braid

Abstract

Provided is a braid of a carbon nanotube (CNT) core yarn excellent in tensile strength and scratch resistance. This braid is obtained by winding a plurality of monofilament or multifilament sheath yarns on a core yarn containing a CNT yarn composed of CNTs. A cord angle formed by the core yarn and the sheath yarn is 3 degrees-15 degrees inclusive.

Description

Braided thread

[0001] The present invention relates to a braided yarn having excellent tensile strength and abrasion resistance.

[0002] Braided yarns having various properties according to the application and purpose have been provided.

[0003] For example, monofilaments made of polyamide resins such as nylon 6 and nylon 6,6, fluororesins such as polyvinylidene fluoride, polyester resins such as polyethylene terephthalate, and polyolefin resins such as ultra-high molecular weight polyethylene are widely used as fishing lines depending on the target fish and fishing method (see Patent Document 1).

[0004] In addition, PE fishing lines, which are multifilament braided with polyethylene fibers, are now widely used as fishing lines. PE fishing lines have the advantages of superior tensile strength (linear strength), lower elongation, and a smaller cross-sectional area than the monofilaments made of synthetic resins mentioned above. On the other hand, PE fishing lines are inferior to these monofilaments in abrasion resistance (wear resistance).

[0005] One material with excellent abrasion resistance is CNT yarn, which is an agglomeration of carbon nanotubes (hereinafter referred to as CNT), which are a type of carbon-based microstructure (see Patent Documents 2 to 4). However, CNT yarn is inferior in tensile strength to PE line.

[0006] Patent No. 2741841 Patent No. 5350635 Patent No. 4512750 Patent No. 7192176

[0007] Although lines having excellent properties in either tensile strength (linear strength) or abrasion resistance (wear resistance) have been developed, a line that combines both tensile strength and abrasion resistance has not yet been developed. It is desired to provide a line that has improved abrasion resistance while maintaining the excellent properties of PE lines, which are widely used as fishing lines, etc.

[0008] The present invention is primarily intended to solve these problems, and has an object to provide a braided CNT core yarn that has excellent tensile strength and abrasion resistance.

[0009] According to one embodiment, the braided yarn is formed by winding a plurality of monofilament or multifilament sheath yarns around a core yarn containing a CNT yarn, which is a thread-like yarn made of CNTs (carbon nanotubes), and the braiding angle formed by the core yarn and the sheath yarn is 3 degrees or more and 15 degrees or less. According to one embodiment, the coefficient of variation of the cross-sectional areas of the plurality of sheath yarns is within 10%, and the plurality of sheath yarns are made of the same or equivalent material, and the braiding angle formed by the core yarn and the sheath yarn is 5 degrees or more and 15 degrees or less. According to one embodiment, the ratio of the cross-sectional area of ​​the core yarn to the cross-sectional area of ​​the braided yarn is 38% or more, and the number of sheath yarns is 3 or more and 24 or less. According to one embodiment, the number of sheath yarns is 7 or more and 24 or less. According to one embodiment, when the braided yarn with a weight fixed to its tip is placed on a file and repeatedly moved back and forth in a certain direction, the durability number, which is the number of reciprocations required until breakage, is 250 or more.

[0010] The present invention can provide a CNT core yarn braid that has excellent tensile strength and abrasion resistance.

[0011] FIG. 1 is a schematic diagram showing the structure of the braided yarn 100. FIG. 2 is a graph showing the evaluation results (breaking load ratio) of the tensile strength of the braided yarn 100. FIG. 3 is a graph showing the evaluation results (breaking load ratio per cross-sectional area) of the tensile strength of the braided yarn 100. FIG. 4 is a schematic diagram showing a method for evaluating the abrasion resistance of the braided yarn 100. FIG. 5 is a graph showing the evaluation results (endurance number ratio) of the abrasion resistance of the braided yarn 100. FIG. 6 is a diagram explaining the cross-sectional area of ​​the braided yarn. FIG. 7 is a diagram explaining the braiding angle.

[0012] Specific embodiments of the present invention will be described in detail below with reference to the drawings.

[0013] <Core Yarn> A braided yarn according to an embodiment of the present invention has a core yarn containing a CNT yarn.

[0014] CNT yarn is a thread made from an aggregation of CNTs. To make CNT yarn, the CNTs are drawn out, and the CNTs are oriented in the direction they are drawn out, but the attractive forces between the individual CNTs result in a continuous thread-like mass. This can then be wound up to produce CNT yarn.

[0015] Individual CNTs are structurally classified as single-walled CNTs (SWCNTs) or multi-walled CNTs (MWCNTs), and multi-walled CNTs with three or more walls are also known. Any of these CNTs can be used to make CNT yarn.

[0016] The average diameter of the individual CNTs that make up the CNT yarn is preferably 3 to 15 nm, and more preferably 7.5 to 15 nm. The length of the CNTs is preferably 50 μm or more, and more preferably 100 μm or more. This is because if the average length of the CNTs is shorter than 50 μm, the number of ends of the individual CNTs increases. The average diameter and length of the CNTs are determined by averaging the diameters and lengths of multiple randomly selected CNTs using a transmission electron microscope.

[0017] The CNT yarn, which is an aggregate of individual CNTs, has a diameter (wire diameter) of 20 μm to 70 μm, preferably 25 μm to 60 μm, and more preferably 30 to 50 μm.

[0018] The length of the CNT yarn can be set to a preferred length depending on the desired application. For example, when used as a core thread for braided lines such as fishing lines, the length can be set to, for example, 100 m to 300 m. However, it is of course possible to set the length to less than 100 m, and if necessary, the length can exceed 300 m.

[0019] The CNT yarn constituting the core yarn may be a single yarn formed by spinning a CNT web into a thread, a bundle of multiple yarns, or a twist of multiple yarns. Preferably, the braided yarn according to the present invention uses a yarn formed by bundling multiple untwisted CNT yarns as the core yarn. This improves the tensile strength of the core yarn. The core yarn may also be formed by bundling or twisting a CNT yarn with other fibers.

[0020] <Sheath Yarn> The braided yarn according to the embodiment of the present invention has a sheath yarn containing fibers with excellent tensile strength, such as UHMW-PE (ultra-high molecular weight polyethylene fibers).

[0021] The UHMW-PE used as the sheath yarn preferably has a thickness of 10T to 440T. Here, T: decitex is a unit that expresses the thickness of a fiber by the weight per certain length. A fiber having a weight of 1 g per 10,000 m of length is expressed as 1T (decitex).

[0022] The material of the sheath thread may be other than UHMW-PE, such as nylon or fluorocarbon, or other synthetic resin filaments, but in that case, the number and thickness of the sheath threads are adjusted to ensure the required tensile strength and flexibility.

[0023] 1 is a schematic diagram showing the structure of a braided yarn 100 according to an embodiment of the present invention. To braid the braided yarn 100, one or more strands of UHMW-PE are wound or braided as sheath yarns 102 around a core yarn 101 containing a CNT yarn.

[0024] The sheath yarn 102 may be one or more braided strands that are then spirally wound around the core yarn 101, or multiple braided strands may be braided to cover the core yarn 101. To increase the tensile strength of the braided yarn 100, it is more desirable to braid multiple strands of the sheath yarn 102 than to wind the sheath yarn 102 spirally around the core yarn 101.

[0025] When multiple sheath yarns 102 are braided around the core yarn 101, if the thickness of each sheath yarn 102 is made approximately the same, braiding becomes easier and the contact between the core yarn 101 and the sheath yarn 102 becomes more stable. Specifically, it is preferable to keep the variation in the cross-sectional area of ​​the multiple sheath yarns 102 used in the braided yarn 100 within a coefficient of variation (CV) of 10%. CV is an index that indicates the percentage of variation relative to the average value, and can be calculated using the following formula: CV (%) = standard deviation ÷ average value × 100

[0026] By using the same or similar material for each of the multiple sheath yarns 102, braiding becomes easier and the contact between the core yarn 101 and the sheath yarn 102 becomes more stable.

[0027] Furthermore, the greater the number of sheath yarns 102, the smoother the outer peripheral surface of the braided yarn 100 will be, with fewer irregularities, and the core yarns 101 will be squeezed from various directions, causing the core yarns 101 to shrink uniformly, resulting in a better balance between tensile strength and abrasion resistance. The number of sheath yarns 102 is preferably three or more from the viewpoint of ensuring tensile strength, seven or more from the viewpoint of ensuring abrasion resistance, and 24 or less from the viewpoint of ensuring flexibility. Note that it is also possible to change the bending of the braided yarn 100 by making one or more sheath yarns 102 different in thickness from the other sheath yarns 102. Alternatively, it is also possible to appropriately change the properties of the braided yarn 100 by making one or more sheath yarns 102 out of a material different from that of the other sheath yarns 102.

[0028] <Tensile Strength Evaluation Test 1> The tensile strength of the braided yarns according to the present invention was evaluated. In this test, to evaluate the effect of the core yarn material on tensile strength, the tensile strengths of four examples (Examples 1 to 4) in which the core yarn was a CNT yarn and the sheath yarn was UHMW-PE (hereinafter referred to as PE material), two comparative examples (Comparative Examples 3 and 4), and two comparative examples (Comparative Examples 1 and 2) in which the core yarn was a PE material and the sheath yarn was a PE material were measured and compared. In addition, to simultaneously evaluate the effect on tensile strength of the ratio of the cross-sectional area of ​​the core yarn to the cross-sectional area of ​​the braided yarn, braids with a CNT yarn as the core yarn and a PE material as the core yarn were prepared with a core cross-sectional area ratio of 38% and 60%, respectively, and the tensile strengths were compared.

[0029] Table 1 shows the thicknesses of the braided yarns and the ratios of the cross-sectional area of ​​the core yarns to the cross-sectional area of ​​the braided yarns according to Examples 1 and 2 and Comparative Examples 1 and 2. Here, the cross-sectional area of ​​the braided yarn refers to the area of ​​a circle (shown by a dashed line in FIG. 6) having a diameter R1, assuming that the braided yarn is approximately cylindrical. Note that this does not refer to the actual area of ​​the core yarns and sheath yarns in the cross-section of the braided yarn (the sum of the areas of the hatched areas in FIG. 6). Similarly, the cross-sectional area of ​​the core yarn refers to the area of ​​a circle having a diameter R2, assuming that the core yarn is approximately cylindrical.

[0030] In both Example 1 and Comparative Example 1, the braided yarn thickness was set to 0.20 mm (equivalent to No. 1), and the ratio of the cross-sectional area of ​​the core yarn to the cross-sectional area of ​​the braided yarn was set to 38%. In both Example 2 and Comparative Example 2, the braided yarn thickness was set to 0.12 mm (equivalent to No. 0.7), and the ratio of the cross-sectional area of ​​the core yarn to the cross-sectional area of ​​the braided yarn was set to 60%.

[0031] Table 2 shows the breaking load, breaking load ratio, breaking load per cross-sectional area, and breaking load ratio per cross-sectional area when a tensile load is applied to these braided yarns in the longitudinal direction. Here, the breaking load ratio is the ratio of the breaking load when the breaking load of Comparative Example 2 is set to 1. The breaking load ratio per cross-sectional area is the ratio of the breaking load per cross-sectional area when the breaking load per cross-sectional area of ​​Comparative Example 1 is set to 1.

[0032] Figure 2 is a graph plotting the breaking load ratio. Example 1, which uses a CNT yarn as the core yarn, has a higher breaking load ratio than Comparative Example 1, which uses a PE core yarn under the same conditions (same thickness and ratio of the cross-sectional area of ​​the core yarn to the cross-sectional area of ​​the braided yarn). Similarly, Example 2 has a higher breaking load ratio than Comparative Example 2, which uses the same conditions.

[0033] 3 is a graph plotting the breaking load ratio per cross-sectional area. It can be seen that the groups of Examples 1 and 2, which used a CNT yarn as the core yarn, had a larger breaking load ratio per cross-sectional area than the groups of Comparative Examples 1 and 2, which used a PE core yarn.

[0034] Therefore, the braided yarn with a CNT yarn core can be evaluated as having superior tensile strength to the braided yarn with a PE core. Furthermore, this evaluation is valid regardless of the thickness of the braided yarn or the ratio of the cross-sectional area of ​​the core yarn to the cross-sectional area of ​​the braided yarn.

[0035] <Tensile strength evaluation test 2> In this test, the influence of the braiding angle of the braided yarn on the tensile strength is evaluated. The braiding angle is the smaller angle θ between the core yarn and the sheath yarn (colored portion) when the braided yarn is observed from the side as shown in Figure 7.

[0036] As shown in Table 3, in this test, the tensile strengths of two examples (Example 3 and Example 4) in which the core yarn was made of CNT yarn and the sheath yarn was made of PE, two comparative examples (Comparative Example 3 and Comparative Example 4), one comparative example (Comparative Example 2) in which the core yarn was made of PE and the sheath yarn was made of PE, and a commercially available PE line No. 0.6 (Reference Example 4) were measured and compared. Examples 3, 4, Comparative Examples 2, 3, and 4 were all manufactured to have the same diameter as Reference Example 4, about No. 0.6.

[0037] Table 3 shows the breaking load, breaking load ratio, breaking load per cross-sectional area, and breaking load ratio per cross-sectional area when a tensile load is applied to these braided yarns in the longitudinal direction.

[0038] Comparing Example 3 with Comparative Example 2, it can be seen that when the braiding angle is the same at 10 degrees, the breaking load ratio per cross-sectional area is 1.48 times larger when the core yarn is a CNT yarn than when the core yarn is made of PE, resulting in a higher tensile strength. Furthermore, comparing Example 3, Example 4, Comparative Examples 3 and 4, it can be seen that when the core yarn is the same CNT yarn, the smaller the braiding angle, the larger the breaking load ratio per cross-sectional area and the higher the tensile strength.

[0039] Therefore, braided yarns with CNT yarn cores can be evaluated as having superior tensile strength to braided yarns with PE cores at the same braiding angle. Furthermore, braided yarns with CNT yarn cores can be evaluated as having higher tensile strength as the braiding angle decreases.

[0040] As a result of extensive testing by the inventors, it was found that from the viewpoint of manufacturability, in which the core yarn is less likely to come out from the sheath yarn, the lower limit of the braiding angle is preferably set to 3 degrees. From the viewpoint of stable production, the lower limit of the braiding angle is more preferably set to 5 degrees.

[0041] <Evaluation of Abrasion Resistance 1> To evaluate the abrasion resistance of the braided yarn according to the present invention, the abrasion resistance of an example in which the core yarn was made of a CNT yarn and the sheath yarn was made of a PE material was measured and compared by the following method, and a comparative example in which the core yarn was made of a PE material and the sheath yarn was made of a PE material. For reference, the abrasion resistance of commercially available multifilament PE lines, monofilament nylon lines, and fluorocarbon lines was also measured by the same method.

[0042] A specific measurement method will be explained using Figure 4. 1 is a reciprocating body. In this test, an STB1225s tension and compression testing machine manufactured by A&D Corporation (reciprocating body speed: 200 mm / min, stroke: 5 mm, number of reciprocations per cycle: 100, load cell: 500 kg, chuck jig: tire cord air jaw) was used as the reciprocating body 1. 2 is a load. In this test, an eggplant-shaped weight (No. 20, 75 g) was used. 3 is a test specimen (braided yarn). 4 is a friction body. In this test, sandpaper (#240) was used.

[0043] One end of the test piece 3 is fixed to the reciprocating body 1, and the other end is fixed to the weight 2. The test piece 3 is moved back and forth by the reciprocating body 1, and is brought into contact with the friction body 4 at a substantially right angle along the path. The number of reciprocations required until the test piece 3 breaks is defined as the durability number.

[0044] Table 4 shows the thicknesses of the yarns used as test specimens. In both Example 1 and Comparative Example 1, the braid thickness was set to 0.20 mm, and the ratio of the cross-sectional area of ​​the core yarn to the cross-sectional area of ​​the braid was set to 38%. For Reference Examples 1 to 3, PE line, nylon line, and fluorocarbon line (all commercially available) with a thickness of approximately 0.20 mm were prepared.

[0045] Table 5 shows the durability and durability ratio when these yarns were rubbed using the method shown in Fig. 4. Here, the durability ratio is the ratio of the durability to the durability of Comparative Example 1, which is set to 1.

[0046] Figure 5 is a graph plotting the durability ratio. Example 1, in which the core yarn was made of CNT yarn, had a durability ratio 11.9 times that of Comparative Example 1, in which the core yarn was made of PE material under the same conditions (same thickness and ratio of the cross-sectional area of ​​the core yarn to the cross-sectional area of ​​the braid). Reference Example 1 (PE line No. 1.0) had a durability ratio 1.9 times that of Comparative Example 1, Reference Example 2 (nylon line No. 1.5) had a durability ratio 6.6 times that of Comparative Example 1, and Reference Example 3 (fluorocarbon line No. 1.5) had a durability ratio 8.5 times that of Comparative Example 1. The durability ratio of Reference Example 1 (PE line No. 1.0) exceeded that of Comparative Example 1, which also used only PE material, to some extent, presumably because Reference Example 1, a commercially available product, utilizes braiding and coating technologies to enhance the durability of the PE line.

[0047] Therefore, the braided yarn with a CNT yarn core can be evaluated as overwhelmingly superior in abrasion resistance to the braided yarn with a PE core. Furthermore, even compared to the monofilament lines of Reference Examples 2 and 3, which are generally considered to have excellent abrasion resistance, the braided yarn with a CNT yarn core showed extremely excellent abrasion resistance.

[0048] The reason for this is thought to be as follows: CNT yarns are bonded by intermolecular forces. Therefore, CNTs on the outer periphery of the core yarn become detached from the CNT yarn due to friction, but because the CNTs are bonded by intermolecular forces, fluff gradually forms on the outer periphery of the core yarn. It is assumed that this CNT fluff acts as a coating that reduces friction for the CNTs inside the core yarn.

[0049] <Evaluation of Abrasion Resistance 2> In this test, the influence of the braiding angle of the braid on the abrasion resistance is evaluated.

[0050] The test specimens used in Table 6 were the same as those shown in Table 2. That is, two examples (Example 3 and Example 4) in which the core yarn was made of CNT yarn and the sheath yarn was made of PE, two comparative examples (Comparative Example 3 and Comparative Example 4), one comparative example (Comparative Example 2) in which the core yarn was made of PE and the sheath yarn was made of PE, and a commercially available PE line No. 0.6 (Reference Example 4) were used, and their abrasion resistance was measured and compared. Example 3, Example 4, Comparative Example 2, Comparative Example 3, and Comparative Example 4 were all manufactured to have a diameter of about No. 0.6, the same as Reference Example 4.

[0051] Table 6 shows the durability test results and durability test ratios when these braided yarns were subjected to the same abrasion test (FIG. 4) as in Evaluation of Abrasion Resistance 1. Here, the durability test ratio is the ratio of the durability test results when the durability test result of Comparative Example 3 is set to 1.

[0052] Comparing Example 3 with Comparative Example 2, it can be seen that when the braiding angle is the same at 10 degrees, the durability ratio is 59.6 times higher when the core yarn is a CNT yarn than when the core yarn is made of PE, indicating a significant improvement in abrasion resistance. Furthermore, comparing Example 3, Example 4, Comparative Examples 3 and 4, it can be seen that when the core yarn is the same CNT yarn, the durability ratio increases and abrasion resistance improves as the braiding angle decreases.

[0053] Therefore, braided yarns with CNT yarn cores can be evaluated as having better abrasion resistance than braided yarns with PE cores at the same braiding angle. Furthermore, braided yarns with CNT yarn cores can be evaluated as having improved abrasion resistance as the braiding angle decreases.

[0054] From the viewpoint of ensuring practical abrasion resistance, it is preferable that the upper limit of the braiding angle for braided yarns with a CNT yarn core is approximately 15 degrees. If the braiding angle is 15 degrees or less, it is possible to ensure a durability of at least twice the durability (approximately 180 times) of the No. 1.5 fluorocarbon line in Reference Example 3, and the advantages of braided yarns with a CNT yarn core can be fully demonstrated.

[0055] According to this embodiment, a braided yarn having a CNT yarn as the core yarn and a PE material as the sheath yarn has superior tensile strength compared to a braided yarn having a PE material as the core yarn, and also has overwhelmingly superior abrasion resistance compared to a braided yarn having a PE material as the core yarn.

[0056] It should be noted that within the scope of the present invention, the embodiments may be freely combined, or any of the components of the embodiments may be modified, or any of the components of the embodiments may be omitted.

[0057] For example, while the above-described embodiment primarily describes fishing line as an application of the braided yarn of the present invention, the present invention is not limited to this and can be applied to a variety of applications requiring both tensile strength and abrasion resistance. For example, by using the braided yarn as a textile fiber, the present invention can be applied to clothing and protective equipment with excellent tensile strength and abrasion resistance, parts or components for vehicles, ships, and aircraft, building and civil engineering materials, parachutes, tents, sails, interior decorations including curtains and wall hangings, etc. Furthermore, by twisting or knotting one or more braided yarns together, the present invention can be applied to nets, ropes, fishing nets, kite lines, fishing tackle, sports equipment including racket strings, wire, etc.

[0058] Furthermore, while the above-described embodiments have primarily shown examples in which PE material is used as the sheath yarn material, the present invention is not limited to this, and other materials may be used for the sheath yarn. In this case, since the tensile strength of the braided yarn is considered to depend mainly on the sheath yarn, it is preferable to use a material with excellent tensile strength for the sheath yarn. Furthermore, since the abrasion resistance of the braided yarn is considered to be a property ensured mainly by the core material of the CNT yarn, it is considered that even if a material other than PE is used for the sheath yarn, overwhelming abrasion resistance will still be exhibited.

[0059] 100 Braid thread 101 Core thread 102 Sheath thread 1 Reciprocating body 2 Load 3 Braid thread 4 Friction body

Claims

1. A twisted yarn comprising a core yarn containing a CNT yarn which is filamentous and composed of CNTs (carbon nanotubes), and a plurality of monofilament or multifilament sheath yarns wound around the core yarn, wherein the twisting angle formed by the core yarn and the sheath yarn is 3 degrees or more and 15 degrees or less.

2. The twisted yarn according to claim 1, wherein the coefficient of variation of the cross-sectional areas of the plurality of sheath yarns is within 10%, and the plurality of sheath yarns are made of the same or equivalent materials, and the twisting angle formed by the core yarn and the sheath yarn is 5 degrees or more and 15 degrees or less.

3. The twisted yarn according to claim 1, wherein the ratio of the cross-sectional area of the core yarn to the cross-sectional area of the twisted yarn is 38% or more, and the number of the sheath yarns is 3 or more and 24 or less.

4. The twisted yarn according to claim 1, wherein the number of the sheath yarns is 7 or more and 24 or less.

5. The twisted yarn according to claim 1, wherein when the twisted yarn with a weight fixed at the tip is placed on a file and a reciprocating motion in a certain direction is repeated, the number of reciprocations required until breakage, which is the number of durable reciprocations, is 250 or more.

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