Resin composition and electromagnetic wave absorber

Abstract

To provide a resin composition having high absorptivity of electromagnetic waves and having low transmittance and reflectivity of electromagnetic waves, which is a resin composition for an electromagnetic-wave absorber having small difference in reflectivity due to the difference in frequency of electromagnetic waves and an electromagnetic-wave absorber.SOLUTION: There is provided a resin composition for an electromagnetic-wave absorber which comprises 0.1 to 10.0 pts.mass of a carbon nanotube based on 100 pts.mass of a thermoplastic resin, wherein when the resin composition is molded into 150 mm×150 mm×2 mm thickness, the absorptivity determined by the expression (A) in the frequency of 76.5 GHz is 40.0 to 100%, and when the resin composition is molded into 150 mm×150 mm×2 mm thickness, the difference between the highest value and the lowest value of the reflectivity determined by the expression (B) in the frequency of 70 to 80 GHz is 20.0% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a resin composition for electromagnetic wave absorbers and an electromagnetic wave absorber. [Background technology]

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

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

[0004] In millimeter-wave radar, both transmitted and reflected electromagnetic waves contribute to noise and can cause malfunctions. Therefore, there is increasing demand for materials with high electromagnetic wave absorption and low transmittance and reflectivity. Furthermore, large differences in reflectivity depending on the electromagnetic wave frequency can affect stability and productivity. The present invention aims to solve the above problems and to provide a resin composition for electromagnetic wave absorbers that has a high absorption rate of electromagnetic waves and low transmittance and reflectance of electromagnetic waves, and that has a small difference in reflectance due to differences in electromagnetic wave frequencies, as well as an electromagnetic wave absorber. [Means for solving the problem]

[0005] Based on the above problems, the inventors conducted studies and found that the above problems were solved by the following means. <1> A resin composition comprising a thermoplastic resin and an electromagnetic wave absorbing material, A resin composition for use as an electromagnetic wave absorber, wherein when the resin composition is molded to a thickness of 150 mm × 150 mm × 2 mm, the absorption rate determined according to formula (A) at a frequency of 76.5 GHz is 40.0 to 100%, and when the resin composition is molded to a thickness of 150 mm × 150 mm × 2 mm, the difference between the highest and lowest reflectance values ​​determined according to formula (B) in the frequency range of 70 GHz to 80 GHz is 20.0% or less. Formula (A)

number

number

Number

Number

Number

[0006] According to the present invention, there is provided a resin composition for an electromagnetic wave absorber having a high electromagnetic wave absorption rate, low electromagnetic wave transmittance and reflectance, and a small difference in reflectance due to differences in the frequency of electromagnetic waves, and an electromagnetic wave absorber can be provided. [Modes for Carrying Out the Invention]

[0007] Hereinafter, modes for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. The following present embodiment is an exemplification for explaining the present invention, and the present invention is not limited only to the present embodiment. In the present specification, "~" is used to mean including the numerical values described before and after it as lower and upper limits. In the present specification, various physical property values and characteristic values are those at 23°C unless otherwise specified. In the present specification, the weight average molecular weight and the number average molecular weight are polystyrene conversion values measured by the GPC (gel permeation chromatography) method unless otherwise specified. In the present specification, the units of the reflection attenuation and the transmission attenuation are "dB" (decibel).

[0008] The resin composition of this embodiment is a resin composition comprising a thermoplastic resin and an electromagnetic wave absorbing material, The resin composition, when molded to a thickness of 150 mm × 150 mm × 2 mm, has an absorption rate of 40.0 to 100% at a frequency of 76.5 GHz, determined according to formula (A), and when molded to a thickness of 150 mm × 150 mm × 2 mm, the difference between the highest and lowest reflectance values ​​determined according to formula (B) in the frequency range of 70 GHz to 80 GHz is 20.0% or less, and is characterized as being suitable for use as an electromagnetic wave absorber. Formula (A)

number

number

[0009] <Thermoplastic resin> The resin composition of this embodiment includes a thermoplastic resin. Examples of thermoplastic resins 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 it is more preferable to include at least one of polyolefin resins (preferably polypropylene resins), polycarbonate resins, polyphenylene ether resins, polyester resins, and polyamide resins, even more preferable to include at least one of polycarbonate resins, polyphenylene ether resins, polyester resins, and polyamide resins, and even more preferable to include polybutylene terephthalate resins.

[0010] In this embodiment, a preferred example of the thermoplastic resin is that it contains a polyester resin (preferably a polybutylene terephthalate resin), and that 90% or more (preferably 95% or more by mass) of the resin composition is polyester resin (preferably a polybutylene terephthalate resin). Another preferred example of the thermoplastic resin in this embodiment is that it includes a polycarbonate resin, wherein 90% or more (preferably 95% or more by mass) of the resin composition is polycarbonate resin. Another preferred example of the thermoplastic resin in this embodiment is that it contains a polyphenylene ether resin, wherein 90% or more (preferably 95% or more by mass) of the resin composition is polyphenylene ether resin. In this embodiment, a preferred example of the thermoplastic resin is that it includes a polyolefin resin (preferably a polypyropylene resin), and that 90% or more (preferably 95% or more by mass) of the resin composition is a polyolefin resin (preferably a polypropylene resin). Another preferred example of the thermoplastic resin in this embodiment is that it contains a polyamide resin, and that 90% or more (preferably 95% or more by mass) of the resin composition is a polyamide resin. Examples of polyamide resins in this embodiment include xylylenediamine-based polyamide resins and aliphatic polyamide resins (preferably polyamide 1010), which will be described later.

[0011] The resin composition of this embodiment may also be an alloy of two or more thermoplastic resins. When two or more thermoplastic resins are blended, they usually do not completely miscible, forming a sea-island structure. Electromagnetic wave absorbing materials (preferably carbon nanotubes) are less likely to exist in these island areas. As a result, the region where electromagnetic wave absorbing materials exist in the resin composition or electromagnetic wave absorber becomes smaller, and various properties such as electromagnetic wave absorption can be effectively achieved even with a reduced amount of electromagnetic wave absorbing material (preferably carbon nanotubes). For example, an embodiment is described in which polybutylene terephthalate resin is blended with polycarbonate resin and / or polystyrene resin.

[0012] The following are preferred blend forms for the resin composition of this embodiment. The first blend form contains 1.0 to 75 parts by mass of polycarbonate resin per 100 parts by mass of polybutylene terephthalate resin. By incorporating polycarbonate resin, the warping of the resulting electromagnetic wave absorber can be effectively suppressed. In the first blend form, preferably 90% or more by mass, more preferably 95% or more by mass, and even more preferably 99% or more by mass of the resin components contained in the resin composition consist of polybutylene terephthalate resin and polycarbonate resin. The lower limit of the polycarbonate resin content in the first blend form is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 40 parts by mass or more, even more preferably 45 parts by mass or more, and even more preferably 50 parts by mass or more. Setting the content above the lower limit tends to reduce the amount of warping of the molded product. The upper limit of the polycarbonate resin content in the first blend form is preferably 70 parts by mass or less, and more preferably 65 parts by mass or less. Setting the content below the upper limit tends to further improve chemical resistance and hydrolysis resistance. In the first blend form, one type of polycarbonate resin may be used, or two or more types may be used. When two or more types are used, it is preferable that the total amount is within the above range.

[0013] The second blend form contains 1.0 to 60 parts by mass of polystyrene resin (preferably AS resin) per 100 parts by mass of polybutylene terephthalate resin. By incorporating polystyrene resin, the warping of the resulting electromagnetic wave absorber can be effectively suppressed. In the second blend form, 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 consist of polybutylene terephthalate resin and polystyrene resin (preferably AS resin). The lower limit of the polystyrene resin (preferably AS resin) content in the second blend form is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, even more preferably 25 parts by mass or more, and even more preferably 30 parts by mass or more. Setting the content above the lower limit tends to reduce the amount of warping of the molded product. The upper limit of the polystyrene resin (preferably AS resin) content in the second blend form is preferably 90 parts by mass or less, and more preferably 80 parts by mass or less. Setting the content below the upper limit tends to improve the effect of chemical resistance. In the second blend form, one type of polystyrene resin may be used, or two or more types may be used. When two or more types are used, it is preferable that the total amount is within the above range.

[0014] The third blend form contains 1.0 to 75 parts by mass of polycarbonate resin and 1.0 to 60 parts by mass of polystyrene resin (preferably HIPS) per 100 parts by mass of polybutylene terephthalate resin. By blending polystyrene resin and polycarbonate resin, the warping of the resulting electromagnetic wave absorber can be effectively suppressed. In the third blend form, preferably 90% or more by mass, more preferably 95% or more by mass, and even more preferably 99% or more by mass of the resin components contained in the resin composition consist of polybutylene terephthalate resin, polycarbonate resin and polystyrene resin (preferably HIPS).

[0015] The lower limit of the styrene resin content (preferably HIPS) in the third blend form is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, even more preferably 35 parts by mass or more, and even more preferably 38 parts by mass or more. Setting the content above the lower limit tends to reduce the amount of warping of the molded product. The upper limit of the styrene resin content in the third blend form is preferably 70 parts by mass or less, more preferably 65 parts by mass or less, even more preferably 60 parts by mass or less, even more preferably 55 parts by mass or less, and even more preferably 50 parts by mass or less. Setting the content below the upper limit tends to improve chemical resistance. The lower limit of the polycarbonate resin content in the third blend form is preferably 4 parts by mass or more, more preferably 8 parts by mass or more, even more preferably 10 parts by mass or more, and even more preferably 12 parts by mass or more. Setting the content above the lower limit tends to reduce the amount of warping of the molded product. The upper limit of the polycarbonate resin content in the third blend form is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, even more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, and even more preferably 18 parts by mass or less. Setting the content below the upper limit tends to improve chemical resistance and hydrolysis resistance. In the third blend form, the mass ratio of polycarbonate resin to styrene resin is preferably 1:2.0 to 4.0, and more preferably 1:2.5 to 3.5. By using such a mass ratio, warping of the molded product is suppressed and mechanical strength tends to be further improved. In the third blend form, styrene resin and polycarbonate resin may be used individually or in combination of two or more types. When using two or more types, it is preferable that the total amount be within the above range.

[0016] The following describes the details of each thermoplastic resin. <<Polyester resin>> As the polyester resin, known thermoplastic polyester resins can be used, with polyethylene terephthalate resin and polybutylene terephthalate resin being preferred, and more preferably containing at least polybutylene terephthalate resin.

[0017] The polybutylene terephthalate resin used in the resin composition of this embodiment is a polyester resin having a structure in which terephthalic acid units and 1,4-butanediol units are ester-bonded, and includes, in addition to the polybutylene terephthalate resin (homopolymer), a polybutylene terephthalate copolymer containing other copolymer components other than terephthalic acid units and 1,4-butanediol units, or a mixture of the homopolymer and the polybutylene terephthalate copolymer.

[0018] Polybutylene terephthalate resin may contain one or more dicarboxylic acid units other than terephthalic acid. Other specific examples of dicarboxylic acids include aromatic dicarboxylic acids such as isophthalic acid, orthophthalic acid, 1,5-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, biphenyl-2,2'-dicarboxylic acid, biphenyl-3,3'-dicarboxylic acid, biphenyl-4,4'-dicarboxylic acid, bis(4,4'-carboxyphenyl)methane, anthracenedicarboxylic acid, and 4,4'-diphenyletherdicarboxylic acid; alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid and 4,4'-dicyclohexyldicarboxylic acid; and aliphatic dicarboxylic acids such as adipic acid, sebacic acid, azelaic acid, and dimer acid. In this embodiment, the polybutylene terephthalate resin preferably contains terephthalic acid units accounting for 80 mol% or more of the total dicarboxylic acid units, and more preferably 90 mol% or more.

[0019] The diol unit may include one or more other diol units in addition to 1,4-butanediol. Other specific examples of diol units include aliphatic or alicyclic diols with 2 to 20 carbon atoms, and bisphenol derivatives. Specific examples include ethylene glycol, propylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, decamethylene glycol, cyclohexanedimethylol, 4,4'-dicyclohexylhydroxymethane, 4,4'-dicyclohexylhydroxypropane, and ethylene oxide addition diols of bisphenol A. In addition to the bifunctional monomers mentioned above, small amounts of trifunctional monomers such as trimellitic acid, trimesic acid, pyromellitic acid, pentaerythritol, and trimethylolpropane can be used to introduce branched structures, and small amounts of monofunctional compounds such as fatty acids can be used to adjust molecular weight. In this embodiment, the polybutylene terephthalate resin preferably contains 1,4-butanediol units accounting for 80 mol% or more of the total diol units, and more preferably 90 mol% or more.

[0020] As described above, the polybutylene terephthalate resin is preferably a polybutylene terephthalate homopolymer obtained by polycondensation of terephthalic acid and 1,4-butanediol. Alternatively, it may be a polybutylene terephthalate copolymer containing one or more dicarboxylic acids other than terephthalic acid as the carboxylic acid unit and / or one or more diols other than 1,4-butanediol as the diol unit. When the polybutylene terephthalate resin is a polybutylene terephthalate resin modified by copolymerization, specific preferred copolymers include polyester ether resins copolymerized with polyalkylene glycols, particularly polytetramethylene glycol, dimer acid copolymerized polybutylene terephthalate resins, and isophthalic acid copolymerized polybutylene terephthalate resins. Among these, it is preferable to use a polyester ether resin copolymerized with polytetramethylene glycol. These copolymers refer to those with a copolymerization amount of 1 mol% or more and less than 50 mol% of the total segments of the polybutylene terephthalate resin. In particular, 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 copolymerization ratios tend to improve fluidity, toughness, and tracking resistance, and are therefore preferable.

[0021] The amount of terminal carboxyl groups in polybutylene terephthalate resin can be appropriately selected and determined, but is usually 60 eq / ton or less, preferably 50 eq / ton or less, and more preferably 30 eq / ton or less. Keeping it below the above upper limit tends to improve alkali resistance and hydrolysis resistance. There is no specific lower limit for the amount of terminal carboxyl groups, but considering the productivity of polybutylene terephthalate resin production, it is usually 10 eq / ton or more.

[0022] The amount of terminal carboxyl groups in polybutylene terephthalate resin is measured by dissolving 0.5 g of polybutylene terephthalate resin in 25 mL of benzyl alcohol and titrating it with a 0.01 mol / L benzyl alcohol solution of sodium hydroxide. The amount of terminal carboxyl groups can be adjusted by any conventionally known method, such as adjusting polymerization conditions like the raw material ratio, polymerization temperature, and reduced pressure method during polymerization, or by reacting with a chelating agent.

[0023] The intrinsic viscosity of the polybutylene terephthalate resin is preferably 0.5 to 2 dL / g. From the viewpoint of moldability and mechanical properties, an intrinsic viscosity in the range of 0.6 to 1.5 dL / g is more preferable. Setting the intrinsic viscosity to 0.5 dL / g or higher tends to further improve the mechanical strength of the resulting resin composition. Conversely, setting it to 2 dL / g or lower tends to further improve the fluidity of the resin composition and thus improve moldability. The intrinsic viscosity of polybutylene terephthalate resin is measured at 30°C in a 1:1 (mass ratio) mixed solvent of tetrachloroethane and phenol.

[0024] Polybutylene terephthalate resin can be produced by melt polymerization of a dicarboxylic acid component mainly composed of terephthalic acid or ester derivatives thereof, and a diol component mainly composed of 1,4-butanediol, in a batch or continuous manner. 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 atmosphere or reduced pressure. The polybutylene terephthalate resin is preferably obtained by a manufacturing method in which a dicarboxylic acid component mainly composed of terephthalic acid and a diol component mainly composed of 1,4-butanediol are continuously melt-polycondensed.

[0025] The catalyst used in carrying out the esterification reaction may be one of the conventionally known ones, such as titanium compounds, tin compounds, magnesium compounds, and calcium compounds. Among these, titanium compounds are particularly preferred. Specific examples of titanium compounds as esterification catalysts include titanium alcoholates such as tetramethyl titanate, tetraisopropyl titanate, and tetrabutyl titanate, and titanium phenolates such as tetraphenyl titanate.

[0026] In addition to the above, the description in paragraphs 0013 to 0016 of Japanese Patent Publication No. 2010-174223 can be given to the polyester resin, and its contents are incorporated herein by reference.

[0027] In the resin composition of this embodiment, the content of polybutylene terephthalate resin is preferably 30% by mass or more, more preferably 35% by mass or more, even more preferably 37% by mass or more, and even more preferably 40% by mass or more. Setting it above the lower limit tends to further improve chemical resistance. Furthermore, when the resin composition contains polybutylene terephthalate resin, the content of polybutylene terephthalate resin is preferably 80% by mass or less, more preferably 75% by mass or less, even more preferably 72% by mass or less, even more preferably 66% by mass or less, even more preferably 60% by mass or less, and may also be 55% by mass or less, 50% by mass or less, or 47% by mass or less. Setting it below the upper limit tends to more effectively reduce the amount of warpage of the molded product. The resin composition of this embodiment may contain only one type of polybutylene terephthalate resin, or it may contain two or more types. When it contains two or more types, it is preferable that the total amount is within the above range.

[0028] <<Polycarbonate resin>> Polycarbonate resin is a branched homopolymer or copolymer obtained by reacting a dihydroxy compound, or a small amount thereof, with a polyhydroxy compound with phosgene or a diester carbonate. The method for producing polycarbonate resin is not particularly limited, and conventionally known methods such as the phosgene method (interfacial polymerization) or the melting method (transesterification) can be used.

[0029] As the raw material dihydroxy compound, aromatic dihydroxy compounds are preferred, including 2,2-bis(4-hydroxyphenyl)propane (=bisphenol A), tetramethylbisphenol A, bis(4-hydroxyphenyl)-p-diisopropylbenzene, hydroquinone, resorcinol, 4,4-dihydroxydiphenyl, and others, with bisphenol A being preferred. In addition, compounds in which one or more tetraalkylphosphonium sulfonates are bonded to the above aromatic dihydroxy compounds can also be used.

[0030] Among the polycarbonate resins mentioned above, aromatic polycarbonate resins derived from 2,2-bis(4-hydroxyphenyl)propane, or aromatic polycarbonate copolymers derived from 2,2-bis(4-hydroxyphenyl)propane and other aromatic dihydroxy compounds are preferred. Alternatively, copolymers mainly composed of aromatic polycarbonate resins, such as copolymers with polymers or oligomers having a siloxane structure, may also be used. Furthermore, two or more of the above-mentioned polycarbonate resins may be mixed and used.

[0031] To adjust the molecular weight of polycarbonate resin, monovalent aromatic hydroxy compounds can be used, such as m- and p-methylphenol, m- and p-propylphenol, p-tert-butylphenol, and p-long-chain alkyl-substituted phenols.

[0032] The viscosity-average molecular weight (Mv) of the polycarbonate resin is preferably 5,000 or more, more preferably 10,000 or more, and even more preferably 13,000 or more. Using a resin with a viscosity-average molecular weight of 5,000 or more tends to improve the mechanical strength of the resulting resin composition. Furthermore, the viscosity-average molecular weight (Mv) of the polycarbonate resin is preferably 60,000 or less, more preferably 40,000 or less, and even more preferably 30,000 or less. Using a resin with a viscosity-average molecular weight of 60,000 or less tends to improve the fluidity of the resin composition and improve its moldability.

[0033] In this embodiment, the viscosity-average molecular weight (Mv) of the polycarbonate resin is calculated using an Ubbelohde viscometer to determine the intrinsic viscosity ([η]) of the methylene chloride solution of the polycarbonate resin at 20°C, and the value is derived from Schnell's viscosity formula. [η] = 1.23 × 10 -4 Mv 0.83

[0034] The method for producing the polycarbonate resin is not particularly limited, and polycarbonate resin produced by either the phosgene method (interfacial polymerization method) or the melting method (transesterification method) can be used. Furthermore, polycarbonate resin produced by the melting method and then subjected to post-treatment to adjust the amount of terminal OH groups is also preferred.

[0035] <<Polystyrene resin>> Examples of polystyrene resins include homopolymers of styrene monomers and copolymers of styrene monomers with other copolymerizable monomers. More specifically, polystyrene-based resins include polystyrene resin, acrylonitrile-styrene copolymer (AS resin), high-impact polystyrene-based resin (HIPS), acrylonitrile-butadiene-styrene copolymer (ABS resin), acrylonitrile-acrylic rubber-styrene copolymer (AAS resin), acrylonitrile-styrene-acrylic rubber copolymer (ASA resin), acrylonitrile-ethylene propylene rubber-styrene copolymer (AES resin), styrene-IPN type rubber copolymer, and other resins.

[0036] When a polystyrene resin contains rubber components, the content of rubber components in the polystyrene resin is preferably 3 to 70% by mass, more preferably 5 to 50% by mass, and even more preferably 7 to 30% by mass. A rubber component content of 3% by mass or more tends to improve impact resistance, while a content of 50% by mass or less tends to improve flame retardancy, which is preferable. Furthermore, the average particle size of the rubber components is preferably 0.05 to 10 μm, more preferably 0.1 to 6 μm, and even more preferably 0.2 to 3 μm. An average particle size of 0.05 μm or more tends to improve impact resistance, while an average particle size of 10 μm or less tends to improve appearance, which is preferable.

[0037] The weight-average molecular weight of polystyrene resins is typically 50,000 or more, preferably 100,000 or more, more preferably 150,000 or more, and also typically 500,000 or less, preferably 400,000 or less, and more preferably 300,000 or less. The number-average molecular weight is typically 10,000 or more, preferably 30,000 or more, more preferably 50,000 or more, and also preferably 500,000 or less, and more preferably 300,000 or less.

[0038] The melt flow rate (MFR) of polystyrene resins, measured in accordance with JIS K7210 (temperature 200°C, load 5 kgf), is preferably 0.1 to 30 g / 10 min, and more preferably 0.5 to 25 g / 10 min. When the MFR is 0.1 g / 10 min or higher, fluidity tends to improve, and when it is 30 g / 10 min or lower, impact resistance tends to improve.

[0039] Known methods for producing such polystyrene resins include emulsion polymerization, solution polymerization, suspension polymerization, and bulk polymerization.

[0040] <<Polyphenylene ether resin>> In this embodiment, a known polyphenylene ether resin can be used. For example, a polymer having a structural unit represented by the following formula in the main chain (preferably, a polymer in which the structural unit represented by the following formula occupies 90 mol% or more of all the structural units excluding the terminal groups) is exemplified. The polyphenylene ether resin may be either a homopolymer or a copolymer.

[0041] [Chemical formula] (In the formula, two Rs a each independently represent a hydrogen atom, a halogen atom, a primary or secondary alkyl group, an aryl group, an aminoalkyl group, a halogenated alkyl group, a hydrocarbon oxy group, or a halogenated hydrocarbon oxy group, and two Rs b each independently represent a hydrogen atom, a halogen atom, a primary or secondary alkyl group, an aryl group, a halogenated alkyl group, a hydrocarbon oxy group, or a halogenated hydrocarbon oxy group. However, the two Rs a do not both become hydrogen atoms.)

[0042] R a and R b are each independently preferably a hydrogen atom, a primary or secondary alkyl group, or an aryl group. Preferred examples of the primary alkyl group include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-amyl group, an isoamyl group, a 2-methylbutyl group, a 2,3-dimethylbutyl group, a 2-, 3-, or 4-methylpentyl group, or a heptyl group. Preferred examples of the secondary alkyl group include, for example, an isopropyl group, a sec-butyl group, or a 1-ethylpropyl group. In particular, R a is preferably a primary or secondary alkyl group having 1 to 4 carbon atoms or a phenyl group. R b is preferably a hydrogen atom.

[0043] Suitable homopolymers of polyphenylene ether resins include, for example, polymers of 2,6-dialkylphenylene ethers such as poly(2,6-dimethyl-1,4-phenylene) ether, poly(2,6-diethyl-1,4-phenylene ether), poly(2,6-dipropyl-1,4-phenylene ether), poly(2-ethyl-6-methyl-1,4-phenylene ether), and poly(2-methyl-6-propyl-1,4-phenylene ether). Examples of copolymers include 2,6-dimethylphenol / 2,3,6-trimethylphenol copolymers, 2,6-dimethylphenol / 2,3,6-triethylphenol copolymers, 2,6-diethylphenol / 2,3,6-trimethylphenol copolymers, 2,6-dipropylphenol / 2,3,6-trimethylphenol copolymers, and other 2,6-dialkylphenol / 2,3,6-trialkylphenol copolymers; graft copolymers obtained by graft polymerization of styrene onto poly(2,6-dimethyl-1,4-phenylene ether); and graft copolymers obtained by graft polymerization of styrene onto 2,6-dimethylphenol / 2,3,6-trimethylphenol copolymers.

[0044] In this embodiment, poly(2,6-dimethyl-1,4-phenylene) ether and 2,6-dimethylphenol / 2,3,6-trimethylphenol random copolymers are particularly preferred as the polyphenylene ether resin. Polyphenylene ether resins with specified terminal group counts and copper content, as described in Japanese Patent Application Publication No. 2005-344065, can also be suitably used.

[0045] The polyphenylene ether resin is preferably one with an intrinsic viscosity of 0.2 to 0.8 dL / g, and more preferably 0.3 to 0.6 dL / g, measured in chloroform at 30°C. A viscosity of 0.2 dL / g or higher tends to improve the mechanical strength of the resin composition, while a viscosity of 0.8 dL / g or lower tends to improve fluidity and facilitate molding. Alternatively, two or more polyphenylene ether resins with different intrinsic viscosities may be used in combination to achieve this viscosity range.

[0046] The method for producing the polyphenylene ether resin used in this embodiment is not particularly limited, and a known method can be employed, for example, by oxidative polymerization of a monomer such as 2,6-dimethylphenol in the presence of an amine copper catalyst. In this case, the intrinsic viscosity can be controlled to a desired range by selecting the reaction conditions. Control of the intrinsic viscosity can be achieved by selecting conditions such as polymerization temperature, polymerization time, and catalyst amount.

[0047] <<Polyolefin resin>> Examples of polyolefin resins include polyethylene, polypropylene, polybutene-1, and poly-4-methylpentene, as well as copolymers thereof. Examples of polyethylene include low-density polyethylene and high-density polyethylene. Examples of polypropylene include crystalline or amorphous polypropylene. Examples of the copolymers include random, block, or graft copolymers of ethylene-propylene, copolymers of α-olefin and ethylene or propylene, ethylene-vinyl acetate copolymers, ethylene-methyl acrylate copolymers, ethylene-ethyl acrylate copolymers, and ethylene-acrylic acid copolymers. Among these, crystalline or amorphous polypropylene, and random, block, or graft copolymers of ethylene-propylene are preferred, with propylene-ethylene block copolymers being more preferred. Furthermore, polypropylene resin is preferred from the viewpoint of being inexpensive and having a low specific gravity, which allows for lighter molded products.

[0048] The melt flow rate (MFR) of the polyolefin resin is preferably 0.1 to 5.0 g / 10 min.

[0049] <<Polyamide resin>> Polyamide resins are polymers whose constituent units are acid amides obtained by ring-opening polymerization of lactams, polycondensation of aminocarboxylic acids, and polycondensation of diamines and dibasic acids. Specifically, examples include polyamides 6, 11, 12, 46, 66, 610, 612, 6I, 6 / 66, 6T / 6I, 6 / 6T, 66 / 6T, 66 / 6T / 6I, 1010, xylylenediamine-based polyamide resins (details to be described later), polytrimethylhexamethylene terephthalamide, polybis(4-aminocyclohexyl)methanedodecamamide, polybis(3-methyl-4-aminocyclohexyl)methanedodecamamide, and polyundemethylenehexahydroterephthalamide. Note that "I" indicates the isophthalic acid component and "T" indicates the terephthalic acid component. Furthermore, as a polyamide resin, reference can be given to the description in paragraphs 0011 to 0013 of Japanese Patent Publication No. 2011-132550, which is incorporated herein by reference.

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

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

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

[0053] The content of the thermoplastic resin (preferably polybutylene terephthalate resin) in the resin composition of this embodiment is preferably 30% by mass or more, more preferably 35% by mass or more, even more preferably 37% by mass or more, and even more preferably 40% by mass or more. Setting it above the lower limit tends to further improve chemical resistance. Furthermore, the content of the thermoplastic resin (preferably polybutylene terephthalate resin) is preferably 80% by mass or less, more preferably 75% by mass or less, even more preferably 72% by mass or less, even more preferably 66% by mass or less, even more preferably 60% by mass or less, and may also be 55% by mass or less, 50% by mass or less, or 47% by mass or less. Setting it below the upper limit tends to more effectively reduce the amount of warpage of the molded product. The resin composition of this embodiment may contain only one type of thermoplastic resin, or it may contain two or more types. When it contains two or more types, it is preferable that the total amount is within the above range.

[0054] <Electromagnetic wave absorbing material> The resin composition of this embodiment includes an electromagnetic wave absorbing material. By including the electromagnetic wave absorbing material, the resin composition can be given electromagnetic wave absorbing properties. Examples of electromagnetic wave absorbing materials used in this embodiment include metals, metal oxides, carbon-containing electromagnetic wave absorbing materials, and conductive polymers, with carbon-containing electromagnetic wave absorbing materials being preferred. Examples of metals include copper, nickel, silver, and stainless steel, with metal fillers, stainless steel fibers, and magnetic fillers being preferred. Examples of metal oxides include alumina and zinc oxide, with alumina fibers and zinc oxide nanotubes being preferred. Preferred carbon-containing electromagnetic wave absorbing materials include carbon black, Ketjencarbon, graphene, graphite, fullerene, carbon nanocoils, carbon nanotubes, and carbon fibers, with carbon nanotubes being more preferred. Fibers coated with metals, metal oxides, or carbon-containing electromagnetic wave absorbing materials are also preferred. Examples include carbon-coated potassium titanate whiskers and metal-coated fibers.

[0055] In this embodiment, the electromagnetic wave absorbing material is preferably in a relatively thin and long shape, such as fibrous, tubular, or whisker-like. The diameter (number-average fiber diameter) of the electromagnetic wave absorbing material is preferably 0.5 nm or more, more preferably 1 nm or more, even more preferably 3 nm or more, and also preferably 50 μm or less, more preferably 20 μm or less, even more preferably 500 nm or less, and even more preferably 100 nm or less. From the viewpoint of providing good electromagnetic wave absorption, the aspect ratio of the electromagnetic wave absorbing material is preferably 5 or higher, and more preferably 50 or higher. There is no specific upper limit, but for example, it is 500 or less.

[0056] As mentioned above, carbon-based electromagnetic wave absorbing materials include carbon black, graphite, carbon fibers, and carbon nanotubes. In this embodiment, by selecting carbon nanotubes from among these carbon-based electromagnetic wave absorbing materials, the absorption rate of electromagnetic waves is high, the transmittance and reflectance of electromagnetic waves are low, and the difference in reflectance is reduced regardless of frequency. In addition, the mechanical strength of the resulting molded body can be increased.

[0057] The carbon nanotubes used in this embodiment may be single-walled carbon nanotubes, multi-walled carbon nanotubes, or a mixture, but it is preferable that they include multi-walled carbon nanotubes. Carbon materials that partially have a carbon nanotube structure can also be used. Furthermore, the carbon nanotubes are not limited to a cylindrical shape, but may have a coiled shape in which a helix completes one turn with a pitch of 1 μm or less. Carbon nanotubes are commercially available, and examples include those from Bayer MaterialScience, NanoSil, Showa Denko Corporation, and Hyperion Catalysis International. They are also sometimes referred to as graphite fibrils or carbon fibrils. The diameter of the carbon nanotubes is preferably 0.5 to 100 nm, and more preferably 1 to 30 nm. The aspect ratio of the carbon nanotubes is preferably 5 or higher, and more preferably 50 or higher, from the viewpoint of providing good electromagnetic wave absorption. There is no specific upper limit, but for example, it is 500 or less.

[0058] The resin composition of this embodiment preferably contains 0.1 to 10.0 parts by mass of an electromagnetic wave absorbing material (preferably carbon nanotubes) per 100 parts by mass of a thermoplastic resin (preferably polybutylene terephthalate resin). By including an electromagnetic wave absorbing material (preferably carbon nanotubes), electromagnetic waves can be effectively absorbed even with a small amount of the material. Furthermore, the transmission and reflection of electromagnetic waves can be effectively suppressed. In addition, the difference in reflectivity for electromagnetic waves with frequencies of 70 to 80 GHz can be reduced. Moreover, the mechanical strength of the resulting molded article can be increased.

[0059] The resin composition of this embodiment preferably contains 0.1 parts by mass or more of an electromagnetic wave absorbing material (preferably carbon nanotubes) per 100 parts by mass of thermoplastic resin, more preferably 1.0 part by mass or more, even more preferably 1.5 parts by mass or more, even more preferably 1.8 parts by mass or more, and even more preferably 2.0 parts by mass or more. By setting the amount above the lower limit, the electromagnetic wave absorbing properties are effectively exhibited. Furthermore, the resin composition of this embodiment preferably contains 10.0 parts by mass or less of an electromagnetic wave absorbing material (preferably carbon nanotubes) per 100 parts by mass of thermoplastic resin, more preferably 8.0 parts by mass or less, more preferably 7.0 parts by mass or less, and even more preferably 6.0 parts by mass or less. By setting the amount below the upper limit, the amount of glass fiber can be relatively increased, and the mechanical strength of the resulting molded article can be increased.

[0060] In particular, when the resin composition of this embodiment contains polybutylene terephthalate resin, and more particularly when the resin component consists substantially only of polybutylene terephthalate resin, the resin composition of this embodiment preferably contains an electromagnetic wave absorbing material (preferably carbon nanotubes) in an amount of 0.1 parts by mass or more, more preferably 1.0 part by mass or more, even more preferably 1.5 parts by mass or more, even more preferably 1.8 parts by mass or more, even more preferably 2.0 parts by mass or more, even more preferably 3.0 parts by mass or more, and most preferably more than 3.0 parts by mass. By setting the amount to above the lower limit, the electromagnetic wave absorbing properties are effectively exhibited. Furthermore, the resin composition of this embodiment preferably contains an electromagnetic wave absorbing material (preferably carbon nanotubes) in an amount of 10.0 parts by mass or less, more preferably 8.0 parts by mass or less, even more preferably 7.0 parts by mass or less, even more preferably 6.0 parts by mass or less, even more preferably 5.0 parts by mass or less, and even more preferably 4.0 parts by mass or less, per 100 parts by mass of polybutylene terephthalate resin. By keeping the amount below the above upper limit, for example, the amount of glass fiber can be relatively increased, and the mechanical strength of the resulting molded article can be increased.

[0061] One embodiment of the resin composition of this embodiment is one in which carbon-based electromagnetic wave absorbing materials other than carbon nanotubes are either not included or included in amounts of less than 3% by mass of the resin composition. By adopting such a configuration, the frequency dependence of the reflectivity of electromagnetic waves tends to be further improved. In this embodiment, the content of carbon-based electromagnetic wave absorbing materials other than carbon nanotubes is preferably less than 2% by mass, more preferably less than 1% by mass, even more preferably less than 0.5% by mass, even more preferably less than 0.1% by mass, even more preferably less than 0.05% by mass, and even more preferably less than 0.01% by mass.

[0062] One embodiment of the resin composition of this embodiment is that it does not contain carbon fibers or contains less than 3% by mass of carbon fibers. This configuration tends to improve the frequency dependence of the electromagnetic wave reflectivity. Furthermore, it can lower the electromagnetic wave reflectivity. In this embodiment, the carbon fiber content is preferably less than 2% by mass, more preferably less than 1% by mass, even more preferably less than 0.5% by mass, even more preferably less than 0.1% by mass, even more preferably less than 0.05% by mass, and even more preferably less than 0.01% by mass.

[0063] Another embodiment of the resin composition of this embodiment is graphite-free or contains less than 3% by mass of graphite. Such a configuration tends to improve the frequency dependence of the electromagnetic wave reflectivity. Furthermore, it allows for a higher electromagnetic wave absorption rate. Additionally, it can further improve the mechanical strength of the resulting electromagnetic wave absorber. In this embodiment, the graphite content is preferably less than 2% by mass, more preferably less than 1% by mass, even more preferably less than 0.5% by mass, even more preferably less than 0.1% by mass, even more preferably less than 0.05% by mass, and even more preferably less than 0.01% by mass.

[0064] Another embodiment of the resin composition of this embodiment also contains no carbon black or has a carbon black content of less than 3% by mass. Such a configuration tends to further improve the frequency dependence of the electromagnetic wave reflectivity. Furthermore, it can further improve the mechanical strength of the resulting electromagnetic wave absorber. In this embodiment, the carbon black content is preferably less than 2% by mass, more preferably less than 1% by mass, even more preferably less than 0.5% by mass, even more preferably less than 0.1% by mass, even more preferably less than 0.05% by mass, and even more preferably less than 0.01% by mass.

[0065] Another embodiment of the resin composition of this embodiment also contains no Ketjenblack or contains less than 3% by mass of Ketjenblack. Such a configuration tends to further improve the frequency dependence of the electromagnetic wave reflectivity. Furthermore, it can further improve the mechanical strength of the resulting electromagnetic wave absorber. In this embodiment, the Ketjenblack content is preferably less than 2% by mass, more preferably less than 1% by mass, even more preferably less than 0.5% by mass, even more preferably less than 0.1% by mass, even more preferably less than 0.05% by mass, and even more preferably less than 0.01% by mass.

[0066] Furthermore, embodiments that satisfy two or more of the above embodiments are also preferred. Moreover, embodiments that satisfy all of the above embodiments are also preferred.

[0067] The content of the electromagnetic wave absorbing material (preferably carbon nanotubes) in the resin composition of this embodiment is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1.0% by mass or more. Setting it above the lower limit tends to yield more stable electromagnetic wave absorption performance. Setting it below the upper limit tends to maintain a high impact resistance strength of the resin composition. The resin composition of this embodiment may contain only one type of electromagnetic wave absorbing material (preferably carbon nanotubes), or it may contain two or more types. When two or more types are included, it is preferable that the total amount is within the above range.

[0068] <Glass fiber> The resin composition of this embodiment contains 10 to 100 parts by mass of glass fiber per 100 parts by mass of thermoplastic resin (preferably polybutylene terephthalate resin). By including glass fiber, the mechanical strength of the electromagnetic wave absorber formed from the resin composition of this embodiment can be improved. The glass fibers are selected from glass compositions such as A glass, C glass, E glass, R glass, D glass, M glass, and S glass, with E glass (alkali-free glass) being particularly preferred. Glass fibers refer to fibrous materials whose cross-sectional shape, when cut perpendicular to the length, is circular or polygonal. Glass fibers typically have a number-average fiber diameter of 1 to 25 μm, preferably 5 to 17 μm. A number-average fiber diameter of 1 μm or more tends to improve the moldability of the resin composition. A number-average fiber diameter of 25 μm or less tends to improve the appearance of the resulting electromagnetic wave absorber and enhance its reinforcing effect. Glass fibers may be single fibers or multiple single fibers twisted together. The glass fibers may take any form, such as glass roving made by continuously winding single fibers or multiple strands twisted together, chopped strands cut to a length of 1 to 10 mm (i.e., glass fibers with a number-average fiber length of 1 to 10 mm), or milled fibers crushed to a length of approximately 10 to 500 μm (i.e., glass fibers with a number-average fiber length of 10 to 500 μm), but chopped strands cut to a length of 1 to 10 mm are preferred. Glass fibers with different forms can also be used in combination. Furthermore, glass fibers having an irregular cross-sectional shape are also preferred. This irregular cross-sectional shape refers to a flattening ratio, which is indicated by the major axis / minor axis ratio of the cross-section perpendicular to the length direction of the fiber, and is, for example, 1.5 to 10, more preferably 2.5 to 10, even more preferably 2.5 to 8, and particularly preferably 2.5 to 5.

[0069] The glass fibers may be surface-treated with, for example, silane compounds, epoxy compounds, or urethane compounds, or oxidized, in order to improve their affinity with the resin components, as long as the properties of the resin composition of this embodiment are not significantly impaired.

[0070] The resin composition of this embodiment contains 10 parts by mass or more of glass fibers per 100 parts by mass of thermoplastic resin (preferably polybutylene terephthalate resin), preferably 20 parts by mass or more, more preferably 35 parts by mass or more, even more preferably 47 parts by mass or more, even more preferably 55 parts by mass or more, and even more preferably 63 parts by mass or more. Setting the amount above the lower limit tends to further increase the mechanical strength. Furthermore, the glass fiber content is 100 parts by mass or less per 100 parts by mass of thermoplastic resin (preferably polybutylene terephthalate resin), preferably 90 parts by mass or less, more preferably 85 parts by mass or less, even more preferably 80 parts by mass or less, and even more preferably 75 parts by mass or less. Setting the amount below the upper limit tends to improve the appearance of the molded product and further improve the fluidity of the molten resin.

[0071] The glass fiber content in the resin composition of this embodiment is preferably 10% by mass or more, more preferably 15% by mass or more, more preferably 50% by mass or less, even more preferably 45% by mass or less, and still more preferably 40% by mass or less. Setting it above the lower limit tends to further increase the mechanical strength. Setting it below the upper limit tends to improve the appearance of the molded product and further improve the fluidity of the molten resin. The resin composition of this embodiment may contain only one type of glass fiber, or it may contain two or more types. When it contains two or more types, it is preferable that the total amount is within the above range.

[0072] In the resin composition of this embodiment, the mass ratio of electromagnetic wave absorbing material (preferably carbon nanotubes) to glass fibers (electromagnetic wave absorbing material / glass fiber) is 0.01 or higher, preferably 0.02 or higher, more preferably 0.025 or higher, even more preferably 0.04 or higher, and even more preferably 0.05 or higher. Setting it above the lower limit tends to yield higher electromagnetic wave absorption performance. Furthermore, the mass ratio of electromagnetic wave absorbing material to glass fiber is 0.30, preferably 0.20 or lower, more preferably 0.10 or lower, and even more preferably 0.07 or lower. Setting it below the upper limit tends to allow for higher impact resistance of the resin composition to be maintained.

[0073] <Reactive Compounds> The resin composition of this embodiment preferably contains 0.01 to 5.0 parts by mass of the reactive compound per 100 parts by mass of the thermoplastic resin (preferably polybutylene terephthalate resin). By including the reactive compound, a resin composition with improved mechanical strength and excellent hydrolysis resistance can be obtained. The reactive compound used in this embodiment preferably includes at least one selected from the group consisting of compounds having an epoxy group, carbodiimide compounds, compounds having an oxazoline group, and compounds having an oxazine group, and more preferably includes a compound having an epoxy group.

[0074] <<Compounds containing epoxy groups (epoxy resins)>> Compounds having epoxy groups are compounds having one or more epoxy groups in one molecule, and examples include glycidyl compounds, aromatic ring-containing compounds having epoxy groups, and alicyclic compounds having epoxy groups. It is preferable that the compound contains at least one aromatic ring-containing compound having epoxy groups.

[0075] Specific examples of epoxy group-containing compounds include bisphenol A type epoxy compounds (including bisphenol A diglycidyl ether), bisphenol F type epoxy compounds (including bisphenol F diglycidyl ether), biphenyl type epoxy compounds (including bis(glycidyloxy)biphenyl), resorcinol type epoxy compounds (including resorcinol diglycidyl ether), novolac type epoxy compounds, epoxy compounds containing aromatic rings such as glycidyl benzoate, diglycidyl terephthalate, and diglycidyl orthophthalate, methyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, decyl glycidyl ether, and stearyl glycidyl ether. Examples include (di)glycidyl ethers such as methyl phenyl glycidyl ether, butylphenyl glycidyl ether, allyl glycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, and propylene glycol diglycidyl ether; paraffinic (e.g., saturated fatty acid) or olefinic (e.g., unsaturated fatty acid) (di)glycidyl esters such as glycidyl sorbate, diglycidyl adipic acid, epoxidized linseed oil, and epoxidized soybean oil; alicyclic epoxy compounds such as vinylcyclohexene dioxide and dicyclopentadiene oxide; and epoxy-modified styrene-acrylic copolymers. Among these, styrene-acrylic copolymers containing glycidyl groups in the side chain, bisphenol A type epoxy compounds, novolac type epoxy compounds, bisphenol F type epoxy compounds, and biphenyl type epoxy compounds are preferred, with bisphenol A type epoxy compounds being more preferred.

[0076] <<Carbodiimide Compounds>> In the resin composition of this embodiment, it is also preferable to include a carbodiimide compound as a reactive compound. A carbodiimide compound is a compound that contains a carbodiimide group (-N=C=N-) in its molecule. As the carbodiimide compound, any of the following can be used: aliphatic carbodiimide compounds with an aliphatic main chain, alicyclic carbodiimide compounds with an alicyclic main chain, or aromatic carbodiimide compounds with an aromatic main chain. Among these, the use of an aliphatic carbodiimide compound, which has good reactivity with polymer ends, is preferred. The type of carbodiimide compound may be monomeric or polymeric, but in this embodiment, the polymeric type is preferred.

[0077] Examples of the above aliphatic carbodiimide compounds include diisopropylcarbodiimide and dioctyldecylcarbodiimide. Examples of the above alicyclic carbodiimide compounds include dicyclohexylcarbodiimide and poly(4,4'-dicyclohexylmethanecarbodiimide), with poly(4,4'-dicyclohexylmethanecarbodiimide) being particularly preferred. Examples of commercially available products include "Carbodilite" (product name; manufactured by Nisshinbo Chemical Co., Ltd.).

[0078] The above-mentioned aromatic carbodiimide compounds include diphenylcarbodiimide, di-2,6-dimethylphenylcarbodiimide, N-triyl-N'-phenylcarbodiimide, di-p-nitrophenylcarbodiimide, di-p-aminophenylcarbodiimide, di-p-hydroxyphenylcarbodiimide, di-p-chlorophenylcarbodiimide, di-p-methoxyphenylcarbodiimide, di-3,4-dichlorophenylcarbodiimide, di-2,5-dichlorophenylcarbodiimide, di-o-chlorophenylcarbodiimide, p-phenylene-bis-di-o-triylcarbodiimide, p-phenylene-bis-dicyclohexylcarbodiimide, p-phenylene-bis-di-p-chlorophenylcarbodiimide, and ethylene-bis-diphenyl Examples include mono- or dicarbodiimide compounds such as ylcarbodiimide, and polycarbodiimide compounds such as poly(4,4'-diphenylmethanecarbodiimide), poly(3,5'-dimethyl-4,4'-biphenylmethanecarbodiimide), poly(p-phenylenecarbodiimide), poly(m-phenylenecarbodiimide), poly(3,5'-dimethyl-4,4'-diphenylmethanecarbodiimide), poly(naphthylenecarbodiimide), poly(1,3-diisopropylphenylenecarbodiimide), poly(1-methyl-3,5-diisopropylphenylenecarbodiimide), poly(1,3,5-triethylphenylenecarbodiimide), and poly(triisopropylphenylenecarbodiimide). Two or more of these can be used in combination.

[0079] <<Compounds containing an oxazoline group>> Examples of compounds having the oxazoline group include oxazolines, alkyloxazolines (alkyloxazolines with 1 to 4 carbon atoms, such as 2-methyloxazoline and 2-ethyloxazoline), and bisoxazoline compounds.

[0080] Examples of the above bisoxazoline compounds include 2,2'-bis(2-oxazoline), 2,2'-bis(alkyl-2-oxazoline) [such as 2,2'-bis(4-methyl-2-oxazoline), 2,2'-bis(4-ethyl-2-oxazoline), 2,2'-bis(4,4-dimethyl-2-oxazoline), etc. (2,2'-bis(alkyl-2-oxazoline with 1 to 6 carbon atoms)], 2,2'-bis(aryl-2-oxazoline) [such as 2,2'-bis(4-phenyl-2-oxazoline)], and 2,2'-bis(cycloalkyl-2-oxazoline). Zoline) [e.g., 2,2'-bis(4-cyclohexyl-2-oxazoline)], 2,2'-bis(aralkyl-2-oxazoline) [e.g., 2,2'-bis(4-benzyl-2-oxazoline)], 2,2'-alkylenebis(2-oxazoline) [e.g., 2,2'-ethylenebis(2-oxazoline), 2,2'-tetramethylenebis(2-oxazoline), etc., alkylenebis(2-oxazoline) with 1 to 10 carbon atoms], 2,2'-alkylenebis(alkyl-2-oxazoline) [e.g., 2,2'-ethylenebis(4-methyl-2-oxazoline)] Zoline), 2,2'-tetramethylenebis(4,4-dimethyl-2-oxazoline), and other alkylenebis (alkyl-2-oxazolines with 1 to 10 carbon atoms) (alkyl-2-oxazolines with 1 to 6 carbon atoms), 2,2'-arylenebis(2-oxazoline) [2,2'-(1,3-phenylene)-bis(2-oxazoline), 2,2'-(1,4-phenylene)-bis(2-oxazoline), 2,2'-(1,2-phenylene)-bis(2-oxazoline), 2,2'-diphenylenebis(2-oxazoline), etc.], 2,2'-arylenebis(alkyl-2 -Oxazoline) [2,2'-(1,3-phenylene)-bis(4-methyl-2-oxazoline), 2,2'-(1,4-phenylene)-bis(4,4-dimethyl-2-oxazoline), etc., 2,2'-phenylene-bis (alkyl-2-oxazoline with 1 to 6 carbon atoms), 2,2'-allyloxyalkanebis(2-oxazoline) [2,2'-9,9'-diphenoxyethanebis(2-oxazoline), etc.], 2,2'-cycloalkylenebis(2-oxazoline) [2,2'-cyclohexylenebis(2-oxazoline), etc.], N,N'-alkylenebis(2-carbamoyl-2-oxazoline) [N,N'-ethylenebis(2-carbamoyl-2-oxazoline), N,N'-tetramethylenebis(2-carbamoyl-2-oxazoline), and other alkylenebis(2-carbamoyl-2-oxazoline) with 1 to 10 carbon atoms, etc.], N,N'-alkylenebis(2-carbamoyl-alkyl-2-oxazoline) [N,N'-ethylenebis(2-carbamo Examples include N,N'-alkylenebis(2-carbamoyl-2-oxazoline), N,N'-tetramethylenebis(2-carbamoyl-4,4-dimethyl-2-oxazoline), N,N'-alkylenebis(2-carbamoyl-2-oxazoline) with 1 to 10 carbon atoms, N,N'-arylenebis(2-carbamoyl-2-oxazoline), N,N'-phenylenebis(2-carbamoyl-oxazoline), etc.

[0081] Compounds containing an oxazoline group also include vinyl polymers containing an oxazoline group (such as the Epocross RPS series, RAS series, and RMS series manufactured by Nippon Shokubai Co., Ltd.). Among these oxazoline compounds, bisoxazoline compounds are preferred.

[0082] <<Compounds containing an oxazine group>> As the compound having the oxazine group described above, oxazines, bisoxazine compounds, and the like can be used.

[0083] Examples of the above-mentioned bisoxazine compounds include 2,2'-bis(5,6-dihydro-4H-1,3-oxazine), 2,2'-bis(alkyl-5,6-dihydro-4H-1,3-oxazine) [such as 2,2'-bis(4-methyl-5,6-dihydro-4H-1,3-oxazine), 2,2'-bis(4,4-dimethyl-5,6-dihydro-4H-1,3-oxazine), 2,2'-bis(4,5-dimethyl-5,6-dihydro-4H-1,3-oxazine), etc., which are 2,2'-bis(alkyl-5,6-dihydro-4H-1,3-oxazines with 1 to 6 carbon atoms)]. ,2'-alkylenebis(5,6-dihydro-4H-1,3-oxazine) [2,2'-methylenebis(5,6-dihydro-4H-1,3-oxazine), 2,2'-ethylenebis(5,6-dihydro-4H-1,3-oxazine), 2,2'-hexanemethylenebis(5,6-dihydro-4H-1,3-oxazine), etc., alkylenebis(5,6-dihydro-4H-1,3-oxazine) with 1 to 10 carbon atoms, etc.], 2,2'-arylenebis(5,6-dihydro-4H-1,3-oxazine) [2,2'-(1,3-phenylene)-bis(5 [,6-dihydro-4H-1,3-oxazine], 2,2'-(1,4-phenylene)-bis(5,6-dihydro-4H-1,3-oxazine), 2,2'-(1,2-phenylene)-bis(5,6-dihydro-4H-1,3-oxazine), 2,2'-naphthylenebis(5,6-dihydro-4H-1,3-oxazine), 2,2'-diphenylenebis(5,6-dihydro-4H-1,3-oxazine), etc.], N,N'-alkylenebis(2-carbamoyl-5,6-dihydro-4H-1,3-oxazine) [N,N'-ethylenebis(2-carbamoyl-5 N,N'-alkylenebis(2-carbamoyl-5,6-dihydro-4H-1,3-oxazine), N,N'-tetramethylenebis(2-carbamoyl-5,6-dihydro-4H-1,3-oxazine), N,N'-alkylenebis(2-carbamoyl-alkyl-5,6-dihydro-4H-1,3-oxazine), N,N'-alkylenebis(2-carbamoyl-alkyl-5,6-dihydro-4H-1,3-oxazine) [N,N'-ethylenebis(2-carbamoyl-4-methyl-5,6-dihydro-4H-1,3-oxazine), N,N'-hexamethylenebis(2-carbamoyl-4,Examples include N,N'-alkylenebis(2-carbamoyl-alkyl-5,6-dihydro-4H-1,3-oxazine) with 1 to 10 carbon atoms, N,N'-arylenebis(2-carbamoyl-5,6-dihydro-4H-1,3-oxazine) [N,N'-phenylenebis(2-carbamoyl-oxazine), etc.]. Among these oxazine compounds, bisoxazine compounds are preferred.

[0084] The content of the reactive compound in the resin composition of this embodiment is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, per 100 parts by mass of the thermoplastic resin. Setting it above the lower limit tends to further improve hydrolysis resistance. Furthermore, the content of the reactive compound is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, even more preferably 2.0 parts by mass or less, and even more preferably 1.2 parts by mass or less, per 100 parts by mass of the thermoplastic resin. Setting it below the upper limit tends to further stabilize the melt viscosity and improve moldability.

[0085] In particular, when the resin composition of this embodiment contains polybutylene terephthalate resin, and more particularly when the resin component consists substantially only of polybutylene terephthalate resin, the content of the reactive compound in the resin composition of this embodiment is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.3 parts by mass or more, even more preferably 0.5 parts by mass or more, and even more preferably 0.8 parts by mass or more, per 100 parts by mass of polybutylene terephthalate resin. Setting it above the lower limit tends to further improve hydrolysis resistance. Furthermore, the content of the reactive compound is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, even more preferably 2.0 parts by mass or less, and even more preferably 1.2 parts by mass or less, per 100 parts by mass of polybutylene terephthalate resin. Setting it below the upper limit tends to further stabilize the melt viscosity and improve moldability. The resin composition of this embodiment may contain only one reactive compound or two or more. When it contains two or more, it is preferable that the total amount is within the above range.

[0086] <Other ingredients> The resin composition of this embodiment may contain other components as needed, as long as they do not significantly impair the desired physical properties. Examples of other components include various resin additives. The other components may be present individually, or two or more in any combination and ratio. Specifically, examples include stabilizers, release agents, pigments, dyes, UV absorbers, antistatic agents, antifogging agents, antiblocking agents, flow improvers, plasticizers, dispersants, and antibacterial agents. The resin composition of this embodiment preferably contains at least one of a stabilizer and a release agent.

[0087] The resin composition of this embodiment is prepared so that the total of the thermoplastic resin (preferably polybutylene terephthalate resin), electromagnetic wave absorbing material (preferably carbon nanotubes), glass fibers, and other selectively blended components is 100% by mass. In the resin composition of this embodiment, it is preferable that the total of the thermoplastic resin (preferably polybutylene terephthalate resin), electromagnetic wave absorbing material (preferably carbon nanotubes), and glass fibers accounts for 95% by mass or more of the resin composition. Furthermore, in the resin composition of this embodiment, it is preferable that the total of the thermoplastic resin (preferably polybutylene terephthalate resin), electromagnetic wave absorbing material (preferably carbon nanotubes), glass fibers, stabilizer, and release agent accounts for 99% by mass or more of the resin composition.

[0088] The resin composition of this embodiment may also be substantially free of polycarbonate resin. "Substantially free of polycarbonate resin" means that the polycarbonate resin content is 10% by mass or less of the thermoplastic resin contained in the resin composition, preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less. A resin composition substantially free of polycarbonate resin is particularly preferred in resin compositions that do not contain glass fibers.

[0089] <<Stabilizer>> The resin composition of this embodiment may contain a stabilizer. Examples of stabilizers include hindered phenol compounds, hindered amine compounds, phosphorus compounds, and sulfur-based stabilizers. Among these, hindered phenol compounds are preferred. It is also preferable to use a combination of hindered phenol compounds and phosphorus compounds. Specifically, as stabilizers, reference can be made to paragraphs 0046-0057 of Japanese Patent Publication No. 2018-070722, paragraphs 0030-0037 of Japanese Patent Publication No. 2019-056035, and paragraphs 0066-0078 of International Publication No. 2017 / 038949, the contents of which are incorporated herein by reference.

[0090] The resin composition of this embodiment preferably contains 0.01 parts by mass or more of stabilizer per 100 parts by mass of thermoplastic resin (preferably polybutylene terephthalate resin), more preferably 0.05 parts by mass or more, and even more preferably 0.08 parts by mass or more. Furthermore, the upper limit of the stabilizer content is preferably 3 parts by mass or less, more preferably 2 parts by mass or less, and even more preferably 1 part by mass or less per 100 parts by mass of thermoplastic resin (preferably polybutylene terephthalate resin). The resin composition of this embodiment may contain only one stabilizer or two or more stabilizers. When two or more stabilizers are included, it is preferable that the total amount is within the above range.

[0091] <<Release agent>> The resin composition of this embodiment preferably contains a mold release agent. A wide range of known release agents can be used as the release agent, with aliphatic carboxylic acid esters, paraffin wax, and polyethylene wax being preferred, and polyethylene wax being more preferred. Specifically, as a mold release agent, reference can be given to the descriptions in paragraphs 0115 to 0120 of Japanese Patent Publication No. 2013-007058, paragraphs 0063 to 0077 of Japanese Patent Publication No. 2018-070722, and paragraphs 0090 to 0098 of Japanese Patent Publication No. 2019-123809, the contents of which are incorporated herein by reference.

[0092] The resin composition of this embodiment preferably contains a release agent in an amount of 0.01 parts by mass or more, more preferably 0.08 parts by mass or more, and even more preferably 0.2 parts by mass or more, per 100 parts by mass of the thermoplastic resin (preferably polybutylene terephthalate resin). Furthermore, the upper limit of the release agent content is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, even more preferably 1 part by mass or less, and even more preferably 0.8 parts by mass or less, per 100 parts by mass of the thermoplastic resin (preferably polybutylene terephthalate resin). The resin composition may contain only one type of release agent or two or more types. If it contains two or more types, it is preferable that the total amount is within the above range.

[0093] <Physical properties of resin compositions> The resin composition of this embodiment preferably has a high electromagnetic wave absorption rate. Specifically, the resin composition of this embodiment has an absorption rate of 40.0 to 100% when molded to a size of 150 mm x 150 mm x 2 mm thickness, as determined by formula (A) at a frequency of 76.5 GHz. Formula (A)

number

[0094] The absorption rate is preferably 50.0% or higher, more preferably 55.0% or higher, even more preferably 60.0% or higher, and even more preferably 65.0% or higher. Ideally, the upper limit is 100%, but even 90.0% or lower will sufficiently satisfy the required performance.

[0095] The resin composition of this embodiment preferably has a low reflectivity of electromagnetic waves. Specifically, the resin composition of this embodiment preferably has a reflectance of 40.0% or less when molded to a size of 150 mm x 150 mm x 2 mm thickness, as determined by formula (B) at a frequency of 76.5 GHz. Formula (B)

number

[0096] The reflectance is preferably 35.0% or less, more preferably 30.0% or less, and even more preferably 25.0% or less. Ideally, the lower limit is 0%, but even if it is 10.0% or more, it will still sufficiently meet the required performance.

[0097] The resin composition of this embodiment preferably has low transmittance. The resin composition of this embodiment preferably has a transmittance of 15.0% or less when molded to a thickness of 150 mm x 150 mm x 2 mm, as determined by formula (C) at a frequency of 76.5 GHz. Formula (C)

number

[0098] The transmittance is preferably 12.0% or less, more preferably 10.0% or less, and may be 5.0% or less. Ideally, the lower limit is 0%, but even if it is 1.0% or more, it will still sufficiently meet the required performance.

[0099] The resin composition of this embodiment preferably exhibits excellent frequency dependence of electromagnetic waves. For example, when the resin composition of this embodiment is molded to a thickness of 150 mm × 150 mm × 2 mm, the difference between the highest and lowest reflectance values ​​calculated according to formula (B) in the frequency range of 70 GHz to 80 GHz is 20.0% or less. Formula (B)

number

[0100] The difference between the highest and lowest reflectance values ​​is preferably 18.0% or less, more preferably 17.0% or less, even more preferably 12.0% or less, and even more preferably 10.0% or less. The lower limit is ideally 0%, but even if it is 1.0% or more, it will still sufficiently satisfy the required performance.

[0101] The resin composition of this embodiment preferably satisfies the difference between the highest and lowest values ​​of the absorptivity determined according to formula (A) and the reflectivity determined according to formula (B) in the frequency range of 70 GHz to 80 GHz, as well as the reflectivity determined according to formula (B) and / or the transmittance determined according to formula (C). The resin composition of this embodiment is also preferably a resin composition containing a thermoplastic resin, wherein the absorptive coefficient determined according to formula (A) is 60.0% or more, the reflectance determined according to formula (B) is 30.0% or less, and the transmittance determined according to formula (C) is 10.0% or less, and is suitable for use as an electromagnetic wave absorber.

[0102] A particularly preferred embodiment of the resin composition of this embodiment is a resin composition comprising 0.1 to 10.0 parts by mass of carbon nanotubes per 100 parts by mass of polybutylene terephthalate resin, wherein the absorptive coefficient determined according to formula (A) at a frequency of 76.5 GHz when the resin composition is molded to a thickness of 150 mm × 150 mm × 2 mm is 40.0 to 100%, and the difference between the highest and lowest reflectance values ​​determined according to formula (B) in the frequency range of 70 GHz to 80 GHz when the resin composition is molded to a thickness of 150 mm × 150 mm × 2 mm is 20.0% or less, and is a resin composition for use as an electromagnetic wave absorber. Preferably, the above resin composition further satisfies the reflectance determined according to formula (B) and / or the transmittance determined according to formula (C).

[0103] The resin composition of this embodiment preferably has excellent mechanical strength. For example, when the resin composition of this embodiment is molded into an ISO multipurpose test specimen (4 mm thick), it is preferable that the maximum tensile strength measured according to ISO 527-1 and ISO 527-2 is 130 MPa or higher. There is no particular upper limit for the maximum tensile strength, but even 200 MPa or less is at a practical level. Furthermore, the resin composition of this embodiment is preferably excellent in terms of bending properties. Specifically, when the resin composition of this embodiment is molded into an ISO multipurpose test piece (4 mm thick), the flexural strength is preferably 180 MPa or higher, and more preferably 190 MPa or higher. Furthermore, there is no upper limit to the flexural strength, but for example, 280 MPa or less is practical. Furthermore, when the resin composition of this embodiment is molded into an ISO multipurpose test piece (4 mm thick), the flexural modulus is preferably 8,000 MPa or higher, and more preferably 9,000 MPa or higher. While there is no specific upper limit for the flexural modulus, for example, 14,000 MPa or less is practical. The details of the above measurement method are measured according to the description in the examples.

[0104] <Method for producing resin compositions> The resin composition of this embodiment can be manufactured by a conventional method for manufacturing resin compositions containing a thermoplastic resin. For example, it can be manufactured by putting a thermoplastic resin (preferably polybutylene terephthalate resin), an electromagnetic wave absorbing material (preferably carbon nanotubes), and other components (such as glass fibers) as needed into an extruder and melt-kneading them together. The components may be pre-mixed and supplied to the extruder all at once, or they may be supplied to the extruder using a feeder, either without pre-mixing them or with only some of them pre-mixed. The extruder may be a single-screw extruder or a twin-screw extruder. In addition, some components, such as electromagnetic wave absorbing material (preferably carbon nanotubes), may be melt-kneaded with a resin component (e.g., polybutylene terephthalate resin) to prepare a masterbatch, and then the remaining components may be blended into this and melt-kneaded. Furthermore, when incorporating glass fibers, it is preferable to supply them from a side feeder located midway through the extruder cylinder. The heating temperature during melting and kneading can usually be appropriately selected from the range of 170 to 350°C.

[0105] <Manufacturing method for electromagnetic wave absorbers> The method for manufacturing the electromagnetic wave absorber is not particularly limited, and any molding method commonly used for resin compositions including thermoplastic resins can be arbitrarily employed. Examples include injection molding, ultra-high-speed injection molding, injection compression molding, two-color molding, hollow molding methods such as gas-assisted molding, molding using a heat-insulating mold, molding using a rapidly heated mold, foam molding (including supercritical fluid), insert molding, IMC (in-mold coating) molding, extrusion molding, sheet molding, thermoforming, rotational molding, lamination molding, press molding, blow molding, etc., with injection molding being preferred among these.

[0106] <Application> The electromagnetic wave absorber of this embodiment is formed from the resin composition of this embodiment. That is, the resin composition of this embodiment is for electromagnetic wave absorbers (also called for electromagnetic wave absorbing members), more preferably for electromagnetic wave absorbers with a frequency of at least 60 to 90 GHz, and even more preferably for electromagnetic wave absorbers with a frequency of at least 70 to 80 GHz. Such electromagnetic wave absorbers are preferably used in radar applications. Specifically, they are used in housings, covers, etc., for millimeter-wave radars. The electromagnetic wave absorber of this embodiment can be suitably used in: on-board millimeter-wave radar used in automatic brake control devices, inter-vehicle distance control devices, pedestrian accident reduction steering devices, unintended acceleration suppression devices, pedal misapplication acceleration suppression devices, approaching vehicle warning devices, lane keeping assist devices, rear-end collision prevention warning devices, parking assist devices, vehicle surrounding obstacle warning devices, etc.; railway and aviation millimeter-wave radar used in platform monitoring / level crossing obstacle detection devices, in-train content transmission devices, tram / railway collision avoidance devices, runway foreign object detection devices, etc.; millimeter-wave radar for traffic infrastructure such as intersection monitoring devices and elevator monitoring devices; millimeter-wave radar for various security devices; medical and nursing care millimeter-wave radar such as child and elderly monitoring systems; millimeter-wave radar for various information content transmission; and the like. [Examples]

[0107] The present invention will be described in more detail below with reference to examples. The materials, amounts used, proportions, processing content, and processing procedures shown in the following examples can be modified as appropriate, as long as they do not depart from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. If the measuring instruments used in the examples are difficult to obtain due to discontinuation or other reasons, measurements can be taken using other instruments with equivalent performance.

[0108] 1.Raw materials The following ingredients were used. [Table 1-1] [Table 1-2]

[0109] Examples 1-8, Comparative Examples 1-10 <Manufacturing of resin compositions (pellets)> As shown in Tables 2 to 6, each component was placed in a stainless steel tumbler and stirred and mixed for 1 hour. The resulting mixture was supplied from the main feed port to a coaxial twin-screw extruder (TEX-30α, manufactured by Japan Steel Works, Ltd., screw diameter 32 mm, L / D = 42). The barrel temperature of the first mixing section was set to 260°C for plasticization, and glass fibers were supplied from the side feeder in the proportions shown in Tables 2 to 6. After adding the glass fibers, the barrel temperature was set to 250°C, and the mixture was melt-mixed under the conditions of a discharge rate of 40 kg / h and a screw rotation speed of 200 rpm. The mixture was then extruded as strands using 4 nozzles (circular (φ4 mm), length 1.5 cm). The extruded strands were introduced into a water tank for cooling, inserted into a pelletizer, and cut to obtain resin compositions (pellets).

[0110] <Maximum tensile strength> The resin pellets obtained above were dried at 120°C for 5 hours, and then ISO multipurpose test specimens (4 mm thick) were injection molded using an injection molding machine (Japan Steel Works, Ltd. "J85AD") under the conditions of a cylinder temperature of 250°C and a mold temperature of 80°C. Using molded multi-purpose ISO test specimens, the maximum point tensile strength (in MPa) and tensile modulus (in MPa) were measured in accordance with ISO 527-1 and ISO 527-2.

[0111] <Increase in tensile strength at the maximum point> The rate of increase in tensile strength at the maximum point was calculated for carbon-based electromagnetic wave absorbing materials when carbon black was incorporated. In this calculation, the rate of increase was calculated for materials with the same resin composition. Specifically, for Examples 1, 2, Comparative Examples 4, 5, and 8, the rate was based on the tensile strength at the maximum point of Comparative Example 1; for Examples 3, 4, 6, and 9, the rate was based on the tensile strength at the maximum point of Comparative Example 2; and for Examples 5, 6, 7, and 10, the rate was based on the tensile strength at the maximum point of Comparative Example 3. For example, in Example 1, the maximum tensile strength of Example 1 is 147 MPa, and the maximum tensile strength of Comparative Example 1 is 134 MPa, so (147 / 134) × 100 = 110 (%).

[0112] <Bending properties> The resin pellets obtained above were dried at 120°C for 5 hours, and then ISO multipurpose test specimens (4 mm thick) were injection molded using an injection molding machine (Japan Steel Works, Ltd. "J85AD") under the conditions of a cylinder temperature of 250°C and a mold temperature of 80°C. Using molded multi-purpose ISO test specimens, flexural strength (in MPa) and flexural modulus (in MPa) were measured in accordance with ISO 178.

[0113] <Low curvature> After drying the above resin composition pellets at 120°C for 5 hours, a 150 × 150 × 2 mm square plate-shaped test piece was injection molded using an injection molding machine (Toshiba "EC160") under conditions of cylinder temperature 260°C and mold temperature 80°C, and the warpage (mm) of the molded product was measured. Low warpage was determined based on the following criteria. Warpage here refers to the straight-line distance between the remaining vertex of the 150 × 150 × 2 mm square plate-shaped test piece and the plane when three of its vertices are fixed to the plane. A: Curvature is less than 3mm B: Curvature of 3mm or more but less than 15mm C: Curvature of 15mm or more

[0114] <Absorption rate, transmittance, reflectance> Using the pellets obtained above, injection molding was performed using an injection molding machine (Toshiba Machine Co., Ltd. "EC160") with a cylinder temperature of 260°C and a mold temperature of 80°C to obtain a test specimen measuring 150 mm × 150 mm × 2 mm thick. Using the obtained test specimen, the absorptivity determined according to equation (A), the reflectivity determined according to equation (B), and the transmittance determined according to equation (C) at a frequency of 76.5 GHz were measured as follows. For the measurements, we used the Anritsu MS4647B Vector Network Analyzer. Furthermore, the test specimen was positioned so that the transverse direction (TD) of the injection-molded product was parallel to the direction of the electric field, and measurements were taken. Formula (A)

number

[0115] Formula (B)

number

[0116] Formula (C)

number

[0117] <Frequency dependence of reflectance> The reflectivity of the test specimens obtained as described above was measured at frequencies of 70-80 GHz. The difference between the maximum and minimum reflectivity was calculated. A smaller difference between the maximum and minimum reflectivity indicates superior frequency dependence and a more stable resin composition.

[0118] <Electromagnetic wave absorption performance assessment> Based on the absorption, reflectance, and transmittance measured above, the following evaluation was performed. A: All of the following (1) to (3) are met. B: At a minimum, it satisfies (1) below (excluding those that fall under A). C: Other than A and B above (1) Absorption rate of 60.0% or higher (2) Reflectance of 30.0% or less (3) Transmittance of 10.0% or less

[0119] <Overall Rating> Based on the absorption rate, reflectance, transmittance, low warpage, maximum tensile strength, and bending strength measured above, the following evaluations were performed. 6: All of the following conditions (1) to (6) are met. 5: You satisfy five of the following conditions (1) to (6). 4: Four of the following conditions (1) to (6) are met. 3: Three of the following conditions (1) to (6) are met. 2: Two of the following conditions (1) to (6) are met. 1: One of the following conditions (1) to (6) is met. (1) Absorption rate of 60.0% or higher (2) Reflectance of 30.0% or less (3) Transmittance of 10.0% or less (4) Low curvature rating is A or B (5) Maximum tensile strength of 130 MPa or more (6) Bending strength of 190 MPa or more

[0120] [Table 2]

[0121] [Table 3]

[0122] [Table 4]

[0123] [Table 5]

[0124] [Table 6]

[0125] In Tables 2 to 6, * indicates that the amount is 100 parts by mass of resin. In Tables 2 to 6, CNT / GF represents the mass ratio of carbon nanotubes to glass fibers (carbon nanotubes / glass fibers). As is clear from the above results, the resin composition of the present invention had a high absorption rate of electromagnetic waves and low transmittance and reflectance of electromagnetic waves. Furthermore, the difference in reflectance due to differences in electromagnetic wave frequency was small. In addition, the resin composition of the present invention had excellent mechanical strength.

Claims

1. A resin composition comprising a thermoplastic resin and an electromagnetic wave absorbing material, When the resin composition is molded to a thickness of 150 mm x 150 mm x 2 mm, the absorptive coefficient determined according to formula (A) at a frequency of 76.5 GHz is 40.0 to 100%, and when the resin composition is molded to a thickness of 150 mm x 150 mm x 2 mm, the difference between the highest and lowest reflectance values ​​determined according to formula (B) in the frequency range of 70 GHz to 80 GHz is 20.0% or less, and it is for use as an electromagnetic wave absorber. The electromagnetic wave absorbing material includes multi-walled carbon nanotubes, The thermoplastic resin is further comprising 10 to 100 parts by mass of glass fiber, The mass ratio of the electromagnetic wave absorbing material to the glass fiber (electromagnetic wave absorbing material / glass fiber) is 0.01 to 0.

30. The thermoplastic resin content is 30 to 80% by mass in the resin composition. A resin composition containing an electromagnetic wave absorbing material in an amount of 0.1 to 10.0 parts by mass per 100 parts by mass of thermoplastic resin. Formula (A) [Math 1] (In the above formula (A), R represents the return loss measured by the free-space method, and T represents the transmission loss measured by the free-space method.) Formula (B) [Math 2] (In equation (B) above, R represents the return loss measured by the free-space method.)

2. Furthermore, the resin composition according to claim 1, further comprising 0.01 to 5.0 parts by mass of a reactive compound with respect to 100 parts by mass of the thermoplastic resin.

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

4. Furthermore, the resin composition according to claim 3, further comprising 1.0 to 75 parts by mass of polycarbonate resin per 100 parts by mass of the polybutylene terephthalate resin.

5. Furthermore, the resin composition according to claim 3, further comprising 1.0 to 60 parts by mass of polystyrene resin per 100 parts by mass of the polybutylene terephthalate resin.

6. Furthermore, the resin composition according to claim 3, comprising 1.0 to 75 parts by mass of polycarbonate resin and 1.0 to 60 parts by mass of polystyrene resin per 100 parts by mass of polybutylene terephthalate resin.

7. The resin composition according to claim 1 or 2, wherein the thermoplastic resin comprises a polypropylene resin.

8. The resin composition according to claim 1 or 2, wherein the thermoplastic resin comprises a polyamide resin.

9. The resin composition according to any one of claims 1 to 8, wherein the resin composition does not contain carbon fibers or contains less than 3% by mass of carbon fibers.

10. The resin composition according to any one of claims 1 to 9, wherein when the resin composition is molded to a thickness of 150 mm x 150 mm x 2 mm, the reflectance determined according to formula (B) at a frequency of 76.5 GHz is 40.0% or less. Formula (B) [Math 3] (In equation (B) above, R represents the return loss measured by the free-space method.)

11. The resin composition according to any one of claims 1 to 10, wherein when the resin composition is molded to a thickness of 150 mm x 150 mm x 2 mm, the transmittance determined according to formula (C) at a frequency of 76.5 GHz is 15.0% or less. Formula (C) [Math 4] (In equation (C) above, T represents the transmission attenuation measured by the free-space method.)

12. A resin composition according to any one of claims 1 to 10, wherein when the resin composition is molded to a thickness of 150 mm x 150 mm x 2 mm, the absorptive rate determined according to formula (A) at a frequency of 76.5 GHz is 60.0% or more, when the resin composition is molded to a thickness of 150 mm x 150 mm x 2 mm, the reflectance determined according to formula (B) at a frequency of 76.5 GHz is 30.0% or less, and when the resin composition is molded to a thickness of 150 mm x 150 mm x 2 mm, the transmittance determined according to formula (C) at a frequency of 76.5 GHz is 10.0% or less, and is for use as an electromagnetic wave absorber. Formula (A) [Math 5] (In the above formula (A), R represents the return loss measured by the free-space method, and T represents the transmission loss measured by the free-space method.) Formula (B) [Math 6] (In equation (B) above, R represents the return loss measured by the free-space method.) Formula (C) [Number 7] (In equation (C) above, T represents the transmission attenuation measured by the free-space method.)

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

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