KR101168537B1 - Carbon fiber manufacturing method and Precipitating bath - Google Patents

Abstract

The present invention relates to a method for producing a carbon fiber and to a coagulation bath for producing a carbon fiber for implementing the same, and more particularly to the flow of the coagulating liquid in the coagulation bath in the same direction as the direction of the fiber spun from the nozzle during wet and dry spinning The present invention relates to a carbon fiber manufacturing method capable of producing high quality and high uniform carbon fibers by minimizing liquid resistance and forming a coagulation bath for producing carbon fibers to implement the same.

Description

Carbon fiber manufacturing method and carbon fiber manufacturing coagulation bath for realizing the same {Carbon fiber manufacturing method and Precipitating bath}

The present invention relates to a method for producing a carbon fiber and to a coagulation bath for producing a carbon fiber for implementing the same, and more particularly to the flow of the coagulating liquid in the coagulation bath in the same direction as the direction of the fiber spun from the nozzle during wet and dry spinning The present invention relates to a carbon fiber manufacturing method capable of producing high quality and high uniform carbon fibers by minimizing liquid resistance and forming a coagulation bath for producing carbon fibers to implement the same.

Carbon fibers made from acrylonitrile polymers, so-called polyacrylonitrile (PAN) carbon fibers, have excellent strength characteristics and are widely used as raw materials for carbon fibers. Recently, more than 90% of all carbon fibers are PAN based. Carbon fiber. The PAN-based carbon fiber has been developed as a carbon electrode material for a secondary battery, a carbon film, and the like, and its application field is also expanding. When producing carbon fibers from acrylonitrile-based polymers, flame-resistant fibers are prepared by flame-resistant acryl fiber obtained by spinning the acrylonitrile-based polymer, that is, precursor for carbon fiber in an oxidizing atmosphere and at 200 to 400 ° C, Carbon fibers are manufactured by carbonizing the prepared fibers in an inert gas atmosphere and from 800 to 2000 ° C. In addition, the carbon fiber may be further treated in a high temperature inert gas to be referred to as graphite fiber.

The present invention has been invented to solve the above problems, the present invention is to minimize the liquid resistance by forming a flow of the coagulating liquid inside the coagulation bath in the same direction as the traveling direction of the fiber spun from the nozzle during wet and dry spinning And to provide a carbon fiber manufacturing method capable of producing a highly uniform carbon fiber and a carbon fiber manufacturing coagulation bath for implementing the same.

The carbon fiber manufacturing method according to the present invention is characterized in that the flow of the coagulating liquid inside the coagulation bath is formed in the same direction as the advancing direction of the fiber radiated from the nozzle during the wet and dry spinning.

According to another preferred feature of the present invention, the flow rate of the coagulating liquid and the traveling speed of the fiber are the same.

The coagulation bath for producing carbon fibers according to the present invention is a coagulation bath for producing carbon fibers, which is used for wet and dry spinning for producing carbon fibers, wherein the coagulation bath forms a coagulation liquid flow in the same direction as the advancing direction of the fibers to be spun. It is characterized in that the solid-liquid injection device is installed.

According to another preferred feature of the present invention, the coagulating liquid injector is provided below the air-gap layer.

According to another preferred feature of the present invention, the coagulating liquid injector is provided with a coagulating liquid speed adjusting means capable of adjusting the speed of the coagulating liquid being injected.

Carbon fiber manufacturing method according to the present invention can minimize the denier difference between the fibers by minimizing the liquid resistance of the fiber in the spinning process, thereby producing a high quality / high uniform carbon fibers.

1 is a schematic diagram of a coagulation bath according to the present invention;
2 is a perspective view of a coagulation liquid injector according to the present invention.

The carbon fiber precursor is obtained from an acrylonitrile-based polymer, and the properties of the carbon fiber precursor are basically dependent on the composition of the acrylonitrile-based polymer. The main component of the acrylonitrile polymer used in the present invention is an acrylonitrile unit, and the content of the acrylonitrile unit is preferably 90% by weight or more, more preferably 95% by weight based on the total acrylonitrile polymer. % Or more, for example, 95 to 99% by weight. Here, when the content of the acrylonitrile unit is too small, there is a fear that the mechanical properties of the carbon fibers are lowered, such as the strength of the carbon fibers obtained in the firing step is lowered.

The acrylonitrile-based polymer is, as necessary, at least one copolymerization component (other auxiliary components other than acrylonitrile), and a unit containing a densification accelerator component, an extension promoter component and the like in the spinning step, It may further comprise a unit comprising a flame-resistant promoting component, a unit containing an oxygen permeation promoting component, the content of which is preferably less than 10% by weight, more preferably 5 to the total acrylonitrile-based polymer Less than% by weight, for example 1 to 5% by weight. The structural unit serving as the densification promoting component is produced by copolymerization of a vinyl compound monomer having a hydrophilic functional group such as a carboxyl group, a sulfone group and an amide group, and examples of the monomer including a densification promoting component having a carboxyl group include acrylic acid and methacrylic. Acids, itaconic acid, crotonic acid, citraconic acid, maleic acid, alkyl esters of these (methyl acrylate, etc.), etc. can be illustrated, It is preferable to use acrylic acid, methacrylic acid, itaconic acid, etc. especially. Specific examples of the densification-promoting component having the sulfonic group include allyl sulfonic acid, metharylsofonic acid, styrene sulfonic acid and 2-acrylamido-2-methylpropanesulfonic acid. (2-acrylamido-2-methyl propane sulfonic acid), vinyl sulfonic acid, sulfo propyl methacrylate, and the like. Specific examples of the structural unit of the densification-promoting component having the amide group include Acrylamide, methacrylamide, dimethyl acrylamide is preferable. In addition, alkylamine and dioctyl such as octyl amine, dodecyl amine, lauryl amine, etc., in order to improve oxygen permeability between single fibers in a flame resistant furnace. Dialkyl components, such as dialkylamine, such as amine, and trialkylamine, such as trioctylamine, ethylene diamine, and hexamethylene diamine, can be used. Among these, in order to improve the uniformity of polymerization, it is preferable to use a component having solubility in a polymerization solvent, a medium, a spinning solvent and the like. In addition, the unit including the oxygen permeation promoting component may be introduced by copolymerization of an alkyl ester of one unsaturated carboxylic acid structure, for example, ethyl methacrylate. The auxiliary component (comonomer) and the main component are added to the organic solvent at 15 to 25wt%. At this time, the initiator is added in an amount of 0.1 to 1wt% based on the weight of the monomer (the main and auxiliary components) and the molecular weight regulator is 0.1 to 1wt%. The polymerization may be performed at 60 to 70 ° C. for at least 10 hours to obtain an acrylonitrile copolymer dissolved in an organic solvent, which becomes a dope stock solution. The organic solvent used for the polymerization is ammonia in the gaseous state or an aqueous solution state is added to maintain the pH of the organic solvent of 8 to 10. The pH of the organic solvent is less than 8, and the intrinsic viscosity is almost the same as the state without addition of ammonia, so there is no synergistic effect of the intrinsic viscosity due to ammonia. It is difficult to stretch and easily gel, which impairs the stability of the dope stock solution.

As the organic solvent, common organic solvents capable of dissolving acrylonitrile polymers such as dimethyl sulfoxide (DMSO), dimethyl formamide (DMF), and dimethyl acetamide (DMAc) are used. Although it can be used, it is most preferable to use dimethyl sulfoxide, which is an organic solvent having no amide bond.

At this time, the dope stock solution is moved to a defoaming tank and, if necessary, undergoes a defoaming process, and is then spun in a wet or dry manner. The spun carbon fiber precursor, i.e. acrylonitrile-based fiber, is drawn in hot water of 50 ° C. or higher and then treated with 0.01 to 5.0 wt% aqueous solution of an emulsion including a modified silicone emulsion, an epoxy modified silicone emulsion, fine particles, an ammonium compound, and the like. After that, if necessary, it can be stretched again in a high temperature fruit such as steam to produce a precursor fiber for carbon fiber. The overall draw ratio of the prepared precursor fibers is usually 7-25 times, and short fiber fineness is 0.5-2.0 dtex. The spun carbon fiber precursor is flameproofed in an oxygen atmosphere and at 200 to 400 ° C. and carbonized at 800 to 2000 ° C. in an inert atmosphere according to a conventional method, thereby having uniform physical properties and less defects caused by voids. Carbon fibers can be produced. The carbon fiber prepared using the precursor of the present invention can be usefully used as a material for forming energy-related substrates such as CNG tanks, wind turbine blades, turbine blades, and structural reinforcing materials such as roads and bridges.

The present invention relates to a spinning process in which the dope stock solution is spun dry in a manufacturing process of the carbon fiber described above.

The carbon fiber manufacturing method of the present invention is characterized by minimizing the generation of liquid resistance of the fiber by forming a flow of the coagulating liquid inside the coagulation bath in the same direction as the traveling direction of the fiber spun from the nozzle during wet and dry spinning. Generally, after the fiber discharged from the nozzle passes through the air-gap layer, the fiber bundle at the turn-guide portion from the coagulation liquid surface causes denier deviation between short fibers due to coagulation liquid resistance. The present invention forms a flow of the coagulating liquid inside the coagulation bath in the same direction as the advancing direction of the fiber spun from the nozzle to minimize the disadvantage of the liquid resistance of the fiber.

In particular, in relation to the speed, it is preferable to adjust the flow rate of the coagulating liquid and the traveling speed of the fiber in the same manner.

In order to form such a flow of the coagulation liquid, the coagulation bath for producing carbon fibers in the present invention is provided with a coagulation liquid injector for forming a flow of coagulation liquid in the same direction as that of the fiber radiated from the nozzle.

1 is a schematic diagram of a coagulation bath according to the present invention. As shown in FIG. 1, the coagulation bath 10 according to the present invention is provided with a coagulation liquid injector 30 therein. The coagulating liquid injector generates a coagulating liquid, and specifically, the coagulating liquid is generated in the same direction as that of the fiber. To this end, the coagulating liquid injector is preferably installed under the air-gap layer. The fiber 40 radiated from the nozzle 20 is brought into contact with the coagulation liquid via the air-gap layer, and the coagulation liquid is coagulated by the coagulation liquid injector 30 in the same direction as the advancing direction of the fiber 40. The flow 50 is formed, which can minimize the liquid resistance of the fiber.

In addition, it is preferable that the coagulating liquid injector is provided with a speed adjusting means capable of adjusting the coagulating liquid spraying speed.

2 is a plan view of the coagulation liquid injector. There is a compressed air injection device 32 in the form of a donut, and is composed of a nozzle 34 through which the injected compressed air can be injected. Compressed air is injected to create a flow of coagulant liquid, and the flow rate is adjusted according to the pressure of the compressed air.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Examples 1 to 3

Carbon fiber was manufactured through a conventional carbon fiber manufacturing process, and carbon fiber was manufactured using a coagulation bath provided with a coagulation liquid injector. In addition, the coagulating liquid injector is provided with a speed adjusting means, to prepare a carbon fiber while adjusting the coagulating liquid injection speed as shown in Table 1.

Comparative Example

In the same manner as in Example, but using a conventional coagulation bath without a coagulation liquid injector to prepare a carbon fiber.

The fiber propagation speed is a value obtained by measuring the rotational linear velocity of the winding roller after the coagulation bath. The coagulation fluid injection speed was measured by using a flowmeter at a depth of 30 cm from the spinning nozzle after the coagulation fluid injection device was operated.

The denier deviation of the precursor means the measurement of the short fiber denier of 25 samples, and the standard deviation of 25 samples divided by the average value.

Precursor denier deviation (CV%) = (denier standard deviation of short fibers / denier average of short fibers) * 100

Carbon fiber cross-sectional diameter deviation (CV%) is a value obtained by dividing the standard deviation value obtained by measuring the cross-sectional diameter of 25 carbon fiber samples using an electron scanning microscope.

Carbon fiber cross section diameter deviation (CV%) = (standard deviation of diameter / average diameter) * 100

The strength variation rate of carbon fiber is obtained by dividing the standard deviation of the strand strengths obtained by testing the tensile strength with five strand specimens by the average of the tensile strengths of the strands.

Carbon Fiber Strength Fluctuation Rate (CV%) = (Strand Average Tensile Strength / Strand Strength Standard Deviation) * 100

The test results are summarized in Table 1.

division Comparative example Example 1 Example 2 Example 3 Coagulant injection device none has exist has exist has exist Fiber running speed (m / min) 20 20 20 20 Coagulation liquid spraying speed (m / min) - 20 10 30 Precursor Denier Deviation (CV%) 12 3 6.5 8.8 Carbon fiber cross-sectional diameter deviation (CV%) 7.5 2.5 4.2 5.6 Carbon Fiber Strand Strength (Gpa) 4.3 4.8 4.5 4.4 Carbon fiber strand strength variation rate (CV%) 5.8 2.1 4.2 4.9

As shown in Table 1 above, the Examples 1 to 3 with the coagulating liquid injector was reduced compared to the precursor denier deviation, compared with the comparative example without the carbon fiber cross-sectional diameter variation was also reduced. On the other hand, as a result of adjusting the injection speed of the coagulating solution as in Examples 1 to 3, it was confirmed that the precursor denier deviation increased when the coagulating solution injection speed was faster than the progressing fiber speed than when the advanced fiber and coagulation solution injection speed were the same. In addition, it was found that the change in the diameter of the carbon fiber cross-section also increased. Also, as the precursor denier deviation became smaller, the carbon fiber strand strength also increased.

10: coagulation bath
20: Nozzle
30: coagulation liquid injector

Claims (5)

The method of producing a carbon fiber, characterized in that for forming the flow of the coagulating liquid inside the coagulation bath in the same direction as the direction of the fiber radiated from the nozzle during wet and dry spinning. The method of claim 1, wherein the flow rate of the coagulating liquid and the running speed of the fiber is the same. In the coagulation bath for producing carbon fibers used during the wet and dry spinning for the production of carbon fiber, the coagulation bath is characterized in that the coagulation liquid injection device for forming a flow of coagulation liquid in the same direction as the traveling direction of the spun fiber is installed A coagulation bath for producing carbon fibers. 4. The coagulation bath for producing carbon fibers according to claim 3, wherein the coagulation solution injector is installed under the air gap layer. 5. The coagulation bath for producing carbon fibers according to claim 4, wherein the coagulation solution injector is provided with a coagulation speed adjusting means capable of adjusting the speed of the coagulation solution being injected.

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