Polyamide resin composition for single-layer hollow molded body

Abstract

Provided is a polyamide resin composition for a single-layer hollow molded article, the polyamide resin composition having polyamide 6 as the main component without substantially using polyamide 11 and polyamide 12, the polyamide resin composition having characteristics equivalent to those of a multi-layer hollow molded article, the hollow molded article having excellent extrusion moldability, and the obtained molded article having excellent flexibility, impact resistance, and durability. A polyamide resin composition for extrusion molding for producing a single-layer hollow molded body, the polyamide resin composition comprising polyamide 6 (a), a polyolefin (b) having a functional group, and a plasticizer (c), the polyamide resin composition being characterized in that: 1 g of the polyamide 6 (a) is dissolved in 100 ml of 96% sulfuric acid in accordance with JIS K6920, and the relative viscosity of the polyamide 6 (a) measured at 25 DEG C is 3.0-4.5; the polyamide resin composition contains 60-90% by mass of the polyamide 6 (a), 3-25% by mass of the polyolefin (b) having a functional group, and 3-20% by mass of the plasticizer (c) per 100% by mass of the polyamide resin composition, and the polyolefin (b) having a functional group is a copolymer of ethylene and an alpha-olefin having 4 or more carbon atoms. The copolymer has a group derived from at least one acid anhydride selected from the group consisting of maleic anhydride and itaconic anhydride.

Description

Technical Field

[0001] The present invention relates to a polyamide resin composition for a single-layer hollow molded body and a single-layer hollow molded body. Background Art

[0002] In chemical solution and / or gas pipelines for automobile piping, such as transmission hydraulic pipelines for general industrial use and air pressure pipelines for automobile air brakes, the main raw materials are gradually replaced from metals to lightweight resins with excellent rust resistance from the perspective of light weight and operability (assembly). Generally, polyamide 11 or polyamide 12 with excellent strength, toughness, chemical resistance, flexibility, hollow moldability, etc. is used as the material for chemical solution and / or gas pipelines.

[0003] However, long-chain polyamides such as polyamide 11 and polyamide 12 have fewer manufacturers than short-chain polyamides such as polyamide 6, and the manufacturers of monomers used as raw materials are also limited, and the supply is unstable. Therefore, a composition that maintains the same performance as a composition containing polyamide 11 and / or polyamide 12 but reduces the amount of polyamide 11 and / or polyamide 12 is sought.

[0004] For example, Patent Document 1 discloses that a polyamide resin composition having flexibility and the like equivalent to those of polyamide 12 and good moldability can be obtained by using polyamide 6 / 12 instead of polyamide 12 and adding specific amounts of a plasticizer and a modified polyolefin thereto.

[0005] In addition, polyamide resin compositions are also known that use polyamide 6 or the like as the polyamide resin instead of polyamide 11 and polyamide 12. For example, Patent Document 2 discloses a polyamide resin composition that contains a polyamide resin such as polyamide 6, an impact reinforcing material, a nylon plasticizer, etc. at a predetermined ratio, and shows that the composition can be applied to a fuel pipe system of an automobile. In addition, in the examples, the physical properties and appearance of the injection molded product are evaluated.

[0006] Patent Document 3 discloses a laminated pipe composed of at least four layers, wherein the (b) layer comprises a polyamide 6 composition (B1) etc. Polyamide 6 is not suitable for producing a hollow molded body by extrusion molding compared to polyamide 12, and is usually not used in the form of a single layer, but is used for a multilayer hollow molded body in combination with a resin layer suitable for producing a hollow molded body by extrusion molding, as in Patent Document 3.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: International Publication No. 2013 / 058027

[0010] Patent Document 2: Japanese Patent Application Publication No. 2001-172498

[0011] Patent Document 3: International Publication No. 2016 / 039445 Summary of the invention

[0012] Problem that the invention aims to solve

[0013] In recent years, from the viewpoint of productivity and economic efficiency, there is a growing expectation for a polyamide resin composition for a single-layer hollow molded product in which the amount of polyamide 11 and polyamide 12 used is reduced or not used at all.

[0014] Although polyamide 6 / 12 of Patent Document 1 does not use polyamide 12, it seeks a polyamide having a high ratio of laurolactam or aminododecanoic acid in monomer form, and a lower or zero ratio of laurolactam or aminododecanoic acid. In the composition containing polyamide 6 of Patent Document 2, the molded products of the examples are molded by injection molding suitable for polyamide 6, and there are no examples of hollow molded products based on extrusion molding. It is not clear whether a single-layer hollow molded body can be molded by extrusion molding. Patent Document 3 only discloses that a layer of a layer containing a composition containing polyamide 6 is used in a laminated pipe composed of at least 4 layers, and there is no record of a single-layer hollow molded body.

[0015] The subject of the present application is to provide a polyamide resin composition for a single-layer hollow molded body which substantially does not use polyamide 11 and polyamide 12 but uses polyamide 6 as a main component, the composition has the same properties as a multilayer hollow molded body, the hollow molded body has excellent extrusion moldability, and the obtained molded body has excellent softness, impact resistance and durability.

[0016] Solutions for solving problems

[0017] The present inventors have conducted intensive studies to solve the above-mentioned problems and have found that a polyamide resin composition comprising a specified polyamide 6, a polyolefin having a functional group and a plasticizer has excellent extrusion moldability of a hollow molded body even when formed into a single layer, and the obtained molded body has excellent softness, impact resistance and durability, thereby completing the present invention.

[0018] The present invention relates to the following [1] to

[13] .

[0019] [1] A polyamide resin composition for extrusion molding for producing a single-layer hollow molded body, comprising polyamide 6 (a), a polyolefin having a functional group (b) and a plasticizer (c), wherein the relative viscosity of the polyamide 6 (a) measured at 25° C. is 3.0 to 4.5 when 1 g of the polyamide 6 (a) is dissolved in 100 ml of 96% sulfuric acid according to JIS K 6920, and the polyamide 6 (a) comprises 60 to 90% by mass of the polyamide 6 (a), 3 to 25% by mass of the polyolefin having a functional group (b) and 3 to 20% by mass of the plasticizer (c) in 100% by mass of the polyamide resin composition, wherein the polyolefin having a functional group (b) is a copolymer of ethylene and an α-olefin having 4 or more carbon atoms and has a group derived from at least one acid anhydride selected from the group consisting of maleic anhydride and itaconic anhydride.

[0020] [2] A polyamide resin composition for extrusion molding for producing a single-layer hollow molded body, comprising polyamide 6 (a), a polyolefin having a functional group (b) and a plasticizer (c), wherein 1 g of the polyamide 6 (a) is dissolved in 100 ml of 96% sulfuric acid according to JIS K 6920, and the relative viscosity of the polyamide 6 (a) measured at 25° C. is 3.0 to 4.5, and the polyamide resin composition comprises 66 to 89% by mass of the polyamide 6 (a), 3 to 25% by mass of the polyolefin having a functional group (b) and 3 to 20% by mass of the plasticizer (c) in 100% by mass of the polyamide resin composition, wherein the polyolefin having a functional group (b) is a copolymer of ethylene and an α-olefin having 3 or more carbon atoms, and has a group derived from at least one acid anhydride selected from the group consisting of maleic anhydride and itaconic anhydride.

[0021] [3] A polyamide resin composition for extrusion molding for producing a single-layer hollow molded body, comprising polyamide 6 (a), a polyolefin having a functional group (b) and a plasticizer (c), and substantially containing no ethylene vinyl acetate, wherein 1 g of the polyamide 6 (a) is dissolved in 100 ml of 96% sulfuric acid in accordance with JIS K 6920, and the relative viscosity of the polyamide 6 (a) measured at 25° C. is 3.0 to 4.5, and the polyamide resin composition comprises 60 to 90% by mass of the polyamide 6 (a), 3 to 25% by mass of the polyolefin having a functional group (b) and 3 to 20% by mass of the plasticizer (c) in 100% by mass of the polyamide resin composition, wherein the polyolefin having a functional group (b) is a copolymer of ethylene and an α-olefin having 3 or more carbon atoms, and has a group derived from at least one acid anhydride selected from the group consisting of maleic anhydride and itaconic anhydride.

[0022] [4] The polyamide resin composition according to any one of [1] to [3], wherein the polyolefin (b) having a functional group is an ethylene / 1-butene copolymer having a group derived from at least one anhydride selected from the group consisting of maleic anhydride and itaconic anhydride.

[0023] [5] The polyamide resin composition according to any one of [1] to [4], wherein the plasticizer (c) is at least one selected from the group consisting of benzenesulfonic acid alkylamides, toluenesulfonic acid alkylamides and hydroxybenzoic acid alkyl esters.

[0024] [6] The polyamide resin composition according to any one of [1] to [5], comprising a thermoplastic resin (d) other than the polyamide 6 (a) and the polyolefin having a functional group (b).

[0025] [7] The polyamide resin composition according to [6], wherein the thermoplastic resin (d) is an aliphatic copolymer polyamide resin.

[0026] [8] The polyamide resin composition according to [7], wherein the aliphatic copolymer polyamide resin is at least one selected from the group consisting of polyamide 6 / 12, polyamide 6 / 66 / 12, polyamide 6 / 11, polyamide 6 / 66 / 11, polyamide 6 / 610 / 12 and polyamide 6 / 612 / 12.

[0027] [9] The polyamide resin composition according to [7] or [8], wherein the polyamide resin composition contains 60.0 to 99.5% by mass of monomer units derived from caprolactam and aminocaproic acid in 100% by mass of the total of the polyamide 6(a) and the aliphatic copolymer polyamide resin.

[0028]

[10] The polyamide resin composition according to any one of [7] to [9], wherein the polyamide resin composition contains 0.25 to 20.0% by mass of monomer units derived from laurolactam, aminododecanoic acid, undecanoic acid and aminoundecanoic acid in 100% by mass of the total of the polyamide 6(a) and the aliphatic copolymerized polyamide resin.

[0029]

[11] The polyamide resin composition according to any one of [7] to

[10] , wherein the polyamide resin composition contains 0.25 to 20.0% by mass of monomer units derived from adipic acid and hexamethylenediamine in 100% by mass of the total of the polyamide 6(a) and the aliphatic copolymerized polyamide resin.

[0030]

[12] A single-layer hollow molded product comprising the polyamide resin composition according to any one of [1] to

[11] .

[0031]

[13] The single-layer hollow molded product according to

[12] , which is at least one selected from the group consisting of a pipe, a tube, a hose and a tank.

[0032] Effects of the Invention

[0033] According to the present invention, there is provided a polyamide resin composition for a single-layer hollow molded body which contains polyamide 6 as a main component without substantially using polyamide 11 and polyamide 12, and the composition has the same properties as a multilayer hollow molded body even if it is not made into a multilayer hollow molded body, the hollow molded body has excellent extrusion moldability, and the obtained molded body has excellent softness, impact resistance and durability. DETAILED DESCRIPTION

[0034] In this specification, the polyamide resin is referred to in accordance with JIS K 6920-1. In addition, regarding the content of each component, when a plurality of substances corresponding to each component are present in the composition, it means the total amount of the plurality of substances unless otherwise specified.

[0035] In this specification, "substantially not used" means not actively used as a raw material. The polyamide resin composition preferably does not substantially contain polyamide 11 and polyamide 12. Specifically, "substantially not used" and "substantially not containing" mean that the total content of polyamide 11 and polyamide 12 in 100% by mass of the polyamide resin composition is less than 0.1% by mass, preferably less than 0.05% by mass, and more preferably less than 0.01% by mass.

[0036] In this specification, “substantially containing no” with respect to ethylene vinyl acetate means that the content of ethylene vinyl acetate in 100 mass % of the polyamide resin composition is less than 0.1 mass %, preferably less than 0.05 mass %, and more preferably less than 0.01 mass %.

[0037] A first aspect of the present invention is a polyamide resin composition for extrusion molding for producing a single-layer hollow molded body, comprising polyamide 6 (a), a polyolefin having a functional group (b) and a plasticizer (c), wherein 1 g of the polyamide 6 (a) is dissolved in 100 ml of 96% sulfuric acid according to JIS K 6920, and the relative viscosity of the polyamide 6 (a) measured at 25° C. is 3.0 to 4.5, and the polyamide resin composition comprises 60 to 90% by mass of the polyamide 6 (a), 3 to 25% by mass of the polyolefin having a functional group (b) and 3 to 20% by mass of the plasticizer (c) in 100% by mass of the polyamide resin composition, wherein the polyolefin having a functional group (b) is a copolymer of ethylene and an α-olefin having 4 or more carbon atoms, and has a group derived from at least one acid anhydride selected from the group consisting of maleic anhydride and itaconic anhydride.

[0038] By setting the relative viscosity of polyamide 6 (a) to 3.0 to 4.5, setting its content to 60 to 90% by mass, and setting the component (b) to a copolymer of ethylene and an α-olefin having 4 or more carbon atoms, wherein the copolymer has a group derived from at least one acid anhydride selected from the group consisting of maleic anhydride and itaconic anhydride, it is possible to produce a polyamide resin composition that does not substantially use polyamide 11 and polyamide 12, has excellent extrusion moldability for hollow molded bodies even when a single layer is produced, and has excellent softness, impact resistance and durability of the obtained molded body.

[0039] A second aspect of the present invention is a polyamide resin composition for extrusion molding for producing a single-layer hollow molded body, comprising polyamide 6 (a), a polyolefin having a functional group (b) and a plasticizer (c), wherein 1 g of the polyamide 6 (a) is dissolved in 100 ml of 96% sulfuric acid according to JIS K 6920, and the relative viscosity of the polyamide 6 (a) measured at 25° C. is 3.0 to 4.5, and the polyamide resin composition comprises 66 to 89% by mass of the polyamide 6 (a), 3 to 25% by mass of the polyolefin having a functional group (b) and 3 to 20% by mass of the plasticizer (c) in 100% by mass of the polyamide resin composition, wherein the polyolefin having a functional group (b) is a copolymer of ethylene and an α-olefin having 3 or more carbon atoms, and has a group derived from at least one acid anhydride selected from the group consisting of maleic anhydride and itaconic anhydride.

[0040] By setting the relative viscosity of polyamide 6 (a) to 3.0 to 4.5, setting its content to 66 to 89% by mass, and setting the component (b) to a copolymer of ethylene and an α-olefin having 3 or more carbon atoms, wherein the copolymer has a group derived from at least one acid anhydride selected from the group consisting of maleic anhydride and itaconic anhydride, it is possible to produce a polyamide resin composition that does not substantially use polyamide 11 and polyamide 12, has excellent extrusion moldability for hollow molded bodies even when a single layer is produced, and has excellent softness, impact resistance and durability of the obtained molded body.

[0041] A third aspect of the present invention is a polyamide resin composition for extrusion molding for producing a single-layer hollow molded body, comprising polyamide 6 (a), a polyolefin having a functional group (b) and a plasticizer (c), and substantially containing no ethylene vinyl acetate, wherein 1 g of the polyamide 6 (a) is dissolved in 100 ml of 96% sulfuric acid according to JIS K 6920, and the relative viscosity of the polyamide 6 (a) measured at 25° C. is 3.0 to 4.5, and the polyamide resin composition comprises 60 to 90% by mass of the polyamide 6 (a), 3 to 25% by mass of the polyolefin having a functional group (b) and 3 to 20% by mass of the plasticizer (c) in 100% by mass of the polyamide resin composition, wherein the polyolefin having a functional group (b) is a copolymer of ethylene and an α-olefin having 3 or more carbon atoms, and has a group derived from at least one acid anhydride selected from the group consisting of maleic anhydride and itaconic anhydride.

[0042] By setting the relative viscosity of polyamide 6 (a) to 3.0 to 4.5, setting its content to 60 to 90% by mass, and setting component (b) to a copolymer of ethylene and an α-olefin having 3 or more carbon atoms, wherein the copolymer has a group derived from at least one anhydride selected from the group consisting of maleic anhydride and itaconic anhydride, a polyamide resin composition can be prepared which substantially does not use polyamide 11 and polyamide 12, and has excellent extrusion moldability of a hollow molded body even when prepared as a single layer, and has excellent softness, impact resistance and durability of the obtained molded body. In addition, even if the polyamide resin composition substantially does not contain ethylene-vinyl acetate, a hollow molded body having no fine protrusions and good appearance can be obtained, and by substantially not containing ethylene-vinyl acetate, a hollow molded body having good heat resistance can be obtained.

[0043] The present invention also relates to a single-layer hollow molded product including the polyamide resin composition of the first to third aspects. The single-layer hollow molded body comprising the polyamide resin composition of the first embodiment is specifically as follows: a single-layer hollow molded body comprising a polyamide resin composition, wherein the polyamide resin composition comprises polyamide 6 (a), a polyolefin having a functional group (b) and a plasticizer (c), wherein according to JIS K 6920, 1 g of the polyamide 6 (a) is dissolved in 100 ml of 96% sulfuric acid, and the relative viscosity of the polyamide 6 (a) measured at 25° C. is 3.0 to 4.5, and 100% by mass of the polyamide resin composition comprises 60 to 90% by mass of the polyamide 6 (a), 3 to 25% by mass of the polyolefin having a functional group (b) and 3 to 20% by mass of the plasticizer (c), wherein the polyolefin having a functional group (b) is a copolymer of ethylene and an α-olefin having 4 or more carbon atoms, and has a group derived from at least one acid anhydride selected from the group consisting of maleic anhydride and itaconic anhydride. The same applies to the single-layer hollow molded product including the polyamide resin composition of the second aspect and the third aspect.

[0044] The present invention also relates to a method for producing a single-layer hollow molded body, comprising the step of extruding the polyamide resin composition of the first to third aspects. The above-mentioned production method involved in the first embodiment of the polyamide resin composition is specifically as follows: a production method for a single-layer hollow molded body, which includes the step of extruding a polyamide resin composition, wherein the polyamide resin composition includes polyamide 6 (a), a polyolefin having a functional group (b) and a plasticizer (c), according to JIS K 6920, 1 g of the above-mentioned polyamide 6 (a) is dissolved in 100 ml of 96% sulfuric acid, and the relative viscosity of the polyamide 6 (a) measured at 25° C. is 3.0 to 4.5. In 100% by mass of the polyamide resin composition, 60 to 90% by mass of the above-mentioned polyamide 6 (a), 3 to 25% by mass of the above-mentioned polyolefin having a functional group (b) and 3 to 20% by mass of the above-mentioned plasticizer (c) are included, and the above-mentioned polyolefin having a functional group (b) is a copolymer of ethylene and an α-olefin having 4 or more carbon atoms, and has a group derived from at least one acid anhydride selected from the group consisting of maleic anhydride and itaconic anhydride. The same applies to the method for producing a single-layer hollow molded product according to the polyamide resin composition of the second aspect and the third aspect.

[0045] The present invention also relates to uses and methods of using the polyamide resin compositions of the first to third aspects for producing a single-layer hollow molded body by extrusion molding. The purpose and use method of the polyamide resin composition of the first embodiment are specifically as follows: the purpose and use method of the polyamide resin composition for producing a single-layer hollow molded body by extrusion molding, wherein the polyamide resin composition comprises polyamide 6 (a), a polyolefin having a functional group (b) and a plasticizer (c), wherein according to JIS K6920, 1 g of the above-mentioned polyamide 6 (a) is dissolved in 100 ml of 96% sulfuric acid, and the relative viscosity of the polyamide 6 (a) measured at 25° C. is 3.0 to 4.5, and in 100% by mass of the polyamide resin composition, 60 to 90% by mass of the above-mentioned polyamide 6 (a), 3 to 25% by mass of the above-mentioned polyolefin having a functional group (b) and 3 to 20% by mass of the above-mentioned plasticizer (c) are contained, and the above-mentioned polyolefin having a functional group (b) is a copolymer of ethylene and an α-olefin having 4 or more carbon atoms, and has a group derived from at least one acid anhydride selected from the group consisting of maleic anhydride and itaconic anhydride. The same applies to the uses and methods of use of the polyamide resin compositions of the second and third aspects.

[0046] [Polyamide 6(a)]

[0047] Polyamide 6(a) is a polyamide resin composed of structural units selected from the group consisting of ε-caprolactam and ε-aminocaproic acid. Polyamide 6(a) may be one kind or a combination of two or more kinds.

[0048] Regarding polyamide 6(a), according to JIS K 6920, 1 g of polyamide 6(a) is dissolved in 100 ml of 96% sulfuric acid, and the relative viscosity measured at 25°C is 3.0 to 4.5. By setting the relative viscosity to the above range, the extrusion moldability of the hollow molded body when made into a single layer can be improved, and the rigidity and durability of the obtained molded body can be improved. When the relative viscosity is less than 3.0, the fluidity is high and the extrusion moldability of the hollow molded body is poor. When it exceeds 4 or 5, the fluidity is low and the extrusion moldability of the hollow molded body is poor. In any case, stable molding cannot be achieved, and even if a hollow molded body can be obtained, the size is unstable and the quality is poor. The relative viscosity of polyamide 6(a) is 3.0 to 4.5, preferably 3.2 to 4.4, and particularly preferably 3.4 to 4.2.

[0049] When polyamide 6(a) contains two or more polyamide resins having different relative viscosities, the relative viscosity of polyamide 6(a) is preferably measured by the above-mentioned method. When the relative viscosities of the various polyamide resin components and their mixing ratios are known, the average value calculated by summing up the values ​​obtained by multiplying the respective relative viscosities by their mixing ratios can be set as the relative viscosity of polyamide 6(a).

[0050] Polyamide 6 (a) is produced by polymerizing or copolymerizing the above-mentioned polyamide raw materials using known methods such as melt polymerization, solution polymerization, and solid phase polymerization. During polymerization, a catalyst such as amines can be used. In addition, after polymerization, the resulting resin can be melt-mixed. The catalyst can be added at any stage during polymerization, or at any stage after polymerization and during melt mixing, preferably at the stage during polymerization.

[0051] The content of polyamide 6 (a) in 100% by mass of the polyamide resin composition is 60 to 90% by mass, preferably 60 to 88% by mass, more preferably 65 to 85% by mass, further preferably 66 to 84% by mass, and particularly preferably 67 to 84% by mass. By setting the content of polyamide 6 (a) to the above range, even when a single layer is formed, the extrusion moldability of the hollow molded body is excellent, and the rigidity, impact resistance and heat resistance of the obtained molded body can be improved. When the content of polyamide 6 (a) is less than 60% by mass, the rigidity, impact resistance and heat resistance are poor, and when it exceeds 90% by mass, the extrusion moldability of the hollow molded body is poor.

[0052] In the first and third embodiments, the content of polyamide 6(a) in 100% by mass of the polyamide resin composition is 60 to 90% by mass, preferably 60 to 88% by mass, more preferably 65 to 85% by mass, further preferably 66 to 84% by mass, and particularly preferably 67 to 84% by mass. In addition, the content of polyamide 6(a) in 100% by mass of the polyamide resin composition may also be 66 to 89% by mass.

[0053] In the second embodiment, the content of polyamide 6(a) in 100% by mass of the polyamide resin composition is 66 to 89% by mass, preferably 66 to 86% by mass, more preferably 66 to 84% by mass, and particularly preferably 67 to 84% by mass.

[0054] [Polyolefin having functional group (b)]

[0055] The polyamide resin composition contains a polyolefin (b) having a functional group. The polyolefin (b) having a functional group is a component that imparts softness and impact resistance to the obtained molded product. It can be inferred that the polyolefin (b) contains a functional group having affinity for polyamide 6 (a) in its molecule, and therefore has reactivity and bonding properties (such as hydrogen bonding) between the amino group of polyamide 6 and the functional group of the polyolefin, and the impact resistance of the polyamide resin composition when it is made into a molded product is improved. The polyolefin (b) having a functional group can be one or a combination of two or more.

[0056] As the functional group of the polyolefin (b) having a functional group, carboxyl group, carboxylic acid anhydride group, carboxylic acid ester group, carboxylic acid metal salt, carboxylic acid imide group, carboxylic acid amide group, epoxy group, etc. can be listed. It can be considered that the amino group of polyamide 6 (a) reacts with at least a part of these functional groups. Among them, from the viewpoint of improving impact resistance, it is preferably at least one selected from the group consisting of carboxyl group, carboxylic acid ester group and carboxylic acid anhydride group, and more preferably a carboxylic acid anhydride group.

[0057] Examples of methods for introducing these functional groups into polyolefins include: (i) a method of copolymerizing a copolymerizable monomer having a functional group during polymerization of the polyolefin; (ii) a method of introducing a functional group into a molecular chain or molecular terminal of the polyolefin using a polymerization initiator, a chain transfer agent, etc.; (iii) a method of grafting a compound having the aforementioned functional group and a functional group capable of grafting (grafting compound) onto the polyolefin, etc. These introduction methods may be used alone or in appropriate combination.

[0058] Examples of the copolymerizable monomers having functional groups, the graft compounds, and the like 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, methyl 2-ethylhexyl acrylate, hydroxyethyl methacrylate, aminoethyl methacrylate, dimethyl maleate, dimethyl itaconate, maleic anhydride, itaconic anhydride, citraconic anhydride, endo-bicyclo-[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, glycidyl citraconic acid, etc. These can be used alone or in combination of two or more. Among these, maleic anhydride, itaconic anhydride or citraconic anhydride is preferred, maleic anhydride or itaconic anhydride is further preferred, and maleic anhydride is particularly preferred.

[0059] From the viewpoint of improving the effect of low-temperature impact resistance and the fluidity of the polyamide resin composition, the content of the functional group in the polyolefin (b) having a functional group is preferably 25 mmol / kg or more and less than 200 mmol / kg, more preferably 35 mmol / kg or more and less than 150 mmol / kg, and particularly preferably 40 mmol / kg or more and less than 120 mmol / kg, in terms of the molar number (mmol) of the functional group / mass (kg) of (b). The content of the functional group in the polyolefin (b) having a functional group is measured by neutralization titration based on a 0.1 mol / L KOH ethanol solution, for example, in the case of having a carboxyl group, anhydride group or carboxylate group, using a sample solution prepared using toluene and ethanol and using phenolphthalein as an indicator.

[0060] From the viewpoint of the effect of improving flexibility, the polyolefin in the polyolefin (b) having a functional group is preferably an (ethylene and / or propylene) / α-olefin copolymer. Specifically, as the polyolefin (b) having a functional group, there can be cited (ethylene and / or propylene) / α-olefin copolymers having the aforementioned functional groups, and (ethylene and / or propylene) / (α,β-unsaturated carboxylic acid and / or α,β-unsaturated carboxylic acid ester) copolymers having or not having the aforementioned functional groups, and one or more of these can be used.

[0061] The aforementioned (ethylene and / or propylene) / α-olefin copolymer may be 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. From the viewpoint of the flexibility and impact resistance of the obtained molded article, the upper limit of the carbon number of the α-olefin is preferably 20, more preferably 10. Examples of the α-olefin 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. One or more of these can be used. Among these, from the viewpoint of the flexibility, impact resistance and durability of the obtained molded body, preferred are ethylene / α-olefin copolymers having 3 or more carbon atoms, more preferred are ethylene / propylene copolymers or ethylene / 1-butene copolymers, and particularly preferred are ethylene / 1-butene copolymers.

[0062] The (ethylene and / or propylene) / α-olefin copolymer can be copolymerized with 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, Polyenes of non-conjugated dienes such as (DMDT), dicyclopentadiene, cyclohexadiene, cyclooctadiene, 5-vinyl norbornene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, 5-isopropylidene-2-norbornene, 6-chloromethyl-5-isopropenyl-2-norbornene, 2,3-diisopropylidene-5-norbornene, 2-ethylidene-3-isopropylidene-5-norbornene, and 2-propenyl-2,5-norbornadiene. One or more of these can be used.

[0063] In the aforementioned ethylene / α-olefin copolymer having 3 or more carbon atoms, the proportion of the α-olefin monomer having 3 or more carbon atoms in the total 100 mol% of the ethylene monomer and the α-olefin monomer having 3 or more carbon atoms constituting the copolymer is preferably greater than 5 mol% and less than 90 mol%, more preferably 7 to 87 mol%, and further preferably 10 to 85 mol%.

[0064] 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 α,β-unsaturated carboxylic acid and / or α,β-unsaturated carboxylic acid ester monomers. 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, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, pentyl acrylate, pentyl methacrylate, hexyl acrylate, hexyl methacrylate, heptyl acrylate, heptyl methacrylate, octyl acrylate, octyl methacrylate, nonyl acrylate, nonyl methacrylate, decyl acrylate, decyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, monomethyl maleate, monomethyl itaconate, dimethyl maleate, dimethyl itaconate, and the like. These can be used alone or in combination of two or more.

[0065] From the viewpoint of the effect of improving impact resistance, the polyolefin (b) having a functional group is more preferably a copolymer of ethylene and an α-olefin having 3 or more carbon atoms, which has a group derived from at least one acid anhydride selected from the group consisting of maleic anhydride and itaconic anhydride, further preferably an ethylene / propylene copolymer or an ethylene / 1-butene copolymer having a group derived from maleic anhydride, and particularly preferably an ethylene / 1-butene copolymer having a group derived from maleic anhydride.

[0066] In the first embodiment, the polyolefin (b) having a functional group is a copolymer of ethylene and an α-olefin having 4 or more carbon atoms, which has a group derived from at least one anhydride selected from the group consisting of maleic anhydride and itaconic anhydride, preferably a copolymer of ethylene and an α-olefin having 4 to 20 carbon atoms, which has a group derived from at least one anhydride selected from the group consisting of maleic anhydride and itaconic anhydride, more preferably an ethylene / 1-butene copolymer, which has a group derived from at least one anhydride selected from the group consisting of maleic anhydride and itaconic anhydride, and particularly preferably an ethylene / 1-butene copolymer having a group derived from maleic anhydride.

[0067] In the second and third embodiments, the polyolefin (b) having a functional group is a copolymer of ethylene and an α-olefin having 3 or more carbon atoms, which has a group derived from at least one acid anhydride selected from the group consisting of maleic anhydride and itaconic anhydride, preferably a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms, which has a group derived from at least one acid anhydride selected from the group consisting of maleic anhydride and itaconic anhydride, and more preferably a copolymer of ethylene and an α-olefin having 4 to 20 carbon atoms, which has a group derived from at least one acid anhydride selected from the group consisting of maleic anhydride and itaconic anhydride. In addition, the polyolefin (b) having a functional group may be an ethylene / propylene copolymer or an ethylene / 1-butene copolymer, which has a group derived from at least one acid anhydride selected from the group consisting of maleic anhydride and itaconic anhydride. In this case, an ethylene / propylene copolymer or an ethylene / 1-butene copolymer having a group derived from maleic anhydride is more preferred, and an ethylene / 1-butene copolymer having a group derived from maleic anhydride is particularly preferred.

[0068] The polyolefin (b) having a functional group may contain a polyolefin having no functional group within a range not impairing the functions and characteristics of the polyamide resin composition.

[0069] The content of the polyolefin (b) having a functional group in 100% by mass of the polyamide resin composition is preferably 3 to 25% by mass, more preferably 7 to 23% by mass, further preferably 10 to 20% by mass, and particularly preferably 10 to 15% by mass. By setting the content of the polyolefin (b) having a functional group to the above range, the extrusion moldability of the hollow molded body and the impact resistance of the obtained molded body can be improved.

[0070] [Plasticizer (c)]

[0071] The polyamide resin composition contains a plasticizer (c). By containing the plasticizer (c), flexibility can be imparted to the obtained molded product.

[0072] From the viewpoint of flexibility, the plasticizer (c) is preferably at least one selected from the group consisting of benzenesulfonic acid alkylamides, toluenesulfonic acid alkylamides and hydroxybenzoic acid alkyl esters.

[0073] Examples of the benzenesulfonic acid alkylamides include benzenesulfonic acid propylamide, benzenesulfonic acid butylamide, benzenesulfonic acid 2-ethylhexylamide, etc. Examples of the toluenesulfonic acid alkylamides include N-ethyl-o-toluenesulfonic acid butylamide, N-ethyl-p-toluenesulfonic acid butylamide, N-ethyl-o-toluenesulfonic acid 2-ethylhexylamide, N-ethyl-p-toluenesulfonic acid 2-ethylhexylamide, etc. Examples of the alkyl hydroxybenzoates include ethylhexyl o-hydroxybenzoate, ethylhexyl p-hydroxybenzoate, hexyldecyl o-hydroxybenzoate, hexyldecyl p-hydroxybenzoate, ethyldecyl o-hydroxybenzoate, ethyldecyl p-hydroxybenzoate, octyloctyl o-hydroxybenzoate, octyloctyl p-hydroxybenzoate, decyldodecyl o-hydroxybenzoate, decyldodecyl p-hydroxybenzoate, methyl o-hydroxybenzoate, methyl p-hydroxybenzoate, butyl o-hydroxybenzoate, butyl p-hydroxybenzoate, hexyl o-hydroxybenzoate, hexyl p-hydroxybenzoate, n-octyl o-hydroxybenzoate, n-octyl p-hydroxybenzoate, decyl o-hydroxybenzoate, decyl p-hydroxybenzoate, dodecyl o-hydroxybenzoate, and dodecyl p-hydroxybenzoate. One or more of these may be used.

[0074] Among these, preferred are benzenesulfonic acid alkylamides such as benzenesulfonic acid butylamide and benzenesulfonic acid 2-ethylhexylamide; toluenesulfonic acid alkylamides such as N-ethyl-p-toluenesulfonic acid butylamide and N-ethyl-p-toluenesulfonic acid 2-ethylhexylamide; and hydroxybenzoic acid alkyl esters such as ethylhexyl p-hydroxybenzoate, hexyldecyl p-hydroxybenzoate and ethyldecyl p-hydroxybenzoate, and more preferred are benzenesulfonic acid butylamide, ethylhexyl p-hydroxybenzoate and hexyldecyl p-hydroxybenzoate.

[0075] The content of the plasticizer (c) in 100% by mass of the polyamide resin composition is preferably 3 to 20% by mass, more preferably 7 to 14% by mass, and particularly preferably 8 to 13% by mass. By setting the content of the plasticizer (c) to the above range, the extrusion moldability of the hollow molded body and the flexibility of the obtained molded body can be improved.

[0076] [Thermoplastic resin (d)]

[0077] From the viewpoint of extrusion moldability of hollow molded bodies and flexibility of molded bodies, the polyamide resin composition preferably further comprises a thermoplastic resin (d) in addition to polyamide 6 (a) and the polyolefin (b) having a functional group. The content of the thermoplastic resin (d) in 100% by mass of the polyamide resin composition is preferably 20% by mass or less, more preferably 5 to 15% by mass, and further preferably 7 to 13% by mass.

[0078] When the polyamide resin composition contains the thermoplastic resin (d), the total content of the polyamide 6 (a), the polyolefin having a functional group (b) and the plasticizer (c) in 100% by mass of the polyamide resin composition is preferably 80 to 98% by mass, more preferably 85 to 95% by mass, and even more preferably 87 to 93% by mass.

[0079] In this case, the content of polyamide 6 (a) in 100% by mass of the polyamide resin composition is preferably 60 to 85% by mass, more preferably 60 to 80% by mass, and further preferably 60 to 75% by mass. The content of the polyolefin (b) having a functional group in 100% by mass of the polyamide resin composition is preferably 3 to 25% by mass, more preferably 7 to 23% by mass, and further preferably 10 to 15% by mass. The content of the plasticizer (c) in 100% by mass of the polyamide resin composition is preferably 3 to 20% by mass, more preferably 7 to 14% by mass, and further preferably 8 to 13% by mass.

[0080] Examples of the thermoplastic resin (d) include high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), ultra-high molecular weight polyethylene (UHMWPE), polypropylene (PP), polybutene (PB), polymethylpentene (TPX) and other polyolefin resins; polystyrene resins such as polystyrene (PS), syndiotactic polystyrene (SPS), methyl methacrylate / styrene copolymer (MS), methyl methacrylate / styrene / butadiene copolymer (MBS); polybutylene terephthalate (PBT), polybutylene terephthalate (PTTE), polybutylene terephthalate (PBT ... Polyester resins such as polyethylene glycol ester (PET), polyethylene isophthalate (PEI), poly(ethylene terephthalate / ethylene isophthalate) copolymer (PET / PEI), polytrimethylene terephthalate (PTT), polycyclohexanedimethanol terephthalate (PCT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), polyarylate (PAR), liquid crystal polyester (LCP), polylactic acid (PLA), polyglycolic acid (PGA); polyether resins such as polyacetal (POM) and polyphenylene ether (PPO); polysulfone (PSU), polyethersulfone (PESU), polyphenylene polysulfone resins such as polyphenylene sulfide (PPSU); polysulfide resins such as polyphenylene sulfide (PPS) and polysulfide ether sulfone (PTES); polyketone resins such as polyketone (PK), polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetheretheretherketone (PEEEK), polyetheretherketoneketone (PEEKK), polyetherketoneketoneketone (PEKKK), polyetherketoneetherketoneketone (PEKEKK); polyacrylonitrile (PAN), polymethacrylonitrile, acrylonitrile / styrene copolymer (AS), methacrylonitrile / styrene copolymer, acrylonitrile / butadiene / styrene copolymer (ABS), acrylonitrile / butadiene copolymer (N Polynitrile resins such as polymethyl methacrylate (PMMA) and polyethyl methacrylate (PEMA); polyvinyl alcohol (PVA), polyvinylidene chloride (PVDC), polyvinyl chloride (PVC), vinyl chloride / vinylidene chloride copolymer, vinylidene chloride / methyl acrylate copolymer and other polyvinyl resins; cellulose resins such as cellulose acetate and cellulose butyrate; polycarbonate resins such as polycarbonate (PC); polyimide resins such as thermoplastic polyimide (TPI), polyetherimide, polyesterimide, polyamideimide (PAI), polyesteramideimide; thermoplastic polyurethane resins;Polyamide elastomer, polyurethane elastomer, polyester elastomer, polyamide resin other than polyamide 6, etc., according to the situation, can be listed polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), polytetrafluoroethylene (PTFE), polychlorofluoroethylene (PCTFE), tetrafluoroethylene / ethylene copolymer (ETFE), ethylene / chlorotrifluoroethylene copolymer (ECTFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), tetrafluoroethylene / hexafluoropropylene / vinylidene fluoride copolymer (THV), tetrafluoroethylene / hexafluoropropylene / vinylidene fluoride / perfluoro (alkyl vinyl ether) copolymer, tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer (PFA), tetrafluoroethylene / hexafluoropropylene / perfluoro (alkyl vinyl ether) copolymer, chlorotrifluoroethylene / perfluoro (alkyl vinyl ether) / tetrafluoroethylene copolymer (CPT) and other fluorine resins. They can be used alone or in combination. It should be noted that, from the viewpoint of heat resistance, the thermoplastic resin (d) preferably does not contain ethylene-vinyl acetate. ;

[0081] The thermoplastic resin (d) is preferably a polyamide resin other than polyamide 6 from the viewpoint of compatibility with polyamide 6 (a) and flexibility of a molded product.

[0082] Examples of the polyamide resin other than polyamide 6 include homopolyamide resins and copolymer polyamide resins other than polyamide 6. Among them, from the viewpoint of fluidity and extrusion moldability of a hollow molded body, preferred are aliphatic homopolyamide resins and aliphatic copolymer polyamide resins other than polyamide 6, and more preferred are aliphatic copolymer polyamide resins. These may be used alone or in combination of two or more.

[0083] (Aliphatic homopolyamide resin)

[0084] The aliphatic homopolyamide resin is a polyamide resin formed of one structural unit derived from an aliphatic monomer. The aliphatic homopolyamide resin may be formed of at least one of a lactam and an aminocarboxylic acid, which is a hydrolyzate of the lactam, or may be formed of a combination of a diamine and a dicarboxylic acid. Here, regarding the combination of a diamine and a dicarboxylic acid, the combination of a diamine and a dicarboxylic acid is regarded as one monomer unit.

[0085] Examples of lactams include enantholactam, α-pyrrolidone, α-piperidone, ω-octyl lactam, ω-nonanolactam, ω-decanolactam, etc. Examples of aminocarboxylic acids include 7-aminoheptanoic acid, 9-aminononanoic acid, and 10-aminodecanoic acid.

[0086] Examples of the diamine include aliphatic diamines such as 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; and 1,3 Alicyclic diamines such as - / 1,4-cyclohexyldiamine, bis(4-aminocyclohexyl)methane, bis(4-aminocyclohexyl)propane, bis(3-methyl-4-aminocyclohexyl)methane, (3-methyl-4-aminocyclohexyl)propane, 1,3- / 1,4-bisaminomethylcyclohexane, 5-amino-2,2,4-trimethyl-1-cyclopentanemethylamine, 5-amino-1,3,3-trimethylcyclohexanemethylamine, bis(aminopropyl)piperazine, bis(aminoethyl)piperazine, and norbornane dimethylenediamine.

[0087] Examples of the dicarboxylic acid include aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, octadecanedioic acid, and eicosanedioic acid; and alicyclic dicarboxylic acids such as 1,3- / 1,4-cyclohexanedicarboxylic acid, dicyclohexanemethane-4,4′-dicarboxylic acid, and norbornanedicarboxylic acid.

[0088] Specific examples of the aliphatic homopolyamide resin include polyamide 4, polyamide 7, polyamide 9, polyamide 10, polyamide 44, polyamide 45, polyamide 46, polyamide 48, polyamide 49, polyamide 54, polyamide 55, polyamide 56, polyamide 66, polyamide 410, polyamide 412, polyamide 58, polyamide 59, polyamide 510, polyamide 512, polyamide 64, polyamide 65, polyamide 68, Polyamide 69, polyamide 610, polyamide 612, polyamide 96, polyamide 98, polyamide 99, polyamide 105, polyamide 616, polyamide 618, polyamide 910, polyamide 912, polyamide 106, polyamide 108, polyamide 109, polyamide 1010, polyamide 1012, polyamide 125, polyamide 126, polyamide 129, polyamide 1210, polyamide 1212, polyamide 122, etc. These aliphatic homopolyamide resins can be used alone or in the form of a mixture of two or more. Among these, polyamide 66 is preferred from the viewpoints of ease of acquisition, economy, impact resistance, rigidity, durability and heat resistance of the obtained molded body.

[0089] (Aliphatic copolymer polyamide resin)

[0090] The aliphatic copolymer polyamide resin is a polyamide resin formed of two or more structural units derived from an aliphatic monomer. The structural unit of the aliphatic copolymer polyamide resin is derived from a monomer selected from the group consisting of a combination of a diamine and a dicarboxylic acid, a lactam, and an aminocarboxylic acid. Here, regarding the combination of a diamine and a dicarboxylic acid, a combination of one diamine and one dicarboxylic acid is regarded as one monomer unit.

[0091] Examples of the diamine include the same diamines as those exemplified as the raw materials of the aliphatic homopolyamide resin.

[0092] Examples of the dicarboxylic acid include the same dicarboxylic acids as those exemplified as the raw materials of the aliphatic homopolyamide resin.

[0093] Examples of the lactam include the same lactams as those exemplified as the raw materials of the aliphatic homopolyamide resin, and further, ε-caprolactam, ω-undecalactam, and lauryl lactam (ω-laurolactam) can be used.

[0094] Examples of the aminocarboxylic acid include the same aminocarboxylic acids as those exemplified as the raw materials of the aliphatic homopolyamide resin, and further, ε-aminocaproic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid can be used.

[0095] These diamines, dicarboxylic acids, lactams, and aminocarboxylic acids may be used alone or in combination of two or more.

[0096] As the aliphatic copolymer polyamide resin, specifically, there can be mentioned copolymers obtained by combining two or more monomers forming the polyamides exemplified as the aliphatic homopolyamide resin, more specifically, there can be mentioned polyamide 4 / 6, polyamide 6 / 66, polyamide 6 / 69, polyamide 6 / 610, polyamide 6 / 611, polyamide 6 / 612, polyamide 6 / 10, polyamide 6 / 11, polyamide 6 / 12, polyamide 6 / 66 / 12, polyamide 6 / 66 / 11, polyamide 6 / 66 / 610, polyamide 6 / 66 / 612, polyamide 6 / 610 / 12, polyamide 6 / 612 / 12, etc. These aliphatic copolymer polyamide resins can be used alone or in the form of a mixture of two or more.

[0097] Among them, from the viewpoint of extrusion moldability of the hollow molded body and the flexibility of the obtained molded body, the aliphatic copolymer polyamide resin is preferably at least one selected from the group consisting of polyamide 6 / 12, polyamide 6 / 66 / 12, polyamide 6 / 11, polyamide 6 / 66 / 11, polyamide 6 / 610 / 12 and polyamide 6 / 612 / 12, more preferably at least one selected from the group consisting of polyamide 6 / 12 and polyamide 6 / 66 / 12, and particularly preferably polyamide 6 / 66 / 12.

[0098] When the thermoplastic resin (d) is a polyamide resin other than polyamide 6, from the viewpoint of ensuring the rigidity and durability of the obtained molded body and setting the viscosity when melted in an appropriate range to ensure the desired extrusion moldability of the molded body, the relative viscosity of the polyamide resin measured at 25° C. by dissolving 1 g of the resin in 100 ml of 96% sulfuric acid in accordance with JIS K 6920 is preferably 2.5 to 5.0, more preferably 3.0 to 4.5.

[0099] The polyamide resins other than polyamide 6 are manufactured by polymerizing or copolymerizing the aforementioned polyamide raw materials using known methods such as melt polymerization, solution polymerization, and solid phase polymerization. During polymerization, catalysts such as amines can be used. In addition, after polymerization, the obtained resin can be melt-mixed. The catalyst can be added at any stage during polymerization or at any stage after polymerization or during melt mixing, preferably at the stage during polymerization.

[0100] [Other ingredients]

[0101] The polyamide resin composition may further contain a conductive filler.

[0102] Conductivity means that when a flammable fluid such as gasoline continuously contacts an insulator such as resin, there is a possibility of static electricity accumulation and ignition, but the electrical property does not accumulate. This can prevent explosions caused by static electricity generated when transporting fluids such as fuel.

[0103] The conductive filler includes all fillers added to impart conductive properties to the resin, and examples thereof include granular, flaky, and fibrous fillers.

[0104] As granular fillers, carbon black, graphite, etc. can be listed. As flaky fillers, aluminum flakes, nickel flakes, mica coated with nickel, etc. can be listed. In addition, as fibrous fillers, carbon fibers, ceramic fibers covered with carbon, carbon whiskers, carbon nanotubes, aluminum fibers, copper fibers, brass fibers, stainless steel fibers, etc. can be listed. These can be used in one or more kinds. Among these, carbon nanotubes and carbon black are preferred.

[0105] Carbon nanotubes are called hollow carbon fibrils, which are essentially cylindrical fibrils with an outer region and an inner hollow region, wherein the outer region is formed by a plurality of essentially continuous layers of regularly arranged carbon atoms, and each layer is substantially concentrically arranged with the hollow region around the cylindrical axis of the fibril. Furthermore, the regularly arranged carbon atoms in the aforementioned outer region are graphite-like, and the diameter of the aforementioned hollow region is preferably more than 2nm and less than 20nm. From the viewpoint of imparting sufficient dispersibility in the resin and good conductivity of the resulting resin molding, the outer diameter of the carbon nanotube is preferably more than 3.5nm and less than 70nm, more preferably more than 4nm and less than 60nm. The aspect ratio (ratio of length / outer diameter) of the carbon nanotube is preferably more than 5, more preferably more than 100, and further preferably more than 500. By satisfying this aspect ratio, a conductive network is easily formed, and excellent conductivity can be exhibited by adding a small amount.

[0106] Carbon black includes all carbon blacks that are usually used to impart conductivity. Preferred carbon blacks include acetylene black obtained by incomplete combustion of acetylene gas, furnace blacks such as Ketjen black produced by incomplete furnace combustion using crude oil as a raw material, petroleum carbon black, naphthalene black, thermal black, lamp black, channel black, roller black, disk black, etc., but are not limited to them. One or more of them can be used. Among these, acetylene black and furnace black are more preferred.

[0107] In addition, carbon black is made from various carbon powders having different characteristics such as particle size, surface area, DBP oil absorption, ash content, etc. The characteristics of the carbon black are not limited, but it is preferred to have a good chain structure and a large aggregation density. From the viewpoint of impact resistance, it is not preferred to mix a large amount of carbon black. From the viewpoint of obtaining excellent conductivity with a smaller amount, the average particle size is preferably 500nm or less, more preferably 5nm or more and 100nm or less, and further preferably 10nm or more and 70nm or less. The surface area (BET method) is preferably 10m 2 / g or more, more preferably 30m 2 / g or more, more preferably 50m 2 / g or more. In addition, the DBP (dibutyl phthalate) oil absorption is preferably 50 ml / 100 g or more, more preferably 100 ml / 100 g, and further preferably 150 ml / 100 g or more. In addition, the ash content is preferably 0.5 mass % or less, more preferably 0.3 mass % or less. The DBP oil absorption mentioned here is a value measured by the method specified in ASTM D-2414. In addition, the volatile component content of carbon black is preferably less than 1 mass %.

[0108] These conductive fillers may be surface treated with a titanate-based, aluminum-based, silane-based, etc. surface treating agent. Furthermore, granulated ones may be used to improve melt kneading workability.

[0109] The content of the conductive filler varies depending on the type of conductive filler used and cannot be generally determined, but is usually preferably 3 parts by mass or more and 30 parts by mass or less based on 100 parts by mass of the polyamide resin composition from the viewpoint of balance with conductivity, fluidity, mechanical strength, etc.

[0110] In the case of containing a conductive filler, the surface resistivity of the melt extrudate is preferably 10 8 Ω / square or less, more preferably 10 6 Ω / square or less. However, the addition of the conductive filler mentioned above easily leads to deterioration of strength and fluidity. Therefore, if the target conductivity level can be obtained, it is desirable that the content of the conductive filler mentioned above is as small as possible.

[0111] Furthermore, the polyamide resin composition may include antioxidants such as phenolic and phosphorus, heat stabilizers, ultraviolet absorbers, light stabilizers, adhesives for additives, lubricants, inorganic fillers, antistatic agents, flame retardants, crystallization accelerators, colorants, etc. as needed. They can be used one or more than two kinds respectively. It should be noted that the polyamide resin composition preferably does not contain a thickener for polyamide resin.

[0112] <Polyamide resin composition>

[0113] From the viewpoint of the extrusion moldability of the hollow molded body and the rigidity and durability of the obtained molded body, the MFR (temperature 235°C and load 2.16 kg) of the polyamide resin composition measured by the method based on ISO 1133 is preferably 0.1 g / 10 min or more and 20 g / 10 min or less, more preferably 0.15 g / 10 min or more and 15 g / 10 min or less, further preferably 0.18 g / 10 min or more and 10 g / 10 min or less, and particularly preferably 0.5 g / 10 min or more and 10 g / 10 min or less.

[0114] (Content of monomer units of polyamide resin)

[0115] From the viewpoint of economic efficiency and the rigidity, durability and impact resistance of the obtained molded product, when the thermoplastic resin (d) is an aliphatic copolymer polyamide resin, the content of the monomer units derived from caprolactam and aminocaproic acid (hereinafter also referred to as monomer units X) in the total of 100 mass % of the polyamide 6 (a) and the aliphatic copolymer polyamide resin is preferably 60.0 to 99.5 mass %, more preferably 70.0 to 99.3 mass %, further preferably 80.0 to 99.0 mass %, and particularly preferably 96.0 to 98.0 mass %.

[0116] From the viewpoint of extrusion moldability of the hollow molded body, when the thermoplastic resin (d) is an aliphatic copolymer polyamide resin, the content of the monomer units derived from laurolactam, aminododecanoic acid, undecanoic acid and aminoundecanoic acid (hereinafter also referred to as monomer units Z) in the total of 100 mass % of the polyamide 6 (a) and the aliphatic copolymer polyamide resin is preferably 0.25 to 20.0 mass %, more preferably 0.35 to 15.0 mass %, further preferably 0.50 to 10.0 mass %, and particularly preferably 1.0 to 3.5 mass %.

[0117] From the viewpoint of the rigidity, durability, impact resistance and heat resistance of the obtained molded product, when the thermoplastic resin (d) is an aliphatic copolymer polyamide resin, the content of the monomer units derived from adipic acid and hexamethylenediamine (hereinafter also referred to as monomer units Y) in the total of 100 mass % of the polyamide 6 (a) and the aliphatic copolymer polyamide resin is preferably 0.25 to 20.0 mass %, more preferably 0.35 to 15.0 mass %, further preferably 0.50 to 10.0 mass %, and particularly preferably 1.0 to 3.5 mass %.

[0118] Among them, from the viewpoint of extrusion moldability of the hollow molded body and the rigidity, durability, impact resistance and heat resistance of the obtained molded body, when the thermoplastic resin (d) is an aliphatic copolymer polyamide resin, the ratio (mass ratio) of the content of the monomer units X to Z in the total 100 mass % of the polyamide 6 (a) and the aliphatic copolymer polyamide resin is preferably 60.0 to 99.5:0.25 to 20.0:0.25 to 20.0, more preferably 70.0 to 99.3:0.35 to 17.5:0.35 to 17.5, further preferably 80.0 to 99.0:0.50 to 15.0:0.50 to 15.0, and particularly preferably 93.0 to 98.0:1.00 to 3.50:1.00 to 3.50.

[0119] [Method for producing polyamide resin composition]

[0120] The method for producing the polyamide resin composition is not particularly limited, and for example, the following method can be applied.

[0121] Methods for mixing polyamide 6 (a), polyolefin having a functional group (b) and plasticizer (c), and optional thermoplastic resin (d) and other components include: using a drum and / or a stirrer, uniformly dry-mixing polyamide 6 (a), polyolefin having a functional group (b) and optional components with liquid components such as plasticizer (c) in the above-mentioned mixing ratio; preliminarily dry-mixing polyamide 6 (a), polyolefin having a functional group (b), plasticizer (c) and optional components at a concentration used in molding, and melt-kneading; after blending a part of the components, melt-kneading, further blending the remaining components and melt-kneading; or, after blending a part of the components, using a side feeder to mix the remaining components during melt-kneading, etc. As pellets, a masterbatch obtained by mixing the components with thermoplastic resin (d) can also be used. Melt-kneading can be carried out using a mixer such as a single-screw extruder, a twin-screw extruder, a kneader, and a Banbury mixer.

[0122] [Application of polyamide resin composition]

[0123] The polyamide resin composition is excellent in extrusion moldability of a hollow molded article even when it is made into a single layer, and the obtained molded article is excellent in flexibility, impact resistance and durability. Therefore, it can be suitably used for single-layer hollow molded articles.

[0124] [Method for producing single-layer hollow molded product]

[0125] The single-layer hollow molded body can be produced by extrusion-molding the polyamide resin composition into a pipe shape, a hose shape, or other various shapes using an extruder or the like.

[0126] There is no particular limitation on the method for producing a single-layer hollow molded body from a polyamide resin composition by extrusion molding, and a known method can be used. Generally speaking, extrusion molding can be performed by extruding a molten resin using a conventional extrusion molding machine and then passing the molten resin into a mold. The preferred resin temperature during extrusion molding is preferably within a temperature range of 10°C to 70°C higher than the melting point of the polyamide resin composition.

[0127] [Single-layer hollow molded body]

[0128] The single-layer hollow molded body may be coated or applied on the outer surface or the inner surface of the hollow molded body within a range not hindering the purpose of the present invention.

[0129] As the single-layer hollow molded body, tanks, pipes, round tubes, hoses, conduits, housings, etc. can be cited. Among them, at least one selected from the group consisting of round tubes, pipes, hoses and tanks is preferred. The hollow molded body does not substantially use polyamide 11 and polyamide 12, has the same properties as the multilayer hollow molded body obtained by using them, has excellent barrier properties and tensile strength for chemical solutions and gases, and is a single layer, so it is excellent in economy and production stability.

[0130] [Application of single-layer hollow molded body]

[0131] The uses of the single-layer hollow molded body include spoilers, intake pipes, resonators, fuel tanks, gas tanks, working oil tanks, fuel filling pipes, fuel transport round pipes, and other various hoses / pipes / tanks and other automotive parts; mechanical parts such as power tool housings and round pipes, such as tanks, pipes, and hoses, electrical / electronic parts; household / office supplies, building material-related parts, and furniture parts.

[0132] Example

[0133] Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

[0134] In addition, the analysis and property measurement methods in Examples and Comparative Examples, and the raw materials used in Examples and Comparative Examples are shown below.

[0135] The physical properties of the polyamide resin composition and raw materials were measured by the following methods.

[0136] [Relative viscosity]

[0137] The relative viscosity of the polyamide resin was measured at 25° C. by a method in accordance with JIS K 6920 using a solution prepared by dissolving 1 g of the resin in 100 ml of 96% sulfuric acid.

[0138] [Flowability (MFR)]

[0139] As an index of the fluidity of the polyamide resin composition, MFR (temperature 235° C. and load 2.16 kg) was measured by a method based on ISO 1133. When MFR was 0.1 to 20 g / 10 minutes, the fluidity was judged to be good.

[0140] [Preparation of test pieces]

[0141] For the polyamide resin composition, a test piece was prepared using an injection molding machine SE100D-C160S manufactured by Sumitomo Heavy Industries, Ltd. in accordance with ISO 294-1.

[0142] [Flexibility (flexural modulus)]

[0143] The obtained test piece was used to measure the flexural modulus by a method based on ISO 178. If the flexural modulus was 1,800 MPa or less, the flexibility was judged to be good, and if it was 1,500 MPa or less, it was judged to be particularly excellent.

[0144] [Impact resistance (Charpy impact strength)]

[0145] The obtained test piece was used to measure the Charpy impact strength by the method based on ISO 179 / 1eA. If the Charpy impact strength is 40 kJ / m 2 If the impact resistance is above 50 kJ / m 2 If the value is above 0.05, the impact resistance is judged to be particularly excellent.

[0146] [Durability against tensile load (tensile elongation at break)]

[0147] The obtained test piece was used to measure the tensile elongation at break by the method based on ISO 527-1, 2. If the tensile elongation at break was 150% or more, it was judged that the durability was sufficient, and if it was 170% or more, it was judged that the durability was particularly excellent.

[0148] The hollow molded body was produced by the following method, and its physical properties were measured.

[0149] [Production of Hollow Molded Product]

[0150] The polyamide resin composition was formed into a tubular body (also referred to as a pipe) using a PAL32 single-layer pipe extruder (manufactured by Mylfair Co., Ltd.) at an extrusion temperature of 220°C to 260°C, with an outer diameter of 8 mm and a thickness of 1 mm as target values.

[0151] [Pipe forming stability]

[0152] The molding stability of the pipe by extraction from the extruder was evaluated according to the following criteria.

[0153] ○: Continuous molding is possible without chattering, and stable molding is possible.

[0154] △: Continuous molding is possible, but vibration occurs and the pipe size is unstable.

[0155] ×: Continuous molding was not possible and chattering also occurred.

[0156] [Moldability (resin pressure)]

[0157] The resin pressure of the extrusion molding machine during the extrusion molding of the pipe is measured. For the measurement, a pressure gauge is installed on the extrusion molding machine and its value is read. If the pressure is low, the burden on the device can be reduced, and stable continuous molding can be achieved. If the resin pressure is 150 bar or less, the moldability is judged to be good, and if it is 115 bar or less, the moldability is judged to be particularly excellent.

[0158] [Durability of pipe shape to tensile load (tensile elongation at break)]

[0159] The obtained pipe was cut into 200 mm long to obtain a test piece. The test piece obtained in this way was used to measure the tensile elongation at break by a method based on SAE J2260. If the tensile elongation at break is 100% or more, it is judged to have sufficient durability, and if it is 150% or more, it is judged to have particularly excellent durability.

[0160] [Appearance of the pipeline]

[0161] The appearance of the obtained pipe was evaluated according to the following criteria.

[0162] ○: There is no disorder in size and surface, and the appearance is good.

[0163] △: There is no dimensional disorder or fluctuation, but chattering scratches occur and the appearance is partially poor.

[0164] ×: Dimensional disturbance or fluctuation occurs, and the appearance is poor.

[0165] [Presence or absence of fine protrusions]

[0166] The presence or absence of fine protrusions in the obtained pipe was visually determined and evaluated according to the following criteria.

[0167] ○: There are no fine protrusions that can be identified with the naked eye.

[0168] ×: Fine protrusions that can be seen with the naked eye are generated.

[0169] [Materials used in Examples and Comparative Examples]

[0170] Polyamide 6 (a): manufactured by UBE, relative viscosity 4.08

[0171] Polyolefin having a functional group (b): Tafmer (registered trademark) MH5020 (manufactured by Mitsui Chemicals, Inc., maleic anhydride-modified ethylene / 1-butene copolymer, anhydride concentration: 100 mmol / kg)

[0172] Plasticizer (c): Proviplast (registered trademark) 024 (manufactured by Proviron, benzenesulfonic acid butylamide)

[0173] Thermoplastic resin (d-1): Polyamide 6 / 66 / 12 (manufactured by UBE, relative viscosity: 3.85) having a mass ratio (X:Y:Z) of monomer units X derived from caprolactam and aminocaproic acid, monomer units Y derived from adipic acid and hexamethylenediamine, and monomer units Z derived from laurolactam and aminododecanoic acid of X:Y:Z=78:11:11

[0174] Thermoplastic resin (d-2): Polyamide 6 / 12 (manufactured by UBE, relative viscosity: 4.08) having a mass ratio (X:Z) of 80:20 of monomer units X derived from caprolactam and aminocaproic acid and monomer units Z derived from laurolactam and aminododecanoic acid.

[0175] Antioxidant: a 9:1 mixture of triethylene glycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate] (manufactured by BASF Japan, IRGANOX (registered trademark) 245) and tris(2,4-di-tert-butylphenyl) phosphite (manufactured by BASF Japan, IRGAFOS (registered trademark) 168)

[0176] Example 1

[0177] Production of polyamide resin composition (A-1)

[0178] A polyolefin (b) having a functional group and an antioxidant were pre-mixed with polyamide 6 (a) and supplied to a twin-screw melt kneader (manufactured by Coperion, model: ZSK). On the other hand, a plasticizer (c) was injected from a metering pump from the middle of the barrel of the twin-screw melt kneader, and melt kneading was performed under the condition of a barrel temperature of 230° C. to 250° C., and the molten resin was extruded into a strand shape. The obtained extrudate was directly introduced into a water tank, cooled, cut, and vacuum dried to obtain pellets of a polyamide resin composition (A-1) composed of polyamide 6 (a) / polyolefin (b) having a functional group / plasticizer (c) / antioxidant = 77.0 / 12.0 / 10.0 / 1.0 (mass ratio).

[0179] Examples 3 to 7 and Comparative Examples 1 to 2

[0180] Pellets of polyamide resin compositions (A-3) to (A-7), (A-9) and (A-10) were obtained in the same manner as in Example 1 except that the blending amounts of the components were changed as described in Table 1.

[0181] Example 2

[0182] Production of polyamide resin composition (A-2)

[0183] A polyolefin (b) having a functional group, a thermoplastic resin (d-1) and an antioxidant were pre-mixed with polyamide 6 (a) and supplied to a twin-screw melt kneader (manufactured by Coperion, model: ZSK). On the other hand, a plasticizer (c) was injected from a metering pump from the middle of the barrel of the twin-screw melt kneader, and melt kneading was performed under the condition of a barrel temperature of 230° C. to 250° C., and the molten resin was extruded into a strand shape. The obtained extrudate was directly introduced into a water tank, cooled, cut and vacuum dried to obtain pellets of a polyamide resin composition (A-2) consisting of polyamide 6 (a) / polyolefin (b) having a functional group / plasticizer (c) / thermoplastic resin (d-1) / antioxidant = 67.0 / 12.0 / 10.0 / 10.0 / 1.0 (mass ratio).

[0184] In the polyamide resin composition (A-2), in the total 100 mass % of the polyamide 6 (a) and the thermoplastic resin (d-1), the monomer unit X derived from caprolactam and aminocaproic acid is 97.14 mass %, the monomer unit Y derived from adipic acid and hexamethylenediamine is 1.43 mass %, and the monomer unit Z derived from laurolactam and aminododecanoic acid is 1.43 mass %.

[0185] Example 8

[0186] Production of polyamide resin composition (A-8)

[0187] In the production of the polyamide resin composition (A-2), except that the thermoplastic resin (d-1) was changed to the thermoplastic resin (d-2), pellets of a polyamide resin composition (A-8) consisting of polyamide 6 (a) / polyolefin having a functional group (b) / plasticizer (c) / thermoplastic resin (d-2) / antioxidant = 67.0 / 12.0 / 10.0 / 10.0 / 1.0 (mass ratio) were obtained by the same method.

[0188] In the polyamide resin composition (A-8), in 100 mass % of the total of polyamide 6 (a) and the thermoplastic resin (d-2), the monomer unit X derived from caprolactam and aminocaproic acid is 97.40 mass %, and the monomer unit Z derived from laurolactam and aminododecanoic acid is 2.60 mass %.

[0189] Comparative Example 3

[0190] Production of polyamide resin composition (A-11)

[0191] In the production of the polyamide resin composition (A-2), except that no plasticizer (c) was used and the amount of polyamide 6 (a) was changed, pellets of a polyamide resin composition (A-11) consisting of polyamide 6 (a) / polyolefin having a functional group (b) / thermoplastic resin (d-1) / antioxidant = 77.0 / 12.0 / 10.0 / 1.0 (mass ratio) were obtained by the same method.

[0192] In the polyamide resin composition (A-11), in the total 100 mass % of the polyamide 6 (a) and the thermoplastic resin (d-1), the monomer unit X derived from caprolactam and aminocaproic acid is 97.48 mass %, the monomer unit Y derived from adipic acid and hexamethylenediamine is 1.26 mass %, and the monomer unit Z derived from laurolactam and aminododecanoic acid is 1.26 mass %.

[0193] Table 1 shows the formulations of Examples 1 to 8 and Comparative Examples 1 to 3, as well as the evaluation results of these pellets and molded products obtained from the pellets. It should be noted that in Comparative Example 1, the pipe could not be molded due to poor molding stability of the pipe, and therefore, the tensile elongation at break, appearance, and presence of fine protrusions of the pipe could not be evaluated.

[0194] [Table 1]

[0195]

[0196] According to Table 1, when the compositions of Examples 1 to 8 are made into a single-layer hollow molded body by extrusion molding, the resin pressure is low, the pipe molding stability and appearance are excellent, and the molded products are excellent in softness, impact resistance and durability. The composition comprises polyamide 6 (a) with a relative viscosity of 3.0 to 4.5, a polyolefin (b) having a functional group and a plasticizer (c), and in 100% by mass of the polyamide resin composition, 60 to 90% by mass of the aforementioned polyamide 6 (a), 3 to 25% by mass of the aforementioned polyolefin (b) having a functional group and 3 to 20% by mass of the aforementioned plasticizer (c) are included. In particular, the composition of Example 2 has extremely high tensile elongation at break when made into a single-layer hollow molded body and excellent durability. The composition of Example 2 contains components (a) to (c) and further contains polyamide 6 / 66 / 12 as a thermoplastic resin (d) (in the total of 100 mass % of polyamide 6 (a) and the thermoplastic resin (d), the monomer unit X derived from caprolactam and aminocaproic acid is 97.14 mass %, the monomer unit Y derived from adipic acid and hexamethylenediamine is 1.43 mass %, and the monomer unit Z derived from laurolactam and aminododecanoic acid is 1.43 mass %).

[0197] The composition of Comparative Example 1, which uses polyamide 6 (a) but does not contain polyolefin (b) having a functional group and plasticizer (c), has a high resin pressure during pipe molding, poor pipe molding stability, and poor softness and impact resistance of the molded product. The composition of Comparative Example 2, which contains polyamide 6 (a) and plasticizer (c) but does not contain polyolefin (b) having a functional group, has poor pipe molding stability, poor pipe appearance, and poor softness, impact resistance, and durability of the molded product. The composition of Comparative Example 3, which mixes thermoplastic resin (d-1) instead of plasticizer (c), has poor composition fluidity and poor softness and durability of the molded product.

[0198] Industrial Applicability

[0199] The polyamide resin composition of the present invention can be suitably used for producing a single-layer hollow molded product.

Claims

1. A polyamide resin composition, which is an extrusion-molding polyamide resin composition for producing a single-layer hollow molded body, comprising polyamide 6 (a), a polyolefin having a functional group (b) and a plasticizer (c), According to JIS K 6920, 1 g of the polyamide 6(a) was dissolved in 100 ml of 96% sulfuric acid, and the relative viscosity of the polyamide 6(a) measured at 25° C. was 3.0 to 4.

5. In 100% by mass of the polyamide resin composition, 60 to 90% by mass of the polyamide 6 (a), 3 to 25% by mass of the polyolefin having a functional group (b) and 3 to 20% by mass of the plasticizer (c) are contained. The polyolefin (b) having a functional group is a copolymer of ethylene and an α-olefin having 4 or more carbon atoms, and has a group derived from at least one acid anhydride selected from the group consisting of maleic anhydride and itaconic anhydride.

2. A polyamide resin composition, which is a polyamide resin composition for extrusion molding for producing a single-layer hollow molded body, comprising polyamide 6 (a), a polyolefin having a functional group (b) and a plasticizer (c), According to JIS K 6920, 1 g of the polyamide 6(a) was dissolved in 100 ml of 96% sulfuric acid, and the relative viscosity of the polyamide 6(a) measured at 25° C. was 3.0 to 4.

5. In 100% by mass of the polyamide resin composition, 66 to 89% by mass of the polyamide 6 (a), 3 to 25% by mass of the polyolefin having a functional group (b) and 3 to 20% by mass of the plasticizer (c) are contained. The polyolefin (b) having a functional group is a copolymer of ethylene and an α-olefin having 3 or more carbon atoms, and has a group derived from at least one acid anhydride selected from the group consisting of maleic anhydride and itaconic anhydride.

3. A polyamide resin composition for extrusion molding for producing a single-layer hollow molded body, comprising polyamide 6 (a), a polyolefin having a functional group (b) and a plasticizer (c), and substantially containing no ethylene vinyl acetate. According to JIS K 6920, 1 g of the polyamide 6(a) was dissolved in 100 ml of 96% sulfuric acid, and the relative viscosity of the polyamide 6(a) measured at 25° C. was 3.0 to 4.

5. In 100% by mass of the polyamide resin composition, 60 to 90% by mass of the polyamide 6 (a), 3 to 25% by mass of the polyolefin having a functional group (b) and 3 to 20% by mass of the plasticizer (c) are contained. The polyolefin (b) having a functional group is a copolymer of ethylene and an α-olefin having 3 or more carbon atoms, and has a group derived from at least one acid anhydride selected from the group consisting of maleic anhydride and itaconic anhydride.

4. The polyamide resin composition according to any one of claims 1 to 3, wherein The polyolefin (b) having a functional group is an ethylene / 1-butene copolymer having a group derived from at least one acid anhydride selected from the group consisting of maleic anhydride and itaconic anhydride.

5. The polyamide resin composition according to any one of claims 1 to 3, wherein The plasticizer (c) is at least one selected from the group consisting of benzenesulfonic acid alkylamides, toluenesulfonic acid alkylamides and hydroxybenzoic acid alkyl esters. 6 . The polyamide resin composition according to claim 1 , comprising a thermoplastic resin (d) other than the polyamide 6 (a) and the polyolefin having a functional group (b).

7. The polyamide resin composition according to claim 6, wherein The thermoplastic resin (d) is an aliphatic copolymerized polyamide resin.

8. The polyamide resin composition according to claim 7, wherein The aliphatic copolymer polyamide resin is at least one selected from the group consisting of polyamide 6 / 12, polyamide 6 / 66 / 12, polyamide 6 / 11, polyamide 6 / 66 / 11, polyamide 6 / 610 / 12, and polyamide 6 / 612 / 12.

9. The polyamide resin composition according to claim 7, wherein The monomer units derived from caprolactam and aminocaproic acid are contained in an amount of 60.0 to 99.5% by mass in 100% by mass of the total of the polyamide 6(a) and the aliphatic copolymer polyamide resin.

10. The polyamide resin composition according to claim 7, wherein The monomer units derived from laurolactam, aminododecanoic acid, undecanoic acid and aminoundecanoic acid are contained in an amount of 0.25 to 20.0% by mass in the total of 100% by mass of the polyamide 6(a) and the aliphatic copolymerized polyamide resin.

11. The polyamide resin composition according to claim 7, wherein The monomer units derived from adipic acid and hexamethylenediamine are contained in an amount of 0.25 to 20.0% by mass in 100% by mass of the total of the polyamide 6(a) and the aliphatic copolymerized polyamide resin. 12 . A single-layer hollow molded body comprising the polyamide resin composition according to claim 1 . 13 . The single-layer hollow molded body according to claim 12 , which is at least one selected from the group consisting of a round tube, a pipe, a hose, and a tank.

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