Patent Application
20200251245
The present disclosure relates to a coated carbon nanotube electric wire in which a carbon nanotube wire configured of a plurality of carbon nanotubes is coated with an insulating material.
A carbon nanotube (hereinafter, also referred to as a “CNT”) is a material that has various characteristics and is expected to be applied to many fields.
For example, the CNT is a three-dimensional mesh structure configured of a single layer of a tubular element that has a hexagonal lattice mesh structure or multiple layers that are substantially coaxially disposed, has a light weight, and has various excellent characteristics such as electroconductivity, heat conductivity, elasticity, and mechanical strength. However, it is not easy to obtain the CNT as a wire, and no technologies using the CNT as a wire have been proposed.
On the other hand, utilization of a CNT has been considered as an alternative of metal, which is an implant material for a via hole formed in a multilayer wiring structure. Specifically, a wiring structure using, as an interlayer wiring of two or more conductive layers, multiple CNT layers adapted such that a plurality of cut surfaces of the multiple CNT layers extending coaxially from a growth base point toward an end on a further side of the multiple CNT layers are brought into contact with the respective conductive layers has been proposed for the purpose of reducing a resistance of the multilayer wiring structure (Japanese Patent Application Publication No. 2006-120730).
As another example, a carbon nanotube material in which an electroconductivity deposit made of metal or the like is formed at an electrical junction point of adjacent CNT wires has been proposed for the purpose of further improving electroconductivity of the CNT material, and there is a disclosure that such a carbon nanotube material can be applied to a wide range of applications (Japanese Translation of PCT International Application Publication No. 2015-523944). Also, a heater that has a heat conductive member produced from a carbon nanotube matrix based on excellent heat conductivity of the CNT wire has been proposed (Japanese Patent Application Publication No. 2015-181102).
Incidentally, coated electrical wires, each of which includes a core wire made of one or a plurality of wires and an insulating coating with which the core wire is coated, have been used as power lines or signal lines in various fields of automobiles, industrial devices, and the like. Although copper or copper alloys are typically used as materials of wires that configure the core wires in terms of electric characteristics, aluminum or aluminum alloys have been proposed in recent years in terms of weight reduction. For example, a specific weight of aluminum is about ⅓ of a specific weight of copper, and electric conductivity of aluminum is about ⅔ of electric conductivity of copper (in a case in which the electric conductivity of pure copper is defined as a reference of 100% IACS, the electric conductivity of pure aluminum is about 66% IACS). In order to cause the same amount of current as that flowing through a copper wire to flow through an aluminum wire, it is necessary to increase the sectional area of the aluminum wire to about 1.5 times the sectional area of the copper wire. However, even if such an aluminum wire with an increased sectional area is used, the mass of the aluminum wire is about a half of the mass of the pure copper wire. Therefore, it is advantageous to use the aluminum wire in terms of weight reduction.
Also, improvements in performance and functions of automobiles, industrial devices, and the like have advanced, the number of disposed various electric devices, control devices, and the like increases with the improvements, and the number of wirings of electric wiring elements used in these devices and heat generated from core wires tend to increase. Thus, there is a requirement for improving heat dissipation characteristics of electric wires without degrading insulation properties of insulating coating. On the other hand, there is also a requirement for weight reduction of wires in order to improve fuel consumption of mobile bodies such as automobiles for environmental compatibility.
Further, it is desirable that a coated electric wire has such characteristics that an insulating coating be not disconnected and be able to be kept in a state in which the electric wire is coated in order to prevent electrical leakage and electrical shock due to exposure of the electric wire even if the electric wire is disconnected due to some burden. Since a part of a CNT wire may be untwisted due to a continuous application of temporal change even if small bends are repeated, the CNT wire may be degraded or disconnected differently from a wire of a metal line. Thus, it is necessary to newly examine durability for a coated CNT electric wire that is unlikely to cause electrical leakage and electrical shock.
The present disclosure is related to providing a coated carbon nanotube electric wire in which an insulating coating layer has excellent durability against disconnection.
According to an aspect of the present disclosure, there is provided a coated carbon nanotube electric wire including: a carbon nanotube wire including one or more carbon nanotube aggregates configured of a plurality of carbon nanotubes; and an insulating coating layer with which the carbon nanotube wire is coated, in which a proportion of a Young's modulus of a material configuring the insulating coating layer with respect to a Young's modulus of the carbon nanotube wire is equal to or greater than 0.001 and equal to or less than 0.01.
In the aspect of the present disclosure, the proportion of the Young's modulus of the material configuring the insulating coating layer with respect to the Young's modulus of the carbon nanotube wire is equal to or greater than 0.0015 and equal to or less than 0.005, in the coated carbon nanotube electric wire.
According to the aspect of the present disclosure, a proportion of a sectional area of the insulating coating layer in a radial direction with respect to a sectional area of the carbon nanotube wire in the radial direction is equal to or greater than 0.02 and equal to or less than 10, in the coated carbon nanotube electric wire.
In the aspect of the present disclosure, a sectional area of the carbon nanotube wire in the radial direction is equal to or greater than 0.0003 mm2 and equal to or less than 100 mm2, in the coated carbon nanotube electric wire.
In the aspect of the present disclosure, the carbon nanotube wire includes a plurality of the carbon nanotube aggregates, and a full-width at half maximum Δθ in azimuth angle in azimuth plot based on small-angle X-ray scattering indicating an orientation of the plurality of carbon nanotube aggregates is equal to or less than 60°, in the coated carbon nanotube electric wire.
In the aspect of the present disclosure, a q value of a peak top at a (10) peak of scattering intensity based on X-ray scattering indicating density of the plurality of carbon nanotubes is equal to or greater than 2.0 nm−1 and equal to or less than 5.0 nm−1, and a full-width at half maximum Δq is equal to or greater than 0.1 nm−1 and equal to or less than 2.0 nm−1, in the coated carbon nanotube electric wire.
In the aspect of the present disclosure, a thickness deviation rate of the insulating coating layer is equal to or greater than 50%, in the coated carbon nanotube electric wire.
According to the aspect of the present disclosure, the sectional area of the insulating coating layer in the radial direction is equal to or greater than 0.07 mm2, and the thickness deviation rate of the insulating coating layer is equal to or greater than 55%, in the coated carbon nanotube electric wire. In the aspect, additionally, the proportion of the sectional area of the insulating coating layer in the radial direction with respect to the sectional area of the carbon nanotube wire in the radial direction is equal to or greater than 0.09.
According to the present disclosure, it is possible to obtain a coated carbon nanotube electric wire in which an insulating coating layer has excellent durability against disconnection.
A carbon nanotube wire using a carbon nanotube as a core wire has anisotropic heat conduction unlike the core wire made of metal, and heat is delivered with higher priority in a longitudinal direction than in a radial direction. In other words, since the carbon nanotube wire has anisotropic heat dissipation characteristics, the carbon nanotube wire has more excellent heat dissipation characteristics as compared with the core wire made of metal. Therefore, it is necessary to design the insulating coating layer with which the core wire using the carbon nanotube is coated differently from design of the insulating coating layer of the core wire made of metal. Hereinafter, a coated carbon nanotube electric wire according to an embodiment of the present disclosure will be described with reference to drawings.
As illustrated in
As for the CNT wire 10, it is possible to obtain a stranded wire by bundling a plurality of single-strand wires and twisting the wires from one end a predetermined number of times in a state in which the other end is fixed. The number of twists of the CNT wire 10 is a number of windings per unit length when the plurality of CNT wires 10, 10, . . . are twisted together. In other words, the number of twists can be represented as a value (unit: T/m) obtained by dividing the number of times of twisting (T) by the length of the wires (m). In a case in which the CNT wire 10 is a stranded wire, the number of twists (T/m) of the CNT wire 10 is preferably equal to or less than 1000 and is more preferably equal to or greater than 200 and equal to or less than 1000. If the number of twists of the CNT wire 10 is excessively large, the CNT wire 10 is likely to peel off with an increase in twisting-back force. Thus, it is possible to obtain a coated CNT electric wire 1 with excellent peeling resistance with respect to the CNT wire 10 by the coated CNT electric wire 1 being a stranded wire in which the number of twists of the CNT wire 10 is equal to or less than 100 or being a single-strand wire.
As illustrated in
The CNT aggregates 11 are a bundle of CNTs 11a with layer structures of one or more layers. The longitudinal direction of the CNTs 11a forms the longitudinal direction of the CNT aggregates 11. The plurality of CNTs 11a, 11a, . . . in the CNT aggregates 11 are disposed such that long-axis directions thereof are substantially aligned. Therefore, the plurality of CNTs 11a, 11a, . . . in the CNT aggregates 11 are oriented. The equivalent circle diameter of the CNT aggregates 11 is equal to or greater than 20 nm and equal to or less than 1000 nm, for example, and is more typically equal to or greater than 20 nm and equal to or less than 80 nm. The width dimension of the outermost layer of the CNTs 11a is, for example, equal to or greater than 1.0 nm and equal to or less than 5.0 nm.
The CNTs 11a configuring the CNT aggregates 11 have tubular elements with single-layer structure or a multiple-layer structure, which are called single-walled nanotubes (SWNT) and multi-walled nanotubes (MWNT), respectively. Although
The CNTs 11a with a two-layer structure have three-dimensional mesh structure in which two tubular elements T1 and T2 with hexagonal lattice mesh structures are substantially coaxially disposed and are called double-walled nanotubes (DWNT). Each hexagonal lattice as a constituent unit is a six-membered ring with carbon atoms disposed at apexes thereof, and these are successively coupled to each other with other six-membered rings being adjacent to each other.
Characteristics of the CNTs 11a depend on chirality of the aforementioned tubular elements. Chirality is roughly classified into an armchair type, a zigzag type, and a chiral type, the armchair type exhibits metallic behaviors, the zigzag type exhibits semiconducting and semi-metallic behaviors, and the chiral type exhibits semiconducting and semi-metallic behaviors. Thus, the electroconductivity of the CNTs 11a significantly differs depending on which of chirality the tubular elements have. In order to further improve electroconductivity, it is preferable to increase the proportion of the armchair-type CNTs 11a that exhibit metallic behaviors in the CNT aggregates 11 that configure the CNT wire 10 of the coated CNT electric wire 1.
On the other hand, it is known that the chiral-type CNTs 11a exhibit metallic behaviors by doping the chiral-type CNTs 11a that exhibit semiconducting behaviors with a substance (a different kind of element) with electron donating properties or electron receiving properties. Also, electroconductivity decreases due to occurrence of scattering of conductive electrons inside typical metal by doping the metal with a different kind of element. Similarly, doping the CNTs 11a that have metallic behaviors with a different kind of element leads to a decrease in electroconductivity.
In this manner, an effect of doping of the CNTs 11a that exhibit metallic behaviors and the CNTs 11a that exhibit semiconducting behaviors has a trade-off relationship in terms of electroconductivity. Thus, it is theoretically desirable to separately produce the CNTs 11a that exhibit metallic behaviors and the CNTs 11a that exhibit semiconducting behaviors, performing doping processing only on the CNTs 11a that exhibit semiconducting behaviors, and then combining these. In a case in which the CNTs 11a that exhibit metallic behaviors and the CNTs 11a that exhibit semiconducting behaviors are produced in a coexisting state, it is preferable to select such a layer structure of the CNTs 11a that the doping processing using a different kind of element or molecule becomes effective. In this manner, it is possible to further improve the electroconductivity of the CNT wire 10 made of a mixture of the CNTs 11a that exhibit metallic behaviors and the CNTs 11a that exhibit semiconducting behaviors.
For example, a CNT with a small number of layers, such as a two-layer structure or a three-layer structure, has relatively higher electroconductivity than that of a CNT with a larger number of layers, and the highest doping effect can be achieved in the CNT with the two-layer structure or the three-layer structure when doping processing is performed. Therefore, it is preferable to increase the proportion of CNTs with a two-layer structure or a three-layer structure for the purpose of further improving electroconductivity of the CNT wire 10. Specifically, the proportion of the CNTs with a two-layer structure or a three-layer structure with respect to all the CNTs is preferably equal to or greater than 50% by number and is more preferably equal to or greater than 75% by number. The proportion of CNTs with a two-layer structure or a three-layer structure can be calculated by observing and analyzing the section of the CNT aggregates 11 using a transmission electron microscope (TEM) and measuring the number of layers in each of 100 CNTs.
Next, orientations of the CNTs 11a and CNT aggregates 11 in the CNT wire 10 will be described.
The SAXS is suitable for evaluating a structure and the like of a size of several nm to several tens of nm. For example, it is possible to evaluate orientations of the CNTs 11a with outer diameters of several nm and the CNT aggregates 11 with outer diameters of several tens of nm by analyzing information of an X-ray scattering image by the following method using the SAXS. If an X-ray scattering image of the CNT wire 10 is analyzed, for example, qy that is a y component is relatively narrowly distributed than qx that is an x component of the scattering vector q (q=2π/d: d is a lattice surface interval) of the CNT aggregates 11 as illustrated in
The full-width at half maximum Δθ in azimuth angle is preferably equal to or less than 60° and is particularly preferably equal to or less than 50° in order to apply excellent heat dissipation characteristics to the CNT wire 10 by obtaining a specific or more orientation represented by a full-width at half maximum Δθ in azimuth angle in azimuth plot based on small-angle X-ray scattering (SAXS) representing the orientation of the plurality of CNT aggregates 11, 11, . . . .
According to the present disclosure, since the full-width at half maximum Δθ in azimuth angle in azimuth plot based on small-angle X-ray scattering of the CNT aggregates 11 in the CNT wire 10 is equal to or less than 60°, the CNTs 11a and the CNT aggregates 11 have high orientations in the CNT wire 10, and the CNT wire 10 thus exhibits excellent heat dissipation characteristics.
Next, an alignment structure and density of the plurality of CNTs 11a that configure the CNT aggregates 11 will be described.
The WAXS is suitable for evaluating a structure and the like of a material with a size of equal to or less than several nm. For example, it is possible to evaluate density of the CNTs 11a with outer diameters of equal to or less than several nm by analyzing information of an X-ray scattering image by the following method using the WAXS. As a result of analyzing a relationship between a scattering vector q and intensity for an arbitrary one CNT aggregate 11, a value of a lattice constant estimated from the q value of the peak top at the (10) peak observed near q=3.0 nm−1 to 4.0 nm−1 is measured as illustrated in
Since the plurality of CNT aggregates 11, 11, . . . have satisfactory orientations and the plurality of CNTs 11a, 11a, . . . that configure the CNT aggregates 11 are aligned with regularity and are disposed with high density as described above, the heat from the CNT wire 10 is likely to be discharged while smoothly delivered along the longitudinal direction of the CNT aggregates 11. Therefore, since it is possible to adjust the heat dissipation route in the longitudinal direction and the radial sectional direction by adjusting the alignment structures and the density of the CNT aggregates 11 and the CNTs 11a, the CNT wire 10 exhibits excellent heat dissipation characteristics as compared with the core wire made of metal.
The q value of the peak top at the (10) peak of the intensity based on the X-ray scattering indicating density of the plurality of CNTs 11a, 11a, . . . is preferably equal to or greater than 2.0 nm−1 and equal to or less than 5.0 nm−1, and the full-width at half maximum Δq is preferably equal to or greater than 0.1 nm−1 and equal to or less than 2.0 nm−1 in order to apply excellent heat dissipation characteristics by obtaining high density.
According to the present disclosure, since the q value of the peak top at the (10) peak of the scattering intensity based on X-ray scattering of the oriented carbon nanotubes is equal to or greater than 2.0 nm−1 and equal to or less than 5.0 nm−1, and the full-width at half maximum Δq is equal to or greater than 0.1 nm−1 and equal to or less than 2.0 nm−1, the CNTs 10 can be present at high density, and the CNT wire 10 thus exhibits excellent heat dissipation characteristics.
The orientations of the CNT aggregates 11 and the CNTs 11a and the alignment structure and the density of the CNTs 11a can be adjusted by appropriately selecting a spinning method such as dry spinning, wet spinning, or liquid crystal spinning and spinning conditions for the spinning method, which will be described later.
Next, the insulating coating layer 21 with which the outer surface of the CNT wire 10 will be described.
As a material of the insulating coating layer 21, a material with high elasticity can be used, an examples thereof include a thermoplastic resin and a thermosetting resin. Examples of the thermoplastic resin includes polytetrafluoroethylene (PTFE) (Young's modulus: 0.4 to 0.6 GPa), polyethylene (Young's modulus: 0.1 to 1.0 GPa), polypropylene (Young's modulus: 1.1 to 1.4 GPa), polyacetal (Young's modulus: 2.8 GPa), polystyrene (Young's modulus: 2.4 to 3.5 GPa), polycarbonate (Young's modulus: 2.5 GPa), polyamide (Young's modulus: 1.1 to 2.9 GPa), polyvinyl chloride (Young's modulus: 2.5 to 4.2 GPa), polymethyl methacrylate (Young's modulus: 3.2 GPa), polyurethane (Young's modulus: 0.07 to 0.7 GPa), and the like. Examples of the thermosetting resin include polyimide (2.1 to 2.8 GPa), a phenol resin (5.2 to 7.0 GPa), and the like. One of these may be used alone, or two or more of these may appropriately be mixed and used. Although the Young's modulus of the material configuring the insulating coating layer 21 is not particularly limited, the Young's modulus is preferably equal to or greater than 0.07 GPa and equal to or less than 7 GPa and is particularly preferably equal to or greater than 0.07 GPa and equal to or less than 4 GPa, for example.
The insulating coating layer 21 may include one layer as illustrated in
In the coated CNT electric wire 1, the insulating coating layer 21 has excellent durability against disconnection since the proportion of the Young's moduli is equal to or greater than 0.001 and equal to or less than 0.01. Also, since the CNT wire 10 has a reduced weight as compared with a case in which a core wire is made of copper, aluminum, or the like, and the thickness of the insulating coating layer 21 can be reduced, it is possible to reduce the weight of the electric wire coated with the insulating coating layer and to obtain excellent heat dissipation characteristics with respect to a heat of the CNT wire 10 without degrading insulation reliability.
Also, the proportion of the sectional area of the insulating coating layer 21 in the radial direction with respect to the sectional area of the CNT wire 10 in the radial direction is preferably within a range of equal to or greater than 0.02 and equal to or less than 10 in the coated CNT electric wire 1. Although the proportion of the sectional areas is not particularly limited as long as the proportion is within the range of equal to or greater than 0.02 and equal to or less than 10, a lower limit value of the proportion is preferably 0.2 and is particularly preferably 0.3 in terms of a balance between insulation reliability and durability. On the other hand, an upper limit value of the proportion of the sectional areas is preferably 1.0 and is particularly preferably 0.7 in order to further reduce the weight of the coated CNT electric wire 1 and to further improve heat dissipation characteristics with respect to a heat of the CNT wire 10.
According to the present disclosure, since the proportion of the sectional area of the insulating coating layer 21 in the radial direction with respect to the sectional area of the CNT wire 10 in the radial direction is equal to or greater than 0.02 and equal to or less than 10, it is possible to obtain a coated CNT electric wire 1 that enables further weight reduction and exhibits excellent heat dissipation characteristics without degrading insulation reliability.
Although there is a case in which it is difficult to maintain the shape in the longitudinal direction only with the CNT wire 10 alone, the coated CNT electric wire 1 can maintain the shape in the longitudinal direction, and deformation working such as bending working can easily be performed thereon since the outer surface of the CNT wire 10 is coated with the insulating coating layer 21 at the aforementioned proportion of the sectional area. Therefore, it is possible to form the coated CNT electric wire 1 into a shape along a desired wiring route.
Further, since minute unevenness is formed on the outer surface of the CNT wire 10, adhesiveness between the CNT wire 10 and the insulating coating layer 21 is improved, and it is possible to curb peeling-off between the CNT wire 10 and the insulating coating layer 21, as compared with a coated electric wire using a core wire made of aluminum or copper.
Although the sectional area of the CNT wire 10 in the radial direction is not particularly limited in a case in which the proportion of the sectional areas is within the range of equal to or greater than 0.02 and equal to or less than 10, the sectional area is preferably equal to or greater than 0.0003 mm2 and equal to or less than 100 mm2 and is particularly preferably equal to or greater than 0.001 mm2 and equal to or less than 10 mm2, for example. Also, although the sectional area of the insulating coating layer 21 in the radial direction is not particularly limited, the sectional area is preferably equal to or greater than 0.00005 mm2 and equal to or less than 50 mm2 and is particularly preferably equal to or greater than 0.0005 mm2 and equal to or less than 5 mm2, for example, in terms of a balance between insulation reliability and durability. In addition, an average thickness of the insulating coating layer 21 is preferably equal to or greater than 0.001 mm and equal to or less than 1 mm and is particularly preferably equal to or greater than 0.01 mm and equal to or less than 0.1 mm. The sectional areas can be measured from a scanning electron microscope (SEM) observation image, for example. Specifically, an SEM image (100 times to 10,000 times) of a section of the coated CNT electric wire 1 in the radial direction is obtained, and an area obtained by subtracting the area of the material of the insulating coating layer 21 incorporated in the CNT wire 10 from the area of the portion surrounded by the periphery of the CNT wire 10 and a total of the area of the portion corresponding to the insulating coating layer 21, with which the periphery of the CNT wire 10 is coated, and the area of the material of the insulating coating layer 21 incorporated in the CNT wire 10 are defined as the sectional area of the CNT wire 10 in the radial direction and the sectional area of the insulating coating layer 21 in the radial direction, respectively. The sectional area of the insulating coating layer 21 in the radial direction also includes the resin incorporated into the CNT wire 10.
The Young's modulus of the CNTs is higher than the Young's moduli of aluminum and copper used in core wires in the related art. While the Young's modulus of aluminum is 70.3 GPa and the Young's modulus of copper is 129.8 GPa, the Young's modulus of the CNTs is 300 to 1500 GPa, which is a value that is about equal to or greater than a double. Therefore, it is possible to use a material with a high Young's modulus (a thermoplastic resin with a high Young's modulus) as the material of the insulating coating layer 21 in the coated CNT electric wire 1 as compared with a coated electric wire using aluminum or copper for the core wire, it is possible to apply excellent abrasion resistance to the insulating coating layer 21 in the coated CNT electric wire 1, and the coated CNT electric wire 1 exhibits excellent durability.
As described above, the Young's modulus of the CNTs is higher than the Young's moduli of aluminum and copper used as the core wire in the related art. Thus, the proportion of the Young's modulus of the material configuring the insulating coating layer with respect to the Young's modulus of the core wire in the coated CNT electric wire 1 is smaller than the proportion of the Young's moduli of the coated electric wire using aluminum or copper in the core wire. Therefore, it is possible to further curb peeling-off of the CNT wire 10 and the insulating coating layer 21 and cracking of the insulating coating layer 21 even if the coated CNT electric wire 1 is repeatedly bent, as compared with the coated electric wire using aluminum or copper in the core wire.
The proportion of the Young's modulus of the material configuring the insulating coating layer 21 with respect to the Young's modulus of the CNT wire 10 is equal to or greater than 0.001 and equal to or less than 0.01. The Young's modulus of the CNT wire 10 and the Young's modulus of the material configuring the insulating coating layer 21 can be measured by causing a coating of the coated CNT electric wire, for example, to peel and conducting a tensile test by a method in accordance with JIS K7161-1 on the coating used as a sample. Although the proportion of the Young's moduli is not particularly limited as long as the proportion is within the range of equal to or greater than 0.001 and equal to or less than 0.01, the range is preferably equal to or greater than 0.0015 and equal to or less than 0.005 and is particularly preferably equal to or greater than 0.002 and equal to or less than 0.0035 as a range in which durability of the coated CNT electric wire 1 tends to be improved.
The thickness of the insulating coating layer 21 in a direction that perpendicularly intersect the longitudinal direction thereof (that is, the radial direction) is preferably uniformized in order to improve mechanical strength such as abrasion resistance of the coated CNT electric wire 1. Specifically, the thickness deviation rate of the insulating coating layer 21 is preferably equal to or greater than 50%, and is particularly preferably equal to or greater than 55%. According to the present disclosure, since the thickness deviation rate of the insulating coating layer 21 is equal to or greater than 50%, the thickness of the insulating coating layer 21 is uniformized, and a coated CNT electric wire 1 with excellent mechanical strength such as abrasion resistance and bendability of the coated CNT electric wire 1 is thus obtained. Further, abrasion resistance of the coated CNT electric wire 1 is further improved by the thickness deviation rate of the insulating coating layer 21 being greater than 55%.
Also, durability is likely to be improved by further appropriately controlling parameters in relation to sectional areas in addition to the thickness deviation rate of the insulating coating layer 21. In particular, it is preferable that the sectional area of the insulating coating layer 21 in the radial direction be equal to or greater than 0.07 mm2 and the thickness deviation rate of the insulating coating layer 21 be equal to or greater than 55%, and in this manner, it is possible to further improve durability of the coated CNT electric wire 1.
Further, in a case in which the sectional area of the CNT wire 10 in the radial direction is also taken into consideration, the proportion of the sectional area of the insulating coating layer 21 in the radial direction with respect to the sectional area of the CNT wire 10 in the radial direction is preferably equal to or greater than 0.09. Note that the “thickness deviation rate” means a value obtained by calculating a value α=(a minimum thickness value of the insulating coating layer 21/a maximum thickness value of the insulating coating layer 21)×100 for each of the same sections in the radial direction at every 10 cm from arbitrary 1.0 m of the coated CNT electric wire 1 on the center side in the longitudinal direction and averaging the values α calculated for the respective sections. Also, the thickness of the insulating coating layer 21 can be measured from an SEM observation image by circularly approximating the CNT wire 10, for example. Here, the center side in the longitudinal direction indicates a region located at the center when seen in the longitudinal direction of the wire.
The thickness deviation rate of the insulating coating layer 21 can be improved by increasing a degree of tension of the CNT wire 10 passing through a die in an extrusion process in the longitudinal direction in a case in which the insulating coating layer 21 is formed on the peripheral surface of the CNT wire 10 using extrusion coating, for example.
Next, an exemplary method of manufacturing the coated CNT electric wire 1 according to the embodiment of the present disclosure will be described. The coated CNT electric wire 1 can be manufactured by manufacturing the CNTs 11a first, forming the CNT wire 10 from the plurality of obtained CNTs 11a, and coating the peripheral surface of the CNT wire 10 with the insulating coating layer 21.
The CNTs 11a can be produced by a method such as a floating catalyst method (U.S. Pat. No. 5,819,888) or a substrate method (U.S. Pat. No. 5,590,603). The single wire of the CNT wire 10 can be produced by dry spinning (Japanese Patent Nos. 5819888, 5990202, and 5350635), wet spinning (Japanese Patent Nos. 5135620, 5131571, and 5288359), liquid crystal spinning (National Publication of International Patent Application No. 2014-530964), or the like.
As a method of coating the peripheral surface of the thus obtained CNT wire 10 with the insulating coating layer 21, a method of coating a core wire of aluminum or copper with an insulating coating layer can be used, and examples thereof include a method of melting a thermoplastic resin that is a raw material of the insulating coating layer 21 and extruding the thermoplastic resin around the CNT wire 10 to coat the CNT wire 10 with the thermoplastic resin.
The coated CNT electric wire 1 according to the embodiment of the present disclosure can be used as a general electric wire such as a wire harness, and also, a cable can be produced from the general electric wire using the coated CNT electric wire 1.
Although examples of the present disclosure will be described below, the present disclosure is not limited to the following examples without departing from the gist of the present disclosure.
First, a single wire (single-strand wire) of a CNT wire with an equivalent circle diameter of 0.2 mm was obtained by a dry spinning method (Japanese Patent No. 5819888) or a wet spinning method (Japanese Patent Nos. 5135620, 5131571, and 5288359) in which CNTs produced by the floating catalyst method were spun directly. Also, the CNT wire with an equivalent circle diameter of greater than 0.2 mm was obtained by adjusting the number of CNT wires with an equivalent circle diameter of 0.2 mm and appropriately twisting the CNT wires to obtain a stranded wire.
Concerning Method of Coating Outer Surface of CNT Wire with Insulating Coating Layer
The insulating coating layer was formed by extrusion-coating the surroundings of the conductive element with a type of resin for the insulating coating layer shown in Table 1 below using an ordinary electric wire manufacturing extrusion molding machine, and the coated CNT electric wire used in Examples 1 to 12 and Comparative Examples 1 to 5 in Table 1 below was produced.
Polypropylene: Sumitomo Noblen (registered trademark) manufactured by Sumitomo Chemical Co., Ltd.
Polystyrene: HIPS manufactured by PS Japan Corporation
Polyimide: AURUM PL450C manufactured by Mitsui Chemicals, Inc.
Polyvinyl chloride: Sekisui PVC-HA manufactured by Sekisui Chemical Co., Ltd.
Polyurethane: TPU3000EA manufactured by Totoku Toryo Co. Ltd.
PTFE: Fluon manufactured by Asahi Kasei Corporation
Filler-containing polyphenylene sulfide (PPS): TPS (registered trademark) PPS manufactured by Toray Plastics Precision Co., Ltd.
A section of the CNT wire in the radial direction was cut using an ion milling device (IM4000 manufactured by Hitachi High-Tech Corporation), and the sectional area of the CNT wire in the radial direction was then measured from an SEM image obtained by a scanning electron microscope (SU8020 manufactured by Hitachi High-Tech Corporation, magnification: 100 times to 10,000 times). Similar measurement was repeated at every 10 cm from arbitrary 1.0 m of the coated CNT electric wire on the center side in the longitudinal direction, and an average value thereof was defined as a sectional area of the CNT wire in the radial direction. Note that the resin incorporated in the CNT wire was not included in the sectional area of the CNT wire.
A section of the CNT wire in the radial direction was cut using an ion milling device (IM4000 manufactured by Hitachi High-Tech Corporation), and the sectional area of the insulating coating layer in the radial direction was then measured from an SEM image obtained by a scanning electron microscope (SU8020 manufactured by Hitachi High-Tech Corporation, magnification: 100 times to 10,000 times). Similar measurement was repeated at every 10 cm from arbitrary 1.0 m of the coated CNT electric wire on the center side in the longitudinal direction, and an average value thereof was defined as a sectional area of the insulating coating layer in the radial direction. Therefore, a resin incorporated in the CNT wire was also included in the sectional area of the insulating coating layer.
A coating layer of 1.0 m of coated CNT electric wire was caused to peel off, and 5 cm test pieces were collected from each of the separated coating and the CNT wire at every 20 cm in the longitudinal direction. A tensile test was conducted by the method in accordance with JIS K7161-1, and the Young's modulus of the material configuring the separated coating and the Young's modulus of the CNT wire were obtained. The aforementioned proportion of Young's moduli was calculated from a value obtained by averaging the Young's modulus of the material configuring the coating and the Young's modulus of the CNT wire.
X-ray scattering measurement was conducted using a small-angle X-ray scattering device (Aichi Synchrotron), and a full-width at half maximum Δθ in azimuth angle was obtained from the obtained azimuth plot.
Wide-angle X-ray scattering measurement was performed using a wide-angle X-ray scattering device (Aichi Synchrotron), and a q value and a full-width at half maximum Δq of the peak top at the (10) peak of intensity were obtained from the obtained q-value-intensity graph.
A value α=(a minimum thickness value of the insulating coating layer/a maximum thickness value of the insulating coating layer)×100 was calculated for the same section in the radial direction at every 10 cm from arbitrary 1.0 m of the coated CNT electric wire on the center side in the longitudinal direction, and the thickness deviation rate was measured using the value obtained by averaging the values a calculated in the respective sections. Also, the thickness of the insulating coating layer can be measured from an SEM observation image as a shortest distance between an interface of the circle-approximated CNT wire 10 and the insulating coating layer 21, for example.
Results of the aforementioned measurement performed on the coated CNT electric wires wire are shown in Table 1 below.
The coated CNT electric wires produced as described above were evaluated as follows.
Four terminals were connected to both ends of a 100 cm coated CNT electric wire, and resistance was measured by a four-terminal method. At this time, an applied current was set to 2000 A/cm2, and a temporal change in resistance value was recorded. Resistance values at the time of starting the measurement and after elapse of 10 minutes were compared, and an increase rate was calculated. Since the resistance of the CNT electric wire increases in proportion to a temperature, it is possible to determine that the CNT electric wire with a smaller resistance increase rate has more excellent heat dissipation characteristics. The resistance increase rate of less than 7% was evaluated as “◯” representing excellent heat dissipation characteristics.
Evaluation was conducted by the method in accordance with Article 13.3 of JIS C3215-0-1. Test results that satisfied the grade 2 or more described in Table 9 in Article 13.3 were evaluated as “◯”, test results that satisfied the grade 1 were evaluated as “Δ”, test results that satisfied no grades were evaluated as “×”, and the evaluation results of equal to or higher than “Δ” were evaluated as satisfactory insulation reliability.
A resistance value of a 20 cm coating wire was measured. The coating wire was then bent 500 times under conditions of a load of 500 gf, a bending speed of about 1 time/second, and a left and right bending angle of 90°. Note that the bending radius r was set to six times (r=6D) the conductive element diameter D. Next, the resistance value was measured again. A result that a value obtained by dividing the resistance value after the bending by the resistance value before the bending was less than 1.2 was evaluated as “⊙”, a result that the value was equal to or greater than 1.2 and less than 1.5 was evaluated as “◯”, a result that the value was equal to or greater than 1.5 and less than 1.8 was evaluated as “Δ”, a result that the value was equal to or greater than 1.8 was evaluated as “×”, and results evaluated as “Δ” and higher were evaluated as exhibiting excellent durability.
Results of the aforementioned evaluation are shown in Table 1 below.
As shown in Table 1 above, coated CNT electric wires with excellent durability were obtained regardless of which of polypropylene, polystyrene, polyimide, and polyvinyl chloride the resin types are in Examples 1 to 12 in each of which the proportion of the Young's modulus of the material configuring the insulating coating layer with respect to the Young's modulus of the CNT wire was equal to or greater than 0.001 and equal to or less than 0.01. Also, the coated CNT electric wires with excellent heat dissipation characteristics were obtained without degrading insulation reliability. The coated CNT electric wires with more excellent durability were obtained in Examples 3, 6, and 9 in each of which the sectional area of the insulating coating layer was equal to or greater than 0.07 mm2, the thickness deviation rate was equal to or greater than 55%, and further, the proportion of the sectional area of the insulating coating layer in the radial direction with respect to the sectional area of the CNT wire in the radial direction was equal to or greater than 0.09, in particular.
Further, since all the full-widths at half maximum Δθ in azimuth angle were equal to or less than 60° in Examples 1 to 12. Therefore, the CNT aggregates had excellent orientations in the CNT wires in Examples 1 to 12. Further, all the q values of the peak tops at the (10) peaks of intensity were equal to or greater than 2.0 nm−1 and equal to or less than 5.0 nm−1, and all the full-widths at half maximum Δq were equal to or greater than 0.1 nm−1 and equal to or less than 2.0 nm−1 in Examples 1 to 12. Therefore, the CNTs also had excellent orientations in the CNT wires in Examples 1 to 12.
On the other hand, no durability against disconnection of the insulating coating was obtained in Comparative Examples 1 to 4 in each of which the proportion of the Young's modulus of the material configuring the insulating coating layer with respect to the Young's modulus of the CNT wire is less than 0.001. Also, In Comparative Example 5 in which the proportion of the Young's modulus of the material configuring the insulating coating layer with respect to the Young's modulus of the CNT wire exceeds 0.01, cracking was likely to occur due to the hard insulating coating layer, and similarly, durability against disconnection of the insulating coating was not obtained.
Next, coated CNT electric wires were produced by changing the sectional area of the insulating coating layer in the radial direction as shown in Table 2 below.
A metal wire made of aluminum (Al) and a metal wire made of copper (Cu) were used in Comparative Examples 6 and 7, respectively, instead of using the CNT wire in the core wire.
All the sectional areas of the CNT wires, the sectional areas of the insulating coating layers, the proportions of the Young's moduli of the materials configuring the insulating coating layers/the Young's moduli of the CNT wires, and the thickness deviation rates were measured by methods that were similar to the methods used in Examples 1 to 12.
The aforementioned evaluation (1) to (3) was similarly conducted on the coated CNT electric wires in Examples 13 to 24, the coated Al electric wire, and the coated Cu electric wire.
The following evaluation was conducted on the coated CNT electric wires, the coated Al electric wire, and the coated Cu electric wire produced as described above.
Evaluation was conducted by the method in accordance with Article 6 of JIS C3216-3. Test results that satisfied the grade 2 described in Table 1 in JIS C3215-4 were evaluated as “◯”, test results that satisfied the grade 1 were evaluated as “Δ”, test results that satisfied no grades were evaluated as “×”, and the evaluation results of equal to or higher than “Δ” were evaluated as satisfactory abrasion resistance.
Note that all heat dissipation characteristics, insulation reliability, and durability were evaluated by the evaluation methods that were similar to the evaluation methods used in Examples 1 to 12.
Results of the aforementioned evaluation are shown in Table 2 below.
As shown in Table 2 above, coated CNT electric wires with excellent durability were obtained similarly to Table 1 regardless of which of polypropylene, polystyrene, polyimide, and polyvinyl chloride the resin types were in Examples 13 to 24 in each of which the proportion of the sectional area of the insulating coating layer in the radial direction with respect to the cross sectional are of the carbon nanotube wire in the radial direction was changed. In Examples 15, 18, and 21 in each of which the sectional area of the insulating coating layer in the radial direction was equal to or greater than 0.07 mm2, the thickness deviation rate was equal to or greater than 55%, and further, the proportion of the sectional area of the insulating coating layer in the radial direction with respect to the sectional area of the CNT wire in the radial direction was equal to or greater than 0.09, in particular, more excellent durability was obtained. Also, in any of Examples 13 to 24, CNT coated electric wires with excellent heat dissipation characteristics as well were obtained without degrading insulation reliability. Further, the thicknesses of the insulating coating layers were uniformized, coated CNT electric wires with excellent abrasion resistance were obtained, by the thickness deviation rate of the insulating coating layer being equal to or greater than 50%, and in particular, more excellent abrasion resistance was achieved in a case in which the thickness deviation rate was equal to or greater than 57%.
On the other hand, it was not possible to obtain insulation reliability in Comparative Examples 6 and 7 in which metal wires were used instead of the CNT wires in the core wire. Also, durability was degraded regardless of the proportions of the Young's moduli of the materials configuring the insulating coating layers with respect to the Young's moduli of the CNT wires being equal to or greater than 0.001 and equal to or less than 0.01. Further, abrasion resistance was also degraded regardless of the thickness deviation rate being equal to or greater than 80%.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-207658 | Oct 2017 | JP | national |
The present application is a continuation application of International Patent Application No. PCT/JP2018/039970 filed on Oct. 26, 2018, which claims the benefit of Japanese Patent Application No. 2017-207658, filed on Oct. 26, 2017. The contents of these applications are incorporated herein by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2018/039970 | Oct 2018 | US |
| Child | 16857349 | US |
