Thermoplastic resin composition for electromagnetic wave absorber, and molded article

Abstract

To provide an electromagnetic wave absorber that suppresses the anisotropy of electromagnetic wave absorption due to the orientation of the electromagnetic wave absorbing material, exhibits excellent electromagnetic wave absorption with low reflection and transmission attenuation, and further possesses excellent moldability and rigidity, as well as a thermoplastic resin composition for electromagnetic wave absorbers used in its formation. To provide a molded material for millimeter-wave absorbers that exhibits excellent electromagnetic wave absorption, even in the specific frequency band of 60-90 GHz known as the E-band within the millimeter-wave spectrum. [Solution] The problem is solved by a thermoplastic resin composition for electromagnetic wave absorbers, comprising a thermoplastic resin (A), carbon black (B), and a filler (C), wherein the filler (C) has a particle size (d50) of 10 μm or less at which the cumulative volume reaches 50%, and the content of the filler (C) is 15% by mass or more in 100% by mass of the thermoplastic resin composition.

Description

[Technical Field]

[0001] The present invention relates to a thermoplastic resin composition for electromagnetic wave absorbers and a molded article. [Background technology]

[0002] Because plastics are easy to mold and process, they are used in a wide range of fields, including electrical and electronic equipment components, automotive parts, medical components, and food containers. There is active research being done on plastic molded products to enhance their decorative properties or to add functionality. In particular, in the automotive sector, molded products with electromagnetic wave absorbing properties are being sold as electromagnetic wave absorbers.

[0003] Electromagnetic waves are emitted from communication devices such as radios, televisions, and wireless communication devices, but in addition, electromagnetic waves are also emitted from electronic devices such as mobile phones and personal computers, which have rapidly increased in number due to recent advances in information technology. Conventionally, one method to avoid malfunctions caused by electromagnetic waves in electronic devices and communication devices has been to install electromagnetic wave absorbers, which efficiently absorb electromagnetic waves and convert the absorbed electromagnetic waves into thermal energy, near or far from the electromagnetic wave generating parts.

[0004] One example of using electromagnetic wave absorbers placed far from the source of electromagnetic wave generation is in the application of ETC (Electronic Toll Collection) systems on expressways. ETC is a system that uses 5.8 GHz microwaves to exchange billing information between roadside antennas and on-board antennas when vehicles pass through expressway toll booth exits. In toll booths where this ETC system is installed, microwaves emitted from the antennas can be reflected off the toll booth roof, etc., causing unwanted electromagnetic waves to leak from adjacent ETC lanes, which can lead to communication problems. Therefore, electromagnetic wave absorbers are installed between the toll booth roof and ETC lanes to suppress communication problems.

[0005] Furthermore, in recent years, millimeter-wave radar has been used in the automotive sector for purposes such as autonomous driving and collision avoidance, and in many cases, millimeter-wave radar devices are installed inside the vehicle. Millimeter waves are electromagnetic waves with wavelengths of 1-10 mm and frequencies of 30-300 GHz. They are used in millimeter-wave radar systems such as automotive radar, full-body scanners that can see through clothing for security checks at airports, and millimeter-wave radar systems for transmitting video from surveillance cameras on train platforms during one-man operation. Millimeter-wave radar systems emit millimeter waves and receive the reflected waves to recognize obstacles. Due to their long detection range and resistance to interference from sunlight, rain, and fog, they are now used in autonomous driving technologies for automobiles and other vehicles. In the case of automotive sensors, millimeter-wave radar systems transmit and receive millimeter waves from an antenna to detect the relative distance and relative speed to obstacles.

[0006] The transmitting and receiving antennas of such millimeter-wave radar systems can sometimes receive electromagnetic waves reflected from surfaces other than the target obstacle, such as the road surface, which can reduce the detection accuracy of the system. To solve this problem, millimeter-wave radar systems incorporate electromagnetic wave absorbers as shielding members between the antenna and the control circuit to block electromagnetic waves. Furthermore, electromagnetic wave absorbers are often used as millimeter-wave radar covers that also serve to fix and protect the millimeter-wave radar system, and therefore rigidity, or resistance to deformation, is also required.

[0007] For example, Patent Documents 1 and 2 describe resin compositions containing radio wave absorbing materials such as carbon black (CB) and carbon nanotubes (CNT) as components of such electromagnetic wave absorbers. Resin compositions containing CB and CNT can efficiently absorb electromagnetic waves due to dielectric loss, and since molded bodies of various shapes can be produced using these resin compositions, they are widely used as electromagnetic wave absorbers for millimeter-wave radar devices. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2019-161210 [Patent Document 2] Special Publication No. 2016-504471 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] However, these conventional electromagnetic wave absorbers do not possess sufficient electromagnetic wave absorption properties, rigidity, or reflectance attenuation to adequately protect millimeter-wave radar equipment from the surrounding environment while preventing interference with signal transmission. Furthermore, incorporating large amounts of electromagnetic wave absorbing material to improve radio wave absorption can worsen moldability. In addition, anisotropy becomes a problem, where the orientation of electromagnetic wave absorbing materials such as CB and CNT during molding causes differences in the electromagnetic wave absorption properties of the molded body depending on the direction of the electromagnetic field. The presence of anisotropy means that only electromagnetic waves in a specific field direction are absorbed, reducing the amount of electromagnetic waves absorbed by the electromagnetic wave absorber. This results in unwanted electromagnetic waves being detected by the antenna of the millimeter-wave radar equipment, reducing the detection accuracy of the equipment. Therefore, it is necessary to have similar electromagnetic wave absorption performance regardless of the direction of the incident electromagnetic field.

[0010] In other words, the problem that the present invention aims to solve is to provide an electromagnetic wave absorber that exhibits excellent electromagnetic wave absorption with low reflection and transmission attenuation, suppresses anisotropy of electromagnetic wave absorption due to the orientation of the electromagnetic wave absorbing material, and further has excellent moldability and rigidity, as well as a thermoplastic resin composition for electromagnetic wave absorbers used in its formation. Furthermore, the objective is to provide a molded material for millimeter-wave absorbers that exhibits excellent electromagnetic wave absorption even in the specific frequency band of 60-90 GHz, known as the E-band, within the millimeter-wave spectrum. [Means for solving the problem]

[0011] As a result of intensive studies by the present inventors, it has been found that the problems of the present invention can be solved in the following aspects, and the present invention has been completed. That is, the present invention includes the following embodiments. 〔1〕A thermoplastic resin composition containing a thermoplastic resin (A), carbon black (B), and a filler (C), where the filler (C) has a particle diameter (d50) at which the cumulative volume is 50% of 10 μm or less, in 100% by mass of the thermoplastic resin composition, the content of carbon black (B) is 10% by mass or more and 30% by mass or less, and the content of the filler (C) is 15% by mass or more and 45% by mass or less, A thermoplastic resin composition for an electromagnetic wave absorber. 〔2〕The thermoplastic resin composition for an electromagnetic wave absorber according to 〔1〕, wherein the thermoplastic resin (A) contains a polyolefin resin (A1). 〔3〕The thermoplastic resin composition for an electromagnetic wave absorber according to 〔1〕 or 〔2〕, wherein the carbon black (B) has a DBP oil absorption of 100 to 300 mL / 100 g. 〔4〕The thermoplastic resin composition for an electromagnetic wave absorber according to any one of 〔1〕 to 〔3〕, wherein the filler (C) contains talc. 〔5〕A molded body formed from the thermoplastic resin composition for an electromagnetic wave absorber according to any one of 〔1〕 to 〔4〕.

Effects of the Invention

[0012] According to the present invention, it is possible to provide an electromagnetic wave absorber that exhibits excellent electromagnetic wave absorption properties with low reflection attenuation and low transmission attenuation, suppresses the anisotropy of electromagnetic wave absorption properties due to the orientation of the radio wave absorption material, and further has excellent rigidity, and a thermoplastic resin composition for an electromagnetic wave absorber used for forming the same. Furthermore, even in millimeter waves, even in the specific frequency band of 60 to 90 GHz called the E band, since both the reflection attenuation and the transmission attenuation are low, it can also be suitably used as a molded body for a millimeter wave absorber.

Brief Description of the Drawings

[0013] [Figure 1]FIG. 1 is a conceptual diagram of measurement of transmission attenuation and reflection attenuation by a millimeter-wave transmitter.

Best Mode for Carrying Out the Invention

[0014] Hereinafter, an example of an embodiment to which the present invention is applied will be described. However, the present invention is not limited to this embodiment, and other embodiments may belong to the scope of the present invention as long as they conform to the gist of the present invention. Also, the numerical range "A to B" specified in this specification means a range that satisfies a value greater than numerical value A and a value less than numerical value B. Further, in this specification, "film", "sheet", and "plate" are synonymous and are not distinguished by thickness. "Carbon black" may be represented as "CB", "particle size (d50) at which the cumulative volume becomes 50%" may be represented as "particle size (d50)", and "thermoplastic resin composition for electromagnetic wave absorber" may be represented as "thermoplastic resin composition". Each of the various components appearing in this specification may be used alone or in combination of two or more, unless otherwise noted. Note that the numerical values specified in this specification are values obtained by the methods disclosed in the embodiments or examples.

[0015] 《Thermoplastic Resin Composition for Electromagnetic Wave Absorber》 The thermoplastic resin composition of the present invention is used to form an electromagnetic wave absorber. The thermoplastic resin composition for electromagnetic wave absorber contains a thermoplastic resin (A), carbon black (B), and a filler (C). The filler (C) has a particle size (d50) at which the cumulative volume becomes 50% of 10 μm or less, and the content of the filler (C) is 15% by mass or more in 100% by mass of the thermoplastic resin composition.

[0016] In this way, by using a predetermined amount of carbon black and a filler with a small average particle size, sufficient electromagnetic wave absorption can be exhibited, and the orientation of carbon black in the molded body can be controlled. Thereby, it is presumed that not only excellent rigidity but also anisotropy of electromagnetic wave absorption when formed into a molded body can be suppressed.

[0017] The weight ratio of carbon black (B) to filler (C) (carbon black (B) / filler (C)) is preferably 0.3 to 1.5, and more preferably 0.5 to 1.1. By keeping it within this range, both electromagnetic wave absorption and suppression of anisotropy of electromagnetic wave absorption can be achieved.

[0018] <Thermoplastic resin (A)> The thermoplastic resin (A) is not particularly limited as long as it is a resin that can be molded by heating and melting. Examples of thermoplastic resins (A) include polyolefin resins (A1) such as polyethylene resin (PE) and polypropylene resin (PP), polyamide resin (PA) (A2), polycarbonate resin (PC) (A3), polyester resins such as polyethylene terephthalate resin (PET) and polybutylene terephthalate resin (PBT), polystyrene resin (PS), polyphenylene ether resin, acrylonitrile-butadiene-styrene copolymer resin (ABS), polyacetal resin (POM), polyvinyl chloride resin, acrylic resin, polyetherimide resin (PEI), polyphenylene sulfide resin, polyurethane resin (PU), and liquid silicone rubber (LSR). From the viewpoint of versatility and rigidity, polyolefin resin (A1), polyamide resin (A2), and polycarbonate resin (A3) are preferred. From the viewpoint of moldability, polyolefin resin (A1) is more preferred, and from the viewpoint of moldability and lightweight properties, polypropylene resin is even more preferred.

[0019] The melt flow mass rate (MFR) of thermoplastic resin (A) is preferably 1 to 100 g / 10 min, more preferably 5 to 80 g / 10 min, and more preferably 7 to 60 g / 10 min, from the viewpoint of moldability and rigidity. The melt flow mass rate (MFR) was measured according to JIS K7210-1:2014. The polypropylene resin was measured at 230°C with a load of 2.16 kgf, the polyamide resin at 240°C with a load of 2.16 kgf, and the polycarbonate resin at 280°C with a load of 1.2 kgf.

[0020] From the viewpoint of electromagnetic wave absorption, the content of thermoplastic resin (A) is preferably 40% by mass or more, based on the thermoplastic resin composition (100% by mass). It is also preferably 85% by mass or less. Furthermore, it is more preferably 50% by mass or more and 70% by mass or less.

[0021] [Polyolefin resin (A1)] Polyolefin resin (A1) is a polymer composed of olefins (monomers). Specifically, examples include polyethylene resins (PE) such as high-density polyethylene (HDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE), polypropylene resin (PP), ethylene-α-olefin copolymers, ethylene-vinyl acetate copolymers, ethylene vinyl alcohol copolymers, ethylene ethyl acrylate copolymers, and cyclic olefin resins such as cycloolefin polymers and cycloolefin copolymers. Low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or polypropylene resin (PP) are preferred in terms of versatility and fluidity. Examples of polypropylene resin (PP) include homopolypropylene, block propylene copolymer, random propylene copolymer, ethylene propylene copolymer rubber, and polypropylene obtained using metallocene compounds as polymerization catalysts, as well as modified polypropylene resins such as maleic anhydride modified polypropylene, glycidyl (meth)acrylate modified polypropylene, and 2-hydroxyethyl (meth)acrylate modified polypropylene. Furthermore, the polyolefin resin (A1) may be an oxidized polyolefin in which the polyolefin is partially oxidized. In addition, the polyolefin resin (A1) can be used alone or in combination of two or more types.

[0022] Furthermore, the polyolefin resin (A1) in the present invention preferably has an MFR of 1 to 100 g / 10 min at a temperature of 230°C and a load of 2.16 kgf, more preferably 5 to 80 g / 10 min, and more preferably 7 to 60 g / 10 min. Being within the above range is preferable in terms of moldability and rigidity.

[0023] [Polyamide resin (A2)] Polyamide resin (A2) is a polycondensate having amide bonds, and specifically includes nylon 4,6, nylon 6, nylon 6,6, nylon 6,10, nylon 6,12, nylon 12, nylon 6,T, nylon 9,T, aromatic nylon resins, etc. From the viewpoint of versatility and fluidity, nylon 6 and nylon 6,6 are preferred. Furthermore, polyamide resin (A2) can be used alone or in combination of two or more types.

[0024] Furthermore, the polyamide resin (A2) in the present invention preferably has an MFR in the range of 5.0 to 50 g / 10 min at a temperature of 240°C and a load of 2.16 kgf, preferably in the range of 15 to 40 g / 10 min, and particularly preferably in the range of 25 to 35 g / 10 min. Being within the above range is preferable in terms of moldability and rigidity.

[0025] [Polycarbonate resin (A3)] Polycarbonate resin (A3) is a polycondensate in which the bonding sites between monomer units consist of carbonate groups. Specifically, resins that can be easily produced by reacting aromatic dihydroxy compounds with carbonate precursors such as phosgene or diester carbonate can be used. For example, when using phosgene as the carbonate precursor, the resin can be obtained by an interfacial method, or when using diester carbonate, by a transesterification method in which the reaction is carried out in a molten state.

[0026] Furthermore, the polycarbonate resin (A3) in this invention has an MFR (Moisture Factor Retention) in the range of 5.0 to 50 g / 10 min at a temperature of 280°C and a load of 1.2 kgf, preferably in the range of 15 to 40 g / 10 min, and particularly preferably in the range of 25 to 35 g / 10 min. Being within the above range is preferable in terms of moldability and rigidity.

[0027] <Radio wave absorbing material> The thermoplastic resin composition for electromagnetic wave absorbers of the present invention contains carbon black (B) as a radio wave absorbing material in an amount of 10% to 30% by mass of 100% by mass of the thermoplastic resin composition. This makes it possible to absorb electromagnetic waves through the dielectric loss of carbon black while maintaining moldability.

[0028] From the viewpoint of electromagnetic wave absorption, the carbon black (B) content is 10 to 30% by mass, with 15 to 20% by mass being preferred, based on 100% by mass of the resin composition.

[0029] If necessary, other electromagnetic wave absorbing materials besides carbon black (B) may be included. Other electromagnetic wave absorbing materials besides carbon black (B) may include carbon nanotubes, carbon fibers, etc., as long as they do not impair the effects of the present invention. However, from the viewpoint of moldability and electromagnetic wave absorption, a higher carbon black (B) content is preferable. The carbon black (B) content in 100% by mass of the electromagnetic wave absorbing material is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, and even more preferably 90 to 100% by mass.

[0030] [Carbon Black (B)] Carbon black (B) is an amorphous carbon with electrical conductivity and can be produced by incomplete combustion of oil or gas, or by thermal decomposition of hydrocarbons. Carbon black (B) can be produced by furnace black, which is manufactured by continuously thermally decomposing gaseous or liquid raw materials in a reactor, particularly Ketjenblack made from ethylene heavy oil, channel black, which is produced by burning raw material gas and rapidly cooling the bottom surface of channel steel to precipitate it, thermal black, which is obtained by periodically repeating combustion and thermal decomposition using gas as a raw material, particularly acetylene black made from acetylene gas. Various types can be used individually or in combination of two or more. In addition, conventionally treated oxidized carbon black and hollow carbon can also be used. From the viewpoint of radio wave absorption and moldability, furnace black or acetylene black is preferred.

[0031] Oxidation of carbon involves directly introducing (covalently bonding) oxygen-containing polar functional groups such as phenolic groups, quinone groups, carboxyl groups, and carbonyl groups to the carbon surface by treating the carbon at high temperatures in air or secondarily with nitric acid, nitrogen dioxide, ozone, etc. This process is commonly performed to improve the dispersibility of carbon. However, since the conductivity of carbon generally decreases as the amount of functional groups introduced increases, it is preferable to use carbon that has not undergone oxidation treatment.

[0032] [Specific surface area] The BET specific surface area of ​​carbon black (B) is 1000 m². 2 It is preferably less than or equal to / g, and more preferably 10 to 800m 2 / g, more preferably 30-500m 2 The value is / g. The BET specific surface area refers to the specific surface area measured by the BET method due to nitrogen adsorption. This BET specific surface area corresponds to the surface area of ​​carbon black, and by setting the BET specific surface area within this range, electromagnetic wave absorption can be further improved.

[0033] [DBP oil absorption] The DBP oil absorption of carbon black (B) is preferably 100 to 300 mL / 100g, and more preferably 100 to 200 mL / 100g. Having the DBP oil absorption within this range is preferable because it allows for improved electromagnetic wave absorption while maintaining moldability and rigidity. The DBP oil absorption is a value measured in accordance with JIS K6217-4:2017, indirectly quantifying the structure of the carbon black by measuring the void volume. "DBP" is an abbreviation for Dibutylphthalate.

[0034] [Average primary particle size] The average primary particle diameter of carbon black can be determined, for example, using a scanning electron microscope (JEOL JSM-6700M). The procedure involves observing the carbon black at an accelerating voltage of 5kV, capturing an image at 50,000x magnification (1024 x 1280 pixels), then measuring the individual particle diameters of 20 arbitrary carbon black particles in the captured image, and calculating the average number of these measurements as the average primary particle diameter of the carbon black. The average primary particle diameter of carbon black (B) is preferably 20-60 nm, and more preferably 25-50 nm. By using carbon black with an average primary particle diameter within this range, the carbon black particles can effectively form conductive paths with each other, enabling stable and higher electromagnetic wave absorption.

[0035] Commercially available carbon blacks include, for example, Shin-Nippon Carbon's furnace blacks such as Nitelon #10, #200 and #300; Tokai Carbon's furnace blacks such as Toka Black #4300, #4400, #4500 and #5500; Degussa's furnace blacks such as Printex L; Colombian's furnace blacks such as Raven 7000, 5750, 5250, 5000ULTRAIII, 5000ULTRA, Conductex SCULTRA, 975ULTRA, PUERBLACK 100, 115 and 205; and #2350, #2400B, #2600B, #30050B, #3030B, #32 Examples include, but are not limited to, furnace blacks manufactured by Mitsubishi Chemical Corporation such as 30B, #3350B, #3400B, and #5400B; furnace blacks manufactured by Cabot Corporation such as MONARCH1400, 1300, 900, VulcanXC-72R, and BlackPearls2000; furnace blacks manufactured by Timcal Corporation such as Ensaco250G, Ensaco260G, Ensaco350G, and SuperP-Li; Ketjenblack manufactured by Akzo Corporation such as Ketjenblack EC-300J and EC-600JD; and acetylene blacks manufactured by Denki Kagaku Kogyo Co., Ltd. such as Denka Black HS-100 and FX-35.

[0036] <Filler (C)> A filler is a compound added to a molded article to improve its performance, increase its volume, or add color. The resin composition of this embodiment contains a filler (C) whose particle size (d50) at which the cumulative volume reaches 50% is 10 μm or less, and furthermore, the content of the filler (C) is 15% by mass or more and 45% by mass or less in 100% by mass of the thermoplastic resin composition. By including a filler (C) with a small particle size (d50) within this range, the anisotropy of the electromagnetic wave absorption of the resulting molded article with respect to the electric field direction of the incident electromagnetic wave can be suppressed, and the electromagnetic wave absorption can be further improved.

[0037] The particle size (d50) of the filler (C) is 10 μm or less, preferably 8.0 μm or less, and more preferably 7.0 μm or less. The smaller the particle size (d50), the better, and it may be 0.001 μm or more. The particle size (d50) of the filler (C) is also called the median diameter, and it is the particle size at which the cumulative volume based on volume, as measured by a laser diffraction scattering particle size distribution device, reaches 50%. Specifically, it can be calculated by the method described in the examples.

[0038] The content of filler (C) is 15% by mass or more and 45% by mass or less per 100% by mass of the thermoplastic resin composition. Preferably it is 18% by mass or more, more preferably 20% by mass or more. Also preferably it is 30% by mass or less.

[0039] By including a specific amount of filler having particle sizes within the aforementioned range, the effect of reducing anisotropy in electromagnetic wave absorption can be improved. The reason for this is not entirely clear, but it is presumed to be as follows: Including a large amount of filler with small particle sizes reduces the fluidity of the resin, but within this range, the viscosity of the resin increases well while maintaining moldability. This allows for control of the orientation of the electromagnetic wave absorbing material during molding, and an effect of reducing anisotropy can be expected. In addition, by including filler with small particle sizes in this range, the filler is uniformly dispersed in the resin. Since there is no electromagnetic wave absorbing material inside the filler, it becomes easier to form conductive paths in the resin. This is thought to improve electromagnetic wave absorption performance.

[0040] The filler (C) in this invention is not particularly limited as long as its particle size (d50) is 10 μm or less, and can be either an inorganic or organic filler. Furthermore, the filler may be a single type or a mixture of multiple types. However, from the viewpoint of rigidity, an inorganic filler is preferred.

[0041] Examples of inorganic fillers include metal oxides, metal hydroxides, metal stearates, carbonates such as calcium carbonate, silicates, aluminosilicates, sulfates, talc, silica, mica, clay, and dolomite. Among these, talc or carbonates are preferred because they have good kneadability with resins, which improves radio wave absorption performance. Calcium carbonate is even more preferred among carbonates. From the viewpoint of rigidity, talc is particularly preferred.

[0042] The content of talc and calcium carbonate is preferably 90% by mass or more, more preferably 95% by mass, and particularly preferably 99% by mass or more, and may be 100% by mass, based on the mass of filler (C) (100% by mass). When both talc and calcium carbonate are included, it is preferable that the talc content be 90% by mass or more, more preferably 95% by mass or more, and particularly preferably 99% by mass or more, based on the mass of filler (C) (100% by mass).

[0043] Examples of metal oxides include calcium oxide, magnesium oxide, and zinc oxide. Examples of metal hydroxides include calcium hydroxide, magnesium hydroxide, and aluminum hydroxide. Examples of metal stearate salts include magnesium stearate, zinc stearate, and calcium stearate. Examples of carbonates include calcium carbonate and magnesium carbonate, while examples of silicates include calcium silicate and magnesium silicate. Examples of aluminosilicates include sodium aluminosilicate and calcium aluminosilicate, while examples of sulfates include calcium sulfate, barium sulfate, and calcium sulfite.

[0044] Examples of organic fillers include organic microballoons made of phenolic resin or vinylidene chloride resin, as well as particles made of resins such as polyvinyl chloride (PVC) and polymethyl methacrylate (PMMA).

[0045] [talc] Talc is a powdered form of "talc" containing water, silicon, oxygen, and magnesium, and is also known as hydrated magnesium silicate. It is a smooth, highly adsorbent inorganic material.

[0046] When two or more types of filler (C) are used, the talc content is preferably 90% by mass or more, more preferably 95% by mass, and particularly preferably 99% by mass or more, with the mass of filler (C) being 100% by mass.

[0047] In the present invention, the particle size (d50) of talc is 10 μm or less, preferably 9.0 μm or less, more preferably 8.0 μm or less, and particularly preferably 7.0 μm or less. Furthermore, the particle size (d50) of talc is preferably 0.5 μm or more, and more preferably 1.0 μm or more. By setting it within the above range, moldability is improved and anisotropy is further suppressed.

[0048] Furthermore, in this invention, the BET specific surface area of ​​talc is 3.0 m². 2It is preferable that it be 5.0m or more per gram. 2 It is more preferable that it be 40m or more. 2 It is preferable that the amount be less than or equal to 20.0 m 2 It is more preferable that the amount is less than or equal to / g. The BET specific surface area of ​​talc can be measured using a BET specific surface area measuring device (Macsorb, manufactured by Mounttech) as follows. By setting it within the above range, moldability is improved and rigidity is also increased.

[0049] First, 0.2g to 0.3g of talc to be measured is placed in the measuring device, and as a pretreatment, it is heated at 200°C for 5 minutes in a mixed gas atmosphere of nitrogen and helium. After that, the BET specific surface area is measured by performing low-temperature, low-humidity physical adsorption in a liquid nitrogen environment.

[0050] [Calcium carbonate] The calcium carbonate may be so-called heavy calcium carbonate, which is obtained by mechanically crushing limestone, or it may be precipitated calcium carbonate, which can be obtained, for example, by carbon dioxide gasification. From the standpoint of workability and cost, heavy calcium carbonate is preferred. High-purity limestone, the raw material for calcium carbonate, is abundant in Japan and can be obtained very economically. One type of calcium carbonate may be used alone, or two or more types may be used in combination.

[0051] To improve the dispersibility or reactivity of calcium carbonate, the surface of the calcium carbonate particles may be pre-modified. Examples of surface modification methods include physical methods such as plasma treatment, and chemical surface treatment with coupling agents or surfactants. Examples of coupling agents include silane coupling agents and titanium coupling agents. Surfactants may be anionic, cationic, nonionic, or amphoteric, and examples include higher fatty acids, higher fatty acid esters, higher fatty acid amides, and higher fatty acid salts.

[0052] In the present invention, the particle diameter (d50) of calcium carbonate is 10 μm or less, preferably 8.0 μm or less, more preferably 6.0 μm or less, and particularly preferably 4.0 μm or less. Also, the particle diameter (d50) of calcium carbonate is preferably 0.5 μm or more. By setting it within the above range, the moldability is improved and the anisotropy of electromagnetic wave absorption is further suppressed.

[0053] The BET specific surface area of calcium carbonate is 1.0 m 2 / g to 3.0 m 2 / g, more preferably 1.2 m 2 / g to 2.8 m 2 / g. By setting it within the above range, the moldability is improved and the rigidity is increased, which is preferable. The BET specific surface area of calcium carbonate can be measured as follows using a BET specific surface area measuring device (Macsorb manufactured by Mountech).

[0054] First, 0.2 g to 0.3 g of calcium carbonate to be measured is filled into the measuring device, and as a pretreatment, heat treatment is performed at 200 °C for 5 minutes in a mixed gas atmosphere of nitrogen and helium. Then, the BET specific surface area is measured by performing low-temperature and low-humidity physical adsorption in an environment of liquid nitrogen.

[0055] Furthermore, in the present invention, the sieve residue of the JIS standard sieve with a mesh opening of 45 μm measured by the following sieve test method for calcium carbonate is 1000 ppm or less, preferably 100 ppm or less. The sieve test method for obtaining the sieve residue is measured in accordance with JIS K5101-14:2004.

[0056] <Other optional components> The thermoplastic resin composition can use other optional components such as fillers other than filler (C), flame retardants, weather resistance stabilizers, antistatic agents, dyes, pigments, coupling agents, crystal nucleating agents, etc.

[0057] Note that the thermoplastic resin composition preferably does not contain volatile components. In 100% by mass of the thermoplastic resin composition, volatile components such as solvents and low molecular weight components are preferably 5% by mass or less, and more preferably 1% by mass or less.

[0058] Examples of flame retardants include one or more combinations of halogenated flame retardants, phosphorus-based flame retardants, and non-phosphorus, non-halogenated flame retardants such as metal hydrates. Examples of halogenated flame retardants include halogenated bisphenol compounds such as halogenated bisphenylalkanes, halogenated bisphenylhalates, halogenated bisphenylthioethers, and halogenated bisphenylsulfones, and bisphenol-bis(alkyl ether) compounds such as brominated bisphenol A, brominated bisphenol S, chlorinated bisphenol A, and chlorinated bisphenol S. Examples of phosphorus-based flame retardants include aluminum tris(diethylphosphonate), bisphenol A bis(diphenylphosphate), triarylisopropyl phosphate, cresyl di2,6-xylenyl phosphate, and aromatic condensed phosphate esters. Examples of metal hydrates include aluminum trihydrate and magnesium dihydrate. In addition to these flame retardants, other flame retardant additives such as antimony oxide (including antimony trioxide and antimony pentoxide), zinc oxide, iron oxide, aluminum oxide, molybdenum oxide, titanium oxide, calcium oxide, and magnesium oxide may also be used in combination.

[0059] <Method for producing thermoplastic resin compositions> The method for producing the thermoplastic resin composition of the present invention is not particularly limited. For example, a thermoplastic resin (A), carbon black (B), a filler (C), and other optional components can be added and mixed in a Henschel mixer, tumbler, disper, etc., and then mixed or melt-kneaded in a batch-type kneader such as a kneader, roll mill, super mixer, Henschel mixer, Shugi mixer, vertical granulator, high-speed mixer, fur matrix, ball mill, steel mill, sand mill, vibratory mill, attritor, or Banbury mixer, or in a twin-screw extruder, single-screw extruder, rotor-type twin-screw kneader, etc., to obtain a resin composition in the form of pellets, powders, granules, or beads. In this invention, it is preferable to use a twin-screw extruder for melt mixing.

[0060] The thermoplastic resin composition of the present invention may be a masterbatch containing a relatively high concentration of carbon black (B) and used after being diluted with thermoplastic resin (A) during molding, or it may be a compound with a relatively low concentration of carbon black (B) and used for molding in its original composition without dilution with thermoplastic resin (A).

[0061] Molded body The molded article is formed from the thermoplastic resin composition of the present invention and can be used as an electromagnetic wave absorber. Molded articles can be obtained by melting and mixing a thermoplastic resin composition, such as a compound or masterbatch, with a diluted resin in a molding machine typically set to 50°C to 350°C, then forming the shape of the molded article and cooling it. The temperature of the molding machine is acceptable as long as it is the temperature at which the thermoplastic resin (A) softens, but it should be at least 30°C higher than the softening point of the main component thermoplastic resin. Preferably, the molded product can be in the shape of a plate, rod, fiber, tube, pipe, bottle, film, or the like.

[0062] The molding method can include, for example, extrusion molding, injection molding, blow molding, compression molding, transfer molding, film molding such as T-die molding and inflation molding, calendering, spinning, etc.

[0063] From the viewpoint of electromagnetic wave absorption, the carbon black (B) content in the molded body is 0.5% by mass or more and 45% by mass or less, based on the molded body as the standard (100% by mass). It is preferably 5% by mass or more. It is more preferably 30% by mass or less, and even more preferably 20% by mass or less.

[0064] Electromagnetic wave absorbers absorb incident electromagnetic waves by converting their energy into thermal energy within the absorber. Unlike electromagnetic wave shielding materials, electromagnetic wave absorbers aim to absorb radio waves within the molded body without reflecting them off the surface. Electromagnetic wave absorbers are used in applications such as ETC (Electronic Toll Collection) systems on expressways, full-body scanners that see through clothing for security checks at airports and other locations, millimeter-wave radar equipment used for transmitting images from surveillance cameras on platforms during one-man train operations, and preventing radar image distortion on ship masts. In particular, molded articles formed from the thermoplastic resin composition of the present invention exhibit excellent electromagnetic wave absorption even in the millimeter-wave band of 60 to 90 GHz, known as the E-band, and are therefore suitable for use in millimeter-wave radar devices. [Examples]

[0065] The present invention will be described in more detail below with reference to examples, but these examples are not intended to limit the present invention in any way. In the examples, "parts" refers to "parts by mass," and "%" refers to "mass percent." Also, the amounts in the table are in mass percent, and blank spaces in the table indicate that an ingredient was not included.

[0066] The melt flow rate (MFR) of the thermoplastic resin, the particle size (d50) and specific surface area of ​​the filler, and the average primary particle size, dibutyl phthalate (DBP) oil absorption, and specific surface area of ​​the carbon black were measured using the following method.

[0067] <Melt Flow Rate (MFR) of Thermoplastic Resins> The melt flow mass rate (MFR) of thermoplastic resin (A) was measured according to JIS K7210-1:2014. Polypropylene resin was measured at 230°C with a load of 2.16 kgf, polyamide resin at 240°C with a load of 2.16 kgf, and polycarbonate resin at 280°C with a load of 1.2 kgf.

[0068] <Particle size of filler (d50)> Samples were prepared by dispersing a packing material using ethanol as the dispersion solvent by ultrasonic irradiation, in accordance with JIS R1629:1997. The resulting dispersion was irradiated with laser light using a Nikkiso Microtrac HRA particle size analyzer, and the particle size distribution was obtained by measuring the distribution pattern of the intensity of the light scattered as the laser light passed through the dispersion. Furthermore, the particle size (d50) at which the cumulative volume reached 50% was determined from the above particle size distribution values.

[0069] <Specific surface area of ​​filler> The BET specific surface area of ​​filler (C) can be measured using a BET specific surface area measuring device (Macsorb, manufactured by Mounttech) as follows. First, 0.2g to 0.3g of the filler to be measured is placed in the measuring device, and as a pretreatment, it is heated at 200°C for 5 minutes in a mixed gas atmosphere of nitrogen and helium. After that, the BET specific surface area is measured by performing low-temperature, low-humidity physical adsorption in a liquid nitrogen environment.

[0070] <Average primary particle size of carbon black> Carbon black was observed using a scanning electron microscope (JEOL JSM-6700M) at an acceleration voltage of 5kV, and images at 50,000x magnification (1024 x 1280 pixels) were captured. Next, the particle size of 20 randomly selected carbon black particles was measured from the captured images, and the number-average value of these measurements was taken as the average primary particle size of the carbon black.

[0071] <Dibutyl phthalate (DBP) oil absorption capacity of carbon black> The amount of dibutyl phthalate (DBP) absorbed was measured according to JIS K6217-4:2017, by determining the amount of dibutyl phthalate absorbed by 100g of carbon black.

[0072] <Specific surface area of ​​carbon black> 0.03 g of carbon black was weighed using an electronic balance (Sartorius MSA225S100DI) and then dried at 110°C for 15 minutes while degassing. After that, the specific surface area of ​​the carbon black was measured using a fully automatic specific surface area analyzer (Mountain Tech HM-model1208).

[0073] The materials used in the example are as follows: <Thermoplastic resin (A)> • (A1-1) Sun Allomer PM600A (Homopolypropylene resin manufactured by Sun Allomer, MFR: 7.5g / 10min at 230℃ × 2.16kgf) • (A1-2) Sun Allomer PM731V (Sun Allomer Co., Ltd. random polypropylene resin, MFR: 9.5g / 10min at 230℃ × 2.16kgf) • (A1-3) Sun Allomer PM870A (Sun Allomer block polypropylene resin, MFR: 17.0 g / 10 min at 230°C × 2.16 kgf) • (A1-4) Prime Polypropylene J107G (Block polypropylene resin manufactured by Prime Polymer, MFR: 100g / 10min at 230℃ × 2.16kgf) • (A2-5) Amiran CM1017 (Toray Industries Nylon 6, MFR: 35g / 10min at 240℃ x 2.16kgf) • (A3-6) Yupiron H3000 (polycarbonate resin manufactured by Mitsubishi Engineering Plastics, MFR: 35g / 10min at 280℃ × 2.16kgf)

[0074] [Table 1]

[0075] <Carbon Black (B)> • (B-1) Mitsubishi Carbon #30B (manufactured by Mitsubishi Chemical Corporation, average primary particle size 30nm, DBP oil absorption 104ml / 100g, specific surface area 74m²) 2 / g) • (B-2) Vulcan XC72 (manufactured by Cabot Specialty Chemicals Inc., average primary particle size 30 μm, DBP oil absorption 173 ml / 100 g, specific surface area 254 m²) 2 / g) • (B-3) Ketjenblack EC300J (manufactured by Lion Specialty Chemicals Co., Ltd., average primary particle size 40 μm, DBP oil absorption 365 ml / 100 g, specific surface area 800 m²) 2 / g)

[0076] <Filler (C)> • (C-1) Microace P-2 (manufactured by Nippon Talc Co., Ltd., talc, particle size (d50) 7.0 μm, BET specific surface area 7.5 m²) 2 / g) • (C-2) Super SSS (manufactured by Maruo Calcium Co., Ltd., calcium carbonate, particle size (d50) 4.0 μm, BET specific surface area 1.2 m²) 2 / g) • (C'-1)PA-OG (manufactured by Nippon Talc Co., Ltd., talc, particle size (d50) 19.0 μm, BET specific surface area 5.5 m²) 2 / g)

[0077] (Manufacturing of thermoplastic resin compositions) (Example 1) Thermoplastic resin (A1-1) was mixed in an amount of 65% by mass, carbon black (B-1) in an amount of 20% by mass, and filler (C-1) in an amount of 15% by mass. The mixture was melt-kneaded, and the mixture was extruded at 200°C using a twin-screw extruder (manufactured by Japan Steel Works, Ltd.) and granulated to obtain thermoplastic resin composition 1.

[0078] (Examples 2-9) Thermoplastic resin compositions 2 to 9 were obtained in the same manner as in Example 1, except that the materials and their respective amounts (mass%) were changed as shown in Table 2.

[0079] (Example 10) Thermoplastic resin (A2-3) was mixed in an amount of 60% by mass, carbon black (B-1) in an amount of 20% by mass, and filler (C-1) in an amount of 20% by mass. The mixture was melt-kneaded, and the mixture was extruded at 260°C using a twin-screw extruder (manufactured by Japan Steel Works, Ltd.) and granulated to obtain thermoplastic resin composition 10.

[0080] (Example 11) Thermoplastic resin (A3-4) was mixed in an amount of 60% by mass, carbon black (B-1) in an amount of 20% by mass, and filler (C-1) in an amount of 20% by mass. The mixture was melt-kneaded, and the mixture was extruded at 280°C using a twin-screw extruder (manufactured by Japan Steel Works, Ltd.) and granulated to obtain thermoplastic resin composition 11.

[0081] (Comparative Example 1) Thermoplastic resin (A1-3) was mixed in an amount of 80% by mass and carbon black (B-1) in an amount of 20% by mass, then melt-kneaded, extruded at 200°C using a twin-screw extruder (manufactured by Japan Steel Works, Ltd.), and granulated to obtain thermoplastic resin composition 12.

[0082] (Comparative Example 2) Thermoplastic resin (A1-1) was mixed in an amount of 80% by mass and filler (C-1) in an amount of 20% by mass, then melt-kneaded, extruded at 200°C using a twin-screw extruder (manufactured by Japan Steel Works, Ltd.), and granulated to obtain thermoplastic resin composition 13.

[0083] (Comparative Example 3) Thermoplastic resin (A1-3) was mixed in an amount of 75% by mass, carbon black (B-2) in an amount of 20% by mass, and filler (C-1) in an amount of 5% by mass. The mixture was melt-kneaded, and the mixture was extruded at 200°C using a twin-screw extruder (manufactured by Japan Steel Works, Ltd.) and granulated to obtain thermoplastic resin composition 14.

[0084] (Comparative Examples 4-7) Thermoplastic resin compositions 15 to 18 were obtained in the same manner as in Comparative Example 1, except that the materials and their respective amounts (mass%) were changed as shown in Table 2.

[0085] Evaluation of thermoplastic resin compositions and molded articles The results of the evaluation of the obtained thermoplastic resin composition and molded articles were determined by the following method. The results are shown in Table 2. <Manufacturing of molded body (1)> Using the thermoplastic resin compositions obtained in the examples and comparative examples, a molded body (1) measuring 90 mm in length, 110 mm in width, and 3 mm in thickness was produced by injection molding using an injection molding machine (manufactured by Toshiba Machine Co., Ltd.) at the cylinder setting temperature and mold temperature described below. The length of the molded body is the injection direction. The thermoplastic resin compositions of Examples 1-9 and Comparative Examples 1-7 were prepared at a cylinder setting temperature of 220°C and a mold temperature of 40°C. The thermoplastic resin composition of Example 10 was prepared at a cylinder setting temperature of 260°C and a mold temperature of 40°C. The thermoplastic resin composition of Example 11 was prepared at a cylinder setting temperature of 280°C and a mold temperature of 80°C.

[0086] <Manufacturing of molded body (2)> The thermoplastic resin compositions obtained in the examples and comparative examples were dried under the following conditions, and a multipurpose test piece (molded body (2)) measuring 80 mm in length, 10 mm in width, and 4 mm in thickness was obtained by cutting the rear portion from the multipurpose test piece to the center using an injection molding machine (manufactured by Toshiba Machine Co., Ltd.) in accordance with JIS K7139:2009, with the cylinder setting temperature and mold temperature as described below. The resin compositions of Examples 1-9 and Comparative Examples 1-7 were dried at 80°C for at least 4 hours, followed by a cylinder setting temperature of 220°C and a mold temperature of 40°C. The thermoplastic resin composition of Example 10 was dried at 100°C for at least 4 hours, followed by a cylinder setting temperature of 260°C and a mold temperature of 40°C. The thermoplastic resin composition of Example 11 was dried at 120°C for at least 4 hours, followed by a cylinder setting temperature of 280°C and a mold temperature of 80°C.

[0087] <Moldability> The moldability was evaluated using the following method. Using the thermoplastic resin compositions obtained in the examples and comparative examples, molded bodies measuring 80 mm (length) x 200 mm (width) x 1.5 mm (thickness) were produced using an injection molding machine (Toshiba Machine Co., Ltd. IS-100F model, maximum injection molding pressure 200 MPa) at the following cylinder setting temperature and mold temperature. The gate diameter was 1 mm x 1.5 mm, and the mold clamping pressure was 50 t. Molding was performed under the following conditions: cylinder setting temperature 220°C, mold temperature 40°C, injection speed 30 mm / sec, injection pressure 40 MPa, holding pressure 40 MPa, injection time 20 seconds, and cooling time 20 seconds. The resin compositions of Examples 1-9 and Comparative Examples 1-7 were dried at 80°C for at least 4 hours, followed by a cylinder setting temperature of 220°C and a mold temperature of 40°C. The thermoplastic resin composition of Example 10 was dried at 100°C for at least 4 hours, followed by a cylinder setting temperature of 260°C and a mold temperature of 40°C. The thermoplastic resin composition of Example 11 was dried at 120°C for at least 4 hours, followed by a cylinder setting temperature of 280°C and a mold temperature of 80°C. When a resin composition with low fluidity is used, the resin is not sufficiently filled into the injection-molded body used for the injection molding evaluation, resulting in sink marks and flow marks on the surface of the injection-molded body. The evaluation criteria were as follows: ◎ Excellent, ○ Good, △ Usable, × Not Usable. [Evaluation Criteria] [Evaluation Criteria] ◎: No sink marks or flow marks are observed. ○: Slight shrinkage and / or flow marks are observed. △: Slight shrinkage and flow marks are observed. ×: At least one of the following is severely visible: shrinkage and / or flow marks.

[0088] <Measurement of electromagnetic wave absorption (transmission attenuation and reflection attenuation)> Using the obtained molded body (1), the return loss RL(MD), transmission loss TL(MD), return loss RL(TD), and transmission loss TL(TD) were measured in the following manner, with the direction of the electromagnetic field parallel to the injection direction of the molded body (1) (MD direction) and perpendicular to the injection direction (TD direction). Figure 1 shows the electromagnetic wave irradiation direction (x), electric field direction (y), and magnetic field direction (z) when electromagnetic waves are incident on the molded body (1) in the thickness direction, with the molded body's surface stationary in the direction of electromagnetic wave emission. 1. is the transmission attenuation TL(MD), 2. is the return attenuation RL(MD), 3. is the transmission attenuation TL(TD), and 4. is the return attenuation RL(TD). These are conceptual diagrams for measurement. As shown in Figures 1-1 and 1-2, the obtained molded body (1) was left to stand for one day, and the return loss RL(MD) and transmission loss TL(MD) were measured when the direction of the electromagnetic field (y-direction in the figure) was parallel to the injection direction (MD direction). Furthermore, as shown in Figures 1-3 and 1-4, after the obtained molded body (1) was left to stand for one day, the return loss RL(TD) and transmission loss TL(TD) were measured when the direction of the electromagnetic field (y-direction in the figure) was perpendicular to the injection direction (TD direction). For the millimeter-wave transmitter, we used E8257D+E8257DS12 (output: 4dBm), for the millimeter-wave receiver, N9030A+M1970V, and for the horn antenna, AAHR015 (WR15, AET,INC) (all manufactured by Keysight Technologies). Under conditions of 24.8°C and 48% relative humidity, we measured the return loss and transmission loss of the resulting molded body at a measurement frequency of 76.5GHz. Smaller return loss and transmission loss indicate better electromagnetic wave absorption.

[0089] The electromagnetic wave absorption performance was evaluated using the following criteria for the return loss RL(MD). [Evaluation Criteria] ◎ (Better): Reflectance less than -5.6dB ○ (Good): Reflectance loss is -5.6dB or higher, and less than -5.3dB. △ (Practical): Return loss of -5.3dB or more, and less than -5.0dB. × (Not practical): Reflectance loss of -5.0dB or higher

[0090] The electromagnetic wave absorption performance was evaluated using the following criteria for transmission attenuation TL(MD). [Evaluation Criteria] ◎ (Better): Transmission attenuation less than -20dB ○ (Good): Transmission attenuation is -20dB or higher, and less than -15dB. △ (Practical): Transmission attenuation of -15dB or more, and less than -10dB. × (Not practical): Transmission attenuation is -10dB or higher.

[0091] The electromagnetic wave absorption performance was evaluated using the following criteria for the return loss RL(TD). [Evaluation Criteria] ◎ (Better): Reflectance less than -5.6dB ○ (Good): Reflectance loss is -5.6dB or higher, and less than -5.3dB. △ (Practical): Return loss of -5.3dB or more, and less than -5.0dB. × (Not practical): Reflectance loss of -5.0dB or higher

[0092] The electromagnetic wave absorption performance was evaluated using the following criteria for transmission attenuation TL(TD). [Evaluation Criteria] ◎ (Better): Transmission attenuation less than -20dB ○ (Good): Transmission attenuation is -20dB or higher, and less than -15dB. △ (Practical): Transmission attenuation of -15dB or more, and less than -10dB. × (Not practical): Transmission attenuation is -10dB or higher.

[0093] <Anisotropy ΔRL of reflection loss and anisotropy ΔTL of transmission loss> Based on the obtained return loss values ​​RL(MD) and RL(TD), and transmission loss values ​​TL(MD) and TL(TD), the anisotropy ΔRL in the return loss and the anisotropy ΔTL in the transmission loss were calculated using the following equations (1) and (2). Equation (1) ΔRL = |RL(MD) - RL(TD)| Equation (2) ΔTL = |TL(MD) - TL(TD)| The anisotropy of the return loss, ΔRL, was evaluated according to the following criteria. [Evaluation Criteria] ◎ (Better): ΔRL is less than 0.5dB ○ (Good): ΔRL is 0.5dB or greater, and less than 1.0dB. △ (Practical): ΔRL is 1.0dB or greater, and less than 1.5dB. × (Not practical): ΔRL is 1.5dB or higher

[0094] The anisotropy of transmission attenuation, ΔRL, was evaluated according to the following criteria. [Evaluation Criteria] ◎ (Better): ΔTL is less than 1.0 dB ○ (Good): ΔTL is 1.0 dB or greater, and less than 3.0 dB. △ (Practical): ΔTL is 3.0dB or higher, and less than 5.0dB. × (Not practical): ΔTL is 5 dB or higher

[0095] <rigidity> Using the obtained multi-purpose test specimen (molded body (2)) measuring 80 mm in length, 10 mm in width, and 4 mm in thickness, the bending modulus was measured in accordance with JIS K7171:2016 using a three-point bending tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.) at a temperature of 23°C. A higher measured value indicates superior rigidity. The rigidity was evaluated according to the following criteria. [Evaluation Criteria] ◎ (Better): Flexural modulus of elasticity of 2300 MPa or higher ○ (Good): Flexural modulus of elasticity is 2000 MPa or more and less than 2300 MPa. △ (Practical): Flexural modulus of elasticity is 1700 MPa or more and less than 2000 MPa × (Not practical): Flexural modulus less than 1700 MPa

[0096] [Table 2-1]

[0097] [Table 2-2]

[0098] Based on the evaluation results above, the thermoplastic resin composition of the present invention and the molded articles using it exhibit excellent electromagnetic wave absorption, with low reflection and transmission attenuation. Furthermore, anisotropy is suppressed, and even when electromagnetic waves are incident with a changed electric field direction, stable electromagnetic wave absorption can be achieved. In addition, excellent moldability and superior rigidity as an electromagnetic wave absorber were confirmed to provide sufficient mechanical strength. Furthermore, it was confirmed that even within the millimeter wave spectrum, specifically in the 60-90 GHz frequency band known as the E-band, the low reflection and transmission attenuation makes it suitable for use as a molded body for millimeter wave absorbers.

Claims

1. A thermoplastic resin composition comprising a thermoplastic resin (A), carbon black (B), and a filler (C), The filler (C) has a particle size (d50) of 10 μm or less at which the cumulative volume reaches 50%. In a thermoplastic resin composition, the content of carbon black (B) is 10% to 30% by mass, and the content of filler (C) is 15% to 45% by mass. Thermoplastic resin composition for electromagnetic wave absorbers.

2. The thermoplastic resin composition for electromagnetic wave absorbers according to claim 1, wherein the thermoplastic resin (A) comprises a polyolefin resin (A1).

3. The thermoplastic resin composition for electromagnetic wave absorbers according to claim 1, wherein the carbon black (B) has a DBP oil supply amount of 100 to 300 mL / 100 g.

4. The thermoplastic resin composition for electromagnetic wave absorbers according to claim 1, wherein the filler (C) contains talc.

5. A molded article formed from a thermoplastic resin composition for electromagnetic wave absorbers according to any one of claims 1 to 4.

Images