KR101264001B1 - Precursor including lyocell/graphene nanocomposite and carbon-fiber by using the same and method of manufacturing the same - Google Patents

Abstract

The present invention relates to precursor fibers for the production of carbon fibers, carbon fibers using the same and a method for producing the same, precursor fibers, characterized in that it comprises a lyocell (grapho) / graphene (graphene) nanocomposite, carbon fibers using the same And it provides a method for producing, the precursor fiber comprising a nanocomposite to which graphene is added to lyocell fiber, to produce a carbon fiber excellent in mechanical properties and production yield, such as strength, elongation, lyocell / It provides a method for producing a new precursor fiber comprising a graphene nanocomposite, and can provide a method for producing a carbon fiber excellent in strength even at low temperature conditions in the carbon fiber manufacturing using the same.

Description

Precursor fiber comprising lyocell / graphene nanocomposite and carbon fiber using same and manufacturing method therefor {PRECURSOR INCLUDING LYOCELL / GRAPHENE NANOCOMPOSITE AND CARBON-FIBER BY USING THE SAME AND METHOD OF MANUFACTURING THE SAME}

The present invention relates to a precursor fiber for producing carbon fiber, a carbon fiber using the same, and a method for manufacturing the same, and more particularly, to a precursor fiber for producing carbon fiber and carbon fiber using the same, which can increase the strength of the carbon fiber It relates to a manufacturing method.

In general, carbon fibers are classified into cellulose-based, polyacrylonitrile (PAN) -based, and pitch-based carbon fibers according to the kind of precursor fibers. Among these, cellulose-based carbon fibers developed from the 1950s have low thermal conductivity of cellulose, low density, low alkali metal ion content, high purity, high flexibility, and carbon fiber with different carbon content when cellulose is made of carbon fiber. Compared to these, there are advantages such as high features.

Conventionally, as such cellulose-based carbon fibers, rayon-based carbon fibers using rayon-based fibers such as viscose rayon as precursor fibers have been produced. However, rayon carbon fiber is not only regulated by the government by using carbon disulfide (CS ₂ ) as a solvent in the manufacturing process, but also has no economic feasibility compared to PAN carbon fiber or pitch carbon fiber. The trend is also decreasing.

Accordingly, lyocells have been developed as precursor fibers capable of manufacturing low-cellulosic carbon fibers, which are environmentally-friendly and low production costs for replacing rayon-based carbon fibers. The lyocell was manufactured in 1978 by Akzo-Nobel, which developed a new process that is free from environmental pollution and harmful substances to the human body.It is N-methylmorpholine-N-oxide (solvent which dissolves natural pulp and pulp, which is a cellulose main ingredient N-methylmorpholine-N-oxide (NMMO) 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.

As such, the lyocell fibers are also cellulosic fibers, which are similar in chemical properties to general cellulosic fibers, but have excellent mechanical and physical properties, and have very different microstructural characteristics such as crystallinity and crystal orientation.

On the other hand, in the production of carbon fibers generally go through a stabilization process and a carbonization process. These processes are carried out in the fiber state, the stabilization and carbonization temperature of the carbon fiber has a great influence on the thermal conductivity, insulation, elastic modulus and the like of the carbon fiber. Here, when carbon fibers are manufactured using lyocell fibers as precursor fibers, they are still fragile even though they have superior mechanical properties than other cellulose-based fibers. The strength of the carbon fiber may be reduced due to occurrence, surface defects caused by peeling of the adhesive site, and the like.

In order to solve this problem, attempts have been made to increase the strength of carbon fibers by improving processes such as stabilization and carbonization in lyocell fibers as precursor fibers. There is little research on increasing the strength of carbon fiber through the modification of the fiber itself.

Therefore, the first problem to be solved by the present invention is not only excellent mechanical properties such as strength, elongation through modification of lyocell fibers, but also lyocell-graphene (graphene) which can increase the yield of carbon fiber production. ) To provide a precursor fiber comprising a nanocomposite.

The second problem to be solved by the present invention is to provide a carbon fiber comprising the precursor fiber.

The third problem to be solved by the present invention is to provide an effective process conditions for producing the precursor fiber and carbon fiber production.

The present invention to achieve the first object,

Provided are precursor fibers comprising lyocell-graphene nanocomposites.

According to one embodiment of the present invention, the graphene may be 0.1-0.75% by weight based on the total weight of the nanocomposite.

According to another aspect of the present invention,

It provides a carbon fiber comprising the precursor fiber.

In order to achieve the third object,

Adding graphite oxide to a cellulose solvent to exfoliate with graphene oxide, dissolving cellulose in the cellulose solvent to produce a lyocell-graphene composite dope, and spinning the composite dope to remove the cellulose solvent. It provides a method for producing a precursor fiber comprising the step of preparing the precursor fiber.

According to one embodiment of the present invention, the graphite oxide may be added 0.001-0.75% by weight based on the total weight of the lyocell-graphene composite.

In addition, the present invention is a method for producing a carbon fiber through a stabilization process and a carbonization process using the precursor fiber, the precursor fiber is a carbon fiber manufacturing method characterized in that the precursor fiber prepared according to the above production method To provide.

According to one embodiment of the present invention, the stabilizing process may be to flameproof the precursor fiber in the air at 160-200 ℃ conditions.

According to one embodiment of the present invention, the carbonization process may be heat treatment and cooling at 1,000-1,200 ℃ conditions in a nitrogen atmosphere.

According to the present invention, by providing a precursor fiber comprising a nanocomposite in which graphene is added to lyocell fibers, carbon fibers having excellent mechanical properties and manufacturing yield, such as strength and elongation, can be manufactured, and lyocell-graphene nano It provides a method for producing a new precursor fiber including a composite, it can provide a manufacturing method that can easily produce a carbon fiber excellent in strength even at low temperature in the carbon fiber production using the same.

1 is a flow chart showing a precursor fiber manufacturing method according to the present invention.
2 is a flow chart showing a carbon fiber manufacturing method according to the present invention.
Figure 3 is a SEM photograph of the lyocell-graphene nanocomposites according to the Examples and Comparative Examples of the present invention.
Figure 4 is a graph showing the results of measuring the elastic modulus for the precursor fiber according to the Examples and Comparative Examples of the present invention.
5 is a graph showing the results of measuring the strength of the precursor fiber according to the Examples and Comparative Examples of the present invention.
Figure 6 is a graph showing the results of measuring the elongation of the precursor fiber according to the Examples and Comparative Examples of the present invention.
7 is a graph showing the results of measuring the ductility of the precursor fiber according to the Examples and Comparative Examples of the present invention.
8 is a graph showing the results of measuring the carbonization rate for the precursor fiber according to the Examples and Comparative Examples of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings.

The terms or words used in this specification and claims are not to be construed as being limited to their ordinary or dictionary meanings, and the inventors may appropriately define the concept of terms in order to best describe their invention. Based on the principle of the present invention, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the configuration of the embodiments described herein is only one of the most preferred embodiments of the present invention and does not represent all of the technical idea of the present invention, various equivalents and modifications that can replace them at the time of the present application It should be understood that there may be

First, the precursor fiber and the carbon fiber including the same according to the present invention will be described in detail.

Precursor fiber according to the present invention is for producing a carbon fiber, characterized in that it comprises a lyocell-graphene nanocomposite.

The lyocell is a material made of cellulose extracted from wood pulp. The lyocell used in the present invention is a generally known process, that is, a wet and dry spinning fiber manufactured using NMMO as a natural pulp solvent in which cellulose is a main component may be used. have.

The graphene is a carbon nano material stripped of the surface layer of graphite, and has excellent electrical conductivity, strength, thermal conductivity, elasticity, and the like. The present inventors form the graphene as a lyocell and a nanocomposite, thereby forming an existing lyocell. This leads to the present invention by discovering that it can provide a carbon fiber having significantly superior physical properties as compared to the carbon fiber produced as a single precursor fiber.

The lyocell-graphene nanocomposite may be prepared by peeling graphite oxide in a cellulose solvent used in the conventional lyocell fiber manufacturing process to disperse graphene oxide and dissolving cellulose, and lyocell alone precursor fiber. Compared to the mechanical properties such as strength and elongation. Specifically, it is possible to provide a precursor fiber having an elastic modulus of about 2 times, an intensity of about 1.5 times, an elongation of about 2 times, and a ductility of about 2 times that of a lyocell alone precursor fiber. Therefore, when the carbon fiber is manufactured using the precursor fiber according to the present invention, the stabilization process, the carbonization process, etc. may be stabilized due to the improved mechanical properties, thereby improving physical properties compared to the carbon fiber using the pure lyocell fiber.

In addition, the carbonization rate is increased by nearly two times in the carbon fiber manufacturing process due to the improved mechanical properties, so that the carbonization process can be easily applied, so that carbon fiber production can be performed more easily and efficiently. For example, when the tire cord is manufactured using the precursor fiber according to the present invention, mechanical properties such as strength may be improved by about 2 times compared to conventional lyocell fibers, and carbon fiber manufacturing yield may also be improved by about 2 times. It becomes possible.

According to one embodiment of the present invention, the graphene may be included 0.1-0.75% by weight based on the total weight of the nanocomposite. Thus, even though a small amount of graphene is added, it was confirmed that precursor fibers having excellent physical properties such as elastic modulus, strength, elongation, and ductility can be made more than conventional lyocell alone precursor fibers. In addition, this physical property improvement effect was found to be remarkable in the graphene addition amount in the range 0.1-0.75% by weight.

Hereinafter, the precursor fiber and the carbon fiber manufacturing method according to the present invention will be described in detail.

1 is a flowchart showing a method for manufacturing a precursor fiber according to the present invention. Referring to FIG. 1, the method for preparing a precursor fiber according to the present invention includes the steps of: (a) adding graphite oxide to a cellulose solvent to peel off the graphene oxide ( S1); (B) dissolving cellulose in the cellulose solvent to produce a lyocell-graphene composite dope (S2) and (c) spinning the composite dope and removing the cellulose solvent to prepare precursor fibers (S3). It characterized by including).

According to the present invention, in order to form a lyocell-graphene nanocomposite, as in step (a), graphite oxide is added to the cellulose solvent and then peeled off with graphene oxide (S1) and (b). As described above, the cellulose is dissolved in the solvent to generate a lyocell-graphene composite dope (S2). Subsequently, by spinning the composite dope as in step (c), the solvent is removed to prepare a precursor fiber including the lyocell-graphene nanocomposite (S3). Since the method is almost used as it is, the composite can be easily produced.

In this case, the cellulose solvent may be used to melt NMMO which is generally used, and the graphite oxide may be added to the NMMO in powder form. In addition, the exfoliation may be sufficiently exfoliated for 4-8 hours with an ultrasonic mill after the addition of the graphite oxide so that the graphene oxide may be uniformly dispersed. At this time, the graphite oxide is preferably added to be 0.1-0.75% by weight of the total weight of the lyocell-graphene nanocomposite. (S1)

As such, after the graphite oxide is peeled off with the graphene oxide in the cellulose solvent, 3-7% by weight of cellulose may be dissolved with respect to the total weight of the cellulose solvent. At this time, it is preferable to dissolve for 2-4 hours using a screw to sufficiently dissolve the cellulose. Through this process, the lyocell-graphene nanocomposite dope is formed, and then degassed for 1 to 3 hours using a decompression device to remove bubbles in the nanocomposite dope. At this time, in order to increase the defoaming efficiency, it is preferable to maintain the temperature conditions at 90-100 ℃. (S2)

Thereafter, the degassed lyocell-graphene nanocomposite dope was spun using a dry-wet spinning apparatus, and then the NMMO was dissolved in water to remove NMMO. Precursor fibers can be prepared by drying after -36 hours. (S3)

FIG. 2 is a flowchart illustrating a carbon fiber manufacturing method according to the present invention. Referring to FIG. 2, a carbon fiber manufacturing method according to another embodiment of the present invention uses precursor fibers including the lyocell-graphene nanocomposite. By the stabilization step (S4) and the carbonization step (S5) to produce a carbon fiber (S6) is characterized in that.

The stabilization process (S4) is a heat treatment step that is generally performed in air (oxygen) during the production of carbon fiber, a serious chemical and physical change occurs rapidly in the stabilization process (S4), after which carbonization is performed in a nitrogen atmosphere The purpose is to give a stable chemical structure capable of withstanding the high heat treatment temperature required for the step (S5).

In the carbon fiber manufacturing method according to the present invention, unlike the case of using a conventional lyocell alone precursor fiber, by using a precursor fiber containing a lyocell-graphene nanocomposite having excellent physical properties in strength, etc., a stable chemistry before the carbonization process It is possible to give a structure, it is possible to manufacture a carbon fiber having excellent physical properties even at relatively low temperature conditions in the stabilization process and the carbonization process.

That is, in the carbon fiber manufacturing method according to the present invention, the stabilization step (S4) is flame-resistant to the precursor fiber at 160-200 ℃ condition in air, the carbonization step (S5) is 1,000-1,200 in a nitrogen atmosphere It can be carried out by heat treatment and cooling to a ℃ condition.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. However, these examples are intended to illustrate the present invention in more detail, it will be apparent to those of ordinary skill in the art that the scope of the present invention is not limited thereto.

<Examples>

&Lt; Example 1 >

NMMO was added to a circular cylinder and dissolved in an oil bath at 95 ° C., and graphite oxide was injected by 0.25 wt% of the total weight of the final lyocell-graphene nanocomposite using an ultrasonic sonicator for 6 hours. After pulverization, 5% by weight of the cellulose was added to the NMMO weight, mixed by using a screw for 2 hours, and then the air bubbles in the dope were removed for 1 hour using a pressure reducing device, and the wet and dry spinner was used. Lyocell-graphene oxide dope was prepared. Thereafter, the lyocell-graphene oxide dope was degassed and introduced into a dry and wet spinneret cylinder at 95 ° C., and the fibers were spun with a 50 μm nozzle while applying a pressure of 0.35 MPa with an air pressure. At this time, air-gap was 1 cm. The fiber thus prepared was placed in water for one day to remove NMMO and dried to prepare a precursor fiber comprising lyocell-graphene nanocomposite. SEM photographs of the prepared nanocomposites are shown in FIG.

In addition, the prepared precursor fibers were stabilized in air and carbonized through a carbonization process in a nitrogen atmosphere to prepare carbon fibers. The stabilization was heated for 1.5 hours at a heating rate of 2 ℃ / min to 180 ℃ at room temperature and maintained at 180 ℃ 1.5 hours. Thereafter, the stabilized fibers were heat-treated for 4 hours at a heating rate of 5 ° C./min from room temperature to 1200 ° C., and then cooled for 4 hours to prepare carbonized fibers.

<Example 2>

A precursor fiber and a carbonized fiber were prepared in the same manner as in <Example 1>, except that 0.5 wt% of graphite oxide was added to the total weight of the final lyocell-graphene nanocomposite in <Example 1>. . SEM photographs of the prepared nanocomposites are shown in FIG. 3 (b).

<Example 3>

A precursor fiber and a carbonized fiber were prepared in the same manner as in <Example 1>, except that 0.75 wt% of graphite oxide was added to the total weight of the final lyocell-graphene nanocomposite in <Example 1>. .

&Lt; Comparative Example 1 &

A precursor fiber and a carbonized fiber were prepared in the same manner as in <Example 1>, except that 1 wt% of graphite oxide was added to the total weight of the final lyocell-graphene nanocomposite in <Example 1>. . SEM photographs of the prepared nanocomposites are shown in FIG. 3 (c).

Comparative Example 2

A precursor fiber and a carbonized fiber were prepared in the same manner as in <Example 1>, except that 3 wt% of graphite oxide was added to the total weight of the final lyocell-graphene nanocomposite in <Example 1>. . SEM photographs of the prepared nanocomposites are shown in FIG. 3 (d).

&Lt; Comparative Example 3 &

A precursor fiber and a carbonized fiber were prepared in the same manner as in Example 1 except that 5 wt% of graphite oxide was added to the total weight of the final lyocell / graphene nanocomposite. SEM images of the prepared nanocomposites are shown in FIG.

Comparative example  4

A precursor fiber and a carbonized fiber were prepared in the same manner as in <Example 1>, except that graphite oxide was not added in <Example 1>.

The mechanical properties and carbonization rate of the precursor fibers according to the Examples and Comparative Examples were measured in the following manner and the results are shown in FIGS. 2 to 6.

[How to measure]

(1) mechanical properties

The mechanical properties of elastic modulus, strength, elongation and ductility were measured. The measurement equipment used a tensile tester (Intron 5564, Intron Co., Ltd.), was measured at a rate of 5mm / min using a 100N load cell for a sample of 3cm height.

(2) carbonization rate

Using a thermogravimetric analyzer (TGA) (TGA-50, SHIMADZU), 10-13 mg of the precursor fiber samples according to the Examples and Comparative Examples were subjected to 10 ° C / min under a nitrogen stream to prevent oxidation by oxygen. The heating rate was measured at a temperature ranging from room temperature to 500 ° C and 1,000 ° C.

Figure 4 is a graph showing the results of measuring the elastic modulus for the precursor fiber according to the Examples and Comparative Examples of the present invention, referring to Figure 4, the elastic modulus of 0.25% by weight, 0.5% by weight of the precursor fiber added graphene oxide It can be seen that (Young's Modulus) increased about two times than that of the lyocell alone precursor fiber. However, when it exceeds 0.75% by weight it can be confirmed that the elastic modulus is lower than that of the lyocell alone precursor fiber.

In addition, Figure 5 is a graph showing the results of measuring the strength of the precursor fiber according to the Examples and Comparative Examples of the present invention, referring to Figure 5 precursor fiber to which 0.25 wt%, 0.5 wt% of graphene oxide is added It can be seen that the Tensile Strength of the lyocell alone precursor fiber increased by about twice.

In addition, Figure 6 is a graph showing the result of measuring the elongation of the precursor fiber according to the Examples and Comparative Examples of the present invention, referring to Figure 6 0.25%, 0.5% by weight, 0.75% by weight of graphene oxide It can be seen that the elongation at break of the added precursor fiber is increased by about 2 times than that of the lyocell alone precursor fiber, and when it exceeds 1% by weight, it is more effective than that of the lyocell alone precursor fiber. In the case of Examples 1-3, it turns out that it does not reach.

In addition, Figure 7 is a graph showing the results of measuring the ductility of the precursor fiber according to the Examples and Comparative Examples of the present invention, referring to Figure 7, 0.25 wt%, 0.5 wt%, 0.75 wt% graphene oxide It can be seen that the ductility (toughness) of the added precursor fiber is increased by about two times than that of the lyocell alone precursor fiber, and when it exceeds 1% by weight, it is more effective than that of the lyocell alone precursor fiber. In the case of Examples 1-3, it turns out that it does not reach.

On the other hand, Figure 8 is a graph showing the result of measuring the carbonization rate for the precursor fiber according to the Examples and Comparative Examples of the present invention, referring to Figure 8 is about 11% of the lyocell alone precursor fiber, 0.25 The precursor fiber added with -1 wt% graphene oxide increased even more, and the carbonization rate increased by nearly 19% in the carbonization rate of the precursor fiber added with 0.5 wt% graphene oxide. have.

Claims (7)

A precursor fiber comprising a lyocell-graphene nanocomposite and comprising 0.1 to 0.75% by weight of graphene relative to the total weight of the nanocomposite.
delete Carbon fiber made from the precursor fiber according to claim 1.
(a) adding graphite oxide to the cellulose solvent to exfoliate with graphene oxide;
(b) dissolving the lyocell in the cellulose solvent to produce a lyocell-graphene composite dope; And
(c) preparing the precursor fiber by removing the cellulose solvent after spinning the composite dope;
And the graphite oxide is a precursor fiber manufacturing method characterized in that the addition of 0.1 to 0.75% by weight relative to the total weight of the lyocell-graphene composite.
delete In the method for producing a carbon fiber through a stabilization process and a carbonization process using the precursor fiber,
The precursor fiber uses a precursor fiber prepared according to claim 4, wherein the stabilization process is to flame the precursor fiber in the air at 160 ~ 200 ℃ condition, the carbonization process is 1,000 ~ 1,200 ℃ in nitrogen atmosphere Carbon fiber manufacturing method characterized in that the heat treatment and cooling under the conditions.












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