Polyester resin composition and molded article thereof

Abstract

This thermoplastic polyester resin composition obtained by mixing, with (A) 100 parts by weight of a thermoplastic polyester resin, (B) 0.1 to 5 parts by weight of a carbon nanotube having a combustion peak at a high temperature side at 650-900 °C in thermogravimetric analysis when the temperature is raised at 10 °C / min in air. Consequently, a polyester resin composition is obtained which makes it possible to obtain a molded article that has high electromagnetic wave absorbing properties, excellent mechanical strength, and excellent laser marking.

Description

Polyester resin composition and molded article thereof

[0001] The present invention relates to a thermoplastic polyester resin composition having excellent electromagnetic wave absorbency, mechanical strength, and laser markability, and to a molded article thereof.

[0002] Thermoplastic polyester resins, particularly polybutylene terephthalate-based resins, are widely used in housings and structural members of office automation equipment, communication equipment, electrical and electronic equipment, and automotive electrical equipment due to their excellent injection moldability, light weight, moldability, mechanical properties, and heat resistance, and demand for them is increasing year by year.

[0003] On the other hand, as 5G communications and autonomous driving technologies become more widespread in order to realize a safer and more comfortable society, it is expected that the scope of use of high-frequency electromagnetic waves will expand further in the future in communication devices such as wireless communication systems used in these technologies, and automotive electrical equipment such as millimeter-wave radar.

[0004] However, the higher the frequency, the more likely it is that noise is emitted when converted into electromagnetic waves, which can cause problems such as malfunctions due to a worsening noise environment inside communication equipment and automotive electrical equipment.For example, with millimeter-wave radar, radio waves reflected by structures such as guardrails can mix with the radio waves reflected from the target the radar is trying to detect, causing false images that do not actually exist to appear on the radar screen.

[0005] To prevent such malfunctions, housings and structural components used in communication devices and automotive electrical equipment are required to have excellent electromagnetic wave absorption while maintaining excellent injection moldability, light weight, moldability, mechanical properties, and heat resistance.

[0006] To address the above-mentioned problems, Patent Document 1 discloses a thermoplastic resin composition containing a thermoplastic resin and carbon nanotubes, and Patent Document 2 discloses a resin composition containing a thermoplastic resin, carbon black, carbon fibers, and a glycerin fatty acid ester.

[0007] International Publication No. 2021 / 256488 Japanese Patent Application Laid-Open No. 2023-28689

[0008] Meanwhile, information such as lot numbers and serial numbers are marked on the surfaces of products such as mechanical parts, electrical / communication parts, and automotive parts. Conventionally, commonly used marking methods include creating irregularities on the product surface, directly printing on the product surface with ink, attaching a printed matter to the product surface, and laser marking on the product surface.

[0009] Among these, laser marking has been increasingly adopted in recent years because it does not require the use of solvents and has a short takt time, and laser marking properties are now being required for resin compositions used in resin molded products. A commonly used laser marking method for resin molded products is a color development method in which a laser beam is used to burn or discolor the surface of the resin molded product.

[0010] However, in the technology of Patent Document 1, in order to improve electromagnetic wave absorption, it is necessary to increase the blending amount of carbon nanotubes, and the balance between electromagnetic wave absorption and laser marking properties is not sufficient. In the technology of Patent Document 2, a considerable amount of carbon black is contained, which has the problem of reducing the strength of the resin composition.

[0011] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a resin composition having good electromagnetic wave absorption properties, excellent mechanical strength, and excellent laser markability of molded articles, and a molded article made from the same.

[0012] In order to solve the above problems, the present invention has the following configurations. (1) A thermoplastic polyester resin composition comprising (A) 100 parts by weight of a thermoplastic polyester resin and (B) 0.1 to 5 parts by weight of carbon nanotubes having a high-temperature combustion peak of 650°C or more and 900°C or less in thermogravimetric analysis when heated in air at a rate of 10°C / min. (2) The thermoplastic polyester resin composition according to (1), wherein a 3 mm thick rectangular plate obtained by molding the thermoplastic polyester resin composition has a reflection loss S11 of -3 dB or less and a transmission loss S21 of -20 dB or less when measured by the free space method in the 60 to 90 GHz band. (3) A thermoplastic polyester resin composition having a volume resistivity of 1.0 x 10 ５ ~1.0 x 10 １５The thermoplastic polyester resin composition according to (1) or (2), having a viscosity of Ω·m. (4) The thermoplastic polyester resin composition according to any one of (1) to (3), further comprising 1 to 100 parts by weight of (D) a vinyl copolymer per 100 parts by weight of the thermoplastic polyester resin (A). (5) The thermoplastic polyester resin composition according to any one of (1) to (4), further comprising 1 to 20 parts by weight of (E) an ethylene / alkyl acrylate copolymer per 100 parts by weight of the thermoplastic polyester resin (A). (6) The thermoplastic polyester resin composition according to any one of (1) to (5), further comprising 0.1 to 10 parts by weight of (F) a compound having two or more functional groups reactive with a carboxyl group per molecule per 100 parts by weight of the thermoplastic polyester resin (A). (7) The thermoplastic polyester resin composition according to (6), wherein the (F) compound having two or more functional groups reactive with a carboxyl group per molecule is an epoxy compound. (8) The thermoplastic polyester resin composition according to any one of (1) to (7), which has electromagnetic wave absorbing properties. (9) A molded article obtained by molding the thermoplastic polyester resin composition according to any one of (1) to (8).

[0013] According to the present invention, a resin composition can be obtained that can give molded articles having high electromagnetic wave absorbency, excellent mechanical strength, and excellent laser markability. Therefore, the thermoplastic polyester resin composition of the present invention is useful for various electromagnetic wave-absorbing molded articles.

[0014] The present invention will be described in detail below.

[0015] The thermoplastic polyester resin (A) used in the present invention (hereinafter sometimes referred to as "component (A)") is a polymer or copolymer having, as its main structural unit, at least one residue selected from the group consisting of (1) residues of a dicarboxylic acid or its ester-forming derivative and a diol or its ester-forming derivative, (2) residues of a hydroxycarboxylic acid or its ester-forming derivative, and (3) residues of a lactone. Here, "having as the main structural unit" refers to having at least one residue selected from the group consisting of (1) to (3) in 50 mol % or more of all structural units, and a preferred embodiment is having 80 mol % or more of these residues. Among these, polymers or copolymers having, as their main structural units, (1) residues of a dicarboxylic acid or its ester-forming derivative and residues of a diol or its ester-forming derivative are preferred because of their superior mechanical properties and heat resistance.

[0016] Examples of the dicarboxylic acid or its ester-forming derivative include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, bis(p-carboxyphenyl)methane, 1,4-anthracenedicarboxylic acid, 1,5-anthracenedicarboxylic acid, 1,8-anthracenedicarboxylic acid, 2,6-anthracenedicarboxylic acid, 9,10-anthracenedicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 5-tetrabutylphosphonium isophthalate, and 5-sodium sulfoisophthalic acid; aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, malonic acid, glutaric acid, and dimer acid; alicyclic dicarboxylic acids such as 1,3-cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid; and ester-forming derivatives thereof. Two or more of these may be used.

[0017] Examples of the diols or ester-forming derivatives thereof include aliphatic or alicyclic glycols having 2 to 20 carbon atoms, such as ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, decamethylene glycol, cyclohexanedimethanol, cyclohexanediol, and dimer diol; long-chain glycols having a molecular weight of 200 to 100,000, such as polyethylene glycol, poly-1,3-propylene glycol, and polytetramethylene glycol; aromatic dioxy compounds, such as 4,4'-dihydroxybiphenyl, hydroquinone, t-butylhydroquinone, bisphenol A, bisphenol S, and bisphenol F; and ester-forming derivatives thereof. Two or more of these may be used.

[0018] Examples of polymers or copolymers having a dicarboxylic acid or its ester-forming derivative and a diol or its ester-forming derivative as structural units include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polypropylene isophthalate, polybutylene isophthalate, polybutylene naphthalate, polypropylene isophthalate / terephthalate, polybutylene isophthalate / terephthalate, polypropylene terephthalate / naphthalate, polybutylene terephthalate / naphthalate, polybutylene terephthalate / decanedicarboxylate, polypropylene terephthalate / 5-sodium sulfoisophthalate, polybutylene terephthalate / 5-sodium sulfoisophthalate, polypropylene terephthalate / polyethylene glycol, and polybutylene terephthalate / polyethylene glycol. Examples of the aromatic polyester resins include ethylene glycol, polypropylene terephthalate / polytetramethylene glycol, polybutylene terephthalate / polytetramethylene glycol, polypropylene terephthalate / isophthalate / polytetramethylene glycol, polybutylene terephthalate / isophthalate / polytetramethylene glycol, polybutylene terephthalate / succinate, polypropylene terephthalate / adipate, polybutylene terephthalate / adipate, polypropylene terephthalate / sebacate, polybutylene terephthalate / sebacate, polypropylene terephthalate / isophthalate / adipate, polybutylene terephthalate / isophthalate / succinate, polybutylene terephthalate / isophthalate / adipate, and polybutylene terephthalate / isophthalate / sebacate. These polymers and copolymers may be used alone or in combination of two or more. Here, " / " indicates a copolymer.

[0019] Among these, from the viewpoint of further improving mechanical properties and heat resistance, polymers or copolymers having, as main structural units, a residue of an aromatic dicarboxylic acid or an ester-forming derivative thereof and a residue of an aliphatic diol or an ester-forming derivative thereof are more preferred, and polymers or copolymers having, as main structural units, a residue of an aromatic dicarboxylic acid selected from terephthalic acid and naphthalenedicarboxylic acid or an ester-forming derivative thereof and a residue of an aliphatic diol selected from propylene glycol and 1,4-butanediol or an ester-forming derivative thereof are even more preferred.

[0020] Among them, at least one aromatic polyester resin selected from polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polypropylene naphthalate, polybutylene naphthalate, polypropylene isophthalate / terephthalate, polybutylene isophthalate / terephthalate, polypropylene terephthalate / naphthalate, polybutylene adipate / terephthalate, polybutylene terephthalate / sebacate, and polybutylene terephthalate / naphthalate is particularly preferred, and at least one selected from polyethylene terephthalate, polybutylene terephthalate, polybutylene isophthalate / terephthalate, polybutylene decanedicarboxylate / terephthalate, polybutylene terephthalate / naphthalate, and polybutylene / ethylene terephthalate is more preferred. Polybutylene terephthalate is even more preferred in terms of the excellent balance between mechanical properties and moldability. Furthermore, these two or more types can be used in any blending amount, but it is preferable to use polybutylene terephthalate as the main component. Here, the term "main component" means that 50% by weight or more of the thermoplastic polyester resin (A) blended in the resin composition is polybutylene terephthalate.

[0021] The carboxyl group concentration of the thermoplastic polyester resin (A) used in the present invention is preferably 50 eq / t or less from the viewpoints of suppressing deterioration of mechanical properties during melt-kneading and retention, and of moldability. The lower limit of the carboxyl group concentration is 0 eq / t. Here, the carboxyl group concentration of the thermoplastic polyester resin (A) is a value measured by dissolving the thermoplastic polyester resin (A) in an o-cresol / chloroform solvent and then titrating with ethanolic potassium hydroxide.

[0022] The thermoplastic polyester resin (A) used in the present invention preferably has a weight average molecular weight (Mw) of 8,000 or more in order to further improve mechanical properties. Furthermore, a weight average molecular weight (Mw) of 500,000 or less is preferable because fluidity can be improved. It is more preferably 300,000 or less, and even more preferably 250,000 or less. In the present invention, the weight average molecular weight (Mw) of the thermoplastic polyester resin (A) is a value calculated as polymethyl methacrylate (PMMA) measured by gel permeation chromatography (GPC) using hexafluoroisopropanol as a solvent.

[0023] The intrinsic viscosity of the thermoplastic polyester resin (A) used in the present invention is preferably 0.36 dL / g or more, more preferably 0.50 dL / g or more, as measured in an o-chlorophenol solution at 25° C., from the viewpoint of further improving mechanical properties. Furthermore, from the viewpoint of improving fluidity, the intrinsic viscosity is preferably 1.60 dL / g or less, more preferably 1.50 dL / g or less.

[0024] The thermoplastic polyester resin (A) used in the present invention can be produced by a known polycondensation method, ring-opening polymerization method, or the like. The production method may be either batch polymerization or continuous polymerization, and either transesterification or direct polymerization can be applied. From the viewpoint of productivity, continuous polymerization is preferred, and direct polymerization is more preferred.

[0025] When the thermoplastic polyester resin (A) used in the present invention is a polymer or copolymer obtained by a condensation reaction of a dicarboxylic acid or its ester-forming derivative and a diol or its ester-forming derivative as the main components, it can be produced by subjecting the dicarboxylic acid or its ester-forming derivative and the diol or its ester-forming derivative to an esterification reaction or an ester exchange reaction, followed by a polycondensation reaction.

[0026] The blending amount of the thermoplastic polyester resin (A) in the resin composition of the present invention is preferably 30 to 99.9% by weight based on the total weight of the resin composition of the present invention. If the blending amount of the thermoplastic polyester resin (A) is less than 30% by weight, the lightness and moldability will decrease. The blending amount is more preferably 50% by weight or more, and even more preferably 60% by weight or more.

[0027] The thermoplastic polyester resin composition of the present invention further contains carbon nanotubes, which can improve the mechanical strength of the resin composition and also improve the electromagnetic wave absorption properties.

[0028] The carbon nanotubes used in the present invention are (B) carbon nanotubes having a high-temperature combustion peak of 650°C or higher and 900°C or lower in thermogravimetric analysis when heated in air at a rate of 10°C / min (hereinafter, sometimes referred to as "(B) carbon nanotubes"). If the combustion peak temperature is lower than 650°C, carbon impurities other than carbon nanotubes and catalysts will be contained in the carbon nanotubes, resulting in reduced electromagnetic wave absorption and mechanical properties of the resin composition. The combustion peak temperature is preferably 670°C or higher, more preferably 680°C or higher. If the combustion peak temperature exceeds 900°C, the crystallinity of the carbon nanotubes will be too high, resulting in reduced dispersibility of the carbon nanotubes in the polyester resin composition and reduced electromagnetic wave absorption. The combustion peak temperature is preferably 850°C or lower, more preferably 800°C or lower. The combustion peak temperature is calculated using the following method. Carbon nanotubes were measured by thermogravimetric analysis, and a differential thermogravimetric (DTG) curve was obtained by differentiating the weight loss curve with respect to time. Next, a graph of a differential thermogravimetric analysis (DTG) curve is created with the x-axis representing temperature (°C) and the y-axis representing DTG (mg / min), and the peak temperature in the DTG curve is taken as the peak combustion temperature. Two or more peak temperatures may appear in the DTG curve of carbon nanotubes, but in the present invention, the highest peak temperature is taken as the peak combustion temperature. If only one peak temperature is observed in the DTG curve, that peak temperature is considered to be the highest peak temperature.

[0029] Generally, carbon impurities burn at temperatures below 400°C, but when they adhere to carbon nanotubes, the combustion temperature of the carbon impurities tends to shift to a higher temperature. On the other hand, carbon nanotubes with carbon impurities attached to them have a combustion peak temperature that is lower than that of the original carbon nanotubes. This is because the combustion temperature of the carbon impurities is lower than that of the carbon nanotubes, so the carbon impurities begin to burn first, and the heat energy generated during this process is transferred to the carbon nanotubes, causing the carbon nanotubes to burn at a lower temperature than their original combustion temperature. Therefore, the higher the degree of graphitization of carbon nanotubes and the lower the carbon impurity content, the higher the combustion peak temperature, and therefore a higher combustion peak temperature indicates a higher purity carbon nanotube. Carbon nanotubes with a combustion peak temperature within the above range can exhibit high electromagnetic wave absorption properties even when the amount of carbon nanotubes incorporated into a resin composition is small, and the volume resistivity of the resin composition can be kept low, resulting in improved laser marking properties.

[0030] The average diameter of the (B) carbon nanotubes used in the present invention is not particularly limited, but is preferably 1000 nm or less, more preferably 300 nm or less, and particularly preferably 100 nm or less. An average diameter of 1000 nm or less is likely to cause dielectric loss, thereby further improving electromagnetic wave absorption. The average diameter of the (B) carbon nanotubes is preferably 0.1 nm or more, more preferably 0.5 nm or more, and particularly preferably 1.0 nm or more. An average diameter of 0.1 nm or more makes it difficult for bundles to form and facilitates fine dispersion in the resin composition, thereby further improving mechanical strength and electromagnetic wave absorption. The average diameter was determined by observing the (B) carbon nanotubes under a transmission electron microscope, measuring the diameters of 100 or more (B) carbon nanotubes, and calculating the average value. Because (B) carbon nanotubes are substances with a large aspect ratio, the diameter was determined as the diameter of a cross section perpendicular to the longitudinal direction of their shape.

[0031] The blending amount of (B) carbon nanotubes in the resin composition of the present invention is 0.1 to 5 parts by weight per 100 parts by weight of (A) thermoplastic polyester resin. If the blending amount of (B) carbon nanotubes is less than 0.1 part by weight, electromagnetic wave absorption properties will decrease. The blending amount is preferably 0.3 parts by weight or more, more preferably 0.5 parts by weight or more. Furthermore, if the blending amount of (B) carbon nanotubes exceeds 5 parts by weight, volume resistivity will decrease and laser marking properties will decrease. The blending amount is preferably 4 parts by weight or less, more preferably 3 parts by weight or less.

[0032] Furthermore, (B) a carbon filler other than carbon nanotubes may be added within a range that does not impair the object of the present invention.

[0033] The thermoplastic polyester resin composition of the present invention preferably further contains (C) a fibrous reinforcing material. By containing (C) a fibrous reinforcing material, the mechanical strength of the molded article can be improved. Examples of (C) a fibrous reinforcing material include glass fiber, aramid fiber, and cellulose fiber, and among these, glass fiber is preferably used.

[0034] The (C) fibrous reinforcing material used in the present invention may have either a circular or flat cross section. It is also possible to use hollow fibers for the purpose of reducing the specific gravity, etc. As the cross-sectional area of ​​the (C) fibrous reinforcing material increases, a sufficient reinforcing effect cannot be obtained. On the other hand, if the cross-sectional area is too small, it may become difficult to manufacture the fibrous reinforcing material and may become difficult to handle. The cross-sectional area of ​​the (C) fibrous reinforcing material is 2 × 10 －５ ~8 x 10 －３ mm ２ is preferred, and 8 × 10 －５ ~8 x 10 －３ mm ２ is more preferable, and 8×10 －５ ~8 x 10 －４ mm ２ is more preferable.

[0035] In the fibrous reinforcing material (C) used in the present invention, it is preferable to use a sizing agent or a surface treatment agent as needed. Examples of the sizing agent or surface treatment agent include functional compounds such as epoxy compounds, isocyanate compounds, and silane compounds. These compounds may be used in advance to perform a surface treatment or sizing treatment on the fibrous reinforcing material, or may be added simultaneously with the fibrous reinforcing material during preparation of the resin composition.

[0036] The blending amount of (C) fibrous reinforcing material in the resin composition of the present invention is preferably 1 part by weight or more and 100 parts by weight or less per 100 parts by weight of (A) thermoplastic polyester resin. If the blending amount of (C) fibrous reinforcing material is 1 part by weight or more, the mechanical strength of the molded product can be improved. The blending amount is preferably 10 parts by weight or more, more preferably 20 parts by weight or more. Furthermore, if the blending amount of (C) fibrous reinforcing material is 100 parts by weight or less, a decrease in fluidity can be suppressed. The blending amount is preferably 80 parts by weight or less, more preferably 50 parts by weight or less.

[0037] The thermoplastic polyester resin composition of the present invention preferably further contains a (D) vinyl copolymer (hereinafter, sometimes referred to as "component (D)"). By including a (D) vinyl copolymer, which has a lower thermal conductivity than a thermoplastic polyester resin, it is possible to suppress heat diffusion through the (B) carbon nanotubes, thereby improving laser marking properties. Furthermore, the improved dispersibility of the (B) carbon nanotubes further improves the electromagnetic wave absorption properties of molded articles. The (D) vinyl copolymer used in the present invention is preferably a copolymer containing at least an unsaturated nitrile monomer and an aromatic vinyl monomer as copolymerization components. Other copolymerizable monomers can also be copolymerized as needed. Generally, these (D) vinyl copolymers are produced by emulsion polymerization, bulk polymerization, or bulk / suspension polymerization, but the methods are not limited thereto.

[0038] The unsaturated nitrile monomer used in the (D) vinyl copolymer is not particularly limited, and examples thereof include acrylonitrile, methacrylonitrile, and ethacrylonitrile, with acrylonitrile being preferred. The aromatic vinyl monomer is also not particularly limited, and specific examples include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, o-ethylstyrene, p-ethylstyrene, and p-t-butylstyrene, with styrene and α-methylstyrene being preferred. Other copolymerizable monomers include acrylic acid and methacrylic acid ester compounds such as butyl acrylate, ethyl acrylate, and methyl methacrylate; N-phenylmaleimide, and maleic anhydride. Among these, a styrene-acrylonitrile copolymer (hereinafter abbreviated as AS resin) containing a total of 85% by mass or more of acrylonitrile as the unsaturated nitrile monomer and styrene as the aromatic vinyl monomer as copolymerization components, and 15% by mass or less of other copolymerizable monomers, is preferred.

[0039] The (D) vinyl copolymer may contain a rubbery polymer to the extent that scratch resistance is not significantly impaired. This includes resins obtained by grafting an unsaturated nitrile monomer and an aromatic vinyl monomer onto a rubbery polymer, as well as resins copolymerized with other copolymerizable monomers. The unsaturated nitrile monomer, aromatic vinyl monomer, and other copolymerizable monomers used may be the same as those listed above. The rubbery polymer used in the (D) vinyl copolymer is not particularly limited, but examples include diene rubber, acrylic rubber, and ethylene rubber. Specific examples of these rubbery polymers include polybutadiene, styrene-butadiene copolymer, styrene-butadiene block copolymer, acrylonitrile-butadiene copolymer, butyl acrylate-butadiene copolymer, polyisoprene, butadiene-methyl methacrylate copolymer, butyl acrylate-methyl methacrylate copolymer, butadiene-ethyl acrylate copolymer, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-isoprene copolymer, ethylene-methyl acrylate copolymer, etc. Of these rubbery polymers, acrylic rubber is preferably used.

[0040] In order to improve compatibility with the thermoplastic polyester resin (A), the vinyl copolymer (D) is also preferably copolymerized with a raw material monomer that forms a glycidyl group-containing vinyl unit. Specific examples of the raw material monomer that forms the glycidyl group-containing vinyl unit include glycidyl esters of unsaturated monocarboxylic acids such as glycidyl (meth)acrylate and glycidyl p-styrylcarboxylate; monoglycidyl esters or polyglycidyl esters of unsaturated polycarboxylic acids such as maleic acid and itaconic acid; and unsaturated glycidyl ethers such as allyl glycidyl ether, 2-methylallyl glycidyl ether, and styrene-4-glycidyl ether.

[0041] The blending amount of (D) vinyl copolymer in the resin composition of the present invention is preferably 1 part by weight or more and 100 parts by weight or less per 100 parts by weight of (A) thermoplastic polyester resin. When the blending amount of (D) vinyl copolymer is 1 part by weight or more, dimensional stability can be improved and the electromagnetic wave absorption properties of the molded product can be stabilized regardless of molding conditions. The blending amount is preferably 10 parts by weight or more, more preferably 20 parts by weight or more. Furthermore, when the blending amount of (D) vinyl copolymer is 100 parts by weight or less, a decrease in heat resistance can be suppressed. The blending amount is preferably 80 parts by weight or less, more preferably 50 parts by weight or less.

[0042] The thermoplastic polyester resin composition of the present invention preferably further contains (E) an ethylene / alkyl acrylate copolymer (hereinafter, sometimes referred to as "component (E)"). By including the (E) ethylene / alkyl acrylate copolymer, which has a lower thermal conductivity than the thermoplastic polyester resin, it is possible to suppress heat diffusion via the (B) carbon nanotubes, thereby improving laser marking properties. Furthermore, the improved dispersibility of the (B) carbon nanotubes further improves the electromagnetic wave absorption properties of the molded article. The (E) ethylene / alkyl acrylate copolymer is preferably a glycidyl-containing terpolymer composed of an α-olefin and an α,β-ethylenically unsaturated carboxylic acid or a derivative thereof, or an α-olefin, an α,β-ethylenically unsaturated carboxylic acid or a derivative thereof, and a glycidyl ester of an α,β-unsaturated acid. Specific examples of the (E) ethylene / alkyl acrylate copolymer include ethylene / methyl acrylate copolymer, ethylene / ethyl acrylate copolymer, ethylene / butyl acrylate copolymer, ethylene / methacrylic acid copolymer, ethylene / glycidyl copolymer, ethylene / methacrylic acid / glycidyl copolymer, ethylene / vinyl acetate / glycidyl methacrylate copolymer, ethylene / ethyl acrylate-g-methyl methacrylate / butyl acrylate copolymer, and ethylene / ethyl acrylate-g-methyl methacrylate copolymer, and these can be used alone or in the form of a mixture.

[0043] Blending (E) an ethylene / alkyl acrylate copolymer with (A) a thermoplastic polyester resin can improve the fluidity and toughness of the (A) thermoplastic polyester resin composition. However, when a glycidyl group-containing terpolymer consisting of an α-olefin, an α,β-ethylenically unsaturated carboxylic acid or its derivative, and a glycidyl ester of an α,β-unsaturated acid is used alone, the glycidyl groups in the ethylene / alkyl acrylate copolymer tend to react with the (A) thermoplastic polyester resin, resulting in reduced fluidity and retention stability. Therefore, from the perspective of imparting fluidity and toughness, it is preferable to blend a copolymer of an α-olefin and an α,β-ethylenically unsaturated carboxylic acid or its derivative in combination with a glycidyl group-containing terpolymer consisting of an α-olefin, an α,β-ethylenically unsaturated carboxylic acid or its derivative, and a glycidyl ester of an α,β-unsaturated acid, and it is more preferable to blend an α-olefin and an α,β-ethylenically unsaturated carboxylic acid or its derivative alone.

[0044] The blending amount of (E) ethylene / alkyl acrylate copolymer is preferably 1 part by weight or more and 20 parts by weight or less per 100 parts by weight of (A) thermoplastic polyester resin. When the blending amount of (E) ethylene / alkyl acrylate copolymer is 1 part by weight or more, heat diffusion via (B) carbon nanotubes can be suppressed, improving laser marking properties. Furthermore, the dispersibility of (B) carbon nanotubes is improved, thereby further improving the electromagnetic wave absorption properties of molded articles. The blending amount is preferably 3 parts by weight or more, and more preferably 5 parts by weight or less. Furthermore, when the blending amount of (E) ethylene / alkyl acrylate copolymer is 20 parts by weight or less, the laser marking properties and electromagnetic wave absorption properties of molded articles can be further improved without impairing the rigidity and fluidity of the polyethylene resin. The blending amount is preferably 15 parts by weight or less, and more preferably 10 parts by weight or less.

[0045] The thermoplastic polyester resin composition of the present invention preferably further contains (F) a compound having two or more functional groups in the molecule capable of reacting with carboxyl groups (hereinafter, sometimes referred to as "(F) compound"). The incorporation of the (F) compound improves the dispersibility of carbon nanotubes and improves electromagnetic wave absorption. Furthermore, the (A) thermoplastic polyester resin increases the carboxyl group concentration in the species due to decomposition of ester bonds by hydrolysis. As the carboxyl group concentration increases, the molecular weight of the (A) thermoplastic polyester resin decreases, resulting in a decrease in mechanical properties. In the present invention, by incorporating the (F) compound together with the (A) thermoplastic polyester resin, the carboxyl groups of the (A) thermoplastic polyester resin generated by hydrolysis react with the functional groups of the (F) compound, suppressing an increase in the carboxyl group concentration. As a result, the high mechanical properties of the (A) thermoplastic polyester resin can be maintained.

[0046] Examples of the compound (F) include an epoxy compound, an oxazoline compound, and a carbodiimide compound.

[0047] The epoxy compound is a compound having an epoxy group as a functional group capable of reacting with a carboxyl group. The epoxy compound is not particularly limited as long as it has two or more epoxy groups in one molecule. Examples of epoxy compounds having two or more epoxy groups in one molecule include glycidyl ether epoxy resins, glycidyl ester epoxy resins, glycidyl amine epoxy resins, alicyclic epoxy resins, and heterocyclic epoxy resins. These may be used alone or in combination of two or more.

[0048] Examples of glycidyl ether type epoxy resins include condensation products of phenol compounds and epichlorohydrin, novolac type epoxy, and glycidyl ethers of polyhydric hydroxyl group compounds.

[0049] Specific examples of the condensation products of a phenol compound and epichlorohydrin include condensations products obtained by condensing a phenol compound such as bisphenol A, resorcinol, hydroquinone, pyrocatechol, bisphenol F, saligenin, bisphenol S, 4,4'-dihydroxybiphenyl, 1,5-dihydroxynaphthalene, 1,4-dihydroanthracene-9,10-diol, 6-hydroxy-2-naphthoic acid, 1,1-methylenebis-2,7-dihydroxynaphthalene, 1,1,2,2-tetrakis-4-hydroxyphenylethane, and cashew phenol with epichlorohydrin.

[0050] Specific examples of novolac type epoxy include phenol novolac type epoxy, cresol novolac type epoxy, naphthol novolac type epoxy, bisphenol A novolac type epoxy, dicyclopentadiene-phenol adduct novolac type epoxy, dimethylenephenylene-phenol adduct novolac type epoxy, and dimethylenebiphenylene-phenol adduct novolac type epoxy.

[0051] The polyhydric hydroxyl group compound is an aliphatic compound having two or more hydroxyl groups, and specific examples thereof include glycol, glycerin, polyglycerin, dipentaerythritol, tripentaerythritol, xylitol, mannitol, sorbitol, galactose, maltitol, lactitol, isomalt, inositol, glucose, and fructose, each of which has 2 to 20 carbon atoms.

[0052] Examples of glycidyl ester type epoxy resins include epoxy resins produced from epichlorohydrin and phthalic acid, tetrahydrophthalic acid, p-oxybenzoic acid or dimer acid, trimesic acid triglycidyl ester, trimellitic acid triglycidyl ester, pyromellitic acid tetraglycidyl ester, epoxidized fatty acid octyl ester, epoxidized soybean oil, and epoxidized linseed oil.

[0053] Examples of glycidylamine-type epoxy resins include epoxy resins produced from epichlorohydrin and aniline, diaminodiphenylmethane, p-aminophenol, meta-xylylenediamine, or 1,3-bis(aminomethyl)cyclohexane, tetraglycidylaminodiphenylmethane, triglycidyl-para-aminophenol, triglycidyl-meta-aminophenol, tetraglycidyl-meta-xylylenediamine, tetraglycidyl-bisaminomethylcyclohexane, triglycidyl cyanurate, and triglycidyl isocyanurate.

[0054] Examples of the alicyclic epoxy resin include compounds having a cyclohexene oxide group, a tricyclodecene oxide group, and a cyclopentene oxide group.

[0055] Examples of heterocyclic epoxy resins include epoxy resins produced from epichlorohydrin and hydantoin or isocyanuric acid.

[0056] Among these, glycidyl ether epoxy resins are preferred from the viewpoint of being able to suppress the reaction between epoxy groups of the compound (F) and to suppress deterioration of retention stability.

[0057] An oxazoline compound is a compound having an oxazoline group as a functional group capable of reacting with a carboxyl group. Specific examples include compounds having an oxazoline group as a functional group capable of reacting with a carboxyl group, such as 2,2'-bis(2-oxazoline), 2,2'-ethylene-bis(4,4'-dimethyl-2-oxazoline), 2,2'-p-phenylene-bis(2-oxazoline), and bis(2-oxazolinylcyclohexane) sulfide, as well as oxazoline group-containing polymers. These compounds may be used alone or in combination. Among these, oxazoline group-containing polymers are preferred due to their ease of handling. Oxazoline group-containing polymers can be obtained by polymerizing addition-polymerizable oxazolines such as 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, and 2-isopropenyl-2-oxazoline. Other monomers may be copolymerized as needed. The polymerization method for the oxazoline group-containing polymer is not particularly limited, and various known polymerization methods can be employed.

[0058] The carbodiimide compound is a compound containing a carbodiimide group as a functional group capable of reacting with a carboxyl group. Specific examples include dicarbodiimides such as N,N'-diisopropylcarbodiimide, N,N'-dicyclohexylcarbodiimide, and N,N'-di-2,6-diisopropylphenylcarbodiimide, as well as poly(1,6-hexamethylenecarbodiimide), poly(4,4'-methylenebiscyclohexylcarbodiimide), poly(1,3-cyclohexylenecarbodiimide), poly(1,4-cyclohexylenecarbodiimide), poly(4,4'-dicyclohexylmethanecarbodiimide), poly(4,4'-diphenylmethanecarbodiimide), and poly(3,3'-dimethyl-4,4'-diphenylmethanecarbodiimide). ), poly(naphthalenecarbodiimide), poly(p-phenylenecarbodiimide), poly(m-phenylenecarbodiimide), poly(tolylcarbodiimide), poly(diisopropylcarbodiimide), poly(methyl-diisopropylphenylenecarbodiimide), poly(1,3,5-triisopropylbenzene)polycarbodiimide, poly(1,3,5-triisopropylbenzene)polycarbodiimide, poly(1,5-diisopropylbenzene)polycarbodiimide, poly(triethylphenylenecarbodiimide), poly(triisopropylphenylenecarbodiimide), and the like.

[0059] Among these, an epoxy compound having an epoxy group as a functional group capable of reacting with a carboxyl group is more preferred, since it can also react with the hydroxyl group terminal of the (A) thermoplastic polyester resin, suppress post-crystallization during hydrolysis of the resin composition, and further improve hydrolysis resistance.

[0060] In the present invention, the vinyl copolymer (D) and the ethylene / alkyl acrylate copolymer (E) are treated as the component (D) and the component (E), respectively, even if they are copolymerized with a raw material monomer containing a reactive functional group such as a glycidyl group and thus also fall under the category of the compound (F).

[0061] In the thermoplastic polyester resin composition of the present invention, the blending amount of the (F) compound is preferably 0.1 parts by weight or more and 10 parts by weight or less per 100 parts by weight of the (A) thermoplastic polyester resin. When the blending amount of the (F) compound is 0.1 parts by weight or more, the dispersibility of the carbon nanotubes in the resin composition is improved, and the electromagnetic wave absorption property and hydrolysis resistance can be improved. The blending amount is more preferably 0.3 parts by weight or more, even more preferably 0.5 parts by weight or more, and particularly preferably 1.0 parts by weight or more. On the other hand, when the blending amount of the (F) compound is 10 parts by weight or less, thickening of the polyester resin composition can be suppressed, and the electromagnetic wave absorption property and hydrolysis resistance can be improved without impairing fluidity. The blending amount is more preferably 8 parts by weight or less, even more preferably 5 parts by weight or less.

[0062] The thermoplastic polyester resin composition of the present invention preferably has a reflection loss S11 of −3 dB or less and a transmission loss S21 of −20 dB or less when a 3 mm thick rectangular plate molded from the thermoplastic polyester resin composition is measured by the free space method in the 60 to 90 GHz band. If the reflection loss S11 is greater than −3 dB, radio waves reflected on the surface of the resin molded article cannot be attenuated, and if the reflected radio waves are reflected again by some component, they may adversely affect electronic devices within the resin molded article. The reflection loss S11 is preferably −4 dB or less, and more preferably −5 dB or less. Furthermore, if the transmission loss S21 is greater than −20 dB, the electromagnetic wave shielding for electronic devices within the resin molded article is insufficient, which may adversely affect the electronic devices within the resin molded article. The transmission loss S21 is preferably −25 dB or less, and more preferably −30 dB or less. Furthermore, if the reflection loss S11 and the transmission loss S21 are below −80 dB, the conductivity of the polyester resin composition becomes too high, resulting in a decrease in laser marking properties. Therefore, it is preferable that both the reflection loss S11 and the transmission loss S21 be −80 dB or more.

[0063] By blending 0.1 parts by weight or more of (B) carbon nanotubes with 100 parts by weight of (A) thermoplastic polyester resin, it is possible to reduce the reflection loss S11 to -3 dB or less and the transmission loss S21 to -20 dB or less.

[0064] The thermoplastic polyester resin composition of the present invention has a volume resistivity of 1.0×10 ５ Ω・m or more 1.0×10 １５ It is preferable that the volume resistivity is 1.0×10 Ω·m or less. ５ By making the volume resistivity Ω·m or more, it is possible to suppress thermal diffusion, which is correlated with volume resistivity, and to efficiently foam the thermoplastic polyester resin with laser light, thereby improving the laser marking properties. ７ A volume resistivity of 1.0×10 Ω·m or more is more preferable because it can impart insulating properties to the thermoplastic polyester resin composition. １５ It is preferably Ω·m or less.

[0065] By adjusting the blending amount of conductive (B) carbon nanotubes to 5 parts by weight or less per 100 parts by weight of (A) thermoplastic polyester resin, the volume resistivity value of the polyester resin composition can be within a preferred range.

[0066] The thermoplastic polyester resin composition of the present invention may contain a thermoplastic resin other than component (A) within the scope of the present invention, thereby improving moldability, toughness, etc. Examples of thermoplastic resins other than component (A) include polyamide resins, polyacetal resins, polyurethane resins, aromatic or aliphatic polyketone resins, polyphenylene sulfide resins, polyether ether ketone resins, polyimide resins, thermoplastic starch resins, polyarylate resins, polysulfone resins, polyether sulfone resins, phenoxy resins, polyphenylene ether resins, polyetherimide resins, cellulose acetate resins, and polyvinyl alcohol resins.

[0067] Furthermore, the thermoplastic polyester resin composition of the present invention may contain other components, such as stabilizers, weather resistance agents (resorcinol-based, salicylate-based, benzophenone-based, etc.), lubricants (montanic acid and its esters, its half esters, stearyl alcohol, polyethylene wax, etc.), pigments, dyes, crystal nucleating agents (talc, polyether ether ketone, etc.), plasticizers, antistatic agents, flame retardants, color inhibitors, other polymers, etc., within the scope of the present invention.

[0068] The thermoplastic polyester resin composition of the present invention can be obtained, for example, by melt-kneading the (A) thermoplastic polyester resin and (B) carbon nanotubes, as well as other components as required.

[0069] Examples of the melt-kneading method include a method in which (A) thermoplastic polyester resin, (B) carbon nanotubes, and various additives are premixed, and the mixture is fed into an extruder or the like to be thoroughly melt-kneaded; or a method in which each component is metered using a quantitative feeder such as a weight feeder to obtain a predetermined composition, and the components are fed into an extruder or the like to be thoroughly melt-kneaded.

[0070] Examples of the premixing include a dry blending method and a mixing method using a mechanical mixer such as a tumbler, a ribbon mixer, or a Henschel mixer.

[0071] Furthermore, the (B) carbon nanotubes can be used as a carbon nanotube masterbatch in which a high concentration of the (B) carbon nanotubes is dispersed in advance in a thermoplastic resin. The use of a carbon nanotube masterbatch is preferred from the viewpoints of ease of handling and uniform dispersion of the carbon nanotubes. In this case, the thermoplastic resin used in the carbon nanotube masterbatch may be the thermoplastic polyester resin (component (A)), or a resin other than component (A), such as a polyamide resin, a polycarbonate resin, a styrene-based resin, or a polyethylene resin. From the viewpoints of ease of dispersing a high concentration of the (B) carbon nanotubes and ease of preparation of the masterbatch, it is preferred to prepare the masterbatch using the (A) thermoplastic polyester resin.

[0072] When melt-kneading is carried out using a multi-screw extruder such as a twin-screw extruder, the fibrous reinforcing material (C) may be added by a side feeder provided midway between the main inlet and the vent.

[0073] In the case of a liquid additive, a method of adding the additive using a plunger pump by installing a liquid addition nozzle midway between the main inlet and the vent of a multi-screw extruder such as a twin-screw extruder, or a method of supplying the additive from the main inlet or the like using a metering pump, may be used.

[0074] The thermoplastic polyester resin composition of the present invention is preferably pelletized and then molded using the pellets. As a pelletization method, for example, the components constituting the resin composition are extruded in the form of strands using a single-screw extruder, twin-screw extruder, triple-screw extruder, conical extruder, kneader-type mixer, etc., and then cut with a strand cutter to obtain pellets.

[0075] The molded article of the present invention is obtained by molding the thermoplastic polyester resin composition of the present invention. By melt molding the thermoplastic polyester resin composition of the present invention, films, fibers, and other molded articles of various shapes can be obtained. Examples of melt molding methods include injection molding, extrusion molding, and blow molding, with injection molding being particularly preferred.

[0076] In addition to the usual injection molding method, other known injection molding methods include gas-assisted molding, two-color molding, sandwich molding, in-mold molding, insert molding, and injection press molding, and any of these molding methods can be applied.

[0077] The thermoplastic polyester resin composition of the present invention has high electromagnetic wave absorption, excellent mechanical strength, and excellent laser marking property. The molded article of the present invention is a molded article excellent in electromagnetic wave absorption, mechanical properties, and hydrolysis resistance, and can be used for various applications such as automobile parts, machine parts, and electric / electronic parts by taking advantage of these characteristics.

[0078] Specific applications include junction boxes, LiBs, insulators, air flow meters, air pumps, thermostat housings, engine mounts, ignition hobbins, ignition cases, clutch bobbins, idle speed control valves, vacuum switching valves, ECU housings, HUD housings, vacuum pump cases, inhibitor switches, housings for sensing parts such as rotation sensors, pressure sensors, acceleration sensors, millimeter-wave radars, and ultrasonic sensors, brackets and their internal parts, distributor caps, coil bases, ABS actuator cases, radiator tank tops and bottoms, cooling fans, fan shrouds, engine covers, cylinder head covers, oil caps, oil pans, oil filters, fuel caps, fuel strainers, distributor caps, and vapor filters. - Automotive underhood parts such as canister housings, air cleaner housings, timing belt covers, brake booster parts, various cases, various tubes, various tanks, various hoses, various clips, various valves, and various pipes; automotive interior parts such as torque control levers, safety belt parts, register blades, washer levers, window regulator handles, window regulator handle knobs, passing light levers, sun visor brackets, and various motor housings; automotive exterior parts such as roof rails, fenders, garnishes, bumpers, door mirror stays, spoilers, hood louvers, wheel covers, hubcaps, grill apron cover frames, lamp reflectors, lamp bezels, and door handles; various automotive connectors such as wire harness connectors, SMJ connectors, PCB connectors, and door grommet connectors;Examples include electrical connectors, relay cases, coil bobbins, optical pickup chassis, motor cases, notebook computer housings and internal parts, CRT display housings and internal parts, printer housings and internal parts, portable terminal housings and internal parts such as mobile phones, mobile personal computers, and handheld mobile devices, recording medium (CD, DVD, PD, FDD, etc.) drive housings and internal parts, copier housings and internal parts, facsimile housings and internal parts, and housings and internal parts of communication electrical and electronic components such as base stations, data communication modules, and various antennas.Further examples include household and office electrical appliance parts such as VTR parts, television parts, irons, hair dryers, rice cooker parts, microwave oven parts, audio parts, video camera parts, projector and other imaging equipment parts, lighting parts, refrigerator parts, air conditioner parts, typewriter parts, word processor parts, etc. Other examples include housings and internal parts for electronic musical instruments, home game consoles, portable game consoles, and the like, various gears, various cases, sensors, LED lamps, connectors, sockets, resistors, relay cases, switches, coil bobbins, capacitors, variable capacitor cases, optical pickups, oscillators, and various terminal boards.

[0079] Among these, the material can be suitably used for housings and internal parts of electrical and electronic components for communications, such as ECU housings, HUD housings, housings for sensing components such as rotation sensors, pressure sensors, acceleration sensors, millimeter-wave radars and ultrasonic sensors, brackets and their internal parts, notebook computer housings and internal parts, CRT display housings and internal parts, printer housings and internal parts, portable terminal housings and internal parts such as mobile phones, mobile personal computers and handheld mobile devices, recording medium (CD, DVD, PD, FDD, etc.) drive housings and internal parts, copier housings and internal parts, facsimile housings and internal parts, base stations, data communication modules, and various antennas, which require particularly high electromagnetic wave absorption properties.

[0080] Next, the present invention will be described in more detail by way of examples, but these are not intended to limit the present invention.

[0081] The abbreviations of the main raw materials used in the examples and their contents are summarized below.

[0082] (A) Thermoplastic polyester resins A-1: ​​Polybutylene terephthalate (terminal carboxyl group concentration 25 eq / t, intrinsic viscosity measured at 25°C using o-chlorophenol solution as a solvent of 0.85 dL / g). A-2: Polyethylene terephthalate (terminal carboxyl group concentration 25 eq / t, intrinsic viscosity measured at 25°C using o-chlorophenol solution as a solvent of 0.80 dL / g).

[0083] (B) Carbon nanotubes B-1: Carbon nanotubes A (average diameter: 12 nm, BET specific surface area: 265 m ２ / g, composition: carbon 95% by mass, thermal gravimetric analysis combustion peak temperature 688°C) B-2: Carbon nanotube B (average diameter: 15 nm, BET specific surface area 205 m ２ / g, composition: carbon 98% by mass, peak combustion temperature by thermogravimetry 675°C) B'-3: carbon nanotube C (average diameter: 15 nm, BET specific surface area: 191 m ２ / g, composition: carbon 98% by mass, thermal gravimetric analysis combustion peak temperature 647°C) B'-4: carbon nanotube D (average diameter: 9.5 nm, BET specific surface area 275 m ２ / g, composition: 90% by mass of carbon, thermogravimetric analysis combustion peak temperature 645 ° C.) B-5: Carbon nanotube masterbatch Using a co-rotating, vented twin-screw extruder (manufactured by The Japan Steel Works, Ltd., TEX-30α) equipped with a screw diameter of 30 mm and an L / D of 35, A-1 (polybutylene terephthalate) and B-1 (carbon nanotube A) were melt-kneaded at a ratio of 11.1 parts by weight of B-1 to 100 parts by weight of A-1 under conditions of a cylinder temperature of 250 ° C. and a screw rotation speed of 150 rpm, and the mixture was extruded in the form of a strand, which was then cut with a strand cutter and pelletized. The resulting pellets were vacuum-dried at a temperature of 110 ° C. for 6 hours to obtain carbon nanotube masterbatch pellets.

[0084] (C) Fibrous reinforcing material C-1: Round cross section chopped strand type glass fiber (manufactured by Nippon Electric Glass Co., Ltd., ECS03T187).

[0085] (D) Vinyl Copolymer D-1: acrylonitrile / styrene / glycidyl methacrylate copolymer (the weight ratio of the acrylonitrile / styrene / glycidyl methacrylate copolymer components was 23.7 / 76.0 / 0.3, and the reduced viscosity was 0.72).

[0086] (E) Ethylene / Alkyl Acrylate Copolymer E-1: Ethylene / Methyl Acrylate Copolymer ("Elvalloy AC" (registered trademark) 22534 (trade name) manufactured by Mitsui DuPont Polychemicals).

[0087] (F) Compound having two or more functional groups capable of reacting with a carboxyl group in the molecule F-1: Epoxy resin (manufactured by DIC Corporation, HP7200H).

[0088] The evaluation methods used in the examples and comparative examples are summarized below.

[0089] (1) Thermogravimetric Analysis (Peak Combustion Temperature of Carbon Nanotubes) Using a thermogravimetric analyzer (TGA-60, manufactured by Shimadzu Corporation), a sample was held in air at 150°C for 30 minutes, and then heated from room temperature to 950°C at a heating rate of 10°C / min. The weight loss at this time was measured, and a weight loss curve was obtained. The obtained weight loss curve was differentiated with respect to time to obtain a differential thermogravimetric (DTG) curve. A graph of the differential thermogravimetric (DTG) curve was created with the x-axis representing temperature (°C) and the y-axis representing DTG (mg / min), and the peak temperature in the DTG curve was taken as the peak combustion temperature. At this time, two or more peak temperatures may appear, but in the present invention, the highest peak temperature was taken as the peak combustion temperature of the carbon nanotubes.

[0090] (2) Tensile Properties Using a SE50-DUZ injection molding machine manufactured by Sumitomo Heavy Industries, Ltd., (A) if the thermoplastic polyester resin is polybutylene terephthalate, the molding temperature was 260 ° C., the mold temperature was 80 ° C., the injection time and dwell time were 10 seconds in total, and the cooling time was 10 seconds. In the case of (A) if the thermoplastic polyester resin is polyethylene terephthalate, the molding temperature was 280 ° C., the mold temperature was 120 ° C., the injection time and dwell time were 20 seconds in total, and the cooling time was 20 seconds. The thermoplastic polyester resin was injection molded, and a test piece for evaluating tensile properties of an ISO-1A dumbbell with a test piece thickness of 4 mm was obtained. For the obtained test piece for evaluating tensile properties, in accordance with ISO527-2:2012, a tensile tester (Autograph AG-50kNXPlus) manufactured by Shimadzu Corporation was used to measure the tensile maximum point strength (tensile strength). The average value of the measurements of three samples was taken as the tensile strength value. Materials with a high tensile strength value were judged to have excellent mechanical properties.

[0091] (3) Hydrolysis Resistance Using an SE50-DUZ injection molding machine manufactured by Sumitomo Heavy Industries, Ltd., 4 mm thick ISO-1A dumbbell test specimens for evaluating tensile properties were obtained under the same molding conditions as those for the tensile properties described in (2). The obtained test specimens were placed in a highly accelerated life testing apparatus EHS-411 manufactured by Espec Corporation, set at a temperature and humidity of 121°C x 100% RH for 50 hours, and subjected to moist heat treatment. The maximum tensile strength of the test specimens after moist heat treatment was measured under the same conditions as those for the tensile properties described in (2), and the average value of the measurements for three samples was recorded as the maximum tensile strength after moist heat treatment. The value of the maximum tensile strength of the test specimen after moist heat treatment relative to the maximum tensile strength of the test specimen before moist heat treatment (untreated) was recorded as the tensile strength retention rate. (Tensile strength at maximum point after moist heat treatment / Tensile strength at maximum point before moist heat treatment (untreated moist heat treatment))×100=Tensile strength retention (%) A material with a higher tensile strength retention value was determined to have better hydrolysis resistance.

[0092] (4) Electromagnetic Wave Absorbency Using an SE50-DUZ injection molding machine manufactured by Sumitomo Heavy Industries, Ltd., a test piece for evaluating electromagnetic wave absorbency having a width of 80 mm, a length of 80 mm, and a thickness of 3 mm was molded under the same molding conditions as those for the tensile properties in section (2).

[0093] The measurements were performed using a network analyzer ME7838A manufactured by Anritsu Corporation, and the values ​​of reflection loss S11 and transmission loss S21 at 79 GHz were calculated from the S parameter measurement results of the incident wave and transmitted wave to the electromagnetic wave absorption evaluation test piece by the free space method. It was determined that the smaller the values ​​of reflection loss S11 and transmission loss S21 at 79 GHz, that is, the larger the attenuation rate, the better the electromagnetic wave absorption.

[0094] (5) Volume Resistivity Test pieces measuring 80 mm wide x 80 mm long x 3 mm thick were prepared under the same molding conditions as those for the tensile properties in section (2) using an SE50-DUZ injection molding machine manufactured by Sumitomo Heavy Industries, Ltd. Volume resistivity was measured in accordance with IEC 62631-3-1 by the double ring method using a high residence meter 4339B manufactured by Agilent Technologies, Inc., under conditions of DC 100 V x 60 seconds.

[0095] (6) Laser Marking Properties Test pieces for laser marking evaluation, measuring 80 mm wide x 80 mm long x 3 mm thick, were prepared using an SE50-DUZ injection molding machine manufactured by Sumitomo Heavy Industries, Ltd. under the same molding conditions as those for the tensile properties described in (2). A 20 mm wide x 20 mm long marking was formed on the surface of the prepared test piece using a Panasonic FAYb laser marker LP-S200 at a wavelength of 1064 nm. The marked area was measured using an SM color computer (SM-T) manufactured by Suga Test Instruments Co., Ltd., and the color difference (ΔE*ab) between the unmarked area and the marked area was measured. The larger the ΔE*ab, the better the laser marking properties.

[0096] [Examples 1 to 12, Comparative Examples 1 to 8] Using a co-rotating, vented twin-screw extruder (TEX-30α, manufactured by The Japan Steel Works, Ltd.) equipped with a screw having a screw diameter of 30 mm and an L / D ratio of 35, (A) thermoplastic polyester resin, (B) carbon nanotubes, and other raw materials were mixed in the compositions shown in Tables 1 and 2, and added to the twin-screw extruder from its base charging section. The amounts of (C) fibrous reinforcing material, (D) vinyl copolymer, (E) component, and (F) compound in Examples 6 to 10 in Table 1 are amounts relative to 100 parts by weight of (A) thermoplastic polyester resin.

[0097] (C) The fibrous reinforcing material was added through a side feeder installed midway between the main feed section and the vent section of the twin-screw extruder.

[0098] When the (A) thermoplastic polyester resin was polybutylene terephthalate, melt mixing was performed under extrusion conditions of a kneading temperature of 250°C and a screw rotation of 150 rpm, and when the (A) thermoplastic polyester resin was polyethylene terephthalate, melt mixing was performed under extrusion conditions of a kneading temperature of 260°C and a screw rotation of 150 rpm, and the obtained thermoplastic polyester resin was discharged in the form of a strand, passed through a cooling bath, and pelletized with a strand cutter.

[0099] The pellets obtained were dried in a hot air dryer at 110° C. for 6 hours and then evaluated by the above-mentioned method. The results are shown in Tables 1 and 2.

[0100]

[0101]

[0102] Compared with Comparative Examples 1 to 8, Examples 1 to 12 contain (A) a thermoplastic polyester resin and specific amounts of (B) carbon nanotubes whose combustion peak temperature is within a specific range, thereby enabling the production of polyester resin compositions with excellent electromagnetic wave absorption properties, mechanical strength, and laser marking properties.

[0103] More specifically, compared to Example 5, the volume resistivities of the resin compositions in Examples 1 to 3 were in a more preferable range, and as a result, polyester resin compositions with better laser marking properties were obtained.

[0104] Compared to Example 3, Example 4 contained compound (F), and thereby a polyester resin composition was obtained which was excellent in electromagnetic wave absorption, mechanical strength, and laser marking property, as well as in hydrolysis resistance.

[0105] Compared to Example 3, Example 6 used a masterbatch of (B) carbon nanotubes, which improved the dispersibility of (B) carbon nanotubes. As a result, a polyester resin composition with superior electromagnetic wave absorption, mechanical strength, and laser marking properties was obtained.

[0106] Compared to Example 6, Example 7 contained component (E), and thereby was able to obtain a polyester resin composition that was excellent in electromagnetic wave absorption, mechanical strength, and laser marking properties, as well as in hydrolysis resistance.

[0107] In comparison with Example 6, Examples 9 and 10 contained component (D), and thus were able to obtain polyester resin compositions with superior laser marking properties.

Claims

1. A thermoplastic polyester resin composition comprising (A) 100 parts by weight of a thermoplastic polyester resin and (B) 0.1 to 5 parts by weight of carbon nanotubes having a high-temperature combustion peak of 650°C or higher and 900°C or lower in thermogravimetric analysis when heated in air at 10°C / min.

2. The thermoplastic polyester resin composition according to claim 1, wherein a 3 mm thick rectangular plate molded from the thermoplastic polyester resin composition has a reflection loss S11 of -3 dB or less and a transmission loss S21 of -20 dB or less when measured by the free space method in the 60 to 90 GHz band.

3. Volume resistivity is 1.0 x 10 ５ ~1.0 x 10 １５ The thermoplastic polyester resin composition according to claim 1 or 2, wherein the modulus of elasticity is Ω·m.

4. A thermoplastic polyester resin composition according to claim 1 or 2, further comprising 1 to 100 parts by weight of (D) a vinyl copolymer per 100 parts by weight of (A) the thermoplastic polyester resin.

5. A thermoplastic polyester resin composition according to claim 1 or 2, further comprising 1 to 20 parts by weight of (E) ethylene / alkyl acrylate copolymer per 100 parts by weight of (A) thermoplastic polyester resin.

6. A thermoplastic polyester resin composition according to claim 1 or 2, further comprising 0.1 to 10 parts by weight of (F) a compound having two or more functional groups capable of reacting with a carboxyl group per 100 parts by weight of the thermoplastic polyester resin (A).

7. The thermoplastic polyester resin composition according to claim 6, wherein (F) the compound having two or more functional groups capable of reacting with a carboxyl group in the molecule is an epoxy compound.

8. A thermoplastic polyester resin composition according to claim 1 or 2, which has electromagnetic wave absorbing properties.

9. A molded article obtained by molding the thermoplastic polyester resin composition according to claim 1 or 2.