Resin composition, molded article, electromagnetic wave absorber, and method for producing resin composition

Abstract

The present invention provides a resin composition, a molded article, an electromagnetic wave absorber, and a method for producing the resin composition, each having a high electromagnetic wave absorptivity. The resin composition comprises a thermoplastic resin and carbon nanotubes. When the resin composition is molded into a 2 mm thickness, the relative dielectric constant at a frequency of 76.5 GHz is 4.50 or greater.

Description

Technical Field

[0001] The present invention relates to a resin composition, a molded body, an electromagnetic wave absorber, and a method for producing the resin composition. Background Art

[0002] Millimeter-wave radar transmits radio waves in the millimeter-wave band (30-300 GHz, particularly 60-90 GHz) with a wavelength of 1-10 mm and receives reflected waves from objects. This allows the radar to detect the presence of obstacles, the distance to the object, and its relative speed. Millimeter-wave radar is being studied for use in a wide range of fields, including automotive collision avoidance sensors, autonomous driving systems, road information systems, safety systems, and medical and nursing devices.

[0003] As a resin composition for millimeter wave radar, the one described in Patent Document 1 is known. In addition, Patent Document 2 discloses a multifunctional resin composition that can be used for electromagnetic interference shielding or radio frequency interference shielding.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2019-197048

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 2010-155993 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] Here, in millimeter-wave radars, penetrating electromagnetic waves are the biggest cause of operational failures. Therefore, a resin composition with a high electromagnetic wave absorptivity is required.

[0010] An object of the present invention is to solve the above problems, and an object of the present invention is to provide a resin composition having a high electromagnetic wave absorptivity, a molded article, an electromagnetic wave absorber, and a method for producing the resin composition.

[0011] Means for solving problems

[0012] Based on the above problems, the present inventors have conducted research and found that, in a resin composition obtained by blending carbon nanotubes into a thermoplastic resin, the electromagnetic wave absorptivity of the obtained resin composition can be improved by increasing the relative dielectric constant to a higher than a predetermined value.

[0013] Specifically, the above-mentioned problems were solved by the following means.

[0014] <1-1> A resin composition comprising a thermoplastic resin and carbon nanotubes, wherein the resin composition has a relative dielectric constant of 4.50 or greater at a frequency of 76.5 GHz.

[0015] <1-2> The resin composition according to <1-1>, wherein the dielectric loss tangent of the resin composition at a frequency of 76.5 GHz is 0.10 or greater.

[0016] <1-3> The resin composition according to <1-1> or <1-2>, wherein the content of carbon nanotubes in the resin composition is 0.01 to 10% by mass.

[0017] <1-4> The resin composition according to any one of <1-1> to <1-3>, 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).

[0018] <1-5> The resin composition according to <1-4>, wherein the thermoplastic resin (A) comprises a polyester resin.

[0019] <1-6> The resin composition according to <1-5>, wherein the polyester resin comprises a polybutylene terephthalate resin.

[0020] <1-7> The resin composition according to any one of <1-4> to <1-6>, wherein the thermoplastic resin (B) comprises a polystyrene-based resin.

[0021] <1-8> The resin composition according to any one of <1-4> to <1-7>, wherein at least a portion of the thermoplastic resin (B) is derived from a masterbatch of the carbon nanotubes.

[0022] <1-9> The resin composition according to <1-8>, wherein the concentration of the carbon nanotubes in the masterbatch is 1 to 50% by mass.

[0023] <1-10> The resin composition according to <1-1>, wherein the thermoplastic resin comprises a polybutylene terephthalate resin and a polystyrene-based resin.

[0024] <1-11> The resin composition according to <1-10>, wherein the content of the carbon nanotubes in the resin composition is 0.01 to 10% by mass.

[0025] <1-12> A resin composition as described in <1-10> or <1-11>, wherein the resin composition has an island-in-sea structure having a sea region containing a large amount of the above-mentioned polybutylene terephthalate resin and an island region containing a large amount of the above-mentioned polystyrene resin, more than 30% by mass of the resin component contained in the above-mentioned resin composition is polybutylene terephthalate resin, and the content of carbon nanotubes contained in the above-mentioned sea region is greater than the content of carbon nanotubes contained in the above-mentioned island region.

[0026] <1-13> The resin composition according to any one of <1-10> to <1-12>, wherein the polystyrene-based resin is derived from a masterbatch of carbon nanotubes.

[0027] <1-14> The resin composition as described in <1-1>, wherein the above-mentioned thermoplastic resin comprises a thermoplastic resin (A) and a thermoplastic resin (B), at least a portion of the above-mentioned thermoplastic resin (B) is derived from the masterbatch of the above-mentioned carbon nanotubes, and satisfies the SP value of the thermoplastic resin (A) ≥ the SP value of the thermoplastic resin (B) (here, the SP value is a solubility parameter).

[0028] <1-15> The resin composition according to <1-14>, wherein the concentration of the carbon nanotubes in the masterbatch is 1 to 50% by mass.

[0029] <1-16> The resin composition according to <1-14> or <1-15>, wherein the thermoplastic resin (A) is selected from polyester resins, polycarbonate resins, and polyamide resins.

[0030] <1-17> The resin composition according to any one of <1-14> to <1-16>, wherein the thermoplastic resin (B) is selected from polyester resins, polystyrene resins, and polyolefin resins.

[0031] <1-18> The resin composition according to any one of <1-14> to <1-17>, 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.

[0032] <1-19> The resin composition according to any one of <1-14> to <1-18>, 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.

[0033] <1-20> The resin composition according to any one of <1-14> to <1-19>, wherein the content of the carbon nanotubes in the resin composition is 0.01 to 10% by mass.

[0034] <1-21> The resin composition according to any one of <1-1> to <1-20>, wherein the resin composition is molded into a thickness of 2 mm and has an absorptivity of 50.0 to 100% at a frequency of 76.5 GHz as determined by formula (A).

[0035] Formula (A)

[0036] [Number 1]

[0037]

[0038] (In the above formula (A), R represents the reflection attenuation measured by the free-space method, and T represents the transmission attenuation measured by the free-space method.)

[0039] <1-22> The resin composition according to any one of <1-1> to <1-21>, wherein the reflectance calculated according to formula (B) at a frequency of 76.5 GHz when the resin composition is molded into a thickness of 2 mm is 40.0% or less.

[0040] Formula (B)

[0041] [Number 2]

[0042]

[0043] (In the above formula (B), R represents the reflection loss measured by the free space method.)

[0044] <1-23> The resin composition according to any one of <1-1> to <1-22>, wherein the transmittance calculated according to formula (C) at a frequency of 76.5 GHz when the resin composition is molded into a thickness of 2 mm is 25.0% or less.

[0045] Formula (C)

[0046] [Number 3]

[0047]

[0048] (In the above formula (C), T represents the transmission attenuation measured by the free space method.)

[0049] <1-24> The resin composition according to any one of <1-1> to <1-23>, wherein the surface resistance of the resin composition when molded into a 2 mm thickness according to IEC60093 is 1.0×10 8 Ω or above.

[0050] <1-25> The resin composition according to any one of <1-1> to <1-24>, which is used for an electromagnetic wave absorber.

[0051] <1-26> A molded article formed from the resin composition according to any one of <1-1> to <1-25>.

[0052] <1-27> An electromagnetic wave absorber formed from the resin composition according to any one of <1-1> to <1-25>.

[0053] <1-28> A method for producing the resin composition according to any one of <1-1> to <1-25>, comprising melt-kneading a thermoplastic resin and carbon nanotubes masterbatched with the thermoplastic resin.

[0054] <1-29> A method for producing a resin composition, comprising melt-kneading a polybutylene terephthalate resin and a styrene-based resin masterbatch of carbon nanotubes.

[0055] <1-30> A method for producing a resin composition described in any one of <1-14> to <1-19>, comprising melt-kneading a thermoplastic resin (A) and carbon nanotubes masterbatched with a 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) (here, the SP value is a solubility parameter).

[0056] <1-31> The method for producing the resin composition according to <1-30>, wherein the resin composition is the resin composition according to any one of <1-1> to <1-25>.

[0057] <2-1> A resin composition comprising a polybutylene terephthalate resin, a polystyrene-based resin, and carbon nanotubes.

[0058] <2-2> The resin composition according to <2-1>, wherein the content of the carbon nanotubes in the resin composition is 0.01% by mass to 10% by mass.

[0059] <2-3> A resin composition as described in <2-1> or <2-2>, wherein the resin composition has an island-in-sea structure having a sea region containing a large amount of the above-mentioned polybutylene terephthalate resin and an island region containing a large amount of the above-mentioned polystyrene resin, more than 30% by mass of the resin component contained in the above-mentioned resin composition is polybutylene terephthalate resin, and the content of carbon nanotubes contained in the above-mentioned sea region is greater than the content of carbon nanotubes contained in the above-mentioned island region.

[0060] <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.

[0061] <2-5> The resin composition according to any one of <2-1> to <2-4>, wherein the resin composition has an absorptivity of 50.0% to 100% at a frequency of 76.5 GHz when molded into a thickness of 2 mm.

[0062] Formula (A)

[0063] [Number 4]

[0064]

[0065] (In the above formula (A), R represents the reflection attenuation measured by the free-space method, and T represents the transmission attenuation measured by the free-space method.)

[0066] <2-6> The resin composition according to any one of <2-1> to <2-5>, wherein the reflectance calculated according to formula (B) at a frequency of 76.5 GHz when the resin composition is molded into a thickness of 2 mm is 40.0% or less.

[0067] Formula (B)

[0068] [Number 5]

[0069]

[0070] (In the above formula (B), R represents the reflection loss measured by the free space method.)

[0071] <2-7> The resin composition according to any one of <2-1> to <2-6>, wherein the transmittance calculated according to formula (C) at a frequency of 76.5 GHz when the resin composition is molded into a thickness of 2 mm is 25.0% or less.

[0072] Formula (C)

[0073] [Number 6]

[0074]

[0075] (In the above formula (C), T represents the transmission attenuation measured by the free space method.)

[0076] <2-8> The resin composition according to any one of <2-1> to <2-7>, wherein the carbon nanotubes include multi-walled carbon nanotubes.

[0077] <2-9> The resin composition according to any one of <2-1> to <2-8>, wherein the polystyrene-based resin comprises butadiene rubber-containing polystyrene.

[0078] <2-10> The resin composition according to any one of <2-1> to <2-9>, which is used for an electromagnetic wave absorber.

[0079] <2-11> A molded article formed from the resin composition according to any one of <2-1> to <2-10>.

[0080] <2-12> An electromagnetic wave absorber formed from the resin composition according to any one of <2-1> to <2-10>.

[0081] <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.

[0082] <2-14> The method for producing the resin composition according to <2-13>, wherein the resin composition is the resin composition according to any one of <2-1> to <2-10>.

[0083] <3-1> 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 the SP value of the thermoplastic resin (A) ≥ the SP value of the thermoplastic resin (B) (herein, the SP value is a solubility parameter).

[0084] <3-2> The resin composition according to <3-1>, wherein the concentration of the carbon nanotubes in the masterbatch is 1 to 50% by mass.

[0085] <3-3> The resin composition according to <3-1> or <3-2>, wherein the thermoplastic resin (A) is selected from polyester resins, polycarbonate resins, and polyamide resins.

[0086] <3-4> The resin composition according to any one of <3-1> to <3-3>, wherein the thermoplastic resin (B) is selected from polyester resins, polystyrene resins, and polyolefin resins.

[0087] <3-5> The resin composition according to any one of <3-1> to <3-4>, 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.

[0088] <3-6> The resin composition according to any one of <3-1> to <3-4>, 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.

[0089] <3-7> The resin composition according to any one of <3-1> to <3-6>, wherein the content of the carbon nanotubes in the resin composition is 0.01 to 10% by mass.

[0090] <3-8> The resin composition according to any one of <3-1> to <3-7>, wherein when the resin composition is molded into a thickness of 2 mm, the absorptivity determined according to formula (A) at a frequency of 76.5 GHz is 50.0% to 100%.

[0091] Formula (A)

[0092] [Number 7]

[0093]

[0094] (In the above formula (A), R represents the reflection attenuation measured by the free-space method, and T represents the transmission attenuation measured by the free-space method.)

[0095] <3-9> The resin composition according to any one of <3-1> to <3-8>, wherein the reflectance calculated according to formula (B) at a frequency of 76.5 GHz when the resin composition is molded into a thickness of 2 mm is 40.0% or less.

[0096] Formula (B)

[0097] [Number 8]

[0098]

[0099] (In the above formula (B), R represents the reflection loss measured by the free space method.)

[0100] <3-10> The resin composition according to any one of <3-1> to <3-9>, wherein the transmittance calculated according to formula (C) at a frequency of 76.5 GHz when the resin composition is molded into a thickness of 2 mm is 25.0% or less.

[0101] Formula (C)

[0102] [Number 9]

[0103]

[0104] (In the above formula (C), T represents the transmission attenuation measured by the free space method.)

[0105] <3-11> The resin composition according to any one of <3-1> to <3-10>, comprising 1.0 to 100 parts by mass of the thermoplastic resin (B) relative to 100 parts by mass of the thermoplastic resin (A).

[0106] <3-12> The resin composition according to any one of <3-1> to <3-11>, which is used for an electromagnetic wave absorber.

[0107] <3-13> A molded article formed from the resin composition according to any one of <3-1> to <3-12>.

[0108] <3-14> An electromagnetic wave absorber formed from the resin composition according to any one of <3-1> to <3-12>.

[0109] <3-15> A method for producing a resin composition, comprising melt-kneading a thermoplastic resin (A) and carbon nanotubes masterbatched with a 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) (here, the SP value is a solubility parameter).

[0110] <3-16> The method for producing the resin composition according to <3-15>, wherein the resin composition is the resin composition according to any one of <3-1> to <3-12>.

[0111] Effects of the Invention

[0112] According to the present invention, a resin composition having high electromagnetic wave absorptivity, a molded article, an electromagnetic wave absorber, and a method for producing the resin composition can be provided. DETAILED DESCRIPTION

[0113] Hereinafter, a mode for carrying out the present invention (hereinafter referred to as "this embodiment") will be described in detail. It should be noted that the following this embodiment is an example for explaining the present invention, and the present invention is not limited to this embodiment.

[0114] In addition, in this specification, "to" is used to mean that the numerical values described before and after it are included as the lower limit and the upper limit.

[0115] In this specification, various physical property values and characteristic values are values at 23°C unless otherwise specified.

[0116] In this specification, the weight average molecular weight and the number average molecular weight are polystyrene-equivalent values measured by GPC (gel permeation chromatography).

[0117] In this specification, the unit of reflection loss and transmission loss is “dB” (decibel).

[0118] The standards shown in this manual are based on the standards as of January 1, 2021, unless otherwise specified, even if the measurement methods etc. vary depending on the year.

[0119] The resin composition of this embodiment is a resin composition comprising a thermoplastic resin and carbon nanotubes, characterized in that the resin composition has a relative dielectric constant of 4.50 or greater at a frequency of 76.5 GHz. By increasing the relative dielectric constant at a frequency of 76.5 GHz, the electromagnetic wave absorptivity of the resulting resin composition at a frequency of approximately 76.5 GHz can be increased. In addition, by adopting the configuration of this embodiment, the reflectivity and transmittance of the resin composition at a frequency of 76.5 GHz can be reduced.

[0120] The reason for increasing the electromagnetic wave absorptivity by increasing the relative dielectric constant is presumably because the shielding effect of the electric field based on the resin composition is improved. Surprisingly, increasing the relative dielectric constant of the resin composition improves the absorptivity of the resin composition. In addition, increasing the dielectric loss tangent also improves the absorptivity. The reason for increasing the absorptivity by increasing the dielectric loss tangent is presumably because the conversion efficiency of electromagnetic waves into heat energy within the resin composition is improved.

[0121] As the method for improving the relative dielectric constant of resin combination, examples can be given: selecting the material with high relative dielectric constant, reducing the use of the material with low relative dielectric constant as much as possible, making the material with high relative dielectric constant well dispersed in resin, increasing the volume ratio of the material with high relative dielectric constant etc. Particularly, by mixing the additive with high relative dielectric constant in the composition consisting of more than two thermoplastic resins, the resin combination with high relative dielectric constant can be obtained. The method for improving the dielectric loss tangent of resin combination is basically the same as the method for improving relative dielectric constant, but owing to also having the material that improves relative dielectric constant height, can reduce the material of dielectric loss tangent, therefore sometimes also need to select.

[0122] Hereinafter, the resin composition according to the present embodiment will be described.

[0123] <Thermoplastic resin>

[0124] The resin composition of the present embodiment contains a thermoplastic resin.

[0125] As thermoplastic resins used in this embodiment, preferred examples include polyester resins (thermoplastic polyester resins); polyamide resins; polycarbonate resins; polystyrene 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; polymethacrylate resins; and the like.

[0126] In the present embodiment, the thermoplastic resin (for example, polyester resin (thermoplastic polyester resin), polyamide resin, polycarbonate resin and polyphenylene ether resin) can be a linear polymer or a branched polymer having a branched structure. In the present embodiment, the thermoplastic resin preferably has a less branched structure. For example, the degree of branching DB (degree of branching) of the thermoplastic resin used in the present embodiment is preferably less than 10%, more preferably 5% or less, and further 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 monomer units bonded to the end, Z is the average number of monomer units forming branches, and L is the average number of monomer units bonded in a chain (in the macromolecules of each substance).

[0127] 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.

[0128] Relative to thermoplastic resin (A) 100 mass parts, the content of the thermoplastic resin (B) in the resin combination of the present embodiment is preferably more than 1.0 mass parts, more preferably more than 2.0 mass parts, and further preferably more than 2.5 mass parts.By being set to more than the above-mentioned lower limit, there is a tendency that electromagnetic wave absorption performance further improves.In addition, relative to thermoplastic resin (A) 100 mass parts, the content of above-mentioned thermoplastic resin (B) is preferably less than 100 mass parts, more preferably less than 80 mass parts, more preferably less than 50 mass parts, and then preferably less than 30 mass parts, more preferably less than 10.0 mass parts, also preferably less than 8.0 mass parts, less than 7.0 mass parts, less than 6.0 mass parts.By being set to less than the above-mentioned upper limit, there is a tendency that the transmittance of the obtained molded article can be made lower.

[0129] In this embodiment, the thermoplastic resin (A) is preferably the main resin (e.g., the component with the highest content) constituting the molded article. Furthermore, in this embodiment, at least a portion of the thermoplastic resin (B) is preferably derived from the aforementioned carbon nanotube masterbatch. This configuration tends to more effectively exhibit the effects of the present invention.

[0130] The resin composition of the present embodiment may contain only one type of thermoplastic resin (A) and thermoplastic resin (B), or may contain two or more types. When containing two or more types, the total amount is preferably within the above range.

[0131] In the present embodiment, the thermoplastic resin (A) preferably comprises a polyester resin (preferably a polybutylene terephthalate resin). Furthermore, in the present embodiment, preferably 95% by mass or more, more preferably 99% by mass or more of the thermoplastic resin (A) is a polyester resin.

[0132] A preferred example of the thermoplastic resin in this embodiment is that 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).

[0133] In a preferred example of the thermoplastic resin in this embodiment, the thermoplastic resin (A) comprises a polyester resin (preferably a polybutylene terephthalate resin), and the thermoplastic resin (B) comprises a polystyrene resin. In this embodiment, the thermoplastic resin preferably comprises 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more of the polyester resin (preferably a polybutylene terephthalate resin) and the polystyrene resin (preferably HIPS, more preferably polystyrene containing butadiene rubber).

[0134] Hereinafter, details of each thermoplastic resin will be described.

[0135] <<Polyester resin>>

[0136] As the polyester resin, a known thermoplastic polyester resin can be used, and polyethylene terephthalate resin and polybutylene terephthalate resin are preferred, and at least polybutylene terephthalate resin is more preferred.

[0137] 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 form ester bonds. In addition to polybutylene terephthalate resin (homopolymer), polybutylene terephthalate copolymers containing copolymer components other than terephthalic acid units and 1,4-butanediol units, and mixtures of homopolymers and polybutylene terephthalate copolymers are included.

[0138] The polybutylene terephthalate resin may contain one or two or more dicarboxylic acid units other than terephthalic acid.

[0139] Specific examples of other dicarboxylic acids include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, 1,5-naphthalene dicarboxylic acid, 2,5-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, biphenyl-2,2'-dicarboxylic acid, biphenyl-3,3'-dicarboxylic acid, biphenyl-4,4'-dicarboxylic acid, bis(4,4'-carboxyphenyl)methane, anthracene dicarboxylic acid, and 4,4'-diphenyl ether dicarboxylic acid; alicyclic dicarboxylic acids such as 1,4-cyclohexane dicarboxylic acid and 4,4'-dicyclohexyl dicarboxylic acid; and aliphatic dicarboxylic acids such as adipic acid, sebacic acid, azelaic acid, and dimer acid.

[0140] The polybutylene terephthalate resin used in this embodiment preferably has terephthalic acid units accounting for 80 mol% or more of all dicarboxylic acid units, more preferably 90 mol% or more, further preferably 95 mol% or more, further preferably 97 mol% or more, and even more preferably 99 mol% or more.

[0141] As the diol unit, in addition to 1,4-butanediol, one or two or more other diol units may be contained.

[0142] 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, decanediol, cyclohexanedimethanol, 4,4'-dicyclohexylhydroxymethane, 4,4'-dicyclohexylhydroxypropane, and ethylene oxide-added diols of bisphenol A. In addition to the aforementioned bifunctional monomers, small amounts of trifunctional monomers such as trimellitic acid, trimesic acid, pyromellitic acid, pentaerythritol, and trimethylolpropane to introduce a branched structure, or monofunctional compounds such as fatty acids to adjust the molecular weight, may also be used.

[0143] The polybutylene terephthalate resin used in this embodiment preferably contains 1,4-butanediol units in 80 mol% or more of all diol units, more preferably 90 mol% or more, further preferably 95 mol% or more, further preferably 97 mol% or more, and still further preferably 99 mol% or more.

[0144] As described above, the polybutylene terephthalate resin is preferably a polybutylene terephthalate homopolymer formed by the polycondensation of terephthalic acid and 1,4-butanediol. Alternatively, it may be a polybutylene terephthalate copolymer comprising one or more dicarboxylic acids other than terephthalic acid as carboxylic acid units and / or comprising one or more diols other than 1,4-butanediol as diol units. When the polybutylene terephthalate resin is a polybutylene terephthalate resin modified by copolymerization, specific preferred copolymers thereof include polyester ether resins formed by copolymerizing polyalkylene glycols, particularly polytetramethylene glycol, dimer acid copolymerized polybutylene terephthalate resins, and isophthalic acid copolymerized polybutylene terephthalate resins. Among these, polyester ether resins formed by copolymerizing polytetramethylene glycol are preferably used.

[0145] It should be noted that these copolymers are copolymers having a copolymerization amount of 1 mol% or more and less than 50 mol% of the total segment of the polybutylene terephthalate resin. The copolymerization amount is preferably 2 mol% or more and less than 50 mol%, more preferably 3 to 40 mol%, and even more preferably 5 to 20 mol%. Such a copolymerization ratio tends to improve fluidity, toughness, and tracking resistance, which is preferred.

[0146] The amount of terminal carboxyl groups in the polybutylene terephthalate resin can be appropriately selected and determined, and is generally 60 eq / ton or less, preferably 50 eq / ton or less, and more preferably 30 eq / ton or less. By setting the amount below the above upper limit, alkali resistance and hydrolysis resistance tend to be improved. The lower limit of the amount of terminal carboxyl groups is not particularly limited, but is generally 10 eq / ton or more, taking into account the productivity of producing the polybutylene terephthalate resin.

[0147] The terminal carboxyl group content of the polybutylene terephthalate resin is determined by dissolving 0.5 g of the polybutylene terephthalate resin in 25 mL of benzyl alcohol and titrating with a 0.01 mol / L sodium hydroxide solution in benzyl alcohol. The terminal carboxyl group content can be adjusted by any conventionally known method, such as adjusting polymerization conditions such as the raw material charge ratio, polymerization temperature, and decompression method during polymerization, or reacting an end-capping agent.

[0148] The intrinsic viscosity of polybutylene terephthalate resin is preferably more than 0.5dL / g, more preferably more than 0.6dL / g.By making intrinsic viscosity be more than 0.5dL / g, there is the tendency that the mechanical strength of obtained resin combination further improves.Above-mentioned intrinsic viscosity is preferably 2.00dL / g, more preferably below 1.50dL / g, more preferably below 1.30dL / g, and then preferably below 1.26dL / g, and then more preferably below 1.23dL / g, and then can be below 1.20dL / g, below 1.17dL / g, below 1.15dL / g, below 1.13dL / g, below 1.07dL / g, below 1.05dL / g, below 1.00dL / g, below 0.97dL / g.By being made below 2.0dL / g, there is the tendency that the fluidity of resin combination further improves, moldability improves. In particular, when carbon nanotubes are masterbatched using polybutylene terephthalate resin and the resulting product is mixed with 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 carbon nanotubes are more easily dispersed as the intrinsic viscosity of the main component polybutylene terephthalate resin decreases. Consequently, electromagnetic wave absorption properties tend to be further improved.

[0149] In addition, the intrinsic viscosity of the polybutylene terephthalate resin is a value measured at 30° C. in a mixed solvent of tetrachloroethane and phenol at a mass ratio of 1:1.

[0150] Polybutylene terephthalate resin can be produced by batchwise or continuous melt polymerization of a dicarboxylic acid component primarily composed of terephthalic acid or its ester derivatives and a diol component primarily composed of 1,4-butanediol. Furthermore, 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-phase polymerization under a nitrogen stream or reduced pressure.

[0151] The polybutylene terephthalate resin is preferably obtained by a production method in which a dicarboxylic acid component containing terephthalic acid as a main component and a diol component containing 1,4-butanediol as a main component are continuously melt-polycondensed.

[0152] The catalyst used in the esterification reaction may be a conventionally known catalyst, and examples thereof include titanium compounds, tin compounds, magnesium compounds, and calcium compounds. Among these, titanium compounds are particularly preferred. Specific examples of titanium compounds used as esterification catalysts include titanium alkoxides such as tetramethyl titanate, tetraisopropyl titanate, and tetrabutyl titanate, and titanium phenolates such as tetraphenyl titanate.

[0153] As the polyester resin, in addition to the above, reference may be made to the description in paragraphs 0013 to 0016 of Japanese Patent Application Laid-Open No. 2010-174223, the contents of which are incorporated herein.

[0154] <<Polystyrene Resin>>

[0155] Examples of the polystyrene resin include homopolymers of styrene monomers and copolymers of styrene monomers and monomers copolymerizable with styrene monomers. Examples of styrene monomers include styrene, α-methylstyrene, chlorostyrene, methylstyrene, and tert-butylstyrene. In the present embodiment, 50 mol% or more of the monomer units of the styrene resin are styrene monomers.

[0156] More specifically, polystyrene resins include polystyrene resins, acrylonitrile-styrene copolymers (AS resins), high-impact polystyrene resins (HIPS), acrylonitrile-butadiene-styrene copolymers (ABS resins), acrylonitrile-acrylic rubber-styrene copolymers (AAS resins), acrylonitrile-styrene-acrylic rubber copolymers (ASA resins), acrylonitrile-ethylene propylene rubber-styrene copolymers (AES resins), and styrene-IPN rubber copolymers.

[0157] In this embodiment, the styrene-based resin is preferably an acrylonitrile-styrene copolymer (AS resin), a high-impact polystyrene resin (HIPS), an acrylonitrile-butadiene-styrene copolymer (ABS resin), an acrylonitrile-acrylic rubber-styrene copolymer (AAS resin), an acrylonitrile-styrene-acrylic rubber copolymer (ASA resin), an acrylonitrile-ethylene propylene rubber-styrene copolymer (AES resin), or a styrene-IPN rubber copolymer, more preferably a high-impact polystyrene resin (HIPS), and even more preferably a polystyrene containing butadiene rubber.

[0158] 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 further preferably 7 to 30% by mass. By making the content of the rubber component 3% or more by mass, there is a tendency to improve impact resistance, and by setting it to 50% or less by mass, there is a tendency to improve flame retardancy, which is preferred. In addition, the average particle size of the rubber component is preferably 0.05 to 10 μm, more preferably 0.1 to 6 μm, and further preferably 0.2 to 3 μm. If the average particle size is 0.05 μm or more, there is a tendency to easily improve impact resistance, and if it is 10 μm or less, there is a tendency to improve appearance, which is preferred.

[0159] 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 is usually 500,000 or less, preferably 400,000 or less, more preferably 300,000 or less. Furthermore, the number average molecular weight is usually 10,000 or more, preferably 30,000 or more, more preferably 50,000 or more, and is preferably 500,000 or less, more preferably 300,000 or less.

[0160] The melt flow rate (MFR) of the polystyrene resin, as 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 greater tends to improve fluidity, while an MFR of 30 g / 10 min or less tends to improve impact resistance.

[0161] Examples of methods for producing such polystyrene-based resins include known methods such as emulsion polymerization, solution polymerization, suspension polymerization, and bulk polymerization.

[0162] The content of the thermoplastic resin in the resin composition of the present embodiment is preferably 30% by mass or more, more preferably 35% by mass or more, further preferably 40% by mass or more, and further preferably 45% by mass or more, and further preferably 50% by mass or more in the resin composition. In the case where the resin composition does not include reinforcing material, the content of the thermoplastic resin is more preferably 60% by mass or more, and further preferably 70% by mass or more, further preferably 80% by mass or more, and further more preferably 90% by mass or more in the resin composition. By being set to more than the above-mentioned lower limit, there is a tendency that the fluidity during injection molding is further improved. In addition, the content of the above-mentioned thermoplastic resin is preferably 99% by mass or less. In the case where the resin composition includes reinforcing material, the content of the thermoplastic resin is more preferably 90% by mass or less, further preferably 80% by mass or less, and further preferably 75% by mass or less in the resin composition. By being set to below the above-mentioned upper limit, there is a tendency that the warpage amount of the molded body can be more effectively reduced.

[0163] <Carbon Nanotubes>

[0164] The resin composition of this embodiment contains carbon nanotubes. By containing carbon nanotubes, electromagnetic wave absorptivity can be imparted to the resin composition.

[0165] The carbon nanotubes used in this embodiment are single-walled carbon nanotubes and / or multi-walled carbon nanotubes, preferably at least multi-walled carbon nanotubes. Alternatively, a carbon material partially comprising a carbon nanotube structure may be used. Furthermore, the carbon nanotubes are not limited to cylindrical shapes and may also have a coiled shape, spirally wound with a pitch of less than 1 μm.

[0166] Carbon nanotubes are commercially available, for example, those manufactured by Bayer MaterialScience, Nanocyl, Showa Denko K.K., and Hyperion Catalysis International, Inc. In addition to the name carbon nanotube, carbon nanotubes are sometimes also referred to as graphite fibrils, carbon fibrils, and the like.

[0167] The diameter (number average fiber diameter) of the carbon nanotube is preferably 0.5 nm or more, more preferably 1 nm or more, and further preferably 5 nm or more. In addition, the diameter (number average fiber diameter) of the above-mentioned carbon nanotube is preferably 100 nm or less, more preferably 50 nm or less, further preferably 30 nm or less, and further preferably 10 nm or less. As the aspect ratio of the carbon nanotube, from the viewpoint of imparting good electromagnetic wave absorptivity, it is preferably 5 or more, more preferably 50 or more. The upper limit is not particularly limited, for example, 500 or less.

[0168] As described above, carbon nanotubes can be mixed in a masterbatch. In this case, the concentration of the carbon nanotubes 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, further preferably 30% by mass or less, and further preferably 20% by mass or less. By setting the range below the above upper limit and above the lower limit, there is a tendency for the dispersibility of the carbon nanotubes in the thermoplastic resin (A) to be further improved. The resin used in the masterbatch can exemplify the above-mentioned thermoplastic resin (B). That is, the resin composition of the present embodiment preferably comprises at least a portion of the thermoplastic resin (B) derived from a masterbatch of the above-mentioned carbon nanotubes.

[0169] The content of the carbon nanotubes in the resin composition of the present embodiment is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, further preferably 0.1% by mass or more, can be 0.2% by mass or more, and then can also be 0.4% by mass or more. By being set to more than the above-mentioned lower limit, electromagnetic wave absorptivity can be effectively brought into play. In addition, the content of the carbon nanotubes in the resin composition of the present embodiment is preferably 10% by mass or less, more preferably 8% by mass or less, further preferably 6% by mass or less, and then preferably 4% by mass or less, further preferably 3% by mass or less, can be 2% by mass or less, and then can also be 1% by mass or less. By being set to below the above-mentioned upper limit, there is a tendency that the fluidity of the resin is further improved.

[0170] In addition, the resin composition of the present embodiment preferably contains more than 0.1 parts by mass of carbon nanotubes relative to 100 parts by mass of thermoplastic resin. By setting it to above the above lower limit, electromagnetic wave absorptivity can be effectively exerted. In addition, the resin composition of the present embodiment preferably contains less than 10.0 parts by mass of carbon nanotubes relative to 100 parts by mass of thermoplastic resin, more preferably less than 8.0 parts by mass, further preferably less than 6.0 parts by mass, and further preferably less than 4.0 parts by mass, further preferably less than 3.0 parts by mass, and further can be less than 2.5 parts by mass, and particularly can be less than 1.5 parts by mass. By setting it to below the above upper limit, there is a tendency for the fluidity of the resin to be further improved.

[0171] The resin composition of the present embodiment may contain only one type of carbon nanotube or two or more types. When containing two or more types, the total amount is preferably within the above range.

[0172] <Other ingredients>

[0173] As long as the desired various physical properties are not significantly damaged, the resin combination of the present embodiment can also contain other components except the above-mentioned substances as required. If the example of other components is given, reinforcing material, various resin additives etc. can be given. It should be noted that, about other components, one can be contained, or more than two can be contained in any combination and ratio.

[0174] Examples of various resin additives include stabilizers, release agents, flame retardants, reactive compounds, pigments, dyes, ultraviolet absorbers, antistatic agents, antifogging agents, antiblocking agents, flow improvers, plasticizers, dispersants, and antimicrobial agents. The resin composition of this embodiment preferably contains at least one of a stabilizer and a release agent.

[0175] The resin combination of the present embodiment is adjusted to a total of 100 mass % of thermoplastic resin, carbon nanotubes and other selectively mixed ingredients. The total of the preferred thermoplastic resin and reinforcing material (preferably glass fiber) of the resin combination of the present embodiment accounts for more than 95 mass % of the resin combination. In addition, the total of the preferred thermoplastic resin, carbon nanotubes, stabilizer and releasing agent of the resin combination of the present embodiment accounts for more than 99 mass % of the resin combination. In addition, the total of the preferred thermoplastic resin, carbon nanotubes, reinforcing material (preferably glass fiber), stabilizer and releasing agent of the resin combination of the present embodiment also accounts for more than 99 mass % of the resin combination.

[0176] <<Stabilizer>>

[0177] The resin composition of this embodiment may contain a stabilizer. Examples of the stabilizer include hindered phenol compounds, hindered amine compounds, phosphorus compounds, and sulfur stabilizers. Among these, hindered phenol compounds are preferred. In addition, it is also preferred to use a hindered phenol compound and a phosphorus compound in combination.

[0178] Specifically, as the stabilizer, reference can be made to paragraphs 0046 to 0057 of JP-A-2018-070722, paragraphs 0030 to 0037 of JP-A-2019-056035, and paragraphs 0066 to 0078 of International Publication No. 2017 / 038949, the contents of which are incorporated herein.

[0179] The resin composition of this embodiment preferably contains 0.01 parts by mass or more of a 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. Furthermore, the upper limit of the amount of the stabilizer 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.

[0180] The resin composition of the present embodiment may contain only one stabilizer or two or more. When containing two or more stabilizers, the total amount is preferably within the above range.

[0181] <<Release Agent>>

[0182] The resin composition of this embodiment preferably contains a release agent.

[0183] As the release agent, a wide range of known release agents can be used, and esters of aliphatic carboxylic acids, paraffin wax, polystyrene wax, and polyolefin wax are preferred, and polyethylene wax is more preferred.

[0184] As the release agent, specifically, reference can be made to paragraphs 0115 to 0120 of JP-A-2013-007058, paragraphs 0063 to 0077 of JP-A-2018-070722, and paragraphs 0090 to 0098 of JP-A-2019-123809, the contents of which are incorporated into this specification.

[0185] The resin composition of this embodiment preferably contains 0.01 parts by mass or more of a release agent per 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. Furthermore, 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, per 100 parts by mass of the thermoplastic resin.

[0186] The resin composition may contain only one type of release agent or two or more types. When containing two or more types, the total amount is preferably within the above range.

[0187] <<Reinforcement Materials>>

[0188] The resin composition of this embodiment may or may not contain a reinforcing material. By containing a reinforcing material, the mechanical strength of the obtained molded body can be improved.

[0189] The type of the reinforcing material that can be used in this embodiment is not particularly limited, and it may be any of fibers, fillers, beads, etc., with fibers being preferred.

[0190] When the reinforcing material is a fiber, it may be a short fiber or a long fiber.

[0191] When the reinforcing material is short fibers, fillers, beads, or the like, the resin composition of the present embodiment can be exemplified by pellets, powdered pellets, and films molded from the pellets.

[0192] When the reinforcing material is a long fiber, examples of the reinforcing material include long fibers for so-called UD materials (Uni-Directional, unidirectional), sheet-shaped long fibers such as fabrics and braids, etc. When these long fibers are used, components other than the reinforcing material of the resin composition of this embodiment can be impregnated in the reinforcing material as the sheet-shaped long fibers to prepare a sheet-shaped resin composition (e.g., a prepreg).

[0193] The raw materials of the reinforcing material can include inorganic substances such as glass, carbon (carbon fiber, etc.), alumina, boron, ceramics, metals (steel, etc.), and organic substances such as plants (including kenaf, bamboo, etc.), aromatic polyamide, polyoxymethylene, aromatic polyamide, poly(p-phenylene benzobisoxazole), ultra-high molecular weight polyethylene, etc., preferably glass.

[0194] The resin composition of the present embodiment preferably contains glass fiber as a reinforcing material.

[0195] The glass fiber is selected from glass compositions such as A glass, C glass, E glass, R glass, D glass, M glass, and S glass, and E glass (alkali-free glass) is particularly preferred.

[0196] Glass fiber refers to a fibrous material having a circular or polygonal cross-sectional shape when cut at a right angle in the longitudinal direction. The number average fiber diameter of the glass fiber single fibers is generally 1 to 25 μm, preferably 5 to 17 μm. By setting the number average fiber diameter to 1 μm or more, there is a tendency for the molding processability of the resin composition to be further improved. By setting the number average fiber diameter to 25 μm or less, there is a tendency for the appearance of the resulting molded article to be improved and the reinforcing effect to be enhanced. The glass fiber may be a single fiber or a fiber formed by twisting a plurality of single fibers.

[0197] The glass fiber may be in the form of a glass roving obtained by continuously winding a single fiber or a fiber obtained by twisting a plurality of single fibers, chopped strands neatly cut into a length of 1 to 10 mm (i.e., glass fibers having a number average fiber length of 1 to 10 mm), or milled fibers crushed into a length of about 10 to 500 μm (i.e., glass fibers having a number average fiber length of 10 to 500 μm). Chopped strands neatly cut into a length of 1 to 10 mm are preferred. Fibers of different forms may also be used in combination.

[0198] Furthermore, the glass fibers are preferably those having a non-uniform cross-section. The non-uniform cross-section means that the flatness, represented by the major diameter / minor diameter ratio of a 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.

[0199] To improve affinity with the resin component, the glass fiber may be surface-treated with, for example, a silane-based compound, an epoxy-based compound, a urethane-based compound, or an oxidized glass fiber, unless the properties of the resin composition of this embodiment are significantly impaired.

[0200] In the case that the resin combination of the present embodiment includes reinforcing material (preferably glass fibre), its content is preferably more than 10 mass parts, more preferably more than 20 mass parts, more preferably more than 30 mass parts, and then preferably more than 40 mass parts relative to 100 mass parts of thermoplastic resin.By being set to more than the above-mentioned lower limit, there is the tendency that the mechanical strength of obtained formed body further increases.In addition, the content of above-mentioned reinforcing material (preferably glass fibre) is preferably less than 100 mass parts, more preferably less than 90 mass parts, more preferably less than 85 mass parts, and then preferably less than 80 mass parts, and further preferably less than 75 mass parts relative to 100 mass parts of thermoplastic resin.By being set to below the above-mentioned upper limit, there is the tendency that the flowability of formed body outward appearance improves and resin combination further improves.

[0201] The content of the reinforcing material (preferably glass fibre) in the resin combination of present embodiment is preferably more than 10 mass %, more preferably more than 15 mass %, more preferably more than 20 mass %, and then preferably more than 25 mass %.In addition, the content of above-mentioned reinforcing material (preferably glass fibre) is more preferably below 50 mass %, more preferably below 45 mass %, more preferably below 40 mass %, and then preferably below 35 mass % in resin combination.By being made as more than the above-mentioned lower limit, there is the tendency that mechanical strength further raises.In addition, by being made as below the above-mentioned upper limit, there is the tendency that fluidity when the outward appearance of formed body improves and the melting of resin combination further improves.

[0202] 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 containing two or more types, the total amount is preferably within the above range.

[0203] <Physical Properties of Resin Composition>

[0204] The relative dielectric constant of the resin combination of the present embodiment at a frequency of 76.5GHz is more than 4.50, preferably more than 4.60, more preferably more than 4.75, more preferably more than 4.90, and then preferably more than 5.00, and more preferably more than 5.10. By being set to more than the above-mentioned lower limit, there is a tendency that the electromagnetic wave absorptivity of the obtained molded body is further improved. In addition, the upper limit of the above-mentioned relative dielectric constant is preferably less than 8.00, more preferably less than 6.00, more preferably less than 5.50, and then preferably less than 5.30, and more preferably less than 5.20. By being set to less than the above-mentioned upper limit, there is a tendency that the electromagnetic wave reflectivity of the obtained molded body can be further reduced.

[0205] The dielectric loss tangent of the resin combination of the present embodiment at a frequency of 76.5GHz is preferably more than 0.10, preferably more than 0.12, more preferably more than 0.14, more preferably more than 0.16, and then preferably more than 0.18, and more preferably more than 0.21. By being set to more than the above-mentioned lower limit, there is a tendency that the electromagnetic wave absorptivity of the obtained molded body is further improved. In addition, the lower limit of the above-mentioned dielectric loss tangent is not particularly limited, for example, less than 0.50, and further can be less than 0.40.

[0206] The resin composition of the present embodiment preferably has a high electromagnetic wave absorptivity.

[0207] Specifically, when the resin composition of the present embodiment is molded into a 2 mm thickness (preferably 100 mm×100 mm×2 mm thickness), the absorptivity calculated according to formula (A) at a frequency of 76.5 GHz is preferably 50.0% to 100%.

[0208] Formula (A)

[0209] [Number 10]

[0210]

[0211] (In the above formula (A), R represents the reflection attenuation measured by the free-space method, and T represents the transmission attenuation measured by the free-space method.)

[0212] The absorptivity (2 mm thickness) is preferably 53.0% or higher, more preferably 55.0% or higher, even more preferably 58.0% or higher, further preferably 60.0% or higher, and even more preferably 64.0% or higher. An upper limit of 100% is ideal, but even 90.0% or lower fully satisfies the required performance.

[0213] Furthermore, when the resin composition of the present embodiment is molded into a 3 mm thickness (preferably 100 mm×100 mm×3 mm thickness), the absorptivity calculated according to formula (A) at a frequency of 76.5 GHz is preferably 63.0% to 100%.

[0214] The absorptivity (3 mm thickness) is preferably 57.0% or higher, more preferably 59.0% or higher, even more preferably 64.0% or higher, further preferably 66.0% or higher, and even more preferably 70.0% or higher. While an upper limit of 100% is ideal, a value of 90.0% or lower fully satisfies the required performance.

[0215] The resin composition of the present embodiment preferably has a low reflectivity of electromagnetic waves.

[0216] Specifically, the resin composition of the present embodiment preferably has a reflectance of 40.0% or less at a frequency of 76.5 GHz when molded into a 2 mm thick film (preferably 100 mm×100 mm×2 mm thick film).

[0217] Formula (B)

[0218] [Number 11]

[0219]

[0220] (In the above formula (B), R represents the reflection loss measured by the free space method.)

[0221] The reflectivity (2 mm thickness) is preferably 35.0% or less, more preferably 30.0% or less, even more preferably 26.0% or less, further preferably 22.0% or less, and even more preferably 18.5% or less. While a lower limit of 0% is ideal, a reflectivity of 5.0% or more, and further preferably 10.0% or more, fully satisfies the required performance.

[0222] Furthermore, the resin composition of this embodiment preferably has a reflectance of 38.0% or less at a frequency of 76.5 GHz when molded into a 3 mm thick film (preferably 100 mm×100 mm×3 mm thick) as determined by formula (B).

[0223] The reflectivity (3 mm thickness) is preferably 33.0% or less, more preferably 28.0% or less, even more preferably 24.0% or less, further preferably 20.0% or less, and even more preferably 16.5% or less. A lower limit of 0% is ideal, but even 3.0% or more, and further 8.0% or more, fully satisfies the required performance.

[0224] The resin composition of the present embodiment preferably has low transmittance.

[0225] The resin composition of the present embodiment preferably has a transmittance of 25.0% or less at a frequency of 76.5 GHz when molded into a 2 mm thick film (preferably 100 mm×100 mm×2 mm thick film) as determined by formula (C).

[0226] Formula (C)

[0227] [Number 12]

[0228]

[0229] (In the above formula (C), T represents the transmission attenuation measured by the free space method.)

[0230] The transmittance (2 mm thickness) is preferably 23.0% or less, more preferably 20.0% or less. The lower limit is preferably 0%, but even 5.0% or more fully satisfies the required performance.

[0231] Furthermore, the resin composition of this embodiment preferably has a transmittance of 26.0% or less at a frequency of 76.5 GHz when molded into a 3 mm thick film (preferably 100 mm×100 mm×3 mm thick) as determined by formula (C).

[0232] The transmittance (3 mm thickness) is preferably 24.0% or less, more preferably 21.0% or less. A lower limit of 0% is ideal, but even 4.0% or more fully satisfies the required performance.

[0233] The resin composition of the present embodiment preferably satisfies any one of the absorptivity determined by the above formula (A), the reflectivity determined by the above formula (B), and the transmittance determined by the above formula (C).

[0234] The resin composition of the present embodiment preferably has excellent mechanical strength.

[0235] The resin composition of the present embodiment preferably has excellent tensile properties.

[0236] For example, when the resin composition of the present embodiment is molded into an ISO multi-purpose test piece (thickness 4 mm), the tensile strength at the maximum point measured according to ISO 527-1 and ISO 527-2 is preferably 40 MPa or more, more preferably 50 MPa or more. The upper limit of the tensile strength at the maximum point is not particularly limited, and for example, even 200 MPa or less is a practical level.

[0237] In addition, the tensile modulus of elasticity measured according to ISO527-1 and ISO527-2 when the resin composition of the present embodiment is molded into an ISO multi-purpose test piece (thickness 4mm) is preferably more than 1500MPa, more preferably more than 1800MPa, further preferably more than 2000MPa. The upper limit of the above-mentioned tensile modulus of elasticity is not particularly limited, for example, even if it is below 12000MPa, it is also a practical level.

[0238] Furthermore, when the resin composition of the present embodiment is molded into an ISO multi-purpose test piece (thickness 4 mm), the tensile strain measured according to ISO 527-1 and ISO 527-2 is preferably 1.0% or more, more preferably 2.0% or more. Furthermore, the upper limit of the tensile strain is not particularly limited, and for example, even 30% or less is a practical level.

[0239] Furthermore, the resin composition of the present embodiment preferably has excellent bending properties.

[0240] Specifically, the flexural strength when the resin composition of the present embodiment is molded into an ISO multi-purpose test piece (thickness 4 mm) is preferably 50 MPa or more, more preferably 70 MPa or more. In addition, the upper limit of the flexural strength is not particularly limited, for example, it is actually 300 MPa or less.

[0241] The resin composition of this embodiment has a flexural modulus of preferably 1,500 MPa or more, more preferably 2,000 MPa or more when molded into an ISO multipurpose test piece (thickness 4 mm). The upper limit of the flexural modulus is not particularly limited, but is practically 15,000 MPa or less, for example.

[0242] Furthermore, the resin composition of the present embodiment preferably has excellent impact resistance.

[0243] Specifically, when the resin composition of the present embodiment is molded into an ISO multipurpose test piece (thickness 4 mm), the notched Charpy impact strength according to ISO 179 is preferably 2.0 kJ / m 2 More preferably, 3.0 kJ / m 2 In addition, the upper limit of the notched Charpy impact strength is not particularly limited, for example, it is actually 50 kJ / m 2 the following.

[0244] When the resin composition of the present embodiment is molded into a 2 mm thick sheet (preferably 100 mm×100 mm×2 mm thick sheet), the surface resistance according to IEC60093 is preferably 1.0×10 8 Ω or more, more preferably 1.0×10 9 Ω or more, more preferably 1.0×10 10 Ω or more, more preferably 1.0×10 11 Ω or more, more preferably 1.0×10 12 Ω or more, more preferably 1.0×10 13 Ω or more, more preferably 1.0×10 14 Ω or more, and preferably 1.0×10 16 Ω or less, more preferably 1.0×10 15 By setting it as such a range, the electromagnetic wave absorptivity of the obtained molded article tends to be higher.

[0245] Furthermore, the resin composition of the present embodiment preferably has a volume resistivity of 1.0×10 10 Ω·cm or more, more preferably 1.0×10 11 Ω·cm or more, more preferably 1.0×10 12 Ω·cm or more, more preferably 1.0×10 13 Ω·cm or less, more preferably 1.0×10 14 Ω·cm or more, more preferably 1.0×10 15 Ω·cm or more, and preferably 1.0×10 17 Ω·cm or less, more preferably 1.0×10 16 By setting it as such a range, the electromagnetic wave absorptivity of the obtained molded article tends to be higher.

[0246] The details of the above-mentioned measurement method were measured according to the description in the Examples.

[0247] <Other specific examples of resin compositions (1)>

[0248] Another specific example (1) of the resin composition according to the present embodiment is a resin composition containing a polybutylene terephthalate resin, a polystyrene-based resin, and carbon nanotubes.

[0249] This configuration allows for a resin composition with a high absorptivity. The reason for this is presumably as follows. By blending carbon nanotubes into the polybutylene terephthalate resin, a certain level of electromagnetic wave absorptivity is achieved. It is speculated that in this embodiment, by further blending a styrene-based resin, the carbon nanotubes can be more effectively dispersed in the polybutylene terephthalate resin, further improving the absorptivity of the resulting resin composition.

[0250] Furthermore, by adopting the configuration of this embodiment, the reflectivity and transmittance of electromagnetic waves of the resin composition can be reduced, and the tensile properties, particularly the tensile strain, can be improved.

[0251] Furthermore, the aforementioned effects can be achieved more effectively by forming a masterbatch of carbon nanotubes with a styrene-based resin and then mixing it with a polybutylene terephthalate resin. This mechanism is speculative, but it is speculated that when the polybutylene terephthalate resin and the styrene-based resin masterbatch of carbon nanotubes are melt-kneaded, the carbon nanotubes emerge from the styrene-based resin and enter and diffuse into the polybutylene terephthalate resin. This driving force dissolves the agglomeration of the carbon nanotubes, allowing them to diffuse more efficiently within the polybutylene terephthalate resin.

[0252] On the other hand, another specific example (1) of the resin composition generally presents the following morphology: a sea-island structure having a sea region containing a large amount of polybutylene terephthalate resin and an island region containing a large amount of polystyrene resin, wherein 30% or more by mass (preferably 45% or more by mass, more preferably 65% or more by mass, and even more preferably 85% or more by mass) 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. By presenting such a morphology, there is a tendency for the electromagnetic wave absorptivity of the resin composition to be improved. It is speculated that this sea-island structure is based on the fact that polybutylene terephthalate resin and polystyrene resin are not easily compatible, and carbon nanotubes are inherently more easily fused with polybutylene terephthalate resin than polystyrene resin.

[0253] <Other specific examples of resin compositions (2)>

[0254] Another specific example (2) of the resin composition of the present embodiment comprises 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 satisfies the SP value of the thermoplastic resin (A) ≥ the SP value of the thermoplastic resin (B) (here, the SP value is a solubility parameter).

[0255] By setting it as such a structure, it is possible to provide a resin composition with a high electromagnetic wave absorption rate. The reason is presumably as follows. That is, the polar groups of the resin with a high SP value are relatively more. On the other hand, if the carbon nanotubes are melt-kneaded together with two or more resins, they tend to be attracted to the resin having polar groups. Therefore, it is presumed that: when the SP value of the resin for masterbatch of the carbon nanotubes is greater than the SP value of the main thermoplastic resin, even if the carbon nanotube masterbatch is melt-kneaded with the main thermoplastic resin, it is difficult for the carbon nanotubes to be dispersed in the main thermoplastic resin. In the present embodiment, by making the SP value of the thermoplastic resin (B) for masterbatch of the carbon nanotubes less than the SP value of the thermoplastic resin (A), it is presumed that during melt-kneading, the carbon nanotubes undergo phase transfer from the thermoplastic resin (B) to the thermoplastic resin (A), thereby being able to be easily dispersed in the thermoplastic resin (A). In particular, by setting the difference between the SP values of thermoplastic resin (A) and thermoplastic resin (B) to 0.1 or greater, it is estimated that the dispersion of carbon nanotubes in thermoplastic resin (A) can be significantly improved. Furthermore, by improving the dispersibility of carbon nanotubes in thermoplastic resin (A), a high electromagnetic wave absorptivity can be achieved.

[0256] In another specific example (2) of the resin composition of this embodiment, the SP value of the thermoplastic resin (A) satisfies ≥ the SP value of the thermoplastic resin (B) (here, the SP value is the solubility parameter). With such a configuration, the dispersibility of the carbon nanotubes in the thermoplastic resin (A) tends to be improved.

[0257] The difference between the SP value of the thermoplastic resin (A) and the SP value of the thermoplastic resin (B) is 0 or greater, preferably 0.1 or greater, more preferably 0.3 or greater, even more preferably 0.5 or greater, further preferably 0.7 or greater, and even more preferably 1.0 or greater. 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, further preferably 6.0 or less, further preferably 5.0 or less, and even more preferably 4.0 or less. By setting the value below the upper limit, compatibility during melt kneading tends to improve.

[0258] In another specific example (2) of the resin composition of this embodiment, the thermoplastic resin (A) and the thermoplastic resin (B) may each contain only one type, or may contain two or more types. When containing two or more types, the SP value of the mixture preferably satisfies the above range.

[0259] In this embodiment, the solubility in a solvent having a known SP value can be determined, and calculation is performed based on the solubility using Hansen Solubility Parameter in Practice ver. 5.0.

[0260] The thermoplastic resin (A) in another specific example (2) of the resin composition according to the present embodiment is usually a main component of the resin component contained in the resin composition.

[0261] As thermoplastic resins used in this embodiment, preferred examples include polyester resins (thermoplastic polyester resins); polyamide resins; polycarbonate resins; polystyrene 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; polymethacrylate resins; and the like. It is more preferred to be selected from polyester resins, polycarbonate resins, and polyamide resins, further preferably to include polyester resins, and further preferably to include polybutylene terephthalate resins.

[0262] The content of the thermoplastic resin (A) in other specific examples (2) of the resin composition of the present embodiment is preferably 30% by mass or more, more preferably 35% by mass or more, further preferably 40% by mass or more, further preferably 45% by mass or more, and further preferably 50% by mass or more in the resin composition. In the case where the resin composition does not include a reinforcing material, the content of the thermoplastic resin (A) is further preferably 60% by mass or more, further preferably 70% by mass or more, further preferably 80% by mass or more, and further preferably 90% by mass or more in the resin composition. By setting it to more than the above lower limit, there is a tendency that the fluidity during injection molding is further improved. In addition, the content of the above-mentioned thermoplastic resin is preferably 99% by mass or less. In the case where the resin composition includes a reinforcing material, the content of the thermoplastic resin (A) is more preferably 90% by mass or less, further preferably 80% by mass or less, and further preferably 75% by mass or less in the resin composition. By setting it to less than the above upper limit, there is a tendency that the mechanical strength of the obtained molded body is further improved.

[0263] Another specific example (2) 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 carbon nanotube masterbatch. By adopting such a configuration, the carbon nanotubes easily migrate from the thermoplastic resin (B) to the thermoplastic resin (A) during melt kneading, thereby improving the dispersibility of the carbon nanotubes in the resin composition.

[0264] Furthermore, a part of the thermoplastic resin (B) may not be derived from the masterbatch of carbon nanotubes.

[0265] The thermoplastic resin (B) is determined by its relationship with 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) is satisfied, the type of thermoplastic resin (B) is not limited and can be appropriately selected.

[0266] Preferred examples of the thermoplastic resin (B) used in this embodiment include polyester resins (thermoplastic polyester resins); polyamide resins; polycarbonate resins; polystyrene 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; polymethacrylate resins; and the like. More preferably, the resin is selected from polyester resins, polystyrene resins, and polyolefin resins, further preferably, the resin is selected from polyester resins and polystyrene resins, further preferably, the resin contains polystyrene resins, and further preferably, the resin contains HIPS (preferably polystyrene containing butadiene rubber).

[0267] The content of the thermoplastic resin (B) in other specific examples (2) of the resin composition of the present embodiment is preferably 1.0 mass parts or more, more preferably 2.0 mass parts or more, and further preferably 2.5 mass parts or more relative to 100 mass parts of thermoplastic resin (A). By setting it to more than the above-mentioned lower limit, there is a tendency that the electromagnetic wave absorption performance is further improved. In addition, the content of the above-mentioned thermoplastic resin (B) is preferably 100 mass parts or less, more preferably 80 mass parts or less, further preferably 50 mass parts or less, and further preferably 30 mass parts or less, further preferably 10.0 mass parts or less, and further preferably 8.0 mass parts or less, 7.0 mass parts or less, and 6.0 mass parts or less relative to 100 mass parts of thermoplastic resin (A). By setting it to less than the above-mentioned upper limit, there is a tendency that the transmittance and reflectivity of the obtained molded body can be further reduced.

[0268] In another specific example (2) of the resin composition of the present embodiment, at least a part of the thermoplastic resin (B) is compounded as a resin for masterbatch formation.

[0269] The concentration of the thermoplastic resin (B) in the masterbatch is preferably 99% by mass or less, preferably 95% by mass or less, and 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 range below the upper limit and above the lower limit, the dispersibility of the carbon nanotubes in the thermoplastic resin (A) tends to be further improved.

[0270] In another specific example (2) of the resin composition according to this embodiment, in one preferred embodiment of the thermoplastic resin blending method, the thermoplastic resin (A) comprises a polyester resin (preferably a polybutylene terephthalate resin), and the thermoplastic resin (B) comprises a polystyrene 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 the polyester resin (preferably a polybutylene terephthalate resin) and the polystyrene resin (preferably HIPS).

[0271] In another preferred example of the thermoplastic resin in another specific example (2) of the resin composition of the present embodiment, the thermoplastic resin (A) comprises a polyester resin (preferably a polybutylene terephthalate resin), and the thermoplastic resin (B) comprises a polyester resin (preferably a polybutylene terephthalate resin). In another specific example (2) of the resin composition of the present 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 component contained in the resin composition is composed of a polyester resin (preferably a polybutylene terephthalate resin).

[0272] <Method for producing resin composition>

[0273] The resin composition of the present embodiment can be produced by a conventional method for producing a resin composition containing a thermoplastic resin, for example, by melt-kneading a thermoplastic resin and carbon nanotubes (preferably carbon nanotubes masterbatched with a thermoplastic resin).

[0274] More specifically, the resin composition of this embodiment is produced by feeding a thermoplastic resin, carbon nanotubes masterbatched with the thermoplastic resin, and other components (such as glass fiber) mixed as needed into an extruder and melt-kneading them. The thermoplastic resin used for masterbatch and the thermoplastic resin as the main component can be the same thermoplastic resin or different thermoplastic resins. The thermoplastic resin as the main component is preferably the thermoplastic resin (A) described above, and the thermoplastic resin used for masterbatch is preferably the thermoplastic resin (B) described above.

[0275] The components may be mixed in advance and fed to the extruder at once, or the components may not be mixed in advance or only a portion of them may be mixed in advance and fed to the extruder using a feeder. The extruder may be a single-screw extruder or a twin-screw extruder.

[0276] When glass fibers are mixed, they are preferably supplied from a side feeder in the middle of the barrel of the extruder.

[0277] The heating temperature during melt kneading can be appropriately selected from the range of usually 170 to 350°C.

[0278] <Method for producing molded article>

[0279] The molded article, particularly the electromagnetic wave absorber, is formed from the resin composition of this embodiment.

[0280] The method for producing the molded article in this embodiment is not particularly limited, and any molding method generally used for a resin composition containing a thermoplastic resin can be adopted. Examples thereof include injection molding, ultra-high-speed injection molding, injection compression molding, two-color molding, hollow molding such as gas-assisted molding, molding using an insulating mold, molding using a rapidly heated mold, foam molding (including supercritical fluid), insert molding, IMC (in-mold coating) molding, extrusion molding, sheet molding, thermoforming, rotational molding, lamination molding, compression molding, and blow molding, among which injection molding is preferred.

[0281] <Purpose>

[0282] The electromagnetic wave absorber of this embodiment is formed from the resin composition of this embodiment. Specifically, the resin composition of this embodiment is preferably used in an electromagnetic wave absorber (also referred to as an electromagnetic wave absorbing component), more preferably in an electromagnetic wave absorber having a frequency of at least 60 to 90 GHz, and even more preferably in 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 in housings, covers, and the like for millimeter-wave radars.

[0283] The electromagnetic wave absorber of this embodiment can be appropriately used for: vehicle-mounted millimeter-wave radars used in automatic braking control devices, inter-vehicle distance control devices, pedestrian accident reduction steering devices, false alarm suppression control devices, acceleration suppression devices when the pedal is accidentally stepped on, approaching vehicle alarm devices, lane keeping assist devices, anti-rear-end collision alarm devices, parking assist devices, vehicle surrounding obstacle alarm devices, etc.; railway / aviation millimeter-wave radars used in platform monitoring / intersection obstacle detection devices, tram in-car information (content) transmission devices, tram / railway collision avoidance devices, runway foreign object detection devices, etc.; millimeter-wave radars for transportation infrastructure such as intersection monitoring devices and elevator monitoring devices; millimeter-wave radars for various safety devices; medical / nursing millimeter-wave radars such as systems for protecting children and the elderly; millimeter-wave radars for transmitting various information content; etc.

[0284] Example

[0285] Below, give embodiment and illustrate the present invention in more detail.As long as do not depart from the gist of the present invention, then the material, consumption, ratio, processing content, processing step etc. shown in following embodiment can suitably change.Therefore, the scope of the present invention is not limited to the specific example shown below.

[0286] If the measuring equipment used in the examples is difficult to obtain due to discontinuation of production, other equipment with equivalent performance may be used for measurement.

[0287] raw material

[0288] The following raw materials were used: In Table 1 below, HIPS refers to high-impact polystyrene, PBT refers to polybutylene terephthalate resin, PA refers to polyamide resin, and CNT refers to carbon nanotube (the same applies to Table 2).

[0289] [Table 1]

[0290]

[0291] The diameter (number average fiber diameter) of the CNTs was 9 nm.

[0292] Examples 1 to 3, Comparative Example 1

[0293] <Manufacture of Resin Composition (Pellets)>

[0294] As shown in Table 2, the components listed in Table 1 were placed in a stainless steel drum mixer and stirred for 1 hour. The resulting mixture was fed from the main feed port to an intermeshing co-rotating twin-screw extruder ("TEX-30α" manufactured by Japan Steel Works, Ltd., screw diameter 32 mm, L / D = 42). The barrel temperature of the first kneading section was set to 250°C, and melt kneading was carried out under the conditions of a discharge rate of 40 kg / h and a screw speed of 200 rpm. The nozzle number was 4 holes (round The extruded strands were introduced into a water tank for cooling, and then inserted into a pelletizer for cutting to obtain a resin composition (pellets).

[0295] <76.5GHz electromagnetic wave absorptivity, reflectivity, and transmittance>

[0296] The pellets obtained above were injection molded using an injection molding machine (NEX80, manufactured by Nissei Plastic Industry Co., Ltd.) at a cylinder set temperature of 260°C and a mold temperature of 80°C to produce test pieces measuring 100 mm × 100 mm × 2 mm thick and 100 mm × 100 mm × 3 mm thick. Using the resulting test pieces, the absorptivity calculated according to equation (A), the reflectivity calculated according to equation (B), and the transmittance calculated according to equation (C) at a frequency of 76.5 GHz were measured as follows.

[0297] For the measurement, a network analyzer "N5252A" manufactured by Keysight was used.

[0298] The test piece was placed and measured so that the TD (transverse direction) of the injection molded body was parallel to the electric field direction.

[0299] Formula (A)

[0300] [Number 13]

[0301]

[0302] (In the above formula (A), R represents the reflection attenuation measured by the free-space method, and T represents the transmission attenuation measured by the free-space method.)

[0303] Formula (B)

[0304] [Number 14]

[0305]

[0306] (In the above formula (B), R represents the reflection loss measured by the free space method.)

[0307] Formula (C)

[0308] [Number 15]

[0309]

[0310] (In the above formula (C), T represents the transmission attenuation measured by the free space method.)

[0311] <Relative permittivity and dielectric loss tangent>

[0312] The pellets obtained above were injection molded using an injection molding machine ("NEX80" manufactured by Nissei Plastic Industry Co., Ltd.) at a cylinder setting temperature of 260°C and a mold temperature of 80°C to obtain a test piece of 100 mm×100 mm×2 mm thick.

[0313] The obtained test piece was used to determine the relative dielectric constant and dielectric loss tangent at a frequency of 76.5 GHz. The test piece was placed so that the TD (transverse direction) of the injection molded article was parallel to the electric field direction, and the measurement was performed.

[0314] The measurements were performed using a network analyzer "N5252A" manufactured by Keysight. The relative permittivity and dielectric loss tangent were estimated using the "N1500A Material Measurement Kit" manufactured by Keysight, using the "NIST Precision" calculation model.

[0315] <Tensile Properties>

[0316] The resin pellets obtained above were dried at 120°C for 5 hours and then injection molded into ISO multi-purpose test pieces (thickness 4 mm) using an injection molding machine ("J85AD" manufactured by The Japan Steel Works, Ltd.) at a cylinder temperature of 250°C and a mold temperature of 80°C.

[0317] The molded multi-purpose ISO multi-purpose test piece was used to measure the maximum point tensile strength (unit: MPa), tensile elastic modulus (unit: MPa), and tensile strain (unit: %) in accordance with ISO 527-1 and ISO 527-2.

[0318] <Bending Characteristics>

[0319] The resin pellets obtained above were dried at 120°C for 5 hours and then injection molded into ISO multi-purpose test pieces (thickness 4 mm) using an injection molding machine ("J85AD" manufactured by The Japan Steel Works, Ltd.) at a cylinder temperature of 250°C and a mold temperature of 80°C.

[0320] The flexural strength (unit: MPa) and flexural modulus (unit: MPa) of the molded multi-purpose ISO multi-purpose test piece were measured in accordance with ISO 178.

[0321] <Notched Charpy Impact Strength>

[0322] The resin pellets obtained above were dried at 120°C for 5 hours and then injection molded into ISO multi-purpose test pieces (thickness 4 mm) using an injection molding machine ("J85AD" manufactured by The Japan Steel Works, Ltd.) at a cylinder temperature of 250°C and a mold temperature of 80°C.

[0323] According to ISO179, the ISO multi-purpose test piece obtained above was cut into the specified size and shape, and the Charpy impact strength (with notch) was measured. The unit is kJ / m 2 express.

[0324] <Surface resistance>

[0325] The pellets obtained above were injection molded using an injection molding machine ("NEX80" manufactured by Nissei Plastic Industry Co., Ltd.) at a cylinder setting temperature of 260°C and a mold temperature of 80°C to obtain a test piece of 100 mm×100 mm×2 mm thick.

[0326] Using the obtained test piece, the surface resistance (unit: Ω) was measured in accordance with IEC60093.

[0327] The measurement was performed using an "R8340 ULTRA HIGH RESISTANCE METER" manufactured by ADVANTEST.

[0328] <Volume Resistivity>

[0329] The pellets obtained above were injection molded using an injection molding machine ("NEX80" manufactured by Nissei Plastic Industry Co., Ltd.) at a cylinder setting temperature of 260°C and a mold temperature of 80°C to obtain a test piece of 100 mm×100 mm×2 mm thick.

[0330] Using the obtained test piece, the volume resistivity (unit: Ω·cm) was measured in accordance with IEC60093.

[0331] The measurement was performed using an "R8340 ULTRA HIGH RESISTANCE METER" manufactured by ADVANTEST.

[0332] [Table 2]

[0333]

[0334] The above results show that the resin composition of the present invention has high electromagnetic wave absorptivity. In addition, it has low electromagnetic wave transmittance and reflectivity. In addition, the molded body formed from the resin composition of the present invention has excellent mechanical strength.

[0335] <Heat resistance>

[0336] For the pellets obtained in Example 1, a 100mm×100mm×2mm thick test piece was made according to the above <76.5GHz electromagnetic wave absorptivity, reflectivity, transmittance>, and the absorptivity, reflectivity and transmittance were measured. In addition, for the above 100mm×100mm×2mm thick test piece, a hot air oven ("DNE400" manufactured by Yamato Scientific) was used to heat treat at 180°C. For the test piece after 500 hours, 1000 hours, 1500 hours and 2000 hours of treatment time, the absorptivity, reflectivity and transmittance were measured according to the above <76.5GHz electromagnetic wave absorptivity, reflectivity, transmittance>. Together with the data before treatment (0 hour), they are shown in Table 3.

[0337] <Hydrolysis resistance>

[0338] For the pellets obtained in Example 1, 100mm×100mm×2mm thick test pieces were made according to the above <76.5GHz electromagnetic wave absorptivity, reflectivity, and transmittance>, and the absorptivity, reflectivity, and transmittance were measured. In addition, the above 100mm×100mm×2mm thick test pieces were left to stand at 121°C, 100% relative humidity, and 2atm using a highly accelerated life tester ("EHS-221M" manufactured by Espec). For the test pieces after 50 hours, 100 hours, and 200 hours of treatment, the absorptivity, reflectivity, and transmittance were measured according to the above <76.5GHz electromagnetic wave absorptivity, reflectivity, and transmittance>. They are shown in Table 3 together with the data before treatment (0 hours).

[0339] [Table 3]

[0340]

[0341] The above results show that the resin composition of the present invention exhibits little change in electromagnetic wave properties even when heated for a long period of time. Furthermore, the resin composition of the present invention also exhibits very excellent hydrolysis resistance.

[0342] Examples 4 to 7

[0343] In Example 1, pellets were obtained in the same manner as described in Table 4 except that the components in the above-mentioned <Production of Resin Composition (Pellets)> were changed.

[0344] Next, the obtained pellets were used to measure the absorptivity, reflectivity, and transmittance according to the above-mentioned <76.5 GHz electromagnetic wave absorptivity, reflectivity, and transmittance>.

[0345] Next, the relative dielectric constant and dielectric loss tangent were measured according to the above-mentioned <Relative dielectric constant and dielectric loss tangent>.

[0346] [Table 4]

[0347] Example 4 Example 5 Example 6 Example 7 (A-1)PBT parts by mass 50.0 100.0 (A-2)PBT parts by mass 100.0 50.0 (A-3)PBT parts by mass 100.0 (B-1)PBT1501 parts by mass 3.6 3.6 3.6 3.6 CNT mixing amount quality% 0.5％ 0.5％ 0.5％ 0.5％ IV PBT dL / g 1.26 1.20 1.09 0.85 76.5GHz electromagnetic wave absorption (2mm) ％ 57.6 57.8 61.7 64.0 76.5GHz electromagnetic wave absorption (3mm) ％ 71.2 71.9 74.3 78.1 76.5GHz electromagnetic wave reflectivity (2mm) ％ 25.0 24.6 23.7 19.7 76.5GHz electromagnetic wave reflectivity (3mm) ％ 23.1 23.0 21.9 19.2 76.5GHz electromagnetic wave transmittance (2mm) ％ 17.4 17.6 14.6 16.3 76.5GHz electromagnetic wave transmittance (3mm) ％ 18.9 18.3 16.9 15.9 Relative dielectric constant - 5.91 5.89 5.88 5.44 Dielectric loss tangent - 0.18 0.18 0.21 0.21

[0348] The resin composition of the present invention exhibits excellent electromagnetic wave absorption properties regardless of the intrinsic viscosity of the thermoplastic resin, but a lower intrinsic viscosity can achieve a higher electromagnetic wave absorption rate.

Claims

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 and 8.00 or less at a frequency of 76.5 GHz. The resin composition has a dielectric loss tangent of greater than 0.10 at a frequency of 76.5 GHz.

2. The resin composition according to claim 1, wherein The content of the carbon nanotubes in the resin composition is 0.01% by mass to 10% by mass.

3. The resin composition according to claim 1 or 2, 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 based on 100 parts by mass of the thermoplastic resin (A).

4. The resin composition according to claim 3, wherein The thermoplastic resin (A) includes a polyester resin.

5. The resin composition according to claim 4, wherein The polyester resin includes polybutylene terephthalate resin.

6. The resin composition according to claim 3, wherein The thermoplastic resin (B) includes a polystyrene-based resin.

7. The resin composition according to claim 3, wherein At least a portion of the thermoplastic resin (B) is derived from the masterbatch of the carbon nanotubes.

8. The resin composition according to claim 7, wherein The concentration of the carbon nanotubes in the masterbatch is 1% to 50% by mass.

9. The resin composition according to claim 1, wherein The thermoplastic resin includes polybutylene terephthalate resin and polystyrene resin.

10. The resin composition according to claim 9, wherein The content of the carbon nanotubes in the resin composition is 0.01% by mass to 10% by mass.

11. The resin composition according to claim 9 or 10, wherein The resin composition has 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 resin, and 30% by mass or more of the resin component contained in the resin composition is the polybutylene terephthalate resin. The content of carbon nanotubes contained in the sea region is greater than the content of carbon nanotubes contained in the island region.

12. The resin composition according to claim 9 or 10, wherein The polystyrene-based resin is derived from a masterbatch of carbon nanotubes.

13. The resin composition according to claim 1, wherein The resin composition comprises a thermoplastic resin (A) and a thermoplastic resin (B), At least a portion of the thermoplastic resin (B) is derived from the masterbatch of the carbon nanotubes, And the SP value of the thermoplastic resin (A) ≥ the SP value of the thermoplastic resin (B) is satisfied, where the SP value is a solubility parameter.

14. The resin composition according to claim 13, wherein The concentration of the carbon nanotubes in the masterbatch is 1% to 50% by mass.

15. The resin composition according to claim 13 or 14, wherein The thermoplastic resin (A) is selected from polyester resins, polycarbonate resins and polyamide resins.

16. The resin composition according to claim 13 or 14, wherein The thermoplastic resin (B) is selected from polyester resins, polystyrene resins and polyolefin resins.

17. The resin composition according to claim 13 or 14, 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.

18. The resin composition according to claim 13 or 14, 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.

19. The resin composition according to claim 13 or 14, wherein The content of the carbon nanotubes in the resin composition is 0.01% by mass to 10% by mass.

20. The resin composition according to claim 1 or 2, wherein When the resin composition is molded into a thickness of 2 mm, the absorption rate calculated according to formula (A) at a frequency of 76.5 GHz is 50.0% to 100%. Formula (A) [Number 1] In the above formula (A), R represents the reflection attenuation measured by the free-space method, and T represents the transmission attenuation measured by the free-space method.

21. The resin composition according to claim 1 or 2, wherein When the resin composition is molded into a thickness of 2 mm, the reflectivity calculated according to formula (B) at a frequency of 76.5 GHz is 40.0% or less. Formula (B) [Number 2] In the above formula (B), R represents the reflection loss measured by the free space method.

22. The resin composition according to claim 1 or 2, wherein When the resin composition is molded into a 2 mm thickness, the transmittance calculated according to formula (C) at a frequency of 76.5 GHz is 25.0% or less. Formula (C) [Number 3] In the above formula (C), T represents the transmission attenuation measured by the free space method.

23. The resin composition according to claim 1 or 2, wherein When the resin composition is molded into a 2 mm thick layer, the surface resistance according to IEC60093 is 1.0×10 8 Ω or above.

24. The resin composition according to claim 1 or 2, which is used for an electromagnetic wave absorber. 25 . A molded article formed from the resin composition according to claim 1 . 26 . An electromagnetic wave absorber formed from the resin composition according to claim 1 .

27. A method for producing the resin composition according to any one of claims 1 to 24, comprising melt-kneading a thermoplastic resin and carbon nanotubes masterbatched with the thermoplastic resin.

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

29. A method for producing the resin composition according to any one of claims 1 to 24, comprising melt-kneading a thermoplastic resin (A) and carbon nanotubes masterbatched with a thermoplastic resin (B); And the SP value of the thermoplastic resin (A) ≥ the SP value of the thermoplastic resin (B) is satisfied, where the SP value is a solubility parameter.

30. The method for producing a resin composition according to claim 29, wherein The resin composition is the resin composition according to any one of claims 13 to 18.

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