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 thermoplastic resin compositions and molded articles. [Background technology]

[0002] Due to their ease of molding and processing, resin molded products are used in a wide range of fields, including automotive parts, medical components, food containers, and electrical and electronic equipment components. In particular, resin molded products containing carbon nanotubes, a type of carbon material, are being actively studied for purposes such as enhancing decorative appeal or adding functionality.

[0003] Carbon nanotubes have a cylindrical structure of graphite layers, are chemically stable, and are mass-produced using chemical vapor deposition (CVV), a highly productive and economical method, leading to their widespread use. They also possess conductivity and mechanical toughness, and by mixing carbon nanotubes with thermoplastic resins, various functionalities such as conductivity, thermal conductivity, improved mechanical strength, and electromagnetic wave absorption can be imparted to molded materials. Therefore, carbon nanotubes are applied in a wide range of fields, including electronics (transistor elements, wiring, etc.), energy (fuel cell electrode materials, solar power generation equipment, gas storage, etc.), electron emission (flat panel devices, etc.), chemistry (adsorbents, catalysts, sensors, etc.), and composite materials (conductive plastics, reinforcing materials, flame-retardant nanocomposites, etc.).

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

[0005] [Patent Document 1] Japanese Patent Publication No. 2016-108524 [Patent Document 2] Japanese Patent Publication No. 2022-076641 [Overview of the project] [Problems that the invention aims to solve]

[0006] In thermoplastic resin compositions, conductive paths are formed when carbon nanotubes dispersed in the thermoplastic resin come into contact with each other, thereby imparting conductivity. Therefore, ideally, the more uniformly fibrous carbon nanotubes are dispersed in the thermoplastic resin, the more efficient a conductive network can be formed. However, carbon nanotubes have high cohesive forces, making it difficult to obtain a thermoplastic resin composition in which they are uniformly dispersed. Furthermore, aggregated carbon nanotubes increase the viscosity of the thermoplastic resin composition, reducing its fluidity. This can lead to uneven dispersion in the molded product, resulting in differences in surface resistance depending on the location in the molded product, or a larger shrinkage rate during molding. Furthermore, under high-temperature conditions, oxidation and decomposition reactions in thermoplastic resins can pose problems to their thermal stability over time.

[0007] Therefore, the present invention aims to provide a molded article that suppresses the aggregation of carbon nanotubes in a thermoplastic resin composition, exhibits excellent uniformity of carbon nanotubes when molded, and possesses high conductivity. Furthermore, the objective is to provide a molded product that also exhibits excellent thermal stability over time. [Means for solving the problem]

[0008] In other words, 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 all of the following conditions (1) and (2). (1) The total metal content is 10,000 ppm or less. (2) In powder X-ray diffraction analysis, the full width at half maximum 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 nanotube (B) has an ash content of 0.001 to 1.0% by 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 nanotube (B) is 10 to 5,000 ppm. [4]; The carbon nanotube (B) has a volume resistivity of 1.0×10 -3 ~3.0×10 -2 Ω·cm. The thermoplastic resin composition according to any one of [1] to [3]. [5]; The carbon nanotube (B) has a BET specific surface area of 200 to 600 m 2 / g. The thermoplastic resin composition according to any one of [1] to [4]. [6]; The thermoplastic resin composition according to any one of [1] to [5], wherein the cobalt content of the carbon nanotube (B) is 10 to 1,000 ppm. [7]; The thermoplastic resin (A) includes any one selected from the group consisting of polyethylene resin, polypropylene resin, acrylonitrile-butadiene-styrene copolymer resin, polycarbonate resin, polyamide resin, and polyester resin. The thermoplastic resin composition according to any one of [1] to [6]. [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 body formed using the thermoplastic resin composition according to any one of [I] to [8]. [Advantages of the Invention] [[ID=DB23]] [[ID=DB24]] [[ID=DB25]]

[0009] [[ID=DB26]] According to the present invention, by using a specific carbon nanotube, aggregation of carbon nanotubes in the thermoplastic resin composition is suppressed, and a thermoplastic resin composition excellent in the dispersibility of carbon nanotubes, and a molded body excellent in conductivity, uniformity, and thermal stability over time formed from the thermoplastic resin composition can be provided. [Embodiments for Carrying Out the Invention]

[0010] Hereinafter, the present invention will be described in detail. In this specification, "film" and "sheet" are synonymous. In this specification, a numerical range specified using "~" shall include the numerical values described before and after "~" as the range of the lower limit value and the upper limit value. Also, "carbon nanotube" may be represented as "CNT", and "thermoplastic resin composition" may be represented as "resin composition". Unless otherwise noted, the various components appearing in this specification may be used alone or in combination of two or more.

[0011] 《Thermoplastic Resin Composition》 The thermoplastic resin composition of the present invention will be described. The thermoplastic resin composition of the present invention is used to form a molded body. The thermoplastic resin composition contains a thermoplastic resin (A) and carbon nanotubes (B), and the carbon nanotubes (B) satisfy all of the following (1) and (2). Thereby, it becomes possible to provide a molded body 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-width of the diffraction peak of the (002) plane is 2.0 to 6.0°.

[0012] [[ID=2Y]] The thermoplastic resin composition of the present invention uses carbon nanotubes (B) in which the total metal content and the half-width of the X-ray diffraction peak are in a specific range, so that the dispersibility of the carbon nanotubes in the thermoplastic resin composition is excellent. Thereby, the obtained molded body has high conductivity, excellent uniformity of carbon nanotubes, and good thermal stability over time.

[0013] Carbon nanotubes may contain metallic impurities, as catalyst particles containing metal components such as iron and cobalt are used during their manufacture. However, the thermoplastic resin composition of the present invention uses carbon nanotubes with a total metal content of 10,000 ppm or less. This suppresses the reduction in the rate of contact between carbon nanotubes and the decrease in dispersibility within the thermoplastic resin composition caused by these metallic impurities, thereby enabling the production of molded articles with excellent conductivity and uniformity. Furthermore, by using carbon nanotubes in which metal impurities that promote oxidation and decomposition reactions of thermoplastic resins under high-temperature conditions are within the above range, it is possible to produce molded articles with excellent thermal stability over time.

[0014] However, simply purifying carbon nanotubes to reduce metallic impurities may result in decreased dispersibility. Therefore, in this invention, we have found that by using highly crystalline carbon nanotubes, which have a total metal content and, in addition, have an X-ray diffraction peak width at half maximum within a specific range, it is possible to create a molded body with excellent uniformity while maintaining conductivity, while suppressing the cohesive force between carbon nanotubes.

[0015] The total metal content in the thermoplastic resin composition is preferably as low as possible, and 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 thermoplastic resins may also contain metal impurities because organometallic catalysts such as metallocene catalysts are used during their manufacture. Furthermore, metal particles originating from the manufacturing process, such as those from equipment and piping, may be present in the thermoplastic resin composition. However, if the total metal content is within the aforementioned range, the contact rate between carbon nanotubes improves, allowing the thermoplastic resin and carbon nanotubes to mix uniformly, preventing uneven dispersion and resulting in superior uniformity. In addition, oxidation and decomposition reactions of the thermoplastic resin due to metal impurities are suppressed, resulting in a molded article with superior conductivity and thermal stability over time.

[0016] To keep 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 of the thermoplastic resin (A) and the manufacturing method of 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. Having the total metal content of the thermoplastic resin (A) within this range allows for superior thermal stability over time of the thermoplastic resin composition.

[0017] <Thermoplastic resin (A)> The thermoplastic resin (A) is not particularly limited as long as it is a resin that can form a molded article by heating and melting. Examples of thermoplastic resins (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 resin (PE), polypropylene resin (PP), acrylonitrile-butadiene-styrene copolymer resin (ABS), polycarbonate resin (PC), polyamide resin (PA), and polyester resins are preferred, and polyethylene resin (PE), polypropylene resin (PP), acrylonitrile-butadiene-styrene copolymer resin (ABS), and polycarbonate resin (PC) are more preferred.

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

[0020] In this invention, MFR is a value obtained by measuring each thermoplastic resin using the melt mass flow rate value in accordance with JIS-K7210.

[0021] <Carbon nanotubes (B)> Carbon nanotubes (B) satisfy the following conditions (1) and (2). (1) The total metal content is 10,000 ppm or less. (2) In powder X-ray diffraction analysis, the full width at half maximum 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 it is a single layer, it is called a single-walled carbon nanotube (SWCNT), and if it is a multi-walled carbon nanotube (MWCNT). Individual carbon nanotubes can be observed using an electron microscope. Carbon nanotubes undergo primary aggregation, where carbon nanotube fibers entangle or form bundle-like primary aggregates. However, primary aggregates can also aggregate to form secondary or higher aggregates.

[0023] Carbon nanotubes (B) may be single-walled carbon nanotubes, multi-walled carbon nanotubes wound in two or more layers, or a mixture of these, but multi-walled carbon nanotubes are preferred from a cost and strength standpoint. In addition, carbon nanotubes with an amorphous structure instead of a graphite structure for their sidewalls may be used.

[0024] Carbon nanotubes (B) can generally be manufactured by methods such as laser ablation, arc discharge, chemical vapor deposition (CVD), and combustion, but any carbon nanotube manufactured by any method is acceptable. In particular, the CVD method is a method that can produce carbon nanotubes inexpensively and in large quantities by contacting catalyst nanoparticles, on which metal catalysts such as iron, cobalt, and nickel are supported on a support such as silica, alumina, magnesium oxide, titanium oxide, silicates, diatomaceous earth, alumina silica, silica titania, and zeolite, with a carbon-containing gas raw material at a high temperature of usually 400 to 1000°C, and is therefore preferred as the carbon nanotube used in the present invention.

[0025] [Metal content] Carbon nanotubes (B) have a total metal content of 10,000 ppm or less, based on the mass of carbon nanotubes (B). The metal content in carbon nanotubes (B) is preferably 500 to 10,000 ppm, and more preferably 500 to 7,500 ppm. Examples of metals include iron, cobalt, aluminum, and molybdenum. Each metal atom in carbon nanotubes (B) can exist as a magnetic material such as a metal or alloy, or as a non-magnetic material such as an oxide or carbide. When the total metal content of carbon nanotubes (B) is within the above range, the purity of carbon nanotubes (B) is increased, and the dispersibility of carbon nanotubes (B) in conductive and thermoplastic resin compositions is excellent.

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

[0027] When using a catalyst containing iron atoms, the iron atom content in 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. Having the iron atom content in carbon nanotubes (B) within this range suppresses degradation of the carbon nanotubes due to the purification process and improves the dispersibility of carbon nanotubes (B) in the thermoplastic resin composition. Iron atoms in carbon nanotubes (B) can exist as magnetic materials such as metals and alloys, or as non-magnetic materials such as oxides and carbides. When the iron atom content of carbon nanotubes (B) is within the above range, the conductivity of carbon nanotubes (B) is increased, and corrosion of metals in contact with carbon nanotubes (B) can be suppressed.

[0028] Methods to keep the amount of iron atoms in carbon nanotubes (B) within the above range include increasing the carbon nanotube (B) yield per unit mass of catalyst particles in the carbon nanotube (B) manufacturing process, using catalyst particles that do not contain iron atoms, reducing the proportion of iron atoms in the catalyst particles, and reducing the amount of iron atoms introduced in the carbon nanotube (B) manufacturing process. Iron atoms may also be removed by known methods such as acid treatment, graphitization treatment, or chlorination treatment, as described later.

[0029] When using a catalyst containing cobalt atoms, the cobalt atom content in carbon nanotubes (B) is preferably 10 to 1,000 ppm or less, more preferably 10 to 800 ppm, and even more preferably 10 to 600 ppm. Having the cobalt atom content in carbon nanotubes (B) within this range suppresses degradation of the carbon nanotubes due to purification treatment and provides excellent dispersibility of carbon nanotubes (B) in the thermoplastic resin composition. The cobalt atoms in carbon nanotubes (B) can exist as magnetic materials such as metals and alloys, or as non-magnetic materials such as oxides and carbides.

[0030] When catalyst particles containing cobalt atoms are used in the manufacturing process of carbon nanotubes (B), the production productivity of carbon nanotubes (B) can be maintained if the cobalt atom content of the carbon nanotubes (B) is within the above range. Furthermore, being within the above range reduces the amount of cobalt atoms acting as a non-magnetic material, thereby lowering the volume resistivity of the molded body. Methods for adjusting the amount of cobalt atoms in the carbon nanotubes to be within the above range include increasing the carbon nanotube yield per unit mass of catalyst particles in the manufacturing process, and reducing the proportion of cobalt atoms in the catalyst particles. In addition, cobalt atoms may be removed by known methods such as acid treatment, graphitization treatment, or chlorination treatment, as described later.

[0031] Metallic components contained in carbon nanotubes may be removed by known methods to the extent that they do not impair the effects of the present invention. Examples include acid treatment, graphitization treatment, and chlorination treatment. When removing metal components by acid treatment, any acid capable of dissolving the metal components contained in carbon nanotubes is acceptable. For example, inorganic acids or carboxylic acids are preferred, and among inorganic acids, hydrochloric acid, sulfuric acid, and nitric acid are particularly preferred. The acid treatment of carbon nanotubes is preferably carried out in a liquid phase, and it is even more preferable to disperse and / or mix the carbon nanotubes in the liquid phase. After acid treatment, the carbon nanotubes are preferably washed with water and dried.

[0032] The graphitization 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] The 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] From a cost perspective, acid treatment or graphitization treatment is preferred as a method for removing metallic components contained in carbon nanotubes.

[0035] [Half-width of X-ray diffraction peaks] The full width at half maximum of the diffraction peak of the (002) plane of carbon nanotube (B) is 2.0 to 6.0°. Preferably, the temperature is between 2.0 and 5.0°. This range results in a thermoplastic resin composition with good carbon nanotube dispersibility. A half-width of 2.0° or higher reduces the amorphous portion of the carbon nanotube, increasing its crystallinity. Furthermore, a half-width of 6.0° or lower increases the number of carbon nanotube layers, resulting in a carbon nanotube with a large specific surface area and high crystallinity while suppressing the cohesive forces between the nanotubes, thus maintaining high dispersibility.

[0036] The (002) plane of carbon nanotube (B) was detected at a 2θ of 25°±2°, and its position changes with the interplane distance of the carbon hexagonal network planes. The higher the angle of the peak, the closer the distance between the carbon hexagonal network planes, indicating a high degree of graphitic regularity in the structure. Furthermore, the sharper the peak (smaller full width at half maximum), the larger the crystallite size and the more developed the crystal structure.

[0037] The full width at half maximum (FWHM) of carbon nanotubes (B) can be calculated as follows: First, carbon nanotubes (B) are packed into a designated sample holder so that the surface is flat, and then placed in a powder X-ray diffraction analyzer. Measurements are taken by varying the irradiation angle of the X-ray source from 5° to 80°. For example, CuKα rays are used as the X-ray source. The step size is 0.010°, and the measurement time is 1.0 second. By reading the diffraction angle 2θ at which the peak appears, it is possible to evaluate carbon nanotubes (B). In graphite, a peak is usually detected at 2θ around 26°, and this is known to be a peak 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 will differ from that of graphite. The appearance of a peak at a value of 2θ of 25°±2° indicates that the composition contains a multilayer structure rather than a single layer. Since the peak that appears at this position is a peak due to interlayer diffraction of a multilayer structure, it is possible to determine the number of layers in carbon nanotubes (B). Since single-walled carbon nanotubes have only one layer, a peak at 25°±2° does not appear in single-walled carbon nanotubes alone. However, even with single-walled carbon nanotubes, it is not 100% single-walled carbon nanotubes, and if multi-walled carbon nanotubes or other materials are mixed in, a peak may appear at 25°±2° of 2θ.

[0038] In the carbon nanotube (B) of this embodiment, a peak appears at a position where 2θ is 25° ± 2°. Also, the layer structure can be analyzed from the half-width of the peak at 25° ± 2° detected by powder X-ray diffraction analysis. That is, it is considered that the smaller the half-width of this peak, the larger the number of layers of the carbon nanotube (B). Conversely, the larger the half-width of this peak, the smaller the number of layers of the carbon nanotube is considered to be.

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

[0040] [Ash content] The ash content of the carbon nanotube is a non-combustible component containing metal components and the like. The carbon nanotube (B) preferably has an ash content of 0.001 to 1.0% by mass, more preferably 0.01 to 0.9% by mass, and even more preferably 0.1 to 0.8% by mass. The value of the ash content of the carbon nanotube can be calculated by measuring the ash residue after firing at 900 °C for 1 hour in air according to formula (i). Ash content of carbon nanotube (mass%) = Mass of ash after firing (g) / Mass of carbon nanotube before firing (g) × 100 ····Formula (i) It is preferable that the ash content is within the above range because the conductivity and dispersibility are further improved.

[0041] [Volume resistivity] The volume resistivity of the carbon nanotube (B) is preferably 1.0×10 -3 ~3.0×10 -2 Ω·cm, more preferably 1.0×10 -3 ~2.5×10 -2 Ω·cm, and even more preferably 1.0×10 -3 ~2.0×10 -2 Ω·cm. When the volume resistivity of the carbon nanotube (B) is within the above range, the conductivity of the molded body becomes better. The volume resistivity of carbon nanotubes (B) can be measured and determined using a powder resistivity measuring device (Rolestar GP Powder Resistivity Measuring System MCP-PD-51, manufactured by Nitto Seikou Analytech Co., Ltd.).

[0042] [BET specific surface area] The BET specific surface area of ​​carbon nanotubes (B) is 200-600 m². 2 It is preferable that the amount be / g, and 200-500m 2 It is more preferable that the value be / g, and 200-400m 2 It is even more preferable that the value is / g. The BET specific surface area of ​​carbon nanotubes can be calculated by the BET method using nitrogen adsorption measurement. 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 carbon nanotubes there are per unit 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 carbon nanotubes there are per unit mass. When the specific surface area of ​​carbon nanotubes is within the above range, the number of carbon nanotubes per unit mass becomes such that a conductive network can be efficiently formed, and the cohesive force is such that carbon nanotubes can be easily dispersed, thus forming a good conductive network and resulting in higher conductivity.

[0043] [G / D ratio of Raman spectrum] Carbon nanotubes (B) show a Raman spectrum of 1560–1600 cm⁻¹. -1 G represents the maximum peak intensity within the range of 1310-1350 cm. -1 When the maximum peak intensity within the range is denoted 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. Having the G / D ratio of carbon nanotubes within the above range allows for superior conductivity and uniformity of the molded article.

[0044] The G / D ratio was determined based on measurements performed using a micro-laser Raman spectrophotometer (JASCO Corporation NRS-3100) with a powder sample and a laser wavelength of 532 nm, resulting in a G / D ratio of 1590 cm². -1 G-bands originating from the nearby graphite structure and 1350cm -1 It can be calculated from the integral value of the D-band peak originating from nearby structural defects. Raman spectrum at 1590 cm⁻¹ -1 The Raman shift observed in the vicinity is called the graphite-derived G-band, and is 1350 cm. -1 The Raman shift observed in the vicinity is called the D band, originating from defects in amorphous carbon and graphite. Carbon nanotubes with a higher G / D ratio have a higher degree of graphitization, crystallinity, and purity.

[0045] [Average diameter] The carbon nanotubes (B) preferably have an average diameter of 5 to 20 nm, and more preferably 8 to 15 nm. Having the average diameter of carbon nanotubes within the above range results in a large specific surface area, making it easier to form a conductive network and create easily dispersed aggregates. This is preferable because it improves conductivity and dispersibility, resulting in excellent conductivity and uniformity of the molded article.

[0046] The average diameter of carbon nanotubes (B) can be determined by image analysis. For example, the average diameter can be determined by observing carbon nanotubes using a scanning electron microscope (JEOL JSM-6700M) at an accelerating voltage of 5kV, and capturing images at 50,000x magnification (1024 x 1280 pixels). Then, the short-axis length of 20 arbitrary carbon nanotubes is measured from the captured image, and the numerical average of the obtained short-axis lengths can be considered the average diameter of the carbon nanotubes.

[0047] <Other ingredients> The molded articles and thermoplastic resin compositions of the present invention may optionally contain oxidation stabilizers, weather stabilizers, antistatic agents, dyes, pigments, dispersants, coupling agents, crystal nucleating agents, resin fillers, and the like.

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

[0049] The thermoplastic resin composition of the present invention may be a compound with a relatively low concentration of carbon nanotubes (B) that can be used for molding in its original composition without dilution with thermoplastic resin (A), or it may be a masterbatch containing a relatively high concentration of carbon nanotubes (B) that is diluted with thermoplastic resin (A) during molding. Both the compound and the masterbatch are preferably in pellet form for easy handling.

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

[0051] In the case of a compound, the carbon nanotube (B) content 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, per 100 parts by mass of thermoplastic resin (A). A carbon nanotube (B) content of 25 parts by mass or less is preferable because it suppresses the re-aggregation of carbon nanotubes and improves dispersibility.

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

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

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

[0055] In the case of a masterbatch, the carbon nanotube (B) content is preferably 10 to 23% by mass, and more preferably 10 to 20% by mass, based on the mass of the masterbatch (100% by 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, and even more preferably 15,000 ppm or less. Particularly preferably, it is 3,000 ppm or less.

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

[0058] Molded body The molded articles of the present invention are formed using the thermoplastic resin composition described herein. While the applications are not particularly limited, they can be used in conductive trays. They can also be used as protective materials for electronic components, such as electronic component packaging bags. Furthermore, they can be used in personal computer bodies and their internal electronic components, external hard drives, home appliances, automotive parts, electromagnetic wave absorbers, and the like.

[0059] The molded article can be formed by melt-kneading a thermoplastic resin composition containing carbon nanotubes (B) and a thermoplastic resin (A), and then molding it. Specifically, the compound or masterbatch and diluted resin can be melted and mixed in a molding machine typically set to 50°C to 350°C, then the molded body is formed and cooled. The temperature of the molding machine can be any temperature at which the thermoplastic resin (A) softens, but preferably it is 30°C or more higher than the softening point of the main component thermoplastic resin (A).

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

[0061] Furthermore, the molding method can include, for example, extrusion molding, injection molding, blow molding, compression molding, transfer molding, film molding such as T-die molding and inflation molding, calendering, spinning, etc., with extrusion molding, injection molding, blow molding, T-die molding and 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 a molded product 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. [Examples]

[0063] The present invention will be described in more detail below with reference to examples, but the following examples are not intended to limit the present invention in any way. In the examples, "parts" refers to "parts by mass" and "%" refers to "percentage 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> Carbon nanotubes were acid-digested using a microwave sample preparation device (Milestone General, ETHOS1) to extract metals (iron, cobalt, etc.) contained within the carbon nanotubes. Subsequently, analysis was performed using a multi-type ICP emission spectrometer (Agilent, 720-ES) to calculate the total metal content, as well as the iron and cobalt atom content of the carbon nanotubes.

[0065] <Powder X-ray diffraction analysis of carbon nanotubes> Carbon nanotubes were 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, weighing paper was placed on the surface on which the sample was placed, and an aluminum high-sheet packing was placed on the surface, and a load of 1 ton was applied to flatten it further. After that, the weighing paper and aluminum high-sheet packing were removed to obtain a sample for powder X-ray diffraction analysis of carbon nanotubes. Subsequently, the sample for powder X-ray diffraction analysis of carbon nanotubes was placed in an X-ray diffractometer (Ultima2100, Rigaku Corporation) and analyzed by operating it from 15° to 35°. Sampling was performed every 0.02°, and the scan speed was 2° / min. The voltage was 40kV, the current was 40mA, and the X-ray source was CuKα. The plots of the (002) plane of carbon nanotubes appearing at diffraction angles 2θ = 25° ± 2° were each subjected to an 11-point simple moving average, and the full width at half maximum (FWHM) of the peaks was taken as the FWHM of the carbon nanotubes. The baseline was defined as the line connecting the plots at 2θ = 16° and 2θ = 34°.

[0066] <Ash content of carbon nanotubes> The ash content of carbon nanotubes (B) was calculated by placing 1.0 g of carbon nanotubes in a porcelain crucible, heating it in a 900°C furnace for 1 hour to ashify it, and then cooling it before calculating the ash content based on formula (i). Ash content (mass%) of carbon nanotubes = (Ash content 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), with a sample mass of 1.2 g, and a powder probe unit (four probes and 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 conductive powder under various pressures was measured, resulting in a value of 1 g / cm³. 3 The volume resistivity of carbon nanotubes at a given density was determined.

[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. Subsequently, the BET specific surface area of ​​the carbon nanotubes was measured using a fully automated specific surface area analyzer (MOUNTECH, HM-model1208).

[0069] <Raman spectroscopy analysis of carbon nanotubes> A carbon nanotube was placed in a micro-laser Raman spectrophotometer (JASCO Corporation NRS-3100), and measurements were performed using a laser wavelength of 532 nm. Measurement conditions were: acquisition time 60 seconds, number of integrations 2, light-reducing 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 glass slide and flattened using a spatula. Of the obtained peaks, the spectral peaks at 1560–1600 cm⁻¹ were obtained. -1 Within the range of G, the maximum peak intensity is 1310-1350 cm. -1 Within the specified range, the maximum peak intensity was defined as D, and the G / D ratio was defined as the G / D ratio for carbon nanotubes.

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

[0071] The materials used in the example are as follows: <Thermoplastic resin (A)> • (A-1) Kernel KJ-640T (manufactured by Nippon Polyethylene Co., Ltd., polyethylene resin, MFR: 30g / 10 mins) • (A-2) Novatec MA1B (manufactured by Nippon Polypropylene Co., Ltd., polypropylene resin, MFR: 21g / 10 min) • (A-3) Stylelac ABS191 (manufactured by Asahi Kasei Chemicals, ABS resin, MFR: 26g / 10 min) • (A-4) Yupiron H-3000 (manufactured by Mitsubishi Engineering Plastics, polycarbonate resin, MFR: 35g / 10 min) • (A-5) Amiran CM1017 (manufactured by Toray Industries, Inc., polyamide resin, MFR: 35g / 10 mins) • (A-6) Juranex 700FP (Polyplastics, polyester resin, MFR: 30g / 10 min) • (A-7) Duracon M90-44 (manufactured by Polyplastics Co., Ltd., polyacetal resin, MFR: 9g / 10 min (measurement conditions: 190℃, 2.16kgf))

[0072] <Carbon nanotubes> • (B-1) Carbon nanotubes from manufacturing example 1 • (B-2) Carbon nanotubes in manufacturing example 2 • (B-3) Carbon nanotubes in manufacturing example 3 • (B-4) Carbon nanotubes in manufacturing example 4 • (B-5) Carbon nanotubes in manufacturing example 5 • (B-6) Carbon nanotubes in manufacturing example 6 • (B-7) Carbon nanotubes in manufacturing example 7 • (B-8) Carbon nanotubes in manufacturing example 8 • (B-9) Carbon nanotubes in manufacturing example 9 • (B'-1) Carbon nanotubes in manufacturing example 10 • (B'-2) Carbon nanotubes in manufacturing example 11 • (B'-3) Carbon nanotubes in manufacturing example 12

[0073] (Manufacturing example 1:B-1) <Catalyst for the synthesis of 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 the cobalt composition and 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. Then, 29 g of the cobalt composition and iron composition were 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 that, it was crushed in a mortar to obtain the catalyst for carbon nanotube (B-1) synthesis.

[0074] <Synthesis of carbon nanotubes (B-1)> A heat-resistant quartz glass dish containing 2 g of the carbon nanotube (B-1) synthesis catalyst was placed in the center of a horizontal reaction tube with an internal volume of 10 L, which was pressurizable and could be heated by an external heater. The reaction tube was evacuated while nitrogen gas was injected, replacing the air inside with nitrogen gas and reducing the oxygen concentration inside the horizontal reaction tube to 1 volume% or less. Next, it was heated with an external heater until the core temperature inside the horizontal reaction tube reached 680°C. After reaching 680°C, propane gas was introduced into the reaction tube at a flow rate of 2 L / min as a carbon source, and the reaction was carried out in a catalytic reaction for 1 hour. After the reaction was complete, the gas inside the reaction tube was replaced with nitrogen gas, and the reaction tube was cooled to below 100°C before being removed to obtain the carbon nanotube (B-1) precursor. 1000g of carbon nanotube (B-1) precursor was weighed into a 7L heat-resistant carbon container, and the container containing the carbon nanotube (B-1) precursor was placed inside the furnace. Then, nitrogen gas was introduced into the furnace, and while maintaining positive pressure, the air inside the furnace was expelled. After the oxygen concentration inside the furnace fell below 0.1%, the furnace temperature was raised to 3000°C over 30 hours, and then maintained at 3000°C for 30 minutes. After that, heating inside the furnace was stopped, and the sample was cooled to obtain carbon nanotube (B-1).

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

[0076] (Manufacturing example 3: B-3) <Synthesis of carbon nanotubes (B-3)> 1000g of the carbon nanotube (B-1) precursor from Production Example 1 was weighed into a 7L heat-resistant carbon container, and the heat-resistant container containing the carbon nanotube (B-1) precursor was placed in a furnace. Then, nitrogen gas was introduced into the furnace, and while maintaining positive pressure, the air inside the furnace was expelled. After the oxygen concentration inside the furnace fell below 0.1%, the furnace temperature was raised to 3000°C over 30 hours, and then maintained at 3000°C for 1 hour. After that, heating inside the furnace was stopped, and the sample was cooled to obtain carbon nanotube (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 the furnace. Then, while injecting nitrogen gas, the furnace was evacuated to replace the air in the reaction tube with nitrogen gas, and the furnace was heated until the ambient temperature in the horizontal reaction tube reached 700°C. After reaching 700°C, ethylene gas was introduced into the reaction tube as a hydrocarbon at a flow rate of 2 L / min, and the reaction was carried out in a catalytic reaction for 15 minutes. After the reaction was complete, the gas in the reaction tube was replaced with nitrogen gas, and the reaction tube was cooled to below 100°C and removed to obtain the carbon nanotube (B-4) precursor. 1000 g of the carbon nanotube (B-4) precursor was weighed into a 7 L carbon heat-resistant container, and the heat-resistant container containing the carbon nanotube (B-4) precursor was placed in the furnace. Then, nitrogen gas was introduced into the furnace, and while maintaining positive pressure, the air in the furnace was evacuated. After the oxygen concentration inside the furnace fell to below 0.1%, the furnace temperature was raised to 3000°C over 30 hours, and then maintained at 3000°C for 30 minutes. After that, heating inside 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)> 1000g of the carbon nanotube (B-1) precursor from Production Example 1 was weighed into a 7L heat-resistant carbon container, and the heat-resistant container containing the carbon nanotube (B-1) precursor was placed in the furnace. Then, nitrogen gas was introduced into the furnace, and while maintaining positive pressure, the air inside the furnace was expelled. After the oxygen concentration inside the furnace fell below 0.1%, the furnace was heated to 3000°C over 30 hours, and then maintained at 3000°C for 1 hour and 20 minutes. The heating inside the furnace was stopped, and the sample was cooled to obtain carbon nanotube (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 inside the furnace. Then, nitrogen gas was introduced into the furnace to maintain positive pressure, and the air inside the furnace was expelled. After the oxygen concentration inside the furnace fell below 0.1%, it 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. Then, nitrogen gas was introduced at 50 L / min to maintain positive pressure while cooling, and carbon nanotube (B-6) was obtained.

[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, 500 g of 60% nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries) was added, and the mixture was thoroughly stirred using a stirrer. Then, it was thoroughly diluted with deionized water and filtered under reduced pressure using a membrane filter. After repeating the dilution and filtration process, the carbon nanotubes were transferred to a PTFE tray and dried in an oven at 140°C to obtain carbon nanotube (B-7).

[0081] (Manufacturing example 8:B-8) <Synthesis of carbon nanotubes (B-8)> 1000g of the carbon nanotube (B-1) precursor from Production Example 1 was weighed into a 7L heat-resistant carbon container, and the heat-resistant container containing the carbon nanotube (B-1) precursor was placed in the furnace. Then, nitrogen gas was introduced into the furnace, and while maintaining positive pressure, the air inside the furnace was expelled. After the oxygen concentration inside the furnace fell to 0.1% or less, the furnace temperature was raised to 2900°C over 30 hours, and then maintained at 2900°C for 2 hours. The heating inside the furnace was stopped, and the sample was cooled to obtain carbon nanotube (B-8).

[0082] (Manufacturing example 9:B-9) <Synthesis of carbon nanotubes (B-9)> 1000g of the carbon nanotube (B-1) precursor from Production Example 1 was weighed into a 7L heat-resistant carbon container, and the heat-resistant container containing the carbon nanotube (B-1) precursor was placed in the furnace. Then, nitrogen gas was introduced into the furnace, and while maintaining positive pressure, the air inside the furnace was expelled. After the oxygen concentration inside the furnace fell below 0.1%, the furnace temperature was raised to 2900°C over 30 hours, and then maintained at 2900°C for 1 hour and 40 minutes. The heating inside the furnace was stopped, and the sample was cooled to obtain carbon nanotube (B-9).

[0083] (Production example 10:B'-1) The carbon nanotube (B-1) precursor in 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 were weighed into a heat-resistant container and dried in an electric oven at an ambient temperature of 170±5℃ for 6 hours. Then, using a pulverizer (Sample Mill KIIW-I type, manufactured by Dalton Co., Ltd.), a 1 mm screen was attached and the mixture was pulverized to obtain dried magnesium acetate pulverized product. 45.8 parts of the dried magnesium acetate pulverized product, 8.1 parts of manganese carbonate, 1.0 part of silicon dioxide (SiO2, 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 Red Devil paint conditioner. After that, the pulverized and mixed powder and steel beads (bead diameter 2.0 mmφ) were separated using a stainless steel sieve to obtain a catalyst support for carbon nanotube (B'-2) synthesis. Subsequently, 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 for 2 hours at an ambient temperature of 170±5℃ to obtain the cobalt composition and iron composition. Furthermore, 54.9 parts by mass of the carbon nanotube (B'-2) synthesis catalyst support and 29 parts by mass of the cobalt composition and iron composition were placed in a pulverizer (Wonder Crusher WC-3, manufactured by Osaka Chemical Co., Ltd.), fitted with a standard lid, the SPEED dial was set to 2, and the mixture was pulverized and mixed for 30 seconds to obtain the carbon nanotube (B'-2) synthesis catalyst precursor. The carbon nanotube (B'-2) synthesis catalyst precursor was transferred to a heat-resistant container and calcined for 30 minutes in an air atmosphere at 450±5℃ using a muffle furnace (FO510, manufactured by Yamato Scientific Co., Ltd.), and then pulverized in a mortar to obtain the carbon nanotube (B'-2) synthesis catalyst.

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

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

[0087] [Table 1]

[0088] (Example 1) (Manufacturing of thermoplastic resin compositions) A thermoplastic resin (A-1) was mixed with carbon nanotubes (B-1) at a ratio of 98.5% by mass and 1.5% by mass, then melt-kneaded the mixture. The mixture was then extruded at 230°C using a twin-screw extruder (manufactured by Japan Steel Works, Ltd.), granulated, and obtained a thermoplastic resin composition.

[0089] (Examples 2-4, 9-15, 18-19, 21-22) A thermoplastic resin composition was obtained in the same manner as in Example 1, except that the materials and their respective amounts (mass%) were changed as shown in Tables 2 and 3.

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

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

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

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

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

[0095] (Comparative Examples 2 and 3) Thermoplastic resin compositions and molded articles were obtained in the same manner as in Comparative Example 1, except that the materials and their respective amounts (mass%) were changed as shown in Tables 1 and 2.

[0096] Measurement and evaluation of physical properties of thermoplastic resin compositions The physical properties of the obtained thermoplastic resin composition were measured and evaluated using the following method. The results are shown in Tables 2 and 3. For the masterbatches in Examples 16 and 17, the same thermoplastic resin (A) used in the production of the masterbatches was used as the diluent, and molded articles were produced using an injection molding machine with the blending amounts (mass%) shown in Tables 2 and 3.

[0097] [Manufacturing of molded body Z1] A thermoplastic resin composition was molded using an injection molding machine (manufactured by Toshiba Machine Co., Ltd.) with a cylinder temperature of 220°C and a mold temperature of 40°C to obtain a molded body Z1 measuring 90 mm in length, 110 mm in width, and 3 mm in thickness. Furthermore, the thermoplastic resin compositions of Examples 5-8 and 20 were used to produce molded bodies Z1 using an injection molding machine (manufactured by Toshiba Machine Co., Ltd.) with a cylinder setting temperature of 250°C and a mold temperature of 80°C.

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

[0099] [Manufacturing of molded body Z3] A thermoplastic resin composition was molded using an injection molding machine (manufactured by Toshiba Machine Co., Ltd.) with a cylinder setting temperature of 220°C and a mold temperature of 40°C to obtain a molded body Z3 measuring 60 mm in length, 60 mm in width, and 2 mm in thickness. Furthermore, the thermoplastic resin compositions of Examples 5-8 and 20 were used to produce molded bodies Z3 using an injection molding machine (manufactured by Toshiba Machine Co., Ltd.) with a cylinder setting temperature of 250°C and a mold temperature of 80°C.

[0100] [Manufacturing of molded body Z4] Using a thermoplastic resin composition, a molded body Z4 of a dumbbell-shaped test specimen of type A1, in accordance with JIS-K7139:2019, was prepared.

[0101] (Total metal content) Thermoplastic resin compositions were subjected to acid hydrolysis using a microwave sample preparation device (Milestone General, ETHOS1) to extract the metals contained in the thermoplastic resin compositions. Subsequently, the total metal content (ppm) of the thermoplastic resin compositions was calculated by analyzing them using a multi-type ICP emission spectrometer (Agilent, 720-ES).

[0102] (conductive) Conductivity was evaluated by surface resistivity. Using the obtained 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 five arbitrary locations using a Loresta-GP MCP-T610 resistivity meter (compliant with JIS-K7194, 4 terminals, 4 probes, statutory current application method) manufactured by Nitto Seiko Analytech Co., Ltd., and the average value was calculated. A lower surface resistivity indicates higher conductivity. The evaluation criteria are as follows: [Evaluation Criteria] ◎: Surface resistivity of the molded product is 1.0 × 10 3 It is less than or equal to Ω / □ and is practically superior. ○: Surface resistivity of the molded body is 1.0 × 10 3 Exceeding Ω / □, 1.0 × 10 5 It is less than or equal to Ω / □ and is practically superior. △: Surface resistivity of the molded body is 1.0 × 10 5 Exceeding Ω / □, 1.0 × 10 7 It is less than or equal to Ω / □ and therefore usable. ×: Surface resistivity of the molded body is 1.0 × 10 7 It exceeds Ω / □ and is therefore unusable.

[0103] (uniformity) The uniformity of CNTs within the molded body was evaluated by surface smoothness, in-plane variation, and molding shrinkage rate. When the surface smoothness is good, the fluidity of the resin is good even when affected by the thickening effect of CNTs, the CNTs are uniformly dispersed without uneven dispersion, and a molded product with a uniform surface without surface variations can be obtained. In-plane variation indicates that the greater the uniformity of the CNT concentration on the molded surface, the smaller the difference in conductivity becomes, suggesting excellent uniformity of CNT concentration on the molded surface. The molding shrinkage rate represents the uniformity of the CNT concentration throughout the molded body. The smaller the difference in molding shrinkage rates, the more uniformly the CNTs are distributed throughout the molded body. Furthermore, since it demonstrates uniformity throughout the molded product, a high molding shrinkage rate is most desirable.

[0104] <Surface smoothness> Surface smoothness was evaluated by the maximum height Sz of the sheet surface. Using the obtained 100 μm thick sheet (molded body Z2), the maximum height Sz (μm) was measured using a Taylor / Hobson TaliSurf CCI MP-HS with a measurement length of 2.5 mm × 2.5 mm and a robust Gaussian filter of 0.08 mm. The smaller the Sz value, the more uniformly and evenly the CNTs are dispersed in the thermoplastic resin composition. [Evaluation Criteria] ◎: The molded product has a Sz of 2.0 μm or less, making it particularly excellent in practical use. ○: The molded product has a Sz value greater than 2.0 μm and less than or equal to 3.0 μm, making it practically superior. △: The molded body's Sz is greater than 3.0 μm and less than or equal to 5.0 μm, making it usable. ×: The molded part's Sz exceeds 5.0 μm, making it unsuitable for practical use.

[0105] <In-plane variation> Using the obtained 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 five arbitrary locations using a Hi-Resta manufactured by Mitsubishi Chemical Corporation. The maximum / minimum value (X) was then calculated from the maximum and minimum values ​​to perform the evaluation. The evaluation criteria are as follows: The smaller the value of maximum / minimum (X), the smaller the in-plane variability. [Evaluation Criteria] ◎: The maximum / minimum surface resistivity (X) of the molded product is 1 ≤ X < 5, which is particularly excellent in practical applications. ○: The maximum / minimum value (X) of the surface resistivity of the molded product is 5 ≤ ​​X < 10, which is practically superior. △: The maximum / minimum value (X) of the surface resistivity of the molded body is 10 ≤ X < 100, making it usable. ×: The maximum / minimum value (X) of the surface resistivity of the molded product is 100 ≤ X, making it impractical.

[0106] <Molding shrinkage rate> In the obtained molded body (molded body Z3) measuring 60 mm in length, 60 mm in width, and 2 mm in thickness, the molding shrinkage rate in the direction parallel to the flow direction (MD) and the molding shrinkage rate in the direction perpendicular to the flow direction (TD) of the thermoplastic resin composition were measured, and the molding shrinkage ratio was determined as the ratio of molding shrinkage rate (TD) to molding shrinkage rate (MD). A smaller molding shrinkage ratio indicates superior uniformity of CNTs throughout the molded body. [Evaluation Criteria] ◎: The molding shrinkage ratio of the molded product is 1.5 or less, making it particularly excellent in practical use. ○: The molding shrinkage ratio of the molded product is greater than 1.5 and less than or equal to 2.5, making it practically superior. △: The molding shrinkage ratio of the molded product is greater than 2.5 and less than or equal to 3.5, making it usable. ×: The molding shrinkage ratio of the molded product exceeds 3.5, making it unsuitable for practical use.

[0107] (Thermal stability over time) Thermal stability over time was evaluated by its resistance to thermal degradation. The dumbbell-shaped test specimens (molded body Z4) obtained from each example were subjected to the following conditions: (1) 24 hours in a 23°C atmosphere (before thermal aging), and (2) 120 hours in a 130°C atmosphere (test specimen after thermal aging). The tensile strength was measured in accordance with JIS-K7161-1:2014. The tensile strength retention rate was calculated from the obtained tensile strengths according to the following formula. A higher tensile strength retention rate indicates greater thermal stability over time. Tensile strength retention rate (%) = Tensile strength of the specimen after thermal aging (MPa) / Tensile strength of the specimen before thermal aging (MPa) × 100 [Evaluation Criteria] ◎: The tensile strength retention rate of the molded product is 95% or higher, making it particularly excellent in practical use. ○: The tensile strength retention rate of the molded article is 90% or higher and less than 95%, making it practically superior. △: The tensile strength retention rate of the molded product is 80% or more and less than 90%, making it usable. ×: The tensile strength retention rate of the molded product is less than 80%, making it unsuitable for practical use.

[0108] [Table 2]

[0109] [Table 3]

[0110] The results shown in Tables 2 and 3 confirm that by using the thermoplastic resin composition of the present invention, the aggregation of carbon nanotubes is suppressed, resulting in a molded article with excellent uniformity of carbon nanotubes and high conductivity. Furthermore, it was confirmed that the degradation of thermoplastic resin compositions due to thermal aging is eliminated, and that thermoplastic resin compositions can be obtained in which thermal degradation is suppressed even in high-temperature atmospheres.

Claims

1. A thermoplastic resin composition for molded articles comprising a thermoplastic resin (A) and carbon nanotubes (B), The carbon nanotube (B) content is 0.1 to 30 parts by mass per 100 parts by mass of thermoplastic resin (A). Carbon nanotubes (B) satisfy all of the following conditions (1) and (2): The total metal content of the thermoplastic resin composition is 3,000 ppm or less. Thermoplastic resin composition for molded objects. (1) The total metal content is 10,000 ppm or less. (2) In powder X-ray diffraction analysis, the full width at half maximum of the diffraction peak of the (002) plane is 2.0 to 6.0°.

2. comprising a thermoplastic resin (A) and carbon nanotubes (B), The carbon nanotube (B) content is 0.1 to 30 parts by mass per 100 parts by mass of thermoplastic resin (A). Carbon nanotubes (B) satisfy all of the following conditions (1) to (3): Thermoplastic resin composition for molded objects. (1) The total metal content is 10,000 ppm or less. (2) In powder X-ray diffraction analysis, the full width at half maximum of the diffraction peak of the (002) plane is 2.0 to 6.0°. (3) The iron content is 10 to 5,000 ppm.

3. comprising a thermoplastic resin (A) and carbon nanotubes (B), The carbon nanotube (B) content is 0.1 to 30 parts by mass per 100 parts by mass of thermoplastic resin (A). Carbon nanotubes (B) satisfy all of the following conditions (1) to (3): Thermoplastic resin composition for molded objects. (1) The total metal content is 10,000 ppm or less. (2) In powder X-ray diffraction analysis, the full width at half maximum of the diffraction peak of the (002) plane is 2.0 to 6.0°. (3) The cobalt content is 10 to 1,000 ppm.

4. The thermoplastic resin composition for molded articles according to any one of claims 1 to 3, wherein the carbon nanotube (B) has an ash content of 0.001 to 1.0% by mass when heated at 900°C for 1 hour.

5. Carbon nanotubes (B) have a volume resistivity of 1.0 × 10⁻⁶ －３ ~3.0 x 10 －２ A thermoplastic resin composition for molded articles according to any one of claims 1 to 3, wherein the density is Ω·cm.

6. Carbon nanotubes (B) have a BET specific surface area of ​​200-600 m². ２ A thermoplastic resin composition for molded articles according to any one of claims 1 to 3, wherein the concentration is / g.

7. The thermoplastic resin composition for molded articles according to any one of claims 1 to 3, 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. A molded article formed using the thermoplastic resin composition for molded articles described in any one of claims 1 to 3.

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