Polyamide resin composition

Abstract

Provided is a polyamide resin composition which gives molded articles excellent in terms of mechanical strength and impact resistance.　The polyamide resin composition comprises 52-88 mass% aliphatic polyamide resin (A), 5-25 mass% copolyolefin resin (B) having functional groups, up to 20 mass% olefin homopolymer (C) containing no functional group, and 0.05-3.0 mass% both a primary antioxidant (D) and a secondary antioxidant (E), the amount of the polyamide resin composition being taken as 100 mass%, wherein the copolyolefin resin (B) having functional groups has an MFR, as determined at a temperature of 230°C and a load of 2,160 g in accordance with ASTM D1238, greater than 1.0 g / 10 min but less than 5.0 g / 10 min, the polyamide resin composition containing the secondary antioxidant (E) in an amount larger than that of the primary antioxidant (D).

Description

[Technical Field]

[0001] The present invention relates to a polyamide resin composition. [Background technology]

[0002] Polyamide resins are known as resins with excellent gas barrier properties, and polyamide resin compositions having gas barrier properties are in demand for a variety of applications.

[0003] As such a polyamide resin composition, a polyamide resin composition containing a polyamide resin, a modified polyolefin resin, and an unmodified polyolefin resin in a predetermined ratio and having predetermined physical properties has been proposed, and it has been shown that blow-molded articles excellent in barrier properties and impact resistance can be obtained with good productivity (see, for example, Patent Document 1). Also, aliphatic polyamide resins having a relative viscosity ηr of less than 2.60 and a density of 0.895 g / cm 3 A polyamide resin composition containing the following modified polyolefin and an unmodified polyolefin having an MFR value of 3.0 to 30 g / 10 min in a predetermined ratio has been proposed, and it has been shown that a polyamide resin composition excellent in low-temperature impact resistance and surface property can be provided (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-88661 [Patent Document 2] International Publication No. 2019 / 54109 Summary of the Invention [Problem to be solved by the invention]

[0005] Although the molded articles of the polyamide resin compositions described in Patent Documents 1 and 2 exhibit excellent gas barrier properties and a certain level of impact resistance, molded articles having even better impact resistance are desired. In particular, in applications where molded articles come into contact with high-pressure gas, molded articles having excellent mechanical strength and impact resistance that can withstand high-pressure gas are desired.

[0006] An object of the present invention is to provide a polyamide resin composition which, when molded into a molded article, has excellent mechanical strength and impact resistance. [Means for solving the problem]

[0007] The present invention relates to the following [1] to

[14] . [1] A polyamide resin composition comprising, per 100 mass% of the polyamide resin composition, 52 to 88 mass% of an aliphatic polyamide resin (A), 5 to 25 mass% of a functional group-containing copolymerized polyolefin resin (B), 20 mass% or less of a functional group-free olefin homopolymer (C), and 0.05 to 3.0 mass% in total of a primary antioxidant (D) and a secondary antioxidant (E), wherein the functional group-containing copolymerized polyolefin resin (B) has an MFR of more than 1.0 g / 10 min and less than 5.0 g / 10 min, as measured in accordance with ASTM D1238 at a temperature of 230°C and a load of 2,160 g, measured in accordance with ASTM D1238 at a temperature of 230°C and a load of 2,160 g, and the polyamide resin composition contains more of the secondary antioxidant (E) than the primary antioxidant (D). [2] The polyamide resin composition according to [1], wherein the functional group-containing copolymerized polyolefin resin (B) has an MFR of more than 1.0 g / 10 min and not more than 3.0 g / 10 min, measured in accordance with ASTM D1238 at a temperature of 230°C and a load of 2,160 g. [3] The polyamide resin composition according to [1] or [2], wherein the aliphatic polyamide resin (A) has a relative viscosity of 2.2 to 2.8 as measured at 25°C in a solution of 1 g of the polyamide resin in 100 ml of 96% sulfuric acid according to JIS K 6920. [4] The polyamide resin composition according to any one of [1] to [3], wherein 100% by mass of the polyamide resin composition contains 60 to 88% by mass of an aliphatic polyamide resin (A). [5] The polyamide resin composition according to any one of [1] to [4], wherein 100% by mass of the polyamide resin composition contains 6 to 22% by mass of a functional group-containing copolymerized polyolefin resin (B). [6] The polyamide resin composition according to any one of [1] to [5], wherein 100% by mass of the polyamide resin composition contains 5 to 20% by mass of a functional group-free olefin homopolymer (C). [7] The polyamide resin composition according to any one of [1] to [6], wherein the content of the primary antioxidant (D) in 100% by mass of the polyamide resin composition is 0.02% by mass or more and less than 1.5% by mass. [8] The polyamide resin composition according to any one of [1] to [7], wherein the content of the secondary antioxidant (E) in 100% by mass of the polyamide resin composition is 0.03% by mass or more and 2.98% by mass or less. [9] The polyamide resin composition according to any one of [1] to [8], wherein the primary antioxidant (D) is at least one selected from the group consisting of phenolic compounds and amine compounds.

[10] The polyamide resin composition according to any one of [1] to [9], wherein the secondary antioxidant (E) is at least one selected from the group consisting of phosphorus-based compounds and sulfur-based compounds.

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

[10] , which has a flexural modulus (at 23°C, 50% RH) of 1,000 to 2,000 MPa and a flexural strength (at 23°C, 50% RH) of 50 to 80 MPa, as measured in accordance with ISO 178.

[12] Charpy impact strength (notched, 23°C 50% RH) of 20 kJ / m2 obtained in accordance with ISO 179-1 / 1eA 2 The polyamide resin composition according to any one of [1] to

[11] above.

[13] Charpy impact strength (notched, 23°C 50% RH) obtained in accordance with ISO 179-1 / 1eA is 45 kJ / m 2 The polyamide resin composition according to any one of [1] to

[12] above.

[14] The polyamide resin composition according to any one of [1] to

[13] , which is for use in a molded article that comes into contact with high-pressure gas. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a polyamide resin composition that has excellent mechanical strength and impact resistance when formed into a molded article. DETAILED DESCRIPTION OF THE INVENTION

[0009] In this specification, the content of each component in a composition means the total amount of each component in the composition unless otherwise specified, when the composition contains multiple substances corresponding to each component. Furthermore, the relative viscosity specified for polyamide resins means the value measured at 25°C in a solution of 1 g of polyamide resin in 100 ml of 96% sulfuric acid in accordance with JIS K 6920.

[0010] The polyamide resin composition of the present invention contains, per 100 mass% of the polyamide resin composition, 52 to 88 mass% of an aliphatic polyamide resin (A), 5 to 25 mass% of a functional group-containing copolymerized polyolefin resin (B), 20 mass% or less of a non-functional group-containing olefin homopolymer (C), and 0.05 to 3.0 mass% in total of a primary antioxidant (D) and a secondary antioxidant (E); the functional group-containing copolymerized polyolefin resin (B) has an MFR of more than 1.0 g / 10 min and less than 5.0 g / 10 min, as measured in accordance with ASTM D1238 at 230°C and a load of 2,160 g; and the polyamide resin composition contains more secondary antioxidant (E) than primary antioxidant (D). The present invention can provide a polyamide resin composition that, when molded into a molded article, exhibits excellent mechanical strength and impact resistance.

[0011] <Aliphatic polyamide resin (A)> The aliphatic polyamide resin (A) includes an aliphatic homopolyamide resin (A-1) and / or an aliphatic copolyamide resin (A-2).

[0012] (Aliphatic homopolyamide resin (A-1)) The aliphatic homopolyamide resin (A-1) refers to a polyamide resin in which the monomer component constituting the aliphatic polyamide resin is a single type. The aliphatic homopolyamide resin (A-1) may be composed of at least one type of lactam and an aminocarboxylic acid that is a hydrolyzate of the lactam, or may be composed of a combination of one type of aliphatic diamine and one type of aliphatic dicarboxylic acid. Here, when the monomer components constituting the aliphatic polyamide resin are a combination of an aliphatic diamine and an aliphatic dicarboxylic acid, the combination of one type of aliphatic diamine and one type of aliphatic dicarboxylic acid is considered to be one type of monomer component.

[0013] Examples of the aliphatic homopolyamide resin (A-1) include aliphatic homopolyamide resins made from aliphatic diamines and aliphatic dicarboxylic acids, and aliphatic homopolyamide resins made from lactams or aminocarboxylic acids.

[0014] Examples of the monomer components constituting the aliphatic homopolyamide resin (A-1) include a combination of an aliphatic diamine having 2 to 20 carbon atoms, preferably 4 to 12 carbon atoms, and an aliphatic dicarboxylic acid having 2 to 20 carbon atoms, preferably 6 to 12 carbon atoms, a lactam or aminocarboxylic acid having 4 to 12 carbon atoms, and the like.

[0015] Examples of aliphatic diamines include ethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, dodecamethylenediamine, tridecanediamine, tetradecanediamine, pentadecanediamine, hexadecanediamine, heptadecanediamine, octadecanediamine, nonadecanediamine, eicosanediamine, 2-methyl-1,8-octanediamine, and 2,2,4 / 2,4,4-trimethylhexamethylenediamine. Examples of aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedionic acid, dodecanedionic acid, tridecanedionic acid, tetradecanedionic acid, pentadecanedioic acid, hexadecanedioic acid, octadecanedioic acid, and eicosanedioic acid.

[0016] Examples of combinations of aliphatic diamines and aliphatic dicarboxylic acids include a combination of tetramethylenediamine and sebacic acid, a combination of hexamethylenediamine and adipic acid, a combination of hexamethylenediamine and sebacic acid, and a combination of hexamethylenediamine and dodecanedioic acid, and equimolar salts of these combinations are preferably used.

[0017] Examples of lactams include ε-caprolactam, enantholactam, undecane lactam, dodecane lactam, α-pyrrolidone, and α-piperidone. From the viewpoint of productivity, the lactam is preferably ε-caprolactam, undecane lactam, or dodecane lactam. Examples of aminocarboxylic acids include 6-aminocaproic acid, 7-aminoheptanoic acid, 9-aminononanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid. From the viewpoint of productivity, the aminocarboxylic acid is preferably 6-aminocaproic acid, 11-aminoundecanoic acid, or 12-aminododecanoic acid.

[0018] Specific examples of the aliphatic homopolyamide resin (A-1) include polycaprolactam (polyamide 6), polyenantholactam (polyamide 7), polyundecane lactam (polyamide 11), polylauryllactam (polyamide 12), polyhexamethylene adipamide (polyamide 66), polytetramethylene decamide (polyamide 410), polytetramethylene dodecamide (polyamide 412), polypentamethylene azelamide (polyamide 59), polypentamethylene sebacamide (polyamide 510), polypentamethylene dodecamide (polyamide 512), polyhexamethylene azelamide (polyamide 69), polyhexamethylene sebacamide (polyamide 610), polyhexamethylene dodecamide (poly amide 612), polynonamethylene adipamide (polyamide 96), polynonamethylene azelamide (polyamide 99), polynonamethylene sebacamide (polyamide 910), polynonamethylene dodecamide (polyamide 912), polydecamethylene adipamide (polyamide 106), polydecamethylene azelamide (polyamide 109), polydecamethylene decamide (polyamide 1010), polydecamethylene dodecamide (polyamide 1012), polydodecamethylene adipamide (polyamide 126), polydodecamethylene azelamide (polyamide 129), polydodecamethylene sebacamide (polyamide 1210), polydodecamethylene dodecamide (polyamide 1212), polyamide 122, and the like.

[0019] From the viewpoint of productivity, the aliphatic homopolyamide resin (A-1) is preferably one or more selected from the group consisting of polyamide 6, polyamide 410, polyamide 66, polyamide 610, polyamide 612, polyamide 11, and polyamide 12, and particularly preferably polyamide 6 and / or polyamide 66.

[0020] The aliphatic homopolyamide resin (A-1) may be one type or a combination of two or more types.

[0021] (Aliphatic copolyamide resin (A-2)) The aliphatic copolyamide resin (A-2) refers to a polyamide resin in which the monomer components constituting the aliphatic polyamide resin are a combination of two or more types. The aliphatic copolyamide resin (A-2) is a copolymer of two or more types selected from the group consisting of a combination of an aliphatic diamine and an aliphatic dicarboxylic acid, a lactam, and an aminocarboxylic acid. Here, the combination of an aliphatic diamine and an aliphatic dicarboxylic acid is considered to be one type of monomer component, with one type of aliphatic diamine and one type of aliphatic dicarboxylic acid being the combination.

[0022] Examples of the aliphatic diamine include the same as those exemplified as the raw materials for the aliphatic homopolyamide resin (A-1).

[0023] Examples of the aliphatic dicarboxylic acid include the same as those exemplified as the raw materials for the aliphatic homopolyamide resin (A-1).

[0024] Examples of lactams include those exemplified as raw materials for the aliphatic homopolyamide resin (A-1). Examples of aminocarboxylic acids include those exemplified as raw materials for the aliphatic homopolyamide resin (A-1).

[0025] These aliphatic diamines, aliphatic dicarboxylic acids, lactams and aminocarboxylic acids may be used alone or in combination of two or more.

[0026] Specific examples of the aliphatic copolymer polyamide resin (A-2) include caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 66), caprolactam / hexamethylenediaminoazelaic acid copolymer (polyamide 6 / 69), caprolactam / hexamethylenediaminosebacic acid copolymer (polyamide 6 / 610), caprolactam / hexamethylenediaminoundecanedicarboxylic acid copolymer (polyamide 6 / 611), caprolactam / hexamethylenediaminododecanedicarboxylic acid copolymer (polyamide 6 / 612), caprolactam / hexamethylenediaminododecanedicarboxylic acid copolymer (polyamide 6 / 613), caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 614), caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 615), caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 616), caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 617), caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 618), caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 619), caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 620), caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 621), caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 622), caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 623), caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 624), caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 625), caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 626), caprolactam / hexamethylenediaminoadi Examples of such copolymers include caprolactam / aminoundecanoic acid copolymer (polyamide 6 / 11), caprolactam / lauryllactam copolymer (polyamide 6 / 12), caprolactam / hexamethylenediaminoadipic acid / lauryllactam copolymer (polyamide 6 / 66 / 12), caprolactam / hexamethylenediaminoadipic acid / hexamethylenediaminosebacic acid copolymer (polyamide 6 / 66 / 610), and caprolactam / hexamethylenediaminoadipic acid / hexamethylenediaminododecanedicarboxylic acid copolymer (polyamide 6 / 66 / 612). From the viewpoint of productivity, the polyolefin copolymer is preferably at least one selected from the group consisting of caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 66), caprolactam / hexamethylenediaminosebacic acid copolymer (polyamide 6 / 610), caprolactam / aminoundecanoic acid copolymer (polyamide 6 / 11), caprolactam / lauryllactam copolymer (polyamide 6 / 12), caprolactam / hexamethylenediaminoadipic acid / lauryllactam copolymer (polyamide 6 / 66 / 12), and caprolactam / hexamethylenediaminoadipic acid / hexamethylenediaminosebacic acid copolymer (polyamide 6 / 66 / 610).

[0027] The aliphatic copolyamide resin (A-2) may be one type or a combination of two or more types.

[0028] (Physical properties and content of aliphatic polyamide resin (A)) From the viewpoint of the mechanical properties and moldability of the polyamide resin composition, the aliphatic polyamide resin (A) preferably has a relative viscosity of 1.5 to 5.0, as measured at 25°C by dissolving 1 g of the polyamide resin in 100 ml of 96% sulfuric acid in accordance with JIS K 6920. The relative viscosity of the aliphatic polyamide resin (A) is more preferably 2.0 to 4.5, more preferably 2.1 to 3.9, more preferably 2.1 to 3.3, still more preferably 2.2 to 2.8, and particularly preferably 2.3 to 2.6.

[0029] When the aliphatic polyamide resin (A) contains two or more polyamide resins with different relative viscosities, the relative viscosity of the aliphatic polyamide resin (A) is preferably measured as described above. However, when the relative viscosity of each polyamide resin and its mixing ratio are known, the relative viscosity of the aliphatic polyamide resin (A) may be determined by adding up the values ​​obtained by multiplying each relative viscosity by the mixing ratio.

[0030] The terminal amino group concentration of the aliphatic polyamide resin (A), as determined by dissolving the resin in a mixed solvent of phenol and methanol and subjecting it to neutralization titration, is preferably 30 μmol / g or more, more preferably 30 μmol / g or more and 110 μmol / g or less, and particularly preferably 30 μmol / g or more and 70 μmol / g or less. Within this range, the polyamide resin composition has good moldability.

[0031] When the aliphatic polyamide resin (A) contains two or more polyamide resins having different terminal amino group concentrations, the terminal amino group concentration in the aliphatic polyamide resin (A) is preferably measured by the neutralization titration method described above. However, when the terminal amino group concentration of each polyamide resin and its mixing ratio are known, the terminal amino group concentration of the aliphatic polyamide resin (A) may be determined by adding up the values ​​obtained by multiplying each terminal amino group concentration by the mixing ratio.

[0032] The polyamide resin composition contains 52 to 88 mass% of an aliphatic polyamide resin (A) based on 100 mass% of the polyamide resin composition. When the content of the aliphatic polyamide resin (A) is within the above range, the polyamide resin composition can have excellent mechanical properties and moldability. The content of the aliphatic polyamide resin (A) based on 100 mass% of the polyamide resin composition is preferably 60 to 88 mass%, more preferably 65 to 88 mass%, even more preferably 70 to 88 mass%, and particularly preferably 70 to 80 mass%.

[0033] (Production of polyamide resin) Examples of polyamide resin production equipment include known polyamide production equipment such as batch-type reaction vessels, single- or multi-vessel continuous reaction equipment, tubular continuous reaction equipment, and kneading reaction extruders such as single-screw kneading extruders and twin-screw kneading extruders. Known polymerization methods, such as melt polymerization, solution polymerization, and solid-phase polymerization, can be used, and polymerization can be carried out by repeating operations under normal pressure, reduced pressure, increased pressure, etc. These polymerization methods can be used alone or in appropriate combination.

[0034] <Functional group-containing copolymer polyolefin resin (B)> The functional group-containing copolymerized polyolefin resin (B) is a component that imparts mechanical strength and impact resistance to the polyamide resin composition. The functional group-containing copolymerized polyolefin resin (B) preferably has a flexural modulus of 500 MPa or less as measured in accordance with ASTM D-790. The functional group-containing copolymerized polyolefin resin (B) contains a functional group in its molecule that has affinity for the aliphatic polyamide resin (A). The reaction between the amino group of the polyamide resin and the functional group of the functional group-containing copolymerized polyolefin resin improves the impact resistance of the molded article produced from the polyamide resin composition. The present inventors discovered that when a functional group-containing olefin homopolymer is blended with a polyamide resin composition, the Charpy impact strength of the molded article produced from the composition is insufficient. After extensive research, they discovered that blending the functional group-containing copolymerized polyolefin resin (B) instead of the functional group-containing olefin homopolymer significantly improves the Charpy impact strength of the molded article produced from the polyamide resin composition.

[0035] Examples of the functional group of the functional group-containing copolymerized polyolefin resin (B) include a carboxyl group, an acid anhydride group, a carboxylic acid ester group, a metal carboxylic acid salt, a carboxylic acid imide group, a carboxylic acid amide group, an epoxy group, etc. It is believed that at least a part of the amino groups of the aliphatic polyamide resin (A) react with these functional groups.

[0036] Methods for introducing these functional groups into a copolymerized polyolefin resin include (i) copolymerizing a copolymerizable monomer having a functional group during polymerization of the copolymerized polyolefin resin, (ii) introducing a functional group into the molecular chain or molecular end of the copolymerized polyolefin resin using a polymerization initiator, chain transfer agent, etc., and (iii) grafting a compound (graft compound) having the functional group and a graftable functional group onto the copolymerized polyolefin resin. These introduction methods can be used alone or in appropriate combination.

[0037] Examples of copolymerizable monomers having these functional groups, the graft compounds, etc. include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, mesaconic acid, citraconic acid, glutaconic acid, cis-4-cyclohexene-1,2-dicarboxylic acid, endo-bicyclo-[2.2.1]-5-heptene-2,3-dicarboxylic acid, and metal salts of these carboxylic acids, monomethyl maleate, monomethyl itaconate, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, hydroxyethyl acrylate, methyl methacrylate, etc. Examples of suitable methacrylates include glycidyl, 2-ethylhexyl methacrylate, hydroxyethyl methacrylate, aminoethyl methacrylate, dimethyl maleate, dimethyl itaconate, maleic anhydride, itaconic anhydride, citraconic anhydride, endobicyclo-[2.2.1]-5-heptene-2,3-dicarboxylic anhydride, maleimide, N-ethylmaleimide, N-butylmaleimide, N-phenylmaleimide, acrylamide, methacrylamide, glycidyl acrylate, glycidyl methacrylate, glycidyl ethacrylate, glycidyl itaconate, and glycidyl citraconate. These may be used alone or in combination of two or more. Among these, maleic anhydride, itaconic anhydride, and / or citraconic anhydride are preferred.

[0038] The content of functional groups in the functional group-containing copolymerized polyolefin resin (B), expressed as the moles of functional groups (μmol) / mass (g) of (B), is preferably more than 25 μmol / g and less than 150 μmol / g, more preferably 35 μmol / g or more and less than 125 μmol, and particularly preferably 40 μmol / g or more and 110 μmol / g or less. For example, when the functional group-containing copolymerized polyolefin resin (B) has a carboxyl group, an acid anhydride group, or a carboxylic acid ester group, the content of the functional groups is measured by neutralization titration with a 0.1 N KOH ethanol solution using a sample solution prepared from toluene and ethanol and phenolphthalein as an indicator.

[0039] Examples of the functional group-containing copolymerized polyolefin resin (B) include (ethylene and / or propylene) / α-olefin copolymers containing the functional groups, (ethylene and / or propylene) / (α,β-unsaturated carboxylic acid and / or α,β-unsaturated carboxylic acid ester) copolymers, etc. In these copolymers, the content of ethylene and / or propylene units is preferably 10 mol% or more and 90 mol% or less, more preferably 20 mol% or more and 80 mol% or less. The functional group-containing copolymerized polyolefin resin (B) can be used singly or in combination of two or more. As the functional group-containing copolymerized polyolefin resin (B), an ethylene / α-olefin copolymer containing the functional group is preferred.

[0040] The (ethylene and / or propylene) / α-olefin copolymer is a polymer obtained by copolymerizing ethylene with an α-olefin having 3 or more carbon atoms and / or a polymer obtained by copolymerizing propylene with an α-olefin having 4 or more carbon atoms. Examples of the α-olefins having 3 or more carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 9-methyl-1-decene, 11-methyl-1-dodecene, and 12-ethyl-1-tetradecene. These may be used alone or in combination of two or more. Among these, the (ethylene and / or propylene) / α-olefin copolymer is particularly preferably an ethylene / 1-butene copolymer.

[0041] The copolymer may also be one obtained by copolymerizing a polyene such as a non-conjugated diene. Examples of the non-conjugated diene include 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, 1,4-octadiene, 1,5-octadiene, 1,6-octadiene, 1,7-octadiene, 2-methyl-1,5-hexadiene, 6-methyl-1,5-heptadiene, 7-methyl-1,6-octadiene, 4-ethylidene-8-methyl-1,7-nonadiene, 4,8-dimethyl-1,4,8-decatriene (DMDT), and dicyclopentadiene. Examples of the alkyl acrylate include butyl acrylate, butyl acrylate, butyl acrylate, butyl acrylate, butyl acrylate (VBAC), ...

[0042] The (ethylene and / or propylene) / (α,β-unsaturated carboxylic acid and / or α,β-unsaturated carboxylic acid ester) copolymer is a polymer obtained by copolymerizing ethylene and / or propylene with an α,β-unsaturated carboxylic acid and / or α,β-unsaturated carboxylic acid ester monomer. Examples of the α,β-unsaturated carboxylic acid monomer include acrylic acid and methacrylic acid. Examples of the α,β-unsaturated carboxylic acid ester monomer include the methyl ester, ethyl ester, propyl ester, butyl ester, pentyl ester, hexyl ester, heptyl ester, octyl ester, nonyl ester, and decyl ester of these α,β-unsaturated carboxylic acids. These may be used alone or in combination of two or more.

[0043] Since the (ethylene and / or propylene) / (α,β-unsaturated carboxylic acid and / or α,β-unsaturated carboxylic acid ester) copolymer has a carboxyl group and / or a carboxylic acid ester group, it is a functional group-containing copolymerized polyolefin resin (B). Even if the (ethylene and / or propylene) / (α,β-unsaturated carboxylic acid and / or α,β-unsaturated carboxylic acid ester) copolymer further has a functional group other than a carboxyl group and a carboxylic acid ester group introduced therein by a compound containing the above-mentioned functional group, it is still considered to be a functional group-containing copolymerized polyolefin resin (B).

[0044] From the viewpoint of mechanical strength and impact resistance when formed into a molded article, the functional group-containing copolymerized polyolefin resin (B) is more preferably an ethylene / α-olefin copolymer into which maleic anhydride, itaconic anhydride or citraconic anhydride has been introduced, even more preferably an ethylene / α-olefin copolymer into which maleic anhydride has been introduced, and particularly preferably an ethylene / 1-butene copolymer into which maleic anhydride has been introduced.

[0045] The functional group-containing copolymerized polyolefin resin (B) may contain a non-functional group-containing copolymerized polyolefin resin to the extent that the functions and properties of the polyamide resin composition are not impaired.

[0046] The functional group-containing copolymerized polyolefin resin (B) has an MFR of more than 1.0 g / 10 min and less than 5.0 g / 10 min, measured in accordance with ASTM D1238 at a temperature of 230°C and a load of 2,160 g. By setting the MFR of the functional group-containing copolymerized polyolefin resin (B) within the above range, a polyamide resin composition can be obtained that has a good balance between rigidity and flexibility and excellent impact resistance when molded into a molded article. The MFR of the functional group-containing copolymerized polyolefin resin (B) measured by the above method is preferably more than 1.0 to 3.0 g / 10 min, particularly preferably more than 1.0 to 2.5 g / 10 min.

[0047] The polyamide resin composition contains 5 to 25 mass% of functional group-containing copolymerized polyolefin resin (B) based on 100 mass% of the polyamide resin composition. When the content of functional group-containing copolymerized polyolefin resin (B) is within the above range, the polyamide resin composition can have excellent impact resistance. The content of functional group-containing copolymerized polyolefin resin (B) is preferably 5 to 24 mass%, more preferably 6 to 22 mass%, and particularly preferably 6 to 12 mass%, based on 100 mass% of the polyamide resin composition.

[0048] <Functional Group-Free Olefin Homopolymer (C)> The polyamide resin composition may contain a non-functional group-containing olefin homopolymer (C). By containing the non-functional group-containing olefin homopolymer (C), the flowability and moldability of the polyamide resin composition can be improved. Note that a homopolymer is a polymer obtained by polymerization of one type of monomer.

[0049] Examples of the olefin in the non-functional group-containing olefin homopolymer (C) include ethylene and α-olefins having 3 or more carbon atoms. Examples of the α-olefins having 3 or more carbon atoms include those exemplified for the functional group-containing copolymerized polyolefin resin (B). Among these, the non-functional group-containing olefin homopolymer (C) is preferably an ethylene homopolymer or a propylene homopolymer, more preferably an ethylene homopolymer. Examples of ethylene homopolymers include high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), etc. The non-functional group-containing olefin homopolymer (C) can be appropriately selected depending on the required performance, the application, and the molding method used.

[0050] The functional group-free olefin homopolymer (C) may be one type or a combination of two or more types.

[0051] The polyamide resin composition contains 20% by mass or less, preferably 5 to 20% by mass, and more preferably 10 to 20% by mass, of the non-functional group-containing olefin homopolymer (C) based on 100% by mass of the polyamide resin composition. When the content of the non-functional group-containing olefin homopolymer (C) is within the above range, the polyamide resin composition can have excellent flowability and moldability.

[0052] <Primary antioxidant (D) and secondary antioxidant (E)> The polyamide resin composition contains a primary antioxidant (D) and a secondary antioxidant (E) in a total amount of 0.05 to 3.0% by mass. Generally, when a resin (R) is exposed to oxygen, heat, light, or the like, free radicals are generated, which then react with oxygen to generate peroxy radicals (ROO·). These peroxy radicals are highly reactive and abstract hydrogen from other organic substances to form hydroperoxides, which then generate new free radicals and undergo a chain reaction (autoxidation), accelerating resin degradation. In the present invention, to prevent such resin degradation, a primary antioxidant and a secondary antioxidant are used in combination, and the ratio of their amounts is specified. The primary antioxidant (D) refers to a compound that captures free radicals generated by the action of oxygen, heat, light, or the like and has the effect of preventing autoxidation, while the secondary antioxidant (E) refers to a compound that has the effect of decomposing hydroperoxides into harmless compounds. The primary antioxidant (D) and the secondary antioxidant (E) may each be one kind or a combination of two or more kinds.

[0053] From the viewpoint of peroxy radical scavenging, the primary antioxidant (D) is preferably at least one selected from the group consisting of phenolic compounds and amine compounds, more preferably a phenolic compound, further preferably a compound having at least one hydroxyphenyl group having a bulky substituent such as a t-butyl group at the ortho-position of the hydroxyl group, and particularly preferably a compound having two or more such hydroxyphenyl groups.

[0054] Specific examples of phenolic compounds include N,N'-hexamethylenebis(3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) (Irganox® 1098, manufactured by BASF Japan Ltd.; SONGNOX® 1098, manufactured by Songwon Industrial Co., Ltd.), pentaerythrityl-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate] (Irganox® 1010, manufactured by BASF Japan Ltd.), and benzophenone-2-one (benzophenone-2-one). Co., Ltd.), ethylene bis(oxyethylene) bis[3-(5-t-butyl-4-hydroxy-m-tolyl)propionate] (Irganox® 245; BASF Japan Ltd.), and 3,9-bis[2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane (Sumilizer® GA-80; Sumitomo Chemical Co., Ltd.).

[0055] Specific examples of amine compounds include N-(3-methacryloyloxy-2-hydroxypropyl)-N'-phenyl-p-phenylenediamine, phenyl-α-naphthylamine, phenyl-β-naphthylamine, aldol-α-naphthylamine, reaction products of phenyl-β-naphthylamine with acetone, p-isopropoxydiphenylamine, p-(p-toluenesulfonylamido)-diphenylamine, reaction products of diphenylamine with acetone, and reaction products of diphenylamine with diisobutylene. Examples of the product include N,N'-diphenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N-cyclohexyl-N'-phenyl-p-phenylenediamine, N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine, polymers of 2,2,4-trimethyl-1,2-dihydroquinoline, 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, and 6-dodecyl-2,2,4-trimethyl-1,2-dihydroquinoline.

[0056] From the viewpoint of decomposing peroxides and stabilizing peroxy radicals, the secondary antioxidant (E) is preferably at least one selected from the group consisting of phosphorus-based compounds and sulfur-based compounds, more preferably a phosphorus-based compound, still more preferably a triaryloxyphosphine-based compound, and particularly preferably a triphenyloxyphosphine-based compound having a bulky substituent such as a t-butyl group at the ortho-position of the oxygen atom bonded to the benzene ring.

[0057] Specific examples of phosphorus-based compounds include tris(2,4-di-t-butylphenyl)phosphite (Irgafos168 (registered trademark), manufactured by BASF Japan Ltd.; SONGNOX (registered trademark) 1680, manufactured by Songwon Industrial Co., Ltd.), bis(2,6-di-t-butyl-4-methylphenyl)pentaerthritol diphosphite (ADEKA STAB (registered trademark) PEP-36; manufactured by ADEKA Corporation), and a reaction product of bifinyl, phosphorus trichloride, and 2,4-di-tert-butylphenol, the main component of which is tetrakis(2,4-di-tert-butylphenoxy)-4,4-bifinyldiphosphine (Hostanox (registered trademark) P-EPQ P; manufactured by Clariant Japan Ltd.).

[0058] Specific examples of sulfur-based compounds include thioether-based compounds such as distearyl-3,3-thiodipropionate (Irganox (registered trademark) PS802; manufactured by BASF Japan Ltd.), pentaerythrityl tetrakis(3-laurylthiopropionate) (Sumilizer (registered trademark) TP-D; manufactured by Sumitomo Chemical Co., Ltd.), and didodecyl (3,3′-thiodipropionate) (Irganox (registered trademark) PS800; manufactured by BASF Japan Ltd.).

[0059] The polyamide resin composition contains a total of 0.05 to 3.0 mass% of a primary antioxidant (D) and a secondary antioxidant (E) based on 100 mass% of the polyamide resin composition. When the total content of the primary antioxidant (D) and the secondary antioxidant (E) is within the above range, the polyamide resin composition is prevented from oxidative degradation and can give molded articles with excellent mechanical strength. The total content of the primary antioxidant (D) and the secondary antioxidant (E) based on 100 mass% of the polyamide resin composition is preferably 0.10 to 2.5 mass%, more preferably 0.15 to 2.0 mass%, and particularly preferably 0.20 to 1.5 mass%.

[0060] The polyamide resin composition contains a secondary antioxidant (E) in an amount greater than the primary antioxidant (D). By including a greater amount of the secondary antioxidant (E) than the primary antioxidant (D), the hydroperoxides generated by the primary antioxidant (D) can be sufficiently stabilized, thereby preventing discoloration of molded articles obtained from the polyamide resin composition and a decrease in mechanical strength due to oxidative degradation. From the viewpoint of balancing the prevention of discoloration of the polyamide resin composition and the antioxidant effect, the content ratio of the secondary antioxidant (E) to the primary antioxidant (D) is preferably more than 1 time but not more than 5 times, more preferably more than 1.2 times but not more than 4 times, and particularly preferably more than 1.5 times but not more than 3 times, the mass of the secondary antioxidant (E) relative to the mass of the primary antioxidant (D).

[0061] The content of the primary antioxidant (D) is preferably 0.02 mass% or more and less than 1.5 mass%, more preferably 0.05 mass% or more and 1.0 mass% or less, and particularly preferably 0.10 mass% or more and 0.50 mass% or less, based on 100 mass% of the polyamide resin composition. The content of the secondary antioxidant (E) is preferably 0.03 mass% or more and 2.98 mass% or less, more preferably 0.10 mass% or more and 2.0 mass% or less, and particularly preferably 0.15 mass% or more and 1.0 mass% or less, based on 100 mass% of the polyamide resin composition.

[0062] <Other ingredients> The polyamide resin composition may contain other components as long as they do not impair the effects of the present invention. Examples of other components include polyamide resins other than the aliphatic polyamide resin (A), such as polyamide resins having alicyclic or aromatic groups in the main chain or side chain, resins other than the functional group-containing copolymerized polyolefin resin (B) and the non-functional group-containing olefin homopolymer (C), plasticizers, antioxidants other than the primary antioxidant (D) and secondary antioxidant (E), such as inorganic antioxidants, reinforcing agents such as organic fibers and inorganic fibers, foaming agents, weathering agents, crystal nucleating agents, crystallization accelerators, crystallization retarders, mold release agents, lubricants, antistatic agents, flame retardants, flame retardant aids, and functionality-imparting agents such as pigments and dyes. The other components are not the aliphatic polyamide resin (A), the functional group-containing copolymerized polyolefin resin (B), the non-functional group-containing olefin homopolymer (C), the primary antioxidant (D), or the secondary antioxidant (E).

[0063] The polyamide resin composition may contain a nucleating agent as another component depending on the intended use of the molded article. Nucleating agents include inorganic and organic nucleating agents. Examples of inorganic nucleating agents include talc, mica, synthetic mica, glass flakes, non-swelling mica, fullerene, carbon nanotubes, carbon black, graphite, metal foil, ceramic beads, clay, sericite, zeolite, bentonite, aluminum hydroxide, dolomite, kaolin, silica, finely powdered silicic acid, feldspar powder, potassium titanate, shirasu balloon, calcium carbonate, magnesium carbonate, barium sulfate, calcium oxide, aluminum oxide, titanium oxide, and magnesium oxide. , aluminum silicate, silicon oxide, magnesium hydroxide, gypsum, novaculite, dawsonite, clay, glass fiber, carbon fiber, graphite fiber, metal fiber, potassium titanate whisker, aluminum borate whisker, magnesium whisker, silicon whisker, wollastonite, sepiolite, slag fiber, zonolite, ellestadite, gypsum fiber, silica fiber, silica-alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron fiber, etc. Among these, when used as a material for a high-pressure gas tank, talc is preferred from the viewpoints of improving the crystallinity of the polyamide resin composition and suppressing gas permeability. Examples of the organic nucleating agent include thermoplastic resins having a melting point higher than that of the aliphatic polyamide resin (A), fatty acid metal salts, benzylidene sorbitol, quinacridone, cyanine blue, and the like.

[0064] [Method of producing polyamide resin composition] The method for producing the polyamide resin composition is not particularly limited, and the following method can be applied, for example. When the aliphatic polyamide resin (A), the functional group-containing copolymerized polyolefin resin (B), the non-functional group-containing olefin homopolymer (C), the primary antioxidant (D), the secondary antioxidant (E), and any other components are mixed and used, a commonly known melt-kneading machine such as a single-screw or twin-screw extruder, a Banbury mixer, a kneader, or a mixing roll is used. For example, any of the following methods may be used: a method in which all raw materials are blended and then melt-kneaded using a twin-screw extruder; a method in which some raw materials are blended and then melt-kneaded, and then the remaining raw materials are blended and melt-kneaded; or a method in which some raw materials are blended and then the remaining raw materials are mixed using a side feeder during melt-kneading.

[0065] [Physical properties of polyamide resin composition] The polyamide resin composition preferably has a flexural modulus (23°C, 50% RH) of 1,000 to 2,000 MPa and a flexural strength (23°C, 50% RH) of 50 to 80 MPa, as measured in accordance with ISO 178. When the flexural modulus and flexural strength are within the above ranges, a molded article exhibits a good balance between rigidity and flexibility, and the molded article is resistant to internal and external pressures. Therefore, the polyamide resin composition is particularly suitable for use in molded articles that come into contact with high-pressure gas. If the flexural modulus is less than 1,000 MPa or the flexural strength is less than 50 MPa, the molded article tends to be prone to fracture. If the flexural modulus is greater than 2,000 MPa or the flexural strength is greater than 80 MPa, further processing of the molded article tends to be difficult, and the molded article tends to have poor flexibility and, conversely, poor impact resistance. The flexural modulus is more preferably 1,200 to 2,000 MPa, even more preferably 1,400 to 2,000 MPa, still more preferably 1,400 to 1,900 MPa, even more preferably 1,400 to 1,700 MPa, and particularly preferably 1,400 to 1,600 MPa. The flexural strength is more preferably 50 to 79 MPa, even more preferably 55 to 78 MPa, and particularly preferably 60 to 75 MPa.

[0066] The polyamide resin composition has a Charpy impact strength (notched, 23°C 50% RH) of 20 kJ / m2 or higher, measured in accordance with ISO 179-1 / 1eA. 2 If the Charpy impact strength is in the above range, the impact resistance of the molded article will be good, and the molded article can be suitably used in applications where the molded article will come into contact with high-pressure gas. The Charpy impact strength is 45 kJ / m or more. 2 More preferably, it is 60 kJ / m or more. 2 More preferably, it is 80 kJ / m or more. 2 The upper limit of the Charpy impact strength is not particularly limited, but is usually 150 kJ / m 2 The following is the result.

[0067] [Uses of polyamide resin composition] The polyamide resin composition is not particularly limited and can be used for producing molded articles using known methods. Specifically, the polyamide resin composition can be used for producing molded articles by press molding, blow molding, extrusion molding, injection molding, rotational molding, etc., and is particularly suitable for producing molded articles by injection molding.

[0068] When molded into a product, the polyamide resin composition has a good balance between rigidity and flexibility and is excellent in gas barrier properties and impact resistance, and is therefore suitable for use in molded products that come into contact with high-pressure gas, specifically compressed gas with a pressure of 1 MPa or more at normal temperatures, such as tanks, tubes, hoses, films, etc. The type of gas is not particularly limited and examples include hydrogen, nitrogen, oxygen, helium, methane, butane, propane, natural gas, etc., with less polar gases being preferred, and hydrogen, nitrogen, and methane being particularly preferred. [Example]

[0069] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0070] [Materials used] 1. Aliphatic polyamide resin (A) Polyamide 6 (manufactured by Ube Industries, Ltd.; relative viscosity measured at 25°C by dissolving 1 g of polyamide resin in 100 ml of 96% sulfuric acid according to JIS K 6920: 2.64) Polyamide 6 (manufactured by Ube Industries, Ltd.; relative viscosity measured at 25°C by dissolving 1 g of polyamide resin in 100 ml of 96% sulfuric acid according to JIS K 6920: 2.47)

[0071] 2. Functional group-containing copolymer polyolefin resin (B): 1.0 g / 10 min < MFR (230°C, load 2,160 g) < 5.0 g / 10 min Maleic anhydride-modified ethylene-1-butene copolymer (Mitsui Chemicals, Inc., Tafmer® MH5020, MFR (230°C, load 2,160 g): 1.2 g / 10 min) Maleic anhydride-modified ethylene-1-butene copolymer (manufactured by Mitsui Chemicals, Inc., Tafmer® MH5020C, MFR (230°C, load 2,160 g): 1.2 g / 10 min)

[0072] 2'. Functional group-containing polyolefin resin (B') other than functional group-containing copolymer polyolefin resin (B) Maleic anhydride-modified polypropylene resin (Prime Polymer Co., Ltd., ZP 648, MFR (230°C, load 2,160 g): 55 g / 10 min) Maleic anhydride-modified ethylene-1-butene copolymer (Mitsui Chemicals, Inc., Tafmer® MA8510, MFR (230°C, load 2,160 g): 5.0 g / 10 min)

[0073] 3. Non-functional group-containing olefin homopolymer (C) Linear low-density polyethylene resin (Prime Polymer Co., Ltd., Evolue® SP0540)

[0074] 3'. Functional group-free copolymer polyolefin resin (C') Ethylene-propylene copolymer (Sumitomo Chemical Co., Ltd., Esprene® SP0 V0132) Ethylene-1-butene copolymer (Tafmer (registered trademark) TX610, manufactured by Mitsui Chemicals, Inc.)

[0075] 4. Primary antioxidants (D) Phenolic compound: N,N'-hexamethylenebis(3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) (Irganox® 1098; manufactured by BASF Japan Ltd.) Phenolic compound: N,N'-hexamethylenebis(3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) (SONGNOX® 1098; manufactured by Songwon Industrial Co., Ltd.)

[0076] 5. Secondary antioxidants (E) Phosphorus compound: tris(2,4-di-t-butylphenyl) phosphite (SONGNOX® 1680; manufactured by Songwon Industrial Co., Ltd.) Phosphorus compound: tris(2,4-di-t-butylphenyl)phosphite (Irgafos® 168; manufactured by BASF Japan Ltd.)

[0077] Examples 1 to 8 and Comparative Examples 1 to 5 Each component shown in Table 1 was melt-kneaded under the following melt-kneading conditions to prepare pellets of the target polyamide resin composition. Note that the units of composition in Table 1 are % by mass, and the total polyamide resin composition is taken as 100% by mass. <Melting and kneading conditions> ZSK32mc twin-screw extruder (manufactured by Coperion) used Cylinder diameter: 32mm L / D:48 Screw rotation speed: 250 rpm

[0078] [Evaluation method] 1. MFR (230°C, load 2,160g) The MFR of the functional group-containing copolymer polyolefin resin (B) and the other functional group-containing polyolefin resin (B') was measured in accordance with ASTM D1238 at a temperature of 230°C and a load of 2,160 g.

[0079] 2. Flexural modulus and flexural strength Using the pellets of Examples 1 to 8 and Comparative Examples 1 to 5, ISO Type-B test pieces having a thickness of 4 mm were prepared under the following injection molding conditions. <Injection molding conditions> Cylinder temperature: 250℃ Mold temperature: 80℃ Average injection speed in the mold: 200mm / sec Cooling time: 20 seconds

[0080] Using the test pieces thus obtained, the flexural modulus and flexural strength were measured under conditions of 23°C and 50% RH in accordance with ISO 178. The measuring device used was a fully automatic plastic bending tester, AG-Xplus model (manufactured by Shimadzu Corporation). When the flexural modulus was 1,000 to 2,000 MPa and the flexural strength was 50 to 80 MPa, the molded article was judged to have a good balance between rigidity and flexibility.

[0081] 3. Charpy impact strength Using the pellets of Examples 1 to 8 and Comparative Examples 1 to 5, ISO Type-B test pieces having a thickness of 4 mm were prepared under the following injection molding conditions. <Injection molding conditions> Cylinder temperature: 250℃ Mold temperature: 80℃ Average injection speed in the mold: 200mm / sec Cooling time: 20 seconds

[0082] Using the test pieces obtained in this way, the Charpy impact strength (with notch) was measured under conditions of 23°C and 50% RH in accordance with ISO 179-1 / 1eA. The measuring device used was Model 141-PC (manufactured by Yasuda Seiki Seisakusho Co., Ltd.). When the Charpy impact strength was 20 kJ / m 2 If the impact strength is 45 kJ / m or more, the impact resistance of the molded product is good, and is 45 kJ / m 2 When the value was equal to or greater than this, the impact resistance of the molded article was determined to be particularly excellent.

[0083] [Table 1]

[0084] As can be seen from Table 1, the polyamide resin compositions of Examples 1 to 8, which contain, per 100 mass% of the polyamide resin composition, 52 to 88 mass% of an aliphatic polyamide resin (A), 5 to 25 mass% of a functional group-containing copolymerized polyolefin resin (B), 20 mass% or less of a non-functional group-containing olefin homopolymer (C), and 0.05 to 3.0 mass% in total of a primary antioxidant (D) and a secondary antioxidant (E), and in which the MFR of the functional group-containing copolymerized polyolefin resin (B) is greater than 1.0 g / 10 min and less than 5.0 g / 10 min, and the amount of the secondary antioxidant (E) is greater than the amount of the primary antioxidant (D), produce molded articles with a flexural modulus and flexural strength of 1,000 to 2,000 MPa and 50 to 80 MPa, respectively, a good balance between rigidity and flexibility, and good impact resistance, making them suitable for use as molded articles that come into contact with high-pressure gas. The polyamide resin compositions of the examples contain a primary antioxidant (D) and a secondary antioxidant (E) in combination, and therefore can prevent a decrease in mechanical strength due to oxidative degradation.

[0085] The polyamide resin compositions of Comparative Examples 1 to 4, in which a maleic anhydride-modified polypropylene resin having an MFR of 5.0 g / 10 min or more was blended instead of the functional group-containing copolymerized polyolefin resin (B), had molded articles with flexural moduli and flexural strengths exceeding 2,000 MPa and 80 MPa, respectively, which resulted in poor flexibility and a Charpy impact strength of 20 kJ / m 2 The polyamide resin composition of Comparative Example 5, which contained a functional group-containing copolymerized polyolefin resin having an MFR of 5.0 g / 10 min, had a flexural strength of more than 80 MPa, was poor in flexibility, and was unsuitable for use as a molded article in contact with high-pressure gas. [Industrial Applicability]

[0086] The polyamide resin composition of the present invention can be used to produce various molded articles by injection molding or the like, and is preferably used for molded articles that come into contact with high-pressure gas.

Claims

1. A polyamide resin composition comprising, per 100% by mass of the polyamide resin composition, 52 to 88% by mass of an aliphatic polyamide resin (A), 5 to 25% by mass of a functional group-containing copolymerized polyolefin resin (B), 20% by mass or less of a functional group-free olefin homopolymer (C), and 0.05 to 3.0% by mass in total of a primary antioxidant (D) and a secondary antioxidant (E), The functional group-containing copolymerized polyolefin resin (B) has an MFR of more than 1.0 g / 10 min and less than 5.0 g / 10 min, as measured in accordance with ASTM D1238 at a temperature of 230°C and a load of 2,160 g; the polyamide resin composition contains the secondary antioxidant (E) in a larger amount than the primary antioxidant (D); the functional group of the functional group-containing copolymerized polyolefin resin (B) is selected from the group consisting of a carboxyl group, an acid anhydride group, a carboxylic acid ester group, a carboxylic acid metal salt, a carboxylic acid imide group, a carboxylic acid amide group, and an epoxy group; A polyamide resin composition, wherein the primary antioxidant (D) is at least one selected from the group consisting of phenolic compounds and amine compounds, and the secondary antioxidant (E) is a phosphorus-based compound.

2. 2. The polyamide resin composition according to claim 1, wherein the functional group-containing copolymerized polyolefin resin (B) has an MFR of more than 1.0 g / 10 min to 3.0 g / 10 min or less, measured in accordance with ASTM D1238 at a temperature of 230°C and a load of 2,160 g.

3. 3. The polyamide resin composition according to claim 1, wherein the aliphatic polyamide resin (A) has a relative viscosity of 2.2 to 2.8, as measured at 25°C in a solution of 1 g of the polyamide resin in 100 ml of 96% sulfuric acid according to JIS K 6920.

4. The polyamide resin composition according to any one of claims 1 to 3, comprising 60 to 88% by mass of the aliphatic polyamide resin (A) per 100% by mass of the polyamide resin composition.

5. The polyamide resin composition according to any one of claims 1 to 4, comprising 6 to 22 mass% of a functional group-containing copolymerized polyolefin resin (B) based on 100 mass% of the polyamide resin composition.

6. The polyamide resin composition according to any one of claims 1 to 5, comprising 5 to 20 mass% of a non-functional group-containing olefin homopolymer (C) based on 100 mass% of the polyamide resin composition.

7. The polyamide resin composition according to any one of claims 1 to 6, wherein the content of the primary antioxidant (D) in 100% by mass of the polyamide resin composition is 0.02% by mass or more and less than 1.5% by mass.

8. The polyamide resin composition according to any one of claims 1 to 7, wherein the content of the secondary antioxidant (E) in 100% by mass of the polyamide resin composition is 0.03% by mass or more and 2.98% by mass or less.

9. The polyamide resin composition according to any one of claims 1 to 8, having a flexural modulus (23°C, 50% RH) of 1,000 to 2,000 MPa and a flexural strength (23°C, 50% RH) of 50 to 80 MPa, as measured in accordance with ISO 178.

10. Charpy impact strength (notched, 23°C 50% RH) obtained in accordance with ISO 179-1 / 1eA is 20 kJ / m ２ The polyamide resin composition according to any one of claims 1 to 9.

11. Charpy impact strength (notched, 23°C 50% RH) obtained in accordance with ISO 179-1 / 1eA is 45 kJ / m ２ The polyamide resin composition according to any one of claims 1 to 10.

12. The polyamide resin composition according to any one of claims 1 to 11, which is used for a molded article that comes into contact with high-pressure gas.

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