Polyamide resin composition, extrusion molded body, and tubular molded body

Abstract

To provide a polyamide resin composition excellent in flexibility, fluidity, and retention stability during thick-wall extrusion molding.SOLUTION: Wherein the semi-aromatic polyamide (A) has a melting temperature of less than 280 °C. and a terminal amino group concentration [NH2] (μ eq / g) of 45 μ eq / g or more, A total content of the modified ethylene / α - olefin copolymer (B) and the styrene-based thermoplastic elastomer (C) is 10 to 40% by mass with respect to a total content of the semi-aromatic polyamide (A), the modified ethylene / α - olefin copolymer (B), and the styrene-based thermoplastic elastomer (C), and the styrene-based thermoplastic elastomer (C) contains less than 0.9% by mass of a unit derived from at least one selected from the group consisting of an unsaturated carboxylic acid and a derivative of an unsaturated carboxylic acid.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyamide resin composition, an extrusion molded article, and a tubular molded article. [Background technology]

[0002] Polyamides are excellent in strength, heat resistance, chemical resistance, etc., and have been used for automobile fuel pipes, oil or gas transport pipes, etc. A method of blending a specific elastomer containing a functional group reactive with polyamide has long been known as a method of imparting flexibility and impact resistance to polyamide.

[0003] For example, Patent Document 1 discloses a semi-aromatic polyamide resin composition containing a semi-aromatic polyamide resin having a specific melting point and structure, an olefin polymer containing a modified ethylene-α-olefin copolymer modified by a specific amount, and a styrene-based thermoplastic elastomer. Patent Document 2 discloses a polyamide resin composition containing a semi-aromatic polyamide, a modified ethylene-α-olefin copolymer as a polyolefin, and a fatty acid metal salt. Patent Document 3 discloses a hose for transporting fluids, which includes an inner layer made of a thermoplastic resin composition containing a thermoplastic resin and an elastomer, a reinforcing layer disposed on the outside of the inner layer, and an outer layer disposed on the outside of the reinforcing layer, in which a polyamide resin is used as the thermoplastic resin and a styrene-based elastomer is used as the elastomer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-135310 [Patent Document 2] International Publication No. 2024 / 029470 [Patent Document 3] Japanese Patent Publication No. 2022-122718 Summary of the Invention [Problem to be solved by the invention]

[0005] Increasing the amount of elastomer contained in a polyamide resin composition can improve the flexibility and impact resistance of the polyamide resin composition. However, when a polyamide resin composition containing an elastomer is extruded into a thick wall, the polyamide resin composition remains in a molten state in a molding machine for a relatively long time, which causes problems such as an excessive increase in the melt viscosity of the polyamide resin composition during the residence time, resulting in a decrease in moldability and residence stability.

[0006] Therefore, an object of the present invention is to provide a polyamide resin composition that is excellent in flexibility, fluidity, and retention stability during thick-wall extrusion molding, an extrusion molded article made of the polyamide resin composition, and a tubular molded article having the extrusion molded article. [Means for solving the problem]

[0007] The present inventors have found that the above-mentioned problems can be solved by providing a polyamide resin composition containing a specific semi-aromatic polyamide (A), a modified ethylene-α-olefin copolymer (B), and a specific styrene-based thermoplastic elastomer (C), and containing specific amounts of the modified ethylene-α-olefin copolymer (B) and the styrene-based thermoplastic elastomer (C), and have thus completed the present invention.

[0008] The present invention relates to the following [1] to

[10] . [1] A polyamide resin composition comprising a semi-aromatic polyamide (A), a modified ethylene-α-olefin copolymer (B), and a styrene-based thermoplastic elastomer (C), The semi-aromatic polyamide (A) has a melting point of less than 280°C and a terminal amino group concentration [NH] (μeq / g) of 45 μeq / g or more, the total content of the modified ethylene-α-olefin copolymer (B) and the styrene-based thermoplastic elastomer (C) is 10 to 40 mass% based on the total content of the semi-aromatic polyamide (A), the modified ethylene-α-olefin copolymer (B), and the styrene-based thermoplastic elastomer (C); The polyamide resin composition, wherein the styrene-based thermoplastic elastomer (C) contains less than 0.9% by mass of units derived from at least one selected from the group consisting of unsaturated carboxylic acids and derivatives of unsaturated carboxylic acids. [2] The semi-aromatic polyamide (A) contains diamine units and dicarboxylic acid units, The diamine unit contains 50 mol% or more of diamine units derived from aliphatic diamines having 4 to 18 carbon atoms relative to the total diamine units, The polyamide resin composition according to the above [1], which contains aromatic dicarboxylic acid units in an amount of 50 mol % or more based on the total carboxylic acid units. [3] The polyamide resin composition according to the above [2], wherein the aliphatic diamine having 4 to 18 carbon atoms is at least one selected from the group consisting of 1,9-nonanediamine and 2-methyl-1,8-octanediamine. [4] The polyamide resin composition according to the above [2] or [3], wherein the aromatic dicarboxylic acid is terephthalic acid. [5] The polyamide resin composition according to any one of the above [1] to [4], wherein the styrene-based thermoplastic elastomer (C) contains units derived from an unsaturated carboxylic acid anhydride. [6] The polyamide resin composition according to any one of the above [1] to [5], wherein the modified ethylene-α-olefin copolymer (B) is modified with at least one selected from the group consisting of unsaturated carboxylic acids and unsaturated carboxylic acid anhydrides. [7] The flexural modulus M (GPa) of a dumbbell-shaped tensile test piece type A1 made of the polyamide resin composition obtained in accordance with JIS K7139:2009, measured in accordance with ISO178:2019, and the shear rate of the polyamide resin composition measured in accordance with JIS K7199:1999 are 121.6 s -1The polyamide resin composition according to any one of the above [1] to [6], wherein the melt viscosity P (Pa·s) satisfies the following formula (I): Flexural modulus M (GPa) × melt viscosity P (Pa·s) < 2092 (GPa × Pa·s) (I) [8] The CIE lightness index L obtained in accordance with JIS Z 8781-4:2013 of a dumbbell-shaped tensile test piece type A1 made of the polyamide resin composition obtained in accordance with JIS K7139:2009 * The polyamide resin composition according to any one of the above [1] to [7], wherein the value of [kJ / kcal] is 39 or less. [9] An extrusion molded article made of the polyamide resin composition according to any one of the above [1] to [8].

[10] A tubular molded article having the extrusion molded article according to [9] above. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a polyamide resin composition that is excellent in flexibility, flowability, and retention stability during thick-wall extrusion molding, an extrusion-molded article made of the polyamide resin composition, and a tubular molded article having the extrusion-molded article. DETAILED DESCRIPTION OF THE INVENTION

[0010] The following describes an example of an embodiment of the present invention (hereinafter, sometimes referred to as "the present embodiment"). However, the embodiment described below is merely an example for embodying the technical idea of ​​the present invention, and the present invention is not limited to the following description. The present invention also includes any selected or combined embodiment of the matters described in this specification. In this specification, preferred definitions can be selected arbitrarily, and combinations of preferred definitions can be considered more preferred. In this specification, the expression "XX to YY" means "XX or more and YY or less." In this specification, for preferred numerical ranges (e.g., ranges of content, etc.), the lower and upper limits described in stages can be independently combined. For example, the description "preferably 10 to 90, more preferably 30 to 60" can be combined with the "preferable lower limit (10)" and the "more preferable upper limit (60)" to form "10 to 60." Furthermore, in this specification, "units of ~" (where "~" indicates a monomer) means "units derived from ~", for example, "dicarboxylic acid units" means "units derived from dicarboxylic acids", and "diamine units" means "units derived from diamines".

[0011] [Polyamide resin composition] The polyamide resin composition according to the present embodiment is a polyamide resin composition comprising a semi-aromatic polyamide (A), a modified ethylene-α-olefin copolymer (B), and a styrene-based thermoplastic elastomer (C), wherein the semi-aromatic polyamide (A) has a melting point of less than 280°C and a terminal amino group concentration [NH2] (μeq / g) of 45 μeq / g or more, the total content of the modified ethylene-α-olefin copolymer (B) and the styrene-based thermoplastic elastomer (C) is 10 to 40 mass% based on the total content of the semi-aromatic polyamide (A), the modified ethylene-α-olefin copolymer (B), and the styrene-based thermoplastic elastomer (C), and the styrene-based thermoplastic elastomer (C) contains less than 0.9 mass% of units derived from at least one selected from the group consisting of unsaturated carboxylic acids and derivatives of unsaturated carboxylic acids.

[0012] The polyamide resin composition contains the modified ethylene-α-olefin copolymer (B), which provides excellent flexibility. However, the modified ethylene-α-olefin copolymer (B) has a high degree of acid modification, which tends to increase the melt viscosity of the polyamide resin composition. In other words, it tends to decrease the flowability of the polyamide resin composition. When the melt viscosity of the polyamide resin composition increases, the molding processability decreases accordingly, and the retention stability during thick-wall extrusion molding may deteriorate. In this embodiment, the polyamide resin composition contains the styrene-based thermoplastic elastomer (C) in addition to the modified ethylene-α-olefin copolymer (B), i.e., contains both the modified ethylene-α-olefin copolymer (B) and the styrene-based thermoplastic elastomer (C), so that the polyamide resin composition not only has excellent flexibility but also excellent flowability and retention stability during thick-wall extrusion molding. Furthermore, when the polyamide resin composition contains the modified ethylene-α-olefin copolymer (B), it becomes easy to uniformly mix the semi-aromatic polyamide (A), the modified ethylene-α-olefin copolymer (B), and the styrene-based thermoplastic elastomer (C).

[0013] When a polyamide resin composition contains a semi-aromatic polyamide (A) and a modified ethylene-α-olefin copolymer (B) but does not contain a styrene-based thermoplastic elastomer (C), it is difficult to obtain a molded article having a desired color tone. This is thought to be because the refractive index difference between the semi-aromatic polyamide (A) and the modified ethylene-α-olefin copolymer (B) is large, and when the polyamide resin composition does not contain a styrene-based thermoplastic elastomer (C), diffused reflection occurs within the polyamide resin composition, making it difficult to obtain a molded article having a desired color tone. On the other hand, the polyamide resin composition of this embodiment contains a styrene-based thermoplastic elastomer (C) in addition to the semi-aromatic polyamide (A) and the modified ethylene-α-olefin copolymer (B), and thus a molded article having a desired color tone can be obtained. This is thought to be because the difference in refractive index between the semi-aromatic polyamide (A) and the styrene-based thermoplastic elastomer (C) is small, and therefore the styrene-based thermoplastic elastomer (C) suppresses the occurrence of diffuse reflection within the polyamide resin composition.

[0014] In the polyamide resin composition of this embodiment, the total content of the modified ethylene-α-olefin copolymer (B) and the styrene-based thermoplastic elastomer (C) is 10 to 40% by mass relative to the total content of the semi-aromatic polyamide (A), the modified ethylene-α-olefin copolymer (B), and the styrene-based thermoplastic elastomer (C). When the total content of the modified ethylene-α-olefin copolymer (B) and the styrene-based thermoplastic elastomer (C) is 10% by mass or more, the polyamide resin composition exhibits excellent flexibility, flowability, and retention stability during thick-wall extrusion molding, and is likely to achieve a desired color tone. Furthermore, when the total content is 40% by mass or less, the components contained in the polyamide resin composition can be uniformly mixed. In order to obtain a polyamide resin composition having even more excellent flexibility, flowability, and retention stability during thick-wall extrusion molding, the total content of the modified ethylene-α-olefin copolymer (B) and the styrenic thermoplastic elastomer (C) is preferably 13% by mass or more, more preferably 16% by mass or more, and even more preferably 18% by mass or more, based on the total content of the semi-aromatic polyamide (A), the modified ethylene-α-olefin copolymer (B), and the styrenic thermoplastic elastomer (C). In order to achieve even more uniform mixing of the components contained in the polyamide resin composition, the total content of the modified ethylene-α-olefin copolymer (B) and the styrenic thermoplastic elastomer (C) is preferably 37% by mass or less, more preferably 34% by mass or less, and even more preferably 32% by mass or less. That is, the total content of the modified ethylene-α-olefin copolymer (B) and the styrenic thermoplastic elastomer (C) is preferably 13 to 37% by mass, more preferably 16 to 34% by mass, and even more preferably 18 to 32% by mass, based on the total content of the semi-aromatic polyamide (A), the modified ethylene-α-olefin copolymer (B), and the styrenic thermoplastic elastomer (C).

[0015] <Semi-aromatic polyamide (A)> The polyamide resin composition according to this embodiment contains a semi-aromatic polyamide (A). That is, the polyamide resin composition according to this embodiment contains at least one semi-aromatic polyamide (A).

[0016] The semi-aromatic polyamide (A) contains, as monomer units, dicarboxylic acid units and diamine units.

[0017] (dicarboxylic acid unit) Examples of the dicarboxylic acid unit include units derived from aromatic dicarboxylic acids such as terephthalic acid, naphthalenedicarboxylic acid, isophthalic acid, 1,4-phenylenedioxydiacetic acid, 1,3-phenylenedioxydiacetic acid, diphenic acid, diphenylmethane-4,4'-dicarboxylic acid, diphenylsulfone-4,4'-dicarboxylic acid, and 4,4'-biphenyldicarboxylic acid. The naphthalenedicarboxylic acid unit includes 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, and 1,4-naphthalenedicarboxylic acid units. Examples of the dicarboxylic acid unit include units derived from aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, dimethylmalonic acid, 2,2-diethylsuccinic acid, 2,2-dimethylglutaric acid, 2-methyladipic acid, trimethyladipic acid, and dimer acid; and units derived from alicyclic dicarboxylic acids such as 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, cycloheptanedicarboxylic acid, cyclooctanedicarboxylic acid, and cyclodecanedicarboxylic acid. The dicarboxylic acid units of the semi-aromatic polyamide (A) may contain only one kind of these dicarboxylic acid units, or may contain two or more kinds of these dicarboxylic acid units.

[0018] The semi-aromatic polyamide (A) in this embodiment preferably contains aromatic dicarboxylic acid units as dicarboxylic acid units, more preferably aromatic dicarboxylic acid units as a main component, where "main component" means that the aromatic dicarboxylic acid units account for 50 mol % or more, preferably 50 to 100 mol %, more preferably 60 to 100 mol %, of the total dicarboxylic acid units.

[0019] The semi-aromatic polyamide (A) preferably contains, as a dicarboxylic acid unit, at least one selected from the group consisting of terephthalic acid units and naphthalenedicarboxylic acid units, and more preferably contains at least one selected from the group consisting of terephthalic acid units and 2,6-naphthalenedicarboxylic acid units.

[0020] The semi-aromatic polyamide (A) preferably contains at least one selected from the group consisting of terephthalic acid units and naphthalenedicarboxylic acid units in an amount of 50 mol% or more relative to the total dicarboxylic acid units. Furthermore, from the viewpoint of easily achieving good chemical resistance and heat resistance, the semi-aromatic polyamide (A) more preferably contains at least 75 mol%, more preferably 90 mol% or more, and even more preferably 95 mol% or more of at least one selected from the group consisting of terephthalic acid units and naphthalenedicarboxylic acid units relative to the total dicarboxylic acid units. From the viewpoint of easily achieving better chemical resistance and heat resistance, the semi-aromatic polyamide (A) preferably contains at least 70 mol%, more preferably 90 mol% or more, and even more preferably 95 mol% or more of terephthalic acid units relative to the total dicarboxylic acid units. The semi-aromatic polyamide (A) may contain 100 mol% of terephthalic acid units relative to the total carboxylic acid units.

[0021] (diamine units) Examples of the diamine unit include units derived from linear aliphatic diamines such as 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,11-undecanediamine, 1,12-dodecanediamine, and 1,13-tridecanediamine; 2-methyl-1,3-propanediamine, 2-methyl-1,5-pentanediamine, 3-methyl-1,5-pentanediamine, 2,2,4-trimethyl-1,6-hexanediamine, 2,4,4-trimethyl-1,6-hexanediamine, and 2-methyl-1,3-propanediamine. Examples of the diamine units include units derived from branched aliphatic diamines such as 1,8-octanediamine, 2-ethyl-1,7-heptanediamine, and 5-methyl-1,9-nonanediamine; units derived from alicyclic diamines such as cyclohexanediamine, methylcyclohexanediamine, and isophoronediamine; and units derived from aromatic diamines such as p-phenylenediamine, m-phenylenediamine, xylylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfone, and 4,4'-diaminodiphenyl ether. The diamine units of the semi-aromatic polyamide (A) may contain only one type of these diamine units, or two or more types.

[0022] The semi-aromatic polyamide (A) in this embodiment preferably contains, as diamine units, aliphatic diamine units having 4 to 18 carbon atoms, and preferably contains, as a main component, aliphatic diamine units having 4 to 18 carbon atoms. Here, "main component" means that the diamine units preferably account for 50 mol % or more of all diamine units, more preferably 50 to 100 mol %, and even more preferably 60 to 100 mol %. Furthermore, the semi-aromatic polyamide (A) preferably contains 10 to 50 mol % of diamine units derived from aliphatic diamines having 4 to 18 carbon atoms based on all monomer units.

[0023] The semi-aromatic polyamide (A) preferably contains 60 mol % or more of aliphatic diamine units having 4 to 18 carbon atoms relative to all diamine units. The use of a semi-aromatic polyamide (A) containing aliphatic diamine units having 4 to 18 carbon atoms in the above ratio allows for the production of a polyamide resin composition excellent in strength, toughness, heat resistance, and chemical resistance. The semi-aromatic polyamide (A) more preferably contains 75 mol % or more, and even more preferably 90 mol % or more, of aliphatic diamine units having 4 to 18 carbon atoms relative to all diamine units.

[0024] Since a polyamide resin composition having even more excellent strength, toughness, heat resistance, and chemical resistance can be obtained, the aliphatic diamine having 4 to 18 carbon atoms is preferably an aliphatic diamine having 6 to 12 carbon atoms, more preferably an aliphatic diamine having 7 to 11 carbon atoms, and even more preferably an aliphatic diamine having 9 to 11 carbon atoms. The diamine unit contained in the semi-aromatic polyamide (A) is preferably at least one selected from the group consisting of 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 2-methyl-1,8-octanediamine, and 1,10-decanediamine, and more preferably at least one selected from the group consisting of 1,9-nonanediamine and 2-methyl-1,8-octanediamine.

[0025] From the viewpoints of strength, toughness, heat resistance, and chemical resistance, the semi-aromatic polyamide (A) preferably contains at least one selected from the group consisting of 1,9-nonanediamine and 2-methyl-1,8-octanediamine in an amount of 75 mol% or more, more preferably 90 mol% or more, and even more preferably 95 mol% or more, of all diamine units.

[0026] The diamine units contained in the semi-aromatic polyamide (A) may contain both 1,9-nonanediamine and 2-methyl-1,8-octanediamine. When the diamine units contain both units derived from 1,9-nonanediamine and 2-methyl-1,8-octanediamine, the molar ratio of 1,9-nonanediamine units to 2-methyl-1,8-octanediamine units (1,9-nonanediamine units / 2-methyl-1,8-octanediamine units) is preferably in the range of 95 / 5 to 40 / 60, more preferably 90 / 10 to 40 / 60, and even more preferably 80 / 20 to 40 / 60.

[0027] The semi-aromatic polyamide (A) preferably contains aromatic dicarboxylic acid units as dicarboxylic acid units and aliphatic diamine units as diamine units. The semi-aromatic polyamide (A) preferably contains 10 to 50 mol % of aromatic dicarboxylic acid units as dicarboxylic acid units and 10 to 50 mol % of aliphatic diamines having 4 to 18 carbon atoms as diamine units, based on the total monomer units.

[0028] Examples of the semi-aromatic polyamide (A) include polynonamethylene terephthalamide (polyamide 9T), poly(2-methyloctamethylene) terephthalamide (nylon M8T), polynonamethylene terephthalamide / poly(2-methyloctamethylene) terephthalamide copolymer (nylon 9T / M8T), polynonamethylene naphthalene dicarboxamide (polyamide 9N), polynonamethylene naphthalene dicarboxamide / poly(2-methyloctamethylene) naphthalene dicarboxamide copolymer (nylon 9N / M8N), polydecamethylene terephthalamide (polyamide 10T), and a copolymer of polyamide 10T and polyundecaneamide (polyamide 11) (polyamide 10T / 11). Among these, polyamide 10T / 11, polynonamethylene naphthalene dicarboxamide (polyamide 9N), polynonamethylene naphthalene dicarboxamide / poly(2-methyloctamethylene) naphthalene dicarboxamide copolymer (nylon 9N / M8N), polynonamethylene terephthalamide (polyamide 9T), polynonamethylene terephthalamide / poly(2-methyloctamethylene) terephthalamide copolymer (nylon 9T / M8T) and At least one selected from polydecamethylene terephthalamide (polyamide 10T) is preferred, and at least one selected from polynonamemethylene naphthalene dicarboxamide / poly(2-methyloctamethylene) naphthalene dicarboxamide copolymer (nylon 9N / M8N), polynonamemethylene terephthalamide / poly(2-methyloctamethylene) terephthalamide copolymer (nylon 9T / M8T), and polyamide 10T / 11 is more preferred. From the viewpoints of ensuring moldability and rigidity at high temperatures, polynonamemethylene terephthalamide / poly(2-methyloctamethylene) terephthalamide copolymer (nylon 9T / M8T) is even more preferred.

[0029] Furthermore, the semi-aromatic polyamide (A) may be a semi-aromatic polyamide containing dicarboxylic acid units mainly composed of aliphatic dicarboxylic acid units and diamine units mainly composed of aromatic diamine units. Examples of the aliphatic dicarboxylic acid units include the units derived from the aliphatic dicarboxylic acids described above, and one or more of these may be included. Examples of the aromatic diamine units include the units derived from the aromatic diamines described above, and one or more of these may be included. Other units may also be included within the scope of not impairing the effects of the present invention. Examples of semi-aromatic polyamides containing dicarboxylic acid units mainly composed of aliphatic dicarboxylic acid units and diamine units mainly composed of aromatic diamine units include polymetaxylylene adipamide (MXD6) and polyparaxylylene sebacamide (PXD10).

[0030] The semi-aromatic polyamide (A) preferably has 10 mol % or more of the terminal groups of its molecular chain blocked with a terminal blocking agent. Use of a semi-aromatic polyamide (A) having a terminal blocking rate of 10 mol % or more tends to produce a polyamide resin composition with better physical properties such as melt stability and hot water resistance.

[0031] As the terminal blocking agent, a monofunctional compound having reactivity with a terminal amino group or a terminal carboxyl group can be used. Specific examples include monocarboxylic acids, acid anhydrides, monoisocyanates, monoacid halides, monoesters, monoalcohols, and monoamines. From the viewpoints of reactivity and the stability of the blocked terminals, monocarboxylic acids are preferred as terminal blocking agents for terminal amino groups, and monoamines are preferred as terminal blocking agents for terminal carboxyl groups. From the viewpoints of ease of handling, monocarboxylic acids are more preferred as terminal blocking agents.

[0032] The monocarboxylic acid used as the terminal blocking agent is not particularly limited as long as it is reactive with an amino group. Examples of the monocarboxylic acid include aliphatic monocarboxylic acids such as acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, lauric acid, tridecanoic acid, myristic acid, palmitic acid, stearic acid, pivalic acid, and isobutyric acid; alicyclic monocarboxylic acids such as cyclopentanecarboxylic acid and cyclohexanecarboxylic acid; aromatic monocarboxylic acids such as benzoic acid, toluic acid, α-naphthalenecarboxylic acid, β-naphthalenecarboxylic acid, methylnaphthalenecarboxylic acid, and phenylacetic acid; and mixtures thereof. Among these, at least one selected from acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, lauric acid, tridecanoic acid, myristic acid, palmitic acid, stearic acid, and benzoic acid is preferred in terms of reactivity, stability of the blocked terminal, cost, and the like.

[0033] The monoamine used as the terminal blocking agent is not particularly limited as long as it is reactive with a carboxyl group. Examples of the monoamine include aliphatic monoamines such as methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, decylamine, stearylamine, dimethylamine, diethylamine, dipropylamine, and dibutylamine; alicyclic monoamines such as cyclohexylamine and dicyclohexylamine; aromatic monoamines such as aniline, toluidine, diphenylamine, and naphthylamine; and mixtures thereof. Among these, at least one selected from butylamine, hexylamine, octylamine, decylamine, stearylamine, cyclohexylamine, and aniline is preferred in terms of reactivity, high boiling point, stability of the blocked terminal, and cost.

[0034] The semi-aromatic polyamide (A) had an intrinsic viscosity η measured in concentrated sulfuric acid as a solvent at a concentration of 0.2 g / dl and a temperature of 30°C. inh is preferably 0.6 dL / g or more, more preferably 0.8 dL / g or more, even more preferably 0.9 dL / g or more, and particularly preferably 1.0 dL / g or more. The intrinsic viscosity η of the semi-aromatic polyamide (A) is preferably 2.0 dL / g or less, more preferably 1.8 dL / g or less, and even more preferably 1.6 dL / g or less. inh If the value is within the above range, various physical properties such as moldability are further improved. Intrinsic viscosity η inh can be calculated from the flow time t0 (seconds) of the solvent (concentrated sulfuric acid), the flow time t1 (seconds) of the sample solution, and the sample concentration c (g / dL) in the sample solution (i.e., 0.2 g / dL) using the following formula (P). η inh =[ln(t1 / t0)] / c Formula (P)

[0035] The melting point of the semi-aromatic polyamide (A) is less than 280°C. When the melting point is less than 280°C, the difference between the temperature at which the semi-aromatic polyamide (A) thermally decomposes and the melting point is large, i.e., the meltable temperature range is wide, resulting in a high degree of freedom in the molding temperature. From the viewpoint of freedom in the molding temperature, the melting point of the semi-aromatic polyamide (A) is preferably 275°C or lower, more preferably 270°C or lower. Furthermore, from the viewpoint of ensuring good heat resistance, it may be, for example, 240°C or higher, 245°C or higher, or 250°C or higher. The melting point of the semi-aromatic polyamide (A) can be measured in accordance with ISO11357-3:2018, specifically by the procedure described in the Examples.

[0036] The terminal amino group concentration (hereinafter also referred to as "terminal amino group concentration") ([NH2]) of the semi-aromatic polyamide (A) is 45 μeq / g or more. When the terminal amino group concentration ([NH2]) is 45 μeq / g or more, the chemical resistance of the polyamide resin composition is good. From the viewpoint of chemical resistance, the terminal amino group concentration is preferably 46 μeq / g or more, more preferably 47 μeq / g or more. Furthermore, from the viewpoint of avoiding the progression of gelation due to an excessive reaction between the terminal amino groups of the semi-aromatic polyamide (A) and the modified portion of the modified ethylene-α-olefin copolymer (B), the terminal amino group concentration is 80 μeq / g or less, more preferably 75 μeq / g or less, and even more preferably 70 μeq / g or less. That is, the terminal amino group concentration is 45 μeq / g or more, preferably 45 to 80 μeq / g, more preferably 46 to 75 μeq / g, and even more preferably 47 to 70 μeq / g. In this specification, the terminal amino group concentration ([NH2]) of the semi-aromatic polyamide (A) refers to the amount of terminal amino groups (unit: μeq) contained in 1 g of the semi-aromatic polyamide (A), and can be determined by neutralization titration using an indicator. [NH2] is specifically measured by the procedure described in the Examples.

[0037] The semi-aromatic polyamide (A) preferably has a ratio [NH2] / [COOH] of the terminal amino group concentration [NH2] to the terminal carboxyl group concentration [COOH] greater than 2 and less than 5. If [NH2] / [COOH] is greater than 2, the chemical resistance will be better, and if [NH2] / [COOH] is less than 5, the retention stability will be better. The terminal carboxyl group concentration ([COOH], unit: μeq / g) of the semi-aromatic polyamide can be measured by potentiometric titration using a reagent, specifically by the procedure described in the Examples.

[0038] Examples of catalysts that can be used in producing the semi-aromatic polyamide (A) include phosphoric acid, phosphorous acid, hypophosphorous acid, and salts or esters thereof. Examples of the salts or esters include salts of phosphoric acid, phosphorous acid, or hypophosphorous acid with metals such as potassium, sodium, magnesium, vanadium, calcium, zinc, cobalt, manganese, tin, tungsten, germanium, titanium, and antimony; ammonium salts of phosphoric acid, phosphorous acid, or hypophosphorous acid; and ethyl esters, isopropyl esters, butyl esters, hexyl esters, isodecyl esters, octadecyl esters, decyl esters, stearyl esters, and phenyl esters of phosphoric acid, phosphorous acid, or hypophosphorous acid. The amount of the catalyst used is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and preferably 1.0% by mass or less, more preferably 0.5% by mass or less, relative to 100% by mass of the total mass of the raw materials. If the amount of catalyst used is above the lower limit, polymerization can proceed smoothly. If the amount is below the upper limit, impurities derived from the catalyst are less likely to be produced, and problems caused by the impurities can be easily prevented, for example, when the polyamide resin composition is extrusion-molded.

[0039] (Semi-aromatic polyamide (A) content) The content of the semi-aromatic polyamide (A) in the polyamide resin composition of this embodiment is preferably 50 to 90 mass%, more preferably 60 to 87 mass%, and even more preferably 65 to 85 mass%, based on the total content of the semi-aromatic polyamide (A), the modified ethylene-α-olefin copolymer (B), and the styrene-based thermoplastic elastomer (C). When the content of the semi-aromatic polyamide (A) is within the above range, a polyamide resin composition having even more excellent flexibility, flowability, and retention stability during thick-wall extrusion molding can be obtained. The content of the semi-aromatic polyamide (A) in the polyamide resin composition of the present embodiment is preferably 50 to 90 mass%, more preferably 60 to 87 mass%, and even more preferably 65 to 85 mass% of the polyamide resin composition. When the content of the semi-aromatic polyamide (A) is within the above range, a polyamide resin composition having even more excellent flexibility, flowability, and retention stability during thick-wall extrusion molding can be obtained.

[0040] <Modified ethylene-α-olefin copolymer (B)> The polyamide resin composition of this embodiment contains a modified ethylene-α-olefin copolymer (B), which exists as a dispersed phase in a matrix of the semi-aromatic polyamide (A). The polyamide resin composition contains the modified ethylene-α-olefin copolymer (B), and thus has excellent flexibility.

[0041] The modified ethylene-α-olefin copolymer (B) is a copolymer containing ethylene units and α-olefin units as monomer units, modified with a modifying group. Examples of α-olefins include hydrocarbons having a double bond and having 3 to 20 carbon atoms, vinyl acetate, vinyl alcohol, (meth)acrylic acid, and (meth)acrylic acid alkyl esters. Examples of copolymers containing ethylene units and α-olefin units include ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-propylene-diene copolymer, ethylene-vinyl acetate copolymer, saponified ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, and ethylene-ethyl acrylate copolymer. Among these, ethylene-butene copolymer is preferred.

[0042] From the viewpoints of flexibility and retention stability during thick-wall extrusion, the modified ethylene-α-olefin copolymer (B) is preferably modified with at least one selected from the group consisting of carboxylic acids and carboxylic acid anhydrides, more preferably modified with at least one selected from the group consisting of unsaturated carboxylic acids and unsaturated carboxylic acid anhydrides, and even more preferably modified with at least one selected from the group consisting of α,β-unsaturated carboxylic acids and carboxylic acid anhydrides having an α,β-unsaturated bond. More specifically, the modified ethylene-α-olefin copolymer (B) is preferably a copolymer containing ethylene units and α-olefin units modified with at least one selected from the group consisting of carboxylic acids and carboxylic acid anhydrides, more preferably modified with at least one selected from the group consisting of unsaturated carboxylic acids and carboxylic acid anhydrides having an unsaturated bond, and even more preferably further modified with at least one selected from the group consisting of α,β-unsaturated carboxylic acids and carboxylic acid anhydrides having an α,β-unsaturated bond. Examples of α,β-unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, etc. Examples of carboxylic acid anhydrides having an α,β-unsaturated bond include maleic anhydride, itaconic anhydride, etc. From the viewpoint of obtaining a polyamide resin composition having even more excellent flexibility and retention stability during thick-wall extrusion molding, the modified ethylene-α-olefin copolymer (B) is preferably one modified with maleic anhydride.

[0043] The modification amount (content of modifying groups) in the modified ethylene-α-olefin copolymer (B) is preferably 0.01 to 5 mass%, more preferably 0.05 to 3 mass%. When the modification amount is 0.01 mass% or more, the effect of improving flexibility and impact resistance is sufficient, while when it is 5 mass% or less, deterioration in moldability is suppressed. In this specification, the modification amount in the modified ethylene-α-olefin copolymer (B) is a value calculated by neutralization titration, and specifically, is measured by the procedure described in the Examples.

[0044] The modified ethylene-α-olefin copolymer (B) of this embodiment may be a commercially available product, such as "TAFMER (registered trademark)" manufactured by Mitsui Chemicals, Inc. or "NOVATEC (registered trademark)" manufactured by Japan Polyethylene Corporation.

[0045] (Modified ethylene-α-olefin copolymer (B) content) The content of the modified ethylene-α-olefin copolymer (B) in the polyamide resin composition of this embodiment is preferably 5 to 39 mass%, more preferably 10 to 35 mass%, and even more preferably 13 to 30 mass%, based on the total content of the semi-aromatic polyamide (A), the modified ethylene-α-olefin copolymer (B), and the styrene-based thermoplastic elastomer (C). When the content of the modified ethylene-α-olefin copolymer (B) is within the above range, a polyamide resin composition having even more excellent flexibility, flowability, and retention stability during thick-wall extrusion molding can be obtained. The content of the modified ethylene-α-olefin copolymer (B) in the polyamide resin composition of this embodiment is preferably 5 to 40 mass %, more preferably 10 to 35 mass %, and even more preferably 13 to 30 mass % in the polyamide resin composition. When the content of the modified ethylene-α-olefin copolymer (B) is within the above range, a polyamide resin composition having even more excellent flexibility, flowability, and retention stability during thick-wall extrusion molding can be obtained.

[0046] <Styrene-based thermoplastic elastomer (C)> The polyamide resin composition of the present embodiment contains a styrene-based thermoplastic elastomer (C), and the styrene-based thermoplastic elastomer (C) contains less than 0.9 mass% of units derived from at least one selected from the group consisting of unsaturated carboxylic acids and derivatives of unsaturated carboxylic acids. By including the styrene-based thermoplastic elastomer (C), the polyamide resin composition of the present embodiment can suppress an increase in melt viscosity during melting, and the composition has excellent flexibility and flowability, and a desired color tone can be easily obtained.

[0047] The styrene-based thermoplastic elastomer (C) of this embodiment contains, as a monomer unit, an aromatic vinyl compound unit, preferably a styrene unit. More preferably, the styrene-based thermoplastic elastomer (C) of this embodiment is a copolymer containing a styrene unit and a conjugated diene compound unit. Examples of conjugated diene compounds include 1,3-butadiene, isoprene, and 2,3-dimethylbutadiene. The copolymer may be a copolymer of a soft component (e.g., a butylene component) and a hard component (e.g., a styrene component). The styrene-based thermoplastic elastomer (C) of this embodiment also includes a copolymer in which the double bond moiety of the copolymer has been hydrogenated (hydrogenated product).

[0048] Examples of the copolymer include random copolymers, block copolymers, and graft copolymers. Examples of the block copolymer include linear block structures and radially branched block structures. From the viewpoint of suppressing an increase in melt viscosity during melting and obtaining a polyamide resin composition that is excellent in flexibility and easily obtains a desired color tone, the copolymer is preferably a block copolymer.

[0049] Examples of the block copolymer include styrene-butadiene block copolymer (SBR), hydrogenated styrene-butadiene block copolymer (SEB), styrene-butadiene-styrene block copolymer (SBS), styrene-butadiene-butylene-styrene block copolymer (SBBS), styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-isoprene block copolymer (SIR), styrene-ethylene-propylene block copolymer (SEP), styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene-propylene-styrene block copolymer (SEPS), styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS), etc. Among these, from the viewpoint of suppressing an increase in melt viscosity during melting and from the viewpoint of obtaining a polyamide resin composition that is excellent in flexibility and easily obtains a desired color tone, styrene-ethylene-butylene-styrene block copolymer (SEBS) is preferred, and a hydrogenated product of styrene-ethylene-butylene-styrene block copolymer (SEBS) is more preferred.

[0050] The following units can be used as the unit derived from at least one selected from the group consisting of unsaturated carboxylic acids and derivatives of unsaturated carboxylic acids contained in the styrene-based thermoplastic elastomer (C). Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, and crotonic acid. Examples of derivatives of unsaturated carboxylic acids include acid halides, amides, imides, anhydrides, and esters of the aforementioned unsaturated carboxylic acids. Specific examples of derivatives of unsaturated carboxylic acids include malenyl chloride, maleimide, succinic anhydride, maleic anhydride, phthalic anhydride, itaconic anhydride, citraconic anhydride, monomethyl maleate, dimethyl maleate, and glycidyl maleate.

[0051] The styrene-based thermoplastic elastomer (C) preferably contains units derived from an unsaturated carboxylic acid anhydride, from the viewpoint of suppressing an increase in melt viscosity during melting and from the viewpoint of obtaining a polyamide resin composition that is excellent in flexibility and that is likely to give a desired color tone. Examples of the unsaturated carboxylic acid anhydride include succinic anhydride, maleic anhydride, phthalic anhydride, and itaconic anhydride. From the viewpoint of further suppressing the increase in melt viscosity during melting, providing a polyamide resin composition that is more excellent in flexibility and that is more likely to give a desired color tone, the styrene-based thermoplastic elastomer (C) preferably contains units derived from an unsaturated carboxylic acid anhydride, and more preferably contains units derived from maleic anhydride.

[0052] The content of units derived from at least one selected from the group consisting of unsaturated carboxylic acids and derivatives of unsaturated carboxylic acids in the styrene-based thermoplastic elastomer (C) is less than 0.9% by mass. The content of units derived from at least one selected from the group consisting of unsaturated carboxylic acids and derivatives of unsaturated carboxylic acids in the styrene-based thermoplastic elastomer (C) is preferably in the range of 0.01 to 0.8% by mass, more preferably in the range of 0.05 to 0.5% by mass, and even more preferably in the range of 0.07 to 0.3% by mass. When the content of units derived from at least one selected from the group consisting of unsaturated carboxylic acids and derivatives of unsaturated carboxylic acids is 0.01% by mass or more, the impact resistance is sufficiently improved, while when it is 0.8% by mass or less, the increase in melt viscosity of the resulting polyamide resin composition when melted is further suppressed. In this specification, the content of units derived from at least one selected from the group consisting of unsaturated carboxylic acids and derivatives of unsaturated carboxylic acids in the styrene-based thermoplastic elastomer (C) is a value calculated by neutralization titration, and specifically, is measured by the procedure described in the Examples.

[0053] The styrene-based thermoplastic elastomer (C) of this embodiment may be a commercially available product, such as "Kraton (registered trademark)" manufactured by Kraton Polymers, "Septon (registered trademark)" manufactured by Kuraray Co., Ltd., or "Tuftec (registered trademark)" manufactured by Asahi Kasei Corporation.

[0054] (Content of styrene-based thermoplastic elastomer (C)) The content of the styrene-based thermoplastic elastomer (C) in the polyamide resin composition of this embodiment is preferably 1 to 20 mass%, more preferably 2 to 18 mass%, and even more preferably 3 to 16 mass%, based on the total content of the semi-aromatic polyamide (A), the modified ethylene-α-olefin copolymer (B), and the styrene-based thermoplastic elastomer (C). When the content of the styrene-based thermoplastic elastomer (C) is within the above range, a polyamide resin composition can be obtained that is more excellent in flexibility, flowability, and retention stability during thick-wall extrusion molding, and that makes it easier to obtain a desired color tone. The content of the styrene-based thermoplastic elastomer (C) in the polyamide resin composition of the present embodiment is preferably 1 to 20 mass%, more preferably 2 to 18 mass%, and even more preferably 3 to 16 mass%, of the polyamide resin composition. When the content of the styrene-based thermoplastic elastomer (C) is within the above range, a polyamide resin composition can be obtained that is more excellent in flexibility, flowability, and retention stability during thick-wall extrusion molding, and that makes it easier to obtain a desired color tone.

[0055] <Additives> The polyamide resin composition of the present embodiment may contain additives as needed in addition to the semi-aromatic polyamide (A), the modified ethylene-α-olefin copolymer (B), and the styrene-based thermoplastic elastomer (C).

[0056] Examples of additives include colorants, ultraviolet absorbers, light stabilizers, antistatic agents, crosslinking agents, flame retardants such as brominated polymers, antimony oxide, metal hydroxides, and phosphinates, flame retardant aids, nucleating agents, plasticizers, lubricants, dispersants, oxygen absorbers, hydrogen sulfide absorbents, antioxidants, mold release agents, inorganic or organic fibrous fillers such as glass fiber, carbon fiber, and wholly aromatic polyamide fiber, powdery fillers such as wollastonite, silica, silica alumina, alumina, titanium dioxide, potassium titanate, magnesium hydroxide, molybdenum disulfide, carbon nanotubes, graphene, and polytetrafluoroethylene, and flake fillers such as hydrotalcite, glass flakes, mica, clay, montmorillonite, and kaolin. These may be contained alone or in combination. From the viewpoint of flowability and retention stability during thick-wall extrusion molding, the polyamide resin composition preferably does not contain a crosslinking agent.

[0057] The content of the additive is not particularly limited as long as it does not impair the effects of the present invention, but is preferably 0.02 to 24 mass %, more preferably 0.05 to 20 mass %, even more preferably 0.07 to 15 mass %, still more preferably 0.07 to 10 mass %, and even more preferably 0.07 to 5 mass % in the resin composition.

[0058] The polyamide resin composition of this embodiment preferably contains an antioxidant as an additive. Examples of antioxidants include phenolic heat stabilizers, amine heat stabilizers, phosphorus-based heat stabilizers, and sulfur-based heat stabilizers. Among these, phenolic heat stabilizers are preferred. By including an antioxidant in the polyamide resin composition, it is possible to further improve long-term heat resistance. The content of the antioxidant in the polyamide resin composition is preferably 0.1 to 5.0 mass %, more preferably 0.5 to 3.0 mass %, and even more preferably 1.0 to 2.0 mass %.

[0059] The polyamide resin composition of the present embodiment preferably contains a lubricant as an additive. Examples of lubricants include ethylene bisstearamide, butyl stearate, calcium stearate, etc. By containing a lubricant in the polyamide resin composition, it is possible to further improve retention stability during thick-wall extrusion molding. The content of the lubricant in the polyamide resin composition is preferably 0.1 to 3.0% by mass, more preferably 0.3 to 2.0% by mass, and even more preferably 0.5 to 1.5% by mass.

[0060] The polyamide resin composition of this embodiment preferably contains a colorant as an additive. Since the polyamide resin composition of this embodiment contains the styrene-based thermoplastic elastomer (C), a desired color tone can be easily obtained. Examples of colorants include carbon black, phthalocyanine, quinacridone, indoline, azo pigments, and red iron oxide. Among these, carbon black is preferred. The content of the colorant in the polyamide resin composition is preferably 0.01 to 3.0% by mass, more preferably 0.05 to 2.0% by mass, and even more preferably 0.1 to 1.0% by mass.

[0061] <Physical properties of polyamide resin composition> In this embodiment, the flexural modulus M (GPa) of a dumbbell-shaped tensile test piece Type A1 made of the polyamide resin composition obtained in accordance with JIS K7139:2009, measured in accordance with ISO178:2019, and the shear rate of the polyamide resin composition measured in accordance with JIS K7199:1999 are -1 It is preferable that the melt viscosity P (Pa·s) satisfies the following formula (I): Flexural modulus M (GPa) × melt viscosity P (Pa·s) < 2092 (GPa × Pa·s) (I) By satisfying formula (I), the polyamide resin composition has even more excellent flexibility and flowability.

[0062] From the viewpoint of flexibility and flowability, the flexural modulus M (GPa)×melt viscosity P (Pa·s) is more preferably less than 2080, further preferably less than 2070, and may be 1700 or more.

[0063] In the present embodiment, the CIE lightness index L obtained in accordance with JIS Z 8781-4:2013 of a dumbbell-shaped tensile test piece Type A1 made of the polyamide resin composition obtained in accordance with JIS K7139:2009 is * is preferably 39 or less. Lightness index L * is more preferably 38 or less, and even more preferably 36 or less. * The lower the better, * is 0 means black, L * may be 0 or may be greater than 0.

[0064] [Method of producing polyamide resin composition] The polyamide resin composition of the present embodiment can be produced, for example, by feeding the semi-aromatic polyamide (A), the modified ethylene-α-olefin copolymer (B), and the styrene-based thermoplastic elastomer (C) into a twin-screw extruder and melt-kneading them.

[0065] The melt-kneading method is not particularly limited, and any method capable of uniformly mixing the semi-aromatic polyamide (A), the modified ethylene-α-olefin copolymer (B), the styrene-based thermoplastic elastomer (C), and any additives used as needed can be preferably employed. As the melt-kneading machine, a single-screw extruder, a twin-screw extruder, a kneader, a Banbury mixer, etc. are preferred, and from the viewpoints of good dispersibility of the modified ethylene-α-olefin copolymer (B) and industrial productivity, a twin-screw extruder is more preferred.

[0066] [Extrusion Molded Product and Its Manufacturing Method] The extrusion molded article according to the embodiment of the present invention is an extrusion molded article made of the above polyamide resin composition. The method for producing an extrusion molded article according to an embodiment of the present invention preferably includes the steps of heating and melting a polyamide resin composition, and extruding the molten polyamide resin composition to obtain an extrusion molded article.

[0067] Because extrusion molding has a slower flow rate than injection molding, the material tends to remain in a molten state and is prone to thermal deterioration. In particular, in thick-wall extrusion molding, the material may remain in the extrusion for several tens of minutes. Therefore, extrusion molding, particularly thick-wall extrusion molding, requires a material with excellent retention stability. The polyamide resin composition according to this embodiment has excellent retention stability, making it less susceptible to thermal deterioration and enabling the production of high-quality extrusion molded articles.

[0068] In general, the melting point of semi-aromatic polyamides is high, and therefore the extrusion temperature tends to be high. The extrusion temperature is preferably in the range of 10 to 60°C higher than the melting point of the semi-aromatic polyamide (A), more preferably in the range of 20 to 50°C higher than the melting point of the semi-aromatic polyamide (A), and even more preferably in the range of 15 to 45°C higher than the melting point of the semi-aromatic polyamide (A).

[0069] <Applications of extrusion molded products> Examples of extrusion molded articles include molded articles in the form of films, sheets, tubes, monofilaments, multifilaments, pipes, round bars, wire coatings, etc., and the molded articles can be used for any parts such as automobile parts, industrial materials, industrial supplies, electrical and electronic parts, machine parts, office equipment parts, household goods, etc. In particular, because of their excellent chemical resistance, heat resistance, flexibility, impact resistance, etc., they can be suitably used as tubes such as chemical pipes, composite pipes, rodless oil recovery pipes, onshore oil transportation pipes, offshore oil transportation pipes, geothermal fluid pipes, umbilical tubes, and flexible pipes.

[0070] <Tubular molded body> A tubular molded article according to an embodiment of the present invention has the above-described extrusion molded article. The tubular molded article may have a single-layer structure or a multilayer structure. The polyamide resin composition of the present embodiment may be used to form at least one layer of the multilayer structure. For example, the polyamide resin composition of the present embodiment can be suitably used for at least one of the constituent layers of a tube having a single-layer structure or a multilayer structure. [Example]

[0071] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0072] [Measurement and Evaluation] Measurement of the physical properties of the materials used in the examples and comparative examples, and measurement and evaluation of the physical properties of the polyamide compositions in the examples and comparative examples were carried out according to the methods shown below. (1) Melting point The melting points of the semi-aromatic polyamides obtained in each production example were measured using a differential scanning calorimeter "DSC7020" manufactured by Hitachi High-Tech Science Corporation in accordance with ISO11357-3 (2011, 2nd edition). Specifically, a sample (polyamide) was first heated from 30°C to 300°C at a rate of 10°C / min in a nitrogen atmosphere, and then held at 300°C for 5 minutes to completely melt the sample. After that, the sample was cooled to 50°C at a rate of 10°C / min and held at 50°C for 5 minutes. The sample was then heated again to 300°C at a rate of 10°C / min, and the peak temperature of the melting peak that appeared was taken as the melting point (°C). If there were multiple melting peaks, the peak temperature of the highest melting peak was taken as the melting point (°C).

[0073] (2) Intrinsic viscosity For the semi-aromatic polyamide (sample) obtained in the Production Examples, the intrinsic viscosity (dl / g) at a temperature of 30°C and a concentration of 0.2 g / dl was determined using concentrated sulfuric acid as a solvent according to the following relational formula (Z). η inh =[ln(t1 / t0)] / c formula (Z) In the above formula (Z), η inhrepresents the intrinsic viscosity (dl / g), t0 represents the flow time (seconds) of the solvent (concentrated sulfuric acid), t1 represents the flow time (seconds) of the sample solution, and c represents the concentration (g / dl) of the sample in the sample solution (i.e., 0.2 g / dl).

[0074] (3) Terminal amino group content 1 g of the semi-aromatic polyamide obtained in the Production Example was dissolved in 35 mL of phenol, and 2 mL of methanol was added to prepare a sample solution. Using thymol blue as an indicator, titration was carried out using a 0.01 N hydrochloric acid solution to measure the terminal amino group content ([NH2], unit: μeq / g) of the semi-aromatic polyamide.

[0075] (4) Terminal carboxyl group content 0.5 g of the semi-aromatic polyamide obtained in the Production Example was dissolved in 40 mL of ortho-cresol to prepare a sample solution. The obtained sample solution was titrated with a 0.01 N ethanolic potassium hydroxide solution using a potentiometric titrator manufactured by Kyoto Electronics Manufacturing Co., Ltd., and the terminal carboxyl group content ([COOH], unit: μeq / g) of the semi-aromatic polyamide was measured by detecting the inflection point of the potential.

[0076] (5) Content of units derived from maleic anhydride The amount of modification by maleic anhydride in the modified ethylene-α-olefin copolymer (B) (the content of units derived from maleic anhydride) and the content of units derived from maleic anhydride in the styrene-based thermoplastic elastomer (C) were measured according to the following methods. 5 g of sample (pellets of modified ethylene-α-olefin copolymer (B) or pellets of styrene-based thermoplastic elastomer (C)) was dissolved in 170 mL of toluene, and 30 mL of ethanol was added and mixed to prepare a sample solution. The content was determined by neutralization titration with 0.1 N potassium hydroxide ethanol solution using phenolphthalein as an indicator.

[0077] (6) Melt viscosity The melt viscosity (Pa·s) of the polyamide compositions obtained in the examples and comparative examples was measured using a Capilograph (manufactured by Toyo Seiki Seisakusho Co., Ltd.) in accordance with JIS K7199:1999 at a barrel temperature of 300°C and a shear rate of 121.6 sec -1 The measurement was carried out under the conditions of (capillary: inner diameter 1.0 mm x length 10 mm, extrusion speed 10 mm / min) and used as an index of fluidity.

[0078] (7) Flexural modulus (Preparation of dumbbell test specimens) Dumbbell-shaped tensile test specimens Type A1 (4 mm thick, 170 mm total length, 80 mm parallel portion length, 10 mm parallel portion width) were prepared in accordance with JIS K7139: 2009. Specifically, an injection molding machine (clamping force: 100 tons, screw diameter: φ32 mm) manufactured by Sumitomo Heavy Industries, Ltd. was used to prepare the dumbbell-shaped tensile test specimens Type A1 using the polyamide resin compositions obtained in the Examples and Comparative Examples, under conditions of a cylinder temperature of 285 to 295°C and a mold temperature of 140°C, using a T-runner mold. (measurement) Using the dumbbell-shaped tensile test specimen Type A1 prepared by the above method, the flexural modulus (GPa) was measured at 23°C and 50% RH using an autograph (manufactured by Instron) in accordance with ISO178:2019. The measurement was performed at a bending speed of 2 mm / min.

[0079] (8) Hydrolysis resistance (Preparation of dumbbell test specimens) Dumbbell-shaped tensile test specimen type A1 (4 mm thick, total length 170 mm, parallel part length 80 mm, parallel part width 10 mm) was prepared in the same manner as in "(6) Flexural modulus" above. (measurement) Using the dumbbell-shaped tensile test piece Type A1 prepared by the above method, the tensile strength (maximum point, MPa) (initial tensile strength) at 23°C was measured using an autograph (manufactured by Instron) in accordance with ISO 527-1 (2012, 2nd edition). Next, the dumbbell-shaped tensile test piece Type A1 was immersed in an automobile engine coolant (Toyota genuine Super Long Life Coolant / water = 50 / 50 volume ratio) in a pressure-resistant container and left to stand for 1,000 hours in a thermostatic chamber ("DE-303" manufactured by Mita Sangyo Co., Ltd.) set at 130°C. After 1,000 hours, the dumbbell-shaped tensile test piece Type A1 was removed and the tensile strength (maximum point, MPa) at 23°C (tensile strength after 1,000 hours) was measured using the same method as above. The tensile strength retention rate was calculated from the obtained tensile strength and the following formula (T) to evaluate the chemical resistance. Tensile strength retention rate (%) = (tensile strength after 1,000 hours / initial tensile strength) x 100 Formula (T) The higher the tensile strength retention, the better the hydrolysis resistance.

[0080] (9) Retention stability during thick extrusion molding Using a tube molding device consisting of a single-screw extruder (screw diameter: φ50 mm, L / D=28) manufactured by IKG Corporation connected to a straight die (die inner diameter: φ35.0 mm, mandrel outer diameter: φ8.5 mm, wall thickness approximately 13 mm), the polyamide resin compositions obtained in the examples and comparative examples were discharged for 30 minutes under conditions of a cylinder / die temperature of 300°C and a screw rotation speed of 10 rpm or 30 rpm, and the appearance of the extruded molded product was visually inspected and evaluated according to the following criteria. A: The surface of the molded product is smooth. B: Irregularities are observed on some parts of the surface of the molded product. C: Irregularities are observed on the entire surface of the molded product. D: Large irregularities are observed on the entire surface of the molded product.

[0081] (10) Lightness index L * (Preparation of dumbbell test specimens) Dumbbell-shaped tensile test specimen type A1 (4 mm thick, total length 170 mm, parallel part length 80 mm, parallel part width 10 mm) was prepared in the same manner as in "(6) Flexural modulus" above. (measurement) The spectral reflectance of the multipurpose test piece type A1 prepared by the above method in the range of 380 to 780 nm was measured using a spectrophotometer SD 7000 (manufactured by Nippon Denshoku Industries Co., Ltd.). From the obtained spectral reflectance, the lightness index L was calculated in accordance with JIS Z 8781-4:2013. * asked for.

[0082] [Manufacturing Example 1] 9871.2 g (59.42 mol) of terephthalic acid, 9639.3 g (60.90 mol) of a 50 / 50 mixture of 1,9-nonanediamine and 2-methyl-1,8-octanediamine (molar ratio), 142.9 g (1.17 mol) of benzoic acid, 9.8 g of sodium hypophosphite monohydrate (0.05% by mass relative to the total mass of the raw materials), and 5 L of distilled water were placed in a 40 L autoclave and purged with nitrogen. While stirring, the temperature inside the autoclave was raised to 220°C over 2 hours. During this time, the pressure inside the autoclave rose to 2 MPa. After continuing the reaction for 2 hours, the temperature was raised to 230°C and maintained at 230°C for another 2 hours, while gradually releasing water vapor to maintain the pressure at 2 MPa. The pressure was then reduced to 1 MPa over 30 minutes, and the reaction was continued for another 1 hour, resulting in an intrinsic viscosity η inh The prepolymer obtained had a viscosity of 0.2 dL / g. This was crushed to a particle size of 2 mm or less using a Hosokawa Micron flake crusher, dried at 100°C under reduced pressure for 12 hours, and then solid-state polymerized at 230°C and 13 Pa (0.1 mmHg) for 10 hours to obtain a white semi-aromatic polyamide (A) (semi-aromatic polyamide PA-1). The semi-aromatic polyamide (A) described above, semi-aromatic polyamide PA-1, consists of terephthalic acid units, 1,9-nonanediamine units, and 2-methyl-1,8-octanediamine units (1,9-nonanediamine units / 2-methyl-1,8-octanediamine units = 50 / 50 (molar ratio)), has a melting point of 265°C, an intrinsic viscosity η inh The content of terminal amino groups ([NH2]) was 51.5 μeq / g, and the content of terminal carboxyl groups ([COOH]) was 23.4 μeq / g.

[0083] [Examples 1 to 5 and Comparative Examples 1 to 6] Semi-aromatic polyamide, modified ethylene-α-olefin copolymer, styrene-based thermoplastic elastomer, antioxidant, lubricant, and colorant were fed into the upstream feed port of a twin-screw extruder (Toshiba Machine Co., Ltd., "TEM-26SS") in the mass ratios shown in Table 1. The mixture was melt-mixed and extruded under conditions of a cylinder temperature of 300°C, a rotation speed of 150 rpm, and a discharge rate of 10 kg / hr. The mixture was then cooled and cut into pellets to produce a polyamide resin composition. Test pieces for evaluating various physical properties were prepared using the pellets, and various evaluations were performed using the methods described above. The results are shown in Table 1.

[0084] Details of each component shown in Table 1 are as follows: <Semi-aromatic polyamide (A)> Semi-aromatic polyamide obtained in Production Example 1: PA-1

[0085] <Modified ethylene-α-olefin copolymer (B)> Mitsui Chemicals, Inc., TAFMER® MH7010: maleic anhydride-modified ethylene-butene copolymer [content of units derived from maleic anhydride: 0.5% by mass]

[0086] <Styrene-based thermoplastic elastomer (C)> Asahi Kasei Corporation's Tuftec (registered trademark) M1911: maleic anhydride-modified styrene-ethylene-butylene-styrene copolymer (content of units derived from maleic anhydride: 0.18% by mass) <Styrenic thermoplastic elastomers other than styrene thermoplastic elastomer (C)> Asahi Kasei Corporation's Tuftec (registered trademark) M1913: maleic anhydride-modified styrene-ethylene-butylene-styrene copolymer (content of units derived from maleic anhydride: 0.9% by mass)

[0087] <Antioxidants> Sumitomo Chemical Co., Ltd., SUMILIZER GA-80 (phenolic heat stabilizer): 3,9-bis{2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl}-2,4,8,10-tetraoxaspiro[5.5]undecane <Lubricant> Kyoeisha Chemical Co., Ltd., Amide Wax Light Amide WH-255 Calcium stearate S, manufactured by NOF Corporation <Coloring agent> Mitsubishi Chemical Corporation carbon black #980B

[0088] [Table 1]

Claims

1. A polyamide resin composition comprising a semi-aromatic polyamide (A), a modified ethylene-α-olefin copolymer (B), and a styrene-based thermoplastic elastomer (C), The semi-aromatic polyamide (A) has a melting point of less than 280° C. and a terminal amino group concentration [NH ２ ] (μeq / g) is 45 μeq / g or more, a total content of the modified ethylene-α-olefin copolymer (B) and the styrene-based thermoplastic elastomer (C) is 10 to 40 mass% based on a total content of the semi-aromatic polyamide (A), the modified ethylene-α-olefin copolymer (B), and the styrene-based thermoplastic elastomer (C); The polyamide resin composition, wherein the styrene-based thermoplastic elastomer (C) contains less than 0.9% by mass of units derived from at least one selected from the group consisting of unsaturated carboxylic acids and derivatives of unsaturated carboxylic acids.

2. The semi-aromatic polyamide (A) contains diamine units and dicarboxylic acid units, The diamine unit contains 50 mol% or more of diamine units derived from an aliphatic diamine having 4 to 18 carbon atoms relative to the total diamine units, 2. The polyamide resin composition according to claim 1, which contains aromatic dicarboxylic acid units in an amount of 50 mol % or more based on the total carboxylic acid units.

3. 3. The polyamide resin composition according to claim 2, wherein the aliphatic diamine having 4 to 18 carbon atoms is at least one selected from the group consisting of 1,9-nonanediamine and 2-methyl-1,8-octanediamine.

4. The polyamide resin composition according to claim 2 or 3, wherein the aromatic dicarboxylic acid is terephthalic acid.

5. The polyamide resin composition according to claim 1 or 2, wherein the styrene-based thermoplastic elastomer (C) contains a unit derived from an unsaturated carboxylic acid anhydride.

6. The polyamide resin composition according to claim 1 or 2, wherein the modified ethylene / α-olefin copolymer (B) is modified with at least one selected from the group consisting of unsaturated carboxylic acids and unsaturated carboxylic acid anhydrides.

7. The flexural modulus M (GPa) of a dumbbell-shaped tensile test piece Type A1 made of the polyamide resin composition obtained in accordance with JIS K7139:2009, measured in accordance with ISO178:2019, and the shear rate of the polyamide resin composition measured in accordance with JIS K7199:1999 are －１ 3. The polyamide resin composition according to claim 1, wherein the melt viscosity P (Pa·s) satisfies the following formula (I): Flexural modulus M (GPa) × melt viscosity P (Pa s) < 2092 (GPa × Pa s) (I)

8. The CIE lightness index L obtained in accordance with JIS Z 8781-4:2013 of a dumbbell-shaped tensile test piece type A1 made of the polyamide resin composition obtained in accordance with JIS K7139:2009 ＊ 3. The polyamide resin composition according to claim 1, wherein the .lambda. of the polyamide resin composition is 39 or less.

9. An extrusion molded article made from the polyamide resin composition according to claim 1 or 2.

10. A tubular molded article comprising the extruded molded article according to claim 9.

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