KR20150058011A - Manufacturing method of carbon filament using isotropic petroleum pitch and carbon filament therefrom - Google Patents

Abstract

The present invention relates to a carbon long fiber and a method for preparing the same. A high-strength, high-elastic carbon long fiber having maximized mechanical properties can be manufactured by using the method mentioned above. The properties can be used for a carbon composite material requiring high strength and elasticity, and thus the carbon long fiber is expected to replace existing PAN-based and anisotropic pitch-based carbon fibers. The method for manufacturing carbon long fiber using an isotropic petroleum pitch comprises the steps of: (a) preparing an isotropic pitch including selected among a petroleum based heavy oil, a high-boiling residue, an aromatic hydrocarbon single material and a naphtha decomposition process residue or its mixture; (b) preparing a pitch fiber melt-spinning the isotropic pitch; (c) heating the spun pitch fiber to stabilize it; and (d) carbonizing the pitch fiber.

Description

[0001] The present invention relates to a method for producing a carbon fiber having an isotropic petroleum pitch and a carbon fiber prepared from the carbon fiber,

The present invention relates to a process for producing carbon fibers using an isotropic petroleum pitch and a carbon fiber prepared from the process. More specifically, the present invention relates to a method for producing carbon fibers using an isotropic petroleum pitch having superior physical properties compared to conventional isotropic carbon fibers by producing fibers from a basic pitch and an isotropic pitch having a softening point in a specific range, Carbon fiber.

The fuel efficiency of automobiles is also increasingly demanded due to depletion of petroleum resources, price hikes and environmental problems. According to the Working Group report, energy efficiency is expected to increase by more than 600% in 2020 than in the past. The hybridization of the engines has the greatest effect. Improvements in engine efficiency, lighter weight, It is said that there is an effect. In particular, according to the US Department of Energy (DOE), a 10% reduction in vehicle body weight indicates that fuel savings of about 7% are possible.

The use of carbon fiber reinforced plastics has been effective, and has already been used in automobile engine hoods, propeller shafts, and hydrogen tanks, although it can be achieved by using high tensile strength steel and aluminum alloys. . When CFRP is used as the main material of the car body structure, weight reduction of about 50% is possible, and impact energy absorbing performance is improved. Above all, research is actively conducted around the world because it is possible to manufacture the lightest body among the currently available materials.

However, there is a weak point in CFRP because tensile strength is weaker than compression, and interlayer delamination occurs due to impact, resulting in a drastic decrease in compressive strength after impact. Also, it has a disadvantage that it is difficult to apply a lot of manufacturing cost.

In general, the carbon fibers contained in the CFRP can be classified into rayon, PAN, and pitch based on the precursor. Among them, the pitch system includes liquid crystal pitch carbon fiber and isotropic pitch carbon fiber depending on the type of the precursor pitch Can be divided. Among them, isotropic pitch type carbon fibers have a lower price than high performance grades and are called general purpose carbon fibers. They are produced by staple type carbon fibers by melt blown method and are used as high temperature heat insulating materials and activated carbon fibers for filters .

The production of carbon fibers from petroleum, coal tar, or chemical pitches has many advantages, one of which is the high carbon-to-hydrogen ratio of these feedstocks. For example, the theoretical yield of carbon fibers produced from PAN resins is only about 50%, but the theoretical yield of carbon fibers produced from well-purified pitches is up to 90%. However, pitch-based carbon fibers with sufficient tensile strength and modulus that can be used as composites in the aerospace and aerospace industries are manufactured from liquid crystal pitches. In order to produce liquid crystal pitches from petroleum, coal tar, or chemical pitches, pretreatment, hydrogenated quinoline insoluble matter And thus the production cost is increased and the cost is high.

Korean Patent Laid-Open Nos. 10-2013-0059174 and 1996-144131 disclose isotropic pitches for producing isotropic pitch-based carbon fibers or carbon fibers. 10-2013-0059174 discloses a method for producing a precursor for carbon fiber having a high softening point, but it has a problem that a heating temperature of the pitch is 360 ° C or higher, so that insoluble solid content is generated or mesophase is produced, There is a disadvantage that physical properties are deteriorated.

Japanese Patent Application Laid-Open No. 1996-144131 proposes an isotropic pitch for producing carbon fibers having a specific range of molecular weight. However, the softening point of the pitch is as low as 180 to 200 占 폚 and the tensile strength of the carbon fiber produced from the pitch is 89.3 kg / (About 0.893 GPa), it shows low physical properties to be used for CFRP for the purpose of steel plates for automobiles.

Thus, there is a strong demand for the development of carbon fiber fabrication technology using an isotropic pitch capable of mass production at a low production cost while satisfying all necessary properties for CFRP.

Korean Patent Publication No. 10-2013-0059174 (June 05, 2013) Japanese Patent Application Laid-Open No. 1996-144131 (June 04, 1996)

The inventors of the present invention have conducted extensive studies to overcome the above problems, and as a result, they have found a process for producing carbon fiber including a specific crystal structure in which an asphaltene type carbon layer is laminated and a carbon fiber prepared from the carbon fiber .

The present invention provides a carbon fiber including a specific crystal structure using an isotropic petroleum pitch, a chemical system pitch and a coal pitch, and a process for producing the carbon fiber.

The present invention is a condensation-average diameter (L _c), the average distance condensed ring compound layers of the layered structure (d _m), the condensed average diameter (L _a) of the ring compound layer of the multilayer structure wherein the aromatic ring compound layer is formed, the condensed (M) of the condensed aromatic ring compound layers contained in the laminated structure which can be represented by the average distance d _? Between the aliphatic chains connected to the aromatic ring compound and (L _c / d _m ) +1 Containing carbonaceous fibers.

The present invention relates to a process for producing an isotropic pitch from a raw material comprising one or a mixture selected from petroleum heavy oils, high boiling point residues, coal tar oils, aromatic hydrocarbon monomers and naphtha cracking residues, And carbonizing the pitch fiber. The present invention also provides a method for producing carbon fiber using isotropic petroleum pitch.

The present invention provides a method for producing carbon fiber having excellent mechanical properties while minimizing the generation of insoluble solids and mesophase in the pitch and minimizing energy consumption by a low temperature carbonization process, Can be applied to carbon fiber reinforced plastic (CFRP) as high strength and high elasticity carbon fiber, and it is expected to be able to replace the existing PAN and anisotropic pitch type carbon fibers.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a flow chart showing the process for producing carbon fiber of the present invention. Fig.
Fig. 2 shows the molecular weight distribution of naphtha-decomposed residual oil in the production process as measured by TOF-MS and shows that the width of the peak is very narrow and the molecular weight is uniform.
FIG. 3 is a SEM photograph of the surface of a carbon fiber prepared according to an embodiment of the present invention.
Fig. 4 shows the results of X-ray diffraction analysis of carbon fibers. (a) is a result of analyzing carbon fibers prepared by the basic method of halogenation, (b) is a result of analyzing carbon fibers prepared by a basic polymerization method using a heat polymerization method, (c) (d) is the result of anisotropic pitch-based carbon fiber analysis.
FIG. 5 is a diagram showing the crystal structure analysis of carbon fiber by X-ray diffraction analysis. FIG. L _a is the average diameter of the fused ring compound layer, L _c is a condensed aromatic ring compound layer having an average diameter of the multilayer structure to form, d _m is a fused interlayer distance ring compound of the layered structure, d _γ is condensed aromatic And M is an average number of the condensed aromatic ring compound layers contained in the laminated structure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings, in which the carbon fiber is produced using the isotropic petroleum pitch according to the present invention and the carbon fiber prepared from the carbon fiber. The following drawings are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the following drawings, but may be embodied in other forms, and the following drawings may be exaggerated in order to clarify the spirit of the present invention. Also, throughout the specification, like reference numerals designate like elements.

Hereinafter, the technical and scientific terms used herein will be understood by those skilled in the art without departing from the scope of the present invention. Descriptions of known functions and configurations that may be unnecessarily blurred may be omitted.

The present invention relates to a carbon fiber and a method for producing the same, and provides a carbon fiber including a structure in which a condensed aromatic ring compound layer forms a laminated structure and a condensed aromatic ring compound linked by an aliphatic chain, and a process for producing the same.

The condensed aromatic ring compound layer is preferably a layer made of a compound in which aromatic rings are condensed or a compound layer in which a condensed aromatic compound is contained, and these may be connected by an aliphatic chain. Such a structure may form a carbon layer in the form of Asphaltene, which is a polymer having a chemical structure in which a condensed ring or a condensed aromatic ring containing a plurality of aromatic rings is linked by an aliphatic chain of an outer group around the aromatic ring.

The carbon fiber of the present invention is maximized in mechanical properties of high strength and high elasticity and can be applied to carbon fiber reinforced plastic (CFRP), and thus can be used as a substitute for conventional PAN-based, anisotropic pitch-based carbon fibers .

First, the carbon fiber of the present invention will be described in detail.

The carbon fiber of the present invention exhibits a gamma band of an aliphatic chain at 16 < 2 < 19 in X-ray diffraction (XRD) (002) plane band, and a condensed aromatic ring compound having a band of (10) at 43 < 2 < 48 is bonded at an isotropic pitch including an aliphatic chain.

The structure is the average diameter (L _c) of the multilayer structure to form the layer condensed ring compound, a condensed aromatic average diameter of the cyclic compound layer (L _a), the average distance condensed ring compound layers of the layered structure (d _m) and ( (M) of the condensed aromatic ring compound layers contained in the laminated structure which can be represented by the following formula: L _c / d _m ) +1, and the condensed aromatic ring compounds are linked by an aliphatic chain, The average distance d _? Between linked aliphatic chains can also be added to account for the structure. The laminated structure formed by the condensed aromatic ring compound layer may be expressed as a nano cluster. Each measurement result of the crystal structure can be represented by Bragg equation and Scherrer equation as a result of XRD measurement.

Specifically, the average diameter (L _c) of a laminated structure in which a condensed aromatic ring compound layer formed is 30 to 60, preferably an average diameter (L _a) of and 30 to 50, condensed ring compound layer is 10 to 50, Preferably in the range of 15 to 40, and in the laminated structure, the average distance d _m between the condensed aromatic ring compounds is 3.50 to 4.20, preferably 3.70 to 4.00, and the average distance d _? Between the aliphatic chains connected to the condensed aromatic compound is 4.00 to 6.00, preferably 4.50 to 5.50, and the average number (M) of the condensed aromatic ring compound layers contained in the laminated structure is 9.0 to 18.0, preferably 9.5 to 14.5.

The carbon fiber produced by the present invention must have a high-strength and high-elasticity physical properties in order to satisfy the above-mentioned range. Outside of the above range, the tensile strength is remarkably decreased, the elongation is lowered or excessively increased, and the elastic modulus is not good.

The carbon fiber of the present invention can be represented as follows according to the result of crystal structure analysis.

(1) to (4) in which the condensed aromatic ring compound is linked by an aliphatic chain, the carbon fiber of the present invention exhibits a (002) plane band at a diffraction angle of 19 <2? <26 in X-ray diffraction analysis (XRD) Lt; / RTI &gt; is a carbon fiber.

30? L _a ? 60? A (1)

10? L _c ? 50? (2)

_{3.50 ≤ d m ≤ 4.20Å --- (} 3)

9.0 ≤ M ? 18.0 - (4)

According to an embodiment of the present invention, when the above formulas (1), (2), and (3) are satisfied and the condition (4) is not satisfied, the tensile strength of the carbon fiber is remarkably decreased or the elongation is decreased. According to another embodiment of the present invention, when the above expressions (2) and (3) are satisfied, the tensile strength is remarkably decreased or the elongation percentage is excessively increased and the elastic modulus is lowered. According to still another embodiment of the present invention, the tensile strength and the elongation percentage are significantly reduced unless the formulas (1) and (2) are satisfied and the conditions (3) and (4) are not satisfied.

The average length (d _? ) Between the aliphatic chains connected to the condensed aromatic ring compound in the structure contained in the carbonaceous fibers may further be expressed to indicate the carbon fiber.

Carbon filaments having better physical properties, in which the formulas (1) to (4) of the present invention and the average distance (d _? ) Between the aliphatic chains connected to the condensed aromatic ring compound are more preferable ranges, respectively, can be produced.

The carbon fiber of the present invention is a high strength, high-elastic carbon fiber having a diameter of 1 to 20 μm, a tensile strength of at least 1.5 GPa and an elongation of 2% or more.

Next, the method for producing carbon fiber of the present invention will be described in detail.

First, a method for producing a carbon fiber using an isotropic petroleum pitch according to an embodiment of the present invention includes:

a) preparing an isotropic pitch from a raw material comprising one or a mixture selected from petroleum heavy oils, high boiling point residues and naphtha cracking process residues;

b) a pitch fiber manufacturing step of melt spinning the isotropic pitch;

c) stabilizing the spun fibers by heat treatment; And

d) carbonizing said pitch fibers;

. &Lt; / RTI &gt;

The raw materials may include aromatic hydrocarbon single substances such as petroleum heavy oil, high boiling point residual oil, coal tar oil, naphthalene, methylnaphthalene or anthracene, or naphtha cracking residues. Pyrolysis heavy residues having a broad molecular weight distribution can also be used.

More specifically, it may include pyrolysis fuel oil (PFO), which is a kind of naphtha-decomposed residual oil. The PFO is produced at the bottom of the naphtha cracking center (NCC) and is highly oriented and can be used as a raw material of the present invention because the content of the resin is abundant.

The pyrolysis fuel oil is produced on the bottom of the naphtha cracking process and may contain various aromatic hydrocarbons. Specific examples of the aromatic hydrocarbons include ethylbenzene, 1-ethenyl-3-methyl benzene, indene, 1-ethyl- ethyl-3-methyl benzene, 1-methylethylbenzene, 2-ethyl-1,3-dimethyl benzene, propylbenzene, 1- Methyl-4- (2-propenyl) benzene, 1,1a, 6,6a-tetrahydro-cyclopropane (1,1a, 6,6a 2-ethyl-1H-indene, 1-methyl-1H-indene, 4,7-dimethyl- 1-methyl-9H-fluorene, 1, 7-dimethyl naphthalene, 2-methyl- 2-methylindene, 4,4'-dimethyl biphenyl, naphthalene, 4-methyl-1,1'-biphenyl, -biphenyl, anthracene, 2-methylnaphthalene and 1-methylnaphthalene. This can be.

The raw material according to one embodiment of the present invention may further include a high boiling point oil. The high boiling point oil according to one embodiment of the present invention refers to a component having a high boiling point and a high carbon number among the components obtained by fractional distillation of crude oil and is mainly composed of a hard or heavy aromatic naphtha having 5 or more carbon atoms, .

High boiling oil fractions, more specifically, may include fractions containing 9 carbon atoms. Specific examples thereof include styrene, vinyltoluene, indene, alpha methylstyrene, and benzene / toluene / xylene (BTX).

As the oil having 9 carbon atoms, indene may be preferably included. Indene is bonded to the side chain of the aromatic component in the raw material, and it is possible to prevent the tendency of being dehydrated and etherified as the side chain of the aromatic component is oxidized in the stabilization step after melt spinning, thereby contributing to lowering the carbonization temperature and time .

The high boiling point oil is preferably contained in an amount of 5 to 15% by weight based on 100% by weight of the whole raw material. When the amount of the high boiling point oil is less than 5% by weight, the effect thereof may be insignificant. May not be clear.

The aromaticity fa of the raw material may be 0.7 to 0.9. If the degree of aromaticization is less than 0.7, the hydrocarbon yield may be lowered. There is no particular limitation on the case where the aromaticity is higher than 0.9, but when the aromaticity is 0.9 or more, the effect of the series of pitch synthesis methods disclosed in the present invention may not be significant.

The molecular weight of the raw material may have a distribution of 75 to 350, preferably 100 to 250.

The step (a) of the method for producing a carbon fiber using the isotropic petroleum pitch of the present invention is, specifically,

a1) a pretreatment step of heat-treating and fractionating the raw material;

a2) a filtration step of removing the solid matter from the pretreated raw material;

a3) preparing a basic pitch with the filtered raw material; And

a4) heating the basic pitch to produce an isotropic pitch;

. &Lt; / RTI &gt;

In the step a1), the pretreatment may include a heating and a fractionation step. In the step a1), a step of removing a low molecular substance which is less likely to form an oligomer by a polymerization reaction is carried out. At the same time, The aim of the present invention is to convert a compound into a more stable and effective compound for producing an isotropic pitch.

The pretreatment may be carried out at atmospheric distillation at a temperature of 130 to 240 ° C, preferably 150 to 230 ° C, more preferably 190 to 220 ° C until no volatile matter is generated. In the pretreatment step, the heating temperature may affect the physical properties of the basic pitch and the isotropic pitch, such as the composition ratio of the raw materials and the degree of aromatization, and furthermore, the mechanical properties of the carbon fiber. Also, the pretreatment step can proceed under atmospheric pressure, but can proceed under reduced pressure. At this time, the pretreatment process can be carried out at a lower temperature through the depressurization, and the pressure and the temperature can be freely adjusted within the range of obtaining the same effect as the normal pressure.

a2) The filtration step is a step of removing the solid matter, and these solid matter may be a solid residue containing impurities such as metal, sulfur, nitrogen and the like, acting as a cracker in the structure of the carbon fiber, have.

The filtration step can be carried out by a method commonly used in the art, for example, filtration, centrifugation, sedimentation, adsorption, extraction and the like.

The filtration step may be carried out after the polymerization of the basic pitch, which is an isotropic pitch intermediate, and in some cases, may be carried out both after the pretreatment step and after the basic pitch polymerization step. That is, the step (a1) may be carried out after the step (a1) and the step (a3), respectively.

a3) In the step of producing a basic pitch, a raw material having been subjected to a filtration step is reacted simultaneously with heating to produce a basic pitch having a high softening point without generating a mesophase, and can be carried out by a halogenation method or a thermal polymerization method.

The halogenation method can be carried out by adding a halogen compound and a radical initiator and then heating. Preferably, a radical initiator is added and then a halogen compound is added and mixed.

The halogen compound is selected from the group consisting of chlorine (Cl ₂ ), thionyl chloride (SOCl ₂ ), sulfuryl chloride (SO ₂ Cl ₂ ), bromine (Br ₂ ), iodine (I ₂ ) Can be used.

The radical initiator may be selected from the group consisting of benzoyl peroxide, di-t-butyl hydroperoxide,

An organic peroxide such as acetyl peroxide or the like and an azo compound such as azobisisobutyronitrile (AIBN;?,? '- Azobisisobutyronitrile), azobismethyl isobutyrate , Or a mixture of two or more thereof.

The radical initiator may be added in an amount of 1 to 30 parts by weight based on 100 parts by weight of the halogen compound, but more preferably 5 to 20 parts by weight.

In the halogenation method, the halogenation reaction is carried out at 100 to 120 ° C for 0.5 to 2 hours to replace the hydrogen in the aromatic alkyl group with halogen, and the polymerization can be carried out at 300 to 330 ° C for 2 to 4 hours by dehalogenation. Further, the dehalogenation reaction is a subsequent step, and it is possible to further increase the purity of the basic pitch produced by decomposing the halogen compound and the radical initiator that may remain in the basic pitch after the reaction. Particularly, in the dehalogenation reaction, it is preferable that the reaction temperature does not exceed 330 ° C. When the temperature exceeds 330 ° C., decomposition of the halogen compound and radical initiator occurs actively, but anisotropy or coking of the basic pitch due to excessive polymerization proceeds, The mechanical properties of the fiber are greatly deteriorated.

The basic pitch produced by the halogenation method may have a softening point of 70 to 130 캜, preferably 115 to 125 캜.

The thermal polymerization may be carried out at 350 to 380 DEG C for 0.1 to 2 hours. The distillation process can proceed in an inert gas atmosphere during the process and can proceed by collecting gaseous by-products generated during nitrogen and poly-condensation. Also, in the thermal polymerization method, it is preferable that the reaction temperature does not exceed 380 ° C like the halogenation method. When the reaction temperature exceeds 380 ° C, an excessive amount of mesophases exceeding the range of the uniform anisotropic pitch, Or coking may proceed to produce non-uniform carbon fibers.

The basic pitch produced by the heat polymerization method may have a softening point of from 85 to 140 캜, preferably from 115 to 125 캜.

The physical properties of the basic pitch can be controlled according to the convenience of the constitution in the process of manufacturing the isotropic pitch. For example, when a process is configured to smooth the flow of fluid continuously flowing from step (c) to step (d), the condensed aromatic ring compound in the basic pitch prepared in step (c) May further include a compound having a low boiling point within a range that does not significantly affect the absolute amount of the oligomer to which the compound is bonded. This effect can be obtained when step (c) is carried out under pressure, wherein the softening point of the basic pitch does not affect the physical properties, molecular structure and laminate structure of the finally produced isotropic pitch And can be freely adjusted within a range that is not limited.

The isotropic pitch preparation step can be carried out by conventional thin film distillation methods, which has the advantage that it does not require an additional process to inhibit mesophase formation and to remove insoluble solids. In addition, the step of manufacturing an isotropic pitch according to an embodiment of the present invention can cope with changes in composition and state of an isotropic pitch produced by a multi-stage thin film distillation apparatus.

The isotropic pitch production step may be carried out by heating at 300 to 350 DEG C for 0.1 to 1 hour in a vacuum atmosphere. Particularly when the heating temperature exceeds 350 ° C, it is preferable to follow the heating temperature and the heating time because meso phase is partially generated and insoluble carbon solid content can be generated by continuous heating.

According to one embodiment of the present invention, the isotropic pitch may have a softening point of 255 to 275 ° C, preferably 260 to 270 ° C. The isotropic pitch average molecular weight (Mw) of the present invention may be 1500 to 3000, preferably 1700 to 2850. [ The average molecular weight and softening point of the isotropic pitch may greatly affect the physical properties of the carbon fiber to be produced, so it is desirable to adhere to the manufacturing process conditions.

The pitch fibers may be produced by melt spinning under a nitrogen atmosphere at a temperature of 300 to 320 DEG C, a pressure of 0.01 to 10 kgf / cm &lt; ² &gt;, and a coiling speed of 500 to 1,500 rpm.

More preferably at a pitch fiber production step may be 0.1 to ² ㎏f / ㎝ 2. However, in case of spinning pressure, the spinning pressure of the present invention is not limited to this, since the spinning pressure may vary depending on the number of spinneret and spinneret packs, the diameter of spinneret, length of spinneret, viscosity and temperature of spinning solution, For example, it may be 100 kgf / cm ² or more on a commercial scale.

The stabilization step is a step in which the oxidation stabilization and thermal stabilization of the radially isotropic pitch fiber are simultaneously proceeded, and the ladder structure is formed by controlling the contraction and expansion, and the ladder structure is provided, Can be stable.

In the stabilization step, the step may be carried out at 180 to 300 ° C for 1 to 5 hours in a batch mode, wherein the temperature increase rate may be 1 to 5 ° C / min. In the continuous mode, the residence time can be from 1 to 10 hours. The gas atmosphere used as the oxidizing agent is not particularly limited and can be carried out in a normal air atmosphere and the supply rate and the like are not limited. However, in the case of using oxygen diluted with a gas used as an oxidizing agent, It may be between 1 and 20% of the volume.

The carbonization step induces an intermolecular reaction by a high temperature heat treatment to promote cross-linking between the ladder-structured polymers, so that a more ordered graphite structure is produced, and high strength carbonaceous fibers can be produced.

The carbonization step may be carried out in an inert gas atmosphere at 700 to 1,500 DEG C for 0.05 to 2 hours. In the case of the batch type, the temperature raising rate may be 1 to 5 占 폚 / min. In the case of the continuous type, the residence time may be 0.05 to 2 hours. However, the amount of the inert gas to be injected in the carbonization step is not limited and can be freely controlled within a range that does not impair the physical properties of the carbon fiber to be produced.

In the case of ordinary carbon fibers, the process proceeds at a temperature of 1,700 ° C or higher, and fibers are produced through several carbonization processes. In contrast, the carbonization step of the present invention can proceed at a temperature lower than that of the carbonization step for producing carbon fibers, has a short carbonization progress time, and can reduce manufacturing costs. The stabilization and carbonization step can be carried out using a conventional apparatus. For example, after the pitch fiber is charged into the tubular electric furnace, air or an inert gas is injected into the tubular electric furnace, and heating can proceed.

The carbon fiber may have a fiber diameter of 1 to 20 탆, a tensile strength of 1.5 GPa or more, and an elongation of 2% or more although it may vary depending on the spinning conditions. In particular, the carbonaceous fibers according to the present invention can have a tensile strength of 1.5 GPa or more, more particularly 1.5 to 3.5 GPa. If the tensile strength is less than 1.5 GPa, the physical properties required in the carbon fiber-reinforced plastic field of the present invention are not satisfied. If the tensile strength is more than 3.5 GPa, it takes a long time to perform the process, Resulting in increased production costs. However, the tensile strength, fiber diameter, and elongation percentage of the carbon fiber may have physical properties in the above range depending on the kind of raw material, composition ratio, heat treatment temperature, basic pitch production method, softening point of pitch, have.

According to the production method of the present invention, it is possible to provide a carbon fiber having a tensile strength of 1.5 GPa or more and an elongation of 2% or more while maintaining the structure of an isotropic pitch including an asphaltene structure. Such a structure can be carbonized at a low temperature of 700 to 1500 ° C or less in the carbonization step, and more specifically, can be minimized in the carbonization process due to a low carbonization temperature of 800 ° C to 1200 ° C or less.

It can be applied to carbon fiber reinforced plastic (CFRP) which requires high strength because tensile strength is 1.5 GPa or more. Its excellent properties can replace CFRP including existing PAN (polyacrylonitrile) carbon fiber. It seems to be.

Hereinafter, the method for producing carbon fiber using the isotropic petroleum pitch according to the present invention and the carbon fiber prepared from the method will be described in more detail with reference to Examples and Comparative Examples. It is to be understood, however, that the following examples and comparative examples are only illustrative of the present invention in order to facilitate understanding or practice of the present invention, and the present invention is not limited to the examples and the comparative examples.

The measurement methods of physical properties measured through Examples and Comparative Examples are as follows.

How to measure property

1. Carbon and hydrogen atomic ratio (H / C)

Analysis with CHNS element analyzer

2. The degree of aromatization (fa)

Analysis by &lt; ¹³ &gt; C NMR (ASTM D5292)

3. Composition of raw materials

   2D-GC analysis

4. Viscosity (Pa · s)

Viscosity is measured by TMA (Thermo Mechanical Analyzer)

5. Softening Point (℃)

The softening point is measured by TMA (Thermo Mechanical Analyzer).

6. Yield

The yield was calculated by the weight of the final pitch obtained relative to the weight of the naphtha cracked residual oil added.

7. Mechanical properties

In order to calculate the tensile strength (GPa) and elongation (%), a stress-strain curve was measured with a universal test machine (UTM) equipped with a 2N load cell for a sample of carbon fiber. The tensile strength was measured by an electron microscope &Lt; / RTI &gt; was calculated from the diameter of the fibers analyzed by the &lt;

8. Molecular composition of pitch

The molecular composition of the pitch was analyzed by GC-AED. The molecular weight distribution was measured by GPC and the average molecular weight was determined from the results.

9. X-ray diffraction analysis

The X-ray diffractometer used for the analysis of the molecular structure of the isotropic pitch was a Cu cathode. The K-alpha ₁ wavelength was 1.540598, the voltage of the X-ray generator was 40 KV, and the tube current was 30 mA.

10. TOF-MS analysis

TOF-MS from JEOL was used to analyze the molecular structure. The laser source was analyzed using Nd: YAG, laser intensity 50%, mass range 10 ~ 3,000, and spiral measurement mode.

<Examples 1 to 4> and <Comparative Examples 1 to 3> Production of Carbon Fiber Yarn by Halogenation in Basic Pitch Making Step

Naphtha Cracker Bottom Oil (NCBO) as shown in Tables 1 to 3 was prepared as a raw material.

Carbon (C, wt%) Hydrogen (H, wt%) Nitrogen (N,% by weight) Sulfur (S, wt%) H / C (atomic ratio) 92.48 7.32 0.10 0.13 0.95

Aliphatic carbide (%) Aromatic carbide (%) The degree of aromaticization (fa) Methyl carbon
(CH3, Ar-CH3) Methylene carbon
(naphthalene) Unsubstituted carbon
(Ar-H) Quaternary carbon Substituted carbon
(Ar-H) 5.85 16.86 49.70 12.38 15.21 0.74

NCBO compound composition content(%) Saturated carbon compounds 1.8 Compounds containing one aromatic ring 51.8 Compounds containing two aromatic rings 43.1 Compounds containing three aromatic rings 3.3 Compounds containing four or more aromatic rings 0 total 100

In Examples 1 to 4, the prepared NCBO was subjected to pre-treatment at 190, 200, 210 and 220 ° C respectively, at 120 ° C for Comparative Example 2 and at 250 ° C for Comparative Example 3, The material was removed. Comparative Example 1 removed the solid matter through filtration without performing the pretreatment step.

After the filtration step, 20 parts by weight of bromine was added to 100 parts by weight of the raw material produced in the intermediate stage. After the bromination reaction was carried out at 110 ° C for 1 hour, the bromination reaction was further carried out at 320 ° C for 3 hours to prepare a basic pitch. The softening point and yield were measured after the basic pitch manufacturing process was finished, and Table 4 shows the measurement results.

Pretreatment temperature (캜) Softening point (℃) Yield (% by weight) Comparative Example 1 - 100 51.3 Comparative Example 2 120 100 50.2 Example 1 190 120 51.2 Example 2 200 130 49.8 Example 3 210 130 57.6 Example 4 220 70 66.9 Comparative Example 3 250 125 68.9

The prepared basic pitch was put into a thin film evaporator, and isotropic pitch was prepared by heating the basic pitch in a vacuum atmosphere at 340 캜 for 30 minutes. After the completion of the process, the softening point, viscosity, and average molecular weight of the isotropic pitch were measured and are shown in Table 5 below.

Pretreatment temperature (캜) Softening point (℃) Viscosity (Pas) Average molecular weight (Mw) Comparative Example 1 - 265 353 1250 Comparative Example 2 120 260 342 1300 Example 1 190 260 320 1900 Example 2 200 265 240 2300 Example 3 210 270 345 2550 Example 4 220 265 480 2800 Comparative Example 3 250 275 365 2900

The isotropic pitch was injected into a cylindrical container, and a pressure of 0.8 kgf / cm &lt; ² &gt; was applied in a nitrogen atmosphere. At this time, the diameter of the winding machine was 150 mm, and the winding speed was 700 rpm.

After the spinning pitch fibers were charged into the tubular electric furnace, air was supplied at a flow rate of 150 ml / min. The temperature was further raised at a rate of 1 占 폚 / min, reached 290 占 폚 and maintained for 1 hour.

The stabilized pitch fiber was injected at a rate of 150 ml / min and simultaneously heated to a temperature of 5 ° C / min. After reaching 800 ° C, the pitch fiber was maintained for 0.5 hour to produce carbon fiber.

The structure of the prepared carbon filaments was analyzed using an X-ray diffractometer. The XRD analysis showed that the γ-band of the aliphatic chain at 16 <2θ <19, the γ-band of the aliphatic chain at 19 <2θ < (002) plane in the laminated structure of the cyclic compound, and (10) plane band at 43 < 2 < As a result of X-ray diffraction analysis, several condensed aromatic ring compound layers were observed overlapping at different diffraction angles in each of Examples and Comparative Examples. As a result of the analysis of the carbon fiber structure from XRD, as shown in FIG. 5, the asphaltene-like structure in which the condensed aromatic ring compound containing 4 to 13 aromatic rings was connected by an aliphatic chain was laminated. The average values of the respective values shown in FIG. 5 are shown in Table 6.

The tensile strength, diameter and elongation of the carbon fiber were measured.

Table 6 shows the results of analyzing the physical properties and structure of the produced carbon fiber.

Tensile Strength (GPa) Diameter (탆) Elongation (%) L _c L _a d _m d _? M Comparative Example 1 1.3 8.71 3.2 28 15 3.82 5.32 8.3 Comparative Example 2 1.1 8.2 3.1 27 15 3.79 5.34 8.1 Example 1 1.8 6.85 2.4 33 17 3.82 5.43 9.6 Example 2 1.9 4.30 2.4 38 36 3.72 4.98 11.2 Example 3 1.6 11.40 2.7 43 31 3.95 5.12 11.9 Example 4 1.5 8.15 2.1 46 34 3.87 5.37 12.9 Comparative Example 3 1.0 7.60 1.9 53 42 14.9 3.82 5.2

- L _a (A) : Average diameter of the condensed aromatic ring compound layer

_- L _C (Å): average diameter of the laminated structure formed by the condensed aromatic ring compound layer

- d _m (A): average distance between condensed aromatic ring compounds in the laminated structure

- d _γ (Å): average distance between the aliphatic chains connected to the condensed aromatic ring compound

- M: the average number of condensed aromatic ring compound layers included in the laminated structure (= (L _c / d _m ) + 1)

&Lt; Examples 5 to 8 > and < Comparative Examples 4 to 6 > Production of carbon filament using a heat polymerization method in the step of producing basic pitch

The same NCBO as those of Examples 1 to 4 and Comparative Examples 1 to 3 was prepared.

In Examples 5 to 8, the prepared NCBO was subjected to pre-treatment at 190, 200, 210 and 220 ° C, respectively, at 120 ° C for Comparative Example 5 and 250 ° C for Comparative Example 6, The material was removed. In Comparative Example 4, the solid matter was removed by filtration without performing the pretreatment step.

After the filtration step, 100 parts by weight of the raw material produced in the intermediate stage was charged into a metal container and heated at 370 DEG C for 0.5 hour to produce a basic pitch. The softening point and yield were measured after the basic pitch manufacturing process was finished, and Table 7 shows the measurement results.

Pretreatment temperature (캜) Softening point (℃) Yield (% by weight) Comparative Example 4 - 100 32.0 Comparative Example 5 120 105 34.2 Example 5 190 120 40.5 Example 6 200 140 43.3 Example 7 210 120 40.4 Example 8 220 85 48.9 Comparative Example 6 250 130 52.3

The prepared basic pitch was put into a thin film evaporator, and isotropic pitch was prepared by heating the basic pitch in a vacuum atmosphere at 340 캜 for 30 minutes. After the end of the process, the softening point, viscosity and average molecular weight of the isotropic pitch were measured and are shown in Table 8 below.

Pretreatment temperature (캜) Softening point (℃) Viscosity (Pas) Average molecular weight (Mw) Comparative Example 4 - 260 375 1350 Comparative Example 5 120 263 384 1300 Example 5 190 265 411 1750 Example 6 200 260 342 2200 Example 7 210 265 353 2350 Example 8 220 260 360 2500 Comparative Example 6 250 270 445 2950

The isotropic pitch was injected into a cylindrical container, and a pressure of 0.8 kgf / cm &lt; ² &gt; was applied in a nitrogen atmosphere. At this time, the diameter of the winding machine was 150 mm, and the winding speed was 700 rpm.

In the stabilization step, the spinning pitch fibers were charged into the tubular electric furnace, and air was supplied at a flow rate of 150 ml / min. The temperature was further raised at a rate of 1 占 폚 / min, reached 290 占 폚 and maintained for 1 hour.

The stabilized pitch fiber was injected at a rate of 150 ml / min of nitrogen and heated at a rate of 5 ° C / min, reached 800 ° C, and maintained for 0.5 hour to produce carbon filament.

The structure of the prepared carbon filaments was analyzed using an X-ray diffractometer. The XRD analysis showed that the γ-band of the aliphatic chain at 16 <2θ <19, the γ-band of the aliphatic chain at 19 <2θ < (002) plane in the laminated structure of the cyclic compound, and (10) plane band at 43 < 2 < As a result of X-ray diffraction analysis, several condensed aromatic cyclic compound layers were observed to overlap each other at different diffraction angles in each of Examples and Comparative Examples. As a result of analyzing the carbon fiber structure from XRD, 4 to 13 aromatic A condensed aromatic ring compound containing a ring is linked with an aliphatic chain to form a layered asphalt-like structure. The average values of the respective values shown in FIG. 5 are shown in Table 9.

The tensile strength, diameter and elongation of the carbon fiber were measured.

Table 9 shows the results of analyzing the physical properties and structure of the produced carbon fiber.

Tensile Strength (GPa) Diameter (탆) Elongation (%) L _c L _a d _m d _? M Comparative Example 4 0.7 7.40 2.5 29 19 3.86 4.79 8.5 Comparative Example 5 0.9 7.80 2.5 30 19 3.82 5.44 8.9 Example 5 2.0 8.10 2.3 37 21 3.89 4.92 10.5 Example 6 1.7 7.30 2.3 43 27 3.95 5.12 11.9 Example 7 1.6 6.80 2.9 46 35 3.91 4.87 12.8 Example 8 1.5 7.10 2.1 49 39 3.84 5.43 13.8 Comparative Example 6 0.9 8.70 1.5 54 45 15.4 3.74 5.2

- L _a (A) : Average diameter of the condensed aromatic ring compound layer

_- L _C (Å): average diameter of the laminated structure formed by the condensed aromatic ring compound layer

- d _m (A): average distance between condensed aromatic ring compounds in the laminated structure

- d _γ (Å): average distance between the aliphatic chains connected to the condensed aromatic ring compound

- M: the average number of condensed aromatic ring compound layers included in the laminated structure (= (L _c / d _m ) + 1)

Manufactured Carbon-fiber  Analysis of physical properties and structure

As a result of XRD analysis of the structure of the prepared carbon fiber, the carbon fibers prepared by the halogenation method and the thermal polymerization method at the production stage of the basic pitch all had the gamma band of the aliphatic chain at 16 <2θ <19 (002) plane in the laminated structure of the condensed aromatic ring compound, and a (10) face band in 43 <2? <48 at 19 <2? <26.

Table 10 below shows the measurement results of the physical properties and structure of the carbon fiber prepared according to all the examples and comparative examples.

Of basic pitch
Manufacturing method Tensile Strength (GPa) Diameter (탆) Elongation (%) L _c L _a d _m d _? M Halogenation method
Comparative Example 1 1.3 8.71 3.2 28 15 3.82 5.32 8.3 Comparative Example 2 1.1 8.20 3.1 27 15 3.79 5.34 8.1 Example 1 1.8 6.85 2.4 33 17 3.82 5.43 9.6 Example 2 1.9 4.30 2.4 38 36 3.72 4.98 11.2 Example 3 1.6 11.40 2.7 43 31 3.95 5.12 11.9 Example 4 1.5 8.15 2.1 46 34 3.87 5.37 12.9 Comparative Example 3 1.0 7.60 1.9 53 42 14.9 3.82 5.2 Heat agglomeration Comparative Example 4 0.7 7.40 2.5 29 19 3.86 4.79 8.5 Comparative Example 5 0.9 7.80 2.5 30 19 3.82 5.44 8.9 Example 5 2.0 8.10 2.3 37 21 3.89 4.92 10.5 Example 6 1.7 7.30 2.3 43 27 3.95 5.12 11.9 Example 7 1.6 6.80 2.9 46 35 3.91 4.87 12.8 Example 8 1.5 7.10 2.1 49 39 3.84 5.43 13.8 Comparative Example 6 0.9 8.70 1.5 54 45 15.4 3.74 5.2

In each of the examples, the condensed aromatic ring compound having a carbon-fiber structure had at least 4 aromatic rings and a maximum of 13 aromatic rings. In Table 10, the average inter-surface distance (d _m ) of the condensed aromatic ring compound layer was 3.72 to 3.95 Å , average diameter (L _a) of the fused ring compound layer 17 and the average distance to belonged, a condensed aromatic ring compound in the aliphatic chain between the attached 39Å _(γ d) is belonged to 4.87 - 5.43Å, condensed ring compound layer is formed The average diameter (L _c ) of the laminated structure belonged to 33 to 49 Å. In addition, the average number (M) of the condensed aromatic ring compound layers stacked in the isotropic pitch clusters in each example can be represented by (L _c / d _m ) +1 and belonged to 9.6 to 13.8.

This structure of the carbon fiber has excellent physical properties, and the structure is clearly distinguished from the PAN-based carbon fiber and the anisotropic pitch-based carbon fiber.

As shown in Table 10, in each of Examples, high strength carbon filament having a tensile strength of at least 1.5 GPa and a maximum of 2.0 GPa was produced, an elongation of 2.1 to 2.7%, and a carbon filament diameter of 4.30 to 11.40 탆 I belonged. On the other hand, in Comparative Examples 1 and 2, the elongation was as high as 3.2% and 3.1%, respectively, so that the elastic modulus was poor. In Comparative Example 3, the elongation was 1.9% and the tensile strength was 1.0, In Examples 4 and 5, the tensile strength was remarkably lowered to 0.7 and 0.9, and in Comparative Example 6, the tensile strength was 1.5% and the tensile strength was 0.9, whereby the properties of the carbon fiber were remarkably lowered.

&Lt; Example 9 >

Carbon fibers were prepared in the same manner as in Examples 1 to 4 and Comparative Examples 1 to 3 except that the preprocessing step was carried out at 220 캜 and the temperature was raised to 1200 캜 after the stabilization step. Table 11 shows the comparison of the physical properties with the carbon fiber of Example 4. [

Carbonization temperature (℃) The tensile strength
(GPa) diameter
(탆) Elongation
(%) Example 4 800 1.5 8.2 2.1 Example 9 1200 1.9 7.6 2.0

As shown in Table 11, when the carbonization temperature was increased to 1200 ° C, the tensile strength increased while maintaining the diameter and elongation.

&Lt; Example 10 >

Carbon fibers were prepared in the same manner as in Examples 5 to 8 and Comparative Examples 4 to 6 except that the preprocessing step was carried out at 220 캜 and the temperature was raised to 1200 캜 after the stabilization step. Table 12 shows the physical properties of the carbon fibers of Example 8 in comparison.

Carbonization temperature (℃) The tensile strength
(GPa) diameter
(탆) Elongation
(%) Example 8 800 1.5 7.1 2.1 Example 10 1200 2.2 7.8 2.1

As shown in Table 12, when the carbonization temperature was increased to 1200 ° C., the tensile strength increased while maintaining the diameter and elongation.

Claims (22)

a) preparing isotropic pitches from raw materials comprising one or a mixture selected from petroleum heavy oils, high boiling point residues, aromatic hydrocarbon monomers and naphtha cracking process residues;
b) a pitch fiber manufacturing step of melt spinning the isotropic pitch;
c) stabilizing the spun fibers by heat treatment; And
d) carbonizing said pitch fibers;
Wherein the isotropic petroleum pitch is in the range of from about 10 &lt; 7 &gt; The method according to claim 1,
Wherein the tensile strength of the carbon filament is 1.5 GPa or more. Comprising producing a carbon fiber using an isotropic pitch produced from a raw material containing one or a mixture selected from petroleum heavy oils, high boiling point residues, aromatic hydrocarbon monomers and naphtha cracking residues, Wherein the carbon fibrous material has an isotropic petroleum pitch having a tensile strength of 1.5 GPa or more. The method of claim 3,
The method for producing carbon fiber using the isotropic petroleum pitch
a) preparing isotropic pitches from raw materials comprising one or a mixture selected from petroleum heavy oils, high boiling point residues, aromatic hydrocarbon monomers and naphtha cracking process residues;
b) a pitch fiber manufacturing step of melt spinning the isotropic pitch;
c) stabilizing the spun fibers by heat treatment; And
d) carbonizing said pitch fibers;
Wherein the isotropic petroleum pitch is in the range of from about 10 &lt; 7 &gt; The method according to claim 1 or 3,
Wherein the carbon fibrous substance has a fiber diameter of 1 to 20 占 퐉 and an elongation percentage of 2% or more. The method according to claim 1 or 4,
The step a)
a1) a pretreatment step of heat-treating and fractionating the raw material;
a2) a filtration step of removing the solid matter from the pretreated raw material;
a3) preparing a basic pitch with the filtered raw material; And
a4) heating the basic pitch to produce an isotropic pitch;
Wherein the isotropic petroleum pitch is in the range of from about 10 &lt; 7 &gt; The method according to claim 6,
Wherein the pretreatment step is carried out by heat treating and fractionating the raw material at 130 to 240 占 폚, wherein the isotropic petroleum pitch is used. The method according to claim 6,
The step a3) is a step of preparing a basic pitch by a halogenation method in which a halogen compound and a radical initiator are further added to the raw material and then heating, or a heat polymerization method in which nitrogen and gaseous byproducts are collected by stirring and heating in an inert gas atmosphere, Process for the production of carbonaceous fibers using petroleum pitch. 9. The method of claim 8,
Wherein the halogenation method comprises halogenating at 100 to 120 ° C for 0.5 to 2 hours and de-halogenating at 300 to 330 ° C for 2 to 4 hours. 9. The method of claim 8,
Wherein the halogen compound is any one selected from chlorine, thionyl chloride, sulfuryl chloride, bromine and iodine, or a mixture thereof. 9. The method of claim 8,
Wherein the radical initiator is selected from the group consisting of carbon fibers of isotropic petroleum pitch, which is any one selected from benzoyl peroxide, dibutyl hydroperoxide, acetyl peroxide, azobisisobutyronitrile and azobismethyl isobutyrate, Gt; 9. The method of claim 8,
Wherein the heat polymerization is carried out at 350 to 380 DEG C for 0.1 to 2 hours. 9. The method of claim 8,
Wherein the softening point of the basic pitch prepared by the halogenation method is 70 to 130 캜 and the softening point of the basic pitch produced by the heat polymerization method is 85 to 140 캜. The method according to claim 6,
Wherein the step a4) is performed by heating at 300 to 350 DEG C for 0.1 to 1 hour in a vacuum atmosphere, and the isotropic petroleum pitch is used. 15. The method of claim 14,
Wherein the softening point of the isotropic pitch is in the range of 260 to 270 ° C. The method according to claim 1 or 4,
Wherein step b) producing a carbon fiber sheet with isotropic petroleum pitch to prepare a pitch fiber under the conditions of a nitrogen atmosphere, a temperature of 300 to 320 ℃, pressure of 0.01 to 10 ㎏f / ㎝ ^2, the take-up velocity of 500 to 1,500rpm Way. The method according to claim 1 or 4,
And the step c) is carried out at 250 to 300 ° C for 1 to 5 hours. The method according to claim 1 or 4,
Wherein the step d) is carried out in an inert gas atmosphere at 800 to 1,200 ° C for 0.5 to 30 hours. (002) plane bands appear at a diffraction angle of 19 <2? <26 in X-ray diffraction analysis (XRD), and the condensed aromatic ring compound contains a crystal structure satisfying the following formulas (1) to (4) connected by an aliphatic chain Carbon Fiber Sheet.
30? L _a ? 60? A (1)
10? L _c ? 50? (2)
_{3.50 ≤ d m ≤ 4.20Å --- (} 3)
9.0 ≤ M ? 18.0 --- (4)
(Wherein L _a represents the average diameter of the condensed aromatic ring compound layer, L _c represents the average diameter of the laminated structure formed by the condensed aromatic ring compound layer, and d _m represents the average of the condensed aromatic ring compound layer And M is the average number (L _c / d _m ) of the condensed aromatic ring compound layers included in the laminated structure) 20. The method of claim 19,
Wherein said carbon fiber is a carbon fiber having a tensile strength of 1.5 GPa or more. 21. The method of claim 20,
The carbon fiber is a carbon fiber having an elongation of 2% or more. 20. The method of claim 19,
4.80 ≤ d _γ ≤ 5.20 Å.
(Wherein R d and _γ means a mean distance between the aliphatic chain attached to the condensed ring.)

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