Resin composition, formed article, and, electromagnetic wave absorber

Abstract

To provide a resin composition, a formed article, and, an electromagnetic wave absorber, all having large absorbance of electromagnetic wave. The resin composition contains: a thermoplastic resin; and an electro-conductive substance, the resin composition, when formed to a 2 mm thick test specimen and a cross section thereof is observed under a digital microscope, giving an aggregate attributable to the electro-conductive substance, with an area percentage of the aggregate, having an equivalent circle diameter of 30 µrn or larger, of 0.80% or smaller.

Description

Resin composition, molded body, and electromagnetic wave absorber

[0001] The present invention relates to a resin composition, a molded article, and an electromagnetic wave absorber.

[0002] Millimeter-wave radar emits millimeter-wave radio waves with a wavelength of 1 to 10 mm at a frequency of 30 to 300 GHz, particularly 60 to 90 GHz, and detects the presence of obstacles as well as the distance and relative speed of the object by receiving the reflected waves that collide with the object and return. Millimeter-wave radar is being considered for use in a wide range of fields, including automobile collision prevention sensors, autonomous driving systems, road information systems, security systems, and medical and nursing care devices. Patent Document 1 discloses a resin composition for such millimeter-wave radar. Patent Document 2 also discloses a multifunctional resin composition that can be used for electromagnetic interference shielding or radio frequency interference shielding.

[0003] JP 2019-197048 A JP 2010-155993 A

[0004] In millimeter-wave radar, penetrating electromagnetic waves are the most significant cause of malfunction. Therefore, there is a demand for resin compositions with high electromagnetic wave absorption. The present invention aims to solve this problem by providing a resin composition, a molded product, and an electromagnetic wave absorber with high electromagnetic wave absorption.

[0005] In light of the above-mentioned problems, the present inventors conducted research and found that, in a resin composition in which a thermoplastic resin is blended with a conductive material, the electromagnetic wave absorption rate can be reduced by reducing large aggregates derived from the conductive material. Specifically, the above-mentioned problems have been solved by the following means. <1-1> A resin composition containing a thermoplastic resin and a conductive material, wherein, when the resin composition is molded into a 2 mm thick test piece and the cross section thereof is observed with a digital microscope, the area ratio of aggregates derived from the conductive material and having an equivalent circle diameter of 30 μm or more is 0.80% or less. <1-2> The resin composition according to <1-1>, wherein the conductive material includes carbon nanotubes. <1-3> The resin composition according to <1-1> or <1-2>, wherein the thermoplastic resin includes a polybutylene terephthalate resin. <1-4> The resin composition according to any one of <1-1> to <1-3>, wherein the content of the conductive material in the resin composition is 0.01 to 10 mass%. <1-5> The resin composition according to <1-1>, wherein the thermoplastic resin comprises a polybutylene terephthalate resin, the conductive material comprises carbon nanotubes, and the content of the conductive material in the resin composition is 0.01 to 10 mass%. <1-6> The resin composition according to <1-1>, wherein the thermoplastic resin comprises a polybutylene terephthalate resin and a polystyrene-based resin, and the conductive material comprises carbon nanotubes. <1-7> The resin composition according to <1-6>, wherein the content of carbon nanotubes in the resin composition is 0.01 to 10 mass%. <1-8> The resin composition according to <1-6> or <1-7>, wherein the resin composition exhibits a sea-island structure having a sea region rich in the polybutylene terephthalate resin and island regions rich in the polystyrene-based resin, 30 mass% or more of the resin components contained in the resin composition is polybutylene terephthalate resin, and the content of carbon nanotubes in the sea region is higher than the content of carbon nanotubes in the island regions. <1-9> The resin composition according to any one of <1-6> to <1-8>, wherein the polystyrene-based resin is derived from a carbon nanotube masterbatch.<1-10> The resin composition according to any one of <1-1> to <1-9>, wherein the conductive substance includes carbon nanotubes, and the resin composition has a relative dielectric constant of 4.50 or more at a frequency of 76.5 GHz. <1-11> The resin composition according to <1-10>, wherein the resin composition has a dielectric loss tangent of 0.10 or more at a frequency of 76.5 GHz. <1-12> The resin composition according to <1-10> or <1-11>, wherein the resin composition contains 0.01 to 10 mass% of carbon nanotubes. <1-13> The resin composition according to any one of <1-10> to <1-12>, wherein the thermoplastic resin includes a thermoplastic resin (A) and a thermoplastic resin (B), and the thermoplastic resin (B) is contained in an amount of 1.0 to 100 parts by mass per 100 parts by mass of the thermoplastic resin (A). <1-14> The resin composition according to <1-13>, wherein the thermoplastic resin (A) includes a polyester resin. <1-15> The resin composition according to <1-14>, wherein the polyester resin contains a polybutylene terephthalate resin. <1-16> The resin composition according to any one of <1-13> to <1-15>, wherein the thermoplastic resin (B) contains a polystyrene-based resin. <1-17> The resin composition according to any one of <1-13> to <1-16>, wherein at least a portion of the thermoplastic resin (B) is derived from a masterbatch of carbon nanotubes. <1-18> The resin composition according to <1-17>, wherein the concentration of carbon nanotubes in the masterbatch is 1 to 50 mass%. <1-19> The resin composition according to any one of <1-1> to <1-18>, wherein, when the resin composition is molded to a thickness of 2 mm, the absorbance at a frequency of 76.5 GHz calculated according to formula (A) is 50.0 to 100%. Formula (A): (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.) <1-20> The resin composition according to any one of <1-1> to <1-19>, wherein when the resin composition is molded into a thickness of 2 mm, the reflectance at a frequency of 76.5 GHz calculated according to formula (B) is 40.0% or less. Formula (B) (In the above formula (B), R represents the return loss measured by the free space method.) <1-21> The resin composition according to any one of <1-1> to <1-20>, wherein when the resin composition is molded into a thickness of 2 mm, the transmittance calculated according to formula (C) at a frequency of 76.5 GHz is 25.0% or less. Formula (C) (In the above formula (C), T represents the transmission attenuation measured by the free space method.) <1-22> When the resin composition is molded into a thickness of 2 mm, the surface resistance in accordance with IEC 60093 is 1.0 × 10 ８ The resin composition according to any one of <1-1> to <1-21>, having a resistance of Ω or more. <1-23> The resin composition according to any one of <1-1> to <1-22>, which is used for an electromagnetic wave absorber. <1-24> A molded article formed from the resin composition according to any one of <1-1> to <1-23>. <1-25> An electromagnetic wave absorber formed from the resin composition according to any one of <1-1> to <1-23>. <1-26> A method for producing a resin composition, comprising melt-kneading a polybutylene terephthalate resin and a styrene-based resin masterbatch of carbon nanotubes. <1-27> A method for producing a resin composition according to <1-26>, wherein the resin composition is the resin composition according to any one of <1-6> to <1-9>. <1-28> A method for producing a resin composition according to any one of <1-10> to <1-18>, comprising melt-kneading a thermoplastic resin and carbon nanotubes masterbatched with the thermoplastic resin.

[0006] <1-29> The resin composition according to any one of <1-10> to <1-23>, which satisfies the requirements of any one of <4-1> to <4-12> described later.

[0007] <2-1> A resin composition comprising a polybutylene terephthalate resin, a polystyrene-based resin, and carbon nanotubes. <2-2> The resin composition according to <2-1>, wherein the carbon nanotube content in the resin composition is 0.01 to 10 mass%. <2-3> The resin composition according to <2-1> or <2-2>, wherein the resin composition exhibits a sea-island structure having a sea region rich in the polybutylene terephthalate resin and an island region rich in the polystyrene-based resin, wherein 30 mass% or more of the resin components contained in the resin composition are polybutylene terephthalate resin, and the content of carbon nanotubes in the sea region is higher than the content of carbon nanotubes in the island region. <2-4> The resin composition according to any one of <2-1> to <2-3>, wherein the polystyrene-based resin is derived from the carbon nanotube masterbatch. <2-5> The resin composition according to any one of <2-1> to <2-4>, wherein when the resin composition is molded into a thickness of 2 mm, the absorption rate at a frequency of 76.5 GHz calculated according to formula (A) is 50.0 to 100%. Formula (A) (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.) <2-6> The resin composition according to any one of <2-1> to <2-5>, wherein when the resin composition is molded into a thickness of 2 mm, the reflectance at a frequency of 76.5 GHz calculated according to formula (B) is 40.0% or less. Formula (B) (In the above formula (B), R represents the return loss measured by the free space method.) <2-7> The resin composition according to any one of <2-1> to <2-6>, wherein when the resin composition is molded into a thickness of 2 mm, the transmittance calculated according to formula (C) at a frequency of 76.5 GHz is 25.0% or less. Formula (C) (In the above formula (C), T represents the transmission attenuation measured by a free space method.) <2-8> The resin composition according to any one of <2-1> to <2-7>, wherein the carbon nanotubes comprise multi-walled carbon nanotubes. <2-9> The resin composition according to any one of <2-1> to <2-8>, wherein the polystyrene-based resin comprises a butadiene rubber-containing polystyrene. <2-10> The resin composition according to any one of <2-1> to <2-9>, wherein the resin is used for an electromagnetic wave absorber. <2-11> A molded article formed from the resin composition according to any one of <2-1> to <2-10>. <2-12> An electromagnetic wave absorber formed from the resin composition according to any one of <2-1> to <2-10>. <2-13> A method for producing a resin composition, comprising melt-kneading a polybutylene terephthalate resin and a styrene-based resin masterbatch of carbon nanotubes. <2-14> The method for producing a resin composition according to <2-13>, wherein the resin composition is the resin composition according to any one of <2-1> to <2-10>.

[0008] <3-1> A resin composition comprising a thermoplastic resin and carbon nanotubes, wherein the resin composition has a relative dielectric constant of 4.50 or more at a frequency of 76.5 GHz. <3-2> The resin composition according to <3-1>, wherein the resin composition has a dielectric dissipation factor of 0.10 or more at a frequency of 76.5 GHz. <3-3> The resin composition according to <3-1> or <3-2>, wherein the content of carbon nanotubes in the resin composition is 0.01 to 10 mass%. <3-4> The resin composition according to any one of <3-1> to <3-3>, wherein the thermoplastic resin comprises a thermoplastic resin (A) and a thermoplastic resin (B), and the thermoplastic resin (B) is contained in an amount of 1.0 to 100 parts by mass per 100 parts by mass of the thermoplastic resin (A). <3-5> The resin composition according to <3-4>, wherein the thermoplastic resin (A) comprises a polyester resin. <3-6> The resin composition according to <3-5>, wherein the polyester resin contains a polybutylene terephthalate resin. <3-7> The resin composition according to any one of <3-4> to <3-6>, wherein the thermoplastic resin (B) contains a polystyrene-based resin. <3-8> The resin composition according to any one of <3-4> to <3-7>, wherein at least a portion of the thermoplastic resin (B) is derived from a masterbatch of the carbon nanotubes. <3-9> The resin composition according to <3-8>, wherein the concentration of carbon nanotubes in the masterbatch is 1 to 50 mass%. <3-10> The resin composition according to any one of <3-1> to <3-9>, wherein, when the resin composition is molded to a thickness of 2 mm, the absorbance at a frequency of 76.5 GHz calculated according to formula (A) is 50.0 to 100%. Formula (A) (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.) <3-11> The resin composition according to any one of <3-1> to <3-10>, wherein when the resin composition is molded into a thickness of 2 mm, the reflectance calculated according to formula (B) at a frequency of 76.5 GHz is 40.0% or less. Formula (B) (In the above formula (B), R represents the return loss measured by the free space method.) <3-12> The resin composition according to any one of <3-1> to <3-11>, wherein when the resin composition is molded into a thickness of 2 mm, the transmittance calculated according to formula (C) at a frequency of 76.5 GHz is 25.0% or less. Formula (C) (In the above formula (C), T represents the transmission attenuation measured by a free space method.) <3-13> The resin composition according to any one of <3-1> to <3-12>, which is for use in an electromagnetic wave absorber. <3-14> A molded article formed from the resin composition according to any one of <3-1> to <3-13>. <3-15> An electromagnetic wave absorber formed from the resin composition according to any one of <3-1> to <3-13>. <3-16> A method for producing the resin composition according to any one of <3-1> to <3-13>, comprising melt-kneading a thermoplastic resin and carbon nanotubes masterbatched with the thermoplastic resin.

[0009] <4-1> A resin composition comprising a thermoplastic resin (A), a thermoplastic resin (B), and carbon nanotubes, wherein at least a portion of the thermoplastic resin (B) is derived from a masterbatch of the carbon nanotubes, and wherein the SP value of the thermoplastic resin (A) is greater than or equal to the SP value of the thermoplastic resin (B) (wherein the SP value is a solubility parameter). <4-2> The resin composition according to <4-1>, wherein the concentration of the carbon nanotubes in the masterbatch is 1 to 50 mass%. <4-3> The resin composition according to <4-1> or <4-2>, wherein the thermoplastic resin (A) is selected from a polyester resin, a polycarbonate resin, and a polyamide resin. <4-4> The resin composition according to any one of <4-1> to <4-3>, wherein the thermoplastic resin (B) is selected from a polyester resin, a polystyrene-based resin, and a polyolefin resin. <4-5> The resin composition according to any one of <4-1> to <4-4>, wherein the difference between the SP value of the thermoplastic resin (A) and the SP value of the thermoplastic resin (B) is 0 to 8.0. <4-6> The resin composition according to any one of <4-1> to <4-4>, wherein the difference between the SP value of the thermoplastic resin (A) and the SP value of the thermoplastic resin (B) is 0.1 to 8.0. <4-7> The resin composition according to any one of <4-1> to <4-6>, wherein the content of carbon nanotubes in the resin composition is 0.01 to 10 mass%. <4-8> The resin composition according to any one of <4-1> to <4-7>, wherein the absorbance at a frequency of 76.5 GHz calculated according to formula (A) is 50.0 to 100% when the resin composition is molded to a thickness of 2 mm. Formula (A) (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.) <4-9> The resin composition according to any one of <4-1> to <4-8>, wherein when the resin composition is molded into a thickness of 2 mm, the reflectance at a frequency of 76.5 GHz calculated according to formula (B) is 40.0% or less. Formula (B) (In the above formula (B), R represents the return loss measured by the free space method.) <4-10> The resin composition according to any one of <4-1> to <4-9>, wherein when the resin composition is molded into a thickness of 2 mm, the transmittance calculated according to formula (C) at a frequency of 76.5 GHz is 25.0% or less. Formula (C) (In the above formula (C), T represents the transmission attenuation measured by a free space method.) <4-11> The resin composition according to any one of <4-1> to <4-10>, comprising 1.0 to 100 parts by mass of the thermoplastic resin (B) per 100 parts by mass of the thermoplastic resin (A). <4-12> The resin composition according to any one of <4-1> to <4-11>, which is for use in an electromagnetic wave absorber. <4-13> A molded product formed from the resin composition according to any one of <4-1> to <4-12>. <4-14> An electromagnetic wave absorber formed from the resin composition according to any one of <4-1> to <4-12>. <4-15> A method for producing a resin composition, comprising melt-kneading a thermoplastic resin (A) and carbon nanotubes masterbatched with the thermoplastic resin (B), wherein the SP value of the thermoplastic resin (A) is greater than or equal to the SP value of the thermoplastic resin (B) (wherein the SP value is a solubility parameter). <4-16> The method for producing a resin composition according to <4-15>, wherein the resin composition is the resin composition according to any one of <4-1> to <4-12>.

[0010] The present invention makes it possible to provide a resin composition, a molded article, and an electromagnetic wave absorber that have a high absorption rate of electromagnetic waves.

[0011] 1 shows electron microscope photographs of test pieces observed in Examples.

[0012] Hereinafter, a detailed description will be given of an embodiment of the present invention (hereinafter simply referred to as "the present embodiment"). Note that the following present embodiment is an example for explaining the present invention, and the present invention is not limited to this embodiment. In this specification, the term "to" is used to mean that the numerical values ​​before and after it are included as lower and upper limits. In this specification, various physical property values ​​and characteristic values ​​are those at 23°C unless otherwise specified. In this specification, weight average molecular weight and number average molecular weight are polystyrene-equivalent values ​​measured by GPC (gel permeation chromatography). In this specification, the unit of reflection loss and transmission loss is "dB" (decibels). If the measurement method, etc., of the specifications shown in this specification differ depending on the year, they shall be based on the specifications as of January 1, 2021, unless otherwise specified.

[0013] The resin composition of this embodiment is a resin composition containing a thermoplastic resin and a conductive material, and is characterized in that when the resin composition is molded into a 2 mm thick test piece and the cross section is observed with a digital microscope, the area ratio of aggregates derived from the conductive material having an equivalent circle diameter of 30 μm or more is 0.80% or less. By reducing the proportion of aggregates derived from the conductive material that are larger than a predetermined size, electromagnetic wave absorption can be significantly improved. Furthermore, electromagnetic wave transmittance and reflectance can be reduced. Furthermore, molded articles formed from the resin composition of this embodiment can have excellent mechanical strength.

[0014] Examples of means for reducing the proportion of aggregates derived from the conductive substance include thoroughly dispersing the conductive substance in the thermoplastic resin. More specifically, these include more thoroughly melt-kneading the thermoplastic resin and the conductive substance in a blended state, supplying the conductive substance in multiple batches when melt-kneading the thermoplastic resin and the conductive substance, blending a dispersant to improve the dispersibility of the conductive substance into the thermoplastic resin, master-batching the conductive substance and blending it into the thermoplastic resin, and utilizing the driving force when the conductive substance diffuses from the master-batch into the thermoplastic resin during melt-kneading to improve dispersibility, and selecting a conductive substance with a shape that is easy to disperse. In particular, for effective dispersion, it is desirable to select two or more of these methods.

[0015] In this embodiment, the area ratio of the conductive substance-derived aggregates having a circle-equivalent diameter of 30 μm or more is preferably 0.70% or less, more preferably 0.60% or less, even more preferably 0.50% or less, and even more preferably 0.42% or less. The lower limit of the area ratio is ideally 0%, but 0.01% or more is practical, and even 0.10% or more sufficiently satisfies the required performance. The area ratio is measured according to the description in the Examples below.

[0016] <Thermoplastic Resin> The resin composition of this embodiment contains a thermoplastic resin. Preferred examples of the thermoplastic resin used in this embodiment include polyester resins (thermoplastic polyester resins), polyamide resins, polycarbonate resins, polystyrene-based resins, polyolefin resins such as polyethylene resins, polypropylene resins, and cyclic cycloolefin resins, polyacetal resins, polyimide resins, polyetherimide resins, polyurethane resins, polyphenylene ether resins, polyphenylene sulfide resins, polysulfone resins, and polymethacrylate resins. Of these, polyester resins (thermoplastic polyester resins), polyamide resins, polycarbonate resins, and polyphenylene ether resins are preferred.

[0017] In this embodiment, the thermoplastic resin (for example, polyester resin (thermoplastic polyester resin), polyamide resin, polycarbonate resin, and polyphenylene ether resin) may be a linear polymer or a branched polymer having a branched structure. In this embodiment, the thermoplastic resin preferably has a small branched structure. For example, the thermoplastic resin used in this embodiment preferably has a degree of branching (DB) of less than 10%, more preferably 5% or less, and even more preferably 3% or less. Here, the degree of branching is defined as DB (%) = 100 × (T + Z) / (T + Z + L), where T is the average number of terminally bonded monomer units, Z is the average number of monomer units that form branches, and L is the average number of linearly bonded monomer units (within the macromolecules of each substance).

[0018] In this embodiment, the thermoplastic resin preferably includes a polyester resin, and more preferably includes a polybutylene terephthalate resin. Furthermore, in this embodiment, preferably 90% by mass or more, more preferably 93% by mass or more of the thermoplastic resin is a polyester resin. The thermoplastic resin also preferably includes a polyester resin (preferably a polybutylene terephthalate resin) and a polystyrene-based resin. In this embodiment, preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more of the total thermoplastic resin is composed of a polyester resin (preferably a polybutylene terephthalate resin) and a polystyrene-based resin (preferably HIPS, more preferably a butadiene rubber-containing polystyrene).

[0019] Each thermoplastic resin will be described in detail below.

[0020] <<Polyester Resin>> As the polyester resin, known thermoplastic polyester resins can be used, and polyethylene terephthalate resin and polybutylene terephthalate resin are preferred, and it is more preferred to include at least a polybutylene terephthalate resin. The polybutylene terephthalate resin used in the resin composition of this embodiment is a polyester resin having a structure in which terephthalic acid units and 1,4-butanediol units are ester-bonded, and includes, in addition to polybutylene terephthalate resin (homopolymer), a polybutylene terephthalate copolymer containing other copolymerization components other than terephthalic acid units and 1,4-butanediol units, and a mixture of a homopolymer and a polybutylene terephthalate copolymer.

[0021] The polybutylene terephthalate resin may contain one or more dicarboxylic acid units other than terephthalic acid. Specific examples of the other dicarboxylic acids include aromatic dicarboxylic acids such as isophthalic acid, orthophthalic acid, 1,5-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, biphenyl-2,2'-dicarboxylic acid, biphenyl-3,3'-dicarboxylic acid, biphenyl-4,4'-dicarboxylic acid, bis(4,4'-carboxyphenyl)methane, anthracenedicarboxylic acid, and 4,4'-diphenyletherdicarboxylic acid, alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid and 4,4'-dicyclohexyldicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid, sebacic acid, azelaic acid, and dimer acid. In the polybutylene terephthalate resin used in the present embodiment, terephthalic acid units preferably account for 80 mol % or more of all dicarboxylic acid units, more preferably 90 mol % or more, even more preferably 95 mol % or more, even more preferably 97 mol % or more, and even more preferably 99 mol % or more.

[0022] The diol unit may contain one or more other diol units in addition to 1,4-butanediol. Specific examples of other diol units include aliphatic or alicyclic diols having 2 to 20 carbon atoms, bisphenol derivatives, and the like. Specific examples include ethylene glycol, propylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, decamethylene glycol, cyclohexanedimethanol, 4,4'-dicyclohexylhydroxymethane, 4,4'-dicyclohexylhydroxypropane, and ethylene oxide addition diol of bisphenol A. In addition to the above-mentioned bifunctional monomers, small amounts of trifunctional monomers such as trimellitic acid, trimesic acid, pyromellitic acid, pentaerythritol, and trimethylolpropane can also be used in combination to introduce a branched structure, or monofunctional compounds such as fatty acids can be used in combination to adjust the molecular weight. In the polybutylene terephthalate resin used in the present embodiment, 1,4-butanediol units preferably account for 80 mol % or more of all diol units, more preferably 90 mol % or more, even more preferably 95 mol % or more, still more preferably 97 mol % or more, and even more preferably 99 mol % or more.

[0023] As described above, the polybutylene terephthalate resin is preferably a polybutylene terephthalate homopolymer obtained by polycondensation of terephthalic acid and 1,4-butanediol. Alternatively, the polybutylene terephthalate copolymer may contain, as the carboxylic acid unit, one or more dicarboxylic acids other than the aforementioned terephthalic acid and / or, as the diol unit, one or more diols other than the aforementioned 1,4-butanediol. When the polybutylene terephthalate resin is a polybutylene terephthalate resin modified by copolymerization, specific preferred copolymers include polyester ether resins copolymerized with polyalkylene glycols, particularly polytetramethylene glycol, dimer acid-copolymerized polybutylene terephthalate resins, and isophthalic acid-copolymerized polybutylene terephthalate resins. Of these, polyester ether resins copolymerized with polytetramethylene glycol are preferred. These copolymers refer to those in which the copolymerization amount is 1 mol% or more but less than 50 mol% of the total polybutylene terephthalate resin segments. In particular, the copolymerization amount is preferably 2 mol % or more but less than 50 mol %, more preferably 3 to 40 mol %, and even more preferably 5 to 20 mol %. By setting the copolymerization ratio in this range, fluidity, toughness, and tracking resistance tend to be easily improved, which is preferable.

[0024] The amount of terminal carboxyl groups in the polybutylene terephthalate resin may 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 setting the amount to the above upper limit or less, alkali resistance and hydrolysis resistance tend to be improved. The lower limit of the amount of terminal carboxyl groups is not particularly specified, but is usually 10 eq / ton or more, taking into consideration the productivity of polybutylene terephthalate resin production.

[0025] The amount of terminal carboxyl groups in the polybutylene terephthalate resin is a value measured by dissolving 0.5 g of the polybutylene terephthalate resin in 25 mL of benzyl alcohol and titrating the solution with a 0.01 mol / L benzyl alcohol solution of sodium hydroxide. The amount of terminal carboxyl groups can be adjusted by any conventionally known method, such as adjusting the polymerization conditions during polymerization, such as the raw material charge ratio, polymerization temperature, and pressure reduction method, or by reacting a terminal blocking agent.

[0026] The intrinsic viscosity of the polybutylene terephthalate resin is preferably 0.5 dL / g or more, more preferably 0.6 dL / g or more. By setting the intrinsic viscosity to 0.5 dL / g or more, the mechanical strength of the resulting resin composition tends to be further improved. The intrinsic viscosity is preferably 2.00 dL / g, more preferably 1.50 dL / g or less, even more preferably 1.30 dL / g or less, even more preferably 1.26 dL / g or less, even more preferably 1.23 dL / g or less, and may even be 1.20 dL / g or less, 1.17 dL / g or less, 1.15 dL / g or less, 1.13 dL / g or less, 1.07 dL / g or less, 1.05 dL / g or less, 1.00 dL / g or less, or 0.97 dL / g or less. By setting the intrinsic viscosity to 2.0 dL / g or less, the fluidity of the resin composition tends to be further improved, and moldability tends to be improved. In particular, when a conductive material (especially carbon nanotubes) masterbatched with polybutylene terephthalate resin is blended into a resin composition in which polybutylene terephthalate resin is the main component of the thermoplastic resin (e.g., 80% by mass or more of the resin component), the conductive material is more easily dispersed when the polybutylene terephthalate resin as the main component has a lower intrinsic viscosity. As a result, the electromagnetic wave absorption properties tend to be improved. The intrinsic viscosity of the polybutylene terephthalate resin is measured at 30°C in a 1:1 (mass ratio) mixed solvent of tetrachloroethane and phenol.

[0027] Polybutylene terephthalate resin can be produced by batch or continuous melt polymerization of a dicarboxylic acid component containing terephthalic acid as the main component or an ester derivative thereof with a diol component containing 1,4-butanediol as the main component. Alternatively, after producing a low-molecular-weight polybutylene terephthalate resin by melt polymerization, the degree of polymerization (or molecular weight) can be increased to a desired value by further solid-state polymerization under a nitrogen gas flow or reduced pressure. The polybutylene terephthalate resin is preferably produced by a continuous melt polycondensation process of a dicarboxylic acid component containing terephthalic acid as the main component and a diol component containing 1,4-butanediol as the main component.

[0028] The catalyst used in carrying out the esterification reaction may be a conventionally known catalyst, such as a titanium compound, a tin compound, a magnesium compound, or a calcium compound. Among these, titanium compounds are particularly preferred. Specific examples of titanium compounds used as esterification catalysts include titanium alcoholates such as tetramethyl titanate, tetraisopropyl titanate, and tetrabutyl titanate, and titanium phenolates such as tetraphenyl titanate.

[0029] In addition to the above, the polyester resin may be found in paragraphs 0013 to 0016 of JP-A-2010-174223, the contents of which are incorporated herein by reference.

[0030] <<Polystyrene-Based Resin>> Examples of polystyrene-based resins include homopolymers of styrene-based monomers and copolymers of styrene-based monomers and monomers copolymerizable with styrene-based monomers. Examples of styrene-based monomers include styrene, α-methylstyrene, chlorostyrene, methylstyrene, and tert-butylstyrene. In the styrene-based resin of this embodiment, 50 mol% or more of the monomer units are styrene-based monomers. More specific examples of polystyrene-based resins include polystyrene resin, acrylonitrile-styrene copolymer (AS resin), high-impact polystyrene resin (HIPS), 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), and styrene-IPN type rubber copolymer. In this embodiment, the styrene-based resin is preferably an acrylonitrile-styrene copolymer (AS resin), high impact polystyrene resin (HIPS), 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, more preferably a high impact polystyrene resin (HIPS), and even more preferably a butadiene rubber-containing polystyrene.

[0031] When the polystyrene resin contains a rubber component, the content of the rubber component in the polystyrene 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, and a rubber component content of 50% by mass or less tends to improve flame retardancy, which is preferable. The average particle size of the rubber component 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, and an average particle size of 10 μm or less tends to improve appearance, which is preferable.

[0032] The weight-average molecular weight of the polystyrene resin is usually 50,000 or more, preferably 100,000 or more, more preferably 150,000 or more, and usually 500,000 or less, preferably 400,000 or less, 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 preferably 500,000 or less, more preferably 300,000 or less.

[0033] The melt flow rate (MFR) of the polystyrene resin, measured in accordance with JIS K7210 (temperature 200°C, load 5 kgf), is preferably 0.1 to 30 g / 10 min, more preferably 0.5 to 25 g / 10 min. An MFR of 0.1 g / 10 min or more tends to improve fluidity, while an MFR of 30 g / 10 min or less tends to improve impact resistance.

[0034] Examples of methods for producing such polystyrene resins include known methods such as emulsion polymerization, solution polymerization, suspension polymerization, and bulk polymerization.

[0035] <<Polycarbonate Resin>> Polycarbonate resins are optionally branched homopolymers or copolymers obtained by reacting a dihydroxy compound or a small amount of a polyhydroxy compound with phosgene or a carbonate diester. The method for producing the polycarbonate resin is not particularly limited, and polycarbonate resins produced by the conventionally known phosgene method (interfacial polymerization method) or melt method (ester exchange method) can be used.

[0036] The dihydroxy compound used as the raw material is preferably an aromatic dihydroxy compound, and examples thereof include 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), tetramethylbisphenol A, bis(4-hydroxyphenyl)-p-diisopropylbenzene, hydroquinone, resorcinol, and 4,4-dihydroxydiphenyl, with bisphenol A being preferred. Also usable are compounds in which one or more tetraalkylphosphonium sulfonates are bonded to the above aromatic dihydroxy compounds.

[0037] Among the polycarbonate resins mentioned above, aromatic polycarbonate resins derived from 2,2-bis(4-hydroxyphenyl)propane or aromatic polycarbonate copolymers derived from 2,2-bis(4-hydroxyphenyl)propane and other aromatic dihydroxy compounds are preferred. Furthermore, copolymers primarily composed of aromatic polycarbonate resins, such as copolymers with polymers or oligomers having a siloxane structure, may also be used. Furthermore, two or more of the above-mentioned polycarbonate resins may be mixed and used.

[0038] To adjust the molecular weight of the polycarbonate resin, a monovalent aromatic hydroxy compound may be used, such as m- and p-methylphenol, m- and p-propylphenol, p-tert-butylphenol, p-long-chain alkyl-substituted phenol, and the like.

[0039] 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 with a viscosity average molecular weight of 5,000 or more, the mechanical strength of the resulting resin composition tends to be further improved. Furthermore, 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 with a viscosity average molecular weight of 60,000 or less, the fluidity of the resin composition tends to be improved, and moldability tends to be improved. When two or more polycarbonate resins are contained, it is preferable that the mixture satisfies the above range (hereinafter, the same applies to molecular weight).

[0040] In this embodiment, the viscosity average molecular weight (Mv) of the polycarbonate resin is a value calculated from the intrinsic viscosity ([η]) obtained by measuring the viscosity of a methylene chloride solution of the polycarbonate resin at 20°C using an Ubbelohde viscometer, and then using the following Schnell viscosity formula: [η] = 1.23 × 10 －４ Mv ０．８３

[0041] The method for producing the polycarbonate resin is not particularly limited, and polycarbonate resins produced by either the phosgene method (interfacial polymerization method) or the melt method (ester interchange method) can be used. Also preferred is a polycarbonate resin produced by the melt method and then subjected to post-treatment to adjust the amount of terminal OH groups.

[0042] <<Polyphenylene Ether Resin>> In this embodiment, a known polyphenylene ether resin can be used, for example, a polymer having a structural unit represented by the following formula in its main chain (preferably a polymer in which the structural unit represented by the following formula accounts for 90 mol % or more of all structural units excluding terminal groups). The polyphenylene ether resin may be either a homopolymer or a copolymer.

[0043] (Wherein, two R ａeach independently represents a hydrogen atom, a halogen atom, a primary or secondary alkyl group, an aryl group, an aminoalkyl group, a halogenated alkyl group, a hydrocarbonoxy group, or a halogenated hydrocarbonoxy group, and two R ｂ each independently represents a hydrogen atom, a halogen atom, a primary or secondary alkyl group, an aryl group, a halogenated alkyl group, a hydrocarbonoxy group, or a halogenated hydrocarbonoxy group. ａ cannot both become hydrogen atoms.)

[0044] R ａ and R ｂ are each independently preferably a hydrogen atom, a primary or secondary alkyl group, or an aryl group. Preferred examples of the primary alkyl group include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-amyl group, an isoamyl group, a 2-methylbutyl group, a 2,3-dimethylbutyl group, a 2-, 3-, or 4-methylpentyl group, or a heptyl group. Preferred examples of the secondary alkyl group include an isopropyl group, a sec-butyl group, or a 1-ethylpropyl group. In particular, R ａ is preferably a primary or secondary alkyl group having 1 to 4 carbon atoms or a phenyl group. ｂ is preferably a hydrogen atom.

[0045] Suitable homopolymers of polyphenylene ether resins include, for example, polymers of 2,6-dialkylphenylene ether such as poly(2,6-dimethyl-1,4-phenylene) ether, poly(2,6-diethyl-1,4-phenylene ether), poly(2,6-dipropyl-1,4-phenylene ether), poly(2-ethyl-6-methyl-1,4-phenylene ether), and poly(2-methyl-6-propyl-1,4-phenylene ether). Examples of the copolymer include 2,6-dialkylphenol / 2,3,6-trialkylphenol copolymers such as 2,6-dimethylphenol / 2,3,6-trimethylphenol copolymer, 2,6-dimethylphenol / 2,3,6-triethylphenol copolymer, 2,6-diethylphenol / 2,3,6-trimethylphenol copolymer, and 2,6-dipropylphenol / 2,3,6-trimethylphenol copolymer; graft copolymers obtained by graft polymerizing styrene onto poly(2,6-dimethyl-1,4-phenylene ether); and graft copolymers obtained by graft polymerizing styrene onto a 2,6-dimethylphenol / 2,3,6-trimethylphenol copolymer.

[0046] In this embodiment, the polyphenylene ether resin is preferably poly(2,6-dimethyl-1,4-phenylene) ether or a 2,6-dimethylphenol / 2,3,6-trimethylphenol random copolymer. Also suitable is a polyphenylene ether resin having a specified number of terminal groups and copper content, as described in JP-A-2005-344065.

[0047] The polyphenylene ether resin preferably has an intrinsic viscosity of 0.2 to 0.8 dL / g, more preferably 0.3 to 0.6 dL / g, measured in chloroform at 30°C. By setting the intrinsic viscosity to 0.2 dL / g or more, the mechanical strength of the molded article tends to be further improved, while by setting the intrinsic viscosity to 0.8 dL / g or less, the fluidity of the resin composition tends to be further improved, making molding processability easier. Furthermore, two or more polyphenylene ether resins with different intrinsic viscosities may be used in combination to achieve an intrinsic viscosity within this range.

[0048] The method for producing the polyphenylene ether resin used in the present embodiment is not particularly limited, and may be any known method, for example, a method of oxidatively polymerizing a monomer such as 2,6-dimethylphenol in the presence of an amine copper catalyst, in which the intrinsic viscosity can be controlled within a desired range by selecting the reaction conditions. The control of the intrinsic viscosity can be achieved by selecting conditions such as the polymerization temperature, polymerization time, and catalyst amount.

[0049] <<Polyamide Resin>> Polyamide resins are polymers whose structural units are acid amides obtained by ring-opening polymerization of lactams, polycondensation of aminocarboxylic acids, or polycondensation of diamines and dibasic acids, and may be aliphatic polyamide resins or semi-aromatic polyamide resins. Specific examples include polyamide 6, 11, 12, 46, 66, 610, 612, 6I, 6 / 66, 6T / 6I, 6 / 6T, 66 / 6T, 66 / 6T / 6I, 9T, and 10T, xylylenediamine-based polyamide resins (described in detail below), polytrimethylhexamethylene terephthalamide, polybis(4-aminocyclohexyl)methanedodecamide, polybis(3-methyl-4-aminocyclohexyl)methanedodecamide, and polyundecamethylenehexahydroterephthalamide. The "I" in the above text represents an isophthalic acid component, and the "T" represents a terephthalic acid component. Regarding the polyamide resin, the description in paragraphs 0011 to 0013 of JP-A-2011-132550 can be referred to, the contents of which are incorporated herein by reference.

[0050] The polyamide resin used in this embodiment is composed of diamine-derived structural units and dicarboxylic acid-derived structural units, and is preferably a xylylenediamine-based polyamide resin in which 50 mol% or more of the diamine-derived structural units are derived from xylylenediamine. The diamine-derived structural units of the xylylenediamine-based polyamide resin are preferably derived from at least one of meta-xylylenediamine and para-xylylenediamine, with 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, and even more preferably 95 mol% or more of the diamine-derived structural units being derived from at least one of meta-xylylenediamine and para-xylylenediamine. The dicarboxylic acid-derived structural units of the xylylenediamine-based polyamide resin are preferably derived from α,ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms, with 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, even more preferably 90 mol% or more, and even more preferably 95 mol% or more of the dicarboxylic acid-derived structural units being derived from α,ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms. Suitable α,ω-straight chain aliphatic dibasic acids having 4 to 20 carbon atoms include adipic acid, sebacic acid, suberic acid, dodecanedioic acid, and eicodionic acid, with adipic acid and sebacic acid being more preferred.

[0051] Diamines other than metaxylylenediamine and paraxylylenediamine that can be used as raw diamine components for xylylenediamine-based polyamide resins include aliphatic diamines such as tetramethylenediamine, pentamethylenediamine, 2-methylpentanediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, dodecamethylenediamine, 2,2,4-trimethyl-hexamethylenediamine, and 2,4,4-trimethylhexamethylenediamine; 1,3-bis( Examples of the diamine include alicyclic diamines such as bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, bis(4-aminocyclohexyl)methane, 2,2-bis(4-aminocyclohexyl)propane, bis(aminomethyl)decalin, and bis(aminomethyl)tricyclodecane; and diamines having an aromatic ring such as bis(4-aminophenyl)ether, paraphenylenediamine, and bis(aminomethyl)naphthalene, and these can be used alone or in combination of two or more.

[0052] Examples of dicarboxylic acid components other than the above-mentioned α,ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms include phthalic acid compounds such as isophthalic acid, terephthalic acid, and orthophthalic acid, and isomers of naphthalenedicarboxylic acids such as 1,2-naphthalenedicarboxylic acid, 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 1,7-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid, and these can be used alone or in combination of two or more.

[0053] The content of the thermoplastic resin in the resin composition of this embodiment is preferably 30% by mass or more, more preferably 35% by mass or more, even more preferably 40% by mass or more, even more preferably 45% by mass or more, and even more preferably 50% by mass or more. When the resin composition does not contain a reinforcing material, the content of the thermoplastic resin in the resin composition is more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more. By setting the content to be equal to or greater than the lower limit, the flowability during injection molding tends to be further improved. Furthermore, the content of the thermoplastic resin is preferably 99% by mass or less. When the resin composition contains a reinforcing material, the content of the thermoplastic resin in the resin composition is more preferably 90% by mass or less, even more preferably 85% by mass or less, and even more preferably 80% by mass or less. By setting the content to be equal to or less than the upper limit, the amount of warpage of the molded article tends to be more effectively reduced. The resin composition of this embodiment may contain only one type of thermoplastic resin, or may contain two or more types of thermoplastic resin. When two or more types are contained, the total amount is preferably within the above range.

[0054] <Conductive Substance> The resin composition of this embodiment contains a conductive substance. By including a conductive substance, the resin composition can be provided with electromagnetic wave absorption properties. Examples of the conductive substance used in this embodiment include metals, metal oxides, conductive carbon compounds, and conductive polymers, with conductive carbon compounds being preferred. Examples of metals include copper, nickel, silver, and stainless steel, with metal fillers, stainless steel fibers, and magnetic fillers being preferred. Examples of metal oxides include alumina and zinc oxide, with alumina fibers and zinc oxide nanotubes being preferred. Examples of conductive carbon compounds include carbon black, ketjen carbon, graphene, graphite, fullerenes, carbon nanocoils, carbon nanotubes, and carbon fibers, with carbon nanotubes being more preferred. Also preferred are fibers coated with metals, metal oxides, or conductive carbon compounds. Examples include carbon-coated potassium titanate whiskers and metal-coated fibers.

[0055] The conductive material in this embodiment is preferably a relatively thin and long shape, such as a fiber, tube, or whisker. The diameter (number average fiber diameter) of the conductive material (preferably carbon nanotubes) is preferably 0.5 nm or more, more preferably 1 nm or more, and even more preferably 5 nm or more. The diameter (number average fiber diameter) of the carbon nanotubes is preferably 100 nm or less, more preferably 50 nm or less, even more preferably 30 nm or less, and even more preferably 10 nm or less. The aspect ratio of the conductive material is preferably 5 or more, more preferably 50 or more, from the viewpoint of imparting good electromagnetic wave absorption properties. There is no particular upper limit, but it is, for example, 500 or less.

[0056] The conductive material used in this embodiment is preferably carbon nanotubes. The carbon nanotubes are single-walled carbon nanotubes and / or multi-walled carbon nanotubes, and preferably contain at least multi-walled carbon nanotubes. Carbon materials partially having a carbon nanotube structure can also be used. The carbon nanotubes are not limited to a cylindrical shape, and may have a coiled shape with a spiral at a pitch of 1 μm or less. Carbon nanotubes are commercially available, and examples include carbon nanotubes available from Bayer MaterialScience, Nanosil, Showa Denko K.K., and Hyperion Catalysis International. In addition to the name carbon nanotubes, they may also be called graphite fibrils, carbon fibrils, etc.

[0057] The content of the conductive material (preferably carbon nanotubes) 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, and may be 0.2% by mass or more, or even 0.4% by mass or more. By making the content equal to or greater than the lower limit, electromagnetic wave absorption properties are effectively exhibited. Furthermore, the content of (preferably carbon nanotubes) 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, or even 1% by mass or less. By making the content equal to or less than the upper limit, the fluidity of the resin tends to be further improved.

[0058] The resin composition of this embodiment also preferably contains 0.1 parts by mass or more of a conductive material (preferably carbon nanotubes) per 100 parts by mass of the thermoplastic resin. By setting the content at or above the lower limit, electromagnetic wave absorption properties are effectively exhibited. Furthermore, the resin composition of this embodiment preferably contains 10.0 parts by mass or less of a conductive material (preferably carbon nanotubes) per 100 parts by mass of the thermoplastic resin, 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 even 2.5 parts by mass or less, particularly 1.5 parts by mass or less. Setting the content at or 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 conductive material, or may contain two or more types. When two or more types are contained, the total amount is preferably within the above range.

[0059] <Other Components> The resin composition of this embodiment may contain other components in addition to those described above, as necessary, as long as the desired physical properties are not significantly impaired. Examples of other components include reinforcing materials and various resin additives. Note that one type of other component may be contained, or two or more types may be contained in any combination and ratio.

[0060] Examples of various resin additives include stabilizers, release agents, flame retardants, 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 stabilizer and release agent. The resin composition of this embodiment is prepared so that the total of the thermoplastic resin, the conductive material, and other optional components is 100% by mass. It is also preferable that the total of the thermoplastic resin, the conductive material, the stabilizer, and the release agent account for 99% by mass or more of the resin composition. Furthermore, it is also preferable that the total of the thermoplastic resin, the conductive material, the reinforcing material (preferably glass fiber), the stabilizer, and the release agent account for 99% by mass or more of the resin composition.

[0061] <<Stabilizer>> The resin composition of this embodiment may contain a stabilizer. Examples of stabilizers include hindered phenol compounds, hindered amine compounds, phosphorus-based compounds, and sulfur-based stabilizers. Among these, hindered phenol compounds are preferred. It is also preferable to use a hindered phenol compound in combination with a phosphorus-based compound. Specific examples of stabilizers can be found in paragraphs

[0046] to

[0057] of JP 2018-070722 A, paragraphs

[0030] to

[0037] of JP 2019-056035 A, and paragraphs

[0066] to

[0078] of WO 2017 / 038949 A, the contents of which are incorporated herein by reference.

[0062] The resin composition of this embodiment preferably contains 0.01 parts by mass or more of the stabilizer per 100 parts by mass of the thermoplastic resin, more preferably 0.05 parts by mass or more, and even more preferably 0.08 parts by mass or more. 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 thermoplastic resin. The resin composition of this embodiment may contain only one type of stabilizer, or two or more types. When two or more types are contained, the total amount is preferably within the above range.

[0063] <<Release Agent>> The resin composition of this embodiment preferably contains a release agent. A wide variety of known release agents can be used as the release agent. Esters of aliphatic carboxylic acids, paraffin wax, polystyrene wax, and polyolefin wax are preferred, with polyethylene wax being more preferred. Specific examples of release agents include those described in paragraphs

[0115] to

[0120] of JP 2013-007058 A, paragraphs

[0063] to

[0077] of JP 2018-070722 A, and paragraphs

[0090] to

[0098] of JP 2019-123809 A, the contents of which are incorporated herein by reference.

[0064] The resin composition of this embodiment preferably contains 0.01 parts by mass or more of the release agent relative to 100 parts by mass of the thermoplastic resin, more preferably 0.08 parts by mass or more, and even more preferably 0.2 parts by mass or more. The upper limit of the amount of the release agent 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, relative to 100 parts by mass of the thermoplastic resin. The resin composition may contain only one type of release agent, or two or more types. When two or more types are contained, the total amount is preferably within the above range.

[0065] <<Reinforcing Material>> The resin composition of this embodiment may or may not contain a reinforcing material. By including a reinforcing material, the mechanical strength of the resulting molded article can be improved. The reinforcing material that can be used in this embodiment is not particularly limited in type, etc., and may be any of fibers, fillers, beads, etc., but fibers are preferred. In particular, glass fibers are preferred because they also function as a dispersant for the conductive material. Furthermore, in the present invention, a substance that corresponds to both the above-mentioned conductive material and a reinforcing material is considered to be a conductive material.

[0066] When the reinforcing material is a fiber, it may be a short fiber or a long fiber. When the reinforcing material is a short fiber, filler, beads, or the like, the resin composition of this embodiment may be in the form of pellets, powdered pellets, or a film formed from the pellets. When the reinforcing material is a long fiber, it may be in the form of a long fiber for a so-called UD material (unidirectional), or a sheet-like long fiber such as a woven or knitted fabric. When using these long fibers, components other than the reinforcing material of the resin composition of this embodiment may be impregnated into the sheet-like long fiber reinforcing material to form a sheet-like resin composition (e.g., a prepreg).

[0067] Examples of raw materials for the reinforcing material include inorganic substances such as glass, carbon (carbon fiber, etc.), alumina, boron, ceramics, and metals (steel, etc.), and organic substances such as plants (including kenaf, bamboo, etc.), aramid, polyoxymethylene, aromatic polyamide, polyparaphenylene benzobisoxazole, and ultra-high molecular weight polyethylene, with glass being preferred.

[0068] The resin composition of this embodiment preferably contains glass fibers as a reinforcing material. The glass fibers are selected from glass compositions such as A-glass, C-glass, E-glass, R-glass, D-glass, M-glass, and S-glass, with E-glass (alkali-free glass) being particularly preferred. Glass fibers refer to fibrous materials having a circular or polygonal cross section when cut perpendicular to the longitudinal direction. The number-average fiber diameter of single fibers of glass fibers is typically 1 to 25 μm, preferably 5 to 17 μm. By setting the number-average fiber diameter to 1 μm or more, the moldability of the resin composition tends to be further improved. By setting the number-average fiber diameter to 25 μm or less, the appearance of the resulting molded product tends to be improved, and the reinforcing effect also tends to be improved. The glass fibers may be single fibers or multiple twisted single fibers. The glass fiber may be in the form of a glass roving obtained by continuously winding a single fiber or a plurality of twisted fibers, a chopped strand cut to a length of 1 to 10 mm (i.e., glass fiber having a number average fiber length of 1 to 10 mm), or a milled fiber pulverized to a length of about 10 to 500 μm (i.e., glass fiber having a number average fiber length of 10 to 500 μm). However, chopped strands cut to a length of 1 to 10 mm are preferred. Glass fibers of different forms can also be used in combination. Glass fibers having an irregular cross-sectional shape are also preferred. This irregular cross-sectional shape refers to a shape in which the flatness, expressed as the ratio of the major axis to the minor axis of the cross section perpendicular to the longitudinal direction of the fiber, is, for example, 1.5 to 10, preferably 2.5 to 10, more preferably 2.5 to 8, and particularly preferably 2.5 to 5.

[0069] The glass fiber may be surface-treated with, for example, a silane-based compound, an epoxy-based compound, a urethane-based compound, or the like, or may be oxidized, in order to improve its affinity with the resin component, as long as the properties of the resin composition of this embodiment are not significantly impaired.

[0070] When the resin composition of this embodiment contains a reinforcing material (preferably glass fiber), the content thereof is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, and even more preferably 40 parts by mass or more, relative to 100 parts by mass of the thermoplastic resin. By setting the content at or above the lower limit, the mechanical strength of the obtained molded body tends to be further increased. Furthermore, the content of the reinforcing material (preferably glass fiber) is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, even more preferably 85 parts by mass or less, even more preferably 80 parts by mass or less, and even more preferably 75 parts by mass or less, relative to 100 parts by mass of the thermoplastic resin. By setting the content at or below the upper limit, the appearance of the molded body tends to be improved, and the flowability of the resin composition tends to be further improved.

[0071] When the resin composition of this embodiment contains a reinforcing material (preferably glass fiber), the content thereof in the resin composition is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, and even more preferably 25% by mass or more. Furthermore, the content of the reinforcing material (preferably glass fiber) in the resin composition is more preferably 50% by mass or less, even more preferably 45% by mass or less, even more preferably 40% by mass or less, and even more preferably 35% by mass or less. By setting the content to be equal to or greater than the lower limit, the mechanical strength tends to be further increased. Furthermore, by setting the content to be equal to or less than the upper limit, the appearance of the molded product tends to be improved, and the fluidity of the resin composition when melted tends to be further improved. The resin composition of this embodiment may contain only one type of reinforcing material (preferably glass fiber), or may contain two or more types. When two or more types are contained, the total amount is preferably within the above range.

[0072] <Physical Properties of Resin Composition> 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 50.0 to 100% at a frequency of 76.5 GHz, calculated according to formula (A), when molded into a 2 mm thick (preferably 100 mm x 100 mm x 2 mm thick) resin. Formula (A) (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.)

[0073] The absorbency (2 mm thickness) is preferably 53.0% or more, more preferably 55.0% or more, even more preferably 58.0% or more, even more preferably 60.0% or more, and even more preferably 64.0% or more. The upper limit is ideally 100%, but even if it is 90.0% or less, the required performance is sufficiently met.

[0074] Furthermore, when the resin composition of this embodiment is molded into a 3 mm thickness (preferably, 100 mm × 100 mm × 3 mm thickness), the absorbance calculated according to formula (A) at a frequency of 76.5 GHz is preferably 63.0 to 100%. The absorbance (3 mm thickness) is preferably 57.0% or more, more preferably 59.0% or more, even more preferably 64.0% or more, even more preferably 66.0% or more, and even more preferably 70.0% or more. Although an upper limit of 100% is ideal, the required performance is sufficiently met even if it is 90.0% or less.

[0075] The resin composition of this embodiment preferably has low electromagnetic wave reflectance. Specifically, the resin composition of this embodiment preferably has a reflectance of 40.0% or less at a frequency of 76.5 GHz, as calculated according to formula (B), when molded into a 2 mm thick (preferably, 100 mm × 100 mm × 2 mm thick). Formula (B) (In the above formula (B), R represents the return loss measured by the free space method.)

[0076] The reflectance (2 mm thickness) is preferably 35.0% or less, more preferably 30.0% or less, even more preferably 26.0% or less, even more preferably 22.0% or less, and even more preferably 18.5% or less. The lower limit is ideally 0%, but even if it is 5.0% or more, or even 10.0% or more, the required performance is sufficiently met.

[0077] Furthermore, when the resin composition of this embodiment is molded into a 3 mm thick piece (preferably 100 mm x 100 mm x 3 mm thick piece), the reflectance calculated according to formula (B) at a frequency of 76.5 GHz is preferably 38.0% or less. The reflectance (3 mm thick) is preferably 33.0% or less, more preferably 28.0% or less, even more preferably 24.0% or less, even more preferably 20.0% or less, and even more preferably 16.5% or less. While a lower limit of 0% is ideal, a reflectance of 3.0% or more, or even 8.0% or more, will sufficiently satisfy the required performance.

[0078] The resin composition of this embodiment preferably has low transmittance. When the resin composition of this embodiment is molded into a 2 mm thick (preferably, 100 mm × 100 mm × 2 mm thick), the transmittance calculated according to formula (C) at a frequency of 76.5 GHz is preferably 25.0% or less. Formula (C) (In the above formula (C), T represents the transmission attenuation measured by the free space method.)

[0079] The transmittance (2 mm thickness) is preferably 23.0% or less, and more preferably 20.0% or less. The lower limit is ideally 0%, but even if it is 5.0% or more, the required performance is sufficiently met.

[0080] Furthermore, when the resin composition of this embodiment is molded into a 3 mm thickness (preferably, 100 mm × 100 mm × 3 mm thickness), the transmittance calculated according to formula (C) at a frequency of 76.5 GHz is preferably 26.0% or less. The transmittance (3 mm thickness) is preferably 24.0% or less, and more preferably 21.0% or less. Although a lower limit of 0% is ideal, a value of 4.0% or more sufficiently satisfies the required performance.

[0081] The resin composition of the present embodiment preferably satisfies all of the absorptance calculated according to the above formula (A), the reflectance calculated according to the above formula (B), and the transmittance calculated according to the above formula (C).

[0082] The resin composition of this embodiment preferably has a high relative dielectric constant. It is also preferable that the resin composition of this embodiment has a high dielectric loss tangent. The resin composition of this embodiment preferably has a relative dielectric constant at a frequency of 76.5 GHz of 4.50 or more, more preferably 4.60 or more, even more preferably 4.75 or more, even more preferably 4.90 or more, even more preferably 5.00 or more, and even more preferably 5.10 or more. By setting the relative dielectric constant to be equal to or greater than the lower limit, the electromagnetic wave absorption rate of the resulting molded article tends to be higher. The upper limit of the relative dielectric constant is preferably 8.00 or less, more preferably 6.00 or less, even more preferably 5.50 or less, even more preferably 5.30 or less, and even more preferably 5.20 or less. By setting the relative dielectric constant to be equal to or less than the upper limit, the electromagnetic wave reflectivity of the resulting molded article tends to be lower. The resin composition of this embodiment preferably has a dielectric loss tangent at a frequency of 76.5 GHz of 0.10 or more, more preferably 0.12 or more, even more preferably 0.14 or more, even more preferably 0.16 or more, even more preferably 0.18 or more, and even more preferably 0.21 or more. By making the dielectric loss tangent equal to or greater than the lower limit, the electromagnetic wave absorption rate of the resulting molded article tends to be higher. Furthermore, the lower limit of the dielectric loss tangent is not particularly specified, but may be, for example, 0.50 or less, or even 0.40 or less. By making the dielectric loss tangent equal to or less than the upper limit, the electromagnetic wave reflectivity of the resulting molded article tends to be lower.

[0083] The resin composition of this embodiment preferably has excellent mechanical strength. The resin composition of this embodiment preferably has particularly excellent tensile properties. For example, when the resin composition of this embodiment is molded into an ISO multipurpose test piece (4 mm thick), the maximum tensile strength measured in accordance with ISO 527-1 and ISO 527-2 is preferably 40.0 MPa or more, and more preferably 50.0 MPa or more. The upper limit of the maximum tensile strength is not particularly specified, but for example, 200.0 MPa or less is still practical. Furthermore, when the resin composition of this embodiment is molded into an ISO multipurpose test piece (4 mm thick), the tensile modulus measured in accordance with ISO 527-1 and ISO 527-2 is preferably 1500 MPa or more, more preferably 1800 MPa or more, and even more preferably 2000 MPa or more. The upper limit of the tensile modulus is not particularly specified, but for example, 12000 MPa or less is still practical. Furthermore, when the resin composition of this embodiment is molded into an ISO multipurpose test piece (thickness 4 mm), the tensile strain measured in accordance with ISO 527-1 and ISO 527-2 is preferably 1.0% or more, more preferably 2.0% or more, and even more preferably 3.5% or more. There is no particular upper limit for the tensile strain, but, for example, a value of 30% or less is also practical.

[0084] The resin composition of this embodiment preferably has excellent bending properties. Specifically, when the resin composition of this embodiment is molded into an ISO multipurpose test piece (thickness 4 mm), the bending strength is preferably 50.0 MPa or more, more preferably 70.0 MPa or more. The upper limit of the bending strength is not particularly specified, but for example, 300.0 MPa or less is practical. The resin composition of this embodiment is molded into an ISO multipurpose test piece (thickness 4 mm), and the bending modulus is preferably 1,500 MPa or more, more preferably 2,000 MPa or more. The upper limit of the bending modulus is not particularly specified, but for example, 15,000 MPa or less is practical.

[0085] Furthermore, the resin composition of this embodiment preferably has excellent impact resistance. Specifically, when the resin composition of this embodiment is molded into an ISO multipurpose test piece (thickness 4 mm), the notched Charpy impact strength according to ISO 179 standard is 2.0 kJ / m ２ It is preferable that the concentration is 3.0 kJ / m or more. ２ More preferably, it is 3.2 kJ / m or more. ２ The upper limit of the notched Charpy impact strength is not particularly limited, but is preferably 50 kJ / m or more. ２ The following is practical:

[0086] The resin composition of the present embodiment also has a surface resistance of 1.0×10 when molded into a 2 mm thick piece (preferably, a 100 mm×100 mm×2 mm thick piece) in accordance with IEC 60093. ８ It is preferably 1.0×10 Ω or more, ９ More preferably, it is 1.0×10 Ω or more. １０ It is more preferable that the resistance is 1.0×10 Ω or more. １１ More preferably, it is 1.0×10 Ω or more. １２ It is more preferable that the resistance is 1.0×10 Ω or more. １３ It is even more preferable that the resistance is 1.0×10 Ω or more. １４ It is particularly preferable that the resistance is 1.0×10 Ω or more. １６ Ω or less, and preferably 1.0×10 １５ It is more preferable that the volume resistivity of the resin composition of this embodiment is 1.0×10 Ω or less. By setting the volume resistivity in this range, the electromagnetic wave absorption rate of the obtained molded article tends to be higher. The resin composition of this embodiment further has a volume resistivity of 1.0×10 Ω or less, as measured on a 2 mm thick (preferably 100 mm×100 mm×2 mm thick) test piece in accordance with IEC 60093. １０ It is preferable that the resistance is Ω cm or more, and 1.0 × 10 １１ More preferably, it is 1.0×10 Ω cm or more. １２ It is more preferable that the resistance is Ω cm or more, and 1.0 × 10 １３ It is more preferable that the resistance is Ω cm or less, and 1.0×10 １４It is more preferable that the resistance is 1.0×10 Ω cm or more. １５ It is even more preferable that the resistivity is Ω cm or more, and 1.0 × 10 １７ It is preferably Ω cm or less, and 1.0 × 10 １６ It is more preferable that the resistivity is Ω·cm or less. By setting the resistivity in this range, the electromagnetic wave absorption rate of the obtained molded article tends to be higher. The details of the above measurement method are measured according to the description in the Examples.

[0087] <Another Specific Example (1) of Resin Composition> Another specific example (1) of the resin composition of this embodiment is a resin composition containing a polybutylene terephthalate resin, a polystyrene-based resin, and carbon nanotubes. This configuration results in a resin composition with high absorption. The reason for this is presumed to be as follows: By blending carbon nanotubes into the polybutylene terephthalate resin, a certain level of electromagnetic wave absorption is achieved. In this embodiment, it is presumed that further blending a styrene-based resin allows the carbon nanotubes to be more effectively dispersed in the polybutylene terephthalate resin, thereby increasing the absorption rate of the resulting resin composition. Furthermore, the configuration of this embodiment can reduce the electromagnetic wave reflectance and transmittance of the resin composition. Furthermore, the tensile properties, particularly the tensile strain, can be increased. Furthermore, by masterbatching carbon nanotubes with a styrene-based resin and blending the masterbatched carbon nanotubes into the polybutylene terephthalate resin, the above-mentioned effects can be achieved more effectively. Although the mechanism is speculative, it is speculated that when a polybutylene terephthalate resin and a styrene-based resin masterbatch of carbon nanotubes are melt-kneaded, the carbon nanotubes leave the styrene-based resin, penetrate into the polybutylene terephthalate resin, and diffuse. The driving force at this time breaks down the carbon nanotube aggregates, allowing the carbon nanotubes to diffuse more effectively within the polybutylene terephthalate resin. Meanwhile, another specific example of a resin composition (1) typically exhibits a sea-island structure having a sea region rich in polybutylene terephthalate resin and an island region rich in polystyrene resin, in which 30% by mass or more (preferably 45% by mass or more, more preferably 65% ​​by mass or more, and even more preferably 85% by mass or more) of the resin components contained in the resin composition is polybutylene terephthalate resin, and the content of carbon nanotubes in the sea region is higher than the content of carbon nanotubes in the island region. This type of structure tends to enhance the electromagnetic wave absorption of the resin composition.This sea-island structure is presumably due to the fact that polybutylene terephthalate resin and polystyrene-based resin are poorly compatible with each other, and that carbon nanotubes are inherently more compatible with polybutylene terephthalate resin than with polystyrene-based resin.

[0088] <Another Specific Example (2) of Resin Composition> Another specific example (2) of the resin composition of this embodiment is a resin composition containing a thermoplastic resin and carbon nanotubes, wherein the resin composition has a relative dielectric constant of 4.50 or more at a frequency of 76.5 GHz. By increasing the relative dielectric constant at a frequency of 76.5 GHz, the electromagnetic wave absorption rate of the resulting resin composition at a frequency around 76.5 GHz can be increased. Furthermore, by adopting the configuration of this embodiment, the reflectance and transmittance of electromagnetic waves at a frequency of 76.5 GHz of the resin composition can be reduced. It is presumed that the reason why the electromagnetic wave absorption rate is improved by increasing the relative dielectric constant is because the electric field shielding effect of the resin composition is improved. It is surprising that the absorption rate of a resin composition is improved by increasing the relative dielectric constant of the resin composition. Furthermore, the absorption rate is improved by also increasing the dielectric loss tangent. It is presumed that the reason why the absorption rate is improved by increasing the dielectric loss tangent is because the efficiency of converting electromagnetic waves into thermal energy is improved within the resin composition. Examples of ways to increase the dielectric constant of a resin composition include selecting a material with a high dielectric constant, minimizing the use of materials that lower the dielectric constant, dispersing the material with a high dielectric constant in the resin, and increasing the volume fraction of the material with a high dielectric constant. In particular, a resin composition with a high dielectric constant can be obtained by incorporating an additive with a high dielectric constant into a composition consisting of two or more thermoplastic resins. Means for increasing the dielectric loss tangent of a resin composition are basically similar to those for increasing the dielectric constant. However, some materials increase the dielectric constant but decrease the dielectric loss tangent, so selection may be necessary. In this embodiment, the thermoplastic resin preferably includes a thermoplastic resin (A) and a thermoplastic resin (B). However, the thermoplastic resin (A) and the thermoplastic resin (B) may be the same resin.

[0089] The content of thermoplastic resin (B) in the resin composition of this embodiment is preferably 1.0 part by mass or more, more preferably 2.0 parts by mass or more, and even more preferably 2.5 parts by mass or more, relative to 100 parts by mass of thermoplastic resin (A). By setting the content at or above the lower limit, electromagnetic wave absorption performance tends to be further improved. Furthermore, the content of thermoplastic resin (B) is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, even more preferably 50 parts by mass or less, even more preferably 30 parts by mass or less, even more preferably 10.0 parts by mass or less, and even more preferably 8.0 parts by mass or less, 7.0 parts by mass or less, or 6.0 parts by mass or less, relative to 100 parts by mass of thermoplastic resin (A). Setting the content at or below the upper limit tends to further reduce the transmittance of the resulting molded body. In this embodiment, it is preferable that thermoplastic resin (A) is the main resin constituting the molded body (e.g., the component with the highest content). Furthermore, in this embodiment, it is preferable that at least a portion of thermoplastic resin (B) is derived from the carbon nanotube masterbatch. By adopting such a configuration, the effects of the present invention tend to be more effectively exhibited. The resin composition of this embodiment may contain only one type of thermoplastic resin (A) and one type of thermoplastic resin (B), or may contain two or more types. When two or more types are contained, it is preferable that the total amount is in the above range.

[0090] In this embodiment, the thermoplastic resin (A) preferably contains a polyester resin (preferably a polybutylene terephthalate resin). Furthermore, in this embodiment, preferably 95 mass% or more, more preferably 99 mass% or more of the thermoplastic resin (A) is a polyester resin.

[0091] In the present embodiment, a preferred example of the thermoplastic resin is one in which the thermoplastic resin (A) and the thermoplastic resin (B) each contain a polyester resin (preferably, a polybutylene terephthalate resin), and 90% by mass or more (preferably, 95% by mass or more, more preferably, 99% by mass or more) of the thermoplastic resin is a polyester resin (preferably, a polybutylene terephthalate resin).

[0092] In a preferred example of the thermoplastic resin in this embodiment, the thermoplastic resin (A) contains a polyester resin (preferably a polybutylene terephthalate resin), and the thermoplastic resin (B) contains a polystyrene-based resin. In this embodiment, preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more of the thermoplastic resin is composed of a polyester resin (preferably a polybutylene terephthalate resin) and a polystyrene-based resin (preferably HIPS, more preferably a butadiene rubber-containing polystyrene).

[0093] <Another Specific Example (3) of Resin Composition> Another specific example (3) of the resin composition of this embodiment includes a thermoplastic resin (A), a thermoplastic resin (B), and carbon nanotubes, wherein at least a portion of the thermoplastic resin (B) is derived from the carbon nanotube masterbatch, and satisfies the relationship: the SP value of the thermoplastic resin (A) ≥ the SP value of the thermoplastic resin (B) (here, the SP value is the solubility parameter). This configuration makes it possible to provide a resin composition with a high electromagnetic wave absorption rate. The reason for this is presumed to be as follows. That is, resins with high SP values ​​have relatively more polar groups. On the other hand, when carbon nanotubes are melt-kneaded with two or more resins, they tend to be attracted to the resin with polar groups. Therefore, it was presumed that if the SP value of the resin used to form the carbon nanotube masterbatch is greater than the SP value of the main thermoplastic resin, the carbon nanotubes will be less likely to disperse in the main thermoplastic resin, even when the carbon nanotube masterbatch and the main thermoplastic resin are melt-kneaded. In this embodiment, by setting the SP value of the thermoplastic resin (B) used to masterbatch carbon nanotubes to be equal to or less than the SP value of the thermoplastic resin (A), it is believed that the carbon nanotubes undergo correlation migration from the thermoplastic resin (B) to the thermoplastic resin (A) during melt-kneading, thereby facilitating dispersion in the thermoplastic resin (A). In particular, it is believed that by setting the difference between the SP values ​​of the thermoplastic resin (A) and the thermoplastic resin (B) to 0.1 or more, the dispersion of the carbon nanotubes in the thermoplastic resin (A) can be more significantly improved. Furthermore, by improving the dispersibility of the carbon nanotubes in the thermoplastic resin (A), a high electromagnetic wave absorption rate can be achieved. In another specific example (3) of the resin composition of this embodiment, the SP value of the thermoplastic resin (A) is greater than or equal to the SP value of the thermoplastic resin (B) (here, the SP value is the solubility parameter). This configuration tends to improve the dispersibility of the carbon nanotubes in the thermoplastic resin (A).The difference between the SP value of the thermoplastic resin (A) and the SP value of the thermoplastic resin (B) is 0 or more, preferably 0.1 or more, more preferably 0.3 or more, even more preferably 0.5 or more, even more preferably 0.7 or more, and even more preferably 1.0 or more. Furthermore, the difference between the SP value of the thermoplastic resin (A) and the SP value of the thermoplastic resin (B) is preferably 8.0 or less, more preferably 7.0 or less, even more preferably 6.0 or less, even more preferably 5.0 or less, and even more preferably 4.0 or less. By keeping the difference below the upper limit, compatibility during melt-kneading tends to be improved. Another specific example (3) of the resin composition of this embodiment may contain only one type of thermoplastic resin (A) and one type of thermoplastic resin (B), or two or more types. When two or more types are contained, it is preferable that the SP value of the mixture satisfy the above range. In this embodiment, the solubility in a solvent with a known SP value is determined, and based on that, calculation can be performed using Hansen Solubility Parameters in Practice ver. 5.0.

[0094] The thermoplastic resin (A) in another specific example (3) of the resin composition of this embodiment is usually the main component of the resin components contained in the resin composition.Preferably exemplified as the thermoplastic resin used in this embodiment are polyester resin (thermoplastic polyester resin); polyamide resin; polycarbonate resin; polystyrene resin; polyethylene resin, polypropylene resin, cyclic cycloolefin resin, etc. polyolefin resin; polyacetal resin; polyimide resin; polyetherimide resin; polyurethane resin; polyphenylene ether resin; polyphenylene sulfide resin; polysulfone resin; polymethacrylate resin; etc., and more preferably selected from polyester resin, polycarbonate resin and polyamide resin, more preferably contain polyester resin, and more preferably contain polybutylene terephthalate resin.

[0095] In another specific example (3) of the resin composition of this embodiment, the content of the thermoplastic resin (A) in the resin composition is preferably 30% by mass or more, more preferably 35% by mass or more, even more preferably 40% by mass or more, even more preferably 45% by mass or more, and even more preferably 50% by mass or more. When the resin composition does not contain a reinforcing material, the content of the thermoplastic resin (A) in the resin composition is more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more. By setting the content to be equal to or greater than the lower limit, the flowability during injection molding tends to be further improved. Furthermore, the content of the thermoplastic resin is preferably 99% by mass or less. When the resin composition contains a reinforcing material, the content of the thermoplastic resin (A) in the resin composition is more preferably 90% by mass or less, even more preferably 80% by mass or less, and even more preferably 75% by mass or less. By setting the content to be equal to or less than the upper limit, the mechanical strength of the resulting molded product tends to be further improved.

[0096] Another specific example (3) of the resin composition of this embodiment includes a thermoplastic resin (B). At least a portion of the thermoplastic resin (B) is derived from the masterbatch of carbon nanotubes. By adopting such a configuration, the carbon nanotubes are more likely to migrate from the thermoplastic resin (B) to the thermoplastic resin (A) during melt-kneading, improving the dispersibility of the carbon nanotubes in the resin composition. Furthermore, a portion of the thermoplastic resin (B) does not have to be derived from the masterbatch of carbon nanotubes.

[0097] The thermoplastic resin (B) is set in relation to the thermoplastic resin (A). That is, as long as the relationship between the SP value of the thermoplastic resin (A) and the SP value of the thermoplastic resin (B) described above is satisfied, the type of thermoplastic resin (B) is not specified and can be selected appropriately. Preferred examples of the thermoplastic resin (B) used in this embodiment include polyester resins (thermoplastic polyester resins); polyamide resins; polycarbonate resins; polystyrene-based resins; polyethylene resins, polypropylene resins, cyclic cycloolefin resins, and other polyolefin resins; polyacetal resins; polyimide resins; polyetherimide resins; polyurethane resins; polyphenylene ether resins; polyphenylene sulfide resins; polysulfone resins; polymethacrylate resins; and the like. It is more preferably selected from polyester resins, polystyrene-based resins, and polyolefin resins, even more preferably selected from polyester resins and polystyrene-based resins, and even more preferably contains a polystyrene-based resin, and even more preferably contains HIPS (preferably butadiene rubber-containing polystyrene).

[0098] In another specific example (3) of the resin composition of this embodiment, the content of the thermoplastic resin (B) is preferably 1.0 part by mass or more, more preferably 2.0 parts by mass or more, and even more preferably 2.5 parts by mass or more, per 100 parts by mass of the thermoplastic resin (A). By setting the content at or above the lower limit, the electromagnetic wave absorption performance tends to be further improved. Furthermore, the content of the thermoplastic resin (B) is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, even more preferably 50 parts by mass or less, even more preferably 30 parts by mass or less, even more preferably 10.0 parts by mass or less, and even more preferably 8.0 parts by mass or less, 7.0 parts by mass or less, or 6.0 parts by mass or less, per 100 parts by mass of the thermoplastic resin (A). By setting the content at or below the upper limit, the transmittance and reflectance of the resulting molded product tend to be lower.

[0099] In another specific example (3) of the resin composition of this embodiment, at least a portion of the thermoplastic resin (B) is blended as a resin for masterbatch formation. The concentration of the thermoplastic resin (B) in the masterbatch is preferably 99% by mass or less, preferably 95% by mass or less, and also preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and even more preferably 80% by mass or more. By setting the concentration within the above-mentioned range of not more than the upper limit and not less than the lower limit, the dispersibility of the carbon nanotubes in the thermoplastic resin (A) tends to be further improved.

[0100] In another specific example (3) of the resin composition of this embodiment, a preferred blend of thermoplastic resins is that the thermoplastic resin (A) contains a polyester resin (preferably, polybutylene terephthalate resin), and the thermoplastic resin (B) contains a polystyrene-based resin. In this embodiment, preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more of the resin components contained in the resin composition are composed of a polyester resin (preferably, polybutylene terephthalate resin) and a polystyrene-based resin (preferably, HIPS). In another specific example (3) of the resin composition of this embodiment, another preferred blend of thermoplastic resins is that the thermoplastic resin (A) contains a polyester resin (preferably, polybutylene terephthalate resin), and the thermoplastic resin (B) contains a polyester resin (preferably, polybutylene terephthalate resin). In this other specific example (3) of the resin composition of this embodiment, preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more of the resin components contained in the resin composition are composed of a polyester resin (preferably, polybutylene terephthalate resin).

[0101] <Method for Producing Resin Composition> The resin composition of this embodiment can be produced by a conventional method for producing a resin composition containing a thermoplastic resin. For example, it can be obtained by melt-kneading a thermoplastic resin, a conductive material, and other components that are optionally blended. The conductive material is preferably blended as a masterbatch with the thermoplastic resin. By masterbatching the conductive material with the thermoplastic resin, the dispersibility of the conductive material in the thermoplastic resin can be effectively improved. The concentration of the conductive material in the masterbatch is preferably 1% by mass or more, preferably 5% by mass or more, and 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-mentioned ranges of not more than the upper limit and not less than the lower limit, the dispersibility of the conductive material in the thermoplastic resin tends to be further improved.

[0102] The components may be premixed and fed to the extruder all at once, or the components may be premixed or only a portion of the components may be premixed and fed to the extruder using a feeder. The extruder may be a single-screw extruder or a twin-screw extruder. When glass fibers are added, they are preferably fed from a side feeder midway through the cylinder of the extruder. The heating temperature during melt-kneading can usually be selected appropriately from the range of 170 to 350°C.

[0103] <Method for Producing Molded Article> A molded article, particularly an electromagnetic wave absorber, is formed from the resin composition of this embodiment. The method for producing the molded article in this embodiment is not particularly limited, and any molding method commonly used for resin compositions containing thermoplastic resins can be used. Examples include injection molding, ultra-high speed injection molding, injection compression molding, two-color molding, gas-assisted or other hollow molding methods, molding using an insulated mold, molding using a rapidly heated mold, foam molding (including supercritical fluids), insert molding, IMC (in-mold coating molding) molding, extrusion molding, sheet molding, thermoforming, rotational molding, laminate molding, press molding, blow molding, etc., of which injection molding is preferred.

[0104] <Applications> 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 used for an electromagnetic wave absorber (also referred to as an electromagnetic wave absorbing member), more preferably for an electromagnetic wave absorber having a frequency of at least 60 to 90 GHz, and even more preferably for an electromagnetic wave absorber having a frequency of at least 70 to 80 GHz. Such an electromagnetic wave absorber is preferably used for radar applications. Specifically, it is used for housings, covers, etc. for millimeter-wave radar. The electromagnetic wave absorber of this embodiment can be suitably used for in-vehicle millimeter-wave radar used in automatic brake control devices, inter-vehicle distance control devices, pedestrian accident reduction steering devices, erroneous transmission suppression control devices, devices for suppressing acceleration when the driver mis-depresses the pedal, devices for warning about approaching vehicles, lane keeping assist devices, rear-end collision prevention warning devices, parking assist devices, devices for warning about obstacles around the vehicle, etc.; railway and aviation millimeter-wave radar used in platform monitoring / railroad crossing obstacle detection devices, in-train content transmission devices, tram / railroad collision prevention devices, foreign object detection devices in runways, etc.; millimeter-wave radar for transportation infrastructure such as intersection monitoring devices and elevator monitoring devices; millimeter-wave radar for various security devices; millimeter-wave radar for medical and nursing care such as systems for watching over children and the elderly; millimeter-wave radar for transmitting various information contents; etc.

[0105] The present invention will be explained in more detail below with reference to examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing 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 the like, measurements can be made using other instruments with equivalent performance.

[0106] Raw Materials The following raw materials were used: In Table 1 below, PBT stands for polybutylene terephthalate resin, HIPS stands for high impact polystyrene, PA stands for polyamide resin, and CNT stands for carbon nanotubes (the same applies to Table 2).

[0107] The diameter (number average fiber diameter) of the CNTs is 9 nm.

[0108] Examples 1 and 2, Comparative Example 1 <Production of Resin Composition (Pellets)> As shown in Table 2, the components listed in Table 1 were placed in a stainless steel tumbler and mixed under stirring for 1 hour. The resulting mixture was fed into an intermeshing co-rotating twin-screw extruder ("TEX-30α" manufactured by The Japan Steel Works, Ltd., screw diameter 32 mm, L / D = 42) through the main feed port. The barrel temperature of the first kneading section was set to 250°C, and the mixture was melt-kneaded at a discharge rate of 40 kg / h and a screw rotation speed of 200 rpm. The mixture was then extruded as a strand using a four-hole nozzle (circular (φ4 mm), length 1.5 cm). The extruded strand was introduced into a water bath, cooled, and then inserted into a pelletizer and cut to obtain a resin composition (pellet).

[0109] <76.5 GHz Electromagnetic Wave Absorption Rate, Reflectance, and Transmittance> Using the pellets obtained above, injection molding was performed using an injection molding machine ("NEX80" manufactured by Nissei Plastic Industrial Co., Ltd.) at a cylinder setting temperature of 260°C and a mold temperature of 80°C to obtain test pieces of 100 mm x 100 mm x 2 mm thickness and 100 mm x 100 mm x 3 mm thickness. Using the obtained test pieces, the absorption rate calculated according to formula (A), the reflectance calculated according to formula (B), and the transmittance calculated according to formula (C) at a frequency of 76.5 GHz were measured as follows. For the measurements, a network analyzer "N5252A" manufactured by Keysight Corporation was used. Note that the test pieces were placed so that the TD (transverse direction) direction of the injection-molded article was parallel to the electric field direction and measured. Formula (A) (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.)

[0110] Formula (B) (In the above formula (B), R represents the return loss measured by the free space method.)

[0111] Formula (C) (In the above formula (C), T represents the transmission attenuation measured by the free space method.)

[0112] <Relative permittivity and dielectric loss tangent> Using the pellets obtained above, an injection molding machine ("NEX80" manufactured by Nissei Plastic Industrial Co., Ltd.) was used to injection mold at a cylinder setting temperature of 260°C and a mold temperature of 80°C to obtain a 100 mm x 100 mm x 2 mm thick test piece. The obtained test piece was used to determine the relative permittivity and dielectric loss tangent at a frequency of 76.5 GHz. The test piece was placed so that the TD (transverse direction) direction of the injection molded article was parallel to the electric field direction. The measurement was performed using a Keysight "N5252A" network analyzer, and the values ​​of the relative permittivity and dielectric loss tangent were estimated using Keysight's "N1500A Materials Measurement Suite" and the calculation model "NIST Precision".

[0113] <Aggregate Area Ratio> 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 setting temperature of 260°C and a mold temperature of 80°C to obtain a 100 mm x 100 mm x 2 mm thick test piece. A mechanically polished rectangular cross section was prepared, including the center point of the obtained test piece and perpendicular to the MD direction (direction of resin flow) during injection molding, measuring 15 mm in the TD direction (direction perpendicular to the MD direction) during injection molding and 2 mm in the thickness direction. To prepare the cross section, the sample was embedded in a cured epoxy resin and the surface was polished in advance to maintain the sample's condition and obtain a smooth surface suitable for optical microscopy. The cross section was observed using a digital microscope "VHX-7000" manufactured by Keyence Corporation. When photographing the observation, the lighting method, image contrast, etc. were adjusted arbitrarily so that the carbon nanotube-derived aggregates appeared clearly black. The lens used was a VHX-E100 medium-magnification objective lens for a high-resolution (HR) head, and images were acquired at a magnification of 100x, with four fields of view per sample. From the images obtained above, the image processing software "WinROOF 2018" manufactured by Mitani Shoji Co., Ltd. was used to determine the equivalent circle diameter and area ratio of carbon nanotube aggregates according to the following steps 1.2.3. 1. Monochrome image of observed image 2. Automatic binarization (selection of carbon nanotube aggregates) (The threshold was set by the measurer at an arbitrary value using a discrimination and sorting method) 3. The equivalent circle diameter and area ratio were calculated, and the average values ​​of the four fields of view per sample were shown. (Note that images with an equivalent circle diameter of less than 30 μm were removed.) The equivalent circle diameter here is calculated as follows: equivalent circle diameter = (area value of the image of the aggregate / π) １／２ The area ratio was calculated using the following formula: Area ratio (%) = (sum of the areas of CNT aggregates) / (area of ​​the observed cross section) x 100

[0114] <Tensile Properties> The resin pellets obtained above were dried at 120°C for 5 hours, and then ISO multipurpose test specimens (thickness 4 mm) were injection molded using an injection molding machine ("J85AD" manufactured by The Japan Steel Works, Ltd.) under conditions of a cylinder temperature of 250°C and a mold temperature of 80°C. The molded multipurpose ISO multipurpose test specimens were used to measure the maximum point tensile strength (unit: MPa), tensile modulus (unit: MPa), and tensile strain (unit: %) in accordance with ISO527-1 and ISO527-2.

[0115] <Flexural Properties> The resin pellets obtained above were dried at 120°C for 5 hours, and then ISO multipurpose test specimens (thickness 4 mm) were injection molded using an injection molding machine ("J85AD" manufactured by The Japan Steel Works, Ltd.) under conditions of a cylinder temperature of 250°C and a mold temperature of 80°C. The molded multipurpose ISO multipurpose test specimens were used to measure the flexural strength (unit: MPa) and flexural modulus (unit: MPa) in accordance with ISO178.

[0116] <Notched Charpy Impact Strength> The resin pellets obtained above were dried at 120°C for 5 hours, and then ISO multipurpose test specimens (thickness 4 mm) were injection molded using an injection molding machine ("J85AD" manufactured by The Japan Steel Works, Ltd.) under conditions of a cylinder temperature of 250°C and a mold temperature of 80°C. In accordance with ISO 179, the ISO multipurpose test specimens obtained above were cut into a predetermined size and shape, and the Charpy impact strength (notched) was measured. The unit is kJ / m ２ As shown.

[0117] <Surface Resistance> The pellets obtained above were injection molded in an injection molding machine ("NEX80" manufactured by Nissei Plastic Industrial Co., Ltd.) at a cylinder setting temperature of 260°C and a mold temperature of 80°C to obtain test pieces of 100 mm x 100 mm x 2 mm thick. The surface resistance (unit: Ω) of the obtained test pieces was measured in accordance with IEC 60093. For the measurement, an "R8340 ULTRA HIGH RESISTANCE METER" manufactured by ADVANTEST was used.

[0118] <Volume Resistivity> The pellets obtained above were injection molded in an injection molding machine ("NEX80" manufactured by Nissei Plastic Industrial Co., Ltd.) at a cylinder setting temperature of 260°C and a mold temperature of 80°C to obtain test pieces of 100 mm x 100 mm x 2 mm thick. The volume resistivity (unit: Ω cm) of the obtained test pieces was measured in accordance with IEC 60093. For the measurement, an "R8340 ULTRA HIGH RESISTANCE METER" manufactured by ADVANTEST was used.

[0119]

[0120] In Table 2, the CNT content indicates the amount of carbon nanotubes in the resin composition. As is clear from the results, the resin composition of the present invention had a high electromagnetic wave absorption rate. Furthermore, the resin composition had low electromagnetic wave transmittance and reflectance. Furthermore, the molded article formed from the resin composition of the present invention had excellent mechanical strength.

[0121] <Heat Resistance> For the pellets obtained in Example 1, 100 mm x 100 mm x 2 mm thick test pieces were prepared according to the above <76.5 GHz Electromagnetic Wave Absorption Rate, Reflectance, and Transmittance>, and the absorbance, reflectance, and transmittance were measured. The 100 mm x 100 mm x 2 mm thick test pieces were also heat-treated at 180°C in a hot air oven (Yamato Scientific Co., Ltd.'s "DNE400"). After 500 hours, 1000 hours, 1500 hours, and 2000 hours of treatment, the absorbance, reflectance, and transmittance of the test pieces were measured according to the above <76.5 GHz Electromagnetic Wave Absorption Rate, Reflectance, and Transmittance>. The data before treatment (0 hours) are shown in Table 3.

[0122] <Hydrolysis Resistance> For the pellets obtained in Example 1, 100 mm x 100 mm x 2 mm thick test pieces were prepared according to the above-mentioned <76.5 GHz Electromagnetic Wave Absorption Rate, Reflectance, and Transmittance>, and the absorbance, reflectance, and transmittance were measured. Furthermore, the 100 mm x 100 mm x 2 mm thick test pieces were left standing at 121°C, 100% relative humidity, and 2 atm using a highly accelerated life tester (Espec Corp., "EHS-221M"). After 50 hours, 100 hours, and 200 hours of treatment, the absorbance, reflectance, and transmittance of the test pieces were measured according to the above-mentioned <76.5 GHz Electromagnetic Wave Absorption Rate, Reflectance, and Transmittance>. The data before treatment (0 hours) are shown in Table 3.

[0123]

[0124] As is clear from the above results, the resin composition of the present invention showed almost no change in electromagnetic wave properties even after heating for a long period of time. Furthermore, the resin composition of the present invention also had excellent hydrolysis resistance.

[0125] Examples 3 to 6 Pellets were obtained in the same manner as in Example 1, except that the components in the above <Production of Resin Composition (Pellets)> were changed as shown in Table 4. The obtained pellets were then used to measure the absorptivity, reflectivity, and transmittance according to the above <76.5 GHz Electromagnetic Wave Absorption Rate, Reflectivity, and Transmittance>. The dielectric constant and dielectric dissipation factor were then measured according to the above <Dielectric Constant and Dielectric Dissipation Factor>. Furthermore, the aggregate area ratio was measured according to the above <Aggregate Area Ratio>.

[0126]

[0127] The resin composition of the present invention exhibited excellent electromagnetic wave absorption properties regardless of the intrinsic viscosity of the thermoplastic resin, but a lower intrinsic viscosity enabled the attainment of a higher electromagnetic wave absorption rate.

Claims

1. A resin composition comprising a thermoplastic resin and a conductive material, wherein when the resin composition is molded into a test piece having a thickness of 2 mm and the cross section of the test piece is observed under a digital microscope, the area ratio of aggregates derived from the conductive material having an equivalent circle diameter of 30 μm or more is 0.80% or less.

2. The resin composition according to claim 1, wherein the conductive material includes carbon nanotubes.

3. The resin composition according to claim 1 or 2, wherein the thermoplastic resin comprises a polybutylene terephthalate resin.

4. The resin composition according to any one of claims 1 to 3, wherein the content of the conductive substance in the resin composition is 0.01 to 10 mass %.

5. The resin composition according to claim 1, wherein the thermoplastic resin comprises a polybutylene terephthalate resin, the conductive material comprises carbon nanotubes, and the content of the conductive material in the resin composition is 0.01 to 10 mass %.

6. The resin composition according to claim 1, wherein the thermoplastic resin comprises a polybutylene terephthalate resin and a polystyrene-based resin, and the conductive material comprises a carbon nanotube.

7. The resin composition according to claim 6, wherein the content of the carbon nanotubes in the resin composition is 0.01 to 10% by mass.

8. The resin composition according to claim 6 or 7, wherein the resin composition exhibits a sea-island structure having a sea region containing a large amount of the polybutylene terephthalate resin and an island region containing a large amount of the polystyrene-based resin, 30 mass% or more of the resin components contained in the resin composition is polybutylene terephthalate resin, and the content of carbon nanotubes contained in the sea region is greater than the content of carbon nanotubes contained in the island region.

9. The resin composition according to any one of claims 6 to 8, wherein the polystyrene resin is derived from a carbon nanotube master batch.

10. A resin composition according to any one of claims 1 to 9, wherein the conductive material contains carbon nanotubes, and the resin composition has a relative dielectric constant of 4.50 or more at a frequency of 76.5 GHz.

11. The resin composition according to claim 10, wherein the resin composition has a dielectric loss tangent of 0.10 or more at a frequency of 76.5 GHz.

12. The resin composition according to claim 10 or 11, wherein the content of the carbon nanotubes in the resin composition is 0.01 to 10 mass %.

13. The resin composition according to any one of claims 10 to 12, wherein the thermoplastic resin comprises a thermoplastic resin (A) and a thermoplastic resin (B), and the thermoplastic resin (B) is contained in an amount of 1.0 to 100 parts by mass per 100 parts by mass of the thermoplastic resin (A).

14. The resin composition according to claim 13, wherein the thermoplastic resin (A) comprises a polyester resin.

15. The resin composition of claim 14, wherein the polyester resin comprises a polybutylene terephthalate resin.

16. The resin composition according to any one of claims 13 to 15, wherein the thermoplastic resin (B) comprises a polystyrene-based resin.

17. The resin composition according to any one of claims 13 to 16, wherein at least a portion of the thermoplastic resin (B) is derived from a master batch of the carbon nanotubes.

18. The resin composition according to claim 17, wherein the concentration of carbon nanotubes in the master batch is 1 to 50 mass %.

19. The resin composition according to any one of claims 1 to 18, wherein the resin composition, when molded into a thickness of 2 mm, has an absorptivity of 50.0 to 100% at a frequency of 76.5 GHz, as determined according to formula (A). (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.) 20. The resin composition according to any one of claims 1 to 19, wherein the resin composition, when molded into a thickness of 2 mm, has a reflectance calculated according to formula (B) at a frequency of 76.5 GHz of 40.0% or less. Formula (B) (In the above formula (B), R represents the return loss measured by the free space method.) 21. The resin composition according to any one of claims 1 to 20, wherein when the resin composition is molded into a thickness of 2 mm, the transmittance calculated according to formula (C) at a frequency of 76.5 GHz is 25.0% or less. Formula (C) (In the above formula (C), T represents the transmission attenuation measured by the free space method.) 22. When the resin composition is molded to a thickness of 2 mm, the surface resistance according to IEC 60093 is 1.0 x 10 ８ The resin composition according to any one of claims 1 to 21, having a modulus of elasticity of Ω or more.

23. The resin composition according to any one of claims 1 to 22, which is used as an electromagnetic wave absorber.

24. A molded article formed from the resin composition according to any one of claims 1 to 23.

25. An electromagnetic wave absorber formed from the resin composition according to any one of claims 1 to 23.

26. A method for producing a resin composition comprising melt-kneading a polybutylene terephthalate resin and a styrene-based resin masterbatch of carbon nanotubes.

27. A method for producing a resin composition according to claim 26, wherein the resin composition is a resin composition according to any one of claims 6 to 9.

28. A method for producing the resin composition according to any one of claims 10 to 18, comprising melt-kneading a thermoplastic resin and carbon nanotubes masterbatched with the thermoplastic resin.