Polybutylene terephthalate resin composition and molded article

Abstract

The present invention addresses the problem of obtaining a molded article which has excellent flame retardancy, tracking resistance, bleeding resistance, and weld strength.　The present invention pertains to a polybutylene terephthalate resin composition obtained by combining 100 parts by mass of (A) a polybutylene terephthalate resin with 10-120 parts by mass of (B) a phosphate ester compound and 1-20 parts by mass of (D) a flame-retardant resin. The flame-retardant resin (D) is dispersed as island phases in a sea phase of the polybutylene terephthalate resin (A), with the average diameter of the island phases being 0.05-5.0 µm.

Description

Polybutylene terephthalate resin composition and molded article

[0001] The present invention relates to a polybutylene terephthalate resin composition and a molded article obtained by molding the same.

[0002] Taking advantage of its excellent injection moldability and mechanical properties, polybutylene terephthalate resins are used in a wide range of fields, including machine parts, electrical and electronic components, and automotive parts. However, because polybutylene terephthalate resins are inherently flammable, their use as industrial materials for machine parts, electrical and electronic components, and automotive parts requires flame safety, i.e., flame retardancy. High flame retardancy, as indicated by UL-94 V-0, is often required. A common method for imparting flame retardancy to polybutylene terephthalate resins is to compound halogenated organic compounds as flame retardants. However, growing environmental awareness has raised concerns about the environmental impact of halogenated organic compounds. Therefore, in recent years, there has been a strong demand for non-halogen flame retardants that do not contain these halogens. Examples of non-halogen flame retardants that have been proposed include phosphorus-based flame retardants such as phosphinates, phosphazene compounds, and phosphate ester compounds, as well as nitrogen-based flame retardants such as melamine cyanurate. Among these, phosphoric acid ester compounds have been proposed as polybutylene terephthalate resin compositions because, although they are less effective in imparting flame retardancy, they are low in cost and have excellent fluidity during molding.

[0003] Examples of flame-retardant resin compositions using phosphate ester compounds include a resin composition containing a thermoplastic polyester, a condensed phosphate ester, and a methacrylic resin (Patent Document 1), a resin composition containing a polyester resin, a phosphate ester, and a resin selected from polyphenylene oxide resins and polyphenylene sulfide resins (Patent Document 2), a resin composition containing a polybutylene terephthalate resin, a phosphate ester, and a multilayer polymer (Patent Document 3), and a resin composition containing a polyester resin, a phosphate ester, a polyphenylene ether resin and / or a polyphenylene sulfide resin, and an epoxy group-containing polystyrene resin. Furthermore, phosphate ester compounds have the problem of easily bleeding out onto the surface of molded articles, and all of these patent documents attempt to suppress bleeding caused by the phosphate ester compound by adding a resin component other than polybutylene terephthalate resin.

[0004] International Publication No. 2014 / 021101 International Publication No. 2003 / 046083 JP 2004-075868 A JP 10-77396 A

[0005] In recent years, the increasing power output of electric vehicles has led to an increase in the voltage of electrical systems to 400V or more. In addition to the flame retardancy that has traditionally been required for insulating parts that are subjected to high voltages, such as connectors and bus bars that connect batteries and inverters, and power module cases, they are now required to have tracking resistance (500V or more), which is resistance to tracking breakdown (continuity due to carbonization degradation) under high voltages, and hydrolysis resistance, which prevents degradation in harsher high-temperature, high-humidity environments.

[0006] Furthermore, as product shapes become more complex for mechanical components, electrical components, electronic components, and automotive components, welds may form during the injection molding process, which can lead to product damage at the welds, which have low mechanical strength.

[0007] Furthermore, due to growing environmental awareness, in addition to being halogen-free, there is a demand for products to be free of PFAS, an organic fluorine compound, and they are also required to be free of fluorine-based resins, which are generally added as anti-dripping agents to increase flame retardancy.

[0008] In the resin composition disclosed in Patent Document 1, the flame retardancy and tracking resistance are improved by using a phosphate ester in combination with a phosphazene or an organic phosphinate, but the hydrolysis resistance and weld strength are insufficient, and further, there is a problem that the tracking resistance decreases in a humid and hot environment.

[0009] In the resin composition disclosed in Patent Document 2, the polyphenylene oxide resin and polyphenylene sulfide resin blended to enhance flame retardancy are prone to carbonization, and the tracking resistance and weld strength are insufficient, and there is also the issue of variation in flame retardancy.

[0010] The resin composition disclosed in Patent Document 3 has a problem in that the multilayer structure polymer blended to exhibit flame retardancy and improve mechanical properties is insufficient in tracking resistance and bleed-out resistance.

[0011] In the resin composition disclosed in Patent Document 4, the polyphenylene oxide resin and polyphenylene sulfide resin blended to enhance flame retardancy are prone to carbonization, and the tracking resistance and weld strength are insufficient, and there is also the issue of variation in flame retardancy.

[0012] For the reasons described above, it was difficult to obtain a material that had excellent flame retardancy, tracking resistance, and bleed-out resistance, while also having high weld strength suitable for molded articles having welds, using the techniques disclosed in Patent Documents 1 to 4. Furthermore, none of Patent Documents 1 to 4 mentions avoiding the use of fluororesin as an anti-dripping agent, and even for compositions that are described as having flame retardancy of V-0, when no fluororesin is used, there is a problem that the burning time varies greatly and the flame retardancy is essentially insufficient, making it difficult to obtain a material with consistent flame retardancy without using a fluororesin.

[0013] An object of the present invention is to provide a polybutylene terephthalate resin composition from which molded articles having excellent flame retardancy, tracking resistance, bleed-out resistance, and weld strength can be obtained, and a molded article thereof.

[0014] The present inventors have conducted extensive research to solve the above-mentioned problems, and have found that the above-mentioned problems can be solved by blending 10 to 120 parts by mass of a (B) phosphate ester compound and 1 to 20 parts by mass of a (D) flame-retardant resin with 100 parts by mass of an (A) polybutylene terephthalate resin, and dispersing island phases of the (D) flame-retardant resin with an average diameter of 0.05 to 5.0 μm within a sea phase of the (A) polybutylene terephthalate resin. This finding led to the completion of the present invention. Specifically, the present invention has the following configuration: [1] A polybutylene terephthalate resin composition comprising 10 to 120 parts by mass of a (B) phosphate ester compound and 1 to 20 parts by mass of a (D) flame-retardant resin with 100 parts by mass of an (A) polybutylene terephthalate resin, and wherein island phases of the (D) flame-retardant resin with an average diameter of 0.05 to 5.0 μm are dispersed within a sea phase of the (A) polybutylene terephthalate resin. [2] The polybutylene terephthalate resin composition according to [1], further comprising 1 to 40 parts by mass of a (C) styrene-based resin blended with 100 parts by mass of the (A) polybutylene terephthalate resin, wherein the ratio of the amount of the (C) styrene-based resin to the amount of the (D) flame-retardant resin blended [amount of (C) styrene-based resin blended / amount of (D) flame-retardant resin blended] is 0.5 to 4.0. [3] The polybutylene terephthalate resin composition according to [1] or [2], wherein composite island phases of the (C) styrene-based resin and the (D) flame-retardant resin are dispersed with an average diameter of 1 to 20 μm within a sea phase of the (A) polybutylene terephthalate resin. [4] The polybutylene terephthalate resin composition according to any one of [1] to [3], wherein the (D) flame-retardant resin is a resin that exhibits a mass loss of 70% by mass or less when heated in air from room temperature to 600°C at a heating rate of 40°C / min. [5] The polybutylene terephthalate resin composition according to any one of [1] to [4], wherein the flame-retardant resin (D) is a polyphenylene sulfide resin. [6] The polybutylene terephthalate resin composition according to any one of [1] to [5], further comprising 10 to 150 parts by mass of (E) a nitrogen-based flame retardant which is a nitrogen-containing heterocyclic compound having a triazine skeleton, per 100 parts by mass of the polybutylene terephthalate resin (A).[7] The polybutylene terephthalate resin composition according to any one of [1] to [6], further comprising 1 to 40 parts by mass of (F) core-shell rubber per 100 parts by mass of the (A) polybutylene terephthalate resin. [8] The polybutylene terephthalate resin composition according to any one of [1] to [7], further comprising 0.3 to 3.0 parts by mass of (G) hindered amine compound per 100 parts by mass of the (A) polybutylene terephthalate resin. [9] The polybutylene terephthalate resin composition according to any one of [1] to [8], wherein the content of each of polyethylene terephthalate resin, polyphenylene ether resin, and polyetherimide resin per 100 parts by mass of the (A) polybutylene terephthalate resin is less than 5 parts by mass.

[10] The polybutylene terephthalate resin composition according to any one of [1] to [9], wherein the content of fluorine-based resin per 100 parts by mass of the (A) polybutylene terephthalate resin is less than 0.5 parts by mass.

[11] (A) The polybutylene terephthalate resin composition according to any one of [1] to

[10] , wherein the content of each of the phosphazene compound and the organic metal phosphinate is less than 5 parts by mass per 100 parts by mass of the polybutylene terephthalate resin.

[12] A molded product obtained by melt molding the polybutylene terephthalate resin composition according to any one of [1] to

[11] .

[13] A high-voltage insulating part made of the polybutylene terephthalate resin composition according to any one of [1] to

[11] .

[14] The high-voltage insulating part according to

[13] , which is any one of a high-voltage connector, a power module case, and a bus bar.

[0015] The polybutylene terephthalate resin composition of the present invention can give molded articles that are excellent in all of flame retardancy, tracking resistance, bleed-out resistance, and weld strength.

[0016] The polybutylene terephthalate resin composition of the present invention comprises 100 parts by mass of (A) polybutylene terephthalate resin (hereinafter sometimes abbreviated as component (A)), 10 to 120 parts by mass of (B) phosphoric acid ester compound (hereinafter sometimes abbreviated as component (B)), and 1 to 20 parts by mass of (D) flame-retardant resin (hereinafter sometimes abbreviated as component (D)), and the polybutylene terephthalate resin composition has island phases of the (D) flame-retardant resin dispersed in a sea phase of the (A) polybutylene terephthalate resin with an average diameter of 0.05 to 5.0 μm.

[0017] Polybutylene terephthalate resins have a low limiting oxygen index and will burn if placed near an open flame or other source of fire. To enhance the flame retardancy of polybutylene terephthalate resins, phosphate ester compounds are blended in combination with flame-retardant resins such as polyphenylene ether resins and polyphenylene sulfide resins. However, poor dispersion of the flame-retardant resin in the polybutylene terephthalate resin composition can lead to the formation of coarse chars due to discharge under high voltage, resulting in reduced insulation and tracking resistance, which in turn leads to inconsistent flame retardancy and reduced weld strength. Furthermore, phosphate ester compounds blended into polybutylene terephthalate resins can bleed out, which is thought to be due to their poor compatibility with polybutylene terephthalate resins. Therefore, blending an amorphous resin with a high affinity for the phosphate ester compound into the polybutylene terephthalate resin composition is generally considered. However, when an amorphous resin has high compatibility with a polybutylene terephthalate resin, the crystallinity of the polybutylene terephthalate resin is reduced, resulting in reduced heat resistance and, conversely, increased susceptibility to bleed-out in high-temperature environments. Meanwhile, when an amorphous resin has low compatibility with a polybutylene terephthalate resin, poor dispersion results in reduced flame retardancy and weld strength. Therefore, in the present invention, the island phases of the flame-retardant resin (D) are dispersed within the sea phase of the polybutylene terephthalate resin (A) so that the average diameter of the island phases is 0.05 to 5.0 μm. During combustion, the island phases of the flame-retardant resin (D) react with the phosphate ester to form a dense, non-combustible carbonized layer. The formation of this non-combustible carbonized layer exhibits high flame retardancy while suppressing the formation of coarse chars due to high-voltage discharge. This allows for the production of molded articles with excellent tracking resistance, bleed-out resistance, and weld strength, and consistent flammability, even without the inclusion of PFAS.

[0018] The polybutylene terephthalate resin composition of the present invention contains reaction products in which components (A), (B), and (D) are each reacted with other components, but these reaction products are produced by complex reactions, and there are circumstances in which it is impractical to identify their structures. Therefore, the present invention is defined by the components to be blended.

[0019] In the present invention, the (A) polybutylene terephthalate resin may be either polybutylene terephthalate or a polybutylene terephthalate copolymer, or a combination of these. From the viewpoints of mechanical strength and bleed-out resistance, polybutylene terephthalate is preferred.

[0020] Polybutylene terephthalate resin is a polymer obtained by polycondensation reaction of terephthalic acid (or its ester-forming derivative such as dimethyl terephthalate) and 1,4-butanediol (or its ester-forming derivative).

[0021] Polybutylene terephthalate copolymer is a polymer that can be obtained by polymerizing terephthalic acid (or an ester-forming derivative thereof, such as dimethyl terephthalate) with 1,4-butanediol (or an ester-forming derivative thereof) in the presence of other dicarboxylic acids (or ester-forming derivatives thereof) or other glycols (or ester-forming derivatives thereof) copolymerizable therewith.

[0022] Specific examples of copolymerizable dicarboxylic acids include isophthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, oxalic acid, malonic acid, succinic acid, itaconic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, dimer acid, and ester-forming derivatives thereof, but are not limited thereto. Any copolymerizable dicarboxylic acid can be used. Furthermore, two or more types can be used simultaneously. From the viewpoint of moldability, the proportion of copolymerizable dicarboxylic acids is preferably in the range of 3 to 30 mol %, and more preferably in the range of 3 to 20 mol %, of the total dicarboxylic acid components.

[0023] On the other hand, examples of copolymerizable glycols include ethylene glycol, propylene glycol, nonanediol, neopentyl glycol, tetramethylcyclobutanediol, isosorbide, dimer diol, polyethylene glycol, polytetramethylene glycol, 2,2-bis(4-hydroxyphenyl)propane, hydroquinone, resorcinol, 1,1-bis(4-hydroxyphenyl)cyclohexane, 2,2-bis(3-methyl-4-hydroxyphenyl)propane, etc., but are not limited to these and any copolymerizable glycols can be used. Furthermore, two or more types can be used simultaneously. From the viewpoint of moldability, the proportion of copolymerizable glycols other than 1,4-butanediol is preferably in the range of 3 to 30 mol %, more preferably 3 to 20 mol %, of the total glycol component.

[0024] Other copolymerizable components include trimellitic acid, pyromellitic acid, glycerin, trimethylolpropane, pentaerythritol, p-hydroxybenzoic acid, ε-caprolactone, and γ-butyrolactone.

[0025] The carboxyl group concentration of the polybutylene terephthalate resin (A) used in the present invention is preferably 35 eq / t or less from the viewpoint of suppressing a decrease in hydrolysis resistance. It is more preferably 30 eq / t or less, and even more preferably 20 eq / t or less. The lower limit of the carboxyl group concentration is 0 eq / t. Here, the carboxyl group concentration of the polybutylene terephthalate resin (A) is a value measured by dissolving the polybutylene terephthalate resin (A) in an o-cresol / chloroform solvent (mixed volume ratio = 2 / 1) and then titrating with ethanolic potassium hydroxide.

[0026] The polybutylene terephthalate resin (A) used in the present invention preferably has a weight-average molecular weight (Mw) of 8,000 or more in order to further improve mechanical properties. Furthermore, a weight-average molecular weight (Mw) of 500,000 or less is preferable because fluidity can be improved. It is more preferably 300,000 or less, and even more preferably 250,000 or less. In the present invention, the weight-average molecular weight (Mw) of the polybutylene terephthalate resin (A) is a value calculated as polymethyl methacrylate (PMMA) measured by gel permeation chromatography (GPC) using hexafluoroisopropanol as a solvent.

[0027] The intrinsic viscosity of the polybutylene terephthalate resin (A) used in the present invention is preferably 0.36 dl / g or more, more preferably 0.50 dl / g or more, as measured in an o-chlorophenol solution at 25° C., from the viewpoint of further improving mechanical properties. Furthermore, from the viewpoint of improving fluidity, the intrinsic viscosity is preferably 1.60 dl / g or less, more preferably 1.50 dl / g or less.

[0028] Examples of the (B) phosphoric acid ester compound used in the present invention include triphenyl phosphate, tris(dimethylphenyl)phosphate, trixylenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, cresyl dixylenyl phosphate, trimethyl phosphate, triethyl phosphate, condensed phosphoric acid ester, acidic phosphoric acid ester, phosphoric acid ester amide, etc. Two or more of these phosphoric acid ester compounds can also be used in any blending amount.

[0029] Among the (B) phosphate ester compounds, condensed phosphate esters are preferred from the viewpoints of flame retardancy and bleed-out resistance. Examples of condensed phosphate esters include resorcinol diphenyl phosphate, hydroquinone diphenyl phosphate, bisphenol A diphenyl phosphate, and biphenyl diphenyl phosphate. Commercially available products thereof include PX-202, CR-741, PX-200, and PX-201 manufactured by Daihachi Chemical Industry Co., Ltd., and FP-500, FP-600, FP-700, and PFR manufactured by Adeka Corporation.

[0030] The blending amount of the (B) phosphate ester compound used in the present invention is 10 to 120 parts by mass per 100 parts by mass of the (A) polybutylene terephthalate resin in terms of the balance between flame retardancy and bleed-out resistance. If the blending amount of the (B) component is less than 10 parts by mass, flame retardancy and tracking resistance will decrease. The blending amount is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 40 parts by mass or more, and particularly preferably 60 parts by mass or more. On the other hand, if the blending amount of the (B) component exceeds 120 parts by mass, bleed-out resistance and weld strength will decrease. The blending amount is preferably 110 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 90 parts by mass or less.

[0031] In the present invention, it is preferable to further blend (C) a styrene-based resin (hereinafter sometimes abbreviated as component (C)).

[0032] In the present invention, the styrene-based resin (C) is a thermoplastic resin obtained by polymerizing styrene as a monomer, and specific examples thereof include polystyrene, styrene / acrylonitrile copolymer, and rubber-modified styrene-based resin. Specific examples of the rubber-modified styrene-based resin include high impact polystyrene (HIPS), ABS resin (acrylonitrile / butadiene / styrene copolymer), AAS resin (acrylonitrile / acrylic / styrene copolymer), and AES resin (acrylonitrile / ethylene propylene / styrene copolymer).

[0033] The styrene-based resin (C) of the present invention is preferably epoxy-modified by graft polymerization or copolymerization with a monomer having an epoxy group such as glycidyl acrylate, from the viewpoint of dispersibility of the island phase of component (D). It may also have a syndiotactic structure formed by polymerization using a metallocene catalyst.

[0034] The amount of component (C) blended is preferably 1 to 40 parts by mass per 100 parts by mass of the polybutylene terephthalate resin (A). If the amount of component (C) blended is less than 1 part by mass, bleed-out resistance may decrease. It is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and particularly preferably 10 parts by mass or more. On the other hand, if the amount of component (C) blended exceeds 40 parts by mass, flame retardancy tends to decrease. It is preferably 35 parts by mass or less, more preferably 30 parts by mass or less, and particularly preferably 25 parts by mass or less.

[0035] In the present invention, the flame-retardant resin (D) refers to a thermoplastic resin that has flame retardancy even without the addition of a flame retardant, and is preferably a resin that exhibits a mass loss of 70% by mass or less when heated in air from room temperature to 600°C at a heating rate of 40°C / min. From the viewpoint of flame retardancy, the upper limit of the mass loss is preferably 60% by mass or less, and more preferably 50% by mass or less. The lower limit of the mass loss is 0% by mass.

[0036] The mass loss can be measured using a calorimeter (TGA-7, manufactured by Perkin Elmer) while supplying air at a flow rate of 40 mL / min and heating from room temperature 30°C to 600°C at a heating rate of 40°C / min, and calculated by {(mass before heating (at room temperature) - mass after heating (600°C)) / mass before heating x 100}.

[0037] Specific examples of the flame-retardant resin (D) of the present invention include polyarylene ether ketone, polyetherimide resin, polyphenylene ether resin, polyphenylene sulfide resin, polysulfone resin, liquid crystalline polyester resin, polyarylate resin, and phenol resin. From the viewpoint of efficiently forming island phases of the component (D), polyphenylene sulfide resin is preferred.

[0038] In the present invention, the polyphenylene sulfide resin is a polymer or copolymer having a repeating unit represented by the following general formula (1).

[0039]

[0040] From the viewpoint of heat resistance, a polymer or copolymer containing 70 mol % or more, more preferably 90 mol % or more of the repeating units represented by the above general formula (1) among all the repeating units is preferred. Furthermore, the polyphenylene sulfide resin can be composed of repeating units having a structure represented by the following general formula (2) at less than 30 mol % of its repeating units.

[0041]

[0042] The melt viscosity of the polyphenylene sulfide resin is not particularly limited as long as it can be melt-kneaded, but is usually 5 to 2000 Pa·s (320°C, shear rate 10 sec －１ ) is used.

[0043] Polyphenylene sulfide resins can be produced by known methods, and commercially available products include, for example, "TORELINA" (registered trademark) (manufactured by Toray Industries, Inc.) and PPS (manufactured by DIC Corporation).

[0044] The blending amount of the (D) component is 1 to 20 parts by mass per 100 parts by mass of the (A) polybutylene terephthalate resin. If the blending amount of the (D) component is less than 1 part by mass, flame retardancy decreases. It is more preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and particularly preferably 6 parts by mass or more. On the other hand, if the blending amount of the (D) component exceeds 20 parts by mass, tracking resistance decreases. It is preferably 18 parts by mass or less, more preferably 16 parts by mass or less, and particularly preferably 14 parts by mass or less.

[0045] The polybutylene terephthalate resin composition of the present invention has a phase structure in which island phases of the flame-retardant resin (D) have an average diameter of 0.05 to 5.0 μm within a sea phase of the polybutylene terephthalate resin (A).

[0046] The average diameter of the island phases of component (D) in the resin composition of the present invention can be determined by electron microscope observation using the following method. Because the phase-separated structure and the size of each phase of a resin composition do not change under typical molding conditions, in the present invention, the phase-separated structure is observed using a test piece obtained by molding the resin composition. First, a rectangular test piece (125 mm long x 13 mm wide x 1.6 mm thick) obtained by injection molding is cut at the center in the cross-sectional direction to a 1-1.6 mm square to obtain a sample for electron microscope. Platinum-palladium is vapor-deposited on the electron microscope sample by sputtering, and then an elemental mapping image is obtained by energy dispersive imaging using a field emission scanning electron microscope (FE-SEM). If necessary, to clearly observe components (A), (C), and (D), the sample may be stained with a stain such as ruthenium oxide depending on the blended resin, and the elements contained in the stain may be used for observation. For example, if a styrene resin is selected as component (C) and a polyphenylene sulfide resin is selected as component (D), each component can be appropriately mapped by the elements contained therein, such as mapping component (A) by oxygen atoms, component (C) by carbon atoms, and component (D) by sulfur atoms, and then the island phases of components (C) and (D) can be observed while being overlaid on an SEM image, allowing for differentiation. Furthermore, if it is difficult to distinguish between components (A) and (D), the components can be distinguished by staining component (A) with ruthenium oxide.

[0047] In the present invention, if island phases of component (D) are formed, the magnification is adjusted so that 100 to less than 200 island phases are present in a square electron microscope photograph in order to determine their average diameter. At this magnification, the 20 largest island phases present in the observation image are selected, and the major and minor diameters of each island phase are measured. The average of the major and minor diameters is taken as the diameter of each island phase, and the average of the diameters of all the measured island phases is taken as the diameter of the island phase. The major and minor diameters of the island phase refer to the longest and shortest diameters of the island phase, respectively. The values ​​were taken as the average of the measurements for three test pieces.

[0048] The average diameter of the island phases of component (D) in the resin composition of the present invention is 0.05 to 5.0 μm. If the average diameter of the island phases is less than 0.05 μm, flame retardancy and bleed-out resistance will decrease. It is preferably 0.1 μm or more, more preferably 0.2 μm or more, and particularly preferably 0.3 μm or more. On the other hand, if the average diameter of the island phases exceeds 5 μm, tracking resistance and weld strength will decrease. It is preferably 4.0 μm or less, more preferably 3.0 μm or less, and particularly preferably 2.0 μm or less.

[0049] In the present invention, the method for achieving a specific average diameter for the island phases of component (D) is not limited as long as it can produce such a resin composition, but examples include a method in which a polyphenylene sulfide resin is selected as component (D), the cylinder temperature, the number of screw kneadings, and the screw rotation speed are increased so that the resin temperature during melt-kneading of the composition is 285°C or higher and 335°C or lower, and the compounding ratio of components (C) to (D) is set to a range of 0.5 to 4.0. Another preferred method is to select a polyphenylene sulfide resin as component (D), the cylinder temperature, the number of screw kneadings, and the screw rotation speed are increased so that the resin temperature during melt-kneading of the composition is 285°C or higher and 335°C or lower, and the compounding amount of component (B) is set to a range of 80 to 120 parts by mass. These conditions vary depending on the combination of resins used and cannot be generalized, but the conditions can be determined by simple preliminary experiments.

[0050] In the present invention, by further blending component (C), it is preferable that component (C) is unevenly distributed at the interface of the island phase of component (D), forming a composite island phase in which the island phase of component (D) is dispersed within the island phase of component (C), thereby further improving flame retardancy and tracking resistance.

[0051] In the resin composition of the present invention, the average diameter of the composite island phases is preferably 1 to 20 μm. When the average diameter of the composite island phases is 1 μm or more, flame retardancy and bleed-out resistance are further improved. It is preferably 2 μm or more, more preferably 3 μm or more, and particularly preferably 4 μm or more. On the other hand, when the average diameter of the composite island phases is 20 μm or less, tracking resistance and weld strength are further improved. It is preferably 18 μm or less, more preferably 16 μm or less, and particularly preferably 14 μm or less. The average diameter of the composite island phases can be determined by the same method as that used to determine the average diameter of the island phases of component (D), i.e., the average diameter of the island phases of component (C) including the island phases of component (D).

[0052] Therefore, from the viewpoint of forming composite island phases, a preferred range can also be set for the ratio (C) / (D), which is the ratio of the amount of (C) styrene-based resin per 100 parts by mass of (A) polybutylene terephthalate resin to the amount of (D) flame-retardant resin per 100 parts by mass of (A) polybutylene terephthalate resin. The lower limit of (C) / (D) is preferably 0.5 or more, more preferably 0.8 or more, even more preferably 1.1 or more, and particularly preferably 1.5 or more. On the other hand, from the viewpoint of setting the upper limit of the average diameter of the island phases of component (D) within a preferred range, the upper limit of (C) / (D) is preferably 4.0 or less, more preferably 3.6 or less, even more preferably 3.0 or less, and particularly preferably 2.5 or less.

[0053] The polybutylene terephthalate resin composition of the present invention preferably further contains 10 to 150 parts by mass of (E) a nitrogen-containing heterocyclic compound having a triazine skeleton (hereinafter sometimes abbreviated as component (E)) per 100 parts by mass of the polybutylene terephthalate resin (A). The inclusion of component (E) is preferred because it improves the flame retardancy and bleed-out resistance of the polybutylene terephthalate resin composition.

[0054] Examples of the nitrogen-containing heterocyclic compound (E) having a triazine skeleton used in the present invention include melamine, benzoguanamine, cyanuric acid, melamine cyanurate, melamine isocyanurate, triphenyltriazine, ammeline, ammelide, thiocyanuric acid, diaminomethyltriazine, and melamine polyphosphate, and melamine cyanurate, melamine isocyanurate, and melamine polyphosphate are preferably used.

[0055] The melamine cyanurate or melamine isocyanurate is preferably an adduct of a triazine compound and cyanuric acid or isocyanuric acid, typically with a molar ratio of 1:1, or in some cases 1:2. These are produced by known methods, for example, by forming a water slurry of a mixture of melamine and cyanuric acid or isocyanuric acid, thoroughly mixing them to form finely divided salts of both compounds, and then filtering and drying the slurry to obtain a powder. The salts do not need to be completely pure; some unreacted melamine, cyanuric acid, or isocyanuric acid may remain. If dispersibility is poor, dispersants such as tris(β-hydroxyethyl)isocyanurate or known surface treatment agents such as polyvinyl alcohol and metal oxides such as silica may be used in combination. The average diameter of the melamine cyanurate or melamine isocyanurate before and after incorporation into a resin is preferably 0.1 to 100 μm, from the viewpoints of flame retardancy, mechanical strength, and surface properties of the molded product. Here, the average diameter is the average diameter measured at 50% cumulative distribution particle diameter by a laser micron sizer method. Commercially available melamine cyanurate or melamine isocyanurate products such as MC-4000, MC-4500, and MC-6000 manufactured by Nissan Chemical Industries, Ltd. are preferably used.

[0056] In addition, from the viewpoint of a balance between flame retardancy and mechanical properties, the blending amount of the nitrogen-containing heterocyclic compound having a triazine skeleton (E) is preferably 10 to 150 parts by mass per 100 parts by mass of the polybutylene terephthalate resin (A). A blending amount of component (E) of 10 parts by mass or more is preferred because it provides excellent flame retardancy and bleed-out resistance, more preferably 50 parts by mass or more, and even more preferably 70 parts by mass or more. On the other hand, a blending amount of component (E) of 150 parts by mass or less is preferred because it provides excellent weld strength, more preferably 130 parts by mass or less, and even more preferably 110 parts by mass or less.

[0057] The polybutylene terephthalate resin composition of the present invention preferably further contains 1 to 40 parts by mass of (F) core-shell rubber (hereinafter sometimes abbreviated as component (F)) per 100 parts by mass of the polybutylene terephthalate resin (A).

[0058] (F) Core-shell rubber is a polymer having a structure known as a core-shell structure, which is composed of an innermost layer (core layer) and one or more layers (shell layers) covering the innermost layer, and in which adjacent layers are composed of different polymers, and has at least one or more rubber layers inside.

[0059] The number of layers constituting the core-shell rubber (F) of the present invention is not particularly limited, and may be two or more, three or more, or four or more.

[0060] In the core-shell rubber (F) of the present invention, the type of rubber layer is not particularly limited, as long as it is composed of a polymer component having rubber elasticity. Examples include rubbers composed of polymerized acrylic components, silicone components, styrene components, nitrile components, conjugated diene components, urethane components, or ethylene propylene components. Preferred rubbers include rubbers composed of polymerized acrylic components such as ethyl acrylate units or butyl acrylate units, silicone components such as dimethylsiloxane units or phenylmethylsiloxane units, styrene components such as styrene units or α-methylstyrene units, nitrile components such as acrylonitrile units or methacrylonitrile units, and conjugated diene components such as butadiene units or isoprene units. Rubbers formed by copolymerizing two or more of these components are also preferred, including, for example, (1) rubbers formed by copolymerizing an acrylic component such as ethyl acrylate units or butyl acrylate units with a silicone component such as dimethylsiloxane units or phenylmethylsiloxane units, (2) rubbers formed by copolymerizing an acrylic component such as ethyl acrylate units or butyl acrylate units with a styrene component such as styrene units or α-methylstyrene units, (3) rubbers formed by copolymerizing an acrylic component such as ethyl acrylate units or butyl acrylate units with a conjugated diene component such as butadiene units or isoprene units, and (4) rubbers formed by copolymerizing an acrylic component such as ethyl acrylate units or butyl acrylate units with a silicone component such as dimethylsiloxane units or phenylmethylsiloxane units with a styrene component such as styrene units or α-methylstyrene units. In addition to these components, rubbers formed by copolymerizing and crosslinking crosslinkable components such as divinylbenzene units, allyl acrylate units, and butylene glycol diacrylate units are also preferred. In the present invention, those that fall under both (C) styrene-based resin and (F) core-shell rubber are included in (F) core-shell rubber.

[0061] In the core-shell rubber (F) of the present invention, the type of layer other than the rubber layer is not particularly limited as long as it is composed of a polymer component having thermoplasticity, but it is preferable that the layer be a polymer component having a higher glass transition temperature than the rubber layer. Examples of the thermoplastic polymer include polymers containing at least one unit selected from unsaturated carboxylic acid alkyl ester-based units, unsaturated glycidyl group-containing units, unsaturated dicarboxylic acid anhydride-based units, aliphatic vinyl-based units, aromatic vinyl-based units, vinyl cyanide-based units, maleimide-based units, unsaturated dicarboxylic acid units, and other vinyl-based units. Among these, polymers containing at least one unit selected from unsaturated carboxylic acid alkyl ester-based units, unsaturated glycidyl group-containing units, and unsaturated dicarboxylic acid anhydride-based units are preferred, and polymers containing at least one unit selected from unsaturated glycidyl group-containing units and unsaturated dicarboxylic acid anhydride-based units are more preferred.

[0062] The unsaturated carboxylic acid alkyl ester unit is not particularly limited, but (meth)acrylic acid alkyl ester is preferably used. Specifically, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, stearyl (meth)acrylate, octadecyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, chloromethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and (meth)acrylic acid alkyl ester are preferred. Examples of such units include 3-hydroxypropyl acrylate, 2,3,4,5,6-pentahydroxyhexyl (meth)acrylate, 2,3,4,5-tetrahydroxypentyl (meth)acrylate, aminoethyl acrylate, propylaminoethyl acrylate, dimethylaminoethyl methacrylate, ethylaminopropyl methacrylate, phenylaminoethyl methacrylate, and cyclohexylaminoethyl methacrylate, and from the viewpoint of the significant effect of improving impact resistance, methyl (meth)acrylate is preferably used. These units may be used alone or in combination of two or more.

[0063] The unsaturated glycidyl group-containing unit is not particularly limited and examples thereof include glycidyl (meth)acrylate, glycidyl itaconate, diglycidyl itaconate, allyl glycidyl ether, styrene-4-glycidyl ether, and 4-glycidylstyrene, with glycidyl (meth)acrylate being preferred from the viewpoint of its significant effect in improving impact resistance. These units may be used alone or in combination of two or more.

[0064] Examples of the unsaturated dicarboxylic acid anhydride unit include maleic anhydride, itaconic anhydride, glutaconic anhydride, citraconic anhydride, and aconitic anhydride, and maleic anhydride is preferred from the viewpoint of its significant effect in improving impact resistance. These units may be used alone or in combination of two or more.

[0065] Examples of the aliphatic vinyl units include ethylene, propylene, and butadiene. Examples of the aromatic vinyl units include styrene, α-methylstyrene, 1-vinylnaphthalene, 4-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-(phenylbutyl)styrene, and halogenated styrenes. Examples of the vinyl cyanide units include acrylonitrile, methacrylonitrile, and ethacrylonitrile. Examples of the maleimide units include maleimide, N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-isopropylmaleimide, N-cyclohexylmaleimide, N Examples of the unsaturated dicarboxylic acid units include maleic acid, maleic acid monoethyl ester, itaconic acid, and phthalic acid. Examples of the other vinyl units include acrylamide, methacrylamide, N-methylacrylamide, butoxymethylacrylamide, N-propylmethacrylamide, N-vinyldiethylamine, N-acetylvinylamine, allylamine, methallylamine, N-methylallylamine, p-aminostyrene, 2-isopropenyloxazoline, 2-vinyloxazoline, 2-acroyloxazoline, and 2-styryloxazoline. These units may be used alone or in combination of two or more.

[0066] In the core-shell rubber (F) of the present invention, the type of the outermost layer is not particularly limited, and examples thereof include at least one type selected from polymers containing unsaturated carboxylic acid alkyl ester units, unsaturated glycidyl group-containing units, aliphatic vinyl units, aromatic vinyl units, vinyl cyanide units, maleimide units, unsaturated dicarboxylic acid units, unsaturated dicarboxylic anhydride units, and other vinyl units, and among these, at least one type selected from polymers containing unsaturated carboxylic acid alkyl ester units, aliphatic vinyl units, aromatic vinyl units, and vinyl cyanide units is preferred, and polymers containing aromatic vinyl units and vinyl cyanide units are even more preferred.

[0067] The unsaturated carboxylic acid alkyl ester unit is not particularly limited, but is preferably a (meth)acrylic acid alkyl ester, and more preferably methyl (meth)acrylate. Furthermore, styrene is more preferably used as the aromatic vinyl unit, and acrylonitrile is more preferably used as the vinyl cyanide unit.

[0068] Preferred examples of the core-shell rubber (F) of the present invention include one in which the core layer is a dimethylsiloxane / butyl acrylate polymer and the outermost layer is a methyl methacrylate polymer, one in which the core layer is a dimethylsiloxane / butyl acrylate polymer and the outermost layer is a styrene / acrylonitrile polymer, one in which the core layer is a butadiene / styrene polymer and the outermost layer is a methyl methacrylate polymer, and one in which the core layer is a butyl acrylate polymer and the outermost layer is a methyl methacrylate polymer, and particularly one in which the core layer is a dimethylsiloxane / butyl acrylate polymer and the outermost layer is a styrene / acrylonitrile polymer is more preferred.

[0069] The particle size of the core-shell rubber (F) of the present invention is not particularly limited, but is preferably 0.01 μm or more and 100 μm or less, more preferably 0.02 μm or more and 10 μm or less, and most preferably 0.05 μm or more and 1 μm or less.

[0070] In the core-shell rubber (F) of the present invention, the mass ratio of the core to the shell is not particularly limited, but it is preferable that the core layer is 10 parts by mass or more and 90 parts by mass or less, and more preferably 30 parts by mass or more and 80 parts by mass or less, of the entire core-shell rubber.

[0071] As the core-shell rubber (F) of the present invention, a commercially available product satisfying the above-mentioned conditions may be used, or one prepared by a known method may also be used.

[0072] Examples of commercially available core-shell rubbers include "Metablen" manufactured by Mitsubishi Chemical Corporation, "Kane Ace" manufactured by Kaneka Corporation, "Paraloid" manufactured by Dow Chemical Industries, Ltd., "Staphyloid" manufactured by Aica Kogyo Co., Ltd., and "Parapet SA" manufactured by Kuraray Co., Ltd., and these may be used alone or in combination of two or more.

[0073] The amount of component (F) blended is preferably 1 to 40 parts by mass per 100 parts by mass of polybutylene terephthalate resin (A). If the amount of component (F) blended is less than 1 part by mass, bleed-out resistance decreases. It is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and particularly preferably 10 parts by mass or more. On the other hand, if the amount of component (F) blended exceeds 40 parts by mass, flame retardancy decreases. It is preferably 35 parts by mass or less, more preferably 30 parts by mass or less, and particularly preferably 25 parts by mass or less.

[0074] In order to improve flame retardancy, bleed-out resistance, weld strength, and molding pressure stability during injection molding, the polybutylene terephthalate resin composition of the present invention preferably further contains (G) a hindered amine compound. The hindered amine compound is a compound having a structure containing at least one 2,2,6,6-tetramethylpiperidine derivative in its molecule.

[0075] Specific examples of the hindered amine compound used in the present invention include 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, bis-(2,2,6,6-tetramethyl-4-piperidyl)adipate, bis-(2,2,6,6-tetramethyl-4-piperidyl)suberate, bis-(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis-(2,2,6,6-tetramethyl-4-piperidyl)phthalate, bis-(2,2,6,6-tetramethyl-4-piperidyl)terephthalate, bis-(1,2,2,6,6-pentamethyl-4-piperidyl) N,N'-bis-(2,2,6,6-tetramethyl-4-piperidyl)isophthalamide, N,N'-bis-(2,2,6,6-tetramethyl-4-piperidyl)adipamide, bis-(1,2,2,6,6-pentamethyl-4-piperidyl)-n-butyl(3,5-di-t-butyl-4-hydroxybenzyl)malonate, bis-(2,2,6,6-tetramethyl-4-piperidyl)-n-butyl(3,5-di-t-butyl-4-hydroxybenzyl) ) malonate, tetra-(2,2,6,6-tetramethyl-4-piperidyl) ester of butanetetracarboxylic acid, 1-[2-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]ethyl]-4-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]2,2,6,6-tetramethylpiperidine, poly[[6-(1,1,3,3-tetramethylbutyl)imino-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethylpiperidyl)imino]hexamethylene[(2,2,6, 6-tetramethyl-4-piperidyl)imino]], tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)1,2,3,4-butanetetracarboxylate, tetrakis(2,2,6,6-tetramethyl-4-piperidyl)1,2,3,4-butanetetracarboxylate, dimethyl-1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine succinate, 1,2,3,4-butanetetracarboxylic acid and 2,2,6,6-tetramethyl-4-piperidinol and β,β,β',β'-tetramethyl-3,9-(2,and a condensation product of 1,2,3,4-butanetetracarboxylic acid, 1,2,2,6,6-pentamethyl-4-piperidinol, and β,β,β',β'-tetramethyl-3,9-(2,4,8,10-tetraoxaspiro[5,5]undecane)diethanol.

[0076] From the viewpoints of flame retardancy, bleed-out resistance, weld strength, and molding pressure stability during injection molding, the blending amount of the (G) hindered amine compound used in the present invention is preferably 0.3 to 3.0 parts by mass per 100 parts by mass of the (A) polybutylene terephthalate resin. A blending amount of the (G) component of 0.3 parts by mass or more is preferred because it provides excellent bleed-out resistance and weld strength, more preferably 0.5 parts by mass or more, even more preferably 0.8 parts by mass or more, and particularly preferably 1.0 parts by mass or more. On the other hand, a blending amount of the (G) component of 3.0 parts by mass or less is preferred because it can suppress decomposition of the (A) polybutylene terephthalate resin by the amine component, thereby providing excellent flame retardancy and weld strength, more preferably 2.5 parts by mass or less, even more preferably 2.0 parts by mass or less, and particularly preferably 1.5 parts by mass or less.

[0077] In the polybutylene terephthalate resin composition of the present invention, the ratio of the parts by mass of the (B) phosphate compound to the parts by mass of the (G) hindered amine compound blended per 100 parts by mass of the (A) polybutylene terephthalate resin ([parts by mass of the (B) component per 100 parts by mass of the (A) component] / [parts by mass of the (G) component per 100 parts by mass of the (A) component]) (hereinafter, sometimes abbreviated as (B) / (G)) is preferably 5 to 50. Controlling the blending amount ratio of the (B) component to the (G) component within the above range results in excellent dispersibility of the (B) component in the (A) polybutylene terephthalate resin composition and efficient reaction with the (G) component, resulting in higher levels of flame retardancy, bleed-out resistance, weld strength, and molding pressure stability during injection molding. From the viewpoints of flame retardancy and mechanical strength, (B) / (G) is more preferably 6 or more, and even more preferably 8 or more. On the other hand, from the viewpoint of bleed-out resistance, weld strength, and stability of molding pressure during injection molding, the molecular weight is more preferably 40 or less, and even more preferably 30 or less.

[0078] The polybutylene terephthalate resin composition of the present invention preferably further contains (H) a fibrous reinforcing material (hereinafter sometimes abbreviated as component (H)). The (H) fibrous reinforcing material can further improve mechanical strength and heat resistance.

[0079] Specific examples of the (H) fibrous reinforcing material include glass fiber, aramid fiber, and carbon fiber. The glass fiber may be a chopped strand type or a roving type, and is preferably treated with a silane coupling agent such as an aminosilane compound or an epoxysilane compound and / or a sizing agent containing urethane, a copolymer of acrylic acid such as an acrylic acid / styrene copolymer, a copolymer of maleic anhydride such as a methyl acrylate / methyl methacrylate / maleic anhydride copolymer, vinyl acetate, bisphenol A diglycidyl ether, or one or more epoxy compounds such as a novolac epoxy compound. Glass fibers treated with a copolymer of maleic anhydride or a sizing agent containing an epoxy compound are more preferred because they can further improve mechanical properties and hydrolysis resistance during high-temperature molding. The silane coupling agent and / or sizing agent may be mixed in an emulsion liquid before use. Furthermore, the fiber diameter of the glass fiber is typically preferably in the range of 1 to 30 μm. From the viewpoint of dispersibility of the glass fiber in the polybutylene terephthalate resin composition, the lower limit is preferably 5 μm, and from the viewpoint of mechanical strength, the upper limit is preferably 15 μm. Furthermore, although the above-mentioned fiber cross section is usually circular, fibrous reinforcing materials having any cross section, such as elliptical glass fibers, flat glass fibers, and cocoon-shaped glass fibers with any aspect ratio, can also be used, which has the characteristics of improving fluidity during injection molding and obtaining molded products with little warpage.

[0080] The blending amount of (H) fibrous reinforcing material is preferably 1 to 170 parts by mass per 100 parts by mass of (A) polybutylene terephthalate resin. Blending 1 part by mass or more of (H) fibrous reinforcing material can further improve mechanical strength, heat resistance, and weld strength. Blending 10 parts by mass or more is more preferable, and 30 parts by mass or more is even more preferable. Blending 170 parts by mass or less of (H) fibrous reinforcing material can further improve mechanical strength and fluidity. Blending 150 parts by mass or less is more preferable, and 130 parts by mass or less is even more preferable.

[0081] In order to improve hydrolysis resistance, it is preferable to further blend a terminal blocking agent in the polybutylene terephthalate resin composition of the present invention. The terminal blocking agent may be any compound capable of reactively blocking the carboxyl terminals of the polybutylene terephthalate resin (A), such as an epoxy compound or a carbodiimide compound.

[0082] The polybutylene terephthalate resin composition of the present invention may contain any additives such as antioxidants, heat stabilizers, ultraviolet absorbers, light stabilizers, plasticizers, mold release agents, antistatic agents, anti-drip agents, carbon black, titanium oxide, and pigments and dyes of various colors, as well as one or more inorganic fillers other than component (H), within the scope of the present invention.

[0083] The polybutylene terephthalate resin composition of the present invention may contain a thermoplastic resin other than component (A) within a range that does not impair the object of the present invention, thereby improving moldability, dimensional accuracy, molding shrinkage, toughness, etc. Examples of thermoplastic resins other than component (A) include polyolefin resins, polyamide resins, polyacetal resins, polyurethane resins, aliphatic polyketone resins, thermoplastic starch resins, poly-4-methylpentene-1, cellulose acetate resins, and polyvinyl alcohol resins. When a thermoplastic resin other than component (A) is contained, it is preferable that the proportion of component (A) be the largest among the thermoplastic resins contained in the polybutylene terephthalate resin composition of the present invention.

[0084] The polybutylene terephthalate resin composition of the present invention is not limited in the amount of the above-mentioned components to be blended as long as the object of the present invention is not impaired, but it has been found that limiting the amount of a specific component can further improve the properties. Four components whose amounts are preferably limited will be described below.

[0085] First, from the viewpoint of preventing a decrease in the crystallinity of the (A) polybutylene terephthalate resin and improving bleed-out resistance, the amount of at least one selected from polyethylene terephthalate resin, polyetherimide resin, and polycarbonate resin per 100 parts by mass of the (A) polybutylene terephthalate resin is preferably less than 5 parts by mass, more preferably less than 3 parts by mass, and particularly preferably less than 1 part by mass.

[0086] Second, from the viewpoint of forming the island phases of component (D) with an appropriate average diameter and improving tracking resistance, the amount of polyphenylene ether resin is preferably less than 5 parts by mass, more preferably less than 3 parts by mass, and particularly preferably less than 1 part by mass per 100 parts by mass of polybutylene terephthalate resin (A).

[0087] Third, from the viewpoint of reducing the PFAS content and improving weld strength, the content of the fluorine-based resin that is generally blended as an anti-dripping agent per 100 parts by mass of (A) polybutylene terephthalate resin is preferably less than 0.5 parts by mass, more preferably less than 0.3 parts by mass, and particularly preferably less than 0.1 parts by mass.

[0088] The fluorine-based resin is a resin containing fluorine in the molecule, and is a compound that falls under the PFAS regulations, and specific examples thereof include polytetrafluoroethylene, polyhexafluoropropylene, (tetrafluoroethylene / hexafluoropropylene) copolymer, (tetrafluoroethylene / perfluoroalkyl vinyl ether) copolymer, (tetrafluoroethylene / ethylene) copolymer, (hexafluoropropylene / propylene) copolymer, polyvinylidene fluoride, (vinylidene fluoride / ethylene) copolymer, etc. Among them, polytetrafluoroethylene, (tetrafluoroethylene / perfluoroalkyl vinyl ether) copolymer, (tetrafluoroethylene / hexafluoropropylene) copolymer, (tetrafluoroethylene / ethylene) copolymer, polyvinylidene fluoride, etc.

[0089] Fourth, from the viewpoint of improving bleed-out resistance, the amount of at least one phosphinate selected from phosphinates and diphosphinates, or a phosphazene compound, which is generally blended as a flame retardant, relative to 100 parts by mass of (A) the polybutylene terephthalate resin is preferably less than 5 parts by mass, more preferably less than 3 parts by mass, and particularly preferably less than 1 part by mass.

[0090] The polybutylene terephthalate resin composition of the present invention can be obtained, for example, by melt-kneading the components (A) to (D) and, if necessary, other components.

[0091] Examples of the melt-kneading method include a method in which the components (A) to (D), and, if necessary, other components and various additives, are premixed, and the mixture is fed into an extruder or the like and thoroughly melt-kneaded; or a method in which a predetermined amount of each component is fed into an extruder or the like using a metering feeder such as a weight feeder, and thoroughly melt-kneaded.

[0092] Examples of the premixing include dry blending and mixing using a mechanical mixer such as a tumbler, ribbon mixer, or Henschel mixer. The (H) fibrous reinforcing material and inorganic fillers other than the fibrous reinforcing material may be added by installing a side feeder between the base and vent sections of a multi-screw extruder such as a twin-screw extruder. In the case of liquid additives, a method of adding the additive using a plunger pump with a liquid addition nozzle installed between the base and vent sections of a multi-screw extruder such as a twin-screw extruder, or a method of supplying the additive from the base using a metering pump, may be used.

[0093] The polybutylene terephthalate resin composition of the present invention is preferably pelletized before molding. Examples of the pelletizing method include a method in which the composition is extruded in the form of strands using a single-screw extruder, twin-screw extruder, triple-screw extruder, conical extruder, or kneader-type mixer equipped with a "Unimelt" or "Dulmage" type screw, and then cut with a strand cutter.

[0094] From the viewpoint of productivity, the polybutylene terephthalate resin composition of the present invention is preferably kneaded using a twin-screw extruder in order to uniformly mix components (A) to (D). The twin-screw extruder is preferably provided with one or more kneading sections, more preferably two or more, in order to improve the dispersibility of the flame retardant. For example, when component (H) is added through a side feeder, the kneading section is preferably provided at two or more locations: one or more upstream of the side feeder to promote plasticization and dispersion of components (A) to (D), and one or more downstream of the side feeder to disperse component (H) in the resin composition while suppressing breakage.

[0095] In order to form composite island phases with a specific average diameter in the polybutylene terephthalate resin composition of the present invention, a preferred range can be set for the resin temperature during kneading of components (A) to (D). The lower limit of the resin temperature during kneading is preferably 285°C or higher, more preferably 288°C or higher, and particularly preferably 290°C or higher, in order to finely disperse and compound components (C) and (D). Meanwhile, the upper limit of the resin temperature during kneading is preferably 335°C or lower, more preferably 320°C or lower, and particularly preferably 310°C or lower, because component (A) suppresses decomposition and improves strength. The resin temperature during kneading can be controlled by the throughput per unit time of the resin composition, the temperature setting of the heating section of the kneader, the rotation speed of the screw and stirring blades, and the like. The resin temperature can be measured by directly contacting a thermocouple with the molten resin composition at the hole in the discharge section of the extruder as the resin composition is discharged from the hole.

[0096] The polybutylene terephthalate resin composition of the present invention can be melt-molded to obtain films, fibers, and other molded articles in various shapes. Examples of melt-molding methods include injection molding, extrusion molding, and blow molding, with injection molding being particularly preferred.

[0097] As injection molding methods, in addition to the usual injection molding method, gas-assisted molding, two-color molding, sandwich molding, in-mold molding, insert molding, injection press molding, and the like are known, and any of these molding methods can be applied.

[0098] The molded article of the present invention can be used as a molded article for mechanical components, electrical components, electronic components, and automotive components, taking advantage of its excellent flame retardancy, tracking resistance, bleed-out resistance, and weld strength. Furthermore, because of its excellent weld strength, it can be used for small, thin-walled molded articles and molded articles containing metal inserts. Furthermore, because of its excellent flame retardancy, tracking resistance, and bleed-out resistance, the molded article of the present invention is particularly useful for electrical and electronic components for automobiles.

[0099] Specific examples of mechanical parts, electrical parts, electronic parts, and automotive parts include breakers, electromagnetic switches, focus cases, flyback transformers, molded parts for fixing devices in copiers and printers, housings for general household electrical appliances and office automation equipment, variable capacitor case parts, various terminal boards, printed wiring boards, housings, terminal blocks, coil bobbins, connectors, relays, disk drive chassis, transformers, switch parts, outlet parts, motor parts, sockets, plugs, capacitors, various cases, resistors, electrical and electronic parts incorporating metal terminals and conductors, computer-related parts, audio parts such as audio components, lighting parts, telegraph equipment-related parts, telephone equipment-related parts, air conditioner parts, home appliance parts such as VTRs and televisions, copier parts, facsimile parts, optical equipment parts, automotive ignition system parts, automotive charging system parts, automotive connectors, automotive high-voltage connectors, insulating materials such as bus bars, and various automotive electrical parts.

[0100] The molded article of the present invention is capable of achieving both high flame retardancy and tracking resistance, and is therefore useful for high-voltage insulating parts. Among these, it is particularly useful for high-voltage connectors, power module cases, and bus bars, particularly when used in high-voltage applications of 400 V or more, because it allows for greater design freedom and allows for further miniaturization.

[0101] Next, the effects of the polybutylene terephthalate resin composition of the present invention will be specifically described using examples. The raw materials used in the examples and comparative examples are shown below. Here, % and parts all represent % by mass and parts by mass, and " / " in the following resin names indicates copolymerization.

[0102] (A) Polybutylene terephthalate resin <A-1> Polybutylene terephthalate resin: manufactured by Toray Industries, Inc., a polybutylene terephthalate resin having a carboxyl group amount of 30 eq / t and an intrinsic viscosity of 0.80 dl / g measured at 25°C using o-chlorophenol as a solvent was used.

[0103] (B) Phosphate Ester Compound <B-1> Resorcinol bis(di-2,6-xylyl phosphate): PX-200 manufactured by Daihachi Chemical Industry Co., Ltd. was used.

[0104] (C) Styrene-based resins <C-1> Polystyrene resin: GPPS and HF77 manufactured by PS Japan Co., Ltd. <C-2> Styrene / acrylonitrile (74 / 26% by mass) copolymer: AS resin manufactured by Toray Industries, Inc. <C-3> Styrene / acrylonitrile / glycidyl methacrylate (74 / 25.5 / 0.5% by mass) copolymer: Epoxy-modified AS resin manufactured by Toray Industries, Inc.

[0105] (D) Flame-Retardant Resin <D-1> Liquid Crystalline Polyester Resin: A liquid crystal polyester resin <D-1> produced as follows was used.

[0106] A 5 L reactor equipped with a stirring blade and a distillation tube was charged with 994 parts by mass of p-hydroxybenzoic acid, 126 parts by mass of 4,4'-dihydroxybiphenyl, 112 parts by mass of terephthalic acid, 216 parts by mass of polyethylene terephthalate having an intrinsic viscosity of approximately 0.6 dl / g, and 960 parts by mass of acetic anhydride (1.10 equivalents of total phenolic hydroxyl groups), and the mixture was reacted at 145°C for 1 hour with stirring under a nitrogen gas atmosphere, and then the temperature was increased from 145°C to 320°C over 4 hours. Thereafter, the polymerization temperature was maintained at 320°C, and the pressure was reduced to 1.0 mmHg (133 Pa) over 1.0 hour. The reaction was further continued, and the polymerization was completed when the torque required for stirring reached 20 kg cm. Next, the polymer was discharged into a strand-like substance from the reactor via a spinneret having one circular discharge port with a diameter of 10 mm, and pelletized using a cutter to obtain a liquid crystalline polyester resin <D-1>. Composition analysis of this liquid crystal polyester resin <D-1> revealed that the proportion of structural units derived from p-hydroxybenzoic acid was 66.7 mol%, the proportion of structural units derived from 4,4'-dihydroxybiphenyl was 6.3 mol%, the proportion of ethylenedioxy units derived from polyethylene terephthalate was 10.4 mol%, and the proportion of structural units derived from terephthalic acid was 16.7 mol%. The liquid crystal polyester resin also had a melting point of 313°C, and a mass loss of 61% by mass when heated in air from room temperature to 600°C at a heating rate of 40°C / min. <D-2> Polyphenylene sulfide resin: manufactured by Toray Industries, Inc., 320°C, shear rate 10 sec －１ A polyphenylene sulfide resin was used that had a melt viscosity of 80 Pa s at room temperature and a mass loss of 34% by mass when heated in air from room temperature to 600°C at a heating rate of 40°C / min. <D-3> Polyphenylene ether resin: "ZYLON" (registered trademark) S201A manufactured by Asahi Kasei Corporation, a polyphenylene ether resin that had a mass loss of 42% by mass when heated in air from room temperature to 600°C at a heating rate of 40°C / min.

[0107] (E) Nitrogen-containing heterocyclic compound having a triazine skeleton <E-1> Melamine cyanurate: MC-4000 manufactured by Nissan Chemical Industries, Ltd. was used. (F) Core-shell rubber <F-1> Core-shell rubber having a core layer of dimethylsiloxane / butyl acrylate polymer and an outermost layer of methyl methacrylate polymer: "Metablen" (registered trademark) S-2001 manufactured by Mitsubishi Chemical Corporation was used. <F-2> Core-shell rubber having a core layer of butyl acrylate polymer and an outermost layer of methyl methacrylate polymer: "Paraloid" (registered trademark) EXL-2315 manufactured by Dow Chemical Japan Co., Ltd. <F-3> Core-shell rubber having a core layer of dimethylsiloxane / butyl acrylate polymer and an outermost layer of methyl methacrylate polymer: "Metablen" (registered trademark) SX-005 manufactured by Mitsubishi Chemical Corporation was used. <F-4> Core-shell rubber having a core of dimethylsiloxane / butyl acrylate polymer and an outermost layer of styrene / acrylonitrile polymer: "Metablen" (registered trademark) SX-006 manufactured by Mitsubishi Chemical Corporation was used.

[0108] (G) Hindered Amine Compound <G-1> Bis-(1,2,2,6,6-pentamethyl-4-piperidyl)-n-butyl(3,5-di-t-butyl-4-hydroxybenzyl)malonate: Tinuvin 144 manufactured by BASF Corporation, melting point 150° C. was used.

[0109] (H) Fibrous Reinforcement <H-1> Glass fiber treated with a sizing agent containing an epoxy compound: Glass fiber ECS03T-187 manufactured by Nippon Electric Glass Co., Ltd., having a cross-sectional diameter of 13 μm and a fiber length of 3 mm, was used.

[0110] (I) Other Components <I-1> Polyethylene terephthalate resin: A polyethylene terephthalate resin manufactured by Toray Industries, Inc., having a carboxyl group content of 40 eq / t and an intrinsic viscosity of 0.63 dl / g measured at 25°C using o-chlorophenol as a solvent, was used. <I-2> Fluorine-based resin: Polytetrafluoroethylene, "Teflon" (registered trademark) 6-J manufactured by DuPont-Mitsui Fluorochemicals Co., Ltd. was used. <I-3> Phosphinic acid metal salt: Aluminum diethylphosphinate, "Exolit" (registered trademark) OP-1240 manufactured by Clariant Japan Co., Ltd. was used. <I-4> Phosphazene compound: "Lavitor" (registered trademark) FP-110 manufactured by Fushimi Pharmaceutical Co., Ltd. was used.

[0111] [Methods for Measuring Each Property] In the examples and comparative examples, the properties were evaluated by the following measurement methods.

[0112] (1) Electron Microscope Observation of the Sea-Island Structure (Average Diameter of Island Phases and Composite Island Phases of Component (D)) Using a Nissei Plastic Industrial Co., Ltd. NEX1000 injection molding machine, strip test specimens measuring 125 mm x 13 mm x 1.6 mm thick were molded under molding cycle conditions of a cylinder temperature of 260°C, a mold temperature of 80°C, a total injection time and dwell time of 10 seconds, and a cooling time of 10 seconds. The cross-sectional center of each strip test specimen was cut into 1-1.6 mm squares to obtain samples for electron microscopy. The electron microscopy samples were stained with ruthenium tetroxide and then vapor-deposited with platinum-palladium by sputtering. SEM images and elemental mapping images were obtained using a field emission scanning electron microscope (FE-SEM) using an energy dispersive method. To identify the island phases of component (D) from the elemental mapping images and SEM images and determine their average diameter, the magnification was adjusted so that 100 to 200 island phases of component (D) were present in each square electron micrograph. At this magnification, the 20 largest island phases of component (D) present in the observed image were selected, and the long and short diameters of each island phase were measured. The average of the long and short diameters was taken as the diameter of each island phase of component (D), and the average of the diameters of all the measured island phases of component (D) was taken as the diameter of the island phase. The long and short diameters of the island phases of component (D) were taken as the longest and shortest diameters, respectively. The values ​​were taken as the average of the measurements of three test pieces.

[0113] When component (C) was blended, observation was performed under an electron microscope in the same manner as above. If island phases of component (D) were contained within island phases of component (C), it was determined that composite island phases had been formed, and the average diameter of the composite island phases was similarly determined.

[0114] (2) Flame Retardancy (Combustion Rank) Using a Nissei Plastic Industrial Co., Ltd. NEX1000 injection molding machine, combustion test specimens measuring 125 mm x 13 mm x 1.6 mm thick were obtained under molding cycle conditions of a cylinder temperature of 260°C, a mold temperature of 80°C, a total injection time and dwell time of 10 seconds, and a cooling time of 10 seconds. The obtained combustion test specimens were used to evaluate the flame retardancy of the 1.6 mm thick test specimens according to the evaluation criteria set forth in the UL94 vertical test. Flame retardancy is ranked in the order of V-0 > V-1 > V-2. Materials with poor flame retardancy that did not fall under the above flame retardancy ranks were classified as out of specification (V-out). Materials ranked V-1 and V-2, or considered out of specification, were determined to have poor flame retardancy. Furthermore, even among materials rated V-0, when 20 test pieces were evaluated, if no test piece had a maximum burning time of more than 10 seconds after the first or second flame contact, it was determined that there was no variation in flammability and that the material had stable flame retardancy.

[0115] (3) Tracking resistance and its wet heat stability: Injection molding was performed under the same injection molding conditions as in (1) above using a Nissei Plastic Industrial NEX1000 injection molding machine to obtain a square plate measuring 80 mm x 80 mm x 3 mm thick. Using the obtained square plate, the comparative tracking index was measured using a 0.1% aqueous ammonium chloride solution as the electrolyte solution in accordance with the measurement method for the comparative tracking index of 600 V or less specified in IEC 60112:2003. For comparative tracking indices exceeding 600 V, the platinum electrode was reversed as specified in IEC 60112:2003 and evaluated. The higher the comparative tracking index value, the better the tracking resistance was evaluated. Values ​​above 500 V were considered particularly excellent, values ​​above 600 V were considered even better, and values ​​above 700 V were considered even better. On the other hand, values ​​below 500 V were considered to be inferior in tracking resistance.

[0116] The resulting square plates were placed in a highly accelerated life tester EHS-411 manufactured by Espec Corp., set to a temperature and humidity of 121°C x 100% RH, and subjected to a 100-hour wet heat treatment. The square plates after the wet heat treatment were evaluated for comparative tracking index in the same manner as above, and a value of 500V or higher was judged to have better tracking resistance.

[0117] (4) Bleeding Resistance (Occurrence of Bleeding After Dry Heat or Wet Heat Treatment) Using a Nissei Plastic Industrial Co., Ltd. NEX1000 injection molding machine, injection molding was performed under the same injection molding conditions as in (1) above, to obtain test specimens measuring 125 mm x 13 mm x 1.6 mm thick. To evaluate bleed-out resistance in a dry heat environment, the obtained test specimens were placed in an Espec Corporation thermostat PHV-222 set at 150°C and subjected to dry heat treatment for 100 hours. To evaluate bleed-out resistance in a wet heat environment, the specimens were placed in an Espec Corporation highly accelerated life tester EHS-411 set at a temperature and humidity of 121°C x 100% RH and subjected to wet heat treatment for 100 hours. The appearance of the molded articles after dry heat treatment and wet heat treatment was visually observed, and bleed-out was evaluated according to the following criteria: A: No liquid or white powdery bleed-out was observed in the molded article. B: Liquid or white powdery bleeding out is observed in some or all parts of the molded article.

[0118] Materials in which no bleed-out was observed after 100 hours of dry heat treatment were evaluated as having excellent bleed-out resistance, and materials in which no bleed-out was observed after 100 hours of moist heat treatment were evaluated as having even better bleed-out resistance, and materials in which bleed-out was observed under either condition were judged to have poor bleed-out resistance.

[0119] (5) Weld Strength (Maximum Tensile Strength of Weld Portion) Injection molding was performed using a Nissei Plastic Industrial NEX1000 injection molding machine under the same injection molding conditions as in (1) above to obtain ASTM No. 1 dumbbell (1 / 8 inch thick) test pieces for evaluating weld characteristics, each with a weld formed in the center. The maximum tensile strength (weld strength) of the resulting ASTM No. 1 dumbbell with a weld portion was measured in accordance with ASTM D638 (2005), and the average of the three measured values ​​was calculated.

[0120] Materials with a higher maximum tensile strength were evaluated as having better weld strength, and materials with a maximum tensile strength of less than 20 MPa were judged to have poor weld strength.

[0121] [Examples 1 to 35], [Comparative Examples 1 to 11] Using a co-rotating, vented twin-screw extruder (TEX-30α, manufactured by The Japan Steel Works, Ltd.) with a screw diameter of 30 mm and an L / D ratio of 35, (A) polybutylene terephthalate resin, (B) phosphate ester compound, (C), (F) styrene-based resin and / or core-shell rubber, and (D) flame-retardant resin, and optionally (E) nitrogen-containing heterocyclic compound having a triazine skeleton, (G) hindered amine compound, (H) fibrous reinforcing material, and (I) other components were mixed in the compositions shown in Tables 1 to 4, and added to the end of the twin-screw extruder. The fibrous reinforcing material (H) was added using a side feeder installed midway between the end of the extrusion and the vent. The cylinder temperature was set as shown in Tables 1 to 4, and melt mixing was carried out under extrusion conditions of a screw rotation of 200 rpm and a throughput per hour of 30 kg / h, and the resin was discharged in the form of a strand from the discharge hole, passed through a cooling bath, and pelletized with a strand cutter. A thermocouple was brought into contact with the molten resin composition in the hole during discharge, and the resin temperature was measured.

[0122] The pellets obtained were dried in a hot air dryer at 130° C. for 6 hours and then evaluated by the above-mentioned methods. The results are shown in Tables 1 to 4.

[0123] The ratio of the parts by mass of the (C) component to the parts by mass of the (D) component ([parts by mass of the (C) component per 100 parts by mass of the (A) component] / [parts by mass of the (D) component per 100 parts by mass of the (A) component]) is expressed as "(C) / (D)".

[0124] The ratio of the parts by mass of the (B) component to the parts by mass of the (G) component ([parts by mass of the (B) component per 100 parts by mass of the (A) component] / [parts by mass of the (G) component per 100 parts by mass of the (A) component]) is expressed as "(B) / (G)".

[0125]

[0126]

[0127]

[0128]

[0129] Comparison of the Examples and Comparative Examples revealed that by blending the (B) and (D) components in specific ranges with 100 parts by mass of the (A) component and by setting the average diameter of the (D) component in a specific range, a material excellent in flame retardancy, tracking resistance, bleed-out resistance, and weld strength was obtained.

[0130] Comparison of Examples 12, 14, 15, 16, and 17 with Comparative Examples 8, 10, and 11 revealed that by incorporating component (C) and setting the (C) / (D) ratio to 0.5 to 4.0, a material with a better balance of flame retardancy, tracking resistance, bleed-out resistance, and weld strength was obtained.

[0131] A comparison of Example 2 with Example 1 and Comparative Example 2 shows that by using polyphenylene sulfide resin as the flame-retardant resin (D), a material with a better balance of flame retardancy, tracking resistance, bleed-out resistance, and weld strength was obtained.

[0132] Comparing Examples 13, 23, 24, and 25 with Example 12, it was found that by further blending a specific amount of (F) core-shell rubber, a material with a better balance of flame retardancy, tracking resistance, bleed-out resistance, and weld strength was obtained.

[0133] A comparison between Example 2 and Example 4 shows that by setting the blending amount of polyethylene terephthalate resin to less than 5 parts by mass per 100 parts by mass of (A) polybutylene terephthalate resin, a material superior in tracking resistance, bleed-out resistance, and maximum tensile strength was obtained.

[0134] Comparing Examples 2 and 3 with Comparative Example 1, by setting the blending amount of polyphenylene ether resin to less than 5 parts by mass per 100 parts by mass of (A) polybutylene terephthalate resin, a material excellent in tracking resistance, bleed-out resistance, and maximum tensile strength was obtained.

[0135] A comparison between Example 2 and Example 5 shows that by setting the blending amount of fluorine-based resin to less than 0.05 parts by mass per 100 parts by mass of (A) polybutylene terephthalate resin, a PFAS-free material with superior weld strength was obtained.

[0136] Comparison of Example 2 with Examples 6 and 7 revealed that by setting the blending amount of metal phosphinate and phosphazene compound to less than 5 parts by mass per 100 parts by mass of (A) polybutylene terephthalate resin, a material with better tracking resistance and bleed-out resistance was obtained.

[0137] Comparison of Examples 2 and 8 with Comparative Examples 3 and 4 revealed that when the resin temperature during melt-kneading was 285°C or higher and 335°C or lower, the average diameter of component (D) was reduced, and materials excellent in flame retardancy, tracking resistance, bleed-out resistance, and weld strength were obtained.

Claims

1. A polybutylene terephthalate resin composition comprising 100 parts by mass of (A) polybutylene terephthalate resin, 10 to 120 parts by mass of (B) a phosphate ester compound, and 1 to 20 parts by mass of (D) a flame-retardant resin, in which island phases of the (D) flame-retardant resin are dispersed within a sea phase of the (A) polybutylene terephthalate resin with an average diameter of 0.05 to 5.0 μm.

2. The polybutylene terephthalate resin composition according to claim 1, further comprising 1 to 40 parts by mass of a styrene-based resin (C) blended with 100 parts by mass of the polybutylene terephthalate resin (A), and the ratio of the amount of the styrene-based resin (C) blended with the flame-retardant resin (D) [amount of the styrene-based resin (C) blended with the flame-retardant resin (D) blended with the flame-retardant resin] is 0.5 to 4.

0.

3. The polybutylene terephthalate resin composition according to claim 2, wherein composite island phases of the styrene-based resin (C) and the flame-retardant resin (D) are dispersed with an average diameter of 1 to 20 μm within a sea phase of the polybutylene terephthalate resin (A).

4. A polybutylene terephthalate resin composition according to claim 1 or 2, wherein the (D) flame-retardant resin is a resin that loses mass by 70% by mass or less when heated in air from room temperature to 600°C at a heating rate of 40°C / min.

5. A polybutylene terephthalate resin composition according to claim 1 or 2, wherein the flame-retardant resin (D) is a polyphenylene sulfide resin.

6. The polybutylene terephthalate resin composition according to claim 1 or 2, further comprising 10 to 150 parts by mass of (E) a nitrogen-based flame retardant which is a nitrogen-containing heterocyclic compound having a triazine skeleton, per 100 parts by mass of the polybutylene terephthalate resin (A).

7. The polybutylene terephthalate resin composition according to claim 1 or 2, further comprising 1 to 40 parts by mass of (F) core-shell rubber per 100 parts by mass of the polybutylene terephthalate resin (A).

8. The polybutylene terephthalate resin composition according to claim 1 or 2, further comprising 0.3 to 3.0 parts by mass of a hindered amine compound (G) blended with 100 parts by mass of the polybutylene terephthalate resin (A).

9. A polybutylene terephthalate resin composition according to claim 1 or 2, in which the content of each of polyethylene terephthalate resin, polyphenylene ether resin, and polyetherimide resin is less than 5 parts by mass per 100 parts by mass of the (A) polybutylene terephthalate resin.

10. A polybutylene terephthalate resin composition according to claim 1 or 2, in which the content of fluororesin per 100 parts by mass of (A) polybutylene terephthalate resin is less than 0.5 parts by mass.

11. A polybutylene terephthalate resin composition according to claim 1 or 2, in which the content of both the phosphazene compound and the organic metal phosphinate is less than 5 parts by mass per 100 parts by mass of (A) polybutylene terephthalate resin.

12. A molded article obtained by melt molding the polybutylene terephthalate resin composition according to claim 1 or 2.

13. A high-voltage insulating part made of the polybutylene terephthalate resin composition according to claim 1 or 2.

14. The high-voltage insulating part according to claim 13, which is a high-voltage connector, a power module case, or a bus bar.

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