Molded articles and composite molded articles made from polyester resin compositions

Abstract

To provide a polyester resin which can achieve stable laser weldability by controlling high laser transmissibility at every part of a molded article and by controlling dimensional characteristics of the molded article.SOLUTION: Provided is a resin composition, comprising a polyester resin (A) as a major component, wherein, with regard to an amount of terminal carboxylic groups of the polyester resin (A) and a metal component amount in the resin composition, a ratio represented by (metal component amount) / (terminal carboxylic group amount) is 0.50 or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyester resin composition having excellent laser weldability, a molded article, and a composite molded article made thereof. [Background technology]

[0002] Polyester resins, especially polybutylene terephthalate resins, are widely used as injection molded products in fields such as machine parts, electrical and communication parts, and automotive parts, due to their excellent injection moldability, mechanical properties, heat resistance, electrical properties, and chemical resistance. However, although injection molded products have good molding efficiency, there are limitations on the shape they can be made into due to their flow properties and mold structure, and molding overly complex parts is difficult.

[0003] Traditionally, joining parts to accommodate the increasingly complex shapes of products has involved methods such as adhesive bonding and mechanical joining using bolts. However, adhesive bonding does not provide sufficient strength, and mechanical joining using bolts and other methods poses problems such as cost, labor required for fastening, and increased product weight. On the other hand, external heat welding such as laser welding and hot plate welding, and frictional heat welding such as vibration welding and ultrasonic welding can join parts in a short time and do not require adhesives or metal parts, eliminating the associated costs, increased product weight, and environmental pollution, and therefore these joining methods are becoming increasingly popular.

[0004] Laser welding, a type of external heat welding, is a method in which laser light is irradiated onto overlapping resin molded bodies, allowing it to pass through one part and be absorbed by the other, melting and fusing the resin.It is a method that is spreading to a wide range of fields, taking advantage of its advantages such as the ability to join three-dimensionally, non-contact processing, and no burrs.

[0005] Polybutylene terephthalate resins, widely used in a variety of applications due to their high dimensional stability and low water absorption, have significantly lower laser beam transmittance than polyamide resins. When using polybutylene terephthalate resins as the laser beam transmitting molded part and applying laser welding, their low laser beam transmittance imposes strict limitations on the molded part's thickness. This necessitates thinning to improve laser beam transmittance, limiting product design flexibility. In addition to the absolute value of laser beam transmittance, large variations in transmittance between the laser beam transmitting side of the molded part can lead to welding defects. Therefore, controlling the transmittance between the laser beam transmitting side of the molded part is desirable for stable laser welding. Furthermore, controlling the dimensional characteristics of the molded part is also required for stable laser welding. In particular, controlling the amount of warpage of the molded part is desirable to reduce gaps and misalignment between the laser beam transmitting side and the laser beam absorbing side of the molded part at the welded area.

[0006] To address the above-mentioned problems, Patent Document 1 discloses a method of adding an alkali metal salt of a fatty acid to a polyester resin in order to improve the transmittance of a laser beam. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Special Publication No. 2014-512420 Summary of the Invention [Problem to be solved by the invention]

[0008] However, although Patent Document 1 provides a satisfactory transmittance required for laser welding, the transmittance is prone to fluctuation, and variations in transmittance occur between regions of the molded product, and the molded product may be significantly warped, which can result in poor welding, making it difficult to obtain stable laser weldability.

[0009] Therefore, an object of the present invention is to provide a polyester resin composition that realizes stable laser weldability by controlling high laser transmittance at each site of a molded article and by controlling the dimensional properties of the molded article, a molded article molded using this composition, and a composite molded article using this molded article. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention comprises the following configuration. (1) A resin composition containing a polyester resin (A) as a main component, characterized in that the ratio of the amount of terminal carboxyl groups in the polyester resin (A) to the amount of metal components contained in the resin composition, expressed as the amount of metal components / the amount of terminal carboxyl groups, is 0.50 or more; (2) The polyester resin composition according to (1), wherein the metal component is an alkali metal. (3) The polyester resin composition according to (1) or (2), wherein the metal component is at least one selected from sodium, potassium, and a mixture thereof. (4) The polyester resin composition according to any one of (1) to (3), which contains the metal salt compound (B) at a concentration of 50 to 150 millimoles of the metal component per 1 kg of the polyester resin (A) relative to 100 parts by mass of the polyester resin (A). (5) The polyester resin composition according to (4), wherein the metal salt compound (B) is at least one aliphatic carboxylic acid sodium salt selected from the group consisting of sodium propionate, sodium caprylate, sodium stearate, and mixtures thereof. (6) A molded article made of the polyester resin composition according to any one of (1) to (5). (7) The method for producing a molded article according to (6), wherein the polyester resin composition is dried at 100°C or higher for 3 hours or more and then molded. (8) The molded article according to (6) or (7), wherein the polyester resin composition is molded for a molten residence time of less than 15 minutes. (9) A composite molded product obtained by laser welding the molded product described in (6). [Effects of the Invention]

[0011] The present invention makes it possible to precisely control high laser transmittance at different locations in a molded article and to control warpage of the molded article. Therefore, the present invention is useful for resin molded articles for various applications requiring laser welding, particularly for molded articles on the laser transmitting side. [Brief explanation of the drawings]

[0012] [Figure 1] The test piece for evaluating laser light transmittance is in the form of a plate with a side length L1 of 80 mm and a thickness D1 of 2 mm. [Figure 2] The test piece for evaluating warpage is box-shaped with a square base, a side length L2 of 30 mm, a height H2 of 30 mm, and a thickness D2 of 1.5 mm. DETAILED DESCRIPTION OF THE INVENTION

[0013] <Polyester resin (A)> The polyester resin composition of the present invention comprises a polyester resin (A) as a main component. Here, "main component" refers to a case where the polyester resin (A) accounts for 30% by weight or more of 100% by weight of the polyester resin composition. The polyester resin (A) used in the present invention is a polymer or copolymer having one or more main structural units selected from (a) a dicarboxylic acid or its ester-forming derivative and a diol or its ester-forming derivative, (b) a hydroxycarboxylic acid or its ester-forming derivative, and (c) a lactone.

[0014] Examples of the dicarboxylic acid or an ester-forming derivative thereof 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-tetrabutylphosphoniumisophthalate, 5-sodiumsulfoisophthalic acid, and diphenic acid; aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, malonic acid, glutaric acid, and dimer acid; and alicyclic dicarboxylic acids such as 1,3-cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid, as well as ester-forming derivatives thereof.

[0015] Examples of the diol or its ester-forming derivative include aliphatic glycols having 2 to 20 carbon atoms, such as ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, decamethylene glycol, cyclohexanedimethanol, cyclohexanediol, and dimer diol; long-chain glycols having a molecular weight of 200 to 100,000, such as polyethylene glycol, poly-1,3-propylene glycol, and polytetramethylene glycol; and aromatic dioxy compounds, such as 4,4'-dihydroxybiphenyl, hydroquinone, t-butylhydroquinone, bisphenol A, bisphenol S, bisphenol F, and bisphenol-C; and ester-forming derivatives thereof.

[0016] (a) Examples of polymers or copolymers having dicarboxylic acid or its ester-forming derivative and diol or its ester-forming derivative as structural units include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polycyclohexanedimethylene terephthalate, polyhexylene terephthalate, polyethylene isophthalate, polypropylene isophthalate, polybutylene isophthalate, polycyclohexanedimethylene 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 / decanedicarboxylate, polyethylene terephthalate / cyclohexanedimethylene terephthalate, polyethylene terephthalate / 5-sodium sulfoisophthalate, polypropylene terephthalate Phthalate / 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 / sebacateExamples of the polyester resin include aromatic polyester resins such as polybutylene terephthalate / sebacate, polyethylene terephthalate / isophthalate / adipate, polypropylene terephthalate / isophthalate / adipate, polybutylene terephthalate / isophthalate / succinate, polybutylene terephthalate / isophthalate / adipate, and polybutylene terephthalate / isophthalate / sebacate; and aliphatic polyester resins such as 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, and polybutylene succinate / adipate. Among these, aromatic polyester resins are preferred, and any one selected from polyethylene terephthalate, polypropylene terephthalate, and polybutylene terephthalate or a copolymer thereof is more preferred, with polybutylene terephthalate or a copolymer thereof being even more preferred.

[0017] (ii) Examples of the hydroxycarboxylic acids or their ester-forming derivatives include glycolic acid, lactic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxybenzoic acid, p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, and ester-forming derivatives thereof. Examples of polymers or copolymers having these as structural units include aliphatic polyester resins such as polyglycolic acid, polylactic acid, polyglycolic acid / lactic acid, and polyhydroxybutyric acid / β-hydroxybutyric acid / β-hydroxyvaleric acid.

[0018] Furthermore, examples of the (c) lactone include ε-caprolactone, valerolactone, propiolactone, undecalactone, 1,5-oxepan-2-one, and γ-butyrolactone, and examples of polymers or copolymers having these as structural units include polycaprolactone, polyvalerolactone, polypropiolactone, poly-γ-butyrolactone, and polycaprolactone / valerolactone.

[0019] Among these, (a) polymers or copolymers having dicarboxylic acid or its ester-forming derivative and diol or its ester-forming derivative as main structural units are preferred, polymers or copolymers having aromatic dicarboxylic acid or its ester-forming derivative and aliphatic diol or its ester-forming derivative as main structural units are more preferred, and polymers or copolymers having terephthalic acid or its ester-forming derivative and aliphatic diol or its ester-forming derivative selected from ethylene glycol, propylene glycol, and butanediol as main structural units are even more preferred, and among these, polyethylene terephthalate, polypropylene terephthalate, polybutylene Aromatic polyester resins such as polyethylene 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, with polyethylene terephthalate, polypropylene terephthalate, and polybutylene terephthalate being particularly preferred, and polybutylene terephthalate being especially preferred.

[0020] In the present invention, the proportion of terephthalic acid or its ester-forming derivative relative to all dicarboxylic acids in the polymer or copolymer having the above (i) 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.

[0021] The viscosity of the polyester resin (A) used in the present invention is not particularly limited as long as it can be melt-kneaded. However, from the viewpoint 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, more preferably in the range of 0.50 to 1.50 dL / g.

[0022] The melting point of the polyester resin (A) used in the present invention is not particularly limited as long as it can be melt-kneaded, but is preferably 200°C or higher from the viewpoint of heat resistance and mechanical strength, and more preferably 215°C or higher, and even more preferably 220°C or higher, from the viewpoint of excellent melt processability. The upper limit of the melting point is not particularly limited, but is preferably 280°C or lower, and more preferably 270°C or lower, from the viewpoint of excellent melt processability. A melting point below 210°C poses a problem of reduced heat resistance, while a melting point above 280°C results in extremely large crystallinity and crystal size, requiring excessive heating during melt processing, which may result in concomitant decomposition of the polyester resin. The melting point referred to here is the peak top temperature of the endothermic peak observed when a differential scanning calorimeter (DSC) is used to increase the temperature from 30°C to 280°C at a rate of 20°C / min, hold the temperature at 280°C for 3 minutes, decrease the temperature from 280°C to 30°C at a rate of 20°C / min, and then increase the temperature from 30°C to 280°C at a rate of 20°C / min.

[0023] In the present invention, the heat of crystalline fusion, expressed by the area of ​​the endothermic peak measured under the above conditions using a 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, from the viewpoint of excellent heat resistance. The upper limit of the heat of crystalline fusion is not particularly limited, but is preferably 60 J / g or less, more preferably 50 J / g or less, from the viewpoint of excellent melt processability.

[0024] The method for producing the polyester resin (A) used in the present invention is not particularly limited, and it can be produced by a conventional polycondensation method or ring-opening polymerization method, etc., and either batch polymerization or continuous polymerization may be used. In addition, any of a method involving a transesterification reaction and a polycondensation reaction, and a reaction by direct polymerization can be applied. However, continuous polymerization is preferred in that it can reduce the amount of terminal carboxyl groups and has excellent laser transmittance, and direct polymerization is preferred in terms of cost.

[0025] When the (A) polyester resin used in the present invention is a polymer or copolymer obtained by a condensation reaction of (i) a dicarboxylic acid or its ester-forming derivative and a diol or its ester-forming derivative as the main components, it can be produced by subjecting (i) a dicarboxylic acid or its ester-forming derivative and a diol or its ester-forming derivative to an esterification reaction or an ester exchange reaction, followed by a polycondensation reaction. In order to effectively promote the esterification reaction or transesterification reaction and polycondensation reaction, it is preferable to add a polymerization catalyst during these reactions. Specific examples of the polymerization catalyst include organotitanium compounds such as methyl ester, tetra-n-propyl ester, tetra-n-butyl ester, tetraisopropyl ester, tetraisobutyl ester, tetra-tert-butyl ester, cyclohexyl ester, phenyl ester, benzyl ester, tolyl ester of titanic acid, or mixed esters thereof; dibutyltin oxide, methylphenyltin oxide, tetraethyltin, hexaethylditin oxide, cyclohexahexylditin oxide, didodecyltin oxide, triethyltin hydroxide, triphenyltin hydroxide; Examples of suitable catalysts include triisobutyltin acetate, dibutyltin diacetate, diphenyltin dilaurate, monobutyltin trichloride, dibutyltin dichloride, tributyltin chloride, dibutyltin sulfide, and butylhydroxytin oxide; alkylstannoic acids such as methylstannoic acid, ethylstannoic acid, and butylstannoic acid; zirconia compounds such as zirconium tetra-n-butoxide; and antimony compounds such as antimony trioxide and antimony acetate. Among these, organic titanium compounds and tin compounds are preferred, and the tetra-n-propyl ester, tetra-n-butyl ester, and tetraisopropyl ester of titanic acid are more preferred, with the tetra-n-butyl ester of titanic acid being particularly preferred. These polymerization catalysts may be used alone or in combination of two or more.The amount of the polymerization catalyst added is preferably in the range of 0.005 to 0.5 parts by mass, more preferably 0.01 to 0.2 parts by mass, per 100 parts by mass of the polyester resin, in terms of mechanical properties, moldability, and color tone.

[0026] The polyester resin (A) of the present invention can be used either alone or in combination of two or more.

[0027] In the present invention, the terminal groups of the polyester resin (A) are not particularly limited and may include terminal carboxyl groups, terminal hydroxyl groups, or other terminal groups. However, in terms of excellent laser transmittance and dimensional properties, a polyester resin composition containing a metal component and having polyester resin (A) as the main component preferably has a ratio of metal component amount / terminal carboxyl group amount of 0.50 or more, more preferably 0.70 or more, even more preferably 0.80 or more, and particularly preferably 0.90 or more. Furthermore, from the viewpoint of laser transmittance and mechanical properties, the value of metal component amount / terminal carboxyl group amount is preferably 2.00 or less. The state of the metal component in the polyester resin is not particularly limited. It may exist as a simple substance or an ion, or may form a metal salt structure or a coordination structure with other compounds. However, in terms of excellent laser transmittance and dimensional properties, it is preferable for the metal component to form a metal salt structure with the terminal carboxyl group of the polyester resin (A). By adjusting the ratio of terminal carboxyl groups to metal components in the polyester resin (A) within the above range, the efficiency of crystal nucleation in the polyester resin is improved, resulting in a finer crystal structure in the injection-molded article, and improved laser transmittance. Furthermore, because the crystallization rate is increased, even if the cooling of various parts of the molded article is uneven during injection molding, the difference in crystallinity between different parts of the molded article is reduced, and the difference in shrinkage rate is reduced, making the resulting molded article less prone to surface warpage or internal warpage. There are no particular limitations on the method for incorporating a metal component into the polyester resin composition so that the ratio (metal component amount / terminal carboxyl group amount) is 0.50 or greater. Examples include blending a metal salt compound (B) with the polyester resin (A) and adjusting melt-kneading and injection molding conditions. There are no particular limitations on the method for quantifying the amount of terminal carboxyl groups in the polyester resin (A). Examples include potentiometric titration, and the amount is expressed as the number of moles relative to the weight of the polyester resin (A). The method for quantifying the metal component is not particularly limited, but examples include atomic absorption spectrometry, and the value expressed as the number of moles relative to the weight of polyester resin (A) is used as the amount of the metal component in the resin composition.

[0028] <Metal components> In the present invention, the metal species of the metal component is not particularly limited and may be any metal species, including metal components selected from lithium, potassium, sodium, magnesium, calcium, aluminum, strontium, titanium, manganese, iron, zinc, silicon, zirconium, yttrium, and barium. Alkali metals are preferred because they have excellent crystallization properties, good laser transmittance, and excellent mechanical and dimensional properties. Sodium, potassium, and at least one of their mixtures are more preferred, and sodium is even more preferred, because they have a particularly excellent crystallization-promoting effect. The method for quantifying the metal component is not particularly limited, but includes atomic absorption spectrometry, and is expressed as the number of moles relative to the weight of polyester resin (A).

[0029] <Metal salt compound (B)> In the present invention, it is preferable to contain the metal salt compound (B) in a concentration of 50 to 150 eq / t of the metal component relative to the weight of the polyester resin from the viewpoint of good crystal nucleation. That is, it is preferable that the metal component in the polyester resin composition is derived from the metal salt compound (B).

[0030] In the present invention, the metal salt compound (B) may be any one of aliphatic carboxylate metal salts, alicyclic carboxylate metal salts, aromatic carboxylate metal salts, sulfonates, amidosulfonates, phosphate metal salts, phosphate metal salts, and borates, or a mixture thereof. In terms of excellent crystallization characteristics, examples of the metal salt compound (B) include one or a mixture of two or more selected from 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 sulfonates metal salts having 1 to 50 carbon atoms, alicyclic sulfonates metal salts having 6 to 60 carbon atoms, aromatic sulfonates metal salts having 6 to 60 carbon atoms, aliphatic phosphate metal salts having 1 to 50 carbon atoms, alicyclic phosphate metal salts having 6 to 60 carbon atoms, and aromatic phosphate metal salts having 6 to 60 carbon atoms. Furthermore, in terms of exhibiting excellent crystallization characteristics, favorable injection moldability, and laser transmittance, the metal salt is preferably one or a mixture of two or more selected from a metal salt of an aliphatic carboxylate having 2 to 40 carbon atoms, a metal salt of an alicyclic carboxylate having 7 to 40 carbon atoms, and a metal salt of an aromatic carboxylate having 7 to 40 carbon atoms, more preferably one or a mixture of two or more selected from a metal salt of an aliphatic carboxylate having 2 to 30 carbon atoms, and a metal salt of an aromatic carboxylate having 7 to 30 carbon atoms, and particularly preferably an aliphatic carboxylate having 2 to 25 carbon atoms.

[0031] An aliphatic carboxylic acid is a compound in which a carboxylic acid group is added to a linear or branched aliphatic group, and may have other substituents such as an unsaturated group, an alicyclic group, a hydroxyl group, or a phosphate ester group as part of the bond.

[0032] 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, and montanic acid.

[0033] Furthermore, in the present invention, in terms of good affinity with the polyester resin (A), metal salts of aliphatic carboxylic acids having 3 to 20 carbon atoms are preferred, metal salts of aliphatic carboxylic acids having 3 to 10 carbon atoms are more preferred, and metal salts of aliphatic carboxylic acids having 3 to 5 carbon atoms are particularly preferred.

[0034] In the present invention, the metal species of the metal salt compound (B) is not particularly limited and may be any metal species, including metal salts selected from lithium, potassium, sodium, magnesium, calcium, aluminum, strontium, titanium, manganese, iron, zinc, silicon, zirconium, yttrium, barium, etc. Alkali metal salts are preferred in that they exhibit excellent crystallization characteristics, good laser transmittance, and excellent mechanical properties and dimensional properties, and at least one selected from sodium, potassium, and a mixture thereof is more preferred in that they have a particularly excellent crystallization-promoting effect, with sodium being even more preferred.

[0035] The metal salt compound (B) in the present invention is preferably incorporated at a concentration of 50 to 150 millimoles of metal component per kg of polyester resin (A). That is, the metal component is preferably incorporated at a concentration of 50 to 150 eq / t relative to the weight of the polyester resin. At a concentration of 50 eq / t or more, the laser transmittance of a molded article made from the polyester resin composition can be maintained, and variations in transmittance between regions of the molded article can be suppressed. Furthermore, at a concentration of 150 eq / t or less, reductions in molecular weight and mechanical strength of the molded article due to decomposition of the polyester resin (A) by the catalytic action of the metal salt compound can be suppressed. The metal salt compound (B) is preferably incorporated at a concentration of 50 to 150 eq / t relative to the weight of polyester resin (A), more preferably 50 to 120 eq / t, and even more preferably 50 to 100 eq / t.

[0036] In the present invention, it is preferable to use, as the metal salt compound (B), at least one aliphatic carboxylic acid sodium salt selected from sodium propionate, sodium caprylate, sodium stearate, and mixtures thereof. By using these sodium-containing compounds, a high laser transmittance improving effect can be obtained.

[0037] <Inorganic fillers> In the present invention, inorganic fillers can be blended to the extent that the objectives of the present invention are not impaired. Examples of components include fibrous reinforcing materials such as glass fiber, carbon fiber, potassium titanate whisker, zinc oxide whisker, aluminum borate whisker, aramid fiber, alumina fiber, silicon carbide fiber, ceramic fiber, asbestos fiber, gypsum fiber, and metal fiber; wollastonite, zeolite, sericite, kaolin, mica, clay, pyrofilament, bentonite, asbestos, talc, and silicates such as alumina, silicon oxide, magnesium oxide, zirconium oxide, titanium oxide, and iron oxide; carbonates such as calcium carbide, magnesium carbonate, and dolomite; sulfates such as calcium sulfate and barium sulfate; and non-fibrous reinforcing materials such as glass beads, ceramic beads, boron nitride, silicon carbide, zinc borate, and silica. These can be used alone or in combination of two or more. A preferred example in the present invention is glass fiber. Furthermore, it is more preferable to use these fillers after pretreating them with a coupling agent such as a silane, epoxy or titanate coupling agent in terms of mechanical strength.

[0038] The glass fiber may have either a circular or flat cross section, but a flat cross section is preferred from the viewpoints of suppressing deformation, reducing warpage, and providing stable laser transparency. Generally, in compositions containing glass fibers, the fibers are oriented in the flow direction during molding, resulting in increased anisotropy of the molding shrinkage rate (the percentage of the dimensional difference between the resin molded product and the mold), and increased deformation and warpage. However, when the cross section is flat, the anisotropy of the molding shrinkage rate is reduced, and deformation and warpage are likely to be improved.

[0039] Glass fibers having a flat cross-sectional shape preferably have an aspect ratio, expressed as the ratio of the major axis (the longest linear distance in the cross section) to the minor axis (the longest linear distance perpendicular to the major axis) in a cross section cut perpendicular to the longitudinal direction, of 1 or more and 10 or less. The lower limit of the aspect ratio is preferably more than 1, more preferably 1.3 or more, and even more preferably 1.5 or more. The upper limit is preferably 5 or less, more preferably 2.5 or less, and most preferably 2 or less. The specific shape may be cocoon-shaped, oval, elliptical, semicircular, arc-shaped, rectangular, or any similar shape, but an oval shape is particularly preferred in terms of fluidity and low warpage.

[0040] When the aspect ratio exceeds 1, deformation and warping during molding are suppressed, and when the aspect ratio is set to 10 or less, it is practically difficult to manufacture such glass fibers. Hollow fibers can also be used for glass fibers for the purpose of reducing the specific gravity, etc. As the cross-sectional area of ​​the glass fiber increases, a sufficient reinforcing effect cannot be obtained. On the other hand, if the cross-sectional area is too small, it becomes difficult to manufacture the glass fiber itself and there is also the problem that it becomes difficult to handle. The cross-sectional area of ​​the glass fiber in the present invention is 2 × 10 -5 ~8×10 -3 mm 2 is preferred, 8 × 10 -5 ~8×10 -3 mm 2 is more preferable, and 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 and deformation suppression of the molded article, a shorter length is preferable to minimize the amount of deformation of the molded article. However, from the viewpoint of mechanical properties, a fiber length of 30 μm or more is preferable, and 50 to 1000 μm is preferable depending on the required performance. In the glass fiber used in the present invention, it is preferable to use a sizing agent or a surface treatment agent as needed. Examples of the sizing agent or surface treatment agent include functional compounds such as epoxy compounds, isocyanate compounds, silane compounds, and titanate compounds. These compounds may be surface-treated or sizing-treated before use, or may be added simultaneously during material preparation. When the glass fiber used in the present invention is flat, it is prepared by spinning using a nozzle having an appropriate hole shape, such as oval, elliptical, rectangular, or slit-shaped, as a bushing used to discharge molten glass. Alternatively, it can be prepared by spinning molten glass from multiple nozzles arranged closely together and having various cross-sectional shapes (including circular cross-sections), and bonding the spun molten glass together to form a single filament.

[0041] The blending amount of the glass fiber used in the present invention is preferably more than 0 and not more than 100 parts by mass, more preferably 10 to 80 parts by mass, and even more preferably 20 to 50 parts by mass, per 100 parts by mass of the polyester resin (A). Blending of the glass fiber is preferred to achieve mechanical strength and low warpage. Furthermore, by keeping the blending amount at 100 parts by mass or less, fluidity during molding can be maintained.

[0042] <Other additives> The resin composition of the present invention may contain other components, such as epoxy resins (bisphenol A type, novolak type, glycidyl ester type, etc.), phosphorus-based stabilizers (phosphate ester type, etc.), weather resistance 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, bisurea, polyethylene wax, etc.), pigments (cadmium sulfide, phthalocyanine, rylene, perylene, naphthocyanine, quinacridone, carbon black, titanium oxide, iron oxide, azo type, monoazo type, etc.), dyes (azine type, azo type, perylene, anthraquinone, etc.), crystal nucleating agents (talc, The resin composition may contain, for example, anionic antistatic agents (such as polyether ether ketone), plasticizers (such as octyl p-oxybenzoate and N-butylbenzenesulfonamide), antistatic agents (such as alkyl sulfate-type anionic antistatic agents, quaternary ammonium salt-type cationic antistatic agents, nonionic antistatic agents such as polyoxyethylene sorbitan monostearate, and betaine-type amphoteric antistatic agents), flame retardants (such as red phosphorus, melamine cyanurate, ammonium polyphosphate, brominated polystyrene, brominated polyphenylene ether, brominated polycarbonate, brominated epoxy resin, or a combination of any of these brominated flame retardants with antimony trioxide), color inhibitors (such as phosphoric acid, phosphorous acid, trimethyl phosphate, triphenyl phosphate, and other phosphoric acid compounds), other polymers, and the like.

[0043] The method for producing the resin composition of the present invention is not particularly limited as long as it satisfies the requirements of the present invention. For example, preferred methods include uniformly melt-kneading the polyester resin (A), the metal salt compound (B), and optionally other components in a single-screw or twin-screw extruder, or mixing them in a solution followed by removing the solvent. From the perspective of productivity, uniform melt-kneading in a single-screw or twin-screw extruder is preferred. Uniform melt-kneading in a twin-screw extruder is more preferred because it produces a resin composition with excellent fluidity and mechanical properties. Among these, melt-kneading using a twin-screw extruder with an L / D ratio > 30, where L is the screw length and D is the screw diameter, is particularly preferred. The screw length here refers to the length from the base of the screw where the raw materials are supplied to the tip of the screw. The upper limit of the L / D ratio of a twin-screw extruder is 150, and preferably, an L / D ratio greater than 30 and less than 100 can be used.

[0044] In the present invention, the screw configuration of a twin-screw extruder is a combination of full flight and kneading discs, and uniform kneading by the screws is necessary to obtain the composition of the present invention. Therefore, the ratio of the total length of the kneading discs (kneading zone) to the total length of the screws is preferably in the range of 5 to 50%, more preferably in the range of 10 to 40%.

[0045] In the present invention, when melt-kneading, the various components can be added by, for example, using an extruder having two inlets and feeding the polyester resin (A), glass fiber, metal components, and other components as required through a main inlet located at the base of the screw, or by feeding the polyester resin (A), metal components, and other components through the main inlet, and feeding the glass fiber through a secondary inlet located between the main inlet and the tip of the extruder, and melt-mixing the components.

[0046] Furthermore, in the case of melt kneading in the present invention, the temperature of the resin discharged from the extruder is preferably 310°C or lower, more preferably 300°C or lower, even more preferably 290°C or lower, and particularly preferably 280°C or lower, in order to obtain a resin composition having excellent laser transmittance and mechanical properties. Furthermore, in terms of processability, the temperature is preferably 200°C or higher, more preferably 210°C or higher, even more preferably 220°C or higher, and particularly preferably 230°C or higher. The temperature of the resin discharged from the extruder can be adjusted by setting the cylinder temperature, screw rotation speed, and discharge rate, but the method for doing so is not particularly limited.

[0047] The resin composition of the present invention can be molded by any conventional method, such as injection molding, extrusion molding, blow molding, press molding, or spinning, and can be processed into various molded products for use. However, injection molding is preferred because of its cost and mass productivity. While molding conditions are not particularly limited, it is preferable to dry the polyester resin composition at a temperature of 100°C or higher for at least 3 hours before molding. The cylinder temperature of the molding machine is preferably 270°C or lower, more preferably 260°C or lower, and even more preferably 250°C or lower. The lower limit is preferably 200°C or higher, more preferably 210°C or higher, and even more preferably 220°C or higher. Furthermore, molding is preferably performed so that the residence time of the polyester resin composition inside the molding machine is less than 15 minutes. By molding in this manner, an increase in the amount of terminal carboxyl groups due to hydrolysis of the polyester resin composition during the molding process is suppressed, resulting in a molded product with excellent laser transparency, mechanical properties, and dimensional characteristics. The mold temperature is not particularly limited, but is preferably 40° C. or higher, more preferably 60° C. or higher, and even more preferably 80° C. or higher, from the viewpoint of facilitating control of the transmittance between regions of the molded article, and the upper limit is preferably 100° C. or lower, from the viewpoint of facilitating shortening of the processing time. The injection speed is not particularly limited, but is preferably set in the range of 10 mm / sec to 300 mm / sec, and more preferably in the range of 50 mm / sec to 200 mm / sec, from the viewpoint of facilitating control of the transmittance between regions of the molded article while suppressing decomposition of the resin due to shear heat during molding.

[0048] The molded products can be used as injection molded products, extrusion molded products, blow molded products, films, sheets, fibers, etc., and the films can be used as various films such as unstretched, uniaxially stretched, and biaxially stretched films, and the fibers can be used as various fibers such as unstretched yarns, stretched yarns, and ultra-stretched yarns.

[0049] In the present invention, the above-mentioned various molded articles can be used for various purposes such as automobile parts, electrical and electronic parts, building materials, various containers, daily necessities, household goods, and sanitary products, and since they can be laser welded in particular, they are suitable as automobile parts and electrical and electronic parts that are to be laser welded.

[0050] 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 hobbins, 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, ABS actuator cases, radiator tank tops and bottoms, 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 automotive underhood parts, torque control levers, safety belt parts, register blades, washer levers, window regulator handles, windows Examples of electrical and electronic components include automotive interior parts such as regulator handle knobs, passing light levers, sun visor brackets, and various motor housings; automotive exterior parts such as roof rails, fenders, garnishes, bumpers, door mirror stays, spoilers, hood louvers, wheel covers, hubcaps, grill apron cover frames, lamp reflectors, lamp bezels, and door handles; various automotive connectors such as wire harness connectors, SMJ connectors, PCB connectors, and door grommet connectors; electrical connectors; relay cases, coil bobbins, optical pickup chassis, motor cases; laptop housings and internal parts; CRT display housings and internal parts; printer housings and internal parts; mobile terminal housings and internal parts for mobile phones, mobile PCs, handheld mobile devices, and the like; housings and internal parts for recording medium (CD, DVD, PD, FDD, etc.) drives; housings and internal parts for copiers; housings and internal parts for facsimiles; and parabolic antennas.

[0051] Further examples include parts for home and office electrical appliances such as VTR parts, television parts, irons, hair dryers, rice cooker parts, microwave oven parts, audio parts, video camera, projector and other visual equipment parts, substrates for optical recording media such as laser discs (registered trademark), compact discs (CD), CD-ROMs, CD-Rs, CD-RWs, DVD-ROMs, DVD-Rs, DVD-RWs, DVD-RAMs and Blu-ray discs, lighting parts, refrigerator parts, air conditioner parts, typewriter parts, word processor parts, etc.

[0052] We also manufacture housings and internal parts for electronic musical instruments, home game consoles, and portable game consoles, as well as various gears, cases, sensors, LEP lamps, connectors, sockets, resistors, relay cases, switches, coil bobbins, capacitors, variable capacitor 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 crystal displays, FDD carriages, FDD chassis, motor brush holders, transformer components, and coil bobbins. Electrical and electronic parts, sash door rollers, blind curtain parts, piping joints, curtain liners, blind parts, gas meter parts, water meter parts, water heater parts, roof panels, insulated walls, adjusters, plastic beams, ceiling fishing tackle, stairs, doors, floors and other building materials, fishing lines, fishing nets, seaweed farming nets, fishing bait bags and other fishery-related materials, vegetation nets, vegetation mats, weed control bags, weed control nets, protective sheets, slope protection sheets, fly ash holding sheets, drain sheets, water-retaining sheets, sludge and sludge dewatering bags, concrete formwork and other civil engineering materials, gears, screws, springs, bearings, levers , key stems, cams, ratchets, rollers, water supply parts, toy parts, fans, fishing line, pipes, cleaning tools, motor parts, microscopes, binoculars, cameras, clocks and other machine parts, mulch film, tunnel film, bird repellent sheets, nonwoven fabric for vegetation protection, seedling pots, vegetation stakes, seed string tape, germination sheets, greenhouse lining sheets, agricultural plastic fasteners, slow-release fertilizers, root barrier sheets, gardening nets, insect nets, young tree nets, print laminates, fertilizer bags, sample bags, sandbags, animal damage prevention nets, attractant strings, windbreak nets and other agricultural components, disposable diapers, sanitary product packaging, cotton swabs, wet towels, toilet seat wipes Hygiene products such as medical nonwoven fabrics (suture reinforcement materials, anti-adhesion membranes, prosthetic organ repair materials), wound dressing materials, wound tape bandages, adhesive tape base fabrics, surgical sutures, fracture reinforcement materials, medical films and other medical supplies, calendars, stationery, clothing, food packaging films, trays, blisters, knives, forks, spoons, tubes, plastic cans, pouches, containers, tanks, baskets and other containers and tableware, hot fill containers, microwave cooking containers, cosmetic containers, plastic wrap, foam cushioning agents, paper laminates, shampoo bottles, beverage bottles, cups, candy packaging, shrink labels,Lid materials, window envelopes, fruit baskets, hand-tearable tape, easy-peel packaging, egg cartons, HDD packaging, compost bags, recording media packaging, shopping bags, containers and packaging such as wrapping film for electrical and electronic components, natural fiber composites, various clothing such as polo shirts, T-shirts, underwear, uniforms, sweaters, socks, and ties, interior goods such as curtains, chair upholstery, carpets, tablecloths, bedding, wallpaper, and furoshiki cloths, carrier tape, print lamination, thermal stencil printing film, release film, porous film, container bags, credit cards, cash The resin composition of the present invention is useful as a hot melt binder for cards, ID cards, IC cards, paper, leather, nonwoven fabrics, etc.; a binder for powders such as magnetic materials, zinc sulfide, and electrode materials; optical elements, conductive embossed tape, IC trays, golf tees, garbage bags, shopping bags, various nets, toothbrushes, stationery, draining nets, body towels, hand towels, tea bags, drain filters, clear files, coating agents, adhesives, bags, chairs, tables, cooler boxes, rakes, hose reels, planters, hose nozzles, dining tables, desk surfaces, furniture panels, kitchen cabinets, pen caps, gas lighters, etc. The resin composition of the present invention not only has high laser transmittance and laser weldability, but also good mechanical properties and injection moldability, making it particularly useful for various automotive parts and electrical / electronic parts that are laser welded.

[0053] In laser welding applications, molded articles made of resin compositions that are laser transmissive and used as laser-transmitting components require high laser transmittance that is precisely controlled at each location of the molded article. High transmittance allows energy to be efficiently transmitted to the welding surface, thereby improving laser welding productivity. Laser transmittance is expressed as laser transmittance measured, for example, using a spectrophotometer, and is calculated as the ratio of the amount of incident light to the amount of transmitted light when light of a specific wavelength is incident on a molded article. For example, for a 2 mm-thick molded article, the laser transmittance at a wavelength of 940 nm is preferably 20% or more, more preferably 25% or more, and even more preferably 30% or more. Furthermore, highly controlled laser transmittance at each location of the molded article reduces welding defects and achieves stable laser weldability. This can be evaluated by the stability of laser transmittance. Specifically, the variation in laser transmittance is evaluated as the variation rate, for example, by dividing the difference between the maximum and minimum transmittance values ​​by the average transmittance when the transmittance is measured at multiple different locations on a molded article. The variation rate is preferably 20% or less, more preferably 15% or less, even more preferably 10% or less, and particularly preferably 5% or less.

[0054] Furthermore, molded products used for laser welding require controlled dimensional characteristics. In particular, if the amount of warpage of a molded product is large, gaps or misalignment are likely to occur between the molded product on the laser beam transmission side and the molded product on the laser beam absorption side at the welded portion, making it difficult to achieve stable laser weldability. The amount of warpage of a molded product can be evaluated, for example, by the amount of inward tilt of a certain surface of a box-shaped molded product, i.e., the amount of inward warpage, which is expressed as the maximum recession dimension from the original plane. When evaluated using a box-shaped molded product with a square base and a height of 30 mm, the amount of warpage is preferably 0.60 mm or less, more preferably 0.50 mm or less, and particularly preferably 0.45 mm or less.

[0055] Molded articles made from the polyester resin composition of the present invention can exhibit stable laser transparency, making them suitable for use as composite molded articles formed by laser welding the molded article to other molded articles. As a material for a composite molded article, the molded article of the present invention can be used on either the laser transmission side or the laser absorption side. However, due to its stable laser transparency, it is particularly suitable for use on the laser transmission side. The material used on the laser absorption side is not particularly limited, but a resin composition having the same composition as the laser transmission side or a resin composition containing the same type of resin is preferred, as it facilitates stronger welding to the laser transmission side material. Additionally, it is preferred to use carbon black or a pigment or dye having an absorption band at the laser light wavelength as a laser light absorbent, as it can efficiently absorb laser light and convert it into thermal energy. The content of the laser light absorbent is preferably 0.1 to 1.0 parts by mass per 100 parts by mass of the resin component.

[0056] The shape of the laser welded part is not particularly limited, but examples include a shape in which the transmission side and the absorption side are in face-to-face contact, and a fitted shape in which the transmission side is a concave rail and the absorption side is a convex rib. In particular, using a concave-convex fitted shape for the welded part not only makes alignment easier, but also makes it possible to control the degree of melting of the resin during laser welding by the amount by which the entire molded product sinks, which is preferable from the perspective of quality control, since the convex rib melts and is crushed during laser welding.

[0057] The type of light source used for laser welding is not particularly limited, but examples include a diode laser and a fiber laser, and the wavelength is preferably 800 nm to 1200 nm.

[0058] Laser welding can be performed under any conditions. For example, conditions such as laser output, laser scanning speed, laser irradiation diameter, number of laser irradiations, pressure applied to the transmitting and absorbing materials, and dwell time can be adjusted to balance weld strength, airtightness, and manufacturing takt time. The laser output is not particularly limited, but is preferably 200 W or less, more preferably 150 W or less, and even more preferably 100 W or less, in order to prevent deterioration due to overheating and thermal decomposition of the resin. The laser scanning speed is not particularly limited, but is preferably 10 mm / sec or more in order to prevent deterioration due to overheating and thermal decomposition of the resin, and is preferably 5000 mm / sec or less in order to efficiently transfer the energy irradiated from the laser to the resin. The laser irradiation diameter is not particularly limited, but is preferably set to 0.5 to 1.5 times the thickness of the welded part in order to efficiently heat the welded part, and more preferably 0.7 to 1.3 times the thickness of the welded part. The number of laser irradiations is not particularly limited, and includes methods using one scan or two or more scans. However, two or more scans are preferred because it allows for a stepwise increase in the temperature of the welded portion and reduces the risk of welding defects. The pressure applied to the transmitting and absorbing materials is not particularly limited, but is preferably 2000 N or less, more preferably 1750 N or less, and even more preferably 1500 N or less, in order to reduce stress on the molded product. The lower limit is preferably 50 N or more, more preferably 75 N or more, and even more preferably 100 N or more, in order to facilitate adhesion between the transmitting and absorbing materials. Furthermore, the method for holding the transmitting and absorbing materials is not particularly limited, but includes methods such as directly holding the welded portion with glass that easily transmits laser light, or holding the inside or outside of the vicinity of the laser welded portion with a dedicated jig. The dwell time is not particularly limited, but is preferably set in the range of 0 to 20 seconds in order to shorten the manufacturing cycle time. [Example]

[0059] The present invention will now be described in more detail with reference to examples, but these examples are not intended to limit the scope of the present invention.

[0060] The abbreviations of the main raw materials used in the examples and their contents are summarized below.

[0061] (A) Polyester resin A-1: Polybutylene terephthalate (terminal carboxyl group content 50 eq / t). A-2: Polybutylene terephthalate (terminal carboxyl group content 30 eq / t). A-3: Polybutylene terephthalate (terminal carboxyl group content 15 eq / t). A-4: Polybutylene terephthalate (terminal carboxyl group amount 9 eq / t).

[0062] (B) Metal salt compounds B-1: Sodium propionate (carbon number 3, molecular weight 96) B-2: Sodium caprylate (carbon number 8, molecular weight 166) B-3: Sodium stearate (carbon number 18, molecular weight 306) B-4: Sodium formate (carbon number 1, molecular weight 68) B-5: Sodium polyacrylate (repeating unit carbon number 3, repeating unit molecular weight 94) B-6: Potassium stearate (carbon number 18, molecular weight 326) B-7: Magnesium stearate (carbon number 36, molecular weight 591).

[0063] (C) Glass fiber C-1: Chopped strand type glass fiber (fiber diameter 13 μm) The evaluation methods used in the examples and comparative examples are summarized below.

[0064] (1) Laser light transmittance A test piece for evaluating laser beam transmittance was molded as shown in Figure 1. The molding conditions were a cylinder temperature of 260°C and a mold temperature of 80°C. The sprue 1 and runner 2 of the molded piece shown in Figure 1 were cut off at gate 3, and the remaining portion was used as test piece 4 for evaluating laser beam transmittance. A Shimadzu UV-3150 ultraviolet / near-infrared spectrophotometer was used, and an integrating sphere was used as the detector. Transmittance is expressed as the ratio of the amount of transmitted light to the amount of incident light, expressed as a percentage. Measurements were performed at three locations, [1] to [3], as shown in Figure 1. [1] and [3] are located 13 mm inward from the edge of the molded piece, and [2] is located at the center of the molded product. The tables showing the examples and comparative examples show the average light transmittance in the near-infrared 940 nm wavelength region measured at three locations as the laser transmittance, and the transmittance variation percentage, calculated using the following formula, as the laser transmittance variation. Transmittance variation rate = (maximum transmittance value - minimum transmittance value) / average transmittance value x 100.

[0065] (2) Amount of terminal carboxyl groups in polyester resin (A) The laser beam transmittance evaluation test piece described in (1) was dissolved in 1,1,1,3,3,3-hexafluoro-2-propanol and centrifuged to remove insoluble materials, and the resin component was extracted. Approximately 0.4 g of this resin component was dissolved in 20 mL of benzyl alcohol by heating in an oil bath at 100 °C, and then 60 mL of chloroform and 20 mL of benzyl alcohol were gradually added to rapidly cool the solution. Potentiometric titration was then performed using a potentiometric titrator (AT-500N) manufactured by Kyoto Electronics Manufacturing Co., Ltd. with 0.01 mol / L sodium hydroxide benzyl alcohol solution, and the obtained inflection point was used as the endpoint. A blank test was also conducted using the same method, and the amount of terminal carboxyl groups (unit: eq / t) was calculated as the number of moles relative to the weight of polyester resin (A).

[0066] (3) Amount of Metal Component in Polyester Resin Composition The laser beam transmittance evaluation test piece described in (1) was dissolved in 1,1,1,3,3,3-hexafluoro-2-propanol, centrifuged to remove insoluble matter, and the resin component was extracted. This resin component was incinerated, and the incinerated material was dissolved in 6N hydrochloric acid to prepare a solution. Atomic absorption spectroscopy was performed using this solution with a Hitachi High-Tech Science atomic absorption spectrophotometer (ZA3300), and the amount of metal components (unit: eq / t) was calculated as the number of moles relative to the weight of polyester resin (A).

[0067] (4) Tensile strength According to ISO527-1, 2, ISO1A dumbbell test pieces were molded at a cylinder temperature of 260°C and a mold temperature of 80°C. The tensile strength was measured using a tensile testing machine (Autograph AG-50kNXPlus) manufactured by Shimadzu Corporation at a test speed of 5 mm / min.

[0068] (5) Amount of inward warping A box-shaped test piece for evaluating warpage was molded, as shown in Figure 2. The base (square) had a side length L2 of 30 mm, a height H2 of 30 mm, and a thickness D2 of 1.5 mm. The molding conditions were a cylinder temperature of 260°C and a mold temperature of 80°C. The sprue and runner were cut at the pin gate 5, and the remaining portion was used as the warpage evaluation test piece 8. Figure 2(a) is a plan view of the box-shaped molded piece, Figure 2(b) is a side view of the same molded piece, and Figure 2(c) is a detailed view of the plan view of the box-shaped molded piece. The molded piece was left in a 23% and 50% RH environment for 24 hours. The amount of inward tilt of the side surface 6 farthest from the side containing the pin gate 5, i.e., the maximum recession from the original plane, was measured five times using a Mitutoyo Corporation three-dimensional dimension measuring instrument (CRYSTA-Apex S776). The average of the measurements was used to determine the amount of warpage 7.

[0069] [Examples 1 to 11, Comparative Examples 1 to 4] The polyester resin (A), metal salt compound (B), and other raw materials were blended together in the proportions shown in Tables 1 and 2. Glass fiber (D) was fed from a side feeder. The resulting resin composition was melt-kneaded using a twin-screw extruder with an L / D ratio of 45 at a cylinder temperature of 260°C and a rotation speed of 250 rpm to obtain a pelletized resin composition. The resulting resin composition was dried with hot air at 130°C for 3 hours and then injection-molded into various evaluation molded articles using a Sumitomo Heavy Industries SE100DU injection molding machine at a cylinder temperature of 260°C and a mold temperature of 80°C, ensuring that the resin composition remained in the injection molding machine for less than 15 minutes. The evaluations were performed using each evaluation molded article. However, in Comparative Example 2, the drying step for the resin composition was omitted during injection molding, and in Comparative Example 3, the resin composition was allowed to remain in the molding machine for 15 minutes after weighing in the injection molding process before injection molding.

[0070] The evaluation results are shown in Tables 1 and 2. Table 1 shows Examples 1 to 11, and Table 2 shows Comparative Examples 1 to 4.

[0071] [Table 1]

[0072] [Table 2]

[0073] The results in Tables 1 and 2 reveal the following.

[0074] In comparison with Comparative Examples 1 to 4, Examples 1 to 11 were able to obtain polyester resin compositions in which high laser transmittance was highly controlled at different locations in the molded article and excellent dimensional properties were achieved by adjusting the ratio of the metal component amount to the terminal carboxyl group amount in the polyester resin to a specific value. Furthermore, by incorporating specific amounts of polyester resin (A), metal salt compound (B), and glass fiber (C), molded articles with excellent laser transmittance, mechanical properties, and dimensional properties were obtained. More specifically, in Example 1, compared with Comparative Example 1, the ratio of the metal component amount to the terminal carboxyl group amount was within a preferred range, and the metal component was contained within a preferred range relative to the weight of the polyester resin (A). This resulted in excellent crystal nucleation efficiency, and as a result, molded articles with excellent laser transmittance and dimensional properties were obtained. Furthermore, in Example 1, molding was performed under more preferred conditions, and the ratio of the metal component amount to the terminal carboxyl group amount was within a more preferred range, resulting in excellent crystal nucleation efficiency, and as a result, molded articles with excellent laser transmittance, mechanical properties, and dimensional properties were obtained. Compared to Comparative Example 4, Example 11 had a preferable ratio of metal component amount / terminal carboxyl group amount, resulting in superior crystal nucleation efficiency. As a result, molded articles with excellent laser transmittance were obtained. Compared to Example 1, Examples 2, 3, and 4 had a more preferable ratio of metal component amount / terminal carboxyl group amount, resulting in superior crystal nucleation efficiency. As a result, molded articles with excellent laser transmittance and dimensional properties were obtained. Compared to Examples 2 and 3, Example 4 had a particularly preferable ratio of metal component amount / terminal carboxyl group amount, resulting in superior crystal nucleation efficiency. As a result, molded articles with even superior laser transmittance and dimensional properties were obtained. Compared to Examples 7 and 8, Examples 3, 5, and 6 contained a metal salt compound (B) with a more preferable carbon number, which provided excellent affinity with the polyester resin (A), resulting in superior crystal nucleation efficiency. As a result, molded articles with even superior laser transmittance and dimensional properties were obtained.Example 3, compared with Examples 5 and 6, has superior affinity with the polyester resin (A), and by containing a metal salt compound (B) with a more preferred carbon number, has superior crystal nucleation efficiency, and as a result, molded articles with superior mechanical properties were obtained. Examples 3, 5, and 6, compared with Examples 9 and 10, contain a metal salt compound (B) with a more preferred metal species, and therefore have superior crystal nucleation efficiency, and as a result, molded articles with superior laser transmittance, mechanical properties, and dimensional properties were obtained. [Explanation of symbols]

[0075] 1. Sprue 2. Runner 3. Gate 4. Laser light transmittance evaluation test piece 5. Pin Gate 6. Side 7. Amount of inward warping 8. Warpage evaluation test piece

Claims

1. A molded article made of a resin composition containing 30% by weight or more of polybutylene terephthalate (A), wherein the molded article is dissolved in 1,1,1,3,3,3-hexafluoro-2-propanol, centrifuged to remove insoluble components, and about 0.4 g of the extracted resin component is dissolved in 20 mL of benzyl alcohol by heating on an oil bath at 100°C, and then 60 mL of chloroform and 20 mL of benzyl alcohol are gradually added to the solution to rapidly cool the solution, and the solution is subjected to potentiometric titration with a 0.01 mol / L sodium hydroxide benzyl alcohol solution to obtain a polyester. A molded article made of a polyester resin composition, characterized in that the ratio expressed as the amount of metal components / the amount of terminal carboxyl groups is 0.50 or more, where the amount of terminal carboxyl groups (unit: eq / t) of polybutylene terephthalate (A) is calculated as the number of moles relative to the weight of resin (A) and the amount of metal components (unit: eq / t) contained in the resin composition is calculated as the number of moles relative to the weight of polyester resin (A) by performing atomic absorption spectrometry using a solution prepared by incinerating the resin component and dissolving the incinerated material in 6N hydrochloric acid.

2. The method for producing a molded article according to claim 1, wherein the polyester resin composition is dried at 100°C or higher for 3 hours or more and then molded.

3. The method for producing a molded article according to claim 1, wherein the polyester resin composition is molded for a molten residence time of less than 15 minutes.

4. A composite molded article obtained by laser welding the molded article according to claim 1.

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