KR20120109227A - Method for preparation of carbon fibers using lignin copolymer and the carbon fibers prepared thereby - Google Patents

Abstract

PURPOSE: A carbon fiber and a method for fabricating the same are provided to improve carbonization yield and to cheaply obtain the carbon fiber. CONSTITUTION: A method for fabricating carbon fibers using a lignin-based copolymer comprises: a step of synthesizing the lignin-based copolymer; a step of preparing lignin-base copolymer spinning solution containing 10-50 wt% of the synthesized lignin-based copolymers; a step of wet-spinning the spinning solution to obtain a wet-spun fiber; a step of oxidation-stabilizing of the wet-spun fiber; and a step of carbonizing the stabilized fibers. A step of synthesizing the lignin-based copolymer comprises: a step of dissolving lignin and anhydrous halogen salt to prepare a lignin solution; a step of adding oxidation/reduction inhibitor to the lignin solution; a step of adding monomer compounds or monomer compound-dissolved solution to the lignin solution and performing graft copolymerization; and a step of terminating the graft copolymerization and drying the lignin-based copolymer. [Reference numerals] (AA) Lignin/AN; (BB) Lignin copolymer; (CC) Wet spinning; (DD) Thermal treatment; (EE) Lignin-based carbon fiber

Description

Method for preparation of carbon fibers using lignin copolymer and the carbon fibers prepared}

The present invention relates to a carbon fiber and a method of manufacturing the same, by producing a carbon fiber using a lignin-based copolymer prepared by copolymerizing lignin with a monomer compound, thereby reducing the content of expensive monomer compounds and improving the carbonization yield at low cost. It relates to a carbon fiber manufacturing method using a lignin-based copolymer capable of producing carbon fibers and a carbon fiber produced by the method.

Environmental and energy problems due to the depletion and overuse of fossil fuels can contribute to the solution by reducing the weight of the vehicle. When the weight of the vehicle is reduced, the consumption of fuel is reduced, and thus the displacement is also reduced, which is great in terms of saving energy and protecting the environment. Meanwhile, the development of electric vehicles is urgently needed to solve this energy environment problem, and the weight reduction is more urgently required because of limited power sources such as batteries and fuel cell capacitors. Therefore, it is proposed to use carbon fiber composite material as a method of lightening the automobile.

However, the price of carbon fiber is so high that it is applicable to automobiles and has been proposed at $ 10- $ 15 / kg, which is about 50% of the current market price (Source: US Department of Defense, Polyacrylonitrile (PAN) Carbon). Fibers Industrial Capability Assessment "OUSD (AT & L) Industrial Policy, October 2005) .The mechanical properties of the fibers require a strength of 1.73 GPa, a tensile modulus of 173 GPa, and an elongation of 1% or more. The price of acrylonitrile (AN) accounts for 42% of the total carbon fiber manufacturing price, while it is a petrochemical product, which is likely to rise further as fossil fuels are depleted. It is inevitable to replace

More recently, the importance of solving energy environmental problems and developing aerospace technology is increasing. At this time, the task of low-cost mass production of carbon fiber must be accomplished urgently.

Therefore, the production of carbon fiber using low-cost raw materials instead of PAN is the basis for low carbon fiber production. For this reason, lignin, which accounts for about 20% of grass plants, is considered a suitable raw material for low-carbon carbon fiber production. If it is possible to produce carbon fiber with 100% lignin, a 40% price reduction is possible.

Lignin is an abundant and sustainable substance present in grass plants and contains aromatic rings, resulting in high carbon yields (60%) at high temperatures, so lignin is a sufficient source of carbon fiber. It can be said to have.

Looking at the structure of lignin, in general, lignin has a very complex and inconsistent structure. In the natural state, lignin is a crosslinked polymer material having side chain structure and iso-chains bonded to each other. Lignin has a different branching structure, which depends on the part of the wood. When the lignin is recovered, its chemical structure changes, and in the case of pure lignin, its molecular weight ranges from 1,000 to 150,000. Lignin may be recovered by Alkali, Sulfide, Ball milling, hydrochloric acid treatment, enzyme treatment, or organic solvent treatment. In particular, Alkali lignin is obtained in the process of preparing Kraft pulp. In other words, in the paper industry using the Kraft pulp process, a large amount of lignin is produced as a black liquor by-product, which is commonly used as a fuel and as additives such as humidifiers and adhesives. It is used.

Removing all Na, K, etc. among the lignin compounds becomes an insoluble alkali lignin in water, whereas lignin containing K, Na, etc. is slightly soluble in water and the pH increases from 7 to 14 solubility It is further increased to dissolve completely in 5% NaOH solution. As a result, about 20 million tonnes of lignin are produced annually in the United States.

On the other hand, the technical configuration of the process for producing carbon fibers using lignin has been known by Oak Ridge patent (US 7,727,932 B2). However, since the US patent uses lignin having a molecular weight that is too small, there is a problem in that the mass production is difficult because the fiber is very weak when the heat treatment process for spinning and stabilizing carbonization is attempted.

The present inventors have made efforts to solve the above disadvantages and problems of the prior art as a result of the present invention by producing a lignin-based copolymer having a large molecular weight, and developing a technology for producing carbon fibers using the lignin-based copolymer It was completed.

Accordingly, an object of the present invention is to produce a carbon fiber using a lignin-based copolymer capable of synthesizing a lignin copolymer having a viscosity and molecular weight suitable for the production of carbon fibers from hard / soft wood and using the same to produce a large amount of carbon fibers It is to provide a method and a carbon fiber produced by the method.

Another object of the present invention is to produce a carbon fiber using a lignin copolymer, not only to produce a low-cost carbon fiber but also to produce a carbon fiber having a carbon yield of more than 50% by an environmentally friendly method in the lignin air It is to provide a carbon fiber manufacturing method using the coalescence and the carbon fiber produced by the method.

The objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

In order to achieve the above object, the present invention comprises the steps of synthesizing the lignin copolymer; Preparing a lignin-based copolymer spinning solution containing 10 to 50% by weight of the synthesized lignin-based copolymer; Wet spinning the spinning solution to obtain wet spinning fibers; Oxidatively stabilizing the wet spinning fibers to obtain stabilizing fibers; And it provides a carbon fiber manufacturing method using a lignin-based copolymer comprising the step of carbonizing the stabilizing fiber to obtain a carbon fiber.

In a preferred embodiment, the step of synthesizing the lignin-based copolymer is a step of preparing a lignin solution by dissolving the lignin and anhydrous halogen salt, adding an oxidation / reduction initiator to the lignin solution, and the oxidation / reduction Performing a graft copolymerization reaction by adding a monomer compound or a solution in which the monomer compound is dissolved in the lignin solution to which the initiator is added, and separating and drying the lignin copolymer produced by terminating the graft copolymerization reaction. do.

In a preferred embodiment, the monomer compound is acrylonitrile (AN, acrylonitrile), acrylic acid (AA, acrylic acid), ethyl acrylate (EA, ethyl acrylate), vinyl alcohol (VA, vinylachol), vinyl ester (VE , vinyl ester), imide, benzimidazol, phenol, ethylene, propylene, P, propylene, vinyl chloride, Styrene (S, styrene), aniline (A, analine), methyl methacrylate (MMA, methylmethacrylate), vinylidene chloride (VDC, vinylidence chloride), vinylidene fluoride (VDF) and various pitches ) Is either one.

In a preferred embodiment, the graft copolymerization reaction uses a monomer compound of 10-50% by weight and 50-90% by weight of lignin.

In a preferred embodiment, the oxidation / reduction initiator is a peroxide.

In a preferred embodiment, the graft copolymerization is terminated by precipitation in an acidic bath having a pH of 1-5.

In a preferred embodiment, the spinning solution includes a solvent in which the lignin copolymer and the monomer compound used in the polymer can be dissolved simultaneously.

In a preferred embodiment, the solvent is any one of dimethyl sulfoside (DMSO), dimethyl acetamide (DMAc), dimethyl formamide (DMF).

In a preferred embodiment, the wet spinning fibers are obtained by wet spinning the spinning solution in a coagulation bath.

In a preferred embodiment, the oxidation stabilization treats the wet spinning fibers at 20-250 ° C. in air.

In a preferred embodiment, the carbonization treats the stabilizing fibers at 1500 ° C or below.

In addition, the present invention provides a carbon fiber using a lignin-based copolymer, characterized in that produced by any one of the carbon fiber manufacturing method described above.

In a preferred embodiment, the carbon fiber has a carbonization yield of at least 50%.

The present invention has the following excellent effects.

First, according to the carbon fiber manufacturing method using the lignin-based copolymer of the present invention and the carbon fiber prepared by the method, a lignin copolymer having a viscosity and molecular weight suitable for the production of carbon fiber from hard / soft wood is synthesized To produce a large amount of carbon fiber.

In addition, according to the carbon fiber manufacturing method using the lignin-based copolymer of the present invention and the carbon fiber prepared by the method, it is possible to produce a carbon fiber using a lignin-based copolymer as well as to produce a low-cost carbon fiber 50% Carbon fibers having the above carbonization yield can be produced by an environmentally friendly method.

1 is a flow chart showing a simplified process for producing a carbon fiber using a lignin-based copolymer according to a preferred embodiment of the present invention,
2 is a synthesis process according to an embodiment of the lignin-based copolymer shown in FIG.
3 is a synthesis process according to another embodiment of the lignin-based copolymer shown in FIG.
4 is a synthetic process for producing carbon fibers from the lignin-based copolymer, as shown in Figure 1,
FIG. 5 is a photograph of a wet spinning fiber made of a lignin-based copolymer as a precursor according to the flowchart shown in FIG. 1; FIG. (a) radiofiber photographs, b) scanning electron microscopy (SEM) photographs,
6 is a photograph of an oxidative stabilized fiber obtained by oxidatively stabilizing the wet spinning fiber of FIG. 5; (a) stabilized fiber image, b) scanning electron microscope (SEM) image
FIG. 7 is a photograph of carbon fibers prepared by carbonizing the oxidative stabilized fiber of FIG. 6; FIG. (a) Carbon fiber photographs, b) Scanning electron microscope (SEM) photographs.

Although the terms used in the present invention have been selected as general terms that are widely used at present, there are some terms selected arbitrarily by the applicant in a specific case. In this case, the meaning described or used in the detailed description part of the invention The meaning must be grasped.

Hereinafter, with reference to the preferred embodiment shown in the accompanying drawings will be described in detail the technical configuration of the present invention.

However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Like reference numerals used to describe the present invention throughout the specification denote like elements.

The technical feature of the present invention is to use a lignin-based copolymer as the material of the carbon fiber.

Therefore, the carbon fiber manufacturing method of the present invention comprises the steps of synthesizing the lignin-based copolymer; Preparing a lignin-based copolymer spinning solution containing 10 to 50% by weight of the synthesized lignin-based copolymer; Wet spinning the spinning solution to obtain a fiber; Oxidatively stabilizing the wet spinning fibers to obtain stabilizing fibers; And carbonizing the stabilizing fibers to obtain carbon fibers.

First, the step of synthesizing the lignin-based copolymer is to prepare a lignin solution by dissolving the lignin and anhydrous halogen salt, adding an oxidation / reduction initiator to the lignin solution, and the lignin added to the oxidation / reduction initiator A graft copolymerization reaction is performed by adding a monomer compound or a solution in which the monomer compound is dissolved in the solution, and separating and drying the lignin copolymer produced by terminating the graft copolymerization reaction. At this time, the lignin solution is preferably prepared in an atmosphere in which oxygen is not present. In addition, the termination of the graft copolymerization reaction is preferably carried out by precipitation in an acid bath having a pH of 1-5.

Particularly, in the present invention, lignin composed of oxyphenylpropene polymer obtained from hard wood was used to synthesize lignin-based copolymer, and hard wood lignin is a propene group having an aromatic ring and an OH ⁻ group substituted with an alkoxy group, as shown in the following [Formula 1]. It is divided into the structure of Coniferyl alcohol and Sinapyl alcohol with repeating units of. Therefore, hardwood lignin may be substituted with an alkyl group in an aromatic ring, or sulfur may be combined with a polymer to replace a sulfonate group.

[Structural formula 1]

As a result, the lignin-based copolymer can be synthesized through a graft copolymerization reaction in which a radical reaction of a monomer compound that can be grafted to the side of the oxyphenylpropene aromatic ring, which is a lignin main chain, is performed. At this time, the graft copolymerization reaction preferably uses 10-50% by weight of lignin and 50-90% by weight of a monomer compound.

In the present invention, the monomer compound that can be used for the graft copolymerization reaction may be -COOH, -C≡N, -H CH ₂ = CHY (Y = COOH, C≡N, H), etc., preferably Is acrylonitrile (AN, acrylonitrile), acrylic acid (AA, acrylic acid), ethyl acrylate (EA, ethyl acrylate), vinyl alcohol (VA, vinylachol), vinyl ester (VE, vinyl ester), imide (I , imide), benzylimidazole (BI, benzimidazol), phenol (phenol), ethylene (E, ethylene), propylene (P, propylene), vinyl chloride (VC, vinylchloride), styrene (S, styrene), aniline (A, analine), methyl methacrylate (MMA, methylmethacrylate), vinylidene chloride (VDC, vinylidence chloride), vinylidene fluoride (VDF, vinylidene fluoride) and various pitch (pitch) and the like can be used. In particular, the acrylonitrile does not interfere with the radical reaction of the nitrile group in the structure, and thus, it is possible to synthesize a graft copolymer in which monomers are arranged on a regular basis in the lignin backbone.

In general, the lower the lignin concentration, the less the side reactions in graft polymerization. The peroxide used herein serves as an initiator as in the following [Scheme 1], and generates a radical in the lignin to polymerize with the AN monomer as shown in the following [Scheme 2].

[Scheme 1]

[Formula 2]

Looking at a specific example of the step of synthesizing the lignin-based copolymer as a specific example, as follows. First, lignin and crushed anhydrous halogen salt are dissolved in a purified solvent to prepare a lignin solution. Hydrogen peroxide is added to the reactants and mixed uniformly while bubbling the dissolved two reactants with nitrogen for 20 minutes. Next, when AN is added to the lignin mixed solution as a monomer compound and the temperature is maintained at 70 ° C., the reactant gradually polymerizes through a polymerization reaction, thereby increasing the viscosity. The reaction temperature is possible in the range of 20-100 ° C. The reaction time for the graft polymerization is 1-12 hours, and a peroxide is used to terminate the reaction. For example, a 1 wt% aqueous hydroquinone aqueous solution may be used, and washed with water. Thereafter, 10 times of water is poured into the reaction product, the mixture is stirred, the product is precipitated, washed with a suitable coagulation solvent, and dried to obtain a lignin copolymer. The yield can be calculated by Equation 1 below.

[Equation 1]

{GPW / (MW + LW)} × 100

GPW: Graft Polymer Weight

MW: weight of monomer compound

LW: weight of lignin

Next, the step of preparing a lignin-based copolymer spinning solution is made by dissolving the lignin-based copolymer synthesized as above in the solvent 10 to 50% by weight. Here, the solvent is preferably a solvent that can dissolve the lignin copolymer and the monomer compound contained in the polymer at the same time, more preferably dimethyl sulfoside (DMSO), dimethyl acetamide (DMAc), dimethyl formamide (DMF) Either one is used.

Next, in the step of obtaining the wet spinning fibers, the wet spinning fibers are obtained by stretching the prepared lignin-based copolymer spinning solution in a coagulation bath and wet spinning in a known manner, as an example of wet spinning, spinning solution It was spun into a 10% v / v DMF coagulation bath using a syringe with a 0.2mm diameter needle, and then wound to obtain a wet spinning fiber.

Next, the step of obtaining a stabilizing fiber is performed by oxidative stabilization of the wet spinning fiber, the oxidation stabilization is to treat the wet spinning fiber at 20-250 ℃ in air.

Next, the step of obtaining the carbon fiber is carried out by carbonizing the stabilizing fibers, the carbonization is carried out by treating the stabilizing fibers in a known method at 1500 ℃ or less.

Carbon fiber using the lignin copolymer prepared by the above-described method has a carbonization yield of 50% or more, and thus it can be seen that the carbonization yield is excellent even though it can be obtained at low cost by using a lignin copolymer and performing a relatively simple process. have.

Example 1

1. Synthesis of Lignin Copolymer 1

In a 250 mL round flask containing 27.52 g of DMSO, 9.44 g of hardwood lignin (PC1369) and 9.40 CaCl ₂ were prepared using the method shown in FIG. 30 mL of hydrogen peroxide solution was added and 8.5 mL was added to react with nitrogen. 9.35 g of AN dissolved in 10 g of DMSO was added to the lignin mixed solution, followed by further reaction at 70 ° C for 12 hours. The reaction was terminated by adding 10 times (v / v) acidic water of the product slurry with pH 2 to the reactants, and the resulting precipitate was washed with a coagulant and dried to synthesize lignin copolymer 1 having a yield of 89.6%. It was.

2. Preparation of lignin copolymer spinning solution

A lignin copolymer spinning solution was prepared by dissolving 20.0% copolymer 1 in DMF solvent.

3. Manufacture of wet spinning fibers

The prepared lignin copolymer spinning solution was wound by spinning in a 10% v / v DMF coagulation bath using a syringe with a 0.2 mm diameter needle. Photographs and electron micrographs (SEM) of the obtained spinning fibers are shown in FIG. 5. SEM images showed that the average diameter of the fiber ranged from 70 to 90 μm and the surface roughness was very large.

4. Stabilized Fiber Manufacturing

The spinning fiber obtained by wet spinning is supplied with hot air circulation at a flow rate of 5 to 20 mL per minute, heated to 225 ° C at a temperature rising rate of 1 ° C per minute, maintained at that temperature for 1 hour, and then to room temperature. Air cooling was carried out for the oxidation stabilization step.

5. Carbon Fiber 1 Manufacturing

As shown in FIG. 4, the stabilized fibers were heated to 1000 ° C. at a temperature increase rate of 5 ° C. per minute using a tubular heat treatment furnace in a nitrogen atmosphere, maintained at that temperature for 1 hour, and then cooled to room temperature. The yield of carbon fiber 1 obtained after the carbonization process was 45.50 ~ 54.90%.

Example 2

Carbon fiber 2 was prepared in the same manner as in Example 1 except that lignin-based copolymer 2 synthesized by the method described below was used.

1. Synthesis of Lignin Copolymer 2

As shown in FIG. 3, the dual initiation method was performed in two stages. In the first step, AN is polymerized using azobisisobutyronitrile (AIBN), and in the second step, the polymerized olygomer / polyacrylonitrile (PAN) is mixed with lignin / CaCl ₂ / peroxide dissolved in DMSO to proceed with the reaction of lignin and PAN. This is how to get coalescence.

Step 1: When 19.8 g of AN and 22 mg of AIBN are dissolved in 50 g of DMSO solvent and reacted at 70 ° C. for 2 hours under a nitrogen atmosphere, a phenomenon that the viscosity becomes bright and yellow is observed. And then mixed with the lignin solution prepared in step 2 and reacted for an additional 4 hours.

Step 2: Add 8.0 g of hardwood lignin and 8.0 g of CaCl ₂ dissolved in 40 g of DMSO, disperse, add 4.3 mL of 30% aqueous hydrogen peroxide solution, and then proceed under nitrogen atmosphere for 6 hours.

The solution prepared in Step 1 and Step 2 was mixed and reacted for 6 hours. The amount of the solid component thus obtained was 17.7 wt% and after 12 hours of reaction, acidic water adjusted to pH 2 was added 10 times (v / v) to terminate the reaction. The resulting precipitate was washed with a suitable coagulant and then dried at 70 ° C. to synthesize lignin based copolymer 2 having a yield of 62.8%.

In the above examples, the concentration used is wt% and the temperature is ° C unless otherwise specified. Hardwood lignin was used as PC1369 and DMSO was used by Yakuri Pure Chemical Co., Korea. Hydrogen peroxide was used as a 30% aqueous solution. Ltd, Korea, and 1% hydroquinone aqueous solution was used.

Experimental Example 1

After dissolving 20.0% copolymer 1 or 2 in DMF solvent to prepare a spinning solution, the viscosity was measured at 25 ° C. using a synthetic Brookfield viscometer and the results are shown in Table 1.

division Synteesis route Copolymer solution wt% in DMF Viscosity (cP) Lignin copolymer 1 CaCl ₂ -H ₂ O ₂ 30 17.96 50 84.03 40 273 Lignin copolymer 2 Double initiation 15 431.90 20 673.07

Experimental Example 2

The appearance of the wet spinning fiber obtained in Example 1 was observed, and the photograph (a) and the electron micrograph (SEM) (b) are shown in FIG. 5. SEM images showed that the average diameter of the fiber ranged from 70 to 90 μm and the surface roughness was very large.

Experimental Example 3

The appearance of the stabilized fiber obtained in Example 1 was observed, and as a result, the photograph (a) and the electron micrograph (SEM) (b) are shown in FIG. 6. SEM images showed that the average diameter of the fibers ranged from 65 to 80 μm.

Experimental Example 4

The appearance of the carbon fiber obtained in Example 1 was observed, and as a result, the photograph (a) and the electron micrograph (SEM) (b) are shown in FIG. 7. SEM images showed that the average diameter of the fibers ranged from 51 to 60 μm.

In the above experimental examples, when the spinning solution prepared from the lignin copolymer was wet-spun as in the manufacturing method of the present invention, carbon fiber using the lignin copolymer having excellent carbonization yield was obtained by performing a relatively simple process. I can see.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, Various changes and modifications will be possible.

Claims (13)

Synthesizing the lignin copolymer;
Preparing a lignin-based copolymer spinning solution containing 10 to 50% by weight of the synthesized lignin-based copolymer;
Wet spinning the spinning solution to obtain wet spinning fibers;
Oxidatively stabilizing the wet spinning fibers to obtain stabilizing fibers; And
Carbon fiber manufacturing method using a lignin-based copolymer comprising the step of carbonizing the stabilizing fiber to obtain a carbon fiber.
The method of claim 1,
The synthesizing of the lignin copolymer may include preparing a lignin solution by dissolving lignin and anhydrous halogen salt, adding an oxidation / reduction initiator to the lignin solution, and adding the oxidation / reduction initiator to the lignin solution. A lignin comprising the step of performing a graft copolymerization reaction by adding a monomer compound or a solution in which the monomer compound is dissolved, and separating and drying the lignin copolymer produced by terminating the graft copolymerization reaction. Carbon fiber manufacturing method using a pore polymer.
The method of claim 2,
The monomer compound is acrylonitrile (AN, acrylonitrile), acrylic acid (AA, acrylic acid), ethyl acrylate (EA, ethyl acrylate), vinyl alcohol (VA, vinylachol), vinyl ester (VE, vinyl ester), I, imide, benzimidazol (BI, benzimidazol), phenol, ethylene (E, ethylene), propylene (P, propylene), vinyl chloride (VC, vinylchloride), styrene (S, styrene ), Aniline (A, analine), methylmethacrylate (MMA, methylmethacrylate), vinylidene chloride (VDC, vinylidence chloride), vinylidene fluoride (VDF) and any one of the various (pitch) Carbon fiber manufacturing method using a lignin copolymer characterized in that.
The method of claim 2,
The graft copolymerization method is a carbon fiber manufacturing method using a lignin copolymer, characterized in that the monomer compound of 10-50% by weight and 50-90% by weight lignin is used.
The method of claim 2,
The oxidation / reduction initiator is a carbon fiber manufacturing method using a lignin-based copolymer, characterized in that the peroxide. The method of claim 2,
Terminating the graft copolymerization reaction is a carbon fiber manufacturing method using a lignin-based copolymer, characterized in that the precipitate is formed in an acidic bath having a pH of 1-5.
The method of claim 1,
The spinning solution is a carbon fiber manufacturing method using a lignin copolymer, characterized in that the lignin copolymer and a monomer compound used in the polymer can be dissolved at the same time.
The method of claim 7, wherein
The solvent is dimethyl sulfoside (DMSO), dimethyl acetamide (DMAc), dimethyl formamide (DMF) carbon fiber manufacturing method using a lignin copolymer, characterized in that any one of.
The method of claim 1,
The wet spinning fiber is a carbon fiber manufacturing method using a lignin-based copolymer, characterized in that obtained by spinning the spinning solution in a coagulation bath and wet spinning.
The method of claim 1,
The oxidation stabilization is a carbon fiber manufacturing method using a lignin copolymer, characterized in that the wet spinning fibers are treated at 20-250 ℃ in air.
The method of claim 1,
The carbonization is a carbon fiber manufacturing method using a lignin-based copolymer, characterized in that for treating the stabilized fiber at 1500 ℃ or less.
Carbon fiber using a lignin-based copolymer, characterized in that produced by any one of carbon fiber manufacturing method of claim 1.
13. The method of claim 12,
The carbon fiber is a carbon fiber using a lignin-based copolymer, characterized in that having a carbonization yield of 50% or more.

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