Thermoplastic resin composition and molded article

Abstract

To provide a molded article which suppresses aggregation of carbon nanotubes in a thermoplastic resin composition, is excellent in uniformity of the carbon nanotubes when formed into a molded article, and has high conductivity. And to provide a molded article excellent in thermal and temporal stability.SOLUTION: A thermoplastic resin composition contains a thermoplastic resin (A) and a carbon nanotube (B), and the carbon nanotube (B) satisfies all of the following (1) and (2). (1) The total content of metals is ≤ 10, 000ppm. (2) In the powder X-ray diffraction analysis, the half width of the diffraction peak of the (002) plane is 2.0 to 6.0°.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a thermoplastic resin composition and a molded article. [Background technology]

[0002] Resin molded products are easy to process and are therefore used in a wide range of fields, including automotive parts, medical parts, food containers, electrical and electronic equipment parts, etc. In particular, resin molded products containing carbon nanotubes, a carbon material, are being actively investigated in order to enhance decorativeness and provide functionality.

[0003] Carbon nanotubes, which have a cylindrical structure consisting of graphite layers, are chemically stable and can be mass-produced using the economical and productive chemical vapor deposition method. They are widely used. Furthermore, they possess electrical conductivity and mechanical toughness. By blending carbon nanotubes with thermoplastic resins, various functionalities can be imparted to the molded product, including electrical conductivity, thermal conductivity, improved mechanical strength, and electromagnetic wave absorption. Therefore, carbon nanotubes are finding applications in a variety of fields, including electronics (transistor elements, wiring, etc.), energy (electrode materials for fuel cells, photovoltaic power generation devices, gas storage devices, etc.), electron emission (flat panel devices, etc.), chemistry (adsorbents, catalysts, sensors, etc.), and composite materials (conductive plastics, reinforced materials, flame-retardant nanocomposites, etc.).

[0004] Resin compositions containing carbon nanotubes have high electrical conductivity that cannot be achieved with carbon black, and are therefore widely used, particularly for conductive applications, in a variety of fields such as automobile parts (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-108524 [Patent Document 2] Japanese Patent Publication No. 2022-076641 Summary of the Invention [Problem to be solved by the invention]

[0006] In the thermoplastic resin composition, conductive paths are formed when the carbon nanotubes dispersed in the thermoplastic resin come into contact with each other, thereby imparting conductivity to the thermoplastic resin composition. Therefore, ideally, the more uniformly fibrous carbon nanotubes are dispersed in a thermoplastic resin, the more efficient the conductive network that can be formed. However, carbon nanotubes have a high cohesive force, making it difficult to obtain a thermoplastic resin composition in which they are uniformly dispersed. Furthermore, the aggregated carbon nanotubes increase the viscosity of the thermoplastic resin composition, reducing its flowability. This can lead to uneven dispersion when the resin is molded, resulting in differences in surface resistance depending on the location on the molded product and a large molding shrinkage rate. Furthermore, in a high temperature atmosphere, the thermal stability over time may become a problem due to oxidation and decomposition reactions of the thermoplastic resin.

[0007] Therefore, an object of the present invention is to provide a molded article that suppresses aggregation of carbon nanotubes in a thermoplastic resin composition, has excellent uniformity of carbon nanotubes when molded, and has high electrical conductivity. Another object is to provide a molded article that is also excellent in thermal stability over time. [Means for solving the problem]

[0008] That is, the present invention includes the following embodiments: The embodiments of the present invention are not limited to the following. [1]: A thermoplastic resin composition comprising a thermoplastic resin (A) and carbon nanotubes (B), wherein the carbon nanotubes (B) satisfy both of the following (1) and (2): (1) The total metal content is 10,000 ppm or less. (2) In powder X-ray diffraction analysis, the half-value width of the diffraction peak of the (002) plane is 2.0 to 6.0°. [2] The thermoplastic resin composition according to [1], wherein the carbon nanotubes (B) have an ash content of 0.001 to 1.0 mass % when heated at 900° C. for 1 hour. [3] The thermoplastic resin composition according to [1] or [2], wherein the iron content of the carbon nanotubes (B) is 10 to 5,000 ppm. [4]: Carbon nanotubes (B) have a volume resistivity of 1.0 × 10 -3 ~3.0×10 -2 The thermoplastic resin composition according to any one of [1] to [3], wherein the modulus of elasticity is Ω·cm. [5]: Carbon nanotubes (B) have a BET specific surface area of ​​200 to 600 m 2 The thermoplastic resin composition according to any one of [1] to [4], wherein the viscosity is 1000 MPa. [6] The thermoplastic resin composition according to any one of [1] to [5], wherein the cobalt content of the carbon nanotubes (B) is 10 to 1,000 ppm. [7] The thermoplastic resin composition according to any one of [1] to [6], wherein the thermoplastic resin (A) comprises any one selected from the group consisting of polyethylene resin, polypropylene resin, acrylonitrile-butadiene-styrene copolymer resin, polycarbonate resin, polyamide resin, and polyester resin. [8] The thermoplastic resin composition according to any one of [1] to [7], wherein the total metal content of the thermoplastic resin composition is 3,000 ppm or less. [9]: A molded article formed using the thermoplastic resin composition according to any one of [1] to [8]. [Effects of the Invention]

[0009] According to the present invention, by using specific carbon nanotubes, aggregation of carbon nanotubes in a thermoplastic resin composition is suppressed, making it possible to provide a thermoplastic resin composition with excellent dispersibility of carbon nanotubes, as well as a molded article formed from the thermoplastic resin composition that has excellent conductivity, uniformity, and thermal stability over time. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below. In this specification, the terms "film" and "sheet" have the same meaning. Furthermore, in this specification, a numerical range specified using "to" is intended to include the numerical values ​​before and after "to" as the range's lower and upper limits. Furthermore, "carbon nanotubes" may be referred to as "CNTs," and "thermoplastic resin compositions" may be referred to as "resin compositions." Unless otherwise noted, the various components appearing in this specification may be used independently either alone or in combination of two or more.

[0011] 《Thermoplastic resin composition》 The thermoplastic resin composition of the present invention will now be described. The thermoplastic resin composition of the present invention is used to form a molded article. The thermoplastic resin composition contains a thermoplastic resin (A) and carbon nanotubes (B), and the carbon nanotubes (B) satisfy both of the following (1) and (2): This makes it possible to provide a molded article that is excellent in conductivity, uniformity, and thermal stability over time. (1) The total metal content is 10,000 ppm or less. (2) In powder X-ray diffraction analysis, the half-value width of the diffraction peak of the (002) plane is 2.0 to 6.0°.

[0012] The thermoplastic resin composition of the present invention uses carbon nanotubes (B) having a total metal content and a half-width of an X-ray diffraction peak within a specific range, thereby achieving excellent dispersibility of the carbon nanotubes in the thermoplastic resin composition, and as a result, the obtained molded body has high conductivity, excellent uniformity of the carbon nanotubes, and good thermal stability over time.

[0013] Carbon nanotubes are produced using catalyst particles containing metal components such as iron and cobalt, and may contain metal impurities. However, the thermoplastic resin composition of the present invention uses carbon nanotubes with a total metal content of 10,000 ppm or less, which can prevent these metal impurities from reducing the degree of contact between carbon nanotubes and reducing dispersibility in the thermoplastic resin composition, thereby enabling the production of molded articles with excellent conductivity and uniformity. Furthermore, by using carbon nanotubes whose metal impurities, which are factors that promote oxidation reactions and decomposition reactions of thermoplastic resins in high-temperature atmospheres, are within the above range, a molded product with excellent thermal stability over time can be obtained.

[0014] However, simply purifying carbon nanotubes to reduce metal impurities may result in a decrease in dispersibility. Therefore, in the present invention, it has been discovered that by using highly crystalline carbon nanotubes that, in addition to the total metal content, have an X-ray diffraction peak half-width within a specific range, it is possible to obtain a molded body with excellent uniformity while maintaining conductivity and suppressing the cohesive force between the carbon nanotubes.

[0015] The total metal content in the thermoplastic resin composition is preferably as low as possible, and is preferably 3,000 ppm or less, more preferably 2,000 ppm or less, even more preferably 1,500 ppm or less, and particularly preferably 1,000 ppm or less. Not only carbon nanotubes, but also thermoplastic resins may contain metal impurities due to the use of organometallic catalysts such as metallocene catalysts during production. Furthermore, metal particles resulting from the manufacturing process, such as equipment and piping, may be present in the thermoplastic resin composition. By ensuring that the total metal content is within the above range, the carbon nanotubes are more likely to come into contact with each other, resulting in a uniform mixture of the thermoplastic resin and the carbon nanotubes, preventing uneven dispersion and achieving excellent uniformity. Furthermore, because oxidation and decomposition reactions of the thermoplastic resin due to metal impurities are suppressed, a molded product with superior electrical conductivity and thermal stability can be obtained.

[0016] In order to set the total metal content in the thermoplastic resin composition within this range, it can be controlled not only by the carbon nanotubes used but also by the metal content contained in the thermoplastic resin (A) and the method for producing the thermoplastic resin composition. Specifically, for example, the total metal content of the thermoplastic resin (A) is preferably 1,000 ppm or less, more preferably 700 ppm or less, and particularly preferably 500 ppm or less. When the total metal content of the thermoplastic resin (A) is within the above range, the thermoplastic resin composition can have better thermal stability over time.

[0017] <Thermoplastic resin (A)> The thermoplastic resin (A) is not particularly limited as long as it is a resin that can be formed into a molded article by heating and melting. Examples of the thermoplastic resin (A) include polyolefin resins such as polyethylene resin (PE) and polypropylene resin (PP), polyester resins such as polyethylene terephthalate resin (PET) and polybutylene terephthalate resin (PBT), polystyrene resin (PS), polyphenylene ether resin, acrylonitrile-butadiene-styrene copolymer resin (ABS), polycarbonate resin (PC), polyamide resin (PA), polyacetal resin (POM), polyvinyl chloride resin, acrylic resin, polyetherimide resin (PEI), polyphenylene sulfide resin, polyurethane resin (PU), and liquid silicone rubber (LSR).

[0018] From the viewpoint of dispersibility of carbon nanotubes (B) in thermoplastic resins, polyethylene resins (PE), polypropylene resins (PP), acrylonitrile-butadiene-styrene copolymer resins (ABS), polycarbonate resins (PC), polyamide resins (PA), and polyester-based resins are preferred, and polyethylene resins (PE), polypropylene resins (PP), acrylonitrile-butadiene-styrene copolymer resins (ABS), and polycarbonate resins (PC) are more preferred.

[0019] The melt flow rate (hereinafter, MFR) of the thermoplastic resin (A) is preferably in the range of 0.1 to 100 g / 10 min, more preferably in the range of 0.3 to 70 g / 10 min. When the MFR of the thermoplastic resin (A) is in this range, the fluidity during melting is suppressed, and the concentration of the carbon nanotubes (B) on the surface and inside of the molded article becomes uniform, making it possible to obtain a molded article with a uniform carbon nanotube concentration. The measurement conditions for the MFR of thermoplastic resin (A) are as follows: temperature 190°C, load 2.16 kgf for polyethylene resin; temperature 230°C, load 2.16 kgf for polyolefin resins other than polyethylene resin; temperature 220°C, load 10 kgf for acrylonitrile-butadiene-styrene copolymer resin; temperature 280°C, load 1.2 kgf for polycarbonate resin; temperature 240°C, load 2.16 kgf for polyamide resin; and temperature 280°C, load 1.2 kgf for polyester resin.

[0020] The MFR in the present invention is a value obtained by measuring each thermoplastic resin in terms of the melt mass flow rate in accordance with JIS-K7210.

[0021] <Carbon nanotubes (B)> The carbon nanotubes (B) satisfy the following (1) and (2). (1) The total metal content is 10,000 ppm or less. (2) In powder X-ray diffraction analysis, the half-value width of the diffraction peak of the (002) plane is 2.0 to 6.0°.

[0022] Carbon nanotubes (B) have a structure similar to a graphene sheet rolled into a cylinder; if they are single-walled they are called single-walled carbon nanotubes (SWCNT), and if they are multi-walled they are called multi-walled carbon nanotubes (MWCNT), and individual carbon nanotubes can be seen using an electron microscope, etc. Carbon nanotubes form primary aggregates of carbon nanotube fibers, entangled or bundled, but primary aggregates can also aggregate to form secondary or higher aggregates.

[0023] The carbon nanotubes (B) may be single-walled carbon nanotubes, multi-walled carbon nanotubes with two or more layers, or a mixture of these, but multi-walled carbon nanotubes are preferred from the standpoints of cost and strength. Furthermore, carbon nanotubes whose sidewalls have an amorphous structure rather than a graphite structure may also be used.

[0024] Carbon nanotubes (B) can generally be produced by laser ablation, arc discharge, chemical vapor deposition (CVD), combustion, etc., but any method may be used. In particular, the CVD method is a method for inexpensively and mass-producing carbon nanotubes by contacting catalyst fine particles, which are formed by supporting a metal catalyst such as iron, cobalt, or nickel on a support such as silica, alumina, magnesium oxide, titanium oxide, silicate, diatomaceous earth, alumina silica, silica titania, or zeolite, with a carbon-containing gas as a raw material at a high temperature of usually 400 to 1000°C, and is preferred for the carbon nanotubes used in the present invention.

[0025] [Metal content] The carbon nanotubes (B) have a total metal content of 10,000 ppm or less based on the mass of the carbon nanotubes (B). The metal content in the carbon nanotubes (B) is preferably 500 to 10,000 ppm, more preferably 500 to 7500 ppm. Examples of metals include iron, cobalt, aluminum, and molybdenum. Each metal atom in the carbon nanotubes (B) can exist as a magnetic substance such as a metal or alloy, or as a non-magnetic substance such as an oxide or carbide. When the total metal content of the carbon nanotubes (B) is within the above range, the purity of the carbon nanotubes (B) is high, and the electrical conductivity and dispersibility of the carbon nanotubes (B) in the thermoplastic resin composition are excellent.

[0026] The content of metal components in carbon nanotubes can be analyzed using inductively coupled plasma (ICP).

[0027] When a catalyst containing iron atoms is used, the content of iron atoms in the carbon nanotubes (B) is preferably 10 to 5,000 ppm, more preferably 10 to 4,000 ppm, and even more preferably 10 to 3,000 ppm. When the content of iron atoms in the carbon nanotubes (B) is within this range, deterioration of the carbon nanotubes due to the purification treatment is suppressed, and the dispersibility of the carbon nanotubes (B) in the thermoplastic resin composition is improved. The iron atoms in the carbon nanotubes (B) can exist as magnetic substances such as metals and alloys, or as non-magnetic substances such as oxides and carbides. When the iron atom content of the carbon nanotubes (B) is within the above range, the electrical conductivity of the carbon nanotubes (B) is increased, and corrosion of metals in contact with the carbon nanotubes (B) can be suppressed.

[0028] Methods for adjusting the amount of iron atoms contained in carbon nanotubes (B) to fall within the above range include a method for increasing the yield of carbon nanotubes (B) per mass of catalyst particles in the production process of carbon nanotubes (B), a method for using catalyst particles that do not contain iron atoms, a method for reducing the proportion of iron atoms in catalyst particles, and a method for reducing the amount of iron atoms mixed in in the production process of carbon nanotubes (B). Iron atoms may also be removed by known methods such as acid treatment, graphitization treatment, and chlorination treatment, which will be described later.

[0029] When a catalyst containing cobalt atoms is used, the content of cobalt atoms in the carbon nanotubes (B) is preferably 10 to 1,000 ppm, more preferably 10 to 800 ppm, and even more preferably 10 to 600 ppm. When the content of cobalt atoms in the carbon nanotubes (B) is within this range, deterioration of the carbon nanotubes due to the purification treatment is suppressed, and the dispersibility of the carbon nanotubes (B) in the thermoplastic resin composition is excellent. The cobalt atoms in the carbon nanotubes (B) can exist as a magnetic substance such as a metal or alloy, or as a non-magnetic substance such as an oxide or carbide.

[0030] When catalyst particles containing cobalt atoms are used in the production process of carbon nanotubes (B), the cobalt atom content of carbon nanotubes (B) within the above range allows for production without reducing the productivity of carbon nanotubes (B). Furthermore, by ensuring that the cobalt atom content is within the above range, the amount of cobalt atoms acting as a non-magnetic substance is reduced, allowing for a reduction in the volume resistivity of the compact. Methods for adjusting the amount of cobalt atoms contained in carbon nanotubes within the above range include increasing the carbon nanotube yield per mass of catalyst particles in the carbon nanotube production process and reducing the proportion of cobalt atoms in the catalyst particles. Furthermore, the cobalt atoms may be removed by known methods such as acid treatment, graphitization, or chlorination, which will be described later.

[0031] Metal components contained in carbon nanotubes may be removed by known methods, such as acid treatment, graphitization treatment, and chlorination treatment, to the extent that the effects of the present invention are not impaired. When metal components are removed by acid treatment, the acid used may be any acid capable of dissolving the metal components contained in the carbon nanotubes, and for example, inorganic acids or carboxylic acids are preferred, with hydrochloric acid, sulfuric acid, and nitric acid being particularly preferred among inorganic acids. The acid treatment of the carbon nanotubes is preferably carried out in a liquid phase, and it is more preferred to disperse and / or mix the carbon nanotubes in the liquid phase. After the acid treatment, the carbon nanotubes are preferably washed with water and dried.

[0032] The graphitization treatment of carbon nanotubes can be carried out, for example, by heating the carbon nanotubes at 1500 to 3500° C. in an inert atmosphere with an oxygen concentration of 0.1% or less.

[0033] Chlorination of carbon nanotubes can be carried out, for example, by introducing chlorine gas into an inert atmosphere with an oxygen concentration of 0.1% or less and heating the carbon nanotubes at 800 to 2000°C.

[0034] As a method for removing metal components contained in carbon nanotubes, acid treatment or graphitization treatment is preferred from the viewpoint of cost.

[0035] [FWHM of X-ray diffraction peak] The half width of the diffraction peak of the (002) plane of the carbon nanotube (B) is 2.0 to 6.0°. Preferably, it is 2.0 to 5.0°. When the angle is within the above range, the thermoplastic resin composition has good dispersibility of carbon nanotubes. A half-value width of 2.0° or more reduces the amorphous portion of the carbon nanotubes, increasing their crystallinity. Also, a half-value width of 6.0° or less increases the number of carbon nanotube walls, suppressing the cohesion between the carbon nanotubes while resulting in carbon nanotubes with a large specific surface area and high crystallinity, thereby maintaining high dispersibility.

[0036] The (002) plane of carbon nanotube (B) is detected at a 2θ of 25°±2°, and varies depending on the distance between the carbon hexagonal mesh planes. The higher the peak position, the closer the distance between the carbon hexagonal mesh planes, indicating a high degree of graphitic regularity in the structure. Furthermore, the sharper the peak (the smaller the half-width), the larger the crystallite size and the more developed the crystalline structure.

[0037] The half width of the carbon nanotube (B) is determined as follows. First, carbon nanotubes (B) are packed into a designated sample holder so that the surface is flat. Then, they are placed in a powder X-ray diffraction analyzer. Measurements are performed by varying the X-ray source angle from 5° to 80°. For example, CuKα radiation is used as the X-ray source. The step width is 0.010°, and the measurement time is 1.0 second. The carbon nanotubes (B) can be evaluated by reading the diffraction angle 2θ at which a peak appears. A peak is typically detected in graphite at 2θ around 26°, which is known to be due to interlayer diffraction. Since carbon nanotubes (B) also have a graphite structure, a peak due to graphite interlayer diffraction is detected in this vicinity. However, because carbon nanotubes have a cylindrical structure, this value differs from that of graphite. The appearance of a peak at 2θ 25° ± 2° indicates that the composition contains a multilayer structure rather than a single layer. Because the peak at this position is due to interlayer diffraction of the multilayer structure, it is possible to determine the number of layers in the carbon nanotubes (B). Since single-walled carbon nanotubes do not have one wall, a peak does not appear at 25°±2° if they are made up of only single-walled carbon nanotubes. However, even single-walled carbon nanotubes are not 100% single-walled carbon nanotubes, and if multi-walled carbon nanotubes or the like are mixed in, a peak may appear at 2θ of 25°±2°.

[0038] The carbon nanotube (B) of this embodiment exhibits a peak at 2θ of 25°±2°. The layer structure can also be analyzed from the half-width of the peak at 25°±2° detected by powder X-ray diffraction analysis. That is, the smaller the half-width of this peak, the greater the number of layers of the carbon nanotube (B). Conversely, the larger the half-width of this peak, the fewer the number of layers of the carbon nanotube.

[0039] When the carbon nanotubes (B) of this embodiment are subjected to powder X-ray diffraction analysis, a peak exists at a diffraction angle 2θ=25°±2°, and the half width of this peak for the (002) plane is 2.0 to 6.0°.

[0040] [ash] The ash content of the carbon nanotubes is a non-combustible component containing metal components, etc. The ash content of the carbon nanotubes (B) is preferably 0.001 to 1.0 mass%, more preferably 0.01 to 0.9 mass%, and even more preferably 0.1 to 0.8 mass%. The ash content of carbon nanotubes can be calculated according to formula (i) by measuring the ash residue after calcining in air at 900°C for 1 hour. Ash content of carbon nanotubes (mass%) = Ash mass after firing (g) / Carbon nanotube mass before firing (g) x 100 Formula (i) The ash content within the above range is preferred because it leads to further improved conductivity and dispersibility.

[0041] [Volume resistivity] The volume resistivity of carbon nanotubes (B) is 1.0×10 -3 ~3.0×10 -2 Ω·cm is preferred, and 1.0×10 -3 ~2.5×10 -2 Ω·cm is more preferable, 1.0×10 -3 ~2.0×10 -2 It is more preferable that the volume resistivity is Ω·cm. When the carbon nanotubes (B) have a volume resistivity within the above range, the conductivity of the molded article becomes better. The volume resistivity of the carbon nanotubes (B) can be determined by measurement using a powder resistivity measuring device (Loresta GP Powder Resistivity Measuring System MCP-PD-51, manufactured by Nitto Seiko Analytech Co., Ltd.).

[0042] [BET specific surface area] The BET specific surface area of ​​carbon nanotubes (B) is 200 to 600 m 2 / g, and 200 to 500m 2 / g, and more preferably 200 to 400m 2 / g is even more preferable. The BET specific surface area of ​​carbon nanotubes can be calculated by the BET method using nitrogen adsorption measurements. There is often a correlation between the specific surface area of ​​carbon nanotubes and the average outer diameter of carbon nanotubes; the smaller the specific surface area, the larger the outer diameter of the carbon nanotubes, and the fewer the number of carbon nanotubes per mass. On the other hand, the larger the specific surface area of ​​carbon nanotubes, the smaller the outer diameter of the carbon nanotubes, and the more the number of carbon nanotubes per mass. When the specific surface area of ​​the carbon nanotubes is within the above range, the number of carbon nanotubes per mass is sufficient to efficiently form a conductive network, and the carbon nanotubes have a cohesive force that makes them easy to disperse, so a good conductive network can be formed and the conductivity is higher.

[0043] [G / D ratio of Raman spectrum] Carbon nanotubes (B) have a Raman spectrum of 1560-1600 cm -1 The maximum peak intensity in the range of 1310 to 1350 cm is G. -1 When the maximum peak intensity within this range is defined as D, the G / D ratio is preferably 0.5 to 5.0, more preferably 0.5 to 4.0, and even more preferably 0.5 to 3.0. When the G / D ratio of the carbon nanotubes is within the above range, the conductivity and uniformity of the molded body can be improved.

[0044] The G / D ratio was measured by placing a powder sample in a microscopic laser Raman spectrophotometer (JASCO Corporation NRS-3100) and using a laser wavelength of 532 nm. -1 The G band and 1350 cm originating from the graphite structure -1 It can be calculated from the integral value of the D band peak derived from the structural defects in the vicinity. In the Raman spectrum, 1590 cm -1 The Raman shift observed around 1350 cm is called the G band derived from graphite. -1 The Raman shift observed around this band is called the D band, which is derived from defects in amorphous carbon and graphite. The higher the G / D ratio of a carbon nanotube, the higher its degree of graphitization, crystallinity, and purity.

[0045] [Average diameter] The carbon nanotubes (B) preferably have an average diameter of 5 to 20 nm, more preferably 8 to 15 nm. When the average diameter of the carbon nanotubes is within the above range, the specific surface area is large, making it easier to form a conductive network, and the carbon nanotubes become aggregates that are easy to disperse, resulting in good conductivity and dispersibility, and thus excellent conductivity and uniformity of the molded body, which is preferable.

[0046] The average diameter of the carbon nanotubes (B) can be determined by image analysis. The average diameter can be determined, for example, by observing carbon nanotubes using a scanning electron microscope (JEOL, JSM-6700M) at an accelerating voltage of 5 kV and taking a 50,000-magnification image (1024 × 1280 pixels). Next, the minor axis length of any 20 carbon nanotubes in the image is measured, and the number-average value of the obtained minor axis lengths can be used as the average diameter of the carbon nanotubes.

[0047] <Other ingredients> The molded article and thermoplastic resin composition of the present invention may contain, as needed, an oxidation stabilizer, a weathering stabilizer, an antistatic agent, a dye, a pigment, a dispersant, a coupling agent, a crystal nucleating agent, a resin filler, and the like.

[0048] <Manufacturing method> The method for producing the thermoplastic resin composition of the present invention is not particularly limited. For example, thermoplastic resin (A), carbon nanotubes (B), and, if necessary, additives, etc., are mixed in a Henschel mixer, tumbler, disper, etc., and then mixed or melt-kneaded in a batch mixer such as a kneader, roll mill, super mixer, Henschel mixer, Schuggie mixer, vertical granulator, high-speed mixer, Farmatrix, ball mill, steel mill, sand mill, vibration mill, attritor, or Banbury mixer, a twin-screw extruder, a single-screw extruder, or a rotor-type twin-screw kneader, to obtain a resin composition in the form of pellets, powder, granules, beads, or the like. In the present invention, it is preferable to use a twin-screw extruder for melt-kneading. In this case, the melt-kneading conditions (temperature, screw rotation speed, etc.) are not particularly limited.

[0049] The thermoplastic resin composition of the present invention may be a compound having a relatively low concentration of carbon nanotubes (B) and used for molding as is without diluting with thermoplastic resin (A), or may be a masterbatch containing a relatively high concentration of carbon nanotubes (B) and used by diluting with thermoplastic resin (A) during molding. Both the compound and the masterbatch are preferably in the form of pellets for easy handling.

[0050] The content of the carbon nanotubes (B) is preferably 0.1 to 30 parts by mass relative to 100 parts by mass of the thermoplastic resin (A).

[0051] In the case of a compound, the content of the carbon nanotubes (B) is preferably 0.1 to 25 parts by mass, more preferably 0.1 to 12 parts by mass, even more preferably 0.5 to 12 parts by mass, and particularly preferably 1.0 to 12 parts by mass, relative to 100 parts by mass of the thermoplastic resin (A). A content of the carbon nanotubes (B) of 25 parts by mass or less is preferred because it is possible to suppress re-aggregation of the carbon nanotubes and improve dispersibility.

[0052] In the case of a compound, the content of carbon nanotubes (B) is preferably 0.1 to 20 mass%, more preferably 0.1 to 10 mass%, even more preferably 0.5 to 10 mass%, and particularly preferably 1.0 to 10 mass%, based on the mass of the compound (100 mass%).By using the thermoplastic resin composition of the present invention, carbon nanotubes can be uniformly dispersed in the thermoplastic resin even at a high concentration of 10 mass% or more.

[0053] In the case of a compound, the metal content in the compound is preferably 3,000 ppm or less, more preferably 2,500 ppm or less.

[0054] In the case of a masterbatch, the content of the carbon nanotubes (B) is preferably 12 to 30 parts by mass, and more preferably 12 to 25 parts by mass, relative to 100 parts by mass of the thermoplastic resin (A). When the content of the carbon nanotubes (B) is 30 parts by mass or less, re-aggregation of the carbon nanotubes can be suppressed, resulting in better dispersibility.

[0055] In the case of the masterbatch, the content of the carbon nanotubes (B) is preferably 10 to 23 mass %, more preferably 10 to 20 mass %, based on the mass of the masterbatch (100 mass %).

[0056] In the case of a masterbatch, the metal content in the masterbatch is preferably 30,000 ppm or less, more preferably 20,000 ppm or less, even more preferably 15,000 ppm or less, and particularly preferably 3,000 ppm or less.

[0057] The metal content in the resin composition after diluting the masterbatch with the thermoplastic resin (A) during molding is preferably 3,000 ppm or less, more preferably 2,500 ppm or less.

[0058] <<Molded body>> The molded article of the present invention is formed using the thermoplastic resin composition described herein. Its uses are not particularly limited, but it can be used for conductive trays. It can also be used as a protective material for electronic components, such as packaging bags for electronic components. It can also be used for personal computer bodies and built-in electronic components, external hard disks, home appliances, automotive parts, electromagnetic wave absorbers, etc.

[0059] The molded article can be formed by melt-kneading and molding a thermoplastic resin composition containing the carbon nanotubes (B) and the thermoplastic resin (A). Specifically, the compound or master batch and diluted resin are melt-mixed in a molding machine usually set at 50° C. to 350° C., then formed into a molded body shape and cooled. The molding machine temperature is not critical as long as it is a temperature at which the thermoplastic resin (A) softens, but is preferably at least 30° C. higher than the softening point of the thermoplastic resin (A) that is the main component.

[0060] The molded product can be in the form of a plate, rod, fiber, tube, pipe, bottle, film, or the like. The thermoplastic resin composition of the present invention has excellent dispersibility of carbon nanotubes, so that a molded product with excellent uniformity can be obtained even if the thickness is 2 mm or more. The thickness of the molded product is not particularly limited and can be set according to the application, but the thickness of the molded product is preferably 0.1 to 100 mm, more preferably 0.1 to 80 mm.

[0061] The molding method may be, for example, extrusion molding, injection molding, blow molding, compression molding, transfer molding, film molding such as T-die molding or inflation molding, calendar molding, or fiber spinning, with extrusion molding, injection molding, blow molding, T-die molding, or inflation molding being preferred, and extrusion molding and injection molding being particularly preferred.

[0062] The metal content in the molded body is preferably 3,000 ppm or less, and more preferably 2,500 ppm or less. The metal content in the molded body can be calculated from the metal content of the thermoplastic resin composition. In the case of a compound, it can be determined from the metal content in the compound, and in the case of a masterbatch, it can be determined from the total metal content of the masterbatch and the diluted resin. [Example]

[0063] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples, "parts" means "parts by mass" and "%" means "% by mass." The measurement methods are as follows.

[0064] <Measurement of total metal content, iron (Fe) atom content, and cobalt (Co) atom content in carbon nanotubes> The carbon nanotubes were acid-decomposed using a microwave sample pretreatment device (Milestone General, ETHOS1) to extract the metals (iron, cobalt, etc.) contained in the carbon nanotubes. Analysis was then performed using a multi-type ICP optical emission spectrometer (Agilent, 720-ES) to calculate the total metal content, iron atom content, and cobalt atom content of the carbon nanotubes.

[0065] <Powder X-ray diffraction analysis of carbon nanotubes> A carbon nanotube was placed in the central recess of an aluminum sample plate (outer diameter φ46 mm, thickness 3 mm, sample area φ26.5 mm, thickness 2 mm) and flattened using a glass slide. Then, a piece of medicine paper was placed on the surface where the sample was placed, and a 1-ton load was applied to the surface where the aluminum high-sheet packing was placed, further flattening the surface. The medicine paper and aluminum high-sheet packing were then removed to obtain a sample for powder X-ray diffraction analysis of the carbon nanotube. The sample for powder X-ray diffraction analysis of the carbon nanotube was then placed in an X-ray diffractometer (Ultima 2100, Rigaku Corporation) and analyzed by operating from 15° to 35°. Sampling was performed every 0.02°, with a scan speed of 2° / min. The voltage was 40 kV, the current was 40 mA, and the X-ray source was CuKα radiation. The plots of the (002) plane of the carbon nanotube, which appeared at a diffraction angle of 2θ = 25° ± 2°, were plotted at 11 points, and the half-width of the peak was taken as the half-width of the carbon nanotube. The baseline was the line connecting the plots at 2θ = 16° and 2θ = 34°.

[0066] <Ash content of carbon nanotubes> The ash content of the carbon nanotubes (B) was calculated based on formula (i) after 1.0 g of the carbon nanotubes was placed in a porcelain crucible, heated in a furnace at 900° C. for 1 hour to be incinerated, and cooled. Ash content of carbon nanotubes (mass%) = Ash mass after firing (g) / Carbon nanotube mass before firing (g) × 100 Formula (i)

[0067] <Volume resistivity of carbon nanotubes> Using a powder resistivity measuring device (Nitto Seiko Analytech Co., Ltd.: Loresta-GP Powder Resistivity Measuring System MCP-PD-51), the sample mass was 1.2 g, and the volume resistivity [Ω·cm] of the conductive powder under various pressures was measured using a powder probe unit (four-point probe ring electrode, electrode spacing 5.0 mm, electrode radius 1.0 mm, sample radius 12.5 mm) with the applied voltage limiter set to 90 V. The volume resistivity [Ω·cm] of the conductive powder under various pressures was measured, and the volume resistivity of the conductive powder under various pressures was measured. 3 The volume resistivity of the carbon nanotubes at the density was calculated.

[0068] <BET specific surface area of ​​carbon nanotubes> 0.03 g of carbon nanotubes were weighed using an electronic balance (Sartorius, MSA225S100DI) and then dried at 110°C for 15 minutes while degassing. The BET specific surface area of ​​the carbon nanotubes was then measured using a fully automatic specific surface area measuring device (MOUNTECH, HM-model1208).

[0069] <Raman spectroscopic analysis of carbon nanotubes> The carbon nanotubes were placed in a microscopic laser Raman spectrophotometer (JASCO Corporation NRS-3100) and measured using a 532 nm laser wavelength. The measurement conditions were: acquisition time 60 seconds, number of integrations 2, neutral density filter 10%, objective lens magnification 20x, confocus hole 500, slit width 100 μm, and measurement wavelength 100–3000 cm. -1 The carbon nanotubes for measurement were separated onto a slide glass and flattened using a spatula. Among the peaks obtained, the peak at 1560 to 1600 cm in the spectrum -1 The maximum peak intensity in the range of G, 1310 to 1350 cm -1 The maximum peak intensity within this range was defined as D, and the G / D ratio was defined as the G / D ratio of the carbon nanotube.

[0070] <MFR (Melt Mass Flow Rate) of Thermoplastic Resin (A)> The MFR of the thermoplastic resin (A) was measured using a melt indexer manufactured by Toyo Seiki Seisakusho in accordance with JIS-K7210. The measurements were performed under the following conditions: temperature 190°C, load 2.16 kgf for polyethylene resin, temperature 230°C, load 2.16 kgf for polyolefin resins other than polyethylene resin, temperature 220°C, load 10 kgf for acrylonitrile-butadiene-styrene copolymer resin, temperature 280°C, load 1.2 kgf for polycarbonate resin, temperature 240°C, load 2.16 kgf for polyamide resin, and temperature 280°C, load 1.2 kgf for polyester resin.

[0071] The materials used in the examples are as follows: <Thermoplastic resin (A)> (A-1) Kernel KJ-640T (Japan Polyethylene Corporation, polyethylene resin, MFR: 30g / 10min) (A-2) Novatec MA1B (Japan Polypropylene Corporation, polypropylene resin, MFR: 21g / 10min) (A-3) Stylac ABS191 (Asahi Kasei Chemicals Corporation, ABS resin, MFR: 26g / 10min) (A-4) Iupilon H-3000 (Mitsubishi Engineering Plastics Corporation, polycarbonate resin, MFR: 35g / 10min) (A-5) Amilan CM1017 (Toray Industries, polyamide resin, MFR: 35g / 10min) (A-6) Duranex 700FP (Polyplastics, polyester resin, MFR: 30g / 10min) (A-7) Duracon M90-44 (Polyplastics Co., Ltd., polyacetal resin, MFR: 9 g / 10 min (measurement conditions: 190°C, 2.16 kgf))

[0072] <Carbon nanotubes> (B-1) Carbon nanotubes of Production Example 1 (B-2) Carbon nanotubes of Production Example 2 (B-3) Carbon nanotubes of Production Example 3 (B-4) Carbon nanotubes of Production Example 4 (B-5) Carbon nanotubes of Production Example 5 (B-6) Carbon nanotubes of Production Example 6 (B-7) Carbon nanotubes of Production Example 7 (B-8) Carbon nanotubes of Production Example 8 (B-9) Carbon nanotubes of Production Example 9 (B'-1) Carbon nanotubes of Production Example 10 (B'-2) Carbon nanotubes of Production Example 11 (B'-3) Carbon nanotubes of Production Example 12

[0073] (Manufacturing example 1:B-1) <Catalyst for synthesizing carbon nanotubes (B-1)> 20 g of cobalt hydroxide and 43 g of iron(III) nitrate nonahydrate were placed in a heat-resistant container and dried in an electric oven at an ambient temperature of 170±5°C for 2 hours to obtain a cobalt composition and an iron composition. 69 g of magnesium acetate tetrahydrate and 4.1 g of manganese(II) carbonate were placed in a heat-resistant container and dried in an electric oven at an ambient temperature of 170±5°C for 2 hours to evaporate the water. 29 g of the cobalt composition and iron composition were then mixed with 2.0 g of Aerosil (AEOSIL® 200, manufactured by Nippon Aerosil Co., Ltd.) as a second support to obtain a catalyst precursor for carbon nanotube (B-1) synthesis. The catalyst precursor for carbon nanotube (B-1) synthesis was then transferred to a heat-resistant container and calcined in a muffle furnace (FO510, manufactured by Yamato Scientific Co., Ltd.) in an air atmosphere at 450±5°C for 30 minutes, after which it was crushed in a mortar to obtain a catalyst for carbon nanotube (B-1) synthesis.

[0074] <Synthesis of Carbon Nanotubes (B-1)> A quartz glass heat-resistant dish, onto which 2 g of the carbon nanotube (B-1) synthesis catalyst had been sprayed, was placed in the center of a 10 L horizontal reactor tube that could be pressurized and heated with an external heater. The reactor was evacuated while nitrogen gas was injected, and the air inside the reactor tube was replaced with nitrogen gas, adjusting the atmosphere inside the horizontal reactor tube to an oxygen concentration of 1% by volume or less. The reactor was then heated with an external heater until the central temperature inside the horizontal reactor tube reached 680°C. After reaching 680°C, propane gas was introduced into the reactor tube as a carbon source at a flow rate of 2 L per minute, and the reaction was carried out for 1 hour. After the reaction was completed, the gas inside the reactor tube was replaced with nitrogen gas, and the temperature of the reactor tube was cooled to 100°C or less and removed, yielding a carbon nanotube (B-1) precursor. 1000 g of carbon nanotube (B-1) precursor was weighed into a 7 L carbon heat-resistant container, and the heat-resistant container containing the carbon nanotube (B-1) precursor was placed in a furnace. Nitrogen gas was then introduced into the furnace, and the air inside the furnace was evacuated while maintaining positive pressure. After the oxygen concentration inside the furnace reached 0.1% or less, the furnace was heated to 3000°C over 30 hours and then held at 3000°C for 30 minutes. Then, heating inside the furnace was stopped, and the sample was cooled to obtain carbon nanotubes (B-1).

[0075] (Manufacturing example 2: B-2) <Synthesis of Carbon Nanotubes (B-2)> 1000 g of the carbon nanotube (B-1) precursor from Production Example 1 was weighed into a 7 L carbon heat-resistant container, and the heat-resistant container containing the carbon nanotube (B-1) precursor was placed in a furnace. Nitrogen gas was then introduced into the furnace, and the air in the furnace was evacuated while maintaining positive pressure. After the oxygen concentration in the furnace reached 0.1% or less, the furnace was heated to 3000°C over 30 hours and then held at 3000°C for 10 minutes. Heating in the furnace was then stopped, and the sample was cooled to obtain carbon nanotubes (B-2).

[0076] (Manufacturing example 3: B-3) <Synthesis of Carbon Nanotubes (B-3)> 1000 g of the carbon nanotube (B-1) precursor from Production Example 1 was weighed into a 7 L carbon heat-resistant container, and the heat-resistant container containing the carbon nanotube (B-1) precursor was placed in a furnace. Nitrogen gas was then introduced into the furnace, and the air inside the furnace was evacuated while maintaining positive pressure. After the oxygen concentration inside the furnace reached 0.1% or less, the furnace was heated to 3000°C over 30 hours and then held at 3000°C for 1 hour. Heating inside the furnace was then stopped, and the sample was cooled to obtain carbon nanotubes (B-3).

[0077] (Manufacturing example 4:B-4) <Synthesis of Carbon Nanotubes (B-4)> 10 kg of the carbon nanotube (B-1) precursor from Production Example 1 was weighed into a 120 L heat-resistant container, and the heat-resistant container containing the carbon nanotube (B-1) precursor was placed in a furnace. The reactor was then evacuated while nitrogen gas was injected, and the air in the reactor was replaced with nitrogen gas. The horizontal reactor was heated until the ambient temperature reached 700 °C. After reaching 700 °C, ethylene gas as a hydrocarbon was introduced into the reactor at a flow rate of 2 L per minute, and the catalytic reaction was carried out for 15 minutes. After the reaction was completed, the gas in the reactor was replaced with nitrogen gas, and the reactor was cooled to below 100 °C and removed to obtain a carbon nanotube (B-4) precursor. 1000 g of the carbon nanotube (B-4) precursor was weighed into a 7 L heat-resistant carbon container, and the heat-resistant container containing the carbon nanotube (B-4) precursor was placed in the furnace. Nitrogen gas was then introduced into the furnace, and the air in the furnace was evacuated while maintaining positive pressure. After the oxygen concentration in the furnace became 0.1% or less, the temperature in the furnace was raised to 3000°C over 30 hours and then maintained at 3000°C for 30 minutes. After that, heating in the furnace was stopped and the sample was cooled to obtain carbon nanotubes (B-4).

[0078] (Manufacturing example 5:B-5) <Synthesis of Carbon Nanotubes (B-5)> 1000 g of the carbon nanotube (B-1) precursor from Production Example 1 was weighed into a 7 L carbon heat-resistant container, and the heat-resistant container containing the carbon nanotube (B-1) precursor was placed in a furnace. Nitrogen gas was then introduced into the furnace, and the air inside the furnace was evacuated while maintaining positive pressure. After the oxygen concentration inside the furnace reached 0.1% or less, the furnace was heated to 3000°C over 30 hours and then held at 3000°C for 1 hour and 20 minutes. Heating inside the furnace was stopped, and the sample was cooled to obtain carbon nanotubes (B-5).

[0079] (Manufacturing example 6:B-6) <Synthesis of Carbon Nanotubes (B-6)> 10 kg of the carbon nanotube (B-1) precursor from Production Example 1 was weighed into a 120 L heat-resistant container, and the heat-resistant container containing the carbon nanotube (B-1) precursor was placed in a furnace. Nitrogen gas was then introduced into the furnace, and the air in the furnace was evacuated while maintaining positive pressure. After the oxygen concentration in the furnace reached 0.1% or less, the furnace was heated to 1600°C over 30 hours. While maintaining the furnace temperature at 1600°C, chlorine gas was introduced at a rate of 50 L / min for 50 hours. Nitrogen gas was then introduced at 50 L / min, and the furnace was cooled while maintaining positive pressure, yielding carbon nanotubes (B-6).

[0080] (Manufacturing example 7:B-7) <Synthesis of Carbon Nanotubes (B-7)> 10 g of the carbon nanotube (B-1) precursor from Production Example 1 was weighed into a 1 L glass container, and 500 g of 60% nitric acid (Fujifilm Wako Pure Chemical Industries, Ltd.) was added, followed by thorough stirring using a stirrer. The mixture was then thoroughly diluted with ion-exchanged water and subjected to vacuum filtration using a membrane filter. After repeated dilution and filtration, the carbon nanotubes were transferred to a PTFE tray and dried in an oven at 140°C to obtain carbon nanotubes (B-7).

[0081] (Manufacturing example 8:B-8) <Synthesis of Carbon Nanotubes (B-8)> 1000 g of the carbon nanotube (B-1) precursor from Production Example 1 was weighed into a 7 L carbon heat-resistant container, and the heat-resistant container containing the carbon nanotube (B-1) precursor was placed in a furnace. Nitrogen gas was then introduced into the furnace, and the air in the furnace was evacuated while maintaining positive pressure. After the oxygen concentration in the furnace reached 0.1% or less, the furnace was heated to 2900°C over 30 hours and then held at 2900°C for 2 hours. Heating of the furnace was stopped, and the sample was cooled to obtain carbon nanotubes (B-8).

[0082] (Manufacturing example 9:B-9) <Synthesis of Carbon Nanotubes (B-9)> 1000 g of the carbon nanotube (B-1) precursor from Production Example 1 was weighed into a 7 L carbon heat-resistant container, and the heat-resistant container containing the carbon nanotube (B-1) precursor was placed in a furnace. Nitrogen gas was then introduced into the furnace, and the air inside the furnace was evacuated while maintaining positive pressure. After the oxygen concentration inside the furnace reached 0.1% or less, the furnace was heated to 2900°C over 30 hours and then held at 2900°C for 1 hour and 40 minutes. Heating inside the furnace was stopped, and the sample was cooled to obtain carbon nanotubes (B-9).

[0083] (Manufacturing example 10:B'-1) The carbon nanotube (B-1) precursor of Production Example 1 was designated as carbon nanotube (B'-1).

[0084] (Manufacturing example 11:B'-2) <Catalyst for carbon nanotube (B'-2) synthesis> 1000 parts by mass of magnesium acetate tetrahydrate was weighed into a heat-resistant container and dried in an electric oven at an ambient temperature of 170±5°C for 6 hours. The mixture was then pulverized using a pulverizer (Sample Mill KIIW-I, manufactured by Dalton Co., Ltd.) fitted with a 1 mm screen to obtain dried and pulverized magnesium acetate. 45.8 parts of the dried and pulverized magnesium acetate, 8.1 parts of manganese carbonate, 1.0 part of silicon oxide (SiO, manufactured by Nippon Aerosil Co., Ltd.: AEROSIL® 200), and 200 parts of steel beads (bead diameter 2.0 mmφ) were placed in an SM sample bottle (manufactured by Sansho Co., Ltd.) and pulverized and mixed for 30 minutes using a Red Devil paint conditioner. The pulverized and mixed powder and the steel beads (bead diameter 2.0 mmφ) were then separated using a stainless steel sieve to obtain a catalyst support for carbon nanotube (B'-2) synthesis. Then, 20 parts by mass of cobalt hydroxide and 43 parts by mass of iron (III) nitrate nonahydrate were weighed into a heat-resistant container and dried at an ambient temperature of 170 ± 5 ° C for 2 hours to obtain a cobalt composition and an iron composition. Furthermore, 54.9 parts by mass of the catalyst support for carbon nanotube (B'-2) synthesis and 29 parts by mass of the cobalt composition and iron composition were charged into a crusher (Wonder Crusher WC-3, manufactured by Osaka Chemical Co., Ltd.), a standard lid was attached, the speed dial was adjusted to 2, and the mixture was crushed and mixed for 30 seconds to obtain a catalyst precursor for carbon nanotube synthesis (B'-2). The catalyst precursor for carbon nanotube (B'-2) synthesis was transferred to a heat-resistant container and calcined in a muffle furnace (FO510, manufactured by Yamato Scientific Co., Ltd.) in an air atmosphere at 450 ± 5 ° C for 30 minutes, and then crushed in a mortar to obtain a catalyst for carbon nanotube (B'-2) synthesis.

[0085] <Synthesis of carbon nanotubes (B'-2)> A quartz glass heat-resistant dish, onto which 1 g of catalyst for carbon nanotube (B'-2) synthesis was dispersed, was placed in the center of a 10 L horizontal reactor tube that could be pressurized and heated with an external heater. The reactor was evacuated while nitrogen gas was injected, and the air inside the reactor tube was replaced with nitrogen gas. The horizontal reactor tube was heated until the ambient temperature reached 680°C. After reaching 680°C, ethylene gas was introduced into the reactor tube at a flow rate of 2 L / min, and the catalytic reaction was carried out for 7 minutes. After the reaction was completed, the gas inside the reactor tube was replaced with nitrogen gas, and the reactor tube was cooled to below 100°C and removed, yielding a carbon nanotube (B'-2) precursor. 1000 g of carbon nanotube (B'-2) precursor was weighed into a heat-resistant carbon container. The carbon container containing the carbon nanotube (B'-2) precursor was then placed in a furnace. The furnace was then evacuated to a vacuum of 1 Torr (133 Pa) or less, and a carbon heater was energized to heat the furnace to 1000°C. Argon gas was then introduced into the furnace, adjusting the pressure inside the furnace to 70 Torr (9.33 kPa), and then 1 L / min of argon gas was introduced into the furnace. Chlorine gas was then introduced into the furnace in addition to the argon gas, adjusting the pressure inside the furnace to 90 Torr (11.99 kPa). After this pressure was reached, 0.3 L / min of chlorine gas was introduced into the furnace. After maintaining this state for 1 hour, the power was turned off, and the introduction of argon gas and chlorine gas was stopped, followed by vacuum cooling. Finally, after vacuum cooling at a pressure of 1 Torr (133 Pa) or less for 12 hours, nitrogen gas was introduced into the furnace until atmospheric pressure was reached after confirming that the furnace had cooled to room temperature, and the heat-resistant container was removed to obtain carbon nanotubes (B'-2).

[0086] (Production example 12:B'-3) <Synthesis of carbon nanotubes (B'-3)> 1000 g of the carbon nanotube (B-1) precursor from Production Example 1 was weighed into a 7 L carbon heat-resistant container, and the heat-resistant container containing the carbon nanotube (B-1) precursor was placed in a furnace. Nitrogen gas was then introduced into the furnace, and the air inside the furnace was evacuated while maintaining positive pressure. After the oxygen concentration inside the furnace reached 0.1% or less, the furnace was heated to 3000°C over 30 hours and then held at 3000°C for 2 hours and 30 minutes. Heating inside the furnace was stopped, and the sample was cooled to obtain carbon nanotubes (B'-3).

[0087] [Table 1]

[0088] Example 1 (Production of Thermoplastic Resin Composition) The thermoplastic resin (A-1) was mixed at 98.5% by mass and the carbon nanotubes (B-1) at 1.5% by mass, melted and kneaded, extruded at 230°C using a twin-screw extruder (manufactured by The Japan Steel Works, Ltd.), and granulated to obtain a thermoplastic resin composition.

[0089] (Examples 2 to 4, 9 to 15, 18 to 19, 21 to 22) Thermoplastic resin compositions were obtained in the same manner as in Example 1, except that the materials and blending amounts (mass %) were changed to those shown in Tables 2 and 3, respectively.

[0090] Example 5 The thermoplastic resin (A-3) was mixed at 95% by mass and the carbon nanotubes (B-1) at 5% by mass, melted and kneaded, extruded at 250°C using a twin-screw extruder (manufactured by The Japan Steel Works, Ltd.), and granulated to obtain a thermoplastic resin composition.

[0091] (Examples 6 to 8, 20) A thermoplastic resin composition was obtained in the same manner as in Example 5, except that the materials and blending amounts (mass %) were changed to those shown in Tables 2 and 3, respectively.

[0092] Example 16 (Masterbatch manufacturing) The thermoplastic resin (A-1) was mixed at 80% by mass and the carbon nanotubes (B-1) at 20% by mass, melted and kneaded, and then extruded at 230°C using a twin-screw extruder (manufactured by The Japan Steel Works, Ltd.) and granulated to obtain a thermoplastic resin composition (masterbatch).

[0093] Example 17 The thermoplastic resin (A-2) was mixed at 80% by mass and the carbon nanotubes (B-1) at 20% by mass, and the mixture was melt-kneaded, extruded at 230°C using a twin-screw extruder (manufactured by The Japan Steel Works, Ltd.), and granulated to obtain a thermoplastic resin composition (masterbatch).

[0094] (Comparative Example 1) The thermoplastic resin (A-1) was mixed at 94 mass % and the carbon nanotubes (B'-1) at 6 mass %, and the mixture was melt-kneaded, extruded at 230°C using a twin-screw extruder (manufactured by The Japan Steel Works, Ltd.), and granulated to obtain a thermoplastic resin composition.

[0095] (Comparative Examples 2 and 3) A thermoplastic resin composition and a molded article were obtained in the same manner as in Comparative Example 1, except that the materials and blending amounts (mass %) were changed to those shown in Tables 1 and 2, respectively.

[0096] <<Measurement and Evaluation of Physical Properties of Thermoplastic Resin Composition>> The physical properties of the resulting thermoplastic resin composition were measured and evaluated by the following methods. The results are shown in Tables 2 and 3. For the masterbatches of Examples 16 and 17, the same thermoplastic resin (A) as that used in the production of the masterbatches was used as a diluent resin, and molded bodies were produced using an injection molding machine in the blending amounts (mass%) shown in Tables 2 and 3.

[0097] [Production of molded body Z1] The thermoplastic resin composition was molded using an injection molding machine (manufactured by Toshiba Machine Co., Ltd.) with a cylinder temperature set at 220°C and a mold temperature of 40°C to obtain a molded product Z1 measuring 90 mm long x 110 mm wide x 3 mm thick. The thermoplastic resin compositions of Examples 5 to 8 and 20 were used to produce molded bodies Z1 using an injection molding machine (manufactured by Toshiba Machine Co., Ltd.) with a cylinder temperature set at 250°C and a mold temperature of 80°C.

[0098] [Production of molded body Z2] A 100 μm thick sheet (molded product Z2) was produced using a T-die molding machine at a temperature 30° C. higher than the melting point of the thermoplastic resin (A) that was the main component used in the thermoplastic resin composition. When the thermoplastic resin (A) was an amorphous thermoplastic resin (resins A-3 and A-4), a 100 μm thick sheet (molded body Z2) was produced using a T-die molding machine at a temperature 130°C higher than the glass transition temperature.

[0099] [Production of molded body Z3] The thermoplastic resin composition was molded using an injection molding machine (manufactured by Toshiba Machine Co., Ltd.) with a cylinder temperature set at 220°C and a mold temperature of 40°C to obtain a molded product Z3 measuring 60 mm long x 60 mm wide x 2 mm thick. The thermoplastic resin compositions of Examples 5 to 8 and 20 were used to produce molded bodies Z3 using an injection molding machine (manufactured by Toshiba Machine Co., Ltd.) with a cylinder temperature set at 250°C and a mold temperature of 80°C.

[0100] [Production of molded body Z4] Using the thermoplastic resin composition, a molded body Z4 of an A1 type dumbbell-shaped test piece conforming to JIS-K7139:2019 was produced.

[0101] (Total metal content) The thermoplastic resin composition was subjected to acid decomposition using a microwave sample pretreatment device (Milestone General, ETHOS1) to extract the metals contained in the thermoplastic resin composition. The extracted metals were then analyzed using a multi-type ICP optical emission spectrometer (Agilent, 720-ES) to calculate the total metal content (ppm) of the thermoplastic resin composition.

[0102] (conductive) The conductivity was evaluated by surface resistivity. Using the resulting molded body (molded body Z1) measuring 90 mm in length, 110 mm in width, and 3 mm in thickness, the surface resistivity was measured at any five points using a Loresta-GP MCP-T610 resistivity meter (JIS-K7194 compliant, 4-terminal 4-probe constant current application method) manufactured by Nitto Seiko Analytech Co., Ltd., and the average value was calculated. The lower the surface resistivity, the higher the conductivity. The evaluation criteria are as follows: [Evaluation criteria] ◎: The surface resistivity of the molded product is 1.0×10 3 Ω / □ or less, excellent for practical use ○: The surface resistivity of the molded product is 1.0 × 10 3 Ω / □, over 1.0×10 5 Ω / □ or less, excellent for practical use △: The surface resistivity of the molded product is 1.0 × 10 5 Ω / □, over 1.0×10 7 Ω / □ or less, so it is practical ×: The surface resistivity of the molded product is 1.0 × 10 7 Exceeds Ω / □ and is not practical

[0103] (uniformity) The uniformity of the CNTs within the molded body was evaluated by surface smoothness, in-plane variation, and molding shrinkage. Good surface smoothness means that the resin has good fluidity even when affected by the thickening effect of the CNTs, the CNTs are dispersed uniformly, and there is no variation in the surface, resulting in a molded product with a uniform surface. With regard to in-plane variations, the more uniform the concentration on the surface of the molded article, the smaller the difference in conductivity, and the more uniform the CNT concentration on the surface of the molded article. The molding shrinkage rate indicates the uniformity of the CNT concentration throughout the molded body, and it can be said that the smaller the difference in molding shrinkage rate, the more uniformly the CNTs are dispersed throughout the molded body. Furthermore, it is most desirable that the molding shrinkage rate is excellent, as this indicates uniformity throughout the molding.

[0104] <Surface smoothness> The surface smoothness was evaluated based on the maximum height Sz of the sheet surface. The obtained sheet (molded body Z2) having a thickness of 100 μm was used to measure the maximum height Sz (μm) using a Talysurf CCI MP-HS manufactured by Taylor / Hobson, with a measurement length of 2.5 mm × 2.5 mm and a robust Gaussian filter of 0.08 mm. It can be said that the smaller the Sz, the more uniformly the CNTs are dispersed in the thermoplastic resin composition. [Evaluation criteria] ◎: The Sz of the molded product is 2.0 μm or less, and is particularly excellent for practical use. ○: The Sz of the molded product is greater than 2.0 μm and less than 3.0 μm, and is excellent for practical use. △: Sz of the molded product is more than 3.0 μm and 5.0 μm or less, and it is practically usable ×: Sz of the molded product exceeds 5.0 μm and is not practical.

[0105] <In-plane variation> The obtained molded body (molded body Z1) having a length of 90 mm, a width of 110 mm, and a thickness of 3 mm was used to measure the surface resistivity at any five points using a Hiresta manufactured by Mitsubishi Chemical Corporation, and the maximum / minimum value (X) was calculated from the maximum and minimum values ​​to evaluate the surface resistivity. The evaluation criteria are as follows: The smaller the maximum value / minimum value (X), the smaller the in-plane variation. [Evaluation criteria] ◎: The maximum / minimum value (X) of the surface resistivity of the molded product is 1≦X<5, and is particularly excellent for practical use. ○: The maximum / minimum value (X) of the surface resistivity of the molded product is 5≦X<10, and is excellent for practical use. △: The maximum / minimum value (X) of the surface resistivity of the molded product is 10≦X<100, and it is practically usable. ×: The maximum value / minimum value (X) of the surface resistivity of the molded product is 100≦X, and it is not practical.

[0106] <Molding shrinkage rate> The resulting molded body (molded body Z3) measuring 60 mm long, 60 mm wide, and 2 mm thick was measured for mold shrinkage in the direction parallel to the flow direction of the thermoplastic resin composition (MD) and the direction perpendicular to the flow direction (TD), and the mold shrinkage ratio (TD / MD) was calculated. The smaller the mold shrinkage ratio, the better the uniformity of the CNTs throughout the molded body. [Evaluation criteria] ◎: The molding shrinkage ratio of the molded product is 1.5 or less, and is particularly excellent for practical use. ○: The molding shrinkage ratio of the molded product is more than 1.5 and 2.5 or less, and is excellent for practical use. △: The molding shrinkage ratio of the molded product is more than 2.5 and 3.5 or less, and it is practically usable. ×: The molding shrinkage ratio of the molded product exceeds 3.5, making it unsuitable for practical use.

[0107] (Thermal stability over time) The thermal stability over time was evaluated by thermal degradation resistance. The obtained dumbbell-shaped test pieces (molded body Z4) of each Example were aged under the following conditions: (1) 24 hours in a 23°C atmosphere (before heat aging) and (2) 120 hours in a 130°C atmosphere (test pieces after heat aging), and the tensile strength was measured according to JIS-K7161-1: 2014. The tensile strength retention rate was calculated from the obtained tensile strength according to the following formula. It can be said that the higher the tensile strength retention rate, the higher the thermal stability over time. Tensile strength retention rate (%) = tensile strength of test piece after heat aging (MPa) / tensile strength of test piece before heat aging (MPa) × 100 [Evaluation criteria] ◎: The tensile strength retention rate of the molded product is 95% or more, which is particularly excellent for practical use. ○: The tensile strength retention rate of the molded product is 90% or more and less than 95%, which is excellent for practical use. △: Tensile strength retention rate of the molded product is 80% or more but less than 90%, and it is practically usable. ×: Tensile strength retention rate of the molded product is less than 80% and it is not practical.

[0108] [Table 2]

[0109] [Table 3]

[0110] From the results shown in Tables 2 and 3, it was confirmed that by using the thermoplastic resin composition of the present invention, aggregation of carbon nanotubes can be suppressed, and when molded into a molded product, a molded product with excellent uniformity of carbon nanotubes and high conductivity can be obtained. Furthermore, it was confirmed that the deterioration of the thermoplastic resin composition due to heat over time was eliminated, and a thermoplastic resin composition in which thermal deterioration was suppressed even in a high-temperature atmosphere could be obtained.

Claims

1. A thermoplastic resin (A) and carbon nanotubes (B), The carbon nanotubes (B) satisfy both of the following (1) and (2): Thermoplastic resin composition. (1) The total metal content is 10,000 ppm or less. (2) In powder X-ray diffraction analysis, the half-value width of the diffraction peak of the (002) plane is 2.0 to 6.0°.

2. The thermoplastic resin composition according to claim 1, wherein the carbon nanotubes (B) have an ash content of 0.001 to 1.0 mass % when heated at 900°C for 1 hour.

3. 2. The thermoplastic resin composition according to claim 1, wherein the iron content of the carbon nanotubes (B) is 10 to 5,000 ppm.

4. Carbon nanotubes (B) have a volume resistivity of 1.0 × 10 －３ ~3.0 x 10 －２ The thermoplastic resin composition according to claim 1, wherein the modulus is Ω·cm.

5. The carbon nanotubes (B) have a BET specific surface area of ​​200 to 600 m ２ The thermoplastic resin composition according to claim 1, wherein the modulus of elasticity is 1 / g.

6. 2. The thermoplastic resin composition according to claim 1, wherein the carbon nanotubes (B) have a cobalt content of 10 to 1,000 ppm.

7. 2. The thermoplastic resin composition according to claim 1, wherein the thermoplastic resin (A) comprises any one selected from the group consisting of a polyethylene resin, a polypropylene resin, an acrylonitrile-butadiene-styrene copolymer resin, a polycarbonate resin, a polyamide resin, and a polyester-based resin.

8. 2. The thermoplastic resin composition according to claim 1, wherein the total metal content of the thermoplastic resin composition is 3,000 ppm or less.

9. A molded article formed using the thermoplastic resin composition according to any one of claims 1 to 8.

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