KR102531748B1 - Polyimide-based carbon fibers and graphite fibers and manufacturing methods thereof - Google Patents

Abstract

The present invention is a polyimide-based carbon fiber and graphite fiber that can be used as core materials in various application fields such as wearable electronic devices, sensors, composite materials, as well as space and aviation fields due to their excellent flexibility and electrical and physical properties, and their manufacturing method It is about.

Description

Polyimide-based carbon fibers and graphite fibers and manufacturing methods thereof { Polyimide-based carbon fibers and graphite fibers and manufacturing methods thereof }

The present invention is flexible enough to be applied to textile processes such as weaving, and has excellent electrical and physical properties, so it can be used as a core material in various application fields such as wearable electronic devices, sensors, composite materials, as well as space and aviation fields. It relates to polyimide-based carbon fibers and graphite fibers and a manufacturing method thereof.

Carbon fiber (carbon fiber) was first carbonized bamboo fiber and used for the filament of a light bulb, and industrial production began in 1959 based on cellulosic fibers.

Carbon fiber was first defined in the literature by R. Bacon and W. A. Schlamon in the United States in 1969, and carbon fiber is a fiber composed only of carbon by thermal decomposition of organic materials at a temperature around the carbonization temperature of 800 ~ 1,500 ℃, and graphite The fiber refers to carbon fiber graphitized by heat treatment at a temperature of 2,000 ° C. or higher.

In general, carbon fibers are classified into rayon-based, polyacrylonitrile (PAN)-based, and pitch-based carbon fibers according to the type of precursor. The PAN-based carbon fiber has a carbon content of 93 to 98%, and the graphite fiber has a carbon content of 99% or more.

These carbon fibers and graphite fibers have excellent heat resistance and impact resistance, are strong against chemicals and have high resistance to pests, and are lighter than aluminum and have greater elasticity and strength than iron because molecules such as oxygen, hydrogen, nitrogen, etc. escape during the heating process and lose weight. is excellent Due to these characteristics, it is widely used as an industrial material in each field of sports goods, aerospace industry, automobile, civil engineering and construction, electrical and electronic, communication, and environmental industries.

Looking at the prior art for carbon fiber and graphite fiber, Korean Patent Publication No. 10-2016-0130583 has excellent strength and durability, but has good flexibility on the surface of carbon fiber, etc., which is characterized by breaking when bent at a certain angle or more. A fiber yarn for manufacturing a reinforcing material for civil engineering coated with a synthetic resin outer shell that safely protects the carbon fiber is disclosed, and Korean Patent Registration No. 10-0702156 (2007. 04. 02.) graphitizes A solution of a halogenated polymer containing a metal compound that induces electrospinning is spun to produce ultrafine fibers having a diameter of 1 to 3,000 nm, and in the process of carbonizing them, a graphitization reaction by a metal catalyst formed from the metal compound A manufactured ultrafine porous graphitic carbon fiber having a high specific surface area and micropores and mesopores is disclosed.

That is, according to the prior art, carbon fibers and graphite fibers in the form of filaments are easily broken when bent or folded due to lack of flexibility, and thus have a property of greatly reducing electrical conductivity, so that carbon fiber and graphite fiber fabrics are woven or There was a problem that was very difficult to organize. In particular, since carbon fiber and graphite fiber do not bend and break within a certain angle due to their characteristics, weaving is structurally difficult and difficult.

In addition, a coating process for improving the flexibility of carbon fiber and graphite fiber is being developed, but the carbon fiber and graphite fiber coated by this coating process have a problem in that electrical characteristics are deteriorated due to an increase in resistance value.

An object of the present invention is to provide carbon fibers and graphite fibers that have excellent physical properties, that is, tensile strength, tensile modulus, and thermal conductivity, and particularly excellent flexibility, so that they can be applied to textile processes such as weaving, and a manufacturing method thereof. However, the technical problem to be achieved by the present invention is not limited to the above-mentioned problem, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

In order to solve the above problems, the method for producing polyimide-based carbon fibers having excellent flexibility of the present invention includes i) diamine having the structure of [Formula 1] below and dianhydride having the structure of [Formula 2] ( A first step of polymerizing polyamic acid by polymerizing dianhydride); ii) a second step of dissolving the polyamic acid in a solvent and wet-spinning; iii) a third step of preparing polyimide precursor fibers by imidizing the wet-spun polyamic acid fibers 100; and iv) a fourth step of producing carbon fibers by continuous carbonization of the polyimide precursor fibers without a stabilization process.

,

,

,

,

,

중 어느 하나이고, 상기 [화학식 2]에서 R₂는

,

,

,

중 어느 하나인 것이 바람직하고, 상기 제 4 단계는 질소 분위기에서 수행되며, 저온탄화공정과 고온탄화공정을 포함하고, 상기 저온탄화공정은 800 ~ 1,000 ℃에서 45 ~ 180초 동안 수행되고, 고온탄화공정은 1,250 ~ 1,500 ℃에서 45 ~ 180초 동안 수행되는 것이 바람직하다. In [Formula 1], R ₁ is

,

,

,

,

,

Any one of, and in [Formula 2] R ₂ is

,

,

,

Preferably any one of, the fourth step is carried out in a nitrogen atmosphere, includes a low-temperature carbonization process and a high-temperature carbonization process, the low-temperature carbonization process is carried out at 800 ~ 1,000 ℃ for 45 to 180 seconds, high-temperature carbonization The process is preferably performed at 1,250 to 1,500 °C for 45 to 180 seconds.

In addition, in the method for producing polyimide-based graphite fibers having excellent flexibility of the present invention, diamine having a structure of [Formula 1] and dianhydride having a structure of [Formula 2] are polymerized to form a polyamic acid. A first step of polymerizing; ii) a second step of dissolving the polyamic acid in a solvent and wet-spinning; iii) a third step of preparing polyimide precursor fibers by imidizing the wet-spun polyamic acid fibers 100; iv) a fourth step of producing carbon fibers by continuously carbonizing the polyimide precursor fibers without flame stabilization; and v) a fifth step of graphitizing the carbon fibers to produce graphite fibers, wherein the fourth step is performed in a nitrogen atmosphere and includes a low-temperature carbonization process and a high-temperature carbonization process, wherein the low-temperature carbonization process comprises: It is carried out at 800 ~ 1,000 ℃ for 45 ~ 180 seconds, the high-temperature carbonization process is carried out at 1,250 ~ 1,500 ℃ for 45 ~ 180 seconds, the fifth step is carried out in an argon atmosphere at a temperature of 2,200 ℃ or more for 45 ~ 180 seconds it is desirable

The polyimide-based carbon fibers and graphite fibers according to the present invention have excellent flexibility and can be applied to textile processes such as weaving or knitting, and have excellent characteristics such as tensile strength, tensile modulus of elasticity, and thermal conductivity. Accordingly, it is possible to provide polyimide-based carbon fiber and graphite fiber that can be used as core materials in various application fields such as wearable electronic devices, sensors, and composite materials as well as space and aviation.

1 is a manufacturing process diagram of polyimide-based carbon fibers and graphite fibers having flexibility according to the present invention;
2 is a schematic diagram of a wet spinning apparatus according to the present invention.

In this application, terms such as "comprise", "have" or "have" are intended to indicate that there is a feature, number, step, component, part, or combination thereof described in the specification, but one or more other It should be understood that it does not preclude the possibility of addition or existence of features, numbers, steps, operations, components, parts, or combinations thereof.

In addition, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in this application, it should not be interpreted in an ideal or excessively formal meaning. don't

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in more detail. In order to facilitate overall understanding in the description of the present invention, the same reference numerals are used for the same components in the drawings, and redundant descriptions of the same components are omitted.

Hereinafter, polyimide-based carbon fiber and graphite fiber and a manufacturing method thereof according to the present invention will be described in detail with reference to the accompanying drawings. 1 is a manufacturing process diagram of polyimide-based carbon fibers and graphite fibers having flexibility according to the present invention, and FIG. 2 is a schematic diagram of a wet spinning apparatus according to the present invention.

As shown in FIG. 1, the method for producing flexible polyimide-based carbon fibers according to the present invention includes: i) diamine having a structure of [Formula 1] and dianhydride having a structure of [Formula 2] A first step (S10) of polymerizing polyamic acid by polymerizing dianhydride; and, ii) a second step (S20) of dissolving the polyamic acid in a solvent and wet-spinning it (S20); and, iii) wet-spun polyamic acid A third step (S30) of preparing polyimide precursor fibers by imidizing the fibers 100; and iv) a fourth step (S40) of producing carbon fibers by continuously carbonizing the polyimide precursor fibers without a stabilization process.

In general, polyimide is prepared by condensation polymerization of aromatic diamine and aromatic dianhydride and then imidization.

Polyimide as described above is an insoluble, insoluble, ultra-high heat-resistant resin, has excellent thermal oxidation resistance, and has a very high heat-resistance with a long-term use temperature of about 260 ° C and a short-term use temperature of about 480 ° C. In addition, it has excellent electrochemical and mechanical properties, radiation resistance, flame retardancy, and chemical resistance.

The imidized polyimide has an oxygen functional group and an aromatic imide ring in the main chain, and has a wide structural range per molecular unit and excellent orientation properties.

In addition, polyimide polymer has excellent thermal stability due to its high melting point, so unlike polyacrylonitrile (PAN) precursor, which is a conventional carbon fiber precursor, carbonization and graphitization processes are possible without going through a stabilization process. Since most of the molecular structures are aromatic, After carbonization, it shows a high carbonization yield.

The polyimide prepared as described above may have various molecular structures depending on the type of monomer used.

According to the present invention, the structures of diamine and dianhydride for condensation polymerization of the polyamic acid used in the first step (S10) are as follows [Formula 1] and [Formula 2].

,

,

,

,

,

중 어느 하나이고, 상기 [화학식 2]에서 R₂는

,

,

,

중 어느 하나인 것이 바람직하다.In Formula 1, R ₁ is

,

,

,

,

,

Any one of, and in [Formula 2] R ₂ is

,

,

,

Any one of these is preferred.

According to the present invention, the polyimide-based carbon fibers and graphite fibers prepared from [Formula 1] and [Formula 2] have particularly excellent characteristics such as flexibility.

According to the present invention, the polyamic acid condensation-polymerized using diamine and dianhydride as described above preferably has a number average molecular weight of 10,000 to 100,000.

If the number average molecular weight of the polymerized polyamic acid is out of the above range, it may be difficult to prepare polyimide precursor fibers having desired strength and modulus of elasticity, and the variation in physical properties of the produced polyimide precursor fibers increases, thereby increasing quality. There may be problems with this degradation

Polyamic acid polymerized to have the range of number average molecular weight as described above is then dissolved in an appropriate solvent and subjected to a second step (S20) of solution spinning.

The polyamic acid polymerized as described above is obtained from the group consisting of dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP) or dimethylformamide (DMF). By dissolving using one or more selected solvents, spinning dope (dope, 10) is prepared. According to the present invention, when preparing the spinning dope 10 for solution spinning by dissolving the polyimic acid, the solvent is particularly preferably dimethylacetamide.

When preparing the spinning dope 10, the mixing ratio of the polyamic acid and the solvent is preferably 15 to 30: 70 to 85% by weight in terms of weight ratio. If the mixing ratio of the polyamic acid is less than 15% by weight during the preparation of the spinning dope 10, the viscosity is too low, resulting in poor spinnability of the fiber. In addition, when the mixing ratio of the polyamic acid exceeds 30% by weight, the viscosity is high and may be unsuitable for spinning.

The spinning dope 10 may be prepared by adding polyamic acid to a solvent and dissolving it for 2 hours while slowly raising the temperature to 80 °C. After that, the spinning dope 10 is prepared through degassing and filtration.

At this time, the spinning dope 10 in which polyamic acid, a precursor of polyimide, is dissolved in an appropriate solvent as described above preferably has a viscosity in the range of 3,000 to 20,000 cps by appropriately adjusting the content of the solvent. In the case of having the viscosity as described above, it is possible to increase the spinning property and increase the spinning speed by preventing the decrease in spinnability such as yarn cutting in the subsequent spinning process.

2 is a schematic diagram of a wet spinning apparatus, which is an apparatus for producing polyimide-based carbon fibers having excellent flexibility according to the present invention.

In the present invention, polyamic acid fibers 100 are produced by spinning the spinning dope 10 into a coagulation bath 50 using a wet spinning apparatus as shown in FIG. 2 .

That is, referring to FIG. 2, the wet spinning apparatus for producing polyimide-based carbon fibers having excellent flexibility of the present invention includes a gear pump 15 for supplying the spinning dope 10 at a constant pressure, and the gear pump 15 A spinneret 20 for spinning the spinning dope 10 supplied from the spinneret 20 in the form of fibers, and a coagulation bath 50 for coagulating the unsolidified polyamic acid fiber bundle 40 discharged from the spinneret 20 ) is provided.

The coagulating liquid 30 provided in the coagulating bath 50 is a non-solvent and is well compatible with the organic solvent used in the preparation of the spinning dope 10. Any solvent capable of solidifying the polymer without dissolving the polymer can be used without limitation. Water may be used as the non-solvent, and preferably a mixture of water and an organic solvent may be used.

When a mixture of a non-solvent and an organic solvent is used as the coagulating liquid 30, the content of the organic solvent is preferably maintained uniformly at 35 to 85% by weight.

In addition, the temperature of the coagulating liquid 30 in the coagulating bath 50 is preferably adjusted to a range of 30 to 60 °C. If the temperature of the coagulating solution 30 is out of the above range, the spinning dope 10 may not be smoothly spun and the efficiency of the spinning process may decrease, and the solvent may not be properly removed.

As shown in FIG. 2, the polyamic acid fiber bundles 40 that have passed through the coagulation bath 50 are then washed with water in the washing device 60 to remove the solvent contained in the polyamic acid fiber bundles 40. Remove. Subsequently, the polyamic acid fiber bundle 40 passed through the washing device 60 is then dried in the drying device 70 and then wound up to complete the production of the polyamic acid fiber 100.

At this time, the orifice formed in the spinneret 20 is preferably circular.

In addition, in the present invention, for smooth spinning operation, the spinning dope 10 is extruded through the spinneret 20 under a pressure of 400 to 1,500 psi during wet spinning to prevent phenomena such as thread breakage in the polyamic acid fiber bundle 40 Radiation can be improved by preventing it.

In addition, according to the present invention, the spinning dope 10 prepared as described above can be fibrous through not only wet spinning, but also dry spinning or blast spinning.

That is, in the solution spinning process, a gap between the spinneret and the surface of the coagulation bath is used to more effectively orient the polymer chain in the fiber axis direction in the dry spinning process in which the solvent is evaporated during spinning, and in the wet spinning or spinning process in which the solvent is extracted and prepared. and air-gap wet spinning with an air-gap.

In general, solution spinning is a process used for spinning polymer materials that are difficult to melt by heat, and is divided into wet spinning, dry spinning, and steamed wet spinning.

The difference between dry spinning and wet spinning is that the process of dissolving a polymer material in a solvent to prepare a spinning solution is the same, but in wet spinning, the spinning solution is discharged directly from the spinneret into a coagulation bath to solidify / solidify. Spinning proceeds with a process of discharging a spinning solution into hot air without a coagulation bath and evaporating and solidifying the solvent.

In addition, in the wet spinning method, there is an air-gap between the spinneret and the coagulating solution, so that the spinning dope 10 discharged from the spinneret does not enter the coagulating solution directly, but is stretched in the direction of the fiber axis in the air layer to improve molecular orientation. This process is carried out.

In the present invention, when performing the second step (S20), it is possible to perform solution spinning, that is, wet spinning, dry spinning, or steamed wet spinning.

As described above, the polyamic acid fiber 100 manufactured through the solution spinning process is then subjected to a third step (S30) of imidizing through heat treatment and converting to polyimide precursor fiber.

Heat treatment at the time of imidation in the third step (S30) may proceed under the condition that the polyamic acid fiber 100 is treated at a temperature of 200 to 300 ° C. for 30 to 80 minutes.

That is, the polyamic acid fiber 100 is imidized by the heat treatment process as described above and converted into a polyimide precursor fiber.

The polyimide precursor fiber prepared as described above is then subjected to a fourth step (S40) of performing carbonization to produce carbon fiber.

Looking at the fourth step (S40) of carbonizing the polyimide precursor fiber according to the present invention, by applying heat to the polyimide precursor fiber, thermal decomposition is performed under high temperature conditions and carbonization proceeds, but conventional PAN-based carbon Unlike textiles, it is possible to do without the stabilization process.

At this time, as a method of applying heat to the polyimide precursor fiber, there is a method of performing carbonization by applying heat to a pyrolysis furnace from the outside, and another heating method includes a microwave heating method or a microwave plasma heating method.

The microwave heating can improve energy efficiency by directly heating the fiber, which is a target material, but the efficiency is variable by the microwave absorbing capacity of the fiber and the dielectric loss tangent is small. The material has the disadvantage of being difficult to heat.

The microwave plasma heating method, which is another method, is an area heating by radiation from plasma that can be generated in a short time, and has the advantage of not being affected by dielectric characteristics of internal materials. However, a device for converting microwaves into plasma is required, and since the inside of the material is not heated, cracks occur in the material due to the large temperature gradient between the inside and outside of the material when heating a material with low thermal conductivity and a large thermal expansion coefficient. there is

As described above, the carbonization process, which can be performed by various heating methods, takes the longest manufacturing time and production cost in the manufacturing process of carbon fiber, and thus acts as a major factor in increasing the carbon fiber manufacturing cost.

In the present invention, the fourth step (S40) of carbonizing the polyimide precursor fiber may be performed under a nitrogen atmosphere, and in the present invention, a low-temperature carbonization process performed at 800 ~ 1,200 ° C. It is preferable to carry out by a carbonization process. At this time, the low-temperature carbonization process and the high-temperature carbonization process are preferably performed for 45 to 180 seconds, respectively.

In addition, according to the present invention, a tension of 0.6 to 1.28 gf/tex may be added to the polyimide precursor fiber during the low-temperature carbonization process, and a tension of 0.9 to 1.8 gf/tex may be added during the high-temperature carbonization process. .

As described above, when the tension is less than the above range during the low-temperature carbonization process and the high-temperature carbonization process, physical properties such as tensile strength, tensile modulus, and thermal conductivity of the carbon fibers and graphite fibers produced are reduced, and exceed the above ranges. In the case of doing so, cutting or the like occurs in the carbonization process, resulting in deterioration in yarn-making properties. Therefore, it is preferable that tension is added to the polyimide precursor fiber in the above range during the low-temperature carbonization process and the high-temperature carbonization process.

When the fourth step (S40) is completed as described above, the production of the polyimide-based carbon fiber having excellent flexibility of the present invention is completed.

The polyimide-based carbon fiber according to the present invention has a tensile strength of 2.5 GPa or more, a tensile modulus of 150 GPa or more, and a thermal conductivity of 150 W/mK or more.

In addition, according to the present invention, a method for producing polyimide-based graphite fibers having flexibility can be provided.

That is, as shown in FIG. 1, the flexible polyimide-based graphite fiber includes: i) diamine having a structure of [Formula 1] and dianhydride having a structure of [Formula 2] A first step of polymerizing polyamic acid by polymerization; and, ii) a second step of dissolving the polyamic acid in a solvent and wet-spinning it; and, iii) imidizing the wet-spun polyamic acid fiber 100 to make the polyimide-free a third step of preparing cursor fibers; and, iv) a fourth step of continuously carbonizing the polyimide precursor fibers without flame stabilization to produce carbon fibers; and v) a fifth step of preparing graphite fibers by graphitizing the carbon fibers.

The method for producing polyimide-based graphite fibers according to the present invention further comprises a fifth step (S50) of graphitizing the polyimide-based carbon fibers after preparing the polyimide-based carbon fibers described above. do.

Therefore, in the method for producing polyimide-based graphite fibers according to the present invention, since the first step (S10) to the fourth step (S40), which are methods for producing polyimide-based carbon fibers, are the same, graphitization of the polyimide-based carbon fibers is performed. The fifth step (S50) will be further described below.

That is, the fifth step (S50) of graphitizing the polyimide-based carbon fiber is characterized in that it is performed at a temperature of 2,200 ° C. or higher in an argon atmosphere.

At this time, the fifth step (S50) is preferably performed for 45 to 180 seconds, and when the fifth step (S50) is performed, a tension of 1.2 to 2.5 gf/tex may be added to the polyimide-based carbon fiber. .

As described above, when the tension is added less than the above range in the fifth step (S50), the physical properties such as tensile strength, tensile modulus and thermal conductivity of the graphite fiber produced are lowered, and when it exceeds the above range, Cutting and the like may occur in the graphitization process, which may degrade yarn-making properties. Therefore, in the fifth step (S50), it is preferable to add tension in the above range.

The graphitization step is a step of crystallization by treating the carbon fiber at a high temperature of 2,200 ^° C or higher, and the graphite fiber according to the present invention is characterized by having a high specific surface area through this.

When the fifth step (S50), that is, the graphitization step is completed using the carbon fiber prepared as described above, the production of the polyimide-based graphite fiber having excellent flexibility of the present invention is completed.

Hereinafter, the present invention will be examined in more detail through examples. However, the present invention is not limited only to the following examples.

In order to measure the physical properties of the polyimide-based carbon fibers and graphite fibers having excellent flexibility manufactured according to the present invention, polyimide-based carbon fibers and graphite fibers were prepared while changing the manufacturing method as in the following examples.

[Example 1]

인 디아민과 R₂는

인 디안하이드라이드를 모노머로 하여 폴리아믹산(수평균 분자량 : 10,000)을 중합하였다. 이후에 상기 폴리아믹산을 DMAc에 용해하여, 15 중량％인 방사도프(10)를 제조하였다. 상기 방사도프(10)를 사용하여, 도 2와 같은 습식방사 장치 즉, 홀(hole) 수가 1,000개 이며, 상기 홀의 직경이 80 ㎛ 인 방사구금(10)으로부터 1,000 psi의 압력을 가하여 폴리아믹산 섬유속(40)을 토출시켰다. 이때 35 중량% 농도의 디메틸아세트아미드(Dimethylacetamide, DMAc) 수용액으로 이루어지고 30 ℃로 조절된 응고욕(50)에서 상기 폴리아믹산 섬유속(40)을 응고시켰다. 이후에 250 ℃에서 60분 동안 열처리함으로써, 상기 폴리아믹산 섬유(100)를 이미드화하여 폴리이미드 프리커서 섬유를 제조하였다. R ₁ is

Phosphorus diamine and R ₂ are

Polyamic acid (number average molecular weight: 10,000) was polymerized using phosphorus dianhydride as a monomer. Then, the polyamic acid was dissolved in DMAc to prepare a 15% by weight spinning dope (10). Using the spinning dope 10, a pressure of 1,000 psi is applied from a wet spinning device as shown in FIG. 2, that is, a spinneret 10 having 1,000 holes and a diameter of 80 μm to obtain polyamic acid fibers Inside (40) was discharged. At this time, the polyamic acid fiber bundle 40 was coagulated in a coagulation bath 50 made of a 35% by weight aqueous solution of dimethylacetamide (DMAc) and controlled at 30 °C. Thereafter, by heat treatment at 250 ° C. for 60 minutes, the polyamic acid fiber 100 was imidized to prepare a polyimide precursor fiber.

The polyimide precursor fiber was subjected to low-temperature carbonization at 800 ° C. for 60 seconds, and then, high-temperature carbonization was performed at 1,400 ° C. for 60 seconds. At this time, a tension of 0.6 gf/tex was applied to the polyimide precursor fiber during the low-temperature carbonization, and a tension of 0.9 gf/tex was applied during the high-temperature carbonization. In addition, polyimide-based carbon fibers were prepared as described above without a graphitization process and used as test pieces of Example 1.

[Example 2]

After preparing polyimide precursor fibers in the same manner as in Example 1, low-temperature carbonization was performed at 1,200 ° C. for 180 seconds, and then high-temperature carbonization was performed at 1,500 ° C. for 180 seconds. At this time, a tension of 1.28 gf/tex was applied to the polyimide precursor fiber during the low-temperature carbonization, and a tension of 1.8 gf/tex was applied during the high-temperature carbonization. In addition, polyimide-based carbon fibers were prepared as described above without a graphitization process and used as test pieces in Example 2.

[Example 3]

인 디아민과 R₂는

인 디안하이드라이드를 모노머로 하여 폴리아믹산(수평균 분자량 : 100,000)을 중합하였다. 이후에 상기 폴리이미드 프리커서 섬유를 800 ℃에서 60초 동안 저온탄화를 실시하고, 이후에 1,400 ℃에서 60초 동안 고온탄화를 실시하였다. 이때 상기 저온탄화시 상기 폴리이미드 프리커서 섬유에 0.6 gf/tex의 장력을 부여하였고, 고온탄화시에는 0.9 gf/tex의 장력을 부여하였다. 그리고, 흑연화 공정없이 상기와 같이 폴리이미드계 탄소섬유를 제조하여 실시예 3의 시험편으로 사용하였다.R ₁ is

Phosphorus diamine and R ₂ are

Polyamic acid (number average molecular weight: 100,000) was polymerized using phosphorus dianhydride as a monomer. Thereafter, the polyimide precursor fiber was subjected to low-temperature carbonization at 800 ° C. for 60 seconds, and then, high-temperature carbonization was performed at 1,400 ° C. for 60 seconds. At this time, a tension of 0.6 gf/tex was applied to the polyimide precursor fiber during the low-temperature carbonization, and a tension of 0.9 gf/tex was applied during the high-temperature carbonization. In addition, polyimide-based carbon fibers were prepared as described above without a graphitization process and used as test pieces in Example 3.

[Example 4]

After preparing the polyimide precursor fiber in the same manner as in Example 3, a tension of 1.28 gf/tex was applied to the polyimide precursor fiber during low-temperature carbonization, and a tension of 1.8 gf/tex was applied during high-temperature carbonization. . In addition, polyimide-based carbon fibers were prepared as described above without a graphitization process and used as test pieces in Example 4.

[Examples 5-6]

A graphitization step was performed on the polyimide-based carbon fibers prepared as in Examples 1 and 2 at 2,300 ° C. for 120 seconds in an argon atmosphere, and at this time, a tension of 1.2 gf / tex was applied. Graphite fibers were prepared as described above and used as test pieces of Examples 5 and 6.

[Examples 7 to 8]

A graphitization step was performed on the polyimide-based carbon fibers prepared in Examples 3 and 4 at 2,300 ° C. for 120 seconds in an argon atmosphere, and at this time, a tension of 2.5 gf / tex was applied. Graphite fibers were prepared as described above and used as test pieces of Examples 7 and 8.

[Comparative Example 1]

A polyimide-based carbon fiber was prepared by the same manufacturing method as in [Example 1], but a tension of 0.4 gf/tex was applied to the polyimide precursor fiber during low-temperature carbonization, and a tension of 0.7 gf/tex was applied during high-temperature carbonization. tension was given. The polyimide-based carbon fiber prepared as described above was used as a test piece of Comparative Example 1.

[Comparative Example 2]

Polyimide-based carbon fibers were prepared by the same manufacturing method as in [Example 2], but at this time, a tension of 0.4 gf/tex was applied to the polyimide precursor fibers during the low-temperature carbonization, and 0.7 gf/tex during the high-temperature carbonization. tex tension was applied. The polyimide-based carbon fiber prepared as described above was used as a test piece of Comparative Example 2.

[Comparative Example 3]

Polyimide-based carbon fibers were prepared in the same manufacturing method as in [Example 3], but at this time, a tension of 1.5 gf/tex was applied to the polyimide precursor fibers during the low-temperature carbonization, and 2.0 gf/tex during the high-temperature carbonization. tex tension was applied. The polyimide-based carbon fiber prepared as described above was used as a test piece of Comparative Example 3.

[Comparative Example 4]

Polyimide-based carbon fibers were prepared by the same manufacturing method as in [Example 4], but at this time, a tension of 1.5 gf/tex was applied to the polyimide precursor fibers during the low-temperature carbonization, and 2.0 gf/tex during the high-temperature carbonization. tex tension was applied. The polyimide-based carbon fiber prepared as described above was used as a test piece of Comparative Example 4.

[Comparative Examples 5 to 8]

The polyimide-based carbon fibers prepared as in Comparative Examples 1 to 4 were subjected to a graphitization step at 2,300 ° C. for 120 seconds in an argon atmosphere, and at this time, a tension of 3.0 gf / tex was applied. Graphite fibers were prepared as described above and used as test pieces of Comparative Examples 5 to 8.

For the test pieces of Examples 1 to 8 and Comparative Examples 1 to 8, tensile strength, tensile strength, thermal conductivity, and flexibility were measured, and the results are shown in Table 1. At this time, the tensile strength, tensile modulus, thermal conductivity, and flexibility were measured in the following manner.

1) Tensile strength and tensile modulus

The tensile strength and tensile modulus were measured according to KS L 2515 (carbon fiber testing method), and the results are shown in Table 1.

2) Thermal conductivity

The thermal conductivity was measured by the vertical thermal conductivity method in accordance with ASTM D5470 (Standard Test Method for Thermal Transmission Properties of Thermally Conductive Electrical Insulation Materials) under conditions ranging from room temperature to 60 ° C and is shown in Table 1.

3) Flexibility evaluation

Flexibility was measured with a flexibility meter for a monofilament yarn with a length of 5 cm, and the smaller the measured value, the more flexible it was. Table 1 shows the flexibility measurement values measured in the same way as above.

4) envoyship

Thread trimming was evaluated by the number of thread breakages per hour when manufacturing carbon fibers or graphite fibers. It was judged to be good if thread breakage did not occur for 1 hour, normal if thread breakage occurred 1 or 2 times, and bad if thread breakage exceeded 2 times.

tensile strength
(GPa) tensile modulus
(GPa) thermal conductivity
(W/mK) flexibility envoyship Example 1 2.5 160 153 40 Good Example 2 2.7 155 158 41 Good Example 3 2.6 154 160 43 Good Example 4 2.5 161 155 42 Good Example 5 2.9 166 154 45 Good Example 6 2.7 157 157 41 Good Example 7 2.6 158 162 40 Good Example 8 2.8 171 163 42 Good Comparative Example 1 1.4 112 132 54 Good Comparative Example 2 1.3 121 133 58 Good Comparative Example 3 2.7 164 164 53 error Comparative Example 4 3.0 172 160 54 error Comparative Example 5 1.5 124 134 53 Good Comparative Example 6 1.5 122 130 55 commonly Comparative Example 7 2.5 160 131 58 error Comparative Example 8 2.6 162 130 57 error

As shown in Table 1, in the case of the test pieces of Examples 1 to 8, it can be seen that the tensile strengths all show measured values exceeding 2.5 GPa, and the tensile modulus also show measured values of 150 GPa or more.

In addition, in the case of the test pieces of Examples 1 to 8, all of the thermal conductivity was 150 W/mK or more, and it could be seen that they exhibit excellent heat dissipation characteristics compared to conventional carbon fibers.

In general, in the case of nylon monofilament yarn, it shows a flexibility measurement value of 40 to 46 levels. Looking at Table 1, since the test pieces of Examples 1 to 8 show measured values of 40 to 45, according to the present invention, polyimide-based carbon fiber and graphite fiber having excellent flexibility at the level of nylon monofilament yarn are prepared It can be seen that

On the other hand, in the case of Comparative Examples 1 and 2 in which the tension applied during the low-temperature carbonization process and the high-temperature carbonization process during carbon fiber manufacturing was 0.4 gf/tex and 0.7 gf/tex, various physical properties such as tensile strength were deteriorated, and the low-temperature carbonization process and high-temperature carbonization process In the case of the test pieces of Comparative Examples 3 to 4 in which the tension applied during the carbonization process was 1.5 gf/tex and 2.0 gf/tex, the physical properties were excellent, but the thread cutting occurred more than 3 times in 1 hour, indicating that the thread cutting performance was poor. there is. ,

In addition, in the case of Comparative Examples 5 and 6, when a low tension is applied during the carbonization process, the trimming properties are excellent, but the physical properties are poor. In the case of Comparative Examples 7 and 8, high tension was added and various physical properties were excellent, but thread cutting occurred three or more times per hour, so it could be confirmed that the thread cutting property was poor.

That is, according to the results of Table 1, according to the present invention, when appropriate tension is applied to the polyimide precursor fiber during the carbonization process and the graphitization process, excellent processability can be secured without an increase in yarn trimming, and various aspects such as tensile strength It can be seen that carbon fibers and graphite fibers having excellent physical properties and flexibility can be produced.

The present invention has been described with reference to the experimental examples shown in the drawings, but these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent other experimental examples are possible therefrom. In addition, those skilled in the art to which the present invention pertains will be able to understand that it can be easily modified into other specific forms without changing the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative and not restrictive in all respects, and the true technical protection scope of the present invention should be defined by the technical spirit of the appended claims.

10: radiation dope
20: spinneret
50: coagulation bath
40: polyamic acid fiber bundle

Claims (10)

i) a first step of polymerizing polyamic acid by polymerizing diamine having a structure of [Formula 1] and dianhydride having a structure of [Formula 2];
ii) a second step of dissolving the polyamic acid in a solvent and wet-spinning;
iii) a third step of preparing polyimide precursor fibers by imidizing the wet-spun polyamic acid fibers 100; and
iv) Continuously carbonizing the polyimide precursor fiber without flame stabilization to prepare carbon fiber, which is carried out in a nitrogen atmosphere, at a low temperature of 800 to 1,000 ° C. for 45 to 180 seconds and a tension of 0.6 to 1.28 gf / tex is added. A method for producing polyimide-based carbon fibers having excellent flexibility, including a carbonization process and a fourth step performed by a high-temperature carbonization process in which a tension of 0.9 to 1.8 gf/tex is added for 45 to 180 seconds at 1,250 to 1,500 ° C.

The method of claim 1,
In [Formula 1], R ₁ is

,

,

,

,

,

Method for producing a polyimide-based carbon fiber having excellent flexibility, characterized in that any one of.
The method of claim 1,
In [Formula 2], R ₂ is

,

,

,

Method for producing a polyimide-based carbon fiber having excellent flexibility, characterized in that any one of.
delete A polyimide-based carbon fiber having excellent flexibility prepared according to any one of claims 1 to 3.
i) a first step of polymerizing polyamic acid by polymerizing diamine having a structure of [Formula 1] and dianhydride having a structure of [Formula 2];
ii) a second step of dissolving the polyamic acid in a solvent and wet-spinning;
iii) a third step of preparing polyimide precursor fibers by imidizing the wet-spun polyamic acid fibers 100;
iv) Continuously carbonizing the polyimide precursor fiber without flame stabilization to prepare carbon fiber, which is carried out in a nitrogen atmosphere, at a low temperature of 800 to 1,000 ° C. for 45 to 180 seconds and a tension of 0.6 to 1.28 gf / tex is added. A fourth step performed by a carbonization process and a high-temperature carbonization process in which a tension of 0.9 to 1.8 gf/tex is added at 1,250 to 1,500 ° C. for 45 to 180 seconds; and
v) a fifth step of graphitizing the carbon fiber to produce a graphite fiber, which is performed in an argon atmosphere at a temperature of 2,200 ° C. or more for 45 to 180 seconds; a method for producing a polyimide-based graphite fiber having excellent flexibility.

The method of claim 6,
In [Formula 1], R ₁ is

,

,

,

,

,

A method for producing a polyimide-based graphite fiber having excellent flexibility, characterized in that any one of the following.
The method of claim 6,
In [Formula 2], R ₂ is

,

,

,

A method for producing a polyimide-based graphite fiber having excellent flexibility, characterized in that any one of the following.
delete A polyimide-based graphite fiber having excellent flexibility prepared according to any one of claims 6 to 8.

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