KR20110078246A - Preparing method for preparing carbon fiber precursor and carbon fiber precursor using it - Google Patents

Abstract

PURPOSE: A method of manufacturing precursor fiber for carbon fiber and a precursor fiber for carbon fiber manufactured by the same are provided to minimize deformations of the itaconic acid by optimizing drying conditions of a polymer. CONSTITUTION: The method of manufacturing precursor fiber for carbon fiber is as follows. A PAN-based copolymer is manufactured by using a water-base suspension polymerization method. The copolymer is dried and a moisture regain is 0.5wt% or less. The dried copolymer is emitted after being dissolved in a solvent.

Description

Preparation method for preparing carbon fiber precursor fiber and carbon fiber precursor fiber produced thereby

The present invention relates to a method for producing carbon fiber precursor fibers and a carbon fiber precursor fiber produced thereby, which relates to a method for reducing the generation of gels generated upon dope dissolution by denaturation of carboxyl groups.

Specifically, acrylonitrile and the copolymerized component are reacted using an aqueous suspension polymerization method, and the obtained polymer is dried in a predetermined time under low temperature / vacuum to form a PAN copolymer, and then dissolved in an organic solvent. The present invention relates to a method for producing carbon fiber precursor fibers having low wool and single yarns, which have a high strength carbon fiber after solidification, carbonization after coagulation in a fiber form, and carbon fiber precursor fibers produced thereby.

The origin of carbon fiber can be found in 1879 when Edison carbonized bamboo fiber for the filament of the bulb. Later, Union Carbide developed rayon-based carbon fibers in 1959, and the development of early carbon fibers began. In 1964, continuous carbon fiber development was successful. Carbon fiber is classified into rayon, PAN, and Pitch based on the raw materials used in the manufacture. Currently, PAN-based carbon fiber manufactured based on acrylonitrile is most commonly used. In order to produce carbon fiber, it has to go through three main processes (polymerization, spinning, firing), which is a complicated and long process.

The PAN-based fiber used as a precursor of carbon fiber has a great influence on the quality and performance of the carbon fiber obtained as an intermediate product for producing the carbon fiber as a final product. In particular, the concentration of the acrironite between the monomer and the copolymer has a great influence on the physical properties of the carbon fiber. The PAN precursor is the most economical precursor of all carbon fiber precursors known to date, and is manufactured into fine fibers through wet, dry or melt spinning according to the purpose.

      Generally, a copolymer of various vinyl compounds is used for various purposes. In particular, the role of the copolymer in the flame resistance process of thermal oxidation of the precursor for carbon fiber can be seen as very important. In the case of precursor fiber made of acrylonitrile only, exothermic phenomenon occurs during oxidation and cyclization reaction, and runaway reaction is likely to occur, and runaway reaction in carbonization process deteriorates physical properties of the finally obtained carbon fiber. Therefore, by using a compound including a carboxyl group (ex. Acrylic acid, methacrylic acid, itaconic acid, crotonic acid, citraconic acid, etacuryl acid, maleic acid, mesaconic acid) as acrylonitrile copolymer, The flameproofing process time is shortened.

However, in the case of the copolymer containing a carboxyl group, deformation by heat occurs easily, and such deformation lowers the solubility of the acrylonitrile-based polymer in the organic solvent and eventually becomes a major cause of gel generation in preparing the dope solution. The gel produced in the dope decreases the fairness during the spinning process and is a direct cause of the occurrence of woolen yarn and single yarn, and also acts as a major factor in the deterioration of carbon fiber properties.

For this reason, many efforts have been made to reduce gels in acrylonitrile solutions. As a method for minimizing the amount of gel produced by the neutralization reaction between carboxyl groups and ammonia, a study on the optimum dosing position of ammonia-based material was recently published by Toray (JP 2008-308775).

In the preparation of polyitaconic acid using itaconic acid, the experimental results of the production of peat anhydride when the reaction temperature is 65 degrees or more have been published by many researchers (Yokota et al. Die Makromolekulare Chemie Vol 176, Year 2007; Grespos et al. Makromol. Chem., Rapid Commun. Vol 5, Year 1984; Velickovic et al. Polymer Bull. Vol 32, Year 1994). However, there have been no published results on the degeneration and the effects of peat acid used in the production of precursor fiber for carbon fiber production.

The present invention has been invented to solve the above problems, the present invention relates to the production of precursor fibers used in the production of high-performance carbon fibers can be minimized deformation of itaconic acid by optimizing the drying conditions of the polymer It is an object of the present invention to provide a method for producing carbon fiber precursor fibers and carbon fiber precursor fibers produced thereby.

Method for producing a carbon fiber precursor fiber according to the present invention is 1) preparing a PAN-based copolymer using the aqueous suspension polymerization method, 2) drying the copolymer and 3) the dried copolymer in a solvent It comprises a step of spinning after dissolution, in particular the moisture content of the copolymer in the drying step is characterized in that less than 0.5wt%.

According to another preferred feature of the invention, the drying temperature in the drying step is 60 degrees or less.

According to another preferred feature of the invention, the degree of vacuum during drying in the drying step is more than 730 Torr.

Carbon fiber precursor fiber according to the present invention is produced by the method described above, characterized in that the degree of modification of the carboxyl group is less than 10%.

In the manufacturing method of PAN precursor fiber, the acrylonitrile-based polymer produced by the aqueous suspension polymerization method is dried under optimum conditions to minimize the carboxyl group deformation of the copolymer. PAN-based precursor fiber suitable for fiber production can be prepared using an existing process without any additional process. This method can be further applied to improve the woolen yarn and single yarn of fiber generated by copolymer modification in the manufacture of PAN-based fibers as well as other synthetic fibers.

In the method for producing a PAN precursor fiber according to the present invention, a PAN polymer is reacted with acrylonitrile (AN), a main monomer component, by using at least one or more carboxyl group-containing vinyl copolymers and aqueous suspension polymerization, and carboxyl. After drying under optimum conditions without any deformation of the group, it is coagulated using wet or dry spinning to produce coagulated yarns in the form of fibers. The prepared precursor fiber is carbonized to produce a high-performance carbon fiber. The present invention provides a method for minimizing the deformation of the carboxyl group in the production of carbon fiber precursor fiber.

The present invention is described in more detail below.

The method for preparing carbon fiber precursor fibers includes 1) preparing a PAN-based copolymer using an aqueous suspension polymerization method, 2) drying the copolymer, and 3) spinning the dried copolymer in a solvent and then spinning. It includes the steps.

The PAN-based copolymer in the step of preparing the PAN-based copolymer by the aqueous suspension polymerization method is one or more copolymerizable with acrylonitrile, the main component monomer of 96-98wt%, by using an oxidation-reduction agent or 2-4 wt% of two or more monomers (ex. Acrylic acid, methacrylic acid, itaconic acid, crotonic acid, citraconic acid, etacuryl acid, maleic acid, mesaconic acid) are prepared by reacting in an aqueous solution. The weight ratio of monomer in the reaction is preferably 15-30wt%, which is related to the physical properties of the PAN polymer.

In the aqueous suspension polymerization, the persulfate compound was used as a reaction initiator, and the bisulfite compound was used as an activator.

In the drying of the copolymer, the polyacrylonitrile-based polymer prepared by the aqueous suspension polymerization method is primarily used to remove moisture through a dehydration process. The first dehydration process removes water using the centrifugation principle. The water-removed polymer is in the form of a powder, but still contains a large amount of water. Secondly, the water is removed to less than 0.5wt% using a vacuum pump at a temperature lower than 65 degrees. If the moisture is 0.5wt% or more, the viscosity of the dope solution becomes high, which causes deterioration of elongation during spinning and gelation phenomenon when excessive moisture is contained.

 When the heating temperature is higher than 60 degrees during drying, two carboxyl groups are transformed into anhydrous carboxyl groups as shown in Chemical Formula 1. Depending on the degree of deformation of itaconic acid, the solubility of the arylonitrile-based polymer in the organic solvent is lowered, which is related to the degree of gel formation in dope preparation.

(Formula 1)

The drying pressure is preferably maintained at a vacuum degree of 730 Torr or more in order to prevent denaturation of the carboxyl group.

As a spinning method in the step of spinning the dried copolymer after dissolving in a solvent, wet or dry spinning is possible, but spinning was used as a wet method, and a more detailed spinning method was performed as follows. The intrinsic viscosity was dissolved in DMSO (Dimethylsulfoxide) at a concentration of 18-22% by weight of the PAN polymer prepared in 1.6-1.9 and ammonia gas pH 8.5 was added at a temperature lower than 70 degrees. Neutralization with ammonia is to improve the hydrophilicity of the copolymer to form a dense coagulation structure. The spinning stock is passed through a spinning nozzle with 12,000 holes and discharged into a coagulation bath containing 45–60 wt% DMSO (relative to distilled water). As the coagulation solvent, in addition to DMSO, DMF and DMAc are also possible. The coagulant produced in the coagulation bath is subjected to a washing bath, and the washing agent that has passed the washing bath has produced a PAN precursor fiber through a post-treatment process.

The carbon fiber precursor fiber prepared by the above method can produce a carbon fiber having excellent physical properties as the degree of modification of the carboxyl group is less than 10%.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited only to the above embodiment.

< Example  1>

The polymerization raw material ratio in aqueous solution was made into acrylonitrile / methyl acrylate / itaconic acid = 96.3 / 2.5 / 1.2 (wt%), and radical polymerization was performed using persulfate / bisulfate. The resulting polymer was vacuum dried (730 Torr) at 60 ° C. for 18 hours to have a water content of 0.5 wt% or less, dissolved in DMSO solution, to prepare a spinning stock solution at 20 wt%, and ammonia gas was added to neutralize the solution. After the spinning stock solution is put into a wet and dry spinning tank, it passes through a spinning nozzle having a hole of 12,000 and moves to a coagulation bath. PAN precursor fibers were prepared by spinning at a speed of 100 m / min. The precursor fiber was flameproofed at 240 degrees under an air atmosphere and carbonized to obtain carbon fiber.

< Example  2>

In Example 1, it carried out similarly to Example 1 except having changed the preparation ratio of the polymerization raw material into acrylonitrile / methyl acrylate / itaconic acid = 97.8 / 1 / 1.2 (wt%).

< Example  3>

The same procedure as in Example 1 was carried out except that the drying temperature in Example 1 was vacuum dried (730 Torr) at 60 ° C. for 24 hours.

< Example  4>

The acrylonitrile polymer obtained after drying in Example 1 was left at 40 degrees for 12 hours before and after the component of the carboxyl group of the polymer was analyzed by ¹ H NMR to measure the degree of denaturation.

< Example  5>

The same procedure as in Example 4 was carried out except that the drying temperature in Example 4 was 60 degrees.

< Comparative example  1>

In Example 1 was the same as in Example 1 except that the drying temperature was dried 18 hours at 120 degrees.

< Comparative example  2>

      In Example 1, drying was carried out in the same manner as in Example 1 except that vacuum drying (600 Torr) was performed at 80 ° C. for 20 hours.

< Comparative example  3>

The same procedure as in Example 1 was carried out except that the drying temperature in Example 1 was vacuum dried (730 Torr) at 80 ° C. for 14 hours.

< Comparative example  4>

In Example 4, it carried out similarly to Example 4 except having set the drying temperature to 80 degree.

< Comparative example  5>

The same procedure as in Example 4 was carried out except that the drying temperature in Example 4 was 100 degrees.

< Comparative example  6>

The same procedure as in Example 4 was carried out except that the drying temperature in Example 4 was 120 degrees.

< Comparative example  7>

In Example 4, it carried out similarly to Example 4 except having set the drying temperature to 140 degree.

The experimental results are summarized in Table 1.

TABLE 1

division Acrylonitrile Drying Conditions Bulb fiber Carbon fiber Temperature (degrees) Hour (hr) Vacuum (Torr) Mou (ea / m) Strength (GPa) Example 1 60 18 730 0.2 3.61 Example 2 60 18 730 0.21 3.59 Example 3 60 24 730 0.5 3.45 Comparative Example 1 120 18 0 3.3 3.06 Comparative Example 2 80 20 600 2.5 3.14 Comparative Example 3 80 14 730 1.1 3.37

In addition, the degree of modification of the carboxyl group according to the temperature of the Example and Comparative Example is shown in FIG. As shown in Figure 1 when the drying temperature exceeds 60 degrees, there is a problem that the degree of denaturation of the carboxyl group exceeds 10%.

1 is a schematic diagram of the degree of denaturation of the carboxyl group with temperature in relation to the examples and comparative examples of the present invention.

Claims (4)

   1) preparing a PAN-based copolymer using an aqueous suspension polymerization method, 2) drying the copolymer, and 3) dissolving the dried copolymer in a solvent and then spinning the carbon fiber precursor fiber In the manufacturing method of The method of producing a carbon fiber precursor fiber, characterized in that the moisture content in the drying step is 0.5wt% or less.   The method of claim 1, wherein the drying temperature in the drying step is 60 degrees or less.   The method of claim 1, wherein the degree of vacuum during drying in the drying step is 730 Torr or more. The carbon fiber precursor fiber produced by any one of claims 1 to 3, wherein the degree of modification of the carboxyl group is less than 10%.

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