Polybutylene terephthalate resin composition, and molded article

Abstract

This polybutylene terephthalate resin composition contains: a polybutylene terephthalate resin (A) having a terminal carboxyl group content of 25 meq / kg or less; and a cyclic carbodiimide compound (B). The content of a polyvalent hydroxyl group-containing compound (C-1), which is a polyhydric alcohol or a partial ester thereof, having a hydroxyl number of 200 or more is less than 0.05 parts by mass with respect to 100 parts by mass of the polybutylene terephthalate resin (A). The polybutylene terephthalate resin composition satisfies formula 1. In formula 1, a represents the carbodiimide group content (meq / kg) per 1 kg of the polybutylene terephthalate resin composition, and b represents the intrinsic viscosity (dL / g) of the polybutylene terephthalate resin (A).　Formula 1: (-15.4×b)+19.3≤a≤(-57.4×b)+59.3

Description

Polybutylene terephthalate resin composition and molded article

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

[0002] Polybutylene terephthalate resin (hereinafter also referred to as "PBT resin") has excellent mechanical properties, electrical properties, other physical properties, and chemical properties, and also has good processability, and is therefore used as an engineering plastic in a wide range of applications, such as automotive parts and electrical / electronic parts. PBT resin is particularly preferred for applications such as cases that house substrates on which electronic parts are mounted, insert-molded products that house sensor cases, connector terminals, etc., and actuator cases that protect gears, motors, etc., for the purpose of protecting against damage caused by external moisture, dust, or impact.

[0003] On the other hand, since PBT resin has ester groups in its molecules, it tends to be easily hydrolyzed in high-temperature and high-humidity environments, which can cause a decrease in physical properties such as toughness. Therefore, when molded articles made of PBT resin are used in environments with severe temperature changes, such as in the engine compartment of an automobile or outdoors, improved hydrolysis resistance is desirable.

[0004] One known method for improving the hydrolysis resistance of PBT resin is, for example, the addition of a carbodiimide compound. However, carbodiimide compounds can cause isocyanate gas generation during molding. Patent Document 1 describes that a resin composition containing an aromatic polyester resin, a cyclic carbodiimide compound having at least two carbodiimide rings, each having one carbodiimide group in each ring, and a polyhydroxyl group-containing compound having a hydroxyl value of 200 or more, has excellent hydrolysis resistance and fluidity and can suppress isocyanate gas generation during molding.

[0005] International Publication No. 2013 / 146625

[0006] In addition to improving hydrolysis resistance, it is desirable for a polybutylene terephthalate resin composition to have good fluidity during molding from the viewpoint of good moldability. Furthermore, from the viewpoint of managing the production and molding of the resin composition, it is desirable that the fluidity of the resin composition does not change significantly during production and molding. An object of an embodiment of the present invention is to provide a polybutylene terephthalate resin composition that has excellent hydrolysis resistance and fluidity during molding, and in which changes in fluidity during production and molding of the resin composition are suppressed, and a molded article obtained using the same.

[0007] One embodiment of the present invention relates to a polybutylene terephthalate resin composition comprising a polybutylene terephthalate resin (A) having a terminal carboxyl group amount of 25 meq / kg or less and a cyclic carbodiimide compound (B), wherein a polyhydric hydroxyl group-containing compound (C-1), which is a polyhydric alcohol or a partial ester thereof and has a hydroxyl value of 200 or more, is less than 0.05 parts by mass per 100 parts by mass of the polybutylene terephthalate resin (A), and wherein the composition satisfies the following formula 1: (-15.4 x b) + 19.3 ≦ a ≦ (-57.4 x b) + 59.3 Formula 1 (In Formula 1, a represents the amount of carbodiimide groups (meq / kg) per 1 kg of the polybutylene terephthalate resin composition, and b represents the intrinsic viscosity (dL / g) of the polybutylene terephthalate resin (A).) Another embodiment of the present invention relates to a molded article obtained using the polybutylene terephthalate resin composition of the above embodiment.

[0008] According to an embodiment of the present invention, it is possible to provide a polybutylene terephthalate resin composition that has excellent hydrolysis resistance and fluidity during molding, and in which changes in fluidity during production and molding of the resin composition are suppressed, and a molded article obtained using the same.

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

[0010] <Polybutylene terephthalate resin composition> The polybutylene terephthalate resin composition according to an embodiment of the present invention contains at least a polybutylene terephthalate resin (A) and a cyclic carbodiimide compound (B).

[0011] [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 (e.g., 1,4-butanediol) or an ester-forming derivative thereof (e.g., an acetylated product thereof) with a glycol component containing an alkylene glycol (1,4-butanediol) having at least 4 carbon atoms (e.g., 1,4-butanediol) or an ester-forming derivative thereof (e.g., an acetylated product thereof). 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. Furthermore, the raw materials for the PBT resin (A), 1,4-butanediol or an ester-forming derivative thereof and terephthalic acid or an ester-forming derivative thereof (e.g., an alkyl terephthalate 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.

[0012] From the viewpoint of hydrolysis resistance, the amount of terminal carboxyl groups in the PBT resin (A) is preferably 25 meq / kg or less, more preferably 20 meq / kg or less, and even more preferably 15 meq / kg or less. From the viewpoint of adhesion to fillers and compatibility with additives, the amount of terminal carboxyl groups in the PBT resin (A) is preferably 2 meq / kg or more, and even more preferably 3 meq / kg or more. The amount of terminal carboxyl groups in the PBT resin (A) is, for example, preferably 2 to 25 meq / kg, more preferably 3 to 20 meq / kg, and even more preferably 3 to 15 meq / kg.

[0013] The intrinsic viscosity (IV) of the PBT resin (A) is preferably a value that satisfies Equation 1. Equation 1 will be described later. The intrinsic viscosity (IV) of the PBT resin (A) is preferably 0.6 to 1.2 dL / g, more preferably 0.7 to 0.9 dL / g, and even more preferably 0.7 to 0.85 dL / g. 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 0.85 dL / g can be prepared by blending a PBT resin having an intrinsic viscosity of 1.00 dL / g with a PBT resin having an intrinsic viscosity of 0.80 dL / g. The intrinsic viscosity (IV) of the PBT resin (A) can be measured, for example, in o-chlorophenol at 35°C.

[0014] 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.

[0015] 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.

[0016] In the PBT resin (A), examples of glycol components (comonomer components) other than 1,4-butanediol or 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.２－１０ 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.

[0017] 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.

[0018] 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).

[0019] As the PBT resin (A), for example, recycled products may be used. For example, market collected products can be used as the PBT resin (A) (material recycling). In addition, PBT resins produced by decomposing 1,4-butanediol, terephthalic acid, etc. from PBT resin waste to the monomer level (chemical recycling) and polycondensing the obtained raw materials can also be used.

[0020] [Cyclic Carbodiimide Compound (B)] In the present disclosure, the cyclic carbodiimide compound (B) is a compound containing a carbodiimide group present in a cyclic structure. More specifically, it is a compound containing a cyclic structure formed by linking two nitrogen atoms of the carbodiimide group via a linking group.

[0021] The cyclic carbodiimide compound (B) can contain one or more cyclic structures containing a carbodiimide group. The number of atoms directly constituting the cyclic structure containing the carbodiimide group is not particularly limited. For example, the number of atoms directly constituting the cyclic structure, including the carbon and nitrogen atoms of the carbodiimide group, is preferably 8 or more, and more preferably 10 or more. Furthermore, the number of atoms directly constituting the cyclic structure is preferably 50 or less, more preferably 30 or less, even more preferably 20 or less, and even more preferably 15 or less. The number of atoms directly constituting the cyclic structure may be, for example, 8 to 50, 8 to 30, 10 to 20, or 10 to 15.

[0022] The number of carbodiimide groups in the cyclic structure containing the carbodiimide group is preferably 1. The cyclic carbodiimide compound (B) may contain, for example, only one cyclic structure containing only one carbodiimide group, or may contain two or more cyclic structures containing only one carbodiimide group.

[0023] The cyclic carbodiimide compound (B) can be represented, for example, by the following formula (1).

[0024]

[0025] In formula (1), L represents a linking group. L may include, for example, an aliphatic group, an alicyclic group, and / or an aromatic group. L may include a heteroatom, and may include, for example, a structure in which groups such as an aliphatic group, an alicyclic group, and / or an aromatic group are linked by a heteroatom. Examples of heteroatoms include an oxygen atom, a nitrogen atom, a sulfur atom, and a phosphorus atom. L may be linear or may include a branched structure. L may include a cyclic structure. For example, L may further have a second cyclic structure containing one or more atoms from among the atoms directly constituting the main chain of L, and for example, such a second cyclic structure may further include a carbodiimide group.

[0026] In L, the number of atoms directly constituting the cyclic structure together with the carbodiimide group is not particularly limited. For example, in L, the number of atoms directly constituting the cyclic structure together with the carbodiimide group is preferably 5 or more, and more preferably 7 or more. Furthermore, in L, the number of atoms directly constituting the cyclic structure together with the carbodiimide group is preferably 47 or less, more preferably 27 or less, even more preferably 17 or less, and even more preferably 12 or less. In L, the number of atoms directly constituting the cyclic structure together with the carbodiimide group may be, for example, 5 to 47, 5 to 27, 7 to 17, or 7 to 12.

[0027] L may include, for example, a divalent to tetravalent aliphatic group having 1 to 20 carbon atoms, a divalent to tetravalent alicyclic group having 3 to 20 carbon atoms, a divalent to tetravalent aromatic group having 5 to 15 carbon atoms, or a combination thereof.

[0028] Examples of divalent to tetravalent aliphatic groups having 1 to 20 carbon atoms include alkylene groups having 1 to 20 carbon atoms such as methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, dodecylene, hexadecylene, heptadecylene, octadecylene, nonadecylene, and eicosylene; methanetriyl, ethanetriyl, propanetriyl, butanetriyl, pentanetriyl, hexanetriyl, heptanetriyl, octanetriyl, nonanetriyl, and decatriyl groups. and alkanetetrayl groups having 1 to 20 carbon atoms such as methanetetrayl group, ethanetetrayl group, propanetetrayl group, butanetetrayl group, pentanetetrayl group, hexanetetrayl group, heptanetetrayl group, octanetetrayl group, nonanetetrayl group, decanetetrayl group, dodecanetetrayl group, hexadecanetetrayl group, and octadecanetetrayl group. Examples of divalent to tetravalent alicyclic groups having 3 to 20 carbon atoms include cycloalkylene groups, cycloalkanetriyl groups, and cycloalkanetetrayl groups.

[0029] Examples of divalent to tetravalent aromatic groups having 5 to 15 carbon atoms include arylene groups such as a phenylene group and a naphthalenediyl group; arenetriyl groups such as a benzenetriyl group and a naphthalenetriyl group; and arenetetrayl groups such as a benzenetetrayl group and a naphthalenetetrayl group.

[0030] In formula (1), L preferably contains one or more selected from the group consisting of a substituted or unsubstituted arylene group such as a substituted or unsubstituted phenylene group, a heteroatom such as an oxygen atom, and a substituted or unsubstituted alkylene group. L may contain, for example, a substituted or unsubstituted arylene group such as a substituted or unsubstituted phenylene group, a heteroatom such as an oxygen atom, and a substituted or unsubstituted alkylene group.

[0031] For example, L may be a linking group represented by the following formula (2): *-Ar １ -O-X-O-Ar ２-* (2)

[0032] In formula (2), Ar １ and Ar ２ are each independently an arylene group, and may be, for example, a substituted or unsubstituted phenylene group. When the phenylene group has a substituent, examples of the substituent include an alkyl group having 1 to 20 carbon atoms. X is a divalent linking group, and examples of X include a substituted or unsubstituted alkylene group. In formula (2), * indicates the bonding site with the nitrogen atom of the carbodiimide group.

[0033] When X is an unsubstituted alkylene group, X may be, for example, —(CH ２ ) ｎ -, etc. n is preferably 1 to 6, more preferably 1 to 4, and may be, for example, 2. When X is an alkylene group having a substituent, examples of X include groups represented by the following formula (3):

[0034]

[0035] In formula (3), * indicates a bonding site with the oxygen atom in formula (2). In formula (3), p and q are each preferably independently an integer of 1 to 3, more preferably 1 or 2, and may be, for example, 1. A and B are each independently a substituent or a hydrogen atom (except when A and B are both hydrogen atoms), or A and B may be bonded to each other to form a cyclic structure together with the carbon atoms to which A and B are bonded. Examples of the substituent include alkyl groups having 1 to 20 carbon atoms. When A and B are bonded to each other to form a cyclic structure together with the carbon atoms to which A and B are bonded, X may be, for example, a group represented by the following formula (4):

[0036]

[0037] In formula (4), * indicates the bonding site with the oxygen atom in formula (2). M is a group formed by mutual bonding of A and B in formula (3), and both ends of M form a cyclic structure together with the carbon atoms to which they are bonded. M may be, for example, a group represented by the following formula (5).

[0038] *-(CH ２ ) ｒ -O-Ar ３ -N=C=N-Ar ４ -O-(CH ２ ) ｓ -* (5) In formula (5), * represents the end of M and indicates the bonding site with the carbon atom. r and s are each independently preferably an integer of 1 to 3, more preferably 1 or 2, and may be, for example, 1. Ar ３ and Ar ４ are each independently an arylene group, and may be, for example, a substituted or unsubstituted phenylene group. When the phenylene group has a substituent, examples of the substituent include an alkyl group having 1 to 20 carbon atoms.

[0039] Specific examples of the cyclic carbodiimide compound include a compound represented by formula (1), in which L is a linking group represented by formula (2), and Ar １ and Ar ２ are each independently a substituted or unsubstituted phenylene group, and X is -(CH ２ ) ２ -; a compound represented by formula (1), in which L is a linking group represented by formula (2), and Ar １ and Ar ２ are each independently a substituted or unsubstituted phenylene group, X is a linking group represented by formula (4), p and q are each 1, M is a group represented by formula (5), r and s are each 1, and Ar ３ and Ar ４ are each independently a substituted or unsubstituted phenylene group.

[0040] The cyclic carbodiimide compound (B) may be contained in the PBT resin composition either alone or in combination of two or more. In the PBT resin composition, the amount of the cyclic carbodiimide compound (B) is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 1 part by mass, and more preferably 0.2 to 0.5 parts by mass, relative to 100 parts by mass of the PBT resin.

[0041] When a cyclic carbodiimide compound is used, the viscosity of the resin increases during injection molding, reducing fluidity, and poor filling may prevent the production of a good molded product. From the viewpoint of improving hydrolysis resistance and improving the viscosity during injection molding, thereby achieving good moldability, it is preferable that the intrinsic viscosity of the PBT resin (A) and the amount of carbodiimide groups per kg of the PBT resin composition satisfy the following formula 1: (-15.4 x b) + 19.3 ≤ a ≤ (-57.4 x b) + 59.3 Formula 1

[0042] In formula 1, a represents the amount of carbodiimide groups per kg of the PBT resin composition (meq / kg), and b represents the intrinsic viscosity (dL / g) of the PBT resin (A).

[0043] From the viewpoint of improving hydrolysis resistance, the PBT resin composition preferably satisfies (-15.4 x b) + 19.3 ≤ a, and more preferably satisfies (-15.4 x b) + 20.3 ≤ a.

[0044] From the viewpoint of improving the fluidity during injection molding and thereby obtaining good moldability, the PBT resin composition preferably satisfies a≦(−57.4×b)+59.3, and more preferably satisfies a≦(−57.4×b)+58.3.

[0045] [Other Components] The PBT resin composition may contain other components as needed, such as, but not limited to, a hydroxyl group-containing compound which is a polyhydric alcohol or a partial ester thereof, an inorganic filler, an antioxidant, a weather stabilizer, a molecular weight modifier, an ultraviolet absorber, an antistatic agent, a dye, a pigment, a lubricant, a crystallization accelerator, a crystal nucleating agent, a near-infrared absorber, a flame retardant, a flame retardant auxiliary, an organic filler, and a colorant.

[0046] Examples of the hydroxyl group-containing compound which is a polyhydric alcohol or a partial ester thereof include a polyhydric alcohol or a partial ester thereof, which has a hydroxyl group value of 200 or more, and a polyhydric alcohol or a partial ester thereof, which has a hydroxyl group value of 10 or more but less than 200, and a hydroxyl group-containing compound (C-2) which is a polyhydric alcohol or a partial ester thereof, which has a hydroxyl group value of 10 or more but less than 200, and ...

[0047] The polyhydroxyl group-containing compound (C-1) is a compound having two or more hydroxyl groups in one molecule and a hydroxyl value of 200 or more.

[0048] In this specification, the hydroxyl value refers to the value measured by Japan Oil Chemists' Society Method 2.3.6.2-1996 (pyridine-acetic anhydride method) (Standard Test Methods for the Analysis of Fats, Oils and Related Materials, established by Japan Oil Chemists' Society).

[0049] In the polyhydric hydroxyl group-containing compound (C-1), examples of the polyhydric alcohol include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, trimethylolmethane, pentaerythritol, dipentaerythritol, tripentaerythritol, and various sorbitols.

[0050] In the polyhydric hydroxy group-containing compound (C-1), examples of the fatty acid partial ester of a polyhydric alcohol include fatty acids having 12 or more carbon atoms, such as lauric acid, oleic acid, palmitic acid, stearic acid, 12-hydroxystearic acid, behenic acid, and montanic acid.

[0051] Examples of the polyhydric hydroxyl group-containing compound (C-1) include ethers obtained by addition polymerization of alkylene oxide to glycerin fatty acid esters or diglycerin. Specific examples of glycerin fatty acid esters include glycerin monostearate, glycerin monobehenate, diglycerin monostearate, triglycerin monostearate, triglycerin stearic acid partial ester, tetraglycerin stearic acid partial ester, decaglycerin lauric acid partial ester, and glycerin mono-12-hydroxystearate. Examples of ethers obtained by addition polymerization of alkylene oxide to diglycerin include polyoxypropylene diglyceryl ether and polyoxyethylene diglyceryl ether.

[0052] From the viewpoint of flowability, the PBT resin composition may contain a polyvalent hydroxyl group-containing compound (C-1). The PBT resin composition may contain one type of polyvalent hydroxyl group-containing compound (C-1) alone or two or more types of polyvalent hydroxyl group-containing compound (C-1) in combination. The PBT resin composition does not necessarily contain the polyvalent hydroxyl group-containing compound (C-1).

[0053] From the viewpoint of suppressing changes in fluidity during production or molding of the resin composition, the amount of the polyvalent hydroxyl group-containing compound (C-1) is preferably less than 0.05 parts by mass per 100 parts by mass of the PBT resin. That is, the PBT resin composition preferably does not contain the polyvalent hydroxyl group-containing compound (C-1), or contains the polyvalent hydroxyl group-containing compound (C-1) in an amount of less than 0.05 parts by mass per 100 parts by mass of the PBT resin. The amount of the polyvalent hydroxyl group-containing compound (C-1) is more preferably 0.045 parts by mass or less, and even more preferably 0.040 parts by mass or less, per 100 parts by mass of the PBT resin. When the polyvalent hydroxyl group-containing compound (C-1) is contained in the PBT resin composition, the amount may be, for example, 0.010 parts by mass or more per 100 parts by mass of the PBT resin composition. The polyvalent hydroxyl group-containing compound (C-1) may be contained in an amount of, for example, 0.010 parts by mass or more but less than 0.05 parts by mass, 0.010 to 0.045 parts by mass, or 0.010 to 0.040 parts by mass relative to 100 parts by mass of the PBT resin.

[0054] The "hydroxyl group-containing compound (C-2)" is a compound having one or more hydroxyl groups in one molecule and a hydroxyl value of 10 or more but less than 200.

[0055] In the hydroxyl group-containing compound (C-2), examples of the polyhydric alcohol include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, trimethylolmethane, pentaerythritol, dipentaerythritol, tripentaerythritol, various sorbitols, etc. In the hydroxyl group-containing compound (C-2), examples of the fatty acid partial ester of the polyhydric alcohol include fatty acids having 12 or more carbon atoms, such as lauric acid, oleic acid, palmitic acid, stearic acid, 12-hydroxystearic acid, behenic acid, and montanic acid. Examples of the hydroxyl group-containing compound (C-2) include ethylene glycol monostearate, ethylene glycol monobehenate, ethylene glycol monomontanate, diglycerol monostearate, glycerol stearic acid partial ester, diglycerol stearic acid partial ester, triglycerol stearic acid partial ester, oleic acid monoglyceride, propylene glycol monobehenate, propylene glycol monomontanate, pentaerythritol monooleate, sorbitan tristearate, and sorbitan trioleate.

[0056] From the viewpoint of fluidity, the PBT resin composition may contain a hydroxyl group-containing compound (C-2). The PBT resin composition may contain one type of hydroxyl group-containing compound (C-2) alone or two or more types in combination. The PBT resin composition may not contain a hydroxyl group-containing compound (C-2). The amount of the hydroxyl group-containing compound (C-2) is, for example, preferably 0.01 to 5 parts by mass, more preferably 0.05 to 1 part by mass, per 100 parts by mass of the PBT resin.

[0057] [Polybutylene terephthalate resin composition] The PBT resin composition of the embodiment has excellent hydrolysis resistance and can suppress, for example, a decrease in toughness after storage under high-temperature and high-humidity conditions. For example, the PBT resin composition preferably has a tensile break strain of 4% or more, more preferably 5% or more, after 60 hours of treatment under conditions of 121°C and 100Rh. The tensile break strain after 60 hours of treatment under conditions of 121°C and 100Rh can be measured by the method described in the examples.

[0058] The PBT resin composition of the embodiment can achieve good flowability during injection molding. For example, the PBT resin composition can be molded at 260°C, a residence time of 9 minutes, and a shear rate of 1000 sec according to ISO 11443. －１ The melt viscosity at a 9-minute residence time (hereinafter also referred to as "melt viscosity at a 9-minute residence time") can be an indicator of fluidity during injection molding. From the viewpoint of good fluidity during injection molding, the melt viscosity at a 9-minute residence time is preferably 0.25 kPa s or less, and more preferably 0.22 kPa s or less. The melt viscosity at a 9-minute residence time can be measured by the method described in the Examples.

[0059] The PBT resin composition of the embodiment can suppress changes in flowability during production and molding of the resin composition. For example, in accordance with ISO 11443, at 260°C, a residence time of 3.5 minutes, and a shear rate of 1000 sec －１ (hereinafter also referred to as "melt viscosity at a residence time of 3.5 minutes") and the melt viscosity at 260°C, residence time of 9 minutes, and shear rate of 1000 sec according to ISO 11443. －１ The difference between the melt viscosity at a residence time of 3.5 minutes and the melt viscosity at a residence time of 9 minutes (melt viscosity at a residence time of 3.5 minutes - melt viscosity at a residence time of 9 minutes) can be an indicator of changes in fluidity during production or molding of the resin composition. From the viewpoint of suppressing changes in fluidity during production or molding of the resin composition, the difference between the melt viscosity at a residence time of 3.5 minutes and the melt viscosity at a residence time of 9 minutes is preferably 0.025 kPa s or less, and more preferably 0.015 kPa s or less. The melt viscosity at a residence time of 3.5 minutes and the melt viscosity at a residence time of 9 minutes can each be measured by the methods described in the Examples.

[0060] [Method for Producing Polybutylene Terephthalate Resin Composition] The method for producing the PBT resin composition is not particularly limited, and a known method can be used, for example, a method in which each component is charged into an extruder, melt-kneaded, and pelletized.

[0061] <Molded Article> A molded article according to one embodiment of the present invention can be obtained using the PBT resin composition described above.

[0062] The method for obtaining a molded article using the PBT resin composition is not particularly limited, and any known method can be used. For example, the PBT resin composition can be fed into an extruder, melt-kneaded, extruded, and pelletized, and the pellets can be fed into an injection molding machine equipped with a predetermined mold and injection-molded.

[0063] The molded article of the present embodiment can be suitably used as a molded article that is exposed to high-temperature, high-humidity environments for a long period of time, for example, in automobiles, trains, the aviation industry, etc. For example, since deterioration due to hydrolysis caused by use in a high-temperature, high-humidity environment can be prevented, the molded article can be used for connectors, etc.

[0064] Embodiments of the present invention include the following, but the present invention is not limited to the following embodiments: <1> A polybutylene terephthalate resin composition comprising a polybutylene terephthalate resin (A) having a terminal carboxyl group amount of 25 meq / kg or less and a cyclic carbodiimide compound (B), in which a polyhydroxyl group-containing compound (C-1) which is a polyhydric alcohol or a partial ester thereof and has a hydroxyl value of 200 or more is less than 0.05 parts by mass per 100 parts by mass of the polybutylene terephthalate resin (A), and which satisfies the following formula 1: (-15.4 × b) + 19.3≦a≦(-57.4 × b) + 59.3 Formula 1 (In Formula 1, a represents the amount of carbodiimide groups per 1 kg of the polybutylene terephthalate resin composition (meq / kg), and b represents the intrinsic viscosity (dL / g) of the polybutylene terephthalate resin (A).) <2> The polybutylene terephthalate resin composition according to <1> above, which contains a hydroxyl group-containing compound (C-2) which is a polyhydric alcohol or a partial ester thereof and has a hydroxyl value of 10 or more and less than 200. <3> The polybutylene terephthalate resin composition according to <1> or <2> above, which contains 0.010 to 0.045 parts by mass of the polyhydric alcohol or a partial ester thereof which has a hydroxyl value of 200 or more. <4> A molded article obtained using the polybutylene terephthalate resin composition according to any one of <1> to <3>.

[0065] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0066] <Production of Polybutylene Terephthalate Resin Composition> The compositions of the PBT resin compositions of each Example and Comparative Example are shown in Tables 1 and 2 below. The content of each component in Tables 1 and 2 is expressed in parts by mass. The components shown in Tables 1 and 2 were melt-kneaded and extruded in the ratios (parts by mass) shown in Tables 1 and 2 using a 30 mmφ twin-screw extruder (TEX30C, manufactured by The Japan Steel Works, Ltd.) with a cylinder temperature of 230°C in the raw material supply section and 240 to 250°C in between, at a discharge rate of 15 kg / h and a screw rotation speed of 130 rpm, to obtain pellets of the PBT resin composition.

[0067] Details of each component in Tables 1 and 2 are as follows:

[0068] (1) PBT Resins A-1: ​​PBT resin manufactured by Polyplastics Co., Ltd. (intrinsic viscosity 0.676 dL / g, terminal carboxyl group amount 15 meq / kg) A-2: PBT resin (intrinsic viscosity 0.733 dL / g, terminal carboxyl group amount 14.1 meq / kg, manufactured by Polyplastics Co., Ltd.) A-3: PBT resin (intrinsic viscosity 0.733 dL / g, terminal carboxyl group amount 30 meq / kg, manufactured by Polyplastics Co., Ltd.) A-4: PBT resin (intrinsic viscosity 0.797 dL / g, terminal carboxyl group amount 13.1 meq / kg, manufactured by Polyplastics Co., Ltd.) A-5: PBT resin (intrinsic viscosity 0.822 dL / g, terminal carboxyl group amount 12.8 meq / kg, manufactured by Polyplastics Co., Ltd.) A-6: PBT resin (intrinsic viscosity 0.878 dL / g, terminal carboxyl group amount 12 meq / kg, manufactured by Polyplastics Co., Ltd.)

[0069] (2) Cyclic carbodiimide compound B: Cyclic carbodiimide compound ("Carbodista TCC-NP" manufactured by Teijin Limited)

[0070] (3) Hydroxyl-containing compounds which are polyhydric alcohols or partial esters thereof (hydroxyl-containing compounds) C-1: Glycerin mono-12-hydroxystearate (hydroxyl value 420, manufactured by Riken Vitamin Co., Ltd., "Rikemal HC-100") C-2: Propylene glycol monobehenate (hydroxyl value 145, manufactured by Riken Vitamin Co., Ltd., "Rikemal PB-100")

[0071] In Tables 1 and 2, "a (meq / kg)" represents the amount of carbodiimide groups per 1 kg of the PBT resin composition (meq / kg), "b (dL / g)" represents the intrinsic viscosity of the PBT resin (dL / g), and "c (meq / kg)" represents the amount of terminal carboxyl groups of the PBT resin (meq / kg).

[0072] <Evaluation> The obtained PBT resin composition pellets were subjected to the following evaluations.

[0073] (1) Melt viscosity: An index of fluidity during injection molding, measured at 260°C, a residence time of 9 minutes, and a shear rate of 1000 sec according to ISO 11443. －1 The melt viscosity at 260°C, a residence time of 3.5 minutes, and a shear rate of 1000 sec was evaluated in accordance with ISO 11443 as an index of the change in fluidity during the production and molding of the resin composition. －1 (hereinafter and in Tables 1 and 2, this is also referred to as "melt viscosity at a residence time of 3.5 minutes") and the melt viscosity at 260°C, residence time of 9 minutes, and shear rate of 1000 sec according to ISO 11443. －1 The difference between the melt viscosity at 9 minutes residence time and the melt viscosity at 9 minutes residence time was evaluated.

[0074] Specifically, the melt viscosities at a residence time of 3.5 minutes and at a residence time of 9 minutes were measured as follows: The pellets of the PBT resin composition obtained above were measured in accordance with ISO 11443 using a Capillograph 1B (manufactured by Toyo Seiki Seisakusho Co., Ltd.) at a furnace temperature of 260°C, a capillary diameter of 1 mm x 20 mm, and a shear rate of 1000 sec. －1 The melt viscosity was measured under conditions of a residence time of 3.5 minutes and 9 minutes.

[0075] Tables 1 and 2 show the melt viscosities (kPa s) after a 9-minute residence time. Tables 1 and 2 also show the difference between the melt viscosities after a 3.5-minute residence time and the melt viscosities after a 9-minute residence time (melt viscosity after a 3.5-minute residence time - melt viscosity after a 9-minute residence time) (kPa s) using X and Y. Specifically, a difference between the melt viscosities after a 3.5-minute residence time and the melt viscosities after a 9-minute residence time of less than 0.025 kPa s is shown as X, and a difference of 0.025 kPa s or more is shown as Y.

[0076] (2) Tensile Breaking Strain After Wet Heat Treatment To evaluate hydrolysis resistance, the tensile breaking strain after wet heat treatment was measured. Specifically, pellets of the PBT resin composition obtained above were dried at 140°C for 3 hours, and then injection molded at a cylinder temperature of 260°C and a mold temperature of 80°C to prepare 1A-type tensile test specimens in accordance with ISO 3167. The obtained test specimens were treated (wet heat treatment) for 60 hours using a pressure cooker (PCT) testing machine under conditions of 121°C, 100% Rh, and 203 kPa, and then the tensile breaking strain was measured in accordance with ISO 527-1 and 2. A tensile breaking strain of 4% or more was considered to have good hydrolysis resistance.

[0077]

[0078]

[0079] As shown in Table 1, Examples 1 to 8 showed good results in all of the melt viscosity at a 9-minute residence time, which was evaluated as an index of fluidity during molding; the difference between the melt viscosity at a 3.5-minute residence time and the melt viscosity at a 9-minute residence time, which was evaluated as an index of change in fluidity during production and molding of the resin composition; and the tensile strain at break after moist heat treatment, which was evaluated as an index of hydrolysis resistance. These results indicate that PBT resin compositions were obtained that were excellent in hydrolysis resistance and fluidity and in which changes in fluidity during production and molding of the resin composition were suppressed. Specifically, in all of Examples 1 to 8, the melt viscosity at a 9-minute residence time was 0.25 kPa s or less, the difference between the melt viscosity at a 3.5-minute residence time and the melt viscosity at a 9-minute residence time was less than 0.025 kPa s, and the tensile strain at break after moist heat treatment was 4% or more.

[0080] In contrast, Comparative Examples 1 and 2, which do not satisfy the formula "(-15.4 x b) + 19.3 ≦ a" in Formula 1, and Comparative Example 5, which used a PBT resin with a terminal carboxyl group content of more than 25 meq / kg, exhibited low tensile strain at break after wet heat treatment. Furthermore, Comparative Examples 3 and 4, which do not satisfy the formula "a ≦ (-57.4 x b) + 59.3" in Formula 1, exhibited high melt viscosities at a residence time of 9 minutes. Furthermore, Comparative Example 6, which used a resin composition containing 0.06 parts by mass of glycerin mono-12-hydroxystearate, a polyhydric alcohol or its partial ester having a hydroxyl value of 200 or more, per 100 parts by mass of PBT resin, exhibited a large difference between the melt viscosity at a residence time of 3.5 minutes and the melt viscosity at a residence time of 9 minutes.

[0081] The disclosure of this application is related to the subject matter described in Japanese Patent Application No. 2023-138122, filed on August 28, 2023, the entire disclosure of which is incorporated herein by reference.

Claims

1. A polybutylene terephthalate resin composition comprising a polybutylene terephthalate resin (A) having a terminal carboxyl group amount of 25 meq / kg or less and a cyclic carbodiimide compound (B), wherein a polyhydric alcohol or a partial ester thereof having a hydroxyl group value of 200 or more and a polyhydric hydroxyl group-containing compound (C-1) is less than 0.05 parts by mass per 100 parts by mass of the polybutylene terephthalate resin (A), and the composition satisfies the following formula 1: (-15.4 x b) + 19.3 ≦ a ≦ (-57.4 x b) + 59.3 Formula 1 (In formula 1, a represents the amount of carbodiimide groups (meq / kg) per 1 kg of the polybutylene terephthalate resin composition, and b represents the intrinsic viscosity (dL / g) of the polybutylene terephthalate resin (A).) 2. The polybutylene terephthalate resin composition according to claim 1, which contains a hydroxyl-containing compound (C-2) which is a polyhydric alcohol or a partial ester thereof and has a hydroxyl value of 10 or more and less than 200.

3. The polybutylene terephthalate resin composition according to claim 1 or 2, comprising 0.010 to 0.045 parts by mass of the polyhydric alcohol or its partial ester having a hydroxyl value of 200 or more (C-1) per 100 parts by mass of the polybutylene terephthalate resin (A).

4. A molded article obtained by using the polybutylene terephthalate resin composition according to any one of claims 1 to 3.

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