JP7699174B2 - Polybutylene terephthalate resin composition and molded article - Google Patents

Description

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

Polybutylene terephthalate resin (hereinafter referred to as "PBT resin") has excellent mechanical properties, electrical properties, other physical properties, and chemical properties, and is also easy to process, so it is used as an engineering plastic in a wide range of applications, such as automobile parts and electrical and electronic parts. PBT resin is particularly preferred for applications such as cases that house circuit boards on which electronic parts are mounted, insert molded products that contain sensor cases and connector terminals, and actuator cases that protect gears and motors, in order to protect against damage caused by external moisture, dust, or impact.

On the other hand, because PBT resin has ester groups in its molecules, it is prone to hydrolysis in hot and humid environments, which can lead to a decrease in physical properties such as toughness. For this reason, when molded products are used in environments subject to severe temperature changes, such as inside the engine compartment of an automobile or outdoors, improved hydrolysis resistance is desirable.

As a method for improving the hydrolysis resistance of PBT resin, for example, the addition of a carbodiimide compound is known. On the other hand, 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 of which has only one carbodiimide group in one ring, and a polyhydric hydroxyl group-containing compound having a hydroxyl value of 200 or more, has excellent hydrolysis resistance and flowability, and can suppress the generation of isocyanate gas during molding.

International Publication No. 2013/146625

In addition to improving hydrolysis resistance, it is desirable for the polybutylene terephthalate resin composition to have good flowability during molding from the viewpoint of good moldability. Also, from the viewpoint of management during production and molding of the resin composition, it is desirable that the flowability during production and molding of the resin composition does not change significantly.
An object of an embodiment of the present invention is to provide a polybutylene terephthalate resin composition that is excellent in 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.

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), in which a polyhydric alcohol or a partial ester thereof having a hydroxyl value of 200 or more and a polyhydric hydroxyl group-containing compound (C-1) is less than 0.05 part by mass per 100 parts by mass of the polybutylene terephthalate resin (A), and the polybutylene terephthalate resin composition 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 (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.

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

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

<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).

[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 an 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, and may be a copolymer containing 60 mol % or more (particularly 75 mol % or more and 95 mol % or less) of butylene terephthalate units.
Furthermore, 1,4-butanediol and terephthalic acid or terephthalic acid alkyl ester, which are the raw materials for the PBT resin (A), 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 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 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 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.

The intrinsic viscosity (IV) of the PBT resin (A) is preferably a value that satisfies the formula 1. The formula 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 a temperature of 35°C.

In the 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 ( _C1-6 alkyl ester derivatives, acid halides, and the like). 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 the 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 2-mol ethylene oxide adducts of bisphenol A and 3-mol propylene oxide adducts 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.

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. 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, _C3-12 lactones such as propiolactone, butyrolactone, valerolactone, and caprolactone (ε-caprolactone, etc.), and ester-forming derivatives of these comonomer components ( _C1-6 alkyl ester derivatives, acid halides, acetylated products, etc.).

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

As the PBT resin (A), for example, a recycled product may be used.
As the PBT resin (A), for example, market collected products can be used (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.

[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, a compound containing a cyclic structure formed by linking two nitrogen atoms of the carbodiimide group with a linking group.

The cyclic carbodiimide compound (B) may 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. 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.

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

The cyclic carbodiimide compound (B) can be represented, for example, by the following formula (1):

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 the heteroatom 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 including one or more atoms that directly constitute the main chain of L, and may further include, for example, a carbodiimide group in such a second cyclic structure.

In L, the number of atoms that directly form a cyclic structure together with the carbodiimide group is not particularly limited. For example, in L, the number of atoms that directly form a cyclic structure together with the carbodiimide group is preferably 5 or more, and more preferably 7 or more. In addition, in L, the number of atoms that directly form a 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 that directly form a cyclic structure together with the carbodiimide group may be, for example, 5 to 47, 5 to 27, 7 to 17, or 7 to 12.

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.

Examples of the divalent to tetravalent aliphatic group 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. and alkanetriyl groups having 1 to 20 carbon atoms, such as a methanetetrayl group, an ethanetetrayl group, a propanetetrayl group, a butanetetrayl group, a pentanetetrayl group, a hexanetetrayl group, a heptanetetrayl group, an octanetetrayl group, a nonanetetrayl group, a decanetetrayl group, a dodecanetetrayl group, a hexadecanetetrayl group, and an octadecanetetrayl group.
Examples of the divalent to tetravalent alicyclic group having 3 to 20 carbon atoms include a cycloalkylene group, a cycloalkanetriyl group, and a cycloalkanetetrayl group.

Examples of divalent to tetravalent aromatic groups having 5 to 15 carbon atoms include arylene groups such as phenylene and naphthalenediyl groups; arenetriyl groups such as benzenetriyl and naphthalenetriyl groups; arenetetrayl groups such as benzenetetrayl and naphthalenetetrayl groups, etc.

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

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

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 a bonding site with a nitrogen atom of a carbodiimide group.

When X is an unsubstituted alkylene group, examples of X include -( _CH2 ) _n- . n is preferably 1 to 6, more preferably 1 to 4, and may be 2, for example.
When X is an alkylene group having a substituent, examples of X include a group represented by the following formula (3).

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 ring structure together with the carbon atom to which A and B are bonded. Examples of the substituent include an alkyl group having 1 to 20 carbon atoms. When A and B are bonded to each other to form a ring structure together with the carbon atom to which A and B are bonded, X may be, for example, a group represented by the following formula (4).

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

*-(CH ₂ ) _r -O-Ar ³ -N=C=N-Ar ⁴ -O-(CH ₂ ) _s -* (5)
In formula (5), * denotes an end of M and indicates a bonding site with a carbon atom. Each of r and s is preferably an integer of 1 to 3, more preferably 1 or 2, and may be, for example, 1. Each of ^Ar3 and ^Ar4 is 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.

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), 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), 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.

The cyclic carbodiimide compound (B) may be contained in the PBT resin composition either alone or in combination of two or more kinds.
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.

When a cyclic carbodiimide compound is used, the viscosity of the resin increases during injection molding, the flowability decreases, and there are cases where good molded products cannot be obtained due to poor filling. From the viewpoint of improving hydrolysis resistance and of improving the viscosity during injection molding and thereby obtaining 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×b)+19.3≦a≦(-57.4×b)+59.3 Formula 1

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

From the viewpoint of improving hydrolysis resistance, it is preferable that the PBT resin composition satisfies (-15.4 x b) + 19.3 ≦ a, and it is more preferable that the PBT resin composition satisfies (-15.4 x b) + 20.3 ≦ a.

From the viewpoint of achieving good flowability during injection molding and thus good moldability, it is preferable for the PBT resin composition to satisfy a≦(-57.4×b)+59.3, and it is even more preferable for the PBT resin composition to satisfy a≦(-57.4×b)+58.3.

[Other ingredients]
The PBT resin composition may contain other components as necessary, such as, for example, 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 regulator, 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 assistant, an organic filler, and a colorant, but is not limited thereto.

Examples of hydroxyl-containing compounds that are polyhydric alcohols or partial esters thereof include polyhydric alcohols or partial esters thereof that have a hydroxyl value of 200 or more (C-1) (hereinafter also referred to as "polyhydric hydroxyl-containing compound (C-1)") and polyhydric alcohols or partial esters thereof that have a hydroxyl value of 10 or more and less than 200 (C-2) (hereinafter also referred to as "hydroxyl-containing compound (C-2)").

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

In this specification, the hydroxyl value refers to the value measured according to Japan Oil Chemists' Society Method 2.3.6.2-1996 (pyridine-acetic anhydride method) (Standard Test Method for Analysis of Fats and Oils Established by Japan Oil Chemists' Society).

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.

In the polyhydric hydroxyl group-containing compound (C-1), examples of fatty acids that are partial esters of polyhydric alcohols 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 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, glycerin mono 12-hydroxystearate, etc. Examples of ethers obtained by addition polymerization of alkylene oxide to diglycerin include polyoxypropylene diglyceryl ether, polyoxyethylene diglyceryl ether, etc.

From the viewpoint of fluidity, 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 in combination. The PBT resin composition may not contain a polyvalent hydroxyl group-containing compound (C-1).

From the viewpoint of suppressing changes in flowability 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 relative to 100 parts by mass of the PBT resin. In other words, it is preferable that the PBT resin composition 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 relative to 100 parts by mass of the PBT resin.
The amount of the polyhydric 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, based on 100 parts by mass of the PBT resin.
When the polyhydric hydroxyl group-containing compound (C-1) is contained in the PBT resin composition, the amount thereof may be, for example, 0.010 parts by mass or more relative to 100 parts by mass of the PBT resin composition. The polyhydric hydroxyl group-containing compound (C-1) may be contained in an amount of, for example, 0.010 parts by mass or more and 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.

"Hydroxyl group-containing compound (C-2)" is a compound that has one or more hydroxyl groups in one molecule and has a hydroxyl value of 10 or more and less than 200.

Examples of the polyhydric alcohol in the hydroxyl group-containing compound (C-2) 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.
In the hydroxyl group-containing compound (C-2), examples of the fatty acid that is the 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 stearate partial ester, diglycerol stearate partial ester, triglycerol stearate partial ester, oleic acid monoglyceride, propylene glycol monobehenate, propylene glycol monomontanate, pentaerythritol monooleate, sorbitan tristearate, and sorbitan trioleate.

From the viewpoint of flowability, 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, and more preferably 0.05 to 1 part by mass, based on 100 parts by mass of the PBT resin.

[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.

The PBT resin composition of the embodiment can realize good fluidity during injection molding. For example, the melt viscosity of the PBT resin composition at 260°C, a residence time of 9 minutes, and a shear rate of 1000 sec ^-1 according to ISO11443 (hereinafter also referred to as "melt viscosity at a residence time of 9 minutes") can be an index of fluidity during injection molding. From the viewpoint of good fluidity during injection molding, the melt viscosity at a residence time of 9 minutes is preferably 0.25 kPa·s or less, more preferably 0.22 kPa·s or less. The melt viscosity at a residence time of 9 minutes can be measured by the method described in the Examples.

The PBT resin composition of the embodiment can suppress changes in fluidity during production or molding of the resin composition. For example, the difference between the melt viscosity at 260 ° C., residence time 3.5 minutes, and shear rate 1000 sec ⁻¹ (hereinafter also referred to as “melt viscosity at residence time 3.5 minutes”) in accordance with ISO11443 and the melt viscosity at 260 ° C., residence time 9 minutes, and shear rate 1000 sec ⁻¹ (melt viscosity at residence time 9 minutes) in accordance with ISO11443 (melt viscosity at residence time 3.5 minutes−melt viscosity at residence time 9 minutes) can be an index 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 residence time 3.5 minutes and the melt viscosity at residence time 9 minutes is preferably 0.025 kPa·s or less, 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 be measured by the method described in the Examples.

[Method of producing polybutylene terephthalate resin composition]
The method for producing the PBT resin composition is not particularly limited, and may be any known method, such as a method in which each component is put into an extruder, melt-kneaded, and pelletized.

<Molded product>
A molded article according to one embodiment of the present invention can be obtained by using the above-mentioned PBT resin composition.

There are no particular limitations on the method for obtaining a molded article using the PBT resin composition, 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 specified mold and injection molded to produce a molded article.

The molded product of this embodiment can be suitably used as a molded product that is exposed to high temperature and high humidity environments for long periods of time, such as in automobiles, trains, and the aviation industry. For example, it can be used for connectors, etc., because it can prevent deterioration due to hydrolysis caused by use in high temperature and high humidity environments.

The embodiments of the present invention include the following, but the present invention is not limited to the following embodiments.
＜1＞
The present invention comprises a polybutylene terephthalate resin (A) having a terminal carboxyl group amount of 25 meq/kg or less, and a cyclic carbodiimide compound (B),
the amount of a polyhydric alcohol or a partial ester thereof having a hydroxyl value of 200 or more and a polyhydric hydroxyl group-containing compound (C-1) is less than 0.05 parts by mass relative to 100 parts by mass of the polybutylene terephthalate resin (A);
A polybutylene terephthalate resin composition satisfying 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 (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 <1>, further comprising 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 <1> or <2>, comprising 0.010 to 0.045 parts by mass of the polyhydric alcohol or a partial ester thereof having a hydroxyl value of 200 or more, based on 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 <1> to <3>.

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.

<Production of polybutylene terephthalate resin composition>
The compositions of the PBT resin compositions of the examples and comparative examples are shown in the following Tables 1 and 2. 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 a PBT resin composition.

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

(1) PBT resin 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.)

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

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

In Tables 1 and 2, "a (meq/kg)" represents the amount of carbodiimide groups per 1 kg of 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).

<Evaluation>
The obtained PBT resin composition pellets were used for the following evaluations.

(1) Melt Viscosity As an index of fluidity during injection molding, the melt viscosity (melt viscosity at 9-minute residence time) was evaluated according to ISO11443 at 260°C, residence time of 9 minutes, and shear rate of 1000 sec ^-1 . In addition, as an index of change in fluidity during production or molding of the resin composition, the difference between the melt viscosity at 260°C, residence time of 3.5 minutes, and shear rate of 1000 sec ^-1 according to ISO11443 (hereinafter and in Tables 1 and 2, also referred to as "melt viscosity at 3.5 minutes residence time") and the melt viscosity at 260°C, residence time of 9 minutes, and shear rate of 1000 sec ^-1 according to ISO11443 ("melt viscosity at 9-minute residence time") was evaluated.

Specifically, the melt viscosities at a residence time of 3.5 minutes and 9 minutes were measured as follows: The melt viscosities of the pellets of the PBT resin composition obtained above were measured in accordance with ISO11443 using Capillograph 1B (manufactured by Toyo Seiki Seisakusho) under the conditions of a furnace temperature of 260°C, a capillary diameter of φ1 mm×20 mmL, a shear rate of 1000 sec ⁻¹ , and residence times of 3.5 minutes and 9 minutes.

Tables 1 and 2 show the melt viscosities (kPa·s) at a residence time of 9 minutes.
In addition, in Tables 1 and 2, 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) (kPa s) is shown using X and Y. Specifically, when 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 less than 0.025 kPa s, it is shown as X, and when it is 0.025 kPa s or more, it is shown as Y.

(2) Tensile strain at break after moist heat treatment To evaluate hydrolysis resistance, the tensile strain at break after moist heat treatment was measured. Specifically, the 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 a 1A type tensile test piece conforming to ISO3167. The obtained test piece was treated (moist heat treatment) for 60 hours under conditions of 121°C, 100% Rh, and 203 kPa using a pressure cooker (PCT) tester, and then the tensile strain at break was measured in accordance with ISO527-1,2. A tensile strain at break of 4% or more is considered to have good hydrolysis resistance.

As shown in Table 1, in Examples 1 to 8, good results were observed in the melt viscosity at a residence time of 9 minutes, which was evaluated as an index of fluidity during molding, 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, which was evaluated as an index of changes in fluidity during production and molding of the resin composition, and the tensile breaking strain after moist heat treatment, which was evaluated as an index of hydrolysis resistance. It can be seen that a PBT resin composition was obtained that had excellent hydrolysis resistance and fluidity and suppressed changes in fluidity during production and molding of the resin composition. Specifically, in all of Examples 1 to 8, the melt viscosity at a residence time of 9 minutes was 0.25 kPa·s or less, 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 was less than 0.025 kPa·s, and the tensile breaking strain after moist heat treatment was 4% or more.

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

Claims (4)

The present invention comprises a polybutylene terephthalate resin (A) having a terminal carboxyl group amount of 25 meq/kg or less, and a cyclic carbodiimide compound (B),
the amount of a polyhydric alcohol or a partial ester thereof having a hydroxyl value of 200 or more and a polyhydric hydroxyl group-containing compound (C-1) is less than 0.05 parts by mass relative to 100 parts by mass of the polybutylene terephthalate resin (A);
A polybutylene terephthalate resin composition satisfying 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 (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) measured in o-chlorophenol at a temperature of 35° C. ) The polybutylene terephthalate resin composition according to claim 1, which contains a hydroxyl-containing compound (C-2) that is a polyhydric alcohol or a partial ester thereof and has a hydroxyl value of 10 or more and less than 200. The polybutylene terephthalate resin composition according to claim 1, comprising 0.010 to 0.045 parts by mass of the polyhydric alcohol or its partial ester, a polyhydroxyl-containing compound (C-1) having a hydroxyl value of 200 or more, per 100 parts by mass of the polybutylene terephthalate resin (A). A molded article obtained using the polybutylene terephthalate resin composition according to any one of claims 1 to 3.