process temperature, 150 degreeC is preferable and 200 degreeC is more preferable. On the other hand, 300 degreeC is preferable and 280 degreeC is more preferable as an upper limit of an incompatible process temperature. If the incompatibility treatment temperature does not fall below the lower limit, there is a fear that the incompatibility becomes insufficient, or the incompatibility treatment time becomes long, resulting in inefficiency. On the contrary, when the insolubilization treatment temperature exceeds the above upper limit, there is a fear that the yarn-like body melts before oxygen crosslinking.

As a minimum of incompatibility treatment time, 10 minutes are preferable and 20 minutes are more preferable. On the other hand, 120 minutes are preferable and 90 minutes are more preferable as an upper limit of the incompatibilization treatment time. If the incompatibility treatment time is less than the lower limit, there is a fear that the incompatibility becomes insufficient. On the contrary, when the incompatibility treatment time exceeds the above upper limit, there is a fear that the manufacturing cost of the carbon fiber is unnecessarily increased.

Carbonization Process

In a carbonization process, carbon fiber is obtained by heating and carbonizing the yarn-shaped object incompatible in the infusible process.

Specifically, the yarn is charged into an arbitrary heating device such as an electric furnace, and the inside is replaced with a non-oxidizing gas, followed by heating while blowing the non-oxidizing gas into the heating device.

As a minimum of the heat processing temperature in a carbonization process, 700 degreeC is preferable and 800 degreeC is more preferable. On the other hand, as an upper limit of heat processing temperature, 3000 degreeC is preferable and 2800 degreeC is more preferable. If the heat treatment temperature does not reach the lower limit, there is a fear that the carbonization becomes insufficient. On the contrary, when heat processing temperature exceeds the said upper limit, there exists a possibility that manufacturing cost may rise from the viewpoint of the heat resistance improvement of a facility, or fuel consumption.

What is necessary is just to set the heating time in a carbonization process suitably also according to the characteristic calculated | required by a carbon material, Although it does not restrict | limit especially, As heating time, 15 minutes or more and 10 hours or less are preferable. When heating time does not reach the said minimum, there exists a possibility that carbonization may become inadequate. On the contrary, when heating time exceeds the said upper limit, there exists a possibility that the production efficiency of a carbon material may fall.

The non-oxidizing gas is not particularly limited as long as the oxidation of the carbon material is suppressed, but nitrogen gas is preferable from an economic point of view.

[Other Embodiments]

The said embodiment does not limit the structure of this invention. Therefore, based on description and technical common sense of this specification, the said embodiment can abbreviate | omit, substitute, or add the component of each said part, and it should be interpreted that they all belong to the scope of the present invention.

For example, in the production method of the raw material pitch for producing carbon fiber, the ash and the like in the slurry may not be separated in the thermal decomposition product forming step, and the ash and the like may be separated together with the insoluble component in the ashless coal in the next separation step.

In addition, in the manufacturing method of the raw material pitch for carbon fiber manufacture, a heat processing process may be abbreviate | omitted.

Example

Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not interpreted limitedly based on description of this Example.

<Raw material pitch for carbon fiber manufacturing>

As described below, Examples 1 to 6 and Comparative Examples 1 and 2 of raw material pitches for producing carbon fiber having different production conditions were tested and manufactured, and Examples 1 to 6 and Comparative Examples 1 and 2 of these raw material pitches were the same. Carbon fibers were each fabricated by melt spinning, infusible, and carbonizing under conditions.

(Example 1)

As raw material coal, bituminous coal from Australia produced with 6.5 mass% of oxygen-free anhydrous ashless base was used. First, 1 kg of the above-mentioned bituminous coal pulverized to 1 mm or less was mixed with 5 kg of methylnaphthalene, loaded into an autoclave, kept at 400 ° C for 1 hour in a nitrogen atmosphere, and cooled to obtain a thermal decomposition product. Subsequently, 5 kg of methylnaphthalene was further added to this pyrolyzed product, and the soluble component was extracted by stirring for 1 hour at the extraction temperature of 60 degreeC, and the filtrate obtained was distilled under reduced pressure, and the soluble component was isolate | separated. The raw material pitch for carbon fiber manufacture of Example 1 was obtained by heat-processing this soluble component for 1 hour in nitrogen atmosphere of the heat processing temperature of 230 degreeC.

(Examples 2 to 6)

Example 2 was produced under the same conditions as in Example 1 except that the extraction temperature was 80 ° C. Example 3 was produced under the same conditions as in Example 1 except that the extraction temperature was 100 ° C. Example 4 was tested and manufactured on the same conditions as the said Example 1 except having made heat processing temperature into 250 degreeC. Example 5 produced and tested on the conditions similar to Example 1 except having made extraction temperature into 80 degreeC and heat processing temperature into 250 degreeC. Example 6 produced and tested on the conditions similar to Example 1 except having made extraction temperature into 100 degreeC, and heat processing temperature into 250 degreeC.

(Comparative Example 1)

1 kg of the same bituminous coal as in Example 1 was pulverized to 1 mm or less, mixed with 5 kg of methylnaphthalene, loaded into an autoclave, and maintained at 400 ° C. for 1 hour in a nitrogen atmosphere. By heat-processing in atmosphere for 1 hour, the raw material pitch for carbon fiber manufacture of the comparative example 1 was obtained.

(Comparative Example 2)

As a raw material pitch for carbon fiber manufacture of the comparative example 2, the commercially available diameter pitch of 0.9 mass% of oxygen content and 64 mass% of toluene soluble content is prepared, and this is heat-processed in nitrogen atmosphere of 350 degreeC of heat processing temperature for 20 hours, The raw material pitch for carbon fiber manufacture of the comparative example 2 was obtained.

<Component Analysis>

The oxygen content rate of the raw material pitch for carbon fiber manufacture of the said Examples 1-6 and Comparative Examples 1 and 2 was measured based on JIS-M8813 (2004). In addition, the toluene soluble content rate of the raw material pitch for carbon fiber manufacture of Examples 1-6 and Comparative Examples 1 and 2 was measured based on JIS-K2207 (1996).

<Carbon fiber>

In the test production of carbon fibers using the raw material pitch for carbon fiber production of Examples 1 to 6 and Comparative Examples 1 and 2, first, a spinning pitch was filled into a spinning machine having a nozzle having a diameter of 0.2 mm and a length of 0.4 mm, and at 250 ° C. Melt spinning was performed. At this time, the yarn-like body to be radiated was wound up to a drum having a diameter of 100 mm rotating at 600 rpm (line speed about 190 m / min). Subsequently, this thread-shaped object was infusible by heating at 250 degreeC for 1 hour in air. In addition, this insoluble fiber was carbonized at 800 ° C. In addition, since the raw material pitch for carbon fiber manufacture of the comparative example 1 could not melt-spin stably even if it heated to 350 degreeC, carbon fiber was not obtained.

Tensile Strength

The tensile strength of each carbon fiber test-tested using the raw material pitch for carbon fiber manufacture of Examples 1-6 and Comparative Examples 1 and 2 was measured based on JIS-L1013 (2010).

Oxygen content rate, toluene soluble content rate, and yield in anhydrous ashless base from raw material coal (light pitch for comparative example 2), and these of the raw material pitch of carbon fiber manufacture of Examples 1-6 and Comparative Examples 1 and 2, and these are used The tensile strength of the carbon fiber produced by the test was shown in Table 1 below.

Thus, it was confirmed that carbon fiber excellent in comparatively tensile strength can be stably produced by setting the oxygen content of the raw material pitch for carbon fiber production to 1.0% by mass or more and the content of toluene soluble content to 20% by mass or more.

The raw material pitch for carbon fiber manufacture of this invention is used suitably for manufacture of carbon fiber.

S1: pyrolysate forming process
S2: Separation Process
S3: heat treatment process

Claims (3)

Obtained from coal, it is a pitch for producing carbon fiber by melt spinning, the oxygen content is 1.7 mass% or more, the toluene soluble content is 20 mass% or more, and the softening temperature is 150 degreeC or more 280 Raw material pitch for carbon fiber manufacture characterized by the below-mentioned. The raw material pitch for producing carbon fibers according to claim 1, wherein the coal is bituminous coal or sub-bituminous coal. The raw material pitch for carbon fiber manufacture of Claim 1 or 2 which heat-processes the soluble component isolate | separated by the solvent extraction process at the temperature below 300 degreeC from the thermal decomposition product in the solvent of coal.

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