Carbon-polymer cowrapped fiber and chopped fiber prepared therefrom

Abstract

The present invention relates to a carbon fiber-polymer composite yarn and a chopped composite yarn produced therefrom. More specifically, the invention relates to a carbon fiber-polymer composite yarn and a chopped composite yarn produced therefrom, which is advantageous for processing a chopped fiber of a certain length by compensating for the high drapeability of the carbon fiber by wrapping (covering) a polymer fiber in a spiral shape around the outside of a carbon fiber core yarn, and which is easy to manufacture wet or dry nonwoven fabrics because the chopped carbon fiber maintains the original dispersibility of the carbon fiber.

Description

Technology Field

[0001] The present invention relates to a carbon fiber-polymer composite yarn and a chopped composite yarn produced therefrom. More specifically, the invention relates to a carbon fiber-polymer composite yarn and a chopped composite yarn produced therefrom, which is advantageous for processing chopped fiber of a certain length by compensating for the high drapeability of the carbon fiber by wrapping (covering) polymer fibers in a spiral shape around the outside of a carbon fiber core yarn, and which facilitates the manufacture of wet or dry nonwoven fabrics because the chopped carbon fiber maintains the original dispersibility of the carbon fiber. Background Technology

[0002] Generally, carbon fibers are materials with excellent mechanical properties and are used to form carbon fiber reinforced composites (CFRP) together with a matrix resin. Because CFRP is lightweight and has very high mechanical strength, such as strength and elastic modulus, it is used as a new material to replace heavy metals. It was initially used for special applications or high-end products, but recently its applications have been continuously expanding.

[0003] There are also various ways to apply these carbon fibers. In addition to using continuous fibers as they are, they can also be processed into chopped fibers and then mixed with resin materials or manufactured into nonwoven fabrics. Among these, nonwoven fabrics can be manufactured using wet or dry methods, and their applications are diverse, such as reinforcing materials for foamed resins, sandwich substrates, or gas diffusion layers for fuel cells.

[0004] In addition, if the carbon fibers in carbon fiber nonwoven fabrics are not evenly dispersed, the performance of the substrate may deteriorate due to the phenomenon where mechanical loads, electricity, or heat are concentrated in one place. Thus, dispersing carbon fibers is very important. While it is possible to improve dispersibility through chemical treatment using wet processes, this has the disadvantage of significantly increasing costs. On the other hand, dry processes are inexpensive to manufacture but have limitations in overcoming low dispersibility.

[0005] In addition, methods to ensure dispersibility in carbon fibers themselves include reducing the sizing agent content to lower cohesion and minimizing the length variation of chopped filaments. Meanwhile, there is also a method of using short chopped filaments, but this results in a deterioration of the physical properties of the nonwoven fabric and is therefore not in line with the intent of the present invention. However, considering the chopped processing process where cutting is more effective as the sizing agent content increases, a contradiction arises in that the sizing agent content must be higher to reduce the length variation. The problem to be solved

[0006] The present invention was devised to solve the above-mentioned problems and meet conventional requirements. The objective of the present invention is to provide a carbon fiber-polymer composite yarn having sufficient drapeability for chop processing, and a chopped composite yarn processed from the carbon fiber-polymer composite yarn having excellent dispersibility and suitable for manufacturing carbon fiber nonwoven fabrics.

[0007] The above and other objects and advantages of the present invention will become more apparent from the following description describing preferred embodiments. means of solving the problem

[0008] The above objective is achieved by a carbon fiber-polymer composite yarn characterized by polymer fibers being wrapped in a spiral shape around the outside of a carbon fiber core yarn.

[0009] Here, the tension of the carbon fiber core yarn is 500 gf or less, and the polymer fiber may be wrapped under a tension condition of 500 to 1,000 gf.

[0010] Preferably, the filament diameter of the carbon fiber can be 5 to 10 μm.

[0011] Preferably, the fineness of the carbon fiber can be 60 to 3,000 Tex.

[0012] Preferably, the polymer fiber may be a thermoplastic polymer fiber.

[0013] Preferably, the polymer fiber may comprise at least one of polypropylene, maleic anhydride-grafted polypropylene, polyester, polyethylene, polyamide, polyvinyl alcohol, and polyurethane fiber.

[0014] Preferably, the polymer fiber may have a twist count (T / M) of 6 to 390 fibers per meter of carbon fiber core yarn.

[0015] Preferably, the diameter of the polymer fiber is 5 to 100 μm, and the fineness can be 25 to 2,825 TEX (g / km).

[0016] Preferably, the carbon fiber content of the total weight of the carbon fiber-polymer composite yarn is 50 to 70 weight%, and the polymer fiber content may be 30 to 50 weight%.

[0017] Preferably, when a carbon fiber-polymer composite is cut to a length of 300 mm, both ends are grasped, one end is released, and the sagging length is measured after 1 second, the height difference between the two ends may be 100 to 240 mm.

[0018] Preferably, the carbon fiber-polymer composite may have a tensile strength property of 200 to 5,000 N.

[0019] Preferably, the carbon fiber-polymer composite may not undergo a heating process during or after the wrapping process.

[0020] In addition, the above objective is achieved by a chopped composite yarn characterized by being formed by cutting a carbon fiber-polymer composite yarn into lengths of 3 to 30 mm.

[0021] Preferably, when the chopped composite yarn is 6 to 12 mm in length, it may spread out to a width of 2 to 4 times after 1 second when dropped onto the surface of distilled water at 25°C. Effects of the invention

[0022] The carbon fiber-polymer composite yarn of the present invention and the chopped composite yarn produced therefrom are advantageous for processing chopped fibers of a certain length by ensuring that polymer fibers are wrapped (covered) in a spiral shape around the outside of the carbon fiber core yarn to compensate for the high drapeability of the carbon fibers, and since the chopped carbon fibers maintain the original dispersibility of the carbon fibers, they have a very useful effect that is easy to manufacture wet or dry nonwoven fabrics.

[0023] However, the effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description below. Brief explanation of the drawing

[0024] FIG. 1 is a diagram illustrating a method for measuring the drapeability of a carbon fiber-polymer composite yarn of the present invention. Specific details for implementing the invention

[0025] The present invention will be described in detail below with reference to the embodiments and drawings. These embodiments are presented merely as examples to explain the invention more specifically, and it will be obvious to those skilled in the art that the scope of the invention is not limited by these embodiments.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. In the event of a conflict, the present specification, including definitions, shall prevail. Additionally, methods and materials similar or equivalent to those described herein may be used in the practice or testing of the present invention, but suitable methods and materials are described herein.

[0027] As used herein, the terms “comprise,” “comprising,” “include,” “including,” “containing,” “characterized by,” “has,” “having,” or any other variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, article, or apparatus comprising a list of elements is not necessarily limited to such elements alone and may include other elements not explicitly listed or inherent to such process, method, article, or apparatus. Furthermore, unless explicitly stated otherwise, “or” means an inclusive “or” and not an exclusive “or.”

[0028] Hereinafter, the technical configuration of the present invention will be described in detail according to a preferred embodiment.

[0029] The carbon fiber-polymer composite of the present invention is configured such that polymer fibers are wrapped (covered) in a spiral shape around the outside of the carbon fiber core. This is because the polymer fibers must be wrapped in a spiral shape to function as a binder (to impart cohesiveness) to the carbon fibers. If the polymer fibers are wrapped horizontally, cohesiveness can be imparted through heat compression, but this is not desirable because it has the side effect of reducing the dispersibility of the chopped composite.

[0030] The carbon fiber used in the present invention preferably comprises at least one of PAN-based carbon fiber, pitch-based carbon fiber, and rayon-based carbon fiber.

[0031] In one embodiment, the filament diameter of the carbon fiber is preferably 5 to 10 μm. This is because if the filament diameter of the carbon fiber is less than 5 μm, the aspect ratio of the chop becomes excessively large, which may be disadvantageous for dispersion, and if it exceeds 10 μm, the aspect ratio is low, which may cause problems such as deterioration of the physical properties of the nonwoven fabric substrate.

[0032] In one embodiment, the fineness of the carbon fiber is preferably 60 to 3,000 Tex. This is because if the fineness of the carbon fiber is less than 60 Tex, the manufacturing cost increases and the effectiveness decreases, and if it exceeds 3,000 Tex, the fiber bundle becomes excessively thick, which is disadvantageous for chop processing.

[0033] The polymer fiber used in the present invention is a material that wraps (covers) the carbon fiber core yarn in a spiral shape and functions to enhance the cohesiveness of the carbon fiber.

[0034] In one embodiment, the polymer fiber is preferably a thermoplastic polymer fiber. Such a thermoplastic polymer fiber may particularly comprise at least one of polypropylene, maleic anhydride-grafted polypropylene, polyester, polyethylene, polyamide, polyvinyl alcohol, and polyurethane fibers.

[0035] In one embodiment, the polymer fiber preferably has a twist count (T / M) of 6 to 390 per meter of carbon fiber core yarn. That is, it is preferable to have 6 to 390 twists (6 to 390 T / M) per meter of carbon fiber core yarn. This is because if the twist count of the polymer fiber is less than 6 T / M, the cohesiveness is low, which may result in poor length uniformity or the occurrence of filaments that are not completely cut during fiber chop processing, and if it exceeds 390 T / M, the content of the polymer fiber becomes too high, which may degrade the physical properties of the nonwoven fabric produced by chop processing.

[0036] When wrapping such polymer fibers, it is preferable to manufacture the product by wrapping under conditions where the tension of the carbon fiber core yarn is 500 gf or less and the polymer fiber is 500 to 1,000 gf. At this time, if the carbon fiber core yarn is supported at a tension exceeding 500 gf, there is a risk that the carbon fiber may be damaged due to friction during the wrapping process. Furthermore, if the tension of the polymer fiber is less than 500 gf, the carbon fiber bundling by wrapping is weak, which is disadvantageous for chop processing, and if it exceeds 1,000 gf, there is a risk that the carbon fiber may be damaged by the polymer fiber. Additionally, in the present invention, it is preferable not to perform separate heating during or after the wrapping process. This is because the polymer material may induce adhesion between carbon fiber filaments, thereby reducing dispersibility.

[0037] In one embodiment, the diameter of the polymer fiber is preferably 5 to 100 μm. At this time, if the diameter is less than 5 μm, there is a risk that the polymer fiber may break during the process and the effectiveness is reduced due to increased manufacturing costs, whereas if it exceeds 100 μm, there is a disadvantage that the thickness uniformity of the nonwoven fabric substrate is reduced.

[0038] In addition, it is preferable that the fineness of the polymer fiber be 25 to 2,825 Tex. This is because if it is less than 25 Tex, more twists are required, which may cause fiber damage due to friction with the carbon fiber during manufacturing, and if it exceeds 2,825 Tex, it is difficult to provide sufficient bundling to the carbon fiber core yarn because fewer twists are required.

[0039] The carbon fiber-polymer composite yarn of the present invention, configured as described above, preferably has a carbon fiber content of 50 to 70 weight% and a polymer fiber content of 30 to 50 weight% of the total weight of the carbon fiber-polymer composite yarn. At this time, if the carbon fiber content exceeds 70 weight%, the bonding between fiber materials is reduced during the manufacture of the nonwoven fabric, making it difficult to manufacture a high-quality nonwoven fabric and causing difficulties during handling. On the other hand, if it is less than 50 weight%, the specific gravity of the carbon fiber in the nonwoven fabric decreases, causing a problem in which the physical properties of the nonwoven fabric and the composite material using it are degraded.

[0040] In the present invention, the carbon fiber-polymer composite yarn preferably has a tensile strength property of 200 to 5,000 N when evaluated according to KS K 0412. At this time, if it is less than 200 N, it means that the carbon fiber filament is severely damaged, so the properties of the nonwoven fabric will deteriorate, and if it exceeds 5,000 N, it means that the polymer fiber content is excessively high, which indicates that the properties of the nonwoven fabric may deteriorate.

[0041] In addition, carbon fiber-polymer composite yarns are processed into chops and used in the manufacture of nonwoven fabrics. As a measure to evaluate the drapeability suitable for ensuring the homogeneity of the chops and the physical properties of the nonwoven fabric, it is desirable that the carbon fiber-polymer composite yarn be cut to a length of 300 mm, both ends are grasped, one end is released, and the sagging length is measured after 1 second, with the height difference between the two ends being 100 to 240 mm. At this time, if the height difference is less than 100 mm, the content of polymer fibers becomes excessive, which may lead to a decrease in the physical properties of the nonwoven fabric, whereas if it exceeds 240 mm, there is a risk that the length variation of the chops will increase when the composite yarn is cut.

[0042] The length of the chopped composite yarn processed from the carbon fiber-polymer composite yarn of the present invention is preferably 3 to 30 mm. At this time, a chopped composite yarn with a length of less than 3 mm is advantageous for dispersion during nonwoven fabric processing, but there is a problem that significant fiber loss may occur during the process and the physical properties of the nonwoven fabric deteriorate. On the other hand, if it exceeds 30 mm, entanglement between fiber filaments easily occurs during the dispersion process, resulting in an uneven surface of the nonwoven fabric, which causes a problem of deterioration in the physical properties of the nonwoven fabric and the composite material using it.

[0043] In one embodiment, it is preferable that the carbon fiber-polymer chopped composite yarn expands to a width (direction perpendicular to the length direction) by 2 to 4 times in 1 second on the surface of distilled water at 25°C when it has a length of 6 to 12 mm. At this time, if the increase in width after 1 second is less than 2 times, it means that the dispersibility is low and it is not suitable for manufacturing nonwoven fabrics, and if it exceeds 4 times, it means that the polymer fibers have not sufficiently bundled the carbon fiber core yarns, that is, that a large length variation occurs during the chopped process, and there is a risk that a lot of entanglement between fiber filaments will occur during the manufacturing of nonwoven fabrics.

[0044] Hereinafter, the structure of the present invention and the resulting effects are to be explained in more detail through examples and comparative examples. However, these examples are intended to explain the present invention more specifically, and the scope of the present invention is not limited to these examples.

[0045] [Example]

[0046] [Example 1]

[0047] 1-1. Manufacture of Carbon Fiber-Polymer Composites and Chopped Composites

[0048] One strand of carbon fiber T700SC-12000-60E (Toray Advanced Materials) was supported at the center of the wrapping machine with a tension of 200 gf.

[0049] 325 Tex PET fibers were used as the polymer fibers, and 1,000 m of carbon fiber-polymer composite yarn was manufactured by wrapping at 6 T / M.

[0050] At this time, the tensile strength of the PET fiber was set to 750 gf. Then, the manufactured carbon fiber-polymer composite yarn was processed into a 12 mm long chop using a guillotine chopper.

[0051] 1-2. Manufacture of Nonwoven Fabric Using Carbon Fiber-Polymer Chopped Composite Yarn

[0052] A nonwoven fabric was produced using an experimental wet papermaking machine by applying the carbon fiber-polymer chopped composite yarn obtained through 1-1 to the following procedure.

[0053] ① Chopped composite yarn was weighed to a weight of 40 gsm based on a 20 cm square and placed into a rectangular prism-shaped tank with a release mesh laid on the bottom. ② 20 L of ordinary water was filled into the tank, and ③ air was blown in for 5 minutes to induce fiber dispersion. Subsequently, ④ the plate at the bottom of the tank was removed to temporarily remove water, allowing the dispersed fibers to be applied onto the release mesh. ⑤ A vacuum was then used to induce further dehydration and ensure the nonwoven fabric surface was formed evenly. Next, ⑥ the mesh on which the nonwoven fabric was placed was separated, ⑦ the opposite side was covered with mesh as well, and ⑧ the nonwoven fabric was obtained by passing it through a roll press heated to 130 ℃ for 5 minutes. The pressure of the roll press was set to 0.6 MPa.

[0054] [Example 2]

[0055] Carbon fiber-polymer composite yarn, chopped composite yarn, and nonwoven fabric were manufactured in the same manner as in Example 1, except that 400 Tex PET fibers were used for the polymer fibers and the number of twists was set to 50 T / M.

[0056] [Example 3]

[0057] Carbon fiber-polymer composite yarn, chopped composite yarn, and nonwoven fabric were manufactured in the same manner as in Example 1, except that 525 Tex PET fibers were used as the polymer fibers and the twist count was set to 100 T / M.

[0058] [Example 4]

[0059] Carbon fiber-polymer composite yarn, chopped composite yarn, and nonwoven fabric were manufactured in the same manner as in Example 1, except that 625 Tex PET fibers were used for the polymer fibers and the twist count was set to 200 T / M.

[0060] [Example 5]

[0061] Carbon fiber-polymer composite yarn, chopped composite yarn, and nonwoven fabric were manufactured in the same manner as in Example 1, except that 750 Tex PET fibers were used for the polymer fibers and the twist count was set to 390 T / M.

[0062] [Example 6]

[0063] The carbon fiber-polymer composite yarn prepared in Example 4 was used as is, and a nonwoven fabric was prepared in the same manner as in Example 4, except that the chopped composite yarn was prepared to a length of 3 mm.

[0064] [Example 7]

[0065] The carbon fiber-polymer composite yarn prepared in Example 4 was used as is, and a nonwoven fabric was prepared in the same manner as in Example 4, except that the chopped composite yarn was prepared to a length of 20 mm.

[0066] [Example 8]

[0067] The carbon fiber-polymer composite yarn prepared in Example 4 was used as is, and a nonwoven fabric was prepared in the same manner as in Example 4, except that the chopped composite yarn was prepared to a length of 30 mm.

[0068] [Comparative Example]

[0069] [Comparative Example 1]

[0070] Carbon fiber-polymer composite yarn, chopped composite yarn, and nonwoven fabric were manufactured in the same manner as in Example 1, except that the number of twists was set to 5 T / M.

[0071] [Comparative Example 2]

[0072] Carbon fiber-polymer composite yarn, chopped composite yarn, and nonwoven fabric were manufactured in the same manner as in Example 5, except that the number of twists was set to 400 T / M.

[0073] [Comparative Example 3]

[0074] Carbon fiber-polymer composite yarn, chopped composite yarn, and nonwoven fabric were prepared in the same manner as in Example 4, except that the polymer fiber tension was set to 400 gf.

[0075] [Comparative Example 4]

[0076] Carbon fiber-polymer composite yarn, chopped composite yarn, and nonwoven fabric were prepared in the same manner as in Example 4, except that the polymer fiber tension was set to 1,200 gf.

[0077] [Comparative Example 5]

[0078] Carbon fiber-polymer composite yarn, chopped composite yarn, and nonwoven fabric were manufactured in the same manner as in Example 4, except that the carbon fiber support tension was set to 650 gf.

[0079] [Comparative Example 6]

[0080] The carbon fiber-polymer composite yarn prepared in Example 4 was used as is, and a nonwoven fabric was prepared in the same manner as in Example 4, except that the chopped composite yarn was prepared to a length of 2 mm.

[0081] [Comparative Example 7]

[0082] The carbon fiber-polymer composite yarn prepared in Example 4 was used as is, and a nonwoven fabric was prepared in the same manner as in Example 4, except that the chopped composite yarn was prepared to a length of 32 mm.

[0083] [Comparative Example 8]

[0084] Carbon fibers and PET fibers were each processed into 12 mm chops without polymer fiber wrapping. However, since binder fibers are required to manufacture nonwoven fabric, 60 parts by weight of carbon fibers and 40 parts by weight of polymer fibers were added, and a nonwoven fabric was manufactured at 40 gsm.

[0085] The physical properties of the carbon fiber-polymer composite yarns, chopped composite yarns, and nonwoven fabrics according to Examples 1 to 8 and Comparative Examples 1 to 8 were measured through the following experimental examples, and the results are shown in Table 1 below.

[0086] [Experimental Example]

[0087] (1) Measurement of tensile strength of carbon fiber-polymer composite yarn

[0088] The carbon fiber-polymer composite yarns or carbon fibers prepared through Examples 1 to 8 and Comparative Examples 1 to 8 were evaluated for tensile strength according to KS K 0412. Five samples were measured for each condition, and the average was adopted as the result.

[0089] (2) carbon fiber - Polymer composite fibers carbon fiber Calculation of content (mass ratio)

[0090] The carbon fiber content of the carbon fiber-polymer composite yarns prepared in Examples 1 to 8 and Comparative Examples 1 to 8 was calculated using the following procedure. Five samples were measured for each condition, and the average was adopted as the result.

[0091] ① Cut a portion of the carbon fiber-polymer composite and measure its mass (Wa (g)).

[0092] ② Heat-treat the polymer fibers for 30 minutes in a high-temperature furnace at 500℃ with air purging to burn and remove them.

[0093] ③ Cool the carbon fiber remaining after pyrolysis in Step ② to 30℃ or below, and measure its mass. (W b (g)

[0094] ④ Calculate the carbon fiber content using the following formula.

[0095]

[0096] (3) Measurement of the drape of carbon fiber-polymer composite yarn

[0097] FIG. 1 is a diagram illustrating a method for measuring the drapeability of a carbon fiber-polymer composite yarn of the present invention.

[0098] Samples were prepared by cutting carbon fiber-polymer composite yarns or carbon fibers manufactured through Examples 1 to 8 and Comparative Examples 1 to 8 into 320 mm lengths. As shown in Fig. 1, 20 mm was placed on a table and pressed down with fingers so that the thickness direction was in close contact with the floor, and the remaining 300 mm was pulled out of the edge of the table so that it was lifted into the air, and the end was grasped by hand. After releasing the hand holding the resin-coated carbon fiber from the area outside the table, the length (mm) of the end sagging was measured after 1 second. For each example and comparative example, the number of measurements was 10, and the average value was calculated.

[0099] (4) Measurement of dispersibility of carbon fiber-polymer chopped composite yarn

[0100] Carbon fiber-polymer composite yarns prepared through Examples 1 to 8 and Comparative Examples 1 to 8 were processed into chops of lengths of 6 mm and 12 mm, and their widths were measured (w1). The chops were dropped onto the surface of distilled water at 25°C, and their widths were measured again after 1 second (w2). The degree of width increase was calculated as a percentage to compare dispersibility. Five samples were measured for each condition, and the average was adopted as the result. [Example) 4 mm → 9 mm: 2.25 times]

[0101] (5) Measurement of nonwoven fabric strength

[0102] The nonwoven fabrics prepared through Examples 1 to 8 and Comparative Examples 1 to 8 were cut into rectangular specimens with a width of 25 mm and a length of 145 mm, and their tensile strength was measured. The 35 mm ends were gripped, the measurement section was 75 mm, and the strain rate was 2 mm / min. Stress was calculated based on the maximum load applied to the nonwoven fabric; when the maximum load was unclear, it was calculated based on the load at the moment the nonwoven fabric tore. Five samples were measured for each condition, and the average was adopted as the result.

[0103] Table 1 below summarizes the experimental results for Examples 1 to 8 and Comparative Examples 1 to 8.

[0104] Diagonal tensile strength (N) Carbon fiber content (weight%) Drape (mm) Dispersibility (times) Non-woven fabric strength (kPa) 6 mm 12 mm Example 1 1282.3 70.8 238.1 3.745 2.741 384.4 Example 2 1255.8 66.1 221.1 3.486 2.678 448.3 Example 3 1267.6 59.9 179.3 3.565 2.711 520.6 Example 4 1285.2 54.4 154.8 3.489 2.801 617.7 Example 5 1324.9 50.3 110.1 3.641 2.900 724.1 Example 6 1285.2 54.4 154.8 3.489 2.801 387.3 Example 7 1285.2 54.4 154.8 3.489 2.801 1074.5 Example 8 1285.2 54.4 154.8 3.489 2.801 1241.5 Comparative Example 1 1278.9 72.1 262.7 3.804 2.790 227.8 Comparative Example 2 1218.1 48.7 92.6 2.997 1.895 514.1 Comparative Example 3 1300.4 54.5 171.1 3.244 2.306 485.7 Comparative Example 4 1211.9 54.5 133.6 2.895 1.929 512.9 Comparative Example 5 1209.9 54.3 155.9 3.236 2.022 539.3 Comparative Example 6 1285.2 54.4 154.8 3.489 2.801 201.4 Comparative Example 7 1285.2 54.4 154.8 3.489 2.801 369.7 Comparative Example 8 1287.2 100.0 270.9 3.841 2.978 515.9

[0105] As can be seen in Table 1 above, Example 1 and Comparative Example 1 were manufactured under the same conditions except for the number of twists of the polymer fibers, but it can be seen that the nonwoven fabric strength differs by more than 150 kPa. In addition, in the case of Comparative Example 1, the number of twists was insufficient, so sufficient cohesive force was not imparted to the carbon fibers, resulting in a high drape value and length variation during chop processing; this length variation can be interpreted as causing entanglement between filaments during the manufacture of the nonwoven fabric.

[0106] On the other hand, Comparative Example 2 had all conditions identical to Example 5 except for having a higher number of twists, but a distinct decrease in nonwoven fabric strength was similarly observed. In Comparative Example 2, there was damage to the carbon fibers because the polymer fibers were excessively wrapped, and it was confirmed that the drape value was low and the dispersibility after chopping was also lower compared to other samples. This can be interpreted as the cause of insufficient fiber dispersion during the manufacture of the nonwoven fabric.

[0107] In addition, Comparative Example 3, in which the tension of the polymer fibers was lowered during the wrapping process, can be seen to have a nonwoven fabric strength approximately 132 kPa lower than that of Example 4 under similar conditions. This point can also be interpreted as the length variation of the chops caused by insufficient cohesive force (higher drape value and lower dispersibility compared to Example 4), similar to the cases of Example 1 and Comparative Example 1, leading to entanglement between filaments during nonwoven fabric manufacturing. Conversely, Comparative Example 4, in which the tension of the polymer fibers is high, can be interpreted as having a low nonwoven fabric strength for the same reason as Comparative Example 2, and it can be seen that the dispersibility after the chop processing is also lower compared to other samples.

[0108] In addition, Comparative Example 5 is a case where the support tension of the carbon fiber core yarn was increased compared to Example 4, but due to damage to the carbon fiber, the tensile strength of the carbon fiber-polymer composite yarn was slightly reduced, and it can be seen that the physical properties of the nonwoven fabric were also affected due to a large amount of lint generated during the wrapping process.

[0109] Furthermore, Comparative Example 6 was excellent for manufacturing nonwoven fabric, but it is characterized by significantly lower physical properties compared to Examples 4, 6 to 8, which were under the same conditions except for the chop length; in particular, it can be seen that the strength of the nonwoven fabric is remarkably low. This result demonstrates that the physical properties of the nonwoven fabric are largely determined by the fiber length, and it shows that the chop length must be managed to an appropriate level when manufacturing nonwoven fabrics using the carbon fiber-polymer composite yarn provided in the present invention. Conversely, Comparative Example 7 is a case where the chop length was excessively long, resulting in severe entanglement between filaments during dispersion and low physical properties of the nonwoven fabric.

[0110] In addition, Comparative Example 8 is a result of producing a wet nonwoven fabric by individually chopping carbon fibers and polymer fibers, and is compared with Example 3. The strength of the nonwoven fabric in both cases is almost identical, which demonstrates that one embodiment of the present invention is effective. Furthermore, unlike Comparative Example 8, one embodiment of the present invention can handle different types of fibers at once, so it can be considered a more efficient method. Also, in the case of Comparative Example 8, since the material is 100 wt% carbon fiber (T700SC-12000-60E), the cohesiveness is not imparted by polymer fiber wrapping, resulting in the carbon fiber having its own unique drape value.

[0111] The carbon fiber-polymer composite yarn of the present invention as described above and the chopped composite yarn produced therefrom are advantageous for processing chopped fibers of a certain length by compensating for the high drapeability of the carbon fibers by wrapping (covering) polymer fibers in a spiral shape around the outside of the carbon fiber core yarn. Furthermore, since the chopped carbon fibers maintain the original dispersibility of the carbon fibers, they have a very useful effect that facilitates the manufacture of wet or dry nonwoven fabrics.

[0112] Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims also fall within the scope of the present invention.

Claims

Claim 1 A carbon fiber-polymer composite yarn characterized in that polymer fibers are wrapped in a spiral shape on the outside of a carbon fiber core yarn, the content of the carbon fiber core yarn is 50 to 70 weight% of the total weight and the content of the polymer fiber is 30 to 50 weight%, the tensile strength of the carbon fiber core yarn is 500 gf or less and the polymer fibers are wrapped under a tensile strength condition of 500 to 1,000 gf, and the polymer fibers have a twist count (T / M) of 6 to 390 per meter of the carbon fiber core yarn. Claim 2 delete Claim 3 A carbon fiber-polymer composite yarn according to claim 1, characterized in that the filament diameter of the carbon fiber is 5 to 10 μm. Claim 4 A carbon fiber-polymer composite yarn according to claim 1, characterized in that the fineness of the carbon fiber is 60 to 3,000 Tex. Claim 5 A carbon fiber-polymer composite yarn according to claim 1, characterized in that the polymer fiber is a thermoplastic polymer fiber. Claim 6 A carbon fiber-polymer composite yarn according to claim 5, characterized in that the polymer fiber comprises at least one of polypropylene, maleic anhydride-grafted polypropylene, polyester, polyethylene, polyamide, polyvinyl alcohol, and polyurethane fibers. Claim 7 delete Claim 8 A carbon fiber-polymer composite yarn according to claim 1, wherein the diameter of the polymer fiber is 5 to 100 μm and the fineness is 25 to 2,825 TEX (g / km). Claim 9 delete Claim 10 A carbon fiber-polymer composite yarn according to claim 1, characterized in that when the carbon fiber-polymer composite yarn is cut to a length of 300 mm, both ends are grasped, one end is released, and the sagging length is measured after 1 second, the height difference between the two ends is 100 to 240 mm. Claim 11 A carbon fiber-polymer composite yarn according to claim 1, characterized in that the carbon fiber-polymer composite yarn has a tensile strength property of 200 to 5,000 N. Claim 12 A carbon fiber-polymer composite yarn according to claim 1, characterized in that the carbon fiber-polymer composite yarn does not undergo a heating process during or after the wrapping process. Claim 13 A chopped composite yarn characterized by being formed by cutting a carbon fiber-polymer composite yarn of any one of claims 1, 3 to 6, 8, and 10 to 12 into a length of 3 to 30 mm. Claim 14 In claim 13, the chopped composite yarn is characterized by expanding to a width of 2 to 4 times after 1 second when dropped onto the surface of distilled water at 25°C when the chopped composite yarn is 6 to 12 mm in length.

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