Polyamide resin composition

Abstract

This polyamide resin composition for a single-layer hollow molding contains an aliphatic polyamide resin (A) and a polyolefin (B) that has a functional group. The polyamide resin composition contains 60-80% by mass of the aliphatic polyamide resin (A) and 20-40% by mass of the polyolefin (B) in 100% by mass of the polyamide resin composition. The average value of the ratio [CH2] / [NHCO] of the number of methylene groups ([CH2]) to the number of amide groups ([NHCO]) in the aliphatic polyamide resin (A) is 3.0-8.0. The functional group in the polyolefin (B) is substantially free of metal atoms. The polyamide resin composition is substantially free of a plasticizer (C), or the amount of an eluted component when the polyamide resin composition is dried and then extracted with methanol is 3% by mass or less based on 100% by mass of the entire resin composition. The melt viscosity as measured at a cylinder temperature of 300°C, an orifice diameter of L / D=10, and a shear rate of 121.6 sec-1 is 600 Pa s or more. Provided are: a resin composition using a short-chain polyamide, the resin composition having excellent hollow moldability, excellent mechanical strength, and high solvent resistance, even when the amount of a component such as a plasticizer is reduced or preferably without using a plasticizer; and a single-layer hollow molding using the resin composition.

Description

Polyamide resin composition

[0001] The present invention relates to a polyamide resin composition useful for hollow molded articles. In particular, it relates to a polyamide resin composition useful for single-layer hollow molded articles used for temperature control.

[0002] Due to issues such as rust caused by metal oxidation, and the demand for lighter weight and energy conservation, the main materials used in piping tubes are increasingly being replaced from metal to lightweight resins with superior corrosion resistance. Typical resins used for piping tubes include polyamide resins, saturated polyester resins, polyolefin resins, and thermoplastic polyurethane resins. Among these, polyamide resins are expected to yield tubes with excellent gas barrier properties, toughness, pinhole resistance, heat resistance, oil resistance, and alcohol resistance.

[0003] Automobiles are one field where the use of resin in tubing is required. Due to the demand for weight reduction in automobiles, there is a strong demand to replace metal components with resin. Tubing for automotive piping, such as coolant tubing for transporting coolant in the engine, is required to have many properties in addition to being light, such as durability against chemicals, temperature, and impact, and moldability as tubing. With resins such as polyamide, compositions that meet the required properties have been designed by rearranging monomer units, and in some cases by blending with other polymers or by using multilayering with different materials (Patent Documents 1 and 2).

[0004] Polyamides used for tubes include polyamide 11 (PA11) and polyamide 12 (PA12) due to their high hollow moldability (Patent Document 3). It is also known that short-chain polyamides such as polyamide 6 (PA6) or copolymers containing PA6 are used (Patent Document 4). In techniques for using short-chain polyamides in tube molding, moldability is improved by mixing PA6 with a plasticizer and / or a resin such as polyolefin (Patent Documents 5-7).

[0005] International Publication No. 2015 / 033982, JP 2008-507436, International Publication No. 2024 / 219100, International Publication No. 2013 / 058027, International Publication No. 2023 / 218686, JP 2023-169601, JP 2017-206639

[0006] Polyamide resins are extremely useful as molding resins due to their flexibility in molecular structure design and the inherent properties of the polyamide itself. However, using short-chain polyamides such as PA6 requires further technical improvements compared to conventional polyamides. First, since a different resin is used than PA12, improvements in mechanical properties such as elasticity against bending and tension, and strength are required. Short-chain polyamides such as PA6 generally have high rigidity, so when using short-chain polyamides in hollow molded bodies, it is necessary to use plasticizers in combination, as disclosed in Patent Document 5, in order to obtain good moldability. However, the use of plasticizers can reduce the mechanical properties of the tube, and when using a chemical solution mainly composed of glycol to control the temperature inside a car, degradation may occur as resin components such as plasticizers leach into the chemical solution. On the other hand, removing plasticizers from the resin components may impair the moldability of the tube, and adopting a multilayer structure to prevent plasticizers from coming into contact with the chemical solution can lead to other problems related to durability, such as interlayer adhesion, and also increase costs.

[0007] For these reasons, there is a strong demand for using short-chain polyamides in tubes for temperature control applications such as chemical transport, but it was necessary to overcome the above-mentioned problems and further improve the resin properties. From this perspective, the present invention aims to provide a resin composition using short-chain polyamides that exhibits excellent hollow moldability, excellent mechanical strength, and high solvent resistance even when the amount of components such as plasticizers is reduced, or preferably without the use of plasticizers, and a single-layer hollow molded article using the resin composition.

[0008] The present invention relates to resin compositions or various molded articles using the same as described in the following items: [1] A polyamide resin composition for a single-layer hollow molded article comprising an aliphatic polyamide resin (A) and a polyolefin having functional groups (B), wherein 100% by mass of the polyamide resin composition contains 60 to 80% by mass of the aliphatic polyamide resin (A) and 20 to 40% by mass of the polyolefin (B), the average ratio [CH2] / [NHCO] of the number of methylene groups ([CH2]) in the aliphatic polyamide resin (A) to the number of amide groups ([NHCO]) is 3.0 to 8.0, the functional groups of the polyolefin (B) substantially do not contain metal atoms, and substantially do not contain a plasticizer (C), cylinder temperature 300°C, orifice diameter L / D = 10, shear rate 121.6 sec －１ A polyamide resin composition for a single-layer hollow molded body, wherein the melt viscosity measured is 600 Pa·s or more. [2] Cylinder temperature 300°C, orifice diameter L / D = 10, shear rate 121.6 sec －１[1] The polyamide resin composition, wherein the melt viscosity measured by [1] is 1000 Pa·s or more. [3] The polyamide resin composition, wherein the average value of the ratio [CH2] / [NHCO] of the number of methylene groups ([CH2]) to the number of amide groups ([NHCO]) in the aliphatic polyamide resin (A) is 4.3 to 6.5. [4] The polyamide resin composition, wherein the aliphatic polyamide resin (A) is at least one selected from the group consisting of aliphatic homopolyamide resins and aliphatic copolymer polyamide resins. [5] The polyamide resin composition, wherein the aliphatic polyamide resin (A) comprises PA56, PA6, PA66, PA6 / 66, PA510 or PA610. [6] The polyamide resin composition, wherein the number average molecular weight of the aliphatic polyamide resin (A) is 10,000 to 50,000. [7] The polyamide resin composition according to any one of [1] to [6], wherein the amount of amino groups per 1 g of aliphatic polyamide resin (A) is 10 μmol / g or more and 120 μmol / g or less. [8] The polyamide resin composition according to any one of [1] to [7], wherein the polyolefin (B) is at least one selected from the group consisting of copolymers having a (ethylene and / or propylene) / α-olefin copolymer as the main backbone and at least a portion thereof having functional groups that react with the terminal groups of the aliphatic polyamide resin, and (ethylene and / or propylene) / (α,β-unsaturated carboxylic acid and / or α,β-unsaturated carboxylic acid ester) copolymers. [9] The polyamide resin composition according to any one of [1] to [8], wherein the functional group of the polyolefin (B) is at least one selected from the group consisting of carboxyl groups, acid anhydride groups, carboxylic acid ester groups, carboxylic acid imide groups, carboxylic acid amide groups, and epoxy groups.

[10] Cylinder temperature 300°C, orifice diameter L / D = 10, shear rate 121.6 sec －１A polyamide resin composition according to any one of [1] to [9], wherein the melt viscosity measured is 1000 Pa·s or more and 2700 Pa·s or less.

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

[10] , wherein the tensile fracture nominal strain when a test specimen prepared according to ISO 294-1 is measured according to ISO 527-1 and ISO 527-2 / 1A / 50 is greater than 100%.

[12] A polyamide resin composition according to any one of [1] to

[11] , wherein the flexural modulus when a test specimen prepared according to ISO 294-1 is measured according to ISO 178 is 1600 MPa or less.

[13] A polyamide resin composition for a single-layer hollow molded article comprising an aliphatic polyamide resin (A) and a polyolefin having functional groups (B), wherein 100% by mass of the polyamide resin composition contains 60 to 80% by mass of the aliphatic polyamide resin (A) and 20 to 40% by mass of the polyolefin (B), the average ratio [CH2] / [NHCO] of the number of methylene groups ([CH2]) in the aliphatic polyamide resin (A) to the number of amide groups ([NHCO]) is 3.0 to 8.0, the functional groups of the polyolefin (B) substantially do not contain metal atoms, the amount of eluted components when the polyamide resin composition is extracted with methanol after drying is 3% by mass or less when the entire resin composition is considered as 100% by mass, and the cylinder temperature is 300°C, orifice diameter L / D = 10, shear rate 121.6 sec －１ A polyamide resin composition for a single-layer hollow molded article, wherein the melt viscosity measured by [1] is 600 Pa·s or more.

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

[13] .

[15] The single-layer hollow molded article according to

[14] , which is at least one selected from the group consisting of pipes, tubes and hoses.

[16] The single-layer hollow molded article according to

[15] , used for temperature control.

[17] The polyamide resin composition according to

[13] , which further satisfies at least one of the following conditions (17-1) to (17-11): (17-1) Cylinder temperature 300°C, orifice diameter L / D = 10, shear rate 121.6 sec －１(17-2) The melt viscosity measured is 1000 Pa·s or more. (17-3) The average ratio [CH2] / [NHCO] of the number of methylene groups ([CH2]) to the number of amide groups ([NHCO]) in the aliphatic polyamide resin (A) is 4.3 to 6.5. (17-4) The aliphatic polyamide resin (A) is at least one selected from the group consisting of aliphatic homopolyamide resins and aliphatic copolymer polyamide resins. (17-5) The aliphatic polyamide resin (A) contains PA56, PA6, PA66, PA6 / 66, PA510 or PA610. (17-6) The number average molecular weight of the aliphatic polyamide resin (A) is 10,000 to 50,000. (17-6) The amount of amino groups per gram of aliphatic polyamide resin (A) is 10 μmol / g or more and 120 μmol / g or less. (17-7) Polyolefin (B) is at least one selected from the group consisting of copolymers having an (ethylene and / or propylene) / α-olefin copolymer as the main backbone and having functional groups having reactivity with terminal groups of an aliphatic polyamide resin, and (ethylene and / or propylene) / (α,β-unsaturated carboxylic acid and / or α,β-unsaturated carboxylic acid ester) copolymers. (17-8) The functional group of polyolefin (B) is at least one selected from the group consisting of carboxyl groups, acid anhydride groups, carboxylic acid ester groups, carboxylic acid imide groups, carboxylic acid amide groups, and epoxy groups. (17-9) Cylinder temperature 300°C, orifice diameter L / D = 10, shear rate 121.6 sec －１ (17-10) The melt viscosity measured is 1000 Pa·s or more and 2700 Pa·s or less. The tensile fracture nominal strain when a test specimen prepared according to ISO 294-1 is measured according to ISO 527-1 and ISO 527-2 / 1A / 50 is greater than 100%. (17-11) The flexural modulus when a test specimen prepared according to ISO 294-1 is measured according to ISO 178 is 1600 MPa or less.

[0009] The present invention provides a resin composition using a short-chain polyamide that exhibits excellent hollow moldability, excellent mechanical strength, and high solvent resistance even when the amount of components such as plasticizers is reduced, as well as a single-layer hollow molded article using the resin composition.

[0010] The polyamide resin composition for a single-layer hollow molded article according to the present invention will be described in detail below for each of its constituent components. In this specification, the content of each component in the composition means the total amount of multiple substances present in the composition, unless otherwise specified, if there are multiple substances corresponding to each component in the composition. In this specification, the "~" indicating a numerical range means that the values ​​written before and after it are included as the lower and upper limits. For example, "50.00 to 90.00 mass%" means "50.00 mass% or more and 90.00 mass% or less".

[0011] <Aliphatic Polyamide Resin (A)> Aliphatic polyamide resin is a polymer having amide bonds (-NHCO-) ​​in a main chain containing aliphatic hydrocarbon groups. Aliphatic polyamide resin is obtained by polymerization or copolymerization using lactam, aminocarboxylic acid, or aliphatic diamine and aliphatic dicarboxylic acid, which are structural units of aliphatic polyamide, as raw materials, by known methods such as melt polymerization, solution polymerization, or solid-phase polymerization. Here, in this specification, "aliphatic polyamide resin" means a polyamide resin substantially composed of monomer units derived from linear or branched hydrocarbon compounds. This does not exclude the inclusion of monomer units derived from cyclic compounds such as alicyclic structures or aromatic hydrocarbons in the polyamide resin, but in the aliphatic polyamide resin of the present invention, the content of such monomer units is 20 mol% or less of the total monomer units. The aliphatic polyamide resin of the present invention is a polyamide resin in which the portion derived from linear or branched hydrocarbon compounds of the total monomer units is 80 mol% or more, and it is preferable that the polyamide resin is composed of monomer units derived from linear or branched hydrocarbon compounds.

[0012] (Average value of the ratio [CH2] / [NHCO] of the number of methylene groups ([CH2]) to the number of amide groups ([NHCO])) The aliphatic polyamide resin used in the present invention contains short-chain polyamides, and its chain length can be expressed by the average value of the ratio [CH2] / [NHCO] of the number of methylene groups ([CH2]) to the number of amide groups ([NHCO]). Here, the average value of the ratio [CH2] / [NHCO] is the average value of the ratio [CH2] / [NHCO] in the aliphatic polyamide resin, and if multiple aliphatic polyamide resins are included, the content ratio is also taken into consideration in the calculation. For example, if the aliphatic polyamide resin contains only PA6 / 12, and the content ratio (mass ratio) of the aliphatic monomer with 6 carbon atoms and the aliphatic monomer with 12 carbon atoms is 1:1, the number of methylene groups is 5 and 11, respectively, so the average value of the ratio [CH2] / [NHCO] in the aliphatic polyamide resin is calculated to be 8. Furthermore, if an aliphatic polyamide resin contains 50% by mass each of PA6 and PA10, the average value of the ratio [CH2] / [NHCO] in the aliphatic polyamide resin is calculated to be 7. Specifically, aliphatic polyamide resins with an average ratio [CH2] / [NHCO] of 3.0 to 8.0 are used. The number of methylene groups can be determined from the raw materials: lactam, aminocarboxylic acid, aliphatic diamine, and aliphatic dicarboxylic acid. When branched hydrocarbon compounds are included in the monomer units of the polyamide resin, the number of methylene groups is calculated by considering the carbon atoms at the branching points of the carbon chain and the methyl groups at the ends of the branched chain as methylene groups. When lactam or aminocarboxylic acid is used as a raw material, the number of methylene groups contained in the lactam or aminocarboxylic acid becomes the methylene group / amide group ratio. When aliphatic diamine and aliphatic dicarboxylic acid are used as raw materials, the methylene group / amide group ratio is obtained by dividing the total number of methylene groups contained in the aliphatic diamine and aliphatic dicarboxylic acid by 2. The average value of the ratio [CH2] / [NHCO] in the aliphatic polyamide resin is 3.0 or higher, preferably 4.0 or higher, more preferably 4.3 or higher, even more preferably 4.5 or higher, and particularly preferably 4.7 or higher.Furthermore, from the viewpoint of raw material availability, the average value of the ratio [CH2] / [NHCO] is preferably 8.0 or less, more preferably 6.5 or less, more preferably 6.0 or less, and even more preferably 5.5 or less. The specific range of the average value of the ratio [CH2] / [NHCO] in aliphatic polyamide resin is 3.0 to 8.0, preferably 4.0 to 7.0, more preferably 4.3 to 6.5, even more preferably 4.5 to 6.0, and particularly preferably 4.5 to 5.5.

[0013] (Raw materials for aliphatic polyamide resins) The aliphatic polyamide resin used in the present invention preferably satisfies the above average value condition of the ratio [CH2] / [NHCO], but any raw material used in the production of aliphatic polyamide resins can be used, as it is a compound having a linear or branched hydrocarbon as its molecular skeleton. Examples of compounds having a linear or branched hydrocarbon as its molecular skeleton that can be used as raw materials for polyamide resins are listed below. In a preferred embodiment of the present invention, as long as the average value of the ratio [CH2] / [NHCO] as an average of the entire polyamide resin is within the above range, it may include monomers in which the number of methylene groups is not in the range of 3.0 to 8.0 when viewed individually.

[0014] Examples of lactams include caprolactam, enantractam, undecanelactam, dodecanelactam, α-pyrrolidone, and α-piperidone. Examples of aminocarboxylic acids include 6-aminocaproic acid, 7-aminoheptanoic acid, 9-aminononanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid. One or more of these can be used.

[0015] Aliphatic diamines include 1,2-ethanediamine, 1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,11-undecanediamine, 1,12-dodecanediamine, 1,13-tridecanediamine, 1,14-tetradecanediamine, 1,15-pentadecanediamine, 1,16 Examples include hexadecanediamine, 1,17-heptadecanediamine, 1,18-octadecanediamine, 1,19-nonadecanediamine, 1,20-eicosanediamine, 2-methyl-1,5-pentanediamine, 3-methyl-1,5-pentanediamine, 2-methyl-1,8-octanediamine, 2,2,4-trimethyl-1,6-hexanediamine, 2,4,4-trimethyl-1,6-hexanediamine, and 5-methyl-1,9-nonanediamine. One or more of these can be used.

[0016] Examples of aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanediic acid, dodecanediic acid, tridecanediic acid, tetradecanediic acid, pentadecanediic acid, hexadecanedioic acid, octadecanediic acid, and eicosanedioic acid. One or more of these can be used. Here, a combination of a diamine and a dicarboxylic acid is considered as one monomer unit for a combination of one type of diamine and one type of dicarboxylic acid.

[0017] Aliphatic polyamide resins can be obtained using the raw materials described above, but it is preferable that they be at least one selected from the group consisting of aliphatic homopolyamide resins and aliphatic copolymer polyamide resins. Aliphatic homopolyamide resins are polyamide resins consisting of one type of structural unit derived from aliphatic monomers. Aliphatic homopolyamide resins may consist of at least one of one lactam and an aminocarboxylic acid which is a hydrolysate of the lactam, or they may consist of a combination of one diamine and one dicarboxylic acid.

[0018] Examples of aliphatic homopolyamide resins include PA4, PA5, PA6, PA7, PA8, PA9, PA10, PA26, PA44, PA45, PA46, PA48, PA49, PA54, PA55, PA56, PA66, PA410, PA412, PA58, PA59, PA510, PA512, PA64, PA65, PA66, PA68, PA69, PA610, PA612, PA96, PA98, PA99, PA105, PA616, PA618, PA910, PA912, PA106, PA108, PA109, PA1010, PA1012, PA125, PA126, PA129, PA1210, PA1212, PA122, etc. Here, "PA" means "polyamide". These aliphatic homopolyamide resins can be used individually or as a mixture of two or more. Among these, PA56, PA6, PA66, PA510, and PA610 are preferred, and PA6 is more preferred. The aliphatic polyamide resin may also be a mixture of two or more polyamides with different number-average molecular weights.

[0019] Aliphatic copolymer polyamide resins are polyamide resins composed of two or more structural units derived from aliphatic monomers. The structural units of aliphatic copolymer polyamide resins are derived from monomers selected from the group consisting of combinations of diamines and dicarboxylic acids, lactams, and aminocarboxylic acids.

[0020] Aliphatic copolymer polyamide resins specifically include copolymers obtained by combining two or more monomers that form polyamides, as exemplified as aliphatic homopolyamide resins. More specifically, examples include PA4 / 6, PA6 / 66, PA6 / 69, PA6 / 610, PA6 / 611, PA6 / 612, PA6 / 10, PA6 / 11, PA6 / 12, PA6 / 66 / 12, PA6 / 66 / 11, PA6 / 66 / 610, PA6 / 66 / 612, PA6 / 610 / 12, PA6 / 612 / 12, and the like. In particular, from the viewpoint of extrusion moldability of the hollow molded article and flexibility of the resulting molded article, the aliphatic copolymer polyamide resin is preferably at least one selected from the group consisting of PA6 / 66, PA6 / 12, PA6 / 66 / 12, PA6 / 11, PA6 / 66 / 11, PA6 / 610 / 12, and PA6 / 612 / 12, and more preferably at least one selected from the group consisting of PA6 / 66, PA6 / 12, and PA6 / 66 / 12. Each monomer constituting the aliphatic copolymer polyamide can be included in any proportion. Even with polyamides of the same composition, two or more types with different monomer proportions or different number-average molecular weights may be mixed and used.

[0021] The aliphatic polyamide resin used in the present invention has an average ratio [CH2] / [NHCO] within the above range for the entire resin. However, in the aliphatic polyamide resin of the present invention, an aromatic polyamide may be used as one component of the aliphatic polyamide resin, such that the content of monomer units derived from linear or branched hydrocarbon compounds is 80 mol% or more, preferably 90 mol% or more, more preferably 98 mol% or more, and even more preferably 99 mol% or more. As the aromatic polyamide, it is preferable to use a semi-aromatic polyamide produced from an aliphatic compound raw material and an aromatic compound raw material. Examples of such polyamides include PA4T, PA6T, PA9T, PA10T, PA6I, PAMXD6, and copolymers using several types of raw materials to form them.

[0022] Non-limiting examples of resins that can be preferably used as aliphatic polyamide resins include PA56, PA6, PA66, PA6 / 66, PA510, or PA610, and it is preferable that the resin contains PA6 or an aliphatic polyamide containing PA6 as a constituent unit. The aliphatic polyamide resin preferably contains 20% by mass or more of PA6 or PA6 as a constituent unit of the copolymer, more preferably 35% by mass or more, even more preferably 50% by mass or more, and particularly preferably 60% by mass or more. It is also possible to use only PA6 as the aliphatic polyamide resin.

[0023] Since polyamide resins are obtained by the reaction of amino groups and carboxyl groups, polyamide resins have amino groups or carboxyl groups at their molecular ends. When the amount of amino groups per gram of aliphatic polyamide resin is [A1] and the amount of carboxyl groups is [B1], the lower limit of [A1] is preferably 10 μmol / g or more, more preferably 20 μmol / g or more, even more preferably 25 μmol / g or more, and particularly preferably 30 μmol / g or more. The upper limit of [A1] is preferably 120 μmol / g or less, more preferably 100 μmol / g or less, more preferably 95 μmol / g or less, even more preferably 90 μmol / g or less, and particularly preferably 85 μmol% or less. [A1] is preferably 10 μmol / g or more and 120 μmol / g or less, preferably 10 μmol / g or more and 100 μmol / g or less, more preferably 20 μmol / g or more and 95 μmol / g or less, even more preferably 25 μmol / g or more and 90 μmol / g or less, and particularly preferably 30 μmol / g or more and 85 μmol% or less. The lower limit of [B1] is preferably 10 μmol / g or more, more preferably 15 μmol / g or more, and even more preferably 25 μmol / g or more. The upper limit of [B1] is preferably 70 μmol / g or less, more preferably 60 μmol / g or less, and even more preferably 50 μmol / g or less. [B1] is preferably 10 μmol / g or more and 70 μmol / g or less, more preferably 15 μmol / g or more and 60 μmol / g or less, and even more preferably 25 μmol / g or more and 50 μmol / g or less. The amount of amino groups [A1] can be measured by dissolving the aliphatic polyamide resin in a phenol / methanol mixed solution and titrating with 0.05 N hydrochloric acid. The amount of carboxyl groups [B1] can be measured by dissolving the polyamide resin in benzyl alcohol and titrating with a 0.05 N sodium hydroxide solution. Furthermore, if multiple aliphatic polyamide resins are used, the amount of amino groups in the aliphatic polyamide resin (A) can also be calculated by multiplying the amount of each amino group in the aliphatic polyamide by the content ratio (mass%) of the corresponding aliphatic polyamide and dividing by the total content ratio of the aliphatic polyamides.

[0024] Examples of known polyamide manufacturing apparatuses include batch reaction vessels, single-tank to multi-tank continuous reaction apparatuses, tubular continuous reaction apparatuses, single-screw kneading extruders, twin-screw kneading extruders, and other kneading reaction extruders. Polymerization can be carried out using known methods such as melt polymerization, solution polymerization, and solid-phase polymerization, by repeatedly operating under atmospheric pressure, reduced pressure, and increased pressure. These polymerization methods can be used individually or in appropriate combinations.

[0025] Aliphatic polyamide resins are produced by polymerization reactions using the above-mentioned raw materials. For example, they are produced by polymerization or copolymerization of the polyamide raw materials by known methods such as melt polymerization, solution polymerization, or solid-phase polymerization. In the production of aliphatic polyamide resins, additional amines may be added to the polyamide raw materials before polymerization or copolymerization. If additional amines are added, the aliphatic polyamide resin may be produced by adding the amines after polymerization and then melt-kneading. Thus, amines can be added at any stage during polymerization, or at any stage during melt-kneading after polymerization. Examples of the above-mentioned amines include monoamines, diamines, triamines, and polyamines. In addition to amines, carboxylic acids such as monocarboxylic acids, dicarboxylic acids, and tricarboxylic acids may be added as needed, as long as they do not exceed the range of the above-mentioned terminal group amount conditions. These amines and carboxylic acids may be added simultaneously or separately. Furthermore, one or more types of amines and carboxylic acids may be used. By adjusting the amount of amines and carboxylic acids, the molecular weight, the amount of terminal amino groups, and the amount of terminal carboxyl groups of the produced aliphatic polyamide can also be adjusted.

[0026] The aliphatic polyamide resin may be a two-component mixture or a copolymer. If it is a copolymer, it may be a block copolymer or a random copolymer.

[0027] The number-average molecular weight (Mn) of the aliphatic polyamide resin is preferably 10,000 or more, and more preferably 12,000 or more, from the viewpoint of obtaining mechanical strength. On the other hand, from the viewpoint of tube moldability, the Mn is preferably 50,000 or less, and more preferably 40,000 or less. When multiple types of polyamide resins are included, it is preferable that the total Mn of the polyamide resins is within the above range. Specifically, the number-average molecular weight of the aliphatic polyamide resin is preferably 10,000 to 50,000, and more preferably 12,000 to 40,000. Furthermore, it is preferable that the aliphatic polyamide resin contains PA6 with a number-average molecular weight of 10,000 to 50,000. Here, the Mn of the polyamide resin is a value calculated by gel permeation chromatography (GPC), and the measurement method is known to those skilled in the art.

[0028] The aliphatic polyamide resin preferably has a melting point of 180°C to 250°C, as determined by differential scanning calorimetry (DSC). The lower limit of the melting point is more preferably 190°C or higher, and particularly preferably 195°C or higher. The upper limit of the melting point is more preferably 240°C or lower, even more preferably 230°C or lower, and particularly preferably 225°C or lower. Having a melting point within this range ensures moldability as a hollow molded article and sufficiently prevents thermal deformation when the article is molded. The melting point of the aliphatic polyamide resin, as determined by differential scanning calorimetry (DSC), can be increased or decreased depending on the composition ratio of each component, relative viscosity, and molecular weight.

[0029] The aliphatic polyamide resin preferably has a crystallization temperature of 140°C to 200°C, as determined by differential scanning calorimetry (DSC). The lower limit of the crystallization temperature is more preferably 150°C or higher, and particularly preferably 160°C or higher. The upper limit of the crystallization temperature is more preferably 190°C or lower, and particularly preferably 185°C or lower. This allows for stable moldability as a hollow molded article. The crystallization temperature of the aliphatic polyamide resin, as determined by differential scanning calorimetry (DSC), can be increased or decreased depending on the composition ratio, relative viscosity, and molecular weight of each component.

[0030] The aliphatic polyamide resin preferably has a relative viscosity of 1.80 to 4.50. The lower limit of the relative viscosity is more preferably 2.00 or higher, even more preferably 2.30 or higher, and particularly preferably 2.40 or higher. The upper limit of the relative viscosity is more preferably 4.40 or lower, and particularly preferably 4.20 or lower. Having a relative viscosity within the above range results in excellent moldability as a hollow molded article. In this specification, ηr (relative viscosity) is the measured value at 25°C (JIS K 6920) of a solution prepared by dissolving the polyamide at a concentration of 1 g / 100 ml in 100 ml of 96% by mass concentrated sulfuric acid as a solvent.

[0031] <Polyolefins having functional groups> The polyamide resin composition of the present invention contains polyolefins having functional groups. Known materials can be used as polyolefins, but it is preferable that they function as impact resistant agents. The polyolefin is preferably of a surface hardness (Shore A) of 80 or less, as measured in accordance with ASTM D2240.

[0032] The polyolefin used has functional groups that are substantially free of metal atoms, and preferably has functional groups that are reactive with the terminal groups of the polyamide resin. Here, "substantially free of metal atoms" means that the molecular structure constituting the functional group does not contain metal atoms, but it does not mean that contamination in amounts that are considered unavoidable impurities rather than intentional introduction is not permitted. Specifically, examples include copolymers having an (ethylene and / or propylene) / α-olefin copolymer as the main backbone, with at least a portion of which are functional groups that are reactive with the terminal groups of the aliphatic polyamide resin, and (ethylene and / or propylene) / (α,β-unsaturated carboxylic acid and / or α,β-unsaturated carboxylic acid ester) copolymers, and it is preferable to use at least one selected from the group consisting of these. These can be used individually or in combination of two or more. The polyolefin is preferably one with an ethylene / α-olefin copolymer as the main backbone. The polyolefin used has functional groups that are substantially free of metal atoms. Since metal atoms are intentionally introduced into the polyolefin during the preparation process, ionomers are substantially free of them. Here, ionomer refers to a resin having carboxyl groups in which all or part of the carboxyl groups are neutralized by a metal or metal ion.

[0033] (Ethylene and / or propylene) / α-olefin copolymers are polymers obtained by copolymerizing ethylene and / or propylene with an α-olefin having 3 or more or 4 or more carbon atoms. Examples of 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 individually or in combination of two or more types.

[0034] The copolymer may also be a copolymer of polyenes such as non-conjugated dienes. Examples of non-conjugated dienes 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 dicyclopene. Examples include tadiene, cyclohexadiene, cyclooctadiene, 5-vinylnorbornene, 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. These may be used individually or in combination of two or more.

[0035] (Ethylene and / or propylene) / (α,β-unsaturated carboxylic acid and / or α,β-unsaturated carboxylic acid ester) copolymers are polymers obtained by copolymerizing ethylene and / or propylene with α,β-unsaturated carboxylic acid and / or α,β-unsaturated carboxylic acid ester monomers. Examples of α,β-unsaturated carboxylic acid monomers include acrylic acid and methacrylic acid. Examples of α,β-unsaturated carboxylic acid ester monomers include methyl esters, ethyl esters, propyl esters, butyl esters, pentyl esters, hexyl esters, heptyl esters, octyl esters, nonyl esters, decyl esters, etc., of these α,β-unsaturated carboxylic acids. These may be used individually or in combination of two or more.

[0036] Furthermore, it is preferable that the (ethylene and / or propylene) / α-olefin copolymer has functional groups that react with terminal amino groups of the aliphatic polyamide resin, at least a portion of which react with the terminal amino groups of the aliphatic polyamide resin. The (ethylene and / or propylene) / (α,β-unsaturated carboxylic acid and / or α,β-unsaturated carboxylic acid ester) copolymer already has the above-mentioned functional groups, but may also have different functional groups.

[0037] Examples of the functional group include carboxyl groups, acid anhydride groups, carboxylic acid ester groups, carboxylic acid imide groups, carboxylic acid amide groups, epoxy groups, and it is preferable that at least one selected from the group consisting of these groups is used.

[0038] Examples of compounds containing these functional groups 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, endobicyclo-[2.2.1]-5-heptene-2,3-dicarboxylic acid, monomethyl maleate, monomethyl itaconic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, hydroxyethyl acrylate, methyl methacrylate, 2-ethylhexyl methacrylate Examples include syl, hydroxyethyl methacrylate, aminoethyl methacrylate, dimethyl maleate, dimethyl itaconate, maleic anhydride, itaconate anhydride, citraconic anhydride, endobicyclo-[2.2.1]-5-hepten-2,3-dicarboxylic acid anhydride, maleimide, N-ethyl maleimide, N-butyl maleimide, N-phenyl maleimide, acrylamide, methacrylamide, glycidyl acrylate, glycidyl methacrylate, glycidyl ethacrylate, glycidyl ethacrylate, glycidyl itaconate, and glycidyl citraconic acid. These can be used individually or in combination of two or more. Among these, maleic anhydride, itaconate anhydride, and citraconic anhydride are preferred, with maleic anhydride or itaconate anhydride being more preferred.

[0039] Methods for introducing these functional groups into polymers used in polyolefins include: (i) copolymerizing copolymerizable monomers having functional groups during polymerization of the polymer; (ii) introducing functional groups to the molecular chains or molecular ends of the polymer using polymerization initiators, chain transfer agents, etc.; and (iii) grafting a compound having a functional group and a graftable functional group (graft compound) onto the polymer. These introduction methods can be used individually or in appropriate combinations.

[0040] The content of functional groups such as acid anhydride groups and carboxylic acid ester groups contained in 1 g of polyolefin (functional group amount [C1]) is preferably more than 10 µmol / g. As examples of specific numerical values, more than 25 µmol / g and less than 100 µmol / g is preferred, 35 µmol / g or more and less than 95 µmol / g is more preferred, and 40 µmol / g or more and 90 µmol / g or less is even more preferred. When the content is more than 10 µmol / g, a composition with high melt viscosity can be obtained, and a target wall thickness dimension can be achieved in tube molding. Furthermore, when the content is less than 100 µmol / g, the melt viscosity does not become excessively high, so the load on an extruder is suppressed and favorable molding processing can be performed. For the content of functional groups in polyolefin, for example, when the polyolefin has a carboxy group, an acid anhydride group, or a carboxylic acid ester group, the content is measured by neutralization titration using a 0.1 normal KOH ethanol solution with phenolphthalein as an indicator, using a sample solution prepared using a xylene / ethanol mixed solution. As the polyolefin, a polyolefin having no functional group reactive with the terminal groups of the polyamide resin may be used in combination, but it is preferably used in such an amount that the content of functional groups relative to the entire polyolefin falls within the above range.

[0041] In the polyamide resin composition of the present invention, the product of the functional group amount [C1] of the polyolefin and the amino group amount [A1] of the aliphatic polyamide resin is 1000 to 5000 ((µmol / g) ２ ), it is preferable that the amounts of the functional groups of both components are controlled so as to satisfy this condition.

[0042] The polyolefin preferably has an MFR measured in accordance with ISO 1133 at a temperature of 190°C and a load of 2.16 kg of 2 g / 10 minutes or less. When the MFR falls within this range, it becomes easier to maintain the MFR of the entire polyamide resin composition in a favorable range.

[0043] <Polyamide Resin Composition> The polyamide resin composition of the present invention is a composition comprising the above aliphatic polyamide resin and polyolefin. Regarding the content of both components, the amount of the aliphatic polyamide resin is in the range of 60 to 80% by mass, and the amount of the polyolefin is in the range of 20 to 40% by mass, based on 100% by mass of the polyamide resin composition. The upper limit of the amount of the aliphatic polyamide resin in 100% by mass of the polyamide resin composition is 80% by mass, preferably less than 80% by mass, more preferably 78% by mass or less, still more preferably 75% by mass or less. The lower limit is 60% by mass or more, preferably more than 60% by mass, more preferably more than 62% by mass. The upper limit of the amount of the polyolefin in 100% by mass of the polyamide resin composition is 40% by mass, preferably less than 40% by mass, more preferably less than 28% by mass. The lower limit is 20% by mass or more, preferably more than 20% by mass, more preferably 22% by mass or more, still more preferably 25% by mass. Preferably, the amount of the aliphatic polyamide resin is in the range of 60 to 78% by mass and the amount of the polyolefin is in the range of 22 to 40% by mass based on 100% by mass of the polyamide resin composition; more preferably, the amount of the aliphatic polyamide resin is in the range of 60 to 75% by mass and the amount of the polyolefin is in the range of 25 to 40% by mass based on 100% by mass of the polyamide resin composition. Further more preferably, the amount of the aliphatic polyamide resin is in the range of more than 62% by mass to 75% by mass and the amount of the polyolefin is in the range of 25% by mass to less than 28% by mass based on 100% by mass of the polyamide resin composition.

[0044] The method for mixing the aliphatic polyamide resin and the polyolefin is not particularly limited. Various additives may be blended as necessary, and various conventionally known methods can be employed. For example, it can be produced by a method in which pellets of the aliphatic polyamide resin and the polyolefin are uniformly dry-blended with a tumbler or a mixer to achieve the aforementioned mixing ratio, or by a method in which the two components together with other optional additives are dry-blended in advance at the concentration used for molding and then melt-kneaded. The melt-kneading can be performed using a kneader such as a single-screw extruder, a twin-screw extruder, a kneader, or a Banbury mixer.

[0045] [Plasticizer (c)] The polyamide resin composition of the present invention is substantially free of plasticizers. Plasticizers are components that impart flexibility to molded articles obtained from resin compositions containing them, but many of them are soluble in chemical solutions, including alcohols such as glycols. Therefore, in molded articles made from resin compositions containing plasticizers, contact with chemical solutions can cause the plasticizer to leach out, leading to deterioration. In contrast, the present invention is based on the discovery of a resin composition that has good moldability despite being substantially free of plasticizers. Here, "substantially free" means intentionally omitting plasticizers, except in cases where they are inevitably mixed in by industrial raw materials, for example, and specifically, "the content of plasticizers in the composition can be 3% by mass or less." The content of plasticizers in the polyamide resin composition of the present invention is preferably 2% by mass or less, more preferably 1% by mass or less, and particularly preferably 0% by mass.

[0046] In this specification, a plasticizer is a substance that, when added to a resin composition containing a polyamide resin, imparts flexibility to a molded article and exhibits solubility in a solvent. Therefore, "substantially free of plasticizers" can also be expressed by the amount of eluting components contained in the composition when dissolved in a solvent, particularly alcohol. Specifically, the polyamide resin composition of the present invention has an amount of eluting components of 3% by mass or less when the composition is extracted with methanol after drying, with the resin composition being 100% by mass. The amount of eluting components is preferably 2% by mass or less, more preferably 1% by mass or less, and particularly preferably 0.5% by mass or less under the same conditions. The conditions for evaluating the amount of eluting components are as described in the examples below.

[0047] Accordingly, one aspect of the present invention relates to a polyamide resin composition for a single-layer hollow molded article, comprising an aliphatic polyamide resin (A) and a functional polyolefin (B), wherein 100% by mass of the polyamide resin composition contains 60 to 80% by mass of the aliphatic polyamide resin (A) and 20 to 40% by mass of the polyolefin (B), the average ratio [CH2] / [NHCO] of the number of methylene groups ([CH2]) in the aliphatic polyamide resin (A) to the number of amide groups ([NHCO]) is 3.0 to 8.0, the functional groups of the polyolefin (B) substantially do not contain metal atoms, and the amount of eluted components when the polyamide resin composition is extracted with methanol after drying is 3% by mass or less when the entire resin composition is considered as 100% by mass. Preferred aspects of this aspect, other than the amount of eluted components, are as described herein.

[0048] Substances considered as plasticizers include those mixed with polyamide resins for the purpose of imparting flexibility. Examples of plasticizers include esters or amides with a molecular weight of 1,000 or less, in which a hydrocarbon group having 4 or more carbon atoms is bonded to the oxygen of the ester group or the nitrogen of the amide group. More specifically, at least one selected from the group consisting of alkyl benzenesulfonates, alkyl toluenesulfonates, and alkyl hydroxybenzoates is included.

[0049] Examples of benzenesulfonate alkylamides include benzenesulfonate propylamide, benzenesulfonate butylamide, and benzenesulfonate 2-ethylhexylamide. Examples of toluenesulfonate alkylamides include N-ethyl-o-toluenesulfonate butylamide, N-ethyl-p-toluenesulfonate butylamide, N-ethyl-o-toluenesulfonate 2-ethylhexylamide, and N-ethyl-p-toluenesulfonate 2-ethylhexylamide. Examples of hydroxybenzoate alkyl esters include o-hydroxybenzoate ethylhexyl, p-hydroxybenzoate ethylhexyl, o-hydroxybenzoate hexyldecyl, p-hydroxybenzoate hexyldecyl, o-hydroxybenzoate ethyldecyl, p-hydroxybenzoate ethyldecyl, o-hydroxybenzoate octyloctyl, p-hydroxybenzoate octyloctyl, o-hydroxybenzoate decyldodecyl, and p-hydroxybenzoate Examples include decyl dodecyl, 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.

[0050] (Additives) The polyamide resin composition may contain, as needed, antioxidants, heat-resistant agents, UV absorbers, light stabilizers, weather-resistant agents, lubricants, inorganic fillers, antistatic agents, flame retardants, crystallization accelerators, colorants, lubricants, etc. Various commercially available materials known to those skilled in the art can be used as these additives, but it is preferable to select materials that have no or low solubility in the chemical solution.

[0051] It is preferable to add antioxidants to the polyamide resin composition. Examples of organic antioxidants include phenolic antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, and the like.

[0052] Hindered phenol antioxidants are preferred as phenolic antioxidants. In this specification, a hindered phenol refers to a compound having a substituent at the ortho position (hereinafter also referred to as the "o position") of the hydroxyl group of phenol. The substituent at the o position is not particularly limited, but examples include alkyl groups, alkoxy groups, amino groups, halogens, etc. Among these, alkyl groups such as methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, sec-butyl group, i-butyl group, and tert-butyl group are preferred, the bulky i-propyl group, sec-butyl group, i-butyl group, and tert-butyl group are more preferred, and the tert-butyl group is the most preferred. Furthermore, it is preferable that both o positions relative to the hydroxyl group of phenol have substituents.

[0053] Hindered phenols having a tert-butyl group at the o-position may be commercially available products, specifically N,N'-(hexane-1,6-diyl)bis[4-hydroxy-3,5-bis(tert-butyl)benzenepropanamide (Irganox® 1098; manufactured by BASF Japan Ltd.) and pentaerythritol=tetrakis[3-(3,5-di-tert-butyl-4'-hydroxyphenyl)propionate (Irganox® 1010; manufactured by BASF Japan Ltd.) Examples include ), ethylenebis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate] (Irganox® 245; manufactured by BASF Japan Ltd.), 3,9-bis[2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane (Smilizer® GA-80; manufactured by Sumitomo Chemical Co., Ltd.). These may be used individually or in combination of two or more.

[0054] Preferred phosphorus-based antioxidants include hindered phenol phosphite compounds and hindered phenol hypophosphite compounds, more preferably hindered phenol phosphite compounds having a tert-butyl group at the o-position and hindered phenol hypophosphite compounds having a t-butyl group at the o-position, and even more preferably hindered phenol phosphite compounds having a t-butyl group at the o-position. Commercially available products may be used, and specific examples of hindered phenol phosphite compounds having a t-butyl group at the o-position include tris(2,4-di-tert-butylphenyl) phosphite (Irgafos® 168; manufactured by BASF Japan Ltd.). Examples of hypophosphite compounds of hindered phenols having a tert-butyl group at the o-position include 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane (ADEKA Stab® PEP-36; manufactured by ADEKA Corporation) and the reaction product of biphenyl, phosphorus trichloride, and 2,4-di-tert-butylphenol, with p,p,p',p'-tetrakis(2,4-di-tert-butylphenoxy)-4,4' (or 3',4)-biphenyldiphosphine as the main component (Hostanox® P-EPQ® P; manufactured by Clariant Japan Co., Ltd.). These may be used individually or in combination of two or more.

[0055] Examples of sulfur-based antioxidants include distearyl-3,3-thiodipropionate, pentaerythrityltetrakis(3-laurylthiopropionate), didodecyl(3,3'-thiodipropionate), and pentaerythrityltetrakis(3-laurylthiopropionate) (SUMILIZER TP-D; manufactured by Sumitomo Chemical Co., Ltd.). These may be used individually or in combination of two or more. These organic antioxidants may be used individually or in combination of two or more.

[0056] As heat-resistant agents, organic and inorganic heat-resistant agents can be used depending on the purpose, and these may be used individually or in combination of two or more. Preferably, the heat-resistant agent is a combination of an inorganic compound and a nitrogen-containing compound, or an inorganic compound.

[0057] Inorganic compounds include metal halides and inorganic compounds other than metal halides. Metal halides are compounds of halogens and metals. Examples of halogens include fluorine, chlorine, bromine, and iodine. Examples of metals include Group 1 elements (alkali metals), Group 2 elements (alkaline earth metals), and Group 3 to Group 12 elements (e.g., transition metals). In metal halides, the metal is preferably a Group 1 element (alkali metal) or a Group 11 element (copper group). When the metal is a Group 1 element (alkali metal), examples of metal halides include potassium iodide, potassium bromide, potassium chloride, sodium iodide, or sodium chloride. When the metal is a Group 11 element (copper group), examples of metal halides include cuprous chloride, cupric chloride, cuprous bromide, cupric bromide, cuprous iodide, and cupric iodide. It is particularly preferable that the metal halide is potassium iodide and / or cuprous iodide.

[0058] Inorganic compounds other than metal halides include metals, metal oxides, metal hydroxides, metal nitrides, metal phosphates, metal phosphites, metal carbonates, metal silicates, metal titanates, metal borates, metal sulfates, and metal nitrates. Specific examples of inorganic compounds other than metal halides include talc, mica, synthetic mica, glass flakes, non-swelling mica, fullerenes, carbon nanotubes, carbon black, graphite, metal foil, ceramic beads, clay, sericite, zeolite, bentonite, aluminum hydroxide, dolomite, kaolin, silica, fine silica powder, feldspar powder, potassium titanate, shirasu balloons, calcium carbonate, magnesium carbonate, barium sulfate, calcium oxide, aluminum oxide, titanium oxide, and acids. Examples include magnesium oxide, aluminum silicate, silicon dioxide, magnesium hydroxide, gypsum, novaculite, dawsonite, white clay, glass fiber, carbon fiber, graphite fiber, metal fiber, potassium titanate whisker, aluminum borate whisker, magnesium-based whisker, silicon-based whisker, warlastenite, sepiolite, slag fiber, zonolite, elestadite, gypsum fiber, silica fiber, silica-alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, and boron fiber.

[0059] Examples of nitrogen-containing compounds include melamine, benguanamine, dimethylolurea, and cyanuric acid.

[0060] Other polyamide resins or other thermoplastic resins may be added to the polyamide resin composition. Examples of such addable resins include the polyamide resins and thermoplastic resins described in paragraphs 0054 to 0055 of WO2015 / 033982. These resins can be used individually or in mixtures of two or more. However, it is preferable to use resins that have little to no solubility in chemical solutions, especially alcohols. The amount of these polyamide resins or other thermoplastic resins is preferably less than 3.5% by mass of the total polyamide resin composition, more preferably less than 3.0% by mass, even more preferably less than 2.0% by mass, even more preferably less than 1.0% by mass, and particularly preferably none.

[0061] Accordingly, a preferred embodiment of the present invention relates to a polyamide resin composition for a single-layer hollow molded article, comprising the aliphatic polyamide resin (A), the polyolefin (B), an antioxidant, and optionally at least one additive selected from the group consisting of a heat resistant agent, an ultraviolet absorber, a light stabilizer, a weather resistant agent, a lubricant, an inorganic filler, an antistatic agent, a flame retardant, a crystallization accelerator, a colorant, and a lubricant, wherein the composition contains 60 to 80% by mass of the aliphatic polyamide resin (A) and 20 to 40% by mass of the polyolefin (B) in 100% by mass of the composition.

[0062] The polyamide resin composition of the present invention preferably has an MFR of 0.01 g / 10 min to 20 g / 10 min at 300°C and 5000 g. This range ensures that the resin does not exhibit excessive fluidity and is suitable for tube molding. The MFR is more preferably 0.05 g / 10 min or higher, and even more preferably 0.10 g / 10 min or higher. Furthermore, the MFR is more preferably 15 g / 10 min or lower, and even more preferably 10 g / 10 min or lower. The MFR is the value measured when 5000 g of the resin composition is heated to 300°C in accordance with ISO 1133.

[0063] The polyamide resin composition of the present invention is obtained by thoroughly drying a sample and then testing it at a cylinder temperature of 300°C, an orifice diameter L / D = 10, and a shear rate of 121.6 sec. －１ The melt viscosity measured is preferably 600 to 2700 Pa·s. If the melt viscosity is 600 Pa·s or higher, the resin will not flow during extrusion molding before the resin composition cools, and the target wall thickness can be obtained. From the viewpoint of dimensional stability during molding, the melt viscosity is more preferably 1000 Pa·s or higher, more preferably 1100 Pa·s or higher, more preferably 1200 Pa·s or higher, even more preferably 1300 Pa·s or higher, and even more preferably 1400 Pa·s or higher. Furthermore, if the melt viscosity is 2700 Pa·s or lower, excessive force is not required for extrusion molding, resulting in a resin with excellent handling and moldability. From the viewpoint of ease of molding, the melt viscosity is more preferably 2670 Pa·s or lower.

[0064] The polyamide resin composition of the present invention preferably has a tensile fracture strain of over 100% when a test specimen prepared according to ISO 294-1 is measured according to ISO 527-1 and ISO 527-2 / 1A / 50. This range sufficiently increases the impact resistance of the resin, making it possible to obtain a molded article with high strength. The tensile fracture strain is preferably over 120%, and more preferably over 140%. While there is no particular upper limit to the tensile fracture strain, it is usually 300% or less.

[0065] The polyamide resin composition of the present invention preferably has a flexural modulus of 1600 MPa or less when a test specimen prepared according to ISO 294-1 is measured according to ISO 178. This range enhances the flexibility of the resin, making it possible to obtain molded articles with excellent flexibility, especially when molded into tubes or hoses. The flexural modulus is preferably 1550 MPa or less, and more preferably 1500 MPa or less. The lower limit of the flexural modulus is preferably 400 MPa or more, from the viewpoint of maintaining resistance to strain.

[0066] <Molded Articles> The polyamide resin composition of the present invention can be used for hollow molded articles. As long as it is a hollow molded article, the shape is not limited and it can take various shapes such as pipes, tubes, and hoses. A preferred shape is cylindrical. Generally, even resins that can be injected without problems tend to be unsuitable for tube molding. Unlike injection molding, which is based on pouring into a mold, the manufacture of hollow molded articles such as tubes and hoses requires that a constant amount of resin be continuously extruded from an extruder and that the extruded resin hardens in that shape. If pulsation of the resin occurs during the extrusion process, the wall thickness may not be constant, and points that are weak against pressure may occur. Also, if the fluidity of the resin is too high, dripping will occur before hardening, and a hollow molded article with a uniform shape will not be formed. Therefore, it is required that the resin has a moderate range of fluidity and can be molded uniformly and continuously. The inventors have found that the polyamide resin composition of the present invention is a resin that has properties that satisfy these needs and is suitable for molding hollow molded articles, especially pipes, tubes, and hoses.

[0067] The polyamide resin composition of the present invention can be used to form a single-layer hollow molded article containing it. In short-chain polyamides, which have high rigidity but are not well formed into tubes, the polyamide resin composition of the present invention has an extremely high effect in that, even as a single layer, it can be used in a shape suitable for transporting chemicals without substantially using components that leach into chemicals. Therefore, one aspect of the present invention is a hollow molded article containing the polyamide resin, which is at least one selected from the group consisting of pipes, tubes, and hoses.

[0068] Tubes, hoses, and pipes can be manufactured using known methods such as extrusion molding or hollow molding, following conventional procedures. In extrusion molding, molten resin is extruded into a circular mold and cooled while being molded. Because it is a relatively simple process that can produce molded bodies of any length, extrusion molding is easy and preferable for general infusion tubes. Single-screw or multi-screw extruders can be used. Hollow molding involves forming a hollow body called a parison and then molding it using internal air pressure. These methods can also be used to mold complex shapes.

[0069] Furthermore, if the resulting hollow molded body has a complex shape, or if the molded product is to be subjected to heat bending after molding, it is also possible to remove residual strain from the molded product by first forming a straight tubular molded body and then heat-treating it at a temperature below the melting point of the resin constituting the molded body for 0.01 hours to 10 hours to obtain the desired molded product.

[0070] In a hollow molded body, a corrugated region may be present. A corrugated region is a region formed in a corrugated shape, bellows shape, accordion shape, or corrugated shape, etc. The corrugated region may not only extend along the entire length of the hollow molded body, but may also be present in a portion of the body. The corrugated region can be easily formed by first forming the body into a straight tube shape, followed by molding to create a predetermined corrugated shape, etc. Having such a corrugated region provides shock absorption and facilitates installation. Furthermore, it is possible to add necessary parts such as connectors, or to create L-shaped, U-shaped, etc. shapes by bending.

[0071] The outer circumference of the hollow molded body formed in this manner may be made of, in whole or in part, natural rubber (NR), butadiene rubber (BR), isoprene rubber (IR), butyl rubber (IIR), chloroprene rubber (CR), carboxylated butadiene rubber (XBR), carboxylated chloroprene rubber (XCR), epichlorohydrin rubber (ECO), acrylonitrile butadiene rubber (NBR), hydrogenated acrylonitrile butadiene rubber (HNBR), carboxylated acrylonitrile butadiene rubber (XNBR), a mixture of NBR and polyvinyl chloride, acrylonitrile isoprene rubber (NIR), chlorinated polyethylene rubber (CM), chlorosulfonated polyethylene rubber (CSM), ethylene propylene rubber ( Solid or sponge-like protective members (protectors) can be provided, composed of materials such as EPR, ethylene propylene diene rubber (EPDM), ethylene vinyl acetate rubber (EVM), NBR and EPDM mixed rubber, acrylic rubber (ACM), ethylene acrylic rubber (AEM), acrylate butadiene rubber (ABR), styrene butadiene rubber (SBR), carboxylated styrene butadiene rubber (XSBR), styrene isoprene rubber (SIR), styrene isoprene butadiene rubber (SIBR), urethane rubber, silicone rubber (MQ, VMQ), fluororubber (FKM, FFKM), fluorosilicone rubber (FVMQ), and thermoplastic elastomers such as vinyl chloride, olefin, ester, urethane, and amide. The protective member may be made into a porous sponge-like material by known methods. By making it porous, a lightweight protective part with excellent heat insulation can be formed. Material costs can also be reduced. Alternatively, glass fibers or the like may be added to improve its strength. The shape of the protective member is not particularly limited, but it is usually a cylindrical member or a block-shaped member having a recess for receiving a molded body. In the case of a cylindrical member, a hollow molded body can be inserted into a pre-fabricated cylindrical member, or a cylindrical member can be extruded onto a hollow molded body to create a tight bond between the two. To bond the two, an adhesive is applied as needed to the inner surface of the protective member or the recessed surface, and the tube is inserted or fitted into it, thereby creating a tight bond between the two and forming an integrated structure of the tube and the protective member.Furthermore, it is possible to reinforce it with metal or other materials.

[0072] The hollow molded body may be painted, coated, or otherwise treated on its outer surface, inner surface, etc., to the extent that it does not hinder the objectives of the present invention. Furthermore, while the hollow molded body is preferably a single-layer hollow molded body, it may also be a multi-layer hollow molded body by combining it with other layers. In that case, it is preferable that the layer using the polyamide resin composition of the present invention is the innermost layer.

[0073] The outer diameter of the hollow molded body is designed considering the flow rate of the chemical solution, and the wall thickness is designed to be such that the amount of chemical solution permeation does not increase, the fracture pressure of the molded body is maintained, and flexibility is maintained to a degree that is good for ease of assembly and vibration resistance during use, but it is not limited to these. Preferably, the outer diameter is 4 mm to 300 mm, the inner diameter is 3 mm to 250 mm, and the wall thickness is 0.5 mm to 25 mm.

[0074] The hollow molded articles using the polyamide resin composition of the present invention can be used in a variety of applications, particularly in the form of pipes, tubes, or hoses, including mechanical parts such as automotive parts, internal combustion engine applications, and power tool housings, as well as industrial materials, industrial supplies, electrical and electronic components, medical equipment, food products, household and office supplies, building materials, and furniture parts.

[0075] The polyamide resin composition of the present invention is suitable as a chemical transport tube. Examples of chemical solutions include aromatic hydrocarbon solvents such as benzene, toluene, and xylene; alcohols and phenolic solvents such as propanol, butanol, pentanol, ethylene glycol, propylene glycol, diethylene glycol, phenol, cresol, polyethylene glycol, and polypropylene glycol; ether solvents such as dimethyl ether, dipropyl ether, methyl tert-butyl ether, ethyl t-butyl ether, dioxane, and tetrahydrofuran; halogenated solvents such as chloroform, methylene chloride, trichloroethylene, dichloroethylene, perchloroethylene, monochloroethane, dichloroethane, tetrachloroethane, perchloroethane, and chlorobenzene; ketone solvents such as acetone, methyl ethyl ketone, diethyl ketone, and acetophenone; castor oil-based brake fluid, glycol ether-based brake fluid, boric acid ester-based brake fluid, brake fluid for extremely cold climates, silicone oil-based brake fluid, mineral oil-based brake fluid, power steering oil, hydrogen sulfide-containing oil, windshield washer fluid, coolant for vehicle engines, urea solution, pharmaceuticals, inks, paints, etc. Tubes using the polyamide resin composition of the present invention are suitable as tubes for transporting the above-mentioned chemical solutions. Specifically, examples include brake tubes, windshield washer fluid tubes, engine coolant (LLC) tubes, reservoir tank tubes, urea solution transport tubes, cooler tubes for coolant, refrigerant, etc., air conditioner refrigerant tubes, heater tubes, road heating tubes, floor heating tubes, infrastructure supply tubes, fire extinguisher and fire extinguishing equipment tubes, medical cooling equipment tubes, ink and paint spraying tubes, and other chemical solution tubes.

[0076] The hollow molded articles using the polyamide resin composition of the present invention are particularly suitable for use as thermal management components in equipment, for temperature control. Thermal management here can refer to cooling, heating, or maintaining a constant temperature. In the case of a thermal management system in an automobile, it is a system for managing the temperature of each component of the vehicle to ensure optimal performance. Specifically, it cools or heats heat-generating components such as batteries, motors, and inverters to maintain an appropriate temperature. This extends the battery life and maximizes the vehicle's driving range. The hollow molded articles of the present invention can be used in conventional automobiles with combustion engines, electric automobiles, hybrid automobiles with electric motors and combustion engines, and fuel cell vehicles equipped with fuel cells, and are preferably used in electric automobiles, hybrid automobiles with electric motors and combustion engines, and fuel cell vehicles equipped with fuel cells. Non-limiting specific applications and transportable chemicals include coolants for automobile engines and chemicals used in the flow paths of heat collectors that accumulate exhaust heat.

[0077] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. The components used in the examples and comparative examples and the methods for measuring the physical properties of the molded articles are shown below.

[0078] [Components] (A) Aliphatic polyamide resin <Aliphatic homopolyamide> (A-1) Polyamide 6 (manufactured by UBE Corporation, average value of [CH2] / [NHCO] = 5.0, relative viscosity 4.07, amino group content 28.7 μmol / g) (A-2) Polyamide 6 (manufactured by UBE Corporation, average value of [CH2] / [NHCO] = 5.0, relative viscosity 3.00, amino group content 30.0 μmol / g) (A-3) Polyamide 6 (manufactured by UBE Corporation, average value of [CH2] / [NHCO] = 5.0, relative viscosity 2.48, amino group content 93.0 μmol / g) (A-9) Polyamide 66 (manufactured by Huafeng Group, average value of [CH2] / [NHCO] = 5.0, relative viscosity 3.66, amino group content 17.8 μmol / g) (A-10) Polyamide 56 (manufactured by Cathay Biotech Incorporated, average value of [CH2] / [NHCO] = 4.5, relative viscosity 2.77, amino group content 52.5 μmol / g) (A-11) Polyamide 510 (manufactured by Cathay Biotech Incorporated, average value of [CH2] / [NHCO] = 6.5, relative viscosity 2.57, amino group content 32.7 μmol / g) (A-12) Polyamide 6 (manufactured by UBE Co., Ltd., average value of [CH2] / [NHCO] = 5.0, relative viscosity 3.35, amino group content 42.0 μmol / g) <Copolymerized Polyamides> ・Aliphatic copolymerized polyamides (A-4) Polyamide 6 / 66 (manufactured by UBE Co., Ltd., average value of [CH2] / [NHCO] = 5.0, relative viscosity 4.08, amino group content 35.0 μmol / g) (A-5) Polyamide 6 / 66 (manufactured by UBE Corporation, average value of [CH2] / [NHCO] = 5.0, relative viscosity 3.99, amino group content 34.0 μmol / g) (A-6) Polyamide 6 / 12 (manufactured by UBE Corporation, average value of [CH2] / [NHCO] = 6.2, relative viscosity 3.81, amino group content 34.0 μmol / g) (A-7) Polyamide 6 / 66 / 12 (manufactured by UBE Corporation, average value of [CH2] / [NHCO] = 5.7, relative viscosity 4.08, amino group content 34.0 μmol / g) ・Semi-aromatic copolymer polyamide: (A-8) Polyamide 6T6I (polyamide manufactured by M's Chemie Japan) Grivory® G21, average value of [CH2] / [NHCO] = 3, amino group content 38.0 μmol / g) The average value of [CH2] / [NHCO] was rounded to two decimal places.

[0079] <Average value of the ratio [CH2] / [NHCO] of the number of methylene groups ([CH2]) to the number of amide groups ([NHCO]) in aliphatic polyamide resin (A)> The average value of [CH2] / [NHCO] in aliphatic polyamide resin (A) was calculated by multiplying the average value of [CH2] / [NHCO] in aliphatic homopolyamide and aliphatic copolymer polyamide by the content percentage (mass%) of the corresponding polyamide and dividing by the total content percentage of aliphatic homopolyamide and aliphatic copolymer polyamide. <Amount of amino groups in aliphatic polyamide resin (A)> The amount of amino groups in aliphatic polyamide resin (A) was calculated by multiplying the amount of amino groups in aliphatic homopolyamide and aliphatic copolymer polyamide by the content percentage (mass%) of the corresponding polyamide and dividing by the total content percentage of aliphatic homopolyamide and aliphatic copolymer polyamide.

[0080] (B) Polyolefins (B-1) Maleic anhydride-modified ethylene / 1-butene copolymer (manufactured by Mitsui Chemicals, Inc., Tuffmer® MH5010, functional group amount (maleic anhydride group amount) = 50 μmol / g) (B-2) Maleic anhydride-modified ethylene / 1-butene copolymer (manufactured by Mitsui Chemicals, Inc., Tuffmer® MH5020, functional group amount (maleic anhydride group amount) = 100 μmol / g) (B-3) Ionomer resin (manufactured by Mitsui-Dow Polychemicals Ltd., Hymiran® ​​1706) (B-3) is a resin in which some of the carboxylic acid groups in the ethylene / methacrylic acid copolymer are neutralized with zinc, and the test using this corresponds to a comparative example.

[0081] In addition to the polyamides and polyolefins mentioned above, a mixture of Irganox® 1098 and Irgafos® 168 from BASF Japan Ltd., and SUMILIZER TP-D from Sumitomo Chemical Co., Ltd. were used as antioxidants. In some comparative examples, a predetermined amount of BBSA (butylamide benzenesulfonate) was added as a plasticizer.

[0082] <Examples> An aliphatic polyamide resin, a polyolefin, and an antioxidant were melt-kneaded with a twin-screw melt kneader in the composition shown in Table 1 to produce pellets of a polyamide resin composition. As comparative examples, no polyolefin was added (Comparative Example 1), no polyolefin was added but a plasticizer was added (Comparative Example 2), the amount of polyolefin was reduced (Comparative Examples 3, 4, 6: a plasticizer was further added in Comparative Example 4), a polyolefin that does not satisfy the requirements of the present invention was used (Comparative Example 5), the amount of polyolefin was varied (Comparative Examples 7, 8), and a plasticizer was added (Comparative Example 9). Pellets of the polyamide resin composition were produced with the composition shown in Table 2 in the same manner except for the above. The compositions of each component in the compositions of the examples and comparative examples are shown in Tables 1 and 2. The numerical values are % by mass.

[0083] <Measurement and Evaluation of Physical Properties> The physical properties of the polyamide resin compositions obtained in the examples and comparative examples were evaluated by the following methods.

[0084] [Measurement of Extracted Components] The weight of a sample is measured, the moisture content is measured in accordance with JIS K 7251, and then the weight before extraction (=sample weight - moisture content) is calculated. The sample is boiled in methanol for 6 hours and dried. After drying, the moisture content is measured and extraction is performed, and the weight after extraction (=weight of sample after extraction and drying - moisture content after extraction and drying) is calculated. The value obtained by subtracting the weight after extraction from the weight before extraction, dividing the result by the weight before extraction, and expressed as a percentage.

[0085] [Continuous Moldability of Tubes] Hollow moldability was evaluated based on the moldability of tubes produced by an extruder. The evaluation criteria are as follows. ○ (Good): Continuous molding is possible. △ (Fair): Continuous molding is possible, and there is no dimensional variation or waviness, but chatter marks occur partially. Alternatively, continuous molding is possible, and there is no waviness or chatter marks, but dimensional variation occurs partially. × (Poor): Continuous molding is impossible.

[0086] [Melt Viscosity] Using Capillograph F-1 manufactured by Toyo Seiki, a sample sufficiently dried in advance, with a moisture value measured by the method in accordance with JIS K 7251 of less than 0.1% was used. Measurement was performed at a cylinder temperature of 300°C, an orifice diameter L / D = 10, and a shear rate of 121.6 sec －１The melt viscosity was measured. It is known that an appropriate melt viscosity is necessary to obtain the target wall thickness dimension when forming a tube, but in this invention, if the melt viscosity is 600 Pa·s or higher, the tube can be formed. Therefore, even for tubes whose formability has not been measured, if the melt viscosity is 600 Pa·s or higher, the formability is rated as good or better.

[0087] [Preparation of Test Specimens] Test specimens of the polyamide resin compositions of the examples and comparative examples were prepared in accordance with ISO 294-1 using an injection molding machine SE100D-C160S manufactured by Sumitomo Heavy Industries, Ltd.

[0088] [Flexural Modulus] The flexural modulus (MPa) was measured using the obtained test specimens in accordance with ISO 178. If the flexural modulus was 1600 MPa or less, it was judged to have excellent flexibility when made into a tube.

[0089] [Tensile Nominal Strain at Fracture] The tensile nominal strain at fracture (εtB, %) was measured using the obtained test specimens in accordance with ISO 527-1 and ISO 527-2 / 1A / 50. If the tensile nominal strain at fracture was greater than 100%, it was judged to have sufficient impact resistance, and if it was 160% or more, it was judged to have particularly excellent impact resistance.

[0090]

[0091]

[0092] As shown in Tables 1 and 2, the polyamide resin composition of the present invention exhibited excellent stability during mixing and moldability when formed into tubes. Furthermore, because it does not require the addition of plasticizers (compared to Comparative Examples 2, 4, and 9), the amount of eluted components was extremely small, and it was able to withstand the transport of chemicals even as a single-layer hollow molded body. In addition, compared to Comparative Examples 1 and 2, which did not contain polyolefins, the polyamide resin composition of the present invention showed good tube moldability and higher impact resistance. Moreover, compared to the compositions of the comparative examples, the polyamide resin compositions of the present invention all had a moderate flexural modulus, making them preferable for molding into tubes, and furthermore, the amount of eluted components was small, making them more suitable for transporting chemicals in single layers.

Claims

A polyamide resin composition for a single-layer hollow molded article, comprising an aliphatic polyamide resin (A) and a polyolefin having functional groups (B), The polyamide resin composition contains 60 to 80% by mass of aliphatic polyamide resin (A) and 20 to 40% by mass of polyolefin (B) in 100% by mass. The average ratio [CH2] / [NHCO] of the number of methylene groups ([CH2]) to the number of amide groups ([NHCO]) in aliphatic polyamide resin (A) is between 3.0 and 8.

0. The functional groups of polyolefin (B) substantially do not contain metal atoms. Substantially free of plasticizers (C), Cylinder temperature 300°C, orifice diameter L / D = 10, shear rate 121.6 sec －１ A polyamide resin composition for single-layer hollow molded articles having a melt viscosity of 600 Pa·s or more, as measured by [method / tool ​​name]. Cylinder temperature 300°C, orifice diameter L / D = 10, shear rate 121.6 sec －１ The polyamide resin composition according to claim 1, wherein the melt viscosity measured is 1000 Pa·s or more. 　 The polyamide resin composition according to claim 1, wherein the average ratio [CH2] / [NHCO] of the number of methylene groups ([CH2]) to the number of amide groups ([NHCO]) in the aliphatic polyamide resin (A) is 4.3 to 6.

5. The polyamide resin composition according to claim 1, wherein the aliphatic polyamide resin (A) is at least one selected from the group consisting of aliphatic homopolyamide resins and aliphatic copolymer polyamide resins. 　 The polyamide resin composition according to claim 1, wherein the aliphatic polyamide resin (A) comprises PA56, PA6, PA66, PA6 / 66, PA510, or PA610. 　 The polyamide resin composition according to claim 1, wherein the number average molecular weight of the aliphatic polyamide resin (A) is 10,000 to 50,000. 　 The polyamide resin composition according to claim 1, wherein the amount of amino groups per gram of aliphatic polyamide resin (A) is 10 μmol / g or more and 120 μmol / g or less. 　 The polyamide resin composition according to claim 1, wherein the polyolefin (B) is at least one selected from the group consisting of copolymers having a (ethylene and / or propylene) / α-olefin copolymer as the main backbone and having functional groups having reactivity with terminal groups of an aliphatic polyamide resin in at least a portion thereof, and (ethylene and / or propylene) / (α,β-unsaturated carboxylic acid and / or α,β-unsaturated carboxylic acid ester) copolymers. 　 The polyamide resin composition according to claim 1, wherein the functional group of polyolefin (B) is at least one selected from the group consisting of a carboxyl group, an acid anhydride group, a carboxylic acid ester group, a carboxylic acid imide group, a carboxylic acid amide group, and an epoxy group. Cylinder temperature 300°C, orifice diameter L / D = 10, shear rate 121.6 sec －１ The polyamide resin composition according to claim 1, wherein the melt viscosity measured is 1000 Pa·s or more and 2700 Pa·s or less. The polyamide resin composition according to claim 1, wherein the tensile fracture nominal strain when a test specimen prepared in accordance with ISO 294-1 is measured in accordance with ISO 527-1 and ISO 527-2 / 1A / 50 is greater than 100%. The polyamide resin composition according to claim 1, wherein the flexural modulus of elasticity when a test specimen prepared in accordance with ISO 294-1 is measured in accordance with ISO 178 is 1600 MPa or less. A polyamide resin composition for a single-layer hollow molded article, comprising an aliphatic polyamide resin (A) and a polyolefin having functional groups (B), The polyamide resin composition contains 60 to 80% by mass of aliphatic polyamide resin (A) and 20 to 40% by mass of polyolefin (B) in 100% by mass. The average ratio [CH2] / [NHCO] of the number of methylene groups ([CH2]) to the number of amide groups ([NHCO]) in aliphatic polyamide resin (A) is between 3.0 and 8.

0. The functional groups of polyolefin (B) substantially do not contain metal atoms. When the polyamide resin composition is extracted with methanol after drying, the amount of eluted components is 3% by mass or less when the total mass of the resin composition is considered to be 100% by mass, and the cylinder temperature is 300°C, orifice diameter L / D = 10, shear rate is 121.6 sec. －１ A polyamide resin composition for single-layer hollow molded articles, wherein the melt viscosity measured is 600 Pa·s or more. 　 A single-layer hollow molded article comprising the polyamide resin composition according to any one of claims 1 to 13. A single-layer hollow molded body according to claim 14, which is at least one selected from the group consisting of pipes, tubes, and hoses. 　 A single-layer hollow molded body according to claim 15, used for temperature control.

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