Coating liquid and badminton string

Abstract

Provided are: a badminton string excellent in abrasion resistance; a coating liquid used for production of the badminton string; and a method for producing the badminton string.　The coating liquid contains a nylon resin, carbon nanotubes, and a solvent, the content of the carbon nanotubes being 0.005-0.1 mass%.

Description

Coating Liquid and Badminton String

[0001] The present disclosure relates to a coating liquid and a badminton string.

[0002] Badminton rackets are advancing in high performance such as weight reduction, and various studies have been conducted on badminton strings strung on the rackets. For example, in Patent Document 1, a badminton string is proposed that features a polyamide multifilament composed of a large number of single filaments of 15 decitex or less coated with a copolymer type thermoplastic resin as a core yarn.

[0003] Japanese Patent Application Laid-Open No. 2005-304678

[0004] Among the main physical properties required for badminton strings, there have been particularly many demands for improvement in wear resistance from users. Therefore, an object of the present disclosure is to provide a badminton string excellent in wear resistance, a coating liquid used in manufacturing the badminton string, and a method for manufacturing the badminton string.

[0005] As a result of intensive research, the present inventors have found that a badminton string excellent in wear resistance can be obtained by using a coating liquid containing a nylon resin, carbon nanotubes, and a solvent, and have completed the present invention.

[0006] In other words, the present invention relates, for example, to the following [1] to [5]: [1] A coating solution comprising a nylon resin, carbon nanotubes, and a solvent, wherein the carbon nanotube content is 0.005 to 0.1% by mass. [2] The coating solution according to [1], wherein the solvent is an organic solvent. [3] A badminton string having a coating layer comprising a nylon resin and carbon nanotubes, wherein the mass ratio of carbon nanotubes to nylon resin (carbon nanotubes: nylon resin) in the coating layer is 1:150 to 1:5000. [4] The badminton string according to [3], wherein the badminton string comprises a core thread and a side thread, and the coating layer is present on at least one surface of the core thread and the side thread. [5] A method for manufacturing a badminton string, comprising the step of coating the surface of at least one of the core thread and the side thread with the coating solution according to [1] or [2].

[0007] According to the present invention, it is possible to provide a badminton string with excellent abrasion resistance, a coating liquid used in the manufacture of the badminton string, and a method for manufacturing the badminton string.

[0008] Figure 1 is a schematic diagram showing one embodiment of the badminton string of the present disclosure.

[0009] The upper and / or lower limits of the numerical ranges described herein can be arbitrarily combined to define a preferred range. For example, the upper and lower limits of the numerical ranges can be arbitrarily combined to define a preferred range, the upper limits of the numerical ranges can be arbitrarily combined to define a preferred range, and the lower limits of the numerical ranges can be arbitrarily combined to define a preferred range.

[0010] Throughout this specification, singular expressions should be understood to include the concept of their plural form unless otherwise specified. Therefore, singular articles (for example, "a," "an," and "the" in English) should be understood to include the concept of their plural form unless otherwise specified.

[0011] In this specification, unless otherwise specified, each component may be used independently, individually, or in combination of two or more.

[0012] In this specification, "carbon nanotube" refers to a cylindrical structure made of graphene sheets. Carbon nanotubes are sometimes referred to as "CNTs".

[0013] In this specification, "single-walled carbon nanotube" refers to a carbon nanotube having one layer of tube structure. "Multi-walled carbon nanotube" refers to a carbon nanotube having two or more layers of tube structure, preferably 2 to 20 layers, more preferably 3 to 15 layers.

[0014] <Coating Solution> The coating solution of the present invention contains nylon resin, carbon nanotubes, and a solvent, with a carbon nanotube content of 0.005 to 0.1% by mass. The coating solution of the present invention is typically used in the manufacturing process of badminton strings. Specifically, the coating solution is used to coat the core threads and side threads of badminton strings. When coating the side threads with the coating solution, the side threads may be coated before braiding or after braiding.

[0015] There are no particular restrictions on the nylon resin, but examples include nylon 6, nylon 66, nylon 11, nylon 12, nylon 46, and nylon 610. In one preferred embodiment, the nylon resin contained in the coating liquid is the same as the material to be coated.

[0016] The amount of nylon resin contained in the coating liquid is, for example, 5 to 45% by mass, preferably 7 to 40% by mass, and more preferably 10 to 30% by mass. This range is preferable because it provides excellent coating properties and abrasion resistance for the resulting badminton strings.

[0017] The following provides a detailed explanation of CNTs. CNTs may be single-walled carbon nanotubes or multi-walled carbon nanotubes with two or more layers. Preferably, CNTs are multi-walled carbon nanotubes. The number of layers in the multi-walled carbon nanotube is not particularly limited, but preferably 2 to 20 layers.

[0018] The average length of the CNTs is preferably 10 to 1000 μm, more preferably 30 to 800 μm, and even more preferably 50 to 500 μm. The average length of the CNTs can be adjusted, for example, by adjusting the time spent performing the CVD method described later, i.e., the CNT growth time.

[0019] The average diameter of the CNTs is preferably 1 to 50 nm, more preferably 3 to 30 nm, and even more preferably 5 to 15 nm. The average diameter of the CNTs can be adjusted, for example, by adjusting the thickness of the catalyst layer and the type of catalyst, as described later.

[0020] The average length and average diameter of a carbon nanotube (CNT) are measured using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Specifically, ten images of the CNT are obtained using an SEM or TEM. Ten arbitrary measurement points are selected for each of the ten images, and the lengths of all 100 points are measured. The average length of the CNT is then calculated by arithmetic mean of these 100 measurement points. Similarly, ten arbitrary measurement points are selected for each of the ten images, and the diameters of all 100 points are measured. The average diameter of the CNT is then calculated by arithmetic mean of these 100 measurement points.

[0021] The carbon purity of CNTs is preferably 95.0 to 99.999%. The lower limit of carbon purity of CNTs is preferably 96.0%, more preferably 97.0%, even more preferably 98.0%, even more preferably 99.0%, and particularly preferably 99.8%. The upper limit of carbon purity of CNTs may be, for example, 99.99% or 99.9%. The carbon purity of CNTs can be determined, for example, by elemental analysis using X-ray fluorescence.

[0022] The crystallinity of carbon nanotubes (CNTs) can be evaluated, for example, using Raman spectroscopy. In Raman spectroscopy, the D / G ratio is used as an indicator for evaluating crystallinity. The D / G ratio is the value at 1580 cm⁻¹ in the Raman spectrum measured by Raman spectroscopy. -1 1360 cm⁻¹ relative to the peak intensity of the G-band appearing in the vicinity -1 This is the ratio of the peak intensities of the D band appearing in the vicinity. A smaller D / G ratio indicates higher crystallinity of the carbon nanotube. The D / G ratio in CNTs is preferably 0.5 to 1.0, more preferably 0.6 to 0.8.

[0023] The carbon purity and crystallinity of the CNTs can be adjusted, for example, by adjusting the thickness of the buffer layer in the catalyst substrate, the type of material used in the buffer layer, the thickness of the catalyst layer, the type of catalyst, the type and flow rate of the raw material gas in the CVD method, and the temperature and pressure in the reaction chamber, as described later.

[0024] CNTs can be manufactured using conventionally known methods. For example, CNTs can be manufactured using chemical vapor deposition (CVD) methods such as thermochemical vapor deposition (thermal CVD) and plasma CVD, laser ablation, arc discharge, or combustion. Among the CVD methods, thermal CVD is preferred.

[0025] The CVD method involves placing a catalyst substrate, which has a catalyst layer provided on a substrate, into a reaction chamber, supplying a raw material gas to the reaction chamber, and growing CNTs as a CNT forest on the surface of the catalyst layer. A CNT forest refers to an aggregate of multiple CNTs provided on a substrate and oriented perpendicular to the surface of the substrate. In a CNT forest, multiple CNTs stand upright on the substrate. The average length and average diameter of the CNTs in the CNT forest are, for example, the same as the average length and average diameter of the CNTs described above. CNT powder is obtained by scraping the CNT forest from the substrate. CNT powder means powder containing multiple CNTs.

[0026] Examples of substrates include silicon substrates, alumina substrates, magnesium oxide substrates, glass substrates, sapphire substrates, and stainless steel substrates.

[0027] The catalyst layer can be formed, for example, by attaching catalyst particles to a substrate by sputtering. Examples of catalysts include metals, specifically iron (Fe), nickel (Ni), cobalt (Co), molybdenum (Mo), gold (Au), and alloys containing at least one metal selected from the group consisting of these. Examples of alloys include iron alloys, nickel alloys, and cobalt alloys. The catalyst may also be a metal precursor, such as a metal oxide or metal compound. Examples of metal oxides include iron oxide, nickel oxide, and cobalt oxide. An example of a metal compound is iron chloride. When using a precursor, it is necessary to convert the precursor to a metal before performing the CVD method, for example, by heating it.

[0028] The catalyst substrate described above may further include a buffer layer between the substrate and the catalyst layer. The buffer layer can be formed, for example, by sputtering. Examples of materials used for the buffer layer include silica (SiO2), alumina (Al2O3), silicon nitride (SiN), zinc oxide (ZnO), copper oxide (Cu2O), and nickel oxide (NiO).

[0029] Sputtering for forming a catalyst layer and sputtering for forming a buffer layer can be carried out using known equipment and conditions depending on the object to be sputtered. The pressure conditions for sputtering are, for example, about 0.001 to 100 Pa.

[0030] As the raw material gas, carbon-containing raw material gases can be used, and examples include hydrocarbons, sulfur-containing organic gases, phosphorus-containing organic gases, carbon monoxide, and alcohols. Examples of hydrocarbons include alkane compounds such as methane and ethane, alkene compounds such as ethylene and butadiene, alkyne compounds such as acetylene, aryl hydrocarbon compounds such as benzene, toluene, and styrene, aromatic hydrocarbons having condensed rings such as indene, naphthalene, and phenanthrene, cycloalkane compounds such as cyclopropane and cyclohexane, cycloolefin compounds such as cyclopentene, and alicyclic hydrocarbon compounds having condensed rings such as steroids. Examples of alcohols include methanol and ethanol. From the viewpoint of the carbon purity of the resulting CNTs, the raw material gas is preferably hydrocarbons.

[0031] Along with the raw material gas, a carrier gas, which is a gas that transports the raw material gas, may also be supplied to the reaction chamber. Examples of carrier gases include helium, neon, argon, nitrogen, and hydrogen.

[0032] In the CVD method, the temperature in the reaction chamber is, for example, 550 to 900°C, from the viewpoint of the growth rate of CNTs and the carbon purity of the resulting CNTs.

[0033] The pressure inside the reaction chamber in the CVD process may be atmospheric pressure, reduced pressure, or pressurized pressure.

[0034] The amount of CNTs contained in the coating liquid is 0.005 to 0.1% by mass, preferably 0.007 to 0.08% by mass, and more preferably 0.009 to 0.05% by mass. This range is preferable because it provides excellent coating properties and abrasion resistance for the resulting badminton strings.

[0035] In the coating solution, the mass ratio of CNTs to nylon resin (carbon nanotubes: nylon resin) is, from the viewpoint of abrasion resistance of badminton strings, for example, 1:150 to 1:5000, preferably 1:200 to 1:4500, and more preferably 1:250 to 1:3000.

[0036] The solvent can be any solvent that can dissolve the nylon resin, and there are no particular restrictions, but organic solvents are preferred, such as xylol and phenols.

[0037] The amount of solvent contained in the coating solution is, for example, 54 to 94% by mass, preferably 59 to 92% by mass, and more preferably 69 to 89% by mass. This range is preferable because it provides excellent coating properties and abrasion resistance for the resulting badminton strings.

[0038] The coating solution of the present invention contains the aforementioned nylon resin, carbon nanotubes, and solvent, but may also contain other components. Examples of other components include various additives that can be used in coating solutions used in the manufacture of badminton strings. Examples of other components include color inhibitors, antioxidants, defoamers, pigments, dyes, and ultraviolet absorbers. The coating solution may contain one or more of these other components. If the coating solution contains other components, the amount of these other components is, for example, 0.01 to 5% by mass, preferably 0.05 to 3% by mass, and more preferably 0.1 to 1% by mass.

[0039] There are no particular limitations on the method for producing the coating liquid of the present invention, but for example, one method is to first mix the components other than CNTs contained in the coating liquid to prepare the solution, then add the CNTs and disperse the CNTs. For example, dispersion of the CNTs is preferably done using a three-roll machine.

[0040] <Badminton String> The badminton string of the present invention has a coating layer containing nylon resin and carbon nanotubes, and the mass ratio of carbon nanotubes to nylon resin (carbon nanotubes: nylon resin) in the coating layer is 1:150 to 1:5000. The badminton string of the present invention has excellent abrasion resistance due to having the coating layer. The reason why the badminton string of the present invention has excellent abrasion resistance is not clear, but it is presumed that the nylon resin contained in the coating liquid causes the CNTs to integrate sufficiently with the coated object, and the performance of the CNTs is fully exhibited. The mass ratio of carbon nanotubes to nylon resin (carbon nanotubes: nylon resin) in the coating layer is preferably 1:200 to 1:4500, and more preferably 1:250 to 1:3000.

[0041] Badminton strings include a core thread and a side thread, and preferably have the coating layer on at least one surface of the core thread and the side thread, and more preferably have the coating layer on both the core thread surface and the side thread surface. The badminton string of the present invention, by having the coating layer on at least one surface, preferably both surfaces of the core thread and the side thread, is highly useful not only because of its abrasion resistance but also because it provides excellent feel when the user (a badminton player or other badminton player) hits the shuttlecock.

[0042] In the badminton string, the configurations of the core yarn and the side yarn are not particularly limited. The core yarn of the badminton string may be composed of a monofilament or a multifilament. Preferably, the core yarn is composed of a multifilament. The side yarn is usually composed of a plurality of strands and is wound around the outer periphery of the core yarn by a conventionally known method such as adhesion or braiding. From the viewpoint of abrasion resistance, it is preferable that the core yarn and the side yarn of the badminton string are made of a nylon resin. Examples of the nylon resin include the same types as those exemplified as the nylon resin contained in the coating liquid. Note that the types of the nylon resin may be the same or different between the core yarn and the side yarn. Also, it is one of the preferred embodiments that the nylon resin contained in the coating liquid to be applied and the nylon resin constituting the core yarn or the side yarn to be coated are of the same resin type.

[0043] <Manufacturing Method of Badminton String> The manufacturing method of the badminton string of the present invention includes a step of applying the aforementioned coating liquid to at least one surface of the core yarn and the side yarn. Preferably, it includes a step of applying the aforementioned coating liquid to the surfaces of the core yarn and the side yarn. Then, by drying, a coating layer that covers the surface of the core yarn and / or the side yarn is formed. When coating the side yarn with the coating liquid, it may be coated on the side yarn before string making or on the side yarn after string making.

[0044] The coating amount of the aforementioned coating liquid can be appropriately set in consideration of the abrasion resistance of the badminton string. The drying method after coating is not particularly limited, and examples include natural drying, ventilation drying, heat drying, vacuum drying, infrared heating, far-infrared heating, etc. The drying temperature is preferably 80 to 180 °C, and the drying time is preferably 0.5 to 5 minutes.

[0045] As an example of the method for manufacturing a badminton string of the present invention, a coating liquid as described above is applied to the surface of a core yarn to form a coating layer, and then a string is made and side yarns are wound around it. The coating liquid as described above is applied to the surface of the side yarns (the surface of the string) to form a coating layer, thereby obtaining a badminton string. At this time, the coating liquid applied to the surface of the core yarn and the coating liquid applied to the surface of the side yarns may be the same coating liquid or different coating liquids. Generally, the coating liquid may be applied to the surface of the string (the surface of the side yarns) multiple times, but at least once the coating liquid as described above may be used, and in other cases, a conventional coating liquid may be used. When the coating liquid as described above is used, it is preferable from the viewpoint of abrasion resistance that the coating liquid first applied to the side yarns is the coating liquid of the present invention.

[0046] Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples.

[0047] [Production Example 1] (Production of carbon nanotube forest) A wafer provided with a catalyst for growing carbon nanotubes was prepared, and vertically aligned carbon nanotubes were grown from the catalyst by chemical vapor deposition to produce a vertically aligned carbon nanotube forest vertically oriented with respect to the wafer. The carbon nanotubes constituting the carbon nanotube forest are multi-walled carbon nanotubes, with an average length of 250 μm per tube, an average diameter of 6 to 10 nm, a carbon purity of 99.8% or more, and a crystallinity (D / G ratio) of 0.6 to 0.8.

[0048] (Production of carbon nanotube powder) The carbon nanotube forest formed on the wafer was scraped off from the wafer using a scraper to obtain carbon nanotube powder.

[0049] [Example 1] (Production of core thread coating agent) A coating solution (1) without CNTs was prepared by mixing 299.25 parts by mass of xylol (solvent), 548.62 parts by mass of phenol (solvent), 1.00 part by mass of primary phosphoric acid (color inhibitor), 1.00 part by mass of Irganox B225 (antioxidant), 149.63 parts by mass of nylon 12, and 0.50 parts by mass of Efka PB2021 (antifoaming agent). Carbon nanotube powder was mixed into the CNT-free coating solution (1) using a three-roll mixer to prepare a core thread coating solution (1) containing 0.02 wt% CNTs.

[0050] [Example 2] (Production of core thread coating agent) 299.25 parts by mass of xylol (solvent), 548.62 parts by mass of phenol (solvent), 1.00 part by mass of primary phosphoric acid (color inhibitor), 1.00 part by mass of Irganox B225 (antioxidant), 149.63 parts by mass of nylon 12, and 0.50 parts by mass of Efka PB2021 (antifoaming agent) were mixed to prepare a coating solution (1) that does not contain CNTs. Carbon nanotube powder was mixed into the coating solution (1) that does not contain CNTs using a three-roll mixer to prepare a coating solution (2) for core threads containing 0.04 wt% CNTs.

[0051] [Example 3] (Production of coating agent for side yarns) A coating solution (2) without CNTs was prepared by mixing 289.28 parts by mass of xylol (solvent), 528.67 parts by mass of phenol (solvent), 1.00 part by mass of primary phosphoric acid (color inhibitor), 1.00 part by mass of Irganox B225 (antioxidant), 179.55 parts by mass of nylon 66, and 0.50 parts by mass of Efka PB2021 (antifoaming agent). Carbon nanotube powder was mixed into the coating solution (2) without CNTs using a three-roll mixer to prepare a coating solution (1) for side yarns containing 0.01 wt% CNTs.

[0052] [Comparative Example 1] In Example 1, CNT was replaced with fullerene, and a core thread coating solution (c1) containing 0.02 wt% fullerene was prepared.

[0053] [Example 4] (Manufacturing of badminton string) A core thread made of nylon 12 was coated with the core thread coating solution (1) prepared in Example 1, and dried at 150°C for 3 minutes to form a coating layer (core thread coating layer). A side thread made of nylon 66 was wound around the core thread on which the coating layer had been formed. The side thread coating solution (1) prepared in Example 3 was applied to the wound side thread and dried at 150°C for 2.5 minutes to form a coating layer (one layer of side thread coating layer). Next, the process of applying the CNT-free coating solution (2) prepared in Example 3 and drying at 150°C for 2.5 minutes was repeated twice to form a total of three coating layers (side thread coating layers) (one layer of side thread coating solution (1) and two layers of CNT-free coating solution (2)) on the surface, and a badminton string was obtained. The structure of the obtained badminton string is shown in Figure 1. The following friction tests were performed on the core yarn and badminton strings that had the resulting coating layer formed on them.

[0054] [Friction Test] A friction test was conducted using core yarn or badminton string with a coated layer as test samples. Two core yarns and two badminton strings with a coated layer were prepared. Test sample (1), with a tension of 11.38 kgf, was placed horizontally, and the other test sample (2) was placed perpendicularly from below. Test sample (2), which was placed below, was lifted, and test sample (1) was lifted by 20 mm. With test sample (1) lifted by 20 mm, test sample (2) was moved in a 50 mm stroke, rubbing test sample (1) and test sample (2) against each other, and the number of strokes until one of them broke was recorded.

[0055] [Example 5] A core thread made of nylon 12 was coated with the core thread coating liquid (2) prepared in Example 2, and dried at 150°C for 3 minutes to obtain a core thread with a coated layer. The obtained core thread with the coated layer was subjected to a friction test in the same manner as in Example 4.

[0056] [Comparative Example 2] A core thread made of nylon 12 was coated with the core thread coating liquid (c1) prepared in Comparative Example 1, and dried at 150°C for 3 minutes to obtain a core thread with a coated layer. The obtained core thread with the coated layer was subjected to a friction test in the same manner as in Example 4.

[0057] [Comparative Example 3] A friction test was conducted on a commercially available badminton string from another company using the same method as in Example 4. The results of the friction test on the core threads with the coating layer formed in Examples 4, 5, and Comparative Example 2 are shown in Table 1. The results of the friction test on the badminton strings of Example 4 and Comparative Example 3 are shown in Table 2. Note that in Table 1, the results of the friction test (number of strokes) for Comparative Example 2 are shown as relative values ​​with the friction test results for Comparative Example 3 set to 100, and in Table 2, the results of the friction test for Comparative Example 3 are shown as relative values ​​with the friction test results set to 100.

[0058]

[0059]

[0060] From Tables 1 and 2 above, it was confirmed that badminton strings using the coating liquid of this disclosure exhibit excellent abrasion resistance.

[0061] 1... Core thread 3... Covering layer (core thread upper covering layer) 5... Side thread 7... Covering layer (side thread upper covering layer)

Claims

1. A coating solution comprising nylon resin, carbon nanotubes, and a solvent, wherein the carbon nanotube content is 0.005 to 0.1% by mass.

2. The coating solution according to claim 1, wherein the solvent is an organic solvent.

3. A badminton string having a coating layer containing nylon resin and carbon nanotubes, wherein the mass ratio of carbon nanotubes to nylon resin in the coating layer (carbon nanotubes:nylon resin) is 1:150 to 1:5000.

4. The badminton string according to claim 3, wherein the badminton string includes a core thread and a side thread, and the coating layer is provided on at least one surface of the core thread and the side thread.

5. A method for manufacturing a badminton string, comprising the step of applying the coating liquid described in claim 1 or 2 to at least one surface of the core thread and the side thread.

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