Thermoplastic polyester resin composition and molded article

Abstract

The present invention provides a thermoplastic polyester resin composition which contains 0.1 part by weight to 10 parts by weight of (B) a compound which has two or more functional groups that are reactive with a carboxyl group in each molecule, and 0.1 part by weight to 25 parts by weight of (C) a carbon-based nanofiller per 100 parts by weight of (A) a thermoplastic polyester resin, wherein the content of metal components in the resin composition is 1,000 ppm or less. Consequently, a polyester resin composition which enables the achievement of a molded article that has high electromagnetic wave absorbing properties, excellent mechanical strength and excellent hydrolysis resistance is achieved by the present invention.

Description

Thermoplastic polyester resin composition and molded article

[0001] The present invention relates to a polyester resin composition having excellent electromagnetic wave absorption properties, mechanical strength, and hydrolysis resistance, and a molded article thereof.

[0002] Thermoplastic polyester resins, particularly polybutylene terephthalate-based resins, are excellent in injection moldability, light weight, moldability, mechanical properties, and heat resistance, and are therefore widely used in housings and structural members of office automation equipment, communication equipment, electric and electronic equipment, and automotive electrical equipment, 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 of electromagnetic waves, the more likely they are to emit noise when they are transmitted, which can cause problems such as malfunctions in communication devices and automotive electrical equipment due to a worsening internal noise environment.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 radio wave absorption properties while maintaining excellent injection moldability, light weight, moldability, mechanical properties, and heat resistance.

[0006] To address the above-mentioned problems, Patent Document 1 discloses an electromagnetic wave shielding / absorbing molded article made of a thermoplastic resin composition containing a thermoplastic resin and carbon black.

[0007] Furthermore, Patent Document 2 discloses a resin composition for a radar cover, which comprises carbon nanotubes and a polymer.

[0008] Japanese Patent Application Laid-Open No. 2019-161210 Japanese Patent Application Laid-Open No. 2017-507211

[0009] Thermoplastic polyester resins deteriorate due to hydrolysis. To be used as industrial materials for machine parts, electrical and communication parts, automobile parts, and the like, they are required to have long-term hydrolysis resistance in addition to mechanical properties and electromagnetic wave absorption. However, in Patent Document 1, a large amount of graphite is added, which reduces the mechanical strength of the resin composition and also results in insufficient hydrolysis resistance. In Patent Document 2, although the electromagnetic wave absorption and mechanical strength are good, the hydrolysis resistance of the resin composition is insufficient.

[0010] 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 hydrolysis resistance of molded articles produced from the composition, and to provide molded articles made from the composition.

[0011] In order to solve the above problems, the present invention has the following features. (1) A thermoplastic polyester resin composition comprising 100 parts by weight of (A) a thermoplastic polyester resin, 0.1 to 10 parts by weight of (B) a compound having two or more functional groups reactive with carboxyl groups in its molecule, and 0.1 to 25 parts by weight of (C) a carbon-based nanofiller, wherein the content of metal components in the resin composition is 1000 ppm or less. (2) The thermoplastic polyester resin composition according to (1), wherein the thermoplastic polyester (A) is primarily composed of polybutylene terephthalate. (3) The thermoplastic polyester resin composition according to (1) or (2), wherein the compound (B) having two or more functional groups reactive with carboxyl groups in its molecule is an epoxy compound. (4) The thermoplastic polyester resin composition according to any one of (1) to (3), wherein the carbon-based nanofiller (C) is a carbon nanotube. (5) The thermoplastic polyester resin composition according to any one of (1) to (4), wherein the metal component in the resin composition is at least one selected from aluminum, magnesium, and iron. (6) The thermoplastic polyester resin composition according to any one of (1) to (5), which has electromagnetic wave absorbing properties. (7) A molded article obtained by molding the thermoplastic polyester resin composition according to any one of (1) to (6).

[0012] The present invention can provide a resin composition that can be used to obtain molded articles having high electromagnetic wave absorption properties, excellent mechanical strength, and excellent hydrolysis resistance. Therefore, the thermoplastic polyester resin composition of the present invention is useful as an electromagnetic wave-absorbing molded article for various applications.

[0013] The present invention will be described in detail below.

[0014] The thermoplastic polyester resin (A) used in the present invention is a polymer or copolymer having, as its main structural unit, at least one residue selected from the group consisting of (1) residues of dicarboxylic acids or their ester-forming derivatives and residues of diols or their ester-forming derivatives, (2) residues of hydroxycarboxylic acids or their ester-forming derivatives, and (3) residues of lactones. Here, "having as the main structural unit" refers to the presence of at least one residue selected from the group consisting of (1) to (3) above in 50 mol % or more of all structural units. A preferred embodiment is one in which 80 mol % or more of these residues are present. Among these, polymers or copolymers having, as their main structural units, (1) residues of dicarboxylic acids or their ester-forming derivatives and residues of diols or their ester-forming derivatives are preferred because of their superior mechanical properties and heat resistance.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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 terephthalic acid, naphthalenedicarboxylic acid or an ester-forming derivative thereof and a residue of an aliphatic diol selected from ethylene glycol, propylene glycol, and 1,4-butanediol or an ester-forming derivative thereof are even more preferred.

[0019] 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 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. In terms of an excellent balance between mechanical properties and moldability, polybutylene terephthalate is even more preferred. In addition, these two or more types can be used in any content, 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.

[0020] 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.

[0021] 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 it can improve fluidity. The weight average molecular weight (Mw) 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 measured by gel permeation chromatography (GPC) using hexafluoroisopropanol as a solvent, converted into polymethyl methacrylate (PMMA).

[0022] 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.

[0023] 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. Furthermore, either polymerization by transesterification or direct polymerization can be applied. From the viewpoint of productivity, continuous polymerization is preferred, and direct polymerization is more preferred.

[0024] 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.

[0025] The thermoplastic polyester resin composition of the present invention (hereinafter referred to as the resin composition of the present invention) further contains (B) a compound having two or more functional groups within the molecule capable of reacting with carboxyl groups (hereinafter sometimes referred to as the (B) compound). The (A) thermoplastic polyester resin is susceptible to decomposition of ester bonds by hydrolysis, resulting in an increase in the carboxyl group concentration of the thermoplastic polyester resin composition. As the carboxyl group concentration increases, a decrease in the molecular weight of the (A) thermoplastic polyester resin is promoted, resulting in a decrease in mechanical properties. In the present invention, by blending the (B) compound 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 (B) compound, thereby suppressing an increase in the carboxyl group concentration. As a result, the high mechanical properties of the (A) thermoplastic polyester resin can be maintained.

[0026] Examples of the compound (B) include an epoxy compound, an oxazoline compound, and a carbodiimide compound.

[0027] The epoxy compound is a compound having an epoxy group as a functional group capable of reacting with a carboxyl group, and 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 type epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, alicyclic epoxy resins, heterocyclic epoxy resins, and glycidyl group-containing copolymers having an α-olefin and a glycidyl ester of an α,β-unsaturated acid as copolymerization components. These may be used alone or in combination of two or more types.

[0028] 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.

[0029] 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.

[0030] A specific example of the bisphenol A type epoxy is jER1004 (manufactured by Mitsubishi Chemical Corporation), and a specific example of the bisphenol F type epoxy is jER4005P (manufactured by Mitsubishi Chemical Corporation).

[0031] Specific examples of novolac type epoxies include phenol novolac type epoxies, cresol novolac type epoxies, naphthol novolac type epoxies, bisphenol A novolac type epoxies, dicyclopentadiene-phenol adduct novolac type epoxies, dimethylenephenylene-phenol adduct novolac type epoxies, and dimethylenebiphenylene-phenol adduct novolac type epoxies.

[0032] A specific example of the phenol novolac type epoxy is EPPN-201 (manufactured by Nippon Kayaku Co., Ltd.), a specific example of the cresol novolac type epoxy is EOCN-102S (manufactured by Nippon Kayaku Co., Ltd.), and a specific example of the dicyclopentadiene-phenol adduct novolac type epoxy is HP7200H (manufactured by DIC Corporation).

[0033] 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.

[0034] 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.

[0035] 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.

[0036] Examples of the alicyclic epoxy resin include compounds having a cyclohexene oxide group, a tricyclodecene oxide group, and a cyclopentene oxide group.

[0037] Examples of heterocyclic epoxy resins include epoxy resins produced from epichlorohydrin and hydantoin or isocyanuric acid.

[0038] Among these, glycidyl ether type epoxy resins are preferred from the viewpoint of being able to suppress the reaction between epoxy groups of the compound (B) and to suppress the deterioration of retention stability.

[0039] Examples of oxazoline compounds include compounds having an oxazoline group as a functional group reactive 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.

[0040] The carbodiimide compound is a compound containing a carbodiimide group as a functional group capable of reacting with a carboxyl group, and examples thereof 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'-dimethylphenylcarbodiimide). Examples of suitable polycarbodiimides include poly(1,3,5-triisopropylbenzene)polycarbodiimide, poly(1,3,5-triisopropylbenzene)polycarbodiimide, poly(1,3,5-triisopropylbenzene)polycarbodiimide, poly(1,5-diisopropylbenzene)polycarbodiimide, poly(triethylphenylenecarbodiimide), and poly(triisopropylphenylenecarbodiimide).

[0041] 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 terminal of the (A) thermoplastic polyester resin, suppress post-crystallization during hydrolysis of the resin composition, and further improve hydrolysis resistance.

[0042] In the resin composition of the present invention, the content of the (B) compound is 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. If the content of the (B) compound is less than 0.1 parts by weight, hydrolysis resistance decreases. The content is more preferably 0.3 parts by weight or more, more preferably 0.4 parts by weight or more, and even more preferably 0.5 parts by weight or more. On the other hand, if the content of the (B) compound exceeds 10 parts by weight, mechanical strength and retention stability decrease, and thickening makes production difficult. The content is more preferably 8 parts by weight or less, and even more preferably 5 parts by weight or less.

[0043] The resin composition of the present invention further contains (C) a carbon-based nanofiller. By including (C) the carbon-based nanofiller, the strength of the resin composition can be improved while improving its electromagnetic wave absorption. Examples of (C) the carbon-based nanofiller include anisotropic carbon-based nanofillers such as carbon nanofibers, carbon nanohorns, carbon nanocones, carbon nanotubes, carbon nanocoils, carbon nanotwists, carbon nanoballoons, carbon nanowalls, graphene, nanographene, graphene nanoribbons, and derivatives thereof, as well as fullerenes and their derivatives. These carbon-based nanofillers may be used alone or in combination of two or more.

[0044] Furthermore, among such carbon-based nanofillers, anisotropic carbon-based nanofillers are preferred because they are more likely to cause dielectric loss and can further improve radio wave absorption, and carbon nanofibers, carbon nanohorns, carbon nanocones, carbon nanotubes, carbon nanocoils, carbon nanowalls, and carbon nanochaplet are more preferred from the viewpoint of further improving thermal conductivity, with carbon nanofibers, carbon nanohorns, carbon nanotubes, and carbon nanocoils being particularly preferred.

[0045] The average diameter of such (C) carbon-based nanofiller 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 likely to occur, and radio wave absorption can be further improved. Furthermore, the average diameter of the (C) carbon-based nanofiller is preferably 0.1 nm or more, more preferably 0.5 nm or more, and particularly preferably 1.0 nm or more. If the average diameter is 0.1 nm or more, bundles are less likely to form and the nanofiller is more easily finely dispersed in the resin composition, thereby further improving mechanical strength and radio wave absorption. The average diameter was calculated by observing the (C) carbon-based nanofiller under a transmission electron microscope, measuring the diameters of 100 or more (C) carbon-based nanofillers, and averaging the results. When the cross section of the (C) carbon-based nanofiller is not circular, e.g., flat, the average of the minor axis and major axis was used as the diameter. (C) When the carbon nanofiller is a substance with a large aspect ratio, such as a carbon nanofiber or a carbon nanotube, the diameter is the cross-sectional diameter of the longitudinal direction of the shape.

[0046] Many (C) carbon-based nanofillers contain metal components derived from synthetic catalysts, such as iron, cobalt, chromium, manganese, molybdenum, tungsten, vanadium, tin, copper, calcium, and nickel, as well as metal components derived from catalyst supports, such as magnesium compounds, silicon oxide, aluminum oxide, zeolite, and titanium oxide. The inventors have discovered that these metal components promote the hydrolysis of the (A) thermoplastic polyester resin by the terminal carboxyl groups of the polyester resin, promote the self-reaction of the functional groups of the (B) compound, and inhibit the reaction between the terminal carboxyl groups of the (A) thermoplastic polyester resin and the functional groups of the (B) compound, thereby reducing the hydrolysis resistance of the resin composition. In the present invention, reducing the content of metal components in the (C) carbon-based nanofiller is preferable because it allows the content of metal components in the resin composition to be reduced, as described below, thereby improving the hydrolysis resistance of the resin composition. In particular, it is preferable that the content of metals selected from iron, magnesium, and aluminum as metal components derived from catalyst carriers such as iron, magnesium compounds, aluminum oxide, zeolite, and titanium oxide, which are free and not incorporated into the carbon-based nanofiller after synthesis and which tend to adversely affect the terminal carboxyl groups of (A) the thermoplastic polyester resin and the functional groups of (B) the compound, is low.The metal components in (C) the carbon-based nanofiller can be identified by elemental analysis using fluorescent X-rays.

[0047] The amount of metal component contained in the (C) carbon-based nanofiller is preferably 2 wt% or less relative to 100 wt% of the (C) carbon-based nanofiller. By setting the amount of metal component in the (C) carbon-based nanofiller to 2 wt% or less, the content of metal component in the resin composition can be reduced, which suppresses hydrolysis of the polyester resin due to carboxyl groups present at the terminals of the (A) thermoplastic polyester resin and also suppresses self-reaction of the functional groups of the (B) compound, thereby improving the reactivity between the carboxyl groups of the (A) thermoplastic polyester resin and the functional groups of the (B) compound, thereby improving hydrolysis resistance.

[0048] (C) The method for reducing the amount of metal components contained in the carbon-based nanofiller to 2% by weight or less is not particularly limited, but examples include a method for producing a carbon-based nanofiller without using a catalyst support such as a magnesium compound, silicon oxide, aluminum oxide, zeolite, or titanium oxide, a method for adding an acid to the carbon-based nanofiller to dissolve and remove the metal, or a method for removing the metal components by passing the carbon-based nanofiller through a magnetic field.

[0049] The amount of metal components contained in the carbon nanofiller can be measured as the amount of metal elements using a fluorescent X-ray analyzer.

[0050] The content of the carbon-based nanofiller (C) in the present invention is 0.1 to 25 parts by weight per 100 parts by weight of the thermoplastic polyester resin (A). If the content of the carbon-based nanofiller (C) is less than 0.1 part by weight, the electromagnetic wave absorption properties decrease. It is preferably 2 parts by weight or more, and more preferably 3 parts by weight or more. Furthermore, if the content of the carbon-based nanofiller (C) exceeds 25 parts by weight, the mechanical strength and fluidity decrease. It is preferably 20 parts by weight or less, more preferably 15 parts by weight or less, and even more preferably 10 parts by weight or less.

[0051] The resin composition of the present invention preferably further contains (D) a fibrous reinforcing material. By containing (D) a fibrous reinforcing material, the mechanical strength of the molded article can be improved. Examples of (D) a fibrous reinforcing material include glass fiber, aramid fiber, and cellulose fiber, with glass fiber being particularly preferred. In the present invention, among (D) a fibrous reinforcing material, a compound that also corresponds to (C) a carbon-based nanofiller, such as carbon nanofiber, is treated as component (C).

[0052] The cross section of the (D) fibrous reinforcing material may be either circular or flat. Hollow fibers may also be used for the purpose of reducing the specific gravity, etc. As the cross section of the (D) fibrous reinforcing material increases, a sufficient reinforcing effect cannot be obtained. On the other hand, if the cross section is too small, it becomes difficult to manufacture the fibrous reinforcing material, and there is also the problem that it becomes difficult to handle. The cross section of the (D) fibrous reinforcing material in the present invention 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.

[0053] The fiber length of the (D) fibrous reinforcing material is not particularly limited. In order to minimize the amount of deformation of a molded article, a shorter fiber length is preferable, taking into account the balance between the mechanical properties and deformation suppression of the molded article. However, in terms of mechanical properties, the fiber length is preferably 30 μm or more, and preferably 50 to 1000 μm depending on the required performance.

[0054] In the fibrous reinforcing material (D) 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 subject the fibrous reinforcing material to surface treatment or sizing treatment, or may be added simultaneously with the fibrous reinforcing material during material preparation.

[0055] When the resin composition of the present invention contains (D) a fibrous reinforcing material, the content thereof is preferably 1 part by weight or more and 100 parts by weight or less per 100 parts by weight of (A) the thermoplastic polyester resin. If the content of (D) a fibrous reinforcing material is 1 part by weight or more, the mechanical strength of the molded article can be improved. The content is preferably 10 parts by weight or more, more preferably 20 parts by weight or more. Furthermore, if the content of (D) a fibrous reinforcing material is 100 parts by weight or less, a decrease in fluidity can be suppressed. The content is preferably 80 parts by weight or less, more preferably 50 parts by weight or less.

[0056] The resin composition of the present invention preferably further contains a vinyl copolymer (E). The inclusion of the vinyl copolymer (E) improves dimensional stability, thereby stabilizing the radio wave absorption properties of the molded product regardless of molding conditions. The vinyl copolymer (E) used in the present invention is a copolymer containing, as structural units, at least units derived from an unsaturated nitrile monomer and units derived from an aromatic vinyl monomer, and can also be copolymerized with other copolymerizable monomers as needed. Generally, these vinyl copolymers (E) are produced by emulsion polymerization, bulk polymerization, or bulk / suspension polymerization, but are not limited thereto.

[0057] The unsaturated nitrile monomer used in the (E) vinyl copolymer is not particularly limited, and examples thereof include acrylonitrile, methacrylonitrile, and ethacrylonitrile, with acrylonitrile being preferred. The aromatic vinyl monomer is 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 acrylonitrile as the unsaturated nitrile monomer and styrene as the aromatic vinyl monomer, with 15% by mass or less of other copolymerizable monomers, is preferred. The (E) vinyl copolymer may contain a rubbery polymer to the extent that it does not significantly impair scratch resistance. These include resins obtained by grafting a rubbery polymer with an unsaturated nitrile monomer and an aromatic vinyl monomer, 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 (E) 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, and ethylene-methyl acrylate copolymer. Of these rubbery polymers, acrylic rubber is preferred.

[0058] Furthermore, in order to improve compatibility with the (A) thermoplastic polyester resin, the (E) vinyl copolymer is preferably copolymerized with a raw material monomer that forms a glycidyl group-containing vinyl unit. Specific examples of raw material monomers that form 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. In the present invention, even if a vinyl copolymer is copolymerized with a raw material monomer that forms a glycidyl group-containing vinyl unit and thus also falls under the category of compound (B), it is treated as component (E).

[0059] When the resin composition of the present invention contains (E) a vinyl copolymer, its content 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 content of (E) vinyl copolymer is 1 part by weight or more, dimensional stability can be improved and the radio wave absorption of the molded product can be stabilized regardless of molding conditions. The content is preferably 10 parts by weight or more, more preferably 20 parts by weight or more. Furthermore, if the content of (E) vinyl copolymer is 100 parts by weight or less, a decrease in heat resistance can be suppressed. The content is preferably 80 parts by weight or less, more preferably 50 parts by weight or less.

[0060] The resin composition of the present invention is characterized in that the metal component content is 1000 ppm or less. If the metal component content exceeds 1000 ppm, hydrolysis of the polyester resin due to the carboxyl groups present at the terminals of the (A) thermoplastic polyester resin is promoted, and the self-reaction of the functional groups of the (B) compound is promoted, preventing the carboxyl groups of the (A) thermoplastic polyester resin from reacting with the functional groups of the (B) compound, resulting in a decrease in the hydrolysis resistance of the resin composition. The metal component content is preferably 500 ppm or less, and more preferably 100 ppm or less. The lower limit of the metal component content is 0 ppm.

[0061] The content of the metal component in the resin composition can be determined by, for example, atomic absorption spectrometry.

[0062] The method for reducing the metal component content in the resin composition to 1000 ppm or less is not particularly limited, but for example, the use of a carbon-based nanofiller (C) with a low metal component content as described above can be mentioned. When the metal component in the resin composition is a component derived from the carbon-based nanofiller (C), the type is at least one selected from iron, magnesium, and aluminum. Therefore, the total content of metal components selected from iron, magnesium, and aluminum in the resin composition is preferably 1000 ppm or less, more preferably 500 ppm or less, and even more preferably 100 ppm or less.

[0063] The resin composition of the present invention may contain a thermoplastic resin other than component (A) to the extent that the object of the present invention is not impaired, 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, polyvinyl alcohol resins, and polyolefin resins. When the resin composition of the present invention contains a thermoplastic resin other than component (A), the content thereof is preferably 1 part by weight or more and 50 parts by weight or less per 100 parts by weight of the thermoplastic polyester resin (A).

[0064] Furthermore, the 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.

[0065] The resin composition of the present invention can be obtained, for example, by melt-kneading the components (A) and (B) and, if necessary, other components.

[0066] Examples of the melt-kneading method include a method in which (A) the thermoplastic polyester resin, (B) the metal salt, and various additives are premixed, and the mixture is fed to an extruder or the like and thoroughly melt-kneaded; or a method in which a predetermined amount of each component is fed to an extruder or the like using a metering feeder such as a weight feeder, and thoroughly melt-kneaded.

[0067] 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.

[0068] Alternatively, a carbon-based nanofiller masterbatch can be prepared by blending (C) the carbon-based nanofiller in a high concentration in advance with a thermoplastic polyester resin, and then subjected to the melt-kneading. The use of a carbon-based nanofiller masterbatch is preferred from the viewpoints of ease of handling and uniform dispersion of the carbon-based nanofiller. In this case, the thermoplastic resin used to prepare the carbon-based nanofiller masterbatch may be the thermoplastic polyester resin (A), or a resin other than the component (A), such as a polyamide resin, a polycarbonate resin, a styrene-based resin, or a polyethylene resin. From the viewpoints of ease of dispersion of a high concentration of carbon-based nanofiller and ease of preparation of a masterbatch, it is preferable to prepare a masterbatch using the thermoplastic polyester resin (A).

[0069] The (D) fibrous reinforcing material may be added by installing a side feeder between the base and vent of a multi-screw extruder such as a twin-screw extruder. In the case of a liquid additive, a method of adding the additive using a plunger pump by installing a liquid addition nozzle between the base and vent of a multi-screw extruder such as a twin-screw extruder, or a method of supplying the additive from the base using a metering pump may be used.

[0070] The resin composition of the present invention is preferably pelletized before being subjected to molding processing. Examples of the pelletization method include melt-kneading the components constituting the resin composition using, for example, a single-screw extruder equipped with a "Unimelt" or "Dulmage" type screw, a twin-screw extruder, a triple-screw extruder, a conical extruder, or a kneader-type kneader, and then discharging the mixture in the form of strands and cutting them with a strand cutter.

[0071] The resin composition of the present invention can be melt-molded to obtain films, fibers, and other molded articles in various shapes. Examples of melt-molding methods include injection molding, extrusion molding, and blow molding, with injection molding being particularly preferred.

[0072] 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.

[0073] The resin composition of the present invention has high electromagnetic wave absorption, excellent mechanical strength, and excellent hydrolysis resistance. 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 in various applications such as automobile parts, machine parts, and electrical and electronic parts, taking advantage of these characteristics.

[0074] Specific applications include junction boxes, LiBs, insulators, air flow meters, air pumps, thermostat housings, engine mounts, ignition hubpins, 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, actuator cases for ABS, tops and bottoms of radiator tanks, 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.

[0075] Among these, the material can be suitably used for housings and brackets for sensing components such as ECU housings, HUD housings, rotation sensors, pressure sensors, acceleration sensors, millimeter-wave radar, and ultrasonic sensors, which require particularly high electromagnetic wave absorption properties, and for these internal components; notebook computer housings and internal components; CRT display housings and internal components; printer housings and internal components; portable terminal housings and internal components for mobile phones, mobile PCs, handheld mobile devices, and the like; housings and internal components for recording medium (CD, DVD, PD, FDD, etc.) drives; housings and internal components for copy machines; housings and internal components for facsimiles; and housings and internal components for communication electrical and electronic components such as base stations, data communication modules, and various antennas.

[0076] Furthermore, in the evaluation of electromagnetic wave absorption of the resin composition of the present invention, S21 at a thickness of 2 mm is preferably 7 dB or more, more preferably 10 dB or more, as measured by the method described below. If S21 is 7 dB or more, incident radio waves are attenuated by 80% or more and transmitted radio waves are 20% or less, thereby protecting communication equipment and automotive electrical equipment from electromagnetic noise in the surrounding environment. If S21 is 10 dB or more, the electromagnetic wave shielding rate is attenuated by 90% or more and transmitted radio waves are 10% or less, thereby further improving the reliability of protecting equipment from electromagnetic noise in the surrounding environment.

[0077] Furthermore, the resin composition of the present invention preferably has a tensile strength retention of 60% or more, more preferably 70% or more, of a molded article after treatment at a temperature of 121°C and a humidity of 100% RH for 50 hours (PCT50h treatment), measured by the method described below. If the PCT50h treatment tensile strength retention is 60% or more, sufficient strength for practical use can be maintained even in applications exposed to high temperature and high humidity conditions, such as automotive parts, electrical and electronic parts, etc. If the PCT50h treatment tensile strength retention is 70% or more, the reliability of the product can be further improved.

[0078] Next, the present invention will be described in more detail by way of examples, but these are not intended to limit the present invention.

[0079] The abbreviations of the main raw materials used in the examples and their contents are summarized below.

[0080] (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).

[0081] (B) Compounds having two or more functional groups capable of reacting with carboxyl groups in the molecule B-1: Epoxy resin (manufactured by DIC Corporation, HP7200H) B-2: Epoxy resin (manufactured by Mitsubishi Chemical Corporation, jER1004).

[0082] (C) Carbon nanofiller C-1: Carbon nanotube A (average diameter: 15 nm, BET specific surface area: 187 m ２ / g, composition: carbon 96 mass%, magnesium 1.27 mass%, aluminum 0.70 mass%, iron 2.00 mass%) C-2: carbon nanotube B (average diameter: 13 nm, BET specific surface area 191 m ２ / g, composition: carbon 98% by mass, magnesium 0.001% by mass, aluminum 0.620% by mass, iron 0.630% by mass) C-3: carbon nanotube masterbatch Using a co-rotating vented twin-screw extruder with a screw diameter of 30 mm and L / D 35 (manufactured by The Japan Steel Works, TEX-30α), 17.6 parts by weight of C-2 (carbon nanotube B) were melt-kneaded with respect to 100 parts by weight of A-1 (polybutylene terephthalate) under conditions of a cylinder temperature of 250 ° C. and a screw rotation speed of 150 rpm, and pelletized with a strand cutter. Then, the mixture was vacuum-dried at a temperature of 110 ° C. for 6 hours to obtain carbon nanotube masterbatch pellets. The metal component content in the (C) carbon-based nanofiller was measured using a Simultix fluorescent X-ray analyzer manufactured by RIGAKU Corporation.

[0083] (D) Fibrous reinforcing material D-1: Round cross section chopped strand type glass fiber (manufactured by Nippon Electric Glass Co., Ltd., ECS03T187).

[0084] (E) Vinyl Copolymer E-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).

[0085] The evaluation methods used in the examples and comparative examples are summarized below.

[0086] (1) Metal Content of Resin Composition 0.2 g of the resin composition was added to 10 ml of sulfuric acid, and nitric acid was further added until decomposition of the resin composition was complete. The solution was filtered, and the metal content of the obtained filtrate was quantified using an atomic absorption spectrophotometer (ZA3300 manufactured by Hitachi High-Technologies Corporation).

[0087] (2) Tensile Properties: Using an SE50-DUZ injection molding machine manufactured by Sumitomo Heavy Industries, Ltd., 4 mm thick ISO-1A dumbbell test pieces for evaluating tensile properties were obtained. (A) When the thermoplastic polyester resin was polybutylene terephthalate, injection molding was performed under molding cycle conditions of a molding temperature of 260°C, a mold temperature of 80°C, a total injection time and dwell time of 10 seconds, and a cooling time of 10 seconds. (A) When the thermoplastic polyester resin was polyethylene terephthalate, injection molding was performed under molding cycle conditions of a molding temperature of 280°C, a mold temperature of 120°C, a total injection time and dwell time of 20 seconds, and a cooling time of 20 seconds. Furthermore, the obtained test pieces for evaluating tensile properties were measured for maximum tensile strength (tensile strength) and maximum tensile elongation (tensile elongation) in accordance with ISO 527-1, 2 (2012) using a tensile testing machine (Autograph AG-50kNXPlus) manufactured by Shimadzu Corporation. The average values ​​of the measurements for three test pieces were used as the values ​​for tensile strength and tensile elongation. Materials with large values ​​for tensile strength and tensile elongation were judged to have excellent mechanical properties.

[0088] (3) Hydrolysis Resistance Using an SE50-DUZ injection molding machine manufactured by Sumitomo Heavy Industries, Ltd., 4 mm thick ISO-1A dumbbell test pieces for evaluating tensile properties were obtained under the same molding conditions as those for the tensile properties described in (2). The obtained ISO dumbbell test pieces were subjected to moist heat treatment for 50 hours in a highly accelerated life tester EHS-411 manufactured by Espec Corporation, set at a temperature of 121°C and a humidity of 100% RH. The maximum tensile strength (tensile strength) of the molded pieces after moist heat treatment was measured under the same conditions as those for the tensile test described in (2), and the average value of the measurements for three test pieces was recorded as the tensile strength. The value of the maximum tensile strength after moist heat treatment relative to the maximum tensile strength before moist heat treatment (untreated moist heat treatment), expressed as a percentage, 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.

[0089] (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 2 mm was molded under the same molding conditions as those for the tensile properties in section (2).

[0090] The electromagnetic wave absorbency was measured by using a network analyzer ME7838A manufactured by Anritsu Corp., and the S21 value was calculated from the measurement results of the incident wave and the transmitted wave to the radio wave absorbency evaluation test piece by the S parameter method. It was determined that the larger the S21 value, i.e., the larger the attenuation rate, the better the radio wave absorbency.

[0091] Examples 1-12, Comparative Examples 1-9: Using a co-rotating, vented twin-screw extruder (TEX-30α, manufactured by Japan Steel Works, Ltd.) with a screw diameter of 30 mm and an L / D ratio of 35, all raw materials except for (D) fibrous reinforcing material, i.e., (A) thermoplastic polyester resin, (B) compound, (C) carbon-based nanofiller, and other raw materials, were mixed in the compositions shown in Tables 1 and 2 and added to the twin-screw extruder's base feeder. (D) Fibrous reinforcing material was added using a side feeder installed midway between the base feeder and the vent. When the (A) thermoplastic polyester resin was polybutylene terephthalate, melt mixing was performed at a mixing temperature of 250°C and a screw rotation of 150 rpm. When the (A) thermoplastic polyester resin was polyethylene terephthalate, melt mixing was performed at a mixing temperature of 260°C and a screw rotation of 150 rpm. The melt-mixed resin composition was extruded into strands, passed through a cooling bath, and pelletized using a strand cutter.

[0092] In Examples 10 and 11, melt kneading was performed using C-3: carbon nanotube masterbatch as a raw material. In Example 10, 1.2 parts by weight of (B) compound and 4.0 parts by weight of (C) carbon-based nanofiller were blended with 100 parts by weight of (A) thermoplastic polyester resin. In Example 11, 1.2 parts by weight of (B) compound and 8.5 parts by weight of (C) carbon-based nanofiller were blended with 100 parts by weight of (A) thermoplastic polyester resin.

[0093] 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.

[0094]

[0095]

[0096] In comparison with Comparative Examples 1 to 6, Examples 1 to 11 contained specific amounts of (A) thermoplastic polyester resin, (B) compound, and (C) carbon-based nanofiller, and by controlling the metal content of the resin composition to a specific concentration or less, polyester resin compositions excellent in all of electromagnetic wave absorption properties, mechanical strength, and hydrolysis resistance could be obtained.

[0097] More specifically, in Examples 2, 5, and 8, the content of the (C) carbon-based nanofiller was in a more preferable range compared to Examples 1 and 9, and as a result, a polyester resin composition having excellent radio wave absorption properties, mechanical strength, and hydrolysis resistance was obtained.

[0098] In Example 5, the content of the carbon-based nanofiller (C) was in a more preferable range compared to Examples 2, 8, and 9. As a result, a polyester resin composition excellent in all of radio wave absorption properties, mechanical strength, and hydrolysis resistance was obtained.

[0099] In Example 5, the content of compound (B) was in a more preferable range compared to Examples 3 and 4, and as a result, a polyester resin composition was obtained which was superior in all of radio wave absorption properties, mechanical strength, and hydrolysis resistance.

[0100] In comparison with Example 5, Examples 10 and 11 used a masterbatch of (C) carbon-based nanofiller, which improved the dispersibility of (C) carbon-based nanofiller. As a result, a polyester resin composition was obtained that was superior in all of radio wave absorption properties, mechanical strength, and hydrolysis resistance.

[0101] In Example 12, a polyester resin composition excellent in all of electromagnetic wave absorption, mechanical strength, and hydrolysis resistance was obtained by incorporating specific amounts of (A) thermoplastic polyester resin, (B) compound, and (C) carbon-based nanofiller, and by controlling the metal content of the resin composition to a specific concentration or less, compared to Comparative Examples 7 to 9. Note that Comparative Example 4 experienced significant viscosity increase during kneading in a twin-screw extruder, making injection molding difficult.

Claims

1. A resin composition obtained by blending 0.1 to 10 parts by weight of (B) a compound having two or more functional groups capable of reacting with a carboxyl group in its molecule, and 0.1 to 25 parts by weight of (C) a carbon-based nanofiller with 100 parts by weight of (A) a thermoplastic polyester resin, wherein (B) the compound having two or more functional groups capable of reacting with a carboxyl group in its molecule is an epoxy compound, and (C) the carbon-based nanofiller is a carbon nanotube, and the content of metal components in the resin composition is 1000 ppm or less.

2. The thermoplastic polyester resin composition according to claim 1, wherein the thermoplastic polyester resin (A) is composed mainly of polybutylene terephthalate.

3. 3. The thermoplastic polyester resin composition according to claim 1, wherein the metal component in the resin composition is at least one selected from the group consisting of aluminum, magnesium, and iron.

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

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