Resin composition and molded article made of the resin composition

Abstract

To provide a resin composition which has shielding property to high-frequency electromagnetic waves of 10 GHz or more, and is excellent in electric insulation property and flowability at the time of melt-molding.SOLUTION: A polybutylene terephthalate resin composition is obtained by blending 100 pts.mass of a polybutylene terephthalate resin (A), 2-6 pts.mass of carbon black (B), 0.3-4 pts.mass of carbon fibers (C) and 0.05-5 pts.mass of a glycerol fatty acid ester (D). The glycerol fatty acid ester (D) is a glycerol fatty acid ester with a hydroxyl value of 200 or more, which is composed of: at least one selected from glycerol and its dehydration condensate; and a fatty acid having 12 or more carbon atoms. Volume resistivity of the resin composition 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, a resin composition with improved electromagnetic shielding properties and thin-wall fluidity, and a molded article made of the resin composition. In particular, the present invention relates to a resin composition having excellent electromagnetic shielding properties in the gigahertz band.

Background Art

[0002] In recent years, electronic devices have been used in all fields. In particular, communication devices are increasing from those using radio waves with relatively long wavelengths such as radio to devices using short-wavelength radio waves such as mobile phones, satellite broadcasts, and wireless LANs, and electromagnetic shielding has become an important technology.

[0003] As technologies for shielding electromagnetic waves to prevent malfunction due to electromagnetic waves, using a housing made of metal, adding conductive fillers such as metal fibers, carbon fibers, carbon fibers coated with metal, and carbon nanotubes to resin, and performing treatments such as conductive films, coatings, and plating are known. (Patent Document 1)

[0004] Although a metal housing has good performance, it increases the weight and reduces the design freedom. Techniques such as applying a film, coating, or plating to a resin housing may peel off, so it is not suitable for use in products with a long life cycle.

[0005] The combined use of carbon black and carbon fibers is known as having electromagnetic shielding properties without using metal (Patent Documents 2 and 3). These documents show shielding properties of about 1 GHz, and it is described that sufficient electromagnetic shielding properties cannot be obtained with a small amount of carbon fibers, and high electromagnetic shielding properties can be obtained by imparting conductivity.

[0006] In addition, with the miniaturization and weight reduction of electronic devices, the requirements for thin-wall fluidity are also increasing. In the case of thin-wall, plate-shaped or box-shaped molded products, such as micro-switch cases, small coil bobbins, thin-wall connectors, and housings for next-generation communication devices, there are problems such as molding defects (insufficient filling of the molded product into the mold) due to a decrease in fluidity, and an increase in warpage due to non-uniform resin flow. A material with good electromagnetic shielding properties and improved thin-wall fluidity has been desired.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] An object of the present invention is to provide a polybutylene terephthalate resin composition having shielding properties against high-frequency electromagnetic waves of 10 GHz or higher, excellent electrical insulation properties, and improved fluidity during melt molding, and a molded product thereof.

Means for Solving the Problems

[0009] The object of the present invention has been achieved as follows. 1. A polybutylene terephthalate resin composition comprising 100 parts by mass of a polybutylene terephthalate resin (A), 2 to 6 parts by mass of carbon black (B), 0.3 to 4 parts by mass of carbon fiber (C), and 0.05 to 5 parts by mass of a glycerin fatty acid ester (D), wherein the glycerin fatty acid ester (D) is a glycerin fatty acid ester having a hydroxyl value of 200 or more, which is composed of at least one selected from glycerin and its dehydration condensate and a fatty acid having 12 or more carbon atoms, and the volume resistivity of the resin composition is 1×1010 ~1×10 17 A polyethylene terephthalate resin composition having a volume resistivity of ~1×10 2. The polyethylene terephthalate resin composition according to item 1, wherein the carbon black (B) is ketjen black. 3. The polyethylene terephthalate resin composition according to item 1 or 2, wherein the fatty acid having 12 or more carbon atoms is lauric acid, stearic acid, or behenic acid. 4. The polyethylene terephthalate resin composition according to any one of items 1 to 3, wherein the measured value of the melt viscosity at a shear rate of 1000 sec -1 at a temperature of 260°C is 0.14 kP·s or less. 5. A molded article comprising the resin composition according to any one of items 1 to 4.

Advantages of the Invention

[0010] According to the present invention, a resin composition having shielding properties against high-frequency electromagnetic waves and excellent electrical insulation and fluidity during melt molding can be provided.

Modes for Carrying Out the Invention

[0011] The resin composition of the present invention is a polyethylene terephthalate resin composition obtained by blending 100 parts by mass of a polyethylene terephthalate resin (A), 2 to 6 parts by mass of carbon black (B), 0.3 to 4 parts by mass of carbon fiber (C), and 0.05 to 5 parts by mass of glycerin fatty acid ester (D). The glycerin fatty acid ester (D) is a glycerin fatty acid ester having a hydroxyl value of 200 or more, which is composed of at least one selected from glycerin and its dehydration condensate and a fatty acid having 12 or more carbon atoms. The volume resistivity of the resin composition is 1×10 10 ~1×10 17 Ω·cm, the transmission loss is -30 dB or less in the band of 75 to 110 GHz, and the electromagnetic wave absorption rate is 30% or more.

[0012] <Polyethylene terephthalate resin (A)> The polybutylene terephthalate resin (A) is a polybutylene terephthalate resin obtained by polycondensing a dicarboxylic acid component containing at least terephthalic acid or its ester-forming derivative (such as C1-6 alkyl esters and acid halides) and a glycol component containing at least an alkylene glycol having 4 carbon atoms (1,4-butanediol) or its ester-forming derivative (such as acetylated products).

[0013] In this embodiment, the polybutylene terephthalate resin (A) is not limited to a homopolybutylene terephthalate resin, and may also be a copolymer containing 60 mol% or more of butylene terephthalate units.

[0014] The amount of terminal carboxyl groups of the polybutylene terephthalate resin (A) is not particularly limited as long as it does not inhibit the object of the present invention, but is preferably 30 meq / kg or less, and more preferably 25 meq / kg or less.

[0015] The intrinsic viscosity of the polybutylene terephthalate resin (A) is not particularly limited as long as it does not inhibit 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. When using a polybutylene terephthalate resin having an intrinsic viscosity within such a range, the resulting polybutylene terephthalate resin composition will be particularly excellent in moldability.

[0016] Also, polybutylene terephthalate resins having different intrinsic viscosities can be blended to adjust the intrinsic viscosity. For example, by blending a polybutylene terephthalate resin having an intrinsic viscosity of 1.0 dL / g and a polybutylene terephthalate resin having an intrinsic viscosity of 0.7 dL / g, a polybutylene terephthalate resin having an intrinsic viscosity of 0.9 dL / g can be prepared. The intrinsic viscosity of the polybutylene terephthalate resin can be measured, for example, in o-chlorophenol under the condition of a temperature of 35°C.

[0017] In the preparation of the polybutylene terephthalate resin (A), when using an aromatic dicarboxylic acid other than terephthalic acid or its ester-forming derivative as a comonomer component, for example, C8-14 aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-dicarboxydiphenyl ether; C4-16 alkanedicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid; C5-10 cycloalkanedicarboxylic acids such as cyclohexanedicarboxylic acid; ester-forming derivatives of these dicarboxylic acid components (C1-6 alkyl ester derivatives, acid halides, etc.) can be used. These dicarboxylic acid components can be used alone or in combination of two or more.

[0018] 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.

[0019] In the preparation of the polybutylene terephthalate resin (A), when using a glycol component other than 1,4-butanediol 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, 1,3-octanediol; polyoxyalkylene glycols such as diethylene glycol, triethylene glycol, dipropylene glycol; alicyclic diols such as cyclohexanedimethanol, hydrogenated bisphenol A; aromatic diols such as bisphenol A, 4,4'-dihydroxybiphenyl; C2-4 alkylene oxide adducts of bisphenol A such as bisphenol A ethylene oxide 2 mol adduct, bisphenol A propylene oxide 3 mol adduct; or ester-forming derivatives of these glycols (acetylates, etc.) can be used. These glycol components can be used alone or in combination of two or more.

[0020] Among these glycol components, C2-6 alkylene glycols such as ethylene glycol and trimethylene glycol, polyoxyalkylene glycols such as diethylene glycol, or alicyclic diols such as cyclohexanedimethanol are more preferable.

[0021] Examples of the 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 (ε-caprolactone, etc.); and ester-forming derivatives of these comonomer components (C1-6 alkyl ester derivatives, acid halides, acetylated products, etc.).

[0022] In addition, as the polybutylene terephthalate resin, commercially available products may be used, or those produced by copolymerizing (polycondensing) terephthalic acid or its reactive derivative and 1,4-butanediol with a copolymerizable monomer, if necessary, by a conventional method such as transesterification or direct esterification method may also be used.

[0023] <Carbon black (B)> The carbon black (B) 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. And the said carbon black can be mix | blended in 2-6 mass parts with respect to 100 mass parts of polybutylene terephthalate resin (A).

[0024] In addition, the primary particle diameter in the present invention was measured by putting carbon black into a solvent, dispersing it by ultrasonic vibration, fixing the dispersion sample on a support film, photographing this with a transmission electron microscope (TEM), and measuring the particle diameter from the diameter. (1000 or more) The primary particle diameter can be determined by the arithmetic mean of those values.

[0025] As the carbon black (B), furnace black, acetylene black, ketjen black, etc. can be used, and ketjen black is preferred in view of the balance between transmission loss and electromagnetic wave absorption rate.

[0026] <Carbon fiber (C)> The carbon fiber (C) of the present invention is a carbon fiber such as PAN-based, pitch-based, rayon-based, etc. Also, metal-coated carbon fibers obtained by coating carbon fibers with metals such as nickel and copper can also be used in the present invention. Although carbon fiber has a high effect of reflecting electromagnetic waves, the reflected electromagnetic waves may cause malfunction of electronic devices. Therefore, the addition amount of carbon fiber (C) 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 with respect to 100 parts by mass of the polybutylene terephthalate resin (A).

[0027] As the carbon fiber of the present invention, a carbon fiber having a tensile fracture elongation of at least 1.5% or more is preferred. In order to impart high mechanical properties, it is preferable to use a carbon fiber having a tensile fracture elongation of 1.5% or more, more preferably a tensile fracture elongation of 1.7% or more, and still more preferably a tensile fracture elongation of 1.9% or more. Although there is no upper limit to the tensile fracture elongation of the carbon fiber used in the present invention, generally it is less than 5%. The diameter of the carbon fiber is preferably 4 to 20 μm, and more preferably 5 to 10 μm.

[0028] More preferably as the carbon fiber, a PAN-based carbon fiber excellent in the balance between strength and elastic modulus is good. The tensile elastic modulus is preferably 100 to 600 GPa, more preferably 200 to 500 GPa, and particularly preferably 230 to 450 GPa. Also, the tensile strength is 2000 MPa to 10000 MPa, preferably 3000 to 8000 MPa.

[0029] In addition, these carbon fibers may be surface-treated with a silane coupling agent, an aluminate coupling agent, a titanate coupling agent, etc., or may be subjected to a bundling treatment 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 crystalline resin, an alcohol or a water-soluble resin, etc.

[0030] The total 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, electromagnetic shielding properties can be achieved while maintaining electrical insulation properties. Here, electrical insulation means that the volume resistivity is 1×10 10 or more.

[0031] <Glycerin fatty acid ester (D)> The feature of the present invention lies in combining a polybutylene terephthalate resin with a specific glycerin fatty acid ester. Usually, when a fluidity improver or the like is added to a polybutylene terephthalate resin, even if the fluidity can be improved, it is impossible to avoid a decrease in the properties such as the mechanical strength inherent in the polybutylene terephthalate resin itself. In the present invention, by using a specific glycerin fatty acid ester, the fluidity of the polybutylene terephthalate resin composition can be efficiently improved while maintaining the above properties at a high level.

[0032] In addition, by combining with an inorganic filler, the strength or rigidity of the resin composition or its molded product can be improved, and such an improvement effect of strength or rigidity is not reduced by the use of the glycerin fatty acid ester, so that it is possible to achieve a good balance between maintaining mechanical strength and improving fluidity.

[0033] The glycerin fatty acid ester (D) is a glycerin fatty acid ester having a hydroxyl value of 200 or more, which is composed of at least one selected from glycerin and its dehydration condensate and a fatty acid having 12 or more carbon atoms. Examples of the fatty acid having 12 or more carbon atoms constituting the ester include lauric acid, oleic acid, palmitic acid, stearic acid, behenic acid, montanic acid, etc. Preferably, fatty acids having 12 to 32 carbon atoms are used, particularly preferably fatty acids having 12 to 22 carbon atoms, and lauric acid, stearic acid or behenic acid is particularly preferred. Those having less than 12 carbon atoms may reduce the heat resistance and are not preferred, and those having more than 32 carbon atoms have little effect on improving fluidity and are not preferred.

[0034] The glycerin fatty acid ester (D) used in the present invention can be produced by a method known per se. The glycerin fatty acid ester (D) used in the present invention is one in which esterification is adjusted so that the hydroxyl value becomes 200 or more, preferably having a hydroxyl value of 250 or more. If the hydroxyl value is less than 200, the effect of improving fluidity is small and it is not preferred. The hydroxyl value was measured in accordance with the Japan Oil Chemists' Society 2.3.6.2-1996 Hydroxyl Value (Pyridine-Acetic Anhydride Method).

[0035] Examples of preferred esters include glycerin monostearate, glycerin monobehenate, diglycerin monostearate, triglycerin monostearate, tetraglycerin stearic acid partial ester, decaglycerin lauric acid partial ester, etc.

[0036] The blending amount of the glycerin fatty acid ester (D) is 0.05 to 5 parts by mass, preferably 0.5 to 3 parts by mass, based on 100 parts by mass of the polybutylene terephthalate resin (A). If the blending amount of the glycerin fatty acid ester (D) is less than 0.05 parts by mass, the effect of improving fluidity may not be sufficiently obtained. If it exceeds 5 parts by mass, the amount of gas generated during molding increases, which may damage the appearance of the molded product or cause mold fouling.

[0037] <Inorganic filler> In the molded article of the present invention, the type of inorganic filler that can be blended to improve heat resistance and mechanical strength is not particularly limited as long as the effects of the present application are not inhibited. However, conductive substances such as metal fibers and carbon nanotubes should preferably be avoided because they reduce insulation.

[0038] For example, glass fiber, glass flake, glass bead, silica, talc, mica, etc. are preferable, and glass fiber is particularly preferable. The fiber length of the glass fiber (in the state before being prepared in the composition by melt kneading etc.) is preferably 1 to 10 mm, and the diameter of the glass fiber is preferably 5 to 20 μm.

[0039] 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 30 to 100 parts by mass, based on 100 parts by mass of the polybutylene terephthalate resin (A).

[0040] <Other components> In the present invention, within a range that does not impair the effects of the present invention, in addition to the above components, known additives generally added to thermoplastic resins and thermosetting resins, namely, barium inhibitors, mold 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 be blended.

[0041] <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 band of 75 to 110 GHz, and an electromagnetic wave absorption rate of 30% or more. These properties can be achieved by adjusting the addition amounts of carbon black (B) and carbon fiber (C).

[0042] The volume resistivity is 1×10 10 ~1×10 17By making it Ω·cm, insulation can be obtained when used in electronic devices. By having a transmission loss of -30 dB or less in the band of 75 to 110 GHz and an electromagnetic wave absorption rate of 30% or more, excellent electromagnetic wave shielding properties can be obtained.

[0043] By adjusting the blending amount of the glycerin fatty acid ester (D) in the resin composition of the present invention, the fluidity (melt viscosity) during melt molding can be suppressed to 0.14 kPa·s or less, and high fluidity can be obtained. Therefore, problems such as molding defects due to a decrease in fluidity and an increase in warpage generation based on non-uniform resin flow can be solved.

[0044] <Molded article> A molded article can be produced from the resin composition of the present invention, and the method is not particularly limited, and a known method can be adopted. For example, the resin composition is put into an extruder, melt-kneaded and pelletized, and these pellets are put into an injection molding machine equipped with a predetermined mold and injection molded to produce it. The molded article of the present invention is useful for electronic devices and the like.

Examples

[0045] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

[0046] <Materials> (A) Polybutylene terephthalate resin (PBT), manufactured by Polyplastics Co., Ltd. (B1) Carbon black (Ketjen black): ECX manufactured by Lion Specialty Chemicals (B2) Carbon black (furnace black): #750B manufactured by Mitsubishi Chemical Corporation (B3) Carbon black (acetylene black): Denka Black Granular manufactured by Denka Co., Ltd. (C) Carbon fiber: HTC432 manufactured by Toray Tenax Co., Ltd. (D) Glycerin fatty acid ester: (D1) Stearic acid partial glyceride (hydroxyl value 280, "Licemal AF-70" manufactured by Riken Vitamin Co., Ltd.) (D2) Glyceryl monobehenate (hydroxyl value 300, "Licemal B-100" manufactured by Riken Vitamin Co., Ltd.) (D3) Glyceryl mono-12-hydroxystearate (hydroxyl value 420, "Licemal HC-100" manufactured by Riken Vitamin Co., Ltd.) (D4) Decaglycerin lauric acid partial ester (hydroxyl value 600, "Poem L-021" manufactured by Riken Vitamin Co., Ltd.) (D5) Glyceryl tristearate (hydroxyl value 87, "Poem S-95" manufactured by Riken Vitamin Co., Ltd.) Antioxidant: Irganox 1010 manufactured by BASF Japan Ltd. Glass fiber: ECS03T-187 manufactured by Nippon Electric Glass Co., Ltd.

[0047] <Preparation of resin composition test pieces> The above materials were dry-blended at the ratios (unit: parts by mass) shown in Table 1 below, supplied from a hopper to a twin-screw extruder (manufactured by Japan Steel Works, Ltd.) having a 30 mmφ screw, and melt-kneaded at 250 °C to obtain a pelletized polybutylene terephthalate resin composition, and test pieces were prepared by injection molding.

[0048] <Evaluation> The evaluation was conducted as follows. The results are shown in Tables 1 and 2. Unless otherwise specified, the measurements were carried out in an atmosphere of 23 °C and 50% RH. ≪Volume resistivity (Ω·cm)≫ In accordance with IEC60093, using a measuring device, a super high resistance meter R8340 (manufactured by Advantest Corporation), the measurement was carried out at an applied voltage of 500 V. The test pieces were 100 mm × 100 mm × 3 mmt.

[0049] ≪Transmission loss (dB)≫ The measurement was carried out using the following device, measurement method, and frequency. The test pieces were 100 mm × 100 mm × 3 mmt. · Measuring device: Horn antenna: FSS-05 (manufactured by HVS Co., Ltd.) Dielectric lens: FSS-06 (manufactured by HVS) Network analyzer: N5227A (manufactured by Keysight Technologies) Millimeter-wave controller: N5261A (manufactured by Keysight Technologies) · Measurement method: Free space method · Frequency: 75 - 110 GHz

[0050] ≪Electromagnetic wave absorption rate≫ Calculated by the following formula. Reflection loss |S11| = Intensity of reflected electromagnetic wave / Intensity of incident electromagnetic wave (amplitude ratio of incident wave and reflected wave) S11(dB) = 20 log |S11| Transmission loss |S21| = Intensity of transmitted electromagnetic wave / Intensity of incident electromagnetic wave (amplitude ratio of incident wave and transmitted wave) S21(dB) = 20 log |S21| Electromagnetic wave absorption rate (%) = (1 - (|S11|^ 2 + |S21|^ 2 )) × 100

[0051] ≪Flowability (melt viscosity) during melt forming≫ After drying the obtained pellets at 140 °C for 3 hours, using a capillary rheometer 1B (manufactured by Toyo Seiki Seisakusho), at a furnace temperature of 260 °C, with a capillary of φ1 mm × 20 mm L, and a shear rate of 1000 sec -1 Measured at. A lower value indicates better flowability during melting and better flowability during forming. <Evaluation results>

[0052]

Table 1

[0053]

Table 2

[0054] As shown in Tables 1 and 2, it can be seen that in the present invention, it has excellent electromagnetic wave shielding performance at high frequencies, excellent high flowability, and also has a high volume resistivity and electrical insulation.

Claims

1. A polybutylene terephthalate resin composition comprising 100 parts by mass of a polybutylene terephthalate resin (A), 2 to 6 parts by mass of carbon black (B), 0.3 to 4 parts by mass of carbon fiber (C), and 0.05 to 5 parts by mass of glycerin fatty acid ester (D), wherein the total of the carbon black (B) and the carbon fiber (C) is 7 parts by mass or less, and the glycerin fatty acid ester (D) is a glycerin fatty acid ester having a hydroxyl value of 200 or more, which is composed of at least one selected from glycerin and its dehydration condensate and a fatty acid having 12 or more carbon atoms. The volume resistivity of the resin composition is 1 × 10 １０ to 1 × 10 １７ Ω·cm, the transmission loss is -30 dB or less in the band of 75 to 110 GHz, and the electromagnetic wave absorption rate is 30% or more, a polybutylene terephthalate resin composition.

2. The polybutylene terephthalate resin composition according to Claim 1, wherein the carbon black (B) is ketjen black.

3. The polybutylene terephthalate resin composition according to Claim 1 or 2, wherein the fatty acid having 12 or more carbon atoms is lauric acid, stearic acid or behenic acid.

4. Shear rate of 1000 sec⁻¹ at a temperature of 260 °C －１ The polybutylene terephthalate resin composition according to any one of claims 1 to 3, wherein the melt viscosity at －１ is 0.14 kPa·s or less.

5. A molded article comprising the resin composition according to any one of Claims 1 to 4.

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