JP7839699B2 - Polybutylene terephthalate resin composite and method for producing polybutylene terephthalate resin composite - Google Patents

Description

Embodiments of the present invention relate to polybutylene terephthalate resin composites and methods for producing polybutylene terephthalate resin composites.

Polyester resins, such as polybutylene terephthalate resin (hereinafter also referred to as "PBT resin"), possess excellent mechanical, electrical, heat-resistant, and moldable properties, and are widely used in various fields, including automotive parts, electrical and electronic equipment parts, and precision instrument parts. Because polyester resins contain ester groups in their molecules, hydrolysis is easily performed in high-temperature and high-humidity environments. Therefore, in automotive parts, which are subject to significant environmental changes, improved hydrolysis resistance is always desired.

To improve the hydrolysis resistance of the polybutylene resin itself, it is generally known that epoxy resins or carbodiimide compounds are added to reduce the amount of terminal carboxyl groups. Patent Document 1 shows that in a resin composition containing polybutylene terephthalate resin with a terminal carboxyl group content of 30 meq/kg or less, a carbodiimide compound, a fibrous filler, and an elastomer, the heat shock resistance and hydrolysis resistance are improved when the amount of carbodiimide compound is such that, when the amount of terminal carboxyl groups in the polybutylene terephthalate resin is set to 1, the amount of carbodiimide functional groups is 0.3 to 1.5 equivalents.

On the other hand, when obtaining molded products using polyester resin, extrusion molding and injection molding are frequently used due to their productivity and cost-effectiveness. Because polyester resin is prone to hydrolysis, it is generally dried before molding. However, during this drying process, a phenomenon known as blocking or sticking, where pellets adhere to each other, can occur. This is generally more likely to occur when the elastic modulus, glass transition temperature, and crystallinity of the resin composition are low. For example, after loading dried pellets into the hopper of an extrusion or injection molding machine, blocking or sticking may occur due to the weight of the pellets within the hopper, or pellets may adhere to the screw opening, preventing molding. Furthermore, when weighing pellets with a screw, stuck pellets can cause the screw to slip or lead to inaccurate weighing due to poor pellet transport. Depending on the pellet shape, insufficient heat from the cylinder or poor feeding may occur, preventing plasticization and resulting in inaccurate weighing.

Patent Document 2 describes that sticking can be suppressed by heating resin pellets at a temperature range above the cold crystallization temperature and 30°C below the melting point to induce crystallization.
Patent Document 3 describes that in elliptical cylindrical thermoplastic aromatic polyester resin pellets, when the ratio of the major axis to the minor axis of the cross-section perpendicular to the longitudinal direction is > 1, the bulk density is > 0.8 g/cm³, ^and the excluded volume density is 0.4 ≤ < 0.5 g/ ^cm³ , variations in metering can be suppressed.
Patent Document 4 describes how, in order to improve the issue of tip penetration into the screw of an injection molding machine, calcium stearate or the like is added to the polybutylene terephthalate tip as an external lubricant, and how, after adding the external lubricant to the polybutylene terephthalate tip, fine powder is removed using an air classifier, thereby allowing the fine powder to be removed while the external lubricant remains attached at an amount of 200 to 500 ppm by weight per tip.

International Publication No. 2009/150831 Japanese Patent Application Publication No. 5-147026 Japanese Patent Publication No. 2015-044363 Japanese Patent Application Publication No. 6-285850

The embodiment of the present invention aims to provide a polybutylene terephthalate resin composite that offers improved hydrolysis resistance and improved metering properties.

One embodiment of the present invention relates to a polybutylene terephthalate resin composite comprising a polybutylene terephthalate resin composition pellet and an external additive, wherein the polybutylene terephthalate resin composition pellet comprises a polybutylene terephthalate resin with a terminal carboxyl group content of 30 meq/kg or less and a carbodiimide compound in an amount of 0.1 to 1.0% by mass of the total mass of the polybutylene terephthalate resin composite, and the external additive comprises a fatty acid metal salt with a number average particle diameter of 20 μm or less in an amount of 0.005 to 0.10% by mass of the total mass of the polybutylene terephthalate resin composite.
Another embodiment of the present invention relates to a method for producing the polybutylene terephthalate resin composite, comprising mixing the polybutylene terephthalate resin composition pellets with the external additive.

According to embodiments of the present invention, a polybutylene terephthalate resin composite can be provided that exhibits improved hydrolysis resistance and improved metering properties.

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

<Polybutylene terephthalate resin composite>
A polybutylene terephthalate resin composite according to one embodiment of the present invention comprises a polybutylene terephthalate resin composition pellet and an external additive, wherein the polybutylene terephthalate resin composition pellet contains a polybutylene terephthalate resin with a terminal carboxyl group content of 30 meq/kg or less, and a carbodiimide compound in an amount of 0.1 to 1.0% by mass of the total mass of the polybutylene terephthalate resin composite, and the external additive contains a fatty acid metal salt with a number average particle diameter of 20 μm or less in an amount of 0.005 to 0.10% by mass of the total mass of the polybutylene terephthalate resin composite.

[Polybutylene terephthalate resin (PBT resin)]
In the polybutylene terephthalate resin composite of the embodiment, the polybutylene terephthalate resin composition pellet contains a polybutylene terephthalate resin with a terminal carboxyl group content of 30 meq/kg or less.

Polybutylene terephthalate resin is a polybutylene terephthalate-based resin obtained by polycondensation of a dicarboxylic acid component containing at least terephthalic acid or its ester-forming derivative ( _C1-6 alkyl ester, acid halide, etc.) and a glycol component containing at least four-carbon alkylene glycol (1,4-butanediol) or its ester-forming derivative (acetylated, etc.).
The polybutylene terephthalate resin is not limited to homopolybutylene terephthalate resin, but may also be a copolymer containing 60 mol% or more (particularly 75 mol% to 95 mol%) of butylene terephthalate units.

In polybutylene terephthalate resins, dicarboxylic acid components (comonomer components) other than terephthalic acid and its ester-forming derivatives include, for example, _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 acid components can be used individually 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 polybutylene terephthalate resins, glycol components other than 1,4-butanediol (comonomer components) include, for example, 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; or ester-forming derivatives (acetylated compounds, etc.) of these glycols. These glycol components can be used individually 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, or alicyclic diols such as cyclohexanedimethanol are more preferred.

Other comonomer components that can be used besides the dicarboxylic acid and glycol components 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 (ε-caprolactone, etc.); and ester-forming derivatives of these comonomer components ( _C1-6 alkyl ester derivatives, acid halides, acetylated compounds, etc.).

The polybutylene terephthalate copolymers obtained by copolymerizing the comonomer components described above can all be suitably used as polybutylene terephthalate resins. Furthermore, a combination of homopolybutylene terephthalate polymers and polybutylene terephthalate copolymers may be used as the polybutylene terephthalate resin.

The intrinsic viscosity (IV) of the polybutylene terephthalate resin is not particularly limited as long as it does not hinder the effects of the polybutylene terephthalate resin composite of the embodiment. From the viewpoint of processability and mechanical properties, the intrinsic viscosity of the polybutylene terephthalate resin is preferably 0.7 to 1.3 dL/g, more preferably 0.75 to 1.2 dL/g, and even more preferably 0.85 to 1.15 dL/g.
Furthermore, the intrinsic viscosity can be adjusted by blending polybutylene terephthalate resins having different intrinsic viscosities. For example, by blending a polybutylene terephthalate resin with an intrinsic viscosity of 1.0 dL/g with a polybutylene terephthalate resin with an intrinsic viscosity of 0.7 dL/g, a polybutylene terephthalate resin with an intrinsic viscosity of 0.85 dL/g can be prepared.
The intrinsic viscosity (IV) of the polybutylene terephthalate resin shall be the value measured in o-chlorophenol at a temperature of 35°C.

From the viewpoint of hydrolysis resistance, the amount of terminal carboxyl groups in the polybutylene terephthalate resin is preferably 30 meq/kg or less, more preferably 20 meq/kg or less, and even more preferably 10 meq/kg or less.

[Carbodiimide compounds]
In the polybutylene terephthalate resin composite of the embodiment, the polybutylene terephthalate resin composition pellet contains a carbodiimide compound.

In the polybutylene terephthalate resin composite of the embodiment, the carbodiimide compound may contribute to improving hydrolysis resistance.

Carbodiimide compounds are compounds having a carbodiimide group (-N=C=N-) in their molecule. Examples of carbodiimide compounds include aliphatic carbodiimide compounds (with an aliphatic main chain), alicyclic carbodiimide compounds (with an alicyclic main chain), and aromatic carbodiimide compounds (with an aromatic main chain). One or more of these can be used. In particular, it is preferable to include aromatic carbodiimide compounds in terms of heat resistance and moisture resistance of the carbodiimide compound.

Examples of aliphatic carbodiimide compounds include diisopropylcarbodiimide and dioctyldecylcarbodiimide. Examples of alicyclic carbodiimide compounds include dicyclohexylcarbodiimide. These can be used individually or in combination of two or more.

Aromatic carbodiimide compounds include diphenylcarbodiimide, di-2,6-dimethylphenylcarbodiimide, N-triyl-N'-phenylcarbodiimide, di-p-nitrophenylcarbodiimide, di-p-aminophenylcarbodiimide, di-p-hydroxyphenylcarbodiimide, di-p-chlorophenylcarbodiimide, di-p-methoxyphenylcarbodiimide, di-3,4-dichlorophenylcarbodiimide, di-2,5-dichlorophenylcarbodiimide, di-o-chlorophenylcarbodiimide, p-phenylene-bis-di-o-triylcarbodiimide, p-phenylene-bis-dicyclohexylcarbodiimide, p-phenylene-bis-di-p-chlorophenylcarbodiimide, and ethylene-bis Examples include mono- or dicarbodiimide compounds such as s-diphenylcarbodiimide; and polycarbodiimide compounds such as poly(4,4'-diphenylmethanecarbodiimide), poly(3,5'-dimethyl-4,4'-biphenylmethanecarbodiimide), poly(p-phenylenecarbodiimide), poly(m-phenylenecarbodiimide), poly(3,5'-dimethyl-4,4'-diphenylmethanecarbodiimide), poly(naphthylenecarbodiimide), poly(1,3-diisopropylphenylenecarbodiimide), poly(1-methyl-3,5-diisopropylphenylenecarbodiimide), poly(1,3,5-triethylphenylenecarbodiimide), and poly(triisopropylphenylenecarbodiimide). These can be used individually or in combination of two or more.

The number-average molecular weight of the carbodiimide compound is preferably 3000 or higher. By keeping the number-average molecular weight within this range, it is possible to prevent the generation of gases and odors during the melt-kneading and molding of thermoplastic resins, especially when the residence time is long.

In the polybutylene terephthalate resin composite of the embodiment, the content of the carbodiimide compound is 0.1 to 1.0% by mass of the total mass of the polybutylene terephthalate resin composite. From the viewpoint of improving hydrolysis resistance, the content of the carbodiimide compound is preferably 0.1% by mass or more of the total mass of the polybutylene terephthalate resin composite. On the other hand, from the viewpoint of suppressing the generation of isocyanates, the content of the carbodiimide compound is preferably 1.0% by mass or less of the total mass of the polybutylene terephthalate resin composite. The content of the carbodiimide compound is more preferably 0.2 to 0.9% by mass of the total mass of the polybutylene terephthalate resin composite, and even more preferably 0.3 to 0.8% by mass.
The total content of polybutylene terephthalate resin and carbodiimide compound is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more, of the total mass of the polybutylene terephthalate resin composite.

[Other components (polybutylene terephthalate resin composition pellets)]
Polybutylene terephthalate resin composition pellets may contain other components besides those listed above, as needed. Examples of other components of polybutylene terephthalate resin composition pellets include other resins, fillers such as inorganic fillers, antioxidants, stabilizers, antistatic agents, lubricants, plasticizers, nucleating agents, colorants, flame retardants, flame retardant aids, and other additives. One or more of these may be included in the polybutylene terephthalate resin composition pellets as needed.

[Fatty acid metal salts]
The polybutylene terephthalate resin composite of this embodiment includes polybutylene terephthalate resin composition pellets along with an external additive containing a fatty acid metal salt with a number average particle size of 20 μm. By using an external additive containing a fatty acid metal salt, the fatty acid metal salt is externally added to the surface of the polybutylene terephthalate resin composition pellets. The action of the fatty acid metal salt, which is externally added and adheres to the pellet surface, can shorten the weighing time and improve weighing efficiency. On the other hand, since polybutylene terephthalate resin has polyester groups, it is easily hydrolyzed by alkaline components, and when a fatty acid metal salt is used, its hydrolysis resistance may decrease. However, by using a fatty acid metal salt with a number average particle size of 20 μm, it is possible to achieve both hydrolysis resistance and weighing efficiency.

Examples of fatty acid metal salts include alkali metal salts of fatty acids and alkaline earth metal salts of fatty acids. Specifically, examples of fatty acid metal salts include calcium salts of fatty acids, sodium salts of fatty acids, magnesium salts of fatty acids, and zinc salts of fatty acids.
The fatty acids in the fatty acid metal salt are preferably fatty acids having 8 to 30 carbon atoms, more preferably fatty acids having 10 to 25 carbon atoms, and even more preferably fatty acids having 13 to 21 carbon atoms. Saturated fatty acids are preferred for the fatty acid metal salt. Specific examples of fatty acids in the fatty acid metal salt include, for example, caprylic acid, lauric acid, myristic acid, pentadecyl acid, palmitic acid, margaric acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, montanic acid, and melissic acid.
Specific examples of fatty acid metal salts include sodium palmitate, calcium palmitate, sodium stearate, potassium stearate, zinc stearate, calcium stearate, magnesium stearate, and calcium montanate. Calcium stearate is preferred as the fatty acid metal salt.

In the polybutylene terephthalate resin composite of the embodiment, the number-average particle size of the fatty acid metal salt is 20 μm or less. More preferably, the number-average particle size of the fatty acid metal salt is 18 μm or less, and even more preferably 16 μm or less.

The number-average particle size of fatty acid metal salts is calculated by measuring the particle size distribution using a laser diffraction scattering particle size distribution analyzer. The LA-960 laser diffraction scattering particle size distribution analyzer manufactured by Horiba, Ltd. can be used as the measuring device. Specifically, a small amount (approximately 10-20 mg) of fatty acid metal salt is placed in a 10 mL vial using a spatula, 10 mL of acetone is added, and the mixture is thoroughly dispersed in an ultrasonic cleaner. The particle size distribution is then measured using the laser diffraction scattering particle size distribution analyzer, and the number-average particle size can be calculated.

In the composite of the embodiment, the amount of fatty acid metal salt is 0.005 to 0.10% by mass of the total mass of the polybutylene terephthalate resin composite. From the viewpoint of improving metering accuracy, it is preferable that the amount of fatty acid metal salt is 0.005% by mass or more of the total mass of the polybutylene terephthalate resin composite. On the other hand, from the viewpoint of good toughness, it is preferable that the amount of fatty acid metal salt is 0.10% by mass or less of the total mass of the polybutylene terephthalate resin composite. If there is too much fatty acid metal salt, the large amount of powder may actually cause metering errors.
The amount of fatty acid metal salt is more preferably 0.010 to 0.05% by mass of the total mass of the polybutylene terephthalate resin composite, and even more preferably 0.02 to 0.03% by mass.

[Other ingredients (external additives)]
External additives may contain other ingredients besides those listed above, as needed.
For example, the external additive may include a binder to better adhere and retain the fatty acid metal salt to the surface of the polybutylene terephthalate resin composition pellets. Using a binder can improve the adhesion of the fatty acid metal salt to the pellets and reduce the shedding of the fatty acid metal salt from the pellets, thereby reducing contamination of the equipment.

Examples of adhesives include polyethylene glycol, liquid paraffin, paraffin wax, water, and glycerin. One or more of these can be used. Polyethylene glycol is particularly preferred.

The amount of adhesive is preferably 0.005 to 0.1% by mass of the total mass of the polybutylene terephthalate resin composite, more preferably 0.01 to 0.05% by mass, and even more preferably 0.01 to 0.03% by mass.

[Shape of polybutylene terephthalate resin composition pellets]
The diameter of the polybutylene terephthalate resin composition pellets is preferably 2.0 to 3.0 mm, more preferably 2.1 to 2.8 mm, and even more preferably 2.2 to 2.5 mm.
The length of the polybutylene terephthalate resin composition pellets is preferably 1.0 to 3.5 mm, more preferably 1.5 to 3.3 mm, and even more preferably 2.0 to 3.1 mm.

<Method for manufacturing polybutylene terephthalate resin composites>
The method for producing the polybutylene terephthalate resin composite described above is not particularly limited.
The method for producing the polybutylene terephthalate resin composite of the embodiment may include, for example, a method of mixing polybutylene terephthalate resin composition pellets with an external additive.

The method for mixing the polybutylene terephthalate resin composition pellets with the external additive is not particularly limited. For example, the polybutylene terephthalate resin composition pellets and the external additive can be mixed using a mixer such as a tumbler mixer. Furthermore, the polybutylene terephthalate resin composition pellets and the external additive may be mixed all at once or in multiple stages. For example, if the external additive contains a binder and a fatty acid metal salt, the polybutylene terephthalate resin composition pellets and the binder may be mixed first, and then this mixture may be mixed with the metal salt oxide.

Polybutylene terephthalate resin composition pellets can be manufactured by various methods known as methods for manufacturing thermoplastic resin composition pellets. For example, the material for the polybutylene terephthalate resin composition pellets can be fed into an extruder, melt-kneaded, extruded, and pelletized to obtain the polybutylene terephthalate resin composition pellets.

<Molded product>
There are no particular limitations on the method for producing resin molded products using the polybutylene terephthalate resin composite of the embodiment, and known methods can be employed. For example, the polybutylene terephthalate resin composite can be introduced into an injection molding machine equipped with a predetermined mold and injected to produce the product.

This resin composition is suitably used as a resin composition for molded products that are exposed to high temperature and high humidity environments for extended periods, such as in automobiles, trains, and the aerospace industry. Molded products made from this resin composition can prevent degradation due to hydrolysis even when used for extended periods in sufficiently high temperature and high humidity environments, making them suitable for use in connectors, housings, valves, clips, pipes, and the like.

The embodiments of the present invention include, but are not limited to, the embodiments described below.

<Section 1>
A polybutylene terephthalate resin composite comprising polybutylene terephthalate resin composition pellets and an external additive,
The polybutylene terephthalate resin composition pellets contain a polybutylene terephthalate resin with a terminal carboxyl group content of 30 meq/kg or less, and a carbodiimide compound in an amount of 0.1 to 1.0% by mass of the total mass of the polybutylene terephthalate resin composite.
The external additive is a polybutylene terephthalate resin composite comprising a fatty acid metal salt with a number average particle size of 20 μm or less, in an amount of 0.005 to 0.10% by mass of the total mass of the polybutylene terephthalate resin composite.
<Section 2>
The polybutylene terephthalate resin composite according to claim 1, wherein the external additive further comprises at least one selected from the group consisting of polyethylene glycol, liquid paraffin, paraffin wax, water, and glycerin.
<Section 3>
The polybutylene terephthalate resin composite according to claim 1 or 2, wherein the polybutylene terephthalate resin composition pellets have a diameter of 2.0 to 3.0 mm and a length of 1.0 to 3.5 mm.
<Section 4>
The polybutylene terephthalate resin composite according to any one of claims 1 to 3, wherein the fatty acid metal salt comprises calcium stearate.
<Section 5>
A method for producing a polybutylene terephthalate resin composite according to any one of claims 1 to 4, comprising mixing the polybutylene terephthalate resin composition pellets with the external additive.

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

<Examples 1-4 and Comparative Examples 1-6>
In each example and comparative example, components (A) (polybutylene terephthalate resin) and (B) (carbodiimide compound) shown in Tables 1 and 2 below were melt-kneaded and extruded in a twin-screw extruder (TEX30, manufactured by Japan Steel Works Ltd.) with a 30 mmφ screw at a cylinder temperature of 260°C and a screw rotation speed of 130 rpm in the ratios (mass%) shown in Tables 1 and 2 below, and then pelletized using a strand cutter to obtain polybutylene terephthalate resin composition pellets with a diameter of 2.3 mm and a length of 3.0 mm.

For Examples 1 to 4 and Comparative Examples 3 to 5, the pellets obtained as described above were put into a tumbler mixer, and then component (D) (adhesive) shown in Tables 1 and 2 below was added to the tumbler mixer in the ratio (mass%) shown in Tables 1 and 2 below and mixed for 10 minutes. Furthermore, component (C) (fatty acid metal salt) shown in Tables 1 to 2 below was added to the tumbler mixer in the ratio (mass%) shown in the table below and mixed for 10 minutes.
In this way, polybutylene terephthalate resin composites of Examples 1 to 4 and Comparative Examples 3 to 5 were obtained.
In Comparative Example 1, components (C) and (D) were not added, and the pellets obtained in Comparative Example 1 were used as is for subsequent evaluation.
In Comparative Example 2, the pellets of Comparative Example 2 obtained as described above were put into a tumbler mixer, and then component (D) (adhesive) shown in Table 2 below was added in the ratio (parts by mass) shown in Table 2 below, and the mixture was mixed for 10 minutes to obtain the polybutylene terephthalate resin composite of Comparative Example 2.

The details of each component shown in Tables 1 and 2 are as follows. The units for the content of each component in Tables 1 and 2 are in mass percent.

(A) Polybutylene terephthalate resin A1: Polybutylene terephthalate resin (intrinsic viscosity (IV) = 1.14 dL/g, amount of terminal carboxyl groups = 7 meq/kg, manufactured by Polyplastics Co., Ltd.)
A2: Polybutylene terephthalate resin (intrinsic viscosity (IV) = 0.83 dL/g, amount of terminal carboxyl groups = 15 meq/kg, manufactured by Polyplastics Co., Ltd.)

(B) Carbodiimide compounds B1: Aromatic polycarbodiimide (Stabaxol P-100, manufactured by Lanxess)

(C): Fatty acid metal salt C1: Calcium stearate (number average particle size 15 μm, manufactured by NOF Corporation)
C2: Calcium stearate (number-average particle size 24 μm, manufactured by NOF Corporation)
C3: Calcium stearate (number-average particle size: 180 μm, manufactured by Nitto Chemical Industries, Ltd.)

(D): Adhesive D1: Polyethylene glycol (CLE-400 manufactured by ADEKA Corporation)

The number-average particle size of component (C), the fatty acid metal salt, was calculated by measuring the particle size distribution using a laser diffraction scattering particle size distribution analyzer, as described below. A small amount (approximately 10-20 mg) of the fatty acid metal salt was placed in a 10 mL vial using a spatula, 10 mL of acetone was added, and the mixture was thoroughly dispersed in an ultrasonic cleaner. The particle size distribution was then measured using a HORIBA LA-960 laser diffraction scattering particle size distribution analyzer, and the number-average particle size was calculated.

<Evaluation>
The following evaluations were performed using the polybutylene terephthalate resin composites of Examples 1-4 and Comparative Examples 2-5, as well as the pellets of Comparative Example 1. The results are shown in Tables 1 and 2.

(1) Measurability The polybutylene terephthalate resin composites of Examples 1 to 4 and Comparative Examples 2 to 5 obtained above, and the pellets of Comparative Example 1 were each dried at 140°C for 3 hours. Then, using a FANUC Corporation injection molding machine S2000i 100B and an ISO multipurpose test piece (two-cavity) mold, continuous molding was performed under the following molding conditions, and the weighing time and cushion amount were monitored and judged according to the following criteria.

(Molding conditions)
Cylinder temperature: (Nozzle) 260-260-260-240°C (Hopper)
Injection speed: 23mm/sec Mold temperature: 80℃
Holding pressure: 50 MPa
Holding time: 25 seconds; Measurement value: 65 mm
Sackback: 3mm
V-P position: 17mm
Cooling time: 25 seconds Back pressure: 5 MPa
Rotation speed: 50 rpm
Number of shots: 20 shots

(Criteria for determining metrological accuracy)
A: In all 20 shots, weighing is completed within the set cooling time (25 seconds), and continuous molding is possible. B: In some of the 20 shots, weighing is not completed within the set cooling time (25 seconds), but in all 20 shots, weighing is completed within the set cooling time (25 seconds), or even if weighing is not completed within the set cooling time (25 seconds), weighing is completed within the set cooling time (25 seconds) + 10 seconds, and continuous molding is possible. C: In some cases, weighing is not completed within the set cooling time (25 seconds) + 10 seconds, and continuous molding is not possible.

(2) Powder drop properties When injection molding as described above, samples in which no calcium stearate powder was observed in the hopper were designated as A, and samples in which calcium stearate powder was observed were designated as B.

(3) Hydrolysis resistance The polybutylene terephthalate resin composites of Examples 1 to 4 and Comparative Examples 2 to 5 obtained above, and the pellets of Comparative Example 1 were each dried at 140°C for 3 hours, and then 1A type tensile test specimens conforming to ISO 3167 were prepared by injection molding at a cylinder temperature of 260°C and a mold temperature of 80°C. The tensile properties of the obtained test specimens were measured as tensile fracture nominal strain in accordance with ISO 527-1,2. Next, using a PCT treatment apparatus (high-accelerated life test apparatus), the test specimens were exposed to moist heat conditions of 121°C and 100% RH for 50 hours, and the tensile fracture nominal strain after 50 hours of exposure to moist heat conditions was measured.

As shown in Table 1, Examples 1-4 demonstrated short weighing times and excellent weighing performance. Furthermore, Examples 1-4 showed minimal decrease from the initial tensile fracture strain (tensile fracture strain before exposure to moist heat conditions) after 50 hours of exposure to moist heat conditions, indicating good hydrolysis resistance.

On the other hand, Comparative Examples 1 and 2, which did not use fatty acid metal salts, exhibited poor metric stability. Comparative Examples 3-5, which used fatty acid metal salts with excessively large average particle sizes, showed a significant decrease in tensile fracture nominal strain after 50 hours of exposure to moist heat conditions from the initial value (tensile fracture nominal strain before exposure to moist heat conditions), indicating poor hydrolysis resistance. Comparative Example 6, which contained an excessive amount of fatty acid metal salt, showed a small initial value of tensile fracture nominal strain, demonstrating poor toughness.

Claims (7)

A polybutylene terephthalate resin composite comprising polybutylene terephthalate resin composition pellets and an external additive,
The polybutylene terephthalate resin composition pellets contain a polybutylene terephthalate resin with a terminal carboxyl group content of 30 meq/kg or less, and a carbodiimide compound in an amount of 0.2 to 1.0% by mass of the total mass of the polybutylene terephthalate resin composite.
The external additive is a polybutylene terephthalate resin composite comprising a fatty acid metal salt with a number average particle size of 20 μm or less, in an amount of 0.005 to 0.10% by mass of the total mass of the polybutylene terephthalate resin composite. The polybutylene terephthalate resin composite according to claim 1, wherein the external additive further comprises at least one selected from the group consisting of polyethylene glycol, liquid paraffin, paraffin wax, water, and glycerin. The polybutylene terephthalate resin composite according to claim 1 or 2, wherein the polybutylene terephthalate resin composition pellets have a diameter of 2.0 to 3.0 mm and a length of 1.0 to 3.5 mm. The polybutylene terephthalate resin composite according to claim 1 or 2, wherein the fatty acid metal salt comprises calcium stearate. The polybutylene terephthalate resin composite according to claim 1 or 2, wherein the number average molecular weight of the carbodiimide compound is 3000 or more. The polybutylene terephthalate resin composite according to claim 2, wherein the amount of at least one selected from the group consisting of polyethylene glycol, liquid paraffin, paraffin wax, water, and glycerin is 0.005 to 0.1% by mass of the total mass of the polybutylene terephthalate resin composite. A method for producing a polybutylene terephthalate resin composite according to claim 1 or 2, comprising mixing the polybutylene terephthalate resin composition pellets with the external additive.