Spinning solution for aramid and carbon nanotube composite fibers and preparation method of aramid and carbon nanotube composite fibers using the solution.

Abstract

This invention relates to spinning solutions for aramid and carbon nanotube composite fibers and methods for preparing aramid and carbon nanotube composite fibers using the same. The spinning solution for aramid and carbon nanotube composite fibers of this invention comprises: aramid; carbon nanotubes; and a superacid exhibiting a lyotropic liquid crystal phase. This invention allows for the preparation of aramid and carbon nanotube composite fibers using a single process without additional steps for adjusting the orientation of the aramid and carbon nanotubes, and enables the preparation of aramid and carbon nanotube composite fibers with improved specific strength and specific conductivity.

Description

TECHNICAL FIELD

[0001] The present application relates to a spinning solution for aramid and carbon nanotube composite fiber and a method for preparing aramid and carbon nanotube composite fiber using the same. BACKGROUND

[0002] Aramid is a short name for aromatic amide, and is a polymer compound in which 85% or more of aromatic compounds having a ring shape are connected by an amide bond (-NHC O-) composed of nitrogen, hydrogen, carbon, and oxygen. Aramid includes para-aramid in which aromatic compounds have a structure connected in a straight line by an amide bond, and meta-aramid which does not have the above structure. Para-aramid has excellent properties such as high strength, high elasticity, and low shrinkage, and due to the high strength, is used not only for bulletproof purposes, but also for various purposes in the high-tech industry in the aerospace field.

[0003] Carbon nanotube (CNT) is an allotrope of carbon having a cylindrical nanostructure. Due to the many special properties of carbon nanotubes, they can be widely used in the fields of nanotechnology, electrical engineering, optics, and material engineering. In particular, they have very special thermal conductivity and mechanical and electrical properties, and are also used as additives for various structural materials.

[0004] Aramid, carbon nanotubes, and the like have excellent properties, and in order to utilize the high properties of the materials as they are, they are prepared in the form of fibers by spinning or the like. There have been attempts to improve rigidity, elasticity, and electrical conductivity by compounding aramid and carbon nanotubes, but due to the very low solubility and dispersibility of each material, such research has been very limited.

[0005] PRIOR ART DOCUMENT

[0006] PATENT DOCUMENT

[0007] (Patent Document 1) Korean Registered Patent No. 10-1108425 SUMMARY

[0008] TECHNICAL PROBLEM

[0009] The present application relates to a spinning solution for aramid and carbon nanotube composite fiber and a method for preparing aramid and carbon nanotube composite fiber using the same.

[0010] The objects of the present application are not limited to the above-mentioned objects. The objects of the present application will become more apparent through the following description, and can be achieved by the solutions recited in the scope of the patent right and combinations thereof.

[0011] TECHNICAL SOLUTION

[0012] A spinning solution for aramid and carbon nanotube composite fiber according to one embodiment of the present application includes aramid, carbon nanotube, and super acid exhibiting a lyotropic liquid crystal phase.

[0013] The spinning solution can include 11 parts by weight to 900 parts by weight of the carbon nanotube, based on 100 parts by weight of the aramid.

[0014] The purity of the carbon nanotube can be 80% or more.

[0015] The IG / ID of the carbon nanotube can be 30 or more.

[0016] The super acid can include at least one selected from the group consisting of sulfuric acid, sulfurochloridic acid, perchloric acid, triflic acid, fluoroboric acid, fluoroantimonic acid, carborane acid, magic acid, and combinations thereof.

[0017] A method of manufacturing aramid and carbon nanotube composite fiber according to one embodiment of the present application can include a step of preparing a spinning solution containing a lyotropic liquid crystal phase by inputting aramid and carbon nanotube into super acid, and a step of spinning the spinning solution to manufacture a composite fiber.

[0018] The spinning solution can have a total weight of aramid and carbon nanotube in a concentration of 0.05 mg to 500 mg per 1 mL of solvent.

[0019] The spinning solution can be spun at 10°C to 150°C to manufacture a composite fiber.

[0020] The composite fiber can have a draw ratio of 0.1 to 50.

[0021] The composite fiber can have a diameter of 0.01 µm to 1,000 µm.

[0022] The composite fiber can have a polarized Raman ratio of 2 or more.

[0023] Technical Effects

[0024] The present application can manufacture aramid and carbon nanotube composite fiber in a single process without an additional step for adjusting the orientation of aramid and carbon nanotube.

[0025] The present application can manufacture aramid and carbon nanotube composite fiber having improved specific strength and specific conductivity.

[0026] The effects of the present application are not limited to the above-mentioned effects. It should be understood that the effects of the present application include all effects that can be inferred from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1a Results of analysis of the dope of Examples 1 to 9 by polarizing optical microscope;

[0028] Figure 1b Results of analysis of the dope of Comparative Examples 1 to 4 by polarizing optical microscope;

[0029] Figure 2 Pictures of winding of the composite fibers of Examples 1 to 9 on a roll;

[0030] Figure 3 Results of analysis of the composite fibers of Examples 1 to 9 by scanning electron microscope;

[0031] Figure 4a Results of analysis of the cross section of the composite fiber of Example 5 cut in a direction perpendicular to the length thereof by transmission electron microscope;

[0032] Figure 4b Results of analysis of the cross section of the composite fiber of Example 5 cut in a direction horizontal to the length direction thereof by transmission electron microscope;

[0033] Figure 5 Results of polarization Raman analysis of the composite fiber of Example 5;

[0034] Figure 6 Results of Thermogravimetric analysis (TGA) of the composite fibers of Examples 1 to 9;

[0035] Figure 7a Results of analysis of the composite fibers of Examples 1 to 9 by X-ray photoelectron spectroscopy (XPS);

[0036] Figure 7b Results of measurement of nitrogen, oxygen element content in the composite fibers of Examples 1 to 9;

[0037] Figure 8a Results of measurement of specific elasticity of the composite fibers of Examples 1 to 9;

[0038] Figure 8b Results of measurement of specific strength of the composite fibers of Examples 1 to 9;

[0039] Figure 9Results of measurement of the electrical conductivity of the composite fibers of Examples 1 to 9. DETAILED DESCRIPTION

[0040] The objects, other objects, features, and advantages of the present application will become more apparent from the following detailed description when read in conjunction with the accompanying drawings, in which like reference numerals refer to like elements throughout. The present application, however, can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the application to those skilled in the art.

[0041] In describing aspects of the drawings, like reference numerals are used to designate like elements throughout. The dimensions of the components in the drawings can be exaggerated to clearly illustrate the present application. The terms first, second, etc. can be used to describe various elements, but the described elements should not be limited by the terms. The terms are used to distinguish one element from another. For example, a first element can be named a second element, and similarly, a second element can be named a first element, without departing from the scope of the present application. The singular expression includes the plural expression unless the context clearly indicates the contrary.

[0042] It should be understood that the terms "comprises" or "has" and the like are used herein not to specify the presence of stated features, numbers, steps, actions, components, members, or a combination thereof, but to encompass the presence or addition of one or more other features, numbers, steps, actions, components, members, or a combination thereof. Also, in the case where a portion is described as being "on" another portion, it can be directly on the other portion, or intervening portions can be present. In the case where a portion is described as being "under" another portion, it can be directly under the other portion, or intervening portions can be present.

[0043] Unless otherwise explicitly provided, all numbers, values and / or expressions indicating amounts of components, reaction conditions, polymerization compositions and formulations used in the present specification are approximations to various uncertainties of measurement that occur when these numbers reflect essentially different numbers, and thus should be understood to be modified by the term "about" in all cases. In addition, in the case where a numerical range is disclosed, such a range is continuous, unless otherwise stated, including all values from the minimum value to the maximum value of the range, and further including all integers within the range, unless otherwise stated, when such a range involves integers.

[0044] The spinning solution of the aramid / carbon nanotube composite fiber of the present application can include aramid, carbon nanotube, and super acid.

[0045] The present application is characterized in that a super acid is used as a solvent of the spinning solution to improve the dispersibility of the aramid and carbon nanotube. The super acid can include at least one selected from the group consisting of sulfuric acid, sulfurochloridic acid, perchloric acid, triflic acid, fluoroboric acid, fluoroantimonic acid, carborane acid, magic acid, and combinations thereof.

[0046] Also, the spinning solution of the present application is characterized in that it exhibits a lyotropic liquid crystal phase in the super acid. Since the aramid and carbon nanotube exist in the lyotropic liquid crystal phase having a certain orientation in the spinning solution, not only the physical, chemical, and electrical properties of the composite fiber can be improved, but also the composite fiber can be continuously produced through a single process. For example, the composite fiber having equivalent or improved properties can be obtained without a solenoid device for generating an electric field for the orientation of carbon nanotubes or additional devices, additional steps such as a special device for stretching the spun composite fiber.

[0047] In order to exhibit the lyotropic liquid crystal phase, the present application proposes a spinning solution containing 11 to 900 parts by weight of the carbon nanotube based on 100 parts by weight of the aramid. In the case where the content of the carbon nanotube is less than 11 parts by weight, the lyotropic liquid crystal phase is not exhibited.

[0048] The purity of the carbon nanotube can be 80% or more, or 90% or more, or 99% or more. In the case where the carbon nanotube having a purity of less than 80% is used, impurities such as amorphous carbon or metal catalysts hinder the one-dimensional long-range interaction between the aramid and carbon nanotube, so that the lyotropic liquid crystal phase can not be exhibited.

[0049] The carbon nanotube can be a carbon nanotube having an IG / ID of 30 or more, or 40 or more, or 50 or more, or 60 or more, or 70 or more, or 80 or more, or 90 or more. The crystallinity and degree of defects of the carbon nanotube can be confirmed by Raman spectroscopy measurement, and the carbon nanotube having an IG / ID of 30 or more can be used. -1 The carbon nanotube having an IG / ID of 30 or more can exhibit a D-band related to defects and impurities near 1300 cm -1 near 1600 cm 2The G-band is related to the bonding of carbon. The IG / ID indicates the relative intensity ratio of the above two peaks. In the case of using a carbon nanotube having a low crystallinity with an IG / ID of less than 30, a serious carbon nanotube aggregation phenomenon can occur in the spinning solution due to a solubility problem.

[0050] Thus, while the π-bonding force between the carbon nanotube and the aramid main chain and the ion repulsion force formed on the surface between different materials are simultaneously controlled, a one-dimensional long-range interaction is formed in the solvent, thereby effectively exhibiting a liquid crystal phase. As in the present application, a carbon nanotube considering purity and crystallinity is added to aramid to exhibit a lyotropic liquid crystal phase, and has a good effect on improving the physical properties of a composite fiber by improving processability.

[0051] The method of manufacturing the aramid and carbon nanotube composite fiber of the present application can include a step of preparing a spinning solution containing a lyotropic liquid crystal phase by feeding the aramid and carbon nanotube to a super acid, and a step of spinning the spinning solution to manufacture a composite fiber.

[0052] The composition of the spinning solution is described above, and will not be described again here.

[0053] After the spinning solution is prepared to have a total weight of aramid and carbon nanotube having a concentration of 0.05 mg to 500 mg per 1 mL of solvent, a composite fiber can be obtained by wet spinning.

[0054] The lyotropic liquid crystal phase of the spinning solution is also maintained in the coagulation bath. In the case of a spinning solution composed only of carbon nanotubes, the super acid as a solvent immediately diffuses while flowing into the coagulation bath, and the carbon nanotubes rapidly aggregate without the opportunity to elongate. In contrast, the spinning solution of the present application in which carbon nanotubes and aramid exist in a lyotropic liquid crystal phase maintains the lyotropic liquid crystal phase in the coagulation bath, and thus the flowability of the polymer main chain responds to the stretching in the uniaxial direction, and the π-bonding force also plays a role so that the carbon nanotubes also participate in the alignment. Ultimately, the composite fiber of the present application exhibits excellent specific strength and specific conductivity characteristics.

[0055] The spinning conditions are not particularly limited, and for example, the spinning solution can be spun at a temperature range in which the solvent does not evaporate, such as 10°C to 150°C, thereby manufacturing a composite fiber.

[0056] The draw ratio of the composite fiber can be 0.1 to 50, or 5 to 20. The draw ratio of the composite fiber can be adjusted by the winding speed.

[0057] The diameter of the composite fiber is not particularly limited. For example, the diameter can be 0.01 μm to 1,000 μm, or 10 μm to 30 μm, and a composite fiber having an appropriate size of diameter can be produced depending on the use, the desired properties, and the like of the composite fiber. The diameter of the composite fiber can be adjusted by the needle or nozzle of a spinning device, the draw ratio, and the like.

[0058] Another aspect of the present application will be described more specifically below by way of examples. The following examples are only for the purpose of helping to understand the present application, and the scope of the present application is not limited thereto.

[0059] Examples 1 to 9 and Comparative Examples 1 to 4

[0060] KM of DUPONT was prepared as aramid. The aramid was re-impregnated with acetone, and stirring was performed for 12 hours to remove remaining impurities. After filtration, vacuum drying was performed at 25°C for 12 hours.

[0061] DX of MEIJO was prepared as carbon nanotube.

[0062] The aramid and carbon nanotube were put into a super acid at the content of Table 1 below, and a spinning solution was prepared by stirring for about 24 hours.

[0063] [Table 1]

[0064]

[0065]

[0066] Each of the spinning solutions was wet-spun using a syringe pump and a needle. The spinning solution was wet-spun at a draw ratio of about 5 or more. Acetone and water were used for a coagulation bath and a water washing bath, respectively, and water washing was performed for 6 hours to remove the solvent inside the composite fiber to the maximum extent. In order to evaporate the last remaining residual solvent, the composite fiber was dried in a vacuum oven at about 65°C for 24 hours.

[0067] Experimental Example 1

[0068] The spinning solutions of Examples 1 to 9 and Comparative Examples 1 to 4 were analyzed using a polarizing optical microscope. Figure 1a is a result of analyzing the spinning solutions according to Examples 1 to 9 using a polarizing optical microscope. Figure 1b is a result of analyzing the spinning solutions of Comparative Examples 1 to 4 using a polarizing optical microscope.

[0069] Referring to Figure 1a and Figure 1b , in the case where the content of carbon nanotube is 11 parts by weight or more, the image on the polarizing microscope has bright birefringence, which is due to the fact that a lyotropic liquid crystal phase is exhibited.

[0070] Figure 2 Images are shown of the composite fibers of Examples 1 to 9 being wound on rollers. This demonstrates that the composite fibers according to the present invention can be continuously produced.

[0071] Experiment Example 2

[0072] The composite fibers of Examples 1 to 9 were analyzed using scanning electron microscopy. The results are as follows: Figure 3 As shown, the diameter of the composite fiber is between 10 μm and 30 μm.

[0073] Experimental Example 3

[0074] The composite fibers of Example 5 were analyzed using transmission electron microscopy. Figure 4a The results are obtained by analyzing the cross-section of the composite fiber cut in a direction perpendicular to its length using transmission electron microscopy. Figure 4b The results are obtained by analyzing the cross-section of the composite fiber cut horizontally along its length direction using transmission electron microscopy. It is evident that the composite fiber of the present invention has a hierarchical liquid crystal phase structure in which carbon nanotubes and aramid fibers are arranged along the length direction of the composite fiber.

[0075] Experiment Example 4

[0076] Polarized Raman analysis was performed on the composite fiber of Example 5. The results are as follows: Figure 5 As shown.

[0077] The polarization Raman ratio is a measure of the degree of alignment of carbon nanotubes constituting the composite fiber, and the degree of alignment of carbon nanotubes is proportional to the polarization Raman ratio.

[0078] The polarization Raman ratio, during polarization Raman analysis, can be measured at 1560 cm⁻¹. -1 Up to 1600cm -1 Within a certain range, the ratio of the maximum G-peak strength of the composite fiber along its length direction to its perpendicular direction (I) GH / I GV )express.

[0079] The composite fiber of the present invention has a polarization Raman ratio of 2 or higher, which indicates that the carbon nanotubes are well aligned along the length direction of the composite fiber during the preparation process.

[0080] Experimental Example 5

[0081] Thermogravimetric analysis (TGA) was performed on the composite fibers of Examples 1 to 9. The results are as follows: Figure 6As shown, the thermal stability increases with the increase of carbon nanotube content, indicating that carbon nanotubes and aramid fibers are well mixed in the composite fiber.

[0082] Experimental Example 6

[0083] The composite fibers of Examples 1 to 9 were analyzed by X-ray photoelectron spectroscopy (XPS). The results are as follows: Figure 7a As shown. Furthermore, based on the above results, the nitrogen and oxygen content within each composite fiber was measured. The results are as follows. Figure 7b As shown.

[0084] See Figure 7a and Figure 7b As the carbon nanotube content increases, the peak values ​​of O1S and N1S decrease, which is due to the reduction in the amide group content of the aramid. Therefore, it can be seen that the carbon nanotube and aramid composite of the present invention exhibits good performance.

[0085] Experimental Example 7

[0086] The mechanical properties of the composite fibers of Examples 1 to 9 were measured.

[0087] Figure 8a The results are for measuring the specific modulus of elasticity of each composite fiber. Specific modulus of elasticity is the initial slope value in the tensile strength graph, expressed by calculating the range in which the strength increases constantly with changes in tensile strength.

[0088] Figure 8b To measure the specific strength of each composite fiber, a single fiber strength tester (FAVIM AT) was used. This device calculates the specific strength (N / tex) by measuring the tensile strength (N) and linear density (tex).

[0089] See Figure 8a and Figure 8b It is known that as the content of carbon nanotubes increases, the specific strength and specific elastic modulus of the composite fiber also increase. Therefore, according to the present invention, composite fibers with improved mechanical properties such as specific strength and specific elastic modulus can be obtained.

[0090] Experimental Example 8

[0091] The electrical conductivity of the composite fibers from Examples 1 to 9 was measured. The results are as follows: Figure 9 As shown, the conductivity of the composite fiber increases with the increase of carbon nanotube content.

[0092] The present invention has been illustrated above with diagrams, but it is not limited to the described embodiments. Various modifications and variations can be made to the invention without departing from its spirit and scope, which are readily apparent to those skilled in the art. Therefore, such modifications or variations should be considered to fall within the scope of the patent claims. The scope of the present invention should be interpreted based on the appended patent claims.

Claims

1. A spinning solution for aramid and carbon nanotube composite fiber, characterized by, consisting of: an aramid fiber; a carbon nanotube; and a super acid, wherein, based on 100 parts by weight of the aramid fiber, the spinning solution for the aramid fiber and carbon nanotube composite fiber contains 11 to 900 parts by weight of the carbon nanotube, the purity of the carbon nanotube is 80% or more, the IG / ID of the carbon nanotube is 30 or more, and the spinning solution for the aramid fiber and carbon nanotube composite fiber exhibits a lyotropic liquid crystal phase.

2. The spinning solution for the aramid fiber and carbon nanotube composite fiber according to claim 1, characterized in that: the super acid is at least one selected from the group consisting of chlorosulfonic acid, trifluoromethanesulfonic acid, fluorantimonic acid, carboric acid, magic acid, and combinations thereof.

3. A method for producing aramid and carbon nanotube composite fiber, characterized by, consisting of: a step of feeding an aramid fiber and a carbon nanotube to a super acid to prepare a spinning solution containing a lyotropic liquid crystal phase; and a step of spinning the spinning solution to prepare a composite fiber; wherein, based on 100 parts by weight of the aramid fiber, the spinning solution contains 11 to 900 parts by weight of the carbon nanotube, the purity of the carbon nanotube is 80% or more, and the IG / ID of the carbon nanotube is 30 or more.

4. The method for producing an aramid fiber and carbon nanotube composite fiber according to claim 3, characterized in that: the super acid is at least one selected from the group consisting of chlorosulfonic acid, trifluoromethanesulfonic acid, fluorantimonic acid, carboric acid, magic acid, and combinations thereof.

5. The method for producing an aramid fiber and carbon nanotube composite fiber according to claim 3, characterized in that: the spinning solution has a total weight of the aramid fiber and the carbon nanotube at a concentration of 0.05 mg to 500 mg per 1 mL of solvent.

6. The method for producing an aramid fiber and carbon nanotube composite fiber according to claim 3, characterized in that: the spinning solution is spun to prepare a composite fiber at 10°C to 150°C.

7. The method for producing an aramid fiber and carbon nanotube composite fiber according to claim 3, characterized in that: the composite fiber has a draw ratio of 0.1 to 50.

8. The method for producing an aramid fiber and carbon nanotube composite fiber according to claim 3, characterized in that: the diameter of the composite fiber is 0.01 μm to 1,000 μm.

9. The method for producing an aramid fiber and carbon nanotube composite fiber according to claim 3, characterized in that: the polarized Raman ratio of the composite fiber is 2 or more.

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