Polyester resin composition and resin molded article

Abstract

Disclosed is a polyester resin composition that contains a polybutylene terephthalate resin (A) and a polyethylene terephthalate resin (B). The amount of terminal hydroxyl groups in the polybutylene terephthalate resin (A) is 30-70 mmol / kg with respect to the total amount of the polybutylene terephthalate resin (A) and the polyethylene terephthalate resin (B).

Description

Polyester resin composition and resin molded article

[0001] An embodiment of the present invention relates to a polyester resin composition and a resin molded article.

[0002] Polybutylene terephthalate resin (hereinafter also referred to as "PBT resin") has excellent properties such as mechanical properties, electrical properties, heat resistance, chemical resistance, and solvent resistance, and is therefore widely used as an engineering plastic for various applications such as automotive parts, electrical and electronic parts, etc.

[0003] In recent years, there has been an increasing demand for miniaturization, weight reduction, and improved appearance of various parts, and PBT resins are often alloyed with low-crystalline polyester resins such as polyethylene terephthalate resin (hereinafter also referred to as "PET resin") and polycarbonate resin to improve the appearance (surface gloss, low roughness, etc.) and low warpage of molded articles. Patent Documents 1 and 2 describe resin compositions containing PBT resin and PET resin.

[0004] International Publication No. 2020 / 246335 JP 8-183114 Publication

[0005] An object of an embodiment of the present invention is to provide a polyester resin composition having excellent mold releasability, and a resin molded article obtained using the same.

[0006] One embodiment of the present invention relates to a polyester resin composition comprising a polybutylene terephthalate resin (A) and a polyethylene terephthalate resin (B), wherein the amount of terminal hydroxyl groups in the polybutylene terephthalate resin (A) is 30 to 70 mmol / kg relative to the total amount of the polybutylene terephthalate resin (A) and the polyethylene terephthalate resin (B). Another embodiment of the present invention relates to a resin molded article obtained using the polyester resin composition.

[0007] According to an embodiment of the present invention, it is possible to provide a polyester resin composition having excellent mold releasability, and a resin molded article obtained using the same.

[0008] Fig. 1 is a perspective view schematically showing a molded article used to evaluate mold releasability in the examples. Fig. 2 is a plan view schematically showing a test piece used to evaluate post-shrinkage in the examples.

[0009] Preferred embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments.

[0010] <Polyester Resin Composition> The polyester resin composition of the present embodiment is a polyester resin composition containing a PBT resin (A) and a PET resin (B), in which the amount of terminal hydroxyl groups in the PBT resin (A) is 30 to 70 mmol / kg relative to the total amount of the PBT resin (A) and the PET resin (B).

[0011] In resin compositions containing PBT resin and PET resin, transesterification tends to occur between the PBT resin and the PET resin under high-temperature conditions, such as during melting. If the transesterification reaction proceeds excessively, the melting point and crystallization temperature of the resin composition may change, resulting in a decrease in temperature characteristics such as deflection temperature under load, as well as a decrease in tensile strength and modulus of elasticity, making it impossible to obtain the expected physical properties. Furthermore, if the crystallization temperature changes and crystallization becomes difficult, the amount of shrinkage during injection molding may decrease, the solidification rate may decrease, resulting in a decrease in rigidity, deformation upon release from the mold, or a longer molding cycle time may result in reduced productivity. Furthermore, if crystallization during injection molding is difficult, crystallization may progress and post-shrinkage may increase when used in a high-temperature environment after molding and assembly. Large post-shrinkage may result in deformation due to dimensional changes, widening of gaps between parts, or damage due to interference between parts.

[0012] The transesterification reaction is a reaction in which the backbone moiety is exchanged by a reaction between an ester group and a hydroxyl group. This reaction is affected by the hydroxyl group concentration, but even if the total amount of hydroxyl groups in the resin in the resin composition is small, the mold release properties may not be improved. After extensive research, the inventors discovered that the amount of terminal hydroxyl groups in the PBT resin in the resin composition can affect the mold release properties. In this embodiment, the mold release properties can be improved by adjusting the amount of terminal hydroxyl groups in the PBT resin to 30 to 70 mmol / kg relative to the total amount of PBT resin (A) and PET resin (B) in the resin composition. Furthermore, the polyester resin composition of this embodiment may also enable reduced post-shrinkage of molded articles.

[0013] [Polybutylene terephthalate resin (A)] The PBT resin (A) contains at least terephthalic acid or its ester-forming derivative (C １－６ The PBT resin (A) is a resin obtained by polycondensation of a dicarboxylic acid component containing an alkylene glycol (e.g., an alkyl ester or acid halide of 1,4-butanediol) having at least 4 carbon atoms, and a glycol component containing an alkylene glycol (1,4-butanediol) or its ester-forming derivative (e.g., an acetylated product) having at least 4 carbon atoms. The PBT resin (A) is not limited to homopolybutylene terephthalate resin, but may also be a copolymer containing 60 mol% or more (particularly 75 mol% to 95 mol%) of butylene terephthalate units. In this embodiment, the raw materials for the PBT resin, 1,4-butanediol or its ester-forming derivative and terephthalic acid or its ester-forming derivative (e.g., terephthalic acid alkyl ester), may be derived from either fossil resources or biomass resources. The PBT resin (A) may be used singly or in combination of two or more types.

[0014] From the viewpoint of hydrolysis resistance, the amount of terminal carboxyl groups in the PBT resin (A) is preferably 50 mmol / kg or less, more preferably 40 mmol / kg or less, and even more preferably 30 mmol / kg or less. From the viewpoint of tensile strength, the amount of terminal carboxyl groups in the PBT resin (A) is preferably 3 mmol / kg or more, more preferably 5 mmol / kg or more, and even more preferably 10 mmol / kg or more. The amount of terminal carboxyl groups in the PBT resin (A) is, for example, preferably 3 to 50 mmol / kg, more preferably 5 to 40 mmol / kg, and even more preferably 10 to 30 mmol / kg.

[0015] From the viewpoint of appearance, the amount of terminal hydroxyl groups in the PBT resin (A) is preferably 40 mmol / kg or more, more preferably 60 mmol / kg or more, and even more preferably 80 mmol / kg or more. On the other hand, from the viewpoint of mold releasability, the amount of terminal hydroxyl groups in the PBT resin (A) is preferably 160 mmol / kg or less, more preferably 140 mmol / kg or less, and even more preferably 120 mmol / kg or less. The amount of terminal hydroxyl groups in the PBT resin (A) is, for example, preferably 40 to 160 mmol / kg, more preferably 60 to 140 mmol / kg, and even more preferably 80 to 120 mmol / kg.

[0016] In this specification, the amount of terminal hydroxyl groups in the PBT resin (A) is a value measured by NMR. The amount of terminal hydroxyl groups in the PET resin (B) described later is also a value measured by NMR. The amount of terminal hydroxyl groups in the PBT resin (A) in the polyester resin composition described later and the amount of terminal hydroxyl groups in the PET resin (B) in the polyester resin composition are also values ​​measured by NMR. As the NMR device, for example, a Bruker NMR "AVANCE III 400" can be used.

[0017] The intrinsic viscosity (IV) of the PBT resin (A) is preferably 0.5 dL / g or more and 1.5 dL / g or less, more preferably 0.55 dL / g or more and 1.4 dL / g or less, and even more preferably 0.6 dL / g or more and 1.3 dL / g or less. The intrinsic viscosity can also be adjusted by blending PBT resins having different intrinsic viscosities. For example, a PBT resin having an intrinsic viscosity of 0.9 dL / g can be prepared by blending a PBT resin having an intrinsic viscosity of 0.7 dL / g with a PBT resin having an intrinsic viscosity of 1.1 dL / g. The intrinsic viscosity (IV) of the PBT resin (A) can be measured, for example, in o-chlorophenol at 35°C.

[0018] In the PBT resin (A), examples of the dicarboxylic acid component (comonomer component) other than terephthalic acid and its ester-forming derivatives include C terephthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-dicarboxydiphenyl ether, etc. ８－１４ aromatic dicarboxylic acids of C, such as succinic acid, adipic acid, azelaic acid, and sebacic acid; ４－１６ alkanedicarboxylic acids such as cyclohexanedicarboxylic acid; ５－１０ cycloalkanedicarboxylic acids of the formula (C); ester-forming derivatives of these dicarboxylic acid components (C １－６ These dicarboxylic acid components may be used alone or in combination of two or more.

[0019] Among these dicarboxylic acid components, C ８－１２ Aromatic dicarboxylic acids such as adipic acid, azelaic acid, and sebacic acid ６－１２ The alkanedicarboxylic acids are more preferred.

[0020] In the PBT resin (A), examples of glycol components (comonomer components) other than 1,4-butanediol and its ester-forming derivatives include C glycols such as ethylene glycol, propylene glycol, trimethylene glycol, 1,3-butylene glycol, hexamethylene glycol, neopentyl glycol, and 1,3-octanediol. ２－１０alkylene glycols such as diethylene glycol, triethylene glycol, dipropylene glycol, and the like; alicyclic diols such as cyclohexanedimethanol and hydrogenated bisphenol A, and the like; aromatic diols such as bisphenol A and 4,4'-dihydroxybiphenyl, and the like; C-type alkylene glycols of bisphenol A such as ethylene oxide 2-mol adduct of bisphenol A and propylene oxide 3-mol adduct of bisphenol A, and the like; ２－４ or ester-forming derivatives of these glycols (acetylated products, etc.). These glycol components can be used alone or in combination of two or more.

[0021] Among these glycol components, C ethylene glycol, trimethylene glycol, etc. ２－６ More preferred are alkylene glycols such as those listed above, polyoxyalkylene glycols such as diethylene glycol, and alicyclic diols such as cyclohexanedimethanol. Examples of comonomer components that can be used in addition to the dicarboxylic acid component and the glycol component include aromatic hydroxycarboxylic acids such as 4-hydroxybenzoic acid, 3-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, and 4-carboxy-4'-hydroxybiphenyl; aliphatic hydroxycarboxylic acids such as glycolic acid and hydroxycaproic acid; C hydroxycarboxylic acids such as propiolactone, butyrolactone, valerolactone, and caprolactone (ε-caprolactone, etc.); ３－１２ lactones; ester-forming derivatives of these comonomer components (C １－６ alkyl ester derivatives, acid halides, acetylated derivatives, etc.

[0022] Any of the polybutylene terephthalate copolymers obtained by copolymerizing the comonomer components described above can be suitably used as the PBT resin (A). Also, a homopolybutylene terephthalate polymer and a polybutylene terephthalate copolymer may be used in combination as the PBT resin (A).

[0023] For the PBT resin (A), recycled products from the market can be used (material recycling). In addition, PBT resins produced by decomposing PBT resin waste to monomer levels (chemical recycling) to extract 1,4-butanediol, terephthalic acid, etc., and then polycondensing the resulting raw materials can also be used.

[0024] The amount of PBT resin (A) is preferably 20% by mass or more, more preferably 25% by mass or more, and even more preferably 30% by mass or more, based on the total amount of the polyester resin composition. On the other hand, the amount of PBT resin (A) is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less, based on the total amount of the polyester resin composition. The amount of PBT resin (A) is, for example, preferably 20 to 80% by mass, more preferably 25 to 70% by mass, and even more preferably 30 to 60% by mass, based on the total amount of the polyester resin composition.

[0025] [Polyethylene terephthalate resin (B)] The PET resin (B) is a polyethylene terephthalate resin (C) containing terephthalic acid or its ester-forming derivative. １－６ The PET resin is a polyester resin obtained by polycondensation of ethylene glycol or its ester-forming derivatives (such as alkyl esters or acid halides) and ethylene glycol or its ester-forming derivatives (such as acetylated products) according to a known method. The main raw materials of the PET resin, ethylene glycol and terephthalic acid or terephthalic acid alkyl esters, may be derived from either fossil resources or biomass resources.

[0026] The PET resin (B) may be modified by copolymerizing a small amount of a modifying component that provides repeating units other than terephthaloyl units and ethylenedioxy units, within the scope of not impairing the object of the present invention. The amount of repeating units other than terephthaloyl units and ethylenedioxy units contained in the PET resin (B) is preferably less than 4 mol%, more preferably 3 mol% or less, and even more preferably 2 mol% or less, of all repeating units of the polyethylene terephthalate resin.

[0027] The PET resin (B) may contain repeating units derived from the above-described modifying component in an amount of 4 mol % or more of all repeating units. In this specification, such a polyethylene terephthalate resin may also be referred to as a "modified PET resin."

[0028] The modified PET resin may contain other dicarboxylic acids than terephthalic acid or their ester-forming derivatives (C １－６ The amount of dicarbonyl units other than terephthaloyl units contained in the modified polyethylene terephthalate resin is preferably 5 mol % or more and 50 mol % or less, more preferably 7 mol % or more and 30 mol % or less, and particularly preferably 10 mol % or more and 25 mol % or less, of all dicarbonyl units.

[0029] Suitable compounds as the dicarboxylic acid or its ester-forming derivative contained in the modifying component include C carboxylic acids such as isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, and 4,4'-dicarboxydiphenyl ether. ８－１４ aromatic dicarboxylic acids of C, such as succinic acid, adipic acid, azelaic acid, and sebacic acid; ４－１６ alkanedicarboxylic acids such as cyclohexanedicarboxylic acid; ５－１０ cycloalkanedicarboxylic acids of the formula (C); ester-forming derivatives of these dicarboxylic acid components (C １－６ These dicarboxylic acids may be used alone or in combination of two or more.

[0030] Among these dicarboxylic acids or their ester-forming derivatives, C carboxylic acids such as isophthalic acid are preferred. ８－１２ Aromatic dicarboxylic acids or their ester-forming derivatives, and aromatic dicarboxylic acids such as adipic acid, azelaic acid, and sebacic acid ６－１２In addition, since the resulting polybutylene terephthalate resin composition has excellent metal adhesion and mechanical properties, isophthalic acid or an ester-forming derivative of isophthalic acid (dimethyl isophthalate, diethyl isophthalate, isophthalic acid dichloride, etc.) is particularly preferred as the dicarboxylic acid or an ester-forming derivative thereof in the modifying component.

[0031] The modifying component used in producing the modified PET resin may contain, in addition to a predetermined amount of dicarboxylic acid or an ester-forming derivative thereof, other glycol components such as ethylene glycol and its ester-forming derivatives, a hydroxycarboxylic acid component, a lactone component, etc., within the range that does not impair the object of the present invention. In the modified polyethylene terephthalate resin composition, the amount of repeating units derived from modifying components such as these glycol components, hydroxycarboxylic acid components, and lactone components is preferably 30 mol % or less, more preferably 25 mol % or less, and particularly preferably 20 mol % or less, of all repeating units in the modified polyethylene terephthalate resin.

[0032] Examples of glycol components contained in the modified component include C propylene glycol, trimethylene glycol, 1,4-butanediol, 1,3-butylene glycol, hexamethylene glycol, neopentyl glycol, and 1,3-octanediol. ２－１０ alkylene glycols such as diethylene glycol, triethylene glycol, dipropylene glycol, and the like; alicyclic diols such as cyclohexanedimethanol and hydrogenated bisphenol A, and the like; aromatic diols such as bisphenol A and 4,4'-dihydroxybiphenyl, and the like; C-type alkylene glycols of bisphenol A such as ethylene oxide 2-mol adduct of bisphenol A and propylene oxide 3-mol adduct of bisphenol A, and the like; ２－４ or ester-forming derivatives of these glycols (acetylated products, etc.). These glycol components can be used alone or in combination of two or more.

[0033] Examples of the hydroxycarboxylic acid component contained in the modified component include aromatic hydroxycarboxylic acids such as 4-hydroxybenzoic acid, 3-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, and 4-carboxy-4'-hydroxybiphenyl; aliphatic hydroxycarboxylic acids such as glycolic acid and hydroxycaproic acid; and ester-forming derivatives of these hydroxycarboxylic acids (C １－６ These hydroxycarboxylic acid components may be used alone or in combination of two or more thereof.

[0034] Examples of lactone components contained in the modified component include C hydroxybenzoates such as propiolactone, butyrolactone, valerolactone, and caprolactone (e.g., ε-caprolactone). ３－１２ These lactone components may be used alone or in combination of two or more.

[0035] From the viewpoint of appearance, the amount of terminal hydroxyl groups in PET resin (B) is preferably 10 mmol / kg or more, more preferably 20 mmol / kg or more, and even more preferably 30 mmol / kg or more. On the other hand, from the viewpoint of mold releasability, the amount of terminal hydroxyl groups in PET resin (B) is preferably 80 mmol / kg or less, more preferably 70 mmol / kg or less, and even more preferably 60 mmol / kg or less. The amount of terminal hydroxyl groups in PET resin (B) is, for example, preferably 10 to 80 mmol / kg, more preferably 20 to 70 mmol / kg, and even more preferably 30 to 60 mmol / kg.

[0036] As the PET resin (B), a recycled product from the market can be used. If the amount of terminal hydroxyl groups in the recycled PET resin (B) is outside the above range, the amount of terminal hydroxyl groups may be adjusted by performing solid-state polymerization in an inert gas atmosphere such as nitrogen. Also usable is a PET resin produced by decomposing PET resin waste to monomers such as ethylene glycol and terephthalic acid and polycondensing the resulting raw materials. The PET resin (B) may be used singly or in combination of two or more.

[0037] The amount of PET resin (B) is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, based on the total amount of the polyester resin composition. On the other hand, the amount of PET resin (B) is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less, based on the total amount of the polyester resin composition. The amount of PET resin (B) is, for example, preferably 10 to 60% by mass, more preferably 15 to 50% by mass, and even more preferably 20 to 40% by mass, based on the total amount of the polyester resin composition.

[0038] From the viewpoint of appearance, the mass ratio of the PET resin (B) to the PBT resin (A) (PET resin (B)) / PBT resin (A)) is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.3 or more. From the viewpoint of mold releasability, the mass ratio of the PET resin to the PBT resin (PET resin (B)) / PBT resin (A)) is preferably 0.8 or less, more preferably 0.7 or less, and even more preferably 0.6 or less. The mass ratio of the PET resin to the PBT resin (PET resin (B)) / PBT resin (A)) is, for example, preferably 0.1 to 0.8, more preferably 0.2 to 0.7, and even more preferably 0.3 to 0.6.

[0039] From the viewpoints of improving mold releasability and reducing post-shrinkage of molded articles, the amount of terminal hydroxyl groups in the PBT resin in the polyester resin composition is preferably 30 to 70 mmol / kg relative to the total amount of the PBT resin (A) and the PET resin (B) (total mass of the PBT resin and the PET resin). In the polyester resin composition, the amount of terminal hydroxyl groups in the PBT resin (A) relative to the total amount of the PBT resin (A) and the PET resin (B) is more preferably 35 to 65 mmol / kg, and even more preferably 40 to 60 mmol / kg.

[0040] In the polyester resin composition, the amount of terminal hydroxyl groups in the PBT resin (A) relative to the total amount of the PBT resin (A) and the PET resin (B) is preferably 70 mmol / kg or less, more preferably 65 mmol / kg or less, and even more preferably 60 mmol / kg or less. On the other hand, in the polyester resin composition, the amount of terminal hydroxyl groups in the PBT resin (A) relative to the total amount of the PBT resin (A) and the PET resin (B) is preferably 30 mmol / kg or more, more preferably 35 mmol / kg or more, and even more preferably 40 mmol / kg or more.

[0041] From the viewpoint of further improving the mold releasability and further reducing the post-shrinkage rate of the molded article, in the polyester resin composition, the total amount of terminal hydroxyl groups of the PBT resin (A) and the PET resin (B) relative to the total amount of the PBT resin (A) and the PET resin (B) is preferably 60 to 90 mmol / kg, more preferably 62 to 85 mmol / kg, even more preferably 65 to 75 mmol / kg, and still more preferably 70 to 75 mmol / kg.

[0042] In the polyester resin composition, the sum of the number of terminal hydroxyl groups of the PBT resin (A) and the number of terminal hydroxyl groups of the PET resin (B) relative to the total amount of the PBT resin (A) and the PET resin (B) is preferably 90 mmol / kg or less, more preferably 85 mmol / kg or less, and even more preferably 75 mmol / kg or less. On the other hand, in the polyester resin composition, the sum of the number of terminal hydroxyl groups of the PBT resin and the number of terminal hydroxyl groups of the PET resin (B) relative to the total amount of the PBT resin and the PET resin is preferably 60 mmol / kg or more, more preferably 62 mmol / kg or more, even more preferably 65 mmol / kg or more, and even more preferably 70 mmol / kg or more.

[0043] [Transesterification Inhibitor (C)] From the viewpoint of inhibiting the transesterification reaction, the polyester resin composition preferably contains a transesterification inhibitor (C). Examples of the transesterification inhibitor (C) include phosphorus-based compounds such as organic phosphite compounds, phosphonite compounds, and metal phosphates. Specific examples include bis(2,4-di-t-4-methylphenyl)pentaerythritol diphosphite, bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, tetrakis(2,4-di-t-butylphenyl)-4,4'-biphenylene phosphonite, and 3,9-bis(2,6-di-t-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro-[5.5]undecane. Examples of metal phosphates include alkaline earth metal phosphates such as monocalcium phosphate (calcium dihydrogen phosphate), and alkali metal phosphates such as monosodium phosphate (sodium dihydrogen phosphate). The metal phosphate may be, for example, an anhydride or a hydrate. From the viewpoint of further improving the mold releasability, the polyester resin composition preferably contains a phosphorus-based compound containing a sodium atom or a calcium atom, and more preferably contains a metal phosphate containing a sodium atom or a calcium atom.

[0044] In the polyester resin composition, the amount of the transesterification inhibitor (C) is preferably 0.03 to 0.5 mass%, more preferably 0.1 to 0.5 mass%, based on the total amount of the polyester resin composition. For example, in the polyester resin composition, the amount of the phosphorus-based compound containing a sodium atom or a calcium atom is preferably 0.1 to 0.5 mass%, more preferably 0.15 to 0.3 mass%, based on the total amount of the polyester resin composition.

[0045] [Crystal Nucleating Agent (D)] The polyester resin composition preferably contains a crystal nucleating agent (D) from the viewpoint of promoting the crystallization of the resin. The crystal nucleating agent (D) may be an organic substance, an inorganic substance, or a combination thereof. Examples of inorganic substances include simple substances such as Zn powder, Al powder, graphite, and carbon black, as well as ZnO, MgO, and Al. ２ O ３ , TiO ２, MnO ２ , SiO ２ , Fe ３ O ４ Metal oxides such as aluminum nitride, silicon nitride, titanium nitride, boron nitride, etc., nitrides such as Na ２ CO ３ , CaCO ３ , MgCO ３ , CaSiO ３ , BaSO ４ , Ca ３ (P.O. ４ ) ３ Inorganic salts such as those mentioned above, and clays such as talc, kaolin, clay, and white clay can be used alone or in combination of two or more thereof. Organic substances include, for example, organic salts such as calcium oxalate, sodium oxalate, calcium benzoate, calcium phthalate, calcium tartrate, magnesium stearate, and polyacrylates, polymers such as polyester, polyethylene, and polypropylene, and cross-linked polymers, which can be used alone or in combination of two or more thereof. Among these, talc, carbon black, and combinations thereof are preferred.

[0046] In the polyester resin composition, the content of the crystal nucleating agent (D) is preferably 0.05 to 2 mass %, more preferably 0.1 to 1.5 mass %, and even more preferably 0.3 to 1 mass %, based on the total amount of the polyester resin composition.

[0047] [Inorganic Filler (E)] The polyester resin composition preferably contains an inorganic filler (E), and the inorganic filler (E) is preferably a fibrous inorganic filler.

[0048] Examples of fibrous inorganic fillers include glass fibers, carbon fibers, silica fibers, silica-alumina fibers, zirconia fibers, boron nitride fibers, silicon nitride fibers, boron fibers, potassium titanate fibers, and metal fibers (e.g., stainless steel, aluminum, titanium, copper, brass, etc.). Representative fibrous inorganic fillers include glass fibers and carbon fibers, with glass fibers being preferred in terms of availability and cost. The type of glass used as the raw material for glass fibers is not particularly limited, but E-glass and corrosion-resistant glass containing zirconium element in its composition are preferred in terms of quality.

[0049] In the polyester resin composition, the inorganic filler (E) is preferably contained in an amount of 5 to 50 mass %, more preferably 10 to 40 mass %, based on the total amount of the polyester resin composition.

[0050] [Other Components] The polyester resin composition may contain other components as needed, including, but not limited to, antioxidants, weather stabilizers, molecular weight modifiers, ultraviolet absorbers, antistatic agents, dyes, pigments, lubricants, crystallization accelerators such as plasticizers, near-infrared absorbers, flame retardants, flame retardant assistants, and colorants.

[0051] [Method for producing polyester resin composition] The method for producing the polyester resin composition is not particularly limited. The polyester resin composition can be produced by various methods known as methods for producing thermoplastic resin compositions.

[0052] A suitable method for producing the polyester resin composition is, for example, a method in which the components are melt-kneaded using a melt-kneading device such as a single-screw or twin-screw extruder, and then extruded into pellets.

[0053] <Resin Molded Article> The resin molded article of this embodiment can be obtained using the polyester resin composition described above.

[0054] The method for producing a resin molded article using the polyester resin composition is not particularly limited, and any known method can be used. For example, the polyester resin composition can be fed into an extruder, melt-kneaded, and pelletized, and the pellets can be fed into an injection molding machine equipped with a predetermined mold and injection-molded to produce a resin molded article.

[0055] The resin composition of the present embodiment has excellent mold releasability and excellent productivity for resin molded articles. Furthermore, resin molded articles obtained using this resin composition have reduced post-shrinkage under high-temperature conditions and can be suitably used as molded articles exposed to high-temperature, high-humidity environments for long periods of time, such as in automobiles, trains, and the aviation industry. The resin molded articles of the present embodiment can be used for connectors, sensors, actuators, ECU housings, levers, switches, relays, etc.

[0056] Embodiments of the present invention include the following, but are not limited to the following. <1> A polyester resin composition comprising a polybutylene terephthalate resin (A) and a polyethylene terephthalate resin (B), wherein the amount of terminal hydroxyl groups in the polybutylene terephthalate resin (A) is 30 to 70 mmol / kg relative to the total amount of the polybutylene terephthalate resin (A) and the polyethylene terephthalate resin (B). <2> The polyester resin composition according to <1>, wherein the sum of the amount of terminal hydroxyl groups in the polybutylene terephthalate resin (A) and the amount of terminal hydroxyl groups in the polyethylene terephthalate resin (B) is 60 to 90 mmol / kg relative to the total amount of the polybutylene terephthalate resin (A) and the polyethylene terephthalate resin (B). <3> The polyester resin composition according to <1> or <2>, further comprising 0.1 to 0.5 mass% of a phosphorus-based compound containing a sodium atom or a calcium atom, relative to the total amount of the polyester resin composition. <4> The polyester resin composition according to any one of <1> to <3>, further comprising a crystal nucleating agent (D). <5> The polyester resin composition according to any one of <1> to <4>, further comprising an inorganic filler (E) in an amount of 5 to 50 mass% based on the total amount of the polyester resin composition. <6> A resin molded product obtained using the polyester resin composition according to any one of <1> to <5>.

[0057] The disclosure of this application is related to the subject matter described in Japanese Patent Application No. 2023-192082, filed November 10, 2023, the entire disclosure of which is incorporated herein by reference.

[0058] The present embodiment will be described in more detail below with reference to examples, but the present embodiment is not limited to the following examples.

[0059] [Examples 1 to 9, Comparative Examples 1 to 3] The materials shown in Tables 1 to 3 were melt-kneaded and extruded in the ratios (mass%) shown in Tables 1 to 3 using a 30 mmφ twin-screw extruder ("TEX30" manufactured by The Japan Steel Works, Ltd.) at a cylinder temperature of 260°C and a screw rotation speed of 130 rpm, to obtain pellets made of the polyester resin compositions of Examples 1 to 9 and Comparative Examples 1 to 3. Details of each component shown in Tables 1 to 3 are provided below.

[0060] (1) PBT Resin (A) (A-1): PBT resin, manufactured by Polyplastics Co., Ltd., terminal hydroxyl group amount 100 mmol / kg (A-2): PBT resin, manufactured by Polyplastics Co., Ltd., terminal hydroxyl group amount 80 mmol / kg (A-3): PBT resin, manufactured by Polyplastics Co., Ltd., terminal hydroxyl group amount 120 mmol / kg

[0061] (2) PET Resin (B) (B-1): PET resin, "N1-100" manufactured by Indorama, terminal hydroxyl group amount 40 mmol / kg (B-2): PET resin, "N1" manufactured by Indorama, terminal hydroxyl group amount 40 mmol / kg

[0062] (3) Inorganic filler (E): Glass fiber, "ECS 03 T-187" manufactured by Nippon Electric Glass Co., Ltd.

[0063] (4) Transesterification inhibitor (C) (C-1): Sodium dihydrogen phosphate, manufactured by Yoneyama Chemical Industry Co., Ltd. (C-2): Phosphite compound, manufactured by ADEKA Corporation "ADEKA STAB PEP36" (3,9-bis(2,6-di-t-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro-[5.5]undecane)

[0064] (5) Nucleating Agent (D) (D-1): Talc, "Talc Powder PK-NN" manufactured by Hayashi Kasei Co., Ltd. (D-2): Carbon black, "#750B" manufactured by Mitsubishi Chemical Corporation

[0065] (6) Antioxidant: "IRGANOX 1010" manufactured by BASF (7) Lubricant: "Unistar H476" manufactured by NOF Corporation

[0066] In Tables 1 to 3, "Amount of PBT terminal hydroxyl groups (mmol / kg)" refers to the amount (mmol / kg) of terminal hydroxyl groups in the PBT resin (A) relative to the total amount of the PBT resin (A) and the PET resin (B) in the polyester resin composition. "Amount of PET terminal hydroxyl groups (mmol / kg)" refers to the amount (mmol / kg) of terminal hydroxyl groups in the PET resin (B) relative to the total amount of the PBT resin (A) and the PET resin (B) in the polyester resin composition. "Total amount of terminal hydroxyl groups (mmol / kg)" refers to the sum (mmol / kg) of the amount of terminal hydroxyl groups in the PBT resin (A) and the amount of terminal hydroxyl groups in the PET resin (B) relative to the total amount of the PBT resin (A) and the PET resin (B) in the polyester resin composition. The amount of terminal hydroxyl groups in the PBT resin (A) and the amount of terminal hydroxyl groups in the PET resin (B) in the polyester resin composition are values ​​measured by NMR using an NMR apparatus "AVANCE III 400" manufactured by Bruker.

[0067] <Evaluation method>

[0068] (1) Cooling time (mold releasability) For the resin compositions in Tables 1 to 3, molded articles having the shapes shown in FIG. 1 were molded using "EC40" manufactured by Toshiba Corporation, and the minimum time required for demolding at a dwell pressure of 70 MPa (cooling time (seconds)) was measured. A shorter cooling time indicates better demolding properties. The results (cooling time (seconds)) are shown in the tables. The molding conditions were as follows:

[0069] (Molding conditions) Cylinder temperature: 250°C Mold temperature: 60°C Injection speed: 20 mm / sec Injection and pressure holding: 5 sec

[0070] Figure 1 is a perspective view showing a molded product used in the evaluation of cooling time (mold releasability). In Figure 1, 1 denotes the molded product, 2 denotes a short side, 3 denotes a cylinder, 4 denotes a long side, and 5 denotes an ejector pin protrusion area. The molded product 1 has a thin, T-shaped shape (long side 4: length 30 mm, width 15 mm, thickness 1 mm; short side 2: height 10 mm, width 15 mm, central thickness 2 mm, maximum thickness 3 mm). A cylinder 3 (diameter 3 mm, height 7 mm) is installed on one side of the long side 4. An ejector pin (not shown) is also installed at the ejector pin protrusion area 5 in the center of the other side of the long side 4.

[0071] (2) Post-shrinkage Rate For the resin compositions in Tables 1 to 3, test specimens measuring 120 mm x 120 mm x 2 mm (thickness) were molded at a cylinder temperature of 260°C and a mold temperature of 60°C. The change in the test specimen dimensions in the direction perpendicular to the flow (post-shrinkage rate) was determined before and after annealing at 140°C for 3 hours. FIG. 2 is a plan view schematically showing the shape of the test specimen. In FIG. 2, 10 indicates the test specimen, X indicates the direction perpendicular to the flow, and Y indicates the flow direction. Also in FIG. 2, L indicates the location where the dimension in the direction perpendicular to the flow was measured. Specifically, after molding of the test specimen and before annealing, and after annealing, the dimension in the direction perpendicular to the flow (mm) was measured at the location indicated by L in FIG. 2. These were defined as the dimension in the direction perpendicular to the flow (mm) before annealing and the dimension in the direction perpendicular to the flow (mm) after annealing, respectively. The post-shrinkage rate (%) in the direction perpendicular to the flow was calculated using the following formula:

[0072] Post-shrinkage rate in the direction perpendicular to the flow (%) = [(dimension in the direction perpendicular to the flow (mm) before annealing) - (dimension in the direction perpendicular to the flow (mm) after annealing)] ÷ 120 (mm) × 100

[0073] For each resin composition, the dimension (mm) in the direction perpendicular to the flow before annealing, the dimension (mm) in the direction perpendicular to the flow after annealing, and the post-shrinkage rate (%) in the direction perpendicular to the flow are shown in the table.

[0074]

[0075]

[0076]

[0077] As shown in the table, in Examples 1 to 9 in which the amount of terminal hydroxyl groups in the PBT resin (A) relative to the total amount of the PBT resin (A) and the PET resin (B) was 30 to 70 mmol / kg, excellent results were shown in both the evaluation of the cooling demolding time and the after-shrinkage rate, and it was found that the mold release properties were excellent and the after-shrinkage after the molded article was exposed to high-temperature conditions, etc., was reduced.

[0078] REFERENCE SIGNS LIST 1 Molded product 2 Short side 3 Cylinder 4 Long side 5 Eject pin protruding portion 10 Test piece X Direction perpendicular to flow Y Flow direction

Claims

1. A polyester resin composition comprising a polybutylene terephthalate resin (A) and a polyethylene terephthalate resin (B), wherein the amount of terminal hydroxyl groups in the polybutylene terephthalate resin (A) is 30 to 70 mmol / kg relative to the total amount of the polybutylene terephthalate resin (A) and the polyethylene terephthalate resin (B).

2. The polyester resin composition according to claim 1, wherein the sum of the amount of terminal hydroxyl groups in the polybutylene terephthalate resin (A) and the amount of terminal hydroxyl groups in the polyethylene terephthalate resin (B) is 60 to 90 mmol / kg relative to the total amount of the polybutylene terephthalate resin (A) and the polyethylene terephthalate resin (B).

3. The polyester resin composition according to claim 1 or 2, further comprising 0.1 to 0.5 mass % of a phosphorus compound containing a sodium atom or a calcium atom, based on the total amount of the polyester resin composition.

4. The polyester resin composition according to any one of claims 1 to 3, further comprising a crystal nucleating agent (D).

5. The polyester resin composition according to any one of claims 1 to 4, further comprising 5 to 50 mass% of an inorganic filler (E) based on the total amount of the polyester resin composition.

6. A resin molded product obtained by using the polyester resin composition according to any one of claims 1 to 5.

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