Resin composition, pellet, molded article, and method for suppressing discoloration

Abstract

Provided is a resin composition comprising, with respect to 100 parts by mass of a thermoplastic resin: 0.001-10.0 parts by mass of a stabilizer; 0.1-10.0 parts by mass of an antibacterial agent containing silver; and 0.1-30 parts by mass of a halogen compound. Also provided are a pellet, a molded article, and a method for suppressing discoloration.

Description

Resin composition, pellets, molded article, and method for inhibiting discoloration

[0001] The present invention relates to a resin composition, a pellet, a molded article, and a method for inhibiting discoloration, and in particular to a resin composition containing a thermoplastic polyester resin as a main component.

[0002] Thermoplastic polyester resins have excellent mechanical strength, electrical properties, and other physical and chemical characteristics. Therefore, they are used as engineering plastics in a wide range of applications, including automobiles, electrical and electronic devices, and sanitary areas such as toilet seats and bathroom fixtures. In recent years, the harmful effects of bacteria on the human body caused by the growth of bacteria in products used in these applications have become a problem. Furthermore, the use of antibacterial properties to add value to products is becoming increasingly common. While kneading a commercially available antibacterial agent into a thermoplastic polyester resin is one method for imparting antibacterial properties to a thermoplastic polyester resin, this has not always been sufficient depending on the type of antibacterial agent. For this reason, thermoplastic polyester resin compositions with excellent antibacterial properties have been investigated. Specifically, Patent Document 1 describes a thermoplastic polyester resin composition comprising: (A) a thermoplastic polyester resin; (B) an alkali metal salt, alkaline earth metal salt, or ammonium salt of zirconium phosphate, in which the ratio of phosphate ions to zirconium ions is 3:2; (C) an antibacterial agent represented by general formula (I), 0.1 to 5 wt % (based on the total composition) Ag; ａ A ｂ H ｃ Zr ２ (P.O. ４ ) ３ ・nH ２ O (I) (wherein A is at least one ion selected from alkali metal ions, alkaline earth metal ions, and ammonium ions; q is the valence of A; a and c are positive numbers; b is 0 or a positive number; q, a, b, and c are numbers that satisfy a+qb+c=1; and n is a number that satisfies 0≦n≦6.) (C) 1 to 30% by weight (based on the total composition) of a halogenated aromatic bisimide compound represented by general formula (II) (wherein R1 represents a divalent organic acid group, and at least one of R2 and R3 represents a divalent organic group having one or more halogen atoms X; n = 1 to 4, n' = 0 to 4) is disclosed.

[0003] Japanese Patent Application Laid-Open No. 2002-348444

[0004] As described above, antibacterial properties can be imparted to a thermoplastic polyester resin by blending a silver-containing antibacterial agent into the thermoplastic polyester resin. Meanwhile, blending a stabilizer into a thermoplastic polyester resin to impart thermal stability is commonly practiced. The present inventors conducted research and found that adding a stabilizer to a thermoplastic polyester resin containing such an antibacterial agent increases the degree of discoloration of the resulting resin composition. The present invention aims to solve this problem by providing a resin composition that exhibits a good balance of antibacterial properties, thermal stability, and color stability, as well as pellets, molded articles, and a method for inhibiting discoloration.

[0005] In light of the above-mentioned problems, the present inventors have conducted research and found that the above-mentioned problems can be solved by blending a halogen compound in addition to a thermoplastic resin, a stabilizer, and a silver-containing antibacterial agent. Specifically, the above-mentioned problems have been solved by the following means. [1] A resin composition comprising, per 100 parts by mass of a thermoplastic resin, 0.001 to 10.0 parts by mass of a stabilizer, 0.1 to 10.0 parts by mass of a silver-containing antibacterial agent, and 0.1 to 30 parts by mass of a halogen compound. [2] The resin composition according to [1], in which the mass ratio of halogen atoms contained in the resin composition to the stabilizer, i.e., halogen atoms / stabilizer, is 1.0 or greater. [3] The resin composition according to [1] or [2], in which the thermoplastic resin comprises a thermoplastic polyester resin. [4] The resin composition according to [3], in which the thermoplastic polyester resin comprises a polybutylene terephthalate resin. [5] The resin composition according to any one of [1] to [4], wherein the stabilizer comprises one or more compounds selected from the group consisting of thioether compounds, hindered phenol compounds, and phosphite compounds. [6] The resin composition according to any one of [1] to [5], wherein the stabilizer comprises a thioether compound. [7] The resin composition according to any one of [1] to [6], wherein the silver-containing antibacterial agent comprises an inorganic silver-based antibacterial agent. [8] The resin composition according to any one of [1] to [7], wherein the silver-containing antibacterial agent comprises a glass-based antibacterial agent. [9] The resin composition according to any one of [1] to [8], wherein the halogen compound comprises a bromine atom and / or a fluorine atom.

[10] The resin composition according to any one of [1] to [9], wherein the halogen compound comprises a fluorine atom.

[11] The resin composition according to any one of [1] to

[10] , wherein the halogen compound comprises a bromine atom.

[12] The resin composition according to

[11] , wherein the halogen compound has a free bromine content of 0.5 mass% or more.

[13] A resin composition for sanitary use, comprising: a thermoplastic polyester resin having an intrinsic viscosity of 1.0 dL / g or more; an antibacterial agent containing silver; and titanium oxide.

[14] The resin composition according to [1], wherein the mass ratio of halogen atoms contained in the resin composition to the stabilizer, i.e., halogen atoms / stabilizer, is 1.0 or more, the thermoplastic resin comprises a polybutylene terephthalate resin, the stabilizer comprises one or more compounds selected from the group consisting of hindered phenol compounds and phosphite compounds, the silver-containing antibacterial agent comprises a glass-based antibacterial agent, and the halogen compound comprises a bromine atom and / or a fluorine atom.

[15] Pellets of the resin composition according to any of [1] to

[14] .

[16] A molded article formed from the resin composition according to any of [1] to

[14] .

[17] A molded article formed from the pellets according to

[15] .

[18] The molded article according to

[16] or

[17] , which is a part for sanitary applications.

[19] A method for inhibiting discoloration of a resin composition containing 0.001 to 10.0 parts by mass of a stabilizer and 0.1 to 10.0 parts by mass of a silver-containing antibacterial agent per 100 parts by mass of a thermoplastic resin, the method comprising blending 0.1 to 30 parts by mass of a halogen compound per 100 parts by mass of the thermoplastic resin.

[20] A method for inhibiting discoloration of a resin composition containing 0.01 to 1.0 part by mass of a stabilizer and 0.1 to 3.0 parts by mass of a silver-containing antibacterial agent per 100 parts by mass of a thermoplastic polyester resin, the method comprising blending 0.1 to 30 parts by mass of a halogen compound per 100 parts by mass of the thermoplastic polyester resin.

[0006] The present invention makes it possible to provide a resin composition having a good balance of antibacterial properties, thermal stability, and color stability, as well as pellets, molded articles, and a method for inhibiting discoloration.

[0007] Hereinafter, a detailed description will be given of an embodiment of the present invention (hereinafter simply referred to as "the present embodiment"). Note that the following present embodiment is an example for explaining the present invention, and the present invention is not limited to this embodiment. In this specification, the term "to" is used to mean that the numerical values ​​before and after the term are included as lower and upper limits. In this specification, various physical property values ​​and characteristic values ​​are those at 23°C unless otherwise specified. In this specification, unless otherwise specified, weight-average molecular weight and number-average molecular weight are measured by GPC (gel permeation chromatography) using a Tosoh HLC-8320GPC EcoSEC with tetrahydrofuran as the solvent and Shodex KF-G, KF-805L x 3, and KF-800D columns at a column temperature of 40°C and a flow rate of 1.2 mL / min, and are polystyrene-equivalent values ​​detected at a detection wavelength of 254 nm. If the measurement methods and the like described in the standards shown in this specification differ depending on the fiscal year, they shall be based on the standards as of January 1, 2023, unless otherwise specified.

[0008] The resin composition of this embodiment is characterized by containing, per 100 parts by mass of thermoplastic resin, 0.001 to 10.0 parts by mass of a stabilizer, 0.1 to 10.0 parts by mass of a silver-containing antibacterial agent, and 0.1 to 30 parts by mass of a halogen compound. This configuration results in a resin composition with a well-balanced antibacterial property, thermal stability, and color stability. It was speculated that silver, due to its high reactivity, would react with sulfur, phosphorus, and other elements contained in the stabilizer, causing discoloration of the resin composition. In this embodiment, it was speculated that the incorporation of a halogen compound would cause the halogen to coordinate around the silver, thereby suppressing the interaction between the silver and the stabilizer. Furthermore, by using a predetermined amount of a halogen-based flame retardant as the halogen compound, it was possible to maintain high levels of antibacterial property, thermal stability, and color stability of the resin composition while also enhancing flame retardancy.

[0009] <Thermoplastic Resin> The resin composition of this embodiment contains a thermoplastic resin. Examples of the thermoplastic resin used in this embodiment include polyester resins (thermoplastic polyester resins), polyamide resins, polycarbonate resins, polystyrene-based resins, polyethylene resins, polypropylene resins, polyolefin resins such as cyclic cycloolefin resins, polyacetal resins, polyimide resins, polyetherimide resins, polyurethane resins, polyphenylene ether resins, polyphenylene sulfide resins, polysulfone resins, and polymethacrylate resins, and the thermoplastic resin polyester resin is preferred. The resin composition of this embodiment may contain only one type of thermoplastic resin, or may contain two or more types.

[0010] The resin composition of the present embodiment may be an alloy of two or more thermoplastic resins blended together, such as a blend of polybutylene terephthalate resin and polycarbonate resin, a blend of polybutylene terephthalate resin and polyethylene terephthalate resin, or a blend of polybutylene terephthalate resin and polystyrene resin.

[0011] <<Thermoplastic Polyester Resin>> The type and other aspects of the thermoplastic polyester resin are not particularly limited, but it preferably contains a polyalkylene terephthalate resin, preferably contains a polyethylene terephthalate resin and / or a polybutylene terephthalate resin, and more preferably contains a polybutylene terephthalate resin.

[0012] The polyalkylene terephthalate resin is a polyester obtained by polycondensation of terephthalic acid as a dicarboxylic acid compound with a diol, and may be either a homopolyester or a copolyester.

[0013] As the dicarboxylic acid compound constituting the polyalkylene terephthalate resin, a terphthalic acid compound or an ester-forming derivative thereof is preferably used. Aromatic dicarboxylic acids other than terephthalic acid can also be used in combination. Examples include isophthalic acid, orthophthalic acid, 1,5-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, biphenyl-2,2'-dicarboxylic acid, biphenyl-3,3'-dicarboxylic acid, biphenyl-4,4'-dicarboxylic acid, diphenylether-4,4'-dicarboxylic acid, diphenylmethane-4,4'-dicarboxylic acid, diphenylsulfone-4,4'-dicarboxylic acid, diphenylisopropylidene-4,4'-dicarboxylic acid, 1,2-bis(phenoxy)ethane-4,4'-dicarboxylic acid, anthracene-2,5-dicarboxylic acid, anthracene-2,6-dicarboxylic acid, p-terphenylene-4,4'-dicarboxylic acid, and pyridine-2,5-dicarboxylic acid. These can be used in the polycondensation reaction as ester-forming derivatives such as dimethyl esters in addition to free acids. Of the above, isophthalic acid or its ester-forming derivatives are particularly preferred.

[0014] In addition, a small amount of terephthalic acid or the above-mentioned aromatic dicarboxylic acid may be used in combination with one or more aliphatic dicarboxylic acids such as adipic acid, azelaic acid, dodecanedioic acid, and sebacic acid, or alicyclic dicarboxylic acids such as 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid.

[0015] Examples of dihydroxy compounds constituting the polyalkylene terephthalate resin include aliphatic diols such as ethylene glycol, propylene glycol, 1,4-butanediol, hexylene glycol, neopentyl glycol, 2-methylpropane-1,3-diol, diethylene glycol, and triethylene glycol, alicyclic diols such as cyclohexane-1,4-dimethanol, and mixtures thereof. Among these, 1,4-butanediol and ethylene glycol are particularly preferred.

[0016] It is also possible to copolymerize one or more long-chain diols having a molecular weight of 400 to 6,000, such as polyethylene glycol, poly-1,3-propylene glycol, polytetramethylene glycol, etc. Also usable are aromatic diols such as hydroquinone, resorcinol, naphthalenediol, dihydroxydiphenyl ether, and 2,2-bis(4-hydroxyphenyl)propane.

[0017] In addition to the above-mentioned bifunctional monomers, a small amount of a trifunctional monomer such as trimellitic acid, trimesic acid, pyromellitic acid, pentaerythritol, or trimethylolpropane can be used in combination to introduce a branched structure, or a monofunctional compound such as a fatty acid can be used in combination to adjust the molecular weight.

[0018] The polyalkylene terephthalate resin is preferably one formed by polycondensation of terephthalic acid and a diol, i.e., one in which the polycondensate accounts for more than 50% by mass of the entire resin, preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, still more preferably 95% by mass or more, and even more preferably 99% by mass or more. The diol is preferably an aliphatic diol, and 1,4-butanediol or ethylene glycol is preferred, with 1,4-butanediol being more preferred.

[0019] The amount of terminal carboxyl groups in the thermoplastic polyester resin (preferably polybutylene terephthalate resin) may be appropriately selected and determined, but is usually 60 eq / ton or less, preferably 50 eq / ton or less, and more preferably 30 eq / ton or less. By setting it to 60 eq / ton or less, gas generation during melt molding of the resin composition tends to be more effectively suppressed. The lower limit of the amount of terminal carboxyl groups is not particularly specified, but is usually 3 eq / ton or more, preferably 5 eq / ton or more, and more preferably 10 eq / ton or more.

[0020] The amount of terminal carboxyl groups in the thermoplastic polyester resin is a value measured by dissolving 0.5 g of the resin in 25 mL of benzyl alcohol and titrating it with a 0.01 mol / L benzyl alcohol solution of sodium hydroxide. The amount of terminal carboxyl groups can be adjusted by any conventionally known method, such as adjusting the polymerization conditions during polymerization, such as the raw material charging ratio, polymerization temperature, and pressure reduction method, or by reacting a terminal blocking agent.

[0021] The intrinsic viscosity of the thermoplastic polyester resin (preferably polybutylene terephthalate resin) is preferably 0.60 dL / g or more, more preferably 0.70 dL / g or more, even more preferably 0.80 dL / g or more, even more preferably 0.90 dL / g or more, and even more preferably 1.00 dL / g or more. By setting the intrinsic viscosity at or above the lower limit, deterioration of physical properties such as strength tends to be effectively suppressed. Furthermore, the intrinsic viscosity of the thermoplastic polyester resin (preferably polybutylene terephthalate resin) is preferably 2.0 dL / g or less, more preferably 1.8 dL / g or less, even more preferably 1.5 dL / g or less, even more preferably 1.3 dL / g or less, and even more preferably 1.2 dL / g or less. By setting the intrinsic viscosity at or below the upper limit, deterioration of fluidity tends to be effectively suppressed.

[0022] Intrinsic viscosity is measured by the following method. Thermoplastic polyester resin pellets are dissolved in a mixed solvent of phenol / 1,1,2,2-tetrachloroethane (1 / 1 by mass ratio) by stirring at 110°C for 1 hour to a concentration of 1.00 g / dL. The solution is then cooled to 30°C. Using a fully automatic solution viscometer, the number of seconds it takes for the sample solution and the solvent alone to fall at 30°C are measured, and the intrinsic viscosity is calculated using the formula: Intrinsic viscosity = ((1 + 4K Ｈ η ｓｐ ) ０．５ -1) / (2K Ｈ C) where η ｓｐ = η / η ０ -1, η is the number of seconds the sample solution falls, η ０ is the number of seconds for the solvent to fall, C is the concentration of the sample solution (g / dL), KＨ is Huggins' constant. Ｈ The intrinsic viscosity of the mixture was used. The fully automatic solution viscometer used was a product of Shibayama Scientific Co., Ltd. When the resin composition of the present embodiment contains two or more thermoplastic polyester resins, the intrinsic viscosity of the mixture was used.

[0023] The catalyst used in carrying out the esterification reaction may be a conventionally known catalyst, such as a titanium compound, a tin compound, a magnesium compound, or a calcium compound. Among these, titanium compounds are particularly preferred. Specific examples of titanium compounds used as esterification catalysts include titanium alcoholates such as tetramethyl titanate, tetraisopropyl titanate, and tetrabutyl titanate, and titanium phenolates such as tetraphenyl titanate.

[0024] The polybutylene terephthalate resin may be a polybutylene terephthalate resin modified by copolymerization (hereinafter, also referred to as a "modified polybutylene terephthalate resin"), and specific preferred copolymers thereof include polyester ether resins copolymerized with polyalkylene glycols (particularly polytetramethylene glycol), dimer acid copolymerized polybutylene terephthalate resins, and isophthalic acid copolymerized polybutylene terephthalate resins.

[0025] When a polyester ether resin copolymerized with polytetramethylene glycol is used as the modified polybutylene terephthalate resin, the proportion of the tetramethylene glycol component in the copolymer is preferably 3 to 40% by mass, more preferably 5 to 30% by mass, and even more preferably 10 to 25% by mass. When a dimer acid copolymerized polybutylene terephthalate resin is used as the modified polybutylene terephthalate resin, the proportion of the dimer acid component in all carboxylic acid components is preferably 0.5 to 30 mol%, more preferably 1 to 20 mol%, and even more preferably 3 to 15 mol%, in terms of carboxylic acid groups. When an isophthalic acid copolymerized polybutylene terephthalate resin is used as the modified polybutylene terephthalate resin, the proportion of the isophthalic acid component in all carboxylic acid components is preferably 1 to 30 mol%, more preferably 1 to 20 mol%, and even more preferably 3 to 15 mol%, in terms of carboxylic acid groups. Among the modified polybutylene terephthalate resins, polyester ether resins copolymerized with polytetramethylene glycol and isophthalic acid copolymerized polybutylene terephthalate resins are preferred.

[0026] <<Styrene-based Resin>> Examples of polystyrene-based resins include homopolymers of styrene-based monomers, copolymers of styrene-based monomers and monomers copolymerizable with styrene-based monomers, etc. In the copolymer of a styrene-based monomer and a monomer copolymerizable with a styrene-based monomer, the styrene-based monomer preferably accounts for 50% by mass or more of the total monomers, more preferably 60% by mass or more, and preferably 100% by mass or less.

[0027] The styrene-based monomer refers to styrene and substituted styrene, and examples thereof include styrene, α-methylstyrene, p-methylstyrene, vinylxylene, ethylstyrene, dimethylstyrene, p-tert-butylstyrene, vinylnaphthalene, methoxystyrene, monobromostyrene, dibromostyrene, fluorostyrene, tribromostyrene, etc., with styrene and α-methylstyrene being more preferred, and styrene being particularly preferred. Furthermore, among the monomers constituting the styrene-based resin, examples of monomers other than styrene-based monomers include (meth)acrylic acid ester-based monomers, maleimide-based monomers such as maleimide, N-methylmaleimide, and N-phenylmaleimide, α,β-unsaturated carboxylic acids and anhydrides thereof such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, phthalic acid, and itaconic acid, and rubbers such as butadiene.

[0028] The polystyrene resin used in this embodiment may contain a rubber-reinforced polystyrene resin. Specific examples of the rubber-reinforced polystyrene resin include acrylonitrile-styrene copolymer (AS resin), high impact polystyrene resin (HIPS), acrylonitrile-butadiene-styrene copolymer (ABS resin), acrylonitrile-acrylic rubber-styrene copolymer (AAS resin), acrylonitrile-styrene-acrylic rubber copolymer (ASA resin), acrylonitrile-ethylene propylene rubber-styrene copolymer (AES resin), and styrene-IPN type rubber copolymer.

[0029] The polystyrene resin used in this embodiment preferably contains a styrene-maleic acid polymer (preferably a styrene-maleic anhydride polymer). The styrene-maleic acid polymer acts as a compatibilizer between the polyester resin and the polystyrene resin and / or rubber-reinforced polystyrene resin. As a result, the strength of the resulting molded article can be increased.

[0030] In this embodiment, the polystyrene resin preferably contains at least one selected from polystyrene resin (GPPS), acrylonitrile-styrene copolymer (AS resin), high-impact polystyrene resin (HIPS), acrylonitrile-butadiene-styrene copolymer (ABS resin), acrylonitrile-acrylic rubber-styrene copolymer (AAS resin), acrylonitrile-styrene-acrylic rubber copolymer (ASA resin), and acrylonitrile-ethylene propylene rubber-styrene copolymer (AES resin), and more preferably contains high-impact polystyrene resin (HIPS). Furthermore, from the viewpoint of heat resistance, polystyrene resin (GPPS) and acrylonitrile-styrene copolymer (AS resin) are more preferable. The styrene resin used in this embodiment may be a virgin styrene resin or a recycled amorphous styrene resin.

[0031] <<Polycarbonate Resin>> A polycarbonate resin is an optionally branched thermoplastic polymer or copolymer obtained by reacting a dihydroxy compound or a dihydroxy compound together with a small amount of a polyhydroxy compound with phosgene or a carbonate diester.

[0032] The dihydroxy compound used as the raw material is one that is substantially free of bromine atoms, and is preferably an aromatic dihydroxy compound. Specific examples include 2,2-bis(4-hydroxyphenyl)propane (i.e., bisphenol A), tetramethylbisphenol A, bis(4-hydroxyphenyl)-p-diisopropylbenzene, hydroquinone, resorcinol, and 4,4-dihydroxydiphenyl, with bisphenol A being preferred. It is also possible to use a compound in which one or more tetraalkylphosphonium sulfonates are bonded to the above aromatic dihydroxy compounds.

[0033] Among the polycarbonate resins mentioned above, aromatic polycarbonate resins derived from 2,2-bis(4-hydroxyphenyl)propane or aromatic polycarbonate copolymers derived from 2,2-bis(4-hydroxyphenyl)propane and other aromatic dihydroxy compounds are preferred. Furthermore, copolymers primarily composed of aromatic polycarbonate resins, such as copolymers with polymers or oligomers having a siloxane structure, may also be used. Furthermore, two or more of the above-mentioned polycarbonate resins may be mixed and used.

[0034] To adjust the molecular weight of the polycarbonate resin, a monovalent aromatic hydroxy compound may be used, such as m- and p-methylphenol, m- and p-propylphenol, p-tert-butylphenol, and p-long-chain alkyl-substituted phenol.

[0035] The viscosity average molecular weight (Mv) of the polycarbonate resin is preferably 10,000 or more, more preferably 12,000 or more, even more preferably 13,000 or more, and particularly preferably more than 14,000. If a viscosity average molecular weight lower than 10,000 is used, the resulting resin composition tends to have low mechanical strength such as impact resistance. Furthermore, Mv is preferably 60,000 or less, more preferably 40,000 or less, even more preferably 35,000 or less, even more preferably 30,000 or less, and may be 25,000 or less, or 20,000 or less. If it is higher than 60,000, the fluidity of the resin composition may be poor and moldability may be impaired.

[0036] In the present invention, the viscosity average molecular weight (Mv) of the polycarbonate resin is a value calculated from the intrinsic viscosity ([η]) obtained by measuring the viscosity of a methylene chloride solution of the polycarbonate resin at 25°C using an Ubbelohde viscometer, and then using the following Schnell viscosity formula: [η] = 1.23 × 10 －４ Mv ０．８３

[0037] The melt flow rate (MFR) of the polycarbonate resin, measured in accordance with JIS K7210 (temperature 300°C, load 1.20 kgf), is preferably 3 to 100 g / 10 min, more preferably 6 to 70 g / 10 min. When the MFR is in the above range, the effects of the present invention tend to be more effectively exhibited. The melt volume rate (MVR) of the polycarbonate resin, measured in accordance with JIS K7210 (temperature 300°C, load 1.20 kgf), is preferably 0.5 to 20 cm. ３ g / 10 min, and 1 to 10 cm ３ When the MVR is in the above range, the effects of the present invention tend to be more effectively exhibited.

[0038] The method for producing the polycarbonate resin is not particularly limited, and polycarbonate resins produced by either the phosgene method (interfacial polymerization method) or the melt method (ester interchange method) can be used. Also preferred is a polycarbonate resin produced by the melt method and then subjected to post-treatment to adjust the amount of terminal OH groups.

[0039] The polycarbonate resin used in this embodiment may be a virgin polycarbonate resin or a recycled polycarbonate resin.

[0040] In one example of a blend form of thermoplastic resin in this embodiment, 70% by mass or more, preferably 80% by mass or more, 85% by mass or more, 90% by mass or more, or 95% by mass or more of the thermoplastic resin contained in the resin composition is a thermoplastic polyester resin (preferably a polyalkylene terephthalate resin, more preferably a polybutylene terephthalate resin).

[0041] In one example of a blend of thermoplastic resins in this embodiment, 70% by mass or more, preferably 80% by mass or more, 85% by mass or more, 90% by mass or more, or 95% by mass or more of the thermoplastic resins contained in the resin composition is a thermoplastic polyester resin (preferably polybutylene terephthalate resin) and a polystyrene resin and / or a polycarbonate resin. In this embodiment, the thermoplastic polyester resin in the thermoplastic resins contained in the resin composition is preferably 50% by mass or more, more preferably 55% by mass or more, and is preferably 80% by mass or less, more preferably 75% by mass or less.

[0042] The content of the thermoplastic resin in the resin composition of this embodiment is preferably 70% by mass or more, more preferably 75% by mass or more, and even more preferably 80% by mass or more, based on 100% by mass of the resin composition. Depending on the application, it may be 85% by mass or more, 90% by mass or more, 95% by mass or more, or preferably 99% by mass or less. Depending on the application, it may be 95% by mass or less, or 90% by mass or less. The resin composition of this embodiment may contain only one type of thermoplastic resin, or may contain two or more types. When two or more types are contained, it is preferable that the total amount is within the above range.

[0043] <Stabilizer> The resin composition of this embodiment preferably contains a stabilizer. By including the stabilizer, a resin composition or molded article having excellent thermal stability can be obtained. The stabilizer preferably contains one or more compounds selected from the group consisting of thioether compounds, hindered phenol compounds, and phosphite compounds, more preferably one or more compounds selected from the group consisting of hindered phenol compounds and phosphite compounds, and even more preferably a thioether compound. In this embodiment, it is also preferable to use two or more thioether compounds, hindered phenol compounds, and phosphite compounds in combination as needed. By using two or more stabilizers in combination in this way, thermal stability is further improved, and the thermal stability tends to be maintained for a long period of time.

[0044] The thioether-based compound may be any conventionally known sulfur-containing compound, and among these, thioethers are preferred. By including the thioether-based compound in the resin composition of the present embodiment, the appearance of the molded article tends to be improved and the thermal stability tends to be improved. Specific examples include didodecylthiodipropionate, ditetradecylthiodipropionate, dioctadecylthiodipropionate, pentaerythritol tetrakis(3-dodecylthiopropionate), 2,2-bis{[3-(dodecylthio)-1-oxopropoxy]methyl}propane-1,3-diylbis[3-(dodecylthio)propionate], thiobis(N-phenyl-β-naphthylamine), 2-mercaptobenzothiazole, 2-mercaptobenzimidazole, tetramethylthiuram monosulfide, tetramethylthiuram disulfide, nickel dibutyldithiocarbamate, nickel isopropyl xanthate, and trilauryl trithiophosphite. Among these, 2,2-bis{[3-(dodecylthio)-1-oxopropoxy]methyl}propane-1,3-diylbis[3-(dodecylthio)propionate] is preferred. Commercially available products include "Seenox 412S" manufactured by Shipro Chemical Co., Ltd. and "ADK STAB AO-412S" manufactured by ADEKA Corporation.

[0045] Examples of hindered phenol compounds include pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, thiodiethylenebis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), pentaerythritol tetrakis(3-(3,5-di-neopentyl-4-hydroxyphenyl)propionate), and 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene. Of these, pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) and octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate are preferred. Commercially available products include those manufactured by ADEKA Corporation under the trade names "ADK STAB AO-60" and "ADK STAB AO-330."

[0046] The phosphite compound is preferably a compound represented by the formula: ２ O-P (OR ３ ) (OR ４ ) (wherein, R ２ , R ３ and R ４ are each a hydrogen atom, an alkyl group having 1 to 30 carbon atoms, or an aryl group having 6 to 30 carbon atoms, and R ２ , R ３ and R ４At least one of the groups is an aryl group having 6 to 30 carbon atoms. Examples of the phosphite compound include triphenyl phosphite, tris(nonylphenyl) phosphite, dilauryl hydrogen phosphite, triethyl phosphite, tridecyl phosphite, tris(2-ethylhexyl) phosphite, tris(tridecyl) phosphite, tristearyl phosphite, diphenyl monodecyl phosphite, monophenyl didecyl phosphite, diphenyl mono(tridecyl) phosphite, tetraphenyl dipropylene glycol diphosphite, tetraphenyl tetra(tridecyl)pentaerythritol tetraphosphite, hydrogenated bisphenol A phenol phosphite polymer, diphenyl hydrogen phosphite, 4,4'-butylidene-bis(3-methyl-6-tert-butylphenyl di(tridecyl) phosphite), tetra(tridecyl) 4,4'-isopropyl phosphate, tetra(tridecyl) ... propylidenediphenyl diphosphite, bis(tridecyl)pentaerythritol diphosphite, bis(nonylphenyl)pentaerythritol diphosphite, dilauryl pentaerythritol diphosphite, distearyl pentaerythritol diphosphite, tris(4-tert-butylphenyl)phosphite, tris(2,4-di-tert-butylphenyl)phosphite, hydrogenated bisphenol A pentaerythritol phosphite polymer, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite, 2,2'-methylenebis(4,6-di-tert-butylphenyl)octyl phosphite, bis(2,4-dicumylphenyl)pentaerythritol diphosphite, and the like. Among these, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite is preferred. An example of a commercially available product is "ADEKA STAB PEP-36" manufactured by ADEKA Corporation.

[0047] Other examples of stabilizers include the following: the descriptions in paragraphs 0067 to 0075 of JP-A-2021-063196, the descriptions in paragraphs 0046 to 0057 of JP-A-2018-070722, the descriptions in paragraphs 0030 to 0037 of JP-A-2019-056035, and the descriptions in paragraphs 0066 to 0078 of WO 2017 / 038949. The contents of these descriptions are incorporated herein by reference.

[0048] The content of the stabilizer in the resin composition of this embodiment is 0.001 parts by mass or more, preferably 0.01 parts by mass or more, more preferably 0.03 parts by mass or more, even more preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more, relative to 100 parts by mass of the thermoplastic polyester resin. By setting the content at or above the lower limit, the effect of suppressing thermal degradation and oxidative degradation of the resin during melt-kneading, molding, and use as a molded product tends to be further improved, and heat resistance tends to be improved. Furthermore, the upper limit of the content of the stabilizer is 10.0 parts by mass or less, preferably 1.0 parts by mass or less, more preferably 0.8 parts by mass or less, more preferably 0.6 parts by mass or less, even more preferably 0.5 parts by mass or less, even more preferably 0.4 parts by mass or less, even more preferably 0.3 parts by mass or less, and even more preferably 0.24 parts by mass or less, relative to 100 parts by mass of the total thermoplastic polyester resin. By setting the content to the upper limit or less, adverse effects on the appearance and physical properties due to aggregation of additives such as stabilizers tend to be effectively suppressed, and discoloration of the resin composition tends to be suppressed. The resin composition of this embodiment may contain only one stabilizer, or may contain two or more stabilizers. When two or more stabilizers are contained, the total amount is preferably within the above range.

[0049] The resin composition of this embodiment can also be configured to be substantially free of stabilizers. "Substantially free of stabilizers" means, for example, that the stabilizer content is less than 0.001 parts by mass per 100 parts by mass of the thermoplastic resin, and may be less than 0.0001 parts by mass or even 0 parts by mass. If no stabilizer is added, discoloration occurs due to retention of the resin composition, but this can be compensated for by adding a colorant. For example, to achieve whiteness, titanium oxide can be added to make the resin composition substantially free of stabilizers.

[0050] <Silver-containing antibacterial agent> The resin composition of this embodiment contains a silver-containing antibacterial agent. By including the antibacterial agent, a resin composition or molded article with excellent antibacterial properties can be obtained. The silver-containing antibacterial agent of this embodiment is usually preferably an inorganic antibacterial agent (inorganic silver-based antibacterial agent) that elutes silver ions. More specifically, the silver-containing antibacterial agent of this embodiment is preferably one in which silver (preferably silver ions) is supported on zeolite, glass, a phosphate-based compound, or the like, and the antibacterial effect is exerted by the release of silver (preferably silver ions). The silver-containing antibacterial agent may also support a metal other than silver in addition to silver (preferably silver ions). Examples of metals other than silver include copper (preferably copper ions) and zinc (preferably zinc ions). The silver-containing antibacterial agent of this embodiment preferably includes a glass-based antibacterial agent.

[0051] The silver-containing antibacterial agent used in this embodiment is also preferably substantially free of zeolite. "Substantially free" means that the zeolite content is less than 10 parts by mass, preferably 1 part by mass or less, more preferably 0.1 parts by mass or less, and even more preferably 0.01 parts by mass or less, when the total weight of the silver-containing antibacterial agent is 100 parts by mass.

[0052] The glass-based antibacterial agent may be a soluble glass that supports silver (preferably silver ions) so that the silver (preferably silver ions) are eluted. ２ O ５ -RO-R ２O-based glass or B ２ O ３ -SiO ２ -R ２ O-based glass (RO is an oxide of alkaline earth metals such as CaO and MgO, and R ２ O is Li ２ O, Na ２ O.K. ２ and alkali metal oxides such as 0.

[0053] The average particle size of the silver-containing antibacterial agent in this embodiment is preferably 20 μm or less, more preferably 15 μm or less, and may be 1.5 μm or less, or may be 0.01 μm or more. The average particle size refers to the diameter of a sphere having the same volume as the silver-containing antibacterial agent, and this value is the number average particle size.

[0054] The silver-containing antibacterial agent may be blended into the resin composition as a masterbatch. When the silver-containing antibacterial agent is made into a masterbatch, the resin used for the masterbatch is preferably a thermoplastic polyester resin, more preferably a polyethylene terephthalate resin and / or a polybutylene terephthalate resin. The concentration of the silver-containing antibacterial agent when made into a masterbatch is preferably 1 to 50 mass%, more preferably 5 to 30 mass%. In particular, when the resin composition of this embodiment contains a flame retardant, it is preferable to also make the silver-containing antibacterial agent into a masterbatch. By adopting such a configuration, the productivity of the resin composition (e.g., pellets) tends to be further improved.

[0055] Commercially available products include "Bactekiller" (BM-102NS (SB), BM-103CL, BM-103CK, BM-103NA, FK-68, etc.) manufactured by Fuji Chemical Co., Ltd., "Million Guard" manufactured by Koa Glass Co., Ltd., and "Novalon" manufactured by Toagosei Co., Ltd.

[0056] The content of the silver-containing antibacterial agent in the resin composition of this embodiment is 0.1 parts by mass or more, preferably 0.2 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.4 parts by mass or more, relative to 100 parts by mass of the total thermoplastic polyester resin. By setting the content at or above the lower limit, the antibacterial properties of the resulting molded article tend to be further improved. Furthermore, the upper limit of the content of the silver-containing antibacterial agent is 10.0 parts by mass or less, preferably 3.0 parts by mass or less, more preferably 2.5 parts by mass or less, more preferably 2.0 parts by mass or less, even more preferably 1.5 parts by mass or less, even more preferably 1.0 parts by mass or less, even more preferably 0.9 parts by mass or less, and even more preferably 0.6 parts by mass or less, relative to 100 parts by mass of the total thermoplastic polyester resin. By setting the content at or below the upper limit, color change in the resulting molded article tends to be more effectively suppressed. Note that if the silver-containing antibacterial agent is in the form of a masterbatch, the amount of resin used in the masterbatch is not included in the above content. The resin composition of the present embodiment may contain only one type of silver-containing antibacterial agent, or may contain two or more types. When two or more types are contained, it is preferable that the total amount is in the above range.

[0057] <Halogen Compound> The resin composition of this embodiment contains a halogen compound. By including a halogen compound, a resin composition or molded article having excellent color stability can be obtained. The halogen compound used in this embodiment preferably contains at least one selected from the group consisting of fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms, more preferably contains at least one selected from the group consisting of fluorine atoms, chlorine atoms, and bromine atoms, and even more preferably contains bromine atoms and / or fluorine atoms. An example of a halogen compound in this embodiment contains a fluorine atom, and more preferably contains polytetrafluoroethylene. When a compound containing a fluorine atom is used as the halogen compound, the type is not particularly limited, but examples include homopolymers or copolymers of fluorine-containing monomers such as tetrafluoroethylene, chlorotrifluoroethylene, vinylidene fluoride, hexafluoropropylene, and perfluoroalkyl vinyl ether. Specific examples include homopolymers such as polytetrafluoroethylene, polychlorotrifluoroethylene, and polyvinylidene fluoride, and copolymers such as tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, ethylene-tetrafluoroethylene copolymer, and ethylene-chlorotrifluoroethylene copolymer. Another example of the halogen compound in this embodiment is one that contains a bromine atom, and more preferably contains a bromine-based flame retardant.

[0058] When a brominated flame retardant is used as the halogen compound, the type is not particularly limited, but brominated phthalimide, brominated poly(meth)acrylate, brominated polycarbonate, brominated epoxy, and brominated polystyrene are preferred, brominated phthalimide, brominated poly(meth)acrylate, brominated polycarbonate, and brominated epoxy are more preferred, brominated poly(meth)acrylate, brominated polycarbonate, and brominated epoxy are even more preferred, and brominated poly(meth)acrylate is even more preferred. In particular, brominated poly(meth)acrylate is more easily mixed with antimony compounds and can achieve better flame retardancy.

[0059] The brominated flame retardant preferably has a free bromine content of 0.5% by mass or more. By setting the content within this range, discoloration of the resin composition can be further suppressed. Furthermore, the free bromine content is preferably 2.0% by mass or less. By setting the content within this range, mold corrosion resistance during molding tends to be further improved.

[0060] The brominated phthalimide is preferably one represented by formula (1). (In formula (1), D represents an alkylene group, an arylene group, or —S(═O) ２ represents a group consisting of a combination of two or more of -, -C(=O)-, and -O-, and i is an integer of 1 to 4.

[0061] In formula (1), D is an alkylene group, an arylene group, or —S(═O) ２ represents a group consisting of a combination of two or more of -, -C(=O)-, and -O-, and is an alkylene group or an arylene group and -S(=O) ２ A group consisting of a combination of at least one of -, -C(=O)-, and -O- is preferred, and an alkylene group or an arylene group and -S(=O) ２ A group formed by combining one of -, -C(=O)-, and -O- is more preferred, and an alkylene group is even more preferred. The group formed by combining an alkylene group and -O- is intended to include, for example, a combination of two alkylene groups and one -O- (the same applies to other combinations). The alkylene group represented by D is preferably an alkylene group having 1 to 6 carbon atoms, and more preferably a methylene group, ethylene group, propylene group, or butylene group. The arylene group is preferably a phenylene group. i is an integer of 1 to 4, and preferably 4.

[0062] Examples of the brominated phthalimide represented by formula (1) include N,N'-(bistetrabromophthalimide)ethane, N,N'-(bistetrabromophthalimide)propane, N,N'-(bistetrabromophthalimide)butane, N,N'-(bistetrabromophthalimide)diethyl ether, N,N'-(bistetrabromophthalimide)dipropyl ether, N,N'-(bistetrabromophthalimide)dibutyl ether, N,N'-(bistetrabromophthalimide)diphenylsulfone, N,N'-(bistetrabromophthalimide)diphenyl ketone, and N,N'-(bistetrabromophthalimide)diphenyl ether.

[0063] The brominated phthalimide represented by formula (1) is preferably a brominated phthalimide represented by formula (2). (In formula (2), i is an integer of 1 to 4.) i is an integer of 1 to 4, and is preferably 4.

[0064] The brominated poly(meth)acrylate is preferably a polymer obtained by polymerizing a bromine atom-containing benzyl (meth)acrylate alone, copolymerizing two or more types of bromine atom-containing benzyl (meth)acrylate, or copolymerizing the bromine atom-containing benzyl (meth)acrylate with another vinyl monomer, and the bromine atoms are attached to a benzene ring, with 1 to 5 bromine atoms, preferably 4 to 5 bromine atoms, attached to each benzene ring.

[0065] Examples of the benzyl acrylate containing a bromine atom include pentabromobenzyl acrylate, tetrabromobenzyl acrylate, tribromobenzyl acrylate, and mixtures thereof. Examples of the benzyl methacrylate containing a bromine atom include methacrylates corresponding to the above-mentioned acrylates.

[0066] Specific examples of other vinyl monomers that can be copolymerized with the bromine atom-containing benzyl (meth)acrylate include acrylic acid esters such as acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, and benzyl acrylate; methacrylic acid esters such as methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, and benzyl methacrylate; unsaturated carboxylic acids or anhydrides thereof such as styrene, acrylonitrile, fumaric acid, and maleic acid; vinyl acetate; and vinyl chloride.

[0067] These are usually used in an equimolar amount or less, preferably 0.5 times or less, of the amount of benzyl (meth)acrylate containing a bromine atom.

[0068] Furthermore, examples of vinyl monomers that can be used include xylene diacrylate, xylene dimethacrylate, tetrabromxylene diacrylate, tetrabromxylene dimethacrylate, butadiene, isoprene, and divinylbenzene. These can usually be used in an amount of 0.5 times or less by mole relative to the bromine atom-containing benzyl acrylate or benzyl methacrylate.

[0069] The brominated poly(meth)acrylate is preferably a polymer obtained by polymerizing a bromine atom-containing (meth)acrylate monomer, particularly benzyl (meth)acrylate, alone or by copolymerizing two or more of them, or by copolymerizing them with other vinyl monomers. The bromine atoms are attached to benzene rings, with 1 to 5 bromine atoms, preferably 4 to 5 bromine atoms attached per benzene ring.

[0070] As the brominated poly(meth)acrylate, pentabromobenzyl poly(meth)acrylate is preferred because of its high bromine content.

[0071] The molecular weight of the brominated poly(meth)acrylate is optional and may be appropriately selected and determined, but the weight average molecular weight (Mw) is preferably 3,000 or more, more preferably 10,000 or more, even more preferably 15,000 or more, even more preferably 20,000 or more, and even more preferably 25,000 or more. By setting it to the lower limit or higher, molded articles with higher mechanical strength tend to be obtained. Furthermore, the upper limit of the weight average molecular weight (Mw) is preferably 100,000 or less, more preferably 80,000 or less, even more preferably 60,000 or less, even more preferably 50,000 or less, and even more preferably 35,000 or less. By setting it to the upper limit or lower, the flowability of the resin composition tends to be further improved.

[0072] A specific example of the brominated polycarbonate is preferably a brominated polycarbonate obtained from brominated bisphenol A, particularly tetrabromobisphenol A. Examples of the terminal structure include a phenyl group, a 4-t-butylphenyl group, and a 2,4,6-tribromophenyl group, and particularly, those having a 2,4,6-tribromophenyl group as the terminal group structure are preferred.

[0073] The average number of carbonate structural units in the brominated polycarbonate may be appropriately selected and determined, but is preferably 2 to 30, more preferably 3 to 15, and even more preferably 3 to 10.

[0074] The molecular weight of the brominated polycarbonate is optional and may be appropriately selected and determined, but preferably has a viscosity average molecular weight of 1,000 to 20,000, more preferably 2,000 to 10,000.

[0075] The brominated polycarbonate obtained from the above brominated bisphenol A can be obtained, for example, by a conventional method of reacting brominated bisphenol with phosgene. The end-capping agent includes an aromatic monohydroxy compound, which may be substituted with a halogen or an organic group.

[0076] Specific preferred examples of the brominated epoxy include bisphenol A type brominated epoxy compounds, such as tetrabromobisphenol A epoxy compounds and glycidyl brominated bisphenol A epoxy compounds.

[0077] The molecular weight of the brominated epoxy compound is optional and may be appropriately selected and determined. However, the weight average molecular weight (Mw) is preferably 3,000 or more, more preferably 10,000 or more, even more preferably 13,000 or more, even more preferably 15,000 or more, and even more preferably 18,000 or more. By setting the weight average molecular weight at or above the lower limit, molded articles with higher mechanical strength tend to be obtained. Furthermore, the upper limit of the weight average molecular weight (Mw) is preferably 100,000 or less, more preferably 80,000 or less, even more preferably 78,000 or less, even more preferably 75,000 or less, even more preferably 70,000 or less, and may even be 50,000 or less, 30,000 or less, or 25,000 or less. By setting the weight average molecular weight at or below the upper limit, the flowability of the resin composition tends to be further improved. The brominated epoxy compound preferably has an epoxy equivalent of 3,000 to 40,000 g / eq, more preferably 4,000 to 35,000 g / eq, and particularly preferably 10,000 to 30,000 g / eq.

[0078] A brominated epoxy oligomer can also be used as the brominated epoxy. In this case, for example, by using an oligomer having a Mw of 5,000 or less in a proportion of about 50% by mass or less, the flame retardancy, mold releasability, and flowability can be appropriately adjusted. The bromine atom content in the brominated epoxy compound is optional, but in order to impart sufficient flame retardancy, it is usually 10% by mass or more, preferably 20% by mass or more, and particularly preferably 30% by mass or more, with the upper limit being 60% by mass, and preferably 55% by mass or less.

[0079] The brominated polystyrene preferably includes a brominated polystyrene containing a constituent unit represented by formula (3). (In formula (3), t is an integer of 1 to 5, and n is the number of constitutional units.)

[0080] Brominated polystyrene may be produced by either brominating polystyrene or polymerizing brominated styrene monomers, but polymerizing brominated styrene is preferred because it has a low amount of free bromine (atoms). In formula (3), the CH group bonded to the brominated benzene may be substituted with a methyl group. Brominated polystyrene may also be a copolymer copolymerized with other vinyl monomers. Examples of vinyl monomers in this case include styrene, α-methylstyrene, (meth)acrylonitrile, methyl (meth)acrylate, butadiene, and vinyl acetate. Brominated polystyrene may be used alone or as a mixture of two or more types with different structures, and may contain units derived from styrene monomers with different bromine numbers in a single molecular chain.

[0081] Specific examples of brominated polystyrene include poly(4-bromostyrene), poly(2-bromostyrene), poly(3-bromostyrene), poly(2,4-dibromostyrene), poly(2,6-dibromostyrene), poly(2,5-dibromostyrene), poly(3,5-dibromostyrene), poly(2,4,6-tribromostyrene), poly(2,4,5-tribromostyrene), poly(2,3,5-tribromostyrene), and poly(4-bromo-α-methylstyrene). Examples of suitable bromine groups include poly(2,4,6-tribromostyrene), poly(2,4,5-tribromostyrene), poly(2,4,6-tribromostyrene), poly(2,4,5-tribromostyrene), and poly(2,4,6-tribromostyrene). Of these, poly(2,4,6-tribromostyrene), poly(2,4,5-tribromostyrene), and polydibromostyrene and polytribromostyrene containing an average of 2 to 3 bromine groups in the benzene ring are particularly preferred.

[0082] The brominated polystyrene preferably has the number n (average degree of polymerization) of structural units in formula (3) of 30 to 1,500, more preferably 150 to 1,000, and particularly preferably 300 to 800. If the average degree of polymerization is less than 30, blooming is likely to occur, while if it exceeds 1,500, poor dispersion is likely to occur and mechanical properties are likely to deteriorate. The weight-average molecular weight (Mw) of the brominated polystyrene is preferably 5,000 to 500,000, more preferably 10,000 to 500,000, even more preferably 10,000 to 300,000, even more preferably 10,000 to 100,000, and even more preferably 10,000 to 70,000. In particular, in the case of the brominated polystyrene described above, the weight average molecular weight (Mw) is preferably 50,000 to 70,000, and in the case of brominated polystyrene obtained by polymerization, the weight average molecular weight (Mw) is preferably about 10,000 to 30,000.

[0083] The bromine concentration in the brominated flame retardant is preferably 45% by mass or more, more preferably 48% by mass or more, even more preferably 50% by mass or more, and may be 55% by mass or more, or may be 60% by mass or more. By setting the bromine concentration at or above the lower limit, the flame retardancy of the molded article tends to be effectively improved. The upper limit of the bromine concentration is preferably 85% by mass or less, more preferably 80% by mass or less, even more preferably 75% by mass or less, and may be 73% by mass or less.

[0084] The content of the halogen compound in the resin composition of this embodiment is 0.1 parts by mass or more, preferably 0.5 parts by mass or more, more preferably 0.7 parts by mass or more, and even more preferably 1 part by mass or more, per 100 parts by mass of the total thermoplastic polyester resin. When flame retardancy is to be imparted to the resin composition, the content is preferably 5 parts by mass or more, even more preferably 8 parts by mass or more, and even more preferably 10 parts by mass or more. By setting the content at or above the lower limit, the flame retardancy of the resulting molded article tends to be further improved and color change tends to be more effectively suppressed. Furthermore, the upper limit of the content of the halogen compound is 30 parts by mass or less, preferably 25 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less, per 100 parts by mass of the total thermoplastic polyester resin. When the resin composition is used for applications that do not require high flame retardancy, the content is preferably 10 parts by mass or less, even more preferably 7 parts by mass or less, even more preferably 5 parts by mass or less, particularly preferably 4 parts by mass or less, and even more particularly preferably 3 parts by mass or less. By setting the content to the upper limit or less, it is likely that changes in color tone of the obtained molded product can be more effectively suppressed, and it is likely that deterioration of physical properties such as strength can be effectively suppressed. The resin composition of this embodiment may contain only one halogen compound, or may contain two or more halogen compounds. When two or more halogen compounds are contained, it is preferable that the total amount is in the above range.

[0085] In the resin composition of this embodiment, the mass ratio of halogen atoms contained in the halogen compound to the stabilizer, i.e., halogen atoms / stabilizer, is preferably 1.0 or more, more preferably 2.0 or more, and even more preferably 3.3 or more. By adjusting the ratio to be equal to or greater than the lower limit, color change can be more effectively suppressed. Furthermore, when high flame retardancy is required for the resin composition, the halogen atoms / stabilizer ratio is preferably 10 or more, more preferably 15 or more, even more preferably 20 or more, even more preferably 25 or more, even more preferably 30 or more, and particularly preferably 35 or more. The upper limit of the halogen atoms / stabilizer ratio is not particularly specified, but is usually 100 or less, and depending on the application, the required performance can be sufficiently met even if it is 70 or less, 50 or less, 40 or less, 20 or less, or even 10 or less or 5 or less.

[0086] <Other Components> The resin composition of this embodiment may contain other components in addition to those described above, as necessary, as long as the desired physical properties are not significantly impaired. The other components may be contained alone or in any combination and ratio of two or more. Examples of other components include reinforcing fillers and resin additives. Specific examples of resin additives include flame retardant aids, release agents, colorants (pigments, dyes), nucleating agents, reactive compounds, antistatic agents, antifogging agents, antiblocking agents, flow improvers, plasticizers, and dispersants. The total amount of these other components is preferably 0 to 10% by mass, more preferably 0 to 5% by mass, and even more preferably 0 to 3% by mass, based on 100% by mass of the resin composition. The resin composition of this embodiment is composed of the thermoplastic polyester resin, stabilizer, silver-containing antibacterial agent, halogen compound, and other components added as needed, totaling 100% by mass. In the resin composition of the present embodiment, the thermoplastic polyester resin, stabilizer, silver-containing antibacterial agent, halogen compound, flame retardant aid, and release agent preferably account for 90% by mass or more of the resin composition, more preferably 95% by mass or more, even more preferably 97% by mass or more, still more preferably 99% by mass or more, and 100% by mass or less.

[0087] <<Flame Retardant Auxiliary Agent>> The resin composition of this embodiment may contain a flame retardant auxiliary agent. By containing a flame retardant auxiliary agent, the flame retardancy of the molded article can be further improved. The flame retardant auxiliary agent is particularly preferably used when a halogen-based flame retardant agent is contained. Examples of the flame retardant auxiliary agent used in this embodiment include antimony compounds, and antimony trioxide (Sb ２ O ３ ), antimony pentoxide (Sb ２ O ５), sodium antimonate, etc. In particular, antimony oxide, especially antimony trioxide, is preferred from the standpoint of flame retardancy and impact resistance. When a flame retardant aid is blended, it may be blended as a masterbatch. The content of the antimony compound in the masterbatch is preferably 30 to 90 mass%, more preferably 40 to 85 mass%, even more preferably 50 to 85 mass%, even more preferably 60 to 85 mass%, and even more preferably 70 to 85 mass%. The resin used in the masterbatch is preferably a polyester resin, more preferably a polybutylene terephthalate resin.

[0088] When the resin composition of this embodiment contains a flame retardant aid (e.g., an antimony compound), the content thereof is preferably 0.1 parts by mass or more, more preferably 1.0 parts by mass or more, even more preferably 3.0 parts by mass or more, even more preferably 4.0 parts by mass or more, and even more preferably 5.0 parts by mass or more, relative to 100 parts by mass of the thermoplastic polyester resin. By setting the content at or above the lower limit, flame retardancy tends to be more effectively exhibited. Furthermore, the upper limit of the content of the antimony compound is preferably 20.0 parts by mass or less, more preferably 15.0 parts by mass or less, even more preferably 10.0 parts by mass or less, and even more preferably 8.0 parts by mass or less, relative to 100 parts by mass of the thermoplastic polyester resin. By setting the content at or below the upper limit, the impact resistance of the resulting molded article tends to be improved. The resin composition of this embodiment may contain only one type of flame retardant aid, or may contain two or more types. When two or more types are contained, the total amount preferably falls within the above range.

[0089] <<Release Agent>> The resin composition of this embodiment may contain a release agent. Examples of the release agent include aliphatic carboxylic acids, salts of aliphatic carboxylic acids, esters of aliphatic carboxylic acids and alcohols, aliphatic hydrocarbon compounds having a number average molecular weight of 200 to 15,000, polysiloxane-based silicone oils, ketone waxes, and light amides. Of these, aliphatic hydrocarbon compounds having a number average molecular weight of 200 to 15,000 are preferred.

[0090] Examples of aliphatic carboxylic acids include saturated or unsaturated aliphatic mono-, di-, or tri-carboxylic acids. Aliphatic carboxylic acids also include alicyclic carboxylic acids. Among these, preferred aliphatic carboxylic acids are mono- or di-carboxylic acids having 6 to 36 carbon atoms, with saturated aliphatic mono-carboxylic acids having 6 to 36 carbon atoms being more preferred. Specific examples of such aliphatic carboxylic acids include palmitic acid, stearic acid, caproic acid, capric acid, lauric acid, arachic acid, behenic acid, lignoceric acid, cerotic acid, melissic acid, tetraliacontanoic acid, montanic acid, adipic acid, and azelaic acid.

[0091] The aliphatic carboxylic acid in the ester of an aliphatic carboxylic acid and an alcohol can be, for example, the same as the aliphatic carboxylic acid described above. On the other hand, the alcohol can be, for example, a saturated or unsaturated monohydric or polyhydric alcohol. These alcohols may have a substituent such as a fluorine atom or an aryl group. Among these, monohydric or polyhydric saturated alcohols having 30 or fewer carbon atoms are preferred, and aliphatic saturated monohydric alcohols or aliphatic saturated polyhydric alcohols having 30 or fewer carbon atoms are even more preferred. The term "aliphatic" is used herein to encompass alicyclic compounds. Specific examples of such alcohols include octanol, decanol, dodecanol, stearyl alcohol, behenyl alcohol, ethylene glycol, diethylene glycol, glycerin, pentaerythritol, 2,2-dihydroxyperfluoropropanol, neopentylene glycol, ditrimethylolpropane, and dipentaerythritol. The esters described above may contain aliphatic carboxylic acids and / or alcohols as impurities. The esters described above may be pure substances or mixtures of multiple compounds. Furthermore, the aliphatic carboxylic acid and alcohol that combine to form one ester may each be used alone, or two or more may be used in any combination and ratio. Specific examples of esters of aliphatic carboxylic acids and alcohols include beeswax (a mixture mainly composed of myricyl palmitate), stearyl stearate, behenyl behenate, stearyl behenate, glycerin monopalmitate, glycerin monostearate, glycerin distearate, glycerin tristearate, pentaerythritol monopalmitate, pentaerythritol monostearate, pentaerythritol distearate, pentaerythritol tristearate, pentaerythritol tetrastearate, and rice wax.

[0092] Examples of aliphatic hydrocarbons having a number-average molecular weight of 200 to 15,000 include liquid paraffin, paraffin wax, microwax, polyethylene wax, Fischer-Tropsch wax, and α-olefin oligomers having 3 to 12 carbon atoms. Aliphatic hydrocarbons also include alicyclic hydrocarbons. These hydrocarbons may be partially oxidized. Among these, microwax, paraffin wax, polyethylene wax, or a partial oxide of polyethylene wax is preferred, with microwax being even more preferred. The number-average molecular weight of the aliphatic hydrocarbon is preferably 5,000 or less, more preferably 400 to 1,000. The aliphatic hydrocarbon may be a single substance, but even in the case of a mixture of substances with various constituent components and molecular weights, it is preferable that the main component is within the above-mentioned range.

[0093] Examples of polysiloxane-based silicone oils include dimethyl silicone oil, methylphenyl silicone oil, diphenyl silicone oil, and fluorinated alkyl silicone.

[0094] For details of the release agent, please refer to paragraphs 0055 to 0061 of JP 2018-095706 A, the contents of which are incorporated herein by reference. When the resin composition of this embodiment contains a release agent, the content thereof in the resin composition is preferably 0.05 to 3 parts by mass, more preferably 0.1 to 0.8 parts by mass, and even more preferably 0.1 to 0.6 parts by mass. The resin composition of this embodiment may contain only one type of release agent, or may contain two or more types. When two or more types are contained, it is preferable that the total amount be in the above range.

[0095] <<Colorant>> The resin composition of this embodiment may contain a colorant (dye and / or pigment). Examples of colorants that may be used in this embodiment include inorganic pigments such as titanium oxide and carbon black, organic dyes, and organic pigments, and inorganic pigments are preferred.

[0096] Examples of inorganic pigments include sulfide pigments such as carbon black, cadmium red, and cadmium yellow; silicate pigments such as ultramarine; oxide pigments such as zinc white, red iron oxide, chromium oxide, iron black, titanium yellow, zinc-iron brown, titanium-cobalt green, cobalt green, cobalt blue, copper-chromium black, and copper-iron black; chromate pigments such as yellow lead and molybdate orange; and ferrocyanide pigments such as Prussian blue, with titanium oxide being preferred. Examples of organic pigments and organic dyes include phthalocyanine dyes or pigments such as copper phthalocyanine blue and copper phthalocyanine green; azo dyes or pigments such as nickel azo yellow; condensed polycyclic dyes or pigments such as thioindigo, perinone, perylene, quinacridone, dioxazine, isoindolinone, and quinophthalone; and anthraquinone, heterocyclic, and methyl dyes or pigments. The colorant may be formulated as a masterbatch. In this case, the concentration of the coloring material in the masterbatch is 30 to 80% by mass. The thermoplastic resin to be made into the masterbatch is exemplified by polyester resin.

[0097] The content of the colorant is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, per 100 parts by mass of the thermoplastic resin. The content of the colorant is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, and even more preferably 2.0 parts by mass or less, per 100 parts by mass of the thermoplastic resin. The resin composition may contain only one type of colorant, or may contain two or more types. When two or more types are contained, the total amount is preferably within the above range.

[0098] <Physical Properties of Resin Composition> The resin composition of this embodiment preferably exhibits little change in color tone due to additives. Specifically, the difference (ΔE) between the color tone of the resin composition of this embodiment and the color tone of a resin composition obtained by removing the stabilizer, antibacterial agent, and halogen compound from the resin composition is preferably 10 or less, more preferably 6 or less, even more preferably 5 or less, even more preferably 4 or less, and particularly preferably 3 or less. The lower limit of ΔE is 0 or more, and even if it is 0.1 or more, the required performance is satisfied.

[0099] The resin composition of this embodiment preferably has excellent flame retardancy. For example, when the resin composition is molded into a 0.8 mm thick test piece and subjected to a UL-94 test, it preferably satisfies V-0. ΔE and flame retardancy are measured according to the description in the Examples below.

[0100] <Method for Producing Resin Composition> The resin composition of this embodiment can be produced by a conventional method for preparing a resin composition (e.g., pellets). Typically, the components and various optional additives are thoroughly mixed together and then melt-kneaded in a single-screw or twin-screw extruder. Alternatively, the resin composition of this embodiment can be prepared without premixing the components, or by premixing only a portion of the components, feeding the mixture into an extruder using a feeder and melt-kneading. A masterbatch may be prepared by melt-kneading some of the components of the silver-containing antibacterial agent or flame retardant aid with a thermoplastic resin to prepare a masterbatch, which may then be blended with the remaining components and melt-kneaded. The reinforcing filler (particularly glass fiber) is preferably supplied from a side feeder midway through the extruder cylinder. The heating temperature during melt-kneading can typically be selected from a range of 220 to 300°C. If the temperature is too high, decomposition gases are likely to be generated, which may cause opacity. Therefore, it is desirable to select a screw configuration that takes into account factors such as shear heat generation.

[0101] <Method for Manufacturing Molded Articles> The resin composition or pellets of this embodiment are molded according to known methods. The method for manufacturing molded articles is not particularly limited, and any molding method commonly used for resin compositions can be used. Examples include injection molding, ultra-high speed injection molding, injection compression molding, two-color molding, gas-assisted hollow molding, molding using an insulated mold, molding using a rapidly heated mold, foam molding (including supercritical fluid), insert molding, IMC (in-mold coating molding), extrusion molding, sheet molding, thermoforming, rotational molding, laminate molding, press molding, and blow molding. Of these, injection molding is preferred. For details of injection molding, see paragraphs 0113 to 0116 of Japanese Patent No. 6183822, the contents of which are incorporated herein by reference. Furthermore, the mold temperature during mold molding, such as injection molding, is preferably 40 to 150°C.

[0102] <Applications> The resin composition of this embodiment is used as a molded article formed from the resin composition or pellets. The applications of the resin composition and pellets are not particularly limited, and the resin composition and pellets can be widely used for home appliances, electrical and electronic equipment materials, automotive materials, housing materials, and materials for manufacturing parts in other industrial fields. More specifically, the resin composition and pellets are preferably used for sanitary parts such as kitchen, washroom, toilet, and other plumbing parts.

[0103] The discoloration suppression method of this embodiment is a method for suppressing discoloration of a resin composition containing 0.001 to 10.0 parts by mass of a stabilizer and 0.1 to 10.0 parts by mass of a silver-containing antibacterial agent relative to 100 parts by mass of a thermoplastic resin, and includes blending 0.1 to 30 parts by mass of a halogen compound relative to 100 parts by mass of the thermoplastic resin. The details of the thermoplastic resin, stabilizer, silver-containing antibacterial agent, and halogen compound are the same as those described above, and the blending amounts and preferred ranges are also the same.

[0104] The present invention will be explained in more detail below with reference to examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. If the measuring instruments used in the examples are difficult to obtain due to discontinuation or the like, measurements can be made using other instruments with equivalent performance.

[0105] 1. Raw materials The following raw materials were used:

[0106] <Free Bromine Content> The free bromine content was quantified by the combustion ion chromatography method described in paragraph 0083 of JP 2013-057009 A. Specifically, the brominated flame retardant or resin composition was heated under an argon atmosphere at 270°C for 10 minutes, and the amount of bromine generated was measured. An automatic sample combustion apparatus "AQF-100" manufactured by Mitsubishi Chemical Analytech Co., Ltd. was used to heat the resin composition, and an "ICS-90" apparatus manufactured by Nippon Dionex Co., Ltd. was used to measure the amount of bromine generated by heating the resin composition.

[0107] 2. Examples 1-1 to 1-13, 2-1 to 2-6, Comparative Examples 1-1 to 1-18, 2-1 to 2-6 <Compound> The components shown in Table 1 were uniformly mixed in a tumbler mixer in the proportions shown in Tables 2 to 6 (each component in Tables 2 to 6 is shown in parts by mass). The resulting mixture was fed to a twin-screw extruder ("TEX30α" manufactured by The Japan Steel Works, Ltd.) from the main feed port. The resin composition was melt-kneaded under conditions of a cylinder setting temperature of 260°C in the first kneading section and a screw rotation speed of 200 rpm, and then quenched in a water bath and pelletized using a pelletizer to obtain pellets of the resin composition.

[0108] <Color Tone> The pellets obtained above were collected and allowed to stand in a room at a temperature of 23°C and a humidity of 50% for 24 hours or more. Then, the color tone (L) was measured using an SE6000 model (light source: C / 2, reflected light) manufactured by Nippon Denshoku Industries Co., Ltd. ＊ , a ＊ , b ＊The color difference ΔE of each resin composition pellet was calculated based on the resin composition pellet containing polybutylene terephthalate resin and a release agent (Comparative Example 1-1).

[0109] <Flame Retardancy (Examples 2-1 to 2-6, Comparative Examples 2-1 to 2-6 only)> The pellets obtained above were dried at 110°C for 5 hours, and then combustion test specimens (12.7 mm width x 127 mm length x 0.8 mm thickness) were injection molded using an injection molding machine ("J-50AD" manufactured by The Japan Steel Works, Ltd.) under conditions of a cylinder temperature of 250°C and a mold temperature of 80°C. The obtained combustion test specimens were allowed to stand in an atmosphere of 70°C for 1 week, and then their flame retardancy was evaluated in accordance with the method of Subject 94 (UL94) of Underwriters Laboratories.

[0110] <Antibacterial Properties> The pellets obtained above were used in an injection molding machine (NEX-80, manufactured by Nissei Plastic Industrial Co., Ltd.) to produce molded specimens (length 100 mm x width 100 mm x thickness 2 mm) under conditions of a resin temperature of 250°C and a mold temperature of 80°C. The obtained molded specimens were cut into lengths of 50 mm x width 50 mm to obtain test specimens. An antibacterial test was carried out in accordance with JIS Z 2801. The test specimens were placed in a petri dish, and 0.4 mL of a test bacterial solution of Escherichia coli or Staphylococcus epidermidis was dropped onto them. The test specimens were then covered with a film (40 mm x 40 mm), and the petri dish was then covered with a lid. The petri dish was left to stand for 24 hours in an environment of 35°C and 90% RH or higher for incubation. Thereafter, 10 mL of lecithin sorbate 80 soybean casein digest agar (SCDLP) medium was added, and the test bacteria were washed out from the film and test piece. The number of bacteria in the liquid was measured by the agar plate culture method, and the antibacterial activity value was calculated according to the formula (a). Formula (a) Antibacterial activity value = log (1 cm of untreated sample) ２ Number of live bacteria per 1cm of processed sample) - log (number of live bacteria per 1cm of processed sample) ２ Antibacterial activity value ≧ 2.0: + Antibacterial activity Antibacterial activity value < 2.0: - No antibacterial activity

[0111] Before conducting the antibacterial test, the test specimens were pretreated by either (water resistance) immersing them in 50±10 mL of deionized water or distilled water at room temperature for 16 to 18 hours, or (light resistance) irradiating them with light for 10±0.5 hours using a xenon weather meter or for 8±0.5 hours using a sunshine weather meter. Under the following four conditions, (1) E. coli - water resistance, (2) E. coli - light resistance, (3) Staphylococcus aureus - water resistance, and (4) Staphylococcus aureus - light resistance, those whose antibacterial activity value was 2.0 or greater under all conditions were rated as A, and those whose antibacterial activity value was <2.0 under any of the conditions were rated as B.

[0112] <Thermal Stability> The pellets obtained above were molded into dumbbell test specimens in accordance with ISO 527 using an injection molding machine (manufactured by The Japan Steel Works, J85-AD) under conditions of a resin temperature of 250°C and a mold temperature of 80°C. Thereafter, the dumbbell test specimens were left to stand for 500 hours at a temperature of 120°C using a thermostatic testing machine (manufactured by Espec Corporation). Thereafter, a tensile test was carried out in accordance with ISO 527. Test specimens with a tensile strength retention rate of 80% or more relative to the test specimen before the heat treatment were rated as A, and those with a tensile strength retention rate of less than 80% were rated as B.

[0113] <Retention Thermal Stability> The pellets obtained above were used in an injection molding machine (NEX-80, manufactured by Nissei Plastic Industrial Co., Ltd.) to produce a "retention molded plate" (length 100 mm x width 100 mm x thickness 2 mm) under conditions of a cylinder temperature of 270°C, a mold temperature of 80°C, and a cooling time of 300 seconds. Furthermore, the pellets obtained above were used in an injection molding machine (NEX-80, manufactured by Nissei Plastic Industrial Co., Ltd.) to produce a "reference plate" (length 100 mm x width 100 mm x thickness 2 mm) under conditions of a cylinder temperature of 270°C, a mold temperature of 80°C, and a cooling time of 15 seconds. The color tone of the obtained plate was measured using a spectrophotometer (CM-36dg, manufactured by Konica Minolta) to measure the color tone (L ＊ , a ＊ , b ＊ The color difference ΔE of the "retention molded plate" relative to the "reference plate" was calculated, and a ΔE of less than 1 was rated A, a ΔE of 1 or more but less than 3 was rated B, and a ΔE of 3 or more was rated C.

[0114]

[0115]

[0116]

[0117]

[0118]

[0119]

[0120] In the above table, the content of "antibacterial agent" refers to the content of the antibacterial agent itself in the resin composition, and does not include resin components in which the antibacterial agent is masterbatched. In the above table, the content of "halogen atoms" refers to the content of the halogen itself contained in the halogen compound. In the above table, the content of "halogen atoms / stabilizer" indicates the mass ratio of the halogen atoms contained in the halogen compound to the stabilizer.

[0121] As is clear from the above results, the resin composition of this embodiment has a good balance of antibacterial property, thermal stability, and color stability. Furthermore, by increasing the content of the flame retardant, it is possible to achieve excellent flame retardancy while maintaining an excellent balance of antibacterial property, thermal stability, and color stability.

Claims

1. A resin composition comprising, per 100 parts by mass of a thermoplastic resin, 0.001 to 10.0 parts by mass of a stabilizer, 0.1 to 10.0 parts by mass of a silver-containing antibacterial agent, and 0.1 to 30 parts by mass of a halogen compound.

2. The resin composition according to claim 1, wherein the mass ratio of the halogen atoms contained in the resin composition to the stabilizer, that is, halogen atoms / stabilizer, is 1.0 or more.

3. The resin composition according to claim 1, wherein the thermoplastic resin comprises a thermoplastic polyester resin.

4. The resin composition according to claim 3, wherein the thermoplastic polyester resin comprises a polybutylene terephthalate resin.

5. The resin composition according to claim 1, wherein the stabilizer comprises one or more compounds selected from the group consisting of thioether compounds, hindered phenol compounds, and phosphite compounds.

6. The resin composition according to claim 1, wherein the stabilizer comprises a thioether compound.

7. The resin composition according to claim 1, wherein the silver-containing antibacterial agent comprises an inorganic silver-based antibacterial agent.

8. The resin composition according to claim 1, wherein the silver-containing antibacterial agent comprises a glass-based antibacterial agent.

9. The resin composition according to claim 1, wherein the halogen compound contains a bromine atom and / or a fluorine atom.

10. The resin composition according to claim 1, wherein the halogen compound contains a fluorine atom.

11. The resin composition according to claim 1, wherein the halogen compound contains a bromine atom.

12. The resin composition according to claim 11, wherein the amount of free bromine in the halogen compound is 0.5 mass% or more.

13. A resin composition for use in sanitary parts, comprising a thermoplastic polyester resin having an intrinsic viscosity of 1.0 dL / g or more, an antibacterial agent containing silver, and titanium oxide.

14. The resin composition according to claim 1, wherein the mass ratio of halogen atoms contained in the resin composition to the stabilizer, halogen atoms / stabilizer, is 1.0 or more, the thermoplastic resin comprises a polybutylene terephthalate resin, the stabilizer comprises one or more compounds selected from the group consisting of hindered phenol compounds and phosphite compounds, the silver-containing antibacterial agent comprises a glass-based antibacterial agent, and the halogen compound comprises a bromine atom and / or a fluorine atom.

15. Pellets of the resin composition according to any one of claims 1 to 14.

16. A molded article formed from the resin composition according to any one of claims 1 to 14.

17. A molded article formed from the pellets of claim 15.

18. The molded article according to claim 16, which is a part for sanitary purposes.

19. A method for inhibiting discoloration of a resin composition containing 0.001 to 10.0 parts by mass of a stabilizer and 0.1 to 10.0 parts by mass of an antibacterial agent containing silver per 100 parts by mass of thermoplastic resin, the method comprising blending 0.1 to 30 parts by mass of a halogen compound per 100 parts by mass of the thermoplastic resin.

20. A method for inhibiting discoloration of a resin composition containing 0.01 to 1.0 part by mass of a stabilizer and 0.1 to 3.0 parts by mass of an antibacterial agent containing silver per 100 parts by mass of thermoplastic polyester resin, the method comprising blending 0.1 to 30 parts by mass of a halogen compound per 100 parts by mass of the thermoplastic polyester resin.

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