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] The present invention relates to a resin composition for an electromagnetic wave absorber and an electromagnetic wave absorber. [Background technology]

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

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-197048 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-155993 Summary of the Invention [Problem to be solved by the invention]

[0004] In millimeter-wave radar, not only transmitted electromagnetic waves but also reflected electromagnetic waves become noise and cause malfunctions. For this reason, there is an increasing demand for materials with high electromagnetic wave absorption rates and low transmittance and reflectance. Furthermore, large differences in reflectance depending on the frequency of the electromagnetic waves affect stability and productivity. The present invention aims to solve such problems and to provide a resin composition for an electromagnetic wave absorber that has a high electromagnetic wave absorption rate and low electromagnetic wave transmittance and reflectance, and in which the difference in reflectance due to differences in electromagnetic wave frequency is small, and an electromagnetic wave absorber. [Means for solving the problem]

[0005] As a result of investigations conducted by the present inventors in light of the above problems, the above problems were solved by the following means. <1> A resin composition containing a thermoplastic resin and an electromagnetic wave absorbing material, The resin composition is suitable for use as an electromagnetic wave absorber, and when the resin composition is molded into a specimen of 150 mm x 150 mm x 2 mm thick, the absorbance at a frequency of 76.5 GHz calculated according to formula (A) is 40.0 to 100%, and when the resin composition is molded into a specimen of 150 mm x 150 mm x 2 mm thick, the difference between the highest and lowest reflectances calculated according to formula (B) in the frequency range of 70 GHz to 80 GHz is 20.0% or less. Formula (A)

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[0006] The present invention makes it possible to provide a resin composition for an electromagnetic wave absorber that has a high absorption rate of electromagnetic waves and low transmittance and reflectance of electromagnetic waves, and in which the difference in reflectance due to differences in electromagnetic wave frequency is small, as well as an electromagnetic wave absorber. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, an embodiment for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. Note that the present embodiment is an example for explaining the present invention, and the present invention is not limited to only this embodiment. In this specification, the symbol "to" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit. In this specification, various physical properties and characteristic values ​​are those at 23°C unless otherwise specified. In this specification, unless otherwise specified, the weight average molecular weight and number average molecular weight are values ​​measured by GPC (gel permeation chromatography) in terms of polystyrene. In this specification, the unit of return loss and transmission loss is "dB" (decibels).

[0008] The resin composition of the present embodiment is a resin composition containing a thermoplastic resin and an electromagnetic wave absorbing material, When the resin composition is molded into a size of 150 mm x 150 mm x 2 mm thick, the absorption rate calculated according to formula (A) at a frequency of 76.5 GHz is 40.0 to 100%, and when the resin composition is molded into a size of 150 mm x 150 mm x 2 mm thick, 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, and the resin composition is characterized in that it is used for an electromagnetic wave absorber. Formula (A)

number

number

[0009] <Thermoplastic resin> The resin composition of the present embodiment contains a thermoplastic resin. Preferred examples of the thermoplastic resin used in this embodiment include polyester resin (thermoplastic polyester resin); polyamide resin; polycarbonate resin; polystyrene-based resin; polyolefin resin such as polyethylene resin, polypropylene resin, and cyclic cycloolefin resin; polyacetal resin; polyimide resin; polyetherimide resin; polyurethane resin; polyphenylene ether resin; polyphenylene sulfide resin; polysulfone resin; polymethacrylate resin; and the like. It is more preferable that the thermoplastic resin contains at least one of polyolefin resin (preferably polypropylene resin), polycarbonate resin, polyphenylene ether resin, polyester resin, and polyamide resin, even more preferable that the thermoplastic resin contains at least one of polycarbonate resin, polyphenylene ether resin, polyester resin, and polyamide resin, and even more preferable that the thermoplastic resin contains polybutylene terephthalate resin.

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

[0011] The resin composition of this embodiment may also be an alloy obtained by blending two or more thermoplastic resins. When two or more thermoplastic resins are blended, they are usually not completely compatible with each other, resulting in a sea-island structure. The electromagnetic wave absorbing material (preferably carbon nanotubes) is unlikely to be present in these island portions, and as a result, the region in which the electromagnetic wave absorbing material is present in the resin composition or electromagnetic wave absorber becomes narrower. Therefore, even if the blending amount of the electromagnetic wave absorbing material (preferably carbon nanotubes) is reduced, various performance properties such as electromagnetic wave absorption can be effectively achieved. For example, an embodiment in which polybutylene terephthalate resin is blended with polycarbonate resin and / or polystyrene resin can be exemplified.

[0012] The resin composition of the present embodiment is preferably in the following blend form. The first blend form is a form in which 1.0 to 75 parts by mass of polycarbonate resin is contained relative to 100 parts by mass of polybutylene terephthalate resin. By blending the polycarbonate resin, warping of the resulting electromagnetic wave absorber can be effectively suppressed. In the first 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 are composed 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. By setting the content at or above the lower limit, the amount of warpage of the molded article tends to be reduced. The upper limit of the polycarbonate resin content in the first blend form is preferably 70 parts by mass or less, more preferably 65 parts by mass or less. By setting the content at or below the upper limit, chemical resistance and hydrolysis resistance tend to be further improved. In the first blend form, only 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 is a form in which 1.0 to 60 parts by mass of a polystyrene-based resin (preferably an AS resin) is contained relative to 100 parts by mass of a polybutylene terephthalate resin. By blending a polystyrene-based resin, 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 are made up of a polybutylene terephthalate resin and a polystyrene-based resin (preferably an AS resin). The lower limit of the content of the polystyrene resin (preferably AS resin) 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. By setting the content at or above the lower limit, the amount of warpage of the molded article tends to be reduced. The upper limit of the content of the polystyrene resin (preferably AS resin) in the second blend form is preferably 90 parts by mass or less, more preferably 80 parts by mass or less. By setting the content at or below the upper limit, the effect of chemical resistance tends to be further improved. In the second blend form, the polystyrene resin may be used alone or in combination of two or more. When two or more types are used, the total amount is preferably within the above range.

[0014] A third blend form contains 1.0 to 75 parts by mass of a polycarbonate resin and 1.0 to 60 parts by mass of a polystyrene-based resin (preferably HIPS) per 100 parts by mass of a polybutylene terephthalate resin. By blending a polystyrene-based resin and a polycarbonate resin, warping of the resulting electromagnetic wave absorber can be effectively suppressed. In the third 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 are made up of a polybutylene terephthalate resin, a polycarbonate resin, and a polystyrene-based resin (preferably HIPS).

[0015] The lower limit of the content of the styrene-based resin (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. By setting the content at or above the lower limit, the amount of warpage of the molded article tends to be reduced. The upper limit of the content of the styrene-based resin 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. By setting the content at or below the upper limit, chemical resistance tends to be further improved. 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. By setting the content at or above the lower limit, the amount of warping of the molded article tends to be reduced. 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. By setting the content at or below the upper limit, chemical resistance and hydrolysis resistance tend to be further improved. In the third blend embodiment, the mass ratio of the polycarbonate resin to the styrene resin is preferably 1:2.0 to 4.0, and more preferably 1:2.5 to 3.5. By setting the mass ratio in this range, warping of the molded article tends to be suppressed and the mechanical strength tends to be further improved. In the third blend form, the styrene resin and the polycarbonate resin may each be used alone or in combination of two or more. When two or more types are used, it is preferable that the total amount is within the above range.

[0016] Each thermoplastic resin will be described in detail below. <<Polyester resin>> As the polyester resin, known thermoplastic polyester resins can be used, and polyethylene terephthalate resin and polybutylene terephthalate resin are preferred, and it is more preferred that the polyester resin contains 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 not only polybutylene terephthalate resin (homopolymer), but also polybutylene terephthalate copolymers containing other copolymerization components other than terephthalic acid units and 1,4-butanediol units, and mixtures of homopolymers and polybutylene terephthalate copolymers.

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

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

[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, the polybutylene terephthalate copolymer may contain, as the carboxylic acid unit, one or more dicarboxylic acids other than the above-mentioned terephthalic acid and / or, as the diol unit, one or more diols other than the above-mentioned 1,4-butanediol. When the polybutylene terephthalate resin is a polybutylene terephthalate resin modified by copolymerization, specific preferred copolymers include polyester ether resins copolymerized with polyalkylene glycols, particularly polytetramethylene glycol, dimer acid-copolymerized polybutylene terephthalate resins, and isophthalic acid-copolymerized polybutylene terephthalate resins. Among these, polyester ether resins copolymerized with polytetramethylene glycol are preferred. These copolymers refer to those in which the copolymerization amount is 1 mol% or more and less than 50 mol% of all 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%. By setting the copolymerization amount in this range, fluidity, toughness, and tracking resistance tend to be easily improved, which is preferable.

[0021] The amount of terminal carboxyl groups in the polybutylene terephthalate resin may be appropriately selected and determined, but is typically 60 eq / ton or less, preferably 50 eq / ton or less, and more preferably 30 eq / ton or less. By setting the amount below the upper limit, alkali resistance and hydrolysis resistance tend to be improved. The lower limit of the amount of terminal carboxyl groups is not particularly specified, but is typically 10 eq / ton or more, taking into account the productivity of polybutylene terephthalate resin production.

[0022] The amount of terminal carboxyl groups in the polybutylene terephthalate resin is determined by dissolving 0.5 g of the polybutylene terephthalate resin in 25 mL of benzyl alcohol and titrating the solution with a 0.01 mol / L benzyl alcohol solution of sodium hydroxide. The amount of terminal carboxyl groups can be adjusted by any conventional method, such as adjusting the polymerization conditions, such as the raw material charge ratio, polymerization temperature, and pressure reduction, or by reacting a terminal blocking 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. By making the intrinsic viscosity 0.5 dL / g or more, the mechanical strength of the resulting resin composition tends to be further improved. Furthermore, by making the intrinsic viscosity 2 dL / g or less, the fluidity of the resin composition tends to be further improved, and moldability tends to be improved. The intrinsic viscosity of the polybutylene terephthalate resin is a value measured at 30° C. in a mixed solvent of tetrachloroethane and phenol in a 1:1 (mass ratio).

[0024] Polybutylene terephthalate resin can be produced by batch or continuous melt polymerization of a dicarboxylic acid component containing terephthalic acid as the main component or an ester derivative thereof with a diol component containing 1,4-butanediol as the main component. 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-state polymerization under a nitrogen gas flow or reduced pressure. The polybutylene terephthalate resin is preferably one obtained by a production method in which a dicarboxylic acid component mainly composed of terephthalic acid and a diol component mainly composed of 1,4-butanediol are subjected to continuous melt polycondensation.

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

[0026] In addition to the above, the polyester resin may be found in paragraphs 0013 to 0016 of JP-A-2010-174223, the contents of which are incorporated herein by reference.

[0027] When the resin composition of this embodiment contains polybutylene terephthalate resin, the content of the polybutylene terephthalate resin in the resin composition 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. By setting the content at or above the lower limit, chemical resistance tends to be further improved. Furthermore, when the resin composition contains polybutylene terephthalate resin, the content of the 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 even be 55% by mass or less, 50% by mass or less, or 47% by mass or less. Setting the content at or below the upper limit tends to more effectively reduce the amount of warpage of the molded article. The resin composition of the present embodiment may contain only one type of polybutylene terephthalate resin, or may contain two or more types. When two or more types are contained, the total amount is preferably in the above range.

[0028] <<Polycarbonate resin>> Polycarbonate resins are homopolymers or copolymers, which may be branched, obtained by reacting a dihydroxy compound or a small amount of a polyhydroxy compound with phosgene or a carbonate diester. The method for producing the polycarbonate resin is not particularly limited, and polycarbonate resins produced by the conventionally known phosgene method (interfacial polymerization method) or melt method (ester interchange method) can be used.

[0029] The dihydroxy compound used as the raw material is preferably an aromatic dihydroxy compound, such as 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), tetramethylbisphenol A, bis(4-hydroxyphenyl)-p-diisopropylbenzene, hydroquinone, resorcinol, or 4,4-dihydroxydiphenyl, with bisphenol A being preferred. It is also possible to use a compound in which one or more tetraalkylphosphonium sulfonates are bonded to the above aromatic dihydroxy compound.

[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. Also, copolymers mainly composed of aromatic polycarbonate resins, such as copolymers with polymers or oligomers having a siloxane structure, may be used. Furthermore, two or more of the above-mentioned polycarbonate resins may be mixed and used.

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

[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. By using a polycarbonate resin having a viscosity average molecular weight of 5,000 or more, the mechanical strength of the resulting resin composition tends to be further improved. Furthermore, the viscosity average molecular weight (Mv) of the polycarbonate resin is preferably 60,000 or less, more preferably 40,000 or less, and even more preferably 30,000 or less. By using a polycarbonate resin having a viscosity average molecular weight of 60,000 or less, the flowability of the resin composition tends to be improved, and moldability tends to be improved.

[0033] In this embodiment, the viscosity average molecular weight (Mv) of the polycarbonate resin is a value calculated from the intrinsic viscosity ([η]) obtained by measuring the viscosity of a methylene chloride solution of the polycarbonate resin at 20°C using an Ubbelohde viscometer, and then using the following Schnell viscosity formula: [η]=1.23×10 -4 Mv 0.83

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

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

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

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

[0038] The melt flow rate (MFR) of the polystyrene resin, measured in accordance with JIS K7210 (temperature 200°C, load 5 kgf), is preferably 0.1 to 30 g / 10 min, more preferably 0.5 to 25 g / 10 min. An MFR of 0.1 g / 10 min or more tends to improve fluidity, while an MFR of 30 g / 10 min or less tends to improve impact resistance.

[0039] Examples of methods for producing such polystyrene resins include known methods such as 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 its main chain (preferably a polymer in which the structural unit represented by the following formula accounts for 90 mol % or more of all structural units excluding terminal groups). The polyphenylene ether resin may be either a homopolymer or a copolymer.

[0041] [ka] (wherein two R a each independently represents a hydrogen atom, a halogen atom, a primary or secondary alkyl group, an aryl group, an aminoalkyl group, a halogenated alkyl group, a hydrocarbonoxy group, or a halogenated hydrocarbonoxy group, and two R b each independently represents a hydrogen atom, a halogen atom, a primary or secondary alkyl group, an aryl group, a halogenated alkyl group, a hydrocarbonoxy group, or a halogenated hydrocarbonoxy group. a cannot both become hydrogen atoms.)

[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 primary alkyl groups 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 secondary alkyl groups include an isopropyl group, a sec-butyl group, or a 1-ethylpropyl group. In particular, R a is preferably a primary or secondary alkyl group having 1 to 4 carbon atoms or a phenyl group. b is preferably a hydrogen atom.

[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 the copolymer include 2,6-dialkylphenol / 2,3,6-trialkylphenol copolymers such as 2,6-dimethylphenol / 2,3,6-trimethylphenol copolymer, 2,6-dimethylphenol / 2,3,6-triethylphenol copolymer, 2,6-diethylphenol / 2,3,6-trimethylphenol copolymer, and 2,6-dipropylphenol / 2,3,6-trimethylphenol copolymer; graft copolymers in which styrene is graft polymerized onto poly(2,6-dimethyl-1,4-phenylene ether); and graft copolymers in which styrene is graft polymerized onto 2,6-dimethylphenol / 2,3,6-trimethylphenol copolymer.

[0044] In this embodiment, the polyphenylene ether resin is preferably poly(2,6-dimethyl-1,4-phenylene) ether or a 2,6-dimethylphenol / 2,3,6-trimethylphenol random copolymer. Also suitable is a polyphenylene ether resin having a specified number of terminal groups and copper content, as described in JP-A-2005-344065.

[0045] The polyphenylene ether resin preferably has an intrinsic viscosity of 0.2 to 0.8 dL / g, more preferably 0.3 to 0.6 dL / g, measured in chloroform at 30°C. By setting the intrinsic viscosity to 0.2 dL / g or higher, the mechanical strength of the resin composition tends to be improved, while by setting the intrinsic viscosity to 0.8 dL / g or lower, the flowability tends to be improved and molding processability tends to be easier. Furthermore, two or more polyphenylene ether resins with different intrinsic viscosities may be used in combination to achieve an intrinsic viscosity within this range.

[0046] The method for producing the polyphenylene ether resin used in the present embodiment is not particularly limited, and may be a known method, for example, a method of oxidatively polymerizing a monomer such as 2,6-dimethylphenol in the presence of an amine copper catalyst, in which the intrinsic viscosity can be controlled within a desired range by selecting the reaction conditions. The intrinsic viscosity can be controlled by selecting conditions such as the 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. The polypropylene may be, for example, crystalline or amorphous polypropylene. Examples of the copolymer include ethylene-propylene random, block or graft copolymers, copolymers of α-olefins 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, ethylene-propylene random, block or graft copolymers are preferred, and propylene-ethylene block copolymers are more preferred. Furthermore, polypropylene resins are preferred from the viewpoints of being inexpensive and having a small specific gravity, which allows for lightweight molded articles.

[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, or polycondensation of diamines and dibasic acids. Specific 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 (described in detail below), polytrimethylhexamethylene terephthalamide, polybis(4-aminocyclohexyl)methanedodecamide, polybis(3-methyl-4-aminocyclohexyl)methanedodecamide, and polyundecamethylenehexahydroterephthalamide. The "I" in the above text indicates the isophthalic acid component, and the "T" indicates the terephthalic acid component. Regarding polyamide resins, the description in paragraphs 0011 to 0013 of JP-A No. 2011-132550 can be referred to, the contents of which are incorporated herein by reference.

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

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

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

[0053] The content of the thermoplastic resin (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 in the resin composition. By making the content equal to or greater than the lower limit, chemical resistance tends to be further improved. 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 even be 55% by mass or less, 50% by mass or less, or 47% by mass or less. By making the content equal to or less than the upper limit, the amount of warpage of the molded article tends to be more effectively reduced. The resin composition of the present embodiment may contain only one type of thermoplastic resin, or may contain two or more types. When two or more types are contained, the total amount is preferably in the above range.

[0054] <Electromagnetic wave absorbing material> The resin composition of the present embodiment contains an electromagnetic wave absorbing material. By containing the electromagnetic wave absorbing material, it is possible to impart electromagnetic wave absorbing properties to the resin composition. Examples of the electromagnetic wave absorbing material 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. Examples of carbon-containing electromagnetic wave absorbing materials include carbon black, ketjen carbon, graphene, graphite, fullerene, carbon nanocoils, carbon nanotubes, and carbon fibers, with carbon nanotubes being more preferred. Also preferred are fibers coated with metals, metal oxides, or carbon-containing electromagnetic wave absorbing materials, such as carbon-coated potassium titanate whiskers and metal-coated fibers.

[0055] The electromagnetic wave absorbing material in this embodiment is preferably in a relatively thin and long shape such as fiber, tube, or whisker. The diameter (number average fiber diameter) of the electromagnetic wave absorber is preferably 0.5 nm or more, more preferably 1 nm or more, and even more preferably 3 nm or more, and is 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 imparting good electromagnetic wave absorbing properties, the aspect ratio of the electromagnetic wave absorbing material is preferably 5 or more, more preferably 50 or more. There is no particular upper limit, but it is, for example, 500 or less.

[0056] As described above, carbon black, graphite, carbon fiber, carbon nanotubes, etc. are known as carbon-based electromagnetic wave absorbers. In this embodiment, by selecting carbon nanotubes from these carbon-based electromagnetic wave absorbers, the electromagnetic wave absorption rate is high, the transmittance and reflectance of electromagnetic waves are low, and the difference in reflectance is small regardless of frequency. In addition, the mechanical strength of the resulting molded article can be increased.

[0057] The carbon nanotubes used in this embodiment may be single-walled carbon nanotubes, multi-walled carbon nanotubes, or a mixture thereof, but preferably contain multi-walled carbon nanotubes. Carbon materials partially having a carbon nanotube structure may also be used. Furthermore, the carbon nanotubes are not limited to a cylindrical shape, and may have a coiled shape with a spiral at a pitch of 1 μm or less. Carbon nanotubes are commercially available, and examples thereof include carbon nanotubes available from Bayer MaterialScience, Nanosil, Showa Denko K.K., and Hyperion Catalysis International, Inc. In addition to the name carbon nanotubes, they are also called graphite fibrils, carbon fibrils, etc. The diameter of the carbon nanotube is preferably 0.5 to 100 nm, more preferably 1 to 30 nm. From the viewpoint of imparting good electromagnetic wave absorption properties, the aspect ratio of the carbon nanotube is preferably 5 or more, more preferably 50 or more. There is no particular upper limit, but it is, for example, 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 containing an electromagnetic wave absorbing material (preferably carbon nanotubes), electromagnetic waves can be effectively absorbed even with a small blend amount. Furthermore, transmission and reflection of electromagnetic waves can be effectively suppressed. Furthermore, the difference in reflectance for electromagnetic waves with frequencies of 70 to 80 GHz can be reduced. Furthermore, 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 the electromagnetic wave absorbing material (preferably carbon nanotubes) relative to 100 parts by mass of the 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 content at or above the lower limit, electromagnetic wave absorption properties are effectively exhibited. Furthermore, the resin composition of this embodiment contains 10.0 parts by mass or less of the electromagnetic wave absorbing material (preferably carbon nanotubes) relative to 100 parts by mass of the thermoplastic resin, 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 content at or below the upper limit, the amount of glass fiber can be relatively increased, and the mechanical strength of the resulting molded product can be increased.

[0060] In particular, when the resin composition of this embodiment contains a polybutylene terephthalate resin, more particularly when the resin component is substantially composed of only 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 part 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, per 100 parts by mass of the polybutylene terephthalate resin. By making the amount equal to or greater than the lower limit, electromagnetic wave absorption properties are effectively exhibited. Furthermore, the resin composition of this embodiment preferably contains 10.0 parts by mass or less of an electromagnetic wave absorbing material (preferably carbon nanotubes) per 100 parts by mass of the polybutylene terephthalate resin, 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. By setting the amount to the above upper limit or less, for example, the amount of glass fiber blended can be relatively increased, and the mechanical strength of the resulting molded product can be increased.

[0061] In one embodiment of the resin composition of the present embodiment, a carbon-based electromagnetic wave absorber other than carbon nanotubes is not included or is included in an amount of less than 3 mass % of the resin composition, which tends to further improve the frequency dependency of the reflectance of electromagnetic waves. In this embodiment, the content of carbon-based electromagnetic wave absorbers 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] In one embodiment of the resin composition of the present embodiment, carbon fiber is not contained or the carbon fiber content is less than 3 mass %. By adopting such a configuration, the frequency dependency of the reflectance of electromagnetic waves tends to be further improved. In addition, the reflectance of electromagnetic waves can be further reduced. The carbon fiber content in this embodiment 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 does not contain graphite or has a graphite content of less than 3 mass %. This configuration tends to further improve the frequency dependency of the reflectance of electromagnetic waves. It also makes it possible to further increase the absorption rate of electromagnetic waves. Furthermore, it makes it possible to 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 the present embodiment does not contain carbon black or has a carbon black content of less than 3 mass %. This configuration tends to further improve the frequency dependence of the electromagnetic wave reflectance. Also, the mechanical strength of the resulting electromagnetic wave absorber can be further improved. 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 does not contain Ketjen black or the Ketjen black content is less than 3 mass %. By adopting such a configuration, the frequency dependence of the reflectance of electromagnetic waves tends to be further improved. In addition, the mechanical strength of the resulting electromagnetic wave absorber can be further improved. In this embodiment, the content of Ketjen Black 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] Also preferred are embodiments that satisfy two or more of the above-mentioned embodiments, and even more preferred are embodiments that satisfy all of the above-mentioned embodiments.

[0067] The content of the electromagnetic wave absorbing material (preferably carbon nanotubes) in the resin composition of this embodiment is preferably 0.1 mass% or more, more preferably 0.5 mass% or more, and even more preferably 1.0 mass% or more in the resin composition. By making the content equal to or greater than the lower limit, more stable electromagnetic wave absorption performance tends to be obtained. Furthermore, by making the content equal to or less than the upper limit, the impact strength of the resin composition tends to be maintained at a high level. The resin composition of the present embodiment may contain only one type of electromagnetic wave absorbing material (preferably carbon nanotubes), or may contain two or more types. When two or more types are contained, the total amount is preferably in the above range.

[0068] <Glass fiber> The resin composition of this embodiment contains 10 to 100 parts by mass of glass fiber relative to 100 parts by mass of thermoplastic resin (preferably polybutylene terephthalate resin). By containing glass fiber, the mechanical strength of the electromagnetic wave absorber formed from the resin composition of this embodiment can be improved. The glass fiber is selected from glass compositions such as A-glass, C-glass, E-glass, R-glass, D-glass, M-glass, and S-glass, with E-glass (alkali-free glass) being particularly preferred. Glass fiber refers to a fibrous material whose cross section, cut perpendicular to the longitudinal direction, is circular or polygonal. The number-average fiber diameter of single fibers of glass fiber is usually 1 to 25 μm, preferably 5 to 17 μm. By making the number-average fiber diameter 1 μm or more, the moldability of the resin composition tends to be further improved. By making the number-average fiber diameter 25 μm or less, the appearance of the obtained electromagnetic wave absorber tends to be improved, and the reinforcing effect also tends to be improved. The glass fiber may be a single fiber or a plurality of single fibers twisted together. The glass fiber may be in the form of a glass roving obtained by continuously winding a single fiber or a plurality of twisted fibers, a chopped strand cut to a length of 1 to 10 mm (i.e., glass fiber having a number average fiber length of 1 to 10 mm), or a milled fiber pulverized to a length of about 10 to 500 μm (i.e., glass fiber having a number average fiber length of 10 to 500 μm), but chopped strand cut to a length of 1 to 10 mm is preferred. Glass fibers of different forms can also be used in combination. Glass fibers having an irregular cross-sectional shape are also preferred. The irregular cross-sectional shape has an oblateness, which is the ratio of the major axis to the minor axis of the cross section perpendicular to the longitudinal direction of the fiber, of, for example, 1.5 to 10, preferably 2.5 to 10, more preferably 2.5 to 8, and even more preferably 2.5 to 5.

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

[0070] The resin composition of this embodiment contains glass fibers in an amount of 10 parts by mass or more, preferably 20 parts by mass or more, more preferably 35 parts by mass or more, even more preferably 47 parts by mass or more, still more preferably 55 parts by mass or more, and even more preferably 63 parts by mass or more, relative to 100 parts by mass of the thermoplastic resin (preferably polybutylene terephthalate resin). By adjusting the amount to be equal to or greater than the lower limit, mechanical strength tends to be further increased. Furthermore, the content of the glass fibers is equal to or less than 100 parts by mass of the 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. By adjusting the amount to be equal to or less than the upper limit, the appearance of the molded article tends to be improved, and the fluidity of the molten resin tends to be further improved.

[0071] The content of glass fibers in the resin composition of this embodiment is preferably 10% by mass or more, more preferably 15% by mass or more, and more preferably 50% by mass or less, even more preferably 45% by mass or less, and even more preferably 40% by mass or less. By making the content equal to or greater than the lower limit, mechanical strength tends to be further increased. On the other hand, by making the content equal to or less than the upper limit, the appearance of the molded article tends to be improved, and the fluidity of the molten resin tends to be further improved. The resin composition of the present embodiment may contain only one type of glass fiber, or may contain two or more types. When two or more types are contained, the total amount is preferably in the above range.

[0072] In the resin composition of this embodiment, the mass ratio of the electromagnetic wave absorbing material (preferably carbon nanotubes) to the glass fiber (electromagnetic wave absorbing material / glass fiber) is 0.01 or more, preferably 0.02 or more, more preferably 0.025 or more, even more preferably 0.04 or more, and even more preferably 0.05 or more. By making the mass ratio equal to or greater than the lower limit, higher electromagnetic wave absorption performance tends to be obtained. Furthermore, the mass ratio of the electromagnetic wave absorbing material to the glass fiber is 0.30, preferably 0.20 or less, more preferably 0.10 or less, and even more preferably 0.07 or less. By making the mass ratio equal to or less than the upper limit, the impact strength of the resin composition tends to be higher and maintained.

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

[0074] <<Compounds with epoxy groups (epoxy resins)>> The compound having an epoxy group is a compound having one or more epoxy groups in one molecule, and examples thereof include a glycidyl compound, an aromatic ring-containing compound having an epoxy group, and an alicyclic compound having an epoxy group, and it is preferable that the compound contains at least an aromatic ring-containing compound having an epoxy group.

[0075] Specific examples of compounds having an epoxy group 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 having an aromatic ring such as benzoic acid glycidyl ester, terephthalic acid diglycidyl ester, orthophthalic acid diglycidyl ester, methyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, decyl glycidyl ether, stearyl glycidyl ether, (di)glycidyl ethers such as glycidyl ether, 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 sorbic acid glycidyl ester, adipic acid diglycidyl ester, 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 chains, bisphenol A type epoxy compounds, novolac type epoxy compounds, bisphenol F type epoxy compounds, biphenyl type epoxy compounds, etc. are preferred, and bisphenol A type epoxy compounds are more preferred.

[0076] <<Carbodiimide compounds>> In the resin composition of this embodiment, it is also preferable to contain a carbodiimide compound as the reactive compound. A carbodiimide compound is a compound containing a carbodiimide group (-N=C=N-) in the molecule. As the carbodiimide compound, any of an aliphatic carbodiimide compound having an aliphatic main chain, an alicyclic carbodiimide compound having an alicyclic main chain, and an aromatic carbodiimide compound having an aromatic main chain can be used. Among them, the use of an aliphatic carbodiimide compound having good reactivity with polymer terminals is preferred. The type of carbodiimide compound may be a monomer type or a polymer type, but in this embodiment, a polymer type is preferred.

[0077] Examples of the aliphatic carbodiimide compound include diisopropylcarbodiimide, dioctyldecylcarbodiimide, etc. Examples of the alicyclic carbodiimide compound include dicyclohexylcarbodiimide, poly(4,4'-dicyclohexylmethanecarbodiimide), etc., with poly(4,4'-dicyclohexylmethanecarbodiimide) being particularly preferred. An example of a commercially available product is "Carbodilite" (trade name; manufactured by Nisshinbo Chemical Inc.).

[0078] Examples of the aromatic carbodiimide compound 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, ethylene-bis-diphenyl Examples of the carbodiimide compounds include mono- or dicarbodiimide compounds such as 4,4'-biphenylmethanecarbodiimide, 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), and two or more of these can also be used in combination.

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

[0080] Examples of the bisoxazoline compound include 2,2'-bis(2-oxazoline), 2,2'-bis(alkyl-2-oxazoline) [2,2'-bis(alkyl-2-oxazoline having 1 to 6 carbon atoms) such as 2,2'-bis(4-methyl-2-oxazoline), 2,2'-bis(4-ethyl-2-oxazoline), and 2,2'-bis(4,4-dimethyl-2-oxazoline)], 2,2'-bis(aryl-2-oxazoline) [2,2'-bis(4-phenyl-2-oxazoline)], 2,2'-bis(cycloalkyl-2-oxazoline), and the like. 2,2'-bis(4-cyclohexyl-2-oxazoline) and the like], 2,2'-bis(aralkyl-2-oxazoline) and the like], 2,2'-alkylenebis(2-oxazoline) and the like], 2,2'-alkylenebis(2-oxazoline) and the like], 2,2'-alkylenebis(2-oxazoline) and the like], 2,2'-alkylenebis(alkyl-2-oxazoline) and the like], 2,2'-ethylenebis(2-oxazoline), 2,2'-tetramethylenebis(2-oxazoline), and the like], 2,2'-C10 alkylenebis(C1-6 alkyl-2-oxazoline) such as 2,2'-tetramethylenebis(4,4-dimethyl-2-oxazoline), 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(2-oxazoline), 2,2'-(1,4-phenylene)-bis(2-oxazoline), 2,2'-(1,2-phenylene)-bis(2-oxazoline), 2,2'-diphenylenebis(2-oxazoline), etc.], -oxazoline) [2,2'-phenylene-bis(alkyl-2-oxazoline having 1 to 6 carbon atoms) such as 2,2'-(1,3-phenylene)-bis(4-methyl-2-oxazoline, 2,2'-(1,4-phenylene)-bis(4,4-dimethyl-2-oxazoline)], 2,2'-aryloxyalkanebis(2-oxazoline) [2,2'-9,9'-diphenoxyethanebis(2-oxazoline)], 2,2'-cycloalkylenebis(2-oxazoline) [2,2'-cyclohexylenebis(2-oxazoline)], N,N'-Alkylenebis(2-carbamoyl-2-oxazoline) [N,N'-C1-10 alkylenebis(2-carbamoyl-2-oxazoline) such as N,N'-ethylenebis(2-carbamoyl-2-oxazoline) and N,N'-tetramethylenebis(2-carbamoyl-2-oxazoline)], N,N'-alkylenebis(2-carbamoyl-alkyl-2-oxazoline) [N,N'-ethylenebis(2-carbamoyl-2-oxazoline)] Examples include N,N'-C10 alkylenebis(2-carbamoyl-C1-6 alkyl-2-oxazoline) such as N,N'-tetramethylenebis(2-carbamoyl-4,4-dimethyl-2-oxazoline), N,N'-arylenebis(2-carbamoyl-2-oxazoline) [N,N'-phenylenebis(2-carbamoyl-oxazoline)], and the like.

[0081] Compounds having 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.) Of these oxazoline compounds, bisoxazoline compounds are preferred.

[0082] << Compounds containing an oxazine group >> As the compound having an oxazine group, an oxazine or bisoxazine compound can be used.

[0083] Examples of the bisoxazine compound include 2,2'-bis(5,6-dihydro-4H-1,3-oxazine) and 2,2'-bis(alkyl-5,6-dihydro-4H-1,3-oxazine) [2,2'-bis(alkyl-5,6-dihydro-4H-1,3-oxazine having 1 to 6 carbon atoms), 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), and 2,2'-bis(4,5-dimethyl-5,6-dihydro-4H-1,3-oxazine)]. , 2,2'-alkylenebis(5,6-dihydro-4H-1,3-oxazine) [2,2'-alkylenebis(5,6-dihydro-4H-1,3-oxazine) having 1 to 10 carbon atoms, such as 2,2'-methylenebis(5,6-dihydro-4H-1,3-oxazine), 2,2'-ethylenebis(5,6-dihydro-4H-1,3-oxazine), and 2,2'-hexanemethylenebis(5,6-dihydro-4H-1,3-oxazine)], 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'-C10 alkylenebis(2-carbamoyl-5,6-dihydro-4H-1,3-oxazine), N,N'-tetramethylenebis(2-carbamoyl-5,6-dihydro-4H-1,3-oxazine), etc.], 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 of suitable oxazine compounds include N,N'-C10 alkylenebis(2-carbamoyl-C1-6 alkyl-5,6-dihydro-4H-1,3-oxazine) such as N,N'-4-dimethyl-5,6-dihydro-4H-1,3-oxazine, and N,N'-arylenebis(2-carbamoyl-5,6-dihydro-4H-1,3-oxazine) [N,N'-phenylenebis(2-carbamoyl-oxazine)]. Of 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, relative to 100 parts by mass of the thermoplastic resin. By setting the content at or above the lower limit, hydrolysis resistance tends to be further improved. 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, relative to 100 parts by mass of the thermoplastic resin. By setting the content at or below the upper limit, the melt viscosity tends to be more stable and moldability tends to be improved.

[0085] In particular, when the resin composition of this embodiment contains a polybutylene terephthalate resin, more particularly when the resin component is substantially composed of only 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 the polybutylene terephthalate resin. By setting the content at or above the lower limit, hydrolysis resistance tends to be further improved. 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 polybutylene terephthalate resin. By setting the content at or below the upper limit, melt viscosity tends to be more stable and moldability tends to be improved. The resin composition of the present embodiment may contain only one type of reactive compound, or may contain two or more types. When two or more types are contained, the total amount is preferably in the above range.

[0086] <Other ingredients> The resin composition of this embodiment may contain other components in addition to those described above, as necessary, as long as the desired physical properties are not significantly impaired. Examples of other components include various resin additives. Note that the other components may be contained alone or in any combination and ratio of two or more. Specific examples include stabilizers, release agents, pigments, dyes, UV absorbers, antistatic agents, antifogging agents, antiblocking agents, flow improvers, plasticizers, dispersants, antibacterial agents, etc. The resin composition of the present embodiment preferably contains at least one of stabilizers and release agents.

[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 fiber, and other optional components is 100% by mass. In the resin composition of this embodiment, the total of the thermoplastic resin (preferably polybutylene terephthalate resin), electromagnetic wave absorbing material (preferably carbon nanotubes), and glass fiber preferably accounts for 95% or more by mass of the resin composition. Furthermore, in the resin composition of this embodiment, the total of the thermoplastic resin (preferably polybutylene terephthalate resin), electromagnetic wave absorbing material (preferably carbon nanotubes), glass fiber, stabilizer, and mold release agent preferably accounts for 99% or more by mass of the resin composition.

[0088] The resin composition of this embodiment may also be configured to be substantially free of polycarbonate resin. "Substantially free of polycarbonate resin" means that the content of polycarbonate resin 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. Resin compositions substantially free of polycarbonate resin are particularly preferably used 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 preferred to use a hindered phenol compound and a phosphorus compound in combination. As the stabilizer, specifically, the descriptions in paragraphs 0046 to 0057 of JP 2018-070722 A, the descriptions in paragraphs 0030 to 0037 of JP 2019-056035 A, and the descriptions in paragraphs 0066 to 0078 of WO 2017 / 038949 A can be referred to, 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 the stabilizer per 100 parts by mass of the 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. The upper limit of the amount of the stabilizer is preferably 3 parts by mass or less, more preferably 2 parts by mass or less, and even more preferably 1 part by mass or less per 100 parts by mass of the thermoplastic resin (preferably polybutylene terephthalate resin). The resin composition of the present embodiment may contain only one stabilizer, or may contain two or more stabilizers. When two or more stabilizers are contained, the total amount is preferably in the above range.

[0091] <<Release Agent>> The resin composition of the present embodiment preferably contains a release agent. As the release agent, a wide variety of known release agents can be used, and esters of aliphatic carboxylic acids, paraffin wax and polyethylene wax are preferred, with polyethylene wax being more preferred. For details of the release agent, please refer to the descriptions in paragraphs 0115 to 0120 of JP-A No. 2013-007058, paragraphs 0063 to 0077 of JP-A No. 2018-070722, and paragraphs 0090 to 0098 of JP-A No. 2019-123809, the contents of which are incorporated herein by reference.

[0092] The resin composition of this embodiment preferably contains 0.01 parts by mass or more of the release agent relative to 100 parts by mass of the thermoplastic resin (preferably polybutylene terephthalate resin), more preferably 0.08 parts by mass or more, and even more preferably 0.2 parts by mass or more. The upper limit of the amount of the release agent contained is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, even more preferably 1 part by mass or less, and even more preferably 0.8 parts by mass or less relative to 100 parts by mass of the thermoplastic resin (preferably polybutylene terephthalate resin). The resin composition may contain only one type of release agent, or may contain two or more types. When two or more types are contained, the total amount is preferably in the above range.

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

number

[0094] The absorbency is preferably 50.0% or more, more preferably 55.0% or more, even more preferably 60.0% or more, and even more preferably 65.0% or more. The upper limit is ideally 100%, but even if it is 90.0% or less, the required performance is sufficiently met.

[0095] The resin composition of this embodiment preferably has low reflectance of electromagnetic waves. Specifically, the resin composition of this embodiment preferably has a reflectance of 40.0% or less at a frequency of 76.5 GHz, as determined according to formula (B), when molded into a size of 150 mm×150 mm×2 mm thick. 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. The lower limit is ideally 0%, but even if it is 10.0% or more, the required performance is sufficiently met.

[0097] The resin composition of the present embodiment preferably has low transmittance. The resin composition of this embodiment preferably has a transmittance of 15.0% or less when molded into a size of 150 mm×150 mm×2 mm thick, as determined according to 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. The lower limit is ideally 0%, but even if it is 1.0% or more, the required performance is sufficiently met.

[0099] The resin composition of this embodiment also preferably has excellent dependency on the frequency of electromagnetic waves. For example, when the resin composition of this embodiment is molded into a size of 150 mm x 150 mm x 2 mm thick, 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, the required performance is sufficiently met.

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

[0102] A particularly preferred embodiment of the resin composition of this embodiment is a resin composition containing 0.1 to 10.0 parts by mass of carbon nanotubes per 100 parts by mass of polybutylene terephthalate resin, wherein when the resin composition is molded into a specimen of 150 mm × 150 mm × 2 mm thick, the absorptivity at a frequency of 76.5 GHz calculated according to formula (A) is 40.0 to 100%, and when the resin composition is molded into a specimen of 150 mm × 150 mm × 2 mm thick, 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, and the resin composition is suitable for use as an electromagnetic wave absorber. The resin composition preferably further satisfies the reflectance calculated according to the above formula (B) and / or the transmittance calculated according to the formula (C).

[0103] The resin composition of the present embodiment preferably has excellent mechanical strength. For example, when the resin composition of this embodiment is molded into an ISO multipurpose test piece (thickness 4 mm), the maximum tensile strength measured according to ISO 527-1 and ISO 527-2 is preferably 130 MPa or more. There is no particular upper limit for the maximum tensile strength, but even a value of 200 MPa or less is still practical. Furthermore, the resin composition of the present embodiment preferably has excellent bending properties. Specifically, when the resin composition of this embodiment is molded into an ISO multipurpose test piece (thickness 4 mm), the bending strength is preferably 180 MPa or more, more preferably 190 MPa or more. The upper limit of the bending strength is not particularly specified, 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 (thickness 4 mm), the flexural modulus is preferably 8,000 MPa or more, more preferably 9,000 MPa or more. The upper limit of the flexural modulus is not particularly specified, but for example, 14,000 MPa or less is practical. The details of the measurement method are as described in the Examples.

[0104] <Method of manufacturing resin composition> The resin composition of this embodiment can be produced by a conventional method for producing a resin composition containing a thermoplastic resin, for example, by feeding a thermoplastic resin (preferably polybutylene terephthalate resin), an electromagnetic wave absorbing material (preferably carbon nanotubes), and optionally other components (such as glass fibers) into an extruder and melt-kneading them. The components may be premixed and fed to the extruder all at once, or the components may be premixed without premixing or only a portion of the components may be premixed and fed to the extruder using a feeder. The extruder may be a single-screw extruder or a twin-screw extruder. Furthermore, some components such as the electromagnetic wave absorbing material (preferably carbon nanotubes) may be melt-kneaded with a resin component (e.g., polybutylene terephthalate resin) to prepare a masterbatch, which may then be blended with the remaining components and melt-kneaded. When glass fibers are compounded, they are preferably fed from a side feeder midway through the cylinder of the extruder. The heating temperature during melt-kneading can usually be appropriately selected from the range of 170 to 350°C.

[0105] <Method of manufacturing an electromagnetic wave absorber> The method for producing the electromagnetic wave absorber is not particularly limited, and any molding method generally used for resin compositions containing thermoplastic resins can be used. Examples include injection molding, ultra-high speed injection molding, injection compression molding, two-color molding, gas-assisted or other blow molding methods, 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, laminate molding, press molding, blow molding, etc., of which injection molding is preferred.

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

[0107] The present invention will be explained in more detail below with reference to examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. If the measuring instruments used in the examples are difficult to obtain due to discontinuation or the like, measurements can be made using other instruments with equivalent performance.

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

[0109] Examples 1 to 8, Comparative Examples 1 to 10 <Production of Resin Composition (Pellets)> The components listed in Tables 2 to 6 were placed in a stainless steel tumbler and mixed for 1 hour. The resulting mixture was fed into a co-rotating intermeshing twin-screw extruder (Japan Steel Works, Ltd., "TEX-30α," screw diameter 32 mm, L / D = 42) through the main feed port. The barrel temperature of the first kneading section was set to 260°C for plasticization. Glass fiber was fed through a side feeder in the proportions listed in Tables 2 to 6. The barrel temperature after adding the glass fiber was set to 250°C, and the mixture was melt-kneaded at a discharge rate of 40 kg / h and a screw rotation speed of 200 rpm. The mixture was then extruded as a strand using a four-hole nozzle (circular, 4 mm diameter, 1.5 cm long). The extruded strand was introduced into a water bath for cooling, then inserted into a pelletizer and cut to obtain a resin composition (pellets).

[0110] <Maximum tensile strength> The resin pellets obtained above were dried at 120°C for 5 hours, and then ISO multipurpose test specimens (thickness 4 mm) were injection molded using an injection molding machine ("J85AD" manufactured by The Japan Steel Works, Ltd.) under conditions of a cylinder temperature of 250°C and a mold temperature of 80°C. Using the molded multipurpose ISO multipurpose test specimens, the maximum tensile strength (unit: MPa) and tensile modulus (unit: MPa) were measured in accordance with ISO527-1 and ISO527-2.

[0111] <Increase in maximum tensile strength> The increase rate of the maximum tensile strength was calculated relative to the case where carbon black was blended as a carbon-based electromagnetic wave absorber. In this case, the increase rate was calculated for materials with the same resin composition. That is, for Example 1, Example 2, Comparative Example 4, Comparative Example 5, and Comparative Example 8, the ratio was based on the maximum tensile strength of Comparative Example 1; for Example 3, Example 4, Comparative Example 6, and Comparative Example 9, the ratio was based on the maximum tensile strength of Comparative Example 2; and for Example 5, Example 6, Comparative Example 7, and Comparative Example 10, the ratio was based on the maximum tensile strength of Comparative Example 3. For example, in the case of Example 1, the tensile strength at maximum point of Example 1 is 147 MPa, and the tensile strength at maximum point 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 (thickness 4 mm) were injection molded using an injection molding machine ("J85AD" manufactured by The Japan Steel Works, Ltd.) under conditions of a cylinder temperature of 250°C and a mold temperature of 80°C. The flexural strength (unit: MPa) and flexural modulus (unit: MPa) were measured using the molded multipurpose ISO multipurpose test specimens in accordance with ISO178.

[0113] <Low warpage> The resin composition pellets were dried at 120°C for 5 hours, and then injection-molded into 150 x 150 x 2 mm square plate-shaped test pieces using an injection molding machine (Toshiba "EC160") at a cylinder temperature of 260°C and a mold temperature of 80°C. The warpage (mm) of the molded pieces was measured. Low warpage was evaluated based on the following criteria. The warpage here refers to the linear distance between the third vertex of a 150 x 150 x 2 mm square plate-shaped test piece and the plane when the three vertices of the test piece were fixed to a plane. A: Warpage is less than 3 mm B: Warpage is 3mm or more and less than 15mm C: Warpage is 15mm or more

[0114] <Absorption rate, transmittance, reflectance> The pellets obtained above were injection molded in an injection molding machine (Toshiba Machine Co., Ltd., "EC160") at a cylinder temperature of 260°C and a mold temperature of 80°C to obtain test pieces measuring 150 mm x 150 mm x 2 mm thick. Using the obtained test pieces, the absorptance calculated according to formula (A), the reflectance calculated according to formula (B), and the transmittance calculated according to formula (C) at a frequency of 76.5 GHz were measured as follows. For the measurements, an Anritsu network analyzer, "MS4647B Vector Network Analyzer," was used. The measurement was performed by placing the test piece so that the TD (transverse direction) direction of the injection molded article was parallel to the direction of the electric field. Formula (A)

number

[0115] Formula (B)

number

[0116] Formula (C)

number

[0117] <Frequency dependence of reflectivity> The reflectance of the test piece obtained above was measured at a frequency of 70 to 80 GHz. The difference between the maximum reflectance and the minimum reflectance was calculated. The smaller the difference between the maximum reflectance and the minimum reflectance, the more excellent the frequency dependency and the more stable the resin composition obtained.

[0118] <Electromagnetic wave absorption performance evaluation> Based on the absorbance, reflectance, and transmittance measured above, the evaluation was carried out as follows. A: All of the following (1) to (3) are met. B: At least the following (1) is met (excluding those that fall under A): C: Other than A and B above (1) Absorption rate is 60.0% or more (2) Reflectance is 30.0% or less (3) Transmittance is 10.0% or less

[0119] <Overall rating> Based on the absorbance, reflectance, transmittance, low warpage, maximum tensile strength, and bending strength measured above, the evaluation was carried out as follows. 6: All of the following (1) to (6) are met. 5: Meet five of the following (1) to (6). 4: Four of the following (1) to (6) are met. 3: Three of the following (1) to (6) are met. 2: Two of the following (1) to (6) are met. 1: One of the following (1) to (6) is met. (1) Absorption rate is 60.0% or more (2) Reflectance is 30.0% or less (3) Transmittance is 10.0% or less (4) Low warpage rating: A or B (5) Maximum tensile strength is 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 indicates 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 high electromagnetic wave absorption and low electromagnetic wave transmittance and reflectance. Furthermore, the difference in reflectance due to differences in electromagnetic wave frequency was small. Furthermore, the resin composition of the present invention had excellent mechanical strength.

Claims

1. A resin composition containing a thermoplastic resin and an electromagnetic wave absorbing material, The resin composition is suitable for use as an electromagnetic wave absorber, and when the resin composition is molded into a shape of 150 mm x 150 mm x 2 mm thick, the absorbance at a frequency of 76.5 GHz calculated according to formula (A) is 40.0 to 100%, and when the resin composition is molded into a shape of 150 mm x 150 mm x 2 mm thick, the difference between the highest and lowest reflectances calculated according to formula (B) in the frequency range of 70 GHz to 80 GHz is 20.0% or less. Formula (A) [Equation 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) [Equation 2] (In the above formula (B), R represents the return loss measured by the free space method.)

2. The resin composition according to claim 1 , wherein the electromagnetic wave absorbing material is a carbon-containing electromagnetic wave absorbing material.

3. For 100 parts by mass of thermoplastic resin, A resin composition containing 0.1 to 10.0 parts by mass of carbon nanotubes, When the resin composition is molded into a shape of 150 mm × 150 mm × 2 mm thick, the absorption rate at a frequency of 76.5 GHz calculated according to formula (A) is 40.0 to 100%, The resin composition according to claim 1 or 2, wherein the difference between the highest and lowest reflectance values ​​calculated according to formula (B) in a frequency range of 70 GHz to 80 GHz when the resin composition is molded into a shape of 150 mm x 150 mm x 2 mm thick is 20.0% or less, and the resin composition is suitable for use as an electromagnetic wave absorber.

4. The resin composition according to any one of claims 1 to 3, further comprising 10 to 100 parts by mass of glass fiber relative to 100 parts by mass of the thermoplastic resin.

5. The resin composition according to claim 4, wherein 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.

6. The resin composition according to any one of claims 1 to 5, further comprising 0.01 to 5.0 parts by mass of a reactive compound relative to 100 parts by mass of the thermoplastic resin.

7. The resin composition according to any one of claims 1 to 6, wherein the thermoplastic resin comprises a polybutylene terephthalate resin.

8. The resin composition according to claim 7, further comprising 1.0 to 75 parts by mass of a polycarbonate resin relative to 100 parts by mass of the polybutylene terephthalate resin.

9. The resin composition according to claim 7, further comprising 1.0 to 60 parts by mass of a polystyrene-based resin relative to 100 parts by mass of the polybutylene terephthalate resin.

10. The resin composition according to claim 7, further comprising 1.0 to 75 parts by mass of a polycarbonate resin and 1.0 to 60 parts by mass of a polystyrene resin relative to 100 parts by mass of the polybutylene terephthalate resin.

11. The resin composition according to any one of claims 1 to 6, wherein the thermoplastic resin comprises a polypropylene resin.

12. The resin composition according to any one of claims 1 to 6, wherein the thermoplastic resin comprises a polyamide resin.

13. The resin composition according to any one of claims 1 to 12, wherein the electromagnetic wave absorbing material comprises multi-walled carbon nanotubes.

14. The resin composition according to any one of claims 1 to 13, wherein the resin composition does not contain carbon fibers or has a carbon fiber content of less than 3 mass%.

15. The resin composition according to any one of claims 1 to 14, wherein the reflectivity calculated according to formula (B) at a frequency of 76.5 GHz when molded into a size of 150 mm x 150 mm x 2 mm thick is 40.0% or less. The resin composition according to any one of claims 1 to 14. Formula (B) [Equation 3] (In the above formula (B), R represents the return loss measured by the free space method.)

16. The resin composition according to any one of claims 1 to 15, wherein the transmittance calculated according to formula (C) at a frequency of 76.5 GHz when molded into a size of 150 mm x 150 mm x 2 mm thick is 15.0% or less. The resin composition according to any one of claims 1 to 15. Formula (C) [Equation 4] (In the above formula (C), T represents the transmission attenuation measured by the free space method.)

17. A resin composition containing a thermoplastic resin, The resin composition is for use as an electromagnetic wave absorber, wherein when the resin composition is molded into a shape of 150 mm x 150 mm x 2 mm (thickness), the absorption rate calculated according to formula (A) at a frequency of 76.5 GHz is 60.0% or more; when the resin composition is molded into a shape of 150 mm x 150 mm x 2 mm (thickness), the reflectance calculated according to formula (B) at a frequency of 76.5 GHz is 30.0% or less; and when the resin composition is molded into a shape of 150 mm x 150 mm x 2 mm (thickness), the transmittance calculated according to formula (C) at a frequency of 76.5 GHz is 10.0% or less. Formula (A) [Equation 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) [Equation 6] (In the above formula (B), R represents the return loss measured by the free space method.) Formula (C) [Equation 7] (In the above formula (C), T represents the transmission attenuation measured by the free space method.)

18. An electromagnetic wave absorber formed from the resin composition according to any one of claims 1 to 17.

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