Polyester resin composition, molded article, and impact-absorbing member for vehicle

Abstract

To provide a polyester resin composition employing a PCR plastic as a recyclable raw material meeting European ELV regulations, the composition enabling realization of high toughness and superior hydrolysis resistance.SOLUTION: A polyester resin composition comprising (A) 5 to 75 pts.mass of polybutylene terephthalate and (B) 25 to 95 pts.mass of polycarbonate, wherein 25 to 100 wt.% of the (B) polycarbonate is (C) a recycled polycarbonate, and the (A) polybutylene terephthalate and (B) polycarbonate form a phase-separated structure having a structural period of 0.01 to 1 μm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyester resin composition having excellent toughness and hydrolysis resistance, a molded article, and a vehicle impact absorbing component. [Background technology]

[0002] Polybutylene terephthalate (hereinafter sometimes abbreviated as PBT) has excellent electrical properties, chemical resistance, heat resistance, dimensional stability, etc., and is therefore widely used as a material for manufacturing various electrical and electronic equipment parts, interior and exterior parts for vehicles such as automobiles, trains, and electric trains, and other general industrial products.

[0003] Furthermore, in automotive parts that require high toughness and impact absorption, such as door handles and vehicle impact absorbing components, alloys with amorphous resins such as polycarbonate are often used. By using an alloy of PBT, a crystalline resin, and polycarbonate, an amorphous resin, the high impact strength required for vehicle impact absorbing components can be achieved.

[0004] However, unlike metal parts such as steel and aluminum, these conventional plastic parts have limitations on the amount of recycled materials they can use. For this reason, the European Commission's proposed regulations on sustainability requirements for automotive design and end-of-life vehicle (ELV) management call for at least 25% of plastics installed in vehicles to be PCR (post-consumer recycled: collecting and recycling products after use in the market) plastics by 2030. Furthermore, 25% of PCR plastics (6.25% of the total) must be made from plastic materials derived from end-of-life vehicles, creating a demand for plastic parts made from recycled materials.

[0005] Patent Document 1 describes a thermoplastic resin composition that can give molded articles that are excellent in moist heat resistance and impact resistance, and in particular discloses its application to automobile impact absorbing components.

[0006] On the other hand, Patent Document 2 discloses a resin composition that uses recycled raw materials and is environmentally friendly, and that can be laser welded and / or laser marked. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-189729 [Patent Document 2] Japanese Patent Application Publication No. 2023-114412 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the physical properties of PCR plastics deteriorate during commercial use, and these conventional technologies therefore have the problem of deteriorating the physical properties of resin compositions made from recycled PCR plastics.

[0009] Therefore, the object of the present invention is to address the problems in the conventional technology as described above, and to provide a polyester resin composition that uses recycled PCR plastics that comply with European ELV regulations as raw materials and has high toughness and hydrolysis resistance. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention comprises the following configuration. (1) A polyester resin composition comprising 5 to 75 parts by weight of (A) polybutylene terephthalate and 25 to 95 parts by weight of (B) polycarbonate, wherein 25 to 100% by weight of the (B) polycarbonate is (C) recycled polycarbonate, and the (A) polybutylene terephthalate and the (B) polycarbonate form a phase-separated structure, with a structural period of 0.01 to 1 μm. (2) The polyester resin composition according to (1), further comprising 0.005 to 0.5 parts by weight of (D) a phosphorus-based stabilizer, based on 100 parts by weight of the total of (A) polybutylene terephthalate and (B) polycarbonate. (3) The polyester resin composition according to (1) or (2), further comprising 0.01 to 1.0 parts by weight of (E) a hindered phenol-based antioxidant, based on 100 parts by weight of the total of (A) polybutylene terephthalate and (B) polycarbonate. (4) The polyester resin composition according to any one of (1) to (3), further comprising 0.01 to 1.0 parts by weight of (F) a sulfur-based antioxidant, based on 100 parts by weight of the total of (A) polybutylene terephthalate and (B) polycarbonate. (5) A molded article obtained by molding the polyester resin composition according to any one of (1) to (4). (6) A shock-absorbing component for a vehicle, which is obtained by molding the polyester resin composition according to any one of (1) to (4). [Effects of the Invention]

[0011] The polyester resin composition of the present invention can be used to obtain molded articles that are particularly compliant with the European ELV regulations and have excellent toughness and hydrolysis resistance. Therefore, molded articles made from the polyester resin composition of the present invention are useful as impact-absorbing components for vehicles. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below.

[0013] <Polybutylene terephthalate> The polybutylene terephthalate (A) used in the present invention is a polymer obtained by a conventional polymerization method such as polycondensation reaction from raw materials containing terephthalic acid or its ester-forming derivative and 1,4-butanediol or its ester-forming derivative as the main components. Other copolymerization components may be copolymerized within a range that does not impair the properties, for example, within a range of about 20% by weight or less of the raw materials. Examples of other copolymerization components include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, bis(p-carboxyphenyl)methane, anthracenedicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 5-tetrabutylphosphonium isophthalate, 5-sodium sulfoisophthalic 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; alicyclic dicarboxylic acids such as 1,3-cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid; and ester-forming derivatives thereof. Other examples include aliphatic diols such as aliphatic glycols having 2 to 20 carbon atoms, such as ethylene glycol, propylene glycol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, decamethylene glycol, 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; alicyclic diols such as cyclohexanedimethanol and cyclohexanediol; aromatic diols such as 4,4'-dihydroxybiphenyl, hydroquinone, t-butylhydroquinone, bisphenol A, bisphenol S, bisphenol F, and bisphenol C; and ester-forming derivatives thereof.

[0014] Preferred examples of (A) polybutylene terephthalate include polybutylene terephthalate, polybutylene (terephthalate / isophthalate), polybutylene (terephthalate / adipate), polybutylene (terephthalate / sebacate), polybutylene (terephthalate / decanedicarboxylate), polybutylene (terephthalate / naphthalate), and poly(butylene / ethylene) terephthalate. Here, " / " indicates a copolymer. Two or more of these may be blended.

[0015] The polybutylene terephthalate (A) used in the present invention preferably has an intrinsic viscosity in the range of 0.60 to 1.60 dL / g when measured in an o-chlorophenol solution at 25°C. If the intrinsic viscosity is 0.60 dL / g or higher, molded articles with more excellent mechanical properties such as tensile strength, flexural strength, flexural modulus, and impact resistance can be obtained. 0.80 dL / g or higher is more preferable. On the other hand, if the intrinsic viscosity is 1.60 dL / g or lower, the flowability can be further improved.

[0016] The method for producing the polybutylene terephthalate (A) used in the present invention is not particularly limited, and examples thereof include known polycondensation methods, ring-opening polymerization methods, etc. Either batch polymerization or continuous polymerization may be used, and either transesterification or direct polymerization polycondensation may be applied. However, continuous polymerization is preferred because it can reduce the amount of carboxyl terminal groups and has a greater effect of improving fluidity, and direct polymerization is preferred from the standpoint of cost.

[0017] In order to effectively promote the esterification reaction, transesterification reaction, and polycondensation reaction, it is preferable to add a catalyst during these reactions. Specific examples of catalysts include organic titanium compounds, tin compounds, zirconia compounds, and antimony compounds. Examples of organic titanium compounds include 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, and mixed esters thereof of titanic acid. Examples of tin compounds include dibutyltin oxide, methylphenyltin oxide, tetraethyltin, hexaethylditin oxide, cyclohexahexylditin oxide, didodecyltin oxide, triethyltin hydroxide, triphenyltin hydroxide, triisobutyltin acetate, dibutyltin diacetate, diphenyltin dilaurate, monobutyltin trichloride, dibutyltin dichloride, tributyltin chloride, dibutyltin sulfide, butylhydroxytin oxide, and alkylstannoic acids such as methylstannoic acid, ethylstannoic acid, and butylstannoic acid. Examples of zirconia compounds include zirconium tetra-n-butoxide. Examples of antimony compounds include antimony trioxide and antimony acetate. Two or more of these compounds may be used. Among these, organic titanium compounds and tin compounds are preferred, with tetra-n-propyl ester, tetra-n-butyl ester, and tetraisopropyl ester of titanic acid being more preferred, and tetra-n-butyl ester of titanic acid being particularly preferred. The amount of catalyst added is preferably in the range of 0.005 to 0.5 parts by weight, more preferably 0.01 to 0.2 parts by weight, per 100 parts by weight of the polybutylene terephthalate resin, in terms of mechanical properties, moldability, and color tone.

[0018] The blending amount of (A) polybutylene terephthalate in the polyester resin composition of the present invention is in the range of 5 to 75 parts by weight, based on 100 parts by weight of the total of (A) polybutylene terephthalate and (B) polycarbonate (described below). If the blending amount of (A) polybutylene terephthalate is less than 5 parts by weight, the flowability of the polyester resin composition decreases. 20 parts by weight or more is preferable. On the other hand, if the blending amount of (A) polybutylene terephthalate is more than 75 parts by weight, the impact resistance of the molded article decreases. 50 parts by weight or less is preferable.

[0019] <Polycarbonate> The polycarbonate (B) used in the present invention is a polymer obtained by reacting raw materials mainly composed of a dihydric phenol and a carbonate precursor such as phosgene or a carbonate ester compound, etc. For example, it is produced by reacting a dihydric phenol with a carbonate precursor such as phosgene in a solvent such as methylene chloride, or by transesterification of a dihydric phenol with a carbonate precursor such as diphenyl carbonate.

[0020] Examples of dihydric phenols include 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), bis(4-hydroxyphenyl)alkane, 1,1-(4-hydroxyphenyl)methane, 1,1-(4-hydroxyphenyl)ethane, hydroquinone, bis(4-hydroxyphenyl)cycloalkane, bis(4-hydroxyphenyl)oxide, bis(4-hydroxyphenyl)sulfide, bis(4-hydroxyphenyl)sulfone, bis(4-hydroxyphenyl)sulfoxide, and bis(4-hydroxyphenyl)ether. Two or more of these may be used. Among these, 2,2-bis(4-hydroxyphenyl)propane (bisphenol A) is preferred.

[0021] Examples of the carbonate ester compound include diaryl carbonates such as diphenyl carbonate, and dialkyl carbonates such as dimethyl carbonate and diethyl carbonate. Two or more of these may be used.

[0022] The polycarbonate (B) used in the present invention preferably has a number-average molecular weight of 10,000 to 60,000. A number-average molecular weight of 10,000 or more further improves the mechanical properties of the molded article, such as tensile strength, flexural strength, flexural modulus, and impact resistance. A number-average molecular weight of 15,000 or more is more preferable. On the other hand, a number-average molecular weight of 60,000 or less further improves the flowability of the polyester resin composition. A number-average molecular weight of 40,000 or less is more preferable. Here, the number-average molecular weight can be determined by gel permeation chromatography. Polycarbonates having such number-average molecular weights are available, for example, from Idemitsu Kosan Co., Ltd. under the trade name "Toughlon" (registered trademark) A2600.

[0023] The blending amount of (B) polycarbonate in the polyester resin composition of the present invention is in the range of 25 to 95 parts by weight per 100 parts by weight of the total of (B) polycarbonate and (A) polybutylene terephthalate. If the blending amount of (B) polycarbonate is less than 25 parts by weight, the impact resistance of the molded article will decrease. It is preferably 50 parts by weight or more. On the other hand, if the blending amount of (B) polycarbonate is more than 95 parts by weight, the flowability of the polyester resin composition will decrease. It is preferably 80 parts by weight or less.

[0024] <Recycled polycarbonate> The polyester resin composition of the present invention contains 25 to 100% by weight of the (B) polycarbonate and (C) recycled polycarbonate.

[0025] The (C) recycled polycarbonate used in the present invention is a polycarbonate resin recovered from molded articles using polycarbonate resin as a base material, and is a material recycled material also known as polycarbonate resin derived from market recovered articles, recovered or reclaimed polycarbonate resin. It may be a polycarbonate resin recovered from used molded articles shipped to the market among polycarbonate resin molded articles, or a polycarbonate resin recovered from waste materials, scraps, or defective products generated in the process of manufacturing molded articles.

[0026] It should be noted that so-called chemically recycled products, in which polycarbonate resin is returned to its starting materials and then converted into polycarbonate resin, do not fall under the category of (C) recycled polycarbonate, but rather correspond to virgin (B) polycarbonate. (C) recycled polycarbonate may be used alone or in combination of two or more types, but polycarbonate resin derived from post-market recovered products, which are PCR plastics, is particularly preferred in terms of compliance with European ELV regulations.

[0027] Preferred types of molded articles from which (C) recycled polycarbonate can be recovered include beverage containers such as water bottles for water dispensers, baby bottles, and thermoses; optical components such as headlamps for automobiles and other vehicles, camera lenses, light guide plates, and transparent covers for electrical components; cases and housings for electronic components in pachinko game machines and the like; sheets; building materials such as corrugated sheets and carport boards; containers for transporting semiconductors; optical recording media such as optical discs like CDs and DVDs; etc. Among these, recycled polycarbonate resin recovered from water bottles for water dispensers and headlamps for automobiles and other vehicles is preferred.

[0028] The blending amount of (C) recycled polycarbonate in the polyester resin composition of the present invention is 25 to 100% by weight relative to the (B) polycarbonate. If the blending amount of (C) recycled polycarbonate is less than 25% by weight, it becomes difficult to comply with the European ELV regulations. It is preferably 30% by weight or more.

[0029] <Phosphorus-based stabilizer> The polyester resin composition of the present invention preferably further contains (D) a phosphorus-based stabilizer.

[0030] (D) Phosphorus-based stabilizer has the effect of suppressing the transesterification reaction between (A) polybutylene terephthalate and (B) polycarbonate and improving retention stability, which allows the phase structure to be maintained even after molding, resulting in high toughness and improved hydrolysis resistance.

[0031] (D) Examples of the phosphorus-based stabilizer include phosphite-based stabilizers (phosphite compounds) and phosphate-based stabilizers (phosphate compounds). Two or more of these may be used. Among these, phosphate-based stabilizers are preferred because they are more effective in improving the retention stability of the polyester resin composition.

[0032] Examples of the phosphite stabilizer include tetrakis[2-t-butyl-4-thio(2'-methyl-4'-hydroxy-5'-t-butylphenyl)-5-methylphenyl]-1,6-hexamethylene-bis(N-hydroxyethyl-N-methylsemicarbazide)-diphosphite, tetrakis[2-t-butyl-4-thio(2'-methyl-4'-hydroxy-5'-t-butylphenyl)-5-methylphenyl]-1,10-decamethylene-dicarboxylic acid-dihydroxyethylcarbonylhydrazide-diphosphite, tetrakis[2-t-butyl-4-thio(2'-methyl-4'-hydroxy-5'-t-butylphenyl)-5-methylphenyl]-1,10-decamethylene-dicarboxylic acid-dihydroxyethylcarbonylhydrazide-diphosphite, and tetrakis[2-t-butyl-4-thio(2'-methyl-4 tetrakis[2-t-butyl-4-thio(2'-methyl-4'-hydroxy-5'-t-butylphenyl)-5-methylphenyl]-N,N'-bis(hydroxyethyl)oxamide-diphosphite, tetrakis[2-t-butyl-4-thio(2'-methyl-4'-hydroxy-5'-t-butylphenyl)-5-methylphenyl]-N,N'-bis(hydroxyethyl)oxamide-diphosphite, and the like. Those in which at least one PO bond is bonded to an aromatic group are preferred, such as tris(2,4-di-t-butylphenyl)phosphite, tetrakis(2,4-di-t-butylphenyl)4,4'-biphenylenephosphonite, bis(2,4-di-t-butylphenyl)pentaerythritol-diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol-diphosphite, 2,2-methylenebis(4,6-di-t -butylphenyl)octyl phosphite, 4,4'-butylidene-bis(3-methyl-6-t-butylphenyl-di-tridecyl) phosphite, 1,1,3-tris(2-methyl-4-ditridecyl phosphite-5-t-butyl-phenyl)butane, tris(mixed mono- and di-nonylphenyl) phosphite, tris(nonylphenyl) phosphite, 4,4'-isopropylidenebis(phenyl-dialkyl phosphite), etc. Two or more of these may be combined.Among these, tris(2,4-di-t-butylphenyl)phosphite, 2,2-methylenebis(4,6-di-t-butylphenyl)octylphosphite, bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol-diphosphite, tetrakis(2,4-di-t-butylphenyl)-4,4'-biphenylenephosphonite, etc. are preferably used. Among these, cyclic neopentanetetraylbis(2,6-di-t-butyl-4-methylphenyl)phosphite is particularly preferred, and is available, for example, from ADEKA Corporation under the trade name "ADEKA STAB" (registered trademark) PEP-36.

[0033] Examples of phosphate stabilizers include monostearyl acid phosphate, distearyl acid phosphate, methyl acid phosphate, isopropyl acid phosphate, butyl acid phosphate, octyl acid phosphate, and isodecyl acid phosphate. Two or more of these may be combined. Among these, monostearyl acid phosphate and distearyl acid phosphate are preferred. A nearly equimolar mixture of these mono- and distearyl acid phosphates is particularly preferred, and is available, for example, under the trade name "ADEKA STAB" (registered trademark) AX-71 manufactured by ADEKA Corporation.

[0034] The amount of (D) phosphorus-based stabilizer is preferably 0.005 to 0.5 parts by weight per 100 parts by weight of the total of (A) polybutylene terephthalate and (B) polycarbonate. If the amount of (D) phosphorus-based stabilizer is 0.005 parts by weight or more, the residence stability of the polyester resin composition is further improved, allowing the phase structure to be maintained even after molding, and high toughness and hydrolysis resistance can be improved. On the other hand, if the amount of (D) phosphorus-based stabilizer is 0.5 parts by weight or less, the phosphorus-based stabilizer (D) itself can be prevented from acting as a hydrolysis catalyst, thereby improving hydrolysis resistance.

[0035] <Hindered phenol antioxidant> The polyester resin composition of the present invention preferably further contains (E) a hindered phenol-based antioxidant. Specific examples of the hindered phenol-based antioxidant include 4,4'-thiobis(3-methyl-t-butylphenol), pentaerythrityl tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2,6-di-t-butyl-4-methylphenol, tetrakis(methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methane, and 1,3,5-tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanuric acid. Particularly preferred is 1,3,5-tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanuric acid, which reduces the incidence of silvering (a defect in appearance where silvery white streaks appear on the surface of a molded article) after retention in a molten state compared to when other phenolic antioxidants are used.

[0036] The amount of (E) hindered phenol-based antioxidant is preferably 0.01 to 1.0 parts by weight per 100 parts by weight of the total of (A) polybutylene terephthalate and (B) polycarbonate. It is preferably 0.05 to 0.2 parts by weight. If the amount of (E) hindered phenol-based antioxidant is 0.01 part by weight or more, the residence stability of the resin component can be improved, the phase structure can be maintained even after molding, and high toughness and hydrolysis resistance can be improved. 0.05 part by weight or more is more preferable. By keeping it 1.0 part by weight or less, gas generation due to decomposition of the hindered phenol-based antioxidant can be suppressed, and problems such as mold fouling can be suppressed. 0.2 part by weight or less is more preferable.

[0037] <Sulfur-based antioxidant> The polyester resin composition of the present invention preferably further contains (F) a sulfur-based antioxidant. The sulfur-based antioxidant used in the present invention exhibits retention stability when used in combination with the aforementioned (E) hindered phenol-based antioxidant. Specific examples of (F) sulfur-based antioxidants include dilauryl-3,3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, and [methylene-3-(dodecylthio)propionate]methane. [methylene-3-(dodecylthio)propionate]methane is particularly preferred, as it reduces the incidence of silver blemishes after retention at high temperatures compared to when other sulfur-based antioxidants are used.

[0038] The blending amount of (F) sulfur-based antioxidant is preferably 0.01 to 1.0 parts by weight per 100 parts by weight of the total of (A) polybutylene terephthalate and (B) polycarbonate. It is preferably 0.05 to 0.2 parts by weight. If the blending amount of (F) sulfur-based antioxidant is 0.01 part by weight or more, the residence stability of the resin component can be improved, the phase structure can be maintained even after molding, and high toughness and hydrolysis resistance can be improved. 0.05 part by weight or more is more preferable. By keeping it 1.0 part by weight or less, gas generation due to decomposition of the sulfur-based antioxidant can be suppressed, and problems such as mold fouling can be suppressed. 0.2 part by weight or less is more preferable.

[0039] <Rubber polymer (G)> The polyester resin composition of the present invention preferably contains a rubbery polymer (G) to improve impact strength. Such rubbery polymers are resins that exhibit rubber elasticity at room temperature, and examples thereof include diene rubbers such as polybutadiene, polyisoprene, styrene-butadiene random copolymers and block copolymers, hydrogenated versions of these block copolymers, acrylonitrile-butadiene copolymers, and butadiene-isoprene copolymers, ethylene-propylene random copolymers and block copolymers, ethylene-butene random copolymers and block copolymers, ethylene-α-olefin copolymers, copolymers with ethylene-unsaturated carboxylic acid esters such as ethylene-methacrylate and ethylene-butyl acrylate, and acrylic rubbers such as acrylic acid ester-butadiene copolymers, for example, butyl acrylate-butadiene copolymers. Particularly preferred are MBS resins obtained by graft polymerizing one or more of methacrylic acid esters, aromatic monovinyl compounds, and vinyl cyanide compounds onto butadiene-based rubbery polymers such as polybutadiene and butadiene-styrene copolymers by a method such as bulk polymerization, suspension polymerization, bulk suspension polymerization, solution polymerization, or emulsion polymerization, particularly emulsion polymerization; ethylene / glycidyl methacrylate copolymers, ethylene / glycidyl methacrylate / vinyl acetate copolymers, ethylene / glycidyl methacrylate / acrylic acid ester copolymers, and ethylene / glycidyl acrylate / vinyl acetate copolymers.

[0040] The amount of the rubber polymer (G) in the present invention is preferably 0.5 to 20 parts by weight per 100 parts by weight of the total of (A) polybutylene terephthalate and (B) polycarbonate. When the amount of the rubber polymer (G) is 0.5 parts by weight or more, toughness can be further improved. 1.0 part by weight or more is more preferable. By setting it to 20 parts by weight or less, deterioration of moldability can be suppressed. 10 parts by weight or less is more preferable.

[0041] <Other additives> The polyester resin composition of the present invention may contain conventional additives such as stabilizers other than (D) phosphorus-based stabilizer, (E) hindered phenol-based antioxidant, and (F) sulfur-based antioxidant, release agents, colorants, and small amounts of other polymers, as long as the effects of the present invention are not impaired. Any stabilizer used in polyester resin compositions can be used. Examples include antioxidants, light stabilizers, and catalyst deactivators. Two or more of these may be used in combination. Any release agent used in polyester resins can be used. Examples include plant-based waxes such as carnauba wax and rice wax, animal-based waxes such as beeswax and lanolin, mineral waxes such as montan wax, petroleum-based waxes such as paraffin wax and polyethylene wax, and fat-based waxes such as castor oil and its derivatives, fatty acids and its derivatives. Two or more of these may be used in combination. Colorants include organic dyes, organic pigments, and inorganic pigments. Two or more of these may be used in combination. The other polymer may be any resin that can be melt-molded, and examples thereof include polyethylene resin, polypropylene resin, polymethylpentene resin, cyclic olefin resin, cellulose resin such as cellulose acetate, polyamide resin, polyacetal resin, polysulfone resin, polyphenylene sulfide resin, polyether ether ketone resin, polyimide resin, polyetherimide resin, etc. Two or more of these may be blended.

[0042] <Polymer alloy> In the polyester resin composition of the present invention, (A) polybutylene terephthalate and (B) polycarbonate form a phase-separated structure with a structural period of 0.01 to 1 μm. By creating a phase-separated structure with such a structural period, even when recycled polycarbonate, which has inferior physical properties compared to virgin polycarbonate, is used, the recycled polycarbonate phase can be prevented from becoming the initiation point of fracture, thereby improving toughness and hydrolysis resistance. If the structural period is less than 0.01 μm, the structure becomes close to a compatible state, making it impossible to bring out the individual characteristics of (A) polybutylene terephthalate and (B) polycarbonate, resulting in reduced toughness and hydrolysis resistance. A structural period of 0.05 μm is more preferable. If the structural period exceeds 1 μm, the overly large phase structure becomes the initiation point of fracture, resulting in reduced toughness and hydrolysis resistance. A structural period of 0.75 μm or less is preferable.

[0043] Such a structure can be obtained by phase separation due to a specific spinodal decomposition, specifically, by forming a bicontinuous structure with a structural period of 0.001 to 0.1 μm in the initial stage of spinodal decomposition, and then further developing it into a bicontinuous structure with a structural period of 0.01 to 1 μm or a dispersed structure with an interparticle distance of 0.01 to 1 μm.

[0044] Phase separation due to spinodal decomposition refers to phase separation that occurs in an unstable state inside the spinodal curve in a phase diagram for conditions such as two different resin compositions and temperature, and phase separation due to nucleation and growth refers to phase separation that occurs in a metastable state inside the binodal curve and outside the spinodal curve in the phase diagram. Such a spinodal curve is the difference (ΔGmix) between the free energy when two different resin components are mixed together with respect to composition and temperature and the sum of the free energies in the two immiscible phases, partially differentiated twice with respect to concentration (φ) (∂ 2 ΔGmix / ∂φ 2 ) is the curve where ∂ is 0, and inside the spinodal curve, 2 ΔGmix / ∂φ 2 <0, and outside ∂ 2 ΔGmix / ∂φ 2 >0.

[0045] The binodal curve is a curve that indicates the boundary between the region where the system is compatible and the region where the system is phase-separated with respect to composition and temperature.

[0046] In the present invention, "compatible" refers to a state in which the two resins are mixed uniformly at the molecular level, specifically, when neither of the two resin-based phases forms a phase structure of 0.001 μm or more, and "incompatible" refers to a state in which the two resin-based phases are not compatible, that is, when the two resin-based phases form a phase structure of 0.001 μm or more. Whether or not the two resins are compatible can be determined by electron microscopy and various other methods, as described in, for example, "Polymer Alloys and Blends," Leszek A. Utracki, Hanser Publishers, Munich Vienna New York, p. 64.

[0047] According to detailed theory, in spinodal decomposition, if the temperature of a mixed system that has been uniformly dissolved in the miscible region is suddenly raised to the unstable region, the system will rapidly begin phase separation toward a coexisting composition. At this time, a bicontinuous structure will be formed in which both separated phases are continuously and regularly entangled with a structural period (Λm). After this bicontinuous structure is formed, the process in which only the concentration difference between the two separated phases increases while the structural period remains constant is called the initial stage of spinodal decomposition.

[0048] Furthermore, the structural period (Λm) in the initial stage of the spinodal decomposition is thermodynamically related as shown in the following equation: Λm~[│Ts-T│ / Ts] -1 / 2 (where Ts is the temperature on the spinodal curve) The term "co-continuous structure" as used herein refers to a structure in which both components of the mixed resins each form a continuous phase and are three-dimensionally entangled with each other. A schematic diagram of this co-continuous structure is described, for example, in "Polymer Alloys: Fundamentals and Applications (2nd Edition) (Chapter 10.1)" (edited by the Society of Polymer Science, Tokyo Kagaku Dojin).

[0049] In spinodal decomposition, after passing through this initial stage, there is a middle stage in which an increase in wavelength and an increase in concentration difference occur simultaneously, and a late stage in which the wavelength increases self-similarly after the concentration difference reaches a coexistence composition, and finally progresses until separation into two macroscopic phases. However, in the present invention, the structure can be fixed at the stage where a desired structural period is reached before the final separation into two macroscopic phases. Furthermore, during the wavelength increase process from the middle stage to the late stage, depending on the influence of the composition and interfacial tension, the continuity of one of the phases may be interrupted, and the above-mentioned cocontinuous structure may change to a dispersed structure. In this case, the structure can be fixed at the stage where the desired interparticle distance is reached.

[0050] The dispersed structure referred to in the present invention refers to a so-called sea-island structure in which particles whose main component is one resin component are scattered in a matrix whose main component is the other resin component.

[0051] In the present invention, by controlling the structural period in the initial stage of spinodal decomposition to a range of 0.001 to 0.1 μm, even if the wavelength and concentration difference increase in the intermediate stage or later, the structure can be controlled to a co-continuous structure with a structural period in the range of 0.01 to 1 μm or a dispersed structure with an interparticle distance in the range of 0.01 to 1 μm. To obtain better mechanical properties, it is preferable to control the structure after structural development to a co-continuous structure with a structural period in the range of 0.01 to 0.5 μm or a dispersed structure with an interparticle distance in the range of 0.01 to 0.5 μm.

[0052] On the other hand, in the nucleation and growth that is phase separation in the metastable region described above, a dispersed structure that is a sea-island structure is formed from the early stage, and this structure grows, making it difficult to form a bicontinuous structure with a structural period in the range of 0.01 to 1 μm as in the present invention.

[0053] Methods for fixing the structure produced by spinodal decomposition include fixing the structure of one or both components of the phase separation phase in a short period of time by rapid cooling or the like, and, when one of the components is a crystalline resin, fixing the structure by utilizing the fact that the crystalline resin phase cannot move freely due to crystallization.However, since the present invention uses (A) polybutylene terephthalate, which is a crystalline resin, structural fixation by crystallization is preferably used.

[0054] Typically, combinations of at least two components that undergo phase separation by spinodal decomposition include those that have a low-temperature miscible phase diagram in which the components become miscible at low temperatures, or combinations of partially miscible systems that have a high-temperature miscible phase diagram in which the components become miscible at high temperatures. Other examples include combinations that are normally immiscible and capable of shear-field-dependent phase dissolution and phase decomposition. The combination of (A) polybutylene terephthalate and (B) polycarbonate of the present invention is a normally immiscible combination, and is a combination that is capable of shear-field-dependent phase dissolution and phase decomposition.

[0055] Spinodal decomposition due to shear-dependent phase dissolution / phase decomposition is a type of spinodal decomposition in which the phases dissolve under shear, such as during melt mixing, and then decompose again under non-shear conditions. In this case, the decomposition proceeds in a spinodal decomposition manner, as in the case of partially miscible systems, resulting in a regular bicontinuous structure. Furthermore, this shear-dependent phase dissolution / phase decomposition method is preferable because the spinodal curve changes with the shear field, expanding the unstable region. This results in a larger effective degree of supercooling (|Ts-T|) for the same temperature change range compared to the temperature-dependent method for partially miscible systems, in which the spinodal curve remains unchanged. Consequently, it is easier to reduce the structural period in the initial stage of spinodal decomposition in the above-mentioned relationship.

[0056] To achieve compatibilization under shear during melt-kneading, it is preferable to add a compatibilizer or apply sufficient shear stress during melt-kneading. While there are no particular limitations on the production method, the use of an extruder, particularly a twin-screw extruder, is preferred. Depending on the resin combination used, compatibilization may also be achieved during the plasticization process of an injection molding machine. Shear stress can be applied under conditions such as a screw arrangement that utilizes a large number of kneading blocks, a low extruder cylinder temperature, or a high screw rotation speed. Melt-kneading under conditions that apply sufficient shear stress expands the unstable state region, thereby reducing the structural period in the initial stage of spinodal decomposition and the fixed structural period, thereby improving toughness and hydrolysis resistance. The temperature for compatibilization, the heat treatment temperature for forming the initial stage, the heat treatment temperature for structural development from the initial stage, and other conditions vary depending on the resin combination used and cannot be generalized. However, conditions can be determined by simple preliminary experiments based on phase diagrams under various shear conditions. As a method for reliably achieving compatibilization in the plasticization step of the injection molding machine, a preferred example is a method in which the material is melt-kneaded in advance in a twin-screw extruder to make it compatibilized, and then cooled after extrusion to fix the structure in the compatibilized state, and then injection molding is performed using the material.

[0057] The phase-separated structure of (A) polybutylene terephthalate and (B) polycarbonate in the present invention can be determined by electron microscope observation using the following method. The pellet is cut perpendicularly to the longitudinal direction in the center, and the cross section is cut into 1-2 mm squares. The cut specimen is stained with ruthenium tetroxide to stain (B) polycarbonate, and then cut into ultrathin sections of 0.1 μm or less (approximately 80 nm) using an ultramicrotome at room temperature to obtain a sample for transmission electron microscopy.

[0058] When determining the structural period of a bicontinuous structure, the magnification of the aforementioned transmission electron microscope sample is adjusted so that a square electron microscope photograph shows 50 to 100 periodic structures. At this magnification, the interface curvature is measured and periodic minimal surfaces are identified from the observed image, and the structural period is calculated based on the periodic minimal surfaces.

[0059] When determining the average diameter of the island phases in the sea-island structure, the magnification of the aforementioned transmission electron microscope sample is adjusted so that 50 to less than 100 island phases are present in a square electron microscope photograph. At this magnification, 50 island phases are randomly selected from the island phases present in the observation image, and the long and short diameters of each island phase are measured. The average of the long and short diameters is taken as the diameter of each island phase, and the average of the diameters of all the measured island phases is taken as the diameter of the island phase. The long and short diameters of the island phase refer to the longest and shortest diameters of the island phase, respectively.

[0060] The polyester resin composition of the present invention can be processed into various molded parts and used by molding it by any known method such as injection molding, extrusion molding, blow molding, or press molding.

[0061] In the present invention, the various molded articles can be used for various purposes such as vehicle components, electrical and electronic components, building components, various containers, daily necessities, household goods, and sanitary products. In particular, the polyester resin composition of the present invention can give molded articles having excellent moist heat resistance and impact resistance, and is therefore particularly suitable for vehicle door handles, impact absorbing components (crash pads), and resin spacers. [Example]

[0062] 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.

[0063] The abbreviations of the main raw materials used in the examples and their contents are summarized below. (A) Polybutylene terephthalate A-1: Polybutylene terephthalate (melting point 223°C, Toray Industries, Inc. "Trecon" (registered trademark) 1100M (product name)) (B) Polycarbonate B-1: Polycarbonate (manufactured by Idemitsu Kosan Co., Ltd., "Toughlon" (registered trademark) A2600 (product name)) (C) Recycled polycarbonate C-1: Recycled polycarbonate: PCR product derived from water bottles used in water dispensers (SunSang, PC110-BL-M (product name)) C-2: Recycled polycarbonate: Collected automobile headlamps (parts with the ISO marking "PC" obtained from used car parts manufacturers and crushed into pellets) (D) Phosphorus stabilizer D-1: Phosphate-based antioxidant (a nearly equimolar mixture of mono- and di-stearyl acid phosphate) (ADEKA Corporation, "ADEKA STAB" (registered trademark) AX-71 (trade name)) (E) Hindered phenolic antioxidants E-1: Hindered phenolic antioxidant (1,3,5-tris-3,5-di-tert-butyl-4-hydroxybenzyl)isocyanuric acid (ADEKA Corporation, "ADEKA STAB" (registered trademark) AO-20 (product name)) (F) Sulfur-based antioxidants F-1: Sulfur-based antioxidant (2,2-bis[[[3(dodecylthio)propionyl]oxy]methyl]-1,3-propanediyl-bis[3(dodecylthio)propionate]) (ADEKA Corporation, "ADEKA STAB" (registered trademark) AO-412S (product name))

[0064] <Evaluation method> The evaluation methods used in each of the examples and comparative examples will be explained below.

[0065] (1) Structural period of phase-separated structure A portion was cut from the center of each pellet obtained in each Example and Comparative Example, and a cross-sectional observation sample of approximately 2 mm x 1 mm was prepared using a Leica ultramicrotome (EM UC7) with a diamond knife, so that the observation surface was perpendicular to the longitudinal direction of the plate. The prepared sample was stained with ruthenium tetroxide to provide sufficient contrast to the morphology, and the phase structure of the cross section of the observation sample was observed using a transmission electron microscope (Hitachi H-7100) at an accelerating voltage of 100 kV to confirm the morphology of the phase-separated structure.

[0066] When determining the structural period of the bicontinuous structure, the magnification of the above-mentioned transmission electron microscope sample was adjusted so that a square electron microscope photograph showed 50 to 100 periodic structures. At this magnification, the area and perimeter of each phase were determined from the observed image using the image analysis software ScionImage, and the structural period was calculated.

[0067] When determining the average diameter of the island phases in the sea-island structure, the magnification of the aforementioned transmission electron microscope sample was adjusted so that 50 to less than 100 island phases were present in a square electron microscope photograph. At this magnification, 50 island phases were randomly selected from the island phases present in the observation image, and the long and short diameters of each island phase were measured. The average of the long and short diameters was taken as the diameter of each island phase, and the average of the diameters of all the measured island phases was taken as the diameter of the island phase. The long and short diameters of the island phase refer to the longest and shortest diameters of the island phase, respectively.

[0068] (2) Tensile strength and tensile elongation Using a Sumitomo Heavy Industries SE50-DUZ injection molding machine, 4 mm thick ISO-1A dumbbell test specimens for tensile property evaluation were obtained under molding cycle conditions of 245 °C, 80 °C mold temperature, 10 seconds injection time and dwell time, and 10 seconds cooling time. The resulting test specimens for tensile property evaluation were then measured for maximum tensile strength (tensile strength) and maximum tensile elongation (tensile elongation) using a Shimadzu Autograph AG-50kNX Plus tensile testing machine in accordance with ISO 527-1, 2 (2019). Values ​​were averaged from five measurements. Materials with high tensile strength and tensile elongation values ​​were considered to have excellent mechanical properties.

[0069] (3) Hydrolysis resistance Using a Sumitomo Heavy Industries SE50-DUZ injection molding machine, 4 mm thick ISO-1A dumbbell test pieces for evaluating tensile properties were obtained under the same injection molding conditions as those for the tensile properties described in (2). The obtained ISO-1A dumbbells were placed in an EHS-411 highly accelerated life testing machine manufactured by Espec Corporation, set at a temperature and humidity of 121°C and 100% RH for 10 hours, and subjected to a moist heat treatment. The maximum tensile strength of the molded pieces after moist heat treatment was measured under the same conditions as the tensile test described in (2), and the values ​​measured for five pieces were averaged. Materials with high tensile strength and tensile elongation values ​​were judged to have excellent hydrolysis resistance.

[0070] (Examples 1 to 8, Comparative Examples 1 to 3) Using a co-rotating, vented twin-screw extruder (TEX-30α, manufactured by The Japan Steel Works, Ltd.) with a screw diameter of 30 mm and an L / D ratio of 35, (A) polybutylene terephthalate, (B) polycarbonate, (C) recycled polycarbonate, and other raw materials were mixed according to the composition shown in Table 1 and added to the twin-screw extruder's base. Furthermore, in Examples 1 to 7, the extrusion conditions were: a mixing temperature of 250°C from the raw material inlet to the first melting zone, 220°C from the first melting zone to the die, and 250°C at the die, with a screw rotation of 200 rpm. In Comparative Example 2, melt mixing was performed under extrusion conditions of 265°C from the raw material inlet to the die, with a screw rotation of 100 rpm, and the mixture was discharged in the form of a strand, passed through a cooling bath, and pelletized using a strand cutter.

[0071] The obtained pellets were dried in a hot air dryer at 110° C. for 6 hours and then evaluated by the above-mentioned method. The results are shown in Table 1.

[0072] [Table 1]

[0073] Compared to Comparative Examples 1 to 3, Examples 1 to 8 contain specific amounts of (A) polybutylene terephthalate, (B) polycarbonate, and / or (C) recycled polycarbonate, and by setting the structural periods of (A) polybutylene terephthalate, (B) polycarbonate, and (C) recycled polycarbonate to a specific size or less, they use recycled PCR plastic that complies with European ELV regulations as the raw material, and were able to obtain molded articles with high toughness and hydrolysis resistance.

[0074] In comparison with Example 2, Examples 3 to 6 contain a specific amount of (D) phosphorus-based stabilizer, and therefore use recycled PCR plastic that complies with European ELV regulations as raw materials, and are able to obtain molded articles with high toughness and hydrolysis resistance.

[0075] In comparison with Example 3, Examples 4 and 6 contain a specific amount of (E) hindered phenol-based antioxidant, and therefore use recycled PCR plastic that complies with the European ELV regulations as the raw material, and are able to obtain molded articles with high toughness and hydrolysis resistance.

[0076] In comparison with Example 3, Examples 5 and 6 contain a specific amount of (F) sulfur-based antioxidant, and therefore use recycled PCR plastic that complies with the European ELV regulations as the raw material, and are able to obtain molded articles with high toughness and hydrolysis resistance.

Claims

1. A polyester resin composition comprising 5 to 75 parts by weight of (A) polybutylene terephthalate and 25 to 95 parts by weight of (B) polycarbonate, wherein 25 to 100% by weight of the (B) polycarbonate is (C) recycled polycarbonate, the (A) polybutylene terephthalate and the (B) polycarbonate form a phase-separated structure, and the structural period of the polyester resin composition is 0.01 to 1 μm.

2. 2. The polyester resin composition according to claim 1, further comprising 0.005 to 0.5 parts by weight of (D) a phosphorus-based stabilizer per 100 parts by weight of the total of (A) polybutylene terephthalate and (B) polycarbonate.

3. 3. The polyester resin composition according to claim 1, further comprising 0.01 to 1.0 parts by weight of (E) a hindered phenol-based antioxidant, based on 100 parts by weight of the total of (A) polybutylene terephthalate and (B) polycarbonate.

4. 3. The polyester resin composition according to claim 1, further comprising 0.01 to 1.0 parts by weight of (F) a sulfur-based antioxidant, based on 100 parts by weight of the total of (A) polybutylene terephthalate and (B) polycarbonate.

5. A molded article obtained by molding the polyester resin composition according to claim 1 or 2.

6. 3. A vehicle impact absorbing component obtained by molding the polyester resin composition according to claim 1 or 2.

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