KR101470261B1 - Pitch based carbon fiber and method of producing the same - Google Patents

Abstract

The present invention relates to a method for manufacturing carbon fiber by obtaining pitch having a high softening point from petroleum or coal-based aromatic hydrocarbon materials at a high yield and conducting insolubilizing and carbonizing processes after melt spinning. More particularly, if pitch is manufactured by adding an additive provided by the present invention to aromatic hydrocarbons such as petroleum-based intermediate oil and coal-based residuum, chain extension reaction occurs such that double bond chains in the additive is unwound and the chains extend while substitution reaction between molecules or in molecules with aromatic hydrocarbon materials occurs. Particularly, pitch with a high softening point having uniform molecular weights can be finally obtained as reaction with low-molecular-weight materials occurs predominantly. Also, pitch-based carbon fiber having excellent properties can be manufactured as cyclization and aromatization occur well to reduce the phenomenon of fusion between filaments owing to the structure of the additive when carbon fiber is manufactured by conducting insolubilizing and carbonizing processes after melt spinning using the pitch.

Description

[0001] PITCH-BASED CARBON FIBER AND METHOD OF PRODUCING THE SAME [0002]

The present invention relates to a method for producing a high softening point pitch for a carbon fiber containing a petroleum or coal aromatic hydrocarbon material and an additive, a method for producing a precursor fiber for carbon fiber by melt spinning the pitch, a method for infusing and carbonizing the precursor fiber The present invention relates to a pitch-based carbon fiber produced by the method of the present invention, which can be applied to civil engineering and construction fields such as reinforced construction materials and concrete structure seismic reinforcement, CNG tanks, alternative energy and clean energy fields such as blades for wind power generation, The present invention relates to a pitch-based carbon fiber excellent in physical properties applicable to a variety of industrial fields such as marine development and deep sea oilfield mining, plastic reinforcement use, electric conduction use, super heat resistance application, and a manufacturing method thereof.

Generally, a method of producing carbon fiber is a method of producing carbon fibers by thermally melting polyacrylonitrile, petroleum or coal pitch, phenolic resin or the like, which is a raw material of carbon fiber, dissolving in melt or melt spraying or dissolving in solvent, It is made by making fiber, insolubilizing it, and carbonizing it. In particular, when carbon fibers are produced by carbonizing a high softening point optically isotropic or anisotropic pitch produced from petroleum or coal pitch, there is an advantage that the carbon fiber yield is high and the mechanical and electrical properties of the obtained carbon fiber are good. , Filler for composite materials, insulation, etc., and has advantages such as low cost, high productivity, and simple manufacturing method.

A high softening point pitch of 150 ° C or higher and a softening point of 150 ° C or higher, which is prepared using petroleum heavy oil, aromatic hydrocarbon (for example, naphthalene, methylnaphthalene or anthracene), coal residue (for example, coal tar or coal tar pitch) In general, it is widely used as a precursor of general-purpose carbon fibers, activated carbon fibers, carbon-carbon composites, and carbon materials for anode active materials for lithium ion secondary batteries.

The high softening point pitch is mainly determined by a method of heat treating coal or petroleum residue or heavy oil in an atmosphere of an inert gas, a method of heat treatment by blowing air, a method of heat treatment by adding nitric acid, a reaction additive such as a nitro compound, And a method in which a halogen compound such as chlorine (Cl ₂ ), bromine (Br ₂ ), iodine (I ₂ ), thionyl chloride (SOCl ₂ ), sulfuryl chloride (SO ₂ Cl ₂ ) Followed by heat treatment. However, the manufacturing method of the pitch for carbon fiber has various problems.

A large amount of air is blown at a relatively high temperature of 250 to 380 ° C to remove the hard component, oxidative dehydration reaction between molecules, and induction of crosslinking reaction by binding between aromatic hydrocarbon substances by oxygen in air , There is a method of producing an optically isotropic pitch at a high softening point. However, as in the above process, it takes much time to use air, and some of the substances formed by oxidation of air are unstable and are decomposed during heat treatment, There are disadvantages. Korean Patent Application No. 2006-7018337 discloses a process for producing pitch in coal tar and distillates thereof, which comprises subjecting the mixture to thermal oxidation treatment using air, oxygen, low-oxygen air or a mixture thereof as a reactant, heat-treating the mixture in an inert atmosphere, To prepare precursor pitch for carbon fiber, but it is not enough to obtain a pitch of high softening point.

There is a method in which the coal tar is treated with acetone, the component dissolving in acetone is treated with fuming nitric acid, the nitrification reaction is carried out, and the polymerization is induced while denitrification is carried out at 300 ° C. However, in the nitrification process, non-affinity reaction occurs between the hydrophobic cobalt and the hydrophilic nitric acid, and it is difficult to control the reaction due to the intense denitrification reaction which may occur at a high temperature. Therefore, it is difficult to manufacture uniform pitches. It is not suitable for mass production.

A method of producing a high softening point isotropic pitch by inducing a Diels-Alder reaction using 1,4-benzoquinone as a crosslinking agent in a coal tar pitch (American Carbon Materials Society p 246 to 247, 1995) Has a problem that the yield of the produced pitch is low and the oxygen functional group of the remaining 1,4-benzoquinone is resistant to oxidation in the unfused process.

A method of producing a high softening isotropic pitch using a boron trifluoride - ether (BF ₃ - ether) complex as a polymerization catalyst has been proposed for the naphtha decomposition residue (Korean Fiber Society, 1997, p 395). However, this method has a disadvantage in that it is not suitable for industrial mass production because the cost of the boron trifluoride-ether complex used as the catalyst is very high.

Recently, Korean Patent Application No. 2005-0112510 discloses a method for producing a substrate pitch for producing a carbon / carbon composite material, which comprises subjecting a carbonaceous isotropic pitch to a heat treatment within a range of 450 to 500 占 폚 for 1 hour or less to obtain a spherical anisotropic mesophase content A method of making an anisotropic mesophase pitch having 50 to 75% is mentioned.

In order to produce carbon fiber and carbon material particles by using a high softening point pitch prepared by subjecting the aromatic hydrocarbon material to a heat treatment at a high temperature, it is molded in a manufacturing process such as spinning and particle production and then subjected to a high temperature heat treatment, ≪ / RTI > However, fibers and particles made of pitch and the like are melted when the heat treatment is performed directly at high temperature, and the shape is destroyed. Therefore, it is generally necessary to carry out an immobilization treatment such as oxidation to maintain the shape in the carbonization process. The infusibilization treatment is performed by treating the precursor fibers and particles prepared in a pitch in an oxidizing gas atmosphere (for example, air, carbon dioxide or nitrogen monoxide) or an oxidizing liquid atmosphere (nitric acid aqueous solution or hydrochloric acid aqueous solution) for a long time, , And the oxidizing heat treatment is performed for 1 minute to several days while maintaining the temperature at 100 to 350 ° C in the air in consideration of environmental aspects. In general, the precursor fibers and particles prepared using a pitch having a softening point of 150 ° C or less are required to be subjected to a long heat treatment in such an incompatible treatment, so energy consumption is significant and the carbonization yield is lowered in the carbonization step, There is a problem that the mechanical properties of the carbon material to be produced are lowered and the production cost is increased. In addition, precursor fibers and particles prepared by using pitches having a high softening point may also be unfavorable, and monofilaments and partial fusion between particles may occur in the carbonization process, thereby deteriorating physical properties of the final carbon fiber and carbon particles Therefore, there is a need for advances in techniques that can improve such fusion phenomena.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above problems, and it is an object of the present invention to provide a method of manufacturing a high softening point pitch using an aromatic hydrocarbon material such as petroleum heavy oil and coal residue.

It is still another object of the present invention to provide a method for producing pitch-based carbon fibers in which the phenomenon of melt-spinning a pitch at a high softening point to produce pitch fibers, and inserting and fusing the pitch fibers to melt the monofilaments when the carbon fibers are produced .

In order to attain the above object, in one aspect of the present invention, in order to obtain a high softening point pitch used as a raw material of a precursor fiber for carbon fibers from an aromatic hydrocarbon material such as petroleum heavy oil and coal residue, 1 < / RTI >

[Chemical Formula 1]

In the above formula (1), R is H or a compound having a carbon number of 1 to 4, and X, Y and Z are H or Cl.

According to another aspect of the present invention, there is provided a pitch-based carbon fiber material having improved physical properties, which is improved in fusion between monofilaments by making pitch fibers by using pitch containing the additive and melt- Lt; / RTI >

The effect of the present invention is that when an additive provided in the present invention is added to an aromatic hydrocarbon material such as petroleum heavy oil or coal residue to prepare a pitch, the double bond chain in the additive is loosened and the intermolecular or intramolecular substitution reaction with the aromatic hydrocarbon material Chain extension reaction occurs in which the chain is extended. Especially, the reaction with the low molecular weight substance predominantly occurs, and finally, the aromatic hydrocarbon substance having the similar molecular weight is produced, so that a high softening point pitch having a uniform molecular weight can be obtained at a high yield.

In addition, when carbon fibers are produced through the melt-spinning process using the above-mentioned pitch and then subjected to an infusibilization process or a carbonization process, structural cyclization or aromatization of the additive easily occurs and fusion phenomenon between the filaments is improved, Carbon fiber can be produced.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention. Therefore, the present invention encompasses all changes and modifications that come within the scope of the invention as defined in the appended claims and equivalents thereof.

The present invention is characterized by pitch-based carbon fibers produced by insolubilizing and carbonizing precursor pitch fibers melt-spun from a high softening point pitch.

The pitch may be at least one selected from petroleum pitch, coal pitch or chemical pitch. At this time, an additive represented by the following formula (1) is added to an aromatic hydrocarbon material such as petroleum heavy oil such as naphthalene, methyl naphthalene or anthracene, or an aromatic hydrocarbon material such as coal-based residue such as coal tar or coal tar pitch, And reacting the mixed reaction mixture by heating.

In the above formula (1), R is H or a compound having a carbon number of 1 to 4, and X, Y and Z are H or Cl.

The aromatic hydrocarbon material may be a C10 + oil fraction of petroleum-derived heavy oil or an aromatic hydrocarbon material from which methylnaphthalene has been removed. These materials have a low volatility due to their strong volatilization characteristics, Highly volatile hydrocarbon materials are also characterized by being able to produce high softening point pitches with excellent spinnability at high yield by reacting with the additives represented by formula (I) according to the present invention.

Specific examples of the above formula (1) include 2,6-dibenzidene cyclohexanone, 2,6-dibenzidene-4-methyl cyclohexanone, 2,6-bis (2- chlorobenzylidene) -4 (2,6-bis (dichlorobenzylidene) -4-methylcyclohexanone, 2,6-bis (3-chlorobenzylidene) -4-methylcyclohexanone, 4-tert-butyl-cyclohexanone, 4-tert-butyl-2,6-bis (4-chlorobenzilidene) cyclohexanone and the like can be used .

The additive of Formula 1 may be used in an amount of 0.1 to 20% by weight, preferably 0.1 to 10% by weight, based on the aromatic hydrocarbon material.

The pitch for the carbon fiber produced using the additive may be prepared by stirring a mixture of the aromatic hydrocarbon and the additive of Formula 1 while heating to form a uniform phase and reacting at a higher temperature.

The mixture is stirred at a temperature of 60 to 180 ° C for 0.1 to 2 hours, then heated and further heated at a temperature of 200 to 400 ° C for 1 to 12 hours.

When the mixture is heated to a temperature of less than 60 DEG C in the step of heating to uniformly mix the aromatic hydrocarbon material in the mixture with the additive of formula 1, the additive may not uniformly mix with the aromatic hydrocarbon material, There may be a problem in that it does not occur very well. On the other hand, if the temperature exceeds 180 ° C, there may be a problem that the addition effect is lowered due to local reaction before uniformly mixing.

The heating at 200 to 400 ° C for 1 to 12 hours is a subsequent step for obtaining a pitch having a softening point suitable for uniformizing the molecular weight range of the reaction product after the reaction and for melt spinning. However, when the temperature exceeds 400 ° C., coking may occur due to excessive polymerization.

In the reaction step, the aromatic hydrocarbon material and the additive of the formula (1) are subjected to a chain extension reaction in which the double bond chain is loosened or the chain is extended as a result of intramolecular or intermolecular substitution reaction. Compounds having an aromatic structure form a new bond through a chain extension reaction and become a polymer pitch having a softening point suitable for melt spinning as a form having a large number of aromatic structures under long chains.

After the reaction, unreacted low-molecular substances are removed at a temperature lower than the reaction temperature by at least 50 ° C. for from 0.1 to 2 hours under a reduced pressure of from 5 to 500 mmHg to obtain a pitch for carbon fiber.

The pitch may be heated to a suitable temperature (350 to 500 ° C) in an inert gas atmosphere, and may be manufactured into a pitch having optical anisotropy finally through various processes such as fractionation and the like.

The pitch may then be melt spun and radiated at a rate of from 100 to 2000 m / min at a temperature of from 200 to 400 DEG C, preferably 20 to 60 DEG C higher than the softening point of the pitch. The spinning pitch fibers may be spun in the form of a monofilament or a tuft of filament bundles.

The precursor pitch fiber prepared above is subjected to an intramolecular cyclization and an addition of oxygen to the ring through an incompatibility process to form a stable precursor fiber having an endothermic chloride structure. Such insolubilization of the precursor fibers is a process necessary for obtaining carbonized or graphitized carbon fibers. When the carbonization or graphitization process is carried out in the next step without performing such a process, the precursor fibers are thermally decomposed or fused Lt; / RTI >

The incompatibility can be carried out by a known method such as treatment with a gas stream such as oxygen or a solution treatment with an acidic aqueous solution or the like, but from the viewpoint of productivity, the immobilization under a gas stream is preferable. As the gas component to be used, those selected from oxygen, nitrogen oxides, halogens or sulfurous acid gases may be used singly or in combination from the viewpoint that the precursor fibers can be rapidly infused at a low temperature. Examples of the halogen gas include fluorine gas, chlorine gas, bromine gas, and iodine gas. Of these, bromine gas and iodine gas, particularly iodine gas, are preferable.

As a specific method of the infusibilization process under a gas stream, the temperature is set to 250 to 450 DEG C for 10 hours or less. If the temperature of the infusibilization treatment is lower than 250 ° C, the dechlorination reaction is insufficient. If the temperature is higher than 450 ° C, the dechlorination reaction occurs vigorously. In the skin layer of the precursor pitch fiber and the core layer, Can be pyrolyzed. More preferably at a temperature of 250 to 400 캜 for 5 hours or less and in a desired gas atmosphere.

During the unfusing process, the pitch fibers are stretched while being stretched while being passed through the incombustible oven. At this time, the elongation is preferably 100 to 200%. When the fiber passes through the incombustion oven without being stretched to the pitch fiber in the range of the elongation lower than 100%, defects according to the thick cross section may appear in a state where the diameter of the fiber is relatively large, Fiber can not be obtained. If the elongation is higher than 200%, yarn splicing may occur. Most preferably from 105 to 150%. The tension applied to the fibers can be imparted by varying the speed of the rollers wound around the rollers and the rollers unwinding the pitch fibers.

It is preferable that the oxygen content of the pitch fibers is in the range of 5 to 15% by weight of the whole of the whole process. If the oxygen content in the pitch fibers is less than 5% by weight, crosslinking due to oxygen atoms is insufficient and the fibers may be melted or fused and may adversely affect the physical properties of the carbon fibers. In addition, if the oxygen content in the pitch fiber is more than 15 wt%, excessively insolubilization may increase the probability of occurrence of defects on the fiber surface, and the yield of carbon fiber due to oxidation may become poor, which is not preferable.

The infusibilized pitch fibers can be carbonized in an inert gas atmosphere or graphitized as necessary to produce carbon fibers and graphite fibers. The carbonization process can be performed at a temperature of 800 to 1,500 占 폚 for 1 minute to 2 hours. When carbonizing or graphitizing, the oxygen concentration is preferably 20 ppm or less, more preferably 10 ppm or less.

When carbonization is performed to make carbon fiber, the carbonization may be insufficient, the hexagonal ring surface may not be developed, the process time may become longer and the profitability may be deteriorated. When the temperature is higher than 1500 ° C., Which is converted into graphite fiber rather than the graphite fiber. Most preferably from 1,000 to 1,300 DEG C for 1 to 60 minutes.

Hereinafter, the present invention will be described with reference to the following examples, but the present invention is not limited thereto.

[Example 1]

98% by weight of coal tar as an aromatic hydrocarbon and 2.0% by weight of 2,6-dibenzylidene cyclohexanone (manufactured by TCI) as an additive were added to the reaction vessel and stirred at 100 ° C for 1 hour under a nitrogen atmosphere to obtain a homogeneous mixture After heating, the reaction was further continued at 300 ° C. for 6 hours. After completion of the reaction, unreacted low-molecular substances were removed at 100 ° C. for 30 minutes under reduced pressure of 10 mmHg to obtain a pitch.

The obtained pitch was melt-spun at a spinning speed of 500 holes at 290 DEG C and wound up at a speed of 500 m / min to produce pitch fibers. The pitch fibers that were spun while being rolled on the rollers were subjected to an immobilization treatment in a stabilizing oven having a temperature gradient of 280 to 320 DEG C for 1 hour, and the elongation was 105%. The incompatible fibers were carbonized for 5 minutes in a carbonization furnace at 1200 캜 to produce carbon fibers.

[Example 2]

In Example 1, 97.4% by weight of coal tar and 2% by weight of 2,6-bis (3-chlorobenzylidene) -4-methylcyclohexanone (manufactured by Sigma-Aldrich Co.) as an aromatic hydrocarbon material were used Carbon fiber was produced in the same manner as in Example 1. [

[Comparative Example]

As an aromatic hydrocarbon material, coal tar was heated in air at 300 ° C for 6 hours to react, and unreacted low-molecular substances were removed at 100 ° C for 30 minutes under a reduced pressure of 10 mmHg to obtain a pitch.

Carbon fiber was prepared in the same manner as in Example 1, except that the obtained pitch was melt-spun at 200 占 폚.

The properties of the pitch and carbon fiber produced through the above Examples and Comparative Examples are summarized in Table 1 below.

Softening point
(° C) yield
(%) Shape change after carbonization process
(Standard: 500fila.) The tensile strength
(GPa) Modulus of elasticity
(GPa) Example 1 253 69.0 Fusing yarn 9 or less 1.3 67.6 Example 2 261 73.0 Not more than 5 fused yarns 1.5 85.5 Comparative Example 151 55.3 More than 30 fused yarns 0.7 35.8

As a result of comparing the pitches obtained by the above-mentioned Examples and Comparative Examples, the pitches obtained from Examples 1 and 2 have higher softening points and higher yields than the pitches obtained by the Comparative Examples. These results are due to the effect of the additive provided by the present invention. As a result, the aromatic hydrocarbon and the used additives are reacted in a uniformly mixed state, resulting in a chain extension reaction in which intramolecular or intermolecular substitution reaction occurs, It can be seen that compounds having an aromatic structure form new bonds through a chain extension reaction and become a form having a large number of aromatic structures under long chains, thereby producing a pitch having a high softening point.

In addition, as shown in the examples, when the pitch obtained from the above Examples and Comparative Examples is melt-spinned, and the fibers are incompatible and carbonized, the fibers exhibit improved fusion bonding per 500 filaments, Or aromatization, resulting in reduced structural defects.

Claims (3)

A method for producing a pitch for a carbon fiber containing a petroleum or coal-based aromatic hydrocarbon material and an additive,
Wherein the additive is a compound represented by the general formula (1).
[Chemical Formula 1]

In the above formula (1), R is H or a compound having a carbon number of 1 to 4, and X, Y and Z are H or Cl. The method of claim 1, wherein the additive is used in an amount of 0.1 to 10% by weight based on the aromatic hydrocarbon material. A process for producing carbon fiber, characterized in that the pitch fiber obtained by melt spinning the pitch produced by the method of claim 1 is insolubilized and carbonized to produce the pitch carbon fiber.