Polyester resin composition, molded article, and composite molded article

Abstract

To provide a polyester resin composition that is favorable in injection moldability, is excellent in mechanical strength and can realize stable laser weldability by controlling high laser transmittance at each part of a molding.SOLUTION: A polyester resin composition characterized in that the degree of crystallinity calculated by the following method using a high-speed calorimetry is 15% or larger. Calculation method: the degree of crystallinity is calculated from a curve obtained when, by using a high speed calorimetry, the polyester resin composition is heated from 30°C to 260°C at 10000°C / second, followed by keeping at 260°C for 0.1 second, further followed by cooling to 80°C at 5000°C / second, further followed by keeping at 80°C for 0.1 second, further followed by cooling to -70°C at 5000°C / second, and still further followed by heating to 260°C at 1000°C / second.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a polyester resin composition excellent in injection moldability and laser weldability, a molded article, and a composite molded article comprising the same.

Background Art

[0002] Polyester resins, particularly polybutylene terephthalate-based resins, are widely used as injection molded articles in fields such as mechanical parts, electrical and communication parts, and automotive parts by utilizing their excellent injection moldability, mechanical properties, heat resistance, electrical properties, chemical resistance, etc. However, although the molding efficiency of injection molded articles is good, there are limitations in shape due to their flow characteristics and mold structure, and it is difficult to mold very complex ones.

[0003] Conventionally, in the joining of each part due to the complication of the product shape, joining with an adhesive, mechanical joining with bolts, etc. have been carried out. However, the strength is not sufficient in the adhesion with an adhesive, and in the mechanical joining with bolts, etc., problems such as cost, fastening labor, and increase in the weight of the product have arisen. On the other hand, regarding external heat welding such as laser welding and hot plate welding, and friction heat welding such as vibration welding and ultrasonic welding, joining can be performed in a short time, and since adhesives and metal parts are not used, problems such as the cost involved, increase in the weight of the product, and environmental pollution do not occur, so the joining by these methods has been increasing.

[0004] Laser welding, which is one of the external heat welding methods, is a method of irradiating a laser beam on an overlapped resin molded body, melting and fusing the resin by transmitting one side and absorbing the other side, and is a method that is spreading in a wide range of fields by utilizing advantages such as the possibility of three-dimensional joining, non-contact processing, and no burr generation.

[0005] Polybutylene terephthalate resins, which are widely used in various applications due to their high dimensional stability and low water absorption, have a very low laser beam transmittance compared to polyamide resins. When using polybutylene terephthalate resins as molded products on the laser beam transmission side and applying the laser welding method, due to the low laser beam transmittance, the thickness limit of the molded products is very strict. To improve the laser beam transmittance, it is necessary to reduce the thickness, resulting in a small degree of freedom in product design.

[0006] In addition to the laser beam transmittance, if there is a large variation in the transmittance between the parts of the molded product on the laser beam transmission side, it will cause welding defects. Therefore, in order to perform stable laser welding, it is desirable to control the transmittance between the parts of the molded product used on the laser beam transmission side.

[0007] In response to the above problems, Patent Document 1 discloses a method of adding an alkali metal salt of a fatty acid to a polyester resin to improve the transmittance of laser beams.

[0008] In addition, Patent Document 2 discloses a method of obtaining a thermoplastic resin with good mechanical strength and laser transmittance by filling a specific glass fiber into a thermoplastic resin.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0010] However, in Patent Document 1, although the transmittance required for laser welding is good, the transmittance is likely to vary, and due to the variation in transmittance between parts of the molded product, welding defects may occur, and there has been a problem that it is difficult to obtain stable laser weldability. Further, since Patent Document 2 uses a polyester resin with low laser transmittance originally, the transmittance is not sufficient. There are also problems in injection moldability, and a laser-transparent material with further excellent productivity has been demanded.

[0011] Therefore, an object of the present invention is to provide a polyester resin composition that has good injection moldability, excellent mechanical strength, and realizes stable laser weldability by controlling high laser transmittance at each part of the molded product, a molded product formed using this composition, and a composite molded product using this molded product.

Means for Solving the Problems

[0012] To solve the above problems, the present invention has the following configuration. (1) A polyester resin composition containing glass fiber (B) in an amount exceeding 0 and not exceeding 100 parts by mass with respect to 100 parts by mass of polyester resin (A), At least one sodium aliphatic carboxylate selected from sodium propionate, sodium caprylate, sodium stearate, and mixtures thereof (C) is a polyester resin composition containing metal ions at a concentration of 50 to 150 millimoles per 1 kg of polyester resin (A), and the crystallinity calculated by the following method using high-speed calorimetry is 15% or more. A polyester resin composition characterized by that. Calculation method: Using high-speed calorimetry, after heating the polyester resin composition from 30 °C to 260 °C at 10000 °C / second, holding at 260 °C for 0.1 second, cooling to 80 °C at 5000 °C / second, holding at 80 °C for 0.1 second, cooling to -70 °C at 5000 °C / second, and then heating to 260 °C at 1000 °C / second, the crystallinity calculated from the curve obtained at this time. (2) The polyester resin composition according to (1), characterized in that the average length in the longitudinal direction of the linear structure observed using a transmission electron microscope is 150 nanometers or less. (3) The polyester resin composition according to (1) or (2), wherein the terminal carboxyl group concentration of the polyester resin (A) is 20 eq / t or less. (4) The polyester resin composition according to any one of (1) to (3), wherein the flatness ratio calculated by the following formula of the glass fiber (B) is 1 to 2. Flatness ratio = major axis of the cross-section of the glass fiber / minor axis ( 5 )(1) to ( 4 ) A molded article made of the polyester resin composition according to any one of the above. ( 6 )( 5 ) A composite molded article obtained by laser welding the molded article according to the above.

Advantages of the Invention

[0013] The polyester resin composition of the present invention is characterized in that it has excellent injection moldability and highly controls the high laser permeability at different sites in the molded article of this resin composition. Therefore, it is useful for laser welding of resin moldings for various applications, particularly for the molded article on the laser transmission side.

Brief Description of the Drawings

[0014]

Figure 1

Embodiments for Carrying Out the Invention

[0015] <Polyester Resin (A)> The polyester resin (A) used in the present invention is a polymer or copolymer having as a main structural unit one or more selected from (a) dicarboxylic acid or its ester-forming derivative and diol or its ester-forming derivative, (b) hydroxycarboxylic acid or its ester-forming derivative, and (c) lactone.

[0016] Examples of the dicarboxylic acid or its ester-forming derivative include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, bis(p-carboxyphenyl)methane, anthracenedicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 5-tetrabutylphosphonium isophthalic acid, 5-sodium sulfoisophthalic acid, diphenic acid; aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, malonic acid, glutaric acid, dimer acid; alicyclic dicarboxylic acids such as 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid; and ester-forming derivatives thereof.

[0017] Examples of the diol or its ester-forming derivative include aliphatic glycols having 2 to 20 carbon atoms, namely ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, decamethylene glycol, cyclohexanedimethanol, cyclohexanediol, dimer diol, etc.; long-chain glycols having a molecular weight of 200 to 100,000, namely polyethylene glycol, poly-1,3-propylene glycol, polytetramethylene glycol, etc.; aromatic dioxy compounds, namely 4,4'-dihydroxybiphenyl, hydroquinone, t-butylhydroquinone, bisphenol A, bisphenol S, bisphenol F, bisphenol-C; and ester-forming derivatives thereof.

[0018] (a) As the polymer or copolymer having a dicarboxylic acid or its ester-forming derivative and a diol or its ester-forming derivative as structural units, there are polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polycyclohexane dimethylene terephthalate, polyhexylene terephthalate, polyethylene isophthalate, polypropylene isophthalate, polybutylene isophthalate, polycyclohexane dimethylene isophthalate, polyhexylene isophthalate, polyethylene naphthalate, polypropylene naphthalate, polybutylene naphthalate, polyethylene isophthalate / terephthalate, polypropylene isophthalate / terephthalate, polybutylene isophthalate / terephthalate, polyethylene terephthalate / naphthalate, polypropylene terephthalate / naphthalate, polybutylene terephthalate / naphthalate, polybutylene terephthalate / decanedicarboxylate, polyethylene terephthalate / cyclohexane dimethylene terephthalate, polyethylene terephthalate / 5-sodium sulfoisophthalate, polypropylene terephthalate / 5-sodium sulfoisophthalate, polybutylene terephthalate / 5-sodium sulfoisophthalate, polyethylene terephthalate / polyethylene glycol, polypropylene terephthalate / polyethylene glycol, polybutylene terephthalate / polyethylene glycol, polyethylene terephthalate / polytetramethylene glycol, polypropylene terephthalate / polytetramethylene glycol, polybutylene terephthalate / polytetramethylene glycol, polyethylene terephthalate / isophthalate / polytetramethylene glycol, polypropylene terephthalate / isophthalate / polytetramethylene glycol, polybutylene terephthalate / isophthalate / polytetramethylene glycol, polyethylene terephthalate / succinate, polypropylene terephthalate / succinate, polybutylene terephthalate / succinate, polyethylene terephthalate / adipate, polypropylene terephthalate / adipate, polybutylene terephthalate / adipate, polyethylene terephthalate / sebacate, polypropylene terephthalate / sebacate,Aromatic polyester resins such as polybutylene terephthalate / sebacate, polyethylene terephthalate / isophthalate / adipate, polypropylene terephthalate / isophthalate / adipate, polybutylene terephthalate / isophthalate / succinate, polybutylene terephthalate / isophthalate / adipate, polybutylene terephthalate / isophthalate / sebacate, polyethylene oxalate, polypropylene oxalate, polybutylene oxalate, polyethylene succinate, polypropylene succinate, polybutylene succinate, polyethylene adipate, polypropylene adipate, polybutylene adipate, polyneopentyl glycol adipate, polyethylene sebacate, polypropylene sebacate, polybutylene sebacate, polyethylene succinate / adipate, polypropylene succinate / adipate, polybutylene succinate / adipate and other aliphatic polyester resins. Among them, aromatic polyester resins are preferred, and any one or copolymer selected from polyethylene terephthalate, polypropylene terephthalate, and polybutylene terephthalate is more preferred, and polybutylene terephthalate or its copolymer is even more preferred.

[0019] In addition, (b) examples of the hydroxycarboxylic acid or its ester-forming derivative include glycolic acid, lactic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxybenzoic acid, p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid and their ester-forming derivatives. Examples of polymers or copolymers having these as structural units include aliphatic polyester resins such as polyglycolic acid, polylactic acid, polyglycolic acid / lactic acid, polyhydroxybutyric acid / β-hydroxybutyric acid / β-hydroxyvaleric acid.

[0020] In addition, examples of the above-mentioned (c) lactone include ε-caprolactone, valerolactone, propiolactone, undecalactone, 1,5-oxepan-2-one, γ-butyrolactone, etc. Examples of polymers or copolymers having these as structural units include polycaprolactone, polyvalerolactone, polypropiolactone, poly-γ-butyrolactone, polycaprolactone / valerolactone, etc.

[0021] Among these, polymers or copolymers having (a) dicarboxylic acids or their ester-forming derivatives and diols or their ester-forming derivatives as main structural units are preferred, polymers or copolymers having aromatic dicarboxylic acids or their ester-forming derivatives and aliphatic diols or their ester-forming derivatives as main structural units are more preferred, and polymers or copolymers having terephthalic acid or its ester-forming derivative and an aliphatic diol selected from ethylene glycol, propylene glycol, and butanediol or its ester-forming derivative as main structural units are even more preferred. Among them, aromatic polyester resins such as polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polycyclohexanedimethylene terephthalate, polyethylene naphthalate, polypropylene naphthalate, polybutylene naphthalate, polyethylene isophthalate / terephthalate, polypropylene isophthalate / terephthalate, polybutylene isophthalate / terephthalate, polyethylene terephthalate / naphthalate, polypropylene terephthalate / naphthalate, and polybutylene terephthalate / naphthalate are preferred, polyethylene terephthalate, polypropylene terephthalate, and polybutylene terephthalate are particularly preferred, and polybutylene terephthalate is particularly preferred.

[0022] In the present invention, the proportion of terephthalic acid or its ester-forming derivative to all dicarboxylic acids in the polymer or copolymer having (a) dicarboxylic acid or its ester-forming derivative and diol or its ester-forming derivative as main structural units is preferably 30 mol% or more, and more preferably 40 mol% or more.

[0023] In the present invention, the end groups of the polyester resin (A) are not particularly limited and can have terminal carboxyl groups, terminal hydroxyl groups, or other end groups. However, in terms of excellent laser transmittance, the terminal carboxyl group concentration is preferably 50 eq / t or less, more preferably 30 eq / t or less, still more preferably 20 eq / t or less, and particularly preferably 15 eq / t or less.

[0024] The viscosity of the polyester resin (A) used in the present invention is not particularly limited as long as melt-kneading is possible. However, in terms of moldability, the intrinsic viscosity measured in an o-chlorophenol solution at 25°C is preferably in the range of 0.36 to 1.60 dl / g, and more preferably in the range of 0.50 to 1.50 dl / g.

[0025] The melting point of the polyester resin (A) used in the present invention is not particularly limited as long as melt-kneading is possible. However, in terms of heat resistance and mechanical strength, it is preferably 200°C or higher, and in terms of excellent melt processability, it is more preferably 215°C or higher, and still more preferably 220°C or higher. The upper limit of the melting point is not particularly limited, but in terms of excellent melt processability, it is preferably 280°C or lower, and more preferably 270°C or lower. If the melting point is less than 210°C, there is a problem of reduced heat resistance. On the other hand, if the melting point exceeds 280°C, the crystallinity and crystal size become extremely large, so excessive heating during melt processing is required, and there is a possibility of concurrent decomposition of the polyester resin. Here, the melting point refers to the peak top temperature of the endothermic peak observed when heating from 30°C to 280°C at a heating rate of 20°C / min using a differential scanning calorimeter (DSC), holding at 280°C for 3 minutes, then cooling from 280°C to 30°C at a cooling rate of 20°C / min, and then heating from 30°C to 280°C at a heating rate of 20°C / min.

[0026] In the present invention, the heat of crystal melting represented by the area of the endothermic peak measured under the above conditions using the differential scanning calorimeter (DSC) is preferably 20 J / g or more, more preferably 30 J / g or more, and even more preferably 40 J / g or more in terms of excellent heat resistance. The upper limit of the heat of crystal melting is not particularly limited, but is preferably 60 J / g or less, more preferably 50 J / g or less in terms of excellent melt processability.

[0027] The method for producing the polyester resin (A) used in the present invention is not particularly limited and can be produced by ordinary polycondensation methods, ring-opening polycondensation methods, etc. It can be either batch polymerization or continuous polymerization, and can also be applied to any of the methods through transesterification reaction and polycondensation reaction, as well as the reaction by direct polymerization. However, continuous polymerization is preferred in terms of reducing the amount of terminal carboxyl groups and excellent laser permeability, and direct polymerization is preferred in terms of cost.

[0028] When the (A) polyester resin used in the present invention is a polymer or copolymer obtained by a condensation reaction mainly composed of (a) a dicarboxylic acid or its ester-forming derivative and a diol or its ester-forming derivative, it can be produced by subjecting (a) the dicarboxylic acid or its ester-forming derivative and the diol or its ester-forming derivative to an esterification reaction or a transesterification reaction, and then a polycondensation reaction. In order to effectively promote the esterification reaction or transesterification reaction and the polycondensation reaction, it is preferable to add a polymerization reaction catalyst during these reactions. Specific examples of the polymerization reaction catalyst include organic titanium compounds such as methyl ester of titanic acid, tetra-n-propyl ester, tetra-n-butyl ester, tetraisopropyl ester, tetraisobutyl ester, tetra-tert-butyl ester, cyclohexyl ester, phenyl ester, benzyl ester, tolyl ester, or mixed esters thereof, dibutyltin oxide, methylphenyltin oxide, tetraethyltin, hexaethyldistannoxide, cyclohexaphenyldistannoxide, didodecyltin oxide, triethyltin hydroxide, triphenyltin hydroxide, triisobutyltin acetate, dibutyltin diacetate, diphenyltin dilaurate, monobutyltin trichloride, dibutyltin dichloride, tributyltin chloride, dibutyltin sulfide and butylhydroxytin oxide, alkylstannonic acids such as methylstannonic acid, ethylstannonic acid, butylstannonic acid, etc., zirconia compounds such as zirconium tetra-n-butoxide, antimony compounds such as antimony trioxide, antimony acetate, etc. Among these, organic titanium compounds and tin compounds are preferable, and further, tetra-n-propyl ester, tetra-n-butyl ester and tetraisopropyl ester of titanic acid are preferable, and tetra-n-butyl ester of titanic acid is particularly preferable. These polymerization reaction catalysts may be used alone or in combination of two or more.The addition amount of the polymerization reaction catalyst is preferably in the range of 0.005 to 0.5 parts by weight, more preferably in the range of 0.01 to 0.2 parts by weight, based on 100 parts by weight of the polyester resin, from the viewpoints of mechanical properties, moldability, and color tone.

[0029] The polyester resin (A) of the present invention can be used alone or in combination of two or more.

[0030] The resin composition containing the polyester resin (A) of the present invention is heated from 30°C to 260°C at 10,000°C / second using high-speed calorimetry, held at 260°C for 0.1 second, then cooled to 80°C at 5,000°C / second, held at 80°C for 0.1 second, then cooled to -70°C at 5,000°C / second, and then heated to 260°C at 1,000°C / second. The heat of crystal fusion (ΔH m ) observed at this time is used to calculate the crystallinity (X c ) according to the following formula, and is characterized in that it is 15% or more. Crystallinity (X c ) = ΔH m / ΔH m 0 × 100 Here, ΔH m 0 is the heat of crystal fusion of the completely crystalline polyester resin (A). By having such characteristics, a stable crystal structure is formed at each part of the molded product even under the rapid cooling conditions in the injection molding die, so that the injection moldability is good and stable laser transmissivity is exhibited at each part of the molded product. In the present invention, the crystallinity is preferably 15% or more, more preferably 20% or more. The upper limit is not particularly limited, but from the viewpoint of excellent melt processability, it is preferably 60% or less, more preferably 50% or less. Here, high-speed calorimetry is a calorimeter capable of high-speed heating and cooling with a sample amount on the nanogram order by miniaturizing the thermal sensor. Although there is a limit to the heating and cooling rate that can follow depending on the type and size of the sample, it has a performance of a maximum heating rate of 10,000°C / second and a maximum cooling rate of 5,000°C / second.

[0031] Further, in the resin composition containing the polyester resin (A) of the present invention, the average length in the longitudinal direction of the linear structure derived from the crystal structure of the polyester resin (A), as observed using a transmission electron microscope, is preferably 150 nanometers or less. Here, the average length in the longitudinal direction of the linear structure can be determined by the following method. Using a resin composition molded to have a thickness of 1 millimeter or more, a sample prepared by cutting out 50 micrometers or more from the surface thereof is stained with ruthenium tetroxide and observed with a transmission electron microscope. The obtained image is taken as an image with a size of 1 μm × 1 μm, and for the structures that can be distinguished by shading, the longitudinal directions of arbitrarily selected 10 linear structures are measured and the average value is taken. By having such a structure, the diffusion of laser light in the resin composition is suppressed and good laser transmissivity is exhibited. In the present invention, the average length in the longitudinal direction of the linear structure is preferably 150 nanometers or less, more preferably 125 nanometers or less, and even more preferably 100 nanometers or less. The lower limit is not particularly limited, but in order to maintain heat resistance, it is preferably 50 nanometers or more.

[0032] Note that the method for making the crystallinity of the polyester resin composition calculated by the above method 15% or more and the average length in the longitudinal direction of the linear structure 150 nanometers or less is not particularly limited. For example, using an aliphatic carboxylic acid sodium salt as the metal salt compound (C) blended in the polyester resin composition, containing the aliphatic carboxylic acid sodium salt in a more preferable range, or using an aliphatic carboxylic acid sodium salt having a more preferable number of carbon atoms can be mentioned.

[0033] <Glass fiber (B)> In the present invention, glass fiber (B) may be blended in the polyester resin composition. The cross-section of the glass fiber (B) may be circular or flat, but in terms of suppressing deformation, reducing warpage, and having stable laser transmissibility, etc., it is preferable that the cross-sectional shape is flat. Generally, in a composition containing glass fiber, the fibers are oriented in the flow direction during molding, so the anisotropy of the molding shrinkage rate (the percentage of the dimensional difference between the resin molded product and the mold) increases, and the deformation and warpage increase. However, when the cross-sectional shape is flat, the anisotropy of the molding shrinkage rate becomes small, and deformation and warpage are easily improved.

[0034] The glass fiber (B) having a flat cross-sectional shape used in the present invention preferably has an aspect ratio, which is represented by the ratio of the major axis (the longest straight-line distance in the cross-section) to the minor axis (the longest straight-line distance in the direction perpendicular to the major axis) in the cross-section cut perpendicular to the length direction, of 1 or more and 10 or less. The lower limit value of the aspect ratio is preferably 1.3 or more, more preferably 1.5 or more. Also, the upper limit value is preferably 5 or less, more preferably 2.5 or less, and most preferably 2 or less. The specific shape may be any of a crescent shape, an oval shape, an elliptical shape, a semi-circle, an arc shape, a rectangle, or similar shapes thereof, but an oval shape is particularly preferable in terms of fluidity and low warpage.

[0035] When the aspect ratio is 1 or more, deformation and warpage during molding are suppressed, and setting it to 10 or less is because it is actually difficult to manufacture such glass fiber itself. Also, for the purpose of reducing the specific gravity, etc., hollow fibers can also be used as the glass fiber (B). As the cross-sectional area of the glass fiber (B) increases, a sufficient reinforcing effect cannot be obtained. On the other hand, if it is too small, its manufacture becomes difficult, and there is also a problem that it becomes difficult to handle. The cross-sectional area of the glass fiber (B) in the present invention is 2×10 -5 ~8×10 -3 mm 2 is preferable, 8×10 -5 ~8×10 -3 mm 2 is more preferable, 8×10 -5 ~8×10 -4 mm 2is more preferable. The length of the glass fiber is not particularly limited, but considering the balance between the mechanical properties of the molded product and deformation suppression, it is preferably short to reduce the amount of deformation of the molded product. However, in terms of mechanical properties, the fiber length is preferably 30 μm or more, and depending on the required performance, 50 to 1000 μm is preferable. In the glass fiber (B) used in the present invention, it is preferably used with a sizing agent or a surface treatment agent as needed. As the sizing agent or surface treatment agent, it is a functional compound such as an epoxy compound, an isocyanate compound, a silane compound, or a titanate compound. These compounds may be used after being subjected to surface treatment or sizing treatment in advance, or may be added simultaneously during material preparation. When the glass fiber (B) used in the present invention is flat, it is prepared by spinning using a nozzle having an appropriate hole shape such as an oval, an ellipse, a rectangle, or a slit shape as a bushing for discharging molten glass. Also, it can be prepared by spinning molten glass from a plurality of nozzles provided adjacent to each other having various cross-sectional shapes (including a circular cross-section) and joining the spun molten glasses together to form a single filament.

[0036] In the present invention, the blending amount of the glass fiber (B) used is preferably more than 0 and 100 parts by mass or less, more preferably 10 to 80 parts by weight, and even more preferably 20 to 50 parts by weight with respect to 100 parts by mass of the polyester resin (A). In order to exhibit mechanical strength and low warpage, it is preferable to blend the glass fiber (B). Also, by setting it to 100 parts by mass or less, the fluidity during molding can be maintained.

[0037] <Metal salt compound (C)> In the present invention, with respect to 100 parts by mass of the polyester resin (A), it is preferable in terms of good crystal nucleation to contain the metal salt compound (C) at a concentration such that the metal ions are 50 to 150 millimoles per 1 kg of the polyester resin.

[0038] In the present invention, the metal salt compound (C) may be any of aliphatic carboxylate metal salts, alicyclic carboxylate metal salts, aromatic carboxylate metal salts, sulfonate metal salts, amidosulfonate metal salts, phosphate metal salts, phosphate ester metal salts, borate metal salts, etc., or may be a mixture thereof. In terms of excellent crystallization characteristics, examples include aliphatic carboxylate metal salts having 2 to 50 carbon atoms, alicyclic carboxylate metal salts having 7 to 60 carbon atoms, aromatic carboxylate metal salts having 7 to 60 carbon atoms, aliphatic sulfonate metal salts having 1 to 50 carbon atoms, alicyclic sulfonate metal salts having 6 to 60 carbon atoms, aromatic sulfonate metal salts having 6 to 60 carbon atoms, aliphatic phosphate ester metal salts having 1 to 50 carbon atoms, alicyclic phosphate ester metal salts having 6 to 60 carbon atoms, and aromatic phosphate ester metal salts having 6 to 60 carbon atoms, and one or more mixtures selected therefrom. Further, in terms of excellent crystallization characteristics and showing good injection moldability and laser transmissibility, it is preferably one or more mixtures selected from aliphatic carboxylate metal salts having 2 to 40 carbon atoms, alicyclic carboxylate metal salts having 7 to 40 carbon atoms, and aromatic carboxylate metal salts having 7 to 40 carbon atoms, more preferably one or more mixtures selected from aliphatic carboxylate metal salts having 2 to 30 carbon atoms and aromatic carboxylate metal salts having 7 to 30 carbon atoms, and particularly preferably aliphatic carboxylate metal salts having 2 to 25 carbon atoms.

[0039] An aliphatic carboxylic acid is a compound in which a carboxyl group is added to a linear or branched aliphatic group, and a part of the bond may have an unsaturated group, an alicyclic group, or other substituents such as a hydroxyl group or a phosphate ester group.

[0040] Preferred examples of the aliphatic carboxylic acid include propionic acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, oleic acid, linoleic acid, montanic acid, etc.

[0041] Furthermore, in the present invention, it is preferably an aliphatic carboxylic acid metal salt having 3 to 20 carbon atoms, more preferably an aliphatic carboxylic acid metal salt having 3 to 10 carbon atoms, and particularly preferably an aliphatic carboxylic acid metal salt having 3 to 5 carbon atoms in terms of good affinity with the polyester resin (A).

[0042] In the present invention, the metal species of the metal salt compound (C) is not particularly limited and any metal species may be used, and examples thereof include metal salts selected from lithium, potassium, sodium, magnesium, calcium, aluminum, strontium, titanium, manganese, iron, zinc, silicon, zirconium, yttrium, or barium. Potassium, lithium, and sodium are preferable in terms of excellent crystallization properties, good injection moldability and laser transmissibility, and excellent mechanical properties, and sodium is more preferable in terms of particularly excellent crystallization promoting effect.

[0043] The compounding amount of the metal salt compound (C) in the present invention is preferably contained at a concentration of 50 to 150 mmol of metal ions per 1 kg of the polyester resin. When it is 50 mmol or more, the laser transmissibility of the molded product made of the polyester resin composition can be maintained, and the variation in transmittance between parts of the molded product can be suppressed. Further, when the metal salt compound (C) is compounded at a concentration of 150 mmol or less per 1 kg of the polyester resin, the polyester resin composition can be decomposed by the catalytic action of the metal salt compound, and a decrease in molecular weight and mechanical strength can be suppressed. The compounding amount of the metal salt compound (C) is preferably contained at a concentration of 50 to 150 mmol, more preferably at a concentration of 50 to 120 mmol, and even more preferably at a concentration of 50 to 100 mmol per 1 kg of the polyester resin (A).

[0044] In the present invention, as the metal salt compound (C), it is preferable to use at least one aliphatic carboxylic acid sodium salt selected from sodium propionate, sodium caprylate, sodium stearate, and mixtures thereof. By using these compounds containing sodium ions, high injection moldability and an effect of improving laser transparency can be obtained.

[0045] <Other Additives> Furthermore, in the resin composition of the present invention, within a range not impairing the object of the present invention, other components such as epoxy resins (bisphenol A type, novolak type, glycidyl ester type, etc.), phosphorus-based stabilizers (phosphate ester type, etc.), weathering agents (resorcinol type, salicylate type, benzotriazole type, benzophenone type, hindered amine type, etc.), lubricants (montanic acid and its esters, its half esters, stearyl alcohol, stearamide, various bisamides, bisureas, and polyethylene wax, etc.), pigments (cadmium sulfide, phthalocyanine, perylene, perylene, naphthotetracyanine, quinacridone, carbon black, titanium oxide, iron oxide, azo type, monoazo type, etc.), dyes (azin type, azo type, perylene, anthraquinone, etc.), crystal nucleating agents (talc, polyetheretherketone, etc.), plasticizers (octyl p -oxybenzoate, N -butylbenzenesulfonamide, etc.), antistatic agents (alkyl sulfate type anionic antistatic agents, quaternary ammonium salt type cationic antistatic agents, non -ionic antistatic agents such as polyoxyethylene sorbitan monostearate, betaine type amphoteric antistatic agents, etc.), flame retardants (for example, red phosphorus, melamine cyanurate, ammonium polyphosphate, brominated polystyrene, brominated polyphenylene ether, brominated polycarbonate, brominated epoxy resin, or a combination of these brominated flame retardants and antimony trioxide, etc.), coloring inhibitors (phosphoric acid compounds such as phosphoric acid, phosphorous acid, trimethyl phosphate, triphenyl phosphate, etc.), and other polymers can be contained.

[0046] The method for producing the resin composition of the present invention is not particularly limited as long as it satisfies the requirements defined in the present invention. For example, a method of uniformly melt-kneading a polyester resin (A), glass fiber (B), metal salt compound (C), and other components as necessary using a single-screw or twin-screw extruder, or a method of mixing in a solution and then removing the solvent, etc. are preferably used. From the viewpoint of productivity, a method of uniformly melt-kneading using a single-screw or twin-screw extruder is preferred, and a method of uniformly melt-kneading using a twin-screw extruder is more preferred in terms of obtaining a resin composition excellent in fluidity and mechanical properties. Among them, when the screw length is L and the screw diameter is D, a method of melt-kneading using a twin-screw extruder with L / D > 30 is particularly preferred. The screw length mentioned here refers to the length from the position where the raw material at the root of the screw is supplied to the tip of the screw. The upper limit of L / D of the twin-screw extruder is 150, and preferably those with L / D exceeding 30 and 100 or less can be used.

[0047] In addition, as the screw configuration when using a twin-screw extruder in the present invention, a full flight and kneading disk are used in combination, but in order to obtain the composition of the present invention, uniform kneading by the screw is necessary. Therefore, the ratio of the total length of the kneading disks (kneading zone) to the total length of the screw is preferably in the range of 5 to 50%, and more preferably in the range of 10 to 40%.

[0048] When melt-kneading in the present invention, the method of charging each component is, for example, using an extruder having two inlets, and supplying the polyester resin (A), glass fiber (B), metal salt compound (C), and other components as necessary from the main inlet installed on the root side of the screw, or supplying the polyester resin (A), metal salt compound (C), and other components from the main inlet, and supplying the glass fiber (B) from the auxiliary inlet installed between the main inlet and the tip of the extruder for melt mixing.

[0049] The resin composition of the present invention can be molded by any commonly known method such as injection molding, extrusion molding, blow molding, press molding, spinning, etc., and can be processed into various molded articles for use. As the molded article, it can be used as an injection molded article, an extrusion molded article, a blow molded article, a film, a sheet, a fiber, etc. As the film, it can be used as various films such as an unstretched film, a uniaxially stretched film, a biaxially stretched film, etc., and as the fiber, it can be used as various fibers such as an unstretched yarn, a stretched yarn, an ultra-stretched yarn, etc.

[0050] In the present invention, the above various molded articles can be used for various applications such as automotive parts, electrical and electronic parts, building members, various containers, daily necessities, household sundries and sanitary products, etc. In particular, since laser welding is possible, it is suitable as automotive parts and electrical and electronic parts for laser welding.

[0051] The resin composition of the present invention can be used for the following specific applications.Specific examples include air flow meters, air pumps, thermostat housings, engine mounts, ignition hobins, ignition cases, clutch bobbins, sensor housings, idle speed control valves, vacuum switching valves, ECU housings, vacuum pump cases, inhibitor switches, rotation sensors, acceleration sensors, distributor caps, coil bases, actuator cases for ABS, tops and bottoms of radiator tanks, cooling fans, fan shrouds, engine covers, cylinder head covers, oil caps, oil pans, oil filters, fuel caps, fuel strainers, distributor caps, vapor canister housings, air cleaner housings, timing belt covers, brake booster parts, various cases, various tubes, various tanks, various hoses, various clips, various valves, various pipes, and other underhood parts for automobiles, torque control levers, safety belt parts, register blades, washer levers, window regulator handles, knobs of window regulator handles, passing light levers, sun visor brackets, various motor housings, and other interior parts for automobiles, roof rails, fenders, garnishes, bumpers, door mirror stays, spoilers, hood louvers, wheel covers, wheel caps, grille apron cover frames, lamp reflectors, lamp bezels, door handles, and other exterior parts for automobiles, wire harness connectors, SMJ connectors, PCB connectors, door grommet connectors, and other various connectors for automobiles, electrical connectors, relay cases, coil bobbins, optical pickup chassis, motor cases, notebook personal computer housings and internal parts, CRT display housings and internal parts, printer housings and internal parts, mobile phones, mobile personal computers, handheld mobiles, and other portable terminal housings and internal parts, housings and internal parts of recording medium (CD, DVD, PD, FDD, etc.) drives, housings and internal parts of copiers, housings and internal parts of facsimiles, and electrical and electronic parts represented by parabolic antennas, etc.

[0052] Furthermore, examples include home and office electrical product parts typified by VTR parts, TV parts, irons, hair dryers, rice cooker parts, microwave oven parts, audio parts, video equipment parts such as video cameras and projectors, substrates of optical recording media such as Laser Disk (registered trademark), Compact Disk (CD), CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-R, DVD-RW, DVD-RAM, and Blu-ray Disc, lighting parts, refrigerator parts, air conditioner parts, typewriter parts, word processor parts, and the like.

[0053] In addition, electrical and electronic components such as the housings and internal parts of electronic musical instruments, home game consoles, portable game consoles, various gears, various cases, sensors, LEP lamps, connectors, sockets, resistors, relay cases, switches, coil bobbins, capacitors, varicon cases, optical pickups, oscillators, various terminal boards, transformers, plugs, printed wiring boards, tuners, speakers, microphones, headphones, small motors, magnetic head bases, power modules, semiconductors, liquid crystals, FDD carriages, FDD chassis, motor brush holders, transformer members, coil bobbins, etc.; building members such as sash door cars, blind curtain parts, pipe joints, curtain liners, blind parts, gas meter parts, water meter parts, water heater parts, roof panels, heat insulation walls, adjusters, wire bundles, ceiling hangers, stairs, doors, floors, etc.; fishery-related members such as fishing lines, fishing nets, seaweed cultivation nets, fishing bait bags, etc.; civil engineering-related members such as vegetation nets, vegetation mats, weed control bags, weed control nets, curing sheets, slope protection sheets, fly ash suppression sheets, drain sheets, water retention sheets, sludge and muck dehydration bags, concrete formworks, etc.; mechanical parts such as gears, screws, springs, bearings, levers, key stems, cams, ratchets, rollers, water supply parts, toy parts, fans, tags, pipes, cleaning jigs, motor parts, microscopes, binoculars, cameras, watches, etc.; agricultural members such as multilayer films, tunnel films, bird-proof sheets, non-woven fabrics for vegetation protection, seedling pots, vegetation stakes, seed string tapes, germination sheets, greenhouse inner lining sheets, agricultural film fasteners, slow-release fertilizers, root prevention sheets, gardening nets, insect-proof nets, young tree nets, printed laminates, fertilizer bags, sample bags, sandbags, pest prevention nets, luring strings, windbreak nets, etc.; sanitary products such as paper diapers, sanitary product packaging materials, cotton swabs, wet wipes, toilet seat cleaners, etc.; medical supplies such as medical non-woven fabrics (suture reinforcement materials, adhesion prevention films, artificial organ repair materials), wound dressing materials, wound tape bandages, base fabrics for sticking materials, surgical sutures, fracture reinforcement materials, medical films, etc.; packaging films for calendars, stationery, clothing, food, etc., trays, blisters, knives, forks, spoons, tubes, plastic cans, pouches, containers, tanks, cages, etc. (container and tableware); hot-fill containers; containers for microwave cooking; cosmetic containers, wraps, foamed buffers, paper laminates, shampoo bottles, beverage bottles, cups, candy packaging, shrink labels,Container and packaging such as lid materials, envelopes with windows, fruit baskets, tear tapes, easy peel packaging, egg packs, HDD packaging, compost bags, recording media packaging, shopping bags, wrapping films for electrical and electronic parts, etc., natural fiber composites, polo shirts, T-shirts, inner wears, unitards, sweaters, socks, neckties, and other various clothing items, interior goods such as curtains, chair coverings, carpets, tablecloths, futon covers, wallpapers, and furoshiki, carrier tapes, printed laminates, films for heat-sensitive stencil printing, release films, porous films, container bags, credit cards, cash cards, ID cards, IC cards, paper, leather, non-woven fabrics, etc., hot melt binders, binders for powders such as magnetic materials, zinc sulfide, and electrode materials, optical elements, conductive embossed tapes, IC trays, golf tees, garbage bags, checkout bags, various nets, toothbrushes, stationery, draining nets, bath towels, hand towels, tea packs, drain filters, clear files, coating agents, adhesives, bags, chairs, tables, cooler boxes, fly swatters, hose reels, planters, hose nozzles, dining tables, table surfaces, furniture panels, kitchen cabinets, pen caps, gas lighters, etc. The resin composition of the present invention is useful as the above. Since the resin composition of the present invention has not only high laser transparency and laser weldability but also good mechanical properties and injection moldability, it is particularly useful for various automotive parts and electrical and electronic parts that perform laser welding among the above.

[0054] In the application of laser welding, for a molded article made of a resin composition having laser transparency and used as a laser transmission member, it is required that high laser transparency be highly controlled at each part of the molded article. By having high transparency, energy can be efficiently transmitted to the welding surface, so the productivity of laser welding can be improved. Laser transparency is expressed, for example, as the laser transmittance measured using a spectrophotometer or the like, and is calculated as the ratio of the incident light amount to the transmitted light amount when light of a specific wavelength is incident on the molded article. For example, in the case of a molded article with a thickness of 2 mm, the laser transmittance is preferably 20% or more, more preferably 25% or more, and even more preferably 30% or more at a wavelength of 940 nm.

[0055] Also, by highly controlling the laser transmissivity at each part of the molded product, it becomes difficult to cause welding defects, and stable laser weldability can be obtained. This can be evaluated by the stability of the laser transmissivity. Specifically, as the variation in laser transmissivity, for example, when the transmittance is measured at a plurality of different parts of the molded product, it is evaluated as the variation ratio obtained by dividing the difference between the maximum value and the minimum value of the transmittance by the average value of the transmittance. The variation ratio is preferably 15% or less, more preferably 10% or less, and even more preferably 5% or less.

Examples

[0056] Next, the present invention will be described in more detail by way of examples, which, however, do not limit the present invention.

[0057] The abbreviations of the main raw materials used in the examples and their details are summarized below.

[0058] (A) Polyester resin A-1: Polybutylene terephthalate (terminal carboxyl group concentration 50 eq / t). A-2: Polybutylene terephthalate (terminal carboxyl group concentration 30 eq / t). A-3: Polybutylene terephthalate (terminal carboxyl group concentration 15 eq / t). A-4: Polybutylene terephthalate (terminal carboxyl group concentration 9 eq / t).

[0059] (B) Glass fiber B-1: Chopped strand type glass fiber with round cross-section (fiber diameter 13 μm, flatness ratio 1) B-2: Chopped strand type glass fiber with oval cross-section (fiber minor axis diameter 10 μm, fiber major axis diameter 20 μm, flatness ratio 2) B-3: Chopped strand type glass fiber with oval cross-section (fiber minor axis diameter 7 μm, fiber major axis diameter 28 μm, flatness ratio 4).

[0060] (C) Metal salt compound C-1: Sodium propionate (carbon number 3, molecular weight 96) C-2: Sodium caprylate (8 carbon atoms, molecular weight 166) C-3: Sodium stearate (18 carbon atoms, molecular weight 306) C-4: Sodium formate (1 carbon atom, molecular weight 68) C-5: Sodium polyacrylate (3 carbon atoms in the repeating unit, molecular weight of the repeating unit 94) C-6: Potassium stearate (18 carbon atoms, molecular weight 326) C-7: Magnesium stearate (36 carbon atoms, molecular weight 591).

[0061] Also, the evaluation methods used in the examples and comparative examples are summarized below.

[0062] (1) Crystallinity Samples cut from the resin pellets of the polyester resin composition to an appropriate size of 100 to 500 nanograms were used as test pieces, and high-speed calorimetry measurement and calculation of crystallinity were performed according to the following temperature program. Flash DSC 1 manufactured by Mettler Toledo was used as the tester, and STARe Software manufactured by Mettler Toledo was used for data processing. The crystallinity is expressed as a percentage of the ratio of the crystal melting heat obtained by high-speed calorimetry measurement to the crystal melting heat of a perfect crystal. The higher the crystallinity, the better the injection moldability and laser permeability. Temperature program: [1] Heated from 30°C to 260°C at 10000°C / second [2] Held at 260°C for 0.1 second [3] Cooled to 80°C at 5000°C / second [4] Held at 80°C for 0.1 second [5] Cooled to -70°C at 5000°C / second [6] Heated to 260°C at 1000°C / second.

[0063] (2) Average length of the linear structure A laser beam transmissivity evaluation test piece with a square shape where L shown in Fig. 1 is 80 mm and a thickness D of 2 mm was molded. The molding conditions were a cylinder temperature of 260 °C and a mold temperature of 80 °C. The sprue 1 and runner 2 parts of the molded piece shown in Fig. 1 were cut at the gate 3, and from the central part of this test piece, starting from 1 mm inside in the thickness direction, a 100-nanometer-thick thin section was prepared using a focused ion beam apparatus / scanning electron microscope composite device (SMI3200SE) manufactured by SIINT Co., Ltd., a micro-sampling system (FB-2000A) manufactured by Hitachi High-Tech Corporation, and a focused ion beam apparatus / scanning electron microscope composite device (Strata400S) manufactured by FEI Company. The thin section was stained with ruthenium tetroxide to obtain a sample. The obtained sample was observed with a high-resolution transmission electron microscope (H9000UHR) manufactured by Hitachi at an acceleration voltage of 300 kV and a magnification of 20,000 times. The obtained image was taken as an image with a size of 1 μm × 1 μm, and for the linear structures distinguishable by shading, the lengths of arbitrarily selected 10 in the length direction were measured, and the average length was calculated.

[0064] (3) Laser beam transmissivity A laser beam transmissivity evaluation test piece with a square shape where L shown in Fig. 1 is 80 mm and a thickness D of 2 mm was molded. The molding conditions were a cylinder temperature of 260 °C and a mold temperature of 80 °C. The sprue 1 and runner 2 parts of the molded piece shown in Fig. 1 were cut at the gate 3, and the remaining part 4 was used as the laser beam transmissivity evaluation test piece. A UV-visible near-infrared spectrophotometer (UV-3150) manufactured by Shimadzu Corporation was used as the testing machine, and an integrating sphere was used as the detector. The transmittance is expressed as a percentage of the ratio of the transmitted light amount to the incident light amount. The measurement locations were the three locations [1] to [3] shown in Fig. 1. [1] and [3] were the parts 13 mm inside from the ends of the molded piece, and [2] was the central part of the molded product. In the table showing the examples and comparative examples, the average value of the light beam transmittance in the near-infrared 940 nm wavelength region measured at three locations as the laser transmissivity, and the variation ratio of the transmittance shown by the following formula as the variation of the laser transmissivity were described. Variation ratio of transmittance = (maximum value of transmittance - minimum value of transmittance) / average value of transmittance × 100.

[0065] (4) Tensile strength Regarding the ISO1A dumbbell test pieces molded at a cylinder temperature of 260°C and a mold temperature of 80°C in accordance with ISO527-1,2, the tensile strength was measured using a tensile testing machine (Autograph AG-50kNXPlus) manufactured by Shimadzu Corporation under the condition of a test speed of 5 mm / min.

[0066] The evaluation results are shown in Tables 1 and 2. Examples are shown in Table 1 and comparative examples are shown in Table 2. Note that Examples 10 and 11 are for reference.

[0067] The evaluation results are shown in Tables 1 and 2. Examples are shown in Table 1 and comparative examples are shown in Table 2.

[0068]

Table 1

[0069]

Table 2

[0070] Examples 1 to 11, compared with Comparative Examples 1 to 3, by setting the crystallinity of the polyester resin composition to a specific value, polyester resin compositions with excellent injection moldability and highly controlled laser permeability at different sites in the molded product were obtained. In addition, by containing specific amounts of polyester resin (A), glass fiber (B), and metal salt compound (C), molded products with good injection moldability, excellent laser permeability, and mechanical strength were obtained. More specifically, Examples 1 to 4, compared with Comparative Examples 2 and 3, contain a preferable metal salt compound (C) in terms of compatibility with the polyester resin (A), so they have excellent crystal nucleation efficiency, and as a result, molded products with good injection moldability and excellent laser permeability were obtained. In addition, Example 5, compared with Comparative Example 1, contains the metal ion addition amount per 1 kg of PBT in a preferable range, so it has excellent crystal nucleation efficiency, and as a result, molded products with good injection moldability and excellent laser permeability were obtained.

[0071] In Example 4, compared with Examples 1 to 3, the terminal carboxyl group concentration of the polyester resin (A) was in a more preferable range, resulting in excellent compatibility with the metal salt compound (C). As a result, good injection moldability was achieved, and molded articles with even better laser permeability could be obtained.

[0072] In Example 3, compared with Examples 5 and 6, in terms of excellent compatibility with the polyester resin (A), by containing a metal salt compound (C) with a more preferable number of carbon atoms, excellent crystal nucleation efficiency was achieved. As a result, even when the amount of metal ions per 1 kg of the polyester resin (A) was small, molded articles with equivalent laser permeability and even better mechanical strength could be obtained.

[0073] In Example 7, compared with Examples 3 and 8, by containing glass fibers (B) with a more preferable flatness ratio, molded articles with even better laser permeability and mechanical strength could be obtained.

[0074] In Example 9, compared with Example 3, the terminal carboxyl group concentration of the polyester resin (A) was in a more preferable range, and by containing glass fibers (B) with a more preferable flatness ratio, excellent compatibility with the metal salt compound (C) was achieved. As a result, good injection moldability was achieved, and molded articles with even better laser permeability and mechanical strength could be obtained.

[0075] In Examples 3, 5, and 6, compared with Examples 10 and 11, since a more preferable metal species of the metal salt compound (C) was blended, excellent crystal nucleation efficiency was achieved. As a result, good injection moldability was achieved, and molded articles with even better laser permeability and mechanical strength could be obtained.

Explanation of Symbols

[0076] 1. Sprue 2. Runner 3. Gate 4. Laser beam transmissivity evaluation test piece

Claims

1. A polyester resin composition containing, based on 100 parts by mass of a polyester resin (A), more than 0 and 100 parts by mass or less of glass fibers (B), and containing an aliphatic carboxylic acid sodium salt (C) which is at least one selected from sodium propionate, sodium caprylate, sodium stearate, and mixtures thereof, in a concentration of 50 to 150 millimoles of metal ions per 1 kg of the polyester resin (A), characterized in that the crystallinity calculated by the following method using high-speed calorimetry is 15% or more. Calculation method: Using high-speed calorimetry, after heating the polyester resin composition from 30°C to 260°C at 10,000°C / second, holding at 260°C for 0.1 second, cooling to 80°C at 5,000°C / second, holding at 80°C for 0.1 second, cooling to -70°C at 5,000°C / second, and then heating to 260°C at 1,000°C / second, the crystallinity calculated from the curve obtained.

2. The polyester resin composition according to claim 1, characterized in that the average length in the longitudinal direction of the linear structure observed using a transmission electron microscope is 150 nanometers or less.

3. The polyester resin composition according to claim 1 or 2, wherein the terminal carboxyl group concentration of the polyester resin (A) is 20 eq / t or less.

4. The polyester resin composition according to any one of claims 1 to 3, characterized in that the flatness ratio calculated by the following formula of the glass fibers (B) is 1 to 2. Flatness ratio = major axis of the cross-section of the glass fiber / minor axis

5. A molded article comprising the polyester resin composition according to any one of claims 1 to 4.

6. A composite molded article obtained by laser welding the molded article according to claim 5.

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