Polybutylene terephthalate resin composition and insert molded article

Abstract

Disclosed is a polybutylene terephthalate resin composition comprising: a polybutylene terephthalate resin (A); glass fibers (B) which have been surface-treated with a sizing agent containing an epoxy resin and a polymer that includes a structural unit derived from a carboxylic acid anhydride and / or a carboxylic acid; an elastomer (C); and an epoxidized natural oil (D), wherein the content of the epoxidized natural oil is 2.0-8.0 parts by mass with respect to 100 parts by mass of the polybutylene terephthalate resin (A).

Description

Polybutylene terephthalate resin composition and insert molding

[0001] FIELD OF THE INVENTION The present invention relates to a polybutylene terephthalate resin composition and an insert molded article.

[0002] Polybutylene terephthalate resin (hereinafter also referred to as "PBT resin") has excellent mechanical properties, electrical properties, heat resistance, and moldability. In particular, the addition of glass fibers improves mechanical properties and heat resistance, and therefore PBT resin is widely used in a variety of fields, including automotive parts, electrical and electronic equipment parts, and precision instrument parts. Such parts are often produced by injection molding, using a glass fiber-reinforced PBT resin composition prepared by kneading melted PBT resin, chopped-strand glass fibers, and various additives in an extruder and processing them into pellets.

[0003] On the other hand, because PBT resin contains ester groups in its molecules, it is prone to hydrolysis in high-temperature, high-humidity environments, and improved hydrolysis resistance is always desired for automotive parts, which are subject to large environmental changes. For example, PBT resin reinforced with glass fiber or the like is used in the housings of sensors and ECUs that control safety and automatic driving, and because it is combined with metal parts such as terminals and collars, it can crack due to heat shock. In particular, hydrolysis of PBT resin in a humid and hot environment accelerates cracking.

[0004] It is generally known that in order to improve the hydrolysis resistance of the PBT resin itself, an epoxy resin or a carbodiimide compound is added to reduce the amount of terminal carboxyl groups (see Patent Documents 1 and 2).

[0005] Patent Document 1 discloses that, with respect to a resin composition comprising a PBT resin having a terminal carboxyl group amount of 30 meq / kg or less, a carbodiimide compound, a fibrous filler, and an elastomer, when the terminal carboxyl group amount of the PBT resin is taken as 1, the heat shock resistance and hydrolysis resistance are improved by blending 0.3 to 1.5 equivalents of carbodiimide functional groups.

[0006] Patent Document 2 shows that hydrolysis resistance can be improved by blending an epoxy compound with a PBT resin having a terminal carboxyl group concentration of 0.1 μeq / g or more and less than 6 μeq / g and an intrinsic viscosity of 0.75 to 1 dL / g.

[0007] It is also known that the hydrolysis resistance of glass fibers themselves can be improved by using an epoxy resin as a sizing agent (see Patent Documents 3 and 4). Patent Document 3 discloses the use of glass fibers that have been surface-treated with a sizing agent containing, as essential components, an unsaturated carboxylic acid and / or a copolymer of an anhydride of an unsaturated carboxylic acid with an unsaturated monomer and an epoxy resin. Patent Document 4 discloses that surface-treated glass fibers containing a novolac-type epoxy resin have excellent long-term heat resistance.

[0008] Furthermore, Patent Document 5 shows that by blending an epoxidized natural oil, a non-crystalline resin, and a fibrous reinforcing material with a thermoplastic polyester resin, the resin has excellent hydrolysis resistance and can suppress leaching in a humid and hot environment.

[0009] International Publication No. 2009 / 150831 JP 2004-277718 A JP 2003-201671 A JP 2015-129073 A JP 2019-116613 A

[0010] As mentioned above, although proposals have been made to improve the hydrolysis resistance and heat shock resistance of PBT resins, these are still insufficient and further improvements are desired.

[0011] An object of an embodiment of the present invention is to provide a glass fiber-reinforced PBT resin composition and an insert-molded article having improved hydrolysis resistance and heat shock resistance compared to conventional compositions.

[0012] As a result of intensive research aimed at solving the above problems, the present inventors have found that by blending glass fibers that have been surface-treated with a sizing agent containing PBT resin, a polymer containing structural units derived from carboxylic acid or the like, and an epoxy resin, an elastomer, and an epoxidized natural oil, the hydrolysis resistance and heat shock resistance are significantly improved compared to conventional methods, and have thus completed the present invention.

[0013] An embodiment of the present invention relates to a polybutylene terephthalate resin composition comprising: a polybutylene terephthalate resin (A); glass fibers (B) that have been surface-treated with a sizing agent containing an epoxy resin and a polymer including structural units derived from a carboxylic acid and / or a carboxylic acid anhydride; an elastomer (C); and an epoxidized natural oil (D), wherein the content of the epoxidized natural oil is 2.0 to 8.0 parts by mass per 100 parts by mass of the polybutylene terephthalate resin (A).

[0014] Another embodiment of the present invention relates to an insert-molded article having the polybutylene terephthalate resin composition and an insert member.

[0015] According to the embodiments of the present invention, it is possible to provide a glass fiber reinforced polybutylene terephthalate resin composition and an insert molded article having improved hydrolysis resistance and heat shock resistance compared to conventional compositions.

[0016] <PBT Resin Composition> The PBT resin composition of this embodiment includes a PBT resin (A), glass fibers (B) surface-treated with a sizing agent containing an epoxy resin and a polymer including structural units derived from a carboxylic acid and / or a carboxylic acid anhydride, an elastomer (C), and an epoxidized natural oil (D), in which the content of the epoxidized natural oil is 2.0 to 8.0 parts by mass per 100 parts by mass of the polybutylene terephthalate resin (A).

[0017] The PBT resin composition of the present embodiment contains PBT resin (A), glass fiber (B) surface-treated with a sizing agent containing a polymer including structural units derived from carboxylic acid or the like and an epoxy resin, elastomer (C), and epoxidized natural oil (D), and these components combine to significantly improve hydrolysis resistance and heat shock resistance.

[0018] Each component of the PBT resin composition of this embodiment will be described below.

[0019] [Polybutylene Terephthalate Resin (A)] PBT resin (A) is a PBT-based resin obtained by polycondensation of a dicarboxylic acid component containing at least terephthalic acid or an ester-forming derivative thereof (such as a C1-6 alkyl ester or acid halide), and a glycol component containing an alkylene glycol having at least 4 carbon atoms (1,4-butanediol) or an ester-forming derivative thereof (such as an acetylated product). 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.

[0020] In this embodiment, 1,4-butanediol and terephthalic acid or terephthalic acid alkyl ester, which are raw materials for the PBT resin, may be derived from either fossil resources or biomass resources.

[0021] The amount of carboxylic acid terminal groups in the PBT resin (A) is preferably 5 meq / kg or more and 30 meq / kg or less, more preferably 5 meq / kg or more and 20 meq / kg or less. By using a PBT resin having a terminal carboxyl group amount in this range, the resulting PBT resin composition is less susceptible to a decrease in strength due to hydrolysis in a humid and hot environment.

[0022] The intrinsic viscosity (IV) of the PBT resin (A) is preferably 0.70 dL / g or more and 1.10 dL / g or less, more preferably 0.80 dL / g or more and 1.00 dL / g or less, and even more preferably 0.83 dL / g or more and 0.90 dL / g or less. When a PBT resin having an intrinsic viscosity within this range is used, the resulting PBT resin composition exhibits excellent hydrolysis resistance and moldability. 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 1.0 dL / g with a PBT resin having an intrinsic viscosity of 0.8 dL / g. The intrinsic viscosity (IV) of the PBT resin (A) can be measured, for example, in o-chlorophenol at 35°C.

[0023] 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, etc.). These dicarboxylic acid components can be used alone or in combination of two or more.

[0024] 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.

[0025] 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 an ethylene oxide 2-mol adduct of bisphenol A and a propylene oxide 3-mol adduct of bisphenol A; and ester-forming derivatives of these glycols (acetylated products, etc.). These glycol components can be used alone or in combination of two or more.

[0026] 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. 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 (e.g., ε-caprolactone); and ester-forming derivatives of these comonomer components (e.g., C1-6 alkyl ester derivatives, acid halides, and acetylated products).

[0027] 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).

[0028] PBT resin (A) can be a recycled product from the market (material recycling). It can also be a PBT resin produced by decomposing PBT resin waste into 1,4-butanediol, terephthalic acid, etc. down to the monomer level (chemical recycling) and polycondensing the resulting raw materials.

[0029] [Glass fiber (B)] In the PBT resin composition of this embodiment, the glass fiber (B) is surface-treated with a sizing agent containing a polymer containing structural units derived from carboxylic acid and / or carboxylic anhydride and an epoxy resin. The inclusion of the glass fiber (B) improves the mechanical strength of the molded article, and the surface treatment with the specific sizing agent also provides excellent hydrolysis resistance.

[0030] The type of glass used as the raw material for the glass fiber (B) is not particularly limited, but in terms of quality, E-glass or corrosion-resistant glass containing zirconium element in its composition is preferably used.

[0031] The average fiber diameter of the glass fiber (B) is preferably 3 to 50 μm, more preferably 6 to 15 μm, from the viewpoints of mechanical properties and prevention of gate clogging during injection molding. The average fiber length of the glass fiber (B) is not particularly limited and can be, for example, 0.1 to 20 mm. The average fiber diameter and average fiber length of the glass fiber (B) are values ​​calculated by analyzing images of the glass fiber after blending into the resin composition taken with a CCD camera and calculating the weighted average. For example, they can be calculated using a dynamic image analysis / particle (state) analyzer PITA-3 manufactured by Seishin Enterprise Co., Ltd. The blended glass fiber (B) can be obtained, for example, by treating it in a constant temperature bath at 600°C for about 2 to 3 hours.

[0032] The glass fiber (B) can be either one having a circular cross section or one having a noncircular cross section. Examples of noncircular cross sections include oval, elliptical, and cocoon shapes. The irregularity ratio (major axis diameter:minor axis diameter) of the noncircular cross section is not particularly limited, but is preferably 1.5:1 to 6:1, more preferably 2:1 to 5:1, and even more preferably 2.5:1 to 4:1. When the irregularity ratio is in the range of 1.5:1 to 6:1, effects such as dimensional stability and reduced warpage due to the flattened cross section can be easily obtained, and a decrease in strength caused by excessive flattening and increased susceptibility to cracking can also be easily suppressed.

[0033] The glass fiber (B) may be used alone or in combination of two or more kinds.

[0034] Furthermore, glass fiber (B) and a non-fibrous inorganic filler may be used in combination. By using glass fiber (B) and a non-fibrous inorganic filler in combination, both low warpage and mechanical properties such as tensile strength can be achieved. The ratio of glass fiber (B) to non-fibrous inorganic filler is not particularly limited, but the glass fiber (B) / non-fibrous inorganic filler (mass ratio) is preferably 80 / 20 to 45 / 55, more preferably 75 / 25 to 55 / 45, and even more preferably 70 / 30 to 60 / 40. When the content of non-fibrous inorganic filler is 20% by mass or more of the glass fiber, better low warpage is likely to be obtained, and when it is 55% by mass or less, better tensile strength is likely to be obtained. The combination of glass fiber (B) and a non-fibrous inorganic filler is not particularly limited, but examples include combinations of glass fiber (B) and a non-fibrous inorganic filler such as glass flakes, mica, and talc.

[0035] Next, the polymer having a structural unit derived from a carboxylic acid and / or a carboxylic acid anhydride and the epoxy resin contained in the sizing agent used in the surface treatment of the glass fiber (B) will be described below.

[0036] (Polymer having structural units derived from carboxylic acid and / or carboxylic acid anhydride) In the polymer having structural units derived from carboxylic acid and / or carboxylic acid anhydride (hereinafter also simply referred to as "polymer"), examples of the carboxylic acid include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, fumaric acid, maleic acid, succinic acid, cinnamic acid, itaconic acid, mesaconic acid, and citraconic acid. These may have a substituent. Among these, acrylic acid, methacrylic acid, and maleic acid are preferred. Examples of the carboxylic acid anhydride include anhydrides of unsaturated carboxylic acids such as maleic anhydride, itaconic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, dodecenylsuccinic anhydride, and chlorendic anhydride.

[0037] The above polymers may be homopolymers in which each carboxylic acid or carboxylic anhydride is polymerized alone, or may be copolymers in which two or more carboxylic acids or carboxylic anhydrides are copolymerized.

[0038] In this embodiment, the weight-average molecular weight of the polymer is not particularly limited, but is particularly preferably 10,000 to 1,000,000. When the weight-average molecular weight is within the range of 10,000 to 1,000,000, sufficient hydrolysis resistance is obtained and sufficient adhesion to the surface of the glass fiber is achieved.

[0039] (Epoxy Resin) Examples of epoxy resins include glycidyl ether type epoxy resins, glycidyl ester type epoxy resins (diglycidyl phthalate, diglycidyl tetrahydrophthalate, diglycidyl hexahydrophthalate, dimethylglycidyl phthalate, dimethylglycidyl hexahydrophthalate, dimer acid glycidyl ester, aromatic diglycidyl ester, cycloaliphatic diglycidyl ester, etc.), glycidyl amine type epoxy resins (tetraglycidyldiaminodiphenylmethane, triglycidyl-paraaminophenol, triglycidyl-methamine), and the like. phenol, diglycidyl toluidine, tetraglycidyl metaxylylenediamine, diglycidyl tribromoaniline, tetraglycidyl bisaminomethylcyclohexane, etc.), heterocyclic epoxy resins (triglycidyl isocyanurate (TGIC), hydantoin-type epoxy resins, etc.), cycloaliphatic epoxy resins (vinylcyclohexene dioxide, dicyclopentadiene oxide, alicyclic diepoxy acetal, alicyclic diepoxy adipate, alicyclic diepoxy carboxylate, etc.), epoxidized polybutadiene, etc.

[0040] Glycidyl ether type epoxy resins include glycidyl ethers of polyhydroxy compounds [glycidyl ethers of aromatic polyhydroxy compounds such as bisphenol type epoxy resins (e.g., bisphenol A type, bisphenol AD ​​type, or bisphenol F type epoxy resins), resorcinol type epoxy resins, etc.; aliphatic epoxy resins (glycidyl ethers of alkylene glycols, polyoxyalkylene glycols, etc.)], novolac type epoxy resins (phenol novolac type, cresol novolac type epoxy resins, etc.), and the like.

[0041] Among epoxy resins, aromatic epoxy resins (such as bisphenol-type epoxy resins, resorcinol-type epoxy resins, and phenol novolac-type epoxy resins) and cyclic aliphatic epoxy resins are preferred, and glycidyl ether-type aromatic epoxy resins, such as bisphenol-type epoxy resins and phenol novolac-type epoxy resins, are particularly preferred.

[0042] The epoxy equivalent of the epoxy resin may be, for example, about 100 to 1600 g / eq, preferably about 100 to 800 g / eq, and more preferably about 150 to 500 g / eq.

[0043] The number average molecular weight of the epoxy resin may be, for example, about 200 to 50,000, preferably about 300 to 10,000, and more preferably about 400 to 6,000.

[0044] In this embodiment, the mass ratio (X / Y) of the polymer (X) to the epoxy resin (Y) in the sizing agent is preferably 0.001 to 1.500 from the viewpoint of improving the mechanical strength of the molded product.

[0045] The content of the sizing agent is preferably 0.1 to 3.0 parts by mass, more preferably 0.3 to 2.5 parts by mass, per 100 parts by mass of the glass fibers (B). By using the sizing agent in an amount of 0.1 to 3.0 parts by mass per 100 parts by mass of the glass fibers (B), it is possible to improve hydrolysis resistance and heat shock resistance.

[0046] In addition to the above components, the sizing agent may contain other components such as urethane resin, silane coupling agent, lubricant, nonionic surfactant, antistatic agent, etc., and the blending ratio of each component may be determined as needed. The urethane resin contributes to the bundling and dispersibility of the glass fibers and is obtained from polyisocyanate and polyol, etc. As the silane coupling agent, aminosilane, epoxysilane, chlorosilane, mercaptosilane, vinylsilane, acrylicsilane, etc. can be used. As the lubricant, fatty acid amide, quaternary ammonium salt, etc. can be used. As the nonionic surfactant, synthetic alcohol, natural alcohol, fatty acid ester, etc. can be used.

[0047] In the PBT resin composition of the present embodiment, the content of the glass fiber (B) is preferably 10 to 100 parts by mass, and more preferably 20 to 80 parts by mass, per 100 parts by mass of the PBT resin (A).

[0048] [Elastomer (C)] The elastomer (C) used in this embodiment is added to improve the heat shock resistance, which is required when a molded article made using the PBT resin composition is used in an environment where heating and cooling are repeated.

[0049] The elastomer (C) imparts toughness to the PBT resin composition, thereby absorbing distortions that occur in the molded article. It is preferable to use a resin that not only has a small shrinkage rate and / or linear expansion coefficient during molding or heat treatment, but also has good compatibility with the PBT resin (A). Examples of such elastomers (C) include olefin-based elastomers, diene-based elastomers, core-shell elastomers, styrene-based elastomers, silicone-based elastomers, and combinations thereof. Among these, olefin-based elastomers and core-shell elastomers are preferred because they provide excellent heat shock resistance. In addition, known compatibilizers may be used in combination to improve the affinity between these elastomers (C) and the PBT resin (A).

[0050] Examples of olefin-based elastomers include ethylene-propylene copolymers (EP copolymers), ethylene-butene copolymers, ethylene-octene copolymers, ethylene-propylene-diene copolymers (EPD copolymers), ethylene-propylene-butene copolymers, ethylene-vinyl acetate copolymers, copolymers containing at least one unit selected from EP copolymers and EPD copolymers, and copolymers of olefins and (meth)acrylic monomers (ethylene-ethyl acrylate copolymers, ethylene-glycidyl methacrylate copolymers, etc.). Preferred olefin-based elastomers include EP copolymers, EPD copolymers, and copolymers of olefins and (meth)acrylic monomers, with ethylene-ethyl acrylate being particularly preferred. These olefin-based elastomers can be used alone or in combination.

[0051] A core-shell elastomer is a polymer in which the core layer is composed of a rubber component (soft component) and the shell layer is composed of a hard component, and the rubber component of the core layer is an acrylic rubber, etc. The rubber component used in the core layer preferably has a glass transition temperature (Tg) of less than 0°C (e.g., −10°C or less), more preferably −20°C or less (e.g., −180°C or more and −25°C or less), and particularly preferably −30°C or less (e.g., −150°C or more and −40°C or less).

[0052] When an acrylic rubber is used as the rubber component, a polymer obtained by polymerizing an acrylic monomer such as alkyl acrylate as the main component is preferred. The alkyl acrylate used as the monomer for the acrylic rubber is preferably a C1 to C12 alkyl ester of acrylic acid such as butyl acrylate, and more preferably a C2 to C6 alkyl ester of acrylic acid.

[0053] The acrylic rubber may be a homopolymer or copolymer of an acrylic monomer. When the acrylic rubber is a copolymer of an acrylic monomer, it may be a copolymer of acrylic monomers or a copolymer of an acrylic monomer and another unsaturated bond-containing monomer. When the acrylic rubber is a copolymer, it may be copolymerized with a crosslinkable monomer.

[0054] Vinyl polymers are preferably used for the shell layer. Vinyl polymers are obtained, for example, by polymerizing or copolymerizing at least one monomer selected from aromatic vinyl monomers, vinyl cyanide monomers, methacrylic acid ester monomers, and acrylic acid ester monomers. The core and shell layers of such core-shell elastomers may be bonded by graft copolymerization. This graft copolymerization can be achieved, if necessary, by adding a graft crossing agent that reacts with the shell layer during polymerization of the core layer, providing reactive groups to the core layer, and then forming the shell layer. When a silicone rubber is used as the graft crossing agent, an organosiloxane having a vinyl bond or an organosiloxane having a thiol group is used, preferably an acryloxysiloxane, a methacryloxysiloxane, or a vinylsiloxane.

[0055] [Epoxidized Natural Oil (D)] In this embodiment, the molecular weight of the natural oil (unsaturated fatty acid ester) that is the raw material for the epoxidized natural oil (D) is preferably about 500 to 1500, more preferably about 600 to 1100. For example, linseed oil or soybean oil is a mixture of fatty acid triglycerides, and in this case, a large amount of C18-carboxylic acid is present.

[0056] Examples of natural oils include esters of saturated or unsaturated aliphatic carboxylic acids having 10 to 40 carbon atoms, preferably 16 to 22 carbon atoms, and saturated aliphatic alcohols having 2 to 40 carbon atoms, preferably 2 to 6 carbon atoms.

[0057] Epoxidized natural oils can be produced by reacting these natural oils with an epoxidizing agent, for example, a peracid such as peracetic acid, to introduce epoxy groups.

[0058] In this embodiment, the epoxidized natural oil (D) is a compound obtained by epoxidizing the unsaturated bond of an unsaturated fatty acid ester of olive oil, almond oil, peanut oil, coconut oil, camellia oil, corn oil, cottonseed oil, sesame oil, mustard oil, rapeseed oil, linseed oil, soybean oil, tung oil, mustard oil, perilla oil, walnut oil, perilla oil, safflower oil, sunflower oil, cod liver oil, sardine oil, herring oil, beef tallow, mutton tallow, butter, etc. Specific examples of the epoxidized natural oil (D) include epoxidized sesame oil, epoxidized mustard oil, epoxidized rapeseed oil, epoxidized linseed oil, epoxidized soybean oil, epoxidized tung oil, epoxidized mustard oil, epoxidized perilla oil, epoxidized walnut oil, epoxidized perilla oil, epoxidized cod liver oil, epoxidized sardine oil, and epoxidized herring oil.

[0059] The epoxidized natural oil in this embodiment is preferably an epoxidized natural oil having an epoxy equivalent of 100 to 400 g / eq, preferably 125 to 375 g / eq, more preferably 150 to 250 g / eq according to DIN EN ISO 3001 (1999-11). Also preferred is an epoxidized compound in which the epoxy group is not bonded at a terminal (i.e., an epoxy group present "internally" in the hydrocarbon chain).

[0060] The epoxy group content is preferably 1 to 20% by mass, more preferably 4 to 15% by mass, and even more preferably 6 to 12% by mass, based on the natural oil. The higher the epoxy group content (1% by mass or more), the greater the effect on hydrolysis resistance, while the lower the epoxy group content (20% by mass or less), the less the viscosity of the PBT resin composition increases, resulting in good flowability during injection molding.

[0061] Among these epoxidized natural oils (D), epoxidized linseed oil and epoxidized soybean oil are preferred because they are easily available and can simultaneously achieve high levels of hydrolysis resistance and heat shock resistance.

[0062] The epoxidized natural oil (D) may be used alone or in combination of two or more. Particularly preferred epoxidized natural oils (D) are available from ADEKA Corporation under the trade names Adeka Cizer (registered trademark) O-130P and Adeka Cizer (registered trademark) O-180A, NOF Corporation under the trade names New Cizer (registered trademark) 510R, and New Japan Chemical Co., Ltd. under the trade names Sanso Cizer E-9000H and Sanso Cizer E-2000H.

[0063] The amount of epoxidized natural oil (D) is 2.0 to 8.0 parts by mass per 100 parts by mass of PBT resin (A). If the amount of epoxidized natural oil (D) is less than 2.0 parts by mass, hydrolysis resistance decreases. The amount is preferably 3.0 parts by mass or more, more preferably 3.5 parts by mass or more. On the other hand, if the amount of epoxidized natural oil (D) exceeds 8.0 parts by mass, unreacted epoxidized natural oil will bleed out and contaminate the molded product. The amount is preferably 7.0 parts by mass or less, more preferably 6.0 parts by mass or less.

[0064] [Other Components] The PBT resin composition of the present embodiment may contain other components as needed, including, but not limited to, inorganic fillers other than the glass fiber (B), antioxidants, weather stabilizers, molecular weight modifiers, ultraviolet absorbers, antistatic agents, dyes, pigments, lubricants, crystallization accelerators, crystal nucleating agents, near-infrared absorbers, flame retardants, flame retardant assistants, organic fillers, and colorants.

[0065] <Method for Producing Polybutylene Terephthalate Resin Composition> The method for producing the PBT resin composition of this embodiment is not particularly limited, and known equipment and methods for preparing resin compositions can be used. For example, the necessary components can be mixed and kneaded using a single-screw or twin-screw extruder or other melt-kneading device to prepare pellets for molding.

[0066] <Insert Molded Article> The insert molded article of this embodiment includes the PBT resin composition of this embodiment and an insert member as described above. Therefore, similar to the PBT resin composition of this embodiment, the insert molded article exhibits the effect of significantly improving hydrolysis resistance and heat shock resistance compared to conventional products.

[0067] The insert-molded article of this embodiment is a composite molded article in which a metal or other insert member is pre-installed in a molding die, and the PBT resin composition is filled around the insert member. Injection molding is a common molding method for filling a mold with a resin. The insert member inserted into the PBT resin composition is used to take advantage of the resin's properties and compensate for its shortcomings, so it must not deform or melt when it comes into contact with the PBT resin composition during molding. For this reason, pre-formed rods, pins, screws, etc. made of metals such as aluminum, magnesium, copper, iron, brass, and alloys thereof, or inorganic solids such as glass and ceramics, can be used.

[0068] The method for producing an insert-molded article using the PBT resin composition of this embodiment is not particularly limited, and any known method can be used. For example, the PBT resin composition of this embodiment can be fed into an extruder, melt-kneaded, and pelletized, and the pellets and the insert member can be fed into an injection molding machine equipped with a predetermined mold and injection-molded.

[0069] The insert-molded article of this embodiment can be suitably used as a molded article that is exposed to high-temperature, high-humidity environments for long periods of time, such as in automobiles, trains, and the aviation industry. This insert-molded article can prevent degradation due to hydrolysis even when used for long periods of time in a sufficiently high-temperature, high-humidity environment, and because it has improved heat shock resistance, it can be used for electrical components such as ECUs, housings, and sensors that are installed around on-board engines, motors, and batteries.

[0070] Examples of embodiments of the present invention are given below: The embodiments of the present invention are not limited to the following examples.

[0071] (1) A polybutylene terephthalate resin composition comprising: a polybutylene terephthalate resin (A); glass fibers (B) surface-treated with a sizing agent containing an epoxy resin and a polymer including structural units derived from a carboxylic acid and / or a carboxylic acid anhydride; an elastomer (C); and an epoxidized natural oil (D), wherein the content of the epoxidized natural oil is 2.0 to 8.0 parts by mass per 100 parts by mass of the polybutylene terephthalate resin (A).

[0072] (2) The polybutylene terephthalate resin composition according to (1), wherein the glass fibers (B) have an average fiber diameter of 3 to 50 μm, and the content of the sizing agent is 0.1 to 3.0 parts by mass per 100 parts by mass of the glass fibers (B).

[0073] (3) The polybutylene terephthalate resin composition according to (1) or (2), wherein the epoxidized natural oil (D) is epoxidized linseed oil or epoxidized soybean oil.

[0074] (4) The polybutylene terephthalate resin composition according to any one of (1) to (3), wherein the elastomer (C) is an olefin-based elastomer or a core-shell-based elastomer.

[0075] (5) An insert-molded product having the polybutylene terephthalate resin composition according to any one of (1) to (4) above and an insert member.

[0076] The disclosure of this application is related to the subject matter described in Japanese Patent Application No. 2023-219541, filed December 26, 2023, the entire disclosure of which is incorporated herein by reference.

[0077] The present embodiment will be described in more detail below with reference to examples, but the present embodiment is not limited to the following examples.

[0078] [Examples 1 to 3, Comparative Examples 1 to 5] In each Example and Comparative Example, components (A) to (D) and an antioxidant were melt-mixed and extruded in the ratios (parts by mass) shown in Table 2 using a 30 mmφ twin-screw extruder (TEX30C, manufactured by The Japan Steel Works, Ltd.) at a cylinder temperature of 260°C at the raw material supply section and the die tip, and 220 to 260°C between them, at a discharge rate of 15 kg / h and a screw rotation speed of 130 rpm, to obtain pellets made of a PBT resin composition. Details of each component shown in Table 2 are provided below.

[0079] (1) Polybutylene terephthalate resin; PBT resin (A): manufactured by Polyplastics Co., Ltd., polybutylene terephthalate resin, intrinsic viscosity: 0.86 dL / g, amount of carboxylic acid terminal group: 12 meq / kg

[0080] (2) Glass fiber (B); Glass fiber (B-1): Glass fiber made of E-glass, average fiber diameter 13 μm (sizing agent: phenol novolac resin 0.5% by mass, copolymer of maleic anhydride, methyl methacrylate and methyl acrylate (0.2% by mass) Glass fiber (B-2): Glass fiber made of E-glass, average fiber diameter 13 μm (sizing agent: phenol novolac resin 0.5% by mass) Glass fiber (B-3): Glass fiber made of E-glass, average fiber diameter 13 μm (sizing agent: copolymer of maleic anhydride, methyl methacrylate and methyl acrylate (0.2% by mass)

[0081] Meanwhile, the components of the sizing agent used in the surface treatment of glass fibers (B-1) to (B-3) are shown in Table 1. The values ​​in Table 1 indicate the content (mass%) of each component relative to the total weight of the glass fiber. The content of the sizing agent relative to 100 parts by weight of the glass fiber is 0.7 parts by weight for glass fiber (B-1), 0.5 parts by weight for glass fiber (B-2), and 0.2 parts by weight for glass fiber (B-3).

[0082]

[0083] (3) Elastomer (C) Elastomer (C-1): Ethylene ethyl acrylate copolymer NUC-6570 manufactured by ENEOS NUC Corporation Elastomer (C-2): Core-shell elastomer, Paraloid EXL-2314 manufactured by Dow Chemical

[0084] (4) Epoxy compound / epoxidized natural oil (D-1): ADEKA Cizer O-180A manufactured by ADEKA Corporation, epoxy equivalent 188 g / eq. Epoxy resin (D-2): Epikote 1004 manufactured by Mitsubishi Chemical Corporation, epoxy equivalent 875 to 975 g / eq.

[0085] (5) Antioxidant: "Irganox 1010" manufactured by BASF Japan Ltd.

[0086] [Evaluation] The pellets obtained in each of the Examples and Comparative Examples were subjected to the following evaluation tests.

[0087] (1) Hydrolysis Resistance PBT resin composition pellets obtained in each Example and Comparative Example with the composition shown in Table 2 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 tensile strength of the obtained test specimens was measured in accordance with ISO 527-1 and 2. The measurement results are shown in Table 2. Next, using a PCT treatment device (highly accelerated life test device), the test specimens were exposed to 121°C and 100% RH, and the tensile strength was measured after a moist heat test (50 hours, 100 hours, and 150 hours), and the strength retention before and after the moist heat treatment was calculated. The calculation results are shown in Table 2.

[0088] (2) Heat Shock Resistance The PBT resin composition pellets of each Example and Comparative Example obtained with the composition shown in Table 2 were dried at 140 ° C for 3 hours, and then the resin temperature was 260 ° C, the mold temperature was 65 ° C, the injection time was 25 seconds, and the cooling time was 10 seconds. The insert molding was performed by insert injection molding into a test piece molding mold (a mold in which an iron core measuring 18 mm in length, 18 mm in width, and 30 mm in height was inserted into a rectangular column measuring 22 mm in length, 22 mm in width, and 51 mm in height) so that the minimum thickness of the resin portion was 1 mm, and an insert molded product was produced. The obtained insert molded product was heated to 140 ° C for 1 hour and 30 minutes using a thermal shock tester, then cooled to -40 ° C, cooled for 1 hour and 30 minutes, and then further heated to 140 ° C., which constituted one cycle. The number of cycles until the molded product cracked was measured, and the heat shock resistance was evaluated. The measurement results for the number of cycles are shown in Table 2.

[0089]

[0090] Table 2 shows that Examples 1 to 3 achieved favorable evaluation results for both hydrolysis resistance and heat shock resistance. On the other hand, Comparative Examples 1 and 2, which differed from Example 2 only in that they used glass fiber (B-2) surface-treated with a phenolic novolac resin sizing agent and glass fiber (B-3) surface-treated with a sizing agent containing only a copolymer of maleic anhydride, methyl methacrylate, and methyl acrylate, exhibited poor hydrolysis resistance. Comparative Example 5, which contained a lower amount of epoxidized natural oil than Examples 1 and 2, also exhibited poor hydrolysis resistance and heat shock resistance. Comparative Example 4, which differed from Example 2 only in that it used an epoxy resin instead of epoxidized natural oil, also exhibited poor hydrolysis resistance and heat shock resistance. Furthermore, Comparative Example 3, which differed from Example 2 in that it did not contain elastomer (C-1), exhibited poor heat shock resistance.

Claims

1. A polybutylene terephthalate resin composition comprising: a polybutylene terephthalate resin (A); glass fibers (B) surface-treated with a sizing agent containing a polymer containing a structural unit derived from a carboxylic acid and / or carboxylic anhydride and an epoxy resin; an elastomer (C); and an epoxidized natural oil (D), wherein the content of the epoxidized natural oil is 2.0 to 8.0 parts by mass with respect to 100 parts by mass of the polybutylene terephthalate resin (A).

2. The polybutylene terephthalate resin composition according to claim 1, wherein the average fiber diameter of the glass fibers (B) is 3 to 50 μm, and the content of the sizing agent with respect to 100 parts by mass of the glass fibers (B) is 0.1 to 3.0 parts by mass.

3. The polybutylene terephthalate resin composition according to claim 1 or 2, wherein the epoxidized natural oil (D) is epoxidized linseed oil or epoxidized soybean oil.

4. The polybutylene terephthalate resin composition according to any one of claims 1 to 3, wherein the elastomer (C) is an olefin-based elastomer or a core-shell-based elastomer.

5. An insert molded article having the polybutylene terephthalate resin composition according to any one of claims 1 to 4 and an insert member.

Images