Resin composition, pellets, molded articles, and electromagnetic wave absorbers

Abstract

To provide a resin composition which has a high absorption rate of electromagnetic waves and small anisotropy of an absorption rate when being formed into a molding, a pellet, a molding, an electromagnetic wave absorber, and a method for manufacturing a resin composition.SOLUTION: A resin composition contains a thermoplastic polyester resin, a styrenic resin, a carbon nanotube, a compatibilizer, and a filler having an aspect ratio of 100 or less and a longest length of 1,000 μm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to resin compositions, pellets, molded articles, and electromagnetic wave absorbers. [Background technology]

[0002] Millimeter-wave radar emits radio waves in the millimeter-wave band with wavelengths of 1 to 10 mm and frequencies of 30 to 300 GHz, particularly 60 to 90 GHz. By receiving the reflected waves that collide with an object and return, it detects the presence of obstacles, as well as the distance and relative speed to the object. Millimeter-wave radar is being considered for use in a wide range of fields, including collision avoidance sensors in automobiles, autonomous driving systems, road information systems, security systems, and medical and nursing care devices. A resin composition for such millimeter-wave radar is known, as described in Patent Document 1. Furthermore, Patent Document 2 discloses a multi-functional resin composition that can be used for electromagnetic interference shielding or radio frequency interference shielding. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-197048 [Patent Document 2] Japanese Patent Publication No. 2010-155993 [Overview of the project] [Problems that the invention aims to solve]

[0004] In millimeter-wave radar, the most significant cause of malfunction is transmitted electromagnetic waves. Therefore, resin compositions with high electromagnetic wave absorption rates are required. Furthermore, in molded articles, if there is a large anisotropy in absorption rates, such as a large difference in absorption rates between the longitudinal (TD) direction and the transverse (MD) direction, it can be problematic depending on the application. The present invention aims to solve the aforementioned problems and to provide a resin composition, a molded article, an electromagnetic wave absorber, and a method for manufacturing the resin composition, which have a high electromagnetic wave absorption rate and low anisotropy in the absorption rate when molded. [Means for solving the problem]

[0005] Based on the above problems, the inventors conducted research and found that the above problems can be solved by using a thermoplastic polyester resin, a styrene-based resin, carbon nanotubes, and a compatibilizer, and by using small fillers. Specifically, the above problem was solved by the following means. <1> A resin composition comprising a thermoplastic polyester resin, a styrene-based resin, carbon nanotubes, a compatibilizer, and a filler having an aspect ratio of 100 or less and a maximum length of 1000 μm or less. <2> The aforementioned compatibilizer contains polycarbonate resin. <1> The resin composition described above. <3> The mixture contains 5 to 20 parts by mass of polycarbonate resin in proportion to a total of 100 parts by mass of the thermoplastic polyester resin and styrene resin. <2> The resin composition described above. <4> A total of 100 parts by mass of the thermoplastic polyester resin and styrene resin, Contains 10 to 50 parts by mass of styrene resin. <1> ~ <3> A resin composition as described in any one of the following. <5> The content of fillers with a maximum length exceeding 1000 μm and an aspect ratio exceeding 100 is 20% by mass or less of the content of fillers with an aspect ratio of 100 or less and a maximum length of 1000 μm or less. <1> ~ <4> A resin composition as described in any one of the following. <6> The carbon nanotubes are carbon nanotubes that have been formed into a masterbatch, and the base resin of the masterbatch is a styrene-based resin. <1> ~ <5> A resin composition as described in any one of the following. <7> The aforementioned filler having an aspect ratio of 100 or less and a maximum length of 1000 μm or less contains talc. <1> ~ <6> A resin composition as described in any one of the following. <8> It is for use as an electromagnetic wave absorber. <1> ~ <7> A resin composition as described in any one of the following. <9> When the aforementioned resin composition is molded to a thickness of 2 mm, the absorption rate determined according to formula (A) at a frequency of 76.5 GHz is 40.0 to 100%. <1> ~ <8> A resin composition as described in any one of the following. Formula (A)

number

number

number

Number

Number

Number

[0006] The present invention makes it possible to provide a resin composition, pellets, molded articles, and electromagnetic wave absorbers that have a high electromagnetic wave absorption rate and low anisotropy in the absorption rate when molded, as well as a method for manufacturing the resin composition. [Modes for carrying out the invention]

[0007] The following describes in detail embodiments for carrying out the present invention (hereinafter simply referred to as "this embodiment"). Note that the following embodiment is illustrative for explaining the present invention, and the present invention is not limited to this embodiment. In this specification, "~" is used to mean that the numbers before and after it are included as the lower and upper limits, respectively. In this specification, all physical properties and characteristic values ​​shall be those at 23°C unless otherwise specified. In this specification, unless otherwise specified, weight-average molecular weight and number-average molecular weight are polystyrene-converted values ​​measured by GPC (gel permeation chromatography). In this specification, the units for reflection loss and transmission loss are "dB" (decibels). If the measurement methods, etc., described in the standards shown herein differ from year to year, unless otherwise specified, the standards as of January 1, 2022 shall apply.

[0008] The resin composition of this embodiment is characterized by comprising a thermoplastic polyester resin, a styrene-based resin, carbon nanotubes, a compatibilizer, and a filler having an aspect ratio of 100 or less and a maximum length of 1000 μm or less. By using this configuration, a resin composition with high electromagnetic wave absorption and low anisotropy of absorption when formed into a molded article can be obtained. The reasons for this are presumed to be as follows: By blending carbon nanotubes with the thermoplastic polyester resin, a certain level of electromagnetic wave absorption is achieved. In this embodiment, by further blending with a styrene-based resin, the carbon nanotubes can be dispersed more effectively in the thermoplastic polyester resin, and it is presumed that the absorption rate of the resulting resin composition can be made even higher. Furthermore, by blending with a compatibilizer, the compatibility between the thermoplastic polyester resin and the styrene-based resin is improved, and it is presumed that the absorption rate of the resin composition can be made even higher. In addition, by using a filler with an aspect ratio of 100 or less and a maximum length of 1000 μm or less, it is presumed that the anisotropy of absorption in the molded article can be made smaller. The following describes this embodiment.

[0009] <Thermoplastic polyester resin> The resin composition of this embodiment includes a thermoplastic polyester resin. The thermoplastic polyester resin used in this embodiment is not specifically defined in terms of type, but examples include polybutylene terephthalate resin and polyethylene terephthalate resin, with polybutylene terephthalate resin being preferred.

[0010] <<Polybutylene terephthalate resin>> Polybutylene terephthalate resin is a resin obtained by polycondensation of terephthalic acid as the main component of the acid component and 1,4-butanediol as the main component of the diol component. When the main component of the acid component is terephthalic acid, it means that 50% or more by mass of the acid component is terephthalic acid, preferably 60% or more by mass, more preferably 70% or more by mass, and may be 80% or more by mass, 90% or more by mass, or 95% or more by mass. When the main component of the diol component is 1,4-butanediol, it means that 50% or more by mass of the diol component is 1,4-butanediol, preferably 60% or more by mass, more preferably 70% or more by mass, and may be 80% or more by mass, 90% or more by mass, or 95% or more by mass. When polybutylene terephthalate resin contains other acidic components, examples include isophthalic acid and dimer acid. Furthermore, when polybutylene terephthalate resin contains other diol components, examples include polyalkylene glycols such as polytetramethylene glycol (PTMG).

[0011] When using a copolymer of polytetramethylene glycol as the polybutylene terephthalate resin, the proportion of the tetramethylene glycol component in the copolymer is preferably 3 to 40% by mass, more preferably 5 to 30% by mass, and even more preferably 10 to 25% by mass. Such copolymerization ratios tend to result in a better balance between laser weldability and heat resistance, which is preferable.

[0012] When using dimer acid copolymerized polybutylene terephthalate as the polybutylene terephthalate resin, the proportion of the dimer acid component to the total carboxylic acid component is preferably 0.5 to 30 mol%, more preferably 1 to 20 mol%, and even more preferably 3 to 15 mol%. Such copolymerization ratios tend to result in an excellent balance of laser weldability, long-term heat resistance, and toughness, which is preferable.

[0013] When using isophthalic acid copolymerized polybutylene terephthalate as the polybutylene terephthalate resin, the proportion of isophthalic acid components to the total carboxylic acid components is preferably 1 to 30 mol%, more preferably 1 to 20 mol%, and even more preferably 3 to 15 mol%. Such copolymerization ratios tend to result in an excellent balance of laser weldability, heat resistance, injection moldability, and toughness, which is preferable.

[0014] The polybutylene terephthalate resin used in this embodiment is preferably a resin (polybutylene terephthalate homopolymer) in which 90% or more by mass of the acid component is terephthalic acid and 90% or more by mass of the diol component is 1,4-butanediol, or a copolymerized polybutylene terephthalate resin obtained by copolymerizing polytetramethylene glycol, or an isophthalic acid copolymerized polybutylene terephthalate resin.

[0015] The intrinsic viscosity of the polybutylene terephthalate resin is preferably 0.5 dL / g or higher, more preferably 0.6 dL / g or higher, preferably 2.0 dL / g or lower, more preferably 1.5 dL / g or lower, and even more preferably 1.1 dL / g or lower. Using a polybutylene terephthalate resin with an intrinsic viscosity of 0.5 dL / g or higher tends to improve the mechanical strength of the resulting molded article. Furthermore, using a polybutylene terephthalate resin with an intrinsic viscosity of 2 dL / g or lower tends to improve the fluidity of the polybutylene terephthalate resin and thus improve moldability. The intrinsic viscosity of polybutylene terephthalate resin is measured at 30°C in a 1:1 (mass ratio) mixed solvent of tetrachloroethane and phenol. If the mixture contains two or more types of polybutylene terephthalate resin, the intrinsic viscosity shall be the intrinsic viscosity of the mixture.

[0016] The amount of terminal carboxyl groups in polybutylene terephthalate resin can be appropriately selected and determined, but is usually 60 eq / ton or less, preferably 50 eq / ton or less, and more preferably 30 eq / ton or less. By limiting the amount of terminal carboxyl groups to 50 eq / ton or less, gas generation during melt molding of polybutylene terephthalate resin can be more effectively suppressed. There is no specific lower limit for the amount of terminal carboxyl groups, but it is usually 5 eq / ton. When two or more types of polybutylene terephthalate resins are included, the amount of terminal carboxyl groups shall be the amount of terminal carboxyl groups in the mixture.

[0017] The amount of terminal carboxyl groups in polybutylene terephthalate resin can be determined by dissolving 0.5 g of polybutylene terephthalate resin in 25 mL of benzyl alcohol and titrating with a 0.01 mol / L benzyl alcohol solution of sodium hydroxide. Methods for adjusting the amount of terminal carboxyl groups include adjusting polymerization conditions such as the raw material ratio, polymerization temperature, and reduced pressure method during polymerization, as well as reacting with end-sealing agents, and any other conventionally known methods.

[0018] <<Polyethylene terephthalate resin>> The polyethylene terephthalate resin used in this embodiment is a resin obtained by polycondensing terephthalic acid as the main component of the acid component and ethylene glycol as the main component of the diol component. When the main component of the acid component is terephthalic acid, it means that 50% by mass or more of the acid component is terephthalic acid, preferably 60% by mass or more, more preferably 70% by mass or more, and may be 80% by mass or more, 90% by mass or more, or 95% by mass or more. When the main component of the diol component is ethylene glycol, it means that 50% by mass or more of the diol component is ethylene glycol, preferably 60% by mass or more, more preferably 70% by mass or more, and may be 80% by mass or more, 90% by mass or more, or 95% by mass or more.

[0019] When polyethylene terephthalate resin contains other acidic components, examples include phthalic acid, isophthalic acid, naphthalenedicarboxylic acid, 4,4'-diphenylsulfondicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-phenylenedioxydiacetic acid and their structural isomers, dicarboxylic acids such as malonic acid, succinic acid, and adipic acid and their derivatives, and oxyacids such as p-hydroxybenzoic acid and glycolic acid or their derivatives. Furthermore, if the polyethylene terephthalate resin contains other acidic components, other diol components may include aliphatic glycols such as 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, pentamethylene glycol, hexamethylene glycol, and neopentyl glycol, alicyclic glycols such as cyclohexanedimethanol, and aromatic dihydroxy compound derivatives such as bisphenol A and bisphenol S.

[0020] Furthermore, the polyethylene terephthalate resin may be copolymerized with a branched component, such as a trifunctional or tetrafunctional acid like tricarbaryl acid, trimellicinic acid, or trimellitic acid, or a trifunctional or tetrafunctional alcohol like pyromellitic acid, at a concentration of 1.0 mol% or less, preferably 0.5 mol% or less, and more preferably 0.3 mol% or less.

[0021] The intrinsic viscosity of the polyethylene terephthalate resin is preferably 0.3 to 1.5 dL / g, more preferably 0.3 to 1.2 dL / g, and even more preferably 0.4 to 0.8 dL / g. The intrinsic viscosity of polyethylene terephthalate resin is measured at 30°C in a 1:1 (mass ratio) mixed solvent of tetrachloroethane and phenol.

[0022] Furthermore, the concentration of terminal carboxyl groups in the polyethylene terephthalate resin is preferably 3 to 60 eq / ton, more preferably 5 to 50 eq / ton, and even more preferably 8 to 40 eq / ton. Setting the terminal carboxyl group concentration to 60 eq / ton or less tends to reduce gas generation during melt molding of the resin material, and the mechanical properties of the resulting molded article tend to improve. Conversely, setting the terminal carboxyl group concentration to 3 eq / ton or more tends to improve the heat resistance, heat retention stability, and color of the resulting molded article, which is preferable. The concentration of terminal carboxyl groups in polyethylene terephthalate resin can be determined by dissolving 0.5 g of polyethylene terephthalate resin in 25 mL of benzyl alcohol and titrating it with a 0.01 mol / L benzyl alcohol solution of sodium hydroxide.

[0023] The content of thermoplastic polyester resin in the resin composition of this embodiment is preferably 45% by mass or more, more preferably 50% by mass or more, even more preferably 55% by mass or more, and even more preferably 57% by mass or more. Setting it above the lower limit tends to improve mechanical strength. Furthermore, the content of thermoplastic polyester resin in the resin composition is preferably 85% by mass or less, more preferably 80% by mass or less, even more preferably 75% by mass or less, even more preferably 70% by mass or less, and even more preferably 68% by mass or less. Setting it below the upper limit tends to improve electromagnetic wave absorption. The resin composition of this embodiment may contain only one type of thermoplastic polyester resin, or it may contain two or more types. When it contains two or more types, it is preferable that the total amount is within the above range.

[0024] <Styrene-based resin> The resin composition of this embodiment includes a styrene-based resin. By using a styrene-based resin, carbon nanotubes tend to diffuse more easily into the polybutylene terephthalate resin, and the electromagnetic wave absorption properties of the resin composition tend to improve. Furthermore, the electromagnetic wave transmittance and reflectance of the resin composition tend to be lower.

[0025] Examples of styrene-based resins include homopolymers of styrene monomers and copolymers of styrene monomers and monomers copolymerizable with styrene monomers. Examples of styrene monomers include styrene, α-methylstyrene, chlorostyrene, methylstyrene, and tert-butylstyrene. In this embodiment, the styrene-based resin contains 50 mol% or more of styrene monomers. More specifically, styrene-based resins include polystyrene resin, acrylonitrile-styrene copolymer (AS resin), high-impact polystyrene resin (HIPS, butadiene rubber-containing polystyrene), acrylonitrile-butadiene-styrene copolymer (ABS resin), acrylonitrile-acrylic rubber-styrene copolymer (AAS resin), acrylonitrile-styrene-acrylic rubber copolymer (ASA resin), acrylonitrile-ethylene propylene rubber-styrene copolymer (AES resin), styrene-IPN type rubber copolymer, and other resins. In this embodiment, the styrene-based resin is preferably an acrylonitrile-styrene copolymer (AS resin), high-impact polystyrene resin (HIPS, butadiene rubber-containing polystyrene), acrylonitrile-butadiene-styrene copolymer (ABS resin), acrylonitrile-acrylic rubber-styrene copolymer (AAS resin), acrylonitrile-styrene-acrylic rubber copolymer (ASA resin), acrylonitrile-ethylene propylene rubber-styrene copolymer (AES resin), or styrene-IPN type rubber copolymer, and more preferably a high-impact polystyrene resin (HIPS, butadiene rubber-containing polystyrene). It is presumed that such a styrene-based resin acts as a driving force when carbon nanotubes diffuse into the polybutylene terephthalate resin, and that the aggregation of carbon nanotubes is loosened. As a result, it is presumed that the dispersion of carbon nanotubes is effectively promoted. In particular, when the styrene-based resin is derived from a carbon nanotube masterbatch, the diffusion of the carbon nanotubes tends to be promoted more effectively.

[0026] When a styrene-based resin contains rubber components, the content of rubber components in the styrene-based resin is preferably 3 to 70% by mass, more preferably 5 to 50% by mass, and even more preferably 7 to 30% by mass. A rubber component content of 3% by mass or more tends to improve impact resistance, while a content of 50% by mass or less tends to improve flame retardancy, which is preferable. Furthermore, the average particle size of the rubber components is preferably 0.05 to 10 μm, more preferably 0.1 to 6 μm, and even more preferably 0.2 to 3 μm. An average particle size of 0.05 μm or more tends to improve impact resistance, while an average particle size of 10 μm or less tends to improve appearance, which is preferable.

[0027] The weight-average molecular weight of the styrene resin is usually 50,000 or more, preferably 100,000 or more, more preferably 150,000 or more, and also usually 500,000 or less, preferably 400,000 or less, and more preferably 300,000 or less. The number-average molecular weight is usually 10,000 or more, preferably 30,000 or more, more preferably 50,000 or more, and also preferably 500,000 or less, and more preferably 300,000 or less.

[0028] The melt volume rate (MVR) of styrene resin, measured according to JIS K7210 (temperature 200°C, load 5kgf), is 0.1cm³. 3 It is preferable that it be 10 minutes or more, and 0.5 cm 3 / More preferably 10 minutes or more, 1 cm 3 It is even more preferable that it be 10 minutes or longer, and also 30 cm 3 Preferably 10 minutes or less, 20cm 3 / More preferably it is 10 minutes or less, 10cm 3 / More preferably it is 10 minutes or less, and 7cm 3 / It is even more preferable that it be 10 minutes or less, and 5cm 3 It is even more preferable that the time is 10 minutes or less. Setting it above the lower limit tends to improve the fluidity of the resin composition, and setting it below the upper limit tends to improve the impact resistance.

[0029] Known methods for producing such styrene-based resins include emulsion polymerization, solution polymerization, suspension polymerization, and bulk polymerization.

[0030] The styrene resin content in the resin composition of this embodiment is preferably 10 parts by mass or more, more preferably 13 parts by mass or more, even more preferably 15 parts by mass or more, even more preferably 18 parts by mass or more, and even more preferably 20 parts by mass or more, based on 100 parts by mass of the total of the thermoplastic polyester resin and the styrene resin. Setting it above the lower limit tends to improve electromagnetic wave absorption performance. It also tends to effectively suppress warping of the resulting molded article. Furthermore, the styrene resin content is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, even more preferably 35 parts by mass or less, even more preferably 30 parts by mass or less, and even more preferably 25 parts by mass or less, based on 100 parts by mass of the total of the thermoplastic polyester resin and the styrene resin. Setting it below the upper limit tends to further improve chemical resistance. The resin composition of this embodiment may contain only one type of styrene-based resin, or it may contain two or more types. When it contains two or more types, it is preferable that the total amount is within the above range.

[0031] <Carbon nanotubes> The resin composition of this embodiment contains carbon nanotubes. By including carbon nanotubes, a resin composition or molded article with a high electromagnetic wave absorption rate can be obtained. The carbon nanotubes used in this embodiment are single-walled carbon nanotubes and / or multi-walled carbon nanotubes, and preferably include at least multi-walled carbon nanotubes. Carbon materials having a partially carbon nanotube structure can also be used. Furthermore, the carbon nanotubes are not limited to a cylindrical shape, but may have a coiled shape in which a helix completes one turn with a pitch of 1 μm or less. Carbon nanotubes are commercially available, and examples include those from Bayer MaterialScience, NanoSil, Showa Denko Corporation, and Hyperion Catalysis International. They are also sometimes referred to as graphite fibrils or carbon fibrils. The diameter (number-average fiber diameter) of the carbon nanotubes is preferably 0.5 to 100 nm, and more preferably 1 to 30 nm. The aspect ratio of the carbon nanotubes is preferably 5 or higher, and more preferably 50 or higher, from the viewpoint of providing good electromagnetic wave absorption. There is no specific upper limit, but for example, it is 500 or less.

[0032] In this embodiment, it is preferable that the carbon nanotubes are derived from carbon nanotubes that have been master-batched with a resin, and it is more preferable that the base resin of the masterbatch is a styrene-based resin. With this configuration, the electromagnetic wave absorption properties of the resulting resin composition or molded article tend to be further improved. As described above, carbon nanotubes may be incorporated in a masterbatch. In this case, the concentration of carbon nanotubes in the masterbatch is preferably 1% by mass or more, more preferably 5% by mass or more, preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, and even more preferably 20% by mass or less. By setting the concentration within the above upper and lower limits, the dispersibility of carbon nanotubes in thermoplastic polyester resin tends to improve.

[0033] The carbon nanotube content in the resin composition of this embodiment is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, may be 0.2% by mass or more, and may even be 0.4% by mass or more. Setting it above the lower limit allows for effective electromagnetic wave absorption. Furthermore, the carbon nanotube content in the resin composition of this embodiment is preferably 10% by mass or less, more preferably 8% by mass or less, even more preferably 6% by mass or less, even more preferably 4% by mass or less, even more preferably 3% by mass or less, may be 2% by mass or less, and may even be 1% by mass or less. Setting it below the upper limit tends to further improve the fluidity of the resin.

[0034] The resin composition of this embodiment preferably contains 0.1 parts by mass or more, and more preferably 0.3 parts by mass or more, of carbon nanotubes per 100 parts by mass of the total of the thermoplastic polyester resin and the styrene resin. By setting it above the lower limit, electromagnetic wave absorption is effectively exhibited. Furthermore, the resin composition of this embodiment preferably contains 10.0 parts by mass or less, more preferably 8.0 parts by mass or less, even more preferably 6.0 parts by mass or less, even more preferably 4.0 parts by mass or less, even more preferably 3.0 parts by mass or less, and may even be 2.5 parts by mass or less, and particularly 1.5 parts by mass or less. By setting it below the upper limit, the fluidity of the resin tends to improve further. The resin composition of this embodiment may contain only one type of carbon nanotube, or it may contain two or more types. When it contains two or more types, it is preferable that the total amount is within the above range.

[0035] <Compatibilizer> The resin composition of this embodiment includes a compatibilizer. The compatibilizer of this embodiment may be any substance that compatibilizes thermoplastic polyester resin and styrene-based resin, and its type is not particularly specified. In this embodiment, the compatibilizer is preferably a polycarbonate resin and / or a styrene-maleic acid copolymer, and more preferably a polycarbonate resin.

[0036] The styrene-maleic acid copolymer has a monomer content of less than 50 mol% styrene monomers. Such a styrene-maleic acid copolymer can be described in paragraphs 0048 to 0050 of Japanese Patent Application Publication No. 2020-176159, the contents of which are incorporated herein by reference.

[0037] Polycarbonate resin is a branched homopolymer or copolymer obtained by reacting a dihydroxy compound, or a small amount thereof, with a polyhydroxy compound with phosgene or a diester carbonate. The method for producing polycarbonate resin is not particularly limited, and conventionally known methods such as the phosgene method (interfacial polymerization) or the melting method (transesterification) can be used.

[0038] As the raw material dihydroxy compound, aromatic dihydroxy compounds are preferred, including 2,2-bis(4-hydroxyphenyl)propane (=bisphenol A), tetramethylbisphenol A, bis(4-hydroxyphenyl)-p-diisopropylbenzene, hydroquinone, resorcinol, 4,4-dihydroxydiphenyl, and others, with bisphenol A being preferred. In addition, compounds in which one or more tetraalkylphosphonium sulfonates are bonded to the above aromatic dihydroxy compounds can also be used.

[0039] As the polycarbonate resin, among those described above, an aromatic polycarbonate resin derived from 2,2-bis(4-hydroxyphenyl)propane or an aromatic polycarbonate copolymer derived from 2,2-bis(4-hydroxyphenyl)propane and another aromatic dihydroxy compound is preferable. Further, a copolymer mainly composed of an aromatic polycarbonate resin, such as a copolymer with a polymer or oligomer having a siloxane structure, may be used. Furthermore, two or more of the above-described polycarbonate resins may be mixed and used.

[0040] To adjust the molecular weight of the polycarbonate resin, a monohydric aromatic hydroxy compound may be used. For example, m- and p-methylphenol, m- and p-propylphenol, p-tert-butylphenol, p-long-chain alkyl-substituted phenol, etc. may be mentioned.

[0041] The viscosity average molecular weight (Mv) of the polycarbonate resin is preferably 5,000 or more, more preferably 10,000 or more, and even more preferably 13,000 or more. By using a polycarbonate resin having a viscosity average molecular weight of 5,000 or more, the mechanical strength of the resulting resin composition tends to be further improved. Also, the viscosity average molecular weight (Mv) of the polycarbonate resin is preferably 60,000 or less, more preferably 40,000 or less, and even more preferably 30,000 or less. By using a polycarbonate resin having a viscosity average molecular weight of 60,000 or less, the fluidity of the resin composition is improved, and the moldability tends to be improved. When two or more polycarbonate resins are included, it is preferable that the mixture satisfies the above range (hereinafter, the same applies to the molecular weight).

[0042] In this embodiment, the viscosity average molecular weight (Mv) of the polycarbonate resin is a value calculated from the following Schnell viscosity formula by measuring the viscosity of a methylene chloride solution of the polycarbonate resin at 20°C using an Ubbelohde viscometer to obtain the intrinsic viscosity ([η]). [η]=1.23×10 -4 Mv 0.83

[0043] The method for producing the polycarbonate resin is not particularly limited, and polycarbonate resin produced by either the phosgene method (interfacial polymerization method) or the melting method (transesterification method) can be used. Furthermore, polycarbonate resin produced by the melting method and then subjected to post-treatment to adjust the amount of terminal OH groups is also preferred.

[0044] The content of the compatibilizer (preferably polycarbonate resin) in the resin composition of this embodiment is preferably 5 parts by mass or more, more preferably 6 parts by mass or more, even more preferably 7 parts by mass or more, even more preferably 8 parts by mass or more, and even more preferably 9 parts by mass or more, based on 100 parts by mass of the total of the thermoplastic polyester resin and the styrene resin. Setting the content above the lower limit tends to further improve the compatibility between the thermoplastic polyester resin and the styrene resin. Furthermore, the upper limit of the content of the compatibilizer (preferably polycarbonate resin) is preferably 20 parts by mass or less, more preferably 18 parts by mass or less, even more preferably 16 parts by mass or less, even more preferably 14 parts by mass or less, and even more preferably 12 parts by mass or less, based on 100 parts by mass of the total of the thermoplastic polyester resin and the styrene resin. Setting the content below the upper limit tends to improve electromagnetic wave absorption. The resin composition of this embodiment may contain only one type of compatibilizer, or it may contain two or more types. When two or more types are included, it is preferable that the total amount is within the above range.

[0045] <Fillers with an aspect ratio of 100 or less and a maximum length of 1000 μm or less> The resin composition of this embodiment includes a filler with an aspect ratio of 100 or less and a maximum length of 1000 μm or less. By including such a filler, it is possible to maintain high mechanical strength in the resulting molded article while reducing the difference in absorption rates between the TD direction and the MD direction. In the filler having an aspect ratio of 100 or less and a maximum length of 1000 μm or less, the aspect ratio is preferably 80 or less, more preferably 70 or less, even more preferably 50 or less, even more preferably 40 or less, even more preferably 30 or less, and even more preferably 20 or less. Setting it below the upper limit tends to further improve the effects of the present invention. The lower limit of the aspect ratio is ideally 1, but 2 or more is practical, and even 5 or more sufficiently satisfies the required performance. In the filler having an aspect ratio of 100 or less and a maximum length of 1000 μm or less, the maximum length is preferably 800 μm or less, more preferably 500 μm or less, even more preferably 300 μm or less, even more preferably 200 μm or less, even more preferably 150 μm or less, even more preferably 100 μm or less, and may also be 80 μm or less, 60 μm or less, 40 μm or less, 30 μm or less, or 20 μm or less. Setting it below the upper limit tends to further improve the effects of the present invention. The lower limit of the maximum length is preferably 1 μm or more, and more preferably 5 μm or more. Setting it above the lower limit tends to further improve the mechanical strength of the resulting molded article. Here, the aspect ratio and maximum length are measured according to the examples described later.

[0046] As a filler with an aspect ratio of 100 or less and a maximum length of 1000 μm or less, talc, milled fiber, wollastonite, and mica are preferred, with talc being more preferred.

[0047] In the resin composition of this embodiment, the content of the filler having an aspect ratio of 100 or less and a maximum length of 1000 μm or less is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 0.8 parts by mass or more, based on 100 parts by mass of the total of the thermoplastic polyester resin and the styrene resin. Setting it above the lower limit tends to further improve the effect of reducing the anisotropy of electromagnetic wave absorption. Furthermore, the upper limit of the content of the filler having an aspect ratio of 100 or less and a maximum length of 1000 μm or less is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, even more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less, based on 100 parts by mass of the total of the thermoplastic polyester resin and the styrene resin. Setting it below the upper limit tends to further improve the fluidity of the resin. The resin composition of this embodiment may contain only one type of filler having an aspect ratio of 100 or less and a maximum length of 1000 μm or less, or it may contain two or more types. When two or more types are included, it is preferable that the total amount is within the above range.

[0048] <Other fillers> The resin composition of this embodiment may or may not contain a filler having a maximum length of more than 100 and an aspect ratio of more than 1000 μm. Examples of fillers with a maximum length exceeding 100 and an aspect ratio exceeding 1000 μm include glass fiber chopped strands and stainless steel fibers. In this embodiment, the content of fillers having a maximum length exceeding 1000 μm and an aspect ratio exceeding 100 is preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, even more preferably 5% by mass or less, and even more preferably 1% by mass or less, of the content of fillers having an aspect ratio of 100 or less and a maximum length of 1000 μm or less. By keeping it below the above upper limit, the anisotropy of the electromagnetic wave absorption rate of the resulting molded article tends to be reduced.

[0049] <Other ingredients> The resin composition of this embodiment may contain other components as needed, as long as they do not significantly impair the desired physical properties. Examples of other components include various resin additives. The other components may be present individually, or two or more in any combination and ratio.

[0050] Examples of various resin additives include stabilizers, release agents, flame retardants, reactive compounds, pigments, dyes, UV absorbers, antistatic agents, antifogging agents, antiblocking agents, flow improvers, plasticizers, dispersants, and antibacterial agents. The resin composition of this embodiment preferably contains at least one of a stabilizer and a release agent. The resin composition of this embodiment is prepared so that the total of a thermoplastic polyester resin, a styrene resin, carbon nanotubes, a compatibilizer, and a filler with an aspect ratio of 100 or less and a maximum length of 1000 μm or less, along with other selectively blended components, amounts to 100% by mass. One example of the resin composition of this embodiment is one in which the total of a plastic polyester resin, a styrene resin, carbon nanotubes, a compatibilizer, and a filler with an aspect ratio of 100 or less and a maximum length of 1000 μm or less accounts for 95% by mass or more of the resin composition. Another example of the resin composition of this embodiment is one in which the total of a plastic polyester resin, a styrene resin, carbon nanotubes, a compatibilizer, a filler with an aspect ratio of 100 or less and a maximum length of 1000 μm or less, a stabilizer, and a release agent accounts for 99% by mass or more of the resin composition.

[0051] <<Stabilizer>> The resin composition of this embodiment may contain stabilizers. These stabilizers include those referred to as heat stabilizers, antioxidants, and light stabilizers. Examples of stabilizers include hindered phenol compounds, hindered amine compounds, phosphorus compounds, and sulfur-based stabilizers. Among these, phosphorus compounds and sulfur-based stabilizers are preferred. Specifically, as stabilizers, reference can be made to paragraphs 0046-0057 of Japanese Patent Publication No. 2018-070722, paragraphs 0030-0037 of Japanese Patent Publication No. 2019-056035, paragraphs 0066-0078 of International Publication No. 2017 / 038949, and paragraphs 0071-0078 of Japanese Patent Publication No. 2020-084037, the contents of which are incorporated herein by reference. Commercially available stabilizers include BASF's "Irganox 1010" and "Irganox 1076" (product names, same below), ADEKA's "ADEKA Stab AO-50", "ADEKA Stab AX-71", "ADEKA Stab AO-60", and "ADEKA Stab AO-412S".

[0052] The resin composition of this embodiment preferably contains 0.01 parts by mass or more of stabilizer per 100 parts by mass of the total of the thermoplastic polyester resin and styrene resin, more preferably 0.05 parts by mass or more, and even more preferably 0.08 parts by mass or more. Furthermore, the upper limit of the stabilizer content is preferably 3 parts by mass or less, more preferably 2 parts by mass or less, and even more preferably 1 part by mass or less, per 100 parts by mass of the total of the thermoplastic polyester resin and styrene resin. The resin composition of this embodiment may contain only one stabilizer or two or more stabilizers. When two or more stabilizers are included, it is preferable that the total amount is within the above range.

[0053] <<Release agent>> The resin composition of this embodiment preferably contains a mold release agent. A wide range of known release agents can be used as the release agent, with aliphatic carboxylic acid esters, paraffin wax, polystyrene wax, and polyolefin wax being preferred, and polyethylene wax being more preferred. Specifically, as a mold release agent, reference can be given to the descriptions in paragraphs 0115 to 0120 of Japanese Patent Publication No. 2013-007058, paragraphs 0063 to 0077 of Japanese Patent Publication No. 2018-070722, and paragraphs 0090 to 0098 of Japanese Patent Publication No. 2019-123809, the contents of which are incorporated herein by reference.

[0054] The resin composition of this embodiment preferably contains 0.01 parts by mass or more, more preferably 0.08 parts by mass or more, and even more preferably 0.2 parts by mass or more, of the mold release agent per 100 parts by mass of the total of the thermoplastic polyester resin and the styrene resin. Furthermore, the upper limit of the mold release agent content is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, even more preferably 1 part by mass or less, and even more preferably 0.8 parts by mass or less, per 100 parts by mass of the total of the thermoplastic polyester resin and the styrene resin. The resin composition may contain only one type of release agent or two or more types. If it contains two or more types, it is preferable that the total amount is within the above range.

[0055] <Physical properties of resin compositions> The resin composition of this embodiment preferably has a high electromagnetic wave absorption rate. Specifically, the resin composition of this embodiment preferably has an absorption rate of 40.0 to 100% when molded to a thickness of 2 mm (preferably 100 mm × 100 mm × 2 mm) and determined according to formula (A) at a frequency of 76.5 GHz. Formula (A)

number

[0056] The absorption rate is preferably 45.0% or higher, more preferably 50.0% or higher, even more preferably 55.0% or higher, even more preferably 60.0% or higher, even more preferably 65.0% or higher, and even more preferably 68.0% or higher. Ideally, the upper limit is 100%, but even 90.0% or lower will sufficiently satisfy the required performance. Such low absorption rates are achieved by using thermoplastic polyester resin, styrene-based resin, carbon nanotubes, and a compatibilizer in combination.

[0057] The resin composition of this embodiment preferably has a low reflectivity of electromagnetic waves. Specifically, the resin composition of this embodiment preferably has a reflectance of 40.0% or less when molded to a thickness of 2 mm (preferably 100 mm × 100 mm × 2 mm) and determined according to formula (B) at a frequency of 76.5 GHz. Formula (B)

number

[0058] The reflectance is preferably 35.0% or less, more preferably 30.0% or less, even more preferably 26.0% or less, even more preferably 24.0% or less, and even more preferably 22.5% or less. The lower limit is ideally 0%, but even 1.0% or more, and even 5.0% or more, will sufficiently satisfy the required performance.

[0059] The resin composition of this embodiment preferably has low transmittance. The resin composition of this embodiment preferably has a transmittance of 15.0% or less when molded to a thickness of 2 mm (preferably 100 mm × 100 mm × 2 mm) and determined according to formula (C) at a frequency of 76.5 GHz. Formula (C)

number

[0060] The transmittance is preferably 12.0% or less, more preferably 10.0% or less, and may be 8.0% or less. Ideally, the lower limit is 0%, but even if it is 1.0% or more, it will still sufficiently meet the required performance.

[0061] The resin composition of this embodiment preferably satisfies all of the following: the absorption rate determined according to formula (A), the reflectance determined according to formula (B), and the transmittance determined according to formula (C). The absorptivity determined according to formula (A), the reflectance determined according to formula (B), and the transmittance determined according to formula (C) are measured according to the method described in the examples below. It is preferable that at least one of the TD direction and MD direction of the molded article formed from the resin composition satisfies the above range. In particular, for the absorptivity determined according to formula (A), it is preferable that both the TD direction and the MD direction satisfy the above range.

[0062] In this embodiment, it is preferable that the resin composition exhibits low anisotropy in the absorption rate of the molded article. For example, it is preferable that the difference in absorption rates between the TD direction and the MD direction, as determined by equation (A), is small when injection molding is performed on a test piece measuring 100 mm × 100 mm × 2 mm in thickness. Specifically, the difference in absorption rates between the TD direction and the MD direction, as determined by equation (A), is preferably 10% or less, more preferably 8% or less, even more preferably 7% or less, even more preferably 6% or less, and even more preferably 5% or less. The lower limit of the difference in absorption rates between the TD direction and the MD direction, as determined by equation (A), is ideally 0%, but greater than 0% is practical. Such low absorption anisotropy is achieved by using a filler with an aspect ratio of 100 or less and a maximum length of 1000 μm or less. Furthermore, this can be achieved by setting the content of fillers with a maximum length greater than 1000 μm and an aspect ratio greater than 100 to 20% by mass or less of the content of fillers with an aspect ratio of 100 or less and a maximum length of 1000 μm or less.

[0063] <Method for producing resin compositions> The resin composition of this embodiment can be manufactured by a conventional method for producing resin compositions containing a thermoplastic resin. For example, it can be obtained by melt-kneading a thermoplastic polyester resin, a styrene-based resin, carbon nanotubes (preferably carbon nanotubes master-batched with a styrene-based resin), a compatibilizer, and a filler having an aspect ratio of 100 or less and a maximum length of 1000 μm or less. One form formed from such a resin composition is a pellet. The components may be pre-mixed and supplied to the extruder all at once, or they may be supplied to the extruder using a feeder, either without pre-mixing them, or with only some of them pre-mixed. The extruder may be a single-screw extruder or a twin-screw extruder. Furthermore, as mentioned above, it is preferable to supply the carbon nanotubes after masterbatching them with a resin (preferably a styrene-based resin). The heating temperature during melting and kneading can usually be appropriately selected from the range of 170 to 350°C.

[0064] <Method for manufacturing molded articles> The molded body, in particular the electromagnetic wave absorber, is formed from the resin composition or pellets of this embodiment. The method for manufacturing the molded article in this embodiment is not particularly limited, and any molding method commonly used for resin compositions containing thermoplastic resins can be arbitrarily employed. Examples include injection molding, ultra-high-speed injection molding, injection compression molding, two-color molding, hollow molding methods such as gas-assisted molding, molding using a heat-insulating mold, molding using a rapidly heated mold, foam molding (including supercritical fluid), insert molding, IMC (in-mold coating) molding, extrusion molding, sheet molding, thermoforming, rotational molding, lamination molding, press molding, blow molding, etc., with injection molding being preferred among them.

[0065] <Application> The electromagnetic wave absorber of this embodiment is formed from the resin composition of this embodiment. That is, the resin composition of this embodiment is preferably for electromagnetic wave absorbers (also called for electromagnetic wave absorbing members), more preferably for electromagnetic wave absorbers with a frequency of at least 60 to 90 GHz, and even more preferably for electromagnetic wave absorbers with a frequency of at least 70 to 80 GHz. Such electromagnetic wave absorbers are preferably used in radar applications. Specifically, they are used in housings, covers, anti-reflective materials, etc., for millimeter-wave radar. The electromagnetic wave absorber of this embodiment can be suitably used in: on-board millimeter-wave radar used in automatic brake control devices, inter-vehicle distance control devices, pedestrian accident reduction steering devices, unintended acceleration suppression devices, pedal misapplication acceleration suppression devices, approaching vehicle warning devices, lane keeping assist devices, rear-end collision prevention warning devices, parking assist devices, vehicle surrounding obstacle warning devices, etc.; railway and aviation millimeter-wave radar used in platform monitoring / level crossing obstacle detection devices, in-train content transmission devices, tram / railway collision avoidance devices, runway foreign object detection devices, etc.; millimeter-wave radar for traffic infrastructure such as intersection monitoring devices and elevator monitoring devices; millimeter-wave radar for various security devices; medical and nursing care millimeter-wave radar such as child and elderly monitoring systems; millimeter-wave radar for various information content transmission; and the like. [Examples]

[0066] The present invention will be described in more detail below with reference to examples. The materials, amounts used, proportions, processing content, and processing procedures shown in the following examples can be modified as appropriate, as long as they do not depart from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. If the measuring instruments used in the examples are difficult to obtain due to discontinuation or other reasons, measurements can be taken using other instruments with equivalent performance.

[0067] 1. Raw materials The following ingredients were used.

[0068] [Table 1]

[0069] In Table 1 above, PBT represents polybutylene terephthalate, and CNT represents carbon nanotubes.

[0070] <Method for measuring aspect ratio and maximum length> The aspect ratio and maximum length were observed and measured using an electron microscope. For plate-shaped fillers, the aspect ratio is defined as the ratio of the length of the longest side of the plate surface (the length of the longest part) to the length of the thickest part in the thickness direction. For fibrous fillers, it is the ratio of the fiber length to the fiber diameter. For ellipsoidal fillers, it is defined as the ratio of the major axis to the minor axis, and the aspect ratio is 1 for a perfect sphere. For fillers of other shapes, it is defined as the ratio of the length of the longest part of the filler to the length of the shortest part perpendicular to the longest part. The aspect ratio and maximum length were taken as the average value for any 100 filler samples.

[0071] 2. Examples 1-3, Comparative Examples 1-4 <Manufacturing of resin compositions (pellets)> As shown in Table 2, each component listed in Table 1 (the proportion of each component is in parts by mass) was placed in a stainless steel tumbler and stirred and mixed for 1 hour. The resulting mixture was supplied from the main feed port to a coaxial twin-screw extruder (TEX-30α, manufactured by Japan Steel Works, Ltd., screw diameter 32 mm, L / D = 42). The barrel temperature was set to 260°C for plasticization, and the mixture was melt-kneaded under conditions of a discharge rate of 40 kg / h and a screw rotation speed of 200 rpm. The mixture was then extruded as strands using 5 nozzles (circular (φ4 mm), length 1.5 cm). The extruded strands were introduced into a water tank for cooling, inserted into a pelletizer, and cut to obtain resin compositions (pellets).

[0072] <76.5GHz electromagnetic wave absorption rate, reflectance rate, transmittance rate> Using the pellets obtained above, injection molding was performed using an injection molding machine (NEX80, manufactured by Nissei Plastic Industrial Co., Ltd.) with a cylinder temperature of 260°C and a mold temperature of 80°C to obtain test specimens measuring 100 mm × 100 mm × 2 mm in thickness. Using the obtained test specimens, the absorptivity determined according to equation (A), the reflectivity determined according to equation (B), and the transmittance determined according to equation (C) at a frequency of 76.5 GHz were measured as follows. For the measurements, we used a Keysight N5252A network analyzer. Measurements were taken for both cases: when the test specimen was positioned so that the TD (transverse direction) of the injection-molded body was parallel to the electric field direction, and when the test specimen was positioned so that the MD (machine direction) was parallel to the electric field direction. Formula (A)

number

[0073] Formula (B)

number

[0074] Formula (C)

number

[0075] <Exterior> Using the pellets obtained above, injection molding was performed using an injection molding machine (NEX80, manufactured by Nissei Plastic Industrial Co., Ltd.) with a cylinder temperature of 260°C and a mold temperature of 80°C to obtain test pieces measuring 100 mm × 100 mm × 2 mm in thickness. The appearance of the surface of the obtained molded product was judged visually. A: The surface is smooth and glossy with minimal unevenness caused by fillers. B: The unevenness caused by the filler material is noticeable, and the surface gloss is low.

[0076] [Table 2]

[0077] As is clear from the above results, the molded articles formed from the resin composition of the present invention had a high absorption rate, a small difference in absorption rates between the TD direction and the MD direction, and low anisotropy of absorption rate. Furthermore, the molded articles also had excellent appearance. In contrast, when styrene-based resins and compatibilizers were not included (Comparative Examples 1-4), the absorption rate was lower.

Claims

1. The material comprises a thermoplastic polyester resin, a styrene-based resin, carbon nanotubes, a compatibilizer, and a filler with an aspect ratio of 100 or less and a maximum length of 100 μm or less. The resin composition wherein the compatibilizer is a polycarbonate resin and / or a styrene-maleic acid copolymer, A resin composition in which the carbon nanotube content is 0.01% by mass or more and 10% by mass or less in the resin composition.

2. The resin composition according to claim 1, wherein the compatibilizer comprises a polycarbonate resin.

3. The resin composition according to claim 2, comprising 5 to 20 parts by mass of polycarbonate resin with respect to a total of 100 parts by mass of the thermoplastic polyester resin and styrene resin.

4. The resin composition according to claim 1, comprising 10 to 50 parts by mass of styrene-based resin with respect to a total of 100 parts by mass of the thermoplastic polyester resin and styrene-based resin.

5. The resin composition according to claim 1, wherein the content of fillers having a maximum length exceeding 1000 μm and an aspect ratio exceeding 100 is 20% by mass or less of the content of fillers having an aspect ratio of 100 or less and a maximum length of 100 μm or less.

6. The resin composition according to claim 1, wherein the carbon nanotubes are carbon nanotubes that have been master-batched, and the base resin of the master-batch is a styrene-based resin.

7. The resin composition according to claim 1, wherein the filler having an aspect ratio of 100 or less and a maximum length of 100 μm or less contains talc.

8. The resin composition according to claim 1, for use as an electromagnetic wave absorber.

9. The resin composition according to claim 1, wherein when the resin composition is molded to a thickness of 2 mm, the absorption rate determined according to formula (A) at a frequency of 76.5 GHz is 40.0 to 100%. Formula (A) [Math 1] (In the above formula (A), R represents the return loss measured by the free-space method, and T represents the transmission loss measured by the free-space method.)

10. The resin composition according to claim 1, wherein when the resin composition is molded to a thickness of 2 mm, the reflectance determined according to formula (B) at a frequency of 76.5 GHz is 40.0% or less. Formula (B) [Math 2] (In equation (B) above, R represents the return loss measured by the free-space method.)

11. The resin composition according to claim 1, wherein when the resin composition is molded to a thickness of 2 mm, the transmittance determined according to formula (C) at a frequency of 76.5 GHz is 15.0% or less. Formula (C) [Math 3] (In the above formula (C), T represents the transmission attenuation measured by the free-space method.)

12. The aforementioned compatibilizer contains polycarbonate resin, The mixture contains 5 to 20 parts by mass of polycarbonate resin in proportion to a total of 100 parts by mass of the thermoplastic polyester resin and styrene resin. A total of 100 parts by mass of the thermoplastic polyester resin and styrene resin, It contains 10 to 50 parts by mass of styrene resin, The content of fillers with a maximum length exceeding 1000 μm and an aspect ratio exceeding 100 is 20% by mass or less of the content of fillers with an aspect ratio of 100 or less and a maximum length of 100 μm or less. The carbon nanotubes are carbon nanotubes that have been formed into a masterbatch, and the base resin of the masterbatch is a styrene-based resin. The aforementioned filler having an aspect ratio of 100 or less and a maximum length of 100 μm or less contains talc. It is for use as an electromagnetic wave absorber. When the resin composition is molded to a thickness of 2 mm, the absorption rate determined according to formula (A) at a frequency of 76.5 GHz is 40.0 to 100%. When the resin composition is molded to a thickness of 2 mm, the reflectance determined according to formula (B) at a frequency of 76.5 GHz is 40.0% or less. The resin composition according to claim 1, wherein when the resin composition is molded to a thickness of 2 mm, the transmittance determined according to formula (C) at a frequency of 76.5 GHz is 15.0% or less. Formula (A) [Math 4] (In the above formula (A), R represents the return loss measured by the free-space method, and T represents the transmission loss measured by the free-space method.) Formula (B) [Math 5] (In equation (B) above, R represents the return loss measured by the free-space method.) Formula (C) [Math 6] (In the above formula (C), T represents the transmission attenuation measured by the free-space method.)

13. A pellet formed from the resin composition according to any one of claims 1 to 12.

14. A molded article formed from the resin composition according to any one of claims 1 to 12.

15. An electromagnetic wave absorber formed from the resin composition according to any one of claims 1 to 12.

16. An electromagnetic wave absorber formed from the pellets described in claim 13.

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