KR101138291B1 - Method for manufacturing Lyocell based carbon fiber and Lyocell based carbon fabric - Google Patents

Abstract

The present invention relates to a method for producing lyocell-based carbon fibers and carbon fabrics, and more particularly, pretreatment process, stabilization process, carbonization process and graphite immersed lyocell fiber or lyocell fabric in a silicone-based polymer solution and flame retardant salt solution It relates to a method for producing carbon fibers and carbon fabrics made through a oxidization process.

Description

Method for manufacturing Lyocell-based carbon fiber and carbon fabric {Method for manufacturing Lyocell based carbon fiber and Lyocell based carbon fabric}

The present invention relates to a method for producing lyocell-based carbon fibers and carbon fabrics, and more particularly, pretreatment process, stabilization process, carbonization process and graphite immersed lyocell fiber or lyocell fabric in a silicone-based polymer solution and flame retardant salt solution It relates to a method for producing carbon fibers and carbon fabrics made through a oxidization process.

In general, carbon fibers are classified into rayon-based, polyacrylonitrile (PAN) -based, and pitch-based carbon fibers according to the kind of precursor.

Until now, rayon-based carbon fibers have been made of high-purity viscose rayon fibers, which are not only regulated by the government using pollutants, that is, carbon disulfide (CS ₂ ) as a solvent, but also PAN-based and pitch-based carbon fibers. Compared with the economy, the market size is gradually decreasing.

The lyocell fiber was manufactured in 1978 by Akzo-Nobel, a company that developed a new process that is free from environmental pollution and harmful substances to humans. (N-methylmorpholine-N-oxide: NMMO) It is a wet and dry spinning fiber manufactured with the main raw material. The raw material of lyocell fiber is cellulose extracted from wood pulp, which is 100% biodegradable polymer and has environmentally friendly characteristics because it is recyclable. In addition, a new method is applied which does not emit pollutants, which is a big problem of existing rayon fibers.

The lyocell fiber is also a cellulose fiber, and the chemical properties are similar to each other, but the mechanical and physical properties are excellent, and the microstructural properties such as crystallinity and crystal orientation are very different. Despite these advantages, it was not produced in the form of spun yarn until early 1990, and commercialized on a small scale as a filament company in early 2000. In 2007, Hyosung Co., Ltd. and Kolon Co., Ltd. have a system for mass production of lyocell filament yarn.

In general, the production of carbon fiber is subjected to three process steps, stabilization (carbonization) and graphitization (graphitization). The processes are carried out in a fibrous or woven fabric, which determines the final carbonization temperature or the graphitization temperature depending on the intended use of the carbon fiber. The carbonization temperature and the graphitization temperature have a great influence on the thermal conductivity, insulation, or modulus of elasticity of the carbon fiber.

In addition, the internal structure and physical properties of the carbon fiber may vary greatly depending on various process factors such as the heat treatment temperature, the temperature increase rate, the temperature increase step, the chemical treatment of the fiber surface, and the atmosphere gas applied during the stabilization process and the carbonization process. The stabilization process is a heat treatment step that is commonly performed on all carbon fibers such as PAN system or pitch system, and is the most important core process in rayon carbon fiber. In general, serious chemical and physical changes occur rapidly during the stabilization process, and its purpose is to provide a stable chemical structure capable of withstanding the high heat treatment temperature required for the carbonization process. In order to further enhance the effect of the stabilization process, a chemical pretreatment process is essential, and development of a technology related to the pretreatment process is required in carbon fiber production.

An object of the present invention is to prepare a lyocell-based carbon fiber and carbon fabric that can further enhance the effect of the stabilization process by performing a pretreatment process to immerse the lyocell fiber or lyocell fabric in the silicone-based polymer solution and flame retardant salt solution before the stabilization process To provide a way.

The method for producing a lyocell-based carbon fiber and carbon fabric of the present invention is characterized in that the lyocell fiber or lyocell fabric is subjected to a pretreatment step, a stabilization step, a carbonization step and a graphitization step of immersing the lyocell fiber or the lyocell fabric in an aqueous solution of a flame retardant salt. It is done.

In the present invention, the pretreatment step is to immerse the lyocell fiber or lyocell fabric in a silicone-based polymer solution and a flame retardant salt solution, examples of the silicone-based polymer is polysiloxane (PS), polydimethylsiloxane (PDMS), room temperature Room temperature vulcanizing silicone (RTV), polymethyl phenyl siloxane (PMPS), polysilazane (Polysilazane) and the like. Examples of the flame retardant salts include phosphoric acid (phosphoric acid: H ₃ PO ₄ ), phosphoric acid Sodium (phosphate: Na ₃ PO ₄ ), ammonium chloride (ammonium chloride: NH ₄ Cl) and the like.

In the silicone polymer solution, a polar solvent is used. Examples of the polar solvent include acetone, perchloroethylene, tetrahydrofurane (THF), and methyl ether ketone (MEK). ), Ethyl alcohol (Ethylalcohol), methyl alcohol (Methylalcohol) and the like.

The concentration range of the silicon-based polymer in the silicon-based polymer solution used in the pretreatment process of the present invention is preferably 1 to 15% by weight, but when the concentration of the silicon-based polymer is less than 1% by weight, the concentration is too low, so the stabilizing effect is not preferable. In addition, when it exceeds 15 weight%, not only unevenness but also brittleness becomes large, and it is unpreferable. In addition, the concentration range of the flame retardant salt in the flame retardant salt aqueous solution is preferably 3 to 20% by weight, but when the concentration of the flame retardant salt is less than 3% by weight, the concentration is low, which is not preferable because the flame retardant effect does not appear, and when it exceeds 20% by weight It is not desirable to have a supersaturated state.

In addition, the immersion treatment is performed by sequentially immersing the silicon-based polymer solution and the flame-retardant salt aqueous solution for 1 hour, preferably 10 minutes to 1 hour at a temperature of room temperature (about 25 ℃) ~ 80 ℃ If the temperature is less than room temperature, it is preferable that the stabilizing effect is not preferable, and if it exceeds 80 ° C, the flexibility of the fiber is not preferable, and if it exceeds 1 hour, the cellulose swells in solution or It is not preferable because the strength may drop. There is no particular restriction on the order of the immersion treatment in the silicone-based polymer solution and the flame-retardant salt aqueous solution during the immersion treatment, it is preferable to be immersed in the silicone-based polymer solution first, and then immersed in the flame-retardant salt aqueous solution.

In the present invention, the stabilization process is carried out in two steps, the first step is carried out by heat treatment for 10 to 30 hours in the temperature range of 100 ~ 250 ℃, the second step is 10 to 100 hours in the temperature range of 300 ~ 500 ℃ It is preferable. In the stabilization process, if the first step is heat-treated at a temperature below 100 ° C., it is not preferable because it is not dried, and if heat-treated at a temperature above 250 ° C., thermal decomposition of the fiber may occur, which is not preferable. The heat treatment for less than the time is not preferable because the fiber may lose flexibility, and if the heat treatment for more than 30 hours, the safety efficiency is inferior. In addition, in the stabilization process, the second step is not preferable because the stabilization effect is not noticeable when the heat treatment at a temperature below 300 ℃, the carbonization effect is more preferable than the stabilization effect when heat treatment at a temperature above 500 ℃. In addition, when the heat treatment for less than 10 hours is not preferable because the fiber may lose flexibility, the heat treatment for more than 100 hours is not preferable because the stabilization effect and efficiency is inferior.

In the present invention, the carbonization process is preferably performed by heat treatment for 10 to 30 hours in the temperature range of 900 ~ 1700 ℃. If the temperature of the carbonization process is less than 900 ° C, the carbonization rate is too low, which is too low at 80% or less.If the temperature of the carbonization process is higher than 1700 ° C, the graphitization effect is more pronounced than carbonization, and the strength is not preferable. If the heat treatment for less than the time is not preferable because the sufficient carbonization process is not made, and if the heat treatment for more than 30 hours, the carbonization yield is not preferable.

In the present invention, the graphitization process that can control the thermal conductivity, insulation, or heat resistance characteristics is raised to a graphitization temperature of 2000 ~ 2800 ℃, the residence time at a temperature of 2000 ~ 2800 ℃ 10 hours or less, that is, 0 ~ It is preferably carried out for 10 hours, the graphitization degree is not preferable when the temperature is less than 2000 ℃, it is not preferable because the graphitization effect compared to economical efficiency is lower than 2800 ℃. The retention time at 2000 ~ 2800 ° C. is 0 hours means that the graphitization temperature is raised and cooled immediately. The retention time is 10 hours. The retention time is maintained at the graphitization temperature for 10 hours and then cooled. Means that. If the residence time at the graphitization temperature exceeds 10 hours, the final carbonization yield is not preferable, which is undesirable.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a flow chart showing an example of a lyocell-based carbon fiber and carbon fabric manufacturing process according to the present invention, first weaving a lyocell fiber as a starting material to make a plain weave, twill or main weave fabric structure after the weaving process (1) To remove impurities and to reduce the residual stress of the fiber, the woven fabric is subjected to a washing process (2) for washing with an organic solvent such as acetone. Thereafter, the fabric which passed through the pretreatment step (3) of sequentially passing through a chemical pretreatment agent containing a silicone-based polymer and a flame retardant salt and then drying, is subjected to a stabilization step (4), a carbonization step (5), and a graphitization step, which are heat treatment steps. Converted to carbon fabric through (6). Thereafter, a lyocell-based carbon fabric according to the present invention is prepared through a washing process 7 for removing tar or impurities remaining on the carbon fabric.

Figure 2 shows an example of the stabilization process cycle in the lyocell-based carbon fiber and carbon fabric manufacturing process according to the present invention, the stabilization process is carried out in two steps, mainly during the dehydrogenation reaction and cyclization reaction, etc. This happens, and weight loss of about 60 to 70% by weight occurs. In the first step of the stabilization process, the temperature is raised to a temperature increase rate of 10 to 30 ° C./hour up to about 100 to 250 ° C., and in the second step, the temperature is raised to a low temperature rising rate of 2 to 10 ° C./hour up to about 300 to 500 ° C. Thereby stabilizing fabric is produced.

Figure 3 shows an example of a carbonization process cycle in the lyocell-based carbon fiber and carbon fabric manufacturing process according to the present invention, the carbonization process is heated to 30 ~ 100 ℃ / hour to about 900 ~ 1700 ℃ in an inert atmosphere It is carried out by heating up at a rate, heat treatment for 10-30 hours and then naturally cooling.

Figure 4 shows an example of the graphitization process cycle in the lyocell-based carbon fiber and carbon fabric manufacturing process according to the present invention, the graphitization process is a conventional heat treatment of the carbon fiber or carbon fabric treated in the carbonization process In an inert atmosphere at about 1000-1500 ° C., and then at a temperature increase rate of 100-200 ° C./hour, and then to a temperature of 2000-2800 ° C., at a temperature increase rate of 50-100 ° C./hour, then 2000-2800. It is carried out by heat treatment with a residence time of 0 to 10 hours at a temperature of ℃.

According to the present invention, the effect of the stabilization process can be further enhanced by performing a pretreatment step of immersing the lyocell fiber or lyocell fabric in the silicone polymer solution and the flame retardant salt solution before the stabilization process.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are illustrative of the present invention, and the contents of the present invention are not limited by the following examples.

[Example]

The lyocell fibers having a fineness of about 300 tex were woven into a twill weave structure using a rapier weaving machine, and then washed by dipping in acetone having a purity of 99.8% for about 2 hours. The washed fabric was immersed in a solution of 5% by weight of RTV silicone, a silicone-based polymer dissolved in perchloroethylene at 25 ° C. for about 30 minutes, and then immersed in an aqueous solution of 15% by weight of ammonium chloride, a flame retardant salt, for about 30 minutes. It dried at the temperature of 80 degreeC. The pretreated fabric was stabilized by raising the temperature to 200 ° C. at a temperature increase rate of 30 ° C./hour in a heat treatment furnace and then raising the temperature to 300 ° C. at a low temperature increase rate of 2 ° C./hour. Thereafter, the temperature was raised to 1700 ° C. at a temperature rising rate of 50 ° C./hour, followed by carbonization for 10 hours. Treatment was carried out. The properties of the carbon fabric thus obtained and the carbon fibers extracted from the carbon fabric are shown in Table 1 below.

[Comparative Example]

Except for omitting the immersion treatment in the silicone-based polymer solution and flame retardant salt solution in the pretreatment step in the above embodiment, the characteristics of the carbon fabric obtained by the same process as the embodiment and the carbon fiber extracted from the carbon fabric It is shown in Table 1 below.

week)

Stabilization rate (%): Carbon content% after stabilization process

1 is a flow chart showing an example of a lyocell-based carbon fabric manufacturing process according to the present invention,

2 is a view showing an example of the stabilization process cycle in the lyocell-based carbon fiber and carbon fabric manufacturing process according to the present invention,

3 is a view showing an example of a carbonization process cycle in the lyocell-based carbon fiber and carbon fabric manufacturing process according to the present invention,

4 is a view showing an example of the graphitization process cycle in the lyocell-based carbon fiber and carbon fabric manufacturing process according to the present invention,

Figure 5 is a shape photograph of the lyocell carbon fabric produced by the present invention.

Claims (14)

In the method for producing a carbon fiber through a stabilization process, a carbonization process and a graphitization process using the fiber, using a lyocell fiber as the fiber, and before the stabilization step lyocell fibers in a silicone-based polymer solution and flame retardant salt solution Method for producing a lyocell-based carbon fiber characterized in that it further comprises a pretreatment step of immersion treatment. The method of claim 1, wherein the silicone polymer is polysiloxane, polydimethylsiloxane, room temperature curable silicone, polymethylphenylsiloxane, or polysilazane. The method of claim 1, wherein the solvent of the silicon-based polymer solution is acetone, perchloroethylene, tetrahydrofuran, methyl ether ketone, ethyl alcohol or methyl alcohol. The method of claim 1, wherein the flame retardant salt is phosphoric acid, sodium phosphate or ammonium chloride. According to claim 1, wherein the stabilization process is carried out in two steps, the first step is 100 ~ 250 ℃, the second step is a method for producing a lyocell-based carbon fiber, characterized in that performed by heat treatment in the temperature range of 300 ~ 500 ℃ . The method of claim 1, wherein the carbonization process is a method of producing a lyocell-based carbon fiber, characterized in that performed by heat treatment for 10 to 30 hours in the temperature range of 900 ~ 1700 ℃. The method of claim 1, wherein the graphitization process is carried out by heating to a graphitization temperature of 2000 ~ 2800 ℃, the treatment is performed by treating the residence time to 10 hours or less at the graphitization temperature characterized in that the production of lyocell-based carbon fiber Way. In the method of producing a carbon fabric through a stabilization process, a carbonization process and a graphitization process using a fabric, using a lyocell fabric as the fabric, and before the stabilization process lyocell fabric to a silicone-based polymer solution and flame retardant salt solution A method for producing a lyocell-based carbon fabric further comprising a pretreatment step of dipping. The method of claim 8, wherein the silicone polymer is polysiloxane, polydimethylsiloxane, room temperature curable silicone, polymethylphenylsiloxane, or polysilazane. The method of claim 8, wherein the solvent of the silicone-based polymer solution is acetone, perchloroethylene, tetrahydrofuran, methyl ether ketone, ethyl alcohol or methyl alcohol. 10. The method of claim 8, wherein the flame retardant salt is phosphoric acid, sodium phosphate or ammonium chloride. The method of claim 8, wherein the stabilization process is carried out in two steps, the first step is 100 ~ 250 ℃, the second step is a method for producing a lyocell-based carbon fabric, characterized in that performed by heat treatment in the temperature range of 300 ~ 500 ℃ . 9. The method of claim 8, wherein the carbonization process is performed by heat treatment for 10 to 30 hours in the temperature range of 900 ~ 1700 ℃. The lyocell-based carbon fabric according to claim 8, wherein the graphitization process is performed by heating up to a graphitization temperature of 2000 to 2800 ° C and treating the residence time at 10 hours or less at the graphitization temperature. Way.

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