Polyester resin compositions and molded articles thereof

Abstract

This invention provides a thermoplastic polyester resin composition, wherein, relative to 100 parts by weight of (A) thermoplastic polyester resin, 0.1 to 5 parts by weight of (B) carbon nanotubes are mixed in, wherein the carbon nanotubes exhibit a high-temperature combustion peak between 650°C and 900°C when subjected to thermogravimetric analysis in air at a heating rate of 10°C / min. According to this invention, a resin composition can be obtained that yields molded articles with high electromagnetic wave absorption, excellent mechanical strength, and excellent laser marking properties.

Description

Technical Field

[0001] This invention relates to thermoplastic polyester resin compositions and molded articles thereof that exhibit excellent electromagnetic wave absorption, mechanical strength, and laser marking properties. Background Technology

[0002] Thermoplastic polyester resins, especially polybutylene terephthalate resins, are widely used in housings and structural components of OA equipment, communication equipment, electrical / electronic equipment, and automotive electrical equipment due to their excellent injection molding properties, lightweight, processability, mechanical properties, and heat resistance. Their demand is increasing year by year.

[0003] On the other hand, in order to achieve a safer and more comfortable society, with the popularization of 5G communication and autonomous driving technologies, the application scope of high-frequency electromagnetic waves is expected to further expand in communication equipment such as wireless communication systems used for these technologies, as well as automotive electronic equipment such as millimeter-wave radar.

[0004] However, the higher the frequency, the easier it is to release noise when converted into electromagnetic waves. This can also lead to a deterioration of the noise environment inside communication equipment or automotive electrical equipment, resulting in malfunctions. For example, in millimeter-wave radar, electromagnetic waves reflected by structures such as guardrails can sometimes mix with electromagnetic waves reflected by the target the radar is trying to detect, thus creating artifacts on the radar screen that do not actually exist.

[0005] To prevent such misoperations, housings and structural components used in communication equipment and automotive electrical systems must maintain excellent injection moldability, lightweight, processability, mechanical properties, and heat resistance, while also possessing excellent electromagnetic wave absorption properties.

[0006] In response to the aforementioned issues, Patent Document 1 discloses a thermoplastic resin composition comprising a thermoplastic resin and carbon nanotubes. Furthermore, Patent Document 2 discloses a resin composition comprising a thermoplastic resin, carbon black, carbon fibers, and glycerol fatty acid esters.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: International Publication No. 2021 / 256488

[0010] Patent Document 2: Japanese Patent Application Publication No. 2023-28689 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] On the other hand, batch numbers, serial numbers, and other information are marked on the surfaces of products such as mechanical parts, electrical / communication parts, and automotive parts. Regarding marking methods, commonly used methods include embossing on the product surface, direct printing with ink on the product surface, pasting printed materials onto the product surface, and laser marking on the product surface.

[0013] Laser marking, which does not use solvents and has a short production cycle, has been increasingly adopted in recent years, and is also needed for the resin compositions used in resin molded products. For laser marking of resin molded products, a common method is to use a laser to scorch or discolor the surface of the resin molded product.

[0014] However, in the technology of Patent Document 1, increasing the amount of carbon nanotubes is required to improve electromagnetic wave absorption, resulting in an insufficient balance between electromagnetic wave absorption and laser marking properties. In the technology of Patent Document 2, a considerable amount of carbon black is contained, leading to a reduction in the strength of the resin composition.

[0015] Therefore, the object of the present invention is to provide a resin composition and its molded articles that have good electromagnetic wave absorption, excellent mechanical strength, and excellent laser marking properties.

[0016] Problem-solving methods

[0017] To address the aforementioned issues, the present invention comprises the following components.

[0018] (1) A thermoplastic polyester resin composition, wherein 0.1 to 5 parts by weight of carbon nanotubes (B) are mixed with 100 parts by weight of (A) thermoplastic polyester resin, wherein the carbon nanotubes exhibit a high-temperature combustion peak at a temperature above 650°C and below 900°C when subjected to thermogravimetric analysis in air at a temperature increase of 10°C / min.

[0019] (2) According to the thermoplastic polyester resin composition described in (1), when the thermoplastic polyester resin composition is molded into a 3mm thick square plate and measured by the free space method in the frequency band of 60~90GHz, the reflection loss S11 is less than -3dB and the transmission loss S21 is less than -20dB.

[0020] (3) The thermoplastic polyester resin composition according to (1) or (2) has a volume resistivity of 1.0 × 10⁻⁶. 5 ~1.0×10 15 Ω·m.

[0021] (4) The thermoplastic polyester resin composition according to any one of (1) to (3), wherein 1 to 100 parts by weight of (D) vinyl copolymer are also mixed with 100 parts by weight of (A) thermoplastic polyester resin.

[0022] (5) The thermoplastic polyester resin composition according to any one of (1) to (4), wherein 1 to 20 parts by weight of (E) ethylene / alkyl acrylate copolymer are further mixed with 100 parts by weight of (A) thermoplastic polyester resin.

[0023] (6) The thermoplastic polyester resin composition according to any one of (1) to (5), wherein, relative to 100 parts by weight of (A) thermoplastic polyester resin, 0.1 to 10 parts by weight of (F) a compound having two or more functional groups in its molecule capable of reacting with carboxyl groups is also mixed.

[0024] (7) According to the thermoplastic polyester resin composition of (6), (F) is an epoxy compound having two or more functional groups in the molecule that can react with carboxyl groups.

[0025] (8) The thermoplastic polyester resin composition according to any one of (1) to (7) has electromagnetic wave absorption properties.

[0026] (9) A molded article obtained by molding the thermoplastic polyester resin composition of any one of (1) to (8).

[0027] Invention Effects

[0028] According to the present invention, a resin composition can be obtained that yields molded articles with high electromagnetic wave absorption, excellent mechanical strength, and excellent laser marking properties. Therefore, the thermoplastic polyester resin composition of the present invention can be used for various electromagnetic wave absorbing molded article applications. Detailed Implementation

[0029] The present invention will now be described in detail.

[0030] The thermoplastic polyester resin (hereinafter, sometimes referred to as "component (A)") used in this invention is a polymer or copolymer with at least one residue selected from (1) a dicarboxylic acid or its esterified derivative and a diol or its esterified derivative, (2) a hydroxycarboxylic acid or its esterified derivative, and (3) a lactone as the main structural unit. Here, "as the main structural unit" means having at least 50 mol% of at least one residue selected from (1) to (3) in all structural units, and having at least 80 mol% of such residues is preferred. Among these, from the viewpoint of superior mechanical properties and heat resistance, polymers or copolymers with residues of (1) a dicarboxylic acid or its esterified derivative and a diol or its esterified derivative as the main structural units are preferred.

[0031] Examples of the aforementioned dicarboxylic acids or their esterified derivatives include, for example, 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-anthracite, 1,5-anthracite, 1,8-anthracite, 2,6-anthracite, 9,10-anthracite, 4,4'-diphenyl ether dicarboxylic acid, 5-tetrabutylphosphonium isophthalate, and sodium 5-sulfonate isophthalate; aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanoic acid, malonic acid, glutaric acid, and dimer acids; alicyclic dicarboxylic acids such as 1,3-cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid; and their esterified derivatives. Two or more of these may be used.

[0032] In addition, examples of the aforementioned diols or their esterified derivatives include aliphatic or alicyclic diols with 2 to 20 carbon atoms, such as ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, decamethyldiol, cyclohexanediol, and dimerized glycol; long-chain diols with a molecular weight of 200 to 100,000, such as polyethylene glycol, poly-1,3-propanediol, and polytetramethylenediol; aromatic dioxygen compounds such as 4,4'-dihydroxybiphenyl, hydroquinone, tert-butylhydroquinone, bisphenol A, bisphenol S, and bisphenol F; and their esterified derivatives. Two or more of these compounds may be used.

[0033] Examples of polymers or copolymers whose structural units are dicarboxylic acids or their esterified derivatives and diols or their esterified derivatives include, for example, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polypropylene isophthalate, polybutylene isophthalate, polybutylene naphthalate, polypropylene isophthalate / propylene terephthalate, and polybutylene isophthalate / butylene terephthalate. Poly(propylene terephthalate) / propylene naphthalate, poly(butylene terephthalate) / butylene naphthalate, poly(butylene terephthalate) / butylene sebacic acid, poly(propylene terephthalate) / sodium 5-sulfonate propylene glycol, poly(butylene terephthalate) / sodium 5-sulfonate butylene glycol, poly(propylene terephthalate) / polyethylene glycol, poly(butylene terephthalate) / polyethylene glycol, poly(propylene terephthalate) Ester / Polytetramethylene glycol, Polybutylene terephthalate / Polytetramethylene glycol, Polypropylene terephthalate / Propylene isophthalate / Polytetramethylene glycol, Polybutylene terephthalate / Butylene isophthalate / Polytetramethylene glycol, Polybutylene terephthalate / Butylene succinate, Polypropylene terephthalate / Propylene adipate, Polybutylene terephthalate / Butylene adipate, Polypropylene terephthalate Aromatic polyester resins such as esters / propylene sebacate, polybutylene terephthalate / butylene sebacate, polypropylene terephthalate / propylene isophthalate / propylene adipate, polybutylene terephthalate / butylene isophthalate / butylene succinate, polybutylene terephthalate / butylene isophthalate / butylene adipate, and polybutylene terephthalate / butylene isophthalate / butylene sebacate, etc. These polymers and copolymers can be used alone or in combination of two or more. Here, " / " indicates a copolymer.

[0034] In order to further improve mechanical properties and heat resistance, polymers or copolymers with residues of aromatic dicarboxylic acids or their esterified derivatives and residues of aliphatic diols or their esterified derivatives as the main structural units are preferred. More preferably, polymers or copolymers with residues of aromatic dicarboxylic acids or their esterified derivatives selected from terephthalic acid and naphthalenedicarboxylic acid and residues of aliphatic diols or their esterified derivatives selected from propylene glycol and 1,4-butanediol as the main structural units are preferred.

[0035] Of particular preference are those selected from polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polypropylene naphthalate, polybutylene naphthalate, polypropylene isophthalate / propylene terephthalate, polybutylene isophthalate / butylene terephthalate, polypropylene terephthalate / propylene naphthalate, polybutylene adipate / butylene terephthalate, and polybutylene terephthalate / sedimentyl phthalate. The resin is an aromatic polyester resin selected from at least one of polybutylene terephthalate (PB) and polybutylene terephthalate / butylene naphthalate (PBNA), more preferably from at least one of polyethylene terephthalate (PET), polybutylene terephthalate (PET), polybutylene isophthalate / butylene terephthalate (PET), polybutylene decanedicarboxylate / butylene terephthalate (PET), polybutylene terephthalate / butylene naphthalate (PETNA), and polybutylene terephthalate / ethylene terephthalate (PET). PBNA is further preferred from the perspective of an excellent balance between mechanical properties and molding processability. Alternatively, two or more of these resins may be used in any blending amount, but PBNA is preferred as the main component. Here, "main component" refers to PBNA in which 50% by weight or more of the thermoplastic polyester resin (A) compounded in the resin composition is PBNA.

[0036] Considering the reduction in mechanical properties during melt mixing and residence, as well as moldability, the carboxyl concentration of the (A) thermoplastic polyester resin used in this invention is preferably 50 eq / t or less. The lower limit of the carboxyl concentration is 0 eq / t. Here, the carboxyl concentration of the (A) thermoplastic polyester resin is the value determined by titration with ethanolic potassium hydroxide after dissolving the (A) thermoplastic polyester resin in o-cresol / chloroform solvent.

[0037] From the perspective of further improving mechanical properties, the weight-average molecular weight (Mw) of the (A) thermoplastic polyester resin used in this invention is preferably 8,000 or more. Furthermore, a weight-average molecular weight (Mw) of 500,000 or less is preferred as it improves flowability. More preferably, it is 300,000 or less, and even more preferably 250,000 or less. In this invention, the weight-average molecular weight (Mw) of the (A) thermoplastic polyester resin is a polymethyl methacrylate (PMMA) conversion value determined by gel permeation chromatography (GPC) using hexafluoroisopropanol as a solvent.

[0038] The intrinsic viscosity of the (A) thermoplastic polyester resin used in this invention, from the perspective of further improving mechanical properties, is preferably 0.36 dL / g or more, more preferably 0.50 dL / g or more when measuring the o-chlorophenol solution at 25°C. Furthermore, from the perspective of improving flowability, the intrinsic viscosity is preferably 1.60 dL / g or less, more preferably 1.50 dL / g or less.

[0039] The thermoplastic polyester resin (A) used in this invention can be manufactured by known methods such as polycondensation and ring-opening polymerization. The manufacturing method can be either batch polymerization or continuous polymerization; additionally, it can be either transesterification or a reaction based on direct polymerization. From a productivity perspective, continuous polymerization is preferred, and direct polymerization is even more preferred.

[0040] When the thermoplastic polyester resin (A) used in this invention is a polymer or copolymer obtained by condensation reaction with dicarboxylic acid or its esterified derivative and diol or its esterified derivative as the main components, it can be manufactured by esterification reaction or transesterification reaction of dicarboxylic acid or its esterified derivative and diol or its esterified derivative, followed by polycondensation reaction.

[0041] The amount of (A) thermoplastic polyester resin in the resin composition of the present invention is preferably 30 to 99.9% by weight relative to the total amount of the resin composition of the present invention. If the amount of (A) thermoplastic polyester resin is less than 30% by weight, the lightweight and molding processability are reduced. The amount is more preferably 50% by weight or more, and even more preferably 60% by weight or more.

[0042] The thermoplastic polyester resin composition of the present invention further contains carbon nanotubes. By containing carbon nanotubes, the mechanical strength of the resin composition can be improved, and its electromagnetic wave absorption can be enhanced.

[0043] The carbon nanotubes used in this invention are (B) carbon nanotubes that exhibit a high-temperature combustion peak at a temperature above 650°C and below 900°C when subjected to thermogravimetric analysis in air at a heating rate of 10°C / min (hereinafter, sometimes referred to as "(B) carbon nanotubes"). If the combustion peak temperature is below 650°C, the carbon nanotubes contain carbon impurities and catalysts other than carbon nanotubes, resulting in reduced electromagnetic wave absorption and mechanical properties of the resin composition. The combustion peak temperature is preferably above 670°C, and more preferably above 680°C. If the combustion peak temperature exceeds 900°C, the crystallinity of the carbon nanotubes is too high, thus reducing the dispersibility of carbon nanotubes in the polyester resin composition and reducing electromagnetic wave absorption. The combustion peak temperature is preferably below 850°C, and more preferably below 800°C. The combustion peak temperature is calculated by the following method: The carbon nanotubes are measured by thermogravimetric analysis, and the weight loss curve is differentiated by time to obtain a differential thermogravimetric (DTG) curve. Next, a differential thermogravimetric analysis (DTG) curve is plotted with the x-axis set to temperature (°C) and the y-axis set to DTG (mg / min). The peak temperature in this DTG curve is taken as the combustion peak temperature. Sometimes more than two peak temperatures appear in the DTG curve of carbon nanotubes, but in this invention, the highest peak temperature is taken as the combustion peak temperature. It should be noted that if only one peak temperature is observed in the DTG curve, that peak temperature is considered as the peak temperature on the high-temperature side.

[0044] Typically, carbon impurities burn below 400°C, but when attached to carbon nanotubes, their combustion temperature tends to shift towards higher temperatures. Conversely, the combustion peak temperature of carbon nanotubes with attached impurities shifts towards lower temperatures compared to the original carbon nanotubes. This is because the combustion temperature of carbon impurities is lower than that of carbon nanotubes; therefore, the carbon impurities begin combustion first, and the resulting heat energy is transferred to the carbon nanotubes. Consequently, the carbon nanotubes burn at a lower temperature than the original combustion temperature. Therefore, the higher the graphitization degree of the carbon nanotubes and the fewer the carbon impurities, the higher the combustion peak temperature will appear on the higher-temperature side. Thus, a higher combustion peak temperature indicates higher purity of the carbon nanotubes. For carbon nanotubes with combustion peak temperatures within the aforementioned range, even a small amount of carbon nanotubes in the resin composition can exhibit high electromagnetic wave absorption, allowing for lower volume resistivity control in the resin composition, thereby improving laser marking performance.

[0045] The average diameter of the (B) carbon nanotubes used in this 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. If the average diameter is 1000 nm or less, dielectric loss is easily induced, which can further improve electromagnetic wave absorption. Furthermore, 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. When the average diameter is 0.1 nm or more, it is less likely to form bundles, and it is easier to achieve micro-dispersion in the resin composition, thus further improving mechanical strength and electromagnetic wave absorption. For the average diameter, the diameter of 100 or more (B) carbon nanotubes is measured under a transmission electron microscope, and the average value is calculated. Since (B) carbon nanotubes are materials with a large aspect ratio, the diameter of the cross-section perpendicular to the length direction of its shape is considered the diameter.

[0046] In the resin composition of the present invention, the amount of carbon nanotubes (B) is 0.1 to 5 parts by weight relative to 100 parts by weight of thermoplastic polyester resin (A). If the amount of carbon nanotubes (B) is less than 0.1 parts by weight, the electromagnetic wave absorption decreases. The amount is preferably 0.3 parts by weight or more, more preferably 0.5 parts by weight or more. Furthermore, when the amount of carbon nanotubes (B) exceeds 5 parts by weight, the volume resistivity decreases, and the laser marking properties decrease. The amount is preferably 4 parts by weight or less, more preferably 3 parts by weight or less.

[0047] Alternatively, carbon fillers other than carbon nanotubes may be added within the scope of the present invention without prejudice to the purpose of the invention.

[0048] The thermoplastic polyester resin composition of the present invention preferably further contains (C) fibrous reinforcing material. By containing (C) fibrous reinforcing material, the mechanical strength of the molded article can be improved. Examples of (C) fibrous reinforcing materials include glass fiber, aramid fiber, and cellulose fiber, among which glass fiber is preferred.

[0049] The cross-section of the (C) fibrous reinforcing material used in this invention can be circular or flat. Additionally, hollow fibers can be used to reduce specific gravity, etc. As the cross-sectional area of ​​the (C) fibrous reinforcing material increases, sufficient reinforcement cannot be obtained. On the other hand, if the cross-sectional area becomes too small, the manufacture of the fibrous reinforcing material becomes difficult, and sometimes even difficult to handle. The preferred cross-sectional area of ​​the (C) fibrous reinforcing material is 2 × 10⁻⁶. -5 ~8×10 -3 mm 2 More preferably 8×10 -5 ~8×10 -3 mm 2 Further preferred is 8×10-5 ~8×10 -4 mm 2 .

[0050] In the fibrous reinforcing material (C) used in this invention, a slugging agent or surface treatment agent is preferably used as needed. Examples of slugging agents or surface treatment agents include functional compounds such as epoxy compounds, isocyanate compounds, and silane compounds. These compounds can be used to pre-treat or slug the fibrous reinforcing material, or they can be added simultaneously with the fibrous reinforcing material during the preparation of the resin composition.

[0051] The 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 relative to 100 parts by weight of (A) thermoplastic polyester resin. If the amount of (C) fibrous reinforcing material is 1 part by weight or more, the mechanical strength of the molded article can be improved. The amount is preferably 10 parts by weight or more, more preferably 20 parts by weight or more. Furthermore, if the amount of (C) fibrous reinforcing material is 100 parts by weight or less, the reduction in flowability can be suppressed. The amount is preferably 80 parts by weight or less, more preferably 50 parts by weight or less.

[0052] The thermoplastic polyester resin composition of the present invention preferably further contains (D) vinyl copolymers (hereinafter, sometimes referred to as "(D) components"). By containing (D) vinyl copolymers with lower thermal conductivity compared to thermoplastic polyester resins, thermal diffusion through (B) carbon nanotubes can be suppressed, thereby improving laser marking properties. Furthermore, due to the improved dispersibility of (B) carbon nanotubes, the electromagnetic wave absorption of the molded article can be further improved. The (D) vinyl copolymers used in the present invention are preferably copolymers containing at least unsaturated nitrile monomers and aromatic vinyl monomers as copolymerizing components. Other copolymerizable monomers may also be copolymerized as needed. Typically, these (D) vinyl copolymers are manufactured by emulsion polymerization, bulk polymerization, or bulk / suspension polymerization, but are not limited thereto.

[0053] There are no particular limitations on the unsaturated nitrile monomers used in (D) vinyl copolymers, and examples include acrylonitrile, methacrylonitrile, and ethylacrylonitrile, with acrylonitrile being preferred. There are no particular limitations on the aromatic vinyl monomers used; specific examples include styrene, such as α-methylstyrene, o-methylstyrene, p-methylstyrene, o-ethylstyrene, p-ethylstyrene, and p-tert-butylstyrene, with styrene and α-methylstyrene being preferred. Other copolymerizable monomers include acrylic and methacrylate compounds such as butyl acrylate, ethyl acrylate, and methyl methacrylate; N-phenylmaleimide; and maleic anhydride. Preferably, a styrene-acrylonitrile copolymer (hereinafter referred to as AS resin) contains a total of 85% by mass or more of acrylonitrile as an unsaturated nitrile monomer and styrene as an aromatic vinyl monomer as a copolymerizing component, and contains 15% by mass or less of other copolymerizable monomers.

[0054] (D) Vinyl copolymers may include rubbery polymers to a extent that does not significantly impair damage resistance. This also includes resins obtained by grafting unsaturated nitrile monomers and aromatic vinyl monomers with rubbery polymers, and resins obtained by further copolymerizing other copolymerizable monomers. The same monomers as those described above can be used as the unsaturated nitrile monomers, aromatic vinyl monomers, and other copolymerizable monomers. (D) There are no particular limitations on the rubbery polymers used in vinyl copolymers; diene rubbers, acrylic rubbers, ethylene rubbers, etc., can be used. Specific examples of these rubbery polymers include polybutadiene, styrene-butadiene copolymers, styrene-butadiene block copolymers, acrylonitrile-butadiene copolymers, butyl acrylate-butadiene copolymers, polyisoprene, butadiene-methyl methacrylate copolymers, butyl acrylate-methyl methacrylate copolymers, butadiene-ethyl acrylate copolymers, ethylene-propylene copolymers, ethylene-propylene-diene copolymers, ethylene-isoprene copolymers, and ethylene-methyl acrylate copolymers, etc. Among these rubbery polymers, acrylic rubbers are preferred.

[0055] Furthermore, for (D) vinyl copolymers, in order to improve compatibility with (A) thermoplastic polyester resin, it is preferable to copolymerize the raw material monomers that form vinyl units containing glycidyl groups. Specific examples of raw material monomers that form vinyl units containing glycidyl groups include glycidyl acrylate (meth)acrylate, glycidyl p-styrene carboxylic acid, and other unsaturated monocarboxylic acids; mono- 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.

[0056] The amount of the (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 relative to 100 parts by weight of the (A) thermoplastic polyester resin. If the amount of the (D) vinyl copolymer is 1 part by weight or more, dimensional stability can be improved, and the electromagnetic wave absorption of the molded article can be stabilized regardless of molding conditions. The amount is preferably 10 parts by weight or more, more preferably 20 parts by weight or more. Furthermore, if the amount of the (D) vinyl copolymer is 100 parts by weight or less, the decrease in heat resistance can be suppressed. The amount is preferably 80 parts by weight or less, more preferably 50 parts by weight or less.

[0057] The thermoplastic polyester resin composition of the present invention further contains (E) ethylene / alkyl acrylate copolymer (hereinafter, sometimes referred to as "(E) component"). By containing the (E) ethylene / alkyl acrylate copolymer, which has a lower thermal conductivity than the thermoplastic polyester resin, thermal diffusion through (B) carbon nanotubes can be suppressed, thereby improving laser marking properties. Furthermore, due to the improved dispersibility of (B) carbon nanotubes, the electromagnetic wave absorption of the molded article can be further improved. The (E) ethylene / alkyl acrylate copolymer is preferably a copolymer formed from α-olefins and α,β-ene unsaturated carboxylic acids or their derivatives, or a ternary copolymer containing glycidyl groups formed from α-olefins and α,β-ene unsaturated carboxylic acids or their derivatives and glycidyl esters of α,β-unsaturated acids. Specific examples of (E) ethylene / alkyl acrylate copolymers include ethylene / methyl acrylate copolymers, ethylene / ethyl acrylate copolymers, ethylene / butyl acrylate copolymers, ethylene / methacrylic acid copolymers, ethylene / glycidyl copolymers, ethylene / methacrylic acid / glycidyl copolymers, ethylene / vinyl acetate / glycidyl methacrylate copolymers, ethylene / ethyl acrylate-g-methyl methacrylate / butyl acrylate copolymers, ethylene / ethyl acrylate-g-methyl methacrylate copolymers, etc., which can be used individually or in the form of mixtures.

[0058] By incorporating (E) ethylene / alkyl acrylate copolymer into (A) thermoplastic polyester resin, the flowability and toughness of the (A) thermoplastic polyester resin composition can be improved. However, if a ternary copolymer containing glycidyl groups, formed by combining α-olefins and α,β-ene unsaturated carboxylic acids or their derivatives with glycidyl esters of α,β-unsaturated acids, is used alone, the glycidyl groups in the ethylene / alkyl acrylate copolymer will react with the (A) thermoplastic polyester resin, thus tending to reduce flowability and retention stability. Therefore, from the perspective of imparting flowability and toughness, it is preferable to combine a copolymer of α-olefins and α,β-ene unsaturated carboxylic acids or their derivatives, and a ternary copolymer containing glycidyl groups, formed by combining α-olefins and α,β-ene unsaturated carboxylic acids or their derivatives with glycidyl esters of α,β-unsaturated acids, more preferably a copolymer of α-olefins and α,β-ene unsaturated carboxylic acids or their derivatives alone.

[0059] The amount of (E) ethylene / alkyl acrylate copolymer is preferably 1 part by weight or more and 20 parts by weight or less relative to 100 parts by weight of (A) thermoplastic polyester resin. If the amount of (E) ethylene / alkyl acrylate copolymer is 1 part by weight or more, thermal diffusion through (B) carbon nanotubes can be suppressed, improving laser marking properties. Furthermore, the dispersibility of (B) carbon nanotubes is improved, thus further enhancing the electromagnetic wave absorption of the molded article. The amount is preferably 3 parts by weight or more, more preferably 5 parts by weight or less. Additionally, if the amount of (E) ethylene / alkyl acrylate copolymer is 20 parts by weight or less, the laser marking properties and electromagnetic wave absorption of the molded article can be further improved without compromising the rigidity and flowability of the polyethylene resin. The amount is preferably 15 parts by weight or less, more preferably 10 parts by weight or less.

[0060] The thermoplastic polyester resin composition of the present invention preferably further contains a compound (hereinafter, sometimes referred to as "(F) compound") having two or more functional groups within its molecule that can react with carboxyl groups. By incorporating the (F) compound, the dispersibility of carbon nanotubes is improved, and electromagnetic wave absorption is enhanced. Furthermore, the (A) thermoplastic polyester resin undergoes ester bond decomposition through hydrolysis, thereby increasing the carboxyl group concentration in the resin. With the increase in carboxyl group concentration, the molecular weight of the (A) thermoplastic polyester resin decreases, leading to a reduction 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 through hydrolysis react with the functional groups of the (F) compound, suppressing the increase in carboxyl group concentration. As a result, the high mechanical properties of the (A) thermoplastic polyester resin can be maintained.

[0061] Examples of (F) compounds include epoxides, oxazoline compounds, and carbodiimides.

[0062] Epoxy compounds are compounds that have epoxy groups as functional groups capable of reacting with carboxyl groups. There are no particular restrictions on the presence of two or more epoxy groups per molecule in an epoxy compound. Examples of epoxy compounds with two or more epoxy groups per molecule include glycidyl ether type epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, alicyclic epoxy resins, and heterocyclic epoxy resins. They can be used alone or in combination of two or more.

[0063] Examples of glycidyl ether type epoxy resins include condensates of phenolic compounds and epichlorohydrin, phenolic varnish type epoxy resins, and glycidyl ethers of polyhydroxy compounds.

[0064] Specific examples of condensates between phenolic compounds and epichlorohydrins include condensates obtained by condensing phenolic compounds such as bisphenol A, resorcinol, hydroquinone, pyrocatechol, bisphenol F, salicin, 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-tetra-4-hydroxyphenylethane, and cashew phenol with epichlorohydrins.

[0065] Specific examples of phenolic varnish-type epoxy resins include phenolic varnish-type epoxy resins, cresol varnish-type epoxy resins, naphthol varnish-type epoxy resins, bisphenol A varnish-type epoxy resins, dicyclopentadiene-phenol addition phenolic varnish-type epoxy resins, dimethylene phenylene-phenol addition phenolic varnish-type epoxy resins, and dimethylene biphenylene-phenol addition phenolic varnish-type epoxy resins.

[0066] Polyhydroxy compounds refer to aliphatic compounds with two or more hydroxyl groups. Specifically, examples include diols, glycerol, polyglycerol, dipentaerythritol, tripentaerythritol, xylitol, mannitol, sorbitol, galactose, maltitol, lactitol, isomaltitol, inositol, glucose, fructose, etc., with 2 to 20 carbon atoms.

[0067] Examples of glycidyl ester type epoxy resins include epoxy resins made from epichlorohydrin and phthalic acid, tetrahydrophthalic acid, p-hydroxybenzoic acid or dimer acid, pyromellitic acid triglycidyl ester, trimellitic acid triglycidyl ester, pyromellitic acid tetraglycidyl ester, epoxidized fatty acid octyl ester, epoxidized soybean oil, epoxidized linseed oil, etc.

[0068] Examples of glycidylamine type epoxy resins include epoxy resins made from epichlorohydrin and aniline, diaminodiphenylmethane, p-aminophenol, m-phenylenediamine, or 1,3-bis(aminomethyl)cyclohexane, tetraglycidylaminodiphenylmethane, triglycidyl-p-aminophenol, triglycidyl-m-aminophenol, tetraglycidyl-m-phenylenediamine, tetraglycidyldiaminomethylcyclohexane, triglycidyl cyanurate, and triglycidyl isocyanurate.

[0069] Examples of alicyclic epoxy resins include compounds with oxidized cyclohexenyl, oxidized tricyclodecenyl, and oxidized cyclopentenyl groups.

[0070] Examples of heterocyclic epoxy resins include epoxy resins made from epichlorohydrin and hydantoin or isocyanuric acid.

[0071] Among them, considering the ability to inhibit the interaction of epoxy groups in (F) compounds and to suppress the deterioration of retention stability, glycidyl ether type epoxy resin is preferred.

[0072] Oxazoline compounds are compounds having an oxazoline group as a functional group capable of reacting with a carboxyl group. Specific examples include compounds with 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-oxazoline-cyclohexane) sulfides, as well as polymers containing an oxazoline group. One or more of these can be used. Among these, polymers containing an oxazoline group are preferred for ease of operation. Polymers containing an oxazoline group 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 can also be copolymerized as needed. There are no particular limitations on the polymerization method of polymers containing an oxazoline group; various known polymerization methods can be used.

[0073] Carbodiimide compounds are compounds 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; poly(1,6-hexamethylenecarbodiimide); poly(4,4'-methylenebicyclohexylcarbodiimide); poly(1,3-cyclohexylcarbodiimide); poly(1,4-cyclohexylcarbodiimide); poly(4,4'-dicyclohexylmethanecarbodiimide); poly(4,4'-diphenylmethanecarbodiimide); and poly(3,3'-dimethyl- Poly(4,4'-diphenylmethane carbodiimide), poly(naphthalene carbodiimide), poly(p-phenylene carbodiimide), poly(m-phenylene carbodiimide), poly(tolyl carbodiimide), poly(diisopropyl carbodiimide), poly(methyldiisopropylphenylene carbodiimide), poly(1,3,5-triisopropylbenzene) polycarbodiimide, poly(1,5-diisopropylbenzene) polycarbodiimide, poly(triethylphenylene carbodiimide), poly(triisopropylphenylene carbodiimide), etc.

[0074] Among these considerations, considering that it can also react with the hydroxyl terminus of (A) thermoplastic polyester resin to inhibit post-crystallization during the hydrolysis of the resin composition and further improve hydrolysis resistance, an epoxy compound having an epoxy group as a functional group that can react with a carboxyl group is more preferred.

[0075] It should be noted that, in this invention, in (D) vinyl copolymers and (E) ethylene / alkyl acrylate copolymers, even compounds that are copolymerized from raw material monomers containing reactive functional groups such as glycidyl groups and are equivalent to compounds (F) are treated as components (D) and (E), respectively.

[0076] In the thermoplastic polyester resin composition of the present invention, the amount of compound (F) is preferably 0.1 parts by weight or more and 10 parts by weight or less relative to 100 parts by weight of thermoplastic polyester resin (A). When the amount of compound (F) is 0.1 parts by weight or more, the dispersibility of carbon nanotubes in the resin composition is improved, the electromagnetic wave absorption is improved, and the hydrolysis resistance can be improved. The amount is more preferably 0.3 parts by weight or more, further preferably 0.5 parts by weight or more, and particularly preferably 1.0 parts by weight or more. On the other hand, when the amount of compound (F) is 10 parts by weight or less, the thickening of the polyester resin composition can be suppressed, and the electromagnetic wave absorption and hydrolysis resistance can be improved without impairing the flowability. The amount is more preferably 8 parts by weight or less, and further preferably 5 parts by weight or less.

[0077] The thermoplastic polyester resin composition of the present invention preferably exhibits a reflection loss S11 of -3 dB or less and a transmission loss S21 of -20 dB or less when the composition is molded into a 3 mm thick square plate and measured using the free-space method in the 60-90 GHz frequency band. When the reflection loss S11 is greater than -3 dB, the electromagnetic waves reflected from the surface of the resin molded article cannot be attenuated, and if the reflected waves are reflected again by some components, it may adversely affect the electronic equipment within the resin molded article. The reflection loss S11 is preferably -4 dB or less, more preferably -5 dB or less. Furthermore, when the transmission loss S21 is greater than -20 dB, the electromagnetic wave shielding of the electronic equipment within the resin molded article is insufficient, and therefore may adversely affect the electronic equipment within the resin molded article. The transmission loss S21 is preferably -25 dB or less, more preferably -30 dB or less. Moreover, when the reflection loss S11 and transmission loss S21 are less than -80 dB, the conductivity of the polyester resin composition becomes too high, thus reducing its laser marking capability. Therefore, the reflection loss S11 and the transmission loss S21 are both preferably -80dB or higher.

[0078] By combining 0.1 parts by weight or more of (B) carbon nanotubes with 100 parts by weight of (A) thermoplastic polyester resin, the reflection loss S11 can be reduced to -3dB or less and the transmission loss S21 to -20dB or less.

[0079] The thermoplastic polyester resin composition of the present invention preferably has a volume resistivity of 1.0 × 10⁻⁶. 5 Ω·m or more and 1.0×10 15 Below Ω·m. By making the volume resistivity 1.0 × 10⁻⁶ 5 Above Ω·m, thermal diffusion, which is correlated with volume resistivity, can be suppressed, allowing for effective foaming of thermoplastic polyester resins using lasers and improving laser marking properties. If the volume resistivity is 1.0 × 10⁻⁶... 7 A volume resistivity of Ω·m or higher is preferred as it imparts insulation properties to the thermoplastic polyester resin composition. Furthermore, to exhibit effective electromagnetic wave absorption, a volume resistivity of 1.0 × 10⁻⁶ is preferable. 15 Below Ω·m.

[0080] By making the amount of conductive (B) carbon nanotubes relative to 100 parts by weight of (A) thermoplastic polyester resin less than 5 parts by weight, the volume resistivity of the polyester resin composition can be within a preferred range.

[0081] In the thermoplastic polyester resin composition of the present invention, a thermoplastic resin other than component (A) may be included within a range that does not impair the purpose of the present invention, thereby improving moldability, toughness, etc. Examples of thermoplastic resins other than component (A) include, for example, polyamide resins, polyacetal resins, polyurethane resins, aromatic or aliphatic polyketone resins, polyphenylene sulfide resins, polyetheretherketone resins, polyimide resins, thermoplastic starch resins, polyarylate resins, polysulfone resins, polyethersulfone resins, phenoxy resins, polyphenylene ether resins, polyetherimide resins, cellulose acetate resins, polyvinyl alcohol resins, etc.

[0082] Furthermore, the thermoplastic polyester resin composition of the present invention may contain other components within a range that does not impair the purpose of the present invention, such as stabilizers, weathering agents (resorcinol derivatives, salicylates, benzophenone derivatives, etc.), lubricants (lignite acid and its esters, half-esters, stearyl alcohol, polyethylene wax, etc.), pigments, dyes, crystallizing nucleating agents (talc, polyether ether ketone, etc.), plasticizers, antistatic agents, flame retardants, anti-coloring agents, other polymers, etc.

[0083] The thermoplastic polyester resin composition of the present invention can be obtained, for example, by melt-blending the above-mentioned (A) thermoplastic polyester resin and (B) carbon nanotubes, as well as other components as needed.

[0084] Examples of melt mixing methods include premixing (A) thermoplastic polyester resin, (B) carbon nanotubes and various additives, and feeding them to an extruder for full melt mixing; or feeding each component to an extruder for full melt mixing while using a quantitative feeder such as a weighing feeder to measure each component in a manner that forms a specified composition.

[0085] Examples of premixing mentioned above include dry mixing, mixing using mechanical mixing devices such as drum mixers, ribbon mixers, and Henschel mixers.

[0086] Furthermore, for (B) carbon nanotubes, they can be used in the form of a carbon nanotube masterbatch formed by pre-dispersing a high concentration of (B) carbon nanotubes in a thermoplastic resin. Considering operability and uniform dispersion of carbon nanotubes, the use of a carbon nanotube masterbatch is preferred. In this case, the thermoplastic resin used as the carbon nanotube masterbatch can be a thermoplastic polyester resin that is component (A), or a resin other than component (A), such as polyamide resin, polycarbonate resin, styrene resin, polyethylene resin, etc. Considering ease of dispersion of high concentrations of (B) carbon nanotubes and ease of masterbatch preparation, the use of (A) thermoplastic polyester resin for masterbatch preparation is preferred.

[0087] In addition, when using a multi-screw extruder such as a twin-screw extruder for melt mixing, (C) fibrous reinforcing material can be added by setting a side feeder between the main feed section and the venting section.

[0088] In addition, in the case of liquid additives, methods such as setting a liquid addition nozzle between the main feed section and the venting section of a multi-screw extruder such as a twin-screw extruder and adding it using a plunger pump, or supplying it from the main feed section using a metering pump, can be used.

[0089] The thermoplastic polyester resin composition of the present invention is preferably processed by molding the granules after granulation. As a granulation method, one can exemplify the following: using, for example, a single-screw extruder, twin-screw extruder, three-screw extruder, conical extruder, or a kneader-type mixer, the components constituting the resin composition are discharged in a filament form, and then cut into granules using a filament cutter.

[0090] The molded articles of the present invention are formed 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.

[0091] In addition to conventional injection molding methods, other known methods for injection molding include gas-assisted molding, two-color molding, sandwich molding, in-mold molding, insert molding, and injection compression molding. Any of these molding methods can be used.

[0092] The thermoplastic polyester resin composition of the present invention exhibits high electromagnetic wave absorption, excellent mechanical strength, and excellent laser marking properties. The molded articles of the present invention possess excellent electromagnetic wave absorption, mechanical properties, and hydrolysis resistance, and can be effectively utilized for various applications such as automotive parts, mechanical components, and electrical and electronic components.

[0093] Specific applications include junction boxes, LiB (Liquid Brake), insulators, air flow meters, air pumps, thermostat housings, engine mounts, ignition coil spools, ignition coil housings, clutch sleeves, idle speed control valves, vacuum switching valves, ECU housings, HUD housings, vacuum pump housings, shift limit switches, speed sensors, pressure sensors, acceleration sensors, millimeter-wave radar, ultrasonic sensors, and other sensor housings, brackets and their internal parts, distributor caps, coil bases, ABS actuator housings, radiator tops and bottoms, cooling fans, fan shrouds, engine hoods, cylinder head covers, oil caps, oil pans, oil filters, fuel caps, fuel filters, distributor caps, vapor recovery tank housings, air filter housings, timing belt covers, brake booster components, various housings, various pipes, various cans, various hoses, various clamps, various valves, various pipelines, and other automotive chassis components, torque control levers, seat belt components, adjusting lever blades, washer levers, window adjusting handles, and more. Interior automotive components such as window adjustment knobs, headlight stalks, sun visor brackets, and various motor housings; exterior automotive components such as roof rails, mudguards, trim strips, bumpers, door mirror brackets, spoilers, hood vents, wheel covers, wheel hubcaps, grille trim frames, lamp reflectors, light rings, and door handles; various automotive connectors such as wiring harness connectors, SMJ connectors, PCB connectors, and door crimp terminal connectors; electrical connectors, relay housings, coil winding spools, optical pickup frames, motor housings, laptop housings and internal parts, CRT monitor housings and internal parts, printer housings and internal parts, portable terminal housings and internal parts for mobile phones, mobile computers, and handheld mobile devices, housings and internal parts for recording media (CD, DVD, PD, FDD, etc.) drives, copier housings and internal parts, fax machine housings and internal parts, and housings and internal parts for communication electrical and electronic components, such as base stations, data communication modules, and various antennas. In addition, examples include parts for household and office electrical products such as VTR parts, television parts, irons, hair dryers, rice cooker parts, microwave oven parts, audio equipment parts, camera parts, projector parts, lighting parts, refrigerator parts, air conditioner parts, typewriter parts, and word processor parts. Furthermore, examples include casings and internal parts for electronic musical instruments, home game consoles, and portable game consoles; various gears; various housings; sensors; LED lights; connectors; sockets; resistors; relay boxes; switches; coil winding spools; capacitors; varistor boxes; optical pickups; oscillators; and various terminal blocks.

[0094] It is particularly suitable for housings, brackets and internal parts of sensing components such as ECU housings, HUD housings, rotation sensors, pressure sensors, acceleration sensors, millimeter-wave radars, and ultrasonic sensors that require electromagnetic wave absorption; housings and internal parts of laptops, CRT monitors, printers, portable terminals such as mobile phones, mobile computers, and handheld mobile computers; housings and internal parts of recording media (CD, DVD, PD, FDD, etc.) drives; housings and internal parts of copiers; housings and internal parts of fax machines; and housings and internal parts of communication electrical and electronic components such as base stations, data communication modules, and various antennas.

[0095] Example

[0096] Next, the present invention will be described in more detail through embodiments, but these embodiments are not intended to limit the present invention.

[0097] The following is a summary of the abbreviations and contents of the main raw materials used in the examples.

[0098] (A) Thermoplastic polyester resin

[0099] A-1: Polybutylene terephthalate (terminal carboxyl group concentration 25 eq / t, intrinsic viscosity measured at 25°C with o-chlorophenol solution as solvent is 0.85 dL / g).

[0100] A-2: Polyethylene terephthalate (terminal carboxyl group concentration 25 eq / t, intrinsic viscosity measured at 25°C with o-chlorophenol solution as solvent is 0.80 dL / g).

[0101] (B) Carbon nanotubes

[0102] B-1: Carbon nanotubes A (average diameter: 12nm, BET specific surface area: 265m²) 2 / g, Composition: Carbon 95% by mass, thermogravimetric analysis combustion peak temperature 688℃)

[0103] B-2: Carbon nanotubes B (average diameter: 15nm, BET specific surface area 205m²) 2 / g, Composition: C98% by mass, thermogravimetric analysis combustion peak temperature 675℃)

[0104] B'-3: Carbon nanotubes (average diameter: 15 nm, BET specific surface area: 191 m²) 2 / g, Composition: C98% by mass, thermogravimetric analysis combustion peak temperature 647℃)

[0105] B'-4: Carbon nanotubes D (average diameter: 9.5 nm, BET specific surface area 275 m²) 2 / g, Composition: C90% by mass, thermogravimetric analysis combustion peak temperature 645℃)

[0106] B-5: Carbon nanotube masterbatch

[0107] Using a twin-screw extruder (Nippon Steel Works, TEX-30 α) with a screw diameter of 30 mm, an L / D ratio of 35, and vents rotating in the same direction, A-1 (polybutylene terephthalate) and B-1 (carbon nanotubes A) were melt-blended at a ratio of 11.1 parts by weight of B-1 to A-1 (100 parts by weight of B-1). The mixture was discharged as a filament and granulated using a filament cutter. The resulting granules were then vacuum-dried at 110°C for 6 hours to obtain carbon nanotube masterbatch particles.

[0108] (C) Fibrous reinforcement materials

[0109] C-1: Circular cross-section chopped fiberglass (manufactured by Nippon Electric Glass Co., Ltd., ECS03T187).

[0110] (D) Vinyl copolymers

[0111] D-1: Acrylonitrile / styrene / glycidyl methacrylate copolymer (the weight ratio of each component in the acrylonitrile / styrene / glycidyl methacrylate copolymer is 23.7 / 76.0 / 0.3, and the specific viscosity is 0.72).

[0112] (E) Ethylene / alkyl acrylate copolymer

[0113] E-1: Ethylene / methyl acrylate copolymer (Mitsui Depoponporikimikar "Erubaroi AC" (registered trademark) 22534 (trade name).

[0114] (F) Compounds with two or more functional groups that can react with carboxyl groups within their molecules.

[0115] F-1: Epoxy resin (manufactured by DIC Corporation, HP7200H).

[0116] In addition, the evaluation methods used in the embodiments and comparative examples are summarized below.

[0117] (1) Thermogravimetric analysis (combustion peak temperature of carbon nanotubes)

[0118] Using a thermogravimetric analyzer (Shimadzu Corporation TGA-60), the sample was held in air at 150°C for 30 minutes, and then heated from room temperature to 950°C at a rate of 10°C / min. The weight loss at this point was measured, yielding a weight loss curve. The weight loss curve was differentiated with respect to time to obtain a differential thermogravimetric (DTG) curve. A DTG graph was plotted with the x-axis set to temperature (°C) and the y-axis set to DTG (mg / min), and the peak temperature in this DTG curve was taken as the combustion peak temperature. Sometimes more than one peak temperature may appear, but in this invention, the highest peak temperature is taken as the combustion peak temperature of the carbon nanotubes.

[0119] (2) Tensile properties

[0120] Using a Sumitomo Heavy Industries SE50-DUZ injection molding machine, with (A) thermoplastic polyester resin being polybutylene terephthalate, the molding temperature was 260°C, the mold temperature was 80°C, and the total injection time and holding time was 10 seconds with a cooling time of 10 seconds. With (A) thermoplastic polyester resin being polyethylene terephthalate, the molding temperature was 280°C, the mold temperature was 120°C, and the total injection time and holding time was 20 seconds with a cooling time of 20 seconds. The resulting ISO-1A dumbbell tensile property evaluation test piece with a thickness of 4 mm was obtained. For the obtained test pieces used for tensile property evaluation, the maximum tensile strength (tensile strength) was determined using a tensile testing machine (Otgraf AG-50kNXPlus) manufactured by Shimadzu Corporation, in accordance with ISO 527-2:2012. The average value of the measured values ​​of three specimens was taken as the tensile strength value. Materials with higher tensile strength values ​​were considered to have superior mechanical properties.

[0121] (3) Hydrolysis resistance

[0122] Using a Sumitomo Heavy Industries SE50-DUZ injection molding machine, ISO-1A dumbbell-shaped test specimens with a thickness of 4 mm were obtained under the same molding conditions as those described in section (2). The obtained test specimens were placed in an EHS-411 high-accelerated life testing apparatus manufactured by Espec Co., Ltd., with a temperature and humidity set at 121°C × 100%RH for 50 hours for hydrothermal treatment. For the test specimens after hydrothermal treatment, the maximum tensile strength was measured under the same conditions as those described in section (2), and the average value of the measured values ​​of 3 specimens was taken as the maximum tensile strength after hydrothermal treatment. The tensile strength retention rate was expressed as the percentage of the maximum tensile strength of the test specimen after hydrothermal treatment to the maximum tensile strength of the test specimen before hydrothermal treatment (without hydrothermal treatment).

[0123] (Maximum tensile strength after hygrothermal treatment / Maximum tensile strength before hygrothermal treatment (without hygrothermal treatment)) × 100 = Tensile strength retention rate (%)

[0124] The higher the tensile strength retention rate of a material, the better its hydrolysis resistance.

[0125] (4) Electromagnetic wave absorption

[0126] Using a Sumitomo Heavy Industries SE50-DUZ injection molding machine, and under the same molding conditions as the tensile properties in item (2), an electromagnetic wave absorption evaluation test piece with a width of 80 mm × length of 80 mm × thickness of 3 mm was molded.

[0127] The measurements were performed using an ME7838A network analyzer manufactured by Anlitz Co., Ltd., employing the free-space method. The values ​​of reflection loss S11 and transmission loss S21 at 79 GHz were calculated from the S-parameter measurements of the incident and transmitted waves of the electromagnetic wave absorption evaluation test piece. The smaller the values ​​of reflection loss S11 and transmission loss S21 at 79 GHz, i.e., the greater the attenuation rate, the better the electromagnetic wave absorption is considered.

[0128] (5) Volume resistivity

[0129] Using a Sumitomo Heavy Industries SE50-DUZ injection molding machine, test pieces with a width of 80 mm × a length of 80 mm × a thickness of 3 mm were produced under the same molding conditions as those described in section (2). Following IEC 62631-3-1, an analogue was used... The volume resistivity was measured using the double-ring method of High Relationship 4339B manufactured by Technologi Co., Ltd. under DC 100V × 60 seconds.

[0130] (6) Laser marking

[0131] Using a Sumitomo Heavy Industries SE50-DUZ injection molding machine, under the same molding conditions as the tensile properties described in section (2), a laser marking evaluation test piece with a width of 80 mm × length of 80 mm × thickness of 3 mm was prepared. A 20 mm wide × 20 mm long marking portion was formed on the surface of the prepared test piece using a Panasonic FAYb laser marking LP-S200 at a wavelength of 1064 nm. The marking portion was color-measured using a Suga Testing Machine Co., Ltd. SM color computer (SM-T), and the color difference (ΔE) between the unmarked portion and the marked portion was measured. ab). ΔE The larger the value of ab, the better the laser marking performance.

[0132] [Examples 1-12, Comparative Examples 1-8]

[0133] Using a twin-screw extruder (manufactured by Nippon Steel, TEX-30α) with a screw diameter of 30 mm, an L / D ratio of 35, and vents rotating in the same direction, (A) thermoplastic polyester resin, (B) carbon nanotubes, and other raw materials were mixed according to the compositions shown in Tables 1 and 2 and added from the main feed section of the twin-screw extruder. The amounts of (C) fibrous reinforcing material, (D) vinyl copolymer, (E) component, and (F) compound in Examples 6-10 of Table 1 are relative to 100 parts by weight of (A) thermoplastic polyester resin.

[0134] A side feeder is installed between the main feed section and the venting section of a twin-screw extruder, from which (C) fibrous reinforcing material is added.

[0135] When (A) thermoplastic polyester resin is polybutylene terephthalate, it is melt-mixed under extrusion conditions with a mixing temperature of 250°C and a screw speed of 150 rpm. When (A) thermoplastic polyester resin is polyethylene terephthalate, it is melt-mixed under extrusion conditions with a mixing temperature of 260°C and a screw speed of 150 rpm. The resulting thermoplastic polyester resin is discharged as a wire and granulated by passing it through a cooling bath and using a wire cutter.

[0136] The obtained granules were dried in a hot air dryer at 110°C for 6 hours and then evaluated using the method described above. The results are listed in Tables 1 and 2.

[0137]

[0138] Compared with Comparative Examples 1-8, Examples 1-12 show that polyester resin compositions with excellent electromagnetic wave absorption, mechanical strength, and laser marking properties can be obtained by using a specific amount of (A) thermoplastic polyester resin and (B) carbon nanotubes with a specific range of combustion peak temperature.

[0139] To provide a more detailed explanation, compared to Example 5, the volume resistivity of the resin compositions in Examples 1-3 is in a more preferred range. Therefore, the result is that a polyester resin composition with better laser marking properties can be obtained.

[0140] Compared with Example 3, Example 4 shows that by containing compound (F), a polyester resin composition with excellent electromagnetic wave absorption, mechanical strength and laser marking properties, as well as excellent hydrolysis resistance, can be obtained.

[0141] Compared with Example 3, Example 6 uses a masterbatch of (B) carbon nanotubes, which improves the dispersibility of (B) carbon nanotubes. As a result, a polyester resin composition with better electromagnetic wave absorption, mechanical strength and laser marking properties can be obtained.

[0142] Compared with Example 6, Example 7 shows that by including component (E), a polyester resin composition with excellent electromagnetic wave absorption, mechanical strength and laser marking properties, as well as excellent hydrolysis resistance, can be obtained.

[0143] Compared with Example 6, Examples 9 and 10 show that polyester resin compositions with better laser marking properties can be obtained by including component (D).

Claims

1. A thermoplastic polyester resin composition, wherein, Relative to 100 parts by weight of (A) thermoplastic polyester resin, 0.1 to 5 parts by weight of (B) carbon nanotubes are mixed in, wherein the carbon nanotubes exhibit a high-temperature combustion peak above 650°C and below 900°C when subjected to thermogravimetric analysis in air at a temperature increase of 10°C / min.

2. The thermoplastic polyester resin composition according to claim 1, when the thermoplastic polyester resin composition is molded into a 3mm thick square plate and measured by the free space method in the frequency band of 60~90GHz, the reflection loss S11 is less than -3dB and the transmission loss S21 is less than -20dB.

3. The thermoplastic polyester resin composition according to claim 1 or 2, wherein the volume resistivity is 1.0 × 10⁻⁶. 5 ~1.0×10 15 Ω·m.

4. The thermoplastic polyester resin composition according to claim 1 or 2, wherein, relative to 100 parts by weight of (A) thermoplastic polyester resin, 1 to 100 parts by weight of (D) vinyl copolymer is further mixed.

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

6. The thermoplastic polyester resin composition according to claim 1 or 2, wherein, relative to 100 parts by weight of (A) thermoplastic polyester resin, 0.1 to 10 parts by weight of (F) a compound having two or more functional groups capable of reacting with carboxyl groups is also mixed.

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

8. The thermoplastic polyester resin composition according to claim 1 or 2, wherein it has electromagnetic wave absorption properties.

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

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