Resin composition and molded article

Abstract

The present invention provides: a resin composition that makes it possible to provide a molded article which can maintain high strength and in which an increase in YI value is suppressed, even after a long period of irradiation with ultraviolet light; and a molded article that is formed from the resin composition. Provided is a resin composition comprising a polyamide resin and a triazine-based ultraviolet absorber, wherein: the polyamide resin contains a xylylenediamine-based polyamide resin which contains a constituent unit derived from a diamine and a constituent unit derived from dicarboxylic acid, in which not less than 70 mol% of the constituent unit derived from the diamine is derived from xylylenediamine, and in which not less than 70 mol% of the constituent unit derived from the dicarboxylic acid is derived from a C6-14 α,ω-linear aliphatic dicarboxylic acid; the triazine-based ultraviolet absorber exhibits an absorbance of not less than 0.50 for the wavelength of 290 nm when in the form of a 10 mg / L chloroform solution; and the content of the triazine-based ultraviolet absorber is not less than 0.5 mass% of the total mass of the resin composition.

Description

Resin composition and molded article

[0001] The present invention relates to a resin composition and a molded article.

[0002] Polyamide resins are known for their excellent moldability, mechanical properties, and chemical resistance. Therefore, they are widely used as materials for various parts in automotive, electrical and electronic applications, industrial materials, and daily necessities and household goods. In particular, the environments in which polyamide resins are used have become increasingly thermally and mechanically severe in recent years. Therefore, there is a demand for polyamide resin materials that exhibit minimal deterioration in mechanical strength even when used outdoors.

[0003] For example, Patent Document 1 discloses a polyamide composition containing (A) an aliphatic polyamide, (B) a semi-aromatic polyamide containing diamine units and dicarboxylic acid units, (C1) a flame retardant, (C2) a flame retardant aid, (D) a white pigment, and (E) an ultraviolet absorber, wherein the tan δ peak temperature of the polyamide composition is 90°C or higher, and the mass ratio (E) / (D) of the ultraviolet absorber to the white pigment contained in the polyamide composition is 0.15 or higher and less than 2.50. Patent Document 1 also teaches that the resin composition can be used to form molded articles that have good weld strength and Rockwell hardness when absorbing water, good surface appearance, and good weather discoloration resistance.

[0004] Japanese Patent Application Laid-Open No. 2019-089905

[0005] However, it has been found that molded articles formed from the resin compositions described in the above-mentioned documents suffer from severe color deterioration (an increase in the YI value) when exposed to ultraviolet light for a long period of time. On the other hand, polyamide resins synthesized from xylylenediamine and aliphatic dicarboxylic acids are resins with various excellent physical properties, but suffer from a significant decrease in strength due to ultraviolet light. That is, the strength of the resins significantly decreases from their initial state when exposed to ultraviolet light for a long period of time. The present invention aims to solve this problem by providing a resin composition capable of providing molded articles that suppress an increase in the YI value and maintain high strength even when exposed to ultraviolet light for a long period of time, and a molded article formed from the resin composition.

[0006] In light of the above-mentioned problems, the present inventors conducted research and found that the above-mentioned problems could be solved by blending a predetermined amount of a specific triazine-based UV absorber with a xylylenediamine-based polyamide resin, leading to the completion of the present invention. Specifically, the above-mentioned problems were solved by the following means. <1> A resin composition containing a polyamide resin and a triazine-based UV absorber, wherein the polyamide resin contains diamine-derived structural units and dicarboxylic acid-derived structural units, and the xylylenediamine-based polyamide resin contains 70 mol % or more of the diamine-derived structural units derived from xylylenediamine and 70 mol % or more of the dicarboxylic acid-derived structural units derived from an α,ω-linear aliphatic dicarboxylic acid having 6 to 14 carbon atoms, and the triazine-based UV absorber has an absorbance of 0.50 or more at a wavelength of 290 nm in a 10 mg / L chloroform solution, and the content of the triazine-based UV absorber is 0.5 mass % or more relative to the total mass of the resin composition. <2> The resin composition according to <1>, wherein the α,ω-linear aliphatic dicarboxylic acid having 6 to 14 carbon atoms includes an α,ω-linear aliphatic dicarboxylic acid having 8 to 14 carbon atoms. <3> The resin composition according to <1>, wherein the α,ω-linear aliphatic dicarboxylic acid having 6 to 14 carbon atoms includes sebacic acid and / or dodecanedioic acid. <4> The resin composition according to <1>, wherein the α,ω-linear aliphatic dicarboxylic acid having 6 to 14 carbon atoms includes dodecanedioic acid. <5> The resin composition according to any one of <1> to <4>, wherein the triazine-based ultraviolet absorber includes an ultraviolet absorber represented by the following formula (1): Formula (1) (In formula (1), each R is independently an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 15 carbon atoms, or a hydroxyl group, and each n is independently an integer of 0 to 4.) <6> The resin composition according to any one of <1> to <5>, wherein the content of the xylylenediamine-based polyamide resin is 90.0 mass% or more based on the total mass of the polyamide resin. <7> The resin composition according to any one of <1> to <6>, wherein the resin composition is for extrusion molding. <8> A molded article formed from the resin composition according to any one of <1> to <7>. <9> The molded article according to <8>, wherein the molded article is an extrusion molded article. <10> The molded article according to <8>, wherein the molded article is a film. <11> The molded article according to <8>, wherein the molded article is a fiber.

[0007] The present invention has made it possible to provide a resin composition capable of providing a molded article that can suppress an increase in YI value and maintain high strength even when irradiated with ultraviolet light for a long period of time, and a molded article formed from the resin composition.

[0008] Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. Note that the following present embodiment is an example for explaining the present invention, and the present invention is not limited to only this embodiment. Note that in this specification, "to" is used to mean that the numerical values ​​written before and after it are included as lower and upper limits. In this specification, various physical property values ​​and characteristic values ​​are at 23°C unless otherwise specified. If the standards shown in this specification differ depending on the year, such as the measurement method, they shall be based on the standards as of January 1, 2021, unless otherwise specified.

[0009] The resin composition of this embodiment is a resin composition containing a polyamide resin and a triazine-based UV absorber, wherein the polyamide resin contains diamine-derived structural units and dicarboxylic acid-derived structural units, wherein 70 mol % or more of the diamine-derived structural units are derived from xylylenediamine, and 70 mol % or more of the dicarboxylic acid-derived structural units are derived from an α,ω-linear aliphatic dicarboxylic acid having 6 to 14 carbon atoms. The triazine-based UV absorber has an absorbance of 0.50 or more at a wavelength of 290 nm in a 10 mg / L chloroform solution, and the content of the triazine-based UV absorber is 0.5% by mass or more relative to the total mass of the resin composition. By using this configuration, a resin composition can be obtained that can provide molded products that suppress an increase in YI value and maintain high strength even when irradiated with UV light for a long period of time. In this specification, a triazine-based ultraviolet absorber having an absorbance of 0.50 or more at a wavelength of 290 nm in a 10 mg / L chloroform solution state may be referred to as a "specific triazine-based ultraviolet absorber."

[0010] Polyamide resins, particularly xylylenediamine-based polyamide resins, tend to lose strength when irradiated with light having a wavelength of 280 to 300 nm. This is presumably because light in this wavelength range easily cleaves the polyamide resin's main chain, particularly the carbon-carbon chain adjacent to the amide bond. In this embodiment, the use of a UV absorber with high absorption capacity for light with a wavelength of 290 nm is presumably effective in suppressing scission of the polyamide resin's main chain. In particular, scission of the polyamide resin's main chain due to UV irradiation promotes crosslinking, making the resin brittle and reducing its strength. In particular, scission of the polyamide resin's main chain and the progress of crosslinking promotes crosslinking, increasing the Mw value but minimizing the change in the Mn value. That is, ΔMw / Mn increases. In this embodiment, the suppression of an increase in ΔMw / Mn even after prolonged UV irradiation is presumably responsible for achieving high strength retention. Furthermore, the use of a triazine-based UV absorber can provide excellent heat resistance during processing, particularly during extrusion molding.

[0011] <Polyamide Resin> The resin composition of this embodiment contains a polyamide resin. The polyamide resin used in this embodiment may be a crystalline polyamide resin or an amorphous polyamide resin, but is preferably a crystalline polyamide resin. A crystalline polyamide resin is one that exhibits a melting point when measured by differential scanning calorimetry (DSC). The polyamide resin contains diamine-derived structural units and dicarboxylic acid-derived structural units, and includes a xylylenediamine-based polyamide resin in which 70 mol % or more of the diamine-derived structural units are derived from xylylenediamine and 70 mol % or more of the dicarboxylic acid-derived structural units are derived from an α,ω-linear aliphatic dicarboxylic acid having 6 to 14 carbon atoms. By including a xylylenediamine-based polyamide resin, molded articles with excellent physical properties can be obtained.

[0012] The xylylenediamine-based polyamide resin preferably contains 80 mol% or more, more preferably 85 mol% or more, even more preferably 90 mol% or more, and even more preferably 95 mol% or more of the diamine-derived structural units derived from xylylenediamine. Furthermore, 100 mol% or less of the diamine-derived structural units of the xylylenediamine-based polyamide resin may be derived from xylylenediamine. The xylylenediamine preferably contains 0 to 100 mol% metaxylylenediamine and 100 to 0 mol% paraxylylenediamine, more preferably 10 to 100 mol% metaxylylenediamine and 90 to 0 mol% paraxylylenediamine, even more preferably 20 to 100 mol% metaxylylenediamine and 80 to 0 mol% paraxylylenediamine, and even more preferably 50 to 90 mol% metaxylylenediamine and 50 to 10 mol% paraxylylenediamine. The total amount of metaxylylenediamine and paraxylylenediamine is preferably 90 mol % or more, and does not exceed 100 mol %.

[0013] Preferably, 80 mol% or more, more preferably 85 mol% or more, even more preferably 90 mol% or more, and even more preferably 95 mol% or more of the dicarboxylic acid-derived structural units of the xylylenediamine-based polyamide resin are derived from α,ω-straight-chain aliphatic dicarboxylic acids having 6 to 14 carbon atoms. Furthermore, 100 mol% or less of the dicarboxylic acid-derived structural units of the xylylenediamine-based polyamide resin may be derived from α,ω-straight-chain aliphatic dicarboxylic acids having 6 to 14 carbon atoms. The α,ω-straight-chain aliphatic dicarboxylic acids having 6 to 14 carbon atoms preferably include α,ω-straight-chain aliphatic dicarboxylic acids having 8 to 14 carbon atoms. By using an α,ω-straight-chain aliphatic dicarboxylic acid having 8 or more carbon atoms, the number of amide bonds in the resin is relatively small, thereby reducing the frequency of main chain cleavage of the polyamide resin due to ultraviolet irradiation. As the α,ω-linear aliphatic dicarboxylic acid having 6 to 14 carbon atoms, adipic acid, sebacic acid, suberic acid, dodecanedioic acid, eicodionic acid, etc. can be suitably used, with adipic acid, sebacic acid, and dodecanedioic acid being more preferred, sebacic acid and / or dodecanedioic acid being even more preferred, and dodecanedioic acid being even more preferred.

[0014] Diamines other than xylylenediamine that can be used as the raw diamine component of the xylylenediamine-based polyamide resin include aliphatic diamines such as tetramethylenediamine, pentamethylenediamine, 2-methylpentanediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, dodecamethylenediamine, 2,2,4-trimethylhexamethylenediamine, and 2,4,4-trimethylhexamethylenediamine; 1,3-bis(aminomethyl)silane; Examples of such diamines include alicyclic diamines such as cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, bis(4-aminocyclohexyl)methane, 2,2-bis(4-aminocyclohexyl)propane, bis(aminomethyl)decalin, and bis(aminomethyl)tricyclodecane; and diamines having an aromatic ring such as bis(4-aminophenyl)ether, paraphenylenediamine, and bis(aminomethyl)naphthalene. These diamines may be used alone or in combination of two or more.

[0015] Examples of dicarboxylic acid components other than the above-mentioned α,ω-linear aliphatic dicarboxylic acids having 6 to 14 carbon atoms include phthalic acid compounds such as isophthalic acid, terephthalic acid, and orthophthalic acid, and isomers of naphthalenedicarboxylic acids such as 1,2-naphthalenedicarboxylic acid, 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 1,7-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid, and these can be used alone or in combination of two or more.

[0016] The xylylenediamine-based polyamide resin used in this embodiment is primarily composed of diamine-derived structural units and dicarboxylic acid-derived structural units, but does not completely exclude other structural units. It goes without saying that it may contain structural units derived from lactams such as ε-caprolactam and laurolactam, and aliphatic aminocarboxylic acids such as aminocaproic acid and aminoundecanoic acid. Here, "major component" refers to the structural units constituting the xylylenediamine-based polyamide resin in which the combined number of diamine-derived structural units and dicarboxylic acid-derived structural units is the largest among all structural units. In this embodiment, the combined total of the diamine-derived structural units and dicarboxylic acid-derived structural units in the xylylenediamine-based polyamide resin preferably accounts for 90% by weight or more of all structural units, more preferably 95% by weight or more, and even more preferably 98% by weight or more of all structural units excluding terminal groups.

[0017] The polyamide resin contained in the resin composition of this embodiment may be entirely (100% by mass) xylylenediamine-based polyamide resin, or may contain other polyamide resins. Examples of other polyamide resins include semi-aromatic polyamide resins such as terephthalic acid-based polyamide resins (polyamide 6T, polyamide 9T, polyamide 10T, polyamide 6T / 6I), and aliphatic polyamide resins such as polyamide 6, polyamide 11, polyamide 12, polyamide 46, polyamide 66, polyamide 610, polyamide 612, polyamide 6 / 66, and polyamide 1010. For example, polyamide 6 is a ring-opening polymer of caprolactam, but may contain structural units derived from other monomers within the scope of the present invention (e.g., 5% by mass or less, preferably 3% by mass or less, particularly 1% by mass or less). The same applies to other polyamide resins such as polyamide 66.

[0018] In this embodiment, the content of the xylylenediamine-based polyamide resin is preferably 90.0 mass% or more, more preferably 93.0 mass% or more, and even more preferably 97.0 mass% or more, based on the total mass of the polyamide resins contained in the resin composition. The resin composition of this embodiment may contain two or more types of xylylenediamine-based polyamide resins, and when two or more types are contained, the total amount is preferably in the above range.

[0019] The weight-average molecular weight (Mw) of the polyamide resin (preferably a xylylenediamine-based polyamide resin) used in this embodiment is preferably 8,000 or more, more preferably 10,000 or more, even more preferably 20,000 or more, even more preferably 30,000 or more, and even more preferably 35,000 or more. The weight-average molecular weight (Mw) of the polyamide resin used in this embodiment is preferably 100,000 or less, more preferably 96,000 or less, even more preferably 94,000 or less, and may even be 60,000 or less. The number-average molecular weight (Mn) of the polyamide resin used in this embodiment is preferably 6,000 or more, more preferably 8,000 or more, even more preferably 10,000 or more, and even more preferably 19,000 or more. Furthermore, the number average molecular weight (Mn) of the polyamide resin (preferably a xylylenediamine-based polyamide resin) used in this embodiment is preferably 50,000 or less, more preferably 48,000 or less, even more preferably 46,000 or less, and even more preferably 40,000 or less. The Mw / Mn of the polyamide resin used in this embodiment is preferably 3.50 or less, more preferably 3.00 or less, even more preferably 2.50 or less, even more preferably 2.30 or less, and even more preferably 2.20 or less. By keeping the Mw / Mn ratio below the upper limit, the stability of the fluidity and melt viscosity during melting is increased, and the processability of melt-kneading and melt-molding is improved. Furthermore, when processed into a film or fiber, the molecular chains are uniformly oriented, which tends to improve toughness and various physical properties such as water absorption resistance, chemical resistance, and heat aging resistance. Although there is no particular lower limit, in a method of polymerization by dehydration polycondensation of a nylon salt aqueous solution or a method of polymerization by dropping a diamine into a molten dicarboxylic acid, which are used in general manufacturing processes, 1.5 is a level close to the limit. When the resin composition of the present embodiment contains two or more polyamide resins, it is preferable that the mixture falls within the above range.

[0020] The resin composition of the present embodiment may contain a polyamide resin other than the xylylenediamine-based polyamide resin.

[0021] The content of the polyamide resin in the resin composition of this embodiment is preferably 85% by mass or more of the resin composition, more preferably 90% by mass or more, even more preferably 93% by mass or more, even more preferably 96% by mass or more, and even more preferably 98% by mass or more. The upper limit of the content of the polyamide resin is when the total of the polyamide resin and the specific triazine-based ultraviolet absorber accounts for 100% by mass of the resin composition. The resin composition of this embodiment may contain only one type of polyamide 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.

[0022] <Specific Triazine-Based UV Absorber> The resin composition of this embodiment contains 0.5% by mass or more of a triazine-based UV absorber (specific triazine-based UV absorber) having an absorbance of 0.50 or more at a wavelength of 290 nm in a 10 mg / L chloroform solution, relative to the total mass of the resin composition. This configuration allows the resulting molded article to maintain its mechanical strength even after a light resistance test. Furthermore, by using a UV absorber represented by the formula (1) described below, a lower YI value can be maintained. The specific triazine-based UV absorber has an absorbance of 0.50 or more at a wavelength of 290 nm in a 10 mg / L chloroform solution, preferably 0.60 or more, more preferably 0.65 or more, and even more preferably 0.70 or more. By adjusting the absorbance to be equal to or greater than the lower limit, ultraviolet light that affects main chain scission of the polyamide resin can be efficiently absorbed, and the effect of suppressing strength reduction due to molecular weight reduction and crosslinking reaction progression tends to be further improved. There is no particular upper limit to the absorbance, but the absorbance of commercially available ultraviolet absorbents is usually 1.5 or less.

[0023] The specific triazine-based ultraviolet absorber preferably contains a triphenyltriazine structure, and more preferably is a compound represented by formula (1): (In formula (1), each R is independently an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 15 carbon atoms, or a hydroxyl group, and each n is independently an integer of 0 to 4.)

[0024] In formula (1), each R is preferably independently an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 4 to 15 carbon atoms, or a hydroxyl group. Each n is preferably independently an integer of 0 to 3, and more preferably an integer of 0 to 2.

[0025] The compound represented by formula (1) preferably includes a compound represented by formula (2). (In formula (2), R ２ is an alkyl group having 1 to 15 carbon atoms, and R ３ are each independently an alkyl group having 1 to 10 carbon atoms, and n2 is each independently an integer having 0 to 4 carbon atoms. ２ is preferably an alkyl group having 4 to 15 carbon atoms, and more preferably an alkyl group having 4 to 12 carbon atoms. ３ are each independently preferably an alkyl group having 1 to 5 carbon atoms, more preferably a methyl group or an ethyl group, and even more preferably a methyl group. n2 are each independently preferably an integer of 0 to 3, and even more preferably an integer of 0 to 2.

[0026] The molecular weight of the specific triazine-based ultraviolet absorber is preferably 310 or more, and is preferably 1,000 or less, more preferably 800 or less, and may be 700 or less.

[0027] The content of the specific triazine-based ultraviolet absorber in the resin composition of this embodiment is 0.5% by mass or more, preferably 0.6% by mass or more, more preferably 0.8% by mass or more, even more preferably 1.0% by mass or more, even more preferably 1.4% by mass or more, and even more preferably 1.7% by mass or more. By ensuring that the content is above the lower limit, the effect of ultraviolet light on main chain scission of the polyamide resin can be significantly suppressed, and the decrease in molecular weight and strength due to the progress of the crosslinking reaction can be more effectively suppressed. Furthermore, the content of the specific triazine-based ultraviolet absorber in the resin composition is preferably 5.0% by mass or less, more preferably 4.0% by mass or less, even more preferably 3.5% by mass or less, and even more preferably 3.0% by mass or less. By ensuring that the content is below the upper limit, an increase in haze due to aggregation of incompletely dispersed ultraviolet absorbers can be more effectively suppressed. The resin composition of this embodiment may contain only one type of specific triazine-based ultraviolet absorber, or may contain two or more types. When two or more types are contained, the total amount is preferably within the above range.

[0028] <Other Components> The resin composition of this embodiment may contain other components within the scope of this embodiment. Examples of such additives include thermoplastic resins other than polyamide resins, fillers, UV absorbers other than specific triazine-based UV absorbers, antioxidants, hydrolysis resistance improvers, weather stabilizers, matting agents, fluorescent brighteners, anti-dripping agents, antistatic agents, anti-fogging agents, anti-blocking agents, flow improvers, plasticizers, dispersants, antibacterial agents, and flame retardants. These components may be used alone or in combination of two or more. For details of these components, please refer to paragraphs

[0130] to

[0155] of Japanese Patent No. 4,894,982, paragraph

[0021] of JP-A-2010-281,027, and paragraph

[0036] of JP-A-2016-223,037, the contents of which are incorporated herein by reference.

[0029] Examples of thermoplastic resins other than polyamide resins include polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polycarbonate resins, polyoxymethylene resins, polyether ketones, polyether sulfones, and thermoplastic polyether imides. In this embodiment, it is preferable that the composition is substantially free of thermoplastic resins other than polyamide resins. "Substantially free" means that the proportion of thermoplastic resins other than polyamide resins among the resin components contained in the resin composition of this embodiment is 5% by mass or less, preferably 3% by mass or less, and may be 1% by mass or less.

[0030] The resin composition of the present embodiment preferably contains substantially no ultraviolet absorbers other than the specific triazine-based ultraviolet absorber. "Substantially no ultraviolet absorbers" means that the proportion of ultraviolet absorbers other than the specific triazine-based ultraviolet absorber among the ultraviolet absorbers contained in the resin composition of the present embodiment is 5% by mass or less, preferably 3% by mass or less, and may be 1% by mass or less.

[0031] Specific examples of the plasticizer include hexyldecyl p-hydroxybenzoate (Exsepal HD-PB, manufactured by Kao Corporation), ethylhexyl p-hydroxybenzoate, ethylhexyl o-hydroxybenzoate, and N-butylbenzenesulfonamide. The disclosures in paragraphs 0033 to 0038 of WO 2017 / 010389 may also be referred to, the contents of which are incorporated herein by reference.

[0032] In the resin composition of this embodiment, the contents of the polyamide resin, the triazine-based UV absorber, and other additives are adjusted so that the total of each component is 100% by mass. In this embodiment, the total of the polyamide resin and the triazine-based UV absorber accounts for 98% by mass or more of the resin composition.

[0033] <Physical Properties of Resin Composition> The resin composition of this embodiment preferably has a small change in Mw / Mn (ΔMw / Mn) before and after ultraviolet irradiation. Specifically, the resin composition is preferably irradiated with a xenon lamp (JIS K 7350-2 A method, irradiation intensity: 60 W / m2 ), the change in Mw / Mn before and after irradiation with ultraviolet light for 400 hours (ΔMw / Mn) is preferably 0.70 or less, more preferably 0.50 or less, even more preferably 0.40 or less, and even more preferably 0.35 or less. The lower limit of ΔMw / Mn is ideally 0, but practically 0.01 or more is used. ΔMw / Mn is measured as described in the Examples below.

[0034] The resin composition of this embodiment preferably has a high strength retention rate before and after ultraviolet irradiation. Specifically, the resin composition is preferably irradiated with a xenon lamp (JIS K 7350-2 A method, irradiation intensity: 60 W / m 2 ) and the tensile strength retention rate after 400 hours of irradiation with ultraviolet light is preferably 40% or more, more preferably 60% or more, even more preferably 65% ​​or more, even more preferably 70% or more, still more preferably 73% or more, and even more preferably 75% or more. The upper limit of the tensile strength retention rate is ideally 100%, but even if it is 90% or less, the performance requirements are sufficiently met. The tensile strength retention rate is measured as described in the Examples below.

[0035] The resin composition of the present embodiment is preferably capable of suppressing a change in color before and after ultraviolet irradiation. Specifically, the resin composition is preferably a resin composition that is irradiated with a xenon lamp (JIS K 7350-2 A method, irradiation intensity: 60 W / m 2 After 400 hours of irradiation with ultraviolet light using a xenon lamp (JIS K 7350-2 A method, irradiation intensity: 60 W / m), the YI value is preferably 15 or less, more preferably 10 or less, even more preferably 7 or less, even more preferably 6 or less, and even more preferably 5 or less. The lower limit of the YI is ideally 0, but practically 0.10 or more. 2 The YI value after 400 hours of irradiation with ultraviolet light is measured according to the method described in the Examples below.

[0036] <Method for Producing Resin Composition> The method for producing the resin composition of this embodiment is not particularly limited, but a method using a single-screw or twin-screw extruder equipped with a vent port for volatilization is preferred. The polyamide resin, triazine-based UV absorber, and other additives to be blended as needed may be fed to the blender all at once, or the polyamide resin component may be fed first, followed by the other blending components. Alternatively, two or more components selected from each component may be mixed and blended in advance.

[0037] <Molded Article> The above-described resin composition (e.g., pellets) is molded into a molded article by various molding methods. That is, the molded article of this embodiment is molded from the resin composition of this embodiment. The shape of the molded article is not particularly limited and can be appropriately selected depending on the use and purpose of the molded article. Examples include film-like, rod-like, cylindrical, annular, circular, elliptical, polygonal, irregularly shaped, hollow, frame-like, box-like, panel-like, and button-like shapes. Of these, film-like, frame-like, panel-like, and button-like shapes are preferred, and the thickness is, for example, about 1 mm to 5 mm in the case of frame-like and panel-like shapes.

[0038] The method for molding the molded article is not particularly limited, and conventionally known molding methods can be used, such as injection molding, injection compression molding, extrusion molding, profile extrusion, transfer molding, blow molding, gas-assisted blow molding, blow molding, extrusion blow molding, IMC (in-mold coating molding), rotational molding, multilayer molding, two-color molding, insert molding, sandwich molding, foam molding, and pressure molding. In particular, the resin composition of this embodiment is suitable for molded articles obtained by injection molding, injection compression molding, and extrusion molding, and is even more suitable for molded articles (extrusion molded articles) obtained by extrusion molding. However, it goes without saying that the resin composition of this embodiment is not limited to molded articles obtained by these methods.

[0039] One embodiment of the molded article formed from the resin composition of this embodiment is a film. It is particularly preferably used as a stretched film. For details of the film, see paragraphs 0036 to 0042 of JP 2020-200405 A, the contents of which are incorporated herein by reference.

[0040] Another embodiment of the molded article formed from the resin composition of this embodiment is a fiber (filament). In particular, it is preferably used as a stretched fiber. For details of the fiber (filament), please refer to paragraphs 0026 to 0031 of WO 2020 / 250564, the contents of which are incorporated herein by reference.

[0041] The resin composition and molded article of the present embodiment are suitable for applications in which they are exposed to ultraviolet rays for long periods of time, and are particularly widely used in transportation vehicle parts such as automobiles, general machine parts, precision machine parts, electronic and electrical device parts, office automation device parts, building materials and housing-related parts, medical devices, leisure and sporting goods, play equipment, defense and aerospace products, etc.

[0042] 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.

[0043] 1. Raw Materials <Polyamide Resin> PA-1: MP12 (polyamide composed of MXDA, PXDA, and dodecanedioic acid, MXDA / PXDA=70 mol% / 30 mol%) PA-2: MP10 (polyamide composed of MXDA, PXDA, and sebacic acid, MXDA / PXDA=70 mol% / 30 mol%) PA-3: MXD6 (polyamide composed of MXDA and adipic acid), manufactured by Mitsubishi Gas Chemical Company, Inc., #6000

[0044] <<Synthesis of MP12>> A reaction vessel equipped with a stirrer, partial condenser, total condenser, thermometer, dropping funnel, nitrogen inlet tube, and strand die was charged with 11,377 g (49.4 mol) of 1,12-dodecanedioic acid and 11.66 g of sodium acetate / sodium hypophosphite monohydrate (molar ratio = 1 / 1.5). After thorough nitrogen replacement, the system was heated to 170°C while stirring under a small nitrogen stream. 6,647 g of a mixed xylylenediamine (34.16 mol meta-xylylenediamine and 14.64 mol para-xylylenediamine) having a molar ratio of meta-xylylenediamine to para-xylylenediamine of 70 / 30 (manufactured by Mitsubishi Gas Chemical Company, Inc.) was added dropwise to the molten mixture in the reaction vessel with stirring. The resulting condensed water was discharged from the system, and the internal temperature was continuously raised to 235°C over 2.5 hours. After the dropwise addition was completed, the internal temperature was increased, and when it reached 240° C., the pressure inside the reaction vessel was reduced, and the internal temperature was further increased to continue the melt polycondensation reaction for 10 minutes at 250° C. Thereafter, the system was pressurized with nitrogen, and the obtained polymer was removed from the strand die and pelletized to obtain a polyamide resin.

[0045] Synthesis Example of MP10: A reaction vessel equipped with a stirrer, partial condenser, total condenser, thermometer, dropping funnel, nitrogen inlet tube, and strand die was charged with 9991 g (49.4 mol) of sebacic acid and 11.66 g of sodium acetate / sodium hypophosphite monohydrate (molar ratio = 1 / 1.5). After thorough nitrogen replacement, the system was heated to 170°C while stirring under a small amount of nitrogen flow. 6647 g of a mixed xylylenediamine (34.16 mol metaxylylenediamine and 14.64 mol paraxylylenediamine) having a molar ratio of metaxylylenediamine to paraxylylenediamine of 70 / 30 (manufactured by Mitsubishi Gas Chemical Company, Inc.) was added dropwise to the molten mixture in the reaction vessel with stirring. The resulting condensed water was discharged from the system, and the internal temperature was continuously raised to 235°C over 2.5 hours. After the dropwise addition was completed, the internal temperature was increased, and when it reached 240° C., the pressure inside the reaction vessel was reduced, and the internal temperature was further increased to continue the melt polycondensation reaction for 10 minutes at 250° C. Thereafter, the system was pressurized with nitrogen, and the obtained polymer was removed from the strand die and pelletized to obtain a polyamide resin.

[0046] <Number Average Molecular Weight (Mn) and Weight Average Molecular Weight (Mw)> The number average molecular weight (Mn) and weight average molecular weight (Mw) of the polyamide resin and resin composition were measured according to GPC measurement. Specifically, a Tosoh Corporation "HLC-8320GPC" was used as the apparatus, and two Tosoh Corporation "TSK gel Super HM-H" columns were used. Measurements were performed under the conditions of an eluent containing hexafluoroisopropanol (HFIP) with a sodium trifluoroacetate concentration of 10 mmol / L, a resin concentration of 0.02 mass%, a column temperature of 40 ° C., and a flow rate of 0.3 mL / min, and the values ​​were calculated as standard polymethyl methacrylate equivalents. A calibration curve was also prepared by dissolving six levels of PMMA in HFIP and measuring.

[0047] <Ultraviolet absorber> UVA-1: KEMISORB 102, manufactured by Chemipro Chemicals Co., Ltd. UVA-2: TINUVIN 1577ED, manufactured by BASF UVA-3: Adekastab LA-31, manufactured by ADEKA Corporation UVA-4: Adekastab LA-F70, manufactured by ADEKA Corporation

[0048] <Measurement of absorbance of UV absorber at a wavelength of 290 nm> The absorbance of a 10 mg / L chloroform solution of the UV absorber at a wavelength of 290 nm was measured as follows. 10.0 mg of the UV absorber was weighed and added to a 100 mL volumetric flask. Chloroform (Kanto Chemical Co., Ltd.) was added to the solution to make the volume constant. Subsequently, 1.0 mL of the solution was weighed and added to a 10 mL volumetric flask, and then chloroform was added to make the volume constant, thereby preparing a 10 mg / L chloroform solution. Using the prepared 10 mg / L chloroform solution, absorbance measurements were performed using an ultraviolet-visible-near-infrared spectrophotometer (Shimadzu Corporation, UV-3600Plus). The measurement wavelength range was 250 to 600 nm.

[0049] 2. Examples 1 to 5 and Comparative Examples 1 to 4 <Film Production> The polyamide resin and the UV absorber were weighed and dry-blended to obtain the compositions shown in Table 1 below, with the amount of UV absorber in the resin composition being the amount shown in Table 1. The materials were then fed into a twin-screw extruder equipped with a T-die (PTM-30, manufactured by Plastics Engineering Research Institute) from the screw base and melt-kneaded to obtain a film having a width of 200 mm and a thickness of 180 μm. The temperature of the extruder was set to 280° C.

[0050] <Preparation of Stretched Film> The obtained film was cut into 135 mm squares. Thereafter, using a batch-type biaxial stretching device (tenter method, EX10-S5, manufactured by Toyo Seiki Seisakusho Co., Ltd.), the film was stretched in both the MD (machine direction) and TD (transverse direction) while heated in an air atmosphere at 70°C, with a stretch ratio of 4 in the MD (machine direction), 2.25 in the TD (transverse direction), and a total stretch ratio of 9, to obtain a stretched film with a thickness of 20 μm. The stretching temperature was 70°C. After stretching, the film was heat-set. The heat-set temperature was 180°C, and the heat-set time was 30 seconds.

[0051] <Lightfastness Test (Measurement of Molecular Weight and YI)> The number average molecular weight (Mn) and weight average molecular weight (Mw) of the obtained unstretched film were measured according to the above-mentioned method, and further, the Mw / Mn value was calculated. The YI value was also measured according to the following method. Next, the film used for the YI value measurement was subjected to a lightfastness test using a lightfastness tester (trade name: Suntest XXL+, manufactured by Atlas Co., Ltd.) with a xenon lamp (in accordance with JIS K 7350-2 Method A, irradiation intensity: 60 W / m 2 ) and was continuously irradiated with ultraviolet light for 400 hours. The test was carried out with the temperature in the test room set to 38°C and the relative humidity set to 50% RH. After measuring the YI value of the irradiated film, the number average molecular weight (Mn) and weight average molecular weight (Mw) were measured according to the method described above, and the Mw / Mn value was calculated. Furthermore, the difference in Mw / Mn before and after ultraviolet irradiation (ΔMw / Mn, Mw / Mn after irradiation - Mw / Mn before irradiation) was calculated.

[0052] <Yellowness Index (YI)> The unstretched film obtained was cut into a 40 mm square, and the YI value was measured using a color / turbidity meter (trade name: COH-400A, manufactured by Nippon Denshoku Industries Co., Ltd.).

[0053] <Solubility in HFIP> The solubility of the resin composition in hexafluoro-2-propanol (HFIP) was evaluated as follows. 5 mg of the sample (obtained film) was weighed into a 13.5 cc vial, and 5 g of HFIP was added. The vial was shaken every 30 minutes, and the state was visually inspected two hours after the addition of HFIP to determine the solubility. As the crosslinking reaction progresses, the resin composition tends to become embrittled, so the solubility of the sample measured by GPC was evaluated as follows: A: Dissolved without problems (no crosslinking observed) B: Other than A and C, for example, some undissolved matter was generated (crosslinking progressed in some areas), etc. C: Partially dissolved, but much undissolved matter remained (crosslinking reaction progressed in most areas)

[0054] <Lightfastness Test (Tensile Strength Retention Rate)> The tensile strength of the obtained stretched film was measured at a test speed of 50 mm / min using a 10 mm wide strip according to JIS K 7127. For the measurement, a tensile test was performed in the MD of the stretched film, with a chuck distance of 50 mm. The tensile speed was set to 50 mm / min. The measurement environment was an atmosphere of 23°C and 50% relative humidity (RH). Next, the obtained stretched film was cut into 100 mm squares and continuously irradiated with ultraviolet light for 400 hours under the same conditions as for the unstretched film. The irradiated stretched film was subjected to a tensile test in the same manner as before irradiation, the tensile strength was measured, and the tensile strength retention rate was calculated using the following formula: Tensile strength retention rate (%) = (tensile strength before ultraviolet light irradiation (MPa) - tensile strength before ultraviolet light irradiation (MPa)) / tensile strength before ultraviolet light irradiation (MPa) × 100

[0055]

[0056] The molded article formed from the resin composition of the present invention exhibited a suppressed increase in YI and a high strength retention rate even after UV irradiation. Furthermore, the increase in ΔMw / Mn was suppressed, indicating that the progress of the crosslinking reaction of the molded article during UV irradiation was suppressed.

Claims

1. A resin composition comprising a polyamide resin and a triazine-based ultraviolet absorber, the polyamide resin comprises a xylylenediamine-based polyamide resin containing a diamine-derived structural unit and a dicarboxylic acid-derived structural unit, in which 70 mol % or more of the diamine-derived structural units are derived from xylylenediamine, and 70 mol % or more of the dicarboxylic acid-derived structural units are derived from an α,ω-linear aliphatic dicarboxylic acid having 6 to 14 carbon atoms; The triazine-based ultraviolet absorber has an absorbance of 0.50 or more at a wavelength of 290 nm in a state of a 10 mg / L chloroform solution, A resin composition, wherein the content of the triazine-based ultraviolet absorber is 0.5 mass% or more based on the total mass of the resin composition.

2. The resin composition according to claim 1, wherein the α,ω-linear aliphatic dicarboxylic acid having 6 to 14 carbon atoms comprises an α,ω-linear aliphatic dicarboxylic acid having 8 to 14 carbon atoms.

3. The resin composition according to claim 1, wherein the α,ω-linear aliphatic dicarboxylic acid having 6 to 14 carbon atoms includes sebacic acid and / or dodecanedioic acid.

4. The resin composition according to claim 1, wherein the α,ω-linear aliphatic dicarboxylic acid having 6 to 14 carbon atoms includes dodecanedioic acid.

5. The resin composition according to any one of claims 1 to 4, wherein the triazine-based ultraviolet absorber comprises an ultraviolet absorber represented by the following formula (1): Formula (1) 【Chemistry 1】 (In formula (1), each R is independently an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 15 carbon atoms, or a hydroxyl group, and each n is independently an integer of 0 to 4.)

6. The resin composition according to any one of claims 1 to 4, wherein the content of the xylylenediamine-based polyamide resin is 90.0 mass% or more based on the total mass of the polyamide resin.

7. The resin composition according to any one of claims 1 to 4, which is for extrusion molding.

8. The triazine-based ultraviolet absorber includes an ultraviolet absorber represented by the following formula (1): The content of the xylylenediamine-based polyamide resin is 90.0% by mass or more based on the total mass of the polyamide resin, The resin composition according to claim 1, which is for extrusion molding. Formula (1) 【Chemistry 2】 (In formula (1), each R is independently an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 15 carbon atoms, or a hydroxyl group, and each n is independently an integer of 0 to 4.)

9. A molded article formed from the resin composition according to any one of claims 1 to 4 and 8.

10. The molded article according to claim 9, wherein the molded article is an extrusion molded article.

11. The molded article according to claim 9, wherein the molded article is a film.

12. The molded article of claim 9 , wherein the molded article is a fiber.

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