KR102220800B1 - Isotropic pitch for manufacturing carbon fiber and method thereof - Google Patents

Abstract

The present invention relates to an isotropic pitch for carbon fiber production and a method for producing the same, and can produce an isotropic pitch having a specific range of softening point, viscosity, molecular weight, and crystal structure, and these features include insoluble solids and mesophase of the pitch. ) It is possible to maximize the mechanical properties of carbon fiber by suppressing the formation, and the carbonization process temperature is low, and energy consumption is also reduced. It relates to an isotropic pitch and a method of manufacturing the same.

Description

Isotropic pitch for manufacturing carbon fiber and method thereof

The present invention relates to an isotropic pitch for carbon fiber production and a method for producing the same, specifically, isotropic pitch that has a specific range of physical properties and structure, and isotropic pitch that can be used in the production of carbon fibers having high strength and high elasticity compared to conventional isotropic carbon fibers. And it relates to a method of manufacturing the same.

The reduction of fuel consumption of automobiles is further demanded due to the depletion of petroleum resources, price hikes, and environmental problems. According to the Working Group report, energy efficiency is predicted to increase by more than 600% in 2020, and the most effective through hybridization of the engine, in the order of improving engine efficiency, weight reduction of the vehicle body, and energy transmission efficiency. Mention that it works. In particular, according to the US Department of Energy (DOE), a 10% reduction in the weight of the vehicle body can reduce fuel consumption by approximately 7%. Therefore, further technology development for the weight reduction of the vehicle body is required.

Body weight reduction can also be achieved by using high-strength steel or aluminum alloy, but the application of carbon fiber reinforced plastic is very effective, and it is already used in engine hoods, propeller shafts and hydrogen tanks in automobiles. . When CFRP is used as the main material of the vehicle body structure, it is possible to reduce the weight by 50%, and the impact energy absorption performance is also improved. First of all, it is possible to manufacture the lightest vehicle body among currently available materials, so research is active in countries around the world.

However, CFRP also has a weakness, its tensile strength is weaker than compression, and delamination is likely to occur due to impact, so the compressive strength after impact decreases rapidly. In addition, there is a disadvantage that many applications are difficult due to high manufacturing cost.

In general, carbon fibers included in CFRP can be divided into rayon-based, PAN-based, and pitch-based depending on the precursor, and among these, the pitch-based is a liquid crystal pitch-based carbon fiber and an isotropic pitch-based carbon fiber depending on the type of pitch that is the precursor. I can share. Among them, isotropic pitch-based carbon fiber is called general-purpose carbon fiber because it has a lower price than high-performance grade, and it is produced as a staple-type carbon fiber by a melt blown method and is used as an activated carbon fiber for high temperature insulation or filter. Is being used.

There are many advantages to producing carbon fibers using petroleum, coal tar, or chemical pitch as raw materials, one of the reasons is that the carbon-to-hydrogen ratio of these raw materials is high. For example, the theoretical yield of carbon fibers made from PAN resin is only about 50%, but the theoretical yield of carbon fibers made from well refined pitch reaches 90%. However, pitch-based carbon fiber with sufficient tensile strength and modulus that can be used as a composite material in the aerospace and aviation fields is manufactured from liquid crystal pitch, and to prepare liquid crystal pitch from petroleum, coal tar, or chemical pitch, pretreatment, hydrogenation, quinoline is insoluble. A complicated process such as separation of powder is required, and accordingly, there is a disadvantage in that the price is high due to an increase in production cost.

As a prior art for isotropic pitch-based carbon fiber or isotropic pitch for the production of carbon fiber, there are Korean Patent Publication 10-2013-0059174, Japanese Patent Publication 1996-144131, and the like. Among these, 10-2013-0059174 describes a method of manufacturing a precursor for carbon fibers having a high softening point, but the heating temperature of the pitch is 360°C or higher, so that insoluble solids are partially generated or mesophase is generated, and the resulting carbon fiber There is a drawback of poor physical properties.

In addition, Japanese Patent Laid-Open Publication No. 1996-144131 claims an isotropic pitch for producing carbon fibers having a specific range of molecular weight, but the softening point of the pitch is as low as 180 to 200°C, and the tensile strength of the carbon fiber produced from the pitch is 89.3 kg/mm2. (About 0.893 GPa), it shows low physical properties to be used for CFRP for the purpose of steel plate for automobiles.

As such, there is a strong demand for the development of carbon fiber manufacturing technology using isotropic pitch that can be mass-produced at low production cost while satisfying all the necessary properties that can be used for CFRP.

Republic of Korea Patent Publication 10-2013-0059174 (June 05, 2013) Japanese Patent Laid-Open Publication No. 1996-144131 (June 04, 1996)

As a result of repeating research in order to solve the above problems, the present inventors invented a method of manufacturing an isotropic pitch having a specific range of physical properties, molecular structure and laminated structure, and the isotropic pitch produced therefrom is compared to the conventional isotropic carbon fiber. It can be used to manufacture carbon fibers with superior mechanical properties.

In the present invention, the average diameter of the layered structure formed by the condensed aromatic ring compound layer (L _c ), the average distance between the layers of the condensed aromatic ring compound in the layered structure (d _m ), the average diameter of the condensed aromatic ring compound layer (L _a ), condensation The structure represented by the average number of condensed aromatic ring compound layers (M) included in the laminated structure, which can be represented by the average distance between aliphatic chains connected to the aromatic ring compound (d _γ ) and (L _c / d _{m) + 1} It provides an isotropic pitch that includes.

The present invention is a step of producing a raw material by pre-treating any one selected from petroleum-based heavy oil, a high boiling point residue, an aromatic hydrocarbon short substance, and a naphtha cracking process residue oil, or a mixture thereof, and removing solid substances from the prepared raw material. It provides a filtration step, a step of polymerizing the filtered raw material to prepare a basic pitch, and a manufacturing method for preparing the isotropic pitch by heating the basic pitch.

The isotropic pitch of the present invention has a specific range of softening point and molecular weight, and the generation of insoluble solids and mesophase is suppressed as much as possible in the pitch, so that the spinnability is very excellent, the elongation is high, and the tensile strength is significantly increased, so that the use of carbon composites It provides isotropic pitch-based carbon fibers that can be used as.

1 is a flow chart of a carbon fiber manufacturing process according to a preferred embodiment of the present invention.
2 is an X-ray diffraction analysis result of an isotropic pitch in a manufacturing method including a halogenation step.
3 is an X-ray diffraction analysis result of an isotropic pitch in a manufacturing method including a thermal polymerization step.
4 is an isotropic pitch structure analysis diagram through X-ray diffraction analysis, where d _m is an average distance between layers of a condensed aromatic ring compound in a layered structure, d _γ is an average distance between aliphatic chains connected to a condensed aromatic ring compound, and L _c Is the average diameter of the layered structure formed by the condensed aromatic ring compound layer, L _a is the average diameter of the condensed aromatic ring compound layer, and M is the average number of condensed aromatic ring compound layers included in the layered structure.

Hereinafter, an isotropic pitch for manufacturing carbon fibers and a method for manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings. The drawings introduced below are provided as examples in order to sufficiently convey the spirit of the present invention to those skilled in the art. Accordingly, the present invention is not limited to the drawings presented below and may be embodied in other forms, and the drawings presented below may be exaggerated to clarify the spirit of the present invention. Also, throughout the specification, the same reference numerals denote the same elements.

At this time, unless there are other definitions in the technical terms and scientific terms used, they have the meanings commonly understood by those of ordinary skill in the technical field to which the present invention belongs, and the gist of the present invention in the following description and accompanying drawings Descriptions of known functions and configurations that may be unnecessarily obscure may be omitted.

The present invention relates to an isotropic pitch for producing carbon fibers, and provides an isotropic pitch for producing carbon fibers including a structure in which a condensed aromatic cyclic compound layer forms a laminated structure, and a condensed aromatic cyclic compound is connected by an aliphatic chain, and a method for producing the same.

The isotropic pitch of the present invention is excellent in spinnability and thus melt spinning is possible, and single yarn does not occur or is extremely rare during spinning, and the carbon fibers produced therefrom have high strength and high elasticity and maximized physical properties.

First, the isotropic pitch of the present invention will be described in detail.

In the isotropic pitch of the present invention, in X-ray diffraction (XRD), a gamma band of an aliphatic chain appears at 17<2θ<18, and a gamma band (γ-band) of an aliphatic chain appears in X-ray diffraction (XRD), and at 23<2θ<25 ( It is an isotropic pitch containing a structure in which a condensed aromatic cyclic compound in which a band of (10) appears at 43<2θ<45 is connected by an aliphatic chain.

The structure includes the average diameter (L _c ) of the laminated structure formed by the condensed aromatic cyclic compound layer, the average diameter of the condensed aromatic cyclic compound layer (L _a ), the average distance between the condensed aromatic cyclic compound layers in the laminated structure (d _m ), and ( It can be described as the average number (M) of the condensed aromatic cyclic compound layers included in the layered structure, which can be represented by L _c /d _{m )+1.} In addition, the condensed aromatic ring compounds are connected by an aliphatic chain, and the average distance (d _γ ) between the aliphatic chains connected to the condensed aromatic ring compound may be added to explain the structure (FIG. 4). The condensed aromatic ring compound may vary depending on the condensed structure, but is a compound containing at least 2 to at most 7 aromatic rings, and the condensed aromatic ring compound layer is preferably a layer or a condensed aromatic ring composed of a compound in which aromatic rings are condensed. It may be a compound layer containing a cyclic compound, and they may be linked by an aliphatic chain. In addition, 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 the XRD measurement results, Bragg and Scherrer equations (FIG. 4).

_{Specifically, the average diameter (L c} ) of the laminated structure formed by the condensed aromatic cyclic compound layer is 10 to 25, preferably 15 to 20, and the average diameter (L _a ) of the condensed aromatic cyclic compound layer is 5 to 15, Preferably it is 8 to 12, and the average distance (d _m ) between the layers of the condensed aromatic ring compound in the laminated structure is 3.50 to 4.50, preferably 3.55 to 4.00, and the average distance between aliphatic chains connected to the condensed aromatic ring compound (d _γ ) Is 4.50 to 5.50, preferably 4.80 to 5.20, and the average number (M) of the condensed aromatic cyclic compound layers included in the laminated structure is 4.00 to 8.00, preferably 5.00 to 7.00.

The isotropic pitch prepared in the present invention has excellent spinnability when the structure satisfies the above range, and there is a very small amount such that unmelted solids and mesophase are not generated or measured, and the mechanical properties of the carbon fiber produced therefrom can be maximized. I can. If it is out of the above range, unmelted solids and mesophase may be generated, and frequent single yarns occur during spinning, and the tensile strength of the carbon fibers produced therefrom is remarkably reduced or the elongation is low or excessively high, resulting in poor elastic modulus.

The isotropic pitch of the present invention can be expressed as follows according to the analysis result.

The isotropic pitch of the present invention has a (002) plane band at 23<2θ<25 in X-ray diffraction analysis, and includes a structure that satisfies the following formulas (1) to (4) in which the condensed aromatic ring compound is connected by an aliphatic chain. It is an isotropic pitch for manufacturing carbon fiber.

5 ≤ L _a ≤ 15Å --- (1)

10 ≤ L _c ≤ 25Å --- (2)

3.50 ≤ d _m ≤ 4.50Å --- (3)

4.00 ≤ M ≤ 8.00Å --- (4)

According to an embodiment of the present invention, even if the above formulas (1), (2) and (3) are satisfied, if (4) is not satisfied, the molecular weight of the isotropic pitch is too small, and thus the desired carbon fiber from the isotropic pitch of the present invention. The tensile strength of is not satisfied and the elongation is too high and the elastic modulus is lowered. According to another embodiment of the present invention, even if the above equations (2) and (3) are satisfied, if (1) and (4) are not satisfied, frequent single yarns occur during spinning of an isotropic pitch, and carbon fibers produced therefrom The tensile strength of is significantly reduced and the elongation is also lowered. According to another embodiment of the present invention, even if the above formulas (1) and (3) are satisfied, if (2) and (4) are not satisfied, not only the molecular weight of the isotropic pitch is small, but also the carbon fiber produced therefrom The tensile strength is significantly reduced.

The isotropic pitch may be expressed in more detail by additionally expressing the _{average distance (d γ} ) between aliphatic chains connected to the condensed aromatic ring compound in the structure included in the isotropic pitch.

_{The average distance (d γ} ) between the aliphatic chains connected to the formulas (1) to (4) and the condensed aromatic ring compound of the present invention is further specified in a preferred range, respectively, isotropic pitch having superior physical properties and radioactivity can be prepared, , The mechanical properties of high strength and high elasticity of the isotropic pitch-based carbon fiber produced therefrom can be further maximized.

The isotropic pitch softening point of the present invention is 255 to 275°C, preferably 260 to 270°C, and if the softening point is too low or high, it is difficult to spin long fibers of a certain length or longer, or even if it is spun longer than a certain length, the uniformity decreases, and the shape and diameter Fibers that are not uniform and weak in terms of physical properties such as tensile strength may be produced.

The isotropic pitch average molecular weight (Mw) of the present invention is 1500 to 3000, preferably 1650 to 2850. The isotropic pitch having an average molecular weight in the above preferred range significantly increases the tensile strength during the production of carbon fibers, and further, may have an effect on increasing the elongation rate.

According to an embodiment of the present invention, the isotropic pitch viscosity is 200 to 500, but may be appropriately adjusted according to the method of manufacturing the carbon fiber.

Next, a method of manufacturing an isotropic pitch for producing carbon fibers of the present invention will be described in detail.

The method for producing an isotropic pitch for producing carbon fibers of the present invention,

a) a pretreatment step of heat-treating and fractionating a raw material including any one selected from petroleum-based heavy oil, high boiling point residue, aromatic hydrocarbon short substance, and naphtha cracking process residue oil, or a mixture thereof;

b) a filtering step of removing solid substances from the pretreated raw materials;

c) preparing a basic pitch from the filtered raw material; And

d) heating the basic pitch to prepare an isotropic pitch;

It is a method for producing an isotropic pitch for producing carbon fiber comprising a.

Among the above manufacturing methods, the filtration step of b) can be performed after preparing the basic pitch of c), and the basic pitch of c) is an intermediate material for manufacturing isotropic pitch, and its composition and physical properties vary according to the convenience of the process configuration. I can.

As a raw material, in more detail, it may include pyrolysis fuel oil (PFO), which is a kind of naphtha cracking residual oil. PFO is produced at the bottom of a naphtha cracking center (NCC) and can be used as a raw material of the present invention due to its high degree of aroma and rich in resin content.

Pyrolysis fuel oil is produced at the bottom of the naphtha cracking process and may contain various aromatic hydrocarbons. Specific examples of aromatic hydrocarbons include ethylbenzene, 1-ethenyl-3-methyl benzene, indene, and 1-ethyl-3-methylbenzene (1- ethyl-3-methyl benzene), 1-methylethylbenzene, 2-ethyl-1,3-dimethyl benzene, propylbenzene, 1- Methyl-4-(2-propenyl)-benzene (1-methyl-4-(2-propenyl) benzene), 1,1a,6,6a-tetrahydro-cyclopropaneden (1,1a,6,6a -tetrahydro-cycloprop[a]indene), 2-ethyl-1H-indene, 1-methyl-1H-indene, 4,7-dimethyl- 1H-indene (4,7-dimethyl-1H-indene), 1-methyl-9H-fluorene (1-methyl-9HFluorene), 1,7-dimethyl naphthalene (1,7-dimethyl naphthalene), 2-methylin Den (2-methylindene), 4,4'-dimethyl biphenyl (4,4'-dimethyl biphenyl), naphthalene (naphthalene), 4-methyl-1,1'-biphenyl (4-methyl-1,1' -biphenyl), anthracene, 2-methylnaphthalene and 1-methylnaphthalene.

The raw material according to an embodiment of the present invention may further contain a high boiling point oil. The high-boiling fraction according to an embodiment of the present invention refers to a component having a high boiling point and a large number of carbon atoms among the components obtained by fractional distillation of crude oil, and mainly includes a light or heavy aromatic naphtha having 5 or more carbon atoms, preferably 7 or more. Can include.

As a high boiling point fraction, more specifically, a C9 fraction may be included. Specifically, for example, it may be made of styrene, vinyl toluene, indene, alpha methyl styrene, and benzene/toluene/xylene (BTX).

Indene may be preferably included as an oil having 9 carbon atoms. Indene combines with the side chain of the aromatic component of the raw material, and as the side chain of the aromatic component is oxidized in the stabilization step after melt spinning, it can prevent the tendency to become ether by dehydration bonding.As a result, it will contribute to lowering the carbonization temperature and time. I can.

It is preferable that the high-boiling-point oil contains 5 to 15% by weight based on 100% by weight of the total raw material, and if it is less than 5% by weight, the effect may be insignificant, and if it exceeds 15% by weight, it is effective for the increased amount. May not be clear

The degree of aromatization (fa) of the raw material may be 0.7 to 0.9. If the degree of aromatization is less than 0.7, the carbonization yield may decrease. There is no particular limitation on the case where the degree of aromaticity is higher than 0.9, but when the degree of aromaticity is more than 0.9, 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 may have a distribution of 100 to 250.

In the method for producing an isotropic pitch, step a) is a step of removing a low-molecular material that is unlikely to generate oligomers by polymerization among the compounds contained in the raw material, and at the same time, the raw material is accompanied by a reaction between the compounds included in the raw material. This is a step of converting the highly reactive and unstable compound contained in the compound to a compound that is more stable and effective for producing an isotropic pitch.

In step a), the pretreatment may be performed by atmospheric distillation at a temperature of 130 to 240°C, preferably 150 to 230°C, and more preferably 190 to 220°C until no volatiles are generated. In the pretreatment, the heating temperature may affect the properties of basic pitch and isotropic pitch, such as the composition ratio of raw materials and degree of aromatization, and further, mechanical properties of carbon fiber. In addition, the pretreatment step may be performed at normal pressure, but may be performed under reduced pressure. At this time, the pretreatment process can be performed at a lower temperature through reduced pressure, and the pressure and temperature can be freely controlled within a range that can obtain the same effect as the normal pressure.

In the method of manufacturing the isotropic pitch, step b) is a filtration step of the pretreated fuel to remove the solid material, and the solid material is a solid residue containing impurities such as metal, sulfur, and nitrogen, and carbon fibers produced from the isotropic pitch. It can cause a decrease in strength by acting as a cracker in its structure.

The filtration step may be performed in a manner commonly performed in the art, for example, filtration, centrifugation, sedimentation, adsorption, extraction, and the like.

The filtration step may be performed after the polymerization of the basic pitch, and in some cases, it may be performed both after the pretreatment step and after the basic pitch polymerization step. That is, in the above manufacturing method, it may be performed after step (c), and in some cases, it may be performed after steps (a) and (c), respectively.

In the manufacturing method of the isotropic pitch, step c) is a step of preparing a basic pitch having a high softening point without generating a mesophase by reacting the raw material that has undergone the filtering step as a basic pitch manufacturing step while heating, by a halogenation method or a thermal polymerization method. You can proceed.

The halogenation method may be carried out by heating after further addition of a halogen compound and a radical initiator, and preferably, after adding a radical initiator, a halogen compound may be 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 ), or a mixture of two or more of them. Can be used.

Radical initiators include organic peroxides such as benzoyl peroxide, di-t-butyl hydroperoxide, and acetyl peroxide, and azobisisobutyronitrile (AIBN). ; Azo compounds such as α,α'-Azobisisobutyronitrile), azobismethyl isobutyrate, or a mixture of two or more of them may be used.

The radical initiator may be included in 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, a halogenation reaction is performed at 100 to 120°C for 0.5 to 2 hours to replace hydrogen in an aromatic alkyl group with halogen, and then polymerization may be performed by dehalogenation at 300 to 330°C for 2 to 4 hours. In addition, the dehalogenation reaction is a subsequent step, and the purity of the basic pitch prepared by decomposing halogen compounds and radical initiators that may remain in the basic pitch after the reaction can be further increased. In particular, it is good that the reaction temperature does not exceed 330°C in the dehalogenation reaction.When the reaction temperature exceeds 330°C, the decomposition of halogen compounds and radical initiators occurs actively, but the anisotropy or coking of the basic pitch due to excessive polymerization proceeds, resulting in carbon fiber. The mechanical properties of are greatly degraded.

According to an embodiment of the present invention, the basic pitch prepared by the halogenation method may have a softening point of 70 to 130°C, preferably 115 to 125°C.

The thermal polymerization method may be performed at 350 to 380°C for 0.1 to 2 hours. The thermal polymerization method can be carried out by stirring in an inert gas atmosphere during the process, and can be carried out by separating nitrogen and gaseous by-products generated during the poly-condensation process. In addition, in the thermal polymerization method, as in the halogenation method, it is good that the reaction temperature does not exceed 380°C. If the reaction temperature exceeds 380°C, as in the halogenation method, an excessive mesophase exceeding the range of the uniform anisotropic pitch aimed at in the present invention. May be generated or coking may proceed to produce non-uniform carbon fibers.

The basic pitch prepared by the thermal polymerization method may have a softening point of 85 to 140°C, preferably 115 to 125°C.

In the manufacturing process of the isotropic pitch, the physical properties of the basic pitch can be adjusted according to the convenience of the configuration. For example, in the case of configuring a process for the purpose of smoothing the flow of fluid continuously flowing from step (c) to step (d) of the above manufacturing method, a condensed aromatic ring compound among the basic pitches prepared from step (c) above A compound having a low boiling point may be further included within a range that does not significantly affect the absolute amount of the linked oligomer. This effect can be obtained when step (c) is carried out in a pressurized state, and at this time, the softening point of the basic pitch does not affect the physical properties, molecular structure, and layered structure of the final isotropic pitch according to the convenience of the process configuration. It can be freely adjusted within a range that is not available.

In the manufacturing method of the isotropic pitch, step d) is an isotropic manufacturing step, and may be a process of heating the basic pitch to promote evaporation, thereby suppressing the generation of mesophase and producing an isotropic pitch capable of melt spinning.

The isotropic pitch manufacturing step can be performed by a conventional thin film distillation method, which has the advantage of not requiring an additional process of suppressing the formation of mesophase and removing insoluble solids. In addition, the isotropic pitch manufacturing step according to an embodiment of the present invention may respond to changes in the composition and state of the isotropic pitch manufactured by having a multi-stage thin film distillation apparatus.

The isotropic pitch manufacturing step may be performed by heating in a vacuum atmosphere, 300 to 350° C. for 0.1 to 1 hour. In particular, when the heating temperature exceeds 350° C., a mesophase is partially generated, and insoluble carbon solids may be generated by continued heating, so it is preferable to observe the heating temperature and heating time.

The isotropic pitch according to an embodiment of the present invention may have a softening point of 255 to 275°C, preferably 260 to 270°C. In addition, the isotropic pitch average molecular weight (Mw) of the present invention may be 1500 to 3000, preferably 1700 to 2850. Since the average molecular weight and softening point of the isotropic pitch can have a great influence on the physical properties of the carbon fiber to be produced, it is desirable to observe the conditions of the manufacturing process.

The isotropic pitch produced in the present invention is capable of melt spinning, and has excellent spinning properties that do not occur or are extremely rare during fiber spinning. Melt spinning is a method of manufacturing continuous fibers by melting a polymer material or pitch, and it is a very economical method that can simplify the configuration of the spinning process and significantly reduce the cost because it does not require the use of expensive solvents required for fiber spinning. to be. In order to enable the melt spinning for the production of carbon fibers, the spinnability of the pitch must be excellent, but the isotropic pitch produced according to the present invention has excellent spinnability, enabling melt spinning for the production of carbon fibers, and single yarn is extremely rare or does not occur. . In addition, the melt-spinning isotropic pitch of the present invention is excellent in spinnability compared to the conventional isotropic pitch, which was used to manufacture short fibers through melt-blowing, and from this, it is possible to manufacture high-strength, high-elastic carbon filaments. May be.

According to an exemplary embodiment of the present invention, as a result of measuring the isotropic pitch as a single yarn frequency as a single yarn frequency as the frequency of breaks during melt spinning for 20 minutes in a row, it can be seen that the single yarn frequency corresponds to 0, so that the spinning property is very good.

In addition, the isotropic pitch of the present invention can be carbonized even at a low temperature of 700 to 1200° C. or less, thereby minimizing energy consumption in the carbonization process.

The isotropic pitch prepared according to the present invention may be melt-spinned and then subjected to a stabilization step and a carbonization step to produce carbon fibers. When manufacturing carbon fibers from the isotropic pitch prepared according to an embodiment of the present invention, an isotropic pitch-based long carbon fiber having a tensile strength of at least 1.5 GPa or more and an elongation of 2% or more may be manufactured. The isotropic pitch-based carbon fiber as described above has maximized physical properties, and can be used in various applications in carbon composites requiring high strength and high elasticity carbon fiber, unlike conventional isotropic pitch-based carbon fiber used as a general-purpose carbon material.

The isotropic pitch of the present invention is preferably used for manufacturing carbon fibers, but is not limited thereto and may be used for manufacturing various carbon materials.

Hereinafter, a method of manufacturing an isotropic pitch according to the present invention and an isotropic pitch produced therefrom will be described in more detail through Examples and Comparative Examples. However, the following examples and comparative examples are only examples to aid understanding or implementation of the present invention, and the present invention is not limited to the examples and comparative examples.

The method of measuring physical properties and the composition ratio of raw materials measured through the Examples and Comparative Examples are as follows.

How to measure physical properties

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

Analysis with CHNS Elemental Analyzer

2. Aromatization degree (fa)

^{Analysis by 13} C NMR (ASTM D5292)

3. Composition of raw materials

Analysis with 2D-GC

4. Viscosity (Pa·s)

Viscosity is measured by TMA (Thermo Mechanical Analyzer)

5. Softening point (℃)

Softening point is measured by TMA (Thermo Mechanical Analyzer)

6. Yield

The yield was calculated by the weight of the finally obtained pitch relative to the weight of the added naphtha decomposition residue.

7. Mechanical properties

In order to calculate the tensile strength (GPa) and elongation (%), the stress-strain curve was measured with a UTM (Universal Test Machine) equipped with a 2N load cell for a sample of carbon fiber, and the tensile strength was determined by the above measurement result and an electron microscope. It was calculated from the diameter of the fiber analyzed by.

8. Molecular composition of pitch

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

9. X-ray diffraction analysis

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

10. TOF-MS analysis

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

<Examples 1 to 4> and <Comparative Examples 1 to 3> Preparation of isotropic pitch using a halogenation method in the basic pitch manufacturing step

Composition and degree of aromatization were prepared using Naphtha Cracker Bottom Oil (NCBO) as shown in Tables 1 to 3 as a raw material.

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

Aliphatic carbide (%) Aromatic carbide (%) Aromatization degree (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

Examples 1 to 4 were prepared NCBO at 190, 200, 210, and 220°C, respectively, in Comparative Example 2 at 120°C, and in Comparative Example 3 at 250°C, each pre-treatment step was performed by atmospheric distillation, and then a solid material through filtration. Was removed. In Comparative Example 1, a solid material was removed through filtration without performing a 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 step. And after the bromination reaction was performed at 110° C. for 1 hour, the bromination reaction was performed again at 320° C. for 3 hours to prepare a basic pitch. After the basic pitch manufacturing process was completed, the softening point and the yield were measured, and Table 4 shows the measurement results.

Pretreatment temperature (℃) 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 130ㅊ 49.8 Example 3 210 130 57.6 Example 4 220 70 66.9 Comparative Example 3 250 125 68.9

After each prepared basic pitch was introduced into a thin film evaporator, an isotropic pitch was prepared by heating the basic pitch at 340° C. for 30 minutes in a vacuum atmosphere. After the process was completed, the softening point, viscosity, and average molecular weight of the isotropic pitch were measured and shown in Table 5 below.

Pretreatment temperature (℃) 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 structure of the prepared isotropic pitch was analyzed using an X-ray diffractometer, and as a result of XRD analysis, the gamma band (γ-band) of the aliphatic chain at 17<2θ<18, and the condensed aromatic ring at 23<2θ<25. In the laminated structure of the compound, bands of (002) plane and (10) plane were shown in 43<2θ<45 (FIG. 2). Table 6 below shows the results of structural analysis.

Pretreatment temperature (℃) Average molecular weight (Mw) L _c L _a d _m d _γ M Comparative Example 1 - 1250 10 7 3.534 5.093 3.5 Comparative Example 2 120 1300 10 7 3.621 4.897 3.8 Example 1 190 1900 16 10 3.739 5.121 5.3 Example 2 200 2300 17 9 3.772 5.160 5.5 Example 3 210 2550 17 10 3.756 5.183 5.5 Example 4 220 2800 19 11 3.594 4.958 6.3 Comparative Example 3 250 2900 27 15 3.642 5.172 8.4

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

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

-d _m (Å) : Average distance between layers of condensed aromatic cyclic compounds in a laminated structure

-d _γ (Å) : Average distance between aliphatic chains linked to condensed aromatic ring compounds

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

<Examples 5 to 8> and <Comparative Examples 4 to 6> Preparation of isotropic pitch using thermal polymerization in the basic pitch manufacturing step

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

Examples 5 to 8 were prepared NCBO at 190, 200, 210 and 220°C, respectively, in Comparative Example 4 at 120°C, and in Comparative Example 5 at 250°C, each pre-treatment step was performed by atmospheric distillation, and then the solid material through filtration. Was removed. In Comparative Example 3, a solid material was removed through filtration without performing a pretreatment step.

After the filtration step, 100 parts by weight of the raw material produced in the intermediate step was put into a container made of metal and heated at 370° C. for 0.5 hours to prepare a basic pitch. After the basic pitch manufacturing process was completed, the softening point and the yield were measured, and Table 7 shows the measurement results.

Pretreatment temperature (℃) 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

After each prepared basic pitch was introduced into a thin film evaporator, an isotropic pitch was prepared by heating the basic pitch at 340° C. for 30 minutes in a vacuum atmosphere. After the process was completed, the softening point, viscosity, and average molecular weight of the isotropic pitch were measured and shown in Table 8 below.

Pretreatment temperature (℃) 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 structure of the prepared isotropic pitch was analyzed using an X-ray diffractometer, and as a result of XRD analysis, the gamma band (γ-band) of the aliphatic chain at 17<2θ<18, and the condensed aromatic ring at 23<2θ<25. In the laminated structure of the compound, a (002) plane and a (10) plane band at 43<2θ<45 were shown (Fig. 3). Table 9 below shows the results of structural analysis.

Pretreatment temperature (℃) Average molecular weight (Mw) L _c L _a d _m d _γ M Comparative Example 4 - 1350 10 16 3.689 5.102 3.7 Comparative Example 5 120 1300 11 16 3.621 4.987 3.9 Example 5 190 1750 18 9 3.965 4.953 5.5 Example 6 200 2200 20 10 3.643 4.829 6.5 Example 7 210 2350 19 9 3.629 4.884 6.2 Example 8 220 2500 19 12 3.696 4.906 6.1 Comparative Example 6 250 2950 30 7 3.716 5.132 9.1

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

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

-d _m (Å): average distance between layers of condensed aromatic cyclic compounds in a layered structure

-d _γ (Å): average distance between aliphatic chains linked to condensed aromatic ring compounds

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

Manufactured Isotropic Analysis of pitch properties and structure

As a result of XRD analysis of the isotropic pitch, the isotropic pitches produced by the production method using the halogenation method and the thermal polymerization method in the production stage of the basic pitch are all gamma bands of the aliphatic chain at 17<2θ<18, 23 In the stacked structure of the condensed aromatic cyclic compound at <2θ<25, a (002) plane and a (10) plane at 43<2θ<45 appeared.

Table 10 below shows the measurement results of the physical properties and structures of the isotropic pitch prepared according to all the Examples and Comparative Examples.

Basic Peach
Manufacturing method Average molecular weight (Mw) Softening point (℃) L _c L _a d _m d _γ M Halogenation method Comparative Example 1 1250 265 10 7 3.534 5.093 3.5 Comparative Example 2 1300 260 10 7 3.621 4.897 3.8 Example 1 1900 260 16 10 3.739 5.121 5.3 Example 2 2300 265 17 9 3.772 5.160 5.5 Example 3 2550 270 17 10 3.756 5.183 5.5 Example 4 2800 265 19 11 3.594 4.958 6.3 Comparative Example 3 2900 275 27 15 3.642 5.172 8.4 Thermal polymerization method Comparative Example 3 1350 260 10 16 3.689 5.102 3.7 Comparative Example 4 1300 263 11 16 3.621 4.987 3.9 Example 5 1750 265 18 9 3.965 4.953 5.5 Example 6 2200 260 20 10 3.643 4.829 6.5 Example 7 2350 265 19 9 3.629 4.884 6.2 Example 8 2500 260 19 12 3.696 4.906 6.1 Comparative Example 4 2950 270 30 7 3.716 5.132 9.1

In each example, in the structure of the isotropic pitch, the condensed aromatic ring compound included a minimum of 2 to a maximum of 7 aromatic rings, and looking at Table 10, the average interplanar distance (d _m ) of the condensed aromatic ring compound layer was 3.594-3.965 Å, The average diameter (L _a ) of the condensed aromatic ring compound layer was 9-12 Å, the average distance between aliphatic chains connected to the condensed aromatic cyclic compound (d _γ ) was 4.829-5.172 Å, and the average diameter of the isotropic pitch cluster ( L _c ) belonged to 16-20 Å. In addition, the average number (M) of the condensed aromatic cyclic compound layers stacked in the isotropic pitch clusters in each example _{can be expressed as (L c} /d _m )+1 and belonged to 5.3 to 6.5. In addition, the average number (M) of the condensed aromatic cyclic compound layers stacked in the isotropic pitch clusters in each example _{can be expressed as (L c} /d _m )+1 and belonged to 5.3 to 6.5.

Isotropic Pitch Carbon fiber Produce

Carbon fibers were prepared using isotropic pitch. First, each isotropic pitch was injected into a cylindrical container, and then melt-spinned by applying a pressure of ^{0.8 kgf/cm 2 in a nitrogen atmosphere.} At this time, the diameter of the take-up machine was 150 mm, and the take-up speed was 700 rpm.

Each of the spun fibers was charged into a tubular electric furnace, and air was supplied at a flow rate of 150 ml/min. In addition, the temperature was raised at a rate of 1°C/min, and after reaching 290°C, it was maintained for 1 hour to stabilize. After the stabilization step, nitrogen was injected at a rate of 150 ml/min and the temperature was raised at a rate of 5° C./min to reach 800° C. and then maintained for 0.5 hours to prepare carbon fibers.

The spinning properties of the isotropic pitch and the physical properties of the prepared carbon fibers are shown in Table 11 below.

Single yarn frequency during spinning
(700rpm, 20min) Carbon fiber diameter
(㎛) Carbon fiber tensile strength
(GPa) Carbon fiber elongation
(%) Comparative Example 1 0 8.71 1.3 3.2 Comparative Example 2 0 8.20 1.1 3.1 Example 1 0 6.85 1.8 2.4 Example 2 0 4.30 1.9 2.4 Example 3 0 11.40 1.6 2.7 Example 4 0 8.15 1.5 2.1 Comparative Example 3 10 7.60 1.0 1.9 Comparative Example 4 7 7.40 0.7 2.5 Comparative Example 5 0 7.80 0.9 2.5 Example 5 0 8.10 2.0 2.3 Example 6 0 7.30 1.7 2.3 Example 7 0 6.80 1.6 2.9 Example 8 0 7.10 1.5 2.1 Comparative Example 6 0 8.70 0.9 1.5

Both Comparative Examples and Examples were melt-spun, and as shown in Table 11, high-strength carbon fibers having a tensile strength of at least 1.5 GPa or more and a maximum of 2.0 GPa were prepared without single yarn in each Example, and elongation was also 2.1 to 2.7%. It belongs to, and the diameter of the carbon fiber belongs to 4.30~11.40㎛. On the other hand, in Comparative Example 1, the elastic modulus was too high as an elongation rate of 3.2% compared to the tensile strength of 1.3 GPa, and Comparative Example 2 also had a low elasticity modulus because the elongation rate was too high compared to the tensile strength of 1.1 GPa. In Comparative Examples 4, 5 and 6, the tensile strength of the prepared carbon fibers was 0.7, 0.9, and 0.9, respectively, and the tensile strength was significantly lower than that of each example.

This shows that the physical properties and structure of the isotropic pitch prepared in each example are suitable for producing high-strength isotropic pitch-based carbon fibers.

Claims (13)

In X-ray diffraction analysis (XRD), a (002) band appears at 23<2θ<25, and a carbon fiber having a structure satisfying the following formulas (1) to (4) in which the condensed aromatic ring compound is connected by an aliphatic chain Isotropic pitch for manufacturing.
5 ≤ L _a ≤ 15Å --- (1)
10 ≤ L _c ≤ 25Å --- (2)
3.50 ≤ d _m ≤ 4.50Å --- (3)
4.00 ≤ M ≤ 8.00Å --- (4)
(In the above formula, L _a means the average diameter of the condensed aromatic ring compound layer, L _c means the average diameter of the layered structure formed by the condensed aromatic ring compound layer, and d _m is the average between the layers of the condensed aromatic ring compound in the layered structure. Means the distance, and M means the average number of condensed aromatic cyclic compound layers included in the laminated structure (L _c / d _m ) + 1) The method of claim 1,
Isotropic pitch for producing carbon fibers with a softening point of 260 to 270°C. delete The method of claim 1,
Isotropic pitch for carbon fiber production with 4.80 ≤ d _{γ ≤ 5.20Å.}
(In the above formula, d _γ means the average distance between aliphatic chains connected to the condensed aromatic ring.) a) a pretreatment step of heat-treating and fractionating a raw material including any one or a mixture thereof selected from petroleum heavy oil, high boiling residue oil, aromatic hydrocarbon short substance, and naphtha cracking process residue oil at 190 to 240°C;
b) a filtering step of removing solid substances from the pretreated raw materials;
c) preparing a basic pitch from the filtered raw material; And
d) heating the basic pitch to prepare an isotropic pitch;
Method for producing an isotropic pitch for producing carbon fiber comprising a. delete According to claim 5, The step c) is a halogenation method prepared by further adding a halogen compound and a radical initiator to the raw material, followed by heating, or a thermal polymerization method in which nitrogen and gas by-products are fractionated by stirring and heating in an inert gas atmosphere. A method for producing an isotropic pitch for producing carbon fiber to produce a. The method of claim 7,
The halogenation method is a method of producing an isotropic pitch for producing carbon fiber, which is subjected to a halogenation reaction at 100 to 120°C for 0.1 to 2 hours, and then dehalogenation at 300 to 330°C for 2 to 4 hours. The method of claim 7,
The halogen compound is any one selected from chlorine, thionyl chloride, sulfuryl chloride, bromine and iodine, or a mixture thereof, a method for producing an isotropic pitch for producing carbon fibers. The method of claim 7,
The radical initiator is any one selected from benzoyl peroxide, dibutyl hydroperoxide, acetyl peroxide, azobisisobutyronitrile and azobismethylisobutylate, or a mixture thereof. The method of claim 7,
The thermal polymerization method is a method of producing an isotropic pitch for producing carbon fiber to proceed for 0.1 to 2 hours at 350 to 380 °C. The method of claim 7,
The softening point of the basic pitch prepared by the halogenation method is 70 to 130°C, and the softening point of the basic pitch prepared by the thermal polymerization method is 85 to 140°C. The method of claim 5,
The step d) is a method of producing an isotropic pitch for producing carbon fiber to proceed by heating at 300 to 350° C. for 0.1 to 1 hour in a vacuum atmosphere.

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