JP7747711B2 - Polyester resin composition and resin molded article - Google Patents

Description

Embodiments of the present invention relate to polyester resin compositions and resin molded articles.

Polybutylene terephthalate resin (hereinafter referred to as "PBT resin") has excellent mechanical properties, electrical properties, heat resistance, chemical resistance, and solvent resistance, and is therefore widely used as an engineering plastic for a variety of applications, including automotive parts and electrical and electronic parts.

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, thereby improving the appearance (surface gloss, low roughness, etc.) and reducing warpage of molded articles.
Patent Documents 1 and 2 describe resin compositions containing PBT resin and PET resin.

International Publication No. 2020/246335 Japanese Patent Application Publication No. 8-183114

An object of one embodiment of the present invention is to provide a polyester resin composition with excellent mold release properties.

One embodiment of the present invention relates to a polyester resin composition comprising a polybutylene terephthalate resin (A) and a polyethylene terephthalate resin (B), in which 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 described above.

According to an embodiment of the present invention, a polyester resin composition with excellent mold release properties can be provided.

FIG. 2 is a perspective view schematically showing a molded article used in evaluating demolding properties in the examples. FIG. 2 is a plan view schematically showing a test piece used for evaluating post-shrinkage in the examples.

The following describes preferred embodiments of the present invention, but the present invention is not limited to the following embodiments.

<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).

Resin compositions containing PBT resin and PET resin tend to undergo transesterification between the PBT resin and the PET resin under high-temperature conditions, such as when melted. 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 achieve 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 slow, resulting in reduced rigidity, deformation upon release from the mold, and a longer molding cycle time may reduce productivity. Furthermore, if crystallization during injection molding is difficult, crystallization may progress and post-shrinkage may increase if the material is used in a high-temperature environment after molding and assembly. Large post-shrinkage may lead to deformation due to dimensional changes, widening of gaps between parts, or damage due to interference between parts.

The transesterification reaction is a reaction in which the main chain portion is exchanged by a reaction between an ester group and a hydroxyl group. The 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 have found 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 the present embodiment may also enable reduction in post-shrinkage of molded articles.

[Polybutylene terephthalate resin (A)]
The PBT resin (A) is a resin obtained by polycondensation of a dicarboxylic acid component containing at least terephthalic acid or an ester-forming derivative thereof (such as a _C1-6 alkyl ester or acid halide), and a glycol component containing an alkylene glycol having at least 4 carbon atoms (1,4-butanediol) or an ester-forming derivative thereof (such as an acetylated product). The PBT resin (A) is not limited to a 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, 1,4-butanediol and terephthalic acid or terephthalic acid alkyl ester, which are raw materials for the PBT resin, may be derived from either fossil resources or biomass resources.
The PBT resin (A) may be used alone or in combination of two or more.

From the viewpoint of hydrolysis resistance, the amount of terminal carboxyl groups in 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 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 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.

From the viewpoint of appearance, the amount of terminal hydroxyl groups in 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 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 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.

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, Bruker NMR "AVANCE III 400" can be used.

The intrinsic viscosity (IV) of 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 with different intrinsic viscosities. For example, a PBT resin with an intrinsic viscosity of 0.9 dL/g can be prepared by blending a PBT resin with an intrinsic viscosity of 0.7 dL/g with a PBT resin with an intrinsic viscosity of 1.1 dL/g. The intrinsic viscosity (IV) of PBT resin (A) can be measured, for example, in o-chlorophenol at 35°C.

In PBT resin (A), examples of dicarboxylic acid components (comonomer components) other than terephthalic acid and its ester-forming derivatives include C8-14 aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, and 4,4'-dicarboxydiphenyl ether; C4-16 alkanedicarboxylic acids such as succinic acid, adipic acid, azelaic acid, and sebacic acid; C5-10 cycloalkanedicarboxylic acids such as cyclohexanedicarboxylic acid; and ester-forming derivatives of these dicarboxylic acid components (such as C1-6 alkyl ester derivatives and acid halides). These dicarboxylic acid components can be used alone or in combination of two or more.

Among these dicarboxylic acid components, C8-12 aromatic dicarboxylic acids such as isophthalic acid, and C6-12 alkanedicarboxylic acids such as adipic acid, azelaic acid, and sebacic acid are more preferred.

In PBT resin (A), examples of glycol components (comonomer components) other than 1,4-butanediol include C2-10 alkylene glycols such as ethylene glycol, propylene glycol, trimethylene glycol, 1,3-butylene glycol, hexamethylene glycol, neopentyl glycol, and 1,3-octanediol; polyoxyalkylene glycols such as diethylene glycol, triethylene glycol, and dipropylene glycol; alicyclic diols such as cyclohexanedimethanol and hydrogenated bisphenol A; aromatic diols such as bisphenol A and 4,4'-dihydroxybiphenyl; C2-4 alkylene oxide adducts of bisphenol A, such as a 2-mol ethylene oxide adduct of bisphenol A and a 3-mol propylene oxide adduct of bisphenol A; and ester-forming derivatives of these glycols (e.g., acetylated products). These glycol components can be used alone or in combination of two or more.

Among these glycol components, C2-6 alkylene glycols such as ethylene glycol and trimethylene glycol, polyoxyalkylene glycols such as diethylene glycol, and alicyclic diols such as cyclohexanedimethanol are more preferred. In addition to the dicarboxylic acid component and glycol component, comonomer components that can be used include, for example, aromatic hydroxycarboxylic acids such as 4-hydroxybenzoic acid, 3-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, and 4-carboxy-4'-hydroxybiphenyl; aliphatic hydroxycarboxylic acids such as glycolic acid and hydroxycaproic acid; C3-12 lactones such as propiolactone, butyrolactone, valerolactone, and caprolactone (e.g., ε-caprolactone); and ester-forming derivatives of these comonomer components (e.g., C1-6 alkyl ester derivatives, acid halides, and acetylated products).

Any of the polybutylene terephthalate copolymers copolymerized with the comonomer components described above can be suitably used as PBT resin (A). Furthermore, a combination of a homopolybutylene terephthalate polymer and a polybutylene terephthalate copolymer may also be used as PBT resin (A).

PBT resin (A) can be made from recycled products (material recycling). It is also possible to use PBT resin produced by decomposing waste PBT resin into monomers (chemical recycling), such as 1,4-butanediol and terephthalic acid, and then polycondensing the resulting raw materials.

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.

[Polyethylene terephthalate resin (B)]
PET resin (B) is a polyester resin obtained by polycondensation of terephthalic acid or its ester-forming derivative (e.g., _C1-6 alkyl ester or acid halide) and ethylene glycol or its ester-forming derivative (e.g., acetylated product) according to a known method. The main raw materials of PET resin, ethylene glycol and terephthalic acid or terephthalic acid alkyl ester, may be derived from either fossil resources or biomass resources.

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, as long as the objectives of the present invention are not impaired. The amount of repeating units other than terephthaloyl units and ethylenedioxy units contained in PET resin (B) is preferably less than 4 mol%, more preferably 3 mol% or less, and even more preferably 2 mol% or less, of the total repeating units of the polyethylene terephthalate resin.

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

The modified PET resin may contain dicarbonyl units derived from dicarboxylic acids other than terephthalic acid or their ester-forming derivatives (C _1-6 alkyl esters, acid halides, etc.) within the scope of not impairing the object of the present invention. 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.

Suitable compounds as the dicarboxylic acid or ester-forming derivative thereof contained in the modifying component include _C8-14 aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, and 4,4'-dicarboxydiphenyl ether; _C4-16 alkanedicarboxylic acids such as succinic acid, adipic acid, azelaic acid, and sebacic acid; _C5-10 cycloalkanedicarboxylic acids such as cyclohexanedicarboxylic acid; and ester-forming derivatives of these dicarboxylic acid components ( _C1-6 alkyl ester derivatives, acid halides, etc.). These dicarboxylic acids can be used alone or in combination of two or more.

Among these dicarboxylic acids or ester-forming derivatives thereof, _C8-12 aromatic dicarboxylic acids such as isophthalic acid or ester-forming derivatives thereof, and _C6-12 alkanedicarboxylic acids or ester-forming derivatives thereof such as adipic acid, azelaic acid, and sebacic acid are more preferred. Furthermore, isophthalic acid or ester-forming derivatives of isophthalic acid (dimethyl isophthalate, diethyl isophthalate, isophthalic dichloride, etc.) are particularly preferred as the dicarboxylic acid or ester-forming derivative thereof in the modifying component, because the resulting polybutylene terephthalate resin composition will have excellent metal adhesion and mechanical properties.

The modifying components used in the production of the modified PET resin may contain, in addition to a specified amount of dicarboxylic acid or its ester-forming derivative, other glycol components such as ethylene glycol and its ester-forming derivatives, hydroxycarboxylic acid components, lactone components, etc., within the scope 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.

Examples of glycol components contained in the modified component include _C2-10 alkylene glycols such as propylene glycol, trimethylene glycol, 1,4-butanediol, 1,3-butylene glycol, hexamethylene glycol, neopentyl glycol, and 1,3-octanediol; polyoxyalkylene glycols such as diethylene glycol, triethylene glycol, and dipropylene glycol; alicyclic diols such as cyclohexanedimethanol and hydrogenated bisphenol A; aromatic diols such as bisphenol A and 4,4'-dihydroxybiphenyl; C2-4 alkylene oxide adducts of bisphenol A, such as an ethylene oxide 2-mol adduct of bisphenol A and a propylene oxide _3-mol adduct of bisphenol A; and ester-forming derivatives of these glycols (acetylated products, etc.). These glycol components can be used alone or in combination of two or more.

Examples of the hydroxycarboxylic acid component contained in the modifying 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 ( _C1-6 alkyl ester derivatives, acid halides, acetylated products, etc.). These hydroxycarboxylic acid components can be used alone or in combination of two or more.

Examples of lactone components contained in the modified component include _C3-12 lactones such as propiolactone, butyrolactone, valerolactone, caprolactone (ε-caprolactone, etc.), etc. These lactone components can be used alone or in combination of two or more.

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 (A) 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.

The PET resin (B) may be a recycled product from the market. 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 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 alone or in combination of two or more.

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.

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 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.

From the viewpoint 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 PBT resin (A) and PET resin (B) (total mass of PBT resin and PET resin). In the polyester resin composition, the amount of terminal hydroxyl groups in the PBT resin (A) relative to the total amount of PBT resin (A) and PET resin (B) is more preferably 35 to 65 mmol/kg, and even more preferably 40 to 60 mmol/kg.

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.

From the viewpoint of further improving mold releasability and further reducing the post-shrinkage rate of molded articles, in the polyester resin composition, the total amount of terminal hydroxyl groups in 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 even more preferably 70 to 75 mmol/kg.

In the polyester resin composition, the sum of the number of terminal hydroxyl groups in the PBT resin (A) and the number of terminal hydroxyl groups in 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 in the PBT resin and the number of terminal hydroxyl groups in 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.

[Transesterification inhibitor (C)]
The polyester resin composition preferably contains a transesterification inhibitor (C) from the viewpoint of inhibiting the transesterification reaction. 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 the metal phosphate 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 anhydrous or hydrated form.
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.

In the polyester resin composition, the content 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 a 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.

[Nucleating Agent (D)]
The polyester resin composition preferably contains a crystal nucleating agent (D) from the viewpoint of promoting crystallization of the resin.
The nucleating agent (D) may be an organic substance, an inorganic substance, or a combination thereof. Examples of inorganic substances include Zn powder, Al powder, graphite, carbon black, and the like, metal oxides such as ZnO, _MgO , _Al2O3 , _TiO2 , _MnO2 , _SiO2 , and _Fe3O4 , nitrides such as aluminum nitride, silicon nitride, titanium _nitride , and boron nitride, inorganic salts such as _Na2CO3 , _CaCO3 , _MgCO3 , _CaSiO3 , _BaSO4 , _{and Ca3} ( _PO4 ) ₃ , and clays such as talc, kaolin, clay, and white clay, which may be used alone or in combination of two or more. Examples of organic substances that can be used alone or in combination include 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. Among these, talc, carbon black, and combinations thereof are preferred.

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.

[Inorganic filler (E)]
The polyester resin composition preferably contains an inorganic filler (E). The inorganic filler (E) is preferably a fibrous inorganic filler.

Fiber-like inorganic fillers include glass fiber, carbon fiber, silica fiber, silica-alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron fiber, potassium titanate fiber, and metal fibers (e.g., stainless steel, aluminum, titanium, copper, brass, etc.). Representative fibrous inorganic fillers include glass fiber and carbon fiber, with glass fiber being preferred due to its ease of availability and cost. There are no particular restrictions on the type of glass used as the raw material for glass fiber, but from the perspective of quality, E-glass and corrosion-resistant glass containing zirconium in its composition are preferred.

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

[Other ingredients]
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.

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

A suitable method for producing a polyester resin composition is, for example, to melt-knead the components using a melt-kneading device such as a single-screw or twin-screw extruder, and then extrude them into pellets.

<Resin molded products>
The resin molded article of this embodiment can be obtained using the polyester resin composition described above.

There are no particular limitations on the method for producing a resin molded product using a polyester resin composition, 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 then be fed into an injection molding machine equipped with a specified mold and injection-molded to produce a resin molded product.

The resin composition of this embodiment has excellent mold release properties and is highly productive for resin molded articles. Furthermore, resin molded articles obtained using this resin composition exhibit reduced post-shrinkage under high-temperature conditions, making them suitable for use as molded articles exposed to high-temperature, high-humidity environments for long periods of time, such as in the automotive, train, and aviation industries. Resin molded articles of this embodiment can be used for connectors, sensors, actuators, ECU housings, levers, switches, relays, and more.

The embodiments of the present invention include the following, but the present invention is not limited to the following embodiments.
<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>
<1> The polyester resin composition according to <1>, wherein the sum of the number of terminal hydroxyl groups in the polybutylene terephthalate resin (A) and the number 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>
<1> or <2>, further comprising 0.1 to 0.5 mass% of a phosphorus-based compound containing a sodium atom or a calcium atom, based on the total amount of the polyester resin composition.
＜4＞
<1> to <3>, further comprising a crystal nucleating agent (D), the polyester resin composition according to any one of <1> to <3>.
<5>
<1> - <4> The polyester resin composition according to any one of <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＞
<5> A resin molded article obtained by using the polyester resin composition according to any one of <1> to <5>.

The present embodiment will be explained in more detail below using examples, but the present embodiment is not limited to the following examples.

[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.

(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

(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

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

(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)

(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

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

In Tables 1 to 3, "Amount of PBT terminal hydroxyl groups (mmol/kg)" refers to the amount of terminal hydroxyl groups (mmol/kg) of PBT resin (A) relative to the total amount of PBT resin (A) and PET resin (B) in the polyester resin composition. "Amount of PET terminal hydroxyl groups (mmol/kg)" refers to the amount of terminal hydroxyl groups (mmol/kg) of PET resin (B) relative to the total amount of PBT resin (A) and 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 of PBT resin (A) and PET resin (B) relative to the total amount of PBT resin (A) and 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 were measured by NMR using a Bruker AVANCE III 400 NMR spectrometer.

<Evaluation Method>

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

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

Figure 1 is a perspective view showing a molded product used to evaluate cooling time (mold releasability). In Figure 1, 1 indicates the molded product, 2 indicates the short side, 3 indicates the cylinder, 4 indicates the long side, and 5 indicates the 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), and has a cylinder 3 (diameter 3 mm, height 7 mm) installed on one side of the long side 4. Furthermore, an ejector pin (not shown) is set to protrude from the ejector pin protrusion area 5 in the center of the other side of the long side 4.

(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:

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

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

As shown in the table, Examples 1 to 9, in which the amount of terminal hydroxyl groups in PBT resin (A) relative to the total amount of PBT resin (A) and PET resin (B) was 30 to 70 mmol/kg, showed excellent results in both the cooling demolding time and post-shrinkage evaluations, demonstrating excellent demolding properties and reduced post-shrinkage after the molded article was exposed to high-temperature conditions.

1 Molded product 2 Short side 3 Cylinder 4 Long side 5 Eject pin protruding portion 10 Test piece X Flow perpendicular direction Y Flow direction

Claims (7)

The composite material contains a polybutylene terephthalate resin (A), a polyethylene terephthalate resin (B), and a fibrous inorganic filler,
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);
The amount of the fibrous inorganic filler is 10 to 50% by mass based on the total amount of the polyester resin composition .
Polyester resin composition. The polyester resin composition according to claim 1, wherein the sum of the number of terminal hydroxyl groups in the polybutylene terephthalate resin (A) and the number 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). The polyester resin composition according to claim 1 or 2, further comprising 0.1 to 0.5 mass% of a phosphorus-based compound containing sodium atoms or calcium atoms, based on the total amount of the polyester resin composition. The polyester resin composition according to claim 1 or 2, further comprising a crystal nucleating agent (D). The polyester resin composition according to claim 1 or 2, wherein the mass ratio of the polyethylene terephthalate resin (B) to the polybutylene terephthalate resin (A) (polyethylene terephthalate resin (B)/polybutylene terephthalate resin (A)) is 0.47 or more. The polyester resin composition according to claim 1 or 2, wherein the fibrous inorganic filler comprises glass fiber, carbon fiber, or a combination thereof. A resin molded article obtained using the polyester resin composition described in claim 1 or 2.