Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/18—Manufacture of films or sheets
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/02—Elements
  • C08K3/04—Carbon
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K7/00—Use of ingredients characterised by shape
  • C08K7/02—Fibres or whiskers
  • C08K7/04—Fibres or whiskers inorganic
  • C08K7/06—Elements
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L101/00—Compositions of unspecified macromolecular compounds
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q17/00—Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K9/00—Screening of apparatus or components against electric or magnetic fields

Definitions

• Embodiments of the present invention relate to a thermoplastic resin composition for an electromagnetic wave absorber and a molded article.
• plastic is easy to mold, it is used in a wide range of fields such as electrical and electronic equipment parts, automobile parts, medical parts, and food containers.
• Plastic molded products are used to enhance decorativeness and add functionality. Coloring is being actively carried out. Particularly in the automobile field, colored molded bodies are on the market for purposes of absorbing electromagnetic waves, and have been imparted with functionality.
• Electromagnetic waves are emitted from communication devices such as radios, televisions, and wireless communications, but in addition to these, electromagnetic waves are also emitted from electronic devices such as mobile phones and computers, which have increased rapidly due to recent advances in information technology.
• electromagnetic wave absorbers that efficiently absorb electromagnetic waves and convert the absorbed electromagnetic waves into thermal energy have been installed near or far from the electromagnetic wave generation site. Installation is underway.
• An example of the use of an electromagnetic wave absorber installed far from the electromagnetic wave generation site is, for example, the use of automatic toll collection systems (ETC) on expressways.
• ETC uses microwaves with a frequency of 5.8 GHz to transmit billing information, etc. between the roadside device antenna installed at the tollgate and the onboard device antenna when a car passes through the tollgate exit of an expressway. It is a system to be replaced.
• microwaves emitted from antennas are reflected by the tollgate roof, etc., and unnecessary electromagnetic waves leak from adjacent ETC lanes, causing communication abnormalities. be. Therefore, communication abnormalities are suppressed by installing electromagnetic wave absorbers on the roofs of toll gates and between ETC lanes.
• millimeter wave radars have been used in the automobile field for the purpose of automatic vehicle driving and collision prevention, and in many cases, millimeter wave radar devices are installed inside automobiles.
• Millimeter waves are electromagnetic waves with a wavelength of 1 to 10 mm and a frequency of 30 to 300 GHz.
• they are used in in-vehicle radars, full-body scanners that see through underneath clothing as a security check at airports, and during one-man operation of trains. It is also used to transmit video from surveillance cameras on the platform.
• Millimeter wave radar equipment is a device that can recognize obstacles by emitting millimeter waves and receiving waves that bounce back.It has a long detection range and is less susceptible to interference from sunlight, rain, and fog. Today, it is used in self-driving technology for automobiles, etc. In the case of automotive sensors, millimeter wave radar devices can detect relative distances and relative speeds to obstacles by transmitting and receiving millimeter waves from an antenna.
• the transmitting/receiving antennas of these millimeter wave radar devices may receive reflected objects other than the target obstacle, such as road surfaces, which may reduce the detection accuracy of the device.
• an electromagnetic wave absorber is provided between the antenna and the control circuit as a shielding member for shielding electromagnetic waves.
• Carbon-based, metallic carbon-based, and magnetic materials are known as electromagnetic wave absorbing materials in the millimeter wave band that constitute such electromagnetic wave absorbers, and in recent years, due to their high conductivity and relatively light weight, Carbon nanotubes (CNTs) are attracting attention as a carbon-based material.
• Resin compositions containing carbon nanotubes have high conductivity, so they are used in parts that require conductivity in the fields of automobiles, home appliances, and building materials (Patent Document 1), and as electromagnetic wave absorbers that take advantage of their electromagnetic properties. (Patent Documents 2 and 3).
• molded bodies using these conventional resin compositions have poor electromagnetic wave absorption performance in terms of reflection loss and transmission loss, which is necessary to sufficiently protect the radar from the surrounding environment and to prevent interference with radar signal transmission. Not enough.
• carbon nanotubes are materials with a relatively high aspect ratio, it is difficult to disperse them, and if the dispersion is insufficient, bumps and welds (a phenomenon in which a wavy pattern appears) may occur on the surface of the molded product. It may damage the appearance. Furthermore, angular dependence is a problem in that carbon nanotubes tend to be oriented in a particular direction during molding, and the electromagnetic wave absorption performance of the molded article varies depending on the incident angle of the electromagnetic wave.
• an object of the present invention is to provide a thermoplastic resin composition for an electromagnetic wave absorber with excellent dispersibility, and to improve reflection loss and transmission loss. It is an object of the present invention to provide a molded article that exhibits excellent radio wave absorption performance with low levels in both cases and also has a small angle dependence of radio wave absorption performance. In particular, it is an object of the present invention to provide a molded body for a millimeter wave absorber that has excellent reflection loss and transmission loss in a specific frequency band of 60 to 90 GHz called millimeter waves.
• the present invention includes the following embodiments.
• One embodiment includes a thermoplastic resin (A), carbon nanotubes (B) having an average diameter of 1 to 15 nm, and carbon black (C) having an average primary particle size of 20 to 50 nm, Satisfies any of the following (i) to (iv), ⁇ RL expressed by the following formula (1) is 3 dB or less, and ⁇ TL expressed by the following formula (2) is 5 dB or less,
• the present invention relates to a thermoplastic resin composition for electromagnetic wave absorbers.
• the thermoplastic resin (A) contains a polyolefin resin (A1) having an MFR of 5.0 to 50 g/10 minutes at a temperature of 230° C. and a load of 2.16 kgf.
• the thermoplastic resin (A) includes a polyamide resin (A2) having an MFR of 5.0 to 50 g/10 minutes at a temperature of 240° C. and a load of 2.16 kgf.
• the thermoplastic resin (A) contains a polyester resin (A3) having an MFR of 5.0 to 50 g/10 minutes at a temperature of 280° C. and a load of 1.2 kgf.
• the thermoplastic resin (A) includes a polycarbonate resin (A4) having an MFR of 5.0 to 50 g/10 minutes at a temperature of 280° C. and a load of 1.2 kgf.
• Formula (1) ⁇ RL
• Formula (2) ⁇ TL
• (RL (MD) and RL (TD) are molded products made from thermoplastic resin compositions for electromagnetic wave absorbers using an injection molding machine, each measuring 90 mm in length, 110 mm in width, and 3 mm in thickness. After the molding, an electromagnetic wave with a frequency of 76.5 GHz was applied to the molded body in the thickness direction so that the electric field direction of the electromagnetic wave was parallel to the injection direction (MD direction) or perpendicular to the injection direction (TD direction). This is the actual transmission attenuation.
• TL (MD) and TL (TD) are molded bodies of 90 mm in length, 110 mm in width, and 3 mm in thickness, each molded from a thermoplastic resin composition for an electromagnetic wave absorber using an injection molding machine, and left for one day. Later, when an electromagnetic wave with a frequency of 76.5 GHz is applied to the thickness direction of the molded body, the electric field direction of the electromagnetic wave is parallel to the injection direction (MD direction) or perpendicular to the injection direction (TD direction). is the return loss. Further, the length of the molded body is the injection direction.
• Another embodiment relates to a molded article formed from the thermoplastic resin composition for an electromagnetic wave absorber.
• thermoplastic resin composition for an electromagnetic wave absorber of the present invention has excellent dispersibility, and the electromagnetic wave absorber obtained thereby exhibits excellent radio wave absorption performance with low reflection loss and transmission loss. Angular dependence is small. Among these, it is excellent in reflection loss and transmission loss in a specific frequency band of 60 to 90 GHz called millimeter waves, so it can be suitably used as a molded body for a millimeter wave absorber.
• FIG. 1 is a conceptual diagram of measurement of transmission attenuation and return attenuation by a millimeter wave transmitter.
• FIG. 2 is a conceptual diagram of measurement of incident angle dependence by a millimeter wave transmitter.
• carbon nanotubes are sometimes expressed as CNTs, such as “carbon nanotubes (B) with an average diameter of 1 to 15 nm,””carbon black (C) with an average primary particle diameter of 20 to 50 nm,” and "a temperature of 230°C.
• the MFR in the embodiment of the present invention is based on JIS. This is a value measured using a melt mass flow rate value according to K7210.
• thermoplastic resin composition for electromagnetic wave absorber.
• the thermoplastic resin composition contains a thermoplastic resin (A), carbon nanotubes (B) having an average diameter of 1 to 15 nm, and carbon black (C) having an average primary particle diameter of 20 to 50 nm, and contains the following (i) ) to (iv).
• the thermoplastic resin (A) contains a polyolefin resin (A1) having an MFR of 5.0 to 50 g/10 minutes at a temperature of 230° C. and a load of 2.16 kgf.
• the thermoplastic resin (A) includes a polyamide resin (A2) having an MFR of 5.0 to 50 g/10 minutes at a temperature of 240° C. and a load of 2.16 kgf.
• the thermoplastic resin (A) contains a polyester resin (A3) having an MFR of 5.0 to 50 g/10 minutes at a temperature of 280° C. and a load of 1.2 kgf.
• the thermoplastic resin (A) includes a polycarbonate resin (A4) having an MFR of 5.0 to 50 g/10 minutes at a temperature of 280° C. and a load of 1.2 kgf.
• thermoplastic resin (A) that satisfies any of (i) to (iv).
• ⁇ RL expressed by the following formula (1) is 3 dB or less
• ⁇ TL expressed by the following formula (2) is 5 dB or less.
• Formula (1) ⁇ RL
• Formula (2) ⁇ TL
• (RL (MD) and RL (TD) are molded products made from thermoplastic resin compositions for electromagnetic wave absorbers using an injection molding machine, each measuring 90 mm in length, 110 mm in width, and 3 mm in thickness. After the molding, an electromagnetic wave with a frequency of 76.5 GHz was applied to the molded body in the thickness direction so that the electric field direction of the electromagnetic wave was parallel to the injection direction (MD direction) or perpendicular to the injection direction (TD direction).
• TL (MD) and TL (TD) are molded bodies of 90 mm in length, 110 mm in width, and 3 mm in thickness, each molded from a thermoplastic resin composition for an electromagnetic wave absorber using an injection molding machine, and left for one day. Later, when an electromagnetic wave with a frequency of 76.5 GHz is applied to the thickness direction of the molded body, the electric field direction of the electromagnetic wave is parallel to the injection direction (MD direction) or perpendicular to the injection direction (TD direction). is the return loss. Further, the length of the molded body is the injection direction. )
• the injection direction here is the direction in which the thermoplastic resin composition flows into the mold from the gate portion of the molding machine. That is, a molded product having a length of 90 mm, a width of 110 mm, and a thickness of 3 mm has a length in the injection direction of 90 mm x a length in a direction perpendicular to the injection direction of 110 mm, and a thickness of 3 mm.
• the total content of carbon nanotubes (B) and carbon black (C) is 6 to 18% by mass based on the thermoplastic resin composition (100% by mass).
• the amount is preferably 6% to 15% by mass, and more preferably 6% to 15% by mass. More preferably, it is 8 to 13% by mass.
• ⁇ RL expressed by formula (1) is 3 dB or less and ⁇ TL expressed by formula (2) is 5 dB or less, but also carbon nanotubes (B) having a smaller average diameter, and a thermoplastic resin that satisfies any of (i), (ii), (iii), or (iv) in addition to carbon black (C) having a relatively small average primary particle size and within a specific particle size range.
• A the orientation of carbon nanotubes and carbon black can be controlled by controlling the amount of each compounded as small as possible and within a specific range, and when electromagnetic waves are incident in a direction parallel to the injection direction of the molded body. In addition, even when electromagnetic waves are incident in the vertical direction, it is possible to exhibit sufficient radio wave absorbing properties, and the angular dependence of the electromagnetic wave absorber can be further suppressed.
• the thermoplastic resin (A) is a resin that can be molded by heating and melting, and the thermoplastic resin composition according to the embodiment of the present invention satisfies any of the following (i) to (iii).
• the thermoplastic resin (A) contains a polyolefin resin (A1) having an MFR of 5.0 to 50 g/10 minutes at a temperature of 230° C. and a load of 2.16 kgf.
• the thermoplastic resin (A) includes a polyamide resin (A2) having an MFR of 5.0 to 50 g/10 minutes at a temperature of 240° C. and a load of 2.16 kgf.
• thermoplastic resin (A) contains a polyester resin (A3) having an MFR of 5.0 to 50 g/10 minutes at a temperature of 280° C. and a load of 1.2 kgf.
• the thermoplastic resin (A) includes a polycarbonate resin (A4) having an MFR of 5.0 to 50 g/10 minutes at a temperature of 280° C. and a load of 1.2 kgf.
• Polyolefin resin (A1), polyamide resin (A2), polyester resin (A3), or polycarbonate resin (A4) has high fluidity when melted, and such thermoplastic resins are selected, and carbon black (C) and By using it in combination with carbon nanotubes (B), it becomes possible to suppress the orientation of carbon nanotubes when formed into a molded body, thereby obtaining a thermoplastic resin composition that has the effect of reducing the angle dependence of radio wave absorption. be able to.
• a skin layer with a relatively low concentration of carbon nanotubes (B) and a core layer with a relatively high concentration of carbon nanotubes (B) form on the surface and inside of the molded body.
• thermoplastic resin it is possible to obtain a molded article with a uniform concentration of carbon nanotubes, and there is an effect that the angular dependence of radio wave absorption is small.
• polyolefin resin (A1), polyamide resin (A2), polyester resin (based on thermoplastic resin (A)) A3) or polycarbonate resin (A4) is preferably used alone, and at least one of polyolefin resin (A1), polyamide resin (A2), polyester resin (A3), and polycarbonate resin (A4) is Preferably, it is the main component.
• main component refers to a component having the highest content among the thermoplastic resins constituting the thermoplastic resin (A).
• the content of the polyolefin resin (A1), polyamide resin (A2), polyester resin (A3), or polycarbonate resin (A4) is based on the thermoplastic resin (A), It is preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 100% by mass.
• Polyolefin resin (A1) The polyolefin resin (A1) has an MFR of 5.0 to 50 g/10 minutes at a temperature of 230° C. and a load of 2.16 kgf.
• Polyolefin resin (A1) is a polymer composed of olefin (monomer, monomer), and specifically, high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (Polethylene resin (PE) such as LLDPE), polypropylene resin (PP), ethylene- ⁇ olefin copolymer, ethylene-vinyl acetate copolymer, ethylene vinyl alcohol copolymer, ethylene ethyl acrylate copolymer, and cycloolefin Examples include polymers, cyclic olefin resins such as cycloolefin copolymers, and the like.
• low density polyethylene LDPE
• linear low density polyethylene LLDPE
• polypropylene resin PP
• polyolefin resins may be oxidized polyolefins in which polyolefins are partially oxidized.
• the polyolefin resin (A1) can be used alone or in combination of two or more kinds.
• the polyolefin resin (A1) in the embodiment of the present invention has an MFR of 5.0 to 50 g/10 minutes at a temperature of 230°C and a load of 2.16 kgf, and an MFR of 15 to 40 g/10 minutes. It is preferably within the range of 25 to 35 g/10 minutes, particularly preferably within the range of 25 to 35 g/10 minutes. It is preferable to fall within the above range from the viewpoint of incidence angle dependence.
• Polyamide resin (A2) The polyamide resin (A2) has an MFR of 5.0 to 50 g/10 minutes at a temperature of 240° C. and a load of 2.16 kgf.
• Polyamide resin (A2) is a polycondensate having an amide bond, specifically, nylon 4,6, nylon 6, nylon 6,6, nylon 6,10, nylon 6,12, nylon 12, nylon 6. , T, nylon 9,T, aromatic nylon resin, and the like. From the standpoint of versatility and fluidity, nylon 6 and nylon 6,6 are preferred.
• the polyamide resin (A2) can be used alone or in combination of two or more kinds.
• the polyamide resin (A2) in the embodiment of the present invention has an MFR of 5.0 to 50 g/10 minutes at a temperature of 240°C and a load of 2.16 kgf, and an MFR of 15 to 40 g/10 minutes. It is preferably within the range of 25 to 35 g/10 minutes, particularly preferably within the range of 25 to 35 g/10 minutes. It is preferable to fall within the above range from the viewpoint of incidence angle dependence.
• the polyester resin (A3) has an MFR of 5.0 to 50 g/10 minutes at a temperature of 280° C. and a load of 1.2 kgf.
• the polyester resin (A3) is a polycondensate having an ester bond, and specifically includes polyethylene terephthalate resin, polybutylene terephthalate resin, polyethylene naphthalate resin, amorphous copolyester resin, and the like. From the viewpoint of versatility and fluidity, polyethylene terephthalate resin or polybutylene terephthalate resin is preferred.
• the polyester resin (A3) can be used alone or in combination of two or more kinds.
• the polyester resin (A3) in the embodiment of the present invention has an MFR of 5.0 to 50 g/10 minutes at a temperature of 280°C and a load of 1.2 kgf, and an MFR of 15 to 40 g/10 minutes. It is preferably within the range of 25 to 35 g/10 minutes, particularly preferably within the range of 25 to 35 g/10 minutes. It is preferable to fall within the above range from the viewpoint of incidence angle dependence.
• the polycarbonate resin (A4) has an MFR of 5.0 to 50 g/10 minutes at a temperature of 280° C. and a load of 1.2 kgf.
• the polycarbonate resin (A4) is a polycondensate in which the joints between monomer units are carbonate groups. Specifically, a resin that is easily produced by reacting an aromatic dihydroxy compound with a carbonate precursor such as phosgene or carbonic diester can be used.
• the resin can be produced, for example, by an interfacial method when using phosgene as a carbonate precursor, or by a transesterification method in which the resin is reacted in a molten state when a carbonic acid diester is used.
• the polycarbonate resin (A4) in the embodiment of the present invention has an MFR of 5.0 to 50 g/10 minutes at a temperature of 280°C and a load of 1.2 kgf, and an MFR of 15 to 40 g/10 minutes. It is preferably within the range of 25 to 35 g/10 minutes, particularly preferably within the range of 25 to 35 g/10 minutes. It is preferable to fall within the above range from the viewpoint of incidence angle dependence.
• the content of the thermoplastic resin (A) is preferably 82% by mass or more, more preferably 84% by mass or more, and 85% by mass, based on the thermoplastic resin composition (100% by mass). The above is more preferable. Further, it is preferably 94% by mass or less, more preferably 92% by mass or less, and even more preferably 90% by mass or less.
• the content of the thermoplastic resin (A) may be, for example, 82 to 94% by mass, 84 to 92% by mass, or 85 to 90% by mass.
• the carbon nanotubes (B) have an average diameter of 1 to 15 nm as determined by a scanning electron microscope. Preferably, it is within the range of 1 to 10 nm. Within this range, the carbon nanotubes in the thermoplastic resin composition have high dispersibility, and the molded article has excellent electromagnetic wave absorption performance.
• the average diameter of carbon nanotubes is specifically determined using, for example, a scanning electron microscope (eg, JSM-6700M manufactured by JEOL). The conditions were to observe carbon nanotubes at an accelerating voltage of 5 kV, take a 50,000x image (pixel count: 1024 x 1280), and then examine the short axis of each of the 20 arbitrary carbon nanotubes in the taken image. The length is measured, and the number average value of these short axis lengths is calculated as the average diameter of the carbon nanotube.
• a scanning electron microscope eg, JSM-6700M manufactured by JEOL.
• the conditions were to observe carbon nanotubes at an accelerating voltage of 5 kV, take a 50,000x image (pixel count: 1024 x 1280), and then examine the short axis of each of the 20 arbitrary carbon nanotubes in the taken image. The length is measured, and the number average value of these short axis lengths is calculated as the average diameter of the carbon nanotube.
• the carbon nanotube (B) may be a single-walled carbon nanotube, a multi-walled carbon nanotube wound with two or more layers, or a mixture of these, but from the viewpoint of cost and strength, it is preferable to use a multi-walled carbon nanotube. preferable. Further, carbon nanotubes whose side walls have an amorphous structure instead of a graphite structure may be used.
• Carbon nanotubes (B) can generally be produced by a laser ablation method, an arc discharge method, a chemical vapor deposition method (CVD), a combustion method, etc., but carbon nanotubes produced by any method may be used.
• the CVD method usually uses a metal catalyst such as iron or nickel on a support such as silica, alumina, magnesium oxide, titanium oxide, silicate, diatomaceous earth, alumina-silica, silica-titania, and zeolite at a high temperature of 400 to 1000°C.
• This is a method that allows carbon nanotubes to be produced inexpensively and in large quantities by bringing catalyst fine particles carrying carbon into contact with a raw material carbon-containing gas, and is also preferable as carbon nanotubes used in the embodiments of the present invention. .
• the content of carbon nanotubes (B) is preferably 0.1% by mass or more, and preferably 0.5% by mass or more, based on the thermoplastic resin composition (100% by mass). It is more preferable that the amount is 1% by mass or more, and even more preferably 1% by mass or more. Moreover, it is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less.
• the content of carbon nanotubes (B) can be, for example, 0.1 to 5% by weight, 0.5 to 5% by weight, 1 to 3% by weight, or 1 to 2% by weight.
• Carbon black (C) has an average primary particle diameter of 20 to 50 nm as determined by a scanning electron microscope.
• the thickness is preferably 25 nm or more. Moreover, it is preferably 40 nm or less, more preferably 35 nm or less.
• the average primary particle diameter of carbon black is specifically determined using, for example, a scanning electron microscope (eg, JSM-6700M manufactured by JEOL). The conditions were to observe carbon black at an accelerating voltage of 5 kV, take a 50,000x image (number of pixels 1024 x 1280), and then determine the particle size of each of 20 arbitrary carbon blacks in the taken image. are measured, and their number average value is calculated as the average primary particle diameter of carbon black.
• a scanning electron microscope eg, JSM-6700M manufactured by JEOL.
• the conditions were to observe carbon black at an accelerating voltage of 5 kV, take a 50,000x image (number of pixels 1024 x 1280), and then determine the particle size of each of 20 arbitrary carbon blacks in the taken image. are measured, and their number average value is calculated as the average primary particle diameter of carbon black.
• thermoplastic resin composition containing only carbon nanotubes as a conductive material has high conductivity even when the carbon nanotubes are sufficiently dispersed in the composition when a molded article is manufactured by injection molding. difficult to express. The reason for this is thought to be that the abundance ratio of the resin increases and a layer (so-called "skin layer") with a low concentration of carbon nanotubes is formed on the surface of the molded product.
• skin layer a layer with a low concentration of carbon nanotubes
• the viscosity (melt viscosity) is different, for example, in extrusion molding, the part with a high abundance of resin with low viscosity and high fluidity will be extruded first during molding, and the surface of the molded object will be covered with a skin layer. It is presumed that the conductivity of the molded body decreases.
• carbon black generally has a lower specific surface area and oil absorption than carbon nanotubes, so a thermoplastic resin composition containing carbon black has a lower melting rate than a thermoplastic resin composition containing only carbon nanotubes.
• the viscosity is less likely to increase, and a skin layer is less likely to be formed on the surface of the molded product.
• carbon black has good affinity with carbon nanotubes, even if carbon nanotubes are taken into the molded product, a conductive path can be formed between the carbon black existing on the surface of the molded product, and therefore, the present invention
• the molded article according to the embodiment can exhibit high electrical conductivity.
• the thermoplastic resin composition combines carbon nanotubes (B) with a small average diameter and carbon black (C) with a relatively small average primary particle size within a specific range.
• the orientation of carbon nanotubes and carbon black in the molded body can be controlled, and sufficient strength can be obtained not only when electromagnetic waves are incident parallel to the injection direction of the molded body, but also when electromagnetic waves are incident perpendicularly to the injection direction of the molded body. It becomes possible to exhibit radio wave absorption properties.
• Carbon black (C) is produced by continuously thermally decomposing gaseous or liquid raw materials in a reactor, especially Ketjen black made from ethylene heavy oil, and by burning the raw material gas and producing the flame.
• Various types of black such as channel black that is rapidly cooled and precipitated on the bottom of channel steel, thermal black that is obtained by periodically repeating combustion and thermal decomposition using gas as a raw material, and acetylene black that is made from acetylene gas as a raw material, are used. They can be used alone or in combination of two or more. Further, commonly used oxidized carbon black, hollow carbon, etc. can also be used.
• Carbon blacks include, for example, Nittetsu Carbon's furnace blacks such as Niteron #10, #200, and #300, and Tokai Carbon's furnace blacks such as Toka Black #4300, #4400, #4500, and #5500.
• Black Degussa furnace black such as Printex L, Columbian furnace black such as Raven7000, 5750, 5250, 5000ULTRAIII, 5000ULTRA, Conductex SC ULTRA, 975 ULTRA, PUER BLACK100, 115, and 205, #30B , #45 Mitsubishi Chemical Furnace Black, MONARCH1400, 1300, 900, VulcanXC-72R, and Black Pearls 2000 etc.
• Furnace black manufactured by Cabot Ensaco 250G, Ensaco 260G, Ensaco 350G, Furnace black manufactured by Imerys such as SuperP-Li, Ketjen black manufactured by Akzo such as Ketjen black EC-300J, and EC-600JD, Denka black HS-100 Examples include, but are not limited to, acetylene black manufactured by Denki Kagaku Kogyo Co., Ltd., such as FX-35.
• the content of carbon black (C) is preferably 3% by mass or more, more preferably 5% by mass or more, based on the thermoplastic resin composition (100% by mass).
• the content is preferably 7% by mass or more, and more preferably 7% by mass or more.
• it is preferably 16% by mass or less, more preferably 15% by mass or less, and even more preferably 12% by mass or less.
• the content of carbon black (C) can be, for example, 3 to 16% by weight, 5 to 15% by weight, or 7 to 12% by weight.
• thermoplastic resin composition may contain other optional components such as an electromagnetic wave absorbing material, a weathering stabilizer, an antistatic agent, a dye, a pigment, a coupling agent, a crystal nucleating agent, a resin filler, etc., as necessary.
• thermoplastic resin composition preferably does not contain volatile components.
• the content of volatile components such as solvents and low molecular weight components is preferably 5% by mass or less, more preferably 1% by mass or less.
• carbon nanotubes and carbon black other than carbon nanotubes (B) and carbon black (C) may be included as long as the effects of the present invention are not impaired.
• the content of electromagnetic wave absorbing materials other than carbon nanotubes (B) and carbon black (C) is preferably 10% by mass or less, more preferably 5% by mass or less, based on 100% by mass of the electromagnetic wave absorbing material.
• the thermoplastic resin composition uses a combination of carbon nanotubes (B) having an average diameter of 1 to 15 nm and carbon black (C) having an average primary particle diameter of 20 to 50 nm, Furthermore, by having a specific relationship between reflection attenuation and transmission attenuation, the molded article can achieve high electromagnetic wave absorption performance and suppress angle dependence without adding a high amount of electromagnetic wave absorbing material.
• thermoplastic resin composition that is an embodiment of the present invention is not particularly limited.
• thermoplastic resin (A), carbon nanotubes (B), carbon black (C), and additives are added as needed, mixed in a Henschel mixer, tumbler, disper, etc., and then mixed in a kneader, roll mill, super mixer, etc.
• twin screw extruders twin screw extruders, single screw extruders, such as Henschel mixers, Shugi mixers, vertical granulators, high speed mixers, fur matrix, ball mills, steel mills, sand mills, vibration mills, attritors, Banbury mixers,
• a resin composition in the form of pellets, powder, granules, beads, or the like can be obtained.
• the thermoplastic resin composition contains carbon nanotubes (B) and carbon black (C) at a relatively high concentration, and is used as a master batch diluted with the thermoplastic resin (A) during molding. It may be a compound in which the concentration of carbon nanotubes (B) and carbon black (C) is relatively low, and the compound may be used for molding as it is without being diluted with the thermoplastic resin (A). good. From the viewpoint of addition cost, inventory cost, etc., it is preferable to use a masterbatch that can be highly concentrated. The masterbatch is preferably in the form of pellets that are easy to handle.
• the molded body is formed from a thermoplastic resin composition that is an embodiment of the present invention, and is used as an electromagnetic wave absorber.
• the molded body can be obtained by melt-mixing a compound, which is a thermoplastic resin composition, or a masterbatch and a diluted resin in a molding machine usually set at 50°C to 350°C, then forming the shape of the molded body, and cooling. I can do it.
• the temperature of the molding machine There is no problem with the temperature of the molding machine as long as it is a temperature at which the thermoplastic resin (A) softens, but it is a temperature that is 30° C. or more higher than the softening point of the thermoplastic resin that is the main component.
• the shape of the molded object can be a plate, rod, fiber, tube, pipe, bottle, film, or the like.
• the thermoplastic resin composition can highly control the orientation of carbon nanotubes (B), so that it can be used in injection molded products or extrusion molded products that are prone to orientation. It can exhibit high electromagnetic wave absorption performance and excellent effects in suppressing angle dependence.
• the content of carbon nanotubes (B) in the molded body is preferably 0.1% by mass or more, based on the thermoplastic resin composition (100% by mass), and 0.5% by mass. % or more, more preferably 1% by mass or more. Moreover, it is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less.
• the content of carbon nanotubes (B) can be, for example, 0.1 to 5% by weight, 0.5 to 5% by weight, 1 to 3% by weight, or 1 to 2% by weight.
• the content of carbon black (C) in the molded body is preferably 3% by mass or more, and 5% by mass or more, based on the thermoplastic resin composition (100% by mass). More preferably, it is 7% by mass or more. Moreover, it is preferably 16% by mass or less, more preferably 15% by mass or less, and even more preferably 12% by mass or less.
• the content of carbon black (C) can be, for example, 3 to 16% by weight, 5 to 15% by weight, or 7 to 12% by weight.
• An electromagnetic wave absorber converts the energy of incident electromagnetic waves into thermal energy inside the absorber and absorbs it. Unlike electromagnetic wave shielding materials, the purpose of electromagnetic wave absorbers is to absorb radio waves inside the molded body without reflecting the waves on the surface of the molded body. Electromagnetic wave absorbers are used in automatic toll collection systems (ETC) on expressways, in-vehicle radars, full-body scanners that see through underneath clothing as a crime prevention check at airports, etc., and video transmission from surveillance cameras on the platform during single-man operation of trains. It is used for millimeter wave radar equipment used in such applications, and for preventing radar false images on ship masts.
• ETC automatic toll collection systems
• the molded body formed from the thermoplastic resin composition according to the embodiment of the present invention has excellent electromagnetic wave absorption performance in the millimeter wave band with a frequency of 60 to 90 GHz, so it can be suitably used for millimeter wave radar devices. I can do it.
• thermoplastic resin A
• carbon nanotubes B
• carbon black C
• ⁇ RL expressed by the following formula (1)
• ⁇ TL expressed by the following formula (2)
• Thermoplastic resin composition for electromagnetic wave absorber (i):
• the thermoplastic resin (A) contains a polyolefin resin (A1) having an MFR of 5.0 to 50 g/10 minutes at a temperature of 230° C.
• the thermoplastic resin (A) includes a polyamide resin (A2) having an MFR of 5.0 to 50 g/10 minutes at a temperature of 240° C. and a load of 2.16 kgf.
• the thermoplastic resin (A) contains a polyester resin (A3) having an MFR of 5.0 to 50 g/10 minutes at a temperature of 280° C. and a load of 1.2 kgf.
• the thermoplastic resin (A) includes a polycarbonate resin (A4) having an MFR of 5.0 to 50 g/10 minutes at a temperature of 280° C. and a load of 1.2 kgf.
• Formula (1) ⁇ RL
• Formula (2) ⁇ TL
• (RL (MD) and RL (TD) are molded products made from thermoplastic resin compositions for electromagnetic wave absorbers using an injection molding machine, each measuring 90 mm in length, 110 mm in width, and 3 mm in thickness. After the molding, an electromagnetic wave with a frequency of 76.5 GHz was applied to the molded body in the thickness direction so that the electric field direction of the electromagnetic wave was parallel to the injection direction (MD direction) or perpendicular to the injection direction (TD direction). This is the actual transmission attenuation.
• TL (MD) and TL (TD) are molded bodies of 90 mm in length, 110 mm in width, and 3 mm in thickness, each molded from a thermoplastic resin composition for an electromagnetic wave absorber using an injection molding machine, and left for one day. Later, when an electromagnetic wave with a frequency of 76.5 GHz is applied to the thickness direction of the molded body, the electric field direction of the electromagnetic wave is parallel to the injection direction (MD direction) or perpendicular to the injection direction (TD direction). is the return loss. Further, the length of the molded body is the injection direction.
• thermoplastic resin composition for use.
• the total content of carbon nanotubes (B) and carbon black (C) may be 6 to 15% by mass.
• the content of the thermoplastic resin (A) may be 85 to 90% by mass.
• thermoplastic resin composition for electromagnetic wave absorber Based on the thermoplastic resin composition for electromagnetic wave absorber, the content of thermoplastic resin (A) is 82 to 94% by mass, the content of carbon nanotubes (B) is 1 to 3% by mass, and carbon black.
• the content of the thermoplastic resin (A) is 85 to 90% by mass
• the content of carbon nanotubes (B) is 1 to 3% by mass
• the content of carbon black (C) is 5 to 12% by mass. good.
• thermoplastic resin (A) the average diameter of carbon nanotubes, the average primary particle diameter of carbon black, and the MFR of thermoplastic resin (A) were measured by the following method.
• ⁇ Average diameter of carbon nanotubes The carbon nanotubes were observed using a scanning electron microscope (manufactured by JEOL, JSM-6700M) at an accelerating voltage of 5 kV, and a 50,000x image (pixel count: 1024 x 1280) was taken. Next, the short axis length of each of 20 arbitrary carbon nanotubes was measured in the photographed image, and the number average value of these short axis lengths was taken as the average diameter of the carbon nanotubes.
• thermoplastic resin (A) ⁇ MFR (melt mass flow rate) of thermoplastic resin (A)>
• the MFR of the thermoplastic resin (A) was measured using a melt indexer manufactured by Toyo Seiki Co., Ltd. according to JIS. Measurement was performed according to K7210. Measurements were conducted for polyolefin resin at a temperature of 230°C and a load of 2.16 kgf, for polyamide resin at a temperature of 240°C and a load of 2.16 kgf, for polyester resin at a temperature of 280°C and a load of 1.2 kgf, and for polycarbonate resin at a temperature of 280°C and a load of 1. It was determined by measuring under the condition of 2 kgf.
• the materials used in the examples are as follows.
• thermoplastic resin composition (Example 1) Thermoplastic resin (A1-1) 89% by mass, carbon nanotubes (B-1) 1% by mass, and carbon black (C-1) 10% by mass were mixed and melt-kneaded. The mixture was extruded and granulated at 230° C. (manufactured by Steel Works Co., Ltd.) to obtain a thermoplastic resin composition.
• thermoplastic resin composition was obtained in the same manner as in Example 1, except that the materials and blending amounts (% by mass) shown in Tables 2 and 3 were changed.
• thermoplastic resin (A2-4) 89% by mass of thermoplastic resin (A2-4), 1% by mass of carbon nanotubes (B-1), and 10% by mass of carbon black (C-1) were mixed and melt-kneaded. The mixture was extruded and granulated at 280° C. (manufactured by Steel Works Co., Ltd.) to obtain a thermoplastic resin composition.
• thermoplastic resin (A3-5), 1% by mass of carbon nanotubes (B-1), and 10% by mass of carbon black (C-1) were mixed and melt-kneaded.
• the mixture was extruded and granulated at 260° C. (manufactured by Steel Works Co., Ltd.) to obtain a thermoplastic resin composition.
• thermoplastic resin (A4-6), 1% by mass of carbon nanotubes (B-1), and 10% by mass of carbon black (C-1) were mixed and melt-kneaded.
• the mixture was extruded and granulated at 280° C. (manufactured by Steel Works Co., Ltd.) to obtain a thermoplastic resin composition.
• thermoplastic resin composition 89% by mass of thermoplastic resin (A5-7), 1% by mass of carbon nanotubes (B-1), and 10% by mass of carbon black (C-1) were mixed and melt-kneaded. The mixture was extruded and granulated at 230° C. (manufactured by Steel Works Co., Ltd.) to obtain a thermoplastic resin composition.
• thermoplastic resin composition was obtained in the same manner as in Comparative Example 1, except that the materials and amounts (% by mass) shown in Tables 3 and 4 were changed.
• thermoplastic resin composition 89% by mass of thermoplastic resin (A5-9), 1% by mass of carbon nanotubes (B-1), and 10% by mass of carbon black (C-1) were mixed and melt-kneaded. The mixture was extruded and granulated at 280° C. (manufactured by Steel Works Co., Ltd.) to obtain a thermoplastic resin composition.
• thermoplastic resin composition Physical property values and evaluation results of the obtained thermoplastic resin composition were determined by the following methods. The results are shown in Tables 2 to 4.
• thermoplastic resin compositions obtained in Examples 1 to 14 and Comparative Examples 1 to 13 were injection molded using an injection molding machine (manufactured by Toshiba Machine Co., Ltd.) with a cylinder temperature setting of 220°C and a mold temperature of 40°C. A molded body with a diameter of 90 mm (in the injection direction), a width of 110 mm (in the direction perpendicular to the injection direction), and a thickness of 3 mm was produced.
• thermoplastic resin compositions obtained in Examples 15 and 17 were injection molded using an injection molding machine (manufactured by Toshiba Machinery Co., Ltd.) with a cylinder temperature setting of 280°C and a mold temperature of 80°C. A molded body with a width of 110 mm (in the direction perpendicular to the injection direction) and a thickness of 3 mm was produced.
• thermoplastic resin composition obtained in Example 16 was injection molded using an injection molding machine (manufactured by Toshiba Machinery Co., Ltd.) with a cylinder temperature setting of 260°C and a mold temperature of 40°C. A molded body having a diameter of 110 mm (in a direction perpendicular to the injection direction) and a thickness of 3 mm was produced. Further, the length of the molded body is the injection direction.
• the return loss RL in which the electric field direction of the electromagnetic wave is parallel to the injection direction of the molded body (MD direction) and perpendicular to the injection direction (TD direction) is determined by the following method.
• (TD) and transmission attenuation TL (TD) were measured.
• Figure 1 shows the irradiation direction (x) of the electromagnetic wave, the electric field direction (y), and The magnetic field direction (z) is 1. is the transmission attenuation TL (MD), 2. is the return loss RL (MD), 3. is the transmission attenuation RL (TD), 4. is a conceptual diagram of measurement of return loss RL (TD).
• the electric field direction of the electromagnetic wave (y direction in the figure) is parallel to the injection direction (MD direction).
• Attenuation RL (MD) and transmission attenuation TL (MD) were measured.
• the electric field direction of the electromagnetic waves (y direction in the figure) was different from the injection direction and the electric field direction of the electromagnetic waves (y direction in the figure).
• the return loss RL (TD) and the transmission loss TL (TD) were measured in a state in which the angle was in the vertical direction (TD direction).
• E8257D+E8257DS12 (output: 4 dBm) was used as the millimeter wave transmitter, N9030A+M1970V was used as the millimeter wave receiver, and AAHR015 (WR15, AET, INC) (all manufactured by Keysight Technologies) was used as the horn antenna.
• Reflection attenuation and transmission attenuation at a measurement frequency of 76.5 GHz were measured for the obtained molded body in an environment with a humidity of 48%.
• the incidence at the return loss is The angle dependence ⁇ RL and the incident angle dependence ⁇ TL in transmission attenuation were calculated.
• Formula (1) ⁇ RL
• Formula (2) ⁇ TL
• thermoplastic resin composition for an electromagnetic wave absorber was extrusion molded using a T-type molding machine (manufactured by Toyo Seiki) with a cylinder temperature setting of 220°C and a mold temperature of 40°C, to form a product having a width of 10 cm x length of 5 m x thickness of 100 ⁇ m.
• a T-die film was produced.
• the obtained T-die film was observed with an optical microscope (manufactured by Keyence), the number of particles of 100 ⁇ m or more was counted, and the dispersibility was evaluated according to the following criteria.
• Return loss (dB) in the millimeter wave frequency band was measured by the following method. E8257D+E8257DS12 (output: 4 dBm) was used as the millimeter wave transmitter, N9030A+M1970V was used as the millimeter wave receiver, and AAHR015 (WR15, AET, INC) (all manufactured by Keysight Technologies) was used as the horn antenna, at a temperature of 24.8°C and relative humidity. For the molded bodies obtained in Examples and Comparative Examples under an environment of 48% The reflection loss was measured.
• reflection loss RL (MD) was evaluated based on the following criteria. [Evaluation criteria] ⁇ (Good): Return loss is less than -6 dB ⁇ (Practical): Return loss is -6 dB or more, less than -5 dB ⁇ (Not practical): Return loss is -5 dB or more
• transmission loss TL (Transmission loss TL (MD))
• transmission loss (dB) in the millimeter wave frequency band was measured by the following method. E8257D+E8257DS12 (output: 4 dBm) was used as the millimeter wave transmitter, N9030A+M1970V was used as the millimeter wave receiver, and AAHR015 (WR15, AET, INC) (all manufactured by Keysight Technologies) was used as the horn antenna, at a temperature of 24.8°C and relative humidity. For the molded bodies obtained in Examples and Comparative Examples under an environment of 48% The transmission loss was measured. As electromagnetic wave absorption performance, transmission loss TL (MD) was evaluated based on the following criteria.
• reflection loss RL (MD) was evaluated based on the following criteria. [Evaluation criteria] ⁇ (Good): Return loss is less than -5 dB ⁇ (Practical): Return loss is -5 dB or more, less than -3 dB ⁇ (Not practical): Return loss is -3 dB or more
• transmission loss TL (MD) was evaluated based on the following criteria.
• ⁇ (Good): Transmission loss is less than -15 dB ⁇
• ⁇ (Practical): Transmission loss is -15 dB or more, less than -10 dB ⁇
• Transmission loss is -10 dB or more
• thermoplastic resin (A2-4), thermoplastic resin (A3-5), and thermoplastic resin (A4-1) were used instead of thermoplastic resin (A1-1), respectively.
• the thermoplastic resin composition formed in place of 6) had the same evaluation results as when thermoplastic resin (A1-1) was used. That is, the effects of all forms (i) to (iv) were confirmed.
• thermoplastic resin composition according to the embodiment of the present invention and the molded article using the same have excellent dispersibility as a resin composition, and the molded article has excellent low reflection loss and transmission loss. It has been confirmed that it exhibits radio wave absorption performance and is able to stably exhibit electromagnetic wave absorption performance even when electromagnetic waves are incident at different incident angles, demonstrating excellent results in suppressing angle dependence. did it. Among these, it is excellent in reflection loss and transmission loss in a specific frequency band of 60 to 90 GHz called millimeter waves, so it can be said that it can be suitably used as a molded article for a millimeter wave absorber.

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