Resin composition, and resin molded body

Abstract

Provided is a resin composition capable of achieving high levels of both mechanical strength, such as bending strength, and electromagnetic wave shielding properties.　The resin composition includes a thermoplastic resin (A), carbon black (B), carbon fiber (C), and graphite (D), wherein the content of the carbon black (B) is 10 to 100 parts by weight with respect to 100 parts by weight of the thermoplastic resin (A).

Description

Resin composition and resin molded product

[0001] The present invention relates to a resin composition and a resin molded article using the resin composition.

[0002] Conventionally, metal plates or thermally conductive resin molded bodies have been used for heat sinks in communication devices used indoors and outdoors, housings for electronic devices such as security cameras and smart meters, multi-information displays for car navigation systems and smart meters, heat dissipation chassis for in-vehicle cameras, LED heat dissipation heat sinks, SoCs, GDCs, etc. Note that SoC stands for "System-on-a-chip" and GDC stands for "Graphics Display Controller."

[0003] Patent Document 1 below discloses a molded body obtained by molding resin pellets containing a thermoplastic resin and carbon fibers. In Patent Document 1, the thermoplastic resin is a crystalline resin. The carbon fibers include PAN-based carbon fibers and pitch-based carbon fibers. The mass average fiber length of the carbon fibers in the resin pellets is 0.1 mm to 0.9 mm. The bending strength of the molded body is 280 MPa or more.

[0004] Japanese Patent Application Laid-Open No. 2020-079412

[0005] In recent years, with the increasing speed of CPUs, there has been a demand for resin moldings having higher electromagnetic wave shielding properties than ever before.

[0006] However, the resin composition disclosed in Patent Document 1 has a problem in that it is difficult to achieve high levels of both mechanical strength such as bending strength and electromagnetic wave shielding properties when molded into an article.

[0007] An object of the present invention is to provide a resin composition that can achieve high levels of both mechanical strength such as bending strength and electromagnetic wave shielding properties, and a resin molded article using the resin composition.

[0008] The resin composition according to the present invention contains a thermoplastic resin (A), carbon black (B), carbon fiber (C), and graphite (D), and the content of the carbon black (B) is 10 parts by weight or more and 100 parts by weight or less per 100 parts by weight of the thermoplastic resin (A).

[0009] In a specific aspect of the resin composition according to the present invention, the content of the carbon fiber (C) is 10 parts by weight or more and 100 parts by weight or less per 100 parts by weight of the thermoplastic resin (A).

[0010] In another specific aspect of the resin composition according to the present invention, the BET specific surface area of ​​the carbon black (B) is 600 m ２ / g or less.

[0011] In still another specific aspect of the resin composition according to the present invention, the carbon fibers (C) have a weight average fiber length of 0.5 mm or more and 15 mm or less.

[0012] In yet another specific aspect of the resin composition according to the present invention, the carbon black (B) is oil furnace black.

[0013] In still another specific aspect of the resin composition according to the present invention, the content of the graphite (D) is 10 parts by weight or more and 200 parts by weight or less per 100 parts by weight of the thermoplastic resin (A).

[0014] In yet another specific aspect of the resin composition according to the present invention, when the molten resin composition is filled into a mold in a direction perpendicular to the thickness direction of the resulting resin molded body and molded to obtain a resin molded body having a length of 100 mm, a width of 100 mm, and a thickness of 2 mm, the resin molded body has an electromagnetic wave shielding effect of 20 dB or more at a frequency of 100 MHz, and when the resin composition is molded in accordance with ISO 294-1 to obtain a rectangular resin molded body, the rectangular resin molded body has a bending strength of 40 MPa or more as measured in accordance with ISO 178.

[0015] In yet another specific aspect of the resin composition according to the present invention, when the molten resin composition is filled into a mold in a direction perpendicular to the thickness direction of the resulting resin molded body and molded to obtain a resin molded body having a length of 100 mm, a width of 100 mm, and a thickness of 2 mm, the thermal conductivity of the resin molded body in the in-plane direction on the main surface is 1.0 W / (m·K) or more.

[0016] The resin molded article according to the present invention is an article molded from a resin composition constructed according to the present invention.

[0017] In a specific aspect of the resin molded article according to the present invention, the resin molded article has a shape of a heat dissipation chassis, a heat dissipation housing, or a heat sink.

[0018] According to the present invention, it is possible to provide a resin composition and a resin molded article using the resin composition that can achieve high levels of both mechanical strength such as bending strength and electromagnetic wave shielding properties.

[0019] Fig. 1 is a schematic perspective view showing a heat dissipation chassis, Fig. 2 is a schematic perspective view showing a heat dissipation housing, and Fig. 3 is a schematic perspective view showing a heat sink shape.

[0020] The present invention will be described in detail below.

[0021] [Resin Composition] The resin composition of the present invention contains a thermoplastic resin (A), carbon black (B), carbon fiber (C), and graphite (D). The content of the carbon black (B) is 10 parts by weight or more and 100 parts by weight or less per 100 parts by weight of the thermoplastic resin (A).

[0022] The resin composition of the present invention contains a thermoplastic resin (A), carbon black (B), carbon fiber (C), and graphite (D), and in particular contains carbon black (B) in the above-mentioned specific content, so that the resin composition can achieve both high levels of mechanical strength such as bending strength and electromagnetic wave shielding properties.

[0023] When the resin composition of the present invention is molded in accordance with ISO 294-1 to obtain a rectangular resin molded product, the bending strength of the rectangular resin molded product is preferably 40 MPa or more, more preferably 50 MPa or more, even more preferably 60 MPa or more, and particularly preferably 90 MPa or more. The upper limit of the bending strength of the resin molded product is not particularly limited, but can be, for example, 250 MPa.

[0024] The bending strength can be measured in accordance with ISO 178. For measuring the bending strength, for example, a Tensilon universal testing machine (manufactured by Orientec Co., Ltd., model number "RTC-1210A") can be used.

[0025] In the present invention, the electromagnetic wave shielding effect at a frequency of 100 MHz of the resin molded article obtained under the following molding conditions is preferably 20 dB or more, more preferably 30 dB or more, and even more preferably 40 dB or more. The upper limit of the electromagnetic wave shielding effect at a frequency of 100 MHz of the resin molded article is not particularly limited, but is, for example, 100 dB.

[0026] <Molding Conditions> A molten resin composition is filled into a mold from a direction perpendicular to the thickness direction of the resin molded article to be obtained, and molded to obtain a resin molded article of length 100 mm x width 100 mm x thickness 2 mm.

[0027] The electromagnetic wave shielding effect (electromagnetic wave shielding property) at a frequency of 100 MHz can be measured, for example, by the KEC (KEC: an abbreviation for Kansai Electronics Industry Development Center) method.

[0028] In the present invention, the thermal conductivity in the in-plane direction of the main surface of the resin molded body obtained under the above-mentioned molding conditions is preferably 1.0 W / (m·K) or more, more preferably 1.5 W / (m·K) or more, even more preferably 2.0 W / (m·K) or more, and particularly preferably 3.5 W / (m·K) or more. When the thermal conductivity in the in-plane direction of the main surface of the resin molded body is equal to or greater than the above-mentioned lower limit, the thermal conductivity of the obtained resin molded body can be further improved. Furthermore, the upper limit of the thermal conductivity in the in-plane direction of the main surface of the resin molded body can be, for example, 50 W / (m·K). Note that the main surface of the resin molded body refers to the surface with the largest area among the multiple surfaces on the outer surface of the resin molded body.

[0029] The thermal conductivity in the in-plane direction of the main surface of the resin molded body can be calculated using the following formula (1).

[0030] Thermal conductivity (W / (m K)) = specific gravity (g / cm ３ ) x specific heat (J / g K) x thermal diffusivity (mm ２ / s)...Formula (1)

[0031] The thermal diffusivity can be measured using, for example, a Xenon Flash Laser Analyzer LFA467 HyperFlash manufactured by Netsch Japan.

[0032] Each component of the resin composition will be described in detail below.

[0033] (Thermoplastic resin (A)) The thermoplastic resin (A) is not particularly limited, and known thermoplastic resins can be used. Specific examples of the thermoplastic resin (A) include polyolefin, polystyrene, polyacrylate, polymethacrylate, polyacrylonitrile, polyester, polyamide, polyurethane, polyethersulfone, polyetherketone, polyimide, polydimethylsiloxane, polycarbonate, or copolymers containing at least two of these. These thermoplastic resins may be used alone or in combination. Note that the thermoplastic resin (A) is preferably a resin with a high elastic modulus. Because they are inexpensive and easy to mold under heat, polyolefin (olefin-based resin) and polyamide (nylon-based resin) are more preferred, and polyolefin is even more preferred.

[0034] The polyolefin is not particularly limited, and known polyolefins can be used. Specific examples of polyolefins include polyethylene-based resins such as ethylene homopolymers, ethylene-α-olefin copolymers, ethylene-(meth)acrylic acid copolymers, ethylene-(meth)acrylic acid ester copolymers, and ethylene-vinyl acetate copolymers. Furthermore, the polyolefin may be polypropylene-based resins such as propylene homopolymers, propylene-α-olefin copolymers, or homopolymers or copolymers of conjugated dienes such as polybutene, butadiene, and isoprene. These polyolefins may be used alone or in combination. From the viewpoint of further enhancing heat resistance and elastic modulus, polypropylene is preferred as the polyolefin.

[0035] The polyolefin (olefin-based resin) preferably contains an ethylene component. The content of the ethylene component is preferably 5% by mass to 40% by mass. When the content of the ethylene component is within the above range, the impact resistance of the resin molded article can be further improved, while the heat resistance can also be further improved.

[0036] The MFR of the thermoplastic resin (A), measured in accordance with JIS K 7210, is preferably 10 g / 10 min or more, more preferably 20 g / 10 min or more, and preferably 200 g / 10 min or less, more preferably 150 g / 10 min or less, even more preferably 100 g / 10 min or less, and particularly preferably 50 g / 10 min or less. When the MFR is within the above range, the fluidity of the thermoplastic resin (A) can be further improved.

[0037] The content of the thermoplastic resin (A) in the resin composition is preferably 25% by weight or more, more preferably 30% by weight or more, and preferably 70% by weight or less, more preferably 60% by weight or less. When the content of the thermoplastic resin (A) is within the above range, the moldability of the resin composition can be further improved.

[0038] (Carbon Black (B)) Examples of carbon black (B) that can be used include ketjen black, oil furnace black, acetylene black, channel black, and thermal black. Of these, oil furnace black is preferred from the viewpoint of further increasing the conductivity of the resulting resin molded product. The ash content of carbon black (B) is preferably 1% or less. Carbon black (B) may also contain metal impurities such as Fe and Ni.

[0039] The BET specific surface area of ​​the carbon black (B) is preferably 10 m ２ / g or more, more preferably 30m ２ / g or more, preferably 1100m ２ / g or less, more preferably 600m ２ / g or less, more preferably 400m ２ / g or less, particularly preferably 300m ２ / g or less. When the BET specific surface area of ​​carbon black (B) is equal to or greater than the above lower limit, the electrical conductivity of the resulting resin molded product can be further increased, and the electromagnetic wave shielding property can be further improved. When the BET specific surface area of ​​carbon black (B) is equal to or less than the above upper limit, the fluidity of the resin composition during molding can be further improved, and the moldability of the resin composition can be further improved.

[0040] The BET specific surface area can be measured from a nitrogen adsorption isotherm in accordance with the BET method. As a measuring device, for example, a product number "NOVAtouchLX2" manufactured by Anton Paar can be used.

[0041] The DBP oil absorption of the carbon black (B) is not particularly limited, but is preferably 30 ml / 100 g or more, more preferably 50 ml / 100 g or more, and preferably 450 ml / 100 g or less, more preferably 400 ml / 100 g or less, and even more preferably 300 ml / 100 g or less. When the DBP oil absorption of the carbon black (B) is within the above range, the electrical conductivity of the resulting resin molded article can be further increased, and the electromagnetic wave shielding property can be further improved.

[0042] In this specification, the DBP oil absorption of carbon black (B) can be obtained by calculating the amount of DBP dropped at 70% of the maximum torque in accordance with JIS K 6217-4. The DBP oil absorption can be measured, for example, using an absorption meter (manufactured by Asahi Research Institute, product number "S-500").

[0043] The primary particle size of carbon black (B) is not particularly limited, but is preferably 5 nm or more, more preferably 10 nm or more, and preferably 70 nm or less, more preferably 60 nm or less. When the primary particle size of carbon black (B) is within the above range, even higher conductivity can be obtained with an even lower carbon black content.

[0044] In this specification, the primary particle size of carbon black (B) refers to the average primary particle size determined using image data of carbon black (B) obtained using a transmission electron microscope, such as a JEOL Ltd. model JEM-2200FS.

[0045] The content of carbon black (B) is 10 parts by weight or more, preferably 15 parts by weight or more, more preferably 20 parts by weight or more, even more preferably 30 parts by weight or more, and 100 parts by weight or less, preferably 95 parts by weight or less, more preferably 90 parts by weight or less, per 100 parts by weight of thermoplastic resin (A). When the content of carbon black (B) is equal to or greater than the above-mentioned lower limit, the electrical conductivity of the resulting resin molded product can be further increased, and the electromagnetic wave shielding property can be further improved. On the other hand, when the content of carbon black (B) is equal to or less than the above-mentioned upper limit, the moldability of the resin composition can be further improved.

[0046] Two or more types of carbon black may be used as the carbon black (B). ２ / g or less and a carbon black having a BET specific surface area of ​​600 m ２ / g, the moldability of the resin composition can be further improved, and the electromagnetic wave shielding properties of the resulting resin molded article can be further enhanced. ２ If the amount of carbon black added is too large, the flowability and moldability of the resin composition may deteriorate. ２ The content of carbon black having a molecular weight of more than 1 / g is preferably 1 part by weight or more and 30 parts by weight or less per 100 parts by weight of the thermoplastic resin (A).

[0047] (Carbon fiber (C)) The carbon fiber (C) is not particularly limited, but may be a PAN-based carbon fiber, a pitch-based carbon fiber, etc. By using the carbon fiber (C), the mechanical strength such as the bending strength and the electromagnetic wave shielding property of the obtained resin molded product can be efficiently increased compared to when other conductive fibers, metal fibers, non-conductive fibers, or resin fibers are used.

[0048] The weight-average fiber length of the carbon fiber (C) is preferably 0.5 mm or more, more preferably 2 mm or more, even more preferably 5 mm or more, and preferably 15 mm or less, more preferably 12 mm or less, and even more preferably 9 mm or less. When the weight-average fiber length of the carbon fiber (C) is equal to or greater than the above-mentioned lower limit, the mechanical strength such as bending strength and electromagnetic wave shielding property of the obtained resin molded product can be both achieved at an even higher level. Furthermore, when the weight-average fiber length of the carbon fiber (C) is equal to or less than the above-mentioned upper limit, the moldability of the resin composition can be even further improved.

[0049] The weight average fiber length of the carbon fibers (C) can be the average value of 100 fibers measured using, for example, a transmission electron microscope (TEM) or a scanning electron microscope (SEM).

[0050] The fiber diameter of the carbon fiber (C) is preferably 3 μm or more, more preferably 5 μm or more, and preferably 30 μm or less, more preferably 25 μm or less, and even more preferably 20 μm or less. When the fiber diameter of the carbon fiber (C) is within the above range, the obtained resin molded product can have both mechanical strength such as bending strength and electromagnetic wave shielding property at an even higher level.

[0051] The fiber diameter of the carbon fiber (C) can be, for example, an average value of 100 fibers measured using a transmission electron microscope (TEM) or a scanning electron microscope (SEM). From the viewpoint of easier observation, it is desirable to heat a test piece cut out from the resin composition or the resin molded product at 600°C to remove the resin, and then observe the test piece with a transmission electron microscope (TEM) or a scanning electron microscope (SEM).

[0052] The content of carbon fiber (C) is preferably 10 parts by weight or more, more preferably 15 parts by weight or more, even more preferably 20 parts by weight or more, and particularly preferably 35 parts by weight or more, relative to 100 parts by weight of thermoplastic resin (A), and is preferably 100 parts by weight or less, more preferably 80 parts by weight or less, and even more preferably 70 parts by weight or less. When the content of carbon fiber (C) is equal to or greater than the above-mentioned lower limit, the mechanical strength such as bending strength and electromagnetic wave shielding property of the obtained resin molded product can be achieved at an even higher level. Furthermore, when the content of carbon fiber (C) is equal to or less than the above-mentioned upper limit, the moldability of the resin composition can be even further improved.

[0053] (Graphite (D)) Graphite (D) is not particularly limited, but is preferably plate-like graphite. The plate-like graphite is not particularly limited as long as it is plate-like graphite, and for example, graphite, exfoliated graphite, graphene, etc. can be used. From the viewpoint of further increasing thermal conductivity and electrical conductivity, graphite or exfoliated graphite is preferred. These may be used alone or in combination.

[0054] Graphite is a laminate of multiple graphene sheets. The number of stacked graphene sheets in graphite is usually about 100,000 to 1,000,000 layers. For example, flake graphite can be used as such graphite. From the viewpoint of further improving flame retardancy, expanded graphite may also be used.

[0055] Exfoliated graphite is obtained by exfoliating original graphite and refers to a graphene sheet laminate that is thinner than the original graphite. The exfoliation treatment for obtaining exfoliated graphite is not particularly limited, and either a mechanical exfoliation method using a supercritical fluid or a chemical exfoliation method using an acid may be used. The number of stacked graphene sheets in the exfoliated graphite may be less than that of the original graphite, but is preferably 50 or more, more preferably 100 or more, and preferably 1,000 or less, more preferably 500 or less, and even more preferably 200 or less. When the number of stacked graphene sheets is within the above range, the thermal conductivity and electrical conductivity of the resulting resin molded product can be further improved.

[0056] The volume average particle diameter of the plate-like graphite is preferably 5 μm or more, more preferably 30 μm or more, even more preferably 60 μm or more, preferably 1000 μm or less, more preferably 500 μm or less, even more preferably 350 μm or less, and particularly preferably 300 μm or less. When the volume average particle diameter of the plate-like graphite is within the above range, the thermal conductivity and electrical conductivity of the resulting resin molded product can be further improved. Furthermore, when the volume average particle diameter of the plate-like graphite is equal to or less than the above upper limit, the bending strength of the resulting resin molded product can be further improved. Furthermore, as the plate-like graphite, one type of graphite particle may be used, or two or more types of graphite particles having different particle diameters may be used in combination, as long as the volume average particle diameter of the plate-like graphite contained in the resin composition is within the above range.

[0057] The volume average particle size refers to a value calculated from a volume-based distribution by a laser diffraction method using a laser diffraction / scattering particle size distribution analyzer in accordance with JIS Z 8825:2013.

[0058] When measuring the volume average particle size, for example, the flake graphite is added to a soapy water solution (containing 0.01% neutral detergent) so that the concentration is 2% by weight, and ultrasonic waves are irradiated at an output of 300 W for 1 minute using an ultrasonic homogenizer to obtain a suspension. Next, the volume particle size distribution of the flake graphite is measured using a laser diffraction / scattering particle size distribution analyzer (manufactured by Nikkiso Co., Ltd., product name "Microtrac MT3300"). The cumulative 50% value of this volume particle size distribution can be calculated as the volume average particle size of the flake graphite.

[0059] The thickness of the platelet graphite is preferably greater than 1 μm, more preferably 5 μm or more, and preferably 50 μm or less, more preferably 40 μm or less. When the thickness of the platelet graphite is within the above range, the thermal conductivity and electrical conductivity of the obtained resin molded product can be further improved.

[0060] The aspect ratio of the platelet graphite is preferably 5 or more, more preferably 21 or more, and preferably less than 2000, more preferably less than 1000, and even more preferably less than 100. When the aspect ratio of the platelet graphite is within the above range, the thermal conductivity and electrical conductivity of the obtained resin molded product can be further improved. In this specification, the aspect ratio refers to the ratio of the maximum dimension of the platelet graphite in the stacking plane direction to the thickness of the platelet graphite.

[0061] The thickness of the platelet graphite can be measured using, for example, a transmission electron microscope (TEM) or a scanning electron microscope (SEM). From the viewpoint of making observation even easier, it is desirable to heat a test piece cut out from the resin composition or the resin molded product at 600°C to remove the resin, and then observe the test piece with a transmission electron microscope (TEM) or a scanning electron microscope (SEM). The test piece may be cut out along a direction along the main surface of the resin molded product, or along a direction perpendicular to the main surface of the resin molded product, as long as the thickness of the platelet graphite can be measured by removing the resin.

[0062] The content of graphite (D) is preferably 10 parts by weight or more, more preferably 15 parts by weight or more, and preferably 200 parts by weight or less, more preferably 150 parts by weight or less, per 100 parts by weight of thermoplastic resin (A). When the content of graphite (D) is equal to or greater than the above lower limit, the thermal conductivity and electrical conductivity can be further increased. On the other hand, when the content of graphite (D) is equal to or less than the above upper limit, the impact resistance can be further increased.

[0063] (Other Additives) The resin composition of the present invention may contain various other additives as optional components, as long as the effects of the present invention are not impaired. Examples of additives include phenol-based, phosphorus-based, amine-based, and sulfur-based antioxidants; benzotriazole-based and hydroxyphenyltriazine-based ultraviolet absorbers; metal inhibitors; various fillers; antistatic agents; stabilizers; and pigments. The resin composition of the present invention may also contain other conductive fibers, metal fibers, non-conductive fibers, or resin fibers, as long as the mechanical strength, such as bending strength, and electromagnetic wave shielding properties of the resulting resin molded article are not impaired. These may be used alone or in combination.

[0064] (Method for Producing Resin Composition) The resin composition of the present invention can be obtained by melt-kneading a thermoplastic resin (A), carbon black (B), carbon fiber (C), graphite (D), and, if necessary, other additives.

[0065] The melt-kneading method is not particularly limited, but examples thereof include a method of kneading under heating using a kneading device such as a twin-screw kneader such as a Plastomill, a single-screw extruder, a twin-screw extruder, a Banbury mixer, a roll, or a pressure kneader. Among these, the melt-kneading method using an extruder is preferred. The form of the resin composition is not particularly limited, but it can be, for example, pellets.

[0066] When pellets are formed, their shape is not particularly limited, but examples include spherical, cylindrical, and prismatic shapes. Among these, a cylindrical shape is preferred from the viewpoint of pellet shape stability. Furthermore, for example, when the pellets are cylindrical, their diameter is preferably 0.5 mm or more, more preferably 1 mm or more, and preferably 5 mm or less, more preferably 3 mm or less. Their length is preferably 1 mm or more, more preferably 3 mm or more, and preferably 10 mm or less, more preferably 7 mm or less. The pellet size can be measured by randomly collecting 100 pellets from a sample and using a vernier caliper.

[0067] The diameter of the pellets (pellet diameter) of the resin composition other than cylindrical is preferably 1 mm or more, more preferably 5 mm or more, and is preferably 15 mm or less, more preferably 10 mm or less. The pellet diameter can be determined by randomly collecting 100 pellets from a sample and measuring the diameter at the longest point using a vernier caliper.

[0068] [Resin Molded Article] The resin molded article of the present invention is an article molded from the resin composition of the present invention described above. Therefore, the resin molded article of the present invention can be obtained by molding the resin composition described above.

[0069] The resin molding of the present invention uses the resin composition of the present invention, and therefore can achieve high levels of both mechanical strength such as bending strength and electromagnetic wave shielding properties.

[0070] The method for molding the resin composition is not particularly limited, and examples thereof include press processing, extrusion processing, extrusion lamination processing, injection molding, etc. Among these, molding the mixture by injection molding is preferred.

[0071] In the present invention, the bending strength of the resin molded article is preferably 40 MPa or more, more preferably 50 MPa or more, even more preferably 60 MPa or more, and particularly preferably 90 MPa or more. The upper limit of the bending strength of the resin molded article is not particularly limited, but can be, for example, 250 MPa.

[0072] In the present invention, the electromagnetic wave shielding effect of the resin molded article at a frequency of 100 MHz is preferably 20 dB or more, more preferably 30 dB or more, and even more preferably 40 dB or more. The upper limit of the electromagnetic wave shielding effect of the resin molded article at a frequency of 100 MHz is not particularly limited, but is, for example, 100 dB.

[0073] In the present invention, the thermal conductivity of the resin molded body in the in-plane direction of the main surface is preferably 1.0 W / (m K) or more, more preferably 1.5 W / (m K) or more, even more preferably 2.0 W / (m K) or more, and particularly preferably 3.5 W / (m K) or more. The upper limit of the thermal conductivity of the resin molded body in the in-plane direction of the main surface can be, for example, 50 W / (m K).

[0074] When measuring the bending strength, electromagnetic wave shielding effect, thermal conductivity, and volume resistivity of the resin molded article of the present invention, the resin molded article is once melted and remolded under the following molding conditions, and then the measurements are carried out.

[0075] <Molding Conditions> A molten resin composition is filled into a mold from a direction perpendicular to the thickness direction of the resin molded article to be obtained, and molded to obtain a resin molded article of length 100 mm x width 100 mm x thickness 2 mm.

[0076] The resin molded article of the present invention has excellent electromagnetic wave shielding properties and can therefore be suitably used for housings of electronic devices such as communication devices, smart meters, and in-vehicle ECUs, which require electromagnetic wave shielding properties.

[0077] The resin molded article of the present invention also has excellent heat dissipation properties, and therefore may be, for example, a heat dissipation chassis 10 as shown in Fig. 1, a heat dissipation housing 20 as shown in Fig. 2, or a heat sink 30 as shown in Fig. 3.

[0078] Furthermore, a circuit may be formed on the surface of such a resin molded body.

[0079] The effects of the present invention will be clarified below by giving specific examples and comparative examples of the present invention, but the present invention is not limited to the following examples.

[0080] Example 1 A resin composition was obtained by melt-kneading 100 parts by weight of polypropylene (PP) as the thermoplastic resin (A), 30 parts by weight of oil furnace black as the carbon black (B), 40 parts by weight of PAN-based carbon fiber as the carbon fiber (C), and 120 parts by weight of flake graphite as the graphite (D) at 180°C using a Laboplastomill (manufactured by Toyo Seiki Seisakusho, product number "R100"). The obtained resin composition was in the form of pellets, and the pellet diameter was 3 mm. The pellet diameter was determined by randomly sampling 100 pellets from the sample and measuring the diameter at the longest point using a vernier caliper. The polypropylene used was manufactured by Japan Polypropylene Corporation under the trade name "BC03B" (MFR: 30 g / 10 min (230°C)). The oil furnace black used was manufactured by Cabot Corporation under the trade name "VulcanXC72" (BET specific surface area: 254 m). ２ / g, DBP oil absorption: 174 ml / 100 g, primary particle diameter: 30 nm). The PAN-based carbon fiber used was manufactured by Mitsubishi Chemical Corporation under the trade name "TR06U" (weight average fiber length: 6 mm, fiber diameter: 7 μm). The flake graphite used was manufactured by Chuetsu Graphite Industries under the trade name "CPB-300" (volume average particle diameter: 300 μm).

[0081] (Example 2) As carbon black (B), oil furnace black (manufactured by Asahi Carbon Co., Ltd., product name "F-200GS", BET specific surface area: 55 m ２ / g, DBP oil absorption: 180 ml / 100 g, primary particle diameter: 38 nm) was used, flake graphite (manufactured by Chuetsu Graphite Industries, trade name "CPB-100B", volume average particle diameter: 80 μm) was used as graphite (D), and the contents of carbon black (B), carbon fiber (C), and graphite (D) were changed as shown in Table 1 below. A resin composition was obtained in the same manner as in Example 1.

[0082] (Example 3) A resin composition was obtained in the same manner as in Example 2, except that a pitch-based carbon fiber (manufactured by Mitsubishi Chemical Corporation, trade name "K237SE", weight average fiber length: 6 mm, fiber diameter: 11 μm) was used as the carbon fiber (C), and the contents of the carbon black (B), carbon fiber (C), and graphite (D) were changed as shown in Table 1 below.

[0083] (Example 4) As carbon black (B), oil furnace black (manufactured by Lion Specialty Chemicals, trade name "Lionite CB", BET specific surface area: 1052 m ２ A resin composition was obtained in the same manner as in Example 1 except that a hydroxypropyl methylcellulose (C10 / C12) was used.

[0084] Example 5 A resin composition was obtained in the same manner as in Example 1, except that the content of carbon fiber (C) was changed to 20 parts by weight as shown in Table 1 below.

[0085] Example 6 A resin composition was obtained in the same manner as in Example 1, except that the content of graphite (D) was changed to 200 parts by weight as shown in Table 1 below.

[0086] Example 7 A resin composition was obtained in the same manner as in Example 1, except that flake graphite (manufactured by Nippon Graphite Industries Co., Ltd., product name "FB-150", volume average particle diameter: 45 μm) was used as the graphite (D) instead of the flake graphite of Example 1.

[0087] Example 8 A resin composition was obtained in the same manner as in Example 1, except that expanded graphite (manufactured by Fuji Graphite Industries Co., Ltd., product name "AED-02", volume average particle diameter: 1000 μm) was used as graphite (D) instead of the flake graphite of Example 1.

[0088] Comparative Example 1 A resin composition was obtained in the same manner as in Example 1, except that the carbon fiber (C) and the graphite (D) were not used and the content of the carbon black (B) was changed as shown in Table 1 below.

[0089] Comparative Example 2 A resin composition was obtained in the same manner as in Example 2, except that carbon black (B) and graphite (D) were not used.

[0090] Comparative Example 3 A resin composition was obtained in the same manner as in Example 2, except that carbon black (B) and carbon fiber (C) were not used and the content of graphite (D) was changed as shown in Table 1 below.

[0091] (Comparative Example 4) As carbon black (B), Ketjen black (manufactured by Lion Specialty Chemicals, product name "EC600J", BET specific surface area: 1270 m ２ / g), as the carbon fiber (C), PAN-based carbon fiber (manufactured by Toray Industries, Inc., trade name "TORAYCA Chopped Carbon Fiber", weight average fiber length: 3 mm, fiber diameter: 7 μm), as the carbon fiber (C), flake graphite (manufactured by Nippon Graphite Industries Co., Ltd., trade name "CB-100", volume average particle diameter: 100 μm) was used as the graphite (D), and the contents of the carbon black (B), carbon fiber (C), and graphite (D) were changed as shown in Table 1 below. A resin composition was obtained in the same manner as in Example 1, except that

[0092] Comparative Example 5 A resin composition was obtained in the same manner as in Example 1, except that graphite (D) was not used and the contents of carbon black (B) and carbon fiber (C) were changed as shown in Table 1 below.

[0093] [Evaluation] (Flexural strength) The resin compositions obtained in Examples 1 to 8 and Comparative Examples 1 to 5 were injection molded to obtain rectangular test pieces conforming to ISO 294-1, each measuring 80 mm in length, 10 mm in width, and 4 mm in thickness, which were used as measurement samples. The injection molding was carried out under the conditions of a resin temperature of 230°C, a mold temperature of 50°C, and an injection speed of 30 mm / s.

[0094] The bending strength of the obtained measurement sample was measured in accordance with ISO 178. The bending strength was measured using a Tensilon universal testing machine (manufactured by Orientec Co., Ltd., model number "RTC-1210A").

[0095] (Electromagnetic wave shielding effect) The resin compositions obtained in Examples 1 to 8 and Comparative Examples 1 to 5 were injection molded to obtain resin molded bodies measuring 100 mm in length, 100 mm in width, and 2 mm in thickness, which were used as measurement samples. The injection molding was performed under the conditions of a resin temperature of 230°C, a mold temperature of 50°C, and an injection speed of 30 mm / s.

[0096] The electromagnetic wave shielding effect (electromagnetic wave shielding performance, unit: dB) of the obtained measurement sample at a frequency of 100 MHz was measured using a KEC method electric field shielding property measuring jig (manufactured by Nippon Shield Enclosure Co., Ltd.). Specifically, electromagnetic waves were emitted from the focal point on the transmitting side, and the intensity of the electromagnetic waves converged on the focal point on the receiving side was measured as the received voltage. The received voltage V when no sample was inserted was ０ The received voltage V when the sample was inserted was measured, and the electromagnetic wave shielding effect was calculated according to the following formula (2).

[0097] Electromagnetic wave shielding effect = 20 x log １０ (V ０ / V)...Formula (2)

[0098] (Spiral flow length) The fluidity of the resin compositions obtained in Examples 1 to 8 and Comparative Examples 1 to 5 was evaluated as spiral flow length. Specifically, the flow length was measured when injection molding was performed using a resin flow length measurement mold having an Archimedean spiral flow path measuring 20 mm wide x 2 mm thick at a cylinder temperature of 230°C, a mold temperature of 40°C, and an injection pressure of 150 MPa.

[0099] (Thermal Conductivity) The resin compositions obtained in Examples 1 to 8 and Comparative Examples 1 to 5 were injection molded to obtain resin molded bodies measuring 100 mm in length, 100 mm in width, and 2 mm in thickness. The center of the obtained resin molded body was punched out to obtain a measurement sample measuring 10 mm in length, 2 mm in width, and 2 mm in thickness. The injection molding was performed under the following conditions: resin temperature 230°C, mold temperature 50°C, and injection speed 30 mm / s.

[0100] The thermal conductivity (in-plane direction) of the obtained measurement sample was measured using a Xenon Flash Laser Analyzer LFA467 HyperFlash manufactured by Netsch Japan Co., Ltd. Specifically, the measurement sample was fitted into a holder in an orientation that allowed for thermal conductivity measurement, and the thermal diffusivity at 30°C was measured, and the thermal conductivity was calculated according to the following formula (1).

[0101] Thermal conductivity (W / (m K)) = specific gravity (g / cm ３ ) x specific heat (J / g K) x thermal diffusivity (mm ２ / s)...Formula (1)

[0102] The results are shown in Tables 1 and 2 below.

[0103]

[0104]

[0105] As is clear from Table 1, the molded articles of the resin compositions of Examples 1 to 8 had a flexural strength of 90 MPa or more and an electromagnetic wave shielding performance of 45 dB or more. Furthermore, as is clear from Table 2, the molded articles of the resin compositions of Comparative Examples 1, 3, and 4 had a flexural strength of 60 MPa or less, and the molded articles of the resin compositions of Comparative Examples 1 to 5 had an electromagnetic wave shielding performance of 35 dB or less. Therefore, it was confirmed that the resin compositions of Examples 1 to 8 were able to achieve a high level of both mechanical strength and electromagnetic wave shielding performance compared to the resin compositions of Comparative Examples 1 to 5. Furthermore, it was confirmed that the resin compositions of Examples 1 to 3, 5, and 7 were able to increase the fluidity of the resin compositions during molding and were also excellent in moldability.

[0106] 10...heat dissipation chassis 20...heat dissipation housing 30...heat sink

Claims

1. A thermoplastic resin (A), carbon black (B), carbon fiber (C), and graphite (D), A resin composition, wherein the content of the carbon black (B) is 10 parts by weight or more and 100 parts by weight or less per 100 parts by weight of the thermoplastic resin (A).

2. The resin composition according to claim 1, wherein the content of the carbon fiber (C) is 10 parts by weight or more and 100 parts by weight or less per 100 parts by weight of the thermoplastic resin (A).

3. The carbon fiber (C) is a PAN-based carbon fiber or a pitch-based carbon fiber, The resin composition according to claim 1 or 2, wherein the content of the carbon fiber (C) is 35 parts by weight or more and 80 parts by weight or less per 100 parts by weight of the thermoplastic resin (A).

4. The BET specific surface area of ​​the carbon black (B) is 600 m ２ The resin composition according to claim 1 or 2, wherein the viscosity is 1 / g or less.

5. The resin composition according to claim 1 or 2, wherein the carbon fibers (C) have a weight average fiber length of 0.5 mm or more and 15 mm or less.

6. The resin composition according to claim 1 or 2, wherein the carbon black (B) is oil furnace black.

7. The resin composition according to claim 1 or 2, wherein the content of the graphite (D) is 10 parts by weight or more and 200 parts by weight or less per 100 parts by weight of the thermoplastic resin (A).

8. The graphite (D) is plate-like graphite, The resin composition according to claim 1 or 2, wherein the thickness of the graphite (D) is greater than 1 μm and less than 50 μm.

9. the resin composition in a molten state is filled into a mold in a direction perpendicular to the thickness direction of the resin molded article to be obtained, and when a resin molded article having a length of 100 mm, a width of 100 mm, and a thickness of 2 mm is obtained, the electromagnetic wave shielding effect of the resin molded article at a frequency of 100 MHz is 20 dB or more; When the resin composition is molded in accordance with ISO294-1 to obtain a rectangular resin molded body, the rectangular resin molded body has a bending strength measured in accordance with ISO178 of 40 MPa or more. The resin composition according to claim 1 or 2.

10. 3. The resin composition according to claim 1, wherein when the molten resin composition is filled into a mold from a direction perpendicular to the thickness direction of the resulting resin molded body and molded to obtain a resin molded body having a length of 100 mm, a width of 100 mm, and a thickness of 2 mm, the thermal conductivity in the in-plane direction of the main surface of the resin molded body is 1.0 W / (m·K) or more.

11. A resin molded article, which is a molded article of the resin composition according to claim 1 or 2.

12. The resin molded article according to claim 11 , which is in the shape of a heat dissipation chassis, a heat dissipation housing, or a heat sink.