KR101755267B1

KR101755267B1 - Carbon fiber using electron beam cross-linked polyacrylonitrile fiber and method for preparing the same

Info

Publication number: KR101755267B1
Application number: KR1020150076682A
Authority: KR
Inventors: 이성호; 조성무; 박세준; 조한익
Original assignee: 한국과학기술연구원
Priority date: 2015-05-29
Filing date: 2015-05-29
Publication date: 2017-07-10
Also published as: KR20160140268A

Abstract

When polyacrylonitrile fiber is used for carbon fiber production, it is crosslinked by electron beam before oxidation and stabilization to improve heat resistance. Followed by oxidation and stabilization, in particular oxidation and stabilization using plasma coupled thermal energy, followed by carbonization to produce carbon fibers. Accordingly, the energy consumption of the oxidation and stabilization process of the polyacrylonitrile fiber can be significantly reduced during the production of the carbon fiber, thereby achieving the cost reduction of the carbon fiber. Further, the heat resistance before oxidation and stabilization process is increased to lower the heat generation amount, and the ignition problem in the oxidation and stabilization process can be solved. Further, homogeneous crosslinking, and uniform oxidation and stabilization are enabled, and the physical properties of the carbon fiber can be improved.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to carbon fibers using crosslinked polyacrylonitrile fibers by electron beam irradiation,

The present invention relates to a high-performance low-cost carbon fiber using electron beam crosslinked polyacrylonitrile fibers and a method for producing the same.

Carbon fiber is one-fifth the weight of steel, but its strength is more than ten times stronger. Accordingly, carbon fiber is used as a high-strength structural material in various industrial fields such as aerospace, sports, automobiles, and bridges. Carbon fiber has begun to attract attention as a next-generation material due to the rapid development and upgrading of the automobile and aerospace industries, and demand is increasing as the automobile industry aims for environment-friendly, low-energy consumption futuristic automobile. In the field of automobiles, there is a growing demand for lighter automobiles as well as environmental regulations related to automobile exhaust gas, which will be a problem in the future. Therefore, the demand for carbon fiber reinforced composites that can maintain the structural mechanical strength while increasing the weight of automobiles has increased rapidly .

However, since the price of carbon fiber is too high to be used for the above purposes, it is necessary to use the carbon fiber suitable for the automobile industry and the construction infra. 1 or more should be lowered.

Generally, carbon fibers are prepared through an oxidation and stabilization process which oxidizes and stabilizes by heating in an oxidizing atmosphere to insolubilize the precursor fibers, and a carbonization process which carbonizes the oxidized and stabilized fibers at a high temperature. And subsequently subjected to a graphitization process. The oxidation and stabilization process is a process for making the molecular structure of the fiber more stable by causing a reaction between oxygen and fiber to cause a cyclization reaction with the dehydrogenation reaction.

As the precursor fiber of the carbon fiber, polyacrylonitrile (PAN), pitch, rayon, lignin and polyethylene are used. Of these, polyacrylonitrile (PAN) fibers are the best precursors for producing high-performance carbon fibers as compared to other precursors because they have a high carbon yield of 50% or higher and a high melting point. Accordingly, most current carbon fibers are made from polyacrylonitrile fibers.

Typically, polyacrylonitrile (PAN) fibers for producing carbon fibers have a carboxylic functional group such as itaconic acid, which is about 95% by weight or more of acrylonitrile (AN) and can act as a catalyst for the stabilization reaction, By weight of acrylic comonomers having a weight average molecular weight of less than about 5% by weight. Such polyacrylonitrile fibers are capable of producing carbon fibers having high performance.

However, the above-mentioned polyacrylonitrile fibers for producing carbon fibers are very expensive compared to ordinary fibers. Typically, carbon fibers have a pricing structure of about 43% for precursor fibers, 18% for oxidation and stabilization processes, 13% for carbonization processes and about 15% for graphitization processes due to the high cost of precursor fibers. Therefore, oxidation and stabilization processes as well as cost reduction of precursor fibers can be a key technology of carbon fiber cost reduction technology. In addition, the oxidation and stabilization process is the most energy consuming process in carbon fiber manufacturing process because it is very slow reaction compared with carbonization process.

Thus, various attempts have been made to reduce the stabilization process time because oxidation and stabilization processes using heat in carbon fiber manufacturing processes account for most of the entire process time.

In place of the thermal stabilization process, oxygen molecules reacting with the fibers are converted into oxygen species having a high reactivity (oxygen atoms, ozone, NxOy, etc.) by plasma generated using RF, DC, microwave or pulsed power sources. Etc.), thereby increasing the reaction rate of the oxygen reacting with the fibers, thereby enabling a quick reaction to occur.

However, according to the study results of the present inventors, the heat resistance of the polyacrylonitrile fiber is not high, so that it is difficult to control the heat generation when the conventional oxidation and stabilization process is performed, and there is a problem that ignition occurs. In the oxidation and stabilization process using the conventional thermal stabilization process or plasma or the like, in particular, when the number of bundles of the used fibers is large, heat or oxygen species penetrate deeply enough into the bundle and do not react, It is difficult to uniformly oxidize and stabilize the fiber strands due to the incomplete stabilization of the fiber strands. In this case, the strength of the finished carbon fiber is remarkably lowered after the carbonization process, resulting in a deterioration in the overall quality.

U.S. Patent No. 3,607,063 U.S. Patent No. 6372,192 U.S. Patent No. 7,824,495 Korean Patent No. 1395811

Embodiments of the present invention minimize energy consumption in the oxidation and stabilization process of polyacrylonitrile fibers during the manufacture of carbon fibers using polyacrylonitrile (PAN) fibers as precursors and increase heat resistance prior to oxidation and stabilization processes Which is capable of solving the problem of ignition in the oxidation and stabilization process by lowering the heat generation amount and capable of uniform crosslinking and uniform oxidation and stabilization to improve the physical properties of the carbon fiber and a manufacturing method thereof .

In the exemplary embodiments of the present invention, as a primary precursor for producing carbon fibers, the polyacrylonitrile fiber is crosslinked by irradiation with an electron beam to improve heat resistance before the oxidation and stabilization of the polyacrylonitrile fiber. Precursor.

Exemplary embodiments of the present invention provide a secondary precursor for carbon fiber manufacturing, wherein the primary precursor is oxidized and stabilized.

In exemplary embodiments of the present invention, as the carbon fiber, there is provided a carbon fiber carbonized with the second precursor.

In exemplary embodiments of the present invention, the step of crosslinking the polyacrylonitrile fiber by irradiation of an electron beam before oxidation and stabilization to improve the heat resistance of the polyacrylonitrile fiber; Oxidizing and stabilizing the crosslinked polyacrylonitrile fibers; And carbonizing the oxidized and stabilized polyacrylonitrile fiber. The present invention also provides a method for producing carbon fiber, comprising the steps of:

In an exemplary embodiment, the exothermic peak for cyclization of the polyacrylonitrile is reduced by the crosslinking.

In an exemplary embodiment, the polyacrylonitrile fibers to be crosslinked preferably comprise polyacrylonitrile fibers for fabrics having an acrylonitrile monomer content of 95% or less.

In an exemplary embodiment, the polyacrylonitrile fibers for fabrics are made from a polyacrylonitrile fiber having a content of acrylonitrile (AN) monomer of 95 wt% or less, a fiber diameter of 15 mu m or more, a tensile strength Tensile strength according to the measurement method) is selected to be not more than 3.5 g / d.

In an exemplary embodiment, the polyacrylonitrile (PAN) fibers for fabrics have an acrylonitrile (AN) monomer content of 60-95 wt% (more specifically 65-90 wt%), Of 15 to 25 탆 and a tensile strength of 1.2 to 3.5 g / d.

In an exemplary embodiment, the polyacrylonitrile fibers to be electron beam crosslinked may comprise polyacrylonitrile fibers for fabrics and polyacrylonitrile fibers for making carbon fibers.

In the exemplary embodiment, electron beam irradiation and the total energy is 50 ~ 3000kGy irradiated fibers of polyacrylonitrile, the temperature range of at least the electron beam irradiation room temperature 300 ^o C or less, preferably made in air.

In an exemplary embodiment, it is particularly preferred that the crosslinked polyacrylonitrile fibers after said electron beam crosslinking are oxidized and stabilized using plasma bonded thermal energy.

In an exemplary embodiment, the polyacrylonitrile fibers during oxidation and stabilization can be oxidized and stabilized using plasma-bonded thermal energy under normal pressure or under vacuum.

In an exemplary embodiment, oxygen can be oxidized and stabilized for 30 to 250 minutes using a plasma at a temperature range of 180 to 350 DEG C under an oxidizing atmosphere in which oxygen is present.

In an exemplary embodiment, the carbon fiber manufacturing method may further perform graphitization.

In an exemplary embodiment, the carbonization or graphitization may be performed using a microwave-induced plasma.

According to the embodiments of the present invention, the energy consumption of the oxidation and stabilization process of the polyacrylonitrile fiber can be greatly reduced during production of carbon fiber using polyacrylonitrile (PAN) fiber as a precursor, . Further, the heat resistance before oxidation and stabilization process is increased to lower the heat generation amount, and the ignition problem in the oxidation and stabilization process can be solved. Further, homogeneous crosslinking, and uniform oxidation and stabilization are enabled, and the physical properties of the carbon fiber can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing a process for producing carbon fibers according to an exemplary embodiment of the present invention. Fig.
2 is a scanning electron microscope (SEM) image showing carbon fiber obtained by carbonization after oxidizing / stabilizing reaction by thermal energy according to Comparative Example 1 of the present invention for 15 minutes (FIG. 2A) and 120 minutes )to be.
Fig. 3 is a graph showing the results of a stabilization reaction by atmospheric plasma-bonded thermal energy according to Comparative Example 2 of the present invention for 15 minutes (Fig. 3a) and 60 minutes (Fig. 3b) Microscope (SEN) is a photograph.
4 is a photograph showing PAN fiber (12K) for carbon fiber irradiation irradiated with various energy in Example 1-1 of the present invention.
FIG. 5A is a photograph showing a carbon fiber 1 for textiles irradiated with electron beams at various energies in the example 2-1 of the present invention after heat stabilization and carbonization, and 5b and 5c are photographs Infrared spectroscopy (FT-IR) and DSC analysis of carbon fiber 1.

As used herein, the precursor for producing carbon fibers refers to a raw material used for producing carbon fibers.

In the present specification, the terms first and second precursors for the production of carbon fibers may be used in particular. These terms are defined. The polyacrylonitrile fiber used for the carbon fiber is oxidized and stabilized, and then carbonized to carbon fiber. Here, the material before oxidation and stabilization is defined as a primary precursor for producing carbon fibers. Further, after the primary precursor is oxidized and stabilized, the material before carbonization is defined as a secondary precursor for carbon fiber production.

Plasma-bonded thermal energy herein refers to the simultaneous provision of thermal energy during plasma oxidation and stabilization of the primary precursor for carbon fiber production.

In the present specification, polyacrylonitrile fibers for fabrics are sometimes referred to as fibers. Polyacrylonitrile fibers for fabrics means that the acrylonitrile monomer is 95% by weight or less.

In this specification, polyacrylonitrile fibers for producing carbon fibers are sometimes referred to as polyacrylonitrile fibers in comparison with polyacrylonitrile fibers for fabrics. Polyacrylonitrile fiber for making carbon fibers as compared to polyacrylonitrile fibers for fabrics means that there are more than 95% by weight of acrylonitrile monomer and acrylic comonomer containing itaconic acid.

Hereinafter, exemplary embodiments of the present invention will be described in detail.

In exemplary embodiments of the present invention, polyacrylonitrile fibers having improved heat resistance through electron beam crosslinking are used as a primary precursor for carbon fiber production (i.e., a precursor before oxidation and stabilization) in the production of carbon fibers. Such electron beam crosslinking serves to improve the heat resistance of the polyacrylonitrile fiber used as the carbon fiber precursor before oxidation and stabilization. That is, the exothermic peak for cyclization of the nitrile group of the polyacrylonitrile is reduced. As a result, the polyacrylonitrile fibers having increased heat resistance have significantly lowered the exothermic temperature and the calorific value of the polyacrylonitrile polymer, so that the oxidation and stabilization reaction can be completed at a lower temperature and at a lower calorific value in a subsequent oxidation and stabilization process . Therefore, it is possible to solve the ignition problem due to a large amount of calorific value, which has been difficult to control in the conventional oxidation and stabilization process.

On the other hand, the electron beam irradiation induces mainly the crosslinking between the chains of the polymer (the C-C bond of the different polymer main chain of the polyacrylonitrile polymer), so that the cyclization reaction of the -CN group of the polyacrylonitrile polymer is very slight. That is, when only the electron beam irradiation is performed on the carbon fiber precursor fiber, only the incomplete oxidation stabilization is obtained, so that carbon fibers having extremely poor physical properties are produced. Therefore, oxidation and stabilization processes for inducing the cyclization reaction of the -CN group after crosslinking of the polyacrylonitrile polymer by electron beam irradiation should be additionally performed.

In connection with this, when the electron beam is irradiated at a temperature of 300 ° C or lower at room temperature to conduct electron beam crosslinking, the cyclization reaction of the -CN group can be partially induced in the electron beam irradiation process by heat. However, even in the case of irradiating electron beams under such a heated temperature atmosphere, since the crosslinking reaction by electron beam irradiation is short within several minutes, the cyclization reaction of -CN group by heat is very insufficient. In addition, if the electron beam irradiation time is prolonged and the cross-linking between the polymer chains is excessively increased, the cross-linked structure hinders the cyclization reaction by the -CN group, so that the cyclization reaction is incomplete and the oxidation and stabilization reaction is not completed As a result, the physical properties of the carbon fiber are lowered. On the other hand, if polyacrylonitrile bridges are incompletely crosslinked, heat generation and ignition problems in the oxidation and stabilization steps can not be solved.

Therefore, in the exemplary embodiments of the present invention, for example, crosslinking is mainly performed by electron beam irradiation at a temperature of room temperature or 300 ° C even if room temperature or heat is applied, and then additional oxidation is performed to complete the cyclization reaction of the -CN group And the stabilization process. Further, in the exemplary embodiments of the present invention, this oxidation and stabilization process can be performed by a thermal energy-bonded plasma to save energy and produce carbon fibers of excellent physical properties.

On the other hand, when the electron beam crosslinking is carried out, since the penetration depth of the electron beam into the polyacrylonitrile fiber is large, uniform crosslinking can be carried out. Generally, the number of filaments of carbon fiber is about 1000 filaments (1K) to 20,000 filaments (20K). If the number of filaments is increased, incomplete oxidation and stabilization occurs in the oxidation and stabilization process, or a problem of ignition due to a rapid heating value is caused. It is possible to uniformly perform cross-linking even in the case of Rajitou, such as more filaments such as 50,000 filaments (50K) and 100,000 filaments (100K).

Also, in exemplary embodiments of the present invention, polyacrylonitrile fibers for fabrics can be used as precursors for carbon fiber fabrication by using electron beam crosslinking.

In the exemplary embodiments of the present invention, the electron beam crosslinked polyacrylonitrile fiber is oxidized and stabilized to be used as a secondary precursor. Carbon fibers are obtained by carbonizing such a second precursor.

The carbon fibers obtained by the exemplary embodiments of the present invention are excellent in physical properties, particularly mechanical properties.

In an exemplary embodiment, the carbon fibers may have a tensile strength of 1.5 to 5.5 GPa.

In one exemplary embodiment, the carbon fibers may have an elasticity of 150-300 GPa.

In an exemplary embodiment, the carbon fiber may have an elongation of 1 to 2.0%.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing a process for producing carbon fibers according to an exemplary embodiment of the present invention. Fig.

A manufacturing method according to exemplary embodiments of the present invention includes the steps of forming a polyacrylonitrile fiber with heat resistance by oxidizing and stabilizing the polyacrylonitrile fiber before stabilization and oxidizing the crosslinked polyacrylonitrile fiber And stabilizing and carbonizing the oxidized and stabilized polyacrylonitrile fibers.

As described above, when the polyacrylonitrile fiber is irradiated with electron beams, cross-linking of the polymer chain by the carbon radicals generated in the polymer chain can be achieved. Such an electron beam irradiation is more efficient and environmentally friendly than a radiation process such as a thermal process, a gamma ray, and an ultraviolet ray. In addition, since the electron beam is penetrated into the polyacrylonilyl fiber at a depth of several centimeters to cause crosslinking, it has the advantage that it can be uniformly crosslinked even in the case of very thick fibers such as Rajitose.

In an exemplary embodiment, it is desirable to oxidize and stabilize the crosslinked polyacrylonitrile fibers after the electron beam crosslinking, especially using plasma-bonded thermal energy.

Oxidation and stabilization reactions by plasma-bonded heat energy can lower the oxidation and stabilization reaction time and temperature compared to heat energy alone. The oxidation and stabilization process using such plasma-coupled heat energy should be performed in conjunction with the use of electron beam crosslinked polyacrylonitrile fibers as described above. This is because, when oxidation and stabilization are performed using plasma-coupled heat energy or plasma alone, uniform oxidation and stabilization of the fiber sample by the plasma can not be obtained. However, when the cross-linked polyacrylonitrile fiber is used by the irradiation of the electron beam, the subsequent oxidation and stabilization reaction can be uniformly completed, thereby obtaining more excellent physical properties.

Accordingly, an exemplary preferred embodiment of the present invention is a method for producing a polyacrylonitrile fiber, comprising: electron-ray cross-linking the polyacrylonitrile fiber before oxidation and stabilization to improve the heat resistance of the polyacrylonitrile fiber; Oxidizing and stabilizing the oxidized and stabilized polyacrylonitrile fibers using plasma coupled thermal energy and carbonizing the oxidized and stabilized polyacrylonitrile fibers.

On the other hand, in the exemplary embodiments of the present invention, graphitization may be further performed after the carbonization step. In a non-limiting embodiment, the carbonization step may be performed using thermal energy and the carbonization or graphitization step may be performed using a Microwave Assisted Plasma (MAP).

Each manufacturing process step according to exemplary embodiments of the present invention will now be described in more detail.

1) By electron beam irradiation Crosslinking

In an exemplary embodiment, in order to perform transcription-line crosslinking on polyacrylonitrile fibers, the electron beam irradiation may be performed at a temperature of 300 DEG C or less at room temperature or room temperature, in air at an energy of 50 kGy to 3000 kGy To crosslink the polyacrylonitrile fibers.

In an exemplary embodiment, the polyacrylonitrile fiber used as the starting material preferably comprises polyacrylonitrile fibers for fabrics (such as for clothing).

This will be described in detail.

Polyacrylonitrile (PAN) fibers for carbon fiber fabrication are very expensive compared to conventional fibers. Contrary to these carbon fiber fabrics, there are polyacrylonitrile (PAN) fibers for textiles.

This polyacrylonitrile (PAN) fiber for textile is widely used in clothes, blankets and carpets, because it is composed of hundreds of thousands of monofilaments, and the production is very high in the process. It is very inexpensive compared to polyacrylonitrile (PAN) fibers. Therefore, polyacrylonitrile (PAN) fibers for fabrics can be said to be very attractive precursor fibers in order to reduce the cost of carbon fibers. However, polyacrylonitrile (PAN) fibers for textiles can not be used directly as precursor fibers for carbon fibers.

First, polyacrylonitrile (PAN) fibers for fabrics have a very low content of acrylonitrile (AN) monomer compared to carbon fiber precursor polyacrylonitrile (PAN) fibers, and itaconic acid is not present in the presence of an acrylic comonomer having a carboxyl functional group. As a result, unlike the acrylonitrile (AN) monomer component, which is very slow in the oxidation and stabilization reaction and is crosslinked by the oxidation and stabilization reaction, the acrylic comonomer is not crosslinked, The chains of the monomer component disappear and exhibit low mechanical properties and a low carbonization yield.

Second, polyacrylonitrile (PAN) fibers for producing carbon fibers have a fiber diameter of about 10 to 11 μm, while polyacrylonitrile (PAN) fibers for fabrics have a relatively large diameter of about 15 to 25 μm. As a result, the oxidation and stabilization reaction, which is a very slow reaction, is prolonged, and energy consumption is great. In addition, the oxidation and stabilization reaction does not proceed uniformly throughout the fiber, and an incomplete reaction occurs only in the surface layer.

Third, polyacrylonitrile (PAN) fibers for fabrics have lower molecular weight than polyacrylonitrile (PAN) fibers for producing carbon fibers and have low mechanical properties due to low polymer chain orientation. In addition, polyacrylonitrile (PAN) fibers for fabrics are uniformly oxidized, stabilized, and carbonized by the tensile filaments of filaments, which are much larger in number than filaments of polyacrylonitrile (PAN) It is difficult to produce carbon fibers having uniform physical properties.

Accordingly, the present inventors have applied the present invention to carbon fiber fabrication through a method of stretching polyacrylonitrile fibers for fabrics (Patent Document 4).

However, the inventors of the present invention have found that, even when the polyacrylonitrile fibers for fabrics are not crosslinked by the above-mentioned stretching method, especially when the crosslinked polyacrylonitrile fibers for fabrics are solved and an additional modification or stretching process is not performed It is possible to further carry out the modification and / or drawing process as described later). It has been confirmed that polyacrylonitrile fibers for fabrics can be suitably used for producing carbon fibers. Especially, penetration depth of the electron beam differs depending on the material, but in the case of the fiber sample, it is possible to carry out the crosslinking by penetration up to a depth of several centimeters, and also the polyacrylonitrile for general purpose fabrics having a fiber diameter of 15 to 25 μm The nitrile fiber is fully crosslinked, and even a large tow of 100 K is sufficiently crosslinked. In addition, since the large exothermic reaction is suppressed in the subsequent oxidation and stabilization process, oxidation and stabilization can be performed stably without ignition, the energy consumption problem is solved, homogeneous oxidation and stabilization are performed, Carbon fiber can be produced.

Thus, in one exemplary embodiment, it is desirable to include polyacrylonitrile fibers for fabrics (such as for clothing) having an acrylonitrile monomer content of 95% by weight or less as a starting material to be crosslinked, in particular, by electron beam crosslinking.

In a non-limiting example, the polyacrylonitrile (PAN) fibers for fabrics have a content of acrylonitrile (AN) monomer of 95 wt% or less, a fiber diameter of 15 탆 or more and a tensile strength Tensile strength according to the fiber tensile strength measurement method) can be selected from not more than 3.5 g / d.

More specifically, the polyacrylonitrile (PAN) fibers for fabrics are characterized in that the content of acrylonitrile (AN) monomer is 60-95 wt% (more specifically 65-90 wt%) and the diameter of the fibers is 15 To 25 m, and a tensile strength of 1.2 to 3.5 g / d. For example, such polyacrylonitrile (PAN) fibers for fabrics have a fiber diameter of 15 to 25 탆, a tensile strength of 1.2 to 3.5 g / d, an elongation of 68% and a polymer chain orientation of carbon Is much lower than the fiber precursor.

In one exemplary embodiment, the polyacrylonitrile fibers to be crosslinked are not only polyacrylonitrile fibers for fabrics, but also carbon fibers containing acrylic comonomers, such as itaconic acid, etc., in an amount of greater than 95% by weight of acrylonitrile monomer And polyacrylonitrile fibers for making fibers.

On the other hand, polyacrylonitrile fibers for woven fabrics generally contain additives in order to increase dyeability during polymer synthesis, and such compounds may be a factor that greatly deteriorates the physical properties of carbon fibers.

Thus, in exemplary embodiments, in order to use polyacrylonitrile fibers for fabrics as a precursor for carbon fiber cost reduction, it is preferable to add the compound for dyeability enhancement to polyacrylonitrile fiber polymer for fabric, It is possible to increase the content of acrylonitrile monomers within a range that does not increase the polymerization cost and to polymerize the polyacrylonitrile fibers for fabrics by adding itaconic acid as an acrylic comonomer to modify the polyacrylonitrile fibers for producing carbon fibers have. Such modification of the polyacrylonitrile polymer for woven fabric can improve the properties of the carbon fiber and improve the yield of carbonization upon conversion to carbon fiber, thereby contributing to cost reduction.

In yet other exemplary embodiments, polyacrylonitrile fibers for stretched fabrics may be used as the polyacrylonitrile fibers for the fabric to be crosslinked.

Such stretched polyacrylonitrile fibers for fabrics can be used by further stretching polyacrylonitrile fibers for general purpose fabrics to reduce their fiber diameters to improve their mechanical properties. However, in the spinning process of polyacrylonitrile fibers for woven fabrics, Can be used after obtaining the mechanical properties of the carbon fiber precursor fiber level. Specifically, when producing a polyacrylonitrile fiber for a fabric, it may be stretched by one or more processes selected from hot drawing and hot drawing to increase the draw magnification. As a result, the polymer chain orientation degree (tensile strength and elastic modulus) and elongation of the general carbon fiber precursor fiber level can be obtained. The application of such a high magnification stretching process allows the physical properties of the polyacrylonitrile fibers for fabrics to have mechanical properties at the level of ordinary carbon fiber precursors and can also significantly reduce the diameter of the fibers.

2) plasma Oxidation and stabilization by coupled thermal energy

Next, the oxidation and stabilization process of oxidizing and stabilizing the polyacrylonitrile fiber crosslinked by electron beam irradiation is carried out.

Oxidation and stabilization processes are very important processes in the production of carbon fibers using polyacrylonitrile fibers. This is an insolubilizing process that changes the molecular structure in the fiber so as to have a salt resistance before the carbonization reaction and induces the intermolecular bonding to form a ladder structure in order to prevent the polymer material from melting at high temperatures during the carbonization or graphitization.

These oxidation and stabilization reactions can be roughly divided into cyclization, dehydrogenation and oxidation. The cyclization reaction is a cyclization of radicals in the fiber molecule due to external energy. The dehydrogenation reaction and the oxidation reaction cause the hydrogen atoms to fall off into molecules in the oxidizing atmosphere (dehydrogenation reaction) (Oxidation reaction). At this time, if the oxygen atoms are uniformly transferred to the inside of the fiber, a stable ladder structure of the whole fiber is formed and excellent salt resistance is obtained.

In the exemplary embodiments, the oxidation and stabilization process preferably utilizes plasma, or more particularly plasma-coupled thermal energy, rather than thermal energy.

In one exemplary embodiment, the polyacrylonitrile fibers crosslinked by electron beams are advanced using plasma at atmospheric pressure or under vacuum. For example, a plasma can be generated and oxidized and stabilized by mixing and injecting argon gas as a plasma generating gas into the reaction chamber and oxygen gas as a reactive gas, for example.

When oxidation and stabilization are carried out using plasma as described above, active oxygen species having a high energy density and a high reactivity are produced. Accordingly, the oxidation and stabilization of the fibers are more uniform and occur more rapidly and have better physical properties than the thermal energy treatment method. Specifically, during the generation of plasma, oxygen species such as oxygen monomers, superoxide (O ₂ -), hydrogen peroxide (H ₂ O ₂ ) and hydroxyl radical (OH) Stable oxidation and stabilization reactions can occur, and oxidation and stabilization reaction times can be shortened.

In an exemplary embodiment, it is desirable to carry out the oxidation and stabilization in oxidizing and stabilizing polyacrylonitrile fibers crosslinked by electron beams, in particular by using plasma-bonded thermal energy.

The oxidation and stabilization reaction by the plasma-bonded thermal energy is carried out, for example, by generating a plasma in the plasma generating section to supply a plasma to the polyacrylonitrile fiber tow, supplying heat to the polyacrylonitrile fiber in the heat supplying section, While simultaneously oxidizing and stabilizing the polyacrylonitrile fibers.

In an exemplary embodiment, the step of oxidizing and stabilizing with plasma-bonded thermal energy may be to oxidize and stabilize using plasma at a temperature range of 180 to 350 DEG C under an oxidizing atmosphere in which oxygen is present, Minute to 250 minutes.

In a non-limiting example, the plasma generator comprises: a power supply for supplying high frequency power; An electrode receiving the high frequency power from the power supply unit; And a ground electrode that is grounded or supplied with a separate high frequency power, and the plasma may be generated between the electrode and the ground electrode. At this time, the power supply unit may be any one selected from the group consisting of DC, RF power, and positive power. At this time, the power applied to the plasma can be controlled by electric power supplied to the electrode or the ground electrode.

The plasma generating unit may further include an impedance matching unit positioned between the power supply unit and the electrode and matching the output impedance of the power supply unit with the impedance of the electrode. The power supply unit supplies the high frequency power to the impedance matching unit.

The power supply can use RF power or DC or positive power. When DC or a positive power source is used, high-frequency power can be supplied to the electrode immediately without an impedance matching portion.

The impedance matching unit matches the output impedance of the power supply unit with the impedance of the electrode. When the output impedance of the power supply unit and the electrode impedance are not matched, power is returned to the power supply unit without generating an amount of difference in impedance. The greater the amount of power being returned, the less the amount of power consumed by the electrodes and the more power the power supply must supply. When DC or a positive power supply is used for the power supply unit, an impedance matching unit is not required. As a non-limiting example, a matching box can be used as the impedance matching portion. The electrode receives high-frequency power through the impedance matching unit or the power supply unit and generates plasma on the surface. At this time, a uniform plasma is generated on the surface of the electrode.

The ground electrode is spaced apart from the electrode, and one side of the ground electrode is grounded or another high frequency power is applied to generate plasma between the electrode and the ground electrode. Instead of a ground connection to the ground electrode, a power device can be connected to apply RF power through it, and the plasma parameters can be varied more widely.

In a non-limiting example, the plasma generating portion may further include an insulator formed on a surface of the ground electrode. At this time, the insulator may be disposed between the ground electrode and the polyacrylonitrile fiber. At this time, the insulator may be an insulating thin film clad on the surface of the ground electrode. The insulator may be made of ceramic.

The heat source is supplied by a heating device, and the supply of heat energy can be controlled by electric power applied to the heating device. The heat supply part supplies heat to the polyacrylonitrile fiber, and the fiber is stabilized by the applied heat. At this time, the heat supply part may be a heating device. The heating device can supply heat of at least 100 캜 to one side of the fiber. However, since the temperature rises due to the plasma, the temperature of the oxidation and stabilization reaction due to the plasma-coupled thermal energy is determined not in accordance with the heating device alone but in conjunction with the plasma energy. The temperature of the oxidation and stabilization reaction can be controlled by the ratio between the power applied to the heating device and the power applied to the plasma.

The heat supply unit may be a heated air inlet for supplying heated air to the polyacrylonitrile fiber. Stabilization of the fiber may be caused by the heated air supplied through the air inlet. The supply of heat energy is controlled by the flow rate and the temperature of the heated air, and the stabilization can be controlled by controlling the flow rate of the heated air, the temperature, and the ratio of the power applied to the plasma. At this time, the heated air may contain oxygen or an oxygen compound. A gas such as oxygen (O ₂ ) or an oxygen compound is blown out together with the heated air to promote the stabilization process of the polymer. The gas may be heated to an elevated temperature for control of the reaction rate and acceleration of the rate.

3) Carbonization

Next, in order to convert the polyacrylonitrile fibers oxidized and stabilized by oxidation and stabilization, preferably plasma bonding heat energy, into carbon fibers after crosslinking, crosslinking is preferably carried out at a high temperature by thermal energy .

In an exemplary embodiment, the carbonization process may proceed in an inert atmosphere, such as nitrogen, through a high temperature furnace or the like. The reason for maintaining the inert atmosphere such as nitrogen is that, when other reactive gas enters, it acts as a large defect in carbonization due to an unnecessary chemical reaction. In addition, an atmosphere of nitrogen or the like is maintained to separate the nitrogen element in the nitrile group. The carbonization reaction is preferably carried out at a temperature of, for example, 1,000 to 1,500 DEG C under a nitrogen atmosphere.

On the other hand, a carbonization process can be performed by microwave assisted plasma (MAP) instead of thermal energy. As described above, when the carbonization reaction proceeds using the microwave-induced plasma (MAP), the carbon fiber having the same level of physical properties as the method using the thermal energy can be produced, and the energy consumption can be further reduced have.

4) Graphitization

Meanwhile, in addition to the above-described steps, the carbon fiber may further include a graphitization step of optionally graphitizing the carbon fibers. The graphitization step proceeds at a temperature higher than the carbonization temperature after the carbonization step. That is, the carbonized polyacrylonitrile stretched fibers through the carbonization process are graphitized at a temperature higher than the carbonization temperature.

In an exemplary embodiment, the graphitization step can proceed by thermal energy. For example, carbonized fibers can be graphitized by heat treatment in a high temperature region of 2,000 to 3,000 DEG C in a carbonization furnace or the like.

In an exemplary embodiment, the graphitization step can induce a graphitization reaction by microwave-induced plasma, such as in a carbonation reaction, to reduce energy consumption.

Hereinafter, specific embodiments according to exemplary embodiments of the present invention will be described in more detail. It should be understood, however, that the invention is not limited to the embodiments described below, but that various embodiments of the invention may be practiced within the scope of the appended claims, It will be understood that the invention is intended to facilitate the practice of the invention to those skilled in the art.

[Preparation of carbon fiber precursor]

Polyacrylonitrile fibers (supplied by Taekwang Industrial Co., Ltd., Korea), which is widely used for general fabrics (for apparel), were prepared and polyacrylonitrile fibers for fabrics (hereinafter referred to as "PAN fibers for fabrics") were prepared The fiber diameter, mechanical properties (tensile strength, elastic modulus, elongation), and polymer chain orientation degree (%) were measured, and the results are shown in Table 1 below.

The fabric PAN fibers had an acrylonitrile (AN) monomer content of 89.3 wt% or less and a vinyl monomer content of 10.7 wt%.

Table 1 also shows the characteristics of polyacrylonitrile fibers (hereinafter, referred to as " PAN fibers for carbon fiber production ") for manufacturing carbon fibers, which are currently used most as carbon fiber precursors. The PAN fiber for making the carbon fiber has an acrylonitrile monomer content of about 95% by weight, about 1% by weight of itaconic acid, and about 4% by weight of an acrylic monomer such as methyl acrylate.

The mechanical properties and the degree of polymer chain orientation (%) were measured as follows.

(a) Mechanical properties of fibers

The single yarns of the fibers were measured using a universal testing machine (UTM-Universal Testing Machine), which is widely used for measuring mechanical properties, according to the ASTM D3822 standard.

(b) Polymer chain orientation degree of fibers (%)

X-ray diffraction analysis was used as a typical method of the degree of polymer chain orientation (%) of the fibers. First, in order to measure the degree of polymer chain orientation of the fiber, the fiber was scanned in the uniaxial direction 2θ using an X-ray diffraction analyzer, and then the azimuthal scan at 2θ = 17 °, ). Then, the polymer chain orientation degree of the fibers was measured according to the following formula (1) using the obtained full width at the half maximum.

[Equation 1]

Polymer chain orientation degree (%) of fiber = [(180 ° - H °) / 180 °] x 100

Where H is the half width of the peak obtained by azimuthal scanning.

The physical properties of the polyacrylonitrile fiber used in this Example are shown in Table 1 below. It can be seen that the diameter of the polyacrylonitrile fibers for fabrics having an acrylic content of 95% or less is larger than that of the polyacrylonitrile fibers for producing carbon fibers. Thus, if the diameter of the fiber is large, it directly affects the mechanical properties of the fiber. For this reason, the overall mechanical property of the carbon fiber is lowered.

The polyacrylonitrile fiber 1 for fabrics was first hot-water-elongated at a draw ratio of 200% in hot water at 90 ° C and then 200% heat-stretched in a chamber maintained at 180 ° C continuously to obtain a total draw ratio of 400% The stretched fiber is the polyacrylonitrile fiber 2 for the fabric.

Comparison of properties of PAN fibers Remarks Fiber diameter
(탆) The tensile strength
(g / d) Elastic modulus
(g / d) Shindo
(%) Polymer chain orientation (%) For textiles
PAN Fiber 1 18 2.8 77.4 68 66.7 For textiles
PAN Fiber 2 10 8.4 184 6.5 93.1 Carbon fiber
For manufacturing
PAN fiber 11 7.4 108 12.0 91.1

Comparative Example One. Crosslinking Oxidation and stabilization reaction using only thermal energy without

The polyacrylonitrile fibers shown in Table 1 were subjected to heat treatment in an electric furnace capable of controlling the temperature, and oxidation and stabilization processes were performed in an air atmosphere. No crosslinking was performed prior to oxidation and stabilization.

Oxidation and stabilization processes are processes for insolubilizing fibers at high temperature during carbonization or graphitization, so oxidizing atmosphere and reaction conditions which can control temperature accurately and oxidation can be important. For this, the hot air circulation was well conducted to allow the oxygen in the outside atmosphere to be supplied well, and the reaction conditions of oxidation and stabilization were carried out as shown in Table 2.

Comparative Example 2. Crosslinking without plasma Oxidation and stabilization reaction by bonding heat energy

Oxidation and stabilization reactions were performed using plasma instead of the oxidation and stabilization reaction in which the heat treatment was performed in the oxidizing atmosphere of Comparative Example 1. [ No crosslinking was performed prior to oxidation and stabilization.

Specifically, a temperature controllable chamber is formed in a plasma module using a RF generator as a power source to maintain a constant temperature in the chamber, and an argon gas and an oxygen gas are mixed with a plasma generating gas and a reactive gas, (O ₂ ^- ), hydrogen peroxide (H ₂ O ₂ ), hydroxyl radical (OH) and the like are generated during the generation of plasma to oxidize and stabilize The reaction was carried out. The reaction conditions of plasma oxidation and stabilization were carried out as described in Table 3.

Polyacrylonitrile fiber For textiles
PAN Fiber 1 For textiles
PAN Fiber 2 For making carbon fiber
PAN fiber Plasma-bonded thermal energy oxidation and stabilization reactions Reaction temperature ( ^o C) 240 240 230 230 Reaction time (min) 195 195 60 120

The carbon fibers oxidized and stabilized through Comparative Examples 1 and 2 were heat treated to carbonize them. The carbonization was carried out at a temperature increase of 5 ° C per minute at 1200 ° C, after which the cooling was cooled by air cooling. At this time, the nitrogen gas was continuously injected into the chamber during the progress of the carbonization reaction to prevent other reactions (oxidation reaction) from occurring. Table 4 shows the physical properties of the carbon fibers produced.

Diameter of carbon fiber (탆) The tensile strength
(GPa) Elastic modulus
(GPa) Shindo
(%) For textiles
PAN Fiber 1 Heat energy
Oxidation and stabilization 13 0.9 ± 0.2 79 ± 8 1.2 ± 0.2 For textiles
PAN Fiber 2 Heat energy
Oxidation and stabilization 7 1.7 ± 0.3 144 ± 12 1.2 ± 0.2 Plasma-coupled thermal energy
Oxidation and stabilization 7 1.75 ± 0.2 150 ± 8 1.2 ± 0.2 Carbon fiber
For manufacturing
PAN fiber Thermal energy
Oxidation and stabilization 6 2.1 ± 0.3 196 ± 5 1.05 + - 0.2 Plasma coupled thermal energy oxidation and stabilization (60 min) 6 2.0 ± 0.3 162 ± 10 1.2 ± 0.2 Plasma-bonded thermal energy oxidation and stabilization
(120 minutes) 6 2.8 ± 0.3 204 ± 5 1.4 ± 0.1

FIG. 2 is a scanning electron microscope (SEM) image showing carbon fiber obtained by carbonization after oxidation and stabilization reaction by thermal energy according to Comparative Example 1 of the present invention for 15 minutes (FIG. 2A) and 120 minutes )to be.

As shown in FIG. 2, when the stabilization reaction was carried out for 15 minutes and 120 minutes in the oxidation and stabilization reaction step by thermal energy and then carbonized, the oxidation and stabilization reaction for 15 minutes resulted in incomplete oxidation and stabilization, Lt; / RTI > In the case of oxidation and stabilization for 120 minutes, the fusion between the carbon fibers did not occur and the myth and stabilization were completely achieved.

FIG. 3 is a graph showing the state of carbon fibers obtained by carbonizing the stabilization reaction by atmospheric pressure plasma-bonded thermal energy for 15 minutes (FIG. 3A) and 60 minutes (FIG. 3B) according to Comparative Example 2 of the present invention. It is a scanning electron microscope (SEN) photograph.

As shown in FIG. 3, when the oxidation and stabilization reaction by the atmospheric plasma-bonded thermal energy was carried out for 15 minutes and 60 minutes and then carbonized, the stabilization reaction for 15 minutes showed incomplete stabilization, In the case of the stabilization reaction for 60 minutes, the fusion between carbon fibers did not occur and the myth and stabilization were completely achieved. In other words, oxidation and stabilization reaction using atmospheric plasma-coupled thermal energy, compared with the oxidation and stabilization reaction using heat energy alone, can be efficiently performed because the oxidation and stabilization of the fiber occurs quickly due to the active oxygen species generated in the plasma, . In addition, it can be seen that the processing time can also be reduced to about two times.

Example 1-1. Electron beam irradiation crosslinking, thermal energy oxidation and stabilization followed by carbonization

The PAN fibers (12K) for producing carbon fibers in Table 1 were crosslinked by electron beam irradiation before oxidation and stabilization. In order to prevent the temperature rise during electron beam irradiation, the sample was placed on a water-cooled stainless steel plate and irradiated with a beam current of 1 mA and an energy of 200 kGy to 1500 kGy using an acceleration voltage of 1.14 MeV. The irradiated energy is calculated by the following equation (2).

&Quot; (2) "

Current (mA) X irradiation time (sec) = total energy (kGy)

4 is a photograph showing PAN fiber (12K) for carbon fiber irradiation irradiated with electron beams at various energies in Example 1-1 of the present invention.

As shown in FIG. 4, the amount of PAN fibers irradiated with electron beams showed yellow as the irradiation amount increased. The gel content was measured by dissolving in dimethylsulphoxide. The gel content was 22% at 200 kGy, 86% at 500, 94% at 1000 kGy, And 100% at 1500 kGy, respectively. The electron beam irradiated specimens were oxidized and stabilized by thermal energy at 230 캜 for about 30 minutes and then carbonized at 1200 캜 to produce carbon fibers. The physical properties of the carbon fiber thus produced are shown in Table 5.

Electron beam
Dose Thermal Energy Oxidation and Stabilization Reaction
Temperature / time Carbon fiber diameter
(탆) The tensile strength
(GPa) Elastic modulus
(GPa) Shindo
(%) 0 230 ° C / 30 min Carbon fiber not formed 200kGy 230 ° C / 30 min 6 2.33 ± 0.4 223 ± 9 1.3 ± 0.1 500 kGy 230 ° C / 30 min 6 2.57 ± 0.5 219 ± 10 1.4 ± 0.2 1000kGy 230 ° C / 30 min 6 2.38 ± 0.4 217 ± 5 1.3 ± 0.4 260 ° C / 120 min 6 2.84 ± 0.4 220 ± 3 1.41 ± 0.2 1500 kGy 230 ° C / 30 min 6 2.59 ± 0.5 223 ± 11 1.5 ± 0.2

Even though the thermal energy was oxidized and stabilized for about 30 minutes after the irradiation with the electron beam, it showed better physical properties than the thermal oxidation and stabilization process for 120 minutes, and showed better physical properties even when oxidized and stabilized at 60 atmospheric plasma bonded thermal energy.

Example 1-2. Electron beam irradiation plasma Oxidation and stabilization after bonding by thermal energy

A sample irradiated with electron beams as in Example 1 was treated with an atmospheric plasma under the same conditions as in Comparative Example 2 at a temperature of 230 ° C for about 30 minutes and then carbonized at 1200 ° C to prepare carbon fibers. The physical properties of the carbon fiber thus produced are shown in Table 6.

Electron beam
Dose Plasma bonding energy oxidation and stabilization reaction
Temperature / time Diameter of carbon fiber (탆) The tensile strength
(GPa) Elastic modulus
(GPa) Shindo
(%) 0 230 ° C / 30 min Carbon fiber not formed 200kGy 230 ° C / 30 min 6 2.83 ± 0.5 231 ± 6 1.3 ± 0.2 500 kGy 230 ° C / 30 min 6 2.97 + - 0.4 228 ± 8 1.4 ± 0.2 1000kGy 230 ° C / 30 min 6 2.88 ± 0.4 225 ± 11 1.5 ± 0.3 1500 kGy 230 ° C / 30 min 6 2.95 ± 0.3 233 ± 10 1.4 ± 0.3

As can be seen from the above, in the oxidation and stabilization reaction by the plasma-bonded thermal energy in Comparative Example 2, oxidation and stabilization reaction time and temperature can be significantly lowered compared with the oxidation and stabilization reaction using the thermal energy alone in Comparative Example 1 . However, when only plasma-coupled thermal energy alone is used without crosslinking by electron beam irradiation, a uniform oxidation and stabilization reaction of the fiber sample can not be obtained. On the other hand, when the polyacrylonitrile fibers crosslinked by electron beam irradiation are used as shown in Examples, particularly Example 1-2, the oxidation and stabilization reaction can be uniformly completed and more excellent physical properties can be obtained .

Example 2-1. For textiles Acrylonitrile Fiber-assisted electron beam Crosslinking Carbonization reaction after oxidation and stabilization using post heat energy

The acrylonitrile fiber 1 (100 K) of the fabric shown in Table 1 was crosslinked by irradiation with electron beams. 500 kGy, 1000 kGy, and 2000 kGy, respectively.

The electron beam irradiated crosslinked fibers were oxidized and stabilized at 200 to 240 ° C. for about 150 minutes at 240 to 260 ° C. for about 90 minutes and then carbonized at 1200 ° C. to prepare carbon fibers. The physical properties of the carbon fiber thus produced are shown in Table 7.

As can be seen from Table 7, when the crosslinked material was irradiated with electron beams, it exhibited excellent physical properties as compared with the case of carbonizing after thermal oxidation and stabilization without irradiation of electron beams. Even though carbonization of 100 K of Rajitowo was performed, The thermal stability was increased and the carbon fibers were formed without ignition in the thermal energy oxidation and stabilization process.

FIG. 5A is a photograph showing carbon fiber 1 for textile fabric irradiated with various energies in Example 2-1 of the present invention, after oxidation and stabilization of heat energy, and after carbonization, and 5b and 5c are electron beams Infrared spectroscopy (FT-IR) and DSC analysis of carbon fiber fabric 1.

As shown in FIG. 5A, the irradiated PAN fibers showed a dark brown color as the irradiation amount increased. As shown in FIG. 5A, the electron beam irradiation sufficiently crosslinked the polyacrylonitrile fibers for general-purpose fabrics having a fiber diameter of 15 to 25 μm, and even the 100 K of Rajitow was sufficiently crosslinked to perform oxidation and stabilization It shows that oxidation and stabilization proceeded steadily without ignition by suppressing a large exothermic reaction in the process, and carbonization was successfully formed when carbonized. This shows that the electron beam crosslinking reaction can make a great contribution to the production of Rajitot carbon fibers.

The polyacrylonitrile fiber for an electron beam crosslinked fabric had no cyclization reaction by electron beam irradiation as shown in the infrared spectroscopy of FIG. 5B, and only crosslinking proceeded. In addition, oxidation and stabilization proceeded without ignition even after thermal energy oxidation and stabilization.

FIG. 5c shows the DSC curve of the electron beam irradiated sample, showing that the exothermic peak for PAN cyclization is greatly lowered by electron beam crosslinking. This shows that the oxidation and stabilization reaction can proceed at a lower temperature.

Example 2-2. For textiles Acrylonitrile Fiber-assisted electron beam Crosslinking after plasma Carbonation reaction after oxidation and stabilization using coupled thermal energy

The acrylic fiber 1 (100 K) for the fabric subjected to the electron beam irradiation in Example 2-1 was oxidized and stabilized at 230 ° C for about 30 minutes using atmospheric pressure plasma-coupled thermal energy under the same conditions as in Comparative Example 2, After the treatment, the carbon fiber was carbonized at 1200 ° C. The physical properties of the carbon fiber thus produced are shown in Table 7. As shown in Table 7, when plasma-bonded thermal energy is used after electron beam irradiation crosslinking, excellent physical properties are shown.

Example 3-1. Stretched For textiles Acrylonitrile Fiber-assisted electron beam Crosslinking Carbonization reaction after oxidation and stabilization using post heat energy

The acrylonitrile fiber 2 (48K) for fabrics shown in Table 1 was subjected to electron beam irradiation. 1000 kGy, respectively.

The electron beam irradiated specimens were oxidized and stabilized at 200 ~ 240 ℃ for about 150 min and at 240 ~ 260 ℃ for about 90 min, and carbonized at 1200 ℃. The physical properties of the carbon fiber thus produced are shown in Table 7. Even though carbonization of 100 K of Rajitou was performed, the thermal stability was increased owing to crosslinking by electron beam, so that it was not ignited in the oxidation and stabilization process of thermal energy Carbon fibers were formed.

Example 3-2. Stretched For textiles Acrylonitrile Fiber-assisted electron beam Crosslinking Oxidation and stabilization after plasma-coupled thermal energy

Instead of thermally stabilizing the acrylic fiber 1 (100 K) for fabrics irradiated with the electron beam in Example 2-1, the atmospheric plasma was treated at a temperature of 230 DEG C for about 30 minutes under the same conditions as in Comparative Example 2, Fiber. The physical properties of the carbon fiber thus produced are shown in Table 7. It can be seen that when plasma-bonded heat energy is used after electron beam irradiation crosslinking, excellent physical properties are exhibited.

sample reaction Diameter of carbon fiber (탆) The tensile strength
(GPa) Elastic modulus
(GPa) Shindo
(%) For textiles
PAN fiber 1 (transcription crosslinked) Thermal energy oxidation and stabilization 13 0.93 + - 0.4 132 ± 2 0.85 + - 0.4 Plasma Bonding Energy Oxidation and Stabilization 13 1.33 ± 0.3 132 ± 5 1.2 ± 0.3 For textiles
PAN fiber 2 (electron beam crosslinked) Thermal energy oxidation and stabilization 7 1.81 + - 0.2 138 ± 3 1.05 + - 0.4 Plasma Bonding Energy Oxidation and Stabilization 7 1.90 ± 0.3 145 ± 7 1.2 ± 0.3

Example 4. Micro Induction On the plasma Perform Carbonization by

The thermal energy oxidation and stabilization after 1000 kGy of the 1000 kGy prepared in Examples 1-1 and 1-2 and the oxidation and stabilization of the plasma-coupled thermal energy oxidized and stabilized the fibers were performed using microwave assisted plasma (MAF) Carbon fiber was produced by carbonization.

As a result of evaluating the physical properties of the carbon fibers prepared above, the tensile strengths were 1.37 GPa and 1.89 GPa, respectively, and exhibited properties similar to the carbonization reaction by thermal energy. The d ₀₀₂ value was about 0.349 nm, which was lower than 0.358 nm of the carbon fiber carbonized by heat energy, but the graphite crystal structure was higher than that of the carbon fiber using heat energy, although the graphite was not completely formed.

As described above, in the embodiments of the present invention, oxidation and stabilization are carried out after pre-heating by electron beam irradiation before proceeding with the oxidation and stabilization process, so that not only carbon fiber of superior physical properties can be produced, By greatly shortening the time, energy consumption can be greatly reduced, heat and ignition problems can be solved, uniform crosslinking, uniform oxidation and stabilization can be achieved. Particularly, in carrying out the oxidation and stabilization process after electron beam irradiation crosslinking, the plasma-coupled thermal energy stabilization process in which the plasma energy is introduced is performed rather than only the thermal energy, thereby shortening the processing time of the oxidation and stabilization process, And the like can be improved.

Claims

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As a second precursor for the production of carbon fibers whose primary precursor for carbon fiber production is oxidized and stabilized,
The primary precursor for producing carbon fibers is a polyacrylonitrile fiber crosslinked by electron beam irradiation before oxidation and stabilization,
Crosslinking by electron beam irradiation induces CC bonding of the different polymer main chains of the polyacrylonitrile polymer and the exothermic peak for cyclization of polyacrylonitrile is reduced by electron beam crosslinking. The cyclization reaction does not proceed,
Which is oxidized and stabilized by plasma-bonded heat energy,
A second precursor for the production of carbon fibers, characterized in that the polyacrylonitrile fibers to be crosslinked by electron beam are polyacrylonitrile fibers for fabrics.

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The carbon fiber as the carbonization of the second precursor for producing carbon fibers according to claim 2.

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5. The method of claim 4,
Characterized in that the polyacrylonitrile (PAN) fiber for woven fabric has a content of acrylonitrile (AN) monomer of 95% by weight or less, a fiber diameter of 15 탆 or more and a tensile strength of 3.5 g / d or less .

Crosslinking the polyacrylonitrile fiber by irradiation of an electron beam to oxidize and stabilize the polyacrylonitrile fiber to improve the heat resistance of the polyacrylonitrile fiber;
Oxidizing and stabilizing the cross-linked polyacrylonitrile fiber after the electron beam cross-linking using plasma-bonded thermal energy; And
Carbonizing the oxidized and stabilized polyacrylonitrile fibers,
Crosslinking by electron beam irradiation induces CC bonding of the different polymer main chains of the polyacrylonitrile polymer and the exothermic peak for cyclization of polyacrylonitrile is reduced by electron beam crosslinking. The cyclization reaction does not proceed,
Wherein the polyacrylonitrile fibers to be crosslinked by electron beam are polyacrylonitrile fibers for fabrics.

9. The method of claim 8,
Wherein the total irradiation energy of the electron beam irradiated on the polyacrylonitrile fiber is 50 to 3000 kGy and the electron beam irradiation is performed in a temperature range of room temperature to 300 캜.

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9. The method of claim 8,
Characterized in that the polyacrylonitrile fibers are oxidized and stabilized under atmospheric pressure or under vacuum using plasma-bonded thermal energy.

9. The method of claim 8,
Characterized in that oxidation and stabilization are carried out for 30 minutes to 250 minutes using plasma at a temperature range of 180 to 350 占 폚 in an oxidizing atmosphere in which oxygen exists.

9. The method of claim 8,
Wherein the carbon fiber manufacturing method further performs graphitization.

14. The method of claim 13,
Wherein the carbonization or graphitization is carried out using a microwave-induced plasma.

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9. The method of claim 8,
Characterized in that the polyacrylonitrile (PAN) fibers for fabrics are drawn.