Polybutylene terephthalate resin composition used for connector for automobiles, and connector for automobiles comprising same

Abstract

Provided are a polybutylene terephthalate resin composition having good mechanical strength and good flame retardancy even under low temperature conditions, and a connector comprising the same.　This polybutylene terephthalate resin composition used in a connector for automobiles contains a polybutylene terephthalate resin (A), a flame retardant (B), a flame retardant aid (C), an elastomer (D), and glass fibers (E).

Description

Polybutylene terephthalate resin composition used in automotive connectors and automotive connectors made therefrom

[0001] The present invention relates to a polybutylene terephthalate resin composition used in automotive connectors and to an automotive connector made therefrom.

[0002] CO ２ To address environmental issues such as reducing emissions, the electrification of automobiles (electric vehicles, hybrid vehicles, fuel cell vehicles) is progressing. These vehicles generally use high-voltage electrical circuits, posing a risk of electrical fires. In particular, electric vehicles and plug-in hybrid vehicles, a type of hybrid vehicle, are intended to be charged at home, and therefore require fire resistance similar to that of household appliances. General fire resistance standards for household appliances include IEC 60335-1, which requires high fire resistance for components carrying currents exceeding 0.2A used in equipment that operates without human supervision (e.g., refrigerators, washing machines). Therefore, resins used in the energized parts of automotive connectors, switches, relays, and wires are increasingly required to have not only high electrical properties (insulation, tracking resistance) but also fire resistance against electrical fires, i.e., flame retardancy. Furthermore, automotive connectors are also required to have high mechanical properties (strength, impact strength, elastic modulus) from the perspective of ensuring waterproofing and reliability when inserting and removing terminals and locks.

[0003] In recent years, signal connectors sometimes use connectors with narrow terminal widths (e.g., 0.5 mm) to connect to various sensors, while connectors with terminal widths of, for example, 9.5 mm or wider locking sections are sometimes used for batteries and drive motors to prevent them from coming loose even when using high currents. Therefore, because the thickness of automotive connectors varies depending on where they are used, they are required to have sufficient flame retardancy even when thin-walled (e.g., 0.75 mm). Thus, although it was possible to make connectors flame-retardant by studying the formulation of various flame retardants into the resin (polybutylene terephthalate resin or polyamide resin) used in automotive connectors, it was difficult to obtain the desired mechanical properties (especially toughness).

[0004] Furthermore, while automobiles are used in a wide range of climates, from warm to cold, there is a risk of breakage of the locking or lance portion of connectors when inserting, fastening, or removing them during production, repair, etc., particularly in cold regions. Therefore, there is a need for resin compositions for automotive connector parts that are less prone to lance breakage even under low-temperature conditions.

[0005] For example, Patent Document 1 discloses a resin composition containing a polyester thermoplastic elastomer, which includes a polyester-ether type polyester thermoplastic elastomer having a specific weight-average molecular weight, in order to improve mechanical strength and bending strain at low temperatures. Patent Document 2 discloses a resin composition containing a polybutylene terephthalate resin, which includes polytetramethylene glycol having a specific molecular weight as a copolymer component. Patent Document 3 discloses a resin composition containing a polybutylene terephthalate resin and polypropylene, which is a polyolefin resin.

[0006] JP 2007-291277 JP 10-046011 JP 06-295761

[0007] According to the inventors' research, while flame retardancy was possible when a flame retardant was added to a conventional polybutylene terephthalate resin composition, it was found that under low-temperature conditions, the mechanical strength decreased and cracking occurred more easily.

[0008] The present invention has been made in view of the above, and aims to provide a polybutylene terephthalate resin composition for use in automotive connectors that has good mechanical strength and good flame retardancy even under low temperature conditions, and an automotive connector made therefrom.

[0009] As a result of diligent research, the inventors have discovered that an automotive connector made of a polybutylene terephthalate resin composition containing a polybutylene terephthalate resin having a specific weight-average molecular weight, a flame retardant, a flame retardant additive, an elastomer, and glass fibers has good mechanical strength and good flame retardancy even under low-temperature conditions, and have completed the present invention. Specifically, the present invention is configured as follows [1] to

[11] .

[0010] [1] A polybutylene terephthalate resin composition for use in automotive connectors, comprising a polybutylene terephthalate resin (A), a flame retardant (B), a flame retardant additive (C), an elastomer (D), and glass fibers (E), wherein the content of the flame retardant additive (C) is 6 to 11 parts by mass per 100 parts by mass of the polybutylene terephthalate resin (A), the content of the elastomer (D) is 7 to 30 parts by mass per 100 parts by mass of the polybutylene terephthalate resin (A), the content of the glass fibers (E) is 15 to 40 parts by mass per 100 parts by mass of the polybutylene terephthalate resin (A), and the weight-average molecular weight of the polybutylene terephthalate resin (A) in the resin composition, as measured by gel permeation chromatography, is 60,000 or more. [2] The polybutylene terephthalate resin composition according to [1], wherein the ratio of the total mass of the elastomer (D) and the glass fiber (E) to the mass of the polybutylene terephthalate resin (A) is 0.2 to 0.6. [3] The polybutylene terephthalate resin composition according to [1] or [2], wherein the flame retardant (B) is a brominated flame retardant. [4] The polybutylene terephthalate resin composition according to any one of [1] to [3], wherein the elastomer (D) is an olefin-based elastomer. [5] An automotive connector made from the polybutylene terephthalate resin composition according to any one of [1] to [4]. [6] The automotive connector according to [5], wherein the tensile strength is 80 MPa or more. [7] The automotive connector according to [5], wherein the flexural modulus is 8000 MPa or less. [8] The automotive connector according to [5], wherein the terminal width is 0.5 mm or more and 9.5 mm or less. [9] The automotive connector according to [5], which is for automotive use with a rated current of 0.2 A or more.

[10] A waterproof automotive connector as described in [5].

[11] An automotive connector as described in [5] for use in electric vehicles, hybrid vehicles, and fuel cell vehicles.

[0011] According to the present invention, it is possible to provide a polybutylene terephthalate resin composition for use in automotive connectors that has good mechanical strength and good flame retardancy even under low temperature conditions, and a connector made therefrom.

[0012] Figure 1 is an overall view of an automotive connector according to one embodiment of the present invention. Figure 2(a) is a front view of an automotive connector according to one embodiment of the present invention, and Figure 2(b) is a cross-sectional view of an automotive connector according to one embodiment of the present invention taken along line A-A'.

[0013] Specific embodiments of the present invention will be described in detail below. However, the present invention is not limited to the embodiments described below, and modifications can be made as appropriate without altering the essence of the invention.

[0014] [Polybutylene terephthalate resin composition used in automotive connectors] A polybutylene terephthalate resin composition used in automotive connectors according to one embodiment of the present invention (hereinafter also simply referred to as "polybutylene terephthalate resin composition") comprises a polybutylene terephthalate resin (A), a flame retardant (B), a flame retardant additive (C), an elastomer (D), and glass fibers (E).

[0015] <Polybutylene terephthalate resin (A)> The polybutylene terephthalate resin contains at least terephthalic acid or its ester-forming derivative (C １ -C ６ The resin is obtained by polycondensation of a dicarboxylic acid component containing alkyl esters, acid halides, etc., and a glycol component containing alkylene glycol (1,4-butanediol) having at least four carbon atoms or its ester-forming derivative (acetylated compound, etc.). The polybutylene terephthalate resin used in the present invention is not limited to homopolybutylene terephthalate resin, but may also be a copolymer containing 60 mol% or more (particularly 75 mol% to 95 mol%) of butylene terephthalate units.

[0016] Examples of dicarboxylic acid components (comonomer components) other than terephthalic acid and its ester-forming derivatives include isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-dicarboxydiphenyl ether, etc. ８ -C １４aromatic dicarboxylic acids; C4-16 alkanedicarboxylic acids such as succinic acid, adipic acid, azelaic acid, and sebacic acid; cycloalkanedicarboxylic acids such as cyclohexanedicarboxylic acid; ester-forming derivatives of these dicarboxylic acid components (C ５ -C １０ cycloalkanedicarboxylic acids); ester-forming derivatives of these dicarboxylic acid components (C １ -C ６ alkyl ester derivatives, acid halides, etc.) are included. These dicarboxylic acid components may be used alone or in combination of two or more.

[0017] Among these dicarboxylic acid components, C ８ -C １２ aromatic dicarboxylic acids such as isophthalic acid, and C ６ -C １２ alkanedicarboxylic acids such as adipic acid, azelaic acid, and sebacic acid are preferred.

[0018] Examples of glycol components (or their ester-forming derivatives) other than 1,4-butanediol include aliphatic alkanediols such as ethylene glycol, trimethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, 1,3-octanediol, 1,8-octanediol, and decanediol; (poly)oxyalkylene glycols such as diethylene glycol, dipropylene glycol, ditetramethylene glycol, triethylene glycol, tripropylene glycol, and polytetramethylene glycol; alicyclic diols such as 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, and hydrogenated bisphenol A; aromatic diols such as hydroquinone, resorcinol, and naphthalenediol; biphenols such as 4,4'-dihydroxybiphenyl; bisphenols such as xylylene glycol; and ester-forming derivatives such as alkyl, alkoxy, or halogen-substituted products.

[0019] Furthermore, polyols such as glycerin, trimethylolpropane, trimethylolethane, and pentaerythritol, or their ester-forming derivatives, may be used in combination. Branched polybutylene terephthalate resins can also be obtained by using such polyfunctional compounds in combination.

[0020] In one embodiment of the present invention, the polybutylene terephthalate resin has a weight-average molecular weight (Mw) of 60,000 or more in the resin composition, as measured by gel permeation chromatography. By using a polybutylene terephthalate resin having a weight-average molecular weight (Mw) of 60,000 or more in the resin composition, it is possible to obtain a molded article (hereinafter also referred to as "automotive connector") that has good mechanical strength and good flame retardancy.

[0021] Furthermore, the weight-average molecular weight (Mw) is preferably 60,000 to 90,000, and more preferably 60,000 to 85,000. By setting the weight-average molecular weight in the resin composition within the above range, it is possible to more effectively reduce the breakage of the connector joints and lance portions under low-temperature conditions. In this specification, the weight-average molecular weight (Mw) is a value measured by gel permeation chromatography (GPC) and converted using a calibration curve created with standard polystyrene.

[0022] The amount of terminal carboxyl groups in the polybutylene terephthalate resin is not particularly limited, but is preferably 1 to 30 meq / kg, more preferably 2 to 19 meq / kg, and even more preferably 3 to 15 meq / kg. By setting the amount of terminal carboxyl groups within the above range, hydrolysis resistance can be imparted to the polybutylene terephthalate resin composition.

[0023] The intrinsic viscosity (IV) of the polybutylene terephthalate resin is not particularly limited, but is preferably 0.81 dL / g or more and 1.2 dL / g or less, and more preferably 0.82 dL / g or more and 1.0 dL / g or less. By using a polybutylene terephthalate resin with an intrinsic viscosity within the above range, a polybutylene terephthalate resin composition with excellent hydrolysis resistance and moldability can be obtained. Furthermore, the intrinsic viscosity can be adjusted by blending polybutylene terephthalate resins having different intrinsic viscosities. The intrinsic viscosity of the polybutylene terephthalate resin can be measured, for example, using an Ubbelohde viscometer in o-chlorophenol at a temperature of 35°C.

[0024] In the present invention, the polybutylene terephthalate resin may be a commercially available product (for example, Duranex® PBT manufactured by Polyplastics Co., Ltd.), or it may be a resin produced by homopolymerization or copolymerization (both condensation polymerization) using conventional methods (for example, transesterification, direct esterification, etc.).

[0025] <Flame retardant (B)> Known flame retardants can be used. Examples of flame retardants include halogenated flame retardants (halogenated aromatic compounds, etc.), phosphorus-based flame retardants (nitrogen-containing phosphate compounds, phosphate esters, etc.), inorganic flame retardants (metal hydroxides, etc.), nitrogen-based flame retardants (guanidine, triazine, melamine and their derivatives, etc.), silicon-containing flame retardants, etc. Among these, halogenated flame retardants are preferred in order to ensure flame retardancy, and among halogenated flame retardants, brominated flame retardants are preferred.

[0026] Examples of brominated flame retardants include brominated acrylate polymers, brominated styrene polymers, brominated polycarbonate polymers, brominated epoxy compounds, brominated bisphenol-type phenoxy resins, brominated polyaryl ether compounds, brominated aromatic imide compounds, brominated bisaryl compounds, and brominated tri(aryloxy)triazine compounds. Among these, brominated acrylate polymers (such as polymers of pentabromobenzyl acrylate, tetrabromobenzyl acrylate, tribromobenzyl acrylate, or mixtures thereof) or brominated epoxy compounds (such as tetrabromobisphenol A type epoxy compounds) are preferred. These brominated flame retardants may be used individually or in combination of two or more types.

[0027] The flame retardant content is preferably 10 to 40 parts by mass, and more preferably 15 to 30 parts by mass, per 100 parts by mass of polybutylene terephthalate resin. By setting the flame retardant content within the above range, sufficient flame retardancy and moldability can be imparted to automotive connectors made from polybutylene terephthalate resin compositions. However, if the flame retardant content exceeds 40 parts by mass, mold corrosion and the generation of foreign matter are more likely to occur.

[0028] <Flame retardant additive (C)> Known substances can be used as flame retardant additives. Examples of flame retardant additives include aromatic compounds (phenolic resins, aniline resins, polyphenylene oxide resins, aromatic epoxy resins (bisphenol-type epoxy resins, novolac-type epoxy resins, etc.), phenoxy resins, polyphenylene sulfide resins, polycarbonate resins, polyarylate resins, aromatic polyamide resins, aromatic polyester resins (for example, aromatic polyester resins that may be liquid crystalline), aromatic polyesteramide resins (for example, aromatic polyesteramide resins that may be liquid crystalline), etc.), phosphorus-containing compounds (phosphorus-containing compounds that do not belong to organic or inorganic salts such as organic phosphinic acids), antimony-containing compounds, molybdenum-containing compounds (molybdenum oxide, etc.), tungsten-containing compounds (tungsten oxide, etc.) These include stainless steel, bismuth-containing compounds (bismuth oxide, etc.), tin-containing compounds (tin oxide, etc.), iron-containing compounds (iron oxide, etc.), copper-containing compounds (copper oxide, etc.), silicon-containing compounds [(poly)organosiloxanes (silicone resins such as polydimethylsiloxane and polymethylphenylsiloxane, silicone oils, polysilsesquioxane, etc.), layered silicates (smectite-based layered silicates such as montmorillonite, Li-type fluoroteniolite, Na-type fluoroteniolite, Li-type tetrasilicon fluorimica, Na-type tetrasilicon fluorimica, etc., vermulite, halloysite, etc.)], sulfur-containing compounds (organosulfonic acid compounds, metal salts of perfluoroalkanesulfonic acid, sulfamic acid compounds or their salts, etc.). Among these, when used in combination with brominated flame retardants, antimony-containing compounds are preferred from the viewpoint of further improving flame retardancy. These flame retardant aids may be used alone or in combination of two or more types.

[0029] Examples of antimony-containing compounds include antimony oxides (antimony trioxide, antimony tetroxide, antimony pentoxide, etc.) and antimonate salts (alkali metal salts such as sodium antimonate, alkaline earth metal salts such as magnesium antimonate, ammonium antimonate, etc.). Among these, antimony trioxide is preferred. These antimony-containing compounds may be used individually or in combination of two or more.

[0030] Antimony-containing compounds may, if necessary, be surface-treated with surface treatment agents such as epoxy compounds, silane compounds, isocyanate compounds, and / or titanate compounds.

[0031] Furthermore, the amount of flame retardant additive is 6 to 11 parts by mass, preferably 6.5 to 10.5 parts by mass, per 100 parts by mass of polybutylene terephthalate resin. By setting the amount of flame retardant additive within the above range, it is less likely that mechanical stress will cause the connector joints and lance portions to become the starting point for fracture, thereby reducing the likelihood of them breaking.

[0032] <Elastomer (D)> Known elastomers can be used. Examples of elastomers include thermoplastic elastomers, thermosetting elastomers, and core-shell elastomers. Among these, thermoplastic elastomers are preferred from the viewpoint of mechanical strength. Examples of thermoplastic elastomers include olefin-based elastomers, diene-based elastomers, styrene-based elastomers, and polyester-based elastomers. Among these, olefin-based elastomers are preferred from the viewpoint of hydrolysis resistance.

[0033] Examples of olefin-based elastomers include copolymers containing at least one unit selected from ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-octene copolymer, ethylene-propylene-diene copolymer, ethylene-propylene-butene copolymer, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, and ethylene-propylene-diene copolymer; copolymers of olefins and (meth)acrylic monomers such as ethylene-ethyl acrylate copolymer and ethylene-glycidyl methacrylate copolymer; and modified olefin resins [for example, acid-modified olefin resins obtained by modifying an olefin resin (olefin alone or copolymer) with an acid component (for example, α,β-unsaturated carboxylic acids ((meth)acrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, nadic acid, etc.) and / or their acid anhydrides, etc.)]. Among these, ethylene-ethyl acrylate copolymer is preferred. These olefin-based elastomers may be used individually or in combination of two or more types.

[0034] Polyester elastomers can be classified into polyether-type ester elastomers and polyester-type ester elastomers. Examples of polyether-type ester elastomers include polyester elastomers in which aromatic polyester is used as the hard segment and polyester consisting of an oxyalkylene glycol polymer and a dicarboxylic acid is used as the soft segment. The aromatic polyester units in the hard segment are preferably polycondensates of dicarboxylic acid compounds and dihydroxy compounds, polycondensates of oxycarboxylic acid compounds, or polycondensates of these three-component compounds. For example, polybutylene terephthalate can be used as the hard segment. For example, compounds obtained by polycondensation of polyalkylene ether and dicarboxylic acid can be used as the soft segment, and examples of these include ester compounds of polyoxytetramethylene glycol derived from tetrahydrofuran.

[0035] Examples of polyester-based ester elastomers include polyester elastomers having an aromatic polyester as a hard segment and an amorphous polyester as a soft segment. The aromatic polyester units in the hard segment are the same as those in the above polyether type. Examples of the soft segment include ring-opening polymers of lactones (polylactones) or aliphatic polyesters derived from aliphatic dicarboxylic acids and aliphatic diols.

[0036] The content of the elastomer is 7 to 30 parts by mass with respect to 100 parts by mass of the polybutylene terephthalate resin. By setting the content of the elastomer within the above range, an automotive connector having good mechanical strength and good flame retardancy can be obtained.

[0037] Moreover, the content of the elastomer is more preferably 7 to 25 parts by mass, and even more preferably 7 to 20 parts by mass with respect to 100 parts by mass of the polybutylene terephthalate resin. By setting the content of the elastomer within the above range, sufficient toughness and flame retardancy can be more effectively imparted to the automotive connector. When the content of the elastomer is more than the above range, the flame retardancy decreases, and when it is less than the above range, sufficient toughness cannot be obtained.

[0038] <Glass fiber (E)> In this specification, "glass fiber" means a fibrous material cut at a right angle to the length direction. Examples of glass fibers include A glass, C glass, D glass, E glass, AR glass, ECR glass, M glass, NE glass, and S glass. The type of glass as a raw material is not particularly limited, but in terms of quality, E glass, low dielectric glass with a small amount of alkaline earth components (CaO, MgO) in the composition, or corrosion-resistant glass containing zirconium elements is preferred.

[0039] The glass fiber preferably has a number average fiber diameter of 3 to 25 μm for single fibers, and more preferably 5 to 17 μm.

[0040] Further, the form of the glass fiber may be any of a single fiber, a glass roving obtained by continuously winding a bundle of a plurality of single fibers, chopped strands cut to a length of 1 to 10 mm (glass fibers having a number average fiber length of 1 to 10 mm), milled fibers ground to a length of about 10 to 500 μm (glass fibers having a number average fiber length of 10 to 500 μm), etc. These may be used alone or in combination of two or more.

[0041] In one embodiment of the present invention, the content of the glass fiber is 15 to 40 parts by mass, preferably 15 to 37 parts by mass, with respect to 100 parts by mass of the polybutylene terephthalate resin. By setting the content of the glass fiber within the above range, an automotive connector having a desired mechanical strength can be obtained. Further, from the viewpoints of fluidity and impact resistance, the content of the glass fiber is preferably 10 to 20% by mass in the total mass of the polybutylene terephthalate resin composition.

[0042] Further, the ratio of the total mass of the elastomer and the glass fiber to the mass of the polybutylene terephthalate resin is preferably 0.2 to 0.6, more preferably 0.2 to 0.5. By setting the ratio within the above range, an automotive connector having good mechanical strength and good flame retardancy can be obtained.

[0043] <Other additives> Further, the polybutylene terephthalate resin composition according to one embodiment of the present invention may contain a lubricant (such as pentaerythritol tetrastearate), a dripping inhibitor (such as polytetrafluoroethylene), a colorant (such as carbon black), an antioxidant (such as a hindered phenol-based antioxidant), etc. at an arbitrary ratio.

[0044] Further, if necessary, known stabilizers (such as ultraviolet absorbers, light stabilizers, etc.), mold release agents, flame retardants and flame retardant aids other than those described above, crystallization nucleating agents, lubricants, plasticizers, etc. may be added.

[0045] <Method for producing polybutylene terephthalate resin composition> Polybutylene terephthalate resin composition can be produced by melt-kneading 100 parts by weight of polybutylene terephthalate resin with a flame retardant, a flame retardant aid, an elastomer, glass fibers, and any additive using a twin-screw continuous extruder mixer, a twin-screw paddle extruder, a vented twin-screw extruder, etc.

[0046] A polybutylene terephthalate resin composition according to one embodiment of the present invention can be used to obtain automotive connectors with a lance width of 0.5 to 4.0 mm. It can also be used to obtain automotive connectors with a terminal width of 0.5 mm to 9.5 mm, and is particularly useful for connectors with a terminal width of 0.64 mm to 6.3 mm.

[0047] [Automotive Connectors] Figure 1 shows the shape (overall view) of an automotive connector according to one embodiment of the present invention. The shape of the connector is not particularly limited and can be selected according to the application. Examples of the shape of the connector include (omitted) square, (omitted) rectangular, (omitted) spherical, (omitted) elliptical, etc. Examples of applications for the connector include automobiles (for example, for automobiles with a rated current of 0.2A or more), electric vehicle engines, motors, batteries, power control units, E-Axles (electric axles), LiDAR, sensors, etc. Waterproof or non-waterproof connectors, connectors with a double locking structure, etc. can also be used depending on the application.

[0048] Figure 2(a) is a front view of the connector 10 shown in Figure 1. Figure 2(b) is a cross-sectional view of the connector 10 shown in Figure 1 along line A-A', showing a cross-section of the terminal insertion opening 11 as an example. As shown in Figure 2(b), a lance 12 is formed inside the terminal insertion opening 11. Figure 2(b) shows an automotive connector with a lance width of 4.0 mm, but is not limited to this. The present invention can be used in automotive connectors with a lance width of 0.5 to 4.0 mm. Furthermore, the present invention can provide automotive connectors with a terminal width of 0.5 mm or more and 9.5 mm or less. In particular, it can be used in automotive connectors with a terminal width of 0.64 mm or more and 6.3 mm or less.

[0049] Furthermore, the tensile breaking strength of the automotive connector according to one embodiment of the present invention at 23°C is 78 MPa or higher, and more preferably 80 MPa or higher. A tensile breaking strength of 78 MPa or higher allows for sufficient terminal retention force and reduces the risk of lance damage when the wire is pulled, thereby maintaining the product function of the connector. The tensile breaking strength and tensile breaking strain can be measured, for example, using a universal testing machine (Autograph®) manufactured by Shimadzu Corporation.

[0050] Furthermore, the flexural modulus of the connector according to one embodiment of the present invention is 8000 MPa or less at 23°C, and more preferably 7000 MPa or less. A flexural modulus of 8000 MPa or less enables stable production because the insertion force required when inserting terminals during connector manufacturing does not become too high. The flexural modulus can be measured, for example, using the universal tester Autograph described above.

[0051] In particular, during production and repair in cold regions, the lance portion of a connector may break when inserting or removing terminals. This is due to a combination of factors, including the impact resistance and toughness of the connector at low temperatures, and it is difficult to predict whether or not the lance portion of the connector will break based on a single characteristic such as tensile fracture strain alone. Therefore, by using a polybutylene terephthalate resin composition that provides mechanical properties such as good low-temperature lance characteristics, terminal retention force (tensile fracture strength), and terminal insertion force (flexural modulus) in addition to flame retardancy, it is possible to realize automotive connectors with high electrical safety and reliability.

[0052] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0053] [Method for Producing Polybutylene Terephthalate Resin Composition] 100 parts by mass of polybutylene terephthalate resin was placed in a container, and the flame retardant, flame retardant aid, elastomer, glass fiber, and additives were mixed in the amounts shown in Table 1. The mixture was then melt-kneaded and extruded in a twin-screw extruder (TEX30, manufactured by Japan Steel Works Ltd.) with a 30 mmφ screw under the conditions of a cylinder temperature of 260°C and a screw rotation speed of 130 rpm to obtain a pellet-shaped polybutylene terephthalate (PBT) resin composition. The units of the values ​​in Table 1 are parts by mass.

[0054] The constituent components of the polybutylene terephthalate resin composition shown in Table 1 are as follows:

[0055] <Polybutylene terephthalate resin (A)> (A-1) Polybutylene terephthalate resin (manufactured by Polyplastics Co., Ltd., weight-average molecular weight (Mw) 84,000, terminal carboxyl group weight 9 meq / kg) (A-2) Polybutylene terephthalate resin (manufactured by Polyplastics Co., Ltd., weight-average molecular weight (Mw) 69,000, terminal carboxyl group weight 12 meq / kg) (A-3) Polybutylene terephthalate resin (manufactured by Polyplastics Co., Ltd., weight-average molecular weight (Mw) 58,000, terminal carboxyl group weight 20 meq / kg)

[0056] <Flame retardant (B)> (B-1) Pentabromobenzyl polyacrylate (FR-1025, manufactured by ICL JAPAN) (B-2) Tetrabromobisphenol A type epoxy resin (CXB-1500C, manufactured by Ushin Polymer Co., Ltd.)

[0057] <Flame retardant additive (C)> (C-1) Antimony trioxide (PATOX-M, manufactured by Nippon Seikou Co., Ltd.)

[0058] <Elastomers (D)> (D-1) Ethylene-ethyl acrylate copolymer (NUC-6570, manufactured by ENEOS NUC Corporation) (D-2) Ethylene-glycidyl methacrylate copolymer (Bondfast 7L, manufactured by Sumitomo Chemical Co., Ltd.) (D-3) Polyester elastomer (Perprene GP400, manufactured by Toyobo Co., Ltd.)

[0059] <Glass Fiber (E)> (E-1) Glass Fiber (ECS03 T-187, manufactured by Nippon Electric Glass Co., Ltd.)

[0060] <Other Additives> <Drip Prevention Agent> (F-1) Polytetrafluoroethylene (Polyflon® MPA FA-500H, manufactured by Daikin Industries, Ltd.) <Antioxidant> (G-1) Hindered phenol antioxidant (IRGANOX® 1010, manufactured by BASF) <Lubricant> (H-1) Pentaerythritol stearate (Unistar H476, manufactured by NOF Corporation) <Coloring Agent> (I-1) Carbon black (MA600B, manufactured by Mitsubishi Chemical Corporation)

[0061] [Evaluation] For polybutylene terephthalate resin compositions 1 to 19, the following evaluations were performed: low-temperature lance breakage evaluation, terminal insertion force evaluation, terminal retention force evaluation, flame retardancy evaluation, tensile fracture strength evaluation, tensile fracture strain evaluation, and flexural modulus evaluation. In addition, the weight-average molecular weight (Mw) and melt viscosity were measured for polybutylene terephthalate resin compositions 1 to 19 as shown below. The evaluation results and measurement results are shown in Table 1. In Table 1, "PBT" means "polybutylene terephthalate".

[0062] <Low-Temperature Lance Breakage Evaluation> Using polybutylene terephthalate resin compositions 1 to 19 shown in Table 1, connectors of the shape shown in Figure 1 were injection molded using an injection molding machine (ROBOSHOT S-2000i 100B, manufactured by FANUC) under the conditions of a cylinder temperature of 260°C, a mold temperature of 80°C, and an injection speed of 90 mm / second. The number of lance breaks was measured when a terminal with a terminal width of 2.3 mm was attached to the obtained connector 20 times at -20°C. A number of lance breaks of 5 or less was considered a pass (○).

[0063] <Terminal Insertion Force Evaluation> The strength of terminal insertion into the connector manufactured using the method described above was measured, referencing the automotive standard (JASO D616, Section 6.6) issued by the Japan Society of Automotive Engineers of Japan. A terminal insertion strength of less than 30N was considered acceptable (○).

[0064] <Terminal Retention Force Evaluation> Referring to JASO D616 Section 6.7, the strength of the terminals when they were pulled from the connector manufactured using the method described above was measured at the time of removal or breakage, and a strength of 100N or more was considered acceptable (○).

[0065] <Flame Retardancy Evaluation> In accordance with the Subject 94 (UL94) method of Underwriters Laboratories, flame retardancy (V-0: total burning time of 50 seconds or less for 5 test specimens) was tested using five test specimens (thickness: 0.75 mm, made of PBT resin composition shown in Table 1). Those that met the V-0 certification criteria were deemed to have passed (○).

[0066] <Tensile Breaking Strength Evaluation> Polybutylene terephthalate resin compositions 1 to 19 were dried at 140°C for 3 hours, and then placed in an injection molding machine (ROBOSHOT α-100iA, manufactured by FANUC Corporation). By injection molding under conditions of cylinder temperature 260°C and mold temperature 80°C, Type 1A test specimens conforming to ISO 3167 were obtained. Using these test specimens, the tensile breaking strength (MPa) was measured using a universal testing machine (Autograph®) manufactured by Shimadzu Corporation in accordance with ISO 527-1,2.

[0067] <Tensile Fracture Strain Evaluation> A Type 1A specimen was prepared in the same manner as for the evaluation of tensile fracture strength, and the tensile fracture strain (%) was measured using the same universal testing machine, Autograph.

[0068] <Evaluation of flexural modulus> The flexural modulus (MPa) of polybutylene terephthalate resin compositions 1 to 19 was measured using the Autograph universal testing machine described above, in accordance with ISO 178, with Type 1A test specimens molded for the evaluation of tensile fracture strength.

[0069] <Measurement of Weight-Average Molecular Weight> Polybutylene terephthalate resin compositions 1 to 19 were dissolved in a hexafluoroisopropanol / chloroform = 1 / 1 solvent to prepare measurement solutions for polybutylene terephthalate resin compositions 1 to 19. Then, the weight-average molecular weight (Mw) of polybutylene terephthalate resin compositions 1 to 19 was measured under the following conditions. Apparatus: High-performance liquid chromatograph "HLC-8320GPC" (Tosoh Corporation) Column: "TSKgel Super HZM-M" (Tosoh Corporation) Sample concentration: 1 mg / mL Eluent: Chloroform Flow rate: 0.35 ml / min Detection device: UV / (254 nm) Measurement temperature: 40°C Reference material: Standard polystyrene (Polymer Laboratories, Mw: 377400-580)

[0070] <Measurement of Melt Viscosity> After drying the polybutylene terephthalate resin composition at 140°C for 3 hours, the melt viscosity was measured in accordance with ISO 11443 using a capillary rheometer "Capillograph (registered trademark) 1B" (manufactured by Toyo Seiki Seisakusho Co., Ltd.) at a furnace temperature of 260°C, with a capillary diameter of φ1 mm × 20 mm L and a shear rate of 1000 sec. －１ The measurements were taken under the following conditions.

[0071]

[0072] As shown in Table 1, it was found that an automotive connector made of a polybutylene terephthalate resin composition can be provided that has good mechanical strength and good flame retardancy even under low temperature conditions.

[0073] The polybutylene terephthalate resin composition of the present invention is particularly effective for automotive connectors that have good mechanical strength and good flame retardancy even under low temperature conditions, as it can be used in parts used at low temperatures.

[0074] 10 Connector 11 Terminal insertion slot 12 Lance

Claims

1. A polybutylene terephthalate resin composition for use in automotive connectors, comprising: polybutylene terephthalate resin (A); flame retardant (B); flame retardant additive (C); elastomer (D); and glass fiber (E), wherein the content of the flame retardant additive (C) is 6 to 11 parts by mass per 100 parts by mass of the polybutylene terephthalate resin (A); the content of the elastomer (D) is 7 to 30 parts by mass per 100 parts by mass of the polybutylene terephthalate resin (A); the content of the glass fiber (E) is 15 to 40 parts by mass per 100 parts by mass of the polybutylene terephthalate resin (A); and the weight-average molecular weight of the polybutylene terephthalate resin (A) in the resin composition, as measured by gel permeation chromatography, is 60,000 or more.

2. The polybutylene terephthalate resin composition according to claim 1, wherein the ratio of the total mass of the elastomer (D) and the glass fiber (E) to the mass of the polybutylene terephthalate resin (A) is 0.2 to 0.

6.

3. The polybutylene terephthalate resin composition according to claim 1 or 2, wherein the flame retardant (B) is a brominated flame retardant.

4. The polybutylene terephthalate resin composition according to claim 1 or 2, wherein the elastomer (D) is an olefin-based elastomer.

5. An automotive connector comprising the polybutylene terephthalate resin composition according to claim 1 or 2.

6. The automotive connector according to claim 5, wherein the tensile strength is 80 MPa or more.

7. The automotive connector according to claim 5, wherein the flexural modulus is 8,000 MPa or less.

8. The automotive connector according to claim 5, wherein the terminal width is 0.5 mm or more and 9.5 mm or less.

9. The automotive connector according to claim 5, wherein the rated current is 0.2A or more and is for automotive use.

10. The automotive connector according to claim 5, which is of the waterproof type.

11. The automotive connector according to claim 5, for use in electric vehicles, hybrid vehicles, and fuel cell vehicles.

Images