Resin composition and molded article made from said resin composition

Abstract

To provide a resin composition which has shielding property with respect to high-frequency electromagnetic waves of 10 GHz or higher, and is excellent in low warpage property and electric insulation property.SOLUTION: A resin composition contains 2-6 pts.mass of carbon black (C) and 0.3-4 pta.mass of carbon fibers (D) with respect to 100 pts.mass of the total of 60-95 pts.mass of a polybutylene terephthalate resin (A), and 5-40 pts.mass of one or more polymer compounds (B) selected from a polycarbonate resin and a styrenic resin, wherein the total of the carbon black (C) and the carbon fibers (D) is 7 pts.mass or less, volume resistivity is 1×1010 to 1×1017 Ω cm, transmission loss at a band of 75-110 GHz is -30 dB or less, and an electromagnetic wave absorption rate is 30% or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin composition having electromagnetic wave shielding properties and a molded article made of the resin composition, particularly to a resin composition having excellent electromagnetic wave shielding properties in the gigahertz band. [Background technology]

[0002] In recent years, electronic devices have been used in a wide range of fields. In particular, communication devices have been shifting from those that use relatively long wavelength radio waves, such as radio waves, to those that use short wavelength radio waves, such as mobile phones, satellite broadcasting, and wireless LAN, making electromagnetic wave shielding an important technology.

[0003] Known techniques for shielding electromagnetic waves to prevent malfunctions caused by electromagnetic waves include using a metal housing or the like, adding conductive fillers such as metal fiber, carbon fiber, metal-coated carbon fiber, or carbon nanotubes to the resin of a resin housing, and applying a conductive film, painting, or plating (Patent Document 1).

[0004] Although metal casings have good performance, they are heavy and have limited design freedom, and methods such as applying film, paint, or plating to plastic casings are likely to peel off, so they are not suitable for use in products with a long life cycle.

[0005] The combined use of carbon black and carbon fiber is known as a material that provides electromagnetic wave shielding properties without using metal (Patent Documents 2 and 3). These documents demonstrate shielding properties of around 1 GHz, and state that a small amount of carbon fiber does not provide sufficient electromagnetic wave shielding properties, but that high electromagnetic wave shielding properties can be achieved by imparting electrical conductivity.

[0006] Furthermore, as electronic devices become smaller and lighter, problems such as increased warpage due to uneven resin flow have arisen in parts such as microswitch cases, small coil bobbins, thin-walled connectors, and disk cartridge shutters. Therefore, there has been a demand for materials that have electrical insulation, good electromagnetic wave shielding properties, and improved low warpage properties. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-229345 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-31257 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-45385 Summary of the Invention [Problem to be solved by the invention]

[0008] Advances in electronic devices have led to a demand for electromagnetic wave shielding against high-frequency electromagnetic waves of 10 GHz and above. Conventional conductive electromagnetic wave shielding materials have had to be combined with electrical insulating materials when used in electrical device components that also require electrical insulation.

[0009] An object of the present invention is to provide a resin composition which has shielding properties against high frequency electromagnetic waves of 10 GHz or higher, excellent electrical insulation properties, and improved low warpage properties. [Means for solving the problem]

[0010] The object of the present invention has been achieved by the following. 1. A resin composition comprising 60 to 95 parts by mass of polybutylene terephthalate resin (A) and 5 to 40 parts by mass of one or more polymeric compounds (B) selected from polycarbonate resins and styrene-based resins, for a total of 100 parts by mass, and containing 2 to 6 parts by mass of carbon black (C) and 0.3 to 4 parts by mass of carbon fiber (D), wherein the total of the carbon black (C) and the carbon fiber (D) is 7 parts by mass or less, and the resin composition has a volume resistivity of 1×1010 to 1×1017 Ω cm, a transmission loss of -30 dB or less in the 75 to 110 GHz band, and an electromagnetic wave absorption rate of 30% or more. 2. The resin composition according to 1 above, wherein the carbon black (C) is Ketjen black. 3. A molded article made from the resin composition described in 1 or 2 above. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a resin composition which has shielding properties against high frequency electromagnetic waves, excellent electrical insulation properties, and improved low warpage properties. DETAILED DESCRIPTION OF THE INVENTION

[0012] The resin composition of the present invention contains 2 to 6 parts by mass of carbon black (C) and 0.3 to 4 parts by mass of carbon fiber (D) relative to a total of 100 parts by mass of 60 to 95 parts by mass of polybutylene terephthalate resin (A) and 5 to 40 parts by mass of one or more polymer compounds (B) selected from polycarbonate resins and styrene-based resins, and the total of (C) and (D) is 7 parts by mass or less, and has a volume resistivity of 1×10 10 ~1×10 17 It is characterized by a resistance of Ω·cm, a transmission loss of -30 dB or less in the 75 to 110 GHz band, and an electromagnetic wave absorption rate of 30% or more.

[0013] <Polybutylene terephthalate resin (A)> The polybutylene terephthalate resin (A) is a polybutylene terephthalate resin obtained by polycondensation of a dicarboxylic acid component containing at least terephthalic acid or an ester-forming derivative thereof (such as a C1-6 alkyl ester or an acid halide), and a glycol component containing at least an alkylene glycol having 4 carbon atoms (1,4-butanediol) or an ester-forming derivative thereof (such as an acetylated product).

[0014] In this embodiment, the polybutylene terephthalate resin (A) is not limited to a homopolybutylene terephthalate resin, but may be a copolymer containing 60 mol % or more of butylene terephthalate units.

[0015] The amount of terminal carboxyl groups in the polybutylene terephthalate resin (A) is not particularly limited as long as it does not impede the object of the present invention, but is preferably 30 meq / kg or less, more preferably 25 meq / kg or less.

[0016] The intrinsic viscosity of the polybutylene terephthalate resin (A) is not particularly limited as long as it does not impair the object of the present invention, but is preferably 0.60 dL / g or more and 1.5 dL / g or less, and more preferably 0.65 dL / g or more and 1.2 dL / g or less.

[0017] When a polybutylene terephthalate resin having an intrinsic viscosity within this range is used, the resulting polybutylene terephthalate resin composition will have particularly excellent moldability. Furthermore, the intrinsic viscosity can be adjusted by blending polybutylene terephthalate resins having different intrinsic viscosities.

[0018] For example, a polybutylene terephthalate resin with an intrinsic viscosity of 0.9 dL / g can be prepared by blending a polybutylene terephthalate resin with an intrinsic viscosity of 1.0 dL / g with a polybutylene terephthalate resin with an intrinsic viscosity of 0.7 dL / g. The intrinsic viscosity of the polybutylene terephthalate resin can be measured, for example, in o-chlorophenol at 35°C.

[0019] In preparing the polybutylene terephthalate resin (A), when an aromatic dicarboxylic acid other than terephthalic acid or its ester-forming derivative is used as a comonomer component, examples of the aromatic dicarboxylic acids that can be used include isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, and 4,4'-dicarboxydiphenyl ether; C4-16 alkanedicarboxylic acids such as succinic acid, adipic acid, azelaic acid, and sebacic acid; C5-10 cycloalkanedicarboxylic acids such as cyclohexanedicarboxylic acid; and ester-forming derivatives of these dicarboxylic acid components (e.g., C1-6 alkyl ester derivatives and acid halides). These dicarboxylic acid components can be used alone or in combination of two or more.

[0020] Among these dicarboxylic acid components, C8-12 aromatic dicarboxylic acids such as isophthalic acid, and C6-12 alkanedicarboxylic acids such as adipic acid, azelaic acid, and sebacic acid are more preferred.

[0021] In preparing the polybutylene terephthalate resin (A), when a glycol component other than 1,4-butanediol is used as a comonomer component, for example, C2-10 alkylene glycols such as ethylene glycol, propylene glycol, trimethylene glycol, 1,3-butylene glycol, hexamethylene glycol, neopentyl glycol, and 1,3-octanediol; polyoxyalkylene glycols such as diethylene glycol, triethylene glycol, and dipropylene glycol; alicyclic diols such as cyclohexanedimethanol and hydrogenated bisphenol A; aromatic diols such as bisphenol A and 4,4'-dihydroxybiphenyl; C2-4 alkylene oxide adducts of bisphenol A, such as an ethylene oxide 2-mol adduct of bisphenol A and a propylene oxide 3-mol adduct of bisphenol A; or ester-forming derivatives of these glycols (e.g., acetylated products). These glycol components can be used alone or in combination of two or more.

[0022] Among these glycol components, C2-6 alkylene glycols such as ethylene glycol and trimethylene glycol, polyoxyalkylene glycols such as diethylene glycol, and alicyclic diols such as cyclohexanedimethanol are more preferred.

[0023] Examples of comonomer components that can be used in addition to the dicarboxylic acid component and the glycol component include aromatic hydroxycarboxylic acids such as 4-hydroxybenzoic acid, 3-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, and 4-carboxy-4'-hydroxybiphenyl; aliphatic hydroxycarboxylic acids such as glycolic acid and hydroxycaproic acid; C3-12 lactones such as propiolactone, butyrolactone, valerolactone, and caprolactone (e.g., ε-caprolactone); and ester-forming derivatives of these comonomer components (e.g., C1-6 alkyl ester derivatives, acid halides, and acetylated products).

[0024] The content of the polybutylene terephthalate resin (A) is preferably 60 to 95 parts by mass, more preferably 70 to 90 parts by mass, and even more preferably 75 to 85 parts by mass, relative to 100 parts by mass of the total resin mass of the resin composition (polybutylene phthalate resin (A) + polymer compound (B)).

[0025] <High molecular compound (B)> The polymer compound (B) is one or more polymer compounds selected from polycarbonate resins and styrene-based resins.

[0026] <Polycarbonate resin> Polycarbonate resins can be produced by a solvent method, i.e., by reacting a dihydric phenol with a carbonate precursor such as phosgene or by transesterification of a dihydric phenol with a carbonate precursor such as diphenyl carbonate in a solvent such as methylene chloride in the presence of a known acid acceptor and molecular weight modifier. Suitable dihydric phenols include bisphenols, with 2,2-bis(4-hydroxyphenyl)propane, i.e., bisphenol A, being particularly preferred. Furthermore, phenol A may be partially or completely substituted with another dihydric phenol.

[0027] Examples of dihydric phenols other than bisphenol A include compounds such as hydroquinone, 4,4-dihydroxydiphenyl, bis(4-hydroxyphenyl)alkane, bis(4-hydroxyphenyl)cycloalkane, bis(4-hydroxyphenyl)sulfide, bis(4-hydroxyphenyl)sulfone, bis(4-hydroxyphenyl)sulfoxide, and bis(4-hydroxyphenyl)ether, as well as halogenated bisphenols such as bis(3,5-dibromo-4-hydroxyphenyl)propane and bis(3,5-dichloro-4-hydroxyphenyl)propane.

[0028] These dihydric phenols may be homopolymers or copolymers of two or more dihydric phenols. Furthermore, the polycarbonate resin used in the present invention may be a thermoplastic random-branched polycarbonate obtained by reacting a polyfunctional aromatic with a dihydric phenol and / or a carbonate precursor. The polycarbonate used in the present invention is preferably one having high fluidity.

[0029] <Styrene-based resin> Styrenic resins include polymers and copolymers containing repeating units derived from aromatic vinyl compounds, such as styrene, α-alkyl-substituted styrene, and nuclear-alkyl-substituted styrene.

[0030] Examples of the monomer other than the aromatic vinyl compound include acrylonitrile, methyl methacrylate, etc. The styrene-based resin may be modified with rubber, and examples of the rubber include polybutadiene, styrene-butadiene copolymer, polyisoprene, ethylene-propylene copolymer, etc.

[0031] The styrene resin may be modified with epoxy. Specific examples of such styrene resins include polystyrene, rubber-modified polystyrene, ABS resin, MBS resin, AS resin, and ESBS resin, with ABS resin, AS resin, ESBS resin, and mixtures thereof being preferred.

[0032] The amount of one or more polymeric compounds (B) selected from polycarbonate resins and styrene-based resins added is 5 to 40 parts by mass, preferably 8 to 30 parts by mass, per 100 parts by mass of the total resin mass of the resin composition (polybutylene phthalate resin (A) + polymeric compound (B)). If the amount of polymeric compound (B) added is too small, the resulting molded product will not exhibit sufficient dimensional stability and low warpage, while if it is too large, molding problems such as an increased molding cycle, poor mold releasability, and even reduced melt thermal stability will occur, which is undesirable.

[0033] <Carbon black (C)> The carbon black (C) of the present invention has a primary particle diameter of 5 to 40 nm and a nitrogen adsorption specific surface area of ​​100 m 2 / g or more of carbon black. The carbon black can be contained in an amount of 2 to 6 parts by mass per 100 parts by mass of the total of the polybutylene terephthalate resin (A) and the polymer compound (B).

[0034] The primary particle size in the present invention is determined by dispersing carbon black in a solvent using ultrasonic vibration, fixing the dispersed sample to a support film, photographing it with a transmission electron microscope (TEM), and measuring the particle size from the diameter (1,000 or more particles). The primary particle size can be calculated by arithmetic averaging these values.

[0035] As the carbon black (C), furnace black, acetylene black, ketjen black, etc. can be used, with ketjen black being preferred in terms of the balance between transmission loss and electromagnetic wave absorption rate.

[0036] <Carbon fiber (D)> The carbon fiber (D) of the present invention is a PAN-based, pitch-based, rayon-based, or other carbon fiber. Metal-coated carbon fiber, in which carbon fiber is coated with a metal such as nickel or copper, can also be used in the present invention. Carbon fiber is highly effective at reflecting electromagnetic waves, but the reflected electromagnetic waves can cause electronic devices to malfunction. Therefore, the amount of carbon fiber (D) added is 0.3 to 4 parts by mass, preferably 0.5 to 3 parts by mass, and more preferably 1 to 2 parts by mass, per 100 parts by mass of the total of the polybutylene terephthalate resin (A) and the polymer compound (B).

[0037] The carbon fiber of the present invention preferably has a tensile breaking elongation of at least 1.5%. To impart high mechanical properties, it is preferable to use carbon fiber having a tensile breaking elongation of 1.5% or more, more preferably a tensile breaking elongation of 1.7% or more, and even more preferably a tensile breaking elongation of 1.9% or more. There is no upper limit to the tensile breaking elongation of the carbon fiber used in the present invention, but it is generally less than 5%. The diameter of the carbon fiber is preferably 4 to 20 μm, more preferably 5 to 10 μm.

[0038] More preferably, the carbon fiber is a PAN-based carbon fiber, which has an excellent balance between strength and modulus. The tensile modulus is preferably 100 to 600 GPa, more preferably 200 to 500 GPa, and particularly preferably 230 to 450 GPa. The tensile strength is 2000 MPa to 10000 MPa, preferably 3000 to 8000 MPa.

[0039] Furthermore, these carbon fibers may be surface-treated with a silane coupling agent, an aluminate coupling agent, a titanate coupling agent, or the like, or bundled with a urethane resin, an epoxy resin, a polyester resin, a styrene resin, an olefin resin, an amide resin, an acrylic resin, a phenolic polymer, a liquid crystal resin, an alcohol- or water-soluble resin, or the like.

[0040] The total amount of carbon black (C) and carbon fiber (D) is preferably 7 parts by mass or less, more preferably 6 parts by mass or less. By making it 7 parts by mass or less, it is possible to maintain electrical insulation while providing electromagnetic wave shielding properties. Here, electrical insulation means a volume resistivity of 1×10 10 This refers to a resistance of Ω·cm or more.

[0041] <Inorganic filler> The molded article of the present invention preferably contains an inorganic filler to improve heat resistance and mechanical strength. The type of inorganic filler is not particularly limited as long as it does not impair the effects of the present invention, but conductive materials such as metal fibers and carbon nanotubes should be avoided because they reduce insulation. For example, glass fibers, glass flakes, glass beads, silica, talc, mica, etc. are preferred, with glass fibers being particularly preferred. The fiber length of the glass fibers (before they are prepared into a composition by melt-kneading, etc.) is preferably 1 to 10 mm, and the diameter of the glass fibers is preferably 5 to 20 μm.

[0042] In the present invention, from the viewpoint of improving heat resistance and mechanical strength, the inorganic filler is preferably contained in an amount of 0 to 150 parts by mass, more preferably 10 to 100 parts by mass, per 100 parts by mass of the total of the polybutylene terephthalate resin (A) and the polymer compound (B).

[0043] <Other ingredients> In the present invention, in addition to the above-mentioned components, known additives generally added to thermoplastic resins and thermosetting resins, namely, burr inhibitors, release agents, lubricants, plasticizers, flame retardants, colorants such as dyes and pigments, crystallization accelerators, crystal nucleating agents, various antioxidants, heat stabilizers, weather resistance stabilizers, corrosion inhibitors, etc. may also be blended within the scope of not impairing the effects of the present invention.

[0044] <Properties of the resin composition> The resin composition of the present invention has a volume resistivity of 1×10 10 ~1×10 17 Ω·cm, a transmission loss of -30 dB or less in the 75 to 110 GHz band, and an electromagnetic wave absorption rate of 30% or more. These properties can be achieved by adjusting the amounts of carbon black B and carbon fiber C added.

[0045] Volume resistivity 1×10 10 ~1×10 17 By achieving a resistivity of Ω·cm, insulation properties can be obtained when used in electronic devices. With a transmission loss of -30 dB or less in the 75 to 110 GHz band and an electromagnetic wave absorption rate of 30% or more, excellent electromagnetic wave shielding properties can be achieved.

[0046] By further combining the polybutylene terephthalate resin (A) with the polymer compound (B), low warpage can be imparted.

[0047] <Molded products> A molded article can be produced from the resin composition of the present invention by any known method, without any particular limitation. For example, the resin composition can be fed into an extruder, melt-kneaded, and pelletized, and the pellets can be fed into an injection molding machine equipped with a predetermined mold and injection-molded. The molded article of the present invention is useful for electronic devices, etc. [Example]

[0048] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0049] <Material> A Polybutylene terephthalate resin (PBT) manufactured by Polyplastics Co., Ltd. B1 Polycarbonate: Teijin Polycarbonate L1225 B2 Acrylonitrile Styrene Copolymer AP-20 (Techno UMG) C1 Carbon Black (Ketjen Black): ECX manufactured by Lion Specialty Chemicals C2 Carbon black (furnace black): Mitsubishi Chemical #750B C3 Carbon black (acetylene black): Denka Black Granules manufactured by Denka Corporation D Carbon fiber: Toho Tenax HTC432 Antioxidant: BASF Japan Irganox 1010 Glass fiber: Nippon Electric Glass ECS03T-187

[0050] <Preparation of Resin Composition Test Pieces> The above materials were dry-blended in the ratios (units: parts by mass) shown in Table 1 below, fed from a hopper into a twin-screw extruder (manufactured by The Japan Steel Works, Ltd.) with a 30 mmφ screw, and melt-kneaded at 250°C to obtain pellets of a polybutylene terephthalate resin composition, which were then injection-molded to prepare test specimens.

[0051] <Evaluation> The evaluation was carried out as follows, and the results are shown in Table 1. Unless otherwise specified, the measurements were carried out in an atmosphere of 23°C and 50% RH. ≪Volume resistivity (Ω cm)≫ In accordance with IEC 60093, measurements were made using an ultra-high resistance meter R8340 (manufactured by Advantest Corporation) at an applied voltage of 500 V. The test piece was 100 mm x 100 mm x 3 mm.

[0052] ≪Transmission loss (dB)≫ Measurements were made using the following equipment, measurement method, and frequency. The test piece was 100 mm x 100 mm x 3 mmt. Measuring equipment: Horn antenna: FSS-05 (HVS) Dielectric lens: FSS-06 (HVS) Network analyzer: N5227A (Keysight Technologies) Millimeter-wave controller: N5261A (Keysight Technologies) ·Measurement method: free space method Frequency: 75~110GHz

[0053] ≪Electromagnetic wave absorption rate≫ It was calculated using the following formula. Reflection loss |S11| = reflected wave electromagnetic wave intensity / incident wave electromagnetic wave intensity (amplitude ratio of incident wave to reflected wave) S11(dB)=20log|S11| Transmission loss |S21| = transmitted electromagnetic wave intensity / incident wave electromagnetic wave intensity (amplitude ratio of incident wave to transmitted wave) S21(dB)=20log|S21| Electromagnetic wave absorption rate (%) = (1-(|S11|^ 2 +|S21|^ 2 ))×100

[0054] <Evaluation of warpage of molded products> A flat plate-shaped molded piece measuring 80 mm x 80 mm x 1 mm was molded under the molding conditions below, and after conditioning for 24 hours or more in an environment of 23°C and 50% humidity, the maximum amount of warping of the flat plate was measured using a height gauge, and a maximum warping amount of less than 3 mm was considered to be acceptable. ·Injection molding machine: FANUC ROBOSHOT α-100iA Cylinder temperature: 260℃ ·Injection speed: 1m / min - Holding pressure: 70MPa Mold temperature: 65℃ Warpage evaluation criteria Pass: Warpage less than 3mm Fail ×: Warpage amount 3 mm or more <Evaluation results>

[0055] [Table 1]

[0056] [Table 2]

[0057] As shown in Tables 1 and 2, the present invention has excellent electromagnetic wave shielding properties at high frequencies, low warpage, and high volume resistivity, providing excellent electrical insulation.

Claims

1. A resin composition comprising 75 to 95 parts by mass of a polybutylene terephthalate resin (A) and 5 to 40 parts by mass of a polymer compound (B) for a total of 100 parts by mass, and containing 2 to 6 parts by mass of carbon black (C) and 0.3 to 4 parts by mass of carbon fiber (D), wherein the total amount of the carbon black (C) and the carbon fiber (D) is 5.8 parts by mass or more and 7 parts by mass or less, the polymer compound (B) is a polycarbonate resin or an acrylonitrile-styrene copolymer, Volume resistivity is 1 x 10 １０ ~1 x 10 １７ Ω·cm, a transmission loss of −30 dB or less in the 75 to 110 GHz band, and an electromagnetic wave absorption rate of 30% or more.

2. 2. The resin composition according to claim 1, wherein the carbon black (C) is Ketjen black.

3. A molded article made from the resin composition according to claim 1 or 2.

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