Polyalkylene terephthalate resin composition for injection molding, and injection molded articles

Abstract

To provide a polyalkylene terephthalate resin composition that allows for reduced mold deposits while having improved hydrolytic stability, and a molded article made therefrom.SOLUTION: The present disclosure pertains to a polyalkylene terephthalate resin composition that contains 100 pts.mass of a polyalkylene terephthalate resin (A) and 0.10-10 pts.mass of an epoxy compound (B) that has a number average molecular weight of 1000 or less, the number of epoxy groups of 1-2 per molecule, and satisfies formula (1): (M×2)+N≤6 . In the formula (1), M represents the number of epoxy groups per one molecule of the epoxy compound (B), and N represents the number of hydroxyl groups per one molecule of the epoxy compound (B).SELECTED DRAWING: None

Description

[Technical Field]

[0001] Embodiments of the present invention relate to a polyalkylene terephthalate resin composition for injection molding and an injection molded article. [Background technology]

[0002] Polyalkylene terephthalate resins are used in many applications because they possess excellent properties such as heat resistance, chemical resistance, electrical properties, mechanical properties, and moldability. However, because polyalkylene terephthalate resins contain ester groups within their molecules, they tend to deteriorate in physical properties due to hydrolysis in high-temperature and high-humidity environments. Methods to improve the hydrolysis resistance of polyalkylene terephthalate resins include, for example, adding compounds containing epoxy groups, oxazoline groups, or carbodiimide groups, or adding elastomers containing glycidyl groups.

[0003] On the other hand, if deposits called mold deposits form on the mold surface in the cavity, it can impair the appearance of the molded product. If mold deposits adhere to gas vents, the gases generated during molding may not be able to be released, potentially causing gas burning. Furthermore, if mold deposits adhere to thin-walled areas, resin may not be able to fill them properly. For these reasons, mold deposits can lead to decreased productivity, such as requiring more frequent mold cleaning.

[0004] Patent Document 1 describes the addition of a glycidyl group-containing copolymer, in which α-olefin and α,β-unsaturated acid glycidyl esters are copolymer components, to a composition containing polybutylene terephthalate and polycarbonate, as a component that has the effect of improving the impact resistance of molded articles and suppressing hydrolysis. Patent Document 1 also describes that the amount of polycarbonate added should be in the range of 52 to 95 parts by weight per 100 parts by weight of the total amount of polybutylene terephthalate and polycarbonate, and that if the amount of polycarbonate added is less than a predetermined amount, mold deposits are likely to occur. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-26449 [Overview of the project] [Problems that the invention aims to solve]

[0006] Patent Document 1 describes a composition containing polycarbonate, but because polycarbonate has ester bonds, its physical properties tend to deteriorate easily due to hydrolysis. The embodiments of the present invention aim to provide a polyalkylene terephthalate resin composition that can reduce the generation of mold deposits while improving hydrolysis resistance, and a molded article obtained using the same. [Means for solving the problem]

[0007] One embodiment of the present invention relates to a polyalkylene terephthalate resin composition for injection molding, comprising (A) 100 parts by mass of a polyalkylene terephthalate resin and (B) 0.10 to 10 parts by mass of an epoxy compound having a number average molecular weight of 1000 or less, 1 to 2 epoxy groups per molecule, and satisfying the following formula (1). (M×2)+N≦6 Formula (1) (In formula (1), M represents the number of epoxy groups in one molecule of the epoxy compound (B), and N represents the number of hydroxyl groups in one molecule of the epoxy compound (B).) Another embodiment of the present invention relates to an injection-molded article obtained using the polyalkylene terephthalate resin composition for injection molding of the above embodiment. [Effects of the Invention]

[0008] According to embodiments of the present invention, it is possible to provide a polyalkylene terephthalate resin composition that can reduce the generation of mold deposits while improving hydrolysis resistance, and a molded article obtained using the same. [Modes for carrying out the invention]

[0009] Preferred embodiments of the present invention are described below, but the present invention is not limited to the embodiments described below.

[0010] <Polyalkylene terephthalate resin composition for injection molding> A polyalkylene terephthalate resin composition for injection molding according to an embodiment of the present invention (hereinafter also referred to as "polyalkylene terephthalate resin composition") comprises at least (A) a polyalkylene terephthalate resin and (B) an epoxy compound. The polyalkylene terephthalate resin composition according to an embodiment of the present invention can be preferably used for injection molding.

[0011] [(A) Polyalkylene terephthalate resin] (A) Polyalkylene terephthalate resin is a thermoplastic polyester resin obtained by the reaction of a dicarboxylic acid component mainly composed of a dicarboxylic acid compound and / or its ester-forming derivative with a diol component mainly composed of a diol compound and / or its ester-forming derivative, wherein the dicarboxylic acid component mainly consists of terephthalic acid and / or its ester-forming derivative, and the diol component mainly consists of alkylene glycol and / or its ester-forming derivative. (A) As for the polyalkylene terephthalate resin, copolyesters can also be used that combine dicarboxylic acid components and diol components other than the main component, as well as other copolymerizable monomers such as oxycarboxylic acid components and lactone components (hereinafter sometimes referred to as copolymerizable monomers).

[0012] Other dicarboxylic acid components besides the main component include, for example, aliphatic dicarboxylic acids (e.g., succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, hexadecanedicarboxylic acid, dimer acid, etc.). 4-40 A dicarboxylic acid of a certain degree, preferably C 4-14Dicarboxylic acids of a certain degree, alicyclic dicarboxylic acids (e.g., hexahydrophthalic acid, hexahydroisophthalic acid, hexahydroterephthalic acid, hymic acid, etc.) 4-40 A dicarboxylic acid of a certain degree, preferably C 8-12 Aromatic dicarboxylic acids other than terephthalic acid (e.g., phthalic acid, isophthalic acid, methylisophthalic acid, methylterephthalic acid, naphthalenedicarboxylic acids such as 2,6-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 4,4'-diphenoxyetherdicarboxylic acid, 4,4'-dioxybenzoic acid, 4,4'-diphenylmethanedicarboxylic acid, 4,4'-diphenylketonedicarboxylic acid, etc.) 8-16 Examples include dicarboxylic acids of a certain degree, or derivatives thereof (e.g., ester-forming derivatives such as lower alkyl esters, aryl esters, and acid anhydrides). Preferred dicarboxylic acid components for use in combination with terephthalic acid include isophthalic acid and naphthalenedicarboxylic acid, and two or more of these can be used in combination. However, it is preferable that 50 mol% or more, more preferably 80 mol% or more, and particularly preferably 90 mol% or more of the total dicarboxylic acid component as copolymerizable monomer is an aromatic dicarboxylic acid compound. Furthermore, if necessary, polycarboxylic acids such as trimellitic acid and pyromellitic acid, or their ester-forming derivatives (alcohol esters, etc.) may be used in combination. By using such polyfunctional compounds in combination, branched polyalkylene terephthalate resins can also be obtained.

[0013] Other diol components besides the main component include aliphatic alkanediols (e.g., ethylene glycol, trimethylene glycol, propylene glycol, 1,4-butanediol, 1,3-butanediol, neopentyl glycol, hexanediol, octanediol, decanediol, etc.). 2-12 A certain degree of aliphatic diol, preferably C 2-10 Among the aliphatic diols of a certain degree, aliphatic alkanediols other than those used as the main component), polyoxyalkylene glycol (C 2-4Glycols having a plurality of oxyalkylene units, such as diethylene glycol, dipropylene glycol, ditetramethylene glycol, triethylene glycol, tripropylene glycol, polytetramethylene glycol, etc., alicyclic diols (such as 1,4 - cyclohexanediol, 1,4 - cyclohexanedimethanol, hydrogenated bisphenol A, etc.) and the like can be mentioned. Further, aromatic diols such as hydroquinone, resorcinol, bisphenol, 2,2 - bis(4 - hydroxyphenyl)propane, 2,2 - bis-(4-(2 - hydroxyethoxy)phenyl)propane, xylylene glycol and the like may be used in combination. However, preferably 50 mol% or more, more preferably 80 mol% or more, and particularly preferably 90 mol% or more of the total diol component as the copolymerizable monomer is alkylene glycol. Further, if necessary, polyols such as glycerin, trimethylolpropane, trimethylolethane, pentaerythritol or their ester - forming derivatives may be used in combination. By using such polyfunctional compounds in combination, a branched thermoplastic polyester resin can also be obtained.

[0014] The oxycarboxylic acid (or oxycarboxylic acid component or oxycarboxylic acids) includes, for example, oxycarboxylic acids such as oxybenzoic acid, oxynaphthoic acid, hydroxyphenylacetic acid, glycolic acid, oxycaproic acid or their derivatives and the like. The lactones include C 3-12 lactones such as propiolactone, butyrolactone, valerolactone, caprolactone (such as ε - caprolactone, etc.) and the like.

[0015] In copolyesters, the proportion of copolymerizable monomers can be selected from a range of, for example, 0.01 mol% to 30 mol%, and is usually 1 mol% to 25 mol%, preferably 3 mol% to 20 mol%, and more preferably 5 mol% to 15 mol%. When homopolyesters and copolyesters are used in combination, the ratio of homopolyesters to copolyesters is in a range where the proportion of copolymerizable monomers is 0.01 mol% to 30 mol% (preferably 1 mol% to 25 mol%, more preferably 3 mol% to 20 mol%, and particularly preferably 5 mol% to 15 mol%) relative to the total monomers, and can usually be selected from a range of former / latter = 99 / 1 to 1 / 99 (mass ratio), preferably 95 / 5 to 5 / 95 (mass ratio), and more preferably 90 / 10 to 10 / 90 (mass ratio).

[0016] Preferred polyalkylene terephthalate resins include homopolyesters or copolyesters having alkylene terephthalate units as the main component (for example, 50 to 100 mol%, preferably about 75 to 100 mol%) [for example, polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), etc.]. 2-4 This includes homopolyesters such as alkylene terephthalate, copolyesters that mainly consist of alkylene terephthalate units and contain alkylene isophthalate units as copolymer components, and copolyesters that mainly consist of alkylene terephthalate units and contain alkylene naphthalate units as copolymer components, and these can be used individually or in combination of two or more.

[0017] Particularly preferred polyalkylene terephthalate resins include C13, ethylene terephthalate, trimethylene terephthalate, tetramethylene terephthalate, etc. 2-4A homopolyester resin or copolyester resin containing 80 mol% or more (particularly 90 mol% or more) of alkylene terephthalate units (for example, polyethylene terephthalate resin, polytrimethylene terephthalate resin, polybutylene terephthalate resin, isophthalic acid-modified polyethylene terephthalate resin, isophthalic acid-modified polytrimethylene terephthalate resin, isophthalic acid-modified polybutylene terephthalate resin, naphthalenedicarboxylic acid-modified polyethylene terephthalate resin, naphthalenedicarboxylic acid-modified polytrimethylene terephthalate resin, naphthalenedicarboxylic acid-modified polybutylene terephthalate resin, etc.).

[0018] Among these, polyethylene terephthalate resin and polybutylene terephthalate resin are preferred, and polybutylene terephthalate resin is particularly preferred.

[0019] (A) The amount of terminal carboxyl groups in the polyalkylene terephthalate resin is not particularly limited as long as it does not inhibit the effects of the present invention. From the viewpoint of hydrolysis resistance, the amount of terminal carboxyl groups in the (A) polyalkylene terephthalate resin is preferably 30 meq / kg or less, and more preferably 25 meq / kg or less.

[0020] (A) The intrinsic viscosity (IV) of the polyalkylene terephthalate resin is not particularly limited as long as it does not impede the effects of the present invention. (A) The intrinsic viscosity of the polyalkylene terephthalate resin is preferably 0.6 to 1.3 dL / g, and more preferably 0.7 to 1.2 dL / g. When a polyalkylene terephthalate resin with an intrinsic viscosity in this range is used, the resulting polyalkylene terephthalate resin composition will have particularly excellent moldability. Furthermore, the intrinsic viscosity can be adjusted by blending polyalkylene terephthalate resins having different intrinsic viscosities. For example, a polyalkylene terephthalate resin with an intrinsic viscosity of 0.9 dL / g can be prepared by blending a polyalkylene terephthalate resin with an intrinsic viscosity of 1.0 dL / g and a polyalkylene terephthalate resin with an intrinsic viscosity of 0.8 dL / g. The intrinsic viscosity (IV) of the polyalkylene terephthalate resin can be measured, for example, in o-chlorophenol at a temperature of 35°C.

[0021] (A) The polyalkylene terephthalate resin may be a commercially available product, or it may be a product prepared by copolymerizing (polycondensing) a dicarboxylic acid component or its reactive derivative with a diol component or its reactive derivative and a copolymerizable monomer as needed by conventional methods, such as transesterification or direct esterification.

[0022] [(B) Epoxy compounds] (B) As the epoxy compound, use an epoxy compound that has a number-average molecular weight of 1000 or less, has 1 to 2 epoxy groups per molecule, and satisfies the following formula (1). (M×2)+N≦6 Formula (1) In formula (1), M represents the number of epoxy groups in one molecule of the epoxy compound, and N represents the number of hydroxyl groups in one molecule of the epoxy compound.

[0023] It is known that epoxy compounds, carbodiimide compounds, and elastomers containing glycidyl groups are added to polyalkylene terephthalate resins to improve hydrolysis resistance, but when such compounds are used, mold deposits may occur. For example, elastomers containing glycidyl groups tend to have a high affinity for metals and may adhere to molds, causing mold deposits. When an epoxy compound having a number average molecular weight of 1000 or less, 1 to 2 epoxy groups per molecule, and satisfying formula (1) is added to a polyalkylene terephthalate resin composition in an amount of 0.10 to 10 parts by mass per 100 parts by mass of (A) polyalkylene terephthalate resin, hydrolysis resistance can be improved and the occurrence of mold deposits can be reduced.

[0024] From the viewpoint of reducing mold deposits, (M×2)+N in equation (1) is preferably 6 or less, and more preferably 4 or less.

[0025] From the viewpoint of reducing mold deposits, (B) the epoxy compound is preferably such that it has 1 to 2 epoxy groups per molecule. From the viewpoint of hydrolysis resistance, it is more preferable that the epoxy compound (B) has two epoxy groups per molecule.

[0026] From the viewpoint of reducing mold deposits, (B) the epoxy compound preferably has 2 or fewer hydroxyl groups per molecule, more preferably 1 or fewer, and even more preferably contains no hydroxyl groups.

[0027] (B) The number-average molecular weight of the epoxy compound is preferably 1000 or less, more preferably 800 or less, and even more preferably 700 or less, from the viewpoint of reducing mold deposits. (B) The number-average molecular weight of the epoxy compound is preferably 100 or more, more preferably 150 or more, and even more preferably 200 or more. (B) The number-average molecular weight of the epoxy compound is preferably 100 to 1000, more preferably 150 to 800, and even more preferably 200 to 700. The number-average molecular weight of the epoxy compound can be determined in terms of polystyrene by gel permeation chromatography (GPC).

[0028] (B) The epoxy compound is not particularly limited as long as it has a number-average molecular weight of 1000 or less, has 1 to 2 epoxy groups in one molecule, and satisfies formula (1). As the affinity with metal and the melting point increase, mold deposits tend to form more easily. From this viewpoint, non-aromatic epoxy compounds are preferred as the (B) epoxy compound. Non-aromatic epoxy compounds refer to non-aromatic epoxy compounds that do not contain aromatic rings in the molecule. From the viewpoint of the affinity of the hydroxyl group formed after the reaction between the epoxy compound and the carboxylic acid terminus of the polyalkylene terephthalate resin to metal, alicyclic epoxy compounds are more preferred as non-aromatic epoxy compounds. As alicyclic epoxy compounds, for example, compounds containing a cycloalkene oxide structure are preferred. A cycloalkene oxide structure is a structure in which two adjacent carbon atoms among the atoms constituting an aliphatic ring form an epoxy group together with an oxygen atom, such as a cyclohexene oxide structure or a cyclopentene oxide structure. Alicyclic epoxy compounds preferably contain 1 to 2 cycloalkene oxide structures in one molecule, and more preferably 2.

[0029] (B) Examples of epoxy compounds include polytetramethylene glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, ethylhexyl glycidyl ether, 1,4-cyclohexanedimethanol diglycidyl ether, tripropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, bisphenol A type epoxy resin, and other glycidyl ether compounds; Glycidyl ester compounds such as diglycidyl terephthalate; Glycidylimide compounds such as N-glycidylphthalimide; Examples include alicyclic epoxy compounds such as 2,2-bis(3',4'-epoxycyclohexyl)propane and 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate. Among these, non-aromatic epoxy compounds such as polytetramethylene glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, ethylhexyl glycidyl ether, 1,4-cyclohexanedimethanol diglycidyl ether, tripropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, 2,2-bis(3',4'-epoxycyclohexyl)propane, 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate are preferred.

[0030] (B) As the epoxy compound, only one compound may be used, or two or more compounds may be used in any combination.

[0031] The amount of epoxy groups in the (B) epoxy compound is not particularly limited. From the viewpoint of hydrolysis resistance, the amount of epoxy groups in the (B) epoxy compound relative to the total amount of the polyalkylene terephthalate resin composition is preferably 7 mmol / kg or more, more preferably 12 mmol / kg or more, and even more preferably 15 mmol / kg or more. On the other hand, from the viewpoint of reducing mold deposits, the amount of epoxy groups in the (B) epoxy compound relative to the total amount of the polyalkylene terephthalate resin composition is preferably 50 mmol / kg or less, more preferably 40 mmol / kg or less, and even more preferably 30 mmol / kg or less. The amount of epoxy groups in the (B) epoxy compound relative to the total amount of the polyalkylene terephthalate resin composition is preferably 7 to 50 mmol / kg, more preferably 12 to 40 mmol / kg, and even more preferably 15 to 30 mmol / kg.

[0032] (B) The amount of hydroxyl groups in the epoxy compound is not particularly limited. From the viewpoint of reducing mold deposits, the amount of hydroxyl groups in the epoxy compound (B) relative to the total amount of the polyalkylene terephthalate resin composition is preferably 40 mmol / kg or less, more preferably 30 mmol / kg or less, and even more preferably 10 mmol / kg or less.

[0033] In the polyalkylene terephthalate resin composition, the content of (B) epoxy compound is preferably 0.10 to 10 parts by mass, more preferably 0.12 to 5 parts by mass, and even more preferably 0.15 to 2 parts by mass, per 100 parts by mass of (A) polyalkylene terephthalate resin.

[0034] From the viewpoint of hydrolysis resistance, the content of (B) epoxy compound is preferably 0.10 parts by mass or more, more preferably 0.12 parts by mass or more, and even more preferably 0.15 parts by mass or more, per 100 parts by mass of (A) polyalkylene terephthalate resin. On the other hand, from the viewpoint of reducing mold deposits, the content of (B) epoxy compound is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 2 parts by mass or less, per 100 parts by mass of (A) polyalkylene terephthalate resin.

[0035] [Other ingredients] The polyalkylene terephthalate resin composition may optionally contain other components besides those listed above. These other components may include other resins, fillers such as inorganic fillers (described later), antioxidants, stabilizers, antistatic agents, lubricants, plasticizers, nucleating agents, colorants, flame retardants, flame retardant enhancers, and other additives. One or more of these may be included as needed.

[0036] The polyalkylene terephthalate resin composition may contain inorganic fillers. The inclusion of inorganic fillers can improve mechanical properties and heat resistance. Furthermore, it can reduce the molding shrinkage rate and coefficient of thermal expansion of the polyalkylene terephthalate resin composition.

[0037] Examples of inorganic fillers include fibrous inorganic fillers [e.g., glass fibers, asbestos fibers, silica fibers, alumina fibers, silica-alumina fibers, zirconia fibers, boron nitride fibers, silicon nitride fibers, boron fibers, potassium titanate fibers, silicon carbide fibers, whiskers (whiskers such as alumina and silicon nitride)], plate-shaped inorganic fillers [e.g., talc, mica, glass flakes, graphite], and powder-shaped inorganic fillers [e.g., glass beads, glass powder, milled fibers (milled fibers such as glass), wollastonite]. Among these inorganic fillers, glass-based fillers (glass fibers, glass flakes, glass beads, etc.), talc, mica, and wollastonite are preferred, and glass fibers are particularly suitable due to their availability, strength, and rigidity. Plate-shaped and powder-shaped fillers are also suitable for use in suppressing the anisotropy of the molding shrinkage rate and linear expansion coefficient of the polyalkylene terephthalate resin composition. When using these fillers, known surface treatment agents may be used as needed.

[0038] When using fibrous fillers as inorganic fillers, their shape is not particularly limited, but for example, the length is about 100 μm to 5 mm, more preferably 500 μm to 3 mm, and the diameter is, for example, about 1 to 50 μm, more preferably 3 to 30 μm. When using plate-shaped or powder-shaped fillers, their average particle size is also not particularly limited, but for example, it is about 0.1 to 100 μm, more preferably 0.1 to 50 μm. These fillers can be used individually or in combination of two or more.

[0039] When a polyalkylene terephthalate resin composition contains an inorganic filler, from the viewpoint of improving mechanical properties, the content of the inorganic filler is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 20 parts by mass or more, per 100 parts by mass of the polyalkylene terephthalate resin. On the other hand, from the viewpoint of toughness, the content of the inorganic filler is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, and even more preferably 80 parts by mass or less, per 100 parts by mass of the polyalkylene terephthalate resin. When a polyalkylene terephthalate resin composition contains an inorganic filler, the content of the inorganic filler is preferably, for example, 5 to 100 parts by mass, more preferably 10 to 90 parts by mass, and even more preferably 20 to 80 parts by mass, per 100 parts by mass of the polyalkylene terephthalate resin.

[0040] <Method for producing polyalkylene terephthalate resin composition> The method for producing the polyalkylene terephthalate resin composition is not particularly limited. The polyalkylene terephthalate resin composition can be produced by various methods known as methods for producing thermoplastic resin compositions.

[0041] In one embodiment, a method for producing a polyalkylene terephthalate resin composition includes melt-kneading the above-described (A) polyalkylene terephthalate resin and the above-described (B) epoxy compound. In this melt-kneading step, at least (A) polyalkylene terephthalate resin and (B) epoxy compound can be melt-kneaded. In the melt-kneading step, for example, (A) polyalkylene terephthalate resin and (B) epoxy compound, and optionally other components such as inorganic fillers can be melt-kneaded. These components may be melt-kneaded together or in separate steps, or the other components may be added after melt-kneading (A) polyalkylene terephthalate resin and (B) epoxy compound to produce the composition.

[0042] A suitable method for producing a polyalkylene terephthalate resin composition is, for example, a method in which each component is melt-kneaded using a melt-kneading device such as a single-screw or twin-screw extruder and then extruded into pellets.

[0043] <Injection molded products> One embodiment of the present invention relates to an injection-molded article obtained using the above-described polyalkylene terephthalate resin composition.

[0044] There are no particular limitations on the method for obtaining injection-molded articles using a polyalkylene terephthalate resin composition, and known methods can be employed. For example, the polyalkylene terephthalate resin composition can be put into an extruder, melt-kneaded and extruded to form pellets, and these pellets can be put into an injection molding machine equipped with a predetermined mold and injected to produce the articles.

[0045] Embodiments of the present invention include, but are not limited to, the following embodiments. <1> A polyalkylene terephthalate resin composition for injection molding, comprising (A) 100 parts by mass of polyalkylene terephthalate resin and (B) 0.10 to 10 parts by mass of an epoxy compound having a number average molecular weight of 1000 or less, 1 to 2 epoxy groups per molecule, and satisfying the following formula (1). (M×2)+N≦6 Formula (1) (In formula (1), M represents the number of epoxy groups in one molecule of the epoxy compound (B), and N represents the number of hydroxyl groups in one molecule of the epoxy compound (B).) <2> The epoxy compound (B) is a non-aromatic epoxy compound. <1> The polyalkylene terephthalate resin composition described above. <3> The epoxy compound (B) is an alicyclic epoxy compound. <2> The polyalkylene terephthalate resin composition described above. <4> The epoxy compound (B) has 2 epoxy groups in one molecule. <1> ~ <3> A polyalkylene terephthalate resin composition according to any one of the items. <5> Further containing inorganic fillers, <1> ~ <4> A polyalkylene terephthalate resin composition according to any one of the items. <6> <1> ~ <5> An injection-molded article obtained using the polyalkylene terephthalate resin composition described in any one of the items. [Examples]

[0046] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0047] <Manufacturing of polyalkylene terephthalate resin composition> Tables 1 and 2 below show the compositions of the polyalkylene terephthalate resin compositions for each example and comparative example. The components shown in Tables 1 and 2 below were mixed in the parts (parts by mass) shown in Tables 1 and 2 below, and the mixture was melt-kneaded and extruded in a twin-screw extruder (TEX30, manufactured by Japan Steel Works Ltd.) with a 30 mmφ screw at a cylinder temperature of 260°C and a screw rotation speed of 130 rpm to obtain a pellet-shaped polyalkylene terephthalate resin composition. Details of each component in the table are as follows:

[0048] (1) Polyalkylene terephthalate resin A-1: Polybutylene terephthalate (PBT) resin manufactured by Polyplastics Co., Ltd. (Intrinsic viscosity: 0.88 dL / g)

[0049] (2) Epoxy compounds B-1: 2,2-bis(3',4'-epoxycyclohexyl)propane (molecular weight 236) B-2: Polytetramethylene glycol diglycidyl ether (number average molecular weight approximately 830) B-3: Mitsubishi Chemical Corporation's "Epicote 1001" (Bisphenol A type epoxy resin, number average molecular weight approximately 900) B-4: Mitsubishi Chemical Corporation's "Epicote 1004" (Bisphenol A type epoxy resin, number average molecular weight approximately 1650)

[0050] (3) Carbodiimide B-5: Stabaxol P-100 (aromatic carbodiimide compound) manufactured by Lanxess. (4) EGMA (ethylene-glycidyl methacrylate copolymer) B-6: Bondfast 2C (ethylene-glycidyl methacrylate copolymer) manufactured by Sumitomo Chemical Co., Ltd.

[0051] (5) Stabilizers C: Irganox 1010 manufactured by BASF Japan Ltd. D: ADEKA Corporation's "ADEKA Stub AO-412S" E: ADEKA Corporation's "ADEKA Stub PEP-36" F: Potassium acetate

[0052] (6) Lubricant G: "B-74" (diglycerin fatty acid ester) manufactured by Riken Vitamin Co., Ltd.

[0053] The units for the content of each component in Tables 1 and 2 are parts by mass.

[0054] <Rating> The following evaluations were performed using the obtained polyalkylene terephthalate resin composition pellets.

[0055] (1) Mold deposit test The polyalkylene terephthalate resin composition pellets obtained in each example and comparative example above were dried at 140°C for 3 hours. Then, using an injection molding machine (J55AD, manufactured by Japan Steel Works Ltd.), 1000 test pieces measuring 40 mm × 40 mm × 2 mmt were molded at a mold temperature of 120°C. Subsequently, the mold deposits on the mold surface were evaluated by visual inspection according to the following criteria. A: No mold deposits are observed on the mold surface. B: Some mold deposits are observed on the mold surface. C: Significant mold deposits are observed on the mold surface.

[0056] (2) Hydrolysis resistance The polyalkylene terephthalate resin composition pellets obtained in each of the above examples and comparative examples were dried at 140°C for 3 hours. Then, multipurpose test specimens were prepared in accordance with ISO 3167 by injection molding under conditions of a cylinder temperature of 260°C and a mold temperature of 80°C. The initial tensile strength (MPa) was measured using a Shimadzu Autograph universal testing machine in accordance with ISO 527-1,2. The test specimens obtained above were subjected to a pressure cooker test (PCT) at 121°C and 100% RH for 48 hours (moist heat treatment). After treatment, the tensile strength (MPa) was measured in the same manner as described above, and the retention rate (%) of the tensile strength after moist heat treatment relative to the initial value was calculated from the measured value and the initial value. The results are shown in Tables 1 and 2.

[0057] [Table 1]

[0058] [Table 2]

[0059] As shown in Table 1, Examples 1 to 4 showed excellent results in the mold deposit test, with either no mold deposits observed on the mold surface or only slight mold deposits observed. Furthermore, Examples 1 to 4 also exhibited good hydrolysis resistance. In contrast, in Comparative Example 1, which used a polyalkylene terephthalate resin composition containing an epoxy compound with a number-average molecular weight greater than 1000 and which does not satisfy formula (1) (i.e., the value of "(M×2)+N" is greater than 6); Comparative Example 2, which used a composition containing a carbodiimide compound; and Comparative Example 3, which used an ethylene-glycidyl methacrylate copolymer, an elastomer having a glycidyl group, all of these results showed significant mold deposits on the mold surface in the mold deposit test. Comparative Example 4, which used a polyalkylene terephthalate resin composition that did not contain epoxy compounds and neither carbodiimide compounds nor ethylene-glycidyl methacrylate copolymers, and Comparative Example 5, which used a polyalkylene terephthalate resin composition with a low epoxy compound content, both exhibited poor hydrolysis resistance.

Claims

1. A polyalkylene terephthalate resin composition for injection molding, comprising (A) 100 parts by mass of polyalkylene terephthalate resin and (B) 0.10 to 1.09 parts by mass of an epoxy compound having a number average molecular weight of 1000 or less, 1 to 2 epoxy groups per molecule, and satisfying the following formula (1), wherein the epoxy compound (B) is at least one selected from the group consisting of polytetramethylene glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, ethylhexyl glycidyl ether, 1,4-cyclohexanedimethanol diglycidyl ether, tripropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, and 2,2-bis(3',4'-epoxycyclohexyl)propane. (M×2)+N≦6 Formula (1) (In formula (1), M represents the number of epoxy groups in one molecule of the epoxy compound (B), and N represents the number of hydroxyl groups in one molecule of the epoxy compound (B).)

2. A polyalkylene terephthalate resin composition for injection molding, comprising (A) 100 parts by mass of a polyalkylene terephthalate resin and (B) 0.10 to 10 parts by mass of an epoxy compound having a number average molecular weight of 1000 or less, 1 to 2 epoxy groups per molecule, and satisfying the following formula (1), wherein the epoxy compound (B) is 2,2-bis(3',4'-epoxycyclohexyl)propane. (M×2)+N≦6 Formula (1) (In formula (1), M represents the number of epoxy groups in one molecule of the epoxy compound (B), and N represents the number of hydroxyl groups in one molecule of the epoxy compound (B).)

3. The polyalkylene terephthalate resin composition for injection molding according to claim 2, wherein the amount of the epoxy compound (B) is 0.10 to 1.09 parts by mass per 100 parts by mass of the polyalkylene terephthalate resin.

4. The polyalkylene terephthalate resin composition for injection molding according to claim 1, wherein the number of epoxy groups in one molecule of the epoxy compound (B) is 2.

5. A polyalkylene terephthalate resin composition for injection molding according to any one of claims 1 to 4, further comprising an inorganic filler.

6. An injection-molded article obtained using the polyalkylene terephthalate resin composition for injection molding described in any one of claims 1 to 5.

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